A polyimide resin prepreg and a method for producing the same

Abstract

This invention discloses a polyimide resin prepreg and its preparation method, belonging to the field of composite material preparation technology, and applicable to aerospace, high-end equipment, and other fields with high requirements for prepreg performance. Addressing the problems of poor environmental friendliness, difficulty in controlling resin content, and poor electrostatic adsorption of polyimide resin powder in traditional preparation processes, this invention first prepares 5-30 μm charged modified polyimide resin powder, then removes the sizing agent from the reinforcing fibers and performs plasma charging activation treatment. By optimizing electrostatic adsorption parameters, precise and uniform adsorption of the powder and fibers is achieved. After melt curing and post-treatment testing, a qualified prepreg is obtained. This method is solvent-free, low-energy, can precisely control the resin content to 35-40%, and the resulting prepreg has a volatile content ≤0.5%, no surface defects, and is simple and easily industrialized.

Description

Technical Field

[0001] This invention relates to the field of composite material preparation technology, and in particular to a polyimide resin prepreg and its preparation method. Background Technology

[0002] Polyimide resin, as one of the best organic polymer materials in terms of comprehensive performance, has a long-term service temperature range of 200~400℃ and a heat resistance temperature of over 600℃. The prepregs made from it are the core intermediates for high-end composite structural or functional parts. They have excellent high temperature resistance, corrosion resistance, mechanical strength and dimensional stability, and are widely used in high-end fields such as aerospace and weaponry.

[0003] Currently, the main methods for preparing polyimide resin prepregs include solution impregnation and hot-melt methods. Solution impregnation involves dissolving polyimide resin in an organic solvent to form a liquid, impregnating the fibers, and then drying to remove the solvent. While this method is mature and provides thorough impregnation, it suffers from drawbacks such as residual organic solvents, VOC emissions polluting the environment, high drying energy consumption, and the prepreg's tendency to absorb moisture, leading to solute precipitation. Furthermore, solvent evaporation can create pores within the prepreg, affecting the mechanical properties of the product. Hot-melt methods use polyamic acid or polyester ammonium salt prepolymers as the matrix, intentionally retaining 25%±5% solvent to reduce viscosity. After compounding, hot-melt coating to form a film, hot-pressing the pretreated fibers, and cooling to set, the prepreg is obtained. This method requires precise control of the solvent content to approximately 25%, as parameter fluctuations can easily lead to stickiness or poor wetting of the prepreg. Residual solvent increases the porosity during subsequent curing, necessitating a temperature-controlled curing process. High solvent purity is required, storage must be strictly moisture-proof, and there is an environmental risk associated with the evaporation of small amounts of solvent.

[0004] Electrostatic adsorption, as a novel solvent-free prepreg preparation process, utilizes the principle of charge adsorption to uniformly adhere resin powder to the surface and interior of reinforcing fibers. It boasts significant advantages such as high production efficiency, stable process, precise control of resin content, no VOC emissions, and good impregnation uniformity, and has been gradually applied to the preparation of some thermoplastic resin prepregs. However, due to the poor charge inherent in polyimide resin powder, difficulty in precisely controlling particle size, insufficient electrostatic adsorption force between powder and reinforcing fibers, and the tendency for powder to detach or agglomerate after adsorption and melting, there is currently no mature technical solution for preparing polyimide resin prepregs using electrostatic adsorption, limiting its widespread application in the polyimide prepreg field.

