Azido-substituted heteroaromatic additives for preparing recyclable polymer compositions and for upcycling plastics wastes

Abstract

The invention is directed to a process for preparing a polymer composition, comprising the steps of: (a) mixing a polymer or a polymers blend, and an azide derivative of formula (I): N3-Ar (I), in which Ar is a heteroaromatic group, at a processing temperature Tmix, (b) heating the mix of step a) to a temperature TR, wherein Tmix is higher than the glass transition temperature or the melting temperature of the polymer used in step (a), or higher than the highest glass transition temperature or melting temperature of all the polymers present in the polymers blend of step (a) at a content of at least 8wt% relative to the total weight of the blend, TR is equal to or higher than the decomposition temperature of the azide of formula (I), and Tmix is strictly lower than TR. The invention is further directed to a polymer composition obtained by the process of the invention. The invention is further directed to use of an additive of formula (I), N3-Ar, for upcycling a plastic or a mixture of plastics.

Description

[0001] Azido-substituted heteroaromatic additives for preparing recyclable polymer compositions and for upcycling plastics wastes

[0002] FIELD OF THE INVENTION

[0003] The present invention relates to a process for preparing a polymer composition by mixing a polymer or polymers blend with an azido-substituted heteroaromatic derivative, and to the polymer composition obtained by the process. The process of the present invention enables to afford polymers and blends of polymers with dynamic crosslinks that may be reprocessed / recycled without altering their mechanical properties. The present invention also relates to the use of the azido-substituted heteroaromatic derivative as an additive for upcycling plastics, especially plastic wastes and unsorted plastic wastes.

[0004] BACKGROUND OF THE INVENTION

[0005] Plastics are a ubiquitous feature of modern life because of their low cost, strength, light weight, durability and processability. However, our capacity to recover and recycle end-of-life plastic products remains limited. In confronting this issue, the European Union has put in place an ambitious initiative to transform the plastics sector into a circular economy that emphasizes the need to make plastics easier to recycle in a cost-effective manner. A critical component of this plan is mechanical recycling, which entails the sorting, purification, and grinding of recovered post-consumer plastic waste. Currently, mechanically recycling is applied only to polyethylene terephthalate (PET) and polyethylene (PE) at a large scale, but projections suggest that mechanical recycling will be the most important process for valorizing plastic waste worldwide.

[0006] The current major drawback of mechanical recycling is that the resulting recycled polymer feedstock exhibits inferior mechanical properties compared to the corresponding virgin materials. Mechanically recycled polymers are thus used in lower-value applications, which is insufficient for realizing a circular plastic economy. Before mechanically recycled polymers can be used in widespread applications, three main challenges must be addressed: chain degradation during processing, incompatible blends of different kinds of polymers, and limited applicability to materials containing permanent and non-dynamic crosslinks (e.g., elastomers).

[0007] During mechanical processing, most kinds of polymers undergo predominantly flow and / or thermally-induced chain scission, affecting their processability and physical properties. Even industrial scraps (e.g., runners produced during injection molding) exhibit worse properties upon being reprocessed. Another unfortunate reality of current recycling technology is that even the most efficient facilities in the EU produce recycled polymer feedstocks that contain approximately 5-10% of polymer contaminants. This issue is problematic because nearly all major polymers in the post-consumer waste stream are incompatible with each other. When mixed together in the absence of compatibilizers, polymers undergo phase-separation and are characterized by poor interfacial adhesion. This phenomenon leads to mechanically weak materials that can only be used in applications where mechanical strength is not necessary.

[0008] Finally, the possibility of mechanically recycling chemically crosslinked materials, such as elastomers used in the automotive, building, and packaging industries, is inherently limited by the permanent and non-dynamic nature of the crosslinks. The vast majority of elastomer waste is either landfilled or incinerated.

[0009] To avoid unwanted side reactions during (re)processing (e.g., shear-induced chain scission), it is common practice to use stabilizers and chain extenders to adjust the melt viscosity into a desired processing window. However, the use of these additives entails several disadvantages, poor thermal stability and high cost (Z. O. G. Schyns, M. P. Schaver. Macromol. Rapid Commun. 2021, 42, 2000415). Furthermore, these additives are typically operating for a specific type of polymers only.

[0010] Industrial polymer users prefer to modify the chemical structure of polymers via reactive processing because it does not require any changes to well-established polymer synthesis protocols (Macosko, C. W. ; Jeon, H. K.; Hoye, T. R. Prog. Polym. Sci. 2005, 30, 939). This strategy is particularly useful for polymers that are inherently reactive (e.g., polyesters that can undergo transesterification reactions). For less reactive polymers such as polyethylene, radical acceptors (e.g., maleic anhydride) are used in conjunction with organic peroxides to introduce functional groups. The resulting grafted structures can reduce the interfacial tension. This strategy is not applicable to polymers that are susceptible to radical-initiated side reactions like polypropylene (PP).

[0011] Regarding the recyclability of conventional thermosets and elastomers, there are only a couple strategies that are practiced on a large scale. Mechanically ground elastomers can be blended with other polymers to reinforce downgraded materials. Efforts to chemically de-crosslink elastomer waste have so far limited success. Currently, most thermoset waste is either landfilled or incinerated. There is thus a need for (i) polymer compositions easily reprocessable and recyclable while maintaining the desired mechanical properties of virgin materials, or even presenting new or improved thermomechanical properties, so as to use the recycled polymer compositions in same applications as virgin materials, or in new applications requiring materials with superior thermomechanical properties, and ii) for upcycling polymer blends, such as plastics and plastic wastes, including unsorted plastic wastes, into polymer compositions having superior thermomechanical properties.

[0012] Surprisingly, the inventors have developed a process for preparing polymer compositions, said compositions combining the mechanical behavior and solvent resistance of thermosets and the recycling ability of thermoplastic polymers. When the process is implemented to plastic wastes, the resulting upcycled polymer compositions have improved thermomechanical properties and can thus be used in same applications as virgin materials and even in thermomechanically demanding application for which plastic wastes were not suitable.

[0013] The present invention is based on preparation of polymers containing heteroaromatic nitrogennitrogen bond(s) that can undergo exchange reactions at high temperature. The exchange of nitrogen-nitrogen bonds has been seldom reported (Breton, G. W.; Martin, K. L. J. Org. Chem. 2020, 85, 10865) and it has not been reported in the context of polymer chemistry. This chemistry is particularly advantageous because the reactive species (i.e., the aminyl radical) is relatively unreactive toward other functional groups. Moreover, it is not sensitive to moisture.

[0014] The present invention can be used to improve the thermomechanical properties of a wide variety of polymers and blends of polymer, including enhanced melt viscosity, enhanced resistance toward environmental stress cracking, enabling adhesion between incompatible polymers, functionalization of polymers, self-healing, reversible crosslinking, and enhanced reprocessability. In particular, this invention can be used to prepare a dynamically crosslinked thermoset that has a high insolubility fraction but remains reprocessable, which addresses a key challenge in the recyclability of crosslinked materials. To the best of the inventor's knowledge, there are no previously published or patented examples of polymers that report a polymer composition obtained by the process of the invention such as those defined in the present disclosure.

[0015] Compared to other strategies in this field used to improve the properties of polymers and polymer blends, the invention features an unmatched combination of broad applicability, enhanced physical properties compared to the corresponding materials that do not contain heteroaromatic N-N bonds, and ease of implementation. SUMMARY OF THE INVENTION

[0016] According to a first aspect, the present invention relates to a process for preparing a polymer composition comprising the steps of:

[0017] (a) mixing a polymer or a polymers blend, and an azide derivative of formula (I):

[0018] N3-Ar (I), in which Ar is a heteroaromatic group, at a processing temperature Tmix, then

[0019] (b) heating the mix of step a) to a temperature TR, wherein

[0020] Tmix is higher than the glass transition temperature or the melting temperature of the polymer used in step (a), or higher than the highest glass transition temperature or melting temperature of all the polymers present in the polymers blend of step (a) at a content of at least 8wt% relative to the total weight of the blend,

[0021] TR is equal to or higher than the decomposition temperature of the azide of formula (I), and Tmix is strictly lower than TR.

[0022] In most cases, preferably all cases, the decomposition temperature of the azide is higher than the glass transition temperature (Tg) or melting temperature (Tm) of the polymer. When the mix of step (a) comprises a blend of polymers, the relevant Tgor Tmis the highest glass transition temperature (Tg) or melting temperature (Tm) of all the polymers being present in the blend at a content of at least 8wt% relative to the total weight of the blend.

[0023] According to a second aspect, the present invention relates to a polymer composition obtained by the process as described herein.

[0024] According to a third aspect, the present invention relates to the use of an azide derivative of formula (I), as an additive for upcycling a plastic or mixture of plastics, in particular waste plastic or mixture of waste plastics, for example unsorted plastic, damaged plastic, mixture of damaged plastics or mixture thereof.

[0025] DEFINITIONS

[0026] According to the present invention, the article "a" or "an", as in the expression "a polymer" or "an atom" for example, means one or more than one. Polymer, linear polymer, branched polymer:

[0027] A polymer comprises a set of polymer chains of different molecular dimensions, notably of different molar masses. The polymer chains are made up from the covalent assembly of a large number of repetitive units called monomer units. The polymer chains so defined have molecular dimensions (characterised by their molar mass) very much largerthan those of simple molecules, and are made up from the covalent assembly of more than 5 monomer units, preferably of more than 20 monomer units, still more preferably of more than 50 monomer units.

[0028] Polymer chains comprising a single type of monomer unit are called homopolymers. Polymer chains comprising several types of monomer unit are called copolymers.

[0029] According to this invention, the term "polymer" designates homopolymers or copolymers.

[0030] According to this invention, polymer and polymer chain designate both linear polymer chains and branched polymer chains.

[0031] The term "polymers blend(s)" or "blend(s) of polymers" as used in the present invention refers to a mixture of at least two polymers (homopolymers or copolymers). The blend can be heterogeneous (the polymers are immiscible), compatible (immiscible polymers that exhibits macroscopically uniform physical properties) or homogeneous (the polymers are miscible).

[0032] The term "polymeric network" as used in the present invention typically designates polymer or blends of polymer as described above that may be crosslinked, eventually further comprising oligomers and / or organic molecules that are either covalently linked to a polymer chain or dispersed into the polymeric network.

[0033] Thermoset polymer and thermoplastics

[0034] By definition, a "thermoset polymer" is a polymer that hardens following an input of energy, in particular on the action of heat. Thermosets are traditionally divided into two families depending on the glass-transition temperature (Tg) of their polymer matrix. Thermosets whose matrix has a Tg higher than the working temperature are called rigid thermosets, while thermosets whose matrix has a Tg lower than the working temperature are called elastomers. According to the present invention, thermoset designates both rigid thermosets and elastomers. Materials manufactured from thermoset polymers have the advantage of being able to be hardened in a way that gives them a high mechanical, thermal and chemical resistance and for this reason they can replace metals in certain applications. They have the advantage of being lighter than metals. They can also be used as matrices in composite materials. Traditional thermosets must be manufactured; in particular, they must be molded and have the appropriate shape for their final use from the start. No transformation other than machining is possible once they are polymerized, and even machining is difficult because of their fragility. Supple and hard parts and composites based on thermoset resins cannot be transformed or shaped; nor can they be recycled. Thermoplastics belong to another class of polymeric materials. Thermoplastics can be shaped at high temperature by molding or by injection, but have mechanical properties and thermal and chemical resistance that are less interesting than those of thermosets. In addition, the shaping of thermoplastics can often only be carried out in a very narrow temperature ranges. When thermoplastics are heated, they become liquids, the fluidity of which varies abruptly around the melting / glass-transition temperatures, which does not allow the application of a range of transformation methods that exist for glass and for metals for example.

[0035] The new polymer compositions, when it comprises crosslinked polymers, can combine the mechanical properties and insolubility of a thermoset while being used like a thermoplastic. In this way, it is possible to develop polymeric networks that show the mechanical properties and insolubility of a thermoset but which can be transformed when hot after hardening. In particular, it is possible to develop materials that can be heated to temperatures at which they become malleable without suffering destruction or degradation of their structure. In addition, the polymeric network is recyclable.

[0036] Pendant group:

[0037] The term "pendant group" as used herein designates a side-group of the polymer chain, i.e., a substituent that is not an oligomer or a polymer. A side-group is not integrated into the main chain of the polymer.

[0038] Free molecule:

[0039] According to this invention, a molecule is said to be "free" if it is not linked by a covalent bond to a polymer of the composition.

[0040] Crosslinking:

[0041] Crosslinking, or polymerchain crosslinking, consists of creating covalent chemical bonds between polymer chains that initially are not linked to other by covalent bonds. Crosslinking is accompanied by an increase in connectivity, through covalent bonds, between the various chains that make up the polymer. The crosslinking of linear or branched polymer chains is accompanied by an increase in the molecular dimensions of the chains, notably of the molar masses, and can lead to a network of crosslinked polymers being obtained. The crosslinking of a network of crosslinked polymers is accompanied by an increase in the mass fraction insoluble in good non- reactive solvents according to the definition given below.

[0042] According to the invention, crosslinking is the result, among other causes, of the formation of nitrogen-nitrogen bonds. The presence of N-N bond(s) in the crosslinks results from the grafting of the azide derivative of formula (I) to a repeating unit of a polymer, and / or from the recombination of aminyl radicals present as pendant groups, and / or from exchange reactions between an aminy radical and a N-N bond present as pendant groups.

[0043] Glass transition temperature:

[0044] The glass transition temperature, Tg, is defined as the temperature at which the value of the damping factor, or loss factor, tan 6 is at a maximum by dynamic mechanical analysis at 1 Hz. The damping factor, or loss factor, tan 6, is defined as the ratio of the loss modulus E" to the conservation modulus E' (Mechanical Properties of Solid Polymers, Author(s): I. M. Ward, J. Sweeney; Editor: Wiley-Blackwell; Edition: 3rd Edition; Print ISBN: 9781444319507; DOI: 10.1002 / 9781119967125).

[0045] Polymer composition:

[0046] A polymer composition is defined as a homogenous or non-homogenous mixture of linear or branched polymers, which may be linked by crosslinks, containing pendant links and crosslinks that are exchangeable by nitrogen-nitrogen exchange reactions and / or exchange reactions between N-N bonds and aminyl radicals, and / or recombination of aminyl radicals, potentially with various charges, additives or solvents, as defined below.

[0047] In this way, "polymer composition" designates both solid formulations that contain little or no solvent(s) and liquid formulations containing a higher mass fraction of solvent(s).

[0048] In this way, "formulation" designates both solid formulations and liquid formulations.

[0049] According to the invention, a solid formulation may contain less than 30% by mass of solvent(s), preferably less than 25% by mass of solvent(s), more preferably less than 20% by mass of solvent(s), still more preferably less than 15% by mass of solvent(s), still more preferably less than 5% by mass of solvent(s), still more preferably less than 2.5% by mass of solvent(s), still more preferably less than 1% by mass of solvent(s) and still more preferably less than 0.5% by mass of solvent(s).

[0050] According to the invention, a solid formulation is a material.

[0051] According to the invention, a liquid formulation may contain more than 30% by mass of solvent(s), preferably more than 50% by mass of solvent(s), more preferably more than 60% by mass of solvent(s), still more preferably more than 70% by mass of solvent(s) and still more preferably more than 75% by mass of solvent(s).

[0052] According to the invention, a liquid formulation may be a material.

[0053] A solvent is defined as a molecule, or a mixture of molecules, that is liquid at ambient temperature and that has the property, at ambient temperature, of dissolving and / or diluting other substances without modifying them chemically and without being modified itself. Among solvents, a distinction is made between good solvents, which present the property of dissolving substances at room temperature without modifying them chemically and without being modified themselves, and poor solvents, which present the property of diluting substances at ambient temperature without dissolving them, modifying them chemically and without being modified themselves.

[0054] A solvent can therefore be a good solvent for one compound and a poor solvent for another compound.

[0055] Non-limiting examples of solvents include ethyl acetate, butyl acetate, acetone, acetonitrile, benzyl alcohol, acetic anhydride, anisole, benzene, butanol, butanone, chlorobenzene, dichlorobenzene, trichlorobenzene, chloroform, cyclohexane, dichloroethane, dichloromethane, dimethylformamide, dimethyl sulfoxide, dioxane, water, ethanol, glycol ether, diethyl ether, ethylene glycol, heptane, hexane, mineral oils, natural oils, synthetic oils, hydrocarbons, methanol, pentane, propanol, propoxypropane, pyridine, tetrachloroethane, tetrachloromethane, tetrahydrofuran, toluene, trichlorobenzene, xylene, and their mixtures. Nitrogen-nitrogen exchange reaction, nitrogen-nitrogen / aminyl raidcal exchange reaction, aminyl radicals' recombination

[0056] According to the invention, the nitrogen-nitrogen exchange reaction that occurs in the crosslinked polymer or polymers blend enables an exchange between the substituents linked to each nitrogen atom of a covalent N-N bond comprised in the crosslink or as pendant groups.

[0057] The term "aminyl radical", as used herein, refers to a nitrogen-centered radical. Aminyl radicals can be single radicals or di-radicals, corresponding to a nitrogen atom carrying one unpaired valence electron or two unpaired valence electrons, respectively. Triplet state nitrenes are examples of aminyl radicals carrying two unpaired valence electrons.

[0058] According to the invention, the nitrogen-nitrogen / aminyl radical exchange reaction that may occur in the crosslinked polymer or polymers blend enables an exchange of one of the two nitrogen atoms of a covalent N-N bond comprised in the crosslinks or as pendant groups by another nitrogen atom of an aminyl radical. In other terms, the new nitrogen atom in the N-N covalent bond after the exchange reaction is the nitrogen atom of the aminyl radical involved in the exchange reaction, while the nitrogen atom that was initially in the N-N bond is now transformed into an aminyl radical after the reaction.

[0059] According to the invention, the recombination of the aminyl radicals corresponds to the recombination of two aminyl radicals to form a covalent N-N bond.

[0060] Non-limiting examples of a nitrogen-nitrogen exchange reaction, a nitrogen-nitrogen / aminyl radical exchange and an aminyl radicals' recombination are provided in figure 1, in which Sub1to Sub8are substituants linked the nitrogen atoms involved in the nitrogen-nitrogen exchange reaction, the nitrogen-nitrogen / aminyl radical exchange and the aminyl radicals' recombination. Said substituents may be the heteroaromatic groups of the azide derivative of formula (I), polymer chains or oligomer chains.

[0061] Said substituents may be identical or different.

[0062] These substituents are bound by covalent bonds, before and after the exchange reaction, to at least one nitrogen atom.

[0063] The nitrogen-nitrogen exchange reaction, the nitrogen-nitrogen / aminyl radical exchange reaction and aminyl radicals' recombination are carried out under processing conditions, i.e. at a suitable temperature. These reactions can be carried out in the presence or absence of catalyst. Preferably the catalyst is stable, easily available, inexpensive and non-toxic. Preferably the reactions are carried out in the absence of catalyst.

[0064] The nitrogen-nitrogen exchange reaction, the nitrogen-nitrogen / aminyl radical exchange and the aminyl radicals' recombination can be carried in solvent(s) or in bulk, i.e. in the absence of solvents.

[0065] These nitrogen-nitrogen exchange reaction, nitrogen-nitrogen / aminyl radical exchange reaction and aminyl radicals' recombination enable polymer compositions to be obtained to have the properties of thermoset polymers and of thermoplastic polymers and which can be insoluble and malleable when hot.

[0066] Groups:

[0067] The term "Ci-yalkyl", as used herein, refers to a straight or branched monovalent saturated hydrocarbon chain containing from 1 to y carbon atoms including, but not limited to, methyl, ethyl, n-propyl, iso-propyl, n-butyl, iso-butyl, sec-butyl, t-butyl, n-pentyl, n-hexyl, and the like. The term "Ci-Cyhaloalkyl" as used herein refers to a Ci-Cyalkyl chain as defined above wherein one or more hydrogen atoms are replaced by a halogen atom selected from fluorine, chlorine, bromine or iodine.

[0068] The term "Ci-yalkyl-aryl", as used herein, refers to a Ci-yalkyl as defined above linked to an aryl group as defined above, said Ci-yalkyl-aryl group being linked to the rest of the molecule via an atom of the alkyl moiety or the aryl moiety.

[0069] "Heteroatom" as used herein designates atoms of sulfur, nitrogen, oxygen, boron, phosphorus or silicon.

[0070] "Aromatic" as used herein designates a monovalent or multivalent group comprising an aromatic hydrocarbon group. The valence of the group will be determined case-by-case.

