ABSTRACT
Titanium dioxide is the preeminent white pigment currently available. The effectiveness of titanium dioxide pigments depends on crystallographic properties, chemical purity, surface character, and the state of dispersion in the application medium. The first three of these attributes are controlled by the pigment manufacturer alone, but the state of dispersion is significantly influenced by the pigment user. Titanium dioxide pigments are normally produced by one of two established techniques, the chloride and sulfate processes. The properties of titanium dioxide pigment can be substantially improved by coating the pigment particles. Many titanium dioxide pigments are also given an organic surface treatment to improve their dispersiblity. The addition of titanium dioxide pigments generally leads to an increase in microroughness because of the presence of particles at the surface leading to a loss of gloss. To reduce the amount of photocatalytic degradation, manufacturers of titanium dioxide pigments dope the crystal with metals such as aluminum that act as hole and electron recombination sites.
