Method of degrading a component of a fibre or fibre composite material

Abstract

A method of degrading a component of a fibre or fibre-composite material (e.g. a fibre or a matrix). The method comprises arranging the fibre or fibre composite material in contact with water, dissolv

Description

FIELD OF THE INVENTION This invention relates to the field of degrading a component of a fibre or fibre composite material, especially components of high-performance materials, and in particular degrading or depolymerising polymeric components, such as para-aramid fibres and / or phenolic resins. TECHNICAL BACKGROUND Recycling of materials used for fibre and fibre composite materials would be highly desirable for a circular economy. Fibre composites typically include fibres embedded in a matrix. The fibres may be made of a polymeric material, such as for example para-aramid, ultra-high molecular weight polyethylene (UHMWPE), or from other materials such as carbon, glass or flax. The matrix may also be made from a polymeric material, typically a resin such as such as epoxy resin, phenolic resin, polyester or polypropylene. Recycling of any component of a fibre or fibre composite material - whether fibre or matrix - is highly desirable. Para-aramid (PA) fibres in particular are used in many fibre and fibre composite materials in many high-tech applications, such as military applications for ‘bullet-proof’ body armour, thanks to the high strength and toughness of the fibres. Para-aramid fibres are also very durable, thanks to their abrasion and cutting resistance, as well as their high chemical resistance and thermal resistance. However, the combination of chemical and thermal durability in particular creates significant issues in disposing of used para-aramid fibres. It is therefore desirable to recycle used para-aramid fibres. Para-aramid is a condensation polymer and can be cleaved at the amide bond in order to break up the polymer chain, eventually returning the para-aramid to its constituent monomers that can be returned to manufacturing supply chains. However, as a result of the unique properties of para-aramid, current degradation techniques make use of energy intensive processes, such as supercritical hydrolysis, pyrolysis, gasification and high temperature solvolysis. These processes all require temperatures in excess of 200°C, and can be as high as 700°C for pyrolysis and gasification processes. The need for high temperatures means the processes are very energy intensive. Current processes often also require the use of harsh chemicals, such as strong acids or bases: these have a significant environmental impact. It is an object of the invention to address the problems noted above in the state of the art. SUMMARY OF THE INVENTION In a first aspect, the invention provides a method of degrading a component of a fibre or fibre-composite material. The method comprises: arranging the fibre or fibre composite material in contact with water, dissolving ozone into the water, irradiating the water with ultraviolet radiation, and allowing the component to degrade. In this sense, degrading the component means breaking the chemical structure of its material into smaller chemical constituents. For example, if the component is made of a polymeric material, degrading the component means breaking down the polymer chains into shorter chains and / or smaller molecules: this may include depolymerising the material to at least some extent. The component may be a fibre material of a fibre or fibre-composite material, or the component may be a matrix material of a fibre-composite material. Embodiments are envisaged in which the method is a method of degrading a component of a fibrecomposite material and a further component of the fibre-composite material, wherein the component is a fibre material and the further component is a matrix material. The component may comprise a carbon-containing material. The carbon-containing material may be a polymeric material. The component may comprise a material selected from the group consisting of: paraaramid, carbon, glass, flax, ultra-high molecular weight polyethylene (UHMWPE), epoxy resin, phenolic resin, polyester or polypropylene. The component may comprise fibres made of para-aramid, UHMWPE, carbon, glass, or flax. The component may comprise a matrix made of epoxy resin, phenolic resin, polyester or polypropylene. Where the component comprises para-aramid fibres, the sample may comprise paraaramid fibres that have been treated with a water-resistant treatment. The para-aramid fibres that have been treated with a water-resistant treatment may comprise para-aramid fibres that are coated with a hydrophobic polymer. Optionally, the water may be at a temperature of between 15°C and 30°C, preferably between 20°C and 25°C. The method may comprise submerging the material in the water, such that substantially the entire surface of the material is in contact with the water. The step of dissolving ozone into the water may comprise introducing ozone gas into the water, optionally by bubbling ozone gas through the water. The component may be allowed to degrade for a reaction period, and ozone gas may be introduced into the water throughout the reaction period, optionally continuously. Irradiating the water with ultraviolet radiation may comprise directing an artificial source of ultraviolet radiation at the water. The artificial source may have a primary output having a wavelength of 254 nm. The method may comprise arranging the water in a reaction vessel