[0071] The aromatic group may include heteroatoms; in this case it is called a "heteroaromatic" group. In particular, it may include ester, amide, ether, thioether, secondary or tertiary amine, carbonate, urethane, carbamide or anhydride functions. An aromatic group may designate one or more rings that are fused or covalently linked. If applicable, the aromatic group may be substituted notably by a halogen, an -Rz, -OH, -NH2, -NHRz, -NRzR'z, -C(O)-H, -C(O)-Rz, -C(O)- OH, -C(O)-NRzR'z, -C(O)-O-Rz, -O-C(O)-Rz, -O-C(O)-O-Rz, -O-C(O)-N(H)-Rz, -N(H)-C(O)-O-Rz, - O-Rz, -SH, -S-Rz, -S-S-Rz, -C(O)-N(H)-Rz, -N(H)-C(O)-Rz group with Rz, R'z, identical or different, representing a C1-C50 alkyl group, or by a functional group chosen from among the functional groups that are polymerisable by radical polymerisation.

[0072] The term "aryl" refers to an aromatic hydrocarbon group preferably comprising from 6 to 12 carbon atoms and comprising one or more fused rings, such as, for example, a phenyl or naphthyl group. Advantageously, it is a phenyl group.

[0073] In particular, in the context of the present invention, the heteroaromatic group is a heteroaryl. The term "heteroaryl", as used herein, refers to an aromatic group comprising one or several, notably one or two, fused hydrocarbon cycles in which one or several, notably one to four, advantageously one or two, carbon atoms each have been replaced with a heteroatom selected from a sulfur atom, an oxygen atom and a nitrogen atom, preferably selected from an oxygen atom and a nitrogen atom. It can be a furyl, thienyl, pyrrolyl, pyridyl, oxazolyl, isoxazolyl, thiazolyle, isothiazolyl, imidazolyl, pyrazolyl, oxadiazolyl, thiadiazolyl, triazolyl, tetrazolyl, pyridazinyl, pyrimidinyl, pyrazinyl, triazinyl, quinolyl, isoquinolyl, quinoxalyl or indyl. Preferably, it is an azinyl, a diazinyl, triazinyl or a purinyl group, more preferably a triazinyl group. DETAILED DESCRIPTION

[0074] The azide derivative of formula (I)

[0075] The azide derivative of formula (I) is preferably selected from the group consisting of: in which one or two, preferably one, of R1to Rxis N3 and the others are each independently selected in the group consisting of a hydrogen atom, a halogen, a C1-12 alkyl group, a C1-12 haloalkyl group, an aryl, a heteroaryl, a Ci- alkyl-aryl group, an oxo group, NRcRd, ORe, C(O)Rf, C(O)ORg, C(O)NRhR', SRJ, CN and NO2 wherein Rcto RJare, independently of one another, a hydrogen atom, a C1-C12 alkyl group, a Ci-ea Ikyl-a ryl group or an aryl,

[0076] Rxbeing the group with the highest index on the compound.

[0077] Advantageously, one or two, preferably one, of R1to Rxis N3 and the others are each independently selected in the group consisting of a hydrogen atom, a halogen atom, a Ci-Ce alkyl group, an aryl, an oxo group, NRcRd, OReand SRJ, wherein Rcto Reand RJare preferably, independently of one another, a hydrogen atom, a C1-C12 alkyl group or an aryl.

[0078] Advantageously, one or two, preferably one, of R1to Rxis N3 and at least one of the others is selected in the group consisting of a halogen, a C1-12 alkyl group, a C1-12 haloalkyl group, an aryl, a heteroaryl, a Ci- alkyl-aryl group, an oxo group, NRcRd, ORe, C(O)Rf, C(O)ORg, C(O)NRhR', SRJ, CN and NO2 wherein Rcto RJare, independently of one another, a hydrogen atom, a Ci-Ce alkyl group, a Ci-ea Ikyl-a ryl group or an aryl. More preferably, one of R1to Rxis N3 and at least one of the others is selected in the group consisting of a halogen atom, a Ci-Ce alkyl group, an aryl, an oxo group, NRcRd, OReand SRJ, wherein Rcto Reand RJare as defined above and preferably, independently of one another, a hydrogen atom, a C1-C12 alkyl group or an aryl, said aryl being notably a phenyl.

[0079] In one embodiment, the azide derivative of formula (I) is a triazine selected in the group consisting of:

[0080] In particular, the triazine is a 1,3,5-triazine of formula (l-A): wherein R2and R3are as defined above, and preferably are each independently selected in the group consisting of a hydrogen atom, a halogen, a Ci-6 alkyl group, an aryl, an oxo group, NRcRd, ORe, SRJwherein Rcto Re and RJare, independently of one another, a hydrogen atom, a C1-C12 alkyl group, a Ci-ea I kyl-a ryl group or an aryl. More preferably, R2and R3are each independently selected in the group consisting of a C1-6 alkyl group, an aryl, NRcRd, ORe, SRJwherein Rcto Reand RJare, independently of one another, a hydrogen atom, a C1-C12 alkyl group, or an aryl, said aryl being notably a phenyl.

[0081] Preferably, R2and R3in compound of formula (l-A) are identical.

[0082] In another embodiment, the azide derivative of formula (I) is an azine selected in the group consisting of:

[0083] In particular, the azine is a pyridine of formula (l-B): wherein R1, R2R4and R5are as defined above and are preferably each independently selected in the group consisting of a hydrogen atom, a halogen, a Ci-6 alkyl group, an aryl, an oxo group, NRcRdand ORewherein Rcto Reare, independently of one another, a hydrogen atom, a C1-C12 alkyl group, a Ci-ea Ikyl-a ryl group or an aryl.

[0084] More preferably, at least one, and notably all, of R1, R2R4and R5in compound of formula (l-B) is (are) not a hydrogen atom.

[0085] Even more preferably R1, R2R4and R5in compound of formula (l-B) are each independently selected in the group consisting of a halogen, such as fluorine, a C1-6 alkyl group, an aryl, NRcRd, wherein Rcand Rdare, independently of one another, a C1-C12 alkyl group, or an aryl, said aryl being notably a phenyl. In particular, R1, R2R4and R5in compound of formula (l-B) are each independently selected in the group consisting of a halogen, such as fluorine, and NRcRd, wherein Rcand Rdare, independently of one another, a Ci-Ce alkyl group, such as a methyl, or an aryl, such as a phenyl.

[0086] In another embodiment, the azide derivative of formula (I) is a diazine selected in the group consisting of:

[0087] In particular, the diazine is a pyrimidine of formula (l-C): wherein R2to R4are as defined above and preferably each independently selected in the group consisting of a hydrogen atom, a halogen, a C1-6 alkyl group, an aryl, an oxo group, NRcRdand ORewherein Rcto Reare, independently of one another, a hydrogen atom, a C1-C12 alkyl group, a Ci- ea Ikyl-a ryl group or an aryl.

[0088] More preferably, at least one of R2to R4in compound of formula (l-C) is not a hydrogen atom. Even more preferably, R2to R4in compound of formula (l-C) are each independently selected in the group consisting of a hydrogen atom and an aryl, notably a phenyl.

[0089] In another embodiment, the azide derivative of formula (I) is a purine of the following formula: wherein R2to R3, R5and R6are as defined above and preferably each independently selected in the group consisting of a hydrogen atom, a halogen, a Ci-6 alkyl group, an aryl, an oxo group, NRcRdand ORewherein Rcto Reare, independently of one another, a hydrogen atom, a C1-C12 alkyl group, a Ci-ea Ikyl-a ryl group or an aryl.

[0090] More preferably, at least one, and notably one, two or three, of R2to R3, R5and R6in compound of formula (l-D) is (are) not a hydrogen atom.

[0091] Even more preferably, R2to R3, R5and R6in compound of formula (l-D) are each independently selected in the group consisting a C1-6 alkyl group, such a methyl, and NRcRd, wherein Rcand Rdare, independently of one another, a hydrogen atom, a Ci-Ce alkyl group, or an aryl, such as a phenyl.

[0092] Preferably, the azide derivative of formula (I) is selected in the group consisting of: which R1to R6are as defined above.

[0093] More preferably, the azide derivative of formula (I) is selected in the group consisting of:

[0094] In particular, the azide derivative of formula (I) is selected in the group consisting of:

[0095] More particularly, the azide derivative of formula (I) is selected in the group consisting of: The polymer or polymers blend

[0096] The advantage of the invention is that the polymer can be selected from a large group encompassing waste plastics. The polymer can be synthetic, natural, bio-sourced, and / or biobased. Advantageously, the polymer used in step (a) of the process of the invention is selected in the group consisting of polyolefins, polyesters, polystyrene (PS), polyurethane (PU), polyamides, poly(vinyl)chloride (PVC), natural polymers, their copolymers and their blends.

[0097] The polymers blend used in step (a) can comprise two or more, polymers selected in the group consisting of polyolefins, polyesters, polystyrene (PS), polyurethane (PU), polyamides, poly(vinyl)chloride (PVC), natural polymers and their copolymers.

[0098] Preferably, the polymer or the polymers blend is not or do not comprise a polydiene.

[0099] In particular, polyolefin is polyethylene, polypropylene (PP or iPP), their copolymers or the terpolymer ethylene propylene diene monomer (EPDM rubber). Polyethylene is notably high- density polyethylene (HDPE) or low-density polyethylene (LDPE), such as linear low density polyethylene (LLDPE), and polyester may be polycaprolactone (PCL) or polyethylene terephthalate (PET) and its copolymers.

[0100] Natural polymers can notably be polysaccharides or polyaromatics that may be selected in the group consisting of starch, chitin, chitosan, alginates, natural gums, cellulose, pectin, polyphenols, such as lignin, and proteins such as gluten, zein, casein, collagen and gelatine.

[0101] The polymer or the polymers blend used in step (a) can in particular be HDPE, LDPE, their copolymers or a blend of HDPE with another polyolefin such as polyethylene, polypropylene or their copolymers.

[0102] Preferably, the polymer or the polymers blend used in step (a) has a number average molar weight Mn, before reticulation, ranging from 300 g / mol to 3 000 000 g / mol, preferably from 1 000 g / mol and 1 000 000 g / mol, more preferably from 5 000 g / mol to 500 000 g / mol, even more preferably from 10000 g / mol to 300000 g / mol.

[0103] In a particular embodiment, the polymer is a plastic or a mixture of plastics. The term "plastics" in the context of the present invention refers to materials that use polymers, including natural, semi-synthetic, synthetic polymers as defined above, as a main ingredient and may comprise further additives such as fillers, antioxidants agents, etc. The plastics in the framework of the invention may be fully or partly bio-based plastics, i.e. "bioplastics", referring to plastics made of, or comprising, renewable polymers notably from animal or vegetable origin. Their plasticity makes it possible for plastics to be molded, extruded or pressed into solid objects of various shapes. The success and dominance of plastics has caused widespread environmental problems, due to their slow decomposition rate in natural ecosystems. The plastic in the present invention includes existing plastic, i.e. a polymer material as aforementioned which has already been shaped according to its intended use, and eventually which has already been used. An important advantage of the invention is that in the process of the invention, the polymer can be waste plastic or mixture of waste plastics, also including damaged plastic, mixture of damaged plastics, unsorted plastic, or mixtures thereof.

[0104] The process for obtaining a polymer composition

[0105] The process of the invention comprises the following steps:

[0106] (a) mixing a polymer or a polymers blend, and an azide derivative of formula (I) :

[0107] N3-Ar (I), in which Ar is a heteroaromatic group, at a processing temperature Tmix, then

[0108] (b) heating the mix of step a) to a temperature TR, wherein

[0109] Tmix is higher than the glass transition temperature or the melting temperature of the polymer used in step (a), or higher than the highest glass transition temperature or melting temperature of all the polymers present in the polymers blend of step (a) at a content of at least 8wt% relative to the total weight of the blend,

[0110] TR is equal to or higher than the decomposition temperature of the azide of formula (I), and Tmix is strictly lower than TR.

[0111] The process of the invention can further comprise one or several step(s) (a') of mixing at a processing temperature T'mix a polymer or a polymers blend that is different from the one of step (a), with an azide derivative of formula (I) that is identical or different from the one of step (a). T'mix is higher than the glass transition temperature or the melting temperature of the polymer used in step (a'), or higher than the highest glass transition temperature or melting temperature of all the polymers present in the polymers blend of step (a') at a content of at least 8wt% relative to the total weight of the blend.

[0112] In such embodiments, the mix of step (a) and the mix of step (a') are typically carried out in separate reactors and then in step (b), the mix of step (a) is heated in the presence of the mix of step (a') to a temperature TR. According to these embodiments, the process of the invention comprises the following steps:

[0113] (a) mixing a polymer or a polymers blend, and an azide derivative of formula (I) :

[0114] N3-Ar (I), in which Ar is a heteroaromatic group, at a processing temperature Tmix,

[0115] (a') mixing a polymer or a polymers blend, and an azide derivative of formula (I):

[0116] N3-Ar (I), in which Ar is a heteroaromatic group, at a processing temperature T'mix, the polymer or polymers blend and / or the azide derivative of formula (I) used in step (a') being different from the polymer or polymers blend and / or the azide derivative of formula (I) used in step (a),

[0117] (b) heating the mix of step a) in the presence of the mix of step (a') to a temperature TR, wherein Tmix, T'mix and TR are as defined above, and Tmix and T'mix are each strictly lower than TR.

[0118] Alternatively, when the process of the invention further comprises one or several step(s) (a'), it may comprise respectively one or more step(s) (b') of heating the mix of step (a') to a temperature TR. In such embodiments, steps (a) and (b) are carried out in a reactor and steps (a') and (b') are carried out in another reactor. Then, the polymer composition resulting from step (b) may be blended with the resulting polymer composition of step (b'). According to these embodiments, the process of the invention comprises the following steps:

[0119] (a) mixing a polymer or a polymers blend, and an azide derivative of formula (I):

[0120] N3-Ar (I), in which Ar is a heteroaromatic group, at a processing temperature Tmix,

[0121] (a') mixing a polymer or a polymers blend, and an azide derivative of formula (I):

[0122] N3-Ar (I), in which Ar is a heteroaromatic group, at a processing temperature T'mix, the polymer or polymers blend and / or the azide derivative of formula (I) used in step (a') being different from the polymer or polymers blend and / or the azide derivative of formula (I) used in step (a),

[0123] Tmix and T'mix being as defined above,

[0124] (b) heating the mix of step (a) to a temperature TR, wherein TR is equal to or higher than the decomposition temperature of the azide of formula (I) used in step (a),

[0125] (b') heating the mix of step (a') to a temperature T'R, wherein T'R is equal to or higher than the decomposition temperature of the azide of formula (I) used in step (a'), wherein steps (a) and (b) are carried out in a reactor and steps (a') and (b') are carried out in another reactor, and

[0126] (c) blending a polymer composition resulting from step (b) with a polymer composition resulting from step (b') at a temperature T"R being equal to the higher temperature among TR and T'R.

[0127] The step (a)

[0128] The step (a') is identical to step (a) but implements a polymer or a blend which is different and / or azide derivative of formula (I) which is different. Steps (a) and (a') are carried out in two different reactors. Steps (a) and (a') are notably carried out concomitantly. Although we only specifically mention one parallel step (a'), several parallel steps (a') can be implemented. In the following, all embodiments disclosed for step (a) also apply to the step(s) (a').

[0129] According to preferred embodiments, the mix of step (a) comprises from 0.05 mol% to 10 mol%, preferably from 0.1 to 3.5 mol%, more preferably from 0.5 to 1.5 mol% of the azide derivative of formula (I), relative to the polymer repeating units. In some embodiments, the mix of step (a) comprises from 0.1 wt% to 40 wt%, preferably from 0.5 wt% to 20 wt%, more pefereably from 1 wt% to 15 wt% of the derivative of formula (I), relative to the total weight of the mix.

[0130] The repeating units of a polymer may be determined by a combination of FTIR, Raman and NMR spectroscopies.

[0131] The azide derivative of formula (I) can be soluble or insoluble in the molten polymer or polymers blend used at step (a). When the azide derivative is completely insoluble or partially soluble, i.e. when a separation of phases is observed by transmission electron microscopy (TEM) as explained in the method below, it is broadly referred to herein as an insoluble azide derivative.

[0132] The solubility of the azide derivative of formula (I) in the mix of step (a) may be determined by transmission electron microscopy (TEM) or according to a solubility theorical model as detailed in the "methods" paragraph below.

[0133] For a given polymer or blend of polymers, the lower the solubility of the azide derivative of formula (I) in the mix of step (a), the higher the crosslinking density in the polymer composition. In other terms, when the azide derivative is insoluble, the polymer composition obtained after step (b) comprises a high proportion of crosslinked polymer, even constituting a polymer network. On the contrary, when the azide derivative is soluble, the polymer composition obtained after step (b) will comprise a high proportion of non crosslinked and / or weakly crosslinked polymers. By implementing a step (a) and a step (a') in which each azide derivative has a different solubility in the mix of step (a) or (a') respectively (depending on the nature of the polymer or polymers blend or of the nature of the azide derivative), a polymer composition comprising a mixture of crosslinked and non-crosslinked polymers may be obtained.

[0134] Preferably, the azide derivative of formula (I) is insoluble in the molten polymer or polymers blend used at step (a), more preferably it is totally insoluble. Therefore, the polymer composition obtained after step (b) preferably comprises a high proportion of crosslinked polymer, more preferably constitutes a polymer network.

[0135] Step (a) is thus a step of premixing that is essential to disperse the azide derivative, notably the insoluble azide derivative, in the polymer or polymers blend. This premixing enables to obtain a polymer composition with enhanced thermomechanical properties, that is reprocessable and recyclable. Typically, this reprocessability and recyclability may be evidenced by comparing the thermomechanical properties after a cycle of reprocessing and reshaping. For example, the polymer composition may be described as reprocessable and recyclable when a consistent rubbery plateau is observed in dynamic mechanical analysis (DMA), and / or by uniaxial tensile testing when consistent tensile properties are observed, and / or by rheological experiments when, for example, a consistent high temperature creep resistance is observed.

[0136] According to preferred embodiments, step (a) comprises the following successive sub-steps : (al) providing a polymer or a polymers blend, (a 2) providing an azide derivative of formula (I),

[0137] (a 3 ) mixing the polymer or polymers blend of step (al) and the azide derivative of formula (I) of step (a2) at a processing temperature Tmix as defined above.

[0138] Preferably, the temperature Tmix is higher than the highest glass transition temperature (Tg) or melting temperature (Tm) of all the polymers being present in the blend at a content of at least 8wt %, and notably at least 4 wt%, and in particular of less than 2 wt%, relative to the total weight of the blend.

[0139] Accordingly, the glass transition temperature or the melting temperature, of the polymers that are present in the blend in a content of less than 8 wt%, notably of less than 4 wt%, and in particular of less than 2 wt%, will not be considered to set up the temperature Tmix.

[0140] It is understood that it is referred to a glass transition temperature (Tg) when the polymer is amorphous and to a melt temperature when the polymer is semicrystalline. The polymer or polymers blend of step (al) may be provided as such or as a suspension or solution in a solvent. Typically, the suspension or solution may be heated, for example to the processing temperature Tmix, before to be mixed in step (a3).

[0141] The azide derivative may be provided at step (a 2) as such or as a masterbatch. By "masterbatch" it is understood that the azide derivative is beforehand dissolved or suspended in a solvent or in a "diluent" polymer in which the azide derivative is soluble. The "diluent" polymer may be a portion of the polymer or polymers blend of step (al), or a polymer or polymers blend different from the one used in step (al) when the azide derivative is poorly soluble in the polymer or polymer blends of step (al). Typically, such a masterbatch comprises from 0.5 wt% to 40 wt% of the azide derivative, relative to the total weight of the masterbatch. Providing the azide derivative as a masterbatch allows to facilitate the dispersion of the additive during the melt processing of step (a3). The masterbatch may be heated before to be mixed with the polymer or polymer blend in step (a 3), typically to the processing temperature Tmix or lower.

[0142] Alternatively, the polymer or polymers blend of step (al) and the azide derivative of step (a 2) may be provided at room temperature and the mix is heated to Tmix only during step (a3).

[0143] According to preferred embodiments, the mixing of step (a3) at the processing temperature Tmix, is carried out for a time ranging from 1 min to 10 min, preferably from 2 min to 6 min.

[0144] The mixing step (a) is performed in a reactor, such as an extruder, an internal mixer or a mold, and notably in the barrel of the extruder.

[0145] The temperature TR and the reaction time tR of step (b)

[0146] TR is the reaction temperature to which the mix of step (a) is heated during step (b). This is the setpoint temperature set by an operator. TR is equal to or higher than the decomposition temperature of the azide of formula (I).

