ASTM E3142-2018a Standard Test Method for Thermal Lag of Thermal Analysis Apparatus.pdf

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1、Designation: E3142 18E3142 18aStandard Test Method forThermal Lag of Thermal Analysis Apparatus1This standard is issued under the fixed designation E3142; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A

2、 number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.INTRODUCTIONIn thermal analysis, the temperature of a test specimen is changed while a physical property ismeasured. The measured physical propert

3、y is the dependent variable and temperature (also measured)is the independent variable. In the majority of thermal analysis apparatus, temperature sensors cannotbe attached directly to the specimen but can only touch the surface or be placed adjacent or close tothe specimen such that the indicated t

4、emperature will be different to that of the specimen itself. Inconsequence the specimen temperature will lag the indicated temperature upon heating and coolingdue to thermal resistance between sensor and specimen. The larger the test specimen, the greater thethermal lag is likely to be. To obtain th

5、e correct specimen temperature, thermal analysis apparatus istemperature calibrated so that the recorded temperature correctly indicates the specimen temperature.Such temperature calibration compensates for the temperature offset () between the specimentemperature and that of the temperature sensor.

6、 This temperature offset changes linearly withtemperature rate-of-change () (heating or cooling). The slope of this linear relationship is known as“thermal lag” (T/). The Knowing the thermal lag for an apparatus permits temperature calibrationdetermined at one temperature rate-of-change to be adjust

7、ed to that at other rates. It is the purpose ofthis standard to aid the user to determine the thermal lag for an apparatus and to apply that thermallag to measurements made at temperature rates-of-change different from that at which the temperaturecalibration is performed.1. Scope1.1 This test metho

8、d addresses the dependence of temperature calibration on the temperature rate-of-change. This test methoddescribes the determination of the thermal lag of thermal analysis apparatus and its application to the modification of thetemperature calibration for that apparatus obtained at alternative linea

9、r temperature rates-of-change.1.2 This test method is applicable, but not limited to, the temperature calibration of differential thermal analyzers (DTAs),differential scanning calorimeters (DSCs), thermogravimetric analyzers (TGAs), thermomechanical analyzers (TMAs), anddynamic mechanical analyzers

10、 (DMAs).1.3 This test method is applicable only to apparatus demonstrating a linear relationship between indicated temperature andtemperature rate-of-change.1.4 The values stated in SI units are to be regarded as the standard. No other units of measurement are included in this standard.1.5 This stan

11、dard 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 appropriate safety, health, and environmental practices and determine the applicability ofregulatory limitations prior to use.1.6 This inter

12、national standard was developed in accordance with internationally recognized principles on standardizationestablished in the Decision on Principles for the Development of International Standards, Guides and Recommendations issuedby the World Trade Organization Technical Barriers to Trade (TBT) Comm

13、ittee.1 This test method is under the jurisdiction ofASTM Committee E37 on Thermal Measurements and is the direct responsibility of Subcommittee E37.10 on Fundamental,Statistical and Mechanical Properties.Current edition approved Jan. 15, 2018Aug. 1, 2018. Published February 2018August 2018. Origina

14、lly approved in 2018. Last previous edition approved in 2018 as E3142 18. DOI: 10.1520/E3142-18.10.1520/E3142-18A.This document is not an ASTM standard and is 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

15、 be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current versionof the standard as published by ASTM is to be considered the official document.Copyright ASTM International, 100 Barr Harbor Dr

16、ive, PO Box C700, West Conshohocken, PA 19428-2959. United States12. Referenced Documents2.1 ASTM Standards:2E473 Terminology Relating to Thermal Analysis and RheologyE698 Test Method for Kinetic Parameters for Thermally Unstable Materials Using Differential Scanning Calorimetry and theFlynn/Wall/Oz

17、awa MethodE967 Test Method for Temperature Calibration of Differential Scanning Calorimeters and Differential Thermal AnalyzersE1142 Terminology Relating to Thermophysical PropertiesE1363 Test Method for Temperature Calibration of Thermomechanical AnalyzersE1582 Test Method for Temperature Calibrati

