A carbonized polybenzoxazine aerogel and its preparation method

Abstract

The present invention discloses a novel carbonized polybenzoxazine aerogel and a preparation method thereof. The novel carbonized polybenzoxazine aerogel is made by carbonizing a novel polybenzoxazine aerogel, belonging to the technical field of aerogel materials. The preparation method comprises: preparing a polybenzoxazine solution; placing the polybenzoxazine solution into a mold to form a wet gel; aging the wet gel, and drying it at normal pressure for 24 hours after aging; washing the aged wet gel with N,N-dimethylformamide to obtain a wet conductive gel; drying the wet gel at normal temperature and pressure to obtain a novel polybenzoxazine aerogel; carbonizing the polybenzoxazine aerogel at 800°C in an argon environment for 6 hours, followed by furnace cooling, and obtaining the novel carbonized polybenzoxazine aerogel after cooling. Advantages of the present invention include: using bisphenol F-type benzoxazine monomer as a raw material, preparing the aerogel through acid-catalyzed polymerization and drying it at normal pressure; and having a simple preparation method; compared with other aerogel materials, the aerogel of the present invention has excellent electromagnetic shielding performance and high resistivity.

Description

Technical Field

[0001] The present invention belongs to the technical field of aerogel materials, and in particular relates to a novel carbonized polybenzoxazine aerogel and a preparation method thereof. Background Art

[0003] Aerogel materials have excellent properties such as ultra-low density, ultra-low thermal conductivity and super sound insulation, and have been widely used in thermal insulation and energy saving, sound insulation, noise reduction and shock absorption, and military fields.

[0004] Polybenzoxazine (PBO) aerogel is a new type of thermosetting material with unique performance advantages such as high modulus, high strength, good heat resistance, and low water absorption. It has broad application prospects in aerospace thermal protection, aviation structures and flame retardancy, electronic devices and other fields.

[0005] On the other hand, today's increasingly serious electromagnetic pollution and electromagnetic protection problems have made the demand for high-performance electromagnetic shielding materials more urgent.

[0006] Generally speaking, the more conductive a material is, the stronger its electromagnetic shielding performance is. This is because the more conductive a material is, the easier it is to form an electrical circuit between materials, absorbing and reflecting electromagnetic waves, thereby improving electromagnetic shielding performance.

[0007] Common electromagnetic shielding materials have a series of problems, such as weight, cost, and secondary electromagnetic pollution. At the same time, electrical conductivity and electronic thermal conductivity are related to the movement of electrons inside the material, which will lead to poor thermal insulation capabilities of the material and increase the loss of electronic components.

[0008] The materials with strong electromagnetic shielding performance reported so far generally have low resistivity. Summary of the Invention

[0009] The present application provides a method for preparing a novel carbonized polybenzoxazine aerogel. The novel carbonized polybenzoxazine aerogel prepared by this method has high resistivity and strong electromagnetic shielding performance, breaking the contradiction between electrical / thermal conductivity and electromagnetic shielding performance, and can greatly expand the scope of application in fields such as precision electronic devices, aerospace, and high-speed network signal transmission.

[0010] The first object of the present invention is to disclose a novel carbonized polybenzoxazine aerogel.

[0011] The second object of the present invention is to disclose a novel method for preparing carbonized polybenzoxazine aerogel.

[0012] The purpose of the present invention is achieved through the following technical solutions:

[0013] A novel carbonized polybenzoxazine aerogel is prepared from the following raw materials in parts by weight: 10-40 parts of bisphenol F-type benzoxazine, 50-200 parts of N,N-dimethylformamide, and 0.5-5 parts of hydrochloric acid, wherein the concentration of the hydrochloric acid is 36%-38%.

[0014] The novel carbonized polybenzoxazine aerogel has a specific surface area of ​​5.38-24.811 square meters per gram, an average pore diameter of 5.95-14.16 nanometers, a resistivity of 4.93-7.34 ohm·meters, and an electromagnetic shielding performance of 28.05-77.51 decibels for 8-12.4 GHz electromagnetic waves.

