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Cosolvency effect of SF 6 on the solubility of poly(tetrafluoroethylene‐ co ‐19 mol % hexafluoropropylene) in supercritical CO 2 and CHF 3
Author(s) -
Mertdogan Cynthia A.,
McHugh Mark A.,
Tuminello William H.
Publication year - 1999
Publication title -
journal of applied polymer science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.575
H-Index - 166
eISSN - 1097-4628
pISSN - 0021-8995
DOI - 10.1002/(sici)1097-4628(19991121)74:8<2039::aid-app19>3.0.co;2-e
Subject(s) - hexafluoropropylene , tetrafluoroethylene , supercritical fluid , sulfur hexafluoride , thermodynamics , solubility , ternary operation , materials science , bar (unit) , ternary numeral system , chemistry , polymer chemistry , phase (matter) , organic chemistry , copolymer , polymer , physics , meteorology , computer science , programming language
Cloud‐point data to 280°C and 2800 bar are reported for a binary mixture of poly(tetrafluoroethylene‐ co ‐19.3 mol % hexafluoropropylene) (FEP 19 ) in fluoroform (CHF 3 ) and for ternary mixtures of FEP 19 –CHF 3 –sulfur hexafluoride (SF 6 ) and FEP 19 –CO 2 –SF 6 . FEP 19 does not dissolve in CHF 3 at a temperatures less than 235°C due to strong dipolar CHF 3 –CHF 3 interactions relative to FEP 19 –CHF 3 cross interactions. However, FEP 19 dissolves in CO 2 if the temperature is greater than ≈185°C and the pressure is in excess of 1000 bar. When SF 6 is added to either FEP 19 –CO 2 or FEP 19 –CHF 3 mixtures, the cloud‐point curve is shifted to lower pressures and temperatures due to the increase in favorable dispersion interactions with nonpolar FEP 19 . The magnitude of the shift in cloud‐point pressure per amount of SF 6 added to solution decreases in a nonlinear manner with increasing amounts of SF 6 . The Sanchez‐Lacombe equation of state can model the binary FEP 19 ‐SCF data if the FEP 19 –CO 2 and FEP 19 –CHF 3 binary interaction parameters are allowed to vary with temperature. However, a poor representation is obtained for the ternary phase behavior. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 2039–2045, 1999