High-temperature-resistant and high-strength adhesive suitable for adhesion of large-size curved honeycomb sandwich structure and preparation method of high-temperature-resistant and high-strength adhesive

Abstract

The invention relates to a high-performance polyimide adhesive and a preparation method thereof, in particular to a high-temperature-resistant high-strength adhesive suitable for adhesion of a large-size curved honeycomb sandwich structure and a preparation method of the high-temperature-resistant high-strength adhesive. The problems that an existing large-size curved surface honeycomb sandwich structure is narrow in machining window, contradictory in flowability and heat resistance and insufficient in high-temperature aging resistance in the cementing process are solved. The high-temperature-resistant high-strength adhesive is prepared from 4-phenylacetylene phthalic anhydride terminated polyimide precursor resin, m-aminophenylacetylene terminated polyimide precursor resin, chopped carbon fibers and a solvent C, the preparation method comprises the following steps: 1, preparing 4-phenylacetylene phthalic anhydride terminated polyimide precursor resin; 2, preparing m-aminophenylacetylene terminated polyimide precursor resin; (3) weighing; and 4, preparing the adhesive. The high-temperature-resistant and high-strength adhesive suitable for bonding of the large-size curved surface honeycomb sandwich structure and the preparation method of the adhesive are provided.

Description

Technical Field

[0001] The invention relates to a high-performance polyimide adhesive and a preparation method thereof. Background Art

[0002] Honeycomb sandwich structures, due to their high specific strength and high specific stiffness, are often used as lightweight, high-load-bearing structural components and are widely used in aircraft, rail transit, and other fields. In recent years, as honeycomb sandwich structures have become increasingly common in applications such as aircraft and high-speed rail, the demand for honeycomb sandwich structures with large dimensions, curved surfaces, and heterogeneous structures has been growing. However, the bonding process for large curved surfaces presents challenges such as difficult flow control and insufficient high-temperature resistance. Therefore, there is an urgent need for an adhesive that combines fluidity, high-temperature bonding strength, and high-temperature aging resistance.

[0003] Polyimide (PI) has excellent heat resistance, and polyimide adhesives can significantly improve the heat resistance of adhesives. However, traditional polyimide adhesives currently struggle to meet the requirements of large-curvature honeycomb molding due to their narrow processing window and the conflict between fluidity and heat resistance. When bonding large-curvature honeycombs, the adhesive often accumulates at the edges of the curved surface due to uncontrolled fluidity, resulting in residual adhesive or localized adhesive gaps. Furthermore, this phenomenon can lead to inconsistent adhesive shrinkage during the curing process, causing stress concentration at the curved interface and reducing bond strength. If the viscosity of polyimide adhesives is too low during high-temperature curing, excessive adhesive fluidity can cause flow and overflow. If the viscosity is too high during high-temperature curing, insufficient adhesive penetration can occur, resulting in high residual adhesive rates on curved surfaces and uneven adhesive bumps, ultimately leading to unsatisfactory bonding results. Therefore, effectively controlling the viscosity of polyimide during high-temperature curing is an important regulatory measure to improve its bonding performance.

[0004] At present, thermosetting polyimide adhesives often use phenylethynyl end-capping to adjust the fluidity and thermal stability of polyimide adhesives. However, in the existing technology, adhesives designed with a single end-capping agent have significant limitations. First, the processing window of a single end-capping agent design is narrow. For example, 4-phenylethynyl phthalic anhydride end-capping can increase the high-temperature viscosity by increasing the rigidity of the molecular chain, but it leads to excessively high viscosity in the initial processing stage (80°C to 150°C), hindering the penetration of the adhesive into the honeycomb micropores, increasing the residual adhesive rate, and insufficient high-temperature curing. If a low molecular weight molecular chain or end-capping agent is used to reduce the initial viscosity, the viscosity will be too low in the mid-processing stage (150°C to 250°C), which can easily cause glue overflow or uncontrolled glue tumors. The molecular structure of a single end-capping agent cannot meet the dual requirements of "low temperature high fluidity" and "high temperature high stability", resulting in an imbalance between fluidity and heat resistance in honeycomb bonding, especially when forming loaded curved surfaces, where interface weakening problems are prone to occur.

[0005] To improve resin viscosity and heat resistance, inorganic fillers are often used. However, traditional fillers, such as glass fibers and inorganic particles, have poor compatibility with polyimide matrix resins and are prone to phase separation or sedimentation, forming a weak interface layer. Furthermore, long fibers or high filler content significantly increase viscosity, hindering adhesive penetration into the honeycomb micropores.

[0006] In summary, the core contradiction in the current bonding of large-scale curved honeycomb sandwich structures lies in: the existing large-scale curved honeycomb sandwich structures have a narrow processing window, a contradiction between fluidity and heat resistance, a weakened filler phase interface, and insufficient high-temperature aging resistance. It is urgent to develop a polyimide adhesive with both controllable fluidity and high-temperature aging resistance, and to achieve efficient and low-cost manufacturing through process innovation. Summary of the Invention

[0007] The present invention aims to solve the problems of narrow processing window, contradiction between fluidity and heat resistance, and insufficient high-temperature aging resistance in the bonding of existing large-scale curved honeycomb sandwich structures, and further provide a high-temperature resistant and high-strength adhesive suitable for bonding large-scale curved honeycomb sandwich structures and a preparation method thereof.

[0008] A high-temperature resistant and high-strength adhesive suitable for bonding large-scale curved honeycomb sandwich structures, which is prepared from 100 parts by weight of a polyimide precursor resin terminated with 4-phenylacetylene phthalic anhydride, 50 to 100 parts by weight of a polyimide precursor resin terminated with m-aminophenylacetylene, 0.1 to 5 parts by weight of chopped carbon fibers, and 100 to 200 parts by weight of a solvent C.

[0009] The 4-phenylacetylene phthalic anhydride-terminated polyimide precursor resin is prepared from 4-phenylacetylene phthalic anhydride, aromatic diamine A, aromatic dianhydride A, and solvent A; the molar ratio of the aromatic diamine A to the aromatic dianhydride A is 1:(0.95-0.97); the molar ratio of the aromatic diamine A to the 4-phenylacetylene phthalic anhydride is 1:(0.06-0.1); and the mass ratio of the aromatic diamine A to the solvent A is 1:(1-10);

[0010] The repeating unit of polyamic acid in the 4-phenylethynylphthalic anhydride terminated polyimide precursor resin is:

[0011]

[0012] The R1 is

[0013] The R2 is

[0014] The m-aminophenylacetylene-terminated polyimide precursor resin is prepared from m-aminophenylacetylene, aromatic diamine B, aromatic dianhydride B, and solvent B; the molar ratio of the aromatic diamine B to the aromatic dianhydride B is 1:(1.2-1.5); the molar ratio of the aromatic diamine B to the m-aminophenylacetylene is 1:(0.4-1); and the mass ratio of the aromatic diamine B to the solvent B is 1:(1-10);

[0015] The repeating unit of the polyamic acid in the m-aminophenylacetylene terminated polyimide precursor resin is:

[0016]

[0017] The R3 is

[0018] The R4 is

[0019] A method for preparing a high-temperature resistant and high-strength adhesive suitable for bonding large-scale curved honeycomb sandwich structures is carried out according to the following steps:

[0020] 1. Preparation of 4-phenylacetylene phthalic anhydride terminated polyimide precursor resin:

