ASTM D4895-18(2023)

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: D4895 − 18 (Reapproved 2023)
Standard Specification for
Polytetrafluoroethylene (PTFE) Resin Produced From
Dispersion
This standard is issued under the fixed designation D4895; 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 2. Referenced Documents
2.1 ASTM Standards:
1.1 This specification covers polytetrafluoroethylene
D618 Practice for Conditioning Plastics for Testing
(PTFE) prepared by coagulation of a dispersion. These PTFE
D638 Test Method for Tensile Properties of Plastics
resins are homopolymers of tetrafluoroethylene or modified
D792 Test Methods for Density and Specific Gravity (Rela-
homopolymers containing not more than 1 % by weight of
tive Density) of Plastics by Displacement
other fluoromonomers. The materials covered herein do not
D883 Terminology Relating to Plastics
include mixtures of PTFE with additives such as colors, fillers,
D1708 Test Method for Tensile Properties of Plastics by Use
or plasticizers; nor do they include reprocessed or reground
of Microtensile Specimens
resin or any fabricated articles because the properties of such
D1895 Test Methods for Apparent Density, Bulk Factor, and
materials have been irreversibly changed when they were
Pourability of Plastic Materials
fibrillated or sintered.
D3892 Practice for Packaging/Packing of Plastics
1.2 The values stated in SI units as detailed in IEEE/ASTM
D4052 Test Method for Density, Relative Density, and API
SI-10 are to be regarded as standard. The values given in
Gravity of Liquids by Digital Density Meter
parentheses are for information only.
D4441 Specification for Aqueous Dispersions of Polytet-
1.3 The following safety hazards caveat pertains only to the
rafluoroethylene
Specimen Preparation Section, Section 9, and the Test Methods
D4591 Test Method for Determining Temperatures and
Section, Section 10, of this specification: This standard does
Heats of Transitions of Fluoropolymers by Differential
not purport to address all of the safety concerns, if any,
Scanning Calorimetry
associated with its use. It is the responsibility of the user of this
D4894 Specification for Polytetrafluoroethylene (PTFE)
standard to establish appropriate safety, health, and environ-
Granular Molding and Ram Extrusion Materials
mental practices and determine the applicability of regulatory
E11 Specification for Woven Wire Test Sieve Cloth and Test
limitations prior to use. See Warning note in 9.1.1 for a specific
Sieves
hazards statement.
E29 Practice for Using Significant Digits in Test Data to
Determine Conformance with Specifications
NOTE 1—Information in this specification is technically equivalent to
E177 Practice for Use of the Terms Precision and Bias in
related information in ISO 20568-1 and ISO 20568-2.
ASTM Test Methods
1.4 This international standard was developed in accor-
IEEE/ASTM SI-10 Use of the International System of Units
dance with internationally recognized principles on standard-
(SI): The Modern Metric System
ization established in the Decision on Principles for the
2.2 ISO Standards:
Development of International Standards, Guides and Recom-
ISO 20568-1 Plastics Fluoropolymer Dispersions and Mold-
mendations issued by the World Trade Organization Technical
ing and Extrusion Materials—Part 1: Designation and
Barriers to Trade (TBT) Committee.
Specification
ISO 20568-2 Plastics Fluoropolymer Dispersions and
Molding and Extrusion Materials—Part 2: Preparation of
This specification is under the jurisdiction of ASTM Committee D20 on
Plastics and is the direct responsibility of Subcommittee D20.15 on Thermoplastic
Materials. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved May 1, 2023. Published May 2023. Originally contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
approved in 1989. Last previous edition approved in 2018 as D4895 – 18. DOI: Standards volume information, refer to the standard’s Document Summary page on
10.1520/D4895-18R23. the ASTM website.
