As an important fine chemical raw material, titanium dioxide is a kind of white inorganic pigment with wide application and great market demand. The following 9 factors should be considered in the selection of titanium dioxide.
Color is an important technical index for marking pigments. Titanium dioxide is known as the "king of white pigment", the color index of titanium dioxide is whiteness. Even the same chemical composition of titanium dioxide, due to the different process route, raw materials, equipment, technical level will also produce different colors, color depends on the chemical composition, but the more important and often decisive factor is its particle shape, size, particle size distribution, crystal form, impurity content.
2. Covering power
The optical essence of covering power is caused by the difference of refractive index between pigment and surrounding medium. The refractive index of rutile titanium dioxide is 2.71, anatase titanium dioxide is 2.55, which is the white pigment with the highest hiding power. The masking effect is mainly due to the scattering caused by titanium dioxide, or the absorption caused by the presence of colored substances, or when the incident light intensity decreases due to the above two reasons. Therefore, the main reasons for determining the hiding power of titanium dioxide are not only the chemical composition and crystal form, but also the particle shape, particle size and particle size distribution of titanium dioxide.
3. Coloring power
Coloring power is an important characteristic index of titanium dioxide, which is the ability of titanium dioxide to show its own pigment after mixing with another pigment. That is to say, for white pigment, the lighter the color of the mixture after it is mixed with a dark pigment, the stronger its coloring power (achromatic power).
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 its dispersion in the medium. In the coating industry, it can be used to estimate the consistency of paint before mixing, guide the formulation of paint, and preliminarily calculate the volume concentration of pigment (PVC).
5. Chemical composition
The chemical composition of titanium dioxide determines the chemical properties of titanium dioxide, which is the main sign of the difference between pigments. In addition to reflecting a series of pigment properties, such as whiteness, achromatic power, oil absorption and so on, it also has a great effect on its application performance, such as weather resistance, dispersion and so on.
6. Light and weather resistance
The light resistance and weather resistance of titanium dioxide is an important index to evaluate the application performance of titanium dioxide. It is meaningless to refer to the light resistance and weather resistance only. Only when titanium dioxide is applied to related application fields (such as automobile paint, profiles, etc.), this index will be meaningful. Therefore, the light resistance and weatherability of titanium dioxide refers to its light resistance and weatherability in a certain field. In addition, to measure the light resistance and weatherability of titanium dioxide, the weatherability of its application carrier should be better than that of titanium dioxide. The main factors affecting the weatherability of titanium dioxide include its chemical composition, chemical form of coating material, crystal structure, application formula and so on.
The glossiness of titanium dioxide is an important index to measure the application performance of titanium dioxide. Generally, titanium dioxide has no luster, so it is meaningless to only refer to its glossiness. Only when titanium dioxide is applied to related application fields (such as automobile paint, ink, profile, masterbatch, etc.), can this index be meaningful.
8. Volatile matter
The volatile content of titanium dioxide is actually the water content. Because there are high energy and hydroxyl groups on the surface of titanium dioxide, it is necessary to adsorb certain amount of water to reduce its surface energy. The amount of water adsorbed is related to the surface organic treatment of titanium dioxide and the humidity and temperature of the surrounding environment. The volatile content of titanium dioxide powder can not determine the quality of the product, but depends on its application system. In general, the volatile content of water-based system has little effect on the application, but for oil-based system and polyolefin system, the lower the volatile content is, the better, because the high volatile content will affect the dispersion performance and product quality in the system.
Dispersion is also called abrasive dispersion or abrasive wettability. When it is used in water medium, it is called water dispersion. When it is used in solvent and other coating systems, it is called oil dispersion. Dispersion index is an important application index of titanium dioxide. The dispersibility not only affects the extinction power, covering power and oil absorption of titanium dioxide pigment, but also affects the gloss and weatherability of coating film forming or profile forming. When grinding and dispersing in the coating factory, the dispersity directly affects the length of grinding and dispersing time, which is one of the important economic indicators in the coating production. Moreover, if the grinding time is too long, it will increase the equipment pollution and make the product whiteness worse. In the production of plastic masterbatch or profile, the dispersity directly affects the cycle of changing the head screen and the performance of the final product.
OKCHEM Distribution Project of Titanium Dioxide