[0021] ① Weigh 4-phenylacetylene phthalic anhydride, aromatic diamine A, aromatic dianhydride A and solvent A;

[0022] The molar ratio of the aromatic diamine A to the aromatic dianhydride A is 1:(0.95-0.97); the molar ratio of the aromatic diamine A to 4-phenylacetylene phthalic anhydride is 1:(0.06-0.1); the mass ratio of the aromatic diamine A to the solvent A is 1:(1-10);

[0023] ② In a nitrogen atmosphere, a temperature of 40°C to 48°C and stirring conditions, solvent A and aromatic diamine A are stirred and dissolved for 1h to 5h, then the reaction temperature is raised to 50°C to 60°C, aromatic dianhydride A is added to the reaction system, and the mixture is stirred and reacted for 3h to 5h in a nitrogen atmosphere, a temperature of 50°C to 60°C and stirring conditions, and then 4-phenylacetylene phthalic anhydride is added, and the mixture is stirred and reacted for 2h to 4h in a nitrogen atmosphere, a temperature of 50°C to 60°C and stirring conditions to obtain a 4-phenylacetylene phthalic anhydride-terminated polyimide precursor resin;

[0024] 2. Preparation of m-aminophenylacetylene terminated polyimide precursor resin:

[0025] ① Weigh m-aminophenylacetylene, aromatic diamine B, aromatic dianhydride B and solvent B;

[0026] The molar ratio of the aromatic diamine B to the aromatic dianhydride B is 1:(1.2-1.5); the molar ratio of the aromatic diamine B to m-aminophenylacetylene is 1:(0.4-1); the mass ratio of the aromatic diamine B to the solvent B is 1:(1-10);

[0027] ② In a nitrogen atmosphere, a temperature of 40°C to 48°C and stirring conditions, solvent B and aromatic diamine B are stirred and dissolved for 1h to 5h, then the reaction temperature is raised to 50°C to 60°C, aromatic dianhydride B is added to the reaction system, and the mixture is stirred and reacted for 3h to 5h in a nitrogen atmosphere, a temperature of 50°C to 60°C and stirring conditions, and then m-aminophenylacetylene is added, and the mixture is stirred and reacted for 2h to 4h in a nitrogen atmosphere, a temperature of 50°C to 60°C and stirring conditions to obtain a m-aminophenylacetylene-terminated polyimide precursor resin;

[0028] 3. Weighing:

[0029] Weigh 100 parts by weight of a polyimide precursor resin terminated with 4-phenylethynyl phthalic anhydride, 50 to 100 parts by weight of a polyimide precursor resin terminated with m-aminophenylethynylene, 0.1 to 5 parts by weight of chopped carbon fibers, and 100 to 200 parts by weight of a solvent C;

[0030] 4. Preparation of adhesive:

[0031] Under nitrogen atmosphere, reaction temperature of 50°C to 60°C and stirring conditions, the weighed 4-phenylacetylene phthalic anhydride-terminated polyimide precursor resin, m-aminophenylacetylene-terminated polyimide precursor resin, chopped carbon fiber and solvent C are stirred for 2h to 3h, and then the reaction temperature is reduced from 50°C to 60°C to 25°C to 30°C to obtain a high-temperature resistant and high-strength adhesive suitable for bonding large-size curved honeycomb sandwich structures.

[0032] The beneficial effects of the present invention are:

[0033] Through molecular design and process innovation, this invention has achieved breakthrough progress in adhesive high temperature resistance and processing viscosity control. Its beneficial effects and mechanism of action are detailed as follows:

[0034] When using end-capping agents to increase the molecular heat resistance and adjust the resin viscosity, the molecular structure of a single end-capping agent is difficult to meet the dual requirements of heat resistance and processing fluidity, resulting in limited use in the field of large curved honeycomb adhesives. The present invention uses multiple means of molecular structure adjustment, long and short molecular chain matching, and inorganic doping to adjust: first, the molecular structure is adjusted, using two end-capping agents to end-cap polyimide precursor segments of different molecular weights, one is a long-chain polyimide precursor with a side phenyl structure capped with 4-phenylacetylene phthalic anhydride, which provides the adhesive with a certain viscosity at high temperature to prevent the adhesive from flowing and overflowing due to too low viscosity; the other is a short-chain polyimide precursor with an isomeric structure capped with meta-aminophenylacetylene. The short-chain molecules with an isomeric structure play a role in lubrication and reducing the viscosity of the resin, providing low viscosity during processing, avoiding the difficulty of glue liquid penetrating into the honeycomb caused by excessive viscosity, a high residual glue rate for curved surface bonding, and uneven glue nodules. Through the synergistic effect of the two end-capping agents, the viscosity control of the adhesive in the processing stage is achieved.

[0035] By regulating the molar ratio of diamine and dianhydride, the repeating units of the polyimide precursor molecular chain are regulated, ultimately achieving the goal of regulating the chain length, precursor molecular weight and viscosity, and the density of the cross-linkable group phenylacetylene. The polyimide precursor terminated with 4-phenylacetylene phthalic anhydride is designed to have a long-chain structure, with the repeating units controlled in the range of 20 to 30 and the molecular weight in the range of approximately 10,000 to 15,000. Due to the π-π stacking of the side phenyl groups and the entanglement of the long chains to form a physical cross-linking network, the final adhesive maintains a high viscosity (400 Pa·s to 600 Pa·s) in the middle of the processing (150 to 250°C), effectively suppressing the flow and overflow behavior of the adhesive at high temperatures. In addition, the longer molecular chain effectively improves the toughness of the adhesive after curing. The m-aminophenylacetylene-terminated polyimide precursor is designed as a short-chain structure with a repeating unit range of 2 to 5 and a molecular weight of approximately 1000 to 3000. Isomerization breaks the symmetry of the molecular structure, and the low molecular weight design acts as a molecular lubricant, significantly reducing the viscosity of the final adhesive solution (1000 Pa·s to 3000 Pa·s) during the initial processing (80°C to 150°C). The low processing viscosity ensures that the adhesive solution infiltrates the honeycomb surface and promotes its penetration into the internal voids of the honeycomb, improving the adhesive's processability and heat resistance.

[0036] For long chain segments terminated with 4-phenylacetylene phthalic anhydride, rigid diamines (p-phenylenediamine, m-phenylenediamine, or 4,4-diaminobiphenyl) are preferred to increase the adhesive's high-temperature heat resistance. Highly symmetrical dianhydrides (3,3'4,4'-biphenyltetracarboxylic dianhydride or pyromellitic dianhydride) are preferred as dianhydrides to improve molecular chain regularity and enhance high-temperature viscosity control. For short chain segments terminated with m-aminophenylacetylene, flexible diamines (4,4'-diaminodiphenyl ether or 4,4'-diaminodiphenyl sulfone) and flexible dianhydrides (bisphenol A diether dianhydride or 4,4'-oxydiphthalic anhydride) are preferred to enhance chain mobility through ether bonds or sulfonyl groups. Based on the ratio of the two end-capped polyimide precursor adhesives and their molecular weight, the double end-capping agent molar ratio is 1:(0.5-0.8). This ensures that the long-chain segments provide moderate viscosity during the mid-processing period (150-200°C), while the short-chain segments maintain fluidity through isomerization. This results in a stable overall viscosity of the final adhesive (400-600 Pa·s). The adhesive, under capillary action, climbs along the honeycomb walls, forming uniform nodules that increase the bonding area and enhance the bonding effect, meeting the gel-setting requirements for honeycomb curved surface bonding. The mass fraction ratio of long to short chains is approximately 1:(0.5-1), which avoids both the loss of heat resistance caused by an excess of short chains and the insufficient penetration caused by an excess of long chains.

