Drying of solvent-borne polymeric coatings: I. Modeling the drying process

Abstract

Solvent evaporation of polymeric coating is modeled as a transient one-dimensional diffusion process in a slab shrinking in the direction perpendicular to the coating surface. The grid is selected in a way that there is always the same mass of the nonvolatile component between two grid lines. Fick's law of diffusion applies to this system with a shrinking coordinate when the diffusion coefficient is chosen as a function of solvent content. The resulting differential equation is solved numerically using finite differences. The boundary condition on the surface of the coating is given by the gas side mass transfer together with the assumption of thermodynamic equilibrium. The model allows the prediction of drying times or the determination of diffusion coefficients from drying experiments.