Special fabric with pulling resistance and preparation method thereof

Abstract

The invention relates to the technical field of special composite materials, in particular to a special fabric with pulling resistance and a preparation method thereof. Comprising a silicon carbide fiber reinforcement, a cyanate ester resin matrix and a multifunctional interface layer located between the silicon carbide fiber reinforcement and the cyanate ester resin matrix, the multifunctional interface layer is combined with the fiber through a silane-metal organic framework hybrid coating, and is connected with the resin matrix through a Diels-Alder dynamic covalent bond. Through innovative'fiber-interface-matrix 'multistage structural design, a self-repairing mechanism of a Diels-Alder bond and a synergistic flame-retardant effect of phosphorus-nitrogen-boron nitride are ingeniously integrated, so that the prepared special cloth has excellent pulling resistance, a high limit oxygen index and damage self-repairing efficiency up to 90% or above; the problems that a traditional composite material interface is prone to damage and single in function are solved.

Description

Technical Field

[0001] This invention relates to the field of special composite materials technology, specifically to a special fabric with tensile strength and its preparation method. Background Technology

[0002] High-performance textiles and composites play a crucial role in cutting-edge fields such as aerospace, military equipment, and special protection. These applications typically require materials with extremely high mechanical strength and excellent tensile strength to withstand complex stresses, while also possessing good flame-retardant properties to ensure safety. Furthermore, the materials are expected to have a certain degree of self-repair capability after damage, thereby extending service life and improving reliability. Traditional specialty fabrics are mostly composed of high-strength fibers (such as carbon fiber and aramid) and thermosetting resins (such as epoxy resin). However, such materials have an inherent bottleneck: the interfacial bonding area between the fiber and the resin matrix is ​​often a weak point in mechanical properties. Under impact or fatigue stress, microcracks easily form and propagate, leading to a sharp decline in the overall performance of the material. Moreover, this internal damage is difficult to detect and repair. In addition, flame-retardant modification of traditional composite materials often comes at the cost of sacrificing mechanical properties and lacks self-repair capabilities for mechanical damage, highlighting the problem of limited functionality.

[0003] To address these challenges, those skilled in the art have undertaken numerous explorations. For example, prior art document 1 (CN109852241A) discloses a heat-resistant, self-healing polysiloxane-epoxy resin composite coating, which endows the coating material with self-healing capabilities by introducing reversible Diels-Alder (DA) chemical bonds based on furan and maleimide into the epoxy resin. Prior art document 2 (CN108440735A) provides a DA-bonded self-healing flame-retardant polyurethane elastomer, which combines a DA-bonded crosslinking network with a phosphazene flame retardant to achieve both self-healing and flame-retardant functions in the elastomer. Both documents demonstrate effective strategies for achieving intrinsic self-healing of polymer materials using dynamic covalent bonds, but their applications are limited to homogeneous polymer coatings or elastomers, failing to address the more critical "interface" repair challenge in fiber-reinforced composite materials. Another prior art document 3 (CN111534902A) relates to a tensile-resistant printed fabric, which improves the tensile strength and comfort of the fabric by blending various fibers such as ice silk fiber and nylon fiber. However, its technical approach remains within the scope of traditional textiles, with a low upper limit for material performance, and does not involve the interface design and flame-retardant modification of self-healing or high-performance composite materials.

[0004] Therefore, developing a novel special composite material that can simultaneously resolve the contradictions between interfacial bonding strength, damage self-healing, and high-efficiency flame retardancy, enabling it to maintain structural integrity and functionality under extreme conditions, has become a pressing technical challenge in this field. The purpose of this invention is to provide a novel "fiber-interface-matrix" synergistic design strategy to prepare tensile-resistant special fabrics with comprehensive performance far exceeding existing technologies. Summary of the Invention

[0005] The purpose of this invention is to overcome the technical bottlenecks commonly found in existing fiber-reinforced composite materials, such as weak interfacial bonding, limited functional properties, and difficulty in self-repair after damage. This invention provides a special fabric with tensile strength and its preparation method. Specifically, this invention aims to solve the interconnected problems of insufficient tensile strength in traditional composite materials due to the interface becoming a stress concentration point and performance bottleneck, the sacrifice of mechanical properties due to the addition of conventional flame retardants, and the inability to achieve self-repair due to the lack of dynamic reversible chemical bonds. Its core objective is to prepare a special composite material that simultaneously possesses excellent tensile strength (achieved through strong interfacial bonding of silicon carbide fibers), superior flame retardant properties with a high limiting oxygen index (achieved through a phosphorus-nitrogen-boron nitride synergistic system), and high-efficiency intrinsic self-repair capability (achieved through dynamic Diels-Alder covalent bonds at the interface). This significantly improves the reliability, safety, and service life of the material under extreme and harsh conditions such as aerospace, military equipment, and special protection, achieving multi-functional integration and performance breakthroughs in a single material.

[0006] A special fabric with tensile strength includes a silicon carbide fiber reinforcement, a cyanate ester resin matrix, and a multifunctional interface layer; the multifunctional interface layer is bonded to the fiber through a silane-metal-organic framework hybrid coating and connected to the resin matrix through dynamic covalent bonds; wherein the volume fraction of the silicon carbide fiber is 45%-65%, the volume fraction of the cyanate ester resin is 25%-45%, and the thickness of the multifunctional interface layer is 50-500 nanometers.

[0007] Preferably, the silane-metal-organic framework hybrid coating is formed by in-situ growth of ZIF-8 particles on the surface of silicon carbide fibers, wherein the silane coupling agent is γ-(2,3-epoxypropoxy)propyltrimethoxysilane, the ZIF-8 particles have a particle size of 50-200 nm and an areal density of 5-20 g / m³. 2 .

