CN116063735A - Method for recycling carbon fiber from carbon fiber composite material and application thereof - Google Patents

Method for recycling carbon fiber from carbon fiber composite material and application thereof Download PDF

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Publication number
CN116063735A
CN116063735A CN202111280571.1A CN202111280571A CN116063735A CN 116063735 A CN116063735 A CN 116063735A CN 202111280571 A CN202111280571 A CN 202111280571A CN 116063735 A CN116063735 A CN 116063735A
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carbon fiber
composite material
fiber composite
carbon
resin
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宋清华
付善龙
张代军
刘瑞丽
陈吉平
郑义珠
袁宇慧
刘奎
张冬梅
刘卫平
马璟瑶
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Shanghai Aircraft Manufacturing Co Ltd
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Shanghai Aircraft Manufacturing Co Ltd
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    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J11/00—Recovery or working-up of waste materials
    • C08J11/04—Recovery or working-up of waste materials of polymers
    • C08J11/10—Recovery or working-up of waste materials of polymers by chemically breaking down the molecular chains of polymers or breaking of crosslinks, e.g. devulcanisation
    • C08J11/12—Recovery or working-up of waste materials of polymers by chemically breaking down the molecular chains of polymers or breaking of crosslinks, e.g. devulcanisation by dry-heat treatment only
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
    • C08K7/00—Use of ingredients characterised by shape
    • C08K7/02—Fibres or whiskers
    • C08K7/04—Fibres or whiskers inorganic
    • C08K7/06—Elements
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J2363/00—Characterised by the use of epoxy resins; Derivatives of epoxy resins
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J2379/00—Characterised by the use of macromolecular compounds obtained by reactions forming in the main chain of the macromolecule a linkage containing nitrogen with or without oxygen, or carbon only, not provided for in groups C08J2361/00 - C08J2377/00
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J2379/00—Characterised by the use of macromolecular compounds obtained by reactions forming in the main chain of the macromolecule a linkage containing nitrogen with or without oxygen, or carbon only, not provided for in groups C08J2361/00 - C08J2377/00
    • C08J2379/04—Polycondensates having nitrogen-containing heterocyclic rings in the main chain; Polyhydrazides; Polyamide acids or similar polyimide precursors
    • C08J2379/08—Polyimides; Polyester-imides; Polyamide-imides; Polyamide acids or similar polyimide precursors
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
    • Y02W30/00—Technologies for solid waste management
    • Y02W30/50—Reuse, recycling or recovery technologies
    • Y02W30/62—Plastics recycling; Rubber recycling

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  • Chemical & Material Sciences (AREA)
  • Health & Medical Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Medicinal Chemistry (AREA)
  • Polymers & Plastics (AREA)
  • Organic Chemistry (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Sustainable Development (AREA)
  • Separation, Recovery Or Treatment Of Waste Materials Containing Plastics (AREA)

Abstract

The invention provides a method for recycling carbon fibers from a carbon fiber composite material and application thereof, wherein the method comprises the steps of heat-treating the carbon fiber composite material for 30-90 min at 400-700 ℃ in an atmosphere with 2-3% of oxygen by volume percent to complete recycling of the carbon fibers from the carbon fiber composite material; according to the method, the volume percentage of oxygen, the heat treatment temperature and the heat treatment time in the heat treatment process are controlled, so that the purity of the recovered carbon fiber is higher and the recovery rate is higher; the whole recovery process of the method is simple to operate, short in process time, free of any chemical reagent, green and environment-friendly, and capable of realizing large-scale application and being very beneficial to sustainable development of carbon fiber industrialization.

Description

Method for recycling carbon fiber from carbon fiber composite material and application thereof
Technical Field
The invention belongs to the technical field of material recovery, and particularly relates to a method for recovering carbon fibers from a carbon fiber composite material and application thereof.
