ASTM_E_3007_-_15.pdf

Designation:E300715Standard Practice forKinetic Values Used to Evaluate the Study of DecompositionReactions by Thermogravimetry1This standard is issued under the fixed designation E3007;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 It is the purpose of this practice to provide kineticparameters for reference material(s)to be used for evaluationof thermogravimetry methods,apparatus,and software wheredecomposition mass loss and associated temperature are mea-sured.This practice addresses nth order reactions.1.2 The values stated in SI units are to be regarded asstandard.No other units of measurement are included in thisstandard.1.3 There is no International Organization of Standards(ISO)equivalent to this standard.1.4 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:2E473 Terminology Relating to Thermal Analysis and Rhe-ologyE1142 Terminology Relating to Thermophysical PropertiesE1641 Test Method for Decomposition Kinetics by Thermo-gravimetry Using the Ozawa/Flynn/Wall MethodE2958 Test Methods for Kinetic Parameters by Factor Jump/Modulated ThermogravimetryNOTE1Test Methods E1641 and E2958 determine the pre-exponential factor A in units of min-1.These results shall be converted tounits of s-1for comparison to values quoted in this practice using:lnA,s21#5 lnA,min21#1ln60 s min#5 lnA,min21#14.0943.Terminology3.1 DefinitionsSpecific technical terms used in this prac-tice are defined in Terminologies E473 and E1142,includingArrhenius equation,derivative,reaction,and thermogravimet-ric analysis.3.1.1 decomposition,nthe process by which a substance isbroken up into constituent parts,elements or simpler com-pounds.3.1.2 kinetics,chemical,nthe study of the dependence ofthe chemical reaction rate on temperature and time.4.Summary of Practice4.1 Kinetics is the measurement and study of the rate of achemical reaction to the independent parameters of time andtemperature.This relationship is often described using theArrhenius expression,where:ddt 5 A f!exp2E/RT#(1)and:=fraction reacted(dimensionless),f()=some function of,E=activation energy(J mol-1),R=gas constant(=8.314 J mol-1K-1),T=absolute temperature(K),t=time(s),exp=natural logarithm base,d/dt=fraction reaction rate(s-1),A=pre-exponential factor(s-1),andn=reaction order.4.2 The functionf!is commonly in the form:f!51 2!n(2)and is known as an nth order reaction model.4.3 Eq 1 may be evaluated in either its exponential orlogarithmic form:lnd/dt#5 lnA#1lnf()#2 ERT(3)4.4 The study of kinetics involves the determination ofvalues of E,A,and n for a given chemical reaction.NOTE2Activation energy and pre-exponential factor are not indepen-dent parameters.NOTE3The descriptions provided in Eq 1-3 are only mathematical1This practice is under the jurisdiction of ASTM Committee E37 on ThermalMeasurements and is the direct responsibility of Subcommittee E37.02 on StandardReference Materials.Current edition approved June 1,2015.Published July 2015.DOI:10.1520/E3007-15.2For 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.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 models.That is,they represent the fitting of mathematical equations tooften“noisy”experimental data.In practice,no such model will faithfullydescribe the complete reaction(s)under all conditions for the materialsdescribed in this practice.4.5 Values for the kinetic parameters are typically in theranges of:20,E,350 kJ/mol,5,lnA#,50 with A in s21,and0.0,n,2.04.6 Some,thermally reactive materials may change withtime.For this reason,certified reference materials may not beavailable for use in the evaluation of kinetic parameters.Forany purchased reference material(s)of high purity from acommercial laboratory supply house or national metrologyinstitute,the source,storage conditions and storage time of thematerial(s)shall be reported.4.7 The recommended kinetic values for the thermallyreactive materials identified in Table 1 are derived from ameta-analysis of literature values.3These reference values maybe used for the evaluation of methods,apparatus or softwarewhere decomposition mass loss and temperature are measured.NOTE4Kinetic parameters are known to be affected by specimenparticle size.Large particle size is thought to retard escaping decompo-sition produced th