This part of the UNE 53-186 series of standards establishes a designation system for polypropylene (PP) thermoplastics. This system can be used as a basis for specifications. 2 The types of propylene plastics are differentiated from each other by a classification system based on the appropriate values of the properties: isotacticity index, fluidity index, as well as by information related to the parameters of the base polymer, intended application, transformation methods, essential characteristics, additives, colorants and fillers. 3 This designation system is applicable to all polypropylene homopolymers, propylene copolymers and mixtures containing at least 50% by weight of the aforementioned polymers. It applies to materials prepared for use in the form of powder, or pellets, unmodified and modified by colorants, additives, fillers, etc. This part of the UNE 53-186 standard is not applicable to rubbers based on propylene or to mixtures of PP with EPDM. 4 The fact that there are materials with the same designation does not imply that they necessarily have the same technical qualities. This part of the UNE standard. 53-186 does not include data on processing qualities or conditions that may require a particular application or transformation method. If additional characteristics are necessary, they must be determined according to the test methods specified in the UNE 53-186/2 standard. 5 In order to specify a material for a particular application or a transformation method that can be reproduced, additional requirements may be encoded in data block number 5 (see chapter 3).