ASTM D4441-04(2010)
(Specification)Standard Specification for Aqueous Dispersions of Polytetrafluoroethylene
Standard Specification for Aqueous Dispersions of Polytetrafluoroethylene
ABSTRACT
This specification establishes the properties and test methods for aqueous dispersions of polytetrafluoroethylene (PTFE) resins, and is used to determine if a shipment, lot, or container of PTFE dispersions is suitable for its intended use. These resins are homopolymers of tetrafluoroethylene, or in some cases modified homopolymers containing not more than 1% by weight of other fluoromonomers, and the dispersions are usually stabilized by one or more surfactants. Other non-PTFE materials may be present in total at 5% or less by weight for special purposes. This specification is for virgin materials only, and does not cover PTFE copolymers or filled dispersions, and recycled materials as they are not appropriate for dispersions. Materials shall be appropriately sampled for testing on the following: pH value; solid and surfactant content by gravimetric weight loss; solid content by hydrometer; test for coagulated polymer; specific gravity; and melting characteristics.
SCOPE
1.1 This specification covers aqueous dispersions of polytetrafluoroethylene (PTFE) resins. These resins are homopolymers of tetrafluoroethylene, or in some cases modified homopolymers containing not more than 1 % by weight of other fluoromonomers.
1.1.1 The dispersion is usually stabilized by one or more surfactants. Other non-PTFE materials may be present in total at 5 % or less by weight for special purposes.
1.1.2 This specification is for virgin material only and does not address recycled material as it is not appropriate for dispersions.
1.2 This specification is used to determine if a shipment, lot, or container of PTFE dispersion is suitable for its intended use. It covers only aqueous dispersions of polytetrafluoroethylene. It does not cover PTFE copolymers or filled dispersions. This specification includes test methods for both aqueous dispersion and the PTFE in the dispersion.
Note 1—Uses for the PTFE dispersion covered by this specification include, but are not limited to, casting of their films, impregnation of mechanical packings and other materials, surface coatings on various substrates, combined impregnation and coating of fibrous materials, and co-coagulation with other materials for subsequent processing into films, sheets, rods, and tubes.
Note 2—Information in this specification is technically equivalent to related information in ISO 12086-1 and ISO 12086-2.
1.3 The values stated in SI units as detailed in are to be regarded as standard. The values given in parentheses are for information only.
1.4 The following precautionary caveat pertains only to the test method portions of this specification. 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 and health practices and determine the applicability of regulatory limitations prior to use. Specific precautionary information is given in Notes 5 and 6.
General Information
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Standards Content (Sample)
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
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Designation:D4441 −04(Reapproved 2010)
Standard Specification for
Aqueous Dispersions of Polytetrafluoroethylene
This standard is issued under the fixed designation D4441; 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.
1. Scope 2. Referenced Documents
1.1 This specification covers aqueous dispersions of poly- 2.1 ASTM Standards:
tetrafluoroethylene (PTFE) resins. These resins are homopoly- D883Terminology Relating to Plastics
mers of tetrafluoroethylene, or in some cases modified ho- D3892Practice for Packaging/Packing of Plastics
mopolymers containing not more than 1% by weight of other D4464Test Method for Particle Size Distribution of Cata-
fluoromonomers. lytic Material by Laser Light Scattering
1.1.1 The dispersion is usually stabilized by one or more D4591Test Method for Determining Temperatures and
surfactants. Other non-PTFE materials may be present in total Heats of Transitions of Fluoropolymers by Differential
at 5% or less by weight for special purposes. Scanning Calorimetry
1.1.2 This specification is for virgin material only and does D4894 Specification for Polytetrafluoroethylene (PTFE)
not address recycled material as it is not appropriate for Granular Molding and Ram Extrusion Materials
dispersions. D4895 Specification for Polytetrafluoroethylene (PTFE)
Resin Produced From Dispersion
1.2 Thisspecificationisusedtodetermineifashipment,lot,
E70Test Method for pH of Aqueous Solutions With the
orcontainerofPTFEdispersionissuitableforitsintendeduse.
Glass Electrode
It covers only aqueous dispersions of polytetrafluoroethylene.
IEEE/ASTM SI-10Use of the International System of Units
It does not cover PTFE copolymers or filled dispersions. This
(SI): The Modern Metric System
specificationincludestestmethodsforbothaqueousdispersion
2.2 ISO Standards:
and the PTFE in the dispersion.