and adding the material to the reaction vessel so that the sample is in contact with the water. In another aspect, the invention provides the use of water, ozone and ultraviolet radiation to degrade a component of a fibre or fibre composite material. In a further aspect, the invention resides in the use of water, ozone and ultraviolet radiation to degrade a polymeric component of fibre or fibre composite material. In another aspect the invention resides in a method of degrading a carbon-containing material. The method comprises: arranging the carbon-containing material in contact with water, dissolving ozone into the water, irradiating the water with ultraviolet radiation, and allowing the carbon-containing material to degrade. The carbon-containing material may be a polymeric material, for example para-aramid. Optionally, the water may be at a temperature of between 15°C and 30°C, preferably between 20°C and 25°C. The method may comprise submerging the material in the water, such that substantially the entire surface of the material is in contact with the water. The step of dissolving ozone into the water may comprise introducing ozone gas into the water, optionally by bubbling ozone gas through the water. The component may be allowed to degrade for a reaction period, and ozone gas may be introduced into the water throughout the reaction period, optionally continuously. Irradiating the water with ultraviolet radiation may comprise directing an artificial source of ultraviolet radiation at the water. The artificial source may have a primary output having a wavelength of 254 nm. The method may comprise arranging the water in a reaction vessel and adding the material to the reaction vessel so that the sample is in contact with the water. Preferred and / or optional features of any of the above embodiments and aspects may be used alone, or in appropriate combination, with the other embodiments and aspects also. BRIEF DESCRIPTION OF THE DRAWINGS So that it may be more readily understood, the invention will now be described with reference to the following drawings, in which: Figure 1 shows a schematic diagram of a reaction apparatus used to carry out the method of the invention; Figure 2a shows a sample of dry para-aramid before degradation; Figure 2b shows the sample of dry para-aramid in situ in the reaction apparatus shown schematically in Figure 1 at the start of the reaction process; Figure 2c shows the sample of dry para-aramid in situ in the reaction apparatus shown schematically in Figure 1 after 10 hours of reaction time; Figure 2d shows the liquid fraction obtained after reacting the sample of dry para-aramid for 10 hours; Figure 2e shows the remaining solid fraction, comprising the degraded dry para-aramid sample, after 10 hours of reaction time; Figure 3 shows scanning electron micrographs of para-aramid fibres in the dry paraaramid sample before degradation; Figure 4 shows a scanning electron micrograph of the para-aramid fibres in the degraded dry para-aramid sample after 10 hours of reaction time; Figure 5 shows Fourier transform infrared spectroscopy spectra for: (a) the dry paraaramid sample before degradation; (b) the degraded para-aramid sample after 10 hours of reaction time; and (c) solid organic components recrystallised from the liquid fraction obtained after reacting the dry para-aramid sample for 10 hours; Figure 6 shows the 1H nuclear magnetic resonance spectrum of the nitrogen dried liquid fraction obtained after reacting the dry para-aramid sample for 10 hours; Figure 7 shows the 1H nuclear magnetic resonance spectrum of the nitrogen dried liquid fraction obtained after reacting a resin-coated para-aramid sample for 10 hours; Figure 8 shows the 1H nuclear magnetic resonance spectrum of the nitrogen dried liquid fraction obtained after reacting a sample of pure Kevlar® K29 fibre for 10 hours; Figure 9 shows a graph detailing the degradation percentage of a dry para-aramid sample as a function of reaction time over a period of 7 hours; Figure 10 shows a graph detailing the degradation percentage of three different dry paraaramid samples after 7 hours of reaction time; Figure 11 shows a graph detailing the degradation percentage of three different paraaramid samples (a), (b) and (c) after 10 hours of reaction time; Figures 12 to 14 are refractive index chromatograms of the liquid products of the process as applied to samples (a), (b) and (c) respectively, obtained using gel permeation chromatography; Figures 15a and 15b are Scanning Electron Microscopy (SEM) images of a fibre composite sample obtained, respectively, before and after being subjected to the method of the invention; Figure 16a and 16b are further SEM images of a fibre composite sample obtained, respectively, before and after being subjected to the method of the invention. DETAILED DESCRIPTION The invention makes use of a hydrolytic process to degrade and / or depolymerise components of a fibre material or a fibre composite material, especially components that are found in high-performance fibre materials or fibre composite materials. Fibre composite materials comprise multiple components: for example, a plurality of fibres and a matrix. One or both of the fibre material and the matrix material may define components that can be degraded by the forgoing method. The method may also be applied to fibre materials (i.e. non-composite materials, such as pure fibres), in which the fibre material defines the component to be degraded. Fibres of a high-performance fibre or fibre-composite