Titanium dioxide types can be divided into anatase TiO2 and rutile TiO2. Titanium dioxide is widely used in various structural surface coatings, paper coatings and fillers, plastics and elastomers. Other applications include ceramics, glass, catalysts, coated fabrics, printing inks, roof coatings and fluxes.
Rutile titanium dioxide has better chalking resistance and gloss retention than anatase titanium dioxide. However, the surface of anatase titanium dioxide particles is photochemically active in the presence of water vapor and oxygen, but not photochemically stable. Anatase titanium dioxide can even promote the degradation of the matrix around its particles. Therefore, it is necessary to photostabilize TiO2. The stability can be obtained by controlling the types and quantities of different inorganic oxides. Namely, treat TiO2 with inorganic coating. A shielding net is formed between the surface around the TiO2 particles and the organic resin, which will no longer promote (or reduce) the degradation of the organic resin.
Both rutile and anatase titanium dioxide have high reflectivity to light in the visible light wavelength range (400-700nm), so they both have good whiteness. However, the performance of the two crystals is quite different in the wavelength range that is smaller than the visible light range, such as in the ultraviolet wavelength range of 300-400 nanometers. In the UV-A waveband (350-400nm) with strong lethality, the reflectivity of rutile titanium dioxide (red line) to UV is much lower than that of blue anatase titanium dioxide. In other words, the absorption rate of rutile titanium dioxide is much higher than that of blue anatase titanium dioxide. In this case, the film-forming organic resin around rutile titanium dioxide will share much less ultraviolet light.
In the market, anatase titanium dioxide is still very popular in the production of plastics, inks, popular printing pastes, New Year pictures, coatings and other industries. Anatase titanium dioxide has a low price and a certain degree of whiteness. However, in the production process, the anatase titanium dioxide should be ground or produced by high-temperature technology to enhence its dispersion force, so as to achieve the ideal state.
Most of rutile TiO2 is used in producing high-grade products. For example, the titanium dioxide in pigment production, ink production, plastic paint, wood paint and high-grade printing mucilage must be rutile titanium dioxide. Only rutile titanium dioxide can provide high-end products with excellent covering power and high gloss. In the process of dispersion, the use of rutile titanium dioxide will save time and effort.
Color is an important technical index to consider when buying titanium dioxide. Titanium dioxide is known as the king of white pigments, and the whiteness is the color index. Even titanium dioxide with the same chemical composition will have different colors due to different process routes, raw materials, equipment and technical levels. The color light depends on the chemical composition, but the more important and decisive factors are the particle shape, size, particle size distribution, crystal form, impurity content, etc.
2. Covering power
The optical nature of covering power is caused by the difference of the refractive index between the pigment and the medium around it. The refractive index of rutile titanium dioxide is 2.71, and that of anatase titanium dioxide is 2.55. Therefore, anatase titanium dioxide is the white pigment with the strongest covering power. Due to the scattering caused by titanium dioxide, or the absorption caused by the presence of colored materials or the above two reasons, the intensity of incident light decreases, and the covering effect occurs. Therefore, in addition to chemical composition and crystal form, the covering power of titanium dioxide is mainly determined by the shape, size and distribution of titanium dioxide particles.
3. Tinting strength
Tinting strength is an important characteristic index of titanium dioxide, which is the ability of titanium dioxide to show its own pigment after it is mixed with another pigment. That is to say, for white pigment, after it is mixed with a dark pigment, the lighter the color of the mixture is, the stronger its tinting strength (lightening power) is.
4. Oil absorption
Oil absorption is also one of the important pigment properties of titanium dioxide, because it relates to the filling state of titanium dioxide in the color developing agent and can explain the dispersion performance of titanium dioxide in the medium. In the coating industry, titanium dioxide can be used to estimate the consistency of the paint before mixing, guide the formulation of the coating, and preliminarily calculate the pigment volume concentration (PVC) according to the following formula.
5. Chemical composition
The chemical composition of titanium dioxide determines titanium dioxide chemical properties. Chemical composition is the main sign of the difference between pigments. In addition to reflecting a series of properties of pigments, such as whiteness, achromatic power and oil absorption, it also plays an important role in its application performance, such as weather resistance and dispersion.