INTERNATIONAL IS0

STANDARD 37
Third edition
1994-05-l 5

Rubber, vulcanized or thermoplastic -

Determination of tensile stress-strain
properties
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(standards.iteh.ai)
Caoutchouc vulcanis ou thermoplastique - Dbtermination des
caractbristiques de contrainte-ddformation en traction
ISO 37:1994
https://standards.iteh.ai/catalog/standards/sist/fc578a15-1f7e-4549-ba1c-
8b14e7eb9fca/iso-37-1994

Reference number
IS0 37:1994(E)
IS0 37:1994(E)

Foreword

IS0 (the International Organization for Standardization) is a worldwide

federation of national standards bodies (IS0 member bodies). The work
of preparing International Standards is normally carried out through IS0
technical committees. Each member body interested in a subject for
which a technical committee has been established has the right to be
represented on that committee. International organizations, governmental
and non-governmental, in liaison with ISO, also take part in the work. IS0
collaborates closely with the International Electrotechnical Commission
(I EC) on all matters of electrotechnical standardization.

Draft International Standards adopted by the technical committees are

circulated to the member bodies for voting. Publication as an International
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Standard requires approval by at least 75 % of the member bodies casting
a vote.

International Standard IS0 37

(standards.iteh.ai)
was prepared by Technical Committee
lSO/TC 45, Rubber and rubber products, Subcommittee SC 2, Physical
and degradation tests. ISO 37:1994
https://standards.iteh.ai/catalog/standards/sist/fc578a15-1f7e-4549-ba1c-
This third edition cancels and replaces the second8b14e7eb9fca/iso-37-1994
edition (IS0 37:1977).

The major changes incorporated in this revision are as follows:

a) Four dumb-bell test pieces are described. Types 1 and 2 are the same
as in the previous edition. The miniature dumb-bell, type 3 in the pre-
vious edition, becomes type 4, with an additional intermediate-size
dumb-bell being added as the new type 3.

b) A reference to IS0 5893 is given in place of detailed requirements for

the tensile-testing machine.

c) The calculation of results is described more clearly.

d) Means of determining the yield point have been included.

e) Definitions of tensile properties, as they relate to rubber, are provided.

Annex A forms an integral part of this International Standard.

0 IS0 1994
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced
or utilized in any form or by any means, electronic or mechanical, including photocopying and
microfilm, without permission in writing from the publisher.
International Organization for Standardization
Case Postale 56 l CH-1211 Geneve 20 l Switzerland
Printed in Switzerland

ii
INTERNATIONAL STANDARD 0 IS0 IS0 37:1994(E)

Rubber, vulcanized or thermoplastic - Determination

of tensile stress-strain properties

1 Scope IS0 4661-l : 1993, Rubber, vulcanized or thermoplastic

- Preparation of samples and test pieces - Part 1:
This International Standard describes a method for the Physical tests.
determination of the tensile stress-strain properties
of vulcanized and thermoplastic rubbers. The proper- IS0 5893:1993, Rubber and plastics test equipment
ties which may be determined are the tensile - Tensile, flexural and compression types (constant
strength, the elongation at break, the stress at a given rate of traverse) - Description.
strain and the elongation at a given stress. Means of
specifying or determining
given.
iTeh STANDARD 3PREVIEW
the yield point are also
Definitions
(standards.iteh.ai)
For the purposes of this International Standard, the
2 Normative references following definitions apply.
ISO 37:1994
The following standardshttps://standards.iteh.ai/catalog/standards/sist/fc578a15-1f7e-4549-ba1c-
contain provisions which, 3.1 tensile stress, S: A stress applied so as to ex-
through reference in this text, constitute 8b14e7eb9fca/iso-37-1994
provisions tend the test piece. It is calculated as the applied
of this International Standard. At the time of publi- force per unit area of the original cross-section of the
cation, the editions indicated were valid. All standards test length.
are subject to revision, and parties to agreements
based on this International Standard are encouraged 3.2 elongation, E: The extension, expressed as a
to investigate the possibility of applying the most re- percentage of the test length, produced in the test
cent editions of the standards indicated below. piece by a tensile stress.
Members of IEC and IS0 maintain registers of cur-
rently valid International Standards. 3.3 tensile strength, TS: The maximum tensile
stress recorded in extending the test piece to break-
IS0 471: -l), Rubber - Times, temperatures and hu- ing point. [See figures 1 a) to 1 c).]
midities for conditioning and testing.
3.4 tensile strength at break, TS,: The tensile
ISO 1826: 1981, Rubber, vulcanized - Time-in ten/al stress recorded at the moment of rupture. [See fig-
between vulcanization and testing - Specification. ures 1 a) to 1 c).]

