Effect of DBD Plasma Deposition of Fluorine Elements on the AFEP Insulation Performance

Gas-insulated switchgear (GIS) is a key piece of equipment in ultrahigh-voltage (UHV) substations. As its core component, the performance of the insulation rod directly determines the operational reliability of the equipment. Aramid fiber-reinforced epoxy resin composite (AFEP) material, due to its excellent insulation and mechanical properties, has become an ideal material for insulation rods. However, aramid fibers have low surface activity and poor interfacial bonding with epoxy resin, which can easily induce partial discharges. Therefore, this article proposes a dielectric barrier discharge (DBD) plasma element deposition modification scheme. Using CF4as a precursor, aramid fibers were modified through the physical etching and chemical grafting effects of plasma. The influence patterns and regulation mechanisms of plasma fluorine element deposition on the interfacial bonding characteristics and insulation properties of AFEP were studied. The results show that plasma can graft fluorine-containing groups onto the surface of aramid fibers, forming a fluorinated layer. This enhances the interfacial bonding strength through chemical bonding and physical anchoring effects, with the interlaminar shear strength (ILSS) increasing by up to 45.19%. Meanwhile, fluorination is beneficial for increasing trap energy levels and significantly improving the breakdown field strength, with a maximum increase of 71.1%. Combined with molecular dynamics simulations, the mechanism by which fluorine element deposition affects insulation properties was revealed.