Plastics : In Architecture and Construction 9783034611947, 9783034603225

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Plastics in Architecture and Construction

Stephan Engelsmann Valerie Spalding Stefan Peters

Plastics in Architecture and Construction

Birkhäuser Basel

preface 

7

1  T he development

CONSTRUCTION

of plastic architecture 

9

5 Finished and semi-finished products 

61

Solid sheets and panels 

PRINCIPLES

61

Profiled sheets and panels  2 Material properties of plastics 

Sandwich panels  Foams 

15

76

Forming characteristics and

Profiles 

the manufacture of building

Special products 

elements 

66

70

77 79

15

Resistance to environmental effects 

6 Building with plastics 

16

Mechanical properties  Thermal properties 

 Thermoplastics 

16

Screwing 

17

Clamping 

performance 

Bonding 

82

Welding 

85

Additives, fillers and reinforcing materials 

81

 Thermosets 

18

86

Screwing  Bonding  3 Basics of plastics  Polymer structure 

86 88

Dimensioning 

21

92

Stability and

21

 The morphology ­

durability 

of macromolecules 

81

81

Flammability and fire 17

81

94

22

 The classification of plastics ­according to their degree ­ of cross-linking 

Case Studies

24

Synthesising techniques 

27

7 Plastics as building envelope 

95

Chanel Mobile Art Pavilion  4 Plastics and their manufacture  Elastomers  Types 

BMW Bubble 

29

98

Frankfurt and Berlin, Germany

29

 Thermoplastics 

Kunsthaus Graz 

100

Graz, Austria

32

Emsdetten railway station 

32

Manufacture 

Idee Workstation 

44

106

Tokyo, Japan

Recycling 

46

 Thermosets 

Reiss Headquarters 

48

London, United Kingdom

Material components  Manufacture  Properties 

57

50

102

Emsdetten, Germany

39

Working methods 

96

Hong Kong, China; Tokyo, Japan; New York, USA

48

108

Fiberline Composites factory and offices 

110

Middelfart, Denmark

Farben des Konsums 

10 Future developments 

112

Berlin, Germany

Laban Creekside 

High-performance material 114

for supporting structures 

London, United Kingdom

 Terminal V 

for building envelopes 

Forum Soft  118 Yverdon, Switzerland

Composite materials 

Polymer Engineering Centre 

160 161

Reinforcement of supporting 120

Melbourne, Australia

structures 

163

Joining technologies appropriate

122

Friedrichshafen, Germany

to the material 

Badajoz congress centre and

New production methods 

auditorium 

Technology transfer 

124

Badajoz, Spain

Glossary 

8 Plastics as building structure 

Plastic tower sculpture 

164

170

About the authors 

128

166

167

Bibliography 

127

173

Stuttgart, Germany

Acknowledgements 

D-Turm 

Name and building index 

130

Doetinchem, Netherlands

Subject index 

Hoofddorp bus station 

Roof Yitzhak Rabin Centre 

136

Tel Aviv, Israel 138

Düsseldorf, Germany

Plastic folded shell structure 

140

Stuttgart, Germany

9 Plastics as building structure and envelope  Clip-On 

143

144

Utrecht, Netherlands

Eiertempel 

146

Bern, Switzerland

Five Bubbles 

148

Vienna, Austria

fg 2000 

150

Altenstadt, Germany

Futuro 

152

Different locations worldwide

MYKO 

154

Weimar and Rostock, Germany

Novartis Campus reception building 

156

Basel, Switzerland

173

174

Illustration credits 

132

Hoofddorp, Netherlands

GRP/Glass Pavilion 

159

High-performance material

116

Lauterach, Austria

Dornier Museum 

159

176

174

165

7



Preface

With this book “Plastics in Architecture and Construction” the authors wish to kindle a greater interest in building with plastics. Buildings made of or with plastic are one of the most interesting fields of architecture for architects and engineers alike. This publication provides relevant information in a clear and understandable form and offers architects and engineers, as well as interested laypeople, the opportunity, without the need for prior knowledge, to examine plastics as a material and their application areas in architecture. The book begins with a short historical overview of plastics in architecture, followed by an introduction to the technical and chemical principles of the material that play important roles in determining the properties of different plastics. The descriptions of material properties are limited to those plastics most commonly used in the building sector and their respective requirements. In addition, the manufacture and working properties of the plastics are detailed as these too are invalu­able for designing and building. The subsequent chapter presents a selection of finished and semi-­finished products, providing architects and engineers an overview of the most interesting plastic products. Detailed knowledge of dimensioning rules, construction principles and bonding and joining techniques is a necessary prerequisite for using plastics in construction and each is described in a further section. Finally, case studies illustrate the potential applications of plastics in architecture. Except for a few isolated cases, this book focuses predominantly on new buildings as a reflection of the current state of the art. Plastic architecture from the 1960s and 1970s has, after all, been dealt with at length in other publications. The descriptions given in this book focus primarily on the architectural context and the design of the construction. The selection of projects is largely subjective and by no means exhaustive, and we have elected to limit the selection to plastic buildings so as not to exceed the volume of this book. Pneumatic and textile structures made of synthetic fabrics and membranes are, therefore, not part of this book, likewise the many diverse and interesting uses of plastics in engineering, for example for bridge building. In the authors’ opinion, this topic merits a book of its own. The book concludes with a discussion of selected current developments in the field, offering a glimpse of future research and development.

9



1

 The development of plastic architecture

Plastics are high-performance materials with very different properties and can be found in the world around us in many different forms and applications. One of the areas where plastics are used is architecture. Building with plastics is an experi­ mental and highly interesting specialist area of architecture. In this chapter we will examine some of the most important developments in the history of plastics in architecture. Plastics are a comparatively recent material, despite the fact that the natural precursor of today’s modern material – natural rubber, harvested from the gum tree – has been known for over 500 years. Today plastics are generally artificially produced. The motivation behind the development of the modern material dates back to the period of early industrialisation and the need for an artificially producible alternative to the highly sought-after but expensive natural raw material. Intensive research activities soon sprang up to find a cost-effective and artificial material capable of replacing the natural product that could be syntheti­cally manu­factured in large quantities. The German name for plastics, “Kunststoff”, meaning literally “artificial material”, became more widely known with the publication of a journal of the same name in 1911. Beside the synthetic manufacture of ­materials, one of the most important motivations for the development of plastics was to be able to optimise special material properties. A significant number of the plastics used today in construction had already 1.1

been developed by the end of the 1940s. These include, for example, ­polyvinyl chloride (PVC), polymethacrylate (PMMA), polystyrene (PS), polyethylene (PE), polyurethane (PUR) and polytetrafluoroethylene (PTFE). Beside these basic types, there are numerous different modifications with special formulas designed by manufacturers to serve specific purposes. Plastics, and in particular fibre-re­ inforced plastics, make it fundamentally possible to fashion a material for a particular application. For this reason the improvement or rather optimisation of material properties focuses less on the creation of new materials than on the ­further development of existing materials as well as their combination in the form of composite materials. The foundation for high-performance composite materials was laid in the 1940s with the development of polyester resin in combination with the industrialscale production of glass fibres. This concept for a composite material was quickly adopted for a variety of uses, for example for the construction of aeroplanes, boats and vehicles, and the new material rapidly established itself in many different industrial fields.

10

INTRODUCTION

1.1  Cover of the first issue of the journal “Kunststoffe”, published on 1 January 1911.  1.2 Geodesic dome made of GRP elements, R. Buckminster Fuller, 1954.  1.3 Mobile hotel cabin,

I. Schein, R.-A. Coulon, Y. Magnant, 1956. The plastic cells made of GRP were conceived as modular units and optimised for transportation.

1.1

1.2

1.3

The specific properties of fibre-reinforced plastics, in particular their light weight, good weather resistance and excellent forming characteristics in conjunction with comparatively high strength, make them of particular interest for architectural applications. The first projects for buildings made of plastic were developed as far back as the 1940s. The buildings were conceived as a serially producible system of prefabricated elements in order to compensate for the lack of conventional building materials after the end of the Second World War. These projects, however, never made it into production. After the war various plastics manufacturers attempted to find new markets 1.2

in the realm of architecture. Pioneering architects and engineers began to experiment with the new material. The first use of glass fibre-reinforced plastics (GRP) in building constructions was in 1954 for military radar domes. The geodesic domes devised by Richard Buckminster Fuller were an ideal application for the light, translucent and electromagnetically permeable GRP material. In contrast to thermoplastics, construction elements made of fibre-reinforced polyester resin are easy to produce without the need for complex machinery and

1.3

are therefore ideally suited for the manufacture of prototypes. The first residential building made of plastic was built in 1956 in France. In collaboration with the French chemical company Camus et Cie., the architects Ionel Schein and René-

THE DEVELOPMENT OF PLASTIC ARCHITECTURE

André Coulon together with the engineer Yves Magnant developed a series of dwelling units and a building out of the new material. Known as the “snail shell house” because of its geometry, it was constructed out of a combination of flat and uniaxially curved GRP sandwich panels with GRP stiffening ribs. The organically formed sanitary cells of the snail shell house and the mobile hotel cabin developed in the same year gave an indication of the design potential of the new material. An important step was made with the development of building elements 1.4

as  sandwich constructions in which fibre-reinforced plastic was combined with PUR insulation materials. The use of this technology, in which an insulating core ­material is sandwiched between two thin GRP layers, made it possible to create lightweight and simultaneously rigid sandwich elements which were ideally suited for self-supporting building skins. The “Monsanto House of the Future” (architects: Richard Hamilton and Marvin Goody, engineer: Albert Dietz, USA, 1957) made use of this principle. It was the first plastic house to be fully developed for mass production. Although it was destined for industrial production, only the prototype was realised. Nevertheless, the building was effective in demonstrating the structural, architectonic and thermal performance of the plastic constructions and, above all, because of its futuristic formal language, the design possibilities of the new material. As a result, interest in plastic houses grew rapidly around the world. Engineers and architects researched the material and numerous projects followed that ex­ploited its benefits. The 1960s in particular were characterised by a variety of architectural experiments aimed at finding a form appropriate to the material. The use of new materials also brought forth a new formal language. In many houses made of plastic, rounded forms and curved building elements are to be found in ­variously pronounced forms. In addition to a general predilection for rounded forms in the 1960s, the use of curved building elements can also be attributed to the desire to lend the comparatively flexible material greater stiffness by curving, folding or creasing the thin material of the building skin to stabilise its form. The ability to prefabricate elements and the low level of maintenance required for ­buildings made of plastic, also played a decisive role. One of the high points in plastic architecture was the IKA (International Plastic Housing Exhibition) in

1.5

Lüdenscheid, Germany, which from 1971 onwards featured a series of prototypes for family dwellings and holiday homes, including the “Futuro” (architect: Matti ­Suuronen, engineer: Yrjö Ronkka), “Rondo” (architects: Casoni & Casoni, engineer: René Walther), “fg 2000” (architect: Wolfgang Feierbach, engineer: Gerhard ­Dietrich, Carsten Langlie) and “Bulle Six Coques” (six-shell bubble house, architect: Jean Benjamin Maneval, engineer: Yves Magnant). The technical requirements of mass production were often the point of departure for planning deliberations, although the prototypes themselves were typically made laboriously by hand. The intention of the designers was to use existing manu­ facturing methods for the cost-effective production of plastic houses of a high technical standard. In 1973, the Darmstadt Institute for Building with Plastics (IBK) published a comprehensive report that documented 232 international concepts and realised projects. The majority of the projects never made it beyond the prototype; only 38 % of the examples shown were built more than once, mostly in small

11

12

INTRODUCTION

quantities. One exception was the so-called “Polyvilla”, a rectangular hybrid construction made of lightweight concrete and plastic with a traditional form, which was built over 500 times within a period of ten years. In the concluding chapter, the report predicted a future for the industrial mass production of plastic houses but recognised that the resulting standardisation would be problematic for marketing them as private houses. The plastic houses that were realised proved that plastics were fundamentally suitable for use in architecture and that in terms of structural stability, thermal performance and durability, they could be used in place of conventional materials. Their use was restricted primarily to single-storey buildings. Beside the production of entire buildings that were delivered as prefabricated products equipped with integrated fittings, further applications included individual components made 1.6

of plastic, for example sandwich panel façade elements, prefabricated ­sanitary cells and roofing elements. The experimental test structures from this period addressed many key considerations and together made a significant contribution to the future of plastic architecture. The structural potential and technical performance of fibre-reinforced plastics was of particular use for wide-span roof structures. A series of engineers developed outstanding concepts for high-performance structures. One example is the

1.8

“  Les échanges” Pavilion by the Swiss engineer Heinz Hossdorf presented at the Expo 1964 in Lausanne, a pre-stressed construction consisting of a grid of multiple umbrella-like elements made of 3 mm thick GRP sections. The modular shell constructions by the French engineer Stéphane du Château are a further example

1.7

of wide-span GRP structures. The segmented dome shell of the market hall roof in Argenteuil, made of 30 prefabricated 6 mm thick GRP shell elements on an underlying lightweight steel construction, spanned a diameter of 30 m. The pioneering buildings of the 1950s to 1970s did not, however, lead to the widespread adoption of housing made of plastic. By 1973, not a single one of the purely plastic houses had been mass-produced. The great expectations that the designers and industry had placed in the new material remained unfulfilled and the envisaged demand failed to materialise. The reasons for this are manifold: for example, the oil crisis in the 1970s led to a considerable rise in the price of plastics. However, the interruption in the development of plastic architecture cannot solely be attributed to the oil crisis. Although the forms were appropriate to the material, their unconventional looks and living concepts were not embraced by the public. Very few clients were willing to realise the dream of their own home in the form of an industrially mass-produced plastic house, particularly as they were not much cheaper than a conventional house. The low level of demand in turn inhibited their mass production, which would have led to a reduction in costs and greater economic competitiveness compared with conventional prefabricated houses. A further problem that ultimately led to the premature cessation of development activities was the difficulty of obtaining building control approval: several prototypes exhibited physical defects (mould etc.) and poor fire safety characteristics. Nevertheless, a series of different plastic buildings, such as the “Futuro” or the “fg 2000” have become milestones in the history of modern architecture. After this period, plastics were still used in a variety of ways for individual com-

13

THE DEVELOPMENT OF PLASTIC ARCHITECTURE

1.4  The “Monsanto House of the Future”, R. Hamilton, M. Goody, A. Dietz, 1957, was the first plastic ­house to be conceived for mass production.  1.5 International Plastic Housing Exhibition, IKA Lüdenscheid, Germany, 1971. Left “Futuro” (M. Suuronen, Y. Ronkka), foreground “Bulle Six Coques” (J. B. Maneval, Y. Magnant), right “Rondo” (Casoni & Casoni, R. Walther).

1.4

1.5

ponents but only rarely and in special circumstances were entire buildings realised in plastic. In recent years, plastics have begun to experience a renaissance in the field of architecture and construction. In addition to building elements and components for technical and constructional installations, for example piping and insulation, plastics are increasingly being used as high-performance materials for supporting structures and building skins. A distinction is drawn here between loadbearing and non-loadbearing building elements. Non-loadbearing applications are, for example, interior fittings and façade cladding in particular. Where sufficient quantities are required, it is possible to manufacture extremely complex, geometric precision elements using highly automated techniques. The use of plastics for building skins depends on the thermal and physical characteristics required. For loadbearing structures, fibre-reinforced plastics are still the most commonly used option. Application areas include supporting structures for buildings as well as industrial architecture and engineering structures. Special building elements with complex geometries are another area where plastics are appropriate. While the manufacture of moulds for such materials usually requires a high degree of manual skilled labour at a corresponding cost, plastics make it possible to produce highly differentiated building elements in large quantities at exacting tolerances. This is particularly relevant for modular systems. The low self-weight of the material is a particular advantage in terms of transportation. The comparatively high investment required for fabrication is compensated for by the ability to produce large quantities. In addition, plastics have long played an important role in construction maintenance, most notably carbon fibre-reinforced plastics for the repair and strengthening of concrete structures. Surprisingly, plastics are all too often regarded as a lower-quality substitute material when, in fact, the reverse is true: plastics are high-tech products. An adequate appreciation of plastics is, however, essential in order to best exploit their diverse, excellent properties and for the emergence of innovative plastic architecture. Of vital importance too is the search for forms of construction that are appropriate to the material. In this respect there is still much room for development.

14

INTRODUCTION

1.6 modular plastic façade made of prefabricated sandwich elements. 1.7 market hall, argenteuil near paris, s. du château, 1967. The dome measuring 30 m in diameter consists of 30 prefabricated 6 mm thick grp shell elements mounted on a supporting tubular steel construction. 1.8 “les échanges” pavilion, expo lausanne, h. hossdorf, 1964. a modular roof structure made of grp hyperbolic paraboloid (hypar) surfaces, bonded to a steel frame and pre-stressed.

1.6

1.8

1.7

15



2

Material properties of plastics

Plastics are a group of materials with a broad spectrum of properties that makes them predestined for numerous different applications. Plastics can be generally divided into four categories of plastics: elastomers and thermosets, which have a cross-linked molecular structures, and thermoplastics that have an uncrosslinked structure. Thermoplastic elastomers (TPE) result from a combination of thermoplastic and elastomeric components and exhibit characteristics of both groups. Depending on the degree of cross-linking, plastics can differ in terms of strength, stiffness and resistance to heat and chemicals. The performance characteristics of individual plastics are generally very specific. Nevertheless, there are several material properties that can be used to characterise plastics in general. This chapter provides an overview of these properties where they are relevant to the field of architecture.

Forming characteristics and the manufacture of building elements An excellent property of many plastics is the ability to shape them freely, which makes plastics ideally suitable for building elements with complex geometric forms. The production of individually shaped special forms, as is often the case 2.1

in architecture, can be comparatively costly. Prototypes made of thermosetting fibre-reinforced plastics with dimensions of up to several metres can be manually manufactured, but this is comparatively labour-intensive and correspond-

2.2

ingly expensive. A number of thermoplastic materials can be shaped with the help of rapid prototyping techniques without the need for the complex manufacture of moulds. In this case, the basis for the manufacture of a three-dimensional building element is a digital model. CNC fabrication methods include, for example, 3D printing or milling. These methods are generally only suitable for elements of a ­limited size. Elastomers and thermoplastics are also suitable for the manufacture of geometrically complex building elements and can be produced industrially in large quantities. The particular advantage of prefabricating elements for the building sector is that constructions can be produced and assembled regardless of weath­er conditions. In the case of plastics, the creation of the material and the moulding of the element are typically one and the same process. The fabrication process makes it possible to manufacture materials that can be adapted to their expected loads, for example through the localised application and embedding of reinforcement fibres in a resin matrix. Properties such as strength or stiffness can therefore be optimised as required.

16

MATERIAL PROPERTIES

2.1 Plastic tower, Stuttgart State Academy of Art and Design, 2007. Special hand-laminated building ­ lements with a complex geometric form.  2.2 Architecture model made by rapid prototyping e techniques.

2.1

2.2

Resistance to environmental effects Plastics are for the most part weather-resistant. Moisture ingress and exposure to UV radiation can, however, have a detrimental effect on the strength and durability of the material. The UV resistance of many plastics can be improved through the inclusion of certain additives. The aging stability is also dependent on protecting the material against the effects of the weather. Most plastics also have a high resistance to chemical attack by salts and acids. Plastics generally require little maintenance.

Mechanical properties A particular quality of fibre-reinforced plastics is their high strength with respect to their comparatively low self-weight. For this reason they are well-suited for use in highly stressed loadbearing structures. A disadvantage, however, with regard to their use in construction is the lack of building control permits for many plastic products. Some standardised products, where the properties are given in manufacturer’s data, have been certified for use in construction, but for special constructions it can sometimes be necessary to conduct cost-intensive testing and enter into complex and lengthy certification procedures. Compared with other materials used in construction, plastics have a low stiffness. In the case of loadbearing building elements, this deficit can be compensated for by shaping the material appropriately. Ways of stiffening these elements

FLAMMABILITY

include folding or creasing the edges, making the entire element curved or using a sandwich construction. Another possibility is to increase the stability of the overall structure by incorporating a rigid supporting spatial framework. Loadbearing structures that employ folded plate or shell constructions are therefore ideal candidates for the use of plastics. Plastic elements, which are usually manufactured in small thicknesses for cost reasons, can therefore be used in various combinations to create high-performance supporting structures. Some thermoplastics exhibit a high impact resistance, while others are more brittle. For many plastics, it is possible to adjust the impact resistance within certain limits. Another possible means of improving the impact resistance of thermoplastics and thermosets is the addition of reinforcing fibres.

 T hermal properties  Thermoplastic materials exhibit a high coefficient of thermal expansion, which needs to be taken into account when detailing. For example, when using PMMA (Plexiglas) or polycarbonate instead of glass in the skin of a building, the designer must plan for a degree of expansion that can be as much as seven times greater than that of glass. Most plastics exhibit good electrical and thermal insulation characteristics and resistance against both hot and cold temperatures. The upper limit of longterm temperature performance for thermoplastics typically used in construction is around 80 °C. At temperatures below –30 °C, plastics that have not been especially modified start to become brittle.

Flammability and fire performance Fire safety regulations are of particular relevance for the use of plastics in architecture. In Germany, the relevant guidelines regulating fire safety are the “Guidelines for the use of flammable materials in architecture (RbBH)” which are anchored in the building regulations of the respective German federal states. Because of their organic composition, plastics are invariably flammable and resist fire for only a short period of time. This fact is one of the main reasons why the use of plastics is limited to building elements and constructions with low fire safety requirements, e.g. façades, temporary buildings or canopies, unless other fire safety provisions have been made. Fire safety concepts consist of a combination of structural, technical and organisational measures. For loadbearing elements, only fibre-reinforced plastics are sufficiently strong; these, however, require individual case-based approval from the building control authorities. Fire tests and fire resistance assessments can be examined with respect to how fire impacts on the mechanical loadbearing properties. The use of fibre-reinforced plastics for the loadbearing structure of multi-storey buildings is therefore very rare. One prototype of such a case is the 2.3

Eyecatcher Building in Basel, Switzerland. There is a difference between flammability and fire performance. The flammability describes the chemical and physical processes within a material when a ­controlled test flame is applied to a test specimen. The fire performance is relevant for the use of materials and/or products that are exposed to an uncontrolled

17

18

MATERIAL PROPERTIES

fire. Flammability and fire performance are not specific material properties as both can be influenced by external parameters such as form and dimensions of the elements, the condition when installed, the kind and intensity of the ignition source and the supply of oxygen. A fire takes place in three phases: the outbreak of fire, the fully developed fire and the diminishing fire. Once a fire has developed fully, plastics always burn as a result of their organic structure. They can, however, be equipped with a flame retardant that can help to inhibit the inflammation of the material during the outbreak of fire and hinder the further spread of fire. An assessment of the fire ­performance of materials and building elements in the case of fire is based on a number of factors including flammability, flame propagation, heat emission, smoke production and toxicity. A specific problem is that certain plastics melt when exposed to fire, producing flaming droplets that contribute to an uncontrolled spread of the source of the fire. Purely plastic products, even when coated with a flame retardant, are classified as building material class B2 (flammable, flame-resistant) according to DIN  4102. Components made of composite materials with a low plastic content 2.4

can be classified as building material class A2 (non-flammable, with organic constituents, proof necessary). The test procedure used to categorise the building material classes is regulated differently in the different member states of the European Union. In the interests of harmonising the technical specifications within the European Union, the German DIN 4102 has been supplemented by DIN EN 13501: “The fire classification of construction products and building elements”. Part 1 regulates the classification of building materials into the fire safety classes A1, A2, B, C, D, E and F. The fire safety class A has the highest level of fire resistance. The regulations also describe the requirements for further characteristics that influence fire behaviour: the classes s1, s2 and s3 describe smoke production, the classes d0, d1 and d2 the production of flaming droplets. These are sub-elements of the respective fire safety classes. The higher the number, the higher the smoke production or the production of flaming droplets or particles.

Additives, fillers and reinforcing materials  The majority of polymeric materials are mixed with additives of different kinds that influence and optimise the properties of the plastic. The list below details some examples of the most important kinds of additives. One can differentiate between fillers and reinforcement materials, which are solid additives, and chemical additives, which are used to modify and improve the different properties of plastics such as flammability, UV stability, impact resistance, colour, strength or workability. Fillers  are used most notably to improve the workability and weight and volume expansion characteristics of a material in order to reduce the material costs of the plastic. They can also contribute to optimising the heat distortion temperature or impact resistance. Fillers include kaolin, chalk, glass beads and talc. In certain circumstances, fillers can have a detrimental effect on the strength of a material.

19

ADDITIVES

2.3 Eyecatcher Building, Swissbau Basel, Artevetro Architekten, Felix Knobel, 1999. The loadbearing

structure of the five-storey office building is made of flame-retardant and self-extinguishing pultruded GRP profiles.  2.4  Testing the fire performance of PMMA panels for the façade of the Kunsthaus Graz, Arbeitsgemeinschaft Kunsthaus, 2003.

2.3

2.4

Reinforcement materials  are used to improve the mechanical properties in the form of fibres, roving strands, matting or textiles which are embedded in a matrix. The matrix material can be an elastomer, thermoplastic or thermoset. Fibre-re­ inforced plastics used in construction are most commonly thermosetting plastics using a polyester resin matrix. Stabilisers  are additives designed to counteract the degeneration of polymers caused by heat or photo-oxidation. Solar radiation, moisture and high temperatures can lead to the decomposition of polymers, reducing their strength and aging stability. Antioxidants and light protection agents can be used to counteract these effects. Fire retardants  such as aluminium hydroxide, magnesium hydroxide, chlorine, bromine or phosphorus work by inhibiting or preventing combustion processes. Reactive fire retarding agents are added to the plastic mixture during polymerisation, whereas additives are added afterwards. Aluminium hydroxide, for example, initiates an endothermic process within the polymer that stops the material reaching the temperature necessary for combustion. Another alternative is the addition

20

MATERIAL PROPERTIES

of inert fillers, effectively diluting the amount of flammable material in the plastic. Intumescent systems are coatings, also used in steel constructions, that in the event of fire expand and foam to form an insulating fire barrier. Flame retardants can have a negative effect on the mechanical material properties and electrical conductivity of plastics. Foaming agents  are additives in liquid or solid form that cause plastics to foam. The gas bubbles that form during polymerisation result in plastic products that are lighter in weight and may also improve their thermal insulating properties. Coupling agents  increase the bond between polymers and other inorganic substances such as glass fibres. They are also used to facilitate the mixing of polymers that are incompatible with one another. Colourants  are added to the moulding compound either in the form of ­insoluble pigments in powder form or as soluble dyes. While organic pigments exhibit a greater brilliance than inorganic colourants, inorganic additives are colourfast and have a greater temperature stability.

21



3

Basics of plastics

 The majority of plastics consist primarily of the elements carbon (C), hydrogen (H) and oxygen (O). Elements such as sulphur (S), nitrogen (N), chlorine (Cl) and fluorine (F) as well as silicon (Si) or boron (B) can also be present. Although most plastics consist of only a few different elements, their properties can differ considerably. The differences can be attributed to the material’s molecular structure. The frequency and distribution of individual elements influence the bonding strength of the polymer chains and with it their arrangement and cohesion with the overall structure. The regularity of the structure and cross-linking between the polymer chains vary, sometimes resulting in very different characteristics with regard to thermal behaviour, workability, hardness or transparency. To fully understand their properties, it is necessary to have a basic knowledge of the molecular structure. Plastics are organic macromolecules whose basic repeating molecular unit is called a monomer. In nature, macromolecules form the basic unit for carbohydrates such as cellulose in plant fibres or hydrocarbons such as crude oil. The majority of raw materials used for the industrial production of plastics originate from the oil and natural gas industries. Bioplastics, which can be obtained from renewable raw materials, are gradually becoming increasingly important. In the production of plastics, monomers are linked using synthesising tech3.1

niques to form polymers. This process is known as polymerisation. For polymeri­ sation to occur, each monomer must have at least two bonding positions with which to connect to neighbouring monomers. The so-called functionality of the material depends on the number of these bonding positions, also called reaction sites. Bifunctional monomers form linear polymer chains, polyfunctional monomers form branched polymers. Their synthesis can be controlled through the use of catalysts, heat and pressure in order to carefully influence how the polymer chains or the molecular structures form. This makes it possible to produce plastics with specific properties.

Polymer structure Polymers that contain only a single type of repeat unit are known as homopoly3.2

mers. If the polymer is composed of different kinds of monomers, it is known either as a copolymer or a polymer blend. In the synthesis of copolymers, the constituent repeat units are bound together by atomic bonding to form a macromolecule. The result is a new material with its own specific qualities which may differ from those of its constituent components. The different types of copolymers are the product of different configurations of the constituent components.

22

BASICS OF PLASTICS

3.1 Monomers are linked to form polymers, in this case polyvinyl chloride (PVC).  3.2  Kinds of polymers.

3.1

3.2 Vinyl chloride monomer

Vinyl chloride monomer

Homopolymer

Copolymer

Sequential polymer

Polymerisation ­ causes dissolution of covalent bond Segmented block copolymer or Examples

Graft copolymer

Polymer polyvinyl chloride or

Blend

Cross-linked polymer matrix

Polymer chains suspended in the matrix

Polymer mixtures, also known as polymer blends, consist of a mixture of different kinds of polymers whose respective chains, unlike copolymers, do not enter into a chemical bond with one another. Heterogeneous polymer blends can be created to combine the advantageous properties of different kinds of source material, for example to improve a material’s workability. Homogenous blends with a molecular basis are an exception, as the mixing process is energy-intensive. Blends were originally developed to improve the workability and impact resistance of plastics. In addition, they can also contribute to improved heat distortion temperature properties and to reducing the formation of stress cracking or flammability.

 T he morphology of macromolecules Polymers form either linear or branched chain structures whose configuration with­in the macromolecule depends on the kind and number of respective bonding for­ 3.3

ces. Strong primary valence forces are responsible for formation and cohesion with­in the monomers and polymer chains, while secondary valence forces act between the polymer chains. Secondary valence bonds are temperature-dependent and can be broken through the input of energy. Polymers whose macromole­cular structure is determined primarily by secondary valence forces can be made to change shape permanently by heating them. The macromolecular structure is, therefore, of particular importance for properties such as the heat distortion temperature.

23

CHEMICAL STRUCTURE

3.3 Macromolecule with primary and secondary valence bonds.  3.4  Basic structure of polymers.  3.5 Coiled bundle of macromolecules consisting of linear polymer chains.  3.6 Polymers with amor-

phous and ordered crystalline regions. The crystalline structure is a product of the cohesion of ­polymer chains which are bound to one another with secondary valence forces. Heat can cause these bonds to break.

3.3

3.4

Primary valency bond

Secondary valency bond Atom

Linear

Branched

Cross-linked

3.5

3.6

Macromolecules have an amorphous or a crystalline or semi-crystalline struc3.5

ture. While the polymer chains of an amorphous macromolecule are randomly oriented, crystalline structures have a regular three-dimensional arrangement. Plastics where the macromolecule has a regular structure and the molecular structure itself is flexible are most conducive to crystallisation because the molecule chains can come close enough to each other to form parallel or folded arrangements that are held together by secondary valence bonds. As the degree of crystallisation rises, so too does the cohesion and the strength and solidity of the material. Plastics, however, are only semi-crystalline. Among the factors that inhibit crystallisation, the entanglement of the polymer chains and the size of the macromolecules to be crystallised are most common. Crystallisation is only possible within a tight temperature range in which the thermal movement of the polymer chains is reduced. Unlike the elements, which have clearly defined freezing, melting and boiling points, plastics typically have fluid temperature transition ranges. The input of energy causes the material state of plastics to change from

3.6

hard to elastic to soft. Plastics disintegrate before they reach a gaseous condition.

24

BASICS OF PLASTICS

 T he classification of plastics according to their degree of cross-linking Plastics are generally differentiated according to their degree of cross-linking. This classification is helpful in that fundamental material properties such as strength, heat distortion temperature, workability and thermoplastic formability are directly related to the degree of cross-linking of the polymers. With regard to the kind and degree of cross-linking, there are four groups: thermosets (also known as duromers), elastomers, thermoplastics and thermoplastic elastomers. The boundaries between them are indistinct and in some cases it 3.4

is not always clear to which group a plastic belongs. Materials with a semi-crystalline structure are uncross-linked and belong to the thermoplastics. Plastics with amorphous structures can be found in all groups and can be both uncrosslinked (thermoplastics) as well exhibit different degrees of cross-linking (thermosets, elastomers).  T hermoplastics   Thermoplastics are uncross-linked and consist of polymer

chains that can be linear or branched. They are heat-deformable because the poly­ mer chains do not form atomic bonds between each other but are linked only by secondary valence forces. The process of heat deformation is repeatable. Thermoplastics can be amorphous or semi-crystalline. In the case of amorphous thermoplastics the linear or branched molecule chains are randomly oriented and tangled. Because of their brittle nature they are particularly prone to stress cracking. Their appearance can be opaque or transparent. Amorphous thermoplastics can 3.7

be dissolved with an appropriate solvent. Examples of amorphous thermoplastics include PMMA, polystyrene (PS) and polyvinyl chloride (PVC). Semi-crystalline thermoplastics, by contrast, exhibit at least in parts a regular three-dimensional structure to the molecule chains. The higher density of the crystalline state compared with the amorphous condition means that heat input causes the volume to expand. Semi-crystalline thermoplastics are harder and

3.8

more resistant to solvents than amorphous structures. Polyethylene (PE), polypropylene (PP) and polyamide (PA) are examples of semi-crystalline thermoplastics. Elastomers  Elastomers exhibit a three-dimensional amorphous structure with

slight cross-linking that cannot be loosened through heat without the material decomposing. For this reason they cannot be heat-deformed, melted or welded. The tangled structure of the polymer chains is the reason for its exceptional elasticity and the fact that once the stress has been removed it returns to its original 3.9

condition. EPDM and the large family of rubber materials are examples of elastomeric plastics.

25

CHEMICAL STRUCTURE

3.7 amorphous thermoplastic: the polymer chains form a random, unordered structure. 3.8 semicrystalline thermoplastic: randomly oriented, amorphous regions alongside regular crystalline regions. 3.9 elastomer: amorphous tangle of polymer chains which are interconnected at larger intervals with atomic bonds. 3.10 Thermoset: amorphous polymer chains tightly cross-linked by atomic bonds. 3.11 Thermoplastic elastomer: example of a polymer blend.

3.7

3.8

3.9

3.10

3.11

26

BASICS OF PLASTICS

3.12 Polymerisation using the example of PVC: the double bonds of a monomer are broken apart ­ llowing it to bond with other monomers.  3.13 Polyaddition: the transfer of the H-atom from ­monomer a 2 to ­monomer 1 breaks the double bond between the N and C atoms, allowing the two monomers to link at the C atom.  3.14 Polycondensation: two monomers connect in a multi-step reaction giving off ­reaction products.

