EN ISO 307:2019

SLOVENSKI STANDARD
01-september-2019
Nadomešča:
SIST EN ISO 307:2007
SIST EN ISO 307:2007/A1:2014
Polimerni materiali - Poliamidi - Določanje števila viskoznosti (ISO 307:2019)
Plastics - Polyamides - Determination of viscosity number (ISO 307:2019)
Kunststoffe - Polyamide - Bestimmung der Viskositätszahl (ISO 307:2019)
Plastiques - Polyamides - Détermination de l'indice de viscosité (ISO 307:2019)
Ta slovenski standard je istoveten z: EN ISO 307:2019
ICS:
83.080.20 Plastomeri Thermoplastic materials
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EN ISO 307
EUROPEAN STANDARD
NORME EUROPÉENNE
May 2019
EUROPÄISCHE NORM
ICS 83.080.20 Supersedes EN ISO 307:2007
English Version
Plastics - Polyamides - Determination of viscosity number
(ISO 307:2019)
Plastiques - Polyamides - Détermination de l'indice de Kunststoffe - Polyamide - Bestimmung der
viscosité (ISO 307:2019) Viskositätszahl (ISO 307:2019)
This European Standard was approved by CEN on 19 March 2019.

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, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania,
Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, 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
© 2019 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 307:2019 E
worldwide for CEN national Members.

Contents Page
European foreword . 3

European foreword
This document (EN ISO 307:2019) 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 November 2019, and conflicting national standards
shall be withdrawn at the latest by November 2019.
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 307:2007.
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, Former Yugoslav Republic of Macedonia,
France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta,
Netherlands, Norway, Poland, Portugal, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland,
Turkey and the United Kingdom.
Endorsement notice
The text of ISO 307:2019 has been approved by CEN as EN ISO 307:2019 without any modification.

INTERNATIONAL ISO
STANDARD 307
Sixth edition
2019-04
Plastics — Polyamides —
Determination of viscosity number
Plastiques — Polyamides — Détermination de l'indice de viscosité
Reference number
ISO 307:2019(E)
©
ISO 2019
ISO 307:2019(E)
© ISO 2019
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.
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Published in Switzerland
ii © ISO 2019 – All rights reserved

ISO 307:2019(E)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 3
5 Reagents and materials . 3
5.1 Solvents and reagents . 3
5.2 Cleaning liquids . 4
6 Apparatus . 4
7 Preparation of test samples . 5
7.1 General . 5
7.2 Samples containing less than 98 % (by mass) polyamide . 6
8 Calculation of test portion . 6
9 Selection of solvent . 6
10 Procedure. 7
10.1 Cleaning of the viscometer . 7
10.2 Preparation of test solution . 7
10.2.1 General. 7
10.2.2 Volumetric method . 8
10.2.3 Volumetric method, in exact relation to the polymer content . 8
10.2.4 Gravimetric method, in exact relation to the polymer content . 8
10.3 Measurement of flow times . 9
11 Expression of results .10
12 Repeatability and reproducibility .11
13 Relationship between the viscosity number determined in 96 % (by mass) sulfuric
acid solution and the viscosity determined in various solvents .11
14 Test report .11
Annex A (informative) Determination of the concentration of commercial sulfuric
acid(95 % to 98 %) and adjustment to 96 % by titration.13
Annex B (informative) Determination of the concentration of sulfuric acid (95 % to 98 %)
and adjustment to 96 % by flow time measurement in a small capillary viscometer .16
Annex C (informative) Determination of the concentration of commercial formic acid and
adjustment to 90 % by titration .18
Annex D (informative) Determination of the concentration of commercial formic acid and
adjustment to 90 % by density measurement .20
Annex E (informative) Relationship between the viscosity number determined in 96 % (by
mass) sulfuric acid solution and the viscosity determined in various solvents .23
Bibliography .35
ISO 307:2019(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 on 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 the following
URL: www .iso .org/iso/foreword .html.
This document was prepared by Technical Committee ISO/TC 61, Plastics, Subcommittee SC 9,
Thermoplastic materials.
This sixth edition cancels and replaces the fifth edition (ISO 307:2007), which has been technically
revised to update Clause 9. It also incorporates the Amendment ISO 307:2007/Amd.1:2013.
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 2019 – All rights reserved

