1、Designation: E1641 15E1641 16Standard 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 Scope*1.1 This test method describes the determination of the kinetic parameters,Arrhenius activation en
3、ergy, and preexponentialpre-exponential factor by thermogravimetry, based on the assumption that the decomposition obeys first-order kineticsusing kineticsusing the Ozawa/Flynn/Wall isoconversional method (1, 2).21.2 This test method is generally applicable to materials with well-defined decompositi
4、on profiles, namely, a smooth, continuousmass change with a single maximum rate.1.3 This test method is normally applicable to decomposition occurring in the range from 400 to 1300K 1300 K (nominally 100to 1000C). The temperature range may be extended depending on the instrumentation used.1.4 This t
5、est method is similar to ISO 11358-2 but differs in its mathematical treatment.1.5 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.1.6 This standard does not purport to address all of the safety concerns, if any, associated wi
6、th its use. It is the responsibilityof the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatorylimitations prior to use.2. Referenced Documents2.1 ASTM Standards:3E29 Practice for Using Significant Digits in Test Data to Determine C
7、onformance 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 Practice for Calibration of Temperature Scale for Ther
8、mogravimetryE1877 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 Plastics Ther
9、mogravimetry (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.4. Summary of T
10、est Method4.1 This test method is based upon the general rate equation that takes the form of:ddT 5A1 2 ! exp2E R T# (1)1 This test 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.Curre
11、nt edition approved March 1, 2015Feb. 15, 2016. Published March 2015February 2016. Originally approved in 1994. Last previous edition approved in 20132015as E1641 13.E1641 15. DOI: 10.1520/E1641-15.10.1520/E1641-16.2 The boldface numbers in parentheses refer to the list of references at the end of t
12、his standard.3 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website.4 Available from American National Standards Ins
13、titute (ANSI), 25 W. 43rd St., 4th Floor, New York, NY 10036, http:/www.ansi.org.This 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 adequ
14、ately depict all changes 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.*A Summary of Changes section appears at the end of this standardCopyright ASTM I
15、nternational, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1where: = fraction reacted (dimensionless),A = pre-exponential factor (min-1), = heating rate (K/min),E = activation energy (J/mol),R = gas constant (=8.316 J/(mol K),T = absolute temperature (K),exp = E
16、ulers number exponential, andd/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)where:E = the derivative of the Doyle approximation (3) with values tabulated in Table 1.4.3 Using a point of constant convers
17、ion from a series of decomposition curves obtained at different heat rates, log#12T! 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
18、 value of b using Table 1.4.6 This iterative 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)where:a = the Do
19、yle approximation 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 and 10 K/min, through their decomposition region. The specimen mass is recorded continuouslyas a function o
20、f temperature. The temperatures for constant conversion are determined from the resultant mass loss curves. TheArrhenius activation energy is then determined from a plot of the logarithm of heating rate versus the reciprocal of the absolutetemperature at constant conversion level.4.9 This activation
21、 energy may then be used to calculate thermal endurance and an estimate of the lifetime of the material ata certain temperature using Test Method E1877.5. Significance and Use5.1 Thermogravimetry provides a rapid method for determining the temperature-decomposition profile of a material.5.2 This tes
22、t method can be used for estimating lifetimes of materials, using Test Method E1877 provided that a relationshiphas been established between the thermal endurance test results and actual lifetime tests.6. Apparatus6.1 The essential equipment required to provide the minimum thermogravimetric analytic
23、al 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/furnacetemperature to
24、 60.1 K; (c) an electrobalance to continuously measure the specimen mass with a minimum capacity of 20 mg anda 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 to 50 6 5 mL/min.mLmi
25、n.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 and 10 K/min to within 60.1 K/min.NOTE 1The precision of results is strongly dependent upon the precision of the
26、 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 A data collection device, to provide a means of acquiring, storing, and displaying measured or calculated signa
27、ls, 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 High-Purity (99.99 %) N
28、itrogen Supply, for purge gas.E1641 162NOTE 2Other atmospheres may be used but shall be reported.6.3 Auxiliary apparatus considered necessary or useful in conducting this test method include:6.3.1 Cryogenic Mill to grind or mill test specimens to a fine powder at temperatures below 173 K (100C).7. P
29、recautions7.1 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
30、be used with caution. 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, and 20 %.Variations in the results among these determinations could indicate the inapplicability of one of
31、them. For instance, volatile,low-level impurities would affect the results of the lowest conversion determination more than those at higher conversions.Consistent results for all conversions validate the method for the range of conversions examined.7.3 Toxic or corrosive effluents, or both, may be r
32、eleased during the heating process and may be harmful to the personnel orapparatus.TABLE 1 Numerical Integration ConstantsE/RT a b8 5.3699 0.53989 5.8980 0.528110 6.4167 0.518711 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
33、.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 16.472 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 20.1
34、41 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 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 2
35、8.7305 0.449159 29.1794 0.448960 29.6281 0.4487E1641 1638. 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 in size and shape. Under cir
36、cumstances 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.These portions should in turn be
37、 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 range of specimen sizes should
38、 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 temperature, or the operation
39、 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 analysis, this treatment and a
40、ny 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 procedural details shall be inc
41、ludedin the report.9. Calibration9.1 Prepare the thermogravimetric analyzer using any procedures described in the manufacturers Operations manual.9.2 Place the temperature sensor within 2 mm of the outside of the specimen holder. Care must be taken to ensure that thespecimen holder is not touched in
42、 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 to 50 mL/min throughout the experiment.NOTE 5In the case of samples that may be sensitive to oxidative degradation, it will be necessary to maintain inert
43、 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 Calibrate the instrument furnace temperature in acco
44、rdance with the calibration procedure in Practice E1582 using the sameheating rate, purge gas, and flow rate to be used for the specimens. The temperature calibration shall be performed both prior toevery change in heating rate and at that heating rate.9.5 Calibrate the mass signal using Test Method
45、 E2040.10. Procedure10.1 Place 3 6 1 mg of the specimen under test into a clean, tared instrument specimen holder.NOTE 6Other specimen sizes may be used but shall be indicated in the report.NOTE 7The specimen holder should be tared in the fully assembled system, with the purge gas flowing.NOTE 8Powd
46、ered 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 rate and known decomposition first-deviation-from-baselinetemperature of the s
47、pecimen, 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
48、, the specimen mass at the equilibrationtemperature can be greater than 100 % due to buoyancy effects. A blank should be run for accurate determination of the buoyancy effect throughout thetemperature range of the experiment. The blank can be a piece of platinum of approximately the same volume as t
49、he specimen. The balance drift at anytemperature can be determined in this manner.10.3 Heat the specimen at a constant rate through the decomposition profile until a constant mass is obtained or the temperatureis well beyond the useful temperature range of the material tested. Record the accompanying thermal curve, with mass orpercentage mass loss displayed on the ordinate and specimen temperature on the abscissa.10.4 Once the decomposition of the test specimen is complete, cool the instrument to room temperature, rem
