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

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Use <strong>of</strong> antioxidant <strong>modified</strong> precipitated <strong>silica</strong> <strong>in</strong> natural rubber,<br />

chloroprene rubber <strong>and</strong> styrene butadiene rubber<br />

better abrasi<strong>on</strong> resistance also po<strong>in</strong>ts towards better b<strong>on</strong>d<strong>in</strong>g with <strong>the</strong> <strong>silica</strong><br />

filler. The lower heat build-up may be due to <strong>the</strong> smooth surface <strong>of</strong> <strong>silica</strong> filler<br />

due to <strong>the</strong> antioxidant coat<strong>in</strong>g which acts as lubricant. The number <strong>of</strong> flex<br />

cycles required for crack <strong>in</strong>itiati<strong>on</strong> was noted <strong>and</strong> it is comparatively high for<br />

vulcanizates filled with antioxidant <strong>modified</strong> <strong>silica</strong>. The flex resistance is<br />

dependent <strong>on</strong> <strong>the</strong> network <strong>of</strong> <strong>the</strong> vulcanizates <strong>and</strong> it is found to be superior<br />

for <strong>the</strong> vulcanizate with antioxidant <strong>modified</strong> <strong>silica</strong>.<br />

7.7.4 Thermal age<strong>in</strong>g studies<br />

Figure 7.9 (a)Variati<strong>on</strong> <strong>of</strong> tensile strength <strong>of</strong><br />

SBR vulcanizates (I-1 <strong>and</strong> I-2 ) with<br />

time <strong>of</strong> age<strong>in</strong>g at 100°C<br />

Modulus at 300% el<strong>on</strong>gati<strong>on</strong><br />

(N/mm 2 )<br />

6<br />

5<br />

4<br />

3<br />

2<br />

1<br />

0<br />

0 24 48 72<br />

Time (Hours )<br />

Figure 7.9(c) Variati<strong>on</strong> <strong>of</strong> modulus <strong>of</strong> <strong>the</strong> SBR<br />

vulcanizates (I -1 <strong>and</strong> I-2) with time <strong>of</strong> age<strong>in</strong>g<br />

at 100°C<br />

El<strong>on</strong>gati<strong>on</strong> at break (%)<br />

1000<br />

900<br />

800<br />

700<br />

600<br />

500<br />

400<br />

300<br />

0 24 48 72<br />

Time (Hours )<br />

Figure 7.9(b) Variati<strong>on</strong> <strong>of</strong> el<strong>on</strong>gati<strong>on</strong> at<br />

break <strong>of</strong> SBR vulcanizates (I-1 <strong>and</strong> I-2)<br />

with time <strong>of</strong> age<strong>in</strong>g at 100°C.<br />

(Antioxidant <strong>modified</strong> precipitated <strong>silica</strong> filled<br />

vulcanizate)<br />

(Neat precipitated <strong>silica</strong> filled vulcanizate.)<br />

145

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