Thermally conductive compositions with adhesive strength

Abstract

Thermally conductive compositions include: an isocyanate component containing: one or more blocked isocyanates; one or more aliphatic epoxy resins; and one or more epoxy silanes; an isocyanate-reactive component containing: one or more polyamines; 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 0.5 W / m.K. Methods of using thermally conductive compositions include 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.

Description

[0001]THERMALLY CONDUCTIVE COMPOSITIONS WITH ADHESIVE STRENGTH FIELD Embodiments relate to thermally conductive compositions for use as thermal interface materials such as adhesives, gap filler, sealant, gap pads, or paste in applications requiring thermal management such as electronics and automotive applications, and methods for using same. BACKGROUND 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 assembling heat sources (e.g., battery components, cells) into contact with a heat sink (e.g., cooling plate )that redirects heat from sensitive components. For efficient cooling, good thermal contact between the heat source and heat sink is needed, which often involves minimizing air gaps that can form from minor variations in opposed surfaces. A thermal interface material bridges air gaps between surfaces and provides thermal contact between the heat source and the heat sink. As battery designs and specifications evolve over time, thermal interface material compositions having higher adhesive properties are needed as operating conditions and mounting options change. However, solutions are limited for thermal interface materials having increased adhesive properties, and current materialsare often associated with disadvantages such as (1) the presence of hazardous materials including residual monomeric isocyanate; (2) incompatibility with low density / cost fillers; and (3) moisture sensitivity and low overall shelf life. Summary In an aspect, embodiments disclosed herein are directed to thermally conductive compositions that include: an isocyanate component containing: one or more blocked isocyanates; one or more aliphatic epoxy resins; and one or more epoxy silanes; an isocyanate-reactive component containing: one or more polyamines; 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 0.5 W / m.K. In another aspect, embodiments disclosed herein are directed to methods of using a thermally conductive composition, 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. Detailed Description Embodiments relate to thermally conductive compositions for forming polyurethane-based materials with high adhesive strength and minimal or no amounts of free isocyanate. Thermally conductive compositions include a two-part polyurethane system having an isocyanate component containing a blocked isocyanate prepolymer, an aliphatic epoxy resin, and an epoxy silane, and a isocyanate-reactive component containing an amine. In some cases, thermally conductive compositions may have high adhesive strength (> 1 MPa lap shear strength), and good mechanical properties such as high elongation (>10%). Compositions disclosed herein may be used in thermal management applications, including enhancing heat transmission in electronic devices, batteries, automotive applications, and the like. Methods disclosed herein may include use of a thermally conductive composition as an adhesive and / or gap filler for applications requiring thermal management, such as electric vehicle batteries. 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. 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 as measured by ISO 22007-2 using hot disc or by ASTM D-5470 of greater than 0.5 W / m•K, 1.0 W / m•K, greater than 1.5 W / m•K, or greater than 2.0 W / m•K. 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, epoxy resins, epoxy silanes, and other additives such as 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% or more, or 2.5% or more, and at the same time, 30% or less, 25% or less, or 20% or less, or in a range of 2.5% to 25%. 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 25% NCO before blocking with a blocking agent such as cardanol. In some cases, the blocked isocyanate is a reaction product of a phenolic blocking agent and a NCO prepolymer. 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 1.5 wt% to 15 wt%. Aliphatic Epoxy Resin The isocyanate component may include an aliphatic epoxy resin that includes reactive oxirane groups, also termed “epoxy groups” or “epoxy functionality.” In some cases, epoxy resins include polyfunctional epoxy resins have an epoxy functionality of 2 or more, or 3 or more, such as in a range of 2 to 8, or 3 to 8. Aliphatic epoxy resins may include polyglycidyl ethers formed by double bond epoxidation or through a reaction with epichlorohydrin. Suitable aliphatic epoxy resins include, for example, polyols having two or more hydroxyl groups modified to contain epoxy functionalities, where the polyol may be derived from an alkyl polyol, polyether, or polyester. Examples of aliphatic epoxy resins include polyglycidyl ethers such as ethane-1,2-diol diglycidyl ether, propane-1,2-diol diglycidyl ether, propane-1,3-diol diglycidyl ether, butanediol diglycidyl ether, pentanediol diglycidyl ether (including neopentyl glycol diglycidyl ether), hexanediol diglycidyl ether, diethylene glycol diglycidyl ether, dipropylene glycol diglycidyl ether, higher polyoxyalkylene glycol diglycidyl ethers, higher polyoxyethylene glycol diglycidyl ethers and polyoxypropylene glycol diglycidyl ethers, co- polyoxyethylene-propylene glycol diglycidyl ethers, polyoxytetramethylene glycol diglycidyl ethers, polyglycidyl ethers of glycerol, hexane-1,2,6-triol, of