Background
The thermosetting resin-based composite material has the characteristics of small density, high specific strength and specific modulus, high fatigue resistance, good breakage safety characteristic and the like, and is very widely applied. Carbon fiber reinforced resin matrix composites (CFRP composites) are composites formed by using carbon fibers or carbon fiber fabrics as reinforcements and epoxy resins, bismaleimide resins, cyanate resins, polyimide resins, and the like as matrixes. The carbon fiber reinforced thermosetting epoxy resin-based composite material is an important branch of a carbon fiber reinforced composite material, has the characteristics of low density, high specific strength and high specific modulus of the thermosetting epoxy resin-based composite material, has the advantages of low thermal expansion coefficient, excellent creep resistance, corrosion resistance, low temperature resistance, designability of material performance and the like, and can be used as a structural bearing material and a functional material. Along with the development of economy and society, CFRP composite materials are increasingly applied to the fields of high and new technology industries such as aerospace, automobile industry, rail transit, new energy sources, sports goods and the like.
Along with the rapid increase of the demand of the composite material, the production technology of the CFRP composite material is continuously optimized, various automatic production technologies are adopted to further reduce the production cost and improve the production efficiency, but a large amount of leftover materials can be produced during mass production of the CFRP composite material, the service life of the CFRP composite material is about 20-30 years, and various products widely applied to the CFRP composite material can be scrapped gradually along with the time.
The carbon fiber reinforced thermosetting epoxy resin-based (CF/EP) composite material is solidified to form a crosslinked network structure, is insoluble and infusible and is not easy to decompose, so that the waste CF/EP composite material is difficult to recycle and reuse, the carbon fiber is expensive, the average production of 1 ton of carbon fiber needs to cost more than 1 ten thousand pounds, the waste CF/EP composite material both pollutes the environment and increases the economic cost, and the recycling and reusing of the waste CF/EP composite material has extremely important ecological and economic values.
The existing recovery treatment method of the waste CF/EP composite material mainly comprises a traditional landfill method, a mechanical crushing method, a high-temperature pyrolysis method, a solvent recovery method, a microwave pyrolysis method, an electrochemical reaction method, a catalytic cracking method and the like. The traditional landfill method is to directly embed the waste CF/EP composite material into the ground, so that the method not only seriously pollutes the environment, but also does not realize the recycling of the carbon fiber, and causes serious harm to the economic and social benefits, so that the method is gradually abandoned. The mechanical crushing method is to crush the waste CF/EP composite material as the raw material of the new material, and the method damages the performance of each component of the original composite material, and cannot recover the carbon fiber, thereby realizing the recycling. The solvent recovery method is to dissolve a matrix resin by using various chemical solvents, thereby recovering carbon fibers therein. CN1974641 discloses a method for decomposing thermosetting epoxy resin and composite material thereof, which solves the problem that thermosetting epoxy resin and composite material thereof are difficult to recycle. The decomposition of the thermosetting epoxy resin comprises the following steps: adding thermosetting epoxy resin and a decomposition solution into a reaction kettle; and decomposing to finish the decomposition of the thermosetting epoxy resin. Decomposition of the thermosetting epoxy resin composite: adding the thermosetting epoxy resin composite material and the decomposition liquid into a reaction kettle; decomposing; solid-liquid separation; and (3) solid phase cleaning and drying to obtain the decomposed thermosetting epoxy resin and reinforcing fiber. The decomposition rate of the thermosetting epoxy resin is high in the invention, namely 90-100%; the epoxy resin decomposition products can be reused as chemical raw materials after being separated. The reinforced fiber in the thermosetting epoxy resin composite material is 100 percent recovered, and the thermosetting epoxy resin and the decomposition liquid which have no defects on the surface and do not remain decomposition can be reused. The method can effectively recover pure carbon fibers, but needs to use strong oxidizing solvents such as nitric acid and the like, needs to be heated to a certain temperature, has high cost and is not suitable for industrial application. The electrochemical reaction method takes the carbon fiber composite material to be recycled as an anode and takes the conductive material as a cathode to form an electrochemical reaction system, and the carbon fiber composite material is subjected to chemical reaction to recycle the carbon fiber. The recycled carbon fiber obtained by the catalytic cracking method has high recovery rate and high resin decomposition efficiency, but various catalysts, oxidants, organic solvents and the like are needed, so that the operation is complex, the hazard is high, the cost is high, and the large-scale application is difficult to realize.
