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

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Chapter 7<br />

b) Oz<strong>on</strong>e age<strong>in</strong>g<br />

132<br />

Figure 7.6 (a-f) shows <strong>the</strong> photographs <strong>of</strong> oz<strong>on</strong>e cracked surface <strong>of</strong> <strong>NR</strong><br />

vulcanizates after 7 hours <strong>in</strong> an oz<strong>on</strong>e chamber. Photographs clearly show<br />

that vulcanizates filled with antioxidants <strong>modified</strong> <strong>silica</strong> develop lesser cracks<br />

compared to vulcanizates with neat <strong>silica</strong> <strong>and</strong> antioxidant. Table 7.7 shows<br />

that all vulcanizates except vulcanizate filled with IPPD <strong>modified</strong> <strong>silica</strong><br />

cracked <strong>in</strong> 6 hours. This shows better resistance to oz<strong>on</strong>e attack for <strong>the</strong><br />

composites filled with antioxidants <strong>modified</strong> <strong>silica</strong>.<br />

Table 7.7 Time for <strong>the</strong> crack <strong>in</strong>itiati<strong>on</strong> <strong>of</strong> various samples <strong>on</strong> oz<strong>on</strong>e age<strong>in</strong>g<br />

Sample E-1 E-2 F-1 F-2 G-1 G-2<br />

Time (hrs) >7 6 6 6 6 6<br />

(a) (b)<br />

(c) (d)

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