The Reaction of Perfluoropolyalkylether Oil with FeF3, AlF3, and AlCl3at Elevated Temperatures

The interaction of perfluoropolyalkylether (PFPE) oil with ferric fluoride (FeF3) and other Lewis acids at elevated temperatures under inert atmosphere was investigated to determine whether the reaction results in lubricant degradation. At 35°C, ∼25°C below the onset of thermal degradation, PFPE'S reaction with FeF3 yields acyl fluoride and ketone degradation products and also a decrease in the oil's number-average molecular weight. In the presence of small quantities of water, the acyl halide products hydrolyze, resulting in carboxylic acids. The oil's reaction with aluminum fluoride at 350°C and aluminum chloride at 200°C also causes it to degrade measurably. The results indicate that PFPE oil can degrade at estimated bearing asperity contact temperatures in the presence of FeF3.