Covalent adaptative network

Abstract

A covalent adaptative network obtained by a method of manufacturing comprising: - preparing a substantially water-free curable composition by mixing: - at least one multifunctional cyclic carbonate having at least two cyclic carbonate groups, notably at least two terminal cyclic carbonate groups (compound A), - at least one epoxide compound comprising at least two oxirane groups (compound B), and - at least one polyprimary polyamine comprising at least 2 primary amine groups (compound C) - curing the substantially water-free curable composition to obtain the covalent adaptative network.

Description

Covalent adaptative network

[0001] The present invention relates to a covalent adaptative network, to a method ofmanufacturing a covalent adaptative network and to a method of reprocessing a covalentadaptative network. The present invention also relates to a method of manufacturing a reprocessable material wherein the reprocessable material is manufactured with the covalent adaptative network as well as to a method of reprocessing the reprocessable material.

[0002] Fiber-reinforced polymer (FRP), in particular carbon fiber-reinforced polymers(CFRP), offers exceptional strength-to-weight ratios compared to traditional metallic structural materials. Advances in such materials led to significant improvements in structuralperformance, durability, and efficiency. As an example, CFRP allows to reach much tallerwind turbines thanks to weight saving to increase electricity production and yield, specifically offshore. Equally, weight saving in the transportation industry, including aircraft andautomotive, leads to substantial fuel savings. Although the exceptional properties are mainlycarried by the fibers, the matrices used remain key to such materials and are most often the limiting factor. Indeed, the polymeric matrix must display high adhesion with the fibers to efficiently transfer the external load to the fiber through the interface. Also, they govern the manufacturing process required to obtain FRP and alter the end-of-life scenarios. While thermosets, mostly epoxy ones, offer the best FRP properties, they require a long processing time to be impregnated along fibers and cured. Besides, the recycling of such FRP isextremely limited due to the inherent chemical and physical stability of thermosets. Whilst thisstability is desired for service life, it is a severe limitation for sustainability and circularityconcerns. It usually causes used FRP structures to be either landfilled or incinerated andcauses the loss of energy-intensive-produced carbon fibers. The loss of such high-added value fibers that could still be used in many applications has a considerable negative impact on the environment as it leads to more unnecessary material production.

[0003] Therefore, it has become necessary to develop alternatives that can offer similarperformances to thermosets and additional options for manufacturing and recycling. Many decades of research on both fiber and matrix have led to highly efficient and competitive materials with optimized manufacturing processes and final properties, that are hard to replace in industries. Solutions developed should take therefore into account both chemical processes to obtain alternatives and end-user requirements, including manufacturing, scalability, cost, sustainability, and final properties.

[0004] Covalent Adaptive Networks (CAN) have emerged as a promising alternative totraditional thermoset applications, including composites, to achieve circular and high-P1694-WO EpoxyPHUperformance materials. CAN are crosslinked polymer networks incorporating dynamiclinkages that can be triggered by external factors such as temperature, pressure, or light tobe reshaped, reformed, or cleaved under specific conditions. Various dynamic chemistries have been brought to light to either make epoxy vitrimeric such as disulfide metathesis, transesterification, siloxane, transimination, but also by bringing new polymer chemistry solutions such as vinylogous urethane, boronic ester, N-S acetal, and many others. They have shown promising results in composite applications by allowing the welding, thermo- forming, and recycling of FRP. Nevertheless, the challenge of developing dynamic networks that can be manufactured on a large scale using cost-effective and environmentally friendly reagents, without compromising the manufacturing process or the final product properties, remains a significant hurdle, and even more, targeting the demanding structural composite field. Most of the solutions, significantly change the composite manufacturing process and require expensive, hazardous reagents, catalysts, and complex synthesis steps that maketheir industrial relevance questionable. The properties are often altered by this dynamicnetwork, in particular, the stress relaxation needed for the dynamic network also leads to creep behaviour. In that sense, developing economically relevant solutions that are easily accessible from renewable feedstocks, without hazardous reagents or complex synthesis, scalable, and with satisfying material properties should become a major effort.

[0005] The inventors have surprisingly found that the synergistic effects between the slowdynamic behaviour of hydroxyurethane, that can be derived from CO2-based cycliccarbonate, and a conventional non-dynamic amine-epoxy network provide a high- performance, fast epoxy vitrimer, even in absence of catalyst. This epoxy-amine naturally incorporates a self-catalyzed amino-alcohol.

[0006] In accordance with one aspect as defined in claim 1, the present invention providesa covalent adaptative network obtained by a method of manufacturing comprising:- preparing a substantially water-free curable composition by mixing:- at least one multifunctional cyclic carbonate having at least two cyclic carbonate groups,notably at least two terminal cyclic carbonate groups (compound A)- at least one epoxide compound comprising at least two oxirane groups (compound B), and- at least one polyprimary polyamine comprising at least 2 primary amine groups (compoundC)- curing the substantially water-free curable composition to obtain the covalent adaptativenetwork.

[0007] The dependent claims define preferred or alternative embodiments.P1694-WO EpoxyPHU

[0008] As used herein, the term compound A refers to the combination of all moleculespresent which fall within the definition of compound A. That is to say, compound A may be a single compound or a combination of two or more compounds (each of which falls within the definition of compound A). Similarly, as used herein, the term compound B refers to the combination of all molecules present which fall within the definition of compound B and the term compound C refers to the combination of all molecules present which fall within the definition of compound C.

[0009] Any feature described herein in relation to a particular aspect of the invention maybe used in relation to any other aspect of the invention.

[0010] As used herein, the term "consisting essentially of" is intended to limit the scope ofa statement or claim to the specified materials or steps and those that do not materially affect the basic and novel characteristic(s) of the invention.

[0011] Terminology used for describing particular embodiments is not intended to belimiting for the invention. As used herein, the singular forms "a", "an" and "the" are intendedto include the plural forms as well, unless the context clearly indicates otherwise. The term "and / or" includes any and all combinations of one or more of the associated listed items. It will be understood that the terms "comprises" and / or "comprising" specify the presence of stated features but do not preclude the presence or addition of one or more other features. It will be further understood that when a particular step of a method is referred to as subsequent to another step, it can directly follow said other step or one or more intermediate steps may be carried out before carrying out the particular step, unless specified otherwise.

[0012] The curable composition obtained by mixing compounds A, B and C is substantiallywater free; indeed, it is preferably water free. It is thus different from compositions that may be obtained by mixing components in the presence of water where the quantity of water has a significant effect upon the nature of the composition obtained, for example causing the formation of a foamed composition. Compound A, compound B and compound C and thecurable composition may comprise residual ambient humidity water, notably it is understoodthat before being used, compound A, compound B and compound C need not to be driedbefore being used but may be used with the inevitable presence of residual humidity. In oneembodiment, the substantially water-free curable composition may comprise no more than 1wt %, preferably no more than 0.5 wt %, more preferably no more than 0.2 wt %, even morepreferably no more than 0.1 wt % of water based on the total weight of the curablecomposition.P1694-WO EpoxyPHU

[0013] The term “dry weight of the curable composition” as used herein means the weightof all components of the curable composition other than any water that is present (whether in the form of liquid water or in the form of water of crystallization).

[0014] As used herein the term “ketone” means a C=O group.The term "heteroatom" means any atom that is not carbon or hydrogen; preferably theheteroatom is an atom selected from N, O, S and Si.The term “alkyl” means a saturated hydrocarbon chain, for example a hydrocarbon chain from 1 to 20 carbon atoms.The term "cycloalkyl" means a saturated hydrocarbon chain wherein at least a portion of thechain is cyclic, notably the cycloalkyl may be a monovalent or bivalent 3 to 8 memberedcarbon ring, for example cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl or cyclooctyl. The term "heterocycle" means a cycloalkyl wherein at least one of the carbon atom of the cyclic chain has been replaced by a heteroatom. The heterocycle may notably be a monovalent or bivalent non-aromatic mono or bi-cyclic radical of four to nine ring atoms inwhich one to three ring atoms are heteroatoms independently selected from N, O S and Si,with the remaining ring atoms being C, for example a piperidyl or a cyclic carbonate.The term "aryl" means a group comprising at least one aromatic ring. The aryl may notablybe a monovalent or bivalent aromatic carbocyclic group containing 6 to 14, particularly 6 to10, carbon atoms and having at least one aromatic ring or multiple condensed rings in which at least one ring is aromatic. Examples include phenyl, benzyl, naphthyl, biphenyl, anthryl, azalenyl or indanyl.The term "heteroaryl" means aryl wherein at least one of the carbon atoms of the aromaticring has been replaced by a heteroatom. The heteroaryl may be a monovalent or bivalentcyclic aromatic group containing 1, 2 or 3 heteroatoms, having at least one aromatic ring or multiple condensed rings in which at least one ring is aromatic. The aromatic ring may be a 6 membered ring, such as pyridinyl, or a 5-membered ring, such as thiazolyl, isoxazolyl, isothiazolyl, oxadiazolyl, imidazolyl, triazolyl or thiadiazolyl. As used herein the term "substituted" means the replacement of one or more hydrogen atoms with other functional groups. Such other functional groups may include hydroxyl, halo, thiol, alkyl, haloalkyl, heteroalkyl, aryl, arylalkyl, arylheteroalkyl, nitro, sulfonic acids and derivatives thereof, carboxylic acids and derivatives thereof.

