Measurement of the average viscometric degree of polymerization of new and aged cellulosic electrically insulating materials

Describes a standardized method for the determination of the average viscometric degree of polymerization (DPv) of new and aged cellulosic electrically insulating materials. It may be applied to all cellulosic insulating materials such as those used in transformer, cable or capacitor manufacturing. The methods described can also be used for the determination of the intrinsic viscosity of solutions of chemically modified kraft papers, provided that these dissolve completely in the selected solvent. Caution should be taken if the method is applied to loaded kraft papers. Note: Within a sample of material, all the cellulose molecules do not have the same degree of polymerization so that the mean value measured by viscometric methods is not necessarily the same as that which may be obtained by, for instance, osmotic or ultra centrifuging methods. Experience has indicated the need for improved description of the experimental method. It describes a revised procedure that overcomes the limitations of the first edition.

Messung des durchschnittlichen viskosimetrischen Polymerisationsgrades von neuen und gealterten cellulosehaltigen Elektroisolierstoffen

Mesure du degré de polymérisation moyen viscosimétrique des matériaux isolants cellulosiques neufs et vieillis à usage électrique

Décrit une méthode normalisée pour déterminer le degré de polymérisation moyen viscosimétrique (DPv) des matériaux isolants cellulosiques neufs et vieillis, à usage électrique. Elle peut s'appliquer à tous les matériaux isolants cellulosiques comme ceux utilisés dans la fabrication des transformateurs, des câbles et des condensateurs. Les méthodes décrites peuvent également être utilisées pour déterminer la viscosité intrinsèque des solutions de papiers kraft modifiés chimiquement, pourvu que ceux-ci se dissolvent totalement dans le solvant choisi. Il convient de prendre des précautions si la méthode s'applique à des papiers kraft chargés. Note: Dans un échantillon de matériau, toutes les molécules de cellulose n'ont pas le même degré de polymérisation de sorte que la valeur moyenne mesurée par les méthodes viscosimétriques n'est pas nécessairement la même que celle obtenue, par exemple, par les méthodes par osmose ou par ultra-centrifugation. L'expérience a mis en évidence le besoin d'améliorer la description de la méthode expérimentale. La procédure ainsi revue permet de surmonter les limitations de la première édition.

Merjenje povprečne viskozimetrične stopnje polimerizacije novih in staranih celuloznih elektroizolacijskih materialov (IEC 60450:2004)

General Information

Status
Published
Publication Date
31-Dec-2004
Technical Committee
Current Stage
6060 - National Implementation/Publication (Adopted Project)
Start Date
01-Jan-2005
Due Date
01-Jan-2005
Completion Date
01-Jan-2005

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SLOVENSKI SIST EN 60450:2005
STANDARD
januar 2005
Merjenje povprečne viskozimetrične stopnje polimerizacije novih in staranih
celuloznih elektroizolacijskih materialov (IEC 60450:2004)
(istoveten EN 60450:2004)
Measurement of the average viscometric degree of polymerization of new and aged
cellulosic electrically insulating materials (IEC 60450:2004)
ICS 29.035.01 Referenčna številka
SIST EN 60450:2005(en)

© Standard je založil in izdal Slovenski inštitut za standardizacijo. Razmnoževanje ali kopiranje celote ali delov tega dokumenta ni dovoljeno

---------------------- Page: 1 ----------------------
EUROPEAN STANDARD EN 60450
NORME EUROPÉENNE
EUROPÄISCHE NORM June 2004
ICS 17.220.99; 29.035.01
English version
Measurement of the average viscometric degree of polymerization
of new and aged cellulosic electrically insulating materials
(IEC 60450:2004)
Mesure du degré de polymérisation Messung des durchschnittlichen
moyen viscométrique des matériaux viskosimetrischen Polymerisationsgrades
isolants cellulosiques neufs et vieillis von neuen und gealterten
à usage électrique cellulosehaltigen Elektroisolierstoffen
(CEI 60450:2004) (IEC 60450:2004)

This European Standard was approved by CENELEC on 2004-06-01. CENELEC 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 Central Secretariat or to any CENELEC 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 CENELEC member into its own language and

notified to the Central Secretariat has the same status as the official versions.

CENELEC members are the national electrotechnical committees of Austria, Belgium, Cyprus, Czech

Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia,

Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Slovakia, Slovenia, Spain, Sweden,

Switzerland and United Kingdom.
CENELEC
European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung
Central Secretariat: rue de Stassart 35, B - 1050 Brussels

© 2004 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members.

