Thermal interface material

Abstract

The present invention relates to a thermal interface material, such as a thermally conductive pad or sheet, having a good balance between thermal conductivity and electrical resistivity. The material is based on at least one elastomeric matrix comprising from 85 phr to 100 phr of a silicone rubber having a weight average molar mass Mw in the range of from 150 kg / mol to 1000 kg / mol; the thermal conductive filler comprises aluminum oxide and graphite, the volume percentage range of the graphite in the thermal conductive filler is 2%-12%, and the total volume percentage of the aluminum oxide and the graphite in the thermal conductive filler is greater than 55%; from 15 phr to 150 phr of a silicone oil, the silicone oil having a viscosity of less than 150,000 mPa.s at 25 DEG C; and from 0.2 phr to 5 phr of a cross-linking agent.

Description

Technical Field

[0001] This invention relates to a thermal interface material particularly suitable for extracting heat from heating elements, for example in the field of batteries. Background Technology

[0002] Lithium-ion technology is increasingly being used in batteries for electric vehicles, whose power systems require ultra-high-power batteries. This technology necessitates that the battery operate within its optimal temperature range, both to fully benefit from its reserve capacity and, more importantly, to avoid damage during repeated charge / discharge cycles. In fact, the high electrical energy applied during use (battery discharge) or recovery (battery charging) results in significant heat generation. To prevent such damage, a battery temperature regulation / control system, called a Battery Management System (BMS), is typically used. The thermal components of a BMS usually include heat exchangers (cooling platforms) with circulating heat exchange fluids and thermal relays for extracting heat from the battery. These thermal relays (or thermal interfaces) are called TMMs or TIMs (Thermal Management / Interface Materials). TMMs come in various forms: spacer fillers and gaskets.

[0003] The gap filler is a liquid composition that cross-links at ambient temperature to solidify and fill the gap volume between the battery and the cooling platform. The gasket itself is a solid composition, formed into a sheet of a specific thickness. Mechanical clamping is required to install the gasket into the battery pack to ensure tight contact between the battery and the cooling platform. This installation necessitates good deformability of the gasket to prevent breakage.

[0004] The thermal conductivity required for gaskets typically necessitates a high volume percentage of thermally conductive filler in the TMM composition. However, increasing the proportion of thermally conductive filler must not compromise the resistivity of the gasket.

[0005] Therefore, the practical requirement is a thermal conductivity (greater than 1.5 W / mK, preferably greater than 2 W / mK) and resistivity (greater than 1.0 × 10⁻⁶). 04 Ω.m, preferably greater than 1.0 × 10 10 Find a good balance between Ω.m.

[0006] Document CN112831187A describes a composition based on an organosilicon elastomer, comprising spherical alumina, alumina nitride, silicone oil, and 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, which exhibits good thermal conductivity, robustness, and tensile strength. Summary of the Invention

[0007] After conducting continuous research, the applicant company unexpectedly discovered that combining a specific mixture of silicone rubber, thermally conductive fillers in a specific ratio, silicone oil, and crosslinking agents in specific amounts can solve the above-mentioned technical problems, while further improving thermal conductivity and maintaining sufficient resistivity.

[0008] Therefore, the subject of this invention is a thermal interface material based on at least: - An elastomer matrix comprising 85 phr to 100 phr of silicone rubber, the silicone rubber exhibiting a weight-average molar mass Mw in the range of 150 kg / mol to 1000 kg / mol. - Thermally conductive fillers with a pressure range of 500 phr to 1300 phr, comprising alumina and graphite, wherein the volume percentage of graphite in the thermally conductive filler ranges from 2% to 12%, and the total volume percentage of alumina and graphite in the thermally conductive filler is greater than 55%. - Silicone oils ranging from 15 phr to 150 phr, exhibiting a viscosity of less than 150,000 mPa·s at 25°C; and - Crosslinking agent from 0.2 phr to 5 phr.

[0009] I – Definition The term "composition-based" should be understood to mean that the composition comprises a mixture of various components used and / or in-situ reaction products, some of which are capable of reacting with each other and / or intended to react with each other (at least partially) during various stages of the composition's manufacture; thus, the composition may be in a fully cross-linked, partially cross-linked, or non-cross-linked state. The term "elastomer matrix" should be understood to mean a combination of elastomers in the composition.

