In 2012, mintage numbers were reduced by over 90%, in line with a similar reduction for the Presidential Dollars, due to large stockpiles of unused dollar coins.he coin was first suggested as a replacement for the Susan B. Anthony dollar, which proved useful for vending machine operators and mass transit systems despite being unpopular with the public.
Butyl rubber is a synthetic rubber, a copolymer of isobutylene with isoprene. The abbreviation IIR stands for isobutylene isoprene rubber. Polyisobutylene, also known as PIB or polyisobutene, (C 4 H 8) n, is the homopolymer of isobutylene, or 2-methyl-1-propene, on which butyl rubber is based.
Synthetic rubber is 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.ynthetic rubber, like natural rubber, has uses in the automotive industry for tires, door and window profiles, hoses, belts, matting, and flooring.