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Effect of hydrolyzable chlorine content on dielectric properties of epoxy/Al2O3 composite hygrothermal aging

The electrical insulation performance of epoxy composites decreases seriously after hygrothermal aging, which threatens the safe operation of electrical equipment. In order to explore the effect of hydrolyzable chlorine content on dielectric properties of epoxy/Al2O3 composite hygrothermal aging, the breakdown strength, volume resistivity, relative permittivity and dielectric loss factor of four kinds of epoxy/Al2O3 composites with different hydrolyzable chlorine content were tested after the hygrothermal aging. The changes of these dielectric properties before and after hygrothermal aging were analyzed and explained from the perspective of hydrolyzable chlorine. The results show that after hygrothermal aging, the breakdown strength of epoxy/Al2O3 composite increases at first and then decreases with increase of hydrolyzable chlorine content, the volume resistivity of epoxy/Al2O3 composite decreases continuously with the increase of hydrolyzable chlorine content, the relative permittivity and dielectric loss factor of epoxy/Al2O3 composite both increase with the increase of hydrolyzable chlorine content. These changes in dielectric properties are related to the electron-absorbing properties of hydrolyzable chlorine atom and hydroxyl group formed after hydrolysis.