Note: Descriptions are shown in the official language in which they were submitted.
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CONFORMABLE MICROPOROUS FIBER
AND WOVEN FABRICS CONTAINING SAME
FIELD OF THE INVENTION
The present invention relates generally to conformable microporous
fibers, and more specifically, to conformable microporous fibers having a node
and fibril structure that are highly breathable. Woven fabrics containing the
conformable microporous fibers are also provided.
BACKGROUND OF THE INVENTION
Waterproof, breathable garments are well-known in the art. These
garments are often constructed from multiple layers in which each layer adds a
certain functionality, For example, a garment could be constructed using an
outer textile layer, a waterproof, breathable film layer, and an inner textile
layer.
The outer and inner textile layers provide protection to the breathable film
layer.
However, the addition of outer and inner fabric layers not only adds weight to
an
article of apparel, it also results in materials having the potential for a
high water
pick-up on the outer surface. The pick-up of water by the outer fabric layer
permits for thermal conductivity and the passage of the temperature of the
water
through the fabric and to the wearer. This may be detrimental in cases where
the
wearer is in a cold environment and the cold is transported to the body of the
wearer. In addition, water pick-up may lead to condensation on the inside of
the
garment, making the wearer feel wet. Further, the color of the outer fabric
may
become discolored or darken upon water pick-up, thus reducing the aesthetic
appearance of the garment. Also, depending on the outer fabric, there may be a
long dry time associated with the fabric itself, forcing the wearer to endure
the
disadvantages associated with the water pick-up for a longer time.
Additionally,
the fibers associated with conventional fabrics used in the inner and outer
layer
are constructed of multifilament fibers, which permit water and/or
contaminants
between the filaments. Additionally, because multifilament fibers are loosely
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packed for breathability in the fabric, water can undesirably fill the space
between the fibers,
Thus, there exists a need in the art for a fiber to make woven fabrics for
use in garments that is highly breathable, has a high water entry pressure,
and
has a low water pick-up,
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a woven fabric that
includes warp and weft expanded polytetrafluoroethylene (ePTFE) fibers that
have a microporous structure of nodes and fibrils, where the width of the
ePTFE
fiber is greater than the width allotted to the ePTFE fiber based on the end
count
or pick count of the woven fabric. This difference in width causes the ePTFE
fiber to fold upon itself to conform to the weave spacing provided between the
crossovers of the warp and weft fibers. The ePTFE fibers may be monofilament
fibers. The ePTFE fibers may have a density less than about 1.2 g/cm', an
aspect ratio greater than about 15, and a substantially rectangular cross
sectional
configuration. Advantageously, the ePTFE woven fabric possesses both a high
moisture vapor transmission and a high water entry pressure. In particular,
the
woven fabric has a moisture vapor transmission rate greater than about 10,000
g/m2/24 hours and a water entry pressure greater than about 1 kPa. Thus, the
woven fabric is highly breathable, has a low water pick-up, and is highly
water
resistant.
It is another object of the present invention to provide a woven fabric
that includes a plurality of warp and weft fibers where each of the warp and
weft
fibers include expanded polytetrafluoroethylene fibers that have a density
less
than about 1.2 g/cm3 and a substantially rectangular cross sectional
configuration. The ePTFE fibers may be monofi lament fibers. At least one of
the warp and weft ePTFE fibers may have an aspect ratio greater than about 15.
In at least one exemplary embodiment, the width of the ePTFE fibers is greater
than the number of picks per inch of the woven fabric. Further, the woven
fabric has an average stiffness less than about 300 g and a water pick-up less
than 30 gsm. The warp fibers and weft fibers may have a fluoroacrylate coating
to render the woven fabric oleophobic. A fluoropolymer membrane, or other
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functional membranes or protective layer, may be affixed to the woven fabric
on
a side opposing the fluoroacrylate coating. In some embodiments, a textile may
be affixed to the fluoropolymer membrane to form a laminated article. In other
embodiments, a fluoropolymer membrane and/or a textile may be affixed to the
woven fabric without the application of a coating.
It is a further object of the invention to provide a woven fabric that
includes warp and weft fibers of expanded polytetrafluoroethylene fibers
having
an aspect ratio greater than about 15 and a substantially rectangular cross-
section configuration. The woven fabric has a water entry pressure greater
than
about 1 kPa and a moisture vapor transmission rate greater than about 10,000
g/m2/24 hours. The ePTFE fibers may be monofilament fibers. Additionally,
the fibers may have a pre-weaving thickness less than about 100 microns, a pre-
weaving width less than about 4.0 mm, and a pre-weaving density less than
about 1.0 g/cm3. Further, the ePTFE fibers have a node and fibril structure
where the nodes are interconnected by fibrils that define passageways through
the fiber. The fibrils may have a length from about 5 microns to about 120
microns.
It is yet another object of the invention to provide a woven fabric that
includes warp and weft fluoropolymer fibers where at least one of the warp and
weft fluoropolymer fibers is in a folded configuration along a length of the
fiber.
In at least one exemplary embodiment, the fluoropolymer fibers are ePTFE
fibers that have a density less than about 1.2 g/cm3 and have a substantially
rectangular configuration. In exemplary embodiments, the ePTFE fibers have a
pre-weaving density less than about 0.85 g/cm3. The woven fabric has a
moisture vapor transmission rate greater than about 10,000 g/m2/24 hours and a
water entry pressure greater than about 1 kPa. In addition, the woven fabric
has
a tear strength of at least 30 N and an average stiffness of less than about
300 g.
In at least one exemplary embodiment, the width of the fluoropolymer fiber is
greater than the width allotted to the fluoropolymer fiber in the woven fabric
based on the end count or pick count of the woven fabric.
It is also an object of the present invention to provide a woven fabric that
includes conformable warp and weft fluoropolymcr fibers where at least one of
the warp and weft fibers have a node and fibril structure that form
passageways
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through the fiber. The fibrils may have a length from about 5 microns to about
120 microns. In at least one embodiment, the fluoropolymer fibers are ePTFE
fibers that have a pre-weaving density less than about 1.0 g/cm3, and in other
embodiments, less than about 0.85 g/cm3. The conformability of the fiber
permits the fiber to curl and/or fold upon itself to conform to weave spacing
provided between the crossovers of the warp and weft fibers in a woven
configuration. Additionally, a functional membrane or protective layer, such
as
a fluoropolymer membrane, may be affixed to the ePTFE woven fabric. In
some embodiments, a textile is affixed to the fluoropolymer membrane to form a
laminated article.
It is yet another object of the present invention to provide a
monofilament fiber that includes expanded polytetrafluoroethylene. The ePTFE
monofilament fiber has a density less than or equal to 1.0 g/cm3, a thickness
less
than about 100 microns, a width less than about 4.0 mm, an aspect ratio
greater
than about 15, and a substantially rectangular cross-section configuration. In
addition, the fiber has a tenacity greater than about 1.6 cN/dtex and a break
strength of at least about 1.5 N. The ePTFE monofilament fiber may have
thereon a fluoroacrylate coating, or other oleophobic treatment. Additionally,
the ePTFE monofilament fibers have a node and fibril configuration where the
nodes and fibrils define passageways through the fiber, The fibril length may
be
from about 5 microns to about 120 microns. Further, the ePTFE monofi lament
fiber is conformable such that in a woven configuration, the ePTFE
monofilament fiber folds upon itself to conform to weave spacing provided
between the crossovers of the warp and weft fibers in the woven fabric. Such
ePTFE monofilament fibers are utilized in exemplary embodiments of the
invention to form woven fabrics that may ultimately be used in an article that
demands high moisture vapor transmission and high water entry pressure (i.e.,
high breathability and high resistance to water).
It is an advantage of the present invention that even when the ePTFE
fiber is tightly woven, the ePTFE woven fabric is highly breathable and has a
high water entry pressure.
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It is another advantage of the present invention that the ePTFE fibers
may be tightly woven into a woven fabric that is highly breathable yet
possesses
a low air permeability,
It is also an advantage of the present invention that the woven fabric is
quiet, soft, and drapable.
It is yet another advantage of the present invention that the high aspect
ratio of the ePTFE fibers enables low weight per area fabric, easier and more
efficient reshaping, and can achieve high water resistance in a woven fabric
with
less picks and ends per inch.
It is a feature of the present invention that the ePTFE fibers curl and/or
fold upon themselves to conform to the weave spacing provided between the
crossovers of the warp and weft fibers in the woven fabric.
It is also a feature of the present invention that woven fabrics constructed
from the ePTFE fibers have a flat or substantially flat weave and a
corresponding smooth surface,
It is another feature of the present invention that the ePTFE fibers have a
substantially rectangular cross-section configuration, particularly prior to
weaving.