[0037] Regarding the inorganic doping interface, after the chopped carbon fibers are treated with acetone to remove the surface sizing agent, a certain amount of carboxyl and hydroxyl groups remain on the fiber surface. These groups form hydrogen bonds and π-π stacking interactions with the polyimide precursor, making them highly compatible with the adhesive and avoiding the phase separation issues associated with traditional inorganic fiber fillers. During the curing process, the carbon fibers form a three-dimensional thermal conductivity path, effectively reducing the curing thermal stress of the adhesive and improving the overall fatigue resistance of the honeycomb structure.

[0038] In terms of heat and aging resistance, the end-phenyl structure of 4-phenylacetylene phthalic anhydride and chopped carbon fibers provide high heat resistance. The isomeric structure of m-aminophenylacetylene inhibits hydrolysis at the interface due to hygrothermal aging. The carbon fiber network further enhances the thermal conductivity of the adhesive, reduces curing thermal stress, and improves the overall heat and aging resistance of the honeycomb structure. Through the collaborative innovation of dual-end-capping agent molecular design and chopped fibers, the challenges of traditional polyimide adhesives in large-curvature honeycomb bonding, such as uncontrolled flow and weakened interfaces, are systematically addressed. This significantly improves high-temperature performance and processability, providing a solution for the reliable manufacture of complex curved honeycomb sandwich structures in fields such as aerospace and rail transportation. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 This is a photo of the honeycomb of the aluminum honeycomb sandwich structure bonded with the high-temperature resistant and high-strength adhesive prepared in Example 1 after plane stretching at 200°C;

[0040] Figure 2This is a photo of the honeycomb of the aluminum honeycomb sandwich structure bonded with the high-temperature resistant and high-strength adhesive prepared in Example 2 after roller peeling at room temperature;

[0041] Figure 3 This is the infrared spectrum of the high-temperature resistant and high-strength adhesive suitable for bonding large-scale curved honeycomb sandwich structures prepared in Example 1 after curing:

[0042] Figure 4 The temperature-viscosity curve of the high-temperature resistant and high-strength adhesive suitable for bonding large-scale curved honeycomb sandwich structures prepared in Example 1;

[0043] Figure 5 A large-scale curved honeycomb sample bonded with a high-temperature resistant, high-strength adhesive suitable for bonding large-scale curved honeycomb sandwich structures prepared in Example 1. (a) is a side view of the large-scale honeycomb bonded composite plate sample, and (b) is a top view of the large-scale honeycomb bonded composite plate sample.

[0044] Figure 6 Comparison diagram of bonding large-scale curved honeycomb samples with high-temperature resistant and high-strength adhesives suitable for bonding large-scale curved honeycomb sandwich structures prepared in Example 1 and Comparative Experiment 4, (a) is Example 1, and (b) is Comparative Experiment 4;

[0045] Figure 7 This is a flat tensile test curve of a large-sized curved honeycomb sample cut into strips by bonding it with a high-temperature resistant and high-strength adhesive suitable for bonding large-sized curved honeycomb sandwich structures prepared in Example 1. DETAILED DESCRIPTION

[0046] Specific embodiment 1: This embodiment is a high-temperature resistant and high-strength adhesive suitable for bonding large-scale curved honeycomb sandwich structures, which is prepared by weight from 100 parts of a polyimide precursor resin terminated with 4-phenylacetylene phthalic anhydride, 50 to 100 parts of a polyimide precursor resin terminated with m-aminophenylacetylene, 0.1 to 5 parts of chopped carbon fibers, and 100 to 200 parts of a solvent C;

[0047] The 4-phenylacetylene phthalic anhydride-terminated polyimide precursor resin is prepared from 4-phenylacetylene phthalic anhydride, aromatic diamine A, aromatic dianhydride A, and solvent A; the molar ratio of the aromatic diamine A to the aromatic dianhydride A is 1:(0.95-0.97); the molar ratio of the aromatic diamine A to the 4-phenylacetylene phthalic anhydride is 1:(0.06-0.1); and the mass ratio of the aromatic diamine A to the solvent A is 1:(1-10);

[0048] The repeating unit of polyamic acid in the 4-phenylethynylphthalic anhydride terminated polyimide precursor resin is:

[0049]

[0050] The R1 is

[0051] The R2 is

[0052] The m-aminophenylacetylene-terminated polyimide precursor resin is prepared from m-aminophenylacetylene, aromatic diamine B, aromatic dianhydride B, and solvent B; the molar ratio of the aromatic diamine B to the aromatic dianhydride B is 1:(1.2-1.5); the molar ratio of the aromatic diamine B to the m-aminophenylacetylene is 1:(0.4-1); and the mass ratio of the aromatic diamine B to the solvent B is 1:(1-10);

[0053] The repeating unit of the polyamic acid in the m-aminophenylacetylene terminated polyimide precursor resin is:

[0054]

[0055] The R3 is

[0056] The R4 is

[0057] In this specific embodiment, a capping agent, aromatic diamine, and aromatic dianhydride are co-polymerized to form a capped polyimide precursor resin.

[0058] This specific embodiment achieves a balance between flow and bonding performance in honeycomb large curvature molding through the coordinated design of double end-capping agents and the doping of chopped fibers.

[0059] The beneficial effects of this specific embodiment are:

[0060] This specific embodiment has achieved breakthrough progress in adhesive high temperature resistance and processing viscosity control through molecular design and process innovation. Its beneficial effects and mechanism of action are detailed as follows:

[0061] When using end-capping agents to increase the molecular heat resistance and adjust the resin viscosity, the molecular structure of a single end-capping agent is difficult to meet the dual requirements of heat resistance and processing fluidity, resulting in limited use in the field of large curved honeycomb adhesives. This specific embodiment is adjusted through multiple means of molecular structure adjustment, long and short molecular chain matching, and inorganic doping: first, the molecular structure is adjusted, using two end-capping agents to end-cap polyimide precursor segments of different molecular weights, one is a long-chain polyimide precursor with a side phenyl structure capped with 4-phenylacetylene phthalic anhydride, which provides the adhesive with a certain viscosity at high temperature to prevent the adhesive from flowing and overflowing due to too low viscosity; the other is a short-chain polyimide precursor with an isomeric structure capped with meta-aminophenylacetylene. The short-chain molecules with an isomeric structure play a role in lubrication and reducing the viscosity of the resin, providing low viscosity during processing, avoiding the difficulty of glue liquid penetrating into the honeycomb caused by excessive viscosity, a high residual glue rate for curved surface bonding, and uneven glue nodules. Through the synergistic effect of the two end-capping agents, the viscosity of the adhesive during the processing stage is controlled.

