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UDC 678.4/678.7 : 620.1
IS0
I N T ER N AT I O N A L O R G A N I2 AT I ON FOR S TA N DARD IZATl O N
IS0 RECOMMENDATION
R 812
METHOD OF TEST FOR TEMPERATURE LIMIT OF BRITTLENESS
FOR VULCANIZED RUBBERS
1st EDITION
September 1968
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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 812, Method of test for temperature limit of brittleness for
vulcanized rubbers, was drawn up by Technical Committee ISO/TC 45, Rubber, the Secretariat of
which is held by the British Standards Institution (BSI).
Work on this question by the Technical Committee led, in 1962, to the adoption of a Draft
IS0 Recommendation.
In November 1963, this Draft IS0 Recommendation (No. 613) was circulated to ail 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 Switzerland
Israel
Canada Italy United Kingdom
Chile Japan U.S.A.
Colombia Korea, Rep. of U.S.S.R.
Czechoslovakia Netherlands Yugoslavia
New Zealand
France
No Member Body opposed the approval of the Draft.
The Draft IS0 Recommendation was then submitted by correspondence to the IS0 Council,
which decided, in September 1968, to accept it as an IS0 RECOMMENDATION.
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UJX 678.4/678.7 : 620.1 Ref. No. : ISO/R 812-1968/Al-1972 (E)
FOREWORD
Amendment 1 to IS0 Recommendation R 812-1968 was drawn up by Technical Committee
ISO/TC 45, Rubber and rubber products. As the Members of ISO/TC 45 considered the modifications
made to that IS0 Recommendation to be of minor importance, this amendment was submitted direct
to the IS0 Council under the abbreviated procedure set forth in clause F.7.1 of the Directives for the
technical work of ISO.
Amendment 1 - June 1972 - to IS0 Recommendation R 812-1968
Amendment 1
to IS0 Recommendation R 812-1968
METHOD OF TEST FOR TEMPERATURE LIMIT OF BRITTLENESS
FOR VULCANIZED RUBBERS
Section 3 : delete the second paragraph and the Note.
Section 4 : clause 4.1.2, delete the second paragraph and replace with the foliowing text :
“A minimum of 6 mm of the length of the test piece (the tab end for type B test pieces) should
be held in the clamp.
A minimum of four test pieces should be tested. The number of test pieces that may be tested
during any one impact is limited by the energy capacity of the apparatus and should not cause the
rectilinear speed of the striker immediately after the impact to fall below 1.83 m/s.”
Number the note after clause 4.1.2 as “1 .” and add a second note :
“2. Four type A test pieces require the same available energy as ten type B test pieces.
For some materials and apparatus it may be necessary to test, at any one impact, a reduced
number of test pieces in order to maintain the required rectilinear speed of the striker,
immediately after the impact.”
Section 5 : add the following new item :
‘‘0 The number of test pieces of any given sample tested at a single impact.”
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ISO/R 812-1968 (
IS0 Recommendation
R 812 Sep te m be r 1 968
METHOD OF TEST FOR TEMPERATURE LIMIT OF BRITTLENESS
FOR VULCANIZED RUBBERS
1. SCOPE
This IS0 Recommendation describes a method for determining the lowest temperature at which
rubber compounds do not exhibit brittle failure when impacted under specified conditions. Brittleness
temperatures thus determined are not necessarily indicative of service performance.
NOTE. - Brittleness temperatures of rubbers are empirical points dependent to a large degree upon test pro-
cedures and apparatus. In order to obtain reproducible brittleness temperature measurements, all pertinent test
variables must be thoroughly defined. The procedure outlined in this IS0 Recommendation defines those variables
at present known to influence the brittleness test.
2. APPARATUS
Test piece clamp and sm'ker. The clamp is designed to hold the test pieces as cantilever beams
2.1
(see Fig. 1). The striking edge moves relative to the test pieces at a rectilinear speed of 1.83 to
2.13 m per second at and immediately after impact. A motor, solenoid or other type of actuator
may be used provided that the radius of the striker, the speed of the striker and the distance
from the test piece clamp are as specified.
NOTE. - Two types of tester currently in use are shown in Figures 3 and 4 in the Annex.
The distance between the centre line of the striking edge and the clamp should be 7.9 f 0.3 mm
at impact. The striking edge should have a radius of 1.6 I O. 1 mm. The striker and test piece
clamp should have a clearance of 6.4 f 0.3 mm at and immediately following impact. These
dimensional requirements are illustrated in Figure 1. The velocity should be checked to make
sure that if the voltage is changed by 6 'k the required velocity is nevertheless obtained.
Test piece clamp
/
Striking edge radius
1.6 IO.1 mm
/
Test piece '
6.4 * 0.3 mm
Its--- 7.9 f 0.3 mm
FIG. 1 - Test piece clamp and striker
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ISO/R 812-1968 (
2.2
Temperature measuring device. A thermocouple or a thermometer may be used. Copper-
constantan thermocouples, used in conjunction with a potentiometer, are highly satisfactory.
The thermometer should be calibrated in degrees Celsius divisions and should have a range
suitable for the temperatures at which determinations are to be made. The temperature
measuring device should be located as near the test pieces as possible.
2.3 Heat-transfer medium. The heat-transfer medium may be either liquid or gaseous. Any medium
which remains fluid at the test temperature and which wiii
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