Plastics - Determination of the viscosity of polymers in dilute solution using capillary viscometers - Part 1: General principles (ISO 1628-1:2021)

This document defines the general conditions for the determination of the reduced viscosity, intrinsic
viscosity and K‑value of organic polymers in dilute solution. It defines the standard parameters that are
applied to viscosity measurement.
This document is used to develop standards for measuring the viscosities in solution of individual types
of polymer. It is also used to measure and report the viscosities of polymers in solution for which no
separate standards exist.

Kunststoffe - Bestimmung der Viskosität von Polymeren in verdünnter Lösung durch ein Kapillarviskosimeter - Teil 1: Allgemeine Grundlagen (ISO 1628-1:2021)

Dieses Dokument legt die allgemeinen Grundlagen für die Bestimmung der reduzierten Viskosität, der intrinsischen Viskosität und des K Wertes von organischen Polymeren in verdünnter Lösung fest. Es legt die bei Viskositätsmessungen angewendeten genormten Parameter fest.
Dieses Dokument wird für die Erarbeitung von Normen zur Messung der Viskositäten bestimmter Polymere in verdünnter Lösung herangezogen. Dieses Dokument wird auch zur Bestimmung der Viskositäten von Polymeren in verdünnter Lösung angewendet, für die es keine spezielle Norm gibt.

Plastiques - Détermination de la viscosité des polymères en solution diluée à l'aide de viscosimètres à capillaires - Partie 1: Principes généraux (ISO 1628-1:2021)

Polimerni materiali - Določanje viskoznosti polimerov v razredčenih raztopinah s kapilarnimi viskozimetri - 1. del: Splošna načela (ISO 1628-1:2021)

General Information

Status
Published
Current Stage
6060 - Definitive text made available (DAV) - Publishing
Due Date
17-Mar-2021
Completion Date
17-Mar-2021

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SLOVENSKI STANDARD
SIST EN ISO 1628-1:2021
01-maj-2021
Nadomešča:
SIST EN ISO 1628-1:2009
SIST EN ISO 1628-1:2009/A1:2012
Polimerni materiali - Določanje viskoznosti polimerov v razredčenih raztopinah s
kapilarnimi viskozimetri - 1. del: Splošna načela (ISO 1628-1:2021)

Plastics - Determination of the viscosity of polymers in dilute solution using capillary

viscometers - Part 1: General principles (ISO 1628-1:2021)

Kunststoffe - Bestimmung der Viskosität von Polymeren in verdünnter Lösung durch ein

Kapillarviskosimeter - Teil 1: Allgemeine Grundlagen (ISO 1628-1:2021)

Plastiques - Détermination de la viscosité des polymères en solution diluée à l'aide de

viscosimètres à capillaires - Partie 1: Principes généraux (ISO 1628-1:2021)
Ta slovenski standard je istoveten z: EN ISO 1628-1:2021
ICS:
83.080.01 Polimerni materiali na Plastics in general
splošno
SIST EN ISO 1628-1:2021 en,fr,de

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST EN ISO 1628-1:2021
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SIST EN ISO 1628-1:2021
EN ISO 1628-1
EUROPEAN STANDARD
NORME EUROPÉENNE
March 2021
EUROPÄISCHE NORM
ICS 83.080.01 Supersedes EN ISO 1628-1:2009
English Version
Plastics - Determination of the viscosity of polymers in
dilute solution using capillary viscometers - Part 1:
General principles (ISO 1628-1:2021)

Plastiques - Détermination de la viscosité des Kunststoffe - Bestimmung der Viskosität von

polymères en solution diluée à l'aide de viscosimètres Polymeren in verdünnter Lösung durch ein

à capillaires - Partie 1: Principes généraux (ISO 1628- Kapillarviskosimeter - Teil 1: Allgemeine Grundlagen

1:2021) (ISO 1628-1:2021)
This European Standard was approved by CEN on 23 February 2021.

CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this

European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references

concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN

member.

This European Standard exists in three official versions (English, French, German). A version in any other language made by

translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management

Centre has the same status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,

Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,

Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and

United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels

© 2021 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 1628-1:2021 E

worldwide for CEN national Members.
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SIST EN ISO 1628-1:2021
EN ISO 1628-1:2021 (E)
Contents Page

European foreword ....................................................................................................................................................... 3

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SIST EN ISO 1628-1:2021
EN ISO 1628-1:2021 (E)
European foreword

This document (EN ISO 1628-1:2021) has been prepared by Technical Committee ISO/TC 61 "Plastics"

in collaboration with Technical Committee CEN/TC 249 “Plastics” the secretariat of which is held by

NBN.

This European Standard shall be given the status of a national standard, either by publication of an

identical text or by endorsement, at the latest by September 2021, and conflicting national standards

shall be withdrawn at the latest by September 2021.

Attention is drawn to the possibility that some of the elements of this document may be the subject of

patent rights. CEN shall not be held responsible for identifying any or all such patent rights.

This document supersedes EN ISO 1628-1:2009.

According to the CEN-CENELEC Internal Regulations, the national standards organizations of the

following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria,

Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland,

Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Republic of

North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the

United Kingdom.
Endorsement notice

The text of ISO 1628-1:2021 has been approved by CEN as EN ISO 1628-1:2021 without any

modification.
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SIST EN ISO 1628-1:2021
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SIST EN ISO 1628-1:2021
INTERNATIONAL ISO
STANDARD 1628-1
Fourth edition
2021-02
Plastics — Determination of the
viscosity of polymers in dilute solution
using capillary viscometers —
Part 1:
General principles
Plastiques — Détermination de la viscosité des polymères en solution
diluée à l'aide de viscosimètres à capillaires —
Partie 1: Principes généraux
Reference number
ISO 1628-1:2021(E)
ISO 2021
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SIST EN ISO 1628-1:2021
ISO 1628-1:2021(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2021

All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may

be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting

on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address

below or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii © ISO 2021 – All rights reserved
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SIST EN ISO 1628-1:2021
ISO 1628-1:2021(E)
Contents Page

Foreword ........................................................................................................................................................................................................................................iv

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ...................................................................................................................................................................................... 1

3 Terms and definitions ..................................................................................................................................................................................... 1

3.1 Terms related to any liquid .......................................................................................................................................................... 1

3.2 Terms related to polymer solutions ...................................................................................................................................... 2

4 Principle ........................................................................................................................................................................................................................ 4

5 Apparatus ..................................................................................................................................................................................................................... 5

6 Solutions ....................................................................................................................................................................................................................... 8

6.1 Preparation ................................................................................................................................................................................................ 8

6.2 Concentration........................................................................................................................................................................................... 9

7 Temperature of measurement ............................................................................................................................................................... 9

8 Procedure..................................................................................................................................................................................................................... 9

8.1 General ........................................................................................................................................................................................................... 9

8.2 Preparing and charging the viscometer ............................................................................................................................ 9

8.3 Efflux time measurement ............................................................................................................................................................10

9 Expression of results .....................................................................................................................................................................................10

9.1 Reduced viscosity and intrinsic viscosity .....................................................................................................................10

9.2 K-value ........................................................................................................................................................................................................11

10 Test report ................................................................................................................................................................................................................11

Annex A (normative) Cleaning of apparatus .............................................................................................................................................12

Annex B (informative) Notes on sources of error .................................................................................................................................13

Bibliography .............................................................................................................................................................................................................................16

© ISO 2021 – All rights reserved iii
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SIST EN ISO 1628-1:2021
ISO 1628-1:2021(E)
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.

The procedures used to develop this document and those intended for its further maintenance are

described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the

different types of ISO documents should be noted. This document was drafted in accordance with the

editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/ directives).

