Abstract: Silica was modified with hexamethyldisilazane and hexamethyltrisiloxane(D₃) via dry method. The influence of pre-treatment temperature on gel time and mechanical properties of modified silica filled polydimethylsiloxane system wasstudied.Modified silica was examined by Fourier transfor- mation infrared spectroscopy(FTIR)，X-ray photoelectron spectroscopy(XPS),and dispersion in sol vent. The mechanical properties of modified silica filled polydimethylsiloxane system were also investi- gated. The results reveal that Me₃Si-and-Me₂Si moieties were grafted on the surface of silica. When pre-treatment temperature was increased, the gel time of silica filled polydimethylsiloxane system increased and mechanical properties decreased. With silica content increasing, the tensile strength and stress at 100 % elongation increased.

Key words: silica, surface modification, gel time, mechanical property