GAS BARRIER FABRIC

Abstract

A gas barrier fabric is disclosed. The barrier fabric includes a fabric substrate. A heat-resistant coating layer disposed over a first side of the fabric substrate. A first gas barrier layer (also referred to herein as simply as a barrier layer) including a polymer is disposed over a second side of the fabric substrate. A second gas barrier layer is disposed over the first air barrier coating layer of the fabric substrate. The second barrier layer has a thickness of 5 nm to 1000 nm and includes aligned nanoplatelets.

Claims

1. A gas barrier fabric, comprising: a fabric substrate; a heat-resistant coating layer over a first side of the fabric substrate; a first gas barrier layer comprising a polymer disposed over a second side of the fabric substrate; and a second gas barrier layer over the first gas barrier coating layer of the fabric substrate having a thickness of 5 nm to 1000 nm comprising aligned nanoplatelets.

2. The barrier fabric of claim 1, wherein the second air barrier layer further comprises a polymer binder.

3. The gas barrier fabric of claim 2, wherein second gas barrier layer comprises from 30 wt. % to 99.5 wt. % of the nanoplatelets, based on the weight of the second gas barrier layer.

4. The barrier fabric of claim 2, wherein the second barrier layer is subjected applied force prior to curing the polymer binder.

5. The barrier fabric of claim 1, wherein the nanoplatelets are deposited by a self-assembly coating process.

6. The barrier fabric of claim 5, wherein the self-assembly coating process is layer-by-layer self-assembly.

7. The barrier fabric of claim 1, wherein the nanoplatelets are selected from graphene, graphene oxide, nanoscopic clays, or ceramics.

8. The barrier fabric of claim 1, wherein the nanoplatelets are selected from Montmorillonite, boron nitride, or mica.

9. The barrier fabric of claim 1, wherein the nanoplatelets have a diameter of from 0.1 m to 50 m.

10. The barrier fabric of claim 1, wherein the nanoplatlets have an aspect ratio of from 5:1 to 10,000:1.

11. The barrier fabric of claim 1, wherein the first air barrier coating has a thickness of 1 m to 100 m.

12. The barrier fabric of claim 1, further comprising a third air barrier layer comprising a polymer over the second air barrier layer.

13. The barrier fabric of claim 12, wherein the third air barrier coating has a thickness of 1 m to 100 m.

14. The barrier fabric of claim 1, further comprising a third air barrier layer comprising aligned nanoplatelets over the heat-resistant layer.

15. The barrier fabric of claim 1, wherein the heat-resistant layer comprises ceramic microspheres, ceramic hollow microspheres and/or aluminum in a polymer matrix.

16. An inflatable structure, comprising an enclosure formed from the barrier fabric of claim 1 and a source of inflating gas inside the enclosure or a closeable opening for introducing inflating gas from outside the enclosure.

17. An inflatable aircraft slide, comprising an inflatable structure according to claim 16.

18. An inflatable aircraft slide, comprising tubular members formed from the barrier fabric of claim 1 and a slide surface, which form a self-supporting structure when inflated.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] The subject matter which is regarded as the present disclosure 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 present disclosure are apparent from the following detailed description taken in conjunction with the accompanying drawings in which:

[0010] FIG. 1 is a schematic depiction of a cross-section of a barrier fabric as described herein;

[0011] FIG. 2 is a schematic depiction of a cross-section of a barrier fabric as described herein;

[0012] FIG. 3 is a schematic depiction of a cross-section of a barrier fabric as described herein;

[0013] FIG. 4 is a schematic depiction of a cross-section of a barrier fabric as described herein;

[0014] FIG. 5 is a side view of an aircraft evacuation slide as described herein; and

[0015] FIG. 6 is a bottom view of an aircraft evacuation slide as described herein.

DETAILED DESCRIPTION

[0016] 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. Carbon fiber is also a viable option but is cost prohibitive in most applications. Fiber diameters can be selected to achieve desired properties such as fiber strength, elongation and environmental resistance and other attributes. Yarns are the assembly of individual fibers and can be assembled in a fashion as to align fibers parallel to each other, twist them or spin them together to form yarns of various strength, elongation, lay length, size, and denier (a characteristic of yarn as measured in grams per 9000 meters of yarn length). Fabrics can then be further defined in terms of fiber spacing, pics per inch, yarns per inch, or total fabric weight per yard or other similar dimension. Yarn counts can range from 3030 yarns per inch to 9090 yarns per inch, or higher, and more particularly from 4040 yarns per inch to 7575 yarns per inch. The yarn count geometry can also be asymmetric (i.e. 4060 yarns per inch) if needed. Areal weight of the fabric substrate can range from 0.1 to greater than 10 oz/yd.sup.2, more specifically 1 to 10 oz/yd.sup.2, and even more specifically 2 to 8 oz/yd.sup.2.

