Performance Evaluation of Insulating Material Prepared From Recycled Anhydride-Cured Epoxy Resin by Alcoholysis

Anhydride-cured epoxy resin (ACER) has excellent performance and is commonly employed as insulation material in power equipment. However, it is difficult to decompose and recycle epoxy resin owing to its 3-D network structure, and conventional waste disposal processes would damage the environment. It is therefore necessary to degrade or even recycle epoxy resin by other techniques. In this article, the chemical degradation of ACER by alcoholysis reaction is realized under mild conditions within a short time, and the degraded epoxy resin (DER) is utilized to replace part of the bisphenol A diglycidyl ether (DGEBA) to prepare new epoxy resins, which can save carbon emissions and benefit the environment. Additionally, the effect of DER content on the insulation, mechanical, and thermal properties is investigated. Meanwhile, ab initio calculations are made on the electrostatic potential, energy level distribution, and dipole moment of the alcoholysis products. The results indicate that the reprepared resins still maintain excellent insulation properties when the content of DER replacing DGEBA is less than 15 wt%, nevertheless, the tensile strength, bending strength, and glass transition temperature decrease with the addition of DER, which is related to the decline in the crosslinking density of the resins. Besides, the small-molecule product (SMP) of alcoholysis has electronegativity and induces an electron trap level in the reprepared resins, playing a role of 'voltage stabilizer,' which could be the explanation for why the electrical performance remains outstanding. It is worth adding that the performance of the reproduced resins is evaluated by relevant standards, and it is believed that the resins with various DER contents can be applied to different working conditions.