MORPHOLOGY VARIETY AND FORMATION MECHANISMS OF POLYMERIC MEMBRANES PREPARED BY WET PHASE INVERSION

The cross-section morphologies of polymeric membranes obtained by scan ning electron microscopy are presented. Membranes are prepared by a we t phase inversion process from cellulose acetate, polysulfone, polyest er and a polyether type of elastomeric polyurethanes, poly(methylmetha crylate), and polyamide-nylon 4,6. Morphologies are qualitatively corr elated with the turbidity appearance and its intensity during the (pro to)membrane formation process and with their permeability to pure wate r. From the morphological characteristics, such as different cellular or dense structures, macrovoids, and polymer beads, and from the turbi dity phenomena during the (proto)membrane formation, the nucleation an d growth of polymer-lean or polymer-rich phase and the spinodal modes of polymer-solvent-nonsolvent ternary system decomposition are postula ted. (C) 1996 John Wiley & Sons, Inc.