Process for the preparation of polyimide resin composites

Abstract

The application provides a preparation method of a polyimide resin composite material, which comprises the following steps: preparing a polyimide resin solution; preparing the polyimide resin solution into a polyimide resin adhesive film; compounding the polyimide resin adhesive film with a reinforcing fiber material to obtain a polyimide resin prepreg; laminating the polyimide resin prepreg on a lamination mold to obtain a polyimide resin prepreg blank; carrying out first packaging and devolatilization treatment to extract reaction small molecule products generated in an imidization process; then carrying out second packaging and curing forming, and then cooling and demolding to obtain the polyimide resin composite material. The application can realize the preparation of the polyimide resin composite material through a vacuum bag molding technology, reduces the dependence on a molding equipment, and greatly reduces the manufacturing cost.

Description

Technical Field

[0001] This invention relates to the field of composite materials technology, and more specifically, to a method for preparing a polyimide resin composite material. Background Technology

[0002] Polyimide resin molecules contain heat-resistant and stable imide groups in their main chain, which can form a three-dimensional cured network through end-group crosslinking reactions. This results in excellent heat resistance and mechanical properties. Polyimide resins and their composites are widely used in advanced manufacturing fields such as aerospace. Since NASA developed PMR-15 polyimide resin in the 1970s, researchers both domestically and internationally have developed a series of heat-resistant polyimide resins with temperature resistance ranging from 316℃ to 426℃, and their composites are widely used in components such as aircraft engine bypass ducts.

[0003] Due to the unique molecular structure of polyimides, bubbles and pores caused by the imidization process become the main challenges in the molding of composite materials. To avoid internal defects in composite materials, current molding methods for polyimide resin-based composites mainly utilize autoclave molding and compression molding to provide molding pressure and curing temperature. This method is also suitable for polyimide material systems with high melt viscosity, such as PMR-II-50 and AFR-700B. This process requires molding equipment to provide high molding temperatures above 300°C and high molding pressures above 2MPa, which places stringent requirements on the equipment and results in high manufacturing costs. Building on this, researchers have further developed a series of liquid molding methods, using isomeric dianhydrides as synthetic raw materials to design and synthesize polyimide resins with lower melt viscosity, such as PETI-375 and TriA-X. These can be prepared using liquid molding processes such as RTM, VARTM, VARI, and RFI. However, liquid molding processes still require supporting heating equipment, dispensing equipment, and other molding equipment, resulting in relatively high manufacturing costs.

[0004] Vacuum bag molding is a low-cost method for molding composite materials. Currently, it is mainly used for molding epoxy, bismaleimide, and other resin composite materials. It is achieved through vacuum resin impregnation or vacuum bag pressing of prepregs. The curing process is usually carried out in an oven, resulting in low equipment dependence, low manufacturing cost, and high manufacturing efficiency. However, due to the high melt viscosity of traditional polyimide resins, high curing temperatures, and difficulties in removing volatiles during the imidization process, vacuum bag molding has not yet been applied to the molding of polyimide composite materials. Summary of the Invention

[0005] (a) Technical problems to be solved

[0006] The technical problem to be solved by the present invention is that when traditional polyimide resin melt is used to form composite materials through vacuum bag molding, there are problems such as high viscosity, high curing temperature, and difficulty in removing volatiles during the imidization process.

[0007] (II) Technical Solution

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0009] In a first aspect, the present invention provides a method for preparing a polyimide resin composite material, comprising the following steps:

[0010] An aromatic diamine monomer is dissolved in an organic solvent and heated to a first preset temperature to obtain an aromatic diamine solution with a mass concentration of 10wt%-80wt%.

[0011] Phenylacetyl phthalic anhydride and aromatic dianhydride are dissolved in an alcohol solvent and heated to a second preset temperature to obtain an esterification solution with a mass concentration of 10wt%-80wt%.

[0012] The esterification solution is added to the aromatic diamine solution and polymerized within a third preset temperature range for 1-4 hours. Then, a vacuum low-pressure polymerization reaction is carried out within a fourth preset temperature range for 1-2 hours. The volatile organic solvents in the reaction process are collected and separated to obtain a polyimide resin solution with a mass concentration of 50wt%-90wt%.

[0013] The polyimide resin solution was used to prepare a polyimide resin film.

[0014] The polyimide resin film is combined with reinforcing fiber material to obtain polyimide resin prepreg.

[0015] Multiple layers of the polyimide resin prepreg are laid on a caulking mold to obtain a polyimide resin prepreg preform;

[0016] The polyimide resin prepreg preform is placed on a vacuum bag forming mold, and the polyimide resin prepreg preform is first encapsulated using a first auxiliary material. After the first encapsulation is completed, the preform is subjected to devolatilization treatment in a high-temperature oven with the first preset process parameters. During the devolatilization treatment, pressure is applied through a vacuum bag to reduce bubbles and pores, and small molecule products generated during the imidization process are extracted by vacuuming.

