Device and method for recycling carbon fibers through microwave-assisted hydraulic contact electrifying treatment

Abstract

The invention relates to the technical field of carbon fiber composite material recycling, in particular to a device and method for recycling carbon fibers through microwave-assisted hydraulic contact electrifying treatment. The method provided by the invention comprises three stages of pretreatment, microwave-electrifying combined heating and post-treatment, and solves the problems of low resin decomposition rate, serious fiber damage and high energy consumption in a traditional recovery method through the synergistic effect of electrifying Joule heat + microwave heat effect / non-heat effect + hydraulic auxiliary contact; the resin decomposition efficiency is remarkably improved, fiber damage and energy consumption are reduced, the method is particularly suitable for recycling complex carbon fiber composite materials, and the composite material industry is promoted to develop towards the environment-friendly and sustainable direction.

Description

Technical Field

[0001] This invention relates to the field of carbon fiber composite material recycling technology, and in particular to a device and method for recycling carbon fiber through microwave-assisted hydraulic contact electrostatic treatment. Background Technology

[0002] The information disclosed in the background section of this invention is intended only to enhance the understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

[0003] Carbon fiber composites, with their superior properties such as high strength, high modulus, and lightweight, are widely used in high-end equipment manufacturing fields such as aerospace, new energy vehicles, and wind power generation. However, this has also led to a growing problem of large-scale waste recycling and disposal. Achieving efficient and high-value recycling and reuse of carbon fiber has become a key link in promoting the green and sustainable development of the composite materials industry, and is currently a focus of common concern in both industry and academia.

[0004] Currently, hydraulic contact electrostatic technology shows promise in carbon fiber composite recycling. This technology primarily utilizes the inherent conductivity of carbon fibers, applying current through electrodes to generate heat within the carbon fiber composite due to the Joule effect, thereby decomposing the resin matrix. However, this method has several limitations in practical applications: First, the Joule heating method easily leads to uneven internal temperature distribution, resulting in incomplete decomposition of deep resins and a high residual rate; second, increasing the temperature or extending the time to improve the decomposition rate can easily cause excessive oxidation of the carbon fiber surface, damaging the fiber itself and leading to a decline in the mechanical properties of the recycled fiber; third, the overall energy consumption is relatively high, and its economic and environmental benefits need to be improved.

[0005] In recent years, microwave recycling technology has attracted widespread attention due to its unique volumetric heating mode and selective heating capability. This technology generates heat through dipole polarization and ion migration within the material, enabling rapid and uniform heating. This helps lower the decomposition temperature, promote resin decomposition and product diffusion, thus overcoming the thermal hysteresis and unevenness problems of traditional external heating methods. However, microwave recycling technology also faces challenges: its effectiveness strongly depends on the dielectric properties of the material. For composite materials with low dielectric loss or containing non-polar components, microwave absorption efficiency is limited, leading to difficulties in overall heating and low resin decomposition efficiency. Furthermore, microwaves experience energy attenuation when penetrating thicker or larger components, easily causing localized overheating or underheating, limiting the applicability of this technology to complex compositions and waste materials of varying thicknesses. Summary of the Invention

[0006] In view of this, the present invention provides an apparatus and method for recovering carbon fibers through microwave-assisted hydraulic contact electrostatic treatment. By leveraging the synergistic effect of "electrostatic Joule heating + microwave thermal / non-thermal effect + hydraulic assisted contact," the problems of low resin decomposition rate, severe fiber damage, and high energy consumption in traditional recycling methods are solved, thereby maximizing the preservation of the mechanical properties of the recovered carbon fibers.

