1、Designation: E1641 13Standard 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 revision, the
2、 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. Scope1.1 This test method describes the determination of thekinetic parameters, Arrhenius activation energy, and preex
3、po-nential factor by thermogravimetry, based on the assumptionthat the decomposition obeys first-order kineticsusing theOzawa/Flynn/Wall isoconversional method (1).21.2 This test method is generally applicable to materialswith well-defined decomposition profiles, namely, a smooth,continuous mass cha
4、nge with a single maximum rate.1.3 This test method is normally applicable to decomposi-tion occurring in the range from 400 to 1300K (nominally 100to 1000C). The temperature range may be extended dependingon the instrumentation used.1.4 This method is similar to ISO 11358-2 but differs in itsmathem
5、atical treatment.1.5 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.6 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
6、to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:3E473 Terminology Relating to Thermal Analysis and Rhe-ologyE691 Practice for Conducting an Interlaboratory Study toDetermine the Pr
7、ecision of a Test MethodE1142 Terminology Relating to Thermophysical PropertiesE1582 Practice for Calibration of Temperature Scale forThermogravimetryE1877 Practice for Calculating Thermal Endurance of Ma-terials from Thermogravimetric Decomposition DataE1970 Practice for Statistical Treatment of Th
8、ermoanalyticalDataE2040 Test Method for Mass Scale Calibration of Thermo-gravimetric Analyzers2.2 Other Standard:4ISO 11358-2 Plastics Thermogravimetry (TG) of PolymersPart 2: Determination of Kinetic Parameters3. Terminology3.1 DefinitionsTechnical terms used in this test methodare defined in Termi
9、nologies E473 and E1142 and includeactivation energy, Celsius, failure, failure criterion, and ther-mogravimetric analyzer.4. Summary of Test Method4.1 This test method consists of heating a series of four ormore test specimens, taken from the original sample, each at adifferent heating rate between
10、 1 and 10 K/min, through theirdecomposition region. The specimen mass is recorded continu-ously as a function of temperature. The temperatures forconstant conversion are determined from the resultant massloss curves.TheArrhenius activation energy is then determinedfrom a plot of the logarithm of hea
11、ting rate versus thereciprocal of the absolute temperature at constant conversionlevel.4.2 This activation energy may then be used to calculatethermal endurance and an estimate of the lifetime of thematerial at a certain temperature using Test Method E1877.5. Significance and Use5.1 Thermogravimetry
12、 provides a rapid method for deter-mining the temperature-decomposition profile of a material.1This test method is under the jurisdiction ofASTM Committee E37 on ThermalMeasurements and is the direct responsibility of Subcommittee E37.01 on Calo-rimetry and Mass Loss.Current edition approved Aug. 1,
13、 2013. Published September 2013. Originallyapproved in 1994. Last previous edition approved in 2012 as E1641 07 (2012).DOI: 10.1520/E1641-13.2The boldface numbers in parentheses refer to the list of references at the end ofthis standard.3For referenced ASTM standards, visit the ASTM website, www.ast
14、m.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.4Available from American National Standards Institute (ANSI), 25 W. 43rd St.,4th Floor, New York, NY 10036, http:/www.ansi.o
15、rg.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States15.2 This test method can be used for estimating lifetimes ofmaterials, using Test Method E1877 provided that a relation-ship has been established between the thermal endurance testres
16、ults and actual lifetime tests.6. Apparatus6.1 The essential equipment required to provide the mini-mum thermogravimetric analytical capability of this testmethod includes:6.1.1 A thermobalance, composed of (a)afurnace toprovide uniform controlled heating of a specimen at a constantrate within the t
17、emperature range from ambient to 1300 K; (b)a temperature sensor to provide an indication of the specimen/furnace temperature to 60.1 K; (c)anelectrobalance tocontinuously measure the specimen mass with a minimumcapacity of 20 mg and a sensitivity of 650 g; and (d) a meansof sustaining the specimen/
18、container under atmospheric con-trol of an inert or reactive purge gas of 99.99 % purity at a rateof 20 to 50 6 5 mL/min.6.1.2 A temperature controller, capable of executing aspecific temperature program by operating the furnace betweenselected temperature limits at a rate of temperature changebetwe
19、en 1 and 10 K/min to within 60.1 K/min.NOTE 1The precision of results is strongly dependent upon theprecision of the heating rate; the greater the heating rate precision, thegreater the precision of results. The precision described here should beconsidered to be the minimum suitable for this test.6.