material may comprise, for example, para-aramid, ultra-high molecular weight polyethylene (UHMWPE), glass fibre, carbon fibre or flax, which may be degraded by the method. The matrix of a high-performance fibre-composite material may comprise, for example epoxy resin, phenolic resin, polyester or polypropylene, which may be degraded by the method. Where both the fibre and matrix are made of a polymeric material, both the fibre and matrix may be degraded by the method. For example, the material may comprise para-aramid fibres that are degraded by the method. In another example, the material may comprise a phenolic resin matrix that is degraded by the method. The material may comprise para-aramid fibres in a phenolic resin matrix, and both the para-aramid fibres and the phenolic resin matrix may be degraded by the method. Throughout this specification, the terms ‘degrade’ and ‘depolymerise’ (and derivatives thereof) may be used to describe the breaking down of a material into smaller chemical constituents (for example the breaking down of polymer chains into shorter chains and / or smaller molecules), without specifically referring to the particular products of this process. According to the inventive process, the degradation takes place in water into which ozone has been introduced, and is assisted by ultraviolet (UV) radiation. The method thus involves arranging a material or sample containing the component to be degraded in contact with water, dissolving ozone in the water, and irradiating the water with UV radiation. In this sense, irradiating the water with UV radiation involves directing an artificial source of UV radiation at the water. UV radiation is typically understood to have wavelengths between 100 nm and 400 nm. The combination of ozone and UV radiation generates hydroxyl radicals (’OH) in the water which degrade the component, by attacking linkage sites within the material to break the material down into smaller chemical constituents. For example, in the case of para-aramid, the hydroxyl radicals attack the C-N bond in the amide linkage that forms the basis of the PA polymer chain. A number of possible radical-generating reactions are shown below, in which UV radiation is represented by hv. a) O3 + H2O 2 «OH + O2 b) O3 + H2O + hvH2O2 + O2 c) H2O2 + hv 2 OH d) 2 O3 + H2O2 2 OH + 3 O2 With the hydroxyl radicals formed, it is expected that selective attack of the susceptible amide link occurs, causing chain scission as shown in Scheme 1 below. Each chain scission event degrades the polymer chain (i.e. reduces the polymer chain length). ¥ i f \ I \ / / / M—N—& j—mh $ \ O OH Scheme 1: Depolymerisation of para-aramid via aqueous hydrolytic reaction. In an idealised reaction mechanism following this process, each PA polymer chain undergoes multiple chain scission events, until eventually the chain is reduced to its constituent monomer building blocks. It will be appreciated that, while a high degree of depolymerisation is desirable, it is not essential that all polymer chains are completely reduced to monomers for the process to be useful. An advantage of the process shown in Scheme 1 is that no unwanted by-products are formed. Naturally, in a practical scenario, it is likely that partially depolymerised oligomers may remain in the reaction solution, but these can theoretically be further degraded into the monomeric material using the same process. Once the organic products of the process are extracted, the only compounds remaining in the reaction solution are hydrogen peroxide and water. Hydrogen peroxide readily decomposes to water and molecular oxygen and thus is of little concern environmentally. The process is therefore a clean and effective depolymerisation with relatively straightforward purification requirements. Advantageously, the reaction can be carried out at room temperature. Indeed, the solubility of ozone at 20°C (570 mg / L) is more than twice the solubility at 40°C (270 mg / L), meaning that room temperature parameters are more desirable than high-temperature parameters. ‘Room temperature’ in the context of this specification shall be taken to mean a temperature between 15°C and 30°C, or preferably a temperature between 20°C and 25°C. While it is theoretically possible that the energy of the UV radiation may heat the water to a limited extent, it should be understood that any heating effect would be negligible in practice and no additional heat source is applied to the water for the process to take place. Crucially, the ability to carry out the degradation reaction at room temperature, i.e. without a heat source, reduces the power requirements and cost of the process, compared to high-temperature processes. In combination with the ‘clean’ reaction products, the process therefore offers a low environmental impact alternative to the current methods employed in the art. Figure 1 shows a schematic diagram of an example of a reaction apparatus that may be used to carry out the degradation process. A sample 10 comprising PA fibres is added to a reaction vessel 12 that contains water 14. An ozone generator 16 generates ozone, in the form of gas bubbles, which is introduced into the water 14 by an inlet tubing 18. The inlet tubing 18 is submerged in the water 14 to ensure that the ozone is introduced directly into the water 14, and not to the air in the reaction vessel 12. The ozone gas dissolves into the water as it bubbles through it. The ozone generator is configured to control the flow rate of ozone into the water. A suitable ozone