Enhanced interfacial interaction and excellent performance of silica/epoxy group-functionalized styrene-butadiene rubber (SBR) nanocomposites without any coupling agent

Epoxy group-functionalized styrene-butadiene rubbers (G-ESBRs) with different epoxy group contents were synthesized through emulsion polymerization using glycidyl methacrylate (GMA) as the epoxy group-included monomer, and the silica/G-ESBR nanocomposites without silane coupling agents were prepared. The covalent bonding interfaces, resulting from a ring-opening reaction between the hydroxyl groups on the silica surfaces and the epoxy groups of G-ESBR, were formed during the preparation of the silica/G-ESBR nanocomposites. By increasing the epoxy group content, the number of covalent bonds at the interface increases, contributing to an improvement of the interfacial interaction between the G-ESBR and silica and the dispersion of silica, which were verified and analyzed in detail by bound rubber measurement, transmission electron microscopy (TEM) and rubber process analyzer (RPA). The silica/G-ESBR nanocomposites with improved dispersion of silica and interfacial interaction showed decreased rolling resistance and increased wet skid resistance. The mechanical properties of the nanocomposites were greatly improved with increasing epoxy group contents. The highest tensile strength reached 29.4 MPa at a GMA content of 4.8 wt%, a 55.6% increase compared with that of the nanocomposite without epoxy group.