Heat-resistant high-strength phenolic resin composite material and preparation method thereof

Abstract

The invention discloses a heat-resistant high-strength phenolic resin composite material and a preparation method thereof. The heat-resistant high-strength phenolic resin composite material is prepared from cardanol modified phenolic resin and a fluorinated graphene nano material, a fluorine atom and a carbon atom in the fluorinated graphene are covalently bonded to form a C-F bond; the cardanol modified phenolic resin is prepared from the following raw materials: phenolic substances and formaldehyde; the phenolic substances comprise phenol and cardanol; when the total mass of the phenolic substances is 100%, the mass ratio of the cardanol is 5%-15%; the mass ratio of the fluorinated graphene is 0.1%-0.5% by taking the total mass of the phenolic substances as 100%. The preparation method of the heat-resistant high-strength phenolic resin composite material comprises the following steps: uniformly mixing ethanol dispersion liquid containing fluorinated graphene with cardanol modified phenolic resin by ultrasonic waves to obtain the heat-resistant high-strength phenolic resin composite material.

Description

Technical Field

[0001] The present invention relates to the technical field of phenolic resin composite materials, and in particular to a heat-resistant high-strength phenolic resin composite material and a preparation method thereof. Background Art

[0002] Advanced rail transit equipment is the primary vehicle for transportation infrastructure and belongs to the high-end equipment manufacturing industry. Within this field, we must accelerate the application of new materials, technologies, and processes, focusing on breakthroughs in systematic safety assurance, energy conservation and environmental protection, and digital, intelligent, and networked technologies, developing advanced, reliable, and applicable products as well as lightweight, modular, and systematic products. The motor system is the core component for achieving electromechanical energy conversion in rail transit vehicles, and the carbon brushes within the motor system are a crucial component, serving as the sliding contact for conducting and importing current. They possess excellent electrical, thermal, and lubricating properties, along with mechanical strength and commutation sparking capabilities. Phenolic composite materials, with their excellent strength, heat resistance, moisture resistance, and dimensional stability, help improve rotary breaking strength and reduce inter-blade step differences, thereby reducing noise and carbon brush wear. Furthermore, their excellent formability makes them a fundamental raw material for carbon brushes.

[0003] Phenolic resins are a class of polymers formed by the condensation of phenol and aldehyde under alkaline or acidic catalysts. Their abundant polar groups and unique network structure provide phenolic composites with excellent properties, including low cost, easy processing, strong plasticity, heat resistance, wear resistance, corrosion resistance, excellent mechanical properties, and strong adhesion. This has led to their widespread application in aerospace, automotive, and building materials fields. Phenolic resins fundamentally determine the ultimate performance of phenolic composites, so the key to developing high-performance, heat-resistant, and high-strength phenolic composites lies in improving their properties through various physical and chemical modifications. The presence of numerous rotationally restricted methylene bridges and rigid benzene rings in pure phenolic resins results in poor mechanical properties. Furthermore, their thermal stability is insufficient to support their use in more extreme environments, limiting their application areas. Therefore, modification of phenolic resins is inevitable and a growing trend. Nanomaterial-modified phenolic resins are an emerging composite material. The introduction of nanomaterials into phenolic resins can effectively improve their fracture toughness and impact resistance. Graphene and carbon nanotubes can also enhance thermal stability, thereby improving the heat resistance of phenolic resins. We noticed that fluorinated graphene is a material that introduces highly electronegative fluorine atoms on the basis of graphene. By doping this substance into the resin matrix, the mechanical properties and thermal stability can be effectively improved.

