Factors to be considered in selecting titanium dioxide
Several factors to pay attention to in choosing titanium dioxide:
1. Relative density
Among the commonly used white pigments, titanium dioxide has the smallest relative density. Among the white pigments of the same quality, titanium dioxide has the largest surface area and the highest pigment volume.
2. Melting and boiling points
The melting and boiling points of the anatase titania are virtually non-existent as the anatase transform into rutile at high temperatures. Only rutile type titanium dioxide has a melting point and boiling point, rutile type titanium dioxide melting point is 1850 ℃, the melting point of (1830 + 15 ℃ in air and oxygen enrichment in the melting point is 1879 ℃, melting point is associated with the purity of titanium dioxide. The boiling point of rutile type titanium dioxide as (3200 + 300 ℃), titanium dioxide under the high temperature slightly volatile.
3. Dielectric constant
Because of its high dielectric constant, titanium dioxide has excellent electrical properties. The orientation of titanium dioxide crystals should be considered when determining some physical properties of titanium dioxide. The dielectric constant of anatase titanium dioxide is low, only 48.
4. Electrical conductivity
Titanium dioxide has the properties of semiconductor, its electrical conductivity increases rapidly with the rise of temperature, and it is also very sensitive to hypoxia. The dielectric constant and semiconductor properties of rutile titanium dioxide are very important to the electronic industry.
5. The hardness
The rutile titanium dioxide is 6~6.5 and the anatase titanium dioxide is 5.5~6.0 according to the scale of 10 mohs hardness, so the rutile titanium dioxide is adopted to avoid wear of spinneret in chemical fiber extinction.
Although titanium dioxide is hydrophilic, its hygroscopicity is not too strong, rutile is smaller than anatase. The hygroscopic property of titanium dioxide is related to its surface area, large surface area and high hygroscopic property.
7. Thermal stability
Titanium dioxide is of good thermal stability.
A uniform mixture of titanium dioxide and resin is formed by dispersing and stirring the clumps of titanium dioxide (clumps and clumps) in storage or packaging. Good dispersion can not only eliminate the phenomenon of speckle and streaks in the final product, but also guarantee the maximum light scattering efficiency. Special attention should be paid to the following three points:
The dispersibility of the titanium grade varies with the manufacturing process. For example, the grade of titanium dioxide treated with inorganic oxide surface is usually easier to disperse in the liquid system (plasticizers, plasticizers) than the untreated grade. But on the other hand, without the surface treatment of the grade usually easy to disperse in the dry mixing grinding (dryblending) such as polyethylene, polystyrene, or other molded with the resin manufacturing process.
An individual titanium dioxide particle cannot be broken. No matter how much energy is involved in the agglomeration process, when the bound agglomerations are broken down, they are simply the separation of the particles from each other.
Dispersion (dispersion), the use of the word is often vague. For example, some of the "dispersion" problems are actually problems of insufficient dilution on the formulation, while insoluble thick spots are left in the plastics.
Titanium dioxide is a popular pigment in plastics applications because it provides the best scattering effect in low pigment content. In addition to optical properties, other important product characteristics may also determine the level of titanium dioxide for special purposes.
9. Optical properties
In the selection of titanium dioxide, we need to consider the basic optical properties such as adaptability, color intensity, background color and color (color). The flexibility and the color of the white pigment strength shows its efficiency of light scattering, resilience shows white opaque pigment use plastic system capacity, and the intensity of the color it shows white paint on the colored plastic system provided by the whiteness, whiteness and brightness (brightness). Because it is easier to measure, the intensity of coloring is most commonly used to indicate the scattering efficiency of white pigments. In order to measure the relative strength of color, 0.008 grams of carbon black were added to each gram of titanium pigment sample. The mixed black pigment group (Masterbatch) was used to disperse the plastics, and the resulting gray plastics were made into even, opaque sheets or moldedchips. Titanium dioxide with the maximum light scattering efficiency provides the lightest shades of gray and the best light reflection.
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