A method of microwave pyrolysis carbon fiber composite materials to regenerate carbon fibers

Abstract

This invention discloses a method for regenerating carbon fiber from carbon fiber composite materials using microwave pyrolysis. The main steps include: cutting a large sheet of carbon fiber composite material into a plurality of carbon fiber composite material sheets; placing these sheets into a microwave heating cavity; subjecting the sheets to a first microwave heat treatment in the microwave heating cavity under an oxygen-free atmosphere containing inert gas to form a plurality of semi-finished carbon fiber materials; subjecting the semi-finished carbon fiber materials to a second microwave heat treatment in the microwave heating cavity under a low-oxygen atmosphere containing mixed air to form a plurality of regenerated carbon fiber materials; and transferring the regenerated carbon fiber materials from the microwave heating cavity into a cooling container. This method is simple and convenient to operate, and the regenerated carbon fiber produced by microwave treatment retains the characteristics of the original carbon fiber, making it a usable renewable resource.

Description

Technical Field

[0001] This invention relates to a method for regenerating carbon fibers from carbon fiber composite materials, and more particularly to a method for regenerating carbon fibers from carbon fiber composite materials using microwave heating treatment. Prior Technology

[0002] Carbon fiber composites possess advantages such as high strength, ultra-light weight, and resistance to high temperatures and pressures, and are widely used in various fields including construction, medical equipment, sports equipment, transportation, aerospace, defense, and energy. Carbon fiber composites are composed of reinforcing carbon fibers and a resin matrix. Carbon fiber is a crucial component of carbon fiber composites, and large quantities of expensive carbon fiber are found in scraps, defective products, and structural components damaged during use. Furthermore, the strength of carbon fiber composites deteriorates due to resin aging, necessitating their disposal as waste. Carbon fiber recycling and reuse are becoming a critical global issue.

[0003] Due to the good interfacial wettability and tight bonding between carbon fibers and the resin matrix, separation is difficult, making the recycling and reuse of carbon fibers challenging. Traditional methods for carbon fiber recycling and regeneration mainly include mechanical crushing, solvent decomposition, and high-temperature pyrolysis.

[0004] Mechanical crushing and recycling methods primarily rely on mechanical equipment to crush thermosetting resins and their composites into bulk particles and short fibers of varying sizes through grinding, pressing, or chopping. While this method is simple to operate and can recover short fibers and composite material particles of different lengths, it causes significant fiber damage during the recycling process, making it impossible to obtain long fibers. For example, Chinese Patent Publication No. CN 102558603 B discloses a one-step method for recycling and modifying carbon fibers: polymer carbon fiber composites are crushed into suitable sizes using mechanical crushing, and the polymer matrix of the carbon fiber composite is decomposed using water at a certain temperature and pressure to ultimately obtain recycled carbon fibers.

[0005] Solvent decomposition utilizes the chemical resistance of carbon fibers, employing solvents to degrade the resin matrix in the composite material, transforming it into a soluble substance. This facilitates the separation, recycling, and reuse of the components within the composite material. While this method is simple, it suffers from long processing times and the need for secondary wastewater treatment. For instance, Chinese Patent Publication No. CN 104592546 A discloses a method for recycling waste carbon fiber / epoxy resin composite materials, which utilizes a combination of solvent and pressure methods.

[0006] High-temperature pyrolysis is currently the commercially available method for recycling carbon fiber composites. By degrading the carbon fiber composite at high temperatures, clean carbon fibers are obtained, and some organic liquid fuels can also be recovered. However, due to the high temperatures and surface oxidation, the mechanical properties of the carbon fiber decrease significantly, which affects its reuse. For example, Chinese Patent Publication No. CN 103665427 B discloses a method for recycling waste carbon fiber composites through pyrolysis. The waste carbon fiber composite is placed in the furnace of a pyrolysis device, heated to 350-900℃, and held for 0.5-5.0 hours to initiate a pyrolysis reaction. The carbon fibers recovered by this invention are prone to carbon buildup on the surface, and the pyrolysis process may also generate harmful gases.

