Composite flame retardant, epoxy resin composite material and preparation method thereof

Abstract

The application discloses a kind of composite flame retardant, epoxy resin composite material and preparation method thereof, the amino functionalized MOF nanoparticles of the present application is synthesized by DMF aqueous solution system one-step solvothermal reaction, then it is prepared MOF@APP flame retardant by the way of in-situ composite mediated by silane coupling agent, ultrasonic auxiliary, overall process is simple, condition is mild, controllability is strong, can stably synthesize the MOF nanoparticles of amino functional group abundance, particle size is uniform, and realize the stable composite of MOF and ammonium polyphosphate, avoid the phase separation, uneven dispersion problem brought by simple physical mixing, finally the flame retardant obtained has the carbon catalysis of MOF, smoke adsorption function and APP's intumescent flame retardant function, and the two form significant flame-retardant synergistic effect, fundamentally solve the problem that traditional APP flame retardant adds large amount, and the compatibility of epoxy resin is poor, easily leading to the serious loss of matrix mechanical property.

Description

Technical Field

[0001] This invention relates to the field of flame retardant materials technology, and in particular to a composite flame retardant, an epoxy resin composite material, and a method for preparing the same. Background Technology

[0002] Epoxy resin (EP), as a high-performance polymer material, is widely used in various industrial fields such as machinery manufacturing, electrical products, construction, aerospace, and electronic packaging due to its excellent chemical resistance, mechanical properties, electrical insulation, and adhesive properties. However, the molecular structure of epoxy resin is mainly composed of C, H, and O elements, making it a flammable material. It is prone to combustion under open flame, releasing large amounts of smoke and toxic gases during combustion, which can cause property damage and pose serious personal safety hazards. This defect greatly limits its further expansion in applications requiring high flame retardancy.

[0003] To improve the flame retardant properties of epoxy resins, additive flame retardants have become the most widely used modification method. Among them, halogen-free flame retardants containing elements such as phosphorus, nitrogen, magnesium, and aluminum have become a research focus in the field of flame retardants because they overcome the drawbacks of halogen-based flame retardants, such as high smoke production and toxic decomposition products, and are in line with EU environmental regulations and the global trend of green environmental protection. Ammonium polyphosphate (APP), as a typical phosphorus-based intumescent halogen-free flame retardant, combines economy and good flame retardant effect. During combustion, it can act as an acid source to catalyze the dehydration of the carbonization source to form a carbon melt. The released non-combustible gas can form a loose carbon layer in the carbon melt, achieving flame retardancy by isolating heat and oxygen transfer. It is a commonly used flame retardant component in the flame retardant modification of epoxy resins. However, there are obvious technical drawbacks to using ammonium polyphosphate alone to modify epoxy resin for flame retardancy: on the one hand, in order to achieve the expected flame retardant effect, the amount of ammonium polyphosphate added usually needs to exceed 10%, and a large proportion of addition will lead to a significant decrease in the mechanical properties of epoxy resin materials, making it difficult to balance the flame retardancy and mechanical properties of the material; on the other hand, ammonium polyphosphate has poor compatibility with epoxy resin matrix, and is prone to uneven dispersion and precipitation after long-term use, which further affects the overall performance stability of composite materials.

[0004] To address the aforementioned issues, researchers have attempted to prepare composite flame retardants by combining metal-organic frameworks (MOFs) with ammonium polyphosphate. For example, patent document CN119463298A discloses a composite flame retardant applicable to epoxy resins and its preparation method. This involves mixing MOF-on-MOF multilayer structures with ammonium polyphosphate, followed by surface modification using a phosphorus-containing silane coupling agent. When applied to epoxy resins, the prepared composite flame retardant improves flame retardant performance while reducing the required addition amount. Another example is patent document CN118027684A, which discloses a MOF-based composite flame retardant, its preparation method, and flame-retardant polymer materials. By modifying MOFs with phytic acid and compounding them with ammonium polyphosphate, the compatibility between the flame retardant and the polymer materials is improved, reducing negative impacts on the physical and mechanical properties of the materials. For example, patent document CN119751977A discloses a method for preparing and applying an ultra-low addition amount of MOF-derived LDH composite flame retardant. The MOF base is loaded onto ammonium polyphosphate and etched to form a layered double hydroxide structure, thereby achieving a low addition amount of flame retardant.

[0005] However, existing MOF-based ammonium polyphosphate composite flame retardants still have many shortcomings: The synthesis process of MOFs in some technologies is complex, such as the MOF-on-MOF layer-by-layer assembly method, which involves cumbersome steps and harsh reaction conditions, resulting in low production efficiency and poor economic benefits. Some composite flame retardants only combine MOFs and ammonium polyphosphate through simple physical mixing, resulting in weak bonding between the two, making them prone to separation during processing and use, affecting the stability of the synergistic flame retardant effect. While some modification methods can improve flame retardant performance, they lack sufficient control over the composite interface between MOFs and ammonium polyphosphate, failing to effectively solve the problem of poor dispersibility of the flame retardant in the epoxy resin matrix, and still resulting in significant loss of mechanical properties. Furthermore, most existing MOF-based composite flame retardants do not fully utilize the structural characteristics of MOFs to introduce functional groups that can participate in the epoxy resin curing reaction, failing to fundamentally solve the technical problems of flame retardant precipitation and poor compatibility. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the technical problem to be solved by this invention is: how to achieve stable composite of MOFs and ammonium polyphosphate, simplify the synthesis process, and improve the dispersibility and compatibility of composite flame retardants in epoxy resin matrix, effectively balancing the flame retardant properties and mechanical properties of epoxy resin.

