BS EN ISO 4577:2019 pdf – Plastics — Polypropylene and propylene- copolymers — Determination of thermal oxidative stability in air — Oven method.
1 Scope This document specifies a method for the determination of the resistance of moulded test specimens of polypropylene and propylene-copolymers to accelerated ageing by heat in the presence of air using a forced draught oven. The method represents an attempt to estimate the service life of parts fabricated from propylene plastics. The stability determined by this method is not directly related to the suitability of the material for use when different environmental conditions prevail. NOTE The specified thermal levels are considered sufficiently severe to cause failure of commercial grades of heat-stable propylene plastics within a reasonable period of time. If desired, lower temperatures can be applied to estimate the performance of propylene plastics with lower heat stabilities. 2 Normative references The following documents are referred to in the text in such a way that some or all of their content constitutes requirements of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. ISO 291, Plastics — Standard atmospheres for conditioning and testing ISO 19069-2, Plastics — Polypropylene (PP) moulding and extrusion materials — Part 2: Preparation of test specimens and determination of properties 3? Terms? and? definitions No terms and definitions are listed in this document. ISO and IEC maintain terminological databases for use in standardization at the following addresses: — ISO Online browsing platform: available at https: //www .iso .org/obp — IEC Electropedia: available at http: //www .electropedia .org/
5 Apparatus 5.1 Oven The oven shall be of mechanical convection type, capable of controlled circulation of air, with adjustable air intake and exhaust, equipped with a specimen holder and a temperature control system capable of adjustment to meet the following conditions. a) Exhaust rate: at least one oven-chamber volume in 10 min. b) Air velocity: from 0, 75 m/s to 1 m/s at any oven position occupied by the test specimens. c) Temperature control: range up to 200 °C and with control throughout the working range to the nearest 1 °C. The temperature control shall include a device to prevent temperature overrides. It is recommended that a device be used for recording the temperature inside the oven. 5.2 Thermometers Thermometers shall cover the temperature range up to 200 °C, graduated in 1 °C intervals or better. Each thermometer shall be tested for bulb stability and shall be calibrated at 150 °C. In order to control the homogeneity of the temperature in the oven, it is recommended that at least two thermometers be used, one in the upper part of the working volume of the oven, and one in the lower part. The test temperature is the mean value of the indications of the two thermometers. 5.3 Specimen holder The specimen holder may be biaxially rotated, uniaxially rotated or stationary, provided that the test specimens are in a stream of air having a relative velocity between 0,75 m/s and 1 m/s. Illustrations of suitable apparatus for biaxially and uniaxially rotated specimen holders are shown in Figures 1 and 2, respectively. Biaxial rotation increases the probability that all specimens will be exposed similarly. In case of dispute, the use of biaxial rotation shall be the reference method. 5.3.1 Biaxially rotated specimen holder (see Figure 1) The frequency of rotation about the horizontal and vertical axes shalt be 1 min −1 to 3 min −1 .
6 Test specimens The test specimens shall be cut from compression moulded sheet prepared from granules or other homogeneous moulding material as described in ISO 19069-2. Specimens prepared by injection moulding or specimens cut from propylene plastics products may be used by agreement between the interested parties. The specimens shall be 10 mm wide, 50 mm long and 1,0 mm ± 0,05 mm thick. Edges shall be smoothed, if necessary, to remove imperfections introduced by cutting. By agreement between the interested parties, specimens of other thicknesses may be used. At least five specimens shall be used for each test. 7 Conditioning In general, conditioning of specimens is not required. In case of dispute, the specimens shall be conditioned in one of the standard atmospheres specified in ISO 291 for not less than 40 h. 8 Test conditions The recommended test temperature is 150 °C. During the course of the test it shall not vary more than ±1 °C, measured at a single location of the working space, or more than ±1,5 °C throughout the oven. In the event that the average time to failure at 150 °C is less than 7 days, the test report shall indicate “less than 7 days at 150 °C” and the test shall be repeated at an oven temperature of 140 °C ± 1 °C and, if necessary, at lower temperatures at intervals of 10 °C until time to failure of 7 days is achieved. NOTE If it is preferred to perform the test at 140 °C, even for materials lasting more than 7 days at 150 °C, this is permitted provided that this is stated in the test report.