[0015] A novel method for preparing carbonized polybenzoxazine aerogel, wherein the preparation method comprises the following steps:

[0016] (1) dissolving bisphenol F type benzoxazine in N,N-dimethylformamide and heating to obtain a bisphenol F solution; adding hydrochloric acid to N,N-dimethylformamide to obtain an acid catalytic solution; mixing the bisphenol F solution and the acid catalytic solution and stirring to obtain a polybenzoxazine solution;

[0017] (2) placing the polybenzoxazine solution obtained in step (1) into a mold to form a wet gel;

[0018] (3) aging the wet gel obtained in step (2), and drying it at normal pressure for 24 hours after aging;

[0019] (4) washing the aged wet gel obtained in step (3) with N,N-dimethylformamide to obtain a wet conductive gel;

[0020] (5) drying the wet conductive gel obtained in step (4) at room temperature and pressure for 24-48 hours to obtain a novel polybenzoxazine aerogel having electrical conductivity and electromagnetic shielding properties;

[0021] (6) The polybenzoxazine aerogel obtained in step (5) was heated to 800°C in an argon environment at a heating rate of 5°C / min. After heating to 800°C, the temperature was kept at that temperature for 6 hours, and then cooled in the furnace. During the heating and cooling, the argon flow rate was ensured to be greater than 50 ml / min. After cooling, a novel carbonized polybenzoxazine aerogel was obtained.

[0022] The above technical solution provides a novel method for preparing carbonized polybenzoxazine aerogel, wherein: in step (1), the amount of bisphenol F-type benzoxazine, the amount of N,N-dimethylformamide, and the amount of hydrochloric acid are 10-40 parts by weight, 50-200 parts by weight, and 0.5-5 parts by weight, and the concentration of the hydrochloric acid is 36%-38%.

[0023] The above technical solution is a method for preparing a novel carbonized polybenzoxazine aerogel, in parts by weight, wherein: in step (1), 10-30 parts of bisphenol F type benzoxazine are placed in 20-40 parts of N,N-dimethylformamide, and heated in a heating box at 80°C for 12 hours, and then cooled to room temperature to obtain a bisphenol F solution; 2-5 parts of concentrated hydrochloric acid are added to 20-40 parts of N,N-dimethylformamide and uniformly stirred to obtain an acid catalytic solution; the acid catalytic solution is added to the bisphenol F solution and rapidly stirred for 30 seconds to obtain a polybenzoxazine solution.

[0024] The method for preparing a novel carbonized polybenzoxazine aerogel described in the above technical solution, wherein: in step (2), the gelation time is greater than 15 minutes.

[0025] The above technical solution provides a novel method for preparing carbonized polybenzoxazine aerogel, wherein: in step (3), the aging environment is normal temperature and pressure; and the aging time is 12-24 hours.

[0026] The above technical solution provides a novel method for preparing carbonized polybenzoxazine aerogel, wherein: in step (4), the wet gel is washed with N,N-dimethylformamide 1-3 times, each washing time being 10-20 hours.

[0027] A novel carbonized polybenzoxazine aerogel is prepared by the preparation method described in the above technical solution.

[0028] The novel carbonized polybenzoxazine aerogel described in the above technical solution has a specific surface area of ​​5.38-24.811 square meters per gram, an average pore size of 5.95-14.16 nanometers, a resistivity of 4.93-7.34 ohm·meters, and an electromagnetic shielding performance of 28.05-77.51 decibels against 8-12.4 GHz electromagnetic waves.

[0029] The present invention has the following beneficial effects:

[0030] 1. The novel carbonized polybenzoxazine aerogel of the present invention uses bisphenol F-type benzoxazine monomer as raw material and can be prepared by acid-catalyzed polymerization and atmospheric pressure drying. The preparation method of the aerogel is simple, and the obtained aerogel has excellent electromagnetic shielding performance.

[0031] 2. During the cleaning process of step (4) of the present invention, N,N-dimethylformamide solution is used to make the reaction of the wet gel more complete and strengthen the newly formed benzoxazine skeleton structure; impurities are removed, the network structure of the gel is strengthened, the gel is easy to dry, and the gel has better electromagnetic shielding performance.

[0032] 3. Compared with other electromagnetic shielding materials, the present invention has stronger electromagnetic shielding performance, higher resistivity and poorer conductivity.

