COMPOSITE SHEET AND CARGO CONTAINER COMPRISING SAME

BACKGROUND

1 . Field of the Invention

This invention pertains to a non-rigid composite sheet having fire resistant properties. The sheet is useful as walls in a cargo container, particularly containers used in aircraft.

2. Description of Related Art

Cargo containers or unitary load devices (ULDs) are used in aircraft, ships, road vehicles and railcars to carry goods. For economic reasons there is a desire to reduce the weight of an empty container while minimizing its operational cost. Shipment of flammable materials in air cargo containers is creating a serious safety issue for airlines and air cargo carriers. There is increasing concern about the capability of existing containers to contain the spread of fire when the ignition source is the cargo itself. An example of such an ignition source is a lithium-ion battery. Consequently, to prevent possible human casualties and cargo equipment losses, airlines and air cargo carriers are looking for flame resistant cargo containers to contain fires that may originate within the containers. A tightening of regulatory requirements is expected over the next few years. There is therefore a need to provide a light weight cargo container having enhanced capability to contain the spread of fire from within the container that meet stringent durability standards while providing an extended lifetime with minimum maintenance.

United States Patent number 8,292,027 to Richardson et al describes a composite laminate comprising in order (a) a flame retardant polymeric moisture barrier (b) an inorganic platelet layer and (c) a flame retardant thermoplastic film layer. SUMMARY OF THE INVENTION

This invention is directed to a non-rigid composite sheet comprising in order

(i) a first component having an areal density of from 102 to 678 gsm comprising a first fabric of filamentary yarns having a tenacity of at least 1 1 g/dtex and a UV and weather impervious first polymeric layer.

(ii) a second component having an areal density of from 10 to 170 gsm comprising a flame resistant inorganic refractory layer adjacent to at least one protective polymeric layer, and

(iii) a third component having an areal density of from 102 to 678 gsm comprising a second fabric of filamentary yarns having a tenacity of at least 1 1 g/dtex and an impact and scratch resistant second polymeric layer, the second fabric of the third component being adjacent to the refractory layer of the second component.

BRIEF DESCRIPTION OF THE DRAWINGS

Figures 1 A and 1 B show a perspective of a cargo container.

Figures 2A to 2D show a cross section through embodiments of a non-rigid composite sheet of this invention.

DETAILED DESCRIPTION

FIG 1A shows at 10, a perspective of a fire resistant cargo container suitable for aircraft, seagoing vessels and the like for containing the effects of a fire within the cargo container comprising a frame assembly 1 1 , side walls 12a, and 12b and a top 13. FIG 1 B shows a container comprising a frame assembly 1 1 , a plurality of side walls 12a to 12d, a top 13 and a base 14. The side walls and ceiling comprise a non- rigid flame resistant composite sheet.

Non-rigid Flame Resistant Composite Sheet

FIGS 2A to 2D show generally at 20 a cross section through the non-rigid flame resistant composite sheet which comprises in order a first component 21 , a second component 22 and a third component 23. The sheet is arranged between the frames of a cargo container such that the third component is the innermost component 31 facing towards the cargo and the first component is the outermost component 30 facing away from the cargo.

Preferably, the composite sheet has a break strength of at least 350 N/cm (200 lb. per in.) when tested according to ASTM D3039 / D3039M - 08. In some embodiments, the composite sheet has a break strength of at least 525 N/cm (300 lb. per in.) or even of at least 700 N/cm (400 lb. per in.) Some embodiments of the composite sheet provides a penetration resistance to a direct flame having a temperature of 927 °C, +/- 38 °C (1700 °F, +/- 100 °F) The specification also requires no flame penetration of the specimen within five minutes after application of the flame source, and with the peak temperature measured at 101 .6 mm (4 inches) above the upper surface of the horizontal test sample not exceeding 204°C (400°F) when tested according to a flame penetration FAA test method 14 CFR 25.855 Appx. F Part III - Test Method To Determine Flame Penetration Resistance of Cargo Compartment Liner (ceiling position).

Preferably, the composite sheet can withstand exposure to a temperature range of from -50°C to +80°C without compromising its reliability and durability over the life span of the end product.

In some embodiments, the first, second and third components may optionally be bonded to each other by means such as adhesives or thermal lamination.

First Component

The first component 21 has an areal density of from 102 to 678 gsm (3 to 20 oz. per sq. yd.) and comprises a first fabric 25 of filamentary yarns having a tenacity of at least 1 1 grams per dtex (10 grams per denier) and a first polymeric layer 24, the polymeric layer being the outermost layer of the composite sheet. The polymeric layer provides chemical and environmental (i.e. weather and UV) resistance to both physical and chemical attack and permeation by liquids. By chemical and environmental/weather resistant is meant that the ability of the polymeric layer to withstand, without excessive degradation, the effects of wind, rain, contaminants such as acidic and/or oily residues found in a typical industrial areas, and sun exposure. Preferably, the polymeric layer has an enhanced ability to resist damage by chemical reactivity, or solvent action, with hydrocarbons, chemicals, ozone, bacteria, fungus, and moisture, as well as skin oils, typically associated with operation and maintenance of a commercial aircraft.

