Preparation And Properties Of Epoxy Resin Matrix Composites With High Thermal Conductivity And Electrical Insulation

Epoxy resin(EP)has the characteristics of easy processing,high adhesion,and excellent electrical insulation properties.It has a wide range of applications in the fields of motors and electronic packaging,but its thermal conductivity as polymer material is rather poor,which limits the further application of epoxy resin.At present,research on enhanced modification of thermal conductivity of epoxy resin is one of the research hotspots in this field.Boron nitride(BN)is divided into hexagonal boron nitride(h-BN)and cubic boron nitride(c-BN).It has excellent thermal conductivity and dielectric properties and can be used as an ideal thermal conductive filler to fabricate polymeric composite with high thermal conductivity.In this paper,BN nanoparticles were used as fillers and EP was used as matrix to prepare BN/EP composites with high thermal conductivity and electric insulation.The structure of BN/EP composites was analyzed by scanning electron microscopy(SEM)and Fourier infrared reflectance spectroscopy(FTIR).The mechanical,electrical and thermal properties of composites were tested by dynamic mechanical property tester,broadband dielectric spectrum tester and laser thermal conductivity tester.The effects of surface modification methods,crystal structure and particle size on the structure and properties of the composites were systematically analyzed.The experimental results show that the surface modification of BN by KH560 can improve the compatibility between BN and EP more effectively.When the filler content is 20 vol%,the thermal conductivity of the BN-560/EP composite is 7% higher than that of BN-550/EP,which indicates that the crystal structure of h-BN is more suitable as a highly thermally conductive filler for composites than c-BN.The storage modulus and flexural strength of BN-560/EP composites are higher than those of BN-550/EP composites.When the filler content is 20 vol%,the thermal conductivity of h-BN/EP composite is 253% higher than that of epoxy resin,which is better than c-BN/EP composite.Moreover,the flexural strength of h-BN/EP composite is also higher than that of c-BN/EP composite.The storage modulus of h-BN/EP at 140 °C is 149 MPa,which is 513% higher than that of epoxy resin;Results further indicate that BN with large particle size is more suitable as a filler than BN with smaller particle size.When the filler content is 20 vol%,the thermal conductivity of BN/EP composites doped with micron-sized BN is 50% higher than that of BNNs/EP composites doped with nano-BN sheets.Based on the above experimental results,some silver nanowires(AgNWs)with a small content was added to the h-BN-KH560/EP composite to prepare hBN/AgNWs/EP,in order to further promote the construction of the internal heat conduction network in EP resin.The performance test results show that the increase of AgNWs content has little effect on the mechanical properties of hBN/AgNWs/EP composites.After adding AgNWs,the thermal conductivity of composites has been improved to some extent,from 0.34 to 0.37.The amplitude is 9%.The electrical property test results show that the addition of Ag NWs has little effect on the dielectric constant,dielectric loss and volume resistivity of the composite,indicating that the insulation of the composite has not been significantly affected.