Kinetic approach to the release of vinyl chloride monomer from polymer films, as related to diffusional theories

Monomer-release kinetics from polyvinyl chloride films, previously saturated by equilibration with monomer solutions in n-hexane, ethylene glycol monomethylether, methanol, and water, were measured by extraction with these model solvents, at 10-50 °C. Solute desorption rate data fitted a linear plot of total amount of solute released vs. the square root of time. Their analysis, in terms of diffusional release theory of a dissolved solute from a polymer matrix with initial solute loading given by the solubility limit, allowed one to obtain diffusivities of vinyl chloride in the polymer as a function of temperature, from which an activation energy of 11.9 ± 0.9 Kcal/mol could be calculated. Release kinetics were practically controlled by the low diffusivities, without any resistance to solute transport due to external mass transfer coefficients. The accelerating influence of solvents, relative to solvent-free experiments reported in the literature, may be compared to a plasticizing penetrant effect, which, however, does not appear to be susceptible, as to its bearing on diffusivities, to the chemical nature of the solvent used.