1、Designation:D385094 (Reapproved 2006) Designation: D3850 12An American National StandardStandard Test Method forRapid Thermal Degradation of Solid Electrical InsulatingMaterials By Thermogravimetric Method (TGA)1This standard is issued under the fixed designation D3850; the number immediately follow
2、ing the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.This standard has been approve
3、d for use by agencies of the Department of Defense.1. Scope1.1 This test method outlines a procedure for obtaining thermogravimetric (TGA) data on solid polymeric materials intendedfor use as electrical insulating materials.1.2 Do not use this standard to quantify an estimate of the long-term therma
4、l 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 andmade public, preferably by comparing data between a candidate and another material known to display similar failure mod
5、es.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 responsibilityof the user of this standard to establish appropriate safety and health practices and determine the applicability o
6、f regulatorylimitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D883 Terminology Relating to PlasticsD1600 Terminology for Abbreviated Terms Relating to PlasticsD1711 Terminology Relating to Electrical InsulationD2307 Test Method for Thermal Endurance of Film-Insulated Round Magnet W
7、ireE220 Test Method for Calibration of Thermocouples By Comparison TechniquesE473 Terminology Relating to Thermal Analysis and RheologyE1582 Practice for Calibration of Temperature Scale for Thermogravimetry3. Terminology3.1 DefinitionsDefinitions are in accordance with Terminology D883, Terminology
8、 D1711, and Terminology E473.3.2 Abbreviations:AbbreviationsAbbreviations are in accordance with Terminology D1600, unless otherwise indicated.4. Summary of Test Method4.1 This thermogravimetric technique uses the record of the mass loss versus the temperature of the specimen during the timeof expos
9、ure 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).4.3 The temperature is measured and recorded at specified mass loss points (recorded as a
10、TGAcurve), using an electronic chartrecorder or other suitable data acquisition device.5. Significance and Use5.1 Thermogravimetry is useful in determining the dynamic functional effect of temperature on the amount of volatile materialsleaving a specimen as the latter is heated progressively to high
11、er temperatures. TGA can be useful for process control, processdevelopment, 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.1This test m
12、ethod is under the jurisdiction of ASTM Committee D09 on Electrical and Electronic Insulating Materials and is the direct responsibility of SubcommitteeD09.17 on Thermal Capabilities.Characteristics.Current edition approved AprilJan. 1, 2006.2012. Published April 2006.February 2012. Originally appro
13、ved in 1979. Last previous edition approved in 20002006 asD3850 94(20006). DOI: 10.1520/D3850-94R06.10.1520/D3850-12.2For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to t
14、he standards Document Summary page on the ASTM website.1This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Becauseit may not be technically possible to adequately depict all changes
15、accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current versionof the standard as published by ASTM is to be considered the official document.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United
16、 States.TGA curves can, therefore, be used as a preliminary screen method in the evaluation of relative behavior of insulating materialsof the same generic family.5.3 The functional temperature-life relationship of an insulating material in any given application depends on a number ofservice and env
17、ironmental factors. Therefore, the information obtained from TGA curves is not adequate by itself to describe thethermal capability of an insulating material.5.4 Refer to the Appendix for further discussion of the interpretation of TGA data.6. Apparatus6.1 Thermogravimetric AnalyzerA system of relat
18、ed instruments comprising:Sample 8.54 mg Heating Rate 5C/min Purging Gas Flow 0.8 mL/sFIG. 1 Curve No. 1, Typical TGA for Polyester FilmSample 5.93 mg Heating Rate 5C/min Purging Gas Flow 0.8 mL/sFIG. 2 Curve No. 2, Typical TGA for Polyimide FilmD3850 1226.1.1 Microbalance, of the null type, sensiti
19、ve to 0.001 mg,6.1.2 Furnace, controllable at a constant rate over a temperature range of interest, typically 25 to 1000C,6.1.3 Temperature Programmer, capable of providing a linear rate of rise of the furnace at a predetermined value (normally5C/min) with a tolerance of 6 0.1C/min,6.1.4 Suitable Da
