Phase separation of poly(vinylidene fluoride) dimethylformamide solution was induced by the penetration of water vapor, and the porous membrane was formed. As the humidity in the gas phase increased, membrane morphology changed in the order of dense, porous (cellular), and lacy-like structures. At t
Phase separation in polyetherimide/solvent/nonsolvent systems and membrane formation
β Scribed by Dongliang Wang; K. Li; W. K. Teo
- Publisher
- John Wiley and Sons
- Year
- 1999
- Tongue
- English
- Weight
- 228 KB
- Volume
- 71
- Category
- Article
- ISSN
- 0021-8995
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β¦ Synopsis
Phase separation phenomena of polyetherimide (PEI)/solvent/nonsolvent systems were investigated by measuring their precipitation values over the temperature range from 20 to 50Β°C. The solvents used are N-methyl-2-pyrrolidone (NMP), dimethylacetamide (DMAC), and dimethylformamide (DMF). Nine nonsolvents were employed including water, methanol, ethanol, 1-propanol, 2-propanol, acetic acid, propionic acid, ethylene glycol, and diethylene glycol. Based on the measured precipitation values, critical solubility parameters for PEI were calculated, and the partial solubility boundary for PEI was obtained in a two-dimensional solubility parameter coordinate graph. The relationship between solvent strength and membrane structure was examined using PEI hollow-fiber membranes prepared from binary polymer solutions containing NMP, DMAC, and DMF as solvents. Water was used both as internal and external coagulants. The cross-sectional structure and gas permeation properties of these hollow fibers were examined.
π SIMILAR VOLUMES
In this work, the ternary phase diagrams in three nonsolvent/solvent/ PMMA systems ( n-hexane/ n-butyl acetate/PMMA, water/acetone/PMMA, and n-hexane/acetone/PMMA) were constructed by theoretical calculation and experimental measurement. Binodal curves were calculated by using the Flory-Huggins theo
In general liquid-liquid demixing processes are responsible for the porous morphology of membranes obtained by immersion precipitation. For rapidly crystallizing polymers, solid-liquid demixing processes also generate porous morphologies. In this study, the interference of both phase transitions has
The isothermal phase diagram for poly(vinylidene fluoride)/dimethyl formamide/water system was derived. The binodal and spinodal were calculated based on the Flory-Huggins theory and the calculated binodal was approximately in agreement with the experimental data of the cloud points. The isothermal