[0015] As used herein, the term “molar ratio” refers to the amount of moles of a compoundversus the amount of moles of a second compound. The amount of moles is calculated by dividing the mass of a compound by its molar mass. In the case of a compound havingP1694-WO EpoxyPHUmultiple functions, the amount of moles is multiplied by the number of functions being able to react. The amount obtained after multiplication by the number of function(s) is referred to as an equivalent amount. In the present case, the amount of moles of cyclic carbonate groups is always taking into account the number of functions being able to react and is thus always an equivalent amount. For example, 1g of a cyclic carbonate compound containing three cyclic carbonate groups having a molar mass of 434 g / mol contains 1 / 434 * 3 = 0.0069 molesof cyclic carbonate groups. The term “equivalent” refers to an amount of moles taking intoaccount the multiplicity of functions in a compound.

[0016] As defined herein, compound A is chosen from multifunctional cyclic carbonateshaving at least two cyclic carbonates, notably at least two terminal cyclic carbonate groups (or so-called multifunctional external cyclic carbonates) or a mixture thereof. In general, saidcompounds A correspond to Formula (Ia) or Formula (Ib).(Formula (Ia)) (Formula (Ib))Preferably compounds A correspond to Formula (Ia) wherein i is an integer higher than or equal to 2, in particular from 2 to 10, more particularly 2 or 3, R1 is a carbon bond between the cyclic carbonate rings or is a linear or branched hydrocarbon chain, which may be unsubstituted or substituted and wherein one or several hydrocarbon groups of said hydrocarbon chain may be replaced by a heteroatom, a ketone, a cycloalkyl, a heterocycle, an aryl or a heteroaryl, each of which may be unsubstituted or substituted, said hydrocarbon chain having at least 2 carbon atoms, in particular from 3 to 60 carbon atoms. In Formula (Ib), R1and R3may be the same or different and have the same definition as R1defined above. i as defined above for Formula (Ia).

[0017] Alternatively, said compound A may correspond to any one of Formula (IIa),Formula (IIb), Formula (IIIa), Formula (IIIb) or Formula (IV)(Formula (IIa)) (Formula (IIb) (Formula (IIIa))P1694-WO EpoxyPHU(Formula (IIIb)) (Formula (IV))wherein i, R1, and R3 are the same as defined for Formula I above. In Formula (IIa), Formula(IIb), Formula (IIIa), Formula (IIIb) and / or Formula (IV), R1 and R3 may be linked to any oneof the carbon of the cyclic carbonate group.

[0018] Particularly preferred compounds for compound A are:P1694-WO EpoxyPHUIn one embodiment, compound A is selected from the group consisting of ResCC, PentCC, TMTPC and combinations thereof. In one embodiment compound A comprises, consists essentially of, or consists of TMTPC.

[0019] In one embodiment, compound A may be obtained from the simple cycloadditionof CO2 into epoxy, in a very straightforward and scalable process (Alves M. et al., CatalysisScience & Technology.2017;7(13):2651-84). The low viscosity of the epoxy and wide libraryof available building blocks would allow the implementation of large-scale composite manufacturing without requiring any change from existing manufacturing protocols.

[0020] Compound B is chosen from epoxide compounds comprising at least two oxiranegroups. In general, compound B correspond to formula (X):(Formula (X)) wherein j is an integer higher than or equal to 2, in particular from 2 to 10, more particularly 2 or 3, R1′ is a carbon bond between the epoxide rings when j is from 2, or is a linear or branched hydrocarbon chain, which may be unsubstituted or substituted and wherein one or several hydrocarbon groups of said hydrocarbon chain may be replaced by a heteroatom, a ketone, a cycloalkyl, a heterocycle, an aryl or a heteroaryl, each of which may be unsubstituted or substituted, said hydrocarbon chain having at least 2 carbon atoms, in particular from 3 to 60 carbon atoms.P1694-WO EpoxyPHU

[0021] Particularly preferred compounds for compound B are:In one embodiment, compound B is selected from the group consisting of RDGE, BADGE,P1694-WO EpoxyPHUMDGA and combinations thereof. In one embodiment compound B comprises, consists essentially of, or consists of RGDE.

[0022] Compound C is chosen from polyprimary polyamines comprising at least 2 primaryamine groups. In general, compound C corresponds to formula (V):R2-( NH2)k (Formula (V))wherein k is an integer higher than or equal to 2, in particular from 2 to 10, more particularly2 or 3, R2 is a carbon bond between the primary amine groups or is a is a linear or branched hydrocarbon chain, which may be unsubstituted or substituted and wherein one or several hydrocarbon groups of said hydrocarbon chain may be replaced by a heteroatom, a ketone, a cycloalkyl, a heterocycle, an aryl or a heteroaryl, each of which may be unsubstituted or substituted, said hydrocarbon chain having at least 2 carbon atoms, in particular from 3 to 60 carbon atoms.

[0023] Particularly preferred compounds for compound C are:In one embodiment compound C comprises, consists essentially of, or consists of mXDA.P1694-WO EpoxyPHU

[0024] During the step of curing the substantially water-free curable composition, dynamichydroxy-urethane moieties, and activated hydroxyl are obtained. This formed polymerexhibits a fast catalyst-free adaptative behaviour that allows the novel network to be recycledunder mild conditions. The synergetic behaviour arises from the amino-alcohol formed by theepoxy-amine reaction while the dynamic hydroxyurethane is obtained from the aminolysis ofcyclic carbonates. The formed amino-alcohol could be expected to act as an internal catalystand therefore promote the dynamicity of the network.

[0025] Preferably, the substantially water-free curable composition is free of any externalcatalyst.

[0026] The substantially water-free curable composition may nevertheless compriseoptional external catalyst D to increase the kinetics of the reaction, either polymerizationand / or the reprocessable behaviour. Particularly preferred external catalysts for use ascompound D are base catalyst such as 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), imidazole,tetrabutyl ammonium oxalate, tetrabutyl ammonium phenolate (TBAP), tetrabutyl ammonium hydroxide, potassium carbonate, cesium carbonate and potassium or sodium phosphate (mono, di or tribasic forms), potassium or sodium or calcium hydroxide, sodium tetraborate,sodium pyrophosphate, tin-derivated catalyst such as dibutyltin dilaurate or stannous octoate.In one embodiment, compound D comprises, consists essentially of, or consists of DBU.

[0027] The substantially water-free curable composition may be prepared by combiningcompounds comprising, preferably consisting essentially of, and more preferably consistingof the 1) compound A, 2) compound B, and 3) compound C.

[0028] The compounds A, B and C, may be mixed all together, or alternatively twocompounds, may be mixed first, followed by the addition of the third compound.

[0029] In the substantially water-free curable composition, compound A, compound B andcompound C, may be mixed such as to have:- a molar ratio of oxirane groups of compound B to cyclic carbonate groups of compound Ain the range of 0.15 to 5, preferably in the range of 0.4 to 2.5, and- a molar ratio of oxirane groups of compound B to primary amine groups of compound C inthe range of 0.5 to 1.1, preferably in the range of 0.9 to 1, and- a molar ratio of cyclic carbonate groups of compound A to primary amine groups ofcompound C in the range of 0.5 to 1.5, preferably in the range of 0.9 to 1.1.

[0030] By way of example, where the “molar ratio of oxirane groups of compound B tocyclic carbonate groups of compound A is in the range of 0.15 to 5”, and compound Bcomprises a mixture of several compounds, such as B1 and B2, it is the total quantity ofP1694-WO EpoxyPHUoxirane groups of B1 and B2 that is considered in the molar ratio. The same applies for all compounds, i.e. compounds A and compounds C.

[0031] When (a) represents the total dry weight of compound A, (b) represents the totaldry weight of compound B, (c) represents the total dry weight of compound C,- (a) represents from 10 wt% to 90 wt%, preferably from 30 wt% to 70 wt% of the total dryweight of (a) and (b);- (b) represents from 10 wt% to 90 wt%, preferably from 30 wt% to 70 wt% of the total dryweight of (a) and (b);- (c) represents from 20 wt% to 60 wt%, preferably from 35 wt% to 55 wt% of the total dryweight of (a) and (b);- (a) + (b) + (c) is at least 90 wt%, preferably 95 wt%, more preferably at least 97 wt%, evenmore preferably at least 98 wt% of the total dry weight of the substantially water-free curable composition.

[0032] If present the amount of compound D represents from 0.1 mol% to 10 mol %,preferably from 2.5 mol% to 7.5 mol %, more preferably from 2.5 mol % to 5.5 mol % of thetotal mol % of compound A; compound B, compound C and compound D of the substantiallywater-free curable composition.

[0033] Curing of the substantially water-free curable composition to obtain the covalentadaptative network may be carried out within a relatively short time after the mixing of thereactants. The duration of the curing step may be in the range of between 5 minutes to 72 hours, preferably between 20 min to 5 hours, more preferably between 45 minutes to 3 hours.

