Flame resistant polyurethane pottant compositions

Abstract

Polyurethane foam compositions include a reaction product of: an isocyanate component; an isocyanate-reactive component containing one or more aromatic polyester polyols; one or more polyether polyols; a silicone surfactant; one or more catalysts water; and a flame resistance (FR) additive at a percent by weight (wt%) ranging from 5 wt% to 20 wt% based upon the total weight of isocyanate-reactive component; wherein the polyurethane composition has a UL 94 vertical burn performance of at least V2. Methods include preparing a composite article that include dispensing a PU foam-forming composition on a substrate, and curing the composition to produce the composite article on the substrate.

Description

[0001] FLAME RESISTANT POLYURETHANE POTTANT COMPOSITIONS FIELD Embodiments relate to flame-resistant polyurethane compositions, methods for preparing and applications utilizing same. BACKGROUND Electric vehicles (EV) operate with a battery pack and the individual cells are arranged in different patterns along with cooling mechanism related components and other parts in the vicinity. The battery geometry can vary and a number of commercial form factors exist, such as cylindrical, rectangular / prismatic, pouch, and the like. To connect cells together into an assembly with supporting components, a pottant like material can be used with different chemistries including silicone, polyurethanes, epoxies, and the like. A large aim of the pottant and / or encapsulants in a battery is to provide isolation between the battery cells during use (minimizing impacts of thermal events, including cascading damage to between neighboring cells) and, in some cases, augment the strength of the battery assembly to resist stress and deformation as a structural element of the vehicle. Polyurethane-based foams are also employed as pottants in some applications or as adhesives in battery assembly of metal or plastic plates to reduce weight to improve efficiency and handling. However, there is often a tradeoff between durability and thermal resistance of such materials. Summary In an aspect, embodiments disclosed herein are directed to polyurethane foam compositions that include a reaction product of: an isocyanate component; an isocyanate-reactive component containing one or more aromatic polyester polyols; one or more polyether polyols; a silicone surfactant; one or more catalysts water; and a flame resistance (FR) additive at a percent by weight (wt%) ranging from 5 wt% to 20 wt% based upon the total weight of isocyanate-reactive component; wherein the polyurethane composition has a UL 94 vertical burn performance of at least V2. In another aspect, embodiments are directed to articles or composites prepared from the polyurethane composition of the present disclosure. In another aspect, embodiments are directed to methods that include preparing a composite article that include dispensing a PU foam-forming composition on a substrate, and curing the composition to produce the composite article on the substrate. In another aspect, embodiments are directed to methods that include preparing the polyurethane foam composition that include combining an isocyanate component and the isocyanate-reactive component to form a mixture; and reacting the mixture to form the polyurethane composition. Detailed Description Embodiments relate to flame resistant (FR) polyurethane (PU) compositions having good mechanical properties and UL 94 FR ratings of V2 or better. PU compositions may contain an aromatic polyester polyol a total foam FR additive concentration of less than 10 wt%. In some cases, PU compositions are prepared from the reaction of an isocyanate component containing a isocyanate prepolymer generated from the reaction of an isocyanate and a hydroxyl-functional phosphonate FR additive, which is then reacted with an isocyanate-reactive component to produce a flame resistant PU matrix. Isocyanate prepolymers may also exhibit extended shelf stability over comparative formulation components containing direct additions of non-covalently incorporated hydroxyl-functionalized FR additives. Methods disclosed herein also include preparing and applying PU compositions, particularly PU foam compositions as a pottant or encapsulant or thermal barrier in electronic and / or automotive applications. PU compositions used as pottants and casing for electronic materials are often supplemented with various FR additives that increase fire resistance to comply with various regulatory standards (e.g., meeting a UL 94 of V1 or better). However, common FR additives can function as plasticizers that alter mechanical properties. Further, FR additives such as acidic phosphorus-based additives can decompose to acidic byproducts that can affect catalytic efficiency and overall shelf life of the PU composition components. PU compositions disclosed herein may be formulated with aromatic polyester polyols and no or reduced concentrations of free (i.e., non-covalently linked to a PU matrix) plasticizing FR additives. In some cases, PU compositions may also include isocyanate prepolymers containing mono-hydroxyl functional phosphonates that improve component stability and shelf-life. PU compositions disclosed herein may be used to produce rigid foams having an elongation value >5% at an isocyanate index below 200. PU compositions disclosed herein may be self-leveling and may be applied with consistent layer coverage and thickness, without concern for over- or under-expansion. In some cases, self- leveling PU compositions disclosed herein may be used as a capping layer in a multilayer configuration with a foaming PU to produce a level finished surface for thermal management applications, such as capping a thermoset pottant dispersed between an assembly of battery cells. The self-leveling composition may be capping on battery surface and forming a uniform layer anywhere from 0.1 to 7 mm thickness on top of the battery above its height. In one application, a first layer containing a low density foam pottant (e.g., 0.75 g / mL or less, or 0.6 g / mL, or 0.5 g / mL, or 0.45 g / mL or less) that covers or encapsulates about 1% to 70% of the height of the battery cells and, while a second layer (capping layer) containing a PU composition disclosed herein is used to cover the remaining height of the battery cells and provide a uniform and level surface. This arrangement allows the incorporation of low density / weight materials for lightweighting and improved fuel economy, increased vehicle range (measured in miles or km), while increasing thermal management properties for function and safety. PU compositions disclosed herein generally include the product obtained from combining a multi-component system containing at least: an isocyanate component (“A-side” or “isocyanate side”) and an isocyanate-reactive component (“B-side” or “polyol side”). During application, the isocyanate component, isocyanate-reactive components, and optional components (if needed) are mixed, creating a curing reaction mixture that is processed to form a polyurethane article, material, or composite. Where the multi-component system is combined in the presence of aqueous fluids and / or blowing catalysts, the PU composition is a PU foam-forming composition that generates a PU foam upon cure. Polyurethane compositions disclosed herein may include an isocyanate component containing one or more isocyanate compounds, such as polymeric isocyanates, aromatic