DRAFT INTERNATIONAL STANDARD ISO/DIS 12058-2.

ISO/TC 61/SC 5 Secretariat: SNV

Voting begins on Voting terminates on

2001-06-21 2001-08-21
INTERNATIONAL ORGANIZATION FOR STANDARDIZATION •    • ORGANISATION INTERNATIONALE DE NORMALISATION

Plastics — Determination of viscosity using a falling-ball

viscometer —
Part 2:
Free-falling-ball method
(Revision of ISO 9371:1990)

Plastiques — Détermination de la viscosité au moyen d'un viscosimètre à chute de bille —

Partie 2: Méthode par chute libre de bille

iTeh STANDARD PREVIEW

(standards.iteh.ai)
ICS 83.080.01
ISO/DIS 12058-2.3
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ISO/DIS 12058-2.3

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ii
 ISO/DIS 12058-2.3

Contents

1 Scope .............................................................................................................................................................. 1
2 Normative references .................................................................................................................................... 1
3 Definition ........................................................................................................................................................ 1
4 Principle.......................................................................................................................................................... 1
5 Apparatus ....................................................................................................................................................... 2
6 Procedure ....................................................................................................................................................... 4
7 Expression of results .................................................................................................................................... 4
8 Precision......................................................................................................................................................... 6
9 Test report ...................................................................................................................................................... 6

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ISO/DIS 12058-2.3

Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO
member bodies). The work of preparing International Standards is normally carried out through ISO 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. ISO collaborates closely with the International Electrotechnical
Commission (IEC) on all matters of electrotechnical standardization.

International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 3.

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 ISO 12058-2 was prepared by Technical Committee ISO/TC 61, Plastics, Subcommittee
SC 5, Physical-chemical properties.

ISO 12058 consists of the following parts, under the general title Plastics - Determination of viscosity using a
falling-ball viscometer.

 Part 1: Inclined-tube methodiTeh STANDARD PREVIEW

 Part 2: Free-falling-ball method (standards.iteh.ai)
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iv © ISO 2001 – All rights reserved

DRAFT INTERNATIONAL STANDARD ISO/DIS 12058-2.3

Plastics — Determination of viscosity using a falling-ball

viscosimeter — Part 2: Free-falling-ball method

1 Scope
This part of ISO 12058 specifies a method, for determining the viscosity of polymers and resins in the liquid
emulsified or dispersed states using a vertical tube falling-ball viscometer. This International Standard is applicable
to such liquids in the viscosity range 100 mPa⋅s to 200 000 mPa⋅s. It is also applicable to other liquids in this
viscosity range that show Newtonian flow behaviour (see ISO 12058-1).

The method is particularly suitable for control of production processes. It allows measurements above 100°C to be
performed, and it can also be used to measure viscosity as a function of pressure.

2 Normative references

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The following standards contain provisions which, through reference in this text, constitute provisions of this
International Standard. At the time of publication, the editions indicated were valid. All standards are subject to
(standards.iteh.ai)
revision, and parties to agreements based on this International Standard are encouraged to investigate the
possibility of applying the most recent editions of the standards indicated below. Members of IEC and ISO maintain
registers of currently valid International Standards.
ISO/DIS 12058-2.3
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ISO 3290, Rolling bearings - Bearing partsba04cdd95fe7/iso-dis-12058-2-3
- Balls for rolling bearings.

ISO 12058-1, Determination of viscosity using a falling-ball viscometer - Part 1: Inclined-tube method.

ISO 31-3, Quantities and units - Part 3: Mechanics.

3 Definition
For the purpose of this part of ISO 12058, the following definition applies:

Dynamic viscosity η or shearing viscosity (often called viscosity) is linked to Newton’s law τ = ηΫ where τ is the
tangential stress (also called shearing stress) in a fluid moving with a speed gradient Ϋ (also called shear gradient
or shear rate) perpendicular to the sliding plane (see ISO 31-3).

The relationship is only valid for laminar flow, and fluids that conform to this relationship are called Newtonian
fluids.

4 Principle
The viscosity of a liquid is determined by observing the motion of a solid sphere under the influence of gravity in a
vertical tube filled with the liquid.

