U.S. patent application number 14/158550 was filed with the patent office on 2014-05-15 for barrier layer for inflatable structures.
This patent application is currently assigned to GOODRICH CORPORATION. The applicant listed for this patent is GOODRICH CORPORATION. Invention is credited to Anthony M. Mazany.
Application Number | 20140134354 14/158550 |
Document ID | / |
Family ID | 50681954 |
Filed Date | 2014-05-15 |
United States Patent
Application |
20140134354 |
Kind Code |
A1 |
Mazany; Anthony M. |
May 15, 2014 |
BARRIER LAYER FOR INFLATABLE STRUCTURES
Abstract
An air-impermeable fabric is disclosed. The air-impermeable
fabric has a fabric substrate, which may also be referred to as a
base fabric. Disposed over the fabric substrate is a barrier layer
comprising a polymer binder and at least 20 weight percent graphene
nanoplatelets, based on the total weight of the barrier layer. A
barrier underlayer, which may or may not also include graphene
nanoplatelets, is disposed between the fabric substrate and the
barrier layer. A barrier overlayer, which may or may not also
include graphene nanoplatelets, is disposed on the opposite side of
the barrier layer from the barrier underlayer
Inventors: |
Mazany; Anthony M.; (Amelia
Island, FL) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
GOODRICH CORPORATION |
Charlotte |
NC |
US |
|
|
Assignee: |
GOODRICH CORPORATION
Charlotte
NC
|
Family ID: |
50681954 |
Appl. No.: |
14/158550 |
Filed: |
January 17, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
13490083 |
Jun 6, 2012 |
8663762 |
|
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14158550 |
|
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61494759 |
Jun 8, 2011 |
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Current U.S.
Class: |
428/12 ; 428/216;
428/219; 442/72 |
Current CPC
Class: |
D06N 3/0063 20130101;
D06N 2209/067 20130101; B64D 25/14 20130101; Y10T 428/24975
20150115; D06N 3/14 20130101; D06N 3/0059 20130101; D06N 3/145
20130101; D06N 2205/08 20130101; B82Y 30/00 20130101; D06N 2205/12
20130101; D06N 2209/125 20130101; Y10T 442/2107 20150401; D06N
2205/103 20130101; A62B 1/20 20130101 |
Class at
Publication: |
428/12 ; 442/72;
428/219; 428/216 |
International
Class: |
D06N 3/00 20060101
D06N003/00 |
Claims
1. An air-impermeable fabric, comprising a fabric substrate; a
barrier layer comprising a first resin binder and graphene
nanoplatelets, said barrier coating comprising at least 20 wt. % of
the graphene nanoplatelets, based on the total weight of the
barrier layer; and a barrier overlayer disposed on the opposite
side of the barrier layer from the barrier underlayer, comprising a
second resin binder.
2. The air-impermeable fabric of claim 1, further comprising a
barrier underlayer disposed between the barrier layer and the
fabric, comprising a third resin binder
3. The air-impermeable fabric of claim 2, wherein the barrier
underlayer comprises from 0.5 wt. % to 5 wt. % of graphene
nanoplatelets, based on the total weight of the barrier
underlayer.
4. The air-impermeable fabric of claim 1, wherein the barrier
overlayer comprises from 0.5 wt. % to 5 wt. % of graphene
nanoplatelets, based on the total weight of the barrier
overlayer.
5. The air-impermeable fabric of claim 2, wherein the barrier
underlayer and the barrier overlayer each independently comprises
from 0.5 wt. % to 5 wt. % of graphene nanoplatelets, based on the
total weight of the barrier underlayer and the barrier overlayer,
respectively.
6. The air-impermeable fabric of claim 1, wherein the barrier layer
comprises from 20 wt. % to 90 wt. % of the graphene nanoplatelets,
based on the total weight of the barrier layer.
7. The air-impermeable fabric of claim 1, wherein the barrier layer
comprises from 20 wt. % to 60 wt. % of the graphene nanoplatelets,
based on the total weight of the barrier layer.
