A flame-retardant composite material and preparation and application thereof, and a flame-retardant epoxy resin composite material and preparation and application thereof

Abstract

This invention belongs to the field of flame-retardant epoxy resin technology, and provides a flame-retardant composite material and its preparation and application, as well as a flame-retardant epoxy resin composite material and its preparation and application. The preparation method of this invention includes: dispersing molybdenum disulfide and flake graphite in water; subjecting the resulting suspension to a first microwave treatment, a second microwave treatment, standing, and freeze-drying sequentially to obtain a flame-retardant composite material precursor; applying an ethanol solution of sodium dodecylbenzenesulfonate to the flame-retardant composite material precursor and drying it to obtain the flame-retardant composite material; the power of the first microwave treatment is 500-800W, and the time is 5-20 min; the power of the second microwave treatment is 200-260W, and the time is 1-4 min. The flame-retardant composite material obtained by this invention has excellent flame-retardant properties; when compounded with IFR, it synergistically retards the epoxy resin and improves the combustion performance of the epoxy resin.

Description

Technical Field

[0001] This invention relates to the field of flame-retardant epoxy resin technology, and more particularly to a flame-retardant composite material and its preparation and application, and a flame-retardant epoxy resin composite material and its preparation and application. Background Technology

[0002] Epoxy resin (EP) is a high molecular weight polymer with the chemical formula (C...). 11 H 12 O3) n Its molecular structure is shown in the following formula: .

[0003] Epoxy resin (EP) possesses excellent adhesive properties, bonding firmly to various materials such as metals, ceramics, and glass. It also exhibits high mechanical strength, abrasion resistance, impact resistance, electrical insulation, and chemical stability, making it widely used in numerous fields, including the electronics and electrical industries, construction, aerospace, and new energy vehicles. However, EP has a low LOI (Lack of Flammability) of only 19.8%, classifying it as a flammable material. It is highly flammable when exposed to an ignition source, potentially causing personal injury and property damage. Therefore, to improve the safety of EP applications, especially in scenarios involving high temperatures or high fire risks, it is crucial to enhance its flame-retardant properties to improve its reliability in practical use.

[0004] Adding flame retardants can effectively improve the flame retardant properties of polymeric materials (EP). Two-dimensional nanomaterials, due to their large specific surface area, good dispersibility, and low pollution, can achieve sufficient contact and stable interfacial interactions within a polymer matrix, making them excellent synergistic flame retardant materials. However, the flame retardant properties of existing two-dimensional nanomaterials need further improvement. Summary of the Invention

[0005] In view of this, the purpose of this invention is to provide a flame-retardant composite material, its preparation and application, and a flame-retardant epoxy resin composite material, its preparation and application. The flame-retardant composite material obtained by the preparation method provided by this invention has excellent flame-retardant properties.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a method for preparing a flame-retardant composite material, comprising the following steps: Molybdenum disulfide (MoS2) and flake graphite (FG) were dispersed in water, and the resulting suspension was subjected to a first microwave treatment, a second microwave treatment, standing, and freeze-drying in sequence to obtain a flame-retardant composite material precursor. An ethanol solution of sodium dodecylbenzenesulfonate (SDBS) was applied to the flame-retardant composite material precursor and dried to obtain the flame-retardant composite material. The power of the first microwave processing is 500~800W, and the time is 5~20min; The power of the second microwave processing is 200~260W, and the time is 1~4min.

[0007] Preferably, the mass ratio of molybdenum disulfide to flake graphite is 7:1 to 1:7.

[0008] Preferably, the settling temperature is room temperature, and the settling time is 12~36 hours; The freeze-drying process includes a freezing procedure and a drying procedure performed sequentially. The freezing procedure is performed at a temperature of -30 to -50°C for 12 hours, and the drying procedure is performed for 24 hours.

[0009] The present invention also provides a flame-retardant composite material obtained by the preparation method described in the above technical solution.

[0010] This invention also provides a flame-retardant epoxy resin composite material, comprising the following raw materials by weight percentage: Epoxy resin 60-90%, intumescent flame retardant (IFR) 10-40%, two-dimensional nanosheet flame retardant 1-5%; The two-dimensional nanosheet flame retardant is the flame-retardant composite material described in the above technical solution.

[0011] Preferably, the preparation method of the intumescent flame retardant includes the following steps: Ammonium polyphosphate (APP), pentaerythritol (PER), and melamine (MEL) are mixed to obtain a mixture; An ethanol solution of the silane coupling agent is applied to the mixture and allowed to evaporate naturally to obtain the intumescent flame retardant.

[0012] Preferably, the mass ratio of ammonium polyphosphate, pentaerythritol and melamine is 20~25:10~18:10~18; The silane coupling agent includes silane coupling agent A-172; The ethanol solution of the silane coupling agent has a mass concentration of 15-30%. The temperature for natural evaporation is 20~30℃, and the time is 1~2 days.

[0013] This invention also provides a method for preparing the flame-retardant epoxy resin composite material described above, comprising the following steps: After mixing epoxy resin, intumescent flame retardant and two-dimensional nanosheet flame retardant, the mixture is degassed and cured sequentially to obtain the flame-retardant epoxy resin composite material.

[0014] Preferably, the degassing is vacuum degassing, and the vacuum degassing time is 15~45 min; the curing temperature is 20~30℃, and the time is 10~24 h.

[0015] The present invention also provides the application of the flame-retardant composite material or the flame-retardant epoxy resin composite material described in the above technical solutions in the field of flame retardancy.

[0016] This invention provides a method for preparing a flame-retardant composite material. The method utilizes a two-stage microwave treatment to effectively exfoliate molybdenum disulfide (MoS2) and flake graphite (FG); followed by freeze-drying to remove excess liquid and prevent the agglomeration of nano-molybdenum disulfide (MDNs) and nano-flake graphite (FGNs). When the flame-retardant composite material of this invention is compounded with IFR, it synergistically retards epoxy resin, improving the combustion performance of the epoxy resin. The preparation method provided by this invention is simple to operate, low in cost, and environmentally friendly.

[0017] This invention also provides a flame-retardant epoxy resin composite material. The flame-retardant epoxy resin composite material provided by this invention has excellent flame-retardant properties. Attached Figure Description

[0018] Figure 1 SEM images of molybdenum disulfide (left) and flake graphite (right) before microwave treatment, scale bar is 1 μm; Figure 2 The images show the SEM and EDS spectra of MDNs / FGNs in group E12, where (a) is the SEM image of MDNs / FGNs, (b) is the EDS analysis area, (c) is the distribution of C element, and (d) is the distribution of S element. Figure 3 The TGA and DTG curves of EP / IFR / MDNs / FGNs composite materials in groups E1 to E16 are shown, where (a) and (b) are TGA curves, and (c) and (d) are DTG curves. Figure 4 The TGA and DTG curves of EP / IFR / MDNs / FGNs composite materials in groups E17~E22 are shown, where (a) and (b) are TGA curves, and (c) and (d) are DTG curves. Figure 5 Slice images of four composite material splines at different locations: EP, EP / IFR, E12, and E21. Figure 6 The DMA curves of four materials, EP, EP / IFR, E12 and E21, are shown. (a) is the E′ curve of EP and its composite material, (b) is the E′′ curve of EP and its composite material, and (c) is the Tanδ curve of EP and its composite material. Figure 7 The DSC curves are for four materials: EP, EP / IFR, E12, and E21. The left figure shows the DSC curve of the material before curing, and the right figure shows the DSC curve of the material after curing. Figure 8 SEM image of the EP section at 100x magnification; Figure 9 SEM image of the EP / IFR section at 1000x magnification; Figure 10 SEM image of section E12 at 1000x magnification; Figure 11 SEM image of section E21 at 1000x magnification; Figure 12 The figures show the thermal stability curves of four materials: EP, EP / IFR, E12, and E21. The left figure is the TGA curve, and the right figure is the DTG curve. Figure 13 HRR (left) and THR (right) curves for four materials: EP, EP / IFR, E12, and E21. Figure 14 SPR (left) and TSP (right) curves for four materials: EP, EP / IFR, E12, and E21. Figure 15 The COP (left) and CO2P (right) curves for four materials: EP, EP / IFR, E12, and E21. Figure 16 Image of charcoal residue from EP; Figure 17 Carbon residue image (left) and SEM image (right) of EP / IFR; Figure 18 The image shows the carbon residue (left) and SEM image (right) of E12. Figure 19 The image shows the carbon residue (left) and SEM image (right) of E21. Figure 20 This is a diagram illustrating the flame-retardant mechanism of the EP / IFR / MDNs / FGNs composite material. Detailed Implementation

[0019] This invention provides a method for preparing a flame-retardant composite material, comprising the following steps: Molybdenum disulfide and flake graphite were dispersed in water, and the resulting suspension was subjected to a first microwave treatment, a second microwave treatment, standing, and freeze-drying in sequence to obtain a flame-retardant composite material precursor. An ethanol solution of sodium dodecylbenzenesulfonate was applied to the flame-retardant composite material precursor and dried to obtain the flame-retardant composite material. The power of the first microwave processing is 500~800W, and the time is 5~20min; The power of the second microwave processing is 200~260W, and the time is 1~4min.

[0020] Unless otherwise specified, the raw materials used in this invention are preferably commercially available products.

[0021] In this invention, molybdenum disulfide and flake graphite are dispersed in water, and the resulting suspension is subjected to a first microwave treatment, a second microwave treatment, standing, and freeze-drying in sequence to obtain a flame-retardant composite material precursor.

