1.1 This part of ISO 1163 establishes a system of designation for unplasticized PVC thermoplastic material which may be used as the basis for specifications. 1.2 The types of PVC-U plastics are differentiated from each other by a classification system based on appropriate levels of the designatory properties a) Vicat softening temperature b) impact strength (Charpy notched) c) modulus of elasticity and on information about basic polymer parameters, intended application and/or method of processing, important properties, additives, colorants, fillers and reinforcing materials. 1.3 This part of ISO 1163 is applicable to all unplasticized compositions of homopolymers and copolymers that contain at least 50 % (m/m) of vinyl chloride. It is also applicable to compositions containing chlorinated poly(vinyl chloride) and to compositions containing blends of one or more of the above-mentioned polymers, provided that the total amount of these polymers represents at least 50 % (m/m) of the polymer content of the composition. It applies to materials ready for normal use in the form of powder, granules or pellets and to materials unmodified or modified by colorants, additives, fillers, etc. This part of ISO 1163 does not apply to cellular plastics. 1.4 It is not intended to imply that materials having the same designation give necessarily the same performance. This part of ISO 1163 does not provide engineering data, performance data or data on processing conditions which may be required to specify a material for a particular application and/or method or processing. If such additional properties are required, they may be determined in accordance with the test methods specified in part 2 of this International Standard, if suitable. 1.5 In order to specify a thermoplastic material for a particular application or to ensure reproducible processing, additional requirements may be given in data block 5 (see clause 3, introductory paragraph).