generator is, for example, BMT 803N. An outlet tubing 20, also submerged in the water 14, removes gases in the water 14, such as unused excess ozone, and any oxygen and hydrogen peroxide generated by the radical-generating reactions of Scheme 1, from the reaction vessel 12. Any unused ozone in these gases is then trapped in an ozone trap 22 in order to decompose safely, while generated oxygen and hydrogen peroxide is free to escape to the surrounding atmosphere, where the hydrogen peroxide can decompose into water and oxygen. The reaction apparatus also contains an immersion well 24 submerged in the water 14 within which is contained a UV lamp head 26. The UV lamp head emits UV radiation generated by a UV source 28. The UV lamp head 26 and UV source 28 are shown as separate components in Figure 1, but the skilled person will appreciate that these two components may be integrated or contiguous without affecting the function of the UV lamp head 26 or UV source 28, or the ability of the reaction apparatus to vary out the method of the invention. The UV light source may emit UV light of any suitable wavelength or wavelength range, and any suitable intensity. One suitable example is a wavelength of 254 nm and an intensity of between 800 and 6900 microwatts / cm2, for example 3300 microwatts / cm2, though other suitable wavelengths and intensities may be used. To use the apparatus, a fibre or fibre composite material is placed in the reaction vessel 12 along with the water 14, the ozone is introduced, and the UV lamp 26 is activated. Ozone is continuously introduced throughout a reaction period. The reaction mixture may be stirred or otherwise agitated during the reaction period. The reaction period may be, for example, up to 24 hours, and is preferably between 4 hours and 10 hours, most preferably 7 hours. Examples The following examples detail experiments that were carried out to determine the efficacy and applicability of the above process. In the experiments, a variety of different PA samples are used. The following nomenclature will be adhered to when discussing these different samples: Dry para-aramid (Dry PA): Twaron CT707 (made by Teijin) with only a water-resistant treatment. Such a water-resistant treatment (which comprises a hydrophobic or lipophilic coating, typically a hydrophobic polymer) comes as standard in all end-user applications and so Dry PA represents the closest representation of end-of-life PA fibres in the current supply chain for uses such as soft body armour, since all such fibres are treated with a water-resistant treatment for ballistic applications to minimise water damage over time. Resin para-aramid (Resin PA): A fibre composite material comprising Twaron CT707 (made by Teijin) with water-resistant treatment and embedded in a matrix comprising phenolic resin. K29: pure Kevlar® K29 fibre (made by DuPont) with no treatments. EXAMPLE 1 Experimental Setup A mass (mi) of Dry PA (maximum 0.2 g) was added to 200 mL of distilled water in a reaction vessel. Pure ozone flow, generated from an ozone generator (BMT 803N, maximum flow rate of 3 L / min), was then charged into the reaction vessel. The ozone flow was 1 L / min, corresponding to a concentration of 125 g / Nm3 and an ozone production rate of 7.5 g / hour. The reaction vessel was than irradiated by a UV lamp having a primary output with a wavelength of 254 nm and an intensity of 3300 microwatts / cm2 W / cm2 with stirring at 500 rpm for up to 10 hours. Any excess ozone was safely scrubbed out using the ozone trap with water at room temperature. Initially, the sample was observed to stay afloat or move on or near the water's surface without sinking. After a few hours of stirring, the Dry PA sample aggregated and began to sink, followed by the reaction mixture turning into a cloudy solution. Figure 2a shows the initial Dry PA sample, while Figures 2b and 2c show the sample in situ in the reaction vessel at the start of the reaction process and after 10 hours of reaction time, respectively. After the conclusion of the process, any remaining PA fibres were removed from the reaction vessel by centrifugation and subsequent filtration. The products obtained after centrifugation included a completely transparent solution containing dissolved degradation products (shown in Figure 2d) and a yellow solid comprising residual PA fibres and any undissolved degradation products (shown in Figure 2e). The yellow solid was dried and weighed (m2), with the mass of degraded PA subsequently calculated using Equation 1: △m = mi-m2 (1) From there, a degradation percentage, D, can be determined using Equation 2: D= (Am / m^x 100 (2) Results The extent of degradation was measured for three different reaction times: 4 hours, 6 hours and 10 hours. The results are shown below in Table 1. my (g) Volume of water (mL) Reaction time (hours) Ozone flow (L per minute) PH m2 (g) D (%) 0.0870 200 4 1 6.5 0.0562 35.38 0.0976 200 6 1 6.5 0.0404 58.66 0.2000 200 10 1 6.5 0.0505 74.75 Table 1: Degradation of Dry PA in water using ozone and UV radiation The degradation results shown here demonstrate ability of the method to successfully degrade PA fibres and highlight the commercial utility of the process since Dry PA is the closest representation of real-world, commercial end-of-life PA fibres. It is especially promising, and indeed, surprising, that the water / ozone / UV system shows strong degradation performance against Dry PA, as this material is coated with a water resistant treatment, which acts as a direct barrier