The Composition and Structure of Organic Silicone Resin

Curing is usually achieved through the condensation of silanols to form silicon oxygen chains. When the Condensation reaction is in progress, the reaction rate decreases due to the gradual decrease of the concentration of silanol, which increases the steric hindrance and poor fluidity. Therefore, in order for the resin to fully solidify, it is necessary to accelerate the reaction by heating and adding a catalyst. Many substances can catalyze the Condensation reaction of silanol, including acids and bases, soluble organic salts of lead, cobalt, tin, iron and other metals, and organic compounds such as dibutyl tin Lauric acid.

The performance of the final processed product of silicone resin depends on the number of organic groups contained (i.e. the ratio of R to Si). Silicone resin, which has practical value, has a molecular composition with a ratio of R to Si ranging from 1.2 to 1.6. The general rule is that the smaller the value of R: Si, the better the silicone resin obtained can cure at lower temperatures; R: The higher the value of Si, the longer the curing time required for the obtained silicone resin to be baked at high temperatures of 200-250 ℃. The resulting paint film has poor hardness, but its thermal elasticity is much better than the former.

In addition, the ratio of methyl to phenyl groups in organic groups also has a significant impact on the performance of silicone resins. The lower the phenyl content in the organic group, the softer the generated paint film, the faster the condensation, the higher the phenyl content, and the harder the generated paint film, which is more thermoplastic. The paint film has the best bending resistance and heat resistance when the phenyl content is between 20% and 60%. In addition, the introduction of benzene can improve the compatibility of silicone resin with pigments, as well as the compatibility of silicone resin with other organic silicone resins and the adhesion of silicone resin to various substrates.