[0033] 4. Compared with other polybenzoxazine aerogels, the novel carbonized polybenzoxazine aerogel prepared in the present invention has a smaller specific surface area and a smaller average pore size. This porous network structure enhances the reflection and scattering of electromagnetic waves, making its electromagnetic shielding effect stronger.

[0034] 5. The present invention adds a carbonization step to step (6). After carbonization, the conductivity of the material itself is enhanced, making it easier to form an electrical circuit inside the material to enhance the reflection of electromagnetic waves, further enhancing the electromagnetic shielding capability. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 A comparison chart of the electromagnetic shielding performance of Examples 1-4.

[0036] Figure 2 This is a comparison chart of the electromagnetic shielding performance of Example 4, Example 5 and Example 6.

[0037] Figure 3 Graph showing the relationship between the electromagnetic shielding performance and resistivity of Examples 2-4.

[0038] Figure 4 This is the thermogravimetric curve of Example 4 in air environment.

[0039] Figure 5 This is a scanning electron microscope image of Example 4.

[0040] Figure 6 This is a scanning electron microscope image of Example 7.

[0041] Figure 7 This is a comparison chart of the electromagnetic shielding performance of Example 2 and Example 8. DETAILED DESCRIPTION

[0042] To facilitate understanding of the technical solution of the present invention, a novel carbonized polybenzoxazine aerogel and a preparation method thereof are further described below in conjunction with specific embodiments.

[0043] The experimental equipment used in the following examples is:

[0044] Magnetic stirrer, model 78-1, produced by Changzhou Xinxin Experimental Instrument Co., Ltd.; box-type heating furnace, model KSL-1200X, produced by Hefei Kejing Material Technology Co., Ltd.; tubular heating furnace, model GSL-1700X, produced by Hefei Kejing Material Technology Co., Ltd.; electric blast drying oven, Shanghai Lichenbang Instrument Technology Co., Ltd., model FX101-1, produced by Shanghai Shuli Instrument Co., Ltd.; constant temperature stirrer, model DF-101S, produced by Shanghai Lichenbang Instrument Technology Co., Ltd.; contact angle meter, model FCA20000A3E, produced by Shanghai Aifeis Precision Instrument Co., Ltd.; microcomputer-controlled electronic universal testing machine, model CMT6503, produced by Meters Industrial Systems (China) Co., Ltd.

[0045] Example 1: Preparation method of new carbonized polybenzoxazine aerogel:

[0046] Dissolve 10g of bisphenol F-type benzoxazine monomer in 40g of N,N-dimethylformamide solvent, and place the mixed solution in an 80°C oven for 12 hours to obtain a gel solution; dissolve 0.5-5g of hydrochloric acid in 40g of N,N-dimethylformamide solvent to obtain an acid catalytic solution, and then evenly mix the two solutions to obtain a polybenzoxazine solution;

[0047] The polybenzoxazine solution was poured into a mold to form a wet gel; the gel was then aged at room temperature for 10-20 hours, and then dried at normal pressure for 24 hours. The wet gel was then washed with N,N-dimethylformamide 1-3 times, each washing time being 10-20 hours, to obtain a wet conductive gel; the wet conductive gel was then dried at room temperature and pressure for 24-48 hours to obtain a novel polybenzoxazine aerogel having electrical conductivity and electromagnetic shielding properties; finally, the dried novel polybenzoxazine aerogel was heated at 800°C in an argon environment for 6 hours to obtain a novel carbonized polybenzoxazine aerogel. The electromagnetic shielding properties of the aerogel are shown in Table 2, the resistivity values ​​are shown in Table 3, and the specific surface area and average pore size are shown in Table 4.

[0048] Example 2: Preparation method of new carbonized polybenzoxazine aerogel:

[0049] 20g of bisphenol F type benzoxazine monomer was dissolved in 40g of N,N-dimethylformamide solvent, and the mixed solution was placed in an oven at 80 degrees Celsius for 12 hours to obtain a gel solution; 0.5-5g of hydrochloric acid was dissolved in 40g of N,N-dimethylformamide solvent to obtain an acid catalytic solution, and the two solutions were uniformly mixed to obtain a polybenzoxazine solution; the polybenzoxazine solution was poured into a mold to form a wet gel; the wet gel was aged at room temperature for 10-20 hours, and then the wet gel was dried at normal pressure for 24 hours, and then the wet gel was The gel was washed with N,N-dimethylformamide 1-3 times, each washing time being 10-20 hours, to obtain a wet conductive gel. The wet conductive gel was then dried at room temperature and pressure for 24-48 hours to obtain a novel polybenzoxazine aerogel having electrical conductivity and electromagnetic shielding properties. Finally, the dried novel polybenzoxazine aerogel was heated in an argon environment at 800°C for 6 hours to obtain a novel carbonized polybenzoxazine aerogel. The electromagnetic shielding properties of the aerogel are shown in Table 2, the resistivity values ​​are shown in Table 3, and the specific surface area and average pore size are shown in Table 4.

[0050] Example 3: Preparation method of new carbonized polybenzoxazine aerogel:

[0051] 30g of bisphenol F type benzoxazine monomer was dissolved in 40g of N,N-dimethylformamide solvent, and the mixed solution was placed in an oven at 80 degrees Celsius for 12 hours to obtain a gel solution; 0.5-5g of hydrochloric acid was dissolved in 40g of N,N-dimethylformamide solvent to obtain an acid catalytic solution, and the two solutions were uniformly mixed to obtain a polybenzoxazine solution; the polybenzoxazine solution was poured into a mold to form a wet gel; the wet gel was aged at room temperature for 10-20 hours, and then the wet gel was dried at normal pressure for 24 hours, and then the wet gel was The gel was washed with N,N-dimethylformamide 1-3 times, each washing time being 10-20 hours, to obtain a wet conductive gel. The wet conductive gel was then dried at room temperature and pressure for 24-48 hours to obtain a novel polybenzoxazine aerogel having electrical conductivity and electromagnetic shielding properties. Finally, the dried novel polybenzoxazine aerogel was heated in an argon environment at 800°C for 6 hours to obtain a novel carbonized polybenzoxazine aerogel. The electromagnetic shielding properties of the aerogel are shown in Table 2, the resistivity values ​​are shown in Table 3, and the specific surface area and average pore size are shown in Table 4.

[0052] Example 4: Preparation method of new carbonized polybenzoxazine aerogel:

[0053] 40g of bisphenol F type benzoxazine monomer was dissolved in 40g of N,N-dimethylformamide solvent, and the mixed solution was placed in an oven at 80 degrees Celsius for 12 hours to obtain a gel solution; 0.5-5g of hydrochloric acid was dissolved in 40g of N,N-dimethylformamide solvent to obtain an acid catalytic solution, and the two solutions were uniformly mixed to obtain a polybenzoxazine solution; the polybenzoxazine solution was poured into a mold to form a wet gel; the wet gel was aged at room temperature for 10-20 hours, and then the wet gel was dried at normal pressure for 24 hours, and then the wet gel was quenched with N , washed with N-dimethylformamide 1-3 times, each washing time is 10-20 hours, to obtain a wet conductive gel; then the wet conductive gel is dried at room temperature and pressure for 24-48 hours to obtain a novel polybenzoxazine aerogel with electrical conductivity and electromagnetic shielding properties; finally, the dried novel polybenzoxazine aerogel is heated in an argon environment at 800°C for 6 hours to obtain a novel carbonized polybenzoxazine aerogel, the residual carbon rate of which is shown in Table 1, the electromagnetic shielding properties of which are shown in Table 2, the resistivity values ​​are shown in Table 3, and the specific surface area and average pore size are shown in Table 4.

[0054] The electromagnetic shielding performance of the products of Examples 1-4 was measured using a 3671G vector network analyzer and a waveguide method; the electromagnetic shielding performance comparison diagram is shown in FIG. Figure 1 As shown in the figure, with the increase of bisphenol F polybenzoxazine content, the electromagnetic shielding performance of the prepared new carbonized polybenzoxazine aerogel is improved.

[0055] The thermogravimetric curve of the novel carbonized polybenzoxazine aerogel prepared in Example 4 was measured using a TGA / DSC 3+ thermogravimetric analyzer (Mettler Toledo, Switzerland). The specific method is as follows: the sample is placed in a special crucible according to the instrument manual. The instrument records the mass loss in real time during heating. The data is then plotted using origin to obtain a thermogravimetric curve. The thermogravimetric curve of the novel carbonized polybenzoxazine aerogel prepared in Example 4 is shown in FIG. Figure 4 The carbonization temperature and residual carbon rate of the novel carbonized polybenzoxazine aerogel prepared in Example 4 are shown in Table 1.