The most industrially applicable method in the prior art is a high-temperature pyrolysis method, which comprises an inert gas pyrolysis method and an air pyrolysis method, wherein the inert gas pyrolysis method is a method of placing waste CF/EP composite materials in inert atmosphere such as nitrogen, helium and the like for thermal decomposition; CN103665430a is a thermal decomposition separation method of resin and carbon fiber in waste carbon fiber composite material, the specific steps of the method are: (1) Placing the waste carbon fiber composite material into a hearth of a pyrolysis device, closing a furnace door, introducing nitrogen with the oxygen content of 3-20 vol% into the furnace door, and completely discharging air in the hearth to form a low-oxygen environment; (2) Heating the materials in the hearth to 400-650 ℃, keeping for a certain time, and stopping the furnace to naturally cool the materials in the hearth, so that the resin undergoes thermal decomposition reaction in the hearth; (3) And opening the cooled hearth to take out a product, and under the reaction conditions, completely decomposing the resin, gasifying and discharging the resin out of the hearth, so that the product is left with carbon fibers with completely clean surfaces, collecting and weighing the carbon fibers, and calculating the recovery rate. The carbon fiber obtained by the method has high recovery rate, small performance damage and simple operation process, and is suitable for industrial production. The method can well protect the surface of the carbon fiber from being damaged, but has long process time, and the recycled carbon fiber surface is easy to remain carbon knots decomposed by resin, so that the recycling of the recycled carbon fiber is influenced.
Therefore, developing a recovery method which has high recovery rate, simple operation process and can obtain carbon fiber with higher purity is a technical problem which is urgently needed to be solved by the technicians in the field at present.
Disclosure of Invention
In view of the shortcomings of the prior art, it is an object of the present invention to provide a method for recovering carbon fibers from a carbon fiber composite material and application thereof, the method comprising: heat-treating the carbon fiber composite material for 30-90 min at 400-700 ℃ in an atmosphere with the volume percentage of oxygen of 2-3%, so as to complete the recovery of the carbon fiber; the method does not use chemical reagents in the recovery process, and is environment-friendly, so that sustainable development of the composite material can be realized; the whole recovery operation process is simple, the recovery time is short, and the method is very suitable for industrial production; most importantly, the carbon fiber recovered by the method has high recovery rate and high performance retention rate, and is beneficial to recycling the recovered carbon fiber.
To achieve the purpose, the invention adopts the following technical scheme:
in a first aspect, the present invention provides a method of recovering carbon fibers from a carbon fiber composite material, the method comprising: the recovery of the carbon fibers is completed by heat-treating the carbon fiber composite material for 30 to 90 minutes (e.g., 35 minutes, 40 minutes, 45 minutes, 50 minutes, 55 minutes, 60 minutes, 65 minutes, 70 minutes, 75 minutes, 80 minutes, 85 minutes, or the like) in an atmosphere having 2 to 3% by volume (e.g., 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, or the like) of oxygen (e.g., 430 ℃, 460 ℃, 490 ℃, 530 ℃, 560 ℃, 590 ℃, 630 ℃, 660 ℃, 690 ℃, or the like).
The invention provides a method for recycling carbon fibers from a carbon fiber composite material, which belongs to a high-temperature pyrolysis method; according to the method, firstly, the volume percentage of oxygen is required to be controlled to be 2-3%, and on one hand, if the content of oxygen is higher, the surface of carbon fiber in the carbon fiber composite material is oxidized, so that the recovery rate of the carbon fiber is lower; on the other hand, if the volume percentage of oxygen in the waste water is low, the recovery process is prolonged, resources are wasted, and the cost is increased.
