Effect Of Nanosilica Modified By Low Temperature Plasma At Low Pressure On Insulation Properties Of Epoxy Resin

Due to the uneven distribution of energy and the increasing demand of electricity in China,the development of ultra-high voltage,large capacity,long-distance transmission has become an inevitable trend,and power equipment also face more complex insulation requirements.Meanwhile,epoxy nanocomposites are widely used in new power equipment because of their simple preparation and significant performance improvement.In this paper,nanosilica was modified by low temperature plasma fluorination and coupling agent at low pressure,and the influence of different content of fluorinated nanosilica on the insulation properties of epoxy resin was studied.Firstly,the experimental platform of low temperature plasma fluorination at low pressure was built,and the discharge characteristics,emission spectrum and plasma temperature of CF4/N2 low temperature plasma at different pressure and voltage conditions were studied.The results showed that the plasma was evenly distributed in the discharge space in the studied pressure and voltage,and its lowest electronic temperature was 0.487 eV,which could break the C-F bond and create conditions for fluorination of nanosilica surface.Then,the modified nanosilica was characterized by XPS,FT-IR and SEM.The parameters reflected that the F element was successfully introduced into the surface of nanosilica in the form of CF2.Finally,the nano-SiO2/epoxy resin composite with a mass fraction of 1-10 wt%was prepared,and its insulation properties were tested before and after thermal aging.As a result,the modified nanosilica has good dispersibility in the epoxy resin.Meanwhile,the partial discharge initial voltage of fluorinated SiO2/epoxy resin reaches 25.2 kV at 5 wt%.In addition,its breakdown field strength is 33.7 kV/mm,and the volume resistivity is 2.5032×1015 ?·cm at 3 wt%content of nanosilica,which is 11.6%and 34.61%higher than that of pure epoxy resin respectively.When the content of the SiO2 modified by low temperature plasma fluorination at low pressure is 1 wt%,the relative permittivity and dielectric loss reache the minimum,which was 0.14 and 0.159%lower than that of the pure epoxy resin.The results of thermal aging experiments show that modified nanosilica can improve the aging properties of epoxy resinIn summary,although the low temperature plasma fluorination at low pressure introduce defects in the material,the introduction of F element can hinder the transfer of carriers.So at low filling amount,it has a positive effect on improving the insulation characteristics of epoxy resin.