BRIEF DESCRIPTIONS OF FIGURES
The advantages of this invention will be apparent upon consideration of
the following detailed disclosure of the invention, especially when taken in
conjunction with the accompanying drawings wherein:
FIG. 1 is a scanning electron micrograph (SEM) of the top surface of an
exemplary ePTFE fiber taken at 1000x magnification according to one
exemplary embodiment of the invention;
FIG. 2 is a scanning electron micrograph of a side of the ePTFE fiber
depicted in FIG. 1 taken at 1000x magnification;
FIG. 3 is scanning electron micrograph of the top surface of a 2/2 woven
twill fabric of the fiber depicted in FIG, I taken at 150x magnification;
FIG. 4 is a scanning electron micrograph of a side of the woven fabric
depicted in FIG. 3 taken at 150x magnification;
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FIG. 5 is a scanning electron micrograph of the top surface of the 2/2
woven twill fabric depicted in FIG. 3 having thereon a fluoroaerylate coating
taken at 150x magnification;
FIG. 6 is a scanning electron micrograph of a side of the woven fabric
depicted in FIG. 5 taken at 150x magnification;
FIG. 7 is a scanning electron micrograph of the top surface of the 2/2
woven twill fabric illustrated in FIG. 5 having laminated thereto an ePTFE
membrane taken at 150x magnification;
FIG. 8 is a scanning electron micrograph of a side of the article depicted
in FIG. 7 taken at 100x magnification;
FIG. 9 is a scanning electron micrograph of a side of the fabric depicted
in FIG. 7 taken at 1000x magnification;
FIG. 10 is a scanning electron micrograph of the top surface of the
woven fabric illustrated in FIG. 5 laminated to a textile taken at 150x
magnification according to another exemplary embodiment of the invention;
FIG. 11 is a scanning electron micrograph of a side of the article
depicted in FIG. 10 taken at 100x magnification;
FIG. 12 is a scanning electron micrograph of a side of the article
depicted in FIG. 10 taken at 500x magnification;
FIG. 13 a scanning electron micrograph of the top surface of a woven
fabric having laminated thereto an ePTFE membrane and a textile according to
an exemplary embodiment or the invention taken at 150x magnification;
FIG. 14 is a scanning electron micrograph of a side of the article
depicted in FIG. 13 taken at 100x magnification;
FIG. 15 is a scanning electron micrograph of a side of the article
depicted in FIG. 13 taken at 300x magnification;
FIG. 16 is a scanning electron micrograph of the top surface of a plain
woven fabric according to one exemplary embodiment of the invention taken at
150x magnification;
FIG, 17 is a scanning electron micrograph of a side of the fabric depicted
in FIG, 16 taken at 250x magnification;
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FIG. 18 is scanning electron micrograph of the top surface of the plain
woven fabric illustrated in FIG. 16 having thereon a fluoroacrylate coating
taken
at 150x magnification;
FIG, 19 is a scanning electron micrograph of a side of the woven fabric
depicted in FIG. 18 taken at 250x magnification;
FIG. 20 is a scanning electron micrograph of the top surface of the
woven fabric depicted in FIG. 16 having laminated thereto an ePTFE membrane
and a textile taken at 150x magnification according to an exemplary
embodiment of the invention;
FIG, 21 is a scanning electron micrograph of a side view of the article
depicted in FIG. 20 taken at 250x magnification;
FIG. 22 is a scanning electron micrograph of the top surface of an
exemplary ePTFE fiber taken at 1000x magnification according to another
exemplary embodiment of the invention;
FIG. 23 is a scanning electron micrograph of a side of the ePTFE fiber
depicted in FIG. 22 taken at 1000x magnification;
FIG. 24 is a scanning electron micrograph of the top surface of a 2/2
twill fabric of the ePTFE fiber depicted in FIG. 22 taken at 150x
magnification;
FIG. 25 is a scanning electron micrograph of a side of the fabric depicted
in FIG. 24 taken at 200x magnification;
FIG. 26 is a scanning electron micrograph of the top surface of the
woven twill fabric depicted in FIG. 16 having thereon a fluoroacrylate coating
taken at 150x magnification;
FIG. 27 is a scanning electron micrograph of a side of the fabric depicted
in FIG. 26 taken at 200x magnification;
FIG. 28 is a scanning electron micrograph of the top surface of an
exemplary ePTFE fiber according to a further embodiment of the invention
taken at 1000x magnification;
FIG. 29 is a scanning electron micrograph of a side of the fiber depicted
in FIG. 28 taken at 1000x magnification;
FIG, 30 is a scanning electron micrograph of the top surface of a 2/2
twill woven fabric of the ePTFE fiber illustrated in FIG. 26 taken at 150x
magnification;
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FIG. 31 is a scanning electron micrograph of a side of the fabric depicted
in FIG, 30 taken at 150x magnification;
FIG. 32 is a scanning electron micrograph of the top surface of a high
density comparative ePTFE fiber taken at 1000x magnification;
FIG. 33 is a scanning electron micrograph of a side of a woven fabric of
the fiber depicted in FIG, 32 taken at 1000x magnification;
FIG. 34 is a scanning electron micrograph of the top surface of a 2/2
twill woven comparative fabric utilizing a comparative high density ePTFE
fiber
taken at 150x magnification;
FIG. 35 is a scanning electron micrograph of a side of the fabric depicted
in FIG. 34 taken at 150x magnification;
FIG. 36 is a scanning electron micrograph of a top surface of an
exemplary fiber taken at 1000x magnification;
FIG. 37 is a scanning electron micrograph of a side of the fiber depicted
in FIG. 36 taken at 1000x magnification;
FIG. 38 is a scanning electron micrograph of the top surface of a woven
fabric of the fiber shown in FIG, 36 taken at 150x magnification;
FIG. 39 is a scanning electron micrograph of a side of the fabric depicted
in FIG. 38 taken at 150x magnification;
FIG, 40 is a schematic illustration depicting a side view of exemplary
fibers folding into a folded configuration to fit into the space allotted to
the fiber
in the woven configuration;
FIG. 41 is a schematic illustration depicting a top view of exemplary
fibers folding into a folded configuration to fit into the space allotted to
the fiber
in the woven configuration;
FIG. 42 is a scanning electron micrograph of the top surface of an
exemplary plain weave fabric with a 40 X 40 thread count taken at 150x
magnification;
FIG. 43 is a scanning electron micrograph of a side of the woven fabric
depicted in FIG. 42 taken at 150x magnification;
FIG. 44 is a scanning electron micrograph of a side of the woven fabric
depicted in FIG. 42 taken at 300x magnification;
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FIG 45 is a scanning electron micrograph of a side of the woven fabric
depicted in FIG. 42 taken at 400x magnification;
FIG. 46 is a scanning electron micrograph of the top surface of a
comparative non-porous ePTFE fiber taken at 1000x magnification;
FIG. 47 is a scanning electron micrograph of a side of the fiber depicted
in FIG. 46 taken at 1000x magnification;
FIG. 48 is a scanning electron micrograph of a woven fabric of the fiber
depicted in FIG. 46 taken at 150x magnification;
FIG. 49 is a scanning electron micrograph of a side of the woven fabric
of FIG. 48 taken at 150x magnification;
FIG. 50 is a scanning electron micrograph of the top surface of a
comparative woven fabric of a comparative high density ePTFE fiber taken at
150x magnification;
FIG. 51 is a scanning electron micrograph of a side surface of the woven
fabric illustrated in FIG. 50 taken at 150x magnification; and
FIG. 52 is a scanning electron micrograph illustrating gap width
measurements.
DEFINITIONS
The terms "monofilament fiber" and "monofilament ePTFE fiber" as
used herein are meant to describe an ePTFE fiber that is continuous or
substantially continuous in nature which may be woven into a fabric.
The terms "fiber" and "ePTFE fiber" as used herein are meant to include
monofilament ePTFE fibers as well as a plurality of monofilament ePTFE fibers,
such as, for example, fibers in a side-by-side configuration, in a bundled
configuration, or in a twisted or otherwise intermingled form.
The term "conformable" and "conformable fiber" as used herein are
meant to describe fibers that are capable of curling and/or folding upon
themselves to conform to weave spacing provided between the crossovers of the
warp and weft fibers and as determined by the number of picks per inch and/or
ends per inch of the warp and weft fibers.
"High water entry pressure" as used herein is meant to describe a woven
fabric with a water entry pressure greater than about 1 kPa.
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The phrase "low water pick-up" as used herein is meant to denote a
woven fabric having a water pick-up less than about 50 gsm.
The term "substantially rectangular configuration" as used herein is
meant to denote that the conformable, microporous fibers have a rectangular or
nearly rectangular cross section, with or without a rounded or pointed edge
(or
side).
DETAILED DESCRIPTION OF THE INVENTION
The present invention relates to conformable microporous fibers having
a node and fibril structure and woven fabrics produced therefrom, A polymer
membrane and/or a textile may be laminated to the woven fabric to produce a
laminated article. The woven fabric concurrently possesses high moisture vapor
transmission (i.e., highly breathable), high water entry pressure, and low
water
pick-up. The woven fabric can be colorized, such as, for example, by printing.
In addition, the woven fabric is quiet, soft, and drapable, making it
especially
suitable for use in garments, gloves, and in footwear applications. It is to
be
noted that the terms "woven fabric" and "fabric" may be used interchangeably
herein. In addition, the terms "ePTFE fiber" and "fiber", may be
interchangeably used within this application.
The conformable fibers have a node and fibril structure where the nodes
are interconnected by fibrils, the space between which defines passageways
through the fibers. Also, the conformable fibers are microporous. Microporous
is defined herein as having pores that are not visible to the naked eye. The
node
and fibril structure within the fiber permits the fiber, and fabrics woven
from the
fiber, to be highly breathable and allow for the penetration of colorants and
olcophobic compositions. Also, the matrix provided by the nodes and fibrils
allows for the inclusion of desired fillers and/or additives,
It is to be appreciated that with respect to the conformable, microporous
fibers; reference is made herein with respect to expanded
polytetrafluorethylene
(eP FFE) fibers for ease of discussion, However, it is to be understood
that any
suitable conformable fluoropolymer having a node and fibril structure may be
used interchangeably with ePTFE as described within this application, Non-
limiting examples of fluoropolymcrs include, but are not limited to, expanded
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PTFE, expanded modified PTFE, expanded copolymers of PTFE, fluorinated
ethylene propylene (FEP), and perfluoroalkoxy copolymer resin (PFA). Patents
have been granted on expandable blends of PTFE, expandable modified PTFE,
and expanded copolymers of PTFE, such as, but not limited to, U.S. Patent No.
5,708,044 to Branca; U.S. Patent No. 6,541,589 to Baillie; U.S. Patent No.
7,531,611 to Sabol et al.; U.S. Patent Application No. 11/906,877 to Ford; and
U.S. Patent Application No. 12/410,050 to Xu et al. The fibril length of the
ePTFE fibers ranges from about 5 microns to about 120 microns, from about 10
microns to about 100 microns, from about 15 microns to about 80 microns, or
from about 15 microns to about 60 microns.
