Epoxy thermosets and composites thereof comprising recyclable amine hardeners and fragmentation method thereof

Abstract

This invention relates to epoxy thermosets and composites thereof, that undergo rapid acidic fragmentation into granular epoxy fragments. The thermoset comprises at least one conventional amine hardener in the range of 95 to 40 wt. % mixed with at least one recyclable amine hardener in the range of 5 to 60 wt. %, wherein the recyclable hardener comprises a linkage selected from the group consisting of an acetal linkage, a ketal linkage, a formal linkage, an orthoester linkage, an orthocarbonate linkage, and a siloxy linkage. The invention is also a method of rapid acidic fragmentation of said thermosets and composites to granular epoxy fragments by soaking in an acid at a temperature from about 20℃ to 110℃. The invention is also a method of preparing said thermosets and composites.

Description

[0001] ABCTL202521000735

[0002] 1

[0003] TITLE OF THE INVENTION

[0004] Epoxy Thermosets and Composites Thereof Comprising Recyclable Amine Hardeners and Fragmentation Method Thereof

[0005] FIELD OF THE INVENTION

[0006]

[0001] The present invention relates to epoxy thermosets and composites thereof, that undergo rapid acidic fragmentation into granular epoxy fragments, said thermoset comprising at least one recyclable amine hardener mixed with at least one conventional amine hardener. The invention is also a method of rapid acidic fragmentation of said thermosets and composites to granular epoxy fragments by soaking in an acid at a temperature from about 20°C to 110°C. The invention is also on a method of preparing said thermosets and composites.

[0007] DESCRIPTION OF THE BACKGROUND ART

[0008]

[0002] Waste generation poses significant environmental and societal challenges. While some of the waste generated each year can be recycled or repurposed into new products, some materials are not currently recyclable. For example, plastics comprise 12% of waste generation in the U.S.

[0009]

[0003] Epoxy, a type of plastic, is typically composed of two different liquid materials, a resin and a curing agent, which harden when mixed and heated. Once ‘set’, thermoset materials and products derived therefrom, cannot be melted and recycled like thermoplastics. They can only be removed from the environment via incineration. The ordinary consumer is likely unaware that there remains a non-recyclable class of plastic obtained from epoxy. This is understandable considering that, historically, thermosets have mainly been used for adhesive and coating applications, but this is changing. Thermosets, such as epoxy polymers, are now commonly used as the plastic matrix in performance composites, also known as fiber reinforced plastics (FRPs). Composites have the lightweight advantages of plastic, and the extra strength generated from the fiber reinforcement. As the cost of carbon fiber has dropped substantially, the prevalence of carbon fiber composites has increased dramatically. Composites are now found in many familiar engineering applications, including automotive and aviation parts, wind turbine blades, structural supports in buildings, and high-performance sporting equipments.

[0010]

[0004] As the composite market continues to grow, the use of non-recyclable thermosets places the industry in a juxtaposition where, on one hand, carbon composites are essential for meeting energy efficiency goals and CAFE standards in the transportation industry, but on the other hand the materials required to make these products are not recyclable. End-of-life products are not easilyABCTL202521000735

[0011] 2

[0012] recyclable and the waste generated by composite original equipment manufacturers is increasingly becoming both an environmental and economic burden.

[0013]

[0005] A few prior art methods for recycling epoxy thermosets do exist. Acid mediated degradation of amine-based epoxy thermosets has been observed. Prolonged exposure of amine-cured epoxy thermosets in acids causes extremely slow crosslinking degradation. This results in a decrease in crosslink density and subsequently affecting the mechanical properties of thermosets. However, this is a very slow process and takes up to 2-3 days.

[0014]

[0006] Acid mediated degradation of epoxy thermosets to recover reinforcement as a model for wind blade recycling has also been explored in Jacob et al, ACS Omega 2019, 4, 10799-10808. In this process, acid slowly penetrates into the epoxy thermosets through a degradation mechanism with the formation of surface cracks and swelling of the thermosets. Eventually, the swelling stress and partial crosslinking degradation leads to the degradation of thermosets. However, this is also very slow and takes up to 2-3 days.

[0015]

[0007] In another study by Johnathan et al, Express Polymer Letters Vol.16, No.5 (2022), 488-499, acidic degradation mechanism of a composite of bisphenol-F epoxy resin and poly(ether)amine was investigated using aqueous H2SO4. The study concluded that physical damage of the amine-cured epoxy resin is caused by a layer-wise penetration process followed by damage of the 2D network by the inorganic acid.

[0016]

[0008] In another report by Minjie et al, ACS Sustainable Chem. Eng. 2021, 9, 1, 438-447, degradation behaviors of bio-based epoxy resin made from epoxidized vanillic acid and anhydride curing agent was investigated in acidic solution.

[0017]

[0009] Zhao et al teaches solvolysis of an amine epoxy, composed of FRP using diglycidyl ether bisphenol A and amine, of size 2.5 x 1.5 x 0.3 cm wherein solvolysis is conducted in ethanolamine with 10 % wt KOH at 160 °C, pressure 1 bar, and for a period of 1.5 hours. Navarro et al teaches composite FRP from diglycidyl ether bisphenol A and aromatic 4,4'-diaminodiphenyl sulfone hardener, of size 10.0 x 2.0 x 0.2 cm, wherein solvolysis was conducted using acetic acid : H2O2 with ScCh (Ratio = 6 : 1 v / v and 30% H2O2) at 110°C, pressure 1 bar and for 6 hours. However, a method that avoids pressure regulation is preferred.

[0018]

[0010] Vestas in WO2024125740A1 reported that wind blades made of conventional amine cured epoxy thermosets can undergo degradation in formic acid and thus thermoset epoxy fractions can be separated from a thermoset epoxy structure such as wind turbine blades. However, this is also a very slow process and takes up to 3-4 days. In this process the structure has been soaked in a swelling fluid comprising formic acid. This allows the thermoset matrix to swell and undergo mechanical breakup into smaller fractions. The swelling was evident from the elongation of theABCTL202521000735

[0019] 3

[0020] thermoset after soaking into a swelling liquid. In the best example, fractionation may take more than 24 hours and the rate of fractionation is significantly slower with the increase of dilution of the formic acid.

[0021] [Oil] There is a need for epoxy thermosets and composites thereof that show faster acidic degradation. There is a need for a method of recycling epoxy thermoset composites that is simple and rapid.

[0022] SUMMARY OF THE INVENTION

[0023]

[0012] According to an embodiment, the present invention relates to an epoxy thermoset that undergoes rapid acidic fragmentation into granular epoxy fragments, said thermoset comprising:

[0024] a. a difunctional epoxy, a multifunctional epoxy or a combination thereof;

[0025] b. at least one conventional amine hardener of a concentration value in the range of 95 to 40 wt. %; and

[0026] c. at least one recyclable amine hardener of a concentration value in the range of 5 to 60 wt. %, wherein the recyclable hardener comprises a linkage selected from the group consisting of an acetal linkage, a ketal linkage, a formal linkage, an orthoester linkage, an orthocarbonate linkage, and a siloxy linkage,

[0027] wherein the at least one conventional amine hardener and the at least one recyclable amine hardener add up to 100 wt. %.

[0028]

[0013] According to an embodiment, the present invention relates to a composite comprising the present epoxy thermoset and a reinforcement material, wherein the composite undergoes rapid acidic fragmentation to yield granular epoxy fragments separated from the reinforcement material.

[0029]

[0014] According to an embodiment, the present invention relates to a method of fragmenting the present epoxy thermoset to granular epoxy fragments comprising soaking the epoxy thermoset in an acid at a temperature from about 20°C to 110°C till the thermoset rapidly fragments completely into granular epoxy fragments.

[0030]

[0015] According to an embodiment, the present invention relates to a method of fragmenting the present composites to granular epoxy fragments comprising soaking the composite in an acid at a temperature from about 20°C to 110°C till the thermoset rapidly fragments completely into granular epoxy fragments and separates away from the reinforcement material.

[0031]

[0016] According to an embodiment, the present invention relates to a method of preparing the present epoxy thermoset, the steps comprising:ABCTL202521000735

[0032] 4

[0033] a. mixing the epoxy, the at least one conventional amine hardener of a concentration value in the range of 95 to 40 wt. %; and the at least one recyclable amine hardener of a concentration value in the range of 5 to 60 wt. % to obtain a mixture;

[0034] b. pouring the mixture into a mould; and

[0035] c. curing by gradually increasing temperature to not more than about 125 °C, and optionally applying a second curing step at a higher temperature from about 125°C to about 180°C, by gradually increasing heat, to obtain the epoxy thermoset.

[0036]

[0017] According to an embodiment, the present invention relates to a method of preparing a composite comprising a reinforcement material and the epoxy thermoset prepared according to the above method, wherein in step a) the mixture is infused into a reinforcement material followed by application of a wettability improvement method before pouring into the mould and curing.

[0037] BRIEF DESCRIPTION OF THE DRAWINGS

[0038]

[0018] Reference will be made to embodiments of the invention, examples of which may be illustrated in accompanying figures. These figures are intended to be illustrative, not limiting. Although the invention is generally described in context of these embodiments, it should be understood that it is not intended to limit the scope of the invention to these particular embodiments.

[0039]

[0019] Figure la shows the fragmentation process by soaking in 80% formic acid at 60°C a GFRP composite made of difunctional conventional epoxy resin YD 128, 80% conventional amine hardener D230 and 20% recyclable amine hardener R301, according to one embodiment

[0020] Figure lb shows the rate of epoxy fraction yield from GFRP composite made of conventional difunctional epoxy resin YD 128, 80% conventional amine hardener D230 and 20% recyclable amine hardener R301, when soaked in 80% formic acid at 60°C, according to one embodiment.

