| Epoxy resin（EP）,commonly used in the electrical field,is an import ant solid insulating material,while showing low intrinsic thermal conductivity.Boron nitride（BN）with excellent insulating properties and thermal conductivity was demonstrated as an effective filler to improve the thermal conductivity of epoxy resin.However,directly adding boron nitride into the epoxy resin matrix is difficult to achieve uniform dispersion,and the large interfacial thermal resistance between the filler and the matrix also impacts the effect of enhancing thermal conductivity.Furthermore,too much boron nitride in epoxy resin might damage the material’s mechanical properties,and random dispersion of a tiny quantity of boron nitride filler in the epoxy resin matrix has a limited effect on improving the heat conductivity.The following is the major research in this study:（1）BN was surface-treated by combining covalent modification and non-covalent modification,and The effects of BN dual modification on filler dispersibility,thermal conductivity,thermal stability,hydrophilic and hydro phobic properties and mechanical properties of composites were studied.The strong interfacial interaction of the polydopamine layer and the interaction between the silane coupling agent and the molecular chains in the epoxy matrix are used to promote the uniform dispersion of boron nitride in the matrix and increase the interface affinity.FTIR,XRD,SEM,EDX and dispersion stability tests were carried out on BN before and after modification.The test results confirmed the success of modification.Using EP as the matrix,composite materials with h-BN,KH-BN and KDBN as thermal conductive fillers were prepared respectively.The results show that the double-modified BN has the most significant effect on improving the thermal conductivity.When the content of KDBN is 15wt%,the composite material with KDBN as the thermal conductive filler can obtain a high thermal conductivity of 0.6295 W·m-1K-1.（2）PES/EP composites with phase separation were made employing reaction-induced phase separation（RIPS）between pol yethersulfone（PES）and epoxy resin,and the BN/PES/EP composites were investigated using SEM and XRD.In addition,thermal conductivity and thermal stability performance tests are conducted.The surface and cross-section of PES/EP composites were observed using confocal scanning microscopy and SEM,and the thermal conductivity of different ratios of polyethersulfone additives was investigated.Micron-sized epoxy microspheres were prepared using 30wt%PES/EP composites.Micron-sized epoxy microspheres were made by using 30wt%PES/EP composites.The composite material with micron-scale BN as the thermal conductive filler and the PES/EP composite as the matrix was made.The results showed that micron-sized boron nitride is distributed on the boundary of the PES and EP phases,which is consistent with the theoretical prediction.The thermal conductivity of BN/PES/EP composites is greater than that of BN/EP composites with the same composition,which enables the building of heat conduction channels with tiny numb er of fillers to be realized.（3）Boron nitride nanosheets（BNNS）prepared by liquid-phase mechanical exfoliation method were dual-modified boron nitride nanosheets（KDBNNS）,which is employed to make BN/EP,BNNS/PES/EP,and KDBNNS/PES/EP composites,respectively.Thermal conductivity,thermal management properties,thermal stability,curing behavior,hydrophilic and hydrophobic properties,as well as microscopic morphology,were observed and tested.Three types of BNNS were prepared using liquid-phase ultrasonication,mechanical exfoliation,and liquid-phase mechanical exfoliation,and their microstructures were observed and discussed using SEM and XRD,respectively.The modified BNNS was characterized using FTIR and its dispersion stability was tested.The results show that the addition of PES increases the glass transition temperature of epoxy resin up to 140°C,and enhances its thermal stability.Under the condition of 1wt%filler of BNNS and KDBNNS,the thermal conductivities of composites of BNNS/PES/EP and KDBNNS/PES/EP were 0.2295W·m-1K-1（125.4%of the EP matrix）and 0.2435 W·m-1K-1（133%of the EP matrix）.Combined with the SEM results,it was demonstrated that the 3D filler network of BNNS was constructed by RIPS,confirming the effect of the modi fication on the enhanced interfacial affinity and thermal conductivity. |
