EFFECTS OF KINETIC AND TRANSPORT PARAMETERS ON ACCELERATED MIGRATION OF REACTIVE ADDITIVE FROM PLASTIC SHEET

The effects of kinetic parameters Hatta number Ha and phi, and transpo rt parameters Biot number Bi and psi on the migration of a reactive ad ditive have been modeled. The convective boundary layer can be conside red inert to fully reactive for Ha --> 0 to 2, respectively. The migra tion is controlled by diffusion. reaction rate, equilibrium partitioni ng of the migrant between the plastic film and the solvent, and bounda ry layer resistance, depending on the time scale and values of the abo ve parameters. For a nonreactive boundary layer, at high Bi, migration is initially diffusion-controlled but becomes reaction-rate controlle d at later times. However, under similar conditions, a slight increase in the reactivity of the boundary layer immediately changes the trans port process from diffusion-controlled to reaction rate-controlled. Wi th fur-ther increase in reactivity, migration spontaneously reaches eq uilibrium, At low Bi, equilibrium partitioning and reactive depletion of the migrant in the fluid phase change predominantly to boundary lay er-controlling mass transport phenomenon. For a given sampling time (t au = 1.0), the migration increases with the increase in Bi only for a reactive boundary layer. At low Bi and (tau = 1.0), migration decrease s only up to phi is-approximately-equal-to 0.3 for nonreactive to part ially reactive boundary layer, but for inter-mediate and high Bi, phi and Ha do not influence migration.