20、ta Acquisition Device, and6.1.5 Supply of Purging Gas.NOTE 1For many applications, the purging gas is nitrogen or air having a dew point of at or below 10C.7. Sampling7.1 Use sampling plans as described in specifications or test methods specific to individual electrical insulating materials.8. Test
21、Specimens8.1 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 are satisfactory, depending on the configuration and test apparatus. Testresults depend in part on the size and shape of speci
22、men, due to thermal equilibrium and diffusion effects.8.3 When the specimen is a coating on a substrate, the total mass may be substantially greater,is greater unless the substrate iscarefully separated, because of the mass contribution of the substrate material.9. Procedure9.1 Calibrate the balance
23、 at full scale to within 6 0.01 mg, following the recommended procedure.9.2 Calibrate the temperature-sensing system to within 6 1C (see Method E220), following the recommended procedure.9.2.1 Position the temperature sensor to prevent contact with specimens which maycan become distorted during heat
24、ing.9.2.2 Temperature calibration is critical and the method employed will vary with the apparatus. Calibrate in accordance withPractice 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
25、 the specimen in the specimen holder and record the initial mass.9.7 Set the heating rate to 5C/min rate of rise.9.8 Start the heating program and record the mass change until there is no further mass loss.NOTE 2Normally the purge rate is 0.7 to 1.6 mL/s.10. Report10.1 Report the following informati
26、on:10.1.1 Identification of the sample and apparatus,10.1.2 Curing time and temperature in the case of resin specimens,10.1.3 Mass, approximate dimensions and form (for example, film, laminate, molded) of the specimen,10.1.4 Heating rate,10.1.5 Rate of flow and type of gas used for purging,10.1.6 TG
27、A curve of material evaluated, and10.1.7 Temperatures at which losses of initial specimen mass, if obtained, of 10, 20, 30, 50, and 75 % occur.NOTE 3Do not list temperatures that exceed the resolution of the instrumentation. Normally this is not to be greater than 2.5C. Report the resolution.11. Pre
28、cision and Bias11.1 This test method is based on the dynamic measurement of mass loss as a function of increasing temperature. Deviationsin results that affect precision are caused by variations in a number of complex factors (for example, physical irregularities of thespecimen, variations in the pu
29、rging gas composition and flow characteristics) and generally will not correlate simply with changesin these factors.11.2 The repeatability of the mass loss measurements as a function of temperature within one laboratory (and one apparatus)is approximately 6 5C.11.3 Limited inter-laboratory testing
30、done as a preliminary preparation for this test method indicate that mass loss measurementsplotted as a function of temperature have a reproducibility of 6 25C.11.4 This test method has no bias because the thermal degradation characteristic is defined by the method.12. Keywords12.1 degradation; insu
31、lating; mass loss; polymeric material; thermogravimetric analysis; TGAD3850 123APPENDIX(Nonmandatory Information)X1. INTERPRETATION OF THERMOGRAVIMETRIC TEST TECHNIQUEX1.1 IntroductionThermogravimetry is the continuous measurement of mass loss of a specimen as the temperature isincreased at a specif
32、ic rate. Since the test method requires the continuous measurement of a varying mass and temperature and thecontrol of temperature rate of rise, differences may exist between instruments, experimenters, or both, even when the precision ofthe individual component sensors are known. Calibration of the
33、 instrumentation system is based upon a comparison under dynamicconditions.X1.2 CalibrationInitial calibration should follow the recommended procedure (when available). This procedure shouldensure that individual sensors are correct. The relationship between the temperature sensor, usually a thermoc
34、ouple, and thespecimen design and the type of atmosphere, including the rate of flow of the gas through the weighing chamber, will affect theoverall calibration of the system.X1.3 AtmosphereThe rate of mass loss is dependent in part upon the atmosphere to which the test specimen is exposed. Forthe b
