Silicone rubber is a low unsaturated linear polysiloxane elastomer whose main chain is alternately composed of silicon atoms and oxygen atoms and whose side chain is methyl or vinyl. According to the vulcanization mechanism, it can be divided into three types: free radical crosslinking vulcanized silicone rubber, polycondensation reaction type room temperature vulcanized silicone rubber, addition reaction type low temperature vulcanized silicone rubber.


(1) hot vulcanized silicone rubber vulcanization system

Hot vulcanized silicone rubber can be divided into organic peroxides, aliphatic azo compounds, inorganic compounds and high-energy ray vulcanization methods. One of the most commonly used is the organic peroxide sulfide system. Because organic peroxides are generally more stable at room temperature, they can be rapidly decomposed at a higher vulcanization temperature (above 150℃), resulting in vulcanization. Under the initiation of organic peroxides, the organic side chain groups of rubber undergo vulcanization reaction, forming C-C bond crosslinking. The more side chain groups such as vinyl, the easier to vulcanize, the higher the degree of cross-linking.


2) room temperature vulcanized silicone rubber vulcanization system

There are active functional groups such as hydroxyl group or acetoxy group at both ends of the main chain of room temperature vulcanized silicone rubber molecule. Under certain conditions, these functional groups are condensed to form a crosslinked structure. According to the mechanism of vulcanization, it can be divided into two kinds: one - component room temperature vulcanized silicone rubber and two - component room temperature vulcanized silicone rubber.


3) low temperature vulcanized silicone rubber vulcanization system

Low temperature vulcanized silicone rubber, also known as liquid silicone rubber, is a kind of end group for vinyl polysiloxane elastomer material, the general vulcanization temperature is 40~120℃, that is, between the hot vulcanization and room temperature vulcanization. It can be used with Si -- H group hanging energy polysiloxane as a crosslinking agent, in the presence of catalyst for addition reaction, complete the crosslinking, also known as the addition molding silicone rubber.

The common catalyst is organic platinum complex. Newer varieties include complex compounds containing vinyl low molecular polysiloxane. Very little catalyst.

In order to adjust the active period of the compound and improve the storage stability, reaction inhibitors can be used, usually alkynes, and compounds containing amine, tin, phosphorus and so on.

The vulcanization system is more active. If stored improperly, the glue will be partially cross-linked at room temperature. Therefore, in addition to the use of a reaction inhibitor, the compound must generally be in the form of two components: one containing a crosslinker and the other containing a catalyst, similar to that of two-component RVSI. When in use, mix according to the prescribed measurement. In this way, the storage period of the glue material is longer, and it can reach more than 1 year at room temperature. The curing rate of addition molding system has a great relationship with temperature.