PORE EVOLUTION AND SOLVENT TRANSPORT DURING DRYING OF GELLED SOL-GEL COATINGS - PREDICTING SPRINGBACK

This paper reports predictions of drying phenomena in deformable porou s gel coatings (i.e. a porous solid elastic network filled with air or solvent). Initially, a gelled coating is saturated with solvent, but as it dries, liquid-vapor menisci begin to recede into larger pores an d the gel becomes a partially-saturated porous medium. The tensile cap illary pressure in the liquid causes a compressive deformation on the solid skeleton and a consequent reduction in thickness and pore-size o f the coating. A theory coupling the large deformation of the solid sk eleton to capillary pressure in the interstitial liquid is used to pre dict the course of drying of dip-coated porous gel coatings. The theor y predicts a 'springback' effect in late stages of drying as the effec ts of capillary pressure diminish, which matches with experimental obs ervations.