Additionally, the ePTFE fibers have a substantially rectangular
configuration. At least FIGS. 4, 6, 12, 14, 17, 19, 21, 27, 30, 39, 43, 44, 45
of
this application depict exemplary ePTFE fibers having substantially
rectangular
configurations. As used herein, the term "substantially rectangular
configuration" is meant to denote that the fibers have a rectangular or nearly
rectangular cross section. That is, the ePTFE fibers have a width that is
greater
than its height (thickness). It is to be noted that the fibers may have a
rounded
or pointed edge (or side). Unlike conventional fibers that must be twisted
prior
to weaving, the ePTFE fibers can be woven while in a flat state without having
to first twist the ePTFE fiber. The ePTFE fibers may be advantageously woven
with the width of the fiber oriented so that it forms the top surface of the
woven
fabric. Thus, woven fabrics constructed from the inventive ePTFE fibers have a
flat or substantially flat weave and a corresponding smooth surface. The
smooth, planar surface of the fabric enhances the softness of the woven
fabric.
In addition, the ePTFE fibers used herein have a low density. More
specifically, the fibers have a pre-weaving density less than about 1.0 g/cm3.
In
exemplary embodiments, the fibers have a pre-weaving density less than about
0.9 g/cm3, less than about 0.85 g/cm3, less than about 0.8 g/cm3, less than
about
0.75 g/cm3, less than about 0.7 g/cm3, less than about 0.65 g/crn3, less than
about
0.6 g/cm3, less than about 0.5 g/cm3, less than about 0.4 g/cm3, less than
about
0.3 g/cm3, or less than about 0.2 g/cm3. Processes used to make a fabric, such
as
weaving, fold the ePTFE fibers and may increase the density of the fibers
while
preserving breathability through the woven fabric. As a result, the fibers may
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have a post-weaving density less than or equal to about 1.2 g/cm3. The low
density of the fiber (both pre- and post-weave) also enhances the
breathability of
the fiber,
Additionally, the fibers may have a weight per length of about 50 dtex to
about 3500 dtex, from about 70 dtex to about 1000 dtex, from about 80 dtex to
about 500 dtex, from about 90 dtex to about 400 dtex, from about 100 dtex to
about 300 dtex, or from about 100 dtex to about 200 dtex. It is to be
appreciated
that a lower dtex provides a lower weight/area fabric, which enhances the
comfort of a garment formed from the fabric, In addition, the low denier of
the
ePTFE fiber enables the woven fabric to have a high pick resistance. Pick
resistance is referred to as the ability of a fabric to resist the grasping
and
moving of individual fibers within the fabric, In general, the finer the fiber
(e.g.,
lower denier or dtex) and tighter the weave, a better pick resistance is
achieved.
The ePTFE fibers also have a height (thickness) (pre- or post- weaving)
less than about 200 microns. In some embodiments, the thickness ranges from
about 20 microns to about 150 microns, from 20 microns to about 100 microns,
from about 20 microns to about 70 microns, from about 20 microns to 50
microns, from about 20 microns to 40 microns, or from about 26 microns to 36
microns, The ePTFE fibers may have a pre- or post- weaving height (thickness)
less than 100 microns, less than 75 microns, less than 50 microns, less then
40
microns, less then 30 microns, or less than 20 microns. The fibers also have a
width (pre- or post- weaving) less than about 4.0 mm. In at least one
exemplary
embodiment, the fibers have a pre- or post- weaving width from about 0.5 mm
to about 4.0 mm, from about 0.40 mm to about 3.0 mm, from about 0.45 mm to
about 2,0 mm, or from about 0.45 mm to about 1.5 mm. The resulting aspect
ratio (i.e., width to height ratio) of the cPTFE fibers is greater than about
10. In
some embodiments, the aspect ratio is greater than about 15, greater than
about
20, greater than about 25, greater than about 30, greater than about 40, or
greater
than about 50, A high aspect ratio, such as is achieved by the ePTFE fibers,
enables low weight per area fabrics, easier and more efficient reshaping, and
can
achieve high water resistance in a woven fabric with less picks and ends per
inch.
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Further, the ePTFE fibers have a tenacity greater than about 1.4 cN/dtex.
In at least one embodiment of the invention, the ePTFE fibers have a tenacity
from about 1.6 cN/dtex to about 5 cN/dtex, from about 1,8 cN/dtex to about 4
cN/dtex, or from about 1.9 cN/dtex to about 3 cN/dtex. Additionally, the ePTFE
fibers have a fiber break strength of at least about 1.5 N. In one or more
embodiments, the ePTFE fibers have a fiber break strength from about 2 N to
about 20 N, from about 2 N to about 15 N, from about 2 N to about 10 N, or
from about 2 N to about 5 N.
The ePTFE fibers described herein may be used to form a woven fabric
having warp and weft fibers interwoven with one another in a repeating weave
pattern. Any weave pattern, such as, but not limited to, plain weaves, satin
weaves, twill weaves, and basket weaves, may be used to form the ePTFE fibers
into a woven fabric. The ePTFE fiber may be woven flat without folds or
creases when the width of the ePTFE fiber is less than the allotted space
provided for the fiber based on the number of the picks per inch and/or ends
per
inch. Such a fiber, when loosely woven, includes visible gaps between the
crossovers (intersections) of the warp and weft fibers. As such, the fabric is
highly breathable but is not water resistant. Such large gaps in the fabric
may be
acceptable in applications where, for example, the water resistance is to be
provided by another layer or in situations where general areal coverage is
desired and water resistance is not critical.
In other embodiments, the fiber is more tightly woven, such as when the
width of the ePTFE fiber exceeds the allotted space in the woven fabric based
on
the number of picks per inch and/or ends per inch. In such a fabric, there is
no,
or substantially no, gaps between the crossovers. The width of the ePTFE fiber
may be greater than 1 times, greater than about 1.5 times, greater than about
2
times, greater than about 3 times, greater than about 4 times, greater than
about
4.5 times, greater than about 5 times, greater than about 5.5 times, or
greater
than about 6 times (or more) the space provided to the fibers based on the
number of picks per inch and/or ends per inch. In other words, the ePTFE
fibers
are woven tighter than the width of the ePTFE fiber, In such embodiments, the
ePTFE fibers begin the weaving process in a substantially rectangular
configuration. However, due to the larger size of the fiber compared to the
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space provided by the picks per inch and/or ends per inch, the ePTFE fibers
curl
and/or fold upon themselves to conform to the weave spacing determined by the
number of picks per inch and/or ends per inch of the warp and weft fibers.
Generally, the folding or curling occurs in the width of the fiber such that
the
width of each individual fiber becomes smaller as the folding or curling of
the
fiber occurs. The fibers are thus in a folded configuration along a length of
the
fiber.
The conformability of the ePTFE fibers is schematically depicted in
FIGS. 40 and 41. In FIGS, 40 and 41, the fibers 10 are to be positioned in
space
(S) in a woven fabric. As shown in FIGS. 40 and 41, the widths (W) of the
fibers 10 are larger than the space (S) allotted for the fibers 10 in the
woven
fabric. In order to fit into the space (S) allotted for the fibers 10, the
fibers 10
fold or curl into a folded configuration 15, such as is illustrated in FIG.
40.
The "foldability" or "folded configuration" of the ePTFE fibers is
evidenced by a line 20 extending along the length of the fibers, as is shown
in at
least FIGS, 3, 5, 7, 10, 13, 16, 18, 20, 24, 26, 30, and 38. FIGS. 44 and 45,
which are cross-section SEMs of an exemplary woven fabric, illustrate the
conformability of the ePTFE fibers, as these figures clearly depict the
folding
(and/or curling) of the fiber upon itself, FIG. 41 depicts a top schematic
view of
the fibers in a curled configuration. The fibers may fold upon themselves in
the
warp and/or the weft direction. As shown in FIG. 41, the Fibers conform to fit
into space (S). In a fabric including warp and weft fibers, at least one of
the
warp and weft fibers is in a folded configuration along, or substantially
along, a
length of the fiber. Thus, the ePTFE fibers fold and/or curl to a smaller
width in
the woven fabric, As one prophetic example, in a 88 ppi X 88 epi woven fabric
and an ePTFE fiber width of 1 mm, the ePTFE fiber will fold upon itself to
produce a Folded width 3.5 times less than its original width in order to
accommodate the space provided in the weave configuration (e.g. 88 ppi divided
by 25.4 mm/1 inch is 3.5 picks per mm).
The conformability of the ePTFE fiber allows larger sized ePTFE fibers
to be utilized in smaller weave spacing. Increasing the number of picks per
inch
and/or ends per inch compared to the width of the fiber reduces or even
eliminates gaps between where the warp and weft fibers intersect, Such tightly
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woven fabrics are concurrently highly breathable and water resistant (e.g.,
have
a high water entry pressure). It is to be appreciated that the fabric breathes
not
only through whatever gap may be present but also through the ePTFE fiber
itself. Even when there are no gaps present, the woven fabric remains
breathable. In contrast, conventional woven fabrics, when tightly woven,
become non-breathable.
Not wishing to be bound by theory, it is believed that the conformability
of the ePTFE fiber as well as the node and fibril structure enables the woven
fabric to achieve many, if not all, of the features and advantages described
herein. For example, the nodes of the ePTFE fiber help the fiber to maintain
an
"open" configuration of the fibrils when the fiber is woven. The open pores of
the ePTFE fibers greatly enhance the breathability of the woven fabric. The
fineness of the pores prevents water into the fiber structure while
maintaining
high breathability. As discussed previously, the conformability of the ePTFE
fibers permits for the fibers to be woven in a tight configuration to render
the
woven fabric water resistant yet breathable.