Attention is drawn to the possibility that some of the elements of this document may be the subject of

patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of

any patent rights identified during the development of the document will be in the Introduction and/or

on the ISO list of patent declarations received (see www .iso .org/ patents).

Any trade name used in this document is information given for the convenience of users and does not

constitute an endorsement.

For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and

expressions related to conformity assessment, as well as information about ISO's adherence to the

World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www .iso .org/

iso/ foreword .html.

This document was prepared by Technical Committee ISO/TC 61, Plastics, Subcommittee SC 5, Physical-

chemical properties, in collaboration with the European Committee for Standardization (CEN) Technical

Committee CEN/TC 249, Plastics, in accordance with the Agreement on technical cooperation between

ISO and CEN (Vienna Agreement).

This fourth edition cancels and replaces the third edition (ISO 1628-1:2009), which has been technically

revised. It also incorporates the Amendment 1 ISO 1628-1:2009/Amd 1:2012.
The main changes compared to the previous edition are as follows:
— ISO 3205 (withdrawn) has been deleted from Clause 2;
— the figure keys have been revised;
— nominal viscometer constant has been added to Table 1;
A list of all parts in the ISO 1628 series can be found on the ISO website.

Any feedback or questions on this document should be directed to the user’s national standards body. A

complete listing of these bodies can be found at www .iso .org/ members .html.
iv © ISO 2021 – All rights reserved
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SIST EN ISO 1628-1:2021
INTERNATIONAL STANDARD ISO 1628-1:2021(E)
Plastics — Determination of the viscosity of polymers in
dilute solution using capillary viscometers —
Part 1:
General principles
1 Scope

This document defines the general conditions for the determination of the reduced viscosity, intrinsic

viscosity and K-value of organic polymers in dilute solution. It defines the standard parameters that are

applied to viscosity measurement.

This document is used to develop standards for measuring the viscosities in solution of individual types

of polymer. It is also used to measure and report the viscosities of polymers in solution for which no

separate standards exist.
2 Normative references

The following documents are referred to in the text in such a way that some or all of their content

constitutes requirements of this document. For dated references, only the edition cited applies. For

undated references, the latest edition of the referenced document (including any amendments) applies.

ISO 3105, Glass capillary kinematic viscometers — Specifications and operating instructions

ISO 80000-1, Quantities and units — Part 1: General
ISO 80000-4, Quantities and units — Part 4: Mechanics
3 Terms and definitions

For the purposes of this document, the terms and definitions given in ISO 80000-1, ISO 80000-4 and the

following apply.

ISO and IEC maintain terminological databases for use in standardization at the following addresses:

— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at http:// www .electropedia .org/
3.1 Terms related to any liquid
3.1.1
viscosity

property of a fluid sheared between two parallel plates, one of which moves relative to the other in

uniform rectilinear motion in its own plane, defined by the Newton formula
τη= γ
where
© ISO 2021 – All rights reserved 1
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SIST EN ISO 1628-1:2021
ISO 1628-1:2021(E)
τ is the shear stress;
η is the viscosity;
dV

is the velocity gradient or rate of shear, given by where V is the velocity of one plane relative

to the other and z the coordinate perpendicular to the two planes.
−1 −1
Note 1 to entry: The dimensions of viscosity are ML T .
Note 2 to entry: The units of viscosity are Pa·s.
Note 3 to entry: For practical use, the sub-multiple 10 Pa·s is more convenient.

Note 4 to entry: Viscosity is usually taken to mean “Newtonian viscosity”, in which case the ratio of shearing

stress to velocity gradient is constant. In non-Newtonian behaviour, which is the usual case with high-

polymer solutions, the ratio varies with the shear rate. Such ratios are often called “apparent viscosities” at the

corresponding shear rate.
3.1.2
viscosity/density ratio
kinematic viscosity
ratio defined by the formula

where ρ is the density of the fluid at the temperature at which the viscosity is measured

2 −1
Note 1 to entry: The dimensions of kinematic viscosity are L T .
2 −1
Note 2 to entry: The units of kinematic viscosity are m ·s .
−6 2 −1 2 −1

Note 3 to entry: For practical use, the sub-multiple 10 m ·s , i.e. mm ·s , is more convenient.

