Silicone resin is an organic silicon polymer with a high degree of branching chain and a Si-O bond as the main chain. Because the Si-O bond has a higher bond energy than the C-C bond in ordinary organic polymers, and the electronegativity of Si and O atoms is different, the polarity of the Si-O bond is large, which can shield the connected hydrocarbon groups. After the hydroxyl connected to the Si atom is heated and oxidized, a more stable Si-O-Si bond is generated, which can prevent the main chain from fracture and degradation, and generate a stable protective layer. Therefore, it has excellent oxidation resistance and heat and weather resistance. In addition, the high degree of branching determines that silicone resin is closer to the inorganic SiO2 structure than conventional linear siloxane materials, which makes it have certain inorganic material characteristics.

The performance of silicone resin mainly depends on the ratio of R/Si (R=Me, Ph) and phenyl content [Ph/(Me+Ph)]. The general rule is that the smaller the R/Si value is, the more the silicone resin obtained can be cured at a lower temperature, and the hardness of the paint film obtained is harder; The higher the R/Si value is, the silicone resin obtained needs to be baked for a long time at a higher temperature to cure it. The hardness of the paint film obtained is poor, but the thermal elasticity is much better than the former. Generally, R/Si is between 1.0 and 1.6. The content of phenyl in organic group also has a great influence on the properties of silicone resin. The lower the phenyl content is, the softer the paint film is, and the faster the condensation is. The higher the phenyl content is, the harder the paint film is, and the more thermoplastic it is. Generally, when the content of phenyl is between 20% and 60%, the bending resistance and heat resistance of the paint film are the best.

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