Thermally conductive gap filler compositions with storage stability

Abstract

Thermally conductive compositions may include: an isocyanate component containing a blocked isocyanate; an isocyanate-reactive component containing: one or more polyetheramines and one or more magnesium oxide particles; and one or more thermally conductive fillers present in one or more of the isocyanate component and the isocyanate-reactive component; wherein the thermally conductive composition has a thermal conductivity of greater than 1 W / m.K. Methods may include combining an isocyanate component and an isocyanate-reactive component; and emplacing the resulting thermally conductive composition between a heat source and a heat sink in an EV battery.

Description

[0001] THERMALLY CONDUCTIVE GAP FILLER COMPOSITIONS WITH STORAGE STABILITY Field Embodiments relate to thermally conductive compositions for use as thermal interface materials such as gap filler, sealant, gap pads, or paste in applications requiring thermal management such as electronics and automotive applications, and methods for using same. Introduction Thermal interface materials such as gap fillers, adhesives, and gels are used widely for thermal management in electronics and automotive applications. For example, electric vehicle (EV) batteries are cooled by mounting one or more battery modules to a cooling plate that redirects heat. For efficient cooling, good thermal contact between the battery modules and the cooling plate is needed. A gap filler bridges this gap and provides thermal contact between the battery modules and the cooling plate. Thermal gap pads and dispensable gap fillers are two of the primary gap filler technologies. Among the two, dispensable gap fillers have the advantage of providing more efficient heat transfer and less wastage of material compared to thermal pads that may require trimming and customization during installation. It is desired to have a thermal interface material composition with a high thermal conductivity (> 1 W / m•K), ability to form a cured solid part with no applied heat, low density, and is easily processed. Moreover, the physical properties of thermal interface materials should remain stable under high temperatures and resist thermal aging effects and degradation. Summary In an aspect, embodiments of the present disclosure are directed to thermally conductive composition, including: an isocyanate component containing a blocked isocyanate; an isocyanate- reactive component containing: one or more polyetheramines and one or more magnesium oxide particles; and one or more thermally conductive fillers present in one or more of the isocyanate component and the isocyanate-reactive component; wherein the thermally conductive composition has a thermal conductivity of greater than 1 W / m.K. In another aspect, embodiments of the present disclosure include methods of using thermally conductive compositions disclosed herein, the method including combining the isocyanate component and the isocyanate-reactive component; and emplacing the thermally conductive composition between a heat source and a heat sink in an EV battery. In some cases methods may include preparing a thermally conductive composition by combining an isocyanate component containing a blocked isocyanate; an isocyanate-reactive component containing: one or more polyetheramines and one or more magnesium oxide particles; and one or more thermally conductive fillers present in one or more of the isocyanate component and the isocyanate-reactive component; and emplacing the thermally conductive composition between a heat source and a heat sink in an EV battery. Detailed Description Embodiments relate to thermally conductive compositions for use as gap fillers in thermal management applications that incorporate magnesium oxide particles and thermally conductive fillers. Thermally conductive compositions may be prepared from an isocyanate component and an isocyanate-reactive component that are substantially free (e.g., containing less than 100 ppm, respectively) of organometallic or amine catalysts, and may have extended storage stability and maintenance of cure properties over time when compared with catalyst-containing compositions utilizing organometallic or amine catalysts. Compositions disclosed herein may be used in thermal management applications, including enhancing heat transmission in electronic devices, batteries, automotive applications, and the like. Described compositions can be used as a thermally conductive gap filler or a pre-cured thermal pad for applications requiring thermal management, such as electric vehicle batteries. Thermally conductive compositions prepared from multi-component isocyanate-based chemistries (e.g., polyurethane, polyurea) may utilize blocked isocyanate components to improve storage stability, while controlling reactivity and workability. Compositions incorporating blocked isocyanates are often formulated with a catalyst to increase reaction kinetics during curing, which may include amines or organometallic catalyst. However, the reactivity profile of formulations incorporating such catalysts can change over time, particularly with exposure to elevated temperatures that may be encountered during shipping and