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I N T E Et N AT I ON A L O R G A N i 2 AT I O N FOR S TA N D A Et D I2 AT I O N
IS0 RECOMMENDATION
R 180
PLASTICS
DETERMINATION OF THE IZOD IMPACT RESISTANCE
OF RIGID PLASTICS
(IZOD IMPACT FLEXURAL TESTS)
1st EDIT1 ON
February 1961
COPYRIGHT RESERVED
The copyright of IS0 Recommendations and IS0 Standards
belongs to IS0 Member Bodies. Reproduction of these
documents, in any country, may be authorized therefore only
by the national standards organization of that country, being
a member of ISO.
For each individual country the only valid standard is the national standard of that country.
Printed in Switzerland
Also issued in French and Russian. Copies to be obtained through the national standards organizations.
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BRIEF HISTORY
The IS0 Recommendation R 180, Determination of the Izod Impact Resistance of Rigid
Plastics (Izod Impact Flexural Tests), was drawn up by Technical Committee ISO/T 61,
Plastics, the Secretariat of which is held by the American Standards Association, Incorpor-
ated (ASA).
Work on this matter which the Technical Committee had begun since 1956, came to
an end in 1957, with the adoption of a proposal as a Draft IS0 Recommendation.
On 8 May 1959, the Draft IS0 Recommendation (No. 214) was distributed to all the
IS0 Member Bodies and was approved, by the following Member Bodies:
Austria India Spain
Sweden
Belgium Israel
Italy Switzerland
Burma
Czechoslovakia Japan Turkey
Finland Netherlands United Kingdom
Germany Portugal U.S.A.
Romania U.S.S.R.
Greece
Two Member Bodies opposed the approval of the Draft :
France, Hungary.
The Draft IS0 Recommendation was then submitted by correspondence to the IS0
Council, which decided, in February 1961, to accept it as an IS0 RECOMMENDATION.
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IS0 Recommendation R 180 February 1961
l
PLASTICS
DETERMINATION OF THE IZOD IMPACT RESISTANCE
OF RIGID PLASTICS*
(IZOD IMPACT FLEXURAL TESTS)
1. SCOPE
The two methods of test described in this IS0 Recommendation are intended to determine the
relative sensitivity to fracture by shock of rigid plastics as indicated by the energy expended by a
standard pendulum type impact machine in breaking in one blow a standard Izod (Cantilever
beam) specimen.
2. TYPES OF TESTS
Either of the two following methods may be employed, according to the circumstances:
2.1 Method A is the Cantilever beam or Izod Type Test in which the specimen is broken by a
blow delivered at a fixed distance from the edge of the specimen clamp. The test requires
a notched specimen in all cases. The notch is intended to produce a standard degree of
stress concentration.
Q
2.2 Method B is the Cantilever beam or Izod Type Test for materials of less than 2.75 kgf cm
per centimetre of notch. Method B adds to Method A a technique for the determination
of the energy expended in tossing the specimen. The value reported is called the " estimated
". This method is recommended in place of Method A for
notched Izod impact strength
materials which have an Izod impact strength of less than 2.75 kgf. cm per centimetre of
notch. It is not to be used for materials which have higher Izod impact strength values
than 2.75 kgf cm per centimetre of notch.
2.3 The instructions contained in sections 3 to 7 (pages 6 to 10) apply to both Method A and
Method B. On the other hand, the instructions contained in Sections 8 and 9 (pages 11
and 12) differ for the two methods.
* For the determination of the Charpy impact resistance, see IS0 Recommendation R 119, Determination of the Charpy Impact Resistance
af Rigid Plastics (Charpy Impact Flexural Test).
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180 I R 180 - I861 (E)’
3. SIGNIFICANCE OF TEST
3.1 The excess energy pendulum impact test indicates the energy to break standard test speci-
mens of specified size under stipulated conditions of specimen mounting, notching (stress
concentration) and rate of loading.
3.2 The energy indicated by the apparatus after breaking a standard test piece is the sum of:
(a) the energy to deform the specimen,
(b) the energy to initiate fracture of the specimen,
(c) the energy to propagate the fracture across the specimen,
(d) the energy to throw the free end of the broken specimen (“ toss factor ”) and
(e) the energy lost through friction and through vibration of the apparatus and its base.
3.3 The notch, which is always present in the standard Izod test specimen, serves to con-
centrate the stress and largely prevents plastic deformation.
