Method for preparing thermosetting polyimide composite material based on dynamic network reconstruction

Abstract

The invention discloses a method for preparing a thermosetting polyimide composite material based on dynamic network reconstruction, and belongs to the technical field of functional materials. The method comprises the following steps: dispersing a diamine monomer in an aprotic polar solvent under an ice-water bath condition, adding a dianhydride monomer, and stirring for reaction to obtain a polyamide acid solution; adding a triamine cross-linking agent into the solution for 5-30 minutes until the solution is in a gel state; carbon fiber fabric is cut and then laid in a prepared container, gel is placed on the carbon fiber fabric and placed in a vacuum oven at the temperature of 120 DEG C, at the moment, the gel is gradually changed into sol to impregnate CF, then vacuumizing is conducted till the solvent is evaporated, and a TCPAA / CF composite material is generated; and placing in a hot press, pre-pressing and cooling, placing in a muffle furnace, preserving heat at 250 DEG C for 1 hour, and preserving heat at 300 DEG C for 1 hour. According to the method, reversible dissociation and reconstruction of a polymer network are achieved through heating / cooling circulation in the third step, the prepared film is good in thermal stability, and the technical problem that a traditional TCPI gel system is poor in CF wettability is solved.

Description

Technical Field

[0001] The present invention belongs to the technical field of functional materials, and in particular relates to a preparation method for constructing a composite material by combining thermosetting polyimide gel with carbon fiber based on dynamic network reconstruction. Background Art

[0002] Thermosetting polyimide (TCPI) composites are widely used in aerospace, electronics, and other fields due to their excellent high-temperature stability, mechanical properties, and chemical resistance. Currently, the preparation of thermosetting polyimide composites typically involves the addition of monomers containing reactive groups such as alkynes. High temperatures and high pressures (above 350°C) are used to form aromatic ring structures that promote the formation of a cross-linked network. This results in difficult processing, high energy consumption, and high material brittleness. Since chemical crosslinking systems at room temperature tend to form a gel state, their interfacial compatibility with materials such as carbon fiber (CF) is significantly reduced. Summary of the Invention

[0003] The present invention aims to address the aforementioned issues with the prior art by providing a method for preparing thermosetting polyimide composites based on dynamic network reconstruction. This method achieves reversible dissociation and reconstruction of the polymer network through a heating / cooling cycle in step three. The resulting films exhibit excellent thermal stability, resolving the technical challenge of poor wettability of conventional TCPI gel systems for CF.

[0004] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0005] A method for preparing a thermosetting polyimide composite material based on dynamic network reconstruction, the method comprising the following steps:

[0006] Step 1: Prepare polyamic acid (PAA) solution: Disperse the diamine monomer in an aprotic polar solvent in an ice-water bath, then slowly add the dianhydride monomer and stir for 18-24 hours to obtain a polyamic acid solution.

[0007] Step 2: Preparation of Thermosetting PAA Gel: Add a triamine crosslinker to the PAA solution, ensuring that the total molar amounts of amino and anhydride functional groups are equivalent during the addition process. 5-30 minutes after adding the crosslinker, the solution will become a gel. For example, if the diamine is X mol, the dianhydride is Y mol, and the triamine is Z mol, and the number of amino functional groups equals the number of anhydride functional groups, then the ratio of the three monomers is 2Y = 2X + 3Z (Z > critical crosslinker content; gel formation occurs only when Z > critical crosslinker content). When the molar ratio of dianhydride monomer to diamine monomer in step 1 is 1:0.9625, the required crosslinker content is the critical crosslinker content.

[0008] Step 3: Preparation of TCPAA / CF composite material: Cut the carbon fiber fabric into sizes of 15 mm × 15 mm to 30 mm × 30 mm and lay it in a prepared container (aluminum foil or glass). Place the TCPAA gel on the carbon fiber fabric and place it in a vacuum oven at 120°C. At this time, the gel gradually changes into a sol and impregnates the CF. Then, vacuum is applied until the solvent is completely evaporated to form a TCPAA / CF composite material.

[0009] Step 4: Preparation of TCPI / CF composite material: Place the TCPAA / CF composite material in a hot press, and the pre-pressing conditions are 180℃ for 10 minutes and 250℃ for 60 minutes. The pressure during the pre-pressing process is 5-10MPa; then after cooling, place the composite material in a muffle furnace, keep it at 250℃ for 1 hour and 300℃ for 1 hour to obtain a TCPI / CF composite material with a glue content of 30%~70%.

