ISO 6721-6:2019

INTERNATIONAL ISO
STANDARD 6721-6
Second edition
2019-04
Plastics — Determination of dynamic
mechanical properties —
Part 6:
Shear vibration — Non-resonance
method
Plastiques — Détermination des propriétés mécaniques
dynamiques —
Partie 6: Vibration en cisaillement — Méthode hors résonance
Reference number
©
ISO 2019
© ISO 2019
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ii © ISO 2019 – All rights reserved

Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 1
5 Apparatus . 2
5.1 Loading assembly . 2
5.1.1 General. 2
5.1.2 Load stage . 2
5.1.3 Transducers. 2
5.2 Electronic data-processing equipment . 3
5.3 Temperature measurement and control . 3
5.4 Devices for measuring test specimen dimensions . 3
6 Test specimens. 3
6.1 General . 3
6.2 Shape and dimensions . 3
6.3 Preparation of polymer specimens . 3
7 Number of test specimens . 3
8 Conditioning . 3
9 Procedure. 4
9.1 Test atmosphere . 4
9.2 Measuring the cross-section of the polymer specimen . 4
9.3 Clamping the test assembly . 4
9.4 Varying the temperature . 4
9.5 Performing the test. 4
10 Expression of results . 5
10.1 Symbols . 5
10.2 Calculation of the shear storage modulus G′ . 5
10.2.1 General. 5
10.2.2 Avoidance of test assembly resonance. 6
10.2.3 Correction for transducer resonance . 6
10.2.4 Correction for apparatus compliance . 6
10.3 Calculation of the shear loss factor tan δ . 7
G
10.4 Calculation of the shear loss modulus . 7
10.5 Presentation of data as a function of temperature . 7
11 Precision . 7
12 Test report . 7
Bibliography .10
Foreword
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This document was prepared by Technical Committee ISO/TC 61, Plastics, Subcommittee SC 5, Physical-
chemical properties.
This second edition cancels and replaces the first edition (ISO 6721-6:1996), which has been technically
revised. It also incorporates the Amendment ISO 6721-6:1996/Amd.1:2007. The main changes compared
to the previous edition are as follows:
— the document has been revised editorially;
— normative references have been changed to undated.
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 © ISO 2019 – All rights reserved

INTERNATIONAL STANDARD ISO 6721-6:2019(E)
Plastics — Determination of dynamic mechanical
properties —
Part 6:
Shear vibration — Non-resonance method
1 Scope
This document describes a forced, non-resonance method for determining the components of the
shear complex modulus G* of polymers at frequencies typically in the range 0,01 Hz to 100 Hz. Higher-
frequency measurements can be made, but significant errors in the dynamic properties measured are
likely to result (see 10.2.2 and 10.2.3). The method is suitable for measuring dynamic storage moduli in
the range 0,1 MPa to 50 MPa.
NOTE Although materials with moduli greater than 50 MPa can be studied, more accurate measurements
of their dynamic shear properties can be made using a torsional mode of deformation (see ISO 6721-2 and
ISO 6721-7).
This method is particularly suited to the measurement of loss factors greater than 0,02 and can
therefore be conveniently used to study the variation of dynamic properties with temperature and
frequency through most of the glass-rubber relaxation region (see ISO 6721-1). The availability of data
determined over wide ranges of both frequency and temperature enables master plots to be derived,
using frequency/temperature shift procedures, which display dynamic properties over an extended
frequency range at different temperatures.
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 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 6721-1 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/
4 Principle
A test-specimen assembly is subjected to a sinusoidal shear force or deformation at a frequency
significantly below the fundamental shear resonance frequency (see 10.2.2). The amplitudes of the
force and displacement cycles applied to the test-specimen assembly and the phase angle between
these cycles are measured. The storage and loss components of the shear complex modulus and the loss
factor are calculated using formulae given in Clause 10.
5 Apparatus
5.1 Loading assembly
5.1.1 General
The requirements for the loading assembly are that it shall permit measurements of the amplitudes of,
and phase angle between, the force and displacement cycles for a test specimen assembly subjected to
a sinusoidal shear force or deformation. Various designs of apparatus are possible: a suitable version is
shown schematically in Figure 1. The shear test-specimen assembly consists of two identical specimens
S of the polymer bonded to or clamped between metal end-pieces P and P . A sinusoidal force is
1 2
generated by the vibrator V and applied to the two outer end-pieces P of the test-specimen assembly
through the clamping device C of the shear load stage. The amplitude and frequency of the vibrator
table displacement are variable and monitored by the transducer D. The test-specimen assembly is held
at its centre P by a fixed clamp C , and thus each specimen S of the polymer is subjected to simple
2 2
shear deformations of equal magnitude. The sinusoid
...