[0005] In existing technologies, such as the invention patent with publication number CN111154260A, an antioxidant polyimide prepreg and its preparation method are disclosed. This method uses a solution impregnation process, which still suffers from drawbacks such as residual organic solvents and poor environmental friendliness. In related foreign technologies, electrostatic adsorption methods are mostly applied to thermoplastic resins such as PEEK. However, due to the special characteristics of polyimide resins, key technical challenges such as powder charge modification, matching electrostatic adsorption parameters, and controlling defects in post-adsorption melting and solidification have not been resolved. Therefore, developing a simple, environmentally friendly, and efficient electrostatic adsorption method that effectively addresses the aforementioned shortcomings and can produce high-performance polyimide resin prepregs has significant practical and industrial application value. Summary of the Invention

[0006] This invention provides a method for preparing polyimide resin prepreg by electrostatic adsorption, which overcomes the shortcomings of the prior art and solves the problems of poor environmental performance, insufficient impregnation, numerous defects, high production costs, and difficulty in accurately controlling resin content in existing polyimide prepreg preparation processes. At the same time, it solves the technical bottlenecks of poor electrostatic adsorption of polyimide resin powder, uneven adsorption, and easy detachment after melting and solidification, thus achieving efficient, environmentally friendly, and high-quality preparation of polyimide prepreg.

[0007] In order to achieve the objectives of this invention, the following technologies are proposed: One method provides a method for preparing polyimide resin prepreg by electrostatic adsorption, characterized by comprising the following steps: Step 001: Preparation of charged modified polyimide resin powder to obtain charged modified polyimide resin powder; Step 002: Reinforcing fiber pretreatment to obtain charged reinforcing fibers; Step 003: The charged modified polyimide resin powder obtained in step 001 and the charged reinforcing fiber obtained in step 002 are impregnated by electrostatic adsorption to obtain a composite resin. Step 004: The composite resin obtained in step 003 is melt-cured and molded to obtain polyimide resin prepreg; Step 005: Cut and trim the polyimide resin prepreg prepared in Step 004 to remove excess resin and fibers from the edges. Perform performance tests on the trimmed prepreg, including resin content, volatile matter content, mechanical properties, surface quality, and electrostatic adsorption uniformity. Select qualified polyimide resin prepregs, seal them in packaging, and store them in a dry, cool environment free from electrostatic interference.

[0008] Among them, qualified polyimide resin prepregs have a polyimide resin content of 35~40% and a volatile content of ≤0.5%. Carbon fiber composites prepared from them have a flexural strength of ≥1300MPa, an interlaminar shear strength of ≥100MPa, and no defects such as dry spots, bubbles, poor glue content, rich glue content, and powder shedding on the surface. The dimensional accuracy error is ≤±0.1mm, and the powder adsorption uniformity deviation is ≤5%.

[0009] Further, the preparation of the charged modified polyimide resin powder in step 001, to obtain the charged modified polyimide resin powder, includes: Step 010: The polyimide resin is initially crushed by physical pulverization. Step 011: The initially crushed polyimide resin is further pulverized at -10℃ to 10℃ at a rotation speed of 2000r / min to 4000r / min for 10 to 30 minutes to obtain polyimide resin powder with a particle size of 5μm to 30μm. During this process, the powder is screened using a grading method, specifically through 100-mesh, 300-mesh, and 500-mesh sieves, to ensure uniform particle size and avoid uneven adsorption or detachment defects caused by large-diameter powder particles. During the low-temperature pulverization process, a small amount of anti-blocking agent, such as talc, can be added to prevent powder agglomeration. The amount of anti-blocking agent added should not exceed 0.1% of the initial mass of the polyimide resin powder.

[0010] Step 012: Add a charged modifier to the polyimide resin powder, mix it in a high-speed mixer at 80°C to 120°C and 800r / min to 1500r / min for 20min to 40min, and cool it to room temperature to obtain charged modified polyimide resin powder.

[0011] Furthermore, the surface charge density of the charged modified polyimide resin powder is 1.0 × 10⁻⁶. -6 C / m 2 Up to 5.0×10 -6 C / m 2 The surface charge density of the charged modified polyimide resin powder can be detected in real time by an electrostatic tester. If the charge density does not meet the standard, a charge-accelerating agent can be added and the mixture can be mixed and modified again to ensure that the electrostatic adsorption requirements are met.

