As a commonly used coating additive, leveling agent can promote the formation of a smooth, smooth and uniform coating film during the drying and film forming process of the coating. Whether the coating film can achieve flat and smooth characteristics is called leveling.

Different coatings use different types of leveling agents, so how do we choose?

After coating, the coating film undergoes extremely complex physical and chemical changes during the drying process. These phenomena and the nature of the coating itself will significantly affect the flow and leveling of the coating.

However, due to poor fluidity and leveling, there may be brush marks during painting, rolling marks during rolling, and orange peel during spraying.

During the drying process, shrinkage, pinholes, sagging and other phenomena may also occur, which are called poor leveling. The occurrence of these phenomena reduces the decorative and protective functions of the coating.

There are many factors that affect paint film defects, such as the volatilization gradient and solubility of solvents, the surface tension of the paint, the wet film thickness and the gradient of surface tension, the rheology of the paint, the construction process and the environment, and so on.

The most important factors are the surface tension of the coating, the surface tension gradient generated by the wet film during the film formation process, and the surface tension uniformity of the wet film surface.

At this time, you can understand the basic principles and selection of leveling agents.

To put it simply, the basic principle of the leveling agent is generally the following two points:

①. It has a certain compatibility with the system. ②. The surface tension needs to be lower than the system.

Both of these points affect the migration of the leveling agent. Only when the leveling agent spontaneously migrates to the surface of the paint film can it be called a leveling effect.

The application of leveling agents in coatings can be divided into two categories:
1. Application in solvent-based oil-based coatings
①. In primers and intermediate paints, acrylic type leveling agents are commonly used; degassing and substrate wettability are required, and high molecular weight acrylic leveling agents are required; stronger substrate wettability is required, Choose silicone leveling agent and modified acrylic leveling agent; if side effects such as foam stabilization and affecting interlayer adhesion occur, choose phosphate modified acrylic leveling agent.

②. For topcoats, relatively high requirements for the appearance of the paint film are required. The use of low molecular weight acrylic leveling agents can achieve good leveling properties and is not easy to produce haze in the paint film; for cross-linked curing systems, choose containing Acrylic leveling agent with reactive functional groups can achieve better leveling and improve the physical and chemical properties of the paint film; if better fluidity or slippage and scratch resistance are required, silicone leveling agents are used.

③. For over-glazing varnishes and solid color high-gloss paints, high gloss and good developability are required. Silicone leveling agents have a short-wave effect, which will affect the gloss, and acrylic leveling agents have a long-wave effect, which has an impact on the developability. If the silicone leveling agent and acrylic leveling agent are used together, the two can restrain each other and reach a perfect state.

2. Application in water-based coatings
①. In the water-based paint system, it is necessary to strongly reduce the surface tension of the system. The most commonly used silicone leveling agents and fluorocarbon leveling agents have the same effect as they are used in solvent-based paint systems. Of course, if a truly flat surface is required, the acrylic leveling agent for water-based systems is necessary.

②. For the latex system, the film forming mechanism is completely different, and the viscosity does not change with the volatilization of the solvent. The use of leveling agents in the formulation may improve the wettability of the coating’s substrate. Acrylic leveling agents can improve the flatness of the paint film, but the main flow properties of the coatings are more controlled and controlled by the addition of rheology control agents. Adjustment.