Troubleshooting Rubber Problems
Contents
1. Form a seal between two rigid moving parts Accommodate misalignment between other components Absorb or isolate vibrations that cannot otherwise be eliminated Since these expectations are often expected to compensate for design shortcomings increasing amounts of rubber are required The rubber industry has been increasingly competitive for many decades especially so in recent times This has often resulted in downsizing that minimizes the practice of pairing senior and junior technical personnel This practice brought newer hires and current technology to an organization senior people shared hard gained experi ence with newer personnel 10 Unfortunately downsizing has set the stage for loss of technical knowledge over time and resulted in frequent reinvention of the wheel B 1 5 Book Organization This book is broadly organized according to the type of rubber involved be it TSE thermosetting rubber or TPE thermoplastic rubber These two types of rubber have been compared in terms of factors that include 11 Recycling ability Bondability Cycle times Upper service temperature Molding equipment While TSEs and TPEs share much in common there are major differences between them that necessitate special consideration and equipment A number of materials and processing options are suggested along with numerous references that will per mit the reader to dig deeper This book concludes with a relevant list of ab2. 4 25 4 26 4 27 4 28 4 29 4 30 4 31 4 32 Air Springs Keyboard Springs Gloves Inflatable Dam Inflatable Trafic HUND 2 3 sso eve ed d Tennis Balls 4 27 1 Tire Manufacturing Systems sseeeeee eee eee ee 4 27 2 Modular Integrated Robotized System 0 lesse 4 27 3 Bridgestone Innovative and Rational Development 4 27 4 Modular Tire Manufacturing seeeee 4 27 5 Advanced Tire Operation Module serene 4 27 6 Automated Production Unit System 0 eee eee eee eee 4 27 7 Integrated Manufacturing Precision Assembled Cellular Technology 4 27 8 Components 4 27 9 Tire Molds 4 27 10 Venting Tire A y ee 4 27 11 Run Elat ROS euere DR n EIU ic en eh 4 27 12 Semi pneum atic LiTeS u esee eme ee ADT AS Tire Aging aNd Safety xxxn ken 4 27 14 Tire Recycling Viridiana Nontire Products 4 28 1 General Design Considerations sees Bridge Bearings Earthquake Mounts Expansion Joints CIS ame nie 4 32 1 Automobile Sunroof Seals sseeeeeee eh 4 32 2 Radial Lip Seals uses an nee ae dus VR RR e Rea 4 32 3 O Ring Seals XI XII Table of Contents 4 33 4 34 4 35 4 36 4 37 4 38 4 39 4 40 4 41 4 42 4 43 4 44 4 45 4 46 4 47 4 48 4 49 4 50 4 32A ASKO ae nn et n Rd es cin AA AGR 189 4 32 5 Wine Bottle Corks ssseeees
3. Stiehler R D Chapter 8 in Basic Compounding and Processing of Rubber Rubber Divi sion ACS Long H Ed 1985 p 170 13 Whitby G S Synthetic Rubber John Wiley amp Sons New York 1954 p 374 14 Callari J Plast Technol May 2011 p 9 TSE Materials and Compounds B 2 1 Introduction Although TSEs and TPEs share many features in common there are substantial dif ferences 1 Table 2 1 contrasts some of these differences Table 2 1 Contrasts Between TSEs and TPEs Consideration TPE TSE Recycling Relatively easy to recycle Crosslinked material very difficult to recycle Energy Easier recycling uses less More complex recycling steps use more energy energy Automation Capitalizes on robotics used in Less amenable to automation plastics industry Bonding Heat welding feasible Generally requires adhesive and chemical bonding Cycle times Typically seconds Typically minutes Upper service Limited to 7 or 7 of TPE Generally higher and limited by thermal stability temperature of TSE backbone and crosslink stability B 2 2 Cost Reduction Cost reduction the one constant in the rubber industry might be considered the most important compounding variable Over time compounds continue to evolve that contain lower rubber content directed toward continuing cost reduction For example a low cost EPDM molding compound contains only 11 7 rubber 2 Other compounds can contain even lower rubber content
4. practice leads to recipes with an excessive number of ingredients the intended function of which may be lost over time 5 Hence the number of ingredients in a compound keeps growing and a compound could contain as many as 25 ingredients Recipes that contain more than two types of carbon black or two types of mineral filler should be viewed with skepticism Production managers typically expect compounders to solve all production prob lems by changing recipes 6 This often results in an excessive number of com pounds and raw materials Several cases showed that the number of compounds and raw materials can be reduced by 30 to 50 without losing customers or harming product performance Overemphasis on materials considerations to the exclusion of processing factors can be problematic 7 One compound could cost more than another on a weight basis but when considering processing factors such as shorter cycle times and easier demolding or extrusion rubber articles might be produced at a lower cost Experiment design DOE judiciously used can serve as a valuable aid in optimiz ing compounds and significantly reducing rubber scrap rates 8 The range of experiment designs runs from simple to complex and comprehensive 9 A compre hensive design established important factors that included compounding process ing design molding and testing for injection molded air ducts 10 The terms rubber and elastomer are used interchangeab
