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.
The chemical name for Nitrile rubber is Butadiene Acrylonitrile. However, most commonly it is referred to as NBR or Buna-N. NBR is probably the most common solenoid valve seal material and it is considered the standard material for neutral fluids by many.NBR is also the standard material for O-rings.NBR can stand media temperatures to approximately 90 degrees Celsius on continuous basis, and higher temperatures intermittently.NBR resists aging caused by heat very well. However, NBR's resistance to sunlight is very poor. Abrasion and tear resistance of NBR is very good.he chemical name for Nitrile rubber is Butadiene Acrylonitrile. However, most commonly it is referred to as NBR or Buna-N. NBR is probably the most common solenoid valve seal material and it is considered the standard material for neutral fluids by many.