By UV resistant is meant that, when exposed to ultraviolet radiation, the polymeric layer retains its appearance and physical integrity without an excessive degradation of its flexibility and mechanical properties (i.e. brittleness). Preferably, the polymeric layer blocks at least 95% of UV rays, more preferably at least 98% and most preferably 100% of UV rays. UV imperviousness of the first polymeric film can be further mitigated by inclusion of additives in the polymeric material. Examples of such additives include fillers, colors, stabilizers and lubricants. The outer surface of the first polymeric layer that is not in contact with the first fabric may optionally be coated or treated with a UV blocking material.

Ultraviolet (UV) is an invisible band of radiation at the upper end of the visible light spectrum. At wavelengths ranging from 10 to 400 nm, ultraviolet (UV) starts at the end of visible light and ends at the beginning of X-rays. As the primary exposure of the composite sheet to ultraviolet light is the sun, the most critical UV resistance is that to the lower- frequency, longer-wavelength rays .

Preferably, outer polymeric layer has soft, non-plastic feel that is ideal for products that come in contact with the human skin and maintains its toughness and flexibility over a wide temperature range, even at temperatures as low as -50°C (-60°F), over the life span of the end product.

In some embodiments, the outer surface of the first polymeric layer, that is to say the surface not in contact with the first fabric, has a release value of no more than 263 N/m (1 .5 Ib/in), more preferably no more than 438 N/m (2.5 Ib/in) when measured according to ASTM D2724 - 07(201 1 )e1 Standard Test Methods for Bonded, Fused, and Laminated Apparel Fabrics. This facilitates cleaning, label removal etc.

In some embodiments, the first fabric layer may be bonded to the first polymeric layer by means such as an adhesive, thermal bonding or by fasteners. In some embodiments, the bond strength between the first fabric and the first polymeric layer is at least 263 N/m (1 .5 Ib/in). In another embodiment, the bond strength between the first fabric and the first polymeric layer is at least 438 N/m (2.5 Ib/in), or even at least 876 N/m (5 Ib/in).

The adhesive layer may be a thermoplastic or thermoset resin.

Thermoset resins include epoxy, epoxy novolac, phenolic, polyurethane, and polyimide. Thermoplastic resins include polyester, polyetherketone, polyetheretherketone, polyetherketoneketone, polyethersulfone, and polyolefin. Thermoplastic resins are preferred.

Preferably, the adhesive layer may optionally contain up to 40 weight percent of a flame retardant ingredient. Suitable flame retardant ingredients include antimony trioxide, halogenated flame retardants including tetrabromobisphenol A, polybrominated biphenyls, pentabrominateddiphenylether(oxide),

octabrominateddiphenylether(oxide),

decabrominateddiphenylyether(oxide) and hexabromocyclododecane. Phosphorus containing flame retardants are also widely used.

Preferably, the adhesive layer blocks at least 95% of UV rays, more preferably at least 98% and most preferably 100% of UV rays. The adhesive may further comprise fillers, colors, stabilizers, and other performance enhancing additives. The adhesive must be capable of activation at a temperature in the range of 75 to 200 degrees C. In some embodiments, the activation range is from 120 to 140 degrees C. By activation we mean that for a thermoset resin, the resin must cure and bond to the polymeric layer and the fabric within the specified temperature range. For a thermoplastic resin, activation means that the resin softens and flows sufficiently to bond to the polymeric layer and the fabric. The adhesive bond between the first polymeric layer and the first fabric is at least 263 N/m (1 .5 lb/in). In some embodiments, the adhesive bond between the first polymeric layer and the first fabric is at least 438 N/m (2.5 lb/in), or even 876 N/m (5 lb/in).

Second Component

The second component 22 has an areal density of from 40 to 170 gsm (0.3 to 5.0 oz. per sq. yd.) and comprises a protective polymeric layer 26 in contact with a refractory layer 27, with polymeric layer of the second component being adjacent to the first fabric 25 of the first component. Such a protective polymeric layer provides mechanical reinforcement and protection against potential handling damage to the refractory layer during manufacturing, installation and service. In a preferred embodiment, the protective polymeric layer is in a form of a self- supporting film capable of withstanding a temperature of at least 200 degrees C for at least 10 minutes. The polymeric layer may be a thermoset or thermoplastic material. A thermoplastic film is preferred. In some embodiments, as shown in FIGS 2B and 2D, the second component may include a second protective polymeric layer 32 in contact with the refractory layer 27. The second protective polymeric layer provides further mechanical reinforcement and protection to the refractory layer during manufacturing, installation and service. In a preferred embodiment, the protective polymeric layer 32 is in a form of a self- supporting film capable of withstanding a temperature of at least 200 degrees C for at least 10 minutes. The polymeric layer 32 may be a thermoset or thermoplastic material. A thermoplastic film is preferred. Preferably the polymeric layers 26 and 32 should have a UL 94 flame classification of V-0. UL 94 flame classification is an Underwriters Laboratory test, The Standard for Flammability of Plastic Materials for Parts in Devices and Appliances, which measures a material's tendency either to extinguish or to spread the flame once the specimen has been ignited. V-0 indicates that the material is tested in a vertical position and self-extinguished within ten seconds after the ignition source is removed.

A further requirement of the polymeric layers 26 and 32 is that they should have a thickness in the range of from 4 to 30 micrometers. More preferably the thickness range should be from 5 to 15 micrometers and most preferably in the range from 5 to 7 micrometers. Suitable film layer materials are polyketone, polyimide, polysulfone, polyarylene sulfide, fluoropolymers, liquid crystal polymers and polycarbonate .

