ISO 25137-1:2009 establishes a system of designation for sulfone polymer moulding and extrusion materials, including polysulfone (PSU), polyethersulfone (PESU) and polyphenylsulfone (PPSU), which may be used as the basis for specifications. The types of sulfone plastic are differentiated from each other by a classification system based on appropriate levels of the designatory properties temperature of deflection under load, melt mass-flow rate, Charpy notched impact strength, tensile modulus and yield stress, and on information about composition, intended application and/or method of processing, important properties, additives, colorants, fillers and reinforcing materials. This part of ISO 25137 is applicable to all sulfone polymers that contain ether oxygen, which is a necessary component of the polymers as in the diphenyl sulfone moiety. It applies to sulfone polymer materials ready for normal use in the form of powder, granules or pellets, unmodified or modified by colorants, additives, fillers, etc.