Coating method for flame-retardant treatment

Abstract

The disclosure relates to methods for forming a flame-retardant coated substrate.

Description

Attorney Docket No. 4960.036W01 Client Ref. No. 655801-1COATING METHOD FOR FLAME-RETARDANT TREATMENTCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of priority from U.S. Appl. No. 63 / 713,959, filed October 30, 2024, which is incorporated by reference as if fully set forth herein.TECHNICAL FIELD

[0002] This disclosure relates to the field of flame-retardant coatings for various substrates such as foams, textiles, fabrics, or films.BACKGROUND

[0003] Fire-related incidents have resulted in substantial property damage and personal injuries across various sectors. Most materials are known to be flammable, posing significant safety risks. To mitigate these hazards, flame retardants have been developed and widely implemented. Halogenated materials, including brominated compounds have been prominent in the use of these flame retardants. However, these halogenated materials have faced increased scrutiny due to potential environmental and health concerns. For instance, some halogenated flame retardants have been associated with the formation of toxic byproducts during combustion or disposal. Additionally, certain brominated compounds have demonstrated limited durability in some applications, further compromising their long-term effectiveness as flame retardants.BRIEF DESCRIPTION OF THE DRAWINGS

[0004] FIG. 1A illustrates vertical flame test results of uncoated and coated fabric in accordance with at least one example of this disclosure.

[0005] FIG. IB illustrates vertical flame test results of uncoated and coated fabric after rinsing in accordance with at least one example of this disclosure.

[0006] FIG. 2A illustrates microscale combustion calorimeter results of uncoated and coated fabric in accordance with at least one example of this disclosure.

[0007] FIG. 2B illustrates microscale combustion calorimeter results of uncoated and coated fabric after rinsing in accordance with at least one example of this disclosure.

[0008] FIG. 3 A illustrates mass and derivative weight loss as a function of temperature for uncoated and coated fabric in accordance with at least one example of this disclosure.Attorney Docket No. 4960.036W01 Client Ref. No. 655801-1

[0009] FIG. 3B illustrates mass and derivative weight loss as a function of temperature for uncoated and coated fabric after rinsing in accordance with at least one example of this disclosure.

[0010] FIG. 4A illustrates differential thermograms of uncoated and coated fabric in accordance with at least one example of this disclosure.

[0011] FIG. 4B illustrates differential thermograms of uncoated and coated fabric after rinsing in accordance with at least one example of this disclosure.DETAILED DESCRIPTION

[0012] Systems and methods described herein can provide a simplified, scalable method to apply a flame-retardant coating to textiles, fabrics, foams, or films. Systems and methods described herein introduces a deposition process for creating a polyelectrolyte (PEC) coating that can impart flame-retardancy to textiles, fabrics, foams, or films.

[0013] Systems and methods described herein can describe a combination that can include a polymeric, polycationic material and an anionic material to form a flame-retardant PEC coating. The process can overcome the limitations of a layer-by-layer assembly method, which can require multiple processing steps to achieve a specified property. By incorporating a volatile base or a volatile acid, the systems and methods described herein can induce complexation upon evaporation, resulting in an ionically crosslinked precipitate that adheres to the substrate. The systems and methods described herein can have the potential to significantly improve the scalability and efficacy of flame-retardant treatments for textiles, fabrics, foams, or films. The coating method and system described herein can be an industrially attractive method to form a flame-retardant coating on a substrate without the need for a chemically reactive process, halogenated materials, or special equipment.

[0014] Systems and methods described herein can be used for coating a substrate with a flame-retardant coating to impart flame-retardant properties. A coating method can provide a substrate with a flame-retardant coating by depositing a coating on the substrate. The coating can comprise a polyelectrolyte complex formed between a polymeric, polycationic material and an anionic material. The coating can be between about 10 nanometers and about 100 microns thick, but certain applications may require a coating that is greater than 100 microns thick (e.g., 1000-10,000+ microns coating (1-10+ mm) in situations where a coating on steel beams may be required) or less than 10 nm thick.

[0015] The disclosure relates to a method for forming a flame-retardant coated substrate, the method comprising: preparing a first aqueous solution, comprising a polymeric,Attorney Docket No. 4960.036W01 Client Ref. No. 655801-1 polycationic material; preparing a second aqueous solution, comprising an anionic material and a volatile base; combining the first aqueous solution and the second aqueous solution to form a combined aqueous solution; exposing a substrate to the combined aqueous solution; and evaporating the combined aqueous solution from the substrate to produce a flameretardant coated substrate, wherein a coating on the flame-retardant coated substrate comprises a polyelectrolyte complex formed between the polymeric, polycationic material and the anionic material.

[0016] The disclosure also relates to a method for forming a flame-retardant coated substrate, the method comprising: preparing a first aqueous solution, comprising a polymeric, polycationic material and a volatile acid; preparing a second aqueous solution, comprising an anionic material; combining the first aqueous solution and the second aqueous solution to form a combined aqueous solution; exposing a substrate to the combined aqueous solution; and evaporating the combined aqueous solution from the substrate to produce a flame-retardant coated substrate, wherein a coating on the flameretardant coated substrate comprises a polyelectrolyte complex formed between the polymeric, polycationic material and the anionic material.

[0017] The disclosure also relates to a method for forming a flame-retardant coated substrate, the method comprising: exposing a substrate to a combined aqueous solution comprising a volatile base, a polymeric, polycationic material, and an anionic material; and evaporating the combined aqueous solution from the substrate to produce a flame-retardant coated substrate, wherein a coating on the flame-retardant coated substrate comprises a polyelectrolyte complex formed between the polymeric, polycationic material and the anionic material.

[0018] The disclosure also relates to a method for forming a flame-retardant coated substrate, the method comprising: exposing a substrate to a combined aqueous solution comprising a volatile acid, a polymeric, polycationic material, and an anionic material; and evaporating the combined aqueous solution from the substrate to produce a flame-retardant coated substrate, wherein a coating on the flame-retardant coated substrate comprises a polyelectrolyte complex formed between the polymeric, polycationic material and the anionic material.

[0019] The flame-retardant coating can be applied to a wide range of substrate materials. For example, the substrate can include a textile, a fabric, a foam, a film, leather, a vinyl compound, plastic, wood, a carpet, hook and loop fasteners, a non-foam padding, a film, or a combination thereof. Without limitation, examples of suitable fabric materials can includeAttorney Docket No. 4960.036W01 Client Ref. No. 655801-1 wool, linen, cotton, polyester, nylon, a polyester-cotton blend, a nylon-cotton blend, or a combination thereof. The substrate can include a hook and loop fastener (i.e., VELCRO®, which is a registered trademark of Velcro Industries, B.V.). The substrate can be a carpet, wherein a carpet can refer to a woven floor or wall covering having an upper pile layer attached to a backing. The substrate can include wood, a wood product, a particle board, balsa wood or the like. In some examples, non-foam padding can refer to a material that provides cushion against contact that does not include foam (e.g., feathers). The substrate can be positively charged, negatively charged, or neutral. Alternatively, or in addition, the substrate can comprise a multi-layered material comprising a combination of the substrates listed above.

[0020] The substrate can include a filmic / film substrate, such as, a polyester film, a polyethylene terephthalate (PET) film, a polypropylene film, a cellulose acetate film, a polyvinyl chloride (PVC) film, a polyethylene films, or a combination thereof.

[0021] The polyelectrolyte complex of the coating can be formed from a polymeric, polycationic material and an anionic material.