[0008] Preferably, the dynamic covalent bond is a Diels-Alder bond, which is formed by a cycloaddition reaction between maleimide groups grafted on the interface layer and furan groups in the resin matrix at 90-120°C.

[0009] Preferably, the cyanate ester resin matrix is ​​coated with boron nitride nanosheets modified with a phosphorus-nitrogen synergistic flame retardant, wherein the modifier is ammonium polyphosphate, the thickness of the boron nitride nanosheets is 1-5 nanometers, the aspect ratio (length to thickness ratio) is 100-500, and the mass fraction in the resin is 3%-8%.

[0010] This invention also discloses a method for preparing a special fabric with tensile strength, comprising the following steps: (a) Surface pretreatment of silicon carbide fibers: Active hydroxyl groups are introduced onto the fiber surface by plasma treatment; (b) Construction of silane-MOF hybrid coating: The pretreated fiber was immersed in a mixed solution containing zinc ions, 2-methylimidazolium and silane coupling agent and reacted at 25-60°C for 2-12 hours to grow ZIF-8 particles in situ on the fiber surface. (c) Preparation of resin matrix: Cyanate ester resin monomers were reacted with furan methanol under the action of a catalyst to synthesize furan group-terminated cyanate ester prepolymer; then, boron nitride nanosheets modified with phosphorus-nitrogen flame retardant were dispersed in the prepolymer; (d) Construction of dynamic covalent bonds at the interface: The fibers treated in step (b) are woven into a fabric and impregnated in the resin system obtained in step (c). The fabric is then cured for 1-3 hours at 100-150℃ and 1-5MPa pressure by hot pressing, so that the maleimide groups on the interface layer react with the furan groups in the resin in a Diels-Alder reaction.

[0011] Preferably, in the mixed solution described in step (b), the zinc ion concentration is 0.1-0.5 mol / L, the 2-methylimidazole concentration is 0.5-2 mol / L, the silane coupling agent volume fraction is 5%-10%, and the solvent is a mixed solvent of methanol and water with a volume ratio of 3:1-5:1.

[0012] Preferably, the synthesis conditions of the furan-terminated cyanate prepolymer in step (c) are as follows: the molar ratio of cyanate monomer to furan-methanol is 1:0.1-0.3, the reaction temperature is 80-120℃, the reaction time is 2-5 hours, the catalyst is triethylamine, and the amount is 0.5%-1.5% of the monomer mass.

[0013] Preferably, the preparation method of the phosphorus-nitrogen flame retardant modified boron nitride nanosheets in step (c) is as follows: disperse boron nitride nanosheets in water, add ammonium polyphosphate, stir and react at 60-90℃ for 4-10 hours, and the mass ratio of ammonium polyphosphate to boron nitride is 1:5-1:10.

[0014] Preferably, the hot-press curing process in step (d) adopts a segmented curing procedure: first, the Diels-Alder reaction is fully carried out by keeping the temperature at 90-120℃ for 0.5-2 hours, and then the temperature is raised to 180-220℃ to complete the final curing of the cyanate ester resin.

[0015] The repair mechanism of the dynamic covalent bond is as follows: when the material is damaged, heat treatment is performed at 120-150℃, and the Diels-Alder bond undergoes reversible breakage, relieving stress concentration; after cooling to below 90℃, the bond reforms, realizing interface self-repair, and the repair efficiency can reach more than 90%.

[0016] Abbreviation for this invention: ZIF-8 stands for zeolite imidazolium ester framework structure material; the Diels-Alder bond is a DA bond; MOF stands for "metal-organic framework".

[0017] Innovation of this invention: 1. A multifunctional interface layer based on a "silane-MOF hybrid coating" was constructed. One of the core innovations of this invention lies in the revolutionary interface engineering design of the silicon carbide fiber surface. Instead of using a traditional single silane coupling agent, we formed an organic-inorganic hybrid coating by in-situ growing zeolite imidazole ester framework structure material (ZIF-8) particles on the fiber surface. In this coating, the silane coupling agent acts as a "molecular bridge," chemically bonded to the active hydroxyl groups on the fiber surface at one end, while the other end is integrated with the ZIF-8 crystal structure. The huge specific surface area and abundant pore structure of ZIF-8 not only greatly increases the contact area between the fiber and the subsequent resin matrix, providing mechanical interlocking force far exceeding that of traditional methods, but its abundant nitrogen atoms can also form strong physical adsorption with the resin. In addition, we pre-introduced silane containing epoxy groups into the ZIF-8 growth system, exposing maleimide active sites on the surface of the hybrid coating that can be further reacted, laying the foundation for the subsequent formation of strong chemical bonds with the resin matrix.

[0018] 2. A "Diels-Alder dynamic covalent bond" is introduced as the intelligent connection and repair unit of the interface. This invention is the first to precisely apply the reversible chemical reaction of Diels-Alder (DA) to the interface connection of fiber-reinforced composite materials. Specifically, maleimide functional groups are pre-programmed into the multifunctional interface layer; while furan functional groups are introduced into the cyanate ester resin matrix through chemical modification. During the hot pressing process of composite material molding, furan and maleimide undergo a DA cycloaddition reaction, forming a strong covalent bond connection at the interface, with a bonding strength far exceeding that of physical adsorption. More importantly, the DA bond is a thermally reversible covalent bond: when the material develops interfacial microcracks due to stress during use, heat treatment at 120-150℃ can be applied to cause the DA bond at the crack to undergo a reverse reaction and break, releasing the stress; subsequently, when the temperature is cooled to below 90℃, the broken furan and maleimide groups can recombine to form a DA bond, thereby achieving "autonomous" repair of interface damage. This mechanism transforms materials from "passive damage" to "active repair," significantly improving their service safety and lifespan.