3.12 Monomer in a polymer chain

Monomer Reactive agent Heat emission Example: vinyl chloride

3.13

Monomer 1

Polyvinyl chloride

Monomer 2

Reactive agent

Heat emission

3.14

Separation of reaction products

 T hermosets   Thermosets, which are also known as duromers or duroplasts, have

a tightly cross-linked three-dimensional and amorphous structure. They are in general manufactured from different liquid components that react chemically with one another to form a strong, three-dimensional, cross-linked molecular structure held together predominantly by primary valence bonds. When subjected to heat, the freedom of movement of the individual atoms is so limited that the melting temperature lies above the decomposition temperature at which the atomic bonds break. Thermosets are hard and brittle due to their tight cross-linked structure and are accordingly resistant to acids and alkali solutions. Their strength and stiffness is much higher than for elastomers. Epoxy and polyester resins are the most commonly used thermosetting plastics in construction. The differentiation

SYNTHESISING TECHNIQUES

between elastomers and thermosets is a matter of general convention and is usu3.10

ally made according to hardness and stiffness.  T hermoplastic elastomers   Thermoplastic elastomers (TPE) unite the elas-

tic properties of elastomers with the workability of thermoplastics. This is possible because the three-dimensional cross-linking of the polymer chains are a product of physical, i.e. thermally reversible bonding. Pure elastomers are, by comparison, cross-linked by non-breakable atomic bonds. Another possibility is the mixing of cross-linked and uncross-linked polymers to form a blend resulting in a material with an elastomer component matrix in which thermoplastic components are embedded. Due to their low cross-linking, TPE exhibit rubber-like elastic properties within a large temperature range, but are not plastically deformable at these temperatures. Above this temperature range, however, they perform like thermoplas3.11

tics and can be formed and welded. Examples of thermoplastic elastomers are TPS made of styrene block and styrene butadiene block, TPV with dynamically crosslinked ­rubber and TPA with polyamide components.

Synthesising techniques Plastics or combinations thereof can be created using different synthesising techniques. The following section describes the three main principles for synthesising plastics. Polymerisation   The source material typically consists of unsaturated, i.e. un-

stable, organic compounds with double bonds or ring bonds. These are broken apart through the introduction of a reactive agent and form long-chain poly­mers while giving off heat. The process is an exothermic chain reaction without the expulsion of side products. The product of polymerisation is called the polymer3.12

izate; examples include polyethylene (PE), polypropylene (PP), polyvinyl chloride (PVC), polystyrene (PS) and unsaturated polyester resin (UP). Polyaddition   The source material for polyaddition, also known as ­addition

polymerisation, are different kinds of monomers where at least one of the monomer groups exhibits double bonds. Through the intermolecular transfer of hydrogen atoms, the double bond is broken making it possible for the monomers to join to  one  another. Like polymerisation, polyaddition requires the introduction of a ­reactive agent. The process takes place in steps giving off heat but without the expulsion of side products. The respective quantities of the individual components need to be precisely measured. The resulting synthesised plastics 3.13

are known as addition polymers. Examples include epoxy resin (EP) and poly­urethane (PUR). Polycondensation   The source components for polycondensation must exhibit

at least two functional groups which are particularly reactive, for example a hydroxide group (–OH). These react giving off volatile low-molecular side products such 3.14

as water or alcohol. Polycondensation is a multi-step reaction in which the side products need to be removed continually to ensure the progress of the reaction.

27

28

BASICS OF PLASTICS

­Examples of substances produced in this way include polyamide (PA) and ­phenolic resin (PF). After polymerisation, it is not always possible to determine which plastics were synthesised with which methods. In certain exceptional cases, a specific polymer can be manufactured using polymerisation, polyaddition or polycondensation. On the other hand, during the synthesis of a plastic, different synthesising methods occur at different stages of the reaction.

29



4

Plastics and  t heir manufacture

 The variety of plastics and plastic products manufactured today is vast. Between 4.1

1950 and 2008 the worldwide production of plastics rose by several orders of magnitude from 1.5 million tonnes to 245 million tonnes. A not insignificant proportion of the plastics produced are used in construction. Plastic products for construction include window and door profiles, pipes and insulation as well as membranes, panels, floor and wall coverings and sealants. The insulation sector has grown most rapidly as a result of the increased need to improve the energy performance of buildings. However, the greater part of plastics used in construction are for

4.2

technical installations in buildings. The use of plastics for loadbearing structures and the building envelope is, with the exception of insulation, comparatively small. The following section describes plastics that are used in architecture along with their typical material properties. The plastics are categorised as in the previous chapter into elastomers, thermoplastics and thermosets. Many plastics are

4.3

better known by the acronym of their chemical name, for example PVC for poly­vinyl chloride. This short form denotes the chemical family to which a product belongs. In many cases the products of a particular manufacturer have specific characteristics that differentiate them from other products in the same family. In such cases they are commonly known not by their acronym but by a trade or brand name given to them by the manufacturer. The trade names that are given in the following section represent a subjective choice and do not represent all the available products.

Elastomers Elastomers exhibit a low modulus of elasticity and are elastic at normal use temperature. They are not heat-deformable or weldable and, should they exceed the working temperature, will disintegrate before they melt. They are typically processed into moulded elements or semi-finished products through extrusion or calendering. Elastomers are most commonly used in construction as a sealant in the form of sealing profiles or membranes as well as for elastomer supports. The Shore hardness A and D according to DIN 53505/ISO 868 are a commonly used and important parameter for elastomers and, to a certain degree, for soft thermoplastics. They represent one of several categories of measures for indicat4.5

ing the hardness of a plastic. Tests are undertaken to determine the resistance of a plastic to indentation with a predefined indenting device. Shore A is used to determine the hardness of softer plastics and is measured using a truncated cone with a 0.79 mm wide tip. For harder plastics of the category Shore D, a ­needle with

30

PLASTICS AND  T HEIR MANUFACTURE

4.1  The use of plastics in Germany, 2007.  4.2  The applications of plastics in construction in ­Germany, 2007.  4.3 Acronyms for plastics according to DIN EN ISO 1043-1 (basic polymers) and DIN ISO 1629 ­(rubbers and latices).

4.1

4.2 Electronics 7.4 % Furniture 3.8 % Household products 2.9 % Agriculture 2.5 % Medicine 1.7 %

Vehicles 9.2 %

Packaging 32.4 %

4.3

Other 14.9 % Insulation 27 % Profiles 34 %

Pipes 24 %

Construction 25.2 %

Other 15 %

Acronym

Chemical name

Acronym

Chemical name

ABS

Acrylonitrile butadiene styrene

PE-HD

Polyethylene high density

ACM

Acrylic rubber

PE-LD

Polyethylene low density

ACS

Acrylonitrile chloroprene-styrene

PE-LLD

Polyethylene linear low density

ASA

Acrylonitrile styrene acrylate

PE-MD

Polyethylene medium density

AU

Polyurethane rubber

PE-UHMW

Polyethylene ultra high molecular weight

BR

Butadiene rubber

PE-ULD

Polyethylene ultra low density

CA

Cellulose acetate

PE-VLD

Polyethylene very low density

CH

Hydrated cellulose, cellulose film (cellophane)

PEEK

Polyetheretherketone

CR

Chloroprene rubber (neoprene)

PEK

Polyetherketone

CSF

Casein formaldehyde (casein plastic)

PET

Polyethylene terephthalate

EP

Epoxy resin

PET-G

Polyethylene terephthalate modified with glycol

EPDM

Ethylene propylene diene rubber

PF

Phenol formaldehyde resin

EPM

Ethylene propylene rubber

PI

Polyimide

ETFE

Ethylene tetrafluoroethylene

PMA

Polymethylacrylate

EU

Polyether urethane rubber

PMMA

Polymethyl methacrylate

EVAC

Ethylene vinyl acetate

PMMI

Polymethyl methacrylimide

IIR

Butyl rubber

POM

Polyoxymethylene (= polyacetal resin)

IR

Isoprene rubber

PP

Polypropylene

LCP

Liquid crystal polymer

PPE

Polyphenylene ether

MF

Melamine formaldehyde resin

PS

Polystyrene

MPF

Melamine phenol formaldehyde resin

PTFE

Polytetrafluoroethylene

MUF

Melamine urea formaldehyde resin

PUR

Polyurethane

NBR

Nitrile butadiene rubber

PVAC

Polyvinyl acetate

NR

Natural rubber

PVB

Polyvinyl butyral

PA

Polyamide

PVC

Polyvinyl chloride

PAC

Polyacetylene

SAN

Styrene acrylonitrile

PAEK

Polyacryletherketone

SB

Styrene Butadiene

PAN

Polyacrylonitrile

SP

Aromatic (saturated) polyester

PB

Polybutylene

TPE

Thermoplastic elastomer

PBT

Polybutylene terephthalate

UF

Urea formaldehyde

PC

Polycarbonate

UP

Unsaturated polyester

PE

Polyethylene

31

ELASTOMERS

4.4 EPDM sealing profiles.

4.5 Test specimen for determining the hardness of plastics according to the

Shore classification.

4.4

4.5

3 1.25

30°

2.5

0.1

shore d

3 1.25

2.5 35° shore a

0.79

a 0.1 mm ball tip is used. each scale results in a value between 0 and 100, with higher values indicating a harder material. The specific Shore scale used is indicated in a suffix. ETHYLENE PROPYLENE DIENE RUBBER (EPDM) of all the elastomers, epdm 4.4

is most widely used in the field of construction. The basis polymer EPM (ethylene propylene rubber) has excellent aging stability, weather and chemical resistance. Through the introduction of a diene, the polymer chains can be cross-linked with sulphur bridges to form ethylene propylene diene rubber (epdm). epdm is permanently elastic and has good mechanical properties even after extensive use. due to its excellent uv and ozone stability, it is ideally suited for long-term use outdoors. The material has a broad working temperature range from – 30 °c to + 140 °c. it is resistant against organic solutions such as alcohol as well as inorganic solutions such as salts, alkali leaches and acids. epdm exhibits strong swelling properties in oils and fuels, which can have a detrimental effect on the longevity of some epdm products. Trade names nordel (dupont), Buna (lanxess), dutral (polimeri), Keltan (dsm), vistalon (exxon mobil chemical) Manufacture Calendering for roofing membranes; extrusion for pipes, profiles and tubing Working, joining Gluing; EPDM-roofing membranes can be joined at their edges of uncross-linked pe, using hot-air welding Applications Bridge supports; waterproofing, for example membranes for flat roofs; sealing strips in windows and façades; joint expansion strips for joints between concrete building elements

32

PLASTICS AND  T HEIR MANUFACTURE

4.6  The molecular structure of polycarbonate.  4.7  Webbed and smooth polycarbonate panels.

4.6

4.7

 T hermoplastics  Thermoplastics are usually processed in the form of granules which are melted at the beginning of the mechanical production process before being formed into finished or semi-finished products. They are used in particular for non-loadbearing building elements in façades and interior fittings. They are also used widely for technical installations. Thermoplastics are machinable, can be melted and thermally formed. As flammable materials, they typically have a building product class of B1 to B3 according to DIN 4102 (roughly equivalent to fire safety classes B, C, D, E and F in DIN EN 13501), depending on the kind of plastic. Certain thermoplastics are recyclable, depending on the degree of purity of the material. The following selection describes the basic properties of the respective chemical groups. The properties may vary depending on the degree of additives or other plastics present in the respective product. Thermoplastics are subdivided into technical and standard plastics, of which the latter accounts for 80 % of worldwide production. Technical plastics include, for example, PC, PMMA, ABS, SAN, PA, POM and PBT. Standard plastics include, among others, PVC, PE, PS and EPS, PP and PET.

 T ypes Polycarbonate (PC)  Polycarbonate belongs to the group of saturated polymers.

Benzene rings lend these polymers good dimensional stability and a high melt4.6

ing temperature. Due to their amorphous molecular structure, polycarbonates are highly transparent and can be used as a substitute for glass: for a polycarbonate with a thickness of 3 mm, the degree of light transmission is 88 %, only fractionally

4.18

lower than clear glass (91.7 %). The advantage of PC over glass is twofold: with a low density of 1.2 g/cm3 the self-weight of the material is approximately half that of glass, while its impact resistance is 250 times greater. Polycarbonate is available in different degrees of transparency and has a very glossy surface. The working temperature range is comparatively large, ranging from – 150 °C to + 130 °C. Compared with glass, the thermal expansion coefficient is seven times

33

THERMOPLASTICS

4.8  The molecular structure of polymethyl methacrylate (PMMA).  4.9 Various products made of PMMA.

4.8

4.9

greater, a fact that has to be taken into account when designing items that use polycarbonates. The low modulus of elasticity of 2300–2400 MPa is typical of ­thermoplastics. PC has good long-term weather resistance but will start to yellow over time without additional measures. For this reason, PC products are given a UV protective coating to prevent premature aging. Its chemical resistance to alkalis, acetone or aromatic hydrocarbon compounds is limited and contact with these substances can lead to stress cracking. PC is also used as a component in blends to produce materials with specially adapted properties. The material is also available with fibre reinforcement, which improves its stiffness and reduces the risk of stress cracking. Trade names Makrolon, Apec (Bayer), Lexan (SABIC) Manufacture Extrusion for panels and multiwall sheeting Working, joining Gluing: dichloromethane-based solvent adhesive, reactive adhesive; welding; screwing; machining; thermal reshaping at 180–220 °C 4.7

Applications Panels, single and multiwall sheeting, corrugated panels for façades and exhibition architecture; shatterproof components of laminated glass; for high mechanical loads Polymethyl methacrylate (PMMA)  Originally developed in 1933 as a replace-

4.8

ment for glass in aeroplane cockpits, polymethyl methacrylate is today one of the most commonly used plastics in construction. Semi-finished products made of PMMA can be poured (PMMA GS) or extruded (PMMA XT). The poured variant offers more potential for design variants than extruded PMMA, as individual adjustments within the extrusion process are more complex to achieve and therefore more costly. The working temperature range lies between – 40 °C and + 70 °C for extruded PMMA and up to 80 °C for poured PMMA. The key characteristic of PMMA is its very high transparency and high UV stability and weather resistance. With a light transmittance of 92 % at a thickness of 3 mm, it has the best light transmittance of all plastics. The amorphous molecular structure responsible for the transparency of the material is also the reason for the brittleness of the material which is susceptible to stress cracking and can only be worked with appropriate tools. With a thermal expansion coefficient eight times

34

PLASTICS AND  T HEIR MANUFACTURE

higher than that of glass, PMMA elements should be mounted unconstrained. The modulus of elasticity of PMMA is comparatively low at 3100–3300 MPa but never­ theless significantly higher than that of polycarbonate. PMMA is impervious to weak acids and alkalis, fats, oils and water. Oriented PMMA GS is classed according to DIN 4102 as building product class B1, no flaming droplets. A further variant is shock-resistant PMM-HA ( = High Impact). It consists of a PMMA-matrix in which styrene-modified acrylate elastomers are finely distributed. This mixture results in a reduced susceptibility to stress cracking and better resistance to hot water. The transparency and weather resistance of the PMMA remains unaffected. PMMA is generally recyclable. Trade names Acrylite, Plexiglas (Evonik Röhm), Perspex (Lucite) Manufacture  Extrusion into profiles, panels or multiwall sheets; injection moulding for prisms for light-deflecting systems; poured to make panels Working, joining  Welding (hot air, warm air, ultrasound); machining (turning, ­milling, drilling); screwing 4.9

Applications Light domes; panels, single and multiwall sheets, corrugated panels for façades, greenhouses; light prisms and light deflection lamellae for light engineering applications: translucent insulation (TI) Polyvinyl chloride (PVC)  Polymerised out of ethylene and chlorine, polyvinyl

4.10

chloride was developed in 1912 and has been industrially produced since 1928. Today some 60 % of the PVC produced in Germany is used in construction for windows, pipes or membranes and foils. PVC is an amorphous material whose properties are largely a product of the degree of polymerisation. The raw material is almost always processed in powder form. PVC is classified into hard or unplasticised PVC (PVC-U) and soft or plasticised PVC (PVC-P). Within this classification there are further modified variants which differ in particular with regard to polymerisation process, transparency, workability, material resistance and water absorption. In addition, PVC is also used in different combinations for copolymers or blends. PVC is generally classified as building product class B1 or B2 (DIN 4102), depending on the respective product. PVC products in construction are extensively recycled thanks to a widespread collection and recycling system in which window profiles, roller shutters and pipes are collected separately for recycling. Hard PVC (PVC-U) is relatively strong for a thermoplastic and has a high modulus of elasticity. The material is not particularly prone to stress cracking and is flame-resistant. Hard PVC needs to be stabilised for outdoor use. A disadvantage of PVC is its low abrasion resistance and low heat deformation temperature of 65–75 °C. At sub-zero temperatures, PVC becomes increasingly brittle. As a whole, hard PVC is a comparatively inexpensive material which, with appropriate modification, can be used for a wide variety of purposes. Soft PVC (PVC-P) is softened with a volumetric proportion of 20–50 % plasticiser which increases the distance between the polymer chains and weakens the molecular bonds. As a result it is more resilient than hard PVC at low temperatures. So-called plasticiser migration, whereby volatile liquid plasticisers leach out of the material, can lead to the product becoming brittle.

35

THERMOPLASTICS

4.10  The molecular structure of polyvinyl chloride.  4.11 Planar PVC products: pigmented board with

­integral foam structure and a membrane.

4.10

4.11

Trade names  Membranes, foils:  Alkorflex (Renolit), Ultrashield (PolyOne Th. Bergmann), Pentadur, Pentalan (Kloeckner Pentaplast) Boards, sheets: Forex (rigid foam, Alcan), Dural (AlphaGary), PVC Glass (Simona) Pipes, profiles: Renodur, Benvic (Solvay)

Manufacture  Calendering for membranes; extrusion for pipes, profiles and sheets; compression moulding for panels Working, joining  Welding; bonding 4.11

Applications  Panels, corrugated panels; window profiles; roller shutters; pipes and guttering; roof membranes, joining strips, handrails, cable sheaths; wall and floor coverings Polystyrene (PS)  Polystyrene is an amorphous, hard thermoplastic with a high

light transmittance that can be made into transparent, clear semi-finished products. It is an inexpensive material that is unaffected by cold temperatures and moisture and resistant to salt solutions and alkali leaches. Its water absorption is 4.14

low. As a homopolymer, polystyrene is brittle and very prone to stress cracking; the temperature needs to be controlled very carefully during manufacture. Thermoplastic forming processes are therefore somewhat restricted. The upper limit for the working temperature of polystyrene lies in the range of 60–80 °C. PS materials need to be UV stabilised but are nevertheless unsuitable for outdoor use in this form. Polystyrene is easily inflammable and continues to burn after ignition.

36

PLASTICS AND THEIR MANUFACTURE

4.12 polystyrene products: eps, Xps and cell-free tinted or transparent panels. 4.13 rigid polyurethane foam and an elastomeric polyurethane membrane. 4.14 The molecular structure of polystyrene.

4.12

4.13

4.14

numerous copolymers and blends based on polystyrene exhibit special properties with regard to susceptibility to stress cracking, heat deformation temperature, stiffness, impact resistance and chemical stability. With the help of foaming agents, expanded foams can be produced from styrene moulding compounds. These represent one of polystyrene’s main uses in construction. expanded polystyrene (eps) is used, for example, for structural moulded forms in multi-stage thermoplastic foam injection moulding. extruded polystyrene (Xps) is a closed-cell foam with a dense surface structure which is extruded in panel form using a sheet die. Trade names styropor, styrodur c (Basf), styraclear (Westlake plastics), Bapolan (Bamberger polymers), Benelit (foil, Benecke-Kaliko) Manufacture Injection moulding; extrusion for profiles and sheets Working, joining Welding; bonding (solvent adhesive, two-component adhesive); machining with appropriate tools; vacuum metallisation with aluminium 4.12

Applications insulation made of expanded polystyrene; model building; illuminated displays POLYURETHANE (PUR) polyurethane is a special case among plastics because

the polymer structure and the forms it can take vary considerably. While it derives its name from the component urethane, this plays only a secondary role in its molecular structure. The properties of this plastic are determined largely by the other constituent components of the polymer, which are also responsible for the 4.13

large variety and different properties of the pur material. pur is manufactured through polyaddition, as a rule from liquid components in different mixtures. alongside hard segments, the molecules also contain soft segments that lend the material a certain elasticity and substantially determine its temperature behaviour. as a cross-linked elastomer, pur exhibits a high tensile and

THERMOPLASTICS

flexural strength. It has good abrasion resistance and as a foil or membrane resists tear propagation. The working temperature range lies between – 40 °C and + 80 °C. The primary relevance of thermoplastic PUR for construction lies in the use of polyurethane as a foam. Using foaming agents, the reaction mass is transformed into blocks of foam in a multi-stage exothermic process. Soft foams with a bulk density of 20–40 kg/m3 have an open-cell structure and are used for soft moulded articles and as a foam filling material. Rigid foam materials have a closed-cell structure and a bulk density of up to 90 kg/m3. They are typically manufactured in the form of blocks or slabs. With a low water absorption they are ideally suited for use as insulation material. In addition, cell-free PUR materials are also available in the form of paints, coatings and adhesives. Trade names Adiprene (Elastomer, Chemtura), Technogel (Technogel), Baydur, Des­modur, Vulkollan (Bayer) Polytetrafluoroethylene (PTFE)   Polytetrafluoroethylene, like ETFE, belongs 4.15

to the group of fluoropolymers in which the hydrogen atoms are wholly or partially replaced by fluorine atoms. Due to their stable fluorine-carbon bonds, fluoro­ polymers invariably exhibit a high chemical and thermal stability. The working temperature range lies between – 270 °C and + 260 °C. PTFE has a comparatively high density of 2.2 g/cm3. Plastics that contain fluorine have a high chemical resistance, are weather-resistant without the need for stabilisation, non-­flammable and hardly ever become brittle. PTFEs resist buckling, wetting and do not absorb water. They are consequently ideal for outdoor use and are used primarily as a membrane material in the form of textiles as well as coatings for glass-fibre textiles. Their disadvantages on the other hand are that they lack strength and stiffness and are expensive. PTFE’s pronounced anti-stick characteristic means that it cannot be joined by welding or bonding. Trade names  Algoflon (Solvay Solexis), Hostaflon (Hoechst), Teflon (DuPont), Tenara (Gore) Ethylene tetrafluoroethylene (ETFE)   The addition of ethylene to PTFE

4.16

results in the plastic ethylene tetrafluoroethylene which improves its thermoplastic workability. While its heat distortion temperature is lowered, its stiffness, tensile strength and tear resistance are considerably improved. The transparent material exhibits a comparable chemical resistance to PTFE but needs to be stabilised against thermal and photochemical decomposition. Its buckle resistance is lower than that of PTFE.

37

38

PLASTICS AND  T HEIR MANUFACTURE

4.15  The molecular structure of Polytetrafluoroethylene (PTFE).  4.16  The molecular structure of Ethy­ lene tetrafluoroethylene (ETFE).  4.17 ETFE foil cushions form the Eden Project roof in St. Austell, UK, Grimshaw Architects, 2001.  4.18 A comparison of the material parameters of plastics.

4.15

4.17

4.16

4.18

PC

PMMA macro­ molecular

PVC-U

PVC-P with DOP 60/40

PP

Glass

Density (g/cm3)

1.2

1.17–1.19

1.38–1.4

1.15–1.3

0.9

2.5

Modulus of elasticity, tension (MPa)

2300–2400

3300

2700–3000

–

1300–1800

70 000

Permissible bending tensile strength (MPa)

–

–

–

–

–

18 (Float) 50 (ESG)

Flexural strength (%)

–

4.5–5.5

-

–

–

Breaking stress (MPa)

–

70–80

-

–

-

Elongation (%)

6–7

–

4–6

–

8–18

Yield stress (MPa)

55–65

–

50–60

–

25–40

Lower working temperature (°C) (onset of brittle behaviour)

–150

–40

–5 (to –40)

–10 to –50

0

Upper working temperature (°C)

+ 130

+ 70–80

+ 65

+ 80

+ 100

Coefficient of linear expansion at 23–55 °C 10–6/K

65–70

70

70–80

230–250

120–150

Building product class DIN 4102

B1(B2*)

B2

B1

9 A1

* with flame-retardant

In contrast to PTFE, which is used in the form of textiles or coatings, ETFE is usually used in the form of thin membranes or foils which are produced using sheet 4.17

die extrusion. Typical applications include pneumatically pre-stressed membrane constructions, for example in the form of air cushions with a foil thickness  of ­0.05–0.25 mm. ETFE foils are in general weldable. They exhibit a light transmittance of approximately 95 %. The strength of ETFE foils is comparatively low and for this reason they can only be used for short spans without extra reinforcements. It is, however, possible to strengthen individual pneumatic cushions with a cable net or to support them with a subconstruction in order to combine several cushions to form a large structure. Trade names  Dyneon ETFE (3M/Dyneon), Nowoflon ET (Nowofol), Toyoflon (Toray)

THERMOPLASTICS

Manufacture T   hermoplastic plastics are industrially produced in the form of semi-finished or finished products. The high investment costs for production facilities for elastomeric and thermoplastic plastics are only amortised when products are produced in sufficient quantity. The apparatus used for their manufacture are termed tools. To minimise the amount of post-processing, formed items are usually manufactured in their final dimensions. For this the tools that form them need to be precision-made. After the initial moulding, thermoplastic semi-finished and finished products can be heat-reformed or machined. The raw materials used for the manufacture of plastics are usually liquid or 4.19

solid components in the form of powders, pellets or granules. To obtain the raw material in powder form it is ground in mills. To prevent the warming and possible premature polymerisation of the mass, the grinding process is usually undertaken in several stages. For the manufacture of granulate, a molten mass is manufactured as an extruded band or cord which is cut and then cooled and dried to produce granules. The subsequent processing of the raw material occurs under heat. The following section describes the basic principles of the most important manu­facturing methods for thermoplastic semi-finished products and formed items. Here the focus is on methods relevant to the construction industry. Injection moulding  Injection moulding, also known as die casting, is the most

4.22

commonly used process for the manufacture of high-quality formed items that require no or only minimal subsequent finishing. A moulding compound, usually in the form of granules, is fed through a funnelled hopper into the tool. A rotating screw-type plunger melts and transports the moulding compound towards the nozzle. The mass is then forced through the nozzle into a temperature-controlled mould that can be opened in order to remove the finished item. This basic principle is varied for different plastics and forms. Sandwich injection moulding   The sandwich injection moulding process is

4.21

used for items with a sandwich structure. Two separate moulding compounds are prepared and injected one after the other through a nozzle into a mould. In the first stage, the mould is partially filled with one of the two moulding compounds which is then forced to the outer surface of the mould by the injection of the second moulding compound. The first moulding compound forms the skin of the end product, the second the core. This approach makes it possible to create different sandwich combinations. Extrusion  In a process similar to injection moulding, the moulding compound is

4.20

fed continually through a hopper into the feeder screw and melted, homogenised and compressed through frictional heat and additional heating of the tool. At the end of the screw the molten mass is forced through a nozzle that gives the mass its final form. The extrusion product is then cooled and cut to length. The tool is adapted to make items with different forms. This process is suitable for the manufacture of hollow profiles such as piping, panels, blown film extrusions and monofilaments up to a length of several metres.

39

40

PLASTICS AND THEIR MANUFACTURE

4.19 19 Thermoplastic granules are melted and then formed into semi-finished or finished products. 4.20 extrusion: the moulding compound is fed through a hopper into a screw-feeder, where it is melted

and passed through a nozzle that shapes the mass into its final form. 4.21 sandwich injection moulding: to begin with moulding compound 1, which will form the surface material, is injected into the form, followed by moulding compound 2 which forces moulding compound 1 to the surface. 4.22 injection moulding: the moulding compound is fed through a hopper into a rotating screw, melted and passed through a nozzle into the mould.

4.19

4.20

extrusion head (die) moulding compound

extruded profile

4.22

mould

granulate screw

4.21 mould

moulding compound 1

moulding compound 2

injection

plastication

ejection

a variant of this method is co-extrusion, also known as multi-layer extrusion. in this process, molten materials from different screw-feeders are combined at or directly after leaving the nozzle aperture where they bond inseparably due to the high temperature. This makes it possible to combine multiple layers of the same or different plastics to form items with combined properties. Typical products include profiles, panels or foils with additional coatings or sleeves. CALENDERING Foils and films can also be produced in a calendering line. A 4.23

moulding compound, typically in powder form, is mixed and kneaded to form a molten mass before being passed through heated and cooled calender rollers in several stages that roll the material into successively thinner foils. Through the use of embossed rolls it is possible to produce embossed patterns. after calendering the foil is wound onto a reel. This technique is especially suitable for plastics with a viscous molten consistency such as pvc. specially adapted calendering lines can process other materials such as pmma or pc.

41

THERMOPLASTICS

4.23 Calendering: a moulding compound in powder form is melted before being passed through heated and cooled rollers in several stages that roll the material into successively thinner foils.  4.24 Compression moulding: the moulding compound is filled into a heated negative or female mould and pressed into shape with a male mould.

4.23 Roller die extruder

Reel Cooling

Moulding compound

Rolling calender

4.24

Mould Moulding

Moulding compound

Multi-layer foils can be manufactured by rolling together different foils under heat, pressure or with an adhesive. A modified version of this process is used for the manufacture of coated membranes through the application of coatings in a ­liquid form to a textile or foil-like base material. Compression moulding  In compression moulding, the moulding compound is 4.24

filled into a heated negative or female mould and a male mould is then applied to press the material into shape. The formed item must first be cooled before opening the tool, which leads to comparatively long production cycles. This process can be used to create slabs and blocks as well as fibre-reinforced thermoplastic semi-­ finished products and prepregs (pre-impregnated glass-fibre material). It is also used as a post-processing surface finishing method for the calendering process. Casting   This manufacturing method does not employ pressure and is used for

4.26

the production of large panels and formed items. Semi-crystalline thermoplastics are particularly suited for the casting of larger items as they can be made into a thin runny mass. The molten material is poured into an open mould and polymerised through the input of energy. As the synthesis of the polymer takes place in the mould itself and the finished item can only be removed from the mould once poly­merisation is complete, the production cycle can take anything up to a week depending on the size of the cast item.

42

PLASTICS AND  T HEIR MANUFACTURE

4.25  Thermoplastic foam casting: through the addition of a foaming agent, a low-density integral skin foam is created.  4.26 Casting: in this pressureless process, the molten material is poured into an open mould and polymerised through the input of energy.  4.27 Foaming: a foaming agent is added to the mass that causes air bubbles to form.

4.25

Foaming

4.26 4.27

Foam block Moulding compound

Prefoaming

Interim storage Polymer

Liquid moulding compound

Openable mould with smooth surface

Heated mould Mould

Foaming agent

Pressure application

This process is commonly used for the manufacture of PMMA GS, which as a semi-finished material is less prone to stress cracking than extruded materials and is therefore more suitable for reshaping and post-processing. Panel thicknesses of between 2–250 mm can be poured, but the polymerisation process of thick ­panels and large items can sometimes take several weeks. Foaming  Foams are materials with a low bulk density and a continuous cellu4.27

lar structure. Foams may be classified according to their structure as open-cell, closed-cell and mixed-cell foams. Bubbles of air form in the mass caused by foaming agents added to the mixture which vaporise under heat or by gases that result from the polymerisation process. The process is divided into stages: prefoaming, interim storage and final foaming. In the final stage the prefoamed material is passed into a mould and shaped into its end form. Common methods include injection moulding or in-mould skinning for items made of integral skin foam or extrusion for semi-finished products. Although theoretically all thermoplastics can be used for foaming, polystyrene and polyurethane are most commonly used. Foams differ from the compact form of the source material primarily in terms of density and a correspondingly much reduced thermal transmittance. For this ­reason they are ideally suited for use as an insulation material. The stiffness of rigid foams can be even higher than the original material in its compact form. The combustibility of the original material remains unchanged. Thermoplastic foam casting is a variant of injection moulding in which the addi-

4.25

tion of a foaming agent such as CO2 or nitrogen causes the production of so-called

4.28

integral skin foam with a lower density. The expansion of the foam is limited by the dimensions of the mould, which in turn is responsible for the smooth surface of the end product. The structure of the end product has a porous foam core and a smooth cell-free surface. Direct Digital Manufacturing   The terms Direct Digital Manufacturing (DDM)

or generative fabrication are used generically for processes such as Rapid Prototyping (RP), Rapid Tooling (RT) and Rapid Manufacturing (RM), all of which make it possible to generate physical items from digital computer data. DDM techniques

THERMOPLASTICS

4.28 Integral skin foam has a porous core and a smooth, cell-free surface.

4.28

are primarily additive fabrication processes in which the three-dimensional body is created through the layer by layer application of a material. An exception is CNC milling (CNC = Computerised Numerical Control) in which a finished item is cut or milled from a massive block of material based on data from a digital model. Because the mould used in conventional processes is replaced by a digital model, the production process is more flexible in terms of form, quantity and lead time. DDM techniques make it possible to realise prototypes and small quantities which could previously only be produced using moulds specially developed for the respective item. The cost-effectiveness of the process depends on the quantity produced and should be weighed up against the costs of conventional production processes such as injection moulding. With DDM techniques, forms can be designed that do not need to take de-moulding (mould removal) into account. The ability to directly test and assess the physical prototype allows one to avoid construction errors in the final production. The dimensions of the items that can be produced are still quite limited, but in some cases elements measuring several metres have been produced. Depending on the production method used, the strength of the resulting items is generally lower than those produced using conventional thermoplastic processes. Rapid prototyping techniques make it possible to realise physical three-dimensional prototypes with complex geometries and cavities. The various techniques are divided into laser-based and non-laser-based approaches. Depending on the method used, different plastics can be used in liquid or solid form, for example ABS, polyamide, polycarbonate or photopolymers as well as elastic plastics, paper, wax, ceramics or metal. The combination of different materials is also possible. Some of the most widespread processes are: Stereolithography (STL)  Layer for layer solidification of a liquid photopolymer using a laser beam. Suitable materials are thermosetting resins. Solid Ground Curing (SGC)  Layer for layer solidification of a photopolymer using UV light. Suitable materials are thermosetting resins. Selective Laser Sintering, Laser Sintering (SLS, LS) Layer for layer localised sintering of a source material in powder form. Suitable materials are thermoplastic plastics, wax and metal.

43

44

PLASTICS AND  T HEIR MANUFACTURE

4.29 Fused Deposition Modelling (FDM): a liquid material is applied in successive layers using an ­extrusion nozzle.

4.29

Thermoplastic

Digital model

Nozzle Base platform

Laminated Object Manufacturing (LOM) Layers of adhesive-coated plastic foils are successively glued together and cut to shape with a laser. Suitable materials are laminate foils made of plastic, paper or ceramics. 4.29

Fused Deposition Modelling (FDM) Layer for layer application of molten material from an extrusion nozzle. Suitable materials include ABS, PC and wax. 3D Printing Layer for layer application of a powder source material with subsequent solidification using a bonding substance (infiltration). Suitable materials are polymers and ceramics. Rapid Manufacturing (RM)  This process uses rapid prototyping techniques for the manufacture of end products in short and medium runs. RM can be used, for example, to produce replacement parts at short notice. Rapid Tooling (RT)  This technique is used to manufacture tools (moulds) with the help of rapid prototyping techniques such as laser sintering or stereolithography, which in turn can be used for mass production. The choice of material to use depends on the thermal and chemical stability requirements of the tools produced using RT.

Working methods Thermal reforming   Thermal reforming processes require semi-finished prod-

ucts with small thicknesses. Where the reforming process increases the material’s surface area, the thickness of the material will be correspondingly reduced. The deep-drawing method employs a mould that is pressed from below into a 4.30

fixed sheet of heated plastic material mounted above it. The mould is slowly raised, pulling the softened plastic sheet upwards. A vacuum then draws the air out of the mould so that the plastic sheet is gradually drawn to assume the three-dimensional shape. The same principle can also be applied with compressed air. The necessary temperature depends on the respective plastic used. Polypropylene and polystyrene can be reformed at around 150 °C, whereas polycarbonate and PMMA require higher temperatures of 180–220 °C. PMMA additionally requires subsequent tempering at a high temperature for two to three hours to reduce internal stresses in the

45

THERMOPLASTICS

4.30  Deep-drawing: a flat sheet of heated plastic is fixed over a mould and formed with the help of  a vacuum to fit the mould.  4.31  Working rigid polyurethane foam with the help of a CNC milling ­machine.  4.32 Cutting a polycarbonate sandwich panel with a circular saw.