Secondly, the method for recycling the carbon fibers from the carbon fiber composite material is quite simple to operate, the carbon fiber composite material is subjected to high-temperature heat treatment for 30-90 min at 400-700 ℃ under the condition that the volume percentage of oxygen is controlled to be 2-3%, so that the matrix material in the carbon fiber composite material is directly heated and decomposed, then the carbon fibers can be directly obtained, the whole recycling process is simple to operate, the process time is short, matrix resin is completely decomposed, no carbon deposition residue exists on the surface, the recycling rate of the obtained carbon fibers is higher, large-scale application can be realized, and industrial production is very facilitated; and the whole process does not use chemical reagents, so that the method is environment-friendly, and the sustainable development of the composite material is realized.
For example, in actual operation, a carbon fiber composite material with a certain mass can be weighed first and then put into a high-temperature resistant container; and heating the high-temperature cracking device to 400-700 ℃, controlling the volume percentage of oxygen to be 2-3%, then placing the container filled with the carbon fiber composite material into a hearth of the high-temperature cracking device, closing a furnace door, keeping for 30-90 min, enabling the resin to undergo thermal decomposition reaction in the hearth, and directly taking out the container after heat preservation is finished, thus obtaining the recycled carbon fiber.
Preferably, the carbon fibers in the carbon fiber composite material include any one or a combination of at least two of polyacrylonitrile-based carbon fibers, pitch-based carbon fibers, or viscose-based carbon fibers.
Preferably, the carbon fiber composite material comprises a carbon fiber reinforced resin matrix composite material.
Preferably, the resin in the carbon fiber reinforced resin matrix composite comprises any one or a combination of at least two of epoxy resin, bismaleimide resin, cyanate resin and polyimide resin.
Preferably, the carbon fiber composite material includes scrap and/or waste carbon fiber composite material generated during prepreg layup.
Preferably, the heat treatment is carried out in a pyrolysis apparatus.
Preferably, the heat treatment further comprises the steps of cooling and cleaning after the heat treatment is finished.
Preferably, the cleaning comprises ultrasonic cleaning.
As a preferred embodiment of the present invention, the method includes: and (3) heat-treating the carbon fiber composite material for 30-90 min at 400-700 ℃ in an atmosphere with the volume percentage of oxygen of 2-3%, cooling, cleaning and removing impurities on the surface of the carbon fiber, and thus, recycling the carbon fiber.
In a second aspect, the present invention provides a carbon fiber recovered by the method of the first aspect.
In the invention, the carbon fiber recovered by the recovery method provided in the first aspect can be well maintained in the state of the carbon fiber tow, the resin matrix is thoroughly decomposed, the surface contains less residual carbon, and the method is suitable for reutilization of the carbon fiber.
In a third aspect, the present invention provides the use of a carbon fibre as described in the second aspect in aerospace, automotive industry, rail transit, new energy or sports goods.
Compared with the prior art, the invention has the following beneficial effects:
(1) The method for recycling carbon fibers from the carbon fiber composite material comprises the steps of heat-treating the carbon fiber composite material for 30-90 min at 400-700 ℃ in an atmosphere with the volume percentage of oxygen of 2-3%, so as to complete recycling of the carbon fibers; according to the method, the volume percentage content of oxygen, the heat treatment temperature and the time in the recovery process are controlled, so that the surface impurity content of the recovered carbon fiber is low, the performance is excellent, and the recovery rate is high.
(2) The method for recycling the carbon fibers from the carbon fiber composite material has the advantages of simple operation in the whole recycling process, short process time, complete matrix resin decomposition, and resin decomposition rate reaching 93.56-98.04%; and the surface has no carbon deposition residue, the recovery rate of the obtained carbon fiber is high, and the large-scale application can be realized, thereby being very beneficial to industrial production.
(3) The method for recycling the carbon fibers from the carbon fiber composite material does not use chemical reagents in the whole process, is environment-friendly, and therefore sustainable development of the composite material is achieved.
Detailed Description
The technical scheme of the invention is further described by the following specific embodiments. It will be apparent to those skilled in the art that the examples are merely to aid in understanding the invention and are not to be construed as a specific limitation thereof.
