Thermally conductive adhesive composition

Abstract

Provided is a thermally conductive adhesive facilitating improved bonding and heat management in electronics applications, with particular benefits to battery systems. The thermally conductive adhesive includes two components, a Part A containing silyl-terminated polymers and amino-functional compounds, and Part B containing an epoxy resin and water. Both components may further include inorganic fillers with high thermal conductivity, such as aluminum oxide, boron nitride, aluminum trihydroxide, or silicon, to further improve heat dissipation and electrical insulation. The silyl-terminated polymers include both α-silyl terminated polymers and conventional or γ-silyl terminated polymers in a specified ratio. The use of both α-silyl terminated polymers and conventional or γ-silyl-terminated polymers enables tunable curing characteristics and precise control over property development.

Description

[0001] WS 12406 KE

[0002] THERMALLY CONDUCTIVE ADHESIVE COMPOSITION

[0003] FIELD OF INVENTION

[0004] The present invention relates to thermally conductive adhesives based on multi-component systems, including silyl-terminated polymers and epoxy-based constituents. Such thermally conductive adhesives provide strong bonds and excellent heat dissipation which can improve the safety and performance of electronics and are particularly beneficial when used in battery infrastructure.

[0005] BACKGROUND

[0006] In the field of electric vehicles (EVs), common battery architectures include cell-to-module (CTM), cell-to-pack (CTP), and cell-to-chassis (CTC). In CTM architectures, conventional gap fillers and pads may be sufficient for thermal management. However, CTM architectures are heavier, more complex, and less energy dense than CTP and CTC architectures. Accordingly, CTP and CTC architectures are growing in popularity. Without a module, batteries in these designs require strong adhesive bonding to prevent cell migration and damage. Additionally, these adhesives are also required to have high thermal conductivity to facilitate heat transfer and mitigate thermal runaway. As battery cells in CTP and CTC designs are less shielded from environmental stresses such as temperature changes, moisture ingress, and mechanical vibrations, thermally conductive adhesives also need to withstand harsh environmental conditions.

[0007] Existing thermally conductive adhesives use epoxy, acrylic, or polyurethane (PU) chemistries. Each type of chemistry results in a unique set of advantages and disadvantages. Epoxy-based systems generally afford strong adhesion and high mechanical strength but lack flexibility and are susceptible to breakage. Urethane adhesives tend to exhibit high elasticity, but typically have lower adhesive strength than epoxies and acrylics. The properties of PU-based materials also tend to degrade over time with exposure to high temperatures, and one-component systems typically require water to fully cure, thereby introducing moisture to the battery system. Acrylic adhesives cure quickly, have good chemical resistance, and high hardness. On the other hand, acrylic systems tend to be brittle and lack flexibility, much like epoxy adhesives, due to their high glass transition temperatures. Furthermore, each of these systems is based on organic polymers and may fail to pass the stringent safety requirements for preventing thermal runaway. WS 12406 KE

[0008] Existing silicone-based thermally conductive adhesive address many of the aforementioned issues. Silicone-based adhesives have high flexibility, broad chemical and thermal stability, and excellent flame retardance. Untreated silicone elastomers exhibit a much lower glass transition temperature than most organic polymers, about -130 to -120 °C, and are stable up to around 200 °C, or 300 °C with the addition of thermal stabilizers. Moreover, key properties including flexibility, dielectric strength (approximately 18-27 kV / mm), chemical resistance, and moisture resistance are nearly constant over temperatures ranging from about -50 to 150 °C. Silicone elastomers are also highly flame-resistant with typical ignition temperatures of approximately 450 °C, flash points of around 750 °C, and limiting oxygen index (LOI) values well above 21%, the approximate concentration of oxygen in the air. Therefore, silicones inherently do not sustain combustion and are well-suited to applications requiring flame retardance. This combination of properties makes silicones well-suited to EV battery applications.

[0009] However, existing silicone-based adhesives suffer from a limited pot life (working time) based on their cure, reducing reworkability and adding complications and costs to manufacturing processes. Existing silicone-based adhesives also offer minimal control over curing characteristics and property development, which makes them unsuitable for certain manufacturing operations. Accordingly, there is a need for a silicone-based, thermally conductive adhesive with highly tunable curing characteristics and property development.

[0010] BRIEF SUMMARY OF INVENTION

[0011] A thermally conductive adhesive is provided. The thermally conductive adhesive is formed by combining a Part A and a Part B to initiate curing. Part A includes a first curing system with silyl- terminated polymers of at least two different formulas and an amino functional compound. Part B includes a second curing system with an epoxy resin and water. Either Part A, Part B, or both parts further include inorganic fillers.

[0012] In some embodiments, the inorganic fillers may have a thermal conductivity of at least 10 W / m-K and may include aluminum oxide, aluminum trihydroxide, magnesium oxide, magnesium hydroxide, zinc oxide, boron nitride, aluminum nitride, or silicon. In certain embodiments, Part A and Part B both include the inorganic filler.

[0013] In some embodiments, the thermally conductive adhesive may further include silicone resins, silicone fluids, or water scavengers. WS 12406 KE

[0014] BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

[0015] The above, as well as other advantages of the present invention will become readily apparent to those skilled in the art from the following detailed description when considered in the light of the accompanying drawings in which:

[0016] FIGS. 1-4 are graphs depicting the development of the storage modulus over time of samples of thermally conductive adhesives.

[0017] FIGS. 5-7 are graphs depicting the development of the loss factor over time of samples of thermally conductive adhesives.

[0018] FIGS. 8-9 are graphs depicting failure modes for samples of thermally conductive adhesives.

[0019] DETAILED DESCRIPTION

[0020] Hereinafter, the present invention will be described in detail. However, it should be understood that the present invention is not limited to the following embodiments, and that various elements may be variously modified or selectively mixed according to need. Accordingly, it is to be understood that the invention includes all modifications, equivalents, and alternatives falling within the spirit and scope of the present invention.

[0021] In addition, throughout this specification, when an element is referred to as "including" an element, it is understood that it may include other elements as well, not meaning excluding other elements unless specifically stated otherwise. The terms "about", "substantially", and the like used in the present specification are to be understood, when manufacturing and material tolerances inherent in the meanings mentioned are presented, as they mean "the numerical value" or "in close proximity to the numerical value", and not in a limiting sense.

[0022] Unless defined otherwise, all terms (including technical and scientific terms) used herein may be used in a sense commonly understood by one of ordinary skill in the art to which this invention belongs. Also, commonly used predefined terms are not ideally or excessively interpreted unless explicitly defined otherwise.