[0017] After the devolatilization process is completed, the first auxiliary material is removed, and the second auxiliary material is used to encapsulate the polyimide resin prepreg preform on the vacuum bag forming mold for the second time to obtain the vacuum bag forming assembly.

[0018] The vacuum bag forming assembly is placed in a high-temperature oven, and the polyimide resin prepreg preform is heated and cured under the second preset process parameters. After cooling and demolding, a polyimide resin composite material is obtained.

[0019] Preferably, the first preset temperature is 40℃-100℃, the second preset temperature is 40℃-120℃, the third preset temperature is 40℃-120℃, the fourth preset temperature is 80℃-140℃, and the vacuum degree is controlled to be ≤-0.095MPa in the vacuum low-pressure polymerization reaction.

[0020] Preferably, the areal density of the polyimide resin film is 10 g / m³. 2 -200g / m 2 The polyimide resin prepreg has a mass fraction of 30wt%-60wt% for the polyimide resin film, a composite temperature of 30℃-150℃, and a composite pressure of 0.01MPa-1MPa.

[0021] Preferably, the molar ratio of aromatic diamine, aromatic dianhydride, and phenylacetyl phthalic anhydride monomers is (n+1):n:2, where n is an integer from 1 to 5.

[0022] Preferably, the aromatic dianhydride monomer comprises at least one of 2,3,3',4'-biphenyltetracarboxylic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 3,3',4,4'-benzophenone tetracarboxylic dianhydride, 4,4'-oxobisphthalic anhydride, and 4,4'-hexafluoroisopropylphthalic anhydride;

[0023] Preferably, the aromatic diamine monomer comprises at least one selected from m-phenylenediamine, 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl ether, 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl, 2,2'-bis(trifluoromethyl)diaminobiphenyl, 1,3-bis(4'-aminophenoxy)benzene, 9,9-bis(4-aminophenyl)fluorene, 4,4'-diaminodiphenylmethane, 4,4'-diaminophenyl sulfone, and 2,2-bis[4-(4-aminophenoxy)phenyl]propane.

[0024] Preferably, the alcohol solvent includes at least one selected from methanol, ethanol, propanol, isopropanol, n-butanol, and isobutanol;

[0025] Preferably, the organic solvent includes at least one of tetrahydrofuran, dioxane, N,N-dimethylacetamide, N,N-dimethylformamide, and N-methylpyrrolidone.

[0026] Preferably, the reinforcing fiber material includes at least one of carbon fiber, glass fiber, aramid fiber, polyimide fiber, poly(p-phenylenebenzodioxazole) fiber, basalt fiber, and silicon carbide fiber.

[0027] Preferably, the first preset process parameters include: heating at 30℃-100℃ for 0.5h-3h and at 100℃-150℃ for 0.5h-3h, and controlling the vacuum degree inside the vacuum bag to ≤-0.1MPa throughout the entire devolatilization process;

[0028] Preferably, the second preset process parameters include: heating at 180℃-250℃ for 0.5h-5h, at 250℃-320℃ for 1h-5h, at 320℃-350℃ for 1h-5h, and at 350℃-400℃ for 2h-8h, and controlling the vacuum degree inside the vacuum bag to be ≤-0.1MPa during the heating and curing process.

[0029] Preferably, the first auxiliary material includes vacuum bag film, tape, putty strip, and breathable felt with an operating temperature below 300°C; the second auxiliary material includes high-temperature vacuum bag film, high-temperature tape, high-temperature putty strip, and high-temperature breathable felt with an operating temperature above 300°C.

[0030] (III) Beneficial Effects

[0031] The above-described technical solution of the present invention has at least the following advantages:

[0032] 1. The method for preparing polyimide resin composite materials provided by this invention enables the preparation of thermosetting polyimide resins with melt viscosity lower than that of traditional polyimide resins. Based on this, polyimide resin prepregs can then be prepared. The resin matrix of this polyimide resin prepreg exhibits good fluidity during the devolatilization process, thereby allowing for the full removal of volatiles from the imidization process during vacuum bag pressurization. This reduces the generation of bubbles and pores within the composite material, ensuring that the final polyimide resin prepreg meets the required molding quality.