[0012] The polyimide resin is one or more of the following: acetylene-terminated polyimide resin, norbornene-terminated polyimide resin, and phenylacetylene-terminated polyimide resin. Specifically, ZTS-550, ZTS-350, PMR-15, etc. can be selected. The charge modifier is one of amino-modified polysiloxane or nano-conductive powder; The nano-conductive powder is one or more of the following: nano-boron carbide, nano-titanium dioxide, and nano-silicon carbide, with a particle size of 30nm to 100nm. The amount of the charged modifier added is 1% to 5% of the mass of the polyimide resin powder.

[0013] Further, step 002, the step of reinforcing fiber pretreatment to obtain charged reinforcing fibers, includes: Step 020: Place the reinforcing fiber in the sizing agent and the desizing agent, immerse it at 40°C to 60°C for 20 to 40 minutes, remove it, rinse it, and dry it to constant weight; Step 021: The reinforcing fiber obtained in step 020 is placed in a plasma processing device and subjected to surface activation treatment under the conditions of power of 100W to 300W, processing time of 5min to 15min, vacuum degree of 0.01MPa to 0.05MPa and inert gas protection, so that the surface of the reinforcing fiber carries a charge with opposite polarity to that of the polyimide resin powder, and charged reinforcing fiber is obtained.

[0014] The pretreated charged reinforcing fibers have increased surface roughness and surface energy, and also carry a stable charge, which can significantly improve the electrostatic adsorption force with charged modified polyimide resin powder, ensuring uniform adsorption.

[0015] Furthermore, the surface charge density of the charged reinforcing fiber is 0.8 × 10⁻⁶. -6 C / m 2 Up to 4.0×10 -6 C / m 2 ; The reinforcing fiber is one or more of carbon fiber, aramid fiber, and glass fiber; The sizing agent remover is a mixture of ethanol and acetone in a volume ratio of 1:1 to 2:1.

[0016] Further, step 003, which involves electrostatically adsorbing the charged modified polyimide resin powder obtained in step 001 and the charged reinforcing fibers obtained in step 002 to obtain the composite resin, includes: Step 030: Add the charged modified polyimide resin powder obtained in step 001 into the powder chamber of the electrostatic adsorption device. Step 031: The charged reinforcing fibers prepared in step 002 are continuously fed into the electrostatic adsorption chamber using a traction method. During electrostatic adsorption, the voltage is 5kV to 20kV, the adsorption distance is 5mm to 20mm, the conveying speed of the charged reinforcing fibers is 0.3m / min to 1.5m / min, the temperature of the adsorption chamber is 25℃ to 45℃, and the relative humidity is 30% to 60%. This allows the charged modified polyimide resin powder to be uniformly adsorbed onto the surface of the charged reinforcing fibers and inside the fiber bundles under the action of electrostatic attraction, resulting in a pre-adsorbed composite resin. During the adsorption process, powder is replenished through a powder circulation conveying device. To ensure a stable powder concentration, the charged modified polyimide resin powder is simultaneously swept with an airflow at a wind speed of 0.5m / s to 1.5m / s to avoid excessive agglomeration and adsorption of the powder.

[0017] Furthermore, the electrostatic adsorption chamber needs to be sealed to prevent external dust and moisture from entering and affecting the adsorption effect. The powder circulation conveying device uses anti-static materials to prevent charge loss during powder conveying and ensure adsorption stability. The electrostatic adsorption equipment adopts a bipolar electrostatic adsorption structure to adjust the polarity and charge density of the fibers and powder, further improving adsorption uniformity. During the adsorption process, the amount of powder adsorbed on the fiber surface is monitored in real time. By adjusting the traction speed and adsorption voltage, the resin content is precisely controlled. After electrostatic adsorption impregnation, the composite resin loading reaches 85% to 95% of the target content of the prepreg.

[0018] Further, in step 004, when the composite resin obtained in step 003 is melt-cured and molded to obtain polyimide resin prepreg, the obtained composite resin is continuously conveyed to a hot air circulating drying and curing device, and is successively subjected to low-temperature drying (to remove trace amounts of moisture and impurities) and high-temperature melt curing treatment. After curing, it is cooled to room temperature to obtain polyimide resin prepreg.

