Modified polyimide resin for carbon fiber composite material, and preparation method and application thereof
By using fluorinated anionic salts and thermoplastic polymers to modify polyimide resin, combined with plasma grafting and segmented gradient curing technology, the problem of uneven wetting caused by the high viscosity of polyimide resin was solved, thereby improving the mechanical properties and stability of carbon fiber composites.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- KAIFENG QUARK NEW MATERIALS CO LTD
- Filing Date
- 2026-02-11
- Publication Date
- 2026-05-29
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Figure SMS_1
Abstract
Description
Technical Field
[0001] This invention relates to the field of polyimide technology, specifically to a modified polyimide resin for carbon fiber composites, its preparation method, and its application. Background Technology
[0002] Carbon fiber reinforced polymer (CFRP) composites, with their high specific strength, high specific modulus, and excellent fatigue resistance, are widely used in aerospace, high-end equipment manufacturing, and new energy vehicles. Prepreg, as the core intermediate material of CFRP, has its performance directly determined by the properties of the resin matrix. Polyimide (PI) resin, due to its temperature resistance >300℃, outstanding chemical stability, and mechanical strength, has become an ideal candidate material for high-performance prepregs. Polyamic acid, as a precursor to PI, directly determines the mechanical and dielectric properties of the final product through its solution processing performance. Currently, the industry generally faces the problem of high viscosity in polyamic acid solutions. The root cause lies in the electrostatic repulsion between carboxyl and amino groups on the molecular chain, leading to chain extension. This not only increases energy consumption but also causes defects such as spinning breakage and uneven coating. Furthermore, conventional PI resins struggle to achieve uniform wetting of carbon fibers, resulting in insufficient interlayer bonding in the prepreg. Simultaneously, the PI curing process easily generates volatile byproducts such as small-molecule water or solvents, which can easily form pore defects within the composite material, significantly reducing overall mechanical properties.
[0003] To address the viscosity issue, researchers have attempted to shield the charge by adding inorganic salts or adjusting the pH value. However, these methods are prone to inducing phase separation or degradation reactions, failing to meet the stringent requirements for material uniformity in high-end electronic devices. Existing technologies primarily employ three specific approaches: ① dilution with small-molecule polar solvents, which, while simple to operate, only reduces viscosity by 15%-20%, while also decreasing solids content and increasing recycling costs; ② introducing strong acid protonated amino groups, which leads to molecular chain degradation and is highly corrosive to equipment; ③ using traditional salts to shield the charge, but due to mismatched ion hydration radii, localized aggregation is likely, and strict temperature control (±0.5℃) is required, making industrial implementation difficult. None of these methods can simultaneously achieve significant viscosity reduction and long-term stability. The main drawbacks are: ① macroscopic phase separation easily occurs after salt addition due to sudden changes in solubility; ② insufficient temperature control precision in traditional processes (±5℃), resulting in inadequate solubility entropy change effect; ③ lack of real-time feedback mechanisms, making it impossible to address viscosity fluctuations caused by batch-to-batch raw material differences.
[0004] Chinese invention patent application CN111534093A discloses a polyimide prepreg and its preparation method. Its core focus is on optimizing the structure of the reinforcing fabric and improving the toughening effect and the stability of the prepreg preparation through fiber weaving process. However, it does not optimize the core issues of the PI resin itself, such as high melt viscosity and defects of curing by-products. Moreover, the toughening effect depends on the weaving distribution and melt synergy of thermoplastic PI fibers, and has limited effect on improving the processability and interfacial adhesion of the resin matrix itself. It still cannot meet the comprehensive requirements of CFRP for the resin matrix. Summary of the Invention
[0005] The first aspect of this invention provides a modified polyimide resin for carbon fiber composite materials. The raw materials for preparation include: a diether anhydride type polyamic acid solution, a keto anhydride type polyamic acid solution, a thermoplastic polymer solution, and a fluorinated anionic salt. The polymer in the thermoplastic polymer solution includes at least one of polyether ether ketone, polysulfone, polyphenylene sulfone, and polyether sulfone. The modified polyimide resin has a viscosity of 5000-10000 cp at 25°C and a solids concentration of 20-25 wt%.
