Thermally induced phase separation (TIPS) process and non-solvent induced phase separation (NIPS) process are useful methods for the preparation of polymeric membranes.In this study,poly(vinylidene) fluoride (PVDF) membranes were prepared from ternary system consisted of polymer,diluent and solvent via combination process of TIPS and NIPS.The effect of composition ratio of solvent and diluent on polymer/solvent/diluent phase diagram was studied.Di-n-butyl phthalate (DBP) was used as diluents and N- methyl-2-pyrrolidone (NMP) was used as solvent.In the NIPS phase diagram increase of DBP content shifted the binodal curve to the left hand side due to immiscibility increase.In the TIPS phase diagram,increase of NMP content depressed the crystallization and melting temperatures.PVDF/diluent/solvent contents and cooling conditions had great influences on structures,and the effects of each parameter were examined.TIPS process was dominant with the increase of DBP content in a dope solution.NIPS process was dominant with the increased the NMP content in a dope solution.In suitable conditions such as DBP/NMP composition and cooling temperature,TIPS and NIPS occurred simultaneously due to the phase separation behavior based on the phase diagrams.PVDF hollow fiber membranes fabricated by melt/solution spinning process from PVDF/DBP/NMP underwent different phase separation mechanisms depending on the composition of DBP and NMP to result in the different structure of the membranes.Membrane structure was changed from isotropic structure with spherulites via TIPS to dense skin layer and finger-like structures via NIPS.As NMP content increased,water permeation rate and mean pore size were decreased due to the dense layer near the outer surface.Tensile strength was increased with dense skin formation,but decreased with finger-like structure and large spherulites.Increase of quenching temperature accelerated the NIPS rate due to the increase solvent/non-solvent exchange rate,while it retarded the TIPS rate due to the decrease of super-cooling.Water or ethyl alcohol was used as coagulant and its effects were also examined in terms of its miscibility with solvent and diluent.It was found that the composition ratio of DBP and NMP affected the morphology,mechanical properties,water permeation rate and pore size distribution of membrane.