GLASS-TRANSITION, CRYSTALLIZATION AND THERMOREVERSIBLE GELATION IN TERNARY PPO SOLUTIONS - RELATIONSHIP TO ASYMMETRIC MEMBRANE FORMATION

Date

1987-11-01

Author

BURGHARDT, WR
Yılmaz, Levent
MCHUGH, AJ

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The phase equilibrium behaviour of PPO (poly 2,6-dimethyl-1,4-phenylene oxide) in mixtures of trichloroethylene with non-solvents ethanol, methanol or octanol has been studied. Attention has been given to the phenomena of glass transition, crystallization and thermoreversible gelation. The effect of solvent-non-solvent mixtures on the glass transition temperature depression was studied using differential scanning calorimetry (d.s.c.) and found to be well described by a ternary form of the Kelley-Bueche equation, using a modified best fit value of 3.67 for the solvent/polymer thermal expansivity ratio. Crystallization and gelation behaviour was studied using both d.s.c. and falling ball methods. D.s.c. scans showed a two-peaked behaviour when solvent trichloroethylene (TCE) or mixtures of TCE with octanol were used. Analysis showed that gel and crystal melting (associated with the higher temperature peak) are in a one-to-one correspondence and both exhibit a behaviour pattern with solvent concentration suggestive of simple melting point depression. However, addition of small amounts of non-solvent methanol or ethanol had a significant effect on the melting behaviour in that only a single endotherm resulted, whose depression in temperature could not be accurately described using the ternary form of the Flory melting point expression. A semiquantitative discussion is given emphasizing the role of these phenomena in controlling both the nature of the ternary phase diagram and the structure formation Processes associated with asymmetric membrane production.

Subject Keywords

Organic Chemistry, Polymers and Plastics

URI

https://hdl.handle.net/11511/44946

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Department of Chemical Engineering, Article