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IS0
I N T E R NAT1 O N AL O R GAN I ZATl O N
F O R S TAN DAR D I ZAT I O N
I SO RE C OM M EN DATI ON
.
R 289
DETERMINATION OF VISCOSITY
OF NATURAL AND SYNTHETIC RUBBERS
BY THE SHEARING DISK VISCOMETER
1st EDITION
January 1963
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 289, Determination of Viscosity of Natural and Synthetic
Rubbers by the Shearing Disk Viscometer, was drawn up by Technical Committee ISO/TC 45,
Rubber, the Secretariat of which is held by the British Standards Institution (B.S.I.).
Work on this question by the Technical Committee began in 1959 and led, in 1960, to the
adoption of a Draft IS0 Recommendation.
In May 1960, this Draft IS0 Recommendation (No. 378) was circulated to all the IS0
Member Bodies for enquiry. It was approved by the following Member Bodies:
Australia Germany
Portugal
Austria Hungary Republic of South Africa
Brazil India Spain
Canada Israel Sweden
Chile Italy Switzerland
Colombia Japan
United Kingdom
Czechoslovakia Netherlands U.S.A.
Denmark New Zealand U.S.S.R.
France Poland Yugoslavia
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 January 1963, to accept it as an IS0 RECOMMENDATION.
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ISO/R 289 - 1963 (E)
IS0 Recommendation R 289 January 1963
DETERMINATION OF VISCOSITY
OF NATURAL AND SYNTHETIC RUBBERS
BY THE SHEARING DISK VISCOMETER
1. SCOPE
The method given in the present IS0 Recommendation describes the procedure for determining
the viscosity, expressed in Mooney viscosity units, of uncompounded or compounded unvulcan-
ized natural or synthetic rubbers or reclaimed rubbers, by means of the shearing disk viscometer.
Caution should be exercised in interpreting viscosity values obtained by this method as a measure
of molecular mass of the higher molecular mass rubbers. For example, as the molecular mass
increases, the viscosity values for butyl rubbers reach an upper limit of about 80 at 100 OC, using
the specified rotor at a speed of 2 revolutions/minute, and may then decrease to considerably
lower values. For these higher molecular mass rubbers, better correlation between viscosity and
molecular mass is obtained if the rotor speed is reduced or the test temperature increased.
2. PRINCIPLE OF TEST
The test involves the determination of the torque which should be applied under specified condi-
A number pro-
tions in order to rotate a metal disk in a cylindrical chamber filled with rubber.
portional to this torque is taken as an index of the viscosity of the rubber.
3. PREPARATION OF TEST PIECES
Two disks of rubber, about 45 mm in diameter and of sufficient thickness to fill completely the
die cavity of the viscometer, are prepared. The test piece should be cut with a die slightly smaller
than the die cavity, but of a thickness to give an excess volume, i.e. about 25 cm3. The rubber disks
should be as free as possible from air and from pockets that may trap air against the rotor and die
surfaces. A hole is pierced or cut through the centre of one disk to permit the insertion of the
rotor stem.
NOTE. - The viscosity is affected by the manner in which the rubber is prepared and the conditions of storage prior
to test. Accordingly, the prescribed procedure in methods for evaluating the particular rubber should be followed
rigorously.
4. APPARATUS
The essential parts of the apparatus are:
a rotor,
a hollow cylindrical die,
a means for rotating the rotor,
a means for indicating the torque required to rotate the rotor, and
controls for maintaining the die at a constant temperature.
The rotor and die cavity have the dimensions shown in either column (a) or column (b) of the
following table, but in order to ensure the greatest accuracy of results, the metric dimensions
should in future be as shown in column (a).
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ISOlR 289 - 1963 (E)
TABLE. - Dimensions of essential parts of the apparatus
@)
(4
millimetres 1 inches millimetres
Rotor diameter 38.10 50.03 1.500 &0.001 38.10 f0.05
Rotor thickness 5.54 +0.03 0.218 f0.001 5.50 f0.05
Die cavity diameter 50.93 50.13 2.005 &0.005 50.80 f0.05
Die cavity depth 10.59 f0.03 j 0.417 fO.001 10.60 f0.05
It is permissible to use a smaller rotor where high viscosity makes this desirable. This small
rotor should have the same dimensions as the large rotor except that the diameter is 30.48 *0.03 mm
(1.200 50.001 in).
Results obtained with the small rotor are not identical with those obtained with the large
rotor. However, for the purposes of comparing rubbers or compounds, they lead to the same
conclusions.
The die cavity should preferably be formed from only two pieces of unplated hardened steel for
improved heat transfer, and have radial V-grooves on the flat surfaces to retard slipping. The
grooves are spaced at 20" intervals, and extend from at least the 7 mm circle to the 47 mm dia-
meter circle; each groove forms a 90" angle in the die surface, with the bisector of the angle
perpendicular to the surface, and is 1.00 +0.25 mm wide at the surface.
The die cavity may alternatively be formed from four pieces of steel with rectangular-section
grooves on the cavity surfaces to retard slipping. The grooves are 0.80 50.02 mm wide, of uni-
form depth between 0.25 and 0.38 mm, and spaced on 1.60 & 0.04 mm centres. The flat surfaces
of the cavity have two sets of these grooves at right angles to each other.
The rotor surfaces are grooved as described for the die cavity formed from four pieces of steel.
The hardened rotor is fastened to a shaft not exceeding 11 mm in diameter and positioned securely,
so that in the closed die cavity the clearance above the rotor does not differ from the clearance
below the rotor by more than 0.25 mm. The eccentricity or runout of the rotor while turning in
the viscometer sh
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