Thermoset resin containing ion cleavable disiloxane

Abstract

A thermoset resin including a plurality of crosslinked ion cleavable disiloxane units incorporated therein from a disiloxane monomer. The thermoset resin is polyester, vinyl ester, polyurethane epoxy, polyurea, rubber, a crosslinked thermoplastic, or a combination thereof. The plurality of crosslinked ion cleavable disiloxane units arc cleavable by a fluoride ion. A composite material including a cured matrix formed of the thermoset resin and a plurality of reinforcing fiber embedded therein. The reinforcing fibers being glass, carbon, aramid, natural, basalt, boron, silicon carbide, polymer, or a combination thereof. The composite material being entirely recyclable. A process for recycling the composite material includes adding the composite material to solvent in a container; introducing fluoride ions to solvent in the container; and maintaining under conditions to dissolve the matrix material and to free more than 95% by weight of the reinforcing fibers from the matrix material.

Description

Docket No.: CSP-0379PCT THERMOSET RESIN CONTAINING ION CLEAVABLE DISILOXANE RELATED APPLICATIONS

[0001] This application claims priority benefit of U.S. Provisional Application Serial Number 63 / 443,112 filed 3 February 2023; the contents of which are hereby incorporated by reference. FIELD OF THE INVENTION

[0002] The present invention in general relates to composite materials such as sheet molding compounds and in particular to an ion cleavable thermoset resin that is easily recyclable to reclaim reinforcing fiber therefrom. BACKGROUND OF THE INVENTION

[0003] The use of composite materials including fiber reinforced composites has continued to increase in recent years in applications such as vehicle components, building materials, and industrial equipment. With the increased use of composite materials, the need for recycling of discarded composite has become more acute to keep the composite based materials from being discarded in landfills, and to conserve resources that are used to form these composites. In general, thermoplastic polymers such as polyethylene and polypropylene may be recycled through remelt processing. However, for thermosetting composites such as fiber reinforced composites (FRCs), melt recycling is difficult because of the cross-linked nature of the resin. That is, the same properties that make thermosets robust and suitable for structural applications render them extremely difficult to recycle efficiently.

[0004] Current thermoset polymer composite recycling techniques include either mechanically, thermally, or chemically treating the composite material. These techniques are characterized byDocket No.: CSP-0379PCT high energy input, harsh chemicals (many with toxic VOCs), and / or expensive capital equipment. Furthermore, the recycled products tend to be of low quality owing to factors such as retention of residual resin and fiber damage associated with the process. Recycling of thermoset resins would be promoted if theoretically high value carbon fiber could be recovered therefrom.

[0005] A recycling method that has been tried to recycle FRC based materials is solvolysis that employs reactive solvents such as benzyl alcohol, diethylene glycol, diethylene glycol monomethyl ether in the presence of a catalyst under an inert atmosphere and elevated temperatures to break down ester bonds in polyester thermoset resins, while effectively keeping the properties of the reinforcing fibers. While this method proved effective in separating resin from glass fiber, the resulting glass fibers were damaged in the process, and the cost of solvents, and reaction times rendered the process impractical. (H. Fukuzawa et al., 2ndIntl. Symp. On Feedstock Recycling of Plastics and Other Innovative Plastics Recycling Techniques, Ostend, BE, Sept. 8-11, 2002.

[0006] Other techniques to recycle FRCs were able to solubilize epoxy resin matrices containing carbon fibers or glass fibers using poly(ethylene glycols) in a sodium hydroxide solution. The carbon fibers and non-alkali fibers recovered after matrix solvolysis retained more than 94% of their original strength; however, the method has met with limited acceptance owing to the specificity of the chemistry towards epoxy matrices and a low overall recycle efficiency. P Yang et al. J. Reinforced Plastics and Composites; 2014, 33(22): 2106-2114.

[0007] Aminolysis of FRCs is attractive in yielding carbon fibers with 97% purity. Vallee, M.; Tersac, G.; Destais-Orvoen, N.; Durand, G. “Chemical Recycling of Class Surface Quality Sheet-Molding Composites” Ind. Eng. Chem. Res., 43, 6317-6324 (2004). The method involves an elevated temperature solvent digestion in excess of ethanolamine in the presence of catalystsDocket No.: CSP-0379PCT such as glacial acetic acid, sodium acetate or potassium sulfate; followed by washing the recovered carbon fibers in a boiling solvent such as methyl ethyl ketone (MEK), sonication and drying. While the aminolysis process is somewhat effective, the method has met with limited acceptance owing to the long process times up to 48 h, as well as the cost and toxicity of the solvents.

[0008] Further processes have been developed to reclaim carbon fiber from a cured thermoset matrix, in which thermoset is added to a polyol solvent composition under conditions to free more than 95% by weight of the carbon fiber from the particles using low cost and low toxicity solvents; however, such processes still rely on techniques such as solvent pre-swell of the particles, size reduction, microwave heating, and sonication to promote thermoset matrix digestion to free reinforcing carbon fibers

[0009] While fluoride cleave of other polymeric materials has been previously explored in mixed organic-inorganic systems, the hydrophobic nature of the additives to thermoset resins, including strengthening fibers dispersed therein and the hydrophobicity of the resulting cured articles has previously disfavored application of this chemistry to thermoset resins. (Krug. et al.)

[0010] Thus, there exists a need for a thermoset resin that is more easily recyclable and for a more efficient recycling process for breaking down a thermoset resin matrix to reclaim a high percentage of reinforcing fibers therefrom, the fibers so recovered being suitable for subsequent reuse. SUMMARY OF THE PRESENT INVENTION

[0011] The present invention provides a thermoset resin that includes a plurality of crosslinked ion cleavable disiloxane units incorporated therein from a disiloxane monomer. The thermosetDocket No.: CSP-0379PCT resin is polyester, vinyl ester, polyurethane epoxy, polyurea, rubber, a crosslinked thermoplastic, or a combination thereof. The plurality of crosslinked ion cleavable disiloxane units are cleavable by a fluoride ion.

[0012] The present invention additionally provides a composite material including a cured matrix formed of the inventive thermoset resin and a plurality of reinforcing fiber embedded therein. The reinforcing fibers being glass fibers, carbon fibers, aramid fibers, all natural fibers, basalt fibers, boron fibers, silicon carbide fibers, polymer fibers, or a combination thereof. The composite material being entirely recyclable.