[0034] Curing of the substantially water-free curable composition to obtain the covalentadaptative network may be carried out at a temperature between 15°C and 220°C, preferablybetween 40°C and 160°C, more preferably between 60°C to 120°C, even more preferably between 60°C to 100°C.

[0035] The step of curing is preferably followed by a step of post-curing. Herein, the term"post-curing" means heating at a temperature above the maximum temperature to which thesubstantially water-free curable composition has been exposed during curing. Post-curing may be carried out at a temperature between 50°C to 250°C, preferably between 100°C to 200°C, more preferably between 120°C to 180°C. The duration of the post-curing may be in the range of between 5 minutes to 24 hours, preferably between 20 min to 3 hours, more preferably between 30 minutes to 1.5 hours.

[0036] The steps of curing and post-curing may be carried out by any suitable technique,such as by a heated press, a conventional oven, hot steam, by electromagnetic radiation P1694-WO EpoxyPHU(notably with a frequency between 1 MHz and 10 GHz) including microwaves and / orelectromagnetic radiation in the radio frequency (RF) range.

[0037] The density of the covalent adaptative network may be between 900 kg / m3 and1500 kg / m3, more preferably between 1200 kg / m3 and 1400 kg / m3.

[0038] The covalent adaptative network may have a Young’s modulus between 1 MPaand 6 GPa, preferably between 1 GPa and 6 GPa, more preferably between 2 GPa and 6GPa as measured in accordance with ASTM D638 / ISO527-4.

[0039] In accordance with one aspect as defined in claim 12, the present inventionprovides a method of reprocessing the covalent adaptative network as defined above,wherein the method comprises:- heating the covalent adaptative network in a mould under pressure.

[0040] The reprocessing temperature of the covalent adaptative network may be achievedat a temperature between 80°C to 250°C, preferably between 100°C to 200°C, more preferably between 120°C to 180°C.

[0041] The step of heating the covalent adaptative network in a mould under pressure,may be made at a pressure which is between 0.1 MPa to 12 MPa, preferably between 1 MPa and 10 MPa, more preferably between 2 MPa and 10 MPa, even more preferably between 4MPa to 8 MPa. The temperature of the mould may be between 80°C to 240°C, preferablybetween 100°C to 220°C, more preferably between 120°C to 200°C. The duration of the stepof heating the covalent adaptative network in a mould under pressure may be in the range ofbetween 5 minutes to 5 hours, preferably between 20 min to 3 hours, more preferably between 30 minutes to 1.5 hours.The step of heating the covalent adaptative network in a mould under pressure may comprisea prior step of pre-heating the mould before applying pressure.

[0042] Prior to reprocessing of the covalent adaptative network, said covalent adaptativenetwork may be cut in pieces in order to be easily entered in to the mould. Alternatively, thecovalent adaptative network may be pre-processed in any useful form in order to be entered in to the mould.

[0043] The reprocessed covalent adaptative network has comparable Young’s modulusto the covalent adaptative network before reprocessing. As used herein comparableproperties means the same value within a range of more or less 50 %. The reprocessedcovalent adaptative network may have a Young’s modulus to the covalent adaptative networkbefore reprocessing within the same value within the range of more or less 25 %. P1694-WO EpoxyPHU

[0044] The covalent adaptative network (CAN) may be reprocessed at least once or twicewith the method as described above without significant loss in regard of Young’s modulus.

[0045] The covalent adaptative network of the present invention exhibits promisingpotential for future application with the ability to be healed, reshaped, and reprocessed. In particular, it opens many doors in the realm of composite manufacturing where welding and reshapability are particularly expected.

[0046] CAN are a breakthrough in the composite industry as they allow high-performancematerials to be reshaped and welded, impossible with conventional thermosets. Thus, prepregs and semi-finished parts can be manufactured by infusing reinforcement using conventional tooling. Complex shapes and final parts could later be obtained by exploiting the fast exchange mechanism.

[0047] In accordance with one aspect as defined in claim 13, the present inventionprovides a method of manufacturing a reprocessable material, the method comprising:- preparing a substantially water-free curable composition by mixing:- at least one multifunctional cyclic carbonate having at least two cyclic carbonate groups,notably at least two terminal cyclic carbonate groups (compound A),- at least one epoxide compound comprising at least two oxirane groups (compound B), and- at least one polyprimary polyamine comprising at least 2 primary amine groups (compoundC)- combining the substantially water-free curable composition with a collection of matter toprovide an intermediate product, and- curing the intermediate product to provide the reprocessable material.

[0048] The reprocessable material of the present method may be a fiber-reinforcedpolymer (FRP), in particular a carbon fiber-reinforced polymer (CFRP). When the material isa FRP, the collection of matter may comprise, consists essentially of, or consists of fibersselected from the group consisting of: carbon fibers, polyester fibers, polyamide fibers,cellulosic fibers, natural fibers, aramid fibers, polypropylene fibers, basalt fibers and glassfibers, and combinations thereof. The FRP may comprise woven and / or non-woven fibers. The FRP may comprise oriented or non-oriented fibers. The length of the fibers can range from 0.5 mm to continuous fibers, preferably from 5 mm to continuous length and morepreferably from 10 cm to continuous fibers. Oriented means all fibers are parallel, non-oriented mean they are randomly put into the matrix, with non control. P1694-WO EpoxyPHU

[0049] The reprocessable material may be a laminate wherein the collection of matter maycomprise, consists essentially of, or consists of one or more fibrous layers, notably of anysuitable fibrous sheet materials. The fibrous layer may be plies of carbon fibers.

[0050] When the reprocessable material is a laminate, the step of combining thesubstantially water-free curable composition with a collection of matter to provide anintermediate product may comprise a step of applying the substantially water-free curablecomposition between each layer.

[0051] The reprocessable material may be a reinforced polymer. When the material is areinforced polymer, the collection of matter may comprise, consists essentially of, or consists of fillers or reinforcement material selected from the group consisting of (nano)clays,hydrotalcite, graphene, carbon nanotube and nano fibers, organic / inorganic particles, ironoxide, silica, wood flour.

[0052] The reprocessable material obtained by the present method, notably CFRP maybe used in the aerospace, automotive, sports, leisure, marine, construction industries, energy(wind turbine). The reprocessable material may be used as a coating for textiles, notably in knitted fibers.

[0053] The step of curing the intermediate product to provide the reprocessable materialmay comprise heating and / or applying pressure to the intermediate product. The step of curing may be carried out in a mould.

[0054] Curing the intermediate product to obtain the reprocessable material may beachieved within a relatively short time. The duration of the curing step may be in the range ofbetween 5 minutes to 72 hours, preferably between 20 min to 24 hours, more preferablybetween 45 minutes to 3 hours.

[0055] Curing the intermediate product to obtain the reprocessable material may becarried out at a temperature between 25°C and 220°C, preferably between 40°C and 160°C, more preferably between 60°C to 120°C, even more preferably between 60°C to 100°C.

[0056] The step of curing the intermediate product to obtain the reprocessable materialmay be carried out under pressure, notably at a pressure which is between 1 MPa to 12 MPa, preferably between 2 MPa and 10 MPa, more preferably between 4 MPa to 8 MPa.

[0057] Curing is preferably followed by a step of post-curing. Post-curing may be carriedout at a temperature between 80°C to 220°C, preferably between 100°C to 200°C, more preferably between 120°C to 180°C. The duration of the post-curing step may be in the range P1694-WO EpoxyPHUof between 5 minutes to 24 hours, preferably between 20 min to 3 hours, more preferably between 30 minutes to 1.5 hours.

[0058] Curing may be made in a mould while post-curing may be carried out outside themould.

[0059] The reprocessable material, notably once cured, may comprise at least 1%, at least20 %, at least 50%, at least 60% or at least 70% by weight of the collection of matter.

[0060] The reprocessable material, notably once cured, may comprise at least 20%, atleast 40%, at least 50% or at least 60% by weight of the covalent adaptative network.

[0061] In accordance with one aspect as defined in claim 25, the present inventionprovides a method of reprocessing a reprocessable material, wherein the method comprises:heating a reprocessable material obtained from a method as disclosed above in a heatedmould to a processing temperature, and pressing the heated reprocessable material at aprocessing pressure to obtain a reshaped, reprocessable material, wherein the processing temperature is in a range from 100°C to 250°C, preferably in the range of 150°C to 200°C; and the processing pressure is at a pressure in the range of 0.1 MPa to 20 MPa.

[0062] The reprocessable material may be reshaped in any geometry within a relativelyshort time. Heating the reprocessable material may be made during a duration in the rangeof between 1 minutes to 7 hours, preferably between 5 min to 5 hours, more preferablybetween 10 minutes to 1 hour.

[0063] As used herein the processing temperature is a temperature allowing deformationof the network and thus reshaping of the reprocessable. The processing temperature is in a range from 100°C to 250°C, preferably in the range of 150°C to 200°C.

[0064] Pressing the heated reprocessable material may be made under pressure, notablyat a pressure which is between 0.1 MPa to 20 MPa, preferably between 1 MPa to 12 MPa, more preferably between 2 MPa and 10 MPa, even more preferably between 4 MPa to 8 MPa.