8. The air-impermeable fabric of claim 1, wherein the barrier layer
comprises from 25 wt. % to 45 wt. % of the graphene nanoplatelets,
based on the total weight of the barrier layer.
9. The air-impermeable fabric of claim 1, wherein the barrier layer
comprises from 25 wt. % to 35 wt. % of the graphene nanoplatelets,
based on the total weight of the barrier layer.
10. The air-impermeable fabric of claim 1, wherein the barrier
layer comprises about 30 wt. % of the graphene nanoplatelets.
11. The air-impermeable fabric of claim 1, wherein the barrier
layer further comprises a phosphorus-based flame retardant.
12. The air-impermeable fabric of claim 1, wherein the barrier
layer has a thickness of from 0.01 .mu.m to 5 .mu.m.
13. The air-impermeable fabric of claim 1, wherein the barrier
layer has a thickness of from 0.1 .mu.m to 2 .mu.m.
14. The air-impermeable fabric of claim 2, wherein each of the
barrier underlayer and the barrier overlayer independently has a
thickness of 0.5 .mu.m to 20 .mu.m.
15. The air-impermeable fabric of claim 1, further comprising a
heat-resistant layer disposed on the opposite side of the fabric
substrate from the barrier layer.
16. The air-impermeable fabric of claim 15, wherein the
heat-resistant layer comprises ceramic microspheres and/or aluminum
in a resin binder.
17. The air-impermeable fabric of claim 1, wherein the fabric
substrate is subjected to calendaring compression prior to
disposition thereon of the barrier layer, barrier underlayer, and
barrier overlayer.
18. The air-impermeable fabric of claim 1, having an areal weight
of less than or equal to 6 oz/yd.sup.2 (170 g/m.sup.2).
19. An inflatable structure comprising the air-impermeable fabric
of claim 1.
20. The inflatable structure of claim 19 that is an aircraft
evacuation slide.
Description
[0001] This is a continuation-in-part of U.S. patent application
Ser. No. 13/490,083, filed Jun. 6, 2012, the disclosure of which is
incorporated herein by reference in its entirety.
BACKGROUND OF THE INVENTION
[0002] This invention relates to air-impermeable fabrics, and more
particularly, to fabrics used for emergency evacuation equipment
for aircraft evacuation such as evacuation slides and life rafts,
as well as other inflatable structures such as for cushions and
other emergency and non-emergency applications.
[0003] The requirement for reliably evacuating airline passengers
in the event of an emergency is well known. Emergencies at take-off
and landing often demand swift removal of the passengers from the
aircraft because of the potential for injuries from fire,
explosion, or sinking in water. A conventional method of quickly
evacuating a large number of passengers from an aircraft is to
provide multiple emergency exits, each of which is equipped with an
inflatable evacuation slide, which often doubles as a life raft in
the event of a water evacuation. These evacuation slides are most
commonly constructed of an air-impervious coated fabric material
that is formed into a plurality of tubular members. When inflated,
these tubular members form a self-supporting structure with a slide
surface capable of supporting the passengers being evacuated. In
addition to being air-impervious, the fabric material from which
the tubular members are constructed must meet FAA specification
requirements of TSO-C69c for resistance to radiant heat,
flammability, contaminants, fungus and other requirements.