[0013] The present invention additionally provides a process for recycling the inventive composite material, the process including adding the composite material to solvent in a container; introducing fluoride ions to solvent in the container; and maintaining the composite material, the solvent, and the fluoride ions in the container under conditions for a period of time to dissolve the matrix material and to free more than 95% by weight of the reinforcing fibers from the matrix material to form free reinforcing fibers. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The present invention is further detailed with respect to the following drawings. These drawings are intended to illustrate various aspects of the present invention, and not be a limitation on the practice thereof.

[0015] FIG. 1 shows traditional styrene crosslinked unsaturated polyester;

[0016] FIG. 2 shows a styrene monomer replaced with a divinylsiloxane crosslinker to provide a crosslinked unsaturated polyester that easily de-crosslinks in the presence of fluoride ion (F-) at room temperature according to embodiments of the present invention;Docket No.: CSP-0379PCT

[0017] FIG. 3 shows a reaction incorporating a cleavable silicon functionality into a thermoset monomer according to embodiments of the present invention;

[0018] FIGS. 4A and 4B show depictions of conventional epoxy-amine materials;

[0019] FIGS. 5A-5D depict the inventive recycling method according to embodiments of the present invention;

[0020] FIGS. 6A-6D depict the inventive recycling method according to embodiments of the present invention;

[0021] FIG. 7A is a graph showing water contact angle versus number of wear cycles for prime coatings at various cure temperatures;

[0022] FIG. 7B is a graph showing water contact angle versus number of wear cycles for recycled (0.01 M TBAF / THF) silicone resin coatings cured at various cure temperatures;

[0023] FIG. 7C is a graph showing water contact angle versus number of wear cycles for varied [F−] to recycle silicone resins cured at 250 °C;

[0024] FIG. 7D shows a silicone recycling loop according to embodiments of the present invention;

[0025] FIGS. 8A-8D are SEM-EDS images with inset WCA photos of silicone resin coatings cured at 250 °C after 200 wear cycles and cross-hatch tape adhesion tests for prime and recycled coatings with wear micrograph magnification 100×, scale bar 300 μm, cross-hatch magnification 35×, scale bar 800 μm, EDS map: yellow = Si, blue = A;

[0026] FIGS. 8E-8H are SEM-EDS images with inset WCA photos of silicone resin coatings cured at 250 °C after 200 wear cycles and cross-hatch tape adhesion tests for 0.002 M TBAF with wear micrograph magnification 100×, scale bar 300 μm, cross-hatch magnification 35×, scale bar 800 μm, EDS map: yellow = Si, blue = A;Docket No.: CSP-0379PCT

[0027] FIGS. 8I-8L are SEM-EDS images with inset WCA photos of silicone resin coatings cured at 250 °C after 200 wear cycles and cross-hatch tape adhesion tests for 0.01 M TBAF with wear micrograph magnification 100×, scale bar 300 μm, cross-hatch magnification 35×, scale bar 800 μm, EDS map: yellow = Si, blue = A;

[0028] FIGS. 8M-8P are SEM-EDS images with inset WCA photos of silicone resin coatings cured at 250 °C after 200 wear cycles and cross-hatch tape adhesion tests for ) 0.010.1 M TBAF with wear micrograph magnification 100×, scale bar 300 μm, cross-hatch magnification 35×, scale bar 800 μm, EDS map: yellow = Si, blue = A;

[0029] FIG. 9A is a graph showing typical TGA in air of prime and recycled (0.01 M TBAF) silicone resins cured at different temperatures with comparison of thermal stabilities defined as temperature at 5% mass loss, Td5%, and the error corresponds to the standard deviation of three experiments for each resin iteration;

[0030] FIG. 9B is a graph showing typical TGA in air of 250 °C cured prime and recycled silicone resins at different TBAF concentrations with comparison of thermal stabilities defined as temperature at 5% mass loss, Td5%, and the error corresponds to the standard deviation of three experiments for each resin iteration;

[0031] FIG. 10A shows a GC-MS of prime silicone resin cured at 150 °C and tested at 150−200 °C to determine the volatile content at different cure temperatures;

[0032] FIG. 10B shows a GC-MS of prime silicone resin cured at 200 °C and tested at 200− 250 °C to determine the volatile content at different cure temperatures;

[0033] FIG. 11A is a graph showing water contact angle versus number of wear cycles for prime and recycles SILRES REN 50 coatings cured at 250 C;Docket No.: CSP-0379PCT

[0034] FIG. 11B is a graph showing typical TGA in air for prime and recycled SILRES REN 50 cured at 250 C;

[0035] FIGS. 11C- 11E are SEM images of prime coating after 0 wear cycles, 200 wear cycles, and tape adhesion test;

[0036] FIGS. 11F-11H are SEM images of recycled coating after 0 wear cycles, 200 wear cycles, and tape adhesion test;

[0037] FIGS. 11I and 11J are EDS map (magnification 27×, scale bar 1000 μm) of prime coating before and after rubbing half with 0.01 M TBAF solution;

[0038] FIG. 12A shows the chemical structures of siloxanes denoted as Es and As;

[0039] FIG. 12B depicts casts of siloxane combinations;

[0040] FIG. 13A is a graph showing TGA plots for the samples of FIG. 12B;

[0041] FIG. 13B is a graph showing TGA plots of FIG. 13A and two additional siloxane combinations;

[0042] FIGS. 14A-14D depict the inventive recycling method according to another embodiment of the present invention;

[0043] FIG. 15 is a schematic showing an unsaturated polyester (UPE) resin monomer containing a clipable crosslinker and a reaction schematic for synthesis thereof; and

[0044] FIG. 16 is a schematic of a batch reactor in which an inventive process is practiced. DESCRIPTION OF THE INVENTION

[0045] The present invention has utility as an ion cleavable thermoset resin that is formable into a thermoset composite material that is easily recyclable and from which reinforcing fibers are easily reclaimed. The present invention has additional utility as an energy efficient, cost effective, and environmentally friendly recycling process for breaking down a thermoset resinDocket No.: CSP-0379PCT matrix to reclaim a high percentage of reinforcing fibers therefrom that are suitable for subsequent reuse. The recovered fibers retaining the majority of the strengthening properties of like fibers in virgin form. Notably, the inventive process takes place at ambient temperature in a suitable solvent, such as Tetrahydrofuran (THF). The present invention is applicable to all thermosets to which a cleaveable siloxane bond may be introduced, including but not limited to polyester, vinyl ester, polyurethane or epoxy matrices; polyurea; and rubber; as well as crosslinked thermoplastics, i.e. thermoplastics copolymerized with units of unsaturation allowing for crosslinking such as crosslinked polystyrene, crosslinked polyethylene (XPE), thermoplastic elastomers, etc.. The present invention is capable of reclaiming a multitude of reinforcing fibers from a matrix formed of any of the aforementioned thermoset resins. For example, the inventive process is able to reclaim reinforcing fibers including glass fibers, carbon fibers, aramid fibers, all natural fibers, basalt fibers, boron fibers, silicon carbide fibers, and polymer fibers such as polyester (PER, PBT, PCDT), polyolefin (PE, PP), Polyvinyl derivatives (PVC, PVA, polyacrylonitrile), and polyurethane.

