Application of Silicone in Coatings

Dec 6, 2021

The application technology of silicone in coatings (including inks) has developed from professional, high-performance coatings to a wider range of fields. Through the application of silicone technology, the insulation, heat resistance, weather resistance, antifouling, abrasion resistance and other properties of the coating can be improved. The following is introduced according to its use.

Insulation Materials
The first application technology of silicone resin as a coating was silicone resin-impregnated glass fiber cloth tape, which was used as a protective layer for wire insulation on U.S. Navy submarines. my country developed silicone resin in the 1950s. At the initial stage, it was mainly used for the insulation impregnation of H-class motor coils, the impregnation of H-class motor wire and glass fiber cloth for slot insulation, and the impregnation of glass fiber insulation sleeves. , Mica tape for insulation, etc.
Therefore, pure silicone resin as an insulating coating is the oldest silicone product. The pure silicone resin produced by the old process has the advantages of high temperature resistance, weather resistance, good insulation and other general organic resins that cannot be compared. However, it also has disadvantages such as high curing temperature, long curing time, poor adhesion, and re-sticking at high temperatures. With the development of science and technology and the development of new materials, silicone is no longer the only H-level insulating paint, and high-performance organic resin H-level insulating paints such as polyimide and polyester have emerged.

Therefore, in order to meet the needs of the situation, silicone coatings must develop in the direction of new processes, new technologies, new varieties, and new uses. Through the reform of the production process of silicone resin and the use of organic resin and silicone resin cold blending or copolymerization modification and other new technologies, the three defects of silicone resin have been greatly improved, and the application field of silicone coatings has also been expanded.
Primer

The bonding force between the coating and the substrate includes mechanical bonding force, chemical bonding force, diffusion force and dipole force. The size of the binding force directly affects the adhesion of the coating.
The main methods to improve the adhesion between the coating and the substrate are: substrate grinding, sandblasting, reducing the construction viscosity of the coating, increasing the construction temperature, and improving the wettability of the substrate (wiping with solvent, corona, flame burning, oxidant Treatment and other methods), related to silicone is the use of adhesion promoters, that is, the use of primers. The silicone materials used for primers are mainly silanes. Alkoxysilane can improve the adhesion, fluidity, leveling, abrasion resistance, pigment and filler dispersion, water resistance and salt spray resistance of coatings and substrates. It has been widely used in various metals and silicon-containing materials. Material in the primer formulation.

Adhesion promoter
Alkoxysilanes (mainly various silane coupling agents) as adhesion promoters must be used at the interface between the coating and the substrate or the interface between the sealant and the adhesive material to increase the viscosity. When using adhesion promoter as primer, silane is usually formulated into a 0.5% to 5% ethanol or alcohol-water diluent and then attached to the surface of the substrate by coating or spraying. In addition to increasing viscosity, the use of silane primers can also improve hydrophobicity, UV resistance, weather resistance, thermal stability, surface activity, chemical resistance and corrosion resistance. The choice of adhesion promoter needs to match the organic molecules in the coating. The matching of common adhesion promoters and polymers is shown.

Zinc-rich primer
Metals include ferrous metals (such as steel) and non-ferrous metals (such as aluminum alloys, etc.). In order to prevent rust, they must be surface treated. There are many surface treatment methods, and cathodic protection surface treatment is a commonly used method. In the cathodic protection process, zinc-rich primers are used. Zinc powder is a chemically active material. The electrode potential of zinc is 0.7628V, and the electrode potential of iron is 0.409V. The zinc powder in the paint film is in contact with each other and in contact with steel to conduct electricity. Therefore, when the steel structure coated with zinc-rich primer is corroded, because the electrode potential of metallic zinc in a wide temperature range is negative than that of iron, zinc is the anode and is corroded, and iron is the cathodic protection and acts as a sacrificial anode. Cathodic protection. At the same time, the product of zinc powder corrosion can fill the pores of the coating film, seal the damaged part of the coating film, and play the role of shielding the corrosive medium. Therefore, although the coating of zinc-rich paint is relatively thin, it still has a good anti-rust effect and a long service life.