[0019] Among them, low-temperature drying is carried out at a temperature of 80℃ to 120℃ for 20min to 40min and a hot air velocity of 1m / s to 3m / s. Curing is carried out at 200℃ to 300℃, with a heating rate of 5℃ / min to 10℃ / min and a curing time of 10min to 20min. Furthermore, during curing, a pressure of 0.1 MPa to 0.3 MPa is applied to ensure that the polyimide resin powder is fully melted and infiltrates the fiber bundles, avoiding defects such as dry spots, insufficient resin, or powder shedding, thereby further improving the density and mechanical properties of the prepreg.

[0020] On the other hand, a polyimide resin prepreg is provided, characterized in that it is prepared by an electrostatic adsorption method, and the polyimide resin content of the obtained polyimide resin prepreg is 35% to 40%, the volatile content is ≤0.5%, and the carbon fiber composite material prepared by the polyimide resin prepreg has a flexural strength ≥1300MPa, an interlaminar shear strength ≥100MPa, and a powder adsorption uniformity deviation ≤5%.

[0021] The advantages of the above technical solution are: This invention uses electrostatic adsorption as the core method to prepare polyimide resin prepreg, achieving truly solvent-free and low-energy preparation. It completely solves the problems of residual organic solvents and VOC emissions that pollute the environment in traditional processes, significantly improving environmental friendliness. At the same time, it reduces the high-temperature resistance requirements of equipment and greatly saves production costs.

[0022] This invention significantly improves the surface charge density and charge stability of polyimide resin powder by introducing a charge modifier through a charge modification treatment. At the same time, the reinforcing fibers are charged and activated to give the fibers opposite polarity charges. The powder and fibers are then precisely and uniformly adsorbed using electrostatic attraction. This completely solves the technical bottlenecks of poor electrostatic adsorption, uneven adsorption, and easy detachment after melting and solidification of polyimide resin powder, ensuring the surface quality and internal density of the prepreg.

[0023] This invention optimizes electrostatic adsorption parameters (adsorption voltage, distance, traction speed, etc.) to precisely control the resin content (35-40%) of prepreg, and the adsorption process is continuous and controllable, enabling large-scale continuous production. The production efficiency is more than 30% higher than that of the traditional powder method.

[0024] The present invention features a simple and controllable process, a wide range of raw material sources, a small amount of charged modifier added, controllable production costs, and a mature electrostatic adsorption equipment structure that is easy to industrialize and promote large-scale application. It is suitable for the batch preparation of high-performance polyimide resin prepregs.

[0025] The conductive nanoparticles selected in this invention not only enhance the charge-carrying properties of the powder and its adsorption force with fibers, but also significantly improve the antioxidant properties and high-temperature carbon residue of polyimide prepregs, further expanding the high-temperature application range of prepregs. At the same time, the charge-activation treatment of fibers not only enhances the electrostatic adsorption effect, but also strengthens the interfacial bonding force between the resin and the fiber, further improving the mechanical properties and service life of the prepregs. Attached Figure Description

[0026] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will now be described in further detail with reference to the accompanying drawings.

[0027] Figure 1 A process flow diagram for preparing polyimide resin prepreg by electrostatic adsorption is shown. Detailed Implementation

[0028] It should be noted that the raw materials used in the following embodiments are all commercially available conventional raw materials and have not undergone special treatment; the equipment used are all conventional industrial equipment and the operating methods are all conventional operations, unless otherwise stated; the surface charge density is detected by an electrostatic tester.