4.30

4.31

4.32

material. The deep-drawing method makes it possible to manufacture prototypes or short runs at a comparatively low cost. The vacuum blowing method is similar to deep drawing and also employs a fixed, pre-heated sheet of plastic that is pneumatically pre-stretched with compressed air and then stamped into a negative mould. Machining  Machining can in principle be used with many different thermoplas-

tics. It is important to note, however, that soft thermoplastic materials such as poly­ethylene are prone to so-called smearing at high tool speeds, i.e. the material begins to soften resulting in a clogged grinding tool. At reduced speeds and with appropriate machining bits, this effect can be avoided. Milling machines are suitable for working the surfaces and edges of flat semi4.31

finished products. CNC milling machines can be used to create three-dimensional building elements. For example, foamed plastics can be formed, using this method, into moulds for constructing fibre-reinforced plastics. Suitable materials include rigid foams made of PUR or PS. Saws, cutters and drills are very much dependent on the respective material’s

4.32

susceptibility to stress cracking. Polycarbonate, for example, can be worked in a similar way to wood, while PMMA is much more prone to stress cracking and can only be worked with special drill bits and saw blades.

46

PLASTICS AND  T HEIR MANUFACTURE

Recycling The sustainable use of plastics in construction is only possible if the plastics used 4.35

are made an integral part of a material cycle. That means that after the useful lifetime of the building in which they have been used, they need to be reusable in some form or other. That does not necessarily have to be in the original form. Due to the many kinds of different materials, integrating plastics into a material lifecycle is no simple task. The degree of cross-linking and the purity are the most important criteria with regard to the kind of recycling. A prerequisite is a widespread take-back system for plastic products as well as the separate collection and preparation of the recycling product by type. Recycling methods include material recycling, raw material reprocessing and energy recovery. The decision as to which recycling method to use depends on ecological as well as economical aspects. Plastic waste that cannot be recycled in one of these methods will need to be disposed of at a landfill site. Material recycling  Material recycling is particularly appropriate for thermo­

plastics in the form of uncontaminated and unmixed waste products from the ­manufacturing process or that have been collected and separated according to 4.33

type and form. Appropriate labelling is advantageous. The material is separated, cleansed and ground down in several successive stages into ground material, regranulate or a similar form that can be fed back into the production process. The recycling product is sorted according to its degree of purity into different quality classes. In many cases, recycled material is only used in part for new products, but

4.34

there are now products on the market that are made wholly from recycled material. The reprocessing of polymer waste depends largely on the additives it contains. For example, plastics that contain certain fire retardants may not be used for recycling. Because the end products have to serve specific requirements, quality control during the sorting process is both logistically as well as financially intensive. The recycling method of collected plastic waste is therefore not only a technical but also an economical question. These different factors need to be carefully considered for an economically competitive use of recycled material in comparison to new material. The recycling of PVC products is an example of how a largely closed material lifecycle can be achieved. Since the beginning of the 1990s, the manufacturers and processors of PVC have established working partnerships to ensure the collection and processing of floor coverings, windows, roller shutters, and roof and sealing membranes made of PVC. The PVC materials are sorted according to product and separated from foreign materials so that they can be reprocessed to make new products. The material recycling of elastomers and thermosets is more limited due to the degree of cross-linking in the material. Waste material from cross-linked polymers can be ground down and used as a filler material in plastics production. In most cases, the proportion of recycled material used is, with a few exceptions, comparatively small.

47

THERMOPLASTICS

4.33  The ground material from PVC profiles can be used as a filler material in the subsequent production of plastics.  4.34 Material samples of a recycled plastic.  4.35 Different methods of recycling ­plastic waste material.

4.33

4.34

4.35 Plastic waste material

Material recycling

Raw material reprocessing

Energy recovery

Separated, cleansed and ground to recycling granulate

Macromolecules broken apart into molecules

Combustion

Oil, gas, wax for use in refineries and chemical plants

Energy recovery in the form of heat and power

Plastic products with recycled proportion

Raw material reprocessing  In the case of raw material (chemical) reproc-

essing, mixed or contaminated plastic waste material is broken down into its parent substances. The macromolecules are broken apart under heat and pressure in a variety of processes and introduced back into the production cycle as monomers, oils or gases. These need not be used solely for the production of new plastics but can also be used in refineries and chemical plants. Energy recovery   The recovery of energy from plastic waste makes use of the

high calorific value of plastics. Heavily contaminated plastics and materials that are difficult to separate are combusted and the energy gained is used for the creation of electricity and process heat. Plastics that cannot be recycled either as a material or reprocessed to raw materials, or where it is prohibitively difficult or costly to do so, can at least contribute towards energy generation.

48

PLASTICS AND  T HEIR MANUFACTURE

 T hermosets Material components 4.36

In practice, fibre-reinforced plastics (FRP) are the main application area for thermosets; non-reinforced thermosets are practically not in use. Fibre-reinforced plastics consist of two main material components, the fibres and a matrix in which they are embedded, which typically consists of a thermosetting plastic resin. In principle it is possible to use thermoplastics as a matrix material, but this plays a minor role in the field of construction. The fibres act as a reinforcing component in the composite material and correspondingly influence its mechanical properties such as strength and stiffness. The matrix as the embedding medium lends the composite material its form and serves a series of purposes: it fixes the fibres in the desired geometric arrangement, transferring the load to the fibres and stabilising the fibres against compression loads while protecting them against external influences (moisture, chemicals etc.). It also plays a key role in the chemical, electrical and thermal properties of the material. Matrix materials  Polyester resins are colourless to pale yellow solutions of

unsaturated polyester (UP) in a reactive solvent such as styrene. The hardening process is initiated through the addition of a hardener of organic peroxides. The hardening process can be controlled using either accelerators or retarders. UP resins are easy to work and can be worked at normal as well as warmer temperatures without pressure. As inexpensive and variable resin systems, they are widely used in manual production processes and by medium-sized manufacturers for building elements such as profiles or façade cladding. For building elements with low strength and dimensional stability requirements, orthophthalic acid-based polyester resins are commonly used. These inexpensive polyester resins can be used for a variety of different application areas and combine good mechanical properties with sufficient temperature and chemi­cal stability. Isophthalic acid-based polyester resins are used where a high degree of moisture, temperature or chemical stability is required. They are more expensive but also offer better mechanical properties such as higher flexural strength and stiffness. Isophthalic acid polyesters are used, for example, for the manufacture of pultruded profiles. Vinylester resins (VE) are likewise dissolved in styrene as a reactive solvent and exhibit particularly good chemical properties. Their heat and chemical stability is better than UP and EP resins. In terms of cost, VE lies between UP and EP resins. Epoxy resins (EP) are solvent-free two-component systems. Both components are mixed in a liquid state with one another. The reaction mechanism takes place as polyaddition and the proportion of resin and reactive partner has to be precisely observed. EP resins are three to four times more expensive than UP resins. In addition to enhanced mechanical properties, their main advantage is better shrinkage behaviour. Unlike UP resins, the shrinkage occurs before gelation, that is while it is still in a “wet” state. This makes it possible to fabricate precision items with low internal stress levels. As with all resin systems, the health hazard during the working process requires suitable protective safety measures.

49

THERMOSETS

4.36  The structure of fibre-reinforced plastics, in this example with a unidirectional fibre arrangement.

4.36 Gelcoat

Matrix resin Coating Unidirectional fibres

Phenolic resins (PF) are among the oldest thermosets in use today. They are a condensation product of phenol and formaldehyde with very good heat resistance. The glass transition temperature of such resins lies at around 300 °C. Reinforcing fibres   Inorganic fibres are most commonly used for FRP building

elements, most notably glass or carbon fibres, occasionally also synthetic fibres such as aramid. The primary advantage of glass fibres is their cost. The fibres can  be optimised for special purposes through the addition of further constituents, for example E‑glass which is both cheap and widely used. Other glass fibres are optimised for chemical stability (C‑glass) or temperature and fatigue resistance (R‑ and S‑glass for “resistance” and “strength”). In contrast to carbon or aramid fibres, glass fibres are isotropic due to their amorphous structure. Glass fibres are non-combustible and even extended exposure to 250 °C does not impact on their mechanical properties. For the manufacture of E‑glass, quartz sand, limestone, kaolin, dolomite, boric 4.37

acid and fluorspar are heated to a molten state at about 1400 °C, homogenised for several days and then in liquid form passed through channels, the so-called forehearths, to nozzles. The nozzles consist of a platinum alloy and are heated to a temperature such that the molten mass can flow through the aperture of the ­nozzle and immediately harden to a thread. The threads have a thickness of ­approximately 2 mm. The viscous threads are then spun onto a rapidly rotating winding mechanism that stretches them to the desired thickness of 9–24 µm. The strands result from the parallel bundling of the individual fibres. After the spinning process, a watery emulsion is applied to the fibres. This coating bonds the filaments into usable strands, protects the sensitive surface of the brittle glass filaments and improves the bond between the organic resin and the inorganic fibres. Carbon fibres are more expensive but offer a higher modulus of elasticity, ­making them appropriate for applications where the stiffness of glass fibres is

4.39

too low. They consist to over 90 % of carbon and have a diameter of 5–10 µm. Carbon fibres are differentiated according to their mechanical properties into standard modulus (HT, high tenacity) fibres, intermediate modulus (IM) fibres and high modulus (HM) fibres. Carbon fibres are very lightweight, have excellent corro-

50

PLASTICS AND  T HEIR MANUFACTURE

4.37  Glass fibre manufacturing: the constituent components of the glass are melted at around 1400 °C, homogenised and then passed through a forehearth to the nozzles.

4.37

Hopper Melting oven

Homogenisation

Forehearth

Molten material

Filament reels

sion resistance properties, are thermally and electrically conductive and almost totally fatigue-resistant. Due to their primarily mono- or two-dimensional molecu­ lar structure in the axis of the fibre, they exhibit a pronounced anisotropy (directionality). The mechanical strength perpendicular to the direction of the fibre is a fraction of its longitudinal strength. There are two main processes for manufacturing carbon fibres which are used at a commercial scale. The first approach is based on the source material polyacrylonitrile (PAN), which is first oriented to obtain a better directionality of the molecules in the axis of the fibre. This is followed by three stages of different temperature treatments of up to 3000 °C in which the fibres are simultaneously drawn. The second approach uses coal tar or petroleum pitch as a raw material. The resulting smelt is then spun into fibres that are highly oriented along the fibres’ axial direction. Finally, the fibres are thermally treated to convert them into carbon. Aramid fibres also have good mechanical properties, most notably a high tensile strength combined with a very low self-weight. Aramid fibres consist of aro4.40

matic polyamides. The organic polymer with high strength and stiffness is produced as fibres with a diameter of approximately 12 µm. Like carbon fibres, the strength properties are strongly anisotropic and the compression strength of the fibres is much less than their tensile strength. Although aramid fibres are used to create laminates with a very high impact resistance (for example bulletproof vests), they have a few disadvantages which explains their relatively rare use in the construction field. Aramid fibres are prone to absorbing moisture which affects the bond between the fibres and the matrix. In addition, the UV and temperature stability of aramid fibres is not particularly good.

Manufacture With fibre-reinforced plastics, the finished material results during the actual forming process; therefore the way it is worked determines not just the form it can take but also influences the material properties. This applies especially to its strength and stiffness. During the fabrication process it is therefore possible to design for the forces that the finished object will later have to sustain by controlling the fibre orientation of the individual layers. The manufacturing techniques for laminates

THERMOSETS

4.38  Glass fibre textile.  4.39  Carbon fibre textile.  4.40  Aramid fibre textile.

4.38 4.39 4.40

made of glass fibre-reinforced thermosets range from the manual fabrication of individual items to fully automated manufacturing processes: hand lamination, fibre spraying, vacuum methods, infusion methods, compression moulding, injection methods, SMC methods, winding, centrifugation, braiding and pultrusion are the most well-known manufacturing techniques. Different forms of fibre products   Glass, carbon and aramid fibres are

available in a variety of different forms. The very thin and long strands from the 4.41

drawing process are formed into rovings or yarn. Rovings are bundles of between 1000 and 10 000 continuous fibres which are formed without twisting into bundles of parallel threads. Yarn and rovings can in turn be woven into sheet-like textiles. These can be chopped-strand mats, non-looped systems (woven fabric, non-woven scrims and braid) or looped systems (knitted). Chopped-strand mats or textile glass mats consist of chopped, randomly oriented E‑glass threads which are bound together in several layers with a bond-

4.38

ing agent. The arrangement of the fibres in the sheet make it possible to lend

4.42

lami­nates isotropic mechanical properties (properties that are equal in all directions). Through the use of different fibre diameters and binding agents, mats can be developed for particular purposes and processing methods. They are used for the manu­facture of tanks, containers, for motor manufacturing and all manner of technical parts. Sandwich mats are a particular variant with a core layer of non-woven glass mat and textile glass mats on both sides. Sandwich mats can be draped in non-impregnated form very easily and are therefore good for the manufacture of curved building elements. Glass filament mats consist of two layers of perpendicularly arranged thread systems made of E‑glass yarn, warp and weft. The weft threads are woven perpendicular to the warp, which lies parallel to the longitudinal direction of the textile. This weaving technique makes it possible to control key properties of the material. Plain weave is a simple weave, in which each weft is woven with every warp it crosses and ensures good dimensional stability and minimum fray when cutting. With twill weave, two or three warp threads are skipped, with satin weave up to seven. The resulting textiles are more supple and easily draped and are especially suitable for curved forms. However, they fray more when cut. Satin weave textiles have a particularly smooth surface. The use of very fine threads makes

51

52

PLASTICS AND  T HEIR MANUFACTURE

it possible to manufacture building elements that are highly transparent. Woven staple-fibre glass textile represents an especially soft and absorbent variant, another type is the spacer fabric. The latter consists of two textile finishing layers 4.43

of E‑glass with a silane coating, which are bound together and held apart by vertical spacer fibres. Once impregnated with polyester resin or epoxy resin, the textile automatically assumes its design thickness. This makes it very easy to fabricate sandwiched laminates. Spacer fabrics are most commonly used for manual laminating methods. The waviness of a textile generally has a negative effect on its orthotropic stiffness. In particular in the direction of the warp a certain degree of structural extension is unavoidable. Manual techniques  Hand lay-up lamination is a comparatively straight­for­

ward process and is suitable for the fabrication of small quantities of freeform 4.44

prototypes and sheet-like building elements. Various materials can be used for the formwork. Simple forms can be made of sheet metal or timber formwork. Rigid polyurethane foam with a density of 400 kg/m3 is easier to use for making freeform or biaxially curved concave forms. Forms that are applied from outside the building element and describe its outer surface are known as negative or female moulds. Forms that describe the inner surface of the element are known as positive or male moulds. An important criteria for the choice of material for the mould is resistance against the solvent used in the resin. A suitably durable material should be chosen for moulds or forms that are to be used repeatedly. Large moulds are made of several individual parts that are assembled and glued together. The surface of the mould defines the surface quality of the resulting formed element. The surface not facing the mould is always rough and may need additional finishing if it needs to be of a certain quality. A constraint for the development of moulds is the fact that not all geometric forms can be removed from the form. For this reason, forms that are undercut or significantly twisted should be avoided. The process of lamination begins with a thin (0.3–0.6 mm) non-reinforced “gelcoat”. This stops the structure of the fibres from showing through and serves as a weather protection layer. It can also be used to lend it a certain colour. The matrix material and fibre matting are then applied wet on wet in alternate layers. A certain degree of skill is required to create evenly dense layers of material with as few trapped air bubbles as possible. Hand lay-up lamination is a rather laborious but low-cost method. The manufacture of high-performance building elements using manual lamination is difficult as it is hard to precisely control the material properties. The fibre proportion is generally less than 45 % by volume. The quality of the laminate can be improved by applying different pressure techniques. With a vacuum forming technique, the still wet laminate is covered with a porous adhesion-preventing film and an absorbent textile. After covering with a vacuum bag and sealing the edges, a vacuum is created. All excess resin and trapped air bubbles are sucked out and the laminate then hardens under normal atmospheric pressure. This results in very dense lami­ nates with a high fibre content. Using this technique it is also possible to impregnate dry lay-up laminates with resin afterwards. This so-called resin infusion

53

THERMOSETS

4.41 Different forms of glass fibre products.

4.41

roving

Thread

core yarn

Textile glass mat

Knitted fabric

unidirectional non-woven

Biaxial non-woven

fabric: plain weave

fabric: braided weave

Wrapped yarn

54

PLASTICS AND  T HEIR MANUFACTURE

4.42  Glass-fibre mat for manufacturing building elements with isotropic mechanical properties.  4.43  Glass-fibre spacer fabric for manufacturing sandwich construction building elements.

4.43

4.42

method uses a container with resin attached to an inflow line opposite the air outflow where the vacuum is created. When the air is evacuated the resin is sucked in. Vacuum systems can also be used with two-part forms where a smooth finish is required on both sides of the part. A related process uses pressure instead of ­vacuum with a reverse form arrangement. The quality of the laminate can be improved significantly through the use of an autoclave. The building element is prepared as for the vacuum procedure and then hardened under pressure and heat. The pressure lies in the region of 2–25 bar at a temperature of around 180 °C. The principal advantage of using an autoclave is that pressure is applied evenly on all sides which makes it possible to harden complex three-dimensional building elements. Compression and injection moulding  Compression moulding, which can

be undertaken hot or cold, is suitable for sheet-like products that need to be partic4.45

ularly strong and of consistently good quality. The shaping process uses a ­two-part mould; the two parts mate in a press with an internal pressure of ­0.2–2.5 ­N­/mm2. As  the machinery necessary for this process is comparatively expensive and re­quires considerable investment, this process is only cost-effective for mass production in large quantities. For cold moulding, resin moulds can be used although it is only possible to achieve a maximum fibre content of 50 % by volume for the moulded item. Larger quantities and prefabricated parts with special requirements are manufactured by using hot-pressing methods with steel or aluminium moulds. With hot-pressing it is possible to achieve a glass content of up to 65 % by volume. Prefabricated prepregs can also be used for compression moulding. Prepregs are reinforcement fibres which have been pre-impregnated with resin. Both textiles as well as unidirectional bands and non-woven scrims are available as prepregs. In most cases, modified epoxy and phenolic resins that do not flow at room temperature are used as the resin matrix. The prepregs are laid cold in the mould and then hardened under pressure and heat. This can be undertaken by hand or with a machine. As the prepreg heats up, the resin liquefies briefly and soaks the fibres before it begins to harden. In addition to compression moulding,

55

THERMOSETS

4.44 Manual hand lay-up lamination.  4.45 Manufacturing using compression moulding.

4.44 Fibre matting / textile Matrix Fibre matting / textile Matrix Finishing layer (gelcoat) Mould release agent

Mould

4.45 Upper mould Upper mould

Reinforcement matting

Resin

Heating elements

Distancing piece

Lower mould

Heating elements Lower mould

Laminate

prepregs can also be used in other processes such as vacuum moulding and autoclave moulding. A further means of processing prepregs for large sheet-like building elements is automated tape lamination. This uses a gantry robot with a special application head to apply prepregs in tape form from a roll to the mould in a controlled pattern. With each successive layer, the previous layer is pressed onto the mould. After lamination, the lay-up assembly is moved to an autoclave for hardening under heat and pressure. Injection methods unite the characteristics of compression moulding with injection moulding. Resin transfer moulding (RTM) involves the placement of a dry fibre reinforcement fabric in a two-part mould. The resin is then injected under pressure into the mould. The additional application of a vacuum removes trapped air bubbles and supports the impregnation process. Winding and braiding methods  A further manufacturing process is a wind4.46

ing method with which hollow volumes can be created. The high degree of mecha­ nisation ensures the production of reproducible and high-precision parts. A core ­mandrel made of aluminium or steel is enveloped with successive windings of matrix-impregnated rovings or tape. By controlling the speed of rotation of the mandrel as well as the speed of fibre application, it is possible to control the fibre reinforcement of the laminate. Building elements can also be dry-wound and then subsequently impregnated using the resin infusion method. This method is used primarily for rotationally symmetric building elements. Depending on the quantity and geometry of the end product, the mandrel core is made of metal (typically in a

56

PLASTICS AND  T HEIR MANUFACTURE

4.46  Manufacturing using filament winding, front and lateral view.

4.46

Transmission Winding mandrel Drive mechanism

Strands of glass fibre Winding mandrel

Resin impregnation trough

Travelling support

Support

conical form to aid removal) or as an enclosed form made of a soluble material. Its main application areas are for pipes and containers. A special variant of winding is the braiding method. Here a large number of filament threads are spun from a travelling, rotating braiding machine onto a stationary core. The crossing fibres create a braided form of reinforcement that is also usable for complex geometries. In addition, this method allows for mixed loading properties through the use of different types of fibres (for example glass and carbon fibres). Unlike the winding method, fibres can also be laid in the rotational axial direction (0° direction) of the core. After the braiding process, resin is applied using the infusion or injection method. Pultrusion process   The pultrusion process can be used for the economical

production of continuous profiles. The shaping of the profile takes place in a die 4.47

through which resin-impregnated roving strands, textiles or mats are pulled. Where products need to have a high bending and flexural strength along the longitudinal axis of the profile, roving reinforcements are used. For products that need to have a high shear strength and shear stiffness, fabric reinforcement with fibres perpendicular to the pultrusion direction is used. Mats or non-woven scrims are introduced predominantly as a surface dressing for the profile. Industrial manufacturing using the pultrusion process makes it possible to control the optimal fibre content, maintain a consistently high quality of the product and minimise vari­ ations in the mechanical properties. It is possible to guarantee precise and reli­ able values for permissible tension, stiffness and loadbearing capacity. This is an advantage over other forming methods that by dint of their manufacturing process are more incalculable, for example hand lamination. In principle almost any cross section can be manufactured using pultrusion, however the initial prior manufacture of an appropriate die is costly. This becomes cost-effective at a demand of 2000 m or more of profile. The profiles available on the market replicate typical cross sections from steel construction as well as special forms from the electrical industry and plant manufacturing. Working methods   The means of working fibre-reinforced plastics are to a large

degree dependent on the consistency of the reinforcement fibres used. With a few

57

THERMOSETS

4.47 Manufacturing using the pultrusion process.

4.47 Ventilation

Injection of resin

Reinforcement

Heating and hardening

Puller

Saw

exceptions, fibre-reinforced plastics can be worked with most conventional tools. In practice tungsten carbide or diamond tipped tools are used most commonly as they wear out less quickly. Flat GRP moulded elements always have overhanging edges that need to be trimmed. Cutting using a water jet cutting machine results in very precise cutting edges while also reducing dust generation. This process, however, can only be used for limited material or profile thicknesses. The surface of a GRP building element is only ever as precise as the surface of the mould, formwork or tool used. Depending on the surface quality requirements for the end product, in many cases a second finishing stage is necessary. This usually consists of sanding, filler application and re-sanding. Such surfaces can then be painted.

Properties Fibre-reinforced plastics are high-performance plastics. They are commonly used in many different fields, including aviation and aeronautic engineering, mecha­nical and plant engineering, and construction. Among their most important technical properties are their high mechanical strength, low self-weight, good thermal insulation, high corrosion resistance and versatile formability. The development of building elements made of fibre-reinforced plastics is, however, subject to particular conditions. In many cases, the material is fabricated for individual applications. A key indicator for the major mechanical properties of fibre-reinforced plas4.48

tics, in particular strength and stiffness, is the proportion of fibre content. The fibre content level in turn depends primarily on the manufacturing method used: pultrusion, for example, can achieve particularly high concentrations and the

4.49

strength of the resulting products comes close to that of metallic materials. Carbon fibre-re­inforced plastics can even exceed these properties. The comparison is most apparent when one takes into account the self-weight of the plastic. Fibrere­inforced plastics, on the other hand, have a comparatively low stiffness. For this reason they are not suitable for constructions susceptible to deformation where slenderness is an issue. Nevertheless, their high strength in conjunction with low stiffness lends them a high degree of flexibility, a particular material property of fibre-reinforced plastics.

58

PLASTICS AND  T HEIR MANUFACTURE

4.48 Fibre content of laminates for different manufacturing methods.  4.49  The material properties of different materials.

4.48

Fibre content (%-volume) 90 80 70 60 50 40 30 20 10 0 Hand lamination

Wet pressing

Fibre injection

4.49

RTM

Tape weave

Pultrusion

Winding SMC pressing

Braiding

Parameters

GRP pultruded

GRP laminated matting

Steel S 235 JR

Timber S 10

Glass Soda-lime glass

Aluminium

Tensile strength (N/mm2)

240

~60

360

14

30–90

150–230

Modulus of elasticity (N/mm2)

23 000

~6 800

210 000

11 000

70 000

72 000

Elongation at fracture (%)

1–3

~1,0

26

~0,8

0,1

2–8

Density (g/cm )

1.8

~1.4

7.85

0.6

2.5

2.7

Thermal expansion coefficient (in the direction of fibres) (10–6/K)

9

~25

12

~4,5

8–9

23

Thermal conductivity (W/mK)

0.25

~0.25

50

0.13

0.8

160

3

Beside the large differences in absolute stiffness compared with metallic materials, they differ considerably with regard to anisotropic and time-dependent 4.50

material behaviour. The modulus of elasticity of fibre-reinforced plastics depends on the direction of the fibres. Additionally, the kind of glass textile used also plays a role. For very thin laminates it is practically impossible for reinforcement fibres to be arranged across the thickness of the material. This circumstance explains the very different strength characteristics in the plane of the panel as opposed to across its thickness. In the case of curved surfaces, inter-laminar tension also arises in the thickness direction which can ultimately lead to delamination. The pronounced anisotropic properties of GRP are a considerable problem in the construction and structural design calculations but also make it possible to develop constructions that respond to particular kinds of loads. Plastics normally exhibit large deformations over time and are prone to creep. Glass and aramid fibres are much less prone to creep compared with the plastic matrix in which they are embedded and carbon fibres exhibit no creep. Where the properties of a laminate are determined more by the matrix, the higher its susceptibility to creep. Creep tests on UP laminates have shown that creep behaviour over a period of years is linear in nature. For dimensioning purposes, this characteris-

59

THERMOSETS

4.50  The material performance curves of different materials.

4.50

 MPa 500

Pultruded GRP

400 Steel

300

200 Aluminium 100

Wood PVC

 % 2 %

tic of fibre-reinforced plastics can be accounted for by applying a reduction factor for the permissible strength over a given load duration. Properties that can strongly limit the use of fibre-reinforced plastics in construction include temperature stability and fire behaviour. Hydrocarbon compounds, as a basic constituent of almost all plastics, are the reason for their flammability. Despite the flammability of fibre-reinforced plastics, products do exist that are classed as flame-resistant or that do not give off toxic vapours when they burn. The temperature dependency of the mechanical properties of the fibres can in most cases be neglected, however the matrix responds much more strongly to high temperatures, although the low thermal conductivity of the material means that they heat up approximately 200 times more slowly than steel. At high temperatures the strength of the material lessens while at low temperatures it increases. For example, the material parameters for GRP profiles by Fiberline Composites are given for a working temperature range of – 20 °C to + 60 °C. At higher temperatures, the strength and stiffness parameters should be modified by the application of an additional safety factor. Compared with steel, the loss of strength sets in much earlier, for example for polyester at a temperature of around 100 °C. This temperature threshold can be raised by using phenolic resins instead. One way or the other, the fire behaviour of GRP plastics is a major disadvantage in their use in loadbearing structures where structures need to fulfil fire resistance durations or where building products need to exhibit a certain fire safety class.

61



5

Finished and semi-finished products

Plastics are usually used in construction in the form of semi-finished or finished products. This section describes a selection of relevant semi-finished products for use in construction. The products and descriptions of product applications presented here are intended as examples – in many cases comparable products are also available from other manufacturers. The product descriptions are reduced to the most salient information; further information can be obtained from the manufacturers.

Solid sheets and panels Material  Polymethyl ­methacrylate (PMMA) Product  Plexiglas, Plexicor, Acrylite Manufacturer  Evonik Röhm GmbH www.evonik.com; www.plexiglas.de; www.plexiglas-shop.de

PMMA, also known as acrylic glass or perspex, is commonly used as an alternative to glass. Evonik Röhm produce a series of PMMA panels under the trade name Plexiglas in a variety of forms. Acrylic glass has excellent weathering properties and aging stability and has a hard and scratch-resistant surface. The chemical composition of Plexiglas is unaffected by UV light. Plexiglas GS is a cast acrylic semi-finished product. Panels are available in thicknesses ranging from 2–120 mm, but custom products of up to 250 mm thick can be cast, for example for underwater theme parks. The standard format is 3050 × 2030 mm, with custom sizes possible up to 3000 × 8000 mm. The upper service temperature is around 80 °C. Plexiglas XT differs from Plexiglas GS in that it is extruded. Standard panel thicknesses of the solid panels range from 1.5–25 mm with a standard dimension of 3050 × 2050 mm. Extended lengths can be produced up to a length of 10 m at a width of 2050 mm. The upper service temperature is 70 °C, a little lower than that of the cast variant Plexiglas GS. Compared with Plexiglas XT, Plexiglas GS has a higher heat distortion tempera­ ture, exhibits slightly better tensile and flexural strength properties and is simpler to work. The material can be cold-formed up to a minimum radius, depending on the thickness of the Plexiglas sheet. The better optical properties of Plexiglas GS are a product of its manufacturing method and the ability to create absolutely smooth surfaces. GS products are also available in a broader range of colours. Properties and design possibilities: —— Excellent transparency —— Transparent, transparent fluorescent and opaque sheets can be coloured

5.3

—— High-gloss or satin-finish surfaces available in a variety of grades

5.6, 5.2

—— Surface can be textured

5.1

62

FINISHED AND SEMI-FINISHED PRODUCTS

5.1  PMMA products with different satin or textured surface finishes.  5.2 Plexiglas SATINICE, tinted

in a variety of colours with a satin finish.  5.3  Plexiglas Fluorescent available in a variety of fluorescent colours.

5.1

5.2

5.3

—— Surface coatings: metallic reflective and dichroic (polarises the spectrum of light into a transmitted and a complementary reflected component) —— Half the weight in comparison to glass —— Absolutely weather-resistant (properties guaranteed for up to 30 years) —— Can be repeatedly polished —— Building material class B2 (DIN 4102), fire classification E (EN 13501) Material  Polymethyl ­methacrylate (PMMA) Product  Chroma Manufacturer  3form www.3form.eu

The Chroma series of products consist of cast sheets of PMMA resin which are available in a variety of colours. Coloured sheets using a water-soluble colourant are suitable for use indoors. The sheet material is also available with an applied coating on the inner surface for outdoor use. The surface is ground to a matt ­finish on one or both sides. Custom variations are also possible as required. The maximum dimensions are 1219 × 3048 mm for 12 or 25 mm sheet thicknesses, or 1200 × 2400 mm for 50 mm thick sheets.

5.5

63

SOLID SHEETS

5.4 Products made of PMMA: PLEXICOR by Evonik Röhm; right: Faux Alabaster by PyraSied.  5.5 Plexi­ glas Radiant with a surface finish on one side that polarises the spectrum of light into a trans­mitted and a complementary reflected component.  5.6  PMMA panels with matt, glossy and metallic ­reflective ­surfaces.  5.7 PyraLED is a light-diffusing panel made of polycarbonate.

5.4

5.5

5.6

5.7

Materials  Polycarbonate, PMMA, polyester material Products  PyraLED, Versato, Faux Alabaster Manufacturer  PyraSied www.pyrasied.nl

PyraSied offers a large selection of innovative design products made of plastic and produces own products in standard forms or according to client requirements. PyraLED and Versato are two of the company’s own products. PyraLED is a trans-

5.7

lucent, light-diffusing panel made of polycarbonate. Special embedded nanoparticles within the plastic ensure exceptionally even light diffusion. The panel is 2 or 3 mm thick and available in different colours. The standard panel dimensions are 1220 × 2440 mm. The elements are impact-resistant and suitable for outdoor use. Versato is the trade name for a range of 15 mm thick cast PMMA sheets available in 22  standard colours. Other material thicknesses can be pro­duced on demand. Versato sheets are manufactured in the formats 1500 × 2100 mm and 2030 × 3050 mm and can have a shiny or matt surface finish. They are classified as building material class B2 (DIN 4102). Faux ­Alabaster is a polyester material with mineral additives. The appearance of the light, brown or black-grey marbled panels is reminiscent of alabaster, hence its name. The 10 mm thick panels are semiopaque and can be lit from behind. The material can be machined normally and is bondable. It is available in standard dimensions of 2400 × 1200 × 10 mm.

5.4

64

FINISHED AND SEMI-FINISHED PRODUCTS

Material  Polycarbonate (PC) Product  Makrolon solid PC sheets Manufacturer  Bayer Sheet Europe GmbH www.bayersheeteurope.com

Makrolon solid polycarbonate sheets are suitable for indoor or outdoor use where thermal stability and shock resistance are of paramount importance and where sheets need to be thermoformable. Compared with PMMA, polycarbonate sheets are not quite as transparent. Makrolon solid sheets are available with UV-protective, scratch-resistant and chemically resistant surfaces as well as functional coatings. Makrolon Hygard is a multi-layer laminated transparent sheet that offers protection against forced entry and ballistic impact. With additional fire safety modifications, certain products in the range are classified as building material class B1 (DIN 4102). Available in thicknesses between 0.75–15 mm, the standard sheet dimensions are 2050 × 1250 mm as well as 3050 × 2050 mm. Larger and custom dimensions can be produced on demand. Properties and design possibilities (product-dependent): —— Possible variants: transparent colourless, transparent coloured and white translucent —— 88 % light transmission for a thickness of 3 mm (Makrolon GP clear 099) —— A range of surface finishes from polished to textured —— Impact-resistant, shatterproof and bulletproof (depending on material thickness and layer structure) —— Reformable at cold and hot temperatures —— Service temperature range: – 100 °C to + 120 °C —— Building material class B2 (DIN 4102); Makrolon GP is also available as B1 for ­indoor use

Material  Ecoresin (PETG synthetic resin) Product  Varia Manufacturer  3form www.3form.eu

The Varia series of products are manufactured as solid sheets from transparent

5.8

Ecoresin. Ecoresin is a thermoplastic resin with a 40 % recycled material content that serves as a matrix for embedding different kinds of materials within the panel. The system of different intermediary layers, along with colours and surface textures, offer numerous different design possibilities. Varia products can also be made according to client’s individual wishes. Properties and design possibilities: —— A variety of possible different intermediate layers and colouring —— Surface finishes of the front and rear can be different —— High chemical stability —— UV-stabilised —— Suitable for use in wet rooms (showers, bathrooms) when edges are sealed —— Bonding using two-component adhesive (as with Plexiglas) —— Can be thermoformed at a temperature of about 110–120 °C —— Can be cold-formed up to a certain minimum radius —— Can be machined (working properties much like MDF) —— Panel thicknesses 1.5, 3, 5, 6, 10, 12, 19 and 25 mm —— Dimensions 1219 × 2438 mm, 1219 × 3048 mm, special dimensions 1524 × 3048 mm —— Fire safety classification: Euro class B, s1, d0

5.9

65

SOLID SHEETS

5.8 PETG synthetic resin: edge sections of Varia product samples showing a range of layer

­c ompositions.  5.9  Varia product samples with different colours, surface finishes and designs, and intermediary layers.

