Thermally conductive gap fillers with improved serviceability

Abstract

Thermally conductive compositions may include an isocyanate component containing a blocked isocyanate; an isocyanate-reactive component comprising: one or more polyetheramines, and one or more catalysts selected from a group of carboxylate salts, tertiary amines, amidines, guanidines, and diazabicyclo compounds; and 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; and a thermally conductive filler, wherein the thermally conductive composition has a thermal conductivity of greater than 1 W / m.K.

Description

[0001] THERMALLY CONDUCTIVE GAP FILLERS WITH IMPROVED SERVICEABILITY Field Embodiments relate to thermally conductive compositions for use as gap fillers in thermal management applications, and having tuned adhesive properties that increase serviceability and disassembly of adhered components. Introduction Thermal management of electric vehicle (EV) battery is critical for range, reliability, and safety of electric vehicles. Battery modules in an EV are typically cooled by using cooling plates with active cooling, where thermal contact between the modules and the cooling plate contributes to the efficiency of heat transfer. A gap filler is a thermally conductive composition that is applied between the battery modules and cooling plate to provide an efficient thermal contact and facilitate heat transfer. High thermal conductivity in the range of 1-3 W / m.K is typically needed for gap fillers. Gap filler formulations typically have high loading (>80 wt. %) of thermally conductive fillers to be able to achieve such high thermal conductivity. During or after the lifetime of a vehicle, battery modules may need to be replaced or repaired. Serviceability of battery module components requires removal of a battery module from the cooling plate and other assembly components. The adhesive properties of the thermally conductive composition must be balanced correctly between having sufficient adhesion to secure battery components during operation, while maintaining adhesion below a “pull force” threshold such that disassembly is possible without undue stress or damage. Some additional desired properties of thermally conductive gap filler compositions are easy applicability with low squeeze force, compatibility with varied material types (e.g., plastics and metals used in battery assembly), and resistance to aging and deterioration when exposed to high temperature. Summary In an aspect, embodiments of the present disclosure are directed to thermally conductive compositions including: an isocyanate component containing blocked isocyanate; an isocyanate- reactive component comprising: one or more polyetheramines, and one or more catalysts selected from a group of carboxylate salts, tertiary amines, amidines, guanidines, and diazabicyclo compounds; and 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; and a thermally conductive filler, wherein the thermally conductive composition has a thermal conductivity of greater than 1 W / m.K. In another aspect, embodiments of the present disclosure are directed to methods of using a thermally conductive compositions that includes combining an isocyanate component and an isocyanate-reactive component to form a thermally conductive composition; 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, and having tuned adhesive properties that allow serviceability and disassembly of adhered components in batteries, electronic devices, automotive applications, and the like. Thermally conductive composition may be prepared from two component mixtures that include an isocyanate component and an isocyanate-reactive component. The two component mixture may exhibit a low squeeze force during application, and cures to form a thermally conductive composition having a thermal conductivity of greater than 1 W / m.K , and a pull force of less than 0.15 MPa. 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 D90is defined as the size wherein 90 volume % of the distribution is smaller than the stated value. D10 is 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” means a composition having a thermal conductivity value greater than 1 W / m•K as measured by ISO 22007-2 using hot disc or by ASTM D-5470. 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 may include an isocyanate component and an isocyanate-reactive component that are combined and applied in situ to cure at room temperature and exhibit durable Shore OO hardness, even when aged at high temperature. The isocyanate component may include a blocked isocyanate prepolymer composition, and the isocyanate- reactive component may include one or more polyetheramines. Thermally conductive compositions may further include one or more of internal mold release (IMR) agents or glycol ether ester plasticizers that may reduce viscosity and improve thermal aging performance. During the battery assembly process, gap filler compositions are applied to a substrate and battery modules are assembled (“squeezed”) onto the pre-dispensed gap filler. Reducing the viscosity and squeeze force of the components of the thermally conductive composition may be beneficial, for example, by reducing the force required to assemble a gap filler between a heat source and a heat sink, such as in an EV battery application. Thermally conductive compositions may be used in thermal management applications, including the 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 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 product 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 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. Isocyanate prepolymers and / or blocked isocyanate prepolymers may be formed using a catalyst in some embodiments, which may include amine-based catalysts and / or tin-based catalysts. 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 15% 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%. Thermally conductive compositions may include an isocyanate component at a percent by weight (wt%) ranging from 15 wt% to 80 wt%, 20 wt% to 80 wt%, or 20 wt% to 70 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 internal mold release agents, plasticizers, catalysts, 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 polyols 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 D50particle 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 D90particle 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 D10particle 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 D50in 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. Catalysts Thermally conductive compositions may include one or more catalysts mixed into at least one of the isocyanate component or the isocyanate-reactive component to promote the reaction of blocked isocyanate functional groups with the polyetheramines. The catalysts may be any one or any combination / mixture of more than one selected from carboxylate salts, tertiary amines, amidines, guanidines, and diazabicyclo compounds. Suitable catalysts include bismuth octoate, bismuth neodecanoate, potassium acetate, potassium 2-ethylhexanoate, or mixtures thereof. Catalysts may include sterically hindered tertiary amines; a long chain tertiary amines (i.e., amine substituents of at least 6 hydrocarbons); or a cyclic tertiary amines. Suitable tertiary amines include dimorpholinodialkyl ether, di((dialkylmorpholino)alkyl)ether such as (di-(2-(3,5- dimethyl-morpholino)ethyl)ether), triethylene diamine, N,N-dimethylcyclohexylamine, N,N- dimethyl piperazine, 4-methoxyethyl morpholine, N-methylmorpholine, N-ethyl morpholine, or mixtures thereof. In some embodiments, the amidine or guanidine are N-hydrocarbyl substituted amidines or guanidines; in a further embodiment the amidine or guanidine are cyclic amidines or cyclic guanidines. Suitable amidines or guanidines include 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), 1,5,7-triazabicyclo[4.4.0]dec-5-ene, diazabicyclo[5.4.0]undec-7-ene, and N-methyl- 1,5,7-triazabicyclododecene. The catalyst may be present in the isocyanate-reactive component at a percent by weight (wt%) ranging from 0.001 wt% to 5.0 wt%, from 0.01 wt% to 2.0 wt%, or from 0.02 wt% to 0.5 wt%. 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 acids and 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 work in combination with the IMR agent(s) to reduce the pull force required to service the components assembled with the thermally conductive composition. Plasticizers may include , organic plasticizers, such as those containing carboxylic acid ester(s), phthalate(s), carboxylates, adipates, or a combination thereof. 