Physical aging and carbon dioxide plasticization of thin polyimide films in mixed gas permeation

Jianzhong Xia, Tai Shung Chung, D. R. Paul*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

67 Scopus citations


The gas permeation properties from thick (bulk) films have long been used as a guide to the performance of asymmetric membranes with a very thin selective skin (~100nm). However, recent research has shown that thin films of glassy polymer with a similar thickness undergo more rapid physical aging than such thick films, leading to different permeation characteristics. Our prior work has dealt with pure gases, and most recently, pure CO2 has been used to explore the difference in plasticization behavior for thick and thin films. This paper is the first effort to look at mixed gases involving CO2 and how thin films differ from thick films. Thick and thin films made of Matrimid, an important polymide for commercial gas separation membranes, have been investigated by monitoring their gas permeability and selectivity simultaneously for CO2/CH4 and CO2/N2 gas mixtures. The effects of film thickness, aging time, pressure, gas pair and gas composition on mixed gas behavior have been discussed in detail. The pressure dependence of pure gas permeability has also been measured as a control. Matrimid films become more vulnerable to CO2 plasticization as the thickness is reduced to the range of thin selective skins of asymmetric membranes and with increasing aging time. Competitive sorption/permeation effects appear to be more pronounced and the combined effect of CO2 plasticization and competitive sorption/permeation on thin Matrimid films seems to be more severe for CO2/CH4 feed mixtures than for CO2/N2 mixtures.

Original languageEnglish (US)
Pages (from-to)457-468
Number of pages12
JournalJournal of Membrane Science
StatePublished - Jan 15 2014

Bibliographical note

Funding Information:
The authors wish to acknowledge the financial support from NUS Grant C279-000-019–101 under the Tan Chin Tuan Centennial Professorship in Faculty of Engineering . The authors would also like to thank Dr. Cher Hon Lau, Dr. Huan Wang and Dr. Rajkiran Tiwari for their kind support.


  • Gas permeability
  • Matrimid
  • Mixed gas permeation
  • Physical aging
  • Thin films

ASJC Scopus subject areas

  • Biochemistry
  • General Materials Science
  • Physical and Theoretical Chemistry
  • Filtration and Separation


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