Nanofiller tribochemical functionality is not sufficient to achieve ultralow wear of PTFE

The functionality of nanofillers in inducing favorable tribochemistry is considered crucial for achieving ultralow wear in polytetrafluoroethylene (PTFE) composites. However, it remains unclear if nanofillers need to meet additional criteria beyond tribochemical functionality. In this study, we investigated the wear performance of PTFE composites filled with nano-sized zero-valent iron (ZVI) and alumina against stainless steel countersamples in a pin-on-disk configuration. The results revealed that ZVI nanofillers induced more favorable tribochemical products but exhibited a wear resistance of the composite approximately 10 times worse than that of alumina fillers. Nanoindentation and cross-sectional characterization demonstrated that the ZVI/PTFE composite produced a thinner and softer tribofilm than the Al2O3/PTFE. This study supports that tribochemistry alone is insufficient for achieving ultralow wear of PTFE. The mechanical strength of nanofillers plays a crucial role in tribochemically reducing the wear of polymers.