[0062] By regulating the molar ratio of diamine and dianhydride, the repeating units of the polyimide precursor molecular chain are regulated, ultimately achieving the goal of regulating the chain length, precursor molecular weight and viscosity, and the density of the cross-linkable group phenylacetylene. The polyimide precursor terminated with 4-phenylacetylene phthalic anhydride is designed to have a long-chain structure, with the repeating units controlled in the range of 20 to 30 and the molecular weight in the range of approximately 10,000 to 15,000. Due to the π-π stacking of the side phenyl groups and the entanglement of the long chains to form a physical cross-linking network, the final adhesive maintains a high viscosity (400 Pa·s to 600 Pa·s) in the middle of the processing (150 to 250°C), effectively suppressing the flow and overflow behavior of the adhesive at high temperatures. In addition, the longer molecular chain effectively improves the toughness of the adhesive after curing. The m-aminophenylacetylene-terminated polyimide precursor is designed as a short-chain structure with a repeating unit range of 2 to 5 and a molecular weight of approximately 1000 to 3000. Isomerization breaks the symmetry of the molecular structure, and the low molecular weight design acts as a molecular lubricant, significantly reducing the viscosity of the final adhesive solution (1000 Pa·s to 3000 Pa·s) during the initial processing (80°C to 150°C). The low processing viscosity ensures that the adhesive solution infiltrates the honeycomb surface and promotes its penetration into the internal voids of the honeycomb, improving the adhesive's processability and heat resistance.

[0063] For long chain segments terminated with 4-phenylacetylene phthalic anhydride, rigid diamines (p-phenylenediamine, m-phenylenediamine, or 4,4-diaminobiphenyl) are preferred to increase the adhesive's high-temperature heat resistance. Highly symmetrical dianhydrides (3,3'4,4'-biphenyltetracarboxylic dianhydride or pyromellitic dianhydride) are preferred as dianhydrides to improve molecular chain regularity and enhance high-temperature viscosity control. For short chain segments terminated with m-aminophenylacetylene, flexible diamines (4,4'-diaminodiphenyl ether or 4,4'-diaminodiphenyl sulfone) and flexible dianhydrides (bisphenol A diether dianhydride or 4,4'-oxydiphthalic anhydride) are preferred to enhance chain mobility through ether bonds or sulfonyl groups. Based on the ratio of the two end-capped polyimide precursor adhesives and their molecular weight, the double end-capping agent molar ratio is 1:(0.5-0.8). This ensures that the long-chain segments provide moderate viscosity during the mid-processing period (150-200°C), while the short-chain segments maintain fluidity through isomerization. This results in a stable overall viscosity of the final adhesive (400-600 Pa·s). The adhesive, under capillary action, climbs along the honeycomb walls, forming uniform nodules that increase the bonding area and enhance the bonding effect, meeting the gel-setting requirements for honeycomb curved surface bonding. The mass fraction ratio of long to short chains is approximately 1:(0.5-1), which avoids both the loss of heat resistance caused by an excess of short chains and the insufficient penetration caused by an excess of long chains.

[0064] Regarding the inorganic doping interface, after the chopped carbon fibers are treated with acetone to remove the surface sizing agent, a certain amount of carboxyl and hydroxyl groups remain on the fiber surface. These groups form hydrogen bonds and π-π stacking interactions with the polyimide precursor, making them highly compatible with the adhesive and avoiding the phase separation issues associated with traditional inorganic fiber fillers. During the curing process, the carbon fibers form a three-dimensional thermal conductivity path, effectively reducing the curing thermal stress of the adhesive and improving the overall fatigue resistance of the honeycomb structure.

[0065] In terms of heat and aging resistance, the end-phenyl structure of 4-phenylacetylene phthalic anhydride and chopped carbon fibers provide high heat resistance. The isomeric structure of m-aminophenylacetylene inhibits hydrolysis at the interface due to hygrothermal aging. The carbon fiber network further enhances the thermal conductivity of the adhesive, reduces curing thermal stress, and improves the overall heat and aging resistance of the honeycomb structure. Through the collaborative innovation of dual-end-capping agent molecular design and chopped fibers, the challenges of traditional polyimide adhesives in large-curvature honeycomb bonding, such as uncontrolled flow and weakened interfaces, are systematically addressed. This significantly improves high-temperature performance and processability, providing a solution for the reliable manufacture of complex curved honeycomb sandwich structures in fields such as aerospace and rail transportation.

[0066] Specific embodiment 2: This embodiment differs from specific embodiment 1 in that the length of the chopped carbon fibers is one of 3 mm, 4 mm, and 5 mm, or a combination thereof; the chopped carbon fibers are pretreated, and the pretreatment process is carried out according to the following steps: the carbon fibers are placed in an acetone solution, heated in a water bath at a temperature of 45°C to 55°C for 10 to 14 hours, then rinsed multiple times with deionized water, and finally dried at a temperature of 55°C to 65°C for 6 to 10 hours. Other aspects are the same as specific embodiment 1.

[0067] Specific embodiment 3: This embodiment differs from specific embodiment 1 or 2 in that the solvent A, solvent B, and solvent C are all N,N-dimethylformamide, N,N-dimethylacetamide, or N-methylpyrrolidone. Other aspects are the same as specific embodiment 1 or 2.

[0068] Specific embodiment 4: This embodiment differs from specific embodiments 1 to 3 in that the aromatic diamine A is p-phenylenediamine, m-phenylenediamine or 4,4-diaminobiphenyl. Other aspects are the same as specific embodiments 1 to 3.

[0069] Specific embodiment 5: This embodiment differs from specific embodiments 1 to 4 in that the aromatic dianhydride A is 3,3'4,4'-biphenyltetracarboxylic dianhydride or pyromellitic dianhydride. Other aspects are the same as specific embodiments 1 to 4.

[0070] Specific embodiment 6: This embodiment differs from specific embodiments 1 to 5 in that the aromatic diamine B is 4,4'-diaminodiphenyl ether or 4,4'-diaminodiphenyl sulfone. Other aspects are the same as specific embodiments 1 to 5.

[0071] Specific embodiment 7: This embodiment differs from specific embodiments 1 to 6 in that the aromatic dianhydride B is bisphenol A diether dianhydride or 4,4'-oxydiphthalic anhydride. Other aspects are the same as specific embodiments 1 to 6.

[0072] Specific embodiment eight: This embodiment provides a method for preparing a high-temperature resistant and high-strength adhesive suitable for bonding large-scale curved honeycomb sandwich structures, which is carried out in the following steps:

[0073] 1. Preparation of 4-phenylacetylene phthalic anhydride terminated polyimide precursor resin:

[0074] ① Weigh 4-phenylacetylene phthalic anhydride, aromatic diamine A, aromatic dianhydride A and solvent A;

[0075] The molar ratio of the aromatic diamine A to the aromatic dianhydride A is 1:(0.95-0.97); the molar ratio of the aromatic diamine A to 4-phenylacetylene phthalic anhydride is 1:(0.06-0.1); the mass ratio of the aromatic diamine A to the solvent A is 1:(1-10);

[0076] ② In a nitrogen atmosphere, a temperature of 40°C to 48°C and stirring conditions, solvent A and aromatic diamine A are stirred and dissolved for 1h to 5h, then the reaction temperature is raised to 50°C to 60°C, aromatic dianhydride A is added to the reaction system, and the mixture is stirred and reacted for 3h to 5h in a nitrogen atmosphere, a temperature of 50°C to 60°C and stirring conditions, and then 4-phenylacetylene phthalic anhydride is added, and the mixture is stirred and reacted for 2h to 4h in a nitrogen atmosphere, a temperature of 50°C to 60°C and stirring conditions to obtain a 4-phenylacetylene phthalic anhydride-terminated polyimide precursor resin;