[0010] Furthermore, in step 1, the aprotic polar solvent is one of N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone or dimethyl sulfoxide.

[0011] Furthermore, in step 1, the diamine monomer is one of 4,4'-diaminodiphenyl ether, 1,3-bis(3-aminophenoxy)benzene or 5-amino-2-(4-aminophenyl)benzimidazole; the dianhydride monomer is one of 4,4'-(4,4'-isopropyldiphenoxy)di(phthalic anhydride), pyromellitic dianhydride or 4,4'-biphenyl ether dianhydride.

[0012] Furthermore, in step 1, the molar ratio of the dianhydride monomer to the diamine monomer is 1:0.7-0.9625, and the mass concentration of the polyamic acid solution is 10%-20%.

[0013] Furthermore, in step 2, the triamine crosslinking agent is one or more of tris(4-aminophenyl)amine, 1,3,5-tris(4-aminophenoxy)benzene, 1,3,5-tris(4-aminophenyl) or tris(4-aminophenyl)amine (TAP).

[0014] TCPI / CF composites are widely used in the aerospace field due to their high-temperature, high-strength, corrosion-resistant, and excellent insulation properties. The TCPI / CF prepared using dynamic reversible network control offers advantages over traditional TCPI / CF: low cost. The low-temperature sol-gel infiltration of the dynamically cross-linked network significantly reduces processing temperatures, energy consumption, and the risk of thermal stress damage compared to traditional hot pressing processes, making it suitable for low-cost mass production of carbon fiber prepregs. Chemical resistance: The synergistic effect of the three-dimensional cross-linked structure and carbon fibers imparts excellent acid, alkali, and solvent resistance to the composite, paving the way for applications in harsh chemical environments such as chemical reactor linings and nuclear waste containment containers. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 Reconstruct molecular mechanism diagrams for dynamic networks;

[0016] Figure 2 This is a physical picture of TCPI-O / CF;

[0017] Figure 3 This is the dynamic thermomechanical analysis (DMA) characterization diagram of TCPI-O / CF;

[0018] Figure 4 This is the thermal performance (TGA) test chart;

[0019] Figure 5 This is the TCPI-O / CF shape memory cycle diagram;

[0020] Figure 6 This is the actual picture of TCPI-B / CF;

[0021] Figure 7 This is a physical picture of TCPI-N / CF; DETAILED DESCRIPTION

[0022] The technical solution of the present invention is further described below with reference to the accompanying drawings and embodiments, but is not limited thereto. Any modification or equivalent replacement of the technical solution of the present invention that does not depart from the spirit and scope of the technical solution of the present invention should be included in the scope of protection of the present invention.

[0023] The innovations of this invention are as follows: (1) Reversible control mechanism of dynamic covalent bond network: Through heating / cooling cycles, the polymer network can be reversibly dissociated and reconstructed, breaking through the processing limitations of traditional thermosetting resins due to permanent cross-linking, and enabling the material to intelligently switch between gel-sol-gel phases. (2) Temperature-driven infiltration: At high temperature, the dynamic bonds break, and the liquid sol achieves defect-free infiltration of CF fabrics and controllable solvent removal; at low temperature, the dynamic bonds reorganize, locking the fiber / resin interface morphology. (3) Synergistic curing process: Through the synergistic effect of pressure and temperature, the interface contact is optimized, and finally, high temperature curing forms a permanent covalent network, which takes into account both high interface strength and heat resistance.

[0024] This invention proposes a new strategy for preparing thermosetting polyimide composite materials based on dynamic reversible covalent bond regulation. The dissociation and reconstruction mechanism is shown in the figure. Figure 1 As shown. By introducing a cross-linking agent into the system to form dynamic chemical bonds at room temperature, the controllable dissociation-reconstruction characteristics of the amide bond are utilized: when the temperature reaches a critical value (120°C), the dynamic cross-linking network dissociates, and the system transforms from a gel state to a liquid sol, effectively improving the resin's wettability to the fiber fabric; when the solvent is completely removed, a stable prepreg body is formed. This prepreg body has a long storage life. When preparing thermosetting polyimide composite materials, the prepreg body is subjected to a gradient hot pressing process to achieve a dual effect: on the one hand, it strengthens the resin-fiber interface bonding, and on the other hand, it promotes the dehydration cyclization reaction of the dynamic amide bond, converting it into a thermodynamically stable imide bond network; finally, it is post-cured at a high temperature of 250-300°C to form a network structure. Compared with traditional processes, the thermosetting polyimide composite materials prepared by this method have the advantages of low cost and good toughness.

