Styrene grafted natural rubber reinforced by in situ silica generated via sol–gel technique

• Sol–gel reaction by NR latex was the absence of use of organic solvent and base catalyst.
• Well dispersed in situ formed silica particles in the rubber matrix were obtained.
• In situ silica was better to improve mechanical properties of rubber vulcanizates.

The filling of styrene graft natural rubber (ST-GNR) with in situ formed silica was performed using the sol–gel reaction via the latex solution method. The mechanical properties of ST-GNR/NR vulcanizate were improved when using the in situ formed silica to levels higher than those obtained with the commercial ex situ formed silica filled ST-GNR/NR vulcanizates at a comparable silica content of 12 parts by weight per hundred parts of rubber. Transmission electron microscopy analysis revealed that the in situ silica particles were small (∼40 nm diameter) and well dispersed, while the commercial silica particles were larger (∼60 nm diameter) and markedly agglomerated in the rubbery matrix. The mechanical properties of the composites prepared via both the solid rubber and latex solution methods were comparable.

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