SiO 2 /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 (SiO 2 ) 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 SiO 2 . Both CFs and SiO 2 improved the impact and tensile strength of quaternary composites, which were arising from the large aspect ratio of CFs and the reinforcement effect of SiO 2 nanoparticle, respectively. Furthermore, CFs–PP/TPU and (CFs + SiO 2 )–PP/TPU composites exhibited superior thermal stability over PP/TPU composites, and (3CFs + 3SiO 2 )–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 SiO 2 . The SEM micrographs revealed the presence of plastic bands for CFs–PP/TPU and (CFs + SiO 2 )–PP/TPU composites and more refined arrangement of the fibers after incorporation of SiO 2 . This refinement resulted in higher electrical conductivity of (CFs + SiO 2 )–PP/TPU composites compared with CFs–PP/TPU composites.