ISO 307:2019(E)
Introduction
This document specifies a method for the determination of the viscosity number of dilute solutions of
polyamides in certain specified solvents. The determination of the viscosity number of a polyamide
provides a value that depends on the molecular mass of the polymer, but does not strictly correlate with
the molecular mass.
Additives such as flame-retardants and modifiers often interfere with the viscosity measurement and
may have an increasing effect on the viscosity number in one solvent and a decreasing effect in another
solvent. The extent of the effect depends among others on the additive, the quantity of the additive, the
presence of other additives and reactions.
The viscosity number of a polyamide sample containing additives that interfere with the viscosity
measurement, measured in a specific solvent, represents a specific viscosity number for the polyamide
under investigation and the actual measurement conditions. The measured viscosity number cannot, in
principle, be converted from one solvent to another and is only suitable for intra-product comparison.
The viscosity number of pure polyamides or polyamides containing additives that do not interfere with
the viscosity measurement can be converted from one solvent to another by a general relationship for
that type of polyamide.
Polyamide test samples for the determination of the viscosity number are intended to be completely
soluble in the solvents mentioned. Additives contained in them, like glass and carbon fibres, are to be
separated from the solution.
As it is not possible to distinguish between extractables such as caprolactam, its oligomers and other
extractable additives, these are considered as an essential part of the sample and therefore included in
the sample mass.
The test method is applicable for production control and intra-product comparison even if the polyamide
contains additives that do interfere with the viscosity measurement. However, it should be realised that
deviations of the viscosity number can be caused by either the polyamide itself, effects caused by the
additives present, or a combination of these.
The interference of additives with the viscosity determination can be checked by comparing the
viscosity results of dry blend mixtures and regular production samples at several concentrations of the
additive under investigation and in the solvents concerned. It should be noted that the other additives
present also could influence the viscosity result.
The repeatability and reproducibility of the test method are strongly influenced by the correctness of
the solvent concentration, the use of the Hagenbach correction if applicable and the temperature of the
solvent on diluting the sample solution.
In this document, two specific viscometers are recommended. Furthermore, other types of viscometers
listed in ISO 3105 may also be used, provided that the results are demonstrated to be equivalent to
those measured with the recommended viscometers. It is to be expected that in the next revision the
use of the other types of viscometers will be excluded.
INTERNATIONAL STANDARD ISO 307:2019(E)
Plastics — Polyamides — Determination of viscosity number
1 Scope
This document specifies a method for the determination of the viscosity number of dilute solutions of
polyamides in certain specified solvents.
The method is applicable to the polyamides designated PA 46, PA 6, PA 66, PA 69, PA 610, PA 612, PA 11,
PA 12, PA 6T/66, PA 6I/6T, PA 6T/6I/66, PA 6T/6I, PA 6I/6T/66 and PA MXD6 as defined in ISO 16396-1,
as well as to copolyamides, compounds of polyamides and other polyamides that are soluble in one of
the specified solvents under the specified conditions.
The method is not applicable to polyamides produced by anionic polymerization of lactams or produced
with cross-linking agents; such polyamides are normally insoluble in the specified solvents.
The viscosity number is determined by the general procedure specified in ISO 1628-1, observing the
particular conditions specified in this document.
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 1042, Laboratory glassware — One‑mark volumetric flasks
ISO 1628-1, Plastics — Determination of the viscosity of polymers in dilute solution using capillary
viscometers — Part 1: General principles
ISO 3105, Glass capillary kinematic viscometers — Specifications and operating instructions
ISO 3451-4, Plastics — Determination of ash — Part 4: Polyamides
ISO 15512, Plastics — Determination of water content
ISO 16396-1, Plastics — Polyamide (PA) moulding and extrusion materials — Part 1: Designation system,
marking of products and basis for specifications
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 1628-1 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
viscosity number
value calculated by the following formula for flow times long enough so that no kinetic
energy correction need be applied:
 