5. with an 80 Mooney viscosity 70 weight percent ethylene and 5 weight percent ENB is said to offer excellent mixing behavior 34 It also offers high green strength and a fast cure in sulfur cured compounds Green strength is a measure of resistance to deformation and fracture before vulcanization 35 Other properties are good filler and plasticizer acceptance and outstanding aging resist ance 2 3 5 SBR Styrene Butadiene Rubber SBR has been available for many decades as E SBR emulsion SBR and later as S SBR solution SBR E SBR the original SBR polymerized at 122 F is known as hot SBR its counterpart polymerized at 41 F is known as cold SBR 36 Cold SBR has less branching and yields vulcanizates with higher resilience relative to hot SBR The S B ratio for all these rubber types can be varied to give a wide range of properties especially low temperature properties with low S B ratios possessing lower T values S SBR in compounds generally results in higher viscosity than E SBR 37 The higher hydrocarbon content in S SBR can be used advantageously by increasing the 2 3 Elastomer Type 13 amount of carbon black and oil and thus lowering compound costs while providing equivalent properties Other potential advantages are said to be improved product uniformity lower rolling resistance and increased abrasion resistance in tires By itself rolling resistance is said to be responsible for a startling 4 of worldwide ca
6. Contents T WPEPrFIOQUCIS o cece hine ERATES ERIS ES ama gea 271 Z3 Athletic PEOGUCIS amp ti eian wie leo Gidea ln get Bid den eR been qve 272 7 2 Hood StOpsuss coder eee ve SEE bre wd eu teen S Rer 272 7 3 Food Traysau sudes een sas ede ae o pd ee Seee BA UR 272 TA Rollers cs cece 00 ese ee o namen E REY EV P EX ne 273 713 SealS acs ces de ee s en a a s E p s EV EE 273 73 1 SSCA DESIGN s st i e o nec ie p ra UR te le eR n uin ARA 273 TO O E aii 274 Tel 3BROSChEUES ti acaed nine al eocod later aie A ate E 274 7 8 CVI BOOS za d goes ac A A A E A a came 274 7 0 PISOS uie oie acts AA rg fete ug ie RU Dee 275 PORUM Opi RC 275 7 11 Appeat tice D ae aa ae 275 712 Conducive SEBS stas anne Bee bus URL Ren 276 7 18 A ee te re ae een 276 Appendix 20 cece cece I I n 279 ADDIE VIALIONS a use cr 279 Appendix renerrien is Baa p een een nen 283 BIA a Meer 283 TSE and TPE Materials Compounds Processes and Products B 1 1 Introduction This book is broadly organized according to the type of rubber or elastomer involved thermosetting elastomer TSE or thermoplastic elastomer TPE The terms elasto mer and rubber are used interchangeably B 1 2 Troubleshooting Difficulties A major difficulty in troubleshooting a rubber problem is clearly defining the prob lem As the old adage goes a problem well stated is a problem half solved 1 Per sons closest to a problem or those who will benefit m
7. Multiple sources of elastomers are available to the compounder for preparation of compounds to perform a specific function Costs vary substantially for these elasto mers and their compounding ingredients Caution must be exercised in selecting an elastomer rubber and its ingredients For example a salesperson might suggest a 8 2 TSE Materials and Compounds lower cost accelerator as an exact replacement for a higher cost one currently used by a manufacturer 3 Because of subtle behavioral differences among different rubber ingredients switch ing to an alternative material without adequate testing can result in nonequivalent performance Hence ideally alternative candidates should be first tested in the lab then in a small scale factory trial followed by a full scale factory evaluation to estab lish that the intended substitution is indeed satisfactory The value of recipes for compounds varies substantially within a company 4 Some recipes fall under commodity status while others have some unique material or pro cess innovation that causes a company to protect a recipe because of its value Hence it can be advantageous to mix commercially sensitive recipes in house reci pes that require less secrecy can be mixed by an outside company 2 2 1 Compounds and Compounders Over time the number of ingredients in a compound tends to increase because a new ingredient is incorporated in a compound to solve the problem of the day This
8. Polyisoprene NR and IR 2th da SER e pace ea 14 2 4 Crystallization uni dass ande e nier ERES Ed eA aT Pam 15 2 5 Crosslinking Factors eii assessed se einer a dg I eR E RE ERES 16 2 6 Silicone RUDDER surreal en 17 2 6 1 NBR Acrylonitrile Butadiene Rubber 0 006 20 2 6 0 HNBR Hydrogenated Nitrile Rubber lessen 20 2 63 CM Chloro Polyethylene cece eee eee eee eterea 21 2 6 4 CSM Chlorosulfonated Polyethylene 00000000 22 2 6 5 AEM Ethylene Acrylic 0 00 ccc mls 22 2 7 Elastomer Blend8 vicioso da dd dare Res heec Du cer teu 22 2 8 Crosslinking Systems voir RR pA E rp DERE PE care 23 VIII Table of Contents 2 9 Dispersion acute es poe eng Ete bere eleg HEN TR nc been ehe 25 2 10 Crosslinking System EHectS eri RR Gn RN Ka an 25 2 11 C CI RP 27 spo dr 27 2 13 Process Aids riesen Re 29 2 14 Plastieizers and OS ove tt et RR a gr 30 2 15 Antidegradants us tedio dues ate ux Re QUSE TRUM fe e Raton x io aod ue 31 2 15 4 Discoloration and Staining 0 eee eee eee eee ee 32 VADEJ CMT 34 2 17 Flame Ret rders ninia eere en ee 36 2 18 Compound Properties eseeeeseeeeee Ih 36 2 19 Testingus eee adda a awe OUR Pieve Pus teure e 37 PAMEG ME 41 2 21 Low Viscosity Elastomers seeeseeeeee Ih 41 2 22 Silicone Rubber Viscosity esses rr 4
