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

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Chapter 8<br />

166<br />

Table 8.8 Cure characteristics <strong>of</strong> mixes C <strong>and</strong> D<br />

Property Mix C Mix D<br />

Scorch time, m<strong>in</strong> 0.438 0.51<br />

Optimum cure time(t90) m<strong>in</strong> 4.45 4.98<br />

Cure rate <strong>in</strong>dex (%) 24.92 22.37<br />

M<strong>in</strong> torque, dNm 0.042 0.052<br />

Max Torque, dNm 6.279 4.723<br />

∆ torque, dNm 6.237 4.671<br />

Compound with antioxidant <strong>modified</strong> RH<strong>silica</strong> exhibited higher rate<br />

<strong>and</strong> extent <strong>of</strong> cure over that <strong>of</strong> compound with neat RH<strong>silica</strong>. The cure graph<br />

<strong>of</strong> <strong>the</strong> compound with antioxidant <strong>modified</strong> RH<strong>silica</strong> (nr rhs brab) <strong>and</strong> with<br />

neat RH<strong>silica</strong> (nr rhs neat) is shown <strong>in</strong> figure 8.9.<br />

Torque (dNm)<br />

8<br />

6<br />

4<br />

2<br />

0<br />

cure graph<br />

0 10 20 30 40<br />

time (m<strong>in</strong>)<br />

nr rhs neat<br />

nr rhs brab<br />

Figure 8.9 Cure graph <strong>of</strong> <strong>the</strong> compounds with <strong>modified</strong> RH<strong>silica</strong> (nr rhs brab) <strong>and</strong><br />

neat RH<strong>silica</strong> (nr rhs neat)<br />

The maximum torque is a measure <strong>of</strong> crossl<strong>in</strong>k density <strong>and</strong> stiffness <strong>in</strong><br />

<strong>the</strong> rubber. 26 It is found that compound with <strong>modified</strong> RH<strong>silica</strong> <strong>in</strong>creases <strong>the</strong><br />

torque values compared to neat RH<strong>silica</strong> compound. This <strong>in</strong>crease is due to

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