Note: Descriptions are shown in the official language in which they were submitted.
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METHOD FOR INCORPORATING POLYTETRAFLUOROETHYLENE
(PTFE) INTO SYNTHETIC MELT SPUN FIBERS TO PRODUCE FIBERS
AND TEXTILES HAVING IMPROVED PROPERTIES
SPECIFICATION
CROSS REFERENCE TO RELATED APPLICATION
The present application claims priority from U.S. Provisional Patent
Application No. 601415,039 filed October I, 2002, the disclosure of which is
I O incorporated herein by reference in its entirety.
FIELD OF THE INVENTION
The present invention generally relates to a method for incorporating
highly dispersible polytetrafluoroethylene (PTFE) powder into synthetic melt
spun
fibers so that the resulting fibers have the improved properties generally
associated
with PTFE, including, for example, low coefficient of friction, improved wear
resistance, improved stain resistance and improved light stability and LTV-
light
resistance, when compared to conventional melt spun fibers. The present
invention
further relates to melt spun fibers made by the method described herein and
textiles,
fabrics, and articles of manufacture, made from these synthetic melt spun
fibers
BACKGROUND OF THE INVENTION
In the textile industry, apparel manufacturers and fiber producers are
constantly trying to modify the basic composition of each generic type of
synthetic
fiber, both chemically and physically, in order to produce fiber variations
which
provide softer feel, greater comfort, brighter and longer lasting colors,
better warmth
or cooling, better moisture transport or wicl~ing, and better blending
properties when
blended with other fibers. "FabricLinlc, Fabric University - Fabric Producers
and
Trademarks," <http://www.fabriclink.com/Producers.html>. Thus, a constant need
exists in the art of fiber production for new and innovative ways to improve
the
properties of synthetic fibers.
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Various manufacturing processes are known in the art for making
synthetic fibers. Many synthetic fibers are created by extrusion, whereby a
thick
viscous liquid polymer precursor or composition is forced through the tiny
holes of a
spinneret to form continuous filaments of semi-solid polymer. As the filaments
emerge from the holes of a spinneret, the liquid polymer is converted ftrst to
a rubbery
state and then is solidified. The process of extruding and solidifying
filaments is
generally known as spinning. Common methods of spinning filaments of melt-spun
synthetic fibers are generally referred to as "melt spinning."
Typically, for melt spinning processes, a fiber-forming substance is
melted to a viscose liquid state for extrusion through the spinneret. After
extrusion
from the spinneret the fiber material or filament is solidified by air-
cooling. Fibers
typically formed by melt spimung include polyester, nylon, and polypropylene,
among others.
Polyester fiber, one of the more common melt spun fibers, is defined
by the Federal Trade Commission as a manufactured fiber in which the fiber-
forming
substance is any long-chain synthetic polymer composed of at least 85% by
weight of
an ester of a substituted aromatic carboxylic acid. Polyester fiber is
commonly
produced by extruding (or spinning) a polyester melt at a high pressure (for
example,
3,000 psig) and a high temperature (for example, 500° F) through
spinnerets having
multiple openings. Once extruded, the polyester fibers are drawn and textured
to the
desired f ber characteristics. Micro contaminants are removed from the molten
polyester stream or feed prior to fiber spinning to preclude blockage of the
small
spinneret holes, which are typically about 25-500 ~,m in diameter. For low
denier
fibers, even small size contaminants or particles must be removed from the
melt prior
to extrusion. "Pall Corporation - Polyester Fiber Production,"
<http://domino.pall.com/www/weblib.nsf/pub/354559E3AFA95F9885256863004BF4
C4?opendocument.>
Additives (e.g., dyes and surfactants) may be added to the polymer or
fiber-forming substance (such as a polyester melt) prior to extrusion in order
to
improve the quality or characteristics of the resulting melt spun fibers.
Until the
present invention, however, it has not been shown that the addition of
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polytetrafluoroethylene (PTFE) powder (where the powder is dispersible to low
micron or submicron particle size or where the PTFE powder particles have a
primary
particle size that is low micron or submicron range) to the fiber-forming
substance
may be of any benefit in forming improved melt spun fibers.
It is generally known that PTFE provides characteristics such as
improved slipperiness and non-wettability to materials into which it is
incorporated.
PTFE is useful when in a powder form or an aqueous or organic dispersion form
for
this purpose. Dry PTFE powder products are known in the art and are generally
available in the industry. Several manufacturers in the fluoropolymer industry
produce PTFE powders, and some of these manufacturers describe the PTFE
particle
size in their powders as being "submicron" or capable of being dispersed to
submicron
size.
A wide array of end uses exists fox small particle size or submicron
PTFE. For example, small amounts (e.g., about 0.1 to 2% by weight) of powdered
PTFE may be incorporated into a variety of compositions to provide the
following
favorable and beneficial characteristics: (i) in inks, PTFE provides excellent
mar and
rub resistance characteristics; (ii) in cosmetics, PTFE provides a silky feel;
(iii) in
sunscreens, PTFE provides increased shielding from UV xays or increased SPF
(sun
protection factor); (iv) in greases and oils, PTFE provides superior
lubrication; and (v)
in coatings and thermoplastics, PTFE provides improved abrasion resistance,
chemical resistance, weather resistance, water resistance, and film hardness.
Other, more specific end uses for submicron PTFE powders and
dispersions include: (i) incorporating a uniform dispersion of submicron PTFE
particles into electroless nickel coatings to improve the friction and wear
characteristics of such coatings (Hadley et al., Metal Finislai~zg, 85:51-53
(December
1987)); (ii) incorporating submicron PTFE particles into a surface finish
layer for an
electrical connector contact, wherein the PTFE particles provide wear
resistance to the
surface finish layer (U.S. Patent No. 6,274,254 to Abys et al.); (iii) using
submicron
PTFE particles in a film-forming binder as a solid lubricant in an interfacial
layer,
wherein the interfacial layer is part of an optical waveguide fiber (U.S.
Patent No.
5,181,268 to Chien); (iv) using a submicron PTFE powder (along with a
granulated
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PTFE powder and Ti02) in a dry engine oil additive, wherein the additive
increases
the slip characteristics of the load bearing surfaces (LJ.S. Patent No.
