1、Designation: E698 18Standard Test Method forKinetic Parameters for Thermally Unstable Materials UsingDifferential Scanning Calorimetry and the Flynn/Wall/OzawaMethod1This standard is issued under the fixed designation E698; the number immediately following the designation indicates the year oforigin
2、al adoption or, in the 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.INTRODUCTIONThe kinetics of exothermic reactions are important in assessing t
3、he potential of materials andsystems for thermal explosion. This test method provides a means for determining Arrheniusactivation energies and pre-exponential factors using differential thermal methods. This test method isto be used in conjunction with other tests to characterize the hazard potentia
4、l of chemicals.1. Scope1.1 This test method covers the determination of the overallkinetic parameters for exothermic reactions using the Flynn/Wall/Ozawa method and differential scanning calorimetry.1.2 This technique is applicable to reactions whose behaviorcan be described by theArrhenius equation
5、 and the general ratelaw.1.3 LimitationsThere are cases where this technique is notapplicable. Limitations may be indicated by curves departingfrom a straight line (see 11.2) or the isothermal aging test notclosely agreeing with the results predicted by the calculatedkinetic values. In particular, t
6、his test method is not applicableto reactions that are partially inhibited. The technique may notwork with reactions that include simultaneous or consecutivereaction steps. This test method may not apply to materials thatundergo phase transitions if the reaction rate is significant atthe transition
7、temperature.1.4 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.5 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 es
8、tablish appro-priate safety, health, and environmental practices and deter-mine the applicability of regulatory limitations prior to use.1.6 This international standard was developed in accor-dance with internationally recognized principles on standard-ization established in the Decision on Principl
9、es for theDevelopment of International Standards, Guides and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2E473 Terminology Relating to Thermal Analysis and Rhe-ologyE691 Practice for Conducting an Interl
10、aboratory Study toDetermine the Precision of a Test MethodE967 Test Method for Temperature Calibration of Differen-tial Scanning Calorimeters and Differential Thermal Ana-lyzersE968 Practice for Heat Flow Calibration of DifferentialScanning CalorimetersE1142 Terminology Relating to Thermophysical Pr
11、opertiesE1231 Practice for Calculation of Hazard Potential Figuresof Merit for Thermally Unstable MaterialsE1445 Terminology Relating to Hazard Potential of Chemi-calsE1860 Test Method for Elapsed Time Calibration of Ther-mal AnalyzersE1970 Practice for Statistical Treatment of ThermoanalyticalDataE
12、2890 Test Method for Kinetic Parameters for ThermallyUnstable Materials by Differential Scanning CalorimetryUsing the Kissinger Method1This test method is under the jurisdiction ofASTM Committee E37 on ThermalMeasurements and is the direct responsibility of Subcommittee E37.01 on Calo-rimetry and Ma
13、ss Loss.Current edition approved June 1, 2018. Published June 2018. Originallyapproved in 1979. Last previous edition approved in 2016 as E698 16. DOI:10.1520/E0698-18.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual
14、 Book of ASTMStandards volume information, refer 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 StatesThis international standard was developed in accordance with internationally rec
15、ognized principles on standardization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.13. Terminology3.1 Technical terms used in this test method are
16、 defined inTerminologies E473, E1142, and E1445 including activationenergy, Arrhenius equation, Celsius, differential scanningcalorimetry, enthalpy, general rate law, Kelvin, kinetics, peakvalue, pre-exponential factor, reaction, reaction order, andtemperature.4. Summary of Test Method4.1 A specimen
17、 is placed in a suitable container andpositioned in a differential scanning calorimeter (DSC).4.2 The temperature surrounding the specimen is increasedat a linear rate and any exothermic reaction peaks recorded.4.3 Steps 4.1 and 4.2 are repeated for several heating ratesin the range from 1 K min1to
18、10 K min1.4.4 Temperatures at which the reaction peak maxima occurare plotted as a function of their respective heating rates.4.5 Kinetic values calculated from the peak temperature-heating rate relationship are used to predict a reaction half-lifeat a selected temperature.4.6 A specimen is aged at
19、the selected temperature for thepredicted half-life time.4.7 The aged specimen is temperature programmed in adifferential scanning calorimeter and its reaction peak areacompared with that for an unaged sample run under the sameconditions.4.8 If the normalized area for the aged specimen is approxi-ma
20、tely half that for the unaged sample, the kinetic values areconfirmed for the temperature selected.5. Significance and Use5.1 The kinetic parameters combined with the general ratelaw and the reaction enthalpy can be used for the determinationof thermal hazard using Practice E1231 (1).36. Apparatus6.
