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, metallurgy, aviation and other industries. At present, heat-resistant powder coatings are still dominated by silicone powder coatings. The selection and control of each component in the silicone powder coating is the basis for a high temperature resistant silicone powder coating.
1. Application of silicone resin in high temperature resistant powder coatings
The silicone resin has a silicon-oxygen bond as the main chain. Due to its high bond energy, the silicone resin is given high oxidation stability, and a stable protective layer can be formed on the surface of the coating film. When using silicone resin alone, the intermolecular force is small, the adhesion is poor, and the price is high; on the premise of satisfying the relevant performance, a moderate silicone resin is generally added to the resin to solve the above problems.
Within a certain range, the greater the amount of silicone resin added, the longer the service life and heat resistance time of the coating film. It is mentioned in the literature that when the dosage of a certain silicone resin is increased from 0.1 to 0.3, the heat resistance time of the coating film increases from about 50h to 100h.
Of course, the actual dosage of different silicone resins has yet to be determined experimentally.
2. The choice of pigments and fillers
Because inorganic pigments are superior to organic pigments in heat resistance, organic pigments are generally not considered in high temperature resistant powder coatings, and the appropriate and stable performance is mainly selected from inorganic pigments; according to relevant literature, the impact resistance of the coating film before baking in the filler The order from good to poor is: wollastonite, mica powder, kaolin> sillimanite> quartz. The mica powder is best after grilling, and the rest is almost the same.
In addition, the amount of pigments and fillers also has a certain influence on the temperature resistance. "The application of silicone resin heat-resistant powder coatings" determines that the optimal amount range is between 60% and 100%. ratio).
3. Selection of additives
Choosing suitable additives is also an important part of improving the high temperature resistance and mechanical properties of high temperature powder coatings. Such as the addition of antioxidants, hardeners, etc. in high temperature resistant powder.