Efficient interface self-repairing carbon fiber bismaleimide composite material based on dual dynamic network structure and preparation method thereof

Abstract

The invention discloses an efficient interface self-repairing carbon fiber bismaleimide composite material based on a dual dynamic network structure and a preparation method thereof, and belongs to the technical field of composite materials. The method comprises the following steps: carrying out surface oxidation on carbon fibers, grafting hyperbranched polyester containing Diels-Alder bonds, mixing and curing with bismaleimide resin and diallyl bisphenol A, and constructing a dual dynamic network structure based on hydrogen bonds and Diels-Alder bonds on an interface. The initial interface repairing efficiency of the composite material reaches 96.4% and still reaches 90.3% after multiple times of repairing, the repairing condition is mild, the technology is simple, industrialization is easy, and the composite material is suitable for the fields of aerospace and high-end equipment.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of composite materials, and particularly relates to a high-efficiency interfacial self-repairing carbon fiber bismaleimide composite material based on a dual dynamic network structure and a preparation method thereof. BACKGROUND

[0002] Composite materials have become the key support materials in the aerospace, high-end equipment, transportation and other industries as the core and frontier direction in the field of material science. Among them, the composite material taking carbon fiber as the reinforcing body and thermosetting resin as the matrix has been most widely applied in many fields due to its light weight, high strength, high modulus, fatigue resistance and other excellent characteristics. However, the inherent heterogeneous characteristics of the composite material make it face severe performance challenges in the long-term service process.

[0003] As a typical two-phase composite material, there is a large number of complex interface phase regions between carbon fibers and resin matrix. The interface phase is the core channel for load transfer such as stress transfer, heat conduction and electric conduction, and its comprehensive performance directly determines the macroscopic mechanical performance and service reliability of the composite material. However, the surface of the carbon fiber is chemically inert in nature and has low surface energy, which leads to generally weak interfacial adhesion strength between the carbon fiber and the resin matrix, and easily forms an interfacial layer with weak mechanical properties. Under the service conditions of external impact, shear action, cyclic load or complex environmental corrosion, microcracks are easily initiated from the weak interfacial layer in the material. These microcracks not only cause local stress concentration, but also rapidly expand and develop into macroscopic delamination or penetrating cracks during the service process, which eventually leads to a sharp decline in the mechanical properties, thermal conductivity and electrical conductivity of the composite material, and seriously threatens the use safety and service life of the engineering structure. Therefore, the interface failure has become the core technical bottleneck restricting the improvement of the reliability and durability of the carbon fiber composite material.

[0004] To solve this key problem, endowing material interface with self-repairing ability is considered as the most potential frontier technology direction. Its core principle is to introduce reversible chemical bonds in the interface region, so that the material can trigger repair reaction through external stimuli such as heat and light after being damaged, realize the automatic healing of microcracks, and then restore the material performance and prolong the service life. Among many repair chemical systems, Diels-Alder reaction is concerned due to its mild reaction conditions and excellent reversibility. Among them, the Diels-Alder reaction between furan and maleimide groups is a typical representative. The reaction can realize reversible combination at moderate temperature (about 60-70℃), and the reverse Diels-Alder dissociation occurs at high temperature (>100℃), which provides a good chemical basis for the realization of self-repairing function. At present, researchers have successfully introduced Diels-Alder chemistry into the interface design of composite materials, and realized the interface repair through the cycle process of "chemical bond breaking-recombination" after damage.

[0005] However, through in-depth research, the skilled person in the art found that the traditional self-repairing system relying on Diels-Alder bond alone has inherent technical limitations, which makes it difficult to achieve the ideal state of interface repair efficiency in actual application. The core of this problem lies in that in the highly cross-linked rigid thermosetting resin network, the functional groups required by Diels-Alder reaction are usually fixed on the rigid molecular chain segment, and the molecular motion ability is severely limited. When microcracks occur in the interface, the furan and maleimide functional groups on both sides of the crack are difficult to realize effective diffusion and sufficient contact under repair conditions due to the lack of chain segment activity, which seriously hinders the efficient regeneration of Diels-Alder reaction. This defect directly leads to the problems of low repair efficiency, long repair cycle and even incomplete repair of the traditional system, which cannot meet the strict requirements of materials on high-efficiency and rapid self-repairing performance in actual working conditions, and limits its large-scale application in key fields such as high-end equipment. SUMMARY

[0006] In view of the above technical problems, the present application provides a kind of high-efficiency interface self-repairing carbon fiber bismaleimide composite material based on double dynamic network structure and its preparation method. The composite material can induce double dynamic network structure fracture and recombination under heating conditions, thereby realizing the efficient self-repairing of the interface microcracks of the composite material.