trimethylolpropane, trimethylolethane, pentaerythritol, or sorbitol, polyglycidyl ethers of oxyalkylated polyols (for example of glycerol, trimethylolpropane, pentaerythritol, and the like), diglycidyl ethers of cyclohexanedimethanol, bis(4-hydroxycyclohexyl)methane, 2,2-bis(4- hydroxycyclohexyl)propane, polyglycidyl ethers of triglycerides such as castor oil, triglycidyl tris(2-hydroxyethyl)isocyanurate, and the like. In some cases, the aliphatic epoxy resin may be a triglycidyl ether of castor oil or a triglycidyl ether of trimethylol ethane. The isocyanate component may include an aliphatic epoxy resin at a percent by weight (wt%) of 0.5 wt% to 20 wt%, 1 wt% to 15 wt%, or 1.5 wt% to 10 wt%. Aliphatic Epoxy resins may have an equivalent epoxy weight (EEW) according to ASTM D1652-11(2019) 100 g / mol epoxy equivalents or more, such as in a range of 50 g / mol to 1200 g / mol, or 100 g / mol to 1000 g / mol. Epoxy Silane Isocyanate components may include one or more epoxy silanes that may function as stabilizers and / or adhesion promoters. Epoxy silanes disclosed herein are bifunctional organosilanes, where “bifunctional” refers to organosilanes that include at least on silane functionality and at least one electrophilic functionality (i.e., epoxy for epoxy silane). In some cases, epoxy silanes may have a general chemical structure of Si(OR)n(R’Y)4-n, where n is an integer from 1 to 3, R is independently a C1 to C5 alkyl group, R’ is a C1 to C20 hydrocarbon, and Y is an electrophilic epoxy functional group. In some cases, R’ is a linear or branched, saturated or unsaturated, cyclic or aromatic C1 to C20 hydrocarbon. For example, epoxy silanes may include 3-glycidoxypropyl trimethoxysilane, 3-glycidoxypropyl triethoxysilane, 3- glycidoxypropyl methyldimethoxysilane, 4-glycidoxybutyl trimethoxysilane, 5,6-epoxyhexyl triethoxysilane, 2-(3,4-epoxycyclohexyl) ethyltrimethoxysilane, or 2-(3,4-epoxycyclohexyl) ethyltriethoxysilane, and the like. Epoxy silanes may be added optionally to the isocyanate component at a percent by weight (wt%) up to 10 wt%, such as ranging from 0.1 wt% to 10 wt%, or 0.25 wt% to 5 wt%. B.) Isocyanate-reactive component The isocyanate-reactive component (or B-side) may contain of one or more of polyamines, catalysts, and additives such as plasticizers and thermally conductive fillers. Polyamines The isocyanate-reactive component may include one or more polyamines containing primary and / or secondary amine functionality, including aliphatic polyamines and polyether polyols terminated with primary and / or secondary amines (i.e., polyetheramines). The polyamines may have an amine functionality of 2 or more, or 3 or more, such as in a range of 2 to 8, or 3 to 8, or 3 to 6. In some cases, polyamines may include ethyleneamines, such as ethylenediamine (EDA), diethylenetriamine (DETA), 2,4-diamino-3,5-diethyl-toluene, 2,6-diamino-3,5-diethyl- toluene (DETDA), dimethylthiotoluenediamine (DMTDA), 4,4'-methylene-bis-(2- chloroaniline)), triethylenetetramine (TETA), tetraethylenepentamine (TEPA), pentaethylenehexamine (PEHA), piperazine, morpholine, substituted morpholine, piperidine, substituted piperidine, diethylenediamine (DEDA), aminoethylpiperazine, 4,4'-methylenebis(3- chloro-2,6-diethylaniline), C1-C3 dialkyl toluenediamines such as 3,5-dimethyl-2,4- toluenediamine, 3,5-dimethyl-2,6-toluenediamine, 3,5-diethyl-2,4-toluenediamine, 3,5-diethyl- 2,6-toluenediamine, 3,5-diisopropyl-2,4-toluenediamine, 3,5-diisopropyl-2,6-toluenediamine, and the like The isocyanate-reactive component may include one or more polyetheramines, including monoamines, diamines, and higher order amines (e.g., triamines, tetramines, etc.). The polyether amines may have a amine functionality of 2 or more, or 3 or more, such as in a range of 2 to 8, or 3 to 8, or 3 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). 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 polyamine 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%. Polyamines may be added to an isocyanate-reactive component at a percent by weight (wt%) of 10 wt% or more, such as in a range of 2 wt% to 60 wt%, 3 wt% to 50 wt%, or 5 wt% to 40 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 2 W / m•K, such as in a range from 1 W / m•K to 1000 W / m•K. Fillers disclosed herein may be low density reduce overall weight of the composition and effective weight in applications such as automotive and EV. In one embodiment, the filler density is less than 6 g / cc, less than 4 g / cc, or less than 2.5 g / cc, such as in a range of 1 g / cc to 5 g / 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, precipitated silica, fused silica, and the like. 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 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. 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. Thermally conductive compositions may include one or more fillers having surface functionalization. The thermally conductive fillers of the present disclosure can be modified with a treating agent before or after 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 in the resulting thermally conductive composition. In some cases, treating agents may be applied to the thermally conductive filler as a pre-treatment prior to introduction into the A-side and / or B-side. The concentration may vary depending on the nature of the treating agent and the thermally conductive filler . Treating agents disclosed herein may be added to thermally conductive filler as a pre- treatment or added in situ during production of part A and part B at a percent by weight (wt%) of the thermally conductive filler of 0.01 wt% to 10 wt%, 0.05 wt% to 7.5 wt%, or 0.5 wt% to 5 wt%. Treatment agents may include fatty acids, silane treating agents, titanates, zirconates, aluminates, or