ASTM D1709:16 pdf free download – Standard Test Methods for Impact Resistance of Plastic Film by the Free-Falling Dart Method.
This is to ensure that the whole of the sheet be represented in the test unless such sampling constitutes a variable under study.
6.2 The specimens shall be free of pinholes, wrinkles, folds, or other obvious imperfections, unless such imperfections constitute variables under study.
7. Conditioning
7. 1 oiu1irioizing—Condition the test specimens at 23 ± 2°C (73.4 ± 3.6°F) and 50 ± 10 % relative humidity for not less than 40 h prior to test in accordance with Procedure A of Practice D6 18 unless otherwise specified by agreement or the relevant ASTM material specification, in cases of disagreement, the tolerances shall he ± 1°C (±1.8°F) and ±5 % relative humidity.
7.2 Test Conditions—Conduct the tests at 23 ± 2°C (73.4 ± 3.6°F) and 50 ± 10 % relative humidity unless otherwise specified by agreement or the relevant ASTM material specification. In cases of disagreement, the tolerances shall be ± 1°C (± 1.8°F) and ±5 % relative humidity.
8. Preparation of Apparatus
8.1 Set up the apparatus for testing by Test Method A or by Test Method B.
8.1.1 For Test Method A select a dart with a 38.10 ± 0.13-mm (1.500 ± 0.005-in.) diameter hemispherical head. For Test Method B. select a dart with a 50.80 ± 0.13-mm (2.000 ± 0.005-in.) diameter hemispherical head.
8.1 .2 Inspect the die head for any visually obvious scratches or other imperfections. If present, reject the use of the die head.
8.1 .3 Activate the dart release mechanism and insert the steel shaft tip into the mechanism. Ensure the dart is securely held in place by the dart release mechanism. Adjust the drop height (the vertical distance from the plane of a clamped specimen to the bottom surface of the dart head) to 0.66 ± 0.01 m (26.0 ± 0.4 in.) for Test Method A or to 1.52 ± 0.03 m (60.0+0.25, —1.70 in.) for Test Method B. (Warning—For safety reasons, remove the dart while making position adjustments.)
8.1.4 With a trial film specimen clamped between the specimen clamps and with no added weights on the dart, release the dart and observe the point at which the dart impacts the specimen, catching the dart after it bounces off the film surface. if necessary, adjust the dart release mechanism so that, in repeated trials, the dart reproducibly impacts the center of the clamped portion of the film.
8.2 Check the apparatus periodically to make sure specimen slippage during testing is not occurring (see 5.1 .2.4). If slippage occurs, this is reason to reject the results.
NOTE 8—The likelihood of occurrence of slippage increases with increasing dart weight and with increasing drop height and is greater with some materials than with others.
Two methods to determine if slippage has occurred are described in the following notes.