Machinery adhesives for locking, retaining, and sealing [1st ed.] 9781351434416, 1351434411, 0-8247-7467-1

Citation preview

Machinery Adhesives for Locking, Retaining, and Sealing

M E C H A N IC A L E N G IN E E R IN G

A Series of Textbooks and Reference Books

EDITORS L. L. FAULKNER

S. B. MENKES

Department o f Mechanical Engineering The Ohio State University Columbus, Ohio

Department o f Mechanical Engineering The City College o f the City University o f N ew York New York, N ew York

1. 2. 3. 4. 5. 6. 7. 8.

9. 10. 11. 12. 13. 14. 15.

Spring Designer’s Handbook, by Harold Carlson Computer-Aided Graphics and Design, by Daniel L. Ryan Lubrication Fundamentals, by J. George Wills Solar Engineering for Domestic Buildings, by William A. Himmelman Applied Engineering Mechanics: Statics and Dynamics, by G. B oothroyd and C. Poli Centrifugal Pump Clinic, by IgorJ. Karassik Computer-Aided Kinetics for Machine Design, by Daniel L. Ryan Plastics Products Design Handbook, Part A: Materials and Components; Part B: Processes and Design for Processes, edited by Edward Miller Turbomachinery: Basic Theory and Applications, by Earl Logan, Jr. Vibrations of Shells and Plates, by Werner Soedel Flat and Corrugated Diaphragm Design Handbook, by Mario Di Giovanni Practical Stress Analysis in Engineering Design, by Alexander Blake An Introduction to the Design and Behavior of Bolted Joints, by John H. Bickford Optimal Engineering Design: Principles and Applications, by James N. Siddall Spring Manufacturing Handbook, by Harold Carlson

16. Industrial Noise Control: Fundamentals and Applications, edited by Lewis H. Bell 17. Gears and Their Vibration: A Basic Approach to Understanding Gear Noise, by J. Derek Sm ith 18. Chains for Power Transmission and Material Handling: Design and Applications Handbook, by the American Chain Association

18. Chains for Power Transmission and Material Handling: Design and Applications Handbook, by the American Chain Association 19. Corrosion and Corrosion Protection Handbook, edited by Philip A. Schweitzer 20. Gear Drive Systems: Design and Application, by Peter Lynwander 21. Controlling In-Plant Airborne Contaminants: Systems Design and Calculations, by John D. Constance 22. CAD/CAM Systems Planning and Implementation, by Charles S. Knox 23. Probabilistic Engineering Design: Principles and Applications, by James N. Siddall 24. Traction Drives: Selection and Application, by Frederick W. Heilich III and Eugene E. Shube 25. Finite Element Methods: An Introduction, by Ronald L. Huston and Chris E. Passerello 26. Mechanical Fastening of Plastics: An Engineering Handbook, by Brayton Lincoln, Kenneth J. Gomes, and James F. Braden 27. Lubrication in Practice, Second Edition, edited by W. S. Robertson 28. Principles of Automated Drafting, by Daniel L. Ryan 29. Practical Seal Design, edited by Leonard J. Martini 30. Engineering Documentation for CAD/CAM Applications, by Charles S. K nox 31. Design Dimensioning with Computer Graphics Applications, by Jerome C. Lange 32. Mechanism Analysis: Simplified Graphical and Analytical Techniques, by Lyndon O. Barton 33. CAD/CAM Systems: Justification, Implementation, Productivity Measurement, by Edward J\ Preston, George W. Crawford, and Mark E. Coticchia 34. Steam Plant Calculations Manual, by V. Ganapathy 35. Design Assurance for Engineers and Managers, by John A. Burgess 36. Heat Transfer Fluids and Systems for Process and Energy Applications, by Jasbir Singh 37. Potential Flows: Computer Graphic Solutions, by R obert H. K irchhoff 38. Computer-Aided Graphics and Design, Second Edition, by Daniel L. Ryan 39. Electronically Controlled Proportional Valves: Selection and Application, by Michael J. Tonyan, edited by Tobi Goldoftas 40. Pressure Gauge Handbook, by AMETEK, U.S. Gauge Division, edited by Philip W. Harland 41. Fabric Filtration for Combustion Sources: Fundamentals and Basic Technology, by R. P. Donovan 42. Design of Mechanical Joints, by Alexander Blake

43. CAD/CAM Dictionary, by Edward J. Preston, George W. Crawford, and M arkE. Coticchia 44. Machinery Adhesives for Locking, Retaining, and Sealing, by Girard S. Haviland OTHER VOLUMES IN PREPARATION

Machinery Adhesives for Locking, Retaining, and Sealing

GIRARD S. HAVI LAND Loctite Corporation Newington, Connecticut

Marcel Dekker, Inc.

New York and Basel

L ib rary of C ongress C ataloging-in-Publication Data H aviland, G irard S ., [date] M achinery adhesives for locking, re ta in in g , and sealing. (Mechanical engineering ; 44) Includes bibliographies and index. 1. Jo ints (E ngineering) 2. A dhesives. 3. Machine p a r ts . 4. Metal bonding. I. T itle. II. Title: M achinery ad h esives. III. S eries. TJ1320.H38 1986 621.8f6 85-25314 ISBN 0-8247-7467-1

COPYRIGHT ©1986 by MARCEL DEKKER, INC.

ALL RIGHTS RESERVED

N either th is book nor any p a rt may be reproduced or transm itted in any form or by any means, electronic or mechanical, including photo­ copying, microfilming, and reco rd in g , or by any inform ation storage and re trie v al system , without perm ission in w riting from the p u b lish er. MARCEL DEKKER, INC. 270 Madison A venue, New Y ork, New York

10016

C u rre n t p rin tin g (last d ig it) : 10 9 8 7 6 5 4 3 2 1 PRINTED IN THE UNITED STATES OF AMERICA

Dedicated to the conquest of inner space and improvement of productivity in the world, and to the Loctite Corporation and its customers who are working to make this happen.

Preface

The spaces left afte r the assembly of th rea d ed , flanged, and p re ssfitted p a rts have always been a source of tro u b le. The amount of m etal-to-m etal contact between th re a d s and heavy p re ss fits varies between 20 and 30% of the total area involved, which means th at 70 to 80% is do-nothing space. Shifting th re a d s, moving flanges, and f r e t­ tin g cylindrical fits will loosen, leak, and allow p a rts to fail c a ta stro ­ phically. Before 1956, the ills of in n er space were tre a te d mechanically by eliminating as much space as possible with closer fits and finer fin ish es, at ev e r-in creasin g cost and with rapidly dim inishing re s u lts. Jamming the space with an interm ediate m aterial such as caulk or solder was effective b u t awkward and sometimes, with solder, therm ally de­ stru ctiv e and irre v e rsib le . Since 1956 the Loctite C orporation has specialized in organic m aterials th at cure exclusively in these airless sp aces, adding convenience to function and re su ltin g in benefits of cost and reliability th at modern engineering cannot ignore. The Loctite C orporation’s assistance in p re p a rin g th is book has been critical to its accuracy and completion. The object of th is book is to guide the d esig n er, process en g in eer, or mechanic in selecting and using anaerobic m achinery adhesives e f­ fectively. It is my hope th a t stu d en ts of engineering also will benefit from th is book, so I will include the ’’why” as well as ’’w hat” and ’’how” about th ese m aterials. By u n d ersta n d in g m achinery adhesive technology, it is possible to be innovative in its application. The early innovators were called ’’Loctite C harlies” because of th e ir addiction for adhesive solutions to mechanical fittin g problem s. I am indebted to them for showing the way and providing examples th at I have categorized into generic classes. These generic examples are shown in the appropriate

v

vi

Preface

c h a p te rs and in the design h in ts section, in o rd e r to s ta rt the in v en ­ tive juices flowing. Most adhesive applications re q u ire a system s approach to be su c­ cessfu l. Although m achinery adhesives have been formulated to achieve success in ord in ary in d u strial environm ents, it is still n ec es­ sary to consider su rfa ces, application method, cure system , and te s t methods before the final benefits are realized. P rofessor Gerald Schne b e rg e r of th e GMI E ngineering and Management In s titu te , an a s ­ tu te teac h er in the adhesive and coating field, had a to ngue-incheek way to point out the needs of a system s approach for adhesives. The following are his ’’Seven Sins of Commission” (o r "How to Hate A nything to Do with A dhesives"):* 1. Skip the te s t in your facility. J u s t use the average re su lts off of th e v e n d o r’s data sh eet. "Typical" p ro p e rtie s show th a t you can squeak b y ; and your application is typical. 2. Keep th e old joint design even if it doesn’t suit an adhesive. Some where th e re must be something with high peel and high tensile stre n g th too. 3. Assume th at on-line tem p eratu re, hum idity, and cleanliness will cu re th e adhesive the same as the conditions in your lab o rato ry . 4. Expect y o u r adhesive to be stro n g er than steel and ju st as stro n g in w ater as it was in your p rototype te s t. 5. Keep th e vendor out of your shop. A fter all, his experience is gained from people like you, and your process is so unique it must be k ep t se c re t. 6. S u rp rise yo u r w orkers at the last minute to im press them with how p ro g ressiv e you were to have the p rocess worked out without th e ir know ing. 7. Keep th e design, m aterials, and production people at arm ’s len g th . They a re n ’t the b est of buddies anyw ay, and they have a habit of asking tough qu estio n s. B esides, if they get in te re ste d in your p ro jec t, th ey will ju st delay your g ettin g th in g s going. What I will do is give you, the d esig n er, en g in eer, u s e r, and a s ­ sem bler, enough data and knowledge about the p ro d u c ts to plan your system s ap p roach. When your requirem ents are not covered by the data in the book, it should be evident th a t you need assistance from specialty chemical form ulators. They can match a material to your r e ­ quirem ents or give you ap p ro p riate data. This is a book of "w hy," "how," and "what" for stan d ard machin­ e ry ad h esiv es. A lot of the data is em pirical, derived scientifically in

♦Adapted with perm ission.

Preface

vii

the lab o rato ry . Where theoretical and analytical approaches help in u n d ersta n d in g and designing, they are given. Data are assembled in tables and g rap h s for ready re fere n ce. As with any book of technology, this one builds on what was done by o th e rs . I am deeply indebted to those who worked with me and came before me. I especially want to thank the Loctite C orporation, o rig in ato r of th is technology, and all the men and women who share its h isto ry . (For more about these people, I highly recommend the book Drop by Drop: The Loctite S t o r y , by Ellsworth G rant, Loctite C orpo­ ra tio n , Newington, C onn., 1983.) My g ra titu d e and th an k s for the assistance of w riting talen ts g re ater th an mine go to B ruce Burnham of B ruce Burnham & Associates for spearheading th e illustration p roduction, and to Gale Sorensen of B arbeau Associates for proofing and co rrectin g s c rip t. Girard S. Haviland

Contents

Preface C h a p te r

v 1General Information A bo u t Machinery A d h e s iv e s

1. 2. 3. 4. 5. 6. Chapter

2 E n g in e e rin g Data B a n k

1. 2. 3. 4.

C h a p te r

Introduction What They Are Like Where They Are Used How They Are Selected Packaging and Handling Government and Independent Laboratories Requirem ents

Summary of P roperties T hread Locking Material Selection V ariables Affecting Cure Speed and Initial S tren g th Surface Coverage and Q uantity Tables Appendix

3 Environmental Effects

1. 2. 3. 4. 5. 6.

1

1 5 6 10 25 33 41

41 42 55 68 77 78

Solvent R esistance Hot S tren g th Heat Aging and Service Life Cold Effects Vacuum and P ressu re Sealing O utgassing

ix

78 90 93 103 106 107

Contents

X

7. 8. 9. 10. Chapter 4

Application M ethods and Safety

1. 2. 3. 4. 5. 6.

Chapter 5

5.

D esigning the Bolted Joint Loosening Tendencies of Bolted Joints P revention of Prem ature Loosening Generic Applications for T hread Locking A dhesives S ecuring of S tuds Appendix R eferences

A d h e s iv e Fitting of C y lin d ric a l P a r ts

1. 2. 3. 4. 5. 6. 7.

Chapter 7

Introduction Application of Liquids Application Tips Tumbling Techniques Preapplied M aterials Safety Appendix

Se cure Boltin g

1. 2. 3. 4.

Chapter 6

Fungus R esistance Corrosion P revention S tress C orrosion Explosive Compatibility

General Problem of In n er Space and Hub S tress Generic Design B enefits Design C alculations Fatigue C onsiderations Compressive S tren g th B ushing Mounting Mounting of Ball and Roller B earings Appendix R eferences Bibliography

S e alin g : Le a ks

1. 2. 3. 4. 5.

109 109 112 112 113

113 115 159 165 171 171 177 180

180 190 200 201 202 211 218 220

220 220 231 242 243 244 252 270 272 272

T h e A r t an d Science of P re v e n tin g

Introduction T raditional T hreaded Systems Four Sealing Techniques Sealing Applications Flanged Systems

273

273 274 279 281 281

Contents

xi 6. 7. 8. 9. 10. 11. 12.

Chapter 8

Flange Design C onsiderations Flange Bolts Gaskets System Reliability Designing with Form ed-in-Place Sealants T hread and Flange Sealing A pplications Porosity Sealing Appendix B ibliography

D e s ig n H in ts

1. 2. 3. 4. 5. 6. 7. 8.

Introduction Simplifying P art M anufacture Making Use of S tandard MachineP arts C entering P arts Injecting Adhesive Shimming and Electrical Insulating S ho rtcu ttin g Machining Conclusion

286 291 293 301 302 304 306 318 319 320

320 320 324 324 328 328 329 330

Glossary

331

Index

335

Machinery Adhesives for Locking, Retaining, and Sealing

Chapter 1 General Information About Machinery Adhesives

I.