[0007] To address the aforementioned technical problems, the first aspect of this invention provides a method for preparing a composite flame retardant, comprising the following steps: S1. Disperse soluble copper salt and amino aromatic carboxylic acid ligand in DMF (N,N-dimethylformamide) aqueous solution, stir evenly, add dispersant, and after ultrasonic dispersion, transfer to high pressure reactor for solvothermal reaction at 80~100℃ for 1~3h. Collect reaction product, wash and dry to obtain amino-functionalized MOF nanoparticles. S2. Dissolve ammonium polyphosphate in a polar solvent to obtain an ammonium polyphosphate solution; S3. The amino-functionalized MOF nanoparticles are ultrasonically dispersed in the same polar solvent as in step S2 to obtain a MOF suspension. S4. Add silane coupling agent to the MOF suspension, mix with ultrasound, and then add the ammonium polyphosphate solution dropwise under ultrasound assistance to obtain a reaction solution. S5. The reaction solution is reacted at 60~100℃ for 3~12h, the reaction product is collected, washed and dried to obtain MOF@APP composite flame retardant.

[0008] This invention synthesizes amino-functionalized MOF nanoparticles through a one-step solvothermal reaction in a DMF aqueous solution system, and then prepares MOF@APP flame retardants via silane coupling agent-mediated, ultrasound-assisted in-situ composite. The overall process is simple, mild, and highly controllable, eliminating the need for complex layer-by-layer assembly and etching modification steps found in existing technologies, making it easy to scale up production. Simultaneously, the core temperature and time windows of the solvothermal and composite reactions are precisely defined, enabling the stable synthesis of MOF nanoparticles rich in amino functional groups and with uniform particle size. Stable composite of MOF and ammonium polyphosphate (APP) is achieved, avoiding phase separation and uneven dispersion problems caused by simple physical mixing. The resulting flame retardant combines the char-forming catalysis and flue gas adsorption functions of MOF with the expansion flame-retardant function of APP, forming a significant synergistic flame-retardant effect. This fundamentally solves the problems of traditional APP flame retardants, such as high dosage requirements, poor compatibility with epoxy resins, and severe loss of matrix mechanical properties.

[0009] In some preferred or optional embodiments, in step S1, the mass ratio of the soluble copper salt to the amino-containing aromatic carboxylic acid ligand is 1:(5~20). Limiting the core ratio of the copper salt to the amino ligand ensures the crystallinity and surface amino loading of the MOF, avoids raw material waste or incomplete coordination, and improves the monodispersity of the MOF.

[0010] In some preferred or optional embodiments, the soluble copper salt is selected from at least one of copper nitrate, copper acetate, and copper chloride; the amino-containing aromatic carboxylic acid ligand is selected from at least one of 5-aminoterephthalic acid, 2-aminoterephthalic acid, and aminoisophthalic acid; and the dispersant is selected from at least one of polyvinylpyrrolidone, polyethylene glycol, and polyvinyl alcohol. This limitation on the types of core raw materials ensures the stability and controllability of the MOF synthesis process, introduces sufficient active amino groups into the MOF, and inhibits nanoparticle aggregation, thus adapting to different preparation and application requirements.

[0011] In some preferred or optional embodiments, in step S2, the concentration of the ammonium polyphosphate solution is 10~30 g / L. This ensures that the APP is fully dissolved to form a homogeneous solution, which is compatible with the concentration of the MOF suspension, achieving uniform compounding between the two, avoiding uneven coating, and ensuring the stable performance of the flame-retardant synergistic effect.

[0012] In some preferred or optional embodiments, in step S3, the concentration of amino-functionalized MOF nanoparticles in the MOF suspension is 5-10 g / L. This ensures uniform monodispersion of the MOF nanoparticles, achieving uniform coating on the APP surface and guaranteeing a stable and controllable MOF loading of the flame retardant.

[0013] In some preferred or optional embodiments, in step S4, the silane coupling agent is selected from at least one of vinyltriethoxysilane, vinyltrimethoxysilane, and vinyltri(β-methoxyethoxy)silane, and the concentration of the silane coupling agent in the MOF suspension is 1~5 g / L. Limiting the type and concentration of vinyl silane coupling agents achieves stable bridging between MOF and APP while fully preserving the reactivity of the amino groups on the MOF surface, avoiding silane self-polymerization residues, and balancing the flame retardant and mechanical properties of the material.

[0014] In some preferred or optional embodiments, steps S2 to S5 are performed under an inert atmosphere. The inert atmosphere protection prevents silane hydrolysis failure, amino oxidation, and APP degradation, ensuring a stable and controllable composite process.

[0015] A second aspect of this invention provides a composite flame retardant prepared by the above-described preparation method. The MOF@APP composite flame retardant of this invention combines the synergistic flame-retardant effects of MOF and APP, exhibiting high flame-retardant efficiency. Furthermore, the active amino groups it contains can participate in the curing of epoxy resin, significantly improving compatibility with the matrix and fundamentally solving the problems of easy precipitation and damage to the mechanical properties of the matrix caused by traditional flame retardants.

[0016] The third aspect of the present invention provides an epoxy resin composite material, comprising the following components by weight: 1-20 parts of the above-mentioned composite flame retardant, 100 parts of epoxy resin, and 15-50 parts of curing agent.

