Method for recycling carbon fiber material from waste wind power blade main beam carbon plate, hydrophilic carbon fiber and wave-absorbing material

Abstract

The invention provides a method for recycling a carbon fiber material from a waste wind power blade main beam carbon plate, hydrophilic carbon fibers and a wave-absorbing material, and belongs to the technical field of waste recycling and reusing and electromagnetic wave absorbing materials. The wave-absorbing material is prepared by the following steps: recycling a carbon fiber material in a waste wind power blade main beam carbon plate by pyrolyzing the waste wind power blade main beam carbon plate, crushing the carbon fiber material into powder by a ball mill, doping recycled carbon fibers and recycled carbon fiber powder according to a certain proportion, preparing the recycled carbon fibers and the recycled carbon fiber powder into a composite wave-absorbing material sample by using epoxy resin as a matrix through a template method, and preparing the composite wave-absorbing material sample into a sample. Finally, a composite wave-absorbing material product with excellent wave-absorbing performance is obtained. The recycled carbon fiber material can be subjected to surface modification in a pyrolysis oxidation mode, clean hydrophilic carbon fibers are obtained, the treated carbon fiber surface has more oxygen-containing groups, the interfacial compatibility and bonding strength of the carbon fiber and a matrix can be improved, and the carbon fiber material can be suitable for compounding of other various materials.

Description

Technical Field

[0001] The present invention belongs to the technical field of waste recycling and electromagnetic wave absorbing materials, and specifically relates to a method for recycling carbon fiber materials from discarded wind turbine blade main beam carbon plates, hydrophilic carbon fibers and absorbing materials. Background Art

[0002] Carbon fiber reinforced polymer (CFRP) has the characteristics of low density, high strength, high modulus, and good corrosion resistance. It is widely used in various industries such as automobiles, aerospace, and wind power generation. The excellent mechanical properties and price advantages of CFRP have led to a rapid increase in its industrial demand. However, as CFRP components fail or become obsolete, a large amount of waste and residue will be generated, resulting in inefficient utilization of carbon fiber resources. Therefore, recycling carbon fiber from CFRP has become an urgent problem to be solved in this field. In order to solve the increasingly serious problem of CFRP waste, researchers have explored various recycling technologies. First, early carbon fiber composite waste would be incinerated and landfilled, but this treatment method will cause soil pollution and has been explicitly prohibited by legislation in many countries. Secondly, there is the physical recycling method, which grinds, cuts or crushes the composite waste to obtain short fibers, particles, powders and other materials. This method is low-cost, simple process and pollutant-free. However, it is only applicable to uncontaminated composite waste, and the strength of the fiber will be seriously reduced after treatment. Then, there is the chemical method, which uses solvents and heat to break the cross-linking bonds in the resin, decomposing the resin into low molecular weight polymers or small organic molecules and dissolving them in the solvent, thereby separating the carbon fiber from the resin matrix. However, this is not a suitable recycling method because it is costly and produces harmful gases such as nitrogen oxides, sulfides and volatile organic solvents. Finally, thermal cracking is the most widely used method. It is a method of decomposing the composite resin matrix in an inert gas or oxygen environment at a high temperature of 300-800°C (the specific operating temperature depends on the cracking temperature of the resin) to achieve the recovery of carbon fiber and other materials.

[0003] With the vigorous development of wireless communication equipment and electronic equipment, the problem of electromagnetic pollution is becoming increasingly serious. The leakage of electromagnetic waves not only affects the precise operation of the equipment and human health, but also endangers national security. Therefore, the development of efficient electromagnetic wave absorbing materials has important research significance and practical application value. Among them, carbon fiber absorbing materials are widely used in military and civilian fields, such as stealth technology and electromagnetic compatibility. In terms of background technology, carbon fiber itself has excellent mechanical properties and electrical properties. It can achieve absorbing function by adjusting the microstructure, surface state and composite method of carbon fiber. However, with the increase in usage and product upgrading, a large amount of carbon fiber absorbing material waste is generated. Therefore, how to recycle and reuse it has great research value.

[0004] However, the residual pyrolytic carbon on the surface of the recycled carbon fiber will hinder the composite of the carbon fiber and the matrix. It is necessary to remove the residual carbon by oxidation and obtain clean hydrophilic carbon fiber. At the same time, solid waste is fully utilized, which conforms to the concept of green and environmentally friendly material synthesis. The process is simple and efficient, achieving multiple goals at one stroke. However, there are few studies on this aspect at present. Therefore, it is of great significance to develop a simple and effective preparation method using low-cost compounds to prepare composite absorbing materials with higher performance to improve their practical applicability. Summary of the invention

[0005] The purpose of the present invention is to solve the problem of recycling and reusing the carbon plates of discarded wind turbine blade main beams, as well as the problem that the structure of electromagnetic wave absorbing materials is easy to diversify, the mechanism of action is difficult to clarify, and the practical applicability is limited, and to provide a method for recycling carbon fiber materials from discarded wind turbine blade main beam carbon plates, hydrophilic carbon fibers and absorbing materials.

[0006] The present invention first provides a method for recycling carbon fiber materials from discarded wind turbine blade main beam carbon plates, comprising:

[0007] The discarded wind turbine blade main beam carbon plate is cut into small pieces of 2-5 cm in length by a cutting machine. Nitrogen is introduced into the furnace before the reaction to exhaust the gas. After nitrogen is introduced into the tubular furnace, the cut carbon plate is placed therein. The temperature in the pyrolysis furnace is gradually increased from the starting temperature to 400-600°C at a heating rate of 10-30°C / min, and the temperature is maintained for 30-50 minutes to fully pyrolyze the resin matrix in the discarded carbon plate into small molecular gaseous products to obtain recycled carbon fiber materials.

[0008] Preferably, the flow rate of nitrogen into the tube furnace is 30-50 mL / min.

[0009] The present invention also provides recycled carbon fiber material obtained by the above method for recycling carbon fiber material from discarded wind turbine blade main beam carbon plates.

[0010] The present invention also provides a hydrophilic carbon fiber, the preparation method of which comprises:

[0011] The recycled carbon fiber material is cooled to room temperature, placed in a tubular furnace, and pure oxygen is introduced in advance, exhausted, and after the oxygen is introduced, the temperature in the pyrolysis furnace is gradually increased from the starting temperature to 450-550°C at a heating rate of 10-30°C / min, and reacted for 20-40 minutes to oxidize the pyrolytic carbon and residual organic matter on the surface of the carbon fiber to obtain hydrophilic carbon fiber.

[0012] Preferably, the gas flow rate of oxygen into the tube furnace is 30 ml / min.