[0007] Microwave heating has three main characteristics: Instantaneous: High thermal efficiency and short heating time. Selectivity: Different materials exhibit significantly different heating characteristics in a microwave field due to their varying dielectric properties. Penetration: Electromagnetic waves can penetrate the interior of a medium, thus microwaves possess strong penetrating power. Numerous studies have demonstrated that waste can be processed through microwave heating and pyrolysis to produce high-quality recyclable materials, achieving the concept of a regenerative circular economy. Compared to traditional heating, microwave heating offers shorter heating times and avoids direct contact with the heated material, improving upon the high energy consumption and low efficiency of traditional methods. For example, Chinese Patent Publication No. CN 105199139 A discloses a method for recycling carbon fiber composite materials, specifically: Waste carbon fiber composite materials are placed in a stirring and cleaning device for cleaning; the fragments are spread evenly on a tray and placed in a microwave oven for heating; an inert gas is filled in the microwave oven to protect the carbon fiber composite material during the degradation reaction, resulting in solid carbon fiber recyclables. Although microwave heating is highly efficient, problems remain, such as the tendency for carbon to form on the carbon fiber surface and the potential generation of harmful gases during the pyrolysis process.

[0008] In laboratory-scale studies, methods for microwave recycling and regenerating carbon fibers from carbon fiber composite waste have been feasible through various processing techniques. However, these laboratory-scale methods are often complex and unsuitable for industrial-scale carbon fiber recycling.

[0009] In view of this, it is necessary to propose an industrial-scale, rapid, and environmentally friendly method for regenerating carbon fibers from microwave-modified carbon fiber composites. Summary of the Invention

[0010] To address the aforementioned problems, the main objective of this invention is to provide a method for regenerating carbon fibers from waste carbon fiber composites by microwave pyrolysis, specifically addressing the shortcomings and deficiencies of existing technologies. This method enables the uniform and efficient recovery of high-value carbon fibers from waste carbon fiber composites at relatively low temperatures and ambient pressure. The method allows the resin organic matter to undergo low-temperature pyrolysis and surface coke oxidation removal under appropriate microwave power density and in a suitable atmosphere, ensuring the integrity of the carbon fibers. This approach simultaneously achieves the recycling of high-quality carbon fibers while meeting the needs of improving the mechanical properties and recovery rate of carbon fibers, shortening reaction time, simplifying the reaction process, saving energy, and protecting the environment.

[0011] To achieve the objectives of this invention, this invention provides a method for regenerating carbon fiber using microwave pyrolysis of carbon fiber composite materials. The main steps include: Step (1): cutting a large sheet of carbon fiber composite material into a plurality of carbon fiber composite material sheets; Step (2): placing the carbon fiber composite material sheets into a microwave heating cavity, the microwave heating cavity having at least one air inlet and at least one air outlet, the air outlet being connected to an external air extraction device via a pipe; Step (3): introducing an oxygen-free atmosphere containing inert gas into the carbon fiber composite material sheets within the microwave heating cavity through the at least one air inlet, and performing a first... A microwave heat treatment is performed to form a plurality of semi-finished carbon fiber materials, wherein the temperature of the first microwave heat treatment is between 450 and 600°C and the time is between 0.2 and 0.8 hours; step (4): the semi-finished carbon fiber materials are introduced into a low-oxygen atmosphere containing mixed air through the at least one air inlet in the microwave heating cavity, and a second microwave heat treatment is performed to form a plurality of recycled carbon fiber materials, wherein the temperature of the second microwave heat treatment is between 450 and 600°C and the time is between 0.1 and 0.7 hours; and step (5): the recycled carbon fiber materials are introduced into a cooling container from the microwave heating cavity.

[0012] According to one feature of the present invention, the microwave heating cavity system is mainly composed of a ceramic container and an outer metal shell.

[0013] According to one feature of the present invention, the at least one air inlet of the microwave heating cavity is located in the lower half of the ceramic container, and the at least one air outlet of the microwave heating cavity is located in the upper half of the ceramic container.

[0014] According to one feature of the present invention, the microwave power density of the first microwave heat treatment is between 5 kW / kg and 10 kW / kg, wherein kg is the unit weight of the carbon fiber composite sheets.

[0015] According to one feature of the invention, the inert gas system introduced into the first microwave heat treatment is nitrogen, and its flow rate is between 10 LPM / kg and 20 LPM / kg, where LPM is liters per minute [L / min] and kg is the unit weight of the carbon fiber composite sheets.

[0016] According to one feature of the present invention, during the first microwave heat treatment, the external evacuation device extracts the gas generated by the semi-finished carbon fiber material from the microwave heating cavity at a velocity equivalent to that of the gas generated by the semi-finished carbon fiber material, so as to keep the microwave heating cavity in the oxygen-free atmosphere.