[0010] Within the meaning of this invention, the expression "parts by weight / 100 parts by weight elastomer" (or phr) should be understood to refer to the elastomer present in the rubber composition under consideration in parts by weight / 100 parts.

[0011] In this document, all percentages (%) indicated are weight percentages (%) unless otherwise expressly stated.

[0012] Furthermore, any numerical interval represented by the expression "between a and b" represents a range of values ​​from greater than a to less than b (i.e., excluding the endpoints a and b), while any numerical interval represented by the expression "from a to b" means a range of values ​​from a to b (i.e., including the strict endpoints a and b). In this document, when a numerical interval is represented by the expression "from a to b," it is also preferable to represent the interval represented by the expression "between a and b."

[0013] The expression "volume percentage of a component in a mixture" means dividing the volume of that component by the sum of the volumes of all components used to prepare the mixture, and then multiplying by 100. For the volume percentage of a component in a thermal interface material, it should be understood as dividing the volume of that component by the sum of the volumes of all components used to prepare the thermal interface material before crosslinking.

[0014] The compounds mentioned in this specification may be fossil-derived or bio-based. In the latter case, they may be partially or wholly produced from biomass, or obtained from renewable raw materials derived from biomass. Similarly, the mentioned compounds may also originate from the recycling of pre-used materials; that is, they may be partially or wholly produced by the recycling process, or obtained from the starting materials themselves. Polymers, plasticizers, fillers, etc., are particularly relevant.

[0015] II - Description of the Invention II-1 Elastomer Matrix According to the present invention, the elastomeric matrix of the thermal interface material is based on silicone rubber of 85 phr to 100 phr, which exhibits a weight-average molar mass (Mw) in the range of 150 kg / mol to 1000 kg / mol. Below 150 kg / mol, the silicone rubber exhibits the consistency and viscoelastic behavior of organosilicon, which complicates its handling and processing. Furthermore, if the Mw of the silicone rubber is too low, the crosslinking effect is weakened. Above 1000 kg / mol, the silicone rubber exhibits high consistency, which complicates its processing and requires high conversion energy. Preferably, the silicone rubber exhibits an Mw in the range of 300 kg / mol to 900 kg / mol, more preferably 500 kg / mol to 800 kg / mol.

[0016] The macroscopic structure of silicone rubber (Mw, Mn, and PDI) was determined by size exclusion chromatography (SEC): solvent tetrahydrofuran; temperature 35°C; concentration 1 g / L; flow rate 1 mL / min; the solution was filtered through a filter with a porosity of 0.45 μm before injection; molar correction was performed using polystyrene standards; a set of three Waters columns in series (Styragel HR4E, HR1, and HR0.5); detection was performed using a differential refractometer (Waters 2410) and its associated operating software (Waters Empower).

[0017] The thermal interface material according to the invention may contain only one type of silicone rubber or a mixture of silicone rubbers exhibiting the aforementioned Mw value. Specifically, the silicone rubber is selected from polydimethylsiloxane (PDMS), polymethylarylsiloxane (especially polymethylphenylsiloxane), and mixtures thereof. Preferably, the silicone rubber is selected from PDMS and mixtures thereof.

[0018] The silicone rubber may have vinyl functional groups. For example, the silicone rubber may not have vinyl functional groups, or its molar content may be less than 2%, preferably less than 1%, and more preferably less than 0.5%. When the silicone rubber has vinyl functional groups, the molar fraction of the vinyl functional groups in the silicone rubber may be between 0.01% and 2%, preferably between 0.05% and 1%, and more preferably between 0.08% and 0.5%.

[0019] The molar fraction of vinyl functional groups in silicone rubber is determined by... 1 H and 13 The determination was performed using C10 NMR spectroscopy. NMR spectra were recorded on a Brüker Avance III 500 MHz spectrometer equipped with a BBI Z-grade 5 mm "broadband" cryoprobe. 1 Quantitative 1H NMR experiments used a simple 30° pulse sequence with a 5-second repetition time between each capture. Accumulations were performed from 64 to 256. 13 Quantitative ¹³C NMR experiments were performed using a 30° single-pulse sequence with proton decoupling and a 10-second repetition time between each acquisition. Accumulations ranged from 10²⁴ to 10²⁴⁰. 1 H / 13 Two-dimensional NMR experiments were used to determine the structure of the polymer. NMR measurements were performed at 25°C, with the copolymer dissolved in a deuterated solvent (approximately 25 mg of elastomer per mL), typically deuterated chloroform (CDCl3).

