Cosolvency effect of SF6 on the solubility of poly(tetrafluoroethylene-co-19 mol % hexafluoropropylene) in supercritical CO2 and CHF3
✍ Scribed by Cynthia A. Mertdogan; Mark A. McHugh; William H. Tuminello
- Publisher
- John Wiley and Sons
- Year
- 1999
- Tongue
- English
- Weight
- 149 KB
- Volume
- 74
- Category
- Article
- ISSN
- 0021-8995
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✦ Synopsis
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 Ϸ185°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.