IS0 3383: 1985, Rubber - General directions for NOTE 1 The values of TS and TS, may be different if,
achieving elevated or subnormal temperatures for test after yield Sv, the elongation continues and is accompanied
purposes. by a drop in stress, resulting in TS, being lower than TS.
[See figure 1 c).]
I SO 4648: 1991, Rubber, vulcanized or thermoplastic
- Determination of dimensions of test pieces and 3.5 elongation at break, &,: The tensile strain in the
products for test purposes. test length at breaking point. [See figures la) to 1 c).]

1) To be published. (Revision of IS0 471:1983)

IS0 37:1994(E)

1 TS=TS,,

a)

Eb

iTeh STANDARD PREVIEW

b) (standards.iteh.ai)
ISO 37:1994
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8b14e7eb9fca/iso-37-1994

Eb E

EY Eb

L5 = Elongation $ = Stress at yield

&, = Elongation at break TS = Tensile strength
q = Elongation at yield TS, = Tensile strength at break
S = Stress Y = Yield point

Figure 1 - Illustration of tensile terms

2
0 IS0 IS0 37:1994(E)

3.6 elongation at a given stress, &: The tensile a) Tensile strength

strain in the test length when the test piece is sub-
jected to a given tensile stress. Dumb-bells are preferable for determination of
tensile strength. Rings give lower, sometimes
3.7 stress at a given elongation, Se: The tensile much lower, values than dumb-bells.
stress in the test length required to produce a given
elongation. b) Elongation at break
NOTE 2 In the rubber industry, this definition is widely Rings give approximately the same values as
identified with the term “modulus”, and care should be dumb-bells, provided that
taken to avoid confusion with the other use of “modulus”
to denote the slope of the stress-strain curve at a given 1) the elongation of rings is calculated as a per-
elongation. centage of the initial internal circumference
and
3.8 tensile stress at yield, &: The tensile stress at
the first point on the stress-strain curve where some 2) dumb-bells are cut at right angles to the grain
further increase in strain occurs without any increase if this is present to a signif icant degree.
in stress. This may correspond to either a point of
inflection [see figure 1 b)] or to a maximum [see fig- Dumb-bells shall be used if it is required to study
ure 1 c)]. grain effects for which rings are not suitable.

3.9 elongation at yield, 4: The tensile strain at the c) Elongation at a given stress and stress at a given
first point on the stress-strain curve where some fur- elongation
ther increase in strain is not accompanied by an in-
crease in stress. [See figures 1 b) and 1 c).] Type 1 and 2 dumb-bell test pieces are preferred,
iTeh STANDARD PREVIEW
3.10 test length of a dumb-bell: The initial distance
and shall be used for specification
wherever possible.
purposes

