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Powder coatings are a new type of solvent-free, 100% solid powder coating. They are characterized by being solvent-free, pollution-free, recyclable, environmentally friendly, energy-saving and resource-efficient, reducing labor intensity, and possessing high mechanical strength.
Powder coatings are completely different from ordinary coatings; they exist in the form of fine powder. Because they do not use solvents, they are called powder coatings. The main characteristics of powder coatings are: harmless, high efficiency, resource-saving, and environmentally friendly.
Powder coatings are a new type of solvent-free, 100% solid powder coating. They are characterized by being solvent-free, pollution-free, energy-saving and resource-efficient, reducing labor intensity, and possessing high mechanical strength.
There are two main categories: thermoplastic powder coatings and thermosetting powder coatings.
Thermoplastic powder coatings are composed of thermoplastic resins, pigments, fillers, plasticizers, and stabilizers. Thermoplastic powder coatings include: polyethylene, polypropylene, polyester, polyvinyl chloride, chlorinated polyether, polyamide-based, cellulose-based, and polyester-based.
Thermosetting powder coatings are composed of thermosetting resins, curing agents, pigments, fillers, and additives. Thermosetting powder coatings include epoxy resin-based, polyester-based, and acrylic resin-based coatings.
Disadvantages: Uneven powder application at edges and corners, difficulty in concealing defects in the cured film, and high curing requirements.
There are many classification standards, and the names of various powders on the market are inconsistent. They can be divided into two main categories according to the properties of the film-forming substance: thermoplastic powder coatings and thermosetting powder coatings. Alternatively, they can be divided according to the appearance of the film-forming substance: matte, high-gloss, artistic, etc. They can also be divided according to the application environment: indoor and outdoor.
Although the variety of powder coatings is not as numerous as solvent-based coatings, there are still many polymer resins that can be used as powder coatings. They can be broadly divided into two categories: thermosetting and thermoplastic.
Thermosetting powder coatings refer to coatings that use thermosetting resins as the film-forming substance, and when heated, form an insoluble and infusible hard coating with the addition of a curing agent that initiates a cross-linking reaction. Even at high temperatures, this coating will not soften like thermoplastic coatings, but will only decompose. Because thermosetting powder coatings use prepolymers with low degrees of polymerization and low molecular weight, the coating has better leveling properties and decorative properties. Furthermore, after curing, the low molecular weight prepolymers can form a network of cross-linked macromolecules, resulting in better corrosion resistance and mechanical properties. Therefore, thermosetting powder coatings have developed particularly rapidly.
Epoxy powder coatings. Due to their excellent adhesion to metals, corrosion resistance, hardness, flexibility, and impact strength, they were the first type of thermosetting powder coating to be used. Epoxy powder coatings are formulated with epoxy resin, curing agent, pigment, filler, and other aids. The contributions of these components to the performance of the resulting powder coating are mutually restrictive and influential; a suitable formulation is actually the result of the coordination of various components.
Polyester powder coatings. Polyester powder coatings have unique properties compared to other types of powder coatings. Polyester resin exhibits better weather resistance and UV resistance than epoxy resin. Furthermore, due to the polar groups in polyester resin, it has a higher powder application rate than epoxy resin, is less prone to yellowing during baking, has high gloss, good leveling properties, a full film, and light color, thus possessing excellent decorative properties. It is commonly used in refrigerators, washing machines, vacuum cleaners, instrument housings, bicycles, furniture, and other fields.
Acrylic Powder Coatings. Acrylic resin powder coatings come in both thermoplastic and thermosetting types. The biggest advantages of thermosetting acrylic resin powder coatings are their excellent weather resistance, color retention, stain resistance, strong metal adhesion, and superior film appearance, making them suitable for decorative powder coatings.
Thermoplastic Powder Coatings. Thermoplastic powder coatings first appeared in 1950. They melt at the spraying temperature and solidify into a film upon cooling. Due to the simplicity of processing and spraying methods, powder coatings only require heating to melt, leveling, and cooling or extraction to solidify into a film, without the need for complex curing equipment. Most of the raw materials used are commercially available polymers, which can meet the performance requirements under most conditions. However, some drawbacks exist, such as high melting temperature, low coloring level, and poor adhesion to metal surfaces. Nevertheless, commonly used thermoplastic powder coatings still exhibit some unique properties. Polyolefin powder coatings have excellent solvent resistance; polyvinylidene fluoride coatings have outstanding weather resistance; polyamides have excellent abrasion resistance; polyvinyl chloride (PVC) has a good price/performance ratio; and thermoplastic polyester powder coatings have the advantages of beautiful appearance and high artistic appeal. These characteristics allow thermoplastic powder coatings to occupy a large proportion of the coating market.
