1、Designation: D 3850 94 (Reapproved 2006)An American National StandardStandard Test Method forRapid Thermal Degradation of Solid Electrical InsulatingMaterials By Thermogravimetric Method (TGA)1This standard is issued under the fixed designation D 3850; the number immediately following the designatio
2、n 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 (e) indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agen
3、cies of the Department of Defense.1. Scope1.1 This test method outlines a procedure for obtainingthermogravimetric (TGA) data on solid polymeric materialsintended for use as electrical insulating materials.1.2 Do not use this standard to quantify an estimate of thelong-term thermal capability for an
4、y electrical insulating ma-terial. If a relationship exists between TGA and the long-termthermal capabilities of a material, then that fact must beestablished and made public, preferably by comparing databetween a candidate and another material known to displaysimilar failure modes.1.3 The values st
5、ated in SI units are the standard.1.4 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limita
6、tions prior to use.2. Referenced Documents2.1 ASTM Standards:2D 883 Terminology Relating to PlasticsD 1600 Terminology for Abbreviated Terms Relating toPlasticsD 1711 Terminology Relating to Electrical InsulationD 2307 Test Method for Thermal Endurance of Film-Insulated Round Magnet WireE 220 Test M
7、ethod for Calibration of Thermocouples ByComparison TechniquesE 473 Terminology Relating to Thermal Analysis and Rhe-ologyE 1582 Practice for Calibration of Temperature Scale forThermogravimetry3. Terminology3.1 DefinitionsDefinitions are in accordance with Termi-nology D 883, Terminology D 1711, an
8、d Terminology E 473.3.2 Abbreviations:AbbreviationsAbbreviations are in ac-cordance with Terminology D 1600, unless otherwise indi-cated.4. Summary of Test Method4.1 This thermogravimetric technique uses the record of themass loss versus the temperature of the specimen during thetime of exposure to
9、a specified prescribed environment using acontrolled time rate of heating.4.2 The record is a TGA curve, with percent of initial massas the ordinate and temperature as the abscissa (see Figs. 1 and2).4.3 The temperature is measured and recorded at specifiedmass loss points (recorded as aTGAcurve), u
10、sing an electronicchart recorder or other suitable data acquisition device.5. Significance and Use5.1 Thermogravimetry is useful in determining the dynamicfunctional effect of temperature on the amount of volatilematerials leaving a specimen as the latter is heated progres-sively to higher temperatu
11、res. TGA can be useful for processcontrol, process development, material evaluation, and foridentification and quality control in specifications.5.2 The thermal stability of a material can be associatedwith the degree and time rate of mass loss as a function oftemperature. TGA curves can, therefore,
12、 be used as a prelimi-nary screen method in the evaluation of relative behavior ofinsulating materials of the same generic family.5.3 The functional temperature-life relationship of an insu-lating material in any given application depends on a numberof service and environmental factors. Therefore, t
13、he informa-tion obtained from TGA curves is not adequate by itself todescribe the thermal capability of an insulating material.1This test method is under the jurisdiction of ASTM Committee D09 onElectrical and Electronic Insulating Materials and is the direct responsibility ofSubcommittee D09.17 on
14、Thermal Capabilities.Current edition approved April 1, 2006. Published April 2006. Originallyapproved in 1979. Last previous edition approved in 2000 as D 3850 94(2000).2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annua
15、l Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.5.4 Refer to the Appendix for further discussion of theinterpretation of TGA
16、data.6. Apparatus6.1 Thermogravimetric AnalyzerA system of related in-struments 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 tem-perature range of interest, typically 25 to 1000 C,6.1.3 Temperature Programmer, capable of
17、 providing alinear 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, and6.1.5 Supply of Purging Gas.NOTE 1For many applications, the purging gas is nitrogen or airhaving a dew point of at or below 10 C.Sampl