3.2 Terms related to polymer solutions
3.2.1
relative viscosity
viscosity ratio

ratio of the viscosity of the polymer solution (of stated concentration) η and the viscosity of the pure

solvent η , at the same temperature:
η =
Note 1 to entry: The ratio has no dimensions.
3.2.2
relative viscosity increment
viscosity ratio increment and specific viscosity
viscosity ratio minus one
ηη−
 
−=1
 
η η
 
0 0
Note 1 to entry: The increment has no dimensions.
2 © ISO 2021 – All rights reserved
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SIST EN ISO 1628-1:2021
ISO 1628-1:2021(E)
3.2.3
reduced viscosity
viscosity number

ratio of the relative viscosity increment to the polymer concentration c in the solution:

ηη−
Ι =
η c
3 −1
Note 1 to entry: The dimensions of reduced viscosity are L M .
Note 2 to entry: The units of reduced viscosity are m /kg.
−3 3 3

Note 3 to entry: For practical use, the sub-multiple 10 m /kg, i.e. cm /g, is more convenient and the commonly

quoted numerical values for reduced viscosity (viscosity number) use these practical units.

Note 4 to entry: The reduced viscosity is usually determined at low concentration (less than 5 kg/m , i.e. 0,005 g/

cm ), except in the case of polymers of low molar mass, for which higher concentrations is necessary.

3.2.4
inherent viscosity
logarithmic viscosity number

ratio of the natural logarithm of the viscosity ratio to the polymer concentration in the solution:

 
 
 
Note 1 to entry: The dimensions and units are the same as those given in 3.2.3.

Note 2 to entry: The inherent viscosity is usually determined at low concentration (less than 5 kg/m , i.e. 0,005 g/

cm ), except in the case of polymers of low molar mass, for which higher concentrations is necessary.

3.2.5
intrinsic viscosity
limiting viscosity number
[η]

limiting value of the reduced viscosity or of the inherent viscosity (3.2.4) at infinite dilution:

ηη−
 
η = lim
 
c→0 η c
 
 
 
 
[]η = lim
c→0
Note 1 to entry: The dimensions and units are the same as those given in 3.2.3.

Note 2 to entry: The effect of the shear rate on the functions defined in 3.2.1 to 3.2.5 has been neglected, since

this effect is usually negligible for values of the reduced viscosity, inherent viscosity and intrinsic viscosity less

3 3

than 0,5 m /kg, i.e. 500 cm /g. Strictly speaking, all these functions can be defined at the limiting (preferably

infinitely small) value of the shear rate.
3.2.6
K-value

constant, independent of the concentration of the polymer solution and peculiar to the polymer sample,

which is a measure of the average degree of polymerization:
K-value=1 000 k
[1]
Note 1 to entry: According to H. Fikentscher , k is calculated as follows:
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SIST EN ISO 1628-1:2021
ISO 1628-1:2021(E)
 
75k
lgη = +kc100
 
1+150kc
 
and therefore
 
15,,lgηη−+11++21+ 51lg ,5lgη
 
rr r
 
150+300c
where
η is the viscosity ratio (see 3.2.1);
η =
3 3 3
c is the concentration, in 10 kg/m , i.e. g/cm .
Note 2 to entry: A limiting viscosity number [η] can be calculated from k:
η =+230,375kk
4 Principle

The data needed for the evaluation of the functions defined in 3.2 are obtained by means of a capillary-

tube viscometer. The efflux times of a given volume of solvent t and of solution t are measured at fixed

temperature and atmospheric-pressure conditions in the same viscometer. The efflux time of a liquid is

related to its viscosity by the Poiseuille-Hagenbach-Couette formula as shown in Formula (1):

η A
 
vC== t− (1)
 
t 
where
v is the viscosity/density ratio ;
C is a constant of the viscometer;
A is a parameter of the kinetic-energy correction;
ρ is the density of the liquid;
t is the efflux time.
 

