Polymer membrane formation through the thermal-inversion process. 1. Experimental study of membrane structure formation

Anisotropic polymer membranes have been successfully obtained via the thermal-inversion process. In contrast to conventional casting procedures by phase inversion, this process is less complicated but more flexible. In addition, the thermal-inversion process yields reproducible membranes with high porosities. In this work, conditions are delineated for the formation of anisotropic membranes on the basis of kinetic and thermodynamic considerations. Experimental findings verify these theoretical predictions for a particular polymer/solvent pair. Finally, asymmetric membranes with graded pore size profiles and a thin dense working skin can be obtained from a variation of the basic thermal-inversion procedure.ed.