Unsaturated rubbers, accelerated-sulfur vulcanization

Accelerated-Sulfur Vulcanization of Various Unsaturated Rubbers... 

Accelerated-Sulfur Vulcanization of Various Unsaturated Rubbers. Over the years, much of the research on accelerated-sulfur vulcanization was done by using natural... 

Vulcanizing additive Thermoset elastomers must be vulcanized or crosslinked to obtain strong, dimensionally stable resilient materials. To accomplish this purpose, a formidable array of chemicals is employed. Classically, sulfur vulcanizes unsaturated elastomers such as SBR and natural rubber however, because the rate of vulcanization is too slow for industrial applications, chemicals like benzothiazyl disulfide (MBTS) are added. The latter is typical of a class called accelerators. 

The filler/silane intermediate can now react with the allyl position of unsaturated sites on the polymer chain. The vulcanization of rubber is known to proceed via reaction of an accelerator, such as a sulfenamide, with sulfur, zinc oxide, and stearic acid, to generate a sulfurating agent (Bateman et al., 1963). 

Since EPR rubber molecules do not contain unsaturation, they can be vulcanized only by organic peroxide curing systems. If a third monomer is added during the polymerization, i.e., a diene monomer (wherein only one of the two double bonds takes part in the polymerization), unsaturation can be introduced into the molecule, and it can then be vulcanized by accelerated sulfur curing systems. A chemical structure for ethylene-propylene-diene-monomer (EPDM) rubbers can be expressed as follows ... 

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