ASTM E1641-2018 Standard Test Method for Decomposition Kinetics by Thermogravimetry Using the Ozawa Flynn Wall Method.pdf

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1、Designation: E1641 16E1641 18Standard Test Method forDecomposition Kinetics by Thermogravimetry Using theOzawa/Flynn/Wall Method1This standard is issued under the fixed designation E1641; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revis

2、ion, 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.1. Scope*1.1 This test method describes the determination of the kinetic parameters, Arrhenius activation energy,

3、 and pre-exponentialfactor by thermogravimetry, based on the assumption that the decomposition obeys first-order kinetics using the Ozawa/Flynn/Wallisoconversional method (1, 2).21.2 This test method is generally applicable to materials with well-defined decomposition profiles, namely, a smooth, con

4、tinuousmass change with a single maximum rate.1.3 This test method is normally applicable to decomposition occurring in the range from 400 K to 1300 K (nominally100100C to 1000C). The temperature range may be extended depending on the instrumentation used.1.4 This test method is similar to ISO 11358

5、-2 but differs in its mathematical treatment.1.4 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibili

6、tyof the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability ofregulatory limitations prior to use.1.6 This international standard was developed in accordance with internationally recognized principles on standardizationestablish

7、ed in the Decision on Principles for the Development of International Standards, Guides and Recommendations issuedby the World Trade Organization Technical Barriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:3E29 Practice for Using Significant Digits in Test Data to Determine

8、 Conformance with SpecificationsE473 Terminology Relating to Thermal Analysis and RheologyE691 Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test MethodE1142 Terminology Relating to Thermophysical PropertiesE1582 Test Method for Temperature Calibration of Thermogra

9、vimetric AnalyzersE1877 Practice for Calculating Thermal Endurance of Materials from Thermogravimetric Decomposition DataE1970 Practice for Statistical Treatment of Thermoanalytical DataE2040 Test Method for Mass Scale Calibration of Thermogravimetric Analyzers2.2 Other Standard:4ISO 11358-2 Plastic

10、s Thermogravimetry (TG) of Polymers Part 2: Determination of Kinetic Parameters3. Terminology3.1 DefinitionsTechnical terms used in this test method are defined in Terminologies E473 and E1142 and include activationenergy, Celsius, failure, failure criterion, and thermogravimetric analyzer.1 This te

11、st method is under the jurisdiction of ASTM Committee E37 on Thermal Measurements and is the direct responsibility of Subcommittee E37.01 on Calorimetryand Mass Loss.Current edition approved Feb. 15, 2016Nov. 1, 2018. Published February 2016November 2018. Originally approved in 1994. Last previous e

12、dition approved in 20152016as E1641 15.E1641 16. DOI: 10.1520/E1641-16.10.1520/E1641-18.2 The boldface numbers in parentheses refer to the list of references at the end of this standard.3 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceast

13、m.org. For Annual Book of ASTM Standardsvolume information, refer to the standardsstandards Document Summary page on the ASTM website.4 Available from American National Standards Institute (ANSI), 25 W. 43rd St., 4th Floor, New York, NY 10036, http:/www.ansi.org.This document is not an ASTM standard

14、 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 accurately, ASTM recommends that users consult prior editions as appropriate. In all cases on

15、ly the current versionof the standard as published by ASTM is to be considered the official document.*A Summary of Changes section appears at the end of this standardCopyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States14. Summary of Test M

16、ethod4.1 This test method is based upon the general rate equation that takes the form of:d dT 5A1 2 ! exp2E R T# (1)d dT 5A1 2 ! exp2E RT# (1)where: = fraction reacted (dimensionless),A = pre-exponential factor (min-1), = heating rate (K/min),E = activation energy (J/mol),R = gas constant (=8.316 J/

17、(mol K),R = gas constant (= 8.316 J/(mol K),T = absolute temperature (K),exp = Eulers number exponential, andd/dT = rate of change of with T.d / dT = rate of change of with T.4.2 Using the method of Ozawa, Flynn, and Wall (1, 2),Eq 1 may be solved for activation energy:E 5R b! log# 1T! (2)E 52R b! l

18、og# 1T! (2)where:E = the derivative of the Doyle approximation (3) with values tabulated in Table 1.E = the derivative of the Doyle approximation (3) with values tabulated in Table 1, andb = value from Table 1.4.3 Using a point of constant conversion from a series of decomposition curves obtained at