IN T R O D U C T IO N

E ver since m achinery has been b u ilt, designers and m achinists have faced th e problem of fittin g assemblies to minimize the in n er space th at allows leaking and moving, or w orking, of apparently tig h t p a r ts . In n er space is eith er the clearance th a t ex ists between p a rts to allow for th e ir assem bly, such as in a th rea d ed assem bly, or th e space th at cannot be filled because a p re ss fit can produce only p eak-to-peak contact of su rface irre g u la ritie s, th u s leaving a su b stan tial 70 to 80% of noncontact in n e r space (Fig. 1 .1 ). In th e early 1800s special machines were developed to tu rn the bores and p a rts of cannon and steam cylinders which, in James WattTs o rig ­ inal experim ents, had "close” fits of about 0.06 in . To produce tig h t jo in ts , s trip s of le a th e r, hem p, and clay were used to caulk th e jo in ts. Since th e n , m achinery to fit cylindrical p a rts has re q u ired more and more precision at hig h er and h ig h er costs (F ig. 1 .2 ). D esig n ers, e n g in ee rs, and m achinists can now eliminate th is p ro b ­ lem on statio n ary fits by using m achinery adhesives. Typical stationary fits would be a bolt in a th rea d ed hole, a p re ss fit of a ball bearin g on a s h a ft, or a clamped flange sealing in tern a l machine p a r ts . In co n trast to s tru c tu ra l ad hesives, which are used as the prim ary holding means in a s tru c tu re (often in direct te n s io n ), m achinery adhesives are gen­ erally used in rigid cylindrical assemblies in a sh ear o r com pressive mode to eliminate leakage and provide a noncreeping joint.

1

General Inform ation A b o u t Machinery Adhesives

(a) FIGURE 1*1

Inner space of a heavy p re ss fit and a class 2 th re a d .

Introduction

4

General Information About Machinery Adhesives

Relative machining co sts, surface fin ish es, and to leran ces. (A dapted from Tool and Manufacturing Engineers Handbook, 3rd edition, Society of M anufacturing E ngineers, D etroit, Michigan, 1976.) F I G U R E 1.2

1.1

M a c h in e r y A d h e s iv e S u b g r o u p s and the F i r s t - C h o ic e M aterials

T hread lockers for stra ig h t and tap ered th re a d s Grade M, N, and 0 , or preapplied MM, NN, SS, and TT Stud s e tte rs Grade K, L, or O Friction im provers for p re ss fits Grade S, T, or U R etaining compounds for slip fits Grade S, T, or U

What They Are Like

5

T hread sealants for tap ered and stra ig h t th re a d s Grade W (tap e red th re a d ), N, o r preapplied NN (s tra ig h t) Sealants and friction im provers for flat surfaces Grade X or Y Porosity sealants for c a stin g s, w elds, and powder metals Grade R or S Shims for flat o r cylindrical surfaces Grade Z

2.

W H AT T H E Y A R E L I K E

B razing, sold ering, and adhesives all look the same to the designer however much th ey differ in detail. Separate p a rts are joined by an interm ediate m aterial—a liquid different from th e base m aterials being joined—which is drawn by w etting and capillary action into the joint, where it h ard en s to form the bond. Soldering and b ra zin g m aterials were the firs t m aterials used for cylindrical fittin g . In soldering and b ra zin g , the h ardening is a physical change of s ta te . In adhesion the hard en in g is usually the re su lt of a chemical change th a t tran sform s a liquid into a d en se, hard polym er. The r e ­ su lt is the same: a bonded, sealed joint where in n er space is filled to achieve th e re s u lt. A lthough solders and brazes are still used e x te n ­ sively because of th e ir stre n g th and liquid fill c h a ra c te ris tic s , they re q u ire tem p eratu res of 600 to 1200°F to melt th e solder to wet the p a r t, which can be a serious draw back. Some metals cannot be wetted at all, and at th ese tem peratures many p a rts are d isto rted or d estro y ed . In 1964 a new line of free -ra d ic a l-c u rin g m aterials th a t were stab il­ ized by th e p resen ce of air was introduced to th e m achinery m arket and aptly given th e name anaerobic. * These com pounds, although complex in th e ir ch em istry, are simple to use and durable afte r c u re . For the most p a r t, anaerobic m aterials cure at room tem perature within minutes afte r th ey are confined betw een p a rts such as a bolt and n u t , a b e a r­ in g and b o re , or two flanges, or in pipe th re a d s. Cure is initiated by a free radical of iron or copper on the su rface. Modern chem istry and engineering have refined th e formulations so th a t many param eters of organic m achinery adhesive can be controlled, including v isco sity , lu b ric ity , cure speed, sh ear s tre n g th , modulus, ultimate s tre n g th , impact re sista n c e , and chemical re sista n c e , as well as minor ch a rac te ristic s such as color and fluorescence. The original anaerobic fre e -ra d ic a l-c u re system has been im proved in some cases with m oisture c u re s , ultraviolet c u re s , and tw o-com ponent, d ry -to -th e touch preapplied films. The preapplication method involves the microencapsulation of the re sin or th e ac tiv a to r, which is mixed into a *They were developed by the American Sealants Company, founded in 1954, which is now the Loctite C orporation.

General Information About Machinery A dhesives

6

s lu rry . The s lu rry is applied to p a rts away from the assembly line and allowed to d ry before assembly tak es place. The material releases a fa s t-c u rin g liquid during the assembly of th re a d s in a manner analo­ gous to squeezing w ater from a sponge. Preapplied m achinery ad h e­ sives are Type VI G rades MM, NN, SS, and TT.

3.

WHERE T H E Y A R E U SED

1. T hread locking and sealing were th e first uses for th ese a n a e r­ obic m aterials. Filling the th re a d s with a h a rd , dense m aterial p r e ­ v en ts self-loosening of n u ts and bolts as in Fig. 1.3, which illu stra te s a n u t and bolt secured with an anaerobic re s in . 2. T hread sealing and p re v en tin g of corrosion are o th er purposes of th re a d locking and sealing m aterials. The disassem bled badly ru s te d bolt in Fig. 1.4 shows how corrosion was p rev en ted in the th re a d s by a Grade N adhesive. 3. P ress fits and bore close-in on b u sh in g m ountings can be avoid­ ed by the use of a m achinery adhesive (F ig. 1 .5 ). Slip fit bu sh in g s may be aligned from the shaft ra th e r than the b o re.

F I G U R E 1.3

r e s in .

In n er space of th re a d s secured with cu red anaerobic

Where They Are Used

7

F I G U R E 1.4 T h read s sealed on a corroded nut and bolt: (A) as co r­ roded for six months in salt sp ra y , (B) a fte r wire b ru sh in g , (C) d is­ assem bled, showing clean th re a d s p rotected by m achinery adhesive N.

4. Ball b earin g assembly using m achinery adhesive allows accurate alignment from sh afts with relaxed tolerances and fits of the b o res. The assembly can be done by hand without p re sse s or hammers. No distortion of the b ea rin g or housing tak es place (F ig. 1 .6 ). 5. Key and keyway fittin g p re v e n ts fre ttin g and loosening from re v ersal to rq u es which occur on most driven sh afts (F ig. 1 .7 ). 6. Most economical is the retain in g and sealing of cylindrical p a rts such as cup p lu g s , s h a f ts , r o to r s , g e a rs , p u lle y s , and oil seals th at may have been previously p re ss fitted with mediocre re su lts or ex p en ­ sive failures (F ig. 1 .8 ). Fragile shafts can be assembled and secured without bending or misalignment. 7. Rigid sh afts can be assembled easily without powered eq u ip ­ ment (Fig. 1 .9 ). 8. Im pregnating powder metal p a r ts , porous ca stin g s, and welds p re v e n ts u n d erp latin g corrosion, holds p re s s u re , and a ssists in m achining by p re v en tin g tool wear (Fig. 1.10). Many p a rts th at needed plating for appearance or protection could not be made from

8

FIGURE 1.5

General Information About Machinery Adhesives

Slip fitted b u sh in g .

FIGURE 1.6 Adhesively mounted m iniature dental tu rb in e drill b earin g s (cutaw ay) illu stra te how alignment from th e shaft can allow operation at 400,000 RPM without shake or loosening.

General Information About Machinery Adhesives

10

FIGURE 1.7 d u ty d riv e.

Keys are fitted with adhesive on a crown gear of a heavy-

any pro cess th a t allowed absorption of p lating solutions. Im pregna­ tion and sealing with anaerobics is an excellent way to overcome th is deficiency and take advantage of th e economies of such net shape p ro cesses as p re sse d powder metal.

4.

HOW T H E Y A R E S E L E C T E D

Like p lastics and metals th a t are molded and h e a t-tre a te d by the manu­ fa c tu rin g p u rc h a s e r, adhesive p ro d u c ts must be applied and cured by th e u s e r. They become p a rt of his p rocessing operation. T herefore, th e u s e r must consider not only the adhesiv e’s cu red p ro p e rtie s but also th e fluid p ro p e rtie s and the variables of application and c u re . In th is re sp ect adhesives are akin to p ain ts. T here are th re e material p ro p e rtie s th a t must be considered in selecting p ro p e r m achinery adhesives: 1. Flow p ro p e rtie s of the liquid 2. Conditions and ch a rac te ristic of the cure 3. P ro p erties of the cured material

How They Are Selected

11

FIGURE 1.8 Cup or core plug sealing and re ta in in g on an automotive head (a) u sin g a ro to sp ray applicator (b ).

12

General Information About Machinery Adhesives

FIGURE 1.9 Bonded with m achinery adhesives are the ro to r, sh a ft, arm atu re, fan , and commutator on a fractional-horsepow er double­ in su lated electric motor.

How They Are Selected

(b) FIGURE 1.9

(C ontinued)

13

General Information About Machinery Adhesives

14

F I G U R E 1.10 Plated p a r ts , u n trea ted (ab o v e), and im pregnated with an anaerobic (below ), both a fte r the stan d ard plating p ro c ess.

4.1

Liquid Properties

The rheology or flow of the liquid must be considered for the type of joint being filled, th e method of filling, and the processing conditions. A v ery th in — 1 to 100 centipoise (c P )—m aterial can be wicked into a heavy p re ss fit provided the material doesn’t s ta rt to thicken and cu re before it completely p e n e tra te s. For hand application before a s­ sem bly, a viscosity of 1000 to 10,000 cP might be ap propriate (a th in to th ick s y ru p ). If machine coating of a bore is d esire d , th en a thixotro p ic material is u sed . (T hixotropy is the flow -rate-sensitive c h a rac­ te ris tic th a t makes ketchup stay in the bottle until it begins to flow, th en suddenly gush afte r flow s t a r t s .) Often th ese m aterials are discsp ra y ed onto a b o re. It is possible for a fin e-sp ray ed rin g of thixotro p ic m aterial to stay on the inside of a bore for many minutes or u n til a plug is pushed into place (Fig. 1.11). P rocessing conditions may also affect th e consideration of liquid p ro p e rtie s. These conditions may dictate the use of a d ry m aterial.

How They Are Selected

F I G U R E 1.11

15

R otospray (rig h t) application to a cup plug bore (le ft).

For in s ta n c e , on an automobile final assembly lin e , where upholstery and finish pain ts are p r e s e n t, the use of liquids may be discouraged or fo rbidden. In th is case, th re a d locking m aterials selected are al­ most always Type VI, preapplied d ry to the touch (Table 1 .1 ).

4.2

C u r e C on d ition s and Speed

D ifferent p ro d u cts develop s tre n g th at different sp ee d s, depending on th e su rface condition of the joined p a r ts , th e gap between p a r ts , the p re s su re and mixing d u rin g assem bly, and the tem perature and h u ­ midity . A typical cu re speed is given in Table 2.1 to help in judging re la ­ tive sp eed s. In many cases, a slow -curing product is selected to allow for assembly of complex p a r ts . Fast cu res are selected for high production ra te s . When selecting speed of cure for high production, be su re to mea­ su re the speed on actual p a rts u n d er production conditions and allow a safety factor of two for v ariab ility . In o th er w ords, a 10-second

16

General Information About Machinery Adhesives

TABLE 1.1

P roperties of the Liquid

T h re a d -tre a tin g materials are produced in th re e liquid types as listed in MIL S-46163. Type I:

Sealing, stan d ard v iscosity—Newtonian8

Grade K

500 cP or m Pa.s

3/8-1 in . 10—24 mm th rea d s

Grade L

7000 cP or m Pa.s

5/8-1 in . 16—24 mm th rea d s

Type I I :

L u b ricatin g —thixotropic8

Grade M

5000 cP or m Pa.s

#2-1/2 in . 2—12 mm th rea d s

Grade N

5000 cP or m Pa.s

1/4-3/4 in . 6—20 mm th rea d s

Grade O

7000 cP or m Pa.s

3/8-1 in . 10—24 mm th rea d s

Type III:

Wicking, th re a d , and porosity sealing8

Grade R 15 cP or m Pa.s

#2-1/2 in . 2—12 mm th re a d s

O ther useful m achinery adhesives have been developed since th e 1974 Mil. Spec. 46163 Type IV:

Newtonian, high s tre n g th or high tem perature8

Grade S (high s tre n g th )

100 cP or m Pa.s

#2-1/2 in . 2 —12 mm

Grade

T (high tem perature) 7000 cP or

m Pa.s

1/4-3

in. 6 —75mm

Grade

U (high s tre n g th )

m Pa.s

1/4-3

in . 6—75mm

Type V :

2000 cP or

P astes for tap ered th rea d and flat flange sealing

Grade

W

550,000 cP or m Pa.s

1/4-1

1/4 in . 9—32

mm pipe

Grade

X 3,800,000 cP or m Pa.s

0.010

i n ., 0.25 mm

max. gap

Grade

Y

0.010

i n ., 0.25 mm

max. gap

Grade

Z 1,200,000 cP or m Pa.s

Type VI:

850,000 cP or m Pa.s

0.010 i n ., 0.25 mm max. gap

P reapplied, d ry -to -th e -to u c h th re a d lockers^

Grade MM

(low s tre n g th , silver)

Grade NN

(medium s tre n g th , green)

Grade

SS

(high s tre n g th , red )

Grade

TT

(high tem p eratu re, yellow)

How They Are Selected T A B L E 1.1

17

(C ontinued)

Prim ers or activators for use with Types I-V Prim er N

Increases cure speed and doubles gap cured on the th in n er m aterials.

Primer T

Increases cure speed. See C hap. 2 for the effect of accelerators on cu rin g and cured p ro p e rtie s.

Lubrication Where p recise clamp loads are re q u ire d , the lu b ricatin g Type II materials are p re fe rre d . They may be used over a lightly oiled su rfa ce. All m aterials have predictable friction factors which should be considered for good clamp load control (T = KDF, C hap. 2). aThe use of accelerators and prim ers doubles the g ap -cu rin g capa­ bility of Types I —IV. ^T ype VI m aterials are usually applied by a b o lt-co n v ertin g manu­ fa c tu re r and shipped as p a rt of the b o lt. Upon assembly th e d ry sponge m aterial exudes a quick cu rin g liq u id , which tu rn s solid and provides th e same bolt sec u rity and sealing as th e normally applied liq u id s. A ctivator is included in th e d ry film so no ex tern al activator o r prim er need be applied.

average fix tu re tim e, as determ ined experim entally, should not be tied to a machine th a t allows less th an 20 seconds before p a rts are u n ­ clamped (F ig. 1.12). Prim er o r activator N or T is used to give active surface re su lts on inactive p a r ts . For fu rth e r cu rin g data see Chap. 2, Sec. 3.

