1、Designation: E2551 13E2551 18Standard Test MethodMethods forHumidity Calibration (or Conformation) of HumidityGenerators for Use with Thermogravimetric Analyzers1This standard is issued under the fixed designation E2551; the number immediately following the designation indicates the year oforiginal
2、adoption or, in the case of revision, the 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 ThisThese test method describesmethods describe the humidity calibra
3、tion (or conformance) of humidity generators for usewith thermogravimetric analyzers and other thermal analysis apparatus. The humidity range covered is 5 to 95 % % relativehumidity (% RH) to 95 % RH and the temperature range is 0 C to 80C.80 C.1.2 The values stated in SI units are to be regarded as
4、 standard. No other units of measurement are included in this standard.1.3 There are no ISO equivalents to this standard.1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibilityof the user of this standard to establish approp
5、riate safety, health, and environmental practices and determine the applicability ofregulatory limitations prior to use.1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibilityof the user of this standard to establish appropr
6、iate safety and health practices and determine the applicability of regulatorylimitations prior to use.1.4 This international standard was developed in accordance with internationally recognized principles on standardizationestablished in the Decision on Principles for the Development of Internation
7、al Standards, Guides and Recommendations issuedby the World Trade Organization Technical Barriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2D1193 Specification for Reagent WaterE177 Practice for Use of the Terms Precision and Bias in ASTM Test MethodsE473 Terminology Relati
8、ng to Thermal Analysis and RheologyE691 Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test MethodE1142 Terminology Relating to Thermophysical Properties1 ThisThese test method ismethods are under the jurisdiction of ASTM Committee E37 on Thermal Measurements and is
9、are the direct responsibility of SubcommitteeE37.10 on Fundamental, Statistical and Mechanical Properties.Current edition approved April 1, 2013Oct. 1, 2018. Published May 2013October 2018. Originally approved in 2007. Last previous edition approved in 20072013 as E2551 07.13. DOI: 10.1520/E2551-13.
10、10.1520/E2551-18.2 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website.This document is not an ASTM standard and is
11、 intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Becauseit may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the
12、current versionof the standard as published by ASTM is to be considered the official document.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1E1582 Test Method for Temperature Calibration of Thermogravimetric Analyzers3. Terminology3.
13、1 Specific technical terms used in this standard are defined in Terminologies E473 and E1142. These terms include thermalcurvefirst-deviation-from-baseline, isohume, relative humidity, thermal curve, and thermogravimetric analysis.3.2 Definitions of Terms Specific to This Standard:3.2.1 relative hum
14、idity, nthe ratio of actual partial pressure of water to the saturated water vapor pressure at the sametemperature, expressed as a percentage.3.2.1 water activity, nthe ratio of actual partial pressure of water to the saturated water vapor pressure at the same temperature,expressed as a decimal frac
15、tion.3.2.1.1 DiscussionWater activity is also known as relative pressure in some applications areas.3.2.3 first-deviation-from-baseline, nthe relative humidity or water activity at which a deflection from the established baselineis first observed.4. Summary of Test Method4.1 Humidity generators are
16、devices aimed at producing a specific level of humidity in the purge gas used by thermogravimetricanalyzers or other thermal analysis apparatus. The requested humidity levels may be held constant (isohum)(isohume) or increasedor decreased in a continuous or stepped fashion.4.2 The humidified purge g
17、as is submitted to a thermogravimetric analyzer in which the weight of a hygroscopic material isobserved. The relative humidity (or activity) of the moisture in the purge gas is stepped or scanned through a humidity range. Ata fixed humidity of the purge gas, the test specimen deliquesces and gains
18、weight. In Test Method A, the humidity of the onsetof this weight gain is taken as the humidity calibration point. In Test Methods B and C, the rate of weight change is zero at thehumidity calibration point.5. Significance and Use5.1 ThisThese test method calibratesmethods calibrate or demonstratesd
19、emonstrate conformity of the humidity level in a purgegas generated by a humidity generator at a fixed temperature. Such calibration or demonstration of conformity may be requiredby quality initiatives.5.2 Conformance demonstrates that the humidified purge gas is within some established limits.5.3 C