[0022] The polymeric, polycationic material can include polyethylenimine (PEI), branched polyethylenimine (BPEI), linear polyethylenimine, polyallylamine, polyvinylamine^ cationic polyacrylamide, cationic poly diallyldimethylammonium-chloride (PDDA), poly(melamine- co-formaldehyde), polymelamine, a copolymer of polymelamine, polyvinylpyridine, a copolymer of polyvinylpyridine, or a combination thereof. The polymeric, polycationic material can include polymers with hydrogen bonding, such as, polyethylene oxide, polyvinylpyrrolidone, or a combination thereof. The polymeric, polycationic material can include, silicon based polymers, polyoligomeric silsesquioxane, carbon nanotubes, graphene, or a combination thereof.

[0023] The polymeric, polycationic material can include a colloidal particle, a nanoparticle, a nitrogen-rich polymer, or a combination thereof. The polymeric, polycation material can take the form of a powder, a flake, a liquid, a solution, a suspension, or a combination thereof.

[0024] The anionic material can include an anionic polymer, a colloidal particle, a sulfated molecule, a boronic acid, a boron containing acid, or a combination thereof. Examples of the anionic material can include sodium hexametaphosphate, poly (sodium phosphate), a phosphonic acid group, or a combination thereof.

[0025] Examples of anionic polymers can include branched polystyrene sulfonate (PSS), polymethacrylic acid (PMAA), polyacrylic acid (PAA), or a combination thereof. ExamplesAttorney Docket No. 4960.036W01 Client Ref. No. 655801-1 of colloidal particles can include organic and / or inorganic materials, such as, clays, colloidal silica, inorganic hydroxides, silicon based polymers, polyoligomeric silsesquioxane, carbon nanotubes, graphene, or a combination thereof. Examples of clays can include sodium montmorillonite, hectorite, saponite, Wyoming bentonite, halloysite, vermiculite, or a combination thereof. Examples of an inorganic hydroxide can include aluminum hydroxide, magnesium hydroxide, or a combination thereof. Examples of a sulfated molecule can include ammonium sulfate, polyethylene glycol sulfate, poly vinyl sulfonic acid, sodium sulfate, or a combination thereof. Examples of boronic acid can include2-methylpropylboronic acid, 2-hydroxy-3 -methylphenyl boronic acid, polymer- bound boronic acid, or a combination thereof. In some examples, the phosphate material can include poly (sodium phosphate) (PSP), ammonium phosphate, ammonium polyphosphate, sodium hexametaphosphate, a material containing a phosphonic acid group, or a combination thereof.

[0026] The systems and methods herein can describe the use of a volatile acid or a volatile base. As described herein, a volatile acid or a volatile base can be defined as an acid or base that can evaporate or vaporize at room temperature, or at elevated temperatures (e.g., at temperatures higher than room temperature, such as 25°C or higher). The term “volatile acid” or “volatile base” can also include acids or bases that can be evaporated, vaporized, or otherwise removed under vacuum without the application of elevated temperatures. The volatile acid and volatile base can, for example, have a low boiling point and high vapor pressure, allowing them to easily transition from a liquid phase to a gas phase. The volatile acid and volatile base can also include an acid or a base that can evaporate, vaporize, or otherwise removed under vacuum when they are each dissolved in an aqueous solution.

[0027] A volatile base can include, for example, ammonia, methylamine, dimethylamine, ethylamine, triethylamine, pyridine, or a combination thereof.

[0028] A volatile base can include, for example, formic acid, acetic acid, propionic acid, butyric acid, carbonic acid, or a combination thereof.

[0029] The coating method can involve preparing one or more aqueous solutions. The aqueous solution can be prepared by any suitable method, such as, direct dissolution, serial dilution, volumetric preparation, gravimetric preparation, sonication, manual mixing, magnetic mixing, shear mixing, static mixing, or a combination thereof.

[0030] The coating method can involve preparing two separate aqueous solutions. The first aqueous solution can include a polymeric, polycationic material, and the second aqueous solution can include an anionic material. The first aqueous solution can include from aboutAttorney Docket No. 4960.036W01 Client Ref. No. 655801-11.0 wt. % polymeric, polycationic material to about 50.0 wt. % polymeric, polycationic material, alternatively from about 0.01 wt. % polymeric, polycationic material to about 1.50 wt. % polymeric, polycationic material, alternatively from about 0.05 wt. % polymeric, polycationic material to about 1.50 wt. % polymeric, polycationic material, alternatively from about 0.01 wt. % polymeric, polycationic material to about 1.00 wt. % polymeric, polycationic material, alternatively from about 0.01 wt. % polymeric, polycationic material to about 50.0 wt. % polymeric, polycationic material, alternatively from about 0.05 wt. % polymeric, polycationic material to about 30.0 wt. % polymeric, polycationic material, alternatively from about 1.0 wt. % polymeric, polycationic material to about 15.0 wt. % polymeric, polycationic material, and alternatively from about 1.0 wt. % polymeric, polycationic material to about 10.0 wt. % polymeric, polycationic material.

[0031] The second aqueous solution can include from about 1.0 wt. % anionic material to about 50.0 wt. % anionic material, alternatively from about 0.01 wt. % anionic material to about 1.50 wt. % anionic material, alternatively from about 0.05 wt. % anionic material to about 1.50 wt. % anionic material, alternatively from about 0.01 wt. % anionic material to about 1.00 wt. % anionic material, alternatively from about 0.01 wt. % anionic material to about 50.0 wt. % anionic material, alternatively from about 0.05 wt. % anionic material to about 30.0 wt. % anionic material, alternatively from about 1.0 wt. % anionic material to about 15.0 wt. % anionic material, and alternatively from about 1.0 wt. % anionic material to about 10.0 wt. % anionic material.

[0032] The first aqueous solution or the second aqueous solution can include a volatile acid or a volatile base. For example, the volatile base can be added to the second aqueous solution. The second aqueous solution can include from about 0.01 wt. % volatile base to about 25.0 wt. % volatile base, alternatively from about 0.05 wt. % volatile base to about 15.0 wt. % volatile base, and alternatively from about 0.01 wt. % volatile base to about 10.0 wt. % volatile base. For example, aqueous ammonia can be added into the second aqueous solution as the volatile base.

[0033] The volatile acid can be added to the first aqueous solution. The first aqueous solution can include from about 0.01 wt. % volatile acid to about 25.0 wt. % volatile acid, alternatively from about 0.05 wt. % volatile acid to about 15.0 wt. % volatile acid, and alternatively from about 0.01 wt. % volatile acid to about 10.0 wt. % volatile acid.

[0034] The first aqueous solution can include a variety of chemical species, such as, water molecules, hydrogen ions, hydroxide ions, polymeric molecules (e.g., PEI), protonated polymeric molecules (e.g., protonated PEI), polycationic molecules (e.g., polycationic PEI),Attorney Docket No. 4960.036W01 Client Ref. No. 655801-1 volatile acid molecules (e.g., acetic acid), conjugate bases of the volatile acid (e.g., acetate ion), or a combination thereof.

[0035] The second aqueous solution can include a variety of chemical species, such as, water molecules, hydrogen ions, hydroxide ions, anionic molecules (e.g., PSP), anions (e.g., hexametaphosphate ions), cations (e.g., sodium cations), volatile base molecules (e.g., ammonia), conjugate acids of the volatile base (e.g., ammonium ion), or a combination thereof.

[0036] When both the first aqueous solution and second aqueous solution have been prepared, the first aqueous solution and second aqueous solution can be combined to form a combined aqueous solution. The combined aqueous solution can include a polymeric, polycationic material, an anionic material, a volatile acid, a volatile base, or a combination thereof.

