Surface Repairing of Damaged EPDM Insulation by Ar/Styrene Plasma Treatment

In order to repair the surface properties of cracked ethylene propylene diene monomer (EPDM) without any impurity element addition, an atmospheric pressure plasma jet (APPJ) repair system with C-H based media (styrene) was established and surface characterization tests are carried out. The results show that a typical polystyrene film is fabricated on EPDM surface after Ar/styrene APPJ treatment, and the surface hydrophilicity is improved significantly, where the water contact angle decreases from 104.21° to 9.79°. In addition, cracks on EPDM surface can lead a decrease in the flashover voltage, but the plasma treatment recovers the electrical properties of the damaged EPDM from 10.2 to 13.4 kV. It is noted that the styrene addition in plasma has a significant effect on EPDM surface properties, where the best modification effect generally occurs at the appropriate medium concentration (20 mL/min). Plasma-driven polymerization of styrene results in the C-H containing films on EPDM surface, which accounts for improvement of hydrophilicity and recovery of electrical insulating properties.