A composite PBO fiber, a composite skeleton and its preparation method, a composite membrane and its preparation method and application

Abstract

The present invention provides a composite PBO fiber, a composite skeleton, a preparation method thereof, a composite membrane, a preparation method thereof, and an application thereof, belonging to the field of composite membranes. The present invention provides a composite PBO fiber, comprising a PBO fiber and a polybenzophenone-type benzoxazine coated on the surface of the PBO fiber. The hydroxyl groups of the polybenzophenone-type benzoxazine in the composite PBO fiber can form hydrogen bonds with the carbonyl groups in PEEK, which weakens the interfacial thermal resistance between the polymer and the filler while increasing the interfacial compatibility. In addition, the hydrogen bonding effect also effectively reduces the p-p stacking between carbon nanofillers, improves the dispersibility of carbon nanomaterials, and improves the thermal conductivity of the composite membrane prepared using the composite PBO fiber and carbon nanomaterials.

Description

Technical Field

[0001] The present invention relates to the field of composite membranes, and in particular to a composite PBO fiber, a composite skeleton and a preparation method thereof, a composite membrane and a preparation method and application thereof. Background Art

[0002] Communication equipment and wearable electronic devices are experiencing explosive growth, and the resulting electromagnetic wave radiation inevitably poses a threat to human health. EMI shielding materials play a vital role in protecting sensitive electronic devices and maintaining human health by shielding external electromagnetic interference (EMI) and radiation. EMI shielding materials are generally designed to have high EMI shielding effectiveness, be lightweight, and be easy to produce. However, these materials need to have more functions for practical application, which has been overlooked. In harsh environments such as low temperatures and high electromagnetic radiation in the polar regions or outer space, electronic devices should be protected from both cold and electromagnetic interference to ensure working efficiency. Therefore, the development of multifunctional devices with electromagnetic shielding, personal thermal management, and heating performance is highly desirable for smart wearable electronic products.

[0003] It is well known that graphene nanosheets (GnPs) have good thermal conductivity, which can be as high as 5000 W·m -1 ·K -1 . In addition, GnPs also have excellent light / electrical heat conversion properties, which makes GnPs an ideal choice for preparing heaters and thermal management materials. Carbon nanotubes (MWCNTs) have a unique spatial structure that allows electrons and phonons to move rapidly in their direction, reducing scattering, and therefore have excellent thermal properties, mechanical properties, and excellent thermal conductivity. MWCNTs (rod-shaped) are introduced into GnPs, which can act as bridges between graphene sheets, facilitating electron transport and stress transfer. In addition, GnPs can also form conductive paths at line-to-line junctions to improve resistance uniformity. However, MWCNTs and GnPs lack functional groups and therefore have poor dispersibility in the substrate resin. Summary of the Invention

[0004] The present invention provides a composite PBO fiber, a composite skeleton and a preparation method thereof, a composite membrane and a preparation method and application thereof. The composite PBO fiber of the present invention can improve the dispersibility of MWCNTs and GnPs in a matrix resin.

[0005] The invention provides a composite PBO fiber, comprising a PBO fiber and a polybenzophenone-type benzoxazine coated on the surface of the PBO fiber.

[0006] The present invention also provides a composite skeleton comprising the composite PBO fiber described in the above technical solution and the conductive coating on the surface of the polybenzophenone-type benzoxazine;

[0007] The conductive coating includes graphene nanosheets and carbon nanotubes.

[0008] The present invention also provides a method for preparing the composite skeleton described in the above technical solution, comprising the following steps:

[0009] The surface of the PBO fiber is treated with plasma to introduce hydroxyl groups on the surface of the PBO fiber to obtain PBO-OH fiber;

[0010] The PBO-OH fiber, benzophenone-type benzoxazine and an organic solvent are first mixed, and the benzophenone-type benzoxazine is adsorbed on the surface of the PBO-OH fiber to obtain a first mixture;

[0011] The first mixture is mixed with graphene nanosheets and carbon nanotubes, and the graphene nanosheets and carbon nanotubes are adhered to form a conductive coating through benzophenone-type benzoxazine, thereby obtaining a PBO-OH fiber containing the conductive coating and benzophenone-type benzoxazine;

[0012] The PBO-OH fiber containing the conductive coating and benzophenone-type benzoxazine is thermally cured to obtain the composite skeleton.

