A pigment is any finely divided, insoluble material that is added to a coating system prior to application on a substrate. Typically, pigments are used to modify the optical properties of a cured film by introducing decorative color, enhancing opacity or controlling gloss. In addition to promoting visual effects, these materials are also commonly used as rheology modifiers, extenders and corrosion inhibitors. However, in all cases, the key to efficiently promoting the desired functionality rests with the ability to control both the distribution and particle size of the added pigment(s) within a coatingĀ formulation.
Achieving the desired pigment distribution within a coating system is not a straightforward process. Pigments are commonly supplied as powders or beads, which themselves are composed of large agglomerates of individual particles. For most purposes, these agglomerates need to be milled to obtain a consistent particle size, preferably as primary particles. The newly formed insoluble particles must then be evenly distributed in the media and prevented from reforming agglomerates. The process by which pigment milling, as well as particle separation and stabilization occurs is called dispersion.1