[0029] Example 1 A method for preparing and applying a polyimide resin prepreg includes the following steps: Step 1: Preparation of charged modified polyimide resin powder ZTS-550 type polyimide resin was selected as the raw material, and primary polyimide resin powder was prepared by physical pulverization. The primary powder was placed in a low-temperature pulverizing device and pulverized for 20 minutes at 0℃ and 3000 r / min. Then, it was sequentially sieved through 100 mesh, 300 mesh, and 500 mesh screens to obtain polyimide resin powder with a particle size of 5~30 μm. A charged modifier was added to the powder at 3% of the powder mass, and the mixture was mixed for 30 minutes in a high-speed mixer at 1200 r / min to obtain charged polyimide resin powder. Its surface charge density was measured to be 2.8 × 10⁻⁻⁻⁶. 6 C / m².

[0030] Step 2: Reinforcing Fiber Pretreatment Carbon fiber was selected as the reinforcing fiber and immersed in a sizing agent remover (ethanol and acetone, volume ratio 1:1) at 40°C for 30 minutes. After immersion, the carbon fiber was dried to constant weight. The dried carbon fiber was then placed in a plasma treatment device for surface activation treatment under conditions of 200W power, 10 minutes treatment time, and 0.03MPa vacuum, while nitrogen gas was introduced simultaneously. The pretreated charged carbon fiber was obtained, and its surface charge density was measured to be 2.2 × 10⁻⁻⁻⁶. 6 C / m².

[0031] Step 3: Electrostatic adsorption impregnation Charged modified polyimide resin powder is added to the powder chamber of the electrostatic adsorption equipment. Charged carbon fibers are fed into the electrostatic adsorption chamber by continuous traction. The electrostatic adsorption parameters are controlled as follows: adsorption voltage 12kV, adsorption distance 12mm, fiber traction speed 0.8m / min, adsorption chamber temperature 35℃, and relative humidity 45%. Powder is replenished through a powder circulation conveying device, and the airflow purging speed is 1.0m / s to obtain the fiber-powder composite after preliminary adsorption.

[0032] Step 4: Melt solidification molding The fiber-powder composite was continuously fed into a hot air circulating drying and curing device. Under a pressure of 0.2 MPa, it was first dried at 100°C and a hot air velocity of 2 m / s for 30 min, and then heated to 250°C at a heating rate of 8°C / min. Nitrogen gas was introduced for protection, and the mixture was melt-cured for 15 min. After cooling to room temperature, polyimide resin prepreg was obtained.

[0033] Step 5: Post-processing and inspection The prepreg was cut and trimmed, and then its performance was tested: resin content 38%, volatile content 0.3%, carbon fiber composite bending strength 1480MPa, interlaminar shear strength 108MPa, smooth surface, no dry spots, bubbles and powder shedding, dimensional accuracy error ±0.08mm, powder adsorption uniformity deviation 3.2%, which meets the qualified standards.

[0034] Example 2 A method for preparing and applying a polyimide resin prepreg includes the following steps: Step 1: Preparation of charged modified polyimide resin powder ZTS-350 type polyimide resin was selected as the raw material, and primary polyimide resin powder was prepared by physical pulverization. The primary powder was placed in a low-temperature pulverizing device and pulverized for 15 min at 0℃ and 4000 r / min. After classification and screening, polyimide resin powder with a particle size of 5~30 μm was obtained. A charged modifier was added to the powder at a dosage of 1% of the powder mass, and the mixture was mixed for 25 min at 1500 r / min in a high-speed mixer. After cooling to room temperature, charged polyimide resin powder was obtained, and its surface charge density was measured to be 1.8 × 10⁻⁻⁻⁶. 6 C / m².

[0035] Step 2: Reinforcing fiber pretreatment (electric activation) Carbon fiber was selected as the reinforcing fiber and immersed in a sizing agent remover (ethanol and acetone, volume ratio 1:1) at 40°C for 30 minutes. After immersion, the fiber was dried to constant weight. The dried fiber was then placed in a plasma treatment device for surface activation treatment at a power of 150W, a treatment time of 12 minutes, and a vacuum degree of 0.02MPa, while argon gas was simultaneously introduced. Pretreated charged fibers were obtained, and their surface charge density was measured to be 1.5 × 10⁻⁻⁻⁻⁶. 6 C / m².