η 1
VN=−1 ×
 
η c
 
ISO 307:2019(E)
where
η is the viscosity of a solution of the polymer in a specified solvent, in Pa/ s or N/m ·s;
η is the viscosity of the solvent, expressed in the same units as η;
η
is the relative viscosity of a solution of the polymer in a specified solvent;
η
c is the concentration, in g/ml, of the polymer in the solution;
VN is the viscosity number, expressed in ml/g
Note 1 to entry: The formula is applicable to the viscometers of the suspended level Ubbelohde type, complying
with the requirements of ISO 3105.
Note 2 to entry: For a particular viscometer used and with substantially equal densities of the solvent and
solution, the viscosity ratio is given by the flow time ratio for the solution concentration:
η
η
η
where is the relative viscosity of a solution of the polymer in a specified solvent.
η
Note 3 to entry: As mentioned in ISO 3105, in case of flow times below 200 s and 60 s, for type 1 and type 2
Ubbelohde viscometers respectively, a correction for kinetic correction has to be applied: the so-called Hagenbach
correction. For other types of viscometers, the kinetic energy correction has to be applied if the correction is
≥0,15 %.
Note 4 to entry: The flow time of a liquid is related to its viscosity by the formula:
η  A 
vC== ×−t
 
ρ
t 
where
η is the viscosity of a solution of the polymer in a specified solvent, in Pa/ s or N/m ⋅s;
v is the viscosity/density ratio, in metres squared per second;
ρ is the density of the liquid, in kilograms per cubic metre;
C is the constant of the viscometer, in metres squared per second squared;
t is the flow time, in seconds;
A is the parameter of the kinetic correction in metres squared seconds.
Note 5 to entry: For a particular viscometer used, with substantially equal densities of the solvent and solution
and a given kinetic factor, the viscosity ratio
η
η
is given by the flow time ratio for the solution concentration in this document, each flow time reduced with the
so-called Hagenbach correction (in seconds) given by the manufacturer for the viscometer as a function of the
flow time.
2 © ISO 2019 – All rights reserved

ISO 307:2019(E)
4 Principle
The times of flow of a solvent and a solution of the polyamide at a concentration of 0,005 g/ml in the
solvent are measured at 25 °C, the same viscometer being used for both measurements. The viscosity
number is calculated from these measurements and from the known concentration of the solution.
5 Reagents and materials
5.1 Solvents and reagents
Only reagents of recognised analytical grade and only distilled water or water of equivalent purity shall
be used.
SAFETY STATEMENT — Persons using this document should be familiar with laboratory practice.
This document does not purport to address all of the safety concerns associated with its use.
Some chemicals, for example 1,1,2,2-tetrachloroethane, are prohibited in some countries. It is
the responsibility of the user to establish appropriate safety and health practices and to ensure
compliance with any regulatory requirements.
WARNING — Avoid contact with the skin and inhalation of any vapours of the solvents and
cleaning liquids.
5.1.1 Sulfuric acid, 96,00 % ± 0,20 % (by mass) solution.
For the determination of the concentration of commercial sulfuric acid (95 % to 98 %) and adjustment
to 96,00 %, is referred to Annexes A and B.
5.1.2 Formic acid, 90,00 % ± 0,15 % (by mass) solution.
The solvent shall be stored in a brown glass bottle. Its concentration shall be checked at least every
2 weeks. It shall not contain more than 0,2 % acetic acid or methyl formate.