2 4
Specifications for other forms of polytetrafluoroethylene are found in Specifi- Available from American National Standards Institute (ANSI), 25 W. 43rd St.,
cations D4441 and D4894. 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
D4895 − 18 (2023)
Test Specimens and Determination of Properties 4. Classification
ISO 13322-2 Particle size analysis—Image analysis
4.1 This specification covers the following types of PTFE:
methods—Part 2: Dynamic image analysis methods
4.1.1 Type I and Type II—Resin produced from dispersion.
Each type of resin has the same requirements for bulk density,
3. Terminology
particle size, water content, melting peak temperature, tensile,
3.1 Definitions—The definitions given in Terminology
and elongation. Each type of resin is divided into grades in
D883 are applicable to this specification.
accordance with standard specific gravity (SSG), Thermal
3.2 Definitions of Terms Specific to This Standard:
Stability Index (TII), and Stretching Void Index (SVI). Grades
3.2.1 bulk density, n—the mass in grams per litre of resin
are divided into classes according to extrusion pressure.
measured under the conditions of the test.
NOTE 2—See Tables 1 and 2 for details about grades and classes.
3.2.2 extended specific gravity (ESG), n—the specific grav-
4.2 A line callout system is used to specify materials in this
ity of a specimen of PTFE material molded as described in this
specification. The system uses predefined cells to refer to
specification and sintered (see 3.2.7) for an extended period of
specific aspects of this specification, as illustrated as follows:
time, compared to the sintering time for the measurement of
SSG (see 3.2.8), using the appropriate sintering schedule given
in this specification.
3.2.3 lot, n—one production run or a uniform blend of two
Specification
or more production runs.
Standard Number Type Grade Class Special Notes
3.2.4 preforming, vb—compacting powdered PTFE material
Block
under pressure in a mold to produce a solid object, called a
| | | | |
preform, that is capable of being handled. Molding and
Example: Specification I 2 C
compaction are terms used interchangeably with preforming
D4895 - XX
for PTFE.
3.2.5 reground resin, n—resin produced by grinding PTFE
material that has been preformed but has never been sintered.
For this example, the line callout would be Specification
3.2.6 reprocessed resin, n—resin produced by grinding
D4895 - XX, I2C, and would specify a coagulated dispersion
PTFE material that has been preformed and sintered.
form of polytetrafluoroethylene that has all of the properties
listed for that type, grade, and class in the appropriate specified
3.2.7 sintering, n—as it applies to PTFE, a thermal treat-
properties or tables, or both, in the specification identified. A
ment during which the PTFE is melted and recrystallized by
comma is used as the separator between the standard number
cooling with coalescence occurring during the treatment.
and the type. Separators are not needed between the type,
3.2.8 standard specific gravity (SSG), n—the specific grav-
grade, and class.
ity of a specimen of PTFE material molded as described in this
specification and sintered using the appropriate sintering
5. Mechanical Properties
schedule given in this specification.
5.1 The resins covered by this specification shall be in
3.2.9 strained specific gravity (strained SG), n—the specific
accordance with the requirements prescribed in Tables 1 and 2,
gravity of a specimen of PTFE material molded, sintered, and
when tested by the procedures specified herein.
strained as described in this specification.
3.2.10 stretching void index (SVI), n—a measure of the
6. Other Requirements
change in specific gravity of PTFE material which has been
subjected to tensile strain as described in this specification. 6.1 The resin shall be uniform and shall contain no additives
or foreign material.
3.2.11 thermal instability index (TII), n—a measure of the
decrease in molecular weight of PTFE material which has been
6.2 The color of the material as shipped by the supplier shall
heated for a prolonged period of time.
be natural white.
3.2.12 unstrained specific gravity (USG), n—the specific
gravity, prior to straining, of a specimen of PTFE material used
in the Stretching Void Index Test (see 10.9) of this specifica- 5
See the Form and Style for ASTM Standards manual, available from ASTM
tion. Headquarters.
A
TABLE 1 Detail Requirements for all Types, Grades and Classes
Melting Peak
Particle Size
Bulk Density, Water Content, Tensile Strength, Elongation at Break,
Temperature, °C
Type Average
g/L max, % min, MPa min, %
Diameter, μm
Initial Second
B
I 550 ± 150 500 ± 200 0.04 327 ± 10 19 200
B
II 550 ± 150 1050 ± 350 0.04 327 ± 10 19 200
A
The types, grades, and classes are not the same as those in previous editions of Specification D4895.
B
Greater than 5.0°C above the second melting peak temperature.