[0013] The present invention also provides a wave absorbing material, and a method for preparing the wave absorbing material comprises:

[0014] The recycled carbon fiber material is ground into powder to obtain recycled carbon fiber powder, and the recycled carbon fiber powder, recycled carbon fiber, or the recycled carbon fiber powder and recycled carbon fiber are doped and compounded with epoxy resin to obtain absorbing materials.

[0015] Preferably, the mass ratio of the recycled carbon fiber to the recycled carbon fiber powder is 1-2:1.

[0016] Preferably, the composite mass ratio of the recycled carbon fiber to the epoxy resin is 1:1.

[0017] Preferably, the composite mass ratio of the recycled carbon fiber powder to the epoxy resin is 1:2.

[0018] Beneficial effects of the present invention

[0019] The present invention provides a method for recycling carbon fiber materials from discarded wind turbine blade main beam carbon plates, hydrophilic carbon fibers and wave-absorbing materials. The wave-absorbing materials are obtained by pyrolyzing discarded wind turbine blade main beam carbon plates to recover the carbon fiber materials therein, crushing the carbon fiber materials into powders by a ball mill, doping the recovered carbon fibers and the recovered carbon fiber powder in a certain proportion, and then preparing them into composite wave-absorbing material samples by a template method with epoxy resin as a matrix, and finally obtaining a composite wave-absorbing material product with excellent wave-absorbing performance.

[0020] The carbon fiber material recycled by the present invention can also be surface-modified by pyrolysis and oxidation to obtain clean hydrophilic carbon fiber. The surface of the treated carbon fiber has more oxygen-containing groups, which can improve its interface compatibility and bonding strength with the matrix, and can also adapt to the composite of various other materials.

[0021] In the present invention, the generation of surface pyrolytic carbon is adjusted by precisely controlling the temperature and time of carbonization in the low-temperature carbonization stage, so as to realize controllable adjustment of the surface composition and microstructure of carbon fiber. The recycled carbon fiber / epoxy resin composite material has multiple loss mechanisms and exhibits excellent microwave absorption performance. The advantages of this design are: first, the single dielectric material can achieve excellent absorbing performance, which is more suitable for practical applications; second, the recycled carbon fiber material is surface-modified by pyrolysis and oxidation, and the treated fiber surface has more oxygen-containing groups, which can improve its interface compatibility and bonding strength with the matrix, and can also adapt to the composite of various other materials; third, the rational use of waste can also meet the urgent needs under the situation of green chemistry concept. Provided is a absorbing material with the characteristics of simple synthesis process, stable structure, high absorbing performance, low cost, and strong applicability. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 The XRD image of the carbon plate of the abandoned wind turbine blade main beam, which is the raw material of Example 1 of the present invention;

[0023] Figure 2 The infrared image of the carbon plate of the main beam of the wind turbine blade which is the raw material of Example 1 of the present invention;

[0024] Figure 3 This is a SEM image of the carbon plate of the abandoned wind turbine blade main beam as the raw material of Example 1 of the present invention;

[0025] Figure 4 This is the XRD image of the recycled carbon fiber material obtained in Example 2-4 of the present invention;

[0026] Figure 5 This is an infrared image of the recycled carbon fiber material obtained in Example 2-4 of the present invention;

[0027] Figure 6 This is a SEM image of the carbon fiber material recovered at a pyrolysis temperature of 400° C. obtained in Example 2 of the present invention;

[0028] Figure 7 This is a SEM image of the carbon fiber material recovered at a pyrolysis temperature of 500° C. obtained in Example 3 of the present invention;

[0029] Figure 8 This is a SEM image of the carbon fiber material recovered at a pyrolysis temperature of 600° C. obtained in Example 4 of the present invention;

[0030] Fig. 9 This is a SEM image of the recycled carbon fiber material obtained in Example 5 of the present invention;

[0031] Fig.10 This is a SEM image of the recycled carbon fiber material obtained in Example 6 of the present invention;

[0032] Fig.11 This is a SEM image of the recycled carbon fiber material obtained in Example 7 of the present invention;

[0033] Fig.12 This is a SEM image of the recycled carbon fiber material obtained in Example 8 of the present invention;

[0034] Fig.13 XRD images of the oxidized recycled carbon fiber materials obtained in Examples 9-11 of the present invention;

[0035] Fig.14 This is an infrared image of the oxidized recycled carbon fiber material obtained in Examples 9-11 of the present invention;

[0036] Fig.15 This is a SEM image of the recycled carbon fiber material with an oxidation temperature of 450° C. obtained in Example 9 of the present invention;

[0037] Fig.16This is a SEM image of the recycled carbon fiber material with an oxidation temperature of 500° C. obtained in Example 10 of the present invention;

[0038] Fig.17 This is a SEM image of the recycled carbon fiber material with an oxidation temperature of 550° C. obtained in Example 11 of the present invention;

[0039] Fig.18 This is a SEM image of the oxidized recycled carbon fiber material of Example 12 of the present invention;

[0040] Fig.19 This is a SEM image of the oxidized recycled carbon fiber material of Example 13 of the present invention;

[0041] Fig. 20 This is a SEM image of the oxidized recycled carbon fiber material of Example 14 of the present invention;

[0042] Fig.21 This is a SEM image of the oxidized recycled carbon fiber material of Example 15 of the present invention;

[0043] Fig. 22 2D reflection loss diagram of the recycled carbon fiber / epoxy resin RCF1 composite absorbing material obtained in Example 16 of the present invention;

[0044] Fig.23 2D reflection loss diagram of the recycled carbon fiber / recycled carbon fiber powder / epoxy resin RCF2-1 composite absorbing material obtained in Example 17 of the present invention;

[0045] Fig.24 2D reflection loss diagram of the recycled carbon fiber / recycled carbon fiber powder / epoxy resin RCF2-1.5 composite absorbing material obtained in Example 18 of the present invention;

[0046] Fig.25 2D reflection loss diagram of the recycled carbon fiber / recycled carbon fiber powder / epoxy resin RCF2-2 composite absorbing material obtained in Example 19 of the present invention;

[0047] Fig.26 This is a 2D reflection loss diagram of the recycled carbon fiber powder / epoxy resin RCF3 composite absorbing material obtained in Example 20 of the present invention. DETAILED DESCRIPTION

[0048] The present invention first provides a method for recycling carbon fiber materials from discarded wind turbine blade main beam carbon plates, comprising:

[0049] The discarded wind turbine blade main beam carbon plate is cut into small pieces of 2-5 cm in length by a cutting machine. Before the reaction, nitrogen is introduced into the furnace to exhaust the gas. The exhaust time is preferably 3 minutes. This process is preferably repeated three times to ensure that the air in the tube is completely removed. After nitrogen is introduced into the tubular furnace, the cut carbon plate is placed therein. The temperature in the pyrolysis furnace is gradually increased from the starting temperature to 400-600°C at a heating rate of 10-30°C / min. The temperature is maintained for 30-50 minutes to fully pyrolyze the resin matrix in the discarded carbon plate into small molecular gaseous products to obtain recycled carbon fiber materials. The flow rate of the nitrogen introduced into the tubular furnace is preferably 30-50mL / min.

