Formation of poly(vinylidene fluoride) (PVDF) membranes via thermally induced phase separation

The effects of diluents, thermodynamic interactions, different quenching conditions and coarsening on the morphology of poly(vinylidene fluoride) (PVDF) membranes via thermally induced phase separation were investigated. Scanning electron microscopy indicated that an interconnected spherulitic structure was obtained in the PVDF–DMP system, while the PVDF–DMP–DOS and PVDF–DMP–DOA systems showed a jagged and sharp-edged spherulitic structure. As the interactions decreased, the spherulitic structure was increasingly non-discernable and the value of porosity increased in the order of PVDF–DMP, PVDF–DMP–DOA, PVDF–DBP and PVDF–DMP–DOS. When quenching in 353 K and 368 K, the spherulities became more discernable, and the size of spherulity increased. When quenching in different conditions, the discernible spherulitic structure was obtained in ice water, a greater spherulitic size was obtained in a water bath at 303 K, and PVDF crystallized much slower and improved in an air bath.