[0007] To achieve the above objectives, the present invention is implemented through the following technical solution: In a first aspect, the present invention provides a device for microwave-assisted hydraulic contact electrostatic treatment and recycling of carbon fibers, comprising: a hydraulic press frame, a hydraulic cylinder, an upper electrode, a microwave transparent film, a carbon fiber composite material, a lower electrode, a hydraulic press worktable, a hydraulic press base, a microwave source, a microwave transmission waveguide, a DC power supply, a hydraulic control system, a cooling water circulation system, and an infrared thermometer. The hydraulic press workbench is located on the hydraulic press base. A lower electrode is placed on the hydraulic press workbench, and a carbon fiber composite material is placed on the lower electrode. An upper electrode is located above the carbon fiber composite material. A microwave transparent film is located on the surface of the upper and lower electrodes. The upper electrode is located below the hydraulic cylinder, which is mounted on the hydraulic press frame. A microwave source is connected to the top cover of the reaction chamber with a microwave waveguide interface through a microwave transmission waveguide. The reaction chamber is formed by the top cover, the hydraulic press workbench, the upper electrode, and the lower electrode. A DC power supply is connected to the upper and lower electrodes to apply DC current to the carbon fiber composite material to generate Joule heating. A cooling water circulation system is connected to the microwave source and the hydraulic control system for cooling the equipment. An infrared thermometer is mounted on the reaction chamber.

[0008] Furthermore, the electrode materials for the upper and lower electrodes are selected from graphite plates, carbon felt, carbon fiber braids, or microwave transparent ceramics.

[0009] Furthermore, the microwave transparent film is selected from polytetrafluoroethylene, polyimide, quartz glass film or ceramic-reinforced composite film.

[0010] In a second aspect, the present invention provides a method for recycling carbon fibers using the microwave-assisted hydraulic contact electrostatic treatment apparatus described in the first aspect, comprising the following steps: (1) Pre-treat the carbon fiber composite material; (2) Place the pretreated carbon fiber composite material at the center of the lower electrode, and place the upper electrode in contact with the upper surface of the carbon fiber composite material. At the same time, cover the surfaces of the upper and lower electrodes with a microwave transparent film. Lower and lock the top cover of the reaction chamber with the microwave waveguide interface, and connect the microwave source of the cooling water circulation system, the hydraulic press and the DC power supply electrical circuit in sequence. Start the hydraulic control system to make the upper and lower electrodes and the carbon fiber composite material press evenly. (3) Set the microwave parameters and start it. At the same time, set the DC power supply current density and start the power-on program. The material is heated to 300-350 ℃. When the volatile gas in the cavity is significantly reduced and the current reading tends to be stable, the reaction is complete. Immediately shut down all energy input systems. (4) After the reaction is completed, the carbon fiber composite material is cooled to room temperature and then intermittently purged. After purging, it is irradiated with low-power microwave to obtain carbon fiber.

[0011] Furthermore, in step (1), the pretreatment includes cutting the carbon fiber composite material into cubic specimens, and then cleaning and drying the outer surface of the specimens. Cleaning mainly involves removing impurities such as oil and dust from the surface.

[0012] Furthermore, in step (1), the side length of the cubic sample is 10-40 mm.

[0013] Further, in step (1), the carbon fiber composite material is a composite material made of 3-24K T300-T1000 carbon fiber bundles and resin; the resin includes epoxy resin, phenolic resin, bismaleimide or polyether ether ketone; preferably, the carbon fiber volume fraction is 45%-65%.

[0014] Furthermore, in step (2), the electrode materials of the upper and lower electrodes are selected from graphite plates, carbon felt, carbon fiber braids or microwave transparent ceramics; the thickness of the electrode materials is 2-15 mm.

[0015] Further, in step (2), the microwave transparent film is selected from polytetrafluoroethylene, polyimide, quartz glass film or ceramic reinforced composite film; the thickness of the microwave transparent film is 0.05-0.2 mm.

[0016] Furthermore, in step (2), the initial pressure of the hydraulic control system is 0.5-1 MPa, and the pressure fluctuation during the reaction is controlled within ±0.2 MPa. The pressure selection can be adjusted according to the material thickness and structural adaptability. The present invention sets up hydraulic assisted contact, and setting an appropriate contact pressure can promote the electrolytic pyrolysis recovery effect. Hydraulic contact can make the upper and lower electrodes and the sample directly and tightly contact each other, forming a low-resistance and uniform conductive path; when the contact is not tight, it is easy to cause electric sparks, and at the same time, it will cause excessive local contact resistance and local overheating of the surface, which will cause rapid carbonization of the sample surface, forming a surface carbonization layer. The carbonization layer will not only hinder current conduction and uniform heat diffusion, but also destroy the surface structure and interface bonding state of the carbon fiber, ultimately leading to a significant decrease in the mechanical properties (such as tensile strength) of the carbon fiber at the contact part, that is, material performance failure.

