The effects of chemical modifications on morphology and performance of 6FDA-ODA/NDA hollow fiber membranes for CO2/CH4 separation

Jizhong Ren, Rong Wang, Tai-Shung Chung*, Dong Fei Li, Ye Liu

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

43 Scopus citations

Abstract

We have studied the rheological characteristics, membrane formation and CO2-induced plasticization phenomenon of almost defect-free copoly(4,4′-diphenylene oxide/1,5-naphthalene-2,2′ -bis(3,4-dicarboxylphenyl) hexafluoropropane diimide) (6FDA-ODA/NDA) hollow fiber membranes. Experimental results indicate that the dope rheology changes from a Newtonian to non-Newtonian fluid with elasticity when increasing shear rate. The asymmetric 6FDA-ODA/NDA hollow fiber membranes exhibit plasticization if the feed pressure is greater than 75psi. Chemical cross-linking modifications with p-xylenediamine were conducted at ambient temperature in order to enhance anti-plasticization characteristics of 6FDA-ODA/NDA hollow fiber membranes. Chemical modified membranes show a significant reduction in CO2-induced plasticization at least up 550psi (37.4atm or 37.9×106Pa) if the immersion time is great 1.5min. However, deteriorations in permeance and permselectivity are clearly observed if the immerse time is greater than 5min. FTIR spectra confirm that the 6FDA-ODA/NDA polyimide can be chemically cross-linked with p-xylenediamine, while wide-angle X-ray diffraction (WAXD) spectra imply the d-space of 6FDA-ODA/NDA membranes slightly decreases with an increase in cross-linking time. SEM pictures show that the outer selective skin as well as substructure becomes denser and thicker after chemical modification. The slight decrease in d-space may account for the permselectivity increase for the cross-linked membranes if the immersion time is short. However, the benefit of d-space reduction is offset by a denser and more compact selective skin and substructure when the immersion is prolonged.

Original languageEnglish (US)
Pages (from-to)133-147
Number of pages15
JournalJournal of Membrane Science
Volume222
Issue number1-2
DOIs
StatePublished - Sep 1 2003

Keywords

  • 6FDA-ODA/NDA copolyimide
  • Anti-plasticization
  • CO-induced plasticization
  • Chemical cross-linking
  • Gas separation

ASJC Scopus subject areas

  • Biochemistry
  • Materials Science(all)
  • Physical and Theoretical Chemistry
  • Filtration and Separation

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