4,888,122 to
McCready); and (v) combining submicron PTFE particles with autocatalytically-
applied nickel/phosphorus for use in a surface treatment system for metals and
metal
alloys, wherein the PTFE imparts lubrication, low fi-iction, and wear
resistance to the
resulting surface ("Niflor Engineered Composite Coatings," Hay N.
International, Ltd.
(1989)). Additional specific examples of end uses for PTFE involve
incorporating
PTFE into engine oils, using PTFE as a thickener in greases, and using PTFE as
an
industrial lubricant additive. Willson, Industs°ial Lubrication arad
Ti°ibology, 44:3-5
(March/Apri11992).
For many applications or end uses incorporating submicron PTFE
powders and submicron PTFE dispersions (such as the end uses described above),
the
beneficial effects imparted to the application or end use system derive from
the
chemical inertness of the PTFE particles and/or the low coefficient of
friction of the
PTFE particles. In addition, submicron PTFE particles that have a low particle
size,
possess a significantly higher ratio of active surface area to weight when
compared to
larger PTFE particles. Thus, submicron PTFE particles axe better able to
propagate
their beneficial effects to a desired application system than the same weight
of larger
size PTFE particles.
In light of the above discussions of the constant need in the fiber
industry for making synthetic fibers having improved properties and the
usefulness of
PTFE in various applications, it is evident that a need exists in the art for
a convenient
and inexpensive method by which PTFE, specifically PTFE powder that is
dispersible
to low micron or submicron particle size, may be incorporated into a fiber-
forming
substance so that, for example, fibers that are spun by a melt spinning
process possess
the improved properties associated with PTFE. Furthermore, a need exists for a
method of incorporating low micron or submicron PTFE particles uniformly and
permanently throughout a melt spun fiber (as opposed to mere surface coatings)
so
that textiles, fabrics and clothing made from such fibers will not lose, over
time, the
beneficial properties associated with PTFE due to surface wear and tear. The
present
invention addresses these and other needs.
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SUMMARY OF THE INVENTION
The present invention relates to a novel method by which
polytetrafluoroethylene (PTFE) is incorporated into a synthetic melt spun
fiber so that
the resulting fiber has many improved properties when compared to conventional
melt
spun fibers. In the present method, PTFE powder that is dispersible to low
micron or
submicron particle size is incorporated into the desired fiber-forming
substance (such
as a polyester melt) from which filaments or fibers are made by a melt
spinning
process. The resulting "PTFE-enhanced" melt spun fibers have PTFE particles
dispersed through out their filament bodies. These PTFE-enhanced melt spun
fibers
in which PTFE is incorporated directly into the filament bodies have improved
properties associated with PTFE. For example, the melt spun fibers resulting
from the
method of the present invention may exhibit a significant decrease in the
coefficient
of friction when compared to conventional melt spun fibers.
The use of low micron or submicron particle size PTFE powder as an
additive to the polymers or fiber-forming substances used to make certain
synthetic
fibers is important in that the PTFE improves the non-wetting properties of
the fibers
and textiles made from such fibers. Thus, fibers incorporating PTFE may be
useful in
making textiles that are used for making industrial filtration and dewatering
devices.
Such fibers incorporating PTFE also may be advantageously used in producing
carpets, fabrics for sportswear and outerwear, hot-air balloons, car aazd
plane seats,
umbrellas, and the like. Furthermore, the fibers of the present invention also
may be
advantageously used to make tightly woven fabrics that are used in parachutes,
boat
sails, and similar applications. The combination of a tight weave and water
shedding
may provide a textile or clothing fabric that is both water shedding and
breathable.
The incorporation of PTFE into such textiles may result in other advantages,
such as
the textile articles being easier to clean.
The method of the present invention is useful in that the resulting
PTFE-enhanced melt spun fibers have several improved properties when compared
to
conventional synthetic melt spun fibers. The improved properties include but
are not
limited to the following: lower coefficient of friction; reduced wettability;
improved
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stain resistance; improved washability; improved opacity; enhanced protection
from
ultraviolet (UV) radiation (which increases the light-fastness and the
lifetime of the
fiber or fabric); increased color fastness; reduced gas permeability; better
abrasion
resistance; tighter weave; improved wear index; increased flexibility of the
fiber;
decreased scroop (where scroop generally refers to sounds of rubbing made by
certain
fabrics); and lowered amounts of wrinkling when the PTFE-enhanced fibers are
incorporated into a fabric or clothing article.
Additionally, not only does the method of the present invention result
in improved melt spun fibers, but also the method serves to significantly
improve the
overall processes by which melt spun synthetic fibers are typically made. For
example, the increased Iubricity or slipperiness of the fiber-forming
substance due to
the addition of PTFE in it may result in Iower production times for fiber
production,
significantly increased processing speeds, increased throughput rates and
overall
production rates. The increased lubricity of the fiber-forming materials due
to the
PTFE addition also may give a longer lifetime to the fiber-making equipment,
and
provide overall savings in energy that is expended in naming the fiber-making
equipment.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a bar graph comparing the tensile strength of PTFE-enhanced
fibers prepared in accordance with the present invention and conventional
fibers ,after
both were exposed to radiation.
FIG. 2 is a bar graph illustrating the relative tensile strength of the
fibers of FTG. 1
FIG. 3 is a bar graph illustrating the static and kinetic coefficients of
friction of a fabric made of PTFE-enhanced fibers prepared in accordance with
the
present invention and the static and kinetic coefficients of friction of a
fabric made of
conventional fibers.
FIG. 4 is a bar graph comparing the static and kinetic coefficients of
friction of another fabric made of PTFE-enhanced fibers prepared in accordance
with
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the present invention and the static and kinetic coefficients of friction of a
fabric made
of conventional fibers.
DETAILED DESCRIPTION OF THE INVENTION
The present invention relates to a method for producing improved melt
spun fibers, wherein the fibers are more wear resistant and have a lower
coefficient of
friction than melt spun fibers that are known in the art. The method of
present
invention improves the quality of a melt spun fiber by introducing PTFE that
is
dispersible to low micron or submicron particle size into the polymer or fiber-
forming
substance as a fiber is being formed by a melt spinning process. The PTFE-
enhanced
melt spun fibers that are produced by the method of the present invention
exhibit,
among other properties, increased wear resistance, stain resistance, water
resistance,
and a significantly decreased coefficient of friction, when compared to
conventional
melt spun fibers known in the art.