For the purposes of this document, the kinetic energy correction shall be regarded as negligible

 
t 

when it is less than 3 % of the viscosity of the solvent. Hence, Formula (1) can be reduced to Formula (2):

vC== t (2)

Moreover, if the solution concentrations are limited so that the solvent density ρ and that of the

solution ρ differ by less than 0,5 %, the viscosity ratio will be given by the so-called “efflux time

ratio” .

The need for these constraints, and the consequences of not observing them, is described in Annex B.

4 © ISO 2021 – All rights reserved
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SIST EN ISO 1628-1:2021
ISO 1628-1:2021(E)
5 Apparatus
5.1 Capillary viscometer, of the suspended-level Ubbelohde type.

The use of a viscometer having the dimensions given in Figure 1 or Figure 2 is strongly recommended.

Furthermore, it is strongly recommended that the size of the viscometer be chosen from among those

listed in Table 1. The choice is determined by the viscosity/density ratio of the solvent at the temperature

of the measurement, as indicated in Table 1. The next-smaller viscometer may also be used.

Other types of viscometer listed in ISO 3105 may be used, provided they give results equivalent to those

given by the particular size of Ubbelohde viscometer chosen on the basis of the criteria specified in the

preceding paragraph. In cases of dispute, an Ubbelohde viscometer shall be used.

With automated apparatus, fitted with special timing devices, equivalent results with larger sizes of

capillary than those listed for the appropriate solvent viscosity/density ratio in Table 1 can be obtained.

5.2 Viscometer holder, suitable to hold the viscometer firmly in the thermostatic bath (5.3) in the

vertical position.
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SIST EN ISO 1628-1:2021
ISO 1628-1:2021(E)
Dimensions in millimetres
Key

A lower reservoir 26 mm internal diameter L mounting tube 11 mm internal diameter

B suspended level bulb M lower vent tube 6 mm internal diameter
C timing bulb N upper vent tube 7 mm internal diameter
D upper reservoir P connecting tube
E and F timing marks R working capillary
G and H filling marks
Figure 1 — Ubbelohde viscometer
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SIST EN ISO 1628-1:2021
ISO 1628-1:2021(E)

5.3 Thermostatic bath, transparent liquid or vapour bath of a size such that, during the measurement,

all sections containing test liquid are at least 20 mm below the surface of the bath medium and at least

20 mm away from all boundaries of the bath tank.

The temperature control shall be such that, within the range 25 °C to 100 °C, the temperature of the bath

does not vary from the specified temperature by more than 0,05 K over the length of the viscometer, or

between the viscometers if several determinations are carried out simultaneously.

At temperatures higher than 100 °C, the tolerance shall be ±0,2 °C.
Dimensions in millimetres
NOTE For key, see Figure 1.
Figure 2 — DIN Ubbelohde viscometer
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SIST EN ISO 1628-1:2021
ISO 1628-1:2021(E)

5.4 Temperature-measuring device, thermometer, reading to 0,02 °C in the range in which it will be

used and in a known state of calibration, is suitable.

5.5 Timing device. Any timing device may be used providing that it can be read to 0,1 s and that its

speed is constant to 0,1 % over 15 min.