4.3

C u r e d Properties

S tren g th and environm ental resistan ce should be considered to g eth er. For in s ta n c e , if a material is to be used n ear th e u p p er limit of its tem p eratu re ra tin g , its stre n g th may be as little as 50% of th e room tem p eratu re ra tin g shown in th e tab les. In such a case, a h ig h ers tre n g th m aterial should be selected. S tren g th s also v ary according to th e su rfaces being bonded. The th re a d locking selection c h a rts , F igs. 2.2 and 2 .3, should be consulted for p artic u la r su rfa ces. Medium s tre n g th (800 p s i, 5.5 MPa) is usually sufficient for most

18

General Information About Machinery Adhesives

cc \— UJ 2 I z O H £ UJ

UJ

F I G U R E 1.12

Typical cure speed c u rv e —Type I I , Grade N.

th re a d locking and cylindrical fits. Higher s tre n g th s are used only for severe du ty and la rg e r, h ig h -stre n g th p a rts th a t can be d isa s­ sembled without damage. O ther cu red p ro p e rtie s may be im portant, depending on the applica­ tio n . Check those th at are n ecessary and select a m aterial accordingly. You can tell th e approxim ate stre n g th of th e liquid formulations by th e ir color. Low stre n g th is purple or medium b lu e, and high is red or g reen . 4.4

Uniform ity o f R e s u lts

M achinery adhesives are difficult to te s t in the com pressive mode in which th ey are often u sed . Precision com pression te s tin g re q u ire s th ick sections of m aterials, which are difficult to produce with anaerobics because of the stability of liquids in large sections. Large chunks of fo rce-cu red m aterials are liable to be highly stre ss e d from uneven sh rin k ag e ; th e re fo re , th e ir relative stre n g th s are usually te ste d in s h e a r. High-modulus m aterials in sh ear give a fairly large variation in re s u lts . Shear failures can be eith er cohesive (th e most co n sisten t) or ad h esiv e, th a t is , th ey b reak free of th e surface of the te s t specim en.

How They Are Selected

19

Shear ty p e re s u lts will depend on surface adhesion with all the ram ­ ifications of m aterial, fin ish , cleanliness, and gap. P redictability from published data will be on the o rd e r of magnitude of ±25%. The p ru d e n t engineer will te s t production p a rts to achieve more precise re s u lts . This not only helps in design bu t is re q u ired where quality control departm ents must check w hether p ro p e r fill and cure have taken place. In most cases where m achinery adhesives are u sed , a nominal 800 to 1000 psi s tre s s (5.5 to 7 MPa) is sufficient evidence th a t the com pres­ sive load can be su p p o rted . In thin films of 0.005 in . or 0.13 mm the m aterials will su p p o rt loads of 35,000 to 55,000 psi (240 to 380 MPa), which encompasses the tensile and com pressive yield stre n g th of low carbon steel. 4.5

D e s ig n i n g with Published Data

Sheer s tre s s d ata are produced on pins and collars 0.5 in . or 12 mm in diam eter and on n u ts and bolts 3/8" xl6" or M10. When the p a rts b e ­ in g designed deviate from those conditions of the te s t specimens by a su b stan tial am ount, the data must be altered to reflect th e predicted conditions. F igs. 1.13 and 1.14 help do th a t. Most of th e m aterials are formulated for diam etral clearances of 0.003 in . (0.08 mm) or less. Those th a t perform well over this value should be dow nrated unless the data are obtained at enlarged gap.

DIAMETRAL CLEARANCE - IN. F I G U R E 1.13

S tren g th v s . gap.

20

General Information About Machinery A dhesives

x hO Z

LU

CC h* C/> LU

>

LU CC

E N GA GEM EN T AREA - IN.

FIGURE 1.14

Shear stre n g th v s. engaged area.

The reason for the decrease in la rg e r gaps is not known, b u t it is a phenomenon th a t can be accurately m easured and documented (F ig. 1*13)2 The decrease in s tre n g th when dealing with areas over 10 in . (65 cm^) conjectured to be the re su lt of g re a te r clearance because of poorer geometry of f i t , chance of poorer fill because of th e g re ater area involved, and elongation of the p a rts with g re ater length of e n ­ gagem ent. An extrem e example of what minimal engagem ent does to th e average s tre s s is dem onstrated by the simple te s t used for s tr u c ­ tu ra l ad h esiv es, the lap sh ea r te s t.* This te s t uses two pieces of su b s tra te 0.062 in . (1.6 mm) thick by 4" x l" (100 x 40 mm) (Fig. 1.15). At firs t one might conclude th a t doubling the length of overlap would double the stre n g th of the joint; how ever, because of s tre s s concen tratio n , doubling th e overlap from 0.5 to 1 in . (13 to 25 mm) in creases the stre n g th by only 1.65 on steel laps (F ig. 1.16). The reaso n can be visualized by ob serv in g th a t the s tre s s d istrib u tio n is en tirely d ifferen t for the doubled-lap len g th . The peak s tre s s th at

*American Society for T esting and Materials (ASTM) Method D1002.

How They Are Selected

21

F I G U R E 1.15 American Society for T esting and M aterials (ASTM) D1002 lap sh ea r specimen.

in itiates failure is th e sam e, b u t th e average s tre s s is less because of th e inability of th e lap ce n te rs to su p p o rt any load. This same phenomenon takes place in cylindrical and th read ed fits as th e p a rts get larg e r and the length of fit longer. In th re a d s and cylindrical fits th e effect does not become significant until en gage­ ments of four times the diam eter are encountered. Within the limits of close fits and good m achinery p ra ctice, the ro u g h e r the finish the b e tte r th e apparent adhesion o r, more accu­ ra te ly , the mechanical keying (F ig. 1.17). Keying is not effective if th e s tre s s works parallel to the lay of the finish (for fu rth e r d iscu s­ sion see C hap. 6, Sec. 3 .2 .1 ). T here is a definite relationship between screw size and achieved s tre n g th . Figure 1.18 shows th a t a material ra te d at 1000 psi (7 MPa) on 3/8 in . bolts will develop a shear s tre s s on a #2 screw of 1600 psi (11 MPa). The th re a d locking perform ance c h a rts (F igs. 2.2 and 2.3 in Chap. 2) have already taken th is effect into consideration. The reason for th e phenomenon is the same as for cylindrical fits: gap and size effect. A 1J in . bolt, for in stan ce , will develop only 60% of the 3/8 in . shear ra tin g (Fig. 1.18). The cu rv e shown in Fig. 1.18 is for a medium adhesion Type II Grade N , which usually b re ak s on a nut or bolt in the a d h e siv e , ra th e r th an cohesive, mode. Surface m aterial can give variability of about two to one.

F I G U R E 1.16

Length

Length

O m

c

c/>

vs. surface m aterial.

N YLO N

BRASS

A L U M IN U M

S T A IN L E S S ST E E L

T IT A N IU M (6AI,4V)

B L A C K O X ID E

C A D M IU M

Z IN C

ST E E L

Z IN C P H O SP H A T E

OILED

CL EA N

C LEA N

£*

CLEAN

01

o

tn o

SH E A R S T R E S S RATIN G ^

GO

C L EA N

O ILE D

O ILED

o o o

SH E A R S T R E S S RAT IN G ~

OILED

OILED

o

Ul o

MPa

O)

LB/IN?

CLEAN

—I—

to o o o

GO

How They Are Selected

24

General Information About Machinery Adhesives

LOAD CYCLES F IG U R E 1.20 Fatigue stre n g th v e rsu s load cycles.

istic of th e m aterials th a t will be 10 to 15% of th e ultim ate, as in Fig. 1.20. O bviously, from our example of lap sh ear s tre s s d is trib u ­ tion , ex acting te s ts should be conducted on actual p a rts if service life involves many cycles of s tre s s ; otherw ise 10% of ultimate should be the maximum safe calculated load. C hap. 6 has a fu rth e r discussion of fatigue of motor sh afts (F ig. 1.20). A nother useful ch aracteristic is th e prevailing to rq u e , which on a n u t and bolt is m easured as the torque at one-half tu rn from where b re ak o c c u rre d .* This prevailing to rq u e used to be called locking to rq u e for th re a d jamming system s, which existed before anaerobics were in v en ted . T hread jammers had no b reak to rq u e . Prevail can be useful for p re v en tin g loss of the fa ste n er if the break has been lost from re to rq u in g afte r relaxation of a gasket or from adjusting an a d ­ ju stin g screw . Grade R is formulated specifically to wick into a d ju s t­ in g screw s and give high prevailing to rq u e is th ey are moved. Re­ sistance is sub stantially lost if p a rts are completely disengaged but will maintain itse lf th ro u g h dozens of small adjustm ents.

*The exception is in Mil-S-22473 and 46163 where prevailing torque is the average of four readings taken o n e -q u a rte r, on e-h alf, th re e q u a r te rs , and one full tu rn from b re a k . The one-half tu rn data are usually within 10% of th e average method data.

Packaging and Handling 5. 5.1

25

P A C K A G IN G A N D H A N D L IN G P a c k a g in g and A g i n g

All of the m achinery adhesives are anaerobic, which means th ey are stabilized by oxygen in the a ir. To maintain sta b ility , bottles and tu b es of m aterial are usually not completely filled, leaving air surface over the liquid. The package is made of low -density polyethylene, which allows air molecules to p ass th ro u g h the wall from th e outside. Shelf life is 1 y ear or more for unopened liquid and p aste p roducts and 4 y ea rs for the preapplied p ro d u cts (see Table 2.1 for specific tim es). Within th ese ages th ey should meet all specifications for v is­ cosity and cu re speed. A lthough th is may sound b rie f for hardw are m ark ets, th e useful life of each of th ese pro d u cts is usually more b e ­ cause all are fail-safe. Liquid p ro d u cts will gradually slow down in th e ir cu re speed bu t still produce specified cu red p ro p e rtie s. If cure speed is critica l, check th e date code on the bottom of the bottle with yo u r su p p lier. T ry some p a r ts . The preapplied p ro d u c ts gradually h ard en on th e bolt and become difficult to assem ble, like a prevailing to rq u e lo ck er, and th u s are easy to in sp ect. Paste p ro d u cts may h arden in th e tube ce n te r; how ever, p aste th a t is left will still perform adequately. Elevated tem p eratu res, hum idity, and sunlight can accel­ erate ag in g , b u t u n d er normal conditions (60°F or —40°F and 40% RH) th e p ro d u c ts last many y e a rs . They are not harmed by subfreezing tem p eratu res b u t most become th ick and inactive below 40°F so they should be applied at com fortable, shirtsleev e tem p eratu res. Accel­ e ra to rs are generally used for su b freezin g cu res (see Chap. 3, Sec. 4). Mixing from one container to another is not recom m ended, since th is action may in tro duce contamination which can cause se t-u p or loss of cu re sp eed . If material must be removed from its original container for application, limited amounts should be removed so it is not n eces­ sary to re tu rn used material to the original container. Often people ask if different m aterials can be mixed to achieve a viscosity o r color more suitable to a p artic u la r application. Although th is has been done successfully in a few in sta n c e s, the successes are more th e exception th an th e ru le . At least no violent reactions have been re p o rte d . These compounds are carefully form ulated combina­ tions of 15 to 20 in g re d ie n ts, some effective in p a rts p e r million. They should not be mixed. For p artic u la r requirem ents of v isco sity , color, sp eed , and s tre n g th some m anufacturers will formulate specials. These form ulators should be consulted. R efrigeration does not impair th e shelf life of anaerobic machinery ad h esiv es, nor is it p articu larly helpful. If th e adhesives would be subject to high tem p eratu res, th en it could be beneficial.

26 5.2

General Information About Machinery Adhesives S a fe ty

Even in to d ay ’s tig h tly reg u lated b u sin ess and safety clim ate, machin­ e ry adhesives are generally considered v ery safe since th ey are used in relatively small quantities and are not aggressively u nsafe. Some of them do contain adhesion prom oters th a t have a low level of toxicity on in g estio n , inhalation, skin absorption, or eye contact. They should be handled usin g good in d u stria l hygiene. Since th e re is some v a ria ­ b ility from m anufacturer to m anufacturer, th e m aterial safety data sheet (MSDS) should be consulted before m aterials are put on line. For fu rth e r discussion of sa fe ty , re fe r to C hap. 4, Sec. 6.