A r esult of the present invention is the incorporation of PTFE
throughout a melt spun fiber so that the fiber material contains a homogeneous
distribution of PTFE particles. This may be contrasted with processes and
fibers
known in the ant where PTFE is applied only on the surface of melt spun fibers
or
only on the surface of a fabric made from melt spun fibers and thus can wear
away.
In preferred embodiments of the method of the present invention, the
following types of PTFE are useful: PTFE powder that is dispersible to
submicron
particle size; PTFE powder that is dispersible to low micron particle size;
aqueous or
organic dispersions of PTFE powder that is dispersible to submicron particle
size; and
aqueous or organic dispersions of PTFE powder that is dispersible to low
micron
particle size. One specific type of PTFE that may be useful in the method of
the
present invention is the PTFE described in co-assigned International Patent
Application No. PCT/LTS03/07978 filed on March 14, 2003, which is hereby
incorporated by reference herein in its entirety.
In the present description, the designation "submicron particle size"
indicates that a given quantity of PTFE powder disperses in isopropyl alcohol
(1PA)
such that more than about 90%, preferably, more than about 95%, and more
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preferably, more than about 99% of the PTFE particles have a particle size
that is less
than about 1.00 ~.m. Furthermore, the designation "low micron particle size"
indicates
that a given quantity of PTFE powder disperses in isopropyl alcohol (IPA) such
that
about 95% or more of the PTFE particles have a particle size that is less than
about
10.00 ~.m.
The dispersibility of the PTFE powder down to low micron or
submicron-sized particles may be important for unhindered practice of melt
spinning
processes. These small size PTFE particles may pass through spinneret holes
with
ease, unlike large sized PTFE particles that can clog spinnerets making fiber
ZO formation difficult. It is also envisioned that the method of the present
invention
allows for PTFE that is dispersible to low micron particle size to be used in
higher
denier fibers, while PTFE that is dispersible to submicron particle size will
be useful
for forming both low and high denier fibers. The PTFE particles may be
uniformly or
homogeneously dispersed through the bodies of the fiber of any denier size.
The dispersibility of the PTFE particles in a powder may be
determined by dispersing an amount of the PTFE powder in isopropyl alcohol
(IPA).
Then by conventional particle size analysis (e.g., light scattering analysis),
an
indication of the mean particle size and the particle size distribution of the
PTFE
powder may be obtained. Thus a user can verify or confirm, for example, if a
sample
of PTFE powder is completely (100%) dispersible to submicron in size or is
otherwise
suitable for use in melt spinning processes.
As mentioned above, aqueous or organic dispersions of PTFE powder,
where the powder is dispersible either to submicron particle size or low
micron
particle size, may be used in the method of the present invention. PTFE
dispersions
that are most useful in the present method typically comprise from about 20%
to
about 60% PTFE by weight. Alternatively, dry PTFE powder that is dispersible
either
to submicron or low micron particle size may be dispersed directly into the
fiber-
forming substance.
Fiber-forming polymer substances that are contemplated for use in the
present invention include but are not limited to polyester, nylon, and
polypropylene,
among other fiber-forming thermoplastic resins.
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In certain preferred embodiments, PTFE powder that is dispersible
either to low micron or subrnicron particle size is first provided.
Subsequently, the
PTFE is incorporated into the fiber-forming polymer to be used in making the
melt
spun fibers. In a typical embodiment, polyethylene) terephthalate (PET) may be
used
as the fiber-forming polymer.
The submicron or low micron dispersible PTFE powder is incorporated
into the fiber-forming polymer (such as PET) in three primary ways: 1) the
dispersible PTFE powder is introduced and dispersed directly into the fiber-
forming
polymer in its dry powder form; 2) the dispersible PTFE powder is introduced
into the
fiber-forming polymer in the form of an aqueous or an organic dispersion; or
3) the
dispersible PTFE powder is introduced into the fiber-forming polymer in the
form of
a pelletized master batch. Essentially, the highly dispersible PTFE described
herein
may be introduced at any stage of a melt spinning process fox making fibers
prior to
the fiber-forming polymer going through the spinneret.
With respect to the third way of incorporating PTFE mentioned above,
a pelletized master batch of PTFE is formed and incorporated into the fiber-
forming
polymer in the same manner that master batches of pigments or flame retardants
are
formed and incorporated into melt spun fibers. In certain embodiments, the
introduction of the highly dispersible PTFE in the form of a pelletized master
batch is
preferred. The master batches of PTFE in a fiber-forming polymer that are
useful in
the present invention typically comprise about 5% to about 60% PTFE, and more
particularly about 40% to about 45% PTFE.
This introduction of highly dispersible PTFE powder into a fiber-
forming polymer results in improved flow characteristics during extrusion,
improved
production rates, and significantly decreased production times because of the
lubricity
added to the overall fiber-forming process.
In certain embodiments, the melt-spun fibers that are made according
to the present invention are thin fibers, having a denier of less than about
10.
However, thicker, coarse melt spun fibers also may be produced having PTFE
incorporated therein.
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The PTFE-enhanced melt spun fibers produced by the method of the
present invention may be incorporated into a fabric or a textile, whereby the
fabric or
textile has the enhanced properties typically associated with the addition of
PTFE to
articles or compositions. For example, fabrics or textiles made with the
fibers of the
present invention can exhibit a significantly decreased coefficient of
friction. Fabrics
or textiles with such properties may be useful for mating apparel intended for
wear in
sports or recreational activities. Other desirable properties of the PTFE-
enhanced
melt spun fibers of the present invention, for example, include the
exceptional wear
resistance and stain resistance exhibited by the fibers, the light-fastness
and W-ray
resistance of the fibers, the colorfastness of the fibers, and the resistance
to
degradation of the fibers.
Specifically, the PTFE-enhanced fibers and/or the fabrics made from
the PTFE-enhanced fibers of the present invention may be wear tested to
determine
the wear resistance of the fibers. The wear testing may include Taber testing,
Mace
testing, and Pilling tests. Similarly, tests may be performed to determine the
tenacity
of the fabric, the elongation of the fabric, and the draw. Generally, the same
full
range of tests that are commonly used in the industry to analyze the
properties of melt
-spun fibers may be employed to test the fibers of the present invention.
Tests used in
other industries and other scientific test methods can also be used to
characterize the
fibers and fabrics of the present invention.
