Silicone rubber is generally highly saturated structure, vulcanization activity is low, so it is usually not vulcanized with sulfur, the most common and most commonly used vulcanizing agent is organic peroxide. Silicone rubber can also use high-energy radiation vulcanization, radiation vulcanization and peroxide vulcanization mechanism is the same, both of the free group reaction and crosslinking.

Dimethylsilicone rubber molecules do not contain vinyl, is saturated rubber, usually use highly active peroxides as vulcanizing agent, peroxide free radicals to seize the hydrogen on the silicone rubber methyl to form macromolecular free radicals, and then the macromolecular free radicals recombine to form cross-linked bonds, such as dibenzoyl peroxide as vulcanizing agent.

It can be seen from the above reaction that silicone rubber containing vinyl can regenerate free radicals that can continue to react in the vulcanized parts, so introducing a small amount of vinyl into the silicone rubber can greatly improve the vulcanization activity, improve the cross-linking efficiency of the vulcanizing agent, reduce the amount of peroxide and improve the performance of the product. Since the initial free group triggering the crosslinking reaction is obtained from the decomposition of peroxides, increasing the amount of peroxides within a certain range can significantly improve the crosslinking degree of silicone rubber vulcanizate, which will lead to the improvement of the fixed elongation strength of the rubber, and improve the dynamic performance and compression deformation, but the tear resistance will be reduced.

According to the sulfurization activity of peroxides, the commonly used peroxides can be divided into general type and vinyl specific type. The universal type has high activity, which can vulcanize all kinds of silicone rubber, such as dibenzoyl peroxide (BP), 2? 4-dichlorodibenzoyl peroxide (DCBP), tert-butyl benzoate peroxide (TBPB), belong to this type. Vinyl-specific activity is low, and can only vulcanize silicone rubber containing vinyl, such as di-tert-butyl peroxide (DTBP), diisopropylbenzene peroxide (DCP and odorless DCP), 2? 5-dimethyl-2? 5-di-tert-butylhexane peroxide (DBPMH) and others belong to this type. Dibenzoyl peroxide is often made into a silicone oil paste with an active component of 50% to ensure production safety and improve its dispersion in the compound. Its decomposition products are benzene, benzoic acid and carbon dioxide, is volatile, in a stage of vulcanization must be pressurized, and because the decomposition products contain acidic substances, so the amount should not be too much to avoid reducing the heat resistance of the product, this product is not suitable for the manufacture of thick wall model products. General 100 parts of dimethyl silicone rubber with dibenzoyl peroxide silicone oil paste 4-6 parts, the amount of vinyl silicone rubber is 0.5 to 2 parts.

2.4-dichlorodibenzoyl peroxide compared with dibenzoyl peroxide, its decomposition temperature is lower than dibenzoyl peroxide, and the decomposition rate is higher, because of the low decomposition temperature, so the coke performance is not good, therefore, the amount of this substance should be as little as possible. Its decomposition products are 2.4-dichlorobenzoic acid and 2.4-dichlorobenzene, which are less volatile, so bubbles can be avoided when vulcanized without pressure, especially suitable for continuous vulcanization of pressed products by atmospheric pressure hot air. The dosage is similar to that of dibenzoyl peroxide.

Dibenzoyl peroxide, 2.4 - dichlorodibenzoyl peroxide is an aryl peroxide and cannot be used in carbon black materials because carbon black interferes with the vulcanization of the peroxide. Light-colored rubber has a strong tendency to scorch, and the acidic substances in its decomposition products will damage the heat resistance of silicone rubber products in the sealing system.

General-purpose grade rubber, plz check MY D9830