Role of reinforcement types and silica nanoparticles on tribofilm growth at PTFE-Steel interface

Tribological behaviors of polytetrafluoroethylene (PTFE) reinforced with carbon fibers (CF), aramid fibers (AF) and hybrid CF + AF were comparatively investigated. It is demonstrated that the hybrid composites reinforced with CF + AF exhibit greatly enhanced wear resistance, when compared to the composites reinforced only with CF or AF. Adding only 0.3 vol% silica (SiO2) nanoparticles into the hybrid composites further reduces wear rate by up to 47.3%. Mechanochemistry of PTFE molecules and nanostructures of the tribofilms were comprehensively explored. Our work provides direct evidence that SiO2 nanoparticles released from the composites are compacted into the tribofilms, while the reinforcement types exert an important influence on mechanochemistry of PTFE molecules. This work puts forward new strategies for developing highly wear-resistant PTFE composites via regulating tribo-physical and -chemical actions.