In some eimbodiments of the present invention, it may be desirable to
form bicomponent fibers using the present method of incorporating PTFE into
the
fiber-forming polymer resin during the spinning of synthetic bicomponent
fibers.
Bicomponent fibers are generally described as fibers, which comprise two
polymers
having different chemical and/or physical properties extruded from the same
spinneret
with both polymers within the same filament. Typically, the advantages
afforded by
bicomponent fibers include thermal bonding of the two palymers, self bulking
of the
f bers, the ability to male fibers having unique cross-sections, and the
ability to reap
the benefits of special polymers or additives at a reduced cost.
Most commercially available bicomponent fibers have one of the
following configurations: sheath/core; side-by-side; or eccentric sheath/core.
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However, any bicomponent fiber configuration may benefit from the method of
the
present invention. Typical polymer combinations used in the synthetic fiber
industry
to make bicomponent fibers include: fibers having a polyester core with a
copolyester
sheath; fibers having a polyester core with a polyethylene sheath; and fibers
having a
polypropylene core with a polyethylene sheath.
In certain embodiments of the present invention where bicomponent
fibers are sought, it may be possible to malce fibers having sheath/core
configurations
where a polyner, such as polyethylene) ter ephthalate (PET), is used as the
core,
while the sheath contains a polymer (such as PET) having highly dispersible
PTFE
particles incorporated therein according to the present method. For example,
in
certain embodiments, bicomponent fibers are made wherein the sheath contains
from
about 2% to about 40% or more PTFE. Several advantages of bicomponent fibers
formed according to the present method include retained tensile strength,
since the
core of the fiber remains very strong, as well as decreased cost because PTFE
is
incorporated only in the sheath portion of the fiber.
The method and compositions of the present invention may be better
understood through the working Examples detailed below, Additionally, several
of
the improved properties of the PTFE-enhanced melt spun fibers of the present
invention are discussed in more detail below in the working Examples. These
Examples are not intended in any way to limit the disclosure of the present
invention,
but are meant to illustrate certain embodiments and features of the method and
the
fibers disclosed by this invention.
EXAMPLES
Example 1: Rub Testing of Fabrics Made with PTFE-Enhanced Melt Suun
Fibers
In the present Example, a rub test was performed to compare the
properties of one knitted sleeve made from melt spun fibers in which PTFE had
been
incorporated into the fibers according to the present method, and another
knitted
sleeve made from conventional melt spun fibers that did not have any
incorporated
PTFE.
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Various rub tests exist in the art for determining the wear resistance,
slipperiness, and overall frictional behavior of melt spun fibers. During this
Example,
it was determined that a specific, very sensitive type of rub testing that is
typically
used with printing inks (according to ASTM D-5181) provided a straightforward
and
definitive method of testing the wear and the frictional characteristics of
these knitted
sleeves. This rub test method, which may performed using a Sutherland Ink Rub
Tester , was suitably adapted in this Example for use with fabrics made from
melt
spun fibers. This rub test may be as sensitive or possibly even more sensitive
to a
trained operator than the other standard rub tests that are typically used in
the fiber or
textile industry.
Specifically, the synthetic fibers used to make the sleeves for this
Example were made of PET, the polymer discussed in detail above that is
typical for
malting polyester fibers. For Sleeve 1, PTFE that is dispersible to low micron
or
submicron particle size was incorporated into the PET polymer resin so that
after the
PTFE-enhanced polyester fibers were formed and manufactured into a sleeve, the
amount of PTFE in the resulting sleeve was about 5% by weight. The denier of
the
PTFE-enhanced fibers was 240, and the Denier Per Filament (DPF) was 7.06.
Sleeve 1 was ltnitted from the inventive PTFE-enhanced polyester
f bers, using 4-inch cylinders and 144 needles in a jersey knit fashion. For
Sleeve 2,
no PTFE was incorporated into the PET polymer resin used to make the polyester
fibers that made up that sleeve. The polyester fibers used in Sleeve 2 were
melt spun
in the same fashion as Sleeve 1. Also, Sleeve 2 was knitted in the same jersey
knit
fashion as Sleeve 1.
Rub tests were then performed on both sleeves to determine the
abrasion resistance of each of the sleeves. The rub test was conducted using a
Sutherland Ink Rub Tester. In the tester a 4-pound weight was robbed over each
sleeve at "slow speed" (i.e., 32 cycles per minute).
During the testing, a Standard Receptor Stock (#5 ASTM D-1581) first
was secured to the 4-pound weight. Sleeve 1 was then placed on the pad of the
Sutherland Inlt Rub Tester. The Standard Receptor Stock was placed over Sleeve
1
and was secured by the weight arm of the Ink Rub Tester. Then, the number of
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strokes was set to 450 and the rub abrasion test begun. After completion of
450
strokes, the 4-pound weight was removed from the fabric. The same testing
procedure was used for Sleeve 2.
Sleeves 1 and 2 were visually compared to determine the level of
abrasion caused by the rub test. Specifically, the sections of each sleeve
that were
rubbed by the Standard Receptor Stock, was visually scrutinized to determine
which
sleeve had a lower numbex of scratches. It was determined that the knitted
sleeve
Sleeve 1 (made of 5% PTFE content fiber) showed fewer scratches than Sleeve 2
(made of 0% PTFE content fiber). These results illustrate the improved
abrasion
resistance imparted to f hers by the incorporation of PTFE.
Examule 2: Rub Testing of Fabrics Made with PTFE-Enhanced Melt Spun
Fibers
In this Example, Sleeves 3 and 4 were formed in exactly the same
manner as Sleeves 1 and 2, respectively, discussed in Example 1 above. Thus,
Sleeve
3 was made of polyester fibers in which PTFE has been incorporated whereas
Sleeve
4 was made of conventional polyester fibers. In this Example, rub testing
using the
Sutherland Ink Rub Tester was again performed. However, in this Example, the
performance of each sleeve was measured against a reference printed film of
Blank
Magenta Ink having no wax.
Sleeve 3 and Sleeve 4 were processed through the Sutherland Ink Rub
Tester using the same general procedure (slow speed and weights) as described
above
in the context of testing Sleeve 1 and Sleeve 2 (Example 1). However, in this
example, the reference printed film was fixst placed on a pad in the tester.