[0037] The combined aqueous solution can also be prepared in one step. For example, the combined aqueous solution can be prepared by including a polymeric, polycationic material, an anionic material, a volatile acid, a volatile base, or a combination thereof. For example, the combined aqueous solution can contain a polymeric, polycationic material, an anionic material, and a volatile base. In another example, the combined aqueous solution can contain a polymeric, polycationic material, an anionic material, and a volatile acid. The combined aqueous solution can include from about 1.0 wt. % polymeric, polycationic material to about 50 wt. % polymeric, polycationic material, alternatively from about 0.01 wt. % polymeric, polycationic material to about 1.50 wt. % polymeric, polycationic material, alternatively from about 0.05 wt. % polymeric, polycationic material to about 1.50 wt. % polymeric, polycationic material, alternatively from about 0.01 wt. % polymeric, polycationic material to about 1.00 wt. % polymeric, polycationic material, alternatively from about 0.01 wt. % polymeric, polycationic material to about 50.0 wt. % polymeric, polycationic material, alternatively from about 0.05 wt. % polymeric, polycationic material to about 30.0 wt. % polymeric, polycationic material, alternatively from about 1.0 wt. % polymeric, polycationic material to about 15.0 wt. % polymeric, polycationic material, and alternatively from about 1.0 wt. % polymeric, polycationic material to about 10.0 wt. % polymeric, polycationic material.

[0038] The combined aqueous solution can include from about 1.0 wt. % anionic material to about 50.0 wt. % anionic material, alternatively from about 0.01 wt. % anionic material to about 1.50 wt. % anionic material, alternatively from about 0.05 wt. % anionic material to about 1.50 wt. % anionic material, alternatively from about 0.01 wt. % anionic materialAttorney Docket No. 4960.036W01 Client Ref. No. 655801-1 to about 1.00 wt. % anionic material, alternatively from about 0.01 wt. % anionic material to about 50.0 wt. % anionic material, alternatively from about 0.05 wt. % anionic material to about 30.0 wt. % anionic material, alternatively from about 1.0 wt. % anionic material to about 15.0 wt. % anionic material, and alternatively from about 1.0 wt. % anionic material to about 10.0 wt. % anionic material.

[0039] The combined aqueous solution can include from about 0.01 wt. % volatile base to about 25.0 wt. % volatile base, alternatively from about 0.05 wt. % volatile base to about 15.0 wt. % volatile base, and alternatively from about 0.01 wt. % volatile base to about 10.0 wt. % volatile base.

[0040] The combined aqueous solution can include from about 0.01 wt. % volatile acid to about 25.0 wt. % volatile acid, alternatively from about 0.05 wt. % volatile acid to about 15.0 wt. % volatile acid, and alternatively from about 0.01 wt. % volatile acid to about 10.0 wt. % volatile acid.

[0041] The combined aqueous solution aqueous solution can include a variety of chemical species, such as, water molecules, hydrogen ions, hydroxide ions, polymeric molecules (e.g., PEI), protonated polymeric molecules (e.g., protonated PEI), polycationic molecules (e.g., polycationic PEI), anionic molecules (e.g., PSP), anions (e.g., hexametaphosphate ions), cations (e.g., sodium cations), volatile acid molecules (e.g., acetic acid), conjugate bases of the volatile acid (e.g., acetate ion), volatile base molecules (e.g., ammonia), conjugate bases of the volatile base (e.g., ammonium ion), or a combination thereof.

[0042] The combined aqueous solution can have an equimolar ratio of the polymeric, polycationic material and the anionic material. The combined aqueous solution can have between a 1 :3 molar ratio and a 1.75: 1 molar ratio of the polymeric, polycationic material to the anionic material. The combined aqueous solution can include a 1 :3 molar ratio of the polymeric, polycationic material and the anionic material, alternatively a 1 :2.75 molar ratio alternatively a 1 :2.5 molar ratio, alternatively a 1 : 1.75 molar ratio, alternatively a 1 : 1.5 molar ratio, alternatively a 1 : 1.25 molar ratio, alternatively a 1 : 1 molar ratio, alternatively a 1.25: 1 molar ratio, alternatively a 1.5: 1 molar ratio, alternatively a 1.75: 1 molar ratio or any ranges in between.

[0043] The pH of the combined aqueous solution can be adjusted. Without being limited by theory, reducing, or increasing the pH of the combined aqueous solution can increase or decrease the growth of the coating. The pH can be adjusted by any suitable means, such as, by adding an acid or a base. The pH can be adjusted by the addition of a volatile acid or a volatile base. For example, the second aqueous solution can have a pH of at least 9,Attorney Docket No. 4960.036W01 Client Ref. No. 655801-1 alternatively the second aqueous solution can have a pH of about 8 to about 10. The first aqueous solution can have a pH of not more than 6, alternatively the first aqueous solution can have a pH of about 4 to about 6. The combined aqueous solution can have a pH of about 8 to about 10, alternatively the combined aqueous solution can have a pH of 9.

[0044] Additives can be added to the coating on the substrate through the first aqueous solution, the second aqueous solution, the combined aqueous solution, or a combination thereof. The additives can be used for a variety of purposes, such as, ultraviolet (UV) light protection or abrasion resistance. An additive for UV protection can include titanium dioxide. An additive for abrasion resistance can include crosslinkers, such as, bromoalkanes, aldehydes, carbodiimides, amine active esters, acrylates, epoxides, or a combination thereof. A suitable aldehyde can include glutaraldehyde. A suitable carbodiimide can include l-ethyl-3 -(3 -dimethylaminopropyl) carbodiimide (EDC). A suitable amine active ester can include a N-hydroxysuccinimide ester, an imidoester, or a combination thereof. A crosslinker can provide resistance to washing and increased durability to the flame-retardant coating.

[0045] The coating can be deposited on the substrate at any suitable temperature. The deposition of the combined aqueous solution can occur at a temperature from about ambient temperature to about 100 °C.

[0046] The combined aqueous solution can be deposited on the substrate by a coating method. The coating method can include any suitable water-based or solution coating technology. Examples of suitable coating methods can include dip coating, bath coating, immersion spray coating, roll-to-roll coating, slot coating, spin coating, curtain coating, gravure coating, reverse roll coating, knife over roll (e.g., gap) coating, blade coating, curtain coating, metering (e.g., Meyer) rod coating, air knife coating, or a combination thereof. In some examples, the coating can be deposited by spraying of the aqueous solution onto the substrate.

[0047] The combined aqueous solution can be deposited on the substrate for any suitable period to produce the flame-retardant coating. The substrate can be exposed to the combined aqueous solution from about 1 second to about 24 hours, alternatively from about 1 second to about 10 minutes, alternatively from about 10 seconds to about 10 minutes, alternatively from about 1 second to about 1 hour, and alternatively from about 30 seconds to about 10 minutes. Without being limited by theory, the exposure time of the substrate to the combined aqueous solution can affect the thickness of the flame-retardant coating. The coating method can include a single exposure (e.g., dip) of the substrate to the combinedAttorney Docket No. 4960.036W01 Client Ref. No. 655801-1 aqueous solution, multiple exposures in the same combined aqueous solution, multiple exposures to different combined aqueous solutions, or a combination thereof. Without being limited by theory, the combined aqueous solution can cover the internal walls of the pores of the substrate without blocking the pores. For example, the substrate can be a fabric comprising threads or fibers. The coating method can coat at least a portion of the thread or fiber with the combined aqueous solution. In a subsequent drying step, the combined aqueous solution can cause complexation of the PEC, resulting in a flame-retardant coating on individual thread or fibers. The flame-retardant coating can impart flame-retardancy to the substrate but continue to allow the threads or fibers to remain soft and flexible.

