*The leveling of the coating film is the combined effect of gravity, surface tension and shear force.
* The premise of leveling is whether the coating can wet the surface of the workpiece and whether it has good fluidity, which is related to the composition, performance and construction method of the coating.
*National Standard GB/T 1750-88 "Determination of Leveling of Coatings" - Leveling *The leveling process of the wet film is the homogenization process of the surface tension of the wet film. These homogenization processes are affected by wet film thickness, solvent evaporation, surface tension differences and viscosity.
*In the process of solvent volatilization, the thicker part of the wet film will have a higher solvent content, so the thinner part is prone to convection up and down to homogenize the substances contained in it. The up and down convection in this area causes surface area The concentration difference and the surface tension difference cause the surface flow of the wet film.
*The wet film loses its effective fluidity due to the continuous volatilization of the solvent. When the surface flow has not been able to equalize the surface tension, that is, it is still flowing, then the surface flow and up-and-down convection are "frozen" and become Surface defects, i.e. defects from wet film leveling, can be improved with leveling aids.
- Leveling
*Leveling aids are linear resins with limited compatibility (for coatings). It can migrate to the surface of the wet film but not to other interfaces because of its immiscibility, and the degree of enrichment at the surface increases with increasing immiscibility.
