Secondary vulcanization, also known as post-vulcanization or secondary vulcanization, refers to the process that rubber products reach a certain degree of vulcanization and continue to be heated and vulcanized without heat source.

In a broad sense, when the rubber products are vulcanized to a certain extent, even if they are not heated, they can continue to deepen the vulcanization process under the action of residual heat, or during the storage process of the products, or produce continuous cross-linking under the dynamic action. Of course, it also includes the process of continuous heating for secondary vulcanization; The purpose of secondary vulcanization is to further cross-link rubber products and improve the mechanical properties and compression set properties of rubber products; The method of secondary vulcanization is oven hot air vulcanization or curing tank hot air secondary vulcanization.

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

Effect of secondary vulcanization of silicone rubber:
When silicone rubber is vulcanized with peroxide, the decomposition of peroxide will lead to the reaction of polymer, which will produce low molecular compounds (such as benzene and benzoic acid), which will affect the mechanical properties of rubber. Moreover, after the silicone rubber is heated and molded in the first stage, its cross-linking density is not enough. Only by further curing reaction can the density, tensile strength, resilience, hardness, swelling degree, density and thermal stability of the silicone rubber be increased. If the secondary vulcanization is not carried out, the performance of the produced silica gel may be affected to some extent, and the product with better performance will not be obtained.

The parameters of primary curing and secondary curing may be different, which is related to actual operation. There are many kinds of silicone rubber vulcanization, including high temperature and room temperature. Take high-temperature silica gel as an example. Before vulcanization, we usually call it raw rubber. Rubber mixing is to blend many additives such as vulcanizing agent and release agent with raw rubber. It can be seen from the appearance. It will break when you pull it with your hand. It has no elasticity.

If the mixed rubber is vulcanized at a certain temperature, the product can be obtained, as we usually see: silicone bottle cover, silicone bracelet, silicone milk bottle cover, silicone sealing ring, silicone tray, silicone pad, silicone mobile phone cover, etc. As long as it is a regular manufacturer, silicone products produced with qualified silicone raw materials are generally non-toxic.

For silicone rubber, please check the details:
https://www.siliconerubbers.net/product-common-grade-htv-silicone-rubber.html