[0020] The elastomeric matrix may contain elastomers other than silicone rubber, but this is neither mandatory nor preferred. Preferably, the elastomeric matrix does not contain any elastomer other than silicone rubber exhibiting a Mw in the range of 150 kg / mol to 1000 kg / mol, or its content is less than 15 phr, preferably less than 10 phr, and more preferably less than 5 phr. More preferably, the elastomeric matrix contains only (i.e., 100 phr) silicone rubber exhibiting a Mw in the range of 150 kg / mol to 1000 kg / mol, preferably 300 kg / mol to 900 kg / mol, and more preferably 500 kg / mol to 800 kg / mol.

[0021] For example, as examples of commercially available silicone rubbers that can be used for the claims of this invention, Elastosil® R401-10, Elastosil® R401-25, Elastosil® R401-30, Elastosil® R401-50, Elastosil® R401-70, Elastosil® R401-75 or Elastosil® R401-90 obtained from Wacker may be mentioned.

[0022] II-2 Thermally Conductive Filler The thermal interface material according to the present invention is based on a thermally conductive filler of 500 phr to 1300 phr, the thermally conductive filler comprising alumina and graphite, wherein the volume percentage of graphite in the thermally conductive filler ranges from 2% to 12%, and the total volume percentage of alumina and graphite in the thermally conductive filler is greater than 55%.

[0023] The thermally conductive filler may contain thermally conductive fillers other than alumina and graphite, but this is neither mandatory nor preferred. Advantageously, the total volume percentage of alumina and graphite in the thermally conductive filler is greater than 60%, preferably greater than 75%, and more preferably greater than 90%. In other words, the thermally conductive filler preferably does not contain fillers other than alumina and graphite, or its content is less than 40% by weight, preferably less than 25% by weight, and more preferably less than 10% by weight.

[0024] The total volume percentage of alumina and graphite in the thermally conductive filler can be 100%. In this case, the volume percentage of alumina in the thermally conductive filler ranges from 88% to 98%.

[0025] The volume percentage of graphite in the thermally conductive filler is preferably 2% to 10%, preferably 3% to 7%, and preferably 4% to 6%.

[0026] Furthermore, the volume percentage of graphite in the thermal interface material is advantageously in the range of 1% to 7%, preferably 2% to 6%, and most preferably 2% to 4%.

[0027] The volume percentage of alumina in the thermally conductive filler is preferably greater than 10% to 98%, preferably 93% to 97%, and preferably 94% to 96%.

[0028] Furthermore, the volume percentage of alumina in the thermal interface material is advantageously in the range of 44% to 69%, preferably 48% to 63%, and more preferably 53% to 61%.

[0029] Alumina can be provided in various forms, particularly in granular form. Preferably, alumina is present in granular form, wherein the value of the diameter D50 ranges from 2 micrometers to 150 micrometers, more preferably from 10 micrometers to 100 micrometers, and more preferably from 20 micrometers to 70 micrometers. D50 represents a particle diameter in which 50% of the volume of all particles has a diameter smaller than D50, while the other 50% of the volume of all particles has a diameter larger than D50.

[0030] Commercially available alumina may be mentioned, such as Silatherm® 1432-006 or 1432-400 from Quarzwerke, or Silatherm® VST1432-006 or VST1432-400.

[0031] Graphite can be provided in various forms, particularly in crystalline form. Preferably, the graphite is in crystalline form with a diameter D90 ranging from 20 micrometers to 60 micrometers, more preferably from 30 micrometers to 55 micrometers, and even more preferably from 40 micrometers to 50 micrometers. D90 represents a particle diameter in which 90% of the volume of all particles has a diameter smaller than D90, while 10% of the volume of all particles has a diameter larger than D90.

[0032] Examples of commercially available graphite include synthetic graphite, such as Timrex KS44, Timrex PP44 or CTherm001 from Imerys, or natural graphite, such as M100 from Imerys.

[0033] Advantageously, the thermally conductive filler content in the thermal interface material according to the invention ranges from 600 phr to 1250 phr, preferably from 700 phr to 1200 phr, and more preferably from 800 phr to 1100 phr.

[0034] Regardless of the content of thermally conductive filler in the thermal interface material in terms of phr, the volume content of thermally conductive filler in the thermal interface material is preferably 45% to 70%, preferably 50% to 65%, and preferably 55% to 63%.

