Powder coating is the coating of a plastic layer on the surface of details that need to be covered. There are two popular types of plastics: thermoplastics and thermosets. Thermoplastic resins are substances that form a coating without having to undergo molecular structural transformation (such as polyethylene, polypropylene, nylon, polyvinyl chloride and thermoplastic polyester). The thermoset resins cross each other to create a heat-resistant permanent film that won’t melt again (epoxy, hybrid, urethane polyester, acrylic, polyester triglycidyl isocyanurate (TGIC)).
– Powder coating is also known as dry paint because of its coating properties in powder form and when used it will be charged with a charge (+) when passing through a device called a powder coating gun, at the same time the paint object a charge (-) will be charged to create the effect between the paint powder and the paint object.
Electro Static Power Coating Technology (Electro Static Power Coating Technology) is a modern technology invented by TS. Erwin Gemmer in the early 1950s. Through many improvements by scientists, manufacturers of powder coatings and equipment have made the electrostatic paint technology more and more complete in terms of quality and design. .
Classification of powder coating:
– Powder coating in the house.
– Outdoor powder coating
Operation principle of electrostatic painting process:
– Powder coating line. Main equipment is spray gun and automatic controller, other equipment such as paint spray booth and powder recovery; Infrared autoclave (autoclave with temperature adjustment and automatic on-off timer). Air compressors, compressed air dehumidifiers … Chemical tanks for surface treatment before painting are made of composite materials.
Materials suitable for powder coating are steel, aluminum, galvanized steel, magnesium, aluminum, zinc and brass. Powder coatings are used commercially for a wide variety of small to medium sized metal products, including lighting fixtures, equipment covers, outdoor equipment, and shelving racks. , window frames, …
– The coating is created by spraying powder which is charged by electrostatic method on the surface of the part and heated, then the coating powder will melt and form a well-bonded surface layer.
Powder coatings are commonly applied in single coatings and are growing in popularity as it is a surface coating technology that produces less emissions than other technologies. This trend stems from the rising costs and extended production times of other technologies, plus increasingly stricter environmental regulations. The main advantage of the electrostatic method is that it does not use volatile organic compounds (VOCs) and therefore does not require expensive VOC decomposition equipment such as incinerators or carbon absorbers.
The efficiency of powder spray systems is much higher than that of solvent or water spraying.
After spraying, the amount of powder that does not stick to the part can be recovered and reused. Compared with wet spray techniques, electrostatic spraying achieves greater coverage because the powder can cover all edges and surfaces of the part not directly with the spray gun.
Before spraying, the part surface needs to be cleaned, dried, and improved surface quality. The improvement of the surface quality can be achieved by acid washing or rinsing. The special processing methods before painting include cleaning with
specialized solvents, by abrasives, or by chemical diluents. The surface finish is more important to electrostatic paint than electroplating because there is no additional cleaning step in the coating process.
There are many types of thermoplastics used for electrostatic painting techniques such as polyethylene, polypropylene, nylon, PVC and thermoplastic polyester. These thermoplastics are mainly used as protective coatings and perform certain functions rather than as substitutes for solvent paints.
Thermosetting plastics will be pulverized into a fine powder and formed a thin film, so the coating surface is almost similar to paint. There are 5 main families of thermosetting resins: epoxy, hybrid, urethane polyester, acrylic, and triglycidyl isocyanurate (TGIC) polyester.
– The raw materials used in powder coating are priced much higher than other traditional paint materials for the same volume. However, there are many cases where the production cost of the finished product is lower, especially when a thick coating is required, and can compensate for the high powder material costs.
– The biggest limitation when applying electrostatic painting technique is the need to heat the object to be painted at high temperature (2600) to melt powder, so it is only applicable to metal items, the size of the part should be adequate for oven filling and batch colors to be uniform and consistent with other commonly used paints.