D4895 − 18 (2023)
A
TABLE 2 Detail Requirements for All Types, Grades and Classes
Standard Specific Gravity
Thermal Instability Index, Stretching Void Index,
Type Grade Class Extrusion Pressure, MPa
max max
min max
B C
I 1 A 2.14 2.18 5 to <15 50 NA
D C
B 2.14 2.18 15 to <55 50 NA
E C
C 2.14 2.18 15 to <75 50 NA
B C
2 A 2.17 2.25 5 to <15 50 NA
D C
B 2.17 2.25 15 to <55 50 NA
E C
C 2.17 2.25 15 to <75 50 NA
E
3 C 2.15 2.19 15 to <75 15 200
E
D 2.15 2.19 15 to <65 15 100
E
E 2.15 2.19 15 to <65 50 200
D
4 B 2.14 2.16 15 to <55 15 50
B C
II 1 A 2.14 2.25 5 to <15 50 NA
A
The types, grades, and classes are not the same as those in previous editions of Specification D4895.
B
Tested at a reduction ratio of 100:1 (reduction ratio is the ratio of the cross-sectional area of the preform to the cross-sectional area of the die).
C
Not applicable.
D
Tested at a reduction ratio of 400:1.
E
Tested at a reduction ratio of 1600:1.
NOTE 3—For maximum precision, these weighing and preforming
6.3 For purposes of determining conformance, all specified
operations shall be carried out at 23 6 2°C (73.4 6 3.6°F) (the “near
limits for this classification system are absolute limits, as
ambient” temperature referred to herein). These operations shall not be
defined in Practice E29.
performed at temperatures below 21°C (70°F) due to the crystalline
6.3.1 With the absolute method, an observed value is not
transition that occurs in PTFE in this temperature region which leads to
rounded, but is to be compared directly with the limiting value.
possible cracks in sintered specimens and differences in specimen density
(as well as changes in other physical properties). Problems caused by the
Example: In Table 2 Type I, Grade 4, Class B, under Specific
effect of temperature on the specific gravity or density of PTFE shall be
Gravity, 2.14 shall be considered as 2.140000 and 2.16 shall be
minimized when the measurement is made using immersion procedures if
considered 2.160000.
a sensitive thermometer (for example, one reading 6 0.1°C) is used in the
liquid and the temperature is adjusted to be at least 22°C.
7. Sampling
9.1.2 Screen 14.5 g of PTFE resin through a No. 10 sieve
7.1 Sampling shall be statistically adequate to satisfy the
into the die. Adjust the lower plug height to allow the resin in
requirements in Section 11.
the die can be leveled by drawing a straightedge in contact with
the top of the die across the top of the die cavity. Insert the die
8. Number of Tests
in a suitable hydraulic press and apply pressure gradually (see
8.1 Lot inspection shall include tests for bulk density,
Note 4) until a pressure of 14 MPa (2030 psi) is attained. Hold
particle size, and extrusion pressure. Periodic tests shall consist
this pressure for 3 min. Remove the disk from the die. Write the
of all the tests specified in Tables 1 and 2 and shall be made at
sample identification number on the preform using an appro-
least once per year.
priate marker that will not affect the PTFE during sintering.
8.2 The tests listed in Tables 1 and 2, as they apply, are
NOTE 4—As a guide, increasing the pressure at a rate of 3.5 MPa (500
sufficient to establish conformity of a material to this specifi-
psi)/min is suggested until the desired maximum pressure is attained.
cation. One set of test specimens as prescribed in Section 9
9.1.3 Place the sintering oven in a laboratory hood (or equip
shall be considered sufficient for testing each sample. The
it with an adequate exhaust system) and sinter the preforms in
average of the results for the specimens tested shall conform to
accordance with Table 3, Procedure A (see Note 5).
the requirements of this specification.
NOTE 5—Although the rate of heat application is not critical, the
9. Specimen Preparation cooling cycle is most important and the conditions cited in this procedure
must be followed very closely. If they are not followed, the crystallinity of
9.1 Test Disks for Tensile Properties:
the disks and the resulting physical properties will be markedly changed.