© ISO 2001 – All rights reserved 1

ISO/DIS 12058-2.3

Dynamic viscosity is expressed in millipascal.second (mPa.s)

NOTE This viscometer is used for the determination of relatively high values of viscosities (see Table 1).

5 Apparatus

5.1 Falling-ball viscometer (see figure 1)

The falling ball viscometer is designed to determine the viscosity of a specimen by letting a ball fall through it over
a given distance. The ball is let to fall down the central axis of a cylinder containing the specimen.

2 cm minimum

3.5 cm minimum
Surface of the
specimen
Thermometer

Stirrer
Upper mark

Thermostatic
iTeh STANDARD PREVIEW L : distance between marks
5 cm minimum
bath (standards.iteh.ai)
Lower mark ISO/DIS 12058-2.3
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Special cylinder ba04cdd95fe7/iso-dis-12058-2-3
holder 3 cm minimum

Figure 1 — Falling ball viscometer and associated apparatus

5.2 Ball

The ball used shall be made from grade 100 steel, as specified in ISO 3290, or shall be a ball whose diameter and
sphericity are known with a precision at least equivalent to that specified in ISO 3290. Where the viscosity of a
specimen is required to be determined with a precision of approximately 1%, the nominal value for the diameter of
the ball described in ISO 3290 may be used. Otherwise the dimensions of the ball shall be measured according to
the procedure given in ISO 3290.

For a ball with diameter of d(cm) and with the upper and lower marks on the viscometer set 5 cm apart, general
experience suggests that the minimum viscosity ηm of a specimen, is given by the following formula (1) :

100 5
η = g ( ρb − ρ ) ρ.d 3 (1)
m 3

2 © ISO 2001 – All rights reserved

 ISO/DIS 12058-2.3

Where :

ηm : lowest viscosity measurable with a ball of diameter d (mPa⋅s)

d: diameter of the ball (cm)

ρb : density of the ball (g/cm )

3

ρ : density of the specimen (g/cm )

3

g : acceleration due to gravity (cm/s²)

Table 1 shows typical calculated values of viscosity ranges using various sizes of glass and steel balls over 5 cm
between 20 s and 500 s, and over 10,4 cm between 10 s and 500 s. The calculations are based on the assumption
3 3
that the steel and glass balls have densities of 8 g/cm and 3 g/cm respectively, while the specimen is assumed to
3
have a density of 1 g/cm .

Table 1 — Typical calculated values of viscosity ranges

Diameter of the Viscosity range on 5 cm distance Viscosity range on 10.4 cm distance

ball 20 s < time < 500 s 10 s < time < 500 s
glass steel glass steel
cm mini maxi mini maxi mini maxi mini maxi
0.16 iTeh STANDARD
760 19'000 2'700 PREVIEW
66'600 180 9'200 640 32'000
0.2 1 200 (standards.iteh.ai)
30'000 4'160 104'000 290 14'300 1 000 50'000
0.24 1 700 43'000 6'000 150'000 410 21'000 1 440 72'000
ISO/DIS 12058-2.3
0.32 3 000 76'000 10'600 267'000 730 36'600
https://standards.iteh.ai/catalog/standards/sist/3a85de97-9802-49c7-9590- 2 560 128'000
0.4 4 700 ba04cdd95fe7/iso-dis-12058-2-3
120'000 16'700 416'000 1 150 57'000 4 000 200'000

5.3 Cylinders

The cylinders used to form the viscometer shall be made of glass, transparent, highly resistant to deformation and
uniform in wall thickness. The inner diameter of the particular cylinder chosen for the determination of the viscosity
of a given specimen shall be at least 5 times larger than the diameter of the ball selected. The inner diameter shall
not vary by more than 3% of its mean value along the length of the cylinder.

The upper and lower marks on the cylinders shall be at least 5 cm apart with the lower mark at least 3 cm from the
bottom of the cylinders, and the upper mark at least 4 cm from the top.

The mark lines shall be in planes normal to the central axis of the cylinders with the markings continuing right round
the circumferences on the outside of the cylinders. It may not be necessary to draw the mark lines on the cylinders,
if a well designed cylinder holder is used to hold the cylinders in the thermostatic bath (see figure 1).

