. u- a 2, 
l&/bO*f //3 Ao / 3 
DEVELOPMENT OF NR/CIIR RUBBER BLENDS WITH 
CARBON BLACK AND SILICA FILLERS FOR 
TYRE INNER LINERS 
LIBRARY 
UNIVERSITY OF MORATUWA, SRI LANKA 
MORATUWA 
T. A. A. I. S iri wardana 
(8208) 
Thesis submitted in partial fulfillment of the requirements for the 
degree Master of Science «i » ! ' . - > 
University of M o r a t u w a 
104531 
Department of Chemical & Processing Engineering 
University of Moratuwa 
Sri Lanka 
g Cot\3) 
T H 
December 2012 
104531 
DECLARATION BY THE CANDIDATE 
The work described in this thesis was carried out by me under the 
supervision of Dr. (Mrs.) Dilhara G. Edirisinghe (Actg. Head Rubber 
Technology & Development Department, Rubber Research Institute of Sri 
Lanaka, Ratmalana) and Dr. (Mrs.) Shantha Egodage (Senior Lecturer, 
Department of Chemical & Process Engineering, University of Moratuwa) 
and report on this has not been submitted in whole or part to any University 
or any other Institution for another Degree/Diploma. I also certify that this 
thesis does not include, without acknowledgement, any materials previously 
submitted for a degree in any universities, and to the best of my knowledge 
and belief it does not contain any materials previously published, written or 
oral communicated by another person. 
T.A.A.I.Siriwardana Date 
DECLARATION OF THR SUPERVISORS 
We certify that the above statement made by the candidate is true and that 
this thesis is suitable for submission to the university for the purpose of 
evaluation. 
Dr (Mrs.) Dilhara G.Edirisinghe 
Actg. Head, 
Rubber Technology & 
Development Department, 
Rubber Research Institute of Sri Lanka, 
Ratmalana 
j f a k . f c t r : 
Dr. (Mrs.) Shantha Egodage 
Senior Lecturer, 
Department Chemical & 
Process Engineering, 
University of Moratuwa 
Date: ..<?.<?:..Q.L.£.Q.13. Date: 
O£ 0t a013 
ACKNOWLEDGEMENTS 
First, and foremost, I would very much like to express my sincere gratitude to Dr. (Mrs.) 
Dilhara Edirisinghe, Actg. Head, Rubber Technology & Development Department of the 
Rubber Research Institute of Sri Lanka, who was my project supervisor, for the 
encouragement, guidance and numerous helpful comments and suggestions given to me 
right throughout the project. 
I wish to express my sincere thanks to Dr. (Mrs.) Shantha Egodage, Senior Lecturer, 
Department of Chemical and Process Engineering, Dr. Jagath Premachandra, Senior 
Lecturer, Department of Chemical and Process Engineering and Dr.Shantha Walpalage, 
Senior Lecturer, Department of Chemical and Process Engineering of the University of 
Moratuwa, Sri Lanka, for the keen interest taken in co-ordinating the MSc. Course in 
Polymer Science & Technology and making arrangements for me to undertake this 
project. 
I wish to express my gratitude to Dr.W.M.G.Seneviratne, Director, and other officers of 
the Rubber Research Institute of Sri Lanka, for providing me the necessary facilities to 
carry out this work at the Institute's Laboratories situated at Ratmalana. The technical 
assistance given by the staff of Rubber Technology & Development Department, 
Polymer Chemistry Department, Raw Rubber and Chemical Analysis Department, and 
Raw Rubber Processing & Chemical Engineering Department of the Rubber Research 
Institute of Sri Lanka also gratefully acknowledged. 
Also, I wish to express my thanks to my colleagues for their invaluable services, advice, 
generous support at all times, too numerous to mention here and above all, for the 
inspiration and encouragement to make this onerous task a success. 
iii 
My special thanks are also to Sri Lanka Institute Nano Technology (SLINTEC), 
D. Samson Industries (Pvt.) Ltd, Associated Motorways (Pvt.) Ltd, and Elastomeric 
Engineering (Pvt.) Ltd, for their unfailing help and kind cooperation given throughout 
the project. 