[0023] In the present invention, a multi-component thermally conductive adhesive is provided. The thermally conductive adhesive is formed by combining a Part A and a Part B, wherein Part A comprises 5 to 50 wt% of silyl-terminated polymers. Part A further includes an amino-functional compound selected from the group consisting of accelerators, adhesion promoters, and WS 12406 KE combinations thereof. Part B includes an epoxy resin and water. At least one of part A and part B includes an inorganic filler.

[0024] Part A is formed by mixing silyl-terminated polymers, an amino functional accelerator and / or adhesion promoter, and optionally fillers, water scavengers, pigments, colorants, and additional additives. Part B is formed by mixing an epoxy resin, water, and optionally fillers, pigments, colorants, and additional additives.

[0025] This mixing operation can be conducted at temperatures between 0 and 30° C, and the pressure of the surrounding atmosphere, i.e., about 900 to 1100 hPa. If desired, the mixing operation may alternatively be conducted at higher temperatures, for example at temperatures in the range from 30 to 130° C. In addition, it is possible to mix intermittently or constantly under reduced pressure, for example at absolute pressures of 30 to 500 hPa, to remove volatile compounds and / or air from each of Part A and Part B. The mixing operation of the invention is preferably conducted without moisture and may be performed continuously or batchwise.

[0026] Part A and Part B are mixed to form a thermally conductive adhesive. Any mixing technique known in the art for multi-component adhesives may be used. Additionally, the aforementioned mixing process to form Part A and Part B individually may be used to effectively combine both parts.

[0027] In embodiments of the present invention, a ratio of Part A to Part B may range from 10: 1 to 1 :10, measured either volumetrically or by weight. In a preferred embodiment, the ratio of Part A to Part B is 1 :1 by volume, as most commercially available mixing and dispensing equipment is best adapted for a 1 :1 volumetric ratio.

[0028] Silyl-terminated Polymer

[0029] Polymer systems possessing reactive alkoxysilyl groups are well-established. On contact with water or atmospheric moisture, these alkoxysilane-terminated polymers condense with each other even at room temperature, with elimination of the alkoxy groups. Such materials are commonly used in the production of adhesives, especially of elastic adhesive systems.

[0030] Adhesives based on alkoxysilane-crosslinking polymers exhibit very good mechanical properties in the fully cured state, with both high tensile strength and elasticity. As an additional advantage, the prepolymers used in silane-crosslinking systems are non-toxic. However, the majority of existing alkoxysilane-crosslinking systems have low moisture reactivity, necessitating aggressive WS 12406 KE catalysis. The corresponding mixtures therefore typically include considerable quantities of toxic tin catalysts.

[0031] This may be overcome through the use of a-silane-terminated polymers, possessing reactive alkoxysilyl groups connected by a methylene spacer, referred to as an a spacer, to an adjacent urethane unit, a-silane-terminated polymers are substantially more reactive than the conventional y-silane-terminated polymers, in which the alkoxysilyl groups are connected via a propylene spacer, referred to as a y spacer, to an adjacent heteroatom, a-silane-terminated polymers generally do not require tin catalysts, strong acids, or bases to achieve high curing rates on air contact. a-silane terminated polymers are known and have been previously described, for example in EP-A 1 414 909. However, due to their extremely high reactivity, such polymers are difficult to work with in a production setting and, moreover, cannot be stabilized with conventional water scavengers such as vinyltrimethoxysilane.

[0032] Water scavengers are used in most adhesive formulations based on silane-terminated polymers, since it is difficult to prevent the ingress of small quantities of water, particularly in the form of the water absorbed on the surfaces of included fillers. Moreover, no container, tube, or cartridge is perfectly watertight, so water scavengers are often present even in filler-free systems. Water scavengers, such as vinyltrimethoxysilane, react with trace amounts of water, preventing the premature condensation of the silane-terminated polymers. However, due to the high reactivity of a-silane-terminated polymers, trace amounts of water preferentially react with the a-silane- terminated polymers, reducing the efficacy of conventional water scavengers.

[0033] In the present invention, the aforementioned problems are solved through the use of mixed silane curing systems, in which highly reactive a-silane-terminated polymers are used in conjunction with less reactive conventional silyl-terminated polymers, including but not limited to Y-silane-terminated polymers. It has been surprisingly found that mixed systems of a-silane- terminated polymers with conventional silyl-terminated polymers can be stabilized with conventional water scavengers, such as vinyltrimethoxysilane. Furthermore, it has been found that by varying the ratio of a-silane-terminated polymers to conventional silyl-terminated polymers (called the a:y ratio) in a multicomponent system with a secondary curing mechanism, curing characteristics and property development can also be adjusted to fit a variety of applications. a-silane-terminated polymers may be described through the formula WS 12406 KE

[0034] Y-[(CRi2)i-Si(OR)mRn]x (I) , and conventional silyl-terminated polymers may be described through the formula

[0035] Y-[(CR12)a-Si(OR)3]x (II), wherein Y is an x-valent polymer radical bonded via nitrogen or oxygen,

[0036] R may be identical or different and is a hydrogen atom or a monovalent, optionally substituted hydrocarbon radical,

[0037] R1may be identical or different and is a hydrogen atom or a monovalent, optionally substituted hydrocarbon radical which may be attached via nitrogen, phosphorus, oxygen, sulfur or carbonyl group to the carbon atom, x is an integer from 2 to 10, m is an integer from 1 to 3, n is an integer from 0 to 2, with the provision that the sum of m and n is 3, and a is an integer from 2 to 10.

[0038] Suitable examples of radicals R include alkyl radicals, such as the methyl, ethyl, n-propyl, isopropyl, 1 -n-butyl, 2-n-butyl, isobutyl, tert-butyl, n-pentyl, isopentyl, neopentyl, tert-pentyl radical; hexyl radicals, such as the n-hexyl radical; heptyl radicals, such as the n-heptyl radical; octyl radicals, such as the n-octyl radical, isooctyl radicals and the 2,2,4-trimethylpentyl radical; nonyl radicals, such as the n-nonyl radical; decyl radicals, such as the n-decyl radical; dodecyl radicals, such as the n-dodecyl radical; octadecyl radicals, such as the n-octadecyl radical; cycloalkyl radicals, such as the cyclopentyl, cyclohexyl, cycloheptyl radical and methylcyclohexyl radicals; alkenyl radicals, such as the vinyl, 1-propenyl and the 2-propenyl radical; aryl radicals, such as the phenyl, naphthyl, anthryl and phenanthryl radical; alkaryl radicals, such as o-, m-, p- tolyl radicals; xylyl radicals and ethylphenyl radicals; and aralkyl radicals, such as the benzyl radical, the a- and the [3-phenylethyl radical.

