▎ 摘　　要

Thermal conductive polymer composite pipes have been used to replace metal pipes that are easy to be corroded. However, the low thermal conductivity of the matrix is the critical factor limiting their applications. Here, large-size exfoliation of graphene and carbon nanotube (CNT) are proposed to prepare thermal-conductive polyethylene nanocomposites with a low filler content. Expanded graphite and CNT are co-dispersed by high pressure homogenizer in presence of polyvinyl pyrrolidone. Such a dispersion method can maintain the high aspect ratio and reduce generation of defects of graphene and CNTs, which is vital for building a long-range thermal conductivity pathway in the nanocomposites. In addition, the graphene and CNT fillers can be obtained with high yield and efficiency. When the fillers are dispersed into the polyethylene by optimizing the composition, thermal conductive composites can be obtained with enhanced mechanical properties. The nanocomposite with 5.22 wt.% filler can reach a thermal conductivity of 1.265 W center dot m(-1)center dot K-1, 3.94 times to that of the neat polyethylene, and the mechanical strength can be increased by 42%, supporting improvement of the thermal conductivity and mechanical strength at the same time.