Powder Coating process for wire shelf surface treatment
Working Principle
When working, the electrostatic spraying gun or spraying disc, spraying cup, the paint particulate part is connected with the negative pole, and the workpiece is connected with the positive pole and grounded. Under the action of high voltage power supply, an electrostatic field is formed between the end of the spraying gun (or spraying disc, spraying cup) and the workpiece. The electric field force of coating particles is proportional to the voltage of electrostatic field and the charged quantity of coating particles, but inversely proportional to the distance between the spray gun and the workpiece. When the voltage is high enough, the area near the end of the spray gun forms an air ionization zone, which intensely ionizes and heats the air, thus forming a dark red halo around the sharp edge of the spray gun or the pole needle, which can be clearly seen in the dark. Space-time air produces intense corona discharge.
The film-forming substances in coatings, such as resins and pigments, are mostly composed of macromolecule organic compounds and conductive media. Besides film-forming substances, solvent-based coatings also contain organic solvents, cosolvents, curing agents, electrostatic diluents, and other additives. Except benzene, xylene and solvent gasoline, these solvents are mostly polar substances with low resistivity and certain conductivity. They can improve the charged performance of coatings.
The molecular structure of dielectrics can be divided into polar and non-polar molecules. The dielectrics consisting of polar molecules exhibit electrical properties under the action of an applied electric field, while the dielectrics consisting of non-polar molecules are excellent.
Coatings are sprayed out after atomization by nozzles. Coatings particles are charged by contact when they pass through the pole needle or spray disc of the muzzle or the edge of the spray cup. When they pass through the ionization zone of the gas generated by corona discharge, their surface charge density will be increased again. Under the action of the electrostatic field of these negatively charged coatings particles, the polar workpiece surface is guided to move and deposited on the workpiece surface to form a uniform coating.
Process introduction
Powder spraying process, also known as powder coating, is a new coating process developed rapidly in recent decades. The raw material used is plastic powder. As early as the 1940s, some countries began to study experiments, but the progress was slow. In 1954, James of Germany successfully coated polyethylene with fluidized bed method. In 1962, after the invention of powder electrostatic spraying by Samms Company of France, powder coating began to be formally used in production. In recent years, due to the importance of environmental protection in various countries, powder coatings without pollution to water and atmosphere have developed rapidly.
Outstanding advantages
(1) Thicker coatings can be obtained by one coating, such as 100-300 micron coatings. It takes about 4-6 times to coat with ordinary solvent coatings, and once coated with powder coatings, the thickness can be reached. The corrosion resistance of the coating is very good.
(2) Powder coatings are solvent-free and pollution-free, which improves the working hygiene conditions.
(3) Powder electrostatic spraying and other new processes have high efficiency and are suitable for automatic pipeline coating. Powder utilization rate is high and can be recycled.
(4) In addition to thermosetting epoxy, polyester and acrylic acid, there are still a large number of thermoplastic resins which can be used as powder coatings, such as polyethylene, polypropylene, polystyrene, fluorinated polyether, nylon, polycarbonate and various fluorinated resins.
Powder coatings began to be used for protection and electrical edge. With the development of science and technology, powder coatings have been widely used in the automotive industry, electrical insulation, corrosion resistant chemical pumps, valves, cylinders, pipes, outdoor steel components, steel furniture, castings and other surface coating. The experimental study of powder coating has been carried out in China since the 1960s and has been applied in production. Development has been widely used.
