Catalytic decomposition of perfluoropolyether lubricants

With the ongoing decrease in magnetic spacing, the chemical durability of the lubricant film on magnetic recording media becomes a major factor in the reliability of the head-disk interface. There are several reports in the literature that have attributed deterioration of lubricant film to catalytic decomposition, and a reaction mechanism has been proposed by Kasai involving chain scission of the lubricant main chain promoted by Lewis acids. In this work, an alternative mechanism is proposed, wherein perfluoropolyether (PFPE) lubricants are catalytically decomposed via a free radical degradation loop. The catalytic decomposition of Fomblin Zdol in the presence of the Lewis acid Al₂O₃ was studied using thermogravimetric analysis (TGA). We show that various types of antioxidants can retard PFPE catalytic decomposition to different degrees, which we attribute to their different roles in breaking the free radical degradation loop. These data provide useful guidance in the development of new lubricants that are resistant to free radical initiated decomposition.