Preparation method and application of thermoplastic polyimide powder

Abstract

The application belongs to the technical field of polymer material preparation, and particularly discloses a preparation method of thermoplastic polyimide powder and application thereof. The preparation method provided by the application is characterized by polymerizing aromatic dianhydride and aromatic diamine in a protic solvent to generate polyamide acid, and separating polyamide acid powder; the polyamide acid powder is subjected to solid-phase polymerization and imidization reaction to obtain polyimide; and the protic solvent is an alcohol organic solvent. The preparation method can effectively control the particle size, compactness and morphology of the obtained polyimide powder, and can realize controllable adjustment of the solubility of the polyimide powder toughening agent in a thermosetting resin system, and further realize efficient toughening of a thermosetting resin-based composite material.

Description

Technical Field

[0001] This invention belongs to the field of polymer material preparation technology, specifically relating to a method for preparing thermoplastic polyimide powder, and the application of the obtained thermoplastic polyimide powder. Background Technology

[0002] The layered structure of composite materials makes interlaminar strength a weak point, easily leading to impact delamination damage. Since the 1980s, international research has focused on toughening techniques for composite materials. Studies have shown that interlaminar toughening is the most effective way to improve the interlaminar toughness of composite materials. There are generally three methods of interlaminar toughening: particle toughening, film toughening, and fiber toughening. Among these, interlaminar particle toughening has become the most practical interlaminar toughening technique.

[0003] There are numerous reports on interlaminar particle toughening technology, and the use of nylon 6 as a toughening agent has been applied in the production of composite materials. For example, Toray Industries of Japan developed the T800H / 3900 series of ultra-high toughness composite materials using nylon 6 powder as an interlaminar toughening agent. 8551-7 and M21 are high-toughness epoxy resin matrices developed by HEXCEL, and their interlaminar toughening agents are also nylon 6 powder. However, nylon 6 has a relatively low glass transition temperature, which usually cannot meet the heat resistance requirements of resin-based composite materials with temperatures above 100℃, especially the toughening requirements of bismaleimide resins.

[0004] To meet the demand for toughening of high-humidity and heat-resistant resin matrices, existing literature reports the use of polyimide powder with high temperature resistance as a toughening agent. Currently, polyimide is generally prepared by solution polymerization in a polar aprotic solvent, high-temperature dehydration with an azeotropic dehydrating agent, followed by washing, drying, and pulverizing. For example, patent application CN 113292726A discloses a polyimide molding powder and its preparation method. The method involves reacting a diamine monomer and a dianhydride monomer in a polar aprotic solvent to obtain a polyamic acid solution. An azeotropic dehydrating agent is added to the obtained polyamic acid solution, and the mixture is heated to reflux. After cooling to crystallize, the powder is filtered, washed, dried, ground, and sieved. It is then subjected to high-temperature drying and aging, and finally sieved and graded to obtain the polyimide molding powder. Existing methods for preparing polyimide involve polymerization in polar aprotic solvents, followed by high-temperature reflux dehydration with an azeotropic dehydrating agent to synthesize polyimide. Afterward, the polyimide powder is obtained by washing with a large amount of deionized water and drying. The disadvantages of this type of preparation method are that the process is long, it is difficult to remove high-boiling-point solvents by washing, it is difficult to control the particle size of the powder, and the resulting powder has low density.

[0005] Therefore, it is necessary to develop a new method for preparing thermoplastic polyimide powder to effectively solve the problems existing in the current preparation methods. Summary of the Invention

[0006] The purpose of this invention is to provide a method for preparing thermoplastic polyimide powder, and the invention also provides applications of the obtained thermoplastic polyimide powder.

[0007] To achieve the above objectives, the present invention adopts the following technical solution.

[0008] In a first aspect, the present invention provides a method for preparing thermoplastic polyimide powder, comprising the steps of:

[0009] S1: Aromatic dianhydrides and aromatic diamines polymerize in a protic solvent to form polyamic acid, and polyamic acid powder is separated out;

[0010] S2: The polyamic acid powder is subjected to solid-state polymerization and imidization reaction to obtain polyimide;

[0011] The proton-type solvent is an alcohol-based organic solvent.

[0012] As one embodiment of the present invention, the alcohol organic solvent is selected from one or more of methanol, ethanol, propanol, isopropanol, n-butanol, isobutanol, tert-butanol, 1-pentanol, 3-pentanol, hexanol, ethylene glycol, and benzyl alcohol.