storage. In contrast, thermally conductive compositions disclosed herein may be formulated with magnesium oxide particles that enhance curing reactions for a multi-component system having an isocyanate component containing a blocked isocyanate prepolymer composition and an isocyanate-reactive component containing polyetheramines. The magnesium oxide particles may be combined with the isocyanate-reactive component, and maintain reactivity after extended storage and heat aging, providing a thermally conductive compositions that cures at room temperature, and exhibits durable and reproducible Shore OO hardness. The numerical ranges disclosed herein include all values from, and including, the lower and upper value and all values in between. Unless stated to the contrary, implicit from the context, or customary in the art, all parts and percentages are based on weight and all test methods are current as of the filing date of this disclosure. As used herein, the term “average particle size” refers to the median particle size or diameter of a distribution of particles as determined for example, by a Multisizer 3 Coulter Counter (Beckman Coulter, Inc., Fullerton, CA) according to the procedure recommended by the manufacturer. The average particle size may be estimated based on measuring the surface area according to 8-11 ASTM D4315 or by using sieves of various mesh sizes and calculating the average from the cumulative weight of each size fractions. The median particle size, D50 is defined as the size wherein 50 volume % of the distribution is smaller than the stated value, D90 is defined as the size wherein 90 volume % of the distribution is smaller than the stated value. D10is defined as the size wherein 10 volume % of the distribution is smaller than the stated value. Particle size distribution can be determined by known methods in the art such as ASTM B822-10 or ASTM B822-20 or ISO 13320 using appropriate suspending medium or in dry state. Span of the filler particle size distribution is defined as (D90-D10) / D50, and is an indication of the width of the particle size distribution. As disclosed herein, “room temperature” means a temperature range from 18°C to 35°C. As disclosed herein, “molecular weight” means number average molecular weight. As disclosed herein, “thermally conductive composition” (which includes both cured and uncured compositions) means a composition having a thermal conductivity value greater than 1.0 W / m•K as measured by ISO 22007-2 using hot disc or by ASTM D-5470. As disclosed herein, “squeeze force” refers to resistance of a thermally conductive composition or component to compression, as measured in Newtons. Squeeze force is measured using a TA.XTplus texture analyzer equipped with a 50 kg load cell. After dispensing the respective sample onto a flat aluminum substrate, an acrylic probe with a diameter of 40 mm is lowered to sandwich the test material against the flat substrate to achieve a standard 5.0 mm gap thickness. Any excess overflow material was trimmed away with a flat-edge spatula. After trimming, the test started and the probe moved to a final thickness of 0.3 mm, at a rate of 1.0 mm / sec while the force was recorded. The specific force value recorded at the gap of 0.5 mm is reported as the “squeeze force”. Viscosity can be measured using methods commonly known in the art using TA instruments ARES-G2, AR2000 type rheometers or Anton Paar MCR rheometers using parallel plate or cone and plate fixtures. Thermally conductive compositions disclosed herein generally include the product obtained from combining a two-component curable composition: an isocyanate component (“A- side”) and an isocyanate-reactive component (“B-side”). During application, the A-side and B- side are mixed, initiating a curing reaction at room temperature, and forming the thermally conductive composition. Thermally conductive compositions may also include one or more thermally conductive fillers in the A-side and / or the B-side to enhance thermal transport properties. A.) Isocyanate component The isocyanate component (or A-side) may contain one or more blocked isocyanate prepolymers, and other additives such as internal mold release (IMR) agents, plasticizers, and thermally conductive fillers. Blocked Isocyanate Prepolymer The isocyanate component may include a blocked isocyanate prepolymer generated by reacting an isocyanate terminated prepolymer (including any residual monomeric diisocyanate) and one or more blocking agents. Reaction with a blocking agent may limit the presence of free isocyanate (e.g., below a concentration of 0.1 wt%) and minimize premature gelation and crosslinking of the prepolymer. In some cases, reacting the isocyanate groups with a blocking agent will reduce the free isocyanate content in the prepolymer to less than 0.1 wt%, less than 0.01 wt%, less than 0.001 wt%, or zero wt%. Isocyanate terminated prepolymers may be any prepolymer(s) prepared by the reaction of one or more polyols with a stoichiometric excess of one or more polyisocyanates containing two or more isocyanate groups. The polyisocyanates may be aromatic, aliphatic, araliphatic or cycloaliphatic polyisocyanates, or mixtures thereof. Suitable polyisocyanates include