[0017] According to one feature of the present invention, the microwave power density of the second microwave heat treatment is between 3 kW / kg and 8 kW / kg, where kg is the unit weight of the carbon fiber composite sheets.

[0018] According to one feature of the invention, the mixed gas system introduced for the second microwave heat treatment contains at least one compressed air with a flow rate between 10 LPM / kg and 20 LPM / kg, where LPM is liters per minute [L / min] and kg is the unit weight of the carbon fiber composite sheets.

[0019] According to one feature of the present invention, during the second microwave heat treatment, the external evacuation device extracts the introduced mixed gas from the microwave heating cavity at a gas velocity equal to or greater than that of the introduced mixed gas, so as to keep the microwave heating cavity in the low-oxygen atmosphere.

[0020] According to one feature of the present invention, the recycled carbon fiber materials are cooled to below 400°C in a microwave-heated cavity under a low-oxygen atmosphere of mixed air before being taken out by a conveyor belt.

[0021] The advantages of the microwave pyrolysis method for regenerating carbon fiber from carbon fiber composites according to the present invention are:

[0022] (1) By utilizing the selective heating characteristics of microwaves on carbon fiber composite waste, the interior of the carbon fiber resin matrix composite material is rapidly heated and the whole is heated uniformly, which shortens the processing time and improves the recycling efficiency and effect of carbon fiber;

[0023] (2) Inert gas or oxygen-containing mixed gas is introduced at different times under normal pressure and a certain temperature is controlled to degrade the resin and then react with oxidation. The carbon fiber does not react, thereby removing the organic matter of the resin and obtaining carbon fiber with good performance, which has a smooth surface and basically no residual resin.

[0024] (3) The heat released by the oxidation reaction is used for heat preservation, which reduces the energy consumption of microwave power and saves energy significantly.

[0025] (4) The recycled carbon fiber obtained by microwave treatment has excellent mechanical properties and can be compounded with various resin matrices to form new carbon fiber reinforced composite materials, which can be applied to different fields. It is a green and environmentally friendly recycling method. Simple Explanation of the Diagram

[0026] To make the above and other objects, features and advantages of the present invention more apparent and understandable, several preferred embodiments are described below in detail with reference to the accompanying drawings.

[0027] Figure 1 shows a flowchart of a method for regenerating carbon fibers using microwave pyrolysis of carbon fiber composites according to the present invention.

[0028] Figure 2 shows a photograph of an embodiment of the present invention, namely (a) a carbon fiber composite sheet before microwave heat treatment and (b) a recycled carbon fiber after microwave pyrolysis. Implementation

[0029] While the present invention may be embodied in various forms, those shown in the accompanying drawings and described herein are preferred embodiments of the invention. Those skilled in the art will understand that the apparatus and methods specifically described herein and illustrated in the drawings are intended as examples of the invention, not limiting illustrative embodiments, and the scope of the invention is defined only by the claims. Features illustrated or described in connection with an illustrative embodiment may be combined with features of other embodiments. Such modifications and variations are included within the scope of the invention.

[0030] Thermal pyrolysis is a thermochemical reaction process that decomposes organic matter into solid matter, condensed liquid, and combustible gas under high temperature, oxygen-free or low oxygen conditions. To achieve the purpose of this invention, this invention provides a method for regenerating carbon fiber from microwave-pyrolyzed carbon fiber composite materials. Please refer to Figure 1, which shows a flowchart of a method for regenerating carbon fiber from microwave-pyrolyzed carbon fiber composite materials according to this invention. The main steps of this method for regenerating carbon fiber from microwave-pyrolyzed carbon fiber composite materials include: Step (1): cutting a large sheet of carbon fiber composite material into a plurality of carbon fiber composite material sheets; Step (2): placing the carbon fiber composite material sheets into a microwave heating cavity, the microwave heating cavity having at least one air inlet and at least one air outlet, the air outlet being connected to an external air extraction device via a pipe; Step (3): introducing an oxygen-free atmosphere containing inert gas into the microwave heating cavity through the at least one air inlet to perform a first microwave heat treatment to form a plurality of semi-finished carbon fiber materials. The temperature of the first microwave heat treatment is between 450 and 600°C, and the time is between 0.2 and 0.8 hours; Step (4): The semi-finished carbon fiber materials are introduced into the microwave heating cavity through the at least one air inlet into a low-oxygen atmosphere containing mixed air, and undergo a second microwave heat treatment to form a plurality of recycled carbon fiber materials. The temperature of the second microwave heat treatment is between 450 and 600°C, and the time is between 0.1 and 0.7 hours; and Step (5): The recycled carbon fiber materials are introduced from the microwave heating cavity into a cooling container.

