Silicone rubbers and silicone elastomers are masses that can be converted into a rubber-elastic state. They contain poly (organo) siloxanes, which contain groups that are accessible for crosslinking reactions. Vinyl groups, as well as hydroxyl groups and water atoms, are predominantly suitable here. These must be located at the ends of the chain or built into the chain.
Reinforcing substances and fillers are components of silicone rubbers. Their type and quantity influence the mechanical and chemical behaviour of the silicone elastomers produced by vulcanization (crosslinking). Also, silicone rubbers can be colored using suitable pigments and dyes and it affects Silicone rubber price (ยางซิลิโคน ราคา, which is the term in Thai).
Depending on the components of the rubber mixture, the following abbreviations are used:
- MQ, for methyl silicone
- VMQ, for vinyl methyl silicone
- PVMQ, for phenyl vinyl methyl silicone
- PMQ, for phenyl modified silicone
- FMQ, for fluoroalkyl silicone
- FVMQ, for fluorine vinyl methyl silicone
Types Of Silicone Rubbers
A distinction is made between cold (RTV) and hot-curing (HTV) silicone rubbers based on the crosslinking temperatures. HTV silicone rubbers are materials that can be plastically deformed. As a rule, they contain organic peroxides, which are necessary for crosslinking.
The crosslinking is carried out at a high temperature. This creates heat-resistant products that are elastic in broad temperature ranges up to around 250 ° C. They are used, among other things, for cable sheathing as well as high-quality electrical insulation components, sealing and damping elements.
RTV Silicone Rubbers
With RTV silicone rubbers, a distinction is made between one-component and two-component systems. RTV-1 crosslink at room temperature, which is influenced by humidity. The crosslinking takes place here through the condensation of SiOH groups, during which Si-O bonds are formed. RTV-2 rubbers are added as crosslinkers, including mixtures of silicic acid esters. Organotin compounds are also used. The crosslinking reaction consists in the formation of a Si-O-Si bridge, from Si-OR and Si-OH through the elimination of alcohol.
The Liquid Rubber Technology, LSR: Liquid Silicone Rubber
Another crosslinking consist of primarily using noble metal compounds for the catalyzed addition of Si-H groups to silicone-bonded vinyl groups. Both of these have to be built into polymer chains or at the end of them. Based on this, the so-called liquid rubber technology LSR has existed since 1980. These silicone rubber components are pumpable because they have low viscosity. They are dosed and mixed using suitable dosing and mixing machines and then mostly processed on injection molding machines. Thanks to the short networking time, this technology allows very high clock rates and therefore, high economic efficiency.
The use of this technology is widespread, for example, for the production of mouthparts, such as baby teats and for the production of elastic baking molds, which, however, is still a very new application for the heat-resistant silicone elastomers.