isocyanates, or carbodiimide-modified isocyanates. Isocyanate compounds may be monomeric, oligomeric, prepolymers, and the like. The isocyanate component can include, for example, one or more isocyanate and / or polyisocyanate compounds. Isocyanate components may include isocyanate compounds having a nominal functionality of greater than 1.5, greater than 2.0, or in a range of 1.5 to 4. Polyurethane compositions may include an isocyanate component at a percent by weight (wt%) ranging from 15 wt% to 80 wt%, 20 wt% to 75 wt%, or 45 wt% to 50 wt%. The isocyanate component may include an isocyanate compound having a number average molecular weight of 150 g / mol to 750 g / mol. In some cases, the isocyanate compound can have a number average molecular weight from a low value of 150 g / mol, 200 g / mol, 250 g / mol or 300 g / mol to an upper value of 350 g / mol, 400 g / mol, 450 g / mol, 500 g / mol or 750 g / mol. The number average molecular weight values reported herein are determined by end group analysis, gel permeation chromatography, and other methods as is known in the art. The isocyanate compound can be monomeric and / or polymeric, as are known in the art. In some cases, isocyanate components may include isocyanate compounds having an isocyanate (NCO) content as a percent by weight (wt%) according to ASTM D5155-19 of 1 wt% or more, 2.7 wt% or more, or 5 wt% or more, and at the same time, 35 wt% or less, 30 wt% or less, or 25 wt% or less, or in a range of 2 wt% to 35 wt%. The isocyanate component may include one or more of aliphatic polyisocyanate, cycloaliphatic polyisocyanate, aromatic polyisocyanate, and the like. Examples of isocyanates include, but are not limited to, polymethylene polyphenylisocyanate; toluene 2,4- / 2,6-diisocyanate (TDI); methylenediphenyl diisocyanate (MDI, including its isomers); polymeric and prepolymeric MDI; triisocyanatononane (TIN); naphthyl diisocyanate (NDI); 4,4’-diisocyanatodicyclohexyl- methane; 3-isocyanatomethyl-3,3,5-trimethylcyclohexyl isocyanate (isophorone diisocyanate, IPDI); tetramethylene diisocyanate; hexamethylene diisocyanate (HDI); 2-methyl- pentamethylene diisocyanate; 2,2,4-trimethylhexamethylene diisocyanate (THDI); dodecamethylene diisocyanate; 1,4-diisocyanatocyclohexane; 4,4’-diisocyanato-3,3’-dimethyl- dicyclohexylmethane; 4,4’-diisocyanato-2,2-dicyclohexylpropane; 3-isocyanatomethyl-1- methyl-1-isocyanatocyclohexane (MCI); 1,3 -diisooctylcyanato-4 -methylcyclohexane; 1,3 - diisocyanato-2-methylcyclohexane; and combinations thereof, among others. In addition to the isocyanates mentioned above, modified or partially modified polyisocyanates including uretdione, isocyanurate, carbodiimide, uretonimine, allophanate or biuret structures, and combinations thereof, among others, may be utilized. For example, isocyanate compounds may include carbodiimide modified MDI. Isocyanate compounds may include isocyanate prepolymers resulting from reaction of an isocyanate-reactive compound with a molar excess of an isocyanate compound or polymeric isocyanate compound under conditions that do not lead to gelation or solidification, the isocyanate prepolymers can have a higher average isocyanate equivalent weight of > 200 g / eq. Formation of isocyanate prepolymers is known in the art, and may include reacting (1) at least one isocyanate compound and (2) at least one polyol compound. Isocyanate prepolymers may be described by an isocyanate index, defined as the ratio of isocyanate groups to isocyanate-reactive groups (such as OH groups) multiplied by 100. Isocyanate prepolymers disclosed herein may have an isocyanate index, defined as the equivalents of isocyanate divided by the total equivalents of isocyanate- reactive hydrogen containing materials, multiplied by 100) in a range of from 30 to 400, 40 to 300, or 40 to 200. Examples of commercial isocyanates include, but are not limited to, polyisocyanates under the trade names VORANATE™, PAPI™ , VORATRON™, VORAFORCE™, and ISONATE™, all of which are available from Dow Chemical Company. Isocyanate components may include one or more phosphorus-containing isocyanate prepolymers generated from the reaction of an isocyanate and a hydroxyl-functional phosphonate under conditions that do not lead to gelation or solidification. Isocyanate prepolymers may include a relative hydroxy-functional phosphonate at a percent by weight (wt%) ranging from 45 wt% to 50 wt%. Phosphorus-containing isocyanate prepolymers may be described by an NCO %, corresponding to the weight percent of NCO groups, remaining after completion of the reaction between isocyanate and isocyanate-reactive compound, that are present in the prepolymer. Suitable hydroxy-functional phosphonates may include at least one hydroxy functional group and may include diethyl (hydroxymethyl) phosphonate, dimethyl hydroxymethylphosphonate, diethyl diethyl hydroxyethylphosphonate, diethyl dipropyl hydroxymethylphosphonate, diisopropyl hydroxymethylphosphonate, methyl ethyl hydroxymethylphosphonate, methyl propyl hydroxymethylphosphonate, methyl isopropyl hydroxymethylphosphonate, ethyl propyl hydroxymethylphosphonate, ethyl isopropyl hydroxymethylphosphonate, propyl isopropyl hydroxymethylphosphonate, dibutyl hydroxymethylphosphonate, dioctyl hydroxymethylphosphonate, propyl pentyl hydroxymethylphosphonate, dicyclohexyl hydroxymethylphosphonate, and the like.. Hydroxy-functional phosphonates may have the general formula (I): where each of R1and R2are each independently a to about 6 carbon atoms, or where R1and R2are joined to or unsubstituted ring of from 2 to about 12 carbon hydrogen or a linear or branched alkyl group of up Phosphorus-containing isocyanate hydroxy- functional phosphonates at a percent by weight (wt%) of 1 wt% to 30 wt%, 1 wt% to 25 wt%, or 1 wt% to 15 wt%. Phosphorus-containing isocyanate prepolymers may have an isocyanate (NCO) content as a percent by weight (wt%) according to ASTM D5155-19 of 1 wt% or more, 2 wt% or more, or 5 wt% or more, and at the same time, 50 wt% or less, 40 wt% or less, or 30 wt% or less, or in a range of 2 wt% to 40 wt%. Isocyanate-reactive components may include a mixture of polyols containing one or more aromatic polyester polyols, polyether polyols, aliphatic polyols, polyol crosslinkers, and other additives such as catalysts, surfactants, and the like. Polyurethane compositions may include an isocyanate-reactive component at a percent by weight (wt%) ranging from 20 wt% to 85 wt%, 20 wt% to 80 wt%, or 25 wt% to 80 wt%. Isocyanate-reactive components may include one or more aromatic polyester polyols at a percent by weight (wt%) ranging from 10 wt% to 30 wt%. As used herein “aromatic polyester polyol” refers to a polyester polyol including an aromatic ring. Aromatic polyester polyols may be produced by the reaction of one or more carboxylic diacids and polyols having an OH functionality 2 to 4. Suitable carboxylic acids may include aromatic diacids or anhydrides such as phthalic acid, phthalic anhydride, isophthalic acid, terephthalic acid, methyl esters of phthalic, isophthalic, or terephthalic acid, dimethyl terephthalate, trimellitic anhydride, pyromellitic dianhydride, naphthalenedicarboxylic acid or mixtures thereof; and C4 to C12 aliphatic diacids. Suitable polyols for the formation of polyesters include one or more alkylene glycols or polyalkylene glycols having a hydroxy functionality of 2 to 4, such as ethylene glycol, 1,2- or 1,3-propylene glycol, 1,4-butanediol, 1,6-hexanediol, diethylene glycol, glycerine, alkylene