Novel experimental approach to evaluate silica–elastomer interactions of vulcanizates

Abstract

The importance of the silica–polymer interaction in enhancing the performance of green tires is well recognized. However, there has been a lack of a standardized method to accurately characterize this interaction in vulcanizates. This paper introduces a new methodology for characterizing the interaction between polymer and silica, focusing on the impact of filler loading, coupling agents, and amount of sulfur on this interaction. The methodology is based on equilibrium swelling experiments. Conducting the swelling test in an ammonia atmosphere facilitates the elimination of physical interactions. Consequently, the resulting crosslink density predominantly encompasses that of the rubber matrix and the chemical silica–polymer interaction. Treatment of vulcanizates with hydrofluoric acid serves to nullify the chemical interaction between silica and rubber. Following this process, the equilibrium swelling test enables the determination of the crosslink density of the rubber matrix. As such, the disparity between the crosslink densities obtained after ammonia and after the hydrofluoric acid treatment signifies the chemical interaction between the polymer and silica. The findings revealed that the polymer–silica interaction facilitated by the coupling agent bis[3‐(triethoxysilyl)propyl]tetrasulfide (TESPT) exhibited a notably higher magnitude compared to that enabled by the coupling agent bis[3‐(triethoxysilyl)propyl]disulfide. Moreover, the silica–polymer interaction demonstrated a positive correlation with both silica/TESPT loading and sulfur content. It is worth noting that this paper provides one solution and theoretical basis for calculating polymer–filler interactions in crosslinked composites by dissolving fillers.Highlights Experimental method for quantitative evaluation of silica–polymer interaction. The method can also be applied to crosslinked polymer/nanofiller composites. TESPT is a more potent silane than TESPD, even sulfur is compensated. Polymer–filler interaction is deeply affected by polysulfide‐polymer reaction.