Particles refer to the phenomenon that there are protrusions in the coating film that are distributed on the surface in the form of particles, which is caused by the coating film being mixed with impurities and foreign matter due to various reasons.
The impurities introduced in the manufacturing process of powder coatings are often the cause of particles in the coating film. Impurities, dust and other impurities brought into the environment.
① The reason for the material of the object to be coated. If there are blisters on the surface of the casting, or the surface of the hot-rolled steel plate is rough and has microscopic pores, particles (particles) or craters will be formed in the coating film. When the powder coating is baked and solidified, the melted leveling will seal the surface of the coated object. As the temperature of the coated object rises, the air pressure in the trachoma or pores of the coated object will increase, which will arch the melted and leveled coating film. When the internal pressure cannot burst the coating film, particles will form. When the coating film is broken and the coating film cannot be bridged, shrinkage cavities or craters are formed. Therefore, adding a defoamer to the formula makes it easy for the air in the trachoma or impurities to escape, and the gaps after the escaped air are easy to level and will not leave particles or shrinkage cavities on the coating film.
② The pre-treatment of the surface of the object to be coated is not good, and impurities such as residues from phosphating and other treatments are still attached to the surface of the object to be coated. It is easy to produce particles in the coating film during spraying, so the object to be coated must be cleaned carefully.
③The coating film is too thin. When the thickness of the coating film is below 50 μm, the powder coating cannot cover the tiny non-melting particles (particles) on the coating film during melting and leveling, but as long as the thickness of the coating film reaches a certain thickness, the particles (particles) on the coating film will decrease, so It should be ensured that the coating has a certain thickness. .In some other cases, the introduction of impurities will also cause particles in the coating film, such as the production environment is not clean, dust and particles in the air are introduced into the powder spraying room or powder coating recovery system, so it is necessary to ensure that the production environment is absolutely clean.