ISO 12086-1Plastics Fluoropolymer Dispersions and Mold-
NOTE 1—Uses for the PTFE dispersion covered by this specification
ing and Extrusion Materials—Part 1: Designation and
include, but are not limited to, casting of their films, impregnation of
Specification
mechanical packings and other materials, surface coatings on various
ISO12086-2 PlasticsFluoropolymerDispersionsandMold-
substrates, combined impregnation and coating of fibrous materials, and
ing and Extrusion Materials—Part 2: Preparation of Test
co-coagulation with other materials for subsequent processing into films,
sheets, rods, and tubes.
Specimens and Determination of Properties
NOTE 2—Information in this specification is technically equivalent to
related information in ISO 12086-1 and ISO 12086-2. 3. Terminology
1.3 The values stated in SI units as detailed in IEEE/ASTM
3.1 Definitions:
SI-10 are to be regarded as standard. The values given in 3.1.1 General—The terminology given in Terminology
parentheses are for information only.
D883 is applicable to this specification.
1.4 The following precautionary caveat pertains only to the 3.2 Definitions of Terms Specific to This Standard:
test method portions of this specification. This standard does
3.2.1 dispersion, n—atwophasesystemofwhichonephase
not purport to address all of the safety concerns, if any, consists of finely divided particles distributed throughout a
associated with its use. It is the responsibility of the user of this
bulk substance, the particles being the disperse phase and the
standard to establish appropriate safety and health practices bulk phase being the continuous phase.
and determine the applicability of regulatory limitations prior
3.2.2 dispersion particle size—a particle size measured in
to use. Specific precautionary information is given in Notes 5
the presence of added surfactant.
and 6.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
This specification is under the jurisdiction of ASTM Committee D20 on Standards volume information, refer to the standard’s Document Summary page on
Plastics and is the direct responsibility of Subcommittee D20.15 on Thermoplastic the ASTM website.
Materials(Section D20.15.12). Specifications for other forms of polytetrafluoroethylene may be found in
Current edition approved Jan. 1, 2010. Published January 2010. Originally Specifications D4894 and D4895.
approved in 1984. Last previous edition approved in 2004 as D4441-04. DOI: Available fromAmerican National Standards Institute (ANSI), 25 W. 43rd St.,
10.1520/D4441-04R10. 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
D4441−04 (2010)
3.2.3 raw dispersion particle size—a particle size measured Separators are not needed between the type, grade, and class.
intheabsenceofaddedsurfactant(exceptforthesmallamount Provisionforspecialnotesisincludedsothatotherinformation
used in polymerization). can be provided when required.
3.2.4 lot, n—one production run or a uniform blend of two
5. Ordering Information
or more production runs.
5.1 Ordersformaterialunderthisspecificationshallcontain
3.2.5 sintering, n—as it applies to PTFE, a thermal treat-
the following information:
ment during which the PTFE is melted and recrystallized by
5.1.1 Quantity, Grade, Class,
cooling with coalescence occurring during the treatment.
5.1.2 Name of material (Aqueous dispersion of PTFE),
3.2.6 standard specific gravity (SSG), n—the specific grav-
5.1.3 ASTM designation and year,
ityofaspecimenofPTFEmaterialmoldedasdescribedinthis
5.1.4 Type,
specification and sintered using the appropriate sintering
5.1.5 Additions to the specification and supplementary
schedule given in this specification.
requirements, if required.
4. Classification
6. Other Requirements
4.1 This specification covers four types of virgin PTFE
6.1 Significance—In addition to tests on the dispersion and
dispersions classified into those equal to or below 40% PTFE
the polymer, the following requirements apply:
and those above 40% PTFE, and those containing added
6.2 The dispersion shall be free of contamination, dirt,
surfactant and those not containing added surfactant. The
mold, etc. It shall be of uniform composition. The expected
dispersionsareclassifiedinto13gradesdependingonthelevel
level of coagulated polymer shall be specified.
of added surfactant. Three classes of Surfactant Tolerance
Level are provided to further differentiate the dispersion
7. Sampling
variability needed.
