Study on the effect of silica-graphite filler on the rheometric, mechanical, and abrasion loss properties of styrene-butadiene rubber vulcanizates

Silica-graphite filler was prepared via two-step grafting procedure by grafting silica particles onto the expanded graphite. In the first step, isocyanatopropyltriethoxysilane was chemically introduced onto the silica aggregates, which was followed by grafting onto the expanded graphite via urethane linkage in the second step. Successful grafting of silica aggregates onto the graphite was corroborated using Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. The presence of a thin graphene layer on silica aggregates corroborated using transmission electron microscopy confirmed the grafting of silica aggregates onto the graphite surface. Styrene-butadiene rubber (SBR) composites with various silica-graphite loadings were prepared by melt processing technique to generate pristine silica and silica-graphite-filled elastomeric composites. Rheometric cure studies revealed that the torque difference (Delta S) increased with pristine silica loading, when compared to the unfilled SBR system, and this effect is more pronounced on loading silica-graphite filler. Improvements in mechanical properties such as modulus and tensile strength were observed with increasing loading of silica particles and this effect is more pronounced on loading silica-graphite fillers, indicating that this is due to the rise in the elastomer-filler interactions in the silica-graphite-loaded SBR systems. This fact was further corroborated using bound rubber content and equilibrium swelling ratios of the unvulcanized and vulcanized SBR composites.