An Introduction to Rubber Technology

189 Pages·1999·8.36 MB·English

by  Andrew Ciesielski

An
Introduction
to Rubber Technology
Andrew Ciesielski
RAPRA
TECHNOLOGY LTD.
Rapra Technology Limited
Shawbury, Shrewsbury, Shropshire SY4 4NR, United Kingdom
Telephone: [phone] Fax: [phone]
http:llwww.rapra.net
First Published 1999 by
Rapra Technology Limited
Shawbury, Shrewsbury, Shropshire, SY4 4NR, UK
01999, Rapra Technology Limited
The right of Andrew Ciesielski to be identified as author of this Work has
been asserted by him in accordance with sections 77 and 78 of the
Copyright, Designs and Patents Act 1988.
All rights reserved. Except as permitted under current legislation no part
of this publication may be photocopied, reproduced or distributed in any
form 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.
ISBN: 1-85957-150-6
Typeset by Rapra Technology Limited
Printed and bound by Hobbs the Printers, Totton, Southampton
Contents
Preface ....................................................................................................... 1
1. History .................................................................................................. 3
1.1 Natural Rubber ........................................................................................... 3
1.2 Synthetic Rubber ........................................................................................ 6
1.3 What Exactly Does the Word ‘Rubber’ Mean? .......................................... 7
References ........................................................................................................... 8
Suggested Further Reading ................................................................................ 9
2. Types of Rubber and Their Essential Properties ............................. 11
2.1 Introduction ................................................................................................. 11
2.2 Interpreting the Properties .......................................................................... 11
2.2.1 Upper Temperature Aging Limits - Heat Aging Resistance ....... 11
2.2.2 Chemical Resistance and Concentration .................................. 12
2.2.3 Chemical Resistance and Temperature ................................... 12
2.2.4 Mechanical Properties and Temperature .................................. 13
2.2.5 Grades Within a Type of Rubber .............................................. 13
2.2.6 The Rubber Compound ............................................................ 13
2.2.7 Conclusion ............................................................................... 14
2.3 Specific Elastomers .................................................................................... 14
2.3.1 Natural Rubber NR ................................................................... 14
2.3.2 Styrene Butadiene Rubber SBR ............................................... 16
2.3.3 Polychloroprene CR ................................................................. 17
2.3.4 Nitrile NBR ............................................................................... 18
2.3.5 Ethylene Propylene Rubber EPM and EPDM ........................... 19
2.3.6 Butyl Rubber IIR and Halobutyl Rubber CIIR and BIIR ............. 20
2.3.7 Silicone Rubber MQ MPQ MVQ and MPVQ ............................. 21
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ii Contents

2.3.8 Hydrogenated Nitrile HNBR (HSN) ........................................... 22
2.3.9 Fluorocarbon Rubber FKM (FPM) ............................................ 23
2.3.10 Aflas TFE/P .............................................................................. 23
2.3.11 Kalrez FFKM ............................................................................ 23
2.3.12 Other Elastomers ..................................................................... 24
Polybutadiene Rubber BR ........................................................... 24
Polyacrylate ACM ........................................................................ 24
Epichlorohydrin ECO CO and GECO .......................................... 24
Chlorosulfonated Polyethylene CSM ........................................... 24
Polynorbornene ........................................................................... 24
2.4 Trade Names .............................................................................................. 25
References ........................................................................................................... 27
Suggested Further Reading ................................................................................ 29
3. The Basic Rubber Compound ............................................................ 31
3.1 Introduction ................................................................................................. 31
3.2 The Basic Compound Formula .................................................................. 31
3.3 Raw Materials ............................................................................................. 32
3.3.1 Raw Gum Elastomer ................................................................ 32
3.3.2 Sulfur ....................................................................................... 33
3.3.3 Zinc Oxide and Stearic Acid ..................................................... 33
3.3.4 Accelerators ............................................................................. 33
3.3.5 Other Cross-Linking Systems ................................................... 35
Peroxides .................................................................................... 35
Electron Beam Curing ................................................................. 36
Miscellaneous .............................................................................. 36
3.3.6 Antioxidants Age Resistors and Antidegradants ....................... 36
3.3.7 Fillers ....................................................................................... 37
Carbon Black ............................................................................... 37
Precipitated Silica ........................................................................ 38
More about Silica, Including Tires (green tires) ........................... 39
Other fillers .................................................................................. 40
3.3.8 Plasticizers ............................................................................... 40
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3.3.9 Miscellaneous Materials ........................................................... 41
Using Recycled Tires as a Compounding Ingredient .................. 41
3.4 Compound Design ...................................................................................... 42
3.4.1 Compound Design for Product Application ............................... 42
3.4.2 Elastomer Blends ..................................................................... 42
3.4.3 Blending for Cured Hardness ................................................... 43
3.4.4 Processing ............................................................................... 44
References ........................................................................................................... 45
Suggested Further Reading ................................................................................ 47
Raw Materials ...................................................................................... 47
Compound Design ............................................................................... 48
