Mechanical and tribological properties of carbon nanotube reinforced polypropylene composites

In this work, carbon nanotube (CNT) reinforced polypropylene (PP) composites (0.5, 1.0, 3.0, and 5.0wt%) were developed using the melt compounding process. The developed composites were injection-molded into tensile specimens and pins to evaluate the mechanical and tribological properties of the composites. As the CNT content increased, the tensile strength and Young's modulus of the PP composites increased. The addition of the CNTs to the PP matrix beyond 1wt% demonstrated agglomeration, and fractured tensile specimens confirmed this behavior. Developed materials demonstrated enhanced crystallinity up to 1wt% CNT and, subsequently, decreased crystallinity beyond 1 wt% CNT, and an X-ray diffraction investigation confirmed this behavior. The measured coefficient of friction, online wear, and weight loss from the sliding wear test confirmed the least frictional resistance and maximum wear resistance for the 1wt% CNT-PP composite. As the CNT content increased, the hardness of the CNT-PP composite increased up to 1wt% CNT and decreased beyond this threshold. The worn-out surfaces of the CNT-PP composite observed using a scanning electron microscope and noncontact three-dimensional profiler confirmed the superior wear resistance of the 1wt% CNT-PP composite. The CNT-PP composites considered in this study exhibited increased surface temperatures in the sliding wear condition because of the addition of the CNTs. The addition of the CNTs to the PP material increased the thermal conductivity of the composite.