Comparison studies on degradation mechanisms of perfluoropolyether lubricants and model lubricants

Abstract

The degradation mechanisms of some perfluoropolyether lubricants, model lubricants and DLC coating were studied in this paper. The degradation fragments from the tests of the PFPE lubricants can be divided into two groups. One group includes the gas fragments containing fluorine atoms, which are generated from the decomposition of the lubricants themselves; while the other group, including H₂, C₂H₃, C₂H₅, and CO₂, is generated from the degradation of the DLC coating on the disk surfaces. The test results from the model lubricants clearly show that the carbon dioxide produced in the tests is generated from the DLC coating, not from the decomposition of the lubricants or model lubricants. The C–O bond is a weak bond in both the lubricant and model lubricant molecules; it is easier to be broken. Because of the polar characteristics of the C–O bond, it is easy to be attacked and broken down by low-energy electrons generated during sliding. Triboelectrical reaction is a dominant degradation mechanism of the lubricants and model lubricants.