Analysis of the chemical composition of the PTFE transfer film produced by sliding against Q235 carbon steel

Polytetranuoroethylene (PTFE) transfer films formed on the surface of Q235 carbon steel were studied using scanning electron microscopy (SEM), energy dispersive spectrometry (EDS), X-ray photoelectron spectroscopy (XPS), molecular dynamics (MD), and density functional theory (DFT) calculations. Changes in the chemical composition of the transfer film were analyzed using XPS measurements. Mechanisms of defluorination, chain scission, and formation of carbonyl and hydroxyl groups were elucidated using DFT transition state calculations. Of these four reactions, defluorination, which has an energy barrier of only 1.0 kcal/mol, is most likely to occur. The formation of a carbonyl group, with an energy barrier of 23.1 kcal/mol, can more easily take place than the chain scission, which has an energy barrier of 44.6 kcal/mol, and is a precursor to the simplest path to the formation of a hydroxyl group. (C) 2014 Elsevier B.V. All rights reserved.