For the determination of the concentration of commercial formic acid (90 %) and adjustment to
90,00 % ± 0,15 %, is referred to Annexes A and B.
5.1.3 m-Cresol, meeting the following specifications:
— appearance: clear and colourless;
— m-cresol content: 99 % (by mass) min.;
— o-cresol content: 0,3 % (by mass) max.;
— water content: 0,13 % (by mass) max.
m-Cresol of the required purity may be obtained by distillation of chemically pure m-cresol, preferably
in vacuum. If distillation is used, nitrogen shall be used for pressure compensation to avoid oxidation.
Its purity may be checked by gas chromatography. The solvent shall be stored in a brown glass bottle.
5.1.4 Phenol, 99 % (by mass) min.
5.1.5 1,1,2,2-tetrachloroethane, 99,5 % (by mass) min.
5.1.6 Phenol/1,1,2,2-tetrachloroethane.
Weigh out 6 parts by mass of phenol (5.1.4) and dissolve in 4 parts by mass of 1,1,2,2-tetrachloroethane
(5.1.5). Work to an accuracy of 1 % or better in the weighings. Stir the mixture in its original container
at 23 °C to prevent crystallization.
ISO 307:2019(E)
5.1.7 Orthophosphoric acid, 85 % (by mass), density 1,71 g/ml.
5.1.8 m-Cresol/phosphoric acid.
Transfer 50 ml of m-cresol (5.1.3) into a weighing flask (6.4) and add with a glass pipette (6.5) 0,14 ml
of orthophosphoric acid (5.1.7). Close the flask and stir with a magnetic stirrer for 30 min at 100 °C.
Add the solution to approximately 800 ml of m-cresol in a volumetric flask while continuously stirring.
Rinse the weighing flask several times with m-cresol and add this to the m-cresol solution. Remove the
magnetic stirrer and dilute to the mark. Stir the solution for 30 min.
5.2 Cleaning liquids
5.2.1 Chromic acid solution, prepared by mixing equal volumes of sulfuric acid (96 %, ρ = 1,84 g/
ml, industrial quality) and a saturated solution of potassium dichromate (99,5 %, industrial quality). If
required, the chromic acid solution may be replaced by other equally effective cleaning liquids.
5.2.2 Acetone (99,5 %, industrial quality), or any water-soluble low-boiling-point solvent (industrial
quality).
6 Apparatus
6.1 Vacuum drying cabinet, with pressure less than 100 kPa.
6.2 Balance, accurate to 0,1 mg.
6.3 Volumetric flask, of capacity 50 ml or 100 ml, complying with the requirements of ISO 1042, fitted
with a ground-glass stopper.
6.4 Weighing flask, 100 ml, fitted with a ground-glass stopper.
6.5 Pipette, 0,2 ml, readable to 0,01 ml.
6.6 Shaking apparatus or magnetic stirrer.
6.7 Sintered‑glass filter, with a pore size between 40 μm and 100 μm (grade P 100), or stainless-steel
sieve, with apertures of about 0,075 mm .
6.8 Viscometer, of the suspended-level Ubbelohde type, complying with the requirements of ISO 3105.
The essential dimensions of the viscometer are shown in Figure 1. For use with the formic acid solution
(5.1.2), the inside diameter of the capillary shall be 0,58 mm ± 2 % (complying with the requirements
of size No. 1 of ISO 3105). For use with the sulfuric acid solution (5.1.1) or m-cresol (5.1.3), the inside
diameter of the capillary shall be 1,03 mm ± 2 % (complying with the requirements of size No. 2 of
ISO 3105).
Other types of viscometer listed in ISO 3105 may be used, provided that the results are demonstrated
to be equivalent to those of the Ubbelohde viscometers specified above. In cases of dispute, the
recommended viscometer shall be used.
ISO 1628-1 shall be followed on selecting other type(s) of viscometer.
In this document, the No. 1 and No. 2 Ubbelohde viscometers according to ISO 3105 are recommended.
It is to be expected that at the next 5 year revision only these two viscometers will be allowed.
4 © ISO 2019 – All rights reserved

