【国外标准】 Standard Test Method for Total Energy Impact of Plastic Films by Dart Drop

5.1 Evaluation of the impact toughness of film is important in predicting the performance of a material in applications such as packaging, construction, and other uses. The test simulates the action encountered in applications where moderate-velocity blunt impacts occur in relatively small areas of film.5.2 The values obtained by this test method are highly dependent on the method and conditions of film fabrication as well as the type and grade of resin.5.3 Test methods employing different missile velocities, impinging surface diameters, or effective specimen diameters will most likely produce different results. Data obtained by this test method cannot necessarily be compared directly with those obtained by other test methods.5.4 The impact resistance of a film, while partly dependent on thickness, does not have a simple correlation with sample thickness. Hence, impact values expressed in joules [ft·lbf] normalized over a range of thickness will not necessarily be linear with thickness. Data from this test method are comparable only for specimens that vary by no more than ±15 % from the nominal or average thickness of the specimens tested.5.5 The test results obtained by this test method are greatly influenced by the quality of film under test. The influence of variability of data obtained by this procedure will, therefore, depend strongly on the sample quality, uniformity of film thickness, the presence of die marks, contaminants, etc.5.6 Several impact test methods are used for film. It is sometimes desirable to know the relationships among test results derived by different test methods. A study was conducted in which four films made from two resins (polypropylene and linear low-density polyethylene), with two film thicknesses for each resin, were impacted using Test Methods D1709 (Test Method A), Test Method D3420 (Procedures A and B), and Test Method D4272. The test results are shown in Appendix X2. Differences in results between Test Methods D1709 and D3420 are expected since Test Methods D1709 represents failure-initiated energy, while Test Method D4272 is initiation plus completion energy. It is possible some films show consistency when the initiation energy is the same as the total energy. This statement and the test data also appear in the significance and appendixes sections of Test Methods D1709 and D3420.1.1 This test method describes the determination of the total energy impact of plastic films by measuring the kinetic energy lost by a free-falling dart that passes through the film.1.2 Units—The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in each system may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from the two systems may result in non-conformance with the standard1.3 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.NOTE 1: Film has been arbitrarily defined as sheeting having nominal thickness not greater than 0.25 mm [0.010 in.].NOTE 2: This test method and ISO 7765–2 address the same subject matter, but differ in technical content (and results cannot be directly compared between the two test methods). The ISO test method calls for a direct readout of energy by using a load cell as part of the impactor head, while Test Method D4272 calls for a constant weight impactor, then measuring the time of travel through a given distance to get energy values.FIG. 1 Elements of an Instrumented Dart Drop System1.4 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.