[0046] While the prior art has attempted to cleave a thermoset cured matrix to create reactive monomers and oligomers therefrom, the present invention is optimized for reclamation of reinforcing fiber from such a matrix. The reinforcing fiber as an inert inclusion in a thermoset matrix is considerably easier to reclaim in reusable form compared to matrix precursors. Additionally, with carbon fiber having a cost of approximately US$22 per kilogram, there is an economical and environmental motivation to preclude such fibers from being discarded.

[0047] In certain embodiments of the present invention, the cost of materials and processing to reclaim reinforcing fibers is less than the cost of new reinforcing fiber upon consideration of the disposal cost of the spent thermoset article containing the reinforcing fiber. It is appreciated thatDocket No.: CSP-0379PCT use of certain solvents and catalysts, while effective to break covalent bonds in a thermoset matrix having inherent costs, handling hazards, or disposal costs that render the resulting process a mere academic curiosity. Exemplary of such processes are those detailed in the prior art. While processing time and energy inputs are factors in the efficiency of the inventive process, it has been found that an ambient temperature process amenable to being performed in an aqueous solution is viable for industrial scale reinforcing fiber reclamation.

[0048] It is to be understood that in instances where a range of values are provided that the range is intended to encompass not only the end point values of the range but also intermediate values of the range as explicitly being included within the range and varying by the last significant figure of the range. By way of example, a recited range of from 1 to 4 is intended to include 1-2, 1-3, 2-4, 3-4, and 1-4.

[0049] It has been surprisingly found that incorporating siloxane bonds into thermoset monomers prior to forming thermoset composite materials affords a robust yet facile bond. This bond allows for easy recycling of cured thermoset composite materials by de-crosslinking of thermoset polymers at room temperature without the need for sophisticated equipment or harmful chemicals. Notably, there are several ions that can cleave (and subsequently rearrange) Si-O-Si bonds such as X=Cl, Br, or I in AlX3, or alkali metals such as K+ for example, but these take place at elevated temperatures and high pressures typically, which are conditions that have proven disadvantageous for large scale recycling efforts. Thus, it has been advantageously found that the incorporation of siloxane bonds into the thermoset monomers uniquely allows for the de- crosslinking of thermoset polymers at room temperature without the need for sophisticated equipment or harmful chemicals. For example, traditional styrene crosslinked unsaturated polyester (i.e. sheet molding compound, SMC), such as that shown in FIG. 1, is not easilyDocket No.: CSP-0379PCT recycled. However, according to embodiments of the present invention, replacement of styrene monomer or any other typical thermoset monomer with a cleavable siloxane bond such as divinylsiloxane crosslinker provides a crosslinked thermoset monomer that is easily de- crosslinked in the presence of a cleaving ion at room temperature, thereby promoting simple recovery of any reinforcing fibers contained within the thermoset resin. Advantageously, upon removal of the cleaving ion, the siloxane bonds reform, allowing reuse of the recovered polymer and reinforcing fibers, thereby creating in some inventive embodiments, a closed loop recycling process. According to still other inventive embodiments, a styrene monomer is replaced with a divinylsiloxane crosslinker to provide a crosslinked unsaturated polyester that easily de- crosslinks in the presence of fluoride ion (F-) as the cleaving ion and at room temperature, as shown in FIG. 2. The present invention is operative in aqueous solutions between 0 and 95 degrees Celsius. Notably, upon removal of the fluoride ion (F-), the siloxane bonds reform allowing reuse of the recovered polymer (and fiber) for the same application. Additional benefits of using a siloxane based crosslinker include increased thermal / oxidative stability (Si-O = 452 kJ / mol), enhanced flame retardancy (inorganic, char promoter), increased UV stability, and low volatile organic content (styrene-free).

[0050] A notable difference between the present invention and previous work regarding recycled siloxane polymers is the fact that the present invention is a hybrid siloxane / conventional hydrocarbon system. In such a system capturing the F- is essential to re-using / recycling the polymer matrix. Leaving the F- ion with the solvate will result in a viscous polymer that never re-hardens even with heat. Accordingly, in the present invention one must capture the F- to re- make a usable, solid matrix. In previous work regarding recycled siloxane polymers, the F- was not sequestered after recycling and the siloxane was still able to re-cast and re-use the siloxanesDocket No.: CSP-0379PCT with F- still present because these were not hybrid systems. Additional work has explored capturing F- ion by reacting with CaCl2 to make insoluble CaF2, which resulted in the intended mixed, solid silsesquioxane cages to precipitate.

[0051] A disiloxane monomer operative herein has the formula (I): R1-[Si(R2)-O]n- Si(R2)-R1(I) where R1is independently in each occurrence H2C=CH-, H2C=CH-R-, H2C(O)CH-, H2C(O)CH- R-, H2N-R, H2C=CH-SiR2-O-, CH2=C(CH3)COO-, CH2=CHCOO-, (CHOH)m- , R-NCO, or (RCO)O(O)-; R is independently in each occurrence C1-C12linear alkyl, C1-C12branched alkyl, C5-C12 cyclic alkyl, C1-C12 linear alkoxy, (C1-C12 alkyl)-C(O))- (C1-C12 alkyl)-O-(C1-C12 linear alkyl), (C1-C12 alkyl)-O-(C1-C12 linear alkyl), C6-C12 aryl, -O-Si(C1-C12 linear alkyl)3, or tri(C1- C12alkyl)-Si-O-; n is an integer of between 1 and 20 inclusive, and m is an integer of between 1 and 4. In some inventive embodiments R is the same in every occurrence. In other inventive embodiments, R1is the same in every occurrence. In still other inventive embodiments, R is the same in every occurrence and R1is the same in every occurrence in a monomer. Other disiloxane monomers operative herein include cyclic analogs thereof. Specific disiloxane monomers operative herein illustratively include O ,Docket No.: CSP-0379PCT O O Si Si O O , orstyrenic monomer need be replaced with an inventive disiloxane monomer in order to achieve the inventive result of aqueous and ambient temperature recycling,

[0052] FIG. 3 shows a reaction incorporating a cleavable silicon functionality into a thermoset monomer. Upon curing of the thermoset resin incorporated with a disiloxane functionality, the thermoset resin crosslinks at the siloxane and retains a moiety susceptible to ion cleavage. This may be used to form thermoset composites that are suitable for structural components. WhenDocket No.: CSP-0379PCT ready to recycle the thermoset composite, the cured thermoset composite is exposed to a cleaving ion, such as fluoride (F-) in aqueous solution. In some inventive embodiments, this reaction occurs at any temperate at which the solution is liquid including room temperature. While the solution can be a solution of an organic solvent miscible with water, in other embodiments, the solvent is merely water with, or without common contaminants therein. Upon exposure to the fluoride ion (F-), the thermoset resin de-crosslinks at the siloxane crosslinks, allowing for recovery of any reinforcing fibers and recovery of the thermoset resin, as shown in FIG. 3.

