1、Designation: E 2070 03Standard Test Method forKinetic Parameters by Differential Scanning CalorimetryUsing Isothermal Methods1This standard is issued under the fixed designation E 2070; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revisio
2、n, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 Test Method A determines kinetic parameters for acti-vation energy, pre-exponential factor and reactio
3、n order usingdifferential scanning calorimetry from a series of isothermalexperiments over a small (; 10 K) temperature range. Thistreatment is applicable to low nth order reactions and toautocatalyzed reactions such as thermoset curing or pyrotech-nic reactions and crystallization transformations i
4、n the tem-perature range from 300 to 900 K (30 to 630 C). This testmethod is applicable only to these types of exothermic reac-tions when the thermal curves do not exhibit shoulders,discontinuities or shifts in baseline.1.2 Test Method B also determines the activation energy ofa set of time-to-event
5、 and isothermal temperature data gener-ated by this or other procedures.1.3 Electronic instrumentation or automated data analysissystems or treatments equivalent to this test method may beused.NOTE 1Since all electronic data systems are not equivalent, the usermust verify the applicability of the tr
6、eatment to this method.1.4 SI units are the standard.1.5 This test method is similar but not equivalent to ISO11357, Part 5, and provides more information than the ISOstandard.1.6 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsib
7、ility 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. Specific precau-tionary statements are given in Section 8.2. Referenced Documents2.1 ASTM Standards:D 3350 Specification for Polyethylene
8、Plastic Pipe2D 3895 Test Method for Oxidative Induction Time of Poly-olefins by Differential Scanning Calorimetry2D 4565 Test Method for Physical and Environmental Per-formance Properties of Insulations and Jackets for Tele-communications Wire and Cable3D 5483 Test Method for Oxidation Induction Tim
9、e of Lu-bricating Greases by Pressure Differential Scanning Calo-rimetry4D 6186 Test Method for Oxidation Induction Time of Lu-bricating Oils by Pressure Differential Scanning Calorim-etry4E 473 Terminology Relating to Thermal Analysis5E 537 Test Method for Assessing the Thermal Stability ofChemical
10、s by Method of Differential Thermal Analysis5E 698 Test Method for Arrhenius Kinetic Constants forThermally Unstable Materials5E 967 Test Method for Temperature Calibration of Differ-ential Thermal Analyzers and Differential Scanning Calo-rimeters5E 968 Test Method for Heat Flow Calibration of Diffe
11、ren-tial Scanning Calorimeters5E 1142 Terminology Relating to Thermophysical Proper-ties5E 1445 Terminology Relating to Hazardous Properties ofMaterials5E 1860 Test Method for Elapsed Time Calibration of Ther-mal Analyzers5E 1958 Test Method for Oxidative Induction Time of Hy-drocarbons by Different
12、ial Scanning Calorimetry5E 1970 Practice for Statistical Treatment of Thermoanalyti-cal Data5E 2041 Test Method for Kinetic Parameters by the Bor-chardt and Daniels Method using Differential ScanningCalorimetry5E 2046 Test Method for Reaction Induction Time by Ther-mal Analysis52.2 ISO Standard:ISO
13、DIS 11357 Part 5 Determination of Temperature and/orTime of Reaction and Reaction Kinetics61This test method is under the jurisdiction ofASTM Committee E37 on ThermalMeasurements and is the direct responsibility of Subcommittee E37.01 on ThermalAnalysis Test Methods.Current edition approved Oct. 1,
14、2003. Published October 2003. Originallyapproved in 2000. Last previous edition approved in 2000 as E 2070 00.2Annual Book of ASTM Standards, Vol 08.02.3Annual Book of ASTM Standards, Vol 10.02.4Annual Book of ASTM Standards, Vol 05.03.5Annual Book of ASTM Standards, Vol 14.02.6Available from Americ
15、an National Standards Institute, 11 W. 42nd St., 13thFloor, New York, NY 10036.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.3. Terminology3.1 Specific technical terms used in this test method aredefined in Terminologies E 473, E 1
16、142, and E 1445.4. Summary of Test Method4.1 A test specimen is held at a constant temperature in adifferential scanning calorimeter throughout an exothermicreaction. The rate of heat evolution, developed by the reaction,is proportional to the rate of reaction. Integration of the heatflow as a funct
17、ion of time yields the total heat of reaction.4.2 An autocatalytic or nth order data treatment7,8,9is usedto derive the kinetic parameters of activation energy, pre-exponential factor and reaction order from the heat flow andtotal heat of reaction information obtained in 4.1 (See Basis forMethodolog