[0019] 3. Achieving synergistic flame retardancy and enhanced mechanical properties through a multi-element approach of phosphorus-nitrogen-boron nitride. Regarding the resin matrix, this invention creatively disperses ammonium polyphosphate-modified boron nitride nanosheets within a cyanate ester resin. The boron nitride nanosheets themselves possess extremely high thermal stability and mechanical strength, and their layered structure effectively hinders the diffusion of thermal decomposition products during combustion, acting as a physical barrier. Ammonium polyphosphate, as a classic phosphorus-nitrogen flame retardant, can function simultaneously in both the gas and condensation phases during combustion, generating non-combustible gases and promoting char formation. The combination of these two elements produces a synergistic flame retardant effect greater than the sum of its parts ("1+1>2"): boron nitride acts as a "skeleton" supporting the dense char layer catalyzed by ammonium polyphosphate, while ammonium polyphosphate significantly improves the gas-phase dilution and free radical termination efficiency of the entire flame retardant system. Meanwhile, the nanoscale boron nitride flakes are uniformly dispersed in the resin, which can also play a role in pinning and crack deflection. Thus, while giving the material an extremely high limiting oxygen index (LOI>48%), it does not weaken its mechanical properties, but instead enhances and toughens the matrix.

[0020] Beneficial technical effects of the present invention: 1. Superior Tensile Strength and Structural Integrity. The special fabric prepared by this invention exhibits extremely superior tensile strength. This is mainly due to the synergistic effect of three levels: First, silicon carbide fibers themselves possess extremely high tensile strength and modulus, providing the main mechanical load-bearing skeleton as reinforcement; second, the innovative silane-MOF hybrid interface layer, through its huge specific surface area and strong mechanical interlocking, achieves efficient load transfer from the relatively flexible resin matrix to the high-strength fibers, maximizing the reinforcing potential of the fibers; finally, the chemical connections formed at the interface through DA dynamic covalent bonds have bond energies far exceeding those of traditional physical adsorption or hydrogen bonding, resulting in an unprecedented level of interfacial bonding strength. Test results show that the tensile strength of the fabrics in the examples is rated as "good" to "excellent," significantly better than all comparative examples.

[0021] 2. Extremely high flame retardant safety and thermal stability. By combining a phosphorus-nitrogen flame retardant (ammonium polyphosphate) with two-dimensional nanomaterials (boron nitride nanosheets), this invention constructs a highly efficient and stable flame retardant system within a resin matrix. When exposed to fire or high temperatures, the ammonium polyphosphate rapidly decomposes to generate polyphosphoric acid, promoting resin dehydration and carbonization, and releasing non-combustible gases such as ammonia to dilute oxygen. Simultaneously, the boron nitride nanosheets form a continuous, dense, and robust ceramic-like protective layer in the condensed phase, effectively isolating the inward transfer of heat and oxygen, as well as the outward diffusion of combustibles. This dual synergistic effect of the gas phase and condensed phase results in a limiting oxygen index (LOI) of over 48% for the special fabrics of this invention, with the optimal embodiment reaching as high as 60.1%, far exceeding the comparative example (approximately 34-39%), achieving a level of flame retardancy or even non-combustibility, providing a solid safety guarantee for applications in high-temperature or open-flame environments.

[0022] 3. Intelligent self-healing capability and ultra-long service life. One of the most outstanding technical effects of this invention is that it endows special fabrics with intelligent self-healing properties. Due to the introduction of Diels-Alder dynamic covalent bonds at the fiber-resin interface, when microcracks occur within the material due to impact or fatigue, no external repair agent is needed. A simple thermal stimulation process (such as heating to 120-150℃ followed by cooling) is sufficient for the reversible breakage and recombination of the DA bonds at the crack interface, achieving "autonomous" healing of micro-damage. Quantitative tests show that the repair efficiency of the fabric of this invention is as high as 90%, reaching up to 95%. This means that after damage, the material's mechanical properties can recover to more than 90% of their initial state, greatly extending the material's service life, reducing maintenance costs, and improving reliability in critical applications—something traditional composite materials cannot match. Attached Figure Description

[0023] Figure 1 This is a flowchart of the preparation process of the present invention.

[0024] Figure 2 This is a schematic diagram of the multi-layer structure of the special fabric of the present invention. Detailed Implementation

[0025] Before further describing specific embodiments of the present invention, it should be understood that the scope of protection of the present invention is not limited to the specific embodiments described below; it should also be understood that the terminology used in the embodiments of the present invention is for describing specific embodiments and not for limiting the scope of protection of the present invention. Test methods in the following embodiments that do not specify specific conditions are generally performed under conventional conditions or as recommended by the respective manufacturers.

[0026] When numerical ranges are given in the embodiments, it should be understood that, unless otherwise stated in this invention, both endpoints of each numerical range and any value between the two endpoints may be selected. Unless otherwise defined, all technical and scientific terms used in this invention have the same meaning as commonly understood by those skilled in the art. In addition to the specific methods, apparatus, and materials used in the embodiments, based on the knowledge of those skilled in the art and the description of this invention, any prior art methods, apparatus, and materials similar to or identical to those described in the embodiments of this invention may be used to implement this invention.

[0027] Unless otherwise stated, the test methods, detection methods and preparation methods disclosed in this invention all adopt conventional techniques in this technical field.