oxide units such as ethylene oxide, propylene oxide, and the like. Example polyester polyols include polyesters of phthalic anhydride and diethylene glycol, and polyesters of a C4 to C12 diacid such as succinic acid or adipic acid and diethylene glycol. Aromatic polyester polyols may have an average hydroxyl number (OH number) as determined according to ASTM D4274-21 in a range of 100 mg KOH / g to 500 mg KOH / g, 150 mg KOH / g to 450 mg KOH / g, 200 mg KOH / g to 400 mg KOH / g, or 250 mg KOH / g to 400 mg KOH / g. Aromatic polyester polyols may have an aromaticity as determined by proton nuclear magnetic resonance spectroscopy of 10 wt% or more, or in a range of 10 wt% to 30 wt%. Isocyanate-reactive components may include one or more aromatic polyester polyols at a percent by weight (wt%) ranging from 10 wt% to 40 wt%, from 15 wt% to 35 wt%, or from 15 wt% to 30 wt%. Isocyanate-reactive components may include one or more polyether polyols prepared by polyaddition of alkylene oxides such as propylene oxide and / or ethylene oxide onto polyhydroxy functional starter compounds in the presence of catalysts known in the art. Polyether polyols may be prepared from a starter compound and one or more alkylene oxides, for example, ethylene oxide, propylene oxide, and / or butylene oxide. Starter compounds may include, but are not limited to, molecules having 1 to 8 hydroxyl groups per molecule, such as ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, triethylene glycol, tripropylene glycol, l,4- butanediol, l,6-hexanediol, triethanolamine, diethanolamine, diisopropanolamine, bisphenol A, glycerol, diglycerol, triglycerol, trimethylolpropane, di(trimethylolpropane) pentaerythritol, dipentaerythritol, tripentaerythritol, sugars and sugar alcohols such as sucrose and sorbitol, and the like. Polyether polyols may also include polyols reacted with polyethers formed from copolymers of alkylene oxides, including block copolymers and polyethers “capped” with hydroxyethyl and / or hydroxypropyl oligomers or polymers. Polyether polyols disclosed herein may have an average hydroxyl number (or OH number) as determined according to ASTM D4274-21 ranging from 20 mg KOH / g to 100 mg KOH / g, 25 mg KOH / g to 90 mg KOH / g, or 25 mg KOH / g to 80 mg KOH / g. The isocyanate-reactive component may include at least one polyether polyol present at a percent by weight (wt%) from 40 wt% to 95 wt%, 45 wt% to 95 wt%, or 50 wt% to 90 wt%. Polyether polyols may include a mixture of polyether polyols, including a mixture of bifunctional polyether polyols and trifunctional polyether polyols. Bifunctional polyether polyols have a functionality of two and a hydroxy number of 20 mg KOH / g or more. Isocyanate-reactive components may include one or more bifunctional polyether polyols at a percent by weight (wt%) ranging from 1 wt% to 20 wt%, or 3 wt% to 10 wt%. In some cases, Isocyanate-reactive components may include one or more trifunctional polyether polyols having a functionality of 3 and a hydroxy number of 20 mg KOH / g or more. Isocyanate-reactive components may include one or more trifunctional polyether polyols at a percent by weight (wt%) ranging from 10 wt% to 30 wt%, or 15 wt% to 25 wt%. In some cases, isocyanate-reactive components may include a ratio of bifunctional polyether polyols to trifunctional polyether polyols may be in a range of 4:1 to 1:4. Isocyanate-reactive components may include one or more catalysts for enhancing polyurethane polymerization to generate the PU composition. Catalysts may be used individually or as a catalyst package containing multiple catalysts, such as gelling catalysts, blowing catalysts, and trimerization catalysts. Gelling and blowing catalysts may be differentiated by a tendency to favor either the urethane (gel) reaction, in the case of the gelling catalyst, or the urea (blow) reaction, in the case of the blowing catalyst. A trimerization catalyst may be utilized to promote the isocyanurate forming reaction in the compositions. The catalyst package can also be added as a separate stream into the reaction mixture of isocyanate and isocyanate-reactive composition. Gelling catalysts include organometallic compounds, cyclic tertiary amines and / or long chain amines, e.g., that contain several nitrogen atoms and combinations thereof. Organometallic compounds include organotin compounds, such as tin(II) salts of organic carboxylic acids, e.g., tin(II) diacetate, tin(II) dioctanoate, tin(II) diethylhexanoate, and tin(II) dilaurate, and dialkyltin(IV) salts of organic carboxylic acids, e.g., dibutyltin diacetate, dibutyltin dilaurate, dibutyltin maleate and dioctyltin diacetate. Bismuth salts of organic carboxylic acids may also be utilized as the gelling catalyst, such as, for example, bismuth octanoate. Cyclic tertiary amines and / or long chain amines include dimethylbenzylamine, triethylenediamine, and combinations thereof. Examples of a commercially available gelling catalysts are POLYCAT®8, DABCO®33-LV, and DABCO®T-12 from Evonik, among other commercially available gelling catalysts. In some cases, a PU composition may include one or more gelling catalysts at a percent by weight (wt%) ranging from 0.1 wt% to 1 wt%, or 0.1 wt% to 0.7 wt%. Blowing catalysts may include bis-(2-dimethylaminoethyl) ether, pentamethyldiethylenetriamine, triethylamine, tributyl amine, N,N-dimethylaminopropylamine, dimethylethanolamine, N,N,N′,N′-tetra-methylethylenediamine, and combinations thereof, among others. An example of a commercial blowing catalyst is POLYCAT®5, from Evonik, among other commercially available blowing catalysts. In some cases, a PU composition may include one or more blowing catalysts (e.g., bis-(2-dimethylaminoethyl) ether) at a percent by weight (wt%) ranging from 0.01 wt% to 1 wt%, or 0.05 wt% to 0.5 wt%. Trimerization catalysts may include any such catalysts known in the art. Examples of trimerization catalysts include N,N',N''-tris(3-dimethylaminopropyl) hexahydro-S-triazine; N,N- dimethylcyclo-hexylamine; 1,3,5-tris(N,N-dimethylaminopropyl)-s-hexahydrotriazine; [2,4,6-tris (dimethylaminomethyl) phenol]; potassium acetate, potassium octoate; tetraalkylammonium hydroxides such as tetramethylammonium hydroxide; alkali metal hydroxides such as sodium hydroxide; alkali metal alkoxides such as sodium methoxide and potassium isopropoxide; and alkali metal salts of long-chain fatty acids having 10 carbon atoms to 20 carbon atoms, and combinations thereof, among others. Some commercially available trimerization catalysts include, for example, DABCO®TMR-2, DABCO®TMR-20, DABCO®TMR-30, DABCO® TMR-7, DABCO®K 2097; DABCO®K15, POLYCAT®41, and POLYCAT®46, each from Evonik, among other commercially available trimerization catalysts. Catalysts may include a “latent catalyst” or “delayed catalyst,” which is defined as a catalyst compound that is of low catalytic activity or is relatively inactive at ambient temperatures, and which becomes more catalytically active, such as by disassociation, decoordination, ring opening, ionization, or tautomerization upon heating to effect catalysis of least one of the chemical reactions involved in making a PU foam. Ambient temperatures may range 15 °C to 40 °C, where room temperature is often around 23 °C. Latent / delayed catalysts can be gelling, blowing, and / or trimerization types of catalysts in terms of their function in the foaming process. The latent catalyst is often a subset of tertiary amine gelling catalysts (e.g., delayed action tertiary amine