[0040]

[0021] Figure 1c shows the rate of epoxy fraction yield of GFRP made from thermoset composed of YD 128 and 100% conventional amine hardener when soaked in 80% formic acid at 60°C, according to one embodiment

[0041]

[0022] Figure Id shows a graphical representation of the time for fragmentation versus % weight loss of GFRP composites prepared using epoxy resin systems comprising YD128 and 100% conventional amine hardener or a mix of YD128 with a recyclable amine hardener, according to one embodiment

[0042]

[0023] Figure le shows pictures testing disassembly at 2.5 hours of GFPR composites prepared from epoxy resin systems using the conventional difunctional epoxy resin and 100% conventionalABCTL202521000735

[0043] 5

[0044] amine hardener or a mix of conventional amine hardener with varying ratios of a recyclable amine hardener when soaked in 80% formic acid at 60°C, according to one embodiment

[0045]

[0024] Figure If shows GFPR disassembly at 2.5 hours, 6 hours and 15 hours of the GFPR composites prepared in Figure le, according to one embodiment

[0046]

[0025] Figure 1g shows a graphical form of the % weight loss data of fragmentation of various embodiments of the present epoxy systems after soaking for 16 hours in 80% formic acid at room temperature, according to one embodiment

[0047]

[0026] Figure 2 shows fragmentation results of YDM441 a multifunctional epoxy resin or YD128 a difunctional epoxy resin mixed with 60% D230 conventional amine hardener + 40% of a recyclable amine hardener, according to one embodiment

[0048]

[0027] Figure 3 shows fragmentation of multifunctional and di-functional epoxy with 100% D230 in aqueous acetic acid, according to one embodiment

[0049]

[0028] Figure 4 shows fragmentation time of cured epoxy thermosets comprising difunctional epoxy resin YD128 with 0-50% of a siloxy linkage recyclable amine hardener and the conventional amine hardener D230, in 80% formic acid at 60 °C, according to one embodiment.

[0050]

[0029] Figure 5 shows fragmentation time in 80% formic acid at 60 °C, of cured epoxy thermoset comprising conventional difunctional epoxy resin YD128 and 60% conventional hardener D230 mixed with 40% of various types of non-siloxy recyclable amine hardeners, according to one embodiment.

[0051]

[0030] Figure 6 shows the appearance of fragmentation in 80% formic acid at 60 °C of the neat-cured epoxy thermosets as described in Figure 4, according to one embodiment.

[0052]

[0031] Figure 7 shows the appearance of fragmentation in 80% formic acid at 60 °C of neat-cured epoxy thermosets as described in Figure 5, according to one embodiment.

[0053]

[0032] Figure 8 shows fragmentation in 80% formic acid at room temperature of cured epoxy thermosets comprising conventional difunctional epoxy resin YD128 with 60% conventional hardener D230 and 40% of various recyclable amine hardeners, according to one embodiment.

[0054]

[0033] Figure 9 shows the appearance of fragmentation in 80% formic acid at room temperature of the epoxy thermosets as described in Figure 8, according to one embodiment.

[0055] DETAILED DESCRIPTION OF THE INVENTION

[0056]

[0034] In the following description, the embodiments are described in sufficient detail to enable those skilled in the art to practice the invention and it is understood that other embodiments may be utilized and that changes may be made without departing from the scope of the invention. To avoid detail not necessary to enable those skilled in the art to practice the embodiments describedABCTL202521000735

[0057] 6

[0058] herein, the description may omit certain information known to those skilled in the art. Accordingly, the description and figures are to be regarded in an illustrative rather than a restrictive sense, and all such modifications are intended to be included within the scope of the present teachings. Although any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention, the preferred methods and materials are described herein. Specific and preferred values listed below for individual process parameters, substituents, and ranges are for illustration only; they do not exclude other defined values or other values falling within the preferred defined ranges.

[0059]

[0035] It is to be understood that the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise. It should be emphasized that the term “comprises / comprising” when used in this specification is taken to specify the presence of stated features, integers, steps or components but does not preclude the presence or addition of one or more other features, integers, steps, components or groups thereof.

[0060]

[0036] In the following description, reference is made to the accompanying figures that form a part hereof, in which like reference numerals, if present, identify the same elements between figures.

[0061]

[0037] The term “amine hardener” when used herein without the term “recyclable” preceding it should be taken to mean those conventional aliphatic amine hardeners, similar to, including but not limited to, polyamides, polyether diamines such as Huntsman Jeffamine D230, Jeffamine D-400 poly etheramine, diethylenetriamine (DETA), triethylenetetramine (TETA), tetraethylenepentamine (TEPA) and cycloaliphatic amine hardeners such as isophorone diamine (IPDA), as well as conventional aromatic amine hardeners similar to, including but not limited to, 4,4'-diaminodiphenylmethane (DDM), 4,4'-diaminodiphenyl sulfone (DDS), and m-phenylenediamine (mPDA).

[0062]

[0038] The term “difunctional epoxy” when used herein should be taken to mean conventional diepoxide compounds similar to those containing two oxirane groups in a molecule, such as, including but not limited to, bisphenol A, bisphenol F, bisphenol S and epoxy resins produced from bisphenol-A and epichlorohydrin such as Epotec® YD128.

[0063]

[0039] The term “multifunctional epoxy” as used herein should be taken to mean conventional epoxides having three or more oxirane groups per molecule, similar to and including, but not limited to, tetra-functional epoxy based on methylene dianiline such as Epotec® YDM441, trifunctional epoxy resin based on para-aminophenol such as Epotec® YDM451, trifunctional epoxy resin based on meta-aminophenol such as Epotec® YDM471, phenol novolac based multifunctional epoxy resins such as Epotec® YDPN631, Epotec® YDPN638, Epotec®ABCTL202521000735

[0064] 7

[0065] YDPN661, and trifunctional epoxy resin based on tris-(hydroxyl phenyl) methane such as Epotec® YDM460.

[0066]

[0040] The term “conventional epoxy thermoset” or “traditional epoxy thermoset” herein should be taken to mean those that are prepared from mixing a conventional difunctional or multifunctional epoxy and conventional aliphatic or aromatic amine hardener / curing agent, neither being designed to have labile linkages intended to create a recyclable thermoset.

[0067]

[0041] The term “recyclable amine hardener” herein should be taken to mean those that have specific linkages that permit synthesizing thermosets that can be recycled or degraded. For instance, a recyclable amine hardener that contains an acetal linkage, a ketal linkage, a formal linkage, an orthoester linkage, an orthocarbonate linkage, or a siloxy linkage. The term intends to also include commercially available Recyclamine® hardeners being a class of high-performance amine-based epoxy curing agents used for preparing recyclable thermoset materials. Recyclamine® technology by Aditya Birla Chemicals, is based on specifically engineered curing agents with cleavage points that convert thermosetting epoxies into liquid thermoplastics under specific set of conditions. These cleavage points are reversible at specific conditions and hence enable disintegration of the thermoset matrix.

[0068]

[0042] The term “a recyclable siloxy linkage” when used in context of the recyclable amine hardener should be taken to mean amine hardeners or curing agents comprising a silicon group attached to -O- groups selected from 1 to 4 numbers. The term intends to include commercially available Recyclamine® silane amine hardeners as well.

[0069]

[0043] The term “epoxy thermoset” as used herein should be taken to mean a thermoset prepared by mixing a conventional difunctional or multifunctional epoxy with a conventional amine hardener and a recyclable amine hardener.

[0070]

[0044] The term “fragmentation” in context of the method herein should be taken to mean that the epoxy thermoset is recovered as granules, fragments, pieces, or chunks. This being different from “recycling” where the epoxy thermoset thermoplastic is recovered in solution form.

[0071]

[0045] Definitions of specific functional groups and chemical terms are described in more detail below. The chemical elements are identified in accordance with the Periodic Table of the Elements, CAS version, Handbook of Chemistry and Physics, 75thEd., inside cover, and specific functional groups are generally defined as described therein. Additionally, general principles of organic chemistry, as well as specific functional moieties and reactivity, are described in Thomas Sorrell, Organic Chemistry, University Science Books, Sausalito, 1999; Smith and March, March’s Advanced Organic Chemistry, 5thEdition, John Wiley & Sons, Inc., New York, 2001; Larock, Comprehensive Organic Transformations, VCH Publishers, Inc., New York, 1989; andABCTL202521000735

[0072] 8

[0073] Carruthers, Some Modern Methods of Organic Synthesis, 3rdEdition, Cambridge University Press, Cambridge, 1987.

[0074]

[0046] When a range of values is listed, it is intended to encompass each value and sub-range within the range. For example “Ci-6 alkyl” is intended to encompass, Ci, C2, C3, C4, C5, Ce, C1-6, Ci-5, CM, C1-3, C1-2, C2M„ C2-5, C2-4, C2-3, C3M„ C3-5, C3-4, C4v„ C4-5, and C5-6alkyl.