[0039] Suitable examples of substituted radicals R include haloalkyl radicals, such as the 3,3,3-trifluoro- n-propyl radical, the 2,2,2,2',2',2'-hexafluoroisopropyl radical and the heptafluoroisopropyl radical, and also haloaryl radicals, such as the o-, m- and p-chlorophenyl radical. WS 12406 KE

[0040] In a prefered embodiment, radical R comprises monovalent hydrocarbon radicals having 1 to 6 carbon atoms, more preferably alkyl radicals having 1 or 2 carbon atoms, most preferably the methyl radical.

[0041] Suitable examples of radicals R1include a hydrogen atom, the radicals indicated for R, and also optionally substituted hydrocarbon radicals bonded via nitrogen, phosphorus, oxygen, sulfur, carbon or carbonyl group to the carbon atom.

[0042] In a preferred embodiment, Radical R1comprises a hydrogen atom or hydrocarbon radicals having 1 to 20 carbon atoms, most preferably a hydrogen atom.

[0043] Polymer radical Y includes all polymers wherein at least 50%, preferably at least 70%, more preferably at least 90% of all the bonds in the main chain are carbon-carbon, carbon-nitrogen or carbon-oxygen bonds. Suitable examples of polymer radical Y include polyester, polyether, polyurethane, polyalkylene and polyacrylate radicals.

[0044] In a preferred embodiment, polymer radical Y comprises organic polymer radicals which as a polymer chain comprise polyoxyalkylenes, such as polyoxyethylene, polyoxypropylene, polyoxybutylene, polyoxytetramethylene, polyoxyethylene-polyoxypropylene copolymer and polyoxypropylene-polyoxybutylene copolymer; hydrocarbon polymers, such as polyisobutylene and copolymers of polyisobutylene with isoprene; polychloroprenes; polyisoprenes; polyurethanes; polyesters; polyamides; polyacrylates; polymethacrylates; vinyl polymer and polycarbonates, and which are preferably bonded via -O-C(=O)-NH-, -NH-C(=O)O-, -NH-C(=O)- NH-, -NR’-C(=O)-NH-, NH-C(=O)-NR’-, -NH-C(=O)-, -C(=O)-NH-, -C(=O)-O-, -O-C(=O)-, -O- C(=O)-O-, -S-C(=O)-NH-, -NH-C(=O)-S-, -C(=O)-S-, -S-C(=O)-, -S-C(=O)-S-, -C(=O)-, -S-, -O-, - NR’- to the group or groups -[(CR12)a-Si(OR)3], where R’ may be identical or different and has a definition indicated for R or is a group -CH(COOR“)-CH2-COOR“ in which R“ may be identical or different and has a definition indicated for R.

[0045] Radical R’ is preferably a group -CH(COOR“)-CH2-COOR“ or an optionally substituted hydrocarbon radical having 1 to 20 carbon atoms, more preferably a linear, branched or cyclic alkyl group having 1 to 20 carbon atoms, or an aryl group having 6 to 20 carbon atoms which is optionally substituted by halogen atoms. Examples of radicals R’ include cyclohexyl, cyclopentyl, n- and isopropyl, n-, iso- and t-butyl, the various stereoisomers of the pentyl radical, hexyl radical or heptyl radical, and the phenyl radical. WS 12406 KE

[0046] The radicals R“ are preferably alkyl groups having 1 to 10 carbon atoms, more preferably methyl, ethyl or propyl radicals.

[0047] In a preferred embodiment of formula (I), m is 2 and n is 1 , as tri-alkoxy a-silane terminated polymers have an increased curing rate which may excessively shorten the working time of the thermally conductive adhesive. In the most preferable embodiment, formula (I) may be expressed as Y-[(CR12)i-Si(OR)mCH3]x.

[0048] In a preferred embodiment of formula (II), the conventional silyl-terminated polymer is a y-silane- terminated polymer, thus a is preferably 3. y-silane-terminated polymers may be preferred due to their widespread commercial availability and lower cost.

[0049] Formula (I) is included in an amount of at least 10 wt%, preferably at least 20 wt%, more preferably at least 40 wt%, most preferably at least 60 wt% of the total weight of silyl-terminated polymers in Part A.

[0050] Formula (II) is included in an amount of at least 10 wt%, preferably at least 20 wt%, more preferably at least 30 wt%, most preferably at least 40 wt% of the total weight of silyl-terminated polymers in Part A.

[0051] The silyl-terminated polymer is included in an amount of 5 to 50 wt%, preferably 10 to 40 wt%, more preferably 15 to 30 wt%, based on a total weight of Part A.

[0052] In the present invention, the curing rate of the thermally conductive adhesive increases with increasing a content. The heteroatom (nitrogen, oxygen, or sulfur) in a-silane-terminated polymers enhances rates of both alkoxysilane hydrolysis and silanol condensation, facilitating reactions between polymer chain ends, adhesion promoters, water scavengers, and inorganic filler surfaces. At higher curing rates, key mechanical properties of interest, including shear modulus, ultimate tensile strength, and hardness, increase more quickly. The thermally conductive adhesive transitions from fluid-like to solid-like more rapidly, resulting in lower tack- free time (also referred to as “open time” or “working time”).

[0053] In certain applications, an increased curing rate with the corresponding increase in property development may be preferable to minimize manufacturing time. Conversely, a slower curing rate allows for debonding and reworking should errors occur during bonding of the substrates. Thus this invention has found that the a:y ratio can be adjusted according to the specific requirements of the manufacturing and assembly process, with higher a content resulting in WS 12406 KE faster development of structural adhesive properties, and higher y content resulting in extended tack-free time and greater re-workability.

[0054] The two-component adhesive does not require heating above room temperature (approximately 20-25 °C) in order to bond substrates and cure. The processes of hydrolysis / silanol condensation and epoxy ring-opening have different activation energies. Reaction enthalpies (i.e. , the quantity of heat evolved or absorbed) also differ. As a result, the curing rates of the two mechanisms exhibit different sensitivity to changes in temperature. By combining both curing mechanisms, curing rate and property development may be altered to fit different applications.

[0055] In general, curing rate increases with increasing temperature; however, the relationship between temperature and curing rate is more complex than in a single-component system. At elevated temperatures, the rates of other reaction mechanisms, such as epoxy etherification, become more significant, resulting in altered mechanical properties, such as higher tensile strength but lower flexibility and elongation. Similarly, higher temperatures will accelerate the hydrolysis and condensation of alkoxysilanes, which become less reactive as the number of alkoxy substituents bonded to the silicon atom decreases. Thus, a network thus formed at higher temperatures will possess higher crosslink density than a network formed at lower temperatures.

[0056] Epoxy Resin

[0057] Part B of the thermally conductive adhesive includes an epoxy resin which functions as a secondary curing system.