[0035] II-3 Silicone Oil The thermal interface material according to the invention is based on a silicone oil of 15 phr to 150 phr, wherein the silicone oil exhibits a viscosity of less than 150,000 mPa·s at 25°C.

[0036] The viscosity of silicone oil is determined according to the Brookfield technique at 25°C and atmospheric pressure. Brookfield viscosity characterizes liquid substances in a known manner. The apparent viscosity according to the Brookfield method is measured at a given temperature (e.g., 25°C) according to the European and international standard ENISO 2555 (1999). For example, a type A viscometer (e.g., the RVT model) or a type B viscometer (e.g., the HAT model) is used, with a rotation frequency preferably equal to 10 or 20 minutes. -1 The number of rotors (1 to 7) is suitable for measuring the viscosity range (according to Annex A of standard EN ISO 2555). Viscosity is expressed in mPa·s or centipoise (cP) (1 cP = 1 mPa·s).

[0037] Advantageously, the silicone oil exhibits a viscosity range of 20 to 90,000 mPa·s at 25°C, preferably 40 to 50,000 mPa·s, and more preferably 50 to 20,000 mPa·s. More preferably, the silicone oil exhibits a viscosity range of 20 to 20,000 mPa·s at 25°C, preferably 40 to 5,000 mPa·s, and more preferably 50 to 2,000 mPa·s. Viscosity affects mechanical properties (elongation at break, stress at break).

[0038] Silicone oils may be functionalized or unfunctionalized. Preferably, the silicone oil does not exhibit hydroxyl functional groups and / or vinyl functional groups. More preferably, the silicone oil does not exhibit polar functional groups and / or functional groups containing double bonds.

[0039] As an example of a commercially available silicone oil that can satisfy the requirements of this invention, references may be made to AK-50, AK-100, AK-1000, or AK-10000 or AK-100000 grades obtained from Wacker.

[0040] The silicone oil content ranges from 15 phr to 150 phr. Outside this range, it has been found that even when the thermally conductive filler content meets the requirements of this invention, the mechanical properties (elongation at break, stress at break) are unsatisfactory. Preferably, the silicone oil content in the thermal interface material ranges from 20 phr to 130 phr, more preferably from 50 phr to 120 phr, and even more preferably from 80 phr to 110 phr.

[0041] Preferably, the weight ratio of thermally conductive filler to silicone oil is greater than 5 to 50, more preferably 10 to 30, and more preferably 15 to less than 25.

[0042] II-4 Crosslinking Agent The thermal interface material according to the present invention is based on a crosslinking agent of 0.2 phr to 5 phr.

[0043] The crosslinking agent can be any crosslinking agent capable of crosslinking silicone rubber. Preferably, the crosslinking agent is a peroxide or a mixture of several peroxides. It can be any peroxide known to those skilled in the art. Among peroxides well known to those skilled in the art, organic peroxides are preferred in the context of this invention.

[0044] "Organic peroxides" should be understood as organic compounds containing -OO- groups (two oxygen atoms linked by a single covalent bond), i.e., carbon-containing compounds. During cross-linking, organic peroxides decompose at their unstable OO bonds, generating free radicals. These free radicals enable the formation of cross-linking bonds.

[0045] The organic peroxide is preferably selected from the group consisting of or including the following: dialkyl peroxides, monoperoxy carbonates, diacyl peroxides, peroxy ketals, and peroxy esters.

[0046] Preferably, the dialkyl peroxide is selected from the group comprising or consisting of: dicumyl peroxide, di(tert-butyl) peroxide, tert-butylcumyl peroxide, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, 2,5-dimethyl-2,5-di(tert-pentylperoxy)hexane, 2,5-dimethyl-2,5-di(tert-butylperoxy)hex-3-yne, 2,5-dimethyl-2,5-di(tert-pentylperoxy)hex-3-yne, bis[α-[(tert-butylperoxy)isopropyl]benzene, bis[α-(tert-pentylperoxy)isopropyl]benzene, di(tert-pentyl) peroxide, 1,3,5-tris[(tert-butylperoxy)isopropyl]benzene, 1,3-dimethyl-3-(tert-butylperoxy)butanol and 1,3-dimethyl-3-(tert-pentylperoxy)butanol.

[0047] Certain monoperoxycarbonates may also be used, such as OO-tert-butyl O-(2-ethylhexyl) monoperoxycarbonate, OO-tert-butyl O-isopropyl monoperoxycarbonate and OO-tert-pentyl O-(2-ethylhexyl) monoperoxycarbonate.

