Degradation and recycling method of carbon fiber resin composite material waste

Abstract

The invention provides a carbon fiber resin composite material waste degradation and reutilization method, which comprises: S1, dissolving an alkali metal hydroxide and an alkyl guanidine compound in an alcohol solvent to obtain a degradation liquid; s2, mixing the carbon fiber resin composite material waste and the degradation liquid, performing heating treatment, and filtering after the waste is degraded; s3, washing and drying filter residues to obtain regenerated carbon fibers; and collecting filtrate for later use. According to the method, the reactive degradation liquid and the composite material waste are subjected to a thermal chemical reaction, and efficient degradation of the composite material waste is achieved. Meanwhile, the regenerated carbon fiber is compounded with phenolic resin and active particles to prepare the thermal protection material for the aerospace craft; by utilizing the characteristic that the waste liquid contains reactive hydrogen atoms, the waste liquid is used as an epoxy resin curing agent, and the problems of treatment and recycling of the waste liquid are synchronously solved.

Description

Technical Field

[0001] The invention relates to the technical field of carbon fiber recycling, and in particular to a method for degrading and recycling waste carbon fiber resin composite materials. Background Art

[0002] Carbon fiber reinforced thermosetting resin composites (CFRP) have excellent comprehensive properties such as light weight, high strength, corrosion resistance, and fatigue resistance. They are widely used in wind turbine blades, aerospace, ships, sports and leisure, and automobiles. With the upgrading of carbon fiber composite products, a large amount of carbon fiber composite waste has been generated. In addition, the preparation process of CFRP will also produce a large amount of waste such as scraps. The efficient degradation and comprehensive application of CFRP waste has broad market prospects.

[0003] At present, supercritical fluid method, subcritical fluid method, strong acid decomposition method and other processes are often used to degrade CFRP waste. Although the degradation of CFRP waste can be achieved under harsh environments, the problem of recycling waste liquid has always plagued the entire industry. Most of the waste liquid is an organic mixture containing acid / alkali. If it is dumped directly, it will inevitably cause serious environmental pollution. The existing technology mainly separates the waste liquid through distillation, vacuum distillation and other technologies, and then reuses it. Patent CN109265736A discloses a method for recycling carbon fiber and resin in waste carbon fiber / resin composite materials. The uncross-linked composite material waste is dissolved by a mixed solvent. The waste liquid needs to undergo a complex distillation process to evaporate the solvent to obtain a resin matrix. Patent CN114479177A discloses an epoxy resin degradation method, a solvent system for epoxy resin degradation, and a recovery method. A mixed solvent of ethylene glycol and N,N-dimethylformamide is used to degrade a carbon fiber / resin composite material at 130-150°C. The waste liquid is subjected to vacuum distillation and separation to obtain a recovered mixed solvent and oligomers. The recovered mixed solvent can be used again to degrade the carbon fiber / resin composite material, and the oligomers are used as added raw materials to prepare new epoxy resins.

[0004] In the above schemes, the waste liquid is treated by distillation, vacuum distillation, etc., which is not only complicated in operation, has a long treatment cycle, but also has high cost. It is necessary to seek a simple and efficient solution to efficiently utilize the waste liquid to improve the benefits of the degradation and reuse of carbon fiber composite waste. Summary of the invention

[0005] In view of this, the present invention proposes a method for degrading and reusing waste carbon fiber resin composite materials, which uses reactive degradation liquid to react with composite material waste to achieve efficient degradation of composite material waste. At the same time, the recycled carbon fiber is compounded with phenolic resin and active particles to prepare thermal protection materials for aerospace vehicles; the waste liquid is used as an epoxy resin curing agent by taking advantage of the property that it contains active hydrogen atoms, thereby simultaneously solving the problem of waste liquid treatment and reuse.

[0006] The technical solution of the present invention is implemented as follows: In the first aspect, the present invention provides a method for degrading and recycling waste carbon fiber resin composite materials, comprising the following steps:

[0007] S1, dissolving an alkali metal hydroxide and an alkylguanidine compound in an alcohol solvent to obtain a degradation solution;

[0008] S2, cutting the carbon fiber resin composite waste into pieces and mixing them with the degradation liquid, heating them, and filtering them after the waste is degraded;

[0009] S3, washing and drying the filter residue to obtain regenerated carbon fiber; collecting the filtrate for later use.