Ref. No. EN 60450:2004 E
---------------------- Page: 2 ----------------------
EN 60450:2004 - 2 -
Foreword

The text of document 15E/229/FDIS, future edition 2 of IEC 60450, prepared by SC 15E, Methods of

test, of IEC TC 15, Insulating materials, was submitted to the IEC-CENELEC parallel vote and was

approved by CENELEC as EN 60450 on 2004-06-01.
The following dates were fixed:
– latest date by which the EN has to be implemented
at national level by publication of an identical
national standard or by endorsement (dop) 2005-03-01
– latest date by which the national standards conflicting
with the EN have to be withdrawn (dow) 2007-06-01
Annex ZA has been added by CENELEC.
__________
Endorsement notice

The text of the International Standard IEC 60450:2004 was approved by CENELEC as a European

Standard without any modification.
__________
---------------------- Page: 3 ----------------------
- 3 - EN 60450:2004
Annex ZA
(normative)
Normative references to international publications
with their corresponding European publications

The following referenced documents are indispensable for the application 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.

NOTE Where an international publication has been modified by common modifications, indicated by (mod), the relevant

EN/HD applies.
Publication Year Title EN/HD Year
1) 2)
IEC 60814 - Insulating liquids - Oil-impregnated paper EN 60814 1997
and pressboard - Determination of water
by automatic coulometric Karl Fischer
titration
ISO 287 - Paper and board - Determination of - -
moisture content - Oven-drying method
ISO 3105 - Glass capillary kinematic viscometers - - -
Specification and operating instructions
Undated reference.
Valid edition at date of issue.
---------------------- Page: 4 ----------------------
NORME CEI
INTERNATIONALE
IEC
60450
INTERNATIONAL
Deuxième édition
STANDARD
Second edition
2004-04
Mesure du degré de polymérisation moyen
viscosimétrique des matériaux isolants
cellulosiques neufs et vieillis à usage électrique
Measurement of the average viscometric degree
of polymerization of new and aged cellulosic
electrically insulating materials
 IEC 2004 Droits de reproduction réservés  Copyright - all rights reserved

Aucune partie de cette publication ne peut être reproduite ni No part of this publication may be reproduced or utilized in any

utilisée sous quelque forme que ce soit et par aucun procédé, form or by any means, electronic or mechanical, including

électronique ou mécanique, y compris la photocopie et les photocopying and microfilm, without permission in writing from

microfilms, sans l'accord écrit de l'éditeur. the publisher.

International Electrotechnical Commission, 3, rue de Varembé, PO Box 131, CH-1211 Geneva 20, Switzerland

Telephone: +41 22 919 02 11 Telefax: +41 22 919 03 00 E-mail: inmail@iec.ch Web: www.iec.ch

CODE PRIX
PRICE CODE
Commission Electrotechnique Internationale
International Electrotechnical Commission
Международная Электротехническая Комиссия
Pour prix, voir catalogue en vigueur
For price, see current catalogue
---------------------- Page: 5 ----------------------
60450  IEC:2004 – 3 –
CONTENTS

FOREWORD...........................................................................................................................5

INTRODUCTION.....................................................................................................................9

1 Scope.............................................................................................................................11

2 Normative references.....................................................................................................11

3 Terms, definitions and symbols ......................................................................................11

3.1 Terms and definitions ............................................................................................11

3.2 Symbols................................................................................................................13

4 Principle.........................................................................................................................15

5 Apparatus and reagents.................................................................................................15

6 Specimens.....................................................................................................................17

6.1 Preparation of specimens......................................................................................17

7 Experimental procedure..................................................................................................19

7.1 Measurement of water content of paper.................................................................19

7.2 Determination of viscosity.....................................................................................19

8 Test report......................................................................................................................31

Annex A (normative) Cuen solution......................................................................................33

Annex B (normative) Preparation of Cuen solution...............................................................35

Annex C (normative) Procedure for the verification of the ratio of the Cuen solution......41

Annex D (informative) Numerical values of the product [v] c as a function of v

according to Martin's formula ................................................................................................43

Bibliography..........................................................................................................................45

Table 1 – Symbols ................................................................................................................13

Table 2 – DP values of specimen .......................................................................................19

Table D.1 – [ν] c as a function of ν (k = 0,14). ..................................................................43