[0075]

[0047] “Alkyl” refers to a radical of a straight-chain or branched saturated hydrocarbon group having from 1 to 6 carbon atoms (“C1-6 alkyl”), also referred to herein as “lower alkyl”). In some embodiments, an alkyl group has 1 to 5 carbon atoms (“C1-5 alkyl”). In some embodiments, an alkyl group has 1 to 4 carbon atoms (“C1-4 alkyl”). In some embodiments, an alkyl group has 1 to 3 carbon atoms (“C1-3 alkyl”). In some embodiments, an alkyl group has 1 to 2 carbon atoms (“Ci-2 alkyl”). In some embodiments, an alkyl group has 1 carbon atom (“Ci alkyl”). In some embodiments, an alkyl group has 2 to 6 carbon atoms (“C2-6 alkyl”). Examples of C1-6 alkyl groups include methyl (Ci), ethyl (C2), n-propyl (C3), isopropyl (C3), n-butyl (C4), tert-butyl (C4), secbutyl (C4), iso-butyl (C4), n-pentyl (C5), 3-pentanyl (C5), amyl (C5), neopentyl (C5), 3-methyl-2-butanyl (C5), tertiary amyl (C5), and n-hexyl (Ce). Unless otherwise specified, each instance of an alkyl group is independently optionally substituted, i.e., unsubstituted (an “unsubstituted alkyl”) or substituted (a “substituted alkyl”) with one or more substituents; e.g., for instance from 1 to 5 substituents, 1 to 3 substituents, or 1 substituent. Common alkyl abbreviations include Me (-CH3), Et (-CH2CH3), Pr (-CH(CH3)2). AS used herein and throughout the specification, the term “optionally” (e.g., as in “optionally substituted with”) means that the moiety at issue is either substituted or not substituted, and that the substitution occurs only when chemically feasible.

[0076]

[0048] As used herein, “alkylene,” “alkenylene,” and “alkynylene,” refer to a divalent radical of an alkyl, alkenyl, and alkynyl group, respectively. When a range or number of carbons is provided for a particular “alkylene,” “alkenylene,” and “alkynylene” group, it is understood that the range or number refers to the range or number of carbons in the linear carbon divalent chain. “Alkylene,” “alkenylene,” and “alkynylene” groups may be substituted or unsubstituted with one or more substituents as described herein.

[0077]

[0049] “Alkylene” refers to an alkyl group wherein two hydrogens are removed to provide a divalent radical, and which may be substituted or unsubstituted. Unsubstituted alkylene groups include, but are not limited to, methylene (-CH2-), ethylene (-CH2CH2-), propylene (-CH2CH2CH2-), butylene (-CH2CH2CH2CH2-), pentylene (-CH2CH2CH2CH2CH2-), hexylene (-CH2CH2CH2CH2CH2CH2-), and the like. Exemplary substituted alkylene groups, e.g., substituted with one or more alkyl (methyl) groups, include but are not limited to, substituted methylene (-CH(CH3)-, (-C(CH3)2-), substituted ethylene (-CH(CH3)CH2-, -CH2CH(CH3)-, -C(CH3)2CH2-,-ABCTL202521000735

[0078] 9

[0079] CH2C(CH3)2-), substituted propylene (-CH(CH3)CH2CH2-, -CH2CH(CH3)CH2-, -CH2CH2CH(CH3)-, -C(CH3)2CH2CH2-, -CH2C(CH3)2CH2-, -CH2CH2C(CH3)2-), and the like.

[0080]

[0050] “Alkenyl” refers to a radical of a straight-chain or branched hydrocarbon group having from 2 to 20 carbon atoms, one or more carbon-carbon double bonds (e.g., 1, 2, 3, or 4 carboncarbon double bonds), and optionally one or more carbon-carbon triple bonds (e.g., 1, 2, 3, or 4 carbon-carbon triple bonds) (“C2-2o alkenyl”). In certain embodiments, alkenyl does not contain any triple bonds. In some embodiments, an alkenyl group has 2 to 10 carbon atoms (“C2-10 alkenyl”). In some embodiments, an alkenyl group has 2 to 9 carbon atoms (“C2-9 alkenyl”). In some embodiments, an alkenyl group has 2 to 8 carbon atoms (“C2-s alkenyl”). In some embodiments, an alkenyl group has 2 to 7 carbon atoms (“C2-7 alkenyl”). In some embodiments, an alkenyl group has 2 to 6 carbon atoms (“C2-6 alkenyl”). In some embodiments, an alkenyl group has 2 to 5 carbon atoms (“C2-5 alkenyl”). In some embodiments, an alkenyl group has 2 to 4 carbon atoms (“C2-4 alkenyl”). In some embodiments, an alkenyl group has 2 to 3 carbon atoms (“C2-3alkenyl”). In some embodiments, an alkenyl group has 2 carbon atoms (“C2alkenyl”). The one or more carbon-carbon double bonds can be internal (such as in 2-butenyl) or terminal (such as in 1-butenyl). Examples of C2-4 alkenyl groups include ethenyl (C2), 1-propenyl (C3), 2-propenyl (C3), 1-butenyl (C4), 2-butenyl (C4), butadienyl (C4), and the like. Examples of C2-6 alkenyl groups include the aforementioned C2-4 alkenyl groups as well as pentenyl (C5), pentadienyl (C5), hexenyl (Ce), and the like. Additional examples of alkenyl include heptenyl (C7), octenyl (Cs), octatrienyl (Cs), and the like. Unless otherwise specified, each instance of an alkenyl group is independently optionally substituted, z.e., unsubstituted (an “unsubstituted alkenyl”) or substituted (a “substituted alkenyl”) with one or more substituents e.g., for instance from 1 to 5 substituents, 1 to 3 substituents, or 1 substituent. In certain embodiments, the alkenyl group is unsubstituted C2-10 alkenyl. In certain embodiments, the alkenyl group is substituted C2-10 alkenyl.

[0081]

[0051] “Alkenylene” refers to an alkenyl group wherein two hydrogens are removed to provide a divalent radical, and which may be substituted or unsubstituted. Exemplary unsubstituted divalent alkenylene groups include, but are not limited to, ethenylene (-CH=CH-) and propenylene (e.g, -CH=CHCH2-, -CH2-CH=CH-). Exemplary substituted alkenylene groups, e.g., substituted with one or more alkyl (methyl) groups, include but are not limited to, substituted ethylene (-C(CH3)=CH-, -CH=C(CH3)-), substituted propylene (e.g, -C(CH3)=CHCH2-, -CH=C(CH3)CH2-, -CH=CHCH(CH3)-, -CH=CHC(CH3)2-, -CH(CH3)-CH=CH-,-C(CH3)2-CH=CH-, -CH2- C(CH3)=CH-, -CH2-CH=C(CH3)-), and the like.

[0082]

[0052] “Alkynyl” refers to a radical of a straight-chain or branched hydrocarbon group having from 2 to 20 carbon atoms, one or more carbon-carbon triple bonds (e.g., 1, 2, 3, or 4 carbon-ABCTL202521000735

[0083] 10

[0084] carbon triple bonds), and optionally one or more carbon-carbon double bonds (e.g., 1, 2, 3, or 4 carbon-carbon double bonds) (“C2-20 alkynyl”). In certain embodiments, alkynyl does not contain any double bonds. In some embodiments, an alkynyl group has 2 to 10 carbon atoms (“C2-10 alkynyl”). In some embodiments, an alkynyl group has 2 to 9 carbon atoms (“C2-9 alkynyl”). In some embodiments, an alkynyl group has 2 to 8 carbon atoms (“C2-8 alkynyl”). In some embodiments, an alkynyl group has 2 to 7 carbon atoms (“C2-7 alkynyl”). In some embodiments, an alkynyl group has 2 to 6 carbon atoms (“C2-6 alkynyl”). In some embodiments, an alkynyl group has 2 to 5 carbon atoms (“C2-5 alkynyl”). In some embodiments, an alkynyl group has 2 to 4 carbon atoms (“C2-4 alkynyl”). In some embodiments, an alkynyl group has 2 to 3 carbon atoms (“C2-3 alkynyl”). In some embodiments, an alkynyl group has 2 carbon atoms (“C2 alkynyl”). The one or more carbon-carbon triple bonds can be internal (such as in 2-butynyl) or terminal (such as in 1-butynyl). Examples of C2-4 alkynyl groups include, without limitation, ethynyl (C2), 1-propynyl (C3), 2-propynyl (C3), 1-butynyl (C4), 2-butynyl (C4), and the like. Examples of C2-6 alkenyl groups include the aforementioned C2-4 alkynyl groups as well as pentynyl (C5), hexynyl (Ce), and the like. Additional examples of alkynyl include heptynyl (C7), octynyl (Cs), and the like. Unless otherwise specified, each instance of an alkynyl group is independently optionally substituted, z.e., unsubstituted (an “unsubstituted alkynyl”) or substituted (a “substituted alkynyl”) with one or more substituents; e.g., for instance from 1 to 5 substituents, 1 to 3 substituents, or 1 substituent. In certain embodiments, the alkynyl group is unsubstituted C2-10 alkynyl. In certain embodiments, the alkynyl group is substituted C2-10 alkynyl.

[0085]

[0053] “Alkynylene” refers to a linear alkynyl group wherein two hydrogens are removed to provide a divalent radical, and which may be substituted or unsubstituted. Exemplary divalent alkynylene groups include, but are not limited to, substituted or unsubstituted ethynylene, substituted or unsubstituted propynylene, and the like.

