Acidic Attack of Perfluorinated Alkyl Ether Lubricant Molecules by Metal Oxide Surfaces

The reactions of linear perfluoropolyalkylether (PFAE) lubricants with α-Fe2O3 and Fe2O3-based solid superacids were studied. The reaction with α-Fe2O3 proceeded in two stages. The first stage was an initial slow catalytic decomposition of the fluid. This reaction released reactive gaseous products which attacked the metal oxide and converted it to FeF3. The second stage was a more rapid decomposition of the fluid, effected by the surface FeF3. A study of the initial breakdown step was performed using α-Fe2O3, α-Fe2O3 preconverted to FeF3, and sulfate-promoted α-Fe2O3 superacids. The results indicate that the breakdown reaction involves acidic attack at fluorine atoms on acetal carbons in the linear PFAE. Possible approaches to combat the problems are outlined.