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What are the advantages of vulcanized shoes?
- Jan 06, 2019 -

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The term "vulcanization" has its history. It was named after the initial natural rubber products were cross-linked with sulfur as a cross-linking agent. With the development of the rubber industry, a variety of non-sulfur cross-linking agents can be used for cross-linking. Therefore, the more scientific significance of vulcanization should be "cross-linking" or "bridge", that is, the process of forming a network polymer by linear polymer crosslinking. From the physical property, it is the process of converting plastic rubber into elastic rubber or hard rubber. The meaning of "vulcanization" includes not only the process of actual cross-linking, but also the method of producing cross-linking.

It can be seen from the measurement of the strength of the compound (or vulcanizer) that the entire vulcanization process can be divided into four stages: vulcanization induction, pre-sulfurization, positive vulcanization and persulfurization (reversion to natural rubber).

During the vulcanization induction period (scorch time), the crosslinking has not yet started, and the rubber compound has good fluidity. This stage determines the scorch and processing safety of the compound. At the end of this phase, the compound begins to crosslink and loses fluidity. The length of the vulcanization induction period is related to the nature of the raw rubber itself, mainly depending on the additives used, such as the use of a retardation accelerator to obtain a longer scorch time and a higher processing safety.

After the vulcanization induction period, the pre-vulcanization stage of crosslinking is carried out at a certain speed. The degree of crosslinking in the pre-vulcanization period is low, and even if the tear strength of the vulcanized rubber is later, the elasticity cannot reach the expected level, but the performance of the tearing and dynamic cracking is better than the corresponding positive vulcanization.

After reaching the positive vulcanization stage, the physical properties of the vulcanized rubber are respectively at or near the optimum point, or the performance balance is achieved.

After the positive vulcanization stage (vulcanization flat zone), it is the supersulfur phase. There are two cases: the natural rubber has a “reversion” phenomenon (decreased strength), and most of the synthetic rubber (except butyl rubber) has a tensile strength. Continuous growth.

For any rubber, not only cross-linking occurs during vulcanization, but also breakage of the cross-linked chains and molecular chains due to heat and other factors. This phenomenon runs through the entire vulcanization process. In the sulfur persulfation stage, if the cross-linking is still dominant, the rubber will be hard and the strength of the extension will continue to rise. Conversely, if the rubber is soft, it will return to the original.