The formation of microporous polyvinylidene difluoride membranes by phase separation

Microporous polyvinylidene fluoride (PVDF) membranes were prepared by casting and coagulating solutions of the polymer in eight different solvents. The membranes were characterized by scanning electron microscope observations, water content measurements and water permeability tests. The possible correlations between the resulting membrane characteristics and the properties of both the polymer-solvent solutions and the solvent-nonsolvent systems are extensively discussed. The analysis indicates that most of the correlations suggested or adopted in the literature do not hold for PVDF membranes, whereas the transport properties of the solvent-nonsolvent system seem to affect significantly the final membrane structure and the resulting performances in separation processes.