Vulcanization kinetics of nano-silica filled styrene butadiene rubber

- Filler-polymer and filler-filler interactions affect rubber vulcanization reaction.
- At low filler loadings, filler-polymer interaction accelerate vulcanization rate.
- At high filler loading, filler-filler interaction decelerate vulcanization rate.
- Reinforcing fillers reduce the conversion of sulfur vulcanization reaction.

It was shown that the physical filler-polymer and filler-filler interactions, apart from the filler surface chemistry, has a substantial role in controlling the vulcanization kinetics of styrene butadiene rubber filled with nano-silica in a sulfur vulcanization system. Kinetic studies by the oscillating disc rheometer, differential scanning calorimeter, and swelling tests revealed that the vulcanization rate goes through a maximum as loading of silica increases, but conversion in crosslinking continuously decreases as the amount of silica increases. The effect of silica loadings on the vulcanization reactions was linked to the immobilization of rubber chains around particles as well as in a polymer-mediated filler network, which were differentiated by the nonlinear viscoelastic behavior of rubber vulcanizates. By surface modification of nano-silica, the accelerating/decelerating effects of nano-silica on the vulcanization reactions were altered corresponding to the non-linear viscoelastic behavior of the vulcanizates. Therefore, a mechanism was proposed which correlates vulcanization kinetics of rubber to the dynamics of chains influenced by the reinforcing fillers.

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