Examples of polyketone are polyetheretherketone (PEEK) and polyetherketoneketone (PEKK). Polyethersulfone and polyphenylsulfone are examples of polysulfone. Poly(p-phenylene sulfide) is a suitable polyarylene sulfide for use in this invention. Polyvinylfluoride (PVF) and polyvinylidinefluoride (PVDF) are examples of fluoropolymers. A suitable fluoropolymer is available from E.I. du Pont de Nemours, Wilmington, DE under the tradename Tedlar. Polyarylate is an example of a suitable liquid crystal polymer. Some of these films may also be coated with a second polymeric material. For example, a polyimide film, Kapton®, may be coated with fluorinated ethylene propylene, FEP, and used in this invention.

In preferred embodiments, the film layer is PEEK, PEKK, Tedlar®, Halar®, or even Kapton®.

The surface of the polymeric layers 26 and 32 may optionally be treated to improve adhesion with another substrate such as an adhesive. Suitable surface treatment methods include, but are not limited to, corona etching and washing with coupling agents such as ammonium, phosphonium or sulfonium salts.

In some embodiments, the protective polymeric layer 26 or / and polymeric layer 32 may be bonded to the refractory layer 27 by means such as adhesive or thermal bonding. In some embodiments, the bond strength between the protective polymeric layer 26 and 32 and the refractory layer is at least 44 N/m (0.25 lb/in). In another embodiment, the bond strength between the protective polymeric layer and the refractory layer is at least 140 N/m (0.8 lb/in) or even at least 262 N/m (1 .5 lb/in.).

If used, the adhesive layer is located between the polymeric layer 26 and 32 and the refractory layer. The adhesive layer may be a thermoplastic or thermoset resin. Thermoset resins include epoxy, epoxy novolac, phenolic, polyurethane, and polyimide. Thermoplastic resins include polyester, polyetherketone, polyetheretherketone, polyetherketoneketone, polyethersulfone, and polyolefin. Thermoplastic resins are preferred. One of the objectives for having a polymeric layer 26 and 32 adhesively bonded to a refractory layer is to improve inter-layer bond strength within the composite sheet and to provide a stronger more durable composite. To prevent possible damage from mechanical stressing exerted by a shrinking or melting or disintegrating polymeric film on an inorganic refractory layer during flame exposure it is preferred that inter-ply bond of the composite laminate would fail (i.e. release or melt or soften) in the early stage of the flame exposure causing internal de-bonding of the composite laminate (i.e. delamination of the refractory layer from the polymeric film) before the polymeric film starts disintegrating. Due to their relatively low activation temperatures, thermoplastic adhesives are a preferred choice over thermoset adhesives for this application. The adhesive layer may optionally contain up to 40 weight percent of a flame retardant ingredient. Suitable flame retardant ingredients include antimony trioxide, halogenated flame retardants including tetrabromobisphenol A, polybrominated biphenyls, Penta-, Octa-, Decabrominated diphenyl ether (oxide) and hexabromocyclododecane. Phosphorus containing flame retardants may also be used.

The adhesive must be capable of activation at a temperature in the range of 75 to 200 degrees C. In some embodiments, the activation range is from 120 to 140 degrees C. By activation we mean that for a thermoset resin, the resin must bond to the polymeric film layer and the refractory layer within the specified temperature range. For a thermoplastic resin, activation means that the resin softens and flows sufficiently to bond to the polymeric film layer and the refractory layer.

The adhesive layer weighs from 2 to 40 gsm. In some embodiments the adhesive layer weighs from 3 to 15 gsm or even from 5 to 10 gsm. If the adhesive weight is below 2 gsm, the bond strength will be too weak. If the adhesive weight is greater than 40 gsm, unnecessary weight will be added.

In some embodiments, at least one of the polymeric layers 26 and 32 are metalized on at least one surface. In some embodiments, the metalized surface is in contact with an adhesive layer.

In some embodiments the second component 22 may be reinforced by a lightweight open weave fabric scrim either bonded to outer side of the polymeric layer 26 or 32 or placed inside the second component between the inorganic refractory layer 27 and one or both polymeric layers 26 and 32 so as to provide additional mechanical strength to the layer. The scrim can be made from natural, organic or inorganic fibers with aramid, carbon, glass, cotton, nylon or polyester being typical examples. A glass fiber scrim is particularly preferred. The scrim may be a woven or knit structure and has a typical areal weight not exceeding 40 grams per square meter.

In some embodiments, the reinforcing lightweight open weave fabric scrim may be bonded to the outer side of the second component by means such as adhesive or thermal bonding. The adhesive may be a thermoplastic or thermoset resin. Thermoset resins include epoxy, epoxy novolac, phenolic, polyurethane, and polyimide. Thermoplastic resins include polyester, polyetherketone, polyetheretherketone, polyetherketoneketone, polyethersulfone, and polyolefin. Thermoplastic resins are preferred. The adhesive layer may optionally contain up to 40 weight percent of a flame retardant ingredient. Suitable flame retardant ingredients include antimony trioxide, halogenated flame retardants including tetrabromobisphenol A, polybrominated biphenyls, pentabrominated diphenyl ether (oxide)-, octabrominated diphenyl ether (oxide), decabrominated diphenyl ether (oxide) and hexabromocyclododecane. Phosphorus containing flame retardants may also be used. FIGS 2A and 2C show alternative orientations of the second component 22 within the composite sheet 20.

