Leveling agent can prevent shrinkage cavity

The anti shrinkage function of leveling agents

Shrinkage on the surface of coatings is a common defect. The contraction cavity is caused by unbalanced surface tension. The surface tension of the substance that produces shrinkage must be lower than the surface tension of the coating film called the shrinkage donor. The surface tension of the coating must be higher than that of the contraction cavity donor, which is called the contraction cavity acceptor. The reasons are as follows:

1. When several resins are mixed together and the solvent is properly matched, they can dissolve together and even form a transparent coating. However, when the solvent is not properly mixed, some resins will separate during the solvent evaporation process, causing colloidal particles to become donors for the contraction cavity.

2. Pollution from external objects, floating objects with low surface energy in the air, and silicone particles in dry tunnels falls on the surface of the coating.

3. Mixing coatings with low surface energy materials such as insoluble oils, silicone oils, colloidal particles, etc.

4. The surface tension of the substrate is unbalanced, and some areas are contaminated by low surface energy substances or the surface energy of the substrate is too low.

5. Add base wetting agent to coatings containing pigments or matte powders that have not been treated with wetting dispersants, and then the base wetting agent will adsorb onto the surface of exposed particles, forming a shrinkage cavity donor. This defect often occurs in water-based matte coatings.

The best way to overcome shrinkage is to use base wetting agents and siloxane surface state control agents. Some primers do not require or cannot use leveling agents, and only substrate wetting agents can be used to prevent shrinkage.