Titania pigment particles dispersion in water-based paint films

The distribution of titanian pigment, in dry water-based paint films in the presence of polymeric dispeersants containing different functional groups was investigated. The polymeric dispersants chosen were polyacrylic acid and polyacrylamide momo-and copolymers modified with hydroxyl and/or carboxylate groups. Atomic force microscopy (AFM) and transmission electron microscopy (TEM) were used to assess the distribution of the titania pigment particles in the surface and bulk, respectively, of the paint films, which was then compared to the gloss and surface roughnes of these films. In the absence of dispersant, the pigment distribution in the paint film was not uniform and relatively large pigment aggregates appeared at the surface, resulting in a rough surface and low gloss value. All dispersants both decreased surface roughness and increased the gloss of the dry paint film, with the dispersant type considerably enhancing the pigment dispersion in the dry paint film, in agreement with results obtained in aqueous pigment suspensions. In the presence of polyacrylamide homopolymer, the paint gloss increased slightly and further increased with the hydroxyl-modified polyacrylamide copolymer. The paint gloss was highest in the presence of polyacrylic acid or carboxylate/hydroxyl-modified polyacrylamide.