Film formation of coatings studied by diffusing-wave spectroscopy

The coating industry is facing nowadays a growth in environmental regulations, and imposed substitution of suspected toxic components or solvents and a constant need for improving performances. The new formulations undergo new film-formation processes, influencing the coating performance and appearance. We have studied the film-formation process of several coating systems (water-based and solvent-based) using a new optical technology based on diffusing-wave spectroscopy. This unique and simple technique allows a non-intrusive monitoring of the drying process on the appropriate substrate (concrete, metal, plastic, wood, etc.). The kinetics of film formation, displayed in real-time, provide a new vision of the successive steps of the mechanisms taking place (evaporation, packing, etc.) as well as accurate information on drying times such as open-time, for an in-depth characterization of the film-formation process. (C) 2007 Elsevier B.V. All rights reserved.