Thermosetting composite resins repairable under oscillating magnetic stimulus, for insulating power modules

Abstract

The present invention relates to a composite material having a vitrimer matrix, the production method thereof, and the uses of same. The material of the invention can remotely self-repair defects that may appear within the material, under the effect of an oscillating magnetic field.

Description

[0001] DESCRIPTION

[0002] TITLE: THERMOSETTING COMPOSITE RESINS REPAIRABLE UNDER OSCILLATORY MAGNETIC STIMULUS FOR THE INSULATION OF POWER MODULES

[0003] Technical field of the invention

[0004] The present invention relates to a vitrimer matrix composite material, its manufacturing method and its uses.

[0005] The material of the invention can remotely self-repair defects that may appear within it under the action of an oscillating magnetic field.

[0006] Technical background

[0007] The technical background includes in particular documents WO201 6 / 199637, KR 2018 0125825 and WO 2018 / 021623.

[0008] Electrical energy is a key element of the energy transition because it represents one of the alternatives to fossil fuels. Aeronautics players are aiming to replace certain systems (hydraulic, mechanical, pneumatic) with electrical systems, with the aim of significant weight savings and therefore a reduction in fuel consumption and pollutant emissions. Thus, the market for electrical systems such as power converters is growing rapidly. Power modules are regularly used in electronics to create energy conversion circuits. A power module consists of the following elements: semiconductor chips, metallized ceramic substrates, baseplate, solders, electrical connections, and housing ([Fig. 1]). The latter contains a polymer encapsulant.The purpose of the encapsulant is, on the one hand, to ensure the dielectric strength of the power module, and on the other hand, to protect the semiconductor chips from external aggressions (humidity, contamination, etc.). In addition, it must reinforce the electrical insulation between the conductors and improve resistance to partial discharges due in particular to defects in the metallization of the substrates. The silicone resins used for encapsulating modules are the products offering the best performance in terms of flexibility and the highest operating temperature range, generally from -45 to 200°C. This material being flexible and soft, it exerts little or no stress on the elements of the power module (for example on the wire wiring also called bridges or bonding wires).

[0009] The arrival on the market of more efficient power components imposes new operating constraints (higher voltage and operating temperature). For example, the phenomenon of field reinforcement at the triple point is amplified: Within a power module, the areas located at the junction between the substrate, the metallization and the polymer insulator are the site of a reinforcement of the electric field, which can lead to the appearance of partial discharges as shown in [Fig. 2].

[0010] A partial discharge is a discharge located in insulation. This is called partial because it does not short-circuit the entire insulation. The extension of the discharge is limited either because the local electric field is not sufficient to cause its total propagation, or because the propagation is blocked by an insulator with a higher breakdown field. Although a partial discharge does not immediately lead to the decommissioning of a device, it is nevertheless detrimental because it causes degradation of the materials under the action of various stresses: thermal stress generated locally by the discharge, chemical stress due to the degradation products generated by the discharge, and mechanical erosion.

[0011] Recent work describes a thermoplastic resin doped with a small amount of superparamagnetic iron oxide nanoparticles. Following a simulated electrical defect, these nanoparticles migrate to the damaged area of ​​the matrix under the effect of an external stimulus (oscillatory magnetic field or "OMF" (Oscillating Magnetic Field in English)).

[0012] A local temperature increase occurs due to Néel-type relaxation, leading to melting of the thermoplastic matrix. The damaged area is thus repaired and the insulating properties of the material are restored ([Fig. 3]). This process is not normally applicable to a crosslinked and infusible matrix such as silicone or epoxy. Indeed, thermosets are polymer materials in which covalent chemical bonds maintain a permanent 3D network connecting all the polymer chains. They have a thermomechanical resistance far superior to that of thermoplastics. However, thermosets adopt a permanent form and cannot be reprocessed or recycled.

[0013] Vitrimers, the initiative of which was launched in 2011 by Leibler et al. (Self-healing and thermoreversible rubber from supramolecular assembly.

[0014] DOI: 10.1038 / nature06669), and highlighted by the 2015 European Inventor Award, overcomes the drawbacks of thermosets by integrating dynamic covalent cross-links into these networks that are managed by exchange reactions in chemical equilibrium. From a certain temperature (dependent on the dynamic bond system present), the chemical equilibrium is fast enough to promote large-scale network reorganization, thus enabling plastic deformation, reprocessing, recycling, or weldability. When the temperature is not high enough to activate dynamic bond exchange, chemical bond rearrangement is extremely slow or nonexistent, and vitrimers behave as permanently interconnected networks with long-term service and excellent solvent resistance.This unique behavior among organic polymers gives vitrimers new properties at the border between thermoplastics and thermosets.