[0007] To achieve the above purpose, the present application provides the following technical solutions: One of the purposes of the present application is to provide a preparation method of a high-efficiency interface self-repairing carbon fiber bismaleimide composite material based on double dynamic network structure, comprising the following steps: The carbon fiber is subjected to surface oxidation treatment to obtain oxidized carbon fiber with reactive carboxyl groups on the surface; The hyperbranched polyester is preheated and added to a carboxyl-containing diene and a catalyst 1 to perform a first heating reaction, and after washing and drying, a hyperbranched polyester containing a diene is obtained; The hyperbranched polyester containing a diene is added to a solvent 1, a bismaleimide compound is added, and a second heating reaction is performed, and after washing and drying, a hyperbranched polyester containing a Diels-Alder bond is obtained; The hyperbranched polyester containing a Diels-Alder bond is soaked in a mixed solution, the oxidized carbon fiber is added, and a third heating reaction is performed, and after drying, a hyperbranched polyester containing a Diels-Alder bond grafted carbon fiber is obtained; The bismaleimide resin and the diallyl bisphenol A are mixed, the hyperbranched polyester containing a Diels-Alder bond grafted carbon fiber is added, and curing treatment is performed, and a carbon fiber / bismaleimide composite material is obtained.

[0008] The application introduces reversible Diels-Alder bonds and hydrogen bonds at the interface of the carbon fiber / bismaleimide composite material by using the hyperbranched polyester containing a Diels-Alder bond, constructs a double dynamic network structure, and realizes the interface self-repairing function of the composite material. The structure enables the interface of the composite material to control the forward and reverse of the Diels-Alder reaction under mild conditions after being damaged, and realizes efficient and multiple self-repairing of the interface microcracks through the reversible breaking and recombination of the double dynamic bonds. The process is simple and easy to industrialize, and the prepared composite material has a wide application prospect in the fields of aerospace, high-end equipment, etc.

[0009] Further, the specific operation steps of the surface oxidation treatment include: immersing the carbon fiber in concentrated nitric acid and performing oxidation treatment at 60-100℃ for 4-10h.

[0010] The concentrated nitric acid oxidation treatment can efficiently introduce reactive carboxyl groups on the surface of the carbon fiber, providing sufficient active sites for the subsequent grafting reaction with the hyperbranched polyester containing a Diels-Alder bond; the oxidation treatment is mild and controllable, avoiding excessive oxidation damage to the carbon fiber structure, retaining the lightweight, high-strength and high-modulus characteristics of the carbon fiber while improving the surface reactivity; laying a chemical foundation for the interface bonding of the carbon fiber and the resin matrix, reducing the formation of the interface weak layer and the probability of microcrack initiation.

[0011] Further, the hyperbranched polyester is selected from Boltorn H20, Boltorn H30 or Boltorn H40. The carboxyl-containing diene is selected from furan carboxylic acid, 2-furanacetic acid or 3-(2-furan)propionic acid.

[0012] The present application limits the specific type of hyperbranched polyester, carboxyl-containing diene, ensures the effective introduction of diene structure, and the raw materials are easy to obtain and have good compatibility.

[0013] Further, the catalyst 1 is selected from p-toluene sulfonic acid or toluene sulfonic acid; The mass ratio of the hyperbranched polyester, carboxyl-containing diene and catalyst 1 is 100: (30-50): (1-2); The specific operation steps of the first heating reaction include: reacting at 120-140℃ for 2-4h under a nitrogen atmosphere.

[0014] The present application clearly defines the mass ratio of raw materials and reaction conditions, accurately controls the reaction process, avoids side reactions, ensures the structural uniformity of the diene-containing hyperbranched polyester, and improves the reaction rate and conversion rate by using toluenesulfonic acid as the catalyst, thereby reducing the difficulty of purifying intermediate products and providing space for the movement of subsequent dynamic bonds, thereby laying a structural foundation for the flexibility of the double dynamic network.

[0015] Further, the solvent 1 is selected from dioxane or 1-methyl-2-pyrrolidone; and / or, The bismaleimide compound is selected from 1,2-bismaleimide ethane, 1,4-bismaleimide butane, 1,6-bismaleimide hexane or N,N'-(4,4-methylene diphenyl) bismaleimide; and / or, The mass ratio of the diene-containing hyperbranched polyester and the bismaleimide compound is 1: (0.4-1); and / or, The specific operation steps of the second heating reaction include: reacting at 50-70℃ for 12-24h under a nitrogen atmosphere.

[0016] The selected solvent 1 has excellent solubility for the diene-containing hyperbranched polyester and the bismaleimide compound, ensures the uniformity of the reaction system, and promotes the full Diels-Alder reaction; the various selections of the bismaleimide compound adapt to different application scenarios, the mass ratio of the bismaleimide compound and the diene can adjust the density of the Diels-Alder bond, and the self-repairing performance is optimized; the reaction conditions are mild, which avoids the functional group failure caused by high temperature, ensures the structural stability and reversible reaction activity of the Diels-Alder bond-containing hyperbranched polyester, and the product has high purity after washing and drying, thereby providing a high-quality intermediate for subsequent grafting reaction.