[0147] The decomposition temperature of the azide derivative of formula (I) is the decomposition temperature of the azide derivative in the mix of step (a). This decomposition temperature corresponds to the temperature at which the azide derivative starts to decompose, i.e. when the covalent bonds of the compound start breaking, in the mix of step (a). The value of the decomposition temperature will thus depend on the nature of the polymer or polymers blend provided in step (a) and with which the azide derivative is mixed. The decomposition temperature of the azide derivative in the mix of step (a) is typically determined by using TGA or DSC measurements according to the methods described in the "methods" paragraph below.

[0148] A temperature Tnequal to the decomposition temperature of the azide derivative is meant to be that TR ranges from -5°C to +5°C as compared to the decomposition temperature of the azide derivative in the mix of step (a).

[0149] Preferably, TR is strictly higher than the decomposition temperature of the azide derivative in the mix of step (a). In particular, the temperature TR ranges from a temperature equal to the decomposition temperature plus 5°C to a temperature equal to the decomposition temperature plus 100°C, in particular from a temperature equal to the decomposition temperature plus 10°C to a temperature equal to the decomposition temperature plus 90°C.

[0150] In most cases, preferably all cases, the decomposition temperature of the azide is higher than the glass transition temperature (Tg) or melting temperature (Tm) of the polymer. When the mix of step (a) comprises a blend of polymers, the relevant Tgor Tmis the highest glass transition temperature (Tg) or melting temperature (Tm) of all the polymers being present in the blend at a content of at least 8 wt% relative to the total weight of the blend.

[0151] Accordingly, when the mix of step (a) comprises one polymer, the temperature TR is strictly higher than the glass transition temperature (Tg) or melting temperature (Tm) of the polymer. Alternatively, when the mix of step (a) comprises a polymers blend, the temperature TR is strictly higher than the highest glass transition temperature (Tg) or melting temperature (Tm) of all the polymers present in the blend at a content of at least 8 wt% relative to the total weight of the blend, preferably at a content of at least 4 wt%, more preferably at a content of at least 2 wt%. In all cases, TR is strictly higher than Tmix.

[0152] According to a preferred embodiment, at step (b), a reaction time tR at the temperature TR is observed. The reaction time tR corresponds to the time needed for 50%, preferably 75%, more preferably 90%, even more preferably 95%, of the azide derivative of formula (I) to be decomposed at the temperature TR. The percentages are expressed in relation to the total amount of the azide derivative of formula (I) provided in step (a). Preferably, the reaction time tR is less than 60 min, more preferably less than 30 min.

[0153] In other terms, the temperature TR and the reaction tR are selected so that 50%, preferably 75%, more preferably 90%, even more preferably 95%, of the azide derivative of formula (I) is decomposed, preferably in as short a time as possible. The reaction time tR may correspond to 1 to 10, preferably 2 to 9, more preferably 4 to 8, more preferably 5, half-lives of the azide derivative of formula (I) in the mix of step (a) at the temperature TR. The half-life is proper to one azide derivative of formula (I) and function of the reaction temperature. The higher the temperature TR, the shorter the half-time.

[0154] According to a preferred embodiment, TR is selected so that the half-life of the azide derivative ranges from 1 s to 15 min, preferably from 1 min to 10 min, more preferably from 2 min to 5 min. In particular, TR is selected so that the half-life of the azide derivative is equal to 2 min. Preferably, the reaction time tR is equal to 10 min accordingly.

[0155] According to some embodiments, the heating time needed for the mix of step (a) to reach the temperature TR, notably the time needed to go from the temperature Tmix to the temperature TR, is equal to or less than 5 half-lives, preferably equal to or less than 2 half-lives, more preferably equal to 1 half live.

[0156] According to some embodiments, step (b) is performed by reactive extrusion, compression molding, injection molding or oven curing. In particular, the reaction may be performed in a twin- screw extruder or by compression molding with hot press.

[0157] The step ( b' ) is identical to step (b) but concern the heating of a mix of step (a') when present. Steps (b) and ( b') are carried out in two different reactors. Steps (b) and (b') are notably carried out concomitantly. Although we only specifically mention one parallel step ( b'), several parallel steps (b') can be implemented when several step (a') are carried out. All embodiments disclosed herein for step (b) also apply to the step(s) (b').

[0158] The grafting of the azide derivative onto the polymer or polymers blend may be assessed by conventional techniques well-known in the art, including NMR, IR, Raman, UV-Vis, EPR spectroscopies, elemental analysis and mass spectrometry.

[0159] The polymer composition obtained by the process as described hereabove

[0160] The process of the invention affords a polymer composition, crosslinked or not, preferably crosslinked, in which the polymer or polymers blend is grafted with a residue of the azide derivative of formula (I) provided in the process. In other terms, the polymer composition contains at least one N-N bond, as it can be evidenced by Raman, UV-Vis and / or NMR spectroscopies, and / or elemental analysis. This N-N bond confers a dynamic behaviour to the polymer composition. As such a N-N bond may be broken and then reformed dynamically, in particular under processing conditions, so that the overall polymer network is able to reconfigure and adapt to the processing and shaping conditions. This N-N bond may be included in a crosslink between polymer chains of the polymer composition, in a pendant group of a polymer chain and / or in free molecules present in the polymer composition. Accordingly, the polymer composition resulting from the process of the present invention may comprise a crosslinked polymer, a non-crosslinked polymer or a mixture thereof, in particular depending on the solubility of the one or more azide derivative of formula (I) in the mix of step (a) of the process.

[0161] According to some embodiments, the polymer composition obtained by the process as described hereabove contains groups of formula (II) and / or (III): in which s is the bond between the group (II) and / or (III) and a carbon atom of a repeating unit of a polymer of the composition, x and y are each independently an integer ranging from 0 to 10, preferably 0 or 1,

[0162] Ar is as defined in the azide derivative of formula (I) used in the process as described above, and

[0163] * is selected from the group consisting of H and a carbon atom of another repeating unit of a polymer of the composition.

[0164] It is understood that the Ar group present in groups of formula (II) and (III) corresponds to the Ar group present in the azide derivative of formula (I) that was provided in step (a) of the process used to afford the polymer composition.

[0165] The polymer composition may comprise a mixture of crosslinked and non-crosslinked polymers or polymers blends. Such a polymer composition discloses an improved processability and ductily as compared to existing polymer compositions. Interesting macroscopic properties, such as superior creep resistance above Tg for amorphous polymers, superior creep resistance above Tg and above Tm for semicristalline polymers, improved elongation at break, improved stress at break, improves toughness, improved solvent resistance, ability to generate adhesion between polymer composition of identical or different chemical nature, may be obtained for these polymer compositions even with a lower overall additive content than for existing polymer compositions. According to preferred embodiments, the polymer composition comprises a high proportion of crosslinked polymer or crosslinked polymers blend, notably due to the insolubility of the one or more azide derivative of formula (I) in the mix of step (a). In particular, the polymer composition comprises crosslinked polymer or crosslinked polymers blend in a proportion sufficient for the composition to be reprocessable and recyclable. Such a polymer composition typically displays an insoluble fraction superior to 10 wt%, preferably superior 25 wt%, more preferably superior to 40 wt% of the total weight of all the polymers present in the composition. The soluble fraction is the mass of dried insoluble polymer remaining after immersion of the composition for at least 10 hours at a temperature and in a solvent or a mixture of solvents in which all the polymers present in the composition are fully soluble in when not crosslinked.

[0166] According to this embodiment, the polymer composition contains groups of formula (II) and (III) as defined above, * in said group (II) being preferably a carbon atom of another repeating unit of a polymer of the composition.

[0167] In particular, the inventors have evidenced that the process of the invention leads to a polymer composition comprising dynamic crosslinks (see example 4). By "dynamic crosslinks" it is understood that the crosslinks made between the polymer chains of the composition may be broken and reformed under processing conditions, i.e. at a suitable temperature and / or high shear.

[0168] As aforementioned, these reversible crosslinks comprise at least one N-N bond, and notably heteroaromatic N-N bond, that thus may be broken and reformed under said processing conditions. The heteroaromatic groups are useful to stabilize the radical species (e.g. aminyl radicals) resulting from the breaking of the N-N bond before to be reformed.

[0169] The inventors have also demonstrated that long-lived radicals comprising at least one N-N bond, notably heteroaromatic N-N bonds, may be present in the crosslinked composition. These persistent radicals may remain in the composition in stable conditions, e.g. during storage or use, and then recombine to form crosslinks under future processing conditions.

[0170] Thanks to the reversibility of the crosslinks of the composition, such crosslinked polymer or polymers blend are reprocessable, and thus recyclable. According to some other embodiments, the polymer composition comprises a high proportion of non-crosslinked polymer or noncrosslinked polymers blend, notably due to the high solubility of the one or more azide derivative of formula (I) in the mix of step (a). Such a polymer composition can present up to 99.5 wt% of soluble polymers relative to the total weight of all the polymers present in the composition. Such a polymer composition typically displays an insoluble fraction inferior to 40wt%, preferably inferior to 25wt%, and notably comprised between, 0,lwt% and 25wt%, in particular between, 0,5wt% and 10 wt%.

[0171] According to this embodiment, the polymer composition contains groups of formula (II) and (III) as defined above, * in said group (II) being preferably H, said group of formula (II) thus being a pendant group.

[0172] Such a non-crosslinked polymer composition may also comprise long-lived radical as defined above.

[0173] In some embodiments, the polymer composition of the invention, mainly crosslinked or not, preferably crosslinked, further comprises pendant groups of formula -NH(Ar) linked to a carbon atom of a repeating unit of a polymer of the composition, in which Ar is as defined in the azide derivative of formula (I) used in the process as described above.

[0174] Without being bound by theory, the polymer composition, mainly crosslinked or not, preferably crosslinked, is likely to contain free compounds containing a heteroaromatic group Ar resulting from the decomposition of the unreacted azide derivative of formula (I) and / or the reaction of the azide derivative of formula (I) with the polymer or polymers blend. Such free compounds may be : a free amine containing a heteroaromatic group Ar, such as a primary amine of formula NH2Ar, a polyazane of formula NHAr-[N(Ar)]x-NHAr, in which x is an integer from 0 to 10, preferably 0 or 1, a polyazane of formula NHAr-[N(Ar)]x-NAr«, in which x is an integer from 0 to 10, preferably 0 or 1, or a derivative of formula (Ar)N=N(Ar).

[0175] The polymer compositions obtained by the process of the invention may thus be recycled under further processing conditions. The processing conditions are those typically used to process thermoplastics, including but not limited to, extrusion, reactive extrusion, injection molding, thermoforming, blow molding, fiber spinning, powder coating, rotational molding, reactive processing and compression molding. Recycling as used herein includes, without being limited to, the shaping of the polymer composition under a new form, the addition of additives and charges in the recycled material, the addition of virgin polymers in the recycled materials.

[0176] In some embodiments, the polymer composition may be recycled by implementing reactive extrusion and then compression molding. In some other embodiments, the polymer composition may be recycled by implementing compression molding without reactive extrusion.

[0177] The use of the azide derivative of formula (I)

[0178] The present invention also relates to the use of an azide derivative of formula (I) as described in the present disclosure as an additive for upcycling a plastic or a mixture of plastics, in particular waste plastic or mixture of waste plastics, for example unsorted plastic, damaged plastic, mixture of damaged plastics or mixture thereof. Preferably, the azide derivative is insoluble in the plastic or a mixture of plastics, in particular waste plastic or mixture of waste plastics, for example unsorted plastic, damaged plastic, mixture of damaged plastics or mixture thereof, to which it is added.

[0179] Thus, according to the present invention is thus provided a process for upcycling a plastic or a mixture of plastics, in particular waste plastic or mixture of waste plastics, for example unsorted plastic, damaged plastic, mixture of damaged plastics or mixture thereof, comprising the steps of:

[0180] (i) mixing a plastic or a mixture of plastics, in particular waste plastic or mixture of waste plastics, for example unsorted plastic, damaged plastic, mixture of damaged plastics or mixture thereof, with a source of an azide derivative of formula (I) as an additive :

[0181] N3-Ar (I)

[0182] Ar is a heteroaromatic group as defined in the present disclosure,

[0183] (ii) heating the mix of step (i) to a temperature TR, wherein TR is higher than the glass transition temperature or the melting temperature of the plastic used in step (i), or higher than the highest glass transition temperature or melting temperature of all the plastics present in the mixture of plastics at a content of at least 8 wt% relative to the total weight of the mixture, and equal to or higher than the decomposition of the azide derivative of formula (I).

[0184] The source of the azide derivative of formula (I) may be the azide derivative of formula (I) itself and / or a polymer composition resulting from the process of the invention as defined herein, in particular a non-crosslinked or weakly crosslinked polymer composition as defined above. It is understood that said non-crosslinked polymer comprises polymer chain grafted with a residue of an azide derivative of formula (I), notably with groups of formula (II) and / or (III): in which is the bond between the group (II) and / or (III) and a carbon atom of a repeating unit of a polymer of the composition, x and y are each independently an integer ranging from 0 to 10, preferably 0 or 1,

[0185] Ar is as defined in the azide derivative of formula (I) used in the process as described above, and

[0186] * is H.

[0187] A source of an azide of formula (I) under the form of a non-crosslinked polymer composition as defined above is particularly useful for facilitating the storage, the handling, the dispersion of the additive into the plastics, especially in large volume of said azide derivative.

[0188] Preferably, the mix of step (i) is achieved at a temperature Tmix, that is higher than the glass transition temperature or the melting temperature of the plastic used in step (i), or higher than the highest glass transition temperature or melting temperature of all the plastics present in the mixture of plastics at a content of at least 8 wt% relative to the total weight of the blend, and lower than the temperature TR.

[0189] In particular, step (i) comprises the following successive sub-steps :

[0190] (i-1) providing a plastic or mixture of plastics, in particular waste plastic or mixture of waste plastics, for example unsorted plastic, damaged plastic, mixture of damaged plastics or mixture thereof,

[0191] (i-2) providing a source of an azide derivative of formula (I),

[0192] (i-3) mixing the plastic or mixture of plastics of step (i-1) and the azide derivative of formula (I) of step (i-2) at a processing temperature Tmix as defined above.

[0193] The use of the polymer composition of the invention

[0194] The present invention also relates to a material obtained from the polymer composition obtained by the process of the present invention, in particular of the polymer composition of the invention as aforementioned. Preferably, said polymer composition from which this material is obtained, comprises a high proportion of crosslinked polymer or crosslinked polymers blend, typically displaying an insoluble fraction superior to 10 wt%, preferably superior to 25 wt%, more preferably superior to 40 wt% of the total weight of all the polymers present in the composition. Another object of the invention is a preparation process of such a material according to the invention, comprising the following steps:

[0195] - preparing a polymer composition according to the process as described above, and

[0196] - shaping the polymer composition obtained therefrom.

[0197] The shaping also includes the compounding of the polymer composition in the form of granules or powder, for example in the preparation of finished products. The shaping may also be carried out by processes known to the person skilled in the art for the shaping of thermoplastic or thermosetting polymers. Notably, the processes of molding, compression, injection, extrusion and thermoforming may be mentioned. Before having the form of the finished object, the material will usually be in the form of granules or powder.

[0198] Advantageously, in this process for preparing a material according to the invention, the preparation and shaping steps may be concomitant.

[0199] The present invention also relates to a formulation comprising a polymer composition obtained bythe process of the present invention, in particularof the polymer composition of the invention as aforementioned.

[0200] The present invention also relates to the use of the non-crosslinked polymer or polymers blend of the invention as a compatibilizing agent.

[0201] A compatibilizing agent typically reduces the tension surface between incompatible domains, notably between incompatible polymers, being in two separated phases. This typically leads to an increase of the interfacial area between the incompatible polymers. The compatibilizing agent operates through the formation of chemical links (such as N-N bonds) and / or physical links between the two polymer phases, favoring stress transmission across the interface.

[0202] METHODS

[0203] Determination of the solubility of the azide derivative

[0204] The solubility of the azide derivative of formula (I) in the mix of step (a) may be determined by transmission electron microscopy (TEM) carried out at room temperature (18°C-22°C), allowing to observed a visible separation of phases when the azide derivative is added to the mix of step (a), meaning that the azide derivative is insoluble or partially soluble, or a homogeneous phase without separation meaning that the azide derivative is soluble in the mix of step (a).

[0205] Alternatively, the solubility of the azide derivative may be estimated on the basis of a solubility theorical model. This model implies to select a model solvent with a polarity that is similar to the polymer or polymers blend provided in step a). This model solvent is then saturated with the azide derivative of interest. The excess of azide derivative is removed by filtration, and the concentration of the azide derivative is assessed by quantitative FITR spectroscopy at room temperature (18-22°C), and / or UV-Vis spectroscopy, and / or1H NMR spectroscopy.

[0206] Determination of the half-life time of the azide derivative of formula (I)

[0207] The half-life of an azide derivative of formula (I) may be determined by DSC measurements and applying the Borchardt-Daniels analytical method (B-D approach; see Swarin, S. J.; Wims, A. M. In Analytical Calorimetry; Porter, R. S., Johnson, J. F., Eds.; Springer: Boston, MA, 1977; Vol. 4 ; and ASTM International. Standard Test Method for Estimating Kinetic Parameters by Differential Scanning Calorimeter Using the Borchardt and Daniels Method; ASTM E2041-13. West Conshohocken, PA, 2018. DOI: 10.1520 / E2041-13R18). This methodology may be applied to pure azide derivative as well as mix of step (a).

[0208] This approach assumes Arrhenius kinetics and allows for the rate constant (k), the activation energy (Ea) and the pre-exponential factor (A) to be determined, which can then be used to calculate a half-life time for azidotriazine at a certain temperature.

[0209] For a reaction following n-th order Arrhenius kinetics, the B-D approach assumes the general rate equation of the form of eq. 1, where a is the fractional conversion, k(T) is the rate constant as a function of temperature T, and n is the order of the reaction. Upon substituting k(T) with the Arrhenius equation (eq. 2; R is the universal gas constant), rearranging, and applying logarithms, the resulting expression (eq. 3) is of the general form z = a + bx + cy, which can be solved using a multiple linear regression method. The terms —, -, and ln(l— a) can be numerically defined based dt T on the data of the DSC experiment.

[0210] ^ = fc(T)(l - a)n(1) at

[0211] ~Eak(T)=Ae~Rr~ (2) Thus, after DSC measurement, the B-D analysis is performed using the time vs. enthalpy integration of DSC data. The fractional conversion a as a function of time is calculated by dividing the values of the running integral by the total enthalpy of the transition. To avoid erroneous edge effects, it is conventional in the B-D approach to only consider the evolution of conversion d(x between 10 and 90 %. Values for the derivative — may calculated using suitable software. With dt these considerations, it is possible to define — , -, and ln(l— a), dt T

[0212] The average kinetic parameters are then used to calculate the half-life time (ti / 2) at a predetermined temperature (TR), or using eq. 4 :

[0213] , ln 2 / 2 ~ (4)

[0214] AeRTR

[0215] For one azide derivative, the kinetics parameters and thus, the temperature TR and the half-life time values depend on the nature of the mix in which the azide derivative is present, i.e. depend on the polymer or polymers blend provided in step (a).

[0216] Determination of the decomposition temperature of the azide derivative of formula (I)

[0217] The decomposition temperature of an azide derivative of formula (I) in the mix of step (a) may be determined by thermogravimetric analysis (TGA). In practice, on a TGA run mix comprising a polymer or a polymers blend in which an azide derivative of formula (I) is dispersed as defined in step (a) of the process of the invention, the decomposition temperature is retrieved from the intersection of lines that are tangent with the TGA curve before decomposition reaction and at the inflection point of the transition. This measurement may be achieved on pure azide derivative of formula (I).

[0218] An alternative method to determine the decomposition temperature is the onset temperature, for the decomposition exotherm as detected during a high-pressure DSC experiment. In a DSC run, this temperature corresponds to the intersection of the line tangent to the curve at the inflection point with the baseline. This approach can be applied to both azide derivative as such and for azide derivative dispersed in a polymer or polymers blend.

[0219] The present invention is illustrated by, without being limited to, the following examples.

[0220] Nuclear magnetic resonance (NMR) spectroscopy

[0221] 1H NMR spectra were acquired at 24 °C using a Bruker Avance-400 spectrometer and a Bruker Avance-Neo 500 spectrometer at 400 and 500 MHz respectively.13C NMR spectra were recorded at 24 °C using a Bruker Avance-400 spectrometer at 100 MHz.15N NMR spectra were recorded at 24 °C using a Bruker Avance-Neo 500 spectrometer at 50 MHz.1H NMR spectra were referenced to the residual hydrogen signal of deuterated solvents: 6 7.26 for CDCI3 and 2.50 for DMSO-de.13C NMR spectra were referenced to the residual carbon signal of deuterated solvents: 6 77.16 for CDCI3 and 39.50 for DMSO-de.