[0058] In certain embodiments, the epoxy resin is one or more selected from a bisphenol A-type epoxy resin, a bisphenol F-type epoxy resin, a bisphenol S-type epoxy resin, a biphenyl-type epoxy resin, a naphthalene diol-type epoxy resin, a phenol novolac-type epoxy resin, a cresol novolac- type epoxy resin, a bisphenol A novolac-type epoxy resin, a cycloaliphatic epoxy resin, a heterocyclic epoxy resin (triglycidyl isocyanurate, diglycidyl hydantoin and the like), denatured epoxy resins obtained by denaturing these epoxy resins by a variety of materials, and bromides and chlorides of these epoxy resins.

[0059] In preferred embodiments, the epoxy resin is selected from bisphenol A-type epoxy resin, a bisphenol F-type epoxy resin, a bisphenol S-type epoxy resin, a biphenyl-type epoxy resin. Most preferably, the epoxy resin is bisphenol A-type epoxy resin. One of these resins may be used singly or two or more may be used in combination. WS 12406 KE

[0060] The epoxy resin has an epoxy index between 0.5 and 20 Eq / kg, preferably between 1 and 10 Eq / kg, more preferably between 3 and 8 Eq / kg.

[0061] The epoxy resin has a viscosity between 5000 - 40000 mPa s, preferably between 5000 - 30000 mPa.s, more preferably between 10000 - 20000 mPa s.

[0062] The epoxy resin may be included in an amount of 5 to 50 wt%, preferably 10 to 40 wt%, more preferably 15 to 30 wt%, based on a total weight of Part B.

[0063] Accelerators

[0064] In embodiments of the present invention, the thermally conductive adhesive may optionally include an amino-functional accelerator capable of reacting with an epoxy group directly or increasing the reactivity of other curative agents (such as amino-functional adhesion promoters) to promote curing of the epoxy resin. The accelerator may be any amino-functional curing agent known in the art for curing of epoxy systems. Other suitable accelerators include those selected from boron-containing complexes, dicyandiamides, polyamidoamines, polyamides, ureas, and anhydrides.

[0065] The accelerator is preferably an amino-functional accelerator as amino functional accelerators also accelerate and are compatible with RTV-1 matrix reactions. Such amino functional accelerators are commercially available, for example those sold as Accelerator 960-1 , a trade name of Huntsman Corporation.

[0066] Adhesion Promoters

[0067] In embodiments of the present invention, the thermally conductive adhesive may optionally include adhesion promoters to improve adhesion of the thermally conductive adhesive. Any adhesion promoter known in the art for systems that cure through silane condensation may be used.

[0068] Preferable adhesion promoters include alkoxysilane-based adhesion promoters, due to their compatibility with a large range of surfaces. Commercially available alkoxysilane-based adhesion promoters suitable for use in the present invention include those sold under the GENIOSIL® line of organofunctional silanes from Wacker Chemie AG. Preferably, the alkoxysilane-based adhesion promoter includes additional functionalities, such as amino functionality, urea functionality, acrylate / methacrylate functionality, or epoxy functionality. Amino WS 12406 KE functional alkoxysilanes are more preferable adhesion promoters as they additionally accelerate the cure of the epoxy resin contained in Part B.

[0069] Suitable examples of alkoxysilane-based adhesion promoters include glycidoxypropyltrimethoxysilane, glycidoxypropylmethyldimethoxysilane, glycidoxypropyl triethoxysilane or glycidoxypropyl-methyldiethoxysilane, 2-(3-triethoxysilylpropyl)maleic anhydride, N-(3-trimethoxysilylpropyl)urea, N-(3-triethoxysilylpropyl)urea, N- (trimethoxysilylmethyl) urea, N-(methyl-dimethoxysilylmethyl) urea, N-(3-triethoxysilylmethyl) urea, N-(3-methyldiethoxysilylmethyl) urea, O-(methylcarbamatomethyl)- methyldimethoxysilane, O-(methylcarbamatomethyl) trimethoxysilane, O-(ethylcarbamatomethyl)methyl diethoxysilane, O-(ethyl-carbamatomethyl)- triethoxysilane, 3-methacryloyloxypropyltri-methoxysilane, methacryloyloxymethyl trimethoxysilane, methacryloyloxymethyl methyldimethoxysilane, methacryloyloxy-methyltriethoxysilane, methacryloyloxymethylmethyldiethoxy-silane, 3- acryloyloxypropyltrimethoxysilane, acryloyloxymethyl-trimethoxysilane, acryloyloxymethyl methyldimethoxysilane, acryloyloxymethyltriethoxysilane and acryloyloxymethylmethyldiethoxysilane, and the partial condensates thereof.

[0070] In embodiments containing adhesion promoters, the adhesion promoters are preferably included in amounts lower than or equal to 3 parts by weight, more preferably lower than or equal to 1 .5 parts by weight, based on 100 parts by weight of the thermally conductive adhesive.

[0071] Inorganic Filler

[0072] The thermally conductive adhesive of the present invention includes an inorganic filler in either Part A, Part B, or both parts. In embodiments of the present invention, inorganic fillers are included to increase the thermal conductivity or provide electrically insulating properties.

[0073] Suitable inorganic fillers may have an average particle diameter D50 of less than 120 pm and a thermal conductivity of 1 W / m K or more. Preferably, the thermal conductivity of the inorganic filler is 10 W / m K or more, more preferably 30 W / m K or more.

[0074] Suitable inorganic fillers may also have a volume resistivity at room temperature (25°C) of 10 Q cm. Preferably, the volume resistivity of the inorganic filler is 105Q cm or more, more preferably 108Q cm or more, most preferably 1013Q cm or more.

[0075] Examples of inorganic fillers that achieve both the necessary thermal conductivity and electrically insulating properties include borides, carbides, nitrides, oxides, silicides, and WS 12406 KE hydroxides. Preferably, the inorganic filler is selected from magnesium oxide (MgO), aluminum oxide (AI2O3), boron nitride (BN), aluminum nitride (AIN), aluminum hydroxide (AI(OH)3), silicon dioxide (SiO2), magnesium hydroxide (Mg(OH)2), titanium oxide (TiO2), zinc oxide (ZnO), silicon, and combinations thereof.

[0076] The inorganic fillers may also include reinforcing fillers, preferably fillers having a BET surface area of more than 50 m2 / g, such as fumed silica, precipitated silica, precipitated chalk, carbon black, such as furnace black and acetylene black, and mixed silicon aluminum oxides of high BET surface area. Reinforcing fillers may also include fillers in the form of hollow beads, such as ceramic microbeads, examples being those available under the tradename Zeeospheres™ from 3M Deutschland GmbH of Neuss, DE, elastic polymeric beads, for instance those available under the tradename EXPANCEL® from AKZO NOBEL, Expancel of Sundsvall, Sweden, or glass beads; fibrous fillers, such as asbestos and also polymeric fibers. Reinforcing fillers may have been hydrophobized, by treatment with organosilanes and / or organosiloxanes or with stearic acid, or by etherification of hydroxyl groups to form alkoxy groups. In certain applications, including use with battery packs, non-electrically conductive reinforcing fillers are preferred.

