Pendulum Impact Resistance of Plastic Film ASTM D 3420

This test method for the determination of tearing strength by the falling pendulum type apparatus is used in the trade for the acceptance testing of commercial shipments of fabrics, but caution is advised since technicians may fail to get good agreement between results on certain fabrics.

Like other techniques to measure toughness, this test method provides a means to determine parameters of a material at strain rates closer to some end-use applications than provided by low-speed uniaxial tensile tests. Dynamic tensile behavior of a film is important, particularly when the film is used as a packaging material. The same uncertainties about correlations with thickness that apply to other impact tests also apply to this test (see section 3.4 of Test Methods D1709). Hence, no provision for rationalizing to unit thickness is provided. Also, no provision is made for testing at non-ambient temperatures.

This test method includes two procedures, similar except with regard to sample size: Procedure A for 60-mm diameter and Procedure B for 89-mm diameter (commonly called the “Spencer”). The data have not been shown relatable to each other.

Several impact test methods are used for film. It is sometimes desirable to know the relationships among test results derived by different 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), 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 D4272 are expected since Test Methods D1709 represents failure initiated energy while Test Method D4272 is initiation plus completion energy. Some films have shown consistency when the initiation energy was the same as the total energy. This statement and the test data also appear in the significance and appendixes sections of Test Methods of D1709 and D4272.

Let see the testing video as per Spencer Impact Test - ASTM D3420:

The Elmendorf Tear Tester is an automated tear tester equipped with an optical encoder for measuring the angular position of the pendulum during tearing and converting this measurement to tear units. A large, full-color touchscreen display with intuitive, easy-to-use software provides a revolutionary new approach to testing and data review.