1.1 This standard specifies the exposure conditions for plastics only exposed in temperature-varying hot air for relatively long time. This standard specifies only the heat exposure method, excluding the test method or specimen. The influence on any performance of plastics from the heat can be tested by selecting proper test methods and specimen. This standard recommends to adopt ASTM D 3826 to test the embrittlement endpoint which is reached while the elongation at break of 75% of tested specimen is 5% or smaller under the initial strain rate of 0.1mm/min.
1.2 This standard gives the guideline for comparing the heat aging performances of materials, and these performances are tested by changing certain relative performance (which is to say that the embrittlement performance is tested by reducing the elongation). This standard is applicable to evaluating plastics easy to oxidize in application.
1.3 Results obtained from this standard are influenced by the type of adopted heat aging test boxes. The user can select one of the two methods to expose the heat aging test boxes. Results based on these two methods shall not confuse mutually.
1.3.1 Method A: gravitational-convection heat aging test box--recommended to be used for the thin specimen with the nominal thickness not greater than 0.25mm.
1.3.2 Method B: forced-draft heat aging test box--recommended to be used for the specimen with the nominal thickness greater than 0.25mm.
1.4 This standard introduces the method to compare the heat aging performances of materials under single temperature. This standard also describes the methods to test the heat aging performances of materials under series of temperatures so as to estimate the duration required by materials in specified characteristic change under certain lower temperature. This standard doesn't estimate the heat aging performance under the interaction of factors like stress, environment, temperature and time control failure.
1.5 This standard doesn't involve the explanation on safety, if any, the explanation is only relative to the application of this standard. The user of this standard is obligated to, prior to use, establish applicable safety and health codes and determine the application rule limits.
Note: No ISO standard identical to this standard is available.
2 Normative References
The following standards contain provisions which, through reference in this standard, constitute provisions of this standard. For dated references, subsequent amendments to (excluding correction to), or revisions of, any of these publications do not apply. However, the parties entering into agreement according to this standard are encouraged to research whether the latest editions of these references apply. For undated references, their latest editions are applicable to this standard.
GB/T 2035 "Terms and Definitions for Plastics" (GB/T 2035-2008; ISO 472: 1999, IDT)
GB/T 2918 "Plastics -- Standard Atmospheres for Conditioning and Testing" (GB/T 2918-1998; idt ISO 291: 1997)
GB/T 7142 "Determination of Time-temperature Limits for Plastics after Prolonged Exposure to Heat" (GB/T 7142-2002; ISO 2578: 1993, MOD)
GB/T 11026.4-1999 "Guide for the Determination of Thermal Endurance Properties of Electrical Insulating Materials -- Part 4: Ageing Ovens -- Single-chamber Ovens" (idt IEC 60216-4-1: 1990)
