UNE 53-188 Pt.2-1991 Plastics. Polythylene(PE) and ethylene copoliner thermoplastics. Part 2: Preparation of test specimens and determination of properties
This part of the UNE 53-188 standard specifies the conditions for molding specimens of thermoplastic polyethylene materials and their copolymers, as well as the methods for measuring their properties. 2 In this part of the UNE 53-188 Standard, the values of these characteristics are not indicated, which are set for the designation of polyethylenes for molding and extrusion, being indicated in the UNE 53-188/1 standard. The other characteristics indicated in this part of the UNE 53-188 standard, and their values, can be obtained by referring to the manufacturers' information. The values are comparable, provided that the molding of the specimens and the determination of the properties is carried out in accordance with this standard. 3 The values determined according to this part of the UNE 53-188 standard will not necessarily be identical to those obtained using specimens of different sizes and/or prepared according to different transformation methods. These values may also be influenced by colorants and other additives. The values obtained for the characteristics of a molded object depend, among others, on the raw material, the shape of the part, the test method and the state or anisotropy. This is a function of the feeding channel and the molding conditions (temperature, pressure, injection speed). Treatment, for example conditioning or annealing, must also be taken into account. 4 The thermal history and internal stresses of the specimen can have a great influence on its thermomechanical properties and its resistance to cracking in a given medium. The electrical properties are less influenced, and depend, above all, on the chemical composition of the material to be molded.