This document describes an experiment to select the best sulfur to accelerator ratio to improve properties in an R4 compound used for tire treads. The experiment tests different vulcanizing systems by varying the ratio of sulfur to accelerator. The conventional system uses a ratio greater than 1, while the efficient system uses a ratio less than 1. The results of the experiment will determine which ratio provides a product with the best performance properties such as tensile strength, elongation, and hardness. Selecting the optimal ratio is important for obtaining the highest quality tire tread.

1. INDUSTRIAL TRANING PROGRAMME
FOR
PST 309 . 3 : INDUSTRIAL PROJECT / SEMINARS
K . G . N . P . SOMARATHNA
AS / 2007457
B . Sc POLIMER GROUP 2006 / 2007
UNIVERSITY OF SRI JAYAWARDENAPURA
NUGEGODA

2. SELECTING THE BEST SULPHUR TO
ACCELERATOR RATIO TO GET THE
PRODUCT GIVING BEST
PERFORMER.

3. Contents Page No:
Preface ………………………………………………………….. 1
Acknowledgement …………………………………………. 2
Chapter 01
Introduction of Dry Rubber Industry ……………………. 3
Rubber Industry in Sri Lanka ……………………………. 5
About AMW ……………………………………………….. 7
Tyre Retreading Manufacturing …………………………. 8
Process line to Manufacture of procured tyre tread …... 9
Tyre Structure …………………………………………….. 10
Properties of tread …………………………………………11
Chapter 02
What is R4 …………………………………………………. 12
Processing Condition & Mixing Sequence ……………… 13
Properties of R4 …………………………………………… 13
Chapter 03
About Experiment …………………………………………. 14
Method ……………………………………………………… 15
Results of Experiment 01 …………………………………. 17
Conclusion of Experiment 01 …………………………….. 21
Experiment 02 ……………………………………………… 22
Results of Experiment 02 …………………………………. 22
Conclusion of Experiment 02 ……………………………… 27
Chapter 04
Discussion, conclusion & References …………………….. 28

4. Preface
The principle objective of this report is to introduce about tyre retarding and to select
the best vulcanizing system to obtain best quality retread for tyres.
In this project, dry rubber products, vulcanizing systems, tyre retreading, selecting
the best Sulpher to accelerator ratio to obtain best quality product in compounds have
been discussed.
K.G.N.P. Somarathna
AS/2007457/2006/2007

5. Acknowledgement
First I would like to express my sincere gratitude to Dr. L.M.K.
Thilakarathne, project supervisor and course coordinator of Polymer Science and
Technology at department of Chemistry, Faculty of applied science, university of Sri
Jayewardenepura for assigning me to AMW group of factories, Nagoda, Sri Lanka and
his valuable guidance extended constructive criticism throughout my study and also
spending his valuable time in bringing my study to successful completion.
I wish to express my sincere thanks to the Prof. Sudantha Liyanage, Dean
of the faculty of applied science, senior lecturer at department of Chemistry faculty of
applied science, university of Sri Jayewardenepura. I also thanks full to Dr. Laleen
Karunanayaka and all of the staff members of the department of chemistry for their
interest and valuable advice during my studies.
My special thanks to Mr. Yugantha Piyadasa, senior Quality Assurance and
Development Manager, and all the staff of AMW group of factories for making me
aware on Dry Rubber technology.
I shall be thankfull to all the friends supported me for giving help to
success of my training and project.
K.G.N.P. Somarathna
AS 2007457/2006/2007

6. DRY RUBBER INDUSTRY
Introduction
Among thousands of industries dry rubber industry has become a major industry in today’s
world. Not only in the world, even in Sri Lanka has dry rubber industry played a vital role among
other industries. It provides dry rubber products for domestic use and also to the export market.
Therefore dry rubber industry contributes largely in our economic growth. With the growth of the
industry world, dry rubber consumption has increased. Also in Sri Lanka there was a rapid growth
in dry rubber industries. Following figures show growth of the dry rubber industry in last two
decade.
Year Dry rubber
Consumption(Mt)
Year Dry rubber
Consumption(Mt)
1981 10789 1992 19960
1982 11980 1993 23670
1983 12856 1994 24780
1984 13783 1995 34690
1985 11344 1996 35520
1986 22764 1997 35440
1987 10563 1998 50200
1988 19720 1999 36830
1989 20128 2000 40250
1990 22500 2001 35550
1991 21040 2002 35600
Figure 1.Locally produced dry NR
consumption in Mt