[0056] Table 1 Carbon Residue Rate Test Results

[0057]

[0058] It can be seen from the data in Table 1 that the novel carbonized polybenzoxazine aerogel prepared in Example 4 has a relatively high high-temperature residual carbon rate and is suitable for use in environments of 400° C. and below.

[0059] The novel carbonized polybenzoxazine aerogel prepared in Example 4 was scanned by a SU8010 scanning electron microscope (HITACHI, Japan) under gold spraying test conditions. The scanning electron microscope image of Example 4 is shown in FIG. Figure 5 As shown by Figure 5It can be seen that when the bisphenol F polybenzoxazine content is within 10-40g, the prepared new carbonized polybenzoxazine aerogel has a normal gel structure.

[0060] The electromagnetic shielding performance of the novel carbonized polybenzoxazine aerogels prepared in Examples 2 to 4 was measured using a 3671G vector network analyzer using a waveguide method; the resistivity was measured using a four-probe method; the relationship between the electromagnetic shielding performance and resistivity of Examples 2 to 4 is shown in the figure below. Figure 3 As shown in FIG, as the content of bisphenol F polybenzoxazine increases, the conductivity of the prepared novel carbonized polybenzoxazine aerogel increases.

[0061] In order to better illustrate the beneficial effects of the present invention, the inventors of the present application modified the parameters of Examples 1-4 to prepare Examples 5-9 as comparative examples. Specific operations are shown in the preparation methods of Examples 5-9.

[0062] Example 5: Preparation method of polybenzoxazine aerogel:

[0063] 50 g of bisphenol F-type benzoxazine monomer was dissolved in 40 g of N,N-dimethylformamide solvent, and the mixed solution was placed in an 80°C oven for 12 hours to obtain a gel solution. 0.5-5 g of hydrochloric acid was dissolved in 40 g of N,N-dimethylformamide solvent to obtain an acid-catalyzed solution, and the two solutions were uniformly mixed to obtain a polybenzoxazine solution. The polybenzoxazine solution was poured into a mold to form a wet gel. The mixture was aged at room temperature for 10-20 hours, and then the wet gel was dried at normal pressure for 24 hours. The wet gel was then washed with N,N-dimethylformamide 1-3 times, each washing time being 10-20 hours, to obtain a wet gel. The wet gel was then dried at room temperature and normal pressure to obtain a polybenzoxazine aerogel. The electromagnetic shielding properties of the aerogel are shown in Table 2, and the resistivity values ​​are shown in Table 3.

[0064] Example 6: Preparation method of polybenzoxazine aerogel:

[0065] 50 g of bisphenol F-type benzoxazine monomer was dissolved in 40 g of N,N-dimethylformamide solvent, and the mixed solution was placed in an 80°C oven for 12 hours to obtain a gel solution. 0.5-5 g of hydrochloric acid was dissolved in 40 g of N,N-dimethylformamide solvent to obtain an acid-catalyzed solution, and the two solutions were uniformly mixed to obtain a polybenzoxazine solution. The polybenzoxazine solution was poured into a mold to form a wet gel. The gel was aged at room temperature for 10-20 hours, and then the wet gel was dried at normal pressure for 24 hours. The wet gel was then washed with N,N-dimethylformamide 1-3 times, each washing time being 10-20 hours, to obtain a wet gel. The wet gel was then dried at room temperature and normal pressure. Finally, the dried aerogel was heated in air at 200°C for 6 hours to obtain a polybenzoxazine aerogel. The electromagnetic shielding properties of the aerogel are shown in Table 2, and the resistivity values ​​are shown in Table 3.

[0066] The electromagnetic shielding performance comparison of Example 4, Example 5 and Example 6 is shown in the figure below: Figure 2 As shown, Examples 5 and 6 are polybenzoxazine aerogels dried at room temperature and 200 degrees Celsius in air, without carbonization treatment. Compared with Example 4, it can be seen that the electromagnetic shielding performance of the aerogel is greatly enhanced after carbonization treatment at 800 degrees Celsius.

