The Reaction of Perfluoropolyalkylether Oil with FeF₃, AlF₃, and AlCl₃ at Elevated Temperatures

Abstract

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.