9.1.1 Use the die shown in Fig. 1 for the molding of test
Therefore, the use of a programmed oven is recommended for the most
precise sintering cycle control and the hood window shall be left down
disks (see Note 2). Place flat aluminum disks, 0.1 to 0.4 mm
during the entire sintering procedure, the latter being an important safety
(0.004 in. to 0.016 in.) thick and 76 mm (3 in.) in diameter, on
consideration.
both sides of the resin. The test resin shall be near ambient
9.2 Test Specimens for Standard Specific Gravity and Ther-
temperature prior to molding (see Note 3). (Warning—PTFE
mal Instability Index:
resins can evolve small quantities of gaseous products when
heated above 204°C (400°F). Some of these gases are harmful. 9.2.1 A cylindrical preforming mold, 29-mm (1.14-in.) in-
Consequently, exhaust ventilation must be used whenever ternal diameter by at least 76 mm (3 in.) deep, is used to
these resins are heated above this temperature, as they are prepare the preforms. Clearance shall be sufficient to ensure
during the sintering operations that are a part of this specifi- escape of air during pressing. Place flat aluminum foil disks,
cation. Since the temperature of burning tobacco exceeds normally 0.13 mm (0.005 in.) thick and 29 mm (1.14 in.) in
204°C (400°F), those working with PTFE resins shall ensure diameter on both sides of the resin. The test resin shall be near
that tobacco is not contaminated.) ambient temperature prior to molding (see Note 3).
D4895 − 18 (2023)
NOTE 1—All dimensions are in millimetres.
FIG. 1 Mold Assembly for the Preparation of Specimens for the Determination of Tensile Properties
TABLE 3 Sintering Procedures
9.2.3.1 For SSG specimens use Procedure A.
A B
9.2.3.2 For ESG specimens use Procedure B.
Initial temperature, °C (°F) 290 (554) 290 (554)
NOTE 6—Improved precision in SSG and ESG test results has been
Rate of heating, °C/h (°F/h) 120 ± 10 120 ± 10
(216 ± 18) (216 ± 18) obtained with the use of an upright, cylindrical oven and an aluminum
Hold temperature, °C (°F) 380 ± 6 380 ± 6
sintering rack. The cylindrical oven has an inside diameter of 140 mm (5.5
(716 ± 10) (716 ± 10)
in.) and an inside depth of 203 mm (8 in.) plus additional depth to
Hold time, min 30 + 2, −0 360 ± 5
accommodate a 51-mm (2-in.) thick cover, and is equipped with suitable
Cooling rate, °C/h (°F/h) 60 ± 5 60 ± 5
heaters and controllers to sinter specimens in accordance with the
(108 ± 9) (108 ± 9)
procedures in Table 3. The rack, as shown in Fig. 2, allows preforms to be
Second hold temperature, °C (°F) 294 ± 6 294 ± 6
placed symmetrically in the center region of the oven. Place six preforms
(561 ± 10) (561 ± 10)
on each of the middle oven rack shelves (if six or fewer preforms are to
Second hold time, min 24 + 0.5, −0 24 + 0.5, −0
be sintered, place them on the middle rack, filling in with “dummies” as
Period to room temperature, min $30 $30
needed). Place “dummies” on the top and bottom shelves. Specimens must
be spaced evenly in a circle on each shelf, with none of them touching. An
oven load must be no less than 18 pieces including “dummies.” “Dum-
mies” are defined as normal 12-g specimens that have previously been
9.2.2 Weigh out 12.0 6 0.1 g of resin and place it in the die.
through the sintering cycle. “Dummies” must only be used for an
Screen resins through a No. 10 sieve. Compacted resins shall additional two or three thermal cycles, due to eventual loss of thermal
stability and physical form.
be broken up by hand-shaking cold resin in a half-filled sealed
glass container. Condition the resin in the sealed glass con-
9.2.4 Remove all flash from each specimen so that no air
tainer in a freezer or dry-ice chest. After breaking up resin
bubbles will cling to the edges when the specimen is immersed
lumps, allow the sealed container to equilibrate to near ambient
in the solution for weighing during the standard specific gravity
temperature. Then screen and weigh the 12.0 6 0.1-g sample.
and thermal instability index tests. It is recommended for this
Insert the die in a suitable hydraulic press and apply pressure
section and during testing that cotton gloves be worn while
gradually (see Note 4) until a pressure of 14 MPa (2030 psi) is
handling test specimens.
attained. Hold this pressure for 2 min. Remove the preform
9.3 Test Disks for Stretching Void Index (SVI):
from the die. Write the sample identification number on the
9.3.1 Mold the disk as in 9.1.1.
preform using an appropriate marker that will not effect the
PTFE during sintering. 9.3.2 Screen 29 g of PTFE resin through a 2.00-mm (No.
