Briefly describe several typical complexes of sulfur sulfide systems
Answer: (1) Constant sulfur vulcanization system (ordinary vulcanization system, CV) ① Dosage: S>1.5 parts, about 1 part (0.5-1 part) of accelerator ② Vulcanized rubber structure: mainly composed of polysulfide bonds (70%), with fewer low sulfur bonds Characteristics of vulcanized rubber: high tensile strength, high elasticity, and good fatigue resistance; Poor heat resistance and aging resistance. This vulcanization system ensures good safety in rubber processing, low processing costs, and basic performance that meets general usage requirements.
⑵ Semi effective vulcanization system (SEV) ① Dosage: S 0.8-1.5 parts or partially substituted with sulfur body, promoter 1-1.5 parts ② Structure of vulcanized rubber: polysulfide bonds, low sulfur bonds generally account for half each ③ Characteristics of vulcanized rubber: moderate tensile strength, elasticity, fatigue resistance, slightly better heat resistance, and aging resistance. This vulcanization system is commonly used for products used under dynamic conditions, such as tire sidewalls.
⑶ Effective vulcanization system (referred to as EV) ① Dosage: low S 0.2-0.5 parts or partially replaced by sulfur donors, 2-4 parts of accelerators ② Structure of vulcanized rubber: absolutely advantageous low sulfur bonds (90%) ③ Characteristics of vulcanized rubber: good heat resistance and aging resistance, but poor tensile strength, elasticity, and fatigue resistance. Products commonly used under static conditions, such as oil resistant sealing rings.
The equilibrium vulcanization system (EC) uses Si-69 tetrasulfide with sulfur, accelerators, and other molar ratios to keep the crosslinking density of the vulcanized rubber in a dynamic constant state, reducing or eliminating the vulcanization return to its original state. The rubber material of this system has advantages such as high strength, tear resistance, heat resistance, resistance to vulcanization, resistance to dynamic fatigue, and low heat generation. Therefore, it has important applications in the manufacturing of long-life dynamic fatigue products, giant engineering tires, and large thick products.
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