Single component room temperature vulcanized silicone rubber has excellent electrical properties, chemical inertness, heat resistance, natural aging resistance, flame resistance, moisture resistance and air permeability. They can maintain elasticity for a long time in the range of -60~200℃. It does not absorb or release heat during curing, and has small shrinkage after curing, and has good adhesion to materials.
Therefore, it is mainly used as adhesive and sealant. Other applications include in situ formed gaskets, protective coatings and caulking materials. Many formulations of single component silicone rubber adhesives exhibit automatic bonding properties to a variety of materials, such as most metals, glass, ceramics and concrete. When bonding is difficult, primer can be applied on the substrate to improve the bonding strength. The primer can be silane monomer or resin with reactive activity. When they are cured on the substrate, a modified surface suitable for silicone bonding is generated.
The rtv room temperature vulcanizing reaction of single component room temperature vulcanized silicone rubber is carried out gradually from the surface to the depth. The thicker the rubber layer, the slower the curing. When the deep part also needs to be cured quickly, the layered pouring step-by-step vulcanization method can be adopted. Some rubber can be added each time, and then added after vulcanization, so as to reduce the total vulcanization time. The addition of magnesium oxide can accelerate the vulcanization of deep rubber.
The vulcanization reaction of two-component room temperature vulcanized silicone rubber is initiated not by water in the air, but by catalyst. Usually, the rubber and catalyst are packaged as one component respectively. Curing occurs only when the two components are completely mixed together. The curing time of two-component condensation room temperature vulcanized silicone rubber mainly depends on the type, dosage and temperature of catalyst.
Two components room temperature vulcanized silicone rubber has excellent anti adhesion performance after vulcanization, and the shrinkage rate is very small during vulcanization. Therefore, it is suitable for manufacturing soft molds and casting molds of epoxy resin, polyester resin, polystyrene, polyurethane, vinyl plastic, paraffin, low melting point alloy and so on. In addition, using the high simulation performance of two-component room temperature vulcanized silicone rubber, various exquisite patterns can be copied on cultural relics. When using two component room temperature vulcanized silicone rubber, we should pay attention to the following: first, weigh the rubber and catalyst respectively, and then mix them in proportion.
The two components addition molded room temperature vulcanized silicone rubber has elastic silica gel and silicone rubber. The former has lower strength and the latter has higher strength. Their vulcanization mechanism is based on the addition reaction between the vinyl group on the end group of silicone raw rubber and the hydro silyl group on the crosslinker molecule. No by-products are released in this reaction.
Due to the low molecular weight compounds are not released in the chain crossing process, the addition room temperature vulcanized silicone rubber does not shrink in the vulcanization process. This kind of vulcanizate has the advantages of non-toxic, high mechanical strength, excellent hydrolysis resistance stability, good low-pressure shrinkage deformation, low flammability, deep vulcanization and vulcanization speed can be controlled by temperature. Therefore, it is a kind of silicone rubber vigorously developed in the world.
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