[0017] By adding the composite flame retardant and curing agent of this invention to the epoxy resin matrix, it is possible to ensure that the material achieves an excellent flame retardant rating while avoiding problems such as incomplete curing and decreased mechanical properties. This adapts to the flame retardant requirements of different application scenarios and solves the pain point of existing technologies that make it difficult to balance flame retardancy and mechanical properties.

[0018] In some preferred or optional embodiments, the epoxy resin is selected from at least one of bisphenol A type epoxy resin, bisphenol F type epoxy resin, phenolic epoxy resin, and alicyclic epoxy resin; the curing agent is selected from at least one of diaminodiphenylmethane, m-phenylenediamine, diethylenetriamine, triethylenetetramine, isophorone diamine, phthalic anhydride, tetrahydrophthalic anhydride, methylhexahydrophthalic anhydride, and dodecenylsuccinic anhydride. The composite flame retardant is compatible with mainstream epoxy matrix systems and curing systems, adaptable to different application scenarios, and can ensure complete curing and structural stability of the epoxy system, significantly expanding the industrial application range of composite materials.

[0019] In summary, compared with the prior art, the present invention has the following beneficial effects: (1) This invention provides a simple and controllable method for preparing MOF@APP composite flame retardant. Amino-functionalized MOF nanoparticles can be synthesized by a one-step solvothermal reaction. Then, MOF and APP are stably combined by bridging with vinyl silane coupling agent and ultrasonic-assisted in-situ composite. The reaction conditions are mild, the raw materials are readily available, and the batch stability is good.

[0020] (2) The MOF@APP composite flame retardant prepared by this invention has abundant active amino functional groups on its surface, which can directly participate in the curing and crosslinking reaction of epoxy resin. On the one hand, it significantly improves the interfacial compatibility between the flame retardant and the epoxy resin matrix, realizes the uniform dispersion of the flame retardant in the matrix, and avoids material performance defects caused by particle agglomeration. On the other hand, it fundamentally solves the problem of easy migration and precipitation and performance decay of traditional additive flame retardants during long-term use. While achieving high-efficiency flame retardancy, it minimizes the negative impact of the flame retardant on the mechanical properties of the epoxy resin matrix, and achieves a synergistic balance between the flame retardant performance and mechanical properties of the material.

[0021] (3) The MOF@APP composite flame retardant of the present invention fully utilizes the synergistic flame retardant effect of multiple components, combining the char-forming catalytic and toxic smoke adsorption functions of MOF materials with the intumescent flame retardant properties of APP. After the two are stably combined by silane coupling agent, the flame retardant efficiency is greatly improved. Even with low addition amount, epoxy resin composite material can achieve flame retardant effect, effectively inhibiting heat release, smoke release and toxic gas generation during combustion. At the same time, this flame retardant is a completely halogen-free system, and does not produce toxic and harmful hydrogen halide gas during combustion, which is in line with the development trend of green flame retardant.

[0022] (4) The MOF@APP composite flame retardant system of the present invention has wide compatibility and is compatible with various mainstream epoxy resin matrices such as bisphenol A, bisphenol F, phenolic, and alicyclic. It is also compatible with various curing systems such as amines and anhydrides. It can be widely used in fields with high requirements for flame retardancy, mechanical properties and environmental protection, such as electronic packaging, electrical insulation, anti-corrosion coatings, and aerospace. It provides reliable technical support for the large-scale application of epoxy resin materials in high-end flame retardant scenarios and has significant economic value and industrial promotion significance. Attached Figure Description

[0023] Figure 1 This is a SEM image of the MOF@APP flame retardant prepared in Example 1 of the present invention.

[0024] Figure 2 This is a curve showing the CO yield over time for the epoxy resin composite materials prepared in the embodiments and comparative examples of the present invention.

[0025] Figure 3 This is a curve showing the total smoke production over time for the epoxy resin composite materials prepared in the embodiments and comparative examples of the present invention.

[0026] Figure 4 The curves show the heat release rate of the epoxy resin composite materials prepared in the embodiments and comparative examples of the present invention, corresponding to the time. Detailed Implementation

[0027] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0028] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0029] 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 obvious to those skilled in the art. This application specification and embodiments are merely exemplary.

[0030] The present invention provides a MOF@APP composite flame retardant, its preparation method, and an epoxy resin composite material using the flame retardant. It specifically addresses the core problems of existing MOF-based ammonium polyphosphate composite flame retardants, such as complex synthesis process, poor bonding stability between MOF and ammonium polyphosphate, insufficient dispersibility and compatibility in epoxy resin matrix, and difficulty in simultaneously achieving the flame retardant and mechanical properties of epoxy resin.

[0031] The preparation process steps of MOF@APP composite flame retardant are as follows: Preparation of S1, amino-functionalized MOF nanoparticles Soluble copper salt and amino aromatic carboxylic acid ligands were dispersed in DMF aqueous solution, stirred evenly, and then a dispersant was added. After ultrasonic dispersion, the mixture was transferred to a high-pressure reactor for solvothermal reaction at 80-100℃ for 1-3 hours. The reaction product was collected, washed, and dried to obtain amino-functionalized MOF nanoparticles.

[0032] In specific embodiments, the soluble copper salt can be selected from copper nitrate, copper acetate, or copper chloride; the amino aromatic carboxylic acid ligand can be selected from 5-aminoterephthalic acid, 2-aminoterephthalic acid, or aminoisophthalic acid; the dispersant can be selected from polyvinylpyrrolidone, polyethylene glycol, or polyvinyl alcohol. The above raw material selection can ensure the stability and controllability of the MOF synthesis process, introduce sufficient active amino groups into the MOF, and inhibit the aggregation of nanoparticles, thus adapting to different preparation and application requirements.

[0033] In a specific embodiment, the mass ratio of soluble copper salt to amino aromatic carboxylic acid ligand is 1:(5~20). This ratio can ensure the crystallinity and surface amino loading of MOF, avoid the problem of raw material waste or incomplete coordination, and improve the monodispersity of MOF.

[0034] S2, Preparation of ammonium polyphosphate solution Ammonium polyphosphate is dissolved in a polar solvent to obtain an ammonium polyphosphate solution.

[0035] In a specific embodiment, the concentration of ammonium polyphosphate solution is controlled at 10~30g / L to ensure that APP is fully dissolved to form a homogeneous solution, which is compatible with the concentration of MOF suspension, so as to achieve uniform compounding of the two, avoid uneven coating, and ensure the stable performance of flame retardant synergy.

[0036] Preparation of S3 and MOF suspensions Amino-functionalized MOF nanoparticles were ultrasonically dispersed in the same polar solvent as in step S2 to obtain a MOF suspension.

[0037] In a specific embodiment, the concentration of amino-functionalized MOF nanoparticles in the MOF suspension is 5~10 g / L, which can ensure that the MOF nanoparticles are uniformly and monodispersed, achieve uniform coating on the APP surface, and ensure that the MOF loading of the flame retardant is stable and controllable.

[0038] S4, Preparation of in-situ composite reaction system A silane coupling agent was added to the MOF suspension, and after ultrasonic mixing, the ammonium polyphosphate solution was added dropwise under ultrasonic assistance to obtain a reaction solution.

[0039] In a specific embodiment, the silane coupling agent may be selected from vinyltriethoxysilane, vinyltrimethoxysilane, or vinyltri(β-methoxyethoxy)silane. The concentration of the silane coupling agent in the MOF suspension is controlled to be 1~5 g / L. The silane coupling agent can stably bridge the MOF and APP, and can completely retain the reactivity of the amino groups on the MOF surface, avoiding silane self-polymerization residue, and taking into account both the flame retardant and mechanical properties of the material.

[0040] Synthesis of S5 and MOF@APP composite flame retardants The reaction solution from step S4 is reacted at 60-100℃ for 3-12 hours. The reaction product is collected, washed, and dried to obtain the MOF@APP composite flame retardant.

[0041] In the specific implementation, steps S2 to S5 are carried out under an inert atmosphere to prevent silane hydrolysis failure, amino oxidation and APP degradation, and to ensure that the composite process is stable and controllable.

[0042] The embodiment of the epoxy resin composite material of the present invention is to use epoxy resin as the matrix, add the above-mentioned MOF@APP composite flame retardant and curing agent, and then mix and cure to obtain the product.

[0043] Specifically, by weight, the composite material comprises the following components: 1-20 parts of MOF@APP composite flame retardant, 100 parts of epoxy resin, and 15-50 parts of curing agent. The MOF@APP composite flame retardant is added to the epoxy resin, and after ultrasonic-assisted stirring to disperse it evenly, the curing agent is added, and stirring continues until completely dissolved. After vacuum degassing and high-temperature curing, the epoxy resin composite material is obtained. This component ratio ensures that the material achieves an excellent flame retardant rating while avoiding problems such as incomplete curing and decreased mechanical properties, thus adapting to the flame retardant requirements of different application scenarios.

[0044] In specific embodiments, the epoxy resin can be selected from bisphenol A type epoxy resin, bisphenol F type epoxy resin, phenolic epoxy resin, or alicyclic epoxy resin; the curing agent can be selected from diaminodiphenylmethane, m-phenylenediamine, diethylenetriamine, triethylenetetramine, isophorone diamine, phthalic anhydride, tetrahydrophthalic anhydride, methylhexahydrophthalic anhydride, or dodecenylsuccinic anhydride. The above selection covers the mainstream epoxy matrix systems and curing systems, ensuring complete curing and structural stability of the epoxy system, and significantly expanding the industrial application range of the composite material.

[0045] In some preferred embodiments, the mass ratio of epoxy resin to curing agent is controlled to be 6:1 to 2:1, and the amount of MOF@APP flame retardant added to the epoxy resin composite material is 1.0wt% to 20.0wt%. This can be adapted to mainstream epoxy curing systems, achieving a wide range of gradient control of flame retardant performance. While ensuring complete curing of epoxy resin, it also takes into account excellent flame retardant and smoke suppression effects and good mechanical properties.

[0046] This invention synthesizes amino-functionalized MOF nanoparticles through a one-step solvothermal reaction in a DMF aqueous solution system, and then prepares MOF@APP flame retardants via silane coupling agent-mediated, ultrasound-assisted in-situ composite method. The overall process is simple, mild, and highly controllable, eliminating the need for complex layer-by-layer assembly and etching modification steps found in existing technologies, making it easy to scale up production. By precisely defined process parameters, MOF nanoparticles with abundant amino functional groups and uniform particle size can be stably synthesized, achieving stable composite of MOF and APP and fully leveraging their synergistic flame-retardant effect. Simultaneously, by utilizing the surface-active amino groups of MOF to participate in the curing and cross-linking of epoxy resin, the dispersibility and compatibility of the flame retardant with the resin matrix are significantly improved, preventing the migration and precipitation of the flame retardant during long-term use. Ultimately, this achieves a synergistic balance between the flame-retardant and mechanical properties of epoxy resin, providing a reliable technical path for the industrial application of flame-retardant epoxy resin materials in high-end fields.

[0047] The technical effects of the present invention will be described below with reference to specific embodiments. Unless otherwise specified, the raw materials used in the embodiments of this application were all purchased through commercial channels.

[0048] Example 1 The MOF@APP composite flame retardant was prepared by the following method: (1) Copper nitrate and 5-aminoterephthalic acid were dispersed in a DMF aqueous solution with a mass ratio of 1:10 at a mass ratio of 700 g / L. The mixture was magnetically stirred at a speed of 800 rpm until the system was completely dispersed and uniform. Polyvinylpyrrolidone (PVP) powder was added to the mixture, and the concentration of PVP in the DMF aqueous solution was controlled to be 10 g / L. The mixture was continuously ultrasonically dispersed until the system was uniform and stable to obtain the MOF precursor solution.

[0049] (2) The MOF precursor solution prepared in step (1) was transferred into a high-pressure reactor, sealed and subjected to a solvothermal reaction at a constant temperature of 80°C for 3 hours. After the reaction was completed, the high-pressure reactor was naturally cooled to room temperature, the solid product in the reactor was collected, washed multiple times with anhydrous ethanol, and then dried under vacuum at 80°C to obtain amino-functionalized MOF nanoparticles.

[0050] (3) The entire process is carried out under nitrogen atmosphere protection: Ammonium polyphosphate (APP) is dissolved in 1,4-dioxane solvent and stirred until completely dissolved to prepare an APP solution with a concentration of 10 g / L; at the same time, the MOF nanoparticles obtained in step (2) are dispersed in 1,4-dioxane solvent and ultrasonically dispersed until the system is uniform to prepare a MOF suspension with a MOF nanoparticle concentration of 5 g / L.

[0051] (4) The entire process is carried out under nitrogen atmosphere protection: Add vinyltriethoxysilane to the MOF suspension prepared in step (3), control the concentration of vinyltriethoxysilane in the MOF suspension to 1 g / L, and after ultrasonic mixing, add the prepared APP solution dropwise to the system at a constant rate under continuous ultrasonic assistance. After the addition is completed, continue ultrasonic stirring until the system is homogeneous to obtain the in-situ composite reaction system.

[0052] (5) The above in-situ composite reaction system was transferred to an oil bath and stirred at 80°C for 5 hours to obtain a MOF@APP mixture. After the reaction, the solid product was collected by centrifugation, washed multiple times with anhydrous ethanol, and then vacuum dried to finally obtain the MOF@APP composite flame retardant, the microstructure of which is as follows: Figure 1 As shown.

[0053] The above-mentioned MOF@APP flame retardant was used to prepare flame-retardant epoxy resin composite materials, and the specific method is as follows: Weigh the following raw materials according to the mass ratio: 100 parts of bisphenol A type epoxy resin, 16.7 parts of diaminodiphenylmethane, and 1.8 parts of MOF@APP composite flame retardant; add the MOF@APP flame retardant to the mixture of epoxy resin and curing agent, stir until completely dispersed and uniform, degas under vacuum, and then carry out a high-temperature curing reaction. After naturally cooling to room temperature, demold to obtain epoxy resin composite material.

[0054] Example 2 The MOF@APP composite flame retardant was prepared by the following method: (1) Copper nitrate and 5-aminoterephthalic acid were dispersed in a DMF aqueous solution with a mass ratio of 1:15 at a mass ratio of 800 g / L. The mixture was magnetically stirred at a speed of 500 rpm until the system was completely dispersed and uniform. PVP powder was added to the mixture and the concentration of PVP in the DMF aqueous solution was controlled to be 15 g / L. The mixture was continuously ultrasonically dispersed until the system was uniform and stable to obtain the MOF precursor solution.

[0055] (2) The MOF precursor solution prepared in step (1) was transferred into a high-pressure reactor, sealed and subjected to a solvothermal reaction at a constant temperature of 90°C for 1 hour. After the reaction was completed, the high-pressure reactor was naturally cooled to room temperature, the solid product in the reactor was collected, washed multiple times with anhydrous ethanol, and then dried under vacuum at 90°C to obtain amino-functionalized MOF nanoparticles.

[0056] (3) The entire process is carried out under nitrogen atmosphere protection: Ammonium polyphosphate is dissolved in acetonitrile solvent and stirred until completely dissolved to prepare an APP solution with a concentration of 15 g / L; at the same time, the MOF nanoparticles obtained in step (2) are dispersed in acetonitrile solvent and ultrasonically dispersed until the system is uniform to prepare a MOF suspension with a MOF nanoparticle concentration of 6 g / L.

[0057] (4) The entire process is carried out under nitrogen atmosphere protection: Add vinyltriethoxysilane to the MOF suspension prepared in step (3), control the concentration of vinyltriethoxysilane in the MOF suspension to be 2 g / L, and after ultrasonic mixing, add the prepared APP solution dropwise to the system at a constant rate under continuous ultrasonic assistance. After the addition is completed, continue ultrasonic stirring until the system is homogeneous to obtain the in-situ composite reaction system.

[0058] (5) The entire process is carried out under nitrogen atmosphere protection: the above in-situ composite reaction system is transferred to an oil bath and stirred at a constant temperature of 65°C for 5 hours to obtain MOF@APP mixture; after the reaction is completed, the solid product is collected by centrifugation, washed multiple times with anhydrous ethanol and then vacuum dried to finally obtain MOF@APP composite flame retardant.

