ASTM E2550-21

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Designation: E2550 − 17 E2550 − 21
Standard Test Method for
Thermal Stability by Thermogravimetry
This standard is issued under the fixed designation E2550; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope Scope*
1.1 This test method describes the assessment of material thermal stability through the determination of the temperature at which
the materials start to decompose or react and the extent of the mass change using thermogravimetry. The test method uses minimum
quantities of material and is applicable over the temperature range from ambient to 800°C.800 °C.
1.2 The absence of reaction or decomposition is used as an indication of thermal stability in this test method under the
experimental conditions used.
1.3 This test method may be performed on solids or liquids, which do not sublime or vaporize in the temperature range of interest.
1.4 This test method shall not be used by itself to establish a safe operating or storage temperature. It may be used in conjunction
with other test methods (for example, Test Methods E487 and E537, and Guide E1981) as part of a hazard analysis of a material.
1.5 This test method is normally applicable to reaction or decomposition occurring in the range from room temperature to 800°C.
800 °C. The temperature range may be extended depending on the instrumentation used.
1.6 This test method may be performed in an inert, a reactive or self-generated atmosphere.
1.7 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.8 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of
regulatory limitations prior to use.
1.9 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2.1 ASTM Standards:
E473 Terminology Relating to Thermal Analysis and Rheology
This test method is under the jurisdiction of ASTM Committee E37 on Thermal Measurements and is the direct responsibility of Subcommittee E37.01 on Calorimetry
and Mass Loss.
Current edition approved Sept. 1, 2017Oct. 1, 2021. Published September 2017November 2021. Originally approved in 2007. Last previous edition approved in 20112017
as E2550 – 11.E2550 – 17. DOI: 10.1520/E2550-17.10.1520/E2550-21.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E2550 − 21
E487 Test Methods for Constant-Temperature Stability of Chemical Materials
E537 Test Method for Thermal Stability of Chemicals by Differential Scanning Calorimetry
E691 Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
E967 Test Method for Temperature Calibration of Differential Scanning Calorimeters and Differential Thermal Analyzers
E1142 Terminology Relating to Thermophysical Properties
E1445 Terminology Relating to Hazard Potential of Chemicals
E1582 Test Method for Temperature Calibration of Thermogravimetric Analyzers
E1981 Guide for Assessing Thermal Stability of Materials by Methods of Accelerating Rate Calorimetry
E2040 Test Method for Mass Scale Calibration of Thermogravimetric Analyzers
3. Terminology
3.1 Definitions:
3.1.1 Specific technical terms used in this test method are defined in Terminologies E473, E1142, and E1445. These terms include
thermogravimetry (TG),thermogravimetric analysis (TGA),thermal stability,onset temperature (T ),derivative, and TG curve.
o
3.2 Definitions of Terms Specific to This Standard:
3.2.1 derivative thermogravimetry or DTG curve, n—a display of the first derivative of thermogravimetry data with respect to
temperature or time.
3.2.2 mass change plateau, n—a region of the thermogravimetry curve with a relatively constant mass; it is accompanied by a
minimum in the DTG curve for a mass loss, or a maximum for a mass gain.
4. Summary of Test Method
4.1 A sample of the material to be examined is placed in an inert container and then heated at a controlled rate (β) of 1°C 1 °C
-1 -1
min to 20°C 20 °C min under a controlled atmosphere. The sample mass is recorded continuously as a function of time and
temperature.
4.2 When the sample undergoes a reaction or thermal decomposition involving a mass change, that change is indicated by a
departure from the initially established baseline of the mass record (see Fig. 1).
4.3 The onset temperature and mass changes are determined and reported.
5. Significance and Use
5.1 Thermogravimetry provides a rapid method for determining the thermal decomposition and reaction mass change of a
material.
FIG. 1 Typical Thermogravimetry and Derivative Thermogravimetry Curves
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5.2 This test method is useful in detecting potentially hazardous reactions and in estimating the temperatures at which these
reactions occur. This test method is recommended as a screening test for detecting the thermal hazards of an uncharacterized
material or mixture (see Section 8).
5.3 Energetic materials, pharmaceuticals and polymers are examples of materials for which this test might be useful. This test is
especially useful for materials having melting points that overlap with the onset of reaction or decomposition.