[0017] Further, the mixed solution is obtained by mixing solvent 2, dehydrating agent and catalyst 2 according to a mass ratio of 100: (4-10): (2-6); The solvent 2 is selected from N,N'-dimethylformamide, N,N'-dimethylacetamide or 1,3-dimethyl-2-imidazolidinone; The dehydrating agent is selected from N,N'-diisopropyl carbodiimide, N,N'-dicyclohexyl carbodiimide or N,N'-di-p-tolyl carbodiimide; The catalyst 2 is selected from 4-dimethylamino pyridine or triethylamine.

[0018] The combination of the selected solvent 2, dehydrating agent and catalyst 2 of the application synergistically promotes the condensation grafting reaction of the hyperbranched polyester containing Diels-Alder bond and the carboxyl group on the surface of the oxidized carbon fiber; the mass ratio of the three is limited to accurately control the reaction rate, avoid side reactions caused by excessive dehydrating agent or incomplete reaction caused by insufficient catalyst; the selection of raw material types takes into account solubility, reactivity and stability to ensure that the mixed solution system is stable, the grafting reaction is controllable and the firmness of the grafting product is improved.

[0019] Further, the specific operation steps of the third heating reaction include: reacting at 20-50℃ for 24-36h.

[0020] The reaction temperature is mild, which avoids the destruction of the formed Diels-Alder bond structure at high temperature and ensures the smooth progress of the grafting reaction. The reaction time length can ensure the sufficient grafting of the hyperbranched polyester containing Diels-Alder bond and the oxidized carbon fiber, improve the grafting rate, and form a uniform functional layer on the surface of the carbon fiber. The reaction conditions do not require high pressure or special equipment, which reduces the production energy consumption and cost and meets the needs of industrial production.

[0021] Further, the mass ratio of the bismaleimide resin and the diallyl bisphenol A is 1:1.

[0022] The mass ratio optimizes the compatibility of the bismaleimide resin and the diallyl bisphenol A, forms a uniform matrix network structure, and stabilizes the mechanical properties.

[0023] The specific operation steps of the curing treatment include: pre-curing at 150-210℃ for 1.5-4h, and then curing at 230-250℃ for 1.5-6h.

[0024] The two-step process of pre-curing + curing defined in the application can gradually complete the crosslinking of the resin, avoid interface cracking caused by excessive internal stress during the curing process, adapt the curing conditions to the molding needs of the composite material, ensure the close combination of the hyperbranched polyester containing Diels-Alder bond grafted carbon fiber and the matrix, and strengthen the interface stress transfer efficiency; the matrix network after curing has both rigidity and certain flexibility, which provides environmental support for the self-repairing reaction of the double dynamic network.

[0025] The second object of the present application is to provide a carbon fiber / bismaleimide composite material prepared by the above preparation method.

[0026] The material prepared by the present application has efficient and multiple interface self-repairing performance, solves the pain point of easy failure of the interface of traditional composite materials, and has the synergistic effect of the double dynamic network and chemical crosslinking at the interface, and has self-repairing ability and excellent mechanical properties (light weight, high strength and high modulus), thermal stability; the material structure is uniform and the performance is reliable, which meets the long-term service requirement, and meets the strict requirements of aerospace, high-end equipment and other fields on material reliability and durability.

[0027] The third object of the present application is to provide an interface repair method of a carbon fiber / bismaleimide composite material, comprising the following steps: heating the damaged carbon fiber / bismaleimide composite material at 110-130 DEG C for 1-3 hours, and then heating at 60-70 DEG C for 1-3 hours.

[0028] The repair condition of the present application is mild, without extreme temperature or complex external stimulation, and the operation is simple and the energy consumption is low; the two-step heating strategy is scientific: the high-temperature stage triggers the reverse Diels-Alder reaction to dissociate the old bond, and the medium-temperature stage promotes the Diels-Alder bond recombination and hydrogen bond repair to realize efficient healing of micro-cracks; the repair speed is fast and the cycle is short, which can quickly recover the interface performance of the material and reduce the maintenance cost and downtime loss of the engineering structure; the repair process does not damage the material structure, which is suitable for multiple repair scenes and further prolongs the service life of the material.

[0029] The fourth object of the present application is to provide an application of a carbon fiber / bismaleimide composite material in the field of aerospace or high-end equipment.

[0030] The present application precisely matches the core requirements of lightweight, high strength, long-term reliability and easy maintenance of the field of aerospace and high-end equipment, solves the safety hidden trouble problem caused by the interface failure of composite materials in this field; the self-repairing performance of the material can reduce the failure probability under extreme working conditions (such as impact, cyclic load and complex environment), and improve the service safety and durability of the equipment; the application boundary of the self-repairing composite material is expanded, which provides key material support for high-end manufacturing industry and promotes the technical upgrading of related industries.

[0031] Compared with the prior art, the present application has the following advantages and technical effects: 1) The present application constructs a double dynamic network structure based on hydrogen bond and Diels-Alder bond at the interface of carbon fiber and bismaleimide resin matrix by chemical grafting method, uses the characteristics of easy breaking and recombination of hydrogen bond to repair Diels-Alder bond, and gives the composite material efficient interface self-repairing performance, and the initial interface repair efficiency is as high as 96.4%.

[0032] 2) The present application can be repaired multiple times, and the repair efficiency after multiple repairs is still as high as 90.3%.