[0013] In a preferred embodiment of the present invention, the alcoholic organic solvent is selected from one or more of methanol, ethanol, propanol, 1-pentanol, and 3-pentanol.

[0014] As a further preferred embodiment of the present invention, the alcoholic organic solvent is selected from ethanol and / or 1-pentanol.

[0015] As one embodiment of the present invention, the polyamic acid powder separated in step S1 is pulverized and then subjected to solid-phase polymerization.

[0016] In one embodiment of the present invention, the reaction temperature of solid-phase polymerization and imidization reaction in step S2 is 150-250℃.

[0017] In one embodiment of the present invention, the reaction pressure of the solid-phase polymerization and imidization reaction in step S2 is 0.1-2.0 MPa.

[0018] In one embodiment of the present invention, the solid-phase polymerization and imidization reaction in step S2 are carried out in a pressure drum dryer.

[0019] As one embodiment of the present invention, the theoretically calculated molecular weight of the polyimide obtained in step S2 is 10,000-200,000 g / mol.

[0020] As one embodiment of the present invention, the polyimide obtained in step S2 is further pulverized to obtain polyimide powder, wherein the particle size D90 of the polyimide powder is 5-50 μm.

[0021] As a specific embodiment of the present invention, step S1 includes:

[0022] S11: The aromatic dianhydride monomer is esterified in a protic solvent to obtain the esterified product;

[0023] S12: The esterified compound is polymerized with an aromatic diamine in a protic solvent to generate polyamic acid;

[0024] The proton-type solvent in step S11 may be the same as or different from the proton-type solvent in step S12.

[0025] As one embodiment of the present invention, the proton solvent is selected from any one or more of methanol, ethanol, propanol, isopropanol, n-butanol, isobutanol, tert-butanol, 1-pentanol, 3-pentanol, hexanol, ethylene glycol, and benzyl alcohol.

[0026] In a preferred embodiment of the present invention, the protonated solvent is selected from one or more of methanol, ethanol, propanol, 1-pentanol, and 3-pentanol.

[0027] As a further preferred embodiment of the present invention, the protonated solvent is selected from ethanol and / or 1-pentanol.

[0028] As one embodiment of the present invention, step S1 further includes:

[0029] S13: Cool the reaction solution after polymerization in step S12 to precipitate polyamic acid solid, then separate it to obtain polyamic acid powder.

[0030] In one embodiment of the present invention, the molar ratio of the aromatic dianhydride to the aromatic diamine is (0.95-1.05):(0.95-1.05).

[0031] Preferably, the molar ratio of the aromatic dianhydride to the aromatic diamine is (0.95-1.05):1.

[0032] More preferably, the molar ratio of the aromatic dianhydride to the aromatic diamine is (0.99-1.01):1.

[0033] In a more preferred embodiment of the present invention, the molar ratio of the aromatic dianhydride to the aromatic diamine is 1:1.

[0034] As one embodiment of the present invention, the aromatic dianhydride is selected from one or more of the following: pyromellitic dianhydride, biphenyl dianhydride or its isomers, 4,4'-oxobisphthalic anhydride or its isomers, triphenyl diether tetracarboxylic anhydride or its isomers, benzophenone tetracarboxylic anhydride, 2,2-bis[4-(3,4-carboxyphenoxy)benzene]propane dianhydride, 4,4'-(hexafluoroisopropyl)diphthalic anhydride, cyclobutane dianhydride, cyclohexane dianhydride, dicyclopentadiene dianhydride, bis(phenoxy)phenyltetracarboxylic anhydride or its isomers.

