ASTM D4441-98
(Specification)Standard Specification for Aqueous Dispersions of Polytetrafluoroethylene
Standard Specification for Aqueous Dispersions of Polytetrafluoroethylene
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 stabilized by one or more surfactants. Other non-PTFE materials may be present in total at 5% or less by weight for special purposes.
1.2 This specification may be 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 both tests on the aqueous dispersion and tests on 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 Practice E 380, are to be regarded as the standard.
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.
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Designation: D 4441 – 98
Standard Specification for
Aqueous Dispersions of Polytetrafluoroethylene
This standard is issued under the fixed designation D 4441; 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 (e) 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- D 883 Terminology Relating to Plastics
mers of tetrafluoroethylene, or in some cases modified ho- D 1898 Practice for Sampling of Plastics
mopolymers containing not more than 1 % by weight of other D 3892 Practice for Packaging/Packing of Plastics
fluoromonomers. D 4464 Test Method for Particle Size Distribution of Cata-
1.1.1 The dispersion is usually stabilized by one or more lytic Material by Laser Light Scattering
surfactants. Other non-PTFE materials may be present in total D 4591 Test Method for Determining Temperatures and
at 5 % or less by weight for special purposes. Heats of Transitions of Fluoropolymers by Differential
1.1.2 This specification is for virgin material only and does Scanning Calorimetry
not address recycled material as it is not appropriate for D 4894 Specification for Polytetrafluoroethylene (PTFE)
5,
dispersions. Granular Molding and Ram Extrusion Materials
1.2 This specification may be used to determine if a ship- D 4895 Specification for Polytetrafluoroethylene (PTFE)
5,6
ment, lot, or container of PTFE dispersion is suitable for its Resins Produced from Dispersion
intended use. It covers only aqueous dispersions of polytet- E 70 Test Method for pH of Aqueous Solutions with the
rafluoroethylene. It does not cover PTFE copolymers or filled Glass Electrode
dispersions. This specification includes test methods for both E 380 Practice for Use of the International System of Units
aqueous dispersion and the PTFE in the dispersion. (SI) (the Modernized Metric System)
2.2 ISO Standards:
NOTE 1—Uses for the PTFE dispersion covered by this specification
ISO 12086-1
include, but are not limited to, casting of their films, impregnation of
ISO 12086-2
mechanical packings and other materials, surface coatings on various
substrates, combined impregnation and coating of fibrous materials, and
3. Terminology
co-coagulation with other materials for subsequent processing into films,
sheets, rods, and tubes.
3.1 Definitions:
NOTE 2—Information in this specification is technically equivalent to
3.1.1 General—The terminology given in Terminology
related information in ISO 12086-1 and ISO 12086-2.
D 883 is applicable to this specification.
1.3 The values stated in SI units, as detailed in Practice
3.1.2 The terminology given in Specification D 4895 is
E 380, are to be regarded as the standard.
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—a two phase system of which one phase
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
to use. Specific precautionary information is given in Notes 5
Annual Book of ASTM Standards, Vol 08.01.
and 6.
Annual Book of ASTM Standards, Vol 08.02.
Annual Book of ASTM Standards, Vol 05.03.
Annual Book of ASTM Standards, Vol 08.03.
Specifications for other forms of polytetrafluoroethylene may be found in
This specification is under the jurisdiction of ASTM Committee D-20 on Specifications D 4894 and D 4895.
Plastics and is the direct responsibility of Subcommittee D20.15 on Thermoplastic Annual Book of ASTM Standards, Vol 15.05.
Materials (Section D20.15.12). Annual Book of ASTM Standards, Vol 14.02.
Current edition approved March 10, 1998. Published January 1999. Originally Available from American National Standards Institute, 11 W. 42nd St., 13th
published as D 4441 - 84. Last previous edition D 4441 - 96. Floor, New York, NY 10036.
*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.
D 4441
3.2.2 dispersion particle size—a particle size measured in 5.1.1 Quantity, Grade, Class,
the presence of added surfactant. 5.1.2 Name of material (Aqueous dispersion of PTFE),
3.2.3 raw dispersion particle size—a particle size measured 5.1.3 ASTM designation and year,
in the absence of added surfactant (except for the small amount 5.1.4 Type,
used in polymerization). 5.1.5 Additions to the specification and supplementary re-
quirements, if required.