ISO 307:2019(E)
Dimensions in millimetres
Key
1 graduation marks for a volume of 4 ml ± 0,2 ml
2 capillary tube of diameter 0,58 mm ± 2 % for formic acid; 1,03 mm ± 2 % for sulfuric acid and m-cresol
3 filling marks
Figure 1 — Ubbelohde viscometer
6.9 Thermometer, a liquid-in-glass, “total immersion” thermometer, reading to 0,05 °C in the range
to be used and in a known state of calibration, is suitable. Other thermometric devices of at least equal
precision may be used.
6.10 Thermostatic bath, capable of being maintained and controlled at 25,00 °C ± 0,05 °C.
6.11 Time device, for example a stop-watch, accurate to 0,1 s.
6.12 Centrifuge.
7 Preparation of test samples
7.1 General
Polyamide test samples for the determination of the viscosity number shall be soluble in the solvents
mentioned, except for additives present, such as reinforcement or fillers.
The sample should contain less than 0,28 % moisture. If it contains more than 0,28 % moisture the
sample should be dried. Generally, drying at 70 °C in a vacuum for 4 h to 6 h is adequate.
NOTE The dissolution time of some samples might be too long for adequate production control. In these cases,
the material can be ground in order to shorten the dissolution time, provided that the results are demonstrated
to be equivalent.
ISO 307:2019(E)
7.2 Samples containing less than 98 % (by mass) polyamide
For samples containing more than 2 % additives, the amount of additives shall be either determined
by a specifically developed method or taken from the recipe. The method of determination shall be
mentioned in the report.
The water content of the sample shall be determined according to ISO 15512. The ash content shall be
determined according to ISO 3451-4.
The correct amount of polyamide sample to be weighed out is calculated using Formula (1).
Some additives, such as antimony trioxide and zinc sulfide, are completely volatilized during the
calcination according to ISO 3451-4. Materials reinforced with glass fibre contain flame-retardant
antimony trioxide and/or other volatilizable additives. If the total content of additives is more than
2 %, these shall be brought into account by the formulation of the sample for calculating the exact test
portion.
NOTE For production quality control purposes, the laboratory response time for determination of the
additives might be too long for adequate production control. In these cases, the additive(s) content in the
production recipe can be used for calculating the amount of sample, if the total variation of the polymer content
is less than 4 % (by mass), e.g. 65 % PA would range from 63 % to 67 %.
8 Calculation of test portion
Calculate the mass m , in milligrams, of the test portion according to Formula (1):
c
m = (1)
c
www++
12 3
1−
where
w is the water content of the sample, expressed as a percentage by mass, determined in accord-
ance with ISO 15512;
w is the content of inorganic materials (for example fillers or glass fibres) in the sample, ex-
pressed as a percentage by mass, determined in accordance with ISO 3451-4;
w is the content of other materials (for example other polymers, such as polyolefins, or additives,
such as flame-retardants), expressed as a percentage by mass, determined by appropriate
methods.
For the content of the additive(s) which cannot be determined, the content according to the product
recipe shall be used.
9 Selection of solvent
The value of the viscosity number of a polyamide depends on the solvent used.
The solvent or solvents to be used for a particular polyamide are specified below.
a) For PA 6, PA 46, PA 66, PA 69, PA 610, PA MXD6 and corresponding copolyamides, formic acid
solution or sulfuric acid shall be used as solvent. For polyamides containing additives that liberate
gases in acidic solvents, m-cresol shall be used as the solvent. In cases of dispute, formic acid shall
be used as a solvent.
b) For PA 612, the sulfuric acid solution or m-cresol shall be used as solvent. In cases of dispute,
m-cresol shall be used.
6 © ISO 2019 – All rights reserved

