Fabrication And Properties Of Co-continuous PP/PS Blends Composites With High Thermal Conductivity By Adding Fillers

With the rapid development of technology,the integration and miniaturization are further improved in the fields of microelectronic packaging materials,light-emitting diodes,etc,resulting in a large amount of heat generation and accumulation in the equipment,so in order to effectively avoid the equipment damage and service life shortened owing to overheating of electronic equipment,a kind of polymer-based composite material with high thermal conductivity,simple preparation process and low price is needed to solve this problem.In this paper,modified boron nitride(BN),silicon carbide(Si C)and carbon fiber(CF)are used as thermal conductive fillers,combined with design of co-continuous structure about polypropylene(PP)/polystyrene(PS)blends.The common compounding composites,the coated hybrid filler composites and the in-situ reactive extrusion composites were prepared by the filler selective location.The specific research contents are as follows:1.The polystyrene microspheres were adsorbed on the surface of BN treated with silane coupling agent by in-situ dispersion polymerization,and then BN@PS/(PP/PS)composites were prepared by two-step melt blending with PS and PP.The microstructure and modification of modified BN(BN@PS)were studied by means of electronic scanning microscopy(SEM),X-ray energy spectrum analyzer(EDS),infrared spectrometer and thermogravimetric analyzer(TGA).It was confirmed by SEM that the polystyrene microspheres adhered to the surface of BN successfully and the morphology was intact.The micromorphology of the fractured section of BN@PS/(PP/PS)composites shows that BN is selectively distributed in the PS phase and is uniformly dispersed.In dynamic mechanical properties test,the increase of the storage modulus and the glass transition temperature(Tg)of BN@PS/(PP/PS)system verifies the distribution of BN@PS in PS phase and the stronger interaction with matrix phase.When the content of BN is 10.6 wt%,the thermal conductivity of BN@PS/(PP/PS)three-phase composites is twice that of pure PP,which is 28% higher than that of PP/BN two-phase composites,17% higher than that of BN/(PP/PS)three-phase composites.2.Firstly,The surface of Si C was coated with PS to obtain p-Si C,then mixed with BN@PS(m BN),using co-continuous PP/PS blend as matrix,blended with flaky filler BN and spherical Si C,which is to prepare the coated hybrid filler system composite(p-Si C/m BN/PP/PS).In addition,the ratio of BN and Si C was changed,and In-situ Si C/BN/PP/PS composites were prepared by in-situ reactive extrusion technique.The micro-morphology,dynamic mechanical properties and thermal conductivity of the common compounding system(Si C/BN/PP/PS),p-Si C/m BN/PP/PS system and In-situ Si C/BN/PP/PS system were compared comprehensively.The results show that the dispersion of the filler in the In-situ Si C/BN/PP/PS composite is the best,and the contact between BN and Si C is relatively tight,forming a structure similar to “spider web”;compared with Si C/BN/PP/PS system,the agglomeration of fillers in p-Si C/m BN/PP/PS system is less,and the co-continuous structure is obvious.The composites show an increase in the storage modulus as the amount of filler increases.And the dynamic mechanical properties of the In-situ Si C/BN/PP/PS composites are the best.When the BN and Si C contents are 14.5 wt% and 40 wt%,respectively,the thermal conductivity of the In-situ Si C/BN/PP/PS system is 0.74 W/m K,which is 61% higher than that of Si C/BN/PP/PS system(0.46 W/m K)and 48% higher than that of the p-Si C/m BN/PP/PS system(0.5 W/m K).3.The thermal conductivity,dielectric properties,mechanical properties,thermal stability and dynamic mechanics of the In-situ CF/BN/PP/PS composites were investigated by in-situ reactive extrusion technique adding a mixture of fibrous CF and flake BN thermally conductive fillers.The results show that,compared with CF/BN/PP/PS composites prepared by common compounding,the thermal conductivity of the In-situ CF/BN/PP/PS system reached 0.62 W/m K,in the case of BN content of 14.5 wt% and CF content of 18 wt%,which is 3 times that of PP/PS blend(0.22 W/m K),which is 51% higher than that of CF/BN/PP/PS.At the same time,the dielectric constant in dielectric properties is 9.1,which is also higher than than of CF/BN/PP/PS system(6.9),and dielectric loss and resistivity change little.The tensile strength of In-situ BN/CF/PP/PS system is also significantly stronger than that of BN/CF/PP/PS system,and the thermal stability of former is superior to the latter.At the same filler content,the storage modulus of the In-situ BN/CF/PP/PS composites is higher than that of the BN/CF/PP/PS composites and the peak of the loss factor is smaller.