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The film formation of color coated board coatings mainly includes two aspects: coating adhesion and coating drying.
Adhesion of A color coated board coating
The first step in adhesion between the steel strip substrate and the coating is the wetting of the color coated board coating on the substrate surface. The coating wetting can replace the air and water originally adsorbed on the steel strip substrate surface. At the same time, the volatilization of the solvent on the substrate surface leads to dissolution or swelling. If the solubility parameters of the film-forming resin of the color coated board coating and the substrate surface are appropriately selected, it will form an immiscible layer between the color coated board substrate surface and the coating film, This is crucial for the good adhesion of the coating.
Drying of B color coated board coating
The adhesion construction of the color coated board coating only completes the first step of coating film formation in the coating process of the color coated board, and the process of becoming a solid continuous film needs to continue, which can complete the entire coating film formation process. The process of changing from “wet film” to “dry film” is usually referred to as “drying” or “curing”. This drying and curing process is the core of the coating film forming process. Coatings with different forms and compositions have their own film-forming mechanisms, which are determined by the properties of the film-forming substances used in the coating. Usually, we divide the film-forming process of coatings into two categories:
(1) Non transformative. Generally, it refers to the physical film-forming method, which mainly relies on the volatilization of solvents or other dispersing media in the coating film, gradually increasing the viscosity of the coating film and forming a solid coating film. For example, acrylic coatings, chlorinated rubber coatings, ethylene coatings, etc.
(2) Transformational. Generally, it refers to the occurrence of chemical reactions during the film forming process, and the coating mainly relies on chemical reactions to form a film. This film-forming process refers to the polymerization of film-forming substances in coatings, called polymers, after application. It can be said to be a special method of polymer synthesis, which completely follows the reaction mechanism of polymer synthesis. For example, alkyd coatings, epoxy coatings, polyurethane coatings, phenolic coatings, etc. However, most modern coatings do not form films in a single way, but rely on multiple methods to ultimately form films, and coil coatings are a typical type of film that relies on multiple methods to ultimately form films.