Performance enhancement of rubber composites using VOC-Free interfacial silica coupling agent

Nano-silica is an important component for producing elastomer composites used for fabricating “green tires.” However, the poor dispersion of silica particles in the rubber matrix and the emission of volatile organic compounds (VOCs) during the silica modification limit the applications of the modifiers. Here, bis-epoxypropyl polysulfide (BEP), a novel epoxy-type coupling agent, was designed and synthesized for nano-silica modification to cause an interfacial interaction between nano-silica and the rubber matrix and avoid VOC emission. The thermogravimetric analysis result and the bound rubber content show that BEP effectively built a bridge between the nano-silica and the rubber, which led to a strong interfacial effect and promising mechanical performance characteristics. The silica dispersion in solution-polymerized styrene-butadiene rubber (SSBR) was studied using a transmission electron microscope and a rubber process analyzer, and the results demonstrate that BEP could significantly improve silica dispersion. The static and dynamic mechanical performance results indicate that BEP is a valid coupling agent that can achieve silica/SSBR composites with high moduli and reinforcement indices. Moreover, the combination of BEP and bis-(γ-triethoxysilylpropyl)-tetrasulfide (TESPT) was also found to demonstrate a synergistic effect, which resulted in excellent static and dynamic performances of silica/SSBR composites for preparing higher-energy-efficient “green tires.”