Inorganic Refractory Layer

The inorganic refractory layer is shown for example at 27 in FIG 2A. Preferably, the refractory layer has a dry areal weight of from 15 to 50 gsm or even from from 20 to 35 gsm. Prefereably the refractory layer has a residual moisture content of no greater than 10 percent by weight, more preferably no greater than 3 percent by weight. The refractory layer comprises platelets. Preferably at least 85% of the layer comprises platelets, more preferably at least 90% and most preferably at least 95%. In some embodiments, platelets comprise 100% of the layer. The refractory layer may comprise some residual dispersant arising from incomplete drying of the platelet dispersion during manufacture.

The refractory layer has a thickness of from 7.0 to 76 micrometers and more preferably from 7.0 to 50 micrometers. Preferably, the layer has a UL 94 flame classification of V-0. The function of the refractory layer, in which adjacent platelets overlap, is to provide a flame and hot gas impermeable barrier. The inorganic platelets may be clay, such as montmorillonite, vermiculite, mica, talc and combinations thereof. Preferably, the inorganic oxide platelets are stable (i.e., do not burn, melt or decompose) at about 600 degrees C, more preferably at about 800 degrees C and most preferably at about 1000 degrees C. Vermiculite is a preferred platelet material for the refractory layer. Vermiculite is a hydrated magnesium aluminosilicate micaceous mineral found in nature as a multilayer crystal. Vermiculite typically comprises by (dry) weight, on a theoretical oxide basis, about 38-46% SiO ₂ , about 16-24% MgO, about 1 1 - 16% AI2O3, about 8-13% Fe2O3 and the remainder generally oxides of K, Ca, Ti, Mn, Cr, Na, and Ba. "Exfoliated" vermiculite refers to vermiculite that has been treated, chemically or with heat, to expand and separate the layers of the crystal, yielding high aspect ratio vermiculite platelets. Suitable vermiculite materials are available from Specialty Vermiculite Products under the trade designations MicroLite 963 and MicroLite 963HS

The thickness of an individual platelet typically ranges from about 5 Angstroms to about 5,000 Angstroms more preferably from about 10 Angstroms to about 4,200 Angstroms. The mean value of the maximum width of a platelet typically ranges from about 10,000 Angstroms to about 30,000 Angstroms. The aspect ratio of an individual platelet typically ranges from 100 to 20,000.

Preferably, the platelets have an average diameter of from 15 to 25 micrometers. In some other embodiments, the platelets have an average diameter of from 18 to 23 micrometers. In a preferred embodiment, the refractory layer further comprises cations arising from contact, at a temperature of from 10 to 50 degrees C, with an aqueous cationic rich solution at a cation concentration of from 0.25 to 2N. The contact with the cationic solution occurs prior to assembling the refractory layer into a composite laminate. This cationic treatment provides enhanced stability to the refractory layer on exposure to fluids.

In some embodiments of this invention, the inorganic platelet layer may be reinforced by a lightweight open weave fabric scrim either laid onto a single platelet layer or placed between two layers of platelets so as to provide additional mechanical strength to the layer. The scrim can be made from natural, organic or inorganic fibers with glass, cotton, nylon or polyester being typical examples. A glass fiber scrim is particularly preferred. The scrim may be a woven or knit structure and has a typical areal weight not exceeding 40 grams per square meter.

Preferably the refractory layer is continuous. By continuous is meant that the layer is capable of being wound onto a roll without breaking apart. In some embodiments, the refractory layer is perforated to enhance bonding to an adhesive layer during subsequent processing. The extent of perforation is determined by experimentation. Preferably, in order to prevent compromising flame barrier properties, an individual perforation should not exceed 2 millimeters in maximum dimension. In a preferable embodiment, individual perforations should be spaced at least 10 millimeters apart. The shape of the perforations is not critical, Suitable perforations include circles, squares, rectangles, ovals and chevrons.

The bond strength between the refractory layer and the surface of the paper is at least 43 N/m (0.25 lb/in), preferably at least 140 N/m (0.8 lb/in), If the bond strength is less than 43 N/m, the inorganic refractory layer can peel off the substrate with a risk of breaks in the refractory layer.

A bond strength of at least 140 N/m ensures that the inorganic refractory layer does not separate from the substrate either during subsequent process steps or, once put in service, during the life span of the intended application. Bond strength is sometimes referred to as Release Value. In this instance, it is the Release Value between the surface of the paper and the intumescent coating applied to the paper.

Flame Barrier

The second component, as described above, may be used as a flame barrier composite layer. Flame barrier layers find use in applications in vehicles such as aircraft, trains, boats or building structures and offshore rigs. In an aircraft, the flame barrier layers may be found in ceiling, sidewalls and floor panels. For aircraft, other uses are in cargo containers, cargo liners and thermal acoustic blankets. Third Component

The third component 23 as shown in FIGS 2A to 2D has an areal density of from 102 to 678 gsm (3 to 20 oz. per sq. yd.) and comprises a second fabric 28 of filamentary yarns having a tenacity of at least 1 1 grams per dtex (10 grams per denier) and a second polymeric layer 29, the second fabric of the third component being adjacent to the refractory layer of the second component. The second polymeric layer is the innermost layer of the composite sheet. The second polymeric layer provides enhanced abrasion/scuff and puncture resistance, improved impact toughness as well as an enhanced resistance to physical mistreatment, chemical contact attack and permeation by liquids.