[0022] In this invention, the particle size of the molybdenum disulfide is preferably 800-1200 mesh, more preferably 1000 mesh. In this invention, the particle size of the flake graphite is preferably 800-1200 mesh, more preferably 1000 mesh. In this invention, the mass ratio of molybdenum disulfide to flake graphite is preferably 7:1 to 1:7, specifically preferably 7:1, 6:2, 5:3, 3:5, 2:6, or 1:7. In this invention, the ratio of the total mass of molybdenum disulfide and flake graphite to the amount of water is preferably 0.5-15 g:100 mL, specifically preferably 2 g:100 mL. In this invention, the dispersion water is preferably ultrapure water. In this invention, the dispersion is preferably carried out under stirring conditions; the stirring speed is preferably 1000-2000 rpm, more preferably 1500 rpm; the stirring time is preferably 10-20 min, more preferably 15 min; the stirring equipment is preferably an electric stirrer equipped with shear blades. In this invention, the power of the first microwave treatment is 500-800W, preferably 500W, 600W, 700W, or 800W; the time is 5-20 minutes, preferably 5 minutes, 10 minutes, 15 minutes, or 20 minutes; the power of the first microwave treatment is preferably a constant power. After the first microwave treatment, this invention preferably further includes cooling the obtained first microwave-treated liquid to room temperature. In this invention, the power of the second microwave treatment is 200-260W, preferably 200W, 220W, 240W, or 260W; the time is 1-4 minutes, preferably 1 minute, 2 minutes, 3 minutes, or 4 minutes; the power of the second microwave treatment is preferably a constant power. After the second microwave treatment is completed, this invention preferably further includes cooling the obtained second microwave-treated liquid to room temperature. In this invention, the settling temperature is preferably room temperature, and the settling time is preferably 12-36 hours, more preferably 24 hours; the settling allows the nanosheet structure to stabilize. In this invention, the freeze-drying preferably includes a freezing process and a drying process sequentially. The freezing process is preferably performed at a temperature of -30 to -50°C, more preferably at -40°C, and for a duration of 12 hours. The drying process is preferably performed for a duration of 24 hours. In this invention, after settling, the liquid in the suspension needs to be removed. If a conventional oven drying method is used, the exfoliated nanosheets are prone to agglomeration. This invention uses freeze-drying, which can avoid the agglomeration of nanosheets.

[0023] After obtaining the flame-retardant composite material precursor, the present invention applies an ethanol solution of sodium dodecylbenzenesulfonate to the flame-retardant composite material precursor and dries it to obtain the flame-retardant composite material. In the present invention, the amount of sodium dodecylbenzenesulfonate is preferably 0.5-1.5% of the mass of the flame-retardant composite material precursor, more preferably 1%. In the present invention, the application method is preferably spraying; the spraying process preferably includes mechanical stirring; the mechanical stirring enables the sodium dodecylbenzenesulfonate to be uniformly and fully modified. In the present invention, the drying temperature is preferably room temperature, and the drying time is preferably 48 hours; the drying process enables the sodium dodecylbenzenesulfonate to uniformly cover the surface of the flame-retardant composite material precursor and fully evaporate the ethanol.

[0024] In this invention, nano-flake graphite and nano-molybdenum disulfide have similar layered structures, which can form a physical barrier during material combustion, effectively inhibiting heat source propagation and blocking the release of harmful gases. This invention uses microwave treatment to exfoliate the layers of molybdenum disulfide and flake graphite, combining them to prepare a binary synergistic flame retardant of MDNs / FGNs, which works synergistically with IFR to improve the flame retardant performance of EP. Furthermore, the microwave treatment process of this invention is simple and low-cost.

[0025] The present invention also provides a flame-retardant composite material obtained by the preparation method described above. In the present invention, the flame-retardant composite material comprises molybdenum disulfide nanoparticles (MDNs) and flake graphite nanoparticles (FGNs), and sodium dodecylbenzenesulfonate on the surface of the molybdenum disulfide nanoparticles (MDNs) and flake graphite nanoparticles (FGNs).

[0026] The present invention also provides a flame-retardant epoxy resin composite material, comprising the following raw materials in weight percentages: Epoxy resin 60-90%, intumescent flame retardant 10-40%, two-dimensional nanosheet flame retardant 1-5%; The two-dimensional nanosheet flame retardant is the flame-retardant composite material described in the above technical solution.

[0027] The raw materials for preparing the flame-retardant epoxy resin composite material provided by the present invention, by weight percentage, include 60-90% epoxy resin, preferably 60%, 65%, 70%, 75%, 80%, 85%, or 90%. In the present invention, the epoxy resin is preferably E51.

[0028] The raw materials for preparing the flame-retardant epoxy resin composite material provided by this invention, by weight percentage, include 10-40% intumescent flame retardant (IFR), preferably 10%, 15%, 18%, 20%, 25%, 30%, 35%, or 40%. In this invention, the preparation method of the intumescent flame retardant preferably includes the following steps: mixing ammonium polyphosphate, pentaerythritol, and melamine to obtain a mixture; applying an ethanol solution of a silane coupling agent onto the mixture, allowing it to evaporate naturally, to obtain the intumescent flame retardant. In this invention, the mass ratio of ammonium polyphosphate, pentaerythritol, and melamine is preferably 20-25:10-18:10-18, more preferably 23:14:13. In this invention, the silane coupling agent includes silane coupling agent A-172. In this invention, the mass concentration of the ethanol solution of the silane coupling agent is preferably 15-30%, more preferably 25%. In this invention, the amount of the silane coupling agent is preferably 0.5-1.5% of the mass of the mixture, more preferably 1%. In this invention, the application method is preferably spraying; after spraying, the invention preferably also includes mechanical stirring. In this invention, the natural evaporation temperature is preferably 20-30°C, more preferably 25°C, and the time is preferably 1-2 days, specifically 1 day. In this invention, IFR improves the flame retardant properties of epoxy resin by forming a dense char layer, while also possessing advantages such as being environmentally friendly, non-toxic, and producing low smoke.

[0029] The raw materials for preparing the flame-retardant epoxy resin composite material provided by the present invention include 1-5% by mass percentage of two-dimensional nanosheet flame retardant, preferably 2%; the two-dimensional nanosheet flame retardant is the flame-retardant composite material described in the above technical solution.

[0030] In this invention, both MDNs and FGNs have good flame retardant properties. This invention combines MDNs and FGNs for synergistic flame retardancy, and then further combines them with IFR to synergistically retard epoxy resin, thereby improving the combustion performance of epoxy resin.

[0031] This invention also provides a method for preparing the flame-retardant epoxy resin composite material described above, comprising the following steps: After mixing epoxy resin, intumescent flame retardant and two-dimensional nanosheet flame retardant, the mixture is degassed and cured sequentially to obtain the flame-retardant epoxy resin composite material.

[0032] In this invention, the degassing is preferably vacuum degassing, and the vacuum degassing time is preferably 15-45 min, specifically 15 min, 20 min, 25 min, 30 min, 35 min, 40 min, or 45 min. After degassing and before curing, this invention preferably further includes placing the obtained degassed mixture in a mold. In this invention, the curing temperature is preferably 20-30°C, and the curing time is preferably 10-24 h, more preferably 12 h.

[0033] The present invention also provides the application of the flame-retardant composite material or the flame-retardant epoxy resin composite material described in the above technical solutions in the field of flame retardancy.

[0034] The present invention does not impose specific limitations on the application of the flame-retardant composite material and the flame-retardant epoxy resin composite material, and any operation known to those skilled in the art can be used.

[0035] The following detailed descriptions, in conjunction with embodiments, illustrate the flame-retardant composite materials, their preparation and application, and the flame-retardant epoxy resin composite materials, their preparation and application. However, these descriptions should not be construed as limiting the scope of protection of this invention.

[0036] Example 1. Raw materials: Epoxy resin E51 (Hangzhou Lanquan Composite Materials Technology Co., Ltd.), molybdenum disulfide 1000 mesh (MoS2, Shijiazhuang Dongming New Materials Technology Co., Ltd.), flake graphite 1000 mesh (FG, Qingdao Pingdu Fukang Graphite Mine), silane coupling agent A-172 (Guangzhou Zhongjie Chemical Co., Ltd.), sodium dodecylbenzenesulfonate (AR, Tianjin Zhiyuan Chemical Reagent Co., Ltd.), anhydrous ethanol (AR, Guangdong Guangshi Reagent Technology Co., Ltd.).

[0037] 2. Material Preparation 2.1 Preparation of MDNs / FGNs under different microwave processing techniques First, MoS2 and FG were added to 400 mL of ultrapure water at a 1:1 mass ratio (total mass 8 g). The mixture was stirred at 1500 rpm for 15 min using an electric stirrer equipped with shear blades to ensure uniform dispersion and form a suspension. Then, the suspension was placed in a microwave reactor for two-stage microwave heating treatment. Specific microwave process parameters are shown in Table 1. In the first microwave treatment stage, the suspension was microwave-heated at a specific constant power for a period of time, followed by natural cooling to room temperature. In the second microwave treatment stage, the suspension was microwave-heated again at another constant power for a period of time, followed by standing at room temperature for 24 h. Afterward, the suspension was frozen in a -40°C freezer for 12 h to ensure complete freezing, and then freeze-dried in a vacuum freeze dryer for 24 h to obtain the flame-retardant composite material precursor. After thoroughly mixing SDBS with anhydrous ethanol, the resulting SDBS ethanol solution was uniformly sprayed onto the surface of the flame-retardant composite precursor. The amount of SDBS used was 1% of the mass of the flame-retardant composite precursor. The mixture was dried at room temperature for 48 hours to allow the modifier to uniformly cover the sample surface and fully volatilize, ultimately yielding a surface-modified MDNs / FGNs synergistic flame retardant, i.e., a flame-retardant composite material, denoted as MDNs / FGNs.