[0017] Furthermore, in step (3), the microwave frequency is set to 2-3 GHz, the power is 500-1500 W, and the microwave action time is 3-10 min.

[0018] Furthermore, in step (3), the current density is 0.3-0.8 A / cm². 2 The voltage is 5-15 V.

[0019] In the combined microwave-electric heating stage, microwaves preferentially heat the resin, rapidly softening it and releasing small-molecule gases. Simultaneously, the Joule heating generated by the electric current further raises the overall material temperature, promoting the complete decomposition of any remaining resin. Throughout the heating process, the hydraulic system automatically monitors and adjusts the contact pressure between the electrodes and the material in real time to compensate for interfacial gaps caused by thermal expansion.

[0020] Further, in step (4), a compressed air gun is used for purging. Specifically, the reaction chamber is opened, the pyrolyzed fiber skeleton is removed with tweezers, and transferred to a negative pressure operating table. Then, in a fume hood, a compressed air gun is used to intermittently purge along the fiber axis until the pyrolysis residue on the fiber surface is completely removed. Preferably, the purging pressure is set to 0.4-0.8 MPa, the distance from the fiber is 10-20 cm, the duration of each purging is 3-8 s, and the interval is 3-5 s.

[0021] Furthermore, in step (4), the low-power microwave treatment time is 60-120 s, the power is 200-500 W, and the temperature of the fiber surface is controlled between 250-350 ℃. The tensile strength retention rate of the obtained recycled carbon fiber is 90%-95%. The low-power microwave irradiation treatment of the fiber can further remove the residual carbonized layer or functional groups on the surface. At the same time, the temperature of the fiber surface is strictly monitored by a real-time infrared temperature measurement system to prevent damage to the fiber body and affect the mechanical properties of the recycled carbon fiber.

[0022] Compared with the prior art, the present invention has achieved the following beneficial effects: (1) The present invention reduces the decomposition temperature of the resin by means of the synergistic effect of microwave and electric current, thereby reducing the damage that may be caused to the fiber during the entire heating process, and making the tensile strength retention rate of the recycled carbon fiber higher.

[0023] (2) This invention improves the pyrolysis and recovery effect by using hydraulically assisted contact and setting appropriate contact pressure, increasing the resin decomposition rate to over 98%, and is especially suitable for the recovery of complex carbon fiber composite materials. In addition, this invention significantly reduces energy consumption by 30%-40% compared to traditional processes, and has strong process adaptability and high recovery efficiency. Attached Figure Description

[0024] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0025] Figure 1 This invention relates to a device for microwave-assisted hydraulic contact electrostatic treatment and recycling of carbon fibers; The components include: 1. Hydraulic press frame; 2. Hydraulic cylinder; 3. Upper electrode; 4. Microwave transparent film; 5. Carbon fiber composite material; 6. Lower electrode; 7. Hydraulic press workbench; 8. Hydraulic press base; 9. Microwave source; 10. Microwave transmission waveguide; 11. DC power supply; 12. Hydraulic control system; 13. Cooling water circulation system; and 14. Infrared thermometer. Detailed Implementation

[0026] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0027] The technical solution of the present invention will be further described below with reference to specific embodiments.

[0028] Example 1 The present invention provides a device for microwave-assisted hydraulic contact electrostatic treatment and recycling of carbon fiber, comprising: a hydraulic press frame (1), a hydraulic cylinder (2), an upper electrode (3), a microwave transparent film (4), a carbon fiber composite material (5), a lower electrode (6), a hydraulic press workbench (7), a hydraulic press base (8), a microwave source (9), a microwave transmission waveguide (10), a DC power supply (11), a hydraulic control system (12), a cooling water circulation system (13), and an infrared thermometer (14). The hydraulic press workbench is located on the hydraulic press base (8). The lower electrode (6) is placed on the hydraulic press workbench (7). The carbon fiber composite material (5) is placed on the lower electrode (6). The upper electrode (3) is located above the carbon fiber composite material (5). The microwave transparent film (4) is located on the surface of the upper and lower electrodes. The upper electrode (3) is located below the hydraulic cylinder (2). The hydraulic cylinder (2) is set on the hydraulic press frame (1). The microwave source (9) is connected to the upper cover of the reaction chamber with a microwave waveguide interface through the microwave transmission waveguide (10). The reaction chamber is formed by the upper cover, the hydraulic press workbench (7), the upper electrode (3), and the lower electrode (6). The DC power supply (11) is connected to the upper electrode (3) and the lower electrode (6) to apply DC power to the carbon fiber composite material (5) to generate Joule heat. The cooling water circulation system (13) is connected to the microwave source (9) and the hydraulic control system (12) to cool the equipment. The infrared thermometer (14) is set on the reaction chamber.