19、 different heat rates, log# 12T!log# 1T! is obtained by linear regression.4.4 Assuming an initial value of b50.457, a first approximation of activation energy (E) is obtained using Eq 2.4.5 This approximate activation energy is then used to determine a new value of b using Table 1.4.6 This iterative

20、 process is continued until the value of activation energy no longer changes with the next iteration.4.7 For first order reactions (n51), the value of the pre-exponential factor (A) may be determined using Eq 3( (4).A52 R E! ln 1 2 #! 10a (3)A 52R E! ln 1 2 #! 10a (3)where:a = the Doyle approximatio

21、n value from Table 1.4.8 This test method consists of heating a series of four or more test specimens, taken from the original sample, each at adifferent heating rate between 1 K/min and 10 K/min, through their decomposition region. The specimen mass is recordedcontinuously as a function of temperat

22、ure. The temperatures for constant conversion are determined from the resultant mass losscurves. The Arrhenius activation energy is then determined from a plot of the logarithm of heating rate versus the reciprocal ofthe absolute temperature at constant conversion level.4.9 This activation energy ma

23、y then be used to calculate thermal endurance and an estimate of the lifetime of the material ata certain temperature using Test Method Practice E1877.5. Significance and Use5.1 Thermogravimetry provides a rapid method for determining the temperature-decomposition profile of a material.5.2 This test

24、 method can be used for estimating lifetimes of materials, using Test Method Practice E1877 provided that arelationship has been established between the thermal endurance test results and actual lifetime tests.6. Apparatus6.1 The essential equipment required to provide the minimum thermogravimetric

25、analytical capability of this test methodincludes:6.1.1 Athermobalance, composed of (a) a furnace to provide uniform controlled heating of a specimen at a constant rate withinthe temperature range from ambient to 1300 K; (b) a temperature sensor to provide an indication of the specimen/furnacetemper

26、ature to 60.1 K; (c) an electrobalance to continuously measure the specimen mass with a minimum capacity of 20 mg andE1641 182a sensitivity of 650 g; and (d) a means of sustaining the specimen/container under atmospheric control of an inert or reactivepurge gas of 99.99 % purity at a rate of 20 mL/m

27、in to 50 6 5 mLmin.6.1.2 A temperature controller, capable of executing a specific temperature program by operating the furnace between selectedtemperature limits at a rate of temperature change between 1 K/min and 10 K/min to within 60.1 K/min.NOTE 1The precision of results is strongly dependent up

28、on the precision of the heating rate; the greater the heating rate precision, the greater theprecision of results. The precision described here should be considered to be the minimum suitable for this test.6.1.3 Adata collection device, to provide a means of acquiring, storing, and displaying measur

29、ed or calculated signals, or both.The minimum output signals required for this test method are mass, temperature, and time.6.1.4 Containers (pans, crucibles, and so forth) which are inert to the specimen and that will remain dimensionally stable overthe temperature range from ambient to 1300 K.6.2 H

30、igh-Purity (99.99 %) Nitrogen Supply, for purge gas.NOTE 2Other atmospheres may be used but shall be reported.6.3 Auxiliary apparatus considered necessary or useful in conducting this test method include:TABLE 1 Numerical Integration ConstantsE/RT a b8 5.3699 0.53989 5.8980 0.528110 6.4167 0.518711

31、6.928 0.51112 7.433 0.50513 7.933 0.50014 8.427 0.49415 8.918 0.49116 9.406 0.48817 9.890 0.48418 10.372 0.48219 10.851 0.47920 11.3277 0.477021 11.803 0.47522 12.276 0.47323 12.747 0.47124 13.217 0.47025 13.686 0.46926 14.153 0.46727 14.619 0.46628 15.084 0.46529 15.547 0.46330 16.0104 0.462931 16.

32、472 0.46232 16.933 0.46133 17.394 0.46134 17.853 0.45935 18.312 0.45936 18.770 0.45837 19.228 0.45838 19.684 0.45639 20.141 0.45640 20.5967 0.455841 21.052 0.45542 21.507 0.45543 21.961 0.45444 22.415 0.45445 22.868 0.45346 23.321 0.45347 23.774 0.45348 24.226 0.45249 24.678 0.45250 25.1295 0.451551

33、 25.5806 0.451152 26.0314 0.450853 26.4820 0.450654 26.9323 0.450355 27.3823 0.450056 27.8319 0.449857 28.2814 0.449558 28.7305 0.449159 29.1794 0.448960 29.6281 0.4487E1641 1836.3.1 Cryogenic Mill to grind or mill test specimens to a fine powder at temperatures below 173 K (100C).7. Precautions7.1

