Preparation And Property Of Thermally Conductive And Electrically Insulating Polysulfone Composites

Polysulfone has been applied in the national defense industry due to its perfect properties such as large rigidity, high strength, good electric insulation,heat and cold resisting and resistance to aging. Because of low thermal conductivity of polysulfone, change of environmental temperature led to heat accumulation, causing some problems of system instability such as thermal fatigue and stress cracking, which obstruct the exertion of its use performances.In this paper, a new kind of thermally conductive and electrically insulating composite were obtained by mixing hexagonal boron nitride flakes(h-BN),silicon carbide whiskers(Si Cw) with polysulfone, and preparation and performances were studied.Through surface modification of fillers by silane coupling agent A-1100, the effect of surface property of fillers on thermal conductivity of polysulfone composites were studied. The results showed that the optimal conditions of conductive fillers modified as coupling agent 2wt%, p H value 4.5, modification time 2 hours.The mixing methods included melt mixing method, roll-milled mixing method and powder mixing method, and polysulfone composites were molded by hot press molding and injection molding. The effect of mixing method and molding method on the thermal conductivity and insulating property of polysulfone composites were studied. The results indicated that as the internal structures of polysulfone composites prepared with different methods were different, the thermal conductivity also had a great difference. The powder mixing could improve thermal conductivity of polysulfone composites more effectively than the melt mixing and the roll-milled mixing, and the hot press molding was superior to the injection molding. Due to the difference between the thermal conduction mechanism and electrical conduction mechanism, the influence of preparation method on the insulating property of polysulfone composites were contrary to that on the thermal conductivity. With the increase of the filler content, the mechanical properties were reduced.Changing the mass ratio of h-BN and Si Cw, the effect of filler proportioning on the thermal conductivity of polysulfone composites were studied. The results indicated that the binary fillers were dispersed homogeneously and formed thermally conductive networks in polymeric matrix. A striking synergistic effect on thermal conductivity of composite was achieved at a suitable h-BN/Si Cw mass ratio. When the filler content was up to 50wt% with a h-BN/Si Cw mass ratio of 8/2, the thermal conductivity of polysulfone composite was up to 2.728W·m-1·K-1.