toluene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), isophorone diisocyanate (IPDI), hexamethylene diisocyanate (HDI), tetramethylene-l,4-diisocyanate, cyclohexane-l,4- diisocyanate, hexahydrotolylene diisocyanate, 1-methoxyphenyl-2,4-diisocyanate, diphenylmethane-4,4'-diisocyanate, diphenylmethane-2,4'-diisocyanate, 4,4'-biphenylene diisocyanate, 3,3'-dimethoxy-4,4'-diphenyl diisocyanate, and 3,3'-dimethyldiphenylpropane-4,4'- diisocyanate; isomers thereof, or mixtures thereof. Suitable polyisocyanates may have an average isocyanate functionality of 1.9 or more, 2.0 or more, 2.1 or more, or 2.2 or more, and at the same time, 3.5 or less, 3.2 or less, 3.0 or less, or 2.8 or less. The isocyanate-terminated prepolymer may have an isocyanate (NCO) content by weight according to ASTM D5155-19 (prior to any blocking) of 1% or more, 2.7% or more, or 5% or more, and at the same time, 30% or less, 25% or less, or 20% or less, or in a range of 2% to 20%. The isocyanates used to prepare the isocyanate terminated prepolymers can include the above stated monomeric polyisocyanates, isomers thereof, polymeric derivatives thereof, or mixtures thereof. In some cases, isocyanates may include toluene diisocyanate (TDI), polymeric derivatives thereof, or mixtures thereof. TDI used to prepare the isocyanate terminated prepolymer may be 2,4-isomer and the 2,6-isomer of toluene diisocyanate among others. Toluene diisocyanate based prepolymers may result in lower deblocking temperatures along with high conversion and reaction rates. Mixtures of two or more polyisocyanates may also be used. The polyols and polyol mixtures used to prepare the isocyanate terminated prepolymer may include ethylene glycol, 1,2-propanediol, 1,3-propanediol, neopentylglycol, bis(hydroxy- methyl) cyclohexanes such as 1,4-bis(hydroxymethyl)cyclohexane, 2-methylpropane-1,3-diol, methylpentanediols, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, dipropylene glycol, polypropylene glycol, polyether polyols, and the like. The isocyanate terminated prepolymer may be prepared by procedures such as those described in U.S. Patent Nos. 4,294,951; 4,555,562; and 4,182,825; and International Publication No. WO 2004 / 074343. The blocked isocyanate prepolymer, in some embodiments, may be formed by mixing and reacting one or more of the isocyanate functionalities on an isocyanate prepolymer with one or more blocking agents. Blocking agents for reaction with the isocyanate terminated prepolymer may include monophenolics; alkyl phenols such as nonylphenol; or alkenyl phenols such as cardanol or mixtures, such as cashew nutshell liquid, and the like, and derivatives and mixtures of any thereof. The blocking agent may be used in an amount such that the equivalents of the functional groups of the blocking agent correspond to the amount of isocyanate groups to be blocked, in molar or excess equivalents. In some embodiments, the blocked isocyanate prepolymer is made from TDI using a propylene oxide polyol of number average equivalent weight of 500 to 2500 Da and functionality 1.9 to 3.1, with 2% to 20% NCO before blocking with a blocking agent such as cardanol. The isocyanate component may include a blocked isocyanate prepolymer at a percent by weight (wt%) of 0.5 wt% to 20 wt%, 1 wt% to 15 wt%, or 1 wt% to 5 wt%. Isocyanate components may include a thermally conductive filler present at a percent by weight (wt%) of 50 wt% to 95 wt%, 75 wt% to 94 wt%, or 80 wt% to 92 wt%. Alkylalkoxysilane Thermally conductive compositions disclosed herein may include an alkylalkoxysilane that, without being bound by theory, may provide significant improvement in the high temperature aging performance of the cured articles when combined with an isocyanate component or isocyanate-reactive component. In some cases, the isocyanate component may include one or more alkylalkoxysilanes having a chemical structure of Si(OR)n(R’)4-n, where n is an integer from 1 to 3, R is independently a C1 to C3 alkyl group, and R’ is independently an alkyl group from C12 or more, such as C12 to C25, or C12 to C20. Suitable alkylalkoxysilanes include dodecyltrimethoxysilane, tridecyltrimethoxysilane, tetradecyltrimethoxysilane, hexadecyltrimethoxysilane, hexadecyltriethoxysilane, and the like. In one embodiment, alkylalkoxysilane is hexadecyltrimethoxysilane. Alkylalkoxysilanes may have a boiling point greater than 200°C, 250 °C or 300 °C, and less than 1000 °C. Alkylalkoxysilanes disclosed herein may be added to isocyanate component or isocyanate reactive component so that the percent by weight (wt%) in the combined composition ranges from 0.75 wt% or more, 0.75 wt% to 5 wt%, 0.75 wt% to 4 wt%, or 0.75 wt% to 2.5 wt%. B.) Isocyanate-reactive component The isocyanate-reactive component (or B-side) may contain of one or more polyetheramines, and one or more additives such as magnesium oxide particles, internal mold release agents, plasticizers, and thermally conductive fillers. Polyether amines The isocyanate-reactive component may include one or more polyetheramines, including polyether polyols terminated with primary and / or secondary amines. Polyetheramines may include monoamines, diamines, and higher order amines (e.g., triamines, tetramines, etc.). The polyether amines may have a functionality of active