[0065] The duration of the step of pressing the heated reprocessable material may be inthe range of 1 minutes to 7 hours, preferably between 5 min to 5 hours, more preferablybetween 10 minutes to 1 hour.

[0066] After the step of pressing the heated reprocessable material at a processingpressure to obtain a reshaped, reprocessable material, the mould and the material may bewater-cooled or let rest to cool down at room temperature before being unmoulded. P1694-WO EpoxyPHU

[0067] In one embodiment the method of reprocessing the reprocessable material enablesto obtain a reshaped reprocessable material wherein only the geometry of the material has been modified. For example, a flat laminate produced with the CAN of the present invention may be reshaped in a different geometry.

[0068] In another embodiment the method of reprocessing the reprocessable materialenables to weld one or more parts of reprocessable materials together. For example, two flatlaminates produced with the CAN of the present invention may be self-welded together bythermocompression.

[0069] The mechanical properties of the obtained reshaped or welded, reprocessablematerial are equivalent to the properties of the reprocessable material before having beenreprocessed.

[0070] The ability to obtain similar properties for the reprocessed material demonstratesthat the system can be extended to new shaping and manufacturing processes. Moreover, an easy-to-store and stable flat pre-composite can be manufactured on a large scale and then shaped and welded into the final part with desired orientations within minutes. Thisopens the door to fast high-performance composite manufacturing processes that were up todate inaccessible due to the long time needed to cure epoxy resins. Additionally, it would leadto the reshaping of end-of-life structures (such as plane wings) to new second-life structureswith outstanding performances and limited cost and environmental footprint. The reshapingand weldability of the material also opens the door to cured pre-impregnated laminates, thatcould be shaped and welded in a fast process This is of particular interest for the automotiveindustry where fast processes are expected and CFRP could help reduce weights and thusenergy consumption.

[0071] The reprocessable material is preferably made in accordance with the above-described methods. When considering CFRP reprocessable materials, CFRP may berecycled into a new material after having been cut and thermo-mechanically processed. Inthis type of process however, since the orientation of the fibers is not kept, the mechanicalproperties of the new material are not equivalent to those of the original CFRP material buthave mechanical properties equivalent to random blocks of aligned fibers. The mechanicalproperties of such recycled material may have a modulus between 0.5 GPa and 10 GPa,preferably between 5 GPa and 10 GPa as measured in accordance with ASTM D790 / ISO178.

[0072] However, at some point, it can be expected that the structures and the compositematerials at their end of first service life do not reach a sufficient safety trust level and should P1694-WO EpoxyPHUbe downgraded. If the composite material integrity can be questioned and thus the thermo- mechanical recycling is not adapted, the carbon fiber themselves could still have sufficient properties for many other applications, including semi-structural and structural ones. Moreover, the cost of carbon fibers and their detrimental environmental footprint make them the most valuable product to recover in composites with a real environmental and economical interest.

[0073] Thus, notably where the reprocessable material is a product comprising high valuefibers, such as carbon fibers, the fibers, notably carbon fibers, may be recycled throughchemical recycling, i.e. by removing the covalent adaptative network by a chemical treatment.The recycling may be obtained through the use for example of a mixture of acetic acid and hydrogen peroxide allowing the generation of in-situ of peracetic acid that is able to cleavethe epoxy-amine linkage. Other chemical solutions may be used to remove the network.

[0074] The recycling may be made at a temperature between 25°C and 250°C, preferablybetween 30°C and 90°C, more preferably between 40°C to 80°C, even more preferably between 50°C to 70°C.

[0075] The duration of the step of recycling may be in the range of between 20 minutes to15 hours, preferably between 1 hour to 10 hours, more preferably between 2 hours to 6 hours.

[0076] After the chemical recycling, the fibers may be recovered by filtration and washedone or more times with water until a neutral pH is obtained. It may be followed by a step of drying in an oven.

[0077] The fibers thus recycled may be reused as the collection of matter to produce anew reprocessable material with the covalent adaptative network of the present invention.

[0078] Embodiments of the inventions will now be described, by way, of example only.

[0079] Materials and InstrumentationMaterials: Ethylene Carbonate, n-butylamine, 1-Dimethylamino-2-propanol, 4-Methyl-2-pentanol, tetrabutylammonium iodide (TBAI), 4,4'-Methylenebis(N,N-diglycidylaniline)(MDGA, EEW = 112 g / eq), and m-xylylene diamine (mXDA, Amine Hydrogen EquivalentWeight (AHEW) = 68 g / eq) were purchased from Sigma-Aldrich. Trimethylol propane triglycidyl ether (TMPTGE, DENACOL EX321, Epoxy Equivalent Weight EEW = 140 g / eq) and resorcinol diglycidyl ether (RDGE, DENACOL EX201, EEW = 117 g / eq) were kindlyprovided by DENACOL NAGASE Chemtex. Pentaerythritol polyglycidyl ether (PEPGE, IPOXCL16eco, EEW =163 g / eq), butanediol diglycidyl ether (BDGE, IPOX RD3 eco, EEW = 135g / eq were provide by IPOX Chemicals. Carbon Dioxide was provided by Air Liquide. AllP1694-WO EpoxyPHUchemicals were used as received without any further purification. Flax unidirectional fiber tape (FlaxTape UD110, 110 g / m2) was purchased from EcoTechnilin. Carbon Fiber quasi- unidirectional tape (CF-UD100, Pyrofil TR50S 15k, 100 g / m2) was purchased from Mitsubishi.1H-Nuclear magnetic resonance (NMR) measurements were carried out on a Bruker Advance300 (300 MHz) spectrometer using deuterated chloroform (CDCl3) as solvent at ambient temperature (298 K).Attenuated total reflection - Fourier-transform infrared spectroscopy (ATR-FTIR)measurements were performed on a Bruker FTIR Tensor 27 spectrometer. Thirty-two scans per recording were performed over a range of 4000–600 cm−mwith a 4 cm−wresolution.X-ray photoelectron spectroscopy (XPS) measurements were performed on a Versaprobe IIIPhysical Electronics (ULVAC) system with a monochromatic Al Kα radiation source (1486.7eV). An initial analysis was carried out to determine the elements present (wide scan: stepenergy 0.2 eV, pass energy 224 eV) and detailed analyses were carried out on the detected elements (detail scan: step energy 0.05 eV, pass energy 27 eV, time per step 20 ms) with an electron exit angle of 45º. The spectrometer was previously calibrated with Ag (Ag 3d5 / 2, 368.26 eV). The spectra were fitted using the CasaXPS 2.3.26 software, which models the contributions after a background subtraction (Shirley).Scanning Electron Microscopy (SEM) was performed with a HITACHI TM3030Plus TabletopScanning Electron Microscope (SEM) at 15 kV. Polymer samples were gold-coated in an SC7620 Mini Sputter Coater (Quorum).Thermogravimetric Analyses (TGA) was performed on a TGAQ500 from TA Instruments.About 10 mg of the product was weighed. The analyses were conducted from 25 to 800°C following a 20°C / min heating ramp under a N2flow of 60 mL.min−f.Dynamical Mechanical Analyses (DMA) were conducted on a TA Instruments DMA Q800 intension mode. Rectangular samples of 20x8x0.8 mm3were used. The gauge length was fixed at 10 mm. The DMA analysis was performed from 25 to 180°C at a 3°C / min heating rate. 0.1% strain was applied at 1 Hz.Stress Relaxation tests were conducted on the DMA Q800 in tension mode. Rectangularsamples of 20x8x0.8 mm3were used. The gauge length was fixed at 10 mm. Once the specified temperature was reached, the sample was held for 1 min before applying a 1% strain. The strain was kept constant for 60 min or when stress relaxation was reached. Stress relaxation of the dynamic crosslinked network is defined using a Maxwell model as describedin the equation below. The dynamic covalent behaviour was highlighted using the Arrheniusrelationship by plotting τ ∗ as a function of 1 / T as shown in the equation below.P1694-WO EpoxyPHUwith G being the relaxation modulus in MPa, τ the time constant in second, Ea the activationenergy in kJ / mol, R the perfect gas constant (8.314 J.mol−.K−K), T the temperature in Kelvin.Tensile Creep was measured in the DMA instrument with the same sample geometry as DMAand stress relaxation. The samples were heated at the desired temperature and maintained for 5 min to ensure equilibrium. Then, a 0.5 MPa stress was applied for 60 min, and the strain was recorded.Monotonic Tensile Tests were performed using an INSTRON 5569 testing equipment. Purepolymer materials were tested following the ASTM D638 standard (type V dog-bone shape) with a 2.5 kN cell force. Tests were performed at a 1 mm / min displacement rate up to failure. Young’s modulus was calculated by linear regression between 0.1% and 1.0% strain. Composite materials were tested following the ASTM D3039 standard with a 50 kN cell at a 1 mm / min displacement rate up to failure. Samples of dimension 200 x 15 x 0.9 mm3 were used. The strain was measured using a 50 mm extensometer.Crosslinking Density was determined via DMA. DMA was conducted on a TA InstrumentsDMA Q800 in tension mode. Rectangular samples of 20x8x0.8 mm3were used. The gauge length was fixed at 10 mm, and a 0.01 N preload was used. The DMA analyses were performed from -80°C to 150°C at a 3°C / min heating rate, and a 0.1% strain was applied at1 Hz. These DMA results were used to determine the crosslinking density νE’ of samplesusing rubber elasticity theory as described in the following equation:with Tα+50 being the temperature of the rubbery plateau set 50K after the α transition taken atthe maximum of the tanδ curve, E’α+50the storage modulus in Pa at the specified temperature and R the perfect gas constant (8.314 J / mol / K).