based on 1,8- Diazabicyclo[5.4.0]undec-7-ene) that include acid salts, phenolic salts, or complexes of a tertiary amine catalyst where the acid or phenolic is often a carboxylic acid or phenol species, but not limited to, such as formic acid, acetic acid, propionic acid, 2-ethylhexanoic acid, phenoxyacetic acid, gluconic acid, tartaric acid, citric acid, phenol, nonylphenol, diisopropyl phenol, and the like; and mixtures thereof. Some useable commercially available latent catalysts include, for example, DABCO®TMR-30, POLYCAT®SA2 LE, POLYCAT®SA-1 / 10, and DABCO®8154 from Evonik; NIAX™ A-107, NIAX™C-31, and NIAX™C-225 from Momentive; and JEFFCAT™ ZF-54, JEFFCAT™ LED-204 from Huntsman Corporation; and mixtures thereof. The catalyst or catalyst package may be present in the PU composition at a percent by weight (wt%) ranging from 0.1 wt% to 10 wt%, or 1 wt% to 7 wt%. In some cases, a catalyst package may be added to the isocyanate-reactive component in amount sufficient to provide the mixture with the corresponding weight percentages above. Polyurethane compositions may include one or FR additives to improve flame resistance. Suitable FR additives may include phosphorus based flame-retardants such as (2,3- dibromopropyl)-phosphate, phosphorus, cyclic phosphates, triaryl phosphate, bis-melaminium pentate, pentaerythritol bicyclic phosphate, dimethyl methyl phosphate, phosphine oxide diol, triphenyl phosphate, tris- (2-chloroethyl) phosphate, trichloropropyl phosphate, triethyl phosphate, phosphate esters such as tricresyl phosphate, trixylenyl phosphate, isodecyl diphenyl phosphate, ethylhexyl diphenyl phosphate, isopropylated triphenyl phosphate, t-butylated triphenyl phosphate, i-butylated triphenyl phosphate, and mixtures thereof. Other FR additives may include carbon black, hydrated aluminum hydroxide, and silicates such as wollastonite, platinum and platinum compounds, carbonates such as calcium carbonate, red phosphorus, sodium citrate, and the like. In some cases, the FR additive may be selected from decabromodiphenyloxide, octabromordiphenyl oxide, hexabromocyclododecane, decabromobiphenyl oxide, diphenyoxybenzene, ethylene bis- tetrabromophthalmide, pentabromoethyl benzene, pentabromobenzyl acrylate, tribromophenyl maleic imide, tetrabromobisphenyl A, bis-(tribromophenoxy) ethane, bis-(pentabromophenoxy) ethane, polydibomophenylene oxide, tribromophenylallyl ether, bis-dibromopropyl ether, tetrabromophthalic anhydride, dibromoneopentyl glycol, dibromoethyl dibromocyclohexane, pentabromodiphenyl oxide, tribromostyrene, pentabromochlorocyclohexane, tetrabromoxylene, hexabromocyclododecane, brominated polystyrene, tetradecabromodiphenoxybenzene, trifluoropropene, and PVC; phosphate salts of various amines such as ammonium polyphosphate, trioctyl, tributyl or tris-butoxyethyl phosphate ester, akylphosphate oligomers; melamine and derivatives such as melamine salts, guanidine, dicyandiamide, ammonium sulfamate, alumina trihydrate, magnesium hydroxide, and the like. The amount of flame retardant can vary depending on factors such as the flame retardant selected and intended use of the polyurethane compositions to achieve the UL-94 vertical burn performance of V2 or better, and more preferably V1 or better, and most preferably V0. The polyurethane composition disclosed herein may result into a PU foam which can achieve a UL-94 horizontal burn rating of HBF (best performance) or HF-1 (performance less than HBF). FR additives may be added to one or more of the isocyanate components and / or the isocyanate- reactive component. The amount of flame retardant in the polyurethane composition may depend on the particular flame retardant employed, if any, and typically may range of up to 15 wt%, or in a range of 3 wt% to 12 wt% based on total weight of the polyurethane composition. Polyurethane compositions may include one or more surfactants, including those known and commercially used to prepared polyurethane foams. Surfactants include silicone surfactants, polyether-modified silicone surfactants, non-silicone surfactants, hydrocarbon-based organic surfactants, and the like. Examples of non-silicone surfactants include, but are not limited to, oxyethylated alkylphenols, oxyethylated fatty alcohols, paraffin oils, castor oil esters, ricinoleic acid esters, turkey red oil, groundnut oil, paraffins, silicone surfactants, and fatty alcohols. Other surfactants include polyethylene glycol ethers of long-chain alcohols, tertiary amine or alkanolamine salts of long-chain allyl acid sulfate esters, alkylsulfonic esters, alkyl arylsulfonic acids, and combinations thereof. Examples of suitable silicone surfactants include, but are not limited to, TEGOSTAB B-8427, B-8454, B-8404, B-1045, B-8407, B-8409, B-84201, B-84711, B-8715, and B-8462 from Evonik; NIAX L-2171, L-5107, L-5130, L-5180, L-5340, L-5440, L- 6100, L-6900, L-6980, and L-6988 from MOMENTIVE, and VORASURF DC 5164, VORASURF SF 2937 from The Dow Chemical Company. Polyurethane compositions may include one or more surfactants at a percent by weight (wt%) of 0.01 wt% to 10 wt%, 0.05 wt% to 2.5 wt%, or 0.05 wt% to 2 wt%. Surfactants may be present in one or more of the isocyanate component, isocyanate-reactive component, or as an optional third component. Polyurethane compositions may include one or more blowing agents. The blowing agent may react under conditions of the foaming reaction to produce a gas. The blowing agent may be referred to as a chemical blowing agent. Examples of the blowing agent include water, formic acid, hydrocarbons, acids, volatile organics, and the like. The physical blowing agents including gases such as chlorofluoro carbons (CFC), hydrochlorofluorocarbons (HCFC), acetone, nitrogen, air, carbon dioxide, solvent or molecule with boiling points < 50 °C at atmospheric pressure, and the like and combinations thereof. One or more embodiments provide that the blowing agent is water. Polyurethane foam-forming compositions disclosed herein may include one or more of chemical blowing agents and physical blowing agents. Blowing agents may be added to the isocyanate-reactive component (i.e., polyol side) or to the isocyanate component and / or during mixing the polyol and isocyanates as third stream in amount sufficient to provide the mixture resulting in density of 0.3 to 0.75 g / mL of foam. Polyurethane compositions may include one or more fillers including fiberglass, fiber, carbon fiber silica, ammonium polyphosphate, CaCO3, kaolin, talc, alumina, alumina trihydrate (ATH), and the like. One or more fillers may be added at a percent by weight (wt%) of the composition ranging from 0 wt% to 25 wt%, or 1 wt% to 20 wt%. In some cases, fillers may be added to the isocyanate component and / or the isocyanate-reactive component in amount sufficient to provide the mixture with the corresponding weight percentages above. The isocyanate-reactive component may also contain one or more additives including blowing agents, surfactants such as silicone surfactants, crosslinkers, plasticizers, smoke suppressants, fragrances, reinforcements, dyes, colorants, pigments, preservatives, odor masks, physical blowing agents, chemical blowing agents, internal mold release agents, biocides, antioxidants, UV stabilizers, antistatic agents, thixotropic agents, adhesion promoters, cell openers, and the like. PU compositions disclosed herein may have a flame resistance according to UL 94 Standards at vertical burn for ≤10 mm thick sample of foam alone of V2 or better, or V1 or