采用固相剪切碾磨预处理结合熔融再加工技术制备了高性能铝粉(Al)/线性低密度聚乙烯(LLDPE)导热复合材料,并与常规熔融共混法对比,系统研究了固相剪切碾磨对复合材料微观形态、结晶性能、热稳定性、流变特性、热导率和力学性能等的影响.结果表明:通过固相剪切碾磨实现了球形Al颗粒应力诱导变形为具有较大径厚比的片状,在基体中均匀分散且与其界面结合得以增强,同时这种大片状的铝粉在Al/LLDPE复合材料成型时更易有效接触形成导热网链并形成一定取向分布,特别是在高填充量下.因此Al/LLDPE复合材料拥有更好的结晶性能和热稳定性、更低的流变逾渗阈值、更高的热导率和力学性能.固相剪切碾磨预处理制备的Al/LLDPE复合材料在铝粉含量超过15%就出现流变逾渗现象,且当Al填充质量分数80%时,复合材料的热导率高达8.86 W/(m·K),拉伸强度和弯曲强度分别为33.0 MPa和31.2 MPa,都明显优于常规熔融共混复合体系,同时其初始分解温度也提高了近13℃.
The solid state shear milling (S3M) followed by melt mixing process was applied to prepare Al /linear low-density polyethylene (LLDPE) composites with high performance.The effects of S3M pretreatment on the microstructure, crystallization, thermal stability, rheological behaviour, thermal conductivity and mechanical properties of the Al/LLDPE composites were systematically investigated.The results indicate the spherical Al particulates are squeezed into flakes during compounding with LLDPE by S3M, and their dispersion and interfacial adhesion are improved as well.Furthermore, the flaky Al with high radius-thickness ratio can be easier to form thermal network and orientation during processing especially at high filler loading.Consequently, the Al/LLDPE composites with S3M pretreatment show better crystallization and thermal properties, lower rheological percolation threshold, higher thermal conductivity and superior mechanical properties than Al/LLDPE composites prepared by conventional melt mixing.In particular, the rheological percolation phenomena of the composites with S3M pretreatment is observed around at 15% mass fraction of Al.When the mass fraction of Al is 80%, the thermal conductivity of Al/LLDPE composite with S3M pretreatment is as high as 8.86 W/(m·K), and its the tensile strength and flexural strength respectively are 33.0 MPa and 31.2 MPa, much higher than those of the untreated composite.And a significant increase of 13℃ in the onset temperature of degradation is also observed.
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