[0036] Step 3: Electrostatic adsorption impregnation Charged modified polyimide resin powder is added to the powder chamber of the electrostatic adsorption equipment. Charged fibers are continuously fed into the electrostatic adsorption chamber. The electrostatic adsorption parameters are controlled as follows: adsorption voltage 8kV, adsorption distance 8mm, fiber traction speed 0.5m / min, adsorption chamber temperature 30℃, and relative humidity 35%. Powder is replenished through a powder circulation conveying device, and the airflow purging speed is 0.8m / s. The fiber-powder composite is obtained after preliminary adsorption.

[0037] Step 4: Melt solidification molding The fiber-powder composite was continuously fed into a hot air circulating drying and curing device. Under a pressure of 0.2 MPa, it was first dried at 80°C and a hot air velocity of 1.5 m / s for 40 min, and then heated to 280°C at a heating rate of 5°C / min, melt-cured for 20 min, and cooled to room temperature to obtain polyimide resin prepreg.

[0038] Step 5: Post-processing and inspection The prepreg was cut and trimmed, and then its performance was tested: resin content 35%, volatile content 0.4%, composite material flexural strength 1520MPa, interlaminar shear strength 109MPa, surface smooth and without defects, dimensional accuracy error ±0.09mm, powder adsorption uniformity deviation 4.1%, which meets the qualified standards.

[0039] Example 3 A method for preparing polyimide resin prepreg by electrostatic adsorption includes the following steps: Step 1: Preparation of charged modified polyimide resin powder ZTS-550 and ZTS-350 mixed polyimide resins were selected as raw materials, and primary polyimide resin powder was prepared by physical pulverization. The primary powder was placed in a low-temperature pulverizing device and pulverized for 25 min at 0℃ and 2500 r / min. After classification and screening, polyimide resin powder with a particle size of 5~30 μm was obtained. A charged modifier was added to the powder at 5% of the powder mass, and the mixture was mixed for 35 min at 1000 r / min in a high-speed mixer. After cooling to room temperature, charged polyimide resin powder was obtained, and its surface charge density was measured to be 4.2 × 10⁻⁻⁻⁶. 6 C / m².

[0040] Step 2: Reinforcing fiber pretreatment (electric activation) A mixture of carbon fiber and glass fiber (mass ratio 2:1) was selected as the reinforcing fiber and immersed in a degreasing agent (ethanol and acetone volume ratio 2:1) at 40℃ for 25 min. After removal, it was dried to constant weight. The dried mixed fiber was then placed in a plasma treatment device for surface activation treatment under conditions of 250W power, 8 min treatment time, and 0.04 MPa vacuum, while nitrogen gas was simultaneously introduced. The resulting pretreated charged mixed fiber had a surface charge density of 3.5 × 10⁻⁻⁻⁻⁶. 6 C / m².

[0041] Step 3: Electrostatic adsorption impregnation Charged modified polyimide resin powder is added to the powder chamber of the electrostatic adsorption equipment. Charged mixed fibers are continuously traction-fed into the electrostatic adsorption chamber. The electrostatic adsorption parameters are controlled as follows: adsorption voltage 18kV, adsorption distance 18mm, fiber traction speed 1.2m / min, adsorption chamber temperature 40℃, and relative humidity 55%. Powder is replenished through a powder circulation conveying device, and the airflow purging speed is 1.4m / s to obtain the fiber-powder composite after preliminary adsorption.

[0042] Step 4: Melt solidification molding The fiber-powder composite was continuously fed into a hot air circulating drying and curing device. Under a pressure of 0.2 MPa, it was first dried at 110°C and a hot air velocity of 2.5 m / s for 25 min, and then heated to 260°C at a heating rate of 5°C / min. Nitrogen gas was introduced for protection, and the mixture was melt-cured for 12 min. After cooling to room temperature, polyimide resin prepreg was obtained.