A very special word of thanks to my parents and family members for their generous help 
towards my academic achievements, at all times. 
iv 
ABSTRACT 
Inner liner of a tubeless tyre is currently constructed using a speciality synthetic rubber 
called chlorobutyl rubber (CIIR). Blending of CIIR with natural rubber (NR) will enable 
to achieve improvement in physico-mechanical properties with a reduced compound 
cost. Also, use of CIIR/NR blends for inner liners are best at retaining air pressure and 
minimizing the temperature dependence of air permeability. The properly increase is 
enhanced by addition of a mix of carbon black and silica fillers, which are reinforcing 
fillers. One reason for carrying out this research is to enhance the market opportunities 
of NR by developing NR/CIIR blends to reach the end product requirements. In this 
study, different series of compounds were prepared, one with CIIR alone by varying the 
carbon black to silica ratio at 10 phr intervals, other with CIIR/NR blends by varying the 
CIIR to NR blend ratio at 20% intervals. Total filler loading was kept constant at 60 phr. 
Melt viscosity, hardness, tensile strength, modulus at 300 % and tear strength 
increased with silica loading, while scorch time, abrasion volume loss and air 
permeability decreased above silica loading of 30 phr.. Cure time did not show any 
variation with type of filler. When replacing CIIR with NR, cure rate index increased 
significantly from 40% NR and hence the cure time decreased. Mechanical properties 
and air permeability varied significantly. Materials used for the inner liner mainly 
chlorobutyl rubber are very expensive and hence by using the above mentioned blend 
with the optimum filler loading, the production cost can be minimized. Results in overall 
showed optimum properties for the 20:80 CIIR/NR blend at 10:50 carbon black /silica 
filler ratio. 
Key words: Chlorobutyl rubber, Natural rubber, Rubber blends, Physico-mechanical 
properties, Air permeability, Combined effect of carbon black and silica 
fillers 
v 
TABLE OF CONTENTS 
Page 
Declaration of the Candidate l 
Declaration of the Supervisor ii 
Acknowledgements iii 
Abstract V 
Table of Contents vi 
List of Figures xiii 
List of Tables xviii 
List of Abbreviations xix 
List of Appendices xxi 
CHAPTER ONE - INTRODUCTION 1 
1.1 Background 1 
1.2 Objectives 4 
CHAPTER TWO - LITERATURE REVIEW 5 
2.1 Natural Rubber 5 
2.1.1 Structure and properties of natural rubber 5 
2.1.2 Applications of natural rubber 6 
2.2 Butyl Rubber 6 
2.2.1 Structure, properties and applications of butyl rubber 6 
2.2.2 Processing and compounding of butyl rubber 8 
vi 
2.3 Reinforcement with Carbon Black and Silica Fillers 9 
2.3.1 The nature of carbon black 9 
2.3.2 The phenomena of reinforcement 10 
2.3.3 The nature of silica 10 
2.3.4 Applications of silica 11 
2.4 Rubber Mixing 12 
2.4.1 Process variables and control 13 
2.5 Compounding and Vulcanization 15 
2.5.1 Compounding 15 
2.5.2 Compounding ingredients 16 
2.5.3 Vulcanization 19 
2.5.4 Sulphur curing system 19 
2.5.5 The chemistry of accelerated sulphur vulcanization 20 
2.5.6 Influence of fillers on vulcanization 22 
2.5.7 Cure system and cure characteristics of chlorobutyl rubber 23 
