Pigment dispersion: I

Pigments are manufactured with the particle size distribution that gives th e best compromise of properties, but the particles often become cemented to gether into aggregates during processing. Breaking these aggregates and for ming stable dispersions of optimally sized pigment particles is a critical process in the manufacture of coatings. Making dispersions involves three a spects: (1) wetting, (2) separation, and (3) stabilization. Most authors ag ree that there are three aspects to dispersion but different terms are used , sometimes with conflicting meanings. Be careful reading papers to know ho w an author is using the terms. Because of effects of the high surface tension and polarity of water, consi deration of pigment dispersion is separated in three sections. In this sect ion we discuss dispersion in organic media, usually solutions of resins in organic solvent. Dispersion in aqueous media is treated in the Formulation of Mill Bases section. The third section covers the use of Dispersion Equip ment and Processes as well as the Evaluation of the Degree of Dispersion.