Polymer, Vol.54, No.17, 4675-4685, 2013
The prediction of polymeric membrane characteristics prepared via nonsolvent induced phase separation by the apparent coagulation time
Model cellulose acetate (CA) membranes were prepared by casting their solutions containing different polymer compositions and formamide (cosolvent) to acetone (solvent) ratios (FAR) followed by their precipitation in a water bath. The selected system provided the opportunity of changing the membranes morphology systematically via phase separation by nucleation and growth of polymer lean phase, spinodal decomposition and nucleation and growth of polymer rich phase mechanisms. The membranes morphological analysis by scanning electron microscopy confirmed their phase separation by various mechanisms leading to finger-like, sponge-like and sintered bead-like structures, respectively. The solution polymer concentration increase at constant FAR decreased the membranes porosity and pure water permeability, while enhanced their thicknesses, whereas it's FAR increase at constant polymer concentration raised the aforementioned characteristics. The application of simple phenomenological eta(0)Delta P-1 model where eta(0) and Delta P stand for the solution zero shear viscosity and the nonsolvent based osmotic pressure difference, respectively, well-predicted the membranes porosities and thicknesses. The model corresponded the apparent coagulation time, which its capabilities further proved by well-predicting the membrane thicknesses of three selected sets of experimentally found literature data representing the effects of polymer additive, cosolvent and polymer concentration. (c) 2013 Elsevier Ltd. All rights reserved.