Room temperature vulcanized silicone rubber (RTV) is a new type of silicone elastomer that came out in the 1960s. The most notable feature of this rubber is that it can be cured in situ at room temperature without heating, such as by pressing, and is extremely convenient to use. Therefore, it quickly became an important part of the entire silicone product as soon as it came out. 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 a viscous paste with a viscosity between 100 and 1,000,000 centistokes. According to the requirements of use, the rubber before vulcanization can be formulated into a self-leveling potting material or a non-flowing but smearable putty. 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 give the vulcanized rubber a tear strength of 10 to 60 kg/cm2. Adding different additives can make the rubber 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 type according to the vulcanization mechanism. Therefore, room temperature vulcanized silicone rubber can be divided into three types according to its composition, vulcanization mechanism and use process, namely single-component room temperature vulcanized silicone rubber, two-component condensation type room temperature vulcanized silicone rubber and two-component addition type room temperature vulcanized silicone rubber.
The raw rubber of single-component and two-component condensation type room temperature vulcanized silicone rubber is α, ω-dihydroxy polysiloxane; addition type room temperature vulcanized silicone rubber is polysiloxane containing alkenyl and hydrogen side groups (or end groups). Because it can achieve good curing effect at a temperature slightly higher than room temperature (50-150°C) during curing, it is also called low temperature vulcanized silicone rubber (LTV).
These three series of room temperature vulcanized silicone rubber each have its own advantages and disadvantages: the advantage of single-component room temperature vulcanized silicone rubber is that it is easy to use, but the deep curing speed is more difficult; the advantage of two-component room temperature vulcanized silicone rubber is that it does not release heat during curing, has a very small shrinkage rate, does not expand, has no internal stress, and can cure simultaneously inside and on the surface, and can be deeply vulcanized; the vulcanization time of addition-type room temperature vulcanized silicone rubber is mainly determined by temperature, so its vulcanization speed can be controlled by adjusting the temperature.