9. Reg eR NF odd abet eede 208 4 39 14 Hose Identification Technology eee 209 Expansion Joints 0 cir de epe kt equ nip he ER Eee 209 COMO AMETE 209 RubbersCovered Rolls scenic Rt date dd 210 Wireand Cable Coating 2 5 siis seres e eniad erp aden a ae E E Res 212 Cellular Rubber 22 22 ae REP gira nern aan 212 Hatd R bber asias e RAT Rr ena ae head 213 Rocket Insulation i e ob gise aaa ice 213 ORIO SS nadar ad A e 214 Earpl gs sudar end ee re bes ceed eae 214 Testing is da adh bee ie 215 Dip Molding 00 be nn pra eed SES 215 4 50 1 Latex usce xe sc ar monde pee een nae tek N een Red aa te 215 4 50 2 Plastisol x coils acai a takes 217 Table of Contents XIII 4 50 38 Materials dre xe ee Meena ee 217 4 50 4 Processing u be team een 217 4 50 5 Design Products and Applications ooooccoooccrocorcnrnocc 218 5 TPE Materials and Compounds ssssss 233 5 l Introduction escitas ea a ac 233 5 2 DPE Types air einen A 234 5 2 1 TPV Thermoplastic Vulcanizate lessen 234 5 2 2 SBC Styrenic Block Copolymer esee 234 5 2 3 SEBS Styrene Ethylene Butylene Styrene 004 234 5 2 4 TPU Thermoplastic Polyurethane 0 0 eee eee eee ee 235 5 2 5 TPO Thermoplastic Polyolefins 00 cece ee eee ee eee ee 235 5 2 0 COP Copolyester u ee ia e e RU RE IPIE EY 236 5 9 DINOS esten qe ceed Soe ia pax ecd RU
10. Rubber I Title T 1890 5665 2013 678 3 dc23 2013031088 Bibliografische Information Der Deutschen Bibliothek Die Deutsche Bibliothek verzeichnet diese Publikation in der Deutschen Nationalbibliografie detaillierte bibliografische Daten sind im Internet ber http dnb d nb de abrufbar ISBN 978 1 56990 553 1 E Book ISBN 978 1 56990 554 8 All rights reserved No part of this book may be reproduced or transmitted in any form or by any means electronic or mechanical including photocopying or by any information storage and retrieval system without permission in writing from the publisher Carl Hanser Verlag Munich 2013 Production Management Steffen J rg Cover art Courtesy of Freudenberg NOK Sealing technologies Coverconcept Marc M ller Bremer www rebranding de M nchen Coverdesign Stephan R nigk Printed and bound by K sel Krugzell Printed in Germany Preface The intent of this book is to compile and present a lifetime of experience involved in research and development in the rubber industry This experience resulted from employment at several rubber companies most notably 28 years in the research division at Gencorp in Akron This was followed by teaching rubber related semi nars at several universities and at the Rubber Division of the American Chemical Society I would like to acknowledge the help encouragement and support of my wife Nancy and also the help with computer related issues provided
11. as a floor mat The relative importance of ingredients in a quality compound follows 13 1 Polymer or blend of polymers 2 Curing system 3 Fillers Selection of the remainder of the ingredients while important is not as important as the main ingredients listed above B 2 3 Elastomer Type Different elastomers offer specific advantages such as oil resistance and tolerance for temperature extremes Resistance to thermal degradation at high temperatures is an important factor in elastomer selection Table 2 2 shows the highest service temperatures suggested for a range of elastomers It should be noted that these are general suggestions as other factors significantly affect the elastomer choice It should be further noted that there are differences in elastomers of a given type 14 For example fluoroelastomers from different suppliers are said not to be interchange able To avoid this problem BMW puts a specific elastomer with a specific process 10 2 TSE Materials and Compounds Table 2 2 Elastomer Type and Highest Suggested Service Temperature Elastomer Highest Service Temperature C Polyurethane 75 Styrene butadiene rubber 75 Natural rubber 85 Polychloroprene rubber 100 Nitrile butadiene rubber 125 Butyl rubber 125 EPDM 125 Chlorosulfonated polyethylene 150 HNBR 150 Polyacrylic rubber 150 Fluoroelastomer 200 Silicone rubber 250 Perfluoroelastomer 300 name and supplier on part specifications to a
12. suggested as activators in sulfur vulcaniza tion of S SBR compounds even though they result in lower cure rate and state of cure 45 2 3 6 FKM Fluoro Rubber of the Polymethylene Type FKM has substituent fluoro and perfluoroalkyl or perfluoroalkoxy groups on the polymer chain FKMs have been polymerized from essentially the same monomers for more than several decades 46 Changes in architecture have advanced their use 14 2 TSE Materials and Compounds substantially because of improvements in processing reduced mold fouling and hot tear strength Fluoroelastomers containing PMVE can demonstrate improved low temperature flexibility 47 Carnauba wax incorporated in FKM reportedly improves mold release 48 O rings prepared from a typical fluoroelastomer formulation that contains iron oxide are thermally stable up to 380 C provided that there is adequate air flow around them 49 In stagnant air that might occur in the center of a large pile of O rings being postcured chemical reactions can build up sufficient heat over time to cause autocatalytic conflagration Several practices can minimize this problem Properly maintain and clean ovens exhaust fans discharge ducting precipitators scrubbers and fire extinguishing systems Avoid overloading postcure ovens Provide sufficient air flow to cool articles to avoid autocatalytic oxidation and pos sible conflagration Finely divided aluminum powder underwent
13. 3 2 224 LSR Molding Factors secs etes een a E eens eee 44 2 23 IA P EE TITMMM 45 2 24 Plastisols esee spem ee dag tie gre gegen dune perita RR QR eu 46 TSE Processes and Equipment ususuuusuusuuu 55 3 1 Adhesioh nc eee beg bre x eeepc rice iege o Re rere dane e d pee a ue 55 ILL UDS OS ii ee ec ar en Ra 55 3 1 2 Substrate Surface Treatments 0 0 eee eee 56 3 2 Effect of Ingredients scrisse EE hte mek rn a re 58 3 2 1 Substrate Considerations 0 0 mir cnie eee eee eee 59 32 2 Adhesive Ly Pe arise nud nade o ce A o Be a 60 30 TESNE TRE 64 OA JPIOGBSSIIB uite RN AAA AAA 67 SED MID ii AAA AAA AAA AAA 68 3 0 1 Mixer Type ans AR enis aaa 70 3 6 E 71 3 7 DISPETSION ouo a a A 72 3 8 Contamination ssai agiis oi aake nahen 73 3 9 Extr sion 4 40 en en TR ang 73 3 9 1 Extrusion of Specific Types of Rubber ooocooooccooocccooo 76 3 9 1 1 Elastomeric Alloy EA lessen 76 391 2 EPDM ich t etin de t ee hte ate etant Rie e oe Mense 76 39 1 3 Silicone Rubber aorta EE a 76 3 9 2 Extrusion PaCtOTS mein pi A es 77 3 9 2 1 Owiput Rate is add 77 3 0 2 2 Wie Swell gr A RARA 77 3 92 37 Die Entrance esoo a 78 3 0 2 4 Extrudate Appearance muii eer x Reni 79 3 10 3 11 3 12 3 13 3 14 3 15 3 16 3 17 3 18 3 19 Equipment 3 10 1 Hot Feed 3 10 2 Cold Feed Ram Extruder Multicut Transfermix Crosshead Extruder Cont