better, or V0. PU compositions may have a density according to ASTM D1622-08 of less than 1 g / mL, or in a range of 0.3 g / mL to 0.75 g / mL, or 0.3 g / mL to 0.7 g / mL. PU compositions may have a viscosity upon mixing of the components of less than 5000 cP at 6 seconds in temperature range of 10 to 35 °C when isocyanate side and isocyanate reactive side are mixed. The isocyanate reactive side by itself should be less than 2000 cP, 1500 cP, or 1000 cP measured using ASTM D4440-15 at 25 °C. l. While formulation components and properties have been disclosed individually, it is envisioned that component elements (e.g., compounds in isocyanate or isocyanate-reactive components) may be included, excluded, or combined in any manner or subcombination utilizing any of the above concentration ranges and nested subranges therein. Further, that the recited formulation properties may be similarly achieved through various combinations of the recited components within the recited ranges. PU compositions may be formed generally by combining the isocyanate component and the isocyanate-reactive component to form a mixture by a suitable method (e.g., static mixing, dynamic mixing, dynamic and static mixing, speedmixing, low or high pressure mixing, overhead mixing with impellers or paint mixers, impingement mixing, and others), and reacting the mixture to form a PU article. PU compositions may be used in any suitable process for developing articles and composites, including molding, injection, vacuum infusion, spraying, and the like. Methods may include applying PU compositions to a substrate by dispensing or coating using spin coating, brush coating; drop coating; spray coating; dip coating; roll coating; flow coating; slot coating; gravure coating; Meyer bar coating; and the like. In some cases, methods may include combining the isocyanate component and the isocyanate- reactive component to form a mixture, applying the mixture to a substate, and reacting the mixture to form a polyurethane article or composite (e.g., coating, encapsulant, pottant). PU compositions may be formed using a suitable process for battery pack / module assembly by dispensing, injecting, and / or spraying into and / or above one or more specific locations of battery pack or module to achieve complete (or partial) encapsulation of the lithium ion or sodium ion battery cells. The isocyanate-reactive component and the isocyanate component can be combined such that the volume ratio of the isocyanate-reactive component to the isocyanate component in the mixed curable composition may be controlled within the range between 0.90:1.2 from 0.95:1.05, from 0.97:1.03, or at the ratio of 1:1. In some cases, PU compositions may have an isocyanate index (ratio of equivalents of isocyanate functional groups to the number of equivalents of active hydrogen expressed as a percentage) ranging from 95 to 130. The mixture of isocyanate component and isocyanate-reactive component may be cured at a temperature from 0oC to 60oC, 10oC to 50oC, 15oC to 45oC, or 18oC to 40oC (e.g., RT). Curing may be indicated by increase in the viscosity after mixing A-side and B-side, with the eventual formation of a cured PU composition having a measurable hardness. PU compositions may have a hardness according to ASTM D-2240-15 in Shore D hardness of 15 or more, 20 or more, or 25 or more, such as in the range of 15 to 80. The compositions disclosed herein may cure in less than 14 days, less than 10 days, or less than 7 days, and generally on a time scale greater than 60 minutes. Complete curing is indicated by no further increase in the hardness over time. In some cases, cured compositions may have a hardness according to ASTM D-2240-15 in Shore D hardness after room temperature curing for 14 days in a range of 15 to 80, or 20 to 80. Methods may include preparing the polyurethane composition by combining the isocyanate component and the isocyanate-reactive component to form a mixture; and reacting the mixture to form the polyurethane composition. Composite articles may be prepared by disposing a composition on a substrate, and curing the composition to produce the composite article comprising a polyurethane article on the substrate. In some cases, substrates may define at least one gap, and disposing may include placing the composition in the at least one gap such that the polyurethane article is present within the gap in the composite article. For example, substrates may include battery cell(s), surfaces or components, and composite articles may include a battery pack and / or module. However, the composite polyurethane article may be used in other end use applications, including as a pottant or encapsulant in end uses other than battery packs, such as for electric circuits, as well as for purposes other than a pottant and / or encapsulant. PU compositions disclosed herein may be formed using a suitable process for battery pack / module assembly without any direct contact with the battery cells but on the substrates. Composite articles may be prepared by disposing a PU-forming composition on a substrate such that the substrates are high surface energy plates including metals such as aluminum, steel or alloys, zinc, and the like of; non-metals, including glass, polar polymers and plastics such as epoxy, polyurethane, or polyester, surface activated non-polar polymers and plastics such as polypropylene, high or low polyethylene; coated materials such as epoxy-coated aluminum, nickel coated steel, polyacrylate-coated aluminum, polyester liner-covered aluminum, polyethylene terephthalate liner-covered steel and the like. In some cases, a multilayer composite can be generated such that the second self-leveling polyurethane composition either foaming or non-foaming type could be applied on top of or under of a first foam layer resulting from the formulations disclosed herein. The self-leveling of the second layer can be quantified such that the difference in the highest and lowest level of the layer is less than 25% of the highest height of the second layer. PU compositions disclosed herein may be used as a pottant or thermal barrier for electrical, battery pack and / or module related applications. Pottants may coat, encapsulate (completely or partially), and / or protect the electrical connections from the abusive environments such as heat, cold, flame, weather elements, dust (e.g., sand or dirt particles), physical impact or vibration, or other abusive elements. The amount of pottant used may be from a minimum quantity sufficient for coating and protecting the electrical connections up to and including a maximum quantity sufficient to fill voids in a battery cell, junction boxes, and the like. PU compositions may also be applied in stationary energy storage applications in private and commercial settings. PU compositions may be formulated to satisfy constraints for automotive and mobility solutions (e.g., EV), but may be modified outside of those constraints for other related electrical and stationary energy storage applications. For example, a stationary storage applications may be formulated at higher densities / weights (>1 g / mL) and higher thermal conductivities (e.g., >0.1 W / m.K), where concerns regarding overall weight and the absence of external cooling are not a driving factor. Examples The following examples are provided to illustrate the embodiments of the invention, but are not intended to limit the scope thereof. Table 1 provides the materials used in the following examples.