The test
sleeve (Sleeve 3 and then Sleeve 4) was secured to the 4-pound weight and
rubbed
against the reference printed film for 450 strokes. After the nabbing strokes,
Sleeves 3
and 4 were visually inspected to assess the ntunber of scratches on them. The
reference printed film. was similarly inspected to assess damage to it. Visual
observations showed that Sleeve 3 had less scratches on it than Sleeve 4.
Further,
Sleeve 3 had caused less damage to the printed ink film than did Sleeve 4.
These
results indicate that Sleeve 3 having PTFE- enhanced fibers has superior
abrasion
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resistance than Sleeve 4 having conventional melt spun fibers, which comprises
no
PTFE.
Example 3: Coefficient of Friction Testing of Fabrics Made with PTFE-
Enhanced Melt Shun Fibers
In this Example, testing was performed to determine and compare the
kinetic coefficient of friction values for fabrics made with conventional
polyester
fibers and fabrics made with polyester fibers in which PTFE had been
incorporated
according to the present invention. Sleeves 5 made from conventional fibers
and
Sleeve 6 made form PTFE-enhanced fibers were tested in this Example. These
sleeves were made or knitted in the same manner as Sleeves 2 and 1,
respectively,
(Example 1).
The coefficient of friction tests performed in this Example were
sliding or pulling tests, which serve to measure the coefficient of friction
of each of
the sleeves. During the testing, Sleeve 5 (having fibers with no PTFE therein)
was
first secured to the surface of a friction-testing machine (Altek Model 9505A
sold by
ALTER Company of 245 East Elm Street, Tornngton, CT 06790 USA), which is
equipped with a 2,000 gram sliding weight. This sliding Weight was placed on
Sleeve
5, and the coeff cient of friction indicator of the friction-testing machine
was engaged.
The pulling speed was set to 20 inches per minute, and the pulling begun. The
coefficient of fi-iction (COF) indicator of the machine gave a number for the
COF.
The test was repeated 6 times to obtain an average COF value for Sleeve 5. The
same
test procedure was employed to obtain an average COF value for Sleeve 6, the
sleeve
containing PTFE-enhanced fibers. The COF results obtained are shown in Table 1
below:
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Table 1
Test Run Number Coefficient of FrictionCoefficient of
(COF) Friction
of Sleeve 5 (COF) of Sleeve
(0% PTFE) 6
5% PTFE
1 0.25 0.22
2 0.25 0.23
3 0.24 0.22
4 0.26 0.23
0.25 0.23
6 0.25 0.23
Avera a 0.25 0.227
The results shown in Table 1 indicate that the knitted sleeve (Sleeve 6)
made of fibers having 5% PTFE had a lower coefficient of friction than the
sleeve
made form fibers with no PTFE in them (Sleeve 5).
Example 4: Coefficient of Friction Testing of Fabrics Made with PTFE-
Enhanced Melt Spun Fibers Using Sliding An~le Testing
In this Example, Sleeves 7 and 8 were formed in exactly the same
manner as Sleeves 5 and 6, respectively, described in Example 3 above. Thus,
Sleeve
7 was made of polyester fibers having no PTFE, while Sleeve 8 was made from
PTFE-enhanced polyester fibers according to the present invention. The COF
testing
procedure used in this example involves a sliding angle test to study the
frictional
properties of each of the sleeves, and to determine the static coefficient of
friction for
each sleeve. A Sliding Angle Coefficient of Friction Tester (Model # 32-35)
was
used for this purpose. In the tester three different counter surface materials
were used:
(1) Mylar film; (2) printing paper (70# opus gloss); and (3) treated C-184
foil.
To begin the testing, Sleeve 7 was secured to a weight. The counter
surface material was placed into a holder in the sliding tester. Then,
weighted Sleeve
7 was properly positioned on the counter surface material in preparation for
measuring its sliding angle. The counter surface was raised from one end to
determine the angle at which weighted Sleeve 7 began to slide. The
measurements
were repeated 5 times, so that an average value for the sliding angle could be
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calculated for Sleeve 7. A COF value was calculated from the average sliding
angle
value. These measurements and COF calculations were repeated fox each of the
tlmee
different types of counter surfaces.
The same testing procedures were employed for Sleeve 8 (having
PTFE-enhanced polyester fibers according to the present invention). The
results of
the testing for this Example are shown in Table 2 below:
Table 2
Sleeve Counter
and Run Surface
and Slidin
An le
Number M lar Film70# Printin Pa C-184 Foil
er
1 22 24 17
2 23 24 17
3 22 22 17
l 4 21 22 16
eeve 7
S
0% 5 22 22 I6
(
PTFE) Average
Sliding 22 22.8 16.6
An le
COF 0.4040 0.4204 0.2981
1 18 23 17
2 18 _23_ 16
3 20 ~ 23 16
Sl 4 19 20 15
8
eeve 5 20 20 15
(~%
PTFE) Average
Sliding 19 21.8 15.8
An le
COF
p.3443 0.4000 0.2830
These results indicate that Sleeve 8, the polyester l~nitted sleeve having
5% PTFE incorporated into its fibers, had a lower coefficient of friction when
compared to Sleeve 7 which was made from conventional polyester fibers without
PTFE additives.
Example 5: Measurement of Increased UV Protection of Fabrics Made with
PTFE-Enhanced Melt Suun Fibers Using Tensile Strength Testing
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W this Example, the resistance of fabrics made with PTFE-enhanced
melt spun fibers to ultraviolet radiation (UV) degradation was investigated.
h1 one investigation, the tensile breaking strength of non-woven fibers
was tested both before and after controlled exposures to ultraviolet radiation
(UV) ) in
a laboratory instrument to simulate radiation degradation of fabrics in field
use. A~~.
industry standard test procedure SAE J1885 was used. This procedure is
commonly
used in the automotive industry to evaluate the light fastness of automotive
interior
fabrics. The procedure as used in the automotive industry may use standard
light
exposures of 226 kJ (e.g., Chrysler Group, DaimlerChrysler Corporation, Auburn
Hills, MI 48326) or 488 kJ (e.g., Ford Motor Company, Dearborn, Michigan
48126).
A PTFE-enhanced fiber material having a PTFE concentration of
2.25%, which had been prepared by incorporating 5% of a 45% PTFE master batch
into the spinning melt, was used as the test material. Conventional fiber
material
prepared without any PTFE content was used as a control material. The tensile
strengths of a test sample and a control sample were determined by loading the
fibers
to determine the breaking force required break the fibers. The samples were
first
tested prior to UV irradiation. The forces required to break the test and
control
sample fibers were measured to be 260 newtons and 270 newtons, respectively.
