Two-component condensation type room temperature vulcanized silicone rubber is the most common type of room temperature vulcanized silicone rubber. The raw rubber is usually a hydroxyl terminated polysiloxane, which is combined with other compounding agents and catalysts to form a rubber compound. The viscosity can range from 100 centistokes to one million centistokes. The vulcanization reaction of the two-component room temperature vulcanized silicone rubber is not caused by the moisture in the air, but by the catalyst. The silicone rubber, filler, and cross-linking agent are usually packaged as one component, the catalyst is packaged as another component, or in other combinations, but the catalyst and the cross-linking agent must be separately packaged. Regardless of the packaging method, curing begins only when the two components are completely mixed together. A commonly used crosslinking agent is ethyl orthosilicate, and the catalyst is dibutyltin dilaurate. Appropriate fillers and additives are added depending on the nature of the desired end product. In recent years, in many countries, because dibutyltin dilaurate is a moderately toxic grade, the addition of dibutyltin in food bags and plasma bags has been largely replaced by low toxicity octyltin.




The vulcanization time of the two-component condensation type room temperature vulcanized silicone rubber mainly depends on the type, amount and temperature of the catalyst. The more the amount of catalyst used, the faster the vulcanization, and the shorter the shelf life. At room temperature, the shelf life is usually a few hours. To extend the shelf life of the compound, a cooling method can be used. The two-component condensation type room temperature vulcanized silicone rubber requires a day or so to reach full curing at room temperature, but it takes only one hour at a temperature of 150 °C. The curing speed can be significantly improved by using the synergistic effect of the accelerator γ-aminopropyltriethoxysilane. Two-component room temperature vulcanized silicone rubber can maintain elasticity for a long time in a temperature range of 65-250 ° C, and has excellent electrical properties and chemical stability, water, ozone and weathering resistance, combined with simple usage and high process applicability Therefore, it is widely used as potting and molding materials. After coating and potting with room temperature vulcanized silicone rubber, various electronic and electrical components can protect against moisture (anti-corrosion, anti-vibration, etc.) and can improve performance and stability parameters. Two-component room temperature vulcanized silicone rubber is especially suitable for deep irrigation. The sealing material has a faster curing time, which is superior to the one-component room temperature vulcanized silicone rubber.




The two-component room temperature vulcanized silicone rubber has excellent anti-sticking properties after vulcanization, and has a small shrinkage rate during vulcanization. Therefore, it is suitable for use in the manufacture of soft molds for casting epoxy resin, polyester resin, polystyrene, Molds of polyurethane, vinyl, paraffin, low melting point alloys, etc. In addition, the high simulation performance of the two-component room temperature vulcanized silicone rubber can be used to replicate a variety of delicate patterns. For example, in the reproduction of cultural relics can be used to copy ancient bronzes, in the production of artificial leather can be used to copy the skin of snakes, crickets, crocodiles and pangolins, to play the role of false real.




Two-component room temperature vulcanized silicone rubber should pay attention to several specific problems when it is used: first, the base material, the crosslinking agent and the catalyst are separately weighed and then mixed in proportion. Usually the two components should be provided in different colors so that the mixing of the two components can be visually observed and the mixing process should be handled carefully to minimize the amount of gas entrained. After the rubber compound is mixed (even color), the bubbles can be removed by standing or decompressing (vacuum degree 700 mmHg). After the bubbles are completely discharged, they are vulcanized into silicon at room temperature or at a predetermined temperature for a certain period of time. Rubber.




The side group on the main component of the two-component room temperature vulcanized silicone rubber siloxane may be substituted with other groups such as phenyl, trifluoropropyl, cyanoethyl or the like in addition to the methyl group to improve its resistance to low temperature and heat. , radiation resistance or solvent resistance. At the same time, heat-resistant, flame-retardant, heat-conductive, and conductive additives may be added as needed to obtain a silicone rubber having ablation resistance, flame retardancy, heat conduction, and electrical conductivity.
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