20、1.3 A data collection device, to provide a means ofacquiring, storing, and displaying measured or calculatedsignals, or both. The minimum output signals required for thismethod are mass, temperature, and time.6.1.4 Containers (pans, crucibles, and so forth) which areinert to the specimen and that wi
21、ll remain dimensionally stableover the temperature range from ambient to 1300 K.6.2 High-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 inconducting this test method include:6.3.1 Cryoge
22、nic Mill to grind or mill test specimens to a finepowder at temperatures below 173 K (100C).7. Precautions7.1 It is essential that the samples be representative sincemilligram quantities of specimen are to be used.7.2 The value of the calculated activation energy is inde-pendent of reaction order in
23、 the early stages of decomposition.This assumption does not hold for the later stages and shall beused with caution. An upper limit of 10 % decomposition issuggested, although 20 % is justified in certain cases. It isstrongly suggested that calculations be made at several differ-ent levels of decomp
24、osition, for example, 5, 10, 15, and 20 %.Variations in the results among these determinations couldindicate the inapplicability of one of them. For instance,volatile, low-level impurities would affect the results of thelowest conversion determination more than those at higherconversions. Consistent
25、 results for all conversions validate themethod for the range of conversions examined.7.3 Toxic or corrosive effluents, or both, may be releasedduring the heating process and may be harmful to the personnelor apparatus.8. Sampling8.1 Powdered or granular specimens that have a highsurface-to-volume r
26、atio, are preferred, although films, fibers,and fabrics may be used providing that care is taken to make allof the specimens uniform in size and shape. Under circum-stances in which material parts are available, the specimensshould be prepared by filing or rasping the part. All specimensshould be mi
27、xed thoroughly prior to sampling if possible, andthey should be sampled by removing portions from variousparts of the container. These portions should in turn becombined and mixed well to ensure a representative specimenfor the determination.NOTE 3Care should be exercised during sample preparation t
28、o avoidcontamination.NOTE 4The specimen size and surface-to-volume ratio are known toaffect the results of this test. A narrow range of specimen sizes should beused, as noted in 10.1. Uniformity in particle size can be achieved, withoutthe loss of volatiles, by using a cryogenic mill to grind the sa
29、mple to a finepowder. To prevent the condensation of moisture, the mill should beopened only after returning fully to ambient temperature, or the operationshould be performed in a glove box filled with dry gas.8.2 In the absence of other information, the samples areassumed to be analyzed as received
30、 except for the mechanicaltreatment noted in 8.1. If some heat treatment, such as drying,is applied to the sample prior to analysis, this treatment and anyresulting mass loss must be noted in the report.8.3 Certain materials require more sophisticatedconditioning, such as maintaining the sample at a
31、 specifiedroom temperature and relative humidity for an extended periodof time. Such conditioning may be conducted, but proceduraldetails shall be included in the report.9. Calibration9.1 Prepare the thermogravimetric analyzer using any pro-cedures described in the manufacturers Operations manual.9.