to the water that is used as a solvent. EXAMPLE 2 This experiment aimed to analyse the solid and liquid products resulting from the reaction carried out on Dry PA in Example 1. Solid Product Analysis The morphology of the residual solid product shown in Figure 2e at the end of the reaction was analysed using scanning electron microscopy (SEM). The micrographs were prepared using a JSM-IT300 (JEOL, Japan), operated at 15 kV, at a working distance of 10 mm, together with an X-max 80 mm2 detector, run with Aztec software. As can be seen in Figure 3, the Dry PA fibres before the reaction have a smooth, uniform surface, with a diameter of 10 to 15 pm. In contrast, Figure 4 shows the SEM micrograph of the solid product of the reaction (i.e., the degraded Dry PA). This shows the fibres to be significantly degraded after exposure to the water / ozone / UV reaction. The fibres were also seen to be visibly shorter, further evidencing the efficacy of the process in breaking down the PA fibre chains. The solid product was also analysed using Fourier transform infrared (FTIR) spectroscopy. Unes (a) and (b) in Figure 5 show the FTIR spectra of the Dry PA before the reaction, and the residual solid product after the reaction, respectively. As might be expected, these spectra showed little difference in the absorption bands present, indicating that chemically, there was minimal difference between the undegraded Dry PA and the residual solid left after the reaction had been carried out. EXAMPLE 3 This experiment aimed to further characterise the degradation of Dry PA over time, and the reproducibility of the process. Experimental setup A total of 15 different Dry PA samples were tested, for five different durations (three samples for each duration). The durations were 1 hour, 2 hours, 3 hours, 4 hours and 7 hours. For each sample, the mass (rm, maximum 0.2 g) of the sample was recorded prior to adding it to 200 mL of distilled water in a reaction vessel. Pure ozone flow at a flow rate of 1 L / min (125 g / Nm3, 7.5 g / hour), generated from an ozone generator (BMT 803N), was then charged into the reaction vessel. The reaction vessel was than irradiated by a UV lamp having a primary output with a wavelength of 254 nm and an intensity of 3300 microwatts / cm2with stirring at 500 rpm for 10 hours. Any excess ozone was safely scrubbed out using the ozone trap with water at room temperature. After the determined reaction duration for each sample, remaining PA fibres were removed from the reaction vessel by centrifugation and subsequent filtration. The solid product of the centrifugation and filtration process was dried and weighed (m2), with the mass of degraded PA (Am) subsequently calculated using Equation 1 above, and a degradation percentage calculated using Equation 2 above. Results Figure 9 shows the trend between the reaction duration and the degradation percentage. The respective average degradation percentages for 1 hour, 2 hours, 3 hours, 4 hours and 7 hours of reaction duration were 4.7%, 3.8%, 20.0%, 35.6% and 58.1%. As can be seen, an approximately linear relationship can be observed, with a high R2 value of 0.9557. Figure 10 shows the degradation percentages for all three samples for which the reaction duration was 7 hours. A high degree of reproducibility can be seen between the three different samples, with a standard deviation calculated to be 0.68 (1.2% of the average degradation percentage value of 58.1%. EXAMPLE 4 This experiment aimed to assess the efficacy of the process across a range of different PA samples. Experimental setup A mass (rm) of a PA sample (0.2 g for each sample) was added to 200 mL of distilled water in a reaction vessel. Three different PA samples were used: Sample (a) a Dry PA sample, Sample (b) a Resin PA sample and Sample (c) a K29 sample. Pure ozone flow at a flow rate of 1 L / min (125 g / Nm3, 7.5 g / hour), generated from an ozone generator (BMT 803N), was then charged into the reaction vessel. The reaction vessel was than irradiated by a UV lamp having a primary output with a wavelength of 254 nm and an intensity of 3300 microwatts / cm2 with stirring at 500 rpm for 10 hours. Any excess ozone was safely scrubbed out using the ozone trap with water at room temperature. After the conclusion of the process, remaining PA fibres were removed from the reaction vessel by centrifugation and subsequent filtration. The solid product of the centrifugation and filtration process was dried and weighed (m2), with the mass of degraded PA (Am) subsequently calculated using Equation 1 above, and a degradation percentage calculated using Equation 2 above. Results Figure 11 shows the degradation percentages of the three PA samples after the 10 hour reaction process. Bars (a), (b) and (c) represent the Dry PA (Sample (a), Resin PA (Sample (b)) and K29 (Sample (c)) samples, respectively. The Dry PA sample recorded a degradation percentage of 74.75% , while the respective values for the Resin PA and K29 samples were 34.65% and 100%, respectively. Degradation of the fibres was therefore observed for all three samples, with complete degradation of the K29 (pure Kevlar) sample. This demonstrates the effectiveness of the method in degrading the fibres in all samples, and especially pure para-aramid fibres that have no additional treatment applied. The result for ‘Resin PA’ demonstrates that the process can effectively degrade not only the fibres but also the phenolic thermoset resin, as this degradation must have occurred in order for degradation of the