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 (–SiO4) 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 –SiO2 to –SiO4 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.