18、on of Thermogravimetric AnalyzersE1867 Test Methods for Temperature Calibration of Dynamic Mechanical AnalyzersE1970 Practice for Statistical Treatment of Thermoanalytical DataE2069 Test Method for Temperature Calibration on Cooling of Differential Scanning Calorimeters3. Terminology3.1 Definitions:

19、3.1.1 Terms applicable to this test method and can be found in Terminologies E473 and E1142 and include the termscalorimeter, differential, differential scanning calorimeter, differential thermal analysis, dynamic mechanical analysis, temperature,thermal analysis, thermogravimetric analysis, and the

20、rmomechanical analysis.3.2 Definitions of Terms Specific to This Standard:3.2.1 temperature offset, nthe difference between the actual specimen temperature and that reported by a temperature sensor.3.2.2 thermal lag, nthe change in indicated temperature offset with temperature rate-of-change.4. Summ

21、ary of Test Method4.1 Following apparatus temperature calibration with a reference material at an identified temperature rate-of-change, thetemperature offset of the apparatus is measured with that sample reference material as a function of additional temperaturerates-of-change. A display of tempera

22、ture (T) versus temperature rate-of-change () produces a linear relationship from which theslope (T/) may be obtained. This slope value is known as thermal lag.NOTE 1This test method is applicable only to apparatus demonstrating a linear relationship between indicated temperature and temperaturerate

23、-of-change.4.1.1 The thermal lag may be used to modify the temperature calibration of an apparatus at temperature rates-of-change otherthan at which it is calibrated.4.1.2 The thermal lag of an apparatus may change with experimental conditions such as temperature, purge gas pressure, purgegas therma

24、l conductivity, or other experimental conditions.conditions or instrument properties. Thermal lag shall be determinedunder the same experimental conditions as that of the test specimen.4.1.3 Thermal lag calculations are rarely shall not be used for temperature rate-of-change values greater than 10 K

25、/min.4.1.4 Thermal lag is known to vary with temperature. If a multipoint temperature calibration is used, then thermal lag shall bedetermined at each calibration temperature.5. Significance and Use5.1 Differing temperature rates-of-change may be required for different measurements (for example, Tes

26、t Method E698).Temperature calibration changes as a function of temperature rate-of-change. The use of the known thermal lag of an apparatusmay be used to adjust the temperature calibration of the apparatus obtained at one temperature rate-of-change with that at anotherrequired for a given applicati

27、ons. This adjustment procedure for temperature calibration is described in 8.1.5.2 This test method may be used in research, quality assurance, and specification acceptance.6. Interferences6.1 Thermal lag varies with experimental conditions such as calibration temperature, purge gas pressure, purge

28、gas thermalconductivity, etc.6.1 Thermal lag on heating may differ from that on cooling.6.2 Where thermal lag is examined upon cooling, the reference material shall be selected to show no supercooling. Liquidcrystal materials and adamantane are examples of materials without supercooling (see Test Me

29、thod E2069).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.E3142 18a27. Procedure7.1 Select the appropriate

30、ASTM standard for temperature calibration of the apparatus (Test Method E967 for differentialscanning calorimeters or differential thermal analyzers, Test Method E1582 for thermogravimetric analyzers, Test Method E1363for thermomechanical analyzers, or Test Methods E1867 for dynamic mechanical analy

31、zers).7.2 Perform the procedure described in the calibration standard and record the determined temperature as T1 and the observedtemperature rate-of-change as 1.NOTE 1The temperature rate-of-change shall be measured. Use of the programmed temperature rate-of-change is not satisfactory.7.3 Perform t

32、he procedure described in the calibration standard at two additional heating rates other than 1 representing thelow, medium, and high heating rate capability of the apparatus. Record these additional data pair values as T2 and 2, and T3 and3.NOTE 2The reliability of the results of this determination

33、 are increased with increased temperature rate-of-change.increases as temperaturerate-of-change increases.7.4 Prepare a display of the values for 7.2 and 7.3, with T-values on the Y-axis and the corresponding -values on the X-axis.NOTE 3The display shall approximate a straight line. If not, then thi

34、s test method is not applicable.7.5 Using linear regression (see Practice E1970), determine and report the slope (T/) and its standard deviation (T/)of the best-fit straight line for these three points.NOTE 4The appropriate SI units for this value is seconds. However, it is easier to leave this valu

