ASTM_E_2781_-_11.pdf

Designation:E278111Standard Practice forEvaluation of Methods for Determination of KineticParameters by Thermal Analysis1This standard is issued under the fixed designation E2781;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 materials used for evaluation ofthermal analysis methods,apparatus and software where en-thalpy and temperature are measured.This practice addressesboth exothermic and endothermic,nth order and autocatalyticreactions.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 for Standardiza-tion(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-ologyE698 Test Method for Arrhenius Kinetic Constants forThermally Unstable Materials Using Differential Scan-ning Calorimetry and the Flynn/Wall/Ozawa MethodE1142 Terminology Relating to Thermophysical PropertiesE1641 Test Method for Decomposition Kinetics by Thermo-gravimetry Using the Ozawa/Flynn/Wall MethodE1981 Guide for Assessing Thermal Stability of Materialsby Methods of Accelerating Rate CalorimetryE2041 Test Method for Estimating Kinetic Parameters byDifferential Scanning Calorimeter Using the Borchardtand Daniels MethodE2070 Test Method for Kinetic Parameters by DifferentialScanning Calorimetry Using Isothermal Methods3.Terminology3.1 DefinitionsSpecific technical terms used in this prac-tice are defined in Terminologies E473 and E1142,includingdifferential scanning calorimetry.4.Summary of Practice4.1 Kinetics is the study of the relationship of the extent ofa chemical reaction to the independent parameters of time andtemperature.This relationship is often described using theArrhenius expression where:d/dt5 Z f!exp2E/RT!(1)where:=fraction left to react,f()=some function of(),E=activation energy(J/mol),R=gas constant(=8.314 J mol1K1),T=absolute temperature(K),andZ=pre-exponential factor(1/sec).4.2 For many reactions of interest the description of thefunction of amount left to react is of the form:f!5 m1 2!n(2)where m and n are the overall reaction orders.This form ofthe concentration dependence is known as the auto-catalyticform or the Sestak-Berggren reaction(1).3If the value of mequals 0,then f()reduces to the form of f()=(1 )ncommonly call nth order reaction.4.3 Eq 1 may be evaluated in either its exponential orlogarithmic form:lnd/dt!5 lnZ1lnf!2 E/RT(3)4.4 The study of kinetics involves the determination ofvalues of E,Z,m,and n for a given reaction.NOTE1Activation energy and pre-exponential factor are not indepen-dent parameters but are inter-related.1This 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 March 1,2011.Published April 2011.DOI:10.1520/E2781-11.2For 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.3The boldface numbers in parentheses refer to a list of references at the end ofthis standard.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 NOTE2The descriptions provided in Eq 1-3 are only mathematicalmodels.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 parameter are typically in theranges indicated below:log Z:8 to 30 with Z in s1E:50 to 250 kJ/moln:0.0 to 2.0m:0 to 2.04.6 By their nature,thermally reactive materials maychange with time.For this reason,certified reference materialsare not available for use in the evaluation of kinetic parameters.The user of this standard may synthesize or purchase from acommercial laboratory supply house materials of suitablepurity for use in this standard.NOTE3Storage of reference materials in a refrigerator may prolongshelf life.Observe manufacturers recommendations.4.7 The recommended values for the thermal active mate-rials identified in this standard are taken from“best values”found in the open literature as