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As a high-quality white pigment for coatings, the whiteness of titanium dioxide is one of the key indicators to measure its quality. In many industrial fields such as coatings, plastics, papermaking, and inks, the whiteness of titanium dioxide directly affects the appearance quality and market competitiveness of the products. 

Definition of whiteness of titanium dioxide dry powder

The whiteness of titanium dioxide dry powder refers to the specular whiteness formed on the surface of titanium dioxide dry powder after it is treated by a specific method and tested by a whiteness meter or a spectrophotometer. Whiteness is a concept that combines the two optical effects of hue and brightness, reflecting the object's ability to reflect and scatter light. Due to its unique physical and chemical properties, titanium dioxide can reflect various visible light wavelengths to the same extent, thus showing high whiteness.

Main factors affecting the whiteness of titanium dioxide dry powder

Impurities

Impurities are one of the key factors affecting the whiteness of titanium dioxide. Especially rutile titanium dioxide is very sensitive to impurities. Even trace impurities, such as non-ferrous metal oxides such as iron, manganese, chromium, and copper, will have a significant effect on the whiteness of titanium dioxide. Iron content is one of the most important factors affecting whiteness, and whiteness decreases significantly with increasing iron content. Therefore, in the production process of titanium dioxide, especially in the sulfuric acid process, most operations are to remove impurities from the product to improve whiteness. 

Particle size and particle size distribution

Particle size and particle size distribution are also the main factors affecting the whiteness of titanium dioxide. The smaller the particle size of titanium dioxide particles, the larger the surface area, the enhanced reflection and scattering ability of light, and thus the whiteness value. According to relevant experiments, the whiteness of samples with SEM particle size of 220~240nm and a proportion of 150~350nm greater than 75% is better. Therefore, in the production process, the whiteness of titanium dioxide can be optimized by controlling the particle size and particle size distribution. 

Particle shape

Particle shape refers to the state of existence of titanium dioxide particles, which can be divided into spherical, rod-shaped and layered. Spherical particles are ideal because they have the largest surface area and the best reflection and scattering effect on light, which is conducive to improving whiteness. However, due to the influence of factors such as coating or gas powder, rod-shaped and layered particles may be produced in actual production. Although these particle shapes have relatively little effect on whiteness, they still need to be considered in some applications. 

Titanium content

Titanium content refers to the total content of titanium dioxide in titanium dioxide. For pigment-grade titanium dioxide, the content of titanium dioxide is generally above 90%, specifically between 92% and 98%. Other substances are mainly coating agents and a small amount of impurities. As the content of titanium dioxide increases, the whiteness value also increases accordingly. Therefore, increasing the titanium content is one of the effective ways to improve the whiteness of titanium dioxide.

Production additives

In the production process, the additives used, such as filter aids, lubricants, etc., may also affect the whiteness of titanium dioxide. These additives may contain organic compounds with long carbon chains, which will carbonize at high temperatures, making the titanium dioxide pink phase dull or even reddish brown. Therefore, when selecting additives, its effect on whiteness needs to be fully considered.