Electrical Treeing Breakdown Voltage of Epoxy/Hollow-silica Nanocomposites

The relative permittivity of epoxy nanocomposites (NCs) containing hollow silica nanoparticles (epoxy/hollow-silica NC) is lower than that of the unfilled epoxy resin. The low permittivity in hollow silica nanoparticles is caused by the nanometric pores present in them; however, the effect of nanometric pores on the dielectric breakdown strength is unclear. In this study, we investigated the electrical treeing breakdown voltage (BDV) of epoxy/hollow-silica NC and compared it with that of the unfilled epoxy resin and epoxy nanocomposites containing solid silica nanoparticles (epoxy/solidsilica NC). The average size and the particle porosity of the hollow silica nanoparticles were approximately 100 nm and 48 vol%, respectively. The filler volume fraction of the silica nanoparticles in the NCs was 5 wt %. The breakdown test was performed using a needle-plate electrode with a gap of 3 mm. The average BDV of the epoxy/hollow-silica NC was almost the same as that of the unfilled epoxy resin and epoxy/solid-silica NC. These results suggest that the nanometric pores in the epoxy/ hollow-silica NC did not behave as defects to reduce the treeing BDV.