[0025] Comparative Example 1: PI / CF Preparation

[0026] (1) Preparation of polyamic acid (PAA) solution: 2.9234 g of 1,3-bis(3-aminophenoxy)benzene (BAB, 10 mmol) was accurately weighed and placed in a 100 mL three-necked flask equipped with a magnetic stirrer, a nitrogen inlet and outlet, and an ice bath. The flask was sealed with a rubber stopper. The system was vacuumed and replaced with nitrogen three times to remove moisture and oxygen. 10 mL of N,N-dimethylacetamide (DMAc) was injected into the system via a syringe. Under continuous flow of dry nitrogen, the system was stirred at room temperature for 30 min to fully dissolve the BAB.

[0027] (2) Accurately weigh 5.2049 g of BPADA and dissolve it in 35 mL of DMAc solvent. Ultrasonicate for 30 min to obtain a clear solution. In a nitrogen atmosphere, slowly add the BPADA solution dropwise to the reaction system using a syringe in four portions (15 min intervals). The entire addition process should be completed within 1 h. After removing the cooling device, the mixture was stirred and reacted at room temperature for 24 h to obtain the PAA solution.

[0028] (3) Preparation of PAA / CF composite material: Carbon fiber plain fabric (CF) was selected as the reinforcement. The carbon fiber fabric was cut into a size of 250 mm × 250 mm and laid in a prepared aluminum foil box. PAA was evenly impregnated in the carbon fiber fabric. The fabric was placed in a vacuum oven at 120 °C and vacuumed until the solvent was completely evaporated to generate a PAA / CF composite material.

[0029] (4) Preparation of PI / CF composites: The PAA / CF composites were placed in a hot press and pre-pressed at 180°C for 10 min and 250°C for 60 min. The pressure was 5-10 MPa. After cooling, the composites were placed in a muffle furnace and kept at 250°C for 1 h and 300°C for 1 h. The PI / CF composites were obtained.

[0030] Example 1: Preparation of TCPI-O (5%) / CF

[0031] (1) Preparation of PAA solution: 2.7041 g of 1,3-bis(3-aminophenoxy)benzene (BAB, 10 mmol) was accurately weighed and placed in a 100 mL three-necked flask equipped with a magnetic stirrer, a nitrogen inlet and outlet, and an ice bath. The flask was sealed with a rubber stopper. The system was vacuumed and replaced with nitrogen three times to remove moisture and oxygen. 10 mL of N,N-dimethylacetamide (DMAc) was injected into the system via syringe. Under continuous flow of dry nitrogen, the solution was stirred at room temperature for 30 min to fully dissolve the BAB.

[0032] (2) Accurately weigh 5.2049 g of BPADA and dissolve it in 35 mL of DMAc solvent. Ultrasonicate for 30 min to obtain a clear solution. In a nitrogen atmosphere, slowly add the BPADA solution dropwise to the reaction system using a syringe in four portions (15 min intervals). The entire addition process should be completed within 1 h. After removing the cooling device, the mixture was stirred and reacted at room temperature for 24 h to obtain a PAA solution.

[0033] (3) Preparation of TCPAA gel: Weigh 0.1997 g of 1,3,5-tris(4-aminophenoxy)benzene (TAPO) and dissolve it in 10 mL of anhydrous DMAc. Inject it with a syringe and continue stirring for 10 min. At this time, the PAA solution turns into a gel state.

[0034] (4) Preparation of TCPAA / CF composite material: Carbon fiber fabric (surface density 0.02g / cm 2 ) Cut into 250 mm*250 mm size and lay in the prepared aluminum foil box, put TCPAA gel on the carbon fiber fabric and place it in a 120 ℃ vacuum oven. At this time, the gel gradually changes into sol and impregnates the CF. Then vacuum is applied until the solvent is completely evaporated to form a TCPAA / CF composite material.