[0006] The modified polyimide resin has a viscosity of 5000-8000 cp at 25°C.
[0007] The fluorinated anionic salt includes at least one of tetrafluoroborate, hexafluorophosphate, trifluoromethanesulfonate, bis(trifluoromethanesulfonyl)imide, hexafluoroantimonate, and pentafluorosulfonate.
[0008] The thermoplastic polymer includes polyethersulfone.
[0009] This invention reveals that the high viscosity of conventional polyimide resins stems from the presence of numerous polar groups in the molecular chains of diether anhydride and keto anhydride polyamic acids. These groups readily form strong hydrogen bonds and van der Waals forces, leading to severe molecular chain entanglement and poor system flowability. By employing a fluorinated anionic salt as a charge shielding agent, the anions preferentially bind to the cationic groups on the polyamic acid molecular chains, neutralizing electrostatic repulsion and eliminating the high viscosity problem caused by electrostatic repulsion between polyamic acid molecular chains. This also avoids phase separation or precipitation phenomena caused by salt addition and ensures the stability of the solution's rheological properties. Polyethersulfone (PES) was selected as the thermoplastic polymer due to its structural compatibility with the polyamic acid system and the precise control of intermolecular interactions. The ether bonds and sulfone groups on its molecular chains exhibit good compatibility with the molecular structures of both polyamic acids, allowing for uniform dispersion in solvents such as N-methylpyrrolidone without phase separation. Simultaneously, PES molecular chains can insert into the spaces between polyamic acid molecular chains, creating a spacer effect that weakens the hydrogen bonding between polyamic acid molecules, breaks the tight entanglement of molecular chains, and reduces friction within the system. Further research revealed that during curing at 50-60℃ for 8-12 hours, PES and polyamic acid achieved thorough molecular-level mixing, further optimizing the system's homogeneity and preventing excessively high local viscosity. Ultimately, without compromising the basic mechanical properties of the polyimide resin, the viscosity at 25℃ was further reduced from 10000 cp to 5000-8000 cp. This solved the processing problem of conventional polyimide resins' difficulty in wetting carbon fibers and provided suitable flowability for subsequent composite material preparation.
[0010] The raw materials for preparing the solute in the diether anhydride type polyamic acid solution include diaminodiphenyl ether and 4,4'-terephthalodioxydiphthalic anhydride.
[0011] The weight ratio of the diaminodiphenyl ether to 4,4'-terephthalodioxydiphthalic anhydride is 1:(0.9-1.1).
[0012] The raw materials for preparing the solute in the keto anhydride-type polyamic acid solution include 2,2'-bis(trifluoromethyl)diaminobiphenyl and 3,3',4,4'-benzophenone tetracarboxylic dianhydride.
[0013] The weight ratio of 2,2'-bis(trifluoromethyl)diaminobiphenyl and 3,3',4,4'-benzophenone tetracarboxylic dianhydride is 1:(0.9-1.1).
[0014] The solvents in the diether anhydride type polyamic acid solution and the keto anhydride type polyamic acid solution are selected from at least one of the following: N,N-dimethylformamide, N,N-dimethylacetamide, N-methylcaprolactam, dimethyl sulfoxide, sulfolane, and N-methylpyrrolidone.
[0015] The solvent content in both the diether anhydride type polyamic acid solution and the keto anhydride type polyamic acid solution is 20-80 wt%.
[0016] Optionally, the solvent content in the diether anhydride type polyamic acid solution and the keto anhydride type polyamic acid solution is 25-75 wt%.
[0017] The weight ratio of the diether anhydride type polyamic acid solution, the keto anhydride type polyamic acid solution, and the thermoplastic polymer solution is 1:(0.9-1.1):(0.3-0.8).
[0018] Optionally, the weight ratio of the diether anhydride polyamic acid solution, the keto anhydride polyamic acid solution, and the thermoplastic polymer solution is 1:(0.95-1.05):(0.4-0.6).