5.8

5.9

66

FINISHED AND SEMI-FINISHED PRODUCTS

Material  Glass fibre-­ reinforced plastic (GRP) Product  Scobaglas – IFG translucent flat sheets Manufacturer  Scobalit www.scobalit.ch

Scobaglas products are translucent sheets of glass fibre-reinforced polyester resin which can be manufactured in a variety of light-fast colours. They are avail­ able as standard in clear, red, blue, yellow and green, and special or RAL specification colours can be produced if required. Individual formats can be made to order within the maximum dimensions. Properties and design possibilities: —— Light transmission: 85 % for a 1.5 mm thick sheet, 72 % for an 8 mm thick sheet (“natural” colour) —— Anti-graffiti coating —— Shockproof and shatterproof —— Weather- and UV-resistant; good aging stability —— Suitable for use indoors and outdoors —— Service temperature range: – 40 °C to + 120 °C —— Working methods: cutting, drilling, edge polishing —— Bonding and joining: screwing, gluing —— Standard panel thicknesses 1.5–9.5 mm; thicker panels possible on request —— Standard formats: maximum width 2500 mm, maximum length 8000 mm —— Building material class B1 flame-resistant (DIN 4102) possible on request

Product  Foils, films and membranes Materials  EPDM, PE, PVC, ETFE, PVB EPDM membrane ­manufacturers  Firestone (www.firestonebpe.com); ­Hertalan (www.hertalan.de) PVC foil manufacturers ­ Renolit AG (www.renolit.com); Daams Kunststoffe GmbH (www.daams-kunststoffe.de) ETFE foil manufacturer  Foiltec (www.foiltec.de)

Thin foils, films and membranes can be made from various materials by calendering or extrusion. The material thickness ranges from less than 1 mm up to 2 mm depending on the material and application; the width of the roll depends on the manufacturer’s facilities. Foils can be transparent or through-coloured. EPDM or PE membranes are commonly used as waterproof sealing liners. ETFE foils are used in building envelopes, for example for pneumatically filled air cushions. Polyvinyl butyral (PVB) is used as a laminating layer between panes of glass in the production of laminated safety glass.

Profiled sheets and panels Profiled sheets, for example corrugated and ribbed multiwall sheeting, are ex­truded  semi-finished products which have been given a profiled cross section to lend them greater stiffness while remaining lightweight. The cross section of corrugated sheeting can have a trapezoidal or sinusoidal wave form and is described by a combination of two numbers: the first number denotes the distance between the peaks of the waves, the second the overall height of the cross section, for example 76 / 18 [mm]. The cross section of ribbed or webbed panels varies depending on the form and number of cavities and the edge detailing. While the width varies from product to product, the length is theoretically variable due to the extrusion pro­cess. In practice products are usually shipped in a range of fixed dimensions.

Material  PMMA Product  Plexiglas XT Manufacturer  Evonik Röhm GmbH www.evonik.com; www.plexiglas.de

Evonik Röhm produces corrugated sheeting made of impact-resistant modified PMMA which is extruded at a thickness of approximately 3 mm. The 1045 mm wide elements are clear-translucent or brown-coloured and can be made up to a length of 7000 mm. The smooth or textured surface can be given a heat-resistant coating.

5.10

67

PROFILED SHEETS

5.10  Glass fibre-reinforced plastic: Scobaglas translucent panels in different colours.

5.10

Corrugated Plexiglas sheets are classified as building material class B2 according to DIN 4102. Material  Polycarbonate

Corrugated sheeting made of polycarbonate is manufactured with a trapezoidal or sinusoidal wave form cross section. When co-extruded with a UV-resistant protective coating, these impact-resistant panels are also suitable for outdoor applications. They can be cold-formed and are available as clear-transparent or bronze-coloured panels. Its upper working temperature of up to 120 °C is very high. Corrugated panels or sheeting made of polycarbonate are generally classified as building material class B1 (DIN 4102).

Material  PVC

Corrugated sheets with various trapezoid or sinus wave form cross sections are also manufactured out of hard or unplasticised PVC. They are exceptionally impact-resistant and are therefore classed as hailproof. They also have good resistance to chemicals and can be equipped with a UV-resistant protective coating. A variety of transparent, white- or grey-coloured products and moulded articles are available, for example corner pieces for ridges or eaves. Corrugated PVC sheeting is generally classified according to DIN 4102 as building material class B1.

Material  Glass fibre-­ reinforced plastic (GRP) Product  Scobalight – ILP translucent corrugated sheets Manufacturer  Scobalit www.scobalit.ch

Scobalight panels are manufactured with different cross sections out of glass fibre-reinforced polyester resin and have good weathering and aging properties. They are also shatter-resistant and unaffected by UV light. In addition to the standard colours – clear, yellow, green and blue – Scobalight products can also be manufactured to order in the palette of RAL colours. The width of the ­elements depends on the profile and typically lies between 900 mm and 1170 mm. The standard lengths of between 1500–6500 mm can be varied according to specific requirements. Scobalight elements can be produced to conform to building material class B1 (DIN 4102).

5.11

68

FINISHED AND SEMI-FINISHED PRODUCTS

Material  Polycarbonate (PC) Product  Makrolon multi UV multiwall sheets Manufacturer  Bayer Sheet Europe GmbH www.bayersheeteurope.com

The Makrolon multi UV range consists of UV-resistant multiwall panels made of

5.13

polycarbonate, which are available in various modifications and cross sections. They are suitable for applications such as roofing and cladding for swimming baths, greenhouses, roof lights, sports halls etc. Products are available with a Ug-value of 1.0 W/m2K. Properties and design possibilities: —— Colouration: colourless, white, transparent bronze, green and blue —— Can be cold-formed —— Hailproof —— Heat-resistant up to 120 °C —— Sheet thicknesses 4–40 mm available with different rib spacings and ­cross-sectional arrangements —— Sheet widths 980, 1200 or 2100 mm; sheet lengths 2000–12 000 mm —— Building material class B1 or B2 (DIN 4102, product-dependent)

Material  Polycarbonate (PC) Product  Translucent façade and roofing panels Manufacturer  Rodeca GmbH www.rodeca.de

The translucent roof and façade panel elements by Rodeca consist of polycarbo­ nate multiwall panels that can be manufactured with different cross sections and numbers of cell cavities. Cellular panels with a standard width of 2100 mm (depending on the product) are available in different thicknesses. The edges can be sealed in the factory. The panels are mounted using conventional façade constructions with clamping strips. A number of different façade panels with multiple multiwall cross sections are available in widths of 500 or 600 mm with a specially developed interlocking tongue and groove seam along their vertical edges. It is possible to create large expanses of apparently seamless façade cladding with a height of up to 25 m without any horizontal joints. The panels are fixed to the supporting structure via retaining clips on the inner surface, making it possible to dispense with external fixing elements altogether. The integration of windows in the façade system is possible. The panel elements can be bent along their axis up to a minimum radius. Protection against UV light is provided by a factory-welded protective layer. Properties and design possibilities: —— COLOR (Design Series): single-colour completely pigmented panels in different colours —— BI-COLOR (Design Series): colourless translucent element with co-extruded colour layer on the inside surface creating a three-dimensional effect (see ­Laban Creekside project, p. 114) —— DECO-COLOR (Design Series): Variants with heat-blocking coating on the ­outside, with glossy, reflective coloured surfaces or with specially produced phosphorescent glowing surface —— Surface is printable —— Anti-graffiti surface coating possible —— IR-reflective coating is possible to reduce the absorption of heat radiation from outside

5.12

69

PROFILED SHEETS

5.11 Corrugated panels made of different materials. From bottom to top: translucent blue Scobalight sheeting made of GRP; opaque white sheeting made of Plexiglas with a heat-­resistant coating; opaque Scobalight sheeting made of GRP.  5.12  Translucent façade ­cladding panels made of polycarbonate. Front: 40 mm thick, transparent panel linked to a panel with a co-extruded orange-coloured interior face. Centre: 50 mm thick, transparent and opal. Rear: multi-­functional, coloured translucent ­panel.  5.13 Multiwall sheeting with different cross sections and ­materials. From bottom to top: Scobaelement made of GRP; webbed Plexiglas sheeting; all other multiwall sheets are part of the Makrolon range.

5.11 5.12 5.13

—— Hailproof —— Ug-value: 1.2 W/m2K, U-values possible up to 0.83 W/m2K (product-dependent) —— Temperature resistance: long-term service temperature: – 40 °C to + 115 °C; short-term up to + 130 °C —— Can be thermoformed as well as cold-formed up to a certain minimum radius —— Building material classes B1 or B2 available (product-dependent) Material  Polypropylene Product  Bee_bo Manufacturer  Deceuninck www.deceuninck.be

The strip-like multiwall panels in the Bee_bo series are made of polypropylene with an 80 % recycled material content and are themselves fully recyclable. They are designed especially for use in interiors and can be used as wall cladding with concealed fasteners. The profiled surface of the elements results in shadow lines and special edge strips are available. Bee_bo panels are available with three different surface textures and a silvery metallic appearance. The 10 mm thick sandwich strips are manufactured in widths of 100 and 250 mm and lengths of 2700, 4500 and 6000 mm.

5.14

70

FINISHED AND SEMI-FINISHED PRODUCTS

5.14  Bee_bo wall cladding elements made of polypropylene.  5.15 ViewPan honeycomb panels in different colours and surface finishes.

5.14

5.15

Sandwich panels Material  PMMA, PET Product  ViewPan translucent honeycomb panel Manufacturer  Wacotech GmbH & Co. KG www.wacotech.de

ViewPan panels consist of a WaveCore honeycomb core made of transparent PETG

5.15

bonded permanently to two 3 mm thick facing layers of acrylic glass (PMMA). The transparent core of the lightweight yet rigid sandwich panels can be used to create interesting optical effects ranging from clear transparency to diffuse scattered light. ViewPan elements are used for interior applications such as trade fair installations and shopfitting, for illuminated ceilings or translucent doors ­(Kandela) and sliding doors. Properties and design possibilities: —— Colour of the facing layer: transparent, satin-finish and/or coloured —— The ability to see through the panel is dependent on the angle of view —— Service temperature range: – 30 °C to + 70 °C —— Standard formats: 1000 × 3000 mm; custom dimensions also possible —— Panel thickness: 19–80 mm possible —— Building material class B2 (DIN 4102), B1 if required

Material  GRP, CFRP, epoxy resin, PMMA, PC Product  Lightweight building element Concept Jens-Hagen Wüstefeld www.leichtbauelement.de

The lightweight building elements can be made of different materials and employ

5.16

a simple construction principle. The core layer consists of thin strips of material which through a system of diagonal incisions can be slotted together and bonded to form an interlocking spatial latticework. The facing layers are then bonded to the core structure. It is possible in principle to use a combination of different materials for the core and facing layers. The constituent elements are flat but can also be manufactured for custom installations to form single- or double-curved panels. The elements have a thickness of at least 30 mm but can also be manufactured in larger thicknesses. They are exceptionally strong and stiff for their weight. ­Special connecting pieces are available for coupling individual panels to form larger surfaces.

5.17

71

SANDWICH PANELS

5.16 Lightweight building element made of CFRP, epoxy resin, GRP and a combination of aluminium core with epoxy resin facing layers.  5.17 Construction principle of the core structure.

5.16

5.17

Properties and design possibilities: —— Core layer can be filled with foam to improve its thermal insulation properties —— Optional openings in the core layer to accommodate pipework and channels —— The dimensions of the elements depend on the material used —— Suitable for use outdoors Material  Polycarbonate, PMMA Product  clear-PEP Manufacturer  Design ­Composite www.design-composite.com

The transparent clear-PEP panels have a TRIcore honeycomb core made of polycarbonate produced using a special core drawing process. In a subsequent stage, the facing layers of polycarbonate or PMMA are bonded to the core layer. The translucent sandwich panels exhibit good flexural rigidity while remaining lightweight. Numerous variants are possible by varying the core height, colour and surface treatment. The clear-PEP panels can also be bent up to a minimum radius. Equipped with a UV-resistant protective coating, they are suitable for outdoor applications. Properties and design possibilities: —— Standard colour of the facing layers: orange, green, light blue, dark blue; special colours and combinations also available —— Glossy transparent or satin-finish translucent surface finish —— Low self-weight —— UV- and weather-resistant —— Service temperature range: – 30 °C to + 80 °C —— Predefined panel thicknesses ranging from 16–150 mm —— Width 1000–2020 mm, length 2000–7800 mm (product-dependent) —— Building material class B1, B2 (DIN 4102, product-dependent)

5.18

72

FINISHED AND SEMI-FINISHED PRODUCTS

5.18 Various kinds of clear-PEP panels.

5.18

Materials  Polycarbonate, PMMA, aluminium Product  AIR-board Manufacturer  Design ­Composite www.design-composite.com

The translucent AIR-board panels consist of a honeycomb core with two bonded

5.19

facing layers. The palette of product variants is the result of varying the combi­ nation of different materials. Their appearance and mechanical properties depend on the materials used. Certain product variants are also suitable for outdoor

5.20

applications, but the edges need to be sealed to prevent moisture ingress. The ­panels can be mounted using conventional clamping profiles or drilled point fixing systems. Properties and design possibilities: —— Facing layers made of PC or PMMA, coloured or transparent, with glossy or satin-finish surface —— Core made of polycarbonate in different colours or of aluminium with diverse cell dimensions —— UV- and weather-resistant variants available —— Element thicknesses 16–150 mm (product-dependent) —— Standard formats 1000 × 3020 mm / 1220 × 3020 mm / 1050 × 2550 mm (product-dependent) —— Maximum formats 2020 × 7080 mm / 1420 × 7080 mm (product-dependent) —— Building material class B1 or B2 (DIN 4102, product-dependent)

Materials  Polypropylene, ­polyethylene, polystyrene Product  VarioLine Manufacturer and ­distributor  PolymerPark ­materials GmbH www.polymer-park.com

The lightweight building boards by VarioLine consist of an integral skin foam structure and can be made of different thermoplastics. The panels are avail­able in a variety of through-coloured plastics. Their basic properties are a factor of the material used for their manufacture but can be modified to a certain degree. The panels are manufactured using a special technique that makes it possible to control the thickness and loadbearing capacity of the facing layers as well as

5.21

73

SANDWICH PANELS

5.19 AIR-board panels made of polycarbonate and PMMA.  5.20 Sandwich panels with metal honeycomb core: AIR-board panels by Design Composite (right and bottom panel), and sandwich panel with metal honeycomb core and GRP facing layers (left panel, other manufacturers).

5.19

5.20

the thickness and compressive strength of the core. The foamed structure of the cross section lends the panel good rigidity while minimising its self-weight. The elements are shatterproof and can sustain high mechanical loads. They are moisture- and weather-resistant and can therefore be used both indoors and outdoors. The panels can be machined. The standard panel formats are 2450 × 1450 mm and 2000 × 1650 mm with thickness of between 6–26 mm. Their homogenous thermoplastic structure means that they can be recycled. The VarioLine elements are classified as building material class B2 (DIN 4102). Materials  Plastic nonwovens, mixed blends of synthetic and natural fibres Product  3D-Tex Manufacturer  Mayser www.mayser.de

3D-Tex Standard is a three-dimensional formable textile with a nubbed structure

5.22

which can be used as a core material for sandwich constructions. The polyester textile is impregnated with resin and can be manufactured to different degrees of stiffness. Product variants include resin-impregnated polyester nonwovens as well blends of natural fibres and polypropylene. The nub height can be varied depending on the material from between 5–14 mm. The polyester textile is provided in roll or panel form at a width of 1450 mm, mixed fibre variants in panels of 1800 × 1000 mm. Alongside decorative interior applications, 3D-Tex is employed as a core material for façade constructions. Depending on the specific product, the material is classified as building material class B2 or B3 (DIN 4102).

Material  Glass fibre-­ reinforced plastic (GRP) Product  Parabeam 3D glass fabric Manufacturer  Parabeam BV www.parabeam.nl

Parabeam offers an easy way of constructing flat or curved building elements with a GRP sandwich structure. It consists of a three-dimensional spacer textile in which the two outer layers of textile are connected to one another by vertical piles. The Parabeam textile is available for use in manual hand lay-up moulding. Once the textile is impregnated with resin, the fibres of the material expand to their full height as a result of capillary action. Once hardened the result is a strong GRP sandwich element with low self-weight. Parabeam is available in standard widths of 1270 mm and in thicknesses of between 3–22 mm.

5.23

74

FINISHED AND SEMI-FINISHED PRODUCTS

5.21 VarioLine is a lightweight building board with integral foam structure made of polypropylene, poly-

ethylene or polystyrene.  5.22  3D-Tex product variants: 3D-Tex Standard (white textile), 3D-Tex 500 R1 (yellowish polyester nonwoven fabric with melamine resin coating), 3D-Tex PP/KHF (mixed-fibre non­ woven with 50 % polypropylene and 50 % natural fibres).  5.23  Parabeam: a 5 mm thick flat translucent panel made of GRP.

5.22

5.21

5.23

Material  Glass fibre-­ reinforced plastic (GRP) Product  Scobaelement – ILE translucent sandwich panels Manufacturer  Scobalit www.scobalit.ch

The translucent light element Scobaelement is made of glass fibre-reinforced poly­ester resin and is available in two different cross-sectional forms as a sandwich element with covering layers and connecting webs. The durability of the elements in outdoor and indoor use is similar to the Scobalight products. The sandwich construction lends them a greater stiffness and is economical in its use of materials. With a span length of 2500 × 2000 mm, the elements can sustain a permissible surface load of up to 180 kg/m2 depending on the element thickness. ­Special inserts need to be inserted during production for drilled holes. Properties and design possibilities: —— Standard colour: natural but can also be manufactured in other colours —— Anti-graffiti coating —— Maximum dimensions 8000 × 2400 mm —— Thicknesses 20, 30 and 50 mm (Type M = waveform webs), 25 and 40 mm (Type P = vertical webs) —— Building material class B1 (DIN 4102) also available

5.13

75

SANDWICH PANELS

5.24 Frontal view of a GRP Scobatherm panel.  5.25  Section through an aerogel granulate-filled

­Scobatherm panel. 5.24

5.25

The translucent Scobatherm insulation element represents a variant of the light

5.24

element that is filled with aerogel. Panels with a thickness of 50 mm can attain a

5.25

U-value of 0.41 W/m2 K Material  GRP, PUR, PS, PVC Product  Sandwich panel with foam core Manufacturer  Various

Sandwich panels with a rigid PUR foam core and GRP facing layers are ideally suitable for lightweight construction due to their high stability and low weight. Depending on their respective thickness, they can also have an insulating function. The sandwich elements can be manufactured to serve specific purposes, for example, the facing layers can be made of different thermosetting matrix resins or alternatively of thin metal sheeting. Properties and design possibilities: —— Core layer made of PS-, PU- or PVC foam with different degrees of firmness —— Facing layer of GRP or metal —— Integration of inserts is possible for fixings or mountings —— Good dimensional accuracy —— Suitable for use outdoors —— Maximum dimensions 3200 × 15000 mm

5.26

76

FINISHED AND SEMI-FINISHED PRODUCTS

5.26 Sandwich panels with GRP facing surfaces and rigid PUR foam core.

5.26

Foams Material  Polystyrene (EPS, XPS) Product  Insulation ­material (Styrodur C, Styropor, Neopor, Peripor) Manufacturer  BASF SE www.basf.com; www.neopor.de; www.styrodur.de

A variety of foamed plastic materials are used as insulation or support core mate-

Material  Polyurethane foam (PUR), polystyrene (EPS, XPS) Product  Core material for sandwich panels

PUR or polystyrene foam is used as a core fill material for sandwich panels. The

rials or for mould construction. Rigid foam panels made of extruded (XPS) or expanded polystyrene (EPS) are used primarily for insulating buildings. Rigid poly­

5.27

styrene foams are most well-known under their BASF trade names: XPS is sold as Styrodur C, EPS as Styropor, Neopor or Peripor. They are typically made available in flat panels with thicknesses of several centimetres. Polystyrene is also used as profiled formwork for concrete construction.

surfaces of the core material are bonded firmly to the facing layers. A large number of products of this kind are available on the market in all manner of core and ­facing layer material combinations. For mould construction, for example for the manual lay-up of GRP building elements, entire blocks of rigid PUR foam are used, which are then worked by hand or machined into shape. Foam blocks are also increasingly being used in geotech-

Material  Expanded poly­ styrene (EPS) Product  Formwork elements made of EPS Manufacturer  Iso-Massiv­ haus www.iso-massivhaus.com

nics as a cost-effective volumetric element with low self-weight for low loadbearing soils. The ISO-Massivhaus building system uses thermally insulating, specially formed interlocking blocks made of Styropor, which are stacked up to the height of one storey before being filled with concrete. The Styropor blocks serve as permanent shuttering either side of the supporting concrete wall and double as effective insulation. The internal and external surfaces are then plastered. The advantage of this construction system is its rapid and simple execution.

5.28

77

PROFILES

5.27 Milling a block of polystyrene foam to shape that will be used for the construction of Hoofddorp bus station (see p. 132).  5.28  Building shell construction for ISO-Massivhaus using formwork elements made of EPS: the interlocking elements are assembled and the resulting cavity filled with concrete.

5.27

5.28

Profiles Profiles are produced, depending on the material, using extrusion or pultrusion methods. Co-extruded profiles can be made of different materials each with different properties. The manufacture of individual special profiles is in principle possible but is usually undertaken upwards of a certain quantity. Material  Glass fibre-­ reinforced plastic (GRP) Product  GRP profiles Manufacturer  Fiberline ­Composites A/S www.fiberline.com

Glass fibre-reinforced plastics are used in loadbearing structures primarily in the form of profiles. GRP profiles are manufactured using a pultrusion process. With

5.30

this manufacturing method, glass fibre content levels of up to 70 % are possible, resulting in very strong elements that are suitable for loadbearing applications. GRP profiles have good UV, weather and chemical stability and, depending on the matrix resin used, are classified as building material class B1 or B2 (DIN 4102). A wide variety of profile types are possible; commercially-marketed profiles typically follow the thin-section girder profiles well-known from steel construction. Standard products include both open and closed profiles of different dimensions

5.29

and wall thicknesses. GRP profiles are particularly suitable for use in bar framework structures. Another area of application is the use of GRP as a roadway deck for bridge constructions. Material  PVC Product  PVC profiles Manufacturer  Roplasto www.roplasto.de

Window frames made of PVC represent a large group within the range of plastic

5.31

profiles where their low thermal conductivity can be turned to an advantage. PVC windows or PVC door profiles are manufactured as hollow-section profiles and welded to form the finished product. To obtain sufficient stability they are often

Material  PMMA Product  Plexiglas rods and tubing Manufacturer  Evonik Röhm GmbH www.evonik.com

strengthened with additional steel reinforcement inserts. Closed profiles with round or square cross sections as well as rods are made of Plexiglas XT or Plexiglas GS to a standard length of 4000 mm. The diameter of the rods can range from 2–100 mm, while tubing is generally produced in diameters

5.32

78

FINISHED AND SEMI-FINISHED PRODUCTS

5.29  GRP profile with open cross section.  5.30  Pultruded GRP profiles.

5.29

5.30

ranging from 5–650 mm. Not all dimensions are available in both extruded or cast form depending on the manufacturing method used. Material  PMMA Product  Rods, tubing and profiles Manufacturer  Gevacril www.gevacril.com

Acrylic rods by Gevacril can be cast or extruded with different cross sections up to a length of 2000 mm. Cast round-section rods can have a maximum diameter of 200 mm at a length of 1000 mm. Acrylic profiles with L-, U- and H-shaped cross sections can be manufactured in lengths of 2, 3 and 6 m. A special variant features metallic-shining coatings which are available in different colours and are suitable for use indoors and outdoors. The product range also includes various individual items such as hinges, hemispheres or screws made of PMMA.

Material  Different thermo­ plastic materials Product  Rods, tubing and profiles Manufacturer  BWF Kunst­ stoffe GmbH & Co. KG www.bwf-group.com

Material  EPDM Product  EPDM profiles Manufacturer  CEFO-elasticprofil-GmbH www.cefo.de

BWF Kunststoffe manufacture diverse extruded products made of thermoplastic materials. The product range varies from rods and tubing with different cross sections and diameters to a number of profile forms with, for example, geometric cross sections, as well as connecting and edging strips made of poly­carbonate for multiwall panels or linear lighting profiles. The products are avail­able in transpa­ rent, translucent or opaque forms in different colours. Elastomer profiles are used in diverse shapes and forms as sealing gaskets for façade constructions. They serve as a sealing joint between façade elements or are incorporated as integral components of elements such as doors and windows. They can also be used to control the dissipation of condensation water. Wire inserts can be integrated to improve their stability.

79

PROFILES

5.31  PVC window frames with concealed steel reinforcement profiles.  5.32 Rods and tubing made

of Plexiglas. 5.31

5.32

Special products In addition to the aforementioned finished and semi-finished products, a wide variety of special products are manufactured for use in constructions. The following represent a selection of particular products of special relevance to construction. Material  Glass fibre-­ reinforced plastic (GRP) Product  Gratings Manufacturer  Fiberline Com­ posites A/S; Lichtgitter GmbH www.fiberline.com; www.lichtgitter.de

GRP gratings are a widely used plastic product available in a variety of sizes with different heights and mesh dimensions. They can be cast or pultruded in the form of profiled gratings. Cast GRP gratings can be omnidirectional while pultruded GRP gratings are directional. GRP gratings are used as a robust and lightweight alternative to metal gratings in industrial buildings, in particular for industrial and offshore facilities where corrosion and weather resistance are particularly important.

Material  Elastomer Product  Elastomeric bearings Manufacturer  Maurer Söhne; Calenberg Ingenieure; Gumba GmbH; SPEBA Bauelemente GmbH www.maurer-soehne.de; www.calenberg-ingenieure. de; www.gumba.de; www.speba.de

Elastomeric bearings are used to accommodate the unconstrained movement of building elements and the absorption of unplanned stresses resulting from eccentricities. They exploit the high elastic formability and high compression resistance of certain elastomers. They are most commonly used at junctions between loadbearing elements, for example as bearing pads for bridge decks as well as in ­buildings, most notably in the case of prefabricated concrete structures. Elastomeric bearings are standard building elements in many types of structures. The forms and dimensions depend on the kind of loading and the envisaged calculated translation or rotation. Elastomeric bearings are available unreinforced or in the case of high loads, reinforced with integral steel plates, inserted during vulcanisation.

80

FINISHED AND SEMI-FINISHED PRODUCTS

Material  PET, PVA, PP and others Product  Geosynthetics, ­geotextiles Manufacturer  DuPont; ­Tensar; Fibertex A/S www.typargeo.com; www.tensar.de; www.fibertex.com

Geoplastics are usually flat, pervious or impervious plastics in the form of meshes, textiles, nonwovens or membranes. They are typically very strong, durable and economical and are easy to install. Geotextiles serve primarily as a separating layer or as a filter, sometimes also as a reinforcement fabric. They are employed in many diverse applications in geotechnics and roadway construction, for example as soil reinforcement or soil stabilisers, for dam foundations and erosion control. They make it possible to improve the mechanical properties of the soil in particular ways. A special variant is their use in construction using reinforced earth in which the geoplastics pick up the tensile forces, then transfer them by friction to the earthworks structure.



6

Building with plastics

Thermoplastics and thermosetting plastics differ from one another both in chemical structure as well as mechanical properties. This has fundamental implications for how they are used in construction in practice. The following section examines construction methods for the different types of plastics in turn.

 T hermoplastics  The four key joining techniques for thermoplastic materials, i.e. screwing, clamping, bonding and welding, are described below:

Screwing Screw connections are reversible connections that can transfer tension and shear 6.1

forces. They make it possible to couple entirely different materials and are most commonly used for connecting flat and profiled sheet material. Screwed or bolted fixings must be designed to avoid constraining movement caused by thermal ex­pansion so that unintended stresses do not occur. Brittle plastics such as PMMA are prone to stress cracking and must be pre-drilled using special tools. The speed of the drill bit should not be too high. Where higher loads are to be expected, elastic sleeves or spacers are recommended as an intermediate layer. Threads cut directly into the plastic are possible but not very wear-resistant if used repeatedly. For screw connections that need to be assembled and disassembled repeatedly, metal thread inserts should be integrated within the element. Screws should only be tightened by hand without excessive force. The use of washers can help distribute stresses more evenly.

Clamping A standard means of connecting plastic building elements is the use of clamp6.2

ing profiles and clips. This method of fixing is used most commonly for flat building elements such as flat or profiled panels and multiwall sheeting. In most cases they take the form of linear clamping strips made of aluminium or stainless steel, occasionally also point fixings. The detailing of fixings needs to take into account the comparatively large thermal expansion of thermoplastics resulting from temperature changes. This is particularly important for façade elements made of plastics such as polycarbonate or PMMA that have a very high coefficient of thermal expansion and are simultaneously exposed to large temperature variations.

81

82

BUILDING WITH PLASTICS

6.1 Screw connections in corrugated and multiwall sheeting showing the use of spacers.  6.2 Examples of clamping profiles: A and B: profiles used for products by Rodeca, C and D: typical fastening profiles for façades consisting of a supporting substructure, multiwall sheets and fixing elements.

6.1

6.2

A

B

C

D

Bonding Adhesive bonds are non-reversible connections. They are in principle ideally suitable for plastics as they do not create point loads. However, it is important to note that adhesive bonds have very low or no dimensional tolerance. Adhesives are nonmetallic materials that connect the pieces to be joined by surface adhesion and internal cohesive strength. Adhesives can be classified according to their chemi­ cal composition and their setting or curing process. Adhesives may be based on organic or inorganic compounds. The greater proportion of adhesives are based on organic compounds, most notably polymers. For the most part they exhibit better adhesiveness and long-term aging stability. Adhesives rely on physical or chemical processes to set or cure: Physically curing adhesives   are substances in which the polymer within the 6.3

adhesive is already present in its end state and in a form that can be worked so that it can be applied to the surfaces to be bonded. The adhesion can be improved through the application of additional pressure during the setting process. The most important physically curing adhesives are:

6.5

Wet bonding adhesives  are polymers suspended or dissolved in a liquid, which are applied in a viscous state to the surfaces to be bonded. The adhesive effect gains strength as the liquid evaporates (for example: all-purpose adhesives, solvent adhesives). Dispersion adhesives  are in principle similar to wet bonding adhesives. In this case, however, the adhesive polymer is dispersed in water and requires longer to cure than wet adhesives (for example: wood glue).

THERMOPLASTICS

Contact adhesives  are rubber-based adhesives generally dissolved in a solvent. The adhesive is applied evenly to both bonding surfaces. After being allowed to begin to dry the two surfaces are pressed together briefly under high pressure. The bond is already fairly strong immediately after contact but reaches full strength only after full evaporation of the solvent (for example: vulcanising adhesives). Hot melt adhesives  are available in different degrees of solidity. When heated they become a viscous workable mass. The adhesive cures on cooling and the bond can immediately be subject to loads (for example: hot-setting adhesives). Chemically curing adhesives   are applied as cross-linked or uncross-linked 6.3

polymers to the surfaces to be bonded. The chemical reaction that sparks the connection of polymers to one another or with the bonding surface can be initiated by two components coming into contact or being exposed to moisture or the air. For this reason such adhesives are known as reactive adhesives. The group of chemically curing adhesives include: Single-component adhesives  already contain the polymerised adhesive. The curing or setting process is initiated by a change in the environmental conditions, for example a rise in temperature, exposure to moisture or other materials. Two-component adhesives and multi-component adhesives  consist of separate components which need to be mixed in the correct quantities to initiate a chemi­ cal reaction causing the polymer chains to form linkages with one another. The bonding surfaces must be held in place during the setting process. Silicones  differ from organic polymer adhesives in that their molecular structure consists of silicon-oxygen compounds. Silicone adhesives are available as ­singleor two-component adhesives. They can be applied in layers of up to several milli­ metres thick, but single-component adhesives will only harden properly up to a thickness of approximately 6 mm. They are elastic and exhibit excellent weather resistance. Aerobic adhesives  set when exposed to air, usually in the presence of atmospheric moisture (for example: mounting glue). Anaerobic adhesives  are single-component adhesives which harden when exposed to oxygen and are used to bond metals. Cyanacrylate adhesives  are single-component adhesives that react with hydroxide groups on the contact surface to be bonded and form a thin but brittle adhesive layer. The reaction takes place almost immediately, but the bond itself is not heat- or water-resistant (for example: superglue). The correct preparation of the surfaces is crucial for the performance of an adhe-

6.4

sive bond. It influences the wettability of the plastic surfaces. Good wett­ability is a prerequisite for a good bond. Typical pre-treatment methods include cleaning and degreasing of the surface. In the case of polymers, such as polyethylene (PE) or polypropylene (PP), which are difficult to wet because of their nonpolar surface, the strength of the bond can be improved by additional measures such as roughening or heating the surface or the application of a primer. The choice of adhesive needs to take into account the compatibility of the bonding surfaces with the

83

84

BUILDING WITH PLASTICS

6.3 Physically and chemically curing adhesives.  6.4 Surface wettability. Left: very good wettability

with the adhesive spreading evenly across the surface. Centre: good wettability where the ­adhesive ­covers part of the surface. Right: poor wettability where the adhesive forms beads that roll off the surface.

6.3

Application of adhesive polymer (premixed)

Bond with the bonded surfaces

Setting process

Solvent

Physically curing adhesive

Application of adhesive components in uncross-linked condition

Bond with the bonded surfaces

Setting process

Chemically curing adhesive

6.4

Very good

Good

Poor

Adhesive

Surface to be bonded

adhesive polymer as well as any possible solvents in the adhesive. In principle, with the use of appropriate adhesives, it is possible to bond different types of plastics. Environmental factors such as humidity, UV radiation and temperature can have a negative effect on the adhesive bond. For this reason, bonding processes are often undertaken in controlled factory conditions to obtain an optimum bond.

THERMOPLASTICS

6.5  The bonding of two polycarbonate surfaces with the help of a solvent adhesive.

6.5

Welding Welding makes it possible to join plastic materials without any additional means of connection. Welding is a process in which surfaces are bonded under heat and pressure. In most cases welding bonds two surfaces made of the same material. In certain exceptional cases where the chemical structures of the two different thermoplastics are sufficiently compatible, it is possible to weld different materials as long as the melting temperatures of both materials are very close together. Heated-tool welding  produces a very good weld seam by heating the surfaces to be bonded with a heated tool to melting temperature and then pressing them together under slight pressure. The heating element of the welding equipment is adapted to fit the geometry of the surfaces to be bonded. This approach is suitable for mass production and is used, for example, in the manufacture of PVC window frames. 6.6

Hot gas welding  is a manual welding process. The bonding surfaces and the welding filler material are melted with hot air and then pressed together. This method is used for small quantities and prototype construction.

6.7

Vibration welding  is a machine welding technique that makes it possible to weld surfaces of up to 300 cm2. With this method two flat elements are clamped to­gether  under slight pressure in a machine. One of the two elements is made to vibrate, ­creating sufficient energy to melt the contact surface. Pressing the two elements together creates a strong and stable bond.

6.8

Ultrasound welding  uses a principle similar to vibration welding in that it produces heat by friction, in this case using sound waves. With this method it is possible to create high-strength bonds in very short cycle times, which makes it ideal for the mass production of small moulded articles.

6.9

Laser welding  makes use of the principle of the different absorption behaviour of two bonding surfaces with respect to laser light. In this approach the upper element to be bonded is transparent for the laser beam which can penetrate to the lower element. When it hits the surface of the lower element it creates heat which is passed in turn back to the upper element. The weld is then created by apply-

85

86

BUILDING WITH PLASTICS

6.6  Hot gas welding: the welding surfaces and welding filler material are melted using hot gas and then pressed together.  6.7 Vibration welding: two building elements are clamped under slight ­pressure. One of the two elements is made to vibrate, causing the surface to melt. The two surfaces are then pressed ­together.  6.8 Ultrasound welding: the surface to be welded is melted using ultrasound waves.  6.9 Laser welding: The upper element is transparent for the laser beam which penetrates to the element below, causing it to warm up.

