The focus of this study was on the reinforcement and reinforcing mechanism of the organically modified silica in styrene–butadiene rubber (SBR).

It was shown that antioxidant 2-mercaptobenzimidazole (MB) modified silica (silica-s-MB) exhibited better dispersion in SBR than silane-modified silica (m-silica) and the interfacial interaction in SBR/silica-s-MB nanocomposites was stronger than that in SBR/m-silica nanocomposites, leading to a remarkable improvement of mechanical properties for SBR/silica-s-MB nanocomposites compared with those for SBR/m-silica nanocomposites containing equivalent antioxidant component.

Based on the analysis of the large strain behavior of SBR nanocomposites, the reinforcing mechanisms of silica-s-MB and m-silica were comparatively investigated.

It was found that the physical entanglements between the crosslinked rubber chains in the immobilized polymer layer and the organic molecules grafted on the silica surface played an important role in the silica reinforcement of rubber, which may be useful for the rational design of filler surface modification.