ASTM D1938-08

This test method is of value in rating the tear-propagation resistance of various plastic films and thin sheeting of comparable thickness. For highly extensible film or sheeting the deformation energy of the specimen legs is significantly greater than the tearing energy. The tear-propagation resistance in slightly extensible or non-extensible film or sheeting is distinguished from the tear-propagation resistance in highly extensible film or sheeting by the load-time or load-displacement data, (Fig. 1 and Fig. 2). The tear-propagation force for slightly extensible or non-extensible material is determined from the average tear force versus the initial and peak force for a highly extensible material.

This test method shall be used for specification acceptance testing only after it has been demonstrated that the data for the particular material are acceptably reproducible.

The data obtained by this test method furnish information for ranking the tear-propagation resistance of plastic films and sheeting of similar composition. Actual use performance may not necessarily correlate with data from this test method. Sets of data from specimens of dissimilar thickness are usually not comparable.

Before proceeding with this test method, reference should be made to the specification of the material being tested. Any test specimen preparation, conditioning, dimensions, or testing parameters, or combination thereof, covered in the relevant ASTM material specification shall take precedence over those mentioned in this test method. If there are no relevant ASTM material specifications, then the default conditions apply. Table 1 of Classification Systems D 4000 lists the ASTM materials standards that currently exist.

FIG. 1 Load-Time Chart for Low-Extensible Film

FIG. 2 Load-Time Chart for Highly Extensible Film

1.1 This test method covers the determination of the force necessary to propagate a tear in plastic film and thin sheeting (thickness of 1 mm (0.04 in.) or less) by a single-tear method. The method is not applicable for film or sheeting material where brittle failures occur during testing.

Note 1—Film has been arbitrarily defined as sheeting having nominal thickness not greater than 0.25 mm (0.010 in.).

1.2 Constant-Rate-of-Grip Separation Test —This test method employs a constant rate of separation of the grips holding the test specimen.

1.2.1 Specimen extension may be measured in this test method by grip separation.

1.3 The values stated in SI units are to be regarded as standard. The values given in parentheses are provided for information only.

1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

Note 2—This standard is similar to ISO 6383-1, but is not considered technically equivalent. The specimen size for ISO 6383-1 is larger, and the method specifies different test speeds.