PORE-SIZE DISTRIBUTIONS IN MICROPOROUS MEMBRANES - A CRITICAL ANALYSIS OF THE BUBBLE POINT EXTENDED METHOD

An extended bubble point method has been used to examine the porous mo rphology of several track-etched microporous polycarbonate membranes w ith nominal pore sits ranging from 0.1 to 5.0 mu m. The technique has been carefully analyzed and corrected to take into account the diverse non-ideal factors in flow along-with the prevalence of Knudsen flow o ver the Hagen-Poiseuille one in the smaller pores. The pore size distr ibutions were obtained in terms of flow or pore numbers. Bulk porosity and pore densities were in good agreement with nominal and SEM values for each filter. Performance wise, measured water permeabilities agre ed well with those obtained from pore density distributions, assuming Knudsen air flow through the narrowest pores.