[0050] The present invention also provides recycled carbon fiber material obtained by the above method for recycling carbon fiber material from discarded wind turbine blade main beam carbon plates.

[0051] The present invention also provides a hydrophilic carbon fiber, comprising:

[0052] The recycled carbon fiber material is cooled to room temperature, placed in a tubular furnace, and pure oxygen is introduced in advance. The gas flow rate is preferably 30 ml / min, and the exhaust is preferably 3 minutes. This process is preferably repeated three times to ensure that the air in the tube is completely removed. After the oxygen is introduced, the temperature in the pyrolysis furnace is gradually increased from the starting temperature to 450-550°C at a heating rate of 10-30°C / min, and the reaction is performed for 20-40 minutes to oxidize the pyrolytic carbon and residual organic matter on the surface of the carbon fiber to obtain hydrophilic carbon fiber.

[0053] The present invention also provides a wave absorbing material, and a method for preparing the wave absorbing material comprises:

[0054] The recycled carbon fiber material is ground into powder to obtain recycled carbon fiber powder, and the recycled carbon fiber powder, recycled carbon fiber, or recycled carbon fiber powder and recycled carbon fiber are doped and compounded with epoxy resin to obtain an absorbing material. The mass ratio of the recycled carbon fiber to the recycled carbon fiber powder is preferably 1-2:1; the mass ratio of the recycled carbon fiber to the epoxy resin is preferably 1:1; the mass ratio of the recycled carbon fiber powder to the epoxy resin is preferably 1:2. The epoxy resin is purchased from a commercial source, and preferably the product produced by Shenzhen Juhengchuang Electronic Materials Co., Ltd. is selected.

[0055] The present invention is further described in detail below with reference to specific examples. The raw materials involved in the examples are commercially available.

[0056] Example 1

[0057] The treatment of discarded wind turbine blade main beam carbon plates is carried out according to the following steps: clean the discarded wind turbine blade main beam carbon plates, cut them into small pieces of 2-5 cm in length with a cutting machine, put them into a ball mill at 30Hz for 15 minutes and grind them into powder to facilitate subsequent blank control tests.

[0058] Figure 1 The XRD image of the carbon plate of the abandoned wind turbine blade main beam, which is the raw material of Example 1 of the present invention, can be seen from the figure that there are two different diffraction peaks in the XRD pattern. The first peak is located at about 2θ = 25.5°, corresponding to the (002) grain plane of the graphite-like microcrystals in the fiber. The second peak is weaker in intensity and can be observed near 2θ = 44.5°, which is attributed to the (100) grain plane of the graphite-like structure.

[0059] Figure 2 The infrared image of the carbon plate of the abandoned wind turbine blade main beam, which is the raw material of Example 1 of the present invention, shows that the surface functional groups of VCF are mainly -OH (3100-3700cm -1 )、-CH(2840-3010cm -1 ,1510-1760cm -1 and 1350-1490cm -1 )、-C=O(1600-1750cm -1 ) and -CO(1000-1250cm -1 ).

[0060] Figure 3 This is a SEM image of the carbon plate of the abandoned wind turbine blade main beam, which is the raw material of Example 1 of the present invention. From the image, the fiber structure and resin structure on the surface of the carbon plate can be seen.

[0061] Example 2

[0062] The waste wind turbine blade main beam carbon plate was cut into small pieces of 2-5 cm in length by a cutting machine. Nitrogen was introduced into the furnace before the reaction and the exhaust was performed for 3 minutes. This process was repeated three times to ensure that the air in the tube was completely removed. After nitrogen was steadily introduced into the tubular furnace at a flow rate of 50 mL / min, the cut carbon plate was placed in it. The temperature in the pyrolysis furnace was gradually increased from the starting temperature to 400°C at a heating rate of 10°C / min. When the temperature in the pyrolysis furnace reached the target temperature, the temperature was maintained for 30 minutes to fully pyrolyze the resin matrix in the waste carbon plate into small molecular gaseous products.

[0063] Figure 6This is the SEM image of the recycled carbon fiber material with a pyrolysis temperature of 400°C obtained in Example 2 of the present invention. It can be seen from the figure that a small amount of carbon residue is attached to the surface of the RCF fiber, and the formation of carbon residue will comprehensively affect the absorption behavior of electromagnetic waves. An appropriate proportion of residual carbon will affect the conductive behavior, which can be regarded as a knot, promoting the migration of electrons in the fiber-based framework, thereby increasing the conductive loss. In addition, decorating the carbon residue on the fiber surface can change the interface characteristics, making it a micro-capacitor structure, thereby improving the interfacial polarization behavior of the fiber. However, excessive carbon residue can lead to the opposite result, causing fiber aggregation, shortening the path of electron migration, and affecting the dissipation of energy. Shortening the path of electron migration affects the heat dissipation of electromagnetic energy, thereby adversely affecting the shielding and attenuation of electromagnetic waves.

[0064] Example 3

[0065] The waste wind turbine blade main beam carbon plate was cut into small pieces of 2-5 cm in length by a cutting machine. Nitrogen was introduced into the furnace before the reaction and the exhaust was performed for 3 minutes. This process was repeated three times to ensure that the air in the tube was completely removed. After nitrogen was steadily introduced into the tubular furnace at a flow rate of 50 mL / min, the cut carbon plate was placed in it. The temperature in the pyrolysis furnace was gradually increased from the starting temperature to 500°C at a heating rate of 10°C / min. When the temperature in the pyrolysis furnace reached the target temperature, the temperature was maintained for 30 minutes to fully pyrolyze the resin matrix in the waste carbon plate into small molecular gaseous products.

