Without wetting and dispersing additives, pigments and fillers in paints could not be properly dispersed, and once dispersed, would not remain evenly suspended in the paint. The demands on pigment dispersion agents in modern binders are ever increasing, and requirements regarding color reproducibility are becoming more stringent. A wide range of chemically distinct pigment wetting agents, dispersants, and wetting and dispersing additives have been developed over time.1 Current product development focuses on the development of environmentally friendly, VOC-free and higher solids products. New polymerization techniques (e.g. group transfer polymerization) provide access to tailor-made, highly effective block copolymer additives with superior performance. This article presents a short overview of the wetting and dispersing process, the development of different additives over time and more recent developments.
Pigments for coatings are typically supplied as powdered materials wherein primary particles form larger agglomerates. These cohesive forces within a pigment agglomerate increase with decreasing particle size. This effect is most pronounced for organic pigments such as carbon blacks. The wetting and dispersing agent has to enable wetting of these particle surfaces, stabilize them and warrant a satisfactory performance of the coating. Table 1 shows the dimensions of typical particles that are dispersed and stabilized in coating formulations.