This part of ISO 7391 establishes a system of designation for polycarbonate thermoplastic material, which may be used as the basis for specifications. The types of polycarbonate plastic are differentiated from each other by a classification system based on appropriate levels of the designatory properties - viscosity number- melt volume-flow rate- Charpy impact strengthand on information about the intended application and/or method of processing, important properties, additives, colorants, fillers and reinforcing materials.This part of ISO 7391 is applicable to thermoplastic polyesters of carbonic acid and aromatic dihydroxy compounds. The polyester may be a