FORMATION OF AN EXTERNALLY UNSKINNED POLYSULFONE CAPILLARY MEMBRANE

The production protocol of internally skinned ultrafiltration membrane s with no exterior skin layer was rationalized. The membranes were int ended for use in bioreactor and filtration operations. The unique subs tructure morphology was designed to have low resistance to liquid tran sport and a large external surface area. The polysulfone and polyether sulfone membranes that were produced had well-defined internal skin la yers, integrally part of a substructure that consisted entirely of clo sely packed and narrow-bore microvoids that extended from just below t he internal skin layer of the membrane to the periphery. The regularly shaped microvoids open into the membrane periphery as there is no out er skin layer to bridge the cavities. The structures formed may be the result of rapid demixing of the internal skin layer, followed by nucl eation and growth of the polymer-lean phase, coupled with coalescence at the membrane periphery.