[0028] Example 1 First, the silicon carbide fiber fabric was subjected to plasma treatment at a power of 300W for 5 minutes to introduce sufficient active hydroxyl groups onto its surface. Next, a silane-MOF hybrid coating was constructed: zinc nitrate hexahydrate (Zn(NO3)2·6H2O) was dissolved in a mixed solvent of methanol and deionized water (volume ratio 3:1) to prepare solution A with a zinc ion concentration of 0.1 mol / L; 2-methylimidazole was dissolved in the same mixed solvent to prepare a solution with a concentration of 0.5 mol / L. B; γ-(2,3-epoxypropoxy)propyltrimethoxysilane (KH560) was added to solution A at a volume fraction of 5% and stirred until homogeneous to obtain a mixed solution; the plasma-treated silicon carbide fiber fabric was immersed in this mixed solution, and then an equal volume of solution B was slowly added. The mixture was allowed to stand in a constant temperature water bath at 25°C for 12 hours. After the reaction, the fabric was rinsed three times with methanol to remove physically adsorbed impurities, and then vacuum dried at 60°C for 6 hours, finally forming a uniform ZIF-8 hybrid coating on the fiber surface. Then, the resin matrix was prepared: 100g of cyanate ester resin monomer was added to a three-necked flask equipped with a stirrer, thermometer, and condenser, and then furan methanol was added at a molar ratio of cyanate ester monomer to furan methanol of 1:0.1. 0.5g (0.5% of the monomer mass) of triethylamine was added as a catalyst, and the mixture was stirred in an oil bath at 80°C for 5 hours to obtain a pale yellow viscous furan-terminated cyanate ester prepolymer. Simultaneously, flame-retardant fillers were prepared: 10g of boron nitride nanosheets were dispersed in 500mL of deionized water and ultrasonically treated for 2 hours. Then, 2g of ammonium polyphosphate (mass ratio of 1:10 to boron nitride) was added, and the mixture was mechanically stirred at 60℃ for 10 hours. After the reaction, the mixture was filtered, washed, and dried to obtain phosphorus-nitrogen flame retardant modified boron nitride nanosheets. 100g of the above prepolymer was taken, and 3g of the modified boron nitride nanosheets were added. The mixture was then sheared and stirred at 60℃ for 1 hour to ensure uniform dispersion, thus obtaining the final resin system. Finally, composite and curing were performed: carbonized materials coated with a hybrid coating were then... The silicon fiber fabric is cut to the required size, laid in a mold, and the above-mentioned resin system is poured in. It is then cured using a hot press at a pressure of 1 MPa. The curing procedure is as follows: the temperature is increased to 100°C at a rate of 2°C / min, and held for 1 hour to allow the Diels-Alder reaction at the interface to proceed fully. Then, the temperature is increased to 180°C at the same rate and held for 2 hours to complete the final three-dimensional cross-linking and curing of the cyanate ester resin. Afterward, the temperature is allowed to cool naturally to below 60°C before demolding to obtain the special fabric. It is calculated that the volume fraction of silicon carbide fiber in the fabric is 45%, and the volume fraction of cyanate ester resin is 45%.

[0029] A schematic diagram of the multilayer structure of the special fabric prepared in Example 1 is shown below. Figure 1 As shown, 201 represents boron nitride nanosheets, 202 represents cyanate ester resin matrix, 203 represents ZIF-8 particles, 204 represents silane-MOF hybrid interface layer, and 205 represents silicon carbide fiber reinforcement.

[0030] Example 2 The plasma pretreatment of silicon carbide fibers was the same as in Example 1; in the construction of the silane-MOF hybrid coating, the zinc ion concentration of solution A was increased to 0.3 mol / L (prepared from zinc nitrate hexahydrate), the 2-methylimidazole concentration of solution B was increased to 1.0 mol / L, the mixed solvent was methanol and deionized water (volume ratio 4:1), and the volume fraction of silane coupling agent KH560 was 7%; after immersing the treated fibers in the mixed solution and adding solution B, the reaction was carried out at 40°C for 6 hours, and the subsequent cleaning and drying steps were the same as in Example 1; in the preparation of the resin matrix, the molar ratio of cyanate monomer to furanol was adjusted to 1:0.2, the amount of triethylamine catalyst was 1.0% of the monomer mass, the reaction temperature was increased to 100°C, and the reaction time was shortened to 3 hours; in the preparation of the flame retardant filler, the mass ratio of ammonium polyphosphate to boron nitride nanosheets was adjusted to 1:7, the reaction temperature was increased to 75°C, and the reaction time was shortened to 7 hours. The modified boron nitride nanosheets were dispersed in furan-modified prepolymer at a mass fraction of 5%. During the composite and curing stage, the hot pressing pressure was increased to 3 MPa, and the curing procedure was adjusted as follows: first, the temperature was raised to 110℃ and held for 1.5 hours to optimize the Diels-Alder reaction kinetics, and then the temperature was raised to 200℃ and held for 2 hours to complete the final curing of the resin. The special fabric obtained contained 55% silicon carbide fiber and 35% cyanate ester resin by volume.

[0031] Example 3 The plasma pretreatment of silicon carbide fibers was the same as in Example 1; the silane-MOF hybrid coating was constructed using more aggressive reaction conditions: the zinc ion concentration in solution A was further increased to 0.5 mol / L, the 2-methylimidazole concentration in solution B was increased to 2.0 mol / L, the mixed solvent was methanol and deionized water (volume ratio 5:1), and the volume fraction of silane coupling agent KH560 was 10%. The reaction was carried out at 60℃ for 2 hours to obtain a ZIF-8 coating with higher density and greater thickness. In the preparation of the resin matrix, the molar ratio of cyanate monomer to furanol was set to the upper limit of 1:0.3 to introduce the highest density of furan functional groups into the resin. The amount of triethylamine catalyst was 1.5% of the monomer mass, the reaction temperature was set at 120℃, and the reaction time was 2 hours. In the preparation of the flame retardant filler, the mass ratio of ammonium polyphosphate to boron nitride nanosheets was 1:5, and the reaction was carried out at 90℃ for 4 hours to achieve more complete modification. This filler was dispersed in the prepolymer at a mass fraction of 8%. In the composite and curing stage, the hot pressing pressure was 5MPa to minimize porosity. The curing procedure was as follows: first, the temperature was kept at 120℃ for 2 hours to ensure complete DA reaction at the interface, and then the temperature was increased to 220℃ (the high-efficiency curing temperature of cyanate resin) and kept at 220℃ for 2 hours. The final special fabric had the highest fiber content, with a silicon carbide fiber volume fraction of 65% and a cyanate resin volume fraction of 25%.