[0080] Synthetic and manufacturing proceduresThe following compounds A, B and C were used in the experiments: Compound A: P1694-WO EpoxyPHUCompound B:Compound C : Synthesis of trimethylolpropane triglycidyl carbonate (TMTPC) Trimethylolpropane tricyclic carbonate (TMTPC, Carbonate Equivalent Weight CEW = 175 g / eq) was synthesized at the kilogram scale from its respective epoxide precursor as described in the following paper incorporated herein by reference (Guillem Seychal et al., Emerging Polyhydroxyurethanes as Sustainable Thermosets: A Structure–Property Relationship. ACS Applied Polymer Materials, page acsapm.3c00879, June 2023). Shortly, TMPTE was introduced in a 2 L high-pressure stainless steel reactor with 2.5 mol% (vs TMPTE) of TBAI as the catalyst. The reactor was closed and stabilized at 110°C and 90 bar for 24 h. The crude was collected, degassed under vacuum, and used without any purification. P1694-WO EpoxyPHUThe complete conversion was confirmed by 1H-NMR. PEPGE, BDGE, and RDGE wererespectively carbonated into PentCC (CEW = 180 g / eq), ButCC (CEW = 157 g / eq), and ResCC (CEW = 158 g / eq),in a similar protocol. Synthesis of the 2-hydroxyethyl n-butylcarbamate In a 25 mL round bottom flask, ethylene carbonate (EC, 1 eq) was mixed with n-butylamine (1.1 eq) and reacted at 60°C for 24 h under constant stirring. The crude was then dissolved in ethyl acetate and washed with water 3 times to remove the unreacted excess of amine.The product was then dried using anhydrous sodium sulfate. Ethyl acetate was then removedusing a rotary evaporator. The obtained product was characterized by1H-NMR.

[0081] Example 1: Transcarbamoylation model reactionA model reaction was first performed to demonstrate the auto-catalytic effect of the epoxy-derived amino-alcohol for the transcarbamoylation of hydroxyurethane. A simple atomistic simulation was used to understand the difference between conventional transcarbamoylationand the synergetic copolymerization autocatalytic approach. Two secondary alcohols withvery similar structures, but one incorporating a neighbouring amine were used. (Fig.1a-b). The amino-alcohol mimics the product obtained from epoxy aminolysis. Figure 1a represents conventional uncatalyzed transcarbamoylation model reaction. Figure 1b represents model reaction scheme of the internallycatalyzed amino-alcohol transcarbamoylation. Electrostatic potential (ESP) charges already reveal a higher potential of the hydroxyl incorporating the amine (-0.655 eV) than the secondary alcohol (-0.632 eV), thus revealing higher nucleophilicity by the hydrogen bonding and the electron-withdrawing effect of theneighbouring amine. Furthermore, the difference in free enthalpy of the amino-alcohol-basedtranscarbamoylation was lower (ΔG0= -1.6 kcal / mol) than the conventionaltranscarbamoylation (ΔG0= -0.76 kcal / mol). This first result indicates that if thetranscarbamoylation is feasible, it requires a catalyst to fasten the exchange rate. In the case of the epoxy-based network, the formed amino-alcohol could be expected to play as the catalyst and the reactant and therefore promote the dynamicity of the network. Based on these promising preliminary results, model exchange reactions were conducted as illustrated in Fig.1a and 1b. Synthesis: Model reactions between the model hydroxyurethane compound (2-hydroxyethyl n-butylcarbamate) and model epoxy compound (1-dimethylamino-2-propanol) were carried out under various temperatures. The two components were mixed in an equimolar ratio andaliquots of the reaction mixture were sampled over time. The reactions were monitored by1H-NMR in CDCl3 to determine the exchange by following the ethylene glycol signal. P1694-WO EpoxyPHURepresentative NMR spectra for the different model reactions are shown in Figure 1c togetherwith the resonances used for quantification. Figure 1c shows the NMR spectrum for the reactant (lower curve, marked as initial) and for the product (higher curved, marked as final). For the sake of comparison, the same reaction was conducted with 4-Methyl-2-pentanol which does not possess the catalyzing amine. The reaction was conducted at 120°C for 24h. Figure 1d represents the kinetic of the exchange reaction. Figure 1e represents the Arrhenius plot obtained from the exchange reaction and its activation energy. Results No ethylene glycol (EG) generation, that would reveal the exchange reaction, was observedin the case of uncatalyzed alcohol-carbamate transcarbamoylation (Fig 1a). This firstconfirmed the impossible use of transcarbamoylation in catalyst-free conditions in mildconditions (temperature lower than 150°C). When the amino-alcohol compound was used(Fig 1b), however, EG release was quickly observed at temperatures as low as 100°C demonstrating the positive effect of this autocatalytic system and the improvement of theexchange rate. An activation energy of 123.6 kJ / mol was calculated (Fig 1d), which correlateswith previous work on catalyzed transcarbamoylation (Bakkali-Hassani C et al.,Transcarbamoylation in Polyurethanes: Underestimated Exchange Reactions, Macromolecules. 2022, Sep;55(18):7974-91). Mass spectra analysis confirmed that the amino-alcohol was reacting with the carbamate moieties forming the new product (m / z=203.17) but also, in a more limited extent, catalyzed the primary alcohol of the hydroxyurethane and thus forming a difunctional urethane (m / z= 283.16). This is particularly important as an external catalytic effect of the tertiary amine would probably be hindered in the copolymer network due to steric hindrance and hydrogen bonding, while the internal activation of the neighbouring hydroxyl group will be encountered in the bulk material. The model reaction demonstrated the internal catalysis of epoxy-derived alcohol to act efficiently in the transcarbamoylation reaction allowing to go on to the copolymer material scale.

[0082] Example 2: Polymer network formationThe epoxy-based CAN was built by the incorporation of cyclic carbonates in the starting epoxy monomer. The diamine is the crosslinking agent by reacting with both epoxy and cycliccarbonates. The cyclic carbonate aminolysis leads to a hydroxyurethane moiety (Fig. 2a).The aminolysis of epoxy leads to secondary and tertiary amines with pendant free-hydroxyl(Fig.2b). The hydroxyurethanes moieties act as the dynamic linkage while the epoxy-derivedhydroxyl acts as the internally catalyzed alcohols to perform transcarbamoylation as represented in Fig.2c. P1694-WO EpoxyPHUSynthesis: The epoxy monomer (RDGE) and the cyclic carbonates (TMTPC) were mixed and degassed before use. The amine (mXDA) was added in an equimolar ratio between reacting functions. The amount of amine was calculated using the equation below. %EP and %CC represent the desired weight fraction of the epoxy and cyclic carbonates respectively, Amine Hydrogen Equivalent Weight (AHEW in g / eq), represent the weight required to obtain an equivalent molar quantity of reactive hydrogen, the Epoxy Equivalent Weight (EEW) is ascribed to the mass required for an equivalent reactive epoxy function and the Carbonate Equivalent Weight to the mass of cyclic carbonates required for an equivalent of reactivecyclic carbonates. The mixture was thoroughly hand-mixed for 5 minutes at room temperatureand then poured into a PTFE mould. The curing was performed for 2 h at 80°C followed by apost-curing step of 1 h at 160°C to guarantee full cure.Results: Several formulations of TMTPC-RDGE with a different mass content of cyclic carbonates,respectively 0, 10, 25, 50, 75, 90, and 100wt% of TMPTC in the TMPTC-RDGE mixture, wereinvestigated in stress relaxation (Fig. 2d). The formulations are detailed in the Table below.Interestingly, only 10% of cyclic carbonates already lead to stress relaxation while the range25%-75% seems to be the most promising with relaxation within 20 min. In all cases, a highcrosslinking density, superior to 600 mol / m3was obtained demonstrating the obtention of a fully crosslinked network, with glass transition superior to 85°C for all covalent adaptable networks.P1694-WO EpoxyPHU(“nc” means “not characterized” as the relaxation was superior to 60 min, the experiment stopped;HTR100 is a pure epoxy network, this network does not relax at all) While previous work has highlighted that pure PHU could stress relax in catalyst-free conditions, it required several hours at a temperature superior to 180°C, leading to partialthermal degradation. Herein, the experiment demonstrates a fastest relaxation for a PHU-based dynamic network, thanks to this copolymerization strategy. The 50% content of cyclic carbonates leads to the fastest relaxation at 180°C in only 7 min. Without wishing to be bound by theory, it is believed that it can be understood as the network needs a good balance between activated hydroxyl and dynamic hydroxyurethane to perform adequately. The higher content of epoxy favours the network dynamicity as it furnishes a sufficient number of activated hydroxyl.The vitrimeric behaviour was assessed in detail for the formulation 50%RDGE-50%TMTPCat several temperatures (Fig.2e). Although the dynamic behaviour of the urethane linkage isdue to both associative (transcarbamoylation) mechanism and dissociative (reverse cyclic carbonates aminolysis), it is believed that the main mechanism in the present invention to be associative and a single decay maxwell model stands a sufficient approximation. A good fit (r2> 0.98) was obtained with a single decay maxwell model in the time-temperature Arrhenius plot (Fig. 2f) confirming the obtention of a fast relaxing catalyst-free dynamic network. Relaxation can be obtained within minutes at a temperature as low as 150°C. The Arrhenius plot highlights a strong time-temperature dependence and thus the easy control of the relaxation through the simple temperature triggering without catalyst side effects. The activation energy (113.6 kJ / mol) is consistent with the value obtained in the model reaction study and with literature on transcarbamoylation.

