High temperature resistant powder coatings generally refer to coatings that do not change color or change color less, do not fall off, and can still maintain appropriate physical properties above 200°C. Under normal circumstances, high temperature resistant powder coatings are mainly composed of high temperature resistant resins, high temperature resistant pigments, high temperature resistant fillers and special effect additives. Because of their outstanding high temperature resistance, they are widely used in chemical, petroleum, metallurgical, aviation and other industries. The amount of high-temperature resistant equipment used in barbecues, heaters, high-power lighting, heating pipes, hot-blast stoves, mufflers, ovens, high-temperature furnaces, motorcycle exhaust pipes, chimneys, etc., is gradually increasing each year.
Conventional powder coatings are generally cured into a film under the conditions of [email protected]℃. They are thermosetting coatings. The coating forms a network crosslinked structure, so the heat resistance of thermoplastic coatings is improved to a certain extent. Heat resistance experiments on epoxy, epoxy/polyester hybrid, polyester/TGIC and other powder coatings show that these coatings can basically be used for a long time under the condition of less than 150℃, but when the temperature is higher than 250 In an environment of ℃, the coating exhibits loss of gloss, decreased adhesion, embrittlement of the coating, decreased flexibility, and chalking, which makes the coating lose its protective effect on the substrate.
At present, the most widely used heat-resistant resins are mainly silicone-oxygen bonds as the main chain. Because of their high bond energy, they have high oxidation stability, and silicone resins can form a stable chain protective layer on the coating surface, reducing For the internal impact of polymers, silicone resins have a wide range of applications in heat-resistant coatings. Generally, the application and selection factors of silicone resins are as follows:
—The order of side groups to thermal stability: phenyl>methyl>ethyl>propyl>butyl>hexyl;
—The content of silica affects the temperature resistance of the coating;
-Silanol content affects the cross-chain density of silicone resin;
—TG affects the storage and sprayability of the coating.
Choose the type and amount of silicone resin to be added according to the temperature resistance requirements and use time. At present, the more commonly used high temperature resistant powder coatings for BBQ are about 350℃, while the exhaust pipe and radiator require temperature resistance of about 500℃, and they are weather resistant. Salt spray has higher requirements. Different temperature-resistant coatings require the correct selection of resins, temperature-resistant pigments and temperature-resistant fillers. Also, for different temperature-resistant requirements, different pre-treatments of materials are required, such as iron-based phosphating, plating, and spraying. Sand etc.