The drying definition of the coating film is: the process of transforming the liquid film-forming substance into a solid film, which is called drying.
(1) Physical drying, that is, all the volatiles in the coating are volatilized. Its drying speed depends entirely on the volatilization speed of the solvent in the acid-forming substance;
(2) Chemical drying, the liquid mold layer is in contact with air, and forms a dry film after oxidation and assembly. Or two-component coatings are composed of two-component chemical reactions (ie, curing reactions), and dry to form a film. The film-forming speed of this type of coating mainly depends on the chemical reaction speed of the film-forming substance.
The drying form of the coating, according to the different performances, is generally divided into volatile drying, melting cooling drying, oxidative polymerization drying, baking polymerization drying, heating catalyst polymerization drying, catalytic drying, photocuring drying, short-shot polymerization drying, oxidative drying, etc.
1) Coagulation or tightness: The solvent is almost completely volatilized, the viscosity of the paint is significantly increased, and the paint film continues to be sticky and dusty.
2) No clay on the surface: no traces are left when touched by hands, and the resistance to slight force is weak.
3) Practical drying: hand-pressed film leaves no traces, the film is hard and resistant to mechanical action.
4) Complete drying: the entire coating film is dry and hard, and the hardness does not increase any more.