Study On Properties Of BN-Tungsal Anhydride-Epoxy Resin High Thermal Conductive Insulation Composite

In recent years,EHV/UHV DC transmission technology has been continuously developed,which has higher requirements for the capacity of large generators.The increase in capacity of large generators will cause heat accumulation,resulting in problems such as shortened service life and high manufacturing costs.In order to solve the above problems,this paper introduces a method to improve the thermal conductivity of the generator stator bar insulation adhesive,and gives a high thermal conductivity insulating composite material based on the tungsten anhydride-epoxy resin matrix and BN as the filler.Preparation method,and analysis of thermal conductivity and electrical properties of the composite.Firstly,the experiment was designed by orthogonal experiment method,which reduced the number of experiments and improved the experimental efficiency.Secondly,the protective heat flow method was used to test the filling of different particle size BN particles in tungsten anhydride-epoxy resin adhesive.The thermal conductivity of the composite material was analyzed to find the critical value of the powder addition amount when the thermal conductivity was rapidly increased,and the composition of the composite filler with the best thermal conductivity was determined.Again,the composite materials of different components were detected by frequency domain dielectric spectroscopy.The variation of relative dielectric constant and dielectric loss at different frequencies and different temperatures focused on the difference in dielectric properties between the best thermal conductivity samples and pure matrix samples.At the same time,the difference of breakdown resistance between the composites and the pure matrix materials was compared.Finally,the dispersibility of BN particles in the epoxy matrix and the bonding state between the particles were detected by scanning electron microscopy(SEM).The research shows that the thermal conductivity of composites increases with the increase of fillers.When the filler content is 68.74%(BN powder quality accounts for the mass of tungsten epoxy adhesive),the thermal conductivity of composites increases rapidly.When the mass ratio of BN particles with particle size of 5μm,BN particles with particle size of 10μm and Tungsten anhydride-epoxy resin reaches 9:5:10,the thermal conductivity of the composite is the best and the thermal conductivity is reached.2.27 W/(m?K),which is about 13 times that of pure epoxy.The relative dielectric constant and dielectric loss of the best thermal conductivity composites do not change much at the power frequency compared with the pure matrix samples.The strength is 192kV/mm,which is about 29% lower than that of the pure matrix sample.The electrical properties can meet the actual production requirements.In the SEM image,it can be seen that the BN dispersibility and bonding state are good,and the composite heat is proved from the microscopic point of view.The reason for the increase in conductivity.