NOTE 1—In Differential Scanning Calorimetrydifferential scanning calorimetry (DSC), the melting endotherm may interfere with the determination of the
onset temperature for reaction or decomposition.
5.4 This test is not suitable for materials that sublime or vaporize in the temperature range of interest. A sample with volatile
impurities needs to be purified prior to testing by thermogravimetric analysis. Alternatively, the sample can be tested as is, however,
special caution is required during the data analysis. The mass loss due to the loss of impurity should not interfere with the
determination of reaction or decomposition temperature.
5.5 The four significant criteria of this test method are: the detection of a sample mass change; the extent of the mass change; the
approximate temperature at which the event occurs; the observance of effects due to the atmosphere.
6. Limitations
6.1 Many environmental factors affect the existence, magnitude and onset temperature of a particular reaction or decomposition.
Some of these, including heating rate, instrumental sensitivity, and atmosphere reactivity, will affect the detectability of a reaction
or decomposition using this procedure. Therefore, it is imperative that the results obtained from the application of this test method
be viewed only as an indication of the thermal stability of a material.
6.2 This test method can only be used to detect reaction or decomposition that involves a mass change, such as a production of
gaseous species or a mass gain in reactive atmosphere. This test method is not suitable for materials that sublime or vaporize in
the temperature of interest.
6.3 This test method may not be reliable for heterogeneous samples.
NOTE 2—For heterogeneous samples, it is recommended to perform replicate measurements to determine the variability of the results. If inconsistent
results are obtained, the study should be carried out using larger-scale apparatus, such as accelerating rate calorimetry.
7. Apparatus
7.1 Thermogravimetric Analyzer (TGA)—The essential instrumentation required to provide the minimum thermogravimetric
analytical capability for this test method includes:
7.1.1 A thermobalance composed of:
7.1.1.1 A furnace to provide uniform controlled heating of a specimen to a constant temperature or at a constant rate within the
applicable temperature range of ambient to 600°C.600 °C.
7.1.1.2 A temperature sensor to provide an indication of the specimen/furnace temperature to 60.1°C.60.5 °C.
7.1.1.3 A continuously recording balance to measure the specimen mass with a minimum capacity of 10 mg and a sensitivity of
610 μg.
NOTE 3—An apparatus with a larger capacity can also be used. The sensitivity must be at least 60.1 mass %.
7.1.1.4 A means of maintaining the specimen/container under atmospheric control of an inert or reactive gas of 99.9+ % purity
-1 -1 -1
at a purge rate of 20 mL min to 100 mL min 6 5 mL min .
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NOTE 4—Purge rate may vary depending on the instrument used. Excessive purge rates should be avoided as this may introduce interferences due to
turbulence effects and temperature gradients.
NOTE 5—Experiments can also be performed in a self generated atmosphere. DSC Differential scanning calorimeter sealed containers with a pinhole of
25-μm to 380-μm diameter have been shown to establish saturation of a gaseous self generated atmosphere.
7.1.2 A temperature controller capable of executing a specific temperature program by operating the furnace between selected
-1 -1
temperature limits at a rate of temperature change between 1°C min1 °C min and 20°C min20 °C min to within
-1
60.1°C min60.1 °C min .
7.1.3 A recording device capable of recording and displaying on the Y-axis any fraction of the specimen mass signal (TGA(TGA
curve) including the signal noise as a function of any fraction of the temperature (or time) signal on the X-axis including the signal
noise.
7.1.4 Containers (pans, crucibles, etc.) that are inert to the specimen and that will remain gravimetrically stable within the
temperature limits of this test method.
NOTE 6—For experiments in a self generated atmosphere, DSC sealed containers with pinhole of 25-μm to 380-μm diameter can be used.
7.2 Auxiliary equipment necessary or useful in conducting this test method includes:
7.2.1 A balance with a capacity of 100 mg or more to weigh specimens or containers, or both, to 60.1 mg.
7.2.2 Device to encapsulate the specimen in DSC differential scanning calorimeter sealable containers for self-generated
atmosphere studies.
8. Safety Precautions
8.1 The use of this test method as an initial test for material whose potential hazards are unknown requires that precautions be
taken during the sample preparation and testing.
8.2 Larger specimens (>5 mg) should be used only after consideration is given to the potential for hazardous reaction(s). For
energetic material or materials whose characteri
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