The vulcanization process of silicone rubber is not completed at one time, but divided into two stages. The rubber material is heated under pressure (such as molding vulcanization, direct steam vulcanization of vulcanization tank, etc.) or under atmospheric pressure (such as hot air continuous vulcanization), which is called a section of vulcanization (or vulcanization); Vulcanization in the oven at high temperature, in order to further stabilize the physical properties of vulcanized rubber, known as two curing (or after curing).

(1) a section of vulcanization

Vulcanization of model products. Plate vulcanization, transfer mold vulcanization and injection vulcanization are available. When vulcanizing silicone rubber products, release agent is generally not used. It should be quickly loaded, sealed and pressurized, otherwise it is easy to burn, especially the rubber containing vulcanizing agent BP and DCBP. Transfer molding vulcanization is a widely used process for processing silicone rubber materials. Compared with flat vulcanization with single hole in each mold, it has the advantage of short processing cycle and can vulcanize complex rubber parts, especially with inserts and pins. Compared with injection pressure vulcanization, the equipment cost is lower. Injection pressure vulcanized mold products, can improve labor productivity, reduce labor intensity, but also can reduce the amount of peroxide, improve the tear resistance of products, improve the compression of permanent deformation performance, but the product shrinkage rate is larger.

Vulcanization of extruded products. Can use steam pressure vulcanization, hot air continuous vulcanization, liquid sulfide tank continuous vulcanization, drum vulcanization and radiation vulcanization methods. The first three methods are more commonly used.

(2) second section vulcanization

After a period of vulcanization of silicone rubber products, some low molecular substances exist in the vulcanization rubber, affecting the properties of products. For example, the use of general vulcanizing agent (such as vulcanizing agent BP or DCBP) of the rubber, after a period of vulcanization, the acid quality of the vulcanizing agent decomposition, will increase the porosity of the sponge hole, reduce the density; Increasing the amount of vulcanizing agent will reduce the porosity of sponge hole, increase the density, and produce a thicker hole wall. In addition, vulcanization temperature has a great influence on the porosity of sponge.