[0004] Fluorinated graphene (FG) is a graphene derivative formed by covalently bonding F atoms to a graphene matrix. Thanks to the high bond energy of the C-F bond (486 kJ / mol) and the inherent properties of graphene, FG exhibits high thermal stability, mechanical strength, hydrophobicity, and low electrical conductivity. Therefore, it is an ideal nanomaterial for applications such as corrosion-resistant and waterproof coatings, insulation materials, and lubricants. The high bond energy and stability of fluorine atoms give FG enhanced thermal properties. Adding FG to a resin matrix can effectively mitigate its thermal degradation process, contributing to improved thermal stability. To obtain FG, graphene fluorination and mechanical and liquid-phase exfoliation of fluorinated graphite are typically used to obtain a single layer of FG. Graphite fluoride is produced by introducing fluorine atoms into the graphite structure through methods such as direct fluorination, plasma fluorination, electrochemical fluorination, and chemical vapor deposition (CVD), forming C-F bonds. Graphene fluoride is then exfoliated mechanically or chemically to form graphene fluoride. For example, Yin Huang et al. (HUANG Y, HE Y, FAN X, et al. Ionic liquid functionalized fluorinated graphene toward excellent anti-wear filler into epoxy coating[J]. Carbon, 2025, 234) used ionic liquid 1-hexadecyl-3-methylimidazolium bromide to intercalate graphene fluoride to produce fluorinated graphene nanosheets. However, in practice, the number of exfoliated layers is difficult to precisely control, resulting in a multilayer structure and uneven fluorine distribution between layers, which can affect material properties. By directly fluorinating a single layer of graphene, single-layer fluorinated graphene can be obtained, allowing for precise control of the fluorine content and distribution, thereby adjusting its electronic structure and physicochemical properties. Cardanol is a natural phenol extracted from cashew nut shell liquid. Its molecular structure consists of a phenolic ring with a 15-carbon alkyl side chain located at the meta position. The degree of saturation of this side chain varies and may be fully saturated or contain one to three unsaturated bonds (double bonds). The structural changes caused by the addition of cardanol may affect the thermal and mechanical properties of the resin matrix. The introduction of long side chains can reduce the crosslink density of the phenolic resin, reduce the brittleness of the resin matrix, and improve its impact resistance.

[0005] Therefore, based on the above research background, this study used ammonium fluoride NH4F and graphene oxide GO to synthesize fluorinated graphene FG-NH4F by covalent bonding in thermal synthesis, and combined it with cardanol with its own flexible long chain to prepare fluorinated graphene / cardanol modified phenolic resin to improve the performance of phenolic resin. Summary of the Invention

[0006] The present invention provides a heat-resistant and high-strength phenolic resin composite material and a preparation method thereof. Cardanol is a bio-based material whose long carbon chain structure effectively improves the brittleness of the phenolic resin and increases the flexibility of the phenolic resin. The nanomaterial fluorinated graphene not only compensates for the decrease in thermal performance caused by the addition of cardanol, but also further improves the mechanical strength of the composite material.

[0007] The specific technical solutions are as follows: In a first aspect, the present invention provides a heat-resistant and high-strength phenolic resin composite material, the raw materials of which include cardanol-modified phenolic resin and fluorinated graphene nanomaterial; the fluorine atoms in the fluorinated graphene are covalently bonded to carbon atoms to form CF bonds; The raw materials of the cardanol-modified phenolic resin include phenolic substances and formaldehyde; The phenolic substances include phenol and cardanol; Based on the total mass of the phenolic substances as 100%, the mass proportion of the cardanol is 5% to 15%, preferably 10% to 15%; Based on the total mass of the phenolic substance being 100%, the mass proportion of the fluorinated graphene is 0.1% to 0.5%, preferably 0.25% to 0.5%.

[0008] The preparation method of the cardanol-modified phenolic resin preferably comprises: in the presence of a catalyst, reacting phenol and formaldehyde for a period of time, and then adding cardanol to continue the reaction to obtain the cardanol-modified phenolic resin.

[0009] In the method for preparing the cardanol-modified phenolic resin, the catalyst preferably includes sodium hydroxide.

[0010] In the preparation method of the cardanol-modified phenolic resin, the amount of the catalyst used is preferably 1% to 3% of the total mass of the phenolic substance, such as 2%.

[0011] In the method for preparing the cardanol-modified phenolic resin, the reaction is preferably carried out in water.

[0012] In the method for preparing the cardanol-modified phenolic resin, the reaction temperature of phenol and formaldehyde is preferably 65-75° C., such as 70° C.

[0013] In some preferred examples, in the method for preparing the cardanol-modified phenolic resin, after adding cardanol, the reaction is first carried out at 65-75°C (for example, 70°C), and then the temperature is raised to 85-95°C (for example, 90°C) for reaction.

[0014] The elemental composition of the fluorinated graphene is preferably 61% to 63% carbon, 29% to 31% oxygen, 3% to 4% fluorine, and 3% to 4% nitrogen, based on atomic ratio, and more preferably 62.2% carbon, 30.3% oxygen, 3.8% fluorine, and 3.7% nitrogen.

[0015] The method for preparing the fluorinated graphene preferably adopts a hydrothermal method. Furthermore, the method for preparing the fluorinated graphene preferably comprises: heating an aqueous dispersion containing graphene oxide and ammonium fluoride in a sealed environment to react to obtain the fluorinated graphene.