[0002] Table 1: Polyethe - 1 Polyethe - 2 Polyethe - 3 Polyethe - 4 Aromati Polyeste - 1 FR Addi Surfacta Catalyst Catalyst Hydroxy function Phospho Isocyana FR Isocy Prepoly FR Isocy Prepoly Example In this example, inventive samples containing polyurethane compositions were tested for physical properties over comparative examples. Sample formulations are shown in Tables 2 and 3. Synthesis of FR Isocyanate Prepolymer – 1 (~23% NCO DEHP Prepolymer): A 0.5 L glass reactor at room temperature was charged with 258.9 grams of Isocyanate - 1 (1932.09 mEq). The Isocyanate - 1 was stirred at 300 rpm at room temperature, followed by the dropwise addition of 42.6 grams of diethyl (hydroxymethyl) phosphonate (DEHP) (267.25 mEq) over 30 min. Upon completing the addition of DEHP, the mixture was heated to 70 °C for 1 hour. Finally, heating was stopped and the resulting prepolymer was stored under nitrogen. Viscosity according to ASTM D4440-15 at 25 °C was 6703 cP, and measured %NCO according to ASTM D5155 was 23.47. Synthesis of FR Isocyanate Prepolymer – 2 (~25% NCO DEHP Prepolymer): A 1 L glass reactor at room temperature was charged with 480.62 grams of Isocyanate - 1 (3586.72 mEq). The Isocyanate - 1was stirred at 300 rpm at room temperature, followed by the dropwise addition of 59.45 grams of diethyl (hydroxymethyl) phosphonate (DEHP) (366.08 mEq.) over 30 min. Upon completing the addition of DEHP, the mixture was heated to 70 °C and kept at this temperature for a period of 1 hour. Finally, the heating was stopped and the resulting prepolymer was stored under nitrogen. Viscosity according to ASTM D4440-15 at 25 °C was 2200 cP, and measured %NCO according to ASTM D5155 was 25.4. Isocyanate- Polyol - 1 Polyol - 2 Polyol - 3 Polyol - 4 Aromatic P Surfactant - Catalyst - 1 Catalyst - 2 FR Additive Water Isocyanate Isocyanate - NCO Index Total Arom (wt%) Total FR A Elemental P Ratio (B:A) Foam Quali

