ASTM E2008-2008 Standard Test Method for Volatility Rate by Thermogravimetry《用热重分析法测定挥发速度的标准试验方法》.pdf

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1、Designation: E 2008 08Standard Test Method forVolatility Rate by Thermogravimetry1This standard is issued under the fixed designation E 2008; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A number in pa

2、rentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers procedures for assessing thevolatility of solids and liquids at given temperatures usingthermogravimetry under prescribed e

3、xperimental conditions.Results of this test method are obtained as volatility ratesexpressed as mass per unit time. Rates $ 5 g/min areachievable with this test method.1.2 Temperatures typical for this test method are within therange from 25 C to 500 C. This temperature range may differdepending upo

4、n the instrumentation used.1.3 This test method is intended to provide a value for thevolatility rate of a sample using a thermogravimetric analysismeasurement on a single representative specimen. It is theresponsibility of the user of this test method to determine theneed for and the number of repe

5、titive measurements on freshspecimens necessary to satisfy end use requirements.1.4 SI units are the standard.1.5 There is no ISO method equivalent to this standard.1.6 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of th

6、e user of this test method to establishappropriate safety and health practices and determine theapplicability of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2E 177 Practice for Use of the Terms Precision and Bias inASTM Test MethodsE 473 Terminology Relating to Ther

7、mal Analysis and Rhe-ologyE 691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test MethodE 1142 Terminology Relating to Thermophysical PropertiesE 1582 Practice for Calibration of Temperature Scale forThermogravimetryE 1860 Test Method for Elapsed Time Calibration o

8、f Ther-mal AnalyzersE 2040 Test Method for Mass Scale Calibration of Thermo-gravimetric Analyzers3. Terminology3.1 Definitions:3.1.1 The following terms are applicable to this test methodand can be found in Terminologies E 473 and E 1142:3.1.1.1 thermogravimetric analysis (TGA),3.1.1.2 thermogravime

9、try (TG),3.1.1.3 volatility.3.2 Definitions of Terms Specific to This Standard:3.2.1 volatility ratethe rate of conversion of a solid orliquid substance into the vapor state at a given temperature;mass per unit time.4. Summary of Test Method4.1 A solid or liquid specimen is confined in an appropriat

10、econtainer with a pinhole opening between 0.33 and 0.38 mm.The confined specimen is heated within a thermogravimetricanalyzer either to a temperature and held constant at thattemperature for a fixed interval of time (Method A, Fig. 1)orat a slow constant heating rate between temperature limits(Metho

11、d B, Fig. 2). The mass of the specimen is measuredcontinuously and it or its rate of change is displayed as afunction of time or temperature. The volatility rate at anytemperature is reported either as the average rate of mass lossper unit time from Method A or as the instantaneous rate ofmass loss

12、(first derivative) per unit time from Method B.5. Significance and Use5.1 Volatility of a material is not an equilibrium thermody-namic property but is a characteristic of a material related to athermodynamic property that is vapor pressure. It is influencedby such factors as surface area, temperatu

13、re, particle size, andpurge gas flow rate; that is, it is diffusion controlled.5.2 The extent of containment achieved for specimens inthis test method by means of a pinhole opening between 0.33to 0.38 mm allows for measurement circumstances that arerelatively insensitive to experimental variables ot

14、her than1This test method is under the jurisdiction ofASTM Committee E37 on ThermalMeasurements and is the direct responsibility of Subcommittee E37.01 on ThermalTest Methods and Practices.Current edition approved Sept. 1, 2008 Published October 2008. Originallyapproved in 1999. Last previous editio

15、n approved in 2007 as E 2008 07.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandardsvolume information, refer to the standards Document Summary page onthe ASTM website.1Copyright ASTM International,

16、 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.temperature. Decreasing the extent of containment by use of pinholes larger than 0.38 mm will increase the magnitude ofFIG. 1 Method A: Rv= Average Volatility RateFIG. 2 Method B: Rv= Instantaneous Volatility RateE2

17、008082the observed rate of mass loss but will also reduce themeasurement precision by increasing the sensitivity to varia-tions in other experimental variables.5.3 Results obtained by this test method are not strictlyequivalent to those experienced in processing or handlingconditions but may be used

18、 to rank materials for their volatilityin such circumstances. Therefore, the volatility rates deter-mined by this test method should be considered as index valuesonly.5.4 The volatility rate may be used to estimate such quan-tifiable values as drying interval or the extent of volatile releasefrom a