35、e in the units of minutes for the purpose of itsapplication. Alternatively, one may use the conversion factor of 1 min = 60 s in the calculations.NOTE 5The thermal lag is known to vary with temperature. If a multipoint temperature calibration is used, then thermal lag shall be determined ateach cali

36、bration temperature.NOTE 6For the purpose of this test method, a goodness-of-fit R2 value greater than 0.95 is considered acceptable.8. Calculation and Interpretation of Results8.1 The value of the thermal lag (T/) determined in 7.5 may be used to determine the off-set value applied to the transitio

37、ntemperature obtained at temperature rates-of-change other than that specified in the corresponding temperature calibration standardusing Eq 1 and Eq 2. 5T ! 3s 2 o! (1)Tt5To1 (2)where:s = the temperature rate-of-change at which the apparatus was temperature calibrated, K/min,o = the temperature rat

38、e-of-change for the observed measurement, K/min, = temperature offset due to thermal lag, KT/ = thermal lag, min, obtained from linear regression,T/ = thermal lag, min, obtained from linear regression,To = observed transition temperature, K, andTt = true transition temperature, K.NOTE 7The values fo

39、r have direction. Heating rates are positive and cooling rates are negative. This convention gives direction to as well.9. Report9.1 Report thermal lag (T/) and its imprecision(glyph507T/glyph507) or relative imprecision (T/(T/).10. Precision and Bias10.1 This standard is used to determine the bias

40、introduced by the thermal lag effect of a thermal analysis measurement and tocorrect for that effect. The precision of temperature offset may be estimated by the principal of propagation of uncertainties by therelative standard deviation of the thermal lag. (3) 5 T 3 !2 1T 3 !2#12 (4)Tt5 To!2 1 !2#1

41、2 (5)where:To = the observed transition temperature, K,To = standard deviation of the absolute temperature measurement, K (obtained from the precision state of the respectivecalibration standard in 7.1),E3142 18a3To = standard deviation of the absolute temperature measurement, K (obtained from the p

42、recision state of the respectivecalibration standard in 7.1),T/ = thermal lag, min,T/ = thermal lag, min,T/ = the thermal lag standard deviation, min, obtained from linear regression, = s o,T/ = the thermal lag standard deviation, min, obtained from linear regression, = s o, = standard deviation of

43、glyph507, and = standard deviation of the temperature rate-of-change measurement.10.1.1 The value of is often much smaller than T and so the imprecision in the corrected temperature Tt is equivalent tothe imprecision of the uncorrected temperature To.10.2 An interlaboratory study is planned from 201

44、82023 to establish within laboratory repeatability, between laboratoryreproducibility, and bias. Anyone wishing to participate in this interlaboratory study should contact the Committee E37 StaffManager at ASTM International Headquarters.E3142 18a410.3 Precision:10.3.1 A limited repeatability study

45、was performed in using four calibration materials in a single laboratory. The results of thatstudy are presented in Table 1 and have been filed at ASTM Headquarters.310.3.2 Within laboratory variability may be described using he repeatability value (r) obtained by multiplying the standarddeviation b

46、y 2.8. The repeatability value estimates the 95 % confidence limit. That is, two results obtained in the same laboratory(using the same apparatus, on the same specimen by the same operator, closely spaced in time) have a 95 % probability of beingwithin the repeatability value of each other.10.3.3 Be

47、tween laboratory variability may be described using the reproducibility value (R) obtained by multiplying thereproducibility standard deviation by 2.8. The reproducibility value estimates the 95 % confidence limit. That is, two resultsobtained in different laboratories, or using different apparatus,

48、 or by different operators, or at different times, have a 95 %probability of being within the repeatability value of each other.10.3.4 The reproducibility of this test method has not yet been determined (see 10.2).10.4 Bias:10.4.1 Bias is the difference between a mean determined value and an accepta

49、ble reference value.10.4.2 The bias of this test method has not been determined (see 10.2).11. Keywords11.1 calibration; differential scanning calorimetry; differential thermal analysis; dynamic mechanical analysis; temperaturecalibration; thermal lag; thermogravimetric analysis; thermomechanical analysisASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedi