1.1 This part of the UNE 53-049 standard establishes a designation system for thermoplastic polystyrene materials that must serve as the basis for the specifications. 1.2 The types of polystyrene materials for molding and extrusion are differentiated from each other by a classification system, which is based on appropriate levels of the following properties that characterize them: a) VICAT softening temperature; b) fluidity index, and, furthermore, by the applications for which they are intended, the transformation methods, the important properties, the additives and the color. 1.3 This designation system applies to all amorphous styrene homopolymers. It is applicable to all materials prepared for use, whether or not they are modified with colorants, additives, etc. This standard is not applicable to expanded polystyrene, nor to styrene copolymers, nor to substituted styrene homopolymers, nor, finally, to those that are modified with other polymers, for example, with elastomers. 1.4 Materials with the same designation do not necessarily have to be applied for the same purpose. In this part of the UNE 53 049 standard, neither engineering nor use data nor the processing conditions required to specify a material for a specific application or for a transformation method are given. If these properties are needed, they must be determined in accordance with the methods specified in the UNE 53-049/2 standard. 1.5 In the event that a thermoplastic material is desired to be specified for a particular application, or a specific process, it must be coded in Data Block 5 (see chapter 3).