[0048] A typical roll-to-roll coater, used for any dip coating of fabrics, can be modified with a drying tunnel and enough baths to scale this coating method for textiles, fabrics, foams, or films. For example, bath coating can be used to coat a foam, by passing the foam through a bath and squeezing between rolls to remove excess liquid. Additionally, and alternatively, spray coating can be used to coat the substrate.

[0049] The coating method can include drying the coated substrate after exposure to the combined aqueous solution to evaporate the combined aqueous solution. The drying can allow the complexation of the polyelectrolyte complex as the volatile base or volatile acid evaporates or volatizes from the combined aqueous solution coated on the substrate. Without being limited by theory, the polyelectrolyte complex formation can function as an adhesion mechanism to the substrate, allowing the adherence of the coating to the substrate. The drying step to enable evaporation of the combined aqueous solution can be accomplished by any suitable method. For example, the drying can include air drying at room temperature, air drying at ambient temperature, forced air drying, heat drying in an oven, infrared drying, applying pressure to the coated substrate, or a combination thereof. The drying gas can include any gas suitable for removing all or a portion of liquid from the coated substrate. For example, the drying gas can include air, filtered air, nitrogen, or a combination thereof. The coated substrate can be dried by the drying gas for any suitable period to remove all or a portion of the liquid.

[0050] Heating the coated substrate can be accomplished by any suitable means to evaporate the combined aqueous solution. For example, heating the coated substrate can include applying a heat source to the coated substrate. Any suitable heat source can be applied. The evaporation of the combined aqueous solution can be performed at a temperature of 25-150 °C. The evaporation of the combined aqueous solution can be performed at a temperature from about 50 °C. to about 200 °C., alternatively from about 50Attorney Docket No. 4960.036W01 Client Ref. No. 655801-1°C. to about 100 °C., alternatively from about 100 °C. to about 200 °C., alternatively from about 70 °C. to about 200 °C., alternatively from about 70 °C. to about 100 °C., alternatively from about 25 °C to about 150 °C, and alternatively from about 50 °C. to about 70 °C

[0051] The evaporation of the combined aqueous solution can be performed between about 10 seconds and about 2 hours, alternatively for about 24 hours, alternatively for about 5 seconds to about 20 minutes, alternatively from about 15 minutes to about 25 minutes, alternatively from about 10 seconds to 24 hours, alternatively from about 10 seconds to about 2 hours, alternatively from about 2 hours to 12 hours, alternatively from about 2 hours to 4 hours, and alternatively from about 5 seconds to about 500 seconds.

[0052] Applying pressure to the coated substrate may be accomplished by any suitable means. For example, applying pressure can include pressing the coated substrate, twisting the coated substrate, squeezing the coated substrate, or a combination thereof.

[0053] The substrate can have a varying thickness of the flame-retardant coating. For example, the coating can be between about 10 nanometers and about 100 microns thick, alternatively between about 10 nanometers and about 100 nanometers, alternatively between about 100 nanometers and about 1 micron, alternatively between about 1 micron and about 5 microns, alternatively between about 5 microns and about 10 microns, alternatively between about 10 microns and about 100 microns, alternatively between about 10 nanometers and about 1 micron, alternatively between about 100 nanometers and about 1 micron, alternatively between about 100 nanometers and about 10 microns, and alternatively between about 1 micron and about 100 microns.

[0054] As described herein, the weight gain (wt. %) of the flame-retardant coating refers to the final weight of the flame-retardant coating after drying as a percent of the weight of the uncoated substrate. For example, the coated substrate has between about 1.0 wt. % and about 99.0 wt.% of the flame-retardant coating, alternatively between about 1.0 wt. % and about 25.0 wt. % of the flame-retardant coating, alternatively between about 5 wt. % and about 25 wt. % of the flame-retardant coating, and alternatively between about 5.0 wt. % and about 12.5 wt. % of the flame-retardant coating. Without limitation, different substrates can have different wt. % of coating to reduce or prevent flammability. For instance, examples include a cotton substrate having a flame-retardant coating wt. % from about 1 wt. % to about 30 wt. %, alternatively from about 5 wt. % to about 25 wt. %, and alternatively from about 5 wt. % to about 20 wt. %.Attorney Docket No. 4960.036W01 Client Ref. No. 655801-1

[0055] The coating method can result in a coated substrate that retains a weight gain after one or more rinses with water when compared to a weight of the substrate before coating. For example, the retained weight gain can be about 25 wt. % after 1 rinse, alternatively about 25 wt. % after 2 rinses, alternatively about 25 wt. % after 3 rinses, alternatively about 25 wt. % after 4 rinses, alternatively about 25 wt. % after 5 rinses, alternatively about 10 wt. % after 1 rinse, alternatively about 10 wt. % after 2 rinses, alternatively about 10 wt. % after 3 rinses, alternatively about 10 wt. % after 4 rinses, alternatively about 10 wt. % after 5 rinses, alternatively about 7.5 wt. % after 1 rinse, alternatively about 7.5 wt. % after 2 rinses, alternatively about 7.5 wt. % after 3 rinses, alternatively about 7.5 wt. % after 4 rinses, alternatively about 7.5 wt. % after 5 rinses, alternatively about 5.0 wt. % after 1 rinse, alternatively about 5.0 wt. % after 2 rinses, alternatively about 5.0 wt. % after 3 rinses, alternatively about 5.0 wt. % after 4 rinses, and alternatively about 5.0 wt. % after 5 rinses.

[0056] The flame-retardant coating can be optically transparent or partially optically transparent. Optical transparency refers to the property of a material that allows light to pass through without significant absorption or scattering, enabling clear visibility of objects on the other side. The flame-retardant coating can impart additional optical properties to the substrate. The flame-retardant coating can be formulated to enhance or modify the optical characteristics of the underlying substrate. For example, the flame-retardant coating can be designed to increase light transmission, reduce glare, or alter the refractive index of the substrate. The flame-retardant coating can be engineered to provide specific color effects or UV protection to the substrate.

[0057] The coating method can result in a coated substrate that can achieve a V-0 rating when tested according to UL 94, with an after flame time not exceeding 10 seconds, a total after flame time not exceeding 50 seconds, and no flaming drips.

[0058] The coating method can result in a coated substrate that can pass the ASTM D6413 vertical flame test with a char length less than or equal to 4 inches, no after flame after 2 seconds, and no melting or dripping of the substrate.

[0059] The coating method can result in a coated substrate that can achieves a Class 1 or a Class 2 rating when tested according to NFPA 701 (Standard Methods of Fire Tests for Flame Propagation of Textiles and Films), with a char length less than 6.5 inches, an after flame time for less than 2 seconds, and the substrate has no flaming residue.

[0060] The coating method can result in a coated substrate that can pass the FMVSS 302 standard (Federal Motor Vehicle Safety Standard for flammability of interior materials),Attorney Docket No. 4960.036W01 Client Ref. No. 655801-1 with a burn rate of less than 4 inches per minute and self-extinguishes in less than 60 seconds.

[0061] The coating method can result in a coated substrate that can pass the BS 5852 standard (British Standard for assessment of the ignitability of upholstered seating by smoldering and flaming ignition sources), with the substrate passing the smoldering cigarette test and the match flame equivalent test.

