ASTM D4591-22

Standard Test Method for Determining Temperatures and Heats of Transitions of Fluoropolymers by Differential Scanning Calorimetry

SIGNIFICANCE AND USE
4.1 DSC analysis may be used with fluoropolymers to achieve at least four different objectives as follows:  
4.1.1 To measure transition temperatures to aid in the identification of the various fluoropolymers, individually or in mixtures;  
4.1.2 To compare the relative levels of crystalline content of two or more specimens of a sample of a fluoropolymer relative to another sample by measuring the heat of fusion;
Note 2: Absolute values of crystalline content cannot be determined until values for heats of fusion of the completely crystalline polymers are available.  
4.1.3 The heat of crystallization of pure PTFE homopolymer is depending on the relative molecular weight of the specimen. Some PTFE resins are modified with small amounts of comonomers. These modifications have profound effects on crystallization behavior and shall be considered when evaluating the results.  
4.1.4 To characterize PTFE (DSC thermal curves determined on powders or products of PTFE that have never been melted convey appreciable information about details of morphology and molecular structure);4  
4.1.5 To supplement the test for standard specific gravity (SSG) described in Specifications D4894 and D4895 by using the heat of crystallization of pure PTFE homopolymer, depending on the relative molecular weight of the specimen. The scopes of these specifications, however, include PTFE resins modified with small amounts of comonomers, and many commercial PTFE resins are modified in this manner. These modifications can have profound effects on crystallization behavior. Published relationships4 between heat of crystallization and molecular weight refer to pure PTFE homopolymers and, therefore, cannot be applied to the modified resins.
SCOPE
1.1 This test method defines conditions for the use of differential 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 applicable to the analysis of powders as well as samples taken from semi-finished or finished products. The nature of fluoropolymers is such that special procedures are needed for running DSC analysis and interpreting the results.  
1.2 The values stated in SI units as detailed in IEEE/ASTM SI-10 are to be regarded as the standard.  
1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.
Note 1: There is currently no ISO standard that duplicates this test method. ISO 20568-1 and ISO 20568-2 cover similar testing and reference this test method for testing conditions.  
1.4 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

General Information

• Status: Published
• Publication Date: 14-Mar-2022
• ICS: 83.080.20 - Thermoplastic materials
• Technical Committee: D20 - Plastics
• Drafting Committee: D20.15 - Thermoplastic Materials

Relations

• Refers: ASTM E473-23b - Standard Terminology Relating to Thermal Analysis and Rheology
• Effective Date: 01-Oct-2023
• Refers: ASTM D4894-19 - Standard Specification for Polytetrafluoroethylene (PTFE) Granular Molding and Ram Extrusion Materials
• Effective Date: 01-May-2019
• Refers: ASTM D1600-18 - Standard Terminology for Abbreviated Terms Relating to Plastics (Withdrawn 2024)
• Effective Date: 01-Jan-2018
• Refers: ASTM D4895-16 - Standard Specification for Polytetrafluoroethylene (PTFE) Resin Produced From Dispersion
• Effective Date: 01-May-2016
• Refers: ASTM D4895-15 - Standard Specification for Polytetrafluoroethylene (PTFE) Resin Produced From Dispersion
• Effective Date: 01-May-2015
• Refers: ASTM D4894-15 - Standard Specification for Polytetrafluoroethylene (PTFE) Granular Molding and Ram Extrusion Materials
• Effective Date: 01-May-2015
• Refers: ASTM E473-14 - Standard Terminology Relating to Thermal Analysis and Rheology
• Effective Date: 15-Aug-2014
• Refers: ASTM D1600-14 - Standard Terminology for Abbreviated Terms Relating to Plastics
• Effective Date: 01-Feb-2014
• Refers: ASTM D1600-13 - Standard Terminology for Abbreviated Terms Relating to Plastics
• Effective Date: 15-Apr-2013
• Refers: ASTM E793-06(2012) - Standard Test Method for Enthalpies of Fusion and Crystallization by Differential Scanning Calorimetry
• Effective Date: 01-Sep-2012
• Refers: ASTM D3418-12e1 - Standard Test Method for Transition Temperatures and Enthalpies of Fusion and Crystallization of Polymers by Differential Scanning Calorimetry
• Effective Date: 01-Aug-2012
• Refers: ASTM D3418-12 - Standard Test Method for Transition Temperatures and Enthalpies of Fusion and Crystallization of Polymers by Differential Scanning Calorimetry
• Effective Date: 01-Aug-2012
• Refers: ASTM D4894-07(2012) - Standard Specification for Polytetrafluoroethylene (PTFE) Granular Molding and Ram Extrusion Materials
• Effective Date: 01-Apr-2012
• Refers: ASTM E473-11a - Standard Terminology Relating to Thermal Analysis and Rheology
• Effective Date: 15-Jun-2011
• Refers: ASTM E473-11 - Standard Terminology Relating to Thermal Analysis and Rheology
• Effective Date: 01-Apr-2011