[0066] Figure 7 This is the SEM image of the recycled carbon fiber material with a pyrolysis temperature of 500°C obtained in Example 3 of the present invention. It can be seen from the figure that a small amount of carbon residue is attached to the surface of the RCF fiber, and the formation of carbon residue will comprehensively affect the absorption behavior of electromagnetic waves. An appropriate proportion of residual carbon will affect the conductive behavior, which can be regarded as a knot, promoting the migration of electrons in the fiber-based framework and increasing the conductive loss. In addition, decorating the carbon residue on the fiber surface can change the interface characteristics, making it a micro-capacitor structure, thereby improving the interfacial polarization behavior of the fiber. However, excessive carbon residue will lead to the opposite result, causing fiber aggregation, shortening the path of electron migration, and affecting the dissipation of energy. Shortening the path of electron migration affects the heat dissipation of electromagnetic energy, thereby adversely affecting the shielding and attenuation of electromagnetic waves.

[0067] Example 4

[0068] The waste wind turbine blade main beam carbon plate was cut into small pieces of 2-5 cm in length by a cutting machine. Nitrogen was introduced into the furnace before the reaction and the exhaust was performed for 3 minutes. This process was repeated three times to ensure that the air in the tube was completely removed. After nitrogen was steadily introduced into the tubular furnace at a flow rate of 50 mL / min, the cut carbon plate was placed in it. The temperature in the pyrolysis furnace was gradually increased from the starting temperature to 600°C at a heating rate of 10°C / min. When the temperature in the pyrolysis furnace reached the target temperature, the temperature was maintained for 30 minutes to fully pyrolyze the resin matrix in the waste carbon plate into small molecular gaseous products.

[0069] Figure 4 The XRD image of the recycled carbon fiber material obtained in Example 2-4 of the present invention shows two different diffraction peaks in the XRD pattern. The first peak is located at about 25.5° (2θ), which is more prominent and corresponds to the (002) grain plane of the graphite-like crystallites in the fiber. The second peak is weaker and can be observed near 44.5° (2θ), which is attributed to the (100) grain plane of the graphite-like structure.

[0070] Figure 5 The infrared images of the recycled carbon fiber materials obtained in Examples 2-4 of the present invention show that after pyrolysis, the content of oxygen-containing functional groups on the surface of the pyrolyzed solid is reduced.

[0071] Figure 8 The SEM image of the recycled carbon fiber material with a pyrolysis temperature of 600°C obtained in Example 4 of the present invention shows that a small amount of carbon residue is attached to the surface of the RCF fiber, and the formation of carbon residue will comprehensively affect the absorption behavior of electromagnetic waves. An appropriate proportion of residual carbon will affect the conductive behavior, which can be regarded as a knot, promoting the migration of electrons in the fiber-based framework, thereby increasing the conductive loss. In addition, decorating the carbon residue on the fiber surface can change the interface characteristics, making it a micro-capacitor structure, thereby improving the interfacial polarization behavior of the fiber. However, excessive carbon residue can lead to the opposite result, causing fiber aggregation, shortening the path of electron migration, and affecting the dissipation of energy. Shortening the path of electron migration affects the heat dissipation of electromagnetic energy, thereby adversely affecting the shielding and attenuation of electromagnetic waves.

[0072] Example 5

[0073] The waste wind turbine blade main beam carbon plate was cut into small pieces of 2-5 cm in length by a cutting machine. Nitrogen was introduced into the furnace before the reaction and the exhaust was performed for 3 minutes. This process was repeated three times to ensure that the air in the tube was completely removed. After nitrogen was steadily introduced into the tubular furnace at a flow rate of 40 mL / min, the cut carbon plate was placed in it. The temperature in the pyrolysis furnace was gradually increased from the starting temperature to 500°C at a heating rate of 10°C / min. When the temperature in the pyrolysis furnace reached the target temperature, the temperature was maintained for 30 minutes to fully pyrolyze the resin matrix in the waste carbon plate into small molecular gaseous products.

[0074] Fig. 9 This is the SEM image of the recycled carbon fiber material obtained in Example 5 of the present invention. It can be seen from the figure that a small amount of carbon residue is attached to the surface of the rcf fiber, and the formation of carbon residue will comprehensively affect the absorption behavior of electromagnetic waves. The appropriate proportion of residual carbon will affect the conductive behavior, which can be regarded as a knot, promoting the migration of electrons in the fiber-based framework, thereby increasing the conductive loss. In addition, decorating the carbon residue on the fiber surface can change the interface characteristics, making it a micro-capacitor structure, thereby improving the interfacial polarization behavior of the fiber. However, excessive carbon residue can lead to the opposite result, causing fiber aggregation, shortening the path of electron migration, and affecting the dissipation of energy. Shortening the path of electron migration affects the heat dissipation of electromagnetic energy, thereby adversely affecting the shielding and attenuation of electromagnetic waves.

[0075] Example 6

[0076] The waste wind turbine blade main beam carbon plate was cut into small pieces of 2-5 cm in length by a cutting machine. Nitrogen was introduced into the furnace before the reaction and the exhaust was performed for 3 minutes. This process was repeated three times to ensure that the air in the tube was completely removed. After nitrogen was steadily introduced into the tubular furnace at a flow rate of 30 mL / min, the cut carbon plate was placed in it. The temperature in the pyrolysis furnace was gradually increased from the starting temperature to 500°C at a heating rate of 10°C / min. When the temperature in the pyrolysis furnace reached the target temperature, the temperature was maintained for 30 minutes to fully pyrolyze the resin matrix in the waste carbon plate into small molecular gaseous products.

[0077] Fig.10The SEM image of the recycled carbon fiber material obtained in Example 6 of the present invention shows that a small amount of carbon residue is attached to the surface of the rcf fiber, and the formation of carbon residue will comprehensively affect the absorption behavior of electromagnetic waves. The appropriate proportion of residual carbon will affect the conductive behavior, which can be regarded as a knot, promoting the migration of electrons in the fiber-based framework, thereby increasing the conductive loss. In addition, decorating the carbon residue on the fiber surface can change the interface characteristics, making it a micro-capacitor structure, thereby improving the interfacial polarization behavior of the fiber. However, excessive carbon residue can lead to the opposite result, causing fiber aggregation, shortening the path of electron migration, and affecting the dissipation of energy. Shortening the path of electron migration affects the heat dissipation of electromagnetic energy, thereby adversely affecting the shielding and attenuation of electromagnetic waves.

[0078] Example 7

[0079] The waste wind turbine blade main beam carbon plate was cut into small pieces of 2-5 cm in length by a cutting machine. Nitrogen was introduced into the furnace before the reaction and the exhaust was performed for 3 minutes. This process was repeated three times to ensure that the air in the tube was completely removed. After nitrogen was steadily introduced into the tubular furnace at a flow rate of 50 mL / min, the cut carbon plate was placed in it. The temperature in the pyrolysis furnace was gradually increased from the starting temperature to 500°C at a heating rate of 10°C / min. When the temperature in the pyrolysis furnace reached the target temperature, the temperature was maintained for 40 minutes to fully pyrolyze the resin matrix in the waste carbon plate into small molecular gaseous products.