9.2.3 Sinter the preforms in accordance with Table 3 (see 10) sieve into the die. Adjust the lower plug to allow the resin
Note 5). to be leveled by drawing a straightedge in contact with the top
D4895 − 18 (2023)
deviation from the standard laboratory temperature is made
because of the necessity for maintaining test temperatures
above approximately 21°C (70°F). See Note 3 for additional
details. Since these resins do not absorb water, the maintenance
of constant humidity during testing is not required.
10. Test Methods
10.1 Melting Characteristics by Thermal Analysis:
10.1.1 Significance and Use—For PTFE resins that have
been melted prior to use, the melting peak temperature char-
acteristics of a resin provide important information about the
thermal history of the material. Melting peak temperatures (see
Fig. 3) are used to determine conformance of a resin to the
melting peak temperature requirements in Table 1 of this
specification.
10.1.2 Apparatus—Use apparatus described in Test Method
D4591.
10.1.3 Procedure—Measure melting peak temperatures in
accordance with procedures given in Test Method D4591. An
initial melting peak temperature above the melting peak
temperature obtained on the second and subsequent melting
(defined as the second melting peak temperature) indicates that
the resin was not melted before the test. The second melting
peak temperature occurs at about 327°C (621°F). The differ-
ence between the initial and second melting peak temperatures
NOTE 1—Aluminum plates tack welded to rods.
is greater than 5°C (9°F). If peak temperatures are difficult to
NOTE 2—All dimensions are in millimetres.
discern from the curves (that is, because the peaks are rounded
FIG. 2 Sintering Rack for SSG Specimens
rather than pointed) straight lines should be drawn tangent to
the sides of the peak. These lines intersect at the peak
temperature. Where more than one peak occurs during the
of the die across the top of the die cavity. Insert the die in a
initial melting test, the presence of any peak corresponding to
suitable hydraulic press and apply pressure gradually (see Note
the second melting peak temperature indicates the presence of
4) until a pressure of 7 MPa (1015 psi) is attained. Hold this
some previously melted material.
pressure for 2 min, then increase the pressure to 14 MPa (2030
psi) and hold for an additional 2 min. Remove the disk from the
10.2 Bulk Density:
die. Write the sample identification number on the preform
10.2.1 Significance and Use—Bulk density gives an indica-
using an appropriate marker that will not effect the PTFE
tion of how a resin performs during the filling of processing
during sintering.
equipment. PTFE resins tend to compact during shipment and
9.3.3 Sinter the preforms in accordance with Table 3,
storage. Because of this tendency to pack under small amounts
Procedure A (see Note 5).
of compression or shear, Test Method D1895 is not applicable
9.3.4 Remove all flash from those portions of these speci-
mens that will be used for determination of specific gravities so
that no air bubbles will cling to their edges when the specimens
are immersed in liquid during these tests. It is recommended
that cotton gloves be worn while handling test specimens.
9.4 Conditioning Test Specimens:
9.4.1 For tests of tensile properties and all tests requiring the
measurement of specific gravities, condition the test specimens
in general accordance with Procedure A of Practice D618, with
the following deviations therefrom: (1) the aging period shall
be a minimum of 4 h immediately prior to testing, (2) the
laboratory temperature shall be 23 6 2°C (73.4 6 3.6°F), and
(3) there shall be no requirement respecting humidity. The
other tests require no conditioning of the molded test speci-
mens.
