Studies on degradation mechanisms of lubricants for magnetic thin-film rigid disks

Abstract

The decomposition mechanisms of the perfluoropolyether (PFPE) lubricants have been studied through calculation of chemical reaction kinetics and several experimental approaches. Four degradation mechanisms were considered: thermal and catalytic decomposition, triboelectrical decomposition and mechanical scission. The results show that the effect of catalytic reaction on the degradation of the PFPE lubricants is negligible in sliding conditions because of the short contact time, small contact area and low interface temperature. Illumination with ultraviolet light is found to accelerate the decomposition of the lubricant, reducing the head-disk interface durability and causing more gaseous fragments because low-energy electrons created by the illumination interact with the lubricant molecules, activating and breaking up the molecules. A decomposition mechanism of the lubricant from the effect of low-energy electrons is proposed. Mechanical shear is also found to have an important effect on the decomposition of the lubricant. The partial pressures of the gaseous fragments of the lubricant increase rapidly with increase in the sliding velocity. The temperature from ambient up to 70 °C has no obvious effect on the decomposition of the PFPE lubricant, although higher temperatures are expected to be detrimental. Dominant degradation mechanisms in the sliding conditions are triboelectrical reaction and mechanical scission.