Studies on the use of nano zinc oxide and modified silica in NR, CR ...

Chapter 6
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Physical properties such as modulus, tensile strength, elongation at
break, tear strength, hardness, heat build-up, compression set, flex resistance,
abrasion resistance and ageing resistance were studied as per the relevant
ASTM standards. Swelling studies were used to study the crosslink density.
The equilibrium swelling studies of the compounds were carried out in
toluene and crosslink densities were calculated using Flory-Rehner equation.
6.3 Results and discussion
6.3.1 Cure characteristics
Torque values of gum and filled compounds are shown in Table 6.2.
Table 6.2 Cure characteristics of SBR compounds
Property S-1 S-2 S-3 S-4 S-5 S-6 S-7 S-8 S-9 S-10
Min torque (dNm) 0.182 0.098 0.124 0.18 0.23 0.33 0.29 0.27 0.34 0.37
Max torque(dNm) 3.239 3.295 3.389 3.03 7.93 8.13 8.06 5.72 5.66 5.70
∆ torque (dNm) 3.057 3.197 3.266 2.85 7.70 7.79 7.76 5.45 5.31 5.32
Compounds with 5phr ZnO(c) showed better torque values compared
to compounds with 2phr ZnO(c). The torque values of filled and gum
compounds with 2phr ZnO(p) and 2phr ZnO(s) are comparable with that of
filled and gum compounds with 5phr of ZnO(c). But the torque values of
filled compounds with 2phr of ZnO(p) and ZnO(s) are better than that with
1phr of ZnO(p) and ZnO(s). So compounds with 2phr ZnO(p) and ZnO(s)
showed higher cross linking in rubber matrix compared to compounds with
1phr of ZnO(p) and ZnO(s). On evaluating the torque values, 2phr ZnO(p)
and ZnO(s) are selected as the optimum dosage of filled compounds that can
give better reinforcement.