Engineering novel coupling agents for interfacial reinforcement and performance optimization in tire tread composites

Silica exhibits exceptional reinforcing properties and functions as a primary filler in the rubber industry. Coupling agents can significantly enhance the overall performance of rubber composites by optimizing the interfacial bonding between the filler and the rubber matrix, and thus are extensively employed in silica-filled rubber composites. In this paper, a series of novel coupling agents, denoted as S1JX (X = 1, 2, 3), were designed and synthesized by reacting bis-[γ-(triethoxysilyl) propyl] tetrasulfide (Si69) with isooctanol polyoxyethylene ether (JFC-2) at different molar ratios. It was found that the grafting efficiency of S1JX to silica was higher than that of Si69, indicating enhanced coupling capacities. Subsequently, S1JX were applied to silica/natural rubber (NR) composites. The results showed that S1JX enhanced the dispersion of silica in rubber due to its long polyether alkyl chains, which shielded the silanol groups on the silica surface through hydrogen bonding. Meanwhile, compared to Si69, the addition of S1J1 reduced the rolling resistance of the silica/NR composites by 11.5 %, increased wet skid resistance by 12.1 %, and maintained excellent abrasion resistance, while also exhibiting superior anti-aging performance. Furthermore, the interfacial phase was directly visualized using AFM-QNM, which quantitatively analyzed that the addition of S1J1 increased the interfacial thickness and enhanced the interfacial interaction between silica and rubber. This paper provides a basis for revealing the coupling mechanism and guiding the performance enhancement of tire tread composites.