Study On Preparation And Properties Of Alumina Filled Polycarbonate Composite

Polycarbonate (PC) is an amorphous thermoplastic with outstanding high unnotched impact strength, high dimensional stability and high heat distortion temperature.So, PC has been widely used in electric motors, television, integrated circuit and other electronic applications. However PC has poor thermal conductivity which restrict its application, so take appropriate methods improve its thermal performance is very important.In this paper, based on industrialized equipments, technics and raw materials, the effect of alumina (Al₂O₃) amount on thermal conductive, mechanical and processing properties of Al₂O₃ filled polycarbonate (PC) composite were studied.As PC is such material sensitive to alkaline Al₂O₃, the incorporation of the second polymer to reduce the impact on PC was useful. In this study, two different types of PC composites were selected.Respectively,one is polycarbonate/polyethylene (PC/PE), immisible system, the other is polycarbonate / hydrogenated styrene-butadiene-styrene block copolymer (PC/SEBS), partially misible system.As for PC/PE/Al₂O₃, the effect of blending procedures, compatibilizers, PC/PE ratios and the content of alumina on properties of the composite were investigated. The PC/LLDPE/PE-MAH composite (5/1/1 mass ratios) containing 40wt% Al₂O₃ processed a 27.2 kJ/m2 of notched impact strength and 0.644 W/m·K of the thermal conductivity. The thermal conductivity of the composite with 60% alumina reached 0.895 W/m·K, which was 3.4 times of that of the PC/PE blend (0.260 W/m·K).As for PC/SEBS/Al₂O₃, sanning electron and rheological dynamic analysis demonstrated that the phase morphology of PC/SEBS blends changed from SEBS dispersed phase in PC matrix to co-continuous phase, on the range of PC/SEBS (85/15⁷5/25 mass ratios). On the basis of this, the effect of blending procedures, SEBS contents and the content of alumina on properties of the composite were investigated. The result showed that two-step method possessed better mechanical properties with high impact strength and thermal conductivity than one-step method. SEM-EDS showed that Al₂O₃ were selective distribution in SEBS phase when take two-step method. Thermal conductivity of the composites increased with the increase of Al₂O₃ content. The thermal conductivity of the composite with 50% alumina reached 0.902 W/m·K, which was 4.3 times of that of the PC/SEBS blend (0.210 W/m·K).We also found that the tensile and bending strength of PC/SEBS/ Al₂O₃ composite decreased with the increase of SEBS content.But notched impact strength increased with the increase of SEBS content. It indicated that the composites possessed higher thermal conductivity with less SEBS content on PC/SEBS co-continuous phase. The PC/SEBS composite (8/2 mass ratios) containing 40wt% Al₂O₃ processed a 0.717 W/m·K of the thermal conductivity.