Fluorocarbon paint is composed of polyvinylidene fluoride resin, pigments, modifiers, etc. In the actual production process, the coating will produce a linear or lattice-like crack similar to the dry riverbed. This phenomenon is called “crackingâ€. ". "Cracking" is usually caused by insufficient solvent when the painted film is melted during the baking process. The following situations will aggravate this phenomenon:
1, the metal surface temperature rose to 235 °C too long;
2. The flash dry speed of the paint film before baking is relatively fast;
3, the profile is too thick and the film is too thick;
4, too high pigment composition, such as white or gray.
The following precautions should be observed to minimize the occurrence of "cracking":
1, the primer should not be sprayed too thick, the proposed dry film thickness 5-10um;
2. The primer should not be flashed too fast before spraying the paint. Otherwise, it will produce dry absorption phenomenon of the topcoat solvent. Adding the slow-drying solvent can prolong the wetting time of the primer film.
3, the topcoat should not be too thick, it is recommended not to exceed 35um, volatile should not be too fast, it is recommended to use slow-drying solvents, ethylene glycol monobutyl ether or butyl carbitol, generally the flash dry time does not exceed 0.5 hours;
4. The process of raising the temperature of the furnace to the set temperature can not be delayed. If it is too slow or there is a cold spot, it can lead to cracking.