Study on the Effect of Absorbing Moisture of Anhydride Curing Agent on the Dielectric Properties of Epoxy Resin Insulation Materials

Anhydride curing agent is one of the most commonly used curing agents for the preparation of epoxy resin insulation materials, but it is easy to absorb external moisture during production, transportation and storage, which affects the dielectric properties of the final prepared epoxy resin insulation materials, due to the hydroscopicity of anhydride. In order to explore the effect of absorbing moisture of anhydride curing agent on the dielectric properties of epoxy resin insulating materials, the samples of methyltetrahydrophthalic anhydride of different mass after hygrothermal aging were added to the pure methyltetrahydrophthalic anhydride as the moisture absorption impurities, and four kinds of anhydride curing agents with different content of moisture absorption impurities were obtained. The infrared spectrum of anhydride before and after absorbing moisture, the heat flow of epoxy resin crosslinking reaction, and the dielectric properties of epoxy cured material such as relative permittivity, dielectric loss factor, breakdown strength and surface resistivity were measured and analyzed. The experimental results show that the relative permittivity and dielectric loss factor of epoxy resin insulation material increase, and the breakdown strength and surface resistivity decrease with the increase of the content of moisture absorption impurities in anhydride curing agent, resulting from the influence of the water molecules and the carboxylic acid, which be brought by the acid anhydride after absorbing moisture.