[0033] 2. The preparation method of polyimide resin composite material provided by this invention enables the preparation of polyimide resin composite material using vacuum bag molding technology. Compared with the existing autoclave molding, compression molding, and liquid molding processes, vacuum bag molding technology only requires heating with an oven and applying pressure to the vacuum bag. It has low dependence on high-cost molding equipment such as autoclaves and injection molding machines, which can reduce equipment procurement costs. It does not require high molding temperature and high molding pressure, which can reduce energy consumption costs. The production process is relatively simple, reducing the molding time and improving manufacturing efficiency, thereby greatly reducing the manufacturing cost of polyimide resin composite material. Attached Figure Description

[0034] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0035] Figure 1 This is one of the flowcharts illustrating the preparation method of the polyimide resin composite material provided in this embodiment of the invention.

[0036] Figure 2 This is the second schematic flowchart of the preparation method of polyimide resin composite material provided in the embodiments of the present invention.

[0037] Figure 3 This is a schematic diagram of the structure of the vacuum bag forming assembly provided in an embodiment of the present invention.

[0038] Figure 4 This is a photograph of the PA-1 polyimide composite material flat plate provided in Embodiment 1 of the present invention.

[0039] Figure 5 This is an ultrasonic C-scan image of the PA-1 polyimide composite flat plate part provided in Embodiment 1 of the present invention.

[0040] Figure 6 This is a photograph of the EW100A glass cloth reinforced PA-1 polyimide composite flat plate provided in Embodiment 2 of the present invention.

[0041] Figure 7 This is an ultrasonic C-scan image of the EW100A glass cloth reinforced PA-1 polyimide composite flat plate part provided in Embodiment 2 of the present invention.

[0042] Figure 8 This is a photograph of the actual PA-1 polyimide composite material T-shaped part provided in Embodiment 3 of the present invention.

[0043] Figure 9 This is an ultrasonic C-scan image of the PA-1 polyimide composite material T-shaped part provided in Embodiment 3 of the present invention.

[0044] Figure 10 This is a photograph of the PF-1 polyimide composite material flat plate provided in Embodiment 4 of the present invention.

[0045] Figure 11 This is an ultrasonic C-scan image of the PF-1 polyimide composite plate part provided in Embodiment 4 of the present invention.

[0046] The labels for the attached figures are as follows:

[0047] 1. Polyimide resin prepreg blank; 2. Vacuum bag forming mold; 3. High temperature vacuum bag film; 4. High temperature putty strip; 5. High temperature breathable felt; 6. High temperature rubber strip; 7. High temperature isolation material; 8. PTFE cloth. Detailed Implementation

[0048] To make the technical problems to be solved, the technical solutions, and the beneficial effects of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present invention and are not intended to limit the present invention.

[0049] In this application, the term "and / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. A and B can be singular or plural. The character " / " generally indicates that the preceding and following related objects have an "or" relationship.

[0050] In this application, "at least one" means one or more, and "more than one" means two or more. "At least one item" or similar expressions refer to any combination of these items, including any combination of single or multiple items. For example, "at least one item of a, b, or c", or "at least one item of a, b, and c", can both mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be single or multiple.

[0051] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating relative importance or the number of technical features. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified. The specific implementation of this invention will be described in more detail below with reference to specific embodiments:

[0052] like Figure 1 , Figure 2 as well as Figure 3 As shown, this embodiment of the invention provides a method for preparing a polyimide resin composite material, comprising the following steps:

[0053] S1. Dissolve the aromatic diamine monomer in an organic solvent and heat it to a first preset temperature to obtain an aromatic diamine solution with a mass concentration of 10wt%-80wt%; specifically, dissolve the aromatic diamine monomer in an organic solvent and heat it to 40℃-100℃ (first preset temperature) under inert gas protection to obtain an aromatic diamine solution with a concentration of 10wt%-80wt%.

[0054] S2. Dissolve phenylethynyl phthalic anhydride and aromatic dianhydride in an alcohol solvent and heat to a second preset temperature to obtain an esterification solution with a mass concentration of 10wt%-80wt%; specifically, dissolve phenylethynyl phthalic anhydride and aromatic dianhydride in an alcohol solvent and heat to 40℃-120℃ (second preset temperature) to obtain an esterification solution with a concentration of 10wt%-80wt%.

[0055] S3. The esterification solution is added to the aromatic diamine solution and polymerized within the third preset temperature range for 1-4 hours, followed by vacuum low-pressure polymerization within the fourth preset temperature range for 1-2 hours. The volatile organic solvents generated during the reaction are collected and separated to obtain a polyimide resin solution with a mass concentration of 50wt%-90wt%. Specifically, the esterification solution is added to the aromatic diamine solution, stirred and heated to 40℃-120℃ (third preset temperature) in a reaction vessel for 1-4 hours; the temperature is further increased to 80℃-140℃ (fourth preset temperature), and vacuum low-pressure polymerization is carried out for 1-2 hours with a vacuum degree ≤-0.095MPa. The volatile organic solvents generated during the reaction are collected and separated by a condenser to obtain a polyimide resin solution with a concentration of 50wt%-90wt%. Through the above steps S1 to S3, a polyimide resin solution with a melt viscosity lower than that of traditional polyimide resin can be obtained, which can then be molded into a polyimide resin film and further combined with reinforcing fiber materials to form a prepreg.

