A synthetic rubber is any artificial elastomer. These petroleum byproducts. They are made by the polymerization of a variety of petroleum- based precursors called monomers. The most prevalent synthetic rubbers are styrene- butadiene rubbers (SBR) derived from the copolymerization of styrene and 1, 3-butadiene. Other synthetic rubbers are prepared from isoprene (2-methyl-1, 3- butadiene), chloroprene (2-chloro-1, 3-butadiene), and isobutylene (methylpropene) with a small percentage of isoprene for cross-linking.