silazane compounds. Treating agents may include the use of silane chemistries including organosilane treating agents, such as those having the formula: R1(4-n)Si(OR2)n, where R1is an alkyl or substituted alkyl group (e.g., substituted with functional groups above) having 1 to 20 carbon atoms, R2is H or C1-C5 alkyl group, and n is an integer from 2 to 4. Examples of organosilanes include dimethoxydimethylsilane, dimethoxydiethylsilane, diethoxydimethylsilane; trimethoxymethylsilane, trimethoxyethylsilane, trimethoxypropylsilane, triethoxymethylsilane, triethoxyethylsilane, trimethoxyhexadecylsilane and the like. In some cases the organosilane treating agent may be a C5 to C20 organosilane. Thermally conductive filler may be present at a percent by weight of the total weight of the composition (wt%) ranging from 5 wt% to 80 wt%, 10 wt% to 80 wt%, or 10 wt% to 70 wt%. The thermally conductive filler may be loaded in the A-side and / or B-side in equal or differing amounts that, when combined, result in an adhesive composition having a thermally conductive filler concentration within any of the above ranges. For example, the isocyanate component and isocyanate-reactive component, respectively, may contain 10 wt% to 80 wt% of thermally conductive filler , resulting in a total wt% of 10 wt% to 80 wt%. Further, different thermally conductive filler sizes / types may be blended to obtain the desired thermally conductive filler loading and viscosity of a formulation. In some cases, thermally conductive filler may be an aluminum trihydrate. Thermally conductive filler may have D10 in the range of 0.1 to 10 microns, D50 in the range of 5 to 50 microns, and D90 in the range of 50 to 200 microns. Plasticizer Thermally conductive compositions disclosed herein may include one or more plasticizers that may reduce the viscosity or squeeze force of the composition before and after combination of the isocyanate and isocyanate-reactive components. 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 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). 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 or 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%. Catalysts can include organometallic compounds, tertiary amines, blocked amines, 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 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 catalysts are POLYCAT®8, DABCO®33-LV, and DABCO®T-12 from Evonik, among other commercially available catalysts. 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. Additional examples of 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 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 t 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. Ambient temperatures may range 15 °C to 35 °C, where room temperature is often around 23 °C. . The latent catalyst is often a subset of tertiary amine 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, tataric 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 thermally conductive composition at a percent by weight (wt%) ranging from 0.1 wt% to 7 wt%, or 1 wt% to 5 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. C. Method of Preparation 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 electrophilic functional groups (i.e., total blocked isocyanate and epoxy groups combined) to amine reactive groups is in the ranges of 1:2 to 1.5:0.5, such as 1.1:0.9, 1.05:0.95, or 1.5:0.5. 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 1:2 to 2:1. 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 or adhesion strength. Cured thermally conductive compositions may have a lap shear strength according to ASTM D3163 on PET / PET of 0.5 MPa or more, 0.8 MPa or more, such as in a range of 0.5 MPa to 12 MPa. Cured thermally conductive compositions may have an elongation at break according to ASTM D1708 of 5% or more, 10% or more, or 15% or more, such as in a range of 5% to 50%, or 10% to 45%. 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 5 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 1.6 to 3.1 gm / cc. Thermally conductive compositions disclosed herein may function as a gap filler and / or adhesive for energy storage devices and in electric vehicle battery assembly and thermal management. In some cases, the compositions may include gap fillers and adhesives that are applied between a heat source and a heat sink to provide a thermally conductive interface, such as between a battery cell or 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 the mixture to a first substrate (optionally allowing time for cure), followed by application of a second substrate to the first substrate. Examples of substrates may include battery cell(s) modules, surfaces or components, cooling plate, and composite articles may include a battery pack and / or module. Additionally, thermally conductive compositions may be used to form pre-cured articles such as thermal interface gap pads and / or adhesives. 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. 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. Table 1 provides the materials used in the following examples. Table 1: Materials used in the examples N m D ri ti n Polyamine-2 Polypropylene glycol triamine; molecular weight of 440 Polyamine-3 Triethylenetetramine a y es s o epo y e s Blocked Prepolymer-2: 124 grams (1424 mEq.) of Toluene diisocyanate (T-80 Type I) was charged in 500 ml oven dry reactor and set up with overhead stirrer under nitrogen.276 grams of polyol (280.6 mEq.) and 100 ppm of dibutyl tin dilaurate (T-12) catalyst (0.04 grams) were then added. The mixture was then stirred and heated to 80oC. Temperature was held for 2 hours until desired NCO was achieved. % NCO = 12.23, Viscosity = 1.12 Pa.s at ambient temperature. For the blocking reaction, 150 grams of 12.23 % TDI Prepolymer (0.4411 Eq. NCO) was charged in a 500 ml dry reactor and set up with overhead stirrer under nitrogen. The mixture was heated to 80oC with stirring and ~1000 ppm of Dabco 33LV catalyst and 139 grams of Cardanol (0.4633 Eq.) were then added and reacted for 2 hours. Isocyanate concentration was analyzed using FT-IR, as a second aliquot of ~1000 ppm of Dabco 33LV catalyst was added and continued for 3 hours. 