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High‐pressure phase behavior in polyethylene/ n ‐butane binary and polyethylene/ n ‐butane/CO 2 ternary systems
Author(s) -
Xiong Yan,
Kiran Erdogan
Publication year - 1994
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.1994.070530905
Subject(s) - upper critical solution temperature , butane , lower critical solution temperature , supercritical fluid , thermodynamics , polyethylene , ternary operation , solubility , materials science , phase (matter) , ternary numeral system , volume (thermodynamics) , polymer chemistry , phase diagram , chemistry , polymer , organic chemistry , physics , copolymer , composite material , catalysis , computer science , programming language
Solubility of polyethylene molecular weight standards ( M w = 2150, 16,400, 108,000, and 420,000 and M w / M n = 1.14, 1.16, 1.32, and 2.66, respectively) has been studied in near‐ and supercritical n ‐butane and n ‐butane/CO 2 mixtures at pressures up to 70 MPa. For each polyethylene/solvent system at selected compositions, demixing pressures have been determined using a high‐pressure variable‐volume view‐cell at temperatures up to 200°C. Solutions in pure n ‐butane are found to display LCST (lower critical solution temperature)‐type behavior. The behavior of the solutions in n ‐butane/CO 2 mixtures are observed to change from the LCST to the UCST (upper critical solution temperature) with increasing CO 2 content in the binary solvent. Sanchez–Lacombe theory has been used to model these systems. The predictions correctly describe the nature of the phase diagrams for both binary and ternary systems and the calculations are in reasonable agreement with experimental data. © 1994 John Wiley & Sons, Inc.