[0032] Comparative Example 1 Comparative Example 1 aims to investigate the key role of the silane-MOF hybrid coating. Its preparation process is basically the same as that of Example 2, except for step (b) in the construction of the silane-MOF hybrid coating. This comparative example does not perform in-situ growth of ZIF-8 particles, but only performs traditional silanization treatment: the plasma-pretreated silicon carbide fiber fabric is immersed in an ethanol solution of 7% KH560 silane coupling agent (ethanol / water = 9 / 1, v / v), soaked at 40°C for 6 hours, rinsed three times with ethanol, and vacuum dried at 60°C for 6 hours. In this process, although the silane coupling agent can hydrolyze and condense with the hydroxyl groups on the fiber surface to form covalent bonds, it does not introduce a porous ZIF-8 particle structure. Therefore, the interface layer formed is a traditional single silane coating with a small specific surface area, which does not have the huge specific surface area, strong mechanical interlocking and richer surface reaction sites brought by the MOF hybrid coating.

[0033] Comparative Example 2 Comparative Example 2 aims to verify the importance of interfacial Diels-Alder dynamic covalent bonds. Its preparation process differs from Example 2 mainly in step (c) resin matrix preparation and step (d) interfacial reaction mechanism. In this comparative example, furanol was not used to modify the cyanate ester resin during resin matrix preparation; instead, 100g of unmodified cyanate ester resin monomer was directly used, along with 5% by mass of ammonium polyphosphate-modified boron nitride nanosheets, and stirred until homogeneous. During the composite and curing process in step (d), since the resin matrix does not contain... The furan functional group means that even if maleimide groups are present on the interface layer, Diels-Alder cycloaddition reaction cannot occur. The hot-press curing process only achieves cross-linking curing of the cyanate ester resin itself (holding at 110℃ for 1.5 hours, then at 200℃ for 2 hours) and physical wetting and adhesion of the fiber. There is a lack of strong chemical bond connection between the fiber and the resin matrix through DA bonds. The interface bonding depends on physical adsorption and covalent bonds generated by a small amount of silane coupling agent, but it lacks the high strength and reversibility brought by the dynamic covalent bonds of DA.

[0034] Comparative Example 3 Comparative Example 3 was used to investigate the contribution of the phosphorus-nitrogen-boron nitride synergistic flame retardant system. Its preparation process was basically the same as that of Example 2, but the addition and modification process of flame retardant filler in step (c) was deliberately omitted. In the preparation of the resin matrix in this comparative example, only furan-terminated cyanate prepolymers were synthesized (formulation same as in Example 2), but no ammonium polyphosphate-modified boron nitride nanosheets or other flame retardants were added. Therefore, the final resin matrix was a pure, unmodified furan-functionalized cyanate resin. The subsequent composite and curing steps (hot pressing pressure of 3 MPa, curing procedure of 110°C followed by 200°C) were exactly the same as in Example 2. The fabric prepared in this way had the same fiber and interfacial DA bond structure as in Example 2, but the resin matrix itself did not have the gas-phase flame retardant, char-forming catalysis and physical barrier effects brought by phosphorus-nitrogen elements and boron nitride nanosheets. This was used to compare and evaluate the key impact of this flame retardant system on the fire safety performance of materials such as limiting oxygen index (LOI).

[0035] Comparative Example 4 Comparative Example 4 was prepared according to the technical solution disclosed in Example 1 of Reference Document 1 (CN109852241A) cited in the background art of this invention, to compare the application effects of different material systems and self-healing mechanisms. First, furan-functionalized hyperbranched polysiloxane was prepared according to the method of Reference Document 1: glycidyl ether silane and 2-furan methylamine were added to anhydrous toluene in equimolar amounts, reacted at 50°C for 12 hours under nitrogen protection, and the toluene was removed by rotary evaporation to obtain furan-functionalized trimethoxysilane; it was added to a 95% (v / v) ethanol solution, and 0.2% glacial acetic acid catalyst was added, reacted at 50°C for 6 hours, and the ethanol and water were removed by rotary evaporation to obtain furan-functionalized hyperbranched polysiloxane; Second, epoxy resin containing thermally reversible dynamic chemical bonds was prepared: in chloroform, a molar ratio of 1:1 was added Furan-functionalized epoxy resin and N,N'-4,4'-diphenylmethane bismaleimide were reacted at 50°C for 96 hours to remove chloroform, resulting in an epoxy resin containing DA bonds. Finally, a coating was prepared: the above-mentioned furan-functionalized hyperbranched polysiloxane, DA-bonded epoxy resin, commercial epoxy resin, and bismaleimide were mixed in chloroform at a mass ratio of 1:0.3:0.2:0.5, and 5% 2-phenylimidazolium curing agent was added. The mixture was then coated onto ordinary plain-weave silicon carbide fiber cloth. After solvent evaporation, it was cured at 40°C for 1 hour, followed by curing at 70°C for 24 hours to form a polymer-coated fabric with self-healing properties. The self-healing mechanism of this comparative example is confined to the interior of the coating, and the matrix is ​​epoxy resin. Its heat resistance and interface compatibility with high-performance silicon carbide fibers differ from the cyanate ester system of this invention.