[0033] 3) The repair method provided by the present application requires a lower repair temperature, has mild repair conditions, fast repair speed, and lower repair cost.

[0034] 4) The hyperbranched polyester containing a Diels-Alder bond contains hydroxyl groups and imide groups, which can form stronger interfacial action with the matrix material through hydrogen bonding and chemical crosslinking, thereby improving the interfacial strength of the composite material. BRIEF DESCRIPTION OF DRAWINGS

[0035] The accompanying drawings, which form a part of the present application, are used to provide further understanding of the present application, and the illustrative embodiments of the present application and their description serve to explain the present application. The accompanying drawings should not be considered as an improper limitation of the present application. In the drawings: Figure 1 The infrared spectra of unmodified carbon fiber (comparative example 1) and Diels-Alder bond-containing hyperbranched polyester grafted carbon fiber (example 1); Figure 2 The thermogravimetric test graph of unmodified carbon fiber (comparative example 1) and Diels-Alder bond-containing hyperbranched polyester grafted carbon fiber (example 1); Figure 3 The interface self-repair efficiency graph of the material prepared in example 1 and comparative example 1; Figure 4 The interface self-repair efficiency graph of the material prepared in example 1 after five times of interface self-repair. DETAILED DESCRIPTION

[0036] Now, various exemplary embodiments of the present application will be described in detail, which should not be considered as a limitation of the present application, but should be understood as a more detailed description of certain aspects, characteristics and embodiments of the present application.

[0037] It should be understood that the terms described in the present application are only for describing the specific embodiments, and are not intended to limit the present application. In addition, for the numerical range in the present application, it should be understood that each intermediate value between the upper limit and the lower limit of the range is also specifically disclosed. Each smaller range between any stated value or intermediate value within the stated range and any other stated value or intermediate value within the stated range is also included in the present application. The upper limit and the lower limit of these smaller ranges can be independently included or excluded from the range.

[0038] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0039] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0040] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0041] This invention provides a method for preparing a high-efficiency self-healing carbon fiber bismaleimide composite material based on a dual dynamic network structure, comprising the following steps: S1. Surface oxidation treatment of carbon fiber: Immerse carbon fiber in concentrated nitric acid and heat it to 60-100°C (exemplary, in the preferred embodiment of the present invention below, the heating temperature is 80°C or 100°C), maintain this temperature for surface oxidation treatment for 4-10 hours (exemplary, in the preferred embodiment of the present invention below, the heating time is 4 hours or 6 hours), and after the reaction is completed, post-treatment is performed to obtain oxidized carbon fiber with reactive carboxyl groups on the surface. S2. Preparation of hyperbranched polyesters containing dienes: Select hyperbranched polyesters (selected from Boltorn H20, Boltorn H30 or Boltorn H20, Boltorn H30, or Boltorn H30) H40), preheat it to 80-120°C, and then add carboxyl-containing diene (selected from furanoic acid, 2-furanoacetic acid or 3-(2-furan)propionic acid) and catalyst 1 (selected from p-toluenesulfonic acid or toluenesulfonic acid) in sequence according to a mass ratio of 100:(30-50):(1-2). Under nitrogen atmosphere protection, heat the reaction system to 120-140°C (exemplary, in the following preferred embodiments of the present invention, the heating temperature is 120°C or 140°C) and react for 2-4 hours (exemplary, in the following preferred embodiments of the present invention, the heating time is 2 hours or 3 hours). After the reaction is completed, wash and dry the product to obtain hyperbranched polyester containing diene. S3. Preparation of Diels-Alder bond-containing hyperbranched polyester: The diene-containing hyperbranched polyester obtained in step S2 is added to solvent 1 (selected from dioxane or 1-methyl-2-pyrrolidone), stirred until fully dissolved, and then a bismaleimide compound (selected from 1,2-...) is added according to a mass ratio of diene-containing hyperbranched polyester to bismaleimide compound of 1:(0.4-1) (exemplarily, in the following preferred embodiments of the present invention, the mass ratio of diene-containing hyperbranched polyester to bismaleimide compound is 1:0.5, 1:0.6 or 1:0.8). The reaction system, consisting of 1,4-dibismaleimide ethane, 1,6-dibismaleimide hexane, or N,N'-(4,4-methylenediphenyl)bismaleimide, is placed in a nitrogen atmosphere at 50-70°C (exemplarily, in the preferred embodiments of the present invention below, the heating temperature is 60°C or 65°C) for 12-24 hours (exemplarily, in the preferred embodiments of the present invention below, the heating time is 16 hours or 24 hours); after the reaction, the mixture is washed and dried to obtain a hyperbranched polyester containing Diels-Alder bonds. S4. Preparation of hyperbranched polyester-grafted carbon fibers containing Diels-Alder bonds: Preparation of the mixed solution: The solvent 2 (selected from N,N'-dimethylformamide, N,N'-dimethylacetamide or 1,3-dimethyl-2-imidazolinone), the dehydrating agent (selected from N,N'-diisopropylcarbodiimide, N,N'-dicyclohexylcarbodiimide or N,N'-di-p-tolylcarbodiimide) and the catalyst 2 (selected from 4-dimethylaminopyridine or triethylamine) are mixed evenly according to a mass ratio of 100:(4-10):(2-6) (exemplary, in the following preferred embodiments of the present invention, the mass ratio of solvent 2, dehydrating agent and catalyst 2 is 100:6:3, 100:7:3 or 100:8:4) to obtain a mixed solution; The hyperbranched polyester containing Diels-Alder bonds obtained in step S3 is pre-soaked in the mixed solution, and then the oxidized carbon fiber obtained in step S1 is added. The reaction system is placed at 20-50°C (exemplarily, in the preferred embodiments of the present invention below, the heating temperature is 25°C, 35°C or 40°C) and reacted for 24-36 h (exemplarily, in the preferred embodiments of the present invention below, the heating time is 16 h or 24 h). After the reaction is completed, the product is dried to obtain hyperbranched polyester grafted carbon fiber containing Diels-Alder bonds. S5. Preparation of carbon fiber / bismaleimide composite material: Bismaleimide resin and diallyl bisphenol A are mixed uniformly in a mass ratio of 1:1 to obtain a bismaleimide resin mixed solution. The hyperbranched polyester grafted carbon fibers containing Diels-Alder bonds obtained in step S4 are added to this mixed solution. After mixing, the system is pre-cured at 150-210℃ (exemplarily, in the preferred embodiments of the present invention, the heating temperature is 180℃, 200℃, or 210℃) for 1.5-4 hours (exemplarily, in the preferred embodiments of the present invention, the heating time is 1.5 hours, 2 hours, or 4 hours). After pre-curing, the system is then heated to 230-250℃ (exemplarily, in the preferred embodiments of the present invention, the heating temperature is 240℃ or 250℃) for 1.5-6 hours (exemplarily, in the preferred embodiments of the present invention, the heating time is 1.5 hours, 2 hours, or 4 hours). After curing, the carbon fiber / bismaleimide composite material is obtained.

