Secondary vulcanization, also known as post vulcanization or secondary vulcanization, refers to the process of heating and vulcanization of rubber products after reaching a certain degree of vulcanization, removing the heat source.

In a broad sense, when rubber products are vulcanized to a certain extent, even without heating, they can still continue to deepen the vulcanization process under the action of waste heat or during the storage process of the product, or generate continuous cross-linking under dynamic action. Of course, it also includes the processing technology of continuing to heat for secondary vulcanization; The purpose of secondary vulcanization is to further crosslink rubber products, improve their mechanical properties and compression permanent deformation performance, etc; The method of secondary vulcanization is either oven hot air vulcanization or using a vulcanization tank hot air secondary vulcanization.

At present, many rubber seals or rubber product production units use secondary vulcanization technology to produce rubber seals, and the technology is constantly updated and optimized with the changes of the times.

The function of secondary vulcanization of silicone gel:
When silicone rubber is vulcanized with peroxide, the decomposition of peroxide triggers a polymer reaction, resulting in the formation of low molecular weight compounds (such as benzene and benzoic acid) that will affect the mechanical properties of the rubber. Moreover, after the first stage of heating and molding, the cross-linking density of silicone rubber is not enough. Further vulcanization reaction is needed to increase the density, tensile strength, resilience, hardness, swelling degree, density, and thermal stability of silicone rubber, all of which are greatly improved compared to single vulcanization. If secondary vulcanization is not carried out, the performance of the produced silicone may be affected to some extent, and better performing products may not be obtained.
The parameters of primary vulcanization and secondary vulcanization may be different, which is related to actual operation. There are various types of silicone vulcanization, including high temperature and room temperature. Taking high-temperature silicone as an example, before vulcanization, it is commonly referred to as raw rubber. Blended rubber is the process of refining many additives such as vulcanizing agents, release agents, etc. together with raw rubber. It can be seen from the appearance. It breaks easily when pulled by hand and lacks elasticity.
If the mixed adhesive is vulcanized and formed at a certain temperature, products can be obtained, as we usually see: silicone bottle covers, silicone bracelets, silicone milk bottle covers, silicone sealing rings, silicone trays, silicone pads, silicone phone cases, etc. As long as it is a legitimate manufacturer and produces silicone products using qualified silicone raw materials, they are generally non-toxic.