The Influence of Thickeners on the Surface Structure of Coatings Evaluated by Pair Distribution Analysis - Correlations to Structure and Porosity, 2006 Coating & Graphic Arts Conference

In this study, the relation between surface structure and porosity of coated layers was investigated. The main objectives were to investigate whether the surface structure correlates with the structure of the dry coated layers and if pair distribution function analysis can be used to give additional structural information compared with traditional methods. The pair distribution function,g(r), was used to measure the effects of thickeners on surface structure and to describe how added thickeners affect surface structure on dry coatings, e.g., in terms of ordered domains. The effects of three different water-soluble thickeners—carboxymethyl cellulose, polyvinyl alcohol, and an alkali-swellable emulsion—on surface structure and porosity were compared. Polystyrene particles were used as model pigments. It was found that the dry surface structure (in terms of ordered domains) was not automatically determined by the bulk structure. Thus, the pair distribution function was found to be a powerful tool to describe how added thickeners affect surface structure on dry coatings. The surfaces of the dry coated layers were characterized with respect to both smoothness (RMS roughness) and order/disorder (ordered domains). These two features seem to be governed by different mechanisms.