[0035] As one embodiment of the present invention, the aromatic diamine is selected from p-phenylenediamine, m-phenylenediamine, mesitylene-m-phenylenediamine, 2,2'-dimethylbenzidine, 1,3-bis(4-aminophenoxy)benzene, 1,3-bis(3-aminophenoxy)benzene, 2,2'-bis(trifluoromethylbenzidine), 4,4'-diaminodiphenylmethane, 3,3'-diaminobenzophenone, 4,4'-diaminodiphenyl sulfone, 3,3'-diaminodiphenyl sulfone, 4,4'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 1,4-bis(4-aminophenoxy)benzene, 1,3'-bis(4-aminophenoxy)benzene, 1,3'-bis(4-aminophenoxy)benzene, 1,4 ... One or more of the following: (4-aminophenoxy)benzene, 1,3-bis(3-aminophenoxy)benzene, 1,4-bis(2-trifluoromethyl-4-aminophenoxy)benzene, 4,4'-bis(4-aminophenoxy)biphenyl, 4,4'-bis(3-aminophenoxy)biphenyl, 2,2'-bis[4-(4-aminophenoxy)phenyl]propane, 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane, 4,4'-bis(3-aminophenoxy)diphenyl sulfone, 9,9-bis(4-aminophenyl)fluorene, and 9,9-bis[4-(aminophenoxy)phenyl]fluorene.

[0036] Secondly, the present invention provides thermoplastic polyimide powder obtained by the preparation method described in the present invention.

[0037] Thirdly, the present invention provides applications of the thermoplastic polyimide powder obtained by the preparation method of the present invention, wherein the applications include the application of the thermoplastic polyimide powder as a toughening agent for resin-based composite materials.

[0038] Preferably, the resin-based composite material is a thermosetting resin-based composite material, and more preferably, epoxy resin, bismaleimide resin, or thermosetting polyimide resin-based composite material.

[0039] More preferably, the resin-based composite material is an AG80 / DDS system.

[0040] The method for preparing thermoplastic polyimide powder provided by this invention employs a PMR monomer mixing method using a proton-type polar solvent as the reaction solvent. The monomer is polymerized from aromatic dianhydride and aromatic diamine. The monomer is polymerized in a proton-type solvent under pressure and high temperature to generate polyamic acid, which then precipitates to obtain polyamic acid powder. The polyamic acid powder is then heated and subjected to solid-state polymerization under pressure, which further increases the molecular weight and completes the imidization reaction to obtain thermoplastic polyimide powder.

[0041] This invention employs a protonated alcohol solvent PMR pressurized method to synthesize polyamic acid powder and then pressurized solid-phase imidization to obtain polyimide powder. This method offers significant advantages over traditional dehydration methods using aprotic solvents and high-temperature dehydrating agents. The invention utilizes a low-boiling-point protonated solvent, minimizing the residue of organic solvents in the thermoplastic polyimide toughening agent. The pressurized polymerization process for polyamic acid allows for rapid polymerization and precipitation into powder at temperatures above the boiling point in a low-boiling-point solvent. The polyamic acid powder is then added to a solid-phase polymerization reactor for pressurized imidization, further increasing the molecular weight of the polyamic acid. This solid-phase polymerization method, compared to aprotic solvent imidization, does not require high-boiling-point organic solvents and offers higher preparation efficiency. Pressurized solid-phase imidization promotes powder densification, allows control over the solubility of the resulting polyimide toughening agent in thermosetting resins, and effectively removes residual alcohol solvents from the polyamic acid synthesis process.

[0042] The preparation method of this invention can effectively control the particle size, density, and morphology of the obtained polyimide powder. The particle size (D90) of the toughening agent powder can be controlled within the range of 5-50 μm, resulting in dense particles with an ellipsoidal or near-spherical morphology. This allows for controllable adjustment of the solubility of the polyimide powder toughening agent in epoxy resin matrices and thermosetting resin systems such as bismaleimide resin, thereby achieving efficient toughening of thermosetting resin-based composite materials and improving their impact resistance. Furthermore, this invention enables the efficient, low-cost, highly reliable, and environmentally friendly synthesis of polyimide toughening agents. Detailed Implementation

[0043] The technical solution of the present invention will be further described in detail below. Those skilled in the art should understand that the specific embodiments described are merely illustrative of the invention and should not be considered as specific limitations thereof.

[0044] It should be noted that, unless otherwise specified, the technical means used in the following examples are conventional means well known to those skilled in the art, and the raw materials used are all commercially available conventional products.

