A qualitative skin layer formation mechanism for membranes made by dry/wet phase inversion

Ingo Pinnau, William J. Koros*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

113 Scopus citations

Abstract

Optimized membranes made by a dry/wet phase inversion process using forced‐convective evaporation consist of an ultrathin and pore‐free skin layer supported by a nodular transition layer underlying open‐cell, sponge‐like substructure. It is suggested that the out‐ermost region of such case membranes undergo phase separation by spinodal decomposition in the initial stages of the evaporation process. As a result of the small scale of phase separation present in polymer‒solvent systems, an appreciable capillary pressure occurs in the interstitial space filled with the polymer‐poor phase in contact with air. The resulting force acts normal to the membrane–air interface, which tends to consolidate the polymer‐rich phase to form a nonporous surface layer. © 1993 John Wiley & Sons, Inc.

Original languageEnglish (US)
Pages (from-to)419-427
Number of pages9
JournalJournal of Polymer Science Part B: Polymer Physics
Volume31
Issue number4
DOIs
StatePublished - Jan 1 1993

Keywords

  • capillary pressure
  • coalescence
  • dry/wet phase inversion process
  • integrally‐skinned asymmetric membranes
  • skin layer formation
  • surface tension

ASJC Scopus subject areas

  • Condensed Matter Physics
  • Physical and Theoretical Chemistry
  • Polymers and Plastics
  • Materials Chemistry

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