| The rapid development of the electronic information industry has promoted the progress of electronic components towards integration and miniaturization,which has led to the continuous increase of heat power densities.Thus,the service life and security of chips are facing great challenges.Polymer-based thermal interface materials have been regarded as the preferred thermal interface materials for electronic devices due to the advantages of light weight,insulation and easy processing.However,the inherent low thermal conductivity and extremely combustible properties of polymeric materials limit their application in the field of high-performance chips.Therefore,researching and developing polymer-based thermal interface materials with simultaneously excellent thermal conductivity and flame retardancy are of great significance for the development of the electronic industry.In this dissertation,different thermally conductive and flame-retardant filler systems consisting of different types and dimensions of thermally conductive fillers were prepared through hybrid,flame-retardant functionalization and construction of three-dimensional（3D）networks,their epoxy resin（EP）based composites were manufactured.Meanwhile,the influences of the dispersion state of the filler,interfacial interaction and the network structure on the thermal conductivity and flame retardant properties of these composites were investigated.The main works are as follows:（1）EP/SNP/Al2O3/APP hybrid composites were prepared by blending epoxy resin containing silica nanoparticles（SNP）with microspherical Al2O3 as thermally conductive filler and ammonium polyphosphate（APP）as flame retardant.The synergistic effects of SNP,Al2O3 and APP on the thermal conductivity and flame retardant properties of the composites were studied respectively.The results showed that the existence of SNP in EP matrix not only effectively inhibited the settlement of Al2O3 particles during the curing process,but also improved the interfacial interaction between Al2O3 and EP,their synergy increased the thermal conductivity of the composites.At a filler loading of 50 wt%Al2O3,the thermal conductivity of EP/SNP/Al2O3/APP composite was 21.8%higher than that of EP/Al2O3/APP composite.Meanwhile,there was a synergistic flame-retardant effect between SNP and APP on promoting the formation of a high-strength,dense and stable carbon protective layer,which resulted in the significantly improvement in the flame retardancy of EP/SNP/Al2O3/APP composites.The peak heat release rate（PHRR）,total heat release（THR）and total smoke production（TSP）of EP/SNP/Al2O3/APP composites decreased by 69.4%,54.8%and 53.6%compared with EP,respectively.（2）For further improving the thermal conductivity of the composites,liquid crystal epoxy resin（LCER）was used as the matrix,and one-dimensional silver nanowires（Ag NWs）as the thermal conductive filler.Si O2-DOPO@Ag NWs with core-shell nanostructure were prepared by sol-gel method.The effect of Si O2-DOPO coating layer and LCER matrix on the thermal conductivity and flame retardancy of LCER/Si O2-DOPO@Ag NWs composites were studied.The results showed that the thermal conductivity of LCER was 42.9%higher than EP due to its ordered LC structure,while the flame retardantcy of LCER was the same as EP.The Si O2-DOPO coating layer not only promoted the dispersion of Ag NWs in LCER matrix,but also improved the interfacial interaction between Ag NWs and LCER,resulting in the reduced interface thermal resistance.Meanwhile,the Si O2-DOPO coating layer inhibited the endothermic melting and wicking action of Ag NWs during combustion,and promoted the formation of the carbonized protective layer.Thus,the thermal conductivity and flame retardancy of the LCER/Si O2-DOPO@Ag NWs composites were simultaneously improved.When the Si O2-DOPO@Ag NWs content was 4 vol%,the thermal conductivity of LCER/Si O2-DOPO@Ag NWs reached to 1.32 W/m K,and the PHRR,THR and TSP decreased by 8.5%,18.1%and 32.3%compared with LCER,respectively.（3）Based on a simple liquid phase ultrasonic process,the ionic liquid flame retardant non-covalently modified boron nitride nanosheets（ILFR-f BNNS）were prepared in one step.Then the EP/ILFR-f BNNS composites were prepared by using ILFR as curing agent.ILFR improved the dispersion of BNNS and reduced the interface thermal resistance between BNNS and EP,which significantly increased the thermal conductivity of EP/ILFR-f BNNS composite.When the ILFR-f BNNS content was 12.1 vol%,the thermal conductivity of the composite reached to 1.04 W/m K.At the same time,the catalytic carbonization ability of ILFR combined with the physical barrier effect of BNNS significantly improved the flame retardancy of the EP/ILFR-f BNNS composites.The PHRR,THR and TSP of the composites containing 12.1 vol%ILFR-f BNNS decreased by 42.4%,37.7%and 53.0%compared with EP,respectively.（4）Thermally conductive and flame-retardant three-dimensional BNNS-GO-APP（3D BNNS-GO-APP）network skeleton was prepared based on liquid nitrogen freezing and freeze-drying technology,where GO was used to assist in forming stable filler skeleton,BNNS and APP as thermally conductive and flame-retardant filler,respectively.Then the EP/3D BNNS-RGO-APP composites were prepared via vacuum-assisted infiltration of epoxy into 3D BNNS-RGO-APP skeleton and following high temperature curing and reduction.The results showed that the 3D BNNS-RGO-APP network provided an efficient heat conduction path for the heat transfer of the composites,thus significantly improving the thermal conductivity of the composites.The thermal conductivity of EP/3D BNNS-RGO-APP composite was as high as 2.35 W/m K with a 10.8 vol%BNNS content,which was about 12 times higher than neat EP.At the same time,the 3D network framework provided structural support for the carbonization of EP and promoted the formation of a dense and stable carbonization protective layer,which improved the flame retardancy of composites.The PHRR,THR and TSP of the EP/3D BNNS-RGO-APP composites decreased by 28.0%,41.0%and 50.2%compared with EP,respectively. |
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