EFFECT OF TEMPERATURE ON THE TRANSPORT-PROPERTIES AND MORPHOLOGY OF POLYMERIC ASYMMETRIC MEMBRANES

Polymeric membranes have not been practical for application to high te mperature processes, due to the thermal instability of most polymers. New materials are being developed with higher glass transition tempera tures and a greater degree of thermal stability. Use of these polymers to perform gas separations at higher temperatures is promising; howev er, the performance of the membrane as the process approaches the poly mer's glass transition temperature is unknown. This study was conducte d to explore this issue. Gas flux and helium/nitrogen ideal selectivit ies through heat treated integrally-skinned asymmetric polysulfone mem branes were measured. Membrane morphology was also evaluated through b ubble point tests and SEM micrographs. Experiments demonstrated that a s the polymer is exposed to temperatures approaching the polymer glass transition temperature, internal pores begin to collapse, causing bot h the gas flux and selectivity to decrease.