Overview

ASTM D4591-22: Standard Test Method for Determining Temperatures and Heats of Transitions of Fluoropolymers by Differential Scanning Calorimetry provides standardized procedures for analyzing fluoropolymers using differential scanning calorimetry (DSC). This method is essential for evaluating the thermal properties of a wide range of fluoropolymer materials, including PTFE, PVDF, PCTFE, PVF, and their various copolymers such as PFA, MFA, FEP, ECTFE, EFEP, and others. The standard applies to powders as well as samples from semi-finished or finished products, supporting quality control, research, and material specification processes in the polymer industry.

Key Topics

• DSC Analysis Conditions: Establishes specific requirements for sample preparation, instrument calibration, and test procedures to ensure accuracy and repeatability in DSC analysis of fluoropolymers.
• Fluoropolymer Identification: Enables identification of various fluoropolymers, whether as pure materials or in mixtures, by measuring transition temperatures.
• Crystallinity Assessment: Assesses the relative crystalline content of samples by comparing heats of fusion, a critical factor influencing material performance.
• Characterization of Morphology: Provides data to characterize the structure and morphology of PTFE and its products, even those that have never been melted, using DSC thermal curves.
• Crystallization Behavior: Highlights the effects of molecular weight and modification with comonomers, particularly in PTFE resins, on crystallization behavior during thermal transitions.
• Supplementary Data for SSG Tests: Supports standard specific gravity (SSG) tests for PTFE by offering additional insight using heat of crystallization measurements.

Applications

ASTM D4591-22 is widely used across the fluoropolymer and plastics industries for:

• Material Quality Control: Ensures batch-to-batch consistency in thermal transition properties during manufacturing of fluoropolymer products.
• Product Development: Assists in the evaluation and comparison of new fluoropolymer formulations and blends, supporting innovation in high-performance applications.
• Identification and Authentication: Facilitates verification of material identity in supply chains where accurate fluoropolymer specification is critical (e.g., PTFE vs. PFA, PVDF, or FEP).
• Performance Prediction: Predicts thermal stability and crystallinity-related properties, which correlate with end-use performance in applications such as chemical processing, electrical insulation, and membrane technology.
• Supplementing Regulatory Tests: Provides thermal transition data to aid compliance with other standards, especially for PTFE resins where both SSG and thermal properties are important.

Related Standards

Several ASTM and ISO standards complement or reference ASTM D4591-22, enhancing its practical value in the plastics and fluoropolymer industries:

• ASTM D3418: Test Method for Transition Temperatures and Enthalpies of Fusion and Crystallization of Polymers by Differential Scanning Calorimetry.
• ASTM D4894 / D4895: Specifications for PTFE granular and dispersion resins, respectively, including requirements for SSG and thermal properties.
• ASTM E793: Test Method for Enthalpies of Fusion and Crystallization by DSC.
• ASTM D1600 / E473: Terminology standards for plastics and thermal analysis.
• IEEE/ASTM SI-10: Standard for Use of the International System of Units (SI).
• ISO 20568-1, ISO 20568-2: International standards referencing DSC conditions for similar fluoropolymer testing.

Keywords: ASTM D4591-22, differential scanning calorimetry, DSC, fluoropolymers, PTFE, PVDF, PCTFE, thermal analysis, heat of fusion, melting point, crystallinity, polymer identification, material characterization, plastics testing standards.