35、est correlation of test results to end use, purge with the air or other gas that relates to the end use conditions. The rate of flowof the gas in the cell will have a significant effect on the calibration of the system. It is, therefore, necessary to select the rate offlow, usually 0.7 to 1.6 mL/s,
36、prior to calibration of the system. After calibrating the system, do not change the flow rate.X1.4 Specimen Design, is dictated by the material under consideration, material application, and the instrumentation. Use aspecimen in the form normally found in use (for example, film and coatings). The si
37、ze will depend on the instrumentation to somedegree. The surface area will affect the overall results. For instance, if a specimen with a large surface is compared to one withsmaller surface area, both of the same mass, the small surface area specimen will normally lose mass at a slower rate, due to
38、thermal equilibrium and thermal effects. Select the specimen configuration and mass prior to system calibration.X1.5 System Calibration:X1.5.1 System calibration of the TGA instrumentation incorporates the comparison of specimen temperature to a measuredphysical change in the specimen. The weakest p
39、oint in the calibration procedure is the temperature sensor, usually a thermocouple.Thermocouples are nonlinear within the normal range of operating temperatures, and after a few times of operation maycan driftfrom calibration. The location of the temperature sensor in the weighing chamber must be s
40、uch that it will provide the best estimateof the specimen temperature. Since no standard measurement will provide this location, it is necessary to make a comparison test.X1.5.2 Practice E1582 can be used for temperature calibration.X1.5.3 Differences between laboratories may always exist. Compariso
41、n to the referenced curves or another mutually selectedTGA curve will provide a reasonably accurate method for communicating various TGA data. Close attention to the overallcalibration on a continual basis will ensure good repeatability within one laboratory over a long period of time.X1.6 Interpret
42、ation of TGA DataThermogravimetry is a relatively fast means of comparing materials. The dynamicrelationship between mass loss and temperature is the only thermal characteristic considered with TGA. How this temperature-mass loss characteristic affects the use of an electrical insulation in the appl
43、ication is unknown. The rate of mass loss affectselectrical insulation life. Mass loss that will result in failure varies with material and temperature. In addition, the mass lossrequired for a failure varies with the failure mode. Due to the many unknown factors in any given application, the exact
44、relationshipbetween mass loss and failure mode for each application should be determined experimentally. Generally, material comparisonsby TGAhave not always been in the same order as the known temperature class.As an example, the round robin testing performedduring the development of this test meth
45、od indicated that polyamide film was thermally superior to a PET film. Both life tests andexperience have verified that PET film is thermally superior to polyamide film in a variety of electrical applications.X1.6.1 In 1967, Sweitzer and Stugart3illustrated that an equivalent polyamide polymer for m
46、agnet wire yielded higher TGAdata and had a lower thermal life (Test Method D2307) in comparison to the same polyamide cured under different conditions.X1.6.2 Thermogravimetry is an important tool in observing the effect of polymer variation due to changes in one thermalcharacteristic. The relations
47、hip between thermogravimetry and application life is unknown.NOTE X1.1The attached Figs. 1 and 2 for polyester film and polyimide film are illustrative of the original round-robin test work carried out in thepreparation of this test method.3Sweitzer and Stugart, “Screening Polymers for Use as Magnet
48、 Wire Enamel,” Proceeding of the Seventh Electrical Insulation Conference, 1967, Paper No. IEEE32C-79-64.D3850 124ASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard. Users of this standard are expressly adv
49、ised that determination of the validity of any such patent rights, and the riskof infringement of such rights, are entirely their own responsibility.This standard is subject to revision at any time by the responsible technical committee and must be reviewed every five years andif not revised, either reapproved or withdrawn. Your comments are invited either for revision of this standard or for additional standardsand should be addressed to ASTM International Headquarters. Your comments will receive careful consideration at a meeting of theresponsible techn
