Evaporation Casting

Evaporation casting or dry-casting involves the evaporation of a solvent (or a mix of solvents) from a starting solution and the subsequent formation of a polymeric membrane by precipitation. In this process a polymer is dissolved in a suitable solvent and the solution obtained is spread out across an appropriate support. Then, the solvent is left to evaporate, in inert atmosphere or controlled environment, inducing the polymer precipitation and generating a membrane generally with a dense structure (Fig. 1). In evaporation casting, in fact, the precipitation process is much slower than the precipitation obtained by immersion casting. As a consequence, the membranes present, usually, an isotropic and less porous structure. Some other components, called commonly nonsolvents, can be also added to the initial polymeric solution. In this case, the solvent, the more volatile element of the system, will evaporate faster leading to a higher polymer/nonsolvent concentration responsible for...