1.0 wt. % MPEG (2.80 grams) was then added and reacted at 80oC for 1 hour. Isocyanate concentration was found to be 0.14% by FT-IR signaling blocking completion. 0.7 grams of Benzoyl Chloride was charged to neutralize amine catalyst, and the product was collected. Blocked Prepolymer-3: 132.15 grams (1517.2 mEq.) of Toluene diisocyanate (T-80 Type I) was charged in 500 ml oven dry reactor and set up with overhead stirrer under nitrogen.168.3 grams of Voranol CP6001 polyol (84.36 mEq.) and 100 ppm of T-12 catalyst (0.03 grams) were added and the mixture was heated to 80oC for 2 hours and desired NCO was achieved. % NCO =19.5, Viscosity = 0.4537 Pa.s at ambient temperature. For the blocking reaction, 140 grams of 19.5 % TDI Prepolymer (0.6489 Eq. NCO) was charged in a 500 ml dry reactor and set up with overhead stirrer under nitrogen and heated to 80oC. ~4200 ppm of T-12 catalyst (1.30 grams) and 166 grams of Cardanol (0.5541 Eq.) were then added. Temperature reached to 65oC in ~ 10 minutes and reaction continued for 16 hours. Viscosity was measured and found to be 24.96 Pa.s at ambient temperature. Blocked Prepolymer-4: 138.75 grams (1593 mEq.) of toluene diisocyanate (T-80 Type I) was charged in 500 ml oven dry reactor with overhead stirrer under nitrogen. 161.45 grams of Voranol 2000LM polyol (163.67 mEq.) and 100 ppm of dibutyl tin dilaurate T-12 catalyst (0.03 grams) were added and the mixture was heated to 80oC for 2 hours. % NCO =19.77, Viscosity = 0.2928 Pa.s at ambient temperature. For the blocking reaction, 140 grams of 19.77 % TDI Prepolymer (0.6590 Eq. NCO) was charged in 500 ml dry reactor with stirrer under nitrogen and heated to 80oC. ~4500 ppm of T-12 catalyst (1.40 grams) and 168 grams of Cardanol (0.56 Eq.) were added and temperature reached to 65oC in 10 minutes. The mixture was reacted for 16 hours. Viscosity was measured and found to be 19.02 Pa.s at ambient temperature. Thermal conductivity: 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: measured using a texture analyzer equipped with a 50 kg load cell. After dispensing the material 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. The test was then 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”. Lap Shear Measurement: Corresponding A and B parts were added to a cup in 1:1 ratio by vol and mixed using a high-speed mixer. Immediately after mixing, the resultant paste material was sandwiched between two rigid metal plates with PET foil affixed using a PSA backing. Adhesive thickness was 1 mm and the area of overlap between the plates was 1 inch x 1 cm. The samples are then allowed to cure at 23°C for one week. After curing, the two aluminum plates were loaded into a mechanical testing frame equipped with 2.5 kN load cell and separated by pulling at a rate of 10 mm / min in a direction parallel to the plane of adhesion. Peak mechanical load during rupture was recorded for each sample and reported as lap shear strength. Elongation at break measurement: performed according to ASTM standard D412. Corresponding A and B parts were mixed using a high-speed mixer. Immediately after mixing, the resultant paste material was sandwiched between two polytetrafluoroethylene sheets and cured for one week at room temperature to give an approximately 2mm thick plaque. Polytetrafluoroethylene sheets were removed from the plaque and dog bone specimens were cut from the plaques according to ASTM D412 Die C specifications and pulled on a mechanical testing frame until rupture. Peak mechanical load and extension of specimens were recorded during rupture. Example 1: Thermally conductive composition preparation and properties For the preparation of the sample formulations, individual components were combined by a high-speed mixer. A-Side and B-Side of the formulation were prepared separately. For curing the two-part system, A and B sides were mixed in 1:1 weight ratio by high-speed mixer. Results are shown in Tables 2-4. For Tables 2 and 3, lap shear samples were cured at 60°C for 1 day. For Tables 4 and 5, lap shear samples were cured at room temperature for 7 days. Table 2: Comparative formulations and properties for Example 1 CE1 CE2 e 5 Table 3: Formulations and properties for Example 1 e Blocked Prepolymer-1 16 0 Blocked Prepolymer-2 16 0 1 5 8 Table 4: Inventive formulations and properties for Example 1 IE-2 IE-3 IE-4 de 2 0 8 Table 5: Inventive formulations and properties for Example 2 e Polyamine-2 2.92 2.92 2.92 Polyamine-3 12.72 12.72 6 5 aliphatic epoxy resin, and exhibited low adhesive strength. Similarly, comparative samples including only added epoxy silane (CE-2) or aliphatic resin (CE-3) exhibited low adhesive strength (lap shear <0.5). In contrast, IE 1-4 show compositions with high adhesion strength. Compositions IE5-IE7 formulated with epoxy resin and epoxy silane exhibited fast curing kinetics, high adhesion strength, and good elongation 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 thermally conductive composition, comprising: an isocyanate component comprising: one or more blocked isocyanates; one or more aliphatic epoxy resins; and one or more epoxy silanes; an isocyanate-reactive component comprising: one or more polyamines; 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 0.5 W / m.K.

