Development of asymmetric 6FDA-2,6DAT hollow fiber membranes for CO2/CH4 separation: Part 2. Suppression of plasticization |
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| Institution: | 1. Department of Chemical and Environmental Engineering, National University of Singapore, 10 Kent Ridge Crescent, Singapore 119260, Singapore;2. Institute of Materials Research and Engineering, 3 Research Link, Singapore 117602, Singapore;3. Institute of Environmental Science and Engineering, 18 Nanyang Drive, Singapore 637723, Singapore;1. Department of Chemical Engineering, Texas Materials Institute, Center for Energy and Environmental Research, The University of Texas at Austin, 10100 Burnet Road, Bldg. 133, Austin, TX 78758, USA;2. Department of Chemistry, Macromolecules and Interfaces Institute, Virginia Tech, Blacksburg, VA 24061, USA;1. Department of Macromolecular Chemistry, Institute of Polymer Science and Technology, ICTP-CSIC, 28006 Madrid, Spain;2. Department of Energy Engineering, Hanyang University, Seoul 133-791, Republic of Korea;3. Group of Porous Materials and Surfaces, SMAP, UVa-CSIC Research Unit, 47011 Valladolid, Spain;4. CINQUIMA, College of Sciences, University of Valladolid, 47011 Valladolid, Spain |
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| Abstract: | We have studied the CO2-induced plasticization phenomenon of asymmetric poly(2,6-toluene-2,2-bis(3,4-dicarboxyphenyl) hexafluoropropane diimide) (6FDA-2,6 DAT) hollow fiber membranes for CO2/CH4 applications. Several processing and thermal approaches have been investigated to study their effectiveness to enhance anti-plasticization characteristics. Experimental results indicate that hollow fiber membranes spun at different shear rates and take-up rates cannot effectively suppress the CO2 induced plasticization. Thermally treated 6FDA-2,6 DAT hollow fiber membranes show significant reduction in CO2-induced plasticization. Wide-angle XRD spectra reveal no visible change in d-space after thermal treatment, while solubility data imply no cross-links occurred. Scanning electron microscopy (SEM) pictures illustrate heat treatment results in more compact selective-skin layer and substructure, thus strengthening the anti-plasticization characteristics of hollow fibers. By considering the degree of plasticization, dense-layer thickness, and heat treatment temperature, an optimal temperature of 250 °C (for 5 min) is identified for the heat treatment of 6FDA-2,6 DAT hollow fiber membranes. NMR spectra suggest the cause of forming a highly densified skin after heat treatment is mainly due to chain relaxation and enhanced nodule interaction at elevated temperatures. |
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