EFFECT OF THICKNESS OF THE PPO MEMBRANES ON THE SURFACE-MORPHOLOGY

The effect of membrane thickness on surface morphology has been studie d for the case of polyphenylene oxide (PPO) membranes cast from soluti ons of PPO in trichloroethylene (TCE). Both roughness and nodule size decrease with increasing membrane thickness up to a certain point afte r which they begin to increase. Minima in roughness and nodule size ar e observed for 9-11 mu m thick films. These minima depend on initial p olymer concentration in the casting solution. At a membrane thickness greater than 11 mu m, super nodular aggregates are formed. A mechanism based on Marangoni and Rayleigh number is presented. (C) 1998 Elsevie r Science B.V.