PHYSICO-MECHANICAL PROPERTIES OF MODIFIED KAOLIN CLAY 
FILLED RUBBER COMPOUNDS 
M.Sc (Polymer Technology) 
A.R.M.W.W.K.Ranasinghe 
University of Moratuwa 
October, 2001 
Phys ico-mechanica l propert ies of modif ied kaol in c lay filled 
rubber c o m p o u n d s 
By 
A.R.M.W.W.K.Ranasinghe 
This thesis was submitted to the Department of Chemical and 
Process Engineering of the University of Moratuwa in partial 
fulfillment of the Degree of Master of Science 
in Polymer Technology 
eSftOQ© S H a Surges. § -i 
(=®)OQS. ' 
Department of Chemical and 
Process Engineering, 
University of Moratuwa, 
Sri Lanka. 
October, 2001 _ ^ 
074446 6 6 " O V 
IJIIIIIIIIIIIIIIIIffllllilll 6 1 6 - 4 1 
University of Moratuwa 
1'IJ-IF-LL-G 
74446 
" I certify th;il this thesis docs not incorporate without acknowledgement any 
material previously submitted for a degree or diploma in any University and to the 
best of my knowledge and belief it does not contain any material previously 
published, written or orally communicated by another person except where due 
reference is made in the text" 
Signature of the candidate 
( Miss A KM WW Is. Kanasinghe) 
" To the best of my knowledge, the above particulars are correct" 
l)r ( Mrs )0lga Gunapala 
Department o f Chemical 
Superv isors 
Dr l \Y. Gunapala 
Department o f Materials l.-ingineerinu 
and 
Process Kiigineering 
ABSTRACT 
A n attempt has made to activate the inert structure ol Rubber grade 
kaol in clays through ion-exchange process. Counter ions absorbed by unsa l i s l l ed 
s i l i con , oxygen and hydroxy l ions at the edges o f planar surfaces o f kaol in i tc 
mineral to preserve electrical neutral i ty were replaced wi th complex organic ions 
containing active functional groups (amine, hyd roxy l , carboxyl ) in their organic 
radicals. S t rong ly attached to the clay surface Ihese complex ions project their 
organic aryl or a lky l radicals outwards to suspending medium rubber matr ix 
making inorganic kaol in surface effectively organic and therefore hydrophobic 
one. Such change in kaol in surface facilitated rubber- f i l ler interaction owing to 
better wetting o f the filler surface wi th organic rubber polymer and formation o f 
suf f ic ient density grafted polymer layer bonding the rubber matr ix to filler. 
Carried out physico-mcchanical testing o f filled rubber compounds showed that 
modif ication o f kaol in wi th chosen basic electrolytes ionized in aqueous medium 
was effective. 
Increase in strength characteristics has made possible in commercial practicability 
o f rubber formulat ion technology the subst i tu t ion o f expensive reinforcing fillers 
w i th lowest in cost appropriately modif ied kaol in Clay. 
A c k n o w l e d g e m e n t s 
I am very much grateful to my supervisors Dr ( Mrs) Olga Gunapala and Dr P.Y 
Gunapala for their encouragement, guidance, and their patience paid through out 
my research. 
Also a special word of thanks to Dr ( Mrs ) B.M.W.P.K .Amarasinghe,the head of 
the department and Mr S.A. Perera former head of the department and all other 
academic staff of the Chemical and Process Engineering and the Materials 
Engineering departments. 
My special thanks are due to Mr K Subramanium, head of the Polymer division, 
Mrs Shantha Maduwage , Mr P. Weragoda for their great support given me 
through out my research. 
Also I would like to thank technical and technical assistant staff of the Polymer 
Processing laboratory, Latex and Testing laboratories, Ceramic laboratory and all 
laboratories of Materials Engineering department. My thanks are due to the 
officers of Polymer department of ITI providing me the facilities to get the 
rheographs. 
My special thanks are due to Miss Duminda Liyanage, Mrs Samadara Jayarathne, 
Mr Nalin Gangodavilage and other colleagues for their great support and the 
encouragement given me to complete my research successfully. 
My heartiest gratitude is for my family members for their great support given me 
through out the research. 
Finally, I would like to thank the Asian Development Bank (ADB) for granting 
me the financial assistance to cany out my research successfully. 
