How moisture driven mechanochemistry stabilizes transfer film adhesion and cohesion in ultralow wear PTFE composite

Prior studies suggest mechanical interlocking, preferential adhesion of polar polymers, and PTFE tribochemistry all contribute to the wear reduction in polar polymer-filled PTFE composites; whereas their relations remain poorly understood. This study aims to decouple the relevant mechanisms by investigating wear and tribofilm environmental sensitivities of a 5 wt% polyamide-imide (PAI) filled PTFE composite. The results highlight (1) strong correlation between a carboxylate-salt-rich transfer film and ultralow wear, and (2) a tribochemical interface gradient that discourages transfer film removal. We proposed that PTFE tribochemistry induces ul-tralow wear by significantly increasing (1) transfer film adhesion through a virtuous cycle of tribochemical accumulation and wear reduction and (2) transfer film cohesion by promoting a surface energy interface gradient beneficial to low wear.

Automated summary

Prior studies have shown that mechanical interlocking, preferential adhesion, and PTFE tribochemistry all play a role in reducing wear in polar polymer-filled PTFE composites, but their relationships are poorly understood. This study aimed to investigate the wear and tribofilm environmental sensitivities of a 5 wt% polyamide-imide (PAI) filled PTFE composite to untangle these mechanisms. The results revealed a strong correlation between a carboxylate-salt-rich transfer film and ultralow wear, as well as a tribochemical interface gradient that discourages transfer film removal. It is proposed that PTFE tribochemistry induces ultralow wear through increased transfer film adhesion and cohesion, promoting a surface energy interface gradient beneficial to low wear.