STUDIES ON POLY(TETRAFLUOROETHYLENE-co-HEXAFLUOROPROPYLENE) HOLLOW FIBER MEMBRANES

Poly(tetrafluoroethylene-co-hexafluoropropylene) (FEP) hollow fiber membranes were prepared by melt spinning method with FEP as polymer matrix, composite of inorganic particles as pore-forming agent and dioctyl phthalate (DOP) as the diluent. The pure water flux and pore size distribution of the hollow fiber membranes were tested. Effect of FEP and composite of inorganic particles contents on the thermal properties, changes in thermodynamic properties and mechanical properties of the hollow fiber membranes were analyzed and discussed. The cross-section and surface morphologies of the hollow fiber membranes were observed by scanning electronic microscopy (SEM). The results showed that the spongy-like structure could be observed obviously in the cross-section of the hollow fiber membrane, which consisted of dissolved micro-voids and interfacial micro-voids formed by stretching. As the pore-forming agent contents increasing, the dispersed homogeneous degree became worse,which would brought about not only larger pores but also wider pore size distribution. The impact of pore-forming and diluent on the thermal properties and thermodynamic properties of the hollow fiber membranes was little. As the FEP contents reached 70 wt%, the compact layers formed on the hollow fiber surface induced the decrease of FEP hollow fiber membrane permeability.