2.6 Swelling of Rubber Networks 24 
2.6.1 Swelling of Filled Rubber 25 
2.7 Air Permeability 26 
2.7.1 Air permeability of inner liners of tubeless tyre 27 
CHAPTER THREE - EXPERIMENTAL 30 
vii 
3.1 Materials 30 
3.2 Experimental Procedures 30 
3.2.1 Determination of Mooney viscosity of raw rubber 30 
3.2.2 Preparation of chlorobutyl rubber compounds with different 
- combinations of fillers 32 
3.2. 3 Preparation of chlorobutyl rubber/natural rubber blend compounds 
- with different blend ratios 33 
3.2.4 Determination of cure characteristics of rubber compounds 37 
3.2.5 Determination of tensile strength of rubber vulcanizates 38 
3.2.6 Determination of tear strength of rubber vulcanizates 40 
3.2.7 Determination of ageing resistance of rubber vulcanizates 41 
3.2.8 Determination of hardness of rubber vulcanizates 42 
3.2.9 Determination of rebound resilience of rubber vulcanizates 42 
3.2.10 Determination of gas permeability of rubber vulcanizates 43 
3.2.11 Determination of compression set of rubber vulcanizates 45 
3.2.12 Determination of abrasion resistance of rubber vulcanizates 46 
3.2.13 Determination of density of rubber vulcanizates 46 
3.2.14 Determination of water swelling of rubber vulcanizates 47 
3.2.15 Determination of rolling resistance of rubber vulcanizates 47 
3.2.16 Determination of flex cracking resistance of rubber vulcanizates 47 
CHAPTER FOUR - RESULTS AND DISCUSSION 49 
4.1 Cure Characteristics of CIIR Compounds 49 
viii 
4.1.1 Minimum torque and scorch time 49 
4.1.2 Maximum torque and delta cure 50 
4.1.3 Cure rate index 50 
4.1.4 Cure time 51 
4.2 Physico-mechanical Properties of CIIR Compounds 52 
4.2.1 Tensile properties (before ageing) 52 
4.2.2 Elongation at break (before ageing) 53 
4.2.3 Tensile properties (after ageing) 53 
4.2.4 Elongation at break (after ageing) 54 
4.2.5 Tear strength (before ageing) 55 
4.2.6 Tear strength (after ageing) 55 
4.2.7 Hardness 56 
4.2.8 Rebound resilience 57 
4.2.9 Compression set 58 
4.2.10 Abrasion volume loss 58 
4.2.11 Water swelling 59 
4.2.12 Tan 5 at 60 °C 60 
4.2.13 Resistance to Flex-cracking 60 
4.3 Cure characteristics of the series of CIIR /NR Blends with a carbon -
black: silica filler ratio of 50:10 61 
4.3.1 Minimum torque and scorch time 61 
4.3.2 Maximum torque and delta cure 62 
4.3.3 Cure time 62 
4.3.4 Cure rate index 63 
ix 
4.4 Physico-mechanical Properties of CIIR /NR Blends with a carbon -
black: silica filler ratio of 50:10 64 
4.4.1 Tensile properties (before ageing) 64 
4.4.2 Elongation at break (before ageing) 65 
4.4.3 Tensile properties (after ageing) 65 
4.4.4 Elongation at break (after ageing) 66 
4.4.5 Tear strength (before ageing) 67 
4.4.6 Tear strength (after ageing) 67 
4.4.7 Hardness 68 
4.4.8 Rebound resilience 69 
4.4.9 Compression set 69 
4.4.10 Abrasion volume loss 70 
4.4.11 Water swelling 71 
4.4.12 Tan 5 at 60 °C 71 
4.4.13 Resistance to Flex-cracking 72 
4.5 Cure characteristics of the series of CIIR /NR Blends with a carbon -
black: silica filler ratio of 20:40 72 
4.5.1 Minimum torque and scorch time 72 
4.5.2 Maximum torque and delta cure 73 
4.5.3 Cure rate index 74 
4.5.4 Cure time 75 
4.6 Physico-mechanical Properties of CIIR /NR Blends with a carbon -
black: silica filler ratio of 20:40 75 
x 