Treatments may be provided to impart one or more desired functionality,
such as, but not limited to, oleophobicity to the woven fabric. When provided
with an oleophobic coating, such as, but not limited to, a fluoroacrylate
olephobic coating, the woven fabric has an oil rating greater than or equal to
1,
greater than or equal to 2, greater than or equal to 3, greater than or equal
to 4,
greater than or equal to 5, or greater than or equal to 6 when tested
according to
the Oil Rating Test described herein. Coatings or treatments, such as a
fluoroacrylate coating, may be applied to one or both sides of the woven
fabric,
and may penetrate through or only partially through the woven fabric. It is to
be
understood that any functional protective layer, functional coating, or
functional
membrane, such as, but not limited to, polyamides, polyesters, polyurethanes,
cellophane, non-fluoropolymer membranes that are both waterproof and
breathable may be attached or otherwise affixed or layered on the woven
fabric.
The woven fabric may be colored by a suitable colorant composition.
The ePTFE fiber has a microstructure where the pores of the ePTFE fiber are
sufficiently tight so as to provide water resistance and sufficiently open to
provide properties such as moisture vapor transmission and penetration by
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coatings of colorants, The ePTFE fiber has a surface that, when printed,
provides a durable aesthetic. Aesthetic durability can be achieved in some
embodiments with colorant coating compositions that comprise a pigment
having a particle size that is sufficiently small to fit within the pores of
the
ePTFE fiber and/or within the woven fabric, Multiple colors may be applied
using multiple pigments, by varying the concentrations of one or more
pigments,
or by a combination of these techniques. Additionally, the coating composition
may be applied in any form, such as a solid, pattern, or print. A coating
composition can be applied to the woven fabric by conventional printing
methods. Application methods for colorizing include but are not limited to,
transfer coating, screen printing, gravure printing, ink-jet printing, and
knife
coating.
Unlike conventional woven fabrics, the ePTFE woven fabric is able to
breathe through the fibers forming the fabric (i.e., the ePTFE fibers) as well
as
through the gaps formed between the ePTFE fibers during weaving. As
discussed above, the ePTFE fibers have a node and fibril construction that
forms
passageways through the fibers that make the ePTFE fiber breathable. When the
cPTFE fiber is woven, the node and fibril structure maintain open passageways.
Thus, even when the ePTFE fiber is tightly woven such that there are no gaps
or
substantially no gaps formed in the woven structure, the ePTFE woven fabric
maintains its high breathability. The ePTFE woven fabrics have a moisture
vapor transmission rate (MVTR) that is greater than about 3000 g/m2/24 hours,
greater than about 5000 g/m2/24 hours, greater than about 8000 g/m2/24 hours,
greater than about 10000 g/m2/24 hours, greater than about 12000 g/m2/24
hours, greater than about 15000 g/m2/24 hours, greater than about 20000
g/m2/24 hours, or greater than about 25000 g/m2/24 hours when tested according
to the moisture vapor transmission rate (MVTR) Test Method described herein.
As used herein, the term "breathable" or "breathability" refers to woven
fabrics
or laminates that have a moisture vapor transmission rate (MVTR) of at least
about 3000 grams/m2/24 hours, Moisture vapor transmission, or breathability,
provides cooling to a wearer of a garment, for example, made from the woven
fabric.
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The woven fabrics also have an air permeability that is less than about
500 cfm, less than about 300 cfm, less than 100 cfm, less than about 50 cfm,
less
than about 25 cfm, less than about 20 cfi-n, less than about 15 cfm, less than
about 10 cfm, less than about 5 cfm, less than about 3 cfm, and even less than
about 2 cfm. It is to be understood that low air permeability correlates to
improved windproofness of the fabric.
ePTFE woven fabrics described herein have a water pick-up less than or
equal to about 50 g/m2, less than or equal to 40 g/m2, less than or equal to
about
30 g/m2, less than or equal to about 25 g/m2, less than or equal to about 20
g/m2,
less than or equal to about 15 g/m2, or less than or equal to about 10 g/m2
and a
water entry pressure of at least about 1 kPa, at least about 1.5 kPa, at least
about
2 kPa, at least about 3 kPa, at least about 4 kPa, at least about 5 kPa, or at
least
about 6 kPa. The ePTFE fibers restrict the entry of water into the woven
fabric
(into, e.g., the fiber structure and through the gaps of the woven fabric),
thus
eliminating problems associated with conventional woven fabrics that absorb
water, which, in turn, makes the fabrics heavier, and permits for thermal
conductivity of the temperature of the water through the fabric. Such thermal
conductivity may be detrimental in cases where the wearer is in a cold
environment and the cold is transported to the body of the wearer.
Additionally, the woven fabrics are thin and lightweight, which permits
the end user to easily carry and/or transport articles formed from the woven
fabrics, The woven fabrics may have a weight from about 50 g/m2 to about 500
g/m2, from about 80 g/m2 to about 300 g/m2, or from about 90 g/m2 to about 250
g/m2. Additionally, the woven fabrics may have a weight per unit area of less
than about 1000 g/m2, less than about 500 g/m2, less than about 400 g/m2, less
than about 300 g/m2, less than about 200 g/m2, less than about 150 g/m2, or
less
than about 100 g/m2. Further, the woven fabrics may have a height (thickness)
from about 0.05 mm to about 2 mm, from about 0,1 mm to about 1 mm, from
about 0.1 mm to about 0.6 mm, from about 0,1 mm to about 0.5 mm, from about
0.1 mm to about 0.4 mm, from about 0,15 mm to about 0,25 mm, or from about
0,1 mm to about 0.3 mm. The thinness of the woven fabric enables articles
formed from the woven fabric to be folded compactly. The thin and light weight
features also contributes to the overall comfort of the wearer of the garment,
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especially during movement of the wearer as the wearer experiences less
restriction to movement.
Further, the woven fabrics have a soft hand and are drapable, making
them suitable for use in garments, gloves, and footwear, The woven fabric has
an average stiffness less than about 1000 g, less than about 500 g, less than
about 400 g, less than about 300 g, less than about 250 g, less than about 200
g,
less than about 150 g, less than about 100 g, and even less than about 50 g.
It
was surprisingly discovered that in addition to a soft hand, the woven fabrics
demonstrated a reduction in noise associated with bending or folding the woven
fabric. It was further discovered that even with the addition of a porous
polymer
membrane, as discussed hereafter, the noise was reduced, particularly when
compared to conventional ePTFE laminates.
The woven fabrics are also resistant to tearing. For example, the woven
fabric has a tear strength from about 10 N to about 200 N (or even greater),
from
about 15 N to about 150 N, or from about 20 N to about 100 N as measured by
the Elemendorf Tear test described herein. Such a high tear strength enables
the
woven fabric to be more durable in use,
In at least one embodiment, a porous or microporous polymer membrane
is laminated or bonded to the woven fabric. Non-limiting examples of porous
membranes including expanded PTFE, expanded modified PTFE, expanded
copolymers of PTFE, fluorinated ethylene propylene (FEP), and perfluoroalkoxy
copolymer resin (PFA). Polymeric materials such as polyolefins (e.g.,
polypropylene and polyethylene), polyurethanes, and polyesters are considered
to be within the purview of the invention provided that the polymeric material
can be processed to form porous or microporous membrane structures. It is to
be appreciated that even when the inventive woven fabric is laminated or
bonded to a porous or microporous membrane, the resulting laminate remains
highly breathable and substantially maintains the breathability of the woven
fabric, In other words, the porous or microporous membrane laminated to the
woven fabric does not affect, or only minimally affects, the breathability of
the
woven fabric, even when laminated.
The microporous membrane may be an asymmetric membrane. As used
herein, "asymmetric" is meant to indicate that the membrane structure includes
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multiple layers of ePTFE within the membrane where at least one layer within
the membrane has a microstructure that is different from the microstructure of
a
second layer within the membrane. The difference between the first
microstructure and the second microstructure may be caused by, for example, a
difference in pore size, a difference in node and/or fibril geometry or size,
and/or a difference in density.
In a further embodiment, a textile may be attached to the microporous
membrane or directly to the woven fabric. As used herein, the term "textile"
is
meant to denote any woven, nonwoven, felt, fleece, or knit and can be composed
of natural and/or synthetic fiber materials and/or other fibers or flocking
materials. For example, the textile may be comprised of materials such as, but
not limited to cotton, rayon, nylon, polyester, and blends thereof The weight
of
the material forming the textile is not particularly limited except as
required by
the application. In exemplary embodiments, the textile is air permeable and
breathable.
Any suitable process for joining the membrane and/or the textile to the
woven fabric (and textile to the membrane) may be used, such as gravure
lamination, fusion bonding, spray adhesive bonding, and the like. The adhesive
may be applied discontinuously or continuously, provided that breathability
through the laminate is maintained. For example, the adhesive may be applied
in the form of discontinuous attachments, such as by discrete dots or grid
pattern, or in the form of an adhesive web to adhere layers of the laminate
together.
The ePTFE woven fabric is suitable for use in various applications,
including but not limited to garments, tents, covers, bivy bags, footwear,
gloves,
and the like. The woven fabric is concurrently highly breathable and water
resistant. These advantageous features are achieved, at least in part, due to
the
high aspect ratio of the ePTFE fiber. The ePTFE woven fabric can be used
alone, or it can be used in conjunction with a fluoropolyrner membrane and/or
textile. The surface of the ePTFE woven fabric can be colorized, for example,
by printing. Additionally, the surface of the ePTFE fabric and/or the ePTFE
fiber can be coated with an oleophobic coating composition to provide
oleophobicity. It should be appreciated that the benefits and advantages
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described herein equally apply to knitted fabrics and articles as well as the
woven fabrics and articles discussed herein.
TEST METHODS
It should be understood that although certain methods and equipment are
described below, any method or equipment determined suitable by one of
ordinary skill in the art may be alternatively utilized.
