1、Designation: E698 11E698 16Standard Test Method forArrhenius Kinetic ConstantsParameters for ThermallyUnstable Materials Using Differential Scanning Calorimetryand the Flynn/Wall/Ozawa Method1This standard is issued under the fixed designation E698; the number immediately following the designation i
2、ndicates the year oforiginal 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 ar
3、e important in assessing the 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 isone of several test methods being developed by ASTM
4、Committee E27 for chemical reactions. Thistest method is to be used in conjunction with other tests to characterize the hazard potential ofchemicals.1. Scope Scope*1.1 This test method covers the determination of the overall kinetic parameters for exothermic reactions using theFlynn/Wall/Ozawa metho
5、d and differential scanning calorimetry.1.2 This technique is applicable to reactions whose behavior can be described by the Arrhenius equation and the general ratelaw.1.3 LimitationsThere are cases where this technique is not applicable. Limitations may be indicated by curves departing froma straig
6、ht line (see 11.2) or the isothermal aging test not closely agreeing with the results predicted by the calculated kinetic values.In particular, this test method is not applicable to reactions that are partially inhibited. The technique may not work with reactionsthat include simultaneous or consecut
7、ive reaction steps. This test method may not apply to materials that undergo phase transitionsif the reaction rate is significant at the transition temperature.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 stand
8、ard may involve hazardous materials, operations, and equipment. This standard does not purport to address allof the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriatesafety and health practices and determine the applicabil
9、ity of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2E473 Terminology Relating to Thermal Analysis and RheologyE691 Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test MethodE968 Practice for Heat Flow Calibration of Differential Sca
10、nning CalorimetersE1142 Terminology Relating to Thermophysical PropertiesE1231 Practice for Calculation of Hazard Potential Figures of Merit for Thermally Unstable MaterialsE1445 Terminology Relating to Hazard Potential of ChemicalsE1860 Test Method for Elapsed Time Calibration of Thermal AnalyzersE
11、1970 Practice for Statistical Treatment of Thermoanalytical Data1 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.Current edition approved March 1, 2011April 15, 2016. Publish
12、ed March 2011April 2016. Originally approved in 1979. Last previous edition approved in 20052011 asE698 05.E698 11. DOI: 10.1520/E0698-11.10.1520/E0698-16.2 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org. For Annual Book of ASTM
13、Standardsvolume information, refer to the standards Document Summary page on the ASTM website.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 poss
14、ible to adequately 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 standardCop
15、yright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1E2890 Test Method for Kinetic Parameters for Thermally Unstable Materials by Differential Scanning Calorimetry Using theKissinger Method3. Terminology3.1 Technical terms used in this test m
16、ethod are defined in Terminologies E473, E1142, and E1445. including activation energy,Arrhenius equation, Celsius, differential scanning calorimetry, enthalpy, general rate law, Kelvin, kinetics, peak value,pre-exponential factor, reaction, reaction order, and temperature.4. Summary of Test Method4
17、.1 A samplespecimen is placed in a suitable container and positioned in a differential scanning calorimeter (DSC).4.2 The sample equipment temperature temperature surrounding the specimen is increased at a linear rate and any exothermicreaction peaks recorded.4.3 Steps 4.1 and 4.2 are repeated for s
18、everal heating rates in the range from 1 to 10 K min1.4.4 Temperatures at which the reaction peak maxima occur are 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-life at ase
19、lected temperature.4.6 A samplespecimen is aged at the selected temperature for the predicted half-life time.4.7 The aged samplespecimen is temperature programmed in a differential scanning calorimeter and its reaction peak areacompared with that for an unaged sample run under the same conditions.4.
