Modeling of multilayer drying of polymer films

A model was developed to predict the drying behavior of multilayer polymer films on inert substrates. The model considers simultaneous heat and mass t ransfer controlled by complex thermodynamic and transport properties of pol ymer solutions. Key components of the model are the incorporation of the fr ee volume theory to predict diffusivities in each polymer layer, the use of heat and mass transfer coefficients to describe complex transport phenomen a in the gas phase, the incorporation of exact equilibrium boundary conditi ons at polymer-polymer interface, and the use of the Flory-Huggins theory t o describe both liquid-liquid and vapor-liquid equilibria. The model can be applied to guide processing, product formulation, scale-up, and oven desig n. As an example, the model is applied to simulate the drying of a two-laye r coating of poly vinyl acetate tin toluene) over polystyrene (also in tolu ene) on a polyester substrate. (C) 1999 John Wiley & Sons, Inc.