[0019] A second aspect of the present invention provides a method for preparing a modified polyimide resin for carbon fiber composites, characterized by comprising the following steps: Step 1: React diaminodiphenyl ether and 4,4'-terephthalodioxydiphthalic anhydride in a solvent to obtain a diether anhydride type polyamic acid solution; Step 2: React 2,2'-bis(trifluoromethyl)diaminobiphenyl and 3,3',4,4'-benzophenone tetracarboxylic dianhydride in a solvent to obtain a keto anhydride-type polyamic acid solution; Step 3: Dissolve the thermoplastic polymer in a solution to prepare a thermoplastic polymer solution; Step 4: Mix the diether anhydride type polyamic acid solution and the keto anhydride type polyamic acid solution, and add tetrafluoroborate in three portions to obtain a mixture; wherein the amount added at one time is 0.05-0.15 wt% of the mass of polyamic acid.
[0020] Step 5: Add thermoplastic polymer solution and mix for curing to obtain modified polyimide resin for carbon fiber composites.
[0021] Optionally, step 1 includes the following steps: adding diaminodiphenyl ether to the solvent, first in 2-5 portions, with an interval of 15-45 min between each portion, adding 80-95% of the total molar amount of 4,4'-terephthalic anhydride, then in 10-20 portions, with an interval of 15-45 min between each portion, adding the remaining 4,4'-terephthalic anhydride, reacting at 40-60℃ for 2-4 h, to obtain a diether anhydride type polyamic acid solution.
[0022] Optionally, step 2 includes the following steps: adding 2,2'-bis(trifluoromethyl)diaminobiphenyl to a solvent, first in 2-5 portions, with an interval of 15-45 min between each portion, adding 80-95% of the total molar amount of 3,3',4,4'-benzophenone tetracarboxylic dianhydride, then in 10-20 portions, with an interval of 15-45 min between each portion, adding the remaining 3,3',4,4'-benzophenone tetracarboxylic dianhydride, reacting at 40-60℃ for 2-4 h to obtain a keto anhydride type polyamic acid solution.
[0023] The ripening temperature is 40-70℃, and the time is 6-12 hours.
[0024] Optionally, the curing temperature is 50-60℃ and the time is 8-12h.
[0025] A third aspect of the present invention provides an application of a modified polyimide resin for carbon fiber composite materials, characterized in that it is used in the preparation of carbon fiber composite materials.
[0026] The weight ratio of modified polyimide resin to carbon fiber in the carbon fiber composite material is 1:(1-3).
[0027] Optionally, the weight ratio of modified polyimide resin to carbon fiber in the carbon fiber composite material is 1:(1-2).
[0028] The method for preparing the carbon fiber composite material includes the following steps: By introducing active functional groups onto the surface of carbon fibers through plasma grafting technology, chemical interlocking structures are formed with resin, thereby simultaneously enhancing interlaminar shear strength and high-temperature stability.
[0029] The prepreg layers are stacked and placed into a mold for vacuum pressing. The mold is equipped with a distributed fiber optic sensor network to provide real-time feedback on the material status in order to achieve dynamic optimization of process parameters.
[0030] After pressing, the material is cooled and shaped to obtain carbon fiber composite material.
[0031] The thickness of a single layer of the prepreg is 0.5-4 mm.
[0032] The segmented gradient curing technology is adopted. The pressing process includes: the first stage of mold filling process, which is maintained at 100-140℃ and 1-3MPa pressure for 10-30min; the second stage of curing process, which is maintained at 280-320℃ and 1-4MPa pressure for 30-60min; and the third stage of cooling and shaping process, which is maintained at 1-3MPa pressure for 30-60min, and the mold is opened after cooling down to below 60 degrees.
[0033] Beneficial effects 1. This invention uses fluorinated anionic salts as charge shielding agents to eliminate the high viscosity caused by electrostatic repulsion between polyamic acid molecular chains. By modifying polyimide resin with specific thermoplastic polymers, the viscosity can be effectively reduced while maintaining mechanical properties.
