Green Preparation of polyvinylidene fluoride Microfiltration Membranes Via Thermally Indueced Phase Separation Method Using Diphenyl Carbonate and Diphenyl Ketone As Diluents

摘要

Diphenyl carbonate (DPC) and diphenyl ketone (DPK) were used as diluents to prepare microporous polyvinylidene fluoride (PVDF) membranes via thermally induced phase-separation (TIPS) method. The liquid - liquid phase-separation phenomena were found in PVDF/DPC and PVDF/DPK systems during the thermally induced phase-separation processes. The monotectic points of PVDF/DPC and PVDF/DPK systems appeared at PVDF concentration approximately 30 and 56 %(wt), respectively. This suggested that PVDF membrane with a bicontinuous or cellular structure could be obtained when the PVDF concentration was less than the point values. The effects of polymer concentration and quenching temperature on the membrane structure, porosity, and tensile strength were also investigated. The results showed that low polymer concentration and high quenching temperature led to a large pore size membrane. The tensile strength of the membrane increased with the increase of the polymer concentration, but the porosity of the membrane decreased. On condition that the PVDF concentration was higher than monotectic points, only polymer crystallization occurred and a typical compact spherulitic structures were obtained.