6.6

6.7 Element 2 Vibration movement

Pressure Element 1 Melting of both surfaces

Welding filler

Element 1

Element 2

6.8

6.9

Heating of the surface through absorption of laser beam

Laser beam

Sound waves

Element 1

Element 1 transparent for the laser Element 2

Element 2

ing light pressure. The absorption behaviour of the two elements to be joined can be adjusted using pigments in such a way that the outward appearance of the two materials appears to be identical despite their different absorption properties. Laser welding is particularly suitable for hard-to-reach welding locations. Using this method it is possible to bond together different thermoplastics and even different materials such as plastics and metal.

 T hermosets Fibre-reinforced plastics (FRP) are the largest group within thermosets  which is why the terms are sometimes used synonymously. For this group of plastics, screwing and bonding are the main means of joining elements.

Screwing 6.10

For fibre-reinforced plastics, screw fixings are used where an assembly may need to be disassembled at a later date or when bonding on site is not possible. In most cases large washers are used to minimise the amount of pressure applied perpendicular to the plane of the fibres.

87

THERMOSETS

6.10 Flow of forces for a screwed connection: the shear force in the screw is transmitted by the ­ om­pression diagonals FD into the building element. Transverse tensile forces F Z resist the horizontal c component of the diagonal compression forces.   6.11 Failure mechanisms for bearing and shear ­connections; A: Fracture of the net section, B: Splitting of the profile, C: Bearing failure at the hole, D: Transverse ­tensile failure, E: Failure in the compression diagonals

6.10

6.11 P/2

P/2

P

FD

FD

A

B

C

D

E

FZ

For bolted or screwed connections subject to shear loads, the primarily unidirectional orientation of the fibres and their general inability to redistribute stresses plastically have a negative effect on the achievable joint strength. On the one hand, screwed connections must be able to accommodate the contact forces between the fibre-reinforced plastic and the screw (bearing stress), while on the other they need to ensure the distribution of forces in the immediate vicinity 6.11

of the load transfer point. In the case of pultruded profiles this can lead to a variety of failure mechanisms for connections acting in shear and bearing, for example transverse tensile failure at the load transfer point. In addition to the above, it is also necessary to demonstrate that the screw or bolt itself has sufficient shear strength. For the above reasons, the transferable loads for bearing and shear connections are therefore comparatively low. The pre-stressing of screw fasteners is in principle possible but must be monitored and where necessary retensioned due to the pronounced creep behaviour of the material. One advantage of screwed connections is that they are easy to assemble and not dependent on the weather. Nevertheless, the rules and practices developed for the transfer of loads at single or groups of bolts in structural steelwork are not always suitable for fixing GRP building elements due to the anisotropic properties

6.12

of the material. For screwed connections in hand-laminated building elements, special steel fixing plates are available that can be embedded during lamination. They consist of a perforated plate with a welded threaded shaft or threaded nut. Typical diameters range from M4 to M12. The embedding of the screwed connection within the building element reduces the latter’s susceptibility to material failure at the fastening.

88

BUILDING WITH PLASTICS

6.12  The steel insert plate is integrated into the hand-laminated GRP building element and reduces the risk of tear-out or material failure at the fastening.

6.12

Bonding Bonding is a joining technique well-suited to GRP plastics as it ensures a planar 6.13

transfer of loads. The selection of adhesives for such bonds can only be made on a case-by-case basis. In any case, the suitability of an adhesive for the materials to be joined needs to be checked with the manufacturer before use. An adhesive bond can be considered to be made up of a number of different lay-

6.15

ers. Between the surfaces of the two items to be bonded, there are three layers: a layer of adhesive and an interface layer between the surface of each item and the adhesive layer. Within the adhesive one can, therefore, differentiate between the

6.14

transfer of forces between the bonding surface and adhesive (adhesion) and the strength of the adhesive itself (cohesion). Different theories exist to explain the very complex mechanisms of adhesion. Heavily simplified, the cause of adhesion forces lies in the structure of the material. Materials consist of molecules and atoms, which are held together by electrical forces. Within the material these forces are evenly distributed. At the surface of the material the molecules have no neighbouring particles on one side and, depending on their structure, are able to attract other materials to its surface, for example dust particles or droplets of water. The polymer molecules within an adhesive form similar forces when they come into contact with the item to be bonded. The polymer structure or the composition of the adhesive adapt to the composition of the bonding surface. This explains why a certain adhesive may only be suitable for use with particular materials. The distance over which adhesion forces act lies in the region of 0.2–1 nm and even extremely smooth surfaces can use these bonding forces. The pre-treatment of the surfaces is therefore particularly important as surfaces that are already covered by dust or moisture are un­able to develop appreciable adhesion forces.

89

THERMOSETS

6.13  Classification of adhesives according to their constituents.

6.13 Adhesive

Organic compounds

Natural basis Proteins Carbohydrates Resins Products such as glues

Inorganic compounds

Artificial basis Carbon compounds with the elements – Hydrogen – Oxygen – Nitrogen – Chlorine – Sulphur

Silicones

Silicates Borates Phosphates Metal oxides Products such as solder glass

Products such as acrylate adhesives, epoxy resin adhesives, polyurethane adhesives

Adhesion may be termed mechanical or specific. Mechanical adhesion de­scribes the mechanical attachment of the bonding cement to the pores or capil­ laries of the bonding surface. This plays a significant role where surfaces are porous or rough such as is the case with wood, foams and cardboard, etc. For very smooth or slightly roughened surfaces, the proportion of mechanical adhesion is comparatively small. Specific adhesion describes the bonding forces that come about as a result of chemical, physical and thermodynamic principles. The second main property responsible for the strength of an adhesive bond is cohesion, that is the binding forces within the adhesive material itself. The term cohesion describes the attraction forces between atoms or molecules within a material. The cohesive strength is a value that is dependent on the material and temperature, and is determined by the different kinds of primary and secondary valence forces. The cohesive strength is also dependent, among other things, on the quality of manufacture. Enclosed air pockets, poorly mixed components, inadequate curing times and non-observance of the necessary setting temperature can all have a negative effect. The relationship of cohesion to adhesion plays an important role in determining the strength of an adhesive. A high cohesive strength is of little use when the adhesive strength is very low and vice versa. Adhesion and cohesion not only determine the adhesion mechanisms at work in a layer of adhesive but also its failure mechanism. Adhesive fracture, cohesive fracture, mixed-type fracture and substrate fracture are the primary patterns of 6.16

failure for adhesive joints. An adhesive or interfacial fracture occurs when the bonding surface and adhesive part company without leaving residual particles of either on the other. Adhesive fracture or debonding is often caused by insufficient pre-treatment of the bonding surfaces or the use of an incompatible adhesive for the particular substrate. In the case of cohesive fracture, the strength of the adhesive itself is exceeded. The adhesion between element surface and adhesive is larger than the cohesion in the adhesive itself. The bonding fails within the

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BUILDING WITH PLASTICS

6.14 Adhesion and cohesion forces in a bonding adhesive.  6.15 Layer structure of an adhesive bond.  6.16 Patterns of failure of adhesive joints.

6.14

6.15 Element 1

Element 1 Boundary layer 1 Adhesive layer

Adhesion

Boundary layer 2 Cohesion Element 2

Element 2

6.16

Adhesive fracture

Cohesive fracture

Mixed adhesion and cohesion fracture

Substrate fracture

adhesive layer. This can occur where the two bonded items are particularly hard, for example when they are metal. If the cohesive strength proved to be less than it should have been, this may point to insufficient curing of the adhesive or to incorrect mixing proportions of the adhesive components. A mixed-type fracture exhibits elements of both kinds of fracture. This can occur when the bonding surfaces have not been evenly degreased. In addition to these three types of fracture, it is also possible that the substrate itself may fracture. This can happen when the adhesive strength and cohesive strength of the adhesive exceed that of the substrate. GRP to GRP bonds are usually designed to exhibit this kind of failure mechanism so that the strength of the GRP material is exploited to the maximum before failure occurs. In addition to the properties of the adhesive, the geometry of the bond line and the 6.17

kind and degree of stresses it is subjected to have an effect on the strength of thejoint. The kind of stresses an adhesive joint is subjected to can be differentiated into normal stresses (usually tension), shear stresses and peeling stresses. The latter in particular – stresses that can lead to the peeling of one substrate from the other – must be avoided wherever possible. Similarly, adhesive joints should be designed to avoid the occurrence of bending stresses. These should be ­broken down into planar tension and compression forces, which can then be examined as standard bonding geometries and evaluated individually as being favourable or unfavourable.

91

THERMOSETS

6.17 Unfavourable (a) and favourable (b) designs for adhesive joints.

6.17

a

b

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BUILDING WITH PLASTICS

In order to ensure the homogenous transfer of loads at the interface, it is important to avoid damaging the fibres when priming or surface treating FRP substrates. Degreasing the surface is the most gentle of the available cleansing methods. Mechanical pre-treatment should be undertaken carefully with the intention of removing only any surface layers present that may impact on the joint strength, such as mould release agents. Fine-grade sandpaper or abrasive burnishing pads are suitable. A special form of mechanical surface treatment is the use of peel-ply fabrics which are applied as a final layer onto a not fully hardened laminate and then peeled off once fully hardened. This method leaves behind a clean and textured surface suitable for bonding. In addition to these methods, various other somewhat more elaborate surface treatment methods are also available.

Dimensioning Standards and norms

The large number of different manufacturing methods, material constituents and manufacturers explain the lack of a consistent, practice-oriented standard that governs the structural engineering design and detailing of GRP building elements. At the time of writing there are no officially approved technical regulations for designing loadbearing constructions made of fibre-reinforced plastics. Standards that are relevant include the German DIN 18820 and the European DIN EN 13706. The structure, manufacture and properties of laminates made of textile glass fibre-reinforced polyester resins are regulated in DIN 18820 Part 1. Part 2 details physical parameters such as the stiffness and strength of the most typical laminates. Part 3 goes on to describe necessary protection measures and reduction factors for strength properties depending on environmental influences, while Part 4 discusses testing procedures and quality control. Parts 1 to 3 of DIN EN 13706 detail specifications for pultruded profiles, regulations for testing procedures and general requirements, and define two quality grades, E23 and E17, along with their minimum properties. Very useful guidelines for the development and calculation of FRP building elements can be found in the VDI Association of German Engineers’ guideline 2014. The draft recommendations by the German BÜV Association for Construction Supervision on “Tragende Kunststoffbauteile im Bauwesen (TKB)” (loadbearing plastic building elements in construction) detail a safety concept for the dimensioning of plastic building elements, and take into account factors such as manu­ facturing technique, exposure period and conditions of use. The EUROCOMP Design Code and Handbook provides a comprehensive overview of the state of the art of designing and constructing building elements made of fibre-reinforced plastics. Various manufacturers also provide sometimes quite extensive technical documentation including details of manufacturer-specific material properties and design principles. Analytical and experimental design methods

There are a number of different analytical methods for designing building elements made of fibre-reinforced plastics. According to the classical lamination theory, a

THERMOSETS

6.18  Testing procedure for a plastic beam with finite-element calculation shown below for comparison.

6.18

building element is broken down into its individual layers. The properties of the individual layers are dependent on the fibres used and the matrix. After determining the extension, the stresses in each of the layers are then determined. For this method it is necessary to know the precise structure of the layers of the laminate. For more simple preliminary dimensioning so-called “carpet plots” can be used. These diagrams provide an indication of the properties of the modulus of elasticity and thermal expansion in different directions with respect to proportional layer thickness for a selection of standard laminates. This means of modelling is only used in certain circumstances in structural design as for most semi-finished products, such as pultruded profiles, it is impossible to know the exact fibre orientation. As a result the stresses are typically determined for the cross section of the entire element and then compared with characteristic strength properties. The behaviour of a building element under load can be determined using traditional structural calculations or finite-element calculation. The fact that many plastic building elements exhibit pronounced creep behaviour over time is compensated for through the use of reduction factors that take account of the load duration, environmental influences and the effects of temperature. The strength of fibre-reinforced plastics is dependent on a large number of influencing factors such as the geometry of the building element, its manufacture and fibre content proportion. In many cases it is not possible to derive sufficiently 6.18

precise material properties through calculations alone. In such cases it is necessary to determine the required properties, such as strength and stiffness, through

93

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BUILDING WITH PLASTICS

material and building element testing procedures. To determine the characteristic limits, tests are usually undertaken on five or more samples.

Stability and durability Fibre-reinforced plastics are very durable and highly resistant to environmental influences. Damages resulting from water ingress within the laminate or UV deterioration have thankfully become less and less common as a result of on­going efforts to optimise the material components. Nevertheless building elements made of FRP need to be coated with a protective surface coating such as gelcoat or a varnish to ensure sufficient long-term durability. In the pultrusion process, synthetic nonwovens are also used to improve the robustness of the surface layers. It is likewise essential to protect all cut edges. Finally, all loadbearing building elements made of fibre-reinforced plastic need to be monitored periodically for mechanical defects, crack formation within the laminate, blistering or swelling.

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7

Plastics as building envelope

The applications of plastics in construction are many and varied, ranging from technical installations to interior furnishings and fittings, from façade applications and plastic coatings for entire buildings to high-performance loadbearing structures made of plastic. After a long period in which plastics were used predominantly only in special fields such as industrial and process engineering or for components of technical installations in buildings, they are now being increasingly used in construction as part of the building envelope and supporting structure. While the rich formal language of plastic buildings from the 1960s and 1970s continues to hold a strong fascination, research and development has progressed significantly since then. In contrast to this pioneering period of plastic architecture, a large range of economically competitive and aesthetically interesting plastic products and semi-finished products are now available. The latter in particular has given rise to cost-motivated approaches to using inexpensive semi-finished products, especially for the building envelope. In addition, plastics are now widely used in numerous areas of everyday life, and prejudices against the application of plastics in architecture are no longer as pronounced as they once were. The projects described in the following sections show predominantly, but not exclusively, new examples of the use of plastics in architecture. A differentiation is drawn between the use of plastics in the building envelope (chapter 7) and for the loadbearing structure (chapter 8), a common categorisation as the building envelope and supporting structure serve different purposes. A combination of both the enveloping and loadbearing functions in a single layer (chapter 9) is a particularly demanding area of building construction. It is not always possible to clearly attribute an example to one or the other categorisation as the enveloping function almost always involves supporting loads, although usually across shorter spans. This chapter shows examples where plastics form either part or the whole of the building envelope. Façades characterise the architectural expression of a building. They separate indoors from outdoors and provide protection against the weather while simultaneously allowing light to pass through. The many different options which plastics offer – in terms of their colour, surface qualities and light transmission properties – are a primary reason for their use in façades. In addition to design considerations, a key aspect of building envelopes is whether or not they are able to fulfil functional requirements such as thermal or noise insulation. For the most part such requirements can only be realised in combination with additional layers, such as thermal insulation or thermal glazing, or by using sandwich elements. Modern façade constructions are, therefore, much more complex than they used to be but also much more effective. Plastics contribute to this efficiency.

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CASE STUDIES

Chanel Mobile Art Pavilion

Location  Hong Kong, China; Tokyo, Japan; New York, USA Material  GRP (façade), ETFE (skylights) Completion  2008

Architecture  Zaha Hadid Architects Structural engineering  ARUP GRP elements manufacturer  Stage One Creative Services Ltd

The mobile pavilion for the fashion company Chanel serves as an exhibition space for artworks inspired by Chanel that have been specially created for the pavilion. It was conceived as a temporary building for use in different metropolitan cities throughout the world. The spatial concept is based on the shape of a torus whose plan has been distorted into a triangular shape. The entrance to the pavilion is via a terrace that lies between the exhibition space and a ticket office. The exhibition area of the 700 m2 pavilion is arranged around a 65 m2 central courtyard that serves as a rest area and can be used for special events. Skylights made of ETFE cushions in the outer ring and over the inner courtyard provide natural illumination during the day. The main construction of the 6 m high pavilion consists of a steel skeleton framework. The curved steel ribs made of I-sections, whose radial arrangement follows almost exactly the complex geometry of the building, serve simultaneously as the supporting construction for the sections of the plastic façade. The GRP elements have a lip around their edges and are bolted to the supporting construction through factory-glued and screwed steel anchor plates at the seams. The seams between the plastic panels rhythmically delineate the surface of the building’s shell. The building geometry was developed with the help of digital design and modelling tools. This made it possible to effect a continuous digital process from the design to the production of the individual elements. Because of the changing curvature of the building volume, an individual mould had to be built for each of the 400 GRP elements. The GRP elements were then manufactured in a hand lay-up process and lacquered. The 12 mm thick elements are a sandwich construction with different core layers and two polyester resin facing layers. The required fire ­behaviour properties of the GRP elements were ascertained using test procedures. The ­surface of the interior is formed by an elastic textile membrane. The dimensions of each of the individual building segments are no wider than 2.25 m for transport reasons. The project is a spectacular demonstration of the uncompromising conversion of a complex design into built reality and showcases impressively the shaping possibilities of plastics.

97

PLASTICS AS BUILDING ENVELOPE

1 Chanel Mobile Art Pavilion in Central Park, New York.  2 Detail of the façade.  3 Erecting the façade.  4 Organisation of building functions.

1

2

3

4

A

Exhibition area

Interior courtyard

B

Cloakroom Terrace

Tickets

Entrance

A 01

5

10 m

B

98

CASE STUDIES

BMW Bubble

Location  Frankfurt and Berlin, Germany Material  PMMA Completion  1999

Architecture  Bernhard Franken with ABB Architekten Structural engineering  Bollinger + Grohmann ­Ingenieure Contractor  Metallbau Pagitz

The BMW Bubble was conceived in 1999 as an exhibition pavilion for the IAA Motor Show in Frankfurt. The computer-generated form is derived from the notion of two droplets of water that are about to merge. The drops of water are a metaphor for the topic of the exhibition – Clean Energy – which describes the development of alternative means of vehicle propulsion. The 24 m long, 16 m wide and 8 m high pavilion was originally intended as an entirely self-supporting, transparent plastic envelope. It would not, however, have been possible to bond the sheets together to form a self-supporting structure within the available time. Instead, an alternative structural approach had to be developed to realise the architectural concept efficiently and economically. The structural concept that was implemented derives from a plywood rib construction that was used as a supporting framework during the trial assembly of the plastic skin. The primary loadbearing structure consists of perpendicular interlocking aluminium ribs. Each of the individual ribs consists of three layers of thin sheet aluminium bolted together. The skin of the building consists of 305 separate spherically curved panes with a thickness of 8 mm, which together cover a total surface area of 960 m2. The individual panes were thermoformed on moulds made of milled PUR blocks. The PMMA panes serve to stiffen the structure and are held to the underlying ribs by clips in the seams between the panes. The joints are wet-sealed with silicon mass. The pavilion has two ground-level fire escapes and is equipped with an indoor sprinkler system to fulfil fire safety requirements. A particularly innovative solution was developed for the entrances. The entrance doors, like the skin, are also spherically curved plastic panes. Supported on standing ribs, the door slides outwards along two rails to allow people to enter. The door opening is clad with an aluminium frame cut to fit the curved surface of the building.

99

PLASTICS AS BUILDING ENVELOPE

1 An innovative solution had to be found for the doors of the spherically curved structure: the door slides

outwards on parallel rails.  2  BMW Bubble at the IAA Motor Show in Frankfurt.  3 Construction phase: the upper section of the Bubble is already covered with panes of PMMA.

1

2

3

100

CASE STUDIES

Kunsthaus Graz

Location  Graz, Austria Material  PMMA Completion  2003

Design team Kunsthaus consortium: ­spacelab-cook fournier, Bollinger + Grohmann Ingenieure, ­Architektur ­Consult ZT

The friendly alien was the result of a competition initiated by the City of Graz. Peter Cook and Colin Fournier’s winning concept represents a spectacular architectural gesture. The planning and realisation of the project was undertaken by an interdisciplinary consortium of architects and engineers formed especially for the project. The footprint of the organically formed museum measures 64 × 40 m. The building is clad with a translucent plastic façade with open panel joints that envelope an inner insulated, weatherproof layer. Its distinct appearance is heightened by the so-called nozzles (light funnels) on the roof, which were originally conceived as being movable to follow the course of the sun. The main structure of the building is a steel triangulated shell construction which forms a polygonal approximation of the building’s geometry. The outer shell is made of sheet steel sandwich panels and an external 160 mm thick layer of insulation covered with a plastic membrane. The weather-impervious skin is clad with spherically curved PMMA panels, each approximately 2 × 3 m, that together create the impression of an organically curved surface. The differently curved individual panels were thermoformed over individually CNC-milled moulds made of PUR blocks. The 20 mm thick, blue-coloured PMMA panels are fixed to mounting brackets via drilled stainless steel point mountings at a distance of approximately 30–70 cm from the underlying structure. The PMMA panels have a statically determinate mounting to avoid constraint stresses arising as a result of thermal expansion. The joints between the panels are open; rainwater flows off the membrane beneath the PMMA panels. Sprinkler nozzles arranged at regular intervals between the panes are an integral part of the fire safety concept. The 1300 cast PMMA ­panels have also been given a flame-retardant coating. Mounted behind the translucent PMMA panels are individually controllable circular fluorescent lamps which together with the plastic skin transform the building’s surface into a media façade.

101

PLASTICS AS BUILDING ENVELOPE

1  Kunsthaus Graz.  2 Mounting of the PMMA elements on the mounting brackets. The grey surface

of the building skin is the water-impervious layer.  3 Detail section through the roof construction.  4 Mounting bracket for the plastic sheets with sprinkler nozzle.

1

2

a Acrylic glass, 20 mm  b  Plexiglas point fixing with elastic supports  c Mounting bracket, positionable  d Sprinkler nozzle  e Sprinkler line  f  BIX media lights  g Electric line  h Stainless steel mounting bar with Ø 30 mm holes  i Plastic waterproofing membrane, glued, 9 mm  j Elastomeric bituminous membrane  k Foam glass insulation, 160 mm  l  Additional waterproofing  m F30 steel panel with rock wool insulation  n Main steel beam  o Cavity for ductwork  p  Internal skin: m ­ etal mesh fabric

d a

b c

h

4

g

e

f i, j

o

n

p

k

l

m

3

102

CASE STUDIES

Emsdetten RAILWAY Station

Location  Emsdetten, Germany Material  GRP, PMMA Completion  2002 (bus station); 2009 (platform roof and subway)

Architecture  OX2architekten Structural engineering  Ingenieurgemeinschaft Führer-Kosch-Jürges (bus station); DB Projektbau GmbH (railway station) Plastics contractor (bus station)  BWH-Bücker Kunststoffe

A railway platform roof with subway and the central bus station are the main elements of the renewal and revitalisation concept for Emsdetten railway station. The first stage to be realised was the bus station. The 50 m long roof of the bus station is supported by a steel construction. The modular structure consists of five three-dimensional X-shaped columns arranged along the central axis of the platform connected by pairs of curved tubular profiles arranged symmetrically about the central axis. The roof covering consists of coloured GRP “sails” and a tiered arrangement of glazing strips made of pointmounted laminated safety glass. The GRP elements with triangular plan span a distance of approximately 10 m stiffened by a 100 cm deep eaves strip along its leading edge that also shields against heavy rain. Each of the 900 kg GRP modules covers an area of 25 m2. The hollow GRP elements consist of an upper and a lower skin assembled together with integral ribbing to form a cantilevering element. For the manufacture of the GRP elements, a positive form of a single module was first constructed from which a negative impression was then taken for use as a mould for laminating. The separate upper and lower skins were then factory-bonded in the workshop and the joints sanded and polished. The approximately 6 mm thick polyester resin laminate is reinforced with scrim matting. The colour is achieved by colouring the protective gelcoat surface coating. Each of the triangular plastic elements are bolted at ten points along their flat edges to the steel supporting construction. A small lip along the inward edge dissipates rainwater. The moulded GRP elements are floodlit at night and serve as indirect lighting for the bus stops. The railway platform roof follows a similar principle to that of the bus station and is likewise a steel construction with coloured GRP elements overhead and coloured glazing mounted between them. The ten yellow-coloured GRP elements each cover a surface area of 23 m2. Further, the entrances to the subway beneath the railway lines are marked on each side by so-called “flyers”. These roof constructions over the entrances consist of a cantilevered steel skeleton construction supported by two columns that flank each entrance. The roof covering over the steel construction consists of translucent PMMA panels which have been ­coloured orange on the top and along the edges and translucent white on the underside. A scalloped arrangement of the panels at the top and sides prevents water from penetrating the construction. The design and plastic covering of the two “flyers” on either side of the railway lines is continued below ground. Here the panels are mounted flush on a steel subconstruction. The plastic panels are fixed by drilled point mountings in the panels.

PLASTICS AS BUILDING ENVELOPE

The lighting is arranged on the ceiling of the subway behind the panels, resulting in an underpass that not only fulfils safety requirements but also creates a continuous aesthetic experience. The use of plastic panels with a B2 fire safety ­rating made it necessary to undertake a fire safety analysis. The plastic building elements used in both constructions demonstrate the successful implementation of modularised construction methods and the prefabrication of plastic elements.

1 Site plan. Railway platform with roof and subway beneath the tracks and central bus station on the

­railway station forecourt.  2  Bus station roof in Emsdetten.

1

0

2

10 m

103

104

CASE STUDIES

3 Longitudinal section and roof plan of the bus station.  4 Diagonal view from above showing the

­ odular steel construction that carries the GRP roof covering. Glazed areas suspended from m the steel ­construction alternate with the coloured GRP elements.  5 Mounting of one of the saillike GRP ­elements of the bus station roof.

3

0 1

4

5

5

10 m

PLASTICS AS BUILDING ENVELOPE

6  “Flyers” with a coloured translucent PMMA covering mark the entrances to the subway between the platforms.  7  Section through the “flyer“ with railway platform subway.  8 Edge detail at the sides: the overlapping PMMA panels are fixed to the steel supporting structure via drilled point mountings.

6

7

8

105

106

CASE STUDIES

Idee Workstation

Location  Tokyo, Japan Material  Polycarbonate Completion  1996

Architecture Klein Dytham architecture Polycarbonate contractor  Asahi Glass

Idee Workstation is a showroom for a Japanese furniture manufacturer that was erected on the site of a former petrol station. The showrooms extend across all three storeys and are fully glazed on the street frontage. In the two upper storeys, the façade is conceived as a twin-skin construction: an inner layer consisting of floor-to-ceiling glazing that extends over the height of the building, with sections covered with transparent, coloured foil; and an outer layer consisting of a plastic screen that acts as a filter to screen off the fragmented urban surroundings of the neighbourhood and create a calm interior for the visitors and shoppers. The external layer of the façade consists of a single curved, colourless poly­ carbonate multiwall panel fixed with the help of U-profiles. The façade profiles are fixed to steel supports that project from the building structure. The façade faces west so that the light of the afternoon sun is filtered by the lightweight trans­ lucent plastic screen, projecting coloured patches of light onto the floor and walls of the interior. The façade sets up an interplay of different degrees of transparency, offering optimal lighting conditions during the day for the showrooms and turning the building into a shining object at night. To fulfil the fire safety requirements, the hung plastic veil is not considered part of the building but has been declared as an applied design element for advertising purposes.

107

PLASTICS AS BUILDING ENVELOPE

1 General view of Idee Workstation.  2 Night view of the façade.  3 Interior view: sunlight shines

through the slightly translucent polycarbonate multiwall panels and through coloured foils applied to the glass panes of the inner façade.

2

1

3

108

CASE STUDIES

Reiss Headquarters

Location  London, United Kingdom Material  PMMA Completion  2007

Architecture  Squire and Partners Structural engineering  Fluid Structures Plastics manufacture  Heinz Fritz Kunststoffverarbeitung

The new headquarters for the British clothing retailer Reiss is a distinctive building that serves both as a flagship store and headquarters with design studios, ateliers and offices on the upper floors. The architectural concept is characterised not least by the striking façade made of milled sheets of PMMA that lends the building a strong and identifiable presence. Conceived as a translucent visual filter, it provides only glimpses of the different activities contained within the building. The plastic sheets form a facing skin with open horizontal and vertical joints mounted 60 cm in front of the glazed exterior of the building. The three-dimensional texture of the plastic surface awakens associations with a garment drawn across the face of the building. The panes of clear cast PMMA are 1.50 m wide and between 3.80 m and 4.20 m high depending on the storey height. The 50 mm thick sheets exhibit a high light transmittance of almost 90 % and have in sections been milled with the help of CNC machinery to a material depth of 30 mm. Vertical stripes of different width and depth have been cut out of the material’s surface, some of which have in turn been given an even finer, more detailed milled surface structure. In combination with further surface treatments, such as partial frosting or polishing, this produces a dramatic three-dimensional effect. LED rails along the bottom edge of the PMMA sheets illuminate the panels, causing the matt surfaces to radiate across the entire building façade. The 72 sheets of plastic that comprise the façade weigh a total of approximately 30 tonnes. The vertical load is borne by a series of linear, horizontal bearings made of steel profiles at the base of the PMMA sheets. To stabilise the panels against wind loads, 10 mm diameter stainless steel rods anchored to the supporting construction slot into channels cut into the centre of the vertical edges of the panels. Mounted at four points over the height of a panel onto the supporting construction, they hold the panel in place.

109

PLASTICS AS BUILDING ENVELOPE

1 Reiss Headquarters.  2 Detail of the façade with logo.  3 CNC-controlled production process.  4 Façade construction detail, horizontal section.  5  Façade construction detail, vertical section.

1

2

3

4

a  80 x 200 mm steel mullion, at door only  b Structural silicone façade system: 2 × 6 mm laminated safety glass with 0.76 mm PVB interlayer; 16 mm argon gap; 6 mm toughened glass  c Cable tray  d PPC-milled bright steel panel, loading ­bracket ­mechanically restrained back to structure  e  Tear drop machining to each ­vertical edge to reduce friction coefficient  f Stainless steel lateral loading rods ­mechanically restrained back to structure  g  50 mm thick acrylic panels with vari­ ous finishes and depths  h  Triangular milling pattern  i Frosted  j  Transparent  k Rectangular milling pattern

a Structural silicone glazing (SSG)  b Maintenance walkway  c LED lighting strip  d External façade ­panels, milled PMMA sheets  e  600 mm wide cavity to create a chimney effect

a b a

c

b d e

c d e f

g h

i

j

k

5

110

CASE STUDIES

Fiberline Composites factory and offices

Location  Middelfart, Denmark Material  GRP Completion  2006

Architecture KHR Arkitekter Structural engineering  Strunge & Hartvigsen GRP manufacture  Fiberline Composites A/S

The Fiberline factory and office building looks a little like an artificial hill embedded in the landscape and serves, among other things, as a demonstration project to showcase the use of the company’s own products made of pultruded fibre-re­ inforced plastic. The 330 m long and up to 20 m high building is conceived as a large space that unites several functions under one roof. The conference rooms behind the three giant window bands that appear to slice through the building are, like the offices, separated from the large space only by glazed partitions. The loadbearing structure of the building is a steel construction. GRP semi-finished products from the company’s own production have been used for the façade and parts of the interior. 40 mm thick and 500 mm wide pultruded multiwall panels with a wall thickness of 4 mm were used for the external cladding of the ventilated, insulated façade. The elements are weather-resistant and connected to one another by a tongue and groove profile. The supporting structure for the façade in the glazed sections, and the subconstruction for mounting the multiwall panels are also made of pultruded GRP profiles. The surface of the façade has a pronounced linear striation that results from the pultrusion process. The translucent façade panels have a glass fibre content of up to 70 % and are classified as building material class B1. They were developed by Fiberline especially for use in façade applications and have also been used in subsequent projects.

1

111

PLASTICS AS BUILDING ENVELOPE

1 Close-up of the façade.  2  Three large bands of windows slice through the building.  3 General view.  4 Detail section of the façade.

2

3 4

a Glass/GRP double-glazed window  b Façade construction: ­ventilated pultruded GRP multiwall panels as external façade cladding; 32 mm vertical façade supporting construction; 200 mm façade ­insulation element  c  Window sill, GRP profile  d Hollow cable duct  e Steel column, HEA 220  f Radiator

a

c d b e

f

112

CASE STUDIES

Farben des Konsums

Location  Berlin, Germany Material  Recycled thermoplastic material Completion  2003 (temporary)

Design  Bär + Knell: Beata Bär, Gerhard Bär, Hartmut Knell

“  Die Farben des Konsums” (The Colours of Consumption) is a light ­installation project made of recycled plastic packaging materials that has been staged at ­several different locations. Originally created as part of an exhibition entitled “  Kunst, Kunststoff, Kunststoffrecycling” (Art, Plastics, Recycling) by the German Asso­ciation for Plastics Recycling (DKR), the wall of coloured light was installed along a 144 m stretch of a tunnel and future underground station of the U3 line beneath the Potsdamer Platz in Berlin. The exhibition also featured the work of various artists and companies that produce high-quality designs, for example furniture, out of recycled plastic material. The intention is that visitors grasp a better understanding of the raw materials cycle through the aesthetic quality of the objects and that this will heighten consumer awareness of plastic packaging and recycling. The name of the project refers to the proportional distribution of colours in the packaging material of everyday consumer goods. For example, the white colour is derived from the plastic bottles used for mineral water. Once the plastic pack­ aging had been sorted by colour, they were then ground down to granulate. The plastic elements were created through hot-pressing. Initially, individual items of furniture and small runs were produced in this way. The plastic panels used in the installation “Die Farben des Konsums” were handmade by the artists and illuminated from behind.

PLASTICS AS BUILDING ENVELOPE

1  “Farben des Konsums” light installation in an unused part of Potsdamer Platz underground station

in Berlin.  2  The surface areas of each colour of the backlit plastic elements is proportional to its use in plastic packaging.

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CASE STUDIES

Laban Creekside

Location  London, United Kingdom Material  Polycarbonate Completion  2003

Architecture  Herzog & de Meuron Structural engineering  Whitby Bird & Partners Façade planner and contractor  Emmer Pfenniger Partner AG Manufacturer of polycarbonate multiwall panels  Rodeca Colour concept  Michael Craig-Martin

Laban Creekside is a complex in the Deptford district of London that consists of a public garden and the Laban Centre building, an internationally renowned centre for modern dance. The 80 × 40 m large building, named after the Austrian-Hungarian dancer Rudolf von Laban (1879–1958), houses a theatre, a lecture hall, a library, 13 dance studios, physiotherapy treatment rooms as well as a café and bar. The theatre for 300 visitors forms the centre of the building. The curved west façade opens with an inviting gesture onto the garden. The building’s envelope consists of two layers. An external plastic skin made of 4 cm thick, triple-layer polycarbonate multiwall panels stands at an offset of 60 cm in front of an insulated concrete wall punctuated with areas of thermal glazing. In the glazed areas the panels serve as a glare shield. Transparent and translucent sections of the façade produce a lively interplay of light and shadow on its surface. This effect is underlined by the colour concept of the plastic elements, developed by the architects in conjunction with the British artist Michael Craig-Martin. The plastic skin consists of polycarbonate multiwall panels with a co-extruded, coloured rear surface that lends the plastic elements a three-dimensional quality depending on the angle of view. The polycarbonate panels are held by small, vertical profiles that hook into a slot in the panels and are fixed to horizontal aluminium box-section rails which in turn are bolted to the structure of the façade. A tongue and groove arrangement along the vertical joints of the extruded multiwall panels ensures a flush external surface. For the corners a custom solution was developed using an acrylic glass cover plate bent to fit the corner. The Laban Centre is a successful example of the potential of plastics for expressing colour and light.

115

PLASTICS AS BUILDING ENVELOPE

1 Garden elevation with coloured polycarbonate multiwall panels.  2 Floor plan, mezzanine level.  3 Horizontal section showing corner detail.

