The plastic industry and titanium dioxide can be described as inseparable. Among the more than 500 titanium dioxide grades in the world, more than 50 are exclusive to plastics, and the average annual growth rate of up to 6% also makes the plastic industry the fastest growing field using titanium dioxide, and "wins" the second largest user of titanium dioxide. Where there is a material application, there are naturally matching indicators, parameter considerations, particle size distribution and particle shape significantly affect the key indicators of titanium dioxide for plastics. The particle size of titanium dioxide for plastics is just within the range of laser particle size analyzer, so for the application of titanium dioxide in the plastic industry, the industry may wish to pay more attention.

   As we all know, the scientific name of titanium dioxide is titanium dioxide, with excellent white performance, high hiding power and high achromatic power, is widely used in ink, paper, coatings, paints and other industries, enjoying the reputation of "white king", which is an important reason for the application of titanium dioxide in plastic products, that is, titanium dioxide can determine the appearance of light or white plastic products. Of course, titanium dioxide has many other benefits for plastics, such as improving the heat, light and weather resistance of plastic products, protecting plastic products from UV light, and improving the mechanical and electrical properties of plastic products. Almost all thermosetting and thermoplastic plastics will use titanium dioxide, they can be mixed with resin dry powder, can also be mixed with plasticizers containing liquid, the dosage is generally about 3-5%, polyolefins (mainly low-density polyethylene), polystyrene, ABS, polyvinyl chloride, etc.

   In the plastic industry, there are four main indicators to measure the quality of titanium dioxide - hiding power, dispersion, weather resistance and whiteness. The better the hiding power of titanium white, the lighter and thinner the plastic products produced; The dispersion affects the production cost of plastic products, the better the dispersion of titanium dioxide, the higher the smoothness and brightness of plastic products; Titanium dioxide with good weather resistance is indispensable for plastic products and plastic doors and windows used outdoors.

   The last big indicator is whiteness, the so-called whiteness refers to the degree of distance from the ideal white. The factors affecting the whiteness of titanium dioxide are mainly as follows. The first point is impurities, in the titanium dioxide process, especially the sulfuric acid titanium dioxide process, most of the operation is to remove impurities in the product, because impurities seriously affect the application performance of titanium dioxide, especially whiteness. Color-developing metal oxide impurities can affect whiteness at very low content, these elements are iron, manganese, chromium, copper, etc., these impurities themselves have color, in the white titanium dioxide is very easy to color.

The second point is the distribution of particle size and particle size, which mainly affects its whiteness through the reflection and scattering of light by titanium dioxide particles. The smaller the particle size of titanium dioxide, the higher the whiteness value, which is mainly due to the smaller the particle size of titanium dioxide, the increase of surface area, and the enhancement of light reflection and diffuse reflection. According to the characteristics of light waves, when the particle size of the pigment particles is less than half of the light wave, the maximum scattering of the color light of the wavelength can be obtained, after analysis, the best particle size for the wavelength blue light scattering is about 0.2 μm, and the maximum particle size of the longer wavelength red light scattering is about 0.35 μm, therefore, the scattered light of the small particle size of titanium dioxide is blue phase, and the transmitted light is blue complementary color red and yellow phase, on the contrary, the scattered light of large particle size titanium dioxide is red phase, and the transmitted light is blue phase. Usually the particle size of titanium dioxide for coatings is 0.2~0.4μm, while most plastics use titanium dioxide particle size is finer, particle size is 0.15~0.3μm, because this can obtain a blue background phase, most of the resins with yellow phase or easy to yellowing resin has a shielding effect.

   In addition, particle shape, titanium content, and coating agent have a certain influence on the whiteness of titanium dioxide. Among them, the influence of particle shape on whiteness is relatively small, in general, the whiteness of layered titanium dioxide is slightly lower, and the whiteness of spherical and rod-shaped is slightly higher. The increase of titanium dioxide content, titanium dioxide whiteness value also increased, aluminum, silicon, zirconium and other coating agent content increased, titanium dioxide whiteness value decreased.

   It is worth mentioning that in the production process of plastic masterbatches, the whiteness of titanium dioxide is also an important quality index, plastic masterbatches are a highly concentrated, high-efficiency color configuration product, that is, the pigment is evenly distributed in the carrier resin at an extraordinary concentration, and forms particles of a certain particle size. It is mainly composed of core layer (pigment), coupling layer (coupling agent or surfactant), dispersion layer (lubricant or dispersant), mixing layer (carrier resin), etc., used as a dye in plastics, widely used in the production of plastic products such as blown film, injection molding, hot pressing, injection molding, etc., masterbatch coloring effect is superior, easy to use, energy saving, no dust and sewage when used, so it is favored by users. Masterbatches are used as industrial raw materials, and the performance is usually manifested in subsequent product applications (such as blown film or injection molding), so the performance of titanium dioxide in color particles is mainly reflected in the application of masterbatches. The coloring ability, dispersion, processing performance, and whiteness of titanium dioxide will have a significant impact on the application of masterbatches, and it is logical that the detection of the particle size distribution of titanium dioxide is indispensable.