1、Designation: D4591 17Standard 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 oforiginal adoption or,
2、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 U.S. Department of Defense.1. Scop
3、e*1.1 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 test method is
4、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-10 are to b
5、e 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, health, and environmental practices and deter-mine the applicability of regulato
6、ry limitations 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 referencethis test method for testing conditions.1.4 This international standard was developed in accor-dance with internationally recognized pr
7、inciples on standard-ization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2D1600 Terminology forAbbrevia
8、ted Terms Relating to Plas-ticsD3418 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 Polytetr
9、afluoroethylene (PTFE)Resin Produced From DispersionE473 Terminology Relating to Thermal Analysis and Rhe-ologyE793 Test Method for Enthalpies of Fusion and Crystalliza-tion by Differential Scanning CalorimetryIEEE/ASTM SI-10 Standard for Use of the InternationalSystem of Units (SI) (the Modern Metr
10、ic System)2.2 ISO Standards: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. Termino
11、logy3.1 Definitions:3.1.1 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 tempe
12、rature.3.1.2 Refer to Terminology 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-pr
13、opene) copolymer.1This 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 Dec. 1, 2017. Published January 2018. Originallyapproved in 1987. Last previous edition approved i
14、n 2012 as D4591 - 07(2012).DOI: 10.1520/D4591-17.2For 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 f
15、rom American National Standards Institute (ANSI), 25 W. 43rd St.,4th Floor, New York, NY 10036, http:/www.ansi.org.*A Summary of Changes section appears at the end of this standardCopyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United StatesThis in
16、ternational standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT)
17、Committee.13.2.5 ETFEethylene-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-hexafluoropr
18、openecopolymer.3.2.11 VDF/TFEvinylidene fluoride-tetrafluoroethylenecopolymer.3.2.12 VDF/TFE/HFPvinylidene fluoride-tetrafluoroethylene-hexafluoropropene copolymer.3.2.13 VDF/CTFEvinylidene fluoride-chlorotrifluoroethylene copolymer.3.2.14 PVFpoly(vinyl fluoride).3.2.15 MFAperfluoromethylvinylether-
19、tetrafluoroethyl-ene copolymer.3.2.16 SSGstandard specific gravity.4. Significance and Use4.1 DSC analysis may be 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, indiv
20、idually or inmixtures;4.1.2 To compare the relative levels of crystalline content oftwo or more specimens of a sample 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
21、completely crystalline polymers areavailable.4.1.3 The heat of crystallization of pure PTFE homopoly-mer is depending on the relative molecular weight of thespecimen. Some PTFE resins are modified with small amountsof comonomers. These modifications have profound effects oncrystallization behavior a
22、nd shall be considered when evaluat-ing the results.4.1.4 To characterize PTFE (DSC thermal curves deter-mined on powders or products of PTFE that have never beenmelted convey appreciable information about details of mor-phology and molecular structure);44.1.5 To supplement the test for standard spe
23、cific gravity(SSG) described in Specifications D4894 and D4895 by usingthe heat of crystallization of pure PTFE homopolymer, depend-ing on the relative molecular weight of the specimen. Thescopes of these specifications, however, include PTFE resinsmodified with small amounts of comonomers, and many
24、commercial PTFE resins are modified in this manner. Thesemodifications can have profound effects on crystallizationbehavior. Published relationships4between heat of crystalliza-tion and molecular weight refer to pure PTFE homopolymersand, therefore, cannot be applied to the modified resins.5. Appara
25、tus5.1 Differential Scanning Calorimeter, capable of heatingand cooling rates of at least 10.0 C/min and of recordingautomatically 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 s
26、ame heating rate shall be used for all calibrations and testruns. Thermal curves are recorded using a computerized datacollection 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-du
27、re. The instrument should have a sensitivity for heat flowsufficient to provide a precision of 61 % when run using asuitable 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 2.0mi
28、n/cm of chart.NOTE 3Most DSC systems report data with a temperature ordinate.The temperature values are directly related 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 are