Fiber Weight per Length
A 45 meter length of fiber was obtained using a skein reel. The 45 meter
length was then weighed on a scale with precision to 0.0001 grams. This weight
was then multiplied by 200 to give the weight per length in terms of denier
(g/9000m). This value was then multiplied by 10 and divided by 9 to give the
weight per length in terms of dtex (g/10,000m).
Fiber Width
Fiber width was measured in a conventional manner utilizing a I Ox eye
loop having gradations to the nearest 0.1 mm. Three measurements were taken
and averaged to determine the width to the nearest 0.05 mm.
Fiber Thickness
Fiber thickness was measured utilizing a snap gauge accurate to the
nearest 0.0001 inch. Care was taken to not to compress the fibers with the
snap
gauge. Three measurements were taken and averaged and then converted to the
nearest 0.0001 mm.
Fiber Density
Fiber density was calculated utilizing the previously measured fiber
weight per length, fiber width and fiber thickness using the Following
formula:
Fiber Density (g/em3) = Fiber wt per length (dtex)
Fiber Width (mm) * Fiber Thickness (mm) * 10,000
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Fiber Break Strength
The fiber break strength was the measurement of the maximum load
needed to break (rupture) the fiber. The break strength was measured by a
tensile tester, such as an Instron Machine of Canton, MA. The Instron
machine was outfitted with fiber (horn type) jaws that are suitable for
securing
fibers and strand goods during the measurement of tensile loading. The cross-
head speed of the tensile tester was 25.4 cm per minute. The gauge length was
25,4 cm. Five measurements of each fiber type were taken with the average
reported in units of Newtons.
Fiber Tenacity
Fiber tenacity is the break strength of the fiber normalized to the weight
per length of the fiber. Fiber tenacity was calculated using the following
formula:
Fiber tenacity (cN/dtex) = Fiber break strength (N) * 100
Fiber weight per length (dtex)
Fabric and Membrane Thickness
The fabric and membrane thicknesses were measured by placing either
the membrane or textile laminate between the two plates of a Mitutoyo 543-
252BS Snap Gauge, The average of the three measurements was used. It is to
be appreciated that the thickness of the fabric and/or the membrane may be
determined by any suitable method as determined by one of skill in the art,
Matrix Tensile Strength (MTS) of Membrane
Matrix Tensile Strength of the membrane was measured using an
Instron 1122 tensile test machine equipped with flat-faced grips and a 0.445
kN
load cell. The gauge length was 5.08 cm and the cross-head speed was 50.8
cm/min. The sample dimensions were 2.54 cm by 15.24 cm. To ensure
comparable results, the laboratory temperature was maintained between 68 F
(20 C) and 72 F (22.2 C ) to ensure comparable results. Data was discarded
if
the sample broke at the grip interface.
21
For longitudinal MTS measurements, the larger dimension of the sample
was oriented in the machine, or "down web," direction. For the transverse
M'I'S
measurements, the larger dimension of the sample was oriented perpendicular to
the machine direction, also known as the "cross web" direction. Each sample
T
was weighed using a Mettler ToledMo Scale Model AG204. The thickness of the
samples was then measured using a Kafer FZ1000/30 snap gauge. The samples
were then tested individually on the tensile tester. Three different sections
of
each sample were measured. The average of the three maximum load (i.e., the
peak force) measurements was used.
The longitudinal and transverse MTS were calculated using the
following equation:
MTS ¨ (maximum load /cross-section arca)*(bulk density of PTFE)/
density of the porous membrane),
where the bulk density of PTFE is taken to be 2.2 g/cm3,
The average of three cross-web measurements was recorded as the
longitudinal and transverse MTS.
Density of Membrane
To calculate the density of the membrane, measurements from the
Matrix Tensile Testing were used. As mentioned above, the sample dimensions
were 2,54 cm by 15.24 cm. Each sample was weighed using a Mettler Toledoi'm
Seale Model AG204 and then the thickness of the samples was taken using a
Kafer FZ1000/30 snap gauge. Using this data, a density of the sample can be
calculated with the following formula:
w*l*t
where: p = density (g/cm3)
m = mass (g)
w = width (1.5 cm)
1¨ length (16.5 cm)
t = thickness (cm)
The reported results are the average of three calculations.
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Gurley Air Flow of Membrane
The Gurley air flow test measures the time in seconds for 100 cm' of air to
flow through a 6.45 cm2 sample at 12.4 cm of water pressure. The samples were
measured in a Gurley Densometer Model 4340 Automatic Densometer. When
multiple tests are performed on the same sample, care must be taken to ensure
that the
edges of the test areas do not overlap. (The compression that occurs to the
material
along the edges of the test area when it is clamped to create a seal during a
Gurley
test can affect the air flow results.) The reported results are the average of
three
measurements.
Moisture Vapor Transmission Rate Test ¨ (MVTR)
The MVTR for each sample fabric was determined in accordance with the
general teachings of ISO 15496 except that the sample water vapor transmission
(WVP) was converted into MVTR moisture vapor transmission rate (MVTR) based
on the apparatus water vapor transmission (WVPapp) and using the following
conversion.
MVTR = (Delta P value * 24)! ( (MVP) + (1 + WVPapp value) )
To ensure comparable results, the specimens were conditioned at 73.4 + 0.4 F
and 50 2% rH for 2 hrs prior to testing and the bath water was a constant
73.4 F +
0.4 F.
The MVTR for each sample was measured once, and the results are reported
as g/m2/24 hours.
Mass/Area
In order to measure mass per area, fabric samples were prepared having an
area of at least 100 cm2. A Karl Schroder 100 cm2 circle cutter may be used.
Each
sample was weighed using a Mettler ToledoTm Scale Model AB204. The scale was
recalibrated prior to weighing specimens, and the results were reported in
grams per
square meter (gsm). For membrane samples, the reported results are the average
of
three measurements. For printed laminate samples, the reported data is the
result of a
single measurement.
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Oil Rating Test
Oil rating of both membranes and laminates were measured. Tests were
conducted following the general teachings of AATCC Test Method 118-1997.
The oil rating number is the highest number oil which does not wet the
material
within a test exposure time of 30 2 seconds. The reported results are the
average of three measurements.
SEM Sample Preparation Method
Cross-section SEM samples were prepared by spraying them with liquid
nitrogen and then cutting the sprayed samples with a diamond knife in a Leica
TM
ultracut UCT, available from Leica Microsystems, Wetzlar, Germany.
Fibril Length Measurement
The surface SEM images were used to measure fibril length. A
magnification was chosen to enable the viewing of multiple fibrils, including
a
clear view of the points where fibrils attached to nodes. The same
magnification
was used for each sample that was measured. Since these node and fibril
structures were irregular, 15 different fibrils, randomly distributed across
each
image, were identified for measurement.
To measure each fibril accurately, lines were drawn with the cursor so
that they were perpendicular to the fibril on both ends where the fibril
attaches
to the node. The distance between the cursor drawn lines were measured, and
recorded for each fibril. The results for each surface image of each sample
were
averaged. The reported value for fibril length represents the average of 15
sample measurements on the SEM image.
Liquidproof Test (Suter) and Water Pick-Up
Liquidproof testing and water pick-up was conducted as follows.
Laminates were tested for liquidproofness by using a modified Suter test
apparatus with water serving as a representative test liquid. Water is forced
against a sample area of about 41/4 inch (10.8 cm) diameter sealed by two
rubber
gaskets in a clamped arrangement. Samples are tested by orienting the sample
so that the outer film surface of the sample is the surface against which
water is
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forced. The water pressure on the sample is increased to about 0.7 psi (4.82
KPa) by a pump connected to a water reservoir, as indicated by an appropriate
gauge and regulated by an in-line valve. The test sample was positioned at an
angle, and the water was recirculated to ensure that water, not air, contacted
the
lower surface of the sample. The surface opposite the outer film surface of
the
sample was observed for a period of 3 minutes for the appearance of any water
which would be forced through the sample. Liquid water seen on the surface
was interpreted as a leak.
A passing (liquidproof) grade was given in cases where no liquid water
is visible on the sample surface within 3 minutes. A sample was deemed
"liquidproof" as used herein if it passed this test. Samples having any
visible
liquid water leakage, e.g. in the form of weeping, pin hole leak, etc. were
not
considered liquidproof and failed the test.
To determine water pick up the sample was weighed before and after the
test. The difference in grams was converted to grams per square meter from a
10,8 cm diameter circle sample, thereby providing the weight increase picked
up
from water. The reported results are the average of three measurements.
Gap Between Fibers Measurement
Surface SEM images were used to measure the gap between fibers. A
magnification was chosen to enable the viewing of at least ten fiber
crossovers,
including a clear view of the gaps where the fibers overlap. For each gap, the
distance (D) between the fibers, at the crossovers 30 as shown in Figure 52,
was
measured to the nearest micrometer in the warp direction. This distance (D)
was
measured and averaged for at least ten crossovers within the field of view. It
is
to be noted that only two crossovers 30 are depicted in FIG. 52, and are for
purposes of illustration only. Also, for each gap, the distance (D')
orthogonal to
the direction corresponding to distance between the fibers at the crossovers
30
was measured to the nearest micrometer in the fill direction. This distance D'
was measured and averaged for at least ten crossovers within the field of
view.
The average gap distance (D) in the warp direction and the average gap
distance
(D') in the fill direction were reported, with the larger value reported
first,
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Water Entry Pressure (WEP)
Water entry pressure provides a test method for water intrusion through
membranes and/or fabrics. A test sample is clamped between a pair of testing
plates. The lower plate has the ability to pressurize a section of the sample
with
water. A piece of paper is placed on top of the sample between the plate on
the non-pressurized side as an indicator of evidence for water entry. The
sample
is then pressurized in small increments, waiting 10 seconds after each
pressure
change until a color change in the pH paper indicates the first sign of water
entry, The water pressure at breakthrough or entry is recorded as the Water
Entry Pressure. The test results are taken from the center of test sample to
avoid
erroneous results that may occur from damaged edges.