14. Crystallization increases the hardness of NR and attempts to mix crystallized NR have severely damaged internal mixers and mill rolls Hence the crystallites must be melted before processing crystalline rubber the rubber must be thawed much like an ice cube thaws and melts Palletized frozen NR can take a considerable time to thaw in a hot room at 50 C it takes about two weeks for the center of the pallet to reach 30 C 52 Crystallization also occurs in vulcanized NR articles 53 Exam ples are elastomeric helicopter bearings that were in service in Alaska laminated rubber bearings for offshore production platforms at subsea depths 3 C and bridge bearings It is important to distinguish between the hardening due to 7 and that due to crys tallization 54 An elastomer below its 7 is hard and brittle and exhibits a modulus 1000 times higher than that in the rubbery state Crystallization in NR will increase its modulus by about 100 fold In this semicrystalline state the NR is tough but not brittle In contrast rubber below its 7 is brittle Crystalline NR is traditionally thawed by storage in a hot room at 40 to 50 C just prior to use the thaw time increases as the square of the block size Figure 2 1 shows a block of NR that was only partially thawed as indicated by the dashed boundary line 55 Crystallized rubber should be thoroughly melted before it is further processed to avoid damage to processing equipment such as an inte
15. D NOR Sees 236 DA COSE loss op pure west eus be wd d bte vi de 237 5 5 Service Temperature sonora RM MERI Pen 237 5 0 CO MER ebenen ee 237 5 61 Panne TEES 239 6 TPE Processes and Equipment usssssssss 243 6 1 Injection Molding u en eg Rex hn RR I EE RETE en 243 6 1 1 Injection Molding Machines sese 244 6 1 1 1 Specialized Machines and Techniques Ls 247 6 1 2 Machine Operation sisses saien aana aA III 248 6 13 DIVING vertikale 249 OLA B rrelandsereW urn en na ann ha e bean 249 6 15 Injection Rate u a nenne an m eo 251 6 1 6 Injection Pressure and Mold Packing eee eee eee 251 6 1 7 Clamp Pressure cuidad Ee eh edd Sie cles ada eae 252 6 1 8 Nonreturm Valve eet once pm ia 252 6 1 9 Mold Temperature and Cooling Time sseseeeeeeeess 253 6 1 10 Heat Transfer a RR a do e Ric EA PRA 254 6 1 11 Mold Fouling i 22 eB ser heise ea 255 6 1 12 Regrind une aan ea pace TR p SURG de neben 255 6 1 13 Injection Molds aan er a e 255 6 1 13 1 Mold Material vun een 255 6 1 13 2 Mold Surface Treatments 0000s eee eee eee eee 256 6 1 13 3 Mold Maintenance 2 0 0 cee eee er eter en 256 6 1 14 Mold Design rn an er 257 6 2 Blow Molding occi ice eed a ea RE eda cea erg 260 6 3 EXGQUSION RR PEDE 263 6 3 1 Extrusion Equipment 1 Beisein 264 6 3 2 General Design Guidelines for Extrusion ssssseeeeeeee 266 XIV Table of
16. John Sommer Troubleshooting Rubber Problems Sommer Troubleshooting Rubber Problems John Sommer Troubleshooting Rubber Problems HANSER Hanser Publishers Munich Hanser Publications Cincinnati The Author John G Sommer 200 Laurel Lake Dr W314 Hudson OH 44236 Distributed in North and South America by Hanser Publications 6915 Valley Avenue Cincinnati Ohio 45244 3029 USA Fax 513 527 8801 Phone 513 527 8977 www hanserpublications com Distributed in all other countries by Carl Hanser Verlag Postfach 86 04 20 81631 M nchen Germany Fax 49 89 98 48 09 www hanser fachbuch de The use of general descriptive names trademarks etc in this publication even if the former are not especially identified is not to be taken as a sign that such names as understood by the Trade Marks and Merchandise Marks Act may accordingly be used freely by anyone While the advice and information in this book are believed to be true and accurate at the date of going to press neither the author nor the editors nor the publisher can accept any legal responsibility for any errors or omissions that may be made The publisher makes no warranty express or implied with respect to the material contained herein Library of Congress Cataloging in Publication Data Sommer John G Troubleshooting rubber problems John Sommer pages cm ISBN 978 1 56990 553 1 hardcover ISBN 978 1 56990 554 8 e book 1 Rubber goods 2
17. a violent exothermic reaction during remilling of a compound 50 Charring occurred during extrusion and transfer molding of cold compound a problem that was remedied by prewarming the Viton compound The above reference provides other precautions to take when working with Viton 2 3 7 Polyisoprene NR and IR Natural rubber NR is important not only for its outstanding properties but also because it is consumed more than any single synthetic elastomer 51 Being a natu ral product there is inherent variability with NR that is not necessarily present in synthetic rubber because control can be exercised in the synthetic manufacturing process Instruments are available today that further distinguish differences in NR Natural rubber and its synthetic counterpart isoprene rubber IR stand apart from other elastomers because of their strain crystallizing capability a property that is useful in many applications Strain crystallization imparts outstanding tack and green strength and yields vulcanizates with good resistance to cut growth at severe deformations The strong tendency for NR to crystallize can be problematic in uncured rubber Strain or distortion in an NR bale can accelerate crystallization especially when temperatures are lower than about 20 C For this reason bales prepared from crumb or comminuted NR crystallizes more slowly than those from sheet NR due to lower strain 2 4 Crystallization 15 B 2 4 Crystallization