[0056] S4. Prepare a polyimide resin film from the polyimide resin solution; specifically, transfer the polyimide resin solution to a film coating machine for coating, wherein the coating temperature is 30℃-120℃, and the areal density of the polyimide resin film is controlled to be 10g / m³. 2 -200g / m 2 They were then compacted and rolled up for later use.

[0057] S5. Composite the polyimide resin film with the reinforcing fiber material to obtain the polyimide resin prepreg.

[0058] S6. Lay multiple layers of polyimide resin prepreg prepared by any of the above-described methods for preparing polyimide resin composite materials on a laying mold to obtain polyimide resin prepreg blank 1; specifically, the polyimide resin prepreg is cut to a suitable size according to the target composite material size, and then laid layer by layer on a laying mold to the target structural form, and then placed on a vacuum bag forming mold to obtain polyimide resin prepreg blank 1.

[0059] S7. Place the polyimide resin prepreg blank 1 on the vacuum bag forming mold 2, and use the first auxiliary material to encapsulate the polyimide resin prepreg blank for the first time. After the first encapsulation is completed, perform devolatilization treatment in a high-temperature oven with the first preset process parameters. During the devolatilization treatment, apply pressure through the vacuum bag to reduce bubbles and pores, and extract the small molecule products generated during the imidization process by vacuuming. Specifically, the first auxiliary material includes a vacuum bag film with a working temperature of less than 300°C, tape, putty strip, and breathable felt. Because polyimide resin presents difficulties in removing volatiles during the imidization process when molding composite materials, this application addresses this issue by performing a devolatilization treatment on the polyimide resin prepreg preform under suitable first preset process parameters. Since the polyimide resin material prepared through steps S1 to S3 exhibits good flowability, the negative pressure generated by the vacuum bag during the devolatilization process applies uniform pressure to the polyimide resin material, allowing the small molecule products generated during the imidization process to be smoothly discharged. Furthermore, the small molecule products generated during the imidization process are extracted through vacuuming, thus eliminating the volatiles from the imidization process. Simultaneously, the negative pressure generated by the vacuum bag during the devolatilization process uniformly presses the resin material to eliminate bubbles and pores generated within the polyimide resin material during imidization, improving the molding quality of the composite material. During the devolatilization process, the small molecule products generated during imidization are adsorbed onto the first auxiliary material. Considering the relatively low temperature used in the devolatilization process, the first auxiliary material is preferably a relatively inexpensive room-temperature auxiliary material to reduce material waste costs.

[0060] S8. After the devolatilization treatment is completed, the first auxiliary material is removed, and the second auxiliary material is used to encapsulate the polyimide resin prepreg blank on the vacuum bag forming mold for the second time to obtain the vacuum bag forming component; specifically, the second auxiliary material includes a high-temperature vacuum bag film 3 with a working temperature higher than 300℃, high-temperature tape, high-temperature putty strip 4, high-temperature insulating material 7, and high-temperature breathable felt 5, and the stacking order of each material is as follows: Figure 3 As shown. Specifically, during encapsulation, PTFE cloth 8 is placed on both sides of the polyimide resin prepreg blank 1 as a release cloth to facilitate demolding after curing. High-temperature rubber baffles 6 are placed at both ends of the polyimide resin prepreg blank 1 to limit the ends of the polyimide resin prepreg blank 1, facilitating the molding of the polyimide resin prepreg blank 1. Specifically, the devolatilized polyimide resin prepreg blank 1 is removed and re-encapsulated using a second auxiliary material (high-temperature vacuum bag film, high-temperature tape, high-temperature putty strip, high-temperature breathable felt, etc.). The connection between the high-temperature vacuum bag and the vacuum bag forming mold is sealed with a high-temperature sealant, and the high-temperature vacuum bag is clamped around the perimeter with I-beam clamps to ensure a seal, thus obtaining the vacuum bag forming assembly.

[0061] S9. Place the vacuum bag forming assembly in a high-temperature oven and heat-cur the polyimide resin prepreg under the second preset process parameters. After cooling and demolding, a polyimide resin composite material is obtained. Specifically, the vacuum bag forming assembly obtained in step S8 is transferred to a high-temperature oven for curing. The prepreg is cured at 180℃-250℃ for 0.5h-5h, 250℃-320℃ for 1h-5h, 320℃-350℃ for 1h-5h, and 350℃-400℃ for 2h-8h. During the curing process, the vacuum degree inside the high-temperature vacuum bag is maintained at ≤-0.1MPa using a vacuum pump. The oven heating is turned off, and the vacuum degree is maintained while cooling down to below 60℃ before demolding to obtain the vacuum-formed polyimide resin composite material.

