Briefly describe several typical combinations of sulfur vulcanization system
Answer: ⑴ Constant sulfur vulcanization system (ordinary vulcanization system, CV) ① Dosage: S>1.5 parts, accelerator about 1 part (0.5-1 part) ② Structure of vulcanized rubber: Mainly composed of polysulfide bonds (70%), with fewer low sulfur bonds. ③ 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 performance that can basically meet general usage requirements.
⑵ Semi effective vulcanization system (SEV) ① Dosage: 0.8-1.5 parts or partially replaced by sulfur donor, 1-1.5 parts of accelerator ② Structure of vulcanized rubber: polysulfide bonds, with low sulfur bonds accounting for roughly half each ③ Characteristics of vulcanized rubber: moderate tensile strength, elasticity, fatigue resistance, heat resistance, and slightly better aging resistance. This vulcanization system is commonly used for products used under dynamic conditions, such as tire sidewalls.
⑶ Effective vulcanization system (EV for short) ① Dosage: 0.2-0.5 parts of low sulfur or partially replaced by sulfur donor, 2-4 parts of accelerator ② Structure of vulcanized rubber: absolute advantage of low sulfur bonds (90%) ③ Characteristics of vulcanized rubber: good heat resistance and aging resistance, but poor tensile strength, elasticity, and fatigue resistance. Commonly used for products used under static conditions, such as oil resistant seals.
⑷ Balanced vulcanization system (EC) uses Si-69 tetrasulfide with sulfur, accelerator and other molar ratios to keep the crosslinking density of the vulcanized rubber in a dynamic constant state, reducing or eliminating the sulfurization return to its original state. The rubber material of this system has the advantages of high strength, tear resistance, heat and oxygen resistance, resistance to vulcanization and reversion, 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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