Acrylonitrile Butadiene Styrene, often abbreviated ABS, is the plastic used in most modern LEGO elements. Its chemical formula is (C8H8)x·(C4H6)y·(C3H3N)z, and it has melting point at about 105 °C. ABS is a thermoplastic consisting of a styrene monomer with the addition of an acrylonitrile momomer and a butadiene monomer. It is the butadiene component (a synthetic rubber mainly used in tires) that is largely responsible for the strength and impact resistance of the plastic. The final form of the plastic was developed as part of the war effort in the mid 1940s.