1. Crystal properties
There are two stable crystal forms: rutile (Rutile-R type) and anatase type (Anatase-A type). In general, R-type titanium dioxide has better weather resistance, water resistance and resistance to yellowing, but its whiteness is slightly worse. Type A titanium dioxide has poor light resistance and weather resistance, but has good whiteness.
2. Optical properties
(1)Refractive index: determines hiding power
Titanium dioxide has a very high refractive index, the anatase type is about 2.55, and the rutile type is about 2.70.
Different refractive index produces different covering power
The higher the refractive index, the more opaque, which means the stronger the hiding power. Because light bends more in a paint film containing high-refractive-index pigments than in a paint film containing low-refractive-index pigments, it is more difficult for light to penetrate the film.
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(2) Light scattering: determines coloring power
Tinting power is the result of the absorption and scattering of light by pigments. Titanium dioxide is a white pigment that absorbs very little light. Unlike colored pigments, light absorption plays an important role. Therefore, its tinting power (achromatic power) mainly depends on its ability to scatter visible light. It has strong scattering power and high tinting power (achromatic power).
Titanium dioxide has two forms: Rutile and Anatase
Rutile and anatase are both used in the white pigmentation of paints, paper, and ceramics. Rutile and anatase provide extra luster to other gems and minerals since they are capable of asterism.
Rutile is deep red while anatase is yellow to blue.
Rutile has a high absorbance property than anatase.
Rutile titanium dioxide is the most common form. It is preferably used in interference applications because of its high refractive index. It is also hard and has chemical resistant properties.
Anatase titanium dioxide is a type of polymorph which becomes a rutile when it is exposed at about 915 degrees centigrade. Its color is brown to black or yellow to blue. Anatase is the rarest form of titanium dioxide, but it has almost the same properties as rutile with regards to its hardness, density, and luster.
For more information, please visit Rutile Titanium Dioxide R-298.