1、Designation: E537 12Standard Test Method forThe Thermal Stability of Chemicals by Differential ScanningCalorimetry1This standard is issued under the fixed designation E537; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year o
2、f last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies of the Department of Defense.INTRODUCTIONCommittee E27 is currently engaged
3、in developing methods to determine the hazard potential ofchemicals. An estimate of this potential may usually be obtained by the use of program CHETAH 7.0to compute the maximum energy of reaction of the chemical or mixture of chemicals.2The expression “hazard potential” as used by this committee is
4、 defined as the degree ofsusceptibility of material to ignition or release of energy under varying environmental conditions.The primary purpose of this test method is to detect enthalpic changes and to approximate thetemperature of initiation and enthalpies (heats) of these events. Differential scan
5、ning calorimetry offersthe advantage of using very small specimens on the order of a few milligrams.1. Scope1.1 This test method describes the ascertainment of thepresence of enthalpic changes in a test specimen, usingminimum quantities of material, approximates the temperatureat which these enthalp
6、ic changes occur and determines theirenthalpies (heats) using differential scanning calorimetry orpressure differential scanning calorimetry.1.2 This test method may be performed on solids, liquids, orslurries.1.3 This test method may be performed in an inert or areactive atmosphere with an absolute
7、 pressure range from 100Pa through 7 MPa and over a temperature range from 300 to800 K (27 to 527C).1.4 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.5 There is no ISO standard equivalent to this test method.1.6 This standar
8、d may involve hazardous materials,operations, and equipment. This standard does not purport toaddress all of the safety concerns associated with its use. It isthe responsibility of the user of this standard to establishappropriate safety and health practices and determine theapplicability of regulat
9、ory limitations prior to use. Specificsafety precautions are given in Section 8.2. Referenced Documents2.1 ASTM Standards:3E473 Terminology Relating to Thermal Analysis and Rhe-ologyE691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test MethodE967 Test Method for T
10、emperature Calibration of Differen-tial Scanning Calorimeters and Differential Thermal Ana-lyzersE968 Practice for Heat Flow Calibration of DifferentialScanning CalorimetersE1445 Terminology Relating to Hazard Potential of Chemi-calsE1860 Test Method for Elapsed Time Calibration of Ther-mal Analyzer
11、s3. Terminology3.1 Definitions:3.1.1 Specific technical terms used in this standard aredefined in Terminologies E473 and E1445, and include1This test method is under the jurisdiction of ASTM Committee E27 on HazardPotential of Chemicals and is the direct responsibility of Subcommittee E27.02 onTherm
12、al Stability and Condensed Phases.Current edition approved Dec. 1, 2012. Published December 2012. Originallyapproved in 1976. Last previous edition approved in 2007 as E537 07. DOI:10.1520/E0537-12.2A complete assessment of the hazard potential of chemicals must take intoaccount a number of realisti
13、c factors not considered in this test method or theCHETAH program.3For 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 web
14、site.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1calorimeter, differential scanning calorimetry, extrapolated on-set value, first-deviation-from baseline, peak, reaction, andthermal stability.3.2 Definitions of Terms Specific to T
15、his Standard:3.2.1 DSC curvea record of a differential scanning calo-rimeter where the change in heat flow (q) is plotted on theordinate and temperature or time is plotted on the abscissa (seeFigs. 1 and 2 and Terminology E473).3.2.2 peak temperature (Tp)the temperature correspond-ing to the maximum
16、 deflection of the DSC curve.3.2.3 onset temperature (To)the temperature at which adeflection from the established baseline is first observed.3.2.3.1 DiscussionThis is also known as the first-deviation-from-baseline.4. Summary of Test Method4.1 In DSC, a measurement is made of the heat flow (q)assoc
