1、Designation: E 793 06Standard Test Method forEnthalpies of Fusion and Crystallization by DifferentialScanning Calorimetry1This standard is issued under the fixed designation E 793; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, th
2、e 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 This test method describes the determination of theenthalpy (heat) of fusion (melting) and crystallization
3、bydifferential scanning calorimetry (DSC).1.2 This test method is applicable to solid samples ingranular form or in any fabricated shape from which anappropriate specimen can be cut, or to liquid samples thatcrystallize within the range of the instrument. Note, however,that the results may be affect
4、ed by the form and mass of thespecimen, as well as by other experimental conditions.1.3 The normal operating temperature range is from 120 to600C. The temperature range can be extended dependingupon the instrumentation used.1.4 This test method is generally applicable to thermallystable materials wi
5、th well defined endothermic or exothermicbehavior.1.5 Computer or electronic based instruments, techniques,or data treatment equivalent to those in this test method mayalso be used.1.6 SI units are the standard.1.7 The enthalpy of melting and crystallization portion ofISO 11357-3 is equivalent to th
6、is standard.1.8 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.
7、Referenced Documents2.1 ASTM Standards:2E 473 Terminology Relating to Thermal Analysis and Rhe-ologyE 794 Test Method for Melting And Crystallization Tem-peratures By Thermal AnalysisE 968 Practice for Heat Flow Calibration of DifferentialScanning CalorimetersE 1142 Terminology Relating to Thermophy
8、sical PropertiesE 1860 Test Method for Elapsed Time Calibration of Ther-mal Analyzers2.2 ISO Standard:3ISO 113573 Plastics Differential Scanning Calorimetry(DSC) Part 3: Temperature and Enthalpy of Melting andCrystallization3. Terminology3.1 DefinitionsSpecialized terms used in this test methodare d
9、efined in Terminologies E 473 and E 1142.4. Summary of Test Method4.1 This test method involves heating (or cooling) a testspecimen at a controlled rate in a controlled environmentthrough the temperature region of fusion or crystallization. Theheat flow associated with fusion, an endothermic process
10、 (andcrystallization, an exothermic process), is recorded and inte-grated over time. Absolute values for the enthalpy of fusion(and enthalpy of crystallization) or relative values for compara-tive purposes can thus be obtained.NOTE 1Melting (or crystallization) temperatures are sometimes de-termined
11、 in conjunction with measurements of the enthalpy of fusion orcrystallization. These temperature values may be obtained by Test MethodE 794.5. Significance and Use5.1 Differential scanning calorimetry provides a rapidmethod for the determination of enthalpic changes accompa-nying first-order transit
12、ions of materials.5.2 This test method is useful for quality control, specifica-tion acceptance, and research.6. Apparatus6.1 DSC, The essential instrumentation required to providethe minimum differential scanning calorimetric capability forthis method includes:6.1.1 DSC Test Chamber composed of:1Th
13、is test method is under the jurisdiction ofASTM Committee E37 on ThermalMeasurements and is the direct responsibility of Subcommittee E37.01 on TestMethods and Recommended Practices.Current edition approved Sept. 1, 2006. Published October 2006. Originallyapproved in 1981. Last previous edition appr
14、oved in 2001 as E 793 01.2For 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.3Available from American National St
15、andards Institute (ANSI), 25 W. 43rd St.,4th Floor, New York, NY 10036, http:/www.ansi.org.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.6.1.1.1 a furnace(s), to provide uniform controlled heatingand cooling of a specimen and refer
16、ence to a constanttemperature or at a constant rate from 120 to 600 C .6.1.1.2 Atemperature sensor, to provide an indication of thespecimen temperature to 6- 0.1 C.6.1.1.3 Differential sensors, to detect a heat flow differencebetween specimen and reference with a range of at least =/- 100mW and a se
17、nsitivity of 6-5mW.6.1.1.4 A means of sustaining a test chamber environmentof an inert purge gas as at rate of 10 to 50 6- 5 mL/min.NOTE 2Typically, 99.99+% pure nitrogen, argon or helium is usedwhen oxidation in air is a concern. Unless effects of moisture are to bestudied, use of dry purge gas is
