The effects of particle size distribution on the optical properties of titanium dioxide rutile pigments and their applications in cool non-white coatings

The particle size distributions of three commercially available titanium dioxide pigments were measured, and their effects on the optical properties of the pigments were investigated. The Altiris 550 and 800 pigments possess larger median particle size and wider size distributions than those of the conventional titanium dioxide rutile. The visible (VIS) reflectance, the solar reflectance and the lightness of the films and coatings singly pigmented with any of these three pigments decrease as the pigment particle size increases. The VIS transmittance and near-infrared (NIR) reflectance both increase as the pigment particle size increases. The main reflection band of the coatings shifts farther into the NIR region with increasing pigment particle size. The partially VIS-transmitting Altiris pigments enable the NIR and the solar reflectance of cool non-white coatings to be improved, thereby yielding metameric matches to the desired colors. •The particle size of Altiris pigments is larger than that of the conventional TiO2.•The solar and VIS reflectances of TiO2 pigments decrease with particle size.•The NIR reflectance of TiO2 pigments increases as particle size increases.•Altiris pigments improve the solar reflectance of colored coatings.•The addition of Altiris pigments yields a metameric match to the desired color.