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

The decomposition mechanisms of the perfluoropolyether (PFPE) lubricants ha ve been studied through calculation of chemical reaction kinetics and sever al experimental approaches. Four degradation mechanisms were considered: th ermal and catalytic decomposition, triboelectrical decomposition and mechan ical scission. The results show that the effect of catalytic reaction on th e degradation of the PFPE lubricants is negligible in sliding conditions be cause of the short contact time, small contact area and low interface tempe rature. Illumination with ultraviolet light is found to accelerate the deco mposition 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 breakin g up the molecules. A decomposition mechanism of the lubricant from the eff ect 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 deg reesC has no obvious effect on the decomposition of the PFPE lubricant, alt hough higher temperatures are expected to be detrimental. Dominant degradat ion mechanisms in the sliding conditions are triboelectrical reaction and m echanical scission.