1、Designation: D4591 07 (Reapproved 2012)Standard Test Method forDetermining Temperatures and Heats of Transitions ofFluoropolymers by Differential Scanning Calorimetry1This standard is issued under the fixed designation D4591; the number immediately following the designation indicates the year oforig
2、inal 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.This standard has been approved for use by agencies of the Department of De
3、fense.1. Scope1.1 This test method defines conditions for the use ofdifferential scanning calorimetry (DSC) with fluoropolymers.It covers the use of DSC analyses with the fluoropolymers,PTFE, PVDF, PCTFE, and PVF and their copolymers PFA,MFA, FEP, ECTFE, EFEP, VDF/HFP, VDF/TFE/HFP, VDF/CTFE. The tes
4、t method is applicable to the analysis of powdersas well as samples taken from semi-finished or finishedproducts. The nature of fluoropolymers is such that specialprocedures are needed for running DSC analysis and interpret-ing the results.1.2 The values stated in SI units as detailed in IEEE/ASTMSI
5、-10 are to be regarded as the standard.1.3 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 l
6、imitations prior to use.NOTE 1There is currently no ISO standard that duplicates this testmethod. ISO 12086-1 and ISO 12086-2 cover similar testing and refer-ence this test method for testing conditions.2. Referenced Documents2.1 ASTM Standards:2D1600 Terminology for Abbreviated Terms Relating toPla
7、sticsD3418 Test Method for Transition Temperatures and En-thalpies of Fusion and Crystallization of Polymers byDifferential Scanning CalorimetryD4894 Specification for Polytetrafluoroethylene (PTFE)Granular Molding and Ram Extrusion MaterialsD4895 Specification for Polytetrafluoroethylene (PTFE)Resi
8、n Produced From DispersionE473 Terminology Relating to Thermal Analysis and Rhe-ologyE793 Test Method for Enthalpies of Fusion and Crystalli-zation by Differential Scanning CalorimetryIEEE/ASTM SI-10 Standard for Use of the InternationalSystem of Units (SI) (the Modern Metric System)2.2 ISO Standard
9、s:3ISO 12086-1 PlasticsFluoropolymer Dispersion andMolding and Extrusion MaterialsPart 1: Designationand SpecificationISO 12086-2 PlasticsFluoropolymer Dispersion andMolding and Extrusion MaterialsPart 2: Preparation ofTest Specimen and Determination of Properties3. Terminology3.1 Definitions:3.1.1
10、differential scanning calorimetry (DSC)a techniquein which the difference in energy inputs into a substance and areference material is measured as a function of temperature,while the substance and reference material are subjected to acontrolled increase or decrease in temperature.3.1.2 Refer to Term
11、inology E473 for general terminologyused in this test method.3.2 Abbreviated Terms:3.2.1 Abbreviations used in this test method are in accor-dance with Terminology D1600.3.2.2 PTFEpolytetrafluoroethylene.3.2.3 PFAperfluoro(alkoxy alkane) resin.3.2.4 FEPperfluoro(ethylene-propene) copolymer.3.2.5 ETF
12、Eethylene-tetrafluoroethylene copolymer.3.2.6 PVDFpoly(vinylidene fluoride).3.2.7 PCTFEpolymonochlorotrifluoroethylene.3.2.8 ECTFEethylene-monochlorotrifluoroethylene co-polymer.3.2.9 EFEPethylene-perfluoroethylene-propene copoly-mer.3.2.10 VDF/HFPvinylidene fluoride-hexafluoropropenecopolymer.1This
13、 test method is under the jurisdiction ofASTM Committee D20 on Plasticsand is the direct responsibility of Subcommittee D20.15 on Thermoplastic Materi-als.Current edition approved April 1, 2012. Published June 2012. Originallyapproved in 1987. Last previous edition approved in 2007 as D4591 - 07. DO
14、I:10.1520/D4591-07R12.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer 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 Stand
15、ards Institute (ANSI), 25 W. 43rd St.,4th Floor, New York, NY 10036, http:/www.ansi.org.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.3.2.11 VDF/TFEvinylidene fluoride-tetrafluoroethylenecopolymer.3.2.12 VDF/TFE/HFPvinylidene fluor
16、ide-tetrafluoroethylene-hexafluoropropene copolymer.3.2.13 VDF/CTFEvinylidene fluoride-chlorotrifluoroethylene copolymer.3.2.14 PVFpoly(vinyl fluoride).3.2.15 MFAperfluoromethylvinylether-tetrafluoroethyl-ene copolymer.3.2.16 SSGstandard specific gravity.4. Significance and Use4.1 DSC analysis may b
17、e used with fluoropolymers toachieve at least four different objectives as follows:4.1.1 To measure transition temperatures to aid in theidentification of the various fluoropolymers, individually or inmixtures;4.1.2 To compare the relative levels of crystalline content oftwo or more specimens of a s
18、ample of a fluoropolymer relativeto another sample by measuring the heat of fusion;NOTE 2Absolute values of crystalline content cannot be determineduntil values for heats of fusion of the completely crystalline polymers areavailable.4.1.3 To characterize PTFE (DSC thermal curves deter-mined on powde