[0013] Preferably, the mass ratio of the PBO-OH fiber to the benzophenone-type benzoxazine is 1:0.25-12.5.

[0014] Preferably, the mass ratio of the graphene nanosheets to the carbon nanotubes is 1:0.1-1.

[0015] Preferably, the thermal curing temperature is 130-210° C., and the time is 0.5-2 hours.

[0016] The present invention also provides a composite membrane comprising a matrix and a composite skeleton dispersed in the matrix;

[0017] The matrix includes fluorinated polyetheretherketone and polyetheretherketone;

[0018] The composite skeleton is the composite skeleton described in the above technical solution or the composite skeleton prepared by the preparation method described in the above technical solution.

[0019] Preferably, the ratio of the mass of the conductive coating in the composite film to the mass of the composite film after deducting the mass of the polybenzophenone-type benzoxazine is 0.05-0.35:1.

[0020] The present invention also provides a method for preparing the composite membrane described in the above and similar embodiments, comprising the following steps:

[0021] Repeatedly mixing the composite skeleton with the dispersion of the matrix and then removing the solvent in the dispersion to obtain a composite;

[0022] The composite is formed into a film to obtain the composite film.

[0023] The present invention also provides the application of the composite film described in the above technical solution or the composite film prepared by the preparation method described in the above technical solution in thermal management.

[0024] The hydroxyl groups of the polybenzophenone-type benzoxazine in the composite PBO fibers can form hydrogen bonds with the carbonyl groups in PEEK, which reduces the interfacial thermal resistance between the polymer and the carbon nanofillers (graphene nanosheets and carbon nanotubes) while increasing interfacial compatibility. Furthermore, hydrogen bonding effectively reduces the p-p stacking between the carbon nanofillers (graphene nanosheets and carbon nanotubes), improving their dispersion and enhancing the thermal conductivity of the composite film prepared using the composite PBO fibers, graphene nanosheets, and carbon nanotubes.

[0025] The introduction of polybenzophenone-type benzoxazine reduces the interfacial thermal resistance problem, improves the thermal conductivity of the composite material, and constructs a composite skeleton with a continuous structure (graphene nanosheets and carbon nanotubes form a conductive coating), thereby improving the electromagnetic shielding performance of the composite material.

[0026] The graphene nanosheets and carbon nanotubes introduced into the composite film of the present invention can significantly improve the electrical conductivity and electromagnetic shielding performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 Flow chart of preparing MWCNTs&GnPs@PBO-PBZ / PEEK composite membrane material in Example;

[0028] Figure 2 The thermal conductivity results of the MWCNTs&GnPs@PBO-PBZ / PEEK composite film materials of Examples 1 to 7 are as follows;

[0029] Figure 3 The thermal conductivity results of the MWCNTs&GnPs@PBO / PEEK composite film materials of Comparative Examples 1 to 7 are as follows;

[0030] Figure 4 EMI shielding performance results of the MWCNTs&GnPs@PBO-PBZ / PEEK composite film materials of Examples 1 to 7;

[0031] Figure 5 These are the Joule thermal performance results of the MWCNTs&GnPs@PBO-PBZ / PEEK composite film material of Example 7. DETAILED DESCRIPTION

[0032] The invention provides a composite PBO fiber, comprising a PBO fiber and a polybenzophenone-type benzoxazine coated on the surface of the PBO fiber.

[0033] The method for preparing the composite PBO fiber preferably comprises the following steps:

[0034] The surface of the PBO fiber is treated with plasma to introduce hydroxyl groups on the surface of the PBO fiber to obtain PBO-OH fiber;

[0035] The PBO-OH fiber, benzophenone-type benzoxazine and an organic solvent are first mixed, and the benzophenone-type benzoxazine is adsorbed on the surface of the PBO-OH fiber, and then thermally cured.