4. Classification
6. Other Requirements
4.1 This specification covers four types of virgin PTFE
dispersions classified into those equal to or below 40 % PTFE
6.1 Significance—In addition to tests on the dispersion and
and those above 40 % PTFE, and those containing added
the polymer, the following requirements apply:
surfactant and those not containing added surfactant. The
6.2 The dispersion shall be free of contamination, dirt,
dispersions are classified into 13 grades depending on the level
mold, etc. It shall be of uniform composition. The expected
of added surfactant. Three classes of Surfactant Tolerance
level of coagulated polymer shall be specified.
Level are provided to further differentiate the dispersion
6.3 Measurements of pH and additives content may be a
variability needed.
requirement.
NOTE 3—The surfactant content is weight percent and is based on the
7. Sampling
solid, dry PTFE.
7.1 PTFE solids in the dispersion tend to settle upon
4.2 A one-line system may be used to specify materials
standing. Therefore, the dispersion should be homogenized by
covered by this specification. The system uses predefined cells
gentle mixing before sampling. Gentle mixing can be accom-
to refer to specific aspects of this specification, illustrated as
plished by rolling a drum for 5 min at 3 to 4 rpm, by stirring
follows:
with a smooth rod for 3- to 4-min, or by other types of gentle
agitation. Caution—Excessive agitation can coagulate the
Specification
dispersion.
Standard Number Block: Special
7.2 After blending, take the sample by removing an aliquot.
Type Grade Class
Notes
A suitable method is by inserting a clean, smooth, dry glass
Example: Specification D 4441 - 98, II 3 A
tube, open at both ends, until it reaches the bottom of the
container. An internal diameter of 6 or 7 mm (0.25 in.) is
suitable. The ends of the tube should be smooth to prevent
For this example, the line callout would be Specification D
injury. Close the upper end of the tube, remove the tube from
4441 – 98, II3A and would specify a virgin PTFE dispersion
the container, and transfer the contents to a clean dry glass jar.
that has all the properties listed for that type, grade, and class
Repeat until the desired sample size is reached.
in the appropriate specified tables. A comma is used as the
7.3 When samples are drawn from several containers, the
separator between the standard number and the type and class.
individual samples may be combined and thoroughly mixed by
Separators are not needed between the type, grade, and class.
gentle stirring when the samples are combined and again
Provision for special notes is included so that other information
before the combined sample is tested.
can be provided when required.
8. Test Methods for Dispersions
5. Ordering Information
8.1 Scope—The specification contains test methods to de-
5.1 Orders for material under this specification shall contain
fine characteristics of the polymer and of the dispersion of the
the following information:
polymer. This section defines tests on the dispersion of the
polymer.
See the ASTM Form and Style Manual available from ASTM Headquarters.
8.2 pH Value—The test method shall be in accordance with
Test Method E 70. Some buyers or sellers attach importance to
TABLE 1 PTFE Level, Surfactant Level, and Tolerance Level
the pH of the PTFE dispersion. The pH value is not specified
Requirements
in this ASTM Standard.
Surfactant
Nominal %
Type % PTFE Grade Class Tolerance
NOTE 4—The PTFE dispersion can coat the electrode, so a thorough
Added Surfactant
Level
cleaning is necessary. Cleaning with toluene on a soft cloth or a
I #40 0 >0–<1 A 60.5 % concentrated surfactant on a soft cloth is suggested.
1 $1–<2 B 61.0 %
NOTE 5—Warning: Toluene is hazardous. Consult appropriate safety
II >40 2 $2–<3 C 62.0 %
information on the material Safety Data Sheet before using.
3 $3–<4
III #40 with 0 % added 4 $4–<5
8.3 Solid Content and Surfactant Content by Gravimetric
surfactant 5 $5–<6
Weight Loss:
6 $6–<7
8.3.1 Significance—The percent PTFE solids and the per-
7 $7–<8
8 $8–<9
cent surfactant can be determined by successive evaporations
IV >40 with 0 % added 9 $9–<10
surfactant 10 $10–<11
11 $11–<12
12 $12–<13 Examples of a suitable surfactant are “Glim” detergent, B. J. Babbitt, Inc.,
“Joy” detergent, Proctor and Gamble, Inc., and “Triton” X-100, Rohm and Haas Co.
D 4441
of water and surfactant. The percent surfactant is based on the the dispersion. The reading shall be accurate to 0.001. Trans-
weight of the PTFE. All percentages are based on weight. late the hydrometer reading to solids content using the table.