[0010] Specifically, alkali metal hydroxides, such as potassium hydroxide and sodium hydroxide, are inorganic strong bases. Alkylguanidine compounds, such as 1,1,3,3-tetramethylguanidine, 1,1,3,3-tetraethylguanidine and 1,1,3,3-tetrapropylguanidine, are organic strong bases. Compared with inorganic strong bases, organic strong bases have better compatibility with alcohols. Organic strong bases are rich in active hydrogen atoms. When alcohols react with inorganic strong bases and organic strong bases at high temperatures, they will also produce substances rich in active hydrogen atoms, which can quickly degrade carbon fiber resin composite waste to obtain recycled carbon fiber. Active hydrogen atoms can participate in the curing of epoxy resin, so the waste liquid produced after degradation can be used as an epoxy resin curing agent.

[0011] On the basis of the above technical solution, preferably, the mass ratio of the alkali metal hydroxide: the alkylguanidine compound: the alcohol solvent is 10-20:3-5:100.

[0012] On the basis of the above technical solution, preferably, the mass ratio of the carbon fiber resin composite material waste to the degradation liquid is 1:1.5-2.

[0013] Based on the above technical solution, preferably, in step S1, the heating temperature is 80-140° C. and the heating time is 0.5-10 h.

[0014] On the basis of the above technical solution, preferably, the alkali metal hydroxide is one or both of potassium hydroxide and sodium hydroxide;

[0015] The alkylguanidine compound is one or more combinations of 1,1,3,3-tetramethylguanidine, 1,1,3,3-tetraethylguanidine and 1,1,3,3-tetrapropylguanidine;

[0016] The alcohol solvent is one or more combinations of n-propanol, isopropanol, n-butanol and isobutanol.

[0017] On the basis of the above technical scheme, preferably, the carbon fiber resin composite material waste is one or more combinations of carbon fiber / epoxy resin waste, carbon fiber / cyanate ester resin waste, carbon fiber / bismaleimide resin waste and carbon fiber / polyimide resin waste.

[0018] On the basis of the above technical solution, preferably, the recycled carbon fiber, phenolic resin and active particles obtained in step S3 are mixed and hot molded to obtain the protective material;

[0019] The active particles are one or a combination of carbide and boride.

[0020] On the basis of the above technical solution, preferably, the carbide is silicon carbide or hafnium carbide, and the boride is titanium boride.

[0021] On the basis of the above technical solution, preferably, the mass ratio of the regenerated carbon fiber: phenolic resin: active particles is 1:1-2:0.2-0.5;

[0022] The parameters for hot molding are 170-190℃, 8-12MPa and molding for 2-3h.

[0023] In a second aspect, the present invention provides an application of a thermal protection material obtained by a method for degrading and recycling waste carbon fiber resin composite materials in a thermal protection material for a solid rocket engine nozzle.

[0024] In a third aspect, the present invention provides a method for degrading and recycling waste carbon fiber resin composite materials, and uses the filtrate obtained in an epoxy resin curing agent.

[0025] On the basis of the above technical solution, preferably, when the filtrate is used as a curing agent, the mass ratio of the waste liquid to the epoxy resin is 3-4:1.

[0026] The method for degrading and recycling waste carbon fiber resin composite materials of the present invention has the following beneficial effects compared with the prior art:

[0027] (1) The present invention utilizes a reactive degradation liquid to undergo a thermochemical reaction with composite waste to achieve efficient degradation of composite waste, with a degradation rate of 100% and a regenerated carbon fiber strength retention rate of up to 99%. Compared with the prior art, the present invention has the advantages of a high degradation rate and no significant effect on the strength performance of the regenerated carbon fiber.

[0028] (2) The present invention composites recycled carbon fiber with phenolic resin and active particles to prepare a solid rocket engine nozzle thermal protection material, whose linear ablation rate can reach -0.006mm / s and mass ablation rate can reach 0.031g / s, showing excellent ablation resistance.