[0036] The present invention also provides a composite skeleton comprising the composite PBO fiber described in the above solution and a conductive coating located on the surface of the polybenzophenone-type benzoxazine;

[0037] The conductive coating includes graphene nanosheets and carbon nanotubes.

[0038] The present invention also provides a method for preparing the composite skeleton described in the above technical solution, comprising the following steps:

[0039] The surface of the PBO fiber is treated with plasma to introduce hydroxyl groups on the surface of the PBO fiber to obtain PBO-OH fiber;

[0040] The PBO-OH fiber, benzophenone-type benzoxazine and an organic solvent are first mixed, and the benzophenone-type benzoxazine is adsorbed on the surface of the PBO-OH fiber to obtain a first mixture;

[0041] The first mixture is mixed with graphene nanosheets and carbon nanotubes, and the graphene nanosheets and carbon nanotubes are adhered to form a conductive coating through benzophenone-type benzoxazine, thereby obtaining a PBO-OH fiber containing the conductive coating and benzophenone-type benzoxazine;

[0042] The PBO-OH fiber containing the conductive coating and benzophenone-type benzoxazine is thermally cured to obtain the composite skeleton.

[0043] The present invention performs plasma treatment on the surface of the PBO fiber, introduces hydroxyl groups on the surface of the PBO fiber, and obtains PBO-OH fiber.

[0044] In the present invention, before the plasma treatment, the method preferably further comprises: removing the sizing agent and contaminants on the surface of the PBO fibers, and then drying and dispersing the fibers.

[0045] In the present invention, the removal preferably includes separating the PBO fibers by sequentially soaking them in acetone and water. The soaking time in acetone and water is not particularly limited, as long as the sizing agent and contaminants are removed. In a specific embodiment of the present invention, the soaking time in acetone and water is 24 hours.

[0046] In the present invention, the drying temperature is preferably 60° C., and the drying time is preferably 4 hours.

[0047] In the present invention, the dispersion preferably includes: immersing the dried PBO fibers in ethanol and then sequentially performing ultrasonic dispersion, separation, and drying.

[0048] In the present invention, the discharge power of the plasma treatment is preferably 120W, the discharge time is preferably 300-400s, and in a specific embodiment of the present invention, the discharge time may be 300s, 310s, 320s, 330s, 340s, 350s, 360s, 370s, 380s, 390s or 400s; the pressure is preferably 30-50Pa, and in a specific embodiment of the present invention, the pressure may be 30Pa, 35Pa, 40Pa, 45Pa or 50Pa; the O2 and A in the plasma treatment are preferably 120W, 300-400s, 310s, 320s, 330s, 340s, 350s, 360s, 370s, 380s, 390s or 400s; the pressure is preferably 30-50Pa, and in a specific embodiment of the present invention, the pressure may be 30Pa, 35Pa, 40Pa, 45Pa or 50Pa; r The volume ratio is preferably 1:0.2 to 1.5. In a specific embodiment of the present invention, the volume ratio can be 1:0.2, 1:0.5, 1:1 or 1:1.5.

[0049] The present invention utilizes plasma treatment to activate the surface of the PBO fiber, generates hydroxyl groups, and increases the roughness of the PBO fiber surface.

[0050] After obtaining the PBO-OH fiber, the present invention first mixes the PBO-OH fiber, benzophenone-type benzoxazine, and an organic solvent, and the benzophenone-type benzoxazine is adsorbed on the surface of the PBO-OH fiber to obtain a first mixture.

[0051] In the present invention, the mass ratio of the PBO-OH fiber to the benzophenone-type benzoxazine is 1:0.25 to 12.5. In a specific embodiment of the present invention, the mass ratio of the PBO fiber to the benzophenone-type benzoxazine may be 1:0.25, 1:1, 14:25, 1:2, 1:0.25, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, 1:10, 1:11 or 1:12.5.

