Why is film levelling so important?

Coatings play an important role in industrial applications, but during the construction process, a rough wet paint film is usually formed, which needs to go through a levelling process to achieve the ideal surface mass. The leveling of the paint film is crucial for the coating process, as it directly affects the final mass and Appearance of the painting.

Poor film leveling can lead to a variety of problems, such as brush marks when brushing, orange peel-like surface textures when lame plating, and roll marks when painting rollers. In particular, the orange peel effect in the lame plating process is very important for industrial applications. The orange peel effect is caused by tiny bumps formed by paint mist particles on the surface of a wet paint film, which sometimes resemble orange peel, hence the name orange peel.

Some Coatings contain highly volatile solvents, which are prone to orange peel effect during lame plating. Usually, fast-volatile and slow-volatile solvents are mixed in Coatings. During lame plating construction, most of the fast-volatile solvents have evaporated, which will increase the viscosity of the Coating and reduce the possibility of the wet paint film flowing down. Slow-volatile solvents allow enough time for the wet paint film to levelling and help remove air from the wet paint film, thereby reducing the risk of bursting during stoving.

However, it should be noted that the volatility of the solvent will affect the change of Coating surface tension, and surface tension directly affects leveling. Usually, the higher the surface tension, the better the leveling of the wet paint film. This is because high surface tension liquids are more prone to levelling. Therefore, during the painting process, the volatility of the Coating will change, resulting in changes in the surface tension of the Coating, which in turn affects the leveling of the Coating.

Water diluting Coatings are a special case in which a fast-evaporating solvent (such as isobutanol) is mixed with water. The surface tension of water is relatively large, while the surface tension of isobutanol is small, so isobutanol volatilizes faster, so that the proportion of water in the mixed solvent gradually increases, resulting in an increase in surface tension, which promotes levelling.

In fact, the levelling of the paint film is a dynamic process and is affected by many factors. In addition to surface tension, the asperity of the surface of the wet paint film, the viscosity of the Coating, and the thickness of the wet paint film also affect the levelling speed. It should be noted that Coatings with too fast levelling speed are often prone to sag problems, which means that the wet paint film is subject to its own gravity to flow down, creating inhomogeneity on the surface.

To sum up, the levelling of the paint film is a complex and critical process in the coating process. In the selection of Coating and the coating process, it is necessary to comprehensively consider factors such as solvent selection, surface tension, Coating viscosity, asperity and thickness of the wet paint film to ensure that a smooth and uniform painting surface is finally obtained to meet the requirements of industrial applications.