[0031] The carbon fiber in this carbon fiber composite material is one or more of polyacrylonitrile-based carbon fiber, pitch-based carbon fiber, or viscose-based carbon fiber. The matrix resin in this carbon fiber composite material is one or more of thermosetting resin or thermoplastic resin. The thermosetting resin includes epoxy resin, unsaturated polyester resin, phenolic resin, urea-formaldehyde resin, vinyl resin, melamine-formaldehyde resin, bismaleimide resin, polyimide resin, polyurethane resin, silicone resin, and furan resin. The thermoplastic resin includes polyphenylene sulfide, polyphenylene ether, polytetrafluoroethylene, polyamide, polyetheretherketone, polycarbonate, PC / ABS (polycarbonate / acrylonitrile-butadiene-styrene) alloy, polyoxymethylene, polypropylene, thermoplastic polyimide, polyethylene, polyarylate, liquid crystal polymer, polyethylene terephthalate, polybutylene terephthalate, polyvinyl chloride, polystyrene, and acrylonitrile-butadiene-styrene copolymer.

[0032] In step (1), the large carbon fiber composite material sheet can be a plate structure or an irregularly shaped part. Since carbon fiber composite material is not a homogeneous material, different shapes and structures will affect heat transfer and thus affect the thermal decomposition effect. Therefore, larger carbon fiber composite materials need to be crushed. The crushing method is mechanical processing. The dimensions of these carbon fiber composite material sheets are approximately 2-40 cm in length and 2-20 cm in width.

[0033] In step (2), the microwave heating cavity system mainly consists of a ceramic container with an outer metal shell. A plurality of microwave power sources are disposed around the metal shell to provide microwave power to the carbon fiber composite sheets inside the ceramic container of the microwave heating cavity. The required microwave power is related to the capacity of the heating cavity and the weight of the carbon fiber composite material being processed. The power of these microwave power sources is adjustable, providing an appropriate power density based on the weight of the heated carbon fiber composite material. Microwaves are electromagnetic waves, using a microwave power at a frequency of 915MHz or 2450MHz. Microwave heating utilizes the principle of radiation, penetrating the surface of the medium to enter the interior of the carbon fiber composite sheets. The carbon fiber composite sheets convert the absorbed microwave energy into heat to achieve the purpose of heating and decomposition. The carbon fiber composite sheets are placed into the microwave heating cavity from above, occupying approximately one-third to two-thirds of the space of the ceramic container within the microwave heating cavity.

[0034] In step (3), the microwave power density of the first microwave heat treatment is between 5 kW / kg and 10 kW / kg, where kg is the unit weight of the carbon fiber composite sheets. The inert gas system introduced for the first microwave heat treatment is nitrogen, with a flow rate between 10 LPM / kg and 20 LPM / kg, where LPM is liters per minute (L / min) and kg is the unit weight of the carbon fiber composite sheets. It should be noted that during the first microwave heat treatment, the external evacuation device extracts the gas generated by the semi-finished carbon fiber material from the microwave heating cavity at a rate equivalent to the gas velocity generated by the semi-finished carbon fiber material, thus maintaining the microwave heating cavity in an oxygen-free atmosphere. This oxygen-free condition means that there is almost no oxygen during the microwave heat treatment process. By continuously introducing an inert gas, such as nitrogen or argon, the oxygen in the microwave heating cavity is consumed, and there is no subsequent oxygen replenishment, achieving the limited air intake design. The inert gas flow rate is proportional to the capacity of the heating cavity.

[0035] In step (3), the first microwave heat treatment decomposes the carbon fiber composite sheets into a gaseous substance and the semi-finished carbon fiber material. The gaseous substance is extracted from the microwave heating cavity by an external vacuum device and, after subsequent condensation, separates into a liquid product, namely biogas, and a gaseous product, namely syngas (mainly hydrogen, methane, and carbon monoxide). Both the liquid and gaseous products can be used as energy fuels.