hydrogen atoms per molecule that include from 2 to 8, of at least 2, at least 3, up to 8, or up to 6. In some cases, the isocyanate-reactive components may include a mixture of high and low molecular weight polyetheramines, such as one or more polyetheramines having a molecular weight of 3000 or more (high MW), and one or more polyetheramines having a molecular weight of 3000 or less (low MW). High MW polyetheramines and low MW polyetheramines may independently be selected from polyetheramines having an amine functionality of at least two, at least three, or in the range of 1.5 to 4, 2 to 4, or 2.5 to 3.5. The molar ratio of high MW:low MW polyetheramines may be in the range of 10:1 to 1:10, 5:1 to 1:5, or 3:1 to 1:3. Suitable polyetheramines include resins made from an appropriate initiator to which lower alkylene oxides, such as ethylene oxide, propylene oxide, butylene oxide or mixtures thereof are added, with the resulting hydroxyl-terminated polyol then being aminated. When two or more oxides are used, they may be present as random mixtures or as blocks of one or the other polyether. In the amination step, the terminal hydroxyl groups in the polyol may be primary or secondary hydroxyl groups. Reductive amination processes are known and described in U.S. Patent 3,654,370. Polyetheramines may include commercially available amines such as primary aliphatic JEFFAMINE™ series of polyether amines available from Huntsman Corporation; including JEFFAMINE™ T-403, JEFFAMINE™ T-3000 and JEFFAMINE™ T-5000; or available from BASF including Baxxodur™ EC 3003, and Baxxodur™ EC 311. In some embodiments, the isocyanate-reactive component may include at least one polyetheramine present at a percent by weight of the isocyanate-reactive component (wt%) from 0.2 wt% to 40 wt%, 0.5 wt% to 30 wt%, or 1 wt% to 15 wt%. In formulations containing mixtures of high MW and low MW polyetheramines, wt% ranges may be applied to each type of polyetheramine independently or as a combined total. Isocyanate-reactive components may include a thermally conductive filler present at a percent by weight (wt%) of 50 wt% to 95 wt%, 75 wt% to 94 wt%, or 80 wt% to 92 wt%. Thermally Conductive Fillers Thermally conductive compositions may also include one or more thermally conductive fillers in the A-side and / or the B-side. Fillers disclosed herein may have a thermal conductivity of at least 1 W / m•K, at least 5 W / m•K, or at least 20 W / m•K, and may have a thermal conductivity of less than 1000 W / m•K, or less than 100 W / m•K. Fillers disclosed herein may be low density and low hardness to reduce overall weight of the composition and reduce weight in automotive, EV, and reduce abrasiveness of the composition. In one embodiment, the filler density is < 6 gm / cc, < 4 gm / cc, or < 2.5 gm / cc. Thermally conductive fillers disclosed herein may include one or more of metal oxides, metal nitrides, metal carbides, metal hydroxides, metal carbonates, metal sulfates, natural and synthetic minerals mainly silicates, and aluminum silicates. Suitable fillers include aluminum trihydrate (ATH), natural or synthetic aluminum oxide, quartz, silica, and the like. Thermally conductive compositions may include one or more fillers, which are either added into the formulation in their end state or formed in-situ. The thermally conductive fillers of the present disclosure can be modified with a treating agent before incorporation in the A-side and / or B-side of a thermally conductive composition that alter the hydrophobicity / hydrophilicity of the surface of a thermally conductive filler, modifying filler and polymer interaction, viscosity, and / or squeeze force of the resulting thermally conductive composition. Treatment agents may include fatty acids, silane treating agents, titanates, zirconates, aluminates, or silazane compounds. Thermally conductive filler disclosed herein may have a broad particle size distribution and / or have a bimodal particle size distribution. The average D50 particle size for fillers disclosed herein may be in the range of from 0.05 μm to 500 μm, from 0.1 μm to 300 μm, from 0.5 μm to 100 μm, or from 0.5 μm to 50 μm. The average D90 particle size for fillers disclosed herein may be in the range of from 0.05 μm to 500 μm, 1 μm to 300 μm, 5 μm to 200 μm, or 10 μm to 150 μm. The average D10 particle size for fillers disclosed herein may be in the range of from 0.05 μm to 30 μm, 0.08 μm to 10 μm, 0.1 μm to 10 μm. The span may be controlled in some cases to reduce the squeeze force of the resulting thermally conductive composition. Thermally conductive filler disclosed herein may have a broad particle size characterized by span of greater than 2, greater than 3, or greater than 4, or less than 50. In some cases, thermally conductive fillers may have a bimodal particle size distribution produced by blending two fillers with one filler having D50 in the range of 0.1 to 20 μm and another filler having D50 in the range of 10 to 200 μm. Thermally conductive filler disclosed herein may be present at a percent by weight of the total weight of the thermally conductive composition (wt%) of 50 wt% to 95 wt%, 75 wt% to 94 wt%, or 80 wt% to 92 wt%. The filler may be loaded in the A-side and / or B-side in equal or differing