[0036] Comparative Example 5 Comparative Example 5 was prepared according to the conventional textile fabric formulation and process disclosed in Example 2 of Reference Document 3 (CN111534902A) cited in the background art of this invention, to highlight the performance gap between the present invention and conventional textiles in the field of high-performance composite materials; according to the description in Reference Document 3, the following raw materials were first weighed: 20% ice silk fiber, 27% nylon fiber, 8% nylon fiber, 15% bamboo charcoal fiber, 15% polyester fiber, 5% polypropylene, 5% dyeing agent, and 3% catalyst. The process involves adding stannous chloride and 2% binder (aqueous binder); followed by melt spinning: after cleaning the reactor, polypropylene is added and heated to 50°C. All fibers except the dye are immersed for 1.5 hours, then removed and drained. The fibers are then mixed with the catalyst and poured into a spinneret, heated to 95°C, and spun. The spinneret is then dried with a cold air blower to obtain the base fabric, which is then sun-dried for 1.5 hours. Next, twisting is performed: the base fabric is divided into warp and weft yarns, twisted in a twisting machine, and then warped and threaded on a warping machine. Afterward, textile processing is carried out: aqueous binder is applied to the warp and weft yarns, left to stand for 15 minutes, then hot-rolled in a hot rolling mill, and finally woven into an interwoven fabric on an air-jet loom at 550 r / min. Finally, the fabric is dyed: the interwoven fabric is placed in a dyeing machine, dyed with a weak alkaline dye, and after reaching the desired color, it is removed, soaked in water for 15 minutes, drained, and sun-dried to obtain the final dyed fabric. This comparative example uses traditional textile processes and ordinary polymer fibers as its material system. It does not have a continuous fiber reinforced composite structure, high-performance resin matrix, intelligent interface, or any self-healing or highly efficient flame-retardant functions.

[0037] Performance testing The tensile strength test standard refers to Chinese invention patent CN111534902A; The limiting oxygen index was tested using a high-temperature oxygen index tester in accordance with GB / T 2406-1993.

[0038] The repair efficiency (η) is defined as the ratio of the tensile fracture stress (σhealed) of the repaired sample to the tensile fracture stress (σvirgin) of the special fabric, i.e., η = σhealed / σvirgin. The repair efficiency of the fabrics prepared in the examples and comparative examples was quantitatively measured.

[0039] Table 1 shows the performance test results of the embodiments and comparative examples of the present invention. Table 1 above clearly shows that the special fabrics prepared by this invention (Examples 1-3) are significantly superior to all comparative examples in terms of the three core indicators of tensile strength, flame retardancy and self-healing efficiency, which fully verifies the overall superiority and innovation of the technical solution of this invention.

[0040] Specifically, the embodiments successfully combine the three usually mutually restrictive properties of high strength, high flame retardancy, and high self-healing efficiency into one by constructing a multi-level synergistic structure of "silane-MOF hybrid interface layer", "Diels-Alder dynamic covalent bond interface connection" and "phosphorus-nitrogen-boron nitride synergistic flame retardant matrix", achieving unexpected technical effects.

[0041] Comparative Examples 1 to 3, by respectively lacking one of the aforementioned core innovative points, intuitively demonstrate that each technical feature is indispensable for achieving the ultimate superior performance, and their performance shortcomings clearly point to the specific missing link. Comparative Examples 4 and 5, as representatives of existing technologies or different technical routes, show a significant performance gap compared to this invention. This not only highlights the breakthrough of this invention in material design and performance but also clearly demonstrates its significant progress and high level of inventiveness compared to existing technologies.

[0042] In summary, the test data strongly demonstrates that this invention provides an advanced special fabric solution that can simultaneously meet the requirements for mechanical performance, safety and reliability, and long service life under extreme conditions.

[0043] Analysis of the reasons for the differences in test results in Examples 1-3: The differences in the test results of Examples 1 to 3 mainly stem from the gradient optimization of key process parameters and component ratios in each example. The synergistic changes in these parameters jointly determine the overall performance of the final product. Specifically, from Example 1 to Example 3, the volume fraction of silicon carbide fiber gradually increased from 45% to 65%. The higher fiber content provides a stronger mechanical load-bearing skeleton for the material, which is the basis for Example 3 to achieve an "excellent" level of tensile strength. Meanwhile, in terms of interface engineering, Example 3 adopted a higher ZIF-8 synthesis concentration (zinc ions 0.5 mol / L, 2-methylimidazole 2.0 mol / L) and reaction temperature (60°C), which is expected to form a denser and more tightly bound hybrid interface layer, thereby optimizing the load transfer efficiency. The higher proportion of furan functional groups in its resin matrix (molar ratio 1:0.3) also provides more sufficient conditions for the formation of Diels-Alder bonds at the interface, making Example 3 the most outstanding in self-healing efficiency (95%). Furthermore, regarding flame retardant performance, the amount of boron nitride nanosheets modified with phosphorus-nitrogen flame retardant in Example 3 reached the upper limit (8%), and the modification ratio was even higher (ammonium polyphosphate:boron nitride = 1:5). This "phosphorus-nitrogen-boron nitride" ternary synergistic flame retardant system constructed a more complete gas-phase and condensed-phase barrier network in the resin matrix, thereby significantly increasing its limiting oxygen index (LOI) to 60.1%. Therefore, the performance progression from Example 1 to Example 3 is the result of the simultaneous increase in fiber content, interfacial bonding strength, and flame retardant system density.

