ISO 6721-11:2019

Plastics - Determination of dynamic mechanical properties - Part 11: Glass transition temperature

This document specifies methods for determining a value of the glass transition temperature (Tg) from the dynamic mechanical properties measured during a linear temperature scan under heating conditions. The glass transition temperature is an indicator of the transition from a hard and relatively brittle glassy state to a rubbery or viscous liquid state in an amorphous polymer or in amorphous regions of a partially crystalline polymer. Usually referred to as dynamic mechanical analysis (DMA), the methods and their associated procedures can be applied to unreinforced and filled polymers, foams, rubbers, adhesives and fibre-reinforced plastics/composites. The methods are limited to materials that are inherently stable above Tg, i.e. amorphous materials that transform into a rubbery state or partially crystalline materials that keep their shape due to crystallinity. Different modes (e.g. flexure, torsion, shear, compression, tension) of dynamic mechanical analysis can be applied, as appropriate, to the form of the source material. Measured Tg values using instrumentation can vary as a result of material characteristics and/or the test set-up. The temperature sensor in a DMA instrument is not in contact with the test specimen and therefore measures temperature of the environment surrounding the specimen under test. The resulting data can vary with the heating rate applied. A procedure is included to take into account the thermal lag influencing the measured data.

Plastiques — Détermination des propriétés mécaniques dynamiques — Partie 11: Température de transition vitreuse

General Information

• Status: Published
• Publication Date: 28-May-2019
• ICS: 83.080.01 - Plastics in general
• Technical Committee: ISO/TC 61/SC 5 - Physical-chemical properties
• Drafting Committee: ISO/TC 61/SC 5/WG 8 - Thermal analysis
• Current Stage: 9093 - International Standard confirmed
• Start Date: 06-Jun-2024
• Completion Date: 13-Dec-2025

Relations

• Revises: ISO 6721-11:2012 - Plastics - Determination of dynamic mechanical properties - Part 11: Glass transition temperature
• Effective Date: 15-Dec-2017

Overview

ISO 6721-11:2019 specifies standardized methods to determine the glass transition temperature (Tg) of plastics using dynamic mechanical analysis (DMA) in a linear heating scan. The standard defines how to extract Tg from temperature-dependent dynamic mechanical properties - storage modulus, loss modulus and loss factor (tan δ) - for amorphous polymers and amorphous regions of partially crystalline polymers. It covers unreinforced and filled polymers, rubbers, foams, adhesives and fibre‑reinforced composites, and includes procedures to account for thermal lag and heating‑rate effects.

Keywords: ISO 6721-11:2019, glass transition temperature, Tg, dynamic mechanical analysis, DMA, plastics testing, thermal lag

Key topics and technical requirements

• Measurement principle: Oscillate a specimen at fixed frequency while performing a controlled linear temperature scan; record load, displacement and phase to calculate storage modulus, loss modulus and tan δ.
• Characteristic Tg definitions: Tg can be determined from:
  • Peak of the loss modulus curve (T_M'')
  • Inflection point of the storage modulus curve (T_M')
  • Peak of the loss factor (tan δ) curve (T_tanδ)
• Heating rates and frequencies: Instruments must support heating rates typically between 1 K/min and 10 K/min and operation at reference frequencies (e.g., 1 Hz or 10 Hz); heating-rate accuracy ±5% is required.
• Thermal lag correction: The temperature sensor measures the chamber environment, not the specimen; the standard provides procedures to assess and correct heating‑rate dependent thermal lag and to extrapolate a zero‑heating‑rate Tg.
• Specimen and apparatus: Test specimen geometry follows ISO 6721-1; DMA modes (flexure, torsion, shear, compression, tension) are allowed as appropriate to sample form. Equipment calibration and identical test atmospheres for calibration and measurement are required.
• Reporting: Results include storage modulus, loss modulus and tan δ curves, the Tg value(s) derived, test conditions and calibration details.

Applications and users

ISO 6721-11:2019 is used in:

• Materials R&D for polymer characterization, formulation optimization and identifying transition behavior.
• Quality control and acceptance testing in plastics manufacturing, composites, adhesives and rubber industries.
• Design and engineering, to select materials with suitable service temperature ranges and predict mechanical performance near Tg.
• Certification and failure analysis, where accurate Tg values inform performance limits and thermal stability assessments.

Typical users: polymer testing laboratories, QA/QC engineers, materials scientists, composite manufacturers, test instrument suppliers and certification bodies.

Related standards

• ISO 6721-1 - Plastics: General principles for dynamic mechanical properties (test modes, specimen requirements).
• ISO 11357-2 - Differential scanning calorimetry (DSC) methods for Tg (alternative technique).
• ISO 472 - Plastics vocabulary (terms and definitions).

This standard helps ensure reproducible, comparable Tg measurements using DMA, offering practical guidance for testing setup, thermal correction and interpretation of dynamic mechanical data.