20、alibration provides an offset and or slope value that may be used for establishing the relative humidity scale of theapparatus.6. Interferences6.1 Temperature regulation of any solution-head space environment to within 60.1C 60.1 C is essential for realizinggenerated relative humidity values stable
21、to within 61 % RH (expected).7. Apparatus7.1 The humidity generator that is the focus of this standard may be an accessory providing a humidified purge gas to some otherthermal analysis apparatus (typically a thermogravimetric analyzer) or it may be part of a self-contained instrument that includesb
22、oth the humidity generator and the thermal analysis apparatus. In the former case, some of the components described below maybe redundant.7.2 Humidity GeneratorThe essential instrumentation required to provide the minimum humidity generator capability for thismethod these test methods includes:7.2.1
23、 Temperature SensorSensor, to provide an indication of the purge gas temperature readable to within 60.1C.60.1 C.7.2.2 Temperature ControllerController, capable of executing a specific temperature program by operating heaters or coolersbetween selected temperature limits at a rate of temperature cha
24、nge of 0.5C/min 0.5 C/min constant to60.1C/min60.1 C/minor at an isothermal temperature constant to within 60.1C.60.1 C.7.2.3 Humidity SensorSensor, capable of indicating the humidity of the purge gas over the range of 5 to 95 % relativehumidity (% RH)% RH to 95 % RH readable to within 60.1 % RH.7.2
25、.4 Humidity ControllerController, capable of executing a specific humidity program by operating purge gas humidifiersbetween selected humidity limits at a rate of humidity change of 0.5 % RHRH/minmin constant to within 60.1 % RH or at anisohumisohume relative humidity to within 60.1 % RH.7.2.5 Purge
26、 Gas Flow SensorSensor, capable of measuring purge gas flow readable to within 60.1 mL/min.E2551 1827.2.6 Purge Gas Flow ControllerController, capable of controlling purge gas flow readable to within 60.1 mL/min.7.2.7 Humdifier elementHumidifier Element, capable of generating purge gases with relati
27、ve humidity continuously over therange of 5 % RH to 95 % RH.7.3 Thermogravimetric Analyzer (TGA)The essential instrumentation required to provide the minimum thermogravimetricanalytical capability for this method includes:7.3.1 A furnace to provide uniform controlled heating or cooling of a specimen
28、 to a constant temperature or at a constant ratewithin the applicable temperature range of this method.7.3.2 A temperature sensor to provide an indication of the specimen or furnace temperature to within 60.1C.60.1 C.7.3.3 A continuously recording balance to measure the specimen weight with a minimu
29、m capacity of 100 mg and sensitivityof 610 g.7.3.4 A means of maintaining the specimen/container under atmospheric control at a purge rate of 10 mL/min to 200 mL/min6 10 mL/min or 1 %, whichever is greater.7.3.5 A temperature controller capable of executing a specific temperature program by operatin
30、g the furnace between selectedtemperature limits at a rate of temperature change of 0.5C/min 0.5 C/min constant to within 60.1 C/min or to an isothermaltemperature that is maintained constant to within 60.1C 60.1 C for a minimum of 100 h.7.3.6 Containers (pans, crucibles, etc.) that are inert to the
31、 specimen and that will remain gravimetrically stable within thetemperature limits of this method.7.3.7 Data storage capable of storage of the weight and relative humidity signals.7.3.8 A display capable of plotting a thermal curve with weight on the ordinate (Y-axis) and relative humidity (or activ
32、ity) onthe abscissa (X-axis) with a sensitivity of 10 g for weight and 0.1 % RH, respectively.8. Reagents and Materials8.1 One or more inorganic salts taken from Table 1 selected to provide the humidity range of interest.8.2 Purity of ReagentsReagent grade chemicals (or better) shall be used for pre
33、paration of all standard solutions.8.3 Purity of WaterReagent water produced by distillation or by ion exchange, or reverse osmosis followed by distillationshall be used (see Specification D1193).9. Hazards9.1 Salt solutions are extremely corrosive to apparatus if spilled. Care shall be taken in the
34、ir preparation and handling to preventcontact with apparatus.10. Preparation of Apparatus10.1 Perform any setup or calibration procedures recommend by the apparatus manufacturer in the operations manual.TABLE 1 Humidity Fixed PointsGreenspan, L., “Humidity Fixed Points of Binary Saturated Aqueous So
35、lutions,”Journal of Research of the National Bureau ofStandards A. Physics and Chemistry, Vol 81A, No. 1, 1977, pp. 8996.NOTE 1Greenspan, L., “Humidity Fixed Points of Binary Saturated Aqueous Solutions,” Journal of Research of the National Bureau of Standards A. Physics and Chemistry, Vol 81A, No.