[0042] When the interface of the composite material is damaged, the following repair operation is performed: First, the damaged carbon fiber / bismaleimide composite material is heated at 110-130℃ (exemplary, in the preferred embodiments of the present invention below, the heating temperature is 110℃, 120℃ or 130℃) for 1-3 hours (exemplary, in the preferred embodiments of the present invention below, the heating time is 1 hour, 2 hours or 3 hours), then the temperature is adjusted to 60-70℃ (exemplary, in the preferred embodiments of the present invention below, the heating temperature is 60℃, 65℃ or 70℃), and heating is continued for 1-3 hours (exemplary, in the preferred embodiments of the present invention below, the heating time is 1 hour, 2 hours or 3 hours), and the interface repair is completed.

[0043] The carbon fiber / bismaleimide composite material prepared by this invention can be applied in the fields of aerospace or high-end equipment.

[0044] Unless otherwise specified, "room temperature" in this invention refers to 25±2℃.

[0045] All raw materials used in this invention were purchased from the market.

[0046] The technical solution of the present invention will be further illustrated by the following embodiments.

[0047] Example 1 A method for preparing a high-efficiency self-healing carbon fiber bismaleimide composite material based on a dual dynamic network structure, comprising the following steps: S1. Immerse the carbon fiber in concentrated nitric acid (concentration of 16 mol / L, the same below), heat it to 80°C, and maintain the temperature for surface oxidation treatment for 6 hours to obtain oxidized carbon fiber with reactive carboxyl groups on the surface. S2. The hyperbranched polyester Boltorn H2O was preheated to 100°C. Then, carboxyl-containing diene (2-furanoacetic acid) and catalyst 1 (p-toluenesulfonic acid) were added sequentially in a mass ratio of 100:45:1. Under nitrogen atmosphere protection, the reaction system was heated to 140°C and reacted for 2 hours. After the reaction was completed, the product was washed and dried to obtain the hyperbranched polyester containing diene. S3. The diene-containing hyperbranched polyester obtained in step S2 is added to solvent 1 (dioxane) (the ratio of diene-containing hyperbranched polyester to solvent 1 is 1g:20mL), and stirred until fully dissolved. Then, according to the mass ratio of diene-containing hyperbranched polyester to bismaleimide compound (N,N'-(4,4-methylenediphenyl)bismaleimide) of 1:0.6, bismaleimide compound is added. Under nitrogen atmosphere protection, the reaction system is placed in an environment of 65℃ and reacted for 24h. After the reaction is completed, it is washed and dried to obtain hyperbranched polyester containing Diels-Alder bonds. S4. Solvent 2 (N,N'-dimethylformamide), dehydrating agent (N,N'-diisopropylcarbodiimide) and catalyst 2 (4-dimethylaminopyridine) are mixed evenly in a mass ratio of 100:6:3 to obtain a mixed solution. The hyperbranched polyester containing Diels-Alder bonds obtained in step S3 was pre-soaked in the mixed solution, and then the carbon oxide obtained in step S1 was added. The reaction system was placed at 25°C and reacted for 24 hours. After the reaction was completed, the product was dried to obtain carbon fibers grafted with hyperbranched polyester containing Diels-Alder bonds. S5. Mix bismaleimide resin and diallyl bisphenol A evenly in a mass ratio of 1:1 to obtain a bismaleimide resin mixed solution. Add the hyperbranched polyester grafted carbon fiber containing Diels-Alder bonds obtained in step S4 to the mixed solution, wherein the mass ratio of the hyperbranched polyester grafted carbon fiber containing Diels-Alder bonds to the mixed solution is 10:8. After mixing, first place the system at 200℃ for pre-curing for 2 hours. After pre-curing, raise the temperature of the system to 240℃ for curing for 2 hours. After curing, the carbon fiber / bismaleimide composite material is obtained.