[0053] Formula (I) includes structures of various disiloxane monomers according to the present invention that are fluoride ion (F-) cleavable. It is appreciated that through inclusion of a small amount of a tri-, quadra- or higher valent siloxane monomer with divalent disiloxane monomer that cure results in a higher degree of crosslinking and three dimensional matrix formation. FIGS. 4A and 4B show depictions of conventional, prior art epoxy-amine materials.

[0054] FIGS. 5A-5D show photographs of the inventive recycling method according to embodiments of the present invention. FIG. 5A shows a photograph of pieces of cast unsaturated polyester (UPE) resin with cleavable siloxane crosslinker. FIG. 5B shows the cast UPE resin of FIG. 5A in a container containing water in which a fluoride ion (F-) is introduced at room temperature. FIG. 5C shows the container of FIG. 5B after 1 to 3 days, at which point the thermoset resin dissolves based on the F- concentration. FIG. 5D shows a photograph of the recast resin solution after the water solvent and the F- ions have been removed. This process can repeat as a continuous loop.

[0055] FIGS. 6A-6D depict the inventive recycling method according to embodiments of the present invention. FIG. 6A depicts of cast UPE resin with cleavable siloxane crosslinkers and glass reinforcing fibers. FIG. 6B depicts the cast UPE resin of FIG. 6A in a container containingDocket No.: CSP-0379PCT water in which fluoride ion (F-) is introduced at room temperature. FIG. 6C depicts the thermoset resin dissolved after 1 to 3 days based on the F- concentration. Notably, this resin may then be collected and recast, as described above with regard to FIGS. 5A-5D. FIG. 6D depicts the glass fibers of the cast UPE resin of FIG. 6A after the reinforcing fibers have been recovered.

[0056] According to some inventive embodiments, the inventive recycling method of inventive ion cleavable thermoset resin yields dry reinforcing fibers with better than 95% yield by weight of reinforcing fibers in the thermoset resin. In other inventive embodiments the yield of dry reinforcing fibers is better than 97% yield by weight of reinforcing fibers in the thermoset resin. In still other inventive embodiments, the yield of dry reinforcing fibers is better than 99% yield by weight of reinforcing fibers in the thermoset. It is appreciated that a cured matrix from which reinforcing fibers can be reclaimed according to the present invention includes any thermoset resin to which a cleavable siloxane bond can be introduced according to embodiments of the present invention. Such thermoset resins illustratively include vinyl esters, polyesters, and epoxies. The reinforcing fiber that are reclaimable according to embodiments of the present invention include carbon fibers and glass fibers.

[0057] The present invention affords an economical and environmentally friendly recycling process for breaking down a thermoset resin matrix to the extent needed to release reusable reinforcing fibers. It has been surprisingly found that thermoset resin matrix digestion to recover reinforcing fiber can be accomplished at room temperature without a solvent other than water when the thermoset resin matrix of the composite material is formed of a thermoset resin that is provided with a cleavable siloxane bond in the polymer chain to enable the chain to be broken apart at various lengths of the chain to break down the matrix.Docket No.: CSP-0379PCT

[0058] Unlike silicone fluids and elastomers, silicone resins also contain T and Q units. These tri- and tetrafunctional units create highly branched and cage-like networks with high crosslink densities, especially compared to silicone elastomers. Combinations of units are typically used to balance the properties. For example, pure T resins can be brittle, but adding D or M units increases elasticity and adhesion. (Moretto, et al.). Silicone resins combine high temperature, oxidation, and UV stabilities, as well as resistance to acids, oils, and water, making them ideal for many coating applications, including release, hydrophobic, oleophobic, abrasion resistance, chemical resistance, anticorrosion, protective, decorative, insulating, antifouling, sealants, and paints. (Moretto et al.)

[0059] Many of silicone’s favorable properties are attributed to their robust inorganic siloxane backbones and cross-links. However, because thermosets do not melt like thermoplastics, it makes it much more difficult to recycle and reuse them. Thermoset polymer recycling is classified into three categories: mechanical, thermal, and chemical recycling. Mechanical recycling involves grinding the thermoset to a powder and using a low loading as filler in a chemically similar polymer, which often results in a reduction of mechanical properties. (Ma et al.,Yigor et al) Thermosets can be thermally recycled (burned) to generate energy and recover fillers, but the process is energy-intensive because of silicone’s high thermal stability and creates unwanted greenhouse gases.

[0060] The silicone resin made from dodecaphenylsilsesquioxane (Ph-T12) and octamethylcyclotetrasiloxane (D4) has a 1 Me:1 Ph ratio and 2 T units:1 D unit. At this ratio of T:D units, the cross-link density of the resin is very high as each T unit creates a cross-link, especially compared to silicone rubber elastomers, with far fewer crosslinkable functionalities. Consistent solution concentrations (10 wt % silicone) in TBAF / THF ensures a uniform thicknessDocket No.: CSP-0379PCT of spray coatings on Al 2024 coupons. Monoliths of resin are cast and cured to produce enough material for recycling reactions, as shown in FIG. 7D. The cured resin is insoluble in THF without an F− source. Dissolution time decreases with increasing [F−] and increases with increasing cure temperature. Wear resistance is evaluated by a linear abrasion test, where the change in water contact angle (WCA) is measured after 50 wear cycle increments (back and forth = one cycle) with a 100 g weighted 2000 grit sandpaper. All prime coatings have consistent initial average WCAs between 90 and 92° with little deviation, as shown in FIG. 9A, but after 50−200 wear cycles, coatings cured at 150° and 200 °C have higher and more variable WCAs. The WCA increase, attributed to surface roughening from the sandpaper, indicates the coatings are not as hard and abrasion-resistant as the coatings cured at 250 °C, which exhibit steady and consistent WCA after 200 wear cycles. Higher cure temperatures possibly decrease plasticizing volatiles and increase cross-link densities as will be evidenced below.