[0059] The above-mentioned MOF@APP flame retardant was used to prepare flame-retardant epoxy resin composite materials, and the specific method is as follows: Weigh the raw materials according to the following mass ratio: 100 parts of bisphenol A type epoxy resin, 20 parts of diaminodiphenylmethane, and 3.7 parts of MOF@APP composite flame retardant; add the MOF@APP flame retardant to the mixture of epoxy resin and curing agent, stir until completely dispersed and uniform, degas under vacuum, and then carry out a high-temperature curing reaction. After naturally cooling to room temperature, demold to obtain epoxy resin composite material.

[0060] Example 3 The MOF@APP composite flame retardant was prepared by the following method: (1) Copper nitrate and 5-aminoterephthalic acid were dispersed in a DMF aqueous solution with a mass ratio of 1:18 in a mass concentration of 900 g / L. The mixture was magnetically stirred at a speed of 600 rpm until the system was completely dispersed and uniform. PVP powder was added to the mixture and the concentration of PVP in the DMF aqueous solution was controlled to be 12 g / L. The mixture was continuously ultrasonically dispersed until the system was uniform and stable to obtain the MOF precursor solution.

[0061] (2) The MOF precursor solution prepared in step (1) was transferred into a high-pressure reactor, sealed and subjected to a solvothermal reaction at a constant temperature of 85°C for 2.5 h. After the reaction was completed, the high-pressure reactor was naturally cooled to room temperature, the solid product in the reactor was collected, washed multiple times with anhydrous ethanol, and then vacuum dried at 85°C to obtain amino-functionalized MOF nanoparticles.

[0062] (3) The entire process is carried out under nitrogen atmosphere protection: Ammonium polyphosphate is dissolved in acetonitrile solvent and stirred until completely dissolved to prepare an APP solution with a concentration of 17 g / L; at the same time, the MOF nanoparticles obtained in step (2) are dispersed in acetonitrile solvent and ultrasonically dispersed until the system is uniform to prepare a MOF suspension with a MOF nanoparticle concentration of 7 g / L.

[0063] (4) The entire process is carried out under nitrogen atmosphere protection: Add vinyltrimethoxysilane to the MOF suspension prepared in step (3), control the concentration of vinyltrimethoxysilane in the MOF suspension to be 3 g / L, and after ultrasonic mixing, add the prepared APP solution dropwise to the system at a constant rate under continuous ultrasonic assistance. After the addition is completed, continue ultrasonic stirring until the system is homogeneous to obtain the in-situ composite reaction system.

[0064] (5) The entire process is carried out under nitrogen atmosphere protection: the above in-situ composite reaction system is transferred to an oil bath and stirred at a constant temperature of 70°C for 2 hours to obtain MOF@APP mixture; after the reaction is completed, the solid product is collected by centrifugation, washed multiple times with anhydrous ethanol and then vacuum dried to finally obtain MOF@APP composite flame retardant.

[0065] The above-mentioned MOF@APP flame retardant was used to prepare flame-retardant epoxy resin composite materials, and the specific method is as follows: Weigh the raw materials according to the following mass ratio: 100 parts of bisphenol A type epoxy resin, 25 parts of diaminodiphenylmethane, and 6.3 parts of MOF@APP composite flame retardant; add the MOF@APP flame retardant to the mixture of epoxy resin and curing agent, stir until completely dispersed and uniform, degas under vacuum, and then carry out a high-temperature curing reaction. After naturally cooling to room temperature, demold to obtain epoxy resin composite material.

[0066] Example 4 The MOF@APP composite flame retardant was prepared by the following method: (1) Copper nitrate and 5-aminoterephthalic acid were dispersed in a DMF aqueous solution with a mass ratio of 1:20 at a mass ratio of 1000 g / L. The mixture was magnetically stirred at a speed of 700 rpm until the system was completely dispersed and uniform. PVP powder was added to the mixture and the concentration of PVP in the DMF aqueous solution was controlled to be 15 g / L. The mixture was continuously ultrasonically dispersed until the system was uniform and stable to obtain the MOF precursor solution.

[0067] (2) The MOF precursor solution prepared in step (1) was transferred into a high-pressure reactor, sealed, and subjected to a solvothermal reaction at a constant temperature of 90°C for 1.5 h. After the reaction was completed, the high-pressure reactor was naturally cooled to room temperature, the solid product in the reactor was collected, washed multiple times with anhydrous ethanol, and then dried under vacuum at 90°C to obtain amino-functionalized MOF nanoparticles.

[0068] (3) The entire process is carried out under nitrogen atmosphere protection: Ammonium polyphosphate is dissolved in 1,4-dioxane solvent and stirred until completely dissolved to prepare an APP solution with a concentration of 20 g / L; at the same time, the MOF nanoparticles obtained in step (2) are dispersed in 1,4-dioxane solvent and ultrasonically dispersed until the system is uniform to prepare a MOF suspension with a MOF nanoparticle concentration of 8 g / L.

[0069] (4) The entire process is carried out under nitrogen atmosphere protection: Add vinyltris(β-methoxyethoxy)silane to the MOF suspension prepared in step (3), control the concentration of vinyltris(β-methoxyethoxy)silane in the MOF suspension to 4 g / L, mix with ultrasound, and then add the prepared APP solution dropwise to the system at a constant rate under continuous ultrasound assistance. After the addition is completed, continue to stir with ultrasound until the system is homogeneous to obtain the in-situ composite reaction system.