[0067] Example 7: Preparation method of polybenzoxazine solid with higher density:

[0068] 60g of bisphenol F-type benzoxazine monomer is dissolved in 40g of N,N-dimethylformamide solvent, and the mixed solution is placed in an 80-degree Celsius oven for 12 hours to obtain a gel solution. 0.5-5g of hydrochloric acid is dissolved in 40g of N,N-dimethylformamide solvent to obtain an acid-catalyzed solution, and the two solutions are uniformly mixed to obtain a polybenzoxazine solution. The polybenzoxazine solution is poured into a mold to form a wet gel. The wet gel is aged at room temperature for 10-20 hours, then dried at normal pressure for 24 hours, and then washed with N,N-dimethylformamide 1-3 times, each washing time for 10-20 hours, to obtain a conductive wet gel. The conductive wet gel is then dried at room temperature and pressure. Finally, the dried aerogel is heated at 800°C in an argon atmosphere for 6 hours to obtain a high-density polybenzoxazine solid.

[0069] The product of Example 7 was scanned under the same electron microscope scanning conditions as the product of Example 4. The scanning electron microscope image is shown in FIG. Figure 6 As shown by Figure 5 and Figure 6 It can be seen that when the bisphenol F polybenzoxazine content is within 10-40g, the prepared polybenzoxazine aerogel has a normal gel structure; however, as the bisphenol F polybenzoxazine content increases, the gel structure is lost at the final content of 60g, and it becomes a polybenzoxazine polymer.

[0070] Example 8: Preparation method of polybenzoxazine aerogel:

[0071] 20g of bisphenol-type benzoxazine monomer is dissolved in 40g of N,N-dimethylformamide solvent, and the mixed solution is placed in an 80-degree Celsius oven for 12 hours to obtain a gel solution. 0.5-5g of hydrochloric acid is dissolved in 40g of N,N-dimethylformamide solvent to obtain an acid-catalyzed solution, and the two solutions are uniformly mixed to obtain a polybenzoxazine solution. The polybenzoxazine solution is poured into a mold to form a wet gel. The wet gel is aged at room temperature for 10-20 hours, then dried at normal pressure for 24 hours. The wet gel is then washed with N,N-dimethylformamide, acetonitrile, n-pentane, and acetone one to three times, each washing for 10-20 hours, to obtain a wet gel. The wet gel is then dried at room temperature and pressure. Finally, the dried aerogel is heated at 800 degrees Celsius under argon to obtain a polybenzoxazine aerogel.

[0072] The electromagnetic shielding performance comparison between Example 2 and Example 8 is shown in the figure below: Figure 7 As shown, the aerogel obtained by the preparation method of the present application has stronger electromagnetic shielding performance compared with the preparation method of CN113603925A (the method of Example 8).

[0073] Example 9: Preparation method of polybenzoxazine aerogel:

[0074] 20g of bisphenol-type benzoxazine monomer is dissolved in 40g of N,N-dimethylformamide solvent, and the mixed solution is placed in an 80-degree Celsius oven for 12 hours to obtain a gel solution. 0.5-5g of hydrochloric acid is dissolved in 40g of N,N-dimethylformamide solvent to obtain an acid-catalyzed solution, and the two solutions are uniformly mixed to obtain a polybenzoxazine solution. The polybenzoxazine solution is poured into a mold to form a wet gel. The wet gel is aged at room temperature for 10-20 hours, then dried at normal pressure for 24 hours, and then washed with N,N-dimethylformamide and acetone 1-3 times, each washing time for 10-20 hours, to obtain a gel. The gel is then supercritically dried with carbon dioxide to obtain a polybenzoxazine aerogel.

