Addition silicone rubber is a kind of synthetic rubber, which is vulcanized by hydrosilylation reaction, and belongs to the silicone sequence. The silicone rubber can be divided into elastic silicone gel and silicone rubber, the former has lower strength, and the latter has higher strength. The viscosity of the added silicone rubber before vulcanization is low, which is convenient for pouring. It does not release heat during vulcanization, and has no low-molecular by-products. The shrinkage rate is small, and it can be deeply vulcanized.
Component addition RTV silicone rubber can be divided into elastic silicone gel and silicone rubber. The former has lower strength, while the latter has higher strength. Their vulcanization mechanism is based on the addition reaction (hydrosilylation reaction) between the vinyl group (or propylene group) on the end group of the silicone rubber and the hydrosilyl group on the molecule of the cross-linking agent.
In this reaction, the polysiloxane with hydride function is used as the cross-linking agent (vulcanizing agent) chloroplatinic acid or other soluble platinum compounds as catalysts.
The vulcanization reaction is carried out under suffocation temperature. No by-products will be released. Due to the fact that low molecular weight is not released during the crosslinking process, the addition RTV silicone rubber does not shrink during the curing process. This kind of vulcanizate has the advantages of non-toxic, high mechanical strength, excellent hydrolysis-resistant stability (even under high pressure steam), 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 at home and abroad.
The packaging method of addition RTV silicone rubber is generally divided into two components: M and N: catalyst and organosilicon polymer containing vinyl functional group as one component; The hydrogen-containing polysiloxane crosslinker is another component.
High strength addition RTV silicone rubber is an excellent material for molding because of its low linear shrinkage and low molecular weight during vulcanization. In the mechanical industry, it has been widely used to make molds for casting epoxy resin, polyester resin, polyurethane, polystyrene, vinyl plastic, paraffin, low melting point alloy, coagulation, etc.
It is suitable for the reproduction of cultural relics and fine arts and crafts by using the characteristics of high imitation, non-corrosion, simple molding process and easy demoulding of the addition and heat vulcanized silicone rubber.