The vulcanization system of rubber includes vulcanizing agent, accelerator and active agent. Generally speaking, the crosslinking density of rubber is mainly related to the amount of vulcanizing agent of rubber. In order to improve the parallel density in the form of disulfide bonds, the amount of accelerator in the sulfur vulcanization system is generally less, so the size of the crosslinking density is mainly determined by the amount of sulfur.

The role of the accelerator is to reduce the cross-linking temperature of sulfur and speed up the vulcanization rate of sulfur. It actually acts as a catalyst. Different types of accelerators have different activation energies, so the types of vulcanized rubber are also different. For example, EPDM and IIR There are few unsaturated double bonds, so the vulcanization speed is slow. Generally, highly active dithiocarbamate accelerators or thiurams are used as the main accelerators, and NR, IR, BR, SBR with many unsaturated double bonds are used. , NBR due to the faster vulcanization speed, generally use thiazole or sulfenamide accelerator as the main accelerator. The selection of main accelerators is generally some acidic accelerators containing vulcanization groups. The vulcanization groups can participate in the vulcanization reaction at the same time, which helps to reduce the extranet substances in the vulcanizate after vulcanization, so as to reduce the blooming phenomenon.

The main accelerator can be used alone or two or more kinds. Generally speaking, the stronger the activity of the accelerator, the higher the activation energy and the stronger the acidity. When using two or more main accelerators, we must pay attention to their simultaneous activation. The amount of the main accelerator is less, and the amount of the main accelerator with weaker activity is more, so as to achieve the effect of acid balance and simultaneous activation.

The main vulcanization accelerators in highly unsaturated rubbers are generally used alone, but sometimes there are two main vulcanization systems in order to achieve the best co-vulcanization characteristics of multiple combined rubbers or to design a vulcanization system with a longer penetration period. Accelerators are used together.

Two or more main accelerators are generally used in low-unsaturated rubber EPDM and IR, because the vulcanization speed of these two rubbers is slow and the solubility of the accelerator in the rubber is low. Greatly increased, as soon as the unreacted accelerator and the reacted material outside the mesh will be sprayed out on the surface to form a bloom. When a variety of main accelerators are used together, they must also be activated simultaneously, otherwise the other accelerator that is activated later will be left in the rubber without complete reaction. When the temperature of the vulcanizate drops or the external environment affects Frosting will occur.