[0038] Table 1 Microwave Processing Parameters

[0039] In Table 1, "Power 1" represents the power of the first microwave processing, "Time 1" represents the time of the first microwave processing, "Power 2" represents the power of the second microwave processing, and "Time 2" represents the time of the second microwave processing.

[0040] 2.2 Preparation of MDNs / FGNs at different mass ratios A mixture of 8 g of MoS2 and FG (with the mass ratio of MoS2 to FG as shown in Table 2) was added to 400 mL of ultrapure water and stirred at 1500 rpm for 15 min using an electric stirrer to ensure uniform dispersion and form a suspension. The suspension was then placed in a microwave reactor for a two-stage microwave heating treatment. In the first microwave treatment stage, the suspension was heated at a constant power of 600 W for 20 min, followed by natural cooling to room temperature. In the second microwave treatment stage, the suspension was heated at a constant power of 260 W for 2 min, followed by standing at room temperature for 24 h. The suspension was then frozen in a freezer at -40°C for 12 h to ensure complete freezing, and then freeze-dried in a vacuum freeze dryer for 24 h to obtain the flame-retardant composite material precursor. After thoroughly mixing SDBS with anhydrous ethanol, the resulting SDBS ethanol solution was uniformly sprayed onto the surface of the flame-retardant composite precursor. The amount of SDBS used was 1% of the mass of the flame-retardant composite precursor. The mixture was dried at room temperature for 48 hours to allow the modifier to uniformly cover the sample surface and fully volatilize, ultimately yielding surface-modified MDNs / FGNs synergistic flame retardants with different component ratios, i.e., flame-retardant composite materials, denoted as MDNs / FGNs.

[0041] Table 2 Mass ratio of MoS2 to FG

[0042] 2.3 Preparation of EP / IFR / MDNs / FGNs composite materials Ammonium polyphosphate, pentaerythritol, and melamine were mechanically mixed in a mass ratio of 23:14:13 to form a mixture. Anhydrous ethanol and silane coupling agent A-172 were prepared in a mass ratio of 3:1 and sprayed onto the mixture. The amount of silane coupling agent A-172 was 1% of the mass of the mixture. The mixture was left to evaporate naturally at 25°C for 1 day to obtain an intumescent flame retardant (IFR).

[0043] Weigh out EP, IFR, and MDNs / FGNs according to the component ratios shown in Table 3. After mechanically mixing them evenly, place them in a vacuum degassing machine for 20 minutes for vacuum degassing. Pour the degassed mixture into a mold coated with a release agent and cure at room temperature for 12 hours. After curing, demold the sample to obtain the final EP / IFR / MDNs / FGNs composite material sample.

[0044] Table 3 Raw material ratio

[0045] 3. Characterization and Analysis Methods (1) Scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) SEM (Sequencing Electron Microscopy) scans the sample surface using a focused high-energy electron beam. The electrons interact with the sample surface, generating signals such as secondary electrons and backscattered electrons. These signals are collected and used to generate high-resolution images of the sample, revealing the microscopic morphology of the sample surface. EDS (Energy Dispersive Spectroscopy) is an energy-dispersive X-ray analysis technique used in conjunction with SEM. When the electron beam bombards the sample, it excites the atoms within the sample, causing their inner-shell electrons to transition and emit characteristic X-rays. Different elements emit characteristic X-rays with specific energies, and EDS determines the elemental composition of the sample by detecting these X-rays.

[0046] The microstructure of the powder before and after microwave exfoliation was characterized using SEM. First, conductive adhesive was attached to a fixed disk, then an appropriate amount of powder was evenly distributed on the surface of the conductive adhesive and sputtered with gold. Observation was performed using SE2 mode, with the operating voltage set from 1 to 10 kV. Elemental analysis of the powder was then conducted using X-ray energy dispersive spectroscopy.

[0047] After undergoing brittle fracture treatment in liquid nitrogen, the samples were placed with the fractured surface facing upwards on a fixed disk, secured with conductive adhesive, and then sputter-coated with gold to allow for observation of the fracture morphology. All samples were observed using SE2 mode, with operating voltages set from 1 to 10 kV.

[0048] (2) Thermogravimetric analysis (TGA) Thermal geometry analysis (TGA) is a technique that measures the change in mass of a material as a function of temperature or time during heating. By recording the mass-temperature change curve of a sample as a function of temperature, it studies the thermal decomposition behavior and thermal stability of the material within a specific temperature range. The TGA curve reflects the relationship between sample mass and temperature, while the DTG curve reflects the rate of mass change as a function of temperature, and is used to identify the temperature range and decomposition stage of the material. This experiment uses TGA to compare the differences in thermal stability of different materials by analyzing their mass changes during heating, thereby selecting the optimal microwave process and the optimal component ratio.

[0049] The mass of the test sample was 10 mg (±0.5 mg), and the test was conducted under a nitrogen atmosphere. The sample heating rate was set to 10 °C / min, and the temperature range was set to 30 °C to 800 °C.

[0050] (3) Industrial carbonization effect (CT) Industrial CT is a non-destructive testing tool based on X-ray tomography technology. It is widely used in the industrial field to detect and analyze defects, structures, and compositions inside various materials, parts, and complex structures.

[0051] To ensure the stability of the sample during scanning, it was fixed in foam and the ends were secured with tape to prevent vibration or displacement during the scanning process. The sample was then scanned using an industrial CT scanner to observe internal defects and the distribution of flame retardant. The scanning voltage was set to 80kV, the scanning current to 400μA, the resolution to 47μm, and the number of projections to 1440.

[0052] (4) Dynamic thermomechanical analysis (DMA) Dynamic mechanical properties (DMA) are a technique used to study the mechanical properties of materials under different temperatures, frequencies, and strain conditions. DMA testing allows us to obtain the relationship between a material's storage modulus, loss modulus, and loss factor as a function of temperature, thereby evaluating the material's elastic, viscoelastic, and rheological properties. This experiment aims to evaluate the dynamic mechanical properties of a material in the temperature range of 40℃ to 105℃ using DMA testing, and to analyze the changes in its storage modulus, loss modulus, and loss factor with temperature.

[0053] The test sample measures 35mm × 13mm × 4mm, with a smooth surface and no cracks. The test was conducted in air, with a heating rate of 5℃ / min, a temperature range of 40℃ to 105℃, a single cantilever beam fixture, a test frequency of 1Hz, and an amplitude of 30μm.

[0054] (5) Differential scanning calorimetry (DSC) DSC (Disseminated Scaling) is an analytical technique used to determine the thermal properties and phase transition behavior of materials. By measuring the difference in heat flow between a sample and a reference material during temperature changes, information about the thermodynamic properties and physical changes of the material can be obtained. This experiment aims to evaluate the degree of curing completion of the material by testing the total heat of reaction and residual heat of curing of the sample using DSC. The test results can be used to optimize the curing process parameters or screen the optimal material formulation to improve the material's performance. The formula for calculating the degree of curing is as follows: (1); In the formula, The degree of curing is %; The total heat of reaction during the curing process of the thermosetting resin is expressed in J / g. The residual heat of curing during the curing process of thermosetting resin, in J / g.

[0055] The mass of the test sample was 10 mg (±0.5 mg), and the sample was uniformly distributed in the crucible. The test was conducted under a nitrogen atmosphere, with a heating rate set at 5 °C / min and a temperature range of 10 °C to 185 °C.

[0056] (6) Comprehensive flame retardant performance test Limiting oxygen index test: The test shall be conducted in accordance with the standard GB / T2406.2-2009, and the sample size shall be 100mm×6mm×4mm.

[0057] Horizontal and vertical combustion test: The test shall be conducted in accordance with the standard GB / T2408-2021, and the sample size shall be 125mm×13mm×4mm.

[0058] Cone calorimetry test: The test was conducted in accordance with ISO 5660-1:2015 standard, and the sample size was 100mm×100mm×4mm.

[0059] The char layer after combustion was evenly distributed on the surface of the conductive adhesive and then sputtered with gold to observe the morphology of the residual char. All samples were observed using SE2 mode with voltage settings ranging from 1 to 10 kV.

[0060] 4. Results and Analysis 4.1 Microstructure and Energy Dispersive Spectrum Analysis of MDNs / FGNs The microstructure and elemental distribution of MoS2 and FG before and after microwave exfoliation were observed using SEM and EDS to evaluate the exfoliation effect. The exfoliation effect was mainly judged by characteristics such as reduced lamellar stacking, increased porosity, and uniformity of elemental distribution. Results are shown in [Figure number missing]. Figure 1 and Figure 2 .from Figure 1 The left image shows that the MoS2 sheets are stacked or aggregated; from Figure 1 The right image shows that the FG lamellae have irregular shapes and are tightly packed together, forming an agglomeration similar to a sphere.

[0061] Figure 2 SEM and EDS spectra of MDNs / FGNs in group E12 are shown. Figure 2 As can be seen in (a), MDNs and FGNs are uniformly distributed, and the layers are not tightly stacked together. EDS spectrum ( Figure 2 (b)~(d) show that carbon and sulfur elements are present in MDNs / FGNs, and the element distribution is relatively uniform. During microwave heating, gas pressure is generated between the MoS2 and FG sheets in the liquid phase. When the gas pressure exceeds the van der Waals force between the sheets, the gaps between the sheets gradually increase, thereby achieving the peeling effect. After peeling, the stacking phenomenon between the sheets is effectively reduced.