Tear Strength
This test is designed to determine the average force required to propagate
a single-rip tongue-type tear starting from a cut in woven fabric. A Thwing-
Albert Heavy Duty Elmendorf Tearing Tester (MAI227) was used. After the
instrument was calibrated and the correct pendulum weight was selected, a
blinking asterisk on the left side of the display will indicate the instrument
is
ready for testing. The pendulum was raised to the starting position. The
specimen was placed in jaws and clamped using the air clamp located on the
lower right side of instrument. The air pressure was between 414 KPa and 621
KPa, The specimen was centered with the bottom edge carefully against the
stops. The upper area of the specimen should be directed towards the pendulum
to ensure a shearing action. The test was performed until a complete tear was
achieved. The digital readout was recorded in Newtons. This was repeated until
a set (1 warp and 1 weft). The reported results are the average of the
measurements for one set.
Stiffness
A Thwing Albert Handle-O-Meter with a 1000g beam and 1/4" slot width
was used to measure the hand (stiffness). A 4" x 4" sample was cut from the
fabric. The specimen was placed face up on the specimen platform. The
specimen was lined up so that the test direction is perpendicular to the slot
to
26
test the warp direction. The START/Test button was pressed until a click is
heard,
then released. The number appearing on the digital display after a second
click is
heard was recorded. The reading will not return to zero but will show the peak
reading of each individual test. The specimen was turned over and tested
again,
recording the number. Then the specimen was turned 90 degrees to test the fill
direction, recording the number. Finally, the specimen was turned over and
tested
again, recording the number. The 4 recorded numbers were added together (1
Warp
Face, 1 Warp Back, I Fill face, I Fill Back) to calculate the overall
stiffness of the
specimen in grams. The results were reported for one sample.
Air Permeability - Frazier Number Method
Air permeability was measured by clamping a test sample in a gasketed
flanged fixture which provided a circular area of approximately 6 square
inches (2.75
inches diameter) for air flow measurement. The upstream side of the sample
fixture
was connected to a flow meter in line with a source of dry compressed air. The
downstream side of the sample fixture was open to the atmosphere.
Testing was accomplished by applying a pressure of 0.5 inches of water to the
upstream side of the sample and recording the flow rate of the air passing
through the
in-line flovvmeter (a ball-float rotameter).
The sample was conditioned at 70 F (21.1 C) and 65% relative humidity for
at least 4 hours prior to testing.
Results are reported in terms of Frazier Number which is air flow in cubic
feet/minute/square foot of sample at 0.5 inches water pressure.
Examples
Example la
A fine powder PTFE resin (Teflon 669 X, commercially available from E.I.
du Pont de Nemours, Inc., Wilmington, DE) was obtained. The resin was blended
with Isopar K in the ratio of 0.184 g/g by weight of powder. The lubricated
powder
was compressed in a cylinder and allowed to dwell at room temperature for 18
hours.
The pellet was then ram extruded at a 169 to one
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reduction ratio to produce a tape of approximately 0.64 mrn thick. The
extruded
tape was subsequently compressed to a thickness of 0.25 mm. The compressed
tape was then stretched in the longitudinal direction between two banks of
rolls,
The speed ratio between the second bank of rolls and the first bank of rolls,
hence the stretch ratio was 1.4:1 with a stretch rate of 30 %/sec. The
stretched
tape was then restrained and dried at 200 C. The dry tape was then expanded
between banks of heated rolls in a heated chamber at a temperature of 300 C
to
a ratio of 1,02:1 at a stretch rate of 0.2 %/sec, followed by an additional
expansion ratio of 1.75:1 at a stretch rate of 46%/sec, followed by an
additional
expansion ratio of 1.02:1 at a stretch rate of 0,5 %/sec. This process
produced a
tape with a thickness of 0.24 mm.
This tape was then slit to create a cross-section of 1.78 mm wide by 0.24
mm thick and having a weight per length of 3494 dtex. The slit tape was then
expanded over a heated plate set to 390 C at a stretch ratio of 6.25:1 with a
stretch rate of 65 %/sec, This was followed by further expansion across a
heated
plate set to 390 C at a stretch ratio of 2.50:1 with a stretch rate of 66
%/sec,
This was followed by a further expansion across a heated plate set to 390 C at
a
stretch ratio of 1.30:1 with a stretch rate of 23 %/sec. This was followed by
running across a heated plate set to 390 C at a stretch ratio of 1.00:1 for a
duration of 1.6 seconds, resulting in an amorphously locked expanded PTFE
fiber.
The final amorphously locked ePTFE fiber measured 172 dtex and had a
rectangular cross-section and possessed the following properties: width ¨ 1.0
mm, height ¨ 0.0356 mm, density = 0.48 g/em3, break strength of 3,51 N,
tenacity of 2.04 eN/dtex, and fibril length ¨ 53.7 microns.
A scanning electron micrograph (SEM) of a side of the resulting fiber
taken at 1000x magnification is shown in FIG. 1. FIG. 2 is a scanning electron
micrograph of the top surface of the fiber taken at 1000x magnification.
The fiber was then used to create a woven fabric, The weaving pattern
was 2/2 twill using a thread count of 88x88 threads/inch, The woven fabric had
the following properties: thickness ¨ 0.20 mm, MVTR = 27860 g/m2/24 hours,
water pick-up = 13 gsm, hand ¨ 71 g, tear strength 75.6 N, WEP 5.38 kPa,
air permeability = 0,81 cfin, and oil rating - <1. A scanning electron
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micrograph of the surface of the fabric taken at 150x magnification is
depicted
in FIG. 3, A scanning electron micrograph of a side view of the fabric taken
at
150x magnification is shown in FIG. 4. The length and width of the gaps
between the warp and weft fibers were less than 0.01 mm. The fabric had a
weight of 135 g/m2.
A fiber (172 dtex) was removed from the woven fabric and dimensional
measurements were taken of its conformed state post-weaving in order to
demonstrate the conformability of the fiber. The fiber was determined to have
a
post-weaving folded width of 0,30 mm, a post-weaving folded height of 0.0699
mm, a post-weaving aspect ratio of 4.3, and a post-weaving density of 0.82
g/cm3. The pre-woven width to the post-weaving folded width ratio was 3.3 to
1.
Example lb
A fluoroacrylate coating was applied to the woven fabric of Example la
in order to render it oleophobic while preserving the porous and microporous
structure.
The resulting oleophobic woven fabric had the following properties:
thickness = 0.20 mm, MVTR = 21206 g/m2/24 hours, water pick-up 11 gsm,
hand = 131 g, tear strength = 63.8 N, WEP = 6.11 KPa, air permeability = 1.72
cfm, and oil rating = 6. A scanning electron micrograph of surface of the
woven
fabric taken at 150x magnification is shown in FIG. 5. A scanning electron
micrograph of a side view of the fabric taken at 150x magnification is shown
in
FIG. 6. The length and width of the gaps between the fibers were less than
0,01
min. The fabric had a weight of 158 g/m2.
Example lc
An amorphously locked ePTFE membrane was obtained having the
following properties: thickness = 0.04 mm, density = 0.47 glee, matrix tensile
strength in the strongest direction = 105.8 MPa, matrix tensile strength in
the
direction orthogonal to the strongest direction = 49,9 MPa, Gurley = 16,2 s,
MVTR = 64168 g/m2/24 hours.
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The woven fabric of Example lb was laminated to the ePTFE membrane
in the following manner. The fabric and the ePTFE membrane were bonded
together by applying a dot pattern of a melted polyurethane adhesive to the
membrane. While the polyurethane adhesive dots were molten, the fabric was
positioned on top of the adhesive side of the membrane. This construct
(article)
was allowed to cool,
The resulting article had the following properties: thickness = 0.22 mm,
MVTR ¨ 12845 g/m2/24 hours, water pick-up = 12 gsm, hand = 196 g, tear
strength = 46.19 N, and oil rating ¨ 6. A scanning electron micrograph of the
top surface of the article taken at 150x magnification is presented in FIG, 7.
A
side view of the article taken at 100x magnification is shown in FIG, 8. A
side
view of the article taken at 1000x magnification is shown in FIG, 9. The
length
and width of the gaps between the fibers were less than 0.01 mm. The fabric
had a weight of 192 g/m2.
Example id
The woven fabric of Example lb was laminated to a plain weave nylon
textile (weight of 18 g/m2, 150 ends per inch, and 109 picks per inch, 17 dtex
(5
filaments) in the following manner. The fabric and the textile were bonded
together by applying a dot pattern of a melted polyurethane adhesive to the
fabric, While the polyurethane adhesive dots were molten, the textile was
positioned on top of the adhesive side of the fabric. This construct was
allowed
to cool.
The resulting article had the following properties: thickness = 0.25 mm,
MVTR = 14407 g/m2/24 hours, water pick-up = 54 gsm, hand = 288 g, tear
strength ¨ 43.18 N, WEP 5,72; KPa, air permeability = 0,86 cfm, and oil
rating = 6. A scanning electron micrograph of the top surface of the article
taken at 150x magnification is presented in FIG. 10. A scanning electron
micrograph of a side view of the article taken at 100x magnification is shown
in
FIG. 11. A scanning electron micrograph of a side view of the article taken at
500x magnification is shown in FIG. 12, The length and width of the gaps
between the fibers were less than 0.01 mm, The fabric had a weight of 192
g/m2.
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Example le
A laminated article was constructed in the following manner, The
membrane and the textile as described in Example in were bonded together by
applying a dot pattern of a melted polyurethane adhesive to the membrane.
While the polyurethane adhesive dots were molten, the textile was positioned
on
top of the adhesive side of the fabric. This construct was allowed to cool.