(standards.iteh.ai)
between reference points within the length of the
Rings and dumb-bells give approximately the
narrow portion of a dumb-bell test piece and used to
measure elongation. (See figure 2.) same values provided that
ISO 37:1994
https://standards.iteh.ai/catalog/standards/sist/fc578a15-1f7e-4549-ba1c-
8b14e7eb9fca/iso-37-19941)
the elongation of rin gs is calculated a s a per-
4 Principle ten tage of the initial
mean circumfere nce and
Standard test pieces, either dumb-bells or rings, are 2) the average value is taken for dumb-bells cut
stretched in a tensile-testing machine at a constant parallel and at right angles to the grain if this
rate of traverse of the driven grip or pulley. Readings is present to a significant degree.
of force and elongation are taken as required during
the .uninterrupted stretching of the test piece and Rings may be preferred in automated testing, due
when it breaks. to the ease of handling of the test pieces, and in
the determination of stress at a given strain.
5 General
d) Miniature test pieces may give somewhat differ-
Dumb-bell and ring test pieces do not necessarily give ent, usually higher, values for tensile strength and
the same values for their respective stress-strain elongation at break than the larger test pieces.
properties. This is mainly because in stretched rings
the stress is not uniform over the cross-section. A Six types of test piece are provided, i.e. dumb-bell-
second factor is in the existence of “grain” which shaped types 1, 2, 3 and 4 and ring-shaped types A
may cause dumb-bells to give different values de- (normal) and B (miniature). The results obtained for a
pending whether their length is parallel or at right an- given material are likely to vary according to the type
gles to the grain. of test piece used, and the results obtained for dif-
ferent materials should therefore not be regarded as
The main points to be noted in choosing between comparable unless the same type of test piece has
rings and dumb-bells are as follows: been used.
IS0 37:1994(E) 0 IS0

When preparation of test pieces requires buffing or 6.2 Rings

thickness adjustment, results may be affected.
The standard type A ring test piece shall have an
Type 3 and 4 dumb-bell test pieces and type B ring internal diameter of 44,6 mm & 0,2 mm. The median
test pieces shall only be used where insufficient ma- axial thickness and median radial width shall be
terial is available for the larger test pieces. 4,0 mm & 0,2 mm. The radial width within any ring
shall nowhere deviate from the median by more than
These test pieces are particularly suitable for testing 0,2 mm and the axial thickness within the ring shall
products and are used in certain product standards, nowhere deviate from the median by more than 2 %.
e.g. type 3 dumb-bells have been used for testing
pipe sealing rings and cables. The standard type B ring test piece shall have an
internal diameter of 8,0 mm + 0,l mm. The median
axial thickness and median radial width shall be
6 Test pieces I,0 mm & 0,l mm. The radial width within any ring
shall nowhere deviate from the median by more than
0,l mm.
6.1 Dumb-bells
If two groups of rings of either size are being com-
Dumb-bell test pieces shall have the outline shown in pared, the median thickness of each group shall be
figure 2. within 7,5 % of the grand median thickness of the
two groups.

7 Apparatus

7.1 Dies and cutters

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(standards.iteh.ai)
All dies and cutters used shall be in accordance
IS0 4661-I. Dies for preparation of dumb-bells
with
shall
have the dimensions given in table 2 and figure3. The
ISO 37:1994
departure from parallelism at any point along the
https://standards.iteh.ai/catalog/standards/sist/fc578a15-1f7e-4549-ba1c-
width of the narrow portion of the die shall nowhere
Figure 2 - Shape of dumb-bell test pieces8b14e7eb9fca/iso-37-1994
exceed 0,05 mm.

7.2 Thickness gauge

The standard thickness of the narrow portion shall be
2,0 mm & 0,2 mm for types 1, 2 and 3 and The instrument for measuring the thickness of
l,Omm+O,l mmfortype4. dumb-bell test pieces and the axial thickness of ring
test pieces shall be in accordance with that used in
The test length shall be in accordance with table 1. method A of IS0 4648:1991.
The other dimensions of the dumb-bells shall be as
produced by the appropriate die (see table 2). The instrument for measuring the radial width of ring
test pieces shall be similar to the above, except that
For non-standard test pieces, e.g. those taken from the contact and base plate shall be shaped to fit the
completed products, the maximum thickness of the curvature of the ring.
narrow portion shall be 3,0 mm for type 1, 2,5 mm for
types 2 and 3, and 2,0 mm for type 4. 7.3 Cone gauge

A calibrated cone gauge or other suitable equipment

Table 1 - Test length of dumb-bells shall be used to measure the internal diameter of ring
Dimensions in millimetres
test pieces. The equipment shall be capable of
measuring the diameter with an error of not more
)pTYiii([ Type 3 1 Type 4 1
than 0,Ol mm. The means of supporting the ring to
be measured shall be such as to avoid any significant
Test length 25,0 & 0,5 20,O * 0,5 10,O f 0,5 IO,0 k 0,5
change in the dimension being measured.
 IS0 37:1994(E)

Dimensions in millimetres

A-A

suit machine n d smooth

iTeh STANDARD PREVIEW

(standards.iteh.ai)
NOTES
ISO 37:1994
1 For dimensions A to F,https://standards.iteh.ai/catalog/standards/sist/fc578a15-1f7e-4549-ba1c-
see table2.
8b14e7eb9fca/iso-37-1994
2 For a method of cutting type B ring test pieces, see annex A.