[0062] 4.2 Effect of microwave process on the thermal stability of EP / IFR / MDNs / FGNs composite materials Sixteen EP / IFR / MDNs / FGNs composite materials prepared using different microwave processes were prepared by compounding MDNs / FGNs synergistic flame retardants with IFR and then adding them to EP. The TGA and DTG curves of these composite materials are shown in the figure. Figure 3 As shown, the thermal stability data are shown in Table 4.

[0063] from Figure 3 As can be seen, the TGA curves of all 16 composite materials exhibit a one-stage thermal degradation trend. Within the temperature range of 30℃ to 200℃, the TGA curves of all composite materials are approximately parallel to the horizontal axis, showing no significant thermal weight loss, indicating high thermal stability of the materials within this temperature range. Within the temperature range of 200℃ to 300℃, the curves gradually slope and slowly decrease, indicating that the composite materials begin to experience thermal weight loss. This is because the APP in the IFR begins to decompose, causing a slight bulge in the DTG curve; however, no substantial thermal degradation has occurred in the composite materials at this stage.

[0064] Within the temperature range of 300℃ to 500℃, the TGA curves showed a steep downward trend, indicating that the composite material had entered the main thermal degradation stage. The DTG curves exhibited a bimodal structure, and the bimodal curves of the 16 composite materials did not completely overlap, indicating differences in the thermal degradation rate and peak temperature among the different composite materials. As shown in Table 4, the peak temperature ranged from 366.99℃ to 436.71℃. Within the temperature range of 500℃ to 800℃, the TGA curves tended to be parallel, indicating that the thermal degradation reaction of the composite material was basically completed. The char content (C) of the composite material... r The differences indicate that microwave process parameters affect the charring ability of the synergistic flame retardant system, thus causing partial deviations in the curves. Overall, all TGA curves exhibit a consistent inverted S-shaped trend, indicating that the thermal degradation process of the materials follows similar thermogravimetric laws. Next, using the data in Table 4, we will further compare and analyze the differences among the 16 groups of composite materials and select the group with the best thermal stability.

[0065] Table 4 Thermal stability data of EP / IFR / MDNs / FGNs composite materials in EP and EP-1 to E1-E16 groups

[0066] Table 4 lists the thermal stability data of EP and 16 groups of EP / IFR / MDNs / FGNs composites processed with different microwave processes, including T 5% V max T max and C r T 5% This is the temperature at which the material's mass decreases to 95%; a higher value indicates better initial thermal stability of the material.max This represents the maximum thermal decomposition rate of the material. A smaller value indicates a slower thermal decomposition, which helps improve the material's thermal stability. max This is the temperature at which a material reaches its maximum decomposition rate; a higher value indicates better thermal stability. C r It is the amount of carbide residue after the material is burned, C r A higher value indicates better thermal stability of the material. The overall thermal stability of a material is determined by four indicators, with V being the most important. max and T max The performance, while also taking into account C r The improvement.

[0067] As shown in Table 4, after using MDNs / FGNs and IFR for synergistic flame retardancy, the T values ​​of each composite material are... 5% All were earlier than expected. Among them, the T of sample E11 was earlier than expected. 5% The most significant advance was observed at 241.96℃. In V max In terms of decomposition rate, E12 had the lowest rate at 0.538%℃. -1 This indicates that its decomposition is slower, which helps to suppress the rapid thermal decomposition of EP. At T max In terms of thermal stability, E8 performed best, with its maximum decomposition rate corresponding to a temperature of 436.71℃, indicating a higher peak decomposition temperature and outstanding thermal stability. In C... r In terms of C, E9 r The highest percentage was 17.20%, indicating that it left the most non-flammable residue after combustion and has high thermal stability.

[0068] Comprehensive analysis revealed that E12 in V max and C r Its performance on the V is relatively good. max Minimum (0.538% ℃) -1 This indicates that the material decomposes at its slowest rate, which helps to delay the thermal decomposition of the material; meanwhile, the C of E12 r Reaching 15.83%, close to the highest level, further enhancing the material's thermal stability. Although E8's T... max The highest (436.71℃), but its V max Relatively large (0.648% ℃) -1 The decomposition rate was relatively fast. Therefore, it was ultimately concluded that the MDNs / FGNs prepared using the 12th group of microwave processes had the best synergistic flame retardant effect with IFR, meaning that sample E12 had the best overall thermal stability.

[0069] 4.3 Effect of component ratio on the thermal stability of EP / IFR / MDNs / FGNs composites Six EP / IFR / MDNs / FGNs composite materials with different component ratios were prepared by compounding MDNs / FGNs synergistic flame retardants with IFR using the optimal microwave process and then adding them to EP. The TGA and DTG curves of these composite materials are shown in the figure. Figure 4 As shown. From Figure 4 As can be seen, the TGA curves of all six composite materials exhibit a one-stage thermal degradation trend. Within the temperature range of 30℃ to 200℃, the TGA curves of all composite materials are approximately parallel to the horizontal axis, showing no significant thermal weight loss, indicating high thermal stability within this temperature range. Within the temperature range of 200℃ to 300℃, the curves gradually slope and slowly decrease, indicating that the composite materials begin to experience thermal weight loss. This is also because the APP in the IFR begins to decompose, causing a slight bulge in the DTG curve, but at this stage, the composite materials do not undergo substantial thermal degradation.

[0070] Within the temperature range of 300℃ to 500℃, the TGA curves of the six composite materials showed a sharp drop, indicating that the composite materials had entered the main thermal degradation stage. The DTG curves also exhibited a bimodal structure, and the bimodal curves of the six composite materials did not completely overlap, indicating that the composition ratio of MDNs / FGNs had a certain influence on the thermal degradation behavior of the composite materials. Within the temperature range of 500℃ to 800℃, the TGA curves tended to stabilize, indicating that the thermal degradation reaction of the composite materials was basically completed, but the C6 of the six composite materials... r Differences also exist. This indicates that the composition ratio of MDNs / FGNs not only affects the thermal degradation rate of the composite material, but also the formation efficiency of the char layer and the amount of residual char. Next, using the data in Table 5, we will further compare and analyze the differences among the six groups of composite materials and select the group with the best thermal stability.

[0071] Table 5 lists the thermal stability data of EP and EP / IFR / MDNs / FGNs composites with six different MDNs / FGNs ratios. The composite material with the best thermal stability was selected according to the method described in 3.2. 5% The temperature values, from lowest to highest, are 230.77℃ (E18), 241.13℃ (E19), and 241.26℃ (E22). V max The values, from smallest to largest, are 0.530%℃. -1 (E21), 0.548% ℃ -1 (E19) and 0.554% ℃ -1 (E18). T max The values, from highest to lowest, are 439.29℃ (E18), 438.44℃ (E20), and 364.39℃ (E21). C rThe values, from highest to lowest, are 16.76% (E21), 16.69% (E20), and 15.79% (E17). Comprehensive analysis reveals that T in E21... max and C r All are at a high level, and V max The lowest value indicates good thermal stability. Therefore, it is concluded that the EP / IFR / MDNs / FGNs composite material has the best overall thermal stability when the composition ratio of MDNs to FGNs is 2:6.

[0072] Table 5 Thermal stability data of EP / IFR / MDNs / FGNs composites in groups EP and E17~E22

[0073] 4.4 Three-dimensional scanning analysis of EP / IFR / MDNs / FGNs composite materials Figure 5 Slice images at different locations of four composite material splines: EP, EP / IFR, E12, and E21. Figure 5 As shown in (a), the internal structure of EP is intact, without common internal defects such as bubbles, cracks, or pores. This structural integrity indicates that the EP material has high density, effectively reducing stress concentration caused by internal defects, thereby improving the material's mechanical properties and service life. This also suggests that the EP preparation method is suitable, avoiding factors that may lead to defects during the molding process, such as uneven mixing or insufficient curing.

[0074] from Figure 5 As shown in (b), (c), and (d), the internal structures of the EP / IFR, E12, and E21 composite material specimens also maintained high integrity, with no obvious defects such as bubbles, cracks, or pores. This indicates that the structural quality of the composite material was not adversely affected by the addition of flame retardants after the addition of IFR and MDNs / FGNs. Furthermore, IFR and MDNs / FGNs showed good dispersion in the EP matrix. The uniform dispersion of the flame retardants ensured the formation of a stable char layer structure in the composite material under high-temperature conditions, improving the strength and integrity of the char layer, preventing heat diffusion, and contributing to enhanced thermal stability and flame retardant properties of the composite material.

[0075] 4.5 Mechanical property analysis of EP / IFR / MDNs / FGNs composite materials Figure 6 DMA curves for four materials, EP, EP / IFR, E12 and E21, are shown in Table 6. DMA data for EP and its composites are also listed in Table 6.

[0076] Storage modulus (E′) represents the stiffness of a material, reflecting its elastic performance. From... Figure 6 As shown in (a), the E′ of all four materials decreases with increasing temperature. In the glassy temperature range, the E′ of the four materials, from highest to lowest, are E12, E21, EP / IFR, and EP. The E′ of E12 and E21 is 45.22% and 43.83% higher than that of EP, respectively, and 13.45% and 12.36% higher than that of EP / IFR, respectively. The increase in E′ is mainly due to the inter-atom sp atoms in MDNs / FGNs. 2 The strong covalent bonds formed by hybridization, and the rigid microstructure constructed by the strong covalent bonds between molybdenum and sulfur atoms.

