Tribochemical driven interfacial energy gradient in ultralow wear PTFE composite

Abstract

Previous studies of certain ultralow wear PTFE composites highlighted the wear rate’s extremely high sensitivity to the interfacial surface energy gradient (Δγ) with a scale factor of nearly 104 times per mJ/m2. This study aims to further elucidate the origin of such gradient and its relation with wear reduction by systematically studying wear and tribofilm’s environmental sensitivities of a 5 wt% PPS-PTFE composite. The results found a scaling factor between wear rate and Δγ of about 1000 fold per mJ/m2. Results also suggest that the interfacial energy gradient is directly driven by transfer film adhesion and coverage, transfer film adhesion is dominated by PTFE tribochemistry rather than PPS enrichment, and a moderate Δγ minimizes bulk wear and stabilizes transfer films.