1、Designation: E794 06 (Reapproved 2012)Standard Test Method forMelting And Crystallization Temperatures By ThermalAnalysis1This standard is issued under the fixed designation E794; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the
2、 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 melting(and crystallization) temperatures of pure materials b
3、y differ-ential scanning calorimetry (DSC) and differential thermalanalysis (DTA).1.2 This test method is generally applicable to thermallystable materials with well-defined melting temperatures.1.3 The normal operating range is from 120 to 600C forDSC and 25 to 1500C for DTA. The temperature range
4、can beextended depending upon the instrumentation used.1.4 Computer or electronic based instruments, techniques,or data treatment equivalent to those in this test method may beused.1.5 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstan
5、dard.1.6 This standard does not purport to address all of thesafety problems, 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. Referen
6、ced Documents2.1 ASTM Standards:2E473 Terminology Relating to Thermal Analysis and Rhe-ologyE793 Test Method for Enthalpies of Fusion and Crystalliza-tion by Differential Scanning CalorimetryE967 Test Method for Temperature Calibration of Differen-tial Scanning Calorimeters and Differential Thermal
7、Ana-lyzersE1142 Terminology Relating to Thermophysical Properties3. Terminology3.1 DefinitionsSpecialized terms used in this test methodare defined in Terminologies E473 and E1142.4. Summary of Test Method4.1 The test method involves heating (or cooling) a testspecimen at a controlled rate in a cont
8、rolled environmentthrough the region of fusion (or crystallization). The differencein heat flow (for DSC) or temperature (for DTA) between thetest material and a reference material due to energy changes iscontinuously monitored and recorded. A transition is markedby absorption (or release) of energy
9、 by the specimen resultingin a corresponding endothermic (or exothermic) peak in theheating (or cooling) curve.NOTE 1Enthalpies of fusion and crystallization are sometimes deter-mined in conjunction with melting or crystallization temperature measure-ments. These enthalpy values may be obtained by T
10、est Method E793.5. Significance and Use5.1 Differential scanning calorimetry and differential ther-mal analysis provide a rapid method for determining the fusionand crystallization temperatures of crystalline materials.5.2 This test is useful for quality control, specificationacceptance, and researc
11、h.6. Interferences6.1 Test specimens need to be homogeneous, since milli-gram quantities are used.6.2 Toxic or corrosive effluents, or both, may be releasedwhen heating the material and could be harmful to personneland to apparatus.7. Apparatus7.1 Apparatus shall be of either type listed below:7.1.1
12、 Differential Scanning Calorimeter (DSC) or Differen-tial Thermal Analyzer (DTA)The essential instrumentationrequired to provide the minimum differential scanning calori-metric or differential thermal analyzer capability for thismethod includes:1This test method is under the jurisdiction ofASTM Comm
13、ittee 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 E794 06. DOI:10.1520/E0794-06R12.2For referen
14、ced 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.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Co
15、nshohocken, PA 19428-2959. United States17.1.1.1 Test Chamber composed of:(1) A furnace or furnaces to provide uniform controlledheating (cooling) of a specimen and reference to a constanttemperature or at a constant rate within the applicable tempera-ture range of this method.(2) A temperature sens
16、or to provide an indication of thespecimen or furnace temperature to within 60.01C.(3) Differential sensors to detect a heat flow difference(DSC) or temperature difference (DTA) between the specimenand reference with a range of at least 100 mW and a sensitivityof 61 W (DSC) or 4C and a sensitivity o
17、f 40 C (DTA).(4) Ameans of sustaining a test chamber environment witha purge gas of 10 to 100 6 5 mL/min.NOTE 2Typically 99.9+% pure nitrogen, argon or helium is employedwhen oxidation in air is a concern. Unless effects of moisture are to bestudied, use of dry purge gas is recommended and is essent
18、ial foroperation at subambient temperatures.7.1.1.2 A temperature controller, capable of executing aspecific temperature program by operating the furnace orfurnaces between selected temperature limits at a rate oftemperature change of 10C/min constant to within 60.1C/min or at an isothermal temperat
19、ure constant to 60.1C.7.1.2 A recording device, capable of recording and display-ing on the Y-axis any fraction of the heat flow signal (DSCcurve) or differential temperature Signal (DTA Curve) includ-ing the signal noise as a function of any fraction of thetemperature (or time) signal on the X-axis
20、 including the signalnoise.7.2 Containers (pans, crucibles, vials, lids, closures, seals,etc.) that are inert to the specimen and reference materials andthat are of suitable structural shape and integrity to contain thespecimen and reference in accordance with the requirements ofthis test method.NOT
21、E 3DSC containers are commonly composed of aluminum orother inert material of high thermal conductivity. DTA containers arecommonly composed of borosilicate glass (for use below 500C),alumina, or quartz (for use below 1200C).7.3 Nitrogen, or other inert purge gas supply.7.4 Auxiliary instrumentation
22、 and apparatus considerednecessary or useful for conducting this method includes:7.4.1 Analytical Balance, with a capacity greater than 100mg, capable of weighing to the nearest 0.01 mg.7.4.2 Cooling capacity to hasten cooling down from el-evated temperatures, to provide constant cooling rates or to
23、sustain an isothermal subambient temperature.7.4.3 A means, tool or device, to close, encapsulate or sealthe container of choice.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.