Example 1
A method of recovering carbon fibers from a carbon fiber composite material, the method comprising the steps of:
(1) Accurately weighing a carbon fiber composite material (M21C prepreg of Hertz company and IMA carbon fiber with resin content of 34%) and placing into a high-temperature resistant container;
(2) Heating a high-temperature cracking device containing 2.5% of oxygen by volume to 600 ℃, putting the high-temperature resistant container filled with the carbon fiber composite material obtained in the step (1) into a hearth of the high-temperature cracking device, closing a furnace door, performing heat treatment for 60min, and taking out the high-temperature resistant container;
(3) Taking out the heat-treated material after the high-temperature resistant container obtained in the step (2) is cooled;
(4) And (3) ultrasonically cleaning and recycling the heat-treated material obtained in the step (3), removing carbon residues and other impurities on the surface, drying, accurately weighing the quality of the recycled carbon fiber, and finishing the recycling of the carbon fiber.
In this example, the mass of the carbon fiber composite material measured in step (1) of this example is denoted as w 1 ，w 1 =487g, the mass of the recovered carbon fiber is measured in step (4) and is denoted as w 2 ，w 2 ＝327g；
According to w 1 And w 2 Calculation of the oxidative weight loss of carbon fiber composite = w 1 -w 2 =160 g; resin decomposition rate=160/(487×0.34) = 96.63%.
Example 2
A method of recovering carbon fibers from a carbon fiber composite material, the method comprising the steps of:
(1) Accurately weighing a carbon fiber composite material (M21C prepreg of Hertz company, IMA carbon fiber and resin content of 34%) and placing the carbon fiber composite material into a high-temperature resistant container;
(2) Heating a high-temperature cracking device containing 2% of oxygen by volume to 400 ℃, putting the high-temperature resistant container filled with the carbon fiber composite material obtained in the step (1) into a hearth of the high-temperature cracking device, closing a furnace door, performing heat treatment for 90min, and taking out the high-temperature resistant container;
(3) Taking out the heat-treated material after the high-temperature resistant container obtained in the step (2) is cooled;
(4) And (3) ultrasonically cleaning and recycling the heat-treated material obtained in the step (3), removing carbon residues and other impurities on the surface, drying, accurately weighing the quality of the recycled carbon fiber, and finishing the recycling of the carbon fiber.
In this example, the mass of the carbon fiber composite material measured in step (1) of this example is denoted as w 1 ，w 1 =458 g, the mass of the recovered carbon fiber is measured in step (4) and is denoted as w 2 ，w 2 ＝306g；
According to w 1 And w 2 Calculation of the oxidative weight loss of carbon fiber composite = w 1 -w 2 =152 g; resin decomposition rate=152/(458×0.34) = 97.61%.
Example 3
A method of recovering carbon fibers from a carbon fiber composite material, the method comprising the steps of:
(1) Accurately weighing a carbon fiber composite material (M21C prepreg of Hertz company, IMA carbon fiber and resin content of 34%) and placing the carbon fiber composite material into a high-temperature resistant container;
(2) Heating a high-temperature cracking device containing 3 mass percent of oxygen to 700 ℃, putting the high-temperature resistant container filled with the carbon fiber composite material obtained in the step (1) into a hearth of the high-temperature cracking device, closing a furnace door, performing heat treatment for 30min, and taking out the high-temperature resistant container;
(3) Taking out the heat-treated material after the high-temperature resistant container obtained in the step (2) is cooled;
(4) And (3) ultrasonically cleaning and recycling the heat-treated material obtained in the step (3), removing carbon residues and other impurities on the surface, drying, accurately weighing the quality of the recycled carbon fiber, and finishing the recycling of the carbon fiber.
In this example, the mass of the carbon fiber composite material measured in step (1) of this example is recorded asw 1 ，w 1 =463 g, the mass of the recovered carbon fiber is measured in step (4) and is denoted as w 2 ，w 2 ＝311g；
According to w 1 And w 2 Calculation of the oxidative weight loss of carbon fiber composite = w 1 -w 2 =152 g; resin decomposition rate=152/(463×0.34) =96.56%.
Example 4
A method for recovering carbon fibers from a carbon fiber composite material is different from example 1 in that the mass percentage of oxygen is 2%, and other conditions and parameters are the same as in example 1.
