Gas and vapor transport properties of amorphous perfluorinated copolymer membranes based on 2,2-bistrifluoromethyl-4,5-difluoro-1,3-dioxole/tetrafluoroethylene

Ingo Pinnau*, Lora G. Toy

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

246 Scopus citations

Abstract

Teflon AF 2400 (Du Pont) is an amorphous, glassy perfluorinated copolymer containing 87 mol% 2,2-bistrifluoromethyl-4,5-difluoro-1,3-dioxole and 13 mol% tetrafluoroethylene. The polymer has an extremely high fractional free volume of 0.327. Permeability coefficients for helium, hydrogen, carbon dioxide, oxygen, nitrogen, methane, ethane, propane, and chlorodifluoromethane (Freon 22) were determined at temperatures from 25 to 60°C and pressures from 20 to 120 psig. Permeation properties were also determined at a feed pressure of 200 psig at 25°C with a 2 mol% n-butane/98 mol% methane mixture. Permeabilities of permanent gases in Teflon AF 2400 are among the highest of all known polymers; the oxygen permeability coefficient at 25°C is 1600 x 10 -10 cm 3 (STP) cm/cm 2 s cmHg and the nitrogen permeability coefficient is 780 x 10 -10 cm 3 (STP) cm/cm 2 s cmHg. The permeabilities of organic vapors increase up to 20-fold as the vapor activity increases from 0.1 to unity, indicating that Teflon AF 2400 is easily plasticized. Although Teflon AF 2400 is an ultrahigh-free-volume polymer like poly(1-trimethylsilyl-1-propyne) [PTMSP], their gas permeation properties differ significantly. Teflon AF 2400 shows gas transport behavior similar to that of conventional, low-free-volume glassy polymers. PTMSP, on the other hand, acts more like a nanoporous carbon than a conventional glassy polymer.

Original languageEnglish (US)
Pages (from-to)125-133
Number of pages9
JournalJournal of Membrane Science
Volume109
Issue number1
DOIs
StatePublished - Jan 10 1996

Keywords

  • 2,2-bistrifluoromethyl-4,5-difluoro-1,3-dioxole
  • Activation energy of permeation
  • Copolymer
  • Gas transport
  • PTMSP
  • Teflon AF 2400
  • Tetrafluoroethylene
  • Vapor separation

ASJC Scopus subject areas

  • Biochemistry
  • Materials Science(all)
  • Physical and Theoretical Chemistry
  • Filtration and Separation

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