5.3

S h ip p i n g

A dhesives No special precaution need be taken for shipping any of the ma­ ch in ery ad h esiv es, eith er as a liquid or a solid. The Code of Federal R egulations (CFR) Title 49, Subtitle B definition of Tfcombustible liq u id ” is one th a t has a closed cup flash point of 100°F (38°C) or le ss. Any p ro d uct containing m ethacrylic acid or any acid base may be a ,fcorrosive liq u id .” N either of th ese re stric tio n s is p ertin e n t to the prim ary su p pliers of th ese m aterials as all show no re stric tio n s by th e D epartm ent of T ransportation (DOT) or International Air T ra n s ­ p o rt Association (IA T A ). To be su re , ask your supplier for the MSDS. Prim ers or A ctivators Prim ers N and T are now classified as ’’po iso n o u s,” ’’flammable,” and ’’com bustible” because of th e ir major co n stitu e n ts, 1 ,1 ,1 -trichloroethane (b o th N and T) and isopropyl alcohol (T o n ly ). These m aterials react violently with acetone, sodium hyd ro x id e, or oxygen. T richlor and alcohol are common in d u stria l so lv en ts. T richlor is often used in vapor d eg rease rs and general cleaning solvents. Isopropyl alcohol (ru b b in g alcohol) is used in stead of trich lo r for cleaning on p a rts sensitive to chlorinated solvents and is often used as an a n ti­ freeze and a cleaner in w indshield w asher solutions. Because of the toxic n atu re of trich lo r [toxicity level value (TLV) 350] and th e flammability of isopropyl alcohol, th e official descriptions for sh ipping are as follows: Prim er N shipping regulations Type o r class DOT ORM-A ( ’’o th er re stric te d m aterial” Group A) IATA Class 6.1 poisonous substance (effective Jan u a ry 1, 1983)

Packaging and Handling

27

P ro p er shipping name DOT 1 ,1 ,1-trichloroethane IATA poisonous liquid, n .o .s . (no o th er specification) (contains 1 ,1 ,1-trichloroethane) Prim er T shipping regulations Type o r class DOT combustible liquid IATA Class 3 flammable liquid (as of Jan u a ry 1, 1983) P roper sh ip p in g name DOT combustible liquid, n .o .s . IATA flammable liquid, toxic, n .o .s . ( 1 ,1 ,1-trichlorethane)

5.4

Metal C o r r o s iv it y and Plastic Compatibility

T ypes I , I I , and III are re q u ired to pass a corrosivity te s t according to Mil-S-46163. Under high-hum idity conditions (40% and u p ), a d is ­ coloration can occur th at appears to be an oxide b u t has been d is­ covered to be a discolored film of cu red m aterial. The o th er ty p es may or may not have adhesion prom oters which can affect th e surface of some m etals. As soon as cure tak es place all effect on th e surface ceases. T hus no te s ts have ever shown corrosion to be a problem even when residual s tre s s or adverse environm ents have been p re se n t. To the c o n tra ry , field and laboratory te s ts in corrosive atm ospheres have shown th a t th e resin-filled in n er space has eliminated corrosion because th e crevice or re se rv o ir for holding electrolyte is g one, as shown in Fig. 1.4. Compatibility with Plastics Without te s tin g , plastic com patibility is predictable only in extrem e cases. A STM S tandard Practice D3929 for evaluating the s tre s s c ra c k ­ in g of p lastics by adhesives u sing the bent-beam method is used for evaluating and p red ictin g the effect of adhesives on various m aterials at d ifferen t s tre s s levels. All m aterials u n d er appropriately high s tre s s become sensitive to liquid and gaseous in tru sio n into th e grain boundaries and betw een molecules. The degree to which th is happens is dependent on the m aterial, the s tr e s s , and th e environm ent. H ydro­ gen em brittlem ent of steel can occur at low s tre s se s in a zinc or cad­ mium p lating b a th . A hardened piece of carbon steel ( e . g . , a highperform ance valve sp rin g in an in tern a l combustion engine) can b e ­ come em brittled by w ater at s tre ss e s over 100,000 l b / i n . 2 (690 MPa). P lastics, which have an o rd e r of m agnitude lower s tre n g th , exhibit similar behavior when u n d er s tre s s even if th ey are highly cro sslinked therm oset m aterials. Machinery adhesives should not be used

28 T A B L E 1.2

General Information About Machinery Adhesives Plastic Compatibility^

Compatible Acetals Alkyd Allyl

S tre s s -s e n s itiv e ; tr y carefully Polyvinyl chloride (PVC) P olyurethane

Not compatible ABS Acrylic Cellulosics

Amino re sin s

Polycarbonate

Epoxy

Polyphenelyne oxide (PPO)

F luroplastics Nylon Phenolic Polyimide /polyamide imide

Polystyrene Poiysulfone S tyrene acrylonitrile (SAN)

Polyethylene Polyphenylene sulfide Polypropylene Therm oset poly ester aT rade names are shown in Table 1.3.

on o r n ear any therm oplastic material unless full cure can be assu red without touching the plastic. Remembering th a t th e s tre s s level in th e plastic is critical to its su sce p tib ility , Table 1.2 can be used for general guidelines only. Applied s tre s se s can often be avoided until cure and cleanup take place; how ever, molding s tre s s e s from therm al gradients often exceed 1000 psi an d , when th ey do, s tre s s cracking can occur within seconds or m inutes of contact with liquid m aterials. Application should be c a re ­ fully trie d on p a rts th a t can be sp ared . If no cracking or crazing o ccurs within 24 hours usually th e combination is safe. Table 1.3 gives th e tra d e names for most common generic p lastics.

29

Packaging and Handling T A B L E 1.3

T rade Names

ABS (a c ry lo n trile , b u tad ien e, sty re n e )

Abson—Abtec Chemical Co. Cycolac—Borg-W arner Chemicals L u stra n —Monsanto Kr alastic—Uniroy al

Acetals

Delrin (acetal homopolymer)—du Pont Celcon (acetal copolym er)—Celanese

Acrylic

A crylite — Cy/Ro In d u stries Lucite—du Pont Plexiglas—Rohm and Haas C orian—du Pont

Alkyd

Plascon—Allied Chemical G laskyd—American Cyanamid

Allyl plastics

CR 39 (allyl diglycol carbonate) — PPG D apex—Acme Resin Company Dapon (diallyl p h th a la te )—FMC C orporation

Amino re sin s (u rea and melamine formaldehide)

Plaskon—Allied Chemical

Celluosics

T enite—Eastman Kodak

Epoxy

Plascon—Allied Chemical

Cymel—American Cyanamid

Poly s e t—Morton Chemical Company Epon — Shell A raldite—Ciba-Geigy Fluoroplastic

Teflon—du Pont Halon—Allied Chemical Tefzel—du Pont K y n ar—Penwalt Corporation

General Information About Machinery Adhesives

30 T A B L E 1.3

(C ontinued)

Ionomer

Surlyn — du Pont

Nylon

Zytel—du Pont Vy d y n e—Monsanto C apran—Allied Chemical

Phenolic

Plascon—Allied Chemical Genal—General Electric D urez—Hooker Chemical Plenco—Plastics Engineering

PPO

N oryl—General Electric

Polyimide /polyamide imide

Tor Ion—Amoco V espel—du Pont Kinel—Rhone-Poulenc

Polyethylene

Dylan—Arco A lathon—du Pont T en ite—Eastman Kodak Norchem—N orthern Petrochemical Marlex—Phillips Petroleum B akelite—Union C arbide M icrothene—U .S . In d u strial Chemicals P etro th en e—U .S. In d u strial Chemicals

Polypropylene

T en ite—Eastman Kodak P ro -F ax —Hercules M arlex—Phillips Petroleum

Therm oset p o ly ester

Hay s ite —Hay site Reinforced Plastics Co. R osite—Rostone C orporation

Packaging and Handling T A B L E 1.3

31

(C ontinued)

Therm oplastic poly­ e s te r (P B T , PET)

V ersel—Allied Chemical Ekkcel— Carborundum T enite—Eastman Kodak C elanex—Celanese Valox—General Electric

Polycarbonate

Lexan—General Electric Merlon—Mobay Chemical

Polypheneylene sulfide

R yton—Phillips Petroleum

Polystyrene

D ylark—Arco S ty ro n —Dow Chemical L u stre x —Monsanto Bakelite — Union C arbide

Polyvinyl chloride (PVC)

Dacovin—Diamond Shamrock FPC—Firestone Geon—B . F . Goodrich

P olyurethane

E stane—B .F . Goodrich T exin—Mobay Chemical O rth an e—Ohio R ubber V ibrathane — Uniroyal Pellethane—Upjohn

Polysulfone

Udel—Union C arbide

Styrene acrylonitrile (SAN)

T y ril—Dow Chemical L u stra n —Monsanto

General Information About Machinery Adhesives

32 5.5

Removal

Like th e problem of the fellow who invented the perfect so lv en t—he d id n ’t know what to hold it in —the removal of misapplied machinery adhesives can be difficult. One of the pu rp o ses of th is book is to describ e how to apply the technology so th a t p a rts can be disassem ­ bled when n ec essary . But we all have had th e dilemma when o rd in ary tools will not remove adhesive. What can be done? O r, if the p a rts are disassem bled, how can th ey be cleaned up for reassem bly? The following tip s are second b est to planning ahead for possible disassem ­ b ly , b u t th ey will be useful to know. 1. H eat—most m achinery adhesives will weaken considerably b e ­ tween 400 and 600°F (200—300°C). (Check th e ra tin g and go 1509F o v er i t .) The p a r t , of c o u rs e , must be able to w ithstand the tem p eratu re. 2. Impact or cleavage—the m aterials are generally weakest in th ese two modes. Tapping a b earin g out of a bore usually gets b e tte r re s u lts th an does a steady p u sh . Likewise, peeling the co rn er of a gasketed cover is more likely to unzip it th an impact or pull will. Once th e p a rts sep a rate, physical b ru sh in g or scrap in g will often com­ plete th e job because b rittle m aterials will pow der. It is not n ecessary to remove all the material for reassem bly; the material th at is well a d ­ hered can be left. New material will be en tirely com patible, although th e covered surface will be in e rt for cu rin g and it is advisable to con­ sid er activation for rapid c u re s. 3. Chemical m ethods—a m ethylene chloride (m ethyl chloroform) soak will usually release th e adhesive and soften th e re sin . Some p a rts (su ch as assembled b earings and fa ste n ers) will have to be soaked for up to 24 hours because so little bondline is exposed. Meth­ ylene chloride is available in handy sp ray form from some adhesive m an u factu rers. These are formulations especially made to lift old g a s k e ts , p a in t, and adhesives from su rfa ces. As with any chlorinated solvent, care should be taken with th e ir u se. Follow th e directions on the can and if in doubt t r y a limited area firs t. If th ey will eat a m achinery a d ­ h esiv e, th ey certainly will d estro y any therm oplastic or elastom er. 4. F u ll-stre n g th Lestoil* will remove some exposed m achinery a d ­ hesives afte r a 24-hour soak. Most affected are G rades W, X, and Y. 5. Lestoil in a 50% w ater solution will remove films of preapplied th re a d lo c k e rs , G rades MM, NN, SS, and TT. Cold solutions will take o v ern ig h t. Hot solutions at 150°F (65°C) will take a couple of h o u rs. 6. O ak itet strip p e r 157 (viscous) or 156 (liquid dip) will remove exposed m achinery adhesive a fte r 24 hours of contact or soak. *Noxell C o ., Household P roducts Division, Baltim ore, MD. to a k ite P roducts In c ., Valley Road, B erkeley H eights, NJ 07922.

Government and Independent Laboratories Requirements

33

S trip p er #157 is a viscous solvent-alkaline product designed to r e ­ move re sista n t finishes from aluminum, magnesium, and steel surfaces too large for tan k immersion. It meets the requirem ents of Mil-R25134A (USAF) ’’Remover, Paint and L,acquer Solvent T y p e .” It is somewhat reactive on zinc, b ra s s , and copper. S trip p er #156 is a nonchlorinated, di-phase solvent formulation designed for strip p in g tough synthetic finishes. It is satisfacto ry for steel and aluminum. It mildly affects the surface of b ra ss and copper b u t attack s magnesium and zinc. Both m aterials are used at full stre n g th and are aggressively alka­ line. M anufacturers’ recommendations for use and safety precautions should be followed rigorously. 7. Removal of liquid m aterial—liquid or uncured m aterial can be removed with most shop solvents. Chlorinated solvents such as tr ichloroethane o r m ethylene chloride are v ery effective w hether used cold or in a vapor d eg rease r. Methyl ethyl ketone (MEK), acetone, methyl alcohol, and freon are effec tiv e. Water is n o t. Good safety and hygiene p ractices should be followed with any of th ese m aterials. This includes avoiding skin contact. So what about skin cleanup? Continuous contact should be avoided, b u t when contact occurs a d ry or w aterless mechanic’s hand soap e f­ fectively releases the m aterial so th a t o rd in ary soap and w ater can remove th e re sid u e . For m aterials spilled on clothes, normal d ry cleaning usually takes care of the problem . A soak in vegetable oil before d ry cleaning often helps to remove pigm ents and d y es.

6. 6.1

G O VER N M EN T AND IN D EP E N D EN T L A B O R A T O R IE S R E Q U IR E M E N T S U n d e rw r ite rs Laboratories

In some m arkets it is desirable and sometimes m andatory th a t in d e ­ pendent laboratory te s tin g be done to establish th e suitability of a m aterial for its intended u se. The U nderw riters Laboratory (UL)* was founded in 1894 as an in d ep en d en t, nonprofit organization. Its pu rpose was to evaluate m aterials, devices, p ro d u c ts, equipm ent, con­ stru ctio n m ethods, and system s with re sp ect to hazards affecting life and p ro p e rty . T estin g em phasis is on product and public safety th ro u g h functional evaluation and follow-up te stin g by experim ental engineers u n d er con­ tra c t to m an u factu rers, government agencies, and o th e rs .

*33 P fingsten Road, N orthbrook, IL 60062.

34

General Information About Machinery Adhesives Service and Product Coverage

1.

Service categories available. a. P roduct listin g serv ic e—the UL maintains lists of qualified p ro d u c ts and controls the use of its symbol. b . C lassification serv ice—laboratory evaluation classifies pro d u cts with re sp ect to specific h az ard s, lim itations, or perform ance co n d itio n s. c. Component recognition serv ic e—th is deals with the evaluation of component p a rts and m aterials (such as ru b b e r or plastic) th a t will later be used in a complete product or system . d . C ertificate serv ic e—certain ty p es of p ro d u c ts, such as building m aterials ( e . g . , shingles) can’t practically b ea r th e UL label and accompanying ce rtificates are provided. e. Inspection serv ic e—UL’s train e d in sp ecto rs worldwide check out p ro d u cts periodically on a contract b a sis. f. Fact finding and re s e a rc h —projects are conducted by th e UL on a co n tract basis for m an u factu rers, tra d e associations, and governm ent agencies. 2. P roduct g ro u p s—lists of p ro d u cts by category are published in d irecto ries if in conformance with requirem ents. a. B uilding m aterials. b . Fire protection equipm ent. c. F ire -re sista n t m aterial. d . Recognized com ponents. e . Electrical appliance and utilization equipm ent. f. Electrical construction m aterials. g. Hazardous location electrical equipm ent. h . Marine p ro d u c ts. i. Classified pro d u cts (m achinery ad h esiv es). j. A ccident, autom otive, and b u rg la ry protection equipm ent. k . Gas and oil equipm ent. M achinery adhesives G rades K, W, and X are covered u n d er product group 2.i above, which classifies them on a fire hazard b asis. The p ro d u c ts so covered are marked on the package; the label for Grade K shown in Fig. 1.21 is typical. The fire hazard class was established for th e uncured m aterial ac­ co rd in g to Table 1.4, which shows classes of familiar m aterials. For req u irem en ts of te s t methods re fe r to Bulletin UL 340. Canadian and B ritish UL facilities are cooperating b u t independent v e n tu re s . A pprovals must be sought from each sep arately .