These similar breaking force values indicate that PTFE-enhaazced fiber and non-
enhanced fiber have comparable tensile strengths.
Next, both the test and the control samples were exposed
various levels of to UV lamp radiation in a laboratory wear simulator (Atlas
Electric
Model No. Ci4000 Weatherometer~, sold by Atlas Electric Devices Company, 4114
N Ravenswood Ave, Chicago, IL 60613 ). This simulator uses xenon arc lamps
with
up to 2X solar irradiance for accelerated weathering of test specimens. The
radiation
exposure levels were in the amounts of 225, 490, 600, 800, and 1100 kJ/mz.
With
increasing radiation exposure (i.e., at 800 kJ/m2) the control sample
disintegrated.
However, the test sample retained it structural integrity at all exposures up
to and
including 1100 kJlm~. In test samples and control samples exposed to 600 kJlm2
of
radiation, the breaking forces were measured to be 169 newtons (lbs./sq.in)
and 85
newtons, respectively. The tensile strength reduction for the test sample and
the
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control sample due to UV irradiation are calculated to be about (260-
169)/(260) = 35
%, and (270-85)/270 = 68%, respectively. These results indicate that addition
of
PTFE to the melt spun fibers improves resistance to LTV degradation by a
factor of
about two.
The tensile strength of the test sample after 800 kJ/m2 and after
1100 kJ/m2 of radiation was measured to be about 150 and 135 newtons,
respectively.
FIG. 1 is a bar graph comparing the tensile strength (lbs./sq.in.) of the two
samples as
a function of radiation exposure. Data in the range of 0 kJ/m2 to 1100 kJlm2
of
radiation exposure is shov~m. FIG. 2 is a bar graph showing the normalized
strengths
of the test and control samples after radiation exposure in the range of 225
kJ/m2 to
1100 kJ/m2.
In another investigation of the radiation resistance, was conducted at
an independent fabric-testing laboratory (LS. LABS, Inc, 209A East Murphy
Street
Madison, NC 27025). At this laboratory, the tensile strength of PTFE-enhanced
and
control materials was measured using the conventional textile industry
procedure
(SAE J1885). The parameters measured included the breaking tenacity and
elongation at breaking load. These parameters were measured before and after
light
exposure under a fadeometer. The post light exposure measurements were carried
out
after exposing the test material to 488.8 kJ of light in an Atlas
Weatherometer
instrument. Samples from four different product categories were tested.
Product
categories 1 and 3 (labeled as 1/150/100 and 1/150/50 control products,
respectively)
were sleeves knitted from yarn with no PTFE additives , respectively. Product
categories 2 and 4 (labeled as 1/150/100 and 1/150/50 PTFE products,
respectively)
were sleeves knitted from PTFE-enhanced yarn. The successive numbers in a
label
respectively refer to the ply, denier and number of filaments in the yarn.
Thus, the
1/150/100 label refers to a one-ply, 150 denier, 100 filament yarn. The PTFE
concentration in both the 1/1001100 and 1/100/50 PTFE-enhanced fibers was
estimated to be about 1.75%. In each product category, tube yarn (i.e., yarn
that is not
knitted or woven into a fabric) specimens, and yarn unraveled from sleeves
knitted
from the product yarns were tested.
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The test results for the various product categories are shown in
Table 3.
Table 3
Product Breaking ElongationComments
category Tenacity at breaking
(g/denier)
Product Tube yarn 4.2 24%
1
1/150/100(calibration)
Control Yarn 3.6 17%
unraveled
from
unexposed
sleeve
Yarn 1.0, 12%, 3 sample
unraveled 0.08, 0.2%, measurements
from 0.07 0.3 %
exposed
sleeve
Product Tube yarn 4.2 22%
2
1/150/100(calibration)
PTFE Yarn 4.0 23%
unraveled
from
unexposed
sleeve
Yarn 3.3 21 %, 3 sample
unraveled 0.2 0.3%, measurements
from 0.05 0.06%
exposed
sleeve
Product Tube yarn 4.3 24%
3
1/150/50(calibration)
Control
Yarn 4.2 25%
unraveled
from
unexposed
sleeve
Yarn 3.2, 0.5%, 3 sample
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unraveled 0.2, 0.7%, measurements
from 0.2 0.3
exposed
sleeve
Product Tube yarn 4.1 22% Average of 2
4
1/150/50(calibration) measurements
Yarn 3.9 22% Average of 2
unraveled measurements
from
unexposed
sleeve
Yarn 1.6, 12%, 3 sample
unraveled 1.4, .9%, measurements
from 1.5 14%
exposed
sleeve
Tn Table 3, the first row in each product category refers to an
instrument calibration or reference measurement of tube yarn. The second row
refers
to measurements of yarn unraveled from the sample sleeves before they were
exposed
to the test light exposure in the Atlas Weatherometer instrument. Similarly
the third
row refers to measurements on yarn unraveled from the sample sleeves after
light
exposure in the Atlas Weatherometer instrument. The last measurement was
repeated
on three separately unraveled strands of yarn for each product category.
The scatter seen in the test results on unraveled yarn from both
exposed and unexposed sleeves may be related to the weave or knitting
structure of
the textile fabrics from which the sleeves are made. The results however on
the whole
indicate that fibers with a concentration of PTFE additives are significantly
stronger
than fiber without PTFE additives.
Examtale 6: hnproved Moisture Management Properties of Fabrics Made with PTFE-
Enhanced Melt Spun Fibers.
In this Example, the moisture handling or management capabilities of
fabrics made with PTFE-enhanced melt spun fibers were investigated. The
moisture
handling or management capabilities of fabrics were determined by measuring
the
extent of capillary wicking in strips of fabric that were dipped in a water
solution.