[0029] The method for recycling carbon fiber using the above-mentioned device is as follows: The selected material is a carbon fiber composite material made of T300 3K carbon fiber bundles and epoxy resin, in which the volume fraction of carbon fiber is 45%. First, the material is cut into cubic samples with a side length of 10 mm, and then the surface is cleaned and dried.

[0030] The integrated reaction system was then constructed. The upper and lower electrodes were made of 2 mm thick graphite plates, tightly bonded to the upper and lower surfaces of the sample. A 0.05 mm thick polytetrafluoroethylene (PTFE) film was then applied over the electrodes. After assembly, the reaction chamber was locked and all auxiliary systems were connected. The hydraulic control system was then activated, with the initial contact pressure set to 1.0 MPa to ensure good contact between the electrodes and the sample. During the combined heating phase, the microwave power was set to 500 W, the microwave frequency to 2.45 GHz, and the reaction time to 3 min. Simultaneously, a direct current was applied at a current density of 0.3 A / cm². 2 The voltage is 10 V, which raises the overall temperature of the material to 325 ℃. Throughout the heating process, the hydraulic system automatically controls the fluctuation of the contact pressure within ± 0.2 MPa, and stops the energy input immediately after the reaction is complete.

[0031] The pyrolysis-exposed fiber skeleton was then removed with tweezers, and its surface was cleaned using a compressed air gun. The pressure was set to 0.4 MPa, and the distance between the gun nozzle and the fiber was 10 cm. The air gun was used in a 3-second working, 3-second intermittent cycle along the fiber axis. Finally, the fiber was irradiated with a low-power microwave of 200 W for 60 seconds, with the fiber surface temperature controlled at 300 °C. Testing showed that the final recycled carbon fiber retained 92% of its tensile strength.

[0032] Example 2 The selected material is a carbon fiber composite material made of T700 12K carbon fiber bundles and phenolic resin, with a carbon fiber volume fraction of 55%. First, the material is cut into cubic samples with a side length of 20 mm, followed by surface cleaning and drying.

[0033] The integrated reaction system was then constructed. The upper and lower electrodes were made of 8 mm thick carbon felt, tightly bonded to the upper and lower surfaces of the sample. A 0.1 mm thick polyimide film was then applied over the electrodes. After assembly, the reaction chamber was locked and all auxiliary systems were connected. The hydraulic control system was then activated, with an initial contact pressure of 0.75 MPa set to ensure good contact between the electrodes and the sample. During the combined heating phase, the microwave power was set to 1000 W, the microwave frequency to 2.45 GHz, and the reaction time to 6 min. Simultaneously, a direct current was applied at a current density of 0.5 A / cm². 2The voltage is 10 V, which raises the overall temperature of the material to 325 ℃. Throughout the heating process, the hydraulic system automatically controls the fluctuation of the contact pressure within ± 0.2 MPa, and stops the energy input immediately after the reaction is complete.

[0034] The pyrolytic fiber skeleton was then removed with tweezers, and its surface was cleaned using a compressed air gun. The pressure was set to 0.6 MPa, and the distance between the gun nozzle and the fiber was 15 cm. The air gun was used in a 5-second cycle followed by a 4-second interval, blowing along the fiber axis. Finally, the fiber was irradiated with a low-power microwave of 350 W for 90 seconds, with the fiber surface temperature controlled at 300 °C. Testing showed that the final recycled carbon fiber retained 90% of its tensile strength.

