Rate-limiting steps in film formation of acrylic latices as elucidated with ellipsometry and environmental scanning electron microscopy

TitleRate-limiting steps in film formation of acrylic latices as elucidated with ellipsometry and environmental scanning electron microscopy
Publication TypeJournal Article
Year of Publication1996
AuthorsKeddie, J. L., Meredith Paul, Jones R. A. L., and Donald A. M.
JournalFilm Formation In Waterborne Coatings
Volume648
Pagination332–348
AbstractOur data indicate that evaporation is the rate-limiting step in film formation when the temperature of a latex is about 20 K or more above its glass transition temperature (T-g). When a latex is nearer to its T-g, the rate-limiting step in film formation is deformation of the latex particles, possibly by viscous flow of the polymer driven by the reduction in surface energy. In this latter case, there is evidence that a drying front first creates air voids. Subsequently, a coalescence front moves inward from the periphery in the plane of the film. Evaporation rates are retarded in a latex that is well-above its T-g, probably as a result of the reduced surface area of water, caused by extensive particle deformation. We studied the kinetics of film formation in an acrylic latex using ellipsometry and environmental-SEM, techniques which allow in situ observation of wet and partially-wet latices. We fit our data to a model describing the coalescence of voids by viscous flow.