Preparation And Characteristic Of BN/Silicon Rubber Composites

With the rapid development of electronic industry,the electronic components are becoming more and more integrated,and the heat dissipation of the electronic equipment has become the bottleneck of the continuous development of the electronic equipment.Silicone rubber is a kind of electronic potting material with excellent processability,thermal stability,but its low thermal conductivity seriously restricts its wider applications.Therefore,the researchers focus on silicone rubber with good comprehensive properties.The purpose of this paper is to fill the silicone rubber matrix with h-BN as a high thermal conductive filler to prepare composites with high thermal conductivity.The effects of BN content,geometry,modification and orientation on the microstructure,thermal conductivity and other properties of the composites were investigated.Firstly,the influence of h-BN content and aggregation state on the composite was studied.The results show that the viscosity of BN/ silicone oil mixture increased rapidly,and the thermal diffusivity and thermal conductivity also increased with the increase of h-BN content.The maximum values are 0.195 mm2/s and 0.785W/(m·K).For the two aggregation states of globular BN and flake BN,the viscosity of globular BN is smaller,which is beneficial to the practical use of composite materials.The thermal conductivity of flake BN composite is higher,the highest thermal conductivity is 0.785 W/(m·K),and the highest thermal conductivity of globular BN composite is 0.681 W/(m·K).BN microfilms were prepared by ball milling,and the composites with 10 wt.%different BN filler were prepared.The results show that ball milling can make filler thinner and thermal conductivity of composite become better.In the experiment,the relationship between the thickness of BN filler and the thermal conductivity of BN/silicone rubber composite has a primary function.The optimum thermal conductivity appears in the composite material filled by the 3h milled filler,with a thermal conductivity of 0.415 W/(m·K),which is increased by 26.7% compared to non ball milled materials.The filler of composite was modified by silane coupling agent.The morphology and properties of composites with different interfacial strength obtained by different silane coupling agents were investigated.The strong interaction interface composite obtained by KH-171 has the best properties,and the thermal conductivity reaches0.414 W/(m·K),which is 26.6% higher than that of the blank control group.The influence of the amount of silane coupling agent on the morphology and properties of the composite was also studied.When silane coupling agent /BN was 1 wt.%,the composite exhibited the highest thermal conductivity of 0.414 W/(m·K)(treated by KH-171)and 0.363 W/(m·K)(treated by KH-550).The oriented BN/ silicone rubber prepolymer slice was prepared by rolling,and the BN/ silicone rubber composite with orientation is obtained by arranging the prepolymer slices crosslink.SEM and XRD demonstrate the orientation of BN microchip in composites.Thermal conductivity tests show that the thermal conductivity in the alignment direction is 0.337 W/(m·K),which is 22% higher than that of the non oriented composite.The oriented composites with different BN content were prepared.The maximum amount of BN filler reached 40 wt%,and the thermal conductivity was 0.901 W/(m·K),which was 5.2 times of the thermal conductivity of pure silicone rubber.