Silicone resin--heat-resistant coating
Since the main chain of silicone polymer is a SI—O—SI—O bond, and the side group is an organic group, it has both inorganic and organic characteristics, and its high temperature resistance is better than most organic resins.

The heat resistance of the resin used for coatings decreases in the following order: pure silicone resin>organic resin modified silicone resin>silicone modified organic resin>styrene-free acrylic resin/polycarboxylic acid resin>polyester/isocyanuric acid Triglycidyl ester>epoxy/carboxyl polyester>acrylic/isocyanate>polyester/isocyanate>epoxy/phenolic>epoxy/dicyandiamide>epoxy/amine, so silicone resin is the main heat-resistant coating Film-forming substances.

If the temperature is increased above 400°C, all the substituents on the silicone resin will be oxidized. At that time, the thermal mass loss rate of the silicone resin containing more phenyl groups is greater than that of the methyl silicone resin. This is because the phenyl group has a larger mass than the methyl group, and it loses more when it is oxidized at high temperature. In addition, the phenyl group attached to the same silicon atom as the hydroxyl group has a steric hindrance effect, which will cause difficulty in cross-linking of silicone resin and vulcanization. The rate drops and its physical performance drops. This limitation needs to be resolved by improving the process and formula. But from another perspective, phenyl can improve the compatibility of silicone resin and organic resin, which provides favorable conditions for modifying organic resin with silicone resin. If the miscibility of the two is not good, an obvious interface will be formed between the resins, which is a weak link of the resin and will also reduce the physical properties of the paint film. Therefore, heat resistance, physical properties, and vulcanization rate should be considered when choosing a resin. And compatibility between these different needs.

The metal filler has high thermal conductivity and can transfer the heat on the coated substrate; in addition, due to the oxidation of the silicone resin, the metal particles and the silicone resin fuse to form a stable structure similar to a ceramic coating containing a metal-siloxane bond. If more reinforcing fillers (such as mica powder or wollastonite powder) are added to the formula, better thermal stability can be obtained.