[0015] The first work on oscillatory magnetic field repair or OMF was published by Corten and Urban in 2009 (Repairing Polymers Using an Oscillating Magnetic Field. DOI: 10.1002 / adma.200901940). These authors demonstrated the possibility of repairing under an oscillatory magnetic field (300 kHz), a thermoplastic terpolymer synthesized from methyl methacrylate, butyl acrylate and heptadecafluorodecyl methacrylate and containing more than 10% by weight of superparamagnetic nanoparticles of gamma iron oxide with a diameter of 12 nm. With the same aim, Ahmed and Ramanujan reported commercial matrices of EVA (poly(ethylene-co-vinyl acetate)) type (Magnetic Field Triggered Multicycle Damage Sensing and Self-Healing. DOI: 10.1038 / srep13773) and NBR (non-crosslinked acrylonitrile and butadiene co-polymers) type (Bio-Inspired Multiple Cycle Healing and Damage Sensing in Elastomer-Magnet Nanocomposites. DOI: 10.1002 / macp.201900168) loaded with Mn-Zn ferrite nanoparticles. Pancholi and Darr investigated superparamagnetic nanocomposites with thermoplastic polycaprolactam (PA6) matrices loaded with iron oxide (Tuneable magnetic nanocomposites for remote self-healing. DOI: 10. 1038 / s41598- 022- 14135- 8). Greenland et al., described the synthesis of a composite polyurethane adhesive that can be heated and thus easily debonded upon exposure to an OMF (Composite polyurethane adhesives that debond-on-demand by hysteresis heating in an oscillating magnetic field. DOI:.

[0016] 10.1016 / j.eurpolymj.2019.109264). Wang et al. demonstrated the possibility of repairing and restoring the dielectric properties of a polypropylene-based thermoplastic matrix doped with a tiny amount (0.1% by volume) of superparamagnetic iron oxide nanoparticles surface-functionalized with polyethylene glycol (Self-healing of electrical damage in polymers using superparamagnetic nanoparticles. DOI: 10.1038 / S41565-018-0327-4).

[0017] So-called "intrinsic" self-repair is based on the inherent reversibility of the polymer matrix, and it can be triggered by various stimuli (e.g., heat, light, electricity). Among the reversible non-covalent interactions, hydrogen bonds can be mentioned. These are dipole-dipole interactions that can be established between a covalently bonded hydrogen atom and a highly electronegative atom carrying a lone pair (e.g., fluorine, oxygen, nitrogen). Hydrogen bonding is weaker than a covalent bond, but directional just like it, thus being able to confer a so-called "supramolecular" network character to polymer matrices. Other reversible non-covalent interactions have been widely exploited in polymer chemistry, including hydrophobic interactions, ionic bonds, pi stacking or "TT-TT stacking" in English, coordination chemistry.Some examples of matrices exhibiting this type of interaction and repairable under OMF are present in the literature. Schmidt et al. prepared superparamagnetic nanocomposites with matrices based on n-butylacrylate and tert-butylacrylate (Remote-controlled activation of self-healing behavior in magneto-responsive ionomeric composites. DOI: 10.1016 / j.polymer.2015.04.024). The tert-butylacrylate units are hydrolyzed to obtain ionic carboxylate functions, which lead to the formation of a supramolecular network. Skov et al. prepared superparamagnetic silicone nanocomposite matrices doped with iron oxide and modified with 2-ureido-4[1 H]-pyrimidone motifs (A thermo-reversible silicone elastomer with remotely controlled self-healing. DOI: 10.1039 / c7ra13686b). These are known to form reversible hydrogen bond networks.

[0018] Thermoplastic elastomers (TPEs) are often made of crystallizable multiblock copolymers that form biphasic materials at room temperature (20±5°C). While the assemblies of hard segments acting as physical crosslinks give the material its elasticity, the soft phase ensures its flexibility. Above their melting temperature, the hard domains dissociate, leading to chain diffusion and a macroscopic solid-liquid transition. On the other hand, when cooled to a certain application-dependent temperature, the hard segments give the material solid-like properties. This dual behavior considerably facilitates the processing of TPEs, allowing reuse, repair, and recycling, unlike vulcanized rubbers. Baeza et al.prepared superparamagnetic TPEs based on a commercial multi-block polyurethane matrix and iron micro- and nanofillers (Ultrafast Remote Healing of Magneto-Responsive Thermoplastic Elastomer-Based Nanocomposites.

[0019] DOI: 10.1021 / acs. macromol.1 c02046). There is therefore a real need for a composite material comprising a crosslinked and infusible polymer matrix, in particular an insulating one, capable of self-repairing under magnetic stimulus following degradation generated locally by an electric discharge, in particular a partial one, and thus having its insulating properties, in particular, restored. More particularly, there is a real need for a composite material comprising a vitrimer matrix, in particular an insulating one, integrating dynamic covalent cross-links into its networks, and in which the defects generated therein by an electric discharge, in particular a partial one, are repairable under the application of an oscillatory magnetic field or OMF.

[0020] More particularly, there is a real need to have a composite material comprising a vitrimer matrix, in particular an insulating one, which integrates dynamic covalent cross-links into its networks, as described above, which can be reprocessed, recycled, or re-welded.

[0021] Summary of the invention

[0022] The present invention aims precisely to meet these needs, by providing a composite material with a vitrimer matrix, characterized in that it comprises

[0023] (A) 50 to 99.9% by volume relative to the total volume of the composite material, of an epoxy resin, and

[0024] (B) 0.1 to 50% by volume relative to the total volume of the composite material, of magnetic particles dispersed in the resin.