[0077] The inorganic filler is included in an amount of 10 to 90 wt%, preferably 20 to 85 wt%, more preferably 60 to 80 wt%, based on a total weight of the thermally conductive adhesive. The inorganic filler may be added to Part A, Part B, or both parts. In preferred embodiments, Part A and Part B both include an inorganic filler, as adding the inorganic filler to both parts permits a higher filler loading in the cured adhesive. The filler used in Part A may be identical or different as the filler used in Part B.

[0078] Water Scavengers

[0079] In certain embodiments, the thermally conductive adhesive composition of the present invention may optionally include water scavengers. Water scavengers known in the art for systems that cure through silane condensation may be used in Part A of the thermally conductive adhesive to prevent premature condensation, improve storage properties and shelf life, and improve adhesion and mechanical properties of the thermally conductive adhesive.

[0080] Examples of suitable water scavengers include vinyltrimethoxysilane, vinyltriethoxysilane, vinylmethyl-dimethoxysilane, O-(methylcarbamatomethyl) methyl dimethoxysilane, O- (methylcarbamatomethyl)trimethoxysilane, O-(ethyl-carbamatomethyl) methyldiethoxysilane, and also O-(ethyl-carbamatomethyl)triethoxysilane, and / or the partial condensates thereof, and also WS 12406 KE orthoesters, such as 1 ,1 ,1 -trimethoxyethane, 1 ,1 ,1 -triethoxyethane, trimethoxymethane and triethoxymethane.

[0081] Preferable water scavengers include vinyl trimethoxysilane, vinyl triethoxysilane, tetraethyl orthosilicate, trimethyl orthoacetate, triethyl orthoacetate, and combinations thereof.

[0082] If water scavengers are included in Part A, the amounts are less than or equal to 2 parts by weight, preferably less than or equal to 1 part by weight, more preferably less than or equal to 0.5 parts by weight, based on 100 parts by weight of the thermally conductive adhesive in each case.

[0083] Silicone Resins

[0084] In certain embodiments, the thermally conductive adhesive may additionally include silicone resins of the formula:

[0085] R3c(R4O)dSiO(4-c-d) / 2 (I I I), wherein R3can be the same or different, and represents a hydrogen atom or an optionally substituted monovalent hydrocarbon group bonded with SiC,

[0086] R4may be the same or different and represents a hydrogen atom or an optionally substituted monovalent hydrocarbon group, c is 0, 1 , 2 or 3, and d is 0, 1 , 2 or 3, wherein the sum of c+d is less than or equal to 3; and c is equal to 0 or 1 in at least 50%, preferably at least 85%, more preferably at least 90%, of the units of formula (III). In a preferred embodiment, c+d is less than 3. In the most preferred embodiments, the silicone resin contains at least 95% by weight of units of formula (III) or only formula (III).

[0087] In formula (III), suitable examples of radicals R3include independently alkyl radicals such as the methyl, ethyl, n-propyl, isopropyl, 1-n-butyl, 2-n-butyl, isobutyl, tert-butyl, n-pentyl, isopentyl, neopentyl, tert-pentyl radical; hexyl radicals such as the n-hexyl radical; heptyl radicals such as the n-heptyl radical; octyl radicals such as the n-octyl radical, isooctyl radicals and the 2,2,4- trimethylpentyl radical; nonyl radicals such as the n-nonyl radical; decyl radicals such as the n- decyl radical; dodecyl radicals such as the n-dodecyl radical; octadecyl radicals such as the n- WS 12406 KE octadecyl radical; cycloalkyl radicals such as the cyclopentyl, cyclohexyl, cycloheptyl radical and methylcyclohexyl radicals; alkenyl radicals such as the vinyl, 1-propenyl and 2-propenyl radical; aryl radicals such as the phenyl, naphthyl, anthryl and phenanthryl radical; alkaryl radicals such as o-, m-, p-tolyl radicals; xylyl radicals and ethylphenyl radicals; and aralkyl radicals such as the benzyl radical and the a- and [3-phenylethyl radicals.

[0088] Radical R3preferably comprises monovalent, SiC-bonded aliphatic or aromatic hydrocarbon radicals which are optionally substituted by halogen atoms and which have 1 to 18 carbon atoms, more preferably the methyl or phenyl radical. In the most preferable embodiment, all radicals R3are exclusively methyl and phenyl radicals.

[0089] In formula (III), suitable examples of radical R4include a hydrogen atom or the examples specified for radical R3.

[0090] Radical R4preferably comprises a hydrogen atom or alkyl radicals having 1 to 10 carbon atoms that are optionally substituted by halogen atoms, more preferably hydrogen atom or alkyl radicals having 1 to 4 carbon atoms, more preferably the methyl, ethyl, or butyl radical, most preferably the methyl radical.

[0091] Suitable silicone resins include phenylsilicone resins of the formula (III) in which at least 10%, preferably at least 50%, more preferably at least 60% of all units of the formula (III) have at least one SiC-bonded phenyl group.

[0092] In one embodiment, phenylsilicone resins are used which contain, based on the total number of units of the formula (III) in each case, at least 50%, more preferably at least 60%, of units of the formula (III) in which c is 1.

[0093] Examples of suitable silicone resins include organopolysiloxane resins which consist substantially, preferably exclusively, of (Q) units of the formulae SiO4 / 2, Si(OR4)O3 / 2, Si(OR4)2O2 / 2, and Si(OR4)3Oi / 2, (T) units of the formulae PhSiO3 / 2, PhSi(OR4)O2 / 2, and PhSi(OR4)2Oi / 2, (D) units of the formulae Me2SiO2 / 2and Me2Si(OR4)Oi / 2, and also (M) units of the formula Me3SiOi / 2, where Me is the methyl radical, Ph is the phenyl radical, and R4is the methyl, ethyl, or butyl radical, preferably the methyl radical, with the resin containing preferably 0-2 mol of (Q) units, 0- 2 mol of (D) units, and 0-2 mol of (M) units per mol of (T) units.

[0094] Preferred examples of silicone resins are organopolysiloxane resins which consist substantially, preferably exclusively, of T units of the formulae PhSiO3 / 2, PhSi(OR4)O2 / 2, and PhSi(OR4)2Oi / 2, WS 12406 KE and T units of the formulae MeSiO3 / 2, MeSi(OR4)O2 / 2, and MeSi(OR4)2Oi / 2, and also, optionally, D units of the formulae Me2SiO2 / 2 and Me2Si(OR4)Oi / 2, where Me is the methyl radical, Ph is the phenyl radical, and R4is the methyl, ethyl, or butyl radical, preferably the methyl radical. The molar ratio of phenylsilicone to methylsilicone units is between 0.5 and 2.0. The amount of D units in these silicone resins is preferably below 10 wt %.