Table 1 — Ubbelohde viscometers recommended for the determination of the dilute-solution

viscosity of polymers
Viscosity/density
Nominal
ratio of solvent at Ubbelohde conforming to DIN Ubbelohde conforming to
viscometer
temperature of ISO 3105 ISO 3105
constant
measurement
Inside Inside
diameter of diameter of
Size No. a Size No. a
tube R tube R
2 −1 2 −2
mm ·s mm ·s mm mm
0,15 to 0,30 0,001 0 0,24 0 0,36
0,31 to 0,50 0,003 0C 0,36 0c 0,47
0,51 to 0,75 0,005 0B 0,46 0a 0,53
0,76 to 1,50 0,01 1 0,58 I 0,63
1,51 to 2,50 0,03 1C 0,77 Ic 0,84
2,51 to 5,00 0,05 1B 0,88 Ia 0,95
5,01 to 15,00 0,1 2 1,03 II 1,13
The tolerance of the inside diameter of tube R is ±2 %.
6 Solutions
6.1 Preparation

The dissolution of the test sample of polymer in the solvent shall give a “true” solution, essentially free

of microgels and associated macromolecules. Polymer degradation shall also be minimized. For these

reasons, it is necessary for the dissolution procedure to be exactly defined and it is recommended that

the following factors be specified:
a) the solvent and its pretreatment, if any;
b) the apparatus and the method of agitation;

c) the temperature range within which the system is maintained during the preparation of the

solution;

d) the time interval necessary for the complete dissolution of the polymer without degradation, or at

constant degradation;
e) the stabilizer and/or the protective atmosphere used;
f) the conditions of filtration of the solution, if applicable;

g) visual homogeneity of the solution and expected nature/composition of the filter residue.

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SIST EN ISO 1628-1:2021
ISO 1628-1:2021(E)
6.2 Concentration

Where no standard exists, careful consideration shall be given to the choice of solvent and the solution

concentration. The solution concentration shall be chosen so that the ratio of the efflux time of the

solution to the efflux time of the solvent is at least 1,2 and less than 2,0.

NOTE A lower limit of 1,2 ensures sufficient precision of the measured difference in efflux times. The upper

limit of 2,0 prevents shear effects and non-linearity of the viscosity number in relation to concentration that can

occur at higher molecular masses.

More than one concentration can therefore be used for a given polymer/solvent system, depending on

the molecular mass of the polymer under test.
3 3 3 3

The concentration is preferably expressed in kg/m of solution or as the multiple 10 kg/m , i.e. g/cm .

7 Temperature of measurement

The temperature shall be chosen with due regard to sufficient solubility and other technical

requirements, but kept constant for any particular polymer/solvent system. The temperature tolerance

shall be specified. A temperature of 25 °C ± 0,05 °C shall be chosen whenever possible. If another

temperature is used, use the temperature that was agreed between the parties concerned and stated in

the test report.
8 Procedure
8.1 General

Measure the efflux times for the solution and the solvent successively in the same viscometer, using the

procedure described in 8.2 and 8.3.
8.2 Preparing and charging the viscometer
8.2.1 Maintain the bath at the specified test temperature.

8.2.2 Charge the dry, clean viscometer (the cleaning procedure is specified in Annex A) by tilting it

about 30° from the vertical and pouring sufficient liquid through tube L (see Figure 1 or Figure 2) so that,

when the viscometer is returned to the vertical, the meniscus is between the filling marks G and H. Avoid

trapping air bubbles in the viscometer. The initial filling may be carried out away from the bath.

8.2.3 Mount the viscometer in a holder in the bath, ensuring that tube N is vertical. Allow time for the

charged viscometer to reach the temperature of the bath. Usually, 15 min will suffice if the measurement

is to be made at 25 °C. At higher temperatures, longer times is necessary. Unnecessary delays should be

avoided as it is found that the most consistent results are obtained shortly after temperature equilibrium

is attained with a freshly charged viscometer.

8.2.4 This procedure shall also be followed when a measured amount of solvent is added to a

solution, already contained in the viscometer, in order to create a more dilute solution for additional

determinations. The additional solvent shall be maintained at the specified test temperature prior to use.

8.2.5 In automated equipment, the viscometer is fixed in the vertical position within a temperature-

controlled bath and the apparatus is designed to fill the viscometer with liquid in this position. The bath

shall be maintained at the specified test temperature and an equilibration time selected in accordance

with 8.2.3.
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SIST EN ISO 1628-1:2021
ISO
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