18、recommended and is essential foroperation at subambient temperatures.6.1.2 A temperature controller, capable of executing aspecific temperature program by operating the furnaces(s)between selected temperature limits at a rate of temperaturechange of up to at least 20 C/min constant to 6- 0.1 C/min.o
19、r at an isothermal temperature constant to 6- 0.1 C.6.1.3 A recording device, capable of recording and display-ing on the Y-axis any portion of the heat flow signal (DSCcurve) including the signal noise as a function of any portion ofthe temperature or time signal on the X-axis including thesignal n
20、oise.6.2 Specimen Containers, (pans, crucibles, vials, lids, clo-sures, seals, etc.) that are inert to the specimen and referencematerials and that are of suitable structural shape and integrityto contain the specimen and reference.6.3 Nitrogen, or other inert gas supply for purging purposes.6.4 Bal
21、ance, with capacity greater than 100 mg, capable ofweighing to the nearest 0.01 mg, or better.NOTE 3Balances readable to 0.01 mg are suitable for use with testspecimens on the order of 10 mg in mass.Abalance readable to 0.001 mgis required for test specimens on the order of 1 mg in mass. to achieve
22、theprecision described in this standard.6.5 Auxiliary instrumentation considered useful or neces-sary for conducting this method includes:6.5.1 Data Analysis capability of integrating the heat flowsignal as a function of time to produce enthalpy information inunits of mJ to a precision of 6-1%.6.5.2
23、 A means, tool or device to close, encapsulate, or sealthe container of choice.6.5.3 A cooling capability to hasten cool down from el-evated temperatures, to provide constant cooling rates, or tosustain an isothermal subambient temperature. .7. Hazards and Interferences7.1 Since milligram quantities
24、 of specimens are used, it isessential that samples are homogeneous.7.2 Toxic or corrosive effluents, or both, may be releasedwhen heating the material and could be harmful to thepersonnel or the apparatus.7.3 Samples that release volatiles upon heating will changemass and invalidate the test.7.4 In
25、 the use of commercial instrumentation, the operatorshould read the manufacturers operations manual to be awareof potential hazards of operation, such as burn hazards fromhot surfaces.8. Sampling8.1 Powdered or granular materials should be mixed thor-oughly prior to sampling and should be sampled by
26、 removingportions from various parts of the container. These portions, inturn, should be combined and mixed well to ensure a repre-sentative specimen for the determination. Liquid samples maybe sampled directly after mixing.8.2 In the absence of other information, samples are as-sumed to be analyzed
27、 as received. If some heat or mechanicaltreatment is applied to the sample prior to analysis, thistreatment, and any mass loss resulting from this treatment,should be noted in the report.9. Calibration9.1 Using the same heating rate, purge gas, and flow rate tobe used for specimens, calibrate the he
28、at flow axis of theinstrument, using the procedure in Practice E 968.9.2 Calibrate the elapsed time signal of the differentialscanning calorimeter using Test Method E 1860.10. Procedure10.1 Weigh 1 to 15 mg of specimen to an accuracy of +/0.1% into a clean, dry specimen capsule.NOTE 4The specimen ma
29、ss to be used depends on the magnitude ofthe transition enthalpy and the volume of the capsule. For comparingmultiple results, use similar mass ( +/5 %) and encapsulation. Weighingto less accuracy than one part per thousand may limit the accuracy of theenthalpy determination.10.2 Seal or crimp the s
30、pecimen capsule with a lid underambient conditions. Minimize the free space between thespecimen and the lid. For specimens sensitive to oxidation,hermetic sealing under an inert atmosphere may be desirable.10.3 Load the specimen into the instrument chamber. Purgethe chamber with dry nitrogen (or oth
31、er inert gas) at a flow rateof 10 to 50 mL/min throughout the experiment.10.4 The specimen may be heated rapidly to 50C below theexpected melting temperature and allowed to equilibrate.NOTE 5For some materials, it may be necessary to start the scansubstantially lower in temperature, for example, bel
32、ow the glass transition,in order to establish a baseline where there is no evidence of melting orcrystallization.10.5 Heat the specimen at 10C/min through the meltingrange until baseline is reestablished above the melting endot-herm.NOTE 6Other heating rates may be used but shall be noted in therepo