19、rs or products of PTFE that have never beenmelted convey appreciable information about details of mor-phology and molecular structure);44.1.4 To supplement the test for standard specific gravity(SSG) described in Specifications D4894 and D4895 by usingthe heat of crystallization of pure PTFE homopol
20、ymer, depend-ing on the relative molecular weight of the specimen. Thescopes of these specifications, however, include PTFE resinsmodified with small amounts of comonomers, and manycommercial PTFE resins are modified in this manner. Thesemodifications can have profound effects on crystallizationbeha
21、vior. Published relationships4between heat of crystalliza-tion and molecular weight refer to pure PTFE homopolymersand, therefore, cannot be applied to the modified resins.5. Apparatus5.1 Differential Scanning Calorimeter, capable of heatingand cooling rates of at least 10.0 C/min and of recordingau
22、tomatically the differential heat flow between a specimenand a reference material as a function of time, both to therequired sensitivity and precision. For comparison purposes,the same heating rate shall be used for all calibrations and testruns. Thermal curves are recorded using a computerized data
23、collection system or on a time-based recorder. The resultingcurves are used for the measurement of peak areas either bycomputer integration or an alternative area measuring proce-dure. The instrument should have a sensitivity for heat flowsufficient to provide a precision of 61 % when run using asui
24、table standard for calibration, such as indium. The instru-ment must have a precision of 61 % for either the computer-ized data collections or over a time-base range of 0.1 to 2.0min/cm of chart.NOTE 3Most DSC systems report data with a temperature ordinate.The temperature values are directly relate
25、d to time based on the heating orcooling rate. Integrated areas measured from the DSC curves will bedirectly proportional to the differential caloric input.NOTE 4Noncomputerized area measurement shall be done with aprecision of 61 % or better.5.2 Specimen Holders and Covers, made from aluminum oroth
26、er materials of high thermal conductivity that do not reactwith the specimen. It is preferable to use holders designed forthe particular DSC instrument being used. For holders forwhich the cover has the shape of a small cup, the top should beinserted with the open side of the cup up.5.3 Nitrogen, or
27、 other inert gas supply for purging purposes.5.4 Balance, with capacity greater than 15 mg, capable ofweighing to the nearest 0.01 mg.6. Procedure6.1 General RequirementsIn general, Test Method D3418shall be used whenever possible. There are instances, however,when following Test Method D3418 will n
28、ot give the desiredresults, will not provide information needed for proper inter-pretation of the resultant thermal curve, or will require moretime for the analysis than need be spent for results havingsuitable precision. Examples of these instances include thefollowing:6.1.1 The requirement that sc
29、ans be started at room tem-perature, a provision usually not required with all fluoropoly-mers;6.1.2 At times the thermal curve that results from theanalysis provides information that cannot be interpreted in auseful manner by Test Method D3418, but can be interpretedfollowing the procedures of Sect
30、ion 7.6.2 CalibrationThe procedures for calibration provided inTest Method E793 shall be used.The comments inTest MethodD3418 are helpful when reviewed. The calibration is carriedout by using an appropriate amount of at least two selectedstandards weighed to the nearest 0.01 mg. Select the standardm
31、aterials so that their range includes the first-order transitiontemperature(s) of the fluoropolymer being tested. It has beenfound that only one standard is needed to validate the instru-ment between calibrations.6.3 A standard specimen mass shall be in the range of 9 to10 mg weighed to an accuracy
32、of 0.01 mg. For routine analysis,a nonstandard specimen size may be used in cases whereequivalence to the standard mass has been established forparticular properties. A specimen mass different from thestandard shall be reported.NOTE 5Thermal curves from such analyses not using the standardspecimen m
33、ass range may not compare with curves obtained using thestandard mass range. Due to the sensitivity of the peak, Tm, to thespecimen size, the results may be outside the expected precision and bias.6.4 Place the test specimen in the DSC sample pan, coverwith pan cover, and crimp. Place the pan with s
34、pecimen in theDSC sample holder or cell at the heating cycle startingtemperature.4Sperati, C. A., “Polytetrafluoroethylene: History of Its Development and SomeRecent Advances” (67 references), High Performance Polymers: Their Origin andDevelopment, Seymour and Kirshenbaume (eds), Marcel Deckker, New