[0016] In the method for preparing fluorinated graphene, in the aqueous dispersion containing graphene oxide and ammonium fluoride, the mass ratio of graphene oxide to ammonium fluoride is preferably 1:2.5-3.5, for example, 1:3.

[0017] In the method for preparing fluorinated graphene, the temperature of the heating reaction is preferably 135-145° C., for example, 140° C.

[0018] In the method for preparing fluorinated graphene, the heating reaction time is preferably 20 to 28 hours, such as 24 hours.

[0019] The flexural strength of the heat-resistant high-strength phenolic resin composite material of the present invention is greater than 55 MPa, further greater than 60 MPa, and further greater than 65 MPa.

[0020] The tensile strength of the heat-resistant high-strength phenolic resin composite material of the present invention is greater than 40 MPa, further greater than 45 MPa, and further not less than 55 MPa.

[0021] The heat-resistant high-strength phenolic resin composite material of the present invention has a residual carbon rate of more than 58% at 800°C and a thermal decomposition temperature of more than 470°C.

[0022] In a second aspect, the present invention provides a method for preparing the heat-resistant and high-strength phenolic resin composite material described in the first aspect, which can be prepared by physical blending, specifically comprising: ultrasonically mixing the ethanol dispersion containing the fluorinated graphene with the cardanol-modified phenolic resin to obtain the heat-resistant and high-strength phenolic resin composite material.

[0023] Compared with the prior art, the present invention has the following beneficial effects: Based on the total mass of the phenolic compounds as 100%, when the addition amounts of cardanol and fluorinated graphene were 10% and 0.5%, respectively, the flexural strength and tensile strength of the composite material reached 67 MPa and 55 MPa, respectively, representing increases of 39.5% and 44.7% compared to traditional phenolic resin. Although the introduction of cardanol resulted in a decrease in the carbon residue rate and thermal decomposition temperature by 14.6% and 98°C, respectively, the synergistic modification with fluorinated graphene improved the thermal stability to a carbon residue rate of 58.1% at 800°C and a thermal decomposition temperature of 473°C, maintaining the excellent heat resistance of the phenolic resin composite. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 Figures 1 and 2 show the mechanical properties test results of the resin matrix and phenolic resin composite material in Example 5, wherein: (a) shows the effect of different amounts of cardanol addition on the bending strength (Bending Strength) and tensile strength (Tensile Strength) of phenolic resin; (b) shows the effect of different amounts of fluorinated graphene addition on the bending strength and tensile strength of cardanol-modified phenolic resin.

[0025] Figure 2 Figures 1 and 2 are the test results of the mechanical properties of the resin matrix and the phenolic resin composite material in Example 5, wherein: (a1), (b1), and (c1) have the same scale; (a1) and (a2) are scanning electron microscope (SEM) photos and actual photos of the cross section of the resin matrix with 0% cardanol addition, respectively; (b1) and (b2) are SEM photos and actual photos of the cross section of the resin matrix with 10% cardanol addition, respectively; (c1) and (c2) are SEM photos and actual photos of the cross section of the phenolic resin composite material with 10% cardanol addition and 0.5% fluorinated graphene addition, respectively.

[0026] Figure 3 Figures 1 and 2 show the thermal stability test results of the resin matrix and the phenolic resin composite material in Example 5, where: (a) is a thermogravimetric (TG) graph; (b) is a differential thermogravimetric (DTG) curve; the label "Phenolic resin" in the figure indicates a resin matrix with 0% cardanol addition, "Cashew phenolic resin" indicates a resin matrix with 10% cardanol addition, and "PRC-FG" indicates a phenolic resin composite material with 10% cardanol addition and 0.5% fluorinated graphene addition. DETAILED DESCRIPTION

[0027] The present invention will be further described below with reference to the accompanying drawings and specific examples. It should be understood that these examples are only used to illustrate the present invention and are not intended to limit the scope of the present invention.

[0028] In the following examples, the operating methods without specifying specific conditions are generally carried out under conventional conditions or conditions recommended by the manufacturer.

[0029] Example 1: Fluorinated graphene (FG) was prepared by pyrolyzing a fluorinated precursor. 1 g of graphene oxide (GO) and 3 g of ammonium fluoride (NH₄F) were uniformly dispersed in 100 mL of deionized water by ultrasonication for 30 min. The dispersion was then placed at 140°C in a sealed tube for 24 h. During this reaction, the ammonium fluoride decomposed at high temperature to produce fluoride. The fluorine atoms then covalently bonded with carbon atoms in GO, forming C₂F bonds, yielding an FG suspension. The resulting suspension was filtered, washed multiple times with deionized water to remove unreacted NH₄F, and dried in an oven at 80°C for 24 h to obtain the final product, fluorinated graphene (FG-NH₄F or FG). Elemental atomic ratio analysis revealed 62.2% C, 30.3% O, 3.8% F, and 3.7% N.