18、e 8.54 mg Heating Rate 5 C/min Purging Gas Flow 0.8 mL/sFIG. 1 Curve No. 1, Typical TGA for Polyester FilmSample 5.93 mg Heating Rate 5 C/min Purging Gas Flow 0.8 mL/sFIG. 2 Curve No. 2, Typical TGA for Polyimide FilmD 3850 94 (2006)27. Sampling7.1 Use sampling plans as described in specifications o
19、r testmethods specific to individual electrical insulating materials.8. Test Specimens8.1 Prepare test specimens in accordance with the testmethod applicable to the material under investigation.8.2 Generally, it is found that specimens of 2 to 20 mg aresatisfactory, depending on the configuration an
20、d test apparatus.Test results depend in part on the size and shape of specimen,due to thermal equilibrium and diffusion effects.8.3 When the specimen is a coating on a substrate, the totalmass may be substantially greater, because of the masscontribution of the substrate material.9. Procedure9.1 Cal
21、ibrate 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 1C (see Method E 220), following the recommended proce-dure.9.2.1 Position the temperature sensor to prevent contactwith specimens which may become distor
22、ted during heating.9.2.2 Temperature calibration is critical and the methodemployed will vary with the apparatus. Calibrate in accordancewith Practice E 1582.9.3 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
23、range.9.6 Place the specimen in the specimen holder and recordthe initial mass.9.7 Set the heating rate to 5 C/min rate of rise.9.8 Start the heating program and record the mass changeuntil there is no further mass loss.NOTE 2Normally the purge rate is 0.7 to 1.6 mL/s.10. Report10.1 Report the follo
24、wing information:10.1.1 Identification of the sample and apparatus,10.1.2 Curing time and temperature in the case of resinspecimens,10.1.3 Mass, approximate dimensions and form (for ex-ample, film, laminate, molded) of the specimen,10.1.4 Heating rate,10.1.5 Rate of flow and type of gas used for pur
25、ging,10.1.6 TGA curve of material evaluated, and10.1.7 Temperatures at which losses of initial specimenmass, if obtained, of 10, 20, 30, 50, and 75 % occur.NOTE 3Do not list temperatures that exceed the resolution of theinstrumentation. Normally this is not to be greater than 2.5 C. Report theresolu
26、tion.11. Precision and Bias11.1 This test method is based on the dynamic measurementof mass loss as a function of increasing temperature. Devia-tions in results that affect precision are caused by variations ina number of complex factors (for example, physical irregulari-ties of the specimen, variat
27、ions in the purging gas compositionand flow characteristics) and generally will not correlatesimply with changes in these factors.11.2 The repeatability of the mass loss measurements as afunction of temperature within one laboratory (and one appa-ratus) is approximately 6 5 C.11.3 Limited inter-labo
28、ratory testing done as a preliminarypreparation for this test method indicate that mass loss mea-surements plotted as a function of temperature have a repro-ducibility of 6 25 C.11.4 This test method has no bias because the thermaldegradation characteristic is defined by the method.12. Keywords12.1
29、degradation; insulating; mass loss; polymeric material;thermogravimetric analysis; TGAAPPENDIX(Nonmandatory Information)X1. INTERPRETATION OF THERMOGRAVIMETRIC TEST TECHNIQUEX1.1 IntroductionThermogravimetry is the continuousmeasurement of mass loss of a specimen as the temperature isincreased at a
30、specific rate. Since the test method requires thecontinuous measurement of a varying mass and temperatureand the control of temperature rate of rise, differences mayexist between instruments, experimenters, or both, even whenthe precision of the individual component sensors are known.Calibration of
31、the instrumentation system is based upon acomparison under dynamic conditions.X1.2 CalibrationInitial calibration should follow therecommended procedure (when available). This procedureshould ensure that individual sensors are correct. The relation-ship between the temperature sensor, usually a ther
32、mocouple,and the specimen design and the type of atmosphere, includingthe rate of flow of the gas through the weighing chamber, willaffect the overall calibration of the system.X1.3 AtmosphereThe rate of mass loss is dependent inpart upon the atmosphere to which the test specimen isexposed. For the
33、best correlation of test results to end use,purge with the air or other gas that relates to the end useconditions. The rate of flow of the gas in the cell will have asignificant effect on the calibration of the system. It is,therefore, necessary to select the rate of flow, usually 0.7 to 1.6mL/s, pr