[0062] The coating method can result in a coated substrate that can achieve a pass rating when subject to the small open flame test as described in 16 CFR Part 1610 (Standard for the Flammability of Clothing Textiles), with an average burn time of less than 3.5 seconds.

[0063] The disclosure also relates to the following numbered Embodiments, which are listed in no particular order of importance:

[0064] 1. A method for forming a flame-retardant coated substrate, the method comprising: preparing a first aqueous solution, comprising a polymeric, polycationic material; preparing a second aqueous solution, comprising an anionic material and a volatile base; combining the first aqueous solution and the second aqueous solution to form a combined aqueous solution; exposing a substrate to the combined aqueous solution; and evaporating the combined aqueous solution from the substrate to produce a flame-retardant coated substrate, wherein a coating on the flame-retardant coated substrate comprises a polyelectrolyte complex formed between the polymeric, polycationic material and the anionic material.

[0065] 2. A method for forming a flame-retardant coated substrate, the method comprising: preparing a first aqueous solution, comprising a polymeric, polycationic material and a volatile acid; preparing a second aqueous solution, comprising an anionic material; combining the first aqueous solution and the second aqueous solution to form a combined aqueous solution; exposing a substrate to the combined aqueous solution; and evaporating the combined aqueous solution from the substrate to produce a flame-retardant coated substrate, wherein a coating on the flame-retardant coated substrate comprises a polyelectrolyte complex formed between the polymeric, polycationic material and the anionic material.Attorney Docket No. 4960.036W01 Client Ref. No. 655801-1

[0066] 3. A method for forming a flame-retardant coated substrate, the method comprising: exposing a substrate to a combined aqueous solution comprising a volatile base, a polymeric, polycationic material, and an anionic material; and evaporating the combined aqueous solution from the substrate to produce a flame-retardant coated substrate, wherein a coating on the flame-retardant coated substrate comprises a polyelectrolyte complex formed between the polymeric, polycationic material and the anionic material.

[0067] 4. A method for forming a flame-retardant coated substrate, the method comprising: exposing a substrate to a combined aqueous solution comprising a volatile acid, a polymeric, polycationic material, and an anionic material; and evaporating the combined aqueous solution from the substrate to produce a flame-retardant coated substrate, wherein a coating on the flame-retardant coated substrate comprises a polyelectrolyte complex formed between the polymeric, polycationic material and the anionic material.

[0068] 5. The method of claim 1 or 2, wherein the first aqueous solution comprises from about 1.0 wt. % polymeric, polycationic material to about 50.0 wt. % polymeric, polycationic material.

[0069] 6. The method of Embodiment 1 or 2, wherein the second aqueous solution comprises from about 1.0 wt. % anionic material to about 50.0 wt. % anionic material.

[0070] 7. The method of Embodiment 3 or 4, wherein the combined aqueous solution comprises from about 1.0 wt. % polymeric, polycationic material to about 50 wt. % polymeric, polycationic material.

[0071] 8. The method of Embodiment 3 or 4, wherein the combined aqueous solution comprises from about 1.0 wt. % anionic material to about 50.0 wt. % anionic material.

[0072] 9. The method of any one of Embodiments 1 to 4, wherein the coating is between about 10 nanometers and about 100 microns thick.

[0073] 10. The method of any one of Embodiments 1 to 4, wherein the substrate comprises a textile, a fabric, a foam, a film, leather, a vinyl compound, plastic, wood, a carpet, hook and loop fasteners, a non-foam padding, a film, or a combination thereof.

[0074] 11. The method of any one of Embodiments 1 to 4, wherein the polymeric, polycationic material comprises a colloidal particle, a nanoparticle, a nitrogen-rich polymer, or a combination thereof.Attorney Docket No. 4960.036W01 Client Ref. No. 655801-1

[0075] 12. The method of any one of Embodiments 1 to 4, wherein the polymeric, polycationic material comprises polyethylenimine (PEI), branched polyethylenimine (BPEI), linear polyethylenimine, polyallylamine, polyvinylamine^ cationic polyacrylamide, cationic poly diallyldimethylammonium-chloride (PDDA), poly(melamine-co- formaldehyde), polymelamine, a copolymer of polymelamine, polyvinylpyridine, a copolymer of polyvinylpyridine, or a combination thereof

[0076] 13. The method of any one of Embodiments 1 to 4, wherein the anionic material comprises an anionic polymer, a colloidal particle, a sulfated molecule, a boronic acid, a boron containing acid, or a combination thereof.

[0077] 14. The method of any one of Embodiments 1 to 4, wherein the anionic material comprises sodium hexametaphosphate, poly (sodium phosphate), a phosphonic acid group, or a combination thereof.

[0078] 15. The method of Embodiment 1 or 3, wherein the volatile base comprises ammonia, methylamine, dimethylamine, ethylamine, triethylamine, pyridine, or a combination thereof.

[0079] 16. The method of Embodiment 2 or 4, wherein the volatile acid comprises formic acid, acetic acid, propionic acid, butyric acid, carbonic acid, or a combination thereof.

[0080] 17. The method of Embodiment 1, wherein the second aqueous solution has a pH of at least 9.

[0081] 18. The method of Embodiment 17, wherein the second aqueous solution has a pH of about 8 to about 10.

[0082] 19. The method of Embodiment 2, wherein the first aqueous solution has a pH of not more than 6.

[0083] 20. The method of Embodiment 19, wherein the first aqueous solution has a pH of about 4 to about 6.

[0084] 21. The method of any one of Embodiments 1 to 4, wherein the combined aqueous solution has a pH of about 8 to about 10.

[0085] 22. The method of Embodiment 21, wherein the combined aqueous solution has a pH of 9.

[0086] 23. The method of any one of Embodiments 1 to 4, wherein the combined aqueous solution has an equimolar ratio of the polymeric, polycationic material and the anionic material.Attorney Docket No. 4960.036W01 Client Ref. No. 655801-1

[0087] 24. The method of any one of Embodiments 1 to 4, wherein the combined aqueous solution has between a 1 :3 molar ratio and a 1.75: 1 molar ratio of the polymeric, polycationic material to the anionic material.

[0088] 25. The method of any one of Embodiments 1 to 4, wherein the evaporating is performed at a temperature of 25-150 °C.

[0089] 26. The method of any one of Embodiments 1 to 4, wherein the evaporating is performed between about 10 seconds and about 2 hours.

[0090] 27. The method of any one of Embodiments 1 to 4, wherein the evaporating is performed for about 24 hours.

[0091] 28. The method of any one of Embodiments 1 to 4, wherein the flame-retardant coated substrate passes an ASTM D6413 vertical flame test with a char length less than or equal to 4 inches, no after flame after 2 seconds, and no melting or dripping of the substrate.

[0092] 29. The method of any one of Embodiments 1 to 4, wherein the flame-retardant coated substrate retains at least a 5 % weight gain after 5 rinses with water when compared to a weight of the substrate before coating.