[0048] After the interface of the carbon fiber / bismaleimide composite material prepared in this embodiment is damaged, the repair operation steps are as follows: First, the damaged carbon fiber / bismaleimide composite material is heated at 120°C for 2 hours, and then the temperature is adjusted to 65°C and heated for another 2 hours to complete the interface repair.

[0049] Example 2 A method for preparing a high-efficiency self-healing carbon fiber bismaleimide composite material based on a dual dynamic network structure, comprising the following steps: S1. Immerse the carbon fiber in concentrated nitric acid, heat it to 80°C, and maintain this temperature for surface oxidation treatment for 6 hours to obtain oxidized carbon fiber with reactive carboxyl groups on the surface. S2. The hyperbranched polyester Boltorn H40 was preheated to 110°C. Then, carboxyl-containing diene (furanic acid) and catalyst 1 (toluenesulfonic acid) were added sequentially in a mass ratio of 100:35:1. Under nitrogen atmosphere protection, the reaction system was heated to 120°C and reacted for 3 hours. After the reaction was completed, the product was washed and dried to obtain the hyperbranched polyester containing diene. S3. Add the diene-containing hyperbranched polyester obtained in step S2 to solvent 1 (dioxane) (the ratio of diene-containing hyperbranched polyester to solvent 1 is 1g:20mL), stir to dissolve completely, and then add bismaleimide compound according to the mass ratio of diene-containing hyperbranched polyester to bismaleimide compound (1,4-dibismaleimide butane) 1:0.5. Under nitrogen atmosphere protection, place the reaction system in an environment of 65℃ and react for 24h. After the reaction is completed, wash and dry to obtain hyperbranched polyester containing Diels-Alder bonds. S4. Solvent 2 (N,N'-dimethylformamide), dehydrating agent (N,N'-dicyclohexylcarbodiimide) and catalyst 2 (triethylamine) are mixed evenly in a mass ratio of 100:8:4 to obtain a mixed solution. The hyperbranched polyester containing Diels-Alder bonds obtained in step S3 was pre-soaked in the mixed solution, and then the carbon oxide obtained in step S1 was added. The reaction system was placed at 35°C and reacted for 16 hours. After the reaction was completed, the product was dried to obtain carbon fibers grafted with hyperbranched polyester containing Diels-Alder bonds. S5. Mix bismaleimide resin and diallyl bisphenol A evenly in a mass ratio of 1:1 to obtain a bismaleimide resin mixed solution. Add the hyperbranched polyester grafted carbon fiber containing Diels-Alder bonds obtained in step S4 to the mixed solution, wherein the mass ratio of the hyperbranched polyester grafted carbon fiber containing Diels-Alder bonds to the mixed solution is 10:8. After mixing, pre-cur the system at 210°C for 1.5 h. After pre-curing, heat the system to 250°C for 1.5 h. After curing, the carbon fiber / bismaleimide composite material is obtained.

[0050] After the interface of the carbon fiber / bismaleimide composite material prepared in this embodiment is damaged, the repair operation steps are as follows: First, the damaged carbon fiber / bismaleimide composite material is heated at 110°C for 3 hours, and then the temperature is adjusted to 60°C and heated for another 3 hours to complete the interface repair.