34、ior to calibration of the system. After calibrating thesystem, do not change the flow rate.D 3850 94 (2006)3X1.4 Specimen Design, is dictated by the material underconsideration, material application, and the instrumentation.Use a specimen in the form normally found in use (forexample, film and coati
35、ngs). The size will depend on theinstrumentation to some degree. The surface area will affect theoverall results. For instance, if a specimen with a large surfaceis compared to one with smaller surface area, both of the samemass, the small surface area specimen will normally lose massat a slower rat
36、e, due to thermal equilibrium and thermal effects.Select the specimen configuration and mass prior to systemcalibration.X1.5 System Calibration:X1.5.1 System calibration of the TGA instrumentation in-corporates the comparison of specimen temperature to ameasured physical change in the specimen. The
37、weakest pointin the calibration procedure is the temperature sensor, usuallya thermocouple. Thermocouples are nonlinear within the nor-mal range of operating temperatures, and after a few times ofoperation may drift from calibration. The location of thetemperature sensor in the weighing chamber must
38、 be such thatit will provide the best estimate of the specimen temperature.Since no standard measurement will provide this location, it isnecessary to make a comparison test.X1.5.2 Practice E 1582 can be used for temperature calibra-tion.X1.5.3 Differences between laboratories may always exist.Compa
39、rison to the referenced curves or another mutuallyselected TGAcurve will provide a reasonably accurate methodfor communicating various TGA data. Close attention to theoverall calibration on a continual basis will ensure goodrepeatability within one laboratory over a long period of time.X1.6 Interpre
40、tation of TGA DataThermogravimetry is arelatively fast means of comparing materials. The dynamicrelationship between mass loss and temperature is the onlythermal characteristic considered with TGA. How thistemperature-mass loss characteristic affects the use of anelectrical insulation in the applica
41、tion is unknown. The rate ofmass loss affects electrical insulation life. Mass loss that willresult in failure varies with material and temperature. Inaddition, the mass loss required for a failure varies with thefailure mode. Due to the many unknown factors in any givenapplication, the exact relati
42、onship between mass loss andfailure mode for each application should be determined experi-mentally. Generally, material comparisons by TGA have notalways been in the same order as the known temperature class.As an example, the round robin testing performed during thedevelopment of this test method i
43、ndicated that polyamide filmwas thermally superior to a PET film. Both life tests andexperience have verified that PET film is thermally superior topolyamide film in a variety of electrical applications.X1.6.1 In 1967, Sweitzer and Stugart3illustrated that anequivalent polyamide polymer for magnet w
44、ire yielded higherTGA data and had a lower thermal life (Test Method D 2307)in comparison to the same polyamide cured under differentconditions.X1.6.2 Thermogravimetry is an important tool in observingthe effect of polymer variation due to changes in one thermalcharacteristic. The relationship betwe
45、en thermogravimetry andapplication life is unknown.NOTE X1.1The attached Figs. 1 and 2 for polyester film and polyim-ide film are illustrative of the original round-robin test work carried out inthe preparation of this test method.ASTM International takes no position respecting the validity of any p
46、atent rights asserted in connection with any item mentionedin this standard. Users of this standard are expressly advised 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 revisi
47、on 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 co
48、mments will receive careful consideration at a meeting of theresponsible technical committee, which you may attend. If you feel that your comments have not received a fair hearing you shouldmake your views known to the ASTM Committee on Standards, at the address shown below.This standard is copyrigh
49、ted by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org).3Sweitzer and Stugart, “Screening Polymers for Use as Magnet Wire Enamel,”Proceeding of the Seventh Electrical Insulation Conference, 1967, Paper No. IEEE32C-79-64.D 3850 94 (2006)4