Standards Content (Sample)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: D4591 − 22
Standard Test Method for
Determining Temperatures and Heats of Transitions of
Fluoropolymers by Differential Scanning Calorimetry
This standard is issued under the fixed designation D4591; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript 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. Scope* D1600TerminologyforAbbreviatedTermsRelatingtoPlas-
tics
1.1 This test method defines conditions for the use of
D3418Test Method for Transition Temperatures and En-
differential scanning calorimetry (DSC) with fluoropolymers.
thalpies of Fusion and Crystallization of Polymers by
It covers the use of DSC analyses with the fluoropolymers,
Differential Scanning Calorimetry
PTFE, PVDF, PCTFE, and PVF and their copolymers PFA,
D4894 Specification for Polytetrafluoroethylene (PTFE)
MFA, FEP, ECTFE, EFEP, VDF/HFP, VDF/TFE/HFP, VDF/
Granular Molding and Ram Extrusion Materials
CTFE.Thetestmethodisapplicabletotheanalysisofpowders
D4895 Specification for Polytetrafluoroethylene (PTFE)
as well as samples taken from semi-finished or finished
Resin Produced From Dispersion
products. The nature of fluoropolymers is such that special
E473Terminology Relating to Thermal Analysis and Rhe-
procedures are needed for running DSC analysis and interpret-
ology
ing the results.
E793Test Method for Enthalpies of Fusion and Crystalliza-
1.2 The values stated in SI units as detailed in IEEE/ASTM
tion by Differential Scanning Calorimetry
SI-10 are to be regarded as the standard.
IEEE/ASTM SI-10Standard for Use of the International
1.3 This standard does not purport to address all of the
System of Units (SI) (the Modern Metric System)
safety concerns, if any, associated with its use. It is the 2.2 ISO Standards:
responsibility of the user of this standard to establish appro-
ISO 20568-1 Plastics—Fluoropolymer Dispersion and
priate safety, health, and environmental practices and deter- Molding and Extrusion Materials—Part 1: Designation
mine the applicability of regulatory limitations prior to use.
and Specification
ISO 20568-2 Plastics—Fluoropolymer Dispersion and
NOTE 1—There is currently no ISO standard that duplicates this test
Molding and Extrusion Materials—Part 2: Preparation of
method.ISO20568-1andISO20568-2coversimilartestingandreference
this test method for testing conditions. Test Specimen and Determination of Properties
1.4 This international standard was developed in accor-
3. Terminology
dance with internationally recognized principles on standard-
3.1 Definitions:
ization established in the Decision on Principles for the
3.1.1 differential scanning calorimetry (DSC)—a technique
Development of International Standards, Guides and Recom-
in which the difference in energy inputs into a substance and a
mendations issued by the World Trade Organization Technical
reference material is measured as a function of temperature,
Barriers to Trade (TBT) Committee.
while the substance and reference material are subjected to a
controlled increase or decrease in temperature.
2. Referenced Documents
3.1.2 Refer to Terminology E473 for general terminology
2.1 ASTM Standards:
used in this test method.
3.2 Abbreviated Terms:
3.2.1 Abbreviations used in this test method are in accor-
ThistestmethodisunderthejurisdictionofASTMCommitteeD20onPlastics
and is the direct responsibility of Subcommittee D20.15 on Thermoplastic Materi-
dance with Terminology D1600.
als.
3.2.2 PTFE—polytetrafluoroethylene.
Current edition approved March 15, 2022. Published March 2022. Originally
3.2.3 PFA—perfluoro(alkoxy alkane) resin.
approved in 1987. Last previous edition approved in 2017 as D4591-17. DOI:
3.2.4 FEP—perfluoro(ethylene-propene) copolymer.
10.1520/D4591-22.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
Standards volume information, refer to the standard’s Document Summary page on Available fromAmerican National Standards Institute (ANSI), 25 W. 43rd St.,
the ASTM website. 4th Floor, New York, NY 10036, http://www.ansi.org.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D4591 − 22
3.2.5 ETFE—ethylene-tetrafluoroethylene copolymer. 5. Apparatus
3.2.6 PVDF—poly(vinylidene fluoride).
5.1 Differential Scanning Calorimeter, capable of heating
3.2.7 PCTFE—polymonochlorotrifluoroethylene.
and cooling rates of at least 10.0 °C/min and of recording
3.2.8 ECTFE—ethylene-monochlorotrifluoroethylene co-
automatically the differential heat flow between a specimen
