ASTM D1938-94
(Test Method)Standard Test Method for Tear-Propagation Resistance (Trouser Tear) of Plastic Film and Thin Sheeting by a Single-Tear Method
Standard Test Method for Tear-Propagation Resistance (Trouser Tear) of Plastic Film and Thin Sheeting by a Single-Tear Method
SCOPE
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 the 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.
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Designation: D 1938 – 94 An American National Standard
AMERICAN SOCIETY FOR TESTING AND MATERIALS
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Reprinted from the Annual Book of ASTM Standards. Copyright ASTM
Standard Test Method for
Tear-Propagation Resistance of Plastic Film and Thin
Sheeting by a Single-Tear Method
This standard is issued under the fixed designation D 1938; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope 3. Terminology
1.1 This test method covers the determination of the force 3.1 Definitions: Definitions of terms applying to this test
necessary to propagate a tear in plastic film and thin sheeting method appear in Terminology D 883.
(thickness of 1 mm (0.04 in.) or less) by a single-tear method.
4. Summary of Test Method
1.2 The values stated in SI units are to be regarded as the
4.1 The force to propagate a tear across a film or sheeting
standard. The values given in parentheses are for information
specimen is measured using a constant-rate-of-grip separation
only.
1.3 This standard does not purport to address all of the machine as described in Method A of Test Methods D 882. The
force necessary to propagate the tear is interpreted from the
safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appro- load-time chart.
priate safety and health practices and determine the applica-
5. Significance and Use
bility of regulatory limitations prior to use.
5.1 This test method is of value in rating the tear-
NOTE 1—This standard and ISO 6383-1 are technically equivalent.
propagation force of various plastic films and thin sheeting of
However, the specimen size is larger for ISO 6383-1.
comparable thickness. The tear-propagation resistance in
highly extensible film or sheeting is distinguished from the
2. Referenced Documents
tear-propagation resistance in slightly extensible or nonexten-
2.1 ASTM Standards:
sible film or sheeting in Fig. 1 and Fig. 2 in 10.1 and 10.2,
D 374 Test Methods for Thickness of Solid Electrical Insu-
respectively.
lation
5.2 This test method should be used for specification accep-
D 618 Practice for Conditioning Plastics and Electrical
tance testing only after it has been demonstrated that the data
Insulating Materials for Testing
for the particular material are acceptably reproducible.
D 882 Test Methods for Tensile Properties of Thin Plastic
5.3 The data obtained by this test method furnish informa-
Sheeting
3 tion for ranking the tear-propagation resistance of plastic films
D 883 Terminology Relating to Plastics
and sheeting of similar composition. Actual use performance
D 4000 Classification System for Specifying Plastic Mate-
4 may not necessarily correlate with data from this test method.
rials
5 Sets of data from specimens of dissimilar thickness are usually
E 4 Practices for Load Verification of Testing Machines
not comparable.
E 691 Practice for Conducting an Interlaboratory Study to
6 5.4 For many materials, there may be a specification that
Determine the Precision of a Test Method
requires the use of this test method, but with some procedural
2.2 ISO Standard:
modifications that take precedence when adhering to the
ISO 6383-1 Film and Sheeting—Determination of Tear
7 specification. Therefore, it is advisable to refer to that material
Resistance Part 1 Trouser Tear Method
specification before using this test method. Table 1 of Classi-
fication System D 4000 lists the ASTM materials standards that
currently exist.
This test method is under the jurisdiction of ASTM Committee D-20 on Plastics
and is the direct responsibility of Subcommittee D20.10 on Mechanical Properties.
6. Apparatus
Current edition approved Feb. 15, 1994. Published April 1994. Originally
published as D 1938 – 62 T. Last previous edition D 1938 – 93.
6.1 Film-Testing Machine, with a force-indicating head that
Annual Book of ASTM Standards, Vol 10.01.
can measure the load applied to tear the specimen. It should be
Annual Book of ASTM Standards, Vol 08.01.
equipped with a device for recording the load carried by the
Annual Book of ASTM Standards, Vol 08.02.
Annual Book of ASTM Standards, Vol 03.01.
specimen and the amount of separation of the grips during the
Annual Book of ASTM Standards, Vol 14.02.
test. The testing machine shall be essentially free from inertia
Available from American National Standards Institute, 11 W. 42nd St., 13th
lag at the specified rate of testing and shall indicate the load
Floor, New York, NY 10036.
D 1938
7.2 Measure the thickness of the specimen below the slit
(see Fig. 3) in several places and record it in millimetres to the
nearest 0.0025 mm (0.0001 in.).
7.3 Cut enough specimens to provide a minimum of five
tear-propagation force determinations each in the machine
direction and in the transverse direction of the material being
tested.
8. Conditioning
FIG. 1 Load-Time Chart for Low-Extensible Film
8.1 Conditioning—Condition the test specimens at 23 6
2°C (73.4 6 3.6°F) and 50 6 5 % relative humidity for not less
than 40 h prior to test in accordance with Procedure A of
Practice D 618, for those tests where conditioning is required.
In cases of disagreement, the tolerances shall be6 1°C
(61.8°F) and 62 % relative humidity.
8.2 Test Conditions—Conduct tests in the standard labora-
tory atmosphere of 23 6 2°C (73.4 6 3.6°F) and 50 6 5%
relative humidity, unless otherwise specified in the test meth-
ods. In cases of disagreement, the tolerances shall be 61°C
(61.8°F) and6 2 % relative humidity.
9. Procedure
9.1 Secure Tongue A (Fig. 3) in one grip and Tongue B in
the other grip of the constant-rate-of-grip separation-testing
FIG. 2 Load-Time Chart for Highly Extensible Film
machine, using an initial grip separation of 50 mm (2 in.).
Align the specimen so that its major axis coincides with an
imaginary line joining the centers of the grips.
with an accuracy of 62 % of the indicated value or better. The
9.2 Using a grip-separation speed of 250 mm (10 in.)/min,
accuracy of the testing machine shall be verified in accordance
start the machine, and record the load necessary to propagate
with Practices E 4. A device shall be included to control the
the tear through the entire unslit 25-mm (1-in.) portion.
grip-separation rate at 250 mm (10 in.)6 5 %/min.
9.3 Test not less than five specimens in each of the principal
6.2 Thickness-Measuring Devices, in accordance with Test
film or sheeting directions.
Methods D 374 or a method of equivalent accuracy.
6.3 Cutter—A sharp razor blade or the equivalent.
10. Calculation
6.4 Conditioning Apparatus, in accordance with Procedure
10.1 For thin films and sheeting that have load-time charts
A of Practice D 618.
characterized by Fig. 1, obtain the average tear propagation
7. Test Specimens
force by averaging the load indicated on the chart over the time
period, disregarding the initial and final portions of the curve.
7.1 The specimens shall be of the single-tear type and shall
This can be done with an integrator or a planimeter. In some
consist of strips 75 mm (3 in.) long by 25 mm (1 in.) wide and
cases, a fairly accurate estimate can be made by eye.
shall have a clean longitudinal slit 50 mm (2 in.) 62 % long cut
10.2 For thin films and sheeting that have
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