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The water was conveniently colored, which allowed visual observation of the
wicking
waterfront as the fabric absorbed water. The colored water solution was
prepared by
adding green food dye to water in a beaker. The amount of dye added to the
water
was cuff cient to raise the conductivity of the dye solution to be about 1000
Mhos ~
100 Mhos.
Two PTFE-enhanced fiber fabric strips (labeled PTFE-1 and PTFE-2)
were tested. The two strips were tested along with two control fabric strips,
Gontrol-
1, and Control-2, respectively. Test samples and control fabric samples were
cut into
1 inch wide by ~ inches long strips. The strips were conditioned in a
65°10 ~ 2°!0
humidity atmosphere at about 70° Fahrenheit for at least 4 hours
immediately prior to
testing. The fabric strips were held vertically over the water solution with
their ends
dipped in a beaker of the colored water solution. One inch of the bottom end
of the
test fabric strip was submerged in the dye solution. A stopwatch was started
when the
bottom one inch of the fabric strip was submerged in the colored water
solution. The
upward wiclcing of the colored water into the fabric strip was observed. The
times it
took for the wicking water front to rise up to marks that were 1 inch, 2
inches and 3
inches above the submersion level in the beaker were timed using the stop
watch.
Two runs were performed on each fabxic using a new fabric strip piece for each
run.
The timing measurements on the various samples are listed in Table 4.
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Table 4
Sample Time Time Time Comments
to to
1" 2" to
Mark Mark 3"
Mark
PTFE-1 Run 2" 35" 8'30" Water
1 front
(1/150/50) remained
just
below
3"
mark
for
the
last
2
minutes
of
the
run
Run 2" 36" 8'30" Reached
2 3"
mark
by
S
min
and
stopped.
Control-1 Run 8" 41" 10' Reached
1 2
3/4"
(1/150/50) inch
mark
by
6
min
and
stopped.
Run 6" 3 7' uneven
2 8" 40" wiclcing
at
3"
mark
PTFE-2 Run 9" 26" 2'S7"
1
(1/150/100) Run 7" 30" 2'30"
2
Control-2 Run S" 33" 2'42"
1
~ (11150/200) Rm 5" 28" 2'
~ 2 ~ i 12"
~
The water wicking front in many instances, as described in comments
column of Table 4, did not rise beyond the 3" level evenly or consistently.
This
indicates that under the test conditions the fabric strips were saturated with
water to a
steady state level before or at about the 3" mark. However, the PTFE-enhanced
fabrics consistently showed faster water wicking up to the 1" and 2" levels
than the
control fabrics did. For example, in the PTFE- 1 strips wicked water up to the
1"
level in about 2 seconds compared to about 6 to 8 seconds observed in the
Control -1
strips. Similarly, the PTFE- 2 strips wicked water up to the 2" level in an
average of
about 28 seconds compared to an average of about 30.5 seconds observed in the
Control -2 strips. These test results indicate that fabrics made of PTFE-
enhanced
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yarns may have moisture management properties that are superior to those of
fabrics
fabricated from yarn without PTFE-additives.
Example 7 ~ Abrasion Testing of Fabrics Made with PTFE-Enhanced Melt
Spun Fibers.
In this Example, the abrasion resistance properties of fabrics made
with PTFE-enhanced melt spun fibers were evaluated. The abrasion properties
were
evaluated using a conventional Taber testing method that is used for
evaluating
textiles. The method involves holding a piece of textile fabric on a base
plate of a test
unit and repeatedly running a wheel under load across the textile fabric
surface to
wear it down. The weight of textile fabric piece is measured before and after
the test.
The weight loss due to wear is an indication of the abrasion resistance
propeuties of
the fabric.
A sample fabric made from PTFE-enhanced fibers was tested. The
fabric was made with a 1/150/100 PTFE-enhanced yarn. The sample was tested
along
with a control fabric sample made with conventional yarn without PTFE
additives.
These samples (labeled PTFE-3 and Control-3, respectively) were wear tested on
a
commercial instrument (Taber Abraser Model 503, sold by Taber Instruments
Corporation, North Tonawanda, NY USA). Each fabric sample was weighed prior to
testing. The fabric sample then was held on the base plate of the instrument
by
vacuum. A wheel (H-10 size) was run over the surface of fabric sample for 200
cycles. The wheel was loaded with 500 grams ~f weight.
General visual observation suggested that the wear of both PTFE-
enhanced fabric and control fabric was similar under the test conditions.
Closer
observation of the tested samples using a digital camera showed that the PTFE-
enhanced fabrics were smoother after wear than the control fabrics. The
fabrics were
weighed after the wear to obtain quantitative measurement of the amount of
wear.
Each fabric type was tested four times. The test data for the various fabric
samples are
listed in Table 5.
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Table 5
150J50 Control vs. PTFE
Sample
11150150 Wear Wheel Load Wt. Wt. Wt.
Control-3 Cycle number grams Before After Loss
g g g
Run 1 200 H-10 500 7.2915 7.2743 0.0172
Run 2 200 H-10 500 7.3687 7.3555 0.0132
Run 3 200 H-10 500 7.3576 7.3436 0.014
Run 4 200 H-10 500 7.3362 7.3254 0.0108
Average 0.013
Wt. 8
Lost (19%)
Samplel/150Wear Wheel Load Wt. Wt. Wt.
/50 PTFE-3 Cycle number ams Before After Loss
g g
Run 1 200 H-10 500 7.3064 7.29320.0132
Run 2 200 H-10 500 7.2697 7.25850.0112
Run 3 200 H-10 500 7.2713 7.25890.0124
Run 4 200 H-10 500 7.295 7.28680.0082
Average 0.01125
Wt.
Lost (15%)
The average weight loss in the PTFE-enhanced fabric sample (15%)
was about three quarters of the weight loss in the conventional control fabric
(19%).
These test results indicate that textile fabrics made with suitable content of
PTFE-
enhanced yarns may have better abrasion resistance properties than fabrics
made
fiom yarn without PTFE-additives.
In another series of tests, wear testing of a PTFE-enhanced fabric
sample (PTFE-4) and a control sample (Control-4) was conducted according to
General Motors standard method GM 2794 fox non-woven carpet applications. The
tests were conducted using a H-18 size wheel under a 1000 g load. The PTFE-4
sample for non-woven carpet applications was made from 18 decitex PET fiber
having a PTFE content of about 2.25% (similar to the PTFE-1 and 2 samples
above)
and containing about 1.5% of color pigment. The control sample was fabricated
from
undrawn PET fiber (80 decitex). The PTFE-4 sample was subject to 2000 wheel
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cycles of wear. The Control-4 sample was subject to only 600 wheel cycles of
wear
as by that time it had disintegrated and roughened sufficiently to interfere
with wheel
motion. Both samples were weighed before and after the wear cycles. The test
results are shown in Table 6.
