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 the leveling process to achieve good surface quality. The flatness of the paint film is crucial to the painting process, because it directly affects the final quality and appearance of the painting.

Poor film levelling can lead to a variety of problems, such as brush marks when brushed, orange peel-like surface textures when sprayed, and roll marks when rolled. In particular, it should be emphasized that the orange peel effect in the spraying 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 the wet paint film, which sometimes resemble orange peel, hence the name orange peel.

Why is film leveling so important?

Some coatings contain highly volatile solvents, and these coatings are prone to produce orange peel effect during spraying. Typically, a mixture of fast and slow volatile solvents is used in coatings. In the spray construction, most of the volatile solvents have evaporated, which will improve the viscosity of the paint and reduce the possibility of wet paint film flowing down. The slow volatile solvent gives the wet film enough time to level itself and helps to expel the air in the wet film, thereby reducing the risk of holes bursting during baking.

However, it should be noted that the volatility of the solvent will affect the change of the surface tension of the coating, and the surface tension directly affects the leveling property. In general, the higher the surface tension, the better the leveling of the wet paint film. This is because liquids with high surface tension flatten more easily. Therefore, during the coating process, the volatility of the coating will change, resulting in a change in the surface tension of the coating, which will affect the leveling property of the coating.

Water-diluted coatings are a special case in which a fast evaporating solvent (such as isobutanol) is used mixed with water. The surface tension of water is relatively large, and 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, thereby promoting leveling.

Why is film leveling so important?

In fact, the leveling of paint film is a dynamic process, which is affected by many factors. In addition to the surface tension, the surface roughness of the wet paint film, the viscosity of the paint film and the thickness of the wet paint film also affect the leveling speed. It should be noted that paint that flattens too quickly is usually prone to flow problems, which means that the wet paint film flows downward under the action of its own gravity, resulting in non-uniformity on the surface.

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