35、York, 1986,p. 274.D4591 07 (2012)26.5 Heating and cooling rates of 10C/min shall be standard(except as noted in Table 1). Other heating rates may be usefulfor some routine analyses. Any rates different from the stan-dard must be reported and thermal curves from such analysesmust not be used in compa
36、rison with curves obtained using thestandard rate.NOTE 6Other heating rates will change the observed melting andcooling temperature values.6.6 Before starting the scan at the controlled rate, heat thespecimen at the highest rate possible with the instrument beingused to the temperature shown in Tabl
37、e 1 for the fluoropolymerbeing tested. The time required to reach thermal equilibrium atthe starting temperature will depend on the particular instru-ment being used. If heats of crystallization are being deter-mined, stop the heating at the end temperature given in Table1. Use a dwell time long eno
38、ugh to remove (or normalize) anyhomogenous crystal nucleation effects of the polymer beforestarting the cooling. For PVDF a dwell time of ten minutes at210C is required. DSC analysis used to determine the pres-ence of other components in the specimens should usually bestarted at room temperature.NOT
39、E 7Residual homogeneous crystal nuclei can affect the values ofTm, Tc, and heats of transition.7. Calculation7.1 Determining Transition TemperaturesAs illustrated inboth Fig. 1 and in Test Method D3418, the temperature of amelting peak on a DSC thermal curve shall be designated Tm1,Tm2, etc., number
40、ed in order of increasing temperature. Thetemperature at which a tangent to the curve intercepts anextension of the base line on the low-temperature side shall bedesignated Tf, and the temperature at which a tangent to thecurve intercepts an extension of the base line on the high-temperature side sh
41、all be designated Te.NOTE 8Fluoropolymers can have various crystal forms. Therefore,the resulting DSC curve can have two or more peaks or peaks withpronounced shoulders. The Tm1value of one sample with one peak maybe the same as the Tm2value of another sample with two peaks.7.1.1 Fig. 1 was selected
42、 to show two endothermic peaksduring a melting cycle, and the peaks are identified on thefigure. Determination of the temperatures for crystallization iscarried out in a comparable manner, as shown both in Fig. 2and in Figure 1 of Test Method D3418.7.2 Determining Heats of TransitionCalculation of h
43、eatsof fusion or crystallization shall be done in accordance withTest Method D3418. Instrumental determination of heats oftransition requires temperature ranges to determine heat con-tent. Due to instrument start-up effects that can last up to 1 or2 min, the integration range should be 10 to 20C abo
44、ve thestarting and below the final temperature. A smaller integrationrange would be Tf 20 or 30C and Te+ 10 or 20C. Thecalculated heat value should not be sensitive to small changes(5C in the integration range).TABLE 1 Recommended Temperature Limits for DSCMeasurements and for Integrating DSC Therma
45、l Curves withVarious FluoropolymersA, BFluoropolymerHeating CurveDwellTime,minCooling CurveRate,C/minTypicalValues,CCStart,CEnd,CStart,CEnd,C(homopolymers)PTFEPCTFE270130380250 538025019527019513010100.2315360200225PVDF(copolymers)25 210 10 210 25 10 160175PFA 200 350 350 200 10 280330MFA 200 350 35
46、0 200 10 260290FEP 200 320 320 200 10 240290ETFE 140 320 320 140 10 210270ECTFE 200 300 300 200 10 230250VDF/HFP 25 210 10 210 25 10 130165VDF/CTFE 25 210 10 210 25 10 130165VDF/TFE 25 200 10 200 25 10 100150VDF/TFE/HFP 25 150 10 150 25 10 130AReport peaks (and shoulders) from lowest to highest (for
47、 example, Tm1 Tm2 Tm3. ).BThe integration range should be 10 to 20C above the starting and below thefinal temperature. A smaller integration range would be Tf 20 or 30C and Te+ 10 or 20C. The calculated heat value should not be sensitive to small changes(5C in the integration range).CTypical values
48、cited represent an expected range of peak values for this test.These values shall not be used for specifications. Copolymer peak values (andintensities) will vary with comonomer ratios and may not be within the cited ranges.FIG. 1 Heating CurveFIG. 2 Cooling CurveD4591 07 (2012)3NOTE 9Multiple cryst
49、al forms and the complicated morphology ofVDF based copolymers can make it difficult to determine heats oftransition on this polymer.7.3 Calculation of Results of Determinations made in ac-cordance with the objectives of 4.1 may include transitionpeaks or shoulders and transition heats. Additional determina-tions may use the steps listed in 7.3.1 and 7.3.2.7.3.1 The ratio of peak heights may be useful in character-izing materials that show two or more distinct peaks orshoulders. This ratio is determined by dividing the