[0051] Example 3 A method for preparing a high-efficiency self-healing carbon fiber bismaleimide composite material based on a dual dynamic network structure, comprising the following steps: S1. Immerse the carbon fiber in concentrated nitric acid, heat it to 100°C, and maintain this temperature for surface oxidation treatment for 4 hours to obtain oxidized carbon fiber with reactive carboxyl groups on the surface. S2. The hyperbranched polyester Boltorn H30 was preheated to 120°C, and then carboxyl-containing diene (3-(2-furan)propionic acid) and catalyst 1 (p-toluenesulfonic acid) were added sequentially in a mass ratio of 100:50:2. Under nitrogen atmosphere protection, the reaction system was heated to 140°C and reacted for 2 hours. After the reaction was completed, the product was washed and dried to obtain the hyperbranched polyester containing diene. S3. The diene-containing hyperbranched polyester obtained in step S2 is added to solvent 1 (1-methyl-2-pyrrolidone) (the ratio of diene-containing hyperbranched polyester to solvent 1 is 1 g: 20 mL), and stirred until fully dissolved. Then, according to the mass ratio of diene-containing hyperbranched polyester to bismaleimide compound (1,2-dibismaleimide ethane) of 1:0.8, bismaleimide compound is added. Under nitrogen atmosphere protection, the reaction system is placed in an environment of 60°C and reacted for 16 h. After the reaction is completed, the product is washed and dried to obtain hyperbranched polyester containing Diels-Alder bonds. S4. Solvent 2 (N,N'-dimethylacetamide), dehydrating agent (N,N'-di-p-tolylcarbodiimide) and catalyst 2 (4-dimethylaminopyridine) are mixed evenly in a mass ratio of 100:7:3 to obtain a mixed solution; The hyperbranched polyester containing Diels-Alder bonds obtained in step S3 was pre-soaked in the mixed solution, and then the carbon oxide obtained in step S1 was added. The reaction system was placed at 40°C and reacted for 24 hours. After the reaction was completed, the product was dried to obtain carbon fibers grafted with hyperbranched polyester containing Diels-Alder bonds. S5. Mix bismaleimide resin and diallyl bisphenol A evenly in a mass ratio of 1:1 to obtain a bismaleimide resin mixed solution. Add the hyperbranched polyester grafted carbon fiber containing Diels-Alder bonds obtained in step S4 to the mixed solution, wherein the mass ratio of the hyperbranched polyester grafted carbon fiber containing Diels-Alder bonds to the mixed solution is 10:8. After mixing, first place the system at 180°C for pre-curing for 4 hours. After pre-curing, raise the temperature of the system to 250°C for curing for 4 hours. After curing, the carbon fiber / bismaleimide composite material is obtained.

[0052] After the interface of the carbon fiber / bismaleimide composite material prepared in this embodiment is damaged, the repair operation steps are as follows: First, the damaged carbon fiber / bismaleimide composite material is heated at 130°C for 1 hour, and then the temperature is adjusted to 70°C and heated for another hour to complete the interface repair.

[0053] Comparative Example 1 Bismaleimide resin and diallyl bisphenol A were mixed evenly in a mass ratio of 1:1 to obtain a bismaleimide resin mixed solution. Unmodified carbon fibers were added to the mixed solution, wherein the mass ratio of unmodified carbon fibers to the mixed solution was 10:8. After thorough mixing, the system was first pre-cured at 200°C for 2 hours. After pre-curing, the system was then heated to 240°C for 2 hours. After curing, the material was obtained.

[0054] After the interface of the material prepared in this comparative example is damaged, the repair operation steps are as follows: First, the damaged material is heated at 120℃ for 2 hours, then the temperature is adjusted to 65℃ and heated for another 2 hours to complete the interface repair.

[0055] Figure 1 The infrared spectra of unmodified carbon fiber (Comparative Example 1) and hyperbranched polyester-grafted carbon fiber containing Diels-Alder bonds (Example 1) are shown below. Figure 1 As can be seen from the infrared spectrum of the hyperbranched polyester grafted carbon fibers containing Diels-Alder bonds prepared in Example 1, characteristic absorption peaks related to Diels-Alder bonds, carbon-hydrogen bonds (CH), and hydroxyl groups (-OH) appear, indicating that the hyperbranched polyester containing Diels-Alder bonds was successfully grafted onto the surface of the oxidized carbon fibers. The infrared spectrum of the unmodified carbon fibers prepared in Comparative Example 1 does not show the aforementioned characteristic peaks, verifying the effectiveness of the chemical modification process in Example 1 and demonstrating that the construction of the dual dynamic network structure has a chemical basis.

[0056] Figure 2 The thermogravimetric analysis (TGA) graphs are shown for unmodified carbon fiber (Comparative Example 1) and hyperbranched polyester-grafted carbon fiber containing Diels-Alder bonds (Example 1).Figure 2 As can be seen, the weight loss rate of Comparative Example 1 is relatively small in the range of 35-800℃, while the weight loss rate of the hyperbranched polyester grafted carbon fiber containing Diels-Alder bonds reaches 17.9% in the same temperature range. This is mainly due to the thermal decomposition of the hyperbranched polyester on the carbon fiber surface. The thermogravimetric test results prove that the hyperbranched polyester containing Diels-Alder bonds was successfully grafted onto the carbon fiber surface.

[0057] Figure 3 The diagram shows the interface self-healing efficiency of the materials prepared in Example 1 and Comparative Example 1. Figure 3 As can be seen, the initial interface self-healing efficiency of Example 1 is as high as 96.4%, while Comparative Example 1 has almost no self-healing ability (repair efficiency less than 20%). The difference stems from the dual dynamic interaction of hydrogen bonds and Diels-Alder bonds in Example 1. Hydrogen bonds are easily broken and recombine, rapidly filling microcrack gaps and assisting the reversible reaction of Diels-Alder bonds (high-temperature dissociation + medium-temperature recombination). This solves the problem of insufficient functional group diffusion in the traditional single Diels-Alder system, achieving efficient repair. Comparative Example 1, lacking dynamic chemical bond support, cannot achieve molecular chain recombination on both sides of the crack, verifying that the dual dynamic network structure is the core key to improving self-healing performance.