[0077] 2. Preparation of m-aminophenylacetylene terminated polyimide precursor resin:

[0078] ① Weigh m-aminophenylacetylene, aromatic diamine B, aromatic dianhydride B and solvent B;

[0079] The molar ratio of the aromatic diamine B to the aromatic dianhydride B is 1:(1.2-1.5); the molar ratio of the aromatic diamine B to m-aminophenylacetylene is 1:(0.4-1); the mass ratio of the aromatic diamine B to the solvent B is 1:(1-10);

[0080] ② In a nitrogen atmosphere, a temperature of 40°C to 48°C and stirring conditions, solvent B and aromatic diamine B are stirred and dissolved for 1h to 5h, then the reaction temperature is raised to 50°C to 60°C, aromatic dianhydride B is added to the reaction system, and the mixture is stirred and reacted for 3h to 5h in a nitrogen atmosphere, a temperature of 50°C to 60°C and stirring conditions, and then m-aminophenylacetylene is added, and the mixture is stirred and reacted for 2h to 4h in a nitrogen atmosphere, a temperature of 50°C to 60°C and stirring conditions to obtain a m-aminophenylacetylene-terminated polyimide precursor resin;

[0081] 3. Weighing:

[0082] Weigh 100 parts by weight of a polyimide precursor resin terminated with 4-phenylethynyl phthalic anhydride, 50 to 100 parts by weight of a polyimide precursor resin terminated with m-aminophenylethynylene, 0.1 to 5 parts by weight of chopped carbon fibers, and 100 to 200 parts by weight of a solvent C;

[0083] 4. Preparation of adhesive:

[0084] Under nitrogen atmosphere, reaction temperature of 50°C to 60°C and stirring conditions, the weighed 4-phenylacetylene phthalic anhydride-terminated polyimide precursor resin, m-aminophenylacetylene-terminated polyimide precursor resin, chopped carbon fiber and solvent C are stirred for 2h to 3h, and then the reaction temperature is reduced from 50°C to 60°C to 25°C to 30°C to obtain a high-temperature resistant and high-strength adhesive suitable for bonding large-size curved honeycomb sandwich structures.

[0085] Specific embodiment 9: This embodiment differs from specific embodiment 8 in that the stirring speed in step 1 ②, step 2 ② and step 4 is 100 rpm to 200 rpm. Other aspects are the same as specific embodiment 8.

[0086] Specific embodiment 10: This embodiment differs from specific embodiment 8 or 9 in that: in step 1 ②, aromatic dianhydride A is added to the reaction system in three equal portions; in step 2 ②, aromatic dianhydride B is added to the reaction system in three equal portions. Other steps are the same as specific embodiment 8 or 9.

[0087] The following examples are used to verify the beneficial effects of the present invention:

[0088] Example 1:

[0089] A high-temperature-resistant, high-strength adhesive suitable for bonding large-scale curved honeycomb sandwich structures, comprising, by weight, 100 parts of a polyimide precursor resin terminated with 4-phenylacetylene phthalic anhydride, 50 parts of a polyimide precursor resin terminated with m-aminophenylacetylene, 2 parts of chopped carbon fibers, and 100 parts of a solvent C.

[0090] The 4-phenylacetylene phthalic anhydride-terminated polyimide precursor resin is prepared from 4-phenylacetylene phthalic anhydride, aromatic diamine A, aromatic dianhydride A, and solvent A; the molar ratio of the aromatic diamine A to the aromatic dianhydride A is 1:0.95; the molar ratio of the aromatic diamine A to the 4-phenylacetylene phthalic anhydride is 1:0.1; and the mass ratio of the aromatic diamine A to the solvent A is 1:10;

[0091] The repeating unit of polyamic acid in the 4-phenylethynylphthalic anhydride terminated polyimide precursor resin is:

[0092]

[0093] The R1 is

[0094] The R2 is

[0095] The m-aminophenylacetylene-terminated polyimide precursor resin is prepared from m-aminophenylacetylene, aromatic diamine B, aromatic dianhydride B, and solvent B; the molar ratio of the aromatic diamine B to the aromatic dianhydride B is 1:1.2; the molar ratio of the aromatic diamine B to m-aminophenylacetylene is 1:0.4; and the mass ratio of the aromatic diamine B to the solvent B is 1:10;

[0096] The repeating unit of the polyamic acid in the m-aminophenylacetylene terminated polyimide precursor resin is:

[0097]

[0098] The R3 is

[0099] The R4 is

[0100] The length of the chopped carbon fiber is 3 mm (Jiangsu Hengshen HF40); the chopped carbon fiber is pretreated chopped carbon fiber, and the pretreatment process is carried out according to the following steps: the carbon fiber is placed in an acetone solution, heated in a water bath at a temperature of 50°C for 12 hours, then washed with deionized water 3 times, and finally dried at a temperature of 60°C for 8 hours.

[0101] The solvent A, solvent B and solvent C are all N,N-dimethylformamide.

[0102] The aromatic diamine A is p-phenylenediamine.

[0103] The aromatic dianhydride A is 3,3'4,4'-biphenyltetracarboxylic dianhydride.

[0104] The aromatic diamine B is 4,4'-diaminodiphenyl ether.

[0105] The aromatic dianhydride B is bisphenol A type diether dianhydride.

[0106] A method for preparing a high-temperature resistant and high-strength adhesive suitable for bonding large-scale curved honeycomb sandwich structures is carried out according to the following steps:

[0107] 1. Preparation of 4-phenylacetylene phthalic anhydride terminated polyimide precursor resin:

[0108] ① Weigh 4-phenylacetylene phthalic anhydride, aromatic diamine A, aromatic dianhydride A and solvent A;

[0109] ② Under the conditions of nitrogen atmosphere, temperature of 40°C and stirring speed of 150 rpm, solvent A and aromatic diamine A were stirred and dissolved for 3 hours, then the reaction temperature was raised to 60°C, aromatic dianhydride A was added to the reaction system in three equal portions, and stirred for 3 hours under the conditions of nitrogen atmosphere, temperature of 60°C and stirring speed of 150 rpm, and then 4-phenylacetylene phthalic anhydride was added, and stirred for 4 hours under the conditions of nitrogen atmosphere, temperature of 60°C and stirring speed of 150 rpm to obtain a 4-phenylacetylene phthalic anhydride-terminated polyimide precursor resin;

[0110] 2. Preparation of m-aminophenylacetylene terminated polyimide precursor resin:

[0111] ① Weigh m-aminophenylacetylene, aromatic diamine B, aromatic dianhydride B and solvent B;

[0112] ② Under the conditions of nitrogen atmosphere, temperature of 40°C and stirring speed of 150 rpm, solvent B and aromatic diamine B were stirred and dissolved for 3 hours, then the reaction temperature was raised to 60°C, aromatic dianhydride B was added to the reaction system in three equal portions, and stirred for 3 hours under the conditions of nitrogen atmosphere, temperature of 60°C and stirring speed of 150 rpm, and then m-aminophenylacetylene was added, and stirred for 4 hours under the conditions of nitrogen atmosphere, temperature of 60°C and stirring speed of 150 rpm to obtain m-aminophenylacetylene-terminated polyimide precursor resin;

[0113] 3. Weighing:

[0114] Weigh 100 parts by weight of a polyimide precursor resin terminated with 4-phenylacetylene phthalic anhydride, 50 parts by weight of a polyimide precursor resin terminated with m-aminophenylacetylene, 2 parts by weight of chopped carbon fibers, and 100 parts by weight of a solvent C;

[0115] 4. Preparation of adhesive:

[0116] Under the conditions of nitrogen atmosphere, reaction temperature of 60°C and stirring speed of 150 rpm, the weighed 4-phenylacetylene phthalic anhydride-terminated polyimide precursor resin, m-aminophenylacetylene-terminated polyimide precursor resin, chopped carbon fiber and solvent C were stirred for 2 hours, and then the reaction temperature was reduced from 60°C to 25°C to obtain a high-temperature resistant and high-strength adhesive suitable for bonding large-scale curved honeycomb sandwich structures.

