Enhanced surface insulation for SiO2/epoxy resin composites through co-modification of nanofiller with silane coupling agent and plasma

Abstract To enhance the surface insulation properties of SiO 2 /epoxy resin composites, the SiO 2 filler is co-modified with a chemical method and dielectric barrier discharge plasma in this work. The effects on the micro-structures, electrical parameters and surface insulation properties of the materials are studied. The results show that chemical modification using the silane coupling agent (KH550) can effectively introduce organo-functional groups into SiO 2 filler. On the other hand, plasma modification shows little effect on the organo-functional group but significantly increases the dispersity of the nanoparticles, therefore reducing filler conglobation in epoxy resin composite. The composite samples with SiO 2 doping concentration of 1 wt.%, 2 wt.%, 3 wt.%, 5 wt.% and 7 wt.% are prepared and characterized. It is found that the synergy of chemical and plasma methods could significantly improve the surface insulation of composite samples. Through doping 2 wt.% of the co-modified SiO 2 filler, the direct current flashover voltage of the composites in dry air at atmospheric pressure can be increased to 1.53 times of the pure epoxy. The enhanced surface insulation properties are explained by the trap effect and the change of electrical parameters through the co-modification process.