18. brevia tions and definitions B 1 6 Nature of Rubber Rubber is composed of long flexible molecules that can be likened to cooked spa ghetti After crosslinking these molecules can be stretched to several times their original length and then return to nearly their original shape upon release of the deforming force Crosslinking connects the individual rubber molecules together such that the joined molecules act as a unit to provide the elastic behavior exhibited 1 7 Training 5 by an ordinary rubber band This behavior is unique to rubber A steel spring also exhibits elastic behavior similar to rubber but only if the degree of stretching is limited to less than about 1 It is useful to compare the tensile properties of steel and rubber Steel possesses high modulus high strength and low breaking elongation Strong forces between atoms account for its high modulus and strength Weak forces between molecules account for the low modulus observed with rubber The high strength of NR natural rubber is due to its ability to crystallize on stretching Other types of rubber for example SBR styrene butadiene rubber attain high strength through incorporation of reinforcing fillers The word rubber is generic and is associated with areas such as rubber types rubber compounds rubber processes and rubber products 12 These different areas vary in complexity but have in common the occurrence of many potential problems Perso
19. by our son John I also acknowledge the information obtained from my students wherein the student became the teacher September 2013 John G Sommer Table of Contents PREISER ke V 1 TSE and TPE Materials Compounds Processes and Products 1 11 Introduction ors eens dee een 1 1 2 Troubleshooting Difficulties 0 2 ee eee eee 1 1 3 Aldsito Troubleshooting u Rr a a EEN 2 1 4 Materials Process and Design Factors 000s eee keines niesi 3 1 5 BOOK Organization 2 cha AAA oad eh 4 1 6 Nature of RubDGE suse ntt O ee qe iUe PUR nt 4 1 7 AMALIA ge Waar onan ceed weak anes 5 1 8 Disclaimer rt oe od p gd d ae Rn A 6 2 TSE Materials and Compounds ssssssn 7 21 IntroduGHOmu si oes oe tL ene ead ret eA mee Wee ede aaah e e xia 7 2 2 Cost Reduction cumpa ad 7 2 2 1 Compounds and Compounders ssis sissies senais ieia eee eee 8 2 2 2 High Viscosity Elastomers and Compounds 00 5 9 2 3 Elastomer Type essen aa deste tau pud adhe 9 2 3 1 QR NeOprene siii rs ei ae 10 2 3 2 CSM Chloro Sulfonyl Polyethylene 0 00 cee RR 11 2 83 IIR Isobutene Isoprene cece IRI 11 2 3 4 EPDM Terpolymer of Ethylene Propylene and a Diene 11 2 8 5 SBR Styrene Butadiene Rubber 000 0 0000008 12 2 3 6 FKM Fluoro Rubber of the Polymethylene Type 13 2 3 7
20. e production lots of materials Zinc bis N N dimethyldithiocarbamate was identified in the bloom EPDM is well known for its good aging characteristics that are associated with its saturated backbone EPDM seals are generally expected to be serviceable for several years 30 When seals began to swell excessively and fail in only six months the cause was found to be chloraminated water High hardness EPDM compounds can be prepared using high crystallinity EPDM 31 High styrene SBR resins can be used for the same purpose but their higher polarity limits compatibility with the EPDM Phenol formaldehyde resins can also be used to increase hardness although their higher polarity can cause bloom prob lems High molecular weight EPDMs with high levels of 5 vinyl 2 norbornene monomer VNB show considerable peroxide crosslinking efficiency 32 Typically thirty to fifty percent of the peroxide and co agent combination can be reduced while main taining desirable vulcanizate properties This approach is said to result in consider able cost savings reduced blooming and improved aging characteristics To ensure that an EPDM compound meets demanding product requirements a gel test methodology was developed that is based on an automated optical detection system 33 The system uses clear polymer sampled directly from the polymer pro duction process to minimize possible contamination and provides consistent and high quality EPDM EPDM K8642
21. eaning Methods eeeeeeee e 131 3 38 9 Eouling Ses ia A guava ae hace SUE 131 3 384 Cases of Fouling au uns ae sea 131 3 38 5 Mold Cleaning ro ere ER eph br mra a a lace aoe acid 132 3 39 GCalendering 22e ere ae RP a DIM eee eee 133 3 39 1 Calendering Equipment seeeeeeeee eee 133 3 39 2 Feed Materi l ii essei aur Rune te er d eus 134 3 39 3 Calendering Factors 22 ooe uote pre RIP RAEURAPDRen dee EN 134 39 39 A SBIISEGES ius 2 ne A ai 135 SES MEI WC 135 3 40 Laser EDgEaVIDE coo see ae prn Fe ee m ee E EOE 135 4 TSEProducts 4 5 0 ae kein 149 4 1 ProductGonsiderations 22552259 Tp re ne inne 149 4 2 Effecto ASINS Lune cde e Rm pede a ERR EM nip Rn ERR Eee 151 42 3 COMPOSITES ic oes edu eere rr ehh a o gelten dus 151 LN MEE CC a ea is 151 45 R bberLinig 56964 e Pes 153 4 6 JBalloOngiso eie ann 153 4 7 4 8 4 11 4 12 4 13 4 15 4 16 4 17 4 18 4 19 Table of Contents ERIN GS ca aces ig A acd but en A AAA Rubber Mirror A d re te une 4 9 Cow Related Applications suere ee a e TRU ge RR 4 10 Regenerative Brake Systems un ana Rubber Covered Horseshoes ceee e e rhe hen Rubber Bullets ya na RR eine nu M RETE 4 14 Rubber Band Ligation 4 uo cad eaten A e Rm eu Rubber Badia EE Eloor Mats acta Ada dia auras Mounts Stress Concentration Roofing 4 20 Finite Element Analysis i i esse ec etr dna LAE Sada E Rp RAP Rea 4 21 4 22 4 23 4 24