[0030] X-ray diffraction (XRD) characterization. The XRD spectrum of the sample was obtained by X-ray powder diffractometer under Cu target Kα radiation, with an angle of 5°~80° and a step size of 0.04°. The XRD test results show that compared with reduced graphene oxide (rGO), the fluorinated graphene treated with NH4F has a new peak at 17.6° (corresponding to an interlayer spacing of 5.04Å), indicating that F - The successful introduction of graphene and the expansion of graphene interlayer spacing.

[0031] Raman characterization. The samples were characterized using a Raman spectrometer with an excitation wavelength of 532 nm, a power of 2.5 mW, an exposure time of 10 s, and a wavenumber range of 100–3000 cm -1 Raman spectroscopy showed that the introduction of fluorine atoms formed C—F covalent bonds on the carbon skeleton, significantly increasing the sp 3 Hybrid structures and structural defects lead to a further decrease in the orderliness of graphene sheets.

[0032] X-ray Photoelectron Spectroscopy (XPS) Characterization. The samples were characterized using an Al Kα light source, a 400 μm spot diameter, an energy step size of 1 eV, and a range of 0–1350 eV. Fitting of the F 1s spectrum revealed a primary peak at approximately 688.5 eV, further confirming that fluorine exists primarily as covalent C–F bonds rather than as inorganic fluorides. The O 1s spectrum still contains a small number of carboxyl and hydroxyl adsorption peaks, indicating that while fluorination treatment introduces fluorine, it does not completely remove all oxygen functional groups. These oxygen-containing hydrophilic groups facilitate the dispersion of the graphene material within the resin matrix.

[0033] Fourier transform infrared spectroscopy (FT-IR) characterization. The sample structure was characterized using a Fourier transform infrared spectrometer with 16 scans in the wavenumber range of 400–4000 cm -1 It can be observed that after the reaction of GO with NH4F, the rGO-based -1 The obvious CF peak appeared, further indicating the successful synthesis of FG-NH4F.

[0034] Example 2: 23.5 g of phenolic substances (including 21.15 g of phenol and 2.35 g of cardanol) and 30.4 g of formaldehyde aqueous solution (37 wt%) were weighed, and the phenol and formaldehyde aqueous solution were added to a reaction flask. 0.47 g of sodium hydroxide (2 wt% of phenolic substances) was added as a catalyst. The mixture was reacted at 70°C for a period of time, and then cardanol was added and reacted for another 1 h. The mixture was then heated to 90°C and reacted for 2 h. Excess water and free phenol were removed under vacuum conditions to obtain a resin matrix, which can be recorded as cardanol-modified phenolic resin (PRC).

[0035] 0.5% of the mass of the phenolic substance prepared in Example 1 was weighed and evenly dispersed in anhydrous ethanol. The mixture was then uniformly mixed with the resin matrix prepared above by ultrasonication to obtain a fluorinated graphene cardanol-modified phenolic resin (PRC-FG), i.e., a heat-resistant and high-strength phenolic resin composite material.

[0036] Fourier transform infrared spectroscopy (FT-IR) characterization. The sample structure was characterized using a Fourier transform infrared spectrometer with 16 scans in the wavenumber range of 400–4000 cm -1 The similar structure of cardanol and phenolic resin can be observed at 3400 cm -1 The phenolic hydroxyl -OH absorption peak was observed at 2910 cm -1 and 2850 cm -1 The methylene -CH2- stretching vibration peak appears at 1604 cm -1 and 1480 cm -1 The C=C skeleton vibration absorption of the benzene ring is also present at 2910 cm, which is highly consistent with the vibration peak position of the phenolic resin skeleton structure. This structural similarity allows cardanol to participate in the polymerization reaction as a partial phenol replacement in the phenolic polycondensation reaction, thereby forming a modified phenolic resin with similar structure but adjustable properties. In addition, the cardanol modified phenolic resin (PRC) sample has a peak absorption of 2910 cm -1 The -CH2- stretching vibration peak is stronger, which is due to the long carbon chain of cardanol. In summary, the successful introduction of the cardanol structure is confirmed.