[0017] The fiber strength of the base cloth can be increased by incorporating nanoreinforcements into the polymeric matrix of the fiber itself. The nanoreinforcements can be carbon nanotubes, carbon nanofibers, graphene nanoplatelets, graphene oxide nanoplatelets, polymeric nanofibers, metallic nanotubes or nanofibers, metal oxide nanotubes, metal oxide nanofibers, metal oxide nanoparticles, metal oxide nanoplatelets, inorganic fibers such as glass, silicon carbide, aluminum nitride, inorganic nano platelets such as montmorillonite other clay or boron nitride or a combination thereof, or combinations 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 by spinning or other fiber-forming processes. The nanoreinforcements can also be incorporated into the monomeric precursors used to synthesize the polymeric composition of the cloth fiber.

[0018] The heat-resistant (HR) coating layer is typically 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 (e.g., aluminum flakes). HR layers can contain at least 5 wt. % aluminum pigment, more specifically from 10 wt. % to 50 wt. %. 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 or heat-insulating additives such as ceramic hollow microspheres. An example formulation contains between 0.1 wt. % and 10 wt. % microspheres. A further exemplary formulation contains between 1 wt. % and 5 wt. % microspheres. All weight percentages are based on the total weight of the layer. The thickness of the HR layer can vary, for example between 0.5 m to 50 m, more specifically from 5 m to 20 m. 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 provides the necessary strength and flexibility to maintain overall coating integrity and air impermeability when subjected to deformation and stress during inflation.

[0019] As mentioned above, the barrier fabric also has a first gas barrier layer comprising a polymer. This layer can have a thickness ranging from 1 m to 100 m, more specifically from 5 m to 50 m. In some aspects, the first barrier layer is free of nanoplatelets, or if it includes nanoplatelets, they are not in a state of alignment as described below. The polymer used for the heat-resistant layer, and also for other polymer-containing layers on the barrier fabric, 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 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.

[0020] The coating compositions used to form the layer(s) on the barrier fabric 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) or polycarbodiimides 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.

[0021] 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 35 wt. %, based on the total weight of the coating composition.

[0022] As mentioned above, the barrier fabric also includes a second barrier layer having a thickness of 5 nm to 1000 nm comprising aligned nanoplatelets. Nanoplatelets can be prepared in various sizes, and those used in the barrier layer described herein can have a thickness ranging from a minimum of 0.3 nm, more specifically 1 nm, and even more specifically 5 nm, up to a maximum of 100 nm, more specifically 50 nm, and even more specifically 15 nm. These maximum and minimum range limits can be combined to create ranges from any of the minimum values to any of the maximum values (e.g., 0.3-100 nm, 5-15 nm, 1-50 nm, 1-15 nm, etc.). The nanoplatelets can have diameters ranging from 0.1 m to 50 m, more particularly from 5 m to 25 m. As used herein, the term diameter, with respect to nanoplatelets, means an average diameter that is calculated as the diameter of a circle having an area the same as that of a flat (i.e., not including surface area in pores) surface occupying the same profile in the x-y direction as one of the faces of the nanoplatelet. The nanoplatelets can have an aspect ratio (ratio of diameter to thickness) ranging from 5:1 to 10,000:1, more specifically from 20:1 to 1000:1. In some example embodiments, the barrier layer comprises at least 30 wt. % nanoplatelets, based on the total weight of the barrier layer (i.e., the cured coating), more specifically at least 40 wt. % nanoplatelets, more specifically at least 60 wt. % nanoplatelets, more specifically at least 85 wt. % nanoplatelets. In some example embodiments, barrier layer has an upper limit on nanoplatelet content of 99.5 wt. % nanoplatelets, more specifically 90 wt. % nanoplatelets, and even more specifically 85 wt. % nanoplatelets. These maximum and minimum range limits can be combined to create ranges from any of the minimum values to any of the maximum values (e.g., 0.3-100 nm, 5-15 nm, 1-50 nm, 1-15 nm, etc.), excluding of course impossible range values where a minimum value would be higher than a maximum value.

