Thermally Stimulated Current Measurements of Epoxy/TiO2 Nanocomposites

Epoxy/TiO
2
nanocomposites (NCs) with controlled nanoparticle dispersion have been developed. Using these NCs, it has been demonstrated that the impulse and AC breakdown strengths of NCs with agglomerate sizes smaller than 0.5
$\mu\mathrm{m}$
are higher than those of unfilled epoxy resin. To apply these NCs in solid insulators of various power apparatus, it is necessary to ascertain other electrical properties besides their breakdown strength. We measured the thermally stimulated currents (TSCs) of an epoxy/TiO
2
NC with agglomerates size-controlled at 79 nm or less and the unfilled epoxy resin to evaluate the electrical properties near the glass transition temperature. As a result, two current peaks appear in the TSC waveform in each sample. The temperature at the current peak on the low-temperature side corresponds to the glass transition temperature of each sample. The temperatures at the two current peaks of the epoxy/TiO
2
NC are lower than those of the unfilled epoxy resin. By using the dispersion-controlled NC, we have clarified the changes in TSC properties caused by dispersed TiO
2
nanoparticles.