With the increase of grid capacity and voltage level,the insulating properties of epoxy composite insulation materials is crucial to the safe and stable operation of electrical equipment.Long-term high temperature and high humidity will lead to a serious decline in insulating properties of materials.Nano-SiO2 was fluorinated(F-SiO2)by the plasma technology of dielectric barrier discharge(DBD)in this paper,and fluorine-containing groups were successfully grafted on the surface of nano-SiO2.The high-temperature and humid state of the material was simulated by the wet heat ageing experiment,and the surface flashover,charge dissipation characteristics and trap distribution characteristics of the samples at different ageing stages were tested.The effect of doping F-SiO2 on the wet heat ageing resistance of epoxy composites was explored,and the inhibition mechanism of F-SiO2 on the water intrusion was revealed from the molecular scale in combination with MD simulation.The experimental results show that doping F-SiO2 reduces the saturated moisture absorption of epoxy composites by 16.16%,increases the surface flashover voltage by 13.06%,and can continue to maintain high insulating properties after wet heat ageing.The simulation results show that F-SiO2 can reduce the free volume fraction of epoxy resin and the mean square displacement of water molecules,and enhance the barrier effect of epoxy composites on moisture.Plasma technology can graft fluorine elements onto the surface of nano-SiO2,effectively inhibiting the intrusion of moisture and enhancing the surface insulating properties of epoxy composites in a humid state.
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