Figure 1 – Chemical structure of cellulose ............................................................................11

Figure 2 – Ubbelohde viscometer tube..................................................................................27

---------------------- Page: 6 ----------------------
60450  IEC:2004 – 5 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
–––––––––––
MEASUREMENT OF THE AVERAGE VISCOMETRIC DEGREE OF
POLYMERIZATION OF NEW AND AGED CELLULOSIC ELECTRICALLY
INSULATING MATERIALS
FOREWORD

1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising

all national electrotechnical committees (IEC National Committees). The object of IEC is to promote

international co-operation on all questions concerning standardization in the electrical and electronic fields. To

this end and in addition to other activities, IEC publishes International Standards, Technical Specifications,

Technical Reports, Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC

Publication(s)”). Their preparation is entrusted to technical committees; any IEC National Committee interested

in the subject dealt with may participate in this preparatory work. International, governmental and non-

governmental organizations liaising with the IEC also participate in this preparation. IEC collaborates closely

with the International Organization for Standardization (ISO) in accordance with conditions determined by

agreement between the two organizations.

2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international

consensus of opinion on the relevant subjects since each technical committee has representation from all

interested IEC National Committees.

3) IEC Publications have the form of recommendations for international use and are accepted by IEC National

Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC

Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any

misinterpretation by any end user.

4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications

transparently to the maximum extent possible in their national and regional publications. Any divergence

between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in

the latter.

5) IEC provides no marking procedure to indicate its approval and cannot be rendered responsible for any

equipment declared to be in conformity with an IEC Publication.

6) All users should ensure that they have the latest edition of this publication.

7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and

members of its technical committees and IEC National Committees for any personal injury, property damage or

other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and

expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC

Publications.

8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is

indispensable for the correct application of this publication.

9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of

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

International Standard IEC 60450 has been prepared by subcommittee 15E: Methods of test,

of IEC technical committee 15: Insulating materials.

This second edition cancels and replaces the first edition, published in 1974, and constitutes

a technical revision. Experience has indicated the need for improved description of the

experimental method. It describes a revised procedure that overcomes the limitations of the

first edition.
The text of this standard is based on the following documents:
FDIS Report on voting
15E/229/FDIS 15E/235/RVD

Full information on the voting for the approval of this standard can be found in the report on

voting indicated in the above table.
---------------------- Page: 7 ----------------------
60450  IEC:2004 – 7 –

This publication has been drafted in accordance with the ISO/IEC Directives, Part 3.

The committee has decided that this publication remains valid until 2008. At this date, in

accordance with the committee’s decision, the publication will be
 reconfirmed;
 withdrawn;
 replaced by a revised edition, or
 amended.
---------------------- Page: 8 ----------------------
60450  IEC:2004 – 9 –
INTRODUCTION

Experience has indicated the need for an improved description of the experimental method for

the reproducible determination of the average viscometric degree of polymerization of new

and aged cellulosic electrically insulating material.

The major error appears to arise from oxidative degradation occurring during processing and

effluxing. Other significant factors include the need to ensure that all of the material is

dissolved and used, as well as the effect of the speed of effluxing.
---------------------- Page: 9 ----------------------
60450  IEC:2004 – 11 –
MEASUREMENT OF THE AVERAGE VISCOMETRIC DEGREE OF
POLYMERIZATION OF NEW AND AGED CELLULOSIC ELECTRICALLY
INSULATING MATERIALS
1 Scope

This International standard describes a standardized method for the determination of the

average viscometric degree of polymerization ( DP ) of new and aged cellulosic electrically

insulating materials. It may be applied to all cellulosic insulating materials such as those used

in transformer, cable or capacitor manufacturing.

The methods described can also be used for the determination of the intrinsic viscosity of

solutions of chemically modified kraft papers, provided that these dissolve completely in the

selected solvent.
Caution should be taken if the method is applied to loaded kraft papers.

NOTE Within a sample of material, all the cellulose molecules do not have the same degree of polymerization so

that the mean value measured by viscometric methods is not necessarily the same as that which may be obtained

by, for instance, osmotic or ultra centrifuging methods.
2 Normative references

The following referenced documents are indispensable for the application 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.

IEC 60814, Insulating liquids – Oil-impregnated paper and pressboard – Determination of

water by automatic coulometric Karl Fischer titration

ISO 287, Paper and board – Determination of moisture content – Oven-drying method

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

3 Terms, definitions and symbols

For the purposes of this document, the following terms, definitions and symbols apply.