Figure 3 - Die for dumb-bell test pieces

Table 2 - Dimensions of dies for dumb-bell test pieces

Dimensions in millimetres

Dimension Type 1 TYPe 2 Type 3 Type 4

A Overall length (minimum)l) 115 75 50 35

B Width of ends 25,0 & I,0 12,5 i- I,0 8,5 I!I 0,5 6,O k 015
c Length of narrow portion 33,0 & 2,0 25,0 f I,0 16,0 & I,0 12,o & 0,5
D Width of narrow portion 6 0 or0
+0,4 410 * 03 4,O * 03 210 rt 03
E Transition radius outside 14,; * I,0 6,O IIZ 0,5 7,5 It 0,5 3,O * 03
F Transition radius inside 25,0 k 2,0 12,5 & I,0 IO,0 * 0,5 3,O * a1

I) A greater overall length may be necessary to ensure that only the wide parallel-sided end portions come into contact
with the machine grips, thus helping to avoid “shoulder breaks”.

5
IS0 37:1994(E) 0 IS0

7.4 Tensile-testing machine evaluations intended to be comparable, the tests, as

far as possible, shall be carried out after the same
7.4.1 The tensile-testing machine shall comply with time interval.
the requirements of IS0 5893:1993, having an accu-
For product tests, whenever possible, the time be-
racy of force measurement complying with grade B
tween vulcanization and testing shall not exceed 3
and, where used, an extensometer accuracy comply-
months. In other cases, tests shall be made within 2
ing with grade Dl for type 1 and 2 dumb-bell and type
months of the date of receipt of the product by the
A ring test pieces, and grade El for type 3 and 4
customer.
dumb-bell and type B ring test pieces. The machine
shall as a minimum be capable of operating at a rate
of traverse of 100 mm/min, 200 mm/min and IO.2 Protection of samples and test pieces
500 mm/min and should preferably be equipped with
facilities for the autographic recording of stress and Samples and test pieces shall be protected as com-
strain. pletely as possible from all external influences likely
to cause damage during the interval between
7.4.2 For tests at temperatures other than standard vulcanization and testing, e.g. they shall be protected
temperature, a suitable thermostated chamber shall from light and heat.
be fitted to the tensile-testing machine. Guidance for
achieving elevated or subnormal temperatures is 10.3 Conditioning of samples
given in IS0 3383.
Condition all samples, other than those from latex, in
accordance with IS0 471 at standard temperature,
8 Number of test pieces
without humidity control, for not less than 3 h prior to
cutting out the test pieces.
A minimum of three test pieces shall be tested.
iTeh STANDARD PREVIEW
Condition all prepared latex samples in accordance
9 Preparation of test pieces (standards.iteh.ai)
with IS0 471 at standard temperature, with humidity
control, for not less than 96 h prior to cutting out the
9.1 Dumb-bells test pieces.
ISO 37:1994
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8b14e7eb9fca/iso-37-1994
The test pieces shall be prepared by the appropriate 10.4 Conditioning of test pieces
methods described in IS0 4661-1. Dumb-bells shall,
wherever possible, be cut parallel to the grain of the Condition all test pieces in accordance with IS0 471.
material unless grain effects are to be studied, in If the preparation of test pieces involves buffing, the
which case a set of dumb-bells shall also be cut per- interval between buffing and testing shall be not less
pendicular to the grain. than 16 h and not greater than 72 h.

For tests at standard temperature, test pieces that do

9.2 Rings not require further preparation may be tested im-
mediately, if cut from conditioned test samples.
Ring test pieces shall be prepared by cutting or
Where additional preparation is involved, a minimum
punching, using the appropriate methods described in
conditioning period of 3 h at standard temperature
IS0 4661-1, or by moulding.
shall be allowed.

