This part of the UNE 53-188 standard establishes a designation system for thermoplastic materials made of polyethylene (PE) and copolymers, which can be used as a basis for specifications. 2 Types of polyethylene plastics are differentiated from each other by a classification system based on appropriate values of the properties: a) density b) fluidity index and information on the application for which they are intended, method of transformation, fundamental properties , additives, color, reinforcing materials and fillers. 3 This designation system can be applied to all ethylene homopolymers and copolymers having a maximum content of other a-olefinic monomers of less than 50% and a content of non-olefinic monomers with functional groups, up to a maximum of 3%. It is applied to materials for normal use in the form of powder, pellets, and unmodified materials or materials modified with colorants, additives, fillers, etc. This part of the UNE 53-188 standard is not valid for EPM concentrates or rubbers. 4 Materials with the same designation do not necessarily have to be applied for the same purpose. In this part of the UNE 53-188 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 Standard UNE 53-188/2. 5 If you wish to specify a thermoplastic material for a particular application, or a specific process, it must be coded in Data Block 5 (see chapter 3).