The Effect of Particle Size on the
Covering Power of Titanium Dioxide
The covering power of titanium dioxide is related to the refractive index and scattering index. The refraction and scattering (reflection) of white pigment occurs at the interface between the pigment and the spreading agent, and the larger the interface, the higher the opacity. Therefore, the covering power is related to the surface area of titanium dioxide particles, as the surface area is inversely proportional to the particle size, the smaller the particle size, the larger the surface area, the greater the covering power. For the incident light of certain wavelength, it has the highest light scattering rate and higher whiteness when the size of pigment particles is half of the wavelength. Since the visible light wavelength is 0.4-0.7μm, so in theory the best particle size of titanium dioxide pigment particles is 0.2-0.35μm range .
TiO2 small particle size is more effective than large particle size in scattering blue light, so it has a more blue base phase and excellent whiteness. Dispersion rate in the particle size of 0.2μm at the highest, at this time the whiteness of the titanium powder, achromatic power and hiding power is optimal. At the same time, the narrower the particle size distribution, the smoother the surface of the coating film made and the higher the gloss. Therefore, as the quality requirements of various fields increase, the subsequent deep processing of titanium dioxide particles is a task that the titanium dioxide industry needs to pay attention to in order to obtain better quality titanium dioxide products. In developing the technology for producing titanium dioxide, reducing the particle size of titanium dioxide particles and ensuring a narrow particle size distribution are important issues to adapt to the new developments in various downstream industries.