[0023] The nanoplatelets can comprise various materials, including but not limited to clays, graphene, or graphene oxide. Examples of nanoplatelet materials include, but are not limited to graphene, phyllosilicate clays such as Montmorillonite clay, Kaolinite clay, boron nitride, mica. Nanoplatelets can be prepared from bulk materials such as graphite, bulk clays, boron nitride, mica by exfoliating the bulk material. Exfoliation can be carried out by various techniques such as ultrasonic treatment, chemical treatments to swell the bulk material to increase separation between adjacent molecular layers, and treatment with oxidants, or ion intercalation/exchange. Surface treatments, heat, or high shear mixing or mechanical work can be applied to promote exfoliation of patelet layers. Specific solvents can also be employed to reach desired exfoliation level.

[0024] The various coatings described herein can be applied using any known coating technique, including but not limited to roll coating, spray coating, dip coating, or brush coating. The nanoplatelet-containing layer can be formed at thicknesses of 5 nm to 1000 nm, more specifically from 10 nm to 800 nm by similar techniques mentioned above including but not limited to roll coating, spray coating, dip coating, or brush coating, optionally followed by processing with an air blade or physical blade to achieve the desired thickness. Coating solutions can be comprised of neat, curable polymer resin, solvent based or aqueous based coating systems. The concentrations of the coating solutions will vary depending on the required viscosity of the solution, how thick the coating is to be applied, and how many nanoplatelet layers are to be applied in one coating pass. Typically concentrations of binder and filler are very low in solvent and aqueous coating systems to allow for better alignment of filler.

[0025] As mentioned above, the nanoplatelets are aligned. As used herein, alignment of the nanoplatelets means that the x-y dimension of nanoplatelets is aligned parallel to the plane of the layer surface. Complete alignment of the nanoplatelets is not required, only that more of the nanoplatelets are more closely aligned in a direction parallel to the layer compared to a random alignment of the nanoplatelets. Alignment can be characterized by .sub.p,p, with a value of 0 representing random alignment of the particles, a value of 1 representing complete alignment of the particles in the direction of layer, and a value of representing complete alignment of the particles perpendicular to the direction of the layer. In exemplary embodiments, .sub.p,p is in a range having a lower level greater than 0, more specifically 0.1, and even more specifically 0.4. The upper end of the range, for which .sub.p,p is less than or equal to, can be 0.9, more specifically 0.8, and more specifically 0.7. Alignment of the nanoplatelets can be achieved by using known layer-by-layer self-assembly techniques where the nanoplatelets are derivatized with charged groups such as carboxyl groups that will be attracted to an oppositely-charged groups on a substrate such as a amine groups on the first barrier layer over which the nanoplatelets dispersed in a solvent are applied. In other embodiments, the nanoplatelets can be incorporated into a curable polymer coating composition, with alignment of the nanoplatelets achieved by applying physical force prior to fully curing the polymer. Examples of physical force include centrifugal force, gravity, and/or shearing force (e.g., by maintaining the coated substrate in a vertical position for a period of time) prior to curing. Derivatization techniques described above used for layer-by-layer self-assembly can also be used provide alignment in polymer coating compositions.

[0026] Turning now to the Figures, FIG. 1 schematically depicts a cross-section of an example barrier fabric. As shown in FIG. 1, a gas barrier fabric 100 comprises a fabric substrate 112. On one side of substrate 112 is a heat-resistant layer 114. On the other side of substrate 12 is a first barrier layer 16. Over the first barrier layer 116 is a second barrier layer 118 comprising aligned nanoplatelets as described above. FIG. 2 depicts a barrier fabric configured similarly to FIG. 1, with the addition of a third barrier layer 120 comprising aligned nanoplatelets over the heat-resistant layer 114. FIG. 3 depicts a barrier fabric configured similarly to FIG. 1, with the addition of a conventional polymer barrier layer 122 over the barrier layer 118 comprising aligned nanoplatelets. FIG. 4 includes both the barrier layer 120 and the barrier layer 122. The barrier layers 116 and 122 can comprise crosslinked polyurethane coating(s) or a crosslinked polyurethane coating with a thermoplastic urethane film. The barrier layer 122 can comprise a thermoplastic urethane film.

[0027] With reference to FIGS. 5 and 6, 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. 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.

[0028] The entire inflatable evacuation slide assembly 10 can be fabricated from the barrier fabric described herein. 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. Of course, the depiction in FIGS. 4 and 5 is an example, and other designs can be utilized. For example, round tubular structures are depicted in FIGS. 5 and 6, but other shapes such as inflatable square tube shapes can be fabricated by known techniques.

[0029] While the present disclosure has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the present disclosure is not limited to such disclosed embodiments. Rather, the present disclosure 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 present disclosure. Additionally, while various embodiments of the present disclosure have been described, it is to be understood that aspects of the present disclosure may include only some of the described embodiments. Accordingly, the present disclosure is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.