[0061] Coatings made from silicone resins recycled in 0.01 M TBAF and then cured at 150 and 200 °C have higher increases in WCA upon wear testing, as shown in FIG. 9B, compared to prime coatings, which suggests that the recycled resin is softer. The recycled resin coating cured at 150 °C had a WCA of 103 ± 3° after 100 wear cycles and then declined to 96 ± 7° after 200 wear cycles. The WCA of the recycled resin coating cured at 200 °C peak at 117 ± 4° after 150 wear cycles before declining, which indicates the 50 °C increase in cure temperature produces a soft (roughenable) coating, but with a better cohesive strength.

[0062] Recycled resin cured at 250 °C offers consistent WCAs from 0 to 200 wear cycles and is similar to the 250 °C cured prime coatings. The 250 °C cure temperature is necessary to produce a harder silicone that does not easily roughen as exhibited by the consistent WCA after wear. SEM-EDS images of both prime, as shown in FIGS. 8A and 8B, and 0.01 M TBAF recycled, asDocket No.: CSP-0379PCT shown in FIGS. 8I and 8J, resin coatings after 200 wear cycles show an intact and complete coating layer with no exposure of Al coupon substrate. Coating adhesion, measured by a cross- hatch score and tape peel adhesion test (ASTM D3359), for both prime, as shown in FIGS. 8C and 8D, and 0.01 M TBAF recycled, as shown in FIGS. 8K and 8L, resin coatings have the highest rating (5B), indicating excellent adhesion to the Al substrate. When cured at 250 °C, this model silicone resin forms a hard, adherent, wear-resistant, and hydrophobic coating that can be easily recycled and reapplied with retention of mechanical properties.

[0063] FIG. 9C shows the influence of [F−] in the recycling solution on the wear resistance and adhesion properties of the silicone resin coating cured at 250 °C. Initial WCA on a coating of resin recycled in 0.01 M TBAF is similar to that of the prime coating. The coating of resin recycled with the highest [F−] solution, 0.1 M TBAF, is hydrophilic with an initial WCA of <90°. The coating is nonuniform, with patches of Al substrate exposed and exhibits a significant loss of coating after 200 wear cycles, as shown in FIGS. 8M and 8N. The high [F−] could result in the formation of many Si−F bonds in the polymer that readily convert to hydrophilic Si−OH in the presence of adventitious water and continually replenish as wear creates new surfaces. Formation of Si−F bonds would also prevent formation of Si−O3 / 2 or SQ linkages, thus reducing the cross-link density and wear resistance. F is not detected by EDS in any of the thin films or in monoliths of resin recycled with 0.002 or 0.01 M TBAF, but F is present in the monolith cast from resin recycled with 0.1 M TBAF solution. Thus, fluorine remains in the recycled resin, but under optimal recycling conditions, 0.01 M TBAF, the amount is too low to be detected by EDS.

[0064] Dissolution of resin cured at 250 °C is attempted in 0.001 M TBAF, but after stirring for 7 days, the solution remains cloudy with solids. After increasing the [F−] to 0.002 M TBAF, the solution becomes clear within 24 h, thus identifying the minimum threshold of F− necessary toDocket No.: CSP-0379PCT disassociate the silicone network into soluble oligomers. The spray coatings from this minimum [F−] recycling solution are also nonuniform, hydrophilic both initially and after 200 wear cycles, as shown in FIG. 9C, and soft enough to roughen after 50 wear cycles as suggested by the WCA increase from 87 ± 2° to 106 ± 3°. An F− deficient system may lead to an insufficient number of reactive Si atoms necessary to reform the highly cross-linked network upon solvent removal, resulting in poor wear resistance, as shown in FIGS. 8E and 8F.

[0065] The thermal stability of the silicone resin, identified as the average temperature at 5% mass loss (Td5%) via TGA in air, increased with cure temperature, as shown in FIG. 9A, to a maximum of 483 ± 7 °C when cured at 250 °C. Td5% of the resin cured at 200 °C was slightly lower, 470 ± 6 °C, but both resins exhibit two main mass losses between 400−575° and 575−700 °C, attributed to the methyl / phenyl groups and char, respectively. Resin cured at the lowest temperature of 150 °C had a 130 °C lower Td5% (353 ± 5 °C) because of a third mass loss below 400 °C attributed to volatiles, which were elucidated by GC−MS.

[0066] A sample of silicone resin cured at 150 °C is heated to 200 °C in a closed thermal desorption system to evolve only the volatiles that would come off from increasing the cure temperature from 150° to 200 °C, as shown in FIG. 10A, which are then injected into the GC−MS. The most abundant compound detected is tributylamine (413 ppm, 46% of total volatiles), which has a boiling point of 214 °C and is the main decomposition product of TBAF. The second most abundant compound is butylated hydroxytoluene (BHT, 123 ppm, 14% of total volatiles), which has a boiling point of 265 °C and is the inhibitor in the THF. These and other TBAF and BHT decomposition products accounted for >90% of the total volatiles detected. These by-products can act as plasticizing impurities that lower network integrity, cross-link density, thermal stability, wear resistance, and adhesion. Cyclic siloxane oligomers D3, D4, andDocket No.: CSP-0379PCT D5, which are common silicone degradation products, are detected in small quantities totaling 2.5% of volatiles.

[0067] Silicone resin cured at 200 °C is heated to 250 °C under similar conditions to evolve only the volatiles that would come off from increasing the cure temperature from 200° to 250 °C, as shown in FIG. 12B, which are then analyzed by GC−MS. The total amount of tributylamine, BHT, and TBAF / BHT decomposition products decreased to 116 ppm, 86% less than the resin cured at 150 °C. Cyclic siloxane oligomer degradation products account for 10% of total volatiles. The primary compound detected is benzene (243 ppm), which accounts for 60% of all volatiles. Benzene is only detected from the resin on heating to 250 °C. A widely accepted free radical sequence first proposed by Sobolevski accounts for benzene evolution from mixed methyl / phenyl polysiloxanes.31−33 Si−C scission generates a phenyl radical (C6H5) that abstracts a hydrogen from a methyl group to form benzene (boiling point = 80 °C). This also forms a methylene group that attacks another Si atom, creating a cross-link and displacing another phenyl radical. The process generates benzene while increasing the cross-link density. Continuation of the process creates degradation products of small sections of the silicone network like bis(di(trimethylsiloxy)phenylsiloxy)–trimethylsiloxyphenylsiloxane, as shown in FIG. 12B.