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a Studio  b  Work room  c  Office  d  Bar  e  Teacher  f  Theatre  g Studio  h Lecture room ­ i Library  j Internal courtyard

a Acrylic glass panel, curved, transparent, 3 mm, bonded with:  b Acrylic glass ­ anel, curved, transparent, 5 mm  c Steel cable, ø 6 mm  d  Three-layer polycarbon­ p ate multiwall panel, 40 × 500 mm, transparent, rear face with co-extruded colour

d i

a e j f b

c g h c

a b

c d

3

116

CASE STUDIES

Terminal V

Location  Lauterach, Austria Material  GRP Completion  2002

Architecture  Hugo Dworzak Structural engineering  TBM-Engineering GmbH GRP manufacture  Hähl Kunststofftechnologie GmbH; SSC AG

Terminal V (V stands for “virtual reality”) is a modern office and presentation building for a large housing contractor with an energy-efficient and user-friendly climatic concept. Attached to one end of a three-storey wing with offices and semi.

nar rooms is a single-storey presentation building clad with GRP façade elements whose interior is reminiscent of an airline cabin. This area is used to provide ­clients with a virtual experience of their prospective living environment by projecting a three-dimensional visualisation onto a curved panorama wall at a scale of 1:1. This section of the building is consciously conceived as a separate volume in order to separate the virtual world from the reality of the working environment. The presentation wing is raised off the ground and accessed by an external stair as well as from the upper floor of the office wing. Much like embarking on a flight, it presents an artificial, introverted environment. The supporting structure for the GRP shell is a steel framework construction that rests on a reinforced concrete foundation slab. The form of the steel profiles corresponds to the cross section of the building. The plastic cladding elements are folded back at the edges to form a lip used to attached them to the building structure. The GRP elements are bolted to the steel construction with the help of thread inserts embedded into the GRP laminate. The segments at the end of the building are shaped to increase their stiffness and fixed only at the top and bottom on each side. Each façade element is no wider than 2.50 m for logistical reasons, and only three basic modules were required for the external skin. The GRP elements were manually fabricated in a hand lay-up process with a polyester resin matrix. Once the resin had hardened, a 30 mm thick layer of insulation was applied to the inner surface of the GRP elements using a vacuum application process. The GRP layers have a thickness of between 3 and 10 mm, depending on the load it has to sustain. In the interior of the presentation wing, the walls are lined with a translucent plastic foil which is illuminated from behind. Using diffuse light together with changing colours it is possible to create different atmospheres in the interior.

117

PLASTICS AS BUILDING ENVELOPE

1 Exterior view.  2 Interior with plastic foil wall lining.  3 Mounting of the GRP shell elements.  4  First floor plan.

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118

CASE STUDIES

Forum Soft

Location  Yverdon, Switzerland Material  Glass fibre-reinforced polyester Completion  2002 (temporary)

Architecture  Vehovar & Jauslin Architektur Structural engineering  Staubli, Kurath & Partner AG, Zurich Concept and manufacture of plastic elements  Swissfiber AG, FVK composite plastic fibre research group at the Zurich University of Applied Sciences Winterthur (ZHAW)

The Forum Soft was realised for the 6th Swiss National Expo in 2002 as part of the Arteplage (“art beach”) in Yverdon. It forms an artificial roof landscape made of coloured GRP elements and covers an area of 12 000 m2 with exhibition areas and pavilions. The 12-month duration of the Expo meant that the project had to be realised within tight cost constraints. A steel construction consisting of slanting columns and fish-belly beams forms the main loadbearing structure of the landscape of roofs. The inclination of the columns and geometry of the trusses changes to fit the irregular overall form resulting in a different shape in each axis. The supporting structure is clad above and below with a total of 42 000 coloured plastic profiles with a U-shaped section. These span the distance between the supporting axes with the help of a 15 cm high stiffening upstand along their edges. With a thickness of only 2 mm, the GRP profiles can be warped and can therefore be easily bent to fit the twists of the ­double-curved surface. The translucent skin of the GRP elements in combination with openings be­t­ ween the different sections of the roof landscape ensure sufficient natural illumination during the day. At night the surface of the roof is floodlit from below. The GRP profiles on the upper surface employ an arrangement familiar from traditional mission roof tiling to facilitate rainwater runoff. The guttering made of clear GRP is fixed at regular intervals to the top flange of the fish-belly beams. The coloured elements on the upper surface are bonded to the rainwater gutters and riveted in place. The GRP profiles on the lower surface of the roof trusses are hung by metal brackets riveted to the plastic elements from the steel construction. The up to 8 metre long and 0.4–0.8 m wide elements were fabricated manually using a hand lay-up process using a few standard moulds. The length was then adjusted to fit during erection on site. The colours were achieved by dyeing the poly­ester resin yellow, orange and red. Due to the temporary nature of the construction, an additional weather-resistant layer of gelcoat was not applied.

119

PLASTICS AS BUILDING ENVELOPE

1 A landscape of plastics with overlapping sections.  2 Interior view.  3 Aerial view.  4 Cross section

showing structural system.

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120

CASE STUDIES

Polymer Engineering Centre

Location  Melbourne, Australia Material  GRP Completion  2001

Architecture  Cox Architects & Planners Structural engineering  Warren and Rowe Façade contractor  Ampelite, Axcess Roofing

The 2200 m2 Polymer Engineering Centre of the Kangan Batman Institute of Tech­ nical and Further Education (TAFE) is a training centre for employees in the plastics industry. Alongside seminar rooms and laboratories, the building contains workshops and fabrication and processing facilities. The use of plastics for the external skin of the building is intended not only to reflect its use and function but also to demonstrate the advantageous properties of the plastics. The form of the 75 m long building has a constant cross section that echoes the extrusion process used in the manufacture of plastics. Trussed beams made of steel, arranged at 9 m centres perpendicular to the longitudinal axis of the 21 m wide building, form the main structure of the building. A curve in the north-west façade lends the building its striking form. The skin of the façade and roof share the same construction. A twin-skin façade provides suffi­ cient natural illumination while also reducing the amount of cooling necessary for the building. The secondary beams slung between the trusses take the form of parallel chord trusses with a construction depth of 40 cm. They represent the bearing points for the corrugated GRP façade elements of the inner and outer skin and define the depth of the space between the two skins of the façade. The corrugated profile of the GRP elements follows the curvature of the building and is sufficiently stiff to span the distance between the cross-members. The radius of curvature is minimal at 4.80 m. The plastic sections are fixed to the steel trusses of the façade with bolts and special sealing washers. The bolt holes were drilled larger than required to allow for stress-free thermal expansion. The clear translucent GRP panels have been given a gelcoat surface covering to reduce the thermal radiation by 23.5 %, which contributes considerably to reducing the energy demand in the hot and arid Australian climate. The façade is also partially insulated. The surface treatment also provides UV protection and prevents the plastic from yellowing over time. The light transmission degree of 38 % allows for suffi­cient overall daytime lighting. At night, the translucent plastic skin is illuminated transforming it into a white shining object.

PLASTICS AS BUILDING ENVELOPE

1 Day view of the long side of the building.  2 Night view.  3 Entrance area of the Polymer Engineering Centre.  4 Cross section.

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a Prototype and testing  b  Toilet  c Open corridor  d Fabrication and thermoforming  e­ C omputer room

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e 10 m

121

122

CASE STUDIES

Dornier Museum

Location  Friedrichshafen, Germany Material  Polycarbonate Completion  2009

Architecture  Allmann Sattler Wappner Architekten Structural engineering  Werner Sobek Engineers Façade consultancy  R + R Fuchs

The building is a private museum that records the history of the legendary aviation company Dornier. It is located directly adjacent to Friedrichshafen regional airport. Models of historical aircraft as well as numerous documents from the time allow visitors to experience the history of aviation and space travel first-hand. The footprint of the museum, which takes the form of a large hangar, mea­sures 112 × 54 m. The scenographic presentation of the individual periods of the company’s history are shown in exhibition boxes placed within the building. Two translucent façades, curved in one axis and made of polycarbonate multiwall panels, bound the interior space to the north and south. To the north, the façade arcs ­gently inwards in response to a pathway in front of the airfield, the oversailing roof protecting the restaurant terrace from the rain. To the south, the steel girders of the roof construction project out of the façade. A curved polycarbonate wall in front of the building forms the entrance area, which is also roofed over with plastic panels. The end walls of the interior to the east and west are fully glazed with transparent glass. The polycarbonate panels extend the full height of the building and are fixed to the supporting structure with metal brackets to form a light-permeable façade with additional insulation. Commonly used as an economical solution for industrial buildings, the material evokes associations with a hangar, responding intentionally to its surroundings. The 40 mm thick façade panels made of whitish polycarbonate are 50 cm wide and divide the façade almost imperceptibly into a pattern of segments. On the south face, a grid of dots has been applied to the exterior of the façade elements to reduce the effects of direct sunshine. The grid disguises the linear pattern of the polycarbonate panels. The lack of a clear structure communicates the impression of a wall; the transparency of the material conveys a contrasting permeability. The occasional door and window openings are framed like shop windows providing an indication of the scale of the building. The polycarbonate panels on the north face of the building have not been printed. The curved arc of the polycarbonate panels appears from outside in part like a filter, offering schematic glimpses of the interior, and in part like a mirror reflecting the expanse of the airfield outside. On the interior, the light-diffusing plastic panels filter the sunlight to create a subdued, naturally illuminated interior.

123

PLASTICS AS BUILDING ENVELOPE

1 General view of the Dornier Museum in Friedrichshafen.  2 Polycarbonate façade in the restaurant area.  3 Detail of the façade mounting bracket with printed polycarbonate panel.  4  Ground floor plan.

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124

CASE STUDIES

BADAJOZ Congress centre and auditorium

Location  Badajoz, Spain Material  GRP, PMMA, polycarbonate Completion  2006

Architecture  SelgasCano Structural engineering  Fhecor GRP design  Pedelta GRP profiles  Fiberline Composites A/S

Plastics have been employed in particularly varied ways in the Badajoz congress centre and auditorium in south-west Spain. The circular shape of the approximately 15 000 m2 large building complex is inspired by the bullring that once stood on the site. Other functions in the building are arranged below ground radially around the auditorium. Surrounding the congress centre building is an external ring with a diameter of 75 m and a height of 14 m, whose design resembles traditional wickerwork. The individual strands of the giant fence-like woven structure consist of pultruded GRP profiles that are both durable and self-supporting. The translucent strands have a horizontal elliptical profile with grooves in one side, which are used to fix the tubes to steel masts at 8 m intervals and to one another at their ends. For the rounded form, the initially straight profiles were first cut to length and then bent to shape. A total length of 12 km of pultruded GRP profiles were used for the lattice construction. The external envelope of the auditorium consists of an inner glass façade with a 1 m offset external sunscreen consisting of horizontal acrylic glass tubes. The whitish-translucent PMMA tubes have a diameter of 120 mm and a wall thickness of 3 mm and filter the bright sunshine, creating a diffuse and evenly illuminated interior. The tubes are anchored to the supporting construction by plastic connecting pieces that join the tubes. At night, floodlights in the space between the inner and outer skin illuminate it from within, lending the congress centre the appearance of a white shining object. Plastics are also used in the interior of the auditorium. White backlit polycarbonate panels are used to clad the walls and balcony parapets. The Badajoz congress centre and auditorium is not just an example of the successful integration of a new public building into the organic historic structure of the city but moreover illustrates the potential of plastics for unusual façade applications.

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PLASTICS AS BUILDING ENVELOPE

1 Section through the auditorium.  2  White PMMA tubes encase the auditorium, creating the ­impression

of an illuminated volume.  3  Ground floor plan of the congress centre and auditorium, which was i­ nserted between the historical bastion walls of Badajoz.

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50 m

125

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CASE STUDIES

4 Interior of the auditorium with backlit parapet cladding made of polycarbonate panels.  5 Door in the

façade of the auditorium.  6 Section through the façade of the auditorium.

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250

a Roof construction, steel  b  Thermal glazing  c Steel column, 500 × 100 mm  d Rectangular section, galvanized steel, 25 × 50 × 3 mm  e Rod, ø 16 mm, welded to the column and supporting structure  f Connecting piece to steel column, rectangular tube, galvanized steel, 50 × 25 × 3 mm  g PMMA tubing, translucent white, ø external 120 mm, wall thickness 3 mm

Section: eaves detail

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Section: connection of the PMMA tubing to the building

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Horizontal section: connection of the PMMA tubing to the building

127



8

Plastics as building structure

Fibre-reinforced plastics are most commonly used for supporting structures because of their comparatively high strength. They are typically used in the form of pultruded semi-finished products or special, individually handmade building elements. The examples and case studies in this chapter show a series of applications for geometrically complex special buildings that could not have been realised as easily with other materials, for example a plastic tower sculpture and an unusual and innovative composite construction made of glass-reinforced plastic and glass. In practice, the use of plastics in loadbearing applications is restricted by the need to fulfil fire safety requirements on the one hand and the relatively low stiffness of plastics on the other. Consequently, structural plastic elements exhibit comparatively large deformations under load, limiting their suitability for use in buildings. As a result, plastics are rarely used for supporting structures with wide spans or limited deformation tolerances. However, for engineering structures such as bridges, where fire resistance durations are not an issue and plastics can be combined with other materials to form high-performance and sufficiently stiff composite constructions, the use of plastics for loadbearing structures is currently an ongoing development.

128

CASE STUDIES

Plastic tower sculpture

Location  Stuttgart, Germany Material  Glass fibre-reinforced polyester resin Completion  2007

Architecture, structural engineering and manufacture  Stuttgart State Academy of Art and Design (SABK), Stephan Engelsmann, Valerie Spalding, Franciska Ganns, Apostolos Michailidis and others

The tower sculpture, designed and fabricated in-house using a hand lay-up pro­ cess, has a complex geometric form and a modular supporting structure made out of a high-performance material. It is an example of an approach to working with fibre-reinforced plastics that is both appropriate to the material and the practicalities of fabrication and as such is well-suited for making special-purpose building elements. For the manufacture of a GRP element a mould has to be made; its fabrication and surface finishing is a significant cost factor. In terms of economics and production, modular structures are advantageous because the individual modules have the same geometric form, allowing the mould to be used repeatedly. For this reason, the plastic tower was designed to have a modular supporting structure consisting of a total of seven identical fibre-reinforced plastic elements. The individual modules measure a maximum of 85 cm in height and 105 cm in width. The elements are stacked above one another and rotated around the central axis by 60° with respect to the element above or below. The tower sculpture reaches a total height of approximately 6 m. The individual elements are manufactured with a wall thickness of just 3 mm. Each finished GRP module weighs around 12 kg; the whole tower excluding the foundation weighs approximately 84 kg. The connection between the individual elements was designed to be detachable so that  the structure can be taken down and re-erected elsewhere. At the joints between the modules, the modules have a 30 mm wide flange allowing them to be bolted together. Four M8 bolts per flange ensure a rigid connection. A further advantage of this form of joint is that it is possible to compensate for unavoid­able tolerances in the production of the flanges. The digitally designed three-dimensional model made it possible to produce a very precise individual element. The mould is made of three identical parts with a polyurethane foam core (volume weight 80 kg/m3) and a deep-drawn covering film of polystyrene. The geometric form of the elements creates the impression of a continuous surface that extends dynamically upwards while the flanges underline the modularity of the structure. The seventh and uppermost individual element has been trimmed to give the structure a more pleasingly shaped termination. The form of the structure dissolves the boundaries between inside and outside and between structure and skin. In terms of structural typology, the tower is a self-supporting, continuously curved shell structure consisting of anticlastic curved individual segments. The stabilisation of the thin-walled sculpture is provided by the curvature of the segments and the flanges at the joints. The geometry of the elements also provides sufficient torsional rigidity. The concrete foundation is designed to resist uplift and overturning forces resulting from wind loads.

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PLASTICS AS BUILDING STRUCTURE

1  The plastic tower on the grounds of the Stuttgart State Academy of Art and Design (SABK).  2 Modular supporting structure.  3 Detail of the connection between modules.  4  The mould consists

of three identical parts.

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130

CASE STUDIES

D-Tower

Location  Doetinchem, Netherlands Material  Glass fibre-reinforced epoxy resin Completion  2004

Architecture  NOX Architects, Lars Spuybroek Structural engineering  Bollinger + Grohmann Ingenieure

The 12 m high tower sculpture is part of an interactive art project. Created together with the artist Q. S. Serafijn, the concept involved the local residents, who were asked to answer regular questionnaires. Their responses were then analysed by computer to determine the general emotional state of the community. The currently predominant emotion is represented by a colour that is then used to illuminate the tower in the evening. The translucent tower consists of 19 individual pieces manufactured out of glass  fibre-reinforced epoxy resin. The complex geometry of the tower can be reduced through the repetition of individual elements to seven basic forms. The stability of the self-supporting GRP structure is ensured through the doublecurved geometry of the skin, reinforcing ribs in the upper section and restraints in the columns. The four columns take the form of tubes with flanges at their bases, which are used to bolt the tower to the concrete foundation. The individual elements were made manually in a hand lay-up process. This method made it possible to vary the thickness of the material as required. For the moulds, Styrofoam blocks were cut to shape with the help of a CNC milling machine and coated with a latex separating layer. The partial repetition of some of the elements made it possible to re-use the individual moulds. Despite being more expensive than polyester resin, epoxy resin was chosen for the laminate for its superior dimensional stability during the hardening process. This made it possible to produce GRP elements of different thicknesses. A further reason for choosing epoxy resin was its greater strength. The material thickness in the upper shelllike sections is 4.5 mm. The glass fibre context varies according to the load that has to be sustained. Wind loads proved to be the critical load case in the structural design of the elements. Additional layers of fibre have been incorporated for added strength along the returned edges of the elements as well as in the columns and the base flanges. The segments are both bonded and bolted to one another along their returned edges. With a total surface area of 193.5 m2, the tower weighs approximately 3000 kg. The tower was prefabricated in two halves before being transported to the site on the back of a large lorry. LEDs installed in small niches illuminate the tower at night in different colours.

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PLASTICS AS BUILDING STRUCTURE

1 Daytime view.  2  Detail: the consistent 45° angle of the glass fibre-reinforcement and the ­returned edges of the GRP moulded items in the flange areas are clearly visible.  3 At night the tower is ­illuminated with LEDs.  4  The D-Tower is made up of 19 individual elements.

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Assembly No. of parts - 19 Total surface area - 193.5 m2

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132

CASE STUDIES

Hoofddorp bus station

Location  Hoofddorp, Netherlands Material  PS foam with GRP skin Completion  2003

Architecture  NIO architecten Structural engineering  Zonneveld; Engiplast Contractors  Ooms Bouwmaatschappij; Poly ­Products BV; MARIN

The bus stop takes the form of a giant sculpture and at a length of 50 m, a width of 10 m and standing 5 m high, it is one of the largest plastic structures in the world. The volume of the building spans over 40 m without intermediate supports and serves as a waiting area for the passengers. A 15 m2 rest room for the bus drivers is the only enclosed space in the entire structure. Lighting, information screens, benches and litter bins are all integrated into the form of the building. The complex geometry of the building, which was originally intended to be made of concrete, was realised as a plastic structure for cost reasons. The structural core made of expanded polystyrene (Styropor) has a weather-resistant covering skin of glass fibre-reinforced polyester resin which closes the joints between the Styropor blocks. The entire form is made of individual 4 × 1.20 × 1.25 m blocks of EPS cut to 5.27

shape  with a CNC milling machine using data from a three-dimensional computer model. The individual elements were then assembled on site in a tent that was erected to protect against weather and moisture. The particle-foam structure rests on a concrete foundation onto which multiplex panels were fixed as a base for the foam blocks. The individual foam segments were bonded with one another without any additional mechanical fixings. The volume consists of two parts, each assembled out of the foam blocks. The two larger sections were temporarily supported by a steel scaffold during the construction process and craned into position. The weight of the structure is approximately 20 tonnes. The 6 mm thick GRP facing layer for the structure was applied with a spray device developed specially for the project in which the resin is mixed with the fibres in the spray nozzle. To avoid the chemical decomposition of the foam core on contact with the polyester resin, a protective coating was first applied to the core material. The GRP covering layer extends right to the ground, covering the foam core and multiplex panels at the base of the structure so that the bus station appears to rest directly on the foundation.

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PLASTICS AS BUILDING STRUCTURE

1 General view of the bus station: the structure resembles a beached whale.  2  Elevation, floor plan and

sections of the plastic structure.

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Southwest elevation

Northeast elevation C-C

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Ground floor plan

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Section B-B

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CASE STUDIES

3  Waiting area with integral seating.  4 Detail of the integral bench.  5  The unusually shaped door fits flush with the surface of the structure.

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135

PLASTICS AS BUILDING STRUCTURE

6  The entire structure was assembled on site within a temporary tent.  7 Detail section through the

bench.  8 Detail section through the wall to the bus drivers’ rest room.

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a Foam core  b  Water runoff, bench seat, fall 16 mm/m  c  4  × 18 mm multiplex  d Fall  e Cobble  f  Bituminous coating  g Sealing  h Sand  i Concrete B 35

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a Foam core  b  Window profile  c  Thermal glazing  d  4  × 18 mm multiplex  e Screed  f  Concrete floor  g Sealing  h Insulation  i Fall  j Cobble  k  Bituminous coating  l Sand  m Concrete B 35

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136

CASE STUDIES

Roof Yitzhak Rabin Centre

Location  Tel Aviv, Israel Material  PUR, GRP Completion  2005

Architecture  Moshe Safdie Architects Roof design  Octatube Engineering Structural engineering  Octatube Engineering; ­Solico ­Engineering Contractor for the GRP roof  Octatube International; ­Holland Composites

Freeform GRP sandwich elements that symbolise white doves of peace form the roof construction over the library and large assembly hall of the Yitzhak Rabin Centre. The roof construction developed by Octatube Engineering is a conceptually impressive, innovative sandwich construction consisting of a foam core with a GRP skin. The manufacturing method for the five shell segments, each of which has a different form, is derived from boat building. The largest element has a maximum length of 30 m, the widest a maximum width of 20 m. In a first stage, the upper covering layer was laminated on a negative mould produced using a CNC machine. Sawn-to-measure layers of core material made of fire-resistant rigid PUR foam were then laid in strips on the covering layer. In the next stage, strands of glass fibre were laid at regular intervals between the strips of foam core and then saturated with resin by vacuum injection. After lamination these strands form a stiffening rib construction that connects the upper and lower outer layers. The roofs elements were manufactured in the Netherlands and had to be di­vided into individual transportable elements. The elements were transported by ship in special containers and from the harbour to the site by helicopter. The plastic segments were initially assembled on a supporting scaffold and bonded along their joints. The partially cantilevering elements are supported at regular intervals by steel columns and additionally support one another by means of connecting steel constructions. Steel fittings embedded in the construction of the sandwich elements make it possible to bolt, or unbolt, the elements. Ball joints at the top of the columns make it possible to accommodate manufacturing tolerances. The construction method and realisation of the geometrically complex GRP sandwich elements are an example of the successful transfer of expertise from another engineering discipline, in this case boat building, to architecture.

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PLASTICS AS BUILDING STRUCTURE

1  The left-hand wing of the building contains a library; the wing to the right, the large assembly hall.  2 Positioning a roof segment.  3 Connection between the core and covering layer during manufacture.

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138

CASE STUDIES

GRP/Glass Pavilion

Location  Düsseldorf, Germany Material  Composite GRP-glass material Completion  2002 (temporary)

Architecture and structural engineering  Institute of Building Structures and Structural Design (ITKE), University of Stuttgart: Jan Knippers, Stefan Peters GRP profile manufacture  Fiberline Composites A/S

The GRP and glass pavilion at glasstec 2002 in Düsseldorf, a biannual fair for developments in glazing, convincingly demonstrates the capabilities of a novel composite material made of glass fibre-reinforced plastic and sheet glass. This material combines the high mechanical strength and low thermal conductivity of fibre-re­ inforced plastics with the transparency of glass. The pavilion has a footprint of 10 × 6 m and consists of a total of eight sheets of glass, each measuring 6 × 2.50 m, and six T-section GRP profiles. Through the symmetrical arrangement of the glass panels at the ends and sides, the pavilion has an entry and exit point at each of the four corners. Because the construction is so transparent, sections of GRP tubing have been slid over the ends of the sheets of glass for safety reasons. They serve simultaneously as a bumper strip and as a tangible material sample. The four wall planes are made of laminated safety glass comprising 2 × 10 mm float glass. The four sheets for the roof have a total weight of 750 kg and are made of 2 × 10 mm laminated tempered safety glass. In order to span the entire width of 5.50 m, the sheets of glass needed to be strengthened with bonded GRP profiles. The tapered GRP beams were sawn out of I-beam profile pultrusions. The GRP and glass are bonded together with a two-component adhesive. The GRP beams end 25 cm from the supporting walls. Through the shear-resistant, 6 mm thick adhesive joint, the sheet of glass and GRP profile combine to form a composite beam-andslab structure, which can then be designed assuming a flexible bond between the glass and GRP. The adhesive joints also act as horizontal stiffening for the pavilion and were designed accordingly. The elements were bonded on site with the help of a temporary scaffold and mobile mixing equipment. The use of adhesive joints throughout and the absence of mechanical fastenings cause the dramatically coloured GRP profiles to appear to float in space and characterise the interior of the pavilion. The end result is a pavilion that is minimal in both appearance and detailing, and a model example of a new composite construction using plastics that has great potential for innovative applications in façade design.

139

PLASTICS AS BUILDING STRUCTURE

1 Perspective view of pavilion.  2 Pavilion with trade fair visitors.  3 Detail of bonding of GRP girders.

1

2

a Laminated safety glass 2 × T VG 10 mm, 6 × 2.50 m  b Silicone ­grouting, 6 mm  c  Silicone profile, 20 × 6 mm, self-adhesive on one side  d  GRP I-beam, 300 mm, bottom flange sawn off, maximum depth 270 mm, length 5 m

a b c d

3

140

CASE STUDIES

Plastic folded shell structure

Location  Stuttgart, Germany Material  Polycarbonate sandwich panels ­(clear-PEP) Completion  2008

Architecture and manufacture  Stuttgart State Academy of Art and Design (SABK), Stephan Engelsmann, Valerie Spalding, Melanie Fischer, Gerlind Baloghy Structural engineering  Engelsmann Peters Consulting Engineers

The plastic folded shell structure is a prototype for the use of cost-effective semifinished products in sheet form for self-supporting building envelopes. What sets this project apart is its use of a highly efficient structure in combination with a novel material and a specially devised jointing technology. The plastic folded shell structure was selected by ThyssenKrupp AG as a contribution to the IdeenPark 2008 exhibition in Stuttgart. The plastic pavilion has a floor plan with a diameter of almost 4 m and a surface area of a total of approximately 23 m2. The structure of the pavilion consists of eight identical sub-segments, which are axisymmetrically arranged about a vertical axis through the centre of the pavilion. The folded structure follows the prin­ ciple of radial diamond folding. The entire building consists of just four distinct panel formats, each used 16 times over. The individual panels of the sub-segments are 19 mm thick translucent plastic sandwich elements made of polycarbonate. They consist of a honeycomb core made in a core-pulling fabrication line with a facing layer on each side. In terms of structural typology, the plastic skin is a folded plate structure made of thin-walled panel elements. Folded plate structures consist of individual components of limited stiffness, which, when configured to form a spatial structure, can become highly efficient loadbearing structures that simultaneously function as the building skin. The stabilisation of the structure is a product of its geometry and the rigid joints along the edges of the panels. In the centre of the pavilion is an opening to allow light into the interior. For the detail planning, the main challenge was how to connect the 19 mm thick sandwich panels to form a continuous surface. The connections between the subsegments are designed to be detachable to allow the pavilion to be disassembled and reassembled as needed. The individual ­panels in each sub-segment are joined in a predetermined sequence, some permanently, some detachable. The joints are made with adhesives and Velcro band. Poly­carbonate panels can only be glued with liquid-solvent adhesives, which are ­unable to bridge inaccuracies in the panel manufacture. Because manufacturing tolerances are unavoidable, only two edges of each individual element are glued to their neighbours. For the detachable joints, a specially developed jointing technology with Velcro band was used. This makes it possible to achieve a structurally solid connection without having to resort to other materials. The construction was made in-house entirely out of plastics and represents a contribution towards developing building methods appropriate to the material. The lighting concept exploits the translucency of the material, illuminating the plastic shell structure at night.

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PLASTICS AS BUILDING STRUCTURE

1 Plastic folded shell structure as a tea house in the grounds of the Stuttgart State Academy of Art and Design (SABK).  2  The plastic folded shell structure at the IdeenPark 2008 Expo in Stuttgart.  3  Section, elevation and floor plan.

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CASE STUDIES

4 Section of the supporting skin.  5 Geometry and modular structure of the folded shell.  6 Individual segment.  7 Detail of the joint and Velcro band.

4

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6

7

a Sandwich panel  b  Sealing profile  c Velcro strip  d PMMA border strip, 3 mm

a b c d

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9

Plastics as building structure and envelope

Unlike engineering structures, building constructions require a skin or envelope that encloses the interior and the functions it contains. Structures without a building envelope are comparatively rare. It would seem a natural conclusion to combine the enveloping and supporting functions, in other words to construct a building envelope that is also loadbearing. The idea in itself is not a new development, indeed it is a tried and tested construction principle as evidenced, for example, by masonry structures. In the case of plastics, the application of this principle can be both sensible and economical. Most of the examples shown in the following section, such as the MYKO and Eiertempel, are prototypes that have not been constructed out of standardised building elements. They demonstrate the variety and different uses of plastics and in particular their potential for use in architecture. It is interesting to note that this category also includes rare examples of serially-produced plastic buildings such as the Futuro or fg 2000. These built examples show how demanding a task it is to combine supporting and enclosing functions within an individual element. This is particularly apparent where building performance requirements have  to be fulfilled because the loadbearing and thermal insulation functions can place competing demands on the design of a building element. Sandwich elements, for example with a GRP covering layer and a solid PUR foam core can resolve this problem and are therefore well-suited for such applications.

144

CASE STUDIES

Clip-On

Location  Utrecht, Netherlands Material  GRP Completion  1997

Design and construction  Atelier van Lieshout with Klaar van der Lippe

The name of the “Clip-On” project aptly says it all: a GRP room cell attached from outside to the surface of a building. Clip-On juts out daringly and provocatively over the internal courtyard of Utrecht’s Centraal Museum and serves as an extension to the Museum Director’s office and as a space in which to work, sleep and relax. The design concept began with a consideration of the three basic functional elements: a table, a bench and a bed. The room cell as an enclosure to house the functional elements then followed in a second stage. The external appearance of the cell was not the product of a design process in the conventional sense. Instead, the form and shape are a product of the functions of the interior. The openings in the roof of the cell, which are made with car windows, illustrate the processural approach to the project. After experimenting with different geometric shapes, the artists finally settled on the irregular shapes of car footwell mats – the footwell mats being the only remaining intact items of a car to survive an accident involving the founder of the practice, Joep van Lieshout. The building is constructed out of rigid PU panels with a facing layer of glass fibre-reinforced polyester on both sides. The surfaces melt into one another to produce the overall form. All electrical cables are embedded in the walls. In terms of structure and construction, the unusual concept exploits the low self-weight of the plastic. The cantilevered element is anchored to the building at four points. A steel band around the perimeter of the object was integrated into the laminate during manufacture and bolted securely at each end to steel plates directly adjoining the plastic cell. These points transfer the load to the masonry of the building. The two upper fixing points transfer tension loads while the lower pair sustain compression loads.

PLASTICS AS BUILDING STRUCTURE AND ENVELOPE

1 Clip-On in the internal courtyard of the Centraal Museum in Utrecht.  2 View of the interior: ­

all ­surfaces are covered with a GRP laminate.

1

2

145

146

CASE STUDIES

Eiertempel

Location  Bern, Switzerland Material  GRP Completion  2008

Architecture  groenlandbasel: Matthias Schnegg, Teresa Flury, Conrad Staub GRP manufacture  Rotaver Composites AG Contractor  Zehnpfennig und Weber

The Eiertempel (“Egg Temple”) in the Natural History Museum in Bern is part of the exhibition “C’est la vie – Stories of Life and Death”. The sculpture is both exhibit and exhibition space in one. The form of the translucent GRP skin represents an egg cell in the process of division and contains a collection of exotic birds’ eggs and specimens as well as representations of conception and birth. The Eiertempel has an almost elliptical floor plan with axis dimensions of 4.70 × 4.90 m. To obtain the form, the designers experimented with a working model made of Styrofoam balls, which served as a basis for the creation of a threedimensional computer model. The three-dimensional model was then output in the form of two-dimensional plans for realisation. The 5 mm thick GRP membrane is suspended on five thin cables from the ceiling and hung over an elliptical exhibition case that stands on the floor. For extra stability, the GRP skin is connected to the exhibition case to stop it swinging. To fulfil fire safety requirements, a flame retardant was mixed into the resin. The hand-laminated hemispheres were fabricated in a negative hemispherical form made of steel with a diameter of 2.20 m which is an industrial relict salvaged from the cellar of a spherical tank-building factory in Emmental, Switzerland. After transportation the hemispheres were then cut to size on site. In the next step, the segments were assembled with the help of a temporary supporting structure. After sewing the joints with transparent nylon wire, the joints were then laminated.

1

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147

PLASTICS AS BUILDING STRUCTURE AND ENVELOPE

1  Elevation and floor plan.  2 Eiertempel illuminated from within. The whitish translucent colour is a product of additional pigments.  3 Eiertempel in Bern Natural History Museum.  4 Interior with ­exhibition case.

2

3

4

148

CASE STUDIES

Five Bubbles

Location  Vienna, Austria Material  GRP Completion  2005

Architecture  Arbeitsgemeinschaft ­Gillmann ­Schnegg: Ursula Gillmann, Matthias Schnegg Structural engineering  Swissfiber AG Manufacture and contractor  Chemowerk GmbH

The five GRP bubbles are part of a permanent exhibition entitled “Der Alltag” ­(Every­day Life) at the Technisches Museum in Vienna, which shows historical objects from the fields of construction, the environment and everyday life. The giant GRP elements are distributed around the exhibition space and contain installations that provide visitors with an associative introduction to different aspects of the exhibition areas. The differently sized, self-supporting skins have a circular plan with a maximum diameter of 5.50 m and a droplet-form cross section with a maximum height of 4 m. They are accessed through a portal-like entrance that was attached afterwards to the bubble using laminated strips. The bubbles are manufactured as a whole unit in a hand lay-up process. A pneumatic inflatable mould was used whose form could be changed to create the different droplet-forms by applying pressure to its zenith. The use of pneumatic moulds is a technique also used in other construction areas; similar techniques are used, for example, to manufacture fuel storage tanks. The translucent GRP skins are between 4 and 6 mm thick. The thickness of the laminate is designed to sustain the load of people, particularly in the lower curved sections of the droplet-like forms. The colour and light effects for the GRP skins were the product of experimentation. Four of the five bubbles were able to be transported in one piece 1.32

for installation on site while one had to be divided into two parts.

1

m

 27

r =

m 5 m

 27

5 m

r = m

48 m

r = 1

20 drilled holes, ø approx. 20 mm

1.32

r = 1

32 m

Slot cutaway for balustrade

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m

Existing balustrade

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149

PLASTICS AS BUILDING STRUCTURE AND ENVELOPE

1  Section and floor plan of a bubble.  2  Bubble in the Technisches Museum in Vienna. The balustrade had to be divided and disassembled to install the bubble, then reassembled outside and inside the ­bubble to reinstate the safety rail.  3  Bubble hung from the roof on a steel construction. The bubble is attached by a hinge and can be let down for monitoring and inspection purposes.  4  The door opening was cut into the droplet form and the portal frame attached afterwards to the bubble using laminated strips.