amounts that, when combined, result in a thermally conductive composition having a filler concentration within any of the above ranges. It should be noted different filler sizes / types could be blended to obtain the desired filler loading and viscosity of a formulation. In some cases, thermally conductive filler may be an aluminum trihydrate. Thermally conductive filler may have a span of >4, D10in the range of 0.1 to 10 microns, D50in the range of 5 to 50 microns, and D90 in the range of 50 to 200 microns. Thermally conductive fillers may also be pre-treated with a C5-C20 silane treating agent to modify hydrophobicity and compatibility with the isocyanate component and / or the isocyanate-reactive component. Magnesium Oxide Particles Thermally conductive composition disclosed herein may include magnesium oxide particles that,without being bound by theory, speed up the curing kinetics and improve shelf stability of the curing profile for mixed A-side and B-side. The average D50 particle size for magnesium oxide particles disclosed herein may be in the range of from 0.05 μm to 500 μm, from 0.1 μm to 200 μm, from 0.5 μm to 100 μm, or from 0.5 μm to 50 μm. The average D90 particle size for magnesium oxide particles disclosed herein may be in the range of from 0.05 μm to 1000 μm, 1 μm to 500 μm, 5 μm to 200 μm, or 10 μm to 100 μm. Magnesium oxide particles disclosed herein may be present at a percent by weight of the total weight of the thermally conductive composition (wt%) of 0.5 wt% to 25 wt%, 1 wt% to 20 wt%, or 1 wt% to 15 wt%. It should be noted different magnesium oxide particle sizes / types could be blended to obtain the desired magnesium oxide particles loading and viscosity of a formulation. In some cases, magnesium oxide is may be lightly calcined, high surface area (i.e., 100 m2 / gm or greater), high purity (i.e., 85% or greater) to enhance high reactivity. As used herein, lightly calcined refers to magnesium oxide particles treated as a calcination temperature ranging from 700-1100 ⁰C during production. Magnesium oxide particles may have a BET surface area ranging from 300 m2 / gm to 120 m2 / gm, or 200 m2 / gm to 150 m2 / gm. Internal Mold Release Agent Thermally conductive compositions disclosed herein may include one or more internal mold release (IMR) agents in at least one of the isocyanate component or the isocyanate reactive component. IMR agents may include branched fatty acid esters. IMR agents may include esters prepared from the reaction of a polyol having two or more hydroxyl groups with one or more equivalents of a fatty acid (e.g., monoester, diester, triester, etc.). IMR agents may have the general formula of R1(OH)n-x(OC=OR2)x, where R1is a branched (i.e., containing one or more secondary and / or tertiary carbons) C3 to C10 carbon chain polyol having n hydroxy functional groups, such as 2 or more, 3 or more, or in a range of 2 to 8; R2is a linear or branched, saturated or unsaturated C8 to C20 carbon chain; and x is an integer from 1 to 4, or 1 to 3. IMR agents disclosed herein may be prepared from the reaction of one or more equivalents of fatty acid(s) with a C3 to C10 polyol such as neopentyl glycol, trimethylol ethane, trimethylol propane, trimethylol butane, di- (trimethylol propane), tri- (trimethylol propane), pentaerythritol, di-(pentaerythritol), tri- (pentaerythritol), and the like. Suitable fatty acids include one or more of C8 to C20 saturated fatty acids such as capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, sebacic acid and the like; C8 to C20 unsaturated fatty acids such as palmitoleic acid, oleic acid, or caproleic acid, synthetic or naturally derived fatty acids such as soya oil acid, lauric acid, cocinic acid, eleostearic acid, tung oil fatty acid, linseed oil fatty acid, castor oil fatty acid, dimers or oligomers thereof, and the like. In some cases, IMR agents may include trimethylolpropane oleate or pentaerythritol oleate. IMR agents may be mixed into at least one of the isocyanate component or the isocyanate- reactive component at a percent by weight of the respective component (wt%) in an amount ranging from 0.1 wt% to 20 wt%, 0.5 wt% to 16 wt%, or 1 wt% to 15 wt%. Plasticizer Thermally conductive compositions disclosed herein may include one or more plasticizers that may increase shelf stability and thermal aging properties. Plasticizers may include organic plasticizers, such as those containing carboxylic acid ester(s), phthalate(s), carboxylates, adipates, and the like. Specific examples include bis(2-ethylhexyl)terephthalate, bis(2-ethylhexyl)-1,4- benzenedicarboxylate, 2-ethylhexyl methyl-1,4-benzenedicarboxylate, 1,2 cyclohexanedicarboxylic acid, dinonyl ester (branched and linear), bis(2-propylheptyl)phthalate, diisononyl adipate, dioctyl adipate and combinations thereof. Plasticizers disclosed herein include various types of glycol ether esters including mixtures of one or more types. Suitable glycol ether esters include monoesters such as those described by Formula (I): (I) wherein R1is a saturated, chain including 2 to 12 carbon atoms, R2 is either hydrogen and / or substituted carbon chain including 2 to 12 carbon atoms, and n is an integer ranging from 1 to 4. Glycol ether esters disclosed herein may also include