Classification of silicone resin Silicone resin is a cross-linked semi-inorganic high polymer with a silicon-oxygen-silicon main chain and an organic group connected to the silicon atom. It has outstanding weather resistance with the direct production of silicone monomer silicone resin, which is beyond the reach of any organic resin. Even under strong ultraviolet radiation, silicone resin is resistant to yellowing. Silicone resin adhesives Silicone adhesives can be divided into adhesives based on silicone resin and adhesives based on silicone rubber according to the source of raw materials. The former is mainly used for bonding metals and heat-resistant silicone resins to iron, aluminum and tin. The metal bonding performance is good, and it is easy to bond to glass and ceramics, but the adhesion to copper is poor. Silicone adhesive based on pure silicone resin.

Silicone resin coatings have many disadvantages: poor film-forming properties, including high curing temperature, long time, inconvenient construction in large areas, and poor adhesion of the coating film to the bottom layer. Modification with fluorination is mainly to increase the solvent resistance, oil repellency (anti-tack) and reduce the surface energy of the silicone resin. The critical surface tension of silicone resins is lower than that of other resins, but higher than that of fluororesins.
Silicone resin is a thermosetting plastic and one of its most outstanding properties is its excellent thermo-oxidative stability. After heating at 250℃ for 24 hours, the weight loss of silicone resin is only 2-8%. Another outstanding property of silicone resin is its excellent electrical insulating properties, which can maintain its good insulating properties in a wide temperature and frequency range.
The number of organic groups contained in the silicone resin, that is, the R/Si value is one of the main indicators to control the quality of the silicone resin. /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 around 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 brittle the paint film, and the lower the impact strength; the larger the R/Si value, the better the silicone resin. It needs to be baked for a long time at high temperature (200-250 ℃) or cured with the help of a drier, so that the flexibility is good, the hardness of the paint film is poor, and it has good impact strength.

In addition, the performance of silicone resin is also closely related to the type of organic group R. When the organic group is -CH3, it can endow the silicone resin with thermal stability, hydrophobicity, mold release and arc resistance; when the organic group is -C6H5 When the organic group is -CH=CH2, it can improve the curing performance of the silicone resin and give coupling; when the organic group is phenyl, ethyl , which can improve the blending of silicone resin and organic matter; when the organic group is -NH2(CH2), it can improve the water solubility of the polymer and give coupling; when the organic group is a long-chain alkyl group, it can improve the silicone Hydrophobicity of the resin. Therefore, siloxane monomers with different groups can be selected to prepare silicone resins according to specific performance requirements.

Features:
(1) Silicone resin has good bonding performance to metals such as iron, aluminum and tin, and is also easy to bond to glass and ceramics, but has poor adhesion to copper;
(2) Organosilicone adhesive based on pure silicone resin, which is made of silicone resin, mixed with inorganic filler and solvent, releases small molecules during curing, and needs to be heated and pressurized;
(3) The curing temperature of the silicone resin-based adhesive is too high, and the application is limited;
(4) Add a small amount of ethyl orthosilicate, potassium acetate and silicate glass, etc., the curing temperature drops to 220-200 °C, and the high-temperature strength is still 392-490MPa;
(5) Pure silicone resin has low mechanical strength. When it is copolymerized and modified with organic resins such as polyester, epoxy or phenolic, it can obtain high temperature resistance and excellent mechanical properties, and can be used for high temperature structural adhesives.