2

3

4

150

CASE STUDIES

fg 2000

Location  Altenstadt, Germany Material  GRP-PUR sandwich Completion  1968

Design and construction  Wolfgang Feierbach Structural engineering  Carsten Langlie

fg 2000 (fg = fibre glass) is a prefabricated detached house conceived and built in a contractor’s workshop. It is a remarkable example of modular construction using plastics. The upper storey is made of plastic and rests on a ground floor of traditional masonry. The dimensions of the upper floor of the prototype, which canti­ levers slightly over the reinforced concrete ceiling slab, measured 10 × 16 m. Both end faces of the upper storey are glazed. The plastic section of the building consists of the linear repetition of modular wall and roof elements, which are both slightly bowed. The supporting structure for the plastic upper storey spans in one direction and distributes loads through its box-like frame structure. The 1.25 m section width is derived from the width in which glass fibre matting was available. The individual elements are sandwich elements with 4–6 mm thick GRP layers either side of a 60 mm thick rigid PUR foam core. The wall and roof elements are rigidly joined and the point at which they meet is shifted inwards away from the corner. The rounded corners at the eaves are a form easy to achieve with the material. 40 cm deep flanges at the edges of the panels provide the necessary structural height to span the width of the room. The individual elements are joined to one another with threaded bolts in the flange area. The seams are filled with a joint sealing compound and covered with three layers of sealing strip. The structural contribution of the sandwich construction was not taken into account in the design of the elements because at the time it was not possible to accurately determine the composite action of hand-laminated elements. The plastic upper storey of the fg 2000 can be erected within one day without the need for heavy lifting machinery. fg 2000 is the only plastic house to have been accorded type approval. In combination with special corner modules, the modular system made it possible to ­produce larger and more flexible floor plans. The construction of the prototype and certification of the structural calculations represented an important development for serial production. By 1979, a total of 35 fg 2000s had been built and the fg 2000 is one of the most important contributions to the serial production of plastic buildings.

151

PLASTICS AS BUILDING STRUCTURE AND ENVELOPE

1 General view of the prototype.  2 Mounting of element.  3  Bathroom.  4 Section through façade.

1

2

3 a Sealant joint  b Sealing strip  c Roof element  d Hole for ­c able, ø 30 mm  e GRP, 5 mm  f Foam insulation, 70 mm  g Steel ­clamping plate, 60 × 100 × 12 mm  h Anchoring rail, 32 × 15 mm  i Reinforced concrete ceiling slab, 180 mm  j  Steel U-profile, 35 × 35 × 2 mm  k Concrete wall

a b c M 12 M 12 M 12 M 12 M 12

d

M 12

e f e

M 12

M 12

e f e

M 12

M 12

M 12

M 10

g h i

j a k

4

152

CASE STUDIES

Futuro

Location  different locations worldwide Material  GRP, PUR, polycarbonate Completion  1968

Architecture  Matti Suuronen Structural engineering  Yrjö Ronkka

Futuro, a house with just one room, is one of the few plastic houses to have been serially-produced and is regarded as a milestone in the history of plastic architecture. The story of the Futuro house began with a client’s desire for a ski chalet that could be heated quickly and was easy to erect in difficult-to-reach terrain. The building needed to be able to be assembled or dismantled within two days and transportable with a helicopter to the desired location. The concept of the Futuro as a modular plastic house is largely a product of these requirements. The form of the rotational ellipsoid with a circular plan can be attributed primarily to geometric considerations and production engineering requirements. Futuro consists of eight upper and eight lower individual segments, all of which are identical to enable them to be produced economically. With a diameter of 7.80 m, the house provides a net area of 50 m2. The house is borne by a slender circular steel ring which is supported by four steel outriggers. The prototype was built in 1968 by Polykem Ltd. in Finland. The Futuro was exhibited alongside numerous other plastic houses at the first plastic housing exhibition in Lüdenscheid, Germany, in 1971. The plastic envelope of the building is able to sustain and dissipate loads as a result of its shell structure and flexural bending. It consists of GRP sandwich elements, which reduce the weight of the structure and provide it with adequate thermal insulation. The overall weight of the plastic building is 2500 kg without contents or 4000 kg with contents. The rigid PUR foam core has grooves on its outer surface to allow condensation runoff. The individual segments are bolted together through stabilising ribs at the edges of the elements. The house is accessed through a trap door that folds out of the wall and when closed fits flush with the exterior of the building. In practice, the Futuro served numerous different functions. A series of interior furnishings and furniture for different uses was specially developed and marketed. The standard furnishings included sanitary cell, kitchen unit, six radially arranged reclining seats, a double or two single beds and an oven grill. Manufacturing licences were sold to 25 countries around the world. Although precise figures are not available, an estimated 60 Futuros are thought to have been built. The Futuro rapidly advanced to become an iconic building of the avant-garde but like many other plastic houses found few admirers among the general public and did not sell as well as envisaged, not least because of its comparatively high price. It represents an experimental attempt to part with conventional notions of housing and develop a new form appropriate to a new material.

153

PLASTICS AS BUILDING STRUCTURE AND ENVELOPE

1 Futuro in the Centraal Museum in Utrecht.  2  The Futuro is assembled out of prefabricated modules.  3 Interior with radially arranged reclining seats.  4  Section and floor plan.

1

2

3 4

0

1

5m

154

CASE STUDIES

MYKO

Location  Weimar and Rostock, Germany Material  GRP Completion  2004

Design and structural engineering  Forschungsgruppe FOMEKK Research Group: Rainer Gumpp, Jürgen Ruth, Veit Bayer, Elke Genzel, ­Pamela Voigt, Thoralf Krause, Stefan Linne, Christian Heidenreich

The MYKO is an experimental construction for a mobile presentation pavilion by FOMEKK, an interdisciplinary research group at the Bauhaus-Universität Weimar. Its aim is to explore and demonstrate the design, constructional and spatial-functional potential of fibre-reinforced plastics for building construction. MYKO is conceived to serve changing purposes, for example an information stand, lounge or open-air cinema. It is large enough for 8–10 people. The pavilion has a total length of 4.80 m and a maximum diameter of 3 m. It consists of a main body and a door element that slots into it. The two main volumes are synclastically curved surfaces with rotational symmetry and are each made of four identical sections. The modular structure needs only two basic moulds for its manufacture, making it economical to manufacture in terms of cost as well as labour. The GRP sandwich structure is the building shell, loadbearing structure and lounger, all in one. The interior furnishings consist of a thermally insulated upholstered cushion made of composite foam matting. Threads integrated into the interior of the GRP shell make it possible to mount various fittings and technical equipment such as lighting, projectors or loudspeakers. The 16 mm thick elements consist of a 10 mm thick core clad on both sides with GRP facing layers. The core material is a synthetic scrim soaked with resin, which can easily be formed to the required shape. The individual sections were handlaminated and have a maximum size of 380 × 215 × 80 cm and a weight of approximately 130 kg without interior fittings. As a result they can be loaded, stacked and transported with a conventional vehicle. The elements have tension clips and can be assembled without the need for special tools. The transfer of loads at the intersections is through flush-meeting steel joint plates embedded in the laminate. An upstand along the edges of the joints provides the necessary depth of effective section for structural stability and serves to clamp the sealing strips in the joints. After assembling the main volume, the hemispherical door element can be lifted into place in the opening of the main volume. Connected to the main volume at two pivots, the door can be rotated freely around its vertical axis. The plinth is made of sandbags, which makes it possible to provide a stable base on uneven ground. MYKO is a model example of the appropriate use and fabrication of fibrereinforced plastics.

155

PLASTICS AS BUILDING STRUCTURE AND ENVELOPE

1 View from the front.  2 Fabrication of one of the shell segments.  3 Connection detail inside the door

element.  4  Turned inward, the door element is large enough to serve as a projection screen.

1

2

3

4

156

CASE STUDIES

Novartis Campus reception building

Location  Basel, Switzerland Material  GRP Completion  2007

Architecture  Marco Serra, Architect Detail planning, roof construction  Ernst Basler + Partner AG Planning application, roof construction  Swissfiber AG with Zurich University of Applied Sciences Winterthur (ZHAW) Technical consultancy, roof construction  Thomas Keller, EPFL–CCLab, Lausanne Roofing contractor  Scobalit AG

The glazed façades of the Novartis Campus reception building in Basel ­support a 400 m2 plastic form with the cross section of an aerofoil wing. Plastic was ­chosen to minimise the self-weight of the partially cantilevered roof construction, so that the glass façades could be made as transparent as possible. The plastic slab structure is manufactured as a sandwich element. The loadbearing structure of the 18.50 × 21.60 m seamless plastic volume consists of GRP facing layers and GRP  webs in both axes stabilised by a rigid PUR foam core. The cross section of the roof is a maximum of 60 cm deep and thins to just 7.5 cm deep at its longer edges. With a mean weight per unit area of approximately 70 kg / m2, the roof weighs a total of 28 tonnes. 460 foam blocks were cut to shape by a CNC milling machine using data from a computer model. In a first step, four of the approximately 90 × 90 cm large core blocks, the depth of which varies according to the position in the roof, were individually wrapped and then enclosed within a GRP skin to form the vertical GRP webs between the individual blocks. In a second step, the resulting packages were then bonded together into four 5.60 m wide and 18.50 m long strip-segments and laminated together with a GRP covering layer. With wall thicknesses of 6–10 mm for the facing layers and 3–24 mm for the webs, the GRP structural elements of the slab are very thin. The load distribution where the elements meet is ensured by sufficiently overlapping the GRP layers. For assembly, the four segments were positioned in place on a supporting scaffold. After bonding the segments to a single slab structure, the façade elements were then installed beneath the roof and sufficiently pre-stressed using tensioned rods in the plane of the façade to ensure watertightness when subjected to uplift wind forces. The load from the plastic roof is transferred through a specially developed detail beneath the GRP webs into the loadbearing laminated safety glass of the façade. Only the GRP elements were considered as loadbearing for the structural design of the slab. The loadbearing capacity and viability of the bonded plastic sandwich construction were proven by a series of load tests. The plastic roof of the Novartis Campus reception building is an example, both in terms of engineering and production, of a particularly sophisticated GRP slab structure.

157

PLASTICS AS BUILDING STRUCTURE AND ENVELOPE

1  The GRP and foam core roof of the Novartis Campus reception building.  2 Cross section through the building.  3 Detail of the junction between roof and glass façade.  4 Section through the junction ­between roof and glass façade.

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0

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5m

a Steel angle section, bonded to glass  b GRP cover plate, removable  c Loadbearing ceiling laminate (GRP)  d  Twin element web (GRP)  e Sliding bearing (not contin­uous)  f Steel band, inside roof construction  g Injected synthetic resin (not continuous)  h Silicon bonding, blocking (not continuous)  i Non-loadbearing laminate (GRP)  j  Thermal glazing  k  Water drip  l Foam block (PUR)

c d k l c c e a

f g

b

h i j

l

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158

CASE STUDIES

5 Laminating a large element.  6  Breaking test at the ETH Lausanne.

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159



10 Future developments

The time has come to reassess the potential of high-performance plastics for architectural applications. High-performance materials such as material composites as well as other plastics make it possible to use plastics intelligently and economically in constructions. Alongside a general readiness to examine the properties and particularities of plastics, further research and development is also essential for the use of plastics to become more widespread. A reappraisal of the role of plastics in construction is, therefore, closely intertwined with the development of construction technologies, design principles and dimensioning and manufacturing techniques. The following section describes selected development trends as well as the potential limitations of the use of plastics in construction.

High-performance material for supporting structures Fibre-reinforced plastics exhibit excellent strength properties. The factory production of semi-finished products makes it possible to manufacture and assemble plastics regardless of weather conditions. Fibre-reinforced plastics are furthermore highly durable. For this reason they are ideally suitable for use in supporting structures. A comparatively new development is the availability of high-strength and corrosion-resistant tension members made of carbon fibre-reinforced plastic. A key limitation in the use of plastics in loadbearing structures is their limited fire performance. Without additional fire protection, this more or less rules out their use for multi-storey buildings with typical fire safety and material flammability requirements. Another significant disadvantage of plastics is their low modulus of elasticity. This results in comparatively large deformations that for many building components exceed permissible limits or can only be compensated for with unfavourably massively dimensioned construction members. However, plastics can be used for loadbearing structures in situations where fire performance requirements are not as strict and where the possible occurrence of deformations is less important, for example roof coverings. Suitable structural systems for plastics include frame structures made of pultruded profiles or folded plate structures made of panelled materials. A current and promising application area for fibre-reinforced plastics is bridge building. Current research and development efforts focus primarily on the use of GRP profiles for bridge decks. The profiles are mounted on a conventional loadbearing structure, for example made of steel profiles. The advantage of plastic lies in the high durability of GRP, especially with regard to frost and road salt, as well as the low self-weight of GRP decks in comparison to concrete. A further advantage

160

FUTURE DEVELOPMENTS

10.1 Road bridge with GRP deck, Friedberg, Germany, Knippers Helbig Advanced Engineering, Institute of Building Structures and Structural Design (ITKE), University of Stuttgart, 2009.

10.1

10.1

for bridge building is that GRP bridge decks can be prefabricated in the workshop. A prototype road bridge has been built over the B 455 in Friedberg in Germany. GRP bridges with a loadbearing structure also made of GRP are very rare. The primary reason for this is the low modulus of elasticity of GRP, which results in deformations that exceed permissible levels for road and rail bridges. As such they can only be used for very short spans. Nevertheless plastics play an important role in bridge building as a technological basis and catalyst for developments in the field of supporting structures.

High-performance material for building envelopes Semi-finished products suitable for use in building envelopes are now being produced by the plastics industry at low cost. For architectural applications they are of particular interest: on the one hand they offer a diverse range of design possibilities – surface textures, colours, coatings, printing and cavity fill options – and on the other they are durable and weather-resistant. A particularly interesting property in this respect is the translucent quality of 10.2

certain plastics. Alongside glass, these plastics are the only materials that can be used for the natural illumination of indoor spaces. In contrast to glass, however, plastic sheets are not at present suitable for manufacturing vacuum or gasfilled insulated window units because the expansion of plastic sheets caused by temperature and moisture level changes means that double-glazed units made of plastic cannot be reliably sealed, which compromises the function of the unit. For this reason, where thermal insulation requirements are an issue, plastics are employed primarily as part of twin-skin façades in combination with glass ­doubleglazed units on the inner face for insulation purposes. A possible and already practiced approach to this problem is the use of translucent polycarbonate multi­wall panels with a comparatively low U-value, or plastic multiwall panels filled with aerogel granules that reduce thermal transmission considerably. Several proto­ typical applications of such translucent all-plastic façade constructions have been realised, but there is as yet not enough long-term experience of their suitability in practice. For transparent building envelopes with low thermal insulation requirements, pneumatic structures made of plastic membranes represent an option that is

HIGH-PERFORMANCE MATERIAL

both economical and a technically interesting alternative to rigid constructions. In the meantime a considerable number of buildings have been realised that illustrate the breadth of possible applications for such constructions. A special variant of the pneumatic principle are negative pressure constructions in which suction is used to stabilise a plastic membrane against an underlying supporting substructure. Lighting technology represents a further extensive field of experimentation using plastics. In addition to the use of translucent or transparent plastics, it is also possible to integrate light-conducting optical fibres or light sources in fibrereinforced plastics or ETFE. Fibre-optic fibres can, for example, be woven into fabrics. In such applications the heat from the light sources must not be allowed to detrimentally affect the plastic. Other experimental applications include the integration of thermochromic or photochromic pigments into the resin matrix. Using such approaches, façades can be realised that react to environmental stimuli such as temperature or change colour when exposed to particular wavelengths of sunlight. GRP profiles are particularly well-suited for use as loadbearing elements of building skins such as façade profiles. In addition to their high mechanical strength,  they are also corrosion-resistant and lightweight. Due to the low thermal conductivity of GRP, plastic elements can be employed in the same plane as the thermal skin or even penetrate it without the risk of significant cold bridging and its associated problems. This would not be possible with metal profiles. GRP has the potential to compete with other materials commonly used in façade construction such as aluminium. A special case in the use of plastics in façades is self-supporting building skins. For building constructions, plastic sheet materials and semi-finished products are of particular interest. From a typological perspective, folded plate structures that consist of flat sheet elements are well-suited for self-supporting building skins. Folded-plate constructions are spatial structures that, unlike skeleton constructions, do not require additional bracing members. The individual elements themselves have a limited degree of stiffness but, when combined to form an appropriate three-dimensional configuration, result in a high-performance loadbearing structure that can also serve as a building envelope. Complex and varied spaces can therefore be created with simple and economical plastic panels. Further re­search is needed to develop suitable joining technologies for structurally rigid, constructionally feasible and architecturally acceptable connections between industrially prefabricated sheet plastic materials.

Composite materials Composite materials now play an important role in loadbearing structures. They make it possible to combine the specific advantageous properties of different materials with one another to create intelligent and at the same time economical solutions. The combination of glass fibre-reinforced plastics and glass is interesting for a number of reasons. For the best transfer of forces between the two materials, they are joined on their faces. The fact that the thermal expansion coefficient of pultruded GRP profiles is similar to that of glass, due to its

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10.2 GRP/glass façade element: a thermally-insulated window pane with bonded GRP profiles.

10.2

high glass fibre ­content, makes it possible to bond both materials directly and almost rigidly with one another without appreciable strains resulting from differential expansion. A particularly interesting development is the principle of composite glazing façade elements that consist of a layer of thermal glazing and a supporting substructure of glass fibre-reinforced plastic. Thermal glazing and plastic profiles are bonded with one another to form a composite, structurally effective cross section. The bonded GRP profiles are a very efficient means of stabilising large-scale glazing against wind loads. Profile types suitable for manufacturing in large quantities can be developed for the GRP profile, depending on the geometry and the kind of wind loads. An optimised cross section with economic use of the material and adequate loadbearing capacity can only be achieved for a composite cross section if the adhesive connection is assumed to behave elastically in the structural engineering design of the façade members. This can be achieved using the principle of flexible composite sections or using finite-element calculations, which are generally calibrated using model tests. In architectural terms, this means that very ­slender façade profiles can be achieved. GRP/glass façade elements are particularly well-suited for tall storey heights. They can be prefabricated in the factory. Element façades made of composite glazing elements are not only very much simpler in terms of their structure than light metal façades but are also easier and more economical to erect. Pilot projects have been undertaken in Birkerod and Middelfart in Denmark. For window manufacture, a combination of GRP and wood has proven advantageous. An industrial development by the Institute of Building Structures and Structural Design (ITKE) 10.3

at the University of Stuttgart, headed by Jan Knippers and developed by Engelsmann Peters Beratende Ingenieure, is the “Fiberwood” window. The principle of the Fiberwood window is a two-part frame consisting of a wooden profile and a GRP profile. The GRP profile contains a foam-filled cavity to improve the U-value of the frame. It is fitted exactly to the wooden window frame and screwed firmly in place to provide excellent weather protection. The three-part casement frame consists of thermal glazing, a GRP adapter profile and the wooden casement. The ther-

COMPOSITE MATERIAL

10.3  “Fiberwood” window, a wood-GRP construction with good thermal properties and a larger window surface for more daylight.

10.3

mal glazing panel is bonded firmly to the adapter profile which is in turn screwed to the wooden frame of the casement. The total frame proportion of a Fiberwood window of normal test size (external dimensions: 123 × 148 cm) is only 25 % compared with 35 % for conventional window frames. This leads to an improved overall U-value and in turn benefits the user by providing more daylight and lower thermal loss through the opening. Wood can also be used in combination with other plastics such as PMMA. A 10.4

footbridge over the Schlossgraben in Darmstadt is the first bridge in the world to be built using a composite wood and PMMA construction. The bridge spans 26 m over the former castle moat. Both of the principal girders consist of 70 mm thick transparent Plexiglas strips with laminated wood profile upper and lower flanges. In this composite cross section the laminated timber elements carry the tension and compression stresses. The Plexiglas web provides a shear-resistant connection between the upper and lower flanges. A disadvantage of composite materials, in particular when they are bonded, is that they are in many cases difficult to separate for recycling purposes. In terms of sustainability this fundamental question has yet to be solved. Further research is required into the recyclability of plastics and plastic composites.

Reinforcement of supporting structures Carbon fibre-reinforcement lamellae or textiles for reinforcing existing concrete 10.5

loadbearing structures have been granted building control certification for some time now and are commonly used in practice. Typical application areas include the reinforcement of bridge structures to sustain greater loads or as an earthquake prevention measure for columns. The very thin carbon fibre lamellae used for structural reinforcement are manufactured using pultrusion and have a high tensile strength and do not corrode. An advantage of this approach is that the CFRP lamellae are generally attached to an existing structure in need of reinforcement using an epoxy resin. The transport, handling and installation is very straightforward thanks to the material’s light weight. Where the CFRP lamellae are fixed to a supporting structure already carrying dead load, only the imposed loads cause

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10.4 Footbridge over the Schlossgraben in Darmstadt, Darmstadt University of Technology, Evonik Röhm, 2007. The bridge is a composite structure made of timber and PMMA.

10.4

elongation in the CFRP lamellae. As a result the ductility of the CFRP is only partly utilised. The high strength of a CFRP lamella can be exploited more effectively by tensioning the element. Research is, therefore, currently being conducted into the development of appropriate anchor grips for fastening and tensioning CFRP lamellae. In principle, elements made of high-strength fibre-reinforced plastics such as GRP rods are suitable also as an alternative to conventional steel reinforcement rods in new concrete structures. As opposed to steel rods, it is, however, not possible to bend them. For this reason and because of the high cost of their use, applications of this kind are currently limited to special fields such as tunnels.

Joining technologies appropriate to the material The joining technologies used in plastic construction, in particular where connections need to be detachable, derive from techniques used in steel construction. A point fixing such as a screw or bolt has the disadvantage that the load distribution within the member is very dependent on the orientation of the fibres and their distribution and that localised peak stresses cannot be redistributed due to the low plasticity of GRP. A joining technology that is appropriate for glass fibre-reinforced plastics is the integral lamination of receiving plates. This reduces the problem of excessive loads concentrated on a single point. Another promising development of screw connections is the friction-grip connection. Through the use of serrated contact parts it is possible to transfer loads over a larger contact area resulting in much stronger connections. The development of joining technologies designed specifically for plastics is still underway. Of particular relevance are adhesive bonds. Adhesive joints are in many respects ideally suited to plastics because loads are transferred evenly across a flat surface. As such they are good for making connections that do not have to rely on positive fitting to transfer forces. There are, however, a number of disadvantages that have yet to be resolved: the long-term durability of adhesive

JOINING TECHNOLOGIES

10.5  Use of CFRP lamellae for the repair of structures: On this bridge in Horgen, Switzerland, the traffic lanes were widened. The cantilevering deck slab had to be reinforced at the top to carry the higher ­moment loads.

10.5

joints, their structural behaviour in the event of a fire and the difficulty of replacing individual parts.

New production methods The typical production methods for manufacturing plastic products and building elements are based on the principle of mass production in large quantities. Buildings, however, are typically prototypes, in most cases one-off productions. Laying-up techniques for forming fibre-reinforced plastic building elements are comparatively labour-intensive and the fabrication of individual building elements is therefore relatively cost-intensive, one of the main reasons for the relatively low number of plastic buildings on the market. Building elements made of plastic are in many cases only able to compete with conventional materials when the form can be used repeatedly or serially-produced. An economically viable approach would, therefore, be to either manufacture entire buildings as prefabricated serial productions or to devise a modular structure in which the individual elements can be economically manufactured in small batches. Modularity is in this respect a key concept in the field of plastic architecture. An important factor for the cost of production is the manufacture of forms and moulds, a problem well-known from concrete shell construction. Modern continuous digital processes from design to production that employ CNC machining techniques for mould manufacture, for example the milling of foam forms, already ­represent a significant simplification of the process. But milling techniques are not economical in their use of materials. The ongoing development of rapid prototyping production methods that can enable the custom production of larger building elements is therefore an area with significant potential. Another possibility is the use of adaptable formwork or moulds that can be easily modified to fit different geometric applications. Hydraulically controlled moulds are conceivable but are currently not used in practice. For thermoplastic plastics, the manufacture of plastic building elements with the help of additive rapid prototyping ­techniques

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is a further interesting option. While such techniques already exist, they are only possible for small objects. This technique cannot be used for fibre-reinforced building elements.

Technology transfer In contrast to architecture, the use of plastics in aircraft construction, automotive engineering and shipbuilding is widespread. The field of architecture stands, in principle, to benefit from the transfer of technological expertise from these disciplines. It is, however, important to note that means of construction and safety concepts are not directly transferable because the functions, requirements and loads are in many respects fundamentally different. Unlike buildings, aircraft and cars are mass-produced items. However, despite all the differences, aspects such as the weight optimisation of loadbearing structures are also relevant for architecture. Another obvious source of technology transfer is the transfer of construction principles and experience from structural engineering. In any case, an interdisciplinary approach and way of thinking has the potential to foster the development of new, more efficient and economically innovative solutions for the use of plastics in architecture.

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glossary Acrylic glass A common term for products made of transparent PMMA, in certain cases also used for opaque coloured PMMA products. Adhesion The bonding force at the boundary surface between two materials. See also ≥ Cohesion. Amorphous An unordered structure of molecules in a solid body. It contrasts with crystalline structures that have a highly ­ordered molecular arrangement. Anisotropy Directional dependency of the physical and chemical properties of a material, conditioned in particular by a lattice structure arrangement at a molecular level. The anisotropy of composite materials such as fibre-reinforced plastic is a product of the arrangement of the reinforcement fibres, which can be used to influence the direction of loading. The opposite of ≥ Isotropy. Aromatic compounds (Arenes) Hydrocarbon compounds that have one or more benzene rings. The benzene rings are responsible for the rigid ­molecular structure of the aromatic compounds and contribute to reduced reactivity and higher thermal stability. ­Example: polycarbonates. Bifunctional, trifunctional and polyfunctional groups The highly reactive constituents of organic molecules, for example –OH (hydroxyl group), –COOH (carboxyl group), –NH2 (amino group), which influence the molecular structure and can be used to control specific product properties during the manufacture of plastics. Calendering A production process for the manufacture of thermo­ plastic foils that employs a series of pressure rollers, the so-called calendering line, to roll successively thinner ­layers of foil. CFRP Carbon fibre-reinforced plastic. Cohesion The binding force between atoms or molecules within a material. See also ≥ Adhesion. Corrugated panel A single-layer panel with a corrugated, i.e. wave-form cross section. Dielectric The properties of a material that serves as an insulator, that is, a material with extremely low electrical conduc­ tivity.

Ductility Ductility describes the ability of a material to undergo plastic deformation without losing its bearing capacity before failing completely. According to safety theory in building construction, notice of failure through defor­ mation is useful and desirable. In structurally indeterminate systems, ductile materials allow the redistribution of the internal forces. Steel and reinforced concrete are examples of materials that have ductile properties. Duromer (thermosetting plastic) Generic term for tightly-meshed cross-linked plastics that are neither dissoluble nor weldable. In architecture, they are used primarily in combination with reinforcement fibres such as fibre-reinforced plastics for high-strength building elements. Elastomer Generic term for loosely-meshed cross-linked plastics that are neither dissoluble nor weldable and exhibit a high degree of elasticity. They are typically used in architecture in the form of sealing profiles or bearings. Endothermic reaction A chemical process that absorbs energy in the form of heat. The end products of an endothermic reaction have more energy than the initial products and therefore ­decompose more easily. The opposite of ≥ Exothermic ­reaction. Epoxy resin A thermosetting plastic (duromer) whose liquid constituents become cross-linked as a result of a chemical reaction (polyaddition). Epoxy resins are commonly used as a matrix for fibre-reinforced plastics for building elements that need to be both strong and dimensionally stable. ETFE Ethylene tetrafluoroethylene is a thermoplastic used most commonly in the form of transparent films or foils. Exothermic reaction A chemical reaction that releases energy in the form of heat. The opposite of ≥ Endothermic reaction. Extrusion A production process for elastomers, thermoplastics or thermosetting semi-finished products with a uniform cross section. Fire safety classes A classification system for materials according to their fire performance properties. It is described in the DIN 4102-1 respectively DIN EN 13501. Materials are differentiated into non-flammable (fire safety class A) and flammable materials (fire safety class B), each with different sub-categories. FRP Fibre-reinforced plastic.

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Gelcoat Unreinforced resin finish layer for moulded articles made of GRP to improve their weathering resistance. Glass transition temperature Tg The temperature region of amorphous materials in which the material changes from a solid to a viscous or liquid (molten) state. The glass transition temperature is characterised by a broader temperature range and contrasts with the precisely defined temperature of the melting point of crystalline materials. GMT Glass mat-reinforced thermoplastic. GRP Glass fibre-reinforced plastic. Hand lamination A term used to describe the manual manufacture of fibrereinforced plastic elements. It is a labour-intensive process that is best suited for the manufacture of prototypes or building elements that need to have different wall thick­nesses. The fibre content is typically relatively low at around 25 %. Integral skin foam A foam structure with a cellular core and a closed surface finish. Polyurethane is typically manufactured as integral skin foam, as well as other thermoplastics such as polypropylene. Isotropy Directional independency of material properties. The ­opposite of ≥ Anisotropy. Laminate A fibre-plastic composite material. Macromolecule A molecule with a high molecular mass that consists of a large number of repeating monomers. The term was coined by Hermann Staudinger to describe the chemical structure of plastics. Natural macromolecules include, for example, cellulose or starch while the majority of ­plastics consist of synthetically manufactured macro­ molecules. Matrix A plastic material that is strengthened using fibres. In principle any plastic can serve as a matrix, but in practice synthetic resins are typically used as a matrix material to ensure better mechanical properties. Modulus of elasticity The modulus of elasticity (Young’s or E modulus) is a ­material characteristic that describes the ratio of tensile stress to strain for predominantly linear material behaviour. A high modulus of elasticity means that a material strongly resists deformation. The E modulus is expressed as E = / where  = tensile stress (F/A) and  = strain (l/l).

Monomer A reactive molecule that can join to other monomers through a process of synthesis to form long-chain ­polymers. A basic module of every plastic. Moulding A generic term in the plastics industry for working processes in which a raw material mixture in a liquid or solid form is formed into plastic products or semi-finished products. Multiwall panel A panel material, also known as cellular sheet, made ­using a process of extrusion that consists of two facing layers with connecting ribs or webs. They are made ­predominantly of PC or PMMA. Orthotropy The term combines the words orthogonal and anisotropy and describes the directional dependency of the loadbearing and deformation characteristics of a material or structure. The directional dependency is exhibited with respect to a coordinate system with orthogonal axes. A particular characteristic of orthotropic materials is the fact that extension and shear deformations are independent of one another. Orthotropy is a special form of ≥ Anisotropy. Phenolic resin A thermosetting plastic with high temperature durability whose initial liquid components form cross-links through a process of condensation. Photopolymer A polymer that hardens when exposed to UV light. This characteristic is exploited for ≥ Rapid prototyping. Plexiglas The trade name used by Evonik Röhm for products made of PMMA. It is often used colloquially to describe transparent PMMA. PMMA Polymethyl methacrylate is a brittle thermoplastic that exhibits excellent transparency and weathering properties. PMMA is often used as a replacement for glass. Polycarbonate Polycarbonate is a thermoplastic that is highly transparent and has a greater impact resistance than PMMA. PC is used in place of PMMA as a replacement for glass, particularly in situations subject to higher mechanical loads or that require better fire safety performance. Polyester A generic term for a family of plastics in the group of thermoplastics. Because of its chemical structure, polyester exhibits a comparatively high melting temperature. Examples are polycarbonate and polyethylene terephthalate (PET).

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Polyester resin A thermosetting plastic whose initial liquid components form cross-links through a process of polymerisation. Compared with other resins, polyester resins are easy to work and have good general properties. Polyethylene A thermoplastic which is used in a variety of modified forms for ancillary building elements such as for technical installations and waterproof membranes. Polymer A linear or branched chain of molecules formed out of a series monomers in a chemical reaction. The word polymer is often used as a generic term for plastics in general. Polymerisation A method of synthesis using a reactive agent. The resulting products are termed polymerizates. Polymerisation describes the general process in which monomers are linked together to form polymers. Polypropylene A versatile thermoplastic with limited strength that is commonly used to make moulding products or plastic panels with different shapes and profiles. Polystyrene Polystyrene in its pure form is an amorphous, brittle thermoplastic with a high degree of transparency. It is most commonly used, however, for foams (EPS, XPS) for use as insulation material. Prepreg A general abbreviation for “pre-impregnated”, that is for fibres that have been pre-impregnated with a thermosetting plastic and can be used as a semi-finished product. The hardening of the plastic resin is delayed by keeping prepregs cool before use. They are then hardened through the application of heat and pressure. Prepregs combine a higher fibre content with the advantage of being easier to use and apply. Primary valency bond Primary valency bonds are a form of bond between the ­individual constituents of a molecule. Examples of primary valency bonds are atomic and ionic bonds. Primary valency bonds have a stronger binding force than ≥ Secondary valency bond. PTFE Polytetrafluoroethylene contains the chemical element ­fluorine and therefore exhibits very high chemical and thermal durability. It is used as a textile or coating in membrane constructions. Pultrusion An industrial manufacturing process for profiles made of fibre-reinforced plastic in which glass fibres, pre-soaked in a resin bath, are pressed through a die or nozzle that shapes its final profile. Pultruded fibre-reinforced plastic products have a very high fibre content and a correspondingly high-strength.

PUR Polyurethanes are a group of plastics whose name refers to their common chemical components from the urethane group. Their actual properties are, however, typically ­determined by the other molecular elements, hence their wide variety of properties. They are most commonly used in construction as sealing foam and as thermal insulation panels. PVC Polyvinyl chloride is a thermoplastic used in the industrial manufacture of finished and semi-finished products such as window and door profiles, roller shutters, tubing and foils. Radicals Reactive atoms or molecule groups with at least two ­unpaired electrons that are commonly produced by photo­ chemical and thermal reactions as short-lived side ­products. Rapid manufacturing A general term for manufacturing processes for building elements and small runs that are produced directly from a digital data model. Rapid prototyping A general term for the manufacture of prototypes produced directly from a digital data model. Recyclate Plastics that consist in part or entirety of recycled plastic materials. Secondary valency bond Secondary valency bonds are a product of electrostatic interactions between the bonding partners. The bonding force is created by the attraction between two differently charged atoms. Secondary valency bonds are not as strong as ≥ Primary valency bond. SFRP Synthetically fibre-reinforced plastics made with aramid fibres. Styropor A trade name used by BASF for expanded polystyrene (EPS). It is most commonly used in the form of thermal ­insulation panels. Synthesis A chemical process for the manufacture of a polymer from monomers. Examples include polymerisation, ­polyaddition and polycondensation. Thermoplastic By far the largest group of plastics, thermoplastics are uncross-linked and have linear or branched polymer chains. They can be melted and welded and are not as strong as thermosetting plastics (duromers).

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Bibliography U-Value A coefficient of thermal transmission measured in W/m2K. The U-value denotes how much energy in watts flows through a 1 m2 area of a building surface over a defined time interval when the temperature difference between the inner and the outer surface is 1 Kelvin. The U-value ­allows one to assess the transmission heat loss through a building element: the smaller the U-value, the higher the degree of insulation. When determining the heat transmission coefficient for a window (Uw -value), the different values for the glazing (Ug -value) and the frame (Uf -value) need to be considered. The Ug -value is particularly relevant for products made of transparent plastic that are to be used in place of glass. Unsaturated double bond Double bonds between two hydrocarbon atoms in a molecule. Due to the relatively unstable bond, the molecule is very reactive. Vinyl ester resin A thermosetting plastic with a high impact resistance and heat and chemical stability. Vulcanisation The cross-linking of raw rubber using sulphur under heat and pressure. The resulting long-chain rubber molecules are connected to one another by so-called sulphur bridges: the material changes from a plastic state to an elastic state and simultaneously becomes more resistant against chemicals and mechanical loads. The process was developed in 1839 by Charles Goodyear. Worm screw A linear, screw-shaped feeder element inside a horizontal metal cylinder that rotates around its axis and mixes and melts the moulding compound before it is fed into a mould or die to receive its final form.

