Mechanical properties editing


The requirements for the mechanical properties of silicone resin mainly depend on the application. People are more concerned about the hardness, elasticity, thermoplasticity and adhesiveness of silicone used as electric insulating paint, coating and adhesive. The hardness and elasticity of silicone film can be changed in a wide range by adjusting the molecular structure of the resin. When the content of three or four functional chains is higher, that is to say, the greater the crosslinking density, the higher the hardness and the lower the elasticity of the paint film can be obtained; the introduction of substituents with large steric hindrance can improve the flexibility and the thermoelasticity, which is the reason why the flexibility and the thermoplasticity of methylphenyl silicone resin are better than that of methylsilicone resin. Therefore, silicone resin does not need to use special plasticizer, but can meet the requirements of plasticity by the proper combination of soft and hard silicone resin.


When it is used as some coatings, the hardness of pure silicone coating is insufficient, but the thermoplastic is surplus. If organic modified silicone is used, this contradiction can be easily solved.


Pigments and catalysts can also affect the hardness and elasticity of silicone. Pigment can accelerate the oxidation of silicone paint film, and make it into harder silica glass. Using low active catalyst, only soft coating can be obtained due to incomplete condensation reaction; on the contrary, using high active catalyst (such as Pb, Al and other compounds), hard and brittle coating can be obtained, but some catalysts (such as titanate) can no longer reduce the elasticity of the front, effectively improving the hardness of the coating.


Silicon resin has good adhesiveness to iron, aluminum, silver, tin, glass and ceramics, but poor adhesiveness to copper. Especially after high temperature and long-term thermal aging, it may accelerate the thermal cracking reaction of silicon resin on the oxide film of copper. The adhesion of silicone grease to organic materials such as plastics and silicone rubber mainly depends on the surface energy of the latter and the compatibility with silicone resin. The lower the surface energy and the worse the compatibility, the more difficult it is to bond. Through the surface treatment of the substrate (including sanding and priming), especially the introduction of tackifier into the silicone resin, the adhesion of the silicone resin to the refractory substrate can be improved to a certain extent.