[0052] In the present invention, the ratio of the mass of the benzophenone-type benzoxazine to the volume of the organic solvent is preferably 1 g:20-80 mL. In a specific embodiment of the present invention, the ratio of the mass of the benzophenone-type benzoxazine to the volume of the organic solvent may be 1 g:20 mL, 1 g:40 mL, 1 g:60 mL or 1 g:80 mL; the organic solvent preferably includes acetone.

[0053] In the present invention, the temperature of the first mixing is preferably 65-75°C, and the time is preferably 6-18 hours. In a specific embodiment of the present invention, the temperature of the first mixing can be 65°C, 70°C or 75°C, and the time can be 6 hours, 8 hours, 10 hours, 12 hours, 14 hours, 16 hours or 18 hours; the first mixing is preferably carried out under reflux conditions.

[0054] In the first mixing, the benzophenone-type benzoxazine is adsorbed on the surface of the PBO-OH fiber through hydrogen bonds with the hydroxyl groups on the PBO-OH fiber due to the nitrogen contained in the benzophenone-type benzoxazine.

[0055] After obtaining the first mixture, the present invention mixes the first mixture with graphene nanosheets and carbon nanotubes, and the graphene nanosheets and carbon nanotubes form a conductive coating through the adhesion of benzophenone-type benzoxazine to obtain PBO-OH fibers containing the conductive coating and benzophenone-type benzoxazine.

[0056] In the present invention, the second mixing preferably includes: adding the graphene nanosheets and carbon nanotubes to the first mixture obtained after the first mixing and then cooling the mixture.

[0057] In the present invention, the mass ratio of the graphene nanosheets to the carbon nanotubes is preferably 1:0.1-1. In a specific embodiment of the present invention, the mass ratio can be 1:0.1, 1:0.2, 1:0.3, 1:0.4, 1:0.5, 1:0.6, 1:0.7, 1:0.8, 1:0.9 or 1:1.

[0058] In the second mixture, graphene nanosheets and carbon nanotubes adhere to the PBO-OH fibers due to the viscosity of benzophenone-type benzoxazine.

[0059] In the present invention, after the second mixing, the method preferably further comprises: separation to obtain the PBO-OH fibers adsorbed with graphene nanosheets, carbon nanotubes and benzophenone-type benzoxazine.

[0060] After obtaining the PBO-OH fiber containing the conductive coating and benzophenone-type benzoxazine, the present invention thermally cures the PBO-OH fiber containing the conductive coating and benzophenone-type benzoxazine to obtain the composite skeleton.

[0061] In the present invention, the thermal curing temperature is preferably 130-210° C., and the curing time is preferably 0.5-2 hours. In specific embodiments of the present invention, the thermal curing temperature can be 130° C., 150° C., 170° C., 175° C., 190° C., or 210° C., and the curing time can be 0.5 hours, 1 hour, 1.5 hours, or 2 hours. Benzophenone-type benzoxazine generates polybenzophenone-type benzoxazine during the thermal curing process.

[0062] The curing reaction process of the benzophenone-type benzoxazine monomer is as follows:

[0063]

[0064] The present invention also provides a composite membrane comprising a matrix and a composite skeleton dispersed in the matrix;

[0065] The matrix includes fluorinated polyetheretherketone and polyetheretherketone;

[0066] The composite skeleton is the composite skeleton described in the above technical solution or the composite skeleton prepared by the preparation method described in the above technical solution.

[0067] In the present invention, the composite membrane includes a matrix, and the matrix includes fluorinated polyetheretherketone and polyetheretherketone; the mass ratio of the fluorinated polyetheretherketone and polyetheretherketone is preferably 1:0.25 to 4. In a specific embodiment of the present invention, the mass ratio of the fluorinated polyetheretherketone and polyetheretherketone can be 1:0.25, 1:0.5, 1:1, 1:1.5, 1:2, 1:2.5, 1:3, 1:3.5 or 1:4.

