MOLECULAR MIGRATION OF HAZARDOUS LIQUIDS INTO THERMOPLASTIC ETHYLENE-PROPYLENE RANDOM COPOLYMER AND ISOTACTIC POLYPROPYLENE MEMBRANES

The molecular migration of hazardous organic halocarbons into thermopl astic polymer blend membranes has been studied using a gravimetric tec hnique. From the sorption results, the diffusion and permeation of liq uids have been calculated. Molecular migration depends on the nature o f the halocarbons, membrane-solvent interactions, temperature, and ava ilability of free volume within the membrane matrix. The size and the polarity of liquids do not show any systematic effect on sorption and desorption phenomena. The liquid migration results have been analyzed using a Fickian mechanism of sorption and diffusion. A numerical metho d based on the finite difference approach has been used to compute the liquid concentration profiles in the membrane materials. The estimate d Arrhenius activation energy for diffusion and the heat of sorption a re indicative of the nature of the liquids and their interactions with the membrane. The rate of evaporation of liquids has been calculated for sorption and desorption runs, and these results depend on the vola tility of the halocarbons.