7.1 PTFE solids in the dispersion tend to settle upon
NOTE 3—The surfactant content is weight percent and is based on the
standing. Therefore, the dispersion shall be homogenized by
solid, dry PTFE.
gentle mixing before sampling. Gentle mixing includes rolling
4.2 Aline callout system is used to specify materials in this
a drum for 5 min at 3 to 4 rpm, by stirring with a smooth rod
specification. The system uses predefined cells to refer to for 3- to 4-min, or by other types of gentle agitation.
specific aspects of this specification, illustrated as follows:
(Warning—Vigorous agitation will coagulate the dispersion.)
7.2 After blending, take the sample by removing an aliquot.
A suitable method is by inserting a clean, smooth, dry glass
Specification
tube, open at both ends, until it reaches the bottom of the
Standard Number Block: Type Grade Class Special Notes
Example: Specification II 3 A container. An internal diameter of 6 or 7 mm (0.25 in.) is
D4441 - XX,
suitable. Smooth the ends of the tube to prevent injury. Close
the upper end of the tube, remove the tube from the container,
and transfer the contents to a clean dry glass jar. Repeat until
the desired sample size is reached.
For this example, the line callout would be Specification
7.3 When samples are drawn from several containers, the
D4441–XX,II3AandwouldspecifyavirginPTFEdispersion
individualsamplesshallbecombinedandthoroughlymixedby
that has all the properties listed for that type, grade, and class
gentle stirring when the samples are combined and again
in the appropriate specified tables. A comma is used as the
before the combined sample is tested.
separator between the standard number and the type and class.
8. Test Methods for Dispersions
8.1 Scope—The specification contains test methods to de-
TABLE 1 PTFE Level, Surfactant Level, and Tolerance Level
fine characteristics of the polymer and of the dispersion of the
Requirements
polymer. This section defines tests on the dispersion of the
Type % PTFE Grade Nominal % Class Surfactant
polymer.
Added Tolerance
Surfactant Level
8.2 pH Value—The test method shall be in accordance with
I #40 0 >0–<1 A ±0.5 %
Test Method E70. Some buyers or sellers attach importance to
1 $1–<2 B ±1.0 %
II >40 2 $2–<3 C ±2.0 %
the pH of the PTFE dispersion. The pH value is not specified
3 $3–<4
in this ASTM Standard.
III #40 with 0 % 4 $4–<5
added 5 $5–<6
NOTE4—IfthePTFEdispersioncoatstheelectrode,cleantheelectrode
surfactant 6 $6–<7
thoroughly using a soft cloth wet with either toluene or concentrated
7 $7–<8
surfactant.
8 $8–<9
IV >40 with 0 % 9 $9–<10
added 10 $10–<11
See the ASTM Form and Style Manual available from ASTM Headquarters.
surfactant 11 $11–<12
12 $12–<13 Examples of a suitable surfactant are “Glim” detergent, B. J. Babbitt, Inc.,
“Joy”detergent,ProctorandGamble,Inc.,and“Triton”X-100,RohmandHaasCo.
D4441−04 (2010)
NOTE 5—Warning: Toluene is hazardous. Consult appropriate safety
8.4.2 Apparatus—A hydrometer or set of hydrometers ca-
information on the material Safety Data Sheet before using.
pable of measuring specific gravity from 1.000 to 1.500.
Accuracy of the hydrometer shall be 60.001. A graduated
8.3 Solid Content and Surfactant Content by Gravimetric
cylinder large enough to hold the hydrometer.
Weight Loss:
8.4.3 Procedure—Fill the graduated cylinder with PTFE
8.3.1 Significance—Determine the percent PTFE solids and
dispersion to float the hydrometer. Place the hydrometer into
the percent surfactant by successive evaporations of water and
the cylinder. Add dispersion until the cylinder is full and the
surfactant.The percent surfactant is based on the weight of the
meniscus is slightly convex. Read the hydrometer at the top of
PTFE. All percentages are based on weight.
the dispersion. The reading shall be accurate to 0.001. Trans-
8.3.2 Apparatus—An aluminum weighing dish, an oven
late the hydrometer reading to solids content using the table.
capable of reaching 120 65°C (248 69°F), and an oven
8.4.4 Precision and Bias—No information can be presented
capable of reaching 380 610°C (716 618°F). Balance ca-
ontheprecisionandbiasbecauseofinsufficientparticipationin
pable of weighing down to 0.0001 g.
the investigation.
