【国外标准】 Standard Practice for Determining Degradation End Point in Degradable Polyethylene and Polypropylene Using a Tensile Test

4.1 The tensile elongation property determined by this practice is of value for the characterization of degradable materials. It is possible that the tensile elongation property will vary with specimen thickness, method of preparation, speed of testing, type of grips used, and manner of measuring test extension. Consequently, where precise comparative results are desired, these factors must be carefully controlled.4.2 It is acceptable to use the tensile elongation property to provide data for research and development and engineering design as well as quality control specifications. However, data from such tests cannot be considered significant for applications differing widely from the load-time scale of the test employed.4.3 Materials that fail by tearing give anomalous data that cannot be compared with those from normal failure.4.4 Before proceeding with this test method, reference needs to be made to the specifications of the material being tested. Any test specimen preparation, conditioning, dimensions, or testing parameters or a combination thereof, covered in the material specifications shall take precedence over those mentioned in this test method. If there are no material specifications, then the default conditions apply.1.1 This practice covers the determination of a degradation-end point (a brittle point) for degradable polyethylene/polypropylene films and sheeting less than 1.0 mm (0.04 in.) thick. This practice is not intended for determination of the rate or degree of degradation of a polyethylene/polypropylene film or sheet, but rather, to assess when in the course of its degradation under some condition, a brittle point is reached. If one wishes to monitor tensile elongation during the degradation process (such as when the tensile elongation is significantly greater than 5 %), Test Method D882 is recommended. This practice is not to be considered the only way of determining a degradation-end point.1.2 Tensile properties of plastics 1.0 mm (0.04 in.) or greater in thickness shall be determined in accordance with Test Method D638.1.3 Use a static weighing-constant rate of grip separation test. This procedure employs a constant rate of separation of the grips holding the sample and a static load cell.NOTE 1: This procedure is based on the use of grip separation as a measure of extension; however, the desirability of using extension indicators accurate to ±1.0 % or better as specified in Test Method D638 is recognized, and a provision for the use of such instrumentation is incorporated in the procedure.1.4 This procedure has been successful for determining the degradation end point of ethylene-carbon-monoxide copolymers and has screened successfully two other additive-type polyethylenes in a round robin test.1.5 The values stated in SI units are to be regarded as the standard. The values in parentheses are for information only.1.6 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.1.7 There is no equivalent ISO standard.1.8 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.