Preferably, the second polymeric layer maintains its toughness and flexibility over a wide temperature range, even at temperatures as low as (-50°C (-60°F)), over the life span of the end product. In some embodiments, the second fabric layer may be bonded to the second polymeric layer by means such as an adhesive, thermal bonding or by fasteners. When an adhesive is used the adhesive layer may be a thermoplastic or thermoset resin. Thermoset resins include epoxy, epoxy novolac, phenolic, polyurethane, and polyimide. Thermoplastic resins include polyester, polyetherketone, polyetheretherketone, polyetherketoneketone, polyethersulfone, and polyolefin. Thermoplastic resins are preferred. The

The adhesive may optionally contain up to 40 weight percent of a flame retardant ingredient. Suitable flame retardant ingredients include antimony trioxide, halogenated flame retardants including tetrabromobisphenol A, polybrominated biphenyls, Pentabrominated diphenyl ether (oxide), Octa brominated diphenyl ether (oxide) Decabrominated diphenyl ether (oxide) and hexabromocyclododecane. Phosphorus containing flame retardants are also widely used.

The adhesive must be capable of activation at a temperature in the range of 75 to 200 degrees C. In some embodiments, the activation range is from 120 to 140 degrees C. By activation we mean that for a thermoset resin, the resin must bond to the polymeric layer and the fabric within the specified temperature range. For a thermoplastic resin, activation means that the resin softens and flows sufficiently to bond to the polymeric layer and the fabric. The adhesive bond between the second polymeric layer and the second fabric is at least 263 N/m (1 .5 lb/in). In some embodiments, the adhesive bond between the second polymeric layer and the second fabric is at least 315 N/m (1 .8 lb/in), or even 876 N/m (5 lb/in). In some embodiments, the bond strength between the second fabric 28 and the second polymeric layer 29 is at least 263 N/m (1 .5 lb/in). In another embodiments, the bond strength between the second fabric and the second polymeric layer is at least 315 N/m (1 .8 lb/in). First and Second Fabrics

In some embodiments the first or second fabrics have an areal weight of from 84 to 508 gsm (2.5 to 15 oz. per sq. yd.). In some other embodiments, the fabric areal weight is from 101 to 373 gsm (3 to 1 1 oz. per sq. yd.). In some embodiments, the first fabric has an areal weight of from 101 to 170 gsm (3 to 5 oz. per sq. yd.). In some embodiments, the second fabric has an areal weight of from 170 to 270 gsm (5 to 8 oz. per sq. yd.).

The first or second fabrics may be woven or non-woven. Typical woven fabric styles are plain, basket, leno twill or satin weaves. In one embodiment, the first fabric is a plain weave fabric comprising 500 denier KM2+ p-aramid yarns in an amount of 1 1 ends per cm (28 ends per inch) in both warp and weft directions. In another embodiment, the second fabric is a plain weave fabric comprising 1000 denier KM2 p-aramid yarns in an amount of 9.4 ends per cm (24 ends per inch) in both warp and weft directions. Fine denier yarn of the fabric combined with a tough polymeric film leads to a significant enhancement in puncture resistance, and thus overall durability, of the non-rigid composite sheet.

Nonwoven fabrics include fabrics in which the filaments are arranged in a random orientation or fabrics comprising filaments that are aligned in only one direction. This latter type of fabric is also known as a non-crimped or unidirectional fabric.

In some embodiments the first and /or second fabrics are scoured or heat cleaned after weaving. Such processes are well known in the textile industry to remove contaminants such as oil from the weaving process.

Preferably, the filamentary yarns of the first and second fabrics comprise aromatic polyamide or aromatic copolyamide. Glass fiber and carbon fiber, especially carbon fiber based on polyacrylonitrile, may also be used. The fabrics 25 and 28 are made from multifilament yarns having a plurality of filaments. The yarns can be intertwined and/or twisted. For purposes herein, the term "filament" is defined as a relatively flexible, macroscopically homogeneous body having a high ratio of length to width across its cross-sectional area perpendicular to its length. The filament cross section can be any shape, but is typically circular or bean shaped. Herein, the term "fiber" is used interchangeably with the term "filament", and the term "end" is used interchangeably with the term "yarn". The filaments can be any length. Preferably the filaments are continuous. Multifilament yarn spun onto a bobbin in a package contains a plurality of continuous filaments. The multifilament yarn can be cut into staple fibers and made into a spun staple yarn suitable for use in the present invention. The staple fiber can have a length of about 1 .5 to about 5 inches (about 3.8 cm to about 12.7 cm). The staple fiber can be straight (i.e., non crimped) or crimped to have a saw tooth shaped crimp along its length, with a crimp (or repeating bend) frequency of about 3.5 to about 18 crimps per inch (about 1 .4 to about 7.1 crimps per cm). In some embodimemts, the yarns have a yarn tenacity of at least 1 1 grams per dtex and a modulus of at least 100 grams per dtex. In some embodiments, the yarns have a linear density of from 333 to 2222 dtex (300 to 2000 denier) or from 555 to 1 1 1 1 dtex (500 to 1000 denier). In some embodiments, the yarns of the first or second fabrics have a linear density of 555 dtex or of 1 1 1 1 dtex.

