ASTM D1043-99

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An American National Standard
Designation: D 1043 – 99
Standard Test Method for
Stiffness Properties of Plastics as a Function of
Temperature by Means of a Torsion Test
This standard is issued under the fixed designation D 1043; 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.
This standard has been approved for use by agencies of the Department of Defense.
1. Scope * taining to plastics used in this test method, see Terminology
D 883 or Terminology D 4805.
1.1 This test method covers the determination of the stiff-
ness characteristics of plastics over a wide temperature range
4. Significance and Use
by direct measurement of the apparent modulus of rigidity.
4.1 The property measured by this test is the apparent
1.2 The values stated in SI units are to be regarded as the
modulus of rigidity, G, sometimes called the apparent shear
standard. The values given in parentheses are for information
modulus of elasticity. It is important to note that this property
only.
is not the same as the modulus of elasticity, E, measured in
1.3 This standard does not purport to address all of the
tension, flexure, or compression. The relationship between
safety concerns, if any, associated with its use. It is the
these properties is shown in Annex A1.
responsibility of the user of this standard to establish appro-
4.2 The measured modulus of rigidity is termed “apparent”
priate safety and health practices and determine the applica-
since it is the value obtained by measuring the angular
bility of regulatory limitations prior to use.
deflection occurring when the specimen is subjected to an
NOTE 1—This test method is not equivalent to ISO 458/1:1985 or ISO
applied torque. Since the specimen may be deflected beyond its
458/2:1985 and results cannot be directly compared between the two
elastic limit, the calculated value may not represent the true
methods.
modulus of rigidity within the elastic limit of the material. In
addition, the value obtained by this test method will also be
2. Referenced Documents
affected by the creep characteristics of the material, since the
2.1 ASTM Standards:
2 load application time is arbitrarily fixed. For many materials,
D 618 Practice for Conditioning Plastics for Testing
there may be a specification that requires the use of this test
D 638 Test Method for Tensile Properties of Plastics
method, but with some procedural modifications that take
D 747 Test Method for Apparent Bending Modulus of
precedence when adhering to the specification. Therefore, it is
Plastics by Means of a Cantilever Beam
2 advisable to refer to that material specification before using this
D 883 Terminology Relating to Plastics
test method. Table 1 in Classification D 4000 lists the current
D 1053 Test Method for Rubber Property—Stiffening at
ASTM materials standards.
Low Temperatures: Flexible Polymers and Coated Fab-
4.3 This test method is useful for determining the relative
rics
changes in stiffness over a wide range of temperatures.
D 4000 Classification System for Specifying Plastic Mate-
rials
5. Apparatus
D 4066 Specification for Nylon Injection and Extrusion
5.1 Testing Machine—A machine capable of exerting a
Materials
torque sufficient to deflect a test specimen in the range of 5 to
D 4805 Terminology of Plastics Standards
100° of arc, depending on the stiffness of the specimen and its
span. A schematic diagram of a suitable machine is shown in
3. Terminology
Fig. 1.
3.1 Definitions—For definitions of the technical terms per-
NOTE 2—Two machines of different torque capacities are being used:
one covers the range of approximately 0.0113 to 0.113 N·m (0.1 to 1.0
This test method is under the jurisdiction of ASTM Committee D-20 on Plastics
in.·lbf) and the other of approximately 0.113 to 1.81 N·m (1.0 to 16 in.·lbf)
and is the direct responsibility of Subcommittee D20.10 on Mechanical Properties.
or higher. Some machines also allow varying the span, which is especially
Current edition approved April 10, 1999. Published July 1999. Originally
important if shearing failures can occur (as in laminates at a span/width of
published as D 1043 – 49. Last previous edition D 1043 – 92.
2 6).
Annual Book of ASTM Standards, Vol 08.01.
NOTE 3—The amount of torque may be varied to suit the stiffness of the
Annual Book of ASTM Standards, Vol 09.01.
test specimen, and various weights should be available for this purpose.
Annual Book of ASTM Standards, Vol 08.02.
Annual Book of ASTM Standards, Vol 08.03. The actual amount of torque being applied by any given combination of
*A Summary of Changes section appears at the end of this standard.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D 1043
transfer liquid are placed to pre-cool before starting the test.
NOTE 6—For time-efficient low-temperature use of the equipment,
space for cooling enough containers of the heat-transfer medium for a
day’s work is desirable. Depending on the temperature ranges involved,
mechanical refrigeration or a dry-ice chest, or both, will be advantageous.
5.2.6 Heater—A controlled electric immersion heater in the
Dewar flask shall be used in conjunction with an agitator to
vary the temperature.