[0025] Magnetic particles can be paramagnetic or superparamagnetic.

[0026] According to one embodiment of the invention, the particles are superparamagnetic. In this state, an external magnetic field can magnetize said particles, as in a paramagnetic material. It should be noted that the magnetic susceptibility of superparamagnetic particles is much greater than that of paramagnetic materials. The invention also relates to a method for manufacturing a vitrimer matrix composite material according to the invention, the method comprising the following steps:

[0027] 1) a mixture of hardener and catalyst (mixture 1) is prepared and the mixture is heated to a temperature between 90 and 200°C, preferably between 100 and 180°C for 1 to 10 hours, preferably for 1 to 5 hours, until the catalyst dissolves;

[0028] 2) a dispersion (mixture 2) is prepared by adding magnetic particles to an epoxy resin with stirring at a temperature of 20 to 50°C, preferably 30 to 40°C for 5 minutes to 3 hours, preferably 30 minutes to 1 hour;

[0029] 3) mixtures 1 and 2 (mixture 3) are brought into contact with stirring and the resulting mixture (mixture 3) is heated to a temperature between 90 and 150°C, preferably between 100 and 130°C for 30 minutes to 10 hours, preferably for 1 to 5 hours;

[0030] 4) at the end of step 3), the mixture 3 is subjected to a temperature of 100 to 130°C for 30 minutes to 5 hours, preferably between 1 and 3 hours, until the mixture is completely crosslinked.

[0031] The material according to the invention can be used in a power module such as, for example, that shown in [Fig. 1], in particular for the insulation of said power module. Thus, the invention relates to the use of a material according to the invention, for the insulation of a power module. The occurrence of partial discharges within an insulating material of a power module can lead to a major material failure. The material of the invention allows self-repair remotely and without opening the protective casing of the power module, thanks to the use of an oscillatory magnetic field or OMF.

[0032] Thus, the invention relates to a method for repairing a defect of electrical origin present within a vitrimer matrix composite material according to the invention, characterized in that an oscillating magnetic field is applied for a duration of 1 second to 300 minutes, preferably less than 60 minutes, with a frequency varying from 100 kHz to 20 MHz, preferably varying from 100 kHz to 900 kHz. The material of the invention makes it possible to repair infusible matrices that are normally non-repairable and non-recyclable and that are used for the insulation of power modules, such as epoxies or silicones. The latter are charged with magnetic particles, in particular superparamagnetic ones, and have dynamic bonds (e.g. ester, disulfides, etc.).Thus, these composite materials with so-called vitrimeric matrices are repaired remotely: under the action of an oscillating magnetic field, the particles migrate towards a defect zone and cause a local increase in temperature, which activates the exchange of dynamic bonds and repairs the defects.

[0033] Brief description of the figures

[0034] Other characteristics and advantages of the invention will appear during the reading of the detailed description which follows for the understanding of which reference will be made to the appended drawings in which:

[0035] [Fig. 1] represents a power module.

[0036] [Fig. 2] represents a power module with the location of a triple point. DBC substrate (Direct Bonding Copper in English) or direct bonding copper substrate is a substrate composed of a ceramic insulator, AI2O3 or AIN on which copper is bonded by high temperature eutectic melting.

[0037] [Fig. 3] represents the repair of a composite thermoplastic matrix under magnetic stimulus as described in: Self-healing of electrical damage in polymers using superparamagnetic nanoparticles. DOI: 10.1038 / S41565-018-0327-4.

[0038] [Fig. 4] represents the repair of a composite vitrimer matrix under magnetic stimulus.

[0039] Detailed description of the invention

[0040] The present invention relates to a vitrimer matrix composite material, characterized in that it comprises

[0041] (A) 50 to 99.9% by volume relative to the total volume of the composite material, of an epoxy resin, and (B) 0.1 to 50% by volume relative to the total volume of the composite material, of magnetic particles dispersed in the resin.

[0042] Vitrimer matrices, which have dynamic covalent bonds, have never been developed into superparamagnetic composites that can be repaired under OMF. The invention is therefore based on the development of a vitrimer matrix material doped with magnetic particles, preferably superparamagnetic, in order to give the matrix self-repair properties under magnetic stimulus and thus eliminate defects that may appear during the life cycle of a power module, in particular those caused by partial discharges.

[0043] In one embodiment of the invention, the vitrimer matrix of the composite material of the invention is loaded with superparamagnetic particles. As described in [Fig. 4], the latter migrate towards a defect zone of electrical origin and allow an increase in the local temperature under the application of an OMF thanks to a Néel-type relaxation. This increase in temperature induces the rapid exchange of the dynamic bonds present within the vitrimer network and therefore a reshaping of the material, in particular the insulating material, allowing the elimination of defects potentially generated by partial discharges.

[0044] A material according to the invention can be used in a power module like that shown in [Fig. 1], in particular for the insulation of said power module.

