Room temperature vulcanized silicone rubber (RTV) is a new type of silicone elastomer, which came out in the 1960s. The most remarkable feature of this rubber is that it can be cured in place at room temperature without heating, such as pressing, and it is extremely convenient to use. Therefore, as soon as it came out, it quickly became an important part of the entire silicone product. Now RTV silicone rubber has been widely used as adhesives, sealants, protective coatings, potting and molding materials in all walks of life.
Room temperature vulcanized silicone rubber is known as liquid silicone rubber because of its low molecular weight. Its physical form is usually flowing fluid or viscous paste, and its viscosity is between 100~1000000 centistokes. According to the requirements of use, the rubber before vulcanization can be prepared into a filling material with automatic leveling or a putty that does not flow but can be coated. The filler used for room temperature vulcanized silicone rubber is similar to that for high-temperature vulcanized silicone rubber, and white carbon black is used for reinforcement, so that the vulcanizate has a tensile strength of 10-60kg/cm2. The addition of different additives can make the rubber compound have different specific gravity, hardness, strength, fluidity and thixotropy, and make the vulcanizate have various special properties such as flame retardancy, electrical conductivity, thermal conductivity and ablation resistance.
Room temperature vulcanized silicone rubber can be divided into single component and two-component room temperature vulcanized silicone rubber according to its packaging mode, and can also be divided into condensation type and addition type according to the vulcanization mechanism. Therefore, RTV silicone rubber can be divided into three types according to its composition, curing mechanism and application process, namely, one component RTV silicone rubber, two component condensation RTV silicone rubber and two component addition RTV silicone rubber.
The raw rubber of one component and two-component condensation RTV silicone rubber is α,ω- Dihydroxypolysiloxane; The addition type RTV silicone rubber is a polysiloxane containing alkenyl and hydrogen side groups (or end groups). It is also called low temperature vulcanized silicone rubber (LTV) because it can achieve good curing effect at a temperature slightly higher than room temperature (50-150 ℃) during curing.
Each of the three series of RTV silicone rubber has its advantages and disadvantages: one component RTV silicone rubber has the advantage of convenient use, but it is difficult to cure in deep; The advantages of two-component RTV silicone rubber are that it does not release heat, has small shrinkage, does not expand, and has no internal stress during curing. The curing can be carried out inside and on the surface at the same time, and can be deep vulcanized; The curing time of addition RTV silicone rubber is mainly determined by temperature. Therefore, the curing speed can be controlled by adjusting the temperature.