[0045] The method for preparing thermoplastic polyimide powder provided by this invention includes the following steps:

[0046] (1) The aromatic dianhydride monomer is added to a reaction vessel containing an alcoholic organic solvent and dissolved by heating and stirring under a nitrogen atmosphere; the esterified product is mixed with the aromatic diamine monomer, the aromatic diamine monomer is added at an equimolar ratio or near-equimolar ratio with the aromatic dianhydride monomer, and a mixture solution with a mass percentage concentration of 10-90% is formed in the alcoholic organic solvent; preferably, the molar ratio of aromatic dianhydride to aromatic diamine is (0.95-1.05):(0.95-1.05), more preferably the molar ratio is 1:1;

[0047] (2) The mixture solution is stirred at 120-160℃ and 0-2.0MPa for 1-5 hours to polymerize into polyamic acid. Then, the reaction solution is gradually cooled to room temperature under continuous stirring. The polyamic acid generated in the reaction precipitates in the alcohol solution and is filtered to obtain solid polyamic acid.

[0048] (3) Pulverize the solid polyamic acid to obtain polyamic acid powder with a particle size (D90) of 5-50 μm;

[0049] (4) The pulverized polyamic acid powder is added to a pressure drum dryer and reacted at 150-250℃ and 0.1-2.0MPa for 2-10 hours to complete the solid-state polymerization and imidization reaction of polyamic acid, thereby achieving further growth of the molecular weight of polyamic acid and densification and imidization reaction of polyamic acid or polyimide powder under pressure conditions, and obtaining polyimide with a molecular weight of 10000-200000g / mol;

[0050] (5) The obtained polyimide is classified by air jet mill to obtain thermoplastic polyimide powder toughening agent with a particle size (D90) of 5-50μm.

[0051] The following examples will provide a detailed explanation.

[0052] Example 1

[0053] This embodiment provides a method for preparing thermoplastic polyimide powder, the steps of which are as follows:

[0054] 1.00786 mol of 1,2,4,5-pyromellitic dianhydride (PMDA) was added to 500 g of anhydrous ethanol and heated to reflux to completely esterify and dissolve the anhydride. Then, 1 mol of 4,4'-diaminodiphenyl ether was added under stirring and stirred until completely dissolved. The reaction solution was transferred to a sealed pressurized reactor, heated to 135 °C (the pressure inside the reactor was simultaneously increased to 0.6 MPa), and stirred for 2 hours to polymerize and form a polyamic acid polymer.

[0055] The reaction solution obtained from polymerization was then cooled to room temperature, and the polyamic acid polymer precipitated into powder. After filtration, the polyamic acid powder was obtained and further pulverized using an air jet mill, with the pulverization diameter D90 controlled at 25 μm.

[0056] Polyamic acid powder was placed in a pressure drum dryer with heating and pressurization functions. The temperature was first raised to 180℃ and held for 1 hour, and then raised to 230℃ and held for 1 hour. The pressure was controlled at 0.1 MPa to complete the imidization reaction and simultaneously increase the molecular weight to obtain thermoplastic polyimide with a molecular weight of 50,000 g / mol.

[0057] The obtained thermoplastic polyimide was pulverized and classified using an air jet mill to obtain a thermoplastic polyimide powder toughening agent with a particle size (D90) of 30 μm. The powder particles were dense and ellipsoidal in shape, and were designated as PO-1.

[0058] The PO-1 thermoplastic polyimide powder obtained in this embodiment was used to toughen CCF300 carbon fiber reinforced (AG80+DDS) resin matrix composites. The untoughened (AG80+DDS) resin matrix composite had a post-impact compressive strength of 154 MPa, while the toughened composite had a post-impact compressive strength of 257 MPa.

[0059] Example 2

[0060] This embodiment provides a method for preparing thermoplastic polyimide powder, the steps of which are as follows:

[0061] 1.0087 mol of isomeric biphenyl dianhydride (α-BPDA) was added to 600 g of anhydrous ethanol and refluxed for esterification. After complete esterification, the mixture was concentrated by distillation and dried to obtain solid diethyl isomeric biphenyl dianhydride. The obtained solid diethyl isomeric biphenyl dianhydride was dissolved in 690 g of n-pentanol, and then 1 mol of 9,9-bis(4-aminophenyl)fluorene was added. The mixture was then heated in a closed pressurized reactor to the boiling point of n-pentanol (approximately 135-140 °C), with the pressure inside the reactor simultaneously increased to approximately 0.6 MPa. The mixture was refluxed for 3 hours to generate a polyamic acid polymer.

[0062] The reaction solution obtained from polymerization was then cooled to room temperature, and the polyamic acid polymer precipitated into powder. After filtration, polyamic acid powder was obtained and further pulverized using an air jet mill, with the pulverization diameter D90 controlled at 10 μm.