those described by Formula (II): wherein R1 and R4 carbon chain including 2 to 12 carbon atoms, R2is either hydrogen or methyl, R3is a saturated, unsaturated, and / or substituted carbon chain including 2 to 12 carbon atoms, and n is an integer ranging from 1 to 4. Suitable glycol ether ester plasticizers include bis(2-(2-butoxyethoxy)ethyl) adipate, bis- dipropylene glycol n-butyl ether adipate, bis-diethylene glycol n-butyl ether malonate, bis- diethylene glycol n-butyl ether glutarate, bis-dipropylene glycol methyl ether maleate, tetraetyleneglycol di-2-ethylhexanoate, and the like. Glycol ether esters disclosed herein may also those described by Formula (III): wherein R1and R3 substituted carbon chain including 2 to 12 carbon atoms, R2 is either hydrogen or methyl, and n is an integer ranging from 1 to 4. Suitable plasticizers also include glycol ether esters prepared from the esterification of a glycol ether with one or more equivalents of a carboxylic acid. Glycol ethers may include 1 to 4 repeats of one or more glycol units, including ethylene glycol, propylene glycol, and the like. Carboxylic acids may include C2 to C12 carboxylic acids such as acetic acid, propanoic acid, isobutanoic acid, adipic acid, 2-ethylhexanoic acid, acrylic acid, methacrylic acid, crotonic acid, itaconic acid, maleic acid, and the like. Carboxylic acids may include mono carboxylic acids and dicarboxylic acids. Examples of suitable plasticizers include ethylene glycol monoethylether acetate, ethylene glycol monomethyl ether acetate, bis-dipropylene glycol n-butyl ether adipate, bis-dipropylene glycol n-butyl ether maleate, triethylene glycol-di-2-ethylhexanoate, bis(2-(2-butoxyethoxy)ethyl) adipate, bis-diethylene glycol n-butyl ether malonate, bis-diethylene glycol n-butyl ether glutarate, bis-dipropylene glycol methyl ether maleate, tetraethyleneglycol di-2-ethylhexanoate, propylene glycol methyl ether acetate, and the like. Plasticizers may be mixed into at least one of the isocyanate component or the isocyanate- reactive component at a percent by weight of the respective composition (wt%) in an amount ranging from 1 wt% to 20 wt%, 2 wt% to 16 wt%, or 4 wt% to 15 wt%. Thermally conductive compositions may include one or more additives added to the isocyanate component and / or the isocyanate reactive component, including moisture scavengers (e.g., zeolites, molecular sieves, p-toluene sulfonylisocyanate), adhesion promoters, thixotropic agents, color agents such as dyes or pigments, antioxidants, wetting agents such as surfactants, filler dispersion agents, thickening agents, compatibilizers, anti-settling agents anti-syneresis agents, flame retardants, and / or filler treatment agents (e.g., silanes). In some cases, thermally conductive compositions may be prepared from an isocyanate component and an isocyanate-reactive component, in which both components, respectively, are substantially free from catalysts, such as organometallic and / or amine catalysts, or Lewis acid and / or Lewis base catalysts. In some cases, the parts per million (ppm) by weight of catalyst in either the isocyanate component and / or the isocyanate reactive component is less than 100 ppm, less than 75 ppm, less than 50 ppm, or less than 25 ppm. C. Method of Preparation Prior to combination to form a thermally conductive composition, the isocyanate component and / or the isocyanate-reactive component may have a squeeze force of 200 N or less, 180 N or less, or 150 N or less, such as in the range of 35 N to 250 N, 35 N to 150 N, or 35 N to 100 N. In some cases, the isocyanate component and the isocyanate-reactive component exhibit a change in squeeze force of less than 50% over 3 days, or less than 20% after heating at 60oC over 7 days, indicating excellent storage stability. Preparation of the thermally conductive compositions of the present disclosure may be achieved by mixing the respective components of the isocyanate component and the isocyanate- reactive component in any sequence, and to combine the components to prepare the final mixture. Suitable mixing techniques include the use of a Ross PD Mixer (Charles Ross), Myers mixer, FlackTek Speedmixer, butterfly mixer and the like. Various components of the composition could also be mixed using a continuous process such as twin-screw extrusion. Various streams could be fed separately to an extruder or premixed in various combinations to form the blocked isocyanate composition and the isocyanate-reactive component. Such a process could be suitable for large volume manufacturing. The isocyanate-reactive component and the isocyanate component can be combined such that the molar ratio of blocked isocyanate groups to amine reactive groups is in the ranges of 0.90:1.1 to 1.1:0.9, such as 0.90:1.1, 0.95:1.05, 0.97:1.03, or 1:1. At the same time, the volume ratio of the isocyanate-reactive component to the isocyanate component in the curable composition may be controlled within the range between 0.90:1.1 from 0.95:1.05, from 0.97:1.03, or at the ratio of 1:1. 