Tribological performance of PTFE/polyimide pulp/GCNT composites

Polytetrafluoroethylene (PTFE) is widely used as a solid lubricant but suffers from poor wear resistance, limiting its application in demanding mechanical components. In this study, PTFE-based composites reinforced with polyimide (PI) pulp and graphitized carbon nanotubes (GCNTs) were prepared via a cold-press sintering process. The tribological properties were evaluated under different loads (2 N and 10 N) and frequencies (1 Hz and 4 Hz) using a ball-on-disk tribometer. The results show that the composite with 5 wt% PI pulp and 1 wt% GCNT (designated as #3) exhibits the best overall performance. At 2 N and 1 Hz, its coefficient of friction (COF) reaches 0.025, which is 69.3% lower than that of pure PTFE. Meanwhile, the wear rate is reduced by up to 75% under 10 N and 4 Hz. Scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) analyses indicate that the improved tribological performance is mainly attributed to the formation of a continuous and uniform transfer film on the counterface. PI pulp constructs a load-bearing fibrous network that enhances mechanical strength, while GCNTs promote the adhesion and stability of the transfer film, effectively changing the sliding contact from composite–steel to film–steel and reducing both friction and wear. This work offers a practical route for developing PTFE-based self-lubricating composites with balanced mechanical and tribological properties.