Modeling of multicomponent drying of polymer films

The drying of volatile solvents from a coated film is a complicated process since it involves simultaneous heat and mass transfer controlled by complex transport and thermodynamic behavior of polymer solutions. In this work, a model is developed to describe the drying behavior of polymer solutions. In this work, a model is developed to describe the drying behavior of multicomponent polymer solutions deposited on the impermeable substrate. A key component of the model is incorporation of multicomponent diffusion coefficients that consist of thermodynamic factors and self-diffusivities. Vrentas-Duda free-volume theory was used for predicting concentration and temperature dependency of self-diffusion coefficients. Drying processes in ovens with different zones in which temperature, velocity, and/or partial pressure of each solvent vary from zone to zone are considered. The predictions from the models provide detailed information about the relative importance of internal and external resistances to drying, effect of operating conditions, effect of the multiple-zone approach, as well as sensitivity of all physical properties on the drying rate. The validity of the model was confirmed by comparing predictions with the drying data available in the literature and the data collected in our laboratories. The experimental data and the simulation results are in good agreement.