[0035] Example 3 The selected material is a carbon fiber composite material made of T800 18K carbon fiber bundles and phenolic resin, in which the volume fraction of carbon fiber is 60%. First, the material is cut into cubic samples with a side length of 30 mm, and then the surface is cleaned and dried.

[0036] The integrated reaction system was then constructed. The upper and lower electrodes were made of 12 mm thick carbon fiber braid and tightly adhered to the upper and lower surfaces of the sample. A 0.15 mm thick quartz glass film was also placed over the electrodes. After assembly, the reaction chamber was locked and all auxiliary systems were connected. The hydraulic control system was then activated, and the initial contact pressure was set to 0.9 MPa to ensure good contact between the electrodes and the sample. During the combined heating phase, the microwave power was set to 1200 W, the microwave frequency to 2.45 GHz, and the reaction time to 8 min. Simultaneously, a direct current was applied at a current density of 0.7 A / cm². 2 The voltage is 12 V, which raises the overall temperature of the material to 340 ℃. Throughout the heating process, the hydraulic system automatically controls the fluctuation of the contact pressure within ±0.2 MPa, and stops the energy input immediately after the reaction is complete.

[0037] The pyrolysis-exposed fiber skeleton was then removed with tweezers, and its surface was cleaned using a compressed air gun. The pressure was set to 0.7 MPa, and the distance between the gun nozzle and the fiber was 18 cm. The air gun was used in a 7-second cycle followed by a 4-second interval, blowing along the fiber axis. Finally, the fiber was irradiated with a low-power microwave of 450 W for 110 seconds, with the fiber surface temperature controlled at 300 °C. Testing showed that the final recycled carbon fiber retained 93% of its tensile strength.

[0038] Example 4 The selected material is a carbon fiber composite material made of T1000 24K carbon fiber bundles and phenolic resin, with a carbon fiber volume fraction of 65%. First, the material is cut into cubic samples with a side length of 40 mm, followed by surface cleaning and drying.

[0039] Subsequently, an integrated reaction system was constructed. The upper and lower electrodes were made of 15 mm thick microwave-transparent ceramic and tightly adhered to the upper and lower surfaces of the sample. A 0.2 mm thick ceramic-reinforced composite film was then applied over the electrodes. After assembly, the reaction chamber was locked and all auxiliary systems were connected. Next, the hydraulic control system was activated, and the initial contact pressure was set to 1.0 MPa to ensure good contact between the electrodes and the sample. During the combined heating phase, the microwave power was set to 1500 W and the reaction time to 10 min, while a direct current was applied at a current density of 0.8 A / cm². 2 The voltage is 15 V, which raises the overall temperature of the material to 350℃. Throughout the heating process, the hydraulic system automatically controls the fluctuation of the contact pressure within ±0.2 MPa, and stops the energy input immediately after the reaction is complete.

[0040] The pyrolytic fiber skeleton was then removed with tweezers, and its surface was cleaned using a compressed air gun. The pressure was set to 0.8 MPa, and the distance between the gun nozzle and the fiber was 20 cm. The air gun was used in a cycle of 8 seconds followed by 5 seconds of rest along the fiber axis. Finally, the fiber was irradiated with a 500W low-power microwave for 120 seconds, with the fiber surface temperature controlled at 300℃. Testing showed that the final recycled carbon fiber retained 95% of its tensile strength.

[0041] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A device for microwave-assisted hydraulic contact electrostatic treatment and recycling of carbon fiber, characterized in that, include: Hydraulic press frame, hydraulic cylinder, upper electrode, microwave transparent film, carbon fiber composite material, lower electrode, hydraulic press worktable, hydraulic press base, microwave source, microwave transmission waveguide, DC power supply, hydraulic control system, cooling water circulation system, infrared thermometer; The hydraulic press workbench is located on the hydraulic press base. A lower electrode is placed on the hydraulic press workbench, and a carbon fiber composite material is placed on the lower electrode. An upper electrode is located above the carbon fiber composite material. A microwave transparent film is located on the surface of the upper and lower electrodes. The upper electrode is located below the hydraulic cylinder, and the hydraulic cylinder is set on the hydraulic press frame. The microwave source is connected to the top cover of the reaction chamber with a microwave waveguide interface through a microwave transmission waveguide. The reaction chamber is formed by the top cover, the hydraulic press worktable, the upper electrode, and the lower electrode. The DC power supply is connected to the upper and lower electrodes and is used to apply DC current to the carbon fiber composite material to generate Joule heat. The cooling water circulation system is connected to the microwave source and the hydraulic control system and is used to cool the equipment. The infrared thermometer is installed on the reaction chamber.