[0077] The loss modulus (E′′) represents the damping characteristics of a material, reflecting its viscous properties, and its magnitude is usually directly related to the material's ability to absorb vibrational energy. Figure 6 As can be seen in (b), the E′′ of all four materials shows a decreasing trend at a high level as the temperature increases. This indicates that the materials exhibit better viscous response in the lower temperature range. However, as the temperature increases, the thermal motion of the molecular chains intensifies, the viscous properties gradually weaken, and E′′ decreases accordingly.

[0078] The E′′ values ​​of the four materials at 40℃, from highest to lowest, are E12, E21, EP / IFR, and EP. The E′′ value of EP / IFR is 11.46% higher than that of pure EP, while E12 and E21 are increased by 45.83% and 40.63%, respectively. This indicates that the addition of IFR and MDNs / FGNs can improve the viscous response of the composite material, giving it stronger damping characteristics. MDNs / FGNs, through their high rigidity structure and excellent interfacial bonding ability, can effectively restrict the movement of EP molecular chains, while improving energy absorption and conversion efficiency.

[0079] Glass transition temperature (T) g This reflects the temperature range from the glassy state to the elastic state of a material. Typically, T... g This can be determined by the peak position of the loss factor (Tanδ) curve. From Figure 6 As can be seen in (c), compared with pure EP, the Tanδ peaks of E12 and E21 shift towards lower temperatures, indicating that their T g It was brought forward somewhat.

[0080] This is due to changes in the movement of molecular chains within the material. The addition of flame retardants affects the spatial structure of EP molecular chains. MDNs / FGNs embed into the EP molecular chains, restricting the free movement of some molecular chains, leading to a reduction in the density of local crosslinking points, and thus shrinking the intermolecular interaction space of EP. This change weakens the rigidity of the EP molecular chains, resulting in T... gIt occurs earlier. For E12 and E21, although their T... g The value is earlier than EP, but its glass transition temperature range is wider. This indicates that both materials exhibit good damping performance over a wide temperature range. Generally speaking, the higher the peak value of Tanδ, the greater the internal friction of the material; while the wider the transition temperature range, the larger the temperature range at which the material can absorb and dissipate vibrational energy. Therefore, E21 has better vibration reduction and noise reduction effects in terms of damping performance.

[0081] Table 6 DMA data for EP and its composite materials

[0082] 4.6 Analysis of Curing Performance of EP / IFR / MDNs / FGNs Composites Figure 7 DSC curves for four materials—EP, EP / IFR, E12, and E21—are presented, and the DSC data are summarized in Table 7. From... Figure 7 As shown in the left figure, the curves of the four materials exhibit consistent patterns, all displaying a distinct exothermic peak. With the addition of IFR and MDNs / FGNs, the exothermic peaks of EP / IFR and EP / IFR / MDNs / FGNs composites are flatter than those of pure EP, with slightly lower peak intensity and a broader peak shape. Table 7 shows that the total heat of reaction of the materials decreases with the addition of IFR and MDNs / FGNs. This is because the added IFR and MDNs / FGNs hinder the release of the heat of reaction in the composite materials, thus reducing the total heat of reaction.

[0083] from Figure 7 As shown in the right figure of the cured DSC curves, all four curves are close to straight lines, with only a weak exothermic peak appearing in the temperature range of 110℃ to 150℃, indicating that the residual heat of reaction after curing is low and the system has basically reached complete curing. According to formula (1), the crosslinking degrees of the four materials are 89.91%, 87.42%, 88.71%, and 87.25%, respectively. It can be found that after adding IFR and MDNs / FGNs, the crosslinking degree of the composite material is reduced compared with pure EP, but the magnitude is small, indicating that the added IFR and MDNs / FGNs have no significant effect on the crosslinking reaction between epoxy groups and hydroxyl groups. Among them, the crosslinking degree of E21 decreased the most, decreasing by 2.96% compared with pure EP. This is because E21 has a high FGNs content. FGNs exist in the form of sheets, occupying part of the volume of reactants in the matrix, forming a physical barrier, and restricting the migration and contact of reactants during the curing process. In addition, the lamellar FGNs increase the viscosity of the system, weakening the thorough mixing and diffusion between the curing agent and the EP matrix, thereby leading to a decrease in the degree of curing crosslinking.

[0084] Table 7 DSC data of EP and its composites

[0085] 4.7 Cross-sectional analysis of EP / IFR / MDNs / FGNs composite materials Figure 8 This is a SEM image of the EP section at 100x magnification. From... Figure 8 As can be seen, the fracture morphology of EP exhibits a grid-like structure, with rapid crack propagation, demonstrating typical brittle fracture characteristics.

[0086] Figure 9 This is a SEM image of the EP / IFR section at 1000x magnification. From... Figure 9 As can be seen, compared with EP, the fracture surface of EP / IFR no longer exhibits a distinct grid-like structure, but rather a rougher surface with a more complex crack morphology, demonstrating characteristics of ductile fracture. Blocky IFR particles can be observed in the fracture surface, indicating a certain degree of incompatibility between EP and IFR.

[0087] Figure 10 This is a SEM image of section E12 at 1000x magnification. Figure 11 The image shows a SEM image of section E21 at 1000x magnification. Figure 10 and Figure 11 As can be seen, the fracture morphology of both materials is similar to that of EP / IFR, exhibiting a rough fracture surface and complex crack morphology, demonstrating ductile fracture characteristics. However, compared to EP / IFR, the particulate matter in the EP / IFR / MDNs / FGNs composite material is more uniformly distributed and exhibits better dispersion, distributed around the EP matrix.

[0088] The uniform dispersion of MDNs / FGNs is mainly attributed to the effect of SDBS, which improves the dispersion state of MDNs / FGNs and enhances their interfacial bonding with the EP matrix. MDNs slow crack propagation through a lubrication effect, thereby improving the plasticity and ductility of the composite material; FGNs enhance the strength and rigidity of the composite material and inhibit crack propagation, thus improving its toughness. The synergistic effect of both enhances the energy absorption capacity of the composite material under stress, creating an interfacial barrier effect, which further improves the toughening properties of the composite material.

[0089] 4.8 Thermal stability analysis of EP / IFR / MDNs / FGNs composite materials Figure 12 The thermal stability curves of four materials—EP, EP / IFR, E12, and E21—are presented, and the thermal stability data are summarized in Table 8. Figure 12 As shown in the left figure, the thermal decomposition curves of all four materials exhibit an inverted S-shape, demonstrating a similar one-stage thermal degradation trend. This indicates that the main structure of EP did not change significantly after the addition of IFR and MDNs / FGNs. Within the temperature range of 30℃ to 200℃, the curves of all four materials are approximately parallel to the horizontal axis, showing no significant downward trend, indicating that no significant thermal degradation reaction occurred within this temperature range.

[0090] Within the temperature range of 200℃ to 300℃, the curves for the four materials begin to slope and slowly decrease, indicating that a certain degree of thermal degradation has occurred at this stage. According to... Figure 12 As shown in the DTG curves on the right, EP / IFR, E12, and E21 all exhibit bulging peaks in the 200℃ to 300℃ range. This is because within this temperature range, APP in IFR decomposes to generate polyphosphoric acid. Polyphosphoric acid, acting as a dehydrating agent, reacts with the hydroxyl groups in the EP molecular chain to undergo denitrification and dehydration, subsequently forming acid ester compounds. These compounds then form a protective carbonized layer on the material surface, thus inhibiting further decomposition of EP. Meanwhile, the peak values ​​of E12 and E21 are reduced by 31.77% and 20.02%, respectively, compared to EP / IFR. This is because MDNs / FGNs establish a certain degree of connection with the EP molecular chain, restricting the movement of some EP molecular chains, thereby further enhancing the protection of EP on top of IFR.

[0091] Within the temperature range of 300℃ to 500℃, the TGA curves of all four materials showed a significant steep decline trend, indicating a marked increase in the weight loss rate compared to the gradual decline phase in the 200℃ to 300℃ range. This suggests that EP has entered the main thermal degradation stage at this point. Figure 12 The DTG curve shown in the right figure has two mass loss rate peaks within this temperature range, which correspond to two different thermal decomposition stages of EP.

[0092] Within the temperature range of 300℃ to 400℃, the DTG curve shows the first relatively high peak in mass loss rate. This stage of thermal degradation is mainly related to the decomposition of aliphatic segments in the EP (epoxygenated polymer). Saturated carbon atoms in the carbon chain structure begin to break within this temperature range, leading to the destruction of the main chain and the generation of small-molecule volatile products, such as acetone and other low-molecular-weight gases. This process primarily involves unstable aliphatic structures, resulting in a rapid decomposition rate, hence the significant peak in mass loss rate on the DTG curve.

[0093] Within the temperature range of 400℃ to 500℃, a second, lower peak in the mass loss rate appears on the DTG curve. This stage is primarily characterized by the cyclization reaction of the vinyl and ether groups in the EP molecule, gradually forming a thermally stable aromatic structure, accompanied by the formation of a char layer on the material surface. As the temperature further increases, this char layer decomposes at high temperatures, releasing gases such as carbon monoxide and carbon dioxide, thus leading to the second peak. Because the decomposition rate of the char layer is relatively slow, this peak is lower than the first.

