Analysis of the causes: After anatomy and analysis of the blistering part of the paint, the foaming layer was all above the middle coating. Only the topcoat film was blistering, and the midcoat did not show any blistering. The main reason is that the sealing ability of the middle coating is relatively poor. Even if water vapor exists in the primer and the middle painting film, it can be volatilized through the micropores of the paint film. The paint film of the topcoat layer is relatively closed, especially after the complete reaction of the two-component paint, if the water vapor contained in the paint film does not volatilize, the paint film is locally stressed due to the weather temperature and the expansion of the bottom layer water vapor. Bubbling occurs
The seasonal appearance of rice-like lacquer vesicles is obvious. Most of them occur in July and August, and are rain and wet weather. Due to the large amount of water contained in the air during this season, even in the spray booth, the humidity is sometimes greater than 70%. . It is difficult to completely volatilize the water after the paint surface is sprayed with paint. If the paint is sprayed on the surface containing water, the amount of water vapor is relatively small, and it is misty on the surface. During the process of covering and filming the paint, the water vapor can evaporate with the volatilization of the solvent. After drying, the paint film seals the water vapor. The water vapor left behind in the paint film encounters climate change and the water vapor in the lower part of the paint film expands. The paint film will be lifted up to form a paint bubble, which generally takes 3-5 days.
In summary, the cause of the paint-like lacquer in the topcoat is mainly the surface of the surface being coated with water.