36、1, 1977, pp. 8996.Temperature(C)LithiumChloridePotassiumAcetateMagnesiumChloridePotassiumCarbonateMagnesiumNitrateSodiumBromideStrontiumChlorideSodiumChloridePotassiumChlorideTemperature(C)LithiumChloridePotassiumAcetateMagnesiumChloridePotassiumCarbonateMagnesiumNitrateSodiumBromideStrontiumChlorid
37、eSodiumChloridePotassiumChloride10 11.3 23.7 33.5 43.1 57.4 62.2 75.66 75.7 86.815 11.3 23.4 33.3 43.2 55.9 60.7 74.13 75.6 85.920 11.3 23.1 33.1 43.2 54.4 59.1 72.52 75.5 85.125 11.3 22.5 32.8 43.2 52.9 57.6 70.85 75.3 84.330 11.3 21.6 32.4 43.2 51.4 56.0 69.12 75.1 83.635 11.3 . 32.1 . 49.9 54.6 .
38、 74.9 83.040 11.2 . 31.6 . 48.4 53.2 . 74.7 82.345 11.2 . 31.1 . 46.9 52.0 . 74.5 81.750 11.1 . 30.5 . 45.4 50.9 . 74.4 81.255 11.0 . 29.9 . . 50.2 . 74.4 80.760 11.0 . 29.3 . . 49.7 . 74.5 80.365 10.9 . 28.5 . . 49.5 . 74.7 79.970 10.8 . 27.8 . . 49.7 . 75.1 79.575 10.6 . 26.9 . . 50.3 . 75.6 79.28
39、0 10.5 . 26.1 . . 51.4 . 76.3 78.9E2551 18310.2 Positioning of the Temperature SensorIf the system employs a temperature sensor that is movable, it shall be located asclose to the specimen as possible without touching it or the balance pan. In addition, it must be located in exactly the same positio
40、nduring calibrations as used during analytical determinations.11. Calibration and Standardization11.1 Calibrate the temperature display of the apparatus according to Test Method E1582 using a heating rate of 0.5 C/min 60.2C/min.0.2 C/min.12. Procedure12.1 Close the system, adjust the atmospheric flo
41、w rate of the purge gas to the selected rate, and zero (tare) the balance.12.2 Open the system and place 5 mg to 10 mg of the reference material in the specimen container in the same position as wouldbe placed for a test specimen. Close the system.12.3 Measure the weight of the reference material an
42、d report its value.E2551 18412.4 Test Method A:12.4.1 Equilibrate the humidity for 60 min at a value that is 5 % RH below the anticipated deliquescence point described inTable 1.NOTE 1Other humidity starting points may be used but shall be reported.12.4.2 Initiate either a humidity program with eith
43、er 0.2 % RH steps and 12 min soak times or 1 % RH/hr linear increase to anending humidity value that is 5 % RH higher than the anticipated deliquescence point in Table 1.NOTE 2Other humidity ending points and rate of humidity change may be used but shall be reported.12.4.3 Plot the results as weight
44、 of the reference material on the ordinate (Y-axis) and the relative humidity on the abscissa(X-axis) of a thermal curve.12.4.4 Determine the first-deviation-from-baseline as the deliquescence point of the reference material (see Fig. 1). Report thecorresponding humidity as Mi.NOTE 3The rate of weig
45、ht gain will increase with relative humidity above the humidity at which the initial weight gain is observed. There is noinflection point. The use of extrapolate onset values shall not be used.12.5 Test Method B:12.5.1 Equilibrate the humidity for 60 min at 5 % RH above the anticipated deliquescence
46、 point described in Table 1.NOTE 4Other humidity starting points and equilibrium times may be used but shall be reported.12.5.2 Initiate decreasing humidity program with either 0.2 % RH steps and 12 min soak times or a linearly decreasing at 1 %RH/hr to an ending value that is 5 % RH lower than the
47、anticipated deliquescence point in Table 1.NOTE 5Other humidity ending points and rates of change may be used but shall be reported.12.5.3 Create a plot of the weight of the reference material on the ordinate (Y-axis) versus the relative humidity on the abscissa(X-axis).12.5.4 Determine the relative
48、 humidity at the peak of the deliquescence curve (see Fig. 2). Report this value as Mp.12.6 Test Method C:12.6.1 Equilibrate the humidity for 60 min at 5 % RH above the anticipated deliquescence point described in Table 1.NOTE 6Other humidity starting points and equilibrium times may be used but sha
49、ll be reported.12.6.2 Initiate a decreasing humidity program with either a 0.2 % RH steps and 12 min soak times or a linearly decreasingprogram at 1 % RH/hr to an ending value that is 5 % RH lower than the anticipated deliquescence point in Table 1.FIG. 1 First-Deviation-From-Baseline as the Deliquescence Point of the reference materialReference MaterialE2551 185NOTE 7Other humidity ending points and rates of change may be used but shall be reported.12.6.3 Create a plot of the rate of weight change as a function of a ch
