Introduction to the types and characteristics of room temperature vulcanized silicone rubber (1)

Room temperature vulcanized silicone rubber (RTV) is a new type of silicone elastomer that came out in the 1960s. The most remarkable feature of this rubber is that it can be cured on-site without heating and pressing at room temperature, 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 room temperature vulcanized silicone rubber has been widely used as adhesives, sealants, protective coatings, potting and molding materials, and has its uses in all walks of life.

Room temperature vulcanized silicone rubber is known as liquid silicone rubber due to its low molecular weight. Its physical form is usually a flowable fluid or viscous paste with a viscosity of 100 to 1,000,000 centistokes. According to the requirements of use, the compound before vulcanization can be made into a self-leveling potting compound or a putty that does not flow but can be applied. The filler used in room temperature vulcanized silicone rubber is similar to that of high-temperature vulcanized silicone rubber. It is reinforced with white carbon black to make the vulcanized rubber have a tensile strength of 10-60 kg/cm2. Adding different additives can make the rubber compound have different specific gravity, hardness, strength, fluidity and thixotropy, and make the vulcanized rubber have various special properties such as flame retardant, 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 method, and can be divided into condensation type and addition molding according to the vulcanization mechanism. Therefore, room temperature vulcanization silicone rubber can be divided into three types according to the composition, vulcanization mechanism and use process, namely, one-component room temperature vulcanization silicone rubber, two-component condensation type room temperature vulcanization silicone rubber and two-component addition type room temperature vulcanization silicone rubber .

The raw rubbers of one-component and two-component condensation RTV silicone rubbers are all α,ω-dihydroxy polysiloxanes; addition-molded RTV silicone rubbers contain alkenyl groups and hydrogen side groups (or end groups) Polysiloxane, because it can get a good curing effect at a temperature slightly higher than room temperature (50～150℃) during curing, it is also called low temperature vulcanized silicone rubber (LTV).

These three series of room temperature vulcanization silicone rubbers have their own advantages and disadvantages: the advantage of single-component room temperature vulcanization silicone rubber is convenient to use, but the deep curing speed is more difficult; the advantage of two-component room temperature vulcanization silicone rubber is that it does not emit heat during curing , The shrinkage rate is very small, no expansion, no internal stress, curing can be carried out at the same time inside and on the surface, and deep vulcanization; the vulcanization time of addition-molded room temperature vulcanized silicone rubber is mainly determined by temperature, so the vulcanization can be controlled by adjusting the temperature speed.