Mechanochemical Effect of Filler Surface Functionality on Fluoropolymer Tribology
Wei Sun, Xiaojun Liu, Qingrui Song, Kun Liu, Wei Wang, Yunxiang Lu, Jiaxin Ye
Abstract
The 10 000× wear resistance improvement of PTFE by a trace amount of nanofillers has been heavily studied in the past decade and attributed to the moisture-dependent, mechanochemical formation of adherent and carboxylate salt-rich transfer films. However, debates still exist on the role of the fillers in wear reduction. Based on experimental and computational studies of selected PTFE nanocomposites, we proposed that (1) filler-driven polymer defluorination was the first and key step in the mechanochemistry; (2) effective wear-reducing fillers lowered the energy barrier of the defluorination; and (3) filler surface functionality, the amount of chelation products in transfer film, and wear resistance were strongly correlated. This hypothesis was further supported by thermal experiments in this study, which showed that the mechanochemistry and wear resistance were both thermally sensitive.