ASTM D3850-19

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it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
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Designation: D3850 − 12 D3850 − 19
Standard Test Method for
Rapid Thermal Degradation of Solid Electrical Insulating
Materials By Thermogravimetric Method (TGA)
This standard is issued under the fixed designation D3850; 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.
This standard has been approved for use by agencies of the U.S. Department of Defense.
1. Scope Scope*
1.1 This test method outlines a procedure for obtaining thermogravimetric (TGA) data on solid polymeric materials intended
for use as electrical insulating materials.
1.2 Do not use this standard to quantify an estimate of the long-term thermal capability for any electrical insulating material.
If a relationship exists between TGA and the long-term thermal capabilities of a material, then that fact must be established and
made public, preferably by comparing data between a candidate and another material known to display similar failure modes.
1.3 The values stated in SI units are the standard.
1.4 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 safety, health, and healthenvironmental practices and determine the
applicability of regulatory limitations prior to use.
1.5 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:
D883 Terminology Relating to Plastics
D1600 Terminology for Abbreviated Terms Relating to Plastics
D1711 Terminology Relating to Electrical Insulation
D2307 Test Method for Thermal Endurance of Film-Insulated Round Magnet Wire
E220 Test Method for Calibration of Thermocouples By Comparison Techniques
E473 Terminology Relating to Thermal Analysis and Rheology
E1582 Test Method for Temperature Calibration of Thermogravimetric Analyzers
3. Terminology
3.1 Definitions—Definitions are in accordance with Terminology D883, Terminology D1711, and Terminology E473.
3.2 Abbreviations—Abbreviations are in accordance with Terminology D1600, unless otherwise indicated.
4. Summary of Test Method
4.1 This thermogravimetric technique uses the record of the mass loss versus the temperature of the specimen during the time
of exposure to a specified prescribed environment using a controlled time rate of heating.
4.2 The record is a TGA curve, with percent of initial mass as the ordinate and temperature as the abscissa (see Figs. 1 and 2).
This test method is under the jurisdiction of ASTM Committee D09 on Electrical and Electronic Insulating Materials and is the direct responsibility of Subcommittee
D09.17 on Fire and Thermal CharacteristicsProperties.
Current edition approved Jan. 1, 2012March 1, 2019. Published February 2012March 2019. Originally approved in 1979. Last previous edition approved in 20062012 as
D3850 – 94D3850 – 12.(2006). DOI: 10.1520/D3850-12.10.1520/D3850-19.
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
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D3850 − 19
Sample 8.54 mg Heating Rate 5°C/min Purging Gas Flow 0.8 mL/s
FIG. 1 Curve No. 1, Typical TGA for Polyester Film
Sample 5.93 mg Heating Rate 5°C/min Purging Gas Flow 0.8 mL/s
FIG. 2 Curve No. 2, Typical TGA for Polyimide Film
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4.3 The temperature is measured and recorded at specified mass loss points (recorded as a TGA curve), using an electronic chart
recorder or other suitable data acquisition device.
5. Significance and Use
5.1 Thermogravimetry is useful in determining the dynamic functional effect of temperature on the amount of volatile materials
leaving a specimen as the latter is heated progressively to higher temperatures. TGA can be useful for process control, process
development, material evaluation, and for identification and quality control in specifications.
5.2 The thermal stability of a material can be associated with the degree and time rate of mass loss as a function of temperature.
TGA curves can, therefore, be used as a preliminary screen method in the evaluation of relative behavior of insulating materials
of the same generic family.
5.3 The functional temperature-life relationship of an insulating material in any given application depends on a number of
service and environmental factors. Therefore, the information obtained from TGA curves is not adequate by itself to describe the
thermal capability of an insulating material.
5.4 Refer to the Appendix for further discussion of the interpretation of TGA data.
6. Apparatus
6.1 Thermogravimetric Analyzer—A system of related instruments comprising:
6.1.1 Microbalance, of the null type, sensitive to 0.001 mg,
6.1.2 Furnace, controllable at a constant rate over a temperature range of interest, typically 25 to 1000°C,
6.1.3 Temperature Programmer, capable of providing a linear rate of rise of the furnace at a predetermined value (normally
5°C/min) with a tolerance of 6 0.1°C/min,
6.1.4 Suitable Data Acquisition Device, and
6.1.5 Supply of Purging Gas.
NOTE 1—For many applications, the purging gas is nitrogen or air having a dew point of at or below −10°C.
7. Sampling
7.1 Use sampling plans as described in specifications or test methods specific to individual electrical insulating materials.
8. Test Specimens
8.1 Prepare test specimens in accordance with the test method applicable to the material under investigation.
8.2 Generally, it is found that specimens of 2 to 20 mg 10 mg are satisfactory, depending on the configuration and test apparatus.
Test results depend in part on the size and shape of specimen, due to thermal equilibrium and diffusion effects.
NOTE 2—A more repeatable result is obtained if a smaller specimen size is used. When a large sample, exceeding 5 mg is used it is recommended that
the specimen be cut into smaller pieces to increase surface area to achieve more uniform degradation.
8.3 When the specimen is a coating on a substrate, the total mass is greater unless the substrate is carefully separated, because
of the mass contribution of the substrate material.
9. Procedure
9.1 Calibrate the balance at full scale to within 6 0.01 mg, following the recommended procedure.
9.2 Calibrate the temperature-sensing system to within 6 1°C (see Method E220), following the recommended procedure.
9.2.1 Position the temperature sensor to prevent contact with specimens which can become distorted during heating.
9.2.2 Temperature calibration is critical and the method employed will vary with the apparatus. Calibrate in accordance with
Practice E1582.
9.3 Adjust the purge rate to the specified value.
9.4 Adjust the Y axis (mass) to chart zero.
9.5 Adjust the X axis to the required temperature range.
9.6 Place the specimen in the specimen holder and record the initial mass.
9.7 Set the heating rate to 5°C/min rate of rise.rise starting at 30ºC.
9.8 Start the heating program and record the mass change until there is no further mass loss.
NOTE 3—Normally the purge rate is 0.7 to 1.6 mL/s. This is to avoid atmospheric stagnation around the specimen during the test.
10. Report
10.1 Report the following information:
10.1.1 Identification of the sample and apparatus,
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10.1.2 Curing time and temperature in the case of resin specimens,
10.1.3 Mass, approximate d
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