polymer.
and a reference material as a function of time, both to the
3.2.9 EFEP—ethylene-perfluoroethylene-propene copoly-
required sensitivity and precision. For comparison purposes,
mer.
the same heating rate shall be used for all calibrations and test
3.2.10 VDF/HFP—vinylidene fluoride-hexafluoropropene
runs. Thermal curves are recorded using a computerized data
copolymer.
collection system or on a time-based recorder. The resulting
3.2.11 VDF/TFE—vinylidene fluoride-tetrafluoroethylene
curves are used for the measurement of peak areas either by
copolymer.
computer integration or an alternative area measuring proce-
3.2.12 VDF/TFE/HFP—vinylidene fluoride-
dure. The instrument should have a sensitivity for heat flow
tetrafluoroethylene-hexafluoropropene copolymer.
sufficient to provide a precision of 61% when run using a
3.2.13 VDF/CTFE—vinylidene fluoride-
suitable standard for calibration, such as indium. The instru-
chlorotrifluoroethylene copolymer.
ment must have a precision of 61% for either the computer-
3.2.14 PVF—poly(vinyl fluoride).
ized data collections or over a time-base range of 0.1 to 2.0
3.2.15 MFA—perfluoromethylvinylether-tetrafluoroethyl-
min/cm of chart.
ene copolymer.
3.2.16 SSG—standard specific gravity. NOTE 3—Most DSC systems report data with a temperature ordinate.
Thetemperaturevaluesaredirectlyrelatedtotimebasedontheheatingor
cooling rate. Integrated areas measured from the DSC curves will be
4. Significance and Use
directly proportional to the differential caloric input.
4.1 DSC analysis may be used with fluoropolymers to
NOTE 4—Noncomputerized area measurement shall be done with a
achieve at least four different objectives as follows:
precision of 61% or better.
4.1.1 To measure transition temperatures to aid in the
5.2 Specimen Holders and Covers, made from aluminum or
identification of the various fluoropolymers, individually or in
other materials of high thermal conductivity that do not react
mixtures;
with the specimen. It is preferable to use holders designed for
4.1.2 Tocomparetherelativelevelsofcrystallinecontentof
the particular DSC instrument being used. For holders for
twoormorespecimensofasampleofafluoropolymerrelative
whichthecoverhastheshapeofasmallcup,thetopshouldbe
to another sample by measuring the heat of fusion;
inserted with the open side of the cup up.
NOTE 2—Absolute values of crystalline content cannot be determined
5.3 Nitrogen,orotherinertgassupplyforpurgingpurposes.
until values for heats of fusion of the completely crystalline polymers are
available.
5.4 Balance, with capacity greater than 15 mg, capable of
4.1.3 The heat of crystallization of pure PTFE homopoly- weighing to the nearest 0.01 mg.
mer is depending on the relative molecular weight of the
specimen. Some PTFE resins are modified with small amounts
6. Procedure
of comonomers. These modifications have profound effects on
6.1 General Requirements—In general,Test Method D3418
crystallization behavior and shall be considered when evaluat-
shallbeusedwheneverpossible.Thereareinstances,however,
ing the results.
when following Test Method D3418 will not give the desired
4.1.4 To characterize PTFE (DSC thermal curves deter-
results, will not provide information needed for proper inter-
mined on powders or products of PTFE that have never been
pretation of the resultant thermal curve, or will require more
melted convey appreciable information about details of mor-
time for the analysis than need be spent for results having
phology and molecular structure);
suitable precision. Examples of these instances include the
4.1.5 To supplement the test for standard specific gravity
following:
(SSG) described in Specifications D4894 and D4895 by using
6.1.1 The requirement that scans be started at room
theheatofcrystallizationofpurePTFEhomopolymer,depend-
temperature,aprovisionusuallynotrequiredwithallfluoropo-
ing on the relative molecular weight of the specimen. The
lymers;
scopes of these specifications, however, include PTFE resins
6.1.2 At times the thermal curve that results from the
modified with small amounts of comonomers, and many
analysis provides information that cannot be interpreted in a
commercial PTFE resins are modified in this manner. These
useful manner by Test Method D3418, but can be interpreted
modifications can have profound effects on crystallization
following the procedures of Section 7.
behavior. Published relationships between hea
...