[0080] Fig.11 The SEM image of the recycled carbon fiber material obtained in Example 7 of the present invention shows that a small amount of carbon residue is attached to the surface of the rcf fiber, and the formation of carbon residue will comprehensively affect the absorption behavior of electromagnetic waves. The appropriate proportion of residual carbon will affect the conductive behavior, which can be regarded as a knot, promoting the migration of electrons in the fiber-based framework, thereby increasing the conductive loss. In addition, decorating the carbon residue on the fiber surface can change the interface characteristics, making it a micro-capacitor structure, thereby improving the interfacial polarization behavior of the fiber. However, excessive carbon residue can lead to the opposite result, causing fiber aggregation, shortening the path of electron migration, and affecting the dissipation of energy. Shortening the path of electron migration affects the heat dissipation of electromagnetic energy, thereby adversely affecting the shielding and attenuation of electromagnetic waves.

[0081] Example 8

[0082] The waste wind turbine blade main beam carbon plate was cut into small pieces of 2-5 cm in length by a cutting machine. Nitrogen was introduced into the furnace before the reaction and the exhaust was performed for 3 minutes. This process was repeated three times to ensure that the air in the tube was completely removed. After nitrogen was steadily introduced into the tubular furnace at a flow rate of 50 mL / min, the cut carbon plate was placed in it. The temperature in the pyrolysis furnace was gradually increased from the starting temperature to 500°C at a heating rate of 10°C / min. When the temperature in the pyrolysis furnace reached the target temperature, the temperature was maintained for 50 minutes to fully pyrolyze the resin matrix in the waste carbon plate into small molecular gaseous products.

[0083] Fig.12 The SEM image of the recycled carbon fiber material obtained in Example 8 of the present invention shows that a small amount of carbon residue is attached to the surface of the rcf fiber, and the formation of carbon residue will comprehensively affect the absorption behavior of electromagnetic waves. The appropriate proportion of residual carbon will affect the conductive behavior, which can be regarded as a knot, promoting the migration of electrons in the fiber-based framework, thereby increasing the conductive loss. In addition, decorating the carbon residue on the fiber surface can change the interface characteristics, making it a micro-capacitor structure, thereby improving the interfacial polarization behavior of the fiber. However, excessive carbon residue can lead to the opposite result, causing fiber aggregation, shortening the path of electron migration, and affecting the dissipation of energy. Shortening the path of electron migration affects the heat dissipation of electromagnetic energy, thereby adversely affecting the shielding and attenuation of electromagnetic waves.

[0084] Example 9

[0085] The discarded wind turbine blade main beam carbon plate is cut into small pieces of 2-5 cm in length with a cutting machine. Nitrogen is introduced into the furnace before the reaction, and the exhaust is carried out for 3 minutes. This process is repeated three times to ensure that the air in the tube is completely removed. After nitrogen is steadily introduced into the tubular furnace at a flow rate of 50 mL / min, the cut carbon plate is placed in it, and the temperature in the pyrolysis furnace is gradually increased from the starting temperature to 500°C at a heating rate of 10°C / min. When the temperature in the pyrolysis furnace reaches the target temperature, the temperature is maintained for 30 minutes to fully pyrolyze the resin matrix in the discarded carbon plate into small molecular gaseous products. After the pyrolysis is completed, the solid is cooled to room temperature, the residual solid is taken out and placed in the tubular furnace, pure oxygen is introduced in advance, and the exhaust is carried out for 3 minutes. This process is repeated three times to ensure that the air is completely removed. Then, after introducing 30% oxygen concentration, the temperature in the pyrolysis furnace was gradually increased from the starting temperature to 450°C at a heating rate of 10°C / min, and the reaction was carried out for 20 minutes to oxidize the pyrolytic carbon and residual organic matter on the surface of the carbon fiber, and finally obtain clean hydrophilic carbon fiber.

[0086] Fig.15This is the SEM image of the recycled carbon fiber material with an oxidation temperature of 450°C obtained in Example 9 of the present invention. It can be seen from the figure that after oxidation, the carbon residue attached to the surface of the rcf fiber is reduced compared to that of the rcf fiber, which proves that the oxidation process can indeed effectively remove the carbon remaining on the fiber surface produced during the resin decomposition process.

[0087] Example 10

[0088] The discarded wind turbine blade main beam carbon plate is cut into small pieces of 2-5 cm long with a cutting machine. Nitrogen is passed into the furnace before the reaction, and the exhaust is carried out for 3 minutes. This process is repeated three times to ensure that the air in the tube is completely removed. After nitrogen is steadily passed into the tubular furnace at a flow rate of 50 mL / min, the cut carbon plate is placed in it, and the temperature in the pyrolysis furnace is gradually increased from the starting temperature to 500°C at a heating rate of 10°C / min. When the temperature in the pyrolysis furnace reaches the target temperature, the temperature is maintained for 30 minutes to fully pyrolyze the resin matrix in the discarded carbon plate into small molecular gaseous products. After the pyrolysis is completed, the solid is cooled to room temperature, the residual solid is taken out and placed in the tubular furnace, pure oxygen is pre-passed, and then the exhaust is carried out for 3 minutes. This process is repeated three times to ensure that the air is completely removed. Then, after introducing 30% oxygen concentration, the temperature in the pyrolysis furnace was gradually increased from the starting temperature to 500°C at a heating rate of 10°C / min, and the reaction was carried out for 20 minutes to oxidize the pyrolytic carbon and residual organic matter on the surface of the carbon fiber, and finally obtain clean hydrophilic carbon fiber.

[0089] Fig.16 This is the SEM image of the recycled carbon fiber material at an oxidation temperature of 500°C in Example 10 of the present invention. It can be seen from the figure that after oxidation, the carbon residue attached to the surface of the rcf fiber is reduced compared to that of the rcf fiber, which proves that the oxidation process can indeed effectively remove the carbon remaining on the fiber surface produced during the resin decomposition process.