8.3.3 Procedure—Weigh the aluminum weighing dish to
NOTE7—Someoftheadditivespermittedinaccordancewith1.1.1may
0.0001 g (W ). Add 10 g of PTFE dispersion and weigh
A
increase the viscosity of the dispersion so much that it is unlikely that the
immediately to 0.0001 g (W ). Dry the sample for2hat
B
hydrometer procedure will be used to determine the density in a reliable
120 65°C.Weighthesampleto0.0001g(W )aftercoolingto
C
manner.
room temperature in a desiccator. After weighing, evaporate
8.5 Test for Coagulated Polymer:
the surfactant by placing the sample in an oven at 380 65°C
8.5.1 Significance—Polymerthathascoagulatedmaynotbe
(716 69°F) for 35 61 min. Allow the sample to cool in a
useful to the purchaser. This test will determine the percent of
desiccator to room temperature and weigh to 0.0001 g (W ).
D
coagulated polymer.
8.3.4 Calculations—For surfactants that are completely
8.5.2 Apparatus—A tared beaker to hold 1000 61gof
volatile use the following:
dispersion; a filter screen, 80 mesh; a funnel, an oven capable
of operating at 120 65°C (248 69°F) desiccator; balance
W 2 W
~ !
D A capable of 1 mg.
PTFE,% 5 3100
~W 2 W !
B A 8.5.3 Materials—Distilled water PTFE dispersion.
8.5.4 Procedure—Weigh a 1000 61 g of dispersion (W )
~W 2 W !
D
C D
surfactant,% 5 3100
intothetaredbeaker.Weighthescreento1.0mgandrecordthe
W 2 W
~ !
D A
weight (W ). Secure the screen to the funnel and filter the
S
8.3.4.1 For surfactants that are not completely volatile use
dispersion through the screen. Rinse the beaker with 25 mLof
the following:
distilled water and use this rinse water to wash the coagulum
on the screen. Gently wash the coagulated polymer on the
~W 2 W ! 2 @~W 2 W ! 3 ~11k!# screen with 25 mL of distilled water from a wash bottle.
C A C D
PTFE,% 5 3100
W 2 W Carefully remove the screen from the funnel and dry at
~ !
B A
120 65°C (248 69°F) for 2 h. Weigh the screen and coagu-
W 2 W 3 11k
~ ! ~ !
C D
surfactant,% 5 3100
lum to 1 mg after allowing it to cool to room temperature in a
~W 2 W ! 2 @~W 2 W ! 3 ~11k!#
C A C D
desiccator. Record the weight as W .
C
where:
8.5.5 Calculation—Calculate the coagulum content as
k = weight of nonvolatile portion of the surfactant/weight of
follows:
volatile portion of the surfactant.
NOTE 6—Upon request, the supplier shall inform the user whether the
W 2 W
~ !
C S
surfactant can be completely removed by the procedures of this specifi- coagulumcontent,% 5 3100
W 3PTFEcontent,%
~ !
D
cation;andifnot,shalldefinethesurfactantorthevolatileandnonvolatile
portions of the surfactant.
where:
8.3.5 Precision and Bias—No information can be presented
W = mass of dispersion sample, g,
D
ontheprecisionandbiasbecauseofinsufficientparticipationin W = mass of screen, g,
S
the investigation. W = mass of screen and coagulated polymer, g, and PTFE
C
content,%,=PTFE,%inthedispersionasdetermined
8.3.6 The results of these tests on solids contents and
in 8.3. It is to be expressed as a decimal fraction.
surfactantshallconformtooneofthetypesofdispersionlisted
in 4.1.
9. Methods for Tests on PTFE in the Dispersion
8.4 Solids Content by Hydrometer:
9.1 Scope—The specification contains test methods to de-
8.4.1 Significance—An approximate solids content in a
fine characteristics for the dispersion and for the PTFE in the
dispersioniscommonlydeterminedfromthespecificgravityof
dispersion. This section specifies tests that will define the
the dispersion. The hydrometer reading is a function of the
solids in the dispersion to be PTFE and to characterize the
solids content, the surfactant content, and other parameters of
PTFE.
the dispersion. Therefore, any single conversion table has
inherent error and cannot be universally applicable. A table 9.2 StandardSpecificGravity—Thetestmethodforstandard
should be
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