[0068] In the present invention, the ratio of the mass of the conductive coating in the composite film to the mass of the composite film after deducting the mass of the polybenzophenone-type benzoxazine is 0.05 to 0.35:1. In a specific embodiment of the present invention, the volume content of the composite skeleton can be 0.05:1, 0.1:1, 0.15:1, 0.2:1, 0.25:1, 0.3:1 or 0.35:1.

[0069] The present invention also provides a method for preparing the composite film according to the above technical solution, comprising the following steps:

[0070] Repeatedly mixing the composite skeleton with the dispersion of the matrix and then removing the solvent in the dispersion to obtain a composite;

[0071] The composite is formed into a film to obtain the composite film.

[0072] In the present invention, the mixing is preferably performed under vacuum conditions.

[0073] In the present invention, the solvent preferably includes NMP.

[0074] In the present invention, the number of repetitions is preferably 3 times, the temperature of the removal is preferably 120° C., and the time is preferably 12 hours.

[0075] In the present invention, the molding process preferably includes preheating, wherein the preheating temperature is preferably 380° C. and the preheating time is preferably 10 minutes;

[0076] In the present invention, the molding pressure is preferably 50 MPa, the temperature is preferably 380° C., and the time is preferably 15 minutes.

[0077] After the molding, the pressure is preferably released and the mixture is naturally cooled to room temperature.

[0078] The present invention also provides the use of the composite film described in the above technical solution or the composite film prepared by the preparation method described in the above technical solution in thermal management.

[0079] The composite PBO fiber, composite skeleton and preparation method thereof, composite membrane and preparation method thereof and application provided by the present invention are described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0080] Figure 1 Flow chart of preparing MWCNTs&GnPs@PBO-PBZ / PEEK composite membrane material in this example.

[0081] Example 1

[0082] Preparation of PBO-OH

[0083] To remove sizing agents and contaminants from the PBO fiber surface, the fibers were immersed in acetone and then in deionized water for 24 hours each. Finally, the cleaned fibers were dried in a vacuum oven at 60°C for 4 hours. The cleaned fibers were then immersed in a watch glass containing a specific amount of ethanol solution. The PBO fiber bundles were ultrasonically dispersed in an ultrasonic cleaner and then dried in an oven.

[0084] The dispersed fibers were evenly fixed on a homemade glass rack. The plasma treatment apparatus was used to activate the surface of the PBO fibers and increase their surface roughness. The treatment parameters were set as follows: discharge power 120W, discharge time 360s, and vacuum chamber pressure of 40Pa (P O2 :P Ar =3:2). After the plasma treatment, the fibers were taken out and set aside for later use, and were recorded as PBO-OH fibers.

[0085] Preparation of continuous structure MWCNTs&GnPs@PBO-PBZ / PEEK composite membrane materials

[0086] Plasma-treated PBO fiber (1.4 g) was placed in a mixed solution of 2.5 g of benzophenone-type benzoxazine monomer and 100 mL of acetone and refluxed at 65 °C for 12 h.

[0087] Subsequently, 0.08 g of graphene nanosheets and 0.03 g of carbon nanotubes (8:3) were added to the above mixed solution. After cooling, the GnPs&MWCNTs@PBO-PBZ composite material was taken out and placed in an electric forced air drying oven for staged thermal curing to obtain a GnPs&MWCNTs@PBO-PBZ composite skeleton; a 30 mg / mL FPEEK / NMP solution was prepared, and an appropriate amount of PEEK ultrafine powder was added to the above solution and ultrasonicated for 30 minutes to obtain a 150 mg / mL uniformly dispersed FPEEK / PEEK / NMP suspension (the mass ratio of FPEEK to PEEK was 1:4). The GnPs&MWCNTs@PBO-PBZ composite skeleton was immersed in the above-mentioned mixed dispersion, vacuum infused and heated at 120°C for 12 hours to remove the NMP solvent. This step was repeated three times, and then preheated at 380°C for 10 minutes, and then heated at 50 MPa for 15 minutes. Finally, the pressure was removed and naturally cooled to room temperature to obtain a MWCNTs&GnPs@PBO-PBZ / PEEK composite material (size 4 cm × 4 cm × 0.2 mm).

