Formation of perfluorocarboxylic acids (PFCAs) from thermolysis of Teflon model compound.

Abstract

It has been widely postulated that thermal degradation of polytetrafluoroethylene (PTFE; commercially known as Teflon) under the presence of moisture presents a likely source for the formation of the notorious perfluorocarboxylic acids (CF3(CF2)nCO(OH) PFCAs) and perfluorinated aldehydes (CF3(CF2)nCO(F/H). Thus, deployment of objects laden with Teflon at the peak of their thermal stability may contribute to the atmospheric budget of PFCAs. However, the underlying mechanism remains largely speculative. This study reports potential energy surfaces for reactions that govern oxidative transformation of n-C8F18 (as a model compound of PTFE) into tridecafluoroheptanoyl fluoride and perfluoroheptanoic acid. Central to computed pathways are dissociative addition reactions of water over the carbonyl group and elimination of hydroperoxylradicals. Facile activation enthalpies are encountered in the involved steps. Our analysis discloses that formation of the building monomer C2F4 should be suppressed under thermolysis oxidation conditions at which synthesis of trifluoroacetic acids is preferred. Constructed kinetic model illustrates a near-complete conversion of the PTFE model compound into perfluorocarboxylic acids (CF3(CF2)nCO(OH) and perfluorinated aldehydes. Outcomes from this study should be instrumental in providing a better understanding of the likely contribution of fluoropolymers in the observed environmental loads of perfluorocarboxylic acids.