2 
CONTENTS 
CHAPTER 1 : Introduct ion 
1.0 Introduction 10 
CHAPTER 2 : L i te ra ture review 
2.1 Types of fillers and their properties 13 
2.2 Structural chemistry and processing 19 
2 .3 Chemical modification of china clay 20 
2.4 . Physical modification of kaolin 24 
CHAPTER 3 : Mater ia ls and Experimental methods 
3.1 Materials used for the experiment 33 
3.2 Experimental procedures 38 
CHAPTER 4 : Results and c a l c u l a t e s 
4.1 Results obtained from the Kjeldahl experiment 46 
4.2 Results obtained from the Mooney Viscometer and 
Monsanto Rheometer 50 
4.3 Tensile properties of vulcanized samples 53 
4.4 Abrasion resistance test Results 56 
4.5 Flex cracking and crack growth lest Results 57 
4.6 Bound rubber content test Results 58 
4.7 Swelling test Results 59 
C H A P T E R 5 : Discussion and conclusions 
5. I D i s c u s s i o n 
5.2 C o n c l u s i o n s 
C H A P T E R 6 : Suggestions and recommendations 
6.1 Sugges t ions 
6.2 Future R e c o m m e n d a t i o n s 
R E F E R E N C E S 
A P P E N D I X I ( T e c h n i c a l data o f k a o l i n ) 
A P P E N D I X I I ( C h a r a c t e r i s t i c C u r i n g c u r v e ) 
A P P E N D I X I l l ( E q u i p m e n t s used for s a m p l e tes t ing) 
LIST OF TABLES 
CHAPTER 3 
Table I : Properties of RSS I Rubber 34 
Table 2 : The standard formulation of 111 led natural rubber 
based compounds 37 
Tabic 3 : The mixing schedule for mixes on an open two roll mill 41 
Table 4 : Required amount of 0.1 I IC'I lor the titration 46 
CHAPTER 4 
fable 5 : Results obtained from the Mooney Viscometer 50 
fable 6 : Results obtained from the Monsanto Rheometcr 50 
fable 7.1 : Tensile properties of mixes, extended with 
modified and standard kaolin before aging 54 
fable 7.11 :Tensile properties of the mixes extended with 
Modified and standard kaolin after aging 54 
Table 8 : Abrasion resistance test results 56 
fable 9 : Results of De-Mattia flex cracking test 57 
fable 10: Results of bound rubber content test 58 
Table I I : Results of swelling test 59 
5 
LIST O F ( IRAPUS 
CHAPTER 4 
6 
Graph ! : Curing curves obtained from Mooney Viscometer 5 I 
Graph 2 : Kheographs obtained from the Monsanto Rheometer 52 
Graph 3 : Comparison of tensile properties before aging 55 
Graph 4 : Comparison of tensile properties after aging 55 
Graph 5 : Comparison of abrasion test results 56 
Graph 6 : Comparison of De-Mattia Ilex cracking and 
crack growth tests results 57 
Graph 7 : Comparison of bound rubber content test results 58 
Graph 8 : Comparison of swelling test results 59 
Graph 9 : Differential thermal analysis (DTA) of raw rubber 
filled with kaolin treated with monoethanolamine 60 
Graph 10: Differential thermal analysis of kaolin sample 
treated with monoethanolamine 61 
LIST OF FIGURES 
CHAPTER 2 
Figure I I I b - Sketch of a Din-Abrader used lo measure abrasion 
resistance 
Figure I I I c - A Pendulum/general type tensile strength tester, 
for measuring force and elongation at 
specified time or at break 
Figure.I l l d - The mechanism of the De-Mattia flexing machine 
used to find the crack initiation and the 
rate of cracks growth 
Figure I.a - Structure of Kaolinilc Layer 
Figure l.b - Micropliotograpli showing Book-shaped 
arrangements of hexagonal plates in kaolin 
Figure 2.a - S i lane coupling agents 
Figure 2. b - Diagram showing polymer strand bound lo kaolin 
through Sikine coupling agents 
Figure 3 - Diagram illustrating the Mechanism of adsorption 
and modification 
APPENDIX II 
Figure 4 - Characteristic Curing cure 
APPENDIX III 
Figure I l i a - Sketch of an Oscillating Disk Rheometer used lo 
monitor the cure characteristics 
NOMENCLATURE 
DTA -. Differencial thermal analysis 
MEA - Monoethanol amine 
PVA - Polyvinyl alcohol 
UF - Urea formaldehyde 
NMR - Nuclear Magnetic Resonance 
Mix N° - Mix Number 
N - Newton 
MPa - MegaPascal 
Q - Toluene uptake per gram of Rubber hydrocarbon 
u - Microns 
RSS - Ribbed Smoked Sheet rubber 
FICI - Hydrochloric acid 
DPG - Diphenyl guanidine. 
MBTS - 2,2, Dithiobis benzothiozole 
ZnO - Zinc Oxide 
DEG - Diethyleneglycol 
PEG - Polyethyleneglycol 
H 3 B O 3 - Boric acid 
NIL) Ac - Ammonium acetate 
Nl l . iCI - Ammonium chloride 
Nm - Newton meter