In this example, the mass of the carbon fiber composite material measured in step (1) of this example is denoted as w 1 ，w 1 =503 g, the mass of the recovered carbon fiber is measured in the step (4) and is denoted as w 2 ，w 2 ＝343g；
According to w 1 And w 2 Calculation of the oxidative weight loss of carbon fiber composite = w 1 -w 2 =160 g; resin decomposition rate=160/(503×0.34) = 93.56%.
Example 5
A method for recovering carbon fibers from a carbon fiber composite material is different from example 1 in that the mass percentage of oxygen is 3%, and other conditions and parameters are the same as in example 1.
In this example, the mass of the carbon fiber composite material measured in step (1) of this example is denoted as w 1 ，w 1 =492 g, the mass of the recovered carbon fiber is measured in step (4) and is denoted as w 2 ，w 2 ＝329g；
According to w 1 And w 2 Calculation of the oxidative weight loss of carbon fiber composite = w 1 -w 2 =163 g; resin decomposition rate=163/(492×0.34) =97.44%.
Example 6
A method for recovering carbon fibers from a carbon fiber composite material is different from example 1 in that the thermal decomposition temperature is 400℃and other conditions and parameters are the same as those of example 1.
At the bookIn the present example, the mass of the carbon fiber composite material measured in the step (1) of the present example is denoted as w 1 ，w 1 =471 g, the mass of the recovered carbon fiber is measured in step (4) and is denoted as w 2 ，w 2 ＝321g；
According to w 1 And w 2 Calculation of the oxidative weight loss of carbon fiber composite = w 1 -w 2 =150g; resin decomposition rate=150/(471×0.34) =93.67%.
Example 7
A method for recovering carbon fibers from a carbon fiber composite material is different from example 1 in that the thermal decomposition temperature is 700 ℃, and other conditions and parameters are the same as in example 1.
In this example, the mass of the carbon fiber composite material measured in step (1) of this example is denoted as w 1 ，w 1 489g, and the mass of the recovered carbon fiber is measured in the step (4) and recorded as w 2 ，w 2 ＝326g；
According to w 1 And w 2 Calculation of the oxidative weight loss of carbon fiber composite = w 1 -w 2 =163 g; resin decomposition rate=163/(489×0.34) =98.04%.
Comparative example 1
A method for recovering carbon fibers from a carbon fiber composite material is different from example 1 in that the mass percentage of oxygen is 1%, and other conditions and parameters are the same as in example 1.
In the step (1) of the comparative example, the mass of the carbon fiber composite material is measured and recorded as w 1 ，w 1 =511 g, and the mass of the recovered carbon fiber is measured in the step (4) and is denoted as w 2 ，w 2 ＝357g；
According to w 1 And w 2 Calculation of the oxidative weight loss of carbon fiber composite = w 1 -w 2 =154 g; resin decomposition rate=154/(511×0.34) =88.63%.
As can be seen from comparing example 1 with comparative example 1, the resin decomposition rate in the method provided in comparative example 1 was only 88.63%, which is far lower than 96.63% of example 1, because the method provided in comparative example 1 has a low oxygen content, resulting in the presence of more resin that has not been decomposed yet.
Comparative example 2
A method for recovering carbon fibers from a carbon fiber composite material is different from example 1 in that the mass percentage of oxygen is 4%, and other conditions and parameters are the same as in example 1.
In the step (1) of the comparative example, the mass of the carbon fiber composite material is measured and recorded as w 1 ，w 1 =497g, the mass of the recovered carbon fiber is measured in step (4) and is denoted as w 2 ，w 2 ＝330g；
According to w 1 And w 2 Calculation of the oxidative weight loss of carbon fiber composite = w 1 -w 2 =167 g; resin decomposition rate=167/(497×0.34) = 98.82%.
As can be seen from comparative examples 1 and 2, although the resin decomposition rate obtained by the method provided in comparative example 2 was 98.82%, the surface of the recovered carbon fiber was observed to be remarkably oxidized, and it was difficult to use it secondarily.
Comparative example 3
A method for recovering carbon fibers from a carbon fiber composite material is different from example 1 in that the thermal decomposition temperature is 300℃and other conditions and parameters are the same as those of example 1.