4.6.1 Tensile properties (before ageing) 75 
4.6.2 Elongation at break (before ageing) 76 
4.6.3 Tensile properties (after ageing) 77 
4.6.4 Elongation at break (after ageing) 77 
4.6.5 Tear strength (before ageing) 78 
4.6.6 Tear strength (after ageing) 79 
4.6.7 Hardness 79 
4.6.8 Rebound resilience 80 
4.6.9 Compression set 81 
4.6.10 Abrasion volume loss 81 
4.6.11 Water swelling 82 
4.6.12 Tan 5 at 60 °C 83 
4.6.13 Resistance to Flex-cracking 83 
4.7 Cure characteristics of the series of CIIR /NR Blends with a carbon -
black: silica filler ratio of 10:50 84 
4.7.1 Minimum torque and scorch time 84 
4.7.2 Maximum torque and delta cure 84 
4.7.3 Cure rate index 85 
4.7.4 Cure time 86 
4.8 Physico-mechanical Properties of CIIR /NR Blends with a carbon -
black: silica filler ratio of 10:50 86 
4.8.1 Tensile properties (before ageing) 86 
4.8.2 Elongation at break (before ageing) 87 
4.8.3 Tensile properties (after ageing) 88 
4.8.4 Elongation at break (after ageing) 89 
xi 
4.8.5 Tear strength (before ageing) 
4.8.6 Tear strength (after ageing) 
4.8.7 Hardness 
4.8.8 Rebound resilience 
4.8.9 Compression set 
4.8.10 Abrasion volume loss 
4.8.11 Water swelling 
4.8.12 Tan 8 at 60 °C 
4.8.13 Resistance to Flex-cracking 
4.9 Air Permeability of Compounds 
CHAPTER FIVE - CONCLUSIONS & RECOMMENDATION FOR 
FUTURE WORK 
5.1 Conclusions 
5.2 Recommendation for Future Work 
REFERENCES 
Appendix 1 
Appendix 2 
Appendix 3 
xii 
LIST OF FIGURES 
Page 
Figure 2.1 Structure of cis-1, 4-polyisoprene 5 
Figure 2.2 Structure of chlorobutyl rubber 7 
Figure 3.1 Description of a cure curve 38 
Figure 3.2 Diagram of a dumb bell test piece used for the analysis of 
tensile strength 40 
Figure 3.3 Diagram of the angle test piece used for the analysis of tear 
Strength 41 
Figure 3.4 Gas permeability tester 45 
Figure 4.1 Variation of minimum torque and scorch time with carbon 
black: silica filler ratio 49 
Figure 4.2 Variation of maximum torque and delta cure with carbon 
black: silica filler ratio 50 
Figure 4.3 Variation of cure rate index with carbon black: silica 
filler ratio 51 
Figure 4.4 Variation of cure time with carbon black: silica filler ratio 51 
Figure 4.5 Variation of tensile properties (before ageing) with carbon 
black: silica filler ratio 52 
Figure 4.6 Variation of elongation at break (before ageing) with carbon 
black: silica filler ratio 53 
Figure 4.7 Variation of tensile properties (after ageing) with carbon 
black: silica filler ratio 54 
Figure 4.8 Variation of elongation at break (after ageing) with carbon 
black: silica filler ratio 54 
Figure 4.9 Variation of tear strength (before ageing) with carbon 
black: silica filler ratio 55 
xiii 
Figure 4.10 Variation of tear strength (after ageing) with carbon 
black: silica filler ratio 56 
Figure 4.11 Variation of hardness with carbon black: silica filler ratio 57 
Figure 4.12 Variation of resilience with carbon black: silica 
filler ratio 57 
Figure 4.13 Variation of compression set with carbon black: silica 
filler ratio 58 
Figure 4.14 Variation of abrasion volume loss with carbon 
black: silica filler ratio 59 
Figure 4.15 Variation of water swelling with carbon black: silica 
filler ratio 59 
Figure 4.16 Variation of tan 8 at 60 °C with carbon black: silica 