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 35oC (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 thermally conductive solid with a measurable hardness. Cured thermally conductive compositions may have a thermal conductivity of greater than 0.5 W / m•K, greater than 1 W / m•K, or greater than 1.5, W / m•K, such as in a range of 0.5 W / m•K to 50 W / m•K. Cured thermally conductive compositions disclosed herein may have a density of 1 gm / cc to 4 gm / cc, 1.5 to 3.5 gm / cc, or 1.8 to 3.1 gm / cc. Cured thermally conductive compositions may have a thermal conductivity >1.0 W / m•K, or >1.5 W / m•K, or >1.9, W / m•K, or < 50 W / m•K. In some embodiments, cured thermally conductive compositions may have a density of 1 gm / cc to 4 gm / cc, 1.5 to 3.5 gm / cc, or 1.8 to 3.1 gm / cc. Cured thermally conductive compositions may have a hardness according to ASTM D- 2240-15 in Shore OO / Shore 00 hardness of 50 or more, 60 or more, or 70 or more, such as in the range of 50 to 85. Thermally conductive 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 30 minutes. Complete curing is indicated by no further increase in the hardness over time. In some cases, cured thermally conductive compositions may have a hardness according to ASTM D-2240-15 in Shore OO hardness after room temperature curing for 14 days in a range of 50 to 85, or 60 to 80. Thermally conductive compositions may exhibit storage stability such that the hardness of the cured composition obtained after combining the individual isocyanate component and the isocyanate-reactive component aged at 60⁰C for 1 week is in the range of 50-85 Shore 00 after room temperature curing. Thermally conductive compositions disclosed herein may be useful as a gap filler for energy storage devices and in electronic vehicle battery thermal management. In some cases, the compositions may include gap fillers and pastes that are applied between a heat source and a heat sink to provide a thermally conductive interface, such as between a battery module and a cooling plate. Manual or automatic dispensing tools can be used to apply thermally conductive compositions directly to the target surface to minimize waste. In an embodiment, a thermally conductive composition may be prepared by combining an isocyanate component and an isocyanate-reactive component and applying to a cooling plate or heat sink using an automated mix-meter-dispense system, followed by installation of a battery cell, module or pack, or other heat source. Additionally, thermally conductive compositions may be used to form pre-cured articles such as thermal interface gap pads. In one example, pre-cured articles may be formed by curing thermally conductive compositions at a desired thickness, cutting the article to a desired shape, and then compressed to fix in place as needed. In some cases, cured articles may also help reduce vibration stress for shock dampening. 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. The numerical ranges disclosed herein include all values from, and including, the lower and upper value and all values in between. Unless stated to the contrary, implicit from the context, or customary in the art, all parts and percentages are based on weight and all test methods are current as of the filing date of this disclosure. Examples The following examples are provided to illustrate the embodiments of the invention, but are not intended to limit the scope thereof. All parts and percentages are by weight unless otherwise indicated. Table 1 lists the materials used in the following examples: Table 1: Component chemicals used in the examples Name Description 90 e m In the following example, comparative and inventive thermally conductive compositions were prepared and analyzed for curing properties upon mixing prior to and after heat aging of the A-side and B-side. Results are shown in Tables 2 and 3. Formulations for the A-side and B-side where prepared separately by high speed mixing, respectively. For curing the two-part system, A-side and B-side were mixed in a 1:1 weight ratio using a high-speed mixer and allowed to cure at ambient conditions. Hardness was measured periodically using a Shore OO durometer per ASTM D2240. For testing cure kinetics after extended storage, the A-side and B-side pastes were aged at 60°C for one week, respectively to mimic extended room temperature storage. Pastes were allowed to cool down to room temperature and A-side and B-side were mixed using a high-speed mixer. Thermal conductivity was measured using the Hot Disk Thermal Constants Analyzer (TPS 2500S, Thermtest Instruments, Canada) per ISO 22007-2. All measurements were completed with a thermal probe using a double-sided measurement with two-6 mm cups, at 150 mW heating power and 5 s measurement time. Squeeze force was measured using a texture analyzer equipped with a 50 kg load cell. After dispensing the gap filler onto a flat heavy-duty aluminum substrate, an acrylic probe with a diameter of 40 mm was lowered to sandwich the test material against the flat substrate to achieve a standard 5.0 mm gap thickness. Any excess overflow material was trimmed away with a flat- edge spatula. After trimming, the test started and the probe moved to a final thickness of 0.3 mm, at a rate of 1.0 mm / sec while the force was recorded. The specific force value recorded at the gap of 0.5 mm is reported as the “squeeze force”. Table 2: Comparative sample compositions and properties Component CE-1 CE-2 CE-3 e 2 0 1

