1、Designation: E 1356 08Standard Test Method for Assignment of theGlass Transition Temperatures by Differential ScanningCalorimetry1This standard is issued under the fixed designation E 1356; the number immediately following the designation indicates the year oforiginal adoption or, in the case of rev
2、ision, 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 This test method covers the assignment of the glasstransition temperatures of materials using diffe
3、rential scanningcalorimetry or differential thermal analysis.1.2 This test method is applicable to amorphous materials orto partially crystalline materials containing amorphous regions,that are stable and do not undergo decomposition or sublima-tion in the glass transition region.1.3 The normal oper
4、ating temperature range is from 120 to500 C. The temperature range may be extended, dependingupon the instrumentation used.1.4 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.5 ISO standards 113572 is equivalent to this standa
5、rd.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 this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Reference
6、d Documents2.1 ASTM Standards:2E 177 Practice for Use of the Terms Precision and Bias inASTM Test MethodsE 473 Terminology Relating to Thermal Analysis and Rhe-ologyE 691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test MethodE 967 Test Method for Temperature Cali
7、bration of Differ-ential Scanning Calorimeters and Differential ThermalAnalyzersE 1142 Terminology Relating to Thermophysical Properties2.2 ISO Standard:113572 Differential Scanning Calorimetry (DSC)-Part 2Determination of Glass Transition Temperature33. Terminology3.1 Definitions:3.1.1 The followin
8、g terms are applicable to this test methodand can be found in Terminology E 473 and TerminologyE 1142: differential scanning calorimetry (DSC); differentialthermal analysis (DTA); glass transition; glass transitiontemperature (Tg); and specific heat capacity.3.2 Definitions of Terms Specific to This
9、 Standard:3.2.1 There are commonly used transition points associatedwith the glass transition region.(See Fig. 1.)3.2.1.1 extrapolated end temperature, (Te), Cthe point ofintersection of the tangent drawn at the point of greatest slopeon the transition curve with the extrapolated baseline followingt
10、he transition.3.2.1.2 extrapolated onset temperature, (Tf), Cthe pointof intersection of the tangent drawn at the point of greatestslope on the transition curve with the extrapolated baselineprior to the transition.3.2.1.3 inflection temperature, (Ti), Cthe point on thethermal curve corresponding to
11、 the peak of the first derivative(with respect to time) of the parent thermal curve. This pointcorresponds to the inflection point of the parent thermal curve.3.2.1.4 midpoint temperature, (Tm), Cthe point on thethermal curve corresponding to12 the heat flow differencebetween the extrapolated onset
12、and extrapolated end.3.2.1.5 DiscussionMidpoint temperature is most com-monly used as the glass transition temperature (see Fig. 1):3.2.2 Two additional transition points are sometimes iden-tified and are defined:3.2.2.1 temperature of first deviation, (To), Cthe point offirst detectable deviation f
13、rom the extrapolated baseline prior tothe transition.3.2.2.2 temperature of return to baseline, (Tr), Cthepoint of last deviation from the extrapolated baseline beyondthe transition.1This test method is under the jurisdiction ofASTM Committee E37 on ThermalMeasurements and is the direct responsibili
14、ty of Subcommittee E37.01 on ThermalTest Methods and Practices.Current edition approved Sept. 1, 2008. Published October 2008. Originallyapproved in 1991. Last previous edition approved in 2003 as E 1356 03.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer
15、 Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Available from American National Standards Institute (ANSI), 25 W. 43rd St.,4th Floor, New York, NY 10036, http:/www.ansi.org.1Copyright ASTM Internation
16、al, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.4. Summary of Test Method4.1 This test method involves continuously monitoring thedifference in heat flow into, or temperature between a referencematerial and a test material when they are heated or cooled ata co
17、ntrolled rate through the glass transition region of the testmaterial and analyzing the resultant thermal curve to providethe glass transition temperature.5. Significance and Use5.1 Differential scanning calorimetry provides a rapid testmethod for determining changes in specific heat capacity in aho
18、mogeneous material. The glass transition is manifested as astep change in specific heat capacity. For amorphous andsemicrystalline materials the determination of the glass transi-tion temperature may lead to important information about theirthermal history, processing conditions, stability, progress