3.1 Terms and definitions
3.1.1
degree of polymerization of a cellulose molecule
number of anhydrous-β-glucose monomers, C H O , in the cellulose molecule
6 10 5
NOTE Figure 1 shows the chemical structure of cellulose.
CH OH
CH OH
O O
CH OH
n – 2
IEC 424/04
Figure 1 – Chemical structure of cellulose
---------------------- Page: 10 ----------------------
60450  IEC:2004 – 13 –
3.1.2
Cuen
1 mol/l aqueous solution of bis(ethylenediamine)copper(II) hydroxide
Cu(H NCH CH NH ) (OH) . [CAS 14552-35-3]
2 2 2 2 2 2

NOTE In some countries the abbreviation CED is used for bis(ethylenediamine)copper(II) hydroxide.

3.1.3
paper

cellulosic electrically insulating material, such as paper, presspaper, pressboard and

components made thereof
NOTE In the present document such paper is termed “paper”.
3.2 Symbols
Symbols used in this standard are shown in Table 1.
Table 1 – Symbols
Symbol Definition
Mark Houwink constant of the cellulose monomer
c Molarity of copper in Cuen solution
Molarity of ethylenediamine in Cuen solution
Constants for viscometer tubes 0, 1 and 2 respectively
C , C and C
0 1 2
c Concentration of solution
Average viscometric degree of polymerization
Kinematic viscosity of solution
v Kinematic viscosity of solvent
K Mark Houwink characteristic constant of the polymer/solvent system
k Constant in Martin's formula
m Mass of dry paper
Mass of swollen paper in tared vessel
Mass of added water
H O
Density of water
H O
v Volume of added water
H O
Volume of added Cuen
Intrinsic viscosity
[ν]
v Specific viscosity
Efflux time for tests A and B on dissolved specimen 1
t t
1A 1B
Efflux time for tests A and B on dissolved specimen 2
t , t
2A 2B
t t Efflux time for tests A and B on pure solvent
0A 0B
t Efflux time for diluted Cuen solvent (50 % Cuen and 50 % water)
t Efflux time for Cuen dissolved specimen
———————
Chemical Abstracts Service (CAS) Registry numbers®
---------------------- Page: 11 ----------------------
60450  IEC:2004 – 15 –
4 Principle

The specific viscosity ν of a solution of the paper in Cuen is determined. From this result the

intrinsic viscosity [ν] of the solution is deduced, and from this the degree of polymerization is

calculated.

NOTE Solutions of cellulose are non-Newtonian fluids. Their viscosity decreases as the flow velocity increases

(sometimes known as “structural viscosity”). Although the viscosity of dilute solutions varies only slightly with the

gradient of the velocity modulus, the use of conditions outside those specified in this standard may result in

unacceptable errors.
Specific viscosity ν is defined by
viscosity of paper solution − viscosity of solvent
ν = (1)
viscosity of solvent
Intrinsic viscosity [ν] is defined by
 
νlim (2)
 
c→0 c
 
where c is the concentration of the solution.

The average viscometric degree of polymerization DP (the ratio of the mean molecular mass

indicated viscometrically to the molecular mass of the monomeric unit) is related to the

intrinsic viscosity [ν] by the equation:
[ν] = K ⋅ DP (3)

K and α being characteristic Mark Houwink coefficients of the polymer-solvent system

(paper/Cuen) and of the monomer respectively.

The intrinsic viscosity [ν] is calculated from the specific viscosity and the concentration c

by Martin’s empirical formula:
� ⋅[]ν�
ν = [ν] ⋅ c ⋅10 (4)
where k is Martin’s constant. For kraft papers k = 0,14.
5 Apparatus and reagents

NOTE 1 Apparatus and reagents for the preparation of Cuen are given separately in Annexes A and B.

During the analysis, unless otherwise specified, use only reagents of recognized analytical

grade and only distilled /de-ionized water or equivalent quality.

A glass fronted, thermostatically controlled bath, suitable for the immersion of the viscometer

tubes, capable of maintaining a temperature of 20 °C to within ±0,1 K and fitted with

appropriate means for illuminating the tubes. It shall be fitted with a means of displaying the

temperature to within an accuracy of ±0,05 K.