filler ratio 60 
Figure 4.17 Variation of minimum torque and scorch time with 
CIIR: NR ratio (carbon black: silica filler ratio is 50:10) 61 
Figure 4.18 Variation of maximum torque and delta cure with 
CIIR: NR ratio (carbon black: silica filler ratio is 50:10) 62 
Figure 4.19 Variation of cure time with CIIR:NR ratio 
(carbon black: silica filler ratio is 50:10) 63 
Figure 4.20 Variation of cure rate index with CIIR:NR ratio 
(carbon black: silica filler ratio is 50:10) 63 
Figure 4.21 Variation of tensile properties (before ageing) with 
CIIR: NR ratio (carbon black: silica filler ratio is 50:10) 64 
Figure 4.22 Variation of elongation at break (before ageing) with 
CIIR: NR ratio (carbon black: silica filler ratio is 50:10) 65 
Figure 4.23 Variation of tensile properties (after ageing) with 
CIIR: NR ratio (carbon black: silica filler ratio is 50:10) 66 
Figure 4.24 Variation of elongation at break (after ageing) with 
CIIR: NR ratio (carbon black: silica filler ratio is 50:10) 66 
xiv 
Figure 4.25 Variation of tear strength (before ageing) with 
CIIR: NR ratio (carbon black: silica filler ratio is 50:10) 
Figure 4.26 Variation of tear strength (after ageing) with 
CIIR: NR ratio (carbon black: silica filler ratio is 50:10) 
Figure 4.27 Variation of hardness with CIIR:NR ratio 
(carbon black: silica filler ratio is 50:10) 
Figure 4.28 Variation of resilience with CIIR:NR ratio 
(carbon black: silica filler ratio is 50:10) 
Figure 4.29 Variation of compression set with CIIR:NR ratio 
(carbon black: silica filler ratio is 50:10) 
Figure 4.30 Variation of abrasion volume loss set with 
CIIR: NR ratio (carbon black: silica filler ratio is 50:10) 
Figure 4.31 Variation of water swelling with CIIR:NR ratio 
(carbon black: silica filler ratio is 50:10) 
Figure 4.32 Variation of tan 5 at 60 °C with CIIR:NR ratio 
(carbon black: silica filler ratio is 50:10) 
Figure 4.33 Variation of minimum torque and scorch time with 
CIIR: NR ratio (carbon black: silica filler ratio is 20:40) 
Figure 4.34 Variation of maximum torque and delta cure with 
CIIR: NR ratio (carbon black: silica filler ratio is 20:40) 
Figure 4.35 Variation of cure rate index with CIIR:NR ratio 
(carbon black: silica filler ratio is 20:40) 
Figure 4.36 Variation of cure time with CIIR:NR ratio 
(carbon black: silica filler ratio is 20:40) 
Figure 4.37 Variation of tensile properties (before ageing) with 
CIIR: NR ratio (carbon black: silica filler ratio is 20:40) 
Figure 4.38 Variation of elongation at break (before ageing) with 
CIIR: NR ratio (carbon black: silica filler ratio is 20:40) 
xv 
Figure 4.39 Variation of tensile properties (after ageing) with 
CIIR: NR ratio (carbon black: silica filler ratio is 20:40) 77 
Figure 4.40 Variation of elongation at break (after ageing) with 
CIIR: NR ratio (carbon black: silica filler ratio is 20:40) 
Figure 4.41 Variation of tear strength (before ageing) with 78 
CIIR: NR ratio (carbon black: silica filler ratio is 20:40) 78 
Figure 4.42 Variation of tear strength (after ageing) with 
CIIR: NR ratio (carbon black: silica filler ratio is 20:40) 79 
Figure 4.43 Variation of hardness with CIIR:NR ratio 
(carbon black: silica filler ratio is 20:40) 80 
Figure 4.44 Variation of resilience with CIIR:NR ratio 