[0045] Advantageously, the material of the invention makes it possible to repair crosslinked matrices commonly used for the insulation of power modules such as epoxies and silicones. The dynamic exchange of bonds will be induced by local heating of the matrix thanks to the presence of magnetic particles, in particular superparamagnetic, subjected to OMF. It is thus possible to regenerate an insulator in a module very easily and without opening any protective case, simply by approaching an OMF source. Furthermore, the presence of a resin with vitrimeric properties makes it possible to have an insulator which is, moreover, capable of self-repairing without an OMF source, for example, in the case where there is a thermal runaway, which could activate the dynamic exchange specific to vitrimers.

[0046] Component (A) of the material of the invention is epoxy resin. Examples of epoxy resins are Novolac epoxy resins, bisphenol A diglycidyl ether (DGEBA), bisphenol F diglycidyl ether (BFDGE), tetraglycidyl methylene dianiline (TGMDA), pentaerythritol tetraglycidyl ether, tetrabromo bisphenol A diglycidyl ether, hydroquinones diglycidyl ether, ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, butylene glycol diglycidyl ether, neopentyl glycol diglycidyl ether, 1,4-butanediol diglycidyl ether, 1,6-hexanediol diglycidyl ether, cyclohexanedimethanol diglycidyl ether, polyethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, polytetramethylene glycol diglycidyl ether, resorcinol diglycidyl ether, neopentyl glycol diglycidyl ether, bisphenol A polyethylene glycol diglycidyl ether, bisphenol A polypropylene glycol diglycidyl ether, terephthalic acid diglycidyl ester,epoxidized vegetable oils such as corn, soybean, safflower and linseed oil etc., epoxidized fish oils such as capelin and menhaden oil etc., epoxidized limonene, and mixtures thereof.,

[0047] According to one embodiment of the invention, the vitrimer matrix composite material comprises (A) 80 to 99.9% by volume relative to the total volume of the composite material, of an epoxy resin.

[0048] The magnetic particles constitute component (B) of the material of the invention. The magnetic particles are chosen from the group consisting of particles of iron, nickel, cobalt, an iron oxide such as FeO, FesO4, Fe4Os, FesOe, FesO , Fe2sO32, FesOi9 and Fe2Os, (phases a, p, y and s), a cobalt oxide such as CoO and CO2O3, a nickel oxide such as NiO and Ni20s, and mixtures thereof. They can be nanometric (1 to 100 nm) or micrometric (0.1 to 100 pm) and of different shapes (spherical, needles, etc.). The sizes indicated correspond to the diameter of the particles when they are spherical and to the total length of the particles when they are needle-shaped.

[0049] The amount of particles in the matrix is ​​0.1 to 50% by volume relative to the total volume of the composite material. According to one embodiment of the invention, the amount of particles (B) in the matrix is ​​0.1 to 20% by volume relative to the total volume of the composite material, of magnetic particles dispersed in the resin magnetic particles.

[0050] The magnetic field is applied for a duration of 1 second to 300 minutes, preferably less than 60 minutes, with a frequency varying from 100 kHz to 20 MHz, preferably varying from 100 kHz to 900 kHz.

[0051] Optionally, the vitrimer matrix materials will also contain one or more micro- and / or nanoscale thermally conductive fillers (C) having the dimensions indicated above for the magnetic particles (B). Examples of thermally conductive fillers (C) include, but are not limited to, AIN (aluminum nitride), BN (boron nitride), MgSiN2 (magnesium silicon nitride), SiC (silicon carbide), graphite, ceramic-coated graphite, expanded graphite, graphene, carbon fiber, carbon nanotube (CNT), or graphitized carbon black, or a mixture thereof. The amount of thermally conductive filler (C) is sufficient for the composition to have a thermal conductivity greater than or equal to 0.5 W / mK. In one embodiment of the invention, the composite material comprises from 0.1% to 80% by volume relative to the total volume of the composite material, of thermally conductive filler(s) (C) as described above.In one embodiment of the invention, the composite material comprises from 5% to 80% by volume relative to the total volume of the composite material, of thermally conductive filler(s) (C) as described above.

[0052] The invention also relates to a method for manufacturing a vitrimer matrix composite material according to the invention, the method comprising the following steps:

[0053] 1) a mixture of hardener and catalyst (mixture 1) is prepared and the mixture is heated to a temperature between 90 and 200°C, preferably between 100 and 180°C for 1 to 10 hours, preferably for 1 to 5 hours, until the catalyst dissolves;

[0054] 2) a dispersion (mixture 2) is prepared by adding magnetic particles to an epoxy resin with stirring at a temperature of 20 to 50°C, preferably 30 to 40°C for 5 minutes to 3 hours, preferably 30 minutes to 1 hour;

[0055] 3) mixtures 1 and 2 (mixture 3) are brought into contact with stirring and the resulting mixture (mixture 3) is heated to a temperature between 90 and 150°C, preferably between 100 and 130°C for 30 minutes to 10 hours, preferably for 1 to 5 hours;

[0056] 4) at the end of step 3), the mixture 3 is subjected to a temperature of 100 to 130°C for 30 minutes to 5 hours, preferably between 1 and 3 hours, until the mixture is completely crosslinked.