17、iated with the observed change of enthalpy. Provisionsare made to measure the absolute temperature (T) of the sampleor reference or the average temperature of both.4.2 A sample of the material to be examined and of athermally inert reference material are placed in separateholders.4.3 The sample and
18、reference materials are simultaneouslyheated at a controlled rate of 2 to 20 K/min under anequilibrated atmosphere. A record of q on the ordinate ismade as a function of temperature (T) on the abscissa.4.4 When the sample undergoes a transition involving achange of enthalpy, that change is indicated
19、 by a departurefrom the initially established baseline of the heat flow record.4.5 The onset temperature (To), extrapolated onset tempera-ture (Te), and the integrated peak area (enthalpy) are deter-mined and reported.5. Significance and Use5.1 This test method is useful in detecting potentiallyhaza
20、rdous reactions including those from volatile chemicalsand in estimating the temperatures at which these reactionsoccur and their enthalpies (heats). This test method is recom-mended as an early test for detecting the thermal hazards of anuncharacterized chemical substance or mixture (see Section 8)
21、.5.2 The magnitude of the change of enthalpy may notnecessarily denote the relative hazard in a particular applica-tion. For example, certain exothermic reactions are oftenaccompanied by gas evolution that increases the potentialhazard. Alternatively, the extent of energy release for certainexotherm
22、ic reactions may differ widely with the extent ofconfinement of volatile products. Thus, the presence of anexotherm and its approximate temperature are the most signifi-cant criteria in this test method (see Section 3 and Fig. 1).5.3 When volatile substances are being studied, it is impor-tant to pe
23、rform this test with a confining pressurized atmo-sphere so that changes of enthalpy that can occur above normalboiling or sublimation points may be detected. As an example,an absolute pressure of 1.14 MPa (150 psig) will generallyelevate the boiling point of a volatile organic substance 100C.Under
24、these conditions exothermic decomposition is oftenobserved.5.4 For some substances the rate of enthalpy change duringan exothermic reaction may be small at normal atmosphericpressure, making an assessment of the temperature of instabil-ity difficult. Generally a repeated analysis at an elevatedpress
25、ure will improve the assessment by increasing the rate ofchange of enthalpy.NOTE 1The choice of pressure may sometimes be estimated by thepressure of the application to which the material is exposed.5.5 The four significant criteria of this test method are: thedetection of a change of enthalpy; the
26、approximate temperatureat which the event occurs; the estimation of its enthalpy and theobservance of effects due to the cell atmosphere and pressure.6. Limitations6.1 A host of environmental factors affect the existence,magnitude, and temperature of an exothermic reaction. Some,including heating ra
27、te, instrument sensitivity, degree ofconfinement, and atmosphere reactivity, will affect the detect-ability of an exothermic reaction using this procedure.Therefore, it is imperative that the qualitative results obtainedfrom the application of this test method be viewed only as anindication of the t
28、hermal stability of a chemical.7. Apparatus7.1 The equipment used in this test method shall be capableof displaying changes of enthalpy as a function of temperature(T), and shall have the capability of subjecting the sample cellto different atmospheres of equilibrated pressures.7.2 Differential Scan
29、ning Calorimeter (DSC)the essentialinstrumentation required to provide the minimum differentialscanning calorimetric capability for this test method include:7.2.1 A test chamber composed of:7.2.1.1 Furnace(s), to provide uniform controlled heating ofa specimen and reference to a constant temperature
30、 or at aconstant rate within the applicable temperature range of thismethod,7.2.1.2 Temperature sensor, to provide an indication of thespecimen/furnace temperature to 60.1 K,7.2.1.3 Differential sensor, to detect a temperature or heatflow difference between the specimen and reference equivalentto 0.