2. The apparatus as claimed in claim 1, characterized in that, The electrode materials for the upper and lower electrodes are selected from graphite plates, carbon felt, carbon fiber braids, or microwave transparent ceramics.

3. The apparatus as described in claim 1, characterized in that, The microwave transparent film is selected from polytetrafluoroethylene, polyimide, quartz glass film or ceramic reinforced composite film.

4. The method for recycling carbon fiber using the microwave-assisted hydraulic contact electrostatic treatment apparatus as described in claim 1, characterized in that, Includes the following steps: (2) (1) Pre-treat the carbon fiber composite material; (2) Place the pretreated carbon fiber composite material at the center of the lower electrode, and place the upper electrode in contact with the upper surface of the carbon fiber composite material. At the same time, cover the surfaces of the upper and lower electrodes with a microwave transparent film. Lower and lock the top cover of the reaction chamber with the microwave waveguide interface, and connect the microwave source of the cooling water circulation system, the hydraulic press and the DC power supply electrical circuit in sequence. Start the hydraulic control system to make the upper and lower electrodes and the carbon fiber composite material press evenly. (3) Set the microwave parameters and start it. At the same time, set the DC power supply current density and start the power-on program. The material is heated to 300-350 ℃. When the volatile gas in the cavity is significantly reduced and the current reading tends to be stable, the reaction is complete. Immediately shut down all energy input systems. (4) After the reaction is completed, the carbon fiber composite material is cooled to room temperature and then intermittently purged. After purging, it is irradiated with low-power microwave to obtain carbon fiber.

5. The method for recycling carbon fiber as described in claim 4, characterized in that, In step (1), the pretreatment includes cutting the carbon fiber composite material into cubic specimens and then cleaning and drying the outer surface of the specimens; preferably, the side length of the cubic specimens is 10-40 mm.

6. The method for recycling carbon fiber as described in claim 4, characterized in that, In step (1), the carbon fiber composite material is a composite material made of 3-24K T300-T1000 carbon fiber bundles and resin; the resin includes epoxy resin, phenolic resin, bismaleimide or polyether ether ketone; preferably, the carbon fiber volume fraction is 45%-65%.

7. The method for recycling carbon fiber as described in claim 4, characterized in that, In step (2), the electrode materials of the upper and lower electrodes are selected from graphite plates, carbon felt, carbon fiber braids or microwave transparent ceramics; the thickness of the electrode materials is 2-15 mm; and / or, the microwave transparent film is selected from polytetrafluoroethylene, polyimide, quartz glass film or ceramic reinforced composite film; the thickness of the microwave transparent film is 0.05-0.2 mm.

8. The method for recycling carbon fiber as described in claim 4, characterized in that, In step (2), the initial pressure of the hydraulic control system is 0.5-1 MPa, and the pressure fluctuation is controlled within ±0.2 MPa during the reaction process.

9. The method for recycling carbon fiber as described in claim 4, characterized in that, In step (3), the microwave frequency is set to 2-3 GHz, and the power is 500-1500 W; and / or, the microwave action time is 3-10 min; and / or, in step (3), the current density is 0.3-0.8 A / cm. 2 The voltage is 5-15 V.

10. The method for recycling carbon fiber as described in claim 4, characterized in that, In step (4), a compressed air gun is used for purging; preferably, the purging pressure is set to 0.4-0.8 MPa, the distance from the fiber is 10-20 cm, the duration of each purging is 3-8 s, and the interval is 3-5 s. And / or, in step (4), the low-power microwave treatment time is 60-120 s, the power is 200-500 W, the temperature of the fiber surface is controlled between 250-350 ℃, and the tensile strength retention rate of the obtained recycled carbon fiber is 90%-95%.

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