[0093] 30. An article comprising a flame-retardant coated substrate made by the method of any one of Embodiments 1-29.EXAMPLES

[0094] The disclosure can be better understood by reference to the following examples which are offered by way of illustration. The disclosure is not limited to the examples given herein.Materials:

[0095] Cotton fabric with an approximate weight of 100 g / m2was purchased from Testfarbic, Inc (West Pittson, Pa.). Sodium hexametaphosphate (PSP, crystalline, 96%), polyethylenimine (PEI, Mw ~ 25,000 g moT1), ammonium hydroxide solution (NH4OH, 28%) and sodium hydroxide (NaOH) were purchased from Sigma Aldrich (Milwaukee, WI). 5 M hydrochloric acid (HC1) was purchased from VWR Chemicals (Batavia, IL).Solution preparation:

[0096] The first aqueous solution was prepared with 18 M deionized (DI) water and PEI. The pH of the first aqueous solution was adjusted to 9 using a 5M HC1 solution. The second aqueous solution was prepared with 18 M Q deionized (DI) water with PSP. A 35 wt. % PSP solution was diluted to 20 wt. % PSP using NH4OH, and the pH subsequently adjustedAttorney Docket No. 4960.036W01 Client Ref. No. 655801-1 to 9 by addition of 5 M NaOH. The first aqueous solution and second aqueous solution were rolled overnight to ensure complete dissolution of any solids. Prior to coating the substrate, the first aqueous solution was added to the second aqueous solution to form the combined aqueous solution.Coating deposition:

[0097] Prior to coating, a 12 inch by 5 inch piece of cotton was rinsed thoroughly with DI water, wrung out manually and dried in an oven at 70 °C for 1-2 hours. The dried rinsed cotton was then dipped in the combined aqueous solution for 1 minute. Next, the sample was wrung out manually and dried in an oven at 70 °C overnight for about 16 hours.Thermal stability:

[0098] Thermal degradation and gas evolution was evaluated using a 5500 thermogravimetric analyzer coupled with a discover mass spectrometer (TA Instruments, New Castle, DE). Samples were held at an isotherm of 120 °C for 20 minutes to remove moisture and then heated at a controlled ramp rate of 10 °C min'1to 800 °C. The heating was conducted under 25 mL min'1sample flow of either air or argon, with a 10 mL min'1purge flow.

[0099] Differential scanning calorimetry was evaluated using a DSC Q20 (TA Instruments, New Castle, DE). Samples of 1-2 g were sealed in a Tzero hermetic pan and held at an isotherm of 100 °C for 20 minutes to remove moisture. The samples were then heated at a controlled ramp rate of 5 min'1to 400 °C under a 50 mL min'1flow of nitrogen.Flammability measurements:

[0100] The flame performance of the samples was evaluated with a 12 second vertical flame test (VFT) according to ASTM D6413 standard in a VC-2 model flame testing cabinet (Govmark. Farmingdale, NY). Both afterburn and percent residue measurements were recorded. Vertical flame tests were run in ambient conditions, which allowed for organic materials to be oxidized (i.e., oxygen catalyzed cellulose decomposition).

[0101] The gas phase flammability of the samples was evaluated according to Method A of ASTM D7309 using an MCC-3 microscale combustion calorimeter (Deatak, McHenry, IL). Samples were pyrolyzed at 1 °C s'1to 500 °C, under a nitrogen flow rate of 80 mL min'1. The pyrolysis products were mixed with a 20 mL min'1flow of oxygen before entering a 900 °C combustion furnace.Example 1 :Attorney Docket No. 4960.036W01 Client Ref. No. 655801-1

[0102] Neat cotton was used in this example, with no additional coating. Example 1 exhibited a weight gain of 0.0 wt. % as no coating was deposited onto the substrate. Example 2:

[0103] A flame-retardant coated cotton substrate was prepared according to the methods disclosed above. The molar ratio of PEI to PSP was about 1 : 1. The combined aqueous solution used in Example 2 had about 6.0 PEI wt. %, 1.4 PSP wt. %, and 9.2 NH3 wt. % in an aqueous solution. Example 2 exhibited a weight gain of 24.9 wt. %.Example 3:

[0104] A flame-retardant coated cotton substrate was prepared according to the methods disclosed above. The molar ratio of PEI to PSP was about 1 :2. The combined aqueous solution used in Example 2 had about 3.5 PEI wt. %, 16.5 PSP wt. %, and 10.6 NH3 wt. % in an aqueous solution. Example 3 exhibited a weight gain of 27.7 wt. %.Example 4:

[0105] A flame-retardant coated cotton substrate was prepared according to the methods disclosed above. The molar ratio of PEI to PSP was about 2: 1. The combined aqueous solution used in Example 2 had about 9.1 PEI wt. %, 10.8 PSP wt. %, and 6.9 NH3 wt. % in an aqueous solution. Example 4 exhibited a weight gain of 29.3 wt. %.Example 5:

[0106] Example 5 is first prepared in the same way as Example 1. Example 5 was then rinsed five times in deionized water. Example 5 exhibited a weight gain of -0.7 wt. %. The negative weight gain can be attributed to the removal of loose fibers during the rinsing process.Example 6:

[0107] Example 6 is first prepared in the same way as Example 2. Example 6 was then rinsed five times in deionized water. Example 6 exhibited a weight gain of 7.0 wt. %.Example 7:

[0108] Example 7 is first prepared in the same way as Example 3. Example 7 was then rinsed five times in deionized water. Example 7 exhibited a weight gain of 7.6 wt. %.Example 8:

[0109] Example 8 is first prepared in the same way as Example 4. Example 8 was then rinsed five times in deionized water. Example 7 exhibited a weight gain of 0.1 wt. %.Attorney Docket No. 4960.036W01 Client Ref. No. 655801-1

[0110] FIG. 1A illustrates vertical flame test results of uncoated and coated fabric in accordance with at least one example of this disclosure. A summary of flame test results is presented in Table 1. Table 1 shows that the coated substrates of Example 2, 3, and 4 had superior flame-retardant properties compared to the uncoated cotton of Example 1.Example Afterburn Time (s) Char Length (in) Char Residue (%)1 32.9 ± 0.9 12.0 ± 0.0 8.3 ± 0.72 0.0 ± 0.0 3.6 ± 0.1 97 ± 1.43 0.0 ± 0.0 3.3 ± 0.3 97 ± 1.44 0.0 ± 0.0 3.7 ± 0.2 86 ± 23.35 17.3 ± 10.5 12.0 ± 0.0 7.8 ± 1.36 0.0 ± 0.0 3.9 ± 0.5 95 ± 1.57 0.0 ± 0.0 4.4 ± 0.4 95 ± 1.78 0.0 ± 0.0 12.0 ± 0.0 35 ± 2.2

[0111] Example 1 continued to burn for 33 seconds after the removal of the flame until the entire length of the sample was consumed. In contrast, Example 2, 3, and 4 all had a flameretardant coating and exhibited self-extinguishing behavior. This self-extinguishing behavior was evidenced by an afterburn time of 0 seconds and a char length of less than 4 inches. Example 2, 3, and 4 also exhibited char residues of 97, 97, and 86 % respectively, compared to the char residue of 8.3 % of Example 1. The high residual char of Example 2, 3, and 4 is indicative of intumescent action of Example 2, 3, and 4. The intumescent action can be achieved by a multi-step process during combustion. Upon exposure to heat, the system releases gases, expands, and promotes char formation. The intumescent action is protective in nature, operating in the condensed phase by promoting the formation of char, which immobilizes the fuel source into a non-pyrolyzable thermal insulation layer.

[0112] The intumescent action can also involve the acid source (PSP) degrading the carbon sources (PEI and the cotton) and inducing crosslinking. Concurrently, the amine pendantAttorney Docket No. 4960.036W01 Client Ref. No. 655801-1 groups on polyethylenimine can decompose, releasing nitrogen-containing gases that act as blowing agents. The gases can cause the forming char to foam and expand, further adding to the formation of the thermal insulation layer.

[0113] When heat is applied, the flame-retardant coating surrounding the cotton fibers can transform into an expanded thermal barrier composed of phosphorocarbonaceous cellular material. The swollen and expanded structure can provide enhanced thermal insulation, effectively protecting the underlying substrate from further combustion.