2. The composition of claim 1,wherein the aliphatic epoxy resin has an epoxy functionality of 2 or more.

3. The composition of claim 1, wherein the aliphatic epoxy resin has an equivalent epoxy weight according to ASTM D1652-11(2019) 100 g / mol epoxy equivalents or more.

4. The composition of claim 1, the blocked isocyanates comprising 2% to 25% NCO prior to blocking.

5. The composition of claim 1, wherein the epoxy silane has a chemical structure of Si(OR)n(R’Y)4-n, where n is an integer from 1 to 3, R is independently a C1 to C5 alkyl group, R’ is a C1 to C20 hydrocarbon, and Y is an epoxy functional group.

6. The composition of claim 1, wherein the blocked isocyanate is a reaction product of a phenolic blocking agent and a NCO prepolymer.

7. The composition of claim 1, wherein the thermally conductive filler is aluminum trihydrate.

8. The composition of claim 1, wherein the one or more polyamines 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.

9. The composition of claim 1, further comprising one or more 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%.

10. A method of using the thermally conductive composition, the method comprising combining an isocyanate component and an isocyanate reactive component; the isocyanate component comprising: one or more blocked isocyanates; one or more aliphatic epoxy resins; and one or more epoxy silanes; and the isocyanate-reactive component comprising: one or more polyamines; 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, wherein the thermally conductive composition has a thermal conductivity of greater than 0.5 W / m.K.