(carbon black: silica filler ratio is 20:40) 80 
Figure 4.45 Variation of compression set with CIIR:NR ratio 
(carbon black: silica filler ratio is 20:40) 81 
Figure 4.46 Variation of abrasion volume loss with CIIR:NR ratio 
(carbon black: silica filler ratio is 20:40) 82 
Figure 4.47 Variation of water swelling with CIIR:NR ratio 
(carbon black: silica filler ratio is 20:40) 82 
Figure 4.48 Variation of tan 5 at 60 °C with CIIR:NR ratio 
(carbon black: silica filler ratio is 10:50) 83 
Figure 4.49 Variation of minimum torque and scorch time with 
CIIR: NR ratio (carbon black: silica filler ratio is 10:50) 84 
Figure 4.50 Variation of maximum torque and delta cure with 
CIIR: NR ratio (carbon black: silica filler ratio is 10:50) 85 
Figure 4.51 Variation of cure rate index with CIIR:NR ratio 
(carbon black: silica filler ratio is 10:50) 85 
Figure 4.52 Variation of cure time with CIIR:NR ratio 
(carbon black: silica filler ratio is 10:50) 86 
xvi 
Figure 4.53 Variation of tensile properties (before ageing) with 
CIIR: NR ratio (carbon black: silica filler ratio is 10:50) 87 
Figure 4.54 Variation of elongation at break (before ageing) with 
CIIR: NR ratio (carbon black: silica filler ratio is 10:50) 88 
Figure 4.55 Variation of tensile properties (after ageing) with 
CIIR: NR ratio (carbon black: silica filler ratio is 10:50) 88 
Figure 4.56 Variation of elongation at break (after ageing) with 
CIIR: NR ratio (carbon black: silica filler ratio is 10:50) 89 
Figure 4.57 Variation of tear strength (before ageing) with 
CIIR: NR ratio (carbon black: silica filler ratio is 10:50) 90 
Figure 4.58 Variation of tear strength (after ageing) with 
CIIR: NR ratio (carbon black: silica filler ratio is 10:50) 90 
Figure 4.59 Variation of hardness with CIIR:NR ratio 
(carbon black: silica filler ratio is 10:50) 91 
Figure 4.60 Variation of resilience with CIIR:NR ratio 
(carbon black: silica filler ratio is 10:50) 92 
Figure 4.61 Variation of compression set with CIIR:NR ratio 
(carbon black: silica filler ratio is 10:50) 93 
Figure: 4.62 Variation of abrasion volume loss with CIIR:NR ratio 
(carbon black: silica filler ratio is 10:50) 93 
Figure: 4.63 Variation of water swelling with CIIR:NR ratio 
(carbon black: silica filler ratio is 10:50) 94 
Figure: 4.64 Variation of tan 8 at 60 °C with CIIR:NR ratio 
(carbon black: silica filler ratio is 10:50) 95 
xvii 
LIST OF TABLES 
Page 
Table 3.1 Formulations of CIIR compounds 32 
Table 3.2 Formulations of CIIR/NR blend compounds containing 
a 50:10 carbon black: silica filler ratio 34 
Table 3.3 Formulations of NR/CIIR blend compounds containing 
a 20:40 carbon black: silica filler ratio 35 
Table 3.4 Formulations of NR/CIIR blend compounds containing 
a 10:50 carbon black: silica filler ratio 36 
Table 3.5 Mixing cycle of NR/CIIR blend compounds 37 
Table 4.1 Air permeability values of compounds prepared with different 
CIIR: NR blend ratios 96 
xviii 
LIST OF ABBREVIATIONS 
Abbreviation Description 
BR Butadiene rubber 
°C Centigrade 
cv Conventional Vulcanization 
CR Chloroprene rubber 
CB Carbon black 
CV Conventional vulcanization 
CIIR Chloro butyl rubber 
CTAB Cetyltrimethylammonium Bromide 
DEG Diethylene Glycol 
EPDM Ethylene propylene diene ter polymer 
