ISO 6721-9:2019

INTERNATIONAL ISO
STANDARD 6721-9
Second edition
2019-04
Plastics — Determination of dynamic
mechanical properties —
Part 9:
Tensile vibration — Sonic-pulse
propagation method
Plastiques — Détermination des propriétés mécaniques
dynamiques —
Partie 9: Vibration en traction — Méthode de propagation de signaux
acoustiques
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 . 2
5 Test device . 2
5.1 Apparatus . 2
5.2 Transducers . 2
5.3 Transducer drive unit . 2
5.4 Pulse arrival time measuring equipment . 3
5.5 Temperature measurement and control equipment . 3
6 Test specimens. 3
6.1 General . 3
6.2 Shape and dimensions . 3
6.3 Preparation . 3
7 Number of specimens . 3
8 Conditioning . 3
9 Procedure. 3
9.1 Test atmosphere . 3
9.2 Mounting the specimen . 3
9.3 Performing the test. 3
9.4 Varying the temperature . 4
10 Calculation and expression of results . 5
10.1 Symbols . 5
10.2 Calculation of the longitudinal wave velocity . 5
10.3 Calculation of the tensile storage modulus, E' . 5
10.4 Significant figures . 5
11 Precision . 5
12 Test report . 5
Annex A (informative) Precision . 7
Bibliography . 8
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
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electrotechnical standardization.
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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
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.org/iso/foreword .html.
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 6721-9:1997), which has been technically
revised. It also incorporates the Amendment ISO 6721-9:1997/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 6721-9:2019(E)
Plastics — Determination of dynamic mechanical
properties —
Part 9:
Tensile vibration — Sonic-pulse propagation method
1 Scope
This document describes a pulse propagation method for determining the storage component of the
complex tensile modulus E' of polymers at discrete frequencies typically in the range 3 kHz to 10 kHz.
The method is suitable for measuring materials with storage moduli in the range 0,01 GPa to 200 GPa
and with loss factors below 0,1 at around 10 kHz. With materials having a higher loss, significant errors
in velocity measurement are introduced through decay of amplitude.
The method allows measurements to be made on thin films or fine fibres and long specimens, typically
tapes of 300 mm × 5 mm × 0,1 mm or fibres of 300 mm × 0,1 mm (diameter).
This method may not be suitable for cellular plastics, composite plastics and multilayer products.
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 1183-1, Plastics — Methods for determining the density of non-cellular plastics — Part 1: Immersion
method, liquid pycnometer method and titration method
ISO 1183-2, Plastics — Methods for determining the density of non-cellular plastics — Part 2: Density
gradient column method
ISO 1183-3, Plastics — Methods for determining the density of non-cellular plastics — Part 3: Gas
pyknometer method
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 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
longitudinal sonic pulse
single sonic pulse where the deformations coincide with the direction of propagation of the pulse
4 Principle
Measurements are made of the velocity of a single longitudinal sonic wave in a longitudinal thin
specimen. The velocity of the longitudinal sonic wave is determined by measuring the transit time of
a sonic pulse between two transducers attached to the specimen over a frequency range from 3 kHz
to 10 kHz. A longitudinal sonic pulse is transmitted along the length of the specimen. The velocity is
independent on the specimen geometry, if the sonic velocity is measured in a long, thin specimen. The
tensile storage modulus is calculated from the product of specimen density and the square of sonic
velocity.
5 Test device
5.1 Apparatus
The requirements for the apparatus shall enable measurement of the velocity of a longitudinal sonic
pulse in a specimen.
Figure 1 shows schematically an example for measuring pulse velocity in a test specimen between the
transmitting and receiving transducers.
Key
1 test specimen 7 direction of vibration
2 sonic pulse 8 transducer edge
3 transmitting transducer 9 transducer
4 receiving transducer R radius of transducer edge
5 transducer drive unit L transducer separation distance (m)
6 arrival time measuring equipment
Figure 1 — Schematic diagram of suitable apparatus for measuring sonic pulse velocity
between a transmitting and a receiving transducer
5.2 Transducers
Two piezoelectric transducers having a resonant frequency in the range from about 3 kHz to 10 kHz
shall be mounted on the frame so that the direction of the vibration of each transducer accurately
coincides with the direction to the position of the other transducer. A mechanical pulse having
longitudinal displacement in the test specimen is generated by the transmitting transducer. A pulse
propagated through a test specimen is detected by the receiving transducer. One transducer shall be
movable so that the distance between them can be varied from about 50 mm to 500 mm, and accurately
measured to ± 0,5 % of the distance between the transducers.
5.3 Transducer drive unit
This unit shall provide a suitable pulse voltage for the transmitting transducer to produce a sonic pulse.
2 © ISO 2019 – All r
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