[0048] Among diacyl peroxides, benzoyl peroxides are preferred.

[0049] In peroxy ketals, the preferred peroxide is selected from the group consisting of or composed of: 1,1-di(tert-butylperoxy)-3,3,5-trimethylcyclohexane, 4,4-bis(tert-butylperoxy)valerate, ethyl 3,3-di(tert-butylperoxy)butyrate, 2,2-di(tert-pentylperoxy)propane, 3,6,9-triethyl-3,6,9-trimethyl-1,4,7-triperoxynonane (or cyclic trimer of methyl ethyl ketone peroxide), 3,3,5,7,7-pentamethyl-1,2,4-trioxacycloheptane, 4,4-bis(tert-pentylperoxy)valerate, ethyl 3,3-di(tert-pentylperoxy)butyrate, 1,1-di(tert-butylperoxy)cyclohexane, 1,1-di(tert-pentylperoxy)cyclohexane, and mixtures thereof. Preferably, the peroxy ester is selected from tert-butyl peroxybenzoate, tert-butyl peroxy-2-ethylhexanoate, and tert-butyl peroxy-3,5,5-trimethylhexanoate.

[0050] In summary, the organic peroxides are particularly preferably selected from dicumyl peroxide, aryl peroxide, diaryl peroxide, diacetyl peroxide, benzoyl peroxide, dibenzoyl peroxide, di(tert-butyl) peroxide, tert-butylcumyl peroxide, 2,5-bis(tert-butylperoxy)-2,5-dimethylhexane, 4,4-bis(tert-butylperoxy)valerate n-butyl ester, OO-(tert-butyl)O-(2-ethylhexyl)monoperoxycarbonate, tert-butylperoxyisopropyl carbonate, tert-butyl peroxybenzoate, tert-3,5,5-trimethylhexanoate tert-butyl ester, 1,3(4)-bis(tert-butylperoxyisopropyl)benzene and mixtures thereof. More preferably, the organic peroxide is selected from dicumyl peroxide, 4,4-bis(tert-butylperoxy)valerate, OO-(tert-butyl)O-(2-ethylhexyl)monoperoxycarbonate, tert-butylperoxyisopropylcarbonate, tert-butylperoxybenzoate, tert-3,5,5-trimethylhexanoate, 1,3(4)-bis(tert-butylperoxyisopropyl)benzene and mixtures thereof.

[0051] Examples of commercially available peroxides that may be used in the context of this invention include Dicup from HerculesPowder Co., Perkadox Y12 from Noury ​​van der Lande, Peroximon F40 from MontecatiniEdison SpA, Trigonox from Noury ​​van der Lande, Varox from RTVanderbilt Co., or Luperko from Wallace & Tiernan Inc.

[0052] II-5 Possible Additives Thermal interface materials may also optionally contain all or part of the commonly used additives typically used in TMMs, such as pigments, protective agents, antioxidants, or flame retardants.

[0053] Preparation of II-6 Composition The material according to the invention can be prepared in a suitable mixer using two consecutive preparation stages known to those skilled in the art: - The first stage of thermomechanical processing or kneading (the “non-preparation” stage), which can be carried out in a single thermomechanical step, involves introducing all necessary components, particularly the elastomer matrix, thermally conductive filler, and various other optional additives, except for the crosslinking system, into a suitable mixer such as a standard closed mixer (e.g., a Banbury type). The filler can be introduced into the elastomer in one or multiple stages during thermomechanical kneading. If the filler has already been wholly or partially introduced into the elastomer in masterbatch form (as described, for example, in applications WO 97 / 36724 and WO 99 / 16600), the masterbatch is kneaded directly, and, where appropriate, other elastomers or fillers not in masterbatch form present in the composition, as well as various other optional additives besides the crosslinking system, are introduced. The non-preparation stage can be carried out at high temperatures, up to between 80°C and 150°C, preferably between 100°C and 120°C, typically for a time between 2 and 10 minutes.

[0054] - The second stage of machining (“preparation” stage), which can be carried out in an external mixer (e.g., an open mill) after the mixture obtained in the first non-preparation stage has been cooled to a lower temperature, typically less than 120°C, for example, between 40°C and 100°C. The crosslinking system is then introduced, and the combined mixture is then mixed for several minutes, for example, between 5 and 15 minutes.

