Powder coatings are solid powder coatings composed of solid resins, pigments, fillers and additives, and are mostly used for anti-corrosion construction. Unlike ordinary solvent-based paints and water-based paints, its dispersion medium is different. The dispersion medium of solvent-based paints is organic solvent, the dispersion medium of water-based paints is water, and the dispersion medium of powder coatings is air. Since powder coatings basically do not contain organic solvents, they are environmentally friendly coatings and have been vigorously promoted in the field of environmental protection. In addition to the characteristics, there are also the advantages of reusability and high comprehensive utilization.
Powder coatings are generally applied by electrostatic spraying. The principle of electrostatic spraying is to use high-voltage electrostatic corona electric field to connect a high-voltage negative electrode to the metal diversion mark of the spray gun head, and the sprayed workpiece is grounded to form a positive electrode, so that the spray gun and the workpiece Form a strong electrostatic electric field. When the compressed air used as the carrier gas sends the powder paint from the powder supply tank to the guide rod of the spray gun through the powder tube, the corona discharge generated by the guide rod connected to the high voltage negative electrode generates a dense negative charge near it , The powder is negatively charged and enters the electrostatic field with high electric field strength. Under the dual action of electrostatic force and carrier gas, the powder uniformly flies to the surface of the grounded workpiece to form a uniform layer of powder, which is then heated and solidified to transform into Durable coating film.
A good powder coating is easy to spray, and the substrate can be covered by spraying 1-3 guns, with less secondary powder recovery and high work efficiency. Poor powder coatings are not easy to apply powder, and the substrate can be covered by spraying 3-5 guns. The secondary recovery of powder is large and the work efficiency is low. Through recycling and construction, the comprehensive utilization rate of a good powder coating can reach 99%.
For powder spraying, the importance of the powder rate must not be ignored. The powder coating rate of powder coating generally refers to the coverage rate of powder coating. Under the premise of ensuring the appearance and mechanical properties of the powder coating film, the amount of powder coating consumed per unit profile is a problem of production cost. Therefore, the powder coating rate is a very important factor, and it is a technical index determined by many factors. So how can we increase the powder coating rate?
Control the particle size distribution of powder coatings, the narrower the better. Since the particle size of the powder coating is related to the charge amount, the larger the particle size, the greater the charge amount. If the particle size distribution of the powder coating is uneven, the larger particle size will reach the surface of the sprayed object first, and the smaller particle size If it arrives later or cannot be reached, the powdering rate at a time is reduced, and the appearance quality of the paint film is prone to problems. Therefore, the particle size of powder coatings needs to be controlled within a certain range, not too large or too small. Each company will formulate its own standards according to the needs of downstream customers, and the general particle size is about 40-50μm.