Add pigments to paint or The filler is evenly distributed in the paint film to create a slightly rough surface. The larger the particles on the surface, the lower the gloss. Sometimes precipitated calcium carbonate or talc is used in the production of matte coatings. The dosage is large, which often leads to deterioration of physical properties and the occurrence of delamination and hard precipitation. The use of matting agents can avoid the critical pigment volume concentration of this paint film. Produce matt coating phenomenon. Commonly used organic matting agents and inorganic components2. The inorganic matting agent is mainly silica matting agent. Its chemical composition is silica, and the surface is divided into organically treated and untreated. The following is an introduction to the application of silica matting agents in coatings.
1. Pyrolysissilica matting agent: Made from ground quartz sand (powder), there are many impurities. The main component is silica, which cannot be called white carbon black. It has no matting properties and can only be used as a filler for coatings. It has no matting effect and uses white carbon as a matting agent. Black paint is mainly synthetic silica, divided into fumed silica and precipitated silica. The microstructure is amorphous or glassy. Precipitated silica uses quartz sand as the main raw material, sodium carbonate or sodium hydroxide reacts with its temperature in the furnace, and then passes through the melting treatment system. Forged silica is made by hydrolyzing silicon tetrachloride in a hydrogen-oxygen flame. Compared with natural silica, the silica of white carbon black has higher purity, greater inertness and UV resistance. 1.46 is the refractive index of amorphous silica, which is similar to the refractive index of many resins in the coatings industry. Therefore, amorphous silica with good optical properties can be used as a matting agent in coatings.
2. Matting mechanism of carbon black and pyrolytic silica matting agents: there is no matting agent When the varnish-coated mirror film is in a leveling state, when light reaches the surface of the film reflector, the incident light is partially absorbed and partially reflected by the film, which appears shiny. The film contains silica matting agent, which is evenly distributed in the film of silica particles to form a slightly rough surface. It can be clearly seen from the scanning electron micrograph of the cross-section of the film that the matting agent particles are evenly distributed in the film and when the incident light reaches the film’s uneven surface, diffuse reflection is scattered to produce low gloss and lack of gloss. Light matte appearance. High porosity, good particle size distribution and suitable surface treatment silica matting agent can achieve good matting effect.
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