[0057] The crosslinking of mixture 3 can be followed by IR spectroscopy. The disappearance of the characteristic bands of the hardener and vc-oc of the epoxy resin, and the appearance of the characteristic band v c =o of the ester shows the progress of crosslinking.

[0058] As indicated, a material according to the invention can be used in a power module such as that shown in [Fig. 1], in particular for the insulation of said power module.

[0059] In this case, steps 1) to 3) of the method described above are followed. In step 3), after heating, the resulting mixture is poured into a power module, such as the one shown in [Fig. 1], In step 4), the module is heated between 100 and 130°C for 30 minutes to 5 hours, until the matrix is ​​completely crosslinked.

[0060] In the method of the invention, a hardener is required to form a crosslinked three-dimensional network from an epoxy resin. Commonly used hardeners are carboxylic acids, amines, anhydrides.

[0061] Examples of amine hardeners are diethylene triamine, triethylene tetramine, tetraethylene pentamine, dihexylene triamine, cadaverine, putrescine, hexanediamine, spermine, isophorone diamine, phenylenediamine, diamino diphenylmethane, diamino diphenylsulfone, methylene bischlorodiethylaniline. Some amines may contain exchangeable disulfide functions in order to confer vitrimeric properties to the network formed. This is the case of 4,4'-dithiodianiline (4-AFD), 2,2'-dithiodianiline, and cystamine. Some amines may contain exchangeable siloxane functions in order to confer vitrimeric properties to the network formed. This is the case of 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyl disiloxane (BAS).

[0062] Examples of anhydride hardeners are phthalic anhydride, methylnadic anhydride, hexahydrophthalic anhydride, dodecylsuccinic anhydride, glutaric anhydride, succinic anhydride, maleic anhydride, chlorendic anhydride, nadic anhydride, tetrachlorophthalic anhydride, pyromellitic dianhydride, 1,2,3,4 cyclopentanetetracarboxylic acid dianhydride, polyazelaic polyanhydride, polysebacic polyanhydride.

[0063] Examples of acid hardeners are Pripol® 1017 from Uniqema or Croda, a mixture of 75-80% dimers and 18-22% trimers with about 1-3% monomeric fatty acids, Pripol® 1048 from Uniqema or Croda, a mixture of 50 / 50% dimers / trimers, Pripol® 1013 from Uniqema or Croda, a mixture of 95-98% dimers and 2-4% trimers with a maximum of 0.2% monomeric fatty acids, Pripol® 1006 from Uniqema or Croda, a mixture of 92-98% dimers and a maximum of 4% trimers with a maximum of 0.4% monomeric fatty acids, Pripol® 1040 from Uniqema or Croda, a mixture of 95-98% dimers and a maximum of 4% trimers with a maximum of 0.4% monomeric fatty acids, Pripol® 1040 from Uniqema or Croda, a mixture of 95-98% dimers and a maximum of 4% trimers with a maximum of 0.4% monomeric fatty acids, and Pripol® 1040 from Uniqema or Croda. Croda, a mixture of fatty acid dimers and trimers with at least 75% trimers and less than 1% monomeric fatty acids, Arizona Chemicals' Unidyme® 60, a mixture of 33% dimers and 67% trimers with less than 1% monomeric fatty acids, Arizona Chemicals' Unidyme® 40, a mixture of 65% dimers and 35% trimers with less than 1% monomeric fatty acids, Arizona Chemicals' Unidyme® 14,mixture of 94% dimers and less than 5% trimers and other higher oligomers with about 1% monomeric fatty acids, Empol® 1008 from Cognis, mixture of 92% dimers and 3% higher oligomers, mainly trimers, with about 5% monomeric fatty acids, Empol® 1018 from Cognis, mixture of 81% dimers and 14% higher oligomers, mainly trimers, with about 5% monomeric fatty acids, Radiacid® 0980 from OIeon, mixture of dimers and trimers with at least 70% trimers. In this process, the quantity of hardener is in particular greater than or equal to the molar quantity of epoxy resin.,

[0064] According to one embodiment of the invention, the hardener is a carboxylic acid.

[0065] Carboxylic acids react with epoxide groups to form esters. The presence of at least one hardening compound comprising at least three carboxylic acid functions makes it possible to form a three-dimensional network. The hardener will preferably be chosen from carboxylic acids in the form of a mixture of fatty acid dimers and trimers.

[0066] In the case of amine hardeners, the amines react with the epoxide groups to form substituted amines. In the case of anhydride hardeners, the anhydrides react with the epoxide groups to form esters.

[0067] If a 1:1 equimolar ratio of carboxylic acids to epoxies is used, a moderately crosslinked polyhydroxyester network is obtained. With a 2:1 ratio of carboxylic acids to epoxies, a highly crosslinked polyester network is obtained, but this network does not contain the free hydroxyl groups required for a transesterification reaction. Thus, a compromise must be found to allow transesterification but also a high crosslink density ensuring robustness and good mechanical properties.

[0068] Activation of the hardener by a catalyst is sometimes necessary.