24、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 information, samples are assumed tobe analyzed as received. If some heat or mechanical treatmentis applied to
25、 the sample prior to analysis, this treatment shouldbe noted in the report. If some heat treatment is applied, recordany mass loss as a result of this treatment.9. Calibration9.1 Using the same heating rate, purge gas, and flow rate asthat to be used for analyzing the specimen, calibrate thetemperat
26、ure axis of the instrument using the procedure inPractice E967.10. Procedure10.1 Weigh 1 to 15 mg of material to an accuracy of 0.01mg into a clean, dry specimen capsule. The specimen mass tobe used depends on the magnitude of the transition enthalpyand the volume of the capsule. For comparing multi
27、ple results,use similar mass (65 %) and encapsulation.10.2 Load the encapsulated specimen into the instrumentchamber, and purge the chamber with dry nitrogen (or otherinert gas) at a constant flow rate of 10 to 50 mL/min throughoutthe experiment. The flow rate should be measured and heldconstant for
28、 all data to be compared. The use of 99.99 % puritypurge gas and a drier is recommended.10.3 When a DSC is used, heat the specimen rapidly to30C (60C in a DTA) below the melting temperature, andallow to equilibrate. For some materials, it may be necessary tostart the scan substantially lower in temp
29、erature, for example,below the glass transition in order to establish a baseline wherethere is no evidence of melting or crystallization.10.4 Heat the specimen at 10C/min through the meltingrange until the baseline is reestablished above the meltingendotherm. Other heating rates may be used but shal
30、l be notedin the report. To allow the DSC system to achieve steady state,provide at least 3 min of scanning time both before and afterthe peak. For DTA instrumentation, allow at least 6 min toensure reaching a steady state. Record the accompanyingthermal curve.FIG. 1 Fusion and Crystallization Tempe
31、ratures for Pure Crys-talline MaterialE794 06 (2012)210.5 Hold the specimen at this temperature for 2 min. Otherperiods may be used but shall be noted in the report.10.6 Cool the specimen at 10C/min through the exothermuntil the baseline is reestablished below the crystallizationexotherm. Other cool
32、ing rates may be used but must beindicated in the report. To allow the system to achieve steadystate, provide at least 3 min of scanning time (six for DTA)both before and after the peak. For some materials, it may benecessary to scan several tens of degrees below the peakmaximum in order to attain a
33、 constant baseline. Record theaccompanying thermal curve.10.7 Reweigh the specimen after completion of the analysisand discard. Report any mass loss observed.NOTE 4Mass loss is only one indication of suspected sampledegradation or decomposition. An accurate determination of mass lossmay not be easil
34、y accomplished for tests in which the measuringthermocouple is embedded in the specimen. For these cases, otherdecomposition indications, such as color change, will suffice and shouldbe reported.10.8 From the resultant curve, measure the temperatures forthe desired points on the curve: Tp,Tm,Tf,Tn,T
35、c. Report Tm,andTn, (see Fig. 1) for a pure crystalline, low molecular weightcompound. For such a material Tmis the best determination ofthe discrete thermodynamic melting temperature, and Tnindi-cates the onset of crystallization. For polymers, alloys ormixtures of materials, report the relevant de
36、scriptive parameter(see Fig. 2). Report multiple Tps and Tcs, if observed.where:Tm= melting temperature,Tp= melting peak maximum,C,Tf= return to baseline,C,Tn= extrapolated crystallization onsetC, andTc= crystallization onset,C.NOTE 5For certain DTA instrumentation, the peak shape obtainedfrom melti
37、ng a pure, low molecular weight crystalline material (such as amelting point standard) may look quite different from that shown in Fig.1. If this is the case, report all of the above parameters for any materialanalyzed. In this case the Tpand Tcvalues are often taken as the meltingand crystallizatio