[0094] Compared to EP, EP / IFR, E12, and E21 all showed reduced peak mass loss rates in the 400°C to 500°C temperature range. This is primarily due to the decomposition of phosphorus groups in IFR to produce acids within the 300°C to 400°C temperature range, which promotes the dehydration, degradation, and carbonization of EP, thereby generating a heat-resistant carbonaceous layer. This carbonaceous layer slows down the mass loss rate of the material in the 400°C to 500°C temperature range and further enhances its flame-retardant effect by forming a highly cross-linked aromatic char layer.

[0095] Within a temperature range of 500℃ to 800℃, the thermal degradation curves of all four materials were approximately parallel to the horizontal axis, indicating that the thermal decomposition process had essentially ended and the materials had entered the char layer combustion stage. Due to the high-temperature resistance of MDNs / FGNs, which enhances the heat resistance of the char layer, the Cr content of E12 and E21 increased by 20.84% ​​and 27.94% respectively compared to EP / IFR. In conclusion, E12 and E21 exhibit superior thermal stability compared to EP / IFR.

[0096] Table 8 Thermal stability data of EP and its composites

[0097] The overall thermal stability coefficients (OSE) of EP / IFR, E12, and E21 can be obtained by integrating the area under the curve (AUC) of the mass loss rate as a function of temperature in the TGA curve. A positive OSE value indicates that the composite material has better thermal stability than the matrix material, while a negative OSE value indicates that the added flame retardant reduces the thermal stability of the matrix material. The formula for calculating OSE is as follows: (2); In the formula, The overall thermal stability coefficient is % For composite materials at temperature Percentage of mass at time, % For EP at temperature The percentage of mass at that time, %.

[0098] The OSE values ​​of the three materials EP / IFR, E12, and E21, calculated according to formula (2), are 1227.10, 2703.87, and 2594.49, respectively, all of which are positive. This indicates that the thermal stability of the three composite materials is significantly improved compared with the matrix material EP. Among them, the OSE values ​​of E12 and E21 are 120.3% and 111.4% higher than those of EP / IFR, respectively. This significant improvement in thermal stability is mainly due to the catalytic carbonization effect of MDNs and the carbon-reinforcing effect of FGNs during combustion, which promotes the formation of carbon layers during combustion and stabilizes the carbon layer structure at high temperatures, effectively inhibiting further decomposition of the carbon layer, thereby significantly improving the thermal stability of the composite materials.

[0099] 4.9 Limiting oxygen index and horizontal / vertical combustion analysis of EP / IFR / MDNs / FGNs composite materials The Limiting Oxygen Index (LOI) test is an important method for characterizing the flame retardant properties of materials; the higher the LOI value, the less flammable the material. According to classification, LOI < 22 is flammable, 22 ≤ LOI ≤ 27 is combustible, and LOI > 27 is flame-retardant. Table 9 shows that EP has an LOI value of 21.7%, classifying it as flammable; EP / IFR has an LOI value of 26.7%, also classifying it as flammable, but approaching the level of flame-retardant materials; E12 and E21 both have LOI values ​​of 33%, indicating they have reached the level of flame-retardant materials. UL-94 is used to evaluate the flame spread performance and flammability rating of materials during combustion, with flammability ratings from low to high as HB, V-2, V-1, and V-0. Table 9 shows that EP failed the rating test, EP / IFR reached the V-1 rating, and E12 and E21 both reached the V-0 rating. This indicates that the flame retardant properties of the EP / IFR / MDNs / FGNs composite material are improved by adding MDNs / FGNs and IFR for synergistic flame retardancy.

[0100] Table 9. LOI and UL-94 test results of EP and its composites.

[0101] 4.10 Cone-shaped calorimetric analysis of EP / IFR / MDNs / FGNs composite materials Cone calorimetry, based on the principle of oxygen consumption, can measure various indicators of materials during combustion, such as heat release rate (HRR), total heat release (THR), smoke release rate (SPR), total smoke release rate (TSR), total smoke release (TSP), carbon monoxide release (COP), and carbon dioxide release (CO2P). These data can be used to simulate the combustion of materials in real fires and analyze their heat release performance, smoke release performance, and harmful gas release performance.

[0102] Figure 13 The graphs show the HRR (left) and THR (right) curves for four materials: EP, EP / IFR, E12, and E21. From... Figure 13 As shown in the left figure and Table 10, the HRR curve of EP has only one combustion exothermic phase. After ignition, the HRR rises rapidly and reaches the peak heat release rate (pHRR) at 98 s, with a value of 1315.90 kW / m³. 2 EP / IFR, E12, and E21 all exhibit two combustion exothermic phases, with the first phase lasting from 0 s to 450 s. The pHRR of EP / IFR is 234.76 kW / m³. 2 It appeared 198 s after ignition; the pHRR for E12 and E21 were 207.10 kW / m³, respectively. 2 and 202.32kW / m 2 The HRR values ​​were reached at 323 s and 266 s after ignition, respectively. The HRR curves for EP / IFR, E12, and E21 showed a slow increase of varying magnitude after 450 s, and then gradually decreased after the second stage until combustion ended. Figure 13 As shown in the right figure and Table 10, the THR curves of EP / IFR, E12, and E21 all show a slow upward trend, with combustion times of 1345s, 1464s, and 1668s, respectively. Among them, the THR value of E21 decreases to 86.77 MJ / m³. 2 It reduced by 16.95 MJ / m compared to EP / IFR. 2 As can be seen from Table 10, the average mass loss rate (AMLR) of EP, EP / IFR, E12 and E21 are 0.158 g / s, 0.034 g / s, 0.035 g / s and 0.025 g / s, respectively.

[0103] The pHRR of EP / IFR was reduced by 82.16% compared to EP, while the pHRR of E12 and E21 was reduced by 11.78% and 13.82% respectively compared to EP / IFR. This reduction is mainly due to the catalytic char formation of MDNs in E12 and E21, which promotes the formation of a char layer rather than volatile combustible gases during the decomposition of the composite material at high temperatures, thereby reducing the intensity of the combustion reaction and effectively lowering the pHRR. The combustion time of E21 was extended by 323 s compared to EP / IFR, indicating that when the composition ratio of MDNs to FGNs is 2:6, the synergistic effect with IFR is more effective in prolonging the combustion process of the composite material.

[0104] Table 10 Conical calorimetric properties of EP and its composites

[0105] To further compare the heat release performance of the composite materials, the calculated av-HRR for EP / IFR, E12, and E21 were 66.30 kW / m². 2 62.79kW / m 2 and 44.98kW / m 2 Compared to EP / IFR, E12 and E21 showed reductions of 5.29% and 32.16%, respectively. This reduction is primarily due to the layered structure of MDNs / FGNs hindering heat transfer during combustion, and the high thermal stability of MDNs / FGNs also helps slow down heat transfer and prevent further heat diffusion. The combustion times of E12 and E21 were extended by 119 s and 323 s, respectively, compared to EP / IFR. Although the combustion time of E21 was extended, its total heat release did not increase, reflecting the good flame suppression effect of the MDNs / FGNs synergistic flame retardant system. Furthermore, the AMLR of E12 and E21 was reduced by 77.85% and 84.18%, respectively, compared to EP, indicating that the MDNs / FGNs synergistic flame retardant system can significantly delay the mass loss of materials during combustion.

[0106] In terms of heat release performance, when the composition ratio of MDNs to FGNs is 2:6, the E21 composite material exhibits better synergistic flame retardant effect. Compared with EP / IFR, the average heat release rate (av-HRR) of E21 is reduced by 32.16%, the THR is reduced by 16.34%, and the combustion time is extended by 323 s. This indicates that the system can effectively extend the combustion time of the composite material and reduce the total heat release, further inhibiting heat diffusion and the formation of volatile combustibles. The ratio of pHRR to the time required to reach the peak value (FIGRA) is a parameter used to characterize the fire development rate; the smaller the value, the lower the fire hazard. As shown in Table 10, the FIGRA of EP and EP / IFR are 13.43 kW·m. -2 / s and 4.17kW·m -2 / s, E12 and E21 were reduced by 11.69% and 16.70% respectively compared with EP / IFR. This indicates that the addition of MDNs / FGNs in synergistic flame retardancy with IFR can effectively slow down the spread of flames and reduce fire hazard.

[0107] Figure 14 The graphs show the SPR (left) and TSP (right) curves for four materials: EP, EP / IFR, E12, and E21. From... Figure 14 As can be seen in the left figure, the SPR curve of EP has only one stage, reaching a maximum value of 0.383m at 106s. 2 / s. Subsequently, the SPR curve rapidly decreased and stabilized between 293s and 646s until the smoke release ended. For the three composite materials EP / IFR, E12, and E21, their SPR curves were divided into two stages. In the first stage, the SPR curves of the three materials slowly increased after the smoke began to form, reaching their first-stage peaks at 244s, 299s, and 243s, respectively, with peak values ​​of 0.074m. 2 / s, 0.056m 2 / s and 0.054m 2 / s. Afterwards, the SPR curves rapidly decreased, with the first stage ending at 488s, 526s, and 391s, respectively. In the second stage, the peak values ​​of the SPR curves for all three materials were lower than in the first stage, reaching their peak values ​​at 589s, 600s, and 464s, with values ​​of 0.022m. 2 / s, 0.014m 2 / s and 0.013m 2 / s, while the end times of the second stage are 1270s, 1048s and 832s respectively.

[0108] from Figure 14 As shown in the right-hand figure, the TSP curve of EP exhibits a sharp linear upward trend, reaching a maximum value of 34.70m at 370s. 2 The TSP curves then stabilized until smoke release ceased at 646 s. In contrast, the TSP curves of the EP / IFR, E12, and E21 composite materials showed a slower upward trend, reaching their maximum values ​​at 1206 s, 1012 s, and 812 s, respectively, with maximum values ​​of 26.81 m. 2 22.18m 2 and 16.94m 2 The TSP curve then stabilizes until the smoke release ends.