[0090] Embodiment 11

[0091] The discarded wind turbine blade main beam carbon plate is cut into small pieces of 2-5 cm long with a cutting machine. Nitrogen is passed into the furnace before the reaction, and the exhaust is carried out for 3 minutes. This process is repeated three times to ensure that the air in the tube is completely removed. After nitrogen is steadily passed into the tubular furnace at a flow rate of 50 mL / min, the cut carbon plate is placed in it, and the temperature in the pyrolysis furnace is gradually increased from the starting temperature to 500°C at a heating rate of 10°C / min. When the temperature in the pyrolysis furnace reaches the target temperature, the temperature is maintained for 30 minutes to fully pyrolyze the resin matrix in the discarded carbon plate into small molecular gaseous products. After the pyrolysis is completed, the solid is cooled to room temperature, the residual solid is taken out and placed in the tubular furnace, pure oxygen is pre-passed, and then the exhaust is carried out for 3 minutes. This process is repeated three times to ensure that the air is completely removed. Then, after introducing 30% oxygen concentration, the temperature in the pyrolysis furnace was gradually increased from the starting temperature to 550°C at a heating rate of 10°C / min, and the reaction was carried out for 20 minutes to oxidize the pyrolytic carbon and residual organic matter on the surface of the carbon fiber, and finally obtain clean hydrophilic carbon fiber.

[0092] Fig.13 The XRD images of the oxidized recycled carbon fiber materials obtained in Examples 9-11 of the present invention show that there are two different diffraction peaks in the XRD pattern. The first peak is located at about 25.5° (2θ), which is more prominent and corresponds to the (002) grain plane of the graphite-like crystallites in the fiber. The second peak is weaker and can be observed near 44.5° (2θ), which is attributed to the (100) grain plane of the graphite-like structure.

[0093] Fig.14 The infrared images of the oxidized recycled carbon fiber materials obtained in Examples 9-11 of the present invention show that the pyrolysis oxidation process successfully introduces various functional groups such as -OH, -CH, hydrogen bonds, -CO and -C=O into the fiber surface. The presence of -OH or -COOH groups on the fiber surface can form covalent bonds with the polymer matrix, effectively combining the fibers and transferring stress between the matrix and the fibers. This phenomenon may potentially enhance interfacial adhesion, thereby improving the future reuse prospects of RCF.

[0094] Fig.17 This is the SEM image of the recycled carbon fiber material with an oxidation temperature of 550°C in Example 11 of the present invention. It can be seen from the figure that after oxidation, the carbon residue attached to the surface of the rcf fiber is reduced compared to that of the rcf fiber, which proves that the oxidation process can indeed effectively remove the carbon remaining on the fiber surface produced during the resin decomposition process.

[0095] Example 12

[0096] The discarded wind turbine blade main beam carbon plate is cut into small pieces of 2-5 cm in length with a cutting machine. Nitrogen is introduced into the furnace before the reaction, and the exhaust is carried out for 3 minutes. This process is repeated three times to ensure that the air in the tube is completely removed. After nitrogen is steadily introduced into the tubular furnace at a flow rate of 50 mL / min, the cut carbon plate is placed in it, and the temperature in the pyrolysis furnace is gradually increased from the starting temperature to 500°C at a heating rate of 10°C / min. When the temperature in the pyrolysis furnace reaches the target temperature, the temperature is maintained for 30 minutes to fully pyrolyze the resin matrix in the discarded carbon plate into small molecular gaseous products. After the pyrolysis is completed, the solid is cooled to room temperature, the residual solid is taken out and placed in the tubular furnace, pure oxygen is introduced in advance, and the exhaust is carried out for 3 minutes. This process is repeated three times to ensure that the air is completely removed. Then, after introducing 30% oxygen concentration, the temperature in the pyrolysis furnace was gradually increased from the starting temperature to 450°C at a heating rate of 20°C / min, and the reaction was carried out for 20 minutes to oxidize the pyrolytic carbon and residual organic matter on the surface of the carbon fiber, and finally obtain clean hydrophilic carbon fiber.

[0097] Fig.18 This is the SEM image of the oxidized recycled carbon fiber material of Example 12 of the present invention. It can be seen from the figure that after oxidation, the carbon residue attached to the surface of the rcf fiber is reduced compared to that of the rcf fiber, which proves that the oxidation process can indeed effectively remove the carbon remaining on the fiber surface produced during the resin decomposition process.

[0098] Embodiment 13

[0099] The discarded wind turbine blade main beam carbon plate is cut into small pieces of 2-5 cm in length with a cutting machine. Nitrogen is introduced into the furnace before the reaction, and the exhaust is carried out for 3 minutes. This process is repeated three times to ensure that the air in the tube is completely removed. After nitrogen is steadily introduced into the tubular furnace at a flow rate of 50 mL / min, the cut carbon plate is placed in it, and the temperature in the pyrolysis furnace is gradually increased from the starting temperature to 500°C at a heating rate of 10°C / min. When the temperature in the pyrolysis furnace reaches the target temperature, the temperature is maintained for 30 minutes to fully pyrolyze the resin matrix in the discarded carbon plate into small molecular gaseous products. After the pyrolysis is completed, the solid is cooled to room temperature, the residual solid is taken out and placed in the tubular furnace, pure oxygen is introduced in advance, and the exhaust is carried out for 3 minutes. This process is repeated three times to ensure that the air is completely removed. Then, after introducing 30% oxygen concentration, the temperature in the pyrolysis furnace was gradually increased from the starting temperature to 450°C at a heating rate of 30°C / min, and the reaction was carried out for 20 minutes to oxidize the pyrolytic carbon and residual organic matter on the surface of the carbon fiber, and finally obtain clean hydrophilic carbon fiber.

[0100] Fig.19This is the SEM image of the oxidized recycled carbon fiber material of Example 13 of the present invention. It can be seen from the figure that after oxidation, the carbon residue attached to the surface of the rcf fiber is reduced compared to that of the rcf fiber, which proves that the oxidation process can indeed effectively remove the carbon remaining on the fiber surface produced during the resin decomposition process.

[0101] Embodiment 14

[0102] The discarded wind turbine blade main beam carbon plate is cut into small pieces of 2-5 cm in length with a cutting machine. Nitrogen is introduced into the furnace before the reaction, and the exhaust is carried out for 3 minutes. This process is repeated three times to ensure that the air in the tube is completely removed. After nitrogen is steadily introduced into the tubular furnace at a flow rate of 50 mL / min, the cut carbon plate is placed in it, and the temperature in the pyrolysis furnace is gradually increased from the starting temperature to 500°C at a heating rate of 10°C / min. When the temperature in the pyrolysis furnace reaches the target temperature, the temperature is maintained for 30 minutes to fully pyrolyze the resin matrix in the discarded carbon plate into small molecular gaseous products. After the pyrolysis is completed, the solid is cooled to room temperature, the residual solid is taken out and placed in the tubular furnace, pure oxygen is introduced in advance, and the exhaust is carried out for 3 minutes. This process is repeated three times to ensure that the air is completely removed. Then, after introducing 30% oxygen concentration, the temperature in the pyrolysis furnace was gradually increased from the starting temperature to 450°C at a heating rate of 10°C / min, and the reaction was carried out for 30 minutes to oxidize the pyrolytic carbon and residual organic matter on the surface of the carbon fiber, and finally obtain clean hydrophilic carbon fiber.