Next,
the fabric was bonded to the membrane by applying a dot pattern of a melted
polyurethane adhesive to the membrane, While the polyurethane adhesive dots
were molten, the fabric was positioned on top of the membrane, This construct
was allowed to cool,
The resulting article had the following properties: thickness = 0.26 mm,
MVTR = 8708 g/m2/24 hours, water pick-up = 11 gsm, hand = 526 g, tear
strength = 37.78 N, and oil rating = 6. A scanning electron micrograph of the
top surface of the article taken at 150x magnification is shown in FIG. 13. A
scanning electron micrograph of a side view of the article taken at 100x
magnification is shown in FIG. 14. A scanning electron micrograph of a side
view of the article taken at 300x magnification is shown in FIG. 15, The
length
and width of the gaps between the fibers were less than 0,01 mm. The fabric
had a weight of 216 g/m2,
Example 2a
A woven fabric was constructed in the same manner as described in
Example la with the exception that the weave pattern was a plain weave. The
woven fabric had the following properties: thickness = 0.15 mm, MVTR =-
21336 g/m2/24 hours, water pick-up ¨ 4 gsm, hand = 83 g, oil rating = <1, WEP
= 3,13 KPa, air permeability = 0,44 cfm, and tear strength = 36.3 N. A
scanning
electron micrograph of the top surface of the fabric taken at 150x
magnification
is shown in FIG, 16. A scanning electron micrograph of a side view of the
article taken at 250x magnification is shown in FIG, 17. The length and width
of the gaps between the fibers were about 0,01 mm and 0.01 mm, respectively.
The fabric had a weight of 142 g/m2.
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A fiber (172 dtex) was removed from the woven fabric and dimensional
measurements were taken of its conformed state post-weaving in order to
demonstrate the conformability of the fiber, The fiber was determined to have
a
post-weaving folded width of 0.25 mm, a post-weaving folded height of 0.0736
mm, a post-weaving aspect ratio of 3.4, and a post-weaving density of 0.94
g/cm3. The pre-woven width to the post-weaving folded width ratio was 4.0 to
1.
Example 2b
The woven fabric of Example 2a was rendered oleophobic in the same
manner as described in Example lb.
The oleophobic woven fabric had the following properties: thickness ¨
0.16 mm, MVTR = 13265 g/m2/24 hours, water pick-up = 7 gsm, hand ¨ 141 g,
tear strength = 30.3 N, WEP = 4.01 KPa, Air permeability = 0.49 cfm, and oil
rating = 6. A scanning electron micrograph of the top surface of the fabric
taken
at 150x magnification is presented in FIG. 18. A scanning electron micrograph
of a side view of the fabric taken at 250x magnification is shown in FIG, 19.
The length and width of the gaps between the fibers were about 0.01 mm and
0.02 mm, respectively. The fabric had a weight of 158 g/m2.
Example 2e
An oleophobic laminated article was constructed in the following
manner. The membrane and the textile were bonded together by applying a dot
pattern of a melted polyurethane adhesive to the membrane. While the
polyurethane adhesive dots were molten, the textile was positioned on top of
the
adhesive side of the fabric. This construct was allowed to cool. Next, the
fabric
was bonded to the membrane by applying a dot pattern of a melted polyurethane
adhesive to the membrane. While the polyurethane adhesive dots were molten,
the fabric was positioned on top of the membrane. This construct was allowed
to cool.
The resulting article had the following properties: thickness = 0,24 mm,
MVTR = 8274 g/m2/24 hours, water pick-up 10 gsm, hand = 465 g, tear
strength ¨ 20,59 N, and oil rating = 6. A scanning electron micrograph of the
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top surface of the article taken at 150x magnification is presented in FIG.
20. A
scanning electron micrograph of a side view of the article taken at 250x
magnification is shown in FIG. 21. The length and width of the gaps between
the fibers were about 0.01 mm and 0.03 mm, respectively. The fabric had a
weight of 214 g/m2.
Example 3a
A tape was produced in the same manner as described in Example la,
This tape was then slit to create a cross-section or 1.14 mm wide by 0.24 mm
thick and having a weight per length of 2184 dtex, The slit tape was then
expanded across a heated plate set to 390 C at a stretch ratio of 6.00:1 with
a
stretch rate of 70 %/sec. This was followed by expansion across a heated plate
set to 390 C at a stretch ratio of 2.50:1 with a stretch rate of 74 %/sec.
This
was followed by a further expansion across a heated plate set to 390 C at a
stretch ratio of 1.30:1 with a stretch rate of 26 %/sec. This was followed by
running across a heated plate set to 390 C at a stretch ratio of 1.00:1 for a
duration of 1.4 seconds resulting in an amorphously locked expanded PTFE
fiber.
The amorphously locked ePTFE fiber measured 112 dtex and had a
rectangular cross-section and possessed the following properties: width = 0.7
mm, height = 0.0356 mm, density = 0.45 g/cm3, break strength of 2,14 N,
tenacity of 1.92 cN/dtex, and fibril length = 57.2 microns,
A scanning electron micrograph of the fiber taken at 1000x
magnification is shown in FIG, 22, A scanning electron micrograph of a side
view of the fiber taken at 1000x magnification is shown in FIG. 23,
The fiber was used to create a woven fabric, The weaving pattern was
2/2 twill and a thread count of 100 x100 threads/inch. The woven fabric had
the
following properties: thickness = 0.15 mm, MVT'R ¨ 32012 g/m2/24 hours,
water pick-up = 21 gsm, hand = 47 g, oil rating = <1, WEP = 2.15 KPa, air
permeability = 1.17 elm, and tear strength = 57.8 N. A scanning electron
micrograph of the woven fabric taken at 150x magnification is shown in FIG.
24, A scanning electron micrograph of a side view of the fabric taken at 200x
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magnification is shown in FIG. 25. The length and width of the gaps between
the fibers were less than 0.01 mm, The fabric had a weight of 102 g/m2.
A fiber (112 dtex) was removed from the woven fabric and dimensional
measurements were taken of its conformed state post-weaving in order to
demonstrate the conformability of the fiber. The fiber had a post-weaving
folded width of 0.25 mm, a post-weaving folded height of 0,0559 mm, a post-
weaving aspect ratio of 4.5, and a post-weaving density of 0.80 g/cm3. The pre-
woven width to the post-weaving folded width ratio was 2.8 to 1.
Example 3b
The woven fabric of Example 3a was rendered oleophobic in the same
manner as described in Example lb. This article had the following properties:
thickness = 0.15 mm, MVTR = 20526 g/m2/24 hours, water pick-up = 15 gsm,
hand = 86 g, tear strength = 48.2 N, WEP = 5.45 KPa, air permeability = 1.85
cfm, and oil rating = 6. A scanning electron micrograph of the fabric taken at
150x magnification is shown in FIG. 26. A scanning electron micrograph of a
side view of the fabric taken at 200x magnification is shown in FIG. 27, The
length and width of the gaps between the fibers were less than 0.01 mm, The
fabric had a weight of 120 g/m2.
Example 4
A fine powder PTFE resin (Teflon 669 X, commercially available from
E,I. du Pont de Nemours, Inc,, Wilmington, DE) was obtained. The resin was
blended with Isopar K in the ratio of 0.184 g/g by weight of powder. The
lubricated powder was compressed in a cylinder and placed in an oven at a
temperature of 49 C for 18 hours. The pellet was then ram extruded at a 169 to
one reduction ratio to produce a tape of approximately 0,64 mm thick. The
extruded tape was subsequently compressed to a thickness of 0.25 mm. The
compressed tape was then stretched in the longitudinal direction between two
banks of rolls. The speed ratio between the second bank of rolls and the first
bank of rolls, hence the stretch ratio was 1.4:1 with a stretch rate of 30
%/sec,
The stretched tape was then restrained and dried at 200 C. The dry tape was
then expanded between banks of heated rolls in a heated chamber at a
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temperature of 300 C to a ratio of 1.02:1 at a stretch rate of 0.2 %/sec,
followed
by an additional expansion ratio of 1.75:1 at a stretch rate of 46%/sec,
followed
by an additional expansion ratio of 1.02:1 at a stretch rate of 0.5 %/sec.
This
process produced a tape with a thickness of 0,24 mm thick.
This tape was then slit to create a cross-section of 1.14 mm wide by 0.24
mm thick and having a weight per length of 2373 dtex. The slit tape was then
expanded across a heated plate set to 390 C at a stretch ratio of 6.00:1 with
a
stretch rate of 69 %/sec. This was followed by further expansion across a
heated
plate set to 390 C at a stretch ratio of 2.20:1 with a stretch rate of 32
%/sec.
This was followed by a further expansion across a heated plate set to 390 C
at a
stretch ratio of 1.40:1 with a stretch rate of 19 %/sec. This was followed by
a
further expansion across a heated plate set to 390 C at a stretch ratio of
1.20:1
with a stretch rate of 12 %/sec. This was followed by running across a heated
plate set to 390 C at a stretch ratio of 1,00:1 for a duration of 2.1
seconds,
resulting in an amorphously locked expanded PTFE fiber,
The final amorphously locked ePTFE fiber measured 107 dtex and had a
rectangular cross-section and possessed the following properties: width = 0.45
mm, height = 0.0279 mm, density = 0.85 g/cm3, break strength of 3.20 N,
tenacity of 3.01 cN/dtex, and fibril length = 16.1 microns.
A scanning electron micrograph of the top surface of the fiber taken at
1000x magnification is shown in FIG, 28. FIG. 29 is a scanning electron
micrograph of a side view of the fiber taken at 1000x magnification.
