Degradation of a branched perfluoropolyalkylether fluid with anhydrous aluminium chloride

Abstract The degradation of a branched perfluoropolyalkylether (PFPAE) fluid with anhydrous AlCl 3 , in the absence of oxygen, has been re‐examined with emphasis on understanding the nature of the volatile products formed. GC/FTIR and GC/MS have been employed for identification of a number of compounds in the complex mixture of volatile products obtained. Hexafluoroacetone was a major component of this mixture. In addition, a number of chlorofluoro compounds and shorter chain oligomers without and with reactive functional groups such as ketone, acyl fluoride, and acyl chloride were formed. While successive losses of end units appear to be the predominant mode of degradation, the possibility of internal bond fission cannot be completely ruled out. There is strong evidence to suggest that carbonyl functional groups are not restricted to the leaving monomer units. They are present to a smaller extent in the residual fluid also. More than one mode of degradation, beginning either at the perfluoropropoxy end‐group or perfluoroethoxy end‐group which involves migration of a chlorine atom or fluorine atom from the end‐group to internal site or vice versa, can explain the formation of the volatile compounds identified. The mechanism of degradation involved in the initial loss of a terminal unit need not be operational in further degradation of the polymer chain, as a carbonyl functionality generated in the end‐group of the degrading polymer chain can alter the course of further reactions. While such a change in the mechanism of degradation is possible due to carbonyl functionality generated, it remains speculative in the absence of experimental support.