1, pyrolytic silica matting agent: by grinding and processing of quartz sand (powder), many impurities, the main component is silica, can not be called silica, and no matting properties only as a filler for coatings, no matting effect, and as matting agent silica coatings are mainly synthetic silica, divided into calcined silica and precipitated silica, the microstructure is amorphous or glassy.
Precipitated silica is made of quartz sand as the main raw material, sodium carbonate or sodium hydroxide and its temperature in the furnace after the reaction, and then through the fusion processing system. Calcined silica is made by hydrolyzing silicon tetrachloride in a hydroxide flame. Compared to natural silica, silica has high purity, inertness and UV resistance.
1.46 is the refractive index of amorphous silica, which is similar to the refractive value of many resins in the coating industry, so amorphous silica with good optical properties can be used as a matting agent in coatings.
2, carbon black and pyrolytic silica matting agent matting mechanism: no varnish coating mirror film containing matting agent is in the leveling state, when the light reaches the surface of the film reflector, the incident light is partially absorbed and partially reflected part of the film showing gloss. The film contains silica matting agent, uniformly distributed in the silica particles of the film to form a slightly rough surface. Scanning electron micrographs of the cross-section of the matting agent particles can be taken from the film, which is uniformly distributed in the film, and when the incident light reaches the uneven surface of the film is clearly visible as diffuse reflection, which is scattered to produce a low gloss and matte appearance.
A silica matting agent with high porosity, good particle size distribution and suitable surface treatment can obtain good matting effect.
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