19、 ofchemical reactions, and mechanical and electrical behavior.5.2 This test method is useful for research, quality control,and specification acceptance.6. Interferences6.1 Achange in heating rates and cooling rates can affect theresults. The presence of impurities will affect the transition,particul
20、arly if an impurity tends to plasticize or form solidsolutions, or is miscible in the post-transition phase. If particlesize has an effect upon the detected transition temperature, thespecimens to be compared should be of the same particle size.6.2 In some cases the specimen may react with air durin
21、gthe temperature program causing an incorrect transition to bemeasured. Whenever this effect may be present, the test shallbe run under either vacuum or an inert gas atmosphere. Sincesome materials degrade near the glass transition region, caremust be taken to distinguish between degradation and gla
22、sstransition.6.3 Since milligram quantities of sample are used, it isessential to ensure that specimens are homogeneous andrepresentative, so that appropriate sampling techniques areused.7. Apparatus7.1 Differential Scanning Calorimeter, The essential instru-mentation required to provide the minimum
23、 differential scan-ning calorimetric capability for this method includes a TestChamber composed of a furnace(s) to provide uniform con-trolled heating (cooling) of a specimen and reference to aconstant temperature or at a constant rate over the temperaturerange from 120 to 500 C, a temperature senso
24、r to provide anindication of the specimen temperature to 60.1 C, differentialsensors to detect heat flow difference between the specimenand reference with a sensitivity of 6 W, a means of sustaininga test chamber environment of a purge gas of 10 to 100mL/min within 4 mL/min, a Temperature Controller
25、, capableof executing a specific temperature program by operating thefurnace(s) between selected temperature limits at a rate oftemperature change of up to 20 C/min constant to 6 0.5 C/min.7.2 A Data Collection Device, To provide a means ofacquiring, storing, and displaying measured or calculatedsig
26、nals, or both. The minimum output signals required for DSCare heat flow, temperature and time.FIG. 1 Glass Transition Region Measured TemperaturesE 1356 0827.3 Containers, (pans, crucibles, vials, etc.) that are inert tothe specimen and reference materials and that are of suitablestructural shape an
27、d integrity to contain the specimen andreferences.7.4 For ease of interpretation, an inert reference materialwith an heat capacity approximately equivalent to that of thespecimen may be used. The inert reference material may oftenbe an empty specimen capsule or tube.7.5 Nitrogen, or other inert purg
28、e gas supply, of purity equalto or greater than 99.9 %.7.6 Analytical Balance, with a capacity greater than 100 mg,capable of weighing to the nearest 0.01 mg.8. Specimen Preparation8.1 Powders or GranulesAvoid grinding if a preliminarythermal cycle as outlined in 10.2 is not performed. Grinding orsi
29、milar techniques for size reduction often introduce thermaleffects because of friction or orientation, or both, and therebychange the thermal history of the specimen.8.2 Molded Parts or PelletsCut the samples with amicrotome, razor blade, paper punch, or cork borer (size No. 2or 3) to appropriate si
30、ze in thickness or diameter, and lengththat will approximate the desired mass in the subsequentprocedure.8.3 Films or SheetsFor films thicker than 40 m, see 8.2.For thinner films, cut slivers to fit in the specimen tubes orpunch disks, if circular specimen pans are used.8.4 Report any mechanical or
31、thermal pretreatment.9. Calibration9.1 Using the same heating rate, purge gas, and flow rate asthat to be used for analyzing the specimen, calibrate thetemperature axis of the instrument following the proceduregiven in Practice E 967.10. Procedure10.1 Use a specimen mass appropriate for the material
32、 to betested. In most casesa5to20mgmass is satisfactory. Anamount of reference material with a heat capacity closelymatched to that of the specimen may be used. An emptyspecimen pan may also be adequate.10.2 If appropriate, perform and record an initial thermalprogram in flowing nitrogen or air envi
33、ronment using a heatingrate of 10 C/min to a temperature at least 20 C above Tetoremove any previous thermal history. (See Fig. 1.)NOTE 1Other, preferably inert, gases may be used, and other heatingand cooling rates may be used, but must be reported.10.3 Hold temperature until an equilibrium as indi
34、cated bythe instrument response is achieved.10.4 Program cool at a rate of 20 C/min to 50 C below thetransition temperature of interest.10.5 Hold temperature until an equilibrium as indicated bythe instrument response is achieved.10.6 Repeat heating at same rate as in 10.2, and record theheating cur