[0095] Additionally, in preferred examples of silicone resins, the sum of T units of the formulae PhSiO3 / 2, PhSi(OR4)O2 / 2, and PhSi(OR4)2Oi / 2accounts for more than 90wt% of all units of silicone resins, preferably more than 95wt%, More preferably 99 wt% or more, where Ph is the phenyl radical and R4is the methyl, ethyl, or butyl radical, preferably the methyl radical, calculated on the basis of all units of silicone resin as 100wt%.

[0096] The silicone resins preferably possess a number-average molar mass Mnof at least 400 g / mol and more preferably of at least 600 g / mol. The average molar mass Mnis preferably not more than 400,000 g / mol, more preferably not more than 100,000 g / mol, most preferably not more than 50,000 g / mol. The silicone resins may be either solid or liquid at 23° C and 1000 hPa, with liquid silicone resins being preferred.

[0097] The silicone resins may be used either in pure form or in the form of a solution in a suitable solvent. However, it is preferable to use silicone resin that does not contain an organic solvent.

[0098] Phenylsilicone resins suitable for this invention include standard commercial products, examples being various SILRES® grades from Wacker Chemie AG, such as SILRES® IO 368, SILRES® IC 678 or SILRES® IO 231 or SILRES® SY231 .

[0099] In embodiments of the present invention, silicone resins may be included in an amount of less than or equal to 4 parts by total weight of the adhesive, preferably less than or equal to 2 parts by total weight of the adhesive. Depending on the chemical functionality, silicone resins expand temperature operating range or flame retardance. In certain formulations, they also increase adhesive strength. Silicone resins may be included Part A, Part B, or both parts prior to mixing. Preferably silicone resins are included in Part A.

[0100] Silicone Fluids

[0101] In some embodiments, the thermally conductive adhesive may further include silicone fluids.

[0102] Suitable silicone fluids include methyl functional and vinyl functional silicone fluids, such as polydimethylsiloxane. Preferably, silicone fluids containing the structure Si-H are excluded due to WS 12406 KE their high reactivity. Suitable silicone fluids are commercially available, for example AK fluids available from Wacker Chemie AG.

[0103] Colorants

[0104] Colorants may be included in the thermally conductive adhesive composition, disposed in either Part A, Part B, or both parts. Suitable colorants include those known in the art to be compatible with alkoxysilane or epoxy-based curing systems. Preferably, the colorant will include a pigment dissolved in a polymer. Inorganic or organic colorants may be used, but inorganic colorants may be preferable due to their improved stability. The polymer may be a reactive or nonreactive polymer and is preferably a silicone polymer or silyl-terminated polymer. Suitable colorants are commercially available, including those sold under the tradenames Elastosil® or Semicosil® from Wacker Chemie AG.

[0105] EXAMPLES

[0106] The following examples are presented solely for the purpose of further illustrating and disclosing certain embodiments of the thermally conductive adhesive of the present invention. Examples of the thermally conductive adhesive include Examples 1 through 3. Comparative Examples 1 and 2, which are not part of the invention, are also described below.

[0107] Samples of the thermally conductive adhesives were extruded with a manual dispensing gun from a 5 mL dual cartridge with a static cylindrical mixing nozzle (56 mm length, 3 mm inner diameter). The first 1 mL of extruded adhesive was discarded to ensure adequate mixing of Part A and Part B within the nozzle. The thermally conductive adhesive was deposited directly onto the rheometer stage at a specified temperature, followed immediately by shear gap setting and initiation of the experiment. Data were collected for 24 hours directly following application. The following examples were prepared in accordance with the mixing procedure described above.

[0108] To demonstrate the pot life and property development of the following examples and comparative examples, oscillatory rheometric experiments were conducted to track the storage modulus (G’) and loss modulus (G”) to provide information about the viscoelastic properties of the thermally conductive adhesive over time and therefore serve as a reliable measure of the extent of cure.

[0109] Curing experiments were performed at a specified temperature using an MCR 302 rheological measuring device from Anton Paar of Ostfildern in Germany equipped with a Peltier temperature WS 12406 KE control device and circulating fluid counter-cooling system. All experiments used a 25 mm parallel-plate geometry with a shear gap of 1000 pm, an oscillatory strain amplitude (g) of 0.05%, and an oscillatory frequency (w) of 10 rad / s. This testing was conducted according to the methods in ASTM D4473.

[0110] The extent of curing was directly related to the increase in both storage modulus (G and loss modulus (G”) and the corresponding decrease in the loss factor, tan 5, which is the ratio of G” to G’. All formulations showed a crossover point wherein the value of G’ became greater than G”, and tan 5 became less than 1 . The rate of G’ increase and the shape of the curve was different according to cure temperature, a:y STP-E ratio, and proportion of ethoxysilyl or methoxysilyl adhesion promoters and water scavengers in the formulation. Regardless of composition or curing temperature, all formulations reached a G’ value of at least 2 MPa within 24 hours, an important benchmark for structural adhesives. The time required to achieve a particular modulus was tunable based on the aforementioned properties, which allows precise control over reworkability.

[0111] 2024 Aluminum alloy lap shear panels were cleaned using isopropanol. Thermally conductive adhesive was then applied following the extrusion procedure described above in an overlap area measuring 1 in x 0.5 in (25.4 mm x 12.7 mm), and the lap shear samples were cured at 25 °C I 50% relative humidity (RH) in a controlled temperature and humidity (CTH) chamber for a specified time. Bond line thickness was 0.06 in (1 .6 mm). Specimens were measured per ASTM D1002 at a rate of 0.05 in / min until failure.

[0112] Example 1

[0113] Part A

[0114] Part A of a thermally conductive adhesive was prepared with silyl-terminated polyethers having a 60:40 a:y molar ratio. The silyl-terminated polyethers were 100% methoxysilyl-functional. The a- silyl-terminated polymer had a number-average molecular weight ( / Wn) of approximately 12 kg / mol, and the g-silyl-terminated polymer had an Mnof approximately 18 kg / mol. Collectively, these silyl-terminated polymers comprised 14.2% of the total weight of Part A. The inorganic filler package consisted of aluminum oxide and hydrophobized aluminum trihydroxide with three distinct particle size distributions, collectively comprising 83.8% of the total weight of Part A. The adhesion promoters A / -[3-(trimethoxysilyl)propyl]ethylenediamine and 3- (aminopropyl)trimethoxysilane, the water scavenger trimethoxyvinylsilane, and the catalyst WS 12406 KE

[0115] Accelerator 960-1 (an aromatic tertiary amine commercially available from Huntsman Corporation) each comprised 0.5% of the total weight of Part A.

[0116] Part B

[0117] Part B of a thermally conductive adhesive was prepared with a difunctional BPA-based epoxy resin containing a monofunctional alkyl reactive diluent, with an epoxy equivalent weight of 196- 212 g / Eq, comprising 13.2% of the total weight of Part B. The inorganic filler package consisted of aluminum oxide and hydrophobized aluminum trihydroxide with three distinct particle size distributions, collectively comprising 85.8% of the total weight of Part B. The remaining 1 % consisted of deionized water (0.95%) and a non-reactive colorant (0.05%).

[0118] Example 2

[0119] Part A

[0120] Part A was prepared as in Example 1 , with the following changes: A / -[3- (triethoxysilyl)propyl]ethylenediamine (0.9 wt%) and 3-(aminopropyl)triethoxysilane (1 wt%) were used as adhesion promoters; triethoxyvinylsilane (1 wt%) was used as a water scavenger; Accelerator 960-1 (0.8% wt%) was used as an accelerator. The adhesion promoters and water scavengers were 100% ethoxysilyl-functional. In contrast to Example 1 , the silyl-terminated polymers comprised 22.5% of the total weight of Part A, and the inorganic filler package comprised 73.8%.

[0121] Part B

[0122] Part B was prepared as in Example 1 , but with the epoxy resin comprising 22.7%, the inorganic filler package comprising 75.5%, deionized water comprising 1 .7%, and colorant comprising 0.1 % of the total weight of Part B.

[0123] Example 3

[0124] Part A

[0125] Part A of a thermally conductive adhesive was prepared as in Example 1 , with the following changes: adhesion promoters A / -[3-(trimethoxysilyl)propyl]ethylenediamine and 3- (aminopropyl)trimethoxysilane; water scavengers: trimethoxyvinylsilane; and an accelerator: Accelerator 960-1 , comprising 0.8% each of the total weight of Part A. The adhesion promoters and water scavengers are 100% methoxysilyl-functional. In contrast to Example 1 , the silyl- WS 12406 KE terminated polymers comprised 23% of the total weight of Part A, and the inorganic filler package comprised 73.8%.

[0126] Part B

[0127] Part B of a thermally conductive adhesive was prepared as in Example 2.

[0128] Comparative Example 1

[0129] A thermally conductive adhesive was prepared as in Example 1 , but the silyl-terminated polymers of Part A contain only a units.

[0130] Comparative Example 2

[0131] A thermally conductive adhesive was prepared as in Example 1 , but the silyl-terminated polymers of Part A contain only y units.

[0132] Curing and Property Development Tests

[0133] All curing and property development tests were conducted at 25 °C for varying a:y ratios of with a 25 mm parallel plate geometry. Oscillatory strain amplitude (y) was 0.05%, oscillatory frequency (co) was 10 rad / s, and the shear gap was 1000 pm for all tests.

[0134] Figure 1 is a graph depicting the storage modulus over time during the cure process of Example 1 , Comparative Example 1 , and Comparative Example 2. By varying the cry ratio of the thermally conductive adhesive, the user may adjust the curing characteristics and final properties with greater control than a system with entirely ct-silyl or y-silyl terminated polymers.

[0135] Figure 2 is a graph depicting the storage modulus G’ over time during the cure process of Example 2 and Example 3. The silyl-terminated polyethers have a 60:40 cry molar ratio. The cure rate can be tailored further by changing the alkoxy substituents of the adhesion promoters and water scavengers. Additionally, ethanol, a byproduct of ethoxy-functional silanes, is less toxic than methanol, a byproduct of methoxy-functional silanes, so ethoxy-functional silanes may be preferred in certain applications.

[0136] Temperature Tests WS 12406 KE

[0137] Temperature tests were conducted using the sample prepared in Example 2 at a range of temperatures from 10°C to 80°C. Oscillatory strain amplitude (y) was 0.05%, oscillatory frequency (co) was 10 rad / s, and the shear gap was 1000 pm for all tests.

[0138] Figure 3 is a graph depicting the storage modulus G’ over time during the cure process of Example 2 over a range of temperatures. The silyl-terminated polyethers have a 60:40 cry molar ratio and the adhesion promoters used were 100% ethoxysilyl. Curing proceeds at room temperature or below (10, 25 °C) but is faster at elevated temperatures. Together with a:y and methoxy:ethoxy molar ratios, temperature is an additional means of controlling adhesive curing rates and mechanical properties.

[0139] Figure 4 is a graph depicting the storage modulus G’ over time during the cure process of Example 3 over a range of temperatures. The silyl-terminated polyethers have a 60:40 cry molar ratio and the adhesion promoters used were 100% methoxysilyl. When using 100% methoxyfunctional adhesion promoters, cure proceeds more rapidly in the initial phase compared to 100% ethoxy-functional adhesion promoters.

[0140] Figure 5 is a graph depicting the loss factor, tan 5 (G” I G’), over time during the cure process of Example 1 , Comparative Example 1 , and Comparative Example 2. The loss factor decreased more rapidly with increasing a content and resulted in a lower final value within 24 hours.

[0141] Figure 6 is a graph depicting the loss factor, tan 5 (G” I G’), over time during the cure process of Example 2 over a range of temperatures. The silyl-terminated polyethers have a 60:40 a:y molar ratio and the adhesion promoters used were 100% ethoxysilyl. The loss factor decreased more rapidly with increasing temperature.

[0142] Figure 7 is a graph depicting the loss factor, tan 5 (G” I G’), over time during the cure process of Example 3 over a range of temperatures. The silyl-terminated polyethers have a 60:40 a:y molar ratio and the adhesion promoters used were 100% methoxysilyl. The loss factor decreased more rapidly with increasing temperature.

[0143] Figure 8 is a graph depicting the loss factor, tan 5 (G” I G’), storage modulus G’, and mean lap shear strength (aluminum bonded to aluminum) over time during the cure processes of Example 3, wherein A = mostly adhesive failure; M = mixed failure; C = mostly cohesive failure. Figure 9 depicts the same properties corresponding to Example 2. Comparing Fig. 8 and Fig. 9, mean lap shear strength was higher, G’ increased more rapidly, and tan 5 decreased more rapidly in the early stages of cure for Example 3 compared to Example 2. WS 12406 KE

[0144] Storage modulus (G’) and loss factor tan 6 may be used to describe network development during the curing of a thermally conductive adhesive. As demonstrated in the foregoing examples, the extent of network development, the time to reach a certain extent of cure, and curing characteristics at various temperatures may all be controlled in the present invention.