Standards Content (Sample)

INTERNATIONAL ISO
STANDARD 6721-11
Second edition
2019-06
Plastics — Determination of dynamic
mechanical properties —
Part 11:
Glass transition temperature
Plastiques — Détermination des propriétés mécaniques
dynamiques —
Partie 11: Température de transition vitreuse
Reference number
©
ISO 2019
© 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
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ii © ISO 2019 – All rights reserved

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 2
5 Apparatus . 3
5.1 Test equipment . 3
5.2 Devices for measuring test specimen dimensions . 3
6 Test specimen . 3
6.1 General . 3
6.2 Shape and dimensions . 3
6.3 Preparation . 4
7 Number of specimens . 4
8 Conditioning . 4
9 Test procedure . 4
9.1 Test atmosphere . 4
9.2 Operation . 5
9.2.1 Method A — Rate-dependent results — Full procedure . 5
9.2.2 Offset method — Rate dependent results . 6
9.2.3 Method B — Rate-independent results . 7
10 Expression of results . 7
11 Precision . 7
12 Test report . 7
Annex A (normative) Calibration procedures. 9
Annex B (informative) Assessment of heating rate sensitivity using reference sample .10
Bibliography .14
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.
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
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URL: www .iso .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 6721-11:2012), which has been technically
revised. The main changes compared to the previous edition are as follows:
— the scope has been revised to specify suitable materials more accurately;
— definitions of specific points in DMA curves have been extended;
— reference to quality assurance purposes have been deleted;
— several methods have been introduced for evaluation of the glass transition temperature;
— the procedure for determination of heat dependent results has been revised;
— curves of storage modulus, loss modulus and loss factor have been added to the test report;
— the temperature calibration procedure has been revised;
— additional temperature reference specimen for different loading modes has been introduced.
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 https: //www .iso .org/members .html.
iv © ISO 2019 – All rights reserved

Introduction
This document covers the use of dynamic mechanical analysis (DMA) procedures, in the temperature
scanning mode, to determine a value for the glass transition temperature of plastics. It provides an
[1]
alternative procedure to the use of differential scanning calorimetry (DSC) (see ISO 11357-2) for this
measurement.
DMA is used to determine the variation of the storage modulus, loss modulus and loss factor as a
function of temperature and frequency. From these data, a value for the glass transition temperature
is determined. Many types of commercial equipment are available that use this technique, and, in
principle, it applies to all the loading modes described in ISO 6721-1.
The procedures minimize errors due to thermal lag of the specimen, which varies with the heating rate
[2]
used, through assuming the specimen temperature is given by the measured oven temperature . This
eliminates the need for the temperature of the specimen to be measured directly by, for example, a
thermocouple embedded in the specimen.
INTERNATIONAL STANDARD ISO 6721-11:2019(E)
Plastics — Determination of dynamic mechanical
properties —
Part 11:
Glass transition temperature
WARNING — The use of this document may involve hazardous materials, operations and
equipment. The document does not purport to address all of the safety problems associated with
its use. It is the responsibility of the user to establish appropriate health and safety practices
and to determine the applicability of any other restrictions prior to its use.
1 Scope
This document specifies methods for determining a value of the glass transition temperature (T )
g
from the dynamic mechanical properties measured during a linear temperature scan under heating
conditions. The glass transition temperature is an indicator of the transition from a hard and relatively
brittle glassy state to a rubbery or viscous liquid state in an amorphous polymer or in amorphous
regions of a partially crystalline polymer.
Usually referred to as dynamic mechanical analysis (DMA), the methods and their associated
procedures can be applied to unreinforced and filled polymers, foams, rubbers, adhesives and fibre-
reinforced plastics/composites. The methods are limited to materials that are inherently stable above
T , i.e. amorphous materials that transform into a rubbery state or partially crystalline materials that
g
keep their shape due to crystallinity.
Different modes (e.g. flexure, torsion, shear, compression, tension) of dynamic mechanical analysis can
be applied, as appropriate, to the form of the source material.
Measured T values using instrumentation can vary as a result of material characteristics and/or
g
the test set-up. The temperature sensor in a DMA instrument is not in contact with the test specimen
and therefore measures temperature of the environment surrounding the specimen under test. The
resulting data can vary with the heating rate applied. A procedure is included to take into account the
thermal lag influencing the measured data.
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 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 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
temperature at peak of loss modulus curve
T
M′′
temperature of the peak of the loss modulus curve vs. temperature
Note 1 to entry: It is expressed in degrees Celsius (°C).
Note 2 to entry: See Figure 1, data point 1.
3.2
temperature at inflection point of storage modulus
T
M′
temperature at inflection point of the curve of storage modulus vs. temperature
Note 1 to entry: It is expressed in degrees Celsius (°C).
Note 2 to entry: See Figure 1, data point 2.
3.3
temperature at peak of loss factor curve
T
tanδ
temperature of the peak in the curve of loss factor vs. temperature
Note 1 to entry: The loss factor is also called tan δ.
Note 2 to entry: It is expressed in degrees Celsius (°C).
Note 3 to entry: See Figure 1, data point 3.
3.4
zero heating rate glass transition temperature
T
g(0)
value of the glass transition temperature extrapolated to 0 K/min heating rate
Note 1 to entry: It is expressed in degrees Celsius (°C).
Note 2 to entry: See 9.2.1, Figure 2, and 9.2.2, Figure 3.
3.5
rate dependent glass transition temperature
T
g(n)
value of the glass transition temperature at n K/min heating rate
Note 1 to entry: It is expressed in degrees Celsius (°C).
Note 2 to entry: See 9.2.1 and 9.2.2.
4 Principle
A specimen of known geometry is placed or held in a suitable mechanical loading system in an enclosed
temperature chamber, or oven, which can be heated at a controlled rate. The specimen is mechanically
oscillated at a fixed frequency, and the resulting changes in the viscoelastic response of the material
are monitored and recorded as a function of the test temperature. The dynamic properties (storage
modulus, los
...