Study on electric properties of epoxy with high mass fraction of alumina fillers

In order to improve the mechanical and thermal properties of the epoxy resin, high mass fraction of micro-alumina has been applied in the epoxy resin which is also considered to be a kind of extender in manufacture. However, the introduction of alumina fillers may cause deterioration of the electric property. In this paper, epoxy with different amounts of the micro alumina fillers ranging from 0 to 300 phr (parts per hundreds of weight of resin) were prepared to investigate their permittivity, dielectric loss, volume resistivity and dielectric strength. The results indicates that the addition of alumina can not only produces interface between matrix and fillers, but also brings impurities into the epoxy, as well as introduces dipole and interfacial polarization to the system. Therefore, the permittivity and dielectric loss of the epoxy system increase and the conductivity of the sample decrease with the addition of alumina fillers. The increase of thermal conductivity and the decrease of the cross linking degree were appeared with the addition of the fillers, along with the defect, leading to the decline of the AC dielectric strength.