[0062] Furthermore, the molar ratio of aromatic diamine, aromatic dianhydride, and phenylacetyl phthalic anhydride monomers is (n+1):n:2, where n is an integer from 1 to 5.

[0063] Furthermore, the aromatic dianhydride monomer includes at least one of 2,3,3',4'-biphenyltetracarboxylic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 3,3',4,4'-benzophenone tetracarboxylic dianhydride, 4,4'-oxobisphthalic anhydride, and 4,4'-hexafluoroisopropylphthalic anhydride;

[0064] Further, the aromatic diamine monomer includes at least one selected from m-phenylenediamine, 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl ether, 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl, 2,2'-bis(trifluoromethyl)diaminobiphenyl, 1,3-bis(4'-aminophenoxy)benzene, 9,9-bis(4-aminophenyl)fluorene, 4,4'-diaminodiphenylmethane, 4,4'-diaminophenyl sulfone, and 2,2-bis[4-(4-aminophenoxy)phenyl]propane.

[0065] Furthermore, the alcohol solvents include at least one of methanol, ethanol, propanol, isopropanol, n-butanol, and isobutanol;

[0066] Furthermore, the organic solvent includes at least one of tetrahydrofuran, dioxane, N,N-dimethylacetamide, N,N-dimethylformamide, and N-methylpyrrolidone.

[0067] Furthermore, the reinforcing fiber material includes at least one of carbon fiber, glass fiber, aramid fiber, polyimide fiber, poly(p-phenylenebenzodioxazole) fiber, basalt fiber, and silicon carbide fiber.

[0068] The following are specific embodiments provided in this application:

[0069] Example 1:

[0070] (1-1) Dissolve 229.42 g of 1,3-bis(4'-aminophenoxy)benzene in 525.32 g of N-methylpyrrolidone solvent, and heat to 60 °C under inert gas protection to obtain an aromatic diamine solution with a concentration of 30 wt%.

[0071] (1-2) Dissolve 97.4 g of phenylethynyl phthalic anhydride and 173.17 g of 2,3,3',4'-biphenyltetracarboxylic dianhydride in 631.34 g of ethanol solvent and heat to 75 °C to obtain an esterification solution with a concentration of 30 wt%.

[0072] (1-3) The esterification solution was added to the aromatic diamine solution, stirred and heated to 75°C in the reaction vessel for 2 hours; the temperature was further increased to 90°C, and a vacuum low-pressure polymerization reaction was carried out for 2 hours, with the vacuum degree controlled to be ≤-0.095MPa. The volatile organic solvents generated during the reaction were collected and separated by a condenser to obtain a PA-1 polyimide resin solution with a concentration of 80wt%.

[0073] (1-4) The PA-1 polyimide resin solution is transferred to a film coating machine for coating. The coating temperature is 45℃, and the areal density of the polyimide resin film is controlled at 100g / m³. 2 The film is then compacted, rolled up, and ready for use to obtain a polyimide resin film.

[0074] (1-5) After the CCF800H carbon fiber (reinforcing fiber material) is unraveled, it is compounded with a polyimide resin film. The mass fraction of the compounded polyimide resin film is controlled at 40wt%, the compounding temperature is 55℃, and the compounding pressure is 0.1MPa to obtain PA-1 polyimide resin prepreg.

[0075] (1-6) Cut the PA-1 polyimide resin prepreg into 350mm × 330mm dimensions, according to [0] 16 A polyimide resin prepreg preform in a flat shape is laid out in a layering sequence. The prepreg preform is then placed on a vacuum bag forming mold and sealed with auxiliary materials (room temperature vacuum bag film, room temperature tape, room temperature putty strip, room temperature breathable felt, etc.) and pre-evacuated for leak testing. The vacuum bag forming mold containing the prepreg preform is then transferred to a high-temperature oven for devolatilization treatment. The heating program is performed at 70℃ for 1 hour and at 120℃ for 1 hour. The vacuum level inside the vacuum bag is continuously maintained at ≤-0.1MPa by a vacuum pump to fully extract the small molecule products of the reaction.