[0088] Examples 2 to 7

[0089] The raw materials and amounts of Examples 2 to 7 are shown in Table 1, and the preparation method is the same as that of Example 1.

[0090] Comparative Examples 1 to 7

[0091] The only difference from Example 1 is that no benzophenone-type benzoxazine monomer is added. The raw materials and amounts of Comparative Examples 1 to 7 are shown in Table 1.

[0092] Table 1 Amount of each raw material in Examples 1 to 7 and Comparative Examples 1 to 7

[0093]

[0094] Note: Mass content = mass of carbon nanotubes and graphene nanosheets (conductive coating) / (mass of composite film - mass of PBZ)

[0095] Table 2 In-plane thermal conductivity and out-of-plane thermal conductivity of the composite film materials of Examples 1 to 7 and Comparative Examples 1 to 7

[0096]

[0097] Note: In-plane refers to the thermal conductivity of the sample in the horizontal direction; out-of-plane refers to the thermal conductivity of the sample in the vertical direction.

[0098] Thermal conductivity

[0099] The thermal conductivity of the MWCNTs & GnPs @ PBO / PEEK composite film materials of Comparative Examples 1 to 7 and the MWCNTs & GnPs @ PBO-PBZ / PEEK composite film materials of Examples 1 to 7 was measured by laser flash method. The results are as follows: Figures 2-3 shown.

[0100] Depend on Figures 2-3 It can be seen that with the continuous increase of filler content, the thermal conductivity of the two composite membrane materials shows a similar trend of change, the thermal conductivity coefficient gradually increases, and the thermal conductivity of the composite membrane material with a continuous structure is higher than that of the composite membrane material with a random blend structure. The in-plane and out-of-plane thermal conductivities of the MWCNTs&GnPs@PBO-PBZ / PEEK composite membrane material of Example 7 are 32.01 W·m -1 K -1 and 3.05W·m -1 K -1 Compared with pure PEEK, the thermal conductivity increases are 13817% and 1226% respectively. The out-of-plane thermal conductivity of the random blend structure composite film material is 2.29W·m -1 K -1 Much lower than the continuous structure composite membrane material (3.05W·m -1 K -1 ), which indicates that the continuous filler network structure and the introduction of PBZ jointly promote the improvement of the thermal conductivity of MWCNTs&GnPs@PBO-PBZ / PEEK composite film materials.

[0101] Electromagnetic shielding performance

[0102] The EMI shielding performance of MWCNTs&GnPs@PBO-PBZ / PEEK composite film materials was measured using a vector network analyzer in the X-band. Figure 4 shown.

[0103] Depend on Figure 4 It can be seen that the absorption loss and reflection loss of the MWCNTs & GnPs@PBO-PBZ / PEEK composite film materials of Examples 1 to 7 show a rapid increase, while the reflection loss of the composite film materials increases slowly. The absorption loss and reflection loss of the MWCNTs & GnPs@PBO-PBZ / PEEK composite film material of Example 7 are 85.5 dB and 15.9 dB, respectively, exceeding the requirement of commercial shielding materials (20 dB). In addition, the MWCNTs & GnPs@PBO-PBZ / PEEK composite film material in Example 7 achieves the best total shielding effectiveness value of 101.3 dB, with a shielding effectiveness of 99.999999993%.

[0104] Joule heating performance

[0105] When electricity is applied to a conductive material, its interior will hinder the movement of electron flow, causing the kinetic energy of the electrons to be converted into heat energy, which is called the Joule heating effect. The excellent electrical conductivity of the MWCNTs&GnPs@PBO-PBZ / PEEK composite membrane material of Example 7, and the continuous network formed by the carbon nanofillers (graphene nanosheets and carbon nanotubes) therein provide the necessary premise for the uniformity of Joule heating. The Joule heating performance of the circular composite membrane material with a diameter of 25.6 mm was studied as a model, and the results are as follows: Figure 5 shown.