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. In some cases, thermally conductive compositions may include a glycol ether ester plasticizer that may increase shelf stability and thermal aging properties. 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): (II) wherein R1 and 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. In one embodiment, one or more plasticizers are selected from a group consisting of bis- dipropylene glycol n-butyl ether adipate, triethylene glycol-di-2 ethylhexanoate, bis(2-(2- butoxyethoxy)ethyl) adipate, and tetraethyleneglycol di-2-ethylhexanoate or a combination thereof. Plasticizer may be present in an amount sufficient to disperse or reduce the viscosity of at least one of the blocked isocyanate prepolymer composition or the amine composition. In some embodiments, plasticizers may have a viscosity of less than 25 cps, less than 30 cps, or less than 35 cps. Plasticizers may have a viscosity in a range of 1 cps to 35 cps, 1 cps to 30 cps, or 5 cps to 30 cps. Plasticizers may also have a boiling point at 1 atmosphere (760 mm Hg) of greater than 300°C to minimize or eliminate loss of plasticizer by evaporation during testing and usage. Plasticizers may have a boiling point at 1 atmosphere (760 mm Hg) in the range of 300oC to 1000oC, 290oC to 1000oC or 290oC to 950oC. The above ranges recited may be combined in any order to define a class of plasticizers. Mixture of different plasticizers could be used. 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). 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 180 N or less, 150 N or less, or 100 N or less. The isocyanate component and / or the isocyanate-reactive component may have a squeeze force in the range of 35 N to 250 N, 35 N to 150 N, or 35 N to 100 N. In some embodiments, 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. The cured thermally conductive composition may have a range of hardness as determined by ASTM D-2240-15 in a range of 40 to 90 Shore OO, 50 to 85 Shore OO, or 60 to 80 Shore OO. In some embodiments, the thermally conductive compositions have a cured hardness as determined by ASTM D-2240-15 of 50-85 Shore OO. 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. Cured thermally conductive compositions may have a thermal conductivity > 0.5 W / m•K, or > 1 W / m•K, or most preferably > 1.5, W / m•K, or < 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. Additionally, the viscosity of A-side and B-side allows for easy processing of the material. 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 thermal compositions may have a Shore OO hardness of 60 or more, 65 or more, or 70 or more, such as in the range of 60 to 85. Thermally conductive compositions may have sufficient adhesion to secure battery components during operation, while also having relatively low pull force during disassembly without undue stress or damage. Pull force measurements are conducted utilizing an MTS frame operating in tensile test mode. To create each test specimen, two Aluminum T-bars with planar surface dimensions of 3” x 3” are employed. The process is conducted by uniformly dispensing the mixed isocyanate and isocyanate-reactive components onto one of the T-bars. To ensure a consistent bond line thickness, several 1 mm diameter steel balls are placed between the top and bottom T-bars. Subsequently, the specimens are cured at 60°C for a duration of twenty-four hours or 14 days at room temperature to achieve complete curing. Following the curing process, the test specimen is affixed within the MTS frame utilizing a manual grip. During each individual test, the bottom T-bar remains stationary while the top T-bar is displaced at 0.25 mm / s. The resulting force exerted during this procedure is recorded using a 1 kN load cell. Typically, the force response exhibits a linear relationship until the point of bond line failure occurs. The maximum force recorded at this juncture is defined as the pull force. Thermally conductive compositions disclosed herein may have a pull force of less than 0.20 MPa, less than 0.15 MPa, or in a range of 0.05 MPa to 0.15 MPa. 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 Component Description Blocked TDI-based blocked isocyanate prepolymer prepared from polypropylene Isocyanate oxide (~3 kDa), with 2.7 % NCO before blocking with cardanol, viscosity Prepolymer 15,000-30,000 Pa•s and equivalent weight NCO 1555 Da Amine-1Triamine based on polypropylene glycol backbone with a molecularweight of 5000 Amine-2Triamine based on polypropylene glycol backbone with a molecularweight of 440 FillerHydrophobically surface treated aluminum trihydrate (ATH) with a D10 of0.5 microns, D50 of 8 microns and D90 of 80 micronsPlasticizerBis(2-(2-butoxyethoxy)ethyl) adipate, viscosity of 18 cps to 23 cps, boilingpoint 417 °C, and water solubility 570 mg / LCatalyst Diazabicyclo[5.4.0]undec-7-ene Silane Hexadecyltrimethoxysilane, boiling point 350 °C Internal Mold Internal mold release agent, fatty acid ester of pentaerythritol and C16-C20 Release (IMR)-1 fatty acids with varying degree of unsaturation. C69H124O8IMR-2Internal mold release agent, fatty acid ester of pentaerythritol andpalmitoleic acid and sebacic acidIMR-3Internal mold release agent, fatty acid ester with pentaerythritol and C16fatty acid with varying degree of unsaturation. C63H114O10Comp. IMR-1 Castor oil Comp. IMR-2 Zinc stearate Comp. IMR-3 2-ethyl hexyl oleate In the following example, were prepared and analyzed for bulk properties and adhesive (pull off) performance. Sample formulations were prepared by mixing the compounds for the isocyanate component (Part A) and the isocyanate-reactive component (Part B) separately in a high speed mixer. For curing, Part A and Part B were mixed in 1:1 weight ratio and allowed to cure at specified conditions. Formulations are shown in Tables 2 and 4, where values are in grams, unless otherwise indicated. For all examples, Part A was held constant, while different formulations of B-side where surveyed. Table 2: Formulations for comparative examples Part A Part BCE-1 CE-2 CE-3 CE-4Blocked Prepolymer15 0 0 0 0Amine-1 0 10 10 10 10 Amine-2 0 0.65 0.65 0.65 0.65 Colorant 0.5 0 0 0 0 Catalyst 0 0.020 0.05 0.05 0.032 Plasticizer 17.5 28.04 23.01 25.51 18.03 Comp. IMR-1 - - 5.00 - - Comp. IMR-2 - - - 2.50 - Comp. IMR-3 - - - 10 Hexadecyltrimethoxy ne5.0- - - - sila0Filler 212 211.29 211.29 211.29 211.29 Total 250.00 250.00 250.00 250.00 250.00 Table 3: Formulations for inventive examples Part A Part BIE-1 IE-2 IE-3Blocked Prepolymer 15 0 0 0 Amine-1 0 10 10 10 Amine-2 0 0.65 0.65 0.65 Colorant 0.5 0 0 0 Catalyst 0 0.045 0.04 0.04 Plasticizer 17.5 23.31 23.02 24.31 IMR-1 - 5.00 - - IMR-2 - - 5.00 - IMR-3 - - - 5.00 Hexadecyltrimethoxy silane 5.00 - - - Filler 212 211 211.29 210 Total 250.00 250.00 250.00 250.00 Physical properties were tested for each cured sample as follows. The thermal conductivity was measured using the Hot Disk Thermal Constants Analyzer (TPS 2500S, Thermtest Instruments, Canada) per ISO 22007-2. All measurements are completed with a thermal probe using a double-sided measurement with two-6 mm cups, at 150 W heating power and 5 s measurement time. Hardness was measured using a Shore OO durometer per ASTM D2240. Target values for inventive samples is a hardness in the range of 60-80 Shore OO. 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 pull force measurement was conducted utilizing an MTS frame operating in tensile test mode. To create each test specimen, two Aluminum T-bars with planar surface dimensions of 3" x 3" were employed. The process commenced by uniformly dispensing the mixed A+B-side onto one of the T-bars. To ensure a consistent bond line thickness, several 1 mm diameter steel balls were placed between the top and bottom T-bars. Subsequently, the specimens were cured at 60°C for a duration of twenty-four hours or at room temperature for 14 days or longer to achieve complete curing. Following the curing process, the test specimen was affixed within the MTS frame utilizing a manual grip. During each individual test, the bottom T-bar remained stationary while the top T-bar underwent displacement at a controlled rate of 0.25 mm / s. The resulting force exerted during this procedure was captured utilizing a 1 kN load cell. Typically, the force response exhibited a linear relationship until the point of bond line failure became apparent. The maximum force recorded at this juncture was documented as the pull force. The qualitative mode of failure was also recorded, where CF designates cohesive failure and AF designates adhesive failure. Results for physical property testing are provided in Tables 4 and 5.