[0004] Although evacuation slides permit passengers to quickly and
safely descend from the level of the aircraft exit door to the
ground, the requirement that each aircraft exit door be equipped
with an inflatable evacuation slide means that substantial payload
capacity must be devoted to account for the weight of multiple
evacuation slides. Accordingly, there has long existed the desire
in the industry to make the inflatable evacuation slides as light
as possible. A significant portion of the weight of an emergency
evacuation slide is the weight of the slide fabric itself
Accordingly, various attempts have been made to reduce the weight
of the slide fabric. One accepted method has been to reduce the
physical size of the structural members of the slide by increasing
the inflation pressure. Increased inflation pressure, however,
causes greater stress on the slide fabric and, therefore, the
benefit of the reduced physical size is at least partially
cancelled out by the need to use a heavier gauge of slide fabric in
order to withstand higher inflation pressures. Current state of the
art slide fabric consists of a 72.times.72 yarns per inch nylon
cloth made of ultra-high-tenacity nylon fibers. This 72.times.72
fabric by itself has a grab tensile strength of approximately 380
lbs in the warp direction and 320 lbs in the fill direction (as
used herein grab tensile strength refers to the strength measured
by grabbing a sample of fabric, typically 4 inches wide, between a
set of one inch wide jaws and pulling to failure.) The fabric is
typically coated with multiple layers of an elastomeric polymer to
render it impermeable to air as well as a radiant-heat-resistant
coating. This results in a strong, but heavy fabric, having a grab
tensile strength of approximately 390 lbs in the warp direction and
in the fill direction, but with an areal weight that can exceed 7.0
oz/yd.sup.2. As can be determined from the foregoing, these
coatings do not contribute significantly to the strength of the
fabric.
[0005] Although the above-described fabrics for inflatable
structures have achieved widespread use in the aviation industry,
the disparate requirements for strength, weight, and flame
resistance, as well as other requirements, have resulted in a
continuing need in the art for new fabrics.
BRIEF DESCRIPTION OF THE INVENTION
[0006] As described in further detail below, the invention provides
a new air-impermeable fabric. The air-impermeable fabric has a
fabric substrate, which may also be referred to as a base fabric.
Disposed over the fabric substrate is a barrier layer comprising a
polymer binder and at least 20 weight percent (wt. %) graphene
nanoplatelets, based on the total weight of the barrier layer. A
barrier underlayer, which may or may not also include graphene
nanoplatelets, can optionally be included between the fabric
substrate and the barrier layer. A barrier overlayer, which may or
may not also include graphene nanoplatelets, is disposed on the
opposite side of the barrier layer from the barrier underlayer.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] The subject matter which is regarded as the invention is
particularly pointed out and distinctly claimed in the claims at
the conclusion of the specification. The foregoing and other
features, and advantages of the invention are apparent from the
following detailed description taken in conjunction with the
accompanying drawings in which:
[0008] FIG. 1 is a cross-sectional view of an air-impermeable
fabric as described herein;
[0009] FIG. 2 is a side view of an aircraft evacuation slide as
described herein;
[0010] FIG. 3 is a bottom view of an aircraft evacuation slide as
described herein; and
[0011] FIG. 4 is a graph plot of air permeation through fabrics as
described herein.
DETAILED DESCRIPTION OF THE INVENTION
[0012] As mentioned above, the invention is directed to an
air-impermeable fabric. It should be noted that, as used herein,
the term "impermeable" does not refer to absolute or permanent
impermeability, but rather to a degree of permeability sufficiently
low to meet the functional requirements needed for any particular
inflatable application. The fabric substrate, or base fabric, can
be formed from any type of fiber possessing desired physical
properties and processability. Nylon fibers are often used, at
least in part due to the strength and strength to weight ratio
possessed by nylon fabrics. Various nylons, such as nylon-6,6 or
nylon-6, can be used, as well as other known nylon polymers. Other
polymer fibers can also be used, such as polyester, other aromatic
and/or aliphatic polyamides, liquid crystal polymers, etc. Natural
fibers such as silk can also be used. Fiber diameters can be
selected to achieve desired properties such as fiber spacings in
woven fabric. Yarn counts can range from 30.times.30 yarns per inch
to 90.times.90 yarns per inch, or higher, and more particularly
from 40.times.40 yarns per inch to 75.times.75 yarns per inch. The
yarn count geometry can also be asymmetric (i.e. 40.times.60 yarns
per inch) if needed.