[0086]

[0054] “Aryl” refers to a radical of a monocyclic or polycyclic (e.g., bicyclic or tricyclic) 4n+2 aromatic ring system (e.g., having 6, 10, or 1471 electrons shared in a cyclic array) having 6-14 ring carbon atoms and zero heteroatoms provided in the aromatic ring system (“Ce-14 aryl”). In some embodiments, an aryl group has six ring carbon atoms (“Ce aryl”; e.g., phenyl). In some embodiments, an aryl group has ten ring carbon atoms (“C10 aryl”; e.g., naphthyl such as 1-naphthyl and 2-naphthyl). In some embodiments, an aryl group has fourteen ring carbon atoms (“C14 aryl”; e.g., anthracyl). “Aryl” also includes ring systems wherein the aryl ring, as defined above, is fused with one or more carbocyclyl or heterocyclyl groups wherein the radical or point of attachment is on the aryl ring, and in such instances, the number of carbon atoms continue to designate the number of carbon atoms in the aryl ring system. Typical aryl groups include, but areABCTL202521000735

[0087] 11

[0088] not limited to, groups derived from aceanthrylene, acenaphthylene, acephenanthrylene, anthracene, azulene, benzene, chrysene, coronene, fluoranthene, fluorene, hexacene, hexaphene, hexalene, as-indacene, s-indacene, indane, indene, naphthalene, octacene, octaphene, octalene, ovalene, penta-2,4-diene, pentacene, pentalene, pentaphene, perylene, phenalene, phenanthrene, picene, pleiadene, pyrene, pyranthrene, rubicene, triphenylene, and trinaphthalene. Particularly aryl groups include phenyl, naphthyl, indenyl, and tetrahydronaphthyl. Unless otherwise specified, each instance of an aryl group is independently optionally substituted, ie., unsubstituted (an “unsubstituted aryl”) or substituted (a “substituted aryl”) with one or more substituents. In certain embodiments, the aryl group is unsubstituted Ce-14 aryl. In certain embodiments, the aryl group is substituted Ce-i4 aryl.

[0089]

[0055] The term “cycloalkyl” as employed herein includes saturated cyclic, bicyclic, tricyclic, or polycyclic hydrocarbon groups having 3 to 12 carbons. Any ring atom can be substituted (e.g., by one or more substituents). The cycloalkyl groups can contain fused rings. Fused rings are rings that share a common carbon atom. Examples of cycloalkyl moieties include, but are not limited to, cyclopropyl, cyclohexyl, methylcyclohexyl, adamantyl, and norbomyl.

[0090]

[0056] Alkyl, aryl, and cycloalkyl as defined herein, are optionally substituted (e.g., “substituted” or “unsubstituted” alkyl, “substituted” or “unsubstituted” carbocyclyl, group). In general, the term “substituted”, whether preceded by the term “optionally” or not, means that at least one hydrogen present on a group (e.g., a carbon or nitrogen atom) is replaced with a permissible substituent, e.g., a substituent which upon substitution results in a stable compound, e.g., a compound which does not spontaneously undergo transformation such as by rearrangement, cyclization, elimination, or other reaction. Unless otherwise indicated, a “substituted” group has a substituent at one or more substitutable positions of the group, and when more than one position in any given structure is substituted, the substituent is either the same or different at each position. The term “substituted” is contemplated to include substitution with all permissible substituents of organic compounds, any of the substituents described herein that results in the formation of a stable compound. The present invention contemplates any and all such combinations in order to arrive at a stable compound. For purposes of this invention, heteroatoms such as nitrogen may have hydrogen substituents and / or any suitable substituent as described herein which satisfy the valencies of the heteroatoms and results in the formation of a stable moiety.

[0091]

[0057] The present invention aims to provide a faster method of acidic fragmentation of epoxy thermosets or composites thereof, wherein the thermoset comprises at least 5-60 wt. % of a recyclable amine hardener mixed with a conventional amine hardener. According to oneABCTL202521000735

[0092] 12

[0093] embodiment, the present invention is an epoxy thermoset that undergoes rapid acidic fragmentation into granular epoxy fragments, said thermoset comprising:

[0094] a. a difunctional epoxy, a multifunctional epoxy or a combination thereof;

[0095] b. at least one conventional amine hardener of a concentration value in the range of 95 to 40 wt. %; and

[0096] c. at least one recyclable amine hardener of a concentration value in the range of 5 to 60 wt. %, wherein the recyclable hardener comprises a linkage selected from the group consisting of an acetal linkage, a ketal linkage, a formal linkage, an orthoester linkage, an orthocarbonate linkage, and a siloxy linkage,

[0097] wherein the at least one conventional amine hardener and the at least one recyclable amine hardener add up to 100 wt. %.

[0098]

[0058] According to one embodiment of the thermoset, the difunctional epoxy is a conventional diepoxide compound containing two epoxide / oxirane groups per molecule. According to one embodiment of the thermoset, the multifunctional epoxy is a conventional multi-epoxide compound containing three or more epoxide / oxirane groups per molecule. According to one embodiment of the thermoset, the conventional amine hardener is an aliphatic, cycloaliphatic, polyetheramine, polyamide or an aromatic amine hardener. In one embodiment, the epoxy thermoset is prepared to be a composite system. In this regard the thermoset further comprises reinforcement material i.e. fibers etc. that may also be separated after acidic fragmentation. Thermoset composites may contain reinforcements including but not limited glass fiber, carbon fiber, basalt fiber, plastic material, aramid fiber, jute, grass, bamboo, pine, balsa, any other natural or plastic fiber, or a combination thereof.

[0099]

[0059] Incorporation of recyclable amine hardeners having an acid labile linkage selected from the group consisting of an acetal linkage, a ketal linkage, a formal linkage, an orthoester linkage, an orthocarbonate linkage, and a siloxy linkage, with the conventional amine hardener in a traditional difunctional or multifunctional amine based epoxy thermoset or composite enhances acidic degradability of the epoxy thermoset by many folds. The recyclable amine hardeners can facilitate the cleavage of the crosslinking network, thereby enhancing the diffusion of acids into the thermosets / composites many folds faster than the traditional epoxy composite. The traditional amine-based epoxy thermosets undergo very slow degradation through a two-stage mechanism under acidic conditions: i) swelling of epoxy composite by diffusion of acids through its crosslinking network, ii) cracking and degradation of the composite induced by swelling stress and partial cleavage of cross-linking bonds. Whereas in the present thermoset embodiments, incorporating the recyclable amine hardener with conventional hardeners results in unexpectedlyABCTL202521000735

[0100] 13

[0101] faster acidic degradation of the thermoset or composite thereof, via a different dual mechanism of cleavage. The acid cleavable links are first broken, allowing faster acid diffusion through the thermoset followed by more weakening due to cleavage of conventional hardener cross-links which further enables acid diffusion through the weakened cross links, resulting in rapid fragmentation. The resulting epoxy granules or fragments are easy to separate from the acid by mere filtration, for reuse. The cleavage process is mild, fast and does not damage the reinforcement material significantly. Thus, in comparison to thermosets prepared using 100 wt. % conventional amine hardeners, the present thermosets and composites would be amenable to rapid acidic degradation resulting in epoxy fragments that can be recycled. The recyclable hardener is preferably in a concentration below 60 wt. % in the total amine hardener mixture. At beyond 60 wt. %, the fragmentation advantage may be reduced, tending more towards recyclinge. The granular epoxy fragments are obtained in the preferred concentration range of 5-60 wt. % of the recyclable amine hardener.

[0102]

[0060] In one embodiment, epoxy thermosets prepared by mixing one or more of the Recyclamine® hardeners, a conventional hardener and any conventional epoxy (difunctional or multifunctional) are envisioned here. In one embodiment, epoxy thermosets or systems based on a mixture of a conventional hardener, a siloxy linkage based silane Recyclamine® hardener, any other Recyclamine® hardener and a conventional epoxy (difunctional or multifunctional) are envisioned herein. These thermosets are suitable for applications including but not limited to thermoforming, weldable, self-healing, repairable materials etc. The fragmentation method would be applicable for sports, wind, automotive and other composite parts made with Recyclamine® as a thermoset component in combination with reinforcement materials. Cost of the present thermosets would be significantly lower than thermosets comprising 100 wt. % of the Recyclamine® hardeners.

[0103]

[0061] According to one embodiment of the thermoset, the at least one recyclable amine hardener comprising the acetal, ketal or formal linkage is a compound selected from the structures of Formula (2-a) and salts thereof or Formula 3 -a and salts thereof,

[0104]

[0105] Formula 2-a

[0106] wherein:

[0107] Rlais independently selected from the group consisting of optionally substituted Ci-6 alkyl and hydrogen;ABCTL202521000735

[0108] 14

[0109] Rlbis independently selected from the group consisting of optionally substituted Ci-6 alkyl and hydrogen; and

[0110] each of R2Cand R2dis independently selected from the group consisting of optionally substituted Ci-6 alkyl, unsubstituted Ci-6 alkyl and hydrogen;

[0111]

[0112] Formula 3-a

[0113] wherein:

[0114] each of R1and R2is independently selected from the group consisting of hydrogen, alkyl group, cycloalkyl group and aromatic group; or

[0115] R1and R2together with the carbon atom to which they are attached form a cyclic ring;

[0116] each of R3and R4is independently selected from the group consisting of hydrogen, alkyl group, cycloalkyl group and aromatic group; or

[0117] R3and R4together with the carbon atom to which they are attached form a cyclic ring;

[0118] each Raand Rbis independently selected from the group consisting of alkyl group, cycloalkyl group and aromatic group; and

[0119] each m and n is independently an integer ranging from 0 to 20.

[0120]

[0062] In some embodiments, the at least one recyclable amine hardener is preferably selected from the group consisting of the compounds represented by the Formula (2-a-I):

[0121]

[0122] Formula (2-a-I)

[0123]

[0063] In some embodiments, the at least one recyclable amine hardener is preferably selected from the group consisting of the compounds represented by the Formula (2-a-II):

[0124]

[0125] Formula (2-a-II)

[0126]

[0064] In some embodiments, the at least one recyclable amine hardener is preferably selected from the group consisting of the compounds represented by the Formula (2-a-III):ABCTL202521000735

[0127]

[0128] Formula (2-a-III)

[0129]

[0065] In some embodiments, the at least one recyclable amine hardener is preferably selected from the group consisting of the compounds represented by the Formula (3-a-l):

[0130]

[0131] Formula (3-a-l).