[0114] FIG. IB illustrates vertical flame test results of uncoated and coated fabric after rinsing in accordance with at least one example of this disclosure. Vertical flame test results of the rinsed samples exhibit a similar flammability trend. This trend shows coated substrates of Example 6, and 7 had superior flame-retardant properties compared to the uncoated cotton of Example 5, even after rinsing.

[0115] A substantial portion of Example 5 was consumed during the burn test, leaving 7.8 % char residue. Examples 6, 7, and 8 all had an afterburn time of 0 seconds, and a respective char residue of 95, 95, and 35 %. The low afterburn time and high residual char of Example 6 and 7 indicate that the flame-retardant coated was still effective after 5 rinses in deionized water.

[0116] FIG. 2A illustrates microscale combustion calorimeter results of uncoated and coated fabric in accordance with at least one example of this disclosure. A summary of microscale combustion calorimeter results is presented in Table 2. Both FIG. 2A and Table 2 show that the coated substrates of Example 2, 3, and 4 had superior flame-retardant properties compared to the uncoated cotton of Example 1.Char pkHRR TpkHRR pkHRR TpkHRR THR FGCExample Yield#1 (W / g) #1 (°C) #2 (W / g) #2 (°C) (kJ / g) (J / g*K) (%)1 229 ± 17 388 ± 3 8.7 ± 2.8 11.4 ± 0.4 181 ± 175.1 ± 23.5 ±2 234 ± 1 319 ± 1 38 ± 2.2 0.8 ± 0.2 8.0 ± 1.40.6 0.34.4 ± 18.5 ±3 236 ± 3 322 ± 2 39 ± 3.1 0.8 ± 0.1 7.1 ± 0.40.5 1.5Attorney Docket No. 4960.036W01 Client Ref. No. 655801-16.8 ± 28.9 ±4 241 ± 3 329 ± 5 38 ± 2.0 2.1 ± 0.1 17.2 ± 0.72.6 3.35 303 ± 3 388 ± 1 - - 5.8 ± 2.7 13.3 ± 0.3 270 ± 56 76 ± 7 317 ± 2 - - 40 ± 1.9 1.3 ± 0.0 14.8 ± 1.37 71 ± 10 315 ± 1 - - 39 ± 6.3 1.5 ± 0.1 16.3 ± 2.48 96 ± 13 325 ± 2 - - 32 ± 1.8 3.4 ± 0.3 33.5 ± 4.3

[0117] Both Table 2 and FIG. 2A shows one degradation event for Example 1. Example 1 comprises cotton fabric and was demonstrated to be flammable. The cellulose in the uncoated cotton of Example 1 degraded into a heavy tar between a temperature range of 280-340° C Example 2, 3, and 4 exhibit a shift of the degradation event of about 70 °C, indicative of an intumescent event. The onset of early degradation shown in Example 2, 3, and 4 of FIG. 2A can be attributed to the catalyzed char formation of the flame-retardant coating, which protects the underlying substrate. The protection afforded by the flameretardant coating delayed the degradation of the substrate. Table 2 shows that Example 1, which does not have the flame-retardant coating, exhibits a high average total heat release (THR) value of 11.4 kJ / g, with a large fire growth capacity (FGC) of 181 J / g-K. Both the THR and FGC values characterizes a material's ability to spread a fire. Table 2 shows that Example 2, 3, and 4 all exhibit a shift in the thermal event to a lower temperature. For example, Table 2 demonstrates significant reductions in THR and FGC for Examples 2, 3, and 4 when compared to Example 1. Specifically, Examples 2, 3, and 4 exhibit THR reductions of 93%, 93%, and 82%, respectively. Similarly, FGC reductions of 95%, 96%, and 90% are observed for Examples 2, 3, and 4, respectively, in comparison to Example 1. Increases in char yield in MCC testing for Example 2, 3, and 4 quantitatively demonstrated modification of the cellulose degradation pathway and provided evidence of an enhanced thermal barrier upon increasing addition of the flame-retardant coating.

[0118] FIG. 2B illustrates microscale combustion calorimeter results of uncoated and coated fabric after rinsing in accordance with at least one example of this disclosure. FIG. 2B and Table 2 show coated substrates of Example 6, and 7 had superior flame-retardant properties compared to the uncoated cotton of Example 5, even after rinsing.

[0119] For example, Table 2 shows, there is a significant reduction in the THR and FGC in Examples 6, 7, and 8 when compared to Example 5. Example 5, which does not contain theAttorney Docket No. 4960.036W01 Client Ref. No. 655801-1 flame-retardant coating, exhibits a THR of 13.3 kJ / g and an FGC value of 270 J / g-K. Example 6 and 7 exhibited a reduction in THR to 1.3 and 1.5 kJ / g respectively, corresponding to a 90 and 89 % reduction in THR value when compared to Example 5. Example 6 and 7 also exhibited a reduction in FGC to 14.8 and 16.3 J / g-K respectively, corresponding to a 95 and 94 % reduction in FGC value when compared to Example 5. This shows that the flame-retardant coating continues to offer significant protection of the substrate even after 5 rinses in deionized water.

[0120] FIG. 3 A illustrates mass and derivative weight loss as a function of temperature for uncoated and coated fabric in accordance with at least one example of this disclosure. FIG. 3A shows that Example 1 exhibited a one-step degradation process occurring between 300 and 380 °C. The degradation of Example 1 can be attributed to chain scission and elimination reactions that result in the formation of volatile gasses and residual char. FIG.3 A shows that Example 2, 3 and 4 exhibit two primary mass loss events, around 210-215 °C and 300-310 °C. The first mass loss event can be attributed to the removal of residual ammonia or the degradation of excess PEI in the flame-retardant coating. The second mass loss of Example 2, 3, and 4 shown in FIG. 3 A can be attributed to the flame-retardant coating degradation and intumescent char formation. The early degradation of the flameretardant coating and the substrate results in a protective char surface formed via condensation and crosslinking reactions. This degradation can typically include low amounts of depolymerization products.

[0121] FIG. 3B illustrates mass and derivative weight loss as a function of temperature for uncoated and coated fabric after rinsing in accordance with at least one example of this disclosure. A similar trend is exhibited for Example 6, 7, and 8 when compared to Example 5. The same trend shows that the flame-retardant coating continues to offer significant protection of the substrate even after five water rinses.

[0122] FIG. 4A illustrates differential thermograms of uncoated and coated fabric in accordance with at least one example of this disclosure. Example 1 exhibits an endothermic event around 260 °C, followed by an exothermic event. The exothermic even can be attributed to a reaction between radicals produced during decomposition. Example 2, 3, and4 experience a shift of the endothermic peak to 225-235 °C. The shift in the endothermic peak can be attributed to catalyzed dehydration, expediting char formation. The exothermic event experienced by Example 2, 3, and 4 can be attributed to the formation of a crosslinked char, the formation of char supported by an increase in residue present at 800 °C as shown in Table 1. This char formation can be attributed to the PEI degrading into nitrogen 1Attorney Docket No. 4960.036W01 Client Ref. No. 655801-1 containing molecules, such as heteroaromatic compounds, which can participate in char formation. PSP can also be phosphorylating and crosslinking cellulose in cotton. The formation of the char layer slows the heat and thermal transport from the flame to the fabric, effectively protecting the substrate and imparting flame-retardant properties.

