During the process of Coating construction, the shrinkage of the paint film may lead to the mass and Appearance of the painting. Therefore, it is necessary to deeply understand the causes and solutions of shrinkage. This article will explore the causes of Coating shrinkage and how to effectively address this challenge.
1. Causes of shrinkage cavities
Shrinkage pores are usually caused by small particles or droplets with low surface tension. These low surface tension substances can exist on the surface of the substrate, in the Coating, or fall out of the air when the wet paint film is just finished Spreader. The following are the main reasons for shrinkage pores:
A. Surface tension layer: When there is a low surface tension material in the Coating or on the surface of the substrate, a surface tension layer will be generated. Coatings in the low surface tension part will try to flow to cover the surrounding high surface tension part, but the volatilization of the solvent will lead to an increase in viscosity, which will eventually hinder the flow and form shrinkage cavities.
B. Thick edge phenomenon: When lame plating, the paint film is usually thicker at the edge and thinner slightly away from the edge. This is because the air flow is strongest at the edge and the solvent evaporates the fastest, resulting in an increase in Resin concentration and surface tension at the edge, so that the Coating of the edge flows to the center.
C. Flying matter effect: During the lame plating process, the flying matter in the air may fall on the wet paint film. If the surface tension of the flying matter is low, shrinkage cavities will occur. Conversely, if the surface tension of the flying matter is high, it will lead to the orange peeling effect.
2. Shrinkage solutions
In order to avoid or reduce the shrinkage of the paint film, the following measures can be taken:
A. Increase the thickness of the wet paint film: Increasing the thickness of the wet paint film can reduce the formation of shrinkage cavities. Thicker wet paint films are not easily affected by impurity particles, so shrinkage cavities are less likely.
B. Increase the viscosity of the wet paint film: By adding thixotropic agents, etc., the viscosity of the wet paint film can be increased, thereby preventing the flow of Coating, and even the possibility of shrinkage can be reduced.
C. Reasonable Coating Selection: The choice of Coating has an important impact on the shrinkage problem. The solubility between different components in Coating should be considered to avoid dissolving or precipitation during the drying process.
D. Control of Coating Formula: The formulation of Coating should be reasonably designed to reduce factors that may lead to shrinkage. In particular, attention should be paid to controlling the formation of impurity particles and droplets in Coating.
E. Use leveling agent: For coatings prone to shrinkage, a leveling agent can be added to reduce surface tension and promote levelling of the coating. leveling agent can also be used to prevent the occurrence of orange peeling effect.
F. Curtain coating: Curtain coating is an effective painting method that reduces shrinkage problems. Under this method, the paint curtain needs to remain intact to ensure that no particles or droplets of low surface tension fall on the paint curtain.
Shrinkage is a possible FAQ in Coating construction, but it can be effectively mitigated or avoided through reasonable control and preventive measures. For applications that require high-mass painting, special attention needs to be paid to shrinkage cavities to ensure that the mass and Appearance of the final film meet the requirements.
