ASTM D256-23e1
(Test Method)Standard Test Methods for Determining the Izod Pendulum Impact Resistance of Plastics
Standard Test Methods for Determining the Izod Pendulum Impact Resistance of Plastics
SIGNIFICANCE AND USE
5.1 Before proceeding with these test methods, reference should be made to the specification of the material being tested. Any test specimen preparation, conditioning, dimensions, and testing parameters covered in the materials specification shall take precedence over those mentioned in these test methods. If there is no material specification, then the default conditions apply.
5.2 The pendulum impact test indicates the energy to break standard test specimens of specified size under stipulated parameters of specimen mounting, notching, and pendulum velocity-at-impact.
5.3 The energy lost by the pendulum during the breakage of the specimen is the sum of the following:
5.3.1 Energy to initiate fracture of the specimen;
5.3.2 Energy to propagate the fracture across the specimen;
5.3.3 Energy to throw the free end (or ends) of the broken specimen (“toss correction”);
5.3.4 Energy to bend the specimen;
5.3.5 Energy to produce vibration in the pendulum arm;
5.3.6 Energy to produce vibration or horizontal movement of the machine frame or base;
5.3.7 Energy to overcome friction in the pendulum bearing and in the indicating mechanism, and to overcome windage (pendulum air drag);
5.3.8 Energy to indent or deform plastically the specimen at the line of impact; and
5.3.9 Energy to overcome the friction caused by the rubbing of the striker (or other part of the pendulum) over the face of the bent specimen.
5.4 For relatively brittle materials, for which fracture propagation energy is small in comparison with the fracture initiation energy, the indicated impact energy absorbed is, for all practical purposes, the sum of factors 5.3.1 and 5.3.3. The toss correction (see 5.3.3) may represent a very large fraction of the total energy absorbed when testing relatively dense and brittle materials. Test Method C shall be used for materials that have an Izod impact resistance of less than 27 J/m (0.5 ft·lbf/in.). (See Appendix X4 for optional units.) T...
SCOPE
1.1 These test methods cover the determination of the resistance of plastics to “standardized” (see Note 1) pendulum-type hammers, mounted in “standardized” machines, in breaking standard specimens with one pendulum swing (see Note 2). The standard tests for these test methods require specimens made with a milled notch (see Note 3). In Test Methods A, C, and D, the notch produces a stress concentration that increases the probability of a brittle, rather than a ductile, fracture. In Test Method E, the impact resistance is obtained by reversing the notched specimen 180° in the clamping vise. The results of all test methods are reported in terms of energy absorbed per unit of specimen width or per unit of cross-sectional area under the notch. (See Note 4.)
Note 1: The machines with their pendulum-type hammers have been “standardized” in that they must comply with certain requirements, including a fixed height of hammer fall that results in a substantially fixed velocity of the hammer at the moment of impact. However, hammers of different initial energies (produced by varying their effective weights) are recommended for use with specimens of different impact resistance. Moreover, manufacturers of the equipment are permitted to use different lengths and constructions of pendulums with possible differences in pendulum rigidities resulting. (See Section 5.) Be aware that other differences in machine design may exist. The specimens are “standardized” in that they are required to have one fixed length, one fixed depth, and one particular design of milled notch. The width of the specimens is permitted to vary between limits.
Note 2: Results generated using pendulums that utilize a load cell to record the impact force and thus impact energy, may not be equivalent to results that are generated using manually or digitally encoded testers that measure the energy remaining in the pendulum after impact.
Note 3: The notch in the Iz...
General Information
Standards Content (Sample)
This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
´1
Designation: D256 − 23
Standard Test Methods for
Determining the Izod Pendulum Impact Resistance of
1
Plastics
This standard is issued under the fixed designation D256; 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 (´) indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the U.S. Department of Defense.
1
ε NOTE—Summary of Changes section was editorially added in April 2023.
of a plastic’s “notch sensitivity” may be obtained with Test Method D by
1. Scope*
comparing the energies to break specimens having different radii at the
1.1 These test methods cover the determination of the
base of the notch.
resistance of plastics to “standardized” (see Note 1) pendulum- NOTE 4—Caution must be exercised in interpreting the results of these
standard test methods. The following testing parameters may affect test
type hammers, mounted in “standardized” machines, in break-
results significantly:
ing standard specimens with one pendulum swing (see Note 2).
Method of fabrication, including but not limited to processing
The standard tests for these test methods require specimens
technology, molding conditions, mold design, and thermal
made with a milled notch (see Note 3). In Test Methods A, C,
treatments;
and D, the notch produces a stress concentration that increases Method of notching;
Speed of notching tool;
the probability of a brittle, rather than a ductile, fracture. In
Design of notching apparatus;
Test Method E, the impact resistance is obtained by reversing
Quality of the notch;
the notched specimen 180° in the clamping vise. The results of Time between notching and test;
Test specimen thickness,
all test methods are reported in terms of energy absorbed per
Test specimen width under notch, and
unit of specimen width or per unit of cross-sectional area under
Environmental conditioning.
the notch. (See Note 4.)
1.2 The values stated in SI units are to be regarded as
NOTE 1—The machines with their pendulum-type hammers have been standard. The values given in parentheses are for information
“standardized” in that they must comply with certain requirements,
only.
including a fixed height of hammer fall that results in a substantially fixed
1.3 This standard does not purport to address all of the
velocity of the hammer at the moment of impact. However, hammers of
different initial energies (produced by varying their effective weights) are safety concerns, if any, associated with its use. It is the
recommended for use with specimens of different impact resistance.
responsibility of the user of this standard to establish appro-
Moreover, manufacturers of the equipment are permitted to use different
priate safety, health, and environmental practices and deter-
lengths and constructions of pendulums with possible differences in
mine the applicability of regulatory limitations prior to use.
pendulum rigidities resulting. (See Section 5.) Be aware that other
differences in machine design may exist. The specimens are “standard-
NOTE 5—These test methods resemble ISO 180:1993 in regard to title
ized” in that they are required to have one fixed length, one fixed depth,
only. The contents are significantly different.
and one particular design of milled notch. The width of the specimens is
1.4 This international standard was developed in accor-
permitted to vary between limits.
dance with internationally recognized principles on standard-
NOTE 2—Results generated using pendulums that utilize a load cell to
record the impact force and thus impact energy, may not be equivalent to
ization established in the Decision on Principles for the
results that are generated using manually or digitally encoded testers that
Development of International Standards, Guides and Recom-
measure the energy remaining in the pendulum after impact.
mendations issued by the World Trade Organization Technical
NOTE 3—The notch in the Izod specimen serves to concentrate the
Barriers to Trade (TBT) Committee.
stress, minimize plastic deformation, and direct the fracture to the part of
the specimen behind the notch. Scatter in energy-to-break is thus reduced.
However, because of differences in the elastic and viscoelastic properties
2. Referenced Documents
of plastics, response to a given notch varies among materials. A measure
2
2.1 ASTM Standards:
D618 Practice for Conditioning Plastics for Testing
1
These test methods are under the jurisdiction of ASTM Committee D20 on
Plastics and are the direct re
...
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