[0145] All lap shear test formulations contained silyl-terminated polyethers in a 60:40 a:y molar ratio (described in the examples below). The mean lap shear strength was higher in the first 4 hours of curing for formulations containing all methoxysilyl-functional adhesion promoters. The mode of structural failure also evolved differently over time, being mostly adhesive up to 3 hours, then mixed from 3-20 hours, then mostly cohesive after 20 hours for formulations containing all ethoxysilyl-functional adhesion promoters. By contrast, failure mode was mixed up to 12 hours, then mostly cohesive after 12 hours for formulations composed of all methoxysilyl-functional adhesion promoters. Failure mode was qualitatively defined as adhesive if > 75% (approximately) of the adhesive sample area de-adhered cleanly from the substrate, as cohesive if > 75% of the adhesive failed internally while maintaining contact with the substrate, and as mixed in the remaining cases. The foregoing examples demonstrate the tailorability of both adhesive strength in the early stages of cure as well as structural failure modes.

[0146] From the foregoing detailed description, it will be apparent that various modifications, additions, and other alternative embodiments are possible without departing from the true scope and spirit. The embodiments and examples discussed herein were chosen and described to provide the best illustration of the principles of the invention and its practical application to thereby enable one of ordinary skill in the art to use the invention in various embodiments and with various modifications as are suited to the particular use contemplated. As should be appreciated, all such modifications and variations are within the scope of the invention.

Claims

WS 12406 KECLAIMS1 . A thermally conductive adhesive formed by combining a Part A and a Part B, wherein Part A comprises5 to 50 wt% of silyl-terminated polymers of the formulasY-[(CRi2)i-Si(OR)mRn]x (I)Y-[(CR12)a-Si(OR)3]x (II) whereinY is an x-valent polymer radical bonded via nitrogen or oxygen,R may be identical or different and is a hydrogen atom or a monovalent, optionally substituted hydrocarbon radical,R1may be identical or different and is a hydrogen atom or a monovalent, optionally substituted hydrocarbon radical which may be attached via nitrogen, phosphorus, oxygen, sulfur or carbonyl group to the carbon atom, x is an integer from 2 to 10, m is an integer from 1 to 3, n is an integer from 0 to 2, wherein the sum of m and n is 3 a is an integer from 2 to 10, wherein the silyl terminated polymers comprise at least 10 wt% of formula (I) and at least 10 wt% of formula (II), and an amino-functional compound selected from the group consisting of accelerators, adhesion promoters, and combinations thereof; andPart B comprises an epoxy resin and water; wherein at least one of part A and part B comprises an inorganic filler.

2. The thermally conductive adhesive of claim 1 , wherein the silyl-terminated polymers comprise at least 20 wt% of formula (I) and at least 20 wt% of formula (II).

3. The thermally conductive adhesive of claim 2, wherein the silyl-terminated polymers comprise at least 40 wt% of formula (I) and at least 40 wt% of formula (II).Page 22WS 12406 KE4. The thermally conductive adhesive of claim 1 , wherein the amino-functional compound accelerates curing of the epoxy resin of Part B.

5. The thermally conductive adhesive of claim 1 , wherein at least one of Part A and Part B comprises a silicone resin, a silicone fluid, or a combination thereof.

6. The thermally conductive adhesive of claim 5, wherein at least one of Part A and Part B comprises a silicone resin of the formulaR3c(R4O)dSiO(4-c-d) / 2 (III), wherein R3can be the same or different, and represents a hydrogen atom or an optionally substituted monovalent hydrocarbon group bonded with SiC,R4may be the same or different and represents a hydrogen atom or an optionally substituted monovalent hydrocarbon group, c is 0, 1 , 2 or 3, and d is 0, 1 , 2 or 3, wherein the sum of c+d is less than or equal to 3.

7. The thermally conductive adhesive of claim 5, wherein at least one of Part A and Part B comprises a silicone fluid, wherein the silicone fluid is selected from the group consisting of vinyl functional silicone fluids, methyl functional silicone fluids, and combinations thereof.

8. The thermally conductive adhesive of claim 1 , wherein at least one of Part A and Part B comprises a colorant.

9. The thermally conductive adhesive of claim 8, wherein the colorant comprises a pigment, wherein the pigment is organic or inorganic, dissolved in a silicone polymer or a silyl-terminated polymer.

10. The thermally conductive adhesive of claim 1 , wherein both Part A and Part B each comprise an inorganic filler.11 . The thermally conductive adhesive of claim 10, wherein the inorganic filler has a thermal conductivity of at least 10 W / m K.Page 23WS 12406 KE12. The thermally conductive adhesive of claim 11 , wherein the inorganic filler is selected from the group consisting of aluminum oxide, aluminum trihydroxide, magnesium oxide, magnesium hydroxide, zinc oxide, boron nitride, aluminum nitride, silicon, and combinations thereof, either with or without a chemical surface treatment.

13. The thermally conductive adhesive of claim 10, wherein the inorganic filler is included in an amount of at least 10 wt% of the total mass of the thermally conductive adhesive.

14. The thermally conductive adhesive of claim 13, wherein the inorganic filler is included in an amount of at least 25 wt% of the total mass of the thermally conductive adhesive.

15. The thermally conductive adhesive of claim 14, wherein the inorganic filler is included in an amount of at least 50 wt% of the total mass of the thermally conductive adhesive.

16. The thermally conductive adhesive of claim 1 , wherein Part A further comprises a water scavenger.

17. The thermally conductive adhesive of claim 16, wherein the water scavenger is selected from the group consisting of vinyl trimethoxysilane, vinyl triethoxysilane, tetraethyl orthosilicate, trimethyl orthoacetate, triethyl orthoacetate, and combinations thereof.

18. The thermally conductive adhesive of claim 1 , wherein the epoxy resin comprises at least one selected from the group consisting of a bisphenol A-type epoxy resin, a bisphenol F-type epoxy resin, a bisphenol S-type epoxy resin, a biphenyl-type epoxy resin, a naphthalene diol- type epoxy resin, a phenol novolac-type epoxy resin, a cresol novolac-type epoxy resin, a bisphenol A novolac-type epoxy resin, a cycloaliphatic epoxy resin, a heterocyclic epoxy resin, denatured epoxy resins, bromides thereof, chlorides thereof, and combinations thereof.

19. The thermally conductive adhesive of claim 18, wherein the epoxy resin comprises at least one selected from the group consisting of a bisphenol A-type epoxy resin, a bisphenol F-type epoxy resin, a bisphenol S-type epoxy resin, a biphenyl-type epoxy resin, and combinations thereof, optionally containing at least one type of epoxy-functional reactive diluent.Page 24

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