[0132] wherein each of R1and R2is independently selected from the group consisting of hydrogen, alkyl, cycloalkyl and aryl; or R1and R2together with the carbon atom to which they are attached form a cyclic ring.

[0133]

[0066] According to one embodiment of the thermoset, the at least one recyclable amine hardener comprising the acetal, ketal or formal linkage is a compound selected from the group consisting of

[0134]

[0135] ABCTL202521000735

[0136]

[0137]

[0067] According to one embodiment of the thermoset, the at least one recyclable amine hardener comprising siloxy linkage is a compound of Formula I-A and salts thereof,

[0138] (R5)f — Si— f-O-W— NH2]

[0139] ' 'q

[0140] Formula (I-A)

[0141] wherein:

[0142] q is 4, 3, 2, or 1;

[0143] t is 0, 1, 2, or 3;

[0144] the sum of q and t is 4;

[0145] each occurrence of W is independently alkylene, cycloalkylene, heterocyclylene, alkenylene, alkynylene, cycloalkenylene, arylene, or heteroarylene; and

[0146] each occurrence of R5is independently hydrogen, alkyl, cycloalkyl, heterocyclyl, alkenyl, alkynyl, cycloalkenyl, aryl, heteroaryl or -ORC, wherein Rcis alkyl, cycloalkyl, heterocyclyl, alkenyl, alkynyl, cycloalkenyl, aryl or heteroaryl.

[0147]

[0068] In some embodiments, the at least one recyclable amine hardener is preferably selected from the group consisting of the compounds represented by Formula (I-A-i) or (I-A-ii), more preferably Formula (I-A-i):ABCTL202521000735

[0148]

[0149] Formula (I-A-ii)

[0150] wherein:

[0151] z is an integer from 1 to 6; each of R4A, R4B, R4C, and R4Dis independently for each occurrence hydrogen or alkyl; and each occurrence of R5Ais independently alkyl (e.g., methyl, ethyl), cycloalkyl, aryl, or -ORC, wherein Rcis alkyl, cycloalkyl, heterocyclyl, alkenyl, alkynyl, cycloalkenyl, aryl or heteroaryl.

[0152]

[0069] In some embodiments, the at least one recyclable amine hardener is preferably selected from the group consisting of the compounds represented by Formula (I-A-iii):

[0153] -iii)

[0154]

[0155] wherein: each of X1, X2, X3, and X4is independently alkylene, cycloalkylene, heterocyclylene, alkenylene, alkynylene, cycloalkenylene, arylene, or heteroarylene.

[0156]

[0070] In some embodiments, the compound of Formula (I-A) is a compound of Formula (I-A-iv)

[0157]

[0158] Formula (I-A-iv)

[0159] wherein:

[0160] z is an integer from 1 to 6; t is an integer from 0 to 1; ql is an integer from 0 to 4; q2 is an integer from 0 to 4; each of R4A, R4B, R4C, and R4Dis independently for each occurrence hydrogen or alkyl; and each occurrence of R5Ais independently alkyl, cycloalkyl, aryl, or -ORC, wherein Rcis alkyl, cycloalkyl, heterocyclyl, alkenyl, alkynyl, cycloalkenyl, aryl or heteroaryl, provided that the sum of / , ql, and q2 is 4.ABCTL202521000735

[0161] 18

[0162]

[0071] According to one embodiment of the thermoset, the at least one recyclable amine hardener comprising siloxy linkage is a compound selected from the group consisting of

[0163]

[0164] ABCTL202521000735

[0165] 19

[0166]

[0167]

[0072] In yet another embodiment, the present invention aims to provide a method of fragmenting the present epoxy thermoset to granular epoxy fragments comprising soaking the epoxy thermoset in an acid at a temperature from about 20°C to 110°C till the thermoset rapidly fragments completely into granular epoxy fragments. In the present method, fragmentation of the epoxy systems results in granular epoxy fragments, which is not the same as recycling or dissolving of epoxy systems as that typically results in thermoplastic solutions. The granular epoxy fragmentsABCTL202521000735

[0168] 20

[0169] obtained at the end of the present method are separated by simple filtration and are suitable for reuse.

[0170]

[0073] In one embodiment of the method, the acid has a concentration in the range of 20-100% and is selected from the group consisting of formic acid, acetic acid, sulfuric acid, methanesulfonic acid, trifluoroacetic acid, trichloroacetic acid, p-toluenesulfonic acid, hydrochloric acid, phosphoric acid, glycolic acid, oxalic acid, lactic acid, citric acid, and a combination thereof. In one embodiment, the acid is about 100% formic acid, about 90% formic acid, about 80% formic acid, about 70% formic acid, about 60% formic acid, about 50% formic acid, about 40% formic acid, about 35% formic acid, about 30% formic acid, about 25% formic acid or about 20% formic acid. In one embodiment, the soaking in acid is carried out at a temperature such as about 20°C, about 30°C, about 40°C, about 50°C, about 60°C, about 70°C, about 80°C, about 90°C, about 100°C or about 110°C. In one embodiment, the acid is about 100% acetic acid, about 80% acetic acid, about 70% acetic acid, about 60% acetic acid, about 50% acetic acid, about 40% acetic acid, about 35% acetic acid, about 30% acetic acid, about 25% acetic acid or about 20% acetic acid. In a preferable embodiment of the method, the acid is 40% to 100% formic acid. In one embodiment of the method, the temperature for fragmentation is 20°C to 100°C.

[0171]

[0074] Fragmentation of the present thermoset can be successfully achieved without the addition of an organic solvent to the acid. In preferred embodiments, the process only requires acid and water. This is a commercial and economic advantage as it operates under conditions that avoid further recovery or disposal of the added solvents. However, this invention would also encompass method embodiments that may optionally use, additionally, other organic solvents, alcohol, and salt. In one embodiment of the method, soaking the epoxy thermoset in the acid optionally involves adding a co-solvent selected from the group consisting of ethylene glycol, ethanol, propylene glycol, propyl alcohol, butyl alcohol, benzyl alcohol, dimethylformamide (DMF), dimethylsulfoxide (DMSO) and a combination thereof.

[0172]

[0075] According to one embodiment the present invention is a method of fragmenting composites to granular epoxy fragments comprising soaking the composite in an acid at a temperature from about 20°C to 110°C till the thermoset rapidly fragments completely into granular epoxy fragments and separates away from the reinforcement material.

[0173]

[0076] According to one embodiment, the invention is a method of preparing the present epoxy thermosets, the steps comprising:

[0174] a. mixing the epoxy, the at least one conventional amine hardener in a concentration value in the range of 95 to 40 wt. %; and the at least one recyclable amine hardener in a concentration value in the range of 5 to 60 wt. % to obtain a mixture;ABCTL202521000735

[0175] 21

[0176] b. pouring the mixture into a mould; and

[0177] c. curing by gradually increasing heat, over a period of time, to not more than about 125°C, and optionally applying a second curing step at a higher temperature from about 125°C to about 180°C, by gradually increasing heat over a period, to obtain the epoxy thermoset.

[0178]

[0077] According to one embodiment, the invention is a method of preparing a composite comprising a reinforcement material and the epoxy thermoset prepared according to the afore method, wherein in step a) the mixture is infused into a reinforcement material followed by application of a wettability improvement method before pouring into the mould and curing.

[0179]

[0078] The following experimental examples are illustrative of the invention but not limitative of the scope thereof:

[0180]

[0079] The examples below test amine hardener mixtures using various types of recyclable amine hardeners obtained from the commercially available Recyclamine® product series. R101, R301, R401, and R501 being non-limiting examples of non-siloxy linkage based recyclable amine hardeners. R802, R804, and R805 being non-limiting examples of siloxy linkage based recyclable amine hardeners. For the amine hardener mixture, where % of the Recyclamine is provided, it is to be understood that the remainder is made up with conventional amine hardener to a total of 100 wt.%.

[0181]

[0080] Example 1A: Fragmentation and weight loss study at 60°C in 80% formic acid of GFRP composites prepared using epoxy thermosets comprising YD128, D230 and R301 or R804

[0182] GFRP composite made from glass fiber sheet and thermoset composed of difunctional conventional epoxy resin YD 128 and 80% conventional amine hardener D230 + 20% recyclable amine hardener R301 (YD128 / D230 / 20%R301) having a size of 17.7cm x 1.5cm x 0.7cm was soaked in 80% formic acid at 60°C. Figure la shows the present fragmentation process of soaking, swelling and then epoxy fraction forming, according to one embodiment. The epoxy fraction may be filtered and reused. Separated glass fiber obtained at the end of the method was dried at 100°C for 4 hrs, to obtain a final product that can also be reused.

[0183]

[0081] Figure lb shows the rate of epoxy fraction yield of GFRP composite composed of YD128 / D230 / 20%R301 when soaked in 80% formic acid at 60°C, according to one embodiment. Figure lb shows the epoxy fraction yield increasing in height from 0.7cm to 1.2cm over 9 hours as the GFRP of 80% D230 / 20% R301 was kept soaking in 80% formic acid at 60°C.

[0184]

[0082] Figure 1c shows the rate of epoxy fraction yield of GFRP composite made from thermoset composed of YD128 and 100% conventional amine hardener D230 when soaked in 80% formic acid at 60°C, according to one embodiment. Figure 1c shows that the epoxy fraction yield did notABCTL202521000735

[0185] 22

[0186] increase significantly over time for 100% D230 after soaking in 80% formic acid at 60°C. It changes from 0.5cm to 0.6cm over 9 hours.

[0187]

[0083] Table 1 below shows weight loss percentage of GFRP composite from epoxy resin systems using YD128 epoxy resin with 20% R301+80% D230 versus YD128 with 100% D230.

