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Effects of addition of micro-sized silica fillers and/or nano-sized clay fillers into epoxy resin on its dielectric properties were examined. The glass transition intermediate temperature (Jg) was found to show a decrease by the addition of a small amount of nanofillers, while it is increased by the addition of abundant microfillers with and without co-addition of a small amount of nanofillers. At temperatures above T g , the samples with abundant microfillers were added have low conductivity, low dielectric constant, and low dielectric loss factor regardless of the co-addition of nanofillers.

Nano-clay and micro-silica mixed composites were made for use as insulating materials for switchgear. Observation of nano-clay dispersion and measurements of insulation breakdown properties under a homogeneous electric field were conducted of these composites. Moreover, simulations were carried out to estimate the curing reaction and rheological behavior of the composite in an automatic pressure gelation system. Experimental results demonstrated that these composites have suitable material characteristics for practical use in switchgear.

This project develops a nanocomposite insulating material with high insulation performance obtained by homogeneous dispersion of nano-fillers to epoxy resin. This project aims to apply solid insulating technology with nanocomposite material to electric power apparatuses for power distribution such as switchgears.

Recent interests concerning nanocomposites are shifting emphasis from fundamental research to application-oriented research. In this study, nano- and micro-filler mixed composites were made and evaluated toward practical use of nanocomposite insulating materials. Some kinds of the nano-filler/micro-filler combinations such as nano-layered silicate/micro-silica, nano-silica/micro-silica and nano-titania/micro-silica were compared from viewpoints of volume resistivitiy, relative permittivity, thermal expansion and insulation breakdown properties. Comprehensive consideration based on experimental results determined a candidate nano- and micro-filler mixed composites to make trial models. An aluminum conductor and a vacuum interrupter were molded from the nano- and micro-filler mixed composites for the first time in nanocomposite research.

A primary concern in recent nanocomposite research is practical application. In this study, various kinds of epoxy-based nanocomposites were made and their properties evaluated to determine their applicability as insulating materials for heavy electric apparatuses. Experimental results demonstrated that nano-fillers enhance insulation breakdown properties in nanocomposites. Moreover, nano- and micro-filler combinations were adopted as an approach toward practical application of nanocomposite insulating materials. These nano- and micro- filler mixed composites had the same low thermal expansion as aluminum, and insulation breakdown properties superior to those of conventional insulating materials. Consequently, an aluminum conductor and a vacuum interrupter were molded by the nano- and micro-filler mixed composites for the first time in nanocomposite research.

Frequency accelerated partial discharge degradation of epoxy nanocomposite with 5 wt % additions of clay (layered silicate) was evaluated by a rod-to-plane electrode system, and investigated in comparison with that of epoxy without clay. Comparisons were made as to erosion depth using a laser surface profilometer. It was found that the change in the erosion depth is far smaller in specimens with clay than those without clay. It was also found that the solubilization method using acid anhydride curing agent seems to give PD resistance characteristics superior to the organic modification method using amine and acid anhydride curing agents and even to the solubilization method using amine curing agent.

Effects of the differences in the curing agent and filler dispersion method on the dielectric properties were examined for epoxy/clay nanocomposites. Measurements of permittivity, conductivity, and space charge distribution suggest that the curing agent gives a strong effect and the presence of nanofillers affects secondly, while the filler dispersion method gives a weak effect.