Effect of dope flow rate on the morphology,separation performance,thermal and mechanical properties of ultrafiltration hollow fibre membranes |
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| Institution: | 1. Department of Chemical Engineering, National University of Singapore, 10 Kent Ridge Crescent, Singapore 119260, Singapore;2. Membrane Research Technology Singapore Ltd, 10 Science Park Road, #02-27, Singapore 117684, Singapore;3. Institute of Materials Research and Engineering, 10 Kent Ridge Crescent, Singapore 119260, Singapore;1. Department of Applied Physics I, Faculty of Physics, University Complutense of Madrid, Av. Complutense s/n, 28040 Madrid, Spain;2. Madrid Institute for Advanced Studies of Water (IMDEA Water Institute), Avda. Punto Com no. 2, Alcalá de Henares, 28805 Madrid, Spain;1. The State Key Laboratory of Fluid Power and Mechatronic Systems, School of Mechanical Engineering, Zhejiang University, Hangzhou, 310028, China;2. Key Laboratory of 3D Printing Process and Equipment of Zhejiang Province, School of Mechanical Engineering, Zhejiang University, Hangzhou, 310028, China;3. Key Laboratory of Soft Machines and Smart Devices of Zhejiang Province, Department of Engineering Mechanics, Zhejiang University, Hangzhou, 310027, China;4. School of Mechanical and Electrical Engineering, Guilin University of Electronic Technology, Guilin, 541004, China;5. Department of Medical Engineering, Ningbo First Hospital, Ningbo, 315010, China;6. Department of Biomedical Engineering, School of Engineering, Virginia Commonwealth University, Richmond, VA, 23284, USA;7. Shanghai East Hospital, Institute for Biomedical Engineering and Nano Science (iNANO), Tongji Medical School, Tongji University, Shanghai, 200120, China;8. Department of Chemical and Life Science Engineering, School of Engineering, Virginia Commonwealth University, Richmond, VA, 23284, USA;9. Department of Mechanical and Aerospace Engineering, University of Florida, Gainesville, FL, 32611, USA;1. Advanced Membrane Technology Research Center (AMTEC), Universiti Teknologi Malaysia (UTM), 81310 Skudai, Johor, Malaysia;2. Department of Chemical Engineering, Gachsaran Branch, Islamic Azad University, Gachsaran, Iran;3. Department of Chemical and Biological Engineering, University of Ottawa, 161 Louis Pasteur St., Ontario K1N 6N5, Canada;1. Advanced Membrane Technology Research Centre (AMTEC), Universiti Teknologi Malaysia, Skudai, Malaysia;2. Chemistry Department, Faculty of Science and Technology, Universitas Airlangga, Surabaya, Indonesia;3. Institute of Molecular Medicine and Biotechnology, Universiti Teknologi MARA Sungai Buloh Campus, Sungai Buloh, Malaysia;1. School of Chemical Engineering, Sichuan University, Chengdu, Sichuan 610065, China;2. State Key Laboratory of Polymer Materials Engineering, Sichuan University, Chengdu, Sichuan 610065, China;3. Jiangsu National Synergetic Innovation Center for Advanced Materials (SICAM), Nanjing, Jiangsu 211816, China |
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| Abstract: | We have determined the effects of dope extrusion speed (or shear rate within a spinneret) during hollow fibre spinning on ultrafiltration membrane's morphology, permeability and separation performance, and thermal and mechanical properties. We purposely chose wet-spinning process to fabricate the hollow fibres without drawing and used water as the external coagulant in the belief that the effects of gravity and elongation stress on fibre formation could be significantly reduced and the orientation induced by shear stress within the spinneret could be frozen into the wet-spun fibres. An 86/14 (weight ratio) NMP/H2O mixture was employed as the bore fluid with a constant ratio of dope fluid to bore fluid flow rate while increasing the spinning speed from 2.0 to 17.2 m/min in order to minimise the complicated coupling effects of elongation stress, uneven external solvent exchange rates, and inner skin resistance on fibre formation and separation performance. Hollow fibre UF membranes were made from a dope solution containing polyethersulphone (PES)/N-methyl-2-pyrrolidone (NMP)/diethylene glycol (DG) with a weight ratio of 18/42/40. This dope formulation was very close to its cloud point (binodal line) in order to speed up the coagulation of nascent fibres as much as possible so that the relaxation effect on molecular orientation was reduced. Experimental results suggested that a higher dope flow rate (shear rate) in the spinneret resulted in a hollow fibre UF membrane with a smaller pore size and a denser skin due to a greater molecular orientation. As a result, when the dope extrusion speed increased, pore size, water permeability, CTE and elongation of the final membranes decreased, but the separation performance, storage modulus, tensile strength and Young's modulus increased. Most surprisingly, for the first time, we found that there was a certain critical value, when the dope extrusion rate was over this value, the final fibre performance could not be influenced significantly. The results suggested that it was possible to dramatically enhance the production efficiency of hollow fibre UF membranes with the same fibre dimension and similar separation performance by the method proposed in this paper. |
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