[0083] Example 3: Mechanical propertiesMechanical properties were tested on the 50 / 50 formulation of RDGE and TMTPC assynthesized above. Figure 3a represents representative tensile stress-strain curves of the neat epoxy and hybrid. Figure 3b represents comparative mechanical properties of the epoxy and the hybrid thermosets normalized to the pristine epoxy.Figure 3c represents thermo-mechanical behaviour DMA curves.Figure 3d represents tensile creep behaviour at 90°C.The mechanical properties were tested under tensile loading. The representative stress-strain curves are presented in Fig.3a. No detrimental modifications of the properties were observed.The newly formulated dynamic copolymer exhibits superior mechanical properties comparedto the pristine epoxy with a high Young’s modulus 3.0 GPa (vs 2.9 GPa), admissible stress P1694-WO EpoxyPHUof 103 ± 7 MPa (vs 89 ± 10 MPa), and an admissible strain of 4.0 ± 0.3% (vs 3.3 ± 0.5%).The modification of the network led to an increase of the modulus by 4% and by 16% and 19% for the strain and stress respectively. These increases represent an improvement of42% of the toughness of the new network from 1.6 MJ / m3 to 2.3 MJ / m3. The stronger H-bondarising from the carbamate moieties maintains a high level of stiffness while allowing moreductility within the networks. This favours the potential durability of such materials by limitingthe nucleation and propagation of micro-cracks, in addition to the perspectives of repairability due to the dynamic nature of the newly developed copolymer network.

[0084] The thermomechanical properties were also assessed by Dynamical MechanicalAnalyses (DMA) and creep testing. The DMA displayed similar glass transitions between the pristine epoxy and the dynamic one with 97°C and 94°C respectively showcasing no alterationof the network and proving suitable for similar applications. The glassy modulus wasincreased for the dynamic copolymer with 4416 MPa for the dynamic one compared to the 2314 MPa of the pristine epoxy. In addition, the crosslinking density of the dynamic copolymer was found to be substantially lower than the pristine epoxy. This is due to the implementation of the urethane moieties through the trifunctional cyclic carbonate that lowers the crosslinkingdensity. Low crosslinking density in the presence of hydroxyurethane leads to stronger H-bond. The H-bond conducts to an increase of the glassy modulus while allowing more motion of the macromolecular backbone, thus permitting more ductility and toughness of the system. DMA results confirmed this tendency in the copoymerization strategy, as previously observedin tensile tests, between polyhydroxyurethane and epoxy and the achievement to moreresilient dynamic epoxy-based materials.

[0085] Creep is a known problematic side effect of CAN as the ability of the network toflow leads them to be subjected to creep behaviour like thermoplastic and contrary to thermosets. This behaviour is strongly dependent on the chemistry involved, the design of the monomer, and the thermal sensitivity of the exchange mechanism. A highly dynamicmechanism will lead to important creep while poor dynamicity involves negligible creep. Thetranscarbamoylation is strongly dependent on the temperature and shows little dynamicity at low temperatures, thus it can be expected that no creep will happen in the operating windowof the formulated network since thermosets for composite applications are expected to beused at temperatures lower than the glass transition. Creep experiments were conducted at90°C, only a few degrees before the alpha transition (Fig. 3d). The viscous behaviour of theCAN was more pronounced than the pristine epoxy with an observable delayed deformation to the applied stress. However, the strain and recovery were identical to the epoxy one, highlighting no sensitivity of the dynamic copolymer up to the glass transition. P1694-WO EpoxyPHUThe covalent adaptative network of the present invention thus demonstrates no alteration of the properties with even some improvement in the epoxy network.

[0086] Example 4: Reprocessing of the covalent adaptative networkReprocessability of the covalent adaptative network obtained from the 50 / 50 formulation ofRDGE and TMTPC as synthesized above has been tested.Figure 4a represents the ability of the material to be efficiently reprocessed; Image Arepresents closed-loop thermomechanical recycling; Image B represents SEM Images of thecryo-broken reprocessed sample; Image C represents solvent swelling in tetrahydrofuran(THF) of the recycled copolymer after two weeks.Figure 4b represents DMA curves of pristine and reprocessed CAN.Figure 4c represents tensile modulus obtained from thermally (re)processed CAN.Experiment:The as-cured CAN was cut into pieces. The mould was preheated to 180°C in a press for 30min. After that, a 6 MPa pressure was slowly applied and maintained for 20 min. The mould was then removed from the press and cooled down at room temperature. The as-obtainedfilm was then removed from the mould and cut for analysis. The samples were also immersedinto THF to evidence the welding of the samples via the formation of covalent bonds at high pressure Results:Homogeneous samples were obtained as shown in Fig. 4aA underlining the ability of thematerial to be efficiently reprocessed. The recycled sample was deep into THF solvent for 2 weeks (Fig.4aB), no destruction or cleavage of the network was observed highlighting theformation of covalent bonding during the reprocessing. Cryogenic breaking with SEM picture(Fig. 4aC) demonstrates efficient welding of the material even at the core of the polymeric network. The thermomechanical behaviour was similar between pristine and reprocessedsamples. DMA curves (Fig.4b) were comparable after two reprocessing steps with no changein the glass transition, behaviour, and glassy modulus. The rubbery modulus was however found to be lower, representing a slight decrease of the crosslinking density, consistent with the mechanical grinding of the polymer that leads to some irreversible damages in thedynamic copolymer (potential breaking of C-C bonds). As already observed by DMA, thetensile Young’s modulus was almost fully recovered with an efficiency of 92% on the firstrecycling cycle and 100% on the second cycle. The covalent adaptative network exhibitspromising potential for future application with the ability to be healed, reshaped, and reprocessed. P1694-WO EpoxyPHU

[0087] Example 5: Manufacturing of a reprocessable materialThe covalent adaptative network used had a 50 / 50 formulation of RDGE and TMTPC as disclosed above. Experiment: Unidirectional composite laminates made of 10 plies of carbon fibers were manufactured by hand lay-up and cured by thermocompression. To impregnate the fibers, the substantially water free curable composition was prepared by weighting about 1.2 times the mass of fibers.The plies were stacked in a Teflon-coated steel mould (200x150 mm2). Between each ply, alayer of the substantially water free curable composition was applied. The two edges in themould length were left open to allow air and matrix excess to flow out from the mould. Themould was then placed into a heating press and a pressure of 8 bar was slowly applied toensure an entire impregnation of the fibers. The plates were then cured under this pressure for 2 h at 80°C. After unmoulding, the post-curing was conducted in an oven at 160°C for 1 h. Samples were precisely cut from the obtained plates using a metallic guillotine for testing. While not further detailed in the present experiments, unidirectional composite laminates made of 10 plies of flax fibers are obtained in the same conditions than the unidirectional composite laminates made of 10 plies of carbon fibers. Tests and resultsFigure 5 represents tensile stress-strain curves of the manufactured composite made of 10plies of carbon fibers.Three samples were tested each time for statistics. The static mechanical performances wereassessed by tensile testing. Extremely high mechanical performance of the carbon-fiberreinforced polymer (CFRP) was obtained with 133 GPa in modulus, and 1700 MPa of stressat break. These results are believed to be due to the good adhesion of the CAN to the fibers.The matrix depicts good compatibility with commercial fibers that incorporate a conventional sizing for epoxy matrix and were used without any further modification.

[0088] Example 6: Reshaping and welding of the cured compositesReshaping and welding of the cured composites obtained in the previous example 5 are disclosed below. Experiment: The reshaping of the composite obtained in Example 5 (unidirectional composite laminates made of 10 plies of carbon fibers) was conducted in a Teflon-coated V-shaped aluminummould in a hydraulic press. The mould was first preheated at 180°C. A unidirectional curedCFRP panel was then put in the mould without pressure for 15 min to preheat. The pressurewas slowly applied up to 5 MPa and maintained for 30 min. The press was then water-cooled P1694-WO EpoxyPHUand the reshaped composites unmoulded. While not further detailed in the present experiments, the reshaping of unidirectional composite laminates made of 10 plies of flax fibers is obtained in the same conditions than the reshaping of the unidirectional composite laminates made of 10 plies of carbon fibers. Tests and resultsFigure 6a represents reshaping of the carbon compositesFigure 6b represents welding of single ply composites.Figure 6c represents adhesion strength of the welded composites. Three samples weretested each time for statistics. Figure 6c also provides a representative broken sample. It shows that it is the full material that completely breaks and not some decohesion of the welded area. This means that the welded area is stronger than the material and thus that the welding was efficient. The (re)shapability of the CFRP composite is illustrated in Fig. 6a where the already fully cured flat laminate was reshaped in a complex geometry within 30 min at 180°C. The newly obtained shape was smooth and defect-free with no buckling at the edges or surface that would highlight detrimental delamination. The fibers’ orientation was kept.