[0034] 2. The thermoplastic polymer of this invention is selected from polyethersulfone. With a curing process of 50-60℃ for 8-12 hours, the viscosity of the modified polyimide resin at 25℃ can be reduced to 5000-8000cp.
[0035] 3. By limiting the weight ratio of diether anhydride type polyamic acid solution, keto anhydride type polyamic acid solution and thermoplastic polymer solution to 1:(0.9-1.1):(0.3-0.8), the mechanical properties of modified polyimide resin can be improved.
[0036] 4. The present invention defines the vacuum pressing parameters for the preparation of carbon fiber composite materials as follows: 290-310℃, 1-3MPa for 100-180min, flexural strength ≥600MPa, flexural modulus ≥40GPa, and thermal decomposition temperature ≥580℃. Detailed Implementation
[0037] Example 1 A modified polyimide resin for carbon fiber composites is prepared from the following raw materials: a diether anhydride type polyamic acid solution, a keto anhydride type polyamic acid solution, and a thermoplastic polymer solution. The polymer in the thermoplastic polymer solution is polyethersulfone (Jiangsu Xinsu New Materials, 4783). The solvents for the diether anhydride type polyamic acid solution and the keto anhydride type polyamic acid solution are N-methylpyrrolidone with a water content of 156 ppm.
[0038] A method for preparing a modified polyimide resin for carbon fiber composites comprises the following steps: S1: Add 1800 kg of N-methylpyrrolidone solvent with a moisture content of 156 ppm to a 5000 L synthesis reactor.
[0039] To meet the requirement of a polymer solid content of 25 wt%, 199.39 kg of diaminodiphenyl ether was added to the polymerization reactor. Stirring was started and the mixture was dissolved for 30 minutes. The temperature of the solution in the reactor was controlled at 25°C using the reactor jacket.
[0040] The temperature of the solution inside the synthesis reactor was controlled by the jacket of the reactor. 360.549 kg of 4,4'-terephthalic anhydride, representing 90% of the total molar mass of the dianhydride, was added to the polymerization reactor in three batches, with each addition 30 minutes apart. The reaction solution temperature was controlled at 40°C. The remaining 40.061 kg of the total mass of 4,4'-terephthalic anhydride was then added to the glass reactor in 12 batches, with each addition 30 minutes apart. After the additions were completed, the mixture was stirred at 50°C for 3 hours, and then cooling water was turned on to lower the polymer solution to 25°C, yielding a diether anhydride-type polyamic acid solution.
[0041] 1800 kg of N-methylpyrrolidone solvent with a moisture content of 156 ppm was added to a 5000 L synthesis reactor.
[0042] S2: To meet the requirement of a polymer solid content of 25 wt%, 299.07 kg of 2,2'-bis(trifluoromethyl)diaminobiphenyl was added to the polymerization reactor. Stirring was started and the mixture was dissolved for 30 minutes. The temperature of the solution in the reactor was controlled at 25°C using the reactor jacket.
[0043] 270.837 kg of 3,3',4,4'-benzophenone tetracarboxylic dianhydride, representing 90% of the total molar mass of the dianhydride, was added to the polymerization reactor in three separate additions, with each addition spaced 30 minutes apart. The reaction solution temperature was maintained at 40°C. The remaining 30.093 kg of the total mass of 3,3',4,4'-benzophenone tetracarboxylic dianhydride was then added to the reactor in 12 separate additions, with each addition spaced 30 minutes apart. After all additions were completed, the mixture was stirred at 50°C for 3 hours. Cooling water was then turned on, and the polymer solution was cooled to 25°C, yielding a keto anhydride-type polyamic acid solution.
[0044] S3: 2000 kg of diether anhydride type polyamic acid solution and 2000 kg of keto anhydride type polyamic acid solution were added to a 10000 L mixing vessel and stirred at 300 rpm for 2 hours. Tetrafluoroborate was added in three portions, 2 hours apart, with a single addition of 4 kg (0.1 wt% of the polyamic acid mass). The temperature of the solution in the reaction vessel was controlled at 25°C using the vessel jacket.