5.3 Micrometer—A micrometer accurate to within 60.0025
mm (60.0001 in.) or better shall be used for measuring
specimen thickness and width.
5.4 Modifications to Testing Equipment— The modifica-
tions described in Annex A4 will increase the accuracy and
sensitivity of the testing equipment. The modifications are
readily adaptable to several types of test equipment used for
testing plastics. Some of the modifications are desirable, but
not a necessity, for obtaining meaningful data.
6. Test Specimens
6.1 Geometry—Test specimens shall be of the rectangular
geometry shown in Fig. 2. They may be cut from compression-
molded sheets, extruded sheet, or from parts of uniform
thickness having flat parallel surfaces. The specimens may also
be injection molded. Care shall be taken to ensure that the test
specimens are isotropic. Where the testing machine permits
varying the span, the span to width (L/a) ratio should be 6 to 8.
FIG. 1 Torsion Tester
It is recommended that spans of 38 to 100 mm (1.5 to 4 in.) be
used. The specimen may be used for nonrigid materials on the
weights, torque wheel radii, and shaft bearings should be determined by
low-range machine which has a span (L) of 38 mm (1.5 in.).
calibration. The accuracy of the apparatus can be subject to change, and
6.2 Thickness—The thickness of the specimen may vary
therefore periodic calibration is necessary to ensure reliable test results.
between approximately 1 and 3 mm (0.040 and 0.125 in.). This
Testing machine calibration procedures are given in Annex A2 and Annex
range normally makes it possible to test materials of widely
A3.
different stiffnesses.
NOTE 4—For operation at low temperatures the shaft of the machine
6.3 Duplicate specimens of each material shall be tested.
must be provided with a heated collar next to the lower bearing to prevent
the formation of ice. More replications are often needed, especially for nonhomo-
geneous materials. If the results from testing the first two
5.2 Temperature Control:
specimens differ significantly, test a third specimen and discard
5.2.1 Flask—A Dewar flask of suitable dimensions.
the outlier (the valve that varies the most from the other two).
5.2.2 Thermometer—A thermometer graduated in 1°C divi-
sions and having the necessary range. The bulb shall be located
7. Conditioning
in close proximity to the test specimen. A digital–readout RTD
7.1 Conditioning—For those tests where conditioning is
thermometer having an accuracy of 6 1°C or better may be
required, condition the test specimens at 23 6 2°C (73.4 6
used.
3.6°F) and 50 6 5 % relative humidity for not less than 40 h
5.2.3 Timer, for controlling load application time.
prior to testing in accordance with Procedure A of Practice
5.2.4 Heat-Transfer Medium—For normal laboratory pur-
D 618. In cases of disagreement, the tolerances shall be6 1°C
poses, a substance that is liquid over the desired temperature
(61.8°F) and 62 % relative humidity.
range shall be used for the heat-transfer medium, provided it
7.1.1 Note that for some hygroscopic materials, such as
has been shown that the liquid does not soften or otherwise
nylons, the material specifications (for example, Specification
affect the test specimen.
D 4066) call for testing “dry as-molded specimens.” Such
NOTE 5—Among the liquids found useful are acetone, ethanol, butanol,
requirements take precedence over the above routine precon-
methanol, normal hexane, silicone oil, and a mixture of methyl phosphate
ditioning at 50 % relative humidity and require sealing the
and water in the ratio of 87 to 13 by volume. For temperatures to −70°C
specimens in water vapor-impermeable containers as soon as
(−94°F), a mixture of 50 parts ethanol, 30 parts ethylene glycol, and 20
parts water may be found useful.
5.2.5 Refrigeration—Means shall be provided for cooling
the heat-transfer medium. This cooling can be by means of a
refrigeration cooling coil built into the instrument and im-
mersed in the Dewar flask of heat transfer fluid or by means of
a low temperature chamber in which Dewar flasks of heat FIG. 2 Test Specimen
D 1043
molded and not removing them until ready for testing.
b = specimen thickness (smaller cross-sectional dimen-
sion), mm (or in.),
8. Procedure
f = angle of deflection of torque pulley, degrees, and
u = value depending on the ratio of a to b. Table 1 gives
8.1 Measure the width and thickness of the specimen to
the values of u for various ratios of a to b. A third
three significant digits.
column gives thickness if the width is 6.350 mm
8.2 Carefully mount the specimen in the apparatus. Adjust
(0.250 in.). If Table 1 is not adequate, u may be
the clamps so that the specimen is not under compression or
calculated by means of the equation given in Annex
tension and is in complete contact with the clamp’s internal
A1.
surfaces.
