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IS0
I NT ERN AT I ON A L O R G A N 1 Z AT I ON F O R S TA N DARD IZATl O N
IS0 RECOMMENDATION
L
R 37
DETERMINATION OF TENSILE STRESS-STRAIN PROPERTIES
OF VULCANIZED RUBBERS
2nd EDITION
September 1968
This second edition supersedes the first edition
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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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I
BRIEF HISTORY
The IS0 Recommendation R 37, Determination of tensile stress-srruin properties of vulcnnized natural and
synthefic rubbers, was drawn up by Technical Committee lSO/TC 45, Rubber, the Secretariat of which is held by
the British Standards Institution (BSI).
Work on this question by the Technical Committee began in 1948 and led, in 1953, to the adoption of a
Draft IS0 Recommendation.
In August 1954, this Draft IS0 Recommendation (No. 53) was circulated to all the IS0 Member Bodies for
enquiry. It was approved by 23 Member Bodies. One Member Body (the U.S.A.) opposed the approval of the Draft.
The Draft IS0 Recommendation was then submitted by correspondence to the IS0 Council which decided,
in March 1957, to accept it as an IS0 RECOMMENDATION
BRIEF HISTORY RELATING TO THE 2nd EDITION
Work for the revision of IS0 Recommendation R 37-1957 was subsequently started and, in
1962, a draft proposal was adopted by the Members of Technical Committee ISO/TC 45 as a Draft
IS0 Revision.
In November 1963, this Draft IS0 Revision (No. 634) was circulated to all the IS0 Member
Bodies for enquiry. It was approved, subject to a few modifications of an editorial nature, by the
following Member Bodies :
Argentina Germany Poland
Australia Hungary Spain
Austria India Sweden
Brazil Israel Switzerland
Canada United Kingdom
Italy
Chile Korea, Rep. of U.S.A.
Colombia Morocco U.S.S.R.
Czechoslovakia Netherlands Yugoslavia
France New Zealand
One Member Body opposed the approval of the Draft :
Japan
The Draft IS0 Revision was then submitted by correspondence to the IS0 Council which
decided, in September 1968, to accept it.
The title of IS0 Recommendation R 37-1957 is amended as follows : Determination oftensile
stress-strain properties of vulcanized rubbers.
This edition (2nd edition) supersedes the first edition of IS0 Recommendation R 37-1957.
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I
ISO/R 37-1%8 (1
IS0 Recommendation R 37 September 1968
DETERMINATION OF TENSILE STRESS-STRAIN PROPERTIES
OF VULCANIZED RUBBERS
1. SCOPE
This IS0 Recommendation describes a method for the determination of tensile stress-strain properties
of vulcanized rubbers.
2. PRINCIPLE OF METHOD
Standard test pieces. either in the shape of rings or dumb-bells, as described below, are stretched to
breakage in a tension-testing machine capable of a substantially constant rate of traverse of the
moving grip or pulley.
NOTES
1. Test pieces in the shape of rings and dumb-bells do not necessarily give the Same values for the stress-strain
properties. This is due mainly to the fact that in stretched rings the stress is not uniform over the cross-section. A
second factor is the existence of grain. which may cause dumb-bells to give different value.; according as their
length is parallel or perpendicular to the pain.
2. Rings give lower. sometimes much lower, tensile strength values than dumb-bells, the latter being much nearer to
the true tensile strength of the rubber. The estimation of true tensile strength. from ring data involves extra-
polation of the stress-strain curve.*
3. APPARATUS
The tensile test machine should be capable of a substantially constant rate of traverse of the moving
grip or pulley. This rate should be 500 t 50 mm/min.
NOTE. - Inertia (pendulum) type dynamometers are apt to give results which differ because of frictional and
intertial effects. An inertia-less (for example, electronic or optical transducer type) dynamometer gives results which
are free from these effects. and is therefore to be preferred.
4. TEST PIECE
4.1 Dimensions of test piece
The test piece should be either in the shape of a ring or a dumb-bell, as described below.
(a) Ring test piece
Rings should be nominally of internal diameter 44.6 mm and external diameter 52.6 mm,
the radial width nowhere deviating by more than f 0.2 mm from the mean width. The
thickness should be preferably between 4 and 6 mm. In any one ring the thickness should
nowhere deviate by more than * 0.2 mm from the mean thickness.
*
See W.H. Reece. Transactions of the Institution of the Rubber Indumy, 1935, 11,312, and J.R. Scott, Journal
ofRubber Research 1949, 18, 30.
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ISO/R 37-1968 (
(b) Dumb-bell test piece
The shape of test piece should be determined by the die dimensioned as given in
...