"A d h e sive / Se a la n t 2 7 1 Fi re Hazard is small. No flash point in liquid state. Ignition tem­ perature 304°C (579°F). For use in devices handling gasoline petroleum oils, natural gas (p re ssu re not ove r 300 p s ig ) , butane and propane. F I G U R E 1.21 Typical package m arking showing the U nderw riters L aboratory m ark. T A B L E 1.4

Numerical fire hazard ra tin g

Fire Hazard Classification Scale

General classification

Flammability tem perature limit °F (°C)

100

With diethyl e th e r

- 4 9 (- 4 5 )

90-100

With gasoline

13 to -4 8 ( - 1 0 .6 to -4 4 .4 )

80-90

Between ethyl alcohol and gasoline

38 to 14 (3 .3 to -1 0 )

70-80

Between ethyl alcohol and gasoline

51 to 39 (10.6 to 3.9)

60-70

With ethyl alcohol

67 to 52 (19.4 to 11.1)

50-60

Between kerosene and ethyl alcohol

83 to 68 (28.3 to 20.0)

40-50

Between kerosene and eth y l alcohol

99 to 84 (37.2 to 28.9)

30-40

With kerosene

129 to 100 (53.9 to 37.8)

20-30

Between paraffin oil and kerosene

256 to 130 (124.4 to 54.4)

10-20

With paraffin oil

440 to 257 (226.7 to 125)

0 -1 0 0

Less hazardous th an paraffin oil With w ater

— Noncombustible

35

General Information About Machinery Adhesives

36 E xtent of Approval

A pprovals do not extend to the p ro d u cts assembled with th ese ma­ te ria ls . For in stan ce , the approval given for a pipe sealant is for the sealant in th e uncured state and does not include a pipe assem bly. S eparate approvals must be sought for the assembled p ro d u c t. For in sta n c e , a gas meter assembled with Grade W needs separate approval even though th is sealant is approved for such an application. 6.2

U . S . Departm ent o f A g r i c u lt u r e

The following p ro d u cts are recognized by the U .S . Departm ent of A g ricu ltu re (USDA)* as "chemically acceptable for th e use in slau g h ter in g , p ro cessin g , tra n sp o rtin g or storage areas in incidental contact with meat or p o ultry food pro d u cts p re p are d u n d er Federal in sp ec­ tio n " : Grades N, K, U, and W, and Prim ers N and T. " . . . Ac­ ceptance is valid as long as the corporation and use remain as d e ­ scrib ed to us [USDA e d .] and provided th e in sp ecto r approves the perform ance. No endorsem ent of th e m aterial of any concomitant claims is in te n d e d ." The p ro d u c ts are not edible in liquid form although th ey become in e rt a fte r c u rin g . Any usage in food handling equipm ent re q u ires full cu re and removal of excess liquid before sterilization or use of th e equipm ent. M achinery adhesives, as normally used to secure and seal th re a d s , b e a rin g s, and p re ss fits , logically qualify as minimal contact elements and are routinely used with local in sp ecto r approval for assembly and re p a ir of food-related equipm ent. 6.3

Food and D r u g Ad m in istration

The Food and D rug A dm inistration (FDA) approval or listin g of p ro d ­ u cts re q u ires th a t th ey be eith er edible or safe in direct contact with food p ro d u c ts. Machinery adhesives are not in e ith er of these c a te ­ gories and are th ere fo re n eith er approved nor disapproved by the FDA They are not eligible for FDA action. 6.4

National Sanitation Foundation

The National Sanitation Foundation (N S F )t does not allow m aterials in potable w ater system s or food p ro cesso rs to have ex tra ct able chemicals or detectable ta ste or odor. Machinery adhesives are detectable afte r c u re . However, individual mechanisms usin g m achinery adhesives can be approved a fte r appropriate cleaning and te s tin g . *Senior S taff O fficer, U .S .D .A . , Compounds and Packaging Section, C hem istry Division—Science, W ashington, D .C . 20250. tNSF B uilding, Ann A rbor, MI 48105.

Government and Independent Laboratories Requirements 6.5

37

M ilita ry and Governm ent Specifications

Army and Navy Government philosophy is changing re g ard in g the issuance and m aintenance of the thousands of intern ally generated specifications u sed to p u rch ase m aterials for its own use. The Office of Management and B udget (OMB) of the U .S . Government has issued C ircular A -119, which says th a t the government should stay out of the d irect genera­ tion of sta n d a rd s. It includes the following d irectiv es: Use v o luntary stan d ard s in the in te re sts of g re ater economy and efficien cy . Give p referen ce to voluntary stan d ard s over nonm andatory government s ta n d a rd s . Review in 5 y ea rs all government sta n d a rd s to cancel those th a t can be replaced by voluntary sta n d a rd s. Have knowledgeable government employees take p a rt in s ta n d a rd s producing bodies at governm ent expense as authorized agency re p ­ re sen tativ es with the objective of eliminating government specifica­ tions . Allow technical su p p o rt such as cooperative te stin g and participation of government employees in the policy-m aking processes of volun­ ta ry sta n d a rd s bodies, including p re p ara tio n , coordination, and review of sta n d a rd s them selves. In spite of th is d ire c tiv e , new military specifications continue to be used and re v is e d , so it is well to u n d ersta n d the basic procedure of issuance and revision as illu stra te d by the following example. 1. A governm ent contractor wants to use a new product or material in th e design or production of his assembly and needs a specification to cover the p ro p e rtie s. He w rites for approval from his govern­ ment co n tractin g office and relays his re q u e st to the controlling b ran ch of th e U .S. Army, N avy, etc. 2. The agency recognizes the need afte r enough in q u iries have been reviewed and w rites or alters a specification. Qualified suppliers are usually contacted for advice in specification p re p ara tio n . 3. A specification or amendment is issu e d . S uppliers may certify to it as re q u ire d . Note th a t th e supplier does not initiate the action b u t only assists afte r action has been s ta rte d . U sers of nonspecified m aterials can get specification recognition by contacting th e Chief of Specifications and Technical Data B oard, Code DRXMR-LS Departm ent of th e Army, Army M aterials and Mechanics R esearch C en ter, W atertown, MA 02172.

38

General Information About Machinery A dhesives Air Force and Aerospace

In 1976 a contract was made between Battelle Columbus Laboratories and the U .S . Air Force for the purpose of the prep aratio n and m ainte­ nance of M il-Std-1515 "F astener Systems for Aerospace A pplications. ’’ This was in response to the aw areness th a t 20 to 30% of the cost of a prim ary airc raft stru c tu re can be a ttrib u te d to th e procurem ent and installation of mechanical fasten in g system s. In Jan u a ry 1982 a task group was formed to ad d ress the use of anaerobic sealing and locking compounds so th a t th ey might be in ­ cluded in Mil-Std-1515. D raft of Std 1515 requirem ent 114 is being circu lated for approval p er the w ritten pro ced u res of the Aero Mechanical F asten ers Requirem ents Group (AMFRG). A ccording to the d ra ft, Type I Preapplied and Type II Liquids may be used for the following p u rp o ses: 1. For locking and sealing perm anently installed fa ste n e rs. They should not be used on any th rea d ed device th a t is normally d isa s­ sembled d u rin g routine m aintenance. 2. As a supplem ent to a prim ary locking device in single-point s tr u c ­ tu ra l connections th a t may be subject to rotation d u rin g normal se rv ic e . 3. As a supplem ent to prim ary locking devices in any single point p r i ­ mary s tru c tu ra l connection, the loss of which might endanger p e r ­ sonnel or th e serviceability of th e flight vehicle. C u rre n t Military Specifications Since specification docum ents are w ritten for specific formulations all "eq u iv alen t” formulations may not match ev e ry element of th e speci­ fication. This is especially tru e of formulations from nonoriginal man­ u fa c tu re rs who are attem pting to qualify. Some form ulations may be a little fa s te r, slow er, th ic k e r, th in n e r, e tc . Some deviation in cu rin g p ro p e rtie s may be to lerated or even desired if production processes are considered and exceptions are fully docum ented. For in stan ce , Specification Mil-S-22473D was w ritten to cover the original Loctite C orporation le tte r grade m aterials. M il-S-46163 covered m aterials in an im proved form th a t had fa s te r, oil-tolerant c u re s. Some are thixotro p ic and include lu b ricatin g p ro p e rtie s. Where the earlier specifica­ tion was in use for many y ea rs before M il-S-46163, many draw ings and u s e r ’s docum ents were committed to the older m aterials. The Grumman C orporation has conducted tem perature and surface com patibility te s ts to determ ine th e functional interchangeability of le tte r grades (22473) and the num ber grades (46163) as shown in Table 1.5.

Government and Independent Laboratories Requirements T A B L E 1.5

Military Specification Interchange Approximate equivalents

M il-S-22 473D g rades

Mil-S-46163 grade

AA

R

A

R

D

0 , L, or K

AVa

0 , L, or K

AVV

L

B

0

ca cv cvv

N N

E

M

EV

M

Ha

M

HV

M

HVV

M

JV

Mil-R-46082A type

N

None S

I

None

II

None

III

aGrumman C orporation compared AV with O , C , with N, and H with M. O ther equivalent p ro d ­ u cts have stre n g th and viscosity differences th at make p re te s tin g advisable.

40

General Information About Machinery Adhesives

A lthough some grades and ty p es have been om itted in th is handbook, the G rades K th ro u g h TT c a rry on the le tte rin g system of Mil-S-46163 and cover most requirem ents of v isco sity , cure sp eed , and s tre n g th . Special requirem ents may necessitate contact with a supplier who has form ulating and engineering capability.

6.6

N uclear Use and Requirements

Effect of Irradiation on S tren g th Irrad iatio n te s ts of G rades K, L, M, N, R, S, T, U, V, W, X, and Y have been done with gamma radiation for total doses up to 200 mega­ ra d s . The effect on s tre n g th as m easured by b re a k /p re v a il to rq u es on steel n u ts and bolts was in general ra th e r minimal. U sually, the b re ak was th e same to 40% lower w hereas th e prevailing torque was 100 to 170% of th e n onirradiated p a r ts . This would imply th a t some em­ brittlem ent had taken place in a m anner similar to heat agin g .* S ulfur and Chlorine C ontent To avoid th e creation of corrosive elements and steel em brittlem ent d u rin g irra d ia tio n , the Nuclear R egulatory Commission re q u ire s th at organic compounds contain no more th an 200 p a rts p e r million (ppm) of chlorine o r 1500 ppm su lfu r (Atomic E nergy Commission R egulatory Guide 1.37 or ANSI N 4 5 .2 .1 ). To achieve th ese levels special p ro cessin g must be followed. None of the m aterials in th is guide should be used in nuclear situations unless specifically certified to meet th e NRC requirem ents. Those m aterials so certified may be used in th e secondary side of a gen eratin g p la n t, th a t is , th e electrical gen­ e ra tin g side. On the prim ary side, none may be used in the contain­ ment area b u t certified m aterials may be used in the rad -w aste control system , in stru m en tatio n , co n tro ls, etc. , u n d er high radiation (200 m egarads) where tem p eratu res are limited to 150°C (300°F). Consult y o u r su p p lier for n u c le a r-ra te d m aterials.

*Isomedix I n c ., 25 Eastman Road, P arsip p an y , NJ 07054, and Loctite C o rp ., 705 N orth Mountain Road, Newington, CT 06111 (R eport T-1221).

Chapter 2 Engineering Data Bank

1.

S U M M A R Y OF P R O P E R T I E S

The p ro p e rtie s listed in Table 2.1 are typical only of the p articu lar m aterials te s te d , which were made by the Loctite C orporation. In most cases th ey are averages of many specimens from many b atch e s. Simi­ lar m aterials are made by o th er organizations. The values in the tables are useful for design p urposes where normal safety factors are used and p ro totype te s ts can confirm re s u lts . They should not be used for receiving or en gineering specifications. The h e a d q u a rte rs of m anufacturers listed in in d u stria l catalogs are listed below. Local directories should be consulted for the closest s e r ­ vice. Apple A dhesives, Inc. 8000 Cooper Avenue Ridgewood, NY 11385 (513) 332-3533

Fel Pro Chemical P roducts Division 7450 North McCormick Boulevard Skokie, Illinois 60076 (312) 761-4500

Bostik Division, Emhart M iddleton, MA 01949 (617) 777-0100

Henkel KGaA P .O .B ox 1100 D-4000 D usseldorf 1, West Germany 0211/7971

Devcon C orporation D an v ers, MA 01923 (617) 777-1100

Hernon Inc. 37-23 27th S treet Long Island C ity, NY 11101 (212) 784-8001

41

42

Engineering Data Bank

Loctite C orporation 705 N orth Mountain Road Newington, CT 06111 (203) 278-1280

Rocol Limited Rocol House, Swillington Leeds LS268BS, England G arforth (09738) 2261

M aster Bond P .O .B o x 522 T eaneck, NJ 07666 (201) 343-8983

Three Bond Co. , Ltd. 1456 Hazama-cho, Hachioji-shi Tokyo, Japan 0426 (61) 1337

Perm abond In ternational 480 South Dean S treet Englewood, NJ 07631 ( 201) 567-9494

2.

T H R E A D L O C K IN G M A T E R IA L S E L E C T IO N

The selection of material is based almost en tirely on th e removal to rq u e and not th e sev e rity of d u ty . The reason for th is is the emphasis on to rq u e as th e one convenient way to in sp ect for presence and cure of th e m aterial. A dditionally, it has been proven th a t a line-to-line fit with v ery low (almost zero) b reak torque has given v ery good re s is ­ tance to self-loosening. Any low -shrink, high-m odulus, cu red liquid will give good perform ance re g ard less of its lack of adhesion to the th re a d s . A naerobics, of all cu rin g m aterials, do th is most conveniently. O ur selection will be based on making the break-loose to rq u e as close to th e tig h te n in g torque as possible. In th a t way th e removal tools and effo rt will imitate th e tig h te n in g p ro cess.

2.1

Selection to Match P ro of S t r e n g t h o f Fastener

T ig htening Torque Tables 2.2 th ro u g h 2.6 provide inform ation to calculate th e allow­ able loads and tig h te n in g to rq u es for various su rfaces and m aterials. The formula T = KDF is explained in C hap. 5, Sec. 1 .1 ., o r ap p ro x i­ mate tig h te n in g to rq u es can be read from Fig. 5.2.

_

2 .6

__

Min Min

SP EC.

UNITS

♦Commercial number,

Film—

MPa

lOOOLb/in

L o c t i t e Corp.

Compressive Str.Thin

1.4 M E C H A N I C A L P R O P E R T I E S Mod. of Elast , Ten. D 4 1 2 ----S h e a r S t r e ngt h, St. P i n / C o l l a r - -Lb/i -MPa S h e a r Str en g t h , N u t & B o l t ------- L b / i n B r e a k / P r e v a i l — St. D e g r e a s e d - M P a „ S h ea r S t r e ngth , N u t & B o l t ------- L b / i n B r e a k / P r e v a i l - Z n . P h o s . ------„

T h e r m a l C o n d . ----------- ---- B T U / h r . f t 2 °F . T h e r m a l C o n d u c t i v i t y — ---- W / m ° C / °c Coef f. Therm. E x p . ---- --------- 1 0

1 .3 C U R E D P H Y S I C A L S

g ap cureP r i m e d 2 0 % u l t . ----- --------------- M i n .

