Although the variety of powder coatings is not as extensive as solvent-based coatings, there are many polymer resins that can be used as powder coatings. The total can be divided into two categories: thermosetting and thermoplastic. [2] 
1. A thermosetting powder coating refers to a thermosetting resin as a film-forming substance, and a curing agent which is subjected to a crosslinking reaction is heated to form an insoluble and infusible hard coating. The temperature is higher and the coating does not soften like a thermoplastic coating, but only decomposes. Since the resin used in the thermosetting powder coating is a prepolymer having a low degree of polymerization, the molecular weight is low, the leveling property of the coating is good, the decoration is good, and the low molecular weight prepolymer is cured. It can form a network cross-linked macromolecule, and thus the coating has better corrosion resistance and mechanical properties. Therefore, the development of thermosetting powder coatings is particularly rapid.
1.1 Epoxy powder coating. It is the first application in thermosetting powder coatings due to its excellent adhesion to metals, corrosion resistance, hardness, flexibility and impact strength. Epoxy powder coatings are formulated from Epoxy Resin, curing agents, pigments, fillers, and other adjuvants. The contribution of these components to the properties of the resulting powder coating is mutually constrained and influential, and a suitable formulation is actually the result of the coordination of the various components.
1.2 Polyester powder coating. Polyester powder coatings have unique properties compared to other types of powder coatings. It is better in weather resistance and UV resistance than [2] epoxy resin. In addition, since the polyester resin has a polar group, the powdering rate is higher than that of the epoxy resin, the yellowing process is not easy to yellow, the gloss is high, the leveling property is good, the paint film is full, and the color is light, so that Very decorative. Generally used in refrigerators, washing machines, vacuum cleaners, instrument housings, bicycles, furniture and other fields.
1.3 Acrylate powder coating. Acrylic resin powder coatings are both thermoplastic and thermoset. The most advantageous advantages of thermosetting acrylic resin powder coatings are excellent weather resistance, color retention, stain resistance, strong metal adhesion, and excellent appearance of the coating film, which are suitable for decorative powder coatings.
2. Thermoplastic powder coatings. Thermoplastic powder coatings began to appear in 1950. They melt at the spray temperature and solidify into a film upon cooling. Due to the simplicity of the processing and spraying methods, the powder coating can be melted, leveled, cooled or extracted and solidified into a film, without the need for complicated curing equipment. Most of the raw materials used are polymers that are common on the market, and in most cases, the performance requirements can be met. However, there are also some disadvantages such as high melting temperature, low coloring level, and poor adhesion to metal surfaces. Despite this, the commonly used thermoplastic powder coatings still exhibit some unique properties, among which polyolefin powder coatings have excellent solvent resistance; polyvinylidene fluoride coatings have outstanding weather resistance; polyamides have excellent wear resistance; Vinyl chloride has a good price/performance ratio; thermoplastic polyester powder coating has the advantages of beautiful appearance and high artistic quality. These properties make thermoplastic powder coatings a large proportion of the coatings market.
2.1 Polyvinyl chloride powder is one of the cheapest polymers for industrial mass production. It has excellent solvent resistance, good corrosion resistance to water and acid, impact resistance, salt spray resistance, food contamination and high dielectric strength for electrostatic spraying. Mainly used for painting metal mesh panels, steel furniture, chemical equipment, etc.
2.2 Polyethylene powder coating has excellent corrosion resistance, chemical resistance and excellent electrical insulation and UV radiation resistance. The disadvantage is that the mechanical strength is not high and the adhesion to the substrate is poor. It can be used in chemical tanks, impellers, pumps, pipe inner walls, instrument housings, sheet metal, refrigerator interior stencils, auto parts, etc.
2.3 Nylon powder coating. Nylon, also known as polyamide, has a high melting point of the polyamide resin because the N atom of the chlorine group on the molecular chain easily forms a hydrogen bond with the hydrogen atom on the adjacent segment. Nylon has the advantages of high mechanical strength, impact resistance, hardness, wear resistance, low friction coefficient, low vacuum, etc. It can be used for special requirements. Such as pump impellers, textile machinery parts, diesel engine starter piston parts, sailboat propellers, car wheels, motorcycle brackets, agricultural machinery, construction and sports equipment. In addition, because nylon is resistant to salt water and inert to mold and bacteria, it is very suitable for making coatings that are immersed in sea water or contact with sea water. At the same time, nylon powder coating is non-toxic, tasteless, not eroded by mold, and does not promote bacterial growth. Suitable for spraying parts of the food industry, drinking water pipes and food packaging.
2.4 Fluororesin powder coating. Fluoropolymers are capable of producing a wide variety of powder coatings, such as polytetrafluoroethylene (PTFE), polychlorotrifluoroethylene (PTFCE), polyvinylidene fluoride (PVDF), and the like. PTFE has a melting point of up to 327 ° C and can be used for a long time in the range of -250 to 250 ° C. In addition, it has excellent corrosion resistance, and it does not corrode even in aqua regia. It has excellent dielectric properties and a very low coefficient of friction. Self-lubricating, it is known as the "plastic king." It is widely used in petroleum, chemical anti-corrosion coatings, seals, bearing lubrication materials, electronic and electrical materials, ship launching guides and non-stick coatings. The price of polychlorotrifluoroethylene is cheaper than PTFE, the processing temperature can be reduced, the coating can be used for a long time below 130 °C, the resistance to alkali and hydrogen fluoride corrosion is better than that of acid-resistant enamel, and it is resistant to hydrochloric acid, dilute sulfuric acid, hydrogen chloride and chlorine. Better than stainless steel equipment. It has been widely used in anti-corrosion equipment in chemical plants, pesticide plants, pharmaceutical plants, detergent plants, etc. The biggest advantage of polyvinylidene fluoride powder coating is that it has excellent weather resistance, high degradation resistance in outdoor exposure, and does not absorb dust, so it is easy to maintain the original gloss. 5 chlorinated polyether powder coating. The chlorinated polyether has excellent chemical stability. The coating film has good corrosion resistance and solubility resistance to various acids, alkalis and solvents. The chemical stability is second only to polytetrafluoroethylene, and the mechanical and friction properties are also good. Chlorinated polyether powder coatings are mainly used in chemical equipment, pipeline lining, instrument equipment enclosures, etc. The disadvantage is that it has poor adhesion to metals. Adhesion to metals can be improved by the addition of additives.
2.5 latex powder coating
Latex powder is prepared by spray drying the emulsion, and most of them are vinyl acetate copolymers. The paint produced with latex powder is called a latex powder coating. Adding water and mixing on site is the most environmentally friendly coating in wall coatings.