SiO2/carbon fiber-reinforced polypropylene–thermoplastic polyurethane composites: electrical conductivity and mechanical and thermal properties

To achieve electrical conductive composites, carbon fibers (CFs) were introduced to polypropylene–thermoplastic polyurethane (PP/TPU) blends. In combination, a definite amount of silica (SiO2) nanoparticles were added as reinforcing agents to impregnate CFs and further improve the mechanical, thermal and electrical properties of CFs-modified PP/TPU composites. These quaternary composites were investigated by X-ray diffractometry technique, thermogravimetric analysis, scanning electron microscopy (SEM), mechanical measurement and electrical conductivity test. The results demonstrated that the crystallinity and flow rate of PP/TPU composites dropped after compounding with CFs, though they increased by the addition of SiO2. Both CFs and SiO2 improved the impact and tensile strength of quaternary composites, which were arising from the large aspect ratio of CFs and the reinforcement effect of SiO2 nanoparticle, respectively. Furthermore, CFs–PP/TPU and (CFs + SiO2)–PP/TPU composites exhibited superior thermal stability over PP/TPU composites, and (3CFs + 3SiO2)–PP/TPU composite exhibited a maximum value. It is attributed to the restriction of polymer chain motion created by the CF fillers and the insulating effect of SiO2. The SEM micrographs revealed the presence of plastic bands for CFs–PP/TPU and (CFs + SiO2)–PP/TPU composites and more refined arrangement of the fibers after incorporation of SiO2. This refinement resulted in higher electrical conductivity of (CFs + SiO2)–PP/TPU composites compared with CFs–PP/TPU composites.