Research Of Poly (Vinylidene Fluoride) (PVDF) Microporous Membrane Molding

Poly(vinylidene fluoride)(PVDF) is one of the widely used membrane material, due to its good physical properties,chemical stability, comp-arative molding properties, corrosion and thermal resistance. PVDF membranes have been widely used in membrane separation fields of organic/water separation, sewage treatment and gas filter and the fields of lithium battery diaphragm and polymer electrolyte membrane prepara-tion.Microporous membrane is most recently fabricated via immerse precipitation method. However, microporous membrane by this method often forms finger-pore microstructure which affects the membrane strength. Therefore, it is disadvantage to extend its applied field. In this paper, PVDF microporous membrane was prepared via dry-cast process (steel belt casting), TIPS and gel extrusion casting, and it was studied that different molding methods affected structure and properties of PVDF microporous membrane. It was found that, in the dry-cast process, structure of microporous membrane became dense and porosity decreased with film temperature rising. Performance of microporous membrane was excellent at the polymer concentration of 15wt% and the temperature of 80℃. Compared with DMAC, the global crystal appeared easily with NMP as solvent. Structure of microporous membranes was greatly influenced by adding the third component additives. When deionized water was added, film holes became larger. But the number of holes decreased with the amount of deionized water increasing. We could get uniform and close microporous membrane structure for DBP concent-ration of llwt% as additives. And it was of great practical value. PVDF microporous membrane preparated by TIPS produced spherulite easily as to influence membrane performance. When mixed diluent was used, the spherulite could be stopped to produce by adjusting the proportion of mixed diluent. We could get microporous membrane of cellular structure when the weight proportion of DBP and DOP was 1:1 and 6:4. Relatively, comprehensive performance of PVDF microporous membrane preparated by gel extrusion casting was good, and its outstanding characteristic was that mechanical performance was improved.Experiments also had some explore for environmental protection re-agents. PVDF microporous membrane was preparated by gel extrusion casting in PVDF/soybean oil, which improve the environmental pollution caused by toxic organic reagents.