[0070] (5) The entire process is carried out under nitrogen atmosphere protection: the above in-situ composite reaction system is transferred to an oil bath and stirred at a constant temperature of 90°C for 2 hours to obtain MOF@APP mixture; after the reaction is completed, the solid product is collected by centrifugation, washed multiple times with anhydrous ethanol and then vacuum dried to finally obtain MOF@APP composite flame retardant.

[0071] The above-mentioned MOF@APP flame retardant was used to prepare flame-retardant epoxy resin composite materials, and the specific method is as follows: Weigh the following raw materials according to the mass ratio: 100 parts of bisphenol A type epoxy resin, 33.3 parts of diaminodiphenylmethane, and 8.5 parts of MOF@APP composite flame retardant; add the MOF@APP flame retardant to the mixture of epoxy resin and curing agent, stir until completely dispersed and uniform, degas under vacuum, and then carry out a high-temperature curing reaction. After naturally cooling to room temperature, demold to obtain epoxy resin composite material.

[0072] Example 5 The MOF@APP composite flame retardant was prepared by the following method: (1) Copper nitrate and 5-aminoterephthalic acid were dispersed in a DMF aqueous solution with a mass ratio of 1:10 at a mass ratio of 1000 g / L. The mixture was magnetically stirred at a speed of 700 rpm until the system was completely dispersed and uniform. PVP powder was added to the mixture and the concentration of PVP in the DMF aqueous solution was controlled to be 20 g / L. The mixture was continuously ultrasonically dispersed until the system was uniform and stable to obtain the MOF precursor solution.

[0073] (2) The MOF precursor solution prepared in step (1) was transferred into a high-pressure reactor, sealed and subjected to a solvothermal reaction at a constant temperature of 100°C for 1 hour. After the reaction was completed, the high-pressure reactor was naturally cooled to room temperature, the solid product in the reactor was collected, washed multiple times with anhydrous ethanol, and then dried under vacuum at 100°C to obtain amino-functionalized MOF nanoparticles.

[0074] (3) The entire process is carried out under nitrogen atmosphere protection: Ammonium polyphosphate is dissolved in 1,4-dioxane solvent and stirred until completely dissolved to prepare an APP solution with a concentration of 20 g / L; at the same time, the MOF nanoparticles obtained in step (2) are dispersed in 1,4-dioxane solvent and ultrasonically dispersed until the system is uniform to prepare a MOF suspension with a MOF nanoparticle concentration of 10 g / L.

[0075] (4) The entire process is carried out under nitrogen atmosphere protection: Add vinyltris(β-methoxyethoxy)silane to the MOF suspension prepared in step (3), control the concentration of vinyltris(β-methoxyethoxy)silane in the MOF suspension to be 5 g / L, mix with ultrasound, and then add the prepared APP solution dropwise to the system at a constant rate under continuous ultrasound assistance. After the addition is completed, continue to stir with ultrasound until the system is homogeneous to obtain the in-situ composite reaction system.

[0076] (5) The entire process is carried out under nitrogen atmosphere protection: the above in-situ composite reaction system is transferred to an oil bath and stirred at 100℃ for 1 hour to obtain MOF@APP mixture; after the reaction is completed, the solid product is collected by centrifugation, washed multiple times with anhydrous ethanol and then vacuum dried to finally obtain MOF@APP composite flame retardant.

[0077] The above-mentioned MOF@APP flame retardant was used to prepare flame-retardant epoxy resin composite materials, and the specific method is as follows: Weigh the following raw materials according to the mass ratio: 100 parts of bisphenol A type epoxy resin, 33.3 parts of diaminodiphenylmethane, and 13.2 parts of MOF@APP composite flame retardant; add the MOF@APP flame retardant to the mixture of epoxy resin and curing agent, stir until completely dispersed and uniform, degas under vacuum, and then carry out a high-temperature curing reaction. After naturally cooling to room temperature, demold to obtain epoxy resin composite material.

[0078] Comparative Example 1 The specific method for preparing pure epoxy resin materials is as follows: Weigh out the raw materials according to the following mass ratio: 100 parts of bisphenol A type epoxy resin and 33.3 parts of diaminodiphenylmethane; mix and stir the epoxy resin and curing agent, degas under vacuum, and then carry out a high-temperature curing reaction. After naturally cooling to room temperature, demold to obtain epoxy resin composite material.

[0079] To verify the flame retardant properties of the epoxy resin composite material prepared in the examples, a cone calorimeter manufactured by FTT (UK) was used to test the samples, with the test radiation power set at 35 kW / m². 2 The specific testing method is as follows: Epoxy resin composite materials are made into standard test strips with dimensions of 100mm × 100mm × 3mm. After the strips cool and are demolded, the sample mass is accurately weighed and a cone calorimetry test is performed to obtain the CO yield curves of the materials. Figure 2 Total tobacco production curve () Figure 3 ) and heat release rate curve ( Figure 4 ).

[0080] Test results show that the epoxy resin composites prepared in Examples 2, 4, and 5 exhibit consistent trends in CO yield and heat release rate, and their flame retardant performance significantly improves with increasing MOF@APP composite flame retardant content. Among these, the composite material prepared in Example 5 shows the most significant improvement in flame retardant performance, with an average CO yield decrease of 25% and total smoke production (TSP) decrease of 55% compared to pure epoxy resin. These results indicate that the MOF@APP composite flame retardant can significantly reduce the release of CO and flue gas during epoxy resin combustion. This is due, on the one hand, to the PO radicals released during the thermal decomposition of APP, which can capture active hydrogen radicals in the flame region, achieving gas-phase flame retardancy; and on the other hand, to the porous metal oxide particles generated during MOF degradation during combustion, which can effectively adsorb toxic and combustible gases such as CO generated during combustion, demonstrating excellent flue gas adsorption properties.