19、process.6. Interferences6.1 Specimens that consist of a mixture of two or morevolatile components or that undergo decomposition during thistest may exhibit curvature in the mass loss versus time plot ofMethod A (see Fig. 3). In such cases the volatility rate is notconstant and shall not be reported

20、as a singular value.7. Apparatus7.1 The essential instrumentation required to provide theminimum thermogravimetric analytical capability for this testmethod includes:7.1.1 A Thermobalance, composed of:7.1.1.1 A Furnace, to provide uniform controlled heating ofa specimen at a constant temperature or

21、at a constant ratewithin the applicable temperature range of this test method;7.1.1.2 A Temperature Sensor, to provide an indication ofthe specimen/furnace temperature to 61K;7.1.1.3 A continuously recording Balance, to measure thespecimen mass with a minimum capacity of 100 mg and asensitivity of 6

22、10 g;7.1.1.4 A means of sustaining the specimen/container underatmospheric control of inert gas (nitrogen, helium, and soforth) of 99.9 % purity at a purge rate of 50 to 100 mL/min65%.7.1.2 A Temperature Controller, capable of executing aspecific temperature program by operating the furnace betweens

23、elected temperature limits at a rate of temperature change of1 to 2 K/min constant to within 60.1 K/min or to rapidly heata specimen at a minimum of 50 K/min to an isothermaltemperature that is maintained constant to 61 K for a mini-mum of 30 min.7.1.3 A Data Collection Device, to provide a means of

24、acquiring, storing, and displaying measured or calculatedsignals, or both. The minimum output signals required forthermogravimetry are mass, temperature, and time.7.1.4 Sealable Containers, (pans, crucibles, and so forth),that are inert to the specimen, that will remain gravimetricallystable within

25、the temperature limits of this test method, andthat contain a pinhole in the lid of diameter between 0.33 and0.38 mm.3NOTE 1The most critical parameters for containers suitable for usewith this test method are the pinhole diameter and the lid thickness.Sealable containers of volumes (25 to 50 L) and

26、 wall thicknesses (80 to150 m) commercially available from Mettler-Toledo, Perkin ElmerCorporation, and TA Instruments, Inc. have been found suitable for thispurpose.7.2 Auxiliary equipment necessary or useful in conductingthis test method includes:7.2.1 While not required, it is convenient to have

27、a dataanalysis device that will continuously calculate and display the3See Appendix X1FIG. 3 Method A- Two Component MixtureE2008083first derivative of mass with respect to time (in mass/min)capable of detecting 0.05 g/min.7.2.2 Device to encapsulate the specimen in sealable con-tainers.7.2.3 Microp

28、ipette or syringe to deliver liquid specimens of1 to 30 L into the containers.8. Sampling8.1 Samples are ordinarily measured as received. If apretreatment is applied to any specimen, this treatment shall benoted in the report.8.2 Since the applicable samples may be mixtures or blends,care shall be t

29、aken to ensure that the analyzed specimen isrepresentative of the sample from which it is taken. If thesample is liquid, mixing prior to taking the specimen issufficient to ensure this consideration. If the sample is solid,take several samplings from different areas and either combineinto a single s

30、pecimen or run as a separate specimen with thefinal analysis representing an average of these determinations.Include the number of determinations in the report.9. Calibration9.1 Perform temperature calibration in accordance withPractice E 1582 using the same purge gas conditions andcontainer type to

31、 be used for the subsequent measurements ata heating rate of 2 K/min. Do not disturb the temperaturesensor position after this calibration.9.2 Perform mass calibration in accordance with TestMethod E 2040.9.3 Perform time scale calibration in accordance with TestMethod E 1860.10. Procedure10.1 Metho

32、d AIsothermal Test:10.1.1 Initiate a purge gas flow through the thermobalancebetween 50 to 100 mL/min 65%.10.1.2 Equilibrate the furnace, gas purge, and so forth atroom temperature, and tare the balance.NOTE 2If the balance is tarred tared with the empty crucible and lidin place, then the mass of th

33、e test specimen may be recorded directly10.1.3 Encapsulate a specimen in an appropriate containerwith the specified pinhole. Specimen sizes between 1 and 30mg are typical for this test method, with the larger mass beingused for more volatile specimens.NOTE 3Caution: Volatile materials may pose a res

34、piratory hazard.Avoid unnecessary exposure to vapors.10.1.4 Place the encapsulated specimen in the thermogravi-metric analyzer, close the furnace, and allow the temperature,purge, and so forth, to become stable within 61 % of settings.NOTE 4For highly volatile substances, a significant mass fraction

