ASTM_E_1641_-_15.pdf

Designation:E164115Standard 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 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 preexpo-nential factor by thermogravimetry,based on the assumptionthat the decomposition obeys first-order kineticsusing theOzawa/Flynn/Wall isoconversional method(1,2).21.2 This test method is generally applicable to materialswith well-defined decomposition profiles,namely,a smooth,continuous mass change 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 test method is similar to ISO 11358-2 but differs inits mathematical 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 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:3E29 Practice for Using Significant Digits in Test Data toDetermine Conformance with SpecificationsE473 Terminology Relating to Thermal Analysis and Rhe-ologyE691 Practice for Conducting an Interlaboratory Study toDetermine the Precision 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 ThermoanalyticalDataE2040 Test Method for Mass Scale Calibration of Thermo-gravimetric Analyzers2.2Other 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 Terminologies E473 and E1142 and includeactivation energy,Celsius,failure,failure criterion,and ther-mogravimetric analyzer.4.Summary of Test Method4.1 This test method is based upon the general rate equationthat takes the form of:ddT 5 A1 2!exp2 E R T#(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/(mol K),T=absolute temperature(K),exp=Eulers number exponential,andd/dT=rate of change of with T.4.2 Using the method of Ozawa,Flynn and Wall(1,2),Eq1 may be solved for activation energy:E 5R b!log#1 T!(2)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 March 1,2015.Published March 2015.Originallyapproved in 1994.Last previous edition approved in 2013 as E1641 13.DOI:10.1520/E1641-15.2The boldface numbers in parentheses refer to the list of references at the end ofthis standard.3For referenced ASTM standards,visit the ASTM website,www.astm.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.org.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 where:E=the derivative of the Doyle approximation(3)withvalues tabulated in Table 1.4.3 Using a point of constant conversion from a series ofdecomposition curves obtained at different heat rates,log#1 2 T!is obtained by linear regression.4.4 Assuming an initial value ofb50.457,a first approxima-tion of activation energy(E)is obtained using Eq 2.4.5 This approximate activation energy is then used todetermine a new value of b using Table 1.4.6 This iterative process is continued until the value ofactivation 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).A 52 R E!ln1 2#!10a(3)where:a=the Doyle approximation value from Table 1.4.8 This test method consists of heating a series of four ormore test specimens,taken from the original sample,each at adifferent heating rate between 1 and 10 K/min,through theirdecomposition region.The specimen mass is recorded continu-ously as a function of temperature.The temperatures