[0044] Analysis of the reasons for the differences between the test results of the Example and Comparative Example 1: The significant difference between the test results of the Example and Comparative Example 1 is fundamentally due to the fundamentally different interfacial layer structures. Comparative Example 1 only uses a traditional silane coupling agent to treat the fiber surface, resulting in a relatively flat monolayer with a limited specific surface area, exhibiting weak mechanical interlocking and physical adsorption capabilities with the resin. In contrast, the Example constructed a silane-MOF hybrid coating with a three-dimensional porous structure by in-situ growing ZIF-8 particles on the fiber surface. The coating's enormous specific surface area provides a much larger interfacial contact area than traditional methods, and its nanoscale ZIF-8 particles can effectively embed into the resin, generating a strong mechanical anchoring effect, thereby greatly improving the interfacial bonding strength and load transfer efficiency. This makes the tensile strength of the Example superior to that of Comparative Example 1. Furthermore, the stronger interfacial bonding also means that during the self-healing process, the crack interface can more accurately align and reform Diels-Alder bonds under thermal stimulation. Therefore, the repair efficiency of the Example (91%) is higher than that of Comparative Example 1 (78%). Furthermore, although flame retardant performance depends primarily on the matrix, a tougher interface helps maintain the integrity of the overall structure during combustion, indirectly supporting the stability of the char layer. Therefore, the LOI value of the embodiment is also slightly higher.

[0045] Analysis of the reasons for the differences between the test results of Example 1 and Comparative Example 2: The core difference in performance between the Examples and Comparative Example 2 lies in whether a strong chemical bond based on Diels-Alder dynamic covalent bonds was established between the fiber and the resin matrix. The resin matrix of Comparative Example 2 was not modified with furan, resulting in the inability of the maleimide groups on the pretreated fiber interface layer to undergo a Diels-Alder cycloaddition reaction with the resin during hot-pressing curing. Therefore, the interfacial bonding between the fiber and resin mainly relied on the physical interlocking of the silane-MOF coating and possibly a small amount of silane coupling agent covalent bonds, with a bonding strength far lower than the covalent bond connection achieved through DA bonds in the Examples. This relatively fragile interface became a stress concentration point and a weakness in mechanical properties, resulting in the tensile strength of Comparative Example 2 being only "average." Regarding self-healing performance, Comparative Example 2 completely lost the intrinsic self-healing ability conferred by the reversible reaction of DA bonds. Its 72% repair efficiency likely stemmed only from a slight plastic flow or physical rearrangement of the resin matrix itself, which is incomparable to the highly efficient and controllable chemical bond repair mechanism of over 90% in the Examples. The slight decrease in flame retardant properties may be related to weaker interfacial bonding, which makes it easier for interfacial debonding to occur during combustion, thereby compromising the integrity of the protective char layer.

[0046] Analysis of the reasons for the differences between the test results of the Example and Comparative Example 3: The performance differences between the Examples and Comparative Example 3, particularly the significant gap in Limiting Oxygen Index (LOI), are directly attributed to the complete absence of the phosphorus-nitrogen-boron nitride synergistic flame-retardant system in the resin matrix of Comparative Example 3. Comparative Example 3 uses pure furan-modified cyanate resin, which possesses some heat resistance but limited flame-retardant efficacy. In the Examples, however, the uniformly dispersed, ammonium polyphosphate-modified boron nitride nanosheets play a crucial role during combustion: ammonium polyphosphate decomposes upon heating, releasing non-combustible gases such as nitrogen in the gas phase to dilute oxygen, and catalyzing resin char formation in the condensed phase; the boron nitride nanosheets act as a two-dimensional nanobarrier, effectively blocking the transport of heat and combustible degradation products, and synergistically forming a denser and stronger expanded char layer with ammonium polyphosphate. This highly efficient "gas-phase-condensed phase" synergistic flame-retardant mechanism enables the LOI value of the Examples to exceed 50%, while that of Comparative Example 3 is only 34.1%, falling into the flammable category. In addition, boron nitride nanosheets, as a high-performance nanofiller, have a certain reinforcing and toughening effect on the resin matrix. Their absence may also slightly affect the overall mechanical properties and interface stability of Comparative Example 3, resulting in its tensile strength and self-healing efficiency being slightly lower than those of the Example.

[0047] Analysis of the reasons for the differences between the test results of Example 1 and Comparative Example 4: The performance differences between the examples and Comparative Example 4 stem from their completely different material systems, self-healing mechanisms, and application forms. Comparative Example 4 is a coated fabric prepared according to Prior Art Document 1, whose self-healing function is limited to a relatively thin polymer coating on the surface of ordinary fiber cloth. The matrix of this coating is epoxy resin, whose heat resistance, modulus, and strength are generally lower than those of the cyanate ester resin used in this invention. More importantly, the self-healing mechanism of Comparative Example 4 occurs within the coating material itself and does not address the repair problem of the most critical and vulnerable "fiber-resin" interface region in fiber-reinforced composite materials. In contrast, the self-healing design of this invention is precisely positioned at this interface, restoring the core load transfer channel through the interface DA bonds, thus exhibiting superior performance in both macroscopic mechanical properties (tensile strength) and repair efficiency. Furthermore, the coating structure and material system of Comparative Example 4 do not possess the highly efficient flame-retardant network constructed by boron nitride nanosheets and ammonium polyphosphate as described in this invention; therefore, its LOI value (37.3%) is significantly lower than that of the examples of this invention. The performance characteristics of Comparative Example 4 are more consistent with the properties of a surface protective coating than with an integral composite material that can be used as a structural component.