[0109] In terms of smoke release performance, the EP / IFR, E12, and E21 composite materials all exhibited two peaks to varying degrees. Specifically, the maximum SPR (smoke release rate) in the first stage of E12 and E21 was reduced by 24.32% and 27.03%, respectively, compared to EP / IFR. Furthermore, the TSP (smoke release propagation) curves of E12 and E21 were generally lower than those of EP / IFR, with their maximum TSP values ​​decreasing by 17.27% and 36.81%, respectively, while their TSR values ​​decreased by 17.27% and 36.91%, respectively. This indicates that when the MDNs and FGNs composition ratio is 2:6, the synergistic flame retardant system is most effective in reducing smoke generation and propagation efficiency. FGNs play a major role in this flame retardant system, effectively reducing smoke generation during combustion, while MDNs, through a synergistic effect, help FGNs maintain a relatively intact layered structure.

[0110] Figure 15 The graphs show the COP (left) and CO2P (right) curves for four materials: EP, EP / IFR, E12, and E21. From... Figure 15 As shown in the left figure, the COP curve of EP has only one stage, reaching a peak CO release of 0.0149 g / s at 99 s. In contrast, the COP curves of EP / IFR and E21 both show two stages. The first stage time ranges are 0 s to 534 s and 0 s to 426 s, respectively, reaching peak values ​​of 0.0095 g / s and 0.0071 g / s at 265 s and 274 s, respectively. The peak CO release of E21 is 25.26% lower than that of EP / IFR. The second stage time ranges are 534 s to 753 s and 426 s to 791 s, with peak values ​​of 0.0008 g / s and 0.0004 g / s, respectively. E21 further reduces the peak CO release by 50% compared to EP / IFR. The COP curve of E12 shows three stages, with time ranges of 172s to 236s, 254s to 310s, and 310s to 369s, respectively, and peak values ​​of 0.0014g / s, 0.00137g / s, and 0.0018g / s, respectively. The overall CO release rate is significantly lower than that of EP and EP / IFR.

[0111] from Figure 15 As shown in the right figure, the CO2P curve of EP has only one stage, reaching a peak CO2 release of 0.57 g / s at 100 s. The CO2P curves of EP / IFR and E21 both exhibit two stages. The first stage has time ranges of 0 s to 533 s and 0 s to 483 s, with peak values ​​of 0.1139 g / s and 0.1006 g / s, respectively. E21 shows a 11.68% reduction compared to EP / IFR. The second stage has time ranges of 533 s to 1251 s and 483 s to 962 s, with peak values ​​of 0.0364 g / s and 0.0333 g / s, respectively. E2 shows a further 8.52% reduction compared to EP / IFR. The CO2P curve of E12 is nearly flat, with a peak of 0.008 g / s only at 589 s, and an overall fluctuation range between 0.003 g / s and 0.008 g / s, significantly lower than the other three materials.

[0112] In terms of harmful gas release performance, E12 and E21 are more effective than EP / IFR in suppressing CO and CO2 release, with E12 showing the best effect. In the COP curves, the peak CO release of E12 and E21 is reduced by 81.05% and 25.26% respectively compared to EP / IFR; in the CO2P curves, this reduction is 92.98% and 11.68% respectively. When the composition ratio of MDNs and FGNs is 1:1, the synergistic flame retardant system exhibits the most significant inhibitory effect on harmful gas release. FGNs enhance the char layer effect, forming a barrier layer during combustion and reducing the gas exchange rate. Simultaneously, MDNs further enhance the flame retardant effect by generating sulfur dioxide and molybdenum dioxide, reducing the oxygen concentration during composite combustion.

[0113] In summary, the MDNs / FGNs synergistic flame retardant system can effectively reduce the heat release rate, smoke release rate, and harmful gas release rate of EP / IFR / MDNs / FGNs composite materials. Firstly, after MDNs / FGNs are added to EP, cross-linking occurs between them and the EP molecular chains, restricting the free movement of some molecular chains. After APP dehydrates and chars, MDNs promote the rapid formation of the char layer through catalytic char formation, while FGNs further enhance the stability of the char layer due to their layered structure and high-temperature stability. This stable char layer not only improves the char residue of EP but also effectively blocks heat conduction and smoke propagation during combustion. The sulfur dioxide and molybdenum dioxide generated by MDNs during combustion can dilute the oxygen concentration during combustion, slowing down the reaction of EP with combustible free radicals such as hydrogen and hydroxyl radicals, thereby reducing the total heat release. When the ratio of MDNs to FGNs is 1:1, the MDNs / FGNs have a better effect on inhibiting smoke propagation than on inhibiting heat propagation; when the ratio is 2:6, the ideal effect on both smoke and heat propagation can be achieved simultaneously.

[0114] Brehme et al. and Wang et al. proposed a method for quantitatively evaluating cone calorimetry results to more comprehensively explain the flame-retardant mechanism of flame retardants. They divided the effects of flame retardants into three aspects: flame suppression effect (FIE), charring effect (CE), and char-derived protective barrier effect (BAPE). FIE occurs in the gas phase, mainly referring to the flame retardant's ability to slow down the combustion rate by inhibiting free radical reactions, diluting oxygen concentration, or blocking combustible gases. CE and BAPE occur in the condensed phase; CE refers to the flame retardant's ability to increase char yield by promoting charring, thereby reducing heat release; BAPE reflects the char layer's ability to isolate heat and smoke propagation and its protective capacity against the matrix. The specific calculation formulas are as follows: (3); In the formula, The effective heat of combustion of the composite material is expressed in MJ / kg. The effective heat of combustion of EP is MJ / kg.

[0115] (4); In the formula, The average mass loss rate of the composite material is expressed in g / s. Let be the average mass loss rate of EP, in g / s.

[0116] (5); In the formula, The peak heat release rate of the composite material is expressed in KW / m. 2 ; The peak heat release rate of EP, KW / m 2 ; The total heat release of the composite material, in MJ / m 2 ; The total heat release of EP, in MJ / m 2 .

[0117] The calculation results for EP / IFR, E12, and E21 are shown in Table 11. As can be seen from Table 11, compared with EP / IFR, the FIE values ​​of E12 and E21 increased by 13.70% and 12.35%, respectively. This is because the phosphorus released by APP in IFR during combustion reacts with the hydrogen and hydroxyl radicals generated during EP combustion, thereby inhibiting the combustion reaction. Furthermore, the sulfur in MDNs generates smoke-suppressing substances such as molybdenum dioxide and sulfur trioxide during combustion, which not only reduces smoke production but also enhances the synergistic flame-retardant effect in the gas phase by diluting combustible gases and radical concentrations. The CE values ​​of E12 and E21 increased by 14.04% and 34.14% compared to EP / IFR, respectively. The carbon in FGNs helps to strengthen and stabilize the char layer during combustion, improving its protective function. Furthermore, the BAPE value of E21 is similar to that of EP / IFR, while the BAPE value of E12 is 4.58% higher than that of EP / IFR. This indicates that when the MDNs to FGNs composition ratio is 1:1, the carbon layer generated by the EP / IFR / MDNs / FGNs composite material has stronger protective ability in the flame.

[0118] Table 11 Quantitative analysis results of the flame retardant synergistic effect of EP / IFR, E12 and E21 composite materials

[0119] 4.11 Morphology analysis of residual carbon in EP / IFR / MDNs / FGNs composite materials Figure 16Images of charcoal residue from EP, from Figure 16 It can be seen that the char residue of EP after combustion is almost completely decomposed, which is clearly visible at the bottom of the container, indicating that pure EP has poor flame retardant properties.

[0120] Figure 17 Carbon residue image (left) and SEM image (right) of EP / IFR; Figure 18 The image shows the carbon residue (left) and SEM image (right) of E12. Figure 19 The image shows the carbon residue (left) and SEM image (right) of E21. From Figures 17-19 It can be seen that all three composite materials formed an expanded carbon layer. This expanded carbon layer effectively insulates against external heat sources and inhibits the contact between flammable gases and oxygen produced during combustion, thus protecting the matrix. Figure 17 As can be seen, the microstructure of the char layer in EP / IFR is relatively loose, with unevenly distributed and numerous pores, and obvious cracks on the surface. This structure results in poor pyrolysis resistance of the char layer, making it easily permeable by oxygen under high-temperature combustion conditions, thereby accelerating the decomposition and degradation of the material and limiting its flame-retardant properties.

[0121] from Figure 18 As can be seen, the char layer structure of E12 is improved compared to EP / IFR. The number of pores is significantly reduced, the overall density is greater, surface cracks are significantly reduced, and closed pores are formed. These closed pores effectively inhibit the spread of heat and smoke during combustion, while also preventing external oxygen from entering and reacting with EP in the gas phase. This indicates that when the composition ratio of MDNs and FGNs is 1:1, the composite material can generate a more stable char layer during combustion. The dense and stable char layer not only better blocks oxygen penetration and heat transfer under high-temperature conditions but also maintains its integrity, effectively slowing down the degradation rate of the material and thus improving its flame-retardant performance.

[0122] from Figure 19 As can be seen, E21, like E12, forms closed pores. However, the carbon layer of E21 is further improved in terms of density and uniformity, while the number of pores is reduced, cracks are almost completely eliminated, and the overall structure of the carbon layer is uniform and dense. This complete and tough carbon layer can provide a stronger barrier effect under high temperature conditions, effectively preventing the penetration of oxygen and heat, thereby significantly enhancing the flame retardant properties of the composite material.

