Wetting agent for leveling agent substrate

The flow and leveling of coatings involve the surface and bottom of the coating (the interface in contact with the substrate). Generally speaking, people tend to focus more on surface features and overlook the bottom surface. In fact, bottom control is very important in terms of flow and leveling. The best additive for controlling the bottom surface is the base wetting agent.

The mechanism of action of substrate wetting agent:

Some people believe that as long as the surface tension of the coating decreases, the coating will have good wetting and spreading properties on the substrate. This viewpoint is incorrect. Alkyl nonylphenol ethoxylated surfactants can reduce the surface tension of water to 35mn/m; Non ionic organic fluorine surfactants can reduce the surface tension of water to 17mn/m. Dropping two equal amounts of aqueous solutions onto a polyester film, the aqueous solution of alkyl nonylphenol ethoxylate undergoes diffusion wetting, while the aqueous solution of fluorine additive forms spheres with very small contact angles and does not diffuse.

1. The substrate wetting agent must be able to be oriented at the interface of the substrate. Therefore, it is required that the molecule must have an amphiphilic structure, with lipophilic and oleophobic groups. Only in this way can the solvent friendly end face the coating and the oil repellent end face the solid interface in the coating, forming an oriented interface layer.

2. The base wetting agent must be a low surface active substance to reduce the interfacial tension at the solid/liquid interface after oriented alignment.

Due to the adsorption of matrix wetting agents at the solid/liquid interface, the surface energy of the coating is lower than that of the matrix, resulting in wetting and spreading, improving the fluidity and leveling of the coating film.