Research On Thermophysical Properties Of Hexagonal/Cubic Boron Nitride/Epoxy Resin Composite Insulation Material

The development of high thermal conductivity epoxy resin composite materials used in the field of UHV electrical equipment and electronic packaging is of great significance for improving the heat dissipation and heat resistance of the equipment.Boron nitride(BN)has received extensive attention due to its high thermal conductivity and good chemical stability,especially polymer composites with fillers.In this paper,a cell model of hexagonal boron nitride/epoxy resin(hBN/EP)composites was established by finite element method,and the effects of filler volume fraction,filler diameter,and filler tilt distribution on the thermal conductivity of composite materials were studied,and compared with the trends of the theory models to verify the feasibility of the theoretical model for predicting the thermal conductivity of the hBN/EP composite cell model.At the same time,using epoxy resin(EP)as the matrix,hexagonal boron nitride(hBN)and cubic boron nitride(cBN)as fillers,hBN/EP,modified hBN(mhBN)/EP and hBN/cBN/EP composites were prepared,the main research work as follows:Firstly,the cell model of hBN/EP composite material under different volume fractions of the filler was established,and its thermal conductivity was calculated and compared with the calculated value of the theoretical model.Secondly,the cell model of hBN/EP composite material under different diameters of the filler was established.The simulated thermal conductivity was compared with the trend calculated by the theoretical model.Finally,the cell model of the hBN/EP composite material under different inclination angles of the filler was established,and the simulated thermal conductivity was analyzed and compared with the thermal conductivity calculated by the theoretical model.The hBN/EP composites,mhBN/EP composites,hBN(1,5-10?m)/EP dual-particle composites,hBN(1,5-10?m)/cBN(1,10?m)/EP composites materials and its corresponding hot-pressed composite materials were prepared through experiments,and characterize and test their microscopic morphology,infrared spectroscopy,thermal stability and thermal conductivity.According to the thermal conductivity characterization test results,the thermal conductivity of hBN/EP composite is 0.444W/m·K when the filler mass fraction is 30%,which is 2.3 times that of pure epoxy resin,mhBN under the same mass fraction the thermal conductivity of the /EP composite is 0.456W/m·K,which is slightly higher than that before the modification,for the hBN/cBN/EP composite,when the filler mass fraction is less than 20%,the thermal conductivity is improved less,and the thermal conductivity of the composite material increases rapidly when it is greater than 20%,for the hBN/cBN/EP hot-pressed composite material,when the filler mass fraction is 30%,the in-plane thermal conductivity is 1.32W/m·K,which is much larger than the normal heat conductivity.According to the infrared characterization results,the silane molecules were successfully grafted to the surface of BN.According to the microscopic morphology results,the cross-section of mhBN/EP composite material is smoother than that of hBN/EP composite material,which shows that modification can improve the compatibility of the filler in the matrix,and multi-particle mixing can also improve the filler content.The degree of dispersion in the matrix.According to the results of thermal stability,the addition of cBN and hot pressing can significantly increase the glass transition temperature of epoxy resin.In addition,surface modification and mixing of different particle size fillers can also increase the glass transition temperature of epoxy resin.