4. Rubber Equipment and Its Use .......................................................... 49
4.1 Introduction ................................................................................................. 49
4.2 Mills ............................................................................................................. 50
4.2.1 Operation ................................................................................. 50
4.2.2 Mill Processing ......................................................................... 51
4.3 Internal Mixing Machines ............................................................................ 53
4.3.1 Operation ................................................................................. 53
4.3.2 Processing ............................................................................... 55
4.4 Extruders ..................................................................................................... 57
4.4.1 Introduction .............................................................................. 58
4.4.2 Operation and Processing ........................................................ 58
4.4.3 Die Swell .................................................................................. 58
4.4.4 Recent Extruder Design ........................................................... 59
4.5 Calenders .................................................................................................... 59
4.5.1 Introduction .............................................................................. 60
4.5.2 Material Thickness Control ....................................................... 61
4.5.3 Feeding the Calender ............................................................... 61
4.6 Curing Equipment ....................................................................................... 62
4.6.1 Molding .................................................................................... 62
The Mold ..................................................................................... 62
Mold Design ................................................................................ 63
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Introducing Compound to the Mold ............................................. 64
4.6.2 Compression Molding .............................................................. 65
Backrind ...................................................................................... 68
Heat Transfer .............................................................................. 71
4.6.3 Transfer Molding ...................................................................... 71
Design Considerations ................................................................ 73
Advantages ................................................................................. 73
Disadvantages ............................................................................. 73
4.6.4 Injection Molding ...................................................................... 74
Advantages ................................................................................. 74
Disadvantages ............................................................................. 75
4.6.5 Autoclave Curing ...................................................................... 75
4.7 Product Dimensional Specifications ........................................................... 76
4.8 Storage of Rubber Parts ............................................................................. 76
References ........................................................................................................... 77
Suggested Further Reading ................................................................................ 77
Books .................................................................................................. 77
Articles ................................................................................................ 78
5. The Rubber Laboratory ...................................................................... 81
5.1 Introduction ................................................................................................. 81
5.2 Raw Material ............................................................................................... 81
5.3 Properties of the Uncured Compound ....................................................... 82
5.3.1 Mooney Viscometer ................................................................. 82
Mooney Scorch ........................................................................... 83
5.3.2 Oscillating Disc Curemeter ....................................................... 84
Testing Procedure ....................................................................... 84
What the Symbols Really Mean .................................................. 87
5.3.3 Rotorless Curemeter ................................................................ 88
5.3.4 Other Instruments .................................................................... 89
5.4 Properties of the Cured Compound ........................................................... 90
5.4.1 Introduction .............................................................................. 90
5.4.2 Hardness ................................................................................. 90
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Use of a Pocket Durometer ......................................................... 91
5.4.3 Tensile properties .................................................................... 92
Tensile Testing ............................................................................ 93
Significance of Tensile Testing .................................................... 94
5.4.4 Tear ......................................................................................... 94
5.4.5 Compression Set ...................................................................... 95
Compression Set as a Predictor of Seal Performance ................ 95
5.4.6 Shear Modulus ......................................................................... 96
5.4.7 Other Laboratory Tests ............................................................ 97
References ........................................................................................................... 97
Suggested Further Reading ................................................................................ 102
6. Chemistry ............................................................................................ 103
6.1 Building a Rubber Molecule ....................................................................... 103
6.1.1 Other Building Blocks ............................................................... 104
6.1.2 Shop Floor Significance of Molecular Weight ........................... 105
6.2 Vulcanization .............................................................................................. 106
6.2.1 Sulfur Vulcanization ................................................................. 106
The Sulfur Cross-Link .................................................................. 107
Sulfur Cross-Links and Properties ............................................... 108
6.2.2 Peroxides ................................................................................. 108
6.3 The Cured Product ..................................................................................... 109
6.3.1 Swelling in Liquids ................................................................... 109
