ASTM E793-2006(2018) 6250 Standard Test Method for Enthalpies of Fusion and Crystallization by Differential Scanning Calorimetry《用差示扫描量热法测定熔融和结晶焓的标准试验方法》.pdf

《ASTM E793-2006(2018) 6250 Standard Test Method for Enthalpies of Fusion and Crystallization by Differential Scanning Calorimetry《用差示扫描量热法测定熔融和结晶焓的标准试验方法》.pdf》由会员分享，可在线阅读，更多相关《ASTM E793-2006(2018) 6250 Standard Test Method for Enthalpies of Fusion and Crystallization by Differential Scanning Calorimetry《用差示扫描量热法测定熔融和结晶焓的标准试验方法》.pdf（4页珍藏版）》请在麦多课文档分享上搜索。

1、Designation: E793 06 (Reapproved 2018)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, health, and environmental practices and deter-mine the applicability of regulatory limitations prior to use.1.9 This international standard was developed in accor-dance with internationally recognized principles on standard-ization established in the Decision on Principles for theDevel

8、opment of International Standards, Guides and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2E473 Terminology Relating to Thermal Analysis and Rhe-ologyE794 Test Method for MeltingAnd Crystallization Tempe

9、ra-tures By Thermal AnalysisE968 Practice 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(D

10、SC) Part 3: Temperature and Enthalpy of 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 co

11、ntrolled environmentthrough the temperature 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)

12、 or relative values for compara-tive purposes 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

13、under the jurisdiction ofASTM Committee E37 on ThermalMeasurements and is the direct responsibility of Subcommittee E37.01 on Calo-rimetry and Mass Loss.Current edition approved April 1, 2018. Published May 2018. Originallyapproved in 1981. Last previous edition approved in 2012 as E793 12. DOI:10.1

14、520/E0793-06R18.2For 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 Standards I

15、nstitute (ANSI), 25 W. 43rd St.,4th 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 StatesThis international standard was developed in accordance with internationally recognized principles on sta

16、ndardization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.15. Significance and Use5.1 Differential scanning calorimetry provides a rapidmethod for

17、 the determination of enthalpic changes accompa-nying 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

18、capability forthis method includes:6.1.1 DSC Test 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 thespecime

19、n temperature to 60.1C.6.1.1.3 Differential sensors, 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 2Typicall

20、y, 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 recommended and is essential foroperation at subambient temperatures.6.1.2 A temperature controller, capable of executing aspecific temperature p

21、rogram by operating the furnaces(s)between selected 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

22、 flow signal (DSCcurve) including the signal noise 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

23、 suitable structural shape and integrityto contain 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

24、 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 theprecision described in this standard.6.5 Auxiliary instrumentation considered useful or neces-sary for conducting this method includes:6.5.1 Data Analy

25、sis capability of integrating the heat flowsignal as 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,

26、to provide constant cooling rates, or tosustain an 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 c

27、ould be harmful to thepersonnel or the apparatus.7.3 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 bur

28、n hazards fromhot surfaces.8. Sampling8.1 Powdered 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

29、 determination. Liquid samples maybe sampled directly 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,

30、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 heat flow axis of theinstrument, using the procedure in Practice E968.9.2 Calibrate the elapsed time signal of the differentialscanning calorimeter using Test

31、Method E1860.10. Procedure10.1 Weigh 1 to 15 mg of 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 encap

32、sulation. Weighing toless accuracy than one part per 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

33、 under an inert atmosphere may be desirable.10.3 Load 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

34、allowed to equilibrate.NOTE 5For some materials, it may be necessary to start the scanE793 06 (2018)2substantially 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

35、through the meltingrange until baseline is reestablished 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

36、 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 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 sy

37、stem 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 scan several tensof degrees below the peak maximum in order to attain a constant baseline.Record the accompanying thermal curve.10.8 Reweigh the speci

38、men after completion of scanningand discard. Discard 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 themeltin

39、g endotherm (or freezing exotherm) deviates from therelatively 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 o

40、f 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,E = Calibration constant from Practice E968,Ho= observed enthalpy of fusion (or crystallization), mJ12. Report12.1 Report the following information:12.1.1

41、 Complete identification and description of the mate-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

42、 the calibration procedure.12.1.5 Identification of 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 determine

43、d in aninterlaboratory investigation in which 18 laboratories 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 enthal

44、py of fusion or crystallization results:13.2.1 Repeatability (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 free

45、dom. Two such averages should beconsidered suspect (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, mat

46、erials melting or crystallizing over a broad tem-perature 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 %.4Supporting data have been filed at

47、 ASTM International Headquarters and maybe obtained by requesting Research Report RR:E37-1001. ContactASTM CustomerService at serviceastm.org.FIG. 1 Melting Endotherm (DSC)FIG. 2 Crystallization Exotherm (DSC)E793 06 (2018)313.2.3 Reproducibility of Pure Materials(Multilaboratory)The coefficient of

48、variation of results (eachthe average of duplicates) for enthalpy of fusion or crystalli-zation for 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 fr

49、eedom. Two such results should beconsidered suspect (95 % confidence level) if they differ bymore than 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 0.30Adipic acidB252 9 238.5 2.4AHultgren, R. R., et al., Selected Values of Thermodynamic Properties of theElements, John Wiley hence, the bias is notsign