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Phase behavior, density, and crystallization of polyethylene in n ‐pentane and in n ‐pentane/CO 2 at high pressures
Author(s) -
Zhang Wei,
Dindar Cigdem,
Bayraktar Zeynep,
Kiran Erdogan
Publication year - 2003
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.12441
Subject(s) - pentane , phase (matter) , analytical chemistry (journal) , atmospheric temperature range , thermodynamics , volume (thermodynamics) , phase boundary , materials science , polyethylene , crystallization , chemistry , chromatography , composite material , organic chemistry , physics
The phase behavior and volumetric properties of polyethylene (PE) in solutions of n ‐pentane and n ‐pentane/CO 2 were studied in a temperature ( T ) range of 370–440 K at pressures up to 60 MPa. Measurements were conducted with a variable‐volume view‐cell system equipped with optical sensors to monitor the changes in the transmitted light intensity as the P or the T of the system was changed. Lower‐critical‐solution‐temperature‐type behavior was observed for all of the liquid–liquid (L–L) phase boundaries, which shifted to higher pressures in solutions containing CO 2 . The solid–fluid (S–F) phase boundaries were investigated over a P range of 8–54 MPa and took place in a narrow T range, from 374 to 378 K in this P interval. The S–F phase boundary showed a unique feature in that the demixing temperatures showed both increasing and decreasing trends with P depending on the P range. This was observed in both the PE/ n ‐pentane and PE/ n ‐pentane/CO 2 mixtures. The density of these solutions were measured as a function of P at selected temperatures or as a function of T at selected pressures that corresponded to the paths followed in approaching the phase boundaries (S–F or L–L) starting from a homogeneous one‐phase condition. The data showed a smooth variation of the overall mixture density along these paths. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2201–2209, 2003