The two ends of the main chain of the room temperature vulcanized silicone rubber molecule contain active functional groups such as hydroxyl or acetoxy. Under certain conditions, these functional groups undergo a condensation reaction to form a cross-linked structure. According to the vulcanization mechanism, it can be divided into one-component RTV silicone rubber and two-component RTV silicone rubber.

a. One-component room temperature vulcanization silicone rubber vulcanization system The hydroxyl-terminated silicone rubber can use silane containing easily hydrolyzable groups as the cross-linking agent. In the presence of a condensation catalyst, a condensation reaction occurs to form Si-O bond cross-linking.

The vulcanization rate of the one-component system is not only affected by the type of crosslinking agent, but also the influence of air humidity and ambient temperature is very important.

The vulcanization of the one-component system starts from the surface layer in contact with air and gradually proceeds to the deep layer. Usually the thickness of the sulfide layer is within 1cm. In order to accelerate vulcanization and prepare thick-layer products, magnesium oxide can be added or layered construction.

b. Two-component RTV silicone rubber vulcanization system This system consists of crosslinking agent and catalyst. In the presence of the catalyst, the terminal hydroxyl groups of the silicone rubber undergo condensation reaction with the functional groups of the cross-linking agent to form a silicon-oxygen bond cross-linking.

Commonly used cross-linking agents are ethyl orthosilicate (propyl), n-butyl titanate, methyltriethoxysilane or their partial hydrolysis condensates. Commonly used crosslinking catalysts are metal organic acid salts, such as dibutyltin dilaurate, dibutyltin diacetate, tin octoate, stannous isooctanoate and lead octoate.

When preparing the rubber compound, usually some raw rubber, cross-linking agent and filler are mixed into one component, and the remaining raw rubber, filler and catalyst are mixed into another component. When using, the two components are mixed according to the calculation regulations. Therefore, it is called two-component room temperature vulcanized silicone rubber.

The dosage of crosslinking agent is generally 2~10 parts; the dosage of catalyst is 0.1~5 parts. Example of vulcanization system formulation: 100 parts of room temperature vulcanized silicone rubber, 0.4 parts of dibutyltin dilaurate; 3.0 parts of ethyl orthosilicate.

The vulcanization rate of the two-component system is mainly determined by the type and amount of catalyst, and is also affected by air temperature and ambient temperature. In addition, amine accelerators can also be used as co-catalysts to accelerate their vulcanization.