ISO 307:2019(E)
c) For PA 11, PA 12, PA 11/12 copolymers, m-cresol shall be used as a solvent. In cases of dispute about
ammonium carboxylate influencing viscosity through the formation of end-group associations,
additional measurements shall be made using m-cresol/phosphoric acid solution as a solvent
(5.1.8).
d) For PA 6T/66, PA 6I/66, PA 6I/6T, PA 6T/6I/66, PA 6T/6I, PA 6I/6T/66, m-cresol, phenol/1,1,2,2-
tetrachloroethane or sulfuric acid shall be used as solvent. In cases of dispute, m-cresol shall be used.
e) For other polyamides, any of the mentioned solvents may be used.
NOTE 1 In the future revision of this document, it is the intention that for a given PA only one solvent will be
allowed.
NOTE 2 Viscosity numbers of polyamides not containing additives that interfere with the viscosity
measurement can be converted from one solvent to another by a general interconversion formula. Graphs for
interconversion are mentioned in Clause 13 and presented in Annex E. The reliability of the conversions is
discussed in Annex E.
10 Procedure
10.1 Cleaning of the viscometer
Clean the viscometer (6.8) prior to the first use, again after discordant readings (for example, when
two successive determinations of the efflux time of the solvent differ by more than 0,4 s) and, further,
at intervals during regular use. For this purpose, allow it to stand for at least 12 h filled with a cleaning
agent (5.2), for example chromic acid solution (5.2.1). Remove the cleaning agent, rinse the viscometer
with water then with acetone (5.2.2) and dry, for example by a slow stream of filtered air or in the
vacuum drying cabinet (6.1).
After each determination, drain the viscometer, rinse with the solvent, then with water, followed by, for
example, acetone (5.2.2) and dry as described above.
However, if the next solution to be measured is of a polyamide of the same type and of a similar viscosity,
it is permissible to drain the viscometer, wash it with the solution to be measured, and then fill it with
this solution.
NOTE In the case of, for example, production control and automated flow time measurement the viscometer
can be filled with the solvent in anticipation of the next sample.
10.2 Preparation of test solution
10.2.1 General
Three different methods for preparing the test solution are described in this document. The first
volumetric method (see 10.2.2), without correction for the volume of insoluble additives in the test
portion, is equal to the method described in the previous version of this document (ISO 307:2007). For
practical reasons, test portion masses of (m ± 5) mg are allowed. For pure polyamide, this results in
c
a concentration range of 0,004 9 g/ml to 0,005 1 g/ml. The actual polymer concentration is taken into
account in the calculation of the viscosity number. For samples containing insoluble additives, a test
portion of exactly the calculated mass will give a solution that is almost equal to 0,005 g/ml.
The second volumetric method (see 10.2.3) and the gravimetric method (see 10.2.4) take into account
the insoluble additives and the polyamide volume. The latter two methods are often used in combination
with (semi-)automatic viscosity measurement equipment.
NOTE For polyamide samples containing only insoluble additives, the concentration of the solution prepared
according to the volumetric or gravimetric method will be exactly 5 mg/ml.
ISO 307:2019(E)
10.2.2 Volumetric method
Weigh, to the nearest 0,2 mg, a test portion of mass m mg, where m lies in the range (m ± 5) mg where
t t c
m is the mass calculated in accordance with Formula (1), working rapidly to minimize moisture pick-up
c
by the polymer. If the weighing takes more than 2 min, reject the material and begin another weighing.
Transfer the test portion to the 50 ml volumetric flask (6.3) and add about 40 ml of the solvent (see
Clause 9). Close the flask and shake the contents, or stir with the magnetic stirrer (6.6), until the
polymer has dissolved. This may take from approximately 0,5 h to several hours, depending on the
type of polyamide and the particle size of the test portion. When sulfuric acid or formic acid solution
is used as the solvent, the temperature shall not exceed 30 °C. When m-cresol or phenol/1,1,2,2-
tetrachloroethane is used as the solvent, the temperature may be raised to 95 °C to 100 °C. If, in the
latter case, dissolution takes more than 2 h, this shall be reported. For PA 6T/66, suitable conditions
have been found to be 2 h at 90 °C.
When dissolution is complete, cool the solution to 25 °C ± 2 °C, dilute to the mark with the solvent and
mix well. If the magnetic stirrer (6.6) is used, remove it from the solution before dilution and rinse it
with the solvent, adding the rinsings to the flask before further dilution.
10.2.3 Volumetric method, in exact relation to the polymer content
Weigh, to the nearest 0,2 mg, a test portion of mass m mg, where m lies in the range (m ± 10 %) mg,
t t c
where m is the mass calculated in accordance with Formula (1), working rapidly to minimize moisture
c
pick-up by the polymer. If the weighing takes more than 2 min, reject the material and begin another
weighing.
Transfer the test portion to the 100 ml volumetric flask (6.3) or weighing bottle (6.4) and add the volume
of the solvent (see Clause 9) required to prepare a concentration of 0,50 g of sample per 100 ml of
solution. The volume of solvent to be added is corrected for the volume of the soluble mass of the sample.
The solvent shall be added by means of a suitable dosing device (e.g. a burette accurate to 0,01 ml). Close
the flask and shake the contents, or stir with the magnetic stirrer (6.6), until the polymer has dissolved.
This may take from approximately 0,5 h to several hours, depending on the type of polyamide and the
particle size of the test portion. When sulfuric acid or formic acid solution is used as the solvent, the
temperature shall not exceed 30 °C. When m-cresol or phenol/1,1,2,2-tetrachloroethane is used as the
solvent, the temperature may be raised to 95 °C to 100 °C. If, in the latter case, dissolution takes more
than 2 h, this shall be reported. For PA 6T/66, suitable conditions have been found to be 2 h at 90 °C.
When dissolution is complete, cool the solution to 25 °C ± 2 °C.
EXAMPLE
Mass of polyamide in the sample 275 mg
Polyamide density 1,130 0 kg/dm
Volume of the polyamide mass 0,275 g/1,130 0 g/ml = 0,243 4 ml
Volume of solvent to be added (275/250) × 50 − 0,243 4 = 54,76 ml
10.2.4 Gravimetric method, in exact relation to the polymer content
Weigh, to the nearest 0,2 mg, a test portion of mass m mg, where m lies in the range (m ± 10 %) mg,
t t c
where m is the mass calculated in accordance with Formula (1), working rapidly to minimize moisture
c
pick-up by the polymer. If the weighing takes more than 2 min, reject the material and begin another
weighing.
Transfer the test portion to a 100 ml volumetric flask (6.3) or weighing bottle (6.4) and add the mass
of solvent (see Clause 9) required to prepare a concentration of 0,50 g of sample per 100 ml of solution.
The mass of solvent to be added is corrected for the volume of the soluble mass of the sample. Close the
flask and shake the contents, or stir with the magnetic stirrer (6.6), until the polymer has dissolved.
This may take from approximately 0,5 h to several hours, depending on the type of polyamide and the
8 © ISO 2019 – All rights reserved

