Premium
Phase behavior and density of polysulfone in binary fluid mixtures of tetrahydrofuran and carbon dioxide under high pressure: Miscibility windows
Author(s) -
Zhang Wei,
Kiran Erdogan
Publication year - 2002
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/app.11243
Subject(s) - miscibility , polysulfone , tetrahydrofuran , carbon dioxide , solvent , phase (matter) , dissolution , phase boundary , binary system , phase diagram , upper critical solution temperature , materials science , polymer , analytical chemistry (journal) , chemistry , thermodynamics , lower critical solution temperature , chromatography , organic chemistry , copolymer , binary number , physics , arithmetic , mathematics
Mixtures of tetrahydrofuran (THF) and carbon dioxide (CO 2 ) were identified as new solvent systems for polysulfone. The miscibility and density of polysulfone in binary fluid mixtures of THF and CO 2 were investigated from 300 to 425 K at pressures up to 70 MPa. The influence of the CO 2 and polysulfone concentrations was studied, with the concentrations of the other two components kept constant. At a 4.5 wt % polymer concentration, the demixing pressures in a 10 wt % CO 2 and 90 wt % THF mixture increased with temperature (310–425 K) from 15 to 40 MPa. With increasing CO 2 concentration (from ca. 10 to 14 wt %), a significant increase (from 15 to 70 MPa at 310 K) was observed in the demixing pressures. Furthermore, with an increasing amount of CO 2 , the nature of the phase boundary shifted from lower critical solution temperature behavior to upper critical solution temperature behavior. The influence of the polymer concentration was studied in the 0–5 wt % range at two CO 2 levels, with solvent compositions of 10 wt % CO 2 and 90 wt % THF and 13 wt % CO 2 and 87 wt % THF. The system with a higher level of CO 2 (13 wt %) showed highly unusual phase behavior: on pressure–composition and temperature–composition diagrams, the system displayed two distinct regions of miscibility. In the system with 10 wt % CO 2 , the distinct regions of miscibility that were observed in the system with 13 wt % CO 2 partially overlapped and led to a W‐shape phase boundary. The densities of the polymer solutions were measured from the one‐phase region through the demixing point into the two‐phase region at a constant temperature. No significant change in density was found around the phase boundary; this indicated that the coexisting phases had similar densities, as is often the case with liquid–liquid phase separation in polymer solutions under high pressure. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 2357–2362, 2002