Two component Condensed Room Temperature Vulcanized Silicone Rubber

Two-component condensation room temperature vulcanized silicone rubber is the most common type of room temperature vulcanized silicone rubber. Its raw rubber is usually hydroxyl-terminated polysiloxane, which is combined with other coordinating agents and catalysts to form a compound. The viscosity range of this compound can range from 100% to 1 million%. The vulcanization reaction of two-component room temperature vulcanized silicone rubber is not initiated by moisture in air, but by catalyst. Generally, the raw silica gel, filler and cross-linking agent are packed as one component, the catalyst is packed as another component alone or in other combinations, but the catalyst and cross-linking agent must be packed separately. Regardless of the packaging method, curing occurs only when the two components are completely mixed together. The commonly used crosslinking agent is tetraethyl orthosilicate and the catalyst is tin dibutyl dilaurate. Adding appropriate fillers and additives according to the nature of the required final product. In recent years, dibutyltin dilaurate has been banned from food and plasma bags in many countries due to its moderate toxicity, and has been largely replaced by low toxicity octyltin.

The curing time of two-component condensation 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 sulfidation, and the shorter the shelf time. At room temperature, shelf time is usually several hours. To prolong shelf time of rubber, cooling method can be used. It takes about one day for the two-component condensation room temperature vulcanized silicone Hawthorn rubber to be fully cured at room temperature, but only one hour at 150 C. The curing rate can be significantly increased by using the synergistic effect of accelerator gamma-aminopropyl triethoxysilane. Two-component room temperature vulcanized silicone rubber can keep elasticity for a long time in the temperature range of 165-250 C. It has excellent electrical properties and chemical stability, water resistance, ozone resistance, climate aging resistance, simple use and strong process applicability. Therefore, it is widely used as filling and moulding materials. After being coated and encapsulated with room temperature vulcanized silicone rubber, various electronic and electrical components can play a protective role of moisture proof (anti-corrosion, anti-shock, etc.). It can improve performance and stabilize parameters. Two-component room temperature vulcanized silicone rubber is especially suitable for deep filling materials and has faster vulcanization time, which is superior to one-component room temperature vulcanized silicone rubber.

The two-component room temperature vulcanized silicone rubber has excellent anti-sticking property after vulcanization, and its shrinkage rate is very small during vulcanization. Therefore, it is suitable for making soft moulds and moulds for casting epoxy resin, polyester resin, polystyrene, polyurethane, vinyl plastics, paraffin, low melting point alloy, etc. In addition, a variety of exquisite patterns can be reproduced by using the high simulation performance of two-component room temperature vulcanized silicone rubber. For example, in the reproduction of cultural relics, ancient bronzes can be reproduced, and in the production of artificial leather, snakes, pythons, crocodiles and pangolins can be reproduced to play a false effect.

Several specific problems should be noticed when using two-component RTV silicone rubber. First, the base material, crosslinking agent and catalyst should be weighed separately, and then mixed proportionally. Usually the two components should be provided in different colors, so that the mixing of the two components can be observed intuitively. The mixing process should be carefully operated to minimize the amount of gas entrapped. After mixing (uniform color), bubbles can be removed by static or decompression (vacuum 700 mm Hg column). After all bubbles are discharged, silicone rubber is vulcanized 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 and cyanoethyl to improve its low temperature, heat resistance, radiation resistance or solvent resistance. At the same time, additives of heat resistance, flame retardant, thermal conductivity and electrical conductivity can be added to prepare silicone rubber with ablation resistance, flame retardant, thermal conductivity and electrical conductivity.