High-strength polyimide aerogel composite film material and preparation method thereof

Abstract

The application provides a high-strength polyimide aerogel composite film material and a preparation method thereof. The composite film material comprises a modified polyimide aerogel matrix and a fabric reinforcement which are integrally formed. The modified polyimide aerogel matrix continuously fills the internal pores of the fabric reinforcement and simultaneously extends to the outside of two opposite surfaces of the fabric reinforcement to form an upper surface layer and a lower surface layer, respectively, so as to form a sandwich composite film structure of the upper and lower aerogel surface layers and the fabric reinforcement. In the application, the integrally continuous sandwich structure between the aerogel matrix and the fabric reinforcement can enhance the interfacial bonding strength, avoid delamination failure, and endow the material with overall flexibility of bending and cutting, so that the material can be attached to a complex curved surface. Therefore, the composite film material has excellent mechanical properties, flexibility and thermal insulation performance, and can meet the comprehensive requirements of high-end thermal protection scenes.

Description

Technical Field

[0001] This invention relates to the field of thermal insulation materials technology, and in particular to a high-strength polyimide aerogel composite membrane material and its preparation method. Background Technology

[0002] With the rapid development of my country's aerospace industry, thermal protection materials are gradually trending towards lightweight and high-performance. Aerogels, as a new type of thermal protection material, have become a research hotspot due to their advantages such as lightweight thermal insulation and wide-temperature-range thermal stability. Among them, flexible thermal protection aerogels have been widely used in scenarios such as Mars exploration and extravehicular activities for astronauts. These materials need to possess ultra-lightweight properties, high-efficiency thermal insulation, high-strength mechanical properties, and thermal stability simultaneously in high-temperature environments.

[0003] Polyimide aerogel is one of the best-performing organic polymer aerogels, possessing characteristics such as low density, low thermal conductivity, and high temperature resistance due to its unique three-dimensional nanoporous structure, making it a promising candidate for application in the aerospace field. However, existing polyimide aerogels still have some drawbacks: on the one hand, high-temperature resistant polyimide aerogels lack flexibility and have poor bending performance, making it difficult to conform to complex curved surfaces; on the other hand, traditional polyimide aerogels have poor mechanical properties, with tensile strength typically only 2-8 MPa, and suffer from low modulus, poor elasticity, and poor flexibility, severely limiting their application in high-end thermal protection scenarios.

[0004] Therefore, there is an urgent need to provide a high-strength polyimide aerogel composite membrane material and its preparation method. Summary of the Invention

[0005] This invention provides a high-strength polyimide aerogel composite membrane material and its preparation method, which can solve the problem that existing polyimide aerogels are difficult to maintain good thermal insulation performance while also having high mechanical strength and excellent flexibility.

[0006] In a first aspect, the present invention provides a high-strength polyimide aerogel composite membrane material, the composite membrane material comprising an integrally formed modified polyimide aerogel matrix and a fabric reinforcement; wherein the modified polyimide aerogel matrix continuously fills the internal pores of the fabric reinforcement and extends to the two opposite surfaces of the fabric reinforcement, forming an upper surface layer and a lower surface layer respectively, thereby forming a sandwich composite membrane structure in which the upper and lower aerogel surface layers are interspersed with the fabric reinforcement.

[0007] Preferably, the fabric reinforcement is one of poly(p-phenylenebenzodioxazole) fiber fabric, aramid fabric, or glass fiber cloth.

[0008] Preferably, the areal density of the fabric reinforcement is 200~230 g / m³. 2 .

[0009] Preferably, the modified polyimide aerogel matrix contains dispersed nano-reinforcing phase, inorganic thermal insulation regulating phase, and interface reinforcing agent.

[0010] More preferably, the nano-reinforcing phase comprises functionalized carbon nanomaterials, preferably carboxylated carbon nanotubes; More preferably, the inorganic heat-insulating conditioning phase includes nano-inorganic oxide fillers, preferably nano-silica.