[0076] (1-7) Remove the devolatilized polyimide resin prepreg blank after devolatilization treatment, remove the first auxiliary material, and re-encapsulate the composite material flat devolatilized blank using the second auxiliary material (high-temperature vacuum bag film, high-temperature tape, high-temperature putty strip, high-temperature breathable felt, etc.). Seal the connection between the high-temperature vacuum bag and the vacuum bag forming mold with a high-temperature sealant, and clamp the high-temperature vacuum bag around its perimeter to ensure a seal, thus obtaining a vacuum bag forming assembly. Then, transfer the vacuum bag forming assembly to a high-temperature oven for curing treatment. The devolatilized blank is cured at 180℃ for 1 hour, 300℃ for 1 hour, 350℃ for 2 hours, and 380℃ for 4 hours. During the curing process, the vacuum degree inside the high-temperature vacuum bag is maintained at ≤-0.1MPa using a vacuum pump. The blank is then cooled to below 60℃ and demolded to obtain the desired product. Figure 4 The PA-1 polyimide composite plate part (polyimide resin composite material) shown was subjected to ultrasonic C-scan of the PA-1 polyimide composite plate part obtained in Example 1, and the results were as follows. Figure 5 The ultrasound C-scan image shown.

[0077] Example 2:

[0078] (2-1) EW100A glass cloth reinforced PA-1 polyimide resin prepreg was prepared using the same method as in Example 1; that is, the reinforcing fiber material was replaced by EW100A glass cloth instead of CCF800H carbon fiber in Example 1, and the other materials and steps were the same.

[0079] (2-2) The polyimide resin prepreg blank is laid in a flat shape according to the [(0 / 90)]8 layering sequence, and placed on the vacuum bag forming mold. The polyimide resin prepreg blank is then sealed with the first auxiliary material (room temperature vacuum bag film, room temperature tape, room temperature putty strip, room temperature breathable felt, etc.) and pre-evacuated for leak testing. The vacuum bag forming mold of the polyimide resin prepreg blank is transferred to a high temperature oven for devolatilization treatment. The heating program is carried out at 75℃ for 2 hours and at 120℃ for 2 hours. The vacuum degree inside the vacuum bag is continuously maintained at ≤-0.1MPa by a vacuum pump to fully extract the small molecule products of the reaction.

[0080] (2-3) The devolatilized polyimide resin prepreg blank is removed and re-encapsulated using a second auxiliary material (high-temperature vacuum bag film, high-temperature tape, high-temperature putty strip, high-temperature breathable felt, etc.). The connection between the high-temperature vacuum bag and the vacuum bag forming mold is sealed with a high-temperature sealant, and the high-temperature vacuum bag is clamped around its perimeter using I-beam clamps to ensure a seal, thus obtaining a vacuum bag forming assembly. This assembly is then transferred to a high-temperature oven for curing. The devolatilized prepreg is cured at 150℃ for 0.5h, 280℃ for 0.5h, 350℃ for 1h, and 380℃ for 2h. During curing, a vacuum pump maintains a vacuum level ≤-0.1MPa inside the high-temperature vacuum bag. The prepreg is then cooled to below 60℃ before demolding to obtain the desired result. Figure 6 The EW100A glass cloth reinforced PA-1 polyimide composite flat plate part (polyimide resin composite material) shown was subjected to ultrasonic C-scan of the EW100A glass cloth reinforced PA-1 polyimide composite flat plate part obtained in Example 2, and the results were as follows. Figure 7 The ultrasound C-scan image shown.

[0081] Example 3:

[0082] (3-1) PA-1 polyimide resin prepreg was prepared using the same preparation method as in Example 1;

[0083] (3-2) Cut PA-1 polyimide resin prepreg into 600mm×80mm sizes, lay it into T-shaped polyimide resin prepreg blanks according to quasi-isotropic layup, place it on a vacuum bag forming mold, and use the first auxiliary materials (room temperature vacuum bag film, room temperature tape, room temperature putty strip, room temperature breathable felt, etc.) to seal the polyimide resin prepreg blanks and pre-evacuate and test for leaks; transfer the vacuum bag forming mold on which the polyimide resin prepreg blanks are laid to a high temperature oven for devolatilization treatment, the heating program is carried out at 75℃ for 3h and at 150℃ for 1h, and the vacuum degree in the vacuum bag is continuously maintained at ≤-0.1MPa by a vacuum pump to fully extract the reaction small molecule products;

[0084] (3-3) The devolatilized polyimide resin prepreg blank is removed and re-encapsulated using a second auxiliary material (high-temperature vacuum bag film, high-temperature tape, high-temperature putty strip, high-temperature breathable felt, etc.). The connection between the high-temperature vacuum bag and the vacuum bag forming mold is sealed with a high-temperature sealant, and the high-temperature vacuum bag is clamped around its perimeter to ensure a seal, thus obtaining a vacuum bag forming assembly. This assembly is then transferred to a high-temperature oven for curing. The devolatilized prepreg is cured at 180℃ for 2 hours, 300℃ for 2 hours, 350℃ for 2 hours, and 380℃ for 6 hours. During curing, a vacuum pump maintains a vacuum level ≤-0.1MPa inside the high-temperature vacuum bag. The prepreg is then demolded when the temperature drops below 60℃ to obtain the desired result. Figure 8 The PA-1 polyimide composite T-shaped part (polyimide resin composite material) shown was subjected to ultrasonic A-scan of the PA-1 polyimide composite T-shaped part obtained in Example 3, and the results were as follows. Figure 9 The ultrasound A-scan image shown.

