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Title: Effect of air-gap distance on the morphology and thermal properties of polyethersulfone hollow fibers
Authors: Chung, T.-S. 
Hu, X.
Keywords: Air-gap effect
Asymmetric membrane
Free volume
Membrane formation
Phase inversion
Issue Date: 7-Nov-1997
Citation: Chung, T.-S.,Hu, X. (1997-11-07). Effect of air-gap distance on the morphology and thermal properties of polyethersulfone hollow fibers. Journal of Applied Polymer Science 66 (6) : 1067-1077. ScholarBank@NUS Repository.
Abstract: By using 30/70 polyethersulfone/NMP (N-methyl-2-pyrrolidone) solutions as an example, we have determined the role of air-gap distance on nascent fiber morphology, performance, and thermal properties. An increase in air-gap distance results in a hollow fiber with a less layer of fingerlike voids and a significant lower permeance. For the first time we have reported that the Tg of a dry-jet wet-spun fiber prepared from one-polymer/one-solvent systems is lower than that of a wet-spun fiber, and Tg decreases with an increase in air-gap distance. These interesting phenomena arise from the fact that different precipitation paths take place during the wet-spinning and dry-jet wet-spinning processes. Wet-spun fibers experience vigorous and almost instantaneous coagulations; it results in hollow fiber skins with a long-range random, unoriented chain entanglement, but loose structure. Dry-jet wet-spun fibers first go through a moisture-induced phase separation process and then a wet-phase inversion process; it results in external fiber skins with a short-range random, compact, and slightly oriented or stretched structure. As a result, the outskin of wet-spun fibers have a greater free volume and a higher first Tg than that of the dry-jet wet-spun ones. Both SEM (scanning electronic microscope) photomicrographs and DSC (differential scanning calorimeter) analyses support our conclusion. © 1997 John Wiley & Sons, Inc.
Source Title: Journal of Applied Polymer Science
ISSN: 00218995
Appears in Collections:Staff Publications

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