Polyvinyl chloride (PVC) powder is one of the cheapest polymers for large-scale industrial production. It has excellent solvent resistance, good resistance to water and acids, impact resistance, salt spray resistance, and can prevent food contamination. It also has high insulation strength for electrostatic spraying. It is mainly used for coating metal mesh, steel furniture, chemical equipment, etc.
Polyethylene powder coating has excellent corrosion resistance, chemical resistance, and excellent electrical insulation and UV radiation resistance. Its disadvantages are low mechanical strength and poor adhesion to the substrate. It can be used for chemical tanks, impellers, pumps, pipe inner walls, instrument housings, metal sheets, refrigerator inner mesh panels, automotive parts, etc.
Nylon powder coating. Nylon, also known as polyamide, has a generally high melting point because the nitrogen atom in the chlorine group of its molecular chain easily forms hydrogen bonds with the hydrogen atoms in adjacent chain segments. Nylon has advantages such as high mechanical strength, impact resistance, hardness, wear resistance, low coefficient of friction, and low dust absorption, making it suitable for parts with special requirements. Examples include water pump impellers, textile machinery parts, diesel engine starter piston parts, motorboat propeller impellers, automobile wheels, motorcycle brackets, agricultural machinery, construction and sports equipment, etc. Furthermore, due to nylon's resistance to salt water and its inertness to mold and bacteria, it is well-suited for manufacturing coatings that are immersed in or in contact with seawater. Nylon powder coating is also non-toxic, odorless, and does not resist mold or promote bacterial growth, making it ideal for spraying parts in the food industry, drinking water pipes, and food packaging.
Fluoropolymer powder coating. Many types of fluoropolymers can be used to prepare powder coatings, such as polytetrafluoroethylene (PTFE), polychlorotrifluoroethylene (PTFCE), and polyvinylidene fluoride (PVDF). PTFE has a high melting point of 327℃ and can be used long-term within a temperature range of -250 to 250℃. It also possesses excellent corrosion resistance, remaining uncorroded even in aqua regia. Furthermore, it exhibits excellent dielectric properties, an extremely low coefficient of friction, and self-lubricating properties, earning it the nickname "King of Plastics." It is widely used in petroleum and chemical anti-corrosion coatings, seals, bearing lubrication materials, electronic and electrical materials, ship launching rails, and non-stick cookware coatings. PVDF is cheaper than PTFE, allows for lower processing temperatures, and its coatings can be used long-term below 130℃. Its resistance to alkali and hydrogen fluoride corrosion is superior to acid-resistant enamel, and its resistance to hydrochloric acid, dilute sulfuric acid, hydrogen chloride, and chlorine corrosion is superior to stainless steel equipment. It is widely used in anti-corrosion equipment in chemical plants, pesticide plants, pharmaceutical plants, and detergent plants. The biggest advantage of polyvinylidene fluoride (PVDF) powder coatings is their excellent weather resistance. They exhibit high resistance to degradation even after outdoor exposure and do not attract dust, easily maintaining their original gloss. 5. Chlorinated polyether powder coatings. Chlorinated polyethers possess excellent chemical stability. The coating film exhibits good resistance to corrosion and dissolution from various acids, alkalis, and solvents. Its chemical stability is second only to polytetrafluoroethylene (PTFE), and its mechanical and tribological properties are also excellent. Chlorinated polyether powder coatings are mainly used in chemical equipment, pipe linings, and instrument housings. Their disadvantage is relatively poor adhesion to metals. Additives can improve this adhesion.
Latex powder coatings. Latex powder is produced by spray drying an emulsion, and most are vinyl acetate copolymers. Coatings produced using latex powder are called latex powder coatings. They are mixed with water on-site and applied, making them the most environmentally friendly wall coating currently available.
The largest growth areas in my country's powder coating market are the shipbuilding and pipeline industries. The existing problems are that impact resistance and moisture absorption need to be improved, and researchers are focusing their efforts on modifying various base materials. Domestically produced epoxy powder coatings for pipeline corrosion protection still lag behind high-quality foreign products in terms of storage stability and application properties.
Due to advancements in foreign automotive powder coating technology, automotive clear coats, wood coatings, and plastic coatings represent the most dynamic potential markets. The automotive industry will be a major consumer, with strong growth momentum in the powder coating markets of Greece, Turkey, and Eastern Europe. The Asia-Pacific region has even greater market potential and is considered the fastest-growing region globally.
Coatings are made by mixing special resins, pigments, fillers, curing agents, and other additives in a specific ratio, followed by processes such as hot extrusion, crushing, and sieving. They are stable at room temperature and can be applied by electrostatic spraying, friction spraying (thermosetting method), or fluidized bed dip coating (thermoplastic method), followed by heating and baking to melt and cure, forming a smooth, glossy, permanent coating film to achieve decorative and corrosion-resistant purposes.
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