5.4 Timer

The time taken by the ball to travel the distance between the two circular marks shall be measured using a
calibrated timer of appropriate precision capable of reading to 0,1 s.

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ISO/DIS 12058-2.3

5.5 Thermometer

A calibrated thermometer of appropriate precision with gradations of at least 0,1K.

5.6 Thermostatic bath

An agitated thermostatic bath deep enough to permit the surface of the specimen to be at least 2 cm below the
surface of the liquid in the bath. For a procedure that uses manual timing, the bath and liquid medium must be
sufficiently transparent so that the upper and the lower marks can be seen through the sides of the cylinder.

The temperature of the bath shall be controlled to 0.05K of the set temperature.

6 Procedure
Select a ball and a cylinder according to the requirements specified in 5.1, rinse well with a suitable volatile solvent
and dry carefully , avoiding contamination

Examine the specimen for the presence of dust or other contamination and filter if necessary.

Introduce sufficient of the specimen into the cylinder so that the upper surface of the specimen is at least 3.5 cm
above the upper mark, taking care to avoid bubble formation.

Install the cylinder vertically in the thermostatic bath so that the surface of the specimen is at least 2 cm below the
iTeh STANDARD PREVIEW
surface of the liquid in the bath. The verticality of the tube can be checked with a T-square with a level. Allow time
for the cylinder and the specimen to reach the temperature for the determination and confirm the absence of
bubbles in the specimen. (standards.iteh.ai)
Drop the ball down the central axis of the cylinder and record the time taken for the top (or bottom) of the ball to fall
ISO/DIS 12058-2.3
between the upper and lower marks. Repeat the determination at least three times.
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NOTE Where the temperature chosen for ba04cdd95fe7/iso-dis-12058-2-3
the determination differs markedly from the atmospheric temperature, the
temperature of the ball should be stabilized at the temperature of the bath.

To prevent bubbles adhering to the surface of the ball, the ball can be "wetted" with the specimen before starting
the determination.

7 Expression of results
Calculate the viscosity using the mean value for the falling time (t) obtained from at least three determinations,
according to the formula

100. d ².( ρb − ρ ). g. J
η= .t (2)
18. L
Where :

η : viscosity (mPa.s)

d : diameter of the ball (cm)

ρb : density of the ball (g/cm )

3

ρ : density of the specimen (g/cm )

3

4 © ISO 2001 – All rights reserved

 ISO/DIS 12058-2.3

g : acceleration due to gravity (cm/s²)

t : falling time between the upper and lower marks (s)

L : distance between the upper and lower marks (cm)

J : calibration constant of the apparatus, related to the diameter of the ball and the inner diameter of the
cylinder.

For fixed construction and dimensions of the viscometer, the constant J can be determined using a standard liquid
of known viscosity and density, such as reference fluids. A new constant can be calculated as an apparatus
constant, related to the ball diameter, the inner tube diameter and the distance between the marks :

100. d 2 . g
K= .J (3)
18. L

and the equation (2) can be rewritten as follows :

η = K .( ρb − ρ ). t (4)
3
Table 2 gives the values for K, expressed in mPa⋅s⋅cm /(g.s), obtained with various diameters of balls and
cylinders, for a distance between the marks of 5 cm and 10,4 cm. The inner diameter of 1,6 cm for the cylinder is
common and readily available commercially.

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Table 2 — Typical values for K in mPa.s.cm /(g.s)
3

Diameter of the
(standards.iteh.ai)
Diameter of the Value of K Value of K
ball cylinder
with marks
ISO/DIS 5 cm apart
12058-2.3 with marks 10,4 cm
apart
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cm cm ba04cdd95fe7/iso-dis-12058-2-3
- -
0,16 1,6 19,017 9,143
0,20 1,6 29,713 14,285
0,24 1,6 42,787 20,571
0,32 1,6 76,066 36,570
0,40 2,0 118,853 57,141

NOTE Practical application

For an apparatus set as:

L = 10,4 cm, d = 0,2 cm, D = 16 cm, ρb = 8 g/cm , ρ = 1 g/cm

3 3

The viscosity is expressed as follows:

η = K .( ρb − ρ ). t

Table 2, column 4, line 2, gives K=14,2853

thus η = 100.t

where: t is the falling time between the upper and lower marks (s).

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