1、Designation: E 2008 07Standard 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 (e) 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
3、experimental 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 25C to 500C. This temperature range may differdepending upon
4、 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 repet
5、itive measurements on freshspecimens necessary to satisfy end use requirements.1.4 Computer- or electronic-based instruments, techniques,or data treatment equivalent to this test method may also beused.NOTE 1Users of this test method are expressly advised that all suchinstruments or techniques may n
6、ot be equivalent. It is the responsibility ofthe user of this test method to determine the necessary equivalency priorto use.1.5 SI units are the standard.1.6 There is no ISO method equivalent to this standard.1.7 This standard does not purport to address all of thesafety concerns, if any, associate
7、d with its use. It is theresponsibility of the 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 T
8、est MethodsE 473 Terminology Relating to Thermal 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 18
9、60 Test Method for Elapsed Time Calibration of 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 thermogra
10、vimetric 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 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
11、 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 thermogravimetricanalyzer either to a temperature and held constant at thattemperature for a fixed interval of time (Method A, Fig. 1)orat a slow constant
12、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 afunction of time or temperature. The volatility rate at anytemperature is reported either as the average rate of mass lossper unit time from Metho
13、d 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 equilibrium thermody-namic property but is a characteristic of a material related to athermodynamic property that is vapor pressure. It is influen
14、ced1This 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 March 1, 2007 Published June 2007. Originallyapproved in 1999. Last previous edition approv
15、ed in 2006 as E 2008 06.2For 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, 100 Bar
16、r Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.FIG. 1 Method A: Rv= Average Volatility RateFIG. 2 Method B: Rv= Instantaneous Volatility RateE2008072by such factors as surface area, temperature, particle size, andpurge gas flow rate; that is, it is diffusion controlled.
17、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 other thantemperature. Decreasing the extent of containment by use ofpinholes lar
18、ger than 0.38 mm will increase the magnitude ofthe 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 process
19、ing or handlingconditions but may be used 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
20、 or the extent of volatile releasefrom a 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
21、is notconstant and shall not be reported 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 o
22、fa specimen at a constant temperature or at a constant ratewithin the applicable temperature range of this test method;7.1.1.2 Atemperature sensor, to provide an indication of thespecimen/furnace temperature to 61K;7.1.1.3 A continuously recording balance, to measure thespecimen mass with a minimum
23、capacity of 100 mg and asensitivity of 610 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%.NOTE 2Excessive purge rates should be avoided as this may intro-duce interfe
24、rences due to turbulence effects and temperature gradients.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 constant to within 60.1 K/min or to rapidly heata s
25、pecimen at a minimum of 50 K/min to an isothermaltemperature that is maintained constant to 61 K for a mini-mum of 30 min.FIG. 3 Method A- Two Component MixtureE20080737.1.3 A recording device, either analog or digital, capable ofrecording and displaying any fraction of the specimen masssignal (TGA
26、curve), including the signal noise versus time ortemperature.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 this test method, andthat contain a pinhole in the lid of diameter between 0.
27、33 and0.38 mm.3NOTE 3The 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 wall thicknesses (80 to150 m) commercially available from Mettler-Toledo, Perkin-ElmerCorporation, and
28、 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 a dataanalysis device that will continuously calculate and display thefirst derivative of mass with res
29、pect 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 into the containers.8. Sampling8.1 Samples are ordinarily measured as received. If apretreatment is applied
30、 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 of the sample from which it is taken. If thesample is liquid, mixing prior to taking the specimen issuffic
31、ient 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 analysis representing an average of these determinations.Include the number of determinations in the report.9. Ca
32、libration9.1 Perform temperature calibration in accordance withPractice E 1582 using the same purge gas conditions andcontainer type to 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 calibrati
33、on in accordance with TestMethod E 2040.9.3 Perform time scale calibration in accordance with TestMethod E 1860.10. Procedure10.1 Method 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 atr
34、oom temperature, and tare the balance.NOTE 4If 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 specimen in an appropriate containerwith the specified pinhole. Specimen sizes between 1 and 30mg are ty
35、pical for this test method, with the larger mass beingused for more volatile specimens.NOTE 5Caution: Volatile materials may pose a respiratory hazard.Avoid unnecessary exposure to vapors.10.1.4 Place the encapsulated specimen in the thermogravi-metric analyzer, close the furnace, and allow the temp
36、erature,purge, and so forth, to become stable within 61 % of settings.NOTE 6For highly volatile substances, a significant mass fraction ofthe specimen could be lost during this period of equilibration. Any largediscrepancy between the specimen mass as delivered and subsequentlyrecorded by the thermo
37、balance 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 the specimen mass inmg or g continually during this heating program versus time.The specimen temperat
38、ure should be recorded during theheating programNOTE 7If the specimen is exhausted before 30 min have elapsed, it isrecommended that the 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 isoth
39、ermal temperature may beused and shall be reported.NOTE 8The initial rapid heating to the desired isothermal temperaturemay result in a 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 w
40、here 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.3If you are aware of suppliers, please provide this information to ASTMHeadquarters. Your comments will receive careful
41、consideration at a meeting of theresponsible technical committee, which you may attend.TABLE 1 Volatility Rate PrecisionMaterial Temperature,KAverageVolatility Rate,g min-1RepeatabilityStandardDeviation, Srg min-1ReproducibilityStandardDeviation,SRg min-1RepeatabilityLimit, r gmin-1ReproducibilityLi
42、mit, 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 102E200807410.1.7 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 Heati
43、ng 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 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, andcalc
44、ulate and display the first derivative (with respect to time)of the mass loss in g/min during heating.NOTE 9If the specimen 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 temper
45、ature, 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 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 addition
46、al 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 volatility rate is obtained from thedifference in mass at the initial time and the mass at the finaltime at the isothermal temp
47、erature divided by 30 min (or otherelapsed 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 10If the mass loss rate is not constant with time at theisothermal temperature, this calculation will result in a
48、n average value ofvolatility rate. Selecting shorter time segments, such as the first fewminutes and the last few minutes, will result in different values that coulddemonstrate the range of volatility rate exhibited by the sample (see alsoFig. 3).11.3 Using Method B, the volatility rate is either th
49、ecomputed 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 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 used.12.1.3 Test conditions, including temperature program ex-ecuted, purge gas composition and fl
