2.0 METHODOLOGY
NR L-grade was supplied by Hockson Rubber Trading, EPDM Nordel P4520 at 50 ethylene and 5 diene was supplied by Dow
Chemical Company. SBR Intol 1502 with MV of 52 was supplied by Polimeri Europa UK Ltd. PSi with surface area of 161-190 m
2
g was supplied by Euro Chemo Sdn. Bhd. ClCy with surface area of 12-16
m
2
g was supplied by Tangshan Madison Kaolin Co. Ltd., while Organosilane,
3-triethoxysilylpropyltetrasulphide TESPT
was supplied by Innova Chemical Co. Ltd. Other ingredients include
CaCO
3
, ZnO white, stearic acid, mercaptobenzothiazole disulphide MBTS, diphenyl guanidine DPG, polyethlene glycol, phenolic
antioxidant, homogenizing resin, Zn soap, parafinic oil and sulfur were the grades customarily used in rubber industries. Compounding
was performed by using a laboratory two-roll mill according to ASTM D3182. The First stage mixing involved preparations of three initial
compounds; i CaCO
3
-filled NR CaCO
3
NR, ii PSi-filled blend rubber PSiBR, and iii ClCy-filled blend rubber ClCyBR. The
blend rubber consists of NR, SBR and EPDM. CaCO
3
NR was referred to an industrial Rubber Mat formulation which was used as a
reference sample in the present study. For PSiBR and ClCyBR, prolonged mixing were performed at temperature of 70-80 °C for 120
min at 1 mm of roller nip in order to improve the dispersion and distribution of fillers and to attain complete silanization of TESPT.
The formulations of the compounds in part per hundred rubber phr are listed in Table 1.
Table 1: Formulation of the initial compounds
Ingredients CaCO
3
NR phr
PSiB R
ClCyBR phr
NR 100.00
68.00 68.00
SBR 13.00
13.00 EPDM
19.00 19.00
CaCO
3
10.00 3.81
3.81 Precipitated
30.44 Calcined clay
30.44 Phenolic
0.50 Zinc oxide
5.00 Stearic acid
3.00 Polyethylene
3.00 DPG
0.20 MBTS
4.00 Paraffinic oil
0.50 6.09
6.09 Metal Soap
0.42 3.81
3.81 Homogenizing
3.04 3.04
TESPT 6.09
6.09
The Second stage involved mixing of 5 compounds in different combinations of PSiBR and ClCyBR with fixed percentage of
CaCO
3
NR as depicted in Table 2. These combinations represent the ratios of rubbers and fillers as shown in Table 3.
Table 2: Different combinations of the initial compounds
Sample No. CaCO
3
NR PSiBR
ClCyBR 1
85.37 -
14.63 2
85.37 5.12
9.51 3
85.37 7.32
7.32 4
85.37 9.51
5.12 5
85.37 14.63
-
Table 3: Compositions of hybrid-filled rubber composites
Sample No. NR phr
SBR phr EPDM phr
CaCO
3
phr PSi phr
ClCy phr 1
95.9 1.7
2.4 9.2
- 3.8
2 95.9
1.7 2.4
9.2 1.3
2.5 3
95.9 1.7
2.4 9.2
1.9 1.9
4 95.9
1.7 2.4
9.2 2.5
1.3 5
95.9 1.7
2.4 9.2
3.8 -
The composites were then added with sulphur and the final vulcanizates were prepared by using compression molding at 165 °C
and pressure of 150 kgcm
2
. Tensile and trouser tear test were performed by using a universal testing machine Zwick Roell, Z005
according to ASTM D412 and ASTM D624, respectively. Morphological analyses at the tear tips of gold-sputter-coated tear test
specimens were performed by using scanning electron microscope Zeiss EVO50 operated at accelerating voltage of 15 kV under a
magnification of 1000 x.
3.0 R E S U L T S A N D D I S C U S S I O N
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