Maxwell–Wagner–Silars relaxations due to glass occlusions in a thermoset composite

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Abstract
Maxwell–Wagner–Silars (MWS) dielectric relaxations have been studied in thermoset composites made with hollow glass microspheres and reinforced with aramid fiber. Over the temperature range reported (140–230 °C) the glass microspheres show a conductivity of 10−10–10−5 (Ω cm)−1 so that MWS loss peaks fall in the 102–105 Hz frequency range. The apparent activation energy for the relaxation is about 20 kcal/mole. The observed MWS relaxation times depend only on temperature and not on volume fraction of microspheres as predicted by MWS theory. Also, the enhancement of activation energy for the relaxation over the activation energy for conduction of the glass seems to be explainable from the standpoint of the frequency and temperature dependence of the glass dielectric constant.