[0002] Table 4: Physical Properties for comparative examples Performance target Part A CE-1 CE-2 CE-3 CE-4 Thermal Conductivity [W / m.K]- 2.250 2.126 2.086 2.142 1.934Squeeze force [N]- 93 67 82 135 47Pull force [MPa] < 0.15 MPa 0.19 0.23 0.195 0.163 Failure mode AF CF CF CF CF Table 5: Physical Properties for inventive examples Performance target Part A IE-1 IE-2 IE-3 Thermal Conductivity [W / m.K] - 2.250 2.160 2.249 2.146 Squeeze force [N] - 93 92 127 108 Hardness-Shore OO 60 - 80 - 70 70 70 Pull force [MPa] < 0.15 MPa - 0.122 0.093 0.115 Failure mode Adhesive failure (AF) - AF AF AF Results indicate that comparative samples, including CE-1 with no IMR agent, all exhibited unacceptably high pull off forces when compared to the inventive samples. In contrast inventive samples IE-1-3 containing IMR agents per this invention show a low pull force (<0.15 MPa) with adhesive failure. 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 catalysts selected from a group consisting of carboxylate salts, tertiary amines, amidines, guanidines, and diazabicyclo compounds; and 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; and a thermally conductive filler, wherein the thermally conductive composition has a thermal conductivity of greater than 1 W / m.K.