21、1 GeneralThe equipment used in this test methodshould be capable of displaying quantitative changes of en-thalpy as a function of time (t) or temperature (T), should belinearly programmable and have the capabilities of subjectingthe sample cell to different atmospheres. The heat sensingelement shoul
22、d be external to the sample.6.2 Differential Scanning Calorimeter (DSC):6.2.1 A test chamber composed of:6.2.1.1 A furnace, to provide uniform controlled heating(cooling) of a specimen and reference to a constant temperatureor at a constant rate within the applicable temperature range ofthis test me
23、thod.6.2.1.2 A temperature sensor, to provide an indication of thespecimen/furnace temperature to 60.1 K.6.2.1.3 A differential sensor, to detect a difference in heatflow between the specimen and reference equivalent to 10 W.6.2.1.4 A means of sustaining a test chamber environment,of an inert purge
24、gas at a rate of 10 mLmin to 50 mLmin.NOTE 1Typically, 99+ % pure nitrogen, argon, or helium are em-ployed when oxidation in air is a concern. Unless effects of moisture areto be studied, use of dry purge gas is recommended; especially foroperation at subambient temperature.6.2.2 A temperature contr
25、oller, capable of executing aspecific temperature program by operating the furnace(s)between selected temperature limits at a rate of temperaturechange between 0.5 K/min and 10 Kmin constant to60.1 Kmin or at an isothermal temperature constant to60.1 K.6.2.3 A data collection device, to provide a me
26、ans ofacquiring, storing, and displaying measured or calculatedsignals, or both. The minimum output signals required fordifferential scanning calorimetry are heat flow, temperature,and time.6.3 Containers (pans, crucibles, vials, etc.), which are inertto the specimen and reference materials and whic
27、h are suitablestructural shape and integrity to contain the specimen andreference in accordance with the specific requirements of thistest method.6.4 A balance, with a capacity of at least 100 mg, to weighspecimens or containers (pans, crucibles, vials, etc.) to within10 g.6.5 Auxiliary equipment us
28、eful for conducting this testmethod below ambient temperature.6.5.1 A coolant system, which can be directly coupled withthe controller to the furnace to hasten its recovery fromelevated temperatures, to provide constant cooling rates, or tosustain an isothermal subambient temperature, or a combina-t
29、ion thereof.7. Safety Precautions7.1 The use of this test method on materials whose potentialhazards are unknown requires that precaution be taken duringsample preparation and testing.7.2 Where particle size reduction by grinding is necessary,the user of this test method should presume that the mate
30、rial isdangerous.7.3 Toxic or corrosive effluents, or both, may be releasedwhen heating the material and could be harmful to thepersonnel or the apparatus. Use of an exhaust system to removesuch effluents is recommended.8. Sampling8.1 Specimen size is kept small to minimize temperaturegradients with
31、in the sample. In general, a sample mass result-ing in a maximum heat generation of less than 8 mJs (8 mW)is satisfactory.NOTE 2The 8 mW maximum heat flow will ensure that the adiabatictemperature rise in the specimen is less than 0.1C .8.2 Specimens shall be representative of the material beingstud
32、ied and should be prepared to achieve good thermal contactbetween sample and container (see Figs. 1 and 2).3The boldface numbers in parentheses refer to the list of references at the end ofthis standard.E698 1828.3 The specimen container should be nonreactive with thesample or reaction products.8.4
33、The reference for the sample is normally an emptycontainer or one filled with inert material.8.5 Specimens which have appreciable volatility over thetemperature range of interest may require sealing in hermeticcontainers or a high-pressure cell, or both, to prevent vapor-ization interference and wei
34、ght loss of unreacted material.NOTE 3 Should deformation of the container be observed followingthe test, repeat the experiment with a smaller specimen size.8.6 The specimen atmosphere should closely represent theconditions of usage.9. Calibration9.1 Perform any calibration procedures recommended byt
35、he manufacturer as described in the operators manual.9.2 Calibrate the heat flow and elapsed time signals usingPractice E968 and Test Method E1860, respectively, using thesame type of specimen container to be used in the subsequentkinetic tests.9.3 Calibrate the temperature signal at 10 Kmin using T