[0036] In step (4), the microwave power density of the second microwave heat treatment is between 3 kW / kg and 8 kW / kg, where kg is the unit weight of the carbon fiber composite sheets. The mixed gas system introduced into the second microwave heat treatment includes at least one compressed air with a flow rate between 10 LPM / kg and 20 LPM / kg, where LPM is liters per minute (L / min) and kg is the unit weight of the carbon fiber composite sheets. It should be noted that during the second microwave heat treatment, the external exhaust device extracts the introduced mixed gas from the microwave heating cavity at a gas velocity equal to or greater than that of the introduced mixed gas, so that the microwave heating cavity is kept in a low-oxygen atmosphere. That is, the low-oxygen condition means that during the microwave heat treatment, the amount of oxygen in the heating cavity is less than the amount of oxygen in ordinary air. This low-oxygen atmosphere can be achieved through a restricted air intake design, meaning that during the reaction process, the heating cavity only extracts air and does not introduce air. Alternatively, the low-oxygen atmosphere can be achieved by continuously introducing a mixed gas system containing at least compressed air, and by using an external extraction device to extract the introduced mixed gas from the microwave heating cavity at a gas velocity equal to or greater than that of the introduced mixed gas. The flow rate of the introduced mixed gas is proportional to the capacity of the heating cavity.

[0037] In step (5), the recycled carbon fiber materials are cooled to below 400°C in a low-oxygen atmosphere mixed with air within the microwave heating cavity, and then fed into a conveyor belt for removal. Once cooled to below 400°C, the recycled carbon fiber materials are fed from below the microwave heating cavity, preventing oxidation and combustion, thus accelerating the cooling to room temperature.

[0038] Please now refer to Figure 2, which shows an embodiment of the present invention: (a) a carbon fiber composite sheet before microwave heat treatment and (b) recycled carbon fiber after microwave pyrolysis.

[0039] The carbon fiber material is removed from the microwave heating cavity, washed with water to remove impurities, and then dried to obtain high-quality carbon fiber material.

[0040] This two-stage microwave heat treatment, involving control methods for different microwave power densities, heating temperatures, heating times, gas compositions and flow rates, and extraction conditions, effectively yields high-quality recycled carbon fibers. The advantages of this invention's method for regenerating carbon fibers from microwave-pyrolyzed carbon fiber composites are:

[0041] (1) By utilizing the selective heating characteristics of microwaves on carbon fiber composite waste, the interior of the carbon fiber resin matrix composite material is rapidly heated and the whole is heated uniformly, which shortens the processing time and improves the recycling efficiency and effect of carbon fiber;

[0042] (2) Inert gas or oxygen-containing mixed gas is introduced at different times under normal pressure and a certain temperature is controlled to degrade the resin and then react with oxidation. The carbon fiber does not react, thereby removing the organic matter of the resin and obtaining carbon fiber with good performance, which has a smooth surface and basically no residual resin.

[0043] (3) The heat released by the oxidation reaction is used for heat preservation, which reduces the energy consumption of microwave power and saves energy significantly.

[0044] (4) The recycled carbon fiber obtained by microwave treatment has excellent mechanical properties and can be compounded with various resin matrices to form new carbon fiber reinforced composite materials, which can be applied to different fields. It is a green and environmentally friendly recycling method.

[0045] Although the present invention has been disclosed with reference to the foregoing preferred embodiments, it is not intended to limit the invention. Anyone skilled in the art can make various modifications and alterations without departing from the spirit and scope of the invention. As explained above, various modifications and variations can be made without destroying the spirit of the invention. Therefore, the scope of protection of this invention shall be determined by the claims outlined in the appended patent claims.