[0188] Table 1:

[0189]

[0190]

[0084] Formula for weight loss percentage calculation is as follows:

[0191]

[0192]

[0085] Figure Id shows a graphical representation of the fragmentation rate of GFRP composite from epoxy resin systems using YD128 epoxy resin with 20% R301+80% D230 versus 100% D230. As seen from Figure Id, composites cured with 20% Recyclamine® R301 exhibit significantly higher fragmentation rates compared to those using 100% D230, under identical conditions of soaking in 80% formic acid at 60°C. The weight loss of composites containing 20% Recyclamine® R301 is approximately 2.6 times greater than those using 100% D230. Percentage weight loss increases over time in the thermoset comprising a mix of conventional amine hardener with a recyclable amine hardener. The thermoset comprising 100% conventional amine hardener (D230) shows very slow increase in weight loss over the same period. Thus, incorporating the recyclable amine hardener significantly speeds up fragmentation.

[0193]

[0086] Figure le shows results of GFRP disassembly in 80% formic acid at 60°C at 2.5 hours. GFRP composites were prepared from epoxy resin systems using YD 128 and 100% D230 or 80% D230 with 20% R301 or 80% D230 with 20% R804 or 60% D230 with 40% R804. At 2.5 hours 100% D230 shows poor, almost no, fragmentation whereas rapid disassembly to epoxy pieces was seen in the others (Figure le). On allowing the process to continue for longer, rapid disassembly was observed at 2.5 hours for 40% R804, at 6 hours for 20% R 804 and at 15 hours for 20% R301 (Figure If). D230+40% R804 showed maximum epoxy fragmentation with complete disassembly seen at 2.5 hours (Figure If). Thus, increasing the concentration of the Recyclamine component increased the rate of fragmentation.

[0194]

[0087] Example IB: Fragmentation of epoxy systems at room temperature in 80% formic acid.ABCTL202521000735

[0195] 23

[0196]

[0088] Next epoxy thermoset discs were prepared with YD128 and 80%D230+20%R301, YD128 and 60%D230+40%R301, YD 128 and 80%D230+20%R804, and YD 128 and 60%D230+40%R804 and were tested for fragmentation at room temperature in 80% formic acid for up to 16 hours. The results showed acceleration of breakdown upon addition of Recyclamine® R804 and R301. The % weight loss is shown in Table 2 below. Figure 1g is a graphical representation of the data.

[0197]

[0089] Table 2:

[0198]

[0199] Although addition of R804 demonstrated a faster fragmentation rate compared to R301, both exhibited rapid fragmentation of the epoxy in comparison to the conventional amine hardener 100% D230 system.

[0200]

[0090] Fragmentation experiments for different Recyclamine® cured systems with di- and multifunctional epoxy resin.

[0201]

[0091] Example 2: Multi-functional epoxy based systems

[0202]

[0092] Fragmentation of neat cured YDM441-D230 with 40% of silane Recyclamine® at the end of 6 hours

[0203]

[0093] Mixture of YDM441, a conventional multi-functional epoxy, with 40% R804 + 60% D230 versus mixture of YDM441 with 100% D230 in 80% formic acid at 40°C shows YDM441 when cured with D230 and incorporating 40% R804, exhibits a much faster fragmentation rate than that of a 100% D230 system. Figure 2 shows the fragmentation results at the end of 6 hours for the epoxy thermosets prepared using YDM441. As seen from Figure 2a results, 100% multifunctional epoxy YDM441 + 100% conventional amine hardener based systems are extremely hard to fragment. Whereas the mixture of YDM441 + 40% R804 + 60% D230 shows faster breakdown into fragments in 80% formic acid at 40°C (Figures 2a & 2b). The multifunctional epoxy system (Figure 2b) shows faster fragmentation than a difunctional epoxy system (Figure 2c), under similar conditions.

[0204]

[0094] Example 2.1 YDM441 with R804 : D230 (40:60)

[0205] According to general Method 1 below, the epoxy resin, YDM441; EEW = 110; (Epotec) was used as the epoxy component. The mixture of 40% Recyclamine® R804 AHEW = 51.3 and 60% of D230 (JEFF AMINE) AHEW = 60 was used as amine hardener, then cast and cured. According toABCTL202521000735

[0206] 24

[0207] general Method 3 below, the cured thermoset was soaked in 80% formic acid solution at a temperature of 40°C. This process effectively completely fragmented the thermoset into granules within a duration of 18 hours.

[0208]

[0095] Example 2.2 YDM441 : D230 - Control

[0209] General Method 1 below was followed to prepare the thermoset. The epoxy resin, YDM441; EEW = 110; (Epotec) was used as the epoxy. 100% D230 (JEFF AMINE) AHEW = 60 was used as amine hardener then cast and cured. According to general Method 3 below, the cured thermoset was soaked in 80% formic acid solution at a temperature of 40°C. This process fragmented merely 30 wt. % (70%wt remained neat) of the thermoset into granules within a duration of 48 hours. As seen, the time taken to partially fragment is more than double in absence of the recyclable amine hardener.

[0210]

[0096] Example 3: Di-functional epoxy based systems

[0211]

[0097] Method 1. Preparing epoxy thermoset compositions containing Recyclamine® compounds

[0212]

[0098] General. For comparison, a general-purpose epoxy resin was used for all entries. The mix ratio of hardener, or formulation of hardeners, was determined by balancing the amine hydrogen equivalent weight (or AHEW) with the epoxide equivalent weight (or EEW) of the resin. Typically, the resin and hardener were mixed for 2-5 minutes and then cast and cured as appropriate. For fragmenting experiments, the epoxy composition was cast into tin cup weighing dishes and cured to yield 20 g (8 mm thickness), 10 g (4 mm thickness) or 5 g (2 mm thickness) epoxy thermoset disks. The curing condition used was first at room temperature to 80°C for 25 minutes to 2 hours and then at 125 to 180°C for 2 to 4 hours.

[0213]

[0099] Method 2. Recycling of epoxy products

[0214]

[0100] General. The use of 25-50 wt. % acetic acid or 20-100 wt. % formic acid and optionally heat was one exemplary condition to convert the epoxy compositions with 100% recyclable amine hardener into a thermoplastic polymer liquid (Data not shown).

[0215]

[0101] Method 3. Fragmentation of epoxy products

[0216]

[0102] General. The use of 25-50 wt. % acetic acid or 20-100 wt. % formic acid and optionally heat was one exemplary condition to convert the epoxy compositions of this invention into small fragments and granules of epoxy.

[0217]

[0103] Method 4. Manufacturing of epoxy composite containing Recyclamine® compounds

[0104] For comparison, a general-purpose epoxy composite was used for all entries. The mixture ratio of hardener, or formulation, was determined by balancing the AHEW with the EEW of the resin. First, the glass fiber was cut into size of 20 x 20 cm. The epoxy resin ratio was generallyABCTL202521000735

[0218] 25

[0219] incorporated with fiber as a composite for 50%wt., corresponding to fiber weight. Typically, the resin and hardener were mixed for 5-10 minutes and then infused into the fiber by hand lay-up technique. De-voiding and / or wettability improvement was done by in-house vacuum bagging method for at least 1 hour at ambient temperature. The curing process was conducted after moving the impregnating uncured composite from the vacuum bag to hot oven. The curing profile used was room temperature to 125°C for 6 hours. The fully cured epoxy composite was trimmed with an electrical sawing machine and the remaining dust was cleaned up with acetone before using in fragmentation process.

[0220]

[0105] Below examples test YD128 cured with a mixture of conventional amine hardener (D230) and recyclable non-silane hardeners or silane based hardeners

[0221]

[0106] Fragmentation tested at 60°C

[0222]

[0107] Example 3.1 YD128 with R101 : D230 (40:60)

[0223] Followed general Method 1. The epoxy resin, YD128; EEW = 186; (Epotec) was used as the epoxy component. The mixture of 40% Recyclamine® R101 AHEW = 40.6 and 60% of D230 (JEFF AMINE) AHEW = 60 was used as amine hardener then cast and cured. According to general Method 3, the cured thermoset of thickness 4 mm was soaked in 80% formic acid solution at a temperature of 60°C. This process effectively fragmented the thermoset into smaller fragments within a duration of 9 hours (Figure 5).

[0224]

[0108] Example 3.2 YD128 with R301 : D230 (40:60)

[0225] Followed general Method 1. The epoxy resin, YD128; EEW = 186; (Epotec) was used as the epoxy component. The mixture of 40% Recyclamine® R301 AHEW = 47.6 and 60% of D230 (JEFF AMINE) AHEW = 60 was used as amine hardener then cast and cured. According to general Method 3, the cured thermoset of thickness 4 mm was soaked in 80% formic acid solution at a temperature of 60°C. This process effectively fragmented the thermoset into smaller fragments within a duration of 9 hours (Figure 5).

[0226]

[0109] Example 3.3 YD128 with R401 : D230 (40:60)

[0227] Followed general Method 1. The epoxy resin, YD128; EEW = 186; (Epotec) was used as the epoxy component. The mixture of 40% Recyclamine® R401 AHEW = 54.6 and 60% of D230 (JEFF AMINE) AHEW = 60 was used as amine hardener then cast and cured. According to general Method 3, the cured thermoset of thickness 4 mm was soaked in 80% formic acid solution at a temperature of 60°C. This process effectively fragmented the thermoset into smaller fragments within a duration of 10 hours (Figure 5).

