Evolution of colloidal coatings due to a wetting and drying process

Abstract

Paints and coatings are usually made by depositing a volatile liquid containing dispersed colloidal particles. The dry film is obtained through the evaporation of the volatile liquid. Depending on the ability of the particles to deform under capillary effect, we show that the drying can yield continuous coatings with no porosity, uniform porous coatings, or the formation of singularities, such as cracks causing the final film to be non-uniform. The evolution of the resulting coatings is then subjected to a wetting and drying process. Wetting leads to an increase in the water content of the unsaturated porous coating while drying results in water reduction. The response of the coatings to such a process can exhibit slight or significant changes in the morphology of the coatings that are related to their rheological properties. In particular, the growth of blisters is reported during the wetting and drying process.