1、Designation: E793 06 (Reapproved 2012)Standard Test Method forEnthalpies of Fusion and Crystallization by DifferentialScanning Calorimetry1This standard is issued under the fixed designation E793; the number immediately following the designation indicates the year oforiginal adoption or, in the case
2、 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 theenthalpy (heat) of fusion (melting) and c
3、rystallization 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 result
4、s may be affected 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 thermallystab
5、le materials with 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 The values stated in SI units are to be regarded asstandard. No other units of measurement are inclu
6、ded in thisstandard.1.7 The enthalpy of melting and crystallization portion ofISO 11357-3 is equivalent to this 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-p
7、riate 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-ologyE794 Test Method for MeltingAnd Crystallization Tempera-tures By Thermal AnalysisE968 Practi
8、ce for Heat Flow Calibration of DifferentialScanning CalorimetersE1142 Terminology Relating to Thermophysical PropertiesE1860 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
9、 Melting andCrystallization3. Terminology3.1 DefinitionsSpecialized terms used in this test methodare defined in Terminologies E473 and E1142.4. Summary of Test Method4.1 This test method involves heating (or cooling) a testspecimen at a controlled rate in a controlled environmentthrough the tempera
10、ture region of fusion or crystallization. Theheat flow associated with fusion, an endothermic process (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 pu
11、rposes can thus be obtained.NOTE 1Melting (or crystallization) temperatures are sometimes de-termined in conjunction with measurements of the enthalpy of fusion orcrystallization. These temperature values may be obtained by Test MethodE794.1This test method is under the jurisdiction ofASTM Committee
12、 E37 on ThermalMeasurements and is the direct responsibility of Subcommittee E37.01 on Calo-rimetry and Mass Loss.Current edition approved Sept. 1, 2012. Published September 2012. Originallyapproved in 1981. Last previous edition approved in 2006 as E793 06. DOI:10.1520/E0793-06R12.2For referenced A
13、STM 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 Standards Institute (ANSI), 25 W. 43rd St.,4
14、th 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 States15. Significance and Use5.1 Differential scanning calorimetry provides a rapidmethod for the determination of enthalpic changes accompa-ny
15、ing first-order transitions 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
16、Chamber composed of:6.1.1.1 a furnace(s), to provide uniform controlled heatingand cooling of a specimen and reference to a constanttemperature or at a constant rate from 120 to 600C.6.1.1.2 Atemperature sensor, to provide an indication of thespecimen temperature to 60.1C.6.1.1.3 Differential sensor
17、s, to detect a heat flow differencebetween specimen and reference with a range of at least 6100mW and a sensitivity of 65mW.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 usedw
18、hen oxidation in air is a concern. Unless effects of moisture are to bestudied, use of dry purge gas is 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
19、 temperature limits at a rate of temperaturechange of up to at least 20C/min constant to 60.1C/min. orat an isothermal temperature constant to 60.1C.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
20、as a function of any portion ofthe temperature or time signal on the X-axis including thesignal noise.6.2 Specimen Containers, (pans, crucibles, vials, lids,closures, seals, etc.) that are inert to the specimen and referencematerials and that are of suitable structural shape and integrityto contain
21、the specimen and reference.6.3 Nitrogen, or other inert gas supply for purging purposes.6.4 Balance, 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.Abalan
22、ce readable to 0.001 mgis required for test specimens on the order of 1 mg in mass. to achieve 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 a
23、s a function of time to produce enthalpy information inunits of mJ to a precision of 61%.6.5.2 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
24、isothermal subambient temperature.7. Hazards and Interferences7.1 Since milligram quantities 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.
25、3 Samples that release volatiles upon heating will changemass and invalidate the test.7.4 In 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
26、or granular materials should be mixed thor-oughly prior to sampling and should be sampled by 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 direct
27、ly after mixing.8.2 In the absence of other information, samples are as-sumed to be analyzed 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 Usi
28、ng the same heating rate, purge gas, and flow rate tobe used for specimens, calibrate the heat flow axis of theinstrument, using the procedure in Practice E968.9.2 Calibrate the elapsed time signal of the differentialscanning calorimeter using Test Method E1860.10. Procedure10.1 Weigh 1 to 15 mg of
29、specimen to an accuracy of 60.1% into a clean, dry specimen capsule.NOTE 4The specimen mass to be used depends on the magnitude ofthe transition enthalpy and the volume of the capsule. For comparingmultiple results, use similar mass (65 %) and encapsulation. Weighing toless accuracy than one part pe
30、r thousand may limit the accuracy of theenthalpy determination.10.2 Seal or crimp the specimen 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 Lo
31、ad the specimen into the instrument chamber. Purgethe chamber with dry nitrogen (or other 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.E793 06 (2012)2NOTE 5For som
32、e materials, it may be necessary to start the scansubstantially lower in temperature, for example, below 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 reestabl
33、ished above the melting endo-therm.NOTE 6Other heating rates may be used but shall be noted in thereport. Results may depend on heating rate and equilibration times.NOTE 7To allow the system to achieve steady state, provide at least3 min of scanning time both before and after the peak.10.6 Hold the
34、specimen at this temperature for 2 min.NOTE 8Other periods may be used, but shall be noted in the report10.7 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
35、 of scanning time both before and after the peak.NOTE 11For some materials, it may be necessary to scan several tensof degrees below the peak maximum in order to attain a constant baseline.Record the accompanying thermal curve.10.8 Reweigh the specimen after completion of scanningand discard. Discar
36、d the data if mass losses exceed 1 % of theoriginal mass or if there is evidence of reaction with 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 th
37、erelatively straight baseline (see Fig. 1 and Fig. 2).11.2 Integrate the area under the fusion 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)wher
38、e:H = enthalpy of fusion (or crystallization) of the sample inJ/g,W = mass of the specimen, mg,E = Calibration constant from Practice E968,Ho= observed enthalpy of fusion (or crystallization), mJ12. Report12.1 Report the following information:12.1.1 Complete identification and description of the mat
39、e-rial tested including source and manufacturer code.12.1.2 Description of the instrument used 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
40、 the specimen environment by gasflow rate, purity, and composition.12.1.6 Enthalpy of fusion (or crystallization) in J/g.12.1.7 The specific dated edition of the method used.13. Precision and Bias413.1 The precision of this test method was determined in aninterlaboratory investigation in which 18 la
41、boratories partici-pated using six instrument models. Polymeric, organic, andinorganic materials 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 Repe
42、atability (Single Analyst)The coefficient ofvariation of results (each the average of duplicates), 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
43、(95 % confidence level) if they differ bymore than 7.8 %.13.2.2 Reproducibility of Polymers (Multilaboratory)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-pe
44、rature range), obtained by analysts in different laboratories,is estimated to be 8.0 % at 30 degrees 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
45、of results (each4Supporting data have been filed at ASTM International Headquarters and maybe obtained by requesting Research Report RR:E37-1001.FIG. 1 Melting Endotherm (DSC)FIG. 2 Crystallization Exotherm (DSC)E793 06 (2012)3the average of duplicates) for enthalpy of fusion or crystalli-zation for
46、 organic 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 t
47、han 8.6 %.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 0.8 23.16 0.30Adip
48、ic acidB252 9 238.5 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 position
49、 respecting the validity of any patent rights asserted in connection with any item mentionedin this standard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the riskof infringement of such rights, are entirely their own responsibility.This standard is subject to revision at any time by the responsible technical committee and must be reviewed every five years andif not revised, either reapproved or withdrawn. Your comments are invited either for revision of this standard or for