[0003] Isocyanate Polyol - 1 Polyol - 2 Aromatic P Surfactant Catalyst - 1 Catalyst - 2 FR Additiv Water Isocyanate Isocyanate FR Isocyan FR Isocyan NCO Index Total Arom (wt%) Total FR A Elemental Ratio (B:A Foam Qual Rigid Polyurethane Foam Sample Preparation Formulations were each prepared as 200 g master batches of polyols, surfactants, catalysts, flame retardant additives, and water as per the formulations in Table 2 and 4. Foam samples were prepared at a ~50 g scale following the formulations in Tables 2 and 4 using an overhead high shear impeller mixer set to 3000 rpm for 7 s. Cream (start of foam rise), gel (stringing), and tack- free times were measured for each sample. Molded plaque samples were prepared using a stainless-steel mold having internal dimensions of 20 cm x 15 cm x 0.5 cm. A similar mix time of 7 s was applied to blend the formulated polyol with the isocyanate component. Samples were allowed a 20 min residence time at 40°C before demolding. Sample formulations were tested for a number of physical characteristics, and testing results for each formulation are shown in Tables 4 and 5. Density: measured dimensions using calipers and weight using an analytical balance respectively of the molded foam samples using the procedure described above. Calculated as the density of the cured pottant plaque samples (i.e., weight / volume), performed pursuant to ASTM D1622-08. The weight of plaque was measured in gram, and the height of plaque was measured in cm. The width and thickness of plaques were 12.5 and 0.5 cm respectively. Density of pottant sample (in g / cc or g / mL): Weight of pottant sample*1000 / (height*12.5*0.5). Tensile strength and elongation at break: ASTM D1708 was followed using a sample set of five specimens to determine tensile strength and elongation at break. For cured pottant plaque samples, elongation at break (%) and tensile strength (MPa) were obtained using ASTM D1708 standard on an MTS machine. The microtensile samples were punched in a dog-bone shape from plaques molded at 2 mm thickness using a metal mold. Viscosity Measurement: Viscosity of the formulated isocyanate-reactive component was measured using ASTM D4440-15 on a DHR rheometer from TA Instruments. A stainless-steel cone plate geometry of 40 mm diameter and 2 ° angle was used at a 54 micron gap with a shear rate of 10 sec-1. The temperature was held at 25°C and data was collected for a period of 300 s. Shore D hardness was obtained using Durometer and was performed pursuant to ASTM D2240 on the molded foam plaque. Storage Modulus: Dynamic mechanical analysis (DMA) was used to determine storage modulus in shear mode (G’) at temperatures -30 °C, 25 °C, and 50 °C. Modulus in torsion mode were obtained by ASTM D5279-21 on an Advanced Rheometric Expansion System (ARES-G2) from TA Instruments equipped with liquid nitrogen environmental control and torsion rectangular fixtures. A rectangular sample were cut from the molded plaques of foams at 5 mm thickness and cut to dimensions of 45 mm length, and 12.8 mm width. The sample length was oriented axially to the torsional axis, and the DMA experiment was performed in torsional mode. The temperature was increased from -70 °C to 150 °C at a ramp rate of 3 °C / min. The frequency of testing was 1 Hz at 0.05% torsional strain, with an axial tensile force of 0.098 N applied to keep sample taut, and at a data collection interval of 30 seconds per point. The output from the characterization was storage modulus in shear mode (G’) at specific temperatures and Tan delta which is a ratio of loss modulus over storage modulus. The peak value of Tan delta is assigned as glass transition temperature or Tg (in °C) of the foam material. UL 94 vertical burn test: The pottant material prepared in metal mold at 5 mm thickness was then cut to 0.5 inch width and ≥ 10 cm length dimensions using the procedure described above. The premade pottant samples (pottant alone) were tested with standard UL 94 vertical burn protocol and performance was categorized in appropriate category of V-0 (best and desired performance), V-1, V-2, and fail (fail means the pottant sample burns all the way to the clamp during and / or after the flame exposure(s)). Measured P Density (g / Tensile Stre Elongation Formulated Viscosity at Foam Hardn D) Tan delta pe (°C) Storage Mo @ -30°C Storage Mo @ 25°C Storage Mo @ 50°C UL 94 Ratin UL 94 Spec Thickness ( Table 5: Measured sample properties Measured P Performance Density (g / Tensile Str Elongation Formulated Viscosity a Foam Hard D) Tan delta p (°C) Storage Mo @ -30°C Storage Mo @ 25°C Storage Mo @ 50°C UL 94 Rati UL 94 Spe Thickness In the examples, comparative sample CE1 containing propylene oxide and ~30 wt% of plasticizing FR additive yield a poor quality foam. Sample CE2 was formulated with polyether polyols containing propylene oxide and less than 10 wt% FR additives to yield a foam that fails the UL 94 test. Sample CE3 formulated with a propylene oxide (i.e., PO) polyether polyol (Polyol - 4) produced a PU foam that failed the UL 94 test. In contrast, inventive sample IE1 formulated with an aromatic polyester polyol having a similar equivalent weight to Polyol – 4 and <10 wt% FR additives yields a UL 94 V-0 rated foam. Inventive sample IE3 was prepared similar to IE1 with increased FR additive (TEP) concentration, which produced a PU foam meeting UL 94 V-0. Comparative sample CE4 contained a similar formulation, but produced a PU foam that failed the UL 94 test. Inventive sample IE4 incorporates an aromatic polyester polyol and FR additive- containing isocyanate prepolymer (DEHP prepolymer), which achieved a UL 94 V-0 rating with excellent mechanical properties (particularly when compared to CE2 and CE3). Comparative sample CE5 contained DEHP prepolymer with no added free FR additive, which failed UL 94 fire test. Sample IE5 was formulated with DEHP prepolymer and < 9 wt% FR additive and achieved UL 94 V-1 rating, while CE6 that increased FR additive loading and decreased DEHP prepolymer loading failed UL 94 fire test. For sample IE6, increasing FR additive loading relative to IE5 and decreased DEHP prepolymer loading to achieve UL 94 V-0 rating with good mechanical properties. While the foregoing is directed to exemplary embodiments, other and further embodiments may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.