[0063] Polyamic acid powder was placed in a pressure drum dryer with heating and pressurization functions. The temperature was first raised to 150℃ and held for 1 hour, then raised to 180℃ and held for 1 hour, and then raised to 230℃ and held for 1 hour. A pressure of 0.2 MPa was applied to complete the imidization reaction and simultaneously increase the molecular weight, resulting in thermoplastic polyimide with a molecular weight of 70,000 g / mol.

[0064] The obtained thermoplastic polyimide was pulverized and classified using an air jet mill to obtain a thermoplastic polyimide powder toughening agent with a particle size (D90) of 15 μm. The powder particles were dense and ellipsoidal in shape, and were designated as BF-1.

[0065] The BF-1 thermoplastic polyimide powder prepared in this embodiment was used to toughen CCF800 carbon fiber reinforced (AG80+DDS) resin matrix composites. The post-impact compressive strength of the untoughened (AG80+DDS) resin matrix composites was 172 MPa, while the post-impact compressive strength of the toughened composites increased to 283 MPa.

[0066] Example 3

[0067] This embodiment provides a method for preparing thermoplastic polyimide powder, the steps of which are as follows:

[0068] 1.00658 mol of isomeric biphenyl tetracarboxylic dianhydride (α-BPDA) was added to 700 g of anhydrous ethanol and refluxed for 2 h to obtain reaction solution 1.

[0069] 1 mol of 4,4'-diaminodiphenyl ether (4,4'-ODA) and 467 g of ethanol were mixed and stirred for 30 min under nitrogen protection to obtain reaction solution 2.

[0070] Combine reaction solution 1 and reaction solution 2 and continue reflux reaction for 2 hours; then transfer to a closed pressurized reactor, heat to the range of 0.8-1.0 MPa, and control the temperature inside the reactor at 150℃-155℃, stir and react for 3 hours to generate polyamic acid polymer.

[0071] The reaction solution obtained from polymerization was then cooled to room temperature, and the polyamic acid polymer precipitated into powder. After filtration, the polyamic acid powder was obtained and further pulverized using an air jet mill, with the pulverization diameter D90 controlled at 20 μm.

[0072] Polyamic acid powder was placed in a pressure drum dryer with heating and pressurization functions. The temperature was first raised to 180℃ and held for 1 hour, then raised to 230℃ and held for 1 hour. The pressure was controlled at 0.15 MPa to complete the imidization reaction and simultaneously increase the molecular weight, resulting in thermoplastic polyimide with a molecular weight of 70,000 g / mol.

[0073] The obtained thermoplastic polyimide was pulverized and classified using an air jet mill to obtain a thermoplastic polyimide powder toughening agent with a particle size (D90) of 25 μm. The powder particles were dense and nearly spherical in shape, and were designated as AO-1.

[0074] By replacing the aromatic dianhydride and aromatic diamine monomer raw materials in Example 3, and using the same preparation method as in Example 3, thermoplastic polyimide toughening agent powders AA-1, BO-1, and BA-1 with different chemical structures were obtained, as shown in Table 1.

[0075] Table 1

[0076]

[0077] In Table 1, BTDA is 3,3',4,4'-benzophenone tetracarboxylic dianhydride, and 1,3,4-APB is 1,3-bis(4-aminophenoxy)benzene.

[0078] The above thermoplastic polyimide toughening agent powder was used to toughen CCF800 carbon fiber reinforced (AG80+DDS) resin matrix composites. The resulting composites showed a significant improvement in post-impact compressive strength compared to the original 172 MPa. See Table 2 for details.

[0079] Table 2

[0080]

[0081] The above thermoplastic polyimide toughening agent powder was used to toughen T700 grade carbon fiber reinforced (AG80+DDS) resin matrix composites. The post-impact compressive strength of the untoughened (AG80+DDS) resin matrix composites was 165 MPa. The performance of the composites was significantly improved after toughening, as shown in Table 3.

[0082] Table 3

[0083]

[0084]

[0085] The above embodiments illustrate that the preparation method of the present invention can effectively control the particle size, density and morphology of the obtained polyimide powder, and achieve controllable adjustment of the solubility of polyimide powder toughening agent in epoxy resin matrix and thermosetting resin systems such as bismaleimide resin, thereby achieving efficient toughening of thermosetting resin-based composite materials and improving the impact resistance of thermosetting resin-based composite materials.