[0081] Heat release rate (HRR) is a key indicator for assessing the thermal risk of a material's combustion. The composite material prepared in Example 5 showed a 35% reduction in peak heat release rate compared to pure epoxy resin, effectively improving its flame retardant performance. This is because the MOF component in the MOF@APP composite flame retardant efficiently catalyzes the dehydration and crosslinking of epoxy resin thermal decomposition products, promoting the formation of a dense, continuous char layer. This char layer effectively isolates heat and oxygen transfer, preventing the flame from spreading into the epoxy resin matrix, thereby significantly inhibiting the material's combustion process.

[0082] To verify the effect of MOF@APP composite flame retardant on the mechanical properties of epoxy resin matrix, the tensile strength, elongation at break and impact strength of the epoxy resin composite material samples prepared in Examples 2, 4 and 5 were tested. The test results are shown in Table 1.

[0083] Table 1. Mechanical property test results of the examples and comparative examples As shown in Table 1, the tensile strength of the pure epoxy resin material in Comparative Example 1 is approximately 69.2 MPa, the elongation at break is approximately 12.0%, and the impact strength is approximately 5.5 kJ⋅m. -2 While the mechanical properties of epoxy resin composites prepared by adding MOF@APP composite flame retardant are slightly lower than those of pure epoxy resin, and show a slight decreasing trend with increasing flame retardant content, their tensile strength remains in the range of 37.7~48.8 MPa, elongation at break remains in the range of 8.5%~10.7%, and impact strength remains in the range of 4.3~4.9 kJ⋅m. -2 The above results fully demonstrate that the MOF@APP composite flame retardant prepared in this invention, while imparting excellent flame retardant properties to epoxy resin, can retain the mechanical properties of the matrix to the greatest extent, effectively solving the technical problem of significant attenuation of the mechanical properties of epoxy resin after the addition of traditional flame retardants.

[0084] While the present invention has been disclosed above, its scope of protection is not limited thereto. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of this disclosure, and all such changes and modifications will fall within the scope of protection of this invention.

Claims

1. A method for preparing a composite flame retardant, characterized in that, Includes the following steps: S1. Disperse soluble copper salt and amino aromatic carboxylic acid ligand in DMF aqueous solution, stir evenly, add dispersant, disperse by ultrasonication, and then transfer to high pressure reactor for solvothermal reaction at 80~100℃ for 1~3h. Collect reaction product, wash and dry to obtain amino-functionalized MOF nanoparticles. S2. Dissolve ammonium polyphosphate in a polar solvent to obtain an ammonium polyphosphate solution; S3. The amino-functionalized MOF nanoparticles are ultrasonically dispersed in the same polar solvent as in step S2 to obtain a MOF suspension. S4. Add silane coupling agent to the MOF suspension, mix with ultrasound, and then add the ammonium polyphosphate solution dropwise under ultrasound assistance to obtain a reaction solution. S5. The reaction solution is reacted at 60~100℃ for 3~12h, the reaction product is collected, washed and dried to obtain MOF@APP composite flame retardant.

2. The method for preparing the composite flame retardant according to claim 1, characterized in that, In step S1, the mass ratio of the soluble copper salt to the amino aromatic carboxylic acid ligand is 1:(5~20).

3. The method for preparing the composite flame retardant according to claim 1 or 2, characterized in that, The soluble copper salt is selected from at least one of copper nitrate, copper acetate, and copper chloride; the amino-containing aromatic carboxylic acid ligand is selected from at least one of 5-aminoterephthalic acid, 2-aminoterephthalic acid, and aminoisophthalic acid; the dispersant is selected from at least one of polyvinylpyrrolidone, polyethylene glycol, and polyvinyl alcohol.

4. The method for preparing the composite flame retardant according to claim 1, characterized in that, In step S2, the concentration of the ammonium polyphosphate solution is 10~30 g / L.

5. The method for preparing the composite flame retardant according to claim 1, characterized in that, In step S3, the concentration of amino-functionalized MOF nanoparticles in the MOF suspension is 5~10 g / L.

6. The method for preparing the composite flame retardant according to claim 1, characterized in that, In step S4, the silane coupling agent is selected from at least one of vinyltriethoxysilane, vinyltrimethoxysilane, and vinyltri(β-methoxyethoxy)silane, and the concentration of the silane coupling agent in the MOF suspension is 1~5 g / L.

7. The method for preparing the composite flame retardant according to any one of claims 4-6, characterized in that, Steps S2 to S5 are performed under an inert atmosphere.

8. A composite flame retardant, characterized in that, It is prepared by the preparation method as described in any one of claims 1-7.

9. An epoxy resin composite material, characterized in that, The product comprises, by weight, the following components: 1-20 parts of the composite flame retardant as described in claim 8, 100 parts of epoxy resin, and 15-50 parts of curing agent.

10. The epoxy resin composite material according to claim 9, characterized in that, The epoxy resin is selected from at least one of bisphenol A type epoxy resin, bisphenol F type epoxy resin, phenolic epoxy resin, and alicyclic epoxy resin; the curing agent is selected from at least one of diaminodiphenylmethane, m-phenylenediamine, diethylenetriamine, triethylenetetramine, isophorone diamine, phthalic anhydride, tetrahydrophthalic anhydride, methylhexahydrophthalic anhydride, and dodecenylsuccinic anhydride.

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