33、rt. Results may depend on heating rate and equilibration times.NOTE 7To allow the system to achieve steady state, provide at least 3min of scanning time both before and after the peak.10.6 Hold the specimen at this temperature for 2 min.NOTE 8Other periods may be used, but shall be noted in the repo
34、rt10.7 Cool the specimen at 10C/min through the exothermNOTE 9Other cooling rates may be used but must be noted in thereport.NOTE 10To allow the system to achieve steady state, provide at least3 min of scanning time both before and after the peak.NOTE 11For some materials, it may be necessary to sca
35、n several tensof degrees below the peak maximum in order to attain a constant baseline.E793062Record the accompanying thermal curve.10.8 Reweigh the specimen after completion of scanningand discard. Discard the data if mass losses exceed 1 % of theoriginal mass or if there is evidence of reaction wi
36、th thespecimen capsule.11. Calculation11.1 Construct a baseline on the differential heat flowthermal curve by connecting the two points at which themelting endotherm (or freezing exotherm) deviates from therelatively straight baseline (see Fig. 1 and Fig. 2).11.2 Integrate the area under the fusion
37、endotherm (orcrystallization exotherm) as a function of time.11.3 Calculate, retaining all meaningful decimal places, theenthalpy of fusion (or enthalpy of crystallization) (Ho) usingEq 1.H 5 EHo/ W (1)where:H = enthalpy of fusion (or crystallization) of the sample inJ/g,W = mass of the specimen, mg
38、,E = Calibration constant from Practice E 968,Ho= observed enthalpy of fusion (or crystallization), mJ12. Report12.1 Report the following information:12.1.1 Complete identification and description of the mate-rial tested including source and manufacturer code.12.1.2 Description of the instrument use
39、d for test.12.1.3 Statement of the mass, dimensions, geometry, andmaterial of the specimen capsule, and the heating (cooling) rateused.12.1.4 Description of the calibration procedure.12.1.5 Identification of the specimen environment by gasflow rate, purity, and composition.12.1.6 Enthalpy of fusion
40、(or crystallization) in J/g.12.1.7 The specific dated edition of the method used.13. Precision and Bias13.1 The precision of this test method was determined in aninterlaboratory investigation in which 18 laboratories partici-pated using six instrument models. Polymeric, organic, andinorganic materia
41、ls were included for measuring both enthalpyof fusion and crystallization.13.2 The following criteria should be used for judging theacceptability of enthalpy of fusion or crystallization results:13.2.1 Repeatability (Single Analyst)The coefficient ofvariation of results (each the average of duplicat
42、es), forenthalpy of fusion or crystallization, obtained by the sameanalyst or instrument on different days, is estimated to be 2.8 %with 88 degrees of freedom. Two such averages should beconsidered suspect (95 % confidence level) if they differ bymore than 7.8 %.13.2.2 Reproducibility of Polymers (M
43、ultilaboratory)Thecoefficient of variation of results (each the average of dupli-cates) for enthalpy of fusion or crystallization for polymers(that is, materials melting or crystallizing over a broad tem-perature range), obtained by analysts in different laboratories,is estimated to be 8.0 % at 30 d
44、egrees of freedom. Two suchresults should be considered suspect (95 % confidence level) ifthey differ by more than 23 %.13.2.3 Reproducibility of Pure Materials(Multilaboratory)The coefficient of variation of results (eachthe average of duplicates) for enthalpy of fusion or crystalli-zation for orga
45、nic and inorganic materials (that is, materialsmelting or crystallizing over a narrow temperature range),obtained by analysts in different laboratories, is estimated to be3.0 % at 58 degrees of freedom. Two such results should beconsidered suspect (95 % confidence level) if they differ bymore than 8
46、.6 %.13.3 An estimation of the accuracy of the enthalpy of fusionmeasurement was obtained by comparing the overall meanvalue obtained during the interlaboratory testing with valuesreported in the literature.Material Heat of Fusion (J/g)Interlaboratory Test LiteratureLeadA22.2 6 0.8 23.166 0.30Adipic
47、 acidB2526 9 238.56 2.4AHultgren, R. R., et al, Selected Values of Thermodynamic Properties of theElements, John Wiley hence, the bias is notsignificant.14. Keywords14.1 crystallization; differential scanning calorimeter; DSC;energy; enthalpy; fusion; heat; meltingASTM International takes no positio
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