期刊
POLYMER
卷 50, 期 23, 页码 5565-5575出版社
ELSEVIER SCI LTD
DOI: 10.1016/j.polymer.2009.09.037
关键词
Physical aging; Gas permeability; Membranes
资金
- Air Liquide/MEDAL
- National Science Foundation [DMR 238979]
- NSF Science and Technology Center for Layered Polymeric Systems [DMR-0423914]
Membrane-based separations play a key role in energy conservation and reducing greenhouse gas emissions by providing low energy routes for a wide variety of industrially-important separations. For reasons not completely understood, membrane permeability changes with time, due to physical aging, and the rate of permeability change can become orders of magnitude faster in films thinner than one micron. The gas transport properties and physical aging behavior of free-standing glassy polysulfone and Matrimid (R) films as thin as 18 nm are presented. Physical aging persists in glassy films approaching the length scale of individual polymer coils. The films studied ranged from 18-550 nm thick. They exhibited reductions in gas permeability, some more than 50%, after similar to 1000 h of aging at 35 degrees C, and increases in selectivity. The properties of these ultrathin films deviate dramatically from bulk behavior, and the nature of these deviations is consistent with enhanced mobility and reduced T-g in ultrathin films. The Struik physical aging model was extended to account for the influence of film thickness on aging rate, and it was shown to adequately describe the aging data. (C) 2009 Elsevier Ltd. All rights reserved.
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