In the step (1) of the comparative example, the mass of the carbon fiber composite material is measured and recorded as w 1 ，w 1 =508 g, the mass of the recovered carbon fiber is measured in step (4) and is denoted as w 2 ，w 2 ＝370g；
According to w 1 And w 2 Calculation of the oxidative weight loss of carbon fiber composite = w 1 -w 2 =138 g; resin decomposition rate=138/(508×0.34) =79.90%.
As can be seen from comparative example 1 and comparative example 1, since the method provided in comparative example 1 was low in heating temperature, there was also much resin which had not been decomposed yet, resulting in a lower final resin decomposition rate of only 79.90%.
Comparative example 4
A method for recovering carbon fibers from a carbon fiber composite material is different from example 1 in that the thermal decomposition temperature is 1000℃and other conditions and parameters are the same as those of example 1.
In the step (1) of the comparative example, the mass of the carbon fiber composite material is measured and recorded as w 1 ，w 1 =521 g, the mass of the recovered carbon fiber is measured in step (4) and is denoted as w 2 ，w 2 ＝341g；
According to w 1 And w 2 Calculation of the oxidative weight loss of carbon fiber composite = w 1 -w 2 =180g; resin decomposition rate=180/(521×0.34) = 101.61%.
As can be seen from comparison of example 1 and comparative example 4, although the resin decomposition rate obtained by the method provided in comparative example 4 was high and the resin decomposition was thorough, it can be seen that the recovered carbon fiber was severely oxidized on the surface and difficult to be used for the second time.
The applicant states that the present invention is described by way of the above examples as a method for recovering carbon fibres from a carbon fibre composite material and its use, but the invention is not limited to, i.e. it is not meant that the invention must be practiced in dependence upon the above examples. It should be apparent to those skilled in the art that any modification of the present invention, equivalent substitution of raw materials for the product of the present invention, addition of auxiliary components, selection of specific modes, etc., falls within the scope of the present invention and the scope of disclosure.

Claims (10)

1. A method of recovering carbon fibers from a carbon fiber composite material, the method comprising: and (3) heat-treating the carbon fiber composite material for 30-90 min at 400-700 ℃ in an atmosphere with the volume percentage of oxygen of 2-3%, so as to complete the recovery of the carbon fiber.
2. The method of claim 1, wherein the carbon fibers in the carbon fiber composite material comprise any one or a combination of at least two of polyacrylonitrile-based carbon fibers, pitch-based carbon fibers, or viscose-based carbon fibers.
3. The method according to claim 1 or 2, wherein the carbon fiber composite material comprises a carbon fiber reinforced resin based composite material;
preferably, the resin in the carbon fiber reinforced resin matrix composite comprises any one or a combination of at least two of epoxy resin, bismaleimide resin, cyanate resin and polyimide resin.
4. A method according to any one of claims 1 to 3, wherein the carbon fibre composite comprises scrap and/or waste carbon fibre composite produced during prepreg layup.
5. The method according to any one of claims 1 to 4, wherein the heat treatment is performed in a pyrolysis apparatus.
6. The method according to any one of claims 1 to 5, further comprising the steps of cooling and cleaning after the heat treatment is completed.
7. The method of claim 6, wherein the cleaning comprises ultrasonic cleaning.
8. The method according to any one of claims 1 to 7, characterized in that it comprises: and (3) heat-treating the carbon fiber composite material for 30-90 min at 400-700 ℃ in an atmosphere with the volume percentage of oxygen of 2-3%, cooling, cleaning and removing impurities on the surface of the carbon fiber, and thus, recycling the carbon fiber.
9. A carbon fiber, characterized in that the carbon fiber is recovered by the method according to any one of claims 1 to 8.
10. Use of the carbon fiber of claim 9 in aerospace, automotive industry, rail traffic, new energy or sporting goods.
CN202111280571.1A 2021-10-29 2021-10-29 Method for recycling carbon fiber from carbon fiber composite material and application thereof Pending CN116063735A (en)

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