29、a measurement shall be done with aprecision of 61 % or better.5.2 Specimen Holders and Covers, made from aluminum orother 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 forwh
30、ich 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 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,
31、 Test Method D3418shall be used whenever possible. There are instances, however,when following Test Method D3418 will not 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 spe
32、nt for results havingsuitable precision. Examples of these instances include thefollowing:6.1.1 The requirement that scans be started at roomtemperature, a provision usually not required with all fluoropo-lymers;6.1.2 At times the thermal curve that results from theanalysis provides information that
33、 cannot be interpreted in auseful manner by Test Method D3418, but can be interpretedfollowing the procedures of Section 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
34、by using an appropriate amount of at least two selectedstandards weighed to the nearest 0.01 mg. Select the standardmaterials so that their range includes the first-order transitiontemperature(s) of the fluoropolymer being tested. It has been4Sperati, C. A., “Polytetrafluoroethylene: History of Its
35、Development and SomeRecent Advances” (67 references), High Performance Polymers: Their Origin andDevelopment, Seymour and Kirshenbaume (eds), Marcel Deckker, NewYork, 1986,p. 274.D4591 172found that only one standard is needed to validate the instru-ment between calibrations.6.3 A standard specimen
36、mass shall be in the range of 9 to10 mg weighed to an accuracy 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 5The
37、rmal curves from such analyses not using the standardspecimen mass range may not compare with curves obtained using thestandard mass range. Due to the sensitivity of the peak, Tm,tothespecimen size, the results may be outside the expected precision and bias.6.4 Place the test specimen in the DSC sam
38、ple pan, coverwith pan cover, and crimp. Place the pan with specimen in theDSC sample holder or cell at the heating cycle startingtemperature.6.5 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
39、different from the stan-dard must be reported and thermal curves from such analysesmust not be used in comparison 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,
40、heat thespecimen at the highest rate possible with the instrument beingused to the temperature shown in Table 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 crystallizati
41、on are beingdetermined, stop the heating at the end temperature given inTable 1. Use a dwell time long enough to remove (ornormalize) any homogenous crystal nucleation effects of thepolymer before starting the cooling. For PVDF a dwell time often minutes at 210C is required. DSC analysis used todete
42、rmine the presence of other components in the specimensshould usually be started at room temperature.NOTE 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
43、D3418, the temperature of amelting peak on a DSC thermal curve shall be designated Tm1,Tm2, etc., numbered 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
44、 at which a tangent to thecurve intercepts an extension of the base line on the high-temperature side shall be designated Te.NOTE 8Fluoropolymers can have various crystal forms or undergoreorganization. Therefore, the resulting DSC curve can have two or morepeaks or peaks with pronounced shoulders.
45、The Tm1value of one samplewith one peak may be the same as the Tm2value of another sample withtwo peaks.7.1.1 Fig. 1 was selected 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 c
46、omparable manner, as shown both in Fig. 2and in Figure 1 of Test Method D3418.7.2 Determining Heats of TransitionCalculation of heatsof fusion or crystallization shall be done in accordance withTest Method D3418. Instrumental determination of heats oftransition requires temperature ranges to determi
47、ne 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 above 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 sma
48、ll changes(5C in the integration range).NOTE 9Multiple crystal forms and the complicated morphology ofTABLE 1 Recommended Temperature Limits for DSCMeasurements for Various FluoropolymersA, BFluoropolymerHeating CurveDwellTime,minCooling CurveRate,C/minTypicalValues,CCStart,CEnd,CStart,CEnd,C(homopo
49、lymers)PTFEPCTFE2701303802505 38025019527019513010100.2315360200225PVDF(copolymers)25 210 10 210 25 10 155180PFA 200 350 350 200 10 280330MFA 200 350 350 200 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 90170VDF/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 example, Tm1 Tm2Tm3. ).BThe integration range should be 10 to 20C
