Epoxy/silica nanocomposite dielectrics used for vacuum pressure impregnating application

This paper evaluated the influences of silica nanoparticles on the dielectric properties, mechanical performances and glass transformation behaviors of epoxy resin by analyzing the temperature dependence of dc conduction and dielectric loss, impact test results and dynamic mechanical data, respectively. The particular attention was given to the correlation between the glass transformation behaviors, the mechanical performances and the dielectric behaviors. The dispersion of silica nanoparticles and the morphology of the nanocomposite samples were investigated by means of transmission electronic microscopy (TEM) and field emission scanning electronic microscopy (FE-SEM). Our results showed that, though silica nanoparticles could effectively increase the toughness of epoxy resin when the silica content is within 3.0 wt%, the dielectric loss and the dc conductivity increase with the increasing silica content. The understanding of the structure-property relationship in epoxy/silica nanocomposites might enable us to choose proper surface treatment approaches of the nanofiller to gain enhanced properties.