32、2 Place the temperature sensor within 2 mm of the outsideof the specimen holder. Care must be taken to ensure that thespecimen holder is not touched in any way by the sensor andthat it is not moved after temperature calibration.9.3 Maintain a constant flow rate of purge gas in the rangefrom 20 to 50
33、 mL/min throughout the experiment.NOTE 5In the case of samples that may be sensitive to oxidativedegradation, it will be necessary to maintain inert gas purging for a timesufficient to ensure that all residual oxygen is removed from the systemprior to the start of the temperature program. It may be
34、necessary toevacuate the system prior to initiating inert gas purging for someinstruments.9.4 Calibrate the instrument furnace temperature in accor-dance with the calibration procedure in Practice E1582 usingthe same heating rate, purge gas, and flow rate to be used forthe specimens. The temperature
35、 calibration shall be performedboth prior to every change in heating rate and at that heatingrate.9.5 Calibrate the mass signal using Test Method E2040.E1641 13210. 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
36、 used but shall be indicated in thereport.NOTE 7The specimen holder should be tared in the fully assembledsystem, with the purge gas flowing.NOTE 8Powdered or granular specimens should be distributed evenlyover the specimen holder so as to maximize the exposed surface. Aone-grain thick layer would b
37、e optimal.10.2 Select an equilibrium temperature based upon theheating rate and known decomposition temperature of thespecimen, where the equilibrium temperature equals the de-composition temperature (10 min heating rate). If thepercentage mass loss is to be recorded, establish zero percentloss at t
38、his time.NOTE 9If zero percent mass loss is established at the time at which thespecimen is placed into the instrument, the specimen mass at theequilibration temperature can be greater than 100 % due to buoyancyeffects. A blank should be run for accurate determination of the buoyancyeffect throughou
39、t the temperature range of the experiment. The blank canbe a piece of platinum of approximately the same volume as the specimen.The balance drift at any temperature can be determined in this manner.10.3 Heat the specimen at a constant rate through thedecomposition profile until a constant mass is ob
40、tained or thetemperature is well beyond the useful temperature range of thematerial tested. Record the accompanying thermal curve, withmass or percentage mass loss displayed on the ordinate andspecimen temperature on the abscissa.10.4 Once the decomposition of the test specimen iscomplete, cool the
41、instrument to room temperature, remove,clean, and replace the specimen holder, and retare the instru-ment in preparation for additional experiments. Use the samespecimen holder for the entire series of runs to eliminatebuoyancy problems.10.5 Repeat the procedures described in 10.1 10.4 at threeaddit
42、ional heating rates covering the range from 1 to 10 K/min.NOTE 10Other heating rates, and more than four, may be used butshall be noted in the report.NOTE 11The use of heating rates greater than 10 K/min affects boththe precision of the temperature measurement and the kinetics of thedecomposition. D
43、iffusion of volatiles from the sample may become therate-controlling process at high heating rates.11. Calculation11.1 Select some mass loss (conversion) as the failurecriterion.NOTE 125 % mass loss is commonly selected as the failure criterion.Other values may be used but shall be reported.11.2 Fro
44、m each of the thermal curves obtained in 10.1 10.5, determine the absolute temperature at constantconversion, , for each of the constant conversion values to beused in the calculations as noted in 7.2. For example, see Fig.1. The temperature corresponding to other conversion levels(not greater than
45、20 %) may be used in the determination, butit must be noted in the report.NOTE 13These calculations are simplified if the percent mass lossrather than actual mass is recorded on the ordinate.NOTE 14The value is determined from the difference of the initial andfinal sample conversion, with the initia
46、l mass taken as the mass at theequilibration temperature and the final mass taken once the plateau hasbeen reached at the end of weight loss. For example, if the initial mass is100.3 % and the final mass is 80 %, 100 % decomposition corresponds to(100.3 to 80.0) or 20.3 % mass loss. Thus, 5 % decomp
47、osition occurs at(0.05 20.3) or 1.02 % mass loss, which occurs on the ordinate at 99.3 %(100.3 % 1.02 % = 99.28 %).11.3 Display the logarithm of the heating rate expressed inK/min against the reciprocal of the absolute temperature in Kat which the conversion level (failure criterion), selected inFIG
48、. 1 Examples of Mass Loss Curves at the Following Heating Rates: 1C/min, 2C/min, 5C/min, 10C/minE1641 13311.1, was reached. A straight line, similar to that in Fig. 2,should result. This test procedure is not applicable if the curveis nonlinear.NOTE 15An apparent nonlinearity may result from erroneo
49、us deter-minations. It is recommended that any nonlinear points be repeated forverification.11.4 Using the least-squares method fit a straight line (seePractice E1970) to these data without weighing factors, anddetermine the slope (m) and its standard deviation (m):m 5 log!/1/T!NOTE 16If the values obtained from this test method are to be used inTest Method E1877, an estimation of the uncertainty for activation energy(E) and preexponential factor (A) is required. These uncertainties may bederived from the uncertainty in the slope value
