How do leveling agents work?

1. Overview of leveling

After the construction of paint, there is a flow and drying film-forming process, and then gradually form a flat, smooth, uniform coating film. Whether the coating film can achieve the characteristics of flat and smooth is called leveling. In the actual construction process of the coating, the film defects that often appear are orange peel, fish-eye, shrinkage, pinhole, shrinkage, Benedict swirl, air sensitivity and due to poor leveling, brush marks when brushing, roller coating roller marks are known as poor leveling, the generation of these phenomena reduces the decorative and protective function of the coating. There are many factors affecting the leveling of coatings, such as solvent volatility gradient and solubility properties, surface tension of coatings, wet film thickness and surface tension gradient, rheology of coatings, construction process and environment, etc., of which the most important factors are the surface tension of coatings, surface tension gradient generated by the wet film in the film-forming process and the surface tension homogenization of the surface layer of the wet film. To improve the leveling of coatings, it is necessary to consider adjusting the formulation and adding suitable additives so that the coatings have suitable surface tension and the ability to reduce the surface tension gradient.
2. Role of leveling agent
After wetting the substrate, the additives that control the flow of the coating to final leveling are called leveling agents, which can solve the following problems
3. The main influencing factors of leveling
3.1. Surface tension gradient – liquid-air interface
● Surface tension gradients in the inner and outer layers lead to Benadryl vortices
● Elimination of the surface tension gradient is an essential element in obtaining a level surface
3.2. Surface tension —- liquid-solid interface
Lower surface tension than the substrate, so that the coating has better substrate wettability
● Lower surface tension of the coating, which leads to better long-wave leveling of the liquid.
4. Influencing factors of leveling speed
● The higher the viscosity, the slower the leveling.
The thicker the film, the faster the leveling.
The higher the surface tension, the faster the leveling.
5. Mechanisms and properties of different leveling agents
5. 1) Eliminate surface tension gradient
5. 2 Reduce the surface tension of the system.
● Organosilicones.
–Significantly reduce surface tension
● Organosilicones: — Significantly reduce surface tension — Good migration properties eliminate surface tension gradient
● Non-silicone and non-fluorine: — No significant reduction in surface tension
–No significant reduction of surface tension
— No surface migration
— Orientation within the coating, adjusting local surface tension homogeneity