22. eeee III 190 4 32 0 Casket Sealg exorto ee RH RR Ue RR ed qug ett Re es UR 190 4 32 7 Aircraft Runway Seals lseeeseeeeeee II 190 4 32 8 TPU Seals uve e tma o bb Bit a P LN Re ek 190 Inner VAUD OS sme e di 191 Windshield Wiper Blades u ee RI eR Y NC a 191 Friction DIVO veste ated vetet i o Ds o fe Paene t een een eed 192 Baby Bottle Nipples ied gre ee 192 hij rs EM 193 4 37 1 Serpentine Belts 2 issus eec ee ee 194 4 97 2 Aircraft Recorder Belts loce cR rr exu eden ks 194 4 97 3 ORINE Bells iuis eI ree mee Ee esp wu bbe abd heey 194 4 97 4 Conveyor Belts nun ana ex Ree Rma A aces 194 4 375 Timing Belts u esta 195 Mountings Bearings and Bushings 2 0 ec see cece eee eee nenn 196 4 38 1 Engine Mounis su 198 Hose and TUBE sees ee ee eek Kaas ea 200 4 39 1 Self Sealing Fuel Cells 0 0 cece cece eee 202 4 39 2 Radiator Hose xxi exe REX RR aa ren 202 4 39 3 Puel Hose un Eme ex Rhet ETE ade 204 4 39 4 Turbocharger Hose iesus nen rer x ex au eden ES 204 4 39 5 Refrigerant Hose un Leere ER er aa 205 4 39 0 Healing OSC aura 205 4 397 Brake HOSE oet RR Ghee ak eee E E eet e 206 4 39 8 Power Steering DOS ids eme Rer ER RE Rees 206 4 39 9 Hose Design 24 2 ica ea ana 207 4 39 10 Hose Manufacture esee le e er terre na ERR Saeed 207 4 39 11 Hose Failure vemoss RERO E UE E REESE RE M ee 208 4 39 12 Hose ADLASION os ht Rr een 208 4 39 13 Medical Hose 225 noseseRtesRerx eedeebeq
23. factors material process and design as shown in Figure 1 1 Figure 1 1 Schematic that shows interaction among material process and design These three factors are often interactive For example it may be possible to manu facture a rubber extrusion to given dimensional tolerances from a harder rubber compound but not a softer one the harder compound will be more dimensionally stable during the extrusion process Likewise the successful molding of rubber articles that contain an undercut depends upon the compound used Articles containing an undercut generally can be removed from their mold if they possess good hot tear strength and the undercut is not too deep Hence it is important to consider both compound and design and view the manufacture of a rubber article as a system 7 During processing a cracked rotor in a Banbury mixer might introduce water into a compound and shorten the scorch life of the compound The shortened life could easily have been interpreted as being caused by a change in the cure system The importance of design on final product cost cannot be overemphasized It has been estimated that while product design may represent only 5 of total product cost its influence on product cost can be as high as 70 8 Hence this 5 must be spent very wisely There are many expectations for rubber products some of these include a capability to 9 4 1 TSE and TPE Materials Compounds Processes and Products
24. inuous Extrusion Extruder Design Table of Contents 3 15 1 Vacuum Extruder 2 22 s ko eR y Rx an 3 15 2 Cavity Transfer Mixer CTM cee eee eee eee eee eee 3 15 3 Pin Barrel Extruder 0 cece ccc eee cece cnet eae eeees 3 15 4 Roller Head Extruder e esee DieDesign Feed Compound Gear Pumps Molding 3191 Molding Methods oxicorte RUE ME adds ee 3 19 1 1 Compression Molding ccs ames niss einni a ei aaa E 3 19 2 Curing Presses o2ecos4e ose a e ER nn 3 19 21 Fomr Post Presses see tuia IRR EP RR ERE 3 19 3 Mold Size 3 19 4 Air Trapping 3 19 5 Flash 3 19 6 Scorch Effects 2 0 cee tte eee teen ene 3 19 7 Shrinkage 3 20 Potential Mold Damage 4 122290 Rb perio io ice 3 21 3 22 3 23 3 24 3 25 3 26 3 27 3 28 3 29 Thermal Considerations ceeeeeeeee RII Microwave Heating Backrinding Mold Construction Insulation Mold Platens Mold Heating Injection Compression iecur eer ne an Transfer Molding 3 29 1 Cavity Filling 3 29 2 Adhesion 3 29 3 Dimensional Factors sseeeeee RII 3 29 4 Shrinkage 3295 Compound Plow anna 3 29 6 Cold Transfer 3 29 7 Sprues Molding quisa ase aeg e tbe abe Bu RAE RR TR 3 29 8 InjectioD TaDSIet sro ecai ewes Re a RR ex ru Redes mdse RR RR RR Rn 3 29 0 Transfer Mold Design sororis wo
25. lways ensure getting a specific mate rial Carbon nanotube rubber is said to operate from 200 C to 1000 C 15 Even at 1000 C when aluminum melts and steel softens it is said to retain its shape Visco elastic properties are similar to those of silicone rubber Carbon nanotubes in rub ber are said to strengthen rubber and increase its conductivity 16 Following are some characteristics of different elastomers along with some of addi tives typically incorporated in them 2 3 1 CR Neoprene Nonstaining antioxidants must be judiciously selected for CR 17 For example nonstaining phenolic antioxidants actually impair the ozone resistance of CR An encapsulated form of magnesium oxide works better with CR than conventional powdered MgO which becomes inactive when exposed to a humid atmosphere 18 Adding even minute amounts of ZnO to CR before the MgO can make CR compounds extremely easily scorched 19 Vanex a proprietary accelerator from R T Vanderbilt is suggested to improve prob lems with marching modulus in CR 20 2 3 Elastomer Type 11 2 3 2 CSM Chloro Sulfonyl Polyethylene The saturated backbone in CSM provides outstanding ozone and weather resistance 21 2 3 3 IIR Isobutene Isoprene IIR known mainly for its very low resilience and low permeability to gases is also available as derivatives 22 These are BIIR bromo isobutene isoprene and CIIR chloro isobutene isoprene which make it mo