[0029] (3) The present invention utilizes the property that the waste liquid contains active hydrogen atoms and uses it as an epoxy resin curing agent. The prepared epoxy cured product has a bending strength test result of 90 MPa, showing excellent mechanical properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0031] Figure 1 This is a physical picture of the thermal protection material prepared in Example 1 after oxygen-acetylene ablation test. DETAILED DESCRIPTION

[0032] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0033] When recycling carbon fiber resin composite waste, it is first cut into blocks with a length of 2 cm, a width of 1 cm, and a thickness of 2 cm for later use.

[0034] The fiber resin composite material waste is a combination of one or more of carbon fiber / epoxy resin waste, carbon fiber / cyanate resin waste, carbon fiber / bismaleimide resin waste and carbon fiber / polyimide resin waste, wherein the resin content is 20%-80%.

[0035] Example 1

[0036] S1, dissolving 10 g of potassium hydroxide and 5 g of 1,1,3,3-tetraethylguanidine in 100 g of isopropanol to obtain a reactive degradation solution.

[0037] S2, adding 20g of the cut carbon fiber / epoxy resin waste and 30g of the reactive degradation liquid into a reactor, mixing them evenly, and reacting them at 140°C for 9h; after the waste is completely degraded, centrifuging and filtering.

[0038] The filter residue was washed with ethanol and deionized water in sequence, and dried at 80°C to obtain regenerated carbon fiber; the filtrate was collected for later use.

[0039] S3, 10g of recycled carbon fiber, 10g of phenolic resin and 2g of hafnium carbide are mixed evenly, and molded at 180°C and 10MPa for 2h to obtain a solid rocket engine nozzle thermal protection material with excellent ablation resistance.

[0040] S4, mixing 35 g of the filtrate with 10 g of bisphenol A epoxy resin, and heating and curing at 130° C. for 3 h to obtain an epoxy cured product with excellent mechanical properties.

[0041] The regenerated carbon fiber obtained in step S2 of this embodiment was weighed and subjected to a single-filament tensile strength test (GB / T31290-2022), and the resin degradation rate and strength retention rate were calculated. The test results showed that the resin degradation rate was 100%, and the strength retention rate of the regenerated carbon fiber was 97%, indicating that this embodiment achieved efficient degradation of carbon fiber / epoxy resin waste.

[0042] The thermal protection material prepared in step S3 of this embodiment is 4.2MW / m 2 The oxygen-acetylene ablation test (GJB 323B-2018) was carried out for 30s under heat flux. Figure 1 The test results show that the linear ablation rate is -0.006 mm / s and the mass ablation rate is 0.031 g / s, indicating that the thermal protection material prepared in this embodiment has excellent ablation resistance.

[0043] The epoxy cured material prepared in step S4 of this embodiment was subjected to a flexural strength test (GB / T2567-2021), and the test result was 90 MPa, indicating that the epoxy cured material prepared in this embodiment has excellent mechanical properties.

[0044] Example 2

[0045] The method for degrading and recycling waste carbon fiber resin composite materials of this embodiment includes the following steps:

[0046] S1, dissolving 15 g of sodium hydroxide and 3 g of 1,1,3,3-tetramethylguanidine in 100 g of n-propanol to obtain a reactive degradation solution.

[0047] S2, adding 20g of the cut carbon fiber / cyanate resin waste and 35g of the reactive degradation liquid into a reactor, mixing them evenly, and reacting them at 135°C for 10h; after the waste is completely degraded, centrifuging and filtering.

[0048] The filter residue was washed with ethanol and deionized water in sequence, and dried at 80°C to obtain regenerated carbon fiber; the filtrate was collected for later use.

[0049] S3, 10g of recycled carbon fiber, 15g of phenolic resin and 4g of silicon carbide were mixed evenly, and molded at 170°C and 12MPa for 3h to obtain a solid rocket engine nozzle thermal protection material with excellent ablation resistance.

