Study On Compatibilization And In-situ Assembly Of BN/Al₂O₃ Polypropylene Composite

With the rapid development of microelectronics integration,light-emitting diode（LED）,aerospace,home appliances and auto parts,the integration of electronic components is getting higher and higher,and the effective heat dissipation of devices is related to its operation stability and service life.Adding a large number of thermal conductive fillers to the polymer substrate is an effective way to improve the thermal conductivity of the composite,but the excessive introduction of thermal conductive fillers will reduce the mechanical properties of the composite.In this paper,the effects of compatibilization and in-situ assembly of thermal conductive fillers on the properties of polypropylene thermal conductive insulation composite are studied（1）Boron nitride（BN）and aluminum oxide（Al₂O₃）thermal conductive fillers treated with（3-aminopropyl）triethoxysilane（KH550）showed that the grafting rate of the coupling agent was 0.46%by TG.Using PP-g-MAH as compatibilizer,the effects of compatibilizer dosage,processing conditions and heat conduction dosage on the thermal conductivity,mechanical properties,electrical properties and micro morphology of PP composite were studied.The results showed that the dosage of PP-g-MAH was 4 g,screw speed was 300 rpm,homogenization temperature was200℃,heat conduction filler dosage was 40%The tensile strength and thermal conductivity of the composite are 18.2 MPa and 0.6 W/（m·K）,respectively.（2）BN（KH550-BN）and Al₂O₃（KH560-Al₂O₃）were treated with KH550,γ-glycidyl ether oxypropyl trimethoxysilane（KH560）,respectively,to obtain BN（KH550-BN）with amino group and Al₂O₃（KH560-Al₂O₃）with epoxy group;XPS showed that the coupling agent was grafted on the surface of the thermal conductive powder by chemical bond,TG showed that the grafting ratio of KH550-BN and KH560-Al₂O₃were 0.53%,respectively and 0.87%.The effects of catalyst dosage of2,4,6-trimethylaminomethyl-phenol（DMP-30）,material residence time（screw speed）and homogenization temperature on heat conduction,mechanics and volume resistance of the composite were studied by filling polypropylene with KH550-BN and KH560-Al₂O₃,and then the in-situ assembly effect of KH550-BN and KH560-Al₂O₃was discussed.The results show that when the catalyst dosage is 4 g,the screw speed is 300 rpm,the homogenization temperature is 200℃,and the volume loading is 16.53%,the comprehensive properties of the composite are better,the thermal conductivity and tensile strength are 0.61 W/（m·K）and 17.0 MPa respectively.KH550-BN and KH560-Al₂O₃were pre assembled in liquid paraffin and filled into polypropylene to obtain pre assembled samples.The thermal conductivity and micro morphology of blank samples,pre assembled samples and in-situ assembled samples（SEM photos）show that the in-situ assembly reaction of KH550-BN and KH560-Al₂O₃takes place in the polypropylene melt,which is beneficial to the improvement of the thermal conductivity of the composite.The blank sample and in-situ assembled sample were tested by DMA.The results show that the assembled sample has high thermal conductivity and low loss factor.