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  • RubberTechnologistsHandbook

    RubberTechnologistsHandbook

    Editors:

    J.R. White

    S.K. De

  • Rubber TechnologistsHandbook

    Edited by Sadhan K. De and Jim R. White

    Rapra Technology Limited

    Shawbury, Shrewsbury, Shropshire, SY4 4NR, United KingdomTelephone: +44 (0)1939 250383 Fax: +44 (0)1939 251118

    http://www.rapra.net

  • First Published 2001 by

    Rapra Technology LimitedShawbury, Shrewsbury, Shropshire, SY4 4NR, UK

    2001, Rapra Technology Limited

    All rights reserved. Except as permitted under current legislation no partof this publication may be photocopied, reproduced or distributed in anyform or by any means or stored in a database or retrieval system, without

    the prior permission from the copyright holder.

    A catalogue record for this book is available from the British Library.

    Typeset by Rapra Technology LimitedPrinted and bound by Polestar Scientifica, Exeter, UK

    ISBN: 1-85957-262-6

  • iPreface

    From a materials point of view a rubber product is made from rubber and a host of otheradditives, including fillers, vulcanising agents and processing aids along with reinforcingmaterials such as textiles. From a manufacturing point of view, a rubber product is madeby following several steps: mixing of additives with the rubber (compounding) whenthe rubber is unvulcanised and in the plastic state; shaping the rubber compound and/orbonding it to a substrate; and finally vulcanising or curing the whole assembly, whenchemical crosslinks are formed between the rubber molecules to give the material itselastic recovery behaviour. The final properties of a rubber product depend on the typeof rubber chosen and the additives used and their concentrations. The properties of therubber can be further manipulated by varying the processing steps or manufacturingoperations. The cost of a rubber product depends not only on the price of the raw materialsbut also on the efficiency of the processing operations. In the last few decades new materialshave emerged and manufacturing has become increasingly automated and more efficient.This handbook aims to provide a basic foundation in rubber technology and to collatethe most recent developments in the form of chapters, written by experts in their respectivefields. The handbook is intended to serve the needs of those who are already in therubber industry and of new entrants who aspire to build a career in rubber and alliedareas. Materials Science students and researchers, designers and engineers should allfind the handbook very helpful.

    Fourteen chapters deal with natural rubber, synthetic rubbers, thermoplastic elastomers,fillers, compounding additives, mixing, engineering design, testing, tyre technology,automotive applications, footwear, rubbers in construction, durability of rubber products,and rubber recycling. It is obvious that several important topics could not beaccommodated in the current volume and it is intended that a second volume of thehandbook will be published by RAPRA Technology Ltd in the near future to extend thecoverage. We gratefully acknowledge the cooperation from all of the contributors, withoutwhom this handbook would not have been a reality. We are especially grateful to thecommissioning editor, Ms Frances Powers, for her unique combination of professionalismand good humour: her prompt and pointed responses to all of our requests for assistancewere invaluable. We wish to commend all of the staff at RAPRA Technology Ltd whocontributed to the excellent production of the handbook, especially Claire Griffiths andSandra Hall.

  • Rubber Technologists Handbook

    ii

    On a personal note, one of us (JRW) is grateful for being granted leave of absence fromthe University of Newcastle upon Tyne for a visit to the Rubber Technology Centre atthe Indian Institute of Technology, Kharagpur in January 2001 during a critical stage ofthe preparation of the handbook. Although the purpose of the visit was to conductresearch and teaching in the most stimulating surroundings of the RTC, time was foundfor the two editors to renew their friendship, tie up the loose ends of the handbook, andto lay plans for Volume 2. Finally we are extremely thankful to our wives, Prajna and LiTong, for their patience and support during the preparation of the handbook.

    S K De and J R WhiteAugust 2001

  • iContents

    1 Introduction .................................................................................................... 1

    1.1 Brief historical review ............................................................................ 1

    1.2 The uniqueness of rubber ....................................................................... 3

    1.3 Survey of the current Handbook ............................................................ 4

    1.4 Closing remarks ................................................................................... 10

    2 Natural rubber .............................................................................................. 11

    2.1 Introduction ......................................................................................... 11

    2.2 Source .................................................................................................. 11

    2.3 Cultivation ........................................................................................... 13

    2.4 Harvesting ........................................................................................... 14

    2.5 Biosynthesis of rubber .......................................................................... 15

    2.6 Composition of latex ........................................................................... 16

    2.7 Crop collection .................................................................................... 17

    2.7.1 Pre-processing of latex ............................................................. 18

    2.8 Crop processing ................................................................................... 19

    2.8.1 Preservation and concentration of latex ................................... 19

    2.8.2 Ribbed smoked sheet (RSS)...................................................... 20

    2.8.3 Pale latex crepe and sole crepe ................................................. 22

    2.8.4 Field coagulum crepe ............................................................... 23

    2.8.5 Technically specified rubbers (TSR) ......................................... 23

    2.9 Modified forms of NR ......................................................................... 25

    2.9.1 Physically modified forms ........................................................ 26

  • Rubber Technologists Handbook

    ii

    2.9.2 Chemically modified forms of NR ........................................... 28

    2.10 Properties of natural rubber ................................................................. 31

    2.10.1 Raw rubber .............................................................................. 31

    2.10.2 Vulcanised rubber .................................................................... 33

    2.11 Vulcanisation ........................................................................................ 36

    2.11.1 Vulcanisation with sulphur ...................................................... 37

    2.11.2 Non-sulphur vulcanisation ...................................................... 38

    2.12 Applications .......................................................................................... 39

    2.12.1 Tyres (see also Chapter 11) ...................................................... 39

    2.12.2 Engineering applications .......................................................... 40

    2.12.3 Conveyor beltings .................................................................... 41

    2.12.4 Linings ..................................................................................... 41

    3 Synthetic elastomers ...................................................................................... 47

    3.1 Synthetic and natural elastomers ......................................................... 47

    3.1.1 Synthesis .................................................................................. 47

    3.1.2 Mechanical properties .............................................................. 48

    3.1.3 The need for synthetic elastomers ............................................ 49

    3.1.4 Compounding and vulcanisation ............................................. 51

    3.1.5 Synthetic elastomer polymerisation .......................................... 51

    3.1.6 Mechanisms ............................................................................. 53

    3.1.7 Polymer synthesis processes ..................................................... 54

    3.2 Diene elastomers .................................................................................. 55

    3.2.1 Polybutadiene (BR) .................................................................. 56

    3.2.2 Polyisoprene (IR) ..................................................................... 58

    3.2.3 Styrene-butadiene rubber (SBR) ............................................... 59

    3.3 Saturated elastomer ............................................................................. 61

    3.3.1 Ethylene-propylene copolymers (EPM) and ethylene-propylene-diene terpolymers (EPDM) ...................................... 61

    3.3.2 Butyl and halobutyl rubbers (IIR and BIIR/CIIR) .................... 64

  • iii

    ContentsContents

    3.3.3 Ethylene-acrylic elastomers (EAM) .......................................... 66

    3.4 Solvent resistant elastomers .........

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