[0089] The weldability was also investigated (Fig. 6b) where two single-ply cured sheetswere self-welded together by thermocompression thanks to the exchange reaction. This was only possible with the covalent adaptative network formulated where the -OH functions can thus form covalent bonding through the transcarbamoylation mechanism at the interface between the two plies. The adhesive strength was evaluated. Adhesive strength values of about 2 MPa were obtained, in the range of similar material and conventional adhesion ofCFRP. Interestingly, the failure did not happen in the welded area but was initiated at thewelded edge due to stress concentration and propagated by splitting within the laminates. This illustrates that the welding was strong and efficient.

[0090] Example 7: Chemical recovery and recycling of the fibersFigure 7a represents recycling of CFRP, A represents CFRP chips; B represents thermo-mechanical recycling through direct thermocompression.Figure 7b represents three-point bending strain-stress curves of the thermomechanicallyrecycled composites. The CFRP obtained as disclosed in example 5 was first recycled through a simple thermo- mechanical process. The chips were cut in parts and then pressed 30 min at 180°C. Thematerial obtained was tested in three-point bending tests. With a modulus of 3.7 GPa and amaximum stress of 28 MPa, the material displays mechanical properties that are consistent with random blocks of aligned fibers that lead to an integral material. P1694-WO EpoxyPHU

[0091] Recovery of the high value carbon fibersExperiment of chemical recovery and recycling of the fibers:The degradation solution was prepared by mixing in a mass ratio of 80:20 glacial acetic acidand hydrogen peroxide (generating in-situ peracetic acid that can cleave the epoxy-aminelinkage) (water solution 30 %wt). The CFRP (10 g) was roughly cut into large pieces and putin a 250 mL round bottom flask with 250 mL of the oxidative solution. The mixture was heated to 60°C until complete degradation of the network (around 4 h) under constant magnetic stirring. The fibers were then recovered by filtration and washed several times with deionized water until a neutral pH was obtained. The fibers were then dried overnight in a ventilated oven at 60°C. The reclaimed fibers were reused as a reinforcement using the CAN by impregnation under thermo-compression. Tests and resultsFigure 7cA and 7cB represents chemical recycling of the CFRP by the network oxidation andfiber separation and the subsequent non-woven carbon composites from recovered fibers.Figure 7d represents three-point bending strain-stress curves of the chemically recycledcomposites made with carbon fibers.Figure 7e represents SEM images of the recovered fibers. Figure 7f represents XPS analyses of the virgin and recovered fibers. Figure 7g represents TGA of the composite virgin carbon fibers and recovered carbon fibers. Figure 7h represents the FTIR of the virgin carbon fibers and the recovered carbon fibers. The recovered fibers were analyzed by SEM (Fig.7e), XPS (Fig.7f), TGA (Fig.7g), and FTIR(Fig 7h) The surface of the fibers was clean of any network residues as observed by FTIRand SEM. No characteristic peak of the polymer network was observed by FTIR. Additionally, the sizing agent was removed (FTIR) which is typical of the chemical recycling of CF. XPS displays the appearance of a new peak located at 288.7 eV revealing the partial oxidation of the carbon fiber surface by the oxidative treatment. The oxygen content at the CF surface increased from 19.9% to 23.8%. A slight oxidation at the carbon fiber surface was characterized but did not lead detrimental effect on the fiber. Overall, the fiber maintained its integrity. Additionally, this local oxidation could be interesting in forming new bond with an amine-based network and act as adhesion promoter for further use. The TGA confirms the similarity between virgin and recycled fiber. To prove the possibility of valorizing such reclaimed fiber in new high-added-value applications, the fibers were re-used as a non-woven mat with the covalent adaptative network and tested in three-point bending (Fig.7d). The recycled material exhibits outstanding properties with a modulus close to 50 GPa, a stress at break of almost 500 MPa, and an admissible strain superior to 2.1%. The P1694-WO EpoxyPHUproperties obtained indicate that the reclaimed fibers can be efficiently used for many applications.

[0092] Example 8: Polymer network formation

[0093] As detailed in example 2 for several formulations of TMTPC-RDGE, several othermonomer combinations were investigated in stress relaxation (Figure 8 and Figure 9) to demonstrate the versatility and efficiency of the approach and the facile access to a widelibrary of epoxy systems suitable for many applications. The formulations are detailed in theTable below.Figure 8 represents the stress relaxation of formulations HRR50, HBR50 and HPR50. Thestress relaxation curves demonstrate the ability of the formed crosslinked network to release internal stress upon a constant strain is released. By doing so, a new thermodynamical equilibrium is obtained with no remaining internal stress. Upon releasing the applied strain, no “spring-back” occur, thus showing the permanent reshaping of the different samples.Figure 9 represents the stress relaxation at different temperatures of formulation HMT50.Similarly to figure 8, the stress relaxation curves of HMT50, a highly crosslinked (9526mol / m3) network, are shown, demonstrating the ability of the network to be reshaped.Figure 10 represents the thermo-mechanical behaviour DMA curves. DMA of the networksexample demonstrate that a network is formed.Example 9: Wingtail Experiment: A commercially available epoxy formulation (Easy Composite IB2), composed of a mix ofepoxy monomers (Diglycidyl Ether of Bisphenol A – DGEBA, Butanediol Diglycidyl Ether –BDGE, an Diglycidyl Ether of Bisphenol F – DGEBF), with unknown weight fraction ofcomponents, was modified with 25% of TMPTC (i.e.1kg of modified resin is composed of P1694-WO EpoxyPHU750g of the epoxy formulation and 250g of TMPTC). The provided commercial hardener is composed of methylpentane diamine (mPDA), trimethylpropanealkylamine (TMPA), and m-Xylylene Diamine, in unknown fractions. The commercial resin is mixed between the neatepoxy monomer and the hardener in a 100:22 weight ratio. Once modified, a 100:27 weight ratio was used to cure the system, the modified resin is referred to as IB2T25.100 g of the modified epoxy was mixed with 27g of hardener. Curing was performed at room temperature (22°C) for 24h followed by a post-curing step of 1 h at 80°C.Figure 11 represents the dynamical mechanical analysis and demonstrates the highperformance obtained with a glass transition of 100 °C and a high crosslinking density of 1284 mol / m3.Figure 12 represents the stress relaxation of the modified commercial epoxy formulation anddemonstrates that a covalent adaptable network is obtained able to be reshaped. A wingtail was produced by hand lay-up using carbon fiber and the modified commercial resin (Figure 13a), following the method ascribed. The tail was then recycled in the oxidative depolymerization mixture to retrieve the carbon fibers (Figure 13b).

[0094] Example 10Experiment: A formulation comprising 60wt% of RDGE and 40wt% of TMPTC was used.Compound C was formulated as a mixture of isophorone diamine (IPDA) and m-xylylene diamine (IPDA) in a 75:25 weight ratio. A 100:37 weight ratio between the epoxy / cycliccarbonate mixture and the compound C formulation (0.95 eq). 400g of epoxy / CC mixturewere prepared with 148g of the compound C. The example is referred to as LResin. A composite was prepared by liquid resin infusion (Figure 14a), and the stress relaxation was confirmed (Figure 14b). P1694-WO EpoxyPHU

Claims

Claims1. Covalent adaptative network obtained by a method of manufacturing comprising:- preparing a substantially water-free curable composition by mixing:- at least one multifunctional cyclic carbonate having at least two cycliccarbonate groups, notably at least two terminal cyclic carbonate groups (compound A), -at least one epoxide compound comprising at least two oxirane groups(compound B), and -at least one polyprimary polyamine comprising at least 2 primary aminegroups (compound C) -curing the substantially water-free curable composition to obtain the covalentadaptative network.

2. Covalent adaptative network according to claim 1, wherein:- the molar ratio of oxirane groups of compound B to cyclic carbonate groups ofcompound A is in the range of 0.15 to 5, preferably in the range of 0.4 to 2.5, and -the molar ratio of oxirane groups of compound B to primary amine groups ofcompound C is in the range of 0.5 to 1.1, preferably in the range of 0.9 to 1, and -the molar ratio of cyclic carbonate groups of compound A to primary amine groupsof compound C is in the range of 0.5 to 1.5, preferably in the range of 0.9 to 1.1.

3. Covalent adaptative network according to claim 1 or claim 2, wherein the substantiallywater-free curable composition is free of catalyst.

