1.1 This part of ISO 8257 establishes a system of designation for poly(methyl methacrylate) (PMMA) thermoplastic materials, which may be used as the basis for specifications. 1.2 The types of PMMA plastics are differentiated from each other by the classification system based on appropriate levels of the designatory properties a) Vicat softening temperature, b) melt mass-flow rate, c) viscosity number (optional), and on information about intended application and/or method of processing, important properties, additives and colorants. 1.3 This part of ISO 8257 is applicable to all poly(methyl methacrylate) homopolymers and to copolymers of methyl methacrylate (MMA) containing at least 80 % (m/m) of MMA and not more than 20 % (m/m) of acrylic esters or other monomers. It applies to materials ready for normal use in the form of beads, granules and pellets and to materials unmodified or modified by colorants, additives, etc. This part of ISO 8257 does not apply to PMMA modified with elastomers. 1.4 It is not intended to imply that materials having the same designation give necessarily the same performance. This part of ISO 8257 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 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).