[0043] Step 5: Post-processing and inspection The prepreg was cut and trimmed, and then its performance was tested: resin content 38%, volatile content 0.3%, composite material flexural strength 1320MPa, interlaminar shear strength 101MPa, smooth surface without defects, dimensional accuracy error ±0.07mm, powder adsorption uniformity deviation 2.8%, which meets the qualified standards.

[0044] Comparative Example 1 (Traditional Solution Method) Polyimide prepreg was prepared by solution impregnation method. The same ZTS-550 type polyimide resin and the same carbon fiber were selected as in Example 1. The prepreg was prepared and tested. The resin content was 40%, the volatile content was 2.1%, the flexural strength of the composite material was 1280 MPa, the interlaminar shear strength was 97 MPa, and there were slight solvent residue marks on the surface.

[0045] Comparative Example 2 (Electrostatic Adsorption Method without Charge Modification) Without performing charged modification of polyimide resin powder and charged activation treatment of reinforcing fibers, the remaining steps are exactly the same as in Example 1. Polyimide prepreg is prepared by ordinary electrostatic adsorption. Test performance: resin content 34%, volatile content 0.4%, composite material flexural strength 1180MPa, interlaminar shear strength 88MPa, surface defects such as dry spots, poor resin content and powder shedding, powder adsorption uniformity deviation 12.5%, which cannot meet the qualified standard.

[0046] As can be seen from the comparison of the above embodiments and comparative examples, the polyimide resin prepreg prepared by the method of the present invention is superior to the prepreg prepared by the traditional solution method and the electrostatic adsorption method without charge modification in terms of resin content control, volatile content, surface quality and powder adsorption uniformity. It can also significantly improve the mechanical properties of composite materials, has no organic solvent residue, and significantly improves environmental friendliness. It solves many defects of the prior art and overcomes the technical bottleneck of poor electrostatic adsorption of polyimide resin powder. It has obvious technical advantages and industrial application value.

[0047] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Obviously, those skilled in the art can make various modifications and variations to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention also intends to include these modifications and variations.

Claims

1. A method for preparing polyimide resin prepreg by electrostatic adsorption, characterized in that, Including the following steps: Step 001: Preparation of charged modified polyimide resin powder to obtain charged modified polyimide resin powder; Step 002: Reinforcing fiber pretreatment to obtain charged reinforcing fibers; Step 003: The charged modified polyimide resin powder obtained in step 001 and the charged reinforcing fiber obtained in step 002 are impregnated by electrostatic adsorption to obtain a composite resin. Step 004: The composite resin obtained in step 003 is melt-cured and molded to obtain polyimide resin prepreg.

2. The method for preparing polyimide resin prepreg by electrostatic adsorption according to claim 1, characterized in that, The preparation of charged modified polyimide resin powder in step 001, to obtain charged modified polyimide resin powder, includes the following steps: Step 010: The polyimide resin is initially crushed by physical pulverization. Step 011: The pre-crushed polyimide resin is pulverized at -10°C to 10°C at a rotation speed of 2000 r / min to 4000 r / min for 10 min to 30 min to obtain polyimide resin powder with a particle size of 5 μm to 30 μm. Step 012: Add a charged modifier to the polyimide resin powder, mix it in a high-speed mixer at 80°C to 120°C and 800r / min to 1500r / min for 20min to 40min, and cool it to room temperature to obtain charged modified polyimide resin powder.

3. The method for preparing polyimide resin prepreg by electrostatic adsorption according to claim 2, characterized in that, The surface charge density of the charged modified polyimide resin powder is 1.0 × 10⁻⁶. -6 C / m 2 Up to 5.0×10 -6 C / m 2 ; The polyimide resin is one or more of the following: acetylene-terminated polyimide resin, norbornene-terminated polyimide resin, and phenylacetylene-terminated polyimide resin; The charge modifier is one of amino-modified polysiloxane or nano-conductive powder; The nano-conductive powder is one or more of the following: nano-boron carbide, nano-titanium dioxide, and nano-silicon carbide, with a particle size of 30nm to 100nm. The amount of the charged modifier added is 1% to 5% of the mass of the polyimide resin powder.