Polarity ........................................................................................ 110
How the Chemist Uses Polarity ................................................... 111
6.3.2 Permeability to Liquids ............................................................. 111
6.3.3 Effects of Low Temperature - Glass Transition ......................... 112
6.3.4 Effects of Low Temperature - Crystallization ............................ 112
6.3.5 Stretching, Strain Induced Crystallization ................................. 113
6.3.6 Aging ........................................................................................ 113
References ........................................................................................................... 114
Suggested Further Reading ................................................................................ 114
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7. Engineering ......................................................................................... 115
7.1 Introduction ................................................................................................. 115
7.2 Rubber and Steel ........................................................................................ 115
7.3 Stress, Strain and Modulus ........................................................................ 116
7.3.1 Tensile Modulus and Young’s Modulus .................................... 118
7.3.2 Young’s Modulus Equals Three Times the Shear Modulus? .... 120
7.4 Compression Modulus, Young’s Modulus and Shape Factor ................... 121
7.4.1 Shape Factor ........................................................................... 122
7.4.2 Construction Bearings .............................................................. 123
7.5 Tensile Stress/Strain and Hysteresis ......................................................... 124
7.6 Viscoelasticity ............................................................................................. 127
7.6.1 The Spring and the Dashpot .................................................... 127
7.6.2 Consequences of the Viscous Component ............................... 128
Creep ........................................................................................... 129
Stress Relaxation ........................................................................ 129
7.6.3 Viscoelasticity and Modulus ..................................................... 129
7.6.4 Viscoelasticity in Cyclic Deformation ........................................ 130
7.6.5 Dynamic Viscoelasticity - Some Warnings ............................... 132
7.7 Rubber Turns to Glass ............................................................................... 133
7.8 Rubber and Vibration .................................................................................. 133
7.8.1 Transmissibility ........................................................................ 134
7.8.2 Translating the Transmissibility Curve ...................................... 135
7.9 Rubber Gets Stiffer as the Temperature Rises! ......................................... 136
7.10 Life Time Prediction .................................................................................... 137
7.11 Finite Element Analysis .............................................................................. 137
7.11.1 Rubber Presents Challenges to FEA ........................................ 140
References ........................................................................................................... 141
Suggested Further Reading ................................................................................ 144
8. Castable Polyurethanes ..................................................................... 147
8.1 Introduction ................................................................................................. 147
8.2 Chemistry .................................................................................................... 148
8.2.1 The 'Curing Chemicals’ - Chain Extenders ............................... 149
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8.2.2 Linking Chemistry to Properties ............................................... 150
Polyols ......................................................................................... 150
Diisocyanates .............................................................................. 150
Curatives ..................................................................................... 150
Miscellaneous .............................................................................. 150
8.2.3 Stoichiometry During Cure ....................................................... 150
8.2.4 Cure Temperature .................................................................... 151
8.2.5 The Cured Product, Properties Versus Temperature ................ 151
8.3 Making the Product - Processing ............................................................... 152
8.3.1 Handbatching ........................................................................... 152
8.3.2 Machine Mixing ........................................................................ 152
8.3.3 Variations of the Basic Molding Process .................................. 153
8.4 Millable Urethanes ...................................................................................... 154
References ........................................................................................................... 154
Suggested Further Reading ................................................................................ 155
Books .................................................................................................. 155
Other General Literature ...................................................................... 155
Engineering ......................................................................................... 156
Processing .......................................................................................... 156
Chemistry ............................................................................................ 157
Organizations & Other Information Sources ....................................................... 157
Appendix ................................................................................................... 159
Some Rubber Journals & Magazines .................................................................. 159
Miscellaneous Information ................................................................................... 160
Books ................................................................................................................... 161
Products and Processing ..................................................................... 162
Rubber Engineering ............................................................................. 163
Miscellaneous Books ........................................................................... 163
Some Web Sites Related to Rubber ................................................................... 164
Abbreviations and Acronyms ............................................................................... 165
Chart for Converting SI Units to Imperial Units ................................................... 168
Index .......................................................................................................... 169
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