[0069] Examples of catalysts are 1,5,7-triazabicyclo[4.4.0]dec-5-ene4-pyrrolidinopyridine, dimethylaminopyridine, salts of Zn, Sn, Mg, Co, Ca, Ti and Zr such as acetylacetonates, including cobalt acetylacetonate, samarium acetylacetonate, tin compounds such as dibutyltin laurate, tin octoate, dibutyltin oxide, dioctyltin, dibutyldimethoxytin, tetraphenyltin, tetrabutyl-1,3-dichlorodistannoxane, rare earth, alkali metal and alkaline earth metal acetates such as calcium acetate, zinc acetate, tin acetate, cobalt acetate, nickel acetate, lead acetate, zinc acetate, lead acetate, zinc acetate, zinc oxide ... lithium, manganese acetate, sodium acetate, cerium acetate, salts of saturated or unsaturated fatty acids and alkali, alkaline earth and rare earth metals, such as zinc stearate, metal oxides such as zinc oxide, antimony oxide, indium oxide,metal alkoxides such as titanium tetrabutoxide, titanium propoxide, titanium isopropoxide, titanium ethoxide, zirconium alkoxides, niobium alkoxides, tantalum alkoxides, alcoholates and hydroxides of alkali, alkaline earth and rare earth metals, such as sodium alcoholate, sodium methylate, potassium alcoholate, lithium alcoholate, sulfonic acids such as sulfuric acid, methanesulfonic acid, para-toluenesulfonic acid, phosphines such as triphenylphosphine, dimethylphenylphosphine, methyldiphenylphosphine, triterbutylphosphine, phosphazenes.,

[0070] In the process of the invention, the amount of the catalyst is from 0.1 to 40 mol% relative to the total molar amount of hydroxyl and epoxy, preferably from 5 to 25 mol% relative to the total molar amount of hydroxyl and epoxy.

[0071] The catalyst is preferentially solubilized in the hardener by heating and stirring.

[0072] The invention also relates to a method for manufacturing a vitrimer matrix composite material, the method comprising the following steps:

[0073] 1) a mixture of hardener and catalyst (mixture 1) is prepared and the mixture is heated to a temperature between 90 and 200°C, preferably between 100 and 180°C for 1 to 10 hours, preferably for 1 to 5 hours, until the catalyst dissolves;

[0074] 2) a dispersion (mixture 2) is prepared by adding magnetic particles to an epoxy resin with stirring at a temperature of 20 to 50°C, preferably 30 to 40°C for 5 minutes to 3 hours, preferably 30 minutes to 1 hour;

[0075] 3) mixtures 1 and 2 (mixture 3) are brought into contact with stirring and the resulting mixture (mixture 3) is heated to a temperature of between 90 and 150°C, preferably between 100 and 130°C for 30 minutes to 10 hours, preferably for 1 to 5 hours; 4) at the end of step 3), mixture 3 is subjected to a temperature of 100 to 130°C for 30 minutes to 5 hours, preferably between 1 and 3 hours, until the mixture is completely crosslinked.

[0076] All the embodiments indicated above also apply here, alone or in combination.

[0077] The invention also relates to a material capable of being obtained by such a process.

[0078] As already indicated, the material according to the invention can be used in a power module such as, for example, that shown in [Fig. 1], in particular for the insulation of said power module. Thus, the invention relates to the use of a material according to the invention, for the insulation of a power module.

[0079] Within a power module, the areas located at the junction between the substrate, the metallization and the polymer insulator are the site of a strengthening of the electric field, which can lead to the appearance of partial discharges. The latter are harmful because they cause degradation of the materials under the action of various constraints. The materials of the invention make it possible to remotely repair defects that may appear within the insulators used in power modules. The vitrimer matrix composite material according to the invention used, for example, for the insulation of a power module, integrating dynamic covalent cross-links in its networks, and whose defects generated therein by an electric discharge, in particular a partial one, are repairable under the application of an oscillatory magnetic field or OMF.

[0080] Thus, the invention relates to a method for repairing a defect of electrical origin present within a vitrimer matrix composite material according to the invention, characterized in that an oscillating magnetic field is applied for a duration of 1 second to 300 minutes, preferably less than 60 minutes, with a frequency varying from 100 kHz to 20 MHz, preferably varying from 100 kHz to 900 kHz. The materials according to the invention can be recycled. EXAMPLES

[0081] Operating mode

[0082] Step 1: Hardener / catalyst mix

[0083] In a 100 ml flask, 10 g of Pripol® 1040 (Cargill Industrial Specialties) and 370 mg of zinc acetate dihydrate (Merck) are introduced, giving a molar ratio [Zn] / [COOH] of 0.05. The mixture is heated under vacuum in steps of 110°C to 170°C for 3 hours until the catalyst is completely dissolved.

[0084] Step 2: Mix magnetic particles / epoxy

[0085] In a 100 ml flask, 20 wt% FesC particles (size less than 5 pm, Merck) were added to a concentrated solution of 4.63 g of DGEBA (Merck) in THF (Merck, 700 mg ml' 1 ). The solution was placed in an ultrasonic bath (Branson Ultrasonics™ CPXH) for 30 minutes to ensure homogeneous dispersion of the particles within the matrix. The solution was placed in an oven (France Etuves XFE050) at 40°C to allow slow evaporation of the solvent.

