Thermally Stimulated Current in TiO 2 /Epoxy Nanocomposites With Different Particle Dispersion

Epoxy resin nanocomposites with TiO2, with different particle dispersions, were prepared by separating and removing agglomerates of TiO2nanoparticles using an innovative centrifugation technique. Their thermally stimulated current (TSC) properties and glass transition temperatures (Tg) were measured. Two TSC peaks appear in all samples when a collecting electric field is applied. The TSC peak on the low-temperature side arises due to the depolarization of dipoles, whereas the higher-temperature peak seems to be due to the de-trapping of trapped charges. Furthermore, the TSC peak temperature and Tgmeasured for the nanocomposites with a high particle dispersion are lower than those measured for the unfilled epoxy resin. However, the two temperatures measured for the nanocomposites containing agglomerates are comparable to those measured for the unfilled epoxy resin. To evaluate the effects of particle dispersion state on the energies required to depolarize and de-trap, peak separation was conducted on the whole TSC curve. The energy required for depolarization increases when the nanoparticles are uniformly dispersed but decreases in the presence of agglomerates. Moreover, uniformly dispersed nanoparticles introduce shallow traps, whereas agglomerates introduce deep traps.