4.1 Test Methods A and B are used to establish the weight of the dart when 508201;% of the specimens fail under the conditions specified. Data obtained by one test method cannot be compared directly with the other test method nor with those obtained from tests employing different conditions of missile velocity, impinging surface diameter, effective specimen diameter, material construction and finish of the dart head, and film thickness. The values obtained by these test variables are highly dependent on the method of film fabrication.
4.2 The results obtained by Test Methods A and B are greatly influenced by the quality of film under test. The confidence limits of data obtained by this procedure can, therefore, vary significantly, depending on the sample quality, uniformity of film gage, die marks, contaminants, etc. (see Section 15).
4.3 Test Methods A and B have been found useful for specification purposes.
Note 4: With sufficient data, correlation between test results and field performance can usually be established.
4.4 The impact resistance of plastic film, while partly dependent on thickness, has no simple correlation with sample thickness. Hence, impact values cannot be normalized over a range of thickness without producing misleading data as to the actual impact resistance of the material. Data from these test methods are comparable only for specimens that vary by no more than ±258201;% from the nominal or average thickness of the specimens tested.
4.5 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 (Method A), D3420 (Procedures A and B), and D4272. The test results are shown in the Appendix. Differences in results between Test Methods D1709 and D4272 are not unusual since Test Methods D1709 represents failure initiated energy, while Test Method D4272 is initiation plus completion energy. Some films exhibit consistency when the initiation energy is the same as the total energy. This statement and the test data also appear in the significance sections and appendixes of Test Methods D3420 and D4272.
1.1 These test methods cover the determination of the energy that causes plastic film to fail under specified conditions of impact of a free-falling dart. This energy is expressed in terms of the weight (mass) of the missile falling from a specified height which would result in 508201;% failure of specimens tested.
1.2 Two test methods are described:
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