[0050] S4, mixing 30 g of the filtrate with 10 g of bisphenol A epoxy resin, and heating and curing at 130° C. for 3 h to obtain an epoxy cured product with excellent mechanical properties.

[0051] The regenerated carbon fiber obtained in step S2 of this embodiment was weighed and subjected to a single-filament tensile strength test (GB / T31290-2022), and the resin degradation rate and strength retention rate were calculated. The test results showed that the resin degradation rate was 100%, and the strength retention rate of the regenerated carbon fiber was 99%, indicating that this embodiment achieved efficient degradation of carbon fiber / cyanate ester resin waste.

[0052] The thermal protection material prepared in step S4 of this embodiment is 4.2MW / m 2 An oxygen-acetylene ablation test (GJB 323B-2018) was carried out for 20 seconds under heat flux density. The test results showed that the linear ablation rate was 0.009 mm / s and the mass ablation rate was 0.035 g / s, indicating that the thermal protection material prepared in this embodiment has excellent ablation resistance.

[0053] The epoxy cured material prepared in step S4 of this embodiment was subjected to a flexural strength test (GB / T2567-2021), and the test result was 82 MPa, indicating that the epoxy cured material prepared in this embodiment has excellent mechanical properties.

[0054] Example 3

[0055] The method for degrading and recycling waste carbon fiber resin composite materials of this embodiment includes the following steps:

[0056] S1, dissolving 20 g of potassium hydroxide and 4 g of 1,1,3,3-tetrapropylguanidine in 100 g of n-butanol to obtain a reactive degradation solution.

[0057] S2, adding 20g of the cut carbon fiber / bismaleimide resin waste and 40g of the reactive degradation liquid into a reactor, mixing them evenly, and reacting them at 120°C for 9h; after the waste is completely degraded, centrifuging and filtering.

[0058] The filter residue was washed with ethanol and deionized water in sequence, and dried at 80°C to obtain regenerated carbon fiber; the filtrate was collected for later use.

[0059] S3, 10g of recycled carbon fiber, 20g of phenolic resin and 5g of titanium boride were mixed evenly, and molded at 190°C and 8MPa for 2.5h to obtain a solid rocket engine nozzle thermal protection material with excellent ablation resistance.

[0060] S4, mixing 40 g of the filtrate with 10 g of bisphenol A epoxy resin, and heating and curing at 130° C. for 3 h to obtain an epoxy cured product with excellent mechanical properties.

[0061] The regenerated carbon fiber obtained in step S2 of this embodiment was weighed and subjected to a single-filament tensile strength test (GB / T31290-2022), and the resin degradation rate and strength retention rate were calculated. The test results showed that the resin degradation rate was 100%, and the strength retention rate of the regenerated carbon fiber was 98%, indicating that this embodiment achieved efficient degradation of carbon fiber / bismaleimide resin waste.

[0062] The thermal protection material prepared in step S3 of this embodiment was subjected to a 20s oxygen-acetylene ablation test (GJB 323B-2018) at a heat flux density of 4.2MW / m2. The test results showed that the linear ablation rate was 0.011mm / s and the mass ablation rate was 0.039g / s, indicating that the thermal protection material prepared in this embodiment has excellent ablation resistance.

[0063] The epoxy cured material prepared in step S4 of this embodiment was subjected to a flexural strength test (GB / T2567-2021), and the test result was 85 MPa, indicating that the epoxy cured material prepared in this embodiment has excellent mechanical properties.

[0064] Example 4

[0065] S1, dissolving 13 g of sodium hydroxide and 5 g of 1,1,3,3-tetraethylguanidine in 100 g of isobutyl alcohol to obtain a reactive degradation solution;

[0066] S2, adding 20g of the cut carbon fiber / polyimide resin waste and 37g of the reactive degradation liquid into a reactor, mixing them evenly, and reacting them at 80°C for 10h; after the waste is completely degraded, centrifuging and filtering.

[0067] The filter residue was washed with ethanol and deionized water in sequence, and dried at 80°C to obtain regenerated carbon fiber; the filtrate was collected for later use.

