The requirements for the mechanical properties of the modification of fluorosilicone resin mainly depend on the application. Silicone resins used as electrical insulating paints, coatings and adhesives, people are more concerned about its hardness, elasticity, thermoplasticity and adhesion. The hardness and elasticity of the silicone resin paint film can be varied in a wide range by adjusting the molecular structure of the resin. When the content of trifunctional or tetrafunctional chain units is higher, that is, the crosslinking density is higher, a paint film with high hardness and low elasticity can be obtained; the introduction of large sterically hindered substituents can improve flexibility and thermoelasticity, which is positive This is the reason why the flexibility and thermoplasticity of methyl phenyl silicone resin is better than that of methyl silicone resin. Therefore, the modification of fluorosilicone resin does not need to use special plasticizers, but can meet the plasticity requirements by the appropriate combination of soft and hard silicone resins.
When used as some coatings, the hardness of the pure silicone resin coating film is insufficient, but the thermoplasticity is more than enough; if the organic modified silicone resin is used, this contradiction can be easily resolved.
Pigments and catalysts can also affect the hardness and elasticity of the modification of fluorosilicone resin. Pigments have the effect of accelerating the oxidation of the silicone paint film and converting it into a harder silica glass. Using low-activity catalysts, due to incomplete condensation reaction, only soft coatings can be obtained; on the contrary, using high-activity catalysts (such as compounds of Pb, Al, etc.), hard and brittle coatings can be obtained, but some catalysts (such as titanium acid ester) can effectively improve the hardness of the coating without seriously reducing the elasticity.
modification of fluorosilicone resin has good adhesion to iron, aluminum, silver, tin, glass and ceramics, but poor adhesion to copper, especially after high temperature and long-term thermal aging, it may cause oxidation of copper on other surfaces The film has the purpose of accelerating the thermal cracking reaction of the silicone resin. The adhesion of silicone grease to organic materials such as plastics and silicone rubber mainly depends on the surface energy of the latter and its compatibility with silicone resins. Materials with lower surface energy and less compatibility are more difficult to bond. By treating the surface of the substrate (including sanding and priming), especially introducing tackifiers into the modification of fluorosilicone resin, the adhesion of silicone resin to difficult-to-stick substrates can be improved to a certain extent.
