Fundamental Investigation of Dielectric Phenomena in Epoxy Composites during Curing Process under a Uniform Electric Field

This paper deals with the filler movement and the dielectric properties in epoxy composites during curing process under a uniform electric field. For the base epoxy resin, a bisphenol A type epoxy resin and an alicyclic polyamine hardener were used. A plate-like micro-size Al2O3 powder was used as filler. After fully mixing the base resin, fillers, and hardener, they were vacuum-defoamed, poured into a mold having two parallel electrodes, and subsequently heat-hardened. In-situ optical observation and continuous measurements of viscosity and impedance were performed. Broadband dielectric spectroscopy was also carried out after full hardening process. As a result, the formation of chain-like structures of particles is related to both the magnitude of the electric field and its frequency. The dielectric properties of the fluid also impact the formation of chain-like structures.