Secondary vulcanization is also called post-vulcanization or two-stage vulcanization, which refers to the process in which rubber products reach a certain degree of vulcanization, and the heat source is removed to continue heating and vulcanization.
In a broad sense, a rubber product is vulcanized to a certain extent, even if it is not heated, it can still continue to deepen the vulcanization process under the action of waste heat, or during the storage process of the product, or continue to cross-link under dynamic action. Of course, it also includes the processing technology of continuous heating for secondary vulcanization; the purpose of secondary vulcanization is to further crosslink rubber products, improve the mechanical properties and compression set properties of rubber products, etc. The method of secondary vulcanization is oven hot air vulcanization or vulcanization Tank hot air post vulcanization.
At present, many rubber seals or rubber product production units use secondary vulcanization technology to make rubber seal products, and the technology is constantly updated and optimized with the changes of the times.
The role of silica gel secondary vulcanization:
When the silicone rubber is vulcanized by peroxide, after the decomposition of the peroxide triggers the polymer reaction, low molecular compounds (such as benzene and benzoic acid) are formed in the rubber, which will affect the mechanical properties of the rubber. Moreover, after the silicone rubber is heated and formed in the first stage, its cross-linking density is not enough, and further vulcanization reaction can increase the density, tensile strength, resilience, hardness, swelling degree, density, and thermal stability of the silicone rubber. Vulcanization has greatly improved. If the secondary vulcanization is not carried out, the performance of the produced silica gel may be affected to a certain extent, and a product with better performance cannot be obtained.
The parameters of primary vulcanization may be different from those of secondary vulcanization, which is related to actual operation. There are many kinds of silica gel vulcanization, high temperature and room temperature. Taking high-temperature silica gel as an example, it is what we usually call raw rubber before vulcanization. Mixing rubber is to refine many additives such as vulcanizing agent, mold release agent, etc. together with raw rubber. It can be seen from the appearance. It breaks as soon as it is pulled by hand, and there is no elasticity.
If the mixed glue is vulcanized at a certain temperature, the product can be obtained, as we usually see: silicone bottle cover, silicone bracelet, silicone bottle cover, silicone sealing ring, silicone tray, silicone pad, silicone Phone cases, etc. As long as it is a regular manufacturer, the silicone products produced by qualified silicone raw materials are generally non-toxic.