Diluent selection of PVDF membrane prepared via thermally induced phase separation

For the preparation of polyvinylidene fluoride (PVDF) membrane with bicontinuous structure via thermally induced phase separation (TIPS), the Hansen soluble parameters and permittivity were utilized for the selection of suitable diuent from dimethyl phthalate, methyl salicylate, carbitol acetate, glyceryl triacetate, dibutyl phthalate, acetophenone and diphenyl ketone. The interaction parameters estimated by Hansen soluble parameters and the difference of permittivity of PVDF-diluents show that liquid-liquid phase separation might occur in PVDF-DBP and PVDF-DPK systems. The measured PVDF crystallization temperature and the observed phase separation process indicate the occurrence of liquid-liquid phase separation in PVDF-DPK system when PVDF mass fraction was less than 30%. According to the phase diagram of PVDF-DPK, the PVDF microporous membranes with bicontinuous structure was prepared by controlling PVDF concentration and temperature without adding non-solvent or stretching process.