[0045] S4: Add 750 kg of N-methylpyrrolidone solvent with a moisture content of 156 ppm to a 2000 L synthesis reactor. Based on the requirement of a polymer solid content of 25 wt%, add 250 kg of polyethersulfone to the polymerization reactor. Start stirring and dissolve for 60 min. Maintain the temperature of the solution in the reactor at 25 °C using the reactor jacket to obtain a polyethersulfone solution.
[0046] S5: Take 1000 kg of polyethersulfone solution and put it into a 10000 L mixing vessel. Mix it with 4012 kg of polyamic acid solution containing tetrafluoroborate at a stirring speed of 300 rpm. Control the temperature of the solution in the mixing vessel using the jacket, gradually increasing the temperature from 25℃ to 55℃ (every 5℃ / 20 minutes) and maintaining this temperature for 10 hours. A modified polyimide resin with a viscosity of 5630 cp (25℃) is obtained.
[0047] Comparative Example 1 The specific implementation method is the same as in Example 1; the difference is that S5 does not add polyethersulfone solution, and a modified polyimide resin with a viscosity of 15102cp (25℃) is obtained.
[0048] Comparative Example 2 The specific implementation method is the same as in Example 1; the difference is: S5: Take 400 kg of polyethersulfone solution and put it into a 10000 L mixing vessel, and mix it with 4613.8 kg of polyamic acid solution containing tetrafluoroborate (2300 kg of diether anhydride type polyamic acid solution, 2300 kg of ketone anhydride type polyamic acid solution, and 13.8 kg of tetrafluoroborate), stirring at 300 rpm. The temperature of the solution in the mixing vessel is controlled by the jacket of the mixing vessel, and the temperature is increased stepwise from 25°C to 55°C (every 5°C / 20 minutes) and maintained for 10 hours. A polyimide resin with a viscosity of 12570 cp (25°C) is obtained.
[0049] Comparative Example 3 The specific implementation method is the same as in Example 1; the difference is: S5: Take 1800 kg of polyethersulfone solution and put it into a 10000 L mixing vessel, and mix it with 3209.6 kg of polyamic acid solution containing tetrafluoroborate (1600 kg of diether anhydride type polyamic acid solution, 1600 kg of ketone anhydride type polyamic acid solution, and 9.6 kg of tetrafluoroborate), stirring at 300 rpm. The temperature of the solution in the mixing vessel is controlled by the jacket of the mixing vessel, and the temperature is increased stepwise from 25°C to 55°C (every 5°C / 20 minutes) and maintained for 10 hours. A polyimide resin with a viscosity of 16105 (25°C) is obtained.
[0050] Comparative Example 4 The specific implementation method is the same as in Example 1; the difference is: S5: Take 1000 kg of polyethersulfone solution and put it into a 10000 L mixing vessel, and mix it with 4012 kg of polyamic acid solution containing tetrafluoroborate, stirring at 300 rpm. The temperature of the solution in the mixing vessel is controlled by the jacket of the mixing vessel, and the temperature is increased stepwise from 25°C to 55°C (every 5°C / 20 minutes) and maintained for 4 hours. A polyimide resin with a viscosity of 10346 cp (25°C) is obtained.
[0051] Comparative Example 5 The specific implementation method is the same as in Example 1; the difference is that polyethersulfone is replaced with polyetheretherketone (Tianmen Hengchang Chemical, HC7366) to obtain a polyimide resin with a viscosity of 21354cp (25℃).
[0052] Comparative Example 6 The specific implementation method is the same as in Example 1; the difference is that polyethersulfone is replaced with polyetherimide (1010 / Sab base) to obtain a polyimide resin with a viscosity of 18744cp (25°C).