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. Because
it 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 current version
of the standard as published by ASTM is to be considered the official document.
Designation: D4591 − 17 D4591 − 22
Standard Test Method for
Determining Temperatures and Heats of Transitions of
Fluoropolymers by Differential Scanning Calorimetry
This standard is issued under the fixed designation D4591; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript 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. Scope*
1.1 This test method defines conditions for the use of differential 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 applicable to the analysis of powders as well as samples taken
from semi-finished or finished products. The nature of fluoropolymers is such that special procedures are needed for running DSC
analysis and interpreting the results.
1.2 The values stated in SI units as detailed in IEEE/ASTM SI-10 are to be regarded as the standard.
1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of
regulatory limitations prior to use.
NOTE 1—There is currently no ISO standard that duplicates this test method. ISO 12086-120568-1 and ISO 12086-220568-2 cover similar testing and
reference this test method for testing conditions.
1.4 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2.1 ASTM Standards:
D1600 Terminology for Abbreviated Terms Relating to Plastics
D3418 Test Method for Transition Temperatures and Enthalpies of Fusion and Crystallization of Polymers by Differential
Scanning Calorimetry
D4894 Specification for Polytetrafluoroethylene (PTFE) Granular Molding and Ram Extrusion Materials
D4895 Specification for Polytetrafluoroethylene (PTFE) Resin Produced From Dispersion
E473 Terminology Relating to Thermal Analysis and Rheology
E793 Test Method for Enthalpies of Fusion and Crystallization by Differential Scanning Calorimetry
IEEE/ASTM SI-10 Standard for Use of the International System of Units (SI) (the Modern Metric System)
This test method is under the jurisdiction of ASTM Committee D20 on Plastics and is the direct responsibility of Subcommittee D20.15 on Thermoplastic Materials.
Current edition approved Dec. 1, 2017March 15, 2022. Published January 2018March 2022. Originally approved in 1987. Last previous edition approved in 20122017
as D4591 - 07D4591 - 17.(2012). DOI: 10.1520/D4591-17.10.1520/D4591-22.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D4591 − 22
2.2 ISO Standards:
ISO 12086-120568-1 Plastics—Fluoropolymer Dispersion and Molding and Extrusion Materials—Part 1: Designation and
Specification
ISO 12086-220568-2 Plastics—Fluoropolymer Dispersion and Molding and Extrusion Materials—Part 2: Preparation of Test
Specimen and Determination of Properties
3. Terminology
3.1 Definitions:
3.1.1 differential scanning calorimetry (DSC)—a technique in which the difference in energy inputs into a substance and a
reference material is measured as a function of temperature, while the substance and reference material are subjected to a controlled
increase or decrease in temperature.
3.1.2 Refer to Terminology E473 for general terminology used in this test method.
3.2 Abbreviated Terms:
3.2.1 Abbreviations used in this test method are in accordance with Terminology D1600.
3.2.2 PTFE—polytetrafluoroethylene.
3.2.3 PFA—perfluoro(alkoxy alkane) resin.
3.2.4 FEP—perfluoro(ethylene-propene) copolymer.
3.2.5 ETFE—ethylene-tetrafluoroethylene copolymer.
3.2.6 PVDF—poly(vinylidene fluoride).
3.2.7 PCTFE—polymonochlorotrifluoroethylene.
3.2.8 ECTFE—ethylene-monochlorotrifluoroethylene copolymer.
3.2.9 EFEP—ethylene-perfluoroethylene-propene copolymer.
3.2.10 VDF/HFP—vinylidene fluoride-hexafluoropropene copolymer.
3.2.11 VDF/TFE—vinylidene fluoride-tetrafluoroethylene copolymer.
3.2.12 VDF/TFE/HFP—vinylidene fluoride-tetrafluoroethylene-hexafluoropropene copolymer.
3.2.13 VDF/CTFE—vinylidene fluoride-chlorotrifluoroethylene copolymer.
3.2.14 PVF—poly(vinyl fluoride).
3.2.15 MFA—perfluoromethylvinylether-tetrafluoroethylene copolymer.
3.2.16 SSG—standard specific gravity.
4. Significance and Use
4.1 DSC analysis may be used with fluoropolymers to achieve at least four different objectives as follows:
4.1.1 To measure transition temperatures to aid in the identification of the various fluoropolymers, individually or in mixtures;
Available from American National Standards Institute (ANSI), 25 W. 43rd St., 4th Floor, New York, NY 10036, http://www.ansi.org.
D4591 − 22
4.1.2 To compare the relative levels of crystalline content of two or more specimens of a sample of a fluoropolymer relative to
another sample by measuring the heat of fusion;
NOTE 2—Absolute values of crystalline content cannot be determined until values for heats of fusion of the completely crystalline polymers are available.
4.1.3 The heat of crystallization of pure PTFE homopolymer is depending on the relative molecular weight of the specimen. Some
PTFE resins are modified with small amounts of comonomers. These modifications have profound effects on crystallization
behavior and shall be considered when evaluating the results.
4.1.4 To characterize PTFE (DSC thermal curves determined on powders or products of PTFE that have never been melted convey
appreciable information about details of morphology and molecular structure);
4.1.5 To supplement the test for standard specific gravity (SSG) described in Specifications D4894 and D4895 by using the heat
of crystallization of pure PTFE homopolymer, depending on the relative molecular weight of the specimen. The scopes of these
specifications, however, include PTFE resins modified with small amounts of comonomers, and many commercial PTFE resins are
modified in this manner. These modifications can have profound effects on crystallization behavior. Published relationships
between heat of crystallization and molecular weight refer to pure PTFE homopolymers and, therefore, cannot be applied to the
modified resins.
5. Apparatus
5.1 Differential Scanning Calorimeter, capable of heating and cooling rates of at least 10.0 °C/min and of recording automatically
the differential heat flow between a specimen and a reference material as a function of time, both to the required sensitivity and
precision. For comparison purposes, the same heating rate shall be used for all calibrations and test runs. Thermal curves are
recorded using a computerized data collection system or on a time-based recorder. The resulting curves are used for the
measurement of peak areas either by computer integration or an alternative area measuring procedure. The instrument should have
a sensitivity for heat flow sufficient to provide a precision of 61 % when run using a suitable standard for calibration, such as
indium. The instrument must have a precision of 61 % for either the computerized data collections or over a time-base range of
0.1 to 2.0 min/cm of chart.
NOTE 3—Most DSC systems report data with a temperature ordinate. The temperature values are directly related to time based on the heating or cooling
rate. Integrated areas measured from the DSC curves will be directly proportional to the differential caloric input.
NOTE 4—Noncomputerized area measurement shall be done with a precision of 61 % or better.
5.2 Specimen Holders and Covers, made from aluminum or other materials of high thermal conductivity that do not react with
the specimen. It is preferable to use holders designed for the particular DSC instrument being used. For holders for which the cover
has the shape of a small cup, the top should be inserted 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 of weighing to the nearest 0.01 mg.
6. Procedure
6.1 General Requirements—In general, Test Method D3418 shall be used whenever possible. There are instances, however, when
following Test Method D3418 will not give the desired results, will not provide information needed for proper interpretation of
the resultant thermal curve, or will require more time for the analysis than need be spent for results having suitable precision.
Examples of these instances include the following:
6.1.1 The requirement that scans be started at room temperature, a provision usually not required with all fluoropolymers;
Sperati, C. A., “Polytetrafluoroethylene: History of Its Development and Some Recent Advances” (67 references), High Performance Polymers: Their Origin and
Development, Seymour and Kirshenbaume (eds), Marcel Dec
...