Formation of defect-free 6FDA-DAM asymmetric hollow fiber membranes for gas separations
| Autor: | Wulin Qiu, William J. Koros, Junqiang Liu, Meha Rungta, Chen Zhang, Liren Xu |
|---|---|
| Rok vydání: | 2014 |
| Předmět: |
Binodal
chemistry.chemical_classification Phase boundary Materials science Lithium nitrate technology industry and agriculture Filtration and Separation Polymer Biochemistry chemistry.chemical_compound Membrane chemistry Polymer chemistry General Materials Science Fiber Gas separation Physical and Theoretical Chemistry Composite material Polyimide |
| Zdroj: | Journal of Membrane Science. 459:223-232 |
| ISSN: | 0376-7388 |
| Popis: | This paper reports the formation of defect-free 6FDA-DAM asymmetric hollow fiber membranes. 6FDA-polyimides are of great interest for advanced gas separation membranes, and 6FDA-DAM polyimide is a representative polymer in this family with attractive dense film properties for several potential applications. The work reported here for the 6FDA-DAM polyimide provides insight for the challenging fabrication of defect-free asymmetric hollow fiber membranes for this class of 6FDA-polyimides, which behave rather different from lower free volume polymers. Specifically, the 6FDA based materials show relatively slow phase separation rate in water quench baths, which presents a challenge for fiber spinning. For convenience, we refer to the behavior as more “non-solvent resistant” in comparison to other lower free volume polymers, since the binodal phase boundary is displaced further from the conventional position near the pure polymer-solvent axis on a ternary phase diagram in conventional polymers like Matrimid ® and Ultem ® . The addition of lithium nitrate to promote phase separation has a useful impact on 6FDA-DAM asymmetric hollow fiber formation. 6FDA-DAM phase diagrams using ethanol and water as non-solvent are reported, and it was found that water is less desirable as a non-solvent dope additive for defect-free fiber spinning. Phase diagrams are also reported for 6FDA-DAM dope formulation with and without the addition of lithium nitrate, and defect-free asymmetric hollow fiber membranes are reported for both cases. The effect of polymer molecular weight on defect-free fiber spinning was also investigated. Gas transport properties and morphology of hollow fibers were characterized. With several thorough case studies, this work provides a systematic guideline for defect-free fiber formation from 6FDA-polymers. |
| Databáze: | OpenAIRE |
| Externí odkaz: |
|
Full Text from ScienceDirect