What are the physical extinction and chemical extinction of powder coatings

I believe people will have many unfamiliar terms in areas they are not familiar with. These terms may sound impressive, but when they are seen, they are actually easy to understand. There are also some names that are simple but play a very important role in production. What do the physical extinction and chemical extinction of powder coatings mean respectively?

Physical extinction

The inorganic filler filling method is used to reduce the gloss of the coating film. However, due to the fact that the density of the filler is more than 1/4 higher than that of the resin, in order to achieve the effect of breaking the smoothness of the coating and obtaining a rough surface, the amount of filler used is relatively large, and the direct consequence will be a significant decrease in the leveling and mechanical properties of the coating. Therefore, this method cannot significantly reduce the gloss. In addition, methods such as adding stearic acid salts, wax and metal salt complexes, metal organic compounds, and polymers that are incompatible with the system can also achieve physical extinction.

Chemical extinction

The main methods are adding IPN matting agent, using matting curing agent, mixing different resins or curing agents, etc. However, there are few matting agents developed for polyurethane systems, and they are rarely sold in the domestic market. A matting agent developed by a certain research institute in China can produce a coating with a minimum gloss of 5% to 9%. However, the formula cost for this product is too high, and the resulting coating has poor flatness at low gloss levels. Extinction curing agents are more commonly used in epoxy powder coatings. Special curing agent for extinction polyurethane powder coating, it is a grafting compound that works by reacting polyester with hydroxyl groups and isocyanate blocked by caprolactam on one hand, and reacting certain hydroxyl or epoxy groups with carboxyl groups on the curing agent on the other hand, thereby reducing the gloss of the coating to below 30%, and even obtaining a matte coating. However, its reproducibility is poor and it is easily affected by factors such as pigments and fillers. The extinction effect of mixed curing agents is not significant, and currently, polyurethane curing agents in China mainly rely on imports with few types, making it difficult to choose suitable varieties.

Powder coatings and plastic powders may not be commonly seen nowadays, but their frequency in industrial production and daily life is increasing. They are very convenient to apply, environmentally friendly, natural, and have simple and even coloring.