On the relationship between permselective membranes porosity and evaporation rate of the casting solutions

✍ Scribed by A. Franceschini; G. Fidilio; G. Actis

• Publisher: Elsevier Science
• Year: 1978
• Tongue: English
• Weight: 422 KB
• Volume: 26
• Category: Article
• ISSN: 0011-9164
• DOI: 10.1016/s0011-9164(00)84126-0

✦ Synopsis

The aim of the present communication is to suggest a correlation among porosity of permselective membranes and some physical variable affecting the membrane wet fabrication process.

It has been shown that porosity may be expressed in a way that allows for the concentration of polymer in the casting solution, and a parameter which in a sense gets together the different physical facets of the evaporation and coagulation steps in fabrication process.

Such a parameter is the shrinkage occurring in the starting polymer solution during the transition to the final, porous membrane; it seems to be dependent on the evaporation rate of the castin, 0 solution, increasing with the latter at first slowly, and afterwards in an abrupt way, until it reaches an asymptotic value.

The experimental finding might be interpreted in the light of the balance between evaporation and diffusion of the volatile solvent during the evaporation stage and of the balance amongst opposite fluxes of water and solvents during the next gelation stage.