[0222] Fourier-transform infrared (FTIR) spectroscopy

[0223] FTIR spectra were acquired using a BrukerTensor 37 spectrometer in attenuated total reflectance (ATR) mode.

[0224] Raman spectroscopy

[0225] Fourier-transform Raman spectroscopic analyses were performed using a near infrared excitation at 1064 nm provided by an Nd-YAG laser diode coupled to an RFS 100 / S FT-Raman spectrometer based on a Michelson-type interferometer. It was equipped with a liquid nitrogen- cooled Ge detector. The spectrometer was coupled to a macroscopic Ramanscope III (Bruker Optics. All materials were recorded using the macroscopic interface with a 90° collecting mirror, allowing the objects to be placed on a horizontal surface. Samples were placed on a gold mirror to improve the collected Raman signal intensity. Spectra were recorded between 3500 and 50 cm1with a 4 cm1resolution. To optimize the signal-to-noise, it was necessary to adjust the laser power and number of scans for different types of samples. The spot size was approximately 100 pm in all cases.

[0226] Gas chromatography coupled with mass spectroscopy (GC-MS)

[0227] GC-MS with electron impact (El) analyses were performed in ethyl acetate, diethyl ether or tetra hydrofuran using a Shimadzu GCMS-QP 2010s (70 eV).

[0228] High resolution mass spectroscopy (HRMS)

[0229] HRMS was performed on an ESI-LTQ Orbitrap XL FTMS (Thermo Fischer Scientific). Samples were prepared in acetonitrile. Full scans were performed between 150 and 2000 m / z in positive polarity mode.

[0230] Electron paramagnetic resonance (EPR)

[0231] EPR spectra were acquired using a JEOL FA300 computerized spectrometer working at around 9.3 GHz (X-band) and 100 kHz field modulation and equipped with a microwave source. Depending on the width and the amplitude of the signals, different modulation widths, amplification factors and microwave powers were used:

[0232] Full range spectra: modulation width between 0.1 mT and 1.0 mT, amplification factor between 10 and 1600, microwave power 2.000 mW

[0233] Zoomed in spectra: modulation width between 0.1 mT and 0.2 mT, amplification factor between 100 and 1000, microwave power 0.125 mW Samples were introduced in the solid state into suprasil tubes, g-factors were calibrated using manganese oxide markers. For comparison purposes, the intensity of the signals was normalized by the mass of triazine units Tr in the sample (if applicable - computed from the overall mass introduced in the tube and the Tr weight fraction in the sample), the modulation width, the amplification factor and the square root of the microwave power.

[0234] Differential scanning calorimetry (DSC)

[0235] DSC analyses were performed using a TA Instruments Discovery 250 DSC equipped with an autosampler and a liquid nitrogen cooling system. The samples were loaded into closed, disposable aluminum pans. Temperature programs consisted of a heating ramp from 0 °C to 250 °C at + 10 °C / min, a cooling ramp from 250 °C to 0 °C at - 10 °C / min and a second heating ramp from 0 °C to 250 °C at + 10 °C / min. The measured heat flow was normalized by the mass of the sample. The reported melting temperature (Tm) and enthalpy of melting (AHm) were determined from the second heating ramp, and the latter were corrected by the weight fraction of polymer in the sample. The reported degree of crystallinity (x) was computed by dividing the corrected enthalpy of melting by the specific enthalpy of melting of the corresponding polymer (polyethylene 8.06 kJ / mol, polypropylene 8.75 kJ / mol, Polymer Handbook 1999).

[0236] High-pressure differential scanning calorimetry (DSC)

[0237] High-pressure DSC analyses were performed using a TA Instruments Discovery 250 DSC equipped with a liquid nitrogen cooling system. The samples were loaded into reusable, hermetically sealed, gold-plated pans. Different temperature programs were used depending on the type of analysis:

[0238] Thermal decomposition of azidotriazines in bulk (full range): heating ramp from 0 °C to 320 °C at + 10 °C / min

[0239] Thermal decomposition of azidotriazines in bulk (for computation): heating ramp from 30 °C to 120 °C at + 10 °C / min, cooling ramp from 120 °C to 0 °C at - 10 °C, isothermal 10 min, heating ramp from 0 °C to 320 °C at + 10 °C / min

[0240] Thermal decomposition of azidotriazines in polymer matrices (full range): heating ramp from O °C to 320 °C at + 10 °C / min, cooling ramp from 320 °C to 0 °C at - 10 °C, heating ramp from 0 °C to 320 °C at + 10 °C / min

[0241] Thermal decomposition of azidotriazines in polymer matrices (for computation): heating ramp from 0 °C to 320 °C at + 10 °C / min

[0242] The measured heat flow was normalized by the mass of the sample. The enthalpy of melting and decomposition were corrected by the weight fraction of azidotriazines in the sample (if applicable). Reported values of temperature and enthalpy are the average of three measurements.

[0243] Thermogravimetric analysis (TGA)

[0244] TGA was performed using a Netzsch TG 209 Fl Libra under a nitrogen atmosphere. The temperature program consisted of heating from 30 to 600 °C at 10°C / min. The sample was loaded into a disposable aluminum pan.

[0245] Size exclusion chromatography (SEC)

[0246] SEC was performed on a Viscotek GPCmax / VE2001 connected to a Triple detection array (TDA 305) from Malvern. Samples were prepared and analyzed in tetrahydrofuran.

[0247] High-temperature SEC of polypropylene samples was performed in 1,2-dichlorobenzene using a Freeslate Rapid-GPC setup equipped with a PolymerChar IR4 infrared detector. Molecular weight distribution parameters were determined based on a universal polystyrene calibration. Reported values of Mn, Mw, and PDI are averages of two measurements.

[0248] Reactive extrusion

[0249] In examples, modification of high molecular weight polymers by Tr-Ns was performed using a DSM Xplore batch twin-screw extruder with a 5 cc or 15 cc barrel capacity. The system is equipped with a corotating conical screw profile and a recirculation channel that allows control over the residence time. Unless stated otherwise, modification was performed with a screw speed of 100 rpm under a flow of nitrogen.

[0250] Compression-molding

[0251] In examples, after reactive extrusion, high molecular weight polymer samples were reshaped by compression molding at 180 °C for 20 min under a normal force of 3 tons equivalent.

[0252] Isolation of the soluble and gel fraction of crosslinked polymer samples

[0253] Unless stated otherwise, in examples, isolation of the gel fraction was performed on high molecular weight polymer samples after compression-molding. Polyolefin-based samples (PE, PP and blends) were introduced in a glass vial at a concentration of around 15 mg / mL in xylene. The medium was heated at 130 °C for 15 h. The gel fraction (single solid-like piece) was then manually separated from the soluble fraction, and dried under reduced pressure at 90 °C overnight. The remaining soluble fraction was concentrated and dried under reduced pressure at 90 °C overnight. The gel fraction was calculated by dividing the mass of the dried insoluble fraction by the initial mass of the sample. Reported values of gel fraction are the average of three independent measurements.

[0254] Dynamic mechanical analysis (DMA) DMA was performed on a TA Instruments Q800 analyzer in tension mode with a heating rate of 3 °C / min from 30 to 250 °C, a strain amplitude of 1 %, and a fixed frequency of 1 Hz. Samples were shaped into rectangular bars (30 mm x 5 mm x 1.5 mm) by compression molding.

[0255] Tensile testing

[0256] Tensile stress-strain experiments were performed on an Instron Universal testing system at a rate of 10 mm / min and at room temperature. At least five specimens of each sample were tested for reproducibility. Young's modulus was calculated in the linear domain for each sample. Dogbone-shaped samples (ISO 527-2 type 5B) were prepared by compression molding. Reported values are the average of the different measurements.

[0257] Rheology measurements

[0258] Rheological measurements were performed using an Anton Paar MCR501 rotational rheometer equipped with a 25 mm parallel plate geometry. The upper geometry and lower geometries were a stainless steel plate and a disposal aluminum plate, respectively. The geometry was enclosed in a convection oven under a 200 L / h nitrogen flow. The temperature control accuracy of the oven was ± 0.5 °C.

[0259] Amplitude sweep: imposed angular frequency 1 rad / s, temperature 180 °C, shear strain range 10’2to 103%

[0260] Frequency sweep: imposed shear strain 1 %, temperature 180 °C, angular frequency range 10-2to 102rad / s

[0261] Creep: imposed continuous shear stress 1 kPa (or 5 kPa) for 30 min (or 3 h) followed by recovery at zero shear stress for 30 min (or 3 h), temperature 180 °C

[0262] For all measurements, a normal force of 10 N for crosslinked samples or 0.1 N for non-crosslinked samples was imposed.

[0263] Rheology samples were prepared by compression molding (disc shape, diameter 25 mm, thickness 1.5 mm).

[0264] Transmission electron microscopy (TEM)

[0265] The compression-molded samples were cut into ultrathin sections (60-70 nm) using a ultracryomicrotome Leica Ultracut UCT equipped with an EM FCS cryogenic block and a 35° diamond knife at a temperature of - 30 °C. The sections were then stained for 30 to 45 seconds with RUO4vapors stemming from a freshly prepared RuO4aqueous solution (20 mg of ruthenium chloride dissolved in 1 mL of 13 % aqueous sodium hypochlorite). Samples were imaged using a JEOL 1011 transmission electron microscope (3 A resolution) equipped with a tungsten thermoionic cannon (100 kV) and a Gatan Orius 4k camera. Masterbatch preparation

[0266] In the examples illustrating the present invention as described hereafter, the azidotriazine 1 is provided for the grafting reaction as a masterbatch of 40wt% of azidotriazine in mixture with a part of the polymer or polymer blends used in the example, prepared by solvent mixing, in order to facilitate the dissolution of the azidotriazine in the lab equipment, to save a maximum of the content of the azidotriazine and to ensure the safest conditions.

[0267] Density functional theory calculations

[0268] Calculations were performed with the ORCA 5.0.4 program package (Neese, F. "The ORCA program system" Wiley Interdisciplinary Reviews: Computational Molecular Science, 2012, Vol. 2, Issue 1, Pages 73-78). Geometry optimization, harmonic vibrational frequencies, infrared intensities, and Raman activities were analytically calculated using the B97-3c generalized gradient approximation (GGA) functional and the polarized valence-triple- basis set mTZP (Brandenburg, J. G.; Bannwarth, C.; Hansen, A.; Grimme, S. B97-3c: A revised low-cost variant of the B97-D density functional method. J. Chem. Phys. 2018, 148, No. 064104). Raman spectra were plotted without any frequency scaling.

[0269] DESCRIPTION OF THE FIGURES

[0270] Figure 1: Examples of a nitrogen-nitrogen exchange reaction, a nitrogen-nitrogen / aminyl radical exchange, and an aminyl radicals' recombination.

[0271] Figure 2: High pressure DSC (exo down) and TGA monitoring (under Nj) of the decomposition of various azidotriazines.

[0272] Figure 3: Size exclusion chromatography (SEC) analysis of the bulk decomposed 6-azido- / V2, / V4- dimethyl- / V2, / \ / 4-diphenyl-l,3,5-triazine-2,4-diamine (black curve; structure depicted in Scheme 1 as 1, also referred to as azotriazine 1) and an authentic standard of the corresponding aminotriazine (grey curve; structure depicted in Scheme 16 as 1').

[0273] Figure 4: Matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI- TOF-MS) analysis of the product of the bulk decomposition of azidotriazine 1.

[0274] Figure 5: Decomposition of azidotriazine 1 in HDPE (5 mol%) followed by TGA (grey curve). The observed mass loss of 5.1% is to be compared to the theoretical mass loss of 3.1% from nitrogen gas evolution during azidotriazine 1 decomposition. The DSC of this sample is also provided (black curve).

[0275] Figure 6: Decomposition of azidotriazine 1 followed by TGA. Figure 7: Monitoring of the decomposition of azidotriazine 1 in HDPE by DSC at a loading of 5 mol% (37 wt%). An 8.1 mg sample was heated in a high-pressure DSC cell at 10 °C / min from 50 to 320 °C. The green curve represents the running integral of the decomposition exotherm.

[0276] Figure 8: A) Normalized Raman spectra (1064 nm laser light source) of grafted paraffin wax (5 mol%), unmodified paraffin wax, a model dimer structure, and the calculated Raman spectrum for the model dimer using density functional theory (DFT). B) Chemical structure of the model dimer. C) Assignments of diagnostic bands based on DFT calculations

[0277] Figure 9: Electron paramagnetic resonance (EPR) spectrum of paraffin wax that had been grafted with 5 mol% of azidotriazine 1. At left, spectra were acquired on the solid state at ambient temperature (black) or in chloroform at 77 K (grey). At right, the same sample had been precipitated twice in acetone before performing the analysis by EPR spectroscopy at ambient temperature in the solid state.

[0278] Figure 10:1H-1H Correlated spectroscopy (COSY) conducted on the product of grafting paraffin wax with azidotriazine 1. The two highlighted signals correspond to the correlations between the methine proton f of the paraffin with the adjacent methylene protons 6' on the paraffin wax backbone (1) and with the N-H proton e on the triazine graft (2).

[0279] Figure 11: A) Heating program used to prepare modified polymers with one matrix. B) Torque profile for the reactive extrusion of HDPE with 1 mol% of azidotriazine 1 to give HDPEm

[0280] Figure 12: A) Heating program used to prepare modified polymers with a blend of two matrices. B) Torque profile for the reactive extrusion of HDPPE and PP (70:30 weight ratio) with 1 mol% of azidotriazine 1 to give (HDPE-PP)m.

[0281] Figure 13: Raman spectrum (1064 nm laser light source) of virgin HDPE (black) and HDPEm(grey). Figure 14: Comparison of DMA curves for virgin HDPE and HDPEm(up) and PE that has been modified with either 0.05, 0.1, 0.5, or 1.0 mol% of azidotriazine 1 (down).

[0282] Figure 15: Creep and recovery experiments of virgin HDPE (up) and HDPEmmodified with 1 mol% of azidotriazine 1 (down) performed at 180 °C.

[0283] Figure 16 : Comparison of DMA curve of virgin HDPE-PP blend (70:30 weight ratio) to that of (HDPE-PP)"1.

[0284] Figure 17: Creep and recovery experiments of a blend of virgin HDPE and virgin PP (up) and the blend of HDPE and PP that was modified with 1 mol% of azidotriazine 1 (down) performed at 180 °C.

[0285] Figure 18: Representative stress-strain curves of virgin PE; virgin PP; the virgin PE-PP blend (70:30); HDPEmwith 1 mol% of azidotriazine 1; (HDPE-PP)m(70:30) that had been modified with either 0.1 or 1 mol% of azidotriazine 1; and a blend of HDPEmand PPm, each having been individually grafted with 1 mol% of azidotriazine 1 prior to being blended.

[0286] Figure 19: Strain sweep experiments performed at 180 °C for HDPEm(up) and (HDPE-PP)m(down). Both samples were modified with 1 mol% of azidotriazine 1.

[0287] Figure 20: Schematic of protocol used for performing recycling experiments for HDPEm(left) and (HDPE-PP)"1(right).

[0288] Figure 21: DMA of HDPEm(up) and (HDPE-PP)m(down) after each cycle of recycling.

[0289] Figure 22: Overview of the tensile properties for HDPEmover the course of 4 reprocessing cycles.

[0290] Figure 23: Overview of the tensile properties for (HDPE-PP)mover the course of 4 reprocessing cycles.

[0291] Figure 24: Creep experiments on HDPEm(left) and (HDPE-PP)m(right) that was modified with 1 mol% of azidotriazine 1 after 4 cycles of reprocessing.

[0292] Figure 25: EPR spectra for PE modified with 1 mol% of azidotriazine 1 either directly after extrusion (samples labelled with X) or after processing by compression molding (samples labelled with CS).

[0293] Figure 26: TEM micrographs of A) virgin PE, B) blend of HDPE and 1 mol% of azidotriazine 1, C) HDPE"1, D) virgin HDPE-PP blend, and E) (HDPE-PP)"1.

[0294] Figure 27: EPR spectra of oligomeric PS that had been grafted with azidotriazine 1 and ^relabelled azidotriazine 1.

[0295] Figure 28: DMA of the modified full mixture (HDPE-LDPE-PP-PETg-PS)mand the corresponding control blend of virgin polymers.

[0296] Figure 29: Stress-strain curves (acquired at ambient temperature) of the modified full mixture (HDPE-LDPE-PP-PETg-PS)m(up) and the corresponding control blend of virgin polymers (down).

[0297] Figure 30: Torque profile for the reactive extrusion of HDPE with 1 mol% of AT-Ph (left) and AT- NBU2 (right), to give HDPEAT'phand HDPEAT'NBu, respectively.

[0298] Figure 31: DMA curves of the modified HDPE depending on the azidotriazine used for reactive extrusion.

[0299] Figure 32: Left: DMA curves of HDPEAT'phand of the materials recycled by extrusion and compression molding or by compression molding only. Right: Engineering stress-strain curves (20 °C, 10 mm / min) of HDPEAT'phand of the material recycled by extrusion and compression molding or by compression molding only. The displayed curves are the closest to the average.

[0300] Figure 33: DMA curves of HDPEm, Sample 1 and Sample 2 of example 8. Figure 34: A) Torque profile for the reactive extrusion of HDPE with 1 mol% of azidodiazine AD-

[0301] Ph to give HDPEAD-ph. B) DMA of curve for HDPEAD Ph.

[0302] EXAMPLES

[0303] Materials

[0304] All chemicals and reagents were purchased from Merck (Sigma-Aldrich).15N labelled reagents were purchased from Eurisotop. All solvents were purchased from Carlo Erba.

[0305] Unless stated otherwise, all reagents and solvent were used without further purification.

[0306] High density polyethylene (PE, Hostalen 4131B, melt flow index MFI 2.2 g / 10 min at 190 °C with 5 kg weight, density 0.94 g / cm3) and isotactic polypropylene (PP, Moplen HF 501N, melt flow index MFI 10 g / 10 min at 230 °C with 2.16 kg weight, density 0.90 g / cm3) were purchased from Albis Plastique France.

[0307] Post-consumer polyethylene and polypropylene samples originated from household laundry detergent bottles.

[0308] Example 1. Synthesis of azido-substituted heteroaromatic derivative according to the invention

[0309] 1.1 Synthesis and characterization of di(N-methylaniline)azidotriazine 1 (6-azido- / V2, / \ / 4- dimethyl- / \ / 2, / \ / 4-diphenyl-l,3,5-triazine-2,4-diamine) or "azidotriazine 1"

[0310] The synthesis of the azido-l,3,5-triazine (1) is described in scheme 1. The synthesis consists of two steps, which were both performed safely on a multi-gram scale.

[0311] Scheme 1: Synthesis of the azidotriazine 1

[0312] Synthesis of di(N-methylaniline)chloro-triazine

[0313] Cyanuric chloride (9.900 g, 53.68 mmol, 1.00 eq) was dissolved in 100 mL of THF (distillated over CaH2) and cooled down to 0°C. DIPEA (6.938 g, 53.68 mmol, 1.00 eq) and then N-methylaniline (5.752 g, 53.68 mmol, 1.00 eq) were added dropwise and the mixture was stirred at 0°C for 1.5h. DIPEA (6.938 g, 53.68 mmol, 1.00 eq) and then N-methylaniline (6.040 g, 56.36 mmol, 1.05 eq) were added dropwise and the mixture was stirred at 0°C for 15 min, and at 30°C for another 18h. THF was removed under reduced pressure. 100 mL of distilled water were added and the mixture was extracted with 4x100 mL of ethyl acetate. The organic phase was washed with 5x100 mL of 0.05M aqueous HCI, 1x100 mL of saturated aqueous NaHCO3 and 1x100 mL of brine, dried over MgSO4 and concentrated under reduced pressure. Di(N-methylaniline)chloro-triazine was obtained as a yellowish solid (16.613 g, 50.99 mmol, 95% yield, purity: 98.5wt% - 94.3mol%, impurity: ethyl acetate).