[0035] (5) Preparation of TCPI-O / CF composite material: The TCPAA / CF composite material was placed in a hot press, and the pre-pressing conditions were: 180 ℃, 10 min; 250 ℃, 60 min. The pressure condition was: 5-10 MPa. After cooling, the composite material was placed in a muffle furnace and kept at 250 ℃ for 1 h; and 300 ℃ for 1 h. The TCPI-O / CF composite material was obtained. Figure 2 As shown, it can be seen that the prepared TCPI-O / CF resin is evenly dispersed. Figure 3 The DMA data of TCPI-O / CF shows that its Tg is 220°C. Figure 4 Figure 2 is the TGA data of TCPI-O / CF. It can be seen that the prepared TCPI-O / CF has excellent thermal stability. Figure 5 TCPI-O / CF shape memory cycle diagram, Table 1 is the shape memory cycle data, it can be seen that the shape recovery rate of the third cycle can still reach 96.56%.

[0036] Example 2: Preparation of TCPI-B (5%) / CF

[0037] (1) Preparation of PAA solution: 2.7041 g of 1,3-bis(3-aminophenoxy)benzene (BAB, 10 mmol) was accurately weighed and placed in a 100 mL three-necked flask equipped with a magnetic stirrer, a nitrogen inlet and outlet, and an ice bath. The flask was sealed with a rubber stopper. The system was vacuumed and replaced with nitrogen three times to remove moisture and oxygen. 10 mL of N,N-dimethylacetamide (DMAc) was injected into the system via a syringe. Under continuous flow of dry nitrogen, the solution was stirred at room temperature for 30 min to fully dissolve the BAB.

[0038] (2) Accurately weigh 5.2049 g of BPADA and dissolve it in 35 mL of DMAc solvent. Ultrasonicate for 30 min to obtain a clear solution. In a nitrogen atmosphere, slowly add the BPADA solution dropwise to the reaction system using a syringe in four portions (15 min intervals). The entire addition process should be completed within 1 h. After removing the cooling device, the mixture was stirred and reacted at room temperature for 24 h to obtain the PAA solution.

[0039] (3) Preparation of TCPAA gel: Weigh 0.1757 g of 1,3,5-tris(4-aminophenyl)benzene (TAB) and dissolve it in 10 mL of anhydrous DMAc. Inject it with a syringe and continue stirring for 10 min. At this time, the PAA solution turns into a gel state.

[0040] (4) Preparation of TCPAA / CF composite material: Cut the carbon fiber fabric into a size of 250 mm*250 mm and lay it in a prepared aluminum foil box. Place the TCPAA gel on the carbon fiber fabric and place it in a vacuum oven at 120°C. At this time, the gel gradually changes into a sol and impregnates the CF. Then, vacuum is applied until the solvent is completely evaporated to form a TCPAA / CF composite material.

[0041] (5) Preparation of TCPI-B / CF composite material: The TCPAA / CF composite material was placed in a hot press, and the pre-pressing conditions were: 180℃, 10min; 250℃, 60min, and the pressure conditions were: 5-10MPa. After cooling, the composite material was placed in a muffle furnace and kept at 250℃ for 1h and 300℃ for 1h to obtain a TCPI-B / CF composite material, as shown in FIG. Figure 6 shown.

[0042] Example 3: Preparation of TCPI-N (5%) / CF

[0043] (1) Preparation of PAA solution: 2.7041 g of 1,3-bis(3-aminophenoxy)benzene (BAB, 10 mmol) was accurately weighed and placed in a 100 mL three-necked flask equipped with a magnetic stirrer, a nitrogen inlet and outlet, and an ice bath. The flask was sealed with a rubber stopper. The system was vacuumed and replaced with nitrogen three times to remove moisture and oxygen. 10 mL of N,N-dimethylacetamide (DMAc) was injected into the system via a syringe. Under continuous flow of dry nitrogen, the solution was stirred at room temperature for 30 min to fully dissolve the BAB.

[0044] (2) Accurately weigh 5.2049 g of BPADA and dissolve it in 35 mL of DMAc solvent. Ultrasonicate for 30 min to obtain a clear solution. In a nitrogen atmosphere, slowly add the BPADA solution dropwise to the reaction system using a syringe in four portions (15 min intervals). The entire addition process should be completed within 1 h. After removing the cooling device, the mixture was stirred and reacted at room temperature for 24 h to obtain the PAA solution.