[0086] Step 3: composite formulation

[0087] 7.9 g of the mixture prepared in step 1 are added to the mixture prepared in step 2. The reaction mixture is homogenized by heating at 130°C for 1 hour with mechanical stirring and then poured into a power module (Safran property) as shown in [Fig. 1], Step 4: crosslinking of the system

[0088] The module is placed in an oven at 130°C (France Etuves XFE050) for 48 hours in order to completely crosslink the system. An IR spectroscopy analysis (Mettler Toledo ReactIR 702L) shows the disappearance of the v band c =o of the acid at 1705 cm' 1 as well as vc-oc of the epoxy function at 915 cm' 1 and the appearance of the v band c =o of the ester at 1735 cm' 1 .

[0089] Step 5: repairing the module under OMF

[0090] To verify the system's repairability, a 2 cm cut is made with a cutter in the insulation and then the module casing is hermetically sealed. The module is then placed in an oscillating magnetic field with a frequency of 850 KHz and an amplitude of 5 mT for 20 seconds using a magnetic inductor (V3+ CEIA). The casing is then opened and it is possible to see with the naked eye and also on a sample analyzed under a microscope (LEICA DVM6) that the material has been regenerated and that the cut has been healed.

[0091] EXAMPLE 1: Catalyzed epoxy-acid system Dynamic exchanges of transesterification type

[0092] Bisphenol A diglycidyl ether (DGEBA, Merck) + Pripol® 1017 (Cargill Industrial Specialties) + zinc acetate (Merck).

[0093] EXAMPLE 2: Eooxy-amine system

[0094] Dynamic disulfide exchanges PDMS-diglycidyl ether (Merck) + 4,4'-dithiodianiline (4-AFD, Molekula).

[0095] EXAMPLE 3: Catalyzed epoxy-amine system

[0096] Dynamic siloxane-type exchanges

[0097] DGEBA (Merck) + 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyl disiloxane (BAS, TCI Chemicals) + 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD, Merck).

Claims

CLAIMS 1. Composite material with a vitrimer matrix, characterized in that it comprises (A) 50 to 99.9% by volume relative to the total volume of the composite material, of an epoxy resin, and (B) 0.1 to 50% by volume relative to the total volume of the composite material, of magnetic particles dispersed in the resin.

2. Material according to claim 1, characterized in that the epoxy resin is chosen from Novolac epoxy resins, bisphenol A diglycidyl ether (DGEBA), bisphenol F diglycidyl ether (BFDGE), tetraglycidyl methylene dianiline (TGMDA), pentaerythritol tetraglycidyl ether, tetrabromo bisphenol A diglycidyl ether, hydroquinones diglycidyl ether, ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, butylene glycol diglycidyl ether, neopentyl glycol diglycidyl ether, 1,4-butanediol diglycidyl ether, 1,6-hexanediol diglycidyl ether, cyclohexanedimethanol diglycidyl ether, polyethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, polytetramethylene glycol diglycidyl ether, resorcinol diglycidyl ether, neopentyl glycol diglycidyl ether, bisphenol A polyethylene glycol diglycidyl ether, bisphenol A polypropylene glycol diglycidyl ether, terephthalic acid diglycidyl ester,epoxidized vegetable oils such as corn, soybean, safflower, and linseed oil, epoxidized fish oils such as capelin and menhaden oil, epoxidized limonene, and mixtures thereof.

3. Material according to one of claims 1 or 2, characterized in that the magnetic particles are chosen from the group consisting of particles of iron, nickel, cobalt, an iron oxide such as FeO, FesO4, Fe4Os, FesOe, FesO, Fe2sO32, FesOi9 and Fe2Os, (phases a, 0, y and s), a cobalt oxide such as CoO and CO2O3, a nickel oxide such as NiO and Ni20s, and mixtures thereof.

4. Material according to any one of claims 1 to 3, characterized in that it comprises one or more thermally conductive fillers (C), the fillers being chosen from AIN (aluminum nitride), BN (boron nitride), MgSiN2 (magnesium and silicon nitride), SiC (silicon carbide), graphite, ceramic-coated graphite, expanded graphite, graphene, carbon fiber, carbon nanotube (CNT) or graphitized carbon black, and mixtures thereof.

5. Material according to claim 4, characterized in that it comprises 0.1% to 80% by volume relative to the total volume of the composite material, of one or more thermally conductive fillers (C).

6. Method for manufacturing a vitrimer matrix composite material according to any one of claims 1 to 5, characterized in that it comprises the following steps: 1) a mixture of hardener and catalyst (mixture 1) is prepared and the mixture is heated to a temperature between 90 and 200°C, for 1 to 10 hours, until the catalyst dissolves; 2) a dispersion (mixture 2) is prepared by adding magnetic particles to an epoxy resin with stirring at a temperature of 20 to 50°C, for 5 minutes to 3 hours; 3) mixtures 1 and 2 (mixture 3) are brought into contact with stirring and the resulting mixture (mixture 3) is heated to a temperature between 90 and 150°C, for 30 minutes to 10 hours; 4) at the end of step 3), mixture 3 is subjected to a temperature of 100 to 130°C for 30 minutes to 5 hours, until the mixture is completely crosslinked.

