Adding appropriate amount of zinc stearate to the coating has obvious effect on the gloss of the coating. At the same time, it is closely related to the gloss and roughness of the surface of the object. When light hits the surface of an object, some of it is absorbed by the object, some is reflected and scattered, and some is refracted. The smaller the roughness of the surface of the object, the more light is reflected, the higher the gloss. On the contrary, if the surface of the object is uneven, more light is scattered, resulting in a reduction in gloss.
The process of coating film formation coating brush on the surface of the object, through the solvent volatilization and curing film. The forming process of coating film is important to the surface roughness and gloss of coating film. In the wet film stage, the solvent volatilization rate is controlled by diffusion on the coating surface. When the volatilization rate of each component of the solvent is not very different, it is possible to obtain a high gloss surface. On the contrary, when the evaporation rate of each component of the solvent is not the same in the wet film stage, it will make the polymer molecules tend to form coils, precipitate, into particles or clumps of different sizes, and the surface of the coating is uneven. In the dry film stage, the evaporation rate of solvent is mainly controlled by the diffusion of solvent in the whole film, which will also affect the roughness of the film surface.
In addition, in the formation of the film, with the evaporation of the solvent, the film will thin and shrink, some suspended heavy particles in the coating will be rearranged on the surface of the film, resulting in the uneven surface of the film. Particle size and distribution of pigments and fine materials The particle size and distribution of pigments and fillers in coatings are one of the important factors affecting the gloss of coatings. When the diameter of pigment particles is less than 0.3μm, high gloss coating can be obtained. The reason is that the pigment particles dispersed in the coating are made of a certain thickness of the film, and after drying, only the upper pigment particles are locally protruded, and the surface roughness of the film caused by the pigment ions with particle diameter less than 0.3μm will not exceed 0.1μm. When the average particle diameter of the pigment is between 3 and 5μm, the coating with better extinction effect can be obtained.
In addition to the above factors can affect the gloss of the coating surface, the volume concentration of the pigment (PVC), the dispersion of the pigment and the surface structure and surface reflection characteristics of the coating surface will also affect the gloss of the coating surface. Among them, with the increase of PVC of the pigment, the gloss of the coating surface is first reduced, and the minimum value appears at the limit volume concentration of the pigment (CPVC), and then with the increase of PVC, the gloss also becomes larger. When the pigment type and dosage are determined, the better the dispersion, the higher the gloss of the coating surface.