Vulcanization system additives play an important role in synthetic rubber formulations and are one of the main factors affecting the performance of rubber products.
The auxiliary agent of the vulcanization system is mainly composed of vulcanizing agent, accelerator and active agent. According to the degree of saturation of the synthetic rubber, various vulcanization systems such as sulfur, metal oxides, peroxides and amine compounds can be used.
1. Vulcanizing agent
According to different rubber types and performance requirements of rubber products, different vulcanization systems such as sulfur, peroxide, quinone oxime, resin, and metal oxide can be used. Among them, sulfur vulcanization system is divided into ordinary vulcanization system, effective vulcanization system and semi-effective vulcanization system.
Sulfur vulcanization system is mostly used in general synthetic rubber and semi-universal synthetic rubber. Metal oxide vulcanization system is mainly used for chloroprene rubber (CR), quinone oxime and resin vulcanization system is mainly used for butyl rubber (IIR), peroxide The material and resin vulcanization system is mainly used for ethylene propylene rubber (EPR), natural rubber (NR) and styrene butadiene rubber (SBR). Special rubber [such as polysulfide rubber (LP), chlorosulfonated polyethylene rubber (CSM), chlorinated polyethylene rubber (CM), fluorine rubber (FKM), silicone rubber (MVQ), fluorosilicone rubber (FVMQ), etc.] Basically, they are saturated rubbers and do not contain double bonds. Sulfur does not have a crosslinking effect on them. Therefore, non-sulfur vulcanization systems such as metal oxides, peroxides, and organic amine salt vulcanization systems are required. In recent years, acrylate rubber (ACM) has basically adopted a sulfur vulcanization system.
(1) Sulfur. Ordinary powder sulfur is the most commonly used vulcanizing agent in the rubber industry. With the development of radial tires and colored rubber products, insoluble sulfur (IS), which does not bloom, does not affect the adhesion performance and product appearance, is widely used. IS is mostly used in NR tire compounds. It has the function of improving the rubber-frame material adhesion performance, avoiding blooming, and extending the storage time of the compound. IS also has a small amount of application in butadiene rubber (BR) tire compounds.
(2) Peroxide. Except for IIR and halogenated butyl rubber (XIIR), other rubbers are especially MVQ, EPDM, nitrile rubber (NBR), hydrogenated nitrile rubber (HNBR), CM, CR and thermoplastic elastomers Almost all can be cured with peroxide. The crosslinking bond of peroxide vulcanized rubber is C—C bond, and its bond energy is larger than that of single sulfur bond, disulfide bond and polysulfide bond of sulfur vulcanized rubber, so the heat resistance of peroxide vulcanized rubber Excellent oxygen aging performance, small compression set, not easy to bloom, no reversion phenomenon, but its tensile performance, strain performance and fatigue resistance are poor.
(3) Resin. In order to improve the heat resistance and aging resistance of rubber compounds, many types of rubber (IIR, NR, SBR and NBR, etc.) have widely used resins (such as alkyl phenolic resins, etc.) as crosslinking agents. The resin-vulcanized IIR compound has good heat resistance and small compression set, and has become the most important compound for manufacturing vulcanization bladder. Phenolic resin curing system is also commonly used in the preparation of EPDM/PP and other rubber-plastic blending materials.
In addition, when petroleum resin is added to rubber tire manufacturing, it can effectively increase viscosity, soften and strengthen, and is a good additive.