Dry-cast process for synthetic microporous membranes: Physico-chemical analyses through morphological studies

The dry-cast process was applied to the preparation of microporous membranes of different structures, using semi-crystalline and amorphous synthetic polymers. It consisted in casting a solution of a polymer in a mixture of a volatile solvent and a less volatile nonsolvent into a film, and leaving the film for a preferential evaporation of the solvents in air. A dry microporous membrane was obtained through liquid–liquid phase inversion with or without polymer crystallization, depending on the polymer nature, without the need to coagulate the membrane in a nonsolvent bath. We analyzed in details the physico-chemical aspects of the membrane formation in the case of poly(vinylidene fluoride), then discussed the applicability of the process to other common polymer materials like poly(vinyl chloride), poly(vinylacetate), poly(styrene) and polysulfone-cardo. The process advantages and drawbacks in the microporous membrane preparation were given.