The effect of surface modification on the friction and wear behavior of carbon nanofiber-filled PTFE composites

Carbon nanofiber (CNF) was treated with HNO₃, coupling agent and HNO₃ followed by coupling agent, respectively. The friction and wear properties of surface-treated CNF were investigated on a ring-on-ring friction and wear tester under dry friction conditions. Scanning electron microscopy (SEM) was utilized to study the worn surfaces of PTFE composites. Experimental results showed that surface modification decreased the friction coefficient of CNF/PTFE composites slightly, and reduced the wear volume loss of the PTFE composites obviously. Among all HNO₃ treatments, 10 min treatment was the best for the improvement of anti-wear properties of PTFE composites. Moreover, the best anti-wear property of the composite was achieved when CNF was treated with HNO₃ followed by coupling agent treatment, which was about 30% lower than that of untreated CNF filled PTFE under 200 N load. SEM studies indicated that surface modification could reduce the abrasive wear of CNF/PTFE composites. And the dispersion of CNF in PTFE composites was also improved after the surface modification, especially for the treatment of HNO₃ followed by coupling agent.