[0117] Example 2: This example differs from Example 1 in that the aromatic diamine A is 4,4-diaminobiphenyl, the molar ratio of the aromatic diamine A to the aromatic dianhydride A is 1:0.96, the molar ratio of the aromatic diamine A to 4-phenylacetylene phthalic anhydride is 1:0.08, the m-aminophenylacetylene-terminated polyimide precursor resin is 80 parts, the molar ratio of the aromatic diamine B to the aromatic dianhydride B is 1:1.3, and the molar ratio of the aromatic diamine B to m-aminophenylacetylene is 1:0.6, the solvent C is 150 parts, and the solvents A, B, and C are all N-methylpyrrolidone. Other modifications are the same as in Example 1.

[0118] Example 3: This example differs from Example 1 in that the molar ratio of aromatic diamine A to aromatic dianhydride A is 1:0.96; the molar ratio of aromatic diamine A to 4-phenylacetylene phthalic anhydride is 1:0.06; the m-aminophenylacetylene-terminated polyimide precursor resin is 80 parts; the aromatic diamine B is 4,4'-diaminodiphenyl sulfone; the molar ratio of aromatic diamine B to aromatic dianhydride B is 1:1.3; the molar ratio of aromatic diamine B to m-aminophenylacetylene is 1:0.6; the solvent C is 150 parts; and solvent A, solvent B, and solvent C are all N-methylpyrrolidone. All other aspects are the same as in Example 1.

[0119] Example 4: This example differs from Example 1 in that: the m-aminophenylacetylene-terminated polyimide precursor resin is present in 90 parts; the chopped carbon fibers are present in 3 parts; the chopped carbon fibers are composed, by mass, of 1 part of 3 mm long carbon fibers and 2 parts of 5 mm long carbon fibers; and the solvent C is present in 200 parts. Other conditions are the same as in Example 1.

[0120] Example 5: This example differs from Example 1 in that the m-aminophenylacetylene-terminated polyimide precursor resin is present in an amount of 60 parts, the amount of solvent C is present in an amount of 120 parts, and solvent A, solvent B, and solvent C are all N-methylpyrrolidone. Other modifications are the same as in Example 1.

[0121] Example 6: This example differs from Example 1 in that: the m-aminophenylacetylene-terminated polyimide precursor resin is present in an amount of 100 parts; the aromatic diamine B is 4,4'-diaminodiphenyl sulfone; the molar ratio of the aromatic diamine B to the aromatic dianhydride B is 1:1.5; the molar ratio of the aromatic diamine B to the m-aminophenylacetylene is 1:0.6; the solvent C is present in an amount of 160 parts; and solvent A, solvent B, and solvent C are all N-methylpyrrolidone. All other aspects are the same as in Example 1.

[0122] Example 7: This example differs from Example 1 in that the aromatic diamine A is 4,4-diaminobiphenyl, the aromatic dianhydride A is pyromellitic dianhydride, and the amount of chopped carbon fibers is 1.5 parts. Other differences are the same as in Example 1.

[0123] Comparative Experiment 1: This comparative experiment differs from Example 1 in that the m-aminophenylacetylene-terminated polyimide precursor resin and chopped carbon fibers are omitted; instead, the high-temperature-resistant, high-strength adhesive is prepared from 100 parts by weight of a 4-phenylacetylene phthalic anhydride-terminated polyimide precursor resin and 100 parts of solvent C. Other procedures are the same as in Example 1.

[0124] Comparative Experiment 2: This comparative experiment differs from Example 1 in that the 4-phenylacetylene phthalic anhydride-terminated polyimide precursor resin and chopped carbon fibers are omitted; instead, the high-temperature-resistant, high-strength adhesive is prepared from 80 parts by weight of the m-aminophenylacetylene-terminated polyimide precursor resin and 100 parts of solvent C. Other procedures are the same as in Example 1.

[0125] Comparative Experiment 3: This comparative experiment differs from Example 1 in that the chopped carbon fibers were omitted; the high-temperature-resistant, high-strength adhesive was prepared from 100 parts by weight of a polyimide precursor resin capped with 4-phenylacetylene phthalic anhydride, 50 parts by weight of a polyimide precursor resin capped with m-aminophenylacetylene, and 100 parts by weight of solvent C. Other procedures were the same as in Example 1.

[0126] Comparative Experiment 4: This comparative experiment differs from Example 1 in that the high-temperature-resistant, high-strength adhesive is prepared from, by weight, 100 parts of a 4-phenylacetylene phthalic anhydride-terminated polyimide precursor resin, 150 parts of a m-aminophenylacetylene-terminated polyimide precursor resin, 2 parts of chopped carbon fibers, and 100 parts of solvent C. Other conditions are the same as in Example 1.

[0127] (1) The adhesives prepared in Examples 1 to 7 and Comparative Experiments 1 to 4 were placed between honeycombs (aramid paper honeycombs, aluminum honeycombs, and polyimide honeycombs) and stainless steel panels (316L stainless steel from Wuxi Datan Stainless Steel Co., Ltd.) for bonding. The bonding size was 10 cm × 10 cm. The aramid paper honeycombs were from Taihe New Materials Co., Ltd. Model, aluminum honeycomb is Hexcel III model, polyimide honeycomb is from Jiangsu Xiannuo New Materials Co., Ltd. Model; the curing process is as follows: first, heating at a temperature of 80°C and a pressure of 0.2 MPa for 1 hour, then heating at a temperature of 180°C and a pressure of 0.2 MPa for 1 hour, heating at a temperature of 300°C and a pressure of 0.2 MPa for 2 hours, and finally heating at a temperature of 370°C and a pressure of 0.1 MPa for 1 hour to obtain a honeycomb sandwich structure, and various performance tests are performed on it. The test conditions refer to the following standards (methods):

[0128] 1. Determination of glue climbing height: Use a vernier caliper to measure the distance between the highest point of the glue climbing and the edge of the honeycomb at the bonding point between the honeycomb and the plate.

[0129] 2. Flat tensile test: GJB 130.4-1986 is used to test the plane tensile test method of the honeycomb sandwich structure; the plane tensile test at 200°C is to perform a plane tensile test on the honeycomb sandwich structure under the condition that the ambient temperature is set to 200°C.

[0130] 3. Peel strength: Tested according to GJB130.7-1986 roller peel test method for bonded aluminum honeycomb sandwich structures.

[0131] 4. Shear strength: The honeycomb shear strength of the adhesive is measured according to GJB1874-94; the room temperature shear strength after wet heat aging is specifically carried out according to the following steps: 85℃85%RH is an aging test on the honeycomb sandwich structure under the conditions of the environment set to 85℃ and 85% humidity. The aging time is 168h and 1000h respectively, and then the room temperature shear strength is tested.