ISO 307:2019(E)
particle size of the test portion. When sulfuric acid or formic acid solution is used as the solvent, the
temperature shall not exceed 30 °C. When m-cresol or phenol/1,1,2,2-tetrachloroethane is used as the
solvent, the temperature may be raised to 95 °C to 100 °C. If, in the latter case, dissolution takes more
than 2 h, this shall be reported. For PA 6T/66, suitable conditions have been found to be 2 h at 90 °C.
When dissolution is complete, cool the solution to 25 °C ± 2 °C.
EXAMPLE
Mass of polyamide in the sample 275 mg
Density of polyamide 1,130 0 kg/dm
Density of solvent 1,204 4 kg/dm
Volume of the polyamide mass 0,275 g/1,130 0 g/ml = 0,243 4 ml
Volume of solvent to be added (275/250) × 50 − 0,243 4 = 54,76 ml
Mass of solvent to be added 54,76 ml × 1,204 4 = 65,95 g
NOTE 1 An automated weighing system for preparing the sample solution is often used in production control.
NOTE 2 In the case of polyamides with extremely high relative molecular masses, solutions free from the
so-called streaking phenomenon cannot always be obtained, in spite of prolonged periods of shaking or stirring.
Such test solutions can only be used for mutual comparison with similar products.
10.3 Measurement of flow times
Determine the mean flow time of the solvent in the same viscometer and in the same manner as that of
the solution. The flow times of the solvents shall be determined at least once each day that they are used,
or at a different frequency if statistically validated by the laboratory. If the flow time of a solvent differs
by more than 0,5 % from the initial value at the time of preparation, the solvent shall be discarded and
fresh solvent prepared.
Filter the solution through the sintered-glass filter (6.7) or the metal sieve into tube L of the viscometer
−1
(see Figure 1). Alternatively, centrifuge the solution at a rotational frequency of approximately 50 s
and pour the clear supernatant liquid into the viscometer (6.8). The volume of liquid shall be such that,
after draining, the level lies between the filling marks. For hand-filled viscometers, the filling should
preferably be done with the viscometer out of the thermostatic bath (6.10) to avoid contamination of
the bath in case of accidental spills.
Mount the viscometer in the thermostatic bath maintained at 25,00 °C ± 0,05 °C ensuring that tube N
is vertical and that the upper graduation mark E is at least 30 mm below the surface of the liquid in the
bath. Allow at least 15 min for the charged viscometer to attain the temperature of the bath.
Close tube M and blow or draw the liquid into the upper bulb of tube N using a rubber bulb or similar
equipment. Close tube N. Open tube M so that the liquid drops away from the lower end of the capillary
tube. Open tube N and measure the flow time, to the nearest 0,2 s, as the time taken for the bottom
of the meniscus to pass from mark E to mark F. With cloudy solutions, view the top of the meniscus.
Repeat the measurement of the flow time until two successive values agree within 0,25 %. Take the
mean of these two values as the flow time of the solution.
With each polyamide sample, carry out at least two determinations of the viscosity number, using a
fresh solution each time, until two successive values meet the repeatability requirement corresponding
to the solvent used (see Clause 12). Report the mean of these two values, rounded off to the nearest
whole number, as the viscosity number of the sample. If two successive determinations of the solution
mean flow time differ by more than 0,5 %, clean the viscometer (see 10.1).
When necessary, filter the solution of the sample through a filter (6.7) before making the measurement.
Any glass fibres contained in the sample will sediment completely after 3 h to 4 h. In such cases, the test
solution can be decanted for the measurement and thus does not need to be filtered.
ISO 307:2019(E)
For automated solution-viscosity-measurement equipment, the procedure may differ from the
described method. However, the requirements concerning the measurement solution, the equipment,
bath temperature and the flow times shall be maintained in all respects.
For production qua
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