Drying and film formation of industrial waterborne latices

Experimental evidence is given for the mechanism of film formation from industrial waterborne latices using Inverse‐Micro‐Raman‐Spectroscopy (IMRS). In the vertical direction of the film drying is gas‐side controlled, indicated by uniform water concentration profiles. In the horizontal direction inhomogeneous drying resulting from a horizontal mass flux toward the edge of the film and the formation of a drying front are observed. The completeness of film formation is tested by so‐called IMRS redispersion experiments. For hard latices (Texperiment ≃ Tmff) particle deformation is incomplete and the final coating—although transparent and optically clear—is a porous structure with a network of surfactant material located at the particle interfaces. The use of a film‐forming aid lowers the polymer's minimum film formation temperature (Tmff) and facilitates particle deformation and polymer interdiffusion. The result is a nonporous film structure where individual particles and a network of surfactant material are no longer observed. IMRS redispersion experiments are compared with pictures of the final coating surface obtained from atomic force microscopy (AFM). © 2007 American Institute of Chemical Engineers AIChE J, 2007