[0068] S3, 10g of recycled carbon fiber, 18g of phenolic resin and 3g of hafnium carbide are uniformly mixed, and molded at 185°C and 9MPa for 2h to obtain a solid rocket engine nozzle thermal protection material with excellent ablation resistance;

[0069] S4, 33 g of the filtrate and 10 g of bisphenol A epoxy resin were mixed, and heated and cured at 130° C. for 3 h to obtain an epoxy cured product with excellent mechanical properties.

[0070] The regenerated carbon fiber obtained in step S2 of this embodiment was weighed and subjected to a single-filament tensile strength test (GB / T31290-2022), and the resin degradation rate and strength retention rate were calculated. The test results showed that the resin degradation rate was 100%, and the strength retention rate of the regenerated carbon fiber was 99%, indicating that this embodiment achieved efficient degradation of carbon fiber / polyimide resin waste.

[0071] The thermal protection material prepared in step S3 of this embodiment is 4.2MW / m 2 An oxygen-acetylene ablation test (GJB 323B-2018) was carried out for 20 seconds under heat flux density. The test results showed that the linear ablation rate was 0.008 mm / s and the mass ablation rate was 0.034 g / s, indicating that the thermal protection material prepared in this embodiment has excellent ablation resistance.

[0072] The epoxy cured material prepared in step S4 of this embodiment was subjected to a flexural strength test (GB / T2567-2021), and the test result was 84 MPa, indicating that the epoxy cured material prepared in this embodiment has excellent mechanical properties.

[0073] Comparative Example 1

[0074] Comparative Example 1 Compared with Example 1, the components of the reactive degradation liquid lack 1,1,3,3-tetraethylguanidine, specifically as follows:

[0075] S1, dissolving 10 g of potassium hydroxide in 100 g of isopropanol to obtain a reactive degradation solution;

[0076] S2, adding 20g of the cut carbon fiber / epoxy resin waste and 30g of the reactive degradation liquid in step S1 into a reactor, mixing them evenly, and reacting them at 140°C for 9h; after the waste is completely degraded, centrifuging and filtering.

[0077] The filter residue was washed with ethanol and deionized water in sequence, and dried at 80°C to obtain regenerated carbon fiber; the filtrate was collected for later use.

[0078] S3, mixing 35 g of the filtrate from step S2 and 10 g of bisphenol A epoxy resin, and heating and curing at 130° C. for 3 h to obtain an epoxy cured product.

[0079] In this comparative example, the lack of 1,1,3,3-tetraethylguanidine will affect the catalytic effect, resulting in incomplete degradation, and will also affect the effect of the subsequent waste liquid as a catalyst, resulting in incomplete curing of the epoxy resin and reduced strength.

[0080] The regenerated carbon fiber obtained in step S2 of this comparative example was weighed, and the resin degradation rate was calculated. The test result was 83%. A lot of resin remained on the surface of the regenerated carbon fiber, making it difficult to reuse directly.

[0081] The epoxy cured product obtained in step S3 of this comparative example was tested for bending strength, and the test result was 70 MPa.

[0082] Comparative Example 2

[0083] Comparative Example 2 Compared with Example 1, the components of the reactive degradation liquid lack potassium hydroxide, specifically as follows:

[0084] S1, dissolving 5 g of 1,1,3,3-tetraethylguanidine in 100 g of isopropanol to obtain a reactive degradation solution;

[0085] S2, adding 20g of the cut carbon fiber / epoxy resin waste and 30g of the reactive degradation liquid in step S1 into a reactor, mixing them evenly, and reacting them at 140°C for 9h; after the waste is completely degraded, centrifuging and filtering.

[0086] The filter residue was washed with ethanol and deionized water in sequence, and dried at 80°C to obtain regenerated carbon fiber; the filtrate was collected for later use.

[0087] S3, mixing 35 g of the filtrate from step S2 and 10 g of bisphenol A epoxy resin, and heating and curing at 130° C. for 3 h to obtain an epoxy cured product.

