Structure and Properties of Reactive Silica Grafted Emulsion Polymerized Styrene-Butadiene Rubber Nanocomposites

The dispersion of silica and its interfacial interaction with styrene butadiene rubber (SBR) can be strongly improved using silane coupling agents. In this study, the reactive silica (r-SiO₂) particles were synthesized via hydrolysis and condensation reactions between siloxanes and hydroxyl groups. Subsequently, the r-SiO₂/emulsion styrene-butadiene rubber (ESBR) nanocomposites were prepared. The effect of various reaction conditions on the grafted content of silane was investigated, and how different r-SiO₂ amounts influence the structure, morphology, and performance of r-SiO₂/ESBR nanocomposites was discussed. The optimum reaction conditions were determined using 3-(methylacryloxyl)propyltrimethoxy silane (KH-570) as a modifier, and ethylene glycol butyl ether acetate (EBA) as the solvent. Under these conditions, when the amount of r-SiO₂ was 30 phr, the bound rubber content of SBR-r-SiO₂ reached 78.0%. The tensile strength and the tear strength were 11.09 and 97.90 MPa, which increased by 2.64 and 6.53 times compared to the raw rubber. Moreover, the vulcanized rubber nanocomposites exhibited significantly improved dynamic mechanical properties. Scanning Electron Microscope (SEM) analysis further revealed that the compatibility between SiO₂ and rubber was greatly enhanced after modification.