NOTE 2 To obtain the required degree of temperature stability, it may be necessary to use a refrigeration unit in

addition to the bath heater.
---------------------- Page: 12 ----------------------
60450  IEC:2004 – 17 –

Calibrated capillary type viscometer tubes according to ISO 3105 with a capillary constant of

0,005 or 0,01. Non calibrated tubes can be used as long as the viscosities of the Cuen solvent

and solution of paper in Cuen are measured in the same tube.
A timer/stopwatch capable of measuring to within an accuracy of ±0,1 s.
Suitable blender or grinder to “activate” the paper sample to allow dissolution.

Suitable vials (typically 25 ml to 50 ml) with lids (not paper) that make an effective seal for the

preparation of paper/Cuen solution. Alternative glass containers can be used. However, these

shall be sealed during dissolution to minimize oxidative degradation of the Cuen.

Cuen (see Annex A).
Distilled or de-ionized water.
Low oxygen content nitrogen supply (minimum 99,9 % nitrogen).
Acetone minimum 99,0 % pure.
Pentane or hexane minimum 99,0 % .
20 % aqueous nitric acid.
Vented drying oven thermostatically controlled to 105 °C ± 2 K.
Analytical balance capable of weighing 20 g to within ±0,1 mg.
Soxhlet extractor.
Pipette to deliver ±0,1 ml.

Mechanical shaker capable of holding the glass vials used to prepare the paper/Cuen

solutions or a magnetic stirrer can be used to dissolve the paper/Cuen solution.
6 Specimens
6.1 Preparation of specimens

The paper under evaluation shall only be handled with gloves or forceps. It shall not be

touched by hand.

Pressboard with a thickness greater than 1 mm, shall be split into layers of less than 1 mm.

The samples shall be cut into pieces sufficiently small to facilitate the subsequent processes.

For very thin paper, the material may be cut into small pieces using scissors.
---------------------- Page: 13 ----------------------
60450  IEC:2004 – 19 –
6.1.1 Impregnated papers
Impregnated papers shall be degreased before weighing and absorbing solution.

Wash a sufficient amount of the paper under evaluation so as to give a degreased mass of

approximately 3 g in a Soxhlet using pentane or hexane for a minimum of five washings, or by

rinsing in five portions of fresh pentane or hexane in an appropriate glass vessel. Allow the

degreased material to dry and leave it exposed to the atmosphere until equilibrium with the

atmospheric humidity is reached. Two portions of the paper are separated, one for use in the

DP determination and one for use in the moisture determination.
6.1.2 Non-impregnated papers

Take a sample having an approximate mass of 3 g and continue with the test procedures. Two

portions of the paper are separated, one for use in the DP determination and one for use in

the moisture determination.
7 Experimental procedure
7.1 Measurement of water content of paper
Measure the water content according to ISO 287 or IEC 60814.

The water content shall be measured at the same time as the Cuen/paper solution is

prepared.
7.2 Determination of viscosity
7.2.1 Number of test specimens

One specimen shall be used in a preliminary experiment to obtain data on which to base a

valid test.

One specimen shall be used for each valid test, unless otherwise specified. If [ν] ⋅ c of the

preliminary experiment is outside of the range 0,5 to 1,5, two test specimens shall be used.

7.2.2 Concentration of the solution

The concentration of the solution to be used is dependent upon the expected DP value as

given in the following table.
Table 2 – DP values of specimen
Specimen condition Approximate resulting
Expected DP
concentration
g/dl or %
New 1 000 to 2 000 0,05 to 0,15
Good 650 to 1 000 0,08 to 0,25
Average 350 to 650 0,15 to 0,45
Aged < 350 0,25 to 0,80

NOTE The purpose of this operation is to achieve a fixed value of the product’s intrinsic viscosity and

concentration which is in the range 0,5 ≤ [ν]⋅c ≤ 1,5 . The higher the product of [ν]⋅c the more accurate its

precision.
---------------------- Page: 14 ----------------------
60450  IEC:2004 – 21 –
7.2.3 Fibre separation

The cellulose fibres need to be separated in order to facilitate dissolution in Cuen. Two

techniques are described as follows.
7.2.3.1 Dry fluffing

Fluff the material in a suitable blender or grinder. Ensure enough sample remains after fluffing

as some sample may be lost during the process. The temperature rise during fluffing must not

cause any detrimental effect to the specimen.

The fluffed sample is left to acclimatize with the atmospheric humidity before determining the

water content.

