Mechanical properties of silica particle-filled styrene-butadiene rubber composites containing polysulfide-type silane coupling agents: Influence of loading method of silane

摘要

Polysulfide-type silane coupling agents containing two or four sulfur atoms were incorporated into a styrene-butadiene rubber/silica composite by two different loading methods and the tensile properties were measured. The pretreatment method and the integral blend method were compared. To improve the 200% modulus of the composite, the combination of silane with four sulfur atoms and the pretreatment method was effective. Whereas, the combination of silane with four sulfur atoms and the integral blend method was effective for improving the fracture elongation. The fracture elongation of the integral blend using the silane with four sulfur atoms was higher than that of the untreated silica-filled composite. The sulfur atoms in the silane should contribute to the crosslinking of rubber in the vulcanization process. The silane with much sulfur atoms strengthens the interface effectively and raises the 200% modulus in the pretreatment method. It is considered that the unreacted silane molecules in the rubber acted as a plasticizer in the integral blend method and the effect was better with four sulfur atoms. The ~1H pulse nuclear magnetic resonance spectroscopy was measured for the unvulcanized rubber/silica mixture. The measured relaxation time was found to be in good correlation with the 200% modulus. It was found that the molecular mobility of rubber is lowered by the entanglement with the silane chains on the silica surface at the interfacial region, and it was more effective in the pretreatment method than in the integral blend method.