[0086] Specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various changes or modifications within the scope of the claims, which do not affect the essence of the present invention. Unless otherwise specified, the embodiments and features described in this application can be arbitrarily combined with each other.

Claims

1. A method for preparing thermoplastic polyimide powder, characterized in that, Including the following steps: S11: Aromatic dianhydride monomers are esterified in alcoholic organic solvents to obtain esterified products; S12: The esterified compound is mixed with an aromatic diamine monomer to form a mixture solution with a mass percentage concentration of 10-90% in an alcoholic organic solvent; the mixture solution is stirred at 120-160℃ and 0.6-2.0MPa for 1-5 hours to polymerize and generate polyamic acid. Then, the reaction solution is gradually cooled to room temperature under continuous stirring, and the generated polyamic acid precipitates in the alcohol solution. After filtration, solid polyamic acid is obtained; the solid polyamic acid is pulverized to obtain polyamic acid powder with a particle size D90 of 5-50μm. S2: The polyamic acid powder is subjected to solid-state polymerization and imidization reaction at a reaction pressure of 0.1-2.0 MPa to obtain polyimide.

2. The preparation method according to claim 1, characterized in that, The alcoholic organic solvent is selected from one or more of methanol, ethanol, propanol, isopropanol, n-butanol, isobutanol, tert-butanol, 1-pentanol, 3-pentanol, hexanol, and benzyl alcohol.

3. The preparation method according to claim 1 or 2, characterized in that, The reaction temperature for solid-state polymerization and imidization in step S2 is 150–250 °C.

4. The preparation method according to claim 3, characterized in that, The solid-phase polymerization and imidization reactions are carried out in a pressure drum dryer.

5. The preparation method according to claim 1, characterized in that, The theoretically calculated molecular weight of the polyimide obtained in step S2 is 10,000 to 200,000 g / mol.

6. The preparation method according to claim 1, characterized in that, The molar ratio of the aromatic dianhydride to the aromatic diamine is (0.95-1.05):(0.95-1.05).

7. The preparation method according to claim 6, characterized in that, The aromatic dianhydride is selected from one or more of the following: pyromellitic dianhydride, biphenyl dianhydride or its isomers, 4,4'-oxobisphthalic anhydride or its isomers, triphenyl diether tetracarboxylic anhydride or its isomers, benzophenone tetracarboxylic anhydride, 2,2-bis[4-(3,4-carboxyphenoxy)benzene]propane dianhydride, 4,4'-(hexafluoroisopropyl)diphthalic anhydride, cyclobutane dianhydride, cyclohexane dianhydride, dicyclopentadiene dianhydride, bis(phenoxy)phenyltetracarboxylic anhydride or its isomers; and / or, The aromatic diamine is selected from p-phenylenediamine, m-phenylenediamine, mesitylene-m-phenylenediamine, 2,2'-dimethylbenzidine, 1,3-bis(4-aminophenoxy)benzene, 1,3-bis(3-aminophenoxy)benzene, 2,2'-bis(trifluoromethylbenzidine), 4,4'-diaminodiphenylmethane, 3,3'-diaminobenzophenone, 4,4'-diaminodiphenyl sulfone, 3,3'-diaminodiphenyl sulfone, 4,4'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 1,4-bis(4-aminophenoxy)benzene, 1,3-bis(4-aminophenoxy)benzene, etc. One or more of the following: 1,3-bis(3-aminophenoxy)benzene, 1,4-bis(2-trifluoromethyl-4-aminophenoxy)benzene, 4,4'-bis(4-aminophenoxy)biphenyl, 4,4'-bis(3-aminophenoxy)biphenyl, 2,2'-bis[4-(4-aminophenoxy)phenyl]propane, 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane, 4,4'-bis(3-aminophenoxy)diphenyl sulfone, 9,9-bis(4-aminophenyl)fluorene, and 9,9-bis[4-(aminophenoxy)phenyl]fluorene.

8. The application of the thermoplastic polyimide powder obtained by any of the preparation methods described in claims 1-7 as a toughening agent for resin-based composite materials; wherein the resin-based composite material is a thermosetting resin-based composite material.

9. The application according to claim 8, characterized in that, The thermosetting resin-based composite material is an epoxy resin, bismaleimide resin, or thermosetting polyimide resin-based composite material.

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