7. The dry rubber based industries in Sri Lanka started during the war years as tube
vulcanizing and tyre retreading industries and they were completely based on locally
produced dry NR. In 1967 Sri Lanka commenced production of cross ply tyres, has
consumed about 5% of domestic NR production. It was started as the Kelani Tyre
manufacturing corporation.
Today Sri Lanka is the world’s fifth largest exporter of natural rubber, generating over
100,000 tons annually. More than 60 percent is exported in an unprocessed form.
On the manufacturing front, Sri Lanka is the world’s leading supplier of solid rubber
tyres for off-road vehicles. Major investments have also been made by producers of
healthcare and surgical rubber products, where high quality raw material is of primary
importance. Globally, there is a good demand for rubber tiles and floor coverings. In
addition, shoe producers obtain rubber heels and sole from Sri Lanka.
Opportunities investment includes the manufacture of tyres, tubes and automotive
rubber products, especially by relocating these facilities from high cost industrialized
or industrializing countries.
Sri Lanka’s Competitive Advantages in the Rubber Industry
• Availability of high quality raw rubber at competitive prices.
• Recognition as a high quality Natural Rubber (Latex Crape) Producer.
• Access to a pool of technical and professional manpower at competitive
wage rates.
• Attractive incentives.
• Good infrastructure.
• Competencies built over 124 years of experience in the industry.
• Availability of supporting services (research and development facilities,
testing and certification services).

8. The Rubber Industry in Sri Lanka
Sri Lanka is the world’s 9th
largest producer of NR. It is also the major supplier of high quality latex
crepe to the world market and the world’s largest manufacturer and exporter of solid tyres for off-
road vehicles. Nearly 60% of the NR production in Sri Lanka is used for value added rubber
products. The bulk of these value-added products are for the export market. Foreign investors
from 2o countries have set up lucrative and long sending world class ventures under BOI approval.
The 59 BOI approved rubber industry projects consume nearly 75% of Sri Lanka’s total domestic
NR production.
Today in Sri Lanka there are several companies which produce branded dry rubber products.
Their production contributes to both domestic and export market. Among these factories,
Associate Motorways Ltd.
Richard P. Exports Ltd.
Loadstar (Pvt) Ltd.
Ceat-Kelani Intern. Tyres (Pvt) Ltd.
Rubber Product Manufacturing in Sri Lanka
Product Type
No of projects Investment
(Rs. Millions)
Employment(No’s)
Tyre Retreading 3 5% 558 4% 235 1%
Pneumatic types &
Tubes
3 5% 4825 31% 4077 25%
Solid Tyres 4 7% 896 6% 667 4%
Footwear 2 4% 855 5% 306 2%
Flooring 2 4% 928 6% 253 2%
Other dry 8 14% 390 2% 942 6%
Latex dipped 26 46% 6652 43% 9244 56%
Latex form 8 14% 547 3% 676 4%
Total 56 100% 15651 100% 16400 100%

9. Dry rubber Industries
Dry rubber Industries
Motor car components
Motor car components
Household’s appliances (Flooring)
Household’s appliances (Flooring)
Other products
Other products
Dry rubber industry can be divided in to three parts.
Among various kinds of dry rubber industries, Tyre manufacturing has become a major and
essential industry in today’s world. Large percentage of the total dry rubber consumption goes to
the tyre industry. This industry becomes more popular with the retreading of tyres.
In Sri Lanka, Ceat-Kelani International Tyres (Pvt) Ltd, Associated Motorways Ltd, Richard
P. Exports Ltd, etc are the main companies that involving in the tyre manufacturing and treading.
Due to environmental issues and very high consumption of dry rubber, treading industry
came into scene. Today it provides large amount of job opportunities while helping to develop the
economy in the country. Also dry rubber industry is a very challenging field. With the economic
growth, competition has increased largely within last few years.

