As an important fine chemical raw material, titanium dioxide is a white inorganic pigment that is widely used and has great market demand. The factors to be considered when choosing titanium dioxide are as follows:
1. Color
Color is an important technical indicator for pigments. Titanium dioxide is called "the king of white pigments", and the color index of titanium dioxide is whiteness. Even titanium dioxide with the same chemical composition will have different colors due to different process routes, raw materials, equipment, and technical levels. Although the color light depends on the chemical composition, the more important and often decisive factor is its particle shape, size, particle size distribution, crystal form, impurity content, etc.
2. Hiding power
The optical nature of hiding power is caused by the difference in refractive index between the pigment and the medium in which it is present. Rutile titanium dioxide has a refractive index of 2.71 and anatase type of 2.55. It is the white pigment with the highest hiding power. The covering effect is mainly caused by the scattering caused by titanium dioxide, or the absorption caused by the presence of colored substances, or the above two reasons to reduce the intensity of incident light. Therefore, in addition to the chemical composition and crystal form, the main factors that determine the hiding power of titanium dioxide are related to the particle shape, particle size, and particle size distribution of titanium dioxide.
3. Tinting power
The tinting power is an important characteristic index of titanium dioxide, that is, the ability of the mixture to show its own pigment after being mixed with another pigment. That is to say, for a white pigment, after mixing with a dark pigment, the lighter the color of the mixture, the stronger its tinting power (decoloring 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 vehicle, and can explain its dispersion performance in the medium. In the coating industry, it is used to estimate the consistency of paint before paint mixing, to guide the formulation of paint, and to estimate the pigment volume concentration (pvc).
5. Chemical composition
The chemical composition of titanium dioxide determines the chemical properties of titanium dioxide. It is the main symbol of the differences between pigments. It not only reflects a series of pigment properties such as whiteness, decolorization, oil absorption, etc., but also
has great effect on its application performance, such as weather resistance, dispersion, etc.
6. Light and weather resistance
Titanium dioxide's light resistance and weather resistance are important indicators to measure the application performance of titanium dioxide, and it is meaningless to simply refer to its light resistance and weather resistance. Only after the titanium dioxide is applied to the relevant application areas (such as automotive paint, profiles, etc.), this index has significance. Therefore, the light resistance and weather resistance of titanium dioxide refers to its light resistance and weather resistance in a certain field. In addition, when measuring the light resistance and weather resistance of titanium dioxide, it is necessary to ensure that the weather resistance of its application carrier is better than titanium dioxide. The main factors affecting the weather ability index of titanium dioxide are its chemical composition, chemical form of coating material, crystal structure, application formula, etc.
7. Gloss
The gloss of titanium dioxide is an important indicator of the application performance of titanium dioxide. Generally, titanium dioxide has no gloss, and it does not make sense to refer to its gloss only. Only when titanium dioxide is applied to the relevant application areas (such as automotive paints, inks, profiles, master batches, etc.) does this index have meaning.
8. Volatile matter
The volatile content of titanium dioxide is actually the water content. Because its surface has high energy and hydroxyl groups, its surface must always adsorb a certain amount of water to reduce its surface energy. The amount of adsorbed water 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 can not judge the quality of the product, it depends on its application system. In general, for water-based systems, the level of volatiles has little effect on the application, but for oily systems and polyolefins systems, the lower the volatiles, the better, because the high volatiles will affect its dispersion properties and product quality in these systems.
9. Dispersibility
Dispersibility is also called grinding dispersibility or grinding wettability. It is called water dispersibility when used in a water medium o
, and oil dispersibility when used in coating systems such as solvents. Dispersibility index is an important application index of titanium dioxide. The dispersibility not only affects the indicators such as discoloration movement, hiding power, oil absorption of titanium dioxide pigment, but also affects the gloss and weather resistance of coating film or profile molding. When grinding and dispersing in a coating production factory, the dispersibility directly affects the length of the grinding and dispersing time. It is one of the important economic indicators during coating production. And the grinding time is too long, it will also increase the equipment pollution and make the product whiteness worse. In the production of plastic masterbatches or profiles, the dispersibility directly affects the cycle of replacing the screen of the machine head and the performance of the final product.
