Surface modification of BaTiO3 particles by silane coupling agents in different solvents and their effect on dielectric properties of BaTiO3/epoxy composites

The surface of BaTiO3 particles was modified by 3-glycidoxypropyltrimethoxysilane (GPTMS) to attach epoxy groups on them and to improve their compatibility with epoxy resin. First, in order to analyze the effect of solvents on the degree of surface modification of BaTiO3 particles, the surfaces of BaTiO3 particles were modified with GPTMS in water, ethanol, and xylene at 80 °C. FT-nIR analysis showed that due to the ring-opening reaction, the epoxy group on BaTiO3 particles was reduced after surface modification in ethanol and disappeared after surface modification in water. In contrast, when BaTiO3 particles were modified in xylene, the epoxy groups remained. Then, the relationships among these surface structure differences, viscosity of BaTiO3/epoxy/N-methyl-2-pyrrolidinon (NMP) suspensions, the surface morphologies of BaTiO3/epoxy composites, and the dielectric properties of BaTiO3/epoxy composites were investigated. While there was no relationship between the suspension viscosity and the dielectric properties of BaTiO3/epoxy composites, a BaTiO3/epoxy composite with a smooth surface and high dielectric properties was obtained when the BaTiO3 surface was modified in xylene and the epoxy groups were effectively retained on the surface.