On the volume resistivity of silica nanoparticle filled epoxy with different surface modifications

It was found that metallic oxide nanoparticles may positively influence insulation properties of polymers working under high electric field. Herewith, four kinds of surface-modified silica nanoparticles were employed to fabricate epoxy nanocomposites. The surface properties of nanoparticles were characterized by Fourier-transform infrared spectroscopy, thermogravimetric analysis and contact angles. The effects of surface modification, filler fraction and test temperature on volume resistivity (ρv) of epoxy nanocomposites were studied. It was found that, at different test temperatures, the long-alkyl-modified nanoparticles resulted in higher ρv values of epoxy and less ρv sensitivity to temperature, compared to the short-alkyl-modified and hydroxyl-modified ones. The surface polarity of nanoparticles was found to correlate with the ρv values well. The surface modification may cause two possible mechanisms that affect the ρv values of the epoxy: (i) to offer the nanoparticles different levels of water absorption; (ii) to change the Maxwell-Wagner-Sillars polarization behaviors of the composites.