Tribological and mechanical properties of PTFE composites filled with the combination of short carbon fiber and carbon nano-fiber

The tribological and mechanical properties of polytetrafluoroethylene (PTFE) composites filled with carbon nano-fiber (CNF), short carbon fiber (SCF) and the combination of them were studied. The results indicate that the wear volume loss of the PTFE composite filled with CNF or SCF, in comparison with that of pure PTFE, decreases by 1-2 orders of magnitude. And the best wear resistant composition is achieved by the combination of SCF with CNF; as an example, PTFE+2 wt% CNF+18 wt% SCF exhibits a specific wear volume loss of 0.88 mm³, which is about 11 times lower when compared to the PTFE composite filled with 18 wt% SCF. Meanwhile, the results also show that the tensile strength of SCF or CNF filled PTFE composites is better than that of pure PTFE. However, the combination of the two fillers decreases the tensile strength of PTFE composites. Worn surfaces were investigated using a scanning electron microscope, from which it is assumed that a mechanism of rolling effect, due to the filling of nanoparticles, which has a positive protective effect for PTFE matrix.