1、Designation: D3850 12Standard 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 following the designation indicates the year oforiginal adoption or, in t
2、he 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 approved for use by agencies of the U.S. Department of Defense.1. Scope1.1
3、 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 any electrical insulating ma-terial. If a relat
4、ionship 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 stated in SI units are the standard.1.4 This st
5、andard 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 limitations prior to use.2. Referenced Documents2.1
6、 ASTM Standards:2D883 Terminology Relating to PlasticsD1600 Terminology forAbbreviated Terms Relating to Plas-ticsD1711 Terminology Relating to Electrical InsulationD2307 Test Method for Thermal Endurance of Film-Insulated Round Magnet WireE220 Test Method for Calibration of Thermocouples ByComparis
7、on TechniquesE473 Terminology Relating to Thermal Analysis and Rhe-ologyE1582 Practice for Calibration of Temperature Scale forThermogravimetry3. Terminology3.1 DefinitionsDefinitions are in accordance with Termi-nology D883, Terminology D1711, and Terminology E473.3.2 AbbreviationsAbbreviations are
8、 in accordance withTerminology D1600, unless otherwise indicated.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 a specified prescribed environment using acontrolled time rate of heatin
9、g.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 a TGAcurve), using an electronicchart recorder or other suitable data acquisition dev
10、ice.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 temperatures. TGA can be useful for processcontrol, process development, materia
11、l 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, be used as a prelimi-nary screen method in the evaluation of relative
12、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, the informa-tion obtained from TGA curves is not adequate by itself tode
13、scribe 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 Thermal Characteristics.Current edition approved Jan. 1, 2012. Publishe
14、d February 2012. Originallyapproved in 1979. Last previous edition approved in 2006 as D3850 94(2006).DOI: 10.1520/D3850-12.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, r
15、efer to the standards Document Summary page onthe ASTM website.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States15.4 Refer to the Appendix for further discussion of theinterpretation of TGA data.6. Apparatus6.1 Thermogravimetric Analyze
16、rA 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 1000C,6.1.3 Temperature Programmer, capable of providing alinear rate of rise of the furnace
17、at a predetermined value(normally 5C/min) with a tolerance of 6 0.1C/min,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 1
18、226.1.4 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 10C.7. Sampling7.1 Use sampling plans as described in specifications or testmethods specific to individual electrical insulating m
19、aterials.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 and test apparatus.Test results depend in part on the size and
20、 shape of specimen,due to thermal equilibrium and diffusion effects.8.3 When the specimen is a coating on a substrate, the totalmass is greater unless the substrate is carefully separated,because of the mass contribution of the substrate material.9. Procedure9.1 Calibrate the balance at full scale t
21、o within 6 0.01 mg,following the recommended procedure.9.2 Calibrate the temperature-sensing system to within 61C (see Method E220), following the recommended proce-dure.9.2.1 Position the temperature sensor to prevent contactwith specimens which can become distorted during heating.9.2.2 Temperature
22、 calibration is critical and the methodemployed will vary with the apparatus. Calibrate in accordancewith 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 s
23、pecimen holder and recordthe initial mass.9.7 Set the heating rate to 5C/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 following information:10.1.1 Identification
24、 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 (forexample, 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 TGA curve of material evalua
25、ted, 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 2.5C. Report theresolution.11. Precision and Bias11.1 This test
26、 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, variations in the purging gas compositionand fl
27、ow 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 5C.11.3 Limited inter-laboratory testing done as a preliminaryprepar
28、ation for this test method indicate that mass loss mea-surements plotted as a function of temperature have a repro-ducibility of 6 25C.11.4 This test method has no bias because the thermaldegradation characteristic is defined by the method.12. Keywords12.1 degradation; insulating; mass loss; polymer
29、ic 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 specific rate. Since the test method requir
30、es thecontinuous measurement of a varying mass and temperatureand the control of temperature rate of rise, differences existbetween instruments, experimenters, or both, even when theprecision of the individual component sensors are known.Calibration of the instrumentation system is based upon acompa
31、rison 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 thermocouple,and the specimen design and the type o
32、f atmosphere, includingthe rate of flow of the gas through the weighing chamber, willD3850 123affect 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 best correlation of test results to en
33、d 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, prior to calibration of the system. Afte
34、r calibrating thesystem, do not change the flow rate.X1.4 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 coatings). The size will depend on theinstrumentation to som
35、e 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 rate, due to thermal equilibrium and thermal effects.Selec
36、t 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 weakest pointin the calibration procedure is the temper
37、ature sensor, usuallya thermocouple. Thermocouples are nonlinear within the nor-mal range of operating temperatures, and can drift fromcalibration. The location of the temperature sensor in theweighing chamber must be such that it will provide the bestestimate of the specimen temperature. Since no s
38、tandardmeasurement will provide this location, it is necessary to makea comparison test.X1.5.2 Practice E1582 can be used for temperature calibra-tion.X1.5.3 Differences between laboratories always exist. Com-parison to the referenced curves or another mutually selectedTGA curve will provide a reaso
39、nably accurate method forcommunicating 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 Interpretation of TGA DataThermogravimetry is arelatively fast means of comparing materials. The
40、 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 application is unknown. The rate ofmass loss affects electrical insulation life. Mass loss that
41、 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 relationship between mass loss andfailure mode for each application should be determined exper
42、i-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 indicated that polyamide filmwas thermally superior to a PET film. Both life tests andexp
43、erience 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 wire yielded higherTGAdata and had a lower thermal life (Test Method D2307)incomparison t
44、o 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 between thermogravimetry andapplication life is unknown.NOTE X1.1The attached Figs. 1 and 2 for
45、polyester film andpolyimide film are illustrative of the original round-robin test work carriedout in the preparation of this test method.ASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard. Users of this st
46、andard 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 revision at any time by the responsible technical committee and must be reviewed every five years a
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48、 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 copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-29
49、59,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). Permission rights to photocopy the standard may also be secured from the Copyright Clearance Center, 222Rosewood Drive, Danvers, MA 01923, Tel: (978) 646-2600; http:/ and Stugart, “Screening Polymers for Use as Magnet Wire Enamel,”Proceeding of the Seventh Electrical Insulatio
