2、 Two component condensation room temperature vulcanized silicone rubber


The two-component Condensation Type RTV silicone rubber is the most common RTV silicone rubber. Its raw rubber is usually polysiloxane with hydroxyl sealing end, and then combined with other additives and catalysts to form a rubber compound. The viscosity range of this rubber compound can be from 100 centistokes to 1 million centistokes. The curing reaction of two-component room temperature vulcanized silicone rubber is not initiated by water in the air, but by catalyst. In general, raw silica gel, filler and crosslinking agent are packed as one component, catalyst is packed as another component separately, or other combination methods are used, but catalyst and crosslinking agent must be packed separately. No matter what kind of packing method is adopted, curing will only occur when the two components are completely mixed. The commonly used crosslinking agent is ethyl orthosilicate, and the catalyst is dibutyl tin dilaurate. Appropriate fillers and additives shall be added according to the properties of the required final products. In recent years, dibutyltin dilaurate is a kind of medium toxic substance in many countries. Dibutyltin is forbidden to be added into food bags and plasma bags. It has been basically replaced by low toxic octyltin.








The curing time of two-component condensation room temperature vulcanized silicone rubber mainly depends on the type, amount and temperature of catalyst. The more catalyst is used, the faster sulfurization and the shorter shelf life. At room temperature, the shelf life is usually a few hours. If you want to extend the shelf life of the compound, you can use cooling method. It takes about one day for two-component condensation RTV silicone rafters to fully cure at room temperature, but only one hour at 150 ℃. The curing rate of γ - aminopropyltriethoxysilane can be significantly increased by using the synergistic effect of accelerator γ - aminopropyltriethoxysilane. The two-component room temperature vulcanized silicone rubber can keep elasticity for a long time in the temperature range of - 65-250 ℃, and has excellent electrical performance and chemical stability. It can resist water, ozone and weather aging. In addition, it has simple usage and strong process applicability. Therefore, it is widely used as filling and molding materials. All kinds of electronic and electrical components can be protected against moisture (corrosion, shock, etc.) after being coated and potted with RTV silicone rubber. Can improve performance and stability parameters. Two component RTV silicone rubber is especially suitable for deep potting materials and has a faster curing time, which is better than one component RTV silicone rubber.








The two-component room temperature vulcanized silicone rubber has excellent anti sticking property after vulcanization, and the shrinkage rate is very small when vulcanized. Therefore, it is suitable for making soft mold, and for casting mold of epoxy resin, polyester resin, polystyrene, polyurethane, vinyl plastic, paraffin, low melting point alloy, etc. In addition, the high simulation performance of two-component RTV silicone rubber can be used to duplicate various exquisite patterns. For example, it can be used to copy ancient bronzes in cultural relics reproduction, and it can be used to copy the skin patterns of snakes, python, crocodile, pangolin and other animals in artificial leather production, with the effect of falsehood and falsehood.








Several problems should be paid attention to when using the two-component RTV silicone rubber: first, weigh the base material, crosslinker and catalyst respectively, and then mix them in proportion. Generally, the two components should be provided with different colors, so that the mixing of the two components can be visually observed, and the mixing process should be carefully operated to minimize the amount of entrapped gas. After the rubber material is evenly mixed (with uniform color), the bubbles can be removed by standing or decompressing (with a vacuum of 700mmhg). After all bubbles are discharged, the rubber can be vulcanized into silicone rubber at room temperature or at a specified temperature for a certain time.








In addition to methyl, the side groups on the main chain of two-component room temperature vulcanized silicone rubber can be replaced by other groups such as phenyl, trifluoropropyl, cyanoethyl, etc., so as to improve its low temperature resistance, heat resistance, radiation resistance or solvent resistance. At the same time, additives such as heat-resistant, flame-retardant, heat-conducting and conductive additives can be added according to the needs to make silicone rubber with the properties of ablation resistance, flame-retardant, heat-conducting and conductive.