[0053] Comparative Example 7 The specific implementation method is the same as in Example 1; the difference is that the polyethersulfone is replaced with diphenylmethane type BMI (PFB002 / Shandong Shengquan) to obtain a polyimide resin with a viscosity of 25591cp (25℃).
[0054] Comparative Example 8 The specific implementation method is the same as in Example 1; the difference is that the polyethersulfone is replaced with bisphenol A type epoxy resin (NEPL128 / Nanya) to obtain a polyimide resin with a viscosity of 14624cp (25℃).
[0055] Comparative Example 9 The specific implementation method is the same as in Example 1; the difference is that the amount of S3 tetrafluoroborate added at one time is 1 kg, which is 0.025 wt% of the mass of polyamic acid. A polyimide resin with a viscosity of 31589 cp (25℃) is obtained.
[0056] Comparative Example 10 The specific implementation method is the same as in Example 1; the difference is that the amount of S3 tetrafluoroborate added at one time is 8 kg, which is 0.2 wt% of the mass of polyamic acid. A polyimide resin with a viscosity of 1141 cp (25°C) is obtained.
[0057] Performance testing methods and data The polyimide resins in the examples and comparative examples were used to prepare carbon fiber reinforced modified polyimide resin-based composites according to the following implementation schemes.
[0058] Implementation plan: ① Carbon fiber cloth (SYT45) is treated with oxygen plasma to generate polar groups such as -OH (hydroxyl) and -COOH (carboxyl) on the fiber surface. The woven carbon fiber cloth is cut to a size of 300×200×0.2mm and laid flat on a glass plate. The glass plate is placed on an automatic coating machine, which draws in resin for coating. The coating amount is 4:6 of the dry weight of the resin to the weight of the fiber.
[0059] ② After the carbon fiber woven fabric is coated with resin, it is placed in an oven at 150℃ and baked for 20 minutes. Then it is removed from the glass plate, cooled, and cut.
[0060] ③ Place the prepared prepreg on the mold in the designed direction, and calculate the number of layers n to be laid based on the product thickness of 2mm, which is 10 layers.
[0061] ④ After the layers are laid up, cover the material and mold with a sealed vacuum bag. Vacuum for 20 minutes at room temperature.
[0062] ⑤ The vacuum-sealed mold is placed in an autoclave, and the resin curing degree is monitored in real time through a distributed fiber optic sensor network.
[0063] ⑥ A phased curing and molding process is adopted. The first stage is the filling process, which is maintained at 140℃ and 2MPa pressure for 30 minutes; the second stage is the curing process, which is maintained at 280-320℃ and 4MPa pressure for 60 minutes; the third stage is the cooling and shaping process, which is maintained at 1MPa pressure for 60 minutes, and the mold is opened after the temperature drops below 60 degrees.
[0064] Eleven types of polyimide resins (Example 1, Comparative Examples 1-10) were subjected to orthogonal experiments according to the above implementation scheme. The resulting composite material samples were designated as Case 1 to Case 11. The following tests were conducted on Case 1 to Case 11, and the experimental data are shown in Table 2: Test item 1: Tensile strength, Test method: GB / T1447-2005 Tensile properties test method for fiber reinforced plastics.
[0065] Test item 2: Tensile modulus, Test method: GB / T1447-2005 Tensile properties test method for fiber reinforced plastics.
[0066] Test item 3: Bending strength, Test method: GB / T1449-2005 Test method for bending properties of fiber reinforced plastics.
[0067] Test item 4: Flexural modulus, Test method: GB / T1449-2005 Test method for flexural properties of fiber reinforced plastics.
[0068] Test item 5: Impact strength, Test method: GB / T1451-2005 Test method for impact toughness of simply supported beams of fiber reinforced plastics.
[0069] Test item 5: Thermal decomposition temperature, Test method: ISO11357-2 / 3-2020 Plastics—Differential scanning calorimetry (DSC).
[0070] Table 2
[0071] In Case 10, the resin matrix used was Comparative Example 9, which had too high a viscosity and could not be applied.