36、estMethod E967 and Test Method E1860, respectively, using thesame type of specimen container to be used in the subsequentkinetic tests.9.4 Determine the temperature calibration corrections forother heating rates by programming a sharply melting standard(for example, pure indium metal) at these heati
37、ng rates andobserving the deviation of the known melt temperature as afunction of the rate.NOTE 4This table of temperature calibration correction values, oncedetermined for a particular apparatus and specimen container, may be usedfor subsequent experiments following temperature calibration at 10 K
38、minheating rate in 9.3.9.5 The thermal resistance of the instrument sample cell isdetermined by measuring the temperature lag observed for themelting of a pure metal standard. See Fig. X1.2 in AppendixX1.10. Procedure10.1 Perform an initial experiment using a specimen of5 mg or less to determine pro
39、per specimen sizes and startingtemperatures.10.2 Place the specimen and reference materials in theinstrument heating unit. Use a specimen size as recommendedin 8.1.10.3 Heat the specimen at 10 Kmin from a point starting atleast 50 K below the first observed exothermic peak deflection.10.4 Record the
40、 differential heat flow signal as a function oftemperature. Continue heating until the peak maximum ofinterest is recorded.10.5 Repeat 10.2 10.4 for various heating rates betweenabout 1 K/min and 10 Kmin.FIG. 1 Arrangement for Good Sample Contact with ContainerFIG. 2 Specimen Pan Collapsed and Colle
41、ctedE698 183NOTE 5Aminimum of four determinations at heating rates between 1K/min and 10 K min are recommended.NOTE 6Reaction curve baselines should be level to minimize slopeerror in peak maxima measurements.11. Calculation11.1 Temperatures of reaction peak maxima are correctedfor temperature scale
42、 nonlinearity, heating rate changes, andthermal lag as in the example in Appendix X1.11.2 Plot log10 (heating rate, K min1) versus 1/T, where Tis the corrected peak maximum temperature in Kelvin. Calcu-late and construct a least squares “best fit” line through thesepoints (see Practice E1970). The s
43、lope of this “best fit” line istaken as the value for d log10 d (1/T).11.3 Calculate an approximate value for E (activation en-ergy) as follows (2):E22.19Rd log10/d1/T!# (1)where R = gas constant (=8.314 J mol1K1).11.4 Refine value of E by:11.4.1 Calculate E/RT approximately.11.4.2 Find correspondin
44、g value of D from Table X2.1.11.4.3 Calculate new value for E as follows:E 5 22.303R/D!d log10/d1/T!# (2)Refining the value of E a second time usually results in aclose approach to its final value. An alternative calculationmethod is shown in Appendix X3.11.5 The pre-exponential factor can be calcul
45、ated as followsunder the assumption of a first-order reaction:Z 5 EeE/RT/RT2(3)where: = a heating rate from the middle of the range.11.6 For the confirming isothermal test, calculate k forvarious temperatures from the Arrhenius equation and theabove E and Z values.11.7 From t = 0.693k, calculate agi
46、ng times (t) for eachtemperature.11.8 Select a temperature requiring at least 1-h aging time,and age the sample isothermally for the calculated half-life ina thermal instrument or other facility capable of 61 K control.Quench immediately to some temperature at least 50 K belowthe aging temperature s
47、o that no significant reaction occursduring subsequent holding time.11.9 Heat the aged specimen in a thermal instrument andrecord its reaction peak and determine temperature.11.10 Heat a similar but unaged specimen in the same wayand record its reaction peak and determine temperature.11.11 On an equ
48、al mass basis, the peak area or displacementfrom baseline of the aged specimen shall be approximately onehalf that of the unaged sample. If so, the reaction kinetics areconfirmed for the temperature range explored.12. Report12.1 The report shall include the following:12.1.1 Identification of the sam
49、ple by name or composition,stating the source, past history, and weight of each specimentogether with its purity (if available).12.1.2 Description of apparatus and type of container used.12.1.3 Identification of specimen environment as to degreeof confinement, composition of atmosphere, and whether theatmosphere is static, self-generated, or dynamic through orover the sample.12.1.4 Description of test conditions, including the heatingrates and peak temperature range investigated.12.1.5 The specific dated version of this test method.13. Pre