18、y, Section 5.)5. Basis of Methodology5.1 Reactions of practical consideration are exothermic innature; that is, they give off heat as the reaction progresses.Furthermore, the rate of heat evolution is proportional to therate of the reaction. Differential scanning calorimetry measuresheat flow as a d
19、ependent experimental parameter. DSC isuseful for the measurement of the total heat of a reaction andthe rate of the reaction as a function of time and temperature.5.2 Reactions may be modeled with a number of suitableequations of the form of:da/dt 5 kT! fa! (1)where:da/dt = reaction rate (min1),a =
20、 fraction reaction or conversion (dimensionless),k (T) = specific rate constant at temperature T (min1),f(a) = conversion function. Commonly used functionsinclude:f1a! 5 1a!n(2)f2a! 5am1a!n(3)where:n and m = partial reaction order terms.NOTE 2There are a large number of conversion function expressio
21、nsfor f(a)7. Those described here are the more common but are not theonly functions suitable for this method. Eq 2 is known as the general rateequation while Eq 3 is the autocatalytic (or Sestak-Berggren) equation8,9.Eq 2 is used for nth order reactions while Eq 3 is used for thermoset cureand cryst
22、allization transformations.5.3 For a reaction conducted at temperature (T), the auto-catalytic rate equation of 5.2 may be cast in its logarithmicform.da/dt 5 kT! am1a!n(4)lnda/dt 5 lnkT!# 1 mlna 1 nln1 a (5)This equation has the form z = a + bx + cy and may be solvedusing multiple linear regression
23、 analysis.NOTE 3Subsequent discussions use the autocatalytic form of the rateequation (Eq 3). It reduces to the simpler general rate equation (Eq 2)when the value of reaction order parameter m equals zero thereby reducingthe number of kinetic parameters to be determined.5.4 The Arrhenius equation de
24、scribes how the reaction ratechanges as a function of temperature:kT! 5 Ze2E/RT(6)where:Z = pre-exponential factor (min1),E = activation energy (J mol1),T = absolute temperature (K),R = gas constant = 8.314 J mol1K1), ande = natural logarithm base = 2.7182818.5.5 Eq 6 cast in its logarithmic form is
25、:lnkT!# 5 lnZE/RT (7)Eq 7 has the form of a straight line, y = mx + b, where a plotof the logarithm of the reaction rate constant (lnk (T) versusthe reciprocal of absolute temperature (l/T) is linear with theslope equal to E/R and an intercept equal to lnZ.5.6 As an alternative to 5.3 and 5.5, the r
26、ate and Arrheniusequations combined and cast in logarithmic form is:lnda/dt 5 lnZE/RT 1 mlna 1 nln1 a (8)Eq 8 has the form, z = a + bw + cx + dy, and may be solvedusing multiple linear regression analysis.5.7 If activation energy values only are of interest, Eq 8 maybe solved under conditions of con
27、stant conversion to yield:ln Dt 5 E/RT 1 c (9)where:Dt = lapsed time at isothermal temperature, T, andc = constant.Eq 9 has the form of a straight line, y = mx + b, where a plotof the logarithm of the lapsed time under a series of differingisothermal conditions versus the reciprocal of absolute tem-
28、perature (l/T) is linear with a slope equal to E/R.5.8 A series of isothermal experiments by Test Method Adescribed in Section 11 at four or more temperatures, deter-mines the kinetic parameters of activation energy, pre-exponential factor and reaction order.Alternatively, the time toa condition of
29、constant conversion for a series of experimentsat four or more temperatures obtained by this or alternativeTest Method B, described in Section 12, may be used todetermine activation energy only.5.9 A series of not less than four isothermal DSC experi-ments, covering a temperature range of approximat
30、ely 10 Kand a time less than 100 min (such as those shown in Fig. 1)provides values for da/dt, a,(1a) and T to solve Eq 5, Eq7, and Eq 8.5.10 A variety of time-to-event experiments such as oxida-tion induction time methods (Test Methods D 3350, D 3895,D 4565, D 5483, D 6186, and E 1958) and reaction
31、 inductiontime methods (E 2046) provide values for Dt and T to solveequation 5.7.7Sbirrazzuoli, N.; Brunel, D.; Elegant, L., J. Therm. Anal., 38, 1509-1524, 1992.8Sestak, J.; Berggren, G.; Thermochim. Acta, 3, 1, 1971.9Gorbachiev, V.M., J. Therm. Anal., 18, 193197, 1980.E20700326. Significance and U
32、se6.1 This test method is useful for research and development,quality assurance, regulatory compliance and specificationacceptance purposes.6.2 The determination of the order of a chemical reaction ortransformation at specific temperatures or time conditions isbeyond the scope of this test method.6.
