Preparation of silica-supported 2-mercaptobenzimidazole and its antioxidative behavior in styrene-butadiene rubber

A novel type of rubber antioxidant, silica-supported 2-mercaptobenzimidazole (SiO2-s-MB), was prepared by reacting 2-mercaptobenzimidazole (MB) with chlorosilane-modified silica (m-SiO2). Raman spectroscopy, FT-IR, XPS and TGA confirmed that MB was chemically bonded onto the surfaces of silica particles. SEM observation showed that SiO2-s-MB was homogeneously dispersed in the styrene-butadiene rubber (SBR) matrix. Based on the measurement of oxidation induction time (OIT) of SBR/SiO2-s-MB and SBR/m-SiO2/MB composites containing equivalent antioxidant components, it was found that the antioxidative efficiency of SiO2-s-MB was superior to that of the corresponding low molecular MB. By determining the changes of tensile strength, elongation at break and crosslinking density of SBR composites during long-term accelerated aging, it was shown that the thermal oxidative stability of SBR/SiO2-s-MB composites was much higher than that of SBR/m-SiO2/MB composites. Furthermore, the color contamination, migration and volatility of SiO2-s-MB were lower than those of MB, indicating that SiO2-s-MB is environmentally friendly.