[0314] 1H NMR (DMSO-d6 400 MHz) 6ppm: 7.7-7.0 (br m, 10H), 3.39 (br s, 6H)

[0315] 13C-{1H} NMR (DMSO-d6 100 MHz) 6ppm: 168.35, 164.42, 143.20, 128.71, 126.41, 126.23, 37.79 GC / MS (El): retention time 9.02 s m / z 325 (+ chlorine isotopes) molecular peak (expected: 325.11)

[0316] Synthesis of di(N-methylaniline)azido-triazine (1)

[0317] Di(N-methylaniline)chloro-triazine (16.613 g, 50.99 mmol, 1.00 eq) was dissolved in 30 mL of anhydrous / V-methylpyrrolidine (NMP). Sodium azide (6.630 g, 101.98 mmol, 2.00 eq) was added slowly and the mixture was stirred at 100°C for 66h. 400 mL of distilled water were added and the mixture was extracted with 3x200 mL of diethyl ether. The organic phase was washed with 5x200 mL of brine, dried over MgSO4 and concentrated under reduced pressure into 3 aliquots. The obtained product was dissolved in 150 mL of a 50:50vol mixture of hexane and ethyl acetate, and passed through a double pad of silica and basic alumina. After concentration and drying under reduced pressure, di(N-methylaniline)azido-triazine (1) was obtained as an off-white solid (12.206 g, 36.72 mmol, 72%yie!d, purity: 99.5wt% - 98.2mol%, impurities: ethyl acetate, hexane).1H NMR (DMSO-d6 400 MHz) 6ppm: 7.7-7.0 (br m, 10H), 3.37 (br s, 6H)

[0318] 13C-{1H} NMR (DMSO-d6 100 MHz) 6ppm: 167.97, 165.05, 143.47, 128.45, 126.35, 125.82, 37.39 FTIR (ATR): 2125 cm-l(N3)

[0319] TLC (silica, ethyl acetate / hexane 50:50vol): Rf = 0.5 1.2 Synthesis and characterization of 6-azido-N2,N2,N4,N4-tetrabutyl-l,3,5-triazine-2,4-diamine or "azidotriazine AT-NBU2"

[0320] Synthesis of N2,N2,N4,N4-tetrabutyl-6-chloro-l,3,5-triazine-2,4-diamine (intermediate A)

[0321] Scheme 2 : synthesis of N2,N2,N4,N4-tetrabutyl-6-chloro-l,3,5-triazine-2,4-diamine (intermediate A)

[0322] Cyanuric chloride (10.0 g, 53.7 mmol) was dissolved in a round bottom flask in 100 mL of THF and cooled down in ice bath. DIPEA (7.02 g, 53.7 mmol, 1.00 eq) and di-n-butylamine (6.98 g, 53.7 mmol, 1.00 eq) were added dropwise and the mixture was stirred for 30 min. Additional DIPEA (7.02 g, 53.7 mmol, 1.00 eq) and di-n-butylamine (6.98 g, 53.7 mmol, 1.00 eq) were then added dropwise and the medium was heated up to 30 °C and left under stirring for 18 h. THF was removed under reduced pressure. 200 mL of distilled water were added and the mixture was extracted with 3 x 100 mL of ethyl acetate. The organic phase was washed with 5 x 100 mL of 0.05M aqueous HCI, 2 x 100 mL of saturated aqueous NaHCCh and 1 x 100 mL of brine, dried over MgSC and dried under reduced pressure. The product was obtained as a yellowish viscous liquid (18.6 g, 50.2 mmol, 94 % isolated yield).

[0323] 1H NMR (CDC , 400 MHz) 6 ppm: 3.49-3.43 (m, 8H), 1.55 (m, 8H), 1.31 (m, 8H), 0.93 (t, 12H).13C NMR (CDCh, 400 MHz) 6 ppm: 168.9, 164.5, 47.4, 30.5, 20.2, 14.0.

[0324] Synthesis of 6-azido-N2,N2,N4,N4-tetrabutyl-l,3,5-triazine-2,4-diamine (AT-NBU2)

[0325] Scheme 3: synthesis of 6-azido-N2,N2,N4,N4-tetrabutyl-l,3,5-triazine-2,4-diamine (AT-NBU2)

[0326] Intermediate A (15.0 g, 40.2 mmol) was dissolved in a round bottom flask in 30 mL of N- methylpyrrolidine. Sodium azide (5.25 g, 80.4 mmol, 2.00 eq) was added slowly and the mixture was stirred for 66 h at 100 °C. The reaction was cooled down at room temperature and poured into 300 mL of distilled water. The mixture was extracted with 3 x 200 mL of Et20. The organic phase was washed with 5 x 200 mL of brine, dried over MgSC and dried under reduced pressure. After further drying under reduced pressure at 50 °C overnight, AT-NBU2 was obtained as yellowish viscous liquid (14.5 g, 3.86 mmol, 96% isolated yield).

[0327] 1H NMR (CDC , 400 MHz) 6 ppm: 3.48-3.46 (m, 8H), 1.55 (m, 8H), 1.31 (m, 8H), 0.93 (t, 12H).

[0328] 13C NMR (CDCh, 400 MHz) 6 ppm: 168.1, 165.1, 47.4, 30.5, 20.2, 14.0.

[0329] 1.3. is of 2-azido-4,6-di -1,3,5-triazine or "azidotriazine AT-Ph"

[0330] Scheme 4: synthesis of 2-azido-4,6-diphenyl-l,3,5-triazine AT-Ph 2-chloro-4,6-diphenyl-l,3,5-triazine (10.0 g, 36.6 mmol) was dissolved in a round bottom flask in 30 mL of N-methylpyrrolidine. Sodium azide (0.24 g, 36.7 mmol, 1.1 eq) was added slowly and the mixture was stirred for 2 h at room temperature. The mixture was then poured into 300 mL of distilled water. The mixture was extracted with 3 x 400 mL of Et20. The organic phase was washed with 5 x 300 mL of brine, dried over MgSC and dried under reduced pressure. After further drying under reduced pressure at 50 °C overnight, AT-Ph was obtained as a white solid (14.5 g, 3.86 mmol, 96% isolated yield).

[0331] 1H NMR (CDCI3, 400 MHz) 5 ppm: 7.53 (t, 4H), 7.61 (tt, 2H), 1.31 (d, 4H).

[0332] 13C NMR (CDCh, 400 MHz) 5 ppm: 128.7, 129.2, 133.2, 135.0, 170.4, 173.1.

[0333] 1.4. Synthesis of 2-azido-4,6-diphenyl-l,3-diazine or "azidodiazine AD-Ph"

[0334] Scheme 5: synthesis of 2-azido-4,6-diphenyl-l,3-diazine or azidodiazine AD-Ph

[0335] 2-chloro-4,6-diphenyl-l,3-diazine (0.5 g, 1.84 mmol) was dissolved in a round bottom flask in 30 mL of NMP. Sodium azide (0.24 g, 3.67 mmol, 2 eq) were added slowly and the mixture was stirred for 16 h at 80 °C. The mixture was then poured into 30 mL of distilled water. The mixture was extracted with 3 x 40 mL of Et20. The organic phase was washed with 5 x 30 mL of brine, dried over MgSC and dried under reduced pressure. After further drying under reduced pressure at 80 °C overnight, a white solid (0.271 g, 0.993 mmol, 54% isolated yield).

[0336] 1H NMR (DMSO-d6, 400 MHz) 5 ppm: 8.46 (dd, 2H, tetrazolo), 8.37 (s, 2.5H, azido), 8.35 (s, 1H, tetrazolo), 8.32 (m, 12.4H, azido / tetrazolo), 7.76-7.5 (m, 22.9H, azido / tetrazolo).

[0337] 13C NMR (DMSO-d6, 400 MHz) 5 ppm: 166.6 (azido), 164.8 (tetrazolo), 162.1 (azido), 156.3 (tetrazolo), 146.5 (tetrazolo), 136.0 (azido), 132.8 (tetrazolo), 132.1 (azido), 129.6 (tetrazolo), 129.4 (azido), 129.3 (tetrazolo), 128.9 (tetrazolo), 127.9 (azido), 109.1 (azido, tetrazolo).

[0338] 1.5 Synthesis of other triazines

[0339] 1.5.1 Synthesis of precursors a) Mono-substituted triazine Tr-Cl2

[0340] Scheme 6: Synthesis of Tr-CL 4,6-dichloro-N-methyl-N-phenyl-l,3,5-triazin-2-amine Tr-Ch Cyanuric chloride (9.900 g, 53.68 mmol, 1.00 eq) was dissolved in 100 mL of THF and cooled down to 0 °C. DIPEA (6.938 g, 53.68 mmol, 1.00 eq) and then N-methylaniline (5.752 g, 53.68 mmol, 1.00 eq) were added dropwise at 0 °C and the mixture was stirred for 3h at 0 °C. THF was removed under reduced pressure, 80 mL of distilled water were added and the aqueous phase was extracted with 3x50 mL of ethyl acetate. The organic phase was washed with 1x50 mL of 0.05 M aqueous HCI, 1x50 mL of aqueous saturated NaHCO3 and 1x50 mL of brine, dried over MgSC and concentrated under reduced pressure. Compound Tr-Ch was obtained as a yellowish solid (13.150 g, 51.55 mmol, 96% yield).

[0341] 1H NMR (CDCI3400 MHz) 5 ppm: 7.46 (tt, J = 8.0 Hz, J = 1.7 Hz, 2H), 7.36 (m, 1H), 7.25 (tt, J = 7.4 Hz, J = 1.8 Hz, 2H), 3.56 (s, 3H)

[0342] 13C-{1H} NMR (CDCI3 100 MHz) 5 ppm: 170.52, 170.10, 165.27, 142.18, 129.67, 127.94, 126.20, 39.33

[0343] GC-MS (El): retention time 6.539 s m / z 253 (+ chlorine isotopes) molecular peak (expected: 254.01) b) Tr(aniline)-CI

[0344] Scheme 7 : Synthesis of Tr(aniline)-CI

[0345] 6-chloro-N2-methyl-N2,N4-diphenyl-l,3,5-triazine-2,4-diamine Tr(aniline)-CI

[0346] Compound Tr-Cfe (2.991 g, 11.72 mmol, 1.00 eq) was dissolved in 50 mL of THF and cooled down to 0 °C. DIPEA (1.515 g, 11.72 mmol, 1.00 eq) and then aniline (1.638 g, 17.59 mmol, 1.50 eq) were added dropwise at 0 °C. The mixture was stirred for 15 min at 0 °C, and for 20h at 30 °C. THF was removed under reduced pressure, 50 mL of distilled water were added and the aqueous phase was extracted with 3x50 mL of ethyl acetate. The organic phase was washed with 1x50 mL of 0.05 M aqueous HCI, 1x50 mL of aqueous saturated NaHCCh and 1x50 mL of brine, dried over MgSC and concentrated under reduced pressure. Compound Tr(aniline)-CI was obtained as a white solid (3.306 g, 10.60 mmol, 90% yield).

[0347] XH NMR (THF-ds 400 MHz) 6 ppm: (a mixture of rotamers was observed) 9.13 (br s, a x 1H), 8.98 (br s, (1-a) x 1H), 7.8-6.7 (br m, 10H), 3.50 (br s, 3H)

[0348] 13C-{1H} NMR (THF-ds 100 MHz) 6 ppm: (a mixture of rotamers was observed) 169.89, 166.62, 164.20, 144.95, 139.94, 129.62, 128.93, 127.66, 127.15, 123.20, 121.07, 120.11, 38.39, 38.01 GC-MS (El): retention time 9.508 s m / z 310 (+ chlorine isotopes) molecular peak (expected: 311.09)

[0349] TLC (silica, hexane / AcOEt 95:5 vol): Rf 0.1 c) Tr(isopropylamine)-CI

[0350] Scheme 8 : Synthesis of Tr(isopropylamine)-CI

[0351] 6-chloro-N2-isopropyl-N4-methyl-N4-phenyl-l,3,5-triazine-2,4-diamine Tr(isopropylamine)-CI

[0352] Compound Tr-Ch (1.496 g, 5.86 mmol, 1.00 eq) was dissolved in 25 mL of THF and cooled down to 0 °C. DIPEA (0.758 g, 5.86 mmol, 1.00 eq) and then isopropyl amine (0.520 g, 8.79 mmol, 1.50 eq) were added dropwise at 0 °C. The mixture was stirred for 15 min at 0 °C, and for 21h at 30 °C. THF was removed under reduced pressure, 30 mL of distilled water were added and the aqueous phase was extracted with 3x30 mL of ethyl acetate. The organic phase was washed with 2x30 mL of 0.05 M aqueous HCI, 1x30 mL of aqueous saturated NaHCCh and 1x30 mL of brine, dried over MgSC and concentrated under reduced pressure. Compound Tr(isopropylamine)-CI was obtained as a white solid (1.081 g, 3.89 mmol, 66% yield).

[0353] XH NMR (DMSO-de 400 MHz) 6 ppm: (a 70:30 mixture of rotamers was observed) 7.89 (br s, 0.7 x 1H), 7.72 (br s, 0.3 x 1H), 7.5-7.1 (br m, 5H), 4.03 (sept, J = 6.61 Hz, 0.7 x 1H), 3.85 (app br s, 0.3 x 1H), 3.40 (s, 0.7 x 3H), 3.35 (s, 0.3 x 3H), 1.09 (br s, 0.3 x 6H), 1.07 (br s, 0.7 x 6H)

[0354] 13C-{1H} NMR (DMSO-de 100 MHz) 6 ppm: (a mixture of rotamers was observed) 168.55, 167.92, 164.84, 164.67, 164.34, 164.08, 143.77, 143.54, 128.99, 128.70, 126.89, 126.63, 126.34, 126.23, 42.15, 41.92, 38.14, 37.82, 22.19, 21.81

[0355] GC-MS (El): retention time 7.497 s m / z 276 (+ chlorine isotopes) molecular peak (expected: 277.11)

[0356] TLC (silica, hexane / AcOEt 95:5 vol): Rf 0.1 d) Tr(phenol)-CI

[0357] Scheme 9 : Synthesis of Tr(phenol)-CI

[0358] 4-chloro-N-methyl-6-phenoxy-N-phenyl-l,3,5-triazin-2-amine Tr(phenol)-CI

[0359] Compound Tr-Cfe (2.000 g, 7.82 mmol, 1.00 eq) was dissolved in 20 mL of THF and cooled down to 0 °C. Phenol (1.478 g, 15.63 mmol, 2.00 eq) and then crushed NaOH (0.516 g, 7.82 mmol, 1.00 eq) were added slowly at 0 °C. The suspension was stirred for 30 min at 0 °C, and for 18h at 30 °C. THF was removed under reduced pressure. 40 mL of water were added and the mixture was extracted with 3x30 mL of ethyl acetate. The organic phase was washed with 3x40 mL of 1 M aqueous NaOH, 2x30 mL of brine, dried over MgSO4 and concentrated under reduced pressure. Compound Tr(phenol)-CI was obtained as a white solid (1.721 g, 5.50 mmol, 70% yield).1H NMR (DMSO-de 400 MHz) 5 ppm: 7.6-7.0 (br m, 10H), 3.45 (br s, 3H)

[0360] 13C-{1H} NMR (DMSO-de 100 MHz) 5 ppm: 170.18, 165.88, 161.59, 151.46, 142.50, 129.48, 129.20, 128.86, 126.42, 125.81, 121.52, 38.40 GC-MS (El): retention time 8.618 s m / z 311 (+ chlorine isotopes) molecular peak (expected: 312.08)

[0361] TLC (silica, hexane / AcOEt 90:10 vol): Rf 0.2 e) Tr(isopropylalcohol)-CI

[0362] Scheme 10 : Synthesis of Tr(isopropylalcohol)-CI

[0363] 4-chloro-6-isopropoxy-N-methyl-N-phenyl-l,3,5-triazin-2-amine Tr(isopropylalcohol)-CI

[0364] Sodium hydride (0.616 g, 15.41 mmol, 2.10 eq) was suspended into 60 mL of dry THF and stirred at room temperature for 20 min under nitrogen. The supernatant was removed and neutralized in a mixture of heptane and isopropanol. The degreasing steps were repeated three times overall. 50 mL of dry THF were added and the suspension was cooled down to 0 °C. Isopropanol (distil lated over CaH2, 0.466 g, 7.76 mmol, 1.05 eq) was dissolved in 5 mL of dry THF and added dropwise to the reaction vessel at 0 °C. The medium was stirred for 1.5h from 0 °C to room temperature until it stopped bubbling. Thereafter, the medium was cooled down to -15 °C. Compound Tr-Ch (1.890 g, 7.39 mmol, 1.00 eq) was dissolved in 30 mL of dry THF and cooled down to -15 °C. The alcoholate solution was transferred dropwise with a cannula into the triazine vessel (another 30 mL of dry THF were used to transfer the alcoholate quantitatively). The mixture was stirred for 45 min at -15 °C and the reaction was quenched by transferring the reaction medium dropwise into 200 mL of a 0.1 M aqueous NH4CI at 0 °C. The aqueous phase was extracted with 3x70 mL of dichloromethane. The organic phase was washed with 2x50 mL of aqueous saturated NaHCOs and 1x50 mL of brine. Drying over MgSO4 and concentration under reduced pressure yielded compound Tr(isopropylalcohol)-CI as a yellow, viscous oil (1.466 g, 5.26 mmol, 71% yield).

[0365] 1H NMR (DMSO-de 400 MHz) 5 ppm: 7.44 (br t, J = 7.5 Hz, 2H), 7.35 (br d, J = 7.4 Hz, 2H), 7.31 (br t, J = 7.3 Hz, 1H), 5.4-4.7 (app br m, 1H), 3.44 (s, 3H), 1.5-1.0 (br m, 6H)

[0366] 13C-{1H} NMR (DMSO-de 100 MHz) 5 ppm: 165.84, 142.85, 129.05, 128.73, 126.97, 126.68, 126.54, 126.23, 71.28, 38.35, 21.56, 21.32 GC-MS (El): retention time 7.017 s m / z 278 (+ chlorine isotopes) molecular peak (expected: 278.09)

[0367] TLC (silica, hexane / AcOEt 95:5 vol): Rf 0.2 f) Tr(isopropylthiol)-CI

[0368] Scheme 11 : Synthesis of Tr(isopropylthiol)-CI

[0369] 4-chloro-6-(isopropylthio)-N-methyl-N-phenyl-l,3,5-triazin-2-amine Tr(isopropylthiol)-CI

[0370] Compound Tr-Cfe (2.000 g, 7.82 mmol, 1.00 eq) was dissolved in 20 mL of THF and cooled down to 0 °C. Isopropylthiol (0.921 g, 11.72 mmol, 1.50 eq) and then crushed NaOH (0.516 g, 7.82 mmol, 1.00 eq) were added slowly at 0 °C. The suspension was stirred for 30 min at 0 °C, and for 18h at 30 °C. THF was removed under reduced pressure. 40 mL of water were added and the mixture was extracted with 3x30 mL of ethyl acetate. The organic phase was washed with 2x30 mL of 1 M aqueous NaOH, 1x30 mL of brine, dried over MgSO4 and concentrated under reduced pressure. Compound Tr(isopropylthiol)-CI was obtained as a yellowish solid (1.982 g, 6.72 mmol, 86% yield).

[0371] 1H NMR (DMSO-de 400 MHz) 5 ppm: 7.44 (m, 2H), 7.38 (m, 2H), 7.32 (tt, J = 7.3 Hz, J = 1.3 Hz, 1H), 3.9-3.3 (br m, 1H), 3.45 (s, 3H), 1.4-0.9 (br m, 6H)

[0372] 13C-CH} NMR (DMSO-de 100 MHz) 5 ppm: 180.74, 167.66, 163.18, 142.60, 129.03, 127.10, 126.71, 126.51, 37.99, 35.52, 22.51

[0373] GC-MS (El): retention time 7.798 s m / z 294 (+ chlorine isotopes) molecular peak (expected: 294.07)

[0374] TLC (silica, hexane / AcOEt 90:10 vol): Rf 0.4 g) Tr(phenyl)-CI

[0375] Scheme 12 : Synthesis of Tr(phenyl)-CI 4-chloro-N-methyl-N,6-diphenyl-l,3,5-triazin-2-amine Tr(phenyl)-CI

[0376] Compound Tr-Cfe (0.499 g, 1.95 mmol, 1.00 eq) was dissolved in 10 mL of THF (distillated over CaH2) in a schlenk tube and cooled down to 0 °C under nitrogen. Phenylmagnesium bromide (1 M solution in THF, 2.7 mL, 2.7 mmol, 1.4 eq) was added dropwise under stirring at 0 °C. The mixture was stirred for 30 min at 0 °C, and for 45h at 15 °C. The reaction mixture was added slowly into 30 mL of distilled water at 0 °C and THF was removed under reduced pressure. The suspension was extracted with 3x20 mL of ethyl acetate. The organic phase was washed with 1x20 mL of 0.1 M aqueous HCI, 1x20 mL of aqueous saturated NaHCOs, 1x20 mL of brine, dried over MgSC and concentrated under reduced pressure. Compound Tr(phenyl)-N3 was purified by silica column chromatography (hexane / AcOEt 99:1 to 90:10) and obtained as a yellowish solid (0.204 g, 0.69 mmol, 35% yield).

