Mechanical properties of silicone resin

The requirements for the mechanical properties of silicone resin mainly depend on its use. Silicone resin used as electrical insulating paint, coating and Adhesive is concerned about its hardness, elasticity, thermoplasticity and adhesion. The hardness and elasticity of silicone paint film can be changed in a large range by adjusting the molecular structure of the resin. When the content of three or four functional chains is higher, that is, the crosslinking density is higher, a paint film with high hardness and low elasticity can be obtained; Introducing substituents with large steric hindrance can improve flexibility and thermoelasticity, which is why methylphenyl silicone resin has better flexibility and thermoplastic properties than methylsilicone resin. Therefore, silicone resin does not require the use of special plasticizers, but can meet the requirements for plasticity through the appropriate combination of soft and hard silicone resins.

When used as certain coatings, the hardness of pure silicone resin coatings is insufficient, while the thermoplastic properties are surplus; If organic modified silicone resin is used, it is easy to solve this contradiction.

Pigments and catalysts can also affect the hardness and elasticity of silicone resins. Pigments have the effect of accelerating the oxidation of silicone resin paint films and converting them into harder silicone glass. With low activity catalyst, only soft coating can be obtained due to incomplete Condensation reaction; On the contrary, using highly active catalysts (such as compounds such as Pb and Al) can obtain a hard and brittle coating, but some catalysts (such as titanates) can effectively improve the hardness of the coating without seriously reducing its elasticity.

Silicone 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, the oxidation film on the copper side may accelerate the Pyrolysis reaction of silicone resin. The adhesion of silicone grease to organic materials such as plastic and silicone rubber mainly depends on the surface energy of the latter and its compatibility with silicone resin. Materials with lower surface energy and poorer compatibility are more difficult to bond. By treating the surface of the substrate (including sanding and priming), especially introducing tackifiers into the silicone resin, the adhesion of the silicone resin to difficult to adhere substrates can be improved to a certain extent.