Preparation And Properties Of Polymer-based Thermal Conductive Composites With High Electrial Insulation

Polymeric composites have been wide applied in aerospace,automotive and electronic packing industries because of their excellentcharacteristics such as electrical insulation, light-weight reduction andeasy-processing. Thermal conduction and electrical insulation havebecome a crucial issue for continuing progress in the electronic industryowing to increased levels of dissipated power and design of the nextgeneration of integrated circuits. Therefore, recent increasing importanceof the thermal and electoral insulating properties of materials is explainedboth by practical needs and fundamental science. In this study, two kindsof composites were prepared, using aluminum nitride (AlN) andalumina-coated graphene sheet hybrids (GS@Al2O3) as filler and Epoxyresin (EP) and Polyvinylidene Fluoride (PVDF) as polymer matrix.In the first section, we carried out hyperbranched aromaticpolyamide (HBP) grafting AlN nanoparticles (AlN-HBP). Then thenanoparticles with three different interface structures, i.e. AlN, AlN-APS,and AlN-HBP have been selected as fillers for epoxy composites. It wasfound that the enhanced interactions between nanoparticles and epoxymatrix, especially AlN-HBP nanoparticles, could lead to an improvementin thermal conductivity, thermal stability, electrical insulating properties,Tgs, and dynamical thermomechanical properties when compared withthe composites with AlN nanoparticles. When10wt%AlN-HBP wasadded, the thermal conductivity of Epoxy/AlN-HBP composites wasimproved from0.236W/m K to0.285W/m K at25°C, increasing21%,the glass transition temperature was enhanced10°C and dielectricstrength reached32.87kV mm-1.In the second section, we have successfully designed and fabricatedGS@Al2O3hybrids by an electrostatic self-assembly route and then incorporated into a PVDF matrix to obtain their composites. The uniquestructure of GS@Al2O3hybrids combines the advantages of both GS andAl2O3. The PVDF/GS@Al2O3composites possess not only high thermalconductivity but also electrical insulation. The thermal conductivity ofPVDF composites with40wt%GS@Al2O3filler (mass ratio of GS toAl2O3of1:20) is up to0.586W/m K, and this value is about2foldhigher than that of neat PVDF matrix. Interestingly, PVDF compositeswith high mass ratio of GS to Al2O3(>1:20) possess not only highthermal conductivities but also high electrical resistivity. For instance,the volume resistivity of the GS@Al2O3composites with different massratio of GS to Al2O3(1:20are4.04×1014Ω cm,1:30are8.1×1015Ω·cm)which only decrease by one or two order from the2.5×1016Ω cm of theneat PVDF matrix.