[0002] Table 3: Inventive sample compositions and properties IE-1 IE-2 e 0 0 6 F or e compara ve examp es, C - s owed cur ng ne cs progressed s owly without a catalyst present or in the presence of CaCO3 (CE-2). CE-3 containing an amine catalyst (DBU) exhibited fast cure prior to aging, but minimal hardness was observed after aging the A side and B side pastes at 60⁰C for 1 week. In contrast, Samples IE-1 and IE-2 containing magnesium oxide particles exhibited fast curing kinetics, which remained stable after heat aging the A-side and B- side pastes for 1 week. 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 thermally conductive composition, comprising: an isocyanate component comprising a blocked isocyanate; an isocyanate-reactive component comprising: one or more polyetheramines and one or more magnesium oxide particles; and one or more thermally conductive fillers present in one or more of the isocyanate component and the isocyanate-reactive component; wherein the thermally conductive composition has a thermal conductivity of greater than 1 W / m.K.

2. The composition of claim 1, wherein the thermally conductive composition has a total catalyst concentration of less than 75 ppm.

3. The composition of claim 1, wherein the magnesium oxide particles have a BET surface area ranging from 300 m2 / gm to 120 m2 / gm.

4. The compositions of claim 1, wherein the cured thermally conductive composition has a hardness according to ASTM D-2240-15 in the range of 50 to 80 Shore OO.

5. The compositions of claim 1, wherein the cured thermally conductive composition has a hardness according to ASTM D-2240-15 in the range of 50 to 80 Shore OO, where the individual isocyanate component and the isocyanate-reactive component are aged at 60⁰C for 1 week.

6. The compositions of claim 1, wherein the cured thermally conductive composition has a hardness in the range of 50 to 80 Shore OO after 14 days curing at room temperature, where the individual isocyanate component and the isocyanate-reactive component are aged at 60⁰C for 1 week.

7. The composition of claim 1, wherein the magnesium oxide particles have a D50 particle size in the range of 0.05 μm to 120 μm.

8. The composition of claim 1, further comprising one or more internal mold release agents present in one or more of the isocyanate component and the isocyanate-reactive component, the internal mold release agent being prepared from the reaction of one or more equivalents of fatty acid with a branched C3 to C10 polyol.

9. The composition of claim 1, wherein the one or more polyetheramines comprise: at least one high molecular weight polyether amine having a functionality of 2.5 to 3.5 and a number average molecular weight of 3000 Da or more; and at least one low molecular weight polyether amine having a functionality of 2.5 to 3.5 and a number average molecular weight of 3000 Da or less.

10. The composition of claim 1, further comprising one or more glycol ether ester plasticizers at a percent by weight (wt%) of at least one of the isocyanate component or the isocyanate- reactive component ranging from 1 wt% to 20 wt%.

11. A method of using the thermally conductive composition of any one of claims 1 to 10, the method comprising combining the isocyanate component and the isocyanate-reactive component; and emplacing the thermally conductive composition between a heat source and a heat sink in an EV battery.

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