Thermal Stability of Plasma‐Assisted Film Deposition for Insulation Modification: In View of Hydrophobicity and Flashover Performances

ABSTRACT Polymer insulation exposed to natural environment inevitably face challenges from material ageing and surface insulating degradation. Surface treatment is an effective method to improve material performance, but traditional processing methods such as room temperature vulcanised silicone rubber (RTV) coating, are subjected to coating degradation after long time operation. Herein, we fabricated a stable cross‐linked Si‐containing (–SiO 4 ) film on polymethyl methacrylate (PMMA) insulation via eco‐friendly atmospheric pressure plasma techniques, and verified its thermal stability performance. By addition of hexamethyldisiloxane (HMDSO) and fluorescent agent in plasma, fragmenting–crosslinking of HMDSO as well as surface functionalising by plasma‐enabled reactions lead to the fabrication of fluorescent Si‐containing film. Accelerating ageing test demonstrates that the plasma‐modified PMMA remains steady hydrophobic performance after ageing. Although the surface insulating performance decreases with the ageing, the aged material still remains the higher flashover voltage compared with the original. It reveals that the Si‐containing film could convert thermal oxygen reactions into itself crosslinking process with the shift of –SiO 2 to –SiO 4 groups, which eventually leads to the variation of material surface performance. Overall, the plasma‐assisted Si‐containing film for surface modification has satisfactory thermal stability, which offers a new avenue for insulation enhancement and service life prolonging.