[0045] (3) Preparation of TCPAA gel: Weigh 0.1452 g of tris(4-aminophenyl)amine (TAP) and dissolve it in 10 mL of anhydrous DMAc. Inject it with a syringe and continue stirring for 10 min. At this time, the PAA solution turns into a gel state.

[0046] (4) Preparation of TCPAA / CF composite material: The carbon fiber fabric was cut into a size of 250 mm × 250 mm and laid in a prepared aluminum foil box. TCPAA gel was placed on the carbon fiber fabric and placed in a vacuum oven at 120 °C. At this time, the gel gradually changed into a sol and impregnated the CF. Then, vacuum was applied until the solvent was completely evaporated to form a TCPAA / CF composite material.

[0047] (5) Preparation of TCPI-N / CF composite material: The TCPAA / CF composite material was placed in a hot press, and the pre-pressing conditions were: 180℃, 10min; 250℃, 60min. The pressure condition was: 5-10MPa. After cooling, the composite material was placed in a muffle furnace and kept at 250℃ for 1h; and 300℃ for 1h. The TCPI-N / CF composite material was obtained, as shown in FIG. Figure 7 shown.

[0048] Table 1 Shape memory cycle data

[0049]

Claims

1. A method for preparing a thermosetting polyimide composite material based on dynamic network reconstruction, characterized in that: The method comprises the following steps: Step 1: Prepare polyamic acid (PAA) solution: Disperse the diamine monomer in an aprotic polar solvent in an ice-water bath, then slowly add the dianhydride monomer and stir for 18-24 hours to obtain a polyamic acid solution. Step 2: Preparation of thermosetting PAA gel: Add triamine crosslinker to the PAA solution, ensuring that the total molar amount of amino and anhydride functional groups is equal during the addition process. After 5-30 minutes of adding the crosslinker, the solution turns into a gel state; Step 3: Preparation of TCPAA / CF composite material: Cut the carbon fiber fabric into sizes of 15 mm × 15 mm to 30 mm × 30 mm and lay it in a prepared container. Place TCPAA gel on the carbon fiber fabric and place it in a vacuum oven at 120°C. At this time, the gel gradually changes into a sol and impregnates the CF. Then, vacuum is applied until the solvent is completely evaporated to form a TCPAA / CF composite material. Step 4: Preparation of TCPI / CF composite material: Place the TCPAA / CF composite material in a hot press, and the pre-pressing conditions are 180℃ for 10 minutes and 250℃ for 60 minutes. The pressure during the pre-pressing process is 5-10MPa; then after cooling, place the composite material in a muffle furnace, keep it at 250℃ for 1 hour and 300℃ for 1 hour to obtain a TCPI / CF composite material with a glue content of 30%~70%.

2. The method for preparing a thermosetting polyimide composite material based on dynamic network reconstruction according to claim 1, characterized in that: In step 1, the aprotic polar solvent is one of N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone or dimethyl sulfoxide.

3. The method for preparing a thermosetting polyimide composite material based on dynamic network reconstruction according to claim 1, characterized in that: In step 1, the diamine monomer is one of 4,4'-diaminodiphenyl ether, 1,3-bis(3-aminophenoxy)benzene or 5-amino-2-(4-aminophenyl)benzimidazole; the dianhydride monomer is one of 4,4'-(4,4'-isopropyldiphenoxy)di(phthalic anhydride), pyromellitic dianhydride or 4,4'-biphenyl ether dianhydride.

4. The method for preparing a thermosetting polyimide composite material based on dynamic network reconstruction according to claim 1, characterized in that: In step 1, the molar ratio of the dianhydride monomer to the diamine monomer is 1:0.7-0.9625, and the mass concentration of the polyamic acid solution is 10%-20%.

5. The method for preparing a thermosetting polyimide composite material based on dynamic network reconstruction according to claim 1, characterized in that: In step 2, the triamine crosslinking agent is one or more of tris(4-aminophenyl)amine, 1,3,5-tris(4-aminophenoxy)benzene, 1,3,5-tris(4-aminophenyl) or tris(4-aminophenyl)amine (TAP).

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