20、8 If the normalized area for the aged samplespecimen is approximately half that for the unaged sample, the kinetic values areconfirmed for the temperature selected.5. Significance and Use5.1 The Arrheniuskinetic parameters combined with the general rate law and the reaction enthalpy can be used for
21、thedetermination of thermal explosion hazards hazard using Practice E1231 (1).36. Apparatus6.1 GeneralThe equipment used in this test method should be capable of displaying quantitative changes of enthalpy as afunction of time (t) or temperature (T), should be linearly programmable and have the capa
22、bilities of subjecting the sample cellto different atmospheres. The heat sensing element should be external to the sample.6.2 Differential Scanning Calorimeter (DSC):6.2.1 A DSC test chamber composed of:6.2.1.1 A furnace, to provide uniform controlled heating (cooling) of a specimen and reference to
23、 a constant temperature or ata constant rate within the applicable temperature range of this test method.6.2.1.2 A temperature sensor, to provide an indication of the specimen/furnace temperature to 60.1 K.6.2.1.3 A differential sensor, to detect a difference in heat flow between the specimen and re
24、ference equivalent to 10 W.6.2.1.4 A means of sustaining a test chamber environment, of an inert purge gas at a rate of 10 50 6 mL10 50 mLmin.NOTE 1Typically, 99+ % pure nitrogen, argon, or helium are employed when oxidation in air is a concern. Unless effects of moisture are to be studied,use of dr
25、y purge gas is recommended; especially for operation at subambient temperature.6.2.2 A temperature controller, capable of executing a specific temperature program by operating the furnace(s) betweenselected temperature limits at a rate of temperature change between 0.5 and 10 Kmin constant to 60.1 K
26、min or at an isothermaltemperature constant to 60.1 K.6.2.3 A data collection device, to provide a means of acquiring, storing, and displaying measured or calculated signals, or both.The minimum output signals required for differential scanning calorimetry are heat flow, temperature, and time.6.3 Co
27、ntainers (pans, crucibles, vials, etc),etc.), which are inert to the specimen and reference materials and which are suitablestructural shape and integrity to contain the specimen and reference in accordance with the specific requirements of this testmethod.6.4 A balance, with a capacity of at least
28、100 mg, to weigh specimens or containers (pans, crucibles, vials, etc), or bht, etc.) towithin 10 g.6.5 Auxiliary equipment useful for conducting this test method below ambient temperature.3 The boldface numbers in parentheses refer to the list of references at the end of this standard.E698 1626.5.1
29、 A coolant system, which can be directly coupled with the controller to the furnace to hasten its recovery from elevatedtemperatures, to provide constant cooling rates, or to sustain an isothermal subambient temperature, or a combination thereof.7. Safety Precautions7.1 The use of this test method o
30、n materials whose potential hazards 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 material isdangerous.7.3 Toxic or corrosive effluents, or both, may
31、be released when heating the material and could be harmful to the personnel orthe apparatus. Use of an exhaust system to remove such effluents is recommended.8. Sampling8.1 SampleSpecimen size is kept small to minimize temperature gradients within the sample. In general, a sample weightmassresulting
32、 in a maximum heat generation of less than 8 mJs (8 mW) is satisfactory.8.2 Samples shouldSpecimens shall be representative of the material being studied and should be prepared to achieve goodthermal contact between sample and container (see Figs. 1 and 2).8.3 The samplespecimen container should be
33、nonreactive with the sample or reaction products.8.4 The reference for the sample is normally an empty container or one filled with inert material.8.5 SamplesSpecimens which have appreciable volatility over the temperature range of interest may require sealing in hermeticcontainers or a high-pressur
34、e cell, or both, to prevent vaporization interference and weight loss of unreacted material.8.6 The samplespecimen atmosphere should closely represent the conditions of usage.9. Calibration9.1 Perform any calibration procedures recommended by the manufacturer as described in the operators manual.9.2
35、 Calibrate the heat flow and elapsed time signals using Practice E968 and Test Method E1860, respectively, using the sametype of specimen container to be used in the subsequent kinetic tests. Perform any calibration procedures recommended by themanufacturer as described in the operators manual.9.3 C