[0011] More preferably, the interface enhancer includes a silane coupling agent, preferably 3-aminopropyltriethoxysilane.

[0012] Preferably, the carboxylated carbon nanotubes have an inner diameter of 5-10 nm, an outer diameter of 10-20 nm, a length of 10-30 μm, and a carboxyl content of 1.2 wt.%.

[0013] Preferably, the particle size of the nano-silica is 10~20 nm.

[0014] Preferably, the mass ratio of the nano-reinforcing phase to the inorganic heat-insulating regulating phase is (0.5~1.5):1.

[0015] Preferably, the amount of interface reinforcing agent added is 10~20 wt.% of the inorganic heat-insulating conditioning phase.

[0016] Secondly, embodiments of the present invention also provide a method for preparing the high-strength polyimide aerogel composite membrane material according to any one of the first aspects above, the preparation method comprising the following steps: (1) Functionalized carbon nanomaterials and nano-inorganic oxide fillers are added to an organic solvent and ultrasonically mixed. Then, an interface enhancer is added and stirred to obtain a modified filler dispersion. (2) Add aromatic diamine and aromatic dianhydride to the modified filler dispersion, and react under an inert atmosphere to obtain a modified polyamic acid solution; (3) The modified polyamic acid solution is mixed with a dehydrating agent and a catalyst, and reacted under an inert atmosphere to obtain a modified polyimide sol; (4) The modified polyimide sol is applied to the fabric reinforcement and the sol is impregnated inside the fabric and covers its two surfaces. Then, the high-strength polyimide aerogel composite membrane material is obtained by solvent replacement and supercritical drying.

[0017] Preferably, in step (1), the organic solvent is N-methylpyrrolidone.

[0018] Preferably, the total mass of functionalized carbon nanomaterials and nano-inorganic oxide fillers accounts for 1 to 4 wt.% of the modified polyamic acid solution.

[0019] Preferably, in step (2), the aromatic diamine is at least one of 4,4'-diaminodiphenyl ether or 4,4'-diamino-2,2'-dimethyl-1,1'-biphenyl; and the aromatic dianhydride is 3,3',4,4'-biphenyltetracarboxylic dianhydride.

[0020] More preferably, the molar ratio of aromatic diamine to aromatic dianhydride is 1:1.05.

[0021] Preferably, in step (3), the dehydrating agent is acetic anhydride and the catalyst is pyridine; preferably, the molar ratio of aromatic dianhydride, catalyst and dehydrating agent is 1:8:8.

[0022] Preferably, in step (4), before applying the modified polyimide sol to the fabric reinforcement, the fabric reinforcement is further pretreated by sequentially immersing it in a solvent and a modified solution.

[0023] More preferably, the solvent is ethanol; the modified solution is obtained by mixing ethanol, water, glacial acetic acid and a silane coupling agent; wherein the concentration of the silane coupling agent is 0.5~1.5 wt.%.

[0024] Preferably, in step (4), the replacement solvent is anhydrous ethanol, which is replaced every 12 h at room temperature for a total of 4 times.

[0025] More preferably, the supercritical drying is supercritical carbon dioxide drying, with a drying pressure of 7.4~8.4 MPa, a temperature of 36~48℃, and a time of 2~4 h.