[0013] The fiber strength of the base cloth can also be increased
by incorporating nanoreinforcements into the polymeric matrix of
the fiber itself The nanoreinforcements can be carbon nanotubes,
carbon nanofibers, graphene nanoplatelets, polymeric nanofibers,
metallic nanotubes or nanofibers, metal oxide nanotubes, metal
oxide nanofibers, metal oxide nanoparticles or metal oxide
nanoplatelets or a combination thereof The nanoreinforcements can
be incorporated into the polymer matrix of the fiber during
synthesis of the fiber matrix or processing of the matrix into
fibers. For example, the nanoreinforcements can be combined with
the neat polymer matrix prior to thermal processing into fibers.
The nanoreinforcements can also be incorporated into the monomeric
precursors used to synthesize the polymeric composition of the
cloth fiber.
[0014] Graphene nanoplatelets are commercially available from
sources such as XG Sciences, and can be prepared by mechanical
and/or thermal exfoliation of graphite. Graphene nanoplatelets can
be prepared in various sizes, and those used in the barrier layer
described herein can have a thickness ranging from 2 nm to 50 nm,
more particularly from 5 nm to 15 nm. The graphene nanoplatelets
can have diameters ranging from 0.5 .mu.m to 50 .mu.m, more
particularly from 5 .mu.m to 25 .mu.m (note that diameter on the
hexagonal-shaped nanoplatelets is defined as the distance between
opposite corners of the hexagon). As mentioned above, the barrier
layer comprises at least 20 wt. % graphene nanoplatelets, based on
the total weight of the barrier layer (i.e., the cured coating). In
some exemplary embodiments, the barrier layer comprises at least 25
wt. % graphene nanoplatelets, and in some embodiments at least 30
wt. % graphene nanoplatelets. Upper limits of graphene nanoplatelet
content in the barrier layer in some embodiments can range up to 90
wt. %, in some embodiments up to 60 wt. %, and in some embodiments
up to 35 wt. %. In one exemplary embodiment, the barrier layer
comprises about 30 wt. % of graphene nanoplatelets. The barrier
underlayer and the barrier overlayer can optionally contain
graphene nanoplatelets. When present in the barrier underlayer
and/or the barrier overlayer, the content level graphene
nanoplatelets can comprise a minimum of 0.5 wt. %, in some
embodiments a minimum of 1 wt. %. When present in the barrier
underlayer and/or the barrier overlayer, the content level of
graphene nanoplatelets have a maximum 5 wt. %, in some embodiments
a maximum of 4 wt. %, and in some embodiments a maximum of 3 wt. %.
In one exemplary embodiment, the barrier underlayer and the barrier
overlayer comprises about 2 wt. % graphene nanoplatelets. In
another exemplary embodiment, the barrier underlayer and the
barrier overlayer has no graphene nanoplatelets. All weight
percentages are based on the total weight of the respective coating
layer.
[0015] The resin used for the barrier layer as well as the barrier
underlayer and the barrier overlayer can be chosen from various
polymers. Polyurethane polymers and polyurethane-containing
copolymers are often used, at least in part due their elasticity
and durability. Well-known polyurethane chemistry allows for
various aromatic and/or aliphatic polyisocyanates and polyols to be
reacted together to provide desired coating characteristics, and
such coating resins are readily commercially available. Other
polymers can be readily copolymerized with polyurethanes, often
through inclusion of hydroxy-terminated prepolymers (e.g.,
OH-terminated polyester or OH-terminated polycarbonate or
polyether) in the polyisocyanate/polyol reaction mix. In some
embodiments, a polymer resin other than polyurethane is used, e.g.,
polyester. Blends of one or more of polymer resins such as those
described above can also be included in a coating composition.
