Poly(vinylidene fluoride-co-hexafluoropropene) (PVDF-HFP) membranes for ethyl acetate removal from water

In this study, poly(vinylidene fluoride-co-hexafluoropropene) (PVDF-HFP) with low crystallinity was applied as the membrane material for pervaporative separating ethyl acetate (EtAc) from its aqueous solutions. The drying conditions during membrane fabrication by means of casting the PVDF-HFP solution dominated the obtained membrane morphologies when the polar solvents such as dimethylacetamide (DMAc) and acetone were used. It was demonstrated that both the DMAc-cast and acetone-cast PVDF-HFP membranes vacuum-dried at 60 °C were dense but had different crystalline structures. Predominantly α and γ crystalline phases were found in the acetone-cast and DMAc-cast PVDF-HFP membranes, respectively. And the different pervaporative separating performances of the two solvent-cast PVDF-HFP membranes were well explained in terms of different solution-diffusion properties which were induced from the permeants/polymer interactions on the base of the polarity differences between permeants and the two solvent-cast PVDF-HFP membranes.