Claims

Claims 1. A polyurethane foam composition, comprising a reaction product of: an isocyanate component; an isocyanate-reactive component comprising: one or more aromatic polyester polyols; one or more polyether polyols; a silicone surfactant; one or more catalysts water; and a flame resistance (FR) additive at a percent by weight (wt%) ranging from 5 wt% to 20 wt% based upon the total weight of isocyanate-reactive component; Commented [CL1]: wherein the polyurethane foam composition has a UL 94 vertical burn performance of at least V2. Commented [DD2R1]:

2. The composition of claim 1, wherein the isocyanate component further comprises a phosphorus-containing isocyanate prepolymer prepared from a reaction comprising: one or more isocyanate compounds, and one or more hydroxy-functional phosphonates.

3. The composition of claim 2, wherein the isocyanate component comprises the prepolymer at a percent by weight (wt%) ranging from 10 wt% to 100 wt%.

4. The composition of claim 2, wherein the prepolymer has a measured %NCO according to ASTM D5155 of greater than 20%.

5. The composition of claim 2, wherein the hydroxy-functional phosphonate is a mono- hydroxy functional phosphonate.

6. The composition of claim 1, wherein the one or more polyether polyols comprise: at least one bifunctional polyether polyol having a hydroxy number of 20 mg KOH / g or more; and at least one trifunctional polyether polyol having a hydroxy number of 400 mg KOH / g or more.

7. The composition of claim 1, wherein the one or more aromatic polyester polyols has a hydroxy number ranging from 250 mg KOH / g to 400 mg KOH / g.

8. The composition of any one of claims 1 to 3, wherein the polyurethane composition has a density according to ASTM D3574-17 in a range of 0.3 g / mL and 0.75 g / mL.

9. An article or composite prepared from the polyurethane foam composition of any one of claims 1 to 8, wherein the polyurethane composition has a Shore D hardness according to ASTM D2240-15 of 20 or more.

10. An pottant prepared from the polyurethane foam composition of any one of claims 1 to 8.

11. A method of preparing a composite article, comprising: dispensing a composition of any one of claims 1-8 on a substrate, and curing the composition to produce the composite article comprising a polyurethane article on the substrate.

12. A method of preparing the polyurethane composition of claim 1, comprising: combining the isocyanate component and the isocyanate-reactive component to form a mixture; and reacting the mixture to form the polyurethane composition.

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