1.1 This classification system covers polybutylene plastics materials suitable for molding and extrusion. 1.2 This classification system is applicable to all butene homopolymers and to copolymers of butene with a maximum This classification system covers polybutylene plastics materials suitable for molding and extrusion that allows the material to be recycled. This system recognizes that polybutylene plastics are identified on the basis of two characteristics which are