Since the main chain of the silicone polymer is an SI—O—SI—O—one bond, and the side group is an organic group, it has the characteristics of both inorganic and organic substances, and has higher temperature resistance than most organic resins.

The heat resistance of the resin used in 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 acid / isocyanate> Polyester / isocyanate> Epoxy / phenolic> Epoxy / Dicyandiamide> Epoxy / amine, so silicone resin is the main heat-resistant coating Film-forming substance.

It has the best heat resistance when the pendant group is phenyl at 250 ° C. Therefore, methylphenyl silicone resin is the most variety and the largest production of silicone resin products. As the phenyl content increases, the heat resistance of the silicone resin increases. For example, the phenyl / methyl ratio of Dow Corning silicone resin is generally 1.1 to 1.2, while the phenyl / methyl ratio of domestic silicone resin is 0.3 to 0.5, so the heat resistance of Dow Corning silicone resin is generally higher than that of domestic silicone resin.

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 phenyl is larger than methyl and loses more when oxidized at high temperature. In addition, phenyl connected to the same silicon atom with hydroxyl group has steric hindrance effect, which will cause silicone resin to be difficult to crosslink and vulcanize. The rate decreases, causing its physical performance to decrease. This limitation needs to be addressed by improved processes and formulations. 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 two are not miscible, 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 selecting the resin And compatibility.

The heat resistance of pure silicone resin is generally only 180-200 ° C. As a heat-resistant coating, it is important to add pigment or solid filler to the silicone resin.