When the polymer is polyamide, aramid is preferred. The term "aramid" means a polyamide wherein at least 85% of the amide (-CONH-) linkages are attached directly to two aromatic rings. Suitable aramid fibers are described in Man-Made Fibres - Science and Technology, Volume 2, Section titled Fibre-Forming Aromatic Polyamides, page 297, W. Black et al., Interscience Publishers, 1968. Aramid fibers and their production are, also, disclosed in U.S. Patents 3,767,756; 4,172,938; 3,869,429; 3,869,430; 3,819,587; 3,673,143; 3,354,127; and 3,094,51 1 . The preferred aramid is a para-aramid. The preferred para-aramid is poly(p-phenylene terephthalamide) which is called PPD-T. By PPD-T is meant the homopolymer resulting from mole-for-mole polymerization of p- phenylene diamine and terephthaloyl chloride and, also, copolymers resulting from incorporation of small amounts of other diamines with the p- phenylene diamine and of small amounts of other diacid chlorides with the terephthaloyl chloride. As a general rule, other diamines and other diacid chlorides can be used in amounts up to as much as about 10 mole percent of the p-phenylene diamine or the terephthaloyl chloride, or perhaps slightly higher, provided only that the other diamines and diacid chlorides have no reactive groups which interfere with the polymerization reaction. PPD-T, also, means copolymers resulting from incorporation of other aromatic diamines and other aromatic diacid chlorides such as, for example, 2,6-naphthaloyl chloride or chloro- or dichloroterephthaloyl chloride or 3,4'-diaminodiphenylether.

Additives can be used with the aramid and it has been found that up to as much as 10 percent or more, by weight, of other polymeric material can be blended with the aramid. Copolymers can be used having as much as 10 percent or more of other diamine substituted for the diamine of the aramid or as much as 10 percent or more of other diacid chloride substituted for the diacid chloride or the aramid. Another suitable fiber is one based on aromatic copolyamide prepared by reaction of terephthaloyl chloride (TPA) with a 50/50 mole ratio of p-phenylene diamine (PPD) and 3, 4'-diaminodiphenyl ether (DPE). Yet another suitable fiber is that formed by polycondensation reaction of two diamines, p-phenylene diamine and 5-amino-2-(p- aminophenyl) benzimidazole with terephthalic acid or anhydrides or acid chloride derivatives of these monomers.

Glass fibers include "E" glass and "S" Glass. E-Glass is a commercially available low alkali glass. One typical composition consists of 54 weight % SiO ₂ , 14 weight % AI ₂ O ₃ , 22 weight % CaO/MgO, 10 weight % B2O3 and less then 2 weight % Na2O K ₂ O. Some other materials may also be present at impurity levels S-Glass is a commercially available magnesia-alumina-silicate glass. This composition is stiffer, stronger and more expensive than E-glass and is commonly used in polymer matrix composites.

In some embodiments the carbon fiber is a standard or intermediate modulus fiber such as those available under the tradename Torayca or HexTow from Toray Industries or Hexcel Corporation. Typically, such fibers have 3,000 or 6,000 or 12,000 or 24,000 filaments per tow.

In some embodiments first and / or second fabrics may optionally be treated with a flame retardant ingredient to aid flame propagation properties of the non-rigid Flame Resistant Composite. Suitable flame retardant ingredients include antimony trioxide, halogenated flame retardants including tetrabromobisphenol A, polybrominated biphenyls, pentabrominateddiphenylether(oxide),

octabrominateddiphenylether(oxide),

decabrominateddiphenylyether(oxide) and hexabromocyclododecane. Phosphorus containing flame retardants are also widely used.

First and Second Polymeric Layers

The polymer of the first or second or both polymeric layers may be a thermoplastic or thermoset polymer. A thermoplastic polymer is preferred.

In a preferred embodiment, the first and second polymeric layers are in a form of a self-supporting film .

Suitable polymers include polyurethane, polyethylene, polypropylene, polyethylenenaphthalate, polyacrylonitrile, fluoropolymer, polyimide, polyketone, polyimide (Kapton®), polysulfone, polyarlene sulfide, liquid crystal polymer, polycarbonate, and ionomers such as ethylenemethacrylicacid copolymer (E/MAA). Exemplary fluoropolymers include polyvinylfluoride (Tedlar®), etyhylenechlorotrifluoroethylene copolymer (Halar®) and polytetrafluroethylene (Teflon®). Exemplary polyketones include polyetheretherketone (PEEK) and polyetherketoneketone (PEKK).

In one embodiment, the first polymeric layer is polyurethane. In another embodiment, the second polymeric layer is an ionomeric resin such as ethylenemethacrylicacid copolymer. In yet another embodiment, the first polymeric layer is non-transparent and impervious to UV rays. By non-transparent and impervious to UV rays we mean that the first polymeric layer blocks at least 95% of UV rays, more preferably at least 98% and most preferably 100% of UV rays especially those rays at the upper end of the UV spectrum. In some embodiments the first and / or second polymeric layers have an areal weight of 17 to 170 gsm (0.5 to 5 oz. per sq. yd.) or from 34 to 136 gsm (1 to 4 oz. per sq. yd.) or even from 67 to 102 gsm (2 to 3 oz. per sq. yd.).

In some embodiments, at least one surface of the first and / or second polymeric layers may be metalized. Preferably in the composite sheet, the metalized surface is on the side of the polymeric layer adjacent to the first or second fabrics.

TEST METHODS

Flame penetration was measured according to 14 CFR 25.855

Appx. F Part III - Test Method To Determine Flame Penetration Resistance of Cargo Compartment Liner (ceiling position

Tensile properties of the composite sheet were determined by ASTM D3039 / D3039M - 08 Standard Test Method for Tensile Properties of Polymer Matrix Composite Materials.

