Surface Coatings including Paints and Inks

The principal components in a paint are pigment, binder, and solvent. The basic steps in the manufacture of paints are [780]  

Most coatings are applied as solutions, emulsions, or suspensions of the pigment, and are converted to solid films after application, usually by allowing the solvent to evaporate. Latex, one of the simplest of paint formulations, is simply a dispersion of high molar mass polymer particles in water. In the first stage of solvent evaporation, the rate of evaporation is essentially independent of the presence of the dissolved or dispersed pigment. As the solvent evaporates, the viscosity increases and the free volume decreases, so that the rate of evaporation becomes dependent on how rapidly solvent molecules can diffuse to the surface of the film [782], 

In organic systems wetting and dispersion of the pigments is usually quite easy but stabilization of the dispersions normally requires steric stabilization, provided by adsorbed layers of polymer molecules. It appears that in most cases the adsorbed polymer layer has to be greater than about 10 nm for such dispersions to be sufficiently stable [782]. 

Both aqueous polymer-based systems (latex), made by emulsion or dispersion polymerization, and oil-modified alkyd resin-based systems are still in wide use [781], Table 12.2 shows the composition of a typical water-based emulsion paint. There is a wide variety of coatings, ranging from broad applicability to highly specialized, including latexes, amino resins, isocyanates, epoxy resins, acrylic resins, polyester 

Paints may also need to contain antifoaming and/or defoaming components since air can become incorporated into a paint during any or all of dispersing, transportation, mixing, filling, and application steps [483,780], Hydrophobic components, such as treated (hydrophobic) silicas or waxes, may be added to water-based paints in accordance with the principles described in Section 7.2.2, although there is a tendency to use quite specific antifoams for specific paints [780]. 

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