[0058] Figure 4 The diagram shows the efficiency of the interface self-healing of the material prepared in Example 1 after five cycles. Figure 4 As can be seen, after five interface repairs, Example 1 still maintained a repair efficiency of 90.3%, with no significant attenuation. This indicates that the reversible reaction between hydrogen bonds and Diels-Alder bonds has good cyclicity, and the spatial structure of the hyperbranched polyester provides a stable molecular environment for the repeated breaking and recombination of dynamic bonds, avoiding functional group loss or interface structure damage after multiple repairs. This result proves that the self-healing performance of the composite material is long-lasting, meeting the repair needs of engineering structures after multiple damages during long-term service, and overcoming the limitation of traditional self-healing systems failing after a single repair.

[0059] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for preparing a high-efficiency interface self-healing carbon fiber bismaleimide composite material based on a dual dynamic network structure, characterized in that, Includes the following steps: Carbon fibers are subjected to surface oxidation treatment to obtain oxidized carbon fibers with reactive carboxyl groups on the surface; After preheating the hyperbranched polyester, carboxyl-containing diene and catalyst 1 are added to carry out the first heating reaction. After washing and drying, the hyperbranched polyester containing diene is obtained. The hyperbranched polyester containing dienes was added to solvent 1, and bismaleimide compounds were added. A second heating reaction was carried out, and after washing and drying, hyperbranched polyester containing Diels-Alder bonds was obtained. The hyperbranched polyester containing Diels-Alder bonds was immersed in a mixed solution, the oxidized carbon fiber was added, a third heating reaction was carried out, and after drying, the hyperbranched polyester grafted carbon fiber containing Diels-Alder bonds was obtained. By mixing bismaleimide resin and diallyl bisphenol A, adding the hyperbranched polyester grafted carbon fibers containing Diels-Alder bonds, and then curing, carbon fiber / bismaleimide composite material is obtained.

2. The preparation method according to claim 1, characterized in that, The specific steps of the surface oxidation treatment include: immersing the carbon fiber in concentrated nitric acid and oxidizing it at 60-100℃ for 4-10 hours.

3. The preparation method according to claim 1, characterized in that, The hyperbranched polyester is selected from Boltorn H20, Boltorn H30, or Boltorn H40; and / or, The carboxyl-containing diene is selected from furanyl carboxylic acid, 2-furanacetic acid, or 3-(2-furan)propionic acid; and / or, The catalyst 1 is selected from p-toluenesulfonic acid or toluenesulfonic acid; and / or, The mass ratio of the hyperbranched polyester, the carboxyl-containing diene, and catalyst 1 is 100:(30-50):(1-2); and / or, The specific steps of the first heating reaction include: reacting at 120-140℃ for 2-4 hours under a nitrogen atmosphere.

4. The preparation method according to claim 1, characterized in that, Solvent 1 is selected from dioxane or 1-methyl-2-pyrrolidone; and / or, The bismaleimide compounds are selected from 1,2-dibismaleimide ethane, 1,4-dibismaleimide butane, 1,6-dibismaleimide hexane, or N,N'-(4,4-methylenediphenyl)bismaleimide; and / or The mass ratio of the diene-containing hyperbranched polyester to the bismaleimide compound is 1:(0.4-1); and / or, The specific steps of the second heating reaction include: reacting at 50-70°C for 12-24 hours under a nitrogen atmosphere.

5. The preparation method according to claim 1, characterized in that, The mixed solution is obtained by mixing solvent 2, dehydrating agent and catalyst 2 in a mass ratio of 100:(4-10):(2-6); The solvent 2 is selected from N,N'-dimethylformamide, N,N'-dimethylacetamide or 1,3-dimethyl-2-imidazolinone; The dehydrating agent is selected from N,N'-diisopropylcarbodiimide, N,N'-dicyclohexylcarbodiimide or N,N'-di-p-tolylcarbodiimide; The catalyst 2 is selected from 4-dimethylaminopyridine or triethylamine.

6. The preparation method according to claim 1, characterized in that, The specific steps of the third heating reaction include: reacting at 20-50℃ for 24-36 hours.

7. The preparation method according to claim 1, characterized in that, The mass ratio of the bismaleimide resin to diallylbisphenol A is 1:1; The specific steps of the curing process include: pre-curing at 150-210℃ for 1.5-4 hours, and then curing at 230-250℃ for 1.5-6 hours.

8. A carbon fiber / bismaleimide composite material, characterized in that, It is prepared by the preparation method described in any one of claims 1-7.

9. A method for interface repair of carbon fiber / bismaleimide composite material as described in claim 8, characterized in that, Includes the following steps: The damaged carbon fiber / bismaleimide composite material was heated at 110-130℃ for 1-3 hours, and then heated at 60-70℃ for 1-3 hours.

10. The application of the carbon fiber / bismaleimide composite material as described in claim 8 in the aerospace or high-end equipment field.

Images