The dry tensile strength of the substrate was measured according to TAPPI T494 om-06 Tensile Properties of Paper and Paperboard (Using Constant Rate of Elongation Apparatus).

The thickness of the substrate was measured by TAPPI T41 1 om- 10 Thickness (Caliper) of Paper, Paperboard, and Combined Board.

The dimensional stability of the substrate was rated based on its ability to hold flat (i.e. no moisture related wrinkles or creases) for at least 2 minutes when exposed to one-sided wetting. The dry areal weight of the refractory layer was measured according to ISO 536 (1995) Determination of Grammage and TAPPI T 410 Grammage of Paper and Paperboard (Weight per Unit Area).

The moisture content of the refractory layer was measured according to ISO 287 (1985) Determination of Moisture Content - Oven Drying Method.

The composite sheets were subjected to a flame test that replicated the temperature and air mass flux test conditions of test method FAA FAR 25.856(b), App. F, Part VII. The somewhat lower heat flux was compensated with a higher air mass flux to replicate a required thermo- mechanical stress level to be exerted on the flame barrier composites during the burn-through test. EXAMPLES

Example 1

A non-rigid composite sheet was prepared.

First Component

The first component comprised a woven fabric (first fabric) thermally bonded to a non-transparent 0.075 mm (3 mil) blown polyurethane film

(first polymeric layer). The fabric had an areal weight of 125 gsm (3.7 oz.

/sq.yd.). The fabric was a plain weave having 1 1 ends per cm (28 ends per inch) in both warp and weft and was woven from 556 dtex (500 denier) p- aramid Kevlar® KM2+ yarns, merge 1 W034. , The bond strength between first polymeric film and first fabric was tested to be at least 437 N/m (2.5 lbs/in).

Second Component

The second component comprised a 30 gsm inorganic refractory layer, treated with a 0.25N cationic dispersion of sodium chloride, adhesively bonded between two 25ga clear PEEK films. A thermoplastic adhesive having a nominal weight of 5 to 7 gsm was used to bond the PEEK film to the refractory layer.

The resulting composite flame barrier film was further coated on one side with a thermoplastic heat-seal layer, containing about 30 weight percent of flame suppressing additives and reinforced with a nylon net scrim with the scrim reinforcement facing the first component.

The inorganic refractory material used in this example was vermiculite. The vermiculite used was an aqueous dispersion of Microlite® 963HS obtained from Specialty Vermiculite Corp., Enoree, SC.

Third Component

The third component comprised a woven fabric (second fabric) thermally bonded to a 0.075 mm (3 mil) ionomeric Surlyn® film (second polymeric layer). The fabric had an areal weight of 220 gsm (6.5 oz. /sq.yd.). The fabric was a plain weave having 9 ends per cm (24 ends per inch) in both warp and weft and was woven from 1 1 1 1 dtex (1000 denier) p-aramid Kevlar® KM2 yarns merge 1 W041 . The bond strength between first polymeric film and first fabric was tested to be at least 262 N/m (1 .5 lbs/in).

The first, second and third components were assembled together as shown in FIG 2A. Component 2 was not bonded to either component 1 or component 3. For ease of handling all three components were sewn together along their edges with Kevlar® thread.

The fabricated composite sheet was subjected, in a ceiling position, to the FAA flame penetration test 14 CFR 25.855. The flame was applied on the Surlyn® film side of the composite. The sample showed a good resistance to flame penetration, with the inorganic refractory layer acting as an effective barrier to 927 °C, +/- 38 °C (1700 °F, +/- 100 °F) -- flame with no flame penetration of the specimen within 5 minutes after application of the flame source. The peak temperature measured at 101 mm (4 inches) above the upper surface of the horizontal test sample did not exceed 204°C (400 °F).

The mechanical strength of the composite sheet was also tested to comply with durability standards set by National Aerospace Standard NAS 3610 for materals used for air cargo Unit Load Devices. The axial tensile strength of 101 mm (4") wide strips of the composite sheet was 771 +/- 22 kg (1 ,700 +/- 50 lbs) (74,375 +/- 2,187 N/m (425 +/- 12.5 ib/in)).

Comparative Example A

A composite sheet was fabricated comprising a 322 gsm (9.5 oz./sq. yd.), woven fabric thermally bonded between a 0.075 mm (3 mil) polyurethane (first polymeric layer) and a 0.075 mm (3 mil) Surlyn® (second polymeric layer) films of Example 1 . The bond strength between the PU film and fabric was at least 44.6 kg/m (2.5 lbs/in). The fabric was a plain weave having 9 ends per cm (24 ends per inch) in both warp and weft and was woven from 1667 dtex (1500 denier) p-aramid Kevlar® 29 yarns, merge 1 F21 1 . The axial tensile strength of a 101 mm (4") wide strip of the single layer composite was no greater than 408 kg (900 lbs) (39,375 N/m (225 lb/in)).

Comparable Example A was tested as complying with flammability requirements of TSO C90a Cargo Pallets, Nets and Containers (Unit Load Devices) specification for vertical and horizontal flame propagation. However, it lacked any effective flame barrier properties as, when exposed to flame, the sample failed flame penetration within 30 seconds after application of the flame source.