[0055] Such stages have been described, for example, in applications EP-A-0 501 227, EP-A-0 735 088, EP-A-0 810 258, WO00 / 05300 and WO 00 / 05301.

[0056] The resulting final composition is then calendered into, for example, sheets or plates.

[0057] These products can then be used to manufacture thermal interface materials, such as thermal pads (or cushioning pads) or thermal sheets, according to techniques known to those skilled in the art. The composition can in particular be molded and crosslinked, for example, under pressure and at temperatures between 130°C and 200°C, to form a thermal interface pad.

[0058] II-7 Thermal Interface Materials The thermal interface material according to the invention can be used in any application capable of extracting heat dissipated by a substance. For example, it is particularly suitable for transferring heat dissipated by the battery of an electric vehicle during use or charging.

[0059] The thermal interface material according to the invention can take any shape and have any thickness, as long as it can fulfill its function. Preferably, the thermal interface material is selected from thermal pads (or cushioning pads) and thermal sheets. Furthermore, the thickness range exhibited by the thermal interface material is preferably 0.2 mm to 10 mm, preferably 0.5 mm to 8 mm, preferably 1 mm to 6 mm, preferably greater than 1 mm to 6 mm, and preferably 1.1 mm to 6 mm. Detailed Implementation

[0060] III-Example III-1 Preparation of the Composition In the following examples, the rubber composition was prepared as described in points II-6 above. Specifically, the “non-preparation” stage was carried out in a 0.4-liter mixer for 3.5 minutes (with an average blade speed of 50 rpm) until the maximum drip temperature of 90°C was reached. The “preparation” stage was carried out in an open mill at 40°C for 5 to 10 minutes. Crosslinking of the composition was carried out under pressure at 150°C for 30 minutes. Test samples for measuring thermal conductivity and resistivity were cut from the resulting crosslinked slab.

[0061] Measurements and tests used in III-2 thermal conductivity Cylindrical samples measuring 40 mm × 8 mm were prepared by molding. Thermal conductivity was determined using a Hot Disk TPS1000 instrument via the transient planar source (TPS) method. A heat flux of 80 mW was applied to the sample for 10 seconds. The thermal conductivity of the sample was thus determined by observing the temperature change, which itself was determined by measuring the change in electrical resistance of the material within the sample using a Wheatstone bridge.

[0062] resistivity Resistivity was measured using a Keithley 6517B resistance electrometer. A disc-shaped test piece of the cross-linked composition, 10 mm in diameter and between 1.5 mm and 2 mm thick, was placed between two steel studs of the same diameter and secured using a miniature clamp to ensure tight contact between the test piece and the studs. Each steel stud on either side of the test piece was connected to the voltage source of the electrometer. A voltage of 100 V was applied, and the resistivity was determined using Ohm's law. Results are expressed in Ω·m. When the resistivity was too low to be measured, it was reported as "ND," indicating "Not Detected," in the table below.

[0063] III-3 Tests on Rubber Compositions The purpose of the following examples is to compare the thermal conductivity and resistivity properties of the compositions (C1 to C5) according to the present invention with those of the control compositions (T1 to T7).

[0064] The tested compositions (in phr) and the results obtained are presented in Tables 1 and 2.

[0065] The composition according to the invention differs from the control composition, particularly in the volume percentage of graphite in the composition.

[0066] [Table 1] (a) R401 / 70 silicone elastomer obtained from Wacker, with a weight Mn = 350 kg / mol and a weight Mw = 620 kg / mol (RI PS SEC). (b) Timrex KS44 D obtained from Imerys 90 45-micron graphite (c) Silatherm 1432-006 alumina obtained from Quarzwerke with a D50 size of 46 micrometers. (d) AK100 silicone oil obtained from Wacker, with a viscosity of 100 mPa·s. (e) Dicumyl peroxide obtained from Sigma-Aldrich [Table 2] (a) to (e): See Table 1 The results shown in Tables 1 and 2 above indicate that the compositions according to the present invention all possess a thermal conductivity greater than 1.5 W / mK and a thermal conductivity greater than 1.0 × 10⁻⁶ W / mK. 04 The resistivity is Ω·m. Composition C5 is particularly advantageous because it has a thermal conductivity greater than 2 W / mK and a resistivity greater than 1.0 × 10⁻⁶ Ω·m. 10 Resistivity in Ω·m.