8.4.4 Precision and Bias—No information can be presented
8.3.2 Apparatus—An aluminum weighing dish, an oven
on the precision and bias because of insufficient participation in
capable of reaching 120 6 5°C (248 6 9°F), and an oven
the investigation.
capable of reaching 380 6 10°C (716 6 18°F). Balance ca-
pable of weighing down to 0.0001 g.
NOTE 7—Some of the additives permitted according to 1.1.1 may
8.3.3 Procedure—Weigh the aluminum weighing dish to increase the viscosity of the dispersion so much that it is unlikely that the
hydrometer procedure can be used to determine the density in a reliable
0.0001 g (W ). Add 10 g of PTFE dispersion and weigh
A
manner.
immediately to 0.0001 g (W ). Dry the sample for2hat
B
120 6 5°C. Weigh the sample to 0.0001 g (W ) after cooling to
8.5 Test for Coagulated Polymer:
C
room temperature in a desiccator. After weighing, evaporate 8.5.1 Significance—Polymer that has coagulated may not be
the surfactant by placing the sample in an oven at 380 6 5°C
useful to the purchaser. This test will determine the percent of
(716 6 9°F) for 35 6 1 min. Allow the sample to cool in a coagulated polymer.
desiccator to room temperature and weigh to 0.0001 g (W ).
8.5.2 Apparatus—A tared beaker to hold 1000 61gof
D
dispersion; a filter screen, 80 mesh; a funnel, an oven capable
8.3.4 Calculations—For surfactants that are completely
of operating at 120 6 5°C (248 6 9°F) desiccator; balance
volatile use the following:
capable of 1 mg.
~W 2W !
D A
PTFE, %5 3100 8.5.3 Materials—Distilled water PTFE dispersion.
~W 2W !
B A
8.5.4 Procedure—Weigh a 1000 6 1 g of dispersion (W )
D
~W 2W !
C D
into the tared beaker. Weigh the screen to 1.0 mg and record the
surfactant, %5 3100
~W 2W !
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 mL of
the following:
distilled water and use this rinse water to wash the coagulum
on the screen. Gently wash the coagulated polymer on the
~W 2W !2@~W 2W !3~11k!#
C A C D
PTFE, %5 3100
screen with 25 mL of distilled water from a wash bottle.
~W 2W !
B A
Carefully remove the screen from the funnel and dry at
~W 2W !3~11k!
C D
surfactant, %5 3100
120 6 5°C (248 6 9°F) for 2 h. Weigh the screen and coagu-
~W 2W !2@~W 2W !3~11k!#
C A C D
lum to 1 mg after allowing it to cool to room temperature in a
where:
desiccator. Record the weight as W .
C
k = weight of nonvolatile portion of the surfactant/weight
8.5.5 Calculation—Calculate the coagulum content as fol-
of volatile portion of the surfactant.
lows:
~W 2W !
C S
NOTE 6—Upon request, the supplier shall inform the user whether the
coagulum content, %5 3100
~W 3PTFE content, %!
surfactant can be completely removed by the procedures of this specifi- D
cation; and if not, shall define the surfactant or the volatile and nonvolatile
where:
portions of the surfactant.
W = mass of dispersion sample, g,
D
8.3.5 Precision and Bias—No information can be presented
W = mass of screen, g,
S
on the precision and bias because of insufficient participation in W = mass of screen and coagulated polymer, g, and PTFE
C
the investigation. content, %, = PTFE, % in the dispersion as deter-
mined in 8.3. It is to be expressed as a decimal
8.3.6 The results of these tests on solids contents and
fraction.
surfactant shall conform to one of the types of dispersion listed
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
dispersion is commonly determined from the specific gravity of
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
9.2 Standard Specific Gravity—The test method for stan-
inherent error and cannot be universally applicable. A table
dard specific gravity is the same as given in Specification
should be obtained from the supplier.
D 4895. However, it is necessary to remove all of the surfactant
8.4.2 Apparatus—A hydrometer or set of hydrometers ca-
before sintering in order to obtain meaningful results.
pable of measuring specific gravity from 1.000 to 1.500.
9.2.1 Apparatus—A 475-mL (16-oz) widemouth bottle with
Accuracy of the hydrometer shall be 60.001. A graduated
sealable top. A 5-in. Buchner funnel; 100-mL graduate cylin-
cylinder large enough to hold the hydrometer.
der, watchglass or aluminum pan. A vacuum oven capable of
8.4.3 Procedure—Fill the graduated cylinder with PTFE operating at 150°C (362°F) and an absolute pressure of 48 mm
dispersion to float the hydrometer. Place the hydr
...
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