31、1 mW,7.2.1.4 Means of sustaining a test chamber environment ofinert (for example, nitrogen, helium or argon) or reactive (forexample, air) gas at a purge rate of 50 6 5 mL/min,NOTE 2Typically, at least 99 % pure nitrogen, argon or helium isemployed when oxidation in air is a concern. Unless effects
32、of moistureare to be studied, use of dry purge gas is recommended and is essential foroperation at subambient temperatures.NOTE 3Other purge gas rates may be used but shall be reported.7.2.1.5 Temperature controller, capable of executing a spe-cific temperature program by operating the furnace(s) be
33、tweenselected temperature limits (ambient temperature to 800 K) ata rate of temperature change of from 2 to 20 K/min constant to60.1 K/min, andE537 122FIG. 1 Typical DSC Curve with ExothermE537123FIG. 2 DSC Curve Illustrating a Melting Process Immediately Followed by an Exothermic DecompositionE5371
34、24NOTE 4The temperature range of the apparatus and the experimentmay be extended to 120 K with the use of appropriate cooling or to 1273K or greater with suitable apparatus.7.2.1.6 A data collection device, to provide a means ofacquiring, storing, and displaying measured or calculatedsignals, or bot
35、h. The minimum output signals required fordifferential scanning calorimetry are, heat flow, temperature,and time .7.2.2 If experiments are to be carried out under pressureconditions:7.2.2.1 Pressure vessel, or similar means of sealing the testchamber at any applied pressure within 0.10 to 1.27 MPa (
36、0 to170 psig) pressure limits required by this test method,7.2.2.2 Pressurized gas source, capable of sustaining aregulated gas pressure in the test chamber between 0.10 and 1.3MPa (0 and 170 psig),7.2.2.3 Pressure transducer, or similar device to measurethe pressure inside the test chamber to 65 %
37、including anytemperature dependence of the transducer,7.2.2.4 Pressure regulator, or similar device to adjust theapplied pressure in the test chamber to 65 % of the desiredvalue,7.2.2.5 Ballast, or similar means to maintain the appliedpressure in the test chamber constant to 65%,7.2.2.6 Valves, to c
38、ontrol pressurizing gas in the test cham-ber or to isolate components of the pressure system, or both.7.2.3 If subambient temperatures are desired:7.2.3.1 Cooling system, to hasten cool down from elevatedtemperatures and to sustain an isothermal subambient tempera-ture.7.3 Containers, (pans, crucibl
39、es, vials, etc.) which are inertto the specimen and reference materials and which are ofsuitable structural shape and integrity to contain the specimenand reference in accordance with the specific requirements ofthis method.7.4 Balance, with a capacity of 100 mg or greater to weighspecimens or conta
40、iners, or both, to a sensitivity of 610 g.8. Safety Precautions8.1 The use of this test method as an initial test for materialwhose potential hazards are unknown requires that precautionsbe taken during the sample preparation and testing.8.2 Where particle size reduction by grinding is necessary,the
41、 user of the test method should presume that the material issensitive to friction and electrostatic discharge. Accordingly,appropriate test shall be conducted on those materials prior togrinding. Use of suitable protective equipment is alwaysrecommended when preparing materials of unknown hazard.The
42、 Material Safety Data Sheet shall be acquired and studiedprior to handling unknown materials.8.3 The use of this test method may require operation atelevated temperatures and pressures.All precautions associatedwith such temperatures and pressures should be observed.8.4 Toxic or corrosive effluents,
43、 or both, may be releasedwhen heating the material and could be harmful to thepersonnel or the apparatus. Use of an exhaust system to removesuch effluents is recommended.9. Calibration9.1 Perform any calibration procedures recommended bythe apparatus manufacturer as described in the operatorsmanual.
44、9.2 Calibrate the temperature signal within 62 K usingPractice E967.9.3 Calibrate the heat flow signal within 61 % using TestMethod E968.9.4 Calibrate the time signal within 60.5 % using TestMethod E1860.10. Sample and Reference Materials10.1 The selection of an adequate sample size will dependupon
45、the availability of the material, the degree of dilutionrequired, the sensitivity of the instrument, the magnitude of thechange of enthalpy, and the heating rate. Additionally, samplesize must be compatible with the potential for a sudden largeenergy release. This test method should, therefore, be c
46、arriedout on as small a quantity of material as possible, typically 1 to50 mg.10.2 Samples should be representative of the material beingstudied including particle size and purity.10.3 The reference material must not undergo any thermaltransformation over the temperature range under study. Typicalre
47、ference materials include calcined aluminum oxide, glassbeads, silicone oil, or an empty container.11. Recommended Conditions of Tests11.1 Specimen SizeA 1 to 5-mg specimen is generallyconsidered adequate. Decrease the specimen size if the re-sponse is greater than 8 mW.NOTE 5For materials whose cha
48、racteristics are unknown, it is safestto start with a specimen size of no more than 1 mg, and then increase thesize if the exothermic response is insufficiently large.11.2 Heating Rate A rate of 10 to 20 K/min is considerednormal. If an endothermic response is immediately followed byan exotherm (see
49、 and Fig. 2), then lower heating rates of 2 to6C/min are recommended.NOTE 6The onset temperature, extrapolated onset temperature, andpeak temperature are affected by heating rate. Only results obtained at thesame heating rate shall be compared.11.3 Temperature RangeThe temperature typically rangesfrom 300 to 800 K (27 to 527C).11.4 Pressure Range An equilibrated absolute pressure of1.2 MPa (150 psig) is adequate for most elevated pressure tests.NOTE 7The applied pressure should be selected based upon thecharacteristics of the material. If the material to b
