Membrane formation and structure development by dry-cast process |
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| Institution: | 1. Department of Environmental Chemistry and Materials, Okayama University, 2-1-1 Tsushima-naka, Okayama 700, Japan;2. Department of Chemistry and Materials Technology, Kyoto Institute of Technology, Matsugasaki, Sakyo-ku, Kyoto 606, Japan;1. State Key Laboratory of Urban Water Resource and Environment (SKLUWRE), Harbin Institute of Technology, 73 Huanghe Road, Nangang District, Harbin 150090, PR China;2. School of Civil Engineering, Wuhan University, Wuhan, Hubei, 430072, PR China;1. Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, MA 02139, USA;2. Department of Chemical Engineering, Northeastern University, Boston, MA 02115, USA;3. Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, MA 02139, USA;4. Department of Bioengineering, Massachusetts Institute of Technology, Cambridge, MA 02139, USA;5. Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, United States;6. Draper Laboratory, 555 Technology Square, Cambridge, MA 02139, USA;7. Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, USA;1. Applied Chemicals and Materials Division, National Institute of Standards & Technology, 325Broadway, MS 647, Boulder, CO 80305, USA;2. Ralph E. Martin Department of Chemical Engineering, 3202 Bell Engineering Center, University of Arkansas, Fayetteville, AR 72701, USA;1. Department of Chemical Engineering, Faculty of Science and Engineering, The University of Manchester, Manchester M13 9PL, UK;2. Department of Chemistry, Faculty of Science and Engineering, The University of Manchester, Manchester M13 9PL, UK;3. Instituto de Nanociencia y Materiales de Aragón (INMA) CSIC-Universidad de Zaragoza, C/ Mariano Esquillor s/n, 50018 Zaragoza, Spain;4. Departamento de Ingeniería Química y Tecnologías del Medio Ambiente, Universidad de Zaragoza, C/ Pedro Cerbuna 12, 50009 Zaragoza, Spain |
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| Abstract: | The various types of porous membranes were prepared by dry-cast process in several cellulose acetate/acetone/nonsolvent systems. The nonsolvents used were 2-methyl-2,4-pentanediol, hexanol and octanol. Because of the high boiling points of the nonsolvents used in this work, only the solvent (acetone) evaporated during the membrane formation. The effects of the nonsolvent weight fraction in the cast solution, the polymer weight fraction, membrane thickness and kinds of the nonsolvents on the membrane structures were studied. As the nonsolvent weight fraction increased, the membrane morphology changed in the order of entirely dense, asymmetric and entirely porous structures. The increase in the polymer weight fraction and the decrease in the membrane thickness suppressed the asymmetric structures. These kinds of nonsolvents significantly influenced the membrane morphology.In order to understand the change of the obtained membrane structures, the phase diagrams for ternary systems were clarified experimentally and theoretically. Moreover, the mass transfer process was analyzed and the changes in the polymer volume fractions during the membrane formation were simulated. Based on both these thermodynamic and kinetic properties, the membrane structures obtained were discussed in detail. The asymmetrc structures obtained in this work were found to be attributable to the kinetic difference in the increase rates of the polymer fractions across the binodal line. |
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