38、n temperatures, respectively.NOTE 6Samples of high purity materials may crystallize with varyingamounts of supercooling; therefore, the use of crystallization temperaturesshould be established prior to use. In general, crystallization temperaturesare useful for polymeric, alloy, and impure organic a
39、nd inorganicchemicals having sufficient nucleation sites for repeatable determinationsof crystallization temperatures.11. Report11.1 Report the following information:11.1.1 Complete identification and description of the mate-rial tested including source, manufacturers code, and anythermal or mechani
40、cal pretreatment.11.1.2 Description of instrument (such as manufacturer andmodel number) used for test.11.1.3 Statement of the mass, dimensions, geometry, andmaterial of specimen encapsulation, and temperature program.11.1.4 Description of temperature calibration procedure.11.1.5 Identification of t
41、he specimen environment by gasflow rate, purity, and composition.11.1.6 Results of the transition measurements using thetemperature parameters (Tp, etc.) cited in Figs. 1 and 2.Ingeneral, temperature results should be reported to the nearest0.1C.11.1.7 Any side reaction (for example, thermal degrada
42、tionand oxidation) shall also be reported and the reactionidentified, if possible.11.1.8 The specific dated version of this standard used.12. Precision and Bias312.1 The precision and bias were determined by an inter-laboratory study in which 17 laboratories participated using3Supporting data have b
43、een filed at ASTM International Headquarters and maybe obtained by requesting Research Report RR:E37-1002.FIG. 2 Fusion and Crystallization Temperatures for Polymeric MaterialE794 06 (2012)3five instrument models. The testing was performed on polymer,pure organic, and inorganic materials.12.2 Based
44、on the results of this study, the following criteriaare recommended for judging the acceptability of results:12.2.1 Repeatability (Single Analyst)The standard devia-tion of results, obtained by the same analyst on different days,is estimated for the:12.2.1.1 Melting Temperature (Me), Melting Peak Ma
45、ximum(Tp), Extrapolated Crystallization onset (Tn), and Peak maxi-mum (Tc) to be 1.1C at 400 degrees of freedom. Two suchresults should be considered suspect (95 % confidence level) ifthey differ by more than 3.1C.12.2.2 Reproducibility(Multilaboratory)The standard de-viation of results, obtained by
46、 analysts in different laboratories,has been estimated for the:12.2.2.1 Melting Temperature (Tm), Melting Peak maximum(Tp), Extrapolated Crystallization onset (Tn), and Crystalliza-tion Peak maximum (Tc) to be 2.1C at 168 degrees of freedom.Two such results should be considered suspect (95 % confi-d
47、ence level) if they differ by more than 5.9C.12.3 An estimation of the accuracy of the melting tempera-ture measurement was obtained by comparing the overall meanvalue obtained during the interlaboratory testing with valuesreported in the literature.Melting Temperatures,CMaterial Interlaboratory Tes
48、t LiteratureLeadA326.4 2.0 327.5 0.03Adipic acidB151.1 0.7 151.4 0.003ARossini, F.O., Pure and Applied Chemistry, Vol 22, 1972, p. 557.BColarusso, V.G., et al, Analytical Chemistry, Vol 40, 1968, p. 1521.12.4 A second interlaboratory test (ILT) was carried out in1997 to determine the extent to which
49、 more modern instru-mentation and computer calculations have improved the pre-cision and bias over the original ILT. The tests were carried outon two materials, one pure material which melts completely ata single temperature, and one polymer which melts over atemperature range. A total of 10 laboratories using 6 differentDSC models from 4 manufacturers participated. The resultsshowed substantial improvement for the onset temperature fora pure material where sample thermal contact is good, but theyshowed no improvement for the polymer w