[0075] Example 10: Preparation method of polybenzoxazine aerogel:

[0076] 20g of bisphenol-type benzoxazine monomer is dissolved in 40g of N,N-dimethylformamide solvent, and the mixed solution is placed in an 80-degree Celsius oven for 12 hours to obtain a gel solution; 0.5-5g of hydrochloric acid is dissolved in 40g of N,N-dimethylformamide solvent to obtain an acid-catalyzed solution, and the two solutions are uniformly mixed to obtain a polybenzoxazine solution; the polybenzoxazine solution is poured into a mold to form a wet gel; the wet gel is aged at room temperature for 10-20 hours, and then dried at normal pressure for 24 hours. Thereafter, the wet gel is washed with N,N-dimethylformamide and acetone 1-3 times, each washing time being 10-20 hours, to obtain a gel; the gel is then supercritically dried with carbon dioxide to obtain a dry aerogel; and the aerogel is then heated to 200 degrees Celsius in an air atmosphere at normal pressure to obtain a polybenzoxazine aerogel.

[0077] The electromagnetic shielding performance of the products prepared in Examples 1 to 8 was tested, and the results are shown in Table 2. The resistivity of the products prepared in Examples 1 to 8 was tested, and the results are shown in Table 3.

[0078] Table 2 Electromagnetic shielding performance test results (12.4GHz)

[0079]

[0080] Table 3 Resistivity test results

[0081]

[0082] The specific surface area and average pore size of the products prepared in Examples 1 to 10 were measured using a Micromeritics ASAP 2020 specific surface area analyzer. The results are shown in Table 4. The product of Example 7 is not a gel structure and is therefore not listed in Table 4:

[0083] Table 4 Comparison of specific surface area and average pore size

[0084]

[0085] From the data in Tables 2, 3, and 4, it can be seen that since the novel polybenzoxazine aerogel of the present invention has a smaller specific surface area and average pore size than other polybenzoxazine aerogels, the reflection loss of electromagnetic waves in the material is greater, and therefore, it has stronger electromagnetic shielding performance than other aerogel materials.

[0086] Examples 1-4 are carbonized aerogels with different bisphenol F contents. It can be seen that within a certain range, the higher the bisphenol F content, the stronger the electromagnetic shielding performance of the carbonized aerogel. However, when the bisphenol F content is too high, such as when the bisphenol F content is 60 parts in Example 7, the prepared polybenzoxazine polymer will lose its gel structure, increase the weight of the material, and reduce its flexibility.

[0087] Examples 5 and 6 are polybenzoxazine aerogels dried at room temperature and 200 degrees Celsius in air, without carbonization treatment. Figure 2 It can be seen that the electromagnetic shielding performance of aerogel is greatly enhanced after carbonization treatment at 800℃.

[0088] Example 8 is a novel polybenzoxazine aerogel obtained by other cleaning methods. Figure 7 It can be seen that the aerogel cleaned only with N,N-dimethylformamide has better electromagnetic shielding performance.

[0089] Examples 9 and 10 are novel polybenzoxazine aerogels obtained by supercritical carbon dioxide drying. Compared with Example 2, it can be seen that the aerogels obtained by normal temperature and pressure drying have smaller surface area and pore size, and have better electromagnetic shielding structure.

[0090] The above description is only a preferred embodiment of the present invention and does not impose any formal or substantial limitation on the present invention. Any technician familiar with the present profession can make use of the technical content disclosed above without departing from the scope of the technical solution of the present invention, and any equivalent changes, modifications and evolutions made by them are equivalent embodiments of the present invention. At the same time, any equivalent changes, modifications and evolutions made to the above embodiments based on the essential technology of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A carbonized polybenzoxazine aerogel, characterized by: The carbonized polybenzoxazine aerogel is prepared from the following raw materials in parts by weight: 10-40 parts of bisphenol F-type benzoxazine, 50-200 parts of N,N-dimethylformamide, and 0.5-5 parts of hydrochloric acid, wherein the concentration of the hydrochloric acid is 36%-38%; The preparation steps are: (1) dissolving bisphenol F type benzoxazine in N,N-dimethylformamide and heating to obtain a bisphenol F solution; adding hydrochloric acid to N,N-dimethylformamide to obtain an acid catalytic solution; mixing the bisphenol F solution and the acid catalytic solution and stirring to obtain a polybenzoxazine solution; (2) placing the polybenzoxazine solution obtained in step (1) into a mold to form a wet gel; (3) aging the wet gel obtained in step (2), and drying it at normal pressure for 24 hours after aging; (4) washing the aged wet gel obtained in step (3) with N,N-dimethylformamide to obtain a wet conductive gel; (5) drying the wet conductive gel obtained in step (4) at room temperature and pressure for 24-48 hours to obtain a polybenzoxazine aerogel having electrical conductivity and electromagnetic shielding properties; (6) The polybenzoxazine aerogel obtained in step (5) was heated to 800°C in an argon environment at a heating rate of 5°C / min, and then kept at 800°C for 6 hours, and then cooled in the furnace. During the heating and cooling, the argon flow rate was ensured to be greater than 50 ml / min. After cooling, the carbonized polybenzoxazine aerogel was obtained; The carbonized polybenzoxazine aerogel has a specific surface area of ​​5.38-24.811 square meters per gram, an average pore diameter of 5.95-14.16 nanometers, a resistivity of 4.93-7.34 ohm·meters, and an electromagnetic shielding performance of 28.05-77.51 decibels for 8-12.4 GHz electromagnetic waves.