1  The Development of Plastic Architecture Balkowski, F. D.: “Das Kunststoffhaus”, Deutsche ­ au­zeitung, no. 1, 1988, p. 68 B “Bauen mit Kunststoffen”, Werk, Bauen und Wohnen, no. 11, 1978 Burgard, R. (ed.): Kunststoffe und freie Formen. Ein ­ erkbuch, Springer Verlag, Vienna/New York, 2004 W Dietz, Albert: Plastics for Architects and Builders, MIT Press, Cambridge, 1969 Doernach, R.: Bausysteme mit Kunststoffen, Deutsche Verlags-Anstalt, Stuttgart, 1974 Ehrenstein, E. W.: Faserverbund-Kunststoffe. ­ Werkstoffe – Verarbeitung – Eigenschaften, Carl Hanser Verlag, ­Munich/Vienna, 1992 Genzel, E.; Voigt, P.: Kunststoffbauten. Teil 1 – Die Pioniere, Bauhaus-Universität Weimar, Universitätsverlag, Weimar, 2005 Genzel, E.: “Zur Geschichte der Konstruktion und der Bemessung von Tragwerken des Hochbaus aus ­faserverstärkten Kunststoffen 1950–1980”, ­ Ph. D. thesis, B ­ auhaus-Universität Weimar, 2006 Home, Marko; Taanila, Mika: Futuro. Tomorrow’s House From Yesterday, Desura, Helsinki, 2002 Institut für das Bauen mit Kunststoffen e. V. (ed.): ­Kunststoffhäuser und Raumzellen, IBK-Verlag, ­ Darmstadt, 1973 Plastic Design, daab, Cologne, 2007 Quarmby, Arthur: The Plastics Architect, Pall Mall Press, London, 1974 Saechtling, Hansjürgen: Bauen mit Kunststoffen, Carl Hanser Verlag, Munich/Vienna, 1973 Tschimmel, U.: Die Zehntausend-Dollar-Idee. KunststoffGeschichte vom Celluloid zum Superchip, Econ Verlag, Düsseldorf/Vienna/New York, 1989 Uffelen, Chris van; Steybe, Sophie: Pure Plastic. New ­Materials for Today’s Architecture, Verlagshaus Braun, Berlin, 2008. Voigt, P.: “Die Pionierphase des Bauens mit glasfaser­ verstärkten Kunststoffen (GFK) 1942 bis 1980”, Ph. D. thesis, Bauhaus-Universität Weimar, 2007

2  Material properties of plastics “Kunststoffe im Brandschutzkonzept”, conference ­proceedings, Würzburg, September 27–28, 1999, VDI Gesellschaft Werkstofftechnik, VDI Verlag, ­Düsseldorf, 1999

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Kramer, E.: “Langzeitverhalten von thermoplastischen Kunststoffen im Außeneinsatz. Ursachen und ­Auswirk­ungen des photooxidativen Abbaus polymerer Werk­stoffe”, Burgard, R. (ed.): Kunststoffe und freie ­Formen. Ein Werkbuch, Springer Verlag, Vienna/ New York, 2004 Ludwig, C.: “Brandverhalten von Bauteilen aus FVK. Tagungsband Faserverbunde in der Architektur”, ­conference, Bauhaus Dessau, December 9–10, 2008 Troitzsch, J.: Plastics Flammability Handbook, Carl Hanser Verlag, Munich/Vienna, 2004

Hufnagl, F. (ed.): Plastics + Design, exhibition catalogue, Neue Sammlung, Staatl. Sammlung für angewandte Kunst, Munich, Arnoldsche Verlagsanstalt, Stuttgart, 1997 Jeska, Simone: Transparent Plastics. Design and ­Technology, Birkhäuser, Basel, 2008 Kaltenbach, F. (ed.): Detail Practice: Translucent Materials, Edition Detail, Munich, and Birkhäuser, Basel, 2004 Michaeli, Walter: Einführung in die Kunststoffverarbeitung, Carl Hanser Verlag, Munich/Vienna, 1992

3  Basics of plastics

Michaeli, Walter; Wegener, Martin: Einführung in die ­Technologie der Faserverbundwerkstoffe, Carl Hanser ­Verlag, Munich/Vienna, 1990

Cowie, J. M. G.: Chemie und Physik der synthetischen Polymere, Vieweg Verlag, Braunschweig/Wiesbaden, 1997

Moser, Kurt: Faser-Kunststoff-Verbund, VDI Verlag, ­Düsseldorf, 1992

Erhard, Gunter: Designing with Plastics, Carl Hanser ­Verlag, Munich/Vienna, 2006 Harper, Charles A.; Petrie, Edward M.: Plastics Materials and Processes: A Concise Encyclopedia, John Wiley & Sons, New York, 2003 Harper, Charles A.: Handbook of Plastics Technologies: The Complete Guide to Properties and Performance, ­McGraw-Hill Professional, New York, 2006, 2nd edition IBK Darmstadt (ed.): Bauen mit Kunststoffen. Jahrbuch 2002, Ernst & Sohn Verlag, Berlin, 2001 Oberbach, K.; Baur, E.; Brinkmann, S.; Schmachtenberg, E.: Saechtling Kunststoff Taschenbuch, Carl Hanser ­Verlag, Munich/Vienna 2004, 29th edition Stoeckhert, K.: Kunststoff Lexikon, Carl Hanser Verlag, Munich/Vienna, 1997, 9th edition Titow, W. V.; De Boer, Remco: Technological Dictionary of Plastics Materials, Pergamon Press, Oxford, 1998

5  Finished and semi-finished products Rahlwes, K.; Maurer, R.: “Lagerung und Lager im Bauwesen”, Beton-Kalender 1995, Ernst & Sohn Verlag, Berlin, part 2, p. 631–737

6  Building with plastics Bauüberwachungsverein e. V (BÜV), “Tragende Kunst­ stoffbauteile im Bauwesen [TKB], Entwurf, Bemessung und Konstruktion”, proposal, October 2002 Clarke, John L.: Structural Design of Polymer Composites, EUROCOMP Design Code and Handbook, E & FN Spon, ­London, 1996 DIN 18 820, parts 1–3: “Laminate aus textilglasverstärkten ungesättigten Polyester- und Phenolacrylatharzen für tragende Bauteile” DIN EN 13 706, parts 1 and 2: “Spezifikationen für ­ ultrudierte Profile” p

4  Plastics and their manufacture Curbach, Manfred, et al: “Sachstandsbericht zum Einsatz von Textilien im Massivbau”, DAfStb (Deutscher ­Ausschuss für Stahlbeton), vol. 488, 1998 Ehrenstein, E. W.: Faserverbund-Kunststoffe. Werkstoffe – Verarbeitung – Eigenschaften, Carl Hanser Verlag, ­Munich/Vienna, 1992 Fiberline Composites A/S: Fiberline Design& Konstruktionshandbuch, 1995 Habenicht, Gerd: Kleben, Springer Verlag, Vienna/ New York, 2002 Hellerich, W.; Harsch, G.; Haenle, S.: Werkstoff-Führer Kunststoffe, Carl Hanser Verlag, Munich/Vienna, 1996, 7th edition

Einsfeld, Ulrich: “Kunststoffe im Bauwesen – Werkstoffe der Zukunft: Eigenschaften – Anwendungen – Brand­ verhalten”, Institut für das Bauen mit Kunststoffen e. V., Darmstadt, das bauzentrum, no. 12, 2000, p. 4–5 Gruber, Werner: Hightech-Industrieklebstoffe, verlag ­moderne industrie, Landsberg, 2000 Habenicht, Gerd: Kleben – erfolgreich und fehlerfrei, Vieweg Verlag, Braunschweig/Wiesbaden, 2003 Keller, Thomas: Use of Fibre Reinforced Polymers in Bridge Construction, International Association for Bridge and Structural Engineering IABSE, Zurich, 2003 Kloft, H.; Mähl, F.; Kling, S.: “Bauen mit Kunststoffen”, ­tek-Themenheft no. 7, chair for structural design and ­construction, Kaiserslautern University of Technology, 2005

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Lotz, Stefan: “Untersuchungen zur Festigkeit und Langzeitbeständigkeit adhäsiver Verbindungen zwischen Fügepartnern aus Floatglas”, Ph. D. thesis, Kaiserslautern University of Technology, 1995

9  Plastics as building structure and envelope “Empfangsgebäude in Basel”, Detail, no. 5, 2008, p. 488–491 (Novartis Campus reception building)

Peters, Stefan: “Kleben von GFK und Glas für bau­ konstruktive Anwendungen”, Ph. D. thesis, University of ­Stuttgart, 2006

Engelsmann, Stephan; Spalding, Valerie: “Ein prototypi­ sches Kunststoff-Faltwerk mit neuartiger Fügetechno­ logie”, Stahlbau, no. 78, 2009, p. 227–231 (Plastic folded shell structure)

Rotheiser, Jordan: Joining of Plastics: Handbook for ­Designers and Engineers, Carl Hanser Verlag, Munich/ Vienna, 2009, 3rd edition

FOMEKK, “Abschlussbericht”, Bauhaus-Universität, ­Weimar, 2004 (MYKO)

Schürmann, Helmut: Konstruieren mit Faser-KunststoffVerbunden, Springer Verlag, Berlin/Heidelberg, 2005

Genzel, Elke; Voigt, Pamela: Kunststoffbauten. Die ­Pioniere, Bauhaus-Universität Weimar, ­Universitätsverlag, 2005, p. 133–160 (Futuro)

Trumpf, Heiko: “Stabilitätsverhalten ebener Tragwerke aus pultrudierten faserverstärkten Polymerprofilen”, Ph. D. thesis, RWTH Aachen, 2006 Verein deutscher Ingenieure, VDI 2014, part 1–3, ­“Entwicklung von Bauteilen aus Faser-Kunststoff-­ Verbund”, VDI code

7  Plastics as building envelope “Flagship Store und Firmenzentrale in London”, Detail, no. 5, 2008, p. 498–502 (Reiss Headquarters) “Omnibus-Bahnhof in Emsdetten”, Detail, no. 12, 2002, p. 1566–1569 (Railway station Emsdetten) Pawlitschko, Roland: “Mobiler Pavillon für zeitgenössische Kunst in Hongkong”, Detail, no. 5, 2008, p. 450 (Chanel Mobile Art Pavilion) Schmal, Peter Cachola (ed.); Bollinger, Klaus; Grohmann, Manfred: Workflow. Architecture – Engineering, Birkhäuser, Basel, 2004, p. 72–77 (BMW Bubble)

8  Plastics as building structure Birk, Stephan: “GFK-Glas-Pavillon”, Ingenieurbaukunst in Deutschland. Jahrbuch 2003/2004, Junius Verlag, ­Hamburg, 2003 (GFK-Glass-Pavilion) Engelsmann, Stephan; Spalding, Valerie: “Eine geo­ metrisch komplexe Plastik-Skulptur mit modularem ­Tragwerk”, Bautechnik, no. 85, 2008, p. 345–348 (Plastic tower sculpture) Knippers, Jan; Peters, Stefan: “GRP-glass composite ­ ystems”, Detail Practice: Translucent Materials, Edition s Detail, Munich, and Birkhäuser, Basel, 2004, p. 36–38 (GRP-Glass-Pavilion) Peters, Stefan: “Kleben von GFK und Glas für bau­ konstruktive Anwendungen”, Ph. D. thesis, University of Stuttgart, 2006 (GFK-Glas-Pavillon)

Henckel, Peter; Kurath, Josef: “Flügeldach auf Glasstützen”, Der Bauingenieur, no. 7/8, 2008, p. 36–45 (Novartis Campus reception building) Home, Marko; Taanila, Mika: Futuro. Tomorrow’s House From Yesterday, Desura, Helsinki, 2002 (Futuro)

10  Future developments Burtscher, Stefan: “Vorspannen – nicht kleben!”, Deutsches Ingenieurblatt, no. 7/8, 2005, p. 22–26 Knippers, Jan; Gabler, Martin: “Faserverbundwerkstoffe im Bauwesen”, Stahlbau-Kalender 2007, Ernst & Sohn ­Verlag, Berlin Park, Don-U.: “Materialgerechte lösbare Fügeverbindungen bei glasfaserverstärkten Kunststoffen”, research ­report 29, Institute of Building Structures and Structural Design, University of Stuttgart, 2007 Betz, Holger; Peters, Stefan: “Fiberwood – Ein innovatives Konzept im Fensterbau”, Glaswelt, no. 1, 2008

173

About the authors

Acknowledgements

Stephan Engelsmann studied structural engineering at the Munich University of Technology and architecture at the University of Bath. After earning his doctorate under Jörg Schlaich and Kurt Schäfer, he worked with Werner Sobek Engineers. He is professor of construction and structural engineering at Stuttgart State Academy of Art and Design as well as a partner in the consultancy for structural engineering Engelsmann Peters Beratende ­Ingenieure in Stuttgart.

We would like to thank the architects and engineers who kindly provided information on the projects they designed as well as illustrations for this publication. Similarly, we are grateful to all the companies who informed us about their products and provided insight into their manufacturing processes. Our special thanks go to Gerhardt Spalding for his numerous helpful notes regarding the section on the chemical properties of plastics. Finally, we would like to thank our editor Ria Stein for her consistently conscientious input.

Valerie Spalding studied architecture at the RWTH Aachen. She has worked for various architecture offices in Germany and abroad, including James Carpenter Design Associates in New York. She is an assistant professor at Stuttgart State Academy of Art and Design and conducts research into building with plastics. Stefan Peters studied structural engineering at the University of Stuttgart and has worked for various engineering offices, including Werner Sobek Engineers. He was an assistant professor at the University of Stuttgart under Jan Knippers and earned his doctorate on adhesive connections between glass and fibre-reinforced plastics. He is a partner in the consultancy for structural engineering Engelsmann Peters Beratende Ingenieure in Stuttgart.

174

Name and building index A

G

S

braids  51, 53

ABB Architekten  98, 99

Ganns, Franciska  128, 129

Schein, Ionel  10

brittleness  17, 24, 26

Genzel, Elke  154, 155

Schnegg, Matthias  146–149

bromine  19

Gillmann, Ursula  148, 149

SelgasCano  124–126

building material classes  18

Architektur Consult ZT  100, 101

Goody, Marvin  11, 13

Serafijn, Q. S.  130

C

Artevetro Architekten  19

groenlandbasel  146, 147

Serra, Marco  156–158

calendering  40

ARUP  96, 97

GRP-Glass-Pavilion  138, 139

Snail shell house  11

carbon  21

Atelier van Lieshout  144, 145

Gumpp, Rainer  154, 155

Spalding, Valerie  128, 129, 140, 141

carbon fibre lamellae  163–165

B

H

Spuybroek, Lars  130, 131

carbon fibre-reinforced plastic  13, 57,

Badajoz congress centre and

Hamilton, Richard  11, 13

Squire and Partners  108, 109

Heidenreich, Christian  154, 155

Staubli, Kurath & Partner AG  118, 119

Allmann Sattler Wappner ­Architekten  122, 123

­auditorium  124–126

159, 163 carbon fibres  49

Baloghy, Gerlind  140–142

Herzog & de Meuron  114, 115

Strunge & Hartvigsen  110, 111

carpet plots  93

Bär + Knell  112, 113

Hoofddorp bus station  77, 132–135

Suuronen, Matti  11, 13, 152, 153

casting  41

Swissfiber AG  118, 119 148, 149,

cellulose  21

Bayer, Veit  154, 155

Hossdorf, Heinz  12, 14

BMW Bubble  98, 99

I

Bollinger + Grohmann ­Ingenieure 

Idee Workstation  106, 107

T

chlorine  20, 21

Ingenieurgemeinschaft Führer-­

TBM-Engineering  116, 117

chopped-strand mats  51

98–101, 130, 131

156–158

Kosch-Jürges  102–105

Bulle Six Coques  11, 13

Institute for Building with ­Plastics

C

(IBK)  11

Camus et Cie.  10 Casoni & Casoni  11, 13

Institute of Building Structures and

CFRP ≥ carbon fibre reinforced plastic

Terminal V  116, 117

clamping  81

U

CNC machining  15, 43–45, 108, 109, 130, 132, 156

University of Stuttgart  138, 160, 162

co-extrusion  40

V

Chanel Mobile Art Pavilion  96, 97

Structural Design (ITKE)  138, 160,

van der Lippe, Klaar  144, 145

cohesion  88, 89

Château, Stéphane du  12, 14

162

Vehovar & Jauslin Architektur  118, 119

cohesive fracture  89

Clip-On  144, 145

K

Voigt, Pamela  154, 155

colourants  20

Coulon, René-André  10, 11

Klein Dytham architecture  106, 107

W

composite materials  9, 127, 138,

Cox Architects & Planners  120, 121

Knippers Helbig Advanced

Walther, René  11, 13

­Engineering  160

Craig-Martin, Michael  114, 115

Warren and Rowe  120, 121

162, 169 compression moulding (thermo­ plastics)  41

D

Knippers, Jan  138, 139, 162

Werner Sobek Engineers  122, 123

Darmstadt University

Knobel, Felix  19

Whitby Bird & Partners  114, 115

compression moulding (thermosets)  54 constraint stresses  81

Krause, Thoralf  154, 155

Y

Design Team Kunsthaus  19, 100, 101

Kunsthaus Graz  19, 100, 101

Yitzhak Rabin Centre  136, 137

contact adhesives  83

Dietrich, Gerhard  11

L

Z

continuous profiles  56

of ­Technology  164

Dietz, Albert  11, 13

Laban Creekside  68, 114, 115

Zaha Hadid Architects  96, 97

copolymer  21, 22, 30, 34, 36

Dornier Museum  122, 123

Langlie, Carsten  11, 150, 151

Zonneveld  132–135

corrugated panels  66, 67

D-Tower  130, 131

Les échanges  12, 14

coupling agents  20

Dworzak, Hugo  116, 117

Linne, Stefan  154, 155

creep  58, 87, 93

E

M

Eiertempel  143, 146, 147

Magnant, Yves  10, 11, 13

Emsdetten railway station  102–105

Maneval, Jean Benjamin  11, 13

Engelsmann Peters Beratende

Market hall, Argenteuil  12, 14

­Ingenieure  140–142, 162 Engelsmann, Stephan  128, 129, ­140–142

Michailidis, Apostolos  128, 129 Mobile hotel cabin  10, 11 Monsanto House of the Future  11, 13

Engiplast  132–135

Moshe Safdie Architects  136, 137

Ernst Basler & Partner AG  156–158

MYKO  143, 154, 155

Evonik Röhm  34, 61, 63, 66, 77,

N

164, 168 Eyecatcher Building, Basel  17, 19

NIO architecten  132–135

Subject index 3D printing  44 A accelerators  48 acronyms  29, 30 addition polymers  27 additives  16, 18 adhesion  82, 89 adhesive connections  162 thermoplastics  82

Novartis Campus reception

thermosets  88, 89

­building  156–158

F Farben des Konsums  112, 113

NOX Architects  130, 131

Feierbach, Wolfgang  11, 150, 151

O

fg 2000  11, 12, 143, 150, 151

Octatube Engineering  136, 137

Fhecor  124–126

OX2architekten  102, 103

Fiberline Composites factory and

P

­offices  110, 111 Fischer, Melanie  140–142

Peters, Stefan  138, 139 Plastic folded shell structure  140–142

Five Bubbles  148, 149 Fluid Structures  108, 109

Plastic tower sculpture, ­Stuttgart  16, 127–129

FOMEKK  154, 155 Footbridge over the Schlossgraben, Darmstadt  163

Polymer Engineering Centre  120, 121 Polyvilla  12

Forum Soft  118, 119

R

Franken, Bernhard  98, 99

Reiss Headquarters  108, 109

Fuller, Richard Buckminster  10

Rondo  11, 13

Futuro  11, 13, 143, 152, 153

Ronkka, Yrjö  11, 13, 152, 153 Ruth, Jürgen  154, 155

surface preparation  83, 92 adhesive fracture  89, 90 adhesives  82, 83 aerobic adhesives  83 aerogel  75, 160 aluminium hydroxide  19 amorphous  23–25 anaerobic adhesives  83 anisotropic  50, 58, 87 aramid fibres  50, 51, 58 autoclave  54–56 B benzene rings  32 blend  21 bonding forces  21–26, 88 boron  21 braiding  54

cross-linking  15, 21–27, 46 crystalline  23 crystallisation  23 cyanacrylate  83 D DDM ≥ Direct Digital Manufacturing deep-drawing  44 delamination  58 dichroic  62 DIN 18820  92 DIN 4102  18, 32 DIN EN 13501  18 DIN EN 13706  92 Direct Digital Manufacturing  42 dispersion adhesives  83 dome shell, segmented  12 double bond  26, 27 E elasticity  24 elastomeric bearings  78 elastomers  15, 24, 29 EPDM  31 EPM  31 epoxy resins  48, 70, 132 EPS ≥ expanded polystyrene ETFE  37, 38, 66, 96 ethylene propylene diene rubber ≥ EPDM ethylene propylene rubber ≥ EPM ethylene tetrafluoroethylene ≥ ETFE

175

EUROCOMP Design Code and

synthesis  21, 25–27

hydrocarbons  21

polymerisation  20, 26, 27

I

polymethylmethacrylate ≥ PMMA

synthesising techniques  21, 25–27

expanded polystyrene  36, 76, 132

impact resistance  18, 22, 32, 36

polystyrene  35, 36, 72, 76

T

extruded polystyrene  36, 76

injection moulding  40, 41

polytetrafluoroethylene ≥ PTFE

tangled structure  24

extrusion  39

injection processes  54

polyurethane ≥ PUR

tape lamination  55

F

in-mould skinning  41

polyvinylchloride ≥ PVC

technical plastics  32

failure mechanisms  89

insulation  34, 37, 42, 57, 75, 76, 95, 100

positive mould  52

temperature transition range  23

failure mechanisms, screwed

insulation characteristics  17, 59

prefabrication  11, 15

textile glass mats  51

integral skin foam  42, 72

prepregs  40, 54

thermal expansion, coefficient  17, 33,

fibre content  52, 54, 57

interface layer  88

primary valence forces  22

fibre-reinforced plastics  50, ­56–58,

intumescent coatings  20

prototype manufacture  10, 15, 42, 51

thermal reforming  44

159

K

PS ≥ polystyrene

thermoplastic elastomers  15, 24, 26

dimensioning  92

knitted fabric  51, 53

PTFE  37

thermoplastic foam casting  42

durability  94

L

pultrusion  56

thermoplastic plastics ≥ thermoplastics thermoplastics  15, 24, 32

­Handbook  92, 93

­c onnections  87

34, 38, 81

mechanical properties  58, 59

laminated object manufacturing  44

PUR  9, 36, 37, 136, 144, 150, 152, 156

modulus of elasticity  57, 92

laminates  52

PVC  34, 35

standards  92

lamination theory  92

PVC profiles  77

machining  45

testing  93

laser sintering  43

R

manufacture  39–44

joining techniques  81–85

fillers  18, 19

laser welding  85

rapid manufacturing  42, 43

material  32–46

finite-element calculations  62, 93, 94

M

rapid prototyping  15, 42, 43, 166

material parameters  38

fire resistance  17, 18

macromolecules  21

rapid tooling  42, 43

recycling  46

fire safety  17–20

magnesium hydroxide  19

reactive adhesives  33, 83

thermal reforming  44, 45

fire safety classes  18

manual laminating  52, 96, 118, 128,

recycled material  46, 112

flame retardant  18, 20

130, 146, 148, 154, 156

thermosets  15, 26, 48–59 available forms  51–59

recycling  46–48

flammability  17–20, 59, 159

matrix  15, 19, 22, 48

reforming process  44

joining techniques  86–91

fluorine  21

molecular structure  15, 21–24

regranulate  46

manufacture  50

fluoropolymers  37

monomer  21

reinforcement materials  18, 19, 49, 50,

material parameters  59

foaming agents  20, 36, 37

mould removal  41, 42, 52

foams  36, 37, 42

multi-component adhesives  83

reinforcing fibres  49–58

foil cushions  38

multilayer extrusion ≥ co-extrusion

resin infusion method  55

TPE ≥ thermoplastic elastomers

foils  66

multiwall sections  68

resin matrix ≥ matrix

transverse tensile failure  87

properties  57

55

working methods  56

ETFE  37

N

resin transfer moulding  55

twill weave  51

manufacture ≥ calendering

negative mould  45, 52, 136

retarders  48

two-component adhesives  83, 138

PTFE  37

non-woven scrims  51, 54

ribbed multiwall sheeting  66, 106, 114,

U

PVC  34

P

122, 160

ultrasound welding  85

FRP ≥ fibre-reinforced plastics

PAN ≥ polyacrylnitrile

rigid foam  37, 45, 46, 52, 75

unsaturated polyester resin  27, 48

functionality  21

PC ≥ polycarbonate

rovings  51, 53, 56

UP ≥ unsaturated polyester resin

fused deposition modelling  44

peeling stresses  90

RTM process ≥ resin transfer moulding

urethane  36

G

peel-ply fabrics  92

S

UV resistance  16

gelcoat  49, 52, 55, 94

phosphorus  20

sandwich construction  11, 95, 136,

generative fabrication ≥ Direct Digital

photopolymer  43

Manufacturing

144, 150, 152, 154, 156

V vacuum methods  51, 52 VDI guideline 2014  92

plain weave  51

sandwich injection moulding  39

geodesic dome  10

plain woven fabric  51, 53

sandwich mats  51

vibration welding  85

geoplastics  80

plastic houses (history)  10–13

sandwich panels  70–76

vinylester resins  48

building control approval  12

satin weave  51

vulcanisation  170

56–58

mass production  11, 12, 150, 152

screwed connections  81, 86, 87

W

applications  10, 96, 102, 110, 116,

prefabrication  11

secondary valence forces  22, 23, 90

weather protection coating  52, 94, 163

118, 120, 128, 130, 132, 136, 138, 144,

prototypes  11, 12

selective laser sintering  43

weather resistance  10, 33, 34, 79, 83,

146, 148, 150, 152, 154, 156, 160

shell construction  12

self-supporting building envelopes  11,

electromagnetically permeable  10

thermal performance  12, 13

glass fibre-reinforced plastics  51,

forming  10, 15, 51–57

wide-span roof structures  12

98, 136, 146, 161 semi-crystalline  23, 24

160 welding  85, 86 wet bonding adhesives  82

prototyping  10

plasticisers  34

shear stresses  90

wettability  83, 84

weather resistance  10, 16, 57

PMMA  32, 33, 61–64, 67, 77, 98, 100,

Shore hardness  29–31

winding  50, 55, 56

102, 108, 124, 163

silicon  21, 83

woven staple-fibre glass textile  52

glass filament mats  51

PMMA GS  33, 41, 61

silicones  83

X

granulate  32, 39

PMMA HA  34

single-component adhesives  83

XPS ≥ extruded polystyrene

GRP grating  78

polyacrylonitrile  50

solid ground curing  43

Y yarn  51–53

glass fibres  49

GRP profiles  77–79, 110, 118, 124, 138, 159, 161 GRP ≥ glass fibre-reinforced plastics H

polyaddition  26, 27, 48

solvent-based adhesives  82

polyamide, aromatic  50

spacer fabric  52, 54

polycarbonate  32, 63, 64, 71, 106, 114,

stabilisers  19

122, 124, 140

standard plastics  32

heat distortion temperature  18, 22, 24

polycondensation  26, 27

stereolithography  43

heated-tool welding  85

polyester resin  48, 49

stress cracking  22, 24, 33, 35, 81

homopolymer  21

polymer blend ≥ blend

structures, repair and streng­

hot gas welding  85

polymer chains  21–26, 31, 34

thening  13, 163

hot melt adhesives  83

polymer structure  19, 36, 88

sulphur bridges  31

Illustration Credits

colophon

1  The Development of Plastic

Pryce, 3–5 Squire and Partners;

Graphic design concept and layout: Muriel Comby, Basel

­Architecture

FIBERLINE COMPOSITES FACTORY AND

Typesetting: Stephan Schinkel, Leipzig/Basel

1.1 Carl Hanser Verlag; 1.2 Buckminster

OFFICES 1 Fiberline Composites A/S,

Editor: Ria Stein, Berlin

Fuller Institute; 1.3 from: Arthur Quarm-

photograph: Poul Elmstrøm, 2 Fiberline

Translation into English: Julian Reisenberger, Weimar

by, The Plastics Archi­tect, Pall Mall

Composites A/S, 3 Fiberline Com­p o­sites

Copyediting: Raymond Peat, Alford, Aberdeenshire

Press, London, 1974; 1.4 Monsanto

A/S, photograph: Poul Elmstrøm,

­Company Records, University Archives,

4 Fiberline ­Composites A/S; Farben

This book is also available in a German edition (Kunststoffe in

­Department of Special Collections,

des Konsums 1, 2 Bär + Knell; L aban

­Architektur und Konstruktion, ISBN 978-3-0346-0321-8) and

­Washington University, St. Louis;

Creekside 1 Christian Fischer-Wasels,

a French edition (Plastiques en architecture et construction,

1.5, 1.6 ­Institut für das Bauen mit Kunst­

2 Herzog & de ­Meuron, 3 from: Detail,

ISBN 978-3-0346-0670-7).

stoffen e.V., Darmstadt; 1.7 Pamela

No. 7/8, 2003; ­T erminal V 1, 2 Craig

Voigt; 1.8 from: Heinz ­Hossdorf – Das

Kuhner, 3, 4 Hugo ­Dworzak; Forum

­Erlebnis Ingenieur zu sein, Birkhäuser

Soft 1–3 Beat ­Widmer, 4 Valerie

Verlag, Basel, 2002

­Spalding; Polymer Engineering

Bibliographic information published by the German National Library:

­Centre 1–4 Cox Archi­tects + Planners;

The German National Library lists this publication in the Deutsche

Library of Congress Control Number: 2010923933

2  Material properties

Dornier ­Museum 1, 2 Allmann Sattler

­Nationalbibliografie; detailed bibliographic data is available on the

of ­p l astics

Wappner, photograph: Jens Passoth,

­Internet at http://dnb.d-nb.de.

2.1, 2.2 Valerie Spalding; 2.3 Fiberline

3 Valerie Spalding, 4 Allmann Sattler

Composites A/S; 2.4 Bollinger + Groh­

Wappner, photograph: Jens Passoth;

This work is subject to copyright. All rights are reserved, whether the

mann, photograph: Gernot Stangl

BADAJOZ CONGRESS CENTRE AND

whole or part of the material is concerned, specifically the rights of

AUDITORIUM 1 SelgasCano, 2 Roland

translation, reprinting, re-use of illustrations, recitation, broadcasting,

3  Basics of plastics

­Halbe, 3 SelgasCano, 4, 5 Roland ­Halbe,

reproduction on microfilms or in other ways, and storage in data banks.

3.1–3.14 Valerie Spalding

6 SelgasCano

For any kind of use, permission of the copyright owner must be

4  Plastics and their manufacture

8  Plastics as building structure

­obtained. 4.1–4.32 Valerie Spalding; 4.33 Arbeits-

PLASTIC TOWER SCULPTURE 1–3 Valerie

© 2010 Birkhäuser GmbH

gemeinschaft PVC und Umwelt e. V.,

Spalding, 4 Valerie Spalding, Franciska

P.O.Box 133, CH-4010 Basel, Switzerland

photograph: Bettina Koch; 4.34–4.36

Ganns; D-Turm 1, 2 Valerie Spalding,

Valerie ­Spalding; 4.37 Engelsmann

3, 4 NOX Architects, Lars Spuybroek;

Printed on acid-free paper produced from chlorine-free pulp. TCF ∞

Peters; 4.38–4.43 Valerie Spalding;

HOOFDDORP BUS STATION 1 Gerhardt

Printed in Spain

4.44–4.46 Engelsmann Peters;

Spalding, 2 NIO architecten, 3 Gerhardt

4.47 ­Fiberline ­Composites A/S;

Spalding, 4 NIO architecten, photograph:

ISBN 978-3-0346-0322-5

4.48–4.50 Engelsmann Peters

Radek Brunecky, 5 Gerhardt Spalding,

9 8 7 6 5 4 3 2 1

6–8 NIO architecten; ROOF YITZHAK 5  Finished and

RABIN CENTRE 1–3 ­Octatube; GRP/

semi-finished products

GLASS PAVILION 1 Valerie Spalding, ­

5.1–5.14 Valerie Spalding; 5.15 Waco­

2 Nigel Young, 3 Engelsmann Peters;

tech GmbH & Co. KG; 5.16–5.26 Valerie

PLASTIC FOLDED SHELL STRUCTURE

­Spalding; 5.27 NIO architecten; 5.28 Iso-

1–7 Valerie ­Spalding

www.birkhauser.ch

Massivhaus; 5.29 Valerie Spalding; 5.30 Fiberline Composites A/S;

9  Plastics as building

5.31 ­Arbeitsgemeinschaft PVC und

structure and envelope

Umwelt e. V., photograph: Bettina Koch;

CLIP-ON 1 Valerie Spalding, 2 Atelier van

5.32 ­Evonik Röhm GmbH

Lieshout; EIERTEMPEL 1–4 groenlandbasel; FIVE BUBBLES 1–4 Arbeitsge-

6  Building with plastics

meinschaft Gillmann Schnegg;

6.1–6.9 Valerie Spalding; 6.10,

fg 2000 1–4 ­Wolfgang ­Feierbach;

6.11 ­Engelsmann Peters; 6.12 Valerie

F ­ uturo 1 ­Boijmans Museum, Rotter-

­Spalding; 6.13 Engelsmann Peters;

dam, © ­Centraal ­Museum, ­Utrecht,

6.14 Valerie Spalding;

2 Museum of Finnish Architecture, Hel-

6.15–6.18 ­Engelsmann Peters

sinki (­Suomen Rakennustaiteen Museo), © Matti ­Suuronen, 3 Boijmans Museum,

7  Pl astics as building envelope

Rotterdam, © Centraal ­Museum,

Chanel Mobile Art Pavilion 1 John

Utrecht, 4 Valerie Spalding; MYKO 1–4

­Linden, 2 Virgile Simon Bertrand,

FOMEKK; NOVARTIS CAMPUS ­RECEPTION

3, 4 Zaha Hadid Architects; BMW

BUILDING 1 Jörg Päffinger, 2 Novartis,

­B ubble 1–3 Franken Architekten;

Marco Serra, 3, 4 Ernst ­Basler + Partner

Kunsthaus Graz 1 Arge Kunsthaus,

AG, 5 Ernst Basler + ­Partner AG, Chris-

2 Bollinger + Grohmann, photograph:

toph Haas, 6 Novartis, Marco Serra

Matthias Michel, 3 Bollinger + Groh­

References to existing patents, registered designs and trademarks have not been explicitly declared in this book. Where there is no such notice,

mann, 4 Bollinger + Grohmann, photo-

10  Future developments

graph: Matthias Michel; RAILWAY

10.1 ITKE, University of Stuttgart;

to the large number of differently named materials and products, it was

­STATION EMSDETTEN 1–8 OX2 Architek-

10.2 ­Valerie Spalding; 10.3 Fenster Betz

not possible to exhaustively check the possible existence of protected

ten; Idee Workstation 1–3 Katsuhisa

GmbH, Albstadt; 10.4 Evonik Röhm

trademarks. In the interests of consistency, we have therefore chosen

Kida; Reiss Headquarters 1, 2 Will

GmbH; 10.5 Sika Deutschland GmbH

not to declare any trademarks (such as ® or ™) in the text.

this does not mean that a product or product name is not protected. Due