CEN ISO/TR 20659-2:2024

SLOVENSKI STANDARD
01-september-2024
Reološke preskusne metode - Osnovni principi in medlaboratorijske primerjave -
2. del: Določanje spremembe strukture v odvisnosti od časa (tiksotropija) (ISO/TR
20659-2:2024)
Rheological test methods - Fundamentals and interlaboratory comparisons - Part 2:
Determination of the time-dependent structural change (thixotropy) (ISO/TR 20659-
2:2024)
Méthodes d'essai rhéologiques - Principes fondamentaux et comparaisons
interlaboratoires - Partie 2: Détermination de la variation structurelle dans le temps
(thixotropie) (ISO/TR 20659-2:2024)
Ta slovenski standard je istoveten z: FprCEN ISO/TR 20659-2
ICS:
87.040 Barve in laki Paints and varnishes
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

Technical
Report
ISO/TR 20659-2
First edition
Rheological test methods —
2024-03
Fundamentals and interlaboratory
comparisons —
Part 2:
Determination of the time-
dependent structural change
(thixotropy)
Méthodes d'essai rhéologiques — Principes fondamentaux et
comparaisons interlaboratoires —
Partie 2: Détermination de la variation structurelle dans le temps
(thixotropie)
Reference number
ISO/TR 20659-2:2024(en) © ISO 2024

ISO/TR 20659-2:2024(en)
© ISO 2024
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Published in Switzerland
ii
ISO/TR 20659-2:2024(en)
Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Measuring technique for the determination of thixotropy . 1
4.1 Conditions for the measuring technique .1
4.2 Flow curves, with evaluation of the hysteresis area (rotational test) .3
4.2.1 Specification of the measuring profile .3
4.2.2 Evaluation .5
4.3 Step test with recovery, as a rotational test with controlled shear rate .7
4.3.1 Specification of the measuring programme .7
4.3.2 Evaluation .8
4.4 Step test with recovery, as a rotational test with alternating controlled shear stress
and shear rate .9
4.4.1 Specification of the measuring programme .9
4.4.2 Evaluation .10
4.5 Step test with recovery, as a combined oscillatory and rotational test with controlled
shear strain and shear rate, respectively .10
4.5.1 Specification of the measuring programme .10
4.5.2 Evaluation . .11
5 Comparative testing programme . 14
5.1 Aim of the comparative testing programme.14
5.2 Performance of the tests .14
5.2.1 Preliminary test .14
5.2.2 Comparative testing programme . 15
5.3 Evaluation . 15
6 Result.16
6.1 General .16
6.2 Measurement of the Newtonian reference sample .17
6.2.1 Flow curve .17
6.3 Step test with specification of the shear rate in measuring segments 1 and 3 .17
6.4 Step test with controlled shear stress in measuring segments 1 and 3 .18
6.5 Step test as oscillatory test in measuring segments 1 and 3 .18
7 Analysis . .18
Annex A (informative) Details of the comparative testing programme .20
Annex B (informative) Explanatory notes .34
Bibliography .36

iii
ISO/TR 20659-2:2024(en)
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 document 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).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent
rights in respect thereof. As of the date of publication of this document, ISO had not received notice of (a)
patent(s) which may be required to implement this document. However, implementers are cautioned that
this may not represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.
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 35, Paints and varnishes, Subcommittee SC 9,
General test methods for paints and varnishes.
A list of all parts in the ISO 20659 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
Technical Report ISO/TR 20659-2:2024(en)
Rheological test methods — Fundamentals and
interlaboratory comparisons —
Part 2:
Determination of the time-dependent structural change
(thixotropy)
1 Scope
This document gives information on an interlaboratory comparison for the determination of the time-
dependent structural change (thixotropy) using rheological test methods. Thixotropy is the reversible, time-
dependent decrease of shear viscosity η at a constant shear rate γ or shear stress τ.
This document provides examples of fields of application, in which important material properties can be
characterized by the thixotropy. These fields of application include:
— effectiveness of rheological additives and thixotropic agents, respectively;
— stability of the structure at rest (e.g. behaviour when starting to pump);
— wet film thickness after processing;
— levelling and sagging behaviour (e.g. without brushmarks or sag formation);
— orientation of effect pigments.
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 3219-1, Rheology — Part 1: Vocabulary and symbols for rotational and oscillatory rheometry
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 3219-1 apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
4 Measuring technique for the determination of thixotropy
4.1 Conditions for the measuring technique
Clause 4 briefly describes methods that are currently in use. In principle, the thixotropy depends on the
temperature, the pressure, and the thermal and mechanical history of the material. A detailed specification
of the measuring profile is therefore a precondition for reproducible measurements and comparable

ISO/TR 20659-2:2024(en)
evaluation; this applies especially for the level of shear load (shear rates, shear stresses, shear strain,
oscillation frequencies), the duration of the individual measuring segments and the number of measuring
points.
Thixotropy can be determined by rotational as well as by oscillatory tests. Measuring devices equipped
with a mechanical bearing or air bearing are suitable for rotational tests. For oscillatory tests, a rheometer
with air bearing is used. It is essential to ensure that the measuring device is used in combination with
the suitable measuring geometry, i.e. in accordance
...