Filler fluorination of nanoTiO₂/ER composites and their surface insulation properties: a comparison of dielectric barrier discharge and chemical solution fluorination

NanoTiO₂/epoxy resin composites, a kind of dielectric materials with excellent thermal, mechanical and electrical properties, has extensive promise in the insulation area of power system. Although the semiconductor property of TiO₂ filler can suppress the electric field mutations in the epoxy insulation devices, the doping of TiO₂ will have bad influence on the charge transmission, thus weakening the surface insulation. To solve this problem, filler fluorination with dielectric barrier discharge (DBD) plasma and chemical methods were designed to modify the TiO₂ filler. The effects of two fluorination methods on the micro-structures, electrical parameters, and insulation properties of the materials were studied. The results have shown that both DBD plasma and chemical fluorination methods can effectively introduce fluorine into TiO₂ filler and its epoxy composites, decreasing its dielectric constant and volume resistivity. Through doping the fluorinated TiO₂ nanoparticles, the direct current flashover voltage and charge dissipation rate of the composites can be at best increased to 1.5 times and 4.6 times of the pure epoxy, respectively. The enhanced surface insulation properties were explained by the trap effect and the change of electrical parameters (containing dielectric constant and volume conductivity) brought by fluorination treatments. The study results of two types of filler fluorinations have guiding significance for nano-modification of epoxy insulation composites. (paper)