26. ly throughout this book The latter term became necessary with the arrival of synthetic rubbers Elastomers are available as high viscosity materials that appear solid like and as low viscosity 2 3 Elastomer Type 9 materials some of which are pourable at room temperature First discussed are high viscosity materials 2 2 2 High Viscosity Elastomers and Compounds It should be noted that elastomers and their ingredients form a compound that can ultimately be shaped into a rubber article A compound should not only be designed for its specification properties at an acceptable cost but it must process with mini mum problems through factory operations Compound processing and other factors significantly affect the final cost of an article For example an expensive process aid incorporated in an extrusion compound might appear initially to be economically unjustified However because the aid improved extrusion output by 10 its cost was justified 11 A compounder may design a compound with wider safety margins than necessary to meet a given specification resulting in unnecessarily high cost 12 The selection of elastomer filler and other ingredient costs should be made on the basis that the resulting compound meets requirements at minimum cost This requires the com pounder to use good judgment in making selections For example contrast a com pound for an aerospace application vs one with substantially less demanding requirements such
27. nd correct No implied or expressed warranty can be made concerning its fitness completeness or accuracy Patent references should not be taken as inducements to use or infringe on any particular patent None of the information contained herein is intended to serve as a recommendation for any product The reader of this book should always consult the supplier of any material process or equipment before use to determine that the particular end use conditions present no health or safety hazards The use of effective health and safety practices cannot be overemphasized and the use of trade names in this book is for identification pur poses only The author will not be liable for any costs damages or liability resulting from any use of material contained in this book for any purpose including typographical errors and technical inaccuracies References 1 Hyzer W G Ind Res Dev Sept 1978 p 8 2 Tsao U Chemtech Dec 1983 p 750 3 Dick J S Rubber World Aug 2006 p 13 4 Dick J S Rubber World Sept 2006 p 15 5 McCauley K M et al U S Patent 8 106 117 Jan 31 2012 6 Sommer J G Engineered Rubber Products Hanser Munich 2009 p 2 7 Sommer J G Elastomer Molding Technology Elastech Hudson Ohio 2003 p 13 8 Smock D Plast World Dec 1989 p 11 9 Shaw D Eur Rubber J Nov 2000 p 44 10 Beall G L Plast Des Forum June 1994 p 68 11 Sommer J G Rubber World Dec 2002 p 33 12
28. nnel must be adequately trained to effectively deal with these problems Sometimes retraining of personnel is necessary as evidenced by the following example 13 Prior to World War II natural rubber NR was extensively used in tires because of its excellent processing and end use properties With the loss of the NR supply dur ing WWII GR S now called SBR was substituted for NR at which time significant processing problems occurred NR possessed building tack that facilitated the build ing of tires SBR lacked this property With the return of the availability of NR after the war workers had forgotten how to deal with the high tack in NR Hence retrain ing was necessary B 1 7 Training In addition to training a number of other factors are very important for running a successful polymer business Bozzelli provides a number of these factors as a check list 14 three positive and three negative factors from his checklist follow Positive factors Solve root causes of problems Make effective use of consultants Provide employee training on request Negative factors Manage business on a financial not technical basis Failure to maintain or advance experience in core competency Work around a problem rather than address its root cause 6 1 TSE and TPE Materials Compounds Processes and Products B 1 8 Disclaimer The information in this book has been compiled from many sources and is believed to be true a
29. ost from its solution often find it difficult to resist the urge to seek an immediate solution Problem solving includes the following steps 1 Gather relevant data 2 Screen and analyze pertinent information 3 Construct a hypothesis from the best available information 4 Test the hypothesis 5 State the problem Several additional troubleshooting suggestions or pitfalls to avoid include 2 Avoid fixed opinions Don t jump to conclusions Take nothing for granted Make firsthand observations Check critical items personally 2 1 TSE and TPE Materials Compounds Processes and Products Problems that occur can vary substantially from one factory to another 3 4 A par tial list of these follows Cold flow of polymers in the receiving area Mixing problems mix quality dispersion stickiness Extrusion die swell extrudate appearance Calendering blisters release from rolls Molding release nonfills porosity Efforts needed to correct these problems vary some can be remedied by technical personnel within a plant Others may use technology developed by outside sources for example reducing cold flow as described in a patent 5 B 1 3 Aids to Troubleshooting The author hopes that this book will provide a dual benefit to the reader Namely that it will provide troubleshooting information of immediate use as well as serve as a conduit to the technical literature via the numerous references pro