2. The compositions of claim 1, wherein the internal mold release agent has a formula of R1(OH)n-x(OC=OR2)x, where R1is a C3 to C10 polyol, n is in a range of 2 to 8; R2is a C8 to C20 carbon chain, x is 1 to 3 with the proviso that n is at least 1 more than x.

3. The compositions of claim 1, wherein the internal mold release agent is present at a percent by weight of the thermally conductive composition ranging from 1 wt% to 5 wt%.

4. The composition of claim 1, wherein the thermally conductive composition has a pull force of 0.15 MPa or less.

5. The compositions of claim 1, wherein the thermally conductive composition has a squeeze force 150 N or less.

6. The compositions of claim 1, wherein the thermally conductive composition has a hardness according to ASTM D-2240-15 in the range of 60 to 80 Shore OO.

7. The composition of claim 1, wherein the one or more polyetheramines comprise: 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 more; andat 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.

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

9. The composition of claim 1, further comprising one or more glycol ether ester plasticizers selected from a group of glycol ether esters of the Formula (I): (I) wherein R1 is a carbon chain including 2 to 12carbon atoms, R2is or a saturated, unsaturated, and / or substituted carbon chain including 2 to 12 carbon atoms, and n is an integer ranging from 1 to 4; Formula (II): (II)substituted 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; or Formula (III): wherein R1and / or 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.

10. A method of using the thermally conductive composition of any one of claims 1 to 9, 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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