In conventional film drying processes, a continuous layer of polymer solution is deposited onto a substrate and this layer is dried in an oven with forced air convection. The structure and properties of the final product are greatly influenced by the course of drying. Phase separation and non-uniformities can be attributed to poorly chosen drying conditions. Recently, a gap dryer has been developed which eliminates the need for forced gas flow, and provides direct solvent recovery.

Drying is a complicated process involving simultaneous heat, mass and momentum transfer. In this report preliminary results of the drying process of a binary polymer-solvent system in a gap-dryer are presented. The model incorporates simultaneous treatment of heat and mass transfer in the polymer and gas phases and jump conditions are used to describe the transport across the interface. The diffusion in the polymer phase is described by the free-volume theory of transport.