รายละเอียดเอกสาร

This test method2 covers the determination of the tear resistance of flexible plastic film and sheeting at very low rates of loading, 51 mm (2 in.)/min. and is designed to measure the force to initiate tearing. The specimen geometry of this test method produces a stress concentration in a small area of the specimen. The maximum stress, usually found near the onset of tearing, is recorded as the tear resistance in newtons (or pounds-force). The method is not applicable for film or sheeting material where brittle failures occur during testing or where maximum extension is greater than 101.6 mm (4 in.). Although resistance to tear can be expressed in newtons per microns, (pounds-force per mil) of specimen thickness, this is only advisable where correlation for the particular material being tested has been established. In most cases, comparison between films of dissimilar thickness is not valid. NOTE 1: Film has been arbitrarily defined as sheeting having nominal thickness not greater than 0.25 mm (0.010 in.). Constant-Rate-of-Grip Separation Test—This test method employs a constant rate of separation of the grips holding the test specimen.

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