Research on the Recycling of EP/Al₂O₃ and its Insulation Performance after Reconstitution

Epoxy resin/alumina (EP/Al₂O₃) employed in GIL is challenging to degrade and recycle due to its insoluble and infusible properties. This paper uses a chemical recycling method, i.e., alcoholysis, to degrade EP/Al₂O₃ under mild conditions, aiming to improve sustainability and alleviate environmental pressure. Degraded EP (DEP) and recycled Al₂O₃ powders can be reused for the preparation of new epoxy composites, and the catalyst used in the alcoholysis reaction is still reactive. The occurrence of the alcoholysis reaction is verified through nuclear magnetic resonance. Meanwhile, the microscopic morphology of the recycled Al₂O₃ powders is observed by scanning electron microscopy. It is found that both the particle size distribution and micromorphology remain basically unchanged. DEP is utilized instead of 15 wt% bisphenol A diglycidyl ether, and the recycled Al₂O₃ powders are reused to prepare new epoxy composites. The insulating properties of the new EP/Al₂O₃ are investigated and found to be comparable to the original sample in terms of resistivity, AC breakdown strength, and impact flashover voltage. Because the addition of DEP slightly increases the deep trap density and energy level center, the new EP/Al₂O₃ still maintains excellent insulating properties. The increased relative permittivity and dielectric loss in DEP are due to the highly polar ester group and some branched chains in DEP. This paper focuses on the degradation and reuse of EP/Al₂O₃ to offer insights into the recycling process of epoxy composites.