2 0 % of Ult. --------------- Hr s. Fu l l c u r e — P r i m e r for i n a c t i v e s u r f a c e o r

1.2 C U R I N G

S ee a l s o T A B L E

Bo l t R a n g e ------------------------in c h M a x Ga p C u r e --------------------- in . (mm) C o l o r --------------------------------S p e c i f i c G r a v i t y ------------------F l a s h P o i n t --------- C l e v e . O C ------ ° Fm(°C) Shelf Life (70°F±20 °F 22±ll°C)-Months C o r r o s i v i t y -----------M i l - S - 2 2 4 7 3 L u b r i c i t y K F a c t o r on O i l y P h o s

C h e m i c a l D e s i g n a t i o n -------------V i s c o s i t y -------------- D 2 5 5 6 -------- m P a . s S u g g e s t e d c l e a r a n c e --------------- inch

spec.

ASTM or ot h e r

steel

GRADE L

T or N

30 60 24

125 860

2900/360 20/2.5

General

--

GRADE M

N o n e or T

15 30 24

None 0.14

24

1 4/14

2100/2100 500/120 3.4/0.8

3 0 0 , 0 0 0 L b / i n / ( 2 1 0 0 MPa)

Gen e r a l 0 1A Ge n e r a l 0 . 1 3 est 5-1 0 —

GRADE K

T or N 2

Oily 15 30 24

1.12 1.12 A b ove 2 0 0 (93)24 24 None N one 0.12 0 .1 4 1.05

#2-1/2 . 0 2 2 ( .6) Purple

5/8-1+ . 025(.6) + T R ed

3/8-1 . 0 2 5 ( .6) + T Red

222

GRADE M

1000

TYPE I GRADE L 277

N e w t o n i a n ------ N e w t o n i a n Anaerobic Dimethacrylate750 70 0 0

TYPE I GR A D E K 271*

125 860

1300/270 9/1.9

—

N

1200/2400 8.3/17

—

GRADE 0

None or T

N o n e or T

GRADE

3 10 72

Nuts and Bolts-

None 0.10

24

1.1

3/ 8-1 . 0 2 5 ( .06) Red

Oily 10 15 24

0.11

24 None

steel

,022(.6)

1/4-3/4 Blu e 1.05

R 2 90

T Y P E III GR A D E

5.5/1.9

880/2800

—

GRADE R

T or N or 4

2 3 24

None 0.16

24

#2-1/2 .016(.< Green 1 .07

15

-

---------------+ W i e k i n g —

262

0

GRADE

Anaerobic Methacrylate 1100 150 0

Thixotropic

GRADE N 242

P ro perties of Machinery Adhesives— Summary

1.1 L I Q U I D P R O P E R T I E S

TABLE 2.1

# 2-

24

ia

30

T

GRADE

GRADE

10

U

1 4 / ---

1200

175

2000 / —

21 /----

300,000 Lb/inz (2100 MPa)4500 3500 24 31

0 . 1 3 e st 10

n

25 72 [+2@250°F(120°C) None+Heat, T N or T

85 24

--

None 0.18

3 0 0 0 / ---

21

— General 3000

— General — General 5- 1 0

GRADE S

N or T

20 [24

--

None 0.17

0.001-0.003 1/4-3/4 . 0 1 5 ( .4) Green 1.08

1250

Newtonian

GRADE U 680

S t e e l P i n s a n d C o l l a r s ------------

--

None 0.26

Above 200°F 24

1.10

, 0 0 3 ( .08) Green

1/2

0 to 0 . 0 0 4 1/2-3 . 0 1 5 ( .4) Green 1.1 5 (93°C)24

0 to 0 . 0 0 3

Thixotropic

100

D i m e t h a c r y l a t e --7000

Newtonian Anaerobic

GRADE T 6 20

GRADE S 60 9

TYPEIV

°PY

UNITS

UNITS

N

**

140% at

3 0 0 ’F

—

— — — —

—

— — — “

—

—

—

— —

Mil-S-46163—

—

1.8 M I L I T A R Y S P E C I F I C A T I O N

82

88 57

—

35 27

100 67

--

70 100 170

30

GRADE M

70 65

100 83 64

TYPE GRADE M 222

59 90 90 90

65 96 50

110

1000 Hours — 100 70

--

--

50 100 135

30 100

75

50

GRADE L

L 277

TYP E I GRADE

75 10 0 0 H o u r s ---

K 3 0 0 °F (149°C)-

GRADE

TYPE I GRADE K 271*

S k y d r o l -------------------------------% G a s o h o l ----------------------------- % T r i c h l o r e t h a n e --------------------- % B u t y l A l c o h o l ---------------------- -% P h o s p h a t e E s t e r -------------------- % T o l u e n e ------------------------------ % I s o p r o p y l A l c o h o l ----------------- %

1.7 C H E M I C A L R E S I S T A N C E 1 8 8 ° F ( 8 7 ° C ) Air R e f e r e n c e -------Mil- S - 2 2 4 7 3 D - -% M o t o r O i l --------------------------- % W a t e r -------------------------------- % G l y c o l / W a t e r ( 5 0 / 5 0 % ) ------------ -% T r a n s m i s s i o n F l u i d ---------------- -% G a s o l e n e ---------------------------- %

benerai Kating H o t S t r . @ R a t e d T e m p . ---- 7 2 ° F — -% of H e a t A g e d at R a t e d Temp. 72°F % Ret. % Ref. C o l d S t r e n g t h - 7 2 ° F ( 2 2 ° C ) A ir M i n u s 1 0 0 oF ( - 7 3 ° C ) - A c e t o n e + C 0 „ - -% Minus 320°F(-196°C)— L iq.N2— - -%

1.6 H E A T / C O L D R E S I S T A N C E

ASTM or o t h e r spec.

(Continued)

1.5 E L E C T R I C A L PROP.

TABLE 2.1 II

-

—

-

Mil-S-46163—

—

— —

100 100 27 30 1 00 95 95 87 — —

1000 Hours

--

130

20 100

GRADE N 3 0 0 ° F (149°C)30 10 0 0 H o u r s ----

H o n o r a 1 9 SO

T Y P E II GRADE N 242

_ —

— —

—

78 —

100 100 98 100 86

100

30 100 87 72

85

GRADE 0

T Y P E II GRADE 0 262

—

— —

1 00 — —

90

90 90

100 86 74 74

--

90 100 90

90

GRADE R

290

GRADE R

T Y P E III

—

— —

— —

—

100

3 0 D a y s at 10 0 100 40 50 100 70

—

—

125 100

IV

GRADE U 680

T Y P E IV

—

91 100

100 110**

110

71

-

—

85 100 58

-

—

110 110 11 0 100

—

— —

—

63 86 14 0 87

—

—

100 60 94

—

—

120 1 00

GRADE GRADE T U 4 5 0 °F ( 2 0 4 ° C - 3 0 0 ° F ) 68 50

GRADE T 620

TYPE

1 8 8 ° F ( 8 7 ° C ) ------

GRADE S 300°F(149°C) 30 1000 H o u r s -----

GRADE S 609

TYPEIV

cn

( L o c t i t e C orp.)

ASTM or o t h e r spec.

on O i l y P h o s

/°C

B r e a k / P r e v a i l - Z n . P h o s . ------„ Co mp ressive Str.Thin Fi lm— lOOOLb/in MP a

S h e a r S t r e n g t h , N u t & B o l t ------- L b / i n 2 B r e a k / P r e v a i l — St. D e g r e a s e d - M P a Sh ear S t r e n g t h , Nut & B o l t ------- L b /in

1.4 M E C H A N I C A L P R O P E R T I E S 9 Mod. of E l ast, Ten. D412-1000Lb/inZ S h e a r S t r e n g t h , St. P i n / C o l l a r — L b /in

T h e r m a l C o n d u c t i v i t y ------ W / m ° C Coeff. T h erm. E x p . ---------------10

1 .3 C U R E D P H Y S I C A L S ASTM UNITS OR O T H E R SPEC. „ T h e r m a l C o n d . --------------- B T U / h r . f t °F

1.2 C U R I N G F i x t u r e ----------------------------- Min. 2 0% of U l t . ------------------------ Min. F u l l c u r e --------------------------- Hrs. P r i m e r for i n a c t i v e S u r f a c e or G a p C u r e ---------------------P r i m e d 2 0 % u l t . ------------------- Min.

L u b r i c i t y K Coe f f . S ee T A B L E 2.6

M a x G a p C u r e --------------------- in.(mm) C o l o r --------------------------------S p e c i f i c G r a v i t y ------------------F l a s h P o i n t --------- C l e v e . O C ------°Fm(°C) R e c e r t i f i c a t i o n T i m e --------------M o n t h s Corrosivity-Mil-S-2Mil-S-22473—

R h e o l o g y ----------------------------C h e m i c a l D e s i g n a t i o n -------------V i s c o s i t y -------------- D 2 5 5 6 ------- m P a . s S u g g e s t e d c l e a r a n c e --------------- inch Bol t R a n g e ------------------------inch

UNITS

(Continued)

1.1 L I Q U I D P R O P E R T I E S

Commercial Number

TABLE 2.1

518

GRADE X Y 5 10

TYPE V GRADE

125 860

490/150 3.4/1

GRADE X

GR A D E W

800 5.5 500/— 3.8/—

240 48

240 24

Pipe Th'ds Fl a t L a p s —

None 0 .1 8

None 0.0 8

St.

24

20

10

10 10 12

1200

175

2 4 0 0 / --1 7 / ---

2200 / 1 5 / ---

21

— General 3000

Z

GRADE

45 72

10

GRADE MM

GRADE NN

of

Nut & Bolt

1700/800 12 / 5 . 5

170/160

1.2/0.8

220/280

15/4.8

1.5/1.9 2200/700

Steel

N ut

30 72

10

and

(9 3°C) 48 None 0.15

1. 1

21/19

2200/3300 15 / 2 3 3100/2800

GRADE SS

4.2/9.0 2700/1400 19/9.6

610/1300

GRADE TT

of

Bolt

Yellow

3Pitch

[ Cure is i n d e p e n d e n t [sur f a c e .

24 72

10

Oi l y

No n e 0.18

None 0.13

[ C ure i s i n d e p e n d a n t [ surface.

st e e l

A bove 200°F 48

6H a n d

48

3 0 0 , 0 0 0 L b / i n z ( 2 1 0 0 M P a ) ---

N or 2 5 0 °F 1 or 30

Oily

Pin & Collar 24 72

0.11

(93°C)48 No n e

Above 200°F 2 0 ( < 5 0 ml) None 0.18

1. 1

[Me t r i c

Solid Sponge [Cl a s s 2 & 3 A & B up to 5 t d / i n

1.1

1. 1

201

GRADE IT

D r y P r e a p p l i e d ------------Anaerobic Dimeth ac ry lat e

GRADE SS 204

1.1

202

GRADE NN

Red

GRADE MM 203

Dry PreappliedDimethacrylate1 ,200,000 S o l i d S p o n g e ---------0 .001 -0 .0 2 0 [ Class 2 & 3 A & B up to 5 td/i [ M e t r i c 6H and 3 P i t c h 0.02(0.5) D a r k Gre y Silver Green

Paste Anaerobic

GRADE Z 660

6. 9

1000

GRADE Y

S t a g e A 90 B 7 2 @ 2 0 0 °F N 15

1200

24 None 0.19

Paste Gel Anaerobic Dimethacrylate850,000 550 , 0 0 0 3,800,000 0 . 0 1 Max. 0 - . 0 . 005 0 .01 Max. 1/2-1 Pipe 1 / 8 - 1 / 2 Pip e 0.02(0.5) 0 . 0 2 (0.5) 0.01(0.25) Red White Purple 1.07 1.16 1.1 Ab o v e 2 00 (93)--------------------------------

567

GRADE W

— — — --- — .—

— — —

— — —

1.8 M I L I T A R Y

SPECIFICATION

—

—

— — 100 — 110 100 8

--

--

— — — — 95 17

—

79 80 74

— — 5 —

— — —

— 98 51

97 77

G a s o l i n e --------------------------- S k y d r o l ---------------------------- G a s o h o l ---------------------------- T r i c h l o r o e t h a n e ------------------ Bu t y l A l c o h o l --------------------- ~ P h o s p h a t e E s t e r ------------------ T o l u e n e ---------------------------- I s o p r o p y l A l c o h o l ---------------- -

% % % % % % % %

Transmission

F l u i d ---------------

— —

1 00 100 64 87

(149)

--

—

—

120

120 74

110 — —

54 — —

3 0 D a y s at 100 120

131 100 —

300 56 P&C

250

—

Air R e f e r e n c e ------- M i l - S - 2 2 4 7 3 D - % M o t o r O i l -------------------------- - % W a t e r ------------------------------- - % G l y c o l / W a t e r ( 5 0 / 5 0 % ) ----------- - %

General GRADE Z

—

15 Days 100 109 66

TYPE V GRADE Z 660

—

—

—

G R ADE Y 400(204) —

GRADE X 250(121)

4 Wks

2 50

Y 510

TYPE V GR A D E

—

— —

400(204) 14 P i p e th'd 21

GRADE W

TYPE V GRADE X 518

1.7 C H E M I C A L R E S I S T A N C E 1 8 8 ° F ( 8 7 ° C )

- °F(°C)

UNITS

— V/mil

TYPE V GRADE W 567

C ol d S t r e n g t h — Ref. 7 2 ° F ( 2 2 ° C ) A i r M i n u s 1 0 0 oF ( - 7 3 ° C ) - A c e t o n e + C 0 , ?-— % M i n u s 3 2 0 ° F ( - 1 9 6 ° C ) — L i q . N 2— -•— %

H ot S t r . @ R a t e d T e m p . ----------H e a t A g e d at R a t e d Temp. % Ret.

General Rsting—— —

1.6 H E A T / C O L D R E S I S T A N C E

1.5 E L E C T R I C A L PROP.

Commercial

(Continued)

ASTM UNITS or o t h e r spec. N u m b e r ( L o c t i t e C o rp.)