9.5 Test Conditions:
9.5.1 Tests shall be conducted at the standard laboratory
temperature of 23 6 2°C (73.4 6 3.6°F), unless otherwise
specified in the test methods or in this specification. This FIG. 3 Melting Characteristics by Thermal Analysis
D4895 − 18 (2023)
to these resins. The procedure given in 10.2.2 through 10.2.5 10.2.2.6 Work Surface—The work surface for holding the
must be used to measure this property. volumetric cup and leveler shall be essentially free from
10.2.2 Apparatus:
vibration. The feeder, therefore, must be mounted on an
10.2.2.1 Funnel—A funnel arrangement as shown in Fig. 4.
adjoining table or wall bracket.
10.2.2.2 Feeder —A feeder with a No. 8 wire screen placed
10.2.2.7 Balance—Balance, having an extended beam, with
over approximately the top two thirds of the trough. The funnel
a capacity of 500 g and a sensitivity of 0.1 g, or equivalent.
shall be mounted permanently in the feeder outlet.
10.2.3 Procedure—Place the clean, dry volumetric cup on
10.2.2.3 Controller
the extended beam of the balance and adjust the tare to zero.
10.2.2.4 Volumetric Cup and Cup Stand (see Fig. 5)—The
Select about 500 mL of the resin to be tested and place it on the
volumetric cup shall be calibrated initially to 250 mL by filling
feeder screen. Put the cup in the cup stand and place the
it with distilled water, placing a planar glass plate on top,
assembly such that the distance of free-polymer fall from the
drying the outside of the cup, and weighing. The net weight
feeder outlet to the top rim of the cup shall be 39 6 3 mm
shall be 250 6 0.5 g. The top and bottom faces of the
(1.5 6 0.012 in.). Increased fall causes packing in the cup and
volumetric cup and the cup stand shall be machined plane and
parallel. higher bulk density values. Set the controller so that the cup is
10.2.2.5 Leveling Device—The leveler (see Fig. 6) shall be
filled in 20 to 30 s. Pour the sample on the vibrating screen and
affixed permanently to the table and adjusted so that the
fill the cup so that the resin forms a mound and overflows. Let
sawtooth edge of the leveler blade passes within 0.8 mm (0.031
the resin settle for about 15 s and then gently push the cup and
in.) of the top of the volumetric cup.
its stand beneath the leveler. Exercise care to avoid agitation of
the resin and cup before leveling. Weigh the resin to the nearest
0.1 g.
6 10.2.4 Calculation—Calculate the bulk density as follows:
A “Vibra-Flow” Feeder, Type FT01A, available from FMC Corp., Material
Handling Division, FMC Building, Homer City, PA 15748, has been found
satisfactory for this purpose.
grams of resin × 4 5 bulk density grams per litre
A “Syntron” controller, Type SCR1B, available from FMC Corp., address as ~ !
shown in Footnote 10, has been found satisfactory for this purpose.
NOTE 1—Funnel Material: type 304 Stainless Steel 16 Gage (1.6-mm thickness).
NOTE 2—All dimensions are in millimetres.
FIG. 4 Details of the Funnel Used for the Determination of Bulk Density
D4895 − 18 (2023)
NOTE 1—All dimensions are in millimetres.
FIG. 5 Volumetric Cup and Cup Stand for the Determination of Bulk Density
NOTE 1—Base plate must be flat and parallel. Saw blade, when mounted, must be square to and parallel with base plate within 0.13 mm from end to
end. Height of saw blade must have 0.8 mm or less clearance between blade and assembled cup and cup stand (as indicated by phantom lines). Welded
construction where indicated. Material: as noted.
NOTE 2—All dimensions are in millimetres.
FIG. 6 Leveler Stand for the Determination of Bulk Density
D4895 − 18 (2023)
10.2.5 Precision and Bias—A precision statement for use will not condense on the sample during this test. Determine the
with this procedure is under development. The procedure in weight of resin retained on each sieve.
this test method has no bias because the value of bulk density
10.3.4 Calculation:
shall be defined only in terms of a test method.
10.3.4.1 Calculate the net percentage of resin on each sieve
as follows:
10.3 Particle Size:
10.3.1 Significance and Use—The fabrication of PTFE res-
ins is affected significantly by particle (or agglomerate) size
net percentage on sieve Y 5 2 × weight of resin in grams on sieve Y.
and size distribution. The average particle size of PTFE resins
10.3.4.2 Calculate the cumulative percentage of resin on
is determined by f
...