2. A method for preparing carbonized polybenzoxazine aerogel, characterized in that: The preparation method comprises the following steps: (1) dissolving bisphenol F type benzoxazine in N,N-dimethylformamide and heating to obtain a bisphenol F solution; adding hydrochloric acid to N,N-dimethylformamide to obtain an acid catalytic solution; mixing the bisphenol F solution and the acid catalytic solution and stirring to obtain a polybenzoxazine solution; (2) placing the polybenzoxazine solution obtained in step (1) into a mold to form a wet gel; (3) aging the wet gel obtained in step (2), and drying it at normal pressure for 24 hours after aging; (4) washing the aged wet gel obtained in step (3) with N,N-dimethylformamide to obtain a wet conductive gel; (5) drying the wet conductive gel obtained in step (4) at room temperature and pressure for 24-48 hours to obtain a polybenzoxazine aerogel having electrical conductivity and electromagnetic shielding properties; (6) The polybenzoxazine aerogel obtained in step (5) was heated to 800°C in an argon environment at a heating rate of 5°C / min. After heating to 800°C, the temperature was kept at that temperature for 6 hours, and then cooled in the furnace. During the heating and cooling, the argon flow rate was ensured to be greater than 50 ml / min. After cooling, the carbonized polybenzoxazine aerogel was obtained.

3. The method for preparing a carbonized polybenzoxazine aerogel according to claim 2, wherein: In step (1), the amount of bisphenol F-type benzoxazine, the amount of N,N-dimethylformamide, and the amount of hydrochloric acid are 10-40 parts by weight, 50-200 parts by weight, and 0.5-5 parts by weight, and the concentration of the hydrochloric acid is 36%-38%.

4. The method for preparing a carbonized polybenzoxazine aerogel according to claim 2, wherein the carbonized polybenzoxazine aerogel comprises: In step (1), 10-30 parts of bisphenol F type benzoxazine are placed in 20-40 parts of N,N-dimethylformamide, and heated in a heating box at 80°C for 12 hours, and then cooled to room temperature to obtain a bisphenol F solution; 2-5 parts of concentrated hydrochloric acid are added to 20-40 parts of N,N-dimethylformamide and uniformly stirred to obtain an acid catalytic solution; the acid catalytic solution is added to the bisphenol F solution and rapidly stirred for 30 seconds to obtain a polybenzoxazine solution.

5. The method for preparing a carbonized polybenzoxazine aerogel according to claim 2, wherein: In step (2), the gel time is greater than 15 minutes.

6. The method for preparing a carbonized polybenzoxazine aerogel according to claim 2, wherein: In step (3), the aging environment is normal temperature and pressure; the aging time is 12-24 hours.

7. The method for preparing a carbonized polybenzoxazine aerogel according to claim 2, wherein: In step (4), the wet gel is washed with N,N-dimethylformamide 1-3 times, with each washing time being 10-20 hours.

8. Carbonized polybenzoxazine aerogel prepared by the preparation method according to any one of claims 2 to 7.

9. The carbonized polybenzoxazine aerogel according to claim 8, wherein: The specific surface area of ​​the carbonized polybenzoxazine aerogel is 5.38-24.811 square meters per gram, the average pore diameter is 5.95-14.16 nanometers, the resistivity is 4.93-7.34 ohm·m, and the electromagnetic shielding performance against 8-12.4 GHz electromagnetic waves is 28.05-77.51 decibels.

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