[0016] The coating composition can also contain one or more
crosslinkers. For example, urethane and polyester resins can
include polyfunctional alcohols (e.g., trimethylolpropane) or
poly-functional alcohol reactive compounds (e.g., melamine
derivatives such as hexamethoxymethylol melamine or melamine resin)
as crosslinking agents. Polyurethane resins can also include
polyfunctional isocyanates (e.g., trifunctional isocyanurate
compounds formed by diisocyanates such as methylenediphenyl
diisocyanate (MDI) or isophorone diisocyanate (IPDI)) as
crosslinkers. Polyesters can also include polyfunctional acids
(e.g., tricarballylic acid) as crosslinkers. The amount of
crosslinker can be adjusted by those skilled in the art to achieve
desired properties. In addition to accelerating cure, added
crosslinker tends to increase coating hardness and decrease
elasticity. The coating composition may also contain one or more
volatile liquids, including water and/or various polar or non-polar
organic solvents. Such volatile liquids are vaporized before or
during cure and do not form part of the cured or finished coating.
Reactive diluents (i.e., organic compounds that function as a
solvent during application of a polymer resin-containing coating
composition, but have functional groups that react with the polymer
during cure so that they form part of the cured coating.
[0017] The coating compositions applied to form the any of the
coatings on the fabric described herein can include various
additives ordinarily incorporated into coating compositions. Such
additives can be mixed at a suitable time during the mixing of the
components for forming the composition, and include fillers,
reinforcing agents, antioxidants, heat stabilizers, biocides,
plasticizers, lubricants, antistatic agents, colorants, surface
effect additives, radiation light stabilizers (including
ultraviolet (UV) light stabilizers), stabilizers, and flame
retardants. Such additives can be used in various amounts,
generally from 0.01 to 15 wt. %, based on the total weight of the
coating composition
[0018] As mentioned above, in some embodiments, the barrier layer
can include one or more flame retardants. Exemplary flame
retardants include phosphorous-containing compounds such as
organophosphates (e.g., tris(2-butoxy)ethylphosphate (TBEP),
tris(2-propylphenyl)phosphate, organophosphonates (e.g.,
dimethylphosphonate), organophosphinates (e.g., aluminum
diethylphosphinate), inorganic polyphosphates (e.g., ammonium
polyphosphate)), organohalogen compounds (e.g., decabromodiphenyl
ethane, decabromodiphenyl ether, and various brominated polymers or
monomers), compounds with both halogen and phosphorous-containing
groups (e.g., tris(2,3-dibromopropyl) phosphate), as well as other
known flame retardants. Brominated flame retardants are often used
in combination with a synergist such as oxides of antimony (e.g.,
SbO.sub.3, Sb.sub.2O.sub.5) and other forms of antimony such as
sodium antimonite. The amount of flame retardant can vary widely
depending on the particular flame retardant or combination of flame
retardants, with exemplary amounts ranging from 5 wt. % to 50 wt.
%, more particularly from 10 wt. % to 25 wt. %.
[0019] Other coating layers can be present in addition the
above-described barrier layer, barrier overlayer, and barrier
underlayer. In some embodiments, a heat-resistant (HR) layer is
also present, often on the side of the fabric that will be the
outside of the inflatable structure. HR layers can comprise a high
temperature polymer resin binder and aluminum pigment. HR layers
can contain at least 10 wt. % aluminum pigment. An exemplary
formulation contains between 0.1 wt. % and 10 wt. % microspheres. A
further exemplary formulation contains between 1 wt. % and 5 wt. %
microspheres. In addition to radiant heat reflecting properties
provided by the aluminum pigment, a heat-resistant layer can also
include heat-absorbing additives such as ceramic microspheres. HR
layers can contain at least 0.11 wt. % microspheres. An exemplary
formulation contains between 0.11 wt. % and 6.2 wt. % microspheres.