10. About AMW
Associated Motor Ways (AMW) is the pioneer privately owned group of
companies located in main rubber growing area in Kaluthara district in Sri Lanka. The
company has been established in 1949. The present assets of the company worth
were US$22 million in 2002-2003. AMW is one of the leading rubber products factories
in Sri Lanka producing motor cycle & three-wheel tyres & retreading small to large
scale tyres using hot cure, pre cure (cold), Dir Hard & vaculug processes.
Associated Auto Ways Associated universal (Pvt) Ltd, Associated CEAT
(Pvt) Ltd are associated companies and their external customers are mainly global
rubber industries, Arpitalian compact soles (Pvt) Ltd, and Oman Vacu-Lng Company.
The company has captured the export market too and is producing Trap straps, Mud
Flaps, Carpets, two and three-wheeler tyres and rubber compounds to be exported to
USA, Canada, and India and Middle East countries.
About AMW Retreading
AMW rebuilds all size ranging from small passenger car tyres to large off
the road earthmover tyres. The tyre retreading process enjoy ISO 9002 certification
and the organization is the market leader in Sri Lanka in this field apart from
rebuilding customer tyres, avarity of tyre retreading material available for sale.

11. Tyre Retreading Manufacturing
As the presences of imported pneumatic tyres are rising sharply, most of
the people are used particular bus and lorry owner used retreaded tyres in their
vehicles. Among 30 tyre trading companies, AMW Company is the oldest tyre
retreading company set up in Sri Lanka as further as late 1949.
At the early stage retreading of tyre was done by the molded process
where green tyre build on a completely buff old tyre & it vulcanized by placing inside
the mould at high temperature and pressure.
The main drawback of this process is that the output is very low and only
one tyre can be retreaded in a mould in about 45 minutes Further ;
 Mould is specific.
One specific tyre size can be compression cured in a particular mould and even a
different quality tyre of the same dimension can’t be cured in this mould. Hence in
order to overcome this incomesinning process, the new pre cured tread system has
been introduced. In this method instead of molding a green tyre inside a mould, fully
prevulcanized tread is pasted on the clean buffed bold surface of the old tyre by
means of rubber cement. Then several of these tread pasted tyres are finally cured
inside an auto clave. Hence large no of tyres of different brands can be cured at once
in this process.

12. Mixing of rubber and
Chemicals
Mixing of rubber and
Chemicals
SulphuringSulphuring
Mystification in two roll
mill
Mystification in two roll
mill
Extrusion of mouldsExtrusion of moulds
Testing the
samples
Testing the
samples
Getting camel backGetting camel back
Place in trunk for
further cooling
Place in trunk for
further cooling
Applied camel
back to mould
Applied camel
back to mould
TreadTread
Process line to manufacturer of pre cured tyre trades.
2 min
(After 4 hours
From mixing) (In bambery)
After 8 hours
Cooling
(By passing in water)
(Curing)

13. Tyre structure
Serial
No Element Functions
01 Tread Tread is the part which comes into contact with road
surface. It protects the carcass & provide high grip,
longer life, maneuverability and durability.
02 Steel Belts This provides stiffness to the tread & protect the
carcass.
03 Spiral Layer This provides high durability & maneuverability.
04 Shoulder Shoulder is the thickest part of the tyre. It protects
carcass from external shocks & damages.
05 Sidewall Sidewall is the most flexible part of the tyre. It protects
carcass & provides comfortable ride
06 Ply cord Ply cord is the main body of a tyre. It sustains the
inflation pressure and endures load and road shocks.
07 Bead Filler This provides high durability & maneuverability.
08 Bead Wires It holds the tyre on rim.
09 Chafer Chafer protects ply cord at the bead area from the heat
generation developed due to the abrasion of bead and
rim flange.

14. Properties of a Tyre Tread
Tread is the most important part of the tyre which is getting in contact with the road surface during
rubbing of the vehicle. Hence wearing resistance of the thread should be very high & it should not
be too hard to discomfort passenger inside vehicle. It should not be too soft or slip ring as well for
the safety of the vehicle.

