Multi-effects of atmospheric He/CF₄ plasma jet treatment on the surface properties of epoxy resin

Surface fluorination by low-temperature plasma treatment is proved to be a useful method to improve surface electrical strength of insulating materials. The electrical performances of modified materials deeply depend on the operation parameters during surface modification. It is necessary to find out the physical and chemical changes on the surface properties of modified materials systematically combined with different parameters. In this paper, an atmospheric pressure plasma jet (APPJ) fed with He/CF₄ mixtures is utilized for treatment of epoxy resin (EP). The surface properties of modified epoxy resin are evaluated by the water contact angle (WCA), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The results show that the He/CF₄ APPJ has multi-effects on the surface properties of epoxy resin. It means that some different changes are found under different operation parameters. The multi-effects are mainly caused by the various physical and chemical processes in the interface between plasma and material surface, and they can be adjusted by changing the plasma exposure time, the applied voltage and the CF₄ volume fraction. The results can offer an evidence for the mechanisms of the enhanced surface electrical strength using plasma-based surface fluorination.