[0377] 1H NMR (DMSO-de 400 MHz) 5 ppm: 8.6-7.3 (br m, 10H), 3.56 (br s, 3H)

[0378] 13C-{1H} NMR (DMSO-de 100 MHz) 5 ppm: 171.18, 169.82, 165.04, 142.86, 134.36, 133.03, 129.11, 128.76, 128.41, 127.05, 126.47, 38.43

[0379] GC-MS (El): retention time 8.629 s m / z 295 (+ chlorine isotopes) molecular peak (expected: 296.08)

[0380] TLC (silica, hexane / AcOEt 95:5 vol): Rf 0.2

[0381] 1.5.2 Synthesis of azidotriazines according to the invention i. Tr(aniline)-N3

[0382] 76 %

[0383] Scheme 13 : Synthesis of Tr(aniline)-N3

[0384] 6-azido-N2-methyl-N2,N4-diphenyl-l,3,5-triazine-2,4-diamine Tr(aniline)-N3

[0385] Compound Tr(aniline)-CI (0.984 g, 3.16 mmol, 1.00 eq) was dissolved in 3 mL of DMF. Sodium azide (0.285 g, 4.73 mmol, 1.50 eq) was suspended in 3 mL of DMF and added dropwise to the triazine solution. The mixture was stirred for 24h at 100 °C, and then transferred into 40 mL of distilled water at 0 °C. The aqueous phase was extracted with 3x30 mL of ethyl acetate. The organic phase was washed with 5x30 mL of brine, dried over MgSC and concentrated under reduced pressure. Compound Tr(aniline)-N3 was purified through a silica pad (hexane / AcOEt 90:10) and obtained as a white solid (0.762 g, 2.39 mmol, 76% yield).

[0386] 1H NMR (THF-ds 400 MHz) 6 ppm: (a mixture of rotamers was observed) 8.91 (br s, 1H), 7.9- 6.6 (br m, 10H), 3.47 (br s, 3H)

[0387] 13C-{1H} NMR (THF-ds 100 MHz) 6 ppm: (a mixture of rotamers was observed) 169.62, 167.18, 165.10, 145.20, 140.36, 129.45, 128.85, 127.71, 126.85, 122.83, 120.15, 37.98

[0388] FTIR (ATR) o cm1: 3345, 3309, 3056, 3037, 2944, 2224, 2131, 1615, 1601, 1575, 1556, 1525, 1489, 1441, 1388, 1348, 1298, 1238, 1193, 1114, 1076, 1031, 1019, 971, 899, 829, 799, 767, 746, 689, 629

[0389] TLC (silica, hexane / AcOEt 90:10 vol): Rf 0.2

[0390] HRMS (ESI-MS): 319.1418 [M+H]+(expected: 319.1414) ii. Tr(isopropylamine)-N3 58 %isol

[0391] Scheme 14 : Synthesis of Tr(isopropylamine)-N3

[0392] 6-azido-N2-isopropyl-N4-methyl-N4-phenyl-l,3,5-triazine-2,4-diamine Tr(isopropylamine)-N3 Compound Tr(isopropylamine)-CI (0.799 g, 2.88 mmol, 1.00 eq) was dissolved in 1 mL of DMF. Sodium azide (0.346 g, 5.75 mmol, 2.00 eq) was suspended in 2 mL of DMF and added dropwise to the triazine solution. The mixture was stirred for 47h at 100 °C, and then transferred into 30 mL of distilled water at 0 °C. The aqueous phase was extracted with 3x20 mL of diethyl ether. The organic phase was washed with 5x20 mL of brine, dried over MgSC and concentrated under reduced pressure. Compound Tr(isopropylamine)-N3 was purified by silica column chromatography (hexane / AcOEt 98:2 to 85:15) and obtained as a white solid (0.479 g, 1.68 mmol, 58% yield).

[0393] XH NMR (DMSO-de 400 MHz) 6 ppm: (a 60:40 mixture of rotamers was observed) 7.58 (br d, J = 7.5 Hz, 0.6 x 1H), 7.47 (br d, J = 7.5 Hz, 0.4 x 1H), 7.4-7.1 (m, 5H), 4.04 (sept, J = 6.6 Hz, 0.6 x 1H), 3.89 (app br s, 0.4 x 1H), 3.41 (s, 0.6 x 3H), 3.37 (s, 0.4 x 3H), 1.08 (m, 6H)

[0394] 13C-{1H} NMR (DMSO-de 100 MHz) 6 ppm: (a mixture of rotamers was observed) 167.99, 167.70, 165.45, 165.31, 165.05, 164.75, 144.04, 143.81, 128.73, 128.44, 126.82, 126.55, 125.92, 125.79, 41.94, 41.81, 37.76, 37.41, 22.23, 21.98 FTIR (ATR) o cm1: 3269, 3162, 3119, 2970, 2930, 2872, 2156, 2127, 1566, 1532, 1487, 1451, 1396, 1344, 1296, 1258, 1205, 1174, 1131, 1105, 1078, 1028, 997, 971, 806, 770, 739, 694, 639 TLC (silica, hexane / AcOEt 90:10 vol): Rf 0.1

[0395] HRMS (ESI-MS): 285.1573 [M+H]+(expected: 285.1571) iii. Tr(phenol)-N3 34 %isol

[0396] Scheme 15 : Synthesis of Tr(phenol)-N3

[0397] 4-azido-N-methyl-6-phenoxy-N-phenyl-l,3,5-triazin-2-amine Tr(phenol)-N3

[0398] Compound Tr(phenol)-CI (1.200 g, 3.81 mmol, 1.00 eq) was dissolved in 2 mL of DMF. Sodium azide (0.460 g, 7.62 mmol, 2.00 eq) was suspended in 3 mL of DMF and added dropwise to the triazine solution. The mixture was stirred for 47h at 100 °C, and then transferred into 50 mL of distilled water at 0 °C. The aqueous phase was extracted with 3x50 mL of diethyl ether. The organic phase was washed with 5x50 mL of brine, dried over MgSC and concentrated under reduced pressure. Compound Tr(phenol)-N3 was purified by silica column chromatography (hexane / AcOEt 92:8), dried under reduced pressure at 50 °C overnight and obtained as a white solid (0.409 g, 1.28 mmol, 34%isol yield).

[0399] 1H NMR (DMSO-de 400 MHz) 5 ppm: 7.6-6.9 (m, 10H), 3.31 (s, 3H)

[0400] 13C-{1H} NMR (DMSO-de 100 MHz) 5 ppm: 171.50, 167.02, 166.38, 151.69, 151.57, 142.85, 142.74, 129.29, 129.23, 128.77, 128.63, 126.36, 126.26, 125.56, 125.38, 121.58, 37.95, 37.80 FTIR (ATR) o cm1: 3061, 2932, 2879, 2163, 2127, 1606, 1570, 1525, 1489, 1456, 1418, 1358, 1291, 1255, 1198, 1162, 1112, 1064, 1028, 1002, 911, 808, 798, 767, 689 TLC (silica, hexane / AcOEt 90:10 vol): Rf 0.2

[0401] HRMS (ESI-MS): 320.1260 [M+H]+(expected: 320.1254) iv. Tr(isopropylalcohol)-N3

[0402] 33 %isol

[0403] Scheme 16 : Synthesis of Tr(isopropylalcohol)-N3

[0404] 4-azido-6-isopropoxy-N-methyl-N-phenyl-l,3,5-triazin-2-amine Tr(isopropylalcohol)-N3

[0405] Compound Tr(isopropylalcohol)-CI (1.617 g, 4.23 mmol, 1.00 eq) was dissolved in 5 mL of DMF. Sodium azide (0.512 g, 8.47 mmol, 2.00 eq) was suspended in 3 mL of DMF and added dropwise to the triazine solution. The mixture was stirred for 69h at 100 °C, and then transferred into 50 mL of distilled water at 0 °C. The aqueous phase was extracted with 3x50 mL of diethyl ether. The organic phase was washed with 5x50 mL of brine, dried over MgSC and concentrated under reduced pressure. Compound Tr(isopropylalcohol)-N3 was purified by silica column chromatography (hexane / AcOEt 90:10), dried under reduced pressure at 40 °C overnight and obtained as a white solid (0.391 g, 1.37 mmol, 33%isol yield).

[0406] 1H NMR (DMSO-de 400 MHz) 5 ppm: 7.42 (br t, J = 8.1 Hz, 2H), 7.35 (br d, J = 8.8 Hz, 2H), 7.29 (br t, J = 7.3 Hz, 1H), 5.4-4.7 (app br s, 1H), 3.44 (s, 3H), 1.24 (app br s, 6H)

[0407] 13C-{1H} NMR (DMSO-de 100 MHz) 5 ppm: 170.01, 166.47, 143.16, 128.85, 126.63, 126.58, 70.53, 37.97, 21.44

[0408] FTIR (ATR) o cm1: 3066, 3022, 2999, 2978, 2930, 2872, 2213, 2131, 1676, 1599, 1556, 1525, 1513, 1450, 1418, 1382, 1360, 1334, 1317, 1288, 1255, 1219, 1179, 1105, 1064, 1026, 918, 803, 763, 740, 699, 660, 615

[0409] TLC (silica, hexane / AcOEt 90:10 vol): Rf 0.3

[0410] HRMS (ESI-MS): 286.1414 [M+H]+(expected: 286.1411) v. Tr(isopropylthiol)-N3 45 %isol

[0411] Scheme 17 : Synthesis of Tr(isopropylthiol)-N3 4-azido-6-(isopropylthio)-N-methyl-N-phenyl-l,3,5-triazin-2-amine Tr(isopropylthiol)-N3

[0412] Compound Tr(isopropylthiol)-CI (1.499 g, 5.08 mmol, 1.00 eq) was dissolved in 2 mL of DMF. Sodium azide (0.611 g, 10.17 mmol, 2.00 eq) was suspended in 3 mL of DMF and added dropwise to the triazine solution. The mixture was stirred for 47h at 100 °C, and then transferred into 50 mL of distilled water at 0 °C. The aqueous phase was extracted with 3x50 mL of diethyl ether. The organic phase was washed with 5x50 mL of brine, dried over MgSC and concentrated under reduced pressure. Tr(isopropylthiol)-N3 was purified by silica column chromatography (hexane / AcOEt 95:5), dried under reduced pressure at 50 °C overnight and obtained as a white solid (0.694 g, 2.30 mmol, 45%isol yield).

[0413] 1H NMR (DMSO-de 400 MHz) 5 ppm: 7.41 (m, 2H), 7.35 (m, 2H), 7.29 (m, 1H), 4.1-3.5 (app br s, 1H), 3.44 (s, 3H), 1.22 (app br s, 6H)

[0414] 13C-{1H} NMR (DMSO-de 100 MHz) 5 ppm: 181.05, 167.10, 163.68, 142.87, 128.79, 126.69, 126.50, 37.79, 35.18, 22.36

[0415] FTIR (ATR) o cm1: 3062, 6042, 2961, 2925, 2865, 2184, 2132, 1604, 1534, 1492, 1449, 1408, 1341, 1302, 1281, 1238, 1220, 1193, 1155, 1099, 1054, 1026, 988, 969, 927, 902, 799, 765, 739, 696, 632

[0416] TLC (silica, hexane / AcOEt 90:10 vol): Rf 0.5

[0417] HRMS (ESI-MS): 302.1186 [M+H]+(expected: 302.1182) vi. Tr(phenyl)-N3

[0418] Scheme 18 : Synthesis of Tr(phenyl)-Na

[0419] 4-azido-N-methyl-N,6-diphenyl-l,3,5-triazin-2-amine Tr(phenyl)-N3

[0420] Compound Tr(phenyl)-CI (0.155 g, 0.52 mmol, 1.00 eq) was dissolved in 1 mL of DMF. Sodium azide (0.047 g, 0.78 mmol, 1.50 eq) was suspended in 2 mL of DMF and added dropwise to the triazine solution. The mixture was stirred for 22h at 100 °C, and then transferred into 30 mL of distilled water at 0 °C. The aqueous phase was extracted with 3x20 mL of ethyl acetate. The organic phase was washed with 5x20 mL of brine, dried over MgSC and concentrated under reduced pressure. Tr(phenyl)-N3 was purified by silica column chromatography (hexane / AcOEt 90:10), dried under reduced pressure at 40 °C overnight and obtained as a white solid (0.022 g,

[0421] 0.07 mmol, 14%isol yield).

[0422] 1H NMR (DMSO-de 400 MHz) 5 ppm: 8.7-7.2 (br m, 10H), 3.58 (br s, 3H)

[0423] FTIR (ATR) o cm1: 3092, 3064, 3035, 2975, 2956, 2920, 2906, 2856, 2425, 2141, 2125, 1602, 1587, 1539, 1501, 1494, 1454, 1444, 1415, 1389, 1341, 1301, 1291, 1236, 1196, 1184, 1129, 1109, 1095, 1071, 1026, 1004, 992, 973, 940, 914, 902, 820, 801, 777, 742, 717, 696, 658, 629, 615

[0424] TLC (silica, hexane / AcOEt 90:10 vol): Rf 0.4 vii. Tr(isopropylsulfone)-N3

[0425] Scheme 19 : Synthesis of Tr(isopropylsulfone)-N3

[0426] 4-azido-6-(isopropylsulfonyl)-N-methyl-N-phenyl-l,3,5-triazin-2-amine Tr(isopropylsulfone)-

[0427] N3

[0428] Compound Tr(isopropylthiol)- N3 (0.250 g, 0.83 mmol, 1.00 eq) was dissolved in 5 mL of THF and m-chloroperbenzoic acid (0.358 g, 2.07 mmol, 2.50 eq) was added slowly at room temperature. The mixture was stirred for 18h at 40 °C, and then concentrated under reduced pressure. Tr(isopropylsulfone)-N3 was purified by silica column chromatography (hexane / AcOEt 70:30), and obtained as a white solid after concentration. Drying under reduced pressure at 50 °C overnight degraded the product into an off-white, viscous paste showing an alteredTH NMR spectrum.

[0429] TLC before drying at 50 °C (silica, hexane / AcOEt 70:30 vol): Rf 0.3

[0430] High pressure DSC (exo down) and TGA monitoring (under N2) of the decomposition of the azidotriazines 1, Tr(aniline)-N3, Tr(isopropylamine)-N3, Tr(phenol)-N3, Tr(isopropanol)-N3, and Tr(isopropylthiol)-N3 are represented in Figure 2.

[0431] The following tables 1 and 2 summarize the temperatures, enthalpies and kinetics parameters retrieved from high pressure DSC for the melting and bulk decomposition of the azidotriazine described hereabove. All azidotriazines presented in this study were microcrystalline solids that exhibited similar onset decompsotion temperatures (between 192 and 199 °C). The measured enthalpy ranged from 111 kJ / mol (forTr(phenol)-N3) to 235 kJ / mol (forTr(isopropylthiol)-N3. In general, higher enthalpies were observed for azidotriazine grafting agents that contain aliphatic C-H and N-H bonds. With respect to the kinetics, all decomposition reactions were found to be 1st order. These parameters allow for the half-life to be calculated for each respective azidotriazine at a desired processing temperature. Table 1. Temperatures and enthalpies obtained by high-pressure DSC for the melting and decomposition in bulk of the azido-substituted heteroaromatic derivative of the library n.a. = not applicable.

[0432] Table 2. Kinetic parameters computed from high-pressure DSC data for the Azido-substituted heteroaromatic derivative of the library

[0433] Table 3. Explosive potentials (according to the Yoshida and Pfizer correlations and the maximum storage temperature (TD24) that are computed according to the literature, in particular as described in Green, S.P et al., J. Org. Chem. 2019, 84, 5893-5898; based on high pressure DSC measurements.

[0434] Negative values of Yoshida and Pfizer correlations indicate stable compounds. Example 2. Decomposition of the azidotriazine 1

[0435] 2.1 Bulk decomposition of the azidotriazine 1

[0436] The azidotriazine 1 is more polar compared to HDPE and PP, and thus it was expected to not be completely soluble with these polyolefins in the melt. Thus, it was important to understand how the azidotriazine 1 reacts to anticipate the structures that would form during reactive extrusion. The reaction scheme for the model decomposition of the azidotriazine is depicted in Scheme 16. The reaction temperature and time were chosen on the basis of a kinetic study performed by differential scanning calorimetry (DSC). The half-life of this molecule is about 2 min at 215 °C. The reaction was set to run for 5 half-lives (10 min), corresponding to a conversion of about 97%. On the basis of 1H NMR spectroscopy, about 9% of the product was assigned as the corresponding aminotriazine, while the remaining 91% were triazine-based derivatives. The resonances observed by 1H NMR spectrum were broad, preventing further structural insight.

[0437] Scheme 20 : Reaction Scheme for the bulf decomposition of azidotriazine 1

[0438] The product distribution was studied using a size excmusion chromatography (SEC) and by matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF-MS).

[0439] By SEC (Fig. 3), the response of the crude product (black curve) was compared to that of an authentic standard of the aminotriazine 1' (grey curve; the aminotriazine structure is shown to as one of the products in Scheme 16). The signal of the decomposition product appears to be a mixture of the aminotriazine 1' (retention volume of 33.5 mL) as well as a broad distribution of higher molecular weight products (retention volume between 30 and 33.5 mL). By MALDI-TOF- MS (Fig. 4), it was found that the higher molecular weight products are oligomeric species that feature a repeat unit of 304.14 m / z, which is consistent with a polyazane structure as depicted in the top-left of Fig. 4. 2.2 The decomposition temperature of azidotriazine 1

[0440] The determination of the decomposition temperature of azidotriazine 1 loaded at 5mol% in HDPE has been achieved using TGA measurement (see Fig. 5). According the method as described heraeabove, a decomposition temperature of 206 °C is retrieved.

[0441] The same method is applied to a sample of bulk azidotriazine 1. The TGA run is reported on Fig. 6 and a decomposition temperature of 196°C is retrieved.

[0442] 2.3 Kinetics of azidotriazine 1 decomposition

[0443] To rationally chose the temperature and time for a grafting reaction, the kinetic parameters for azidotriazine 1 decomposition were determined by DSC measurements and applying the Borchardt-Daniels (B-D) analytical method (as described hereabove in the "methods" paragraph). This methodology was applied to bulk samples of azidotriazine 1 as well as mixtures of azidotriazine 1 with a polymer or polymers blend to be grafted.

[0444] The decomposition of azidotriazine 1 in HDPE at a loading of 5.0 mol% was studied by DSC (Fig. 7). The decomposition was carried out on an 8.1 mg sample in a high-pressure, hermetically- sealed gold DSC cell by heating the sample from 50 to 320 °C at a constant rate of 10 °C / min. After the polyethylene (PE) melted at 126 °C, the azidotriazine 1 underwent an exothermic decomposition reaction with onset and peak temperatures of 195 and 227 °C, respectively. Integration of this signal gave a total enthalpy of 172 J / (g sample), which corresponds to 154 kJ / (mol azidotriazine).

[0445] The B-D analysis was performed using the time vs. enthalpy integration data for this measurement. In this example, the resulting coefficients allowed for the calculation of A, Ea, and n, giving 2.366-1015, 164.9 kJ / mol, and 1.140, respectively.

[0446] An analogous analysis was carried out on bulk azidotriazine (i.e., the pure compound not dispersed in a polymer) as well as in a series of other matrices. The main calorimetric characteristics for each experiment are provided in Table 3. All kinetic parameters reported used in this study were calculated on the basis of three DSC measurements and averaging the results obtained by three separate B-D analyses. The summary of these analyses are provided in Table 4.

[0447] In all cases, it was found that the decomposition of azidotriaine 1 followed 1storder kinetics. The average kinetic parameters were then used to calculate the half-life time (tl / 2) at a desired temperature (TR), or the contrary, using eq. 4. In Table 5, the TR that would correspond to a tl / 2 of 2 min and 24 s was calculated. As an example, to graft each sample for 5 half-lives, then these two temperatures would give a total grafting time of 10 and 2 min, respectively. Table 4. Summary of calorimetric characterization of azidotriazine 1 dispersed in matrices and as bulk. PETg = polyethylene glycol, glycol modified; PCL = polycaprolactone; PS = polystyrene;

[0448] PP = polypropylene; PE = polyethylene; PB = polybutadiene; bulk = pure azidotriazine, not dispersed in a matrix). Table 5. Summary of kinetic parameters determined for azidotriazine 1 on the basis of DSC measurements using the Borchardt-Daniels (B-D) approach. All parameters are based on the average of three DSC runs and three B-D analyses. Table 6. Half-life times for azidotriazine 1 decomposition calculated on the basis of the B-D kinetic parameters in each matrix.