[0068] The Td5% increase from raising the cure temperature from 200° to 250 °C can be explained by the GC−MS findings of decreased total volatile species, increased cross-link density, and reduced organic content from benzene generation. Resins recycled with 0.01 M TBAF had nearly the same Td5% as the prime resin at a given cure temperature, as shown in FIG. 9B, indicating no significant loss of thermal stability. GC−MS showed similar levels of volatiles in both the prime and 0.01 M TBAF recycled resins cured at 250 °C (Figure S3).Docket No.: CSP-0379PCT However, the Td5% of silicone resin recycled with 0.1 M TBAF decreass 51°C to 432 ± 6 °C because of a mass loss event below 400 °C. This is attributed to the order of magnitude increase in TBAF concentration, which resulted in a five times increase in TBAF degradation products.

[0069] Optimized recycling conditions (0.01 M TBAF / THF at RT) are used to evaluate the inventive technique on a commercial mixed phenyl / methyl silicone resin. SILRES REN 50 (Wacker Chemie) cured at 250 °C is stirred at RT in 0.01 M TBAF / THF until completely dissolved, which takes 55 min. The cured resin is insoluble in THF alone as well as toluene and xylene. Solutions (10 wt %) of prime and recycled SILRES spray-coated on clean Al coupons and cured at 250 °C are tested for hydrophobicity, wear resistance, adhesion, and thermal stability. Initial WCAs for both coatings were 90°. After 50−200 wear cycles, the prime coating is roughened and then significantly worn away as indicated by the abrupt increase in WCA to 116 ± 4° after 50 cycles followed a decline (FIG. 11A) and the large amount of substrate is exposed after 200 wear cycles (FIG. 11D).

[0070] The recycled SILRES coating shows little WCA change and less wear (FIG. 11G) after 200 cycles. Coating adhesion of the recycled coating is equal to or better than the prime coating (FIGS. 11E and 11H). The thermal stability of the SILRES is 73 °C higher after recycling (FIG. 11B). Mechanical and thermal property increases after recycling are attributed to the formation of a more cross-linked network as evidenced by the GC−MS spectra, showing less silicone network degradation products and the evolution of benzene due to cross-linking upon heating. Lastly, a cotton swab soaked in 0.01M TBAF is used to selectively remove a portion of cured SILRES (FIGS. 11I and 11J) to demonstrate the modification, patterning, and repair capabilities of our technique. This technique also works for silicone rubbers, which is unsurprising because rubbers have lower cross-link densities than resins. A common room-temperature curing siliconeDocket No.: CSP-0379PCT rubber, ELASTOSIL E10 (Wacker Chemie), dissolved in less than 15 min when stirred in 0.01 M TBAF / THF.

[0071] According to some inventive embodiments, the inventive recycling method of inventive ion cleavable thermoset resin yields dry reinforcing fibers with better than 95% yield by weight of reinforcing fibers in the thermoset resin. In other inventive embodiments the yield of dry reinforcing fibers is better than 97% yield by weight of reinforcing fibers in the thermoset resin. In still other inventive embodiments the yield of dry reinforcing fibers is better than 99% yield by weight of reinforcing fibers in the thermoset. It is appreciated that a cured matrix from which reinforcing fibers can be reclaimed according to the present invention includes any thermoset resin to which a cleavable siloxane bond can be introduced according to embodiments of the present invention. Such thermoset resins illustratively include vinyl esters, polyesters, and epoxies. The reinforcing fiber that are reclaimable according to embodiments of the present invention include carbon fibers and glass fibers.

[0072] The present invention affords an economical and environmentally friendly recycling process for breaking down a thermoset resin matrix to the extent needed to release reusable reinforcing fibers. It has been surprisingly found that thermoset resin matrix digestion to recover reinforcing fiber can be accomplished at room temperature without a solvent other than water when the thermoset resin matrix of the composite material is formed of a thermoset resin that is provided with a cleavable siloxane bond in the polymer chain to enable the chain to be broken apart at various lengths of the chain to break down the matrix.

[0073] Embodiments of the inventive recycling process may be conducted in a process as follows. The cured thermoset matrix is optionally ground to a particle size that while increasing surface area limits shearing of reinforcing fibers. A typical length of a carbon fiber in an SMCDocket No.: CSP-0379PCT matrix is between 6 and 40 millimeters (mm) in length. Grind particle sizes for an inventive process typically range from 1 to 25 mm in diameter for spherical particulate and a longest linear extent in a X-Y-Z coordinate system for anisotropic particles on average of between 5 and 80 mm. The cured resin grind is combined with a water in a ratio of resin:water of 1:2-20 by weight. According to the present invention, a batch process is run involving at least 0.75 kilograms of reinforcing fiber to achieve economies of scale. Solvent is present in a ration sufficient to free more than 95% by weight of the reinforcing fiber from the composite. Advantageously, typical reaction temperatures range from 15-25 degrees Celsius. According to some inventive embodiments, other components such as surfactant, antifoaming agent, viscosity reducer, or boiling chip are readily added.

[0074] Co-reactants operative in the present invention illustratively include hydroxides, carbonates, hydrogen carbonates and phosphates of alkali metals such as sodium carbonate, sodium hydroxide, sodium hydrogen carbonate, potassium hydroxide, potassium carbonate, potassium hydrogen carbonate, tripotassium phosphate, or a combination thereof. Typical loadings of catalyst range from 0 to 5 total weight percent.

[0075] After reaction, the separated reinforcing fibers are washed and optionally sonicated. The washing is conducted with water. The resulting separated fibers are dried. According to some inventive embodiments, the separated fibers may undergo anti-static, coupling, film-former, or other sizing being applied as a coating on the outside of the dried, reclaimed reinforcing fibers.

[0076] Embodiments of the inventive process may be a closed loop process where the byproducts obtained during the fiber recovery are used in the formation of new FRC materials, as shown in FIGS. 7A-7D and FIGS. 8A-8D.Docket No.: CSP-0379PCT

[0077] In some inventive embodiments, the reaction mixture is exposed to sonication prior to or during exposure to the reaction mixture. Sonication appears to loosen the reinforcing fibers from the cured resin matrix and cleans and detangles the fibers as well.