Weigh the necessary amount of sample to the nearest 0,1 mg according to Table 2 and place

it in a suitable vessel for dissolution. Calculate the mass of dry paper as m .
Add water and allow the fibres to disperse.
7.2.3.2 Wet mulching

Weigh the necessary amount of sample to the nearest 0,1 mg and place in the blender cup

with sufficient distilled/de-ionized water to cover it. Mulch the paper by operating the blender

at approximately 18 000 r/min for about 30 s or until the fibres are well separated. After

mulching, remove the excess water by either centrifuging or using a Grade 3 sintered glass

filter.

Place the swollen paper in a tared vial and weigh it to within ±0,1 mg (m ). Calculate the total

mass of water (i.e. original mass of water plus the mass of water remaining after mulching) by

subtracting the dry paper mass (m ) and the tare mass from m .
D T

Calculate the quantity of water required to make the total water content up to 10,000 g.

Selecting this amount to within ±0,5 mg, use a sufficient amount of this water to rinse any

residual paper out of the centrifuge/filter into the vial and then place the remainder of the

water into the vial. Alternatively, make up to 10,000 g, then weigh to within ±0,5 mg and

calculate the concentration.
7.2.4 Dissolution of specimen

Before use, the Cuen solution sample shall be inspected, refurbished and verified as follows:

• ensure that the solution contains no precipitate by filtering or decanting;
• using the method described in Annex C, verify that the ratio = 2,0 ± 0,1
• in the event of non-conformance, reject the solution and prepare a new sample.

Transfer into the same vial the same volume (±0,1 ml, using a pipette) of Cuen as the quantity

of water already added to the cellulose fibres.
---------------------- Page: 15 ----------------------
60450  IEC:2004 – 23 –

If there is some contact between the solution and the atmospheric air in the vial, flush the vial

with nitrogen and shake by hand to ensure good mixing of the components. Flush the vial

again with nitrogen and seal it to ensure a low oxygen environment. Preferably the vial should

be flushed with nitrogen throughout the whole time of dissolution.

NOTE 1 The solution is placed in a nitrogen environment and sealed in the vial because the alkaline solvent is

susceptible to oxidative degradation.
Mechanically shake or stir the specimen until dissolution is complete.

NOTE 2 The time taken is dependent upon the type of paper and the extent of degradation.

a) For heavily aged papers ( DPν < 350) a shaking time of 1h to 2 h is usually adequate.

b) For most papers ( DP > 350) shaking for a period of 16 h (overnight) usually ensures

complete dissolution.

c) Some types of new or nearly new papers do not dissolve easily at room temperature. The

dissolution rate may be increased by using a magnetic stirrer to stir the specimen at 4 °C,

in a refrigerator overnight. The use of a few glass balls can also aid the dispersion of the

cellulose fibres.

When testing heavily degraded papers ( DP < 150) they should be tested immediately after

dissolution.
7.2.5 Determination of the viscosity
7.2.5.1 Selection and filling of the viscometer tube

Select a viscometer tube and support it in a constant temperature bath at 20 °C ± 0,1 K.

Ensure that the viscometer tube is dry, dust free and flushed thoroughly with nitrogen.

Fill the viscometer according to the manufacturer’s instructions. Figure 2 gives an example of

a viscometer.

During the filling and the following measurement procedure, visually observe the solution to

determine the presence of any undissolved matter. In the event of finding undissolved matter,

reject the solution and repeat the experiment.

Wait for 5 min to 10 min before the first measurement of the viscosity, until the solution has

reached its temperature equilibrium.
7.2.5.2 Measurement procedure

An Ubbelohde viscometer is used as an example (see Figure 2). For other viscometers, see

ISO 3105 as well as the manufacturer’s instructions.

Seal the ventilation tube (1) with a finger, a stopper or with plastic film and apply a vacuum to

the capillary tube (2) until the lower reservoir ( 10), the working capillary (6), the timing bulb

( 5), and the upper reservoir ( 4) are filled.
---------------------- Page: 16 ----------------------
60450  IEC:2004 – 25 –
Remove the vacuum and seal.
Ensure that the liquid separates at the lower end of the capillary.

Measure and record the time interval (t , efflux time) with an accuracy of ±0,5 s for the upper

meniscus to travel between the two timing marks M and M on the timing bulb ( 5).
1 2

Repeat the measurement on the same specimen and record as t . Record the percentage

difference between the two results.
Inspect the resul
...

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