[0123] In summary, compared with EP / IFR, E21 and E12 exhibit a more complete and denser char layer structure. The addition of MDNs / FGNs, in synergistic flame retardancy with IFR, plays a significant role in the formation and structural optimization of the char layer. When the ratio of MDNs to FGNs is 2:6, the expanded char layer generated during combustion demonstrates superior thermal stability and flame retardant performance.

[0124] 4.12 Flame retardant mechanism analysis of EP / IFR / MDNs / FGNs composite materials Compared to pure EP and EP / IFR, the EP / IFR / MDNs / FGNs composite material exhibits superior flame retardant properties. This performance improvement primarily relies on a multi-layered synergistic flame retardant mechanism involving both the condensed and gaseous phases, as detailed in [link to article]. Figure 20 .

[0125] The initial carbonization stage occurs at temperatures below 300℃. The EP matrix begins to pyrolyze, breaking chemical bonds such as carbon-oxygen bonds, carbon-hydrogen bonds, and carbon-carbon bonds, generating small molecule compounds and free radicals. Simultaneously, APP in the IFR decomposes to generate polyphosphoric acid, which reacts with the hydroxyl groups in the EP to initially form a carbonized layer. This carbonized layer lays the foundation for subsequent expansion and protection.

[0126] The expansion and charring stage occurs between 300℃ and 500℃. The pyrolysis of the EP matrix intensifies further, releasing more volatile gases and reactive free radicals such as hydrogen and hydroxyl radicals. At this stage, the polyphosphoric acid generated from the decomposition of APP in the IFR promotes the carbonization of PER and simultaneously acts as a catalytic catalyst for charring by MDNs / FGNs, forming a carbon-rich char layer. Furthermore, non-combustible gases such as ammonia and nitrogen produced from the decomposition of MEL drive the expansion of the char layer, forming a protective barrier that provides both thermal and oxygen insulation. Simultaneously, amino radicals can capture reactive free radicals in the combustion chain reaction, effectively inhibiting flame propagation.

[0127] At temperatures above 500℃, a stable protective phase is reached, during which the expanded char layer becomes denser and more stable. The layered structure of MDNs / FGNs constructs an efficient barrier network, limiting the diffusion of heat and volatile products, further enhancing the thermal insulation performance of the char layer. Simultaneously, the carbon elements in MDNs / FGNs form a dense char layer at high temperatures, further improving the flame-retardant properties of the condensed phase. In the gas phase, the sulfur elements in MDNs / FGNs decompose to generate sulfur dioxide and molybdenum dioxide, which further suppress flame propagation by physically diluting the oxygen concentration and chemically inhibiting free radical reactions in the flame. Furthermore, the thermal stability and mechanical strength of MDNs / FGNs also contribute to improving the integrity and strength of the expanded char layer at high temperatures.

[0128] The technical solution provided by this invention has the following characteristics and advantages: (1) By simultaneously stripping MoS2 and FG using 16 microwave processes, the optimal microwave stripping process parameters were selected as follows: the first microwave power was 600W, and the duration was 20min; the second microwave power was 260W, and the duration was 2min. Under these optimal microwave process conditions, the optimal composition ratio of MDNs and FGNs was 2:6. SEM observation revealed that the stripped MDNs / FGNs exhibited a layered microstructure with significantly reduced interlayer stacking, achieving a relatively ideal stripping effect.

[0129] (2) Thermogravimetric analysis showed that the EP / IFR / MDNs / FGNs composites treated with different microwave processes exhibited significant differences in thermal stability. Among them, the E12 and E21 composites showed the best thermal stability. The V12 composite showed the best thermal stability. max Compared to other microwave-processed composite materials, C reduced by 2.18% to 33.62%. r The V of the E21 composite material increased by 0.25% to 29.34%. max Compared to composites with other component ratios, C decreased by 3.28% to 29.24%. r It increased by 0.42% to 8.97%.

[0130] (3) Industrial CT tests show that the EP, EP / IFR and EP / IFR / MDNs / FGNs composite materials all exhibit good internal structural integrity and no defects such as bubbles, cracks and pores are found, indicating that the material preparation process is appropriate and ensures high density and uniformity.

[0131] (4) DMA tests showed that the damping performance of the EP composite material was significantly improved after the addition of MDNs / FGNs. The storage modulus of the E12 and E21 composite materials at room temperature was increased by 45.22% and 43.83% respectively compared with pure EP. When the composition ratio of MDNs to FGNs was 2:6, the composite material had better vibration reduction and noise reduction performance.

[0132] (5) DSC test showed that the crosslinking degree of the composite material was slightly lower than that of EP after adding IFR and MDNs / FGNs, but the overall effect on the crosslinking degree of EP matrix was not significant. The crosslinking degrees of EP, EP / IFR, E12 and E21 were 89.91%, 87.42%, 88.71% and 87.25%, respectively.

[0133] (6) SEM tests of the material cross sections showed that EP exhibited typical brittle fracture characteristics, while EP / IFR and EP / IFR / MDNs / FGNs composites exhibited ductile fracture characteristics. MDNs slowed crack propagation through a lubrication effect, thereby improving the plasticity and ductility of the composite material, while FGNs improved the toughness of the composite material by enhancing its strength and rigidity and inhibiting crack propagation.

[0134] (7) Limiting oxygen index (LOI) test results show that the EP / IFR / MDNs / FGNs composite material meets the standard for flame-retardant materials. Horizontal and vertical combustion test results show that the EP / IFR / MDNs / FGNs composite material reaches the V-0 level. Cone calorimetry test results show that the heat release performance and smoke release performance of the E21 composite material are significantly improved compared with EP / IFR, with av-HRR and pHRR reduced by 32.16% and 13.82% respectively, SPR, TSP and TSR reduced by 27.03%, 36.81% and 36.91% respectively, and the combustion time extended by 323s. The E12 composite material performs even better in terms of harmful gas release performance.

[0135] (8) SEM analysis of the char residue of the composite material showed that the char layer structure of EP / IFR was loose, with many pores and obvious cracks, resulting in limited flame retardant effect. In contrast, the char layer structure of E12 composite material was denser, with significantly reduced pores and cracks, and significantly improved flame retardant performance; while the char layer structure of E21 composite material was further optimized, showing uniform density, with almost no pores and cracks, and the best flame retardant effect. The synergistic flame retardant effect of MDNs / FGNs and IFR significantly improved the stability and flame retardant performance of the char layer structure of the composite material, especially when the ratio of MDNs to FGNs was 2:6, the synergistic flame retardant effect with IFR was the best.

[0136] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a flame-retardant composite material, characterized in that, Includes the following steps: Molybdenum disulfide and flake graphite were dispersed in water, and the resulting suspension was subjected to a first microwave treatment, a second microwave treatment, standing, and freeze-drying in sequence to obtain a flame-retardant composite material precursor. An ethanol solution of sodium dodecylbenzenesulfonate was applied to the flame-retardant composite material precursor and dried to obtain the flame-retardant composite material. The power of the first microwave processing is 500~800W, and the time is 5~20min; The power of the second microwave processing is 200~260W, and the time is 1~4min.

2. The preparation method according to claim 1, characterized in that, The mass ratio of molybdenum disulfide to flake graphite is 7:1 to 1:

7.

3. The preparation method according to claim 1, characterized in that, The settling temperature is room temperature, and the time is 12~36h; The freeze-drying process includes a freezing procedure and a drying procedure performed sequentially. The freezing procedure is performed at a temperature of -30 to -50°C for 12 hours, and the drying procedure is performed for 24 hours.

4. The flame-retardant composite material obtained by the preparation method according to any one of claims 1 to 3.

5. A flame-retardant epoxy resin composite material, characterized in that, The raw materials include the following percentage by weight: Epoxy resin 60-90%, intumescent flame retardant 10-40%, two-dimensional nanosheet flame retardant 1-5%; The two-dimensional nanosheet flame retardant is the flame-retardant composite material described in claim 4.

6. The flame-retardant epoxy resin composite material according to claim 5, characterized in that, The preparation method of the intumescent flame retardant includes the following steps: Ammonium polyphosphate, pentaerythritol and melamine are mixed to obtain a mixture; An ethanol solution of the silane coupling agent is applied to the mixture and allowed to evaporate naturally to obtain the intumescent flame retardant.

7. The flame-retardant epoxy resin composite material according to claim 6, characterized in that, The mass ratio of ammonium polyphosphate, pentaerythritol and melamine is 20~25:10~18:10~18; The silane coupling agent includes silane coupling agent A-172; The ethanol solution of the silane coupling agent has a mass concentration of 15-30%. The temperature for natural evaporation is 20~30℃, and the time is 1~2 days.

8. The method for preparing the flame-retardant epoxy resin composite material according to any one of claims 5 to 7, characterized in that, Includes the following steps: After mixing epoxy resin, intumescent flame retardant and two-dimensional nanosheet flame retardant, the mixture is degassed and cured sequentially to obtain the flame-retardant epoxy resin composite material.

9. The preparation method according to claim 8, characterized in that, The degassing is performed under vacuum, and the vacuum degassing time is 15~45 min; the curing temperature is 20~30℃, and the time is 10~24 h.

10. The application of the flame-retardant composite material according to claim 4 and the flame-retardant epoxy resin composite material according to any one of claims 5 to 7 in the field of flame retardancy.

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