10 Conditioning of samples and test For tests at temperatures other than standard tem-
perature, condition the test pieces at the temperature
pieces
at which the test is to be conducted for a period suf-
ficient to enable test pieces to attain substantial
10.1 Time between vulcanization and equilibrium in accordance with IS0 3383 (see 7.4.2).
testing

The time interval between vulcanization and testing 11 Marking of dumb-bell test pieces
shall be in accordance with IS0 1826. For all test
purposes, the minimum time between vulcanization If using a non-contact extensometer, mark the dumb-
and testing shall be 16 h. bell test pieces with two reference marks to define
the test length as specified in table 1, using a suitable
For non-product tests the maximum time between marker. The test piece shall be unstrained when it is
vulcanization and testing shall be 4 weeks and, for marked.

6
Q IS0 IS0 37:1994(E)

The lines shall be marked on the narrow part of the The nominal rate of traverse of the moving grip shall
test piece, as shown in figure2, i.e. equidistant from be 500 mm/min for type 1 and type 2 test pieces and
the centre of the test piece and at right angles to its 200 mm/min for type 3 and type 4 test pieces.
longitudinal axis.
Any test piece that breaks outside the test length (see
figure 2) shall be discarded and a repeat test con-
ducted on an additional test piece.
12 Measurement of test pieces
NOTE 3 In making visua I measurements, care should be
taken to avoid inaccuracies due to parallax.
12.1 Dumb-bells

Measure the thickness at the centre and at each end 13.2 Ring test pieces
of the test length with the thickness gauge. The me-
dian value of the three measurements shall be used Place the test piece with a minimum of tension
in calculating the area of the cross-section. In any one around the two pulleys. Start the machine and moni-
dumb-bell, none of the three thickness measure- tor continuously the distance between the pulleys and
ments of the narrow portion shall differ by more than the increase in stress throughout the test to an accu-
2 % from the median thickness. If two groups of test racy of + 2 % or as required for the purposes of
pieces are being compared, the median thickness of clause 15.
each group shall be within 7,5 % of the median
thickness of the two groups. The width of the test The nominal rate of traverse of the moving pulley shall
piece shall be taken as the distance between the be 500 mm/min for type A ring test pieces and
cutting edges of the die in the narrow part, and this 100 mm/min for type B ring test pieces.
distance shall be measured in accordance with
IS0 4661-1 to the nearest 0,05 mm. iTeh STANDARD 14PREVIEWTemperature of test

12.2 Rings
(standards.iteh.ai)
The test shall normally be carried out at one of the
standard temperatures specified in IS0 471. When
ISO 37:1994 other temperatures are required, these shall be
Measure the radial width and axial thickness at six
https://standards.iteh.ai/catalog/standards/sist/fc578a15-1f7e-4549-ba1c-
selected from the list of preferred temperatures given
approximately equally spaced positions around the
8b14e7eb9fca/iso-37-1994in IS0 471.
ring. The median value of each set of measurements
shall be used in calculating the area of the cross- The same temperature shall be used throughout any
section. The internal diameter shall be measured to one test or series of tests intended to be comparable.
the nearest 0,l mm. It may be measured on a suitable
cone and the internal circumference and the mean
circumference calculated as follows: 15 Calculation of results
Internal circumference = n: x internal diameter
15.1 Dumb-bells
Mean circumference = n: x (internal diameter
+ radial width)
151.1 Calculate the tensile strength TS, expressed
in megapascals, using the equation

I3 Procedure TS =- h-l
wt

13.1 Dumb-bell test pieces 15.1.2 Calculate the tensile strength at break TS,,
expressed in megapascals, using the equation
Insert the test piece into the tensile-testing machine,
ensuring that the parallel-sided portions of the tab TS b =- Fb
ends are gripped symmetrically so that the tension is wt
distributed uniformly over the cross-section. If
necessary, set up the extensometry device. Start the 15.1.3 Calculate the elongation at break &, ex-
machine and monitor continuously the change in test pressed as a percentage, using the equation
length and force throughout the test to an accuracy
within & 2 %, as required for the purposes of lwb -Lo)
Et, =
clause 15. b