BS ISO 3384-2:2012 pdf download – Rubber, vulcanized or thermoplastic — Determination of stress relaxation in compression Part 2: Testing with temperature cycling 7.2 Measurement of dimensions of test pieces The dimensions of test pieces shall be measured as specified in ISO 23529. 7.3 Number of test pieces Thepreferrednumberoftestpiecesisthree,butforroutineandscreeningteststwotestpiecesareacceptable. 7.4 Time interval between forming and testing The interval between forming and testing shall be in accordance with ISO 23529. 7.5 Conditioning of test pieces 7.5.1 Prior to testing, the test pieces shall undergo first thermal and then mechanical conditioning as detailed in 7.5.2 and 7.5.3. When using method A at elevated temperature, the thermal conditioning might not be required, as the preheating of the test piece before compression acts as thermal conditioning. 7.5.2 Thermal conditioning shall be carried out by heating the test pieces at 70 °C for 3 h. Following thermal conditioning, the test pieces shall be allowed to stand for a period of not less than 16 h and not more than 48 h at standard laboratory temperature prior to mechanical conditioning or testing. NOTE Some test samples, especially of thermoplastic elastomers, might contain moulding stresses, and thermal conditioning to relieve these stresses might improve the reproducibility of the results. 7.5.3 Mechanical conditioning shall be carried out at one of the standard laboratory temperatures specified in ISO 23529, as follows: Compress the test pieces to the same compression that will be used during the rest of the test and then immediately return them to zero stress; repeat this procedure to give a total of five cycles of deformation and immediate return. Following mechanical conditioning, the test pieces shall be allowed to stand for a period of not less than 16 h and not more than 48 h at standard laboratory temperature prior to testing. Mechanical conditioning has been found to improve test reproducibility, particularly for compounds containing substantial proportions of filler, but is not always appropriate for finished products and can, therefore, lead to results that are not typical of service. Such conditioning may be omitted provided thermal conditioning is still undertaken. This omission shall be mentioned in the test report. 8 Duration, temperature and test liquid 8.1 Duration of test The test period begins after the initial compression. If test times longer than one week are used, a logarithmic time-scale shall be employed. 8.2 Temperature of exposure Thetemperatureofexposureshallbechosenfromthelistoftesttemperaturesin ISO 23529. Temperatures of exposure which cause rapid degradation...
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