[0048] Analysis of the reasons for the differences between the test results of the Example and Comparative Example 5: The performance difference between the examples and Comparative Example 5 is fundamental, stemming from the generational differences in material science principles and structure between "high-performance fiber-reinforced composite materials" and "traditional blended textile fabrics." Comparative Example 5 is made from common textile fibers such as ice silk, nylon, and cotton through traditional processes like twisting and weaving. Its mechanical properties mainly rely on the strength of the fibers themselves and the friction and entanglement between them. It lacks a continuous, dense, high-performance resin matrix to effectively transfer and disperse the load, resulting in a very low upper limit for its tensile strength, only "average." Furthermore, this material system completely lacks any intrinsic self-healing chemical mechanisms (such as Diels-Alder bonds). Its so-called repair may only be a physical re-bonding, with extremely low efficiency (68%). Regarding flame retardancy, most of these natural and synthetic polymer fibers are flammable or combustible materials. Even with a small amount of bamboo charcoal fiber, it lacks systematic gas-phase and condensed-phase flame-retardant synergistic components. Therefore, its LOI value (38.2%) is only slightly higher than the oxygen concentration in the air, failing to meet the high safety standards of special fields. This invention achieves a high level of comprehensive performance that cannot be matched by Comparative Example 5 through advanced composite material design and innovation at the fiber, interface, and matrix levels.

[0049] Finally, it should be noted that the above embodiments are used to illustrate the technical solutions of the present invention and not to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A special fabric with tensile strength, characterized in that: It includes a silicon carbide fiber reinforcement, a cyanate ester resin matrix, and a multifunctional interface layer; The multifunctional interface layer is bonded to the fiber through a silane-metal-organic framework hybrid coating and connected to the resin matrix through dynamic covalent bonds. The silicon carbide fiber has a volume fraction of 45%-65%, the cyanate ester resin has a volume fraction of 25%-45%, and the multifunctional interface layer has a thickness of 50-500 nanometers.

2. The special fabric with tensile strength according to claim 1, characterized in that: The silane-metal-organic framework hybrid coating is formed by in-situ growth of ZIF-8 particles on the surface of silicon carbide fibers, wherein the silane coupling agent is γ-(2,3-epoxypropoxy)propyltrimethoxysilane, and the ZIF-8 particles have a particle size of 50-200 nm and an areal density of 5-20 g / m³. 2 .

3. The special fabric with tensile strength according to claim 1, characterized in that: The dynamic covalent bond is a Diels-Alder bond, which is formed by the cycloaddition reaction between maleimide groups grafted on the interface layer and furan groups in the resin matrix at 90-120℃.

4. The special fabric with tensile strength according to claim 1, characterized in that: The cyanate ester resin matrix is ​​compounded with boron nitride nanosheets modified with a phosphorus-nitrogen synergistic flame retardant, the modifier being ammonium polyphosphate. The thickness of the boron nitride nanosheets is 1-5 nanometers, the aspect ratio is 100-500, and the mass fraction in the resin is 3%-8%.

5. A method for preparing a special fabric with tensile strength as described in any one of claims 1-4, characterized in that, Includes the following steps: (a) Surface pretreatment of silicon carbide fibers: Active hydroxyl groups are introduced on the fiber surface by plasma treatment; argon atmosphere, power 300-350W, time 5-8 minutes; (b) Construction of silane-MOF hybrid coating: The pretreated fiber was immersed in a mixed solution containing zinc ions, 2-methylimidazolium and silane coupling agent and reacted at 25-60°C for 2-12 hours to grow ZIF-8 particles in situ on the fiber surface. (c) Preparation of resin matrix: Cyanate ester resin monomers were reacted with furan methanol under the action of a catalyst to synthesize furan group-terminated cyanate ester prepolymer; then, boron nitride nanosheets modified with phosphorus-nitrogen flame retardant were dispersed in the prepolymer; (d) Construction of dynamic covalent bonds at the interface: The fibers treated in step (b) are woven into a fabric and impregnated in the resin system obtained in step (c). The fabric is then cured for 1-3 hours at 100-150℃ and 1-5MPa pressure by hot pressing, so that the maleimide groups on the interface layer react with the furan groups in the resin in a Diels-Alder reaction.

6. The method for preparing the tensile-resistant special fabric according to claim 5, characterized in that: In the mixed solution described in step (b), the zinc ion concentration is 0.1-0.5 mol / L, the 2-methylimidazole concentration is 0.5-2 mol / L, the silane coupling agent volume fraction is 5%-10%, and the solvent is a mixed solvent of methanol and water with a volume ratio of 3:1-5:

1.

7. The method for preparing the tensile-resistant special fabric according to claim 5, characterized in that, The synthesis conditions for the furan-terminated cyanate prepolymer described in step (c) are as follows: the molar ratio of cyanate monomer to furan-methanol is 1:0.1-0.3, the reaction temperature is 80-120℃, the reaction time is 2-5 hours, the catalyst is triethylamine, and the amount used is 0.5%-1.5% of the monomer mass.

8. The method for preparing the tensile-resistant special fabric according to claim 5, characterized in that, The preparation method of the phosphorus-nitrogen flame retardant modified boron nitride nanosheets in step (c) is as follows: disperse boron nitride nanosheets in water, add ammonium polyphosphate, stir and react at 60-90℃ for 4-10 hours, and the mass ratio of ammonium polyphosphate to boron nitride is 1:5-1:

10.

9. The method for preparing the tensile-resistant special fabric according to claim 5, characterized in that, The hot-press curing process described in step (d) adopts a segmented curing procedure: first, the Diels-Alder reaction is fully carried out by holding the temperature at 90-120℃ for 0.5-2 hours, and then the temperature is raised to 180-220℃ to complete the final curing of the cyanate ester resin; the heating rate is 2±0.5℃ / min.

10. The special fabric with tensile strength according to claim 1, characterized in that, The repair mechanism of the dynamic covalent bond is as follows: when the material is damaged, heat treatment is performed at 120-150℃, and the Diels-Alder bond undergoes reversible fracture, relieving stress concentration. After cooling to below 90°C, the bonds reform, achieving interface self-repair with a repair efficiency of over 90%.

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