[0132] 5. Honeycomb water absorption rate: The cured honeycomb sandwich structure is placed in an environment of 25°C and 100% humidity for 100 hours, and the weight of the honeycomb sandwich structure before and after placement is weighed. Honeycomb water absorption rate = (weight after water absorption - weight before water absorption) / weight before water absorption × 100%; Honeycomb boiling water absorption rate: The cured honeycomb sandwich structure is placed in a water bath with water covering the honeycomb sandwich structure, and boiled in water at 80°C for 2 hours. After boiling, the surface moisture of the honeycomb is wiped off, and the honeycomb is placed in an oven at 60°C for 8 hours. The honeycomb boiling water absorption rate = (weight after boiling and drying - weight before boiling) / weight before boiling × 100%.

[0133] 6. The bonding effect with the honeycomb interlayer is visually inspected to observe the damaged or detached surface. Honeycomb damage is honeycomb damage, no residual glue is interface debonding, residual glue is adhesive layer damage; and adhesive failure is detachment.

[0134] (2) Adhesive test:

[0135] 1. Molecular weight test: The number average molecular weight (Mn) of the polyimide precursor resin terminated with phenylacetylene phthalic anhydride prepared in step 1 of Example 1 and the polyimide precursor resin terminated with m-aminophenylacetylene prepared in step 2 were tested using a FEI Sirion 200 chromatograph. The mobile phase was chromatographic grade tetrahydrofuran, and polystyrene was used as the internal standard. The samples were placed in an oven at 80° C. for 6 h to remove the solvent and then dissolved in chromatographic grade tetrahydrofuran.

[0136] 2. Infrared testing: The high-temperature resistant, high-strength adhesive suitable for bonding large-size curved honeycomb sandwich structures prepared in Example 1 was cured, and then the infrared spectrum was tested. Curing process: The adhesive was placed in an oven and heated at 80°C for 1 hour, 180°C for 1 hour, 300°C for 2 hours, and 370°C for 1 hour to complete the curing process.

[0137] (3) Bonding large curved honeycombs:

[0138] The adhesives prepared in Examples 1 to 7 and Comparative Experiments 1 to 4 were placed between a large-sized curved polyimide honeycomb and a polyimide composite plate for bonding. The bonding size was 45 cm × 12 cm with a large curvature (10 cm < curvature radius < ∞) curved honeycomb. The polyimide honeycomb was manufactured by Jiangsu Xiannuo New Materials Co., Ltd. Model, the polyimide composite board is homemade (glass cloth is immersed in a polyimide precursor solution, fished out and dried to obtain a prepreg, and the three-layer prepreg is placed in an autoclave for curing to obtain a polyimide composite board, wherein the polyimide precursor solution is prepared from 3,3',4,4'-biphenyltetracarboxylic dianhydride BPDA and p-phenylenediamine PDA); the curing process for bonding the composite board and the honeycomb is as follows: first, heating at a temperature of 80°C and a pressure of 0.2 MPa for 1 h, then heating at a temperature of 180°C and a pressure of 0.2 MPa for 1 h, heating at a temperature of 300°C and a pressure of 0.2 MPa for 2 h, and finally heating at a temperature of 370°C and a pressure of 0.1 MPa for 1 h to obtain a polyimide composite board / large-size curved honeycomb adhesive part.

[0139] The large-sized curved honeycomb was cut into 2.5×10 cm strips before relevant tests.

[0140] 1. Peel strength: Tested according to GJB130.7-1986 roller peeling test method for bonded aluminum honeycomb sandwich structures.

[0141] 2. Flat tensile test: GJB 130.4-1986 is used to test the flat tensile test method of honeycomb sandwich structures.

[0142] Table 1

[0143]

[0144]

[0145]

[0146] Table 2

[0147]

[0148] Table 3

[0149]

[0150]

[0151] Figure 1 This is a photo of the honeycomb of an aluminum honeycomb sandwich structure bonded with the high-temperature resistant and high-strength adhesive prepared in Example 1 after being stretched at 200°C. As can be seen from the figure, the adhesive in Example 1 can form good nubs by climbing along the honeycomb.

[0152] Figure 2 This is a photo of the honeycomb after room temperature roller peeling of the aluminum honeycomb sandwich structure bonded with the high-temperature resistant and high-strength adhesive prepared in Example 2. Figure 1 It can be seen that the viscosity of Example 2 is lower than that of Example 1, and a colloid can be formed, but the height of the adhesive climbing along the honeycomb is reduced.

[0153] Figure 3 The infrared spectrum of the high-temperature resistant and high-strength adhesive suitable for bonding large-scale curved honeycomb sandwich structures prepared in Example 1 after curing: As can be seen from the figure, from 1780cm -1 and 1720cm -1 The presence of a symmetrical carbonyl absorption peak proves that the imidization is complete.

[0154] Figure 4 This is the temperature-viscosity curve of the high-temperature-resistant, high-strength adhesive suitable for bonding large-scale curved honeycomb sandwich structures, prepared in Example 1. As can be seen from the figure, the viscosity of the high-temperature-resistant, high-strength adhesive suitable for bonding large-scale curved honeycomb sandwich structures is low (1000 Pa·s to 3000 Pa·s) in the initial processing stage (80°C to 140°C), which facilitates the penetration of the adhesive into the internal voids of the honeycomb. In the middle processing stage (150°C to 250°C), the final adhesive maintains a relatively high viscosity (400 Pa·s to 600 Pa·s), effectively suppressing the adhesive from flowing and overflowing at high temperatures.

[0155] Figure 5 A large-scale curved honeycomb sample was bonded using the high-temperature-resistant, high-strength adhesive suitable for bonding large-scale curved honeycomb sandwich structures, as prepared in Example 1. (a) shows a side view of the large-scale honeycomb composite panel sample, and (b) shows a top view of the large-scale honeycomb composite panel sample. As can be seen from the figures, the high-temperature-resistant, high-strength adhesive suitable for bonding large-scale curved honeycomb sandwich structures exhibited no adhesive overflow after bonding the large-scale curved honeycomb.

[0156] Figure 6Comparison of large-scale curved honeycomb specimens bonded using a high-temperature-resistant, high-strength adhesive suitable for bonding large-scale curved honeycomb sandwich structures, as prepared in Example 1 and Comparative Experiment 4. (a) is Example 1, and (b) is Comparative Experiment 4. As can be seen from the figures, the high-temperature-resistant, high-strength adhesive suitable for bonding large-scale curved honeycomb sandwich structures exhibited no adhesive overflow after bonding the large-scale curved honeycomb. However, in Comparative Experiment 4, significant adhesive overflow occurred due to a low viscosity caused by the excessive m-aminophenylacetylene content.

[0157] Figure 7 This is a flat tensile test curve of a large-scale curved honeycomb sample cut into strips using the high-temperature-resistant, high-strength adhesive suitable for bonding large-scale curved honeycomb sandwich structures, prepared in Example 1. The figure demonstrates that the high-temperature-resistant, high-strength adhesive suitable for bonding large-scale curved honeycomb sandwich structures achieves a maximum flat tensile strength of 8.4 MPa, demonstrating high bonding strength.

