Fumed silica is one of the most important high-tech ultra-fine inorganic new materials. Because of its small particle size, it has a large specific surface area, strong surface adsorption, large surface energy, high chemical purity, good dispersion performance, and thermal resistance., Resistance and other aspects have specific properties. With its superior stability, reinforcement, thickening and thixotropy, it has unique characteristics in many disciplines and fields and has an irreplaceable role. Today Xiaobian and everyone together to learn the application of fumed silica in silicone rubber.
Application of High Temperature Vulcanized (HTV) Silicone Rubber
The use of fumed silica can be divided into silicone materials and other fields. The amount of fumed silica in silicone materials accounts for nearly 60% of the total amount of fumed silica. Silicone rubber is the most used fumed silica in silicone materials, and its addition amount can be as high as 50% or more. Fumed silica mainly plays a reinforcing role in HVT silicone rubber. Because the molecular chain of silicone rubber is very flexible and the interaction force between chains is weak, the strength of silicone rubber without reinforcement is very low, while the strength of silicone rubber reinforced by fumed silica can be increased by 40 times.
The reinforcing effect of fumed silica on HTV silicone rubber is affected by its particle size, comparative area and structure. Generally, the smaller the particle size, the higher the specific surface area, the higher the structure, the better the reinforcing effect, and the higher the strength and hardness of the vulcanized rubber. The tear strength of vulcanized rubber is similar to the tensile strength, which increases with the increase of the reinforcement of fumed silica, increases first with the increase of the amount of fumed silica, and decreases slightly after reaching the peak.
In the mixing process, the structure control agent is added or the surface-treated gas phase silica is selected to reduce the number of surface hydroxyl groups, so that the number of hydrogen bonds formed with silicone rubber is reduced, the mixing time of the mixture is shortened, the plasticity is increased, and the purpose of reducing the structural effect and improving the processing performance and storage stability is reduced.
Application of Room Temperature Vulcanized (RTV) Silicone Rubber
Room temperature vulcanization (RTV) silicone rubber, in the product form is divided into one-component (RTV-1) and two-component (RTV-2) two categories; from the vulcanization mechanism is divided into condensation and molding two systems. Various forms of room temperature vulcanized silicone rubber need to be reinforced with fillers to have use value. At present, fumed silica is the most used and most effective RTV silicone rubber reinforcing filler. Since RTV silicone rubber is generally used as a sealing material for pouring, caulking, coating, etc., in order to maintain the viscosity and fluidity before vulcanization, the addition amount of fumed silica is generally much less than that of high-temperature vulcanized silicone rubber, and it is often used with other reinforcing and semi-reinforcing fillers to facilitate construction operations.
RTV silicone rubber generally uses fumed silica with relatively low specific surface area as a filler. The unreinforced silicone rubber is brittle after vulcanization, and the hardness of the silicone rubber increases with the increase of the amount of silica added after the addition of fumed silica.
Add in RTV silicone rubberWhen fumed silica, attention must be paid to the degree of dispersion in the polymer. Under the same dispersion conditions, fumed silica products containing a larger specific surface area generally have better transparency.
In summary, fumed silica is an essential reinforcing material for silicone rubber. Due to its unique properties, it is also used in other fields, such as coatings, inks, pharmaceuticals, cosmetics, and chemical mechanical polishing (CMP). It has been widely used, and its development prospects are also very bright.