Enhanced surface-insulating performance of EP composites by doping plasma-fluorinated ZnO nanofiller

The surface flashover of epoxy resin (EP) composites is a pivotal problem in the field of high-voltage insulation. The regulation of the interface between the filler and matrix is an effective means to suppress flashover. In this work, nano ZnO was fluorinated and grafted using low-temperature plasma technology, and the fluorinated filler was doped into EP to study the DC surface flashover performance of the composite. The results show that plasma fluorination can effectively inhibit the agglomeration by grafting –CF_x groups onto the surface of nano-ZnO particles. The fluorine-containing groups at the interface provide higher charge binding traps and enhance the insulation strength at the interface. At the same time, the interface bond cooperation caused by plasma treatment also promoted the accelerating effect of nano ZnO on charge dissipation. The two effects synergistically improve the surface flashover performance of epoxy composites. When the concentration of fluorinated ZnO filler is 20%, the flashover voltage has the highest increase, which is 31.52% higher than that of pure EP. In addition, fluorinated ZnO can effectively reduce the dielectric constant and dielectric loss of epoxy composites. The interface interaction mechanism was further analyzed using molecular dynamics simulation and density functional theory simulation.