Physical aging of thin glassy polymer films monitored by gas permeability

被引:287
作者
Huang, Y
Paul, DR [1 ]
机构
[1] Univ Texas, Dept Chem Engn, Austin, TX 78712 USA
[2] Univ Texas, Texas Mat Inst, Austin, TX 78712 USA
基金
美国国家科学基金会;
关键词
physical aging; permeability; thin films;
D O I
10.1016/j.polymer.2004.10.019
中图分类号
O63 [高分子化学(高聚物)];
学科分类号
070305 ; 080501 ; 081704 ;
摘要
The physical aging at 35 degreesC of three glassy polymers, polysulfone, a polyimide and poly(2,6-dimethyl-1,4-phenylene oxide), has been tracked by measurement of the permeation of three gases, O-2, N-2, and CH4, for over 200 days. Several techniques were used to accurately determine the thickness of films (similar to400 nm-62 mum) in order to obtain absolute permeability coefficients and to study the effects of film thickness on the rate of physical aging. Each film was heated above the polymer T-g to set the aging clock to time zero; ellipsometry revealed that this procedure leads to isotropic films having initial characteristics independent of film thickness. A substantial pronounced aging response, attributed to a decrease in polymer free volume, was observed at temperatures more than 150 degreesC below T-g for thin films of each polymer compared to what is observed for the bulk polymers. The films with thicknesses of approximately 400 nm of the three polymers exhibit an oxygen permeability decrease by as much as two-fold or more and about 14-15% increase in O-2/N-2, selectivity at an aging time of 1000 h. The results obtained in this study were compared with prior work on thickness dependent aging. The effects of crystallinity on physical aging were examined briefly. (C) 2004 Elsevier Ltd. All rights reserved.
引用
收藏
页码:8377 / 8393
页数:17
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