1、Designation: E2008 08 (Reapproved 2014)1Standard Test Methods forVolatility Rate by Thermogravimetry1This standard is issued under the fixed designation E2008; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revisi
2、on. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1NOTEWarning notes were editorially updated throughout in March 2014.1. Scope1.1 These test methods cover procedures for assessing thevolatil
3、ity of solids and liquids at given temperatures usingthermogravimetry under prescribed experimental conditions.Results of these test methods are obtained as volatility ratesexpressed as mass per unit time. Rates 5 g/min areachievable with these test methods.1.2 Temperatures typical for these test me
4、thods are withinthe range from 25C to 500C. This temperature range maydiffer depending upon the instrumentation used.1.3 These test methods are intended to provide a value forthe volatility rate of a sample using a thermogravimetricanalysis measurement on a single representative specimen. It isthe r
5、esponsibility of the user of these test methods to determinethe need for and the number of repetitive measurements onfresh specimens necessary to satisfy end use requirements.1.4 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1
6、.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 the user of these test methods to establishappropriate safety and health practices and determine theapplicability
7、 of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2E177 Practice for Use of the Terms Precision and Bias inASTM Test MethodsE473 Terminology Relating to Thermal Analysis and Rhe-ologyE691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a
8、Test MethodE1142 Terminology Relating to Thermophysical PropertiesE1582 Practice for Calibration of Temperature Scale forThermogravimetryE1860 Test Method for Elapsed Time Calibration of Ther-mal AnalyzersE2040 Test Method for Mass Scale Calibration of Thermo-gravimetric Analyzers3. Terminology3.1 D
9、efinitions:3.1.1 The following terms are applicable to these testmethods and can be found in Terminologies E473 and E1142:3.1.1.1 thermogravimetric analysis (TGA),3.1.1.2 thermogravimetry (TG),3.1.1.3 volatility.3.2 Definitions of Terms Specific to This Standard:3.2.1 volatility ratethe rate of conv
10、ersion 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 appropriatecontainer with a pinhole opening between 0.33 and 0.38 mm.The confined specimen is heated within a thermogravimetri
11、canalyzer 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(Method B, Fig. 2). The mass of the specimen is measuredcontinuously and it or its rate of change is displayed as afunctio
12、n 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 (first derivative) per unit time from Method B.5. Significance and Use5.1 Volatility of a material is not an equilib
13、rium thermody-namic property but is a characteristic of a material related to athermodynamic property that is vapor pressure. It is influenced1These test methods are under the jurisdiction of ASTM Committee E37 onThermal Measurements and are the direct responsibility of Subcommittee E37.01 onCalorim
14、etry and Mass Loss.Current edition approved March 15, 2014. Published April 2014. Originallyapproved in 1999. Last previous edition approved in 2008 as E2008 08. DOI:10.1520/E2008-08R14E01.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at servic
15、eastm.org. For Annual Book of ASTMStandardsvolume information, refer to the standards Document Summary page onthe ASTM website.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1by such factors as surface area, temperature, particle size
16、, and purge gas flow rate; that is, it is diffusion controlled.FIG. 1 Method A: Rv= Average Volatility RateFIG. 2 Method B: Rv= Instantaneous Volatility RateE2008 08 (2014)125.2 The extent of containment achieved for specimens inthese test methods by means of a pinhole opening between 0.33to 0.38 mm
17、 allows for measurement circumstances that arerelatively insensitive to experimental variables other thantemperature. Decreasing the extent of containment by use ofpinholes larger than 0.38 mm will increase the magnitude ofthe observed rate of mass loss but will also reduce themeasurement precision
18、by increasing the sensitivity to varia-tions in other experimental variables.5.3 Results obtained by these test methods are not strictlyequivalent to those experienced in processing or handlingconditions but may be used to rank materials for their volatilityin such circumstances. Therefore, the vola
19、tility rates deter-mined by these test methods should be considered as indexvalues only.5.4 The volatility rate may be used to estimate such quan-tifiable values as drying interval or the extent of volatile releasefrom a process.6. Interferences6.1 Specimens that consist of a mixture of two or morev
20、olatile 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 as a singular value.7. Apparatus7.1 The essential instrumentation required to p
21、rovide theminimum thermogravimetric analytical capability for these testmethods 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 at a constant ratewithin the applicable temperature range of these test metho
22、ds;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 610 g;7.1.1.4 A means of sustaining the specimen/container underatmospheric
23、control of inert gas (nitrogen, helium, and soforth) of 99.9 % purity at a purge rate of 50 to 100 mL/min 65%.7.1.2 A Temperature Controller, capable of executing aspecific temperature program by operating the furnace betweenselected temperature limits at a rate of temperature change of1 to 2 K/min
24、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 ofacquiring, storing, and displaying measured or calculatedsignals, or both.