A further exemplary formulation contains between 1.1 wt. % and 2.1
wt. % microspheres. All weight percentages are based on the total
weight of the layer. Tie coat layers can also be present. Tie coats
are utilized to provide greater adhesion to the substrate than
might be provided by the various functional layers. For example, a
polyurethane-polycarbonate copolymer resin can be used in a tie
coat applied directly to the fabric surface where its relatively
low modulus of elasticity provides good conformation of the resin
to the cloth morphology while the relatively higher modulus of
elasticity of a polyurethane polymer resin used as binder for a
barrier layer, barrier underlayer, and/or barrier overlayer
provides the necessary strength and flexibility to maintain overall
coating integrity and air impermeability when subjected to
deformation and stress during inflation.
[0020] Turning now to the figures, FIG. 1 schematically depicts a
cross-section view of an exemplary air-impermeable fabric 100
according to the invention. As shown in FIG. 1, fabric substrate
110 has barrier underlayer 120 disposed thereon. Barrier layer 130
comprising at least 20 wt. % graphene nanoplatelets is disposed
over barrier underlayer 120. Barrier overlayer 140 is disposed over
barrier layer 130. Barrier layer 130 along with barrier underlayer
120 and barrier overlayer 140 are disposed on one side of the
fabric substrate 110 such as a side of the fabric that would be
face the interior of an inflatable structure. On the other side of
fabric substrate 110 is a heat-resistant layer 150 such as an
aluminized coating. The above arrangement provides air retention
(AR) layers on one side of the fabric that can face the interior of
an inflatable structure and a heat-resistant layer 150 on the other
side of the fabric that would be the exterior of an inflatable
structure. This arrangement provides resistance to heat from
external sources such as fire on the outside of an inflatable
structure while keeping the critical AR layers further away from
such external heat sources. Of course, other layer arrangements can
be used as well. For example, the AR layers could be disposed
between the base fabric and an outermost heat-resistant layer.
[0021] Turning now to FIG. 2, an inflatable evacuation slide
assembly 10 is depicted incorporating features of the present
invention. Evacuation slide assembly 10 generally comprises a head
end 12, and a foot end 14 terminating at toe end 16. Head end 12 is
configured to couple evacuation slide assembly 12 to an exit door
18 of an aircraft 20 while foot end 14 is in contact with the
ground 22 such that the slide assembly 10 provides a sloping
surface to permit the rapid egress of passengers from aircraft
20.
[0022] With reference to FIGS. 2 and 3, the main body of evacuation
slide assembly 10 comprises a plurality of inflatable flexible
members including side rail tubes 24, 26 which extend from head end
truss assembly 28 to the ground 22. A slide surface 30 comprising a
fabric membrane is stretched between side rail tubes 24 and 26 to
provide a sliding surface for the disembarking passengers. A right
hand rail 32 and a left hand rail (not shown) are positioned atop
side rail tubes 24 and 26, respectively, to provide a hand hold for
passengers descending evacuation slide assembly 10. Head end truss
assembly 28 comprises a plurality of strut tubes 36, 38, upright
tubes 40, 42 and a transverse tube 44 adapted to hold head end 12
of evacuation slide assembly 10 against the fuselage of aircraft 20
in an orientation to permit escape slide assembly 10 to unfurl in a
controlled manner as it extends toward the ground.
[0023] The spaced apart configuration of side rail tubes 24 and 26
is maintained by a head end transverse tube 46, a toe end
transverse tube 48, a foot end transverse truss 52 and medial
transverse truss 54. The bending strength of escape slide assembly
10 is enhanced by means of one or more tension straps 50 stretched
from toe end 16 over foot end transverse truss 52, medial
transverse truss 54 and attached proximal head end 12 of evacuation
slide assembly 10. As described, evacuation slide assembly 10
provides a lightweight structure that consumes a minimum amount of
inflation gas while providing the necessary structural rigidity to
permit passengers to safely evacuate an aircraft under emergency
conditions.
