Elmendorf Tear ASTM D1922

Propagation Tear Resistance of Plastic Film and Thin Sheeting by Pendulum Method (Elmendorf Tear) ASTM D1922

Pendulum impact testers are widely used in the testing of flexible materials such as plastic films to determine the force required to propagate a pre-existing slit a fixed distance to the edge of the sample. This test is crucial in the determination of material thickness specifications for plastic films used in packaging. Depending on the application, either a high or low propagation force may be desirable.

To carry out this test, ten samples are taken from the plastic film, five in the machine direction and five in the transverse direction. The samples are clamped into the tester and a slit is created using a cutting knife. The pendulum is then released to propagate the slit through the remaining distance of 43mm. The energy loss by the pendulum is then used to calculate an average tearing force.

There are three standard samples for Elmendorf Tear testing. The most commonly used sample for plastic films is the constant radius sample, which provides a constant radius from the start of the tear strength measurement. This is useful for materials where the tear may not propagate directly up the sample as intended. Another common sample is a 63mm x 76mm rectangle. For textiles, a modified rectangle is used, which adds height on the ends of the sample to help minimize unraveling of the outside edges.

The test results are presented as tearing force in milli-newtons (or grams-force). Sample thickness is also reported, although there is no direct relationship between thickness and tearing force. Therefore, only results for samples of the same thickness can be compared. The results of this test can be used for quality control or as a means of specifying the material and thickness required for plastic films used in packaging.