RTV Silicone Rubber Anti-Fouling Sparkle Coating Base Components

RTV silicone rubber anti-fouling flashing coating uses polydimethylsiloxane, also known as methylvinylsiloxane, as the base material, which is an elastic polymer with polysiloxane as the main backbone. Its mechanical properties are very low, and the tensile strength after vulcanization is only 0.3~0.5 MPa. By adding reinforcing fillers, the tensile strength can reach more than 13 MPa.

Silicone rubber can be divided into three categories according to its vulcanization mechanism: high-temperature vulcanization type, addition reaction type, and room temperature vulcanization type. High-temperature vulcanization silicone rubber uses organic peroxide as the vulcanizing agent, which is heated to cross-link the rubber to obtain vulcanized rubber; addition vulcanization type silicone rubber refers to a kind of silicone rubber obtained by addition reaction of polydimethylsiloxane under the catalysis of platinum compounds; Room temperature vulcanization type silicone rubber does not require heating and pressure, and can be vulcanized by contacting with moisture in the air or mixed with a curing agent. RTV silicone rubber coating is mainly made by modifying organic silicone rubber, curing agent, catalyst, and various functional enhancers through chemical and physical processes. All of the above components are included in the solvent, and the solvent can be used as a carrier to brush or spray the silicone rubber on the surface of the insulator.

Reinforcing fillers for RTV silicone rubber coatings

Reinforcing filler for mechanical strength

Currently, the most commonly used reinforcing filler for RTV silicone rubber coatings is fumed silica (SiO2) in the gas phase. It has high purity, small particle size, large specific surface area, and good reinforcement effect. It is the most studied, mature, and widely used reinforcing filler for silicone rubber. The addition of curing agent and catalyst can affect the curing time of RTV coatings. The commonly used curing agent for RTV silicone rubber coatings is methyltris(methylethylketoxime)silane, and the catalyst is an organic tin catalyst. Increasing the amount of curing agent can shorten the curing time of the coating, and increasing the amount of catalyst can also shorten the curing time. The curing time is also affected by the coating thickness and environmental conditions. Therefore, the coating formula needs to be adjusted comprehensively according to various factors such as geography and climate during actual use.

Reinforcing filler for adhesion

In order to improve the adhesion of polydimethylsiloxane coatings to materials such as ceramics and glass, suitable silane coupling agents need to be added. Silane coupling agent is an organic silicone compound with two different reactive chemical groups in its molecular structure: one is a hydrolyzable group, which can adsorb on the surface of inorganic materials; the other is an organic functional group that can react with the polymer matrix. These two silane coupling agent groups can "couple" two materials with different properties together, which can greatly improve the adhesion of the coating. Reinforcing filler for flame retardancy. Insulators inevitably suffer from the effects of operating phenomena such as corona, sparks, and arc discharge during use. Polydimethylsiloxane is a combustible material with weak arc erosion resistance. As an external insulating coating, it is easily eroded by arcs, which can damage its insulation performance. Adding a small amount of flame retardant can have a good flame retardant effect. The commonly used flame retardant is aluminum hydroxide trihydrate. When the arc burns the material surface, the temperature of the local material surface will significantly increase. When the aluminum hydroxide trihydrate is heated to about 220°C, it will quickly decompose and release crystal water and absorb a large amount of heat, thereby reducing the temperature of the material surface. The released crystal water can react with the free carbon produced when the organic material decomposes under the catalysis of Al2O3, producing volatile CO and CO2, preventing the formation of conductive carbonization channels.

Anti-fouling and flashing performance of RTV silicone rubber coatings

The excellent hydrophobicity and hydrophobic migration of RTV silicone rubber coatings are the main reasons for their wide application as anti-fouling and flashing coatings at home and abroad. Hydrophobicity. The hydrophobicity of materials is described by the surface energy or surface tension of materials. The greater the difference between the surface tension of the material and that of water, the better the hydrophobicity of the material, and the larger the static contact angle of water droplets on the material surface. Generally, for non-aged RTV silicone rubber coatings, the static contact angle of water droplets formed on their surface is greater than 90°. Under severe weather conditions such as heavy fog, light rain, dew, melted snow, and dissolved water, the RTV silicone rubber coating surface forms separated water droplets rather than a continuous water film. The conductivity of the fouling layer is very low, so the leakage current is small, and it is not easy to cause strong local arcs, and the local arcs are difficult to further develop, leading to the flashing of the external insulation. On the other hand, the rolling water droplets can take away the adhered dirt on the surface of the insulator, so that the insulator surface has a certain self-cleaning function. Therefore, the hydrophobicity of the low-energy surface is the main reason for its moisture and pollution resistance performance.