Thermal Conductivity And Electrical Insulation Of Unsaturated Epoxy/Aluminum Nitride Composites

In recent years, the insulating thermal conductive polymeric composites with excellent electrical insulating performance and high thermal conductivity had attracted a great deal of attention and been widely used in electrical and electronic industry for electronic packaging and components cooling. In this dissertation, a type of thermal conductive and electrical insulating epoxy matrix composites were prepared by sand mill with unsaturated epoxy as matrix and the inorganic aluminum nitride (AlN) ceramic particles as thermal conductive filler.The rheological behaviors of unsaturated epoxy/AlN system were analyzed through rotational rheometer. The effects of size and content of fillers on the micro-structure, thermal stability, volume resistivity and thermal conductivity of composites were investigated systematically by means of x-ray diffraction, scanning electron microscopy, thermo-gravimetric analyzer, high resistance meter,thermal conductivity tester, etc. Moreover, the thermal conductivity experimental values were compared with the simulation analysis results from different thermal conductive model. Based on experimental results, the conclusions were drawn as following:The micro-level aluminum nitride particles can be dispersed uniformly in the unsaturated epoxy by means of sand mill, and the crystalline structure of AlN isn't changed during the dispersion and curing process of unsaturated epoxy/AlN system. The addition of aluminum nitride decreases the flow property of unsaturated epoxy composites, and the influence of the temperature on rheological behaviors of composites is evident. At same time, the unsaturated epoxy/AlN composites at high filler content exhibit non-Newtonian shear-thinning behaviors, in which the viscosities decrease sharply with increasing shear rates. Meanwhile, the aluminum nitride improves the thermal stability and volume resistivity of unsaturated epoxy/AlN composites while reduces slightly the dielectric loss and electric breakdown strength of the composites.Adding aluminum nitride particles can effectively improve the thermal conductivity of unsaturated epoxy composites. When the mass fraction of AlN is up to 66.4%, the thermal conductivity of the composites achieves 0.43W/(m·K), which improves 1.4 times comparing with the neat epoxy.The sizes of AlN particle impact evidently the thermal conductivity of unsaturated epoxy/AlN composites. At low filler content, the composites with large sized aluminum nitride shows better thermal conductivity while the composites with small sized aluminum nitride reveals more excellent thermal conductivity when the loading of composites is higher. When comparing the thermal conductivity experimental values of the composites with the prediction results from some typical thermal conductive model, it is found that Bruggeman's and Hamilton-Crosser's equation can predict well the thermal conductivity of unsaturated epoxy/AlN composites.