Fabrication and properties of poly(tetrafluoroethylene-co-hexafluoropropylene) hollow fiber membranes

Poly(tetrafluoroethylene-co-hexafluoropropylene) (FEP) hollow fiber membranes have been fabricated for the first time via the melt spinning method. Dioctyl phthalate (DOP) as the diluent and a composite powder (composed of soluble and insoluble particles) as the pore-creating agent were used in this study. The addition of the composite powder brought about a dissolved pore structure and interfacial microvoids (IFMs) in the membrane. The membrane's corresponding microfiltration performance was characterized in terms of pure water flux, a mechanical strength test, a mean pore size measurement and morphology observations by a field emission scanning electron microscope (FESEM). The results show that the FEP hollow fiber membrane was a kind of homogeneous membrane, with mean pore sizes ranging from 0.4 to 1 mu m. The increase of the composite powder addition and the stretching process brought about an obvious enhancement of the pure water flux and porosity. Compared with the available commercial PTFE hollow tube membranes, the smaller size of the FEP hollow fiber membrane provides a higher filled density in the membrane modules. Moreover, the smaller thickness of the membrane improves membrane permeability.