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IS0
O N
I NT ERN AT I ON AL ORGAN lZATl O N FOR STANDARD lZATl
IS0 RECOMMENDATION
R 34
DETERMINATION OF TEAR STRENGTH
OF VULCANIZED NATURAL AND SYNTHETIC RUBBERS
(CRESCENT TEST PIECE)
1 st EDITION
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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
Copies to be obtained through the national standards organizations.
Also issued in French and Russian.
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BRIEF HISTORY
The IS0 Recommendation R 34, Determination of Tear Sfrength of Vul-
canized Nafural and Synthetic Rubbers (Crescent Test Piece), was drawn up by
the Technical Committee ISO/TC 45, Rubber, the Secretariat of which is held by
the British Standards Institution (B.S. I.).
The draft proposal put forward by the Secretariat was considered and
amended at the meetings held in London (1948), the Hague (1949), Akron (1950),
Oxford (1951) and Paris (1953).
On 28 August 1954, the Draft IS0 Recommendation proposed by the
Technical Committee ISO/TC 45 was submitted to all IS0 Member Bodies
and approved, subject to certain editorial amendments, by the following 23
(out of a total of 34) Member Bodies:
Austria *New Zealand
*Canada Pakistan
Denmark Portugal
Finland Spain
France Sweden
India Switzerland
*Ireland Union of South Africa
Israel United Kingdom
Italy U.S.A.
*Japan U.S.S.R.
"Mexico Yugoslavia
Netherlands
No Member Body opposed 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.
* These Member Bodies stated that they had no objection to the Draft being approved.
Date of the flrst edition: April 1957.
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lSO/R 34 - 1957 (E)
IS0 Recommendation R 34 March 1957
DETERMINATION OF TEAR STRENGTH
OF VULCANIZED NATURAL AND SYNTHETIC RUBBERS
(CRESCENT TEST PIECE)
1. SUMMARY
The test consists in inserting a slit of accurate depth in a special test piece
and measuring the force required to tear across the width of the unnicked
portion.
2. TEST PIECE
The test piece conforms to the shape of the die shown in the figure below.
The dimensions of the die are as given in the table. The test piece is
cut from a sheet by punching with the die using a single blow of a mallet
or (preferably) a single stroke of a press; the rubber may be wetted with
water or a soap solution and should be supported on a sheet of slightly
yielding material (e.g. leather, rubber belting or cardboard) on a flat, rigid
surface.
A
N
DIMENSIONS OF TEST PIECE
I Dimension 1 Millimetres 1 Inches I Dimension 1 I\lillimetres 1 Inches 1
A 110 4.3
1.7
B
25 1 H 29 1.14
C 45 1.80 12.5
J 0.5
D
9 0.375 K 8.5 0.34
E
16 0.625 L 10.2
0.4
F
9 0.375 M 7.5 0.3
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ISO/R 34 - 1957 (E)
The tear strength is particularly susceptible to grain effects in vulcanized
rubber. Kormally, all test pieces are prepared with the grain at right
angles to their length, but in cases where grain effects are significant and
are to be evaluated, two sets of test pieces are cut from the sheet, at right
angles, and parallel to the grain.
The thickness of the test piece should not fall outside the limits of either
1.8 mm to 2.8 mm or 0.07 inch to 0.11 inch and should be measured by means
of a micrometer gauge having a pressure foot approximately 6 nim or 0.25 inch
in diameter which exerts a pressure of either 200 g/cm2 or 3 lb/in2 on the
At least three gauge readings are taken in the region of test. If an
rubber.
of readings is taken, the value to be used is the middle value.
odd number
If an even number of readings
...