[0228]

[0110] Example 3.4 YD128 with R501 : D230 (40:60)ABCTL202521000735

[0229] 26

[0230] Followed general Method 1. The epoxy resin, YD128; EEW = 186; (Epotec) was used as the epoxy component. The mixture of 40% Recyclamine® R501 AHEW = 54.6 and 60% of D230 (JEFF AMINE) AHEW = 60 was used as amine hardener then cast and cured. According to general Method 3, the cured thermoset of thickness 4 mm was soaked in 80% formic acid solution at a temperature of 60°C. This process effectively fragmented the thermoset into smaller fragments within a duration of 11 hours (Figure 5).

[0231]

[0111] Example 3.5 YD128 with R802 : D230 (40:60)

[0232] Followed general Method 1. The epoxy resin, YD128; EEW = 186; (Epotec) was used as the epoxy component. The mixture of 40% Recyclamine® R802 AHEW = 44.23 and 60% of D230 (JEFF AMINE) AHEW = 60 was used as amine hardener then cast and cured. According to general Method 3, the cured thermoset of thickness 4 mm was soaked in 80% formic acid solution at a temperature of 60°C. This process effectively fragmented the thermoset into smaller fragments within a duration of 9 hours (Figure 5).

[0233]

[0112] Example 3.6 YD128 with R804 : D230 (40:60)

[0234] Followed general Method 1. The epoxy resin, YD128; EEW = 186; (Epotec) was used as the epoxy component. The mixture of 40% Recyclamine® R804 AHEW = 51.3 and 60% of D230 (JEFF AMINE) AHEW = 60 was used as Hardener then cast and cured. According to general Method 3, the cured thermoset of thickness 4 mm was soaked in 80% formic acid solution at a temperature of 60°C. This process effectively fragmented the thermoset into smaller fragments within a duration of 11 hours (Figure 5).

[0235]

[0113] YD128 with 40% R805 showed effective fragmentation within 9 hours (Figure 5; experiment repeated hereinbelow). YD128 with 100% D230, showed longer fragmentation time of 14 hours (Figure 5; experiment repeated hereinbelow). In summary, Figure 5 shows that incorporating recyclable amine hardeners significantly reduced fragmentation time to about 9 hours, on average, in comparison to the thermoset with 100% D230 which took up to 14 hours. In other words, incorporation of 40% Recyclamine reduced fragmentation time by up to about 36%. Figure 7 shows the appearance of the epoxy thermosets of Figure 5 after undergoing fragmentation.

[0236]

[0114] Example 3.7 YD128 with R805 : D230 (10:90)

[0237] Followed general Method 1. The epoxy resin, YD128; EEW = 186; (Epotec) was used as the epoxy component. The mixture of 10% Recyclamine® R805 AHEW = 51.3 and 80% of D230 (JEFF AMINE) AHEW = 60 was used as amine hardener then cast and cured. According to general Method 3, the cured thermoset of thickness 4 mm was soaked in 80% formic acid solution at a temperature of 60°C. This process effectively fragmented the thermoset into smaller fragments within a duration of 12 hours (Figure 4).ABCTL202521000735

[0238] 27

[0239]

[0115] Example 3.8 YD128 with R805 : D230 (20:80)

[0240] Followed general Method 1. The epoxy resin, YD128; EEW = 186; (Epotec) was used as the epoxy component. The mixture of 20% Recyclamine® R805 AHEW = 51.3 and 80% of D230 (JEFF AMINE) AHEW = 60 was used as amine hardener then cast and cured. According to general Method 3, the cured thermoset of thickness 4 mm was soaked in 80% formic acid solution at a temperature of 60°C. This process effectively fragmented the thermoset into smaller fragments within a duration of 11 hours (Figure 4).

[0241]

[0116] Example 3.9 YD128 with R805 : D230 (40:60)

[0242] Followed general Method 1. The epoxy resin, YD128; EEW = 186; (Epotec) was used as the epoxy component. The mixture of 40% Recyclamine® R805 AHEW = 51.3 and 60% of D230 (JEFF AMINE) AHEW = 60 was used as amine hardener then cast and cured. According to general Method 3, the cured thermoset of thickness 4 mm was soaked in 80% formic acid solution at a temperature of 60°C. This process effectively fragmented the thermoset into smaller fragments within a duration of 9 hours (Figure 4). Figures 5 and 7 also show data repeating these parameters.

[0243]

[0117] Example 3.10 YD128 with R805 : D230 (50:50)

[0244] Followed general Method 1. The epoxy resin, YD128; EEW = 186; (Epotec) was used as the epoxy component. The mixture of 50% Recyclamine® R805 AHEW = 51.3 and 60% of D230 (JEFF AMINE) AHEW = 60 was used as amine hardener then cast and cured. According to general Method 3, the cured thermoset of thickness 4 mm was soaked in 80% formic acid solution at a temperature of 60°C. This process effectively fragmented the thermoset into smaller fragments within a duration of 7 hours (Figure 4).

[0245]

[0118] Example 3.11 YD128 with D230 - Control

[0246]

[0119] Followed general Method 1. The epoxy resin, YD128; EEW = 186; (Epotec) was used as the epoxy component. D230 AHEW = 60 was used as amine hardener then cast and cured, the cured thermoset of thickness 4 mm was soaked in 80% formic acid solution at a temperature of 60°C. This process effectively fragmented the thermoset into smaller fragments within a duration of 13 hours (Figure 4). Figures 5 and 7 also show data repeating these parameters.

[0247]

[0120] In summary, Figure 4 shows that incorporating recyclable amine hardeners significantly reduced fragmentation time in comparison to the thermoset with 100% D230, and ineffectively so. There is a steady decrease in fragmentation time with increase in the % of recyclable amine hardener in the thermoset system. Figure 6 shows the appearance of the neat-cured epoxy thermosets as described in Figure 4 after undergoing fragmentation. 100% R805 is also shown in Figure 6 as a liquid thermoplastic solution.

[0248]

[0121] Example 3.12 YD128 with R805: D230 (80:20)ABCTL202521000735

[0249] 28

[0250] Followed general Method 1. The epoxy resin, YD128; EEW = 128; (Epotec) was used as the epoxy. The mixture of 80% Recyclamine® R805 AHEW = 51.3 and 20% of D230 AEW = 60: (JEFF AMINE) was used as amine hardener then cast and cured. Tg of the neat cured thermoset is 116 °C. According to general Method 3, the cured thermoset was soaked in 50% acetic acid solution at a temperature of 95°C. This process effectively fragmented the thermoset into big piece of fragments within a duration of 24 hours.

[0251]

[0122] Fragmentation tested at room temperature (rt)

[0252]

[0123] Example 3.13 YD128 with R101 : D230 (40:60)

[0253] Followed general Method 1. The epoxy resin, YD128; EEW = 186; (Epotec) was used as the epoxy component. The mixture of 40% Recyclamine® R101 AHEW = 40.6 and 60% of D230 (JEFF AMINE) AHEW = 60 was used as amine hardener then cast and cured. According to general Method 3, the cured thermoset of thickness 2 mm was soaked in 80% formic acid solution at a room temperature. This process effectively completely fragmented the thermoset into smaller fragments within a duration of 17 hours (Figure 8).

[0254]

[0124] Example 3.14 YD128 with R301 : D230 (40:60)

[0255] Followed general Method 1. The epoxy resin, YD128; EEW = 186; (Epotec) was used as the epoxy component. The mixture of 40% Recyclamine® R301 AHEW = 47.6 and 60% of D230 (JEFF AMINE) AHEW = 60 was used as amine hardener then cast and cured. According to general Method 3, the cured thermoset of thickness 2 mm was soaked in 80% formic acid solution at a room temperature. This process effectively completely fragmented the thermoset into smaller fragments within a duration of 16 hours (Figure 8).

[0256]

[0125] Example 3.15 YD128 with R401 : D230 (40:60)

[0257] Followed general Method 1. The epoxy resin, YD128; EEW = 186; (Epotec) was used as the epoxy. The mixture of 40% Recyclamine® R401 AHEW = 54.6 and 60% of D230 (JEFF AMINE) AHEW = 60 was used as amine hardener then cast and cured. According to general Method 3, the cured thermoset of thickness 2 mm was soaked in 80% formic acid solution at a room temperature. This process effectively completely fragmented the thermoset into smaller fragments within a duration of 19 hours (Figure 8).

[0258]

[0126] Example 3.16 YD128 with R501 : D230 (40:60)

[0259] Followed general Method 1. The epoxy resin, YD128; EEW = 186; (Epotec) was used as the epoxy. The mixture of 40% Recyclamine® R501 AHEW = 54.6 and 60% of D230 (JEFF AMINE) AHEW = 60 was used as amine hardener then cast and cured. According to general Method 3, the cured thermoset of thickness 2 mm was soaked in 80% formic acid solution at a room temperature.ABCTL202521000735

[0260] 29

[0261] This process effectively completely fragmented the thermoset into smaller fragments within a duration of 20 hours (Figure 8).

[0262]

[0127] Example 3.17 YD128 with R802 : D230 (40:60)

[0263] Followed general Method 1. The epoxy resin, YD128; EEW = 186; (Epotec) was used as the epoxy. The mixture of 40% Recyclamine® R802 AHEW = 44.23 and 60% of D230 (JEFF AMINE) AHEW = 60 was used as amine hardener then cast and cured. According to general Method 3, the cured thermoset of thickness 2 mm was soaked in 80% formic acid solution at a room temperature. This process effectively completely fragmented the thermoset into smaller fragments within a duration of 11 hours (Figure 8).