[0078] In still other embodiments, the reaction mixture is exposed to microwave radiation to speed the matrix digestion. Microwaves have frequencies of from 100 MHz to 1000 GHz. 915 MHz and 2450 MHz are conventional klystron output frequencies. Reaction vessels particularly well suited for use with microwave radiation have limited absorption of these wavelengths and illustratively include glass, ceramic or fluoropolymers. It is appreciated that a large reaction vessel is readily equipped with a window of quartz glass or heat-resistant glass operating as a microwave permeable portal. Alternatively, a metallic waveguide serves to allow deliver microwaves into a vessel absorptive of microwaves. After reaction, the separated reinforcing fibers are washed and optionally sonicated. The washing is conducted with water. The resulting separated fibers are dried. According to some inventive embodiments, the separated fibers may undergo anti-static, coupling, film-former, or other sizing being applied as a coating on the outside of the dried, reclaimed reinforcing fibers.

[0079] FIG. 12A shows the chemical structures of siloxanes denoted as Esand As. FIG. 12B depicts casts of equal parts by weight of siloxane combinations and the corresponding glass transition temperature of the polymers formed from those siloxanes.

[0080] FIG. 13A is a graph showing TGA plots for the samples of FIG. 12B. The glass transition temperatures are noted therein. FIG. 13B is a graph showing TGA plots of FIG. 13A and two additional siloxane combinations of 50:50 Ec / Es+ Asparts by weight and 75:25 Ec / Es+ Asparts by weight.Docket No.: CSP-0379PCT

[0081] FIGS. 14A-14D depict the inventive recycling method according to another embodiment of the present invention consistent with one of the FIG. 13B compositions showing steps consistent with those detailed in FIGS. 5A-5B, the details of which are hereby incorporated by reference.

[0082] FIG. 15 is a schematic showing an unsaturated polyester (UPE) resin monomer containing a clipable crosslinker and a reaction schematic for synthesis thereof.

[0083] An exemplary reaction apparatus for the inventive process is shown generally at 10 in FIG. 16. The hopper 12 includes pieces of cured thermoset based composite materials containing reinforcing fibers. A screw 14 conveys particles from the hopper 12 to the reaction vessel 16. The vessel 16 is adapted to include the water and any catalysts and other material as the particles are metered into the vessel 16 by way of the screw 14. A motor 18 drives a mechanical stirrer 20 to homogenize the reaction conditions. An ion introduction conduit 22 is provided so that cleaving ions can be introduced into the reaction container. A microwave generator or sonicator 24 is provided to impart energy to the reaction volume within the vessel 16. A drain 26 is provided to facilitate liquid removal from the vessel 16. A filter 28 allows for transmission and collection of size excluded substances such a filler particulate from the reaction mixture via a side siphon valve 30 as well as collection of the cleavable ions.

[0084] Upon matrix digestion to liberate reinforcing fibers, the fibers are either collected after transmission through a filter 18 or decanted from the reaction mixture and a settled precipitate. The collected reinforcing fibers are in some embodiments further filtered to remove various insoluble fillers present in typical SMC, which illustratively include calcium carbonate, thickeners, glass beads, glass microspheres, paint pigments, and natural fibers. The weight ofDocket No.: CSP-0379PCT water added to wash the resulting carbon fibers is typically 10 to 100 times the weight of the reinforcing fiber released from the thermoset matrix.

[0085] The resulting reclaimed reinforcing fibers are readily dried in a conventional oven or vacuum oven to remove residual water from the reinforcing fibers. The resulting reinforcing fibers are used as if virgin reinforcing fibers or chemical treating to apply a sizing coating thereto. A sizing is used to modify fiber surface properties and as a result interactions with a new matrix in which the reclaimed carbon fibers will be embedded.

[0086] The collected filtrate can be distilled to recover the cleavable ions. The recovered cleavable ions can then be used for subsequent reinforcing fiber recovery reactions while maintaining a recovered reinforcing fiber purity of >95%.

[0087] The recovered and concentrated organic, in some inventive embodiments, after neutralization, can be incorporated into new polymer systems due to and depending upon the nature of the functional groups present. At loadings of 5-50 wt% recovered organics and 95-50 wt% virgin polymer the properties are similar to 100% virgin systems. Alternately the recovered organics can be used as a fuel.

[0088] Patent documents and publications mentioned in the specification are indicative of the levels of those skilled in the art to which the invention pertains. These documents and publications are incorporated herein by reference to the same extent as if each individual document or publication was specifically and individually incorporated herein by reference.

[0089] The foregoing description is illustrative of particular embodiments of the invention, but is not meant to be a limitation upon the practice thereof. The following claims, including all equivalents thereof, are intended to define the scope of the invention. ReferencesDocket No.: CSP-0379PCT

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[0091] Murphy, C. M.; Saunders, C. E.; Smith, D. C. Thermal and Oxidation Stability of Polymethylphenylsiloxanes. Ind. Eng. Chem. 1950, 42, 2462−2468.

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[0095] Lucas, P.; Robin, J. J. Silicone-Based Polymer Blends: An Overview of the Materials and Processes. In Advances in Polymer Science: Functional Materials and Biomaterials; Springer-Verlag: Berlin, Germany, 2007; Vol. 209, pp 111−147 DOI: 10.1007 / 12_2007.

[0096] Ma, M.; Hill, R. M. Superhydrophobic Surfaces. Curr. Opin. Colloid Interface Sci. 2006, 11, 193−202.

[0097] Yilgör, E.; Yilgör, I. Silicone Containing Copolymers: Synthesis, Properties and Applications. Prog. Polym. Sci. 2014, 39, 1165−1195. (9) Gong, D.; Long, J.; Jiang, D.; Fan, P.; Zhang, H.; Li, L.; Zhong, M. Robust and Stable Transparent Superhydrophobic Polydimethylsiloxane Films by Duplicating via a Femtosecond Laser-Ablated Template. ACS Appl. Mater. Interfaces 2016, 8, 17511−17518.

[0098] Ghosh, A.; Antony, P.; Bhattacharya, A. K.; Bhowmick, A. K.; De, S. K. Replacement of Virgin Rubbers by Waste Ground Vulcanizates in Blends of Silicone RubberDocket No.: CSP-0379PCT and Fluororubber Based on Tetrafluoroethylene / Propylene / Vinylidene Fluoride Terpolymer. J. Appl. Polym. Sci. 2001, 82, 326−2341.

[0099] Ghosh, A.; Rajeev, R. S.; Bhattacharya, A. K.; Bhowmick, A. K.; De, S. K. Recycling of Silicone Rubber Waste: Effect of Ground Silicone Rubber Vulcanizate Powder on the Properties of Silicone Rubber. Polym. Eng. Sci. 2003, 43, 279−296. (12) Hsiao, Y.-C.; Hill, L. W.; Pappas, S. P. Reversible Amine Solubilization of Cured Siloxane Polymers. J. Appl. Polym. Sci. 1975, 19, 2817−2820.