9.2 Plot the apparent modulus of rigidity values, calculated
8.3 Place the thermometer in position with it’s bulb or
in accordance with 9.1, on a logarithmic scale versus tempera-
sensing tip in close proximity to the test specimen.
ture on a linear scale.
8.4 Fill the Dewar flask with the heat-transfer medium. The
9.3 If desired, read from the graph the temperature at which
heat-transfer medium may be precooled to a temperature lower
the apparent modulus of rigidity is equal to a specific value,
than the lowest desired test temperature.
such as 68.95 MPa, 241.3 MPa, 310.3 MPa, or 930.8 MPa (10
8.5 Place the flask in position on the instrument, and start
000 psi, 35 000 psi, 45 000 psi, or 135 000 psi). The
the agitator.
temperature at which the apparent modulus of rigidity is equal
8.6 By intermittent use of the immersion heater, bring the
to 310 MPa (45 000 psi) has been designated T (see Note
F
bath to the desired test temperature. This heating can be
A1.1).
controlled by an automatic temperature controller, if the
NOTE 9—If the increments of temperature change used in the test are
instrument is so equipped.
relatively small (for example about 3°C or 5°F) it may be possible to
8.7 Condition the specimen at the test temperature for a
interpolate between test points to determine the temperature for a specific
minimum of 3 min.
apparent modulus of rigidity, such as 310.3 MPa or 45 000 psi. However,
8.8 Release the torque pulley. After 5 s note the angular
this interpolation should be done on a semi-log basis to be approximately
deflection of the pulley and return the torque pulley to its initial
equivalent to the results of the semi-log plot. That is, the log of the
position. If the reading thus obtained does not fall within the
modulus must be used to interpolate between the test temperatures, using
the following formula, which is an example for interpolating to determine
range from 5 to 100° of arc, vary the applied torque in such a
the T (310 MPa or 45 000 psi).
way as to produce such a reading. For nonrigid materials, this F
reading should fall between 10 and 100°. If it necessary to vary ~T – T ! X ~log G – log 45000!
2 1 T1
T 5 T 1 (2)
F 1
the applied torque, wait another 3 min. and repeat the proce- ~log G – log G !
T1 T2
dure at the same temperature.
where:
NOTE 7—In order to obtain measured values of apparent modulus of
T = lower of the two test temperatures,
rigidity, G, that are comparable to the true value of G, it is desirable that
T = higher of the two test temperatures,
measurements be made within the elastic limit of the material being tested.
G = apparent modulus of rigidity at temperature T , psi,
T1 1
Therefore, torques shall be chosen that will cause deflections that are as
and
small as practical to measure accurately on the machine being used. It is
G = apparent modulus of rigidity at temperature T , psi.
T2 2
often desirable to reduce the torque slightly before taking successive
readings, particularly in the temperature range where the material is
10. Report
rapidly decreasing in rigidity.
10.1 Report the following information:
NOTE 8—Better reproducibility is obtained if torques are chosen such
10.1.1 Complete identification of the material, including
that the deflection obtained at a given temperature is similar to or greater
than that obtained at the previous lower temperature. name, stock or code number, date made, form, etc.,
10.1.2 Dimensions of the test specimen,
8.9 After each suitable reading is obtained, repeat the steps
10.1.3 Details of conditioning the specimen prior to testing,
indicated in 8.6-8.8 for the next desired temperature. The
10.1.4 Identification of the heat transfer medium used,
torque may be lowered prior to each reading, if desired (Note
7 and Note 8).
A
TABLE 1 Values for u
Ratio of
Thickness when Width is
9. Calculation
Width, a,to u
6.350 mm (0.250 in.)
Thickness, b
9.1 Calculate the apparent modulus of rigidity, G, for each
2.00 3.66 3.175 mm (0.125 in.)
temperature as follows:
2.25 3.84 2.819 mm (0.111 in.)
2.50 3.99 2.540 mm (0.100 in.)
G 5 917TL/ab uf (1)
2.75 4.11 2.311 mm (0.091 in.)
3.00 4.21 2.108 mm (0.083 in.)
3.50 4.37 1.829 mm (0.072 in.)
where:
4.00 4.49 1.600 mm (0.063 in.)
G = apparent modulus of rigidity, Pa (or psi),
4.50 4.59 1.422 mm (0.056 in.)
5.00 4.66 1.270 mm (0.050 in.)
T = applied torque, N·m (or in.·lbf),
6.00 4.77 1.067 mm (0.042 in.)
L = specimen length (span), mm (or in.),
7.0
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