The vulcanizing agents used for hot vulcanized silicone rubber mainly include organic peroxides, aliphatic azo compounds, inorganic compounds, high-energy radiation, etc. Among them, the most commonly used are organic peroxides. This is because organic peroxides are generally stable at room temperature, but can rapidly decompose and produce free radicals at higher vulcanization temperatures, thereby crosslinking silicone rubber.

Peroxides can be divided into two categories based on their activity. One type is the universal type, which has high activity and can cure various silicone rubbers; The other type is ethylene based special type, which has lower activity and can only vulcanize silicone rubber containing ethylene groups.

Apart from the general differences between the two types of peroxides mentioned above, each peroxide has its own characteristics. Vulcanizing agent BP is the most commonly used vulcanizing agent for molded products, with fast vulcanization speed and high production efficiency, but it is not suitable for the production of thick products. The vulcanizing agent DCBP is particularly suitable for continuous vulcanization of products with hot air, as its products are not easily volatile and bubbles can be generated without pressure during vulcanization. However, its decomposition temperature is low, which can easily cause burning and shorten the storage time of the rubber material. Both vulcanizing agents BP and DCBP are crystalline powders that are explosive. For safe operation and ease of dispersion, they are usually dispersed in a paste like form in silicone oil or silicone rubber, with a general content of 50%. The boiling point of vulcanizing agent is 110 ℃, which is highly volatile. When the rubber material is stored at room temperature, the vulcanizing agent evaporates, and it is best to use molecular sieves as carriers. The vulcanizing agent DTBP does not react with air or carbon black and can be used to manufacture conductive rubber and products that are difficult to mold. DBPMH vulcanizing agent is similar to DTBP, but it does not evaporate at room temperature. Its decomposition products are highly volatile, which can shorten the secondary vulcanization time. The vulcanizing agent DCP does not evaporate at room temperature and has the characteristics of ethylene based specific type. At the same time, the volatility of decomposition products is also low, which can be used for vulcanization in situations with low external pressure. The vulcanizing agent TBPB is used to manufacture sponge products.

The amount of peroxide used is influenced by various factors. For example, the variety of raw rubber, type and amount of filler, processing technology, etc. Generally speaking, as long as the required cross-linking can be achieved, the amount of vulcanizing agent should be minimized. But the actual dosage is much higher than the theoretical dosage, because various processing factors must be considered, such as uneven mixing, loss of peroxides during rubber storage, and inhibition of air and other compounding agents during vulcanization. For the rubber compound used in ethylene based silicone rubber molded products, the commonly used weight ranges of various peroxides are as follows: vulcanizing agent BP0.5-1; Vulcanizing agent DCBP1-2; Vulcanizing agent DTBP1-2; Sulfurizing agent DCP0.5~1; Sulfurizing agent DBPMH0.5-1; Sulfurization agent TBPB0.5-1. As the vinyl content increases, the amount of peroxide used should be reduced. The amount of peroxide in adhesive paste, extruded product adhesive and adhesive material should be higher than that in molding material. In certain situations, using a combination of two peroxides can reduce the amount of vulcanizing agent and appropriately lower the vulcanization temperature to improve the vulcanization effect.

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