[0103] Fig. 20 This is the SEM image of the oxidized recycled carbon fiber material of Example 14 of the present invention. It can be seen from the figure that after oxidation, the carbon residue attached to the surface of the rcf fiber is reduced compared to that of the rcf fiber, which proves that the oxidation process can indeed effectively remove the carbon remaining on the fiber surface produced during the resin decomposition process.

[0104] Embodiment 15

[0105] The discarded wind turbine blade main beam carbon plate is cut into small pieces of 2-5 cm in length with a cutting machine. Nitrogen is introduced into the furnace before the reaction, and the exhaust is carried out for 3 minutes. This process is repeated three times to ensure that the air in the tube is completely removed. After nitrogen is steadily introduced into the tubular furnace at a flow rate of 50 mL / min, the cut carbon plate is placed in it, and the temperature in the pyrolysis furnace is gradually increased from the starting temperature to 500°C at a heating rate of 10°C / min. When the temperature in the pyrolysis furnace reaches the target temperature, the temperature is maintained for 30 minutes to fully pyrolyze the resin matrix in the discarded carbon plate into small molecular gaseous products. After the pyrolysis is completed, the solid is cooled to room temperature, the residual solid is taken out and placed in the tubular furnace, pure oxygen is introduced in advance, and the exhaust is carried out for 3 minutes. This process is repeated three times to ensure that the air is completely removed. Then, after introducing 30% oxygen concentration, the temperature in the pyrolysis furnace was gradually increased from the starting temperature to 450°C at a heating rate of 10°C / min, and the reaction was carried out for 40 minutes to oxidize the pyrolytic carbon and residual organic matter on the surface of the carbon fiber, and finally obtain clean hydrophilic carbon fiber.

[0106] Fig.21 This is the SEM image of the oxidized recycled carbon fiber material of Example 15 of the present invention. It can be seen from the figure that after oxidation, the carbon residue attached to the surface of the rcf fiber is reduced compared to that of the rcf fiber, which proves that the oxidation process can indeed effectively remove the carbon remaining on the fiber surface produced during the resin decomposition process.

[0107] Example 16

[0108] The discarded wind turbine blade main beam carbon plate is cut into small pieces of 2-5 cm in length by a cutting machine. Nitrogen is introduced into the furnace before the reaction and exhausted for 3 minutes. This process is repeated three times to ensure that the air in the tube is completely removed. After nitrogen is steadily introduced into the tubular furnace at a flow rate of 50 mL / min, the cut carbon plate is placed in it, and the temperature in the pyrolysis furnace is gradually increased from the starting temperature to 500°C at a heating rate of 10°C / min. When the temperature in the pyrolysis furnace reaches the target temperature, the temperature is maintained for 30 minutes to fully pyrolyze the resin matrix in the discarded carbon plate into small molecular gaseous products. The epoxy resin AB glue is prepared in a mass ratio of 3:1, and then the obtained recycled carbon fiber and epoxy resin are compounded in a mass ratio of 1:1 to make a coaxial absorbing ring, and finally a recycled carbon fiber / epoxy resin composite absorbing material is obtained.

[0109] Fig. 22 This is a 2D reflection loss diagram of the recycled carbon fiber / epoxy resin RCF1 composite absorbing material of Example 16 of the present invention. It can be seen from the figure that the absorbing material has excellent absorbing ability. When the material thickness is 2.5 mm, the effective bandwidth reaches 1.92 GHz (6.8-8.72 GHz), and the minimum RL value reaches -40.06 dB at a thickness of 3.0 mm.

[0110] Embodiment 17

[0111] The abandoned wind turbine blade main beam carbon plate is cut into small pieces of 2-5cm long by a cutting machine. Then, nitrogen is introduced into the furnace before the reaction and exhausted for 3 minutes. This process is repeated three times to ensure that the air in the tube is completely removed. After nitrogen is steadily introduced into the tubular furnace at a flow rate of 50mL / min, the cut carbon plate is placed in it, and the temperature in the pyrolysis furnace is gradually increased from the starting temperature to 500℃ at a heating rate of 10℃ / min. When the temperature in the pyrolysis furnace reaches the target temperature, the temperature is maintained for 30min to fully pyrolyze the resin matrix in the abandoned carbon plate into small molecular gaseous products. The epoxy resin AB glue is prepared in a ratio of 3:1, and then the obtained recycled carbon fiber is ball milled at 15Hz for 5min to powder, and then the recycled carbon fiber powder is mixed with the recycled carbon fiber in a mass ratio of 1:1, and then the recycled carbon fiber powder and the recycled carbon fiber are compounded with epoxy resin in a mass ratio of 1:1, and finally the recycled carbon fiber / recycled carbon fiber powder / epoxy resin RCF2-1 composite absorbing material is obtained.

[0112] Fig.23 This is a 2D reflection loss diagram of the recycled carbon fiber / recycled carbon fiber powder / epoxy resin RCF2-1 composite absorbing material of Example 17 of the present invention. It can be seen from the figure that when the material thickness of the absorber is 3 mm, the effective bandwidth reaches 1.20 GHz (5.36-6.56 GHz), and the minimum RL value reaches -37.72 dB at a thickness of 5.0 mm, which has good absorbing performance.

[0113] Embodiment 18

[0114] The abandoned wind turbine blade main beam carbon plate is cut into small pieces of 2-5cm in length by a cutting machine. Before the reaction, nitrogen is introduced into the furnace and exhausted for 3 minutes. This process is repeated three times to ensure that the air in the tube is completely removed. After nitrogen is steadily introduced into the tubular furnace at a flow rate of 50mL / min, the cut carbon plate is placed in it, and the temperature in the pyrolysis furnace is gradually increased from the starting temperature to 500℃ at a heating rate of 10℃ / min. When the temperature in the pyrolysis furnace reaches the target temperature, the temperature is maintained for 30min to fully pyrolyze the resin matrix in the abandoned carbon plate into small molecular gaseous products. The epoxy resin AB glue is prepared in a ratio of 3:1, and then the obtained recycled carbon fiber is ball milled at 15Hz for 5min to powder, and then the recycled carbon fiber powder is mixed with the recycled carbon fiber in a mass ratio of 1.5:1, and then the recycled carbon fiber powder and the recycled carbon fiber are compounded with epoxy resin in a mass ratio of 1:1, and finally the recycled carbon fiber / recycled carbon fiber powder / epoxy resin RCF2-1.5 composite wave absorbing material is obtained.