33、3 The activation energy results obtained by this methodmay be compared with those obtained fromTest Method E 698for nth order and autocatalytic reactions. Activation energy,pre-exponential factor and reaction order results by this methodmay be compared to those for Test Method E 2041 for nthorder re
34、actions.7. Interferences7.1 The approach is applicable only to exothermic reactions.NOTE 4Endothermic reactions are controlled by the rate of the heattransfer of the apparatus and not by the kinetics of the reaction and maynot be evaluated by this test method.7.2 This test method is intended for a r
35、eaction mechanismthat does not change during the transition. This methodassumes a single reaction mechanism when the shape of thethermal curve is smooth (as in Fig. 2 and Fig. 3) and does notexhibit shoulders, multiple peaks or discontinuation steps.7.3 Method precision is enhanced with the selectio
36、n of theappropriate conversion function f (a) that minimizes thenumber of experimental parameters determined. The shape ofthe thermal curve, as described in Appendix X1, may confirmthe selection of the nth order or autocatalytic models.7.4 Typical nth order reactions include those in which allbut on
37、e of the participating species are in excess.7.5 Typical autocatalytic reactions include thermoset cure,crystallization and pyrotechnic reactions.7.6 For nth order kinetic reactions, this test method antici-pates that the value of n is small, non-zero integers, such as 1or 2. This test method should
38、 be used carefully when values ofn are greater than 2 or are not a simple fraction, such as12 =0.5.7.7 Autocatalytic kinetic reactions anticipate that m and nare fractions between 0 and 1 and that their sum (m + n) is lessthan 2.7.8 Since this method uses milligram quantities it is essen-tial that t
39、he test specimens are homogeneous and representativeof the larger samples from which they are taken.7.9 Test specimens may release toxic and corrosive effluentsthat may be harmful to personnel or apparatus. Operation witha venting or exhaust system is recommended.NOTE 1This figure is for a crystalli
40、zation application in which the reaction rate increases with decreasing temperature. Chemical reactions show anincrease in reaction rate with increasing temperature.FIG. 1 Heat Flow Curves at a Series of Isothermal TemperaturesE20700338. Hazards8.1 Special precautions shall be taken to protect perso
41、nneland equipment when the apparatus in use requires the insertionof specimens into a heated furnace. These special precautionsinclude adequate shielding and ventilation of equipment andface and hand protections for users (See Note 8.)9. Apparatus9.1 A differential scanning calorimeter (DSC) that pr
42、ovidesthe minimum calorimetric capability for this method includes:9.1.1 A DSC Test Chamber, composed of:9.1.1.1 A Furnace(s), that provides uniform controlled heat-ing of a specimen and reference to constant temperature at aconstant rate within the applicable temperature range of thistest method.9.
43、1.1.2 A Temperature Sensor, that indicates the specimen/furnace temperature to 6 0.01 K.9.1.1.3 A Differential Sensor, that detects heat flow differ-ences between the specimen and reference equivalent to 1 W.9.1.1.4 Ameans of sustaining a purge gas rate of 10 to 50 6mL/minute in the test chamber.NOT
44、E 5Typically inert purge gases that inhibit sample oxidation are99.9+ % pure nitrogen, helium or argon. Dry gases are recommended forall experiments unless the effect of moisture is part of the study.9.1.2 A Temperature Controller, for furnace(s) temperatureprograms between selected temperature limi
45、ts (that is, 300 to900 K) capable of controlling the rate of temperature change ofup to 100 K min1constant to 6 0.1 K min1.9.1.3 A Recording Device, capable of recording and display-ing fractions of the heat flow signal (DSC curve), including thesignal noise, on the Y-axis versus fractions of time,
46、includingthe signal noise, on the X-axis.9.2 Containers (pans, crucibles, vials, etc. and lids) that areinert to the specimen and reference materials of suitablestructural shape and integrity to contain the specimen andreference in accordance with the requirements of this testmethod.9.3 A Balance, t
47、o weigh specimens and/or containers to 610 g with a capacity of at least 100 mg.9.4 Calculation, capability to perform multiple linear re-gression analysis for four or more unknowns.10. Calibration10.1 Perform set up and calibration procedures according tothe instrument operators manual.10.2 Calibra
48、te the DSC temperature signal over the range ofthe reaction at a heating rate of1Kmin1using Test MethodE 967.10.3 Calibrate the DSC heat flow signal using Test MethodE 968.10.4 Confirm that the elapsed time conformity of the ther-mal analyzer “clock” is better than 0.1 % using Test MethodE 1860.FIG.
49、 2 Heat Flow Curve for an nth Order ReactionE207003411. Procedure (Test Method A)11.1 Weigh 4 to 7 6 1 mg of test specimen in a tared samplecontainer. Seal the container. Record the total weight of thespecimen and the container to 6 10 g.11.2 Place the test specimen and a similar empty referencecontainer in the apparatus. Close the DSC sample chamber andprepare the apparatus for an experimental run.11.3 Use a temperature program of 20 K min1to raise thefurnace temperature quickly from room temperature to theexpe
copyright@ 2008-2019 麦多课文库（www.mydoc123.com）网站版权所有
备案/许可证编号：苏ICP备17064731号-1