treated fibres to take place. See also Example 5. EXAMPLE 5, 6 and 7 These experiments aimed to analyse the liquid products resulting from the reactions carried out on Samples (a), (b) and (c) in Example 4. Example 5 The liquid products of the reactions carried out on Sample (a) in Example 4 were analysed by FTIR spectroscopy. To prepare the liquid products for FTIR analysis, vacuum filtration was first used to separate the liquid and solid products of the reaction. The collected liquid product was kept at 4°C, with dichloromethane then added to the solution to dissolve the organic degradation products present in the water. The dichloromethane, together with the dissolved organic products, was then separated from the water. The dichloromethane was evaporated in a vacuum evaporator, allowing the dissolved organic products to crystallise. Finally, the crystals were dried at 45°C. Line (c) in Figure 5 shows the FTIR spectra of the dried crystals of Sample (a). Unlike lines (a) and (b) representing respectively the undegraded Dry PA and the degraded solid product, line (c) shows additional absorption bands characteristic of an additional N-H stretch, and two absorption bands characteristic of carboxylic acids (C=O and C-0 bands at 1720 cm’1 and 1475 cm’1, respectively) that were not present in the former two samples. The additional signals indicate that amine and carboxylic acid groups are present. The formation of these chemical groups is characteristic of monomer and oligomer formation and indicates that the process could be used to produce a recycled chemical feedstock. Example 6 The liquid reaction products of the reaction carried out on samples (a), (b) and (c) from Example 4 were also analysed using 1H Nuclear Magnetic Resonance (NMR) spectroscopy. The liquid products were first nitrogen dried before being dissolved in deuterated DMSO. Figures 6, 7 and 8 show the resultant spectrum from this analysis for samples (a), (b) and (c) respectively. The triple peak at approximately 7 ppm (actual values 6.97, 7.09 and 7.22 ppm), which is present in all three spectra of Figures 6, 7 and 8, is indicative of the presence of phenylamine (aniline). The peaks at approximately 3.5 ppm and 2.5 ppm are from water and small concentrations of undeuterated DMSO, respectively. Aniline is an important raw aromatic material used in a variety of industrial applications including rubber accelerators and antioxidants, dyes and intermediates, photographic chemicals, as isocyanates for urethane foams, in pharmaceuticals, explosives, petroleum refining, and in production of diphenylamine, phenolics, herbicides and fungicides. The triple peak indicates that a common degradation product is being formed in all three samples. Example 7 The liquid reaction products of the reaction carried out on samples (a), (b) and (c) from Example 4 were further analysed using gel permeation chromatography (GPC) analysis. Refractive index (RI) chromatograms were obtained for each sample using the following standard operating conditions: • Eluent: 0.02% NaNs solution • Column Set: 2xA2500M + guard • Flow Rate: 0.8 mL / min • Column Temperature: 40 °C • Detector Oven Temperature: 40 °C • Autosampler Temperature: 20 °C • Run Length: 60 min • Injection Volume: 100 uL Figures 12, 13 and 14 show the RI chromatograms from samples (a), (b) and (c) respectively. Molecular weight data is shown in the table below (Mn = number average molecular weight and Mw = weight average molecular weight). Sample Peak Mn (Da) Mw (Da) Mw / Mn Weight Fraction (a) 1 11 042 11 108 1.006 48% 2 7 015 7 033 1.003 52 % (b) 1 10 631 10 697 1.006 79% 2 6 771 6 795 1.004 21 % (c) 1 10 775 10 834 1.006 44% 2 6 668 6 691 1.003 56% All three samples show peaks at substantially the same position, indicating that the same degradation products are formed. EXAMPLE 8 This experiment aimed to assess the efficacy of the process in degrading a resin matrix of a fibre composite sample comprising resin PA Experimental setup, by analysing the solid product of the process as applied to the resin PA sample. 0.2g of a resin PA sample was added to 200 mL of distilled water in a reaction vessel. Pure ozone flow at a flow rate of 1 L / min (125 g / Nm3, 7.5 g / hour), generated from an ozone generator (BMT 803N), was then charged into the reaction vessel. The reaction vessel was than irradiated by a UV lamp having a primary output with a wavelength of 254 nm and an intensity of 3300 microwatts / cm2 with stirring at 500 rpm for 10 hours. Any excess ozone was safely scrubbed out using the ozone trap. The water was at room temperature. After the conclusion of the process, remaining PA fibres were removed from the reaction vessel by centrifugation and subsequent filtration. Scanning electron microscope images were obtained of i) the sample before the degradation process and ii) the sample after the degradation process. The images are shown in Figures 15a and 15b, and Figures 16a and 16b. Figure 15a shows the sample before degradation in an edge region of the sample. Woven PA fibres are embedded in the phenolic resin matrix: the ends of the fibres are visible at the edge of the sample, protruding from the matrix. Figure 16a shows a closeup image of the fibres of the sample before degradation. Figure 15b shows the sample after degradation. The resin matrix has been removed from the sample, indicating that the resin has degraded to release the fibres. Figure 16b is a close-up of the fibres after degradation: the fibres are intact and substantially free from damage.