TABLE 2.1 T Y P E VI T Y P E VI

--

—

—

100 110 100

64 110 61 —

100 — — __

1 00 100 110 95 __

80 / 1 2 6 100 102 90

35 break/prevail

GRADE NN

GRADE NN 202

69 — — —

188°F(87°C) 100 56 100 40 —

—

1000 Hours 86/100 1 00 —

24

GRADE MM

GRADE MM 20 3

T Y P E VI

--

100 100 94

90 100 — — — —

30 D a y s ---1 00 93 120 110

—

GRADE SS JUU(LHy) 57 1000 hours 50/115 100 100

GRADE SS 20 4

--

—

100 88 94

94 — — —

100 88 1 10 120 —

—

Break/prevail5/33 __ __

74

GRADE TT Anns 9 n/. \

T Y P E VI GRADE IT 201

Oi

Engineering Data Bank

47

Thread Locking Material Selection TABLE

2.2

Proof Load of Steel Bolts (English) Minimum tensile ( l b / i n .2)

Proof loada ( l b /i n .2)

1/4 to 3/4 in .

74,000

55, 000

7/8 to 1 1/2 in .

60,000

33,000

1/4 to 1 in .

120,000

85,000

1 1/8 to 1 1/2 in .

105,000

74,000

Up to 1 1/2 in .

150,000

120,000

SAE grade 2

5

8

a 75% of th e proof load is commonly used as the working load for com puting the tig h te n in g to rq u e . Many o th er grades and m aterials are available. See Fig. 5.2 and check with th e bolt su p p lier.

T A B L E 2.3

Bolt size (nominal i n . th r e a d s /in .)

S tress Area of T hreads (English)

S tress area ( i n . 2)

Bolt size (nominal i n . th r e a d s /in .)

S tress area ( i n . 2)

1 /4 -2 0

0.0317

9/16-12

0.1816

1 /4 -2 8

0.0362

9/16-18

0.2026

5/16-18

0.0522

5 /8 -1 1

0.2256

5/16-24

0.0579

5 /8 -1 8

0.2555

3 /8 -1 6

0.0773

3 /4 -1 0

0.3340

3/8 -2 4

0.0876

3 /4 -1 6

0.3724

7/16-14

0.1060

7 /8 -9

0.4612

7/16-20

0.1185

7 /8 -1 4

0.5088

1 /2 -1 3

0.1416

1 -8

0.6051

1 /2 -2 0

0.1597

1-14

0.6791

Engineering Data Bank

48 TABLE 2.4 (M etric)

Proof Loads of Steel Bolts

C lassa

Minimum tensile (m egapascal)

Proof load8 (m egapascal)

4.6

400

240

8.8

830

660

9.8

900

720

10.9

1040

940

12.9

1200

1100

aThe metric class num bering system uses the ultimate stre n g th as the first d ig it(s) in 100s of MPa and the first digit afte r the decimal point as th e minimum yield (or proof) load in p ercen t of ten sile, e . g . , Class 4.6 is a 400 MPa steel with a minimum yield of 0.6 x 400 = 240 MPa.

T orque Augmentation Normal loosening to rq u e of a Unified National Coarse T hreaded (UNC) bolt will be 70% ± 10% of the to rq u e to which it has been tightened (UNF = 80%). The application of a m achinery adhesive adds to the normal loosen­ in g to rq u e . The amount by which it does th is is called to rq u e augm enta­ tion. This is shown in the shaded area in Fig. 2.1. The to rq u e value of augm entation is related to th e breakaw ay torque* and may v ary betw een 70 and 140% of th e breakaw ay. For the compounds shown th e b reak is essentially equal to augm entation. Most s tru c tu ra l fa ste n ers are to rq u ed to at least 75% of th e ir mini­ mum yield s tre n g th (proof lo a d ). To p re v en t damage to a secured bolt d u rin g removal, a locking m aterial should be used th at has an augm en­ tation o r breakaw ay th a t would make th e break-loose to rq u e roughly equal to th e tig h te n in g to rq u e . As a design r u l e , to p re v en t sh earin g on removal select a material so th a t: Breakaway = 30% of tig h te n in g torque *Breakaway to rq u e is the torsional s tre n g th of adhesive on an unto rq u ed bolt ( e . g . , p re to rq u e = 0).

Thread Locking Material Selection TABLE 2.5

49

S tress Area of T hreads (Metric)

Nominal size (mm)

S tre ss area (mm2)

Nominal size (mm)

S tre ss area (mm2)

M 2.0

2.1

M 10.0

58.0

M 2.5

3.4

M 12.0

84.3

M 3.0

5.0

M 14.0

115.0

M 3.5

6.8

M 16.0

157.0

M 4.0

8.8

M 20.0

245.0

M 5.0

14.2

M 24.0

353.0

M 6.0

20.1

M 30.0

561.0

M 6.3

22.6

M 36.0

817.0

M 8.0

36.6

M 42.0

1120.0

TORQUE A U G M EN T A T IO N

n

U

W

0

" A S R E C E IV E D " P L A IN -3SS T E E L NUTS ■■■!SSSSS5i 3S535SQCO^&QOQiOOOOOOQOOOOOOOQQOflQQO^PW^^

100

200

300

400

SQG

P RETO R Q U E, IN ,-LB FIGURE 2.1

Torque augmentation.

TO

Q

T A BLE 2.6 Torque Coefficient Ka

Type I Oil only

K

Type II L

M

N

Type III O

R

S

Lubricated with 5% Solution of Soluble Oil (Heat Bath Corp. #72D) Steel

0.15

0.23

0.20

0.16

0.14

0.13

—

0.23

Phosphate

0.13

0.12

0.14

0.14

0.11

0.10

0.16

0.26

Cadmium

0.14

0.13

0.14

0.12

0.13

0.13

—

0.19

Stainless 404

0.22

0.18

0.18

0.21

0.17

0.14

—

—

Zinc

0.18

0.17

0.20

0.16

0.16

0.13

0.19

0.30

Brass

0.16

0.22

0.15

0.14

0.09

0.10

—

0.30

Silicon bronze

0.18

0.25

0.24

0.15

0.24

0.17

—

—

Al. 6262Ta

0.17

0.21

0.25

0.20

0.29

0.18

—

—

Black oxide

0.17

0.23

0.20

0.19

0.20

0.15

0.21

0.21

Ti 6A1 4V

0.33

—

—

—

—

—

—

0.36

Degreased Fasteners Steel

0.20

0.22

0.26

0.18

0.20

0.18

—

0.29

Black oxide

0.40

—

—

—

—

—

—

0.19

Phosphate

0.22

0.19

0.20

0.15

0.14

0.11

—

0.28

Brass

0.26

—

—

—

—

—

—

0.28

Nylon

0.05

0.18

0.12

0.15

0.13

0.15

—

—

Zinc

0.38

0.23

0.23

0.17

0.17

0.12

0.24

0.34

Stainless 18-8

0.17

0.20

0.19

0.13

0.16

0.10

0.19

—

Cadmium

0.20

0.20

0.17

0.15

0.19

0.12

0.20

0.20

Ti 6A1 4V

0.35

—

—

—

0.25

0.22

—

0.32

—

—

—

—

—

0.16

—

—

Ti commer­ cial pure

&Accuracy of the above results can vary depending on the contact area, thread form, finish, oxide contamination, and place the application. In all cases the nut was turned against a soft washer. To insure consistency of torque with the liquid m aterials, the threads and the th ru st face were both

Type IV T

Type V U

0.21 0.17

0.18

0.14 0.18

—

0.18 0.20 0.27

W

X

Type VI Y

0.13

0.23

0.26

0.08

0.18

0.19

0.12

0.20

0.20

—

—

—

0.14

0.26

0.33

0.15

0.22

0.23

—

Z

MM

NN

SS

Tx

0.18

0.11

0.13

0.18

0.15

—

—

—

—

—

—

—

—

—

—

0.28 0.21

—

0.13

0.23

0.25

—

—

—

—

—

—

—

0.16

0.28

0.30

—

—

—

—

—

0.28

0.20

0.13

0.28

0.31

0.11

0.20

0.28

—

—

—

—

—

—

0.14

0.29

0.33

0.20

0.14

0.29

0.33

0.09

0.20

0.19

0.20 0.16 0.23 0.22 0.20 0.23

_

0.16

0.28

0.31

—

—

—

0.22

—

—

—

—

—

—

—

—

—

—

—

covered with material. With Type VI dry materials, only the external threads were filled with material, and normal processing included a Lab oil overcoat. Nuts were oily or dry according to the chart. Products M, N, and O are es­ pecially formulated to give close control of lubricity on lightly oiled p arts.

Engineering Data Bank

52

To find th e correct th re a d lo c k e r, e n te r the perform ance c h a rts shown in F igs. 2.2 and 2.3 with 30% of your bolt tig h te n in g to rq u e. 2.2

S e v e rity of Se rvice

A lthough th e s tre n g th of the adhesive bond is not directly re sp o n si­ ble for secu rin g against self-loosening, it is an indication of th e mod­ ulus and ability to re sist th rea d sliding motion. For all Grade 5 and 8 (8 .8 and 10.9) fa ste n ers the stro n g est m aterial is generally used b e ­ cause the use of these stro n g bolts usually indicates severe d u ty . Care must be taken to adjust the to rq u es for th re a d engagem ent if stan d ard n u ts are not u sed . The breakaw ay to rq u e is directly proportional to th e len g th of th re a d engagem ent up to 3XD. Even the stro n g est bolt may not disassem ble pro p erly in a long tap p ed hole. 2.3

Selection of V isc o sity to A s s u r e T h rea d Filling

Select a viscosity th a t will apply easily, not ru n off, and will fill th e maximum clearance (Table 2 .7 ). 2.4

C on sid e ration of the C u re Speed Needed

If quality control checks or functional s tre s se s are to be applied soon afte r assem bly, be sure th a t material has cu red enough to avoid bond failu re. A discussion of cure speed and breakaw ay to rq u es v s . time can be found in Sect. 3 in th is c h a p te r. 2.5

Selection of Application Method

The method of application may dictate the p artic u la r grade selected. Application methods covered in Chap. 4 v ary from full off-line au to ­ mation with preapplied G rades MM, NN, SS, and TT to usin g a hand applicator to wick G rades R and S. For complex applications you will benefit by w orking closely with a supplier who has system capability. 2.6

R e u sa b ility

Preapplied m aterials MM, NN, SS, and TT will pass the In d u strial F asten ers In stitu te * Specification IFI 124 for five re u s e s . O ther m achinery adhesives will not. In the a u th o rTs experience th is sp ec­ ification is too low to prove th a t the th re a d s are completely filled.

*1505 East Ohio B uilding, 1717 East 9th S tre e t, C leveland, OH 44114.

CAD.

Z IN C

e .g . T+T = G R A D E U SIN G P R IM E R " T " T = G R A D E T, NO P R IM E R

STEEL

(See co n stru ctio n notes in A ppendix, p . 77.)

E X A M P L E : 3/8 x 16 G5 R E C O M M E N D E D T O R Q U E IS 3 60 LB IN. 3 0 % IS 108 LB-IN. M A T E R IA L S B E L O W T H E H O R IZ O N T A L L IN E A R E S A F E T O U SE W IT H S T A N D A R D N U T

TO R Q U E : B R E A K A W A Y O R A U G M E N T A T IO N TO S E L E C T M A T E R IA L : S T A R T H E R E W IT H 3 0 % O F T H E R E C O M M E N D E D T IG H T E N IN G T O R Q U E

FIGURE 2.2 T h read locking perform ance ch a rt (E n g lish ).

+T = P R IM E R " T " +N = P R IM E R " N "

PHO S O IL

at CO

Thread Locking Material Selection

FIGURE 2.3 T hread locking perform ance ch art (m etric).

(See construction notes in A ppendix, p . 77.)

SA F E TO U SE W ITH 4t 2 S T A N D A R D NUT

Variables A ffecting Cure Speed and Initial Streng th

55

The safest way to reuse a fa ste n er with any locking material or d e­ vice is to apply a th rea d locker M, N , or O over the re u sed o n e . When re u sin g a m achinery adhesive-locked fasten er clean the th re a d s by blowing off loose material and rin se with a sq u irt of activ ato r. The same treatm ent will re sto re a nylon p atch , crimped th re a d , or lock w asher to b e tte r perform ance than when new.

3. 3.1

V A R IA B L E S A F F E C T IN G C U R E S P E E D A N D IN IT IA L S T R E N G T H Gap or Volume C u red

In th e ir co n tain e rs, anaerobic m achinery adhesives are stabilized by th e p resence of a ir, which perm eates the bottles and the liquid by molecular movement. To make these adhesives cure and cro sslin k , the air must be excluded so th a t metallic ions can s ta rt the p ro cess. Since any given surface will have only a set num ber of ions to overbalance the dissolved oxygen it follows th at the lowest volum e-to-surface ratio will cure most readily. Large volumes of material can passivate an otherw ise active su rface. T h u s, if p a rts are disassem bled before or afte r cure th ey should be reactiv ated with prim er T or N. Bondlines of 0.001 to 0.003 in . (0.025 to 0.075 mm) are ideal for ra p ­ id cu re and maximum s tre n g th . In general, cu res will be effective up to 0.010 in . (0.25 mm) with about four times longer fix tu rin g and 60% of the stre n g th . Average gap or bondline th ickness does not tell the whole sto ry b e ­ cause fix tu rin g can occur where p a rts are touching even though the maximum clearance is larg e r than ideal. Gap cu res have been tested in specimens with controlled gaps. P ressu re retention was used as the criterio n of cure (F igs. 2.4 and 2.11). 3.2

Presence o f A ir

The distance of the material from the closest air surface influences the cu re speed. Incomplete fill (tra p p ed air bubble) is the most common cause of slow or noncure. It is im portant to avoid air entrapm ent and to provide excess m aterial at the ju n ctu re between the p a r ts . The shape of the mating su rfaces has a small influence on gap cu rin g . A 3/8 x 16 bolt and n u t assembly has intim ate contact on the loaded th rea d flank, leaving the unloaded flank in clearance. The helical gap th u s formed is 5 in . (127 mm) long, so th at most of the volume of mate­ rial is remote from any air su rface. This special configuration of a th re a d creates more tolerance to gap cure than does a cylindrical fit, where th e air trav e l is stric tly longitudinal. F o rtu n ately , m achinery adhesives can overcome th e ir anaerobicity if given a little more time for cu re.

1100

1500

750

7000

12

M

N

0

K

L

R

High

High

High

# 2 -1 /2

5 /8-1+

3 /8 -1

3 /8 -1

1/4—3/4

Medium

High

# 2 -1 /2

(in .)

Low

S tr e n g th , relativ e

2 .2 -1 2

16-24+

10-24

10-24

6-20

2 .2 -1 2

(mm)

0.016

0.025

0.025

0.025

0.022

0.016

( in .)