[0088] Due to the lack of potassium hydroxide, the alkalinity of the degradation liquid in this comparative example is insufficient, and the structure of the epoxy resin cannot be effectively destroyed, resulting in a reduced degradation rate. If there is a lot of residual resin, the strength retention rate of the regenerated carbon fiber will also decrease, because the surface residue will introduce defects. At the same time, the waste liquid will also lack sufficient catalysts, which will affect the formation of epoxy cured products, thereby reducing mechanical properties.

[0089] The regenerated carbon fiber obtained in step S2 of this comparative example was weighed, and the resin degradation rate was calculated. The test result was 86%. A lot of resin remained on the surface of the regenerated carbon fiber, making it difficult to reuse directly.

[0090] The epoxy cured product obtained in step S3 of this comparative example was tested for bending strength, and the test result was 75 MPa.

[0091] Comparative Example 3

[0092] Comparative Example 3 Compared with Example 1, the solid rocket engine nozzle thermal protection material is lacking in hafnium carbide during preparation, as follows:

[0093] S1, the preparation of reactive degradation liquid is the same as in Example 1.

[0094] S2, the regenerated carbon fiber recovery and filtrate collection are the same as in Example 1.

[0095] S3, 10g of recycled carbon fiber and 10g of phenolic resin are mixed evenly, and molded at 180°C and 10MPa for 2h to obtain a solid rocket engine nozzle thermal protection material.

[0096] The thermal protection material prepared in step S3 of this embodiment is 4.2MW / m 2 The oxygen-acetylene ablation test (GJB 323B-2018) was carried out for 30s under heat flux. Figure 1 The test results show that the line ablation rate is 0.034 mm / s and the mass ablation rate is 0.056 g / s, indicating that the thermal protection material prepared in this embodiment has very poor ablation resistance.

[0097] Comparative Example 4

[0098] Comparative Example 4 Compared with Example 1, the usage ratio of the alkali metal hydroxide and the alkylguanidine compound in the reactive degradation liquid exceeds the limited range, specifically 10:1. 10g of potassium hydroxide and 1g of 1,1,3,3-tetraethylguanidine are dissolved in 100g of isopropanol to obtain a reactive degradation liquid.

[0099] Due to the insufficient amount of 1,1,3,3-tetraethylguanidine, the insufficient catalytic activity leads to incomplete breaking of the β-hydroxyethyl bond of the epoxy resin and a decrease in the degradation rate of the resin. Incomplete degradation can cause residual resin on the surface of the regenerated carbon fiber, affecting the performance in subsequent steps. For example, in S3, the regenerated carbon fiber is mixed with phenolic resin and hafnium carbide. If there is residual resin on the fiber surface, it will affect the interface bonding, thereby reducing the ablation resistance of the thermal protection material. In addition, insufficient residual degradation agent in the filtrate may affect the curing of the epoxy resin, resulting in a decrease in mechanical properties.

[0100] The regenerated carbon fiber obtained in step S2 of this comparative example was weighed, and the resin degradation rate was calculated. The test result was 81%, and the resin degradation rate was greatly reduced.

[0101] The thermal protection material prepared in step S3 of this comparative example is 4.2MW / m 2 A 20s oxygen-acetylene ablation test (GJB 323B-2018) was carried out under heat flux density. The test results showed that the linear ablation rate was 0.028mm / s, the mass ablation rate was 0.047g / s, and the ablation resistance was weakened.

[0102] The epoxy cured material obtained in step S4 of this comparative example was subjected to a bending strength test (GB / T2567-2021), and the test result was 78 MPa, indicating that the mechanical properties of the epoxy cured material were reduced.

[0103] Comparative Example 5

[0104] Comparative Example 5 Compared with Example 1, the usage ratio of the alkali metal hydroxide and the alkylguanidine compound in the reactive degradation liquid exceeds the specified range, specifically 1:1, that is, 10g of potassium hydroxide and 10g of 1,1,3,3-tetraethylguanidine are dissolved in 100g of isopropanol to obtain a reactive degradation liquid.