[0037] Example 3: Referring to the preparation process of the resin matrix in Example 2, the mass ratio of phenol and cardanol was changed while the total mass of the phenolic substance remained unchanged, so that the addition amount of cardanol was 0, 5%, 15%, and 20% of the total mass of the phenolic substance, respectively. The rest was consistent with Example 2 to obtain the corresponding resin matrix.

[0038] Example 4: Referring to Example 2, the addition amounts of FG-NH4F prepared in Example 1 were changed to 0.1%, 0.25%, and 0.75% of the mass of the phenolic substance, respectively, and the rest were consistent with Example 2 to obtain the corresponding phenolic resin composite materials.

[0039] Example 5: The resin matrix or phenolic resin composite material obtained in Examples 2 to 4 is poured into a PTFE mold, and the resin is cured under high temperature and high pressure conditions in a hot press to obtain a standard test specimen, which is then subjected to bending and tensile tests. The bending strength of the sample is tested with reference to the standard GB 9341-08 "Plastics - Determination of Flexural Properties", and the standard sample size is 80 mm × 10 mm × 4 mm; the tensile strength of the sample is tested with reference to the standard GB T 1040.2-2022 "Plastics - Determination of Tensile Properties - Part 2: Experimental Conditions for Molded and Extruded Plastics", and the sample is a 5A dumbbell shape. The test results obtained under a universal testing machine are as follows Figure 1 As shown in the figure, it can be seen that when the addition amount of cardanol is 10%, the mechanical properties of the modified resin matrix are the best. The flexural strength and tensile strength can reach 61 MPa and 43 MPa respectively, which are 27% and 13% higher than those of pure phenolic resin. This improvement comes from the introduction of flexible long-chain structure, which improves the brittleness and internal stress distribution of phenolic resin, thereby effectively improving its flexural strength and tensile strength. On this basis, 0.1%, 0.25%, 0.5% and 0.75% FG are added, and the mechanical properties results are shown in the figure below. Figure 1 As shown in Figure 2 (b), it can be observed that the mechanical properties improve with increasing FG content. The optimal FG addition is achieved at 0.5%, with flexural strength and tensile strength reaching 67 MPa and 55 MPa, respectively, representing increases of 39.5% and 44.7% compared to pure phenolic resin. Further addition leads to a decrease in performance, which may be due to FG agglomeration within the resin matrix.

[0040] Scanning electron microscopy (SEM) was used to characterize the fractured cross-section of the resin. The samples were gold-sprayed before testing, and the test voltage was 15 kV. Figure 2 (a1), Figure 2Figure (a2) shows that the cross section of phenolic resin is relatively flat overall, showing typical brittle fracture characteristics. The cracks are straight and the cross section lacks plastic deformation structure, indicating that its toughness is low and the material is prone to rapid fracture under the action of external force. Figure 2 (b1), Figure 2 (b2) shows that with the introduction of cardanol, irregular crack lines begin to appear on the cross-section of the material, the interface becomes slightly rough, and the cracks undergo a certain degree of deflection. This indicates that the branched structure of cardanol has, to a certain extent, destroyed the original density and rigidity, increased the flexibility between the molecular chains, and thus enhanced the fracture toughness of the phenolic resin. Figure 2 (c1), Figure 2 In (c2), the fracture surface of the PRC-FG sample exhibits significant roughness and a more complex internal structure, including distinct microcrack deflections, lamellar delamination, and fracture distortion. This phenomenon demonstrates that the fluorinated graphene effectively blocks cracks and dissipates energy within the matrix, helping to slow crack propagation and further enhance the toughness of the composite. Furthermore, the absence of significant FG agglomeration indicates good dispersion within the resin matrix, enhancing interfacial interactions.

[0041] In order to verify the change of thermal properties, we adopted a thermogravimetric method to test the thermal stability of the synthesized resin. The TG test used a synchronous thermal analyzer to heat a 3-5 mg sample from room temperature to 800℃ at a heating rate of 10℃ / min in a N2 atmosphere. The results are shown in Figure 2. Figure 3 As shown in the figure: Thanks to the three-dimensional network structure of the phenolic resin, its carbon residue rate reached 59.1% at 800°C at a heating rate of 10°C / min in an N2 atmosphere, and the main thermal decomposition temperature was 530°C, demonstrating excellent thermodynamic properties. However, after the addition of cardanol, the introduction of its long chains destroyed the structure of the phenolic resin, resulting in a decrease in the density of crosslinking points within the resin matrix, leading to a significant decline in the thermodynamic properties of the resin: the carbon residue rate dropped to 44.5%, and the thermal decomposition temperature was 432°C, which greatly limited the application of the resin under high-temperature conditions. After the addition of FG-NH4F, the carbon residue rate returned to 58.1%, and the thermal decomposition temperature was 473°C. While improving the mechanical properties, it also maintained certain thermodynamic properties, achieving the synthesis of heat-resistant and high-strength phenolic resin.