15. What is R4
R-4 is the tread compound to make a procured rubber tread for three wheel tyres.
Chemical composition of R-4
Master compound
Material
Qty(kg)
Sc 3x 94.000
Br 01 23.500
Accimel 0.188
Z no 5.875
Stearic acid 2.350
CBN-375 70.500
Processing oil 17.000
Permanex TQ 0.880
Batch weight 214.293
R-4 is a sulfuring process.
Material Qty(kg)
2nd
stage master 190.000
Santo cure(TBBS)
(Accelerator)
1.256
Sulphur
(Vulcanizing agent)
1.345
6 PPD (activator) 1.020
PVI (Pre vulcanizing inhibitor) 0.110

16. Processing conditions & mixing sequence
1st
Stage Time (min)
NR+BR+ (black+ Accimel + chem. B-)
(2 no 95 + stearic Acid)…………………………………………………………………. 0.00
Process oil……………………………………………………………………………...... 2:00
Sweep……………………………………………………………………………............. 3:30
Dump……………………………………………………………………………………… 5:00
2nd
stage (After 4 hours from mixing)
Re-pass (in Banbarry) ………………………………………………………………….. 2:00
Sulphuring (After 4 hours from 2nd
stage mixing) Weight (Kg)
Master compound ……………………………………………………………………190.000 kg
NS (TBBS)……………………………………………………………………………..1.256 kg
Sulphur…………………………………………………………………………………1.345 kg
6 PPD…………………………………………………………………………………..1.020 kg
PVI ……………………………………………………………………………………..0.110 kg
Properties of R-4
Property Value
Tensile strength (TS) kgcm-2
………………………………………………….. 190-200
Elongation at break (%)………………………………………………………… 500-550
Moduless at 300% (kgcm-2
) …………………………………………………… 85 -107
Hardness (shore A) (IR)………………………………………………………... 60-62
Specific gravity (gcm-3
) ………………………………………………………… 1.135 +/- 0.01
Abrasion loss (mm-3
) …………………………………………………………… 60-67
Rheometer properties
T Minimum
T s2
/ s T Max
T90%
/s
1.15-1.80 45-60 9.5-12.8 84-115

17. Experiment
Improving properties in the R-4 compound by changing the Sulphur to accelerator ratio
Objective: - Selecting the best Sulphur to accelerator
ratio to get the product giving best performance.
Vulcanizing System
There are three vulcanizing systems available for curing. Those are conventional
vulcanizing system, semi-efficient vulcanizing system (Semi EV),efficient vulcanizing system(EV).
Vulcanizing System Amount-ratio of Sulphur to accelerator
Conventional vulcanizing system Greater than 1
(Sulphur =2 to 4 per)
(Accelerator = 1 to 0.5 per)
Efficient vulcanizing system (EV) Less than 1
(Sulpher =0.4 to 0.8 per)
(Accelerator = 3 to 0.5 per)
Semi-efficient vulcanizing system (semi-
EV)
Approaches 1
Sulpher =1 to 1.5 per)
(Accelerator = 1.5 to 1.0 per)
AMW use only conventional vulcanizing system for R-4 sulfuring. Because it gives better cross
linking

18. Method
Here we have sulfur zing process. Following procedure was carried out;
•Master compound was obtained
•It was masticated by using two roll mill
•After 2 minutes, immediately it was added TBBS, Sulfur, PVI, 6 PPD to two roll mill
•Then the sulfured compound was obtained from the two roll mill in sheet of 1cm in thickness.
•After an hour one piece of compound was cut and it was subjected to curing characteristic test
using a Rheometer.
•Then after 24 hours two samples were obtained from the sulfur compound and one vulcanized
sample was subjected to the tensile strength, of using thetensometer and the other vulcanized
sample was subjected to test obresion loss by means of a abrasion tester.
Note: - 1. Before testing tensile strength the sample should be cut to the shape of bumble using
dumbel cutter.
Usually thickness =2mm
Cut
width=0.41 m
0.4 cm
2. Also before testing abrasion loss of the sample, sample was
obtained as in the following shape by using a mould.
Properties obtained from Rheometer
Scotch time (TS2
)
T90
Modulus (T max
)
T Min
Properties obtained from tensile meter
Tensile strength = Breaking load (kg)
Area (cm2
)
Modulus at 300% = Load at 300% (kg)
Area (cm2
)
Properties obtained from Abrasion tester
Abrasion = Weight Lost(w1
-w2
)
Specific gravity (Sp)