[0100] Pappas, S. P.; Just, R. L. Aminolysis of Crosslinked Polysiloxanes: Tautomeric Catalysis by 2-Pyridone. J. Polym. Sci., Polym. Chem. Ed. 1980, 18, 527−531.

[0101] Okamoto, M.; Suzuki, S.; Suzuki, E. Polysiloxane Depolymerization with Dimethyl Carbonate Using Alkali Metal Halide Catalysts. Appl. Catal., A 2004, 261, 239−245.

[0102] Enthaler, S. Zinc-Catalyzed Depolymerization of End-of-Life Polysiloxanes. Angew. Chem., Int. Ed. 2014, 53, 2716−2721.

[0103] Enthaler, S.; Kretschmer, R. Low-Temperature Depolymerization of Polysiloxanes with Iron Catalysis. ChemSusChem 2014, 7, 2030−2036.

[0104] Enthaler, S. Iron-Catalyzed Depolymerization of Polysiloxanes to Produce Dichlorodimethylsilane, Diacetoxydimethylsilane, or Dimethoxydimethylsilane. J. Appl. Polym. Sci. 2015, 132, 41287.

[0105] Weidauer, M.; Heyber, B.; Woelki, D.; Tschiersch, M.; Köhler- Krützfeldt, A.; Enthaler, S. Iron-Catalyzed Depolymerizations of Silicones with Hexanoic Anhydride Provide a Potential Recycling Method for End-of-Life Polymers. Eur. J. Lipid Sci. Technol. 2015, 117, 778−785.Docket No.: CSP-0379PCT

[0106] Döhlert, P.; Pfrommer, J.; Enthaler, S. Recycling Concept for End-of-Life Silicones: Boron Trifluoride Diethyl Etherate as Depolymerization Reagent to Produce Difluorodimethylsilane as Useful Commodity. ACS Sustainable Chem. Eng. 2015, 3, 163−169.

[0107] Döhlert, P.; Enthaler, S. Depolymerization Protocol for Linear, Branched, and Crosslinked End-of-Life Silicones with Boron Trifluoride Diethyl Etherate as the Depolymerization Reagent. J. Appl. Polym. Sci. 2015, 132, 1−7.

[0108] Gou, Z.; Zuo, Y.; Feng, S. Thermally Self-Healing Silicone- Based Networks with Potential Application in Recycling Adhesives. RSC Adv. 2016, 6, 73140−73147.

[0109] Xiang, H. P.; Rong, M. Z.; Zhang, M. Q. A Facile Method for Imparting Sunlight Driven Catalyst-Free Self-Healability and Recyclability to Commercial Silicone Elastomer. Polymer 2017, 108, 339−347.

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Claims

Docket No.: CSP-0379PCT CLAIMS 1. A thermoset resin comprising: a plurality of crosslinked ion cleavable disiloxane units incorporated therein from a disiloxane monomer.

2. The thermoset resin of claim 1 wherein the thermoset resin is polyester, vinyl ester, polyurethane epoxy, polyurea, rubber, a crosslinked thermoplastic, or a combination thereof.

3. The thermoset resin of claim 1 wherein the plurality of crosslinked ion cleavable disiloxane units are cleavable by a fluoride ion.

4. The thermoset resin of claim 1 wherein the disiloxane monomer operative herein has the formula (I): R1-[Si(R2)-O]n- Si(R2)-R1(I) where R1is independently in each occurrence H2C=CH-, H2C=CH-R-, H2C(O)CH-, H2C(O)CH- R-, H2N-R, H2C=CH-SiR2-O-, CH2=C(CH3)COO-, CH2=CHCOO-, (CHOH)m- , R-NCO, or (RCO)O(O)-; R is independently in each occurrence C1-C12 linear alkyl, C1-C12 branched alkyl, C5-C12cyclic alkyl, C1-C12linear alkoxy, (C1-C12alkyl)-C(O))- (C1-C12alkyl)-O-(C1-C12linear alkyl), (C1-C12 alkyl)-O-(C1-C12 linear alkyl), C6-C12 aryl, -O-Si(C1-C12 linear alkyl)3, or tri(C1- C12alkyl)-Si-O-; n is an integer of between 1 and 20 inclusive, and m is an integer of between 1 and 4.Docket No.: CSP-0379PCT 5. The thermoset resin of claim 4 the disiloxane monomer includes at least one of: O O or6. A composite material comprising:Docket No.: CSP-0379PCT a cured matrix formed of the thermoset resin of claim 1; and a plurality of reinforcing fibers embedded in the cured matrix.

7. The composite material of claim 6 wherein the plurality of reinforcing fibers are glass fibers, carbon fibers, aramid fibers, all natural fibers, basalt fibers, boron fibers, silicon carbide fibers, polymer fibers, or a combination thereof.

8. The composite material of claim 6 wherein the composite material is entirely recyclable.

9. A process to recycle a composite material of claim 6, the process comprising: adding the composite material to solvent in a container; introducing fluoride ions to solvent in the container; and maintaining the composite material, the solvent, and the fluoride ions in the container under conditions for a period of time to dissolve the matrix material and to free more than 95% by weight of the reinforcing fibers from the matrix material to form free reinforcing fibers.

10. The process of claim 9 further comprising washing the free reinforcing fibers.

11. The process of claim 10 wherein the washing is with water.

12. The process of claim 9 wherein the solvent is water.Docket No.: CSP-0379PCT 13. The process of claim 9 further comprising drying the free reinforcing fibers.

14. The process of claim 9 further comprising reusing the reclaimed reinforcing fibers in a new composite material.

15. The process of claim 9 further comprising collecting the dissolved matrix material.

16. The process of claim 11 further comprising filtering out the fluoride ions from the collected dissolved matrix material.

17. The process of claim 11 further comprising reusing the filtered dissolved matrix material in a new composite material.

18. The process of claim 11 further comprising collecting the filtered-out fluoride ions.

19. The process of claim 14 further comprising reusing the collected filtered-out fluoride ions in a new recycling process.

20. The process of any one of claims 9 to 15 wherein more than 97% by weight of the reinforcing fiber is freed from the matrix material.Docket No.: CSP-0379PCT 21. The process of any one of claims 9 to 15 wherein more than 95% by weight of the matrix material is reclaimed.

22. The process of any one of claims 9 to 15 wherein the conditions comprise a temperature of between 15 and 25 °C.

23. The process of any one of claims 9 to 15 wherein the conditions comprise atmospheric pressure.

24. The process of any one of claims 9 to 15wherein the time period is 1 to 3 days.

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