Abstract: Nano-silica was modified with hexamethyl disilylamine, which was introduced in polyethylene terephthalate (PET) during its synthesis process. The effects of nano-silica on the crystallization behavior, mechanical and electrical properties of PET were studied using Fourier transform infrared spectrometer, thermogravimetry, and scanning electron microscope. It showed that the surface modification reduced the aggregation of nano-silica resulting in finer dispersion. When the content of SiO2 was 0.1 %, the tensile, flexural, and impact strengths of the composites were 12.8 %, 14 %, and 11.4 % higher than those of neat PET, respectively. When the content of SiO2 was 1 %，the crystallization rate was the fastest. With the content of SiO2 increasing from 0.25 % to 1 %, the dielectric constant decreased and the volume resistivity increased gradually.

Key words: nano-silica, crystallization behavior, poly(ethylene terephthalate), mechanical property, electrical property