[0085] Example 4

[0086] (4-1) Dissolve 251.33 g of 9,9-bis(4-aminophenyl)fluorene in 586.43 g of N-methylpyrrolidone solvent, and heat to 80 °C under inert gas protection to obtain an aromatic diamine solution with a concentration of 30 wt%.

[0087] (4-2) Dissolve 89.52g of phenylethynyl phthalic anhydride and 159.16g of 2,3,3',4'-biphenyltetracarboxylic dianhydride in 580.24g of ethanol solvent and heat to 75℃ to obtain an esterification solution with a concentration of 30wt%.

[0088] (4-3) The esterification solution was added to the aromatic diamine solution, stirred and heated to 75°C in the reaction vessel for 2 hours; the temperature was further increased to 90°C, and a vacuum low-pressure polymerization reaction was carried out for 2 hours with a vacuum degree ≤ -0.095MPa. The volatile organic solvents generated during the reaction were collected and separated by a condenser to obtain a PF-1 polyimide resin solution with a concentration of 80wt%.

[0089] (4-4) The PF-1 polyimide resin solution is transferred to a film coating machine for coating. The coating temperature is 55℃, and the areal density of the polyimide resin film is controlled to be 100 g / m³. 2 It is then compacted and wound up for later use; a polyimide resin film is obtained.

[0090] (4-5) After the CCF800H carbon fiber (reinforcing fiber material) is unrolled, it is compounded with a polyimide resin film. The mass fraction of the compounded polyimide resin film is controlled at 40wt%, the compounding temperature is 65℃, and the compounding pressure is 0.1MPa to obtain PF-1 polyimide resin prepreg.

[0091] (4-6) Cut the PF-1 polyimide resin prepreg into 350mm × 330mm dimensions, according to [0] 16 The polyimide resin prepreg preform, laid in a flat shape, is placed on a vacuum bag forming mold. First auxiliary materials (room temperature vacuum bag film, room temperature tape, room temperature putty strip, room temperature breathable felt, etc.) are used to encapsulate the polyimide resin prepreg preform, and a pre-vacuum test is performed to check for leaks. The vacuum bag forming mold containing the polyimide resin prepreg preform is then transferred to a high-temperature oven for devolatilization treatment. The heating program is performed at 80℃ for 1 hour and at 130℃ for 1 hour. A vacuum pump is used to continuously maintain the vacuum level inside the vacuum bag at ≤-0.1MPa to fully extract the small molecule products from the reaction.

[0092] (4-7) Remove the devolatilized polyimide resin prepreg blank after devolatilization treatment, and re-encapsulate the composite material flat devolatilized blank using a second auxiliary material (high-temperature vacuum bag film, high-temperature tape, high-temperature putty strip, high-temperature breathable felt, etc.). Seal the connection between the high-temperature vacuum bag and the vacuum bag forming mold with a high-temperature sealant, and clamp the high-temperature vacuum bag around its perimeter to ensure a seal, thus obtaining a vacuum bag forming assembly. Then, transfer the vacuum bag forming assembly to a high-temperature oven for curing treatment. The devolatilized blank is cured at 180℃ for 1 hour, 280℃ for 1 hour, 350℃ for 1 hour, and 380℃ for 6 hours. During the curing process, the vacuum degree inside the high-temperature vacuum bag is maintained at ≤-0.1MPa using a vacuum pump. The mold is then removed when the temperature drops below 60℃. Figure 10 The PF-1 polyimide composite plate part (polyimide resin composite material) shown is subjected to ultrasonic C-scan of the PF-1 polyimide composite plate part obtained in Example 1, and the results are as follows. Figure 11 The ultrasound C-scan image shown.

[0093] Based on the ultrasonic A-scan and ultrasonic C-scan images of the polyimide resin composites prepared in Examples 1 to 4, it can be seen that the polyimide resin composites prepared using the preparation methods provided in this application do not have obvious internal defects and have good molding quality. Specifically, the preparation methods provided in this application are suitable for the rapid preparation of thermosetting polyimide resin systems with a minimum melt viscosity ≤1 Pa·s.