[0105] If the dosage of 1,1,3,3-tetraethylguanidine is too high, there will be excess 1,1,3,3-tetraethylguanidine remaining. In the degradation step, excessive 1,1,3,3-tetraethylguanidine will excessively erode the surface of the carbon fiber. Although the resin degradation rate may increase, it will damage the fiber structure and reduce the strength retention rate. At the same time, the excessive 1,1,3,3-tetraethylguanidine remaining in the filtrate reacts too quickly with the epoxy resin in step S4, affecting the curing process, resulting in incomplete curing or internal stress, and reducing the bending strength. In addition, excessive catalyst will also affect the curing of phenolic resin in the thermal protection material, change the material structure, and thus affect the ablation resistance.

[0106] The regenerated carbon fiber obtained in step S2 of this comparative example was weighed and subjected to a single-filament tensile strength test (GB / T31290-2022), and the resin degradation rate and strength retention rate were calculated. The test results showed that the resin degradation rate was 100% and the strength retention rate of the regenerated carbon fiber was 72%.

[0107] The thermal protection material prepared in step S3 of this comparative example is 4.2MW / m 2 The oxygen-acetylene ablation test (GJB 323B-2018) was carried out for 20s under heat flux density. The test results showed that the linear ablation rate was 0.031mm / s and the mass ablation rate was 0.050g / s.

[0108] The epoxy cured material obtained in step S4 of this comparative example was subjected to a flexural strength test (GB / T2567-2021), and the test result was 68 MPa.

[0109] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for degrading and recycling waste carbon fiber resin composite materials, characterized in that: The following steps are involved: S1, dissolving an alkali metal hydroxide and an alkylguanidine compound in an alcohol solvent to obtain a degradation solution; S2, cutting the carbon fiber resin composite waste into pieces and mixing them with the degradation liquid, heating them, and filtering them after the waste is degraded; S3, washing and drying the filter residue to obtain regenerated carbon fiber; collecting the filtrate for later use.

2. The method for degrading and recycling waste carbon fiber resin composite materials according to claim 1, characterized in that: The mass ratio of the alkali metal hydroxide: the alkylguanidine compound: the alcohol solvent is 10-20:3-5:

100.

3. The method for degrading and recycling waste carbon fiber resin composite materials according to claim 1, characterized in that: The mass ratio of the carbon fiber resin composite material waste to the degradation liquid is 1:1.5-2.

4. The method for degrading and recycling waste carbon fiber resin composite materials according to claim 1, characterized in that: In step S1, the heating temperature is 80-140° C. and the heating time is 0.5-10 h.

5. The method for degrading and recycling waste carbon fiber resin composite materials according to claim 1, characterized in that: The alkali metal hydroxide is one or both of potassium hydroxide and sodium hydroxide; The alkylguanidine compound is one or more combinations of 1,1,3,3-tetramethylguanidine, 1,1,3,3-tetraethylguanidine and 1,1,3,3-tetrapropylguanidine; The alcohol solvent is one or more combinations of n-propanol, isopropanol, n-butanol and isobutanol.

6. The method for degrading and recycling waste carbon fiber resin composite materials according to claim 1, characterized in that: The carbon fiber resin composite material waste is one or more combinations of carbon fiber / epoxy resin waste, carbon fiber / cyanate resin waste, carbon fiber / bismaleimide resin waste and carbon fiber / polyimide resin waste.

7. The method for degrading and recycling waste carbon fiber resin composite materials according to claim 1, characterized in that: The regenerated carbon fiber, phenolic resin and active particles obtained in step S3 are mixed and hot-molded to obtain a protective material; The active particles are one or a combination of two of silicon carbide, hafnium carbide and titanium boride.

8. The method for degrading and recycling waste carbon fiber resin composite materials according to claim 7, characterized in that: The mass ratio of the regenerated carbon fiber: phenolic resin: active particles is 1:1-2:0.2-0.5; The parameters for hot molding are 170-190℃, 8-12MPa and molding for 2-3h.

9. Use of the thermal protection material obtained by the method for degrading and recycling waste carbon fiber resin composite materials according to claim 7 or 8 in the thermal protection material of the nozzle of a solid rocket engine.

10. Use of the filtrate obtained by the method for degrading and recycling waste carbon fiber resin composite materials according to claim 1 in epoxy resin curing agent.

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