[0072] In Case 11, the resin matrix used was Comparative Example 10. The amount of tetrafluoroborate added was too much, making the resin unstable and prone to segregation. White salt was precipitated during the pressing process, resulting in appearance defects and rendering the resin unusable.
[0073] Analysis of Table 2 shows that the polyimide resin obtained in Example 1 of this invention, combined with the carbon fiber reinforced modified polyimide resin matrix composite material prepared in the first construction case, exhibits the best overall performance.
Claims
1. A modified polyimide resin for carbon fiber composite materials, characterized in that, The raw materials for preparation include: diether anhydride type polyamic acid solution, keto anhydride type polyamic acid solution, thermoplastic polymer solution, and fluorine-containing anionic salt. The polymer in the thermoplastic polymer solution includes at least one of polyether ether ketone, polysulfone, polyphenylsulfone, and polyether sulfone. The modified polyimide resin has a viscosity of 5000-10000 cp at 25°C and a solids concentration of 20-25 wt%.
2. The modified polyimide resin for carbon fiber composites according to claim 1, characterized in that, The thermoplastic polymer includes polyethersulfone.
3. The modified polyimide resin for carbon fiber composites according to claim 2, characterized in that, The raw materials for preparing the solute in the diether anhydride type polyamic acid solution include diaminodiphenyl ether and 4,4'-terephthalodioxydiphthalic anhydride; the raw materials for preparing the solute in the keto anhydride type polyamic acid solution include 2,2'-bis(trifluoromethyl)diaminobiphenyl and 3,3',4,4'-benzophenone tetracarboxylic dianhydride.
4. The modified polyimide resin for carbon fiber composites according to claim 3, characterized in that, The solvents in the diether anhydride type polyamic acid solution, keto anhydride type polyamic acid solution, and thermoplastic polymer solution are all selected from at least one of the following: N,N-dimethylformamide, N,N-dimethylacetamide, N-methylcaprolactam, dimethyl sulfoxide, sulfolane, and N-methylpyrrolidone.
5. The modified polyimide resin for carbon fiber composites according to claim 4, characterized in that, The weight ratio of the diether anhydride type polyamic acid solution, the keto anhydride type polyamic acid solution, and the thermoplastic polymer solution is 1:(0.9-1.1):(0.3-0.8).
6. A method for preparing a modified polyimide resin for carbon fiber composites according to claim 4 or 5, characterized in that, The process includes the following steps: reacting diaminodiphenyl ether and 4,4'-terephthalodioxydiphthalic anhydride in a solvent to obtain a diether anhydride-type polyamic acid solution; reacting 2,2'-bis(trifluoromethyl)diaminobiphenyl and 3,3',4,4'-benzophenone tetracarboxylic dianhydride in a solvent to obtain a keto anhydride-type polyamic acid solution; dissolving a thermoplastic polymer in the solution to prepare a thermoplastic polymer solution; mixing the diether anhydride-type polyamic acid solution and the keto anhydride-type polyamic acid solution and then adding a fluorinated anion salt to obtain a mixture; adding the thermoplastic polymer solution to the mixture for aging to obtain a modified polyimide resin for carbon fiber composites.
7. The method for preparing the modified polyimide resin for carbon fiber composites according to claim 6, characterized in that, The ripening temperature is 50-60℃, and the time is 8-12 hours.
8. An application of a modified polyimide resin according to any one of claims 1-5, characterized in that, This method is applied to the preparation of carbon fiber composite materials, wherein the weight ratio of modified polyimide resin to carbon fiber in the carbon fiber composite material is 1:(1-2).
9. The application of the modified polyimide resin according to claim 8, characterized in that, The method for preparing the carbon fiber composite material includes the following steps: coating modified polyimide resin onto carbon fibers to obtain a prepreg; stacking the prepreg layers into a mold for vacuum pressing; and cooling and shaping to obtain the carbon fiber composite material.
10. The application of the modified polyimide resin according to claim 9, characterized in that, The vacuum pressing process includes maintaining a temperature of 290-310℃ and a pressure of 1-3MPa for 100-180 minutes.