[0026] Compared with the prior art, the present invention has at least the following beneficial effects: (1) In this invention, the high-strength polyimide aerogel composite membrane material includes an integrally formed modified polyimide aerogel matrix and a fabric reinforcement. The modified polyimide aerogel matrix continuously fills the internal pores of the fabric reinforcement and extends to the two opposite surfaces of the fabric reinforcement, forming an upper surface layer and a lower surface layer with continuous and dense surface and porous interior, respectively. The upper and lower surface layers can effectively block heat conduction, heat convection and heat radiation, and achieve efficient heat insulation. The fabric reinforcement can serve as a core layer to provide a load-bearing skeleton, significantly improving the tensile and tear strength of the material. Furthermore, the integrated continuous through sandwich structure between the aerogel matrix and the fabric reinforcement can enhance the interfacial bonding strength, avoid delamination failure, and give the material overall flexibility to be bent and cut, so that it can fit complex curved surfaces. Thus, the composite membrane material has excellent mechanical properties, flexibility and heat insulation properties, and can meet the comprehensive needs of high-end thermal protection scenarios. (2) In some preferred embodiments, by introducing a nano-reinforcing phase, an inorganic heat-insulating regulating phase and an interface reinforcing agent into the aerogel matrix, not only can the chemical bonding between the reinforcing phase and the regulating phase and the polyimide matrix be achieved, but the interfacial bonding force between the fabric and the aerogel can also be improved, thereby giving the aerogel matrix excellent flexibility and heat insulation performance; when combined with a fabric reinforcement with excellent mechanical properties, the resulting material can simultaneously possess good flexibility, high-efficiency heat insulation and high mechanical strength, effectively overcoming the problem of insufficient mechanical properties of traditional polyimide aerogels while maintaining lightweight. (3) The preparation method in this invention is simple and highly designable. By adjusting the fabric type, aerogel monomer type, nano-reinforcing phase and inorganic heat insulation adjustment phase ratio and material thickness, the mechanical properties and heat insulation properties of the material can be optimized, thereby meeting the application needs of lightweight, high-strength and heat-insulating materials in aerospace and other fields. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments or prior art of this specification, the drawings used in the description of the embodiments or prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this specification. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 This is a physical image depicting the bendability of the high-strength polyimide aerogel composite membrane material provided in Embodiment 1 of the present invention. Figure 2 This is a cross-sectional microstructure diagram of the high-strength polyimide aerogel composite membrane material provided in Embodiment 1 of the present invention. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0030] This invention provides a high-strength polyimide aerogel composite membrane material, which includes an integrally formed modified polyimide aerogel matrix and a fabric reinforcement. The modified polyimide aerogel matrix continuously fills the internal pores of the fabric reinforcement and extends to the two opposite surfaces of the fabric reinforcement, forming an upper surface layer and a lower surface layer, respectively, to form a sandwich composite membrane structure in which the upper and lower aerogel surface layers are interspersed with the fabric reinforcement.

[0031] In this embodiment of the invention, the high-strength polyimide aerogel composite membrane material includes an integrally molded modified polyimide aerogel matrix and a fabric reinforcement. The modified polyimide aerogel matrix continuously fills the internal pores of the fabric reinforcement and extends beyond the two opposite surfaces of the fabric reinforcement, forming a continuous, dense, and porous upper surface layer and a lower surface layer, respectively. These upper and lower surface layers can effectively block heat conduction, heat convection, and heat radiation, achieving efficient heat insulation. The fabric reinforcement serves as a core layer, providing a load-bearing skeleton and significantly improving the tensile and tear strength of the material. Furthermore, the integrated continuous through-layer structure between the aerogel matrix and the fabric reinforcement enhances the interfacial bonding strength, prevents delamination failure, and gives the material overall flexibility to be bent and cut, allowing it to conform to complex curved surfaces. Thus, the composite membrane material possesses excellent mechanical properties, flexibility, and heat insulation properties, meeting the comprehensive needs of high-end thermal protection scenarios.

[0032] According to some preferred embodiments, the fabric reinforcement is one of poly(p-phenylene benzodioxazole) fiber (PBO) fabric, aramid fabric, or glass fiber cloth; the areal density of the fabric reinforcement is 200~230 g / m³. 2 (For example, it can be 200 g / m 2 210 g / m 2 Or 230 g / m 2 ).

