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, cellulose, and polyester.
Thermosetting powder coatings are composed of thermosetting resins, curing agents, pigments, fillers and additives. Thermosetting powder coatings include: epoxy resin, polyester, and acrylic resin.
Disadvantages: The powder on the corners is uneven, the defects of the coating film after curing are difficult to cover, and the curing conditions are high.
There are many classification standards, and the names of various powders on the market are uneven. According to the properties of film-forming substances, they are divided into two categories: thermoplastic powder coatings and thermosetting powder coatings. Or according to the appearance of the film-forming material, it can be divided into: extinction type, high-gloss type, art type, etc. It can also be divided into two categories according to the use environment: indoor type and outdoor type.
Although the variety of powder coatings is not as diverse as solvent-based coatings, there are also many polymer resins that can be used as powder coatings. Generally, it can be divided into two categories: thermosetting and thermoplastic.
1. Thermosetting powder coating refers to the use of thermosetting resin as a film-forming substance, adding a curing agent for cross-linking reaction and heating to form an insoluble and infusible hard coating. At higher temperatures, the coating will not soften like a thermoplastic coating, but will only decompose. Since the resin used in the thermosetting powder coating is a prepolymer with a lower degree of polymerization and a lower molecular weight, the coating has better leveling and decorative properties, and the low molecular weight prepolymer is cured. It can form network-like cross-linked macromolecules, so the coating has better corrosion resistance and mechanical properties. Therefore, the development of thermosetting powder coatings is particularly rapid.
1.1 Epoxy powder coating. Because of its excellent adhesion to metal, corrosion resistance, hardness, flexibility and impact strength, it is the first variety used in thermosetting powder coatings. The formulation of epoxy powder coating is composed of epoxy resin (Epoxy Resin), curing agent (curing agent), pigment (pigment), filler (filler) and other assistants (assistant). The contributions of these components to the properties of the powder coating formed are mutually restricted and influenced. A suitable formulation is actually the result of the coordination of various components.
1.2 Polyester powder coating. Polyester powder coatings have unique properties compared to other types of powder coatings. It is better than epoxy resin in terms of weather resistance and UV resistance. In addition, because polyester resin has polar groups, the powder rate is higher than that of epoxy resin, it is not easy to yellow during the baking process, has high gloss, good leveling, full paint film, light color and other characteristics. Very decorative. Generally used in refrigerators, washing machines, vacuum cleaners, instrument housings, bicycles, furniture and other fields.
1.3 Acrylic powder coating. Acrylic resin powder coatings are available in thermoplastic and thermoset. The biggest advantage of thermosetting acrylic resin powder coating is that it has excellent weather resistance, color retention, pollution resistance, strong metal adhesion, and excellent film appearance. It is suitable for decorative powder coatings.