[0024] The entire inflatable evacuation slide assembly 10 can be
fabricated from an air impervious material described more fully
hereinafter. The various parts of the inflatable evacuation slide
assembly 10 may be joined together with a suitable adhesive whereby
the structure will form a unitary composite structure capable of
maintaining its shape during operation. The entire structure of the
inflatable evacuation slide assembly 10 can be formed such that all
of the chambers comprising the structure are interconnected
pneumatically, such that a single pressurized gas source, such as
compressed carbon dioxide, nitrogen, argon, a pyrotechnic gas
generator or combination thereof may be utilized for its
deployment.
[0025] The invention is further illustrated by the following
non-limiting examples.
Examples
[0026] Fabrics prepared using a nanocomposite resin incorporating
about 1.5 weight % of graphene nanoplatelets were evaluated for
radiant heat resistance. Sample A (4.87 oz./yd.sup.2 estimated
areal weight) had two air-retentive layers having approximately
0.40 oz./yd.sup.2 areal weight each, and Sample B (5.97
oz./yd.sup.2 estimated areal weight) incorporated two air-retentive
layers approximately 0.85 oz./yd.sup.2 areal weight each.
Additional samples were prepared using a resin mixture
incorporating 22.5 weight % graphene nanoplatelets, which was
applied directly onto the nylon fabric. This resin application was
followed by an additional layer of a nanocomposite resin
incorporating 1.5 weight % graphene nanoplatelets. Sample C (5.10
oz./yd.sup.2 estimated areal weight) was selected from this group.
All samples also have a radiant heat resistant coating
approximately 0.50 oz./yd.sup.2 estimated areal weight. The samples
were subjected to radiant heat testing according to ASTM F828-83,
and the results are shown in FIG. 4.
[0027] As shown in FIG. 4, the conventional sample (Sample B)
maintained a pressure above the minimum passing pressure of 3.5 psi
throughout the test, but required a relatively high areal weight of
5.97 oz/yd.sup.2 to do so. The sample with two conventional
coatings containing graphene nanoplatelets (Sample A) provide a low
areal weight of 4.87 oz/yd.sup.2, but fell below the minimum
passing pressure after 240 seconds. However, the sample according
to the invention (Sample C) maintained a pressure above the minimum
passing pressure of 3.5 psi throughout the test, with a reduced
areal weight of 5.10 oz/yd.sup.2.
[0028] As used herein, the singular forms "a," "an," and "the"
include plural referents unless the context clearly dictates
otherwise, and "or" means "and/or". The modifier "about" used in
connection with a quantity is inclusive of the stated value and has
the meaning dictated by the context (e.g., includes the degree of
error associated with measurement of the particular quantity). The
terms "front", "back", "bottom", and/or "top" are used herein,
unless otherwise noted, merely for convenience of description, and
are not limited to any one position or spatial orientation. The
endpoints of all ranges directed to the same component or property
are inclusive and independently combinable (e.g., ranges of "less
than or equal to 25 wt %, or 5 wt % to 20 wt %," is inclusive of
the endpoints and all intermediate values of the ranges of "5 wt %
to 25 wt %," etc.). The suffix "(s)" is intended to include both
the singular and the plural of the term that it modifies, thereby
including at least one of that term (e.g., "the colorant(s)"
includes a single colorant or two or more colorants, i.e., at least
one colorant). "Optional" or "optionally" means that the
subsequently described event or circumstance can or can not occur,
and that the description includes instances where the event occurs
and instances where it does not. Unless defined otherwise,
technical and scientific terms used herein have the same meaning as
is commonly understood by one of skill in the art to which this
invention belongs.
[0029] While the invention has been described in detail in
connection with only a limited number of embodiments, it should be
readily understood that the invention is not limited to such
disclosed embodiments. Rather, the invention can be modified to
incorporate any number of variations, alterations, substitutions or
equivalent arrangements not heretofore described, but which are
commensurate with the spirit and scope of the invention.
Additionally, while various embodiments of the invention have been
described, it is to be understood that aspects of the invention may
include only some of the described embodiments. Accordingly, the
invention is not to be seen as limited by the foregoing
description, but is only limited by the scope of the appended
claims.
* * * * *