[0033] In this embodiment of the invention, the above-mentioned type of fabric reinforcement is combined with the modified polyimide aerogel matrix. The fabric reinforcement is preferably aramid fabric, more preferably para-aramid fabric, and the fabric structure is preferably plain weave with a suitable fabric density, which is conducive to the aerogel matrix fully penetrating the fabric reinforcement and combining with it, thereby ensuring the integration degree of the composite membrane material.

[0034] According to some preferred embodiments, the modified polyimide aerogel matrix contains a dispersed nano-reinforcing phase, an inorganic thermal insulation regulating phase, and an interface reinforcing agent; the nano-reinforcing phase includes functionalized carbon nanomaterials, preferably carboxylated carbon nanotubes; the inorganic thermal insulation regulating phase includes nano-inorganic oxide fillers, preferably nano-silica; and the interface reinforcing agent includes a silane coupling agent, preferably 3-aminopropyltriethoxysilane.

[0035] According to some preferred embodiments, the carboxylated carbon nanotubes have an inner diameter of 5-10 nm (e.g., 5 nm, 6 nm, 7 nm, 8 nm, 9 nm, or 10 nm), an outer diameter of 10-20 nm (e.g., 10 nm, 12 nm, 15 nm, 18 nm, or 20 nm), a length of 10-30 μm (e.g., 10 μm, 12 μm, 15 μm, 18 μm, 20 μm, 22 μm, 25 μm, 28 μm, or 30 μm), and a carboxyl content of 1.2 wt.%; the nano-silica has a particle size of 10-20 nm (e.g., 10 nm, 12 nm, 15 nm, 18 nm, or 20 nm).

[0036] In this embodiment of the invention, a nano-reinforcing phase, an inorganic thermal insulation regulating phase, and an interface reinforcing agent are introduced into the aerogel matrix. The nano-reinforcing phase is preferably carboxylated carbon nanotubes, the inorganic thermal insulation regulating phase is preferably nano-silica, and the interface reinforcing agent is preferably 3-aminopropyltriethoxysilane. Carboxylated carbon nanotubes significantly enhance the mechanical properties of the aerogel matrix, while nano-silica helps reduce the thermal conductivity of the aerogel matrix. The two phases are mixed and dispersed and bridged by 3-aminopropyltriethoxysilane, which facilitates the uniform dispersion and tight bonding of the reinforcing and regulating phases. This not only achieves chemical bonding between the reinforcing and regulating phases and the polyimide matrix but also improves the interfacial bonding between the fabric and the aerogel, thereby endowing the aerogel matrix with excellent flexibility and thermal insulation properties. When combined with a fabric reinforcement with excellent mechanical properties, the resulting material simultaneously possesses good flexibility, efficient thermal insulation, and high mechanical strength, effectively overcoming the shortcomings of traditional polyimide aerogels in terms of mechanical properties while maintaining lightweight properties.

[0037] According to some preferred embodiments, the mass ratio of the nano-reinforcing phase to the inorganic heat-insulating conditioning phase is (0.5~1.5):1 (e.g., it can be 0.5:1, 0.8:1, 1.0:1, 1.2:1 or 1.5:1); the amount of interface reinforcing agent added is 10~20 wt.% of the inorganic heat-insulating conditioning phase (e.g., it can be 10 wt.%, 12 wt.%, 15 wt.%, 18 wt.% or 20 wt.%).

[0038] In this embodiment of the invention, by rationally controlling the ratio of the nano-reinforcing phase and the inorganic thermal insulation regulating phase, it is beneficial to ensure that the modified polyimide aerogel possesses good flexibility, mechanical strength, and thermal insulation performance. Experiments of this invention have confirmed that if the content of the nano-reinforcing phase is too low, it is not conducive to significantly improving the mechanical properties of the aerogel; while if the content of the nano-reinforcing phase is too high, it is easy to induce agglomeration of the nano-reinforcing phase, destroying the uniform nanoporous structure of the aerogel and leading to a decrease in the thermal insulation performance of the aerogel. Simultaneously, an appropriate content of