Wrinkling means that the surface of the paint film is wrinkled into many hills and valleys, some of which are too thin to be seen by the naked eye, but the paint film has low gloss rather than wrinkles, and some wrinkles are wide and thick and clearly visible to the naked eye. The formation of wrinkles is caused by the high viscosity of the surface layer of the wet film while the bottom layer still has a certain degree of fluidity. The surface solvent volatilizes and cross-links. wrinkle pattern. Thick paint films are more prone to wrinkling than thin ones.
Wrinkle paint has been used extensively in office equipment in the past. Like hammer paint, it is used to cover uneven metal castings. Many metal castings have been replaced by molded plastic parts, so the usage has dropped.
Wrinkling is now an undesirable paint film defect. What is usually encountered is that in MF cross-linked coatings with improper formulation or construction, amines are used to neutralize the acid in the coating, or amines are used to block the sulfonic acid catalyst. With the increase of the volatility of the amine, the possibility of wrinkling Increased resistance, such as using dimethylaminoethanol without wrinkling, but wrinkling with volatile triethylamine. Both thicker paint film and increased blocking catalyst concentration will increase wrinkling.
Acrylic paints cured by UV radicals will wrinkle when they contain pigments, because the pigments absorb UV light and make the surface of the paint film cross-link quickly, while the bottom layer cross-links very slowly, resulting in wrinkling. Wrinkling is more serious in an inert atmosphere than in air, and the inhibition of oxygen in air reduces the difference in cure speed. Cationic polymerized UV-cured coatings are more prone to wrinkling because oxygen does not inhibit polymerization.
When tung oil is catalyzed with cobalt salt, the surface layer is cured first, and the lower layer is not dry to form surface layer wrinkles. What determines the size of wrinkles is the ratio of tung oil to other drying oils, and the ratio of drill drier to other drier (such as lead and lead salts) in the oil-based paint.
