Molecular elucidation of morphology and mechanical properties of PVDF hollow fiber membranes from aspects of phase inversion, crystallization and rheology

Panu Sukitpaneenit, Tai-Shung Chung*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

278 Scopus citations

Abstract

This study explores the fundamental science of fabricating poly(vinylidene fluoride) (PVDF) hollow fiber membranes as well as elucidates the correlation among membrane morphology, crystallinity and mechanical properties as functions of non-solvent additives and dope rheology in the phase inversion process. A series of non-solvents (i.e. water, methanol, ethanol, isopropanol) are used either as non-solvent additives in the dope or as a component in the external coagulant. Depending on the strength of the non-solvent, the phase inversion of semi-crystalline PVDF membranes is dominated by liquid-liquid demixing or solid-liquid demixing accompanying crystallization. As a result, the membrane morphology transforms from an interconnected-cellular type to an interconnected-globule transition type with lower mechanical strengths when adding water, methanol, ethanol, or isopropanol into the spinning dopes or into the coagulation bath. The crystallinity and size of spherulitic globules in the morphology are controlled by the amounts of non-solvents presented in the systems. The rheological behavior of dope solutions is explored and the relationship between elongation viscosity and mechanical properties has been elaborated. Analytical methods and molecular dynamics simulations are employed to provide insights mechanisms from the views of thermodynamic and kinetic aspects as well as the state of polymer chains involved in the phase inversion process.

Original languageEnglish (US)
Pages (from-to)192-205
Number of pages14
JournalJournal of Membrane Science
Volume340
Issue number1-2
DOIs
StatePublished - Sep 15 2009

Keywords

  • Mechanical properties
  • Membrane morphology
  • Non-solvent additives
  • PVDF hollow fiber membranes
  • Rheological properties

ASJC Scopus subject areas

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

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