Investigation Of The Thermal Conductivity And Electrical Property Of Epoxy Resin With Nano Or Micro Alumina Fillers

With the elevation of the operating voltage and power class of electricaldevices, epoxy composites are increasingly important for electrical devices ofelectrical industry with high electrical insulation and thermal conductivityrequirments because of its good performances on thermal conductivity andelectrical insulation. On the basis of surveying of the relative literatures aboutelectrical insulation and thermal conductivity on epoxy composite material,micro and nano alumina fillers are filled into pure epoxy resin to prepareepoxy nanocomposite and microcomposite. The properties of epoxycomposite on thermal conductivity, short time breakdown strength, impedanceon electrical tree have been researched.The thermal conductivity of epoxy resin is obviously elevated filled withhigh percents of micro alumina filler. With the20wt%micro alumina thethermal conductivty of micro composite is163percents of pure epoxy resin while the5wt%nano alumina do not obviously elevate the thermalconductivity of epoxy resin because of the low weight percents of nanoalumina filler. The breakdown strength of epoxy resin is reduced by40%filled with20wt%micro alumina filler. The breakdown strength of epoxyresin and epoxy microcomposite is reduced by10%filled with2wt%nanoalumina filler while improved by5%filled with5wt%nano alumina filler.This phenomenon is related to the influences between nano or micro aluminafiller and epoxy resin.The step-up voltage method has been chosen as the method to research theinfluence of various kinds of samples on the development of electrical trees.The micro alumina epoxy composite has a higher ability of impedance onelectrical tree growing than the nano alumina epoxy composite. The ability ofimpedance on electrical tree growing has not been obviously improved whennano alumina filler is filled into it and even has been reduced when the radiusof the needletip of nano alumina sample is50m. The ability of impedanceon electrical tree growing is reduced when the ratio of nano alumina filler andmicro alumina filler in nano and micro epoxy composite is high and improvedwhen the ratio is approprite.20wt%micro,0.5wt%nano alumina epoxycomposite and5wt%micro epoxy composite have a better property on theimpedence on the growth of electrical trees. The above two kinds of samples have not been broken under the voltage of37.5kV for ten minutes. Dendritictrees could be initiated in pure epoxy while Bush-like trees could be initiatedin nano alumina epoxy composite.The ability of impedance on electrical tree growing is improved when theratio of nano alumina filler and micro alumina filler in nano and micro epoxycomposite is approprite and the ability of impedance on electrical treegrowing and breakdown strength are improved at one time.