35、 ofthe specimen could be lost during this period of equilibration. Any largediscrepancy between the specimen mass as delivered and subsequentlyrecorded by the thermobalance should be noted in the report.10.1.5 Heat the specimen rapidly at 50 K/min to the desiredisothermal temperature, and thereafter

36、, maintain the isothermaltemperature to 61 K for 30 min. Record the specimen mass inmg or g continually during this heating program versus time.The specimen temperature should be recorded during theheating programNOTE 5If the specimen is exhausted before 30 min have elapsed, it isrecommended that th

37、e test be repeated with a larger specimen mass. Ifexcessively large specimen mass is required to complete a 30-min testtime, a shorter time interval or a lower isothermal temperature may beused and shall be reported.NOTE 6The initial rapid heating to the desired isothermal temperaturemay result in a

38、 momentary overshoot in the furnace temperature.Overshoot in itself does not create a measurement question provided thedata in 10.1.7 is taken only from the region where the isothermaltemperature is stable and provided the entire specimen has not beenexhausted.10.1.6 Restore the furnace to ambient t

39、emperature, andremove the specimen container.10.1.7 Calculate the volatility rate in accordance with11.2.10.1.8 Repeat 10.1.2-10.1.7 for additional samples.10.2 Method BConstant Heating Rate Test:10.2.1 Follow the instructions given in 10.1.1-10.1.4.10.2.2 Heat the specimen at a constant heating rat

40、e of 260.1 K/min between ambient temperature and the desired limittemperature. Record the specimen mass in mg or g continu-ally during this heating program versus temperature, andcalculate and display the first derivative (with respect to time)of the mass loss in g/min during heating.NOTE 7If the sp

41、ecimen is exhausted before reaching the desired limittemperature, repeat the test using a larger specimen mass. If excessivelylarge specimen mass is required to reach the limit temperature, it may benecessary to terminate the test at a lower limit temperature, and this shallbe noted in the report.10

42、.2.3 Restore the furnace to ambient temperature, andremove the specimen container.10.2.4 Calculate the volatility rate in accordance with 11.3.10.2.5 Repeat 10.2.1-10.2.4 for additional samples.TABLE 1 Volatility Rate PrecisionMaterial Temperature,KAverageVolatility Rate,g min-1RepeatabilityStandard

43、Deviation, Srg min-1ReproducibilityStandardDeviation,SRg min-1RepeatabilityLimit, r gmin-1ReproducibilityLimit, R gmin-1Camphor 333 2.31 0.194 0.271 0.543 0.760Squalane 573 113 24.2 49.3 67.8 138Water 323 44.4 6.54 8.12 18.3 22.7Water 353 205 23.9 36.6 67.0 102E200808411. Calculation11.1 Use all ava

44、ilable decimals for each value in thecalculations. Round the final volatility rate to the nearest 0.1g/min.11.2 Using MethodA, the volatility rate is obtained from thedifference in mass at the initial time and the mass at the finaltime at the isothermal temperature divided by 30 min (or otherelapsed

45、 time used, see Fig. 1):volatility rate, rv5 mimf!/tfti! or mimf!/30 (1)where:mi= mass at initial time (ti), andmf= mass at final time (tf).NOTE 8If the mass loss rate is not constant with time at the isothermaltemperature, this calculation will result in an average value of volatilityrate. Selectin

46、g shorter time segments, such as the first few minutes and thelast few minutes, will result in different values that could demonstrate therange of volatility rate exhibited by the sample (see also Fig. 3).11.3 Using Method B, the volatility rate is either thecomputed first derivative of the mass los

47、s curve at any specifictemperature(s) of interest or is the rate obtained by determiningthe slope of the mass loss curve overa4K(2min) intervalcentered about the specific temperature of interest (see Fig. 2).12. Report12.1 Report the following information:12.1.1 A complete identification and descrip

48、tion of thematerial tested, including any pretreatment of a specimen.12.1.2 A description of the instrumentation used.12.1.3 Test conditions, including temperature program ex-ecuted, purge gas composition and flow rate, initial specimensize, and pinhole size.12.1.4 The mass loss curve or the first d

49、erivative withrespect to time of mass loss, or both.12.1.5 The volatility rate (g/min) and the associated tem-perature (K or C).12.1.6 The specific dated version of this method used.13. Precision and Bias13.1 The precision and bias of this standard method weredetermined in an interlaboratory test (ILT) in 2003. Eightlaboratories using thermogravimetric analyzers from threemanufacturers and four instrument models participated in theILT. The volatility rates for camphor at 333 K and squalane at573 K were determined using the isothermal test. The co