[0042] In summary, the present invention introduces cardanol into the three-dimensional network structure of a phenolic resin through an internal toughening method, leveraging its long, flexible chains to enhance the mechanical properties of the phenolic resin. This structure is then physically blended with hydrothermally synthesized nanomaterial, fluorinated graphene, to prepare a graphene oxide-modified phenolic resin (PCR-FG). The introduction of cardanol reduces crosslink density and improves mechanical properties to a certain extent, but at the expense of some thermodynamic properties. The addition of fluorinated graphene inhibits crack propagation and absorbs some stress. Furthermore, the high bond energy of C—F bonds imparts enhanced thermal stability to fluorinated graphene, compensating for the negative thermal performance loss caused by the addition of cardanol. The combined introduction of these two materials successfully yields a high-strength, heat-resistant phenolic resin.

[0043] In addition, it should be understood that after reading the above description of the present invention, those skilled in the art may make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the claims attached to this application.

Claims

1. The raw materials of the cardanol-modified phenolic resin include phenolic substances and formaldehyde; The phenolic substances include phenol and cardanol; Based on the total mass of the phenolic substances as 100%, the mass proportion of the cardanol is 5% to 15%, preferably 10% to 15%; Based on the total mass of the phenolic substance being 100%, the mass proportion of the fluorinated graphene is 0.1% to 0.5%, preferably 0.25% to 0.5%.

2. The heat-resistant high-strength phenolic resin composite material according to claim 1, characterized in that: The preparation method of the cardanol-modified phenolic resin comprises: reacting phenol and formaldehyde for a period of time in the presence of a catalyst, and then adding cardanol to continue the reaction to obtain the cardanol-modified phenolic resin.

3. The heat-resistant high-strength phenolic resin composite material according to claim 2, characterized in that: In the preparation method of the cardanol-modified phenolic resin: The catalyst includes sodium hydroxide; The amount of the catalyst is 1% to 3% of the total mass of the phenolic substance; The reaction is carried out in water; The temperature for the reaction of phenol and formaldehyde is 65~75℃; After adding cardanol, first react at 65~75℃, then heat to 85~95℃.

4. The heat-resistant and high-strength phenolic resin composite material according to claim 1, characterized in that: Calculated by atomic ratio, the elemental composition of the fluorinated graphene is: 61% to 63% carbon, 29% to 31% oxygen, 3% to 4% fluorine and 3% to 4% nitrogen, preferably: 62.2% carbon, 30.3% oxygen, 3.8% fluorine and 3.7% nitrogen.

5. The heat-resistant high-strength phenolic resin composite material according to claim 1 or 4, characterized in that: The preparation method of the fluorinated graphene comprises: heating a water dispersion containing graphene oxide and ammonium fluoride in a sealed environment for reaction to obtain the fluorinated graphene.

6. The heat-resistant and high-strength phenolic resin composite material according to claim 5, characterized in that: In the preparation method of the fluorinated graphene: In the aqueous dispersion containing graphene oxide and ammonium fluoride, the mass ratio of graphene oxide to ammonium fluoride is 1:2.5-3.5; The temperature of the heating reaction is 135-145°C; The heating reaction time is 20 to 28 hours.

7. The heat-resistant and high-strength phenolic resin composite material according to claim 1, characterized in that: The flexural strength of the heat-resistant high-strength phenolic resin composite material is greater than 55 MPa, further greater than 60 MPa, and further greater than 65 MPa; The tensile strength of the heat-resistant high-strength phenolic resin composite material is greater than 40 MPa, further greater than 45 MPa, and further not less than 55 MPa; The heat-resistant high-strength phenolic resin composite material has a residual carbon rate of greater than 58% at 800°C and a thermal decomposition temperature of greater than 470°C.

8. The method for preparing the heat-resistant high-strength phenolic resin composite material according to any one of claims 1 to 7, wherein: include: The ethanol dispersion containing the fluorinated graphene and the cardanol-modified phenolic resin are ultrasonically mixed to obtain the heat-resistant and high-strength phenolic resin composite material.

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