[0449] Example 3. Model grafting of azidotriazine 1 onto paraffin wax It is generally difficult to directly study the structure of high molecular weight polyolefins after grafting because of its low solubility in organic solvents. Thus, model grafting reactions of the azidotriazine 1 were carried out with paraffin wax, which is essentially an oligomeric analogue of HDPE, according to Scheme 17 below. One equivalent of the azidotriazine 1 was reacted with an excess of paraffin wax at 214 °C for 13 minutes.

[0450] Scheme 21 : Reaction scheme for the model grafting of azidotriazine 1 on paraffin wax.

[0451] Upon heating, the mixture evolved a gas (presumably N2), and it became red in color. On the basis of NMR spectroscopy, 24% of the azidotriazine 1 was transformed into the corresponding aminotriazine derivative, while the remaining 76% was covalently grafted onto the paraffin wax.

[0452] A wide range of techniques were employed to elucidate the product distribution of the grafted paraffin wax structures; three of the most important findings are described below.

[0453] By Raman spectroscopy (Fig. 8), the presence of key functional groups in the grafted paraffin wax was confirmed. Assignments were made by comparing with the spectrum of a model dimer structure and a spectrum that was calculated using density functional theory. A signal at 975 cm-1(vi) is assigned to the in-phase radial bending of the triazine ring stretching mode. Two other bands are observed in this range as well: a signal at 1003 cm-1(V2), which is assigned to an in- phase radial bending of the phenyl ring, and a signal at 1030 cm-1(V3), which is assigned to the out-of-plane bending of the phenyl C-H groups (Lin-Vien, D.; Colthup, N. B.; Fateley, W. G.; Grasselli, J. G. The Handbook of Infrared and Raman Characterisitic Frequencies of Organic Molecules; Academic Press, 1991).

[0454] These materials were also studied by electron paramagnetic resonance (EPR) spectroscopy (Fig. 9). Grafted materials exhibited a singlet resonance both in the solid state and in solution. The observed resonance corresponds to a g-factor of about 2, which is consistent with an organic radical species (Weil, J. A.; Bolton, J. R. Electron Paramagnetic Resonance, Elementary Theory and Practical Applications; 2nd ed.; John Wiley & Sons: Hoboken, NJ, USA, 2007). The singlet nature of this resonance suggests that the radical is delocalized over the triazinyl structure. To establish that the radical-bearing species was covalently grafted to the paraffin wax chains, the grafted material was purified by sequential precipitations (Fig. 9, right). The purified material still exhibited a singlet EPR signal; this result indicates that the radical species is grafted to the paraffin wax chains. It should be noted that these measurements were performed on samples that had been stored under air with no special precautions for over two weeks, suggesting that the radicals are long-lived.

[0455] The grafted paraffin wax was also subjected to an in-depth analysis by ID and 2D NMR spectroscopy, in Fig. 10, 1H-1H correlation spectroscopy (COSY) revealed key proton coupling that unambiguously establishes the covalent linkage between the paraffin wax chain and a monomeric aminotriazine graft.

[0456] Example 4. Grafting of azidotriazine 1 onto HDPE, PP and HDPE-PP blend by reactive processing

[0457] 4.1 Grafting of azidotriazine 1 onto HDPE, PP and HDPE-PP blend according to the process of the invention

[0458] The grafting of azidotriazine 1 was implemented into a reactive processing protocol. The general protocol for grafting a single matrix is schematically depicted in Fig. 11A, and the experimental torque profile for the grafting of HDPE with 1 mol% azidotriazine is presented in Fig. 11B.

[0459] In a first step, a masterbatch of azidotriazine 1 in HDPE was prepared according to the following procedure. Azidotriazine 1 (6.000 g) was dissolved into xylene (15 mL) and the solution was pre- heated to 100 °C. HDPE (9.000 g) was suspended into xylene (250 mL) and nitrogen was bubbled for 5 min. The suspension was heated and stirred at 140 °C under nitrogen. When reaching complete solubilization of the polymer, the solution of azidotriazine was added and the mixture was stirred was for another 5 min at 140 °C under nitrogen. Xylene was evaporated under reduced pressure at 90 °C and the obtained masterbatch was dried overnight in the same conditions (obtained mass: 15.090 g, final loading in azidotriazine: 40 wt%).

[0460] Then, in a second step, the masterbatch of azidotriazine 1 was loaded together with virgin HDPE into a 15 cubic centimers (cc) twin-screw extruder at the processing temperature Tmix of 160 °C. This mixing phase was incorporated to ensure homogenization of the melt before grafting (the half-life of the azidotriazine 1 at this temperature is nearly 3 h). After mixing for 5 min with a screw speed of 100 rpm, the temperature was quickly increased to the reaction temperature TR, which is 214 °C in the case of HDPE. As can be seen in Fig. 11B, the torque increases shortly after reaching TR, indicating an increase in viscosity. Given that the half-life of azidotriazine 1 is 2 min at this temperature, the reaction was carried out for 10 min (5 half-lives for about 97% conversion) before extruding the material, referred to as HDPEm, from the barrel.

[0461] A similar protocol was applied for grafting of PP with azidotriazine 1, yielding a material referred to as PPm.

[0462] A similar protocol was applied for grafting a blend of HDPE-PP (70:30 weight ratio) with azidotriazine 1 (Fig. 12A). An example of a torque profile for the reactive grafting of this blend with 1 mol% azidotriazine 1 is depicted in Fig. 12B. This ratio of HDPE and PP was chosen because it represents the weight ratio of polyethylene and polypropylene in typical municipal waste streams ("Plastics The Facts 2017." PlasticsEurope, 2018, Accessed on 4 Nov. 2018, https: / / www.plasticseurope.org / application / files / 5715 / 1717 / 4180 / Plastics_the_facts_2017_FI NAL_for_website_one_page.pdf). The resulting materials is referred to as (HDPE-PP)m.

[0463] The resulting HDPEmand (HDPE-PP)mwere both crosslinked materials, exhibiting a gel fraction of 63 and 58%, respectively. To determine if the crosslinks were chemically constituted of crosslinks made up of triazinyl units, Raman spectroscopy was performed as described above for paraffin wax (Fig. 13). The same diagnostic signals were observed in HDPEmas in the grafted paraffin wax. No such vibrational mode was observed in the virgin HDPE.

[0464] To further establish that the crosslinks were due to triazine-based linkages and not simply due to chain coupling via C-C bond formation, HDPEmwas subjected to numerous reaction conditions that were expected to chemically decompose the aminotriazine bonds. Two reactions reaction conditions were successfully identified: the treatment of HDPEmwith either a) 1-naphthol with KOH or b) 1-aminodecane with triazabicyclodecene (TBD) at 160 °C resulted in the complete dissolution of the material. These results suggest that aminotriazine linkages were indeed responsible for connecting the polymer chains as opposed to irreversible C-C bond chain coupling.

[0465] In the case of (HDPE-PP)m, another key question was whether covalent bonds are generated between HDPE and PP chains, as such a structural feature is expected to have an important impact on the mechanical properties of the material. Systematic gel fraction experiments were thus conducted on a series of HDPE-PP blends that were modified in different ways. As presented in Table 6, the first column gives the theoretical gel fraction expected for each blend on the basis of the gel fraction of each pure component (i.e., for virgin HDPE, virgin PP, HDPEm, and PPm, the gel fractions were determined to be 0, 0, 63, and 0%, respectively). As expected, the blend of virgin HDPE with virgin PP exhibited no insoluble fraction (entry 1). In the case of (HDPE-PP)m, the gel fraction is higher than expected for a 70:30 mixture, which is consistent with covalent bonds being formed between HDPE and PP chains (entry 2). A blend of HDPEmand PPmalso resulted in a higher gel fraction than theoretically expected, suggesting that crosslinks are reversible during melt processing at high temperature (entry 3). As a control experiment to validate the methodology of this experiment, a blend of HDPEmand PP gave the expected gel fraction assuming that no new connections were made between HDPEmand virgin PP chains (entry 4).

[0466] Table 7. Gel fraction experiments3for control and modified blends of PE-PP (all with a 70:30 weight ratio).

[0467] “Experiments were conducted in triplicate with xylenes at 130 °C for 16 h.bCalculated on the basis of the gel fraction of each component (0% for both virgin PE and virgin PP; 63% for HDPEm; 0%for PPm) 4.2. Thermomechanical properties of HDPEmand (HDPE-PP)m(polymer compositions according to the invention)

[0468] Remarkably, despite having a high gel fraction, both HDPEmand (HDPE-PP)mcould be reshaped by compression molding— this feature is consistent with the systematic gel fraction experiments presented in Table 7 that suggest that the crosslinks are reversible under processing conditions. This behavior allows for facile shaping and analysis by dynamic mechanical analysis (DMA) and rheometry. In Fig. 14 (top), the DMA of HDPEmexhibits a clear rubbery plateau at temperatures above the melting transition of the HDPE matrix (black curve), consistent with the formation of a crosslinked network. This behavior is in contrast to that of the virgin HDPE control (grey curve), which flows under its own weight above the melting transition. When the azidotriazine 1 loading was varied from 0.05 to 1 mol% (Fig. 14, bottom), the elastic modulus of the rubbery plateau increased going from 0.05 to 0.5 mol%; the rubbery plateau of the 0.5 mol% sample was essentially at the same elastic modulus of that of the 1 mol% sample, suggesting a "saturation" of thecrosslinking. The triazine-based crosslinking of HDPEmimparted excellent creep resistance at 180 °C compared to the virgin HDPE control (Fig. 15).

[0469] A very similar trend was observed for (HDPE-PP)m, as the DMA exhibited a clear rubbery plateau above the melting temperature of the PE and PP matrices (Fig. 16). The triazine-based crosslinking also gave excellent creep resistance to this material compared to the virgin HDPE-PP control blend (Fig. 17). For (HDPE-PP)m, we also highlight its tensile properties that were measured at ambient temperature (representative stress-strain curves presented in Fig. 18). While the virgin HDPE and virgin PP are ductile materials, the untreated blend exhibits a strain at break of about 30%, rendering it too fragile for practical usage. Remarkably, (HDPE-PP)mexhibits an elongation at break of over 300%. The treatment with azidotriazine 1 results in the recovery of a significant degree of ductility— combined with its processability and creep resistance at high temperature, this material represents an impressive step toward upcycling this mixture of plastics.

[0470] 4.3. Flow properties of HDPEmand (HDPE-PP)m(polymer compositions according to the invention)

[0471] Despite being covalently crosslinked, both HDPEmand (HDPE-PP)mcan be passed through a twin- screw extruder and can be reshaped by compression molding, suggesting that the crosslinks are reversible under high-shear and high temperature. As an example of experiments illustrating the flow properties of the obtained materials, strain sweep experiments for HDPEm(top) and (HDPE- PP)m(bottom) are presented in Fig. 19. These measurements were performed at 180 °C (i.e., the typical temperature used during compression molding) at a frequency of 1 rad / s. Both materials behave in a similar way: up to about 80% strain, an approximately linear response is observed with the storage modulus exceeding the loss modulus. Above 80%, both materials reach a critical strain value of about 120%, at which a crossover between the storage and loss modulus is observed. This material undergoes melt fracture at high strain and high temperature, but the material is capable of quickly healing this fracture via the reformation of crosslinks. This flow behavior is comparable to that of polyethylene vitrimers based on dioxa borolane metathesis (see Ricarte, R. G.; Tournilhac, F.; Cloitre, M.; Leibler, L. Linear Viscoelasticity and Flow of Self- Assembled Vitrimers: The Case of a Polyethylene / Dioxaborolane System. Macromolecules 2020, 53, 1852-1866).

[0472] 4.4. Recyclability of modified HDPE and HDPE-PP blends

[0473] The recyclability of modified HDPE and HDPE-PP blends wastested by subjecting HDPEmand (HDPE-PP)mto recycling experiments as depicted in Fig. 20. During each cycle, the materials were compression molded into suitable shapes for analysis by a range of techniques (DMA, tensile testing, Raman spectroscopy, and EPR spectroscopy; rheololgical measurements were performed on the first and last cycle). After performing the analyses, the test samples from tensile testing were recovered, cut, and re-extruded before compression re-molding. Both HDPEmand (HDPE- PP)"1exhibited remarkable stability over the four cycles on the basis of DMA (Fig 21) and tensile testing (Figs. 22-23). By DMA, it is clear that the effective crosslinking density for both materials does not change as a function of recycling. The tensile properties remain essentially constant as a function of recycling, with the exception of the Young's modulus that may increase with recycling cycles. Upon reaching the last cycle, a high temperature creep-recovery experiment was performed for each material (Fig. 24). The performance after the fourth cycle was essentially the same as the performance at the first cycle (as presented in Fig. 15 and 17).

[0474] This stability in performance over multiple cycles is remarkable for a crosslinked material and direct evidences for the reversible nature of the N-N bond-based crosslinking. To gain insight into the mechanism of reprocessing, EPR spectra were acquired after each cycle of recycling just after extrusion and after compression molding (Fig. 25). The intensity of the signal was normalized to the weight of the sample so that a qualitative comparison in radical concentration could be made. It is evident that the EPR signal becomes more intense after each cycle, suggesting the breaking of N-N bonds after each cycle. Nevertheless, it appears that the concentration of radicals decreases after compression molding, which is consistent with radical coupling reactions.

[0475] 4.5. Morphology of modified HDPE and HDPE-PP blends

[0476] A comprehensive study of the morphology by transmission electron microscopy (TEM) has been achieved. TEM results are presented in Fig. 26, where HDPEmand (HPDE-PP)mare compared to their respective virgin precursors. All samples were cryo-microtomed and stained with RuC . In Fig. 26A, the fine texture of the crystalline HDPE extends across the entire field of view (the visible inhomogeneity is due to mechanical creases in the microtomed film). Blending the azidotriazine 1 with HDPE in the melt but at low temperature (i.e., at Tmix) results in a phase-separated mixture (Fig. 26B). The azidotriazine 1 is dispersed as large droplets (dark regions) in the HDPE matrix. By contrast, HDPEmfeatures an additional phase that presents itself as dark nodules in the HDPE matrix (Fig. 26C). The nodules feature a sharp yet smooth interface with the HDPE matrix. The size distribution is broad, spanning from approximately 10 to over 100 nm in diameter.

[0477] In the case of the virgin HDPE-PP 70:30 blend (Fig. 26D), the coarse macrophase separation between HDPE and PP is clearly observed. The light-colored droplets correspond to PP, while the dark matrix corresponds to HDPE. The interface between the HDPE and PP is sharp and weak— it appears that the HDPE phase has somewhat delaminated from the PP droplet surface as a result of microtoming. By contrast, (HDPE-PP)mexhibits a morphology that is similar to that of HDPEm(Fig. 26E). Dark nodules of the triazine-rich phase are distributed throughout the blend of HDPE and PP. The interface between the HDPE and PP phases is less distinctly observed in this case.

[0478] Example 5. Grafting of azidotriazine 1 onto LDPE, PETg, PS, PCL, and HDPE-blends thereof as model of waste plastics

[0479] The polymers low density polyethylene (LDPE), polyethylene terephthalate glycol-modified (PETg), polystyrene (PS), and polycaprolactone (PCL) have been individually modified with 1 mol% of azidotriazine 1 by reactive processing using the process described in Fig. 11A. Blends of these polymers with HDPE (70:30 weight ratio) were either grafted together with 1 mol% of azidotriazine 1 as described in Fig. 12A or were prepared by mixing the individual modified materials (e.g., HDPEmwas blended with LDPEmto give HDPEm-LDPEm). Finally, a five-component mixture of HDPE, LDPE, PP, PETg, and PS (18:26:28:12:9) was also grafted with 1 mol% of azidotriazine 1 using an adaptation of the process depicted in Fig. 12A.

[0480] A concise understanding of these materials can be acquired by carefully considering the gel fraction experiments presented in Table 7. Among the one component compositions, LDPEmand PCLmwere both reprocessable crosslinked networks, while PETgmand PSmresulted in soluble thermoplastics. For the latter two matrices, 1H NMR spectroscopy on precipitated samples of PETgmand PSmrevealed that the grafting yield was 50 and 61%, respectively. On the basis of SAXS measurements, neither PETgmand PSmexhibited a phase-separated phase. In the case of PS, an analysis by EPR spectroscopy was performed, and confirm that PSmcontains long-lived radicals (Fig. 27). Thus, we believe that the lack of crosslinking in PETgmand PSmis likely attributable to the higher miscibility of the azidotriazine 1 grafting agent in the polymer. To generate N-N bonds, there naturally needs to be a locally high concentration of radical-bearing grafts, and nanophase separation is an effective means to satisfy this requirement.

[0481] Concerning the blends with HDPE, all examples resulted in insoluble networks. Interestingly, both processes for generating the blends (i.e., either directly grafting the blend or blending the two pre-grafted components) resulted in a gel fraction that was higher than the theoretical gel fraction that was calculated on the basis of the gel content of the individual components. Just as described above in the case of HDPE and PP, this finding strongly suggests that N-N bonds are generated between the different matrices during processing.

[0482] Concerning the 5-component mixture (HDPE-LDPE-PP-PETg-PS)m, it also exhibited a gel fraction that was superior to that of the theoretical gel fraction. The DMA and tensile properties of (HDPE- LDPE-PP-PETg-PS)mcompared to the corresponding blend of virgin polymers are presented in Figs. 28 and 29, respectively. A clear rubbery plateau is observed for (HDPE-LDPE-PP-PETg-PS)m, consistent with the formation of a chemical network. The tensile properties are mildly improved, with an elongation at break that is improved by nearly a factor of two. Although not optimized, these results already demonstrate the appeal of this strategy for upcycling complex mixtures of plastics.

[0483] Table 8. Gel fraction experiments0for control and modified blends of PE-PP (all with a 70:30 weight ratio).

[0484] “Experiments were conducted in triplicate with xylenes at 130 °C for 16 h.bCalculated on the basis of the gel fraction of each component.cNot applicable.dThe weight ratio was 70:30.eThe weight ratio was 18:26:28:12:9.

[0485] Example 6. Application to other polymer and polymers blend All modified, high molecular weight materials were prepared by reactive extrusion using a DSM Xplore twin-screw extruder with a 5 or 15 cc barrel volume. The setup includes a co-rotating conical screw profile and a recirculation channel that allows control over the residence time. All extrusions were performed under a flow of nitrogen.

[0486] Table 9. Half-life times for azidotriazine 1 at various temperatures

[0487] The half-life times for azidotriazine 1 at various temperatures have been determined by DSC measurements and applying the Borchardt-Daniels analytical method (see Swarin, S. J.; Wims, A. M. In Analytical Calorimetry; Porter, R. S., Johnson, J. F., Eds.; Springer: Boston, MA, 1977; Vol. 4 ; and ASTM International. Standard Test Method for Estimating Kinetic Parameters by Differential Scanning Calorimeter Using the Borchardt and Daniels Method; ASTM E2041-13.

[0488] West Conshohocken, PA, 2018. DOI: 10.1520 / E2041-13R18). 6.1. Single-component commercial thermoplastics

[0489] Reactive processing by extrusion with a with 15 cc extruder

[0490] The barrel was preheated at temperature Tm,-Xand purged with nitrogen for 5 min. The screw speed was set to 50 rpm and virgin polymer P and the 40 wt% masterbatch of azidotriazine 1 in P were sequentially loaded into the barrel over approximately 5 min. The screw speed was increased to 100 rpm and mixing was continued at temperature Tmmfor another 5 min. Then, the barrel was heated to temperature TR over approximately 2 min. After a subsequent residence time of 10 min at temperature TR, the material was extruded and cooled down at room temperature. Reactive processing by extrusion with a with 5 cc extruder

[0491] The barrel was preheated at temperature Tmmand purged with nitrogen for 5 min. The screw speed was set to 100 rpm and virgin polymer P and the 40 wt% masterbatch of azidotriazine 1 in P were sequentially loaded into the barrel over approximately 5 min. Mixing was continued at temperature Tmmfor another 5 min. Then, the barrel was heated to temperature TR over approximately 2 min. After a subsequent residence time of 10 min at temperature TR, the material was extruded and cooled down at room temperature.

[0492] Table 10. Experimental parameters for reaction of single-component commercial thermoplastics with azidotriazine 1. “In the case of P = iPP, stabilizers were added directly as a dry blend with the virgin polymer pellets (Irganox 1010 at 0.05 wt%, Irgafos 168 at 0.10 wt%).bTU stands for triazine units, i.e. the loading in mol% compared to the polymer repeating units.