36、alibrate the temperature signal at 10 Kmin using Practice E968 and Test Method E1860, respectively, using the same typeof specimen container to be used in the subsequent kinetic tests.9.4 Determine the temperature calibration corrections for other heating rates by programming a sharply melting stand
37、ard (forexample, pure indium metal) at these heating rates and observing the deviation of the known melt temperature as a function of therate.NOTE 2This table of temperature calibration correction values, once determined for a particular apparatus and specimen container, may be used forsubsequent ex
38、periments following temperature calibration at 10 K min heating rate in 9.3.9.5 The thermal resistance of the instrument sample cell is determined by measuring the temperature lag observed for themelting of a pure metal standard. See Fig. X1.2 in Appendix X1.FIG. 1 Arrangement for Good Sample Contac
39、t with ContainerE698 16310. Procedure10.1 RunPerform an initial sample experiment using a specimen of 5 mg or less to determine proper samplespecimen sizes andstarting temperatures.10.2 Place the samplespecimen and reference materials in the instrument heating unit. Use a samplespecimen size asrecom
40、mended in 8.1.10.3 ProgramHeat the temperature at a rate between 1 and specimen at 10 Kmin from a point starting at least 50 K below thefirst observed exothermic peak deflection.10.4 Record the differential heat flow signal as a function of temperature. Continue heating until the peak maximum of int
41、erestis recorded.10.5 Repeat 10.2 10.4 for various heating rates between about 1 and 10 Kmin.NOTE 3A minimum of four determinations at heating rates between 1 and 10 K min are recommended.NOTE 4Reaction curve baselines should be level to minimize slope error in peak maxima measurements.11. Calculati
42、on11.1 Temperatures of reaction peak maxima are corrected for temperature scale nonlinearity, heating rate changes, and thermallag as in the example in Appendix X1.11.2 Plot log10 (heating rate, KminK min1) versus 1/T, where T is the corrected peak maximum temperature in Kelvin.Calculate and constru
43、ct a least squares “best fit” line through these points (see Practice E1970). The slope of this “best fit” lineis taken as the value for d log10 d (1/T).11.3 Calculate an approximate value for E (activation energy) as follows (2):E22.19Rdlog10 /d1/T!# (1)where R = gas constant (=8.314 J mol1 K1).11.
44、4 Refine value of E by:11.4.1 Calculate E/RT approximately.11.4.2 Find corresponding value of D from Table X2.1.11.4.3 Calculate new value for E as follows:E 522.303R/D!dlog10 /d1/T!# (2)Refining the value of E a second time usually results in a close approach to its final value. An alternative calc
45、ulation methodis shown in Appendix X3.11.5 The Arrhenius pre-exponential factor can be calculated as follows:follows under the assumption of a first-order reaction:Z 5EeE/RT/RT2 (3)Z 5EeE/RT/RT2 (3)where: = a heating rate from the middle of the range.11.6 For the confirming isothermal test, calculat
46、e k for various temperatures from the Arrhenius equation and the above E andZ values.11.7 From t = 0.693k, calculate aging times (t) for each temperature.11.8 Select a temperature requiring at least 1-h aging time, and age the sample isothermally for the calculated half-life in athermal instrument o
47、r other facility capable of 61 K control. Quench immediately to some temperature at least 50 K below theaging temperature so that no significant reaction occurs during subsequent holding time.FIG. 2 SampleSpecimen Pan Collapsed and CollectedE698 16411.9 RunHeat the aged samplespecimen in a thermal i
48、nstrument and record its reaction peak.peak and determine temperature.11.10 RunHeat a similar but unaged samplespecimen in the same way and record its reaction peak.peak and determinetemperature.11.11 On an equal weightmass basis, the peak area or displacement from baseline of the aged sample should
49、specimen shall beapproximately one half that of the unaged sample. If so, the reaction kinetics are confirmed for the temperature range explored.12. Report12.1 The report shall include the following:12.1.1 Identification of the sample by name or composition, stating the source, past history, and weight of sample each specimentogether with its purity (if available).12.1.2 Description of apparatus and type of container used.12.1.3 Identification of samplespecimen environment as to degree of confinement, composition of atmosphere, a
