Drying gels. II. Film and flat plate

An analysis is presented of stresses and strains that develop during the drying of a gel. The theory presented in Part I of this series is used to simulate the drying behavior of a film of gel on a rigid substrate and of a flat plate. The stress in the film is always tensile. The plate contains regions of compressive, as well as tensile, stress. If the permeability is low enough to inhibit contraction of the gel, tension appears at the exterior suface; otherwise, tension appears in the wet (solvent-saturated) region. The dried gel is predicted to contain a density gradient. The exterior is less dense than the interior if permeability does not restrict contraction during drying, and conversely.