EB Elongation at Break 
EV Efficient Vulcanization 
F Maximum force 
G Specific gravity 
IR Isoprene rubber 
IIR Butyl rubber 
IPPD N- phenyl, N'- isopropyl paraphenylene Diammine 
IRHD International Rubber Hardness Degrees 
Kg Kilogram 
M Mass 
m Meter 
mm Milli meter 
MPa Mega Pascal 
MDR Moving Die Rheometer 
MBT Mercaptobenzthiazole 
MBTS Dibenzothiazyl di sulfide 
M h maximum torque 
xix 
ML Minimum torque 
MOD Modulus 
1 0 0 % MOD Modulus at 100 % elongation 
300 % MOD Modulus at 300 % elongation 
500 % MOD Modulus at 500 % elongation 
NR Natural Rubber 
N Normal cure 
NBR Acrylonitrile butadiene rubber (Nitrile Rubber) 
o 2 Oxygen 
o 3 Ozone 
% Percentage 
phr Parts per hundred rubber 
PVI Pre vulcanizing inhibitor 
S Sulphur 
Semi EV Semi Efficient Vulcanization 
Si 69 bis-(3-triethoxysilylpropyl) tetrasulfane 
SBR Styrene butadiene rubber 
VGC Viscosity gravity constant 
ZnO Zinc Oxide 
XX 
Appendix 
Appendix 1 
Table 1 
Table 2 
Table 3 
Table 4 
Appendix 2 
Table 1 
Table 2 
Table 3 
Table 4 
Appendices 
Description Page 
Cure characteristics and physico-mechanical properties 
of CIIR compounds 103 
Cure characteristics and physico-mechanical properties of 
CIIR /NR blend compounds with 50:10 carbon black: silica 
filler ratio 105 
Cure characteristics and physico-mechanical properties of 
CIIR /NR blend compounds with 20:40 carbon black: silica 
filler ratio 107 
Cure characteristics and physico-mechanical properties of 
CIIR /NR blend compounds with 10:50 carbon black: silica 
filler ratio 109 
Tensile properties of CIIR: NR blends for selected carbon 
black: silica ratios 111 
Tear strength of CIIR: NR blends for selected carbon 
black: silica ratios 112 
Elongation at break of CIIR: NR blends for selected 
carbon black: silica ratios 113 
Hardness of CIIR: NR blends for selected carbon 
black: silica ratios 113 
xxi 
Table 5 Abrasion volume loss of CIIR: NR blends for selected 
carbon black: silica ratios 114 
Table 6 Resilience of CIIR: NR blends for selected carbon 
black: silica ratios 114 
Table 7 Compression set of CIIR: NR blends for selected carbon 
black: silica ratios 115 
Table 8 Water swelling of CIIR: NR blends for selected carbon 
black: silica ratios 116 
Appendix 3 
Figure 1 Rheograph of compound No. F-l 117 
Figure 2 Rheograph of compound No. F-2 117 
Figure 3 Rheograph of compound No. F-3 118 
Figure 4 Rheograph of compound No. F-4 118 
Figure 5 Rheograph of compound No. F-5 119 
Figure 6 Rheograph of compound No. F-6 119 
Figure 7 Rheograph of compound No. F-7 120 
Figure 8 Rheograph of compound No. F-2-2 120 
Figure 9 Rheograph of compound No. F-2-3 121 
Figure 10 Rheograph of compound No. F-2-4 121 
Figure 11 Rheograph of compound No. F-2-5 122 
Figure 12 Rheograph of compound No. F-2-6 122 
Figure 13 Rheograph of compound No. F-5-2 123 
Figure 14 Rheograph of compound No. F-5-3 123 
Figure 15 Rheograph of compound No. F-5-4 124 
Figure 16 Rheograph of compound No. F-5-5 124 
Figure 17 Rheograph of compound No. F-5-6 125 
Figure 18 Rheograph of compound No. F-6-2 125 
xxii 
Figure 19 Rheograph of compound No. F-6-3 126 
Figure 20 Rheograph of compound No. F-6-4 126 
Figure 21 Rheograph of compound No. F-6-5 127 
Figure 22 Rheograph of compound No. F-6-6 127 
xxiii