0.4b

0.6b

0.6b

0.6

0.6

0.4

(mm)

Maximum diam etral clearance

^Grade SS is su g g ested for adhesion to plated fa ste n e rs. P rim er/activ ato r T is recommended for cu rin g in th e maximum g ap s.

1000

Grade

Suggested bolt range

Viscosity and T hread Clearance

Viscosity (cP or m P.s)

TABLE 2.7

SS o r TT

SS o r TT

SS or TT

NN, SS, o r TT

NN

MM

E quivalent p reap p lied g ra d e a

Engineering Data Bank

Variables A ffectin g Cure Speed and Initial S tren gth

57 -0.25

-

0.20

mm

-0.15

-

0.10

■0.05

L-0 TIME-HOURS

F IG U R E 2.4

3.3

Gap v s. cure time, Grade Y.

A ctive or Inactive S u rfa ce s

A ctivity of th e surface will also influence cu rin g re s u lts . The th in n er g rades can have th e ir effective gap cure doubled with th e presence of activator T or N on the su rface. In general, the chemical activation of th e su rface will speed the c u re , b u t sometimes the tra d e -o ff is lower s tre n g th . The cure speed graphs for the effect of various surfaces should be carefully o b serv ed . Data are not available on all grades and all su rfa ces. More surfaces are shown in Fig. 1.19 for Grade N. This b a r grap h shows relative s tre n g th s on a wide v ariety of su rfa ces; how ever, one should not assume the identical relationship for o th er m aterials. Individual te s ts should be conducted. In general, active and inactive su rfaces are divided as follows (see also F igs. 2 .5 —2.13):

Engineering Data Bank

58 Active Zinc phosphate Steel or iron C opper o r b ra ss Aluminum (commercial)

Titanium (6A1 4V and commercially p u re) Magnesium alloys Nickel Manganese

Inactive o r slow Zinc

Dacromet steel

Cadmium

All therm oset plastics

Zinc dichrom ate

Stainless steel

Polyseal

Aluminum (p u re)

Anodized o r passivated surfaces

Glass

Magnesium (p u re)

Glass epoxy

Gold, silver

Ceramics

Platinum

Data for Fig. 2.11 were obtained on 0.375 in . (9 .5 mm) thick steel flanges with gaps controlled between the mating surfaces at zero, 0.005 in . (0.13 mm), and 0.010 in . (0.25 mm). Test p re ssu re s were limited to 300 p sig (2.7 MPa) in a fix tu re as illu stra te d . H ig h -p ressu re te s t fix tu re s (not shown) could be sealed at 1000 psi with a 0.05 in . (1 .3 mm) gap , and cure was a ssu re d by using accelerato r/p rim er N and a 48-hour cu re time. (See F igs. 2.12—2.14.) 3.4

P rim er/A ctivator N and T

Prim ers N and T are surface p re p a ra to ry rin ses th at provide mild d eg reasin g action and accelerate normal room tem perature cu res of all of th e m achinery adhesives. In general, use the first one mentioned in Table 2.1. Prim ers T and N are used to assu re cure on inactive su rfaces or at reduced tem peratures and to remove variability of cure time from active su rfa ces. On the th in n e r grades they will double the gap c u rin g ability. R epair and maintenance operations on d irty mate­ rials of unknown composition should include a rin se with one of the a c tiv a to rs .

TORQUE, IN .-L B

O ILY S T E E L

O IL Y ZN. P H O S P H A T E

C U R E TIM E

C A D M IU M PL A T E

GRADE *K' (Activator recommended)

PT = Prim er

Z IN C PLA T E

cn co

Cure Speed and Initial S tren g th

FIGURE 2.5 Cure speed on 3/8 x 16 n u ts and b o lts, G rades K, L, and M. T ; PN = Primer N ; NP = no p rim e r.

BREAKAW AY

Variables Affecting

TORQUE, IN .-L B

O ILY S T E E L

O ILY ZN. P H O S P H A T E

C U R E TIM E

CADM IU M PLAT E

PT = Prim er T;

Z IN C PLAT E

FIGURE 2.6 C ure speed on 3/8 x 16 n u ts and b o lts, G rades N, O, and R. PN = Prim er N ; NP = no prim er.

BREAKAWAY

GRADE *N*

Engineering Data Bank

Variables A ffectin g Cure Speed and Initial S tren gth C LEA N ST EEL

C U R E T IM E - H O U R S

61

A L U M IN U M

C U R E T IM E - H O U R S

Cure speed on pins and collars, Grade S.

FIGURE 2.8

Cure speed on pins and collars, Grade T.

Megapascal

FIGURE 2.7

Engineering Data Bank

62

SHEAR

ST REN G T H

GRADE U

TIME-HOURS

FIGURE 2.9

Cure speed on pins and collars, Grade U.

C U R E SP EED GRADEW 3/8 PIPE T H R E A D S

-

-V E R Y

a p t ix /p

S U R F A C E (P R M E rc W

% U L T IM A T E

STREN GTH

100

1 MIN.

10 MIN.

1 HR

3 HR

6 HR 12 HR 1 D A Y

3 D AY 1 WK

C U R E T IM E

FIGURE 2.10

Cure speed on pipe th re a d s , Grade W.

2 WK

Variables A ffectin g Cure Speed and Initial Streng th

300 —

TEST

63

I

250

200

< LU w

150

oc

A sse m b ly Force

D

Greater T h a n

100

Se p aratin g Fo rce

50 S h im P ins

Pressure In.

TEST FIXTURE

CURE TIME - HOURS

FI CURE 2.11

Cure speed on flanges, Grade X.

MPa

£

TIME-HOURS

FIGURE 2.12

Cure speed on steel laps, Grade Y.

64

Engineering Data Bank

M IN .

FIGURE 2.13

Cure speed on steel lap s, Grade Z.

FIGURE 2.14 Cure speed on 3/8 x 16 n u ts and b o lts, preapplied MM, NN, SS, and TT.

Variables A ffectin g Cure Speed and Initial S tren gth

65

Production applications usually are clean and th e composition of p a rts known. Grades M, N, O, T, U, and Z are responsive to mod­ erately inactive surfaces and seldom need the assistance of an activ ato r. A ctivator specifications for prim ers N and T are as follows: P ro p erty

Primer N

Primer T

Color

Green

Yellow

Solvent

T richlorethane

T richlorethane

V iscosity cP (k P a .s)

3

3

Flash point

None

138°F (59°C)

Toxicity TLV PPM

350

350

Specific g rav ity

1.32

1.3

C oncentrate / solventa

1:30 by volume

1: 9 by volume

Mil. Spec.

Mil-S-22 47 3D

D rying time (m inutes)

3

3

O n -p art life (weeks)

4

1

Shelf life (unopened)

1 year

1 year

M a te ria l is usually shipped ready to use b u t is available as co n cen trate. 3.5

Tem perature

All chemical reactions can be speeded by elevating the te m p e ra tu re , b u t th e re are limits above which molecules do not combine; instead they te a r them selves a p a rt. For m achinery adhesives th e u p p er limit is about 325°F (163°C). Above th is tem perature some of th e co n stitu en ts will evaporate before they c u re . As a rule of thum b, small p a rts assem ­ bled with m achinery adhesive will cure completely given the following oven times and tem p eratu res. Included is a 10-minute soak to get the bondline up to tem p eratu re. T em perature °F (°C )

Oven time (m inutes)

300°F ( 149°C)

15

250 (121)

30

200 (93)

60

150 (66)

180

Engineering Data Bank

66 COLD

25

20

UJ

cc

Z)


LU

>

LU

CC

25

I

50

1--------------100 150

M

200 °C

TEMPERATURE

FIGURE 3.1 Hot stre n g th of G rades K, L, and R on ste e l—Types I and III Newtonian.

H LU S■ Z

o h£ LU

Z

D

O CC O l-

T

25

50

nr

100 150 TEMPERATURE

■"TI

200 °C

FIGURE 3.2 Hot s tre n g th of Formulas M, N, and O on ste e l—Type II lu b ricatin g th ixotropic.

Environmental Effects

92

25

50

100

150

200 °C

T E M P ER A T U R E

FIGURE 3.3

Hot stre n g th of Formulas S, T, and U on steel—Type IV.

T EM P ER A T U R E

FIGURE 3.4 Type V.

Hot stre n g th of Formulas W, X, Y, and Z on steel—

Heat Aging and Service Life

I I 25 50

I 100

I 150

93

I” 200

T EST T E M P E R A T U R E - °C F I G U R E 3.5

Hot stre n g th of Formulas MM, NN, SS, and TT on steel—

Type VI.

3. 3.1

H E A T A G IN G A N D S E R V IC E LIFE Heat A g i n g T e s ts

A fter months or y ears of exposure to elevated tem perature in a ir, most organic m aterials react with oxygen, causing a degradation of physical p ro p e rtie s. Similar degradation occurs u n d er the influence of m oisture, ozone, and many o th er chemicals. It is most convenient and practical to te s t in air without the complication of o th er facto rs. This gives a com parative ra tin g th a t is highly rep eatab le. M achinery adhesives are somewhat more complicated than plastics to te s t because th ey are always tied to a su b stra te and cure may not be en tirely complete when th e degradation te s t is s ta rte d . If the s u b s tra te oxidizes at the same time as the adhesive then it may become as significant to the bond in te g rity as the adhesive. This is exactly what happens with adhesively bonded copper and co p p e r-b e arin g alloys. The copper forms a loose oxide film u n d er the adhesive and effectively p ries it loose. This occurs only at tem pera­ tu re s over 150°F (66°C) and re q u ire s the presence of some m oisture. Fig. 3.6 illu stra te s p u re catalytic degradation of a therm oset plastic. Some m achinery adhesives are not so re g u la r in th e ir aging pro cess. They always s ta rt as monomers or m ixtures of monomers and polym ers. The cu rin g p rocess s ta rts afte r assembly and involves the hooking of molecules to g eth er both e n d -to -en d on the monomer chains an d , most

94

Environmental Effects

FIGURE 3.6 Heat aging cu rv es for catalytic degradation of a fully cu red organic compound.

im po rtan tly , at midsections or backbones of th e chains. This la tte r p ro cess is called crosslinking. From it re su lt th e perm anent p ro p e r­ ties of an irre v e rsib le , polym erized, therm oplastic adhesive. C rosslinking occurs rapidly for an hour or so, th en continues at a v ery slow ra te somewhat dependent on th e tem p eratu re. The process is roughly analogous to a bowl of sp ag h etti which, when fresh ly cooked and drain ed of w ater, flows easily and has no physical shape without r e ­ s tra in t of th e bowl. If allowed to d ry , th e flour forms paste and finally glues th e long chains to g eth er at midpoints u ntil the whole bowlful becomes a relatively homogeneous lump. If th is lump is put into th e oven to "age" it will get h a rd e r and s tro n g e r for a while until it gets so d ry and crisp y th a t crosslinking bonds s ta rt to b reak and th e lump s ta rts to fall a p a rt. At aging tem p eratu re, most m achinery adhesives will crosslink more th an o ccu rred d u rin g th e prelim inary low er-tem perature c u re . This means th a t linking and unlinking are o ccu rrin g sim ultaneously, which causes seemingly stran g e in creases in stre n g th and ballooning cu rv es th a t do not fit th e idealized concepts typical of a w ell-cured plastic (F ig. 3 .6 ). For th is reason th e cu rv es for S, T , and U in F igs. 3.8— 3.10 are not plotted u n d er 500 h o u rs. T heir secondary cu rin g gives ra th e r wild re s u lts with little usefulness until th ey settle into the aging p ro c ess. The crosslinking effect even re v e rse d the position of th e 325 and 300°F cu rv es for Grade U. The A rrhenius technique (S ec­ tion 3.2) is questionable for this m aterial. Heat aging of m achinery adhesives is usually done in specimen joints of pins and co llars, n u ts and b o lts, or lap -sh e ar s trip s . Plain steel is th e p re fe rre d fin ish. Shear s tre s s is the p ro p e rty observed to d e ­ te rio ra te , and 2000 hours are usually enough to show a tre n d and to

Heat Aging and Service Life

95

ra te the combination for tem perature re sistan c e. Room -tem perature controls are aged for th e same time as the heated specim ens. The tem ­ p e ra tu re th a t causes 50% reduction in th e room -tem perature shear s tre s s afte r 2000 hours is called the adhesive tem perature limit. Such a ra tin g is highly a r b itr a r y , for often m aterials can be used well over th e ir limits an d , conversely, sometimes safe operation is well sh o rt of th e limit. The te s ts are repeatable and provide a way to compare various form ulations. See F igs. 3.7—3.14. Less emphasis is pu t onto s tre s se d specimens th an is usual with plastic p a rts for two reaso n s. The firs t is th a t m achinery adhesives are relatively b rittle and are re stra in e d between rigid p a rts so creep ru p tu re values will be close to ultimate s tre n g th . Second, th ey are usually cu red completely s tre s s -fre e in v ery thin films. The th in films are usually s tre s se d only in com pression d u rin g u se. Com pressively s tre sse d films are not subject to s tre s s cracking o r in te rg ra n u la r d eterioration as would be tensile or tensile shear assem blies. 3.2

Life Extrapolation by A r r h e n i u s Plots

In g eneral, th e estim ation of service life of any organic material is predictable on a theoretical basis afte r certain assum ptions are ac­ cep ted . We know th a t, for many nonmetallic m aterials, the degradation process can be defined by a single tem perature dependent reaction th a t follows th e A rrhenius equation: k = Ae- ( E a /K b T | where k = reaction ra te

Ea = activation energy

A = frequency factor

Kb = Boltzmann’s constant

e = base e = 2.718

T= absolute tem perature

For many re a c tio n s , the activation en erg y is considered to be con­ stan t over the applicable tem perature ran g e. The accuracy of the A rrhenius method is based on the use of tem­ p e ra tu re as the sole accelerating means for deg rad in g the adhesive and the stra ig h t-lin e relationship between tem perature and the time to failure. U nderw riters L aboratory Method 746 B re q u ire s te stin g to be conducted at four or more tem p eratu res. The highest tem perature should last at least 500 h o u rs. The Nuclear R egulatory Commission will accept d ata from as sh o rt a period as 100 h o u rs. Any conditions can be imposed in addition to tem perature as long as th ey are kept constant and only the tem perature is changed. For

Environmental Effects

96 - 30 RA DE IL 200

— ------*"

150

20(3°F

oc

300°F

- 20 jg

UJ

z

200° F

100 GlRADE )

.___30