Table 6
Sample Wear Wt. Wt. Wt. Wt.
Cycles Before After Loss gramsLoss
g g
PTFE-4 2000 13.8850 13.3835 0.5015 36.11%
Control-4600 9.8820 9.5500 0.3320 41.2%
The test data shows that the PTFE- 4 sample even though subject to a
larger number of wheel cycles of wear (2000 v. 600) showed less wear that the
control-4 sample. Accordingly, PTFE-enhanced fibers may be expected show less
wear than conventional fibers in non-woven carpet applications.
Example 8: Coefficient of friction Testing of Textile Fabrics Made with PTFE-
Enhanced Melt Spun Fibers.
In this Example, static and kinetic friction characteristics of fabrics
with PTFE-enhanced melt spun fibers in them were evaluated according to the
ASTM
D-1894-00 with modified weights. An ALTER Coefficient of Friction Test
Instrument (sold by ALTEK Company of 245 East Ehn Street, Torrington, CT 06790
USA) was used for this purpose. In general the testing apparatus is similar to
the slide
and pulley arraalgement described in Example 3, above. In the test procedure,
a
fabric-covered metal slide is slid on a fabric-covered steel platen. The slide
is pulled
across the steel platen at a constant speed. The force to get the sled started
(static) and
to maintain motion (kinetic) is measured using a strain or force gauge. The
gauge
readings are divided by the weight of the slide to obtain raw static and
kinetic friction
numbers. These numbers are converted to coefficient of friction numbers by
reference to instrument calibration values using a 2000 gram standard metal
sled
(COF = scale reading x 2000)/slide weight).
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Two PTFE-enhanced fiber fabrics (labeled PTFE-5 and PTFE-6) were
tested. The two fabrics were made from 1/100150 and 1/150/100 PTFE-enhanced
yarns, respectively. Samples from these PTFE-enhanced fiber fabric strips were
tested along with samples from two control fabrics (labeled Control-5 and
Control-6)
that were made from conventional fiber.
For the friction testing, square pieces of fabric (2.5" x 2.5") were cut
and attached to the bottom surfaces of slides (i.e. the metal sled blocks).
Another
rectangular piece of the same fabric (4"x 12") was attached to the surface of
a steel
platen. Each slide was slid or pulled on the steel platen at a speed of about
5"/min.
Starting or initial strain gauge readings at the start of slide motion were
recorded as a
measure of static friction. Average visual strain gauge readings over a 3" run
of the
moving slide were recorded as a measure of kinetic friction. Three different
slide
weights (obtained by adding 100 gram and 200 gram weights on top of a slide )
were
used for the friction testing. The three slide weights used including the
attached
fabric weighed about 184, 284 and 384 grams respectively. Each fabric was
tested
four times with each slide weight. The test data (strain gauge readings) and
the scaled
coefficients of friction (strain gauge readings x 2000/slide weight) are shown
in
Tables 8 and 9. Tables 8 and 9 also show the percentage improvement in COF for
each of the PTFE-enhanced fabrics tested relative to the control fabrics.
Table 8
Sample Slide
Wei
ht
Control-184 .42 _ .39 g 384.43
g 284
5 Static KineticStatic Kinetic Static Kinetic
Run 0.0650 0.065 0.0975 0.0925 0.1350 0.1300
1
Run 0.0675 0.065 0.1025 0.0950 0.1275 0.1260
2
Run 0.065 0.065 0.1020 0.0950 0.1250 0.1250
3
Run 0.0625 0.062 0.1000 0.0950 0.1250 0.1225
4
Average0.065 0.064250.1005 0.094375 0.1281250.125875
Avg. 0.7048 0.696700.70675 0.66367790.66653660.654831
COF 36 4 11 6
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Sample Slide
Wei
ht
PTFE-5 184.44 284.4 384.45
g g
StaticKinetic Static Kinetic Static Kinetic
Run 1 0.600 0.0525 0.0925 0.0825 0.1150 0.1075
Run 2 0.05750.0560 0.0925 0.0850 0.1125 0.1050
Run 3 0.05750.0550 0.0850 0.0800 0.1150 0.1050
Run 4 0.05750.0550 0.0875 0.0825 0.11100 0.1050
Average 0.05810.054625 0.089375 0.0825 O.lI3I25 0.1056
25 25
Avg. 0.63020.592334 0.62851620.58016880.58850310.5494
COF 86 863
Improve 10.59%14.99% 11.075 12.59% 11.71 16.09%
%
meat
relative
to
Control-
Table 9
Sample Slide
Wei
ht
Control-184.94 284.93 384.75
g
6 Static Kinetic Static Kinetic Static I~ineti
c
Run 0.0550 0.0535 0.0825 0.0810 0.1050 0.102
1
5
Run 0.0540 0.0515 0.0800 0.0785 0.1200 0.107
2
5
Run 0.0510 0.0510 0.0825 0.0800 0.1050 0.107
3
5
Run 0.520 0.0510 0.0785 0.0785 0.1075 0.106
4
0
Average0.0530 0.05175 0.0808750.0795 0.109375 0.105
875
Avg. 0.57471 0.561158 0.5687410.559072 0.568995 0.550
COF 3 787
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Sample Slide
Weight
_
PTFE-6 184.84 284.77 384.86
g g g
Static Kinetic Static Kinetic Static Kinetic
Run 1 0.0350 0.0350 0.0525 0.0500 0.0700 0.0675
Run 2 0.0360 0.0340 0.0525 0.0510 0.0680 0.0660
Run 3 0.0340 0.0325 0.0520 0.0495 0.0675 0.0650
Run 4 0.0340 0.0325 0.0510 0.0490 0.0675 0.0650
Average 0.0347 0.0335 0.0520 0.049875 0.06825 0.0658
5 75
Avg. 0.3768 0.3632620.365682 0.350738 0.355053 0.3426
COF 16 97
Improve 34.40% 35.23% 35.67% 37.23% 37.61% 37.80
ment
relative
to
Control-6
The data in tables 8 and 9 are also shown as comparative bar graphs in FIGS.
3 and 4. The data confirms that addition of PTFE to fibers reduces the
coefficient of
friction of textile fabrics.
_2g_