Claims

1. A method for regenerating carbon fiber using microwave pyrolysis of carbon fiber composite material, comprising the following main steps: Step (1): cutting a large sheet of carbon fiber composite material into a plurality of carbon fiber composite material sheets; Step (2): placing the carbon fiber composite material sheets into a microwave heating cavity, the microwave heating cavity having at least one air inlet and at least one air outlet, the air outlet being connected to an external air extraction device via a pipe, the carbon fiber composite material sheets being placed into the microwave heating cavity from above, the carbon fiber composite material sheets occupying approximately one-third to two-thirds of the space of the ceramic container of the microwave heating cavity; Step (3): introducing an oxygen-free atmosphere containing inert gas into the carbon fiber composite material sheets in the microwave heating cavity through the at least one air inlet, performing a first microwave heat treatment to form a plurality of semi-finished carbon fiber materials, the temperature of the first microwave heat treatment being between 450 and 600°C, the time being 0.2 to 0.8 hours, the microwave power density of the first microwave heat treatment being between 5 kW / kg and 10 kW / kg, the first microwave... The inert gas system introduced for heat treatment is nitrogen, with a flow rate between 10 LPM / kg and 20 LPM / kg, where LPM is liters per minute (L / min) and kg is the unit weight of the carbon fiber composite sheets; Step (4): The semi-finished carbon fiber materials are introduced into the microwave heating cavity through the at least one air inlet into a low-oxygen atmosphere containing mixed air to undergo a second microwave heat treatment to form a plurality of recycled carbon fiber materials. The temperature of the second microwave heat treatment is between 450 and 600°C, the time is between 0.1 and 0.7 hours, the microwave power density of the second microwave heat treatment is between 3 kW / kg and 8 kW / kg, and the mixed gas system introduced for the second microwave heat treatment contains at least one compressed air with a flow rate between 10 LPM / kg and 20 LPM / kg, where LPM is liters per minute (L / min) and kg is the unit weight of the carbon fiber composite sheets; and Step (5): The recycled carbon fiber materials enter a cooling container from the microwave heating cavity; wherein, During the first microwave heat treatment, the external extraction device extracts the gas generated by the semi-finished carbon fiber material from the microwave heating cavity at a gas velocity equivalent to that generated by the semi-finished carbon fiber material, so as to keep the microwave heating cavity in the oxygen-free atmosphere; and during the second microwave heat treatment, the external extraction device extracts the mixed gas introduced into the microwave heating cavity at a gas velocity equivalent to or greater than that of the introduced mixed gas, so as to keep the microwave heating cavity in the low-oxygen atmosphere.

2. The method for regenerating carbon fibers using microwave-pyrolyzed carbon fiber composite material as described in claim 1, wherein the microwave heating cavity system is primarily a ceramic container with an outer metal shell.

3. The method for regenerating carbon fiber using microwave-pyrolyzed carbon fiber composite material as described in claim 2, wherein the at least one air inlet of the microwave heating cavity is located in the lower half of the ceramic container, and the at least one air outlet of the microwave heating cavity is located in the upper half of the ceramic container.

4. The method for regenerating carbon fibers using microwave-disrupted carbon fiber composite materials as described in claim 1, wherein the carbon fiber composite material sheets are approximately 2 to 40 cm long and 2 to 20 cm wide.

5. The method for regenerating carbon fibers using microwave-pyrolyzed carbon fiber composite material as described in claim 1, wherein the carbon fibers in the carbon fiber composite material are one or more of polyacrylonitrile-based carbon fibers, pitch-based carbon fibers, or viscose-based carbon fibers.

6. The method for regenerating carbon fibers using microwave-pyrolyzed carbon fiber composite material as described in claim 1, wherein the matrix resin in the carbon fiber composite material is one or more of thermosetting resin or thermoplastic resin.

7. The method for regenerating carbon fibers using microwave-pyrolyzed carbon fiber composite materials as described in claim 6, wherein the thermosetting resin includes epoxy resin, unsaturated polyester resin, phenolic resin, urea-formaldehyde resin, melamine-formaldehyde resin, bismaleimide resin, polyimide resin, polyurethane resin, organosilicon resin, and furan resin.

8. The method for regenerating carbon fibers using microwave-pyrolyzed carbon fiber composites as described in claim 6, wherein the thermoplastic resin includes polyphenylene sulfide, polyphenylene ether, polytetrafluoroethylene, polyamide, polyetheretherketone, polycarbonate, PC / ABS (polycarbonate / acrylonitrile-butadiene-styrene) alloy, polyoxymethylene, polypropylene, thermoplastic polyimide, polyethylene, polyarylate, liquid crystal polymer, polyethylene terephthalate, polybutylene terephthalate, polyvinyl chloride, polystyrene, and acrylonitrile-butadiene-styrene copolymer.

9. The method for regenerating carbon fibers using microwave-induced pyrolysis of carbon fiber composite materials as described in claim 2, wherein the microwave frequencies of the first microwave heat treatment and the second microwave heat treatment are either 915MHz or 2450MHz.

10. The method for regenerating carbon fibers using microwave-pyrolyzed carbon fiber composites as described in claim 1, wherein the regenerated carbon fiber materials are cooled to below 400°C and then fed into a conveyor belt for removal.

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