ISO 6721-10:2025

International
Standard
ISO 6721-10
Fourth edition
Plastics — Determination of
2025-04
dynamic mechanical properties —
Part 10:
Complex shear viscosity using a
parallel-plate and a cone-and-plate
oscillatory rheometer
Plastiques — Détermination des propriétés mécaniques
dynamiques —
Partie 10: Viscosité complexe en cisaillement à l'aide d'un
rhéomètre à oscillations à plateaux parallèles ou à géométrie
cône/plan
Reference number
© ISO 2025
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
Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 2
5 Apparatus . 2
5.1 Measurement apparatus .2
5.2 Temperature-controlled enclosure .4
5.3 Temperature measurement and control .4
5.4 Measurement geometry .4
5.4.1 Parallel plates geometry.4
5.4.2 Cone and plate geometry .5
5.5 Calibration .5
6 Sampling . 6
7 Procedure . 6
7.1 Test temperature .6
7.2 Zeroing the gap .6
7.3 Introducing the test specimen .6
7.4 Conditioning the test specimen .7
7.5 Test mode (controlled stress or controlled strain) .7
7.5.1 General .7
7.5.2 Controlled strain mode .7
7.5.3 Controlled stress mode . .7
7.6 Determination of thermal stability of sample material .7
7.7 Determination of region of linear-viscoelastic behaviour .8
7.7.1 Controlled-strain mode .8
7.7.2 Controlled-stress mode .8
7.7.3 Confirmation of linear-viscoelastic behaviour .8
7.8 Frequency sweep .8
7.9 Temperature sweep .9
7.10 Air entrapment .9
8 Expression of results . 9
8.1 Symbols used .9
8.2 Calculation of complex shear modulus and complex shear viscosity .10
9 Precision .11
10 Test report .12
Annex A (informative) Uncertainty limits . 14
Annex B (informative) Verification of rheometer performance .16
Bibliography .20

iii
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 61, Plastics, Subcommittee SC 5, Physical-
chemical properties.
This fourth edition cancels and replaces the third edition (ISO 6721-10:2015), which has been technically
revised.
The main changes are as follows:
— rheometer geometry has been described in detail for both parallel-plate and cone-and-plate geometry;
— in 7.5, controlled stress mode and controlled strain mode have been defined in separate subclauses.
A list of all parts in the ISO 6721 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
International Standard ISO 6721-10:2025(en)
Plastics — Determination of dynamic mechanical
properties —
Part 10:
Complex shear viscosity using a parallel-plate and a cone-
and-plate oscillatory rheometer
1 Scope
This document specifies the general principles of a method for determining the dynamic rheological
-1 -1
properties of polymer melts at angular frequencies typically in the range of 0,01 rad s to 100 rad s by
means of an oscillatory rheometer with a parallel-plate or a cone-and-plate geometry. Angular frequencies
outside this range can also be used.
The method is applicable for determining values of the following dynamic rheological properties: complex
shear viscosity η*, dynamic shear viscosity η', the out-of-phase component of the complex shear viscosity η”,
complex shear modulus G*, shear loss modulus G”, shear storage modulus G', phase angle δ, and loss factor
tanδ. It is suitable for measuring complex shear viscosity values typically up to ~10 MPa s.
NOTE The shear loss modulus G´´ is sometimes also called viscous shear modulus and the shear storage modulus G´
is sometimes also called elastic shear modulus.
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 472, Plastics — Vocabulary
ISO 5725-1, Accuracy (trueness and precision) of measurement methods and results — Part 1: General principles
and definitions
ISO 6721-1, Plastics — Determination of dynamic mechanical properties — Part 1: General principles
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 472, ISO 5725-1, ISO 6721-1 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 https:// www .electropedia .org/
3.1
controlled-strain mode
testing by applying a sinusoidal angular displacement of constant amplitude

3.2
controlled-stress mode
testing by applying a sinusoidal torque of constant amplitude
3.3
complex shear viscosity
η*
ratio of dynamic stress, given by σ(t) = σ exp (iωt), and dynamic rate of strain where the shear strain γ t
()
is given by γ(t) = γ exp {i(ωt - δ)
...