SIST ISO 12644:1997

SLOVENSKI STANDARD
SIST ISO 12644:1997
01-junij-1997
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Graphic technology -- Determination of rheological properties of paste inks and vehicles
by the falling rod viscometer
Technologie graphique -- Détermination des caractéristiques rhéologiques des encres et
excipients projetés, à l'aide d'un viscosimètre à tige tombante
Ta slovenski standard je istoveten z: ISO 12644:1996
ICS:
87.080 Barvila. Tiskarske barve Inks. Printing inks
SIST ISO 12644:1997 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST ISO 12644:1997

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SIST ISO 12644:1997
INTERNATIONAL
IS0
STANDARD
12644
First edition
1996-12-01
Graphic technology - Determination of
rheological properties of paste inks and
vehicles by the falling rod viscometer
Technologie graphique -
D6 termina tion des carat t&-k tiques rh6ologiques
des encres et excipien ts projet&, il /‘aide d’un viscosim&tre in tige
tomban te
Reference number
IS0 12644:1996(E)

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SIST ISO 12644:1997
IS0 12644:1996(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
(IEC) 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
Standard requires approval by at least 75 % of the member bodies casting
a vote.
International Standard IS0 12644 was prepared by Technical Committee
lSO/TC 130, Graphic technology.
Annex A forms an integral part of this International Standard.
0 IS0 1996
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-121 IG eneve 20 l Switzerland
Printed in Switzerland
ii

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SIST ISO 12644:1997
INTERNATIONAL STANDARD @ IS0 IS0 12644:1996(E)
Graphic technology - Determination of rheological
properties of paste inks and vehicles by the falling rod
viscometer
1 Scope
This International Standard specifies the procedure for determining the viscosity and yield value of paste inks and
vehicles which are unreactive under normal room conditions.
It is applicable to inks in the apparent viscosity range of 2 Pa - s to 200 Pa - s.
2 Definitions
For the purposes of this International Standard, the following definitions apply.
2.1
viscosity: Measure of the internal friction of a liquid in motion. The viscosity is generally defined as the ratio
of the shear stress (2.2) to the shear rate (2.3):
2.2 shear stress, 0: Force per area in a direction parallel to the applied force. Unit: Pa.
NOTES
1 For the falling rod viscometer, the shear stress is proportional to the total weight of the rod and the weight loads in
accordance with the equation
W
mg
=-=-
cl- . . .
(2)
A zm-1
where (see figures 1 and 2)
is the shear stress;
CT
W is the total weight of the rod and the weight loads;
A is the apparent shearing area;
is the gravitational acceleration;
g
is the total mass;
m
r is the radius of the rod;
1 is the length of the aperture.
2 The shearing length of the aperture of a falling rod viscometer usually contains both a tapered and a parallel section;
therefore, it is understood that A is not the true shearing area but an apparent shearing area.

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SIST ISO 12644:1997
@ IS0
IS0 12644:1996(E)
2.3 shear rate, y: Velocity gradient through a stressed liquid in a direction perpendicular to the shearing area.
Unit: s-1.
For the falling rod viscometer, yis inversely proportional to all fall time according to the equation
NOTE -
L
. . .
(3)
=
Y
r - In (R/r) . t
is the shear rate;
Y
L is the falling distance of the rod;
r is the radius of the rod;
R is the radius of the aperture;
t is the fall time.
If the ratio of the radii of the rod and aperture is close to unity, the term may be simplified to
L
. . .
(4)
=-
Y
st
where s is the thickness of the ink in the nip determined by the difference between radii of the aperture and of the rod.
24 apparent viscosity, IJ~: Ratio of the shear stress CT to the shear rate yfor a given shear stress or shear rate.
.
.
u;l,t . Pa-s.
25 . Newtonian liquid: Liquid whose shear stress is proportional to shear rate.
26 . non-Newtonian liquid: Liquid whose shear stress is not proportional to shear rate.
NOTES
1 There are two types of non-Newtonian liquids: With shear thickening liquids, the viscosity increases with shear rate; with
shear thinning liquids, the viscosity decreases with shear rate.
2 If the viscosity of a liquid decreases with application of steady mechanical stress from a value at the state of rest to a final
value and increases again if the stress ceases, the liquid is called thixotropic.
2.7 flow curve: Graph of the shear stress oas a function of the shear rate yor vice versa.
2.8 Casson model (see A.l): Flow model which assumes a non-linear increase of shear stress CT with increasing
shear rate y A minimum stress o-0 IS required to initiate flow.
Bingham model (see A.2): Flow model which ass
29 umes a linear increase of the shear stress owith increasing
s;ear rate y A minimum stress 00 is required to initiate
2.10 Power Law model (see A.3): Flow model which assumes an increase of the shear stress o of a liquid
proportional to the Nth power of the shear rate y
2.11 yield stress, 00: Minimum stress required to initiate flow of a liquid. Unit: 1 Pa.
2.12 pseudo yield stress, 0~: Shear stress at a defined low shear rate when applying the Power Law model,
typically to 2,5 s-1.
2

