Microstructure Evolution in Latex Coatings, 1995 Coating Fundamentals Symposium Proceedings

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Experiments of rewetting of latex films by water show that latex particle deformation in film formation processes can be reversible under certain conditions. Latex particle deformation rate is correlated with the colloidal stability of the suspension. Water roughens latex films and raises their topographic contrast. Sodium dodecyl sulphate promotes redispersion of latex particles. Fronts of rewetting are observed. Water-soluble materials appear on rewetted film.

The consolidation and pore-emptying or ’dry-out’ fronts of dip-coated model latex-pigment coatings are recorded. Near the consolidation front, the suspension reaches what has been called the first critical concentration; near the pore-emptying or ’dry-out’ front, the suspension passes through the so-called second critical concentration. The microstructure development in latex-pigment coatings is continuous behind the consolidation front although the second critical concentration has been observed there. The slightly carboxylated poly (styrene-butadiene) latex and the medium carboxylated poly (styrene-acrylate) latex particles deform in seconds in coatings of precipitated calcium carbonate with latex binder. The highly carboxylated poly (styrene-butadiene) latex deformed only slightly in air-dried coating. The results indicate that latex particle deformation is not finished at the second critical concentration.