ABSTRACT
Waterborne coatings are mainly used for decorative purposes, but two-component, heavy-duty protective waterborne coatings are also available. This chapter discusses how waterborne paints differ from their solvent-borne counterparts. In both water-reducible coatings and water-soluble polymers, the polymer chain, which is naturally hydrophobic, is altered; hydrophilic segments such as carboxylic acid groups, sulfonic acid groups, and tertiary amines are grafted onto the chain to confer a degree of water solubility. In an emulsion coating, a liquid polymer is dispersed in water. In an aqueous dispersion coating, the polymer is not water soluble at all. Waterborne function in the paint is to help the film formation process. Trade literature commonly implies that waterborne coatings are somehow sensitive to high-humidity conditions. Real waterborne latex coatings contain much more: pigments of different kinds; coalescing agents to soften the outer part of the polymer particles; and surfactants, emulsifiers, and thickeners to control wetting and viscosity and maintain dispersion.
