纳米Al_2O_3分布对Al_2O_3/PE-EVA复合材料导热性能与力学性能的影响

旨在将纳米Al2O3分散在聚乙烯(PE)和乙烯醋酸乙烯共聚物(EVA)的共混物中,构建具有选择性分布结构的局域高粒子浓度导热复合材料。采用纳米Al2O3为导热填料,以PE和EVA为基体树脂,使用熔融共混法制备了Al2O3/PE-EVA导热复合材料。利用选择性溶液萃取方法和SEM研究了PE-EVA共混物的相结构及纳米Al2O3在共混物中的分布,评价了Al2O3/PE-EVA复合材料的导热性能与力学性能。结果表明:在PE与EVA质量比为1∶1时可获得具有两相共连续结构的共混物;在两相共连续PE-EVA共混物中引入纳米Al2O3后,发现纳米Al2O3主要分布在PE相中;纳米Al2O3的分布行为及共连续结构的形成有助于提高复合材料的导热性能,在纳米Al2O3质量分数为50%时,与Al2O3/PE复合材料相比,具有选择分布和相连续结构的Al2O3/PEEVA复合材料的热导率提高了21.2%;随着纳米Al2O3质量分数的增加,Al2O3/PE-EVA复合材料的拉伸强度与Al2O3/PE复合材料的拉伸强度相近,同时由于EVA相的增韧作用,其断裂伸长率优于Al2O3/PE复合材料。

Effects of nano Al2O3 distribution on thermal conductivity and mechanical property of Ai2O3/PE-EVA composites

This paper aims at dispersing nano Al₂O₃ in polyethylene(PE) and ethylene vinyl acetate copolymer (EVA) blends to build thermal conductive composites with high local particle concentration and selective distribution structure. With nano Al₂O₃ as thermal conductive filler, PE and EVA as matrix resin, Al₂O₃/PE-EVA thermal conductive composites were prepared by melt blending method. The phase structure of PE-EVA blends and distribution of Al₂O₃ in blends were investigated by selective solution extraction method and SEM. The thermal conductivity and mechanical properties of Al₂O₃/PE-EVA composites were evaluated. The results show that blends with two-phase co-continuous structure are obtained at PE to EVA mass ratio of 1:1. By introducing Al₂O₃ into PE-EVA two-phase co-continuous blends, Al₂O₃ is mainly dispersed in PE phase. The distribution behavior of Al₂O₃ and the formation of co-continuous structure are helpful to improve the thermal conductivity of composites. 21.2% increase of thermal conductivity is obtained for Al₂O₃/PE-EVA composites with selective distribution and co-continuous structure, in comparison to that of Al₂O₃/PE composites at Al₂O₃ mass fraction of 50%. With the increase of Al₂O₃ mass fraction, the tensile strength of Al₂O₃/PE-EVA composites tends to be similar to that of Al₂O₃/PE composites. The elongation at break of Al₂O₃/PE-EVA composites is also superior than that of Al₂O₃/PE composites thanks to the toughing effect of EVA phase.