34、It is essential that the samples be representative since milligram quantities of specimen are to be used.7.2 The value of the calculated activation energy is independent of reaction order in the early stages of decomposition. Thisassumption does not hold for the later stages and shall be used with c

35、aution. An upper limit of 10 % decomposition is suggested.It is strongly suggested that calculations be made at several different levels of decomposition, for example, 5, 10, 15,5 %, 10 %,15 %, and 20 %. Variations in the results among these determinations could indicate the inapplicability of one o

36、f them. Forinstance, volatile, low-level impurities would affect the results of the lowest conversion determination more than those at higherconversions. Consistent results for all conversions validate the method for the range of conversions examined.7.3 Toxic or corrosive effluents, or both, may be

37、 released during the heating process and may be harmful to the personnel orapparatus.8. Sampling8.1 Powdered or granular specimens that have a high surface-to-volume ratio, are preferred, although films, fibers, and fabricsmay be used providing that care is taken to make all of the specimens uniform

38、 in size and shape. Under circumstances in whichmaterial parts are available, the specimens should be prepared by filing or rasping the part. All specimens should be mixedthoroughly prior to sampling if possible, and they should be sampled by removing portions from various parts of the container.The

39、se portions should in turn be combined and mixed well to ensure a representative specimen for the determination.NOTE 3Care should be exercised during sample preparation to avoid contamination.NOTE 4The specimen size and surface-to-volume ratio are known to affect the results of this test. A narrow r

40、ange of specimen sizes should be used,as noted in 10.1. Uniformity in particle size can be achieved, without the loss of volatiles, by using a cryogenic mill to grind the sample to a fine powder.To prevent the condensation of moisture, the mill should be opened only after returning fully to ambient

41、temperature, or the operation should be performedin a glove box filled with dry gas.8.2 In the absence of other information, the samples are assumed to be analyzed as received except for the mechanical treatmentnoted in 8.1. If some heat treatment, such as drying, is applied to the sample prior to a

42、nalysis, this treatment and any resulting massloss must be noted in the report.8.3 Certain materials require more sophisticated conditioning, such as maintaining the sample at a specified room temperatureand relative humidity for an extended period of time. Such conditioning may be conducted, but pr

43、ocedural details shall be includedin the report.9. Calibration9.1 Prepare the thermogravimetric analyzer using any procedures described in the manufacturersmanufacturers Operationsmanual.9.2 Place the temperature sensor within 2 mm of the outside of the specimen holder. Care must be taken to ensure

44、that thespecimen holder is not touched in any way by the sensor and that it is not moved after temperature calibration.9.3 Maintain a constant flow rate of purge gas in the range from 20 mL/min to 50 mL/min throughout the experiment.NOTE 5In the case of samples that may be sensitive to oxidative deg

45、radation, it will be necessary to maintain inert gas purging for a time sufficientto ensure that all residual oxygen is removed from the system prior to the start of the temperature program. It may be necessary to evacuate the systemprior to initiating inert gas purging for some instruments.9.4 Cali

46、brate the instrument furnace temperature in accordance with the calibration procedure in Practice Test Method E1582using the same heating rate, purge gas, and flow rate to be used for the specimens. The temperature calibration shall be performedboth prior to every change in heating rate and at that

47、heating rate.9.5 Calibrate the mass signal using Test Method E2040.10. Procedure10.1 Place 3 6 13 mg 6 1 mg of the specimen under test into a clean, tared instrument specimen holder.NOTE 6Other specimen sizesquantity may be used but shall be indicated in the report.NOTE 7The specimen holder should b

48、e tared in the fully assembled system, with the purge gas flowing.NOTE 8Powdered or granular specimens should be distributed evenly over the specimen holder so as to maximize the exposed surface. A one-grainthick layer would be optimal.10.2 Select an equilibrium temperature based upon the heating ra

49、te and known decomposition first-deviation-from-baselinetemperature of the specimen, where the equilibrium temperature equals the decomposition temperature (10 min heating rate).If the percentage mass loss is to be recorded, establish zero percent loss at this time.NOTE 9If zero percent mass loss is established at the time at which the specimen is placed into the instrument, the specimen mass at the equilibrationE1641 184temperature can be greater than 100 % due to buoy