35、ve until all desired transitions have been completed.Other heating rates may be used but must be reported.10.7 Determine temperatures Tm(preferred) Tf,orTi, (SeeFig. 1.)where:Tig= inflection temperature, CTf= extrapolated onset temperature, C, andTm= midpoint temperature, C.Increasing the heating ra
36、te produces greater baseline shiftsthereby improving detectability. In the case of DSC the signalis directly proportional to the heating rate in heat capacitymeasurements.NOTE 2The glass transition takes place over a temperature range andis known to be affected by time dependent phenomena, such as t
37、he rate ofheating (cooling). For these reasons, the establishment of a single numberfor the glass transition needs some explanation. Either Tfor Tmor Timaybe selected to represent the temperature range over which the glasstransition takes place. The particular temperature chosen must be agreedon by
38、all parties concerned. In selecting which value should be taken asTg, the reader may wish to consider the following:(a)Tmwas found to have higher precision than Tf(see 12.3).(b) The measurement of Tfis often easier for those who construct therespective tangents by hand.(c)Tm(preferred) or Tiis more
39、likely to agree with the measurement ofTgby other techniques since it is constructed closer to the middle of thetemperature range over which the glass transition occurs.(d)Tfmay be taken to more closely represent the onset of thetemperature range over which the glass transition occurs.Any comparison
40、of glass transition temperatures should contain a statement of how the testwas run and how the value was obtained.10.8 Recheck the specimen mass to ensure that no loss ordecomposition has occurred during the measurement.11. Report11.1 Report the following information:11.1.1 A complete identification
41、 and description of thematerial tested.11.1.2 Description of instrument used for the test.11.1.3 Statement of the dimensions, geometry, and materialof the specimen holder.11.1.4 The scan rate in C/min.11.1.5 Description of temperature calibration procedure.11.1.6 Identification of the specimen envir
42、onment by pres-sure, gas flow rate, purity and composition, including humidity,if applicable.11.1.7 Results of the transition measurements using tem-perature parameters (Tg, etc.) cited in Fig. 1, or any combina-tion of parameters that were chosen.11.1.8 Tg(half extrapolated heat capacity temperatur
43、e) ispreferred.11.1.9 Any side reactions (for example, crosslinking, ther-mal degradation, oxidation) shall also be reported and thereaction identified, if possible.12. Precision and Bias412.1 Interlaboratory Test ProgramAn interlaboratorystudy for the determination of glass transition temperature a
44、sindicated by both the midpoint and the extrapolated onset wasconducted in 1984. Three polymeric materials were tested;4Supporting data have been filed at ASTM International Headquarters and maybe obtained by requesting Research Report RR: E37-1012.E 1356 083polyurethane, polystyrene, and epoxy glas
45、s. Each of six par-ticipants tested four specimens of each material. (One did notreport test data on polyurethane.) Practice E 691 was followedfor the design and the analysis of the data.12.2 Test ResultThe precision information given below inCelsius degrees is for the comparison of two test results
46、, eachof which is a single determination.12.3 Precision:DSC Determination of Tg:TfData95 % Limit, CMaterial Tf, C Repeatability ReproducibilityPolyurethane 4.5 4.59 6.53Polystyrene 103.6 2.05 3.18Epoxy Glass 118.4 3.90 6.88DSC Determination of Tg:TmData95 % Limit, CMaterial Tm, C Repeatability Repro
47、ducibilityPolyurethane 12.2 2.24 4.15Polystyrene 106.3 1.85 2.02Epoxy Glass 123.0 2.77 5.17The above terms repeatability and reproducibility limit areused as specified in Practice E 177. The respective standarddeviations among test results may be obtained by dividing thenumbers in the third and four
48、th columns by 2.8.12.4 The bias for these measurements is undeterminedbecause there are no reference values available for the mate-rials used.13. Keywords13.1 differential scanning calorimetry (DSC); differentialthermal analysis (DTA); glass transition; specific heat capacityASTM International takes
49、 no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the riskof infringement of such rights, are entirely their own responsibility.This standard is subject to revision at any time by the responsible technical committee and must be reviewed every five years andif not revised, either reapproved or withdrawn. Your comments are invited either for revision of this
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