Degradation of thin-film disk PFPE lubricants by ceramic powders

Perfluoropolyether lubricants have been. the lubricants of choice on thin-film magnetic disks because of their superior properties. However studies have shown that they can degrade at lower temperatures in the presence of metal oxides such as Al2O3 and Fe2O3. In this paper, the degradation behavior of three widely used disk lubricants which have a Z-backbone structure were studied in the presence of the following ceramic powders: AlN, Al2O3, Fe2O3, SiC, Si3N4, SiO2, TiC, TiO2, and ZrO2. Experiments involved monitoring the weight loss of a continuously stirred mixture of lubricant containing 1 wt% of powder with time, at a fixed temperature of 250 degrees C. In the case of ZDOL 4000, there was a 10% loss in the first 60 minutes and then a very low and constant rate of weight loss. TiC, AlN and Al2O3 were very aggressive in degrading the lubricant while SiC and Si3N4 had no effect at all. ZDOL 2000 exhibited a 60% loss in the first 100 minutes and then a low and constant rate of loss with time. ZrO2, Al2O3, TiC and AlN were very effective in degrading the lubricant, while SiC and Si3N4 had negligible effect. Heating the AM 2001 lubricant alone at 250 degrees C caused the Lubricant to quickly turn into a black sludge; however, at 180 degrees C, it exhibited a slow and constant weight loss with time. At 180 degrees C, the presence of ceramic powders did not appear to have any effect on the rate of weight loss. X-ray diffraction of residues left behind after degradation tests showed that, except for the tests with SiC and Si3N4, most of the residues left behind after complete lubricant degradation were found to contain fluorides.