[0123] FIG. 4B illustrates differential thermograms of uncoated and coated fabric after rinsing in accordance with at least one example of this disclosure. The thermal stability of Example 5, 6, 7, and 8 showed similar thermal analysis trends. Under an inert environment, Example 6, 7, and 8 exhibited earlier degradation steps and product formation. The elimination of the initial mass loss event around 210-215 °C suggest that there is an excess of PEI or ammonia that is removed upon rinsing. Like the unrinsed examples, Examples 6, 7, and 8 exhibit a significant increase in residue compared to Example 5, as shown in Table 1. This increase in residue can be attributed to the successful formation of the intumescent coating. The endothermic shift of Example 6, 7, and 8, shown in FIG. 4B, to lower temperatures can be attributed to expedited char formation.

[0124] Weak polyelectrolyte complexes formed from polyethylenimine and sodium hexametaphosphate deposited on textile, fabric, foams, and filmic material can result in a flame-retardant coated substrate. This flame-retardant coated substrate can be achieved by utilizing an evaporation induced polyelectrolyte complex on the specified substrate to be coated. The flame-retardant coated substrate can exhibit self-extinguishing properties, even after multiple rinsing cycles. The flame-retardant performance can be attributed to the complexation between polyelectrolytes, resulting in a rinse-durable intumescent system that can protect a substrate from fire. This method can result in a scalable method of production of flame-retardant substrates.

Claims

Attorney Docket No. 4960.036W01 Client Ref. No. 655801-1CLAIMSWhat is claimed is:

1. A method for forming a flame-retardant coated substrate, the method comprising: preparing a first aqueous solution, comprising a polymeric, polycationic material; preparing a second aqueous solution, comprising an anionic material and a volatile base; combining the first aqueous solution and the second aqueous solution to form a combined aqueous solution; exposing a substrate to the combined aqueous solution; and evaporating the combined aqueous solution from the substrate to produce a flameretardant coated substrate, wherein a coating on the flame-retardant coated substrate comprises a polyelectrolyte complex formed between the polymeric, polycationic material and the anionic material.

2. A method for forming a flame-retardant coated substrate, the method comprising: preparing a first aqueous solution, comprising a polymeric, polycationic material and a volatile acid; preparing a second aqueous solution, comprising an anionic material; combining the first aqueous solution and the second aqueous solution to form a combined aqueous solution; exposing a substrate to the combined aqueous solution; and evaporating the combined aqueous solution from the substrate to produce a flameretardant coated substrate, wherein a coating on the flame-retardant coated substrate comprises a polyelectrolyte complex formed between the polymeric, polycationic material and the anionic material.

3. A method for forming a flame-retardant coated substrate, the method comprising: exposing a substrate to a combined aqueous solution comprising a volatile base, a polymeric, polycationic material, and an anionic material; and evaporating the combined aqueous solution from the substrate to produce a flameretardant coated substrate, wherein a coating on the flame-retardant coated substrate comprises a polyelectrolyte complex formed between the polymeric, polycationic material and the anionic material.Attorney Docket No. 4960.036W01 Client Ref. No. 655801-14. A method for forming a flame-retardant coated substrate, the method comprising: exposing a substrate to a combined aqueous solution comprising a volatile acid, a polymeric, polycationic material, and an anionic material; and evaporating the combined aqueous solution from the substrate to produce a flameretardant coated substrate, wherein a coating on the flame-retardant coated substrate comprises a polyelectrolyte complex formed between the polymeric, polycationic material and the anionic material.

5. The method of claim 1 or 2, wherein the first aqueous solution comprises from about 1.0 wt. % polymeric, polycationic material to about 50.0 wt. % polymeric, polycationic material.

6. The method of claim 1 or 2, wherein the second aqueous solution comprises from about 1.0 wt. % anionic material to about 50.0 wt. % anionic material.

7. The method of claim 3 or 4, wherein the combined aqueous solution comprises from about 1.0 wt. % polymeric, polycationic material to about 50 wt. % polymeric, polycationic material.

8. The method of claim 3 or 4, wherein the combined aqueous solution comprises from about 1.0 wt. % anionic material to about 50.0 wt. % anionic material.

9. The method of any one of claims 1 to 4, wherein the coating is between about 10 nanometers and about 100 microns thick.

10. The method of any one of claims 1 to 4, wherein the substrate comprises a textile, a fabric, a foam, a film, leather, a vinyl compound, plastic, wood, a carpet, hook and loop fasteners, a non-foam padding, a film, or a combination thereof.

11. The method of any one of claims 1 to 4, wherein the polymeric, polycationic material comprises a colloidal particle, a nanoparticle, a nitrogen-rich polymer, or a combination thereof.Attorney Docket No. 4960.036W01 Client Ref. No. 655801-112. The method of any one of claims 1 to 4, wherein the polymeric, polycationic material comprises polyethylenimine (PEI), branched polyethylenimine (BPEI), linear polyethylenimine, polyallylamine, polyvinylamine^ cationic polyacrylamide, cationic poly diallyldimethylammonium-chloride (PDDA), poly(melamine-co-formaldehyde), polymelamine, a copolymer of polymelamine, polyvinylpyridine, a copolymer of polyvinylpyridine, or a combination thereof.

13. The method of any one of claims 1 to 4, wherein the anionic material comprises an anionic polymer, a colloidal particle, a sulfated molecule, a boronic acid, a boron containing acid, or a combination thereof.

14. The method of any one of claims 1 to 4, wherein the anionic material comprises sodium hexametaphosphate, poly (sodium phosphate), a phosphonic acid group, or a combination thereof.

15. The method of claim 1 or 3, wherein the volatile base comprises ammonia, methylamine, dimethylamine, ethylamine, triethylamine, pyridine, or a combination thereof.

16. The method of claim 2 or 4, wherein the volatile acid comprises formic acid, acetic acid, propionic acid, butyric acid, carbonic acid, or a combination thereof.

17. The method of claim 1, wherein the second aqueous solution has a pH of at least 9.

18. The method of claim 17, wherein the second aqueous solution has a pH of about 8 to about 10.

19. The method of claim 2, wherein the first aqueous solution has a pH of not more than 6.

20. The method of claim 19, wherein the first aqueous solution has a pH of about 4 to about 6.

21. The method of any one of claims 1 to 4, wherein the combined aqueous solution has a pH of about 8 to about 10.Attorney Docket No. 4960.036W01 Client Ref. No. 655801-122. The method of claim 21, wherein the combined aqueous solution has a pH of 9.

23. The method of any one of claims 1 to 4, wherein the combined aqueous solution has an equimolar ratio of the polymeric, polycationic material and the anionic material.

24. The method of any one of claims 1 to 4, wherein the combined aqueous solution has between a 1 :3 molar ratio and a 1.75: 1 molar ratio of the polymeric, polycationic material to the anionic material.

25. The method of any one of claims 1 to 4, wherein the evaporating is performed at a temperature of 25-150 °C.

26. The method of any one of claims 1 to 4, wherein the evaporating is performed between about 10 seconds and about 2 hours.

27. The method of any one of claims 1 to 4, wherein the evaporating is performed for about 24 hours.

28. The method of any one of claims 1 to 4, wherein the flame-retardant coated substrate passes an ASTM D6413 vertical flame test with a char length less than or equal to 4 inches, no after flame after 2 seconds, and no melting or dripping of the substrate.

29. The method of any one of claims 1 to 4, wherein the flame-retardant coated substrate retains at least a 5 % weight gain after 5 rinses with water when compared to a weight of the substrate before coating.

30. An article comprising a flame-retardant coated substrate made by the method of any one of claims 1 to 4.

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