1.1 This part of ISO 1060 establishes a system of designation for vinyl chloride thermoplastic resins, which may be used as the basis for specifications. 1.2 The types of vinyl chloride plastics are differentiated from each other by a classification system based on appropriate levels of the designatory properties: a) reduced viscosity b) apparent density c) retention on a 63 μm mesh sieve d) plasticizer absorption at room temperature (for general-purpose resins and filler resins only) e) the viscosity and the type of rheological behaviour of a standard paste (for paste resins only) and on information about basic polymer parameters, polymerization processes and intended applications. 1.3 This part of ISO 1060 is applicable to resins in powder form which consist of homopolymers of the monomer vinyl chloride and copolymers, terpolymers, etc., of vinyl chloride with one or more other monomers, but where vinyl chloride is the main constituent. The resins may contain small amounts of non-polymerized substances (e.g. emulsifying or suspending agents, catalyst residues, etc.) and other substances added during the course of polymerization. 1.4 It is not intended to imply that materials having the same designation give necessarily the same performance. This part of ISO 1060 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 of processing. If such additional properties are required, they shall 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 resin for a particular application or to ensure reproducible processing, additional requirements may be given in data block 5 (see clause 3, introductory paragraph).