[0493] 6.2. In situ reactive processing of blends of commercial thermoplastics

[0494] Reactive processing by extrusion with a with 15 cc extruder

[0495] The barrel was preheated at temperature Tm / Xand purged with nitrogen for 5 min. The screw speed was set to 50 rpm and a dry blend of virgin polymers Pi and P2 was loaded into the barrel over approximately 2 min. The screw speed was increased to 100 rpm and mixing was continued at temperature TmiXfor another 5 min. Then, the 40 wt% masterbatch of azidotriazine 1 in Pi was loaded over approximately 2 min and mixing was continued at temperature Tm / Xfor another 5 min. Thereafter, the barrel was heated to temperature TR over approximately 2 min. After a subsequent residence time of 10 min at temperature TR, the material was extruded and cooled down at room temperature.

[0496] Reactive processing by extrusion with a 5 cc extruder

[0497] The barrel was preheated at temperature Tm / Xand purged with nitrogen for 5 min. The screw speed was set to 100 rpm and a dry blend of virgin polymers Pi and P2 was loaded into the barrel over approximately 2 min. Mixing was continued at temperature Tmix for another 5 min. Then, the 40 wt% masterbatch of azidotriazine 1 in Pi was loaded over approximately 2 min and mixing was continued at temperature Tm / Xfor another 5 min. Thereafter, the barrel was heated to temperature TR over approximately 2 min. After a subsequent residence time of 10 min at temperature TR, the material was extruded and cooled down at room temperature.

[0498] Table 11. Experimental parameters for in-situ processing of blends of commercial thermoplastics with azidotriazine 1. “In the case of P2 = iPP, stabilizers were added directly as a dry blend with the virgin polymer pellets (Irganox 1010 at 0.05 wt%, Irgafos 168 at 0.10 wt%).faTU stands for triazine units, i.e., the loading in mol% compared to the polymer repeating units.

[0499] Reactive processing by compression molding with a hot press

[0500] This process was exemplified using HDPE as the matrix. First, a 10 wt% mixture of azidotriazine 1 in HDPE was prepared by compounding a 40 wt% masterbatch of azidotriazine 1 in HDPE with virgin HDPE on 5 cc extruder at 160 °C for 5 min. The resulting material was cured on a hot press by heating to 214 °C for 10 min under 3 T pressure within a stainless-steel mold. After curing, the material was allowed to cool to room temperature on the benchtop before ejecting it from the mold.

[0501] 6.3. Reactive blending of modified single-component materials

[0502] Reactive blending by extrusion with a 5 cc extruder

[0503] The barrel was preheated at temperature TR and purged with nitrogen for 5 min. The screw speed was set to 100 rpm and a dry blend of modified single-component materials Pim (a)and P2mwas loaded into the barrel over approximately 2 min. After a subsequent residence time of 10 min at temperature TR, the material was extruded and cooled down at room temperature.

[0504] (a) Pxmdesignates a material that is the result of grafting azidotriazine 1 with the virgin polymer

[0505] Table 12. Experimental parameters for reactive blending of modified single-component materials.

[0506] “TU stands for triazine units, i.e., the loading in mo % compared to the polymer repeating units.

[0507] 6.4. Preparation of control materials

[0508] Processing of single component control materials by extrusion with a 15 cc extruder

[0509] The barrel was preheated at temperature Tm / x and purged with nitrogen for 5 min. The screw speed was set to 50 rpm and virgin polymer P was loaded into the barrel over approximately 5 min. The screw speed was increased to 100 rpm and mixing was continued at temperature Tm / x for another 5 min. Then, the barrel was heated to temperature TR over approximately 2 min. After a subsequent residence time of 10 min at temperature TR, the material was extruded and cooled down at room temperature. Table 13. Experimental parameters for preparing single-component control materials.

[0510] “In the case of P = iPP, stabilizers were added directly as a dry blend with the virgin polymer pellets (Irganox 1010 at 0.05 wt%, Irgafos 168 at 0.10 wt%)

[0511] Processing of two-component control materials by extrusion with a 15 cc extruder The barrel was preheated at temperature Tm / x and purged with nitrogen for 5 min. The screw speed was set to 50 rpm and a dry blend of virgin polymers Pi and P2 was loaded into the barrel over approximately 2 min. The screw speed was increased to 100 rpm and mixing was continued at temperature TmiXfor another 5 min. Thereafter, the barrel was heated to temperature TR over approximately 2 min. After a subsequent residence time of 10 min at temperature TR, the material was extruded and cooled down at room temperature.

[0512] Table 14. Experimental parameters for preparing two-component control materials.

[0513] °ln the case of P2 = iPP, stabilizers were added directly as a dry blend with the virgin polymer pellets (Irganox 1010 at 0.05 wt%, Irgafos 168 at 0.10 wt%) Control blends of modified single-component material Pimand virgin polymer P2

[0514] The barrel was preheated at temperature TR and purged with nitrogen for 5 min. The screw speed was set to 100 rpm and a dry blend of modified single-component material Pimand virgin polymer P2 was loaded into the barrel over approximately 2 min. After a subsequent residence time of 10 min at temperature TR, the material was extruded and cooled down at room temperature.

[0515] Table 15. Experimental parameters for preparing two-component control blends of a modified polymer with a virgin polymer.

[0516] “In the case of P2 = iPP, stabilizers were added directly as a dry blend with the virgin polymer pellets (Irganox 1010 at 0.05 wt%, Irgafos 168 at 0.10 wt%).faTU stands for triazine units, i.e. the loading in mol% compared to the polymer repeating units.

[0517] Example 7. Grafting of azidotriazines AT-Ph and AT-NBU2 onto HDPE by reactive processing

[0518] 7.1. Grafting of azidotriazines AT-Ph and AT-NBU2 onto HDPE according to the process of the invention

[0519] The grafting of AT-Ph and AT-NBU2 were perfomed using the same reactive processing protocol used with azidotriazine 1 in example 4 (see Fig.llA). The experimental torque profile for the grafting of HDPE with 1 mol% AT-Ph, respectively 1 mol% of AT-NBU2, is presented in Fig. 30-left, respectively Fig. 30-right.

[0520] In a first step, a masterbatch of AT-Ph in HDPE was prepared according to the following procedure. AT-Ph (1.6 g) was dissolved into xylene (5 mL) and the solution was pre-heated to 100 °C. HDPE (2.4 g) was suspended into xylene (50 mL) and nitrogen was bubbled for 5 min. The suspension was heated and stirred at 140 °C under nitrogen. When reaching complete solubilization of the polymer, the solution of azidotriazine was added and the mixture was stirred was for another 5 min at 140 °C under nitrogen. Xylene was evaporated under reduced pressure at 90 °C and the obtained masterbatch was dried overnight in the same conditions (obtained mass: 4.05 g, final loading in AT-Ph: 40 wt%).

[0521] Then, in a second step, the masterbatch of AT-Ph was loaded together with virgin HDPE into a 15 cubic centimers (cc) twin-screw extruder at the processing temperature Tmix of 160 °C. This mixing phase was incorporated to ensure homogenization of the melt before grafting. After mixing for 5 min with a screw speed of 100 rpm, the temperature was quickly increased to the reaction temperature TR, which is 214 °C in the case of HDPE. As can be seen in Fig. 30-left, the torque increases shortly after reaching TR, indicating an increase in viscosity. According to the process used for azidotriazine 1, the reaction was carried out for 10 min before extruding the material, referred to as HDPEAT'ph, from the barrel. The same protocol was applyed using AT- NBu2 to yield the material referred as HDPEAT'NBu. The resulting HDPEAT'phand HDPEAT'NBuare both crosslinked materials, exhibiting a gel fraction of 58% and 60%, respectively (Table 16).

[0522] Table 16. Gel fraction experiments3for control and modified HDPE.

[0523] “Experiments were conducted in triplicate in xylenes at 130 °C for 16 h.

[0524] To further establish that the crosslinks were due to triazine-based linkages and not simply due to chain coupling via C-C bond formation, HDPEAT'phand HDPEAT'NBuwere subjected to conditions that were expected to chemically decompose the aminotriazine bonds. The treatment of HDPEAT'phand HDPEAT'NBUwith 1-aminodecane with triazabicyclodecene (TBD) at 160 °C resulted in the complete dissolution of the material. These results suggest that aminotriazine linkages were indeed responsible for connecting the polymer chains as opposed to irreversible C-C bond chain coupling. 7.2. Thermomechanical properties of HDPEAT'ph, HDPEmand HDPEAT'NBu(polymer compositions according to the invention)

[0525] Despite having a high gel fraction, HDPEAT'phcould be shaped by compression molding. HDPEAT'NBucould be reshaped by a two-steps reshaping process involving reactive extrusion and then compression molding. This behavior allows for facile shaping and analysis by dynamic mechanical analysis (DMA). The DMA of HDPEAT'ph, HDPEmand HDPEAT'NBuall exhibit clear rubbery plateau at temperatures above the melting transition of the HDPE matrix, consistent with the formation of a crosslinked network (Fig. 31). This behavior is in contrast to that of the virgin HDPE control (grey curve ; Fig. 31), which flows under its own weight above the melting transition.

[0526] 7.3 Recyclability of HDPEAT'ph

[0527] The recyclability of HDPEAT'phwas further assessed through the ability of this material to be reshaped either directly by compression molding, or after an additional cycle of extrusion followed by compression molding as depicted on Figure 20. The materials were compression molded into suitable shapes for DMA and tensile testing. After performing the tensile testing to rupture, the tested samples were recovered, cut, and either reshaped directly by compressionmolding or were extruded and then reshaped by compression-modling. HDPEAT'phexhibited excellent recyclability with both protocol tested, as evidenced by DMA and and tensile testing (Fig. 32). By DMA, it is clear that a crosslinked material is obtained after recycling, with the presence of a plateau above the melting transition. The tensile properties remain essentially constant after recycling (Table 17).

[0528] In addition, HDPEAT'phremained insoluble after recycling, with an insoluble fraction of 49 ± 7 % after 16 hours in xylenes at 130°C for the HDPEAT'phrecycled by estrusion and compression molding for example.

[0529] Table 17. Tensile properties of HDPEAT'phand of the materials recycled by extrusion and compression molding or by compression molding only.

[0530] Example 8. Comparative example of the process implemented without step (a)

[0531] 8.1. Sample 1: Reactive extrusion without mixing step

[0532] The virgin HDPE (73.5 wt%) and of the masterbatch of azidotriazine 1 (26.5 wt%) were loaded into a 15 cubic centimers (cc) twin-screw extruder at 160°C with 100 rpm screw speed. This composition corresponds to 1 mol% of azidotriazine 1 in HDPE. Once the introduction of all the material was completed, the temperature was quickly increased to 214 °C. The reaction was carried out for 10 min before extruding the material, referred to as Sample 1, from the barrel.

[0533] 8.2. Sample 2: Reactive compression molding without melt homogenization

[0534] The virgin HDPE (73.5 wt%), as received commercial pellets, and the masterbatch of azidotriazine 1 (26.5 wt%), under the form of particles of dimeter of ca. 5 mm, were introduced into a plastic box, which was capped and manually shaken for approximately 1 minute. This composition corresponds to 1 mol% of azidotriazine 1 in HDPE. The mixture was then introduced in stainless- steel molds, which were subsequently placed in a preheated bench top manual Carver press. The compression molding was performed at 214 °C for 10 minutes with a normal force of 3 tons. Samples, referred to as Sample 2, were subsequently cooled down to ambient temperature on the benchtop.

[0535] After immersion in xylene at 130 °C for 15 hours, Sample 1 and Sample 2 diplayed insoluble fractions of 78 ± 2 % and 67 ± 2 %, respectively, which is higher than the insoluble fraction of HDPEm, which is 63±2 %. However, despite their high insoluble fractions, Sample 1 and Sample 2 displayed poor thermomechanical properties, as evidence by DMA with a lower valuer of E' below the melting temperature of HDPE as compared to HDPEm, and with the absence of a rubbery plateau in contrast to HDPEm(Fig. 33).

[0536] Example 9. Grafting of azidodiazine AD-Ph onto HDPE by reactive processing

[0537] 9.1 Grafting of azidodiazine AD-Ph onto HDPE according to the process of the invention

[0538] The grafting of AD-Ph was performed according to the same reactive processing process as described in Examples 4 and 7 (see Fig.llA). In a first step, a masterbatch of AD-Ph in HDPE was prepared according to the following procedure. AD-Ph (2.02 g) was dissolved into xylene and nitrogen was bubbled for 5 min. HDPE (3.015 g) was suspended into xylene (50 mL) and nitrogen was bubbled for 5 min. The suspension was heated and stirred at 140 °C under nitrogen. When reaching complete solubilization of the polymer, the solution of azidodiazine was added and the mixture was stirred was for another 5 min at 140 °C under nitrogen. Xylene was evaporated under reduced pressure at 90 °C and the obtained masterbatch was dried overnight in the same conditions (obtained mass: 5 g, final loading in AD-Ph: 40 wt%).

[0539] Then, in a second step, the masterbatch of AD-Ph (2.692 g) was loaded together with virgin HDPE (9.308 g) into a 15 cubic centimers (cc) twin-screw extruder at the processing temperature Tmix of 180 °C. This mixing phase was incorporated to ensure homogenization of the melt before grafting. After mixing for 5 min with a screw speed of 100 rpm, the temperature was quickly increased to the reaction temperature TR, which is 240 °C in this case. The higher values for Tmix and TR used for AD-Ph in this example compared to the values for Tmix and TR used for azidotriazine 1 (Example 4) is based on the slower decomposition kinetics of AD-Ph, which can be rationalized based on the Borchardt-Daniels kinetic parameters (Table 2); at 240 °C, the halflife of AD-Ph is 2 min. As can be seen in Fig. 34A, the torque increases upon reaching TR, indicating an increase in viscosity. The reaction was carried out for 10 min before extruding the material, referred to as HDPEAD'ph, from the barrel. The resulting HDPEAD'phis a crosslinked material with a gel fraction of 79±6%

[0540] 9.2 Thermomechanical properties of HPPEAD'ph

[0541] Despite having a high gel fraction, HDPEAD'phcan be easily reshaped by compression molding. This behavior allows for facile shaping and analysis by DMA. The DMA of HDPEAD'phexhibits a clear rubbery plateau at temperatures above the melting transition of the HDPE matrix, consistent with a crosslinked network (Fig.34B).

Claims

CLAIMS1. A process for preparing a polymer composition, comprising the steps of:(a) mixing a polymer or a polymers blend, and an azide derivative of formula (I) :N3-Ar (I), in which Ar is a heteroaromatic group, at a processing temperature Tmix, then(b) heating the mix of step a) to a temperature TR, whereinTmix is higher than the glass transition temperature or the melting temperature of the polymer used in step (a), or higher than the highest glass transition temperature or melting temperature of all the polymers present in the polymers blend of step (a) at a content of at least 8wt% relative to the total weight of the blend,TR is equal to or higher than the decomposition temperature of the azide of formula (I), and Tmix is strictly lower than TR.

2. The process of claim 1, wherein the azide derivative of formula (I) is selected from the group consisting of:in which one or two, preferably one, of R1to Rxis N3 and the others are each independently selected in the group consisting of a hydrogen atom, a halogen, a C1-12 alkyl group, a C1-12 haloalkyl group, an aryl, a heteroaryl, a Ci- a I ky l-a ryl group, an oxo group, NRcRd, ORe, C(O)Rf,C(O)ORg, C(O)NRhR', SRJ, CN and NO2 wherein Rcto RJare, independently of one another, a hydrogen atom, a C1-C12 alkyl group, a Ci-ea Ikyl-a ryl group or an aryl, Rxbeing the group with the highest index on the compound.

3. The process of claim 2, wherein the azide derivative of formula (I) is selected in the group consisting of:more preferably the azide derivative i4. The process of any one of claims 1 to 3, wherein the polymer or polymers blend is selected in the group consisting of of polyolefins, polyesters, polystyrene (PS), polyurethane (PU), polyamides, poly(vinyl)chloride (PVC), natural polymers and their copolymers or a blend thereof.

5. The process according to claim 4, wherein polymer or polymers blend is a plastic or a mixture of plastics, in particular waste plastic or mixture of waste plastics, for example unsorted plastic, damaged plastic, mixture of damaged plastics or mixture thereof.

6. The process of any one of claims 1 to 5, wherein the decomposition temperature of the azide derivative of formula (I) is higher than the glass transition temperature (Tg) or melting temperature (Tm) of the polymer of step (a) provided that, when the mix of step (a) comprises a blend of polymers, the relevant Tgor Tmis the highest glass transition temperature (Tg) or melting temperature (Tm) of all the polymers being present in the blend at a content of at least 8wt% relative to the total weight of the blend.

7. The process of any one of claims 1 to 6, wherein in step (b), a reaction time tR at the temperature TR is observed, tR corresponding to the time needed for 50%, preferably 75%, more preferably 90%, even more preferably 95% of the azide derivative of formula (I) to be decomposed at the temperature TR.

8. The process of any one of claims 1 to 7, wherein the mix of step a) comprises from 0.05 mol% to 10 mol%, preferably from 0.1 to 3.5mol%, more preferably from 0.5 to 1.5 mol% of azide derivative of formula (I) compared to the polymer repeating units.

9. The process of any one of claims 1 to 8, wherein the azide derivative of formula (I) is soluble, partially soluble or insoluble in the molten polymer or polymers blend used at step (a).

10. The process of any one of claims 1 to 9, wherein step b) is performed by reactive extrusion, by compression molding, injection molding or oven curing.

11. The process of any one of claim 1 to 10, comprising a step (a') before step (b) of:(a') mixing a polymer or a polymers blend, and an azide derivative of formula (I) :N3-Ar (I), in which Ar is a heteroaromatic group, at a processing temperature T'mix, the polymer or polymers blend and / or the azide derivative of formula (I) used in step (a') being different from the polymer or polymers blend and / or the azide derivative of formula (I) used in step (a), wherein T'mix is higher than the glass transition temperature or the melting temperature of the polymer used in step (a'), or higher than the highest glass transition temperature or melting temperature of all the polymers present in the polymers blend of step (a') at a content of at least 8wt% relative to the total weight of the blend, T'mix is strictly lower than TR, and wherein step (b) comprises heating the mix of steps (a) in the presence of the mix of step (a') to a temperature TR.

12. The process of any one of claim 1 to 10, comprising steps (a'), ( b') and (c) of :(a') mixing a polymer or a polymers blend, and an azide derivative of formula (I) :N3-Ar (I), in which Ar is a heteroaromatic group, at a processing temperature Tmix, the polymer or polymers blend and / or the azide derivative of formula (I) used in step (a') being different from the polymer or polymers blend and / or the azide derivative of formula (I) used in step (a), wherein T'mix is higher than the glass transition temperature or the melting temperature of the polymer used in step (a'), or higher than the highest glass transition temperature or melting temperature of all the polymers present in the polymers blend of step (a') at a content of at least 8wt% relative to the total weight of the blend, T'mix is strictly lower than TR,(b') heating the mix of step (a') to a temperature T'R, wherein T'R is equal to or higher than the decomposition temperature of the azide of formula (I) used in step (a'), wherein steps (a) and (b) are carried out in a reactor and steps (a') and (b') are carried out in another reactor, and(c) blending a polymer composition resulting from step (b) with a polymer composition resulting from step (b') at a temperature T"R being equal to the higher temperature among TR and T'R.

13. A polymer composition obtained by the process of any one of claims 1 to 12.

14. The polymer composition of claim 13 containing groups of formula (II) and / or (III):in which is the bond between the group and a carbon atom of a repeating unit of a polymer of the composition, x and y are each independently an integer ranging from 0 to 10, preferably 0 or 1,Ar is as defined in the azide derivative of formula (I) used in the process as described above, and* is selected from the group consisting of -H and a carbon atom of another repeating unit of a polymer chain of the composition.

15. The polymer composition of claim 14, further comprising pendant groups of formula -NH(Ar), linked to a carbon atom of a repeating unit of a polymer of the composition, in which Ar is as defined in the azide derivative of formula (I) used in the process of any one of claims 1 to 13.

16. The polymer composition of any one of claims 13 to 15, further comprising a free compound containing a heteroaromatic group Ar resulting from the decomposition of the unreacted azide derivative of formula (I) and / or the reaction of the azide derivative of formula (I) with the polymer or polymers blend, for example selected in the group consisting of :- a free amine containing a heteroaromatic group Ar, such as a primary amine of formula NH2Ar,- a polyazane of formula NHAr-[N(Ar)]x-NHAr, in which x is an integer from 0 to 10, preferably O or l,- a polyazane of formula NHAr-[N(Ar)]x-NAr«, in which x is an integer from 0 to 10, preferably 0 or 1, or - a derivative of formula (Ar)N=N(Ar).

17. The use of an additive of formula (I)N3-Ar (I) as defined in any one of claims 1 to 3, for upcycling a plastic or a mixture of plastics, in particular waste plastic or mixture of waste plastics, for example unsorted plastic, damaged plastic, mixture of damaged plastics or mixture thereof.

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