4. The method for preparing polyimide resin prepreg by electrostatic adsorption according to claim 1, characterized in that, Step 002, the step of reinforcing fiber pretreatment to obtain charged reinforcing fibers, includes: Step 020: Place the reinforcing fiber in the sizing agent and the desizing agent, immerse it at 40°C to 60°C for 20 to 40 minutes, remove it, rinse it, and dry it to constant weight; Step 021: The reinforcing fiber obtained in step 020 is placed in a plasma processing device and subjected to surface activation treatment under the conditions of power of 100W to 300W, processing time of 5min to 15min, vacuum degree of 0.01MPa to 0.05MPa and inert gas protection, so that the surface of the reinforcing fiber carries a charge with opposite polarity to that of the polyimide resin powder, and charged reinforcing fiber is obtained.

5. The method for preparing polyimide resin prepreg by electrostatic adsorption according to claim 4, characterized in that, The surface charge density of the charged reinforcing fiber is 0.8 × 10⁻⁶. -6 C / m 2 Up to 4.0×10 -6 C / m 2 ; The reinforcing fiber is one or more of carbon fiber, aramid fiber, and glass fiber; The sizing agent remover is a mixture of ethanol and acetone in a volume ratio of 1:1 to 2:

1.

6. The method for preparing polyimide resin prepreg by electrostatic adsorption according to claim 1, characterized in that, Step 003, which involves electrostatically adsorbing the charged modified polyimide resin powder obtained in step 001 and the charged reinforcing fibers obtained in step 002 to obtain the composite resin, includes the following steps: Step 030: Add the charged modified polyimide resin powder obtained in step 001 into the powder chamber of the electrostatic adsorption device. Step 031: The charged reinforcing fiber prepared in step 002 is continuously traction-fed into the electrostatic adsorption chamber. During electrostatic adsorption, the voltage is 5kV to 20kV, the adsorption distance is 5mm to 20mm, the conveying speed of the charged reinforcing fiber is 0.3m / min to 1.5m / min, the temperature of the adsorption chamber is 25℃ to 45℃, and the relative humidity is 30% to 60%. The charged modified polyimide resin powder is blown by an airflow with a wind speed of 0.5m / s to 1.5m / s.

7. The method for preparing polyimide resin prepreg by electrostatic adsorption according to claim 6, characterized in that, The electrostatic adsorption equipment uses a bipolar electrostatic adsorption structure to adjust the polarity and charge density of the fibers and powders; After electrostatic adsorption impregnation, the resin loading of the composite reaches 85% to 95% of the target content of the prepreg.

8. The method for preparing polyimide resin prepreg by electrostatic adsorption according to claim 1, characterized in that, In step 004, when the composite resin obtained in step 003 is melt-cured and molded to obtain polyimide resin prepreg, the obtained composite resin is continuously conveyed to a hot air circulating drying and curing device, sequentially... Low-temperature drying is carried out at a temperature of 80℃ to 120℃ for 20 to 40 minutes and a hot air velocity of 1 m / s to 3 m / s. Curing is carried out at 200℃ to 300℃, with a heating rate of 5℃ / min to 10℃ / min and a curing time of 10min to 20min. After curing, the material is cooled to room temperature to obtain a polyimide resin prepreg.

9. The method for preparing polyimide resin prepreg by electrostatic adsorption according to claim 1, characterized in that, During curing, the process is carried out under a pressure of 0.1 MPa to 0.3 MPa.

10. A polyimide resin prepreg, characterized in that, The polyimide resin prepreg is prepared by the electrostatic adsorption method as described in any one of claims 1 to 9, wherein the polyimide resin content of the obtained polyimide resin prepreg is 35% to 40%, the volatile content is ≤0.5%, and the carbon fiber composite material prepared from the polyimide resin prepreg has a flexural strength ≥1300MPa, an interlaminar shear strength ≥100MPa, and a powder adsorption uniformity deviation ≤5%.

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