Example 2

First Component The first component comprised a woven fabric (first fabric) thermally bonded to a non-transparent 0.075 mm (3 mil) blown polyurethane film (first polymeric layer). The fabric had an areal weight of 220 gsm (6.5 oz. /sq.). The fabric was a plain weave having 9 ends per cm (24 ends per inch) in both warp and weft and was woven from 1 1 1 1 dtex (1000 denier) p-aramid Kevlar® KM2 yarns, merge 1 W041 . The bond strength between first polymeric film and first fabric was tested to be at least 437 N/m (2.5 lbs/in). Second Component

The second component comprised a 30 gsm inorganic refractory layer, treated with a 0.25N cationic dispersion of sodium chloride, adhesively bonded between two 25ga clear PEEK films. A thermoplastic adhesive having a nominal weight of from 5 to 7 gsm was used to bond the PEEK films to the refractory layer.

The resulting composite flame barrier film was further coated on one side with a thermoplastic heat-seal layer, containing about30 weight percent of flame suppressing additives and reinforced with a nylon net scrim with the scrim reinforcement facing the first component.

The inorganic refractory material used in this example was vermiculite. The vermiculite used was an aqueous dispersion of Microlite® 963HS obtained from Specialty Vermiculite Corp., Enoree, SC.

Third Component

The third component comprised a woven fabric (second fabric) thermally bonded to a 0.075 mm (3 mil) ionomeric Surlyn® film (second polymeric layer). The fabric had an areal weight of 125 gsm (3.7 oz. /sq.yd.). The fabric was a plain weave having 1 1 ends per cm (28 ends per inch) in both warp and weft and was woven from 556 dtex (500 denier) p- aramid Kevlar® KM2+ yarns, merge 1W034. The bond strength between first polymeric film and first fabric was tested to be at least 262 N/m (1 .5 lbs/in). The first, second and third components were assembled together as shown in FIG 2A. Component 2 was not bonded to either component 1 or component 3. For ease of handling all three components were sewn together along their edges with Kevlar® thread.

A composite sheet of this example showed similar resistance to flame penetration and had a similar axial tensile strength as the composite sheet of Example 1 . Example 3

A non-rigid composite sheet was prepared.

First Component

The first component comprised a woven fabric (first fabric) thermally bonded to a non-transparent 0.075 mm (3 mil) cast polyurethane film, the film containing up to 50 weight percent of a flame retardant ingredient (first polymeric layer). The fabric had an areal weight of 125 gsm (3.7 oz.

/sq.yd.). The fabric was a plain weave having 1 1 ends per cm (28 ends per inch) in both warp and weft and was woven from 556 dtex (500 denier) p- aramid Kevlar® KM2+ yarns, merge 1 W034. The bond strength between first polymeric film and first fabric was tested to be at least 437 N/m (2.5 lbs/in).

Second Component

The second component comprised a 30 gsm inorganic refractory layer, treated with a 0.25N cationic dispersion of sodium chloride, adhesively bonded between two 0.025 mm (1 mil) white polyvinyly fluoride films available from DuPont under the tradename Tedlar. A thermoplastic adhesive having a nominal weight of 8 to 12 gsm and containing up to 50 weight percent of a flame retardant ingredient was used to bond the Tedlar® film to the refractory layer. The inorganic refractory material used in this example was vermiculite. The vermiculite used was an aqueous dispersion of Microlite® 963HS obtained from Specialty Vermiculite Corp., Enoree, SC. Third Component

The third component comprised a woven fabric (second fabric) thermally bonded to a 0.075 mm (3 mil) ionomeric Surlyn® film (second polymeric layer). The fabric had an areal weight of 220 gsm (6.5 oz.

/sq.yd.). The fabric was a plain weave having 9 ends per cm (24 ends per inch) in both warp and weft and was woven from 1 1 1 1 dtex (1000 denier) p-aramid Kevlar® KM2 yarns merge 1 W041 . The bond strength between first polymeric film and first fabric was tested to be at least 262 N/m (1 .5 lbs/in). The first, second and third components were assembled together as shown in FIG 2A. Component 2 was not bonded to either component 1 or component 3.

The fabricated composite sheet was subjected, in a ceiling position, to the FAA flame penetration test 14 CFR 25.855. The flame was applied on the Surlyn® film side of the composite. The sample showed a good resistance to flame penetration, with the inorganic refractory layer acting as an effective barrier to 927 °C, +/- 38 °C (1700 °F, +/- 100 °F) -- flame with no flame penetration of the specimen within 5 minutes after application of the flame source. The peak temperature measured at 101 mm (4 inches) above the upper surface of the horizontal test sample did not exceed 204°C (400 °F).

The mechanical strength of the composite sheet was also tested to comply with durability standards set by National Aerospace Standard NAS 3610 for materals used for air cargo Unit Load Devices. The axial tensile strength of 101 mm (4") wide strips of the composite sheet was 771 +/- 22 kg (1 ,700 +/- 50 lbs) (74,375 +/- 2,187 N/m (425 +/- 12.5 ib/in)). Example 4

The same as Example 3 with the exception that component 2 was thermally bonded/attached to component 3 with a 0.025 mm (1 mil) cast polyurethane film containing up to 50 weight percent of a flame retardant ingredient. Component 1 remained unattached.

Example 5

The same as Example 3 with the exception that component 2 was thermally bonded/attached to component 1 with a 0.025 mm (1 mil) cast polyurethane film containing up to 50 weight percent of a flame retardant ingredient. Component 3 remained unattached.

Example 6

The same as Example 3 with the exception that component 2 was thermally bonded/attached/sanwitched between component 1 and component 3 with two layers of a 0.025 mm (1 mil) cast polyurethane film containing up to 50 weight percent of a flame retardant ingredient.