Vapor Pressure of Nine Perfluoroalkyl Substances (PFASs) Determined Using the Knudsen Effusion Method

Mengke Zhang, Kyle Yamada, Stephen Bourguet, Jennifer Guelfo, Eric M. Suuberg

Research output: Contribution to journalArticlepeer-review


Sublimation vapor pressures of nine pure perfluoroalkyl substances, including ammonium perfluoro(2-methyl-3-oxahexanoate) (GenX), 1H,1H,2H,2H-perfluoro-1-decanol (8:2 FTOH), 1H,1H,2H,2H-perfluoro-1-dodecanol (10:2 FTOH), and C6 to C11 perfluorocarboxylic acids (PFCAs), were measured using the Knudsen technique at near-ambient temperatures. Melting temperatures and fusion enthalpies of these compounds were also measured by differential scanning calorimetry. The vapor pressure of GenX ammonium salt is comparable to that of the much higher molecular weight perfluoroundecanoic acid. GenX ammonium salt also did not show actual melting behavior but instead decomposed at around 470 K. The measured near-ambient temperature sublimation vapor pressures of the PFCAs and FTOHs were compared with some earlier reported liquid phase vapor pressures obtained at higher temperatures, and reasonable agreement exists between the data obtained in the different studies. The sublimation enthalpies of the PFCAs indicate that the contribution to the sublimation enthalpy of the CF2 group in the alkyl chain is comparable to that of the CH2 group in the corresponding nonfluorinated analogues, even though the PFCAs show consistently higher vapor pressures than do the corresponding carbon number alkanoic acids.

Original languageEnglish
Pages (from-to)2332-2342
JournalJournal of Chemical and Engineering Data
StatePublished - May 14 2020


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