Claims

1. A thermal interface material, based on at least: - An elastomer matrix comprising 85 phr to 100 phr of silicone rubber, the silicone rubber exhibiting a weight-average molar mass Mw in the range of 150 kg / mol to 1000 kg / mol. - Thermally conductive fillers with a pressure range of 500 phr to 1300 phr, comprising alumina and graphite, wherein the volume percentage of graphite in the thermally conductive filler ranges from 2% to 12%, and the total volume percentage of alumina and graphite in the thermally conductive filler is greater than 55%. - Silicone oils ranging from 15 phr to 150 phr, wherein the silicone oils exhibit a viscosity of less than 150,000 mPa·s at 25°C; and - Crosslinking agent from 0.2 phr to 5 phr.

2. The thermal interface material according to claim 1, wherein, The silicone rubber is selected from polydimethylsiloxane (PDMS), polymethylarylsiloxane, and mixtures thereof; preferably, the silicone rubber is selected from polydimethylsiloxane and mixtures thereof.

3. The thermal interface material according to any one of the preceding claims, wherein, The content of the thermally conductive filler ranges from 600 phr to 1250 phr, preferably from 700 phr to 1200 phr, and more preferably from 800 phr to 1100 phr.

4. The thermal interface material according to any one of the preceding claims, wherein, The total volume percentage of alumina and graphite in the thermally conductive filler is greater than 60%, preferably greater than 75%, and more preferably greater than 90%.

5. The thermal interface material according to any one of the preceding claims, wherein, The volume percentage of graphite in the thermally conductive filler ranges from 2% to 10%, preferably from 3% to 7%, and more preferably from 4% to 6%.

6. The thermal interface material according to any one of the preceding claims, wherein, The volume percentage of graphite in the thermal interface material ranges from 1% to 7%, preferably from 2% to 6%, and more preferably from 2% to 4%.

7. The thermal interface material according to any one of the preceding claims, wherein, The volume percentage of the thermally conductive filler in the thermal interface material ranges from 45% to 70%, preferably from 50% to 65%, and more preferably from 55% to 63%.

8. The thermal interface material according to any one of the preceding claims, wherein, The alumina exists in particulate form, with a mean diameter D50 ranging from 2 micrometers to 150 micrometers, preferably from 10 micrometers to 100 micrometers, and more preferably from 20 micrometers to 70 micrometers.

9. The thermal interface material according to any one of the preceding claims, wherein, The graphite exists in crystalline form, and its diameter D90 ranges from 20 micrometers to 60 micrometers, preferably from 30 micrometers to 55 micrometers, and more preferably from 40 micrometers to 50 micrometers.

10. The thermal interface material according to any one of the preceding claims, wherein, The silicone oil exhibits a viscosity range of 20 mPa.s to 20,000 mPa.s at 25°C, preferably 40 mPa.s to 5,000 mPa.s, and more preferably 50 mPa.s to 2,000 mPa.s.

11. The thermal interface material according to any one of the preceding claims, wherein, The silicone oil content ranges from 20 phr to 130 phr, preferably from 50 phr to 120 phr, and more preferably from 80 phr to 110 phr.

12. The thermal interface material according to any one of the preceding claims, wherein, The weight ratio of thermally conductive filler to silicone oil ranges from greater than 5 to 50, preferably from 10 to 30, and more preferably from 15 to less than 25.

13. The thermal interface material according to any one of the preceding claims, wherein, The crosslinking agent is an organic peroxide, preferably selected from dicumyl peroxide, aryl peroxide, diaryl peroxide, diacetyl peroxide, benzoyl peroxide, dibenzoyl peroxide, di(tert-butyl) peroxide, tert-butylcumyl peroxide, 2,5-bis(tert-butylperoxy)-2,5-dimethylhexane, 4,4-bis(tert-butylperoxy)valerate, OO-(tert-butyl)O-(2-ethylhexyl)monoperoxycarbonate, tert-butylperoxyisopropylcarbonate, tert-butylperoxybenzoate, tert-3,5,5-trimethylhexanoate, 1,3(4)-bis(tert-butylperoxyisopropyl)benzene and mixtures thereof.

14. The thermal interface material according to any one of the preceding claims, wherein the material is selected from thermal pads and thermal sheets.

15. The thermal interface material according to any one of the preceding claims, wherein the material exhibits a thickness ranging from 0.2 mm to 10 mm, preferably from 0.5 mm to 8 mm, and more preferably from 1 mm to 6 mm.

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