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SIST ISO 12644:1997
0 IS0 IS0 12644:1996(E)
2.13 reference temperature: Temperature (25 “C) for which all results are reported. Unit: “C.
Measurements made at temperatures different from this temperature are corrected (see 62.2).
NOTE -
2.14 test temperature: Actual temperature of the aperture ring during measurements. Unit: “C.
2.15 shortness ratio: Ratio of yield stress or pseudo yield stress to the apparent viscosity. Unit: 1 s-1.
3 Test method
3.1 Principle
The principle of this test is the measurement of the relative velocity between a vertical rod and an aperture ring.
The bottom of the rod is inserted into the aperture. The gap is filled with the test fluid, which is sheared when the
rod falls.
By loading the rod with different load weights, different shear rates are obtained. By applying linear regression
methods to the measured fall times as a function of load weight, the viscosity and the yield stress can be
calculated.
3.2 Apparatus
3.2.1 Falling rod viscometer
The viscometer consists of
- a cylindrical rod ( figure I) made from metal or any other hard material. In order to obtain comparable values for
S hear stress and result ng shear rate the mass of the steel rod should be (132 + 1) g.
- a metal ring (figure 2) with a defined cylindrical or conical aperture. The ring is fixed on a support and should be
temperature controlled. Since the diameter of rod and aperture are critical they are manufactured within low
tolerances. These dimensions shall be supplied by the manufacturer. To minimize possible gap differences,
only matching sets of rod and aperture ring shall be used.
loaded on top of t he rod. Series of load weights are combined to sets. Sets of load weig hts
- load weights to be
with the following masses should be used:
5000, 4000, 3000,
A . . 2000, 1000
B . . 3000, 2000, 1500, 500
C . . 1500, 1 000, 800, 500
D . . 800, 600, 400,
200
E . . 400, 300, 200, 100
F . . 200, 100, 50, 0
The tolerance for the masses of load weights shall be k 0,2 g;
- a designated measuring distance marked on the strut. The tolerance shall be + 0,2 mm. Sensors may be
placed at the marks.
- a levelling device.
- a timing device. The tolerance shall be & 0,l s (should be + 0,Ol s).

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SIST ISO 12644:1997
IS0 12644:1996(E)
8
I-
Key
1 Ring
9 Level
2 Aperture
10 Horizonta ly adjusting screw
3 Rod ?I Strut
4 I- Radius of the rod
Support
5 Measuring distance, upper mark R Radius of the aperture
I
6 Measuring distance, lower mark Length of the aperture
L Measuring distance
7 Weight
8 Water jacket
Figure 1 - Falling rod viscometer

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SIST ISO 12644:1997
IS0 12644:1996(E)
Figure 2 - Aperture ring
3.2.2 Temperature control
Means shall be provided for measurement and control of the test temperature.
3.2.3 Others
Non-scratching spatulas.
Standard viscosity oils (at least 2) for calibration.
NOTE - The viscosity of the standard viscosity oils shall be in the same range as that of the test samples. The viscosity of
these oils shall be traceable to a standards institution. An internal standard may be used for comparative studies only.
3.3 Ambient temperature control
The test shal I be carried out under controlled ambi ent temperatu re. This can be ac hieved eithe r by placing the
viscometer in a th ermosta tically cant rolled cabinet or working un der constant room tempe ‘rature
bY
If working in a cabinet, the inner temperature should not vary from the test temperature by more than +_ 0,5 “C. For
room conditioning, a difference of +_ 2 “C to the test temperature is allowed. The standard reference temperature
shall be (25 rfI 0,2) “C.
3.4 Preparation for testing
be kneaded by a spatula and equilibrated to test temperature. The
Prior to use, the test sa mple (about 5 g) shall
sample shall be h omoge neous and not contain any coarse particles.
The proper set of load weights is selected according to the expected results.
NOTE - The fall time with the highest load weight should normally be in the range 4 s to 10 s. For heat-set printing inks it
may be desirable to use a shorter fall time for the highest weight.

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SIST ISO 12644:1997
@ IS0
IS0 12644:1996(E)
An amount of the test sample sufficient to coat the rod and aperture is applied to the lower part of the rod. By
turning the rod, the sample is distributed uniformly. Running a single pass with the highest weight load, the rod and
the aperture ring are wetted by the liquid. The rod is inserted into the aperture and rests on the support before the
test run is started.
3.5 Test procedure
The samp
...