[0094] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a polyimide resin composite material, characterized in that, Includes the following steps: Aromatic diamine monomers are dissolved in an organic solvent and heated to 40℃-100℃ to obtain an aromatic diamine solution with a mass concentration of 10wt%-80wt%. Phenylacetyl phthalic anhydride and aromatic dianhydride are dissolved in an alcohol solvent and heated to 40℃-120℃ to obtain an esterification solution with a mass concentration of 10wt%-80wt%. The esterification solution is added to the aromatic diamine solution and polymerized at 40℃-120℃ for 1-4 hours, followed by vacuum low-pressure polymerization at 80℃-140℃ for 1-2 hours. The volatile organic solvents are collected and separated during the reaction to obtain a polyimide resin solution with a mass concentration of 50wt%-90wt%. The vacuum degree is controlled to be ≤-0.095MPa during the vacuum low-pressure polymerization reaction. The polyimide resin solution was used to prepare a polyimide resin film. The polyimide resin film is combined with reinforcing fiber material to obtain polyimide resin prepreg. Multiple layers of the polyimide resin prepreg are laid on a caulking mold to obtain a polyimide resin prepreg preform; The polyimide resin prepreg preform is placed on a vacuum bag forming mold, and the polyimide resin prepreg preform is first encapsulated using a first auxiliary material. After the first encapsulation is completed, the preform is subjected to devolatilization treatment in a high-temperature oven with the first preset process parameters. During the devolatilization treatment, pressure is applied through a vacuum bag to reduce bubbles and pores, and small molecule products generated during the imidization process are extracted by vacuuming. The first preset process parameters include: heating at 30℃-100℃ for 0.5h-3h and at 100℃-150℃ for 0.5h-3h, and controlling the vacuum degree inside the vacuum bag to ≤-0.1MPa throughout the entire devolatilization process; After the devolatilization process is completed, the first auxiliary material is removed, and the second auxiliary material is used to encapsulate the polyimide resin prepreg preform on the vacuum bag forming mold for the second time to obtain the vacuum bag forming assembly. The vacuum bag forming assembly is placed in a high-temperature oven, and the polyimide resin prepreg preform is heated and cured under the second preset process parameters. After cooling and demolding, a polyimide resin composite material is obtained.

2. The method for preparing the polyimide resin composite material according to claim 1, characterized in that, The areal density of the polyimide resin film is 10 g / m³. 2 -200g / m 2 The polyimide resin prepreg has a mass fraction of 30wt%-60wt% for the polyimide resin film, a composite temperature of 30℃-150℃, and a composite pressure of 0.01MPa-1MPa.

3. The method for preparing the polyimide resin composite material according to claim 1, characterized in that, The molar ratio of aromatic diamine, aromatic dianhydride, and phenylacetyl phthalic anhydride monomers is (n+1):n:2, where n is an integer from 1 to 5.

4. The method for preparing the polyimide resin composite material according to claim 1, characterized in that, The aromatic dianhydride monomers include at least one of 2,3,3',4'-biphenyltetracarboxylic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 3,3',4,4'-benzophenone tetracarboxylic dianhydride, 4,4'-oxobisphthalic anhydride, and 4,4'-hexafluoroisopropylphthalic anhydride. And / or the aromatic diamine monomer includes at least one of m-phenylenediamine, 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl ether, 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl, 2,2'-bis(trifluoromethyl)diaminobiphenyl, 1,3-bis(4'-aminophenoxy)benzene, 9,9-bis(4-aminophenyl)fluorene, 4,4'-diaminodiphenylmethane, 4,4'-diaminophenyl sulfone, and 2,2-bis[4-(4-aminophenoxy)phenyl]propane.

5. The method for preparing the polyimide resin composite material according to claim 1, characterized in that, The alcohol solvents include at least one of methanol, ethanol, propanol, isopropanol, n-butanol, and isobutanol; And / or the organic solvent includes at least one of tetrahydrofuran, dioxane, N,N-dimethylacetamide, N,N-dimethylformamide, and N-methylpyrrolidone.

6. The method for preparing the polyimide resin composite material according to claim 1, characterized in that, The reinforcing fiber material includes at least one of carbon fiber, glass fiber, aramid fiber, polyimide fiber, poly(p-phenylenebenzodioxazole) fiber, basalt fiber, and silicon carbide fiber.

7. The method for preparing the polyimide resin composite material according to claim 1, characterized in that, The second preset process parameters include: heating at 180℃-250℃ for 0.5h-5h, at 250℃-320℃ for 1h-5h, at 320℃-350℃ for 1h-5h, and at 350℃-400℃ for 2h-8h, and controlling the vacuum degree inside the vacuum bag to be ≤-0.1MPa during the heating and curing process.

8. The method for preparing the polyimide resin composite material according to claim 1, characterized in that, The first auxiliary materials include vacuum bag film, tape, putty strips, and breathable felt with an operating temperature below 300°C; the second auxiliary materials include high-temperature vacuum bag film, high-temperature tape, high-temperature putty strips, and high-temperature breathable felt with an operating temperature above 300°C.

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