The number of organic groups contained in silicone resin, that is, R / Si value, is one of the main indicators to control the quality of silicone resin. Curability, film flexibility, hardness, heat resistance and heat crack resistance of silicone resin are all similar to R / Si related. Generally, the R / Si of linear silicone oil is slightly greater than 2, the R / Si of silicone rubber is close to 2, and the R / Si of silicone resin is about 1.0. The smaller the R / Si value, the better the curing performance of the silicone resin, the smaller the thermal weight loss, the harder the paint film, but the lower the flexibility, the paint film becomes brittle, and the impact resistance decreases; the larger the R / Si value, the better the silicone resin is. It needs to be baked at high temperature (200-250 ℃) for a long time or be cured by the action of a drier, so that the flexibility is good, the hardness of the paint film is poor, and the impact resistance is good.