ISO 6721-11:2012
(Main)Plastics — Determination of dynamic mechanical properties — Part 11: Glass transition temperature
Plastics — Determination of dynamic mechanical properties — Part 11: Glass transition temperature
Plastiques — Détermination des propriétés mécaniques dynamiques — Partie 11: Température de transition vitreuse
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INTERNATIONAL ISO
STANDARD 6721-11
First edition
2012-04-01
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 6721-11:2012(E)
©
ISO 2012
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ISO 6721-11:2012(E)
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ISO 6721-11:2012(E)
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.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO 6721-11 was prepared by Technical Committee ISO/TC 61, Plastics, Subcommittee SC 2, Mechanical properties.
ISO 6721 consists of the following parts, under the general title Plastics — Determination of dynamic
mechanical properties:
— Part 1: General principles
— Part 2: Torsion-pendulum method
— Part 3: Flexural vibration — Resonance-curve method
— Part 4: Tensile vibration — Non-resonance method
— Part 5: Flexural vibration — Non-resonance method
— Part 6: Shear vibration — Non-resonance method
— Part 7: Torsional vibration — Non-resonance method
— Part 8: Longitudinal and shear vibration — Wave-propagation method
— Part 9: Tensile vibration — Sonic-pulse propagation method
— Part 10: Complex shear viscosity using a parallel-plate oscillatory rheometer
— Part 11: Glass transition temperature
— Part 12: Compressive vibration — Non-resonance method
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ISO 6721-11:2012(E)
Introduction
This part of ISO 6721 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 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 tan delta as a function of
temperature and frequency. From these data, a value for the glass transition 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 used,
1)
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.
1) See Sims G.D., Gnaniah S.J.P., Calibration Procedures for Increased Confidence in DMA Measurements, ICCM 11,
Edinburgh, July 2009.
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INTERNATIONAL STANDARD ISO 6721-11:2012(E)
Plastics — Determination of dynamic mechanical properties —
Part 11:
Glass transition temperature
WARNING — The use of this part of ISO 6721 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 regulatory limitations prior to its use.
1 Scope
This part of ISO 6721 specifies methods for determining a value of the glass transition temperature (T ) from
g
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 glassy state to a rubbery state.
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. Different modes (e.g. flexure, compression, tension) of dynamic mechanical analysis can
be applied, as appropriate, to the form of the source material.
NOTE For tests undertaken in the flexure or torsion mode, an additional procedure is included to identify the severity
of the influences of thermal lag on the measured data (see Annex B).
2 Normative references
The following referenced documents are indispensable for the application 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 6721-1:2011, 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.
3.1
glass transition temperature
T
g
temperature of the point of inflection of the decrease in the storage modulus curve corresponding to the transition
NOTE 1 This temperature often agrees with the temperature at the peak of the loss modulus data.
NOTE 2 It is expressed in degrees Celsius (°C).
NOTE 3 See Figure 1, data point 1.
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ISO 6721-11:2012(E)
3.2
temperature at onset
T
onset
temperature corresponding to the onset of the transition from glassy state, as defined by the intercept of two
tangents in the storage modulus curve
NOTE 1 The first tangent is extrapolated from a linear portion of the curve prior to the transition, and the second tangent
is extrapolated from the point of inflection of the decrease in the curve corresponding to the glass-rubber transition .
NOTE 2 It is expressed in degrees Celsius (°C).
NOTE 3 See Figure 1, data point 5.
3.3
temperature at peak of loss modulus data
T
loss
temperature of the peak of the loss modulus curve
NOTE 1 It is expressed in degrees Celsius (°C).
NOTE 2 See Figure 1, data point 2.
3.4
temperature at peak of tan delta data
T
tan delta
temperature of the peak in the tan delta curve
NOTE 1 It is expressed in degrees Celsius (°C).
NOTE 2 See Figure 1, data point 3.
3.5
reference glass transition temperature
T
g(0)
value of the extrapolated temperature at 0 °C/min heating rate that is used for specification and contract requirements
NOTE 1 It is expressed in degrees Celsius (°C).
NOTE 2 See Figure 2.
3.6
QA glass transition temperature
T
g(n)
value taken from the calibration curve at n °C/min heating rate that is used for quality assurance purposes, by
agreement, with heating rate dependent equipment (i.e. not the extrapolated T value]
g(0)
NOTE 1 It is expressed in degrees Celsius (°C).
NOTE 2 See 9.3.2.
4 Principle
A specimen of known geometry is placed or held in a suitable mechanical loading system in an enclosed
temperature chamber, or oven, that can be heated at a controlled rate. The specimen is mechanically oscillated
at a fixed frequency, and changes in the viscoelastic response of the material are monitored and recorded as
a function of the test temperature. The dynamic properties (storage modulus, loss modulus and tan delta) are
determined from the load and displacement data recorded throughout the test (see ISO 6721-1). The glass
transition temperature (T ) is determined as the point of inflection in the storage modulus vs. the temperature
g
plot. The test procedure described minimizes errors due to the thermal lag, which varies with the heating rate
used, of the specimen temperature through assuming the specimen temperature is given by the measured
oven temperature.
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ISO 6721-11:2012(E)
5 Equipment
5.1 Dynamic mechanical analyser
The test equipment shall be capable of heating at rates from 1 °C/min to 10 °C/min over the required temperature
range and mechanically oscillating the specimen at the reference frequency of 1 Hz. The equipment should be
capable of applying the temperature ramp profile to within ±5 % of the required heating rate.
The instrument shall continuously monitor and record the load applied to the specimen, and the corresponding
displacement as a function of the measured temperature, in order to determine the storage modulus, loss
modulus and tan delta. The load and displacement capabilities of the equipment shall be sufficient for the
specimens tested.
The equipment shall be calibrated, as required by the equipment user manual — see Annex A.
5.2 Devices for measuring test specimen dimensions
These shall be in accordance with ISO 6721-1:2011, 5.6.
6 Test specimen
6.1 General
The test specimen shall be in accordance with ISO 6721-1:2011, 6.1.
6.2 Shape and dimensions
The dimensions of the specimen shall be as required by the equipment for the selected test mode.
6.3 Preparation
The preparation of the test specimen shall be in accordance with I
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