Abstract
The molecular transport characteristics of poly(ethylene-co-vinyl acetate) (EVA) with aliphatic chlorinated hydrocarbons as probe molecules have been investigated by simple sorption gravimetric analysis. Uncrosslinked and crosslinked EVA membranes were prepared. The cross links were introduced by peroxide technique using dicumyl peroxide (DCP). Samples with different crosslinking densities were also prepared. The influence of crosslinking, different crosslinking density, temperature, size and polarity of penetrants on transport were analyzed. It has been observed that a critical concentration of crosslinker is necessary for maximum sorption. D1 sample showed a higher solvent uptake than the uncrosslinked sample. But when the extent of crosslinking increases, the equilibrium uptake decreases. The influence of temperature on the sorption and the activation energies of sorption have been calculated. Thermodynamic parameters were also estimated. The mechanism of transport showed anomalous behavior in all solvents. Sorption (S), desorpion (D), resorption (RS), redesorption (RD) experiments have been performed for studying the transport phenomenon. After attaining equilibrium, EVA sample was allowed to desorbe fully. The desorbed sample is then exposed to solvents for resorption followed by redesorption. Transport parameters namely diffusion coefficient, sorption coefficient and permeation coefficient have been calculated. The values of polymer-solvent interaction parameter and molar mass between crosslinks were calculated using Flory-Rehner theory. First order kinetics model was used to investigate the transport kinetics.
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