Simultaneous enhancement on thermal and mechanical properties of polypropylene composites filled with graphite platelets and graphene sheets

Thermoplastic composites have aroused extensive academic and industrial concern because of their recyclability and versatility. In this work, polypropylene (PP) composites filled with multilayer graphene sheets (GSs) and graphite platelets (GPs) were successfully fabricated via a facile melt-mixing procedure. The hybrid fillers exhibit simultaneous enhancement on thermal and mechanical properties of composites. With the loading of 3 wt% GSs and 20 wt% GPs, the thermal conductivity (TC) of GSs/GPs/PP composites reaches 1.72 Wm−1 K−1, which is much higher than that of single filler composites with the same loading. Besides, this composite material displays enhanced mechanical properties. Usually, high filler content leads to high thermal conductivity, but decreases mechanical properties. However, this work shows a simultaneous enhancement effect which could be explained by the unique connected microstructure. It is found that the small GSs are filled into the interspaces of large GPs, which not only facilitates the heat transfer, but also enhances the resistance to fracture, thus leading to better thermal and mechanical performances. The excellent properties of the composites endow a promising potential in industrial application.