[0264]

[0128] Example 3.18 YD128 with R804 : D230 (40:60)

[0265] Followed general Method 1. The epoxy resin, YD128; EEW = 186; (Epotec) was used as the epoxy. The mixture of 40% Recyclamine® R804 AHEW = 51.3 and 60% of D230 (JEFF AMINE) AHEW = 60 was used as amine hardener then cast and cured. According to general Method 3, the cured thermoset of thickness 2 mm was soaked in 80% formic acid solution at a room temperature. This process effectively completely fragmented the thermoset into smaller fragments within a duration of 18 hours (Figure 8).

[0266]

[0129] Example 3.19 YD128 with R805 : D230 (40:60)

[0267] Followed general Method 1. The epoxy resin, YD128; EEW = 186; (Epotec) was used as the epoxy. The mixture of 40% Recyclamine® R805 AHEW = 51.3 and 60% of D230 (JEFF AMINE) AHEW = 60 was used as amine hardener then cast and cured. According to general Method 3, the cured thermoset of thickness 2 mm was soaked in 80% formic acid solution at a room temperature. This process effectively completely fragmented the thermoset into smaller fragments within a duration of 15 hours (Figure 8).

[0268]

[0130] Example 3.20 YD128 with D230 - Control

[0269] Followed general Method 1. The epoxy resin, YD128; EEW = 186; (Epotec) was used as the epoxy. D230 AHEW = 60 was used as amine hardener then cast and cured, the cured thermoset of thickness 2 mm was soaked in 80% formic acid solution at a room temperature. This process effectively fragmented the thermoset into smaller fragments within a duration of 23 hours (Figure 8).

[0270]

[0131] Figure 9 shows the appearance of fragmentation of the epoxy thermosets as described in Figure 8 in 80% formic acid at room temperature. Although tested for room temperature degradation, this would not be the preferred temperature from a commercial stand point. Solvolysis at higher temperature (above atmospheric condition) may be more desirable. The present method may use 60°C to 80°C as a moderate temperature condition for degradation. At 60°C, theABCTL202521000735

[0271] 30

[0272] degradation is faster, safer for operation due to less acid vapor exposure as the condition is at a much lower temperature than the boiling point of formic acid (or higher acids).

[0273]

[0132] Example 4: The degradation of multifunctional or di-functional epoxy with 100% conventional amine hardener D230 in acetic acid

[0274] Experiments were conducted with 100% conventional amine hardener as a control. Acetic acid degradation of thermoset made from 100% conventional amine hardener and 100% conventional difunctional epoxy resin YD128 showed no noticeable degradation. After soaking for 3 months in 25% acetic acid the piece of thermoset showed no degradation (Figure 3a). Degradation of thermoset made of 100% conventional amine hardener and 100% multifunctional epoxy YDM441 over 3 months in 25% acetic acid is also very poor (Figure 3b).

[0275]

[0133] Example 5: Degradation data using one or more Recyclamines®

[0276] Table 3 below shows successful degradation data of Recyclamines® blends when combined with conventional multifunctional epoxies such as YDM441 and YDPN638.

[0277] Table 3:

[0278]

[0279]

[0134] Example 6: Tg experiments of present thermoset blends, according to some embodiments

[0280] Various embodiments of the instant blends were tested to identify their Tg values. As seen from Tables 4 below, each blend has a distinct Tg value, different from that of 100% D230, but sufficiently close that the blend would be suitable for use in similar applications (Table 4a). The Tg values of thermosets prepared using 100% Recyclamine® are generally higher (Table 4b), as expected.

[0281] Table 4a:ABCTL202521000735

[0282]

[0283] Table 4b:

[0284]

[0285]

[0135] In summary, 100% conventional amine hardener composites with difunctional or multifunctional epoxies undergo very slow acidic fragmentation, over several days. Incorporation of 5-60 wt.% recyclable amine hardeners such as Recyclamines® along with commercial amine hardeners significantly speeds up the breakdown into fragments.

[0286]

[0136] The following description is not to be taken in a limiting sense and the scope of the illustrative embodiments are defined only by the claims accompanying the complete specification.

Claims

ABCTL2025210007351Claims:

1. An epoxy thermoset that undergoes rapid acidic fragmentation into granular epoxy fragments, said thermoset comprising:a. a difunctional epoxy, a multifunctional epoxy or a combination thereof;b. at least one conventional amine hardener of a concentration value in the range of 95 to 40 wt. %; andc. at least one recyclable amine hardener of a concentration value in the range of 5 to 60 wt. %, wherein the recyclable hardener comprises a linkage selected from the group consisting of an acetal linkage, a ketal linkage, a formal linkage, an orthoester linkage, an orthocarbonate linkage, and a siloxy linkage,wherein the at least one conventional amine hardener and the at least one recyclable amine hardener add up to 100 wt. %.

2. The thermoset as claimed in claim 1, wherein the difunctional epoxy is a conventional diepoxide compound containing two epoxide / oxirane groups per molecule.

3. The thermoset as claimed in claim 1, wherein the multifunctional epoxy is a conventional multi-epoxide compound containing three or more epoxide / oxirane groups per molecule.

4. The thermoset as claimed in claim 1, wherein the conventional amine hardener is an aliphatic, cycloaliphatic, polyetheramine, polyamide or an aromatic amine hardener.

5. The thermoset as claimed in claim 1, wherein the at least one recyclable amine hardener comprising the acetal, ketal or formal linkage is a compound of Formula (2-a) and salts thereof or Formula 3 -a and salts thereof,Formula 2-awherein:Rlais independently selected from the group consisting of optionally substituted Ci-6 alkyl and hydrogen;Rlbis independently selected from the group consisting of optionally substituted Ci-6 alkyl and hydrogen; andeach of R2cand R2dis independently selected from the group consisting of optionally substituted Ci-6 alkyl, unsubstituted Ci-6 alkyl and hydrogen;ABCTL202521000735Formula 3-awherein:each of R1and R2is independently selected from the group consisting of hydrogen, alkyl group, cycloalkyl group and aromatic group; orR1and R2together with the carbon atom to which they are attached form a cyclic ring; each of R3and R4is independently selected from the group consisting of hydrogen, alkyl group, cycloalkyl group and aromatic group; orR3and R4together with the carbon atom to which they are attached form a cyclic ring; each Raand Rbis independently selected from the group consisting of alkyl group, cycloalkyl group and aromatic group; andeach m and n is independently an integer ranging from 0 to 20.

6. The thermoset as claimed in claim 1 or 5, wherein the at least one recyclable amine hardener comprising the acetal, ketal or formal linkage is a compound selected from the group consisting ofABCTL20252100073537. The thermoset as claimed in claim 1, wherein the at least one recyclable amine hardener comprising the siloxy linkage is a compound of Formula I-A and salts thereof,Formula (I-A)wherein:q is 4, 3, 2, or 1;t is 0, 1, 2, or 3;the sum of q and t is 4;each occurrence of W is independently alkylene, cycloalkylene, heterocyclylene, alkenylene, alkynylene, cycloalkenylene, arylene, or heteroarylene; andeach occurrence of R5is independently hydrogen, alkyl, cycloalkyl, heterocyclyl, alkenyl, alkynyl, cycloalkenyl, aryl, heteroaryl or -ORC, wherein Rcis alkyl, cycloalkyl, heterocyclyl, alkenyl, alkynyl, cycloalkenyl, aryl or heteroaryl.ABCTL20252100073548. The thermoset as claimed in claim 1 or 7, wherein the at least one recyclable amine hardener comprising the siloxy linkage is a compound selected from the group consisting ofABCTL2025210007359. A composite comprising the epoxy thermoset as claimed in claim 1 and a reinforcement material, wherein the composite undergoes rapid acidic fragmentation to yield granular epoxy fragments separated from the reinforcement material.

10. A method of fragmenting the epoxy thermoset as claimed in claim 1 to granular epoxy fragments comprising soaking the epoxy thermoset in an acid at a temperature from about 20 °C to 110 °C till the thermoset rapidly fragments into granular epoxy fragments.

11. A method of fragmenting the composite as claimed in claim 9 to granular epoxy fragments and the reinforcement material comprising soaking the composite in an acid at a temperature from about 20 °C to 110°C till the thermoset rapidly fragments into granular epoxy fragments and separates away from the reinforcement material.ABCTL202521000735612. The method as claimed in claims 10 or 11, wherein the acid has a concentration in the range of 20-100% and is selected from the group consisting of formic acid, acetic acid, sulfuric acid, methanesulfonic acid, trifluoroacetic acid, trichloroacetic acid, p-toluenesulfonic acid, hydrochloric acid, phosphoric acid, glycolic acid, oxalic acid, lactic acid, citric acid, and a combination thereof.

13. The method as claimed in claims 10 or 11, wherein soaking the epoxy thermoset in the acid involves optionally adding a co-solvent selected from the group consisting of ethylene glycol, ethanol, propylene glycol, propyl alcohol, butyl alcohol, benzyl alcohol, dimethylformamide, dimethyl sulfoxide and a combination thereof.

14. The method as claimed in claims 10 or 11, wherein the acid is 40% to 100% formic acid and the temperature is 20°C to 80°C.

15. A method of preparing the epoxy thermoset as claimed in claim 1, the steps comprising:a. mixing the epoxy, the at least one conventional amine hardener in the concentration value in the range of 95 to 40 wt. %; and the at least one recyclable amine hardener in the concentration value in the range of 5 to 60 wt. % to obtain a mixture;b. pouring the mixture into a mould; andc. curing by gradually increasing temperature to not more than about 125°C, and optionally applying a second curing step at a higher temperature from about 125°C to about 180°C, by gradually increasing heat, to obtain the epoxy thermoset.

16. A method of preparing a composite comprising a reinforcement material and the epoxy thermoset prepared according to the method as claimed in claim 15, wherein in step a) the mixture is infused into the reinforcement material followed by application of a wettability improvement method before pouring into the mould and curing.

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