[0106] from Figure 5 As can be seen in the figure, the temperature of the composite film material increases rapidly when the DC power supply voltage is adjusted from 2 to 12V, and stabilizes at the saturation temperature within 120 seconds at all voltages. When the load voltage is 12V, the surface temperature of the composite film material reaches approximately 134.6°C, approximately 112.6°C higher than room temperature (22°C). These experimental results demonstrate that the MWCNTs & GnPs@PBO-PBZ / PEEK composite film material exhibits excellent Joule heating performance at relatively low voltages, showing great potential for application in personal thermal management.

[0107] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A composite skeleton, characterized in that: The invention relates to a composite PBO fiber and a conductive coating on the surface of a polybenzophenone-type benzoxazine; the composite PBO fiber comprises a PBO fiber and a polybenzophenone-type benzoxazine coated on the surface of the PBO fiber; The conductive coating comprises graphene nanosheets and carbon nanotubes; The preparation method of the composite skeleton comprises the following steps: The surface of the PBO fiber is treated with plasma to introduce hydroxyl groups on the surface of the PBO fiber to obtain PBO-OH fiber; The PBO-OH fiber, benzophenone-type benzoxazine and an organic solvent are first mixed, and the benzophenone-type benzoxazine is adsorbed on the surface of the PBO-OH fiber to obtain a first mixture; The first mixture is mixed with graphene nanosheets and carbon nanotubes, and the graphene nanosheets and carbon nanotubes are adhered to form a conductive coating through benzophenone-type benzoxazine, thereby obtaining a PBO-OH fiber containing the conductive coating and benzophenone-type benzoxazine; The PBO-OH fiber containing the conductive coating and benzophenone-type benzoxazine is thermally cured to obtain the composite skeleton.

2. The method for preparing the composite skeleton according to claim 1, characterized in that: The following steps are involved: The surface of the PBO fiber is treated with plasma to introduce hydroxyl groups on the surface of the PBO fiber to obtain PBO-OH fiber; The PBO-OH fiber, benzophenone-type benzoxazine and an organic solvent are first mixed, and the benzophenone-type benzoxazine is adsorbed on the surface of the PBO-OH fiber to obtain a first mixture; The first mixture is mixed with graphene nanosheets and carbon nanotubes, and the graphene nanosheets and carbon nanotubes are adhered to form a conductive coating through benzophenone-type benzoxazine, thereby obtaining a PBO-OH fiber containing the conductive coating and benzophenone-type benzoxazine; The PBO-OH fiber containing the conductive coating and benzophenone-type benzoxazine is thermally cured to obtain the composite skeleton.

3. The preparation method according to claim 2, characterized in that The mass ratio of the PBO-OH fiber to benzophenone-type benzoxazine is 1:0.25-12.

5.

4. The preparation method according to claim 2, characterized in that The mass ratio of the graphene nanosheets to the carbon nanotubes is 1:0.1-1.

5. The preparation method according to claim 2, characterized in that The thermal curing temperature is 130-210° C., and the curing time is 0.5-2 hours.

6. A composite membrane, characterized in that It comprises a matrix and a composite skeleton dispersed in the matrix; the matrix comprises fluorinated polyetheretherketone and polyetheretherketone; The composite skeleton is the composite skeleton according to claim 1 or the composite skeleton prepared by the preparation method according to any one of claims 2 to 5.

7. The composite membrane according to claim 6, characterized in that The ratio of the mass of the conductive coating in the composite film to the mass of the composite film after deducting the mass of the polybenzophenone-type benzoxazine is 0.05-0.35:

1.

8. The method for preparing the composite membrane according to claim 6 or 7, characterized in that: The following steps are involved: Repeatedly mixing the composite skeleton with the dispersion of the matrix and then removing the solvent in the dispersion to obtain a composite; The composite is formed into a film to obtain the composite film.

9. Application of the composite film according to claim 6 or 7 or the composite film prepared by the preparation method according to claim 8 in thermal management.

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