Friction losses are largely eliminated by careful design and proper operation of the testing
machine. Energy losses due to vibration of the apparatus are generally assumed to be
negligible for plastics, but may be considerable if the machine is not correctly designed
with sufficient mass for the specified range and is not of rigid construction.
3.4 Thus, the indicated impact strength of a material for all practical purposes is based on
items (a), (b), (c) and (d) as indicated in clause 3.2. In the case of relatively brittle
materials, the tearing energy is small compared with the fracture energy, whereas in the case
of tough, ductile materials of fibre filled or cloth laminated materials, the reverse is true,
the toss factor may represent a very large fraction of the total energy absorbed when
testing relatively brittle materials (less than 2.75 kgf cm per centimetre of notch). A
correction for the toss factor is specified in clause 8. 2.4 (Method B). This correction is
especially important when comparing materials of widely ranging densities.
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IPU / K WU - 1101 (t)
4. APPARATUS
4.1 The machine should be of the pendulum type, as illustrated in Figure 1, of rigid construc-
tion, accurate to 0.14 kgf. cm for readings of less than 14 kgf . cm and to 1 per cent for
higher values. Accurate correction should be made for friction and windage losses.
Fig. 1.-Cantilever beam (hod Type) impact machine
O
4.2 The dimensions of the machine should be such that the centre of percussion of the striker
(see Note 1) is at the point of impact; that is, the centre of the striking edge.
4.3 The pendulum should be released from such a position that the linear velocity of the centre
of the striking edge (centre of percussion) at the instant of impact should be approximately
335 cm/s, which corresponds to an initial elevation of this point of 61 cm.
NOTES
1. The distance from the axis of support to the centre of percussion may be determined experimentally from the
period of oscillation of the pendulum through a small angle, by means of the following equation:
I = 24.1 TP
where
I = distance, in centimetres, from the axis of support to the centre of percussion,
T = time, in seconds, for a complete swing (to and fro).
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IS0 / R 180 - I961 (E)
The striking edge of the pendulum should be a cylindrical surface of 0.8 mm, with its axis
4.4
horizontal. The cylindrical surface should be, when the pendulum is hanging free, tangent
to the specimen in a line 2.20 cm above the surface of the vice. The pendulum above the
cylindrical portion of the striking edge should be recessed or inclined at a suitable angle so
that there is no chance of its coming into contact with the specimen during break.
4.5 Means should be provided for clamping the specimen rigidly in position with the edges of
the supporting surfaces at 90" angles (see Note 2).
4.6 Means should be provided for determining the impact value of the specimen, which is the
energy expended in breaking the specimen. This value is equal to the difference in energy
in the pendulum blow and the energy remaining in the pendulum after breaking the speci-
men, after suitable correction has been made for energy losses due to windage and friction.
5. SPECIMENS
The test specimen should conform to the dimensions shown in Figure 2, except as modified
5.1
in accordance with clauses 5.2,5.3 and 5.4. To insure the correct contour and condition of
the specified notch, all specimens should be notched as directed in section 6.
Dimensions in millimetres
Thickness of specimen should be
63.5 4 lr = 0.25 f 0.025
in accordance with section 5.
Fig. 2.43peeimen for Cantilever beam (hod Type) impact machine
Nmes (continued)
2. Some plastics are sensitive to clamping pressure; therefore cooperating laboratories should agree on means
of standardizing the gripping form, such as by using a torque mnsh on the screw of the specimen vice.
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c
ISO/ R 180 - lM1 (E)
5.2 For moulded material (see Note 3), the specimen should be 1.27 cm by any dimension
from 0.32 to 1.27 cm, agreed upon as representative of the cross-section in which the
particular material is to be used. For all specimens having one dimension less than 1.27
cm, the notch should be cut in the narrower side (see Note 4). For all compression-moulded
specimens, the notch should be in the side parallel to the direction of application of the
moulding pressure (see Note 5).
5.3 For sheet material the specimens should be cut from the sheet in both the lengthwise and
crosswise directions, unless otherwise specified (see Note 6).
The thickness should be the thickness of the sheet, except that it should not exceed 1.27 cm.
Sheet material thicker than 1.27 cm should be machined down to 1.27 cm. Such material
may be tested either edgewise or flatwise, as specified. When specimens are tested flatwise,
the notch should be made on the machined surface if the specimen is machined on one side
only. When the specimen is cut from a thick sheet, notation should be made from what
portion of the thickness of the sheet the specimen is cut, for example, centre, top surface
or bottom surface.
5.4 For sheet materials less than 1.27 cm in thickness, the test speci
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