The document discusses nitrile rubber, which is a polymeric mixture of butadiene and acrylonitrile in a 2:1 ratio. Higher levels of acrylonitrile yield properties like low temperature flexibility and increased hardness. Nitrile rubber is a highly polar elastomer that exhibits large and reversible elastic deformation. It has excellent tensile strength, elongation, low temperature flexibility, compression set, tear resistance, and abrasion resistance. However, it has fair to poor flame resistance and gas permeability.