Claims

1. A high-temperature resistant and high-strength adhesive suitable for bonding large-scale curved honeycomb sandwich structures, characterized in that The invention is prepared from 100 parts by weight of a polyimide precursor resin terminated by 4-phenylacetylene phthalic anhydride, 50 to 100 parts by weight of a polyimide precursor resin terminated by m-aminophenylacetylene, 0.1 to 5 parts by weight of chopped carbon fibers and 100 to 200 parts by weight of a solvent C. The 4-phenylacetylene phthalic anhydride-terminated polyimide precursor resin is prepared from 4-phenylacetylene phthalic anhydride, aromatic diamine A, aromatic dianhydride A, and solvent A; the molar ratio of the aromatic diamine A to the aromatic dianhydride A is 1:(0.95-0.97); the molar ratio of the aromatic diamine A to the 4-phenylacetylene phthalic anhydride is 1:(0.06-0.1); and the mass ratio of the aromatic diamine A to the solvent A is 1:(1-10); The repeating unit of polyamic acid in the 4-phenylethynylphthalic anhydride terminated polyimide precursor resin is: The R1 is The R2 is The m-aminophenylacetylene-terminated polyimide precursor resin is prepared from m-aminophenylacetylene, aromatic diamine B, aromatic dianhydride B, and solvent B; the molar ratio of the aromatic diamine B to the aromatic dianhydride B is 1:(1.2-1.5); the molar ratio of the aromatic diamine B to the m-aminophenylacetylene is 1:(0.4-1); and the mass ratio of the aromatic diamine B to the solvent B is 1:(1-10); The repeating unit of the polyamic acid in the m-aminophenylacetylene terminated polyimide precursor resin is: The R3 is The R4 is 2. The high-temperature resistant and high-strength adhesive suitable for bonding large-scale curved honeycomb sandwich structures according to claim 1, characterized in that The length of the chopped carbon fiber is one of 3 mm, 4 mm and 5 mm or a combination thereof; the chopped carbon fiber is pretreated chopped carbon fiber, and the pretreatment process is carried out according to the following steps: placing the carbon fiber in an acetone solution, heating it in a water bath for 10 h to 14 h at a temperature of 45 ° C to 55 ° C, then washing it with deionized water for multiple times, and finally drying it at a temperature of 55 ° C to 65 ° C for 6 h to 10 h.

3. The high-temperature resistant and high-strength adhesive suitable for bonding large-scale curved honeycomb sandwich structures according to claim 1, characterized in that The solvent A, solvent B and solvent C are all N,N-dimethylformamide, N,N-dimethylacetamide or N-methylpyrrolidone.

4. The high-temperature resistant and high-strength adhesive suitable for bonding large-scale curved honeycomb sandwich structures according to claim 1, characterized in that The aromatic diamine A is p-phenylenediamine, m-phenylenediamine or 4,4-diaminobiphenyl.

5. The high-temperature resistant and high-strength adhesive suitable for bonding large-scale curved honeycomb sandwich structures according to claim 1, characterized in that The aromatic dianhydride A is 3,3'4,4'-biphenyltetracarboxylic dianhydride or pyromellitic dianhydride.

6. The high-temperature resistant and high-strength adhesive suitable for bonding large-scale curved honeycomb sandwich structures according to claim 1, characterized in that The aromatic diamine B is 4,4'-diaminodiphenyl ether or 4,4'-diaminodiphenyl sulfone.

7. The high-temperature resistant and high-strength adhesive suitable for bonding large-scale curved honeycomb sandwich structures according to claim 1, characterized in that The aromatic dianhydride B is bisphenol A type diether dianhydride or 4,4'-oxydiphthalic anhydride.

8. The method for preparing a high-temperature resistant and high-strength adhesive suitable for bonding large-scale curved honeycomb sandwich structures according to claim 1, characterized in that It is carried out in the following steps:

1. Preparation of 4-phenylacetylene phthalic anhydride terminated polyimide precursor resin: ① Weigh 4-phenylacetylene phthalic anhydride, aromatic diamine A, aromatic dianhydride A and solvent A; The molar ratio of the aromatic diamine A to the aromatic dianhydride A is 1:(0.95-0.97); the molar ratio of the aromatic diamine A to 4-phenylacetylene phthalic anhydride is 1:(0.06-0.1); the mass ratio of the aromatic diamine A to the solvent A is 1:(1-10); ② In a nitrogen atmosphere, a temperature of 40°C to 48°C and stirring conditions, solvent A and aromatic diamine A are stirred and dissolved for 1h to 5h, then the reaction temperature is raised to 50°C to 60°C, aromatic dianhydride A is added to the reaction system, and the mixture is stirred and reacted for 3h to 5h in a nitrogen atmosphere, a temperature of 50°C to 60°C and stirring conditions, and then 4-phenylacetylene phthalic anhydride is added, and the mixture is stirred and reacted for 2h to 4h in a nitrogen atmosphere, a temperature of 50°C to 60°C and stirring conditions to obtain a 4-phenylacetylene phthalic anhydride-terminated polyimide precursor resin; 2. Preparation of m-aminophenylacetylene terminated polyimide precursor resin: ① Weigh m-aminophenylacetylene, aromatic diamine B, aromatic dianhydride B and solvent B; The molar ratio of the aromatic diamine B to the aromatic dianhydride B is 1:(1.2-1.5); the molar ratio of the aromatic diamine B to m-aminophenylacetylene is 1:(0.4-1); the mass ratio of the aromatic diamine B to the solvent B is 1:(1-10); ② In a nitrogen atmosphere, a temperature of 40°C to 48°C and stirring conditions, solvent B and aromatic diamine B are stirred and dissolved for 1h to 5h, then the reaction temperature is raised to 50°C to 60°C, aromatic dianhydride B is added to the reaction system, and the mixture is stirred and reacted for 3h to 5h in a nitrogen atmosphere, a temperature of 50°C to 60°C and stirring conditions, and then m-aminophenylacetylene is added, and the mixture is stirred and reacted for 2h to 4h in a nitrogen atmosphere, a temperature of 50°C to 60°C and stirring conditions to obtain a m-aminophenylacetylene-terminated polyimide precursor resin; 3. Weighing: Weigh 100 parts by weight of a polyimide precursor resin terminated with 4-phenylethynyl phthalic anhydride, 50 to 100 parts by weight of a polyimide precursor resin terminated with m-aminophenylethynylene, 0.1 to 5 parts by weight of chopped carbon fibers, and 100 to 200 parts by weight of a solvent C; 4. Preparation of adhesive: Under nitrogen atmosphere, reaction temperature of 50°C to 60°C and stirring conditions, the weighed 4-phenylacetylene phthalic anhydride-terminated polyimide precursor resin, m-aminophenylacetylene-terminated polyimide precursor resin, chopped carbon fiber and solvent C are stirred for 2h to 3h, and then the reaction temperature is reduced from 50°C to 60°C to 25°C to 30°C to obtain a high-temperature resistant and high-strength adhesive suitable for bonding large-size curved honeycomb sandwich structures.

9. The method for preparing a high-temperature resistant and high-strength adhesive suitable for bonding large-scale curved honeycomb sandwich structures according to claim 8, characterized in that The stirring speed in step 1②, step 2② and step 4 is 100rpm~200rpm.

10. The method for preparing a high-temperature resistant and high-strength adhesive suitable for bonding large-scale curved honeycomb sandwich structures according to claim 8, characterized in that Step 1 ② Add aromatic dianhydride A to the reaction system in three equal portions; Step 2 ② Add aromatic dianhydride B to the reaction system in three equal portions.

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