19. Above procedures were done for following trials. Here in these trails only varying
sulfur & accelerators, master compound and other chemicals are same for all the
trails.
Experiment 01
In lab scale testing we had to convert amount of ingredients as follows,
Weight
Master batch…………………………………………… 250 g
NS…………………………………………………………… 1.652 g
Sulfur ………………………………………………....... 1.769 g
PVI ………………………………………………….........1.144 g
6 PPD ………………………………………………….... 1.02 g
In experiment 1, amount of sulfur was kept constant an amount of accelerator was
varied as follows.
Weight
Sulfur amount = 1.769 g
Accelerator amount; A 1.550 g
B  1.600 g
C  1.700 g
D  1.650 g
E  1.750 g

20. Results:-
Rheograph for composition type A
Rheograph for composition type B

21. Reograph for composition type C
Reograph for composition type D

22. Rheograph for composition type E
Rheograph for composition type all together
( 1=A, 2=B, 3=C, 4=D, 5=E)

23. Tensile Strength Results
Compositi
on
type
Thickne
ss
/cm
Cut
width
/cm
Area
/cm2
Lord at
300% /
Kg
Elongati
on
at break
%
Breaki
ng
load/K
g
Modules
at
300%/Kgc
m-2
Tensile
strengt
h
/Kgcm-2
0.253 0.39 0.0986 9.2 500 20.8 93.3 210.9
0.264 0.41 0.1082 10.8 500 21.8 99.8 210.5
(A) 0.212 0.4 0.0848 9.9 490 17.5 114.4 206.4
0.24 0.38 0.0912 9.8 500 18.7 107.5 205
0.251 0.39 0.0999 10.8 510 21 110.3 214.5
500 209.5
0.242 0.41 0.0992 9.8 490 18.5 98.8 186.5
0.28 0.41 0.1148 13 470 20.8 113.2 181.2
(B) 0.21 0.41 0.0861 10.1 450 16.5 117.3 191.6
0.266 0.4 0.1064 13.8 450 21.4 129.9 201.1
0.242 0.41 0.0992 12.5 460 18.8 126 189.5
464 189.9
0.215 0.4 0.085 10.2 480 17.8 118.6 206.9
0.208 0.42 0.0873 10.8 470 17.2 123.7 197
(C) 0.198 0.39 0.0772 9.8 480 16.8 126.9 217.6
0.232 0.38 0.0882 10.2 470 18.5 115.6 209.7
0.18 0.4 0.072 8.8 500 15 122.2 208.3
480 207.9
0.252 0.4 0.1008 12.8 500 21 126.9 208
0.22 0.4 0.088 9.5 500 19.8 107.9 225
(D) 0.22 0.4 0.088 10.5 500 17.8 119.3 202.3
0.21 0.38 0.0798 10 510 18.2 125.3 228
0.232 0.38 0.0881 10 520 19.2 113.5 217.9
506 216.2
0.263 0.4 0.1052 11.4 500 20.2 108.4 192
0.24 0.37 0.0888 11.2 480 126.1
(E) 0.253 0.41 0.1037 13.5 450 20.4 130.2 196.9
0.22 0.42 0.0924 11.8 470 18 127.7 194.8
0.255 0.4 0.102 11.2 450 16 109.8 156.8
470 185.4

24. Abrasion testing Results
Composition (A) (B) (C) (D) (E)
type
Hardness 63 59 63 59 59
(IRHD)
Specific 1.124 1.138 1.122 1.136 1.127
gravity (g/cm3)
Weight loss (g) 1.61 1.62 1.63 1.96 1.59
1.53 1.56 1.56 1.6 1.5
0.08 0.05 0.07 0.07 0.09
Abrasion(mm3) 71.1 52.7 62.3 61.6 79.8

25. 71.1
61.6 62.3
52.7
79.8
0
10
20
30
40
50
60
70
80
90
A B C D E
Composite Type
Abrasionloss(mm3)
Tensile strength with composition type
Abrasion loss with composition Type
Conclusion:
According to that experiment,
Recipe containing sulfur amount = 1.769 g
And accelerator amount = 1.6505 g (Composition Type D) was the best. Hence the sample
containing 1.650 g of accelerator, keeping sulfur constant was the best.