30. r bon dioxide emissions from fossil fuels 38 A study showed that rolling resistance depends on molecular weight distribution and microstructure while wet tire performance depends on 7 39 As T increases abrasion resistance decreases in an approximately linear manner Wet grip improves approximately linearly with increasing 7 Table 2 4 contains the contribution of dif ferent regions of tires to rolling resistance 40 Table 2 4 Contribution of the Different Regions of Tires to Rolling Resistance Tire Components Rolling Resistance Belts 43 Tread 42 Sidewalls 13 Beads 2 Table 2 4 shows that the belt and tread regions are mainly responsible for rolling resistance SBRs with high S B ratios 1 1 and higher can be blended with SBR that has a con ventional S B ratio to produce high hardness vulcanizates at a relatively low cost 41 Fillers used to obtain high hardness increase viscosity and eventually cause a compound to become nonprocessable High styrene SBR can provide high hardness with acceptable processing 42 An alternative to this is the use of a reinforcing phenyl formaldehyde resin 43 to obtain high hardness as exemplified by a high hardness compound for a tire bead apex SBR masterbatches for example SBR 1606 are available wherein the manufacturer has incorporated carbon black in the raw rubber 44 Their use shortens mixing time and can improve dispersion Calcium oxide and magnesium oxide are
31. re compatible with general purpose elastomers 10 to 20 phr of CR added to IIR eliminates the tendency of IIR vulcani zates to become softer with heat aging 23 2 3 4 EPDM Terpolymer of Ethylene Propylene and a Diene The residual unsaturated portion of the diene is in the side chain EPDM with low crystallinity is best used in compounds intended to have low compression set 24 Use of a 2 maleic anhydride modified EPDM in a blend with NR is said to signifi cantly improve the flex resistance of the blend Black scorch is a problem unrelated to curatives that occurs with EPDM 25 It can sometimes be improved by adding a small amount of sulfur to the compound or by the use of a lower structure carbon black Bloom that occurs with EPDM compounds can sometimes be remedied by using the triple 8 cure system shown below in Table 2 3 26 Table2 3 Triple 8 Cure System Sulfur 2 0 phr MBT 1 5 phr TeDEC 0 8 phr DPTT 0 8 phr TMTD 0 8 phr Bloom can occur on the surface of a rubber article when a partially soluble ingredi ent is used at a level in excess of its solubility at a given temperature 27 It is affected by humidity and it reduces tack with the most severe tack loss occurring in the first 24 hours 28 Excessive amounts of an accelerator caused bloom in a rubber grip on a camera 29 As a result of slightly higher than usual accelerator levels grips could turn 12 2 TSE Materials and Compounds white in som
32. rnal mixer Figure 2 1 Coexisting amorphous and crystalline regions in NR In Figure 2 1 above and to the right of the dashed line the NR remained crystalline To the left and below this line the crystallites melted Hence further warming would have been necessary to totally melt the crystallites before additional process ing of the rubber
33. s 0 cee eee eee ene 3 29 10 Parting Line IX X Table of Contents 9 29 11 A E ed Rex ide a Ro Rc hitb vs ut one ee era ine 109 3 29 12 OI M pr 109 3 30 Injection Molding esee e e he nn 110 3 30 1 Injection Molding Problems esses 111 3 30 2 Injection Molding Machines 0 00 cee e eee eee 113 3 31 Molds ess toe so x en en eR e deep deed RR dada eka ees 115 3 31 1 Mold Materials iecore FR ERR ech 116 3 312 Mold Handling iil icR tee a ED ELE ELE 117 3 31 3 Cavity Finish is sere shox ttm RR pe RR RR RAI RN e RE t 117 3 914 Mold Heating nica nad 117 3 31 41 Heating Methods el rr ae dere ne Ege 118 3 315 GaleS rin ri a a adi s 119 3 31 0 Leader Pins src en aa E E 119 3 31 6 1 Core Pins and Bushings sees 120 DONT Lands us e E et Ra ea e edge nee 120 3 92 OVBPIlUWS dust ite N pesti en ee t Rn eut vtae rane 122 3 32 1 Overflow Design o cono co e hh hh hehe 123 3 39 HOLES c o x REX a a X axe AA 124 3 34 Rumners 24004505 RI ERR Re OR MOSER Ae a RARI UR UR 125 3 941 Hot RUNDET e re Rie eee Sect oe RUNE nan ns ag o Rus 125 3842 Cold Runner i e eode Re hr ree COR eee RO eae 126 3 35 Mold Design uuo eek ovs EUR ERR vad vp diu nn 126 3 36 Gates and Venting 2 3 ccc en os kant a ETE ET 128 3 37 COST FACTIONS cidad da 129 3 38 Fouling and Cleaning naar 129 3 38 1 Mold Fouling Factors 220 20200086 Seda Ha br me ae a a a 130 3 38 2 Mold Cl
34. vided These references include current as well as older relevant references Among the many information sources for rubber literature is the science and tech nology library at the Rubber Division of the American Chemical Society at the Uni versity of Akron Technical information is also provided by the myriad manufactur ers of rubber chemicals and processing and manufacturing equipment Problems with rubber are to be expected considering the complexity of the many materials processing design and testing steps Table 1 1 involved in rubber prod uct manufacture Some of these are summarized below 6 Table 1 1 Materials Processing Design and Testing Steps Involved in Rubber Product Manufacture Raw materials including rubber chemicals fillers steel wire etc Mixers internal mien and rubber mills Mixed rubber compound Shaping operations ealenderine extrusion molding etc Vulcanizing also seed crosslinking or curing Post vulcanization deflashing trimming etc Testing and quality assurance 1 4 Materials Process and Design Factors Problems can and do happen during these steps either singularly or in combina tion This book is intended to identify and examine these problems and then to con sider potential actions directed toward correcting them B 1 4 Materials Process and Design Factors It should be emphasized here that rubber products are basically systems that involve three main
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