[0115] Fig.24This is a 2D reflection loss diagram of the recycled carbon fiber / recycled carbon fiber powder / epoxy resin RCF2-1.5 composite absorbing material of Example 18 of the present invention. It can be seen from the figure that when the material thickness of the absorber is 3 mm, the effective bandwidth reaches 2.4 GHz (7.04-9.44 GHz), and the minimum RL value reaches -33.99 dB at a thickness of 3.5 mm, which has good absorbing performance.

[0116] Embodiment 19

[0117] The abandoned wind turbine blade main beam carbon plate was cut into small pieces of 2-5 cm in length by a cutting machine. Nitrogen was introduced into the furnace before the reaction and exhausted for 3 minutes. This process was repeated three times to ensure that the air in the tube was completely removed. After nitrogen was steadily introduced into the tubular furnace at a flow rate of 50 mL / min, the cut carbon plate was placed in it, and the temperature in the pyrolysis furnace was gradually increased from the starting temperature to 500 ° C at a heating rate of 10 ° C / min. When the temperature in the pyrolysis furnace reached the target temperature, the temperature was maintained for 30 minutes to fully pyrolyze the resin matrix in the abandoned carbon plate into small molecular gaseous products. The epoxy resin AB glue was prepared in a ratio of 3:1, and then the obtained recycled carbon fiber was ball milled at 15Hz for 5min to powder, and then the recycled carbon fiber powder was mixed with the recycled carbon fiber in a mass ratio of 2:1, and then the recycled carbon fiber powder and the recycled carbon fiber were compounded with epoxy resin in a mass ratio of 1:1, and finally the recycled carbon fiber / recycled carbon fiber powder / epoxy resin RCF2-2 composite absorbing material was obtained.

[0118] Fig.25 This is a 2D reflection loss diagram of the recycled carbon fiber / recycled carbon fiber powder / epoxy resin RCF2-2 composite absorbing material of Example 19 of the present invention. It can be seen from the figure that when the material thickness of the absorber is 2.5 mm, the effective bandwidth reaches 1.84 GHz (6.88-8.72 GHz), and the minimum RL value reaches -24.37 dB at a thickness of 3.0 mm, which has good absorbing performance.

[0119] Embodiment 20

[0120] The abandoned wind turbine blade main beam carbon plate is cut into small pieces of 2-5cm in length by a cutting machine. Nitrogen is introduced into the furnace before the reaction and exhausted for 3 minutes. This process is repeated three times to ensure that the air in the tube is completely removed. After nitrogen is steadily introduced into the tubular furnace at a flow rate of 50mL / min, the cut carbon plate is placed in it, and the temperature in the pyrolysis furnace is gradually increased from the starting temperature to 500℃ at a heating rate of 10℃ / min. When the temperature in the pyrolysis furnace reaches the target temperature, the temperature is maintained for 30min to fully pyrolyze the resin matrix in the abandoned carbon plate into small molecular gaseous products. The epoxy resin AB glue is prepared in a ratio of 3:1, and then the obtained recycled carbon fiber is ball milled at 15Hz for 5min to be powdered, and then compounded with epoxy resin in a ratio of 1:2, and then made into a coaxial absorbing ring, and finally the recycled carbon fiber powder / epoxy resin composite absorbing material is obtained.

[0121] Fig.26 This is a 2D reflection loss diagram of the recycled carbon fiber powder / epoxy resin RCF3 composite absorbing material of Example 20 of the present invention. It can be seen from the figure that when the material thickness of the composite absorber is 3 mm, the effective absorbing range reaches 2.08 GHz (6.64-8.72 GHz), and when the thickness is 3.5 mm, the maximum RL value reaches -31.89 dB, which has good absorbing performance.

[0122] The above description is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by any technician familiar with the technical field within the technical scope disclosed by the present invention should be covered by the protection scope of the present invention.

Claims

1. A method for recycling carbon fiber materials from discarded wind turbine blade main beam carbon plates, characterized in that: include: The discarded wind turbine blade main beam carbon plate is cut into small pieces of 2-5 cm in length by a cutting machine. Nitrogen is introduced into the furnace before the reaction to exhaust the gas. After nitrogen is introduced into the tubular furnace, the cut carbon plate is placed therein. The temperature in the pyrolysis furnace is gradually increased from the starting temperature to 400-600°C at a heating rate of 10-30°C / min, and the temperature is maintained for 30-50 minutes to fully pyrolyze the resin matrix in the discarded carbon plate into small molecular gaseous products to obtain recycled carbon fiber materials.

2. The method for recycling carbon fiber materials from discarded wind turbine blade main beam carbon plates according to claim 1, characterized in that: The flow rate of nitrogen into the tube furnace was 30-50 mL / min.

3. Recycled carbon fiber material obtained by the method for recycling carbon fiber material from discarded wind turbine blade main beam carbon plate as described in claim 1 or 2.

4. A hydrophilic carbon fiber according to claim 3, characterized in that: The preparation method comprises: The recycled carbon fiber material is cooled to room temperature, placed in a tubular furnace, and pure oxygen is introduced in advance, exhausted, and after the oxygen is introduced, the temperature in the pyrolysis furnace is gradually increased from the starting temperature to 450-550°C at a heating rate of 10-30°C / min, and the reaction is performed for 20-40 minutes to oxidize the pyrolytic carbon and residual organic matter on the surface of the carbon fiber to obtain hydrophilic carbon fiber.

5. A hydrophilic carbon fiber according to claim 4, characterized in that: The gas flow rate of oxygen into the tube furnace was 30 ml / min.

6. The absorbing material according to claim 3, characterized in that: The preparation method of the wave absorbing material comprises: The recycled carbon fiber material is ground into powder to obtain recycled carbon fiber powder, and the recycled carbon fiber powder, the recycled carbon fiber, or the recycled carbon fiber powder and the recycled carbon fiber are doped and compounded with epoxy resin to obtain the absorbing material.

7. The wave absorbing material according to claim 6, characterized in that: The mass ratio of the recycled carbon fiber to the recycled carbon fiber powder is 1-2:

1.

8. The wave absorbing material according to claim 6, characterized in that: The composite mass ratio of the recycled carbon fiber to the epoxy resin is 1:

1.

9. The wave absorbing material according to claim 6, characterized in that: The composite mass ratio of the recycled carbon fiber powder to the epoxy resin is 1:2.

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