Study on the ageing effect of alumina/epoxy composites modified by atmospheric plasma jet

Abstract Alumina/epoxy resin (Al₂O₃/EP) composite material is widely used in the manufacture of insulators. However, the operation environment of long‐term high‐voltage direct current will destroy Al₂O₃/EP surface insulating performance. In this article, Al₂O₃/EP was modified by atmospheric pressure Ar and Ar/CF₄ plasma jet, and its aging effect was studied by investigating the physicochemical characteristics and the electrical performances of the sample 0 ~ 100 days after modification. The experimental results show that after plasma treatment the surface roughness of the material increases; the O/C ratio on the surface of the material increases after Ar treatment, and the F element is grafted on the surface after Ar/CF₄ treatment. These changes lead to the increase of surface energy and hydrophilicity, and the improvement of electrical performance. The surface properties change within 100 days owing to the oxidation reactions and the variability of recombination chemical bonds and molecular chains after high‐energy plasma treatment. The surface O/C ratio of the materials treated by Ar plasma is obviously reduced, the hydrophobicity is restored to some extent, and the electrical properties are also obviously weakened. In comparison, the properties of Ar/CF₄ plasma‐modified materials do not change significantly.