7. Method according to claim 6, characterized in that the hardener is chosen from - an amine hardener chosen from diethylene triamine, triethylene tetramine, tetraethylene pentamine, dihexylene triamine, cadaverine, putrescine, hexanediamine, spermine, isophorone diamine, phenylene diamine, diamino diphenylmethane, diamino diphenylsulfone, methylene bischlorodiethylaniline , 4,4'-dithiodianiline (4-AFD), 2,2'-dithiodianiline, 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyl disiloxane (BAS); - an anhydride hardener chosen from phthalic anhydride, methylnadic anhydride, hexahydrophthalic anhydride, dodecylsuccinic anhydride, glutaric anhydride, succinic anhydride, maleic anhydride, chlorendic anhydride, nadic anhydride, tetrachlorophthalic anhydride, pyromellitic dianhydride, 1,2,3,4 cyclopentanetetracarboxylic acid dianhydride, polyazelaic polyanhydride, polysebacic polyanhydride; or - an acid hardener chosen from, the mixture of 75-80% of dimers and 18-22% of trimers with around 1-3% of monomeric fatty acids known as “Pripol® 1017 marketed by Uniqema or Croda” the mixture of 50 / 50% of dimers / trimers known as “Pripol® 1048 marketed by Uniqema or Croda”, the mixture of 95-98% of dimers and 2-4% of trimers with a maximum of 0.2% of monomeric fatty acids known as “Pripol® 1013 marketed by Uniqema or Croda”, the mixture of 92-98% of dimers and a maximum of 4% of trimers with a maximum of 0.4% of monomeric fatty acids known as “Pripol® 1006 marketed by Uniqema or Croda”, the mixture of fatty acid dimers and trimers with at least 75% trimers and less than 1% monomeric fatty acids known as "Pripol® 1040 marketed by Uniqema or Croda, the mixture of 33% dimers and 67% trimers with less than 1% monomeric fatty acids known as "Unidyme® 60 marketed by Arizona Chemicals", the mixture of 65% dimers and 35% trimers with less than 1% monomeric fatty acids known as "Unidyme® 40 marketed by Arizona Chemicals, the mixture of 94% dimers and less than 5% trimers and other higher oligomers with about 1% monomeric fatty acids known as "Unidyme® 14 marketed by Arizona Chemicals", the mixture of 92% dimers and 3% higher oligomers, mainly trimers, with about 5% monomeric fatty acids known as "Empol® 1008 marketed by Cognis”, the mixture of 81% dimers and 14% higher oligomers, mainly trimers, with order of 5% monomeric fatty acids known as “Empol® 1018 marketed by Cognis”, the mixture of dimers and trimers with at least 70% trimers known as “Radiacid® 0980 marketed by Oleon”.

8. Method according to claim 7, characterized in that the quantity of hardener is greater than or equal to the molar quantity of epoxy resin.

9. Process according to any one of claims 6 to 8, characterized in that the catalyst is chosen from 1,5,7-triazabicyclo[4.4.0]dec-5-ene4-pyrrolidinopyridine, dimethylaminopyridine, salts of Zn, Sn, Mg, Co, Ca, Ti and Zr such as acetylacetonates, in particular cobalt acetylacetonate, samarium acetylacetonate, tin compounds such as dibutyltin laurate, tin octoate, dibutyltin oxide, dioctyltin, dibutyldimethoxytin, tetraphenyltin, tetrabutyl-1,3-dichlorodistannoxane acetates of rare earths, alkali metals and alkaline earth metals such as calcium acetate, zinc acetate, tin acetate, cobalt, nickel acetate, lead acetate, lithium acetate, manganese acetate, sodium acetate, cerium acetate, salts of saturated or unsaturated fatty acids and alkali, alkaline earth and rare earth metals, such as zinc stearate,metal oxides such as zinc oxide, antimony oxide, indium oxide, metal alkoxides such as titanium tetrabutoxide, titanium propoxide, titanium isopropoxide, titanium ethoxide, zirconium alkoxides, niobium alkoxides, tantalum alkoxides, alcoholates and hydroxides of alkali, alkaline earth and rare earth metals, such as sodium alcoholate, sodium methylate, potassium alcoholate, lithium alcoholate, sulfonic acids such as sulfuric acid, methanesulfonic acid, para-toluenesulfonic acid, phosphines such as triphenylphosphine, dimethylphenylphosphine, methyldiphenylphosphine, triterbutylphosphine, phosphazenes., 10. Method according to claim 9, characterized in that the amount of catalyst is from 0.1 to 40 mol% relative to the total molar amount of hydroxyl and epoxy.

11. Use of a material according to any one of claims 1 to 5, for the insulation of a power module.

12. Method for repairing a defect of electrical origin present within a vitrimer matrix composite material according to any one of claims 1 to 5, characterized in that an oscillating magnetic field is applied for a duration of 1 second to 300 minutes, with a frequency varying from 100 kHz to 20 MHz.

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