'fhe fiber was used to create a woven fabric. The weaving pattern was
2/2 twill and a thread count of 100x100 threads/inch, The woven fabric had the
following properties: thickness = 0.13 mm, MVTR = 28497 g/m2/24 hours,
water pick-up = 5 gsm, hand 72 g, oil rating = < 1, WEP - 1.96 KPa, Air
permeability = 2,4 cfm, and tear strength = 71,2 N. A scanning electron
micrograph of the top surface of the fabric taken at 150x magnification is
shown
in FIG. 30. A side view of the fabric taken at 150x magnification is shown in
FIG, 31. The length and width of the gaps between the fibers were less than
0.01 mm. The fabric had a weight of 93 g/m2.
A fiber (107 dtex) was removed from the woven fabric and dimensional
measurements were taken of its conformed state post-weaving in order to
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demonstrate the conformability of the fiber. The fiber had a post-weaving
folded width of 0.25 mm, a post-weaving folded height of 0,0356 mm, a post-
weaving aspect ratio of 7.0, and a post-weaving density of 1.20 g/cm3. The pre-
woven width to the post-weaving folded width ratio was 1.8 to 1.
Example 5
A tape was produced in the same way as in Example la. This tape was
then slit to create a cross-section of 4.57 mm wide by 0.236 mm thick and
having a weight per length of 7937 dtex. The slit tape was then expanded
across
a heated plate set to 390 C at a stretch ratio of 6.00:1 with a stretch rate
of 70
%/sec. This was followed by another expansion across a heated plate set to
390 C at a stretch ratio of 2,50:1 with a stretch rate of 74 %/sec. This was
followed by a further expansion across a heated plate set to 390 C at a
stretch
ratio of 1.30:1 with a stretch rate of 26 %/sec. This was followed by running
across a heated plate set to 390 C at a stretch ratio of 1.00:1 for a duration
of 1,4
seconds, resulting in an amorphously locked expanded FITE fiber.
The amorphously locked ePTFE fiber measured 452 dtex and had a
rectangular cross-section and possessed the following properties: width = 2,2
mm, height = 0,0406 mm, density = 0.51 g/cm3, break strength of 11.48 N,
tenacity of 2.55 cN/dtex, and fibril length = 60 microns. A scanning electron
micrograph of the fiber surface taken at 1000x magnification is shown in FIG.
36. A scanning electron micrograph of a side view of the fiber taken at 1000x
magnification is shown in FIG. 37,
The weaving pattern was a plain weave and had a thread count of 50 x
50 threads/inch (19.7 x 19.7 threads/cm). The ratio of the pre-woven fiber
width
to the calculated allotted space per fiber within the weave pattern was 4.3 to
1.
The woven fabric had the following properties: thickness ¨ 0.24 mm, MVTR =
14798 g/m2/24 hours, water pick-up = 15 gsm, hand = 281 g, oil rating = <1,
WEP = 1.86 kPa, air permeability = 2.1 cfm. A scanning electron micrograph of
the woven fabric taken at 150x magnification is shown in FIG. 38. A scanning
electron micrograph of a side view of the fabric taken at 150x magnification
is
shown in FIG. 39. The length and width of the gaps between the fibers were
about 0.04 mm and 0.01 mm, respectively. Scanning electron micrographs of
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the top surface of the fabric taken at 120x magnification depicting the gap
width
measurements in the horizontal direction and the gap width measurements in the
vertical direction are shown in FIGS. 40 and 41, respectively. The fabric had
a
weight of 211 g/m2.
A fiber (452 dtex) was removed from the woven fabric and dimensional
measurements were taken of its conformed state post-weaving in order to
demonstrate the conformability of the fiber. The fiber had a post-weaving
folded width of 0.40 mm, a post-weaving folded height of 0,1524 mm, a post-
weaving aspect ratio of 2.6, and a post-weaving density of 0.74 g/cm3. The pre-
woven width to the post-weaving folded width ratio was 5.5 to 1.
Example 6
A woven fabric was constructed in the same manner as described in
Example 5 with the exception that the plain weave pattern had a thread count
of
40 x 40 threads/inch (15.7 x 15.7 threads/cm). The woven fabric had the
following properties: thickness - 0,25 mm, MVTR = 27846 g/m2/24 hours,
water pick-up = 7 gsm, hand = 71 g, oil rating = <1, WEP = 1.69 KPa, and air
permeability = 3.87 cfm. A scanning electron micrograph of the top surface of
the fabric taken at 150x magnification is shown in FIG. 42. A scanning
electron
micrograph of a side view of the fabric taken at 150x magnification is shown
in
FIG. 43. Scanning electron micrographs of side views of the fabric taken at
300x and 400x magnifications are shown in FIGS. 44 and 45, respectively. FIG.
45 clearly depicts the conforming of the fiber to the weave spacing, as the
fiber
has folded upon itself.
The length and width of the gaps between the fibers were about 0.08 mm
and 0.02 mm, respectively. The fabric had a weight of 157 g/m2.
A fiber (452 dtex) was removed from the woven fabric and dimensional
measurements were taken or its conformed state post-weaving in order to
demonstrate the conformability of the fiber. The fiber had a post-weaving
folded width of 0,50 mm, a post-weaving folded height of 0.1219 mm, a post-
weaving aspect ratio of 4,1, and a post-weaving density of 0,74 g/cm3. The pre-
woven width to the post-weaving folded width ratio was 4.4 to I.
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Comparative Example 1
An ePTFE fiber by W.L. Gore & Associates (part number V111776,
W.L. Gore & Associates, Inc., Elkton, MD) was obtained. The ePTFE fiber
measured 111 dtex and had a rectangular cross-section and possessed the
following properties: width = 0.5 mm, height = 0,0114 mm, density = 1.94
g/cm3, break strength = 3.96 N, tenacity = 3.58 cN/dtex, and fibril length ¨
indeterminate (no visible nodes to define an endpoint for the fibrils). A
scanning electron micrograph of the top surface of the fiber taken at 1000x
magnification is shown in FIG. 32. A scanning electron micrograph of a side
view of the fiber taken at 1000x magnification is shown in FIG. 33,
In order to successfully weave this fiber, it was twisted at 315
turns/meter. This twisted fiber was then woven into a fabric using a 2/2 twill
pattern and a thread count of 100x100 threads/inch.
The woven fabric had the following properties: thickness = 0,12 mm,
MVTR = 36756 g/m2/24 hours, water pick-up = 4 gsm, hand = 102 g, WEP =-
0.39 kPa, air permeability ¨ 367 cfm, and oil rating = < 1. A scanning
electron
micrograph of the top surface of the fabric taken at 150x magnification is
shown
in FIG. 34. A scanning electron micrograph of a side view of the fabric, taken
at
150x magnification is shown in FIG. 35. The length and width of the gaps
between the fibers were about 0.09 aim and 0,12 mm, respectively. The fabric
had a weight of 94 g/m2.
Comparative Example 2
A non-microporous commercially available ePTFE fiber available from
W,L. Gore & Associates (part number V112961, W.L. Gore & Associates, Inc.,
Elkton, MD) was obtained. The ePTFE fiber measured 457 dtex and had a
rectangular cross-section and possessed the following properties: width ¨ 0.6
mm, height = 0,0419 mm, density = 1,82 g/cm3, break strength = 18.33 N,
tenacity = 4.03 cN/dtex, and fibril length = indeterminate (no visible nodes
to
define an endpoint for the fibrils), A scanning electron micrograph of the top
surface of the fiber taken at 1000x magnification is shown in FIG. 46. A
scanning electron micrograph of a side view of the fiber taken at 1000x
magnification is shown in FIG. 47,
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In order to successfully weave this ePTFE fiber, it was twisted at 118
turns/meter. This twisted fiber was then woven into a fabric using a plain
weave
pattern and a thread count of 50X50 threads/inch.
The woven fabric had the following properties: thickness = 0,21 mm,
MVTR = 11659 g/m2/24 hours, water pick-up = 10 gsm, hand = 380 g, WEP =
0.49 kPa, air permeability = 70 cfm, and oil rating = < 1. A scanning electron
micrograph of the top surface of the fabric taken at 150x magnification is
shown
in FIG. 48. A scanning electron micrograph of a side view of the fabric taken
at
150x magnification is shown in FIG. 49. The length and width of the gaps
between the fibers were about 0.11 mm and 0.08 mm, respectively. The fabric
had a weight of 201 g/m2,
Comparative Example 3
A commercially available ePTFE fiber available from W.L. Gore &
Associates (part number V112961, W.L. Gore & Associates, Inc., Elkton, MD)
was obtained. The ePTFE fiber measured 457 dtex and had a rectangular cross-
section and possessed the following properties: width = 0.6 mm, height =
0,0419
mm, density = 1.82 g/cm3, break strength = 18.33 N, tenacity - 4.03 cNidtex,
and fibril length = indeterminate (no visible nodes to define an endpoint for
the
fibrils). A scanning electron micrograph of the top surface of the fiber taken
at
1000x magnification is shown in FIG. 46. A side view of the fiber taken at
1000x magnification is shown in FIG. 47.
In order to successfully weave this ePTFE fiber, it was twisted at 138
turns/meter. This twisted fiber was then woven into a fabric using a plain
weave
pattern and a thread count of 64X64 threads/inch.
The woven fabric had the following properties: thickness = 0.24 mm,
MVTR = 7840 g/m2/24 hours, water pick-up ¨ 9 gsm, hand = 698 g, WEP =
1.12 kPa, air permeability = 26 cfin, and oil rating = < 1. A scanning
electron
micrograph of the top surface of the fabric taken at 150x magnification is
shown
in FIG. 50. A side view of the fabric taken at 150x magnification is shown in
FIG. 51. The length and width of the gaps between the fibers were about 0.07
mm and 0.02 mm, respectively. The fabric had a weight of 261 g/m2.
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The invention of this application has been described above both
generically and with regard to specific embodiments. It will be apparent to
those skilled In the art that various modifications and variations of the
invention
can be made without departing from the spirit or scope of the invention, as
defined in the appended claims.