4. A covalent adaptative network according to any preceding claim, wherein compoundA corresponds to Formula (Ia)(Formula (Ia)) wherein i is an integer higher than or equal to 2, in particular from 2 to 10, more particularly 2 or 3, P1694-WO EpoxyPHUR1 is a carbon bond between the cyclic carbonate rings or is a linear or branched hydrocarbon chain, which may be unsubstituted or substituted and wherein one or several hydrocarbon groups of said hydrocarbon chain may be replaced by a heteroatom, a ketone, a cycloalkyl, a heterocycle, an aryl or a heteroaryl, each of which may be unsubstituted or substituted, said hydrocarbon chain having at least 2 carbon atoms, in particular from 3 to 60 carbon atoms, and wherein compound A is preferably selected from the group consisting of ResCC, PentCC, TMTPC and combinations thereof, and more preferably compound A isTMTPC.

5. A covalent adaptative network according to any preceding claim, wherein compoundB corresponds to formula X(Formula (X)) wherein: j is an integer higher than or equal to 2, in particular from 2 to 10, more particularly 2 or 3, R1′ is a carbon bond between the epoxide rings when j is from 2, or is a linear orbranched hydrocarbon chain, which may be unsubstituted or substituted and wherein one or several hydrocarbon groups of said hydrocarbon chain may be replaced by a heteroatom, a ketone, a cycloalkyl, a heterocycle, an aryl or a heteroaryl, each of which may be unsubstituted or substituted, said hydrocarbon chain having at least 2 carbon atoms, in particular from 3 to 60 carbon atoms, and wherein compound B is preferably selected from the group consisting of RDGE,BADGE, MDGA and combinations thereof, and more preferably compound B isRGDE.

6. A covalent adaptative network according to any preceding claim, wherein the at leastone polyprimary polyamine comprising at least 2 primary amine groups (compound C) corresponds to formula (V) R2-( NH2)k (Formula (V)) wherein k is an integer higher than or equal to 2, in particular from 2 to 10, more particularly 2 or 3, P1694-WO EpoxyPHUR2 is a carbon bond between the primary amine groups or is a is a linear or branched hydrocarbon chain, which may be unsubstituted or substituted and wherein one or several hydrocarbon groups of said hydrocarbon chain may be replaced by a heteroatom, a ketone, a cycloalkyl, a heterocycle, an aryl or a heteroaryl, each of which may be unsubstituted or substituted, said hydrocarbon chain having at least 2 carbon atoms, in particular from 3 to 60 carbon atoms, and wherein compound C is preferably mXDA.

7. Covalent adaptative network according to any preceding claim, wherein curing thesubstantially water-free curable composition to obtain the covalent adaptative network is carried out at a temperature between 15°C and 220°C, preferably between 40°C and 160°C, more preferably between 60°C to 120°C, even more preferably between 60°C to 100°C.

8. Covalent adaptative network according to any preceding claim, wherein curing thesubstantially water-free curable composition to obtain the covalent adaptative network is carried out during a duration between 5 minutes to 72 hours, preferably between 20 min to 5 hours, more preferably between 45 minutes to 3 hours.

9. Covalent adaptative network according to any preceding claim, wherein curing isfollowed by a step of post-curing, and wherein the post-curing is carried out at a temperature between 50°C to 250°C, preferably between 100°C to 200°C, more preferably between 120°C to 180°C.

10. Covalent adaptative network according to claim 9, wherein post-curing is carried outduring a duration between 5 minutes to 24 hours, preferably between 20 min to 3 hours, more preferably between 30 minutes to 1.5 hours.

11. Covalent adaptative network according to any preceding claim, wherein the covalentadaptative network has a Young’s modulus between 1 MPa and 6 GPa, preferablybetween 1 GPa and 6 GPa, more preferably between 2 GPa and 6 GPa as measured in accordance with ASTM D638 / ISO527-4.

12. A method of reprocessing the covalent adaptative network in accordance with anypreceding claim, wherein the method comprises:P1694-WO EpoxyPHU- heating the covalent adaptative network in a mould under pressure.

13. A method of manufacturing a reprocessable material, the method comprising:- preparing a substantially water-free curable composition by mixing:- at least one multifunctional cyclic carbonate having at least two cycliccarbonate groups, notably at least two terminal cyclic carbonate groups (compound A), -at least one epoxide compound comprising at least two oxirane groups(compound B), and -at least one polyprimary polyamine comprising at least 2 primary aminegroups (compound C) -combining the substantially water-free curable composition with a collection of matterto provide an intermediate product, and- curing the intermediate product to provide the reprocessable material.

14. A method according to claim 13, wherein:- the molar ratio of oxirane groups of compound B to cyclic carbonate groups ofcompound A is in the range of 0.15 to 5, preferably in the range of 0.4 to 2.5, and -the molar ratio of oxirane groups of compound B to primary amine groups ofcompound C is in the range of 0.5 to 1.1, preferably in the range of 0.9 to 1, and -the molar ratio of cyclic carbonate groups of compound A to primary amine groupsof compound C is in the range of 0.5 to 1.5, preferably in the range of 0.9 to 1.1.

15. A method according to claim 13 or claim 14, wherein the substantially water-freecurable composition is free of catalyst.

16. A method according to any one of claims 13 to 15 wherein the collection of mattercomprises fibers and the reprocessable material is a fiber-reinforced composite material.

17. A method in accordance with claim 16, wherein the fibers are selected from the groupconsisting of mineral fibers, aramid fibers, ceramic fibers, metal fibers, carbon fibers, polyimide fibers, polyester fibers, rayon fibers, and cellulosic fibers. P1694-WO EpoxyPHU18. A method in accordance with any one of claims 13 to 17, wherein compound Acorresponds to Formula (Ia)(Formula (Ia)) wherein i is an integer higher than or equal to 2, in particular from 2 to 10, more particularly 2 or 3, R1 is a carbon bond between the cyclic carbonate rings or is a linear or branched hydrocarbon chain, which may be unsubstituted or substituted and wherein one or several hydrocarbon groups of said hydrocarbon chain may be replaced by a heteroatom, a ketone, a cycloalkyl, a heterocycle, an aryl or a heteroaryl, each of which may be unsubstituted or substituted, said hydrocarbon chain having at least 2 carbon atoms, in particular from 3 to 60 carbon atoms, and wherein compound A is preferably selected from the group consisting of ResCC, PentCC, TMTPC and combinations thereof, and more preferably compound A isTMTPC.

19. A method in accordance with any one of claims 13 to 18, wherein compound Bcorresponds to formula X(Formula (X)) wherein: j is an integer higher than or equal to 2, in particular from 2 to 10, more particularly 2 or 3, R1′ is a carbon bond between the epoxide rings when j is from 2, or is a linear orbranched hydrocarbon chain, which may be unsubstituted or substituted and wherein one or several hydrocarbon groups of said hydrocarbon chain may be replaced by a heteroatom, a ketone, a cycloalkyl, a heterocycle, an aryl or a heteroaryl, each of which may be unsubstituted or substituted, said hydrocarbon chain having at least 2 carbon atoms, in particular from 3 to 60 carbon atoms, P1694-WO EpoxyPHUand wherein compound B is preferably selected from the group consisting of RDGE,BADGE, MDGA and combinations thereof, and more preferably compound B isRGDE.

20. A method in accordance with any one of claims 13 to 19, wherein the at least onepolyprimary polyamine comprising at least 2 primary amine groups (compound C) corresponds to formula (V) R2-( NH2)k (Formula (V)) wherein k is an integer higher than or equal to 2, in particular from 2 to 10, more particularly 2 or 3, R2 is a carbon bond between the primary amine groups or is a is a linear or branched hydrocarbon chain, which may be unsubstituted or substituted and wherein one or several hydrocarbon groups of said hydrocarbon chain may be replaced by a heteroatom, a ketone, a cycloalkyl, a heterocycle, an aryl or a heteroaryl, each of which may be unsubstituted or substituted, said hydrocarbon chain having at least 2 carbon atoms, in particular from 3 to 60 carbon atoms, and wherein compound C is preferably mXDA.

21. A method in accordance with any one of claims 13 to 20, wherein curing theintermediate product to provide the reprocessable material is carried out at atemperature between 25°C and 220°C, preferably between 40°C and 160°C, more preferably between 60°C to 120°C, even more preferably between 60°C to 100°C.

22. A method in accordance with any one of claims 13 to 21, wherein curing theintermediate product to provide the reprocessable material is carried out during aduration between 5 minutes to 72 hours, preferably between 20 min to 5 hours, more preferably between 45 minutes to 3 hours.

23. A method in accordance with any one of claims 13 to 22, wherein curing is followedby a step of post-curing, and wherein the post-curing is carried out at a temperature between 80°C to 220°C, preferably between 100°C to 200°C, more preferably between 120°C to 180°C. P1694-WO EpoxyPHU24. A method in accordance with claim 23, wherein post-curing is carried out during aduration between 5 minutes to 24 hours, preferably between 20 min to 3 hours, more preferably between 30 minutes to 1.5 hours.

25. A method of reprocessing a reprocessable material, wherein the method comprises: heating a reprocessable material obtained in a method in accordance with any one of claims 13 to 24 in a heated mould to a processing temperature, and pressing theheated reprocessable material at a processing pressure to obtain a reshaped, reprocessable material, wherein the processing temperature is in a range from 100 °C to 250 °C, preferably in the range of 150°C to 200 °C; and the processing pressure is at a pressure in the range of 0.1 MPa to 20 MPa. P1694-WO EpoxyPHU

Images