Fashion, good-looking, with the classic jeans, dirty is relatively good care, affordable. "vulcanization " The word has its historical, because the original natural rubber products with sulfur as crosslinking agent for cross-linking and name, with the development of the rubber industry, can be cross-linked with a variety of non-sulfur crosslinking agents. Therefore, the more scientific significance of vulcanization should be "cross-linked" or "bridging", that is, the linear polymer through the cross-linking effect of the formation of the network polymer process. It is the process of converting plastic rubber into elastic rubber or hard rubber from physical property.
The meaning of "vulcanization" includes not only the actual cross-linking process, but also the method of producing cross-linking.
Through the knew tensile strength of the measurement (or vulcanizing instrument) can be seen, the entire vulcanization process can be divided into vulcanization induction, pre-sulfur, positive vulcanization and over sulfur (for natural rubber is vulcanization back to the original) four stages. The vulcanization induction period (scorch time), the crosslinking has not yet begun, the rubber material has very good fluidity. This stage determines the coke-burning and processing safety of the compound. At the end of this phase, the rubber material begins to cross-linked and loses its fluidity.
The length of vulcanization induction period is related to the nature of the raw rubber itself, mainly depends on the additives used, such as the delay promoter can get a longer scorch time, and high processing safety. After the induction period of vulcanization, it is the pre-vulcanization stage of cross-linking at a certain speed.
The degree of crosslinking of the pre-curing period is low, even to the late vulcanization of the tensile strength, elasticity can not reach the desired level, but the tear and dynamic crack performance is better than the corresponding positive vulcanization.
After reaching the positive vulcanization stage, the physical properties of vulcanized rubber meet or close to the optimum point respectively, or achieve the full balance of the performance.
The positive vulcanization stage (cured flat area), that is, the sulfur phase, there are two cases: natural rubber appearance "Return to the original" phenomenon (elongation strength decreased), most of the synthetic adhesive (except butyl gum) The strength of the extension continues to increase. For any rubber, vulcanization does not only produce cross-linking, but also due to the effects of heat and other factors on the production chain and the fracture of the molecular chain. This phenomenon runs through the vulcanization process. In the sulfur phase, if the cross-linking is still dominant, the rubber is hard, the strength of the extension continues to rise, on the contrary, rubber weakness, that is, the return of the original.