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.
Styrene-butadiene rubber (SBR) is one of the most versatile copolymer rubber compounds. It consists of the organic compound styrene and the chemical budatiene, with the amount of budatiene usually being about three times more than the amount of styrene. SBR is a stable synthetic that is resistant to abrasion. It is used in a wide variety of products, such as automobile tires, children's toys, shoe soles and even chewing gum. This compound is produced either through ionic polymerization of a solution or as an emulsion through free radical polymerization.