Claims

1. A method of degrading a component of a fibre material or fibre-composite material, the method comprising:arranging the fibre material or fibre composite material in contact with water;dissolving ozone into the water;irradiating the water with ultraviolet radiation; and allowing the component to degrade.

2. The method of Claim 1, wherein the component is a fibre of a fibre or fibrecomposite material, or wherein the component is a matrix material of a fibre-composite material.

3. The method of Claim 1 or Claim 2, wherein the component comprises a carbon-containing material.

4. The method Claim 3, wherein the carbon-containing material is a polymeric material.

5. The method of any preceding claim, wherein the component comprises a material selected from the group consisting of: para-aramid, carbon, glass, flax, ultra-high molecular weight polyethylene (UHMWPE), epoxy resin, phenolic resin, polyester or polypropylene.

6. The method of Claim 4, wherein the component comprises para-aramid fibres or a phenolic resin matrix.

7. The method of any preceding claim, wherein the water is at a temperature of between 15°C and 30°C, preferably a temperature of between 20°C and 25°C.

8. The method of any preceding claim, wherein the step of dissolving ozone into the water comprises introducing ozone gas into the water, optionally by bubbling ozone gas through the water.

9. The method of any preceding claim, comprising allowing the component to degrade fora reaction period, the reaction period being at least four hours, preferably at least seven hours.

10. The method of any preceding claim, comprising irradiating the water with ultraviolet radiation having a wavelength of 254 nm.

11. The method of any preceding claim, wherein the loading of component in the water is at least 0.1 % by weight.

12. The method of any preceding claim, comprising stirring or agitating the material while allowing the component to degrade.

13. The method of Claim 2 or any claim dependent thereon, wherein the component comprises fibres that have been treated with a water-resistant treatment, optionally wherein the component comprises fibres coated with a hydrophilic polymeric material.

14. Use of water, ozone and ultraviolet radiation to degrade a component of a fibre or fibre-composite material.

15. Use of water, ozone and ultraviolet radiation to degrade a carbon-containing component in a fibre or fibre composite material.

Images