26. Experiment 2
In experiment 2 following trails were done as the procedure mentioned in experiment 1. For
all the trails accelerator amount was kept as 1.650 g (conclusion of experiment 1) and sulfur amount was
varied.
Weight
Accelerator amount = 1.650 g
Sulfur amount; F1.770 g
G1.870 g
H1.820 g
I1.720 g
J1.670 g
Results:-
Rheograph for composition type F

27. Rheograph for composition type G
Rheograph for composition type H

28. Rheograph for composition type I
Rheograph for composition type J

29. Rheograph for composition type all together
(1=F, 2=G, 3=H,4=I, 5=J )

30. Tensile strength Results
Composition
type
Thickness
/cm
Cut
width
/cm
Area
/cm2
Lord at
300%
/Kg
Elongati
on
at break
%
Breaking
load/Kg
Modules at
300%/Kgcm-2
Tensile
strength
/Kgcm-2
0.2165 0.41 0.1086 11.5 480 20 105.9 184.2
0.275 0.41 0.11 12.6 470 114.5
(F) 0.248 0.41 0.1017 12.8 480 19.8 125.8 194.7
0.18 0.41 0.0738 9.4 470 15.4 127.4 208.9
0.216 0.4 0.0864 10.2 470 16.8 118 194.4
474 195.5
0.252 0.42 0.1058 12.8 480 22.6 120.9 213.6
0.23 0.4 0.092 11.5 470 19.8 125 215.2
(G) 0.238 0.41 0.0975 11.8 470 19.8 121 203.1
0.21 0.4 0.084 10 500 17.2 119 204.9
0.22 0.4 0.088 10.8 500 18.8 122.7 213.6
484 210
0.228 0.4 0.0912 11.8 480 19.6 129.4 214.9
(H) 0.235 0.38 0.0893 13.3 490 21.4 148.9 239.6
0.23 0.38 0.0874 12.8 480 21.1 146.4 241.4
0.252 0.4 0.1008 11 490 20.6 109.1 204.3
485 225
0.267 0.41 0.1093 11.1 500 19.8 101.3 180.8
0.232 0.42 0.0974
(I) 0.3 0.41 0.123 13.2 500 22.8 107.3 185.3
0.245 0.4 0.098 11.2 500 19.4 114.3 197.9
0.185 0.42 0.0777 7.6 520 13.4 97.8 198.2
505 190.5
0.272 0.4 0.1088 12.5 470 19.2 114.8 176.5
0.253 0.39 0.0986 11.2 470 19.8 113.6 200.8
(J) 0.252 0.39 0.0983 8.8 480 19 89.5 193.3
0.224 0.4 0.0896 10.6 470 17.8 118.3 198.6
0.295 0.38 0.1121 13.8 470 23 133.1 205.2
472 194.8

31. Abrasion testing results
Composition
type
(F) (G) (H) (I) (J)
Hardness(IRH
D)
60 61 60 60 60
Specific
gravity(g/cm3)
1.139 1.134 1.139 1.127 1.126
Weight loss(g) 1.63
1.55
1.63
1.57
1.61
1.55
1.63
1.56
1.63
1.56
0.08 0.06 0.06 0.07 0.07
Abrasion(mm
3)
70.2 52.9 52.6 62.1 62.1

32. en
sil
e
St
re
ng
th
K
gc
m-
2
210
225
190.5
194.8
170
180
190
200
210
220
230
F G H I J
195.
5
Composition Type
Tensile strength with composite type
Abrasion lost with composition type
Conclusion:-
•According to the experiment 2 composition type H was found is the best. So the sulfur amount
should be 1.82 g to get optimum physical properties.

33. Discussion:-
According to the results, the best level of sulfur and accelerator to obtain
best technological properties were 1.820 g and 1.650 g respectively
But according to AMW, they were using sulfur and accelerators in quantities 1.769 g
and 1.650 g respectively . But according to the results discussed above sulfur amount
should be 1.820 g. But AMW does not use that amount, because of the cost. However
based on my observations AMW agreed to change sulfur and accelerator contents
recommended by me above.
Conclusion:-
In order to obtain best properties for the retreading, best sulfur to
accelerator ratio to the need is 1.820 g to 1.650 g respectively.
References:-
• Handbook for rubber of Dr. Subramanian, senior lecturer of university of Moratuwa
• AMW company case study
• www.wikipedia.com