Preparation of microporous poly(vinylidene fluoride) membranes via phase inversion in supercritical CO2

Microporous poly(vinylidene fluoride) (PVDF) membranes were prepared from PVDF/N,N-dimethylacetamide (DMAC) solutions by using upercritical CO2 phase inversion process. As revealed by scanning electron microscope (SEM) and differential scanning calorimeter (DSC), he PVDF membranes exhibit morphological characteristics resulting from both liquid–liquid phase separation and crystallization, i.e., cellular ores surrounded by interlinked PVDF particulate crystallites. This indicates that both types of phase separation processes take place in the upercritical CO2 phase inversion process. The effects of pressure, temperature, and initial polymer concentration on the final membrane structures ere investigated. We also investigated the effect of addition of poly(methyl methacrylate) (PMMA) in the casting dope on the PVDF membrane tructure. The membrane structure changed significantly with the variation of PVDF/PMMA mass ratio in the casting dope as well as polymer oncentration. It was found that the variation of temperature and pressure has a minor influence on the membrane structure. 2007 Elsevier B.V. All rights reserved.