25、 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 the temperature limits of these test methods, andthat contain a pinhole in
26、 the lid of diameter between 0.33 and0.38 mm.3NOTE 1The most critical parameters for containers suitable for use3See Appendix X1.FIG. 3 Method ATwo Component MixtureE2008 08 (2014)13with these test methods are the pinhole diameter and the lid thickness.Sealable containers of volumes (25 to 50 L) and
27、 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 conductingthese test methods includes:7.2.1 While not required, it is convenient to ha
28、ve a dataanalysis device that will continuously calculate and display thefirst 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 Micropipette or syringe to deliver liquid specimens of1 to 30 L i
29、nto 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 taken to ensure that the analyzed specimen isrepresentative
30、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 specimen or run as a separate specimen with thefinal analysi
31、s representing an average of these determinations.Include the number of determinations in the report.9. Calibration9.1 Perform temperature calibration in accordance withPractice E1582 using the same purge gas conditions andcontainer type to be used for the subsequent measurements ata heating rate of
32、 2 K/min. Do not disturb the temperaturesensor position after this calibration.9.2 Perform mass calibration in accordance with TestMethod E2040.9.3 Perform time scale calibration in accordance with TestMethod E1860.10. Procedure10.1 Method AIsothermal Test:10.1.1 Initiate a purge gas flow through th
33、e thermobalancebetween 50 to 100 mL/min 6 5%.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 the test specimen may be recorded directly10.1.3 Encapsulate a
34、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. (WarningVolatile mate-rials may pose a respiratory hazard. Avoid unnecessary expo-sure to vapors.)10.1.4 Pla
35、ce 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 3For highly volatile substances, a significant mass fraction ofthe specimen could be lost during this period of equilibrati
36、on. 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, maintain the isothermaltemperature to 61 K for 30 min. Record
37、 the specimen mass inmg or g continually during this heating program versus time.The specimen temperature should be recorded during theheating programNOTE 4If the specimen is exhausted before 30 min have elapsed, it isrecommended that the test be repeated with a larger specimen mass. Ifexcessively l
38、arge 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 5The initial rapid heating to the desired isothermal temperaturemay result in a momentary overshoot in the furnace temperature.Overshoot in it
39、self 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 temperature, andremove the specimen container.10.1.7 Calculate t
40、he 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 rate of 2 60.1 K/min between ambient temperature and the desired l
41、imittemperature. 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 6If the specimen is exhausted before reaching the desired limittemperatu
42、re, 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.10.2.3 Restore the furnace to ambient temperature, andremove the
43、 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.11. Calculation11.1 Use all available decimals for each value in thecalculations. Round the final volatility rate to the nearest 0.1g/min.11.2 Using MethodA, the volati
44、lity 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 time used, see Fig. 1):volatility rate, rv5 mi2 mf!/tf2 ti! or mi2 mf!/30 (1)where:mi= mass at initial time (ti), andmf= mass at final t
45、ime (tf).NOTE 7If the mass loss rate is not constant with time at the isothermaltemperature, this calculation will result in an average value of volatilityrate. Selecting shorter time segments, such as the first few minutes and thelast few minutes, will result in different values that could demonstr
46、ate theE2008 08 (2014)14range 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 loss curve at any specifictemperature(s) of interest or is the rate obtained by determiningthe slope of the mass loss
47、 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 description of thematerial tested, including any pretreatment of a specimen.12.1.2 A description of the instrumentation u
48、sed.12.1.3 Test conditions, including temperature programexecuted, purge gas composition and flow rate, initial specimensize, and pinhole size.12.1.4 The mass loss curve or the first derivative withrespect to time of mass loss, or both.12.1.5 The volatility rate (g/min) and the associated tem-peratu
49、re (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 constantheating rate test was used to determine the volatility rates forwater at 323 and 353 K. Each laborat
