Titanium dioxide (TiO2) only exhibits its best properties when it is well stabilized against flocculation in the organic binder. This paper deals with the proper selection of dispersants for titanium dioxide according to the isoelectric point of the pigment, followed by review of results regarding gloss and haze development and gloss retention improvements in high-quality topcoat applications. Properties of typical additive chemistries that are useful for TiO2 stabilization will be discussed along with a description of their positive and negative side effects, especially the improvement of chalking resistance/gloss retention.
Titanium dioxide, as used for coating applications, is predominantly the rutile-type, high-purity titanium dioxide, manufactured by the chloride or sulphate process. The primary particle size of TiO2 for "hiding"-type applications is usually 0.25-0.3 µm. To reduce the photoactivity of the pigment, the rutile TiO2 crystal is modified with other metal oxides. In addition, very thin films of inorganic oxides (alumina, silica, zirconia) are deposited onto the pigment surface to influence the adsorption of additives.