Comparison of the effects of nanofiller materials on the dielectric properties of epoxy nanocomposites

Composites of organic polymers and well-dispersed nm-sized inorganic fillers, called polymer nanocomposites (NCs), have been attracting much attention as new electrical insulating materials. In this paper, experimental results on the typical dielectric properties, namely, complex permittivity (ε_r\´ and ε_r"), conductivity, and thermally stimulated depolarization current (TSDC) are evaluated for bisphenol-A epoxy resin and its NCs with boehmite alumina, titania, and silica. The increase in ε_r\´ and ε_r" and the magnitudes of the TSDC peaks as well as the increase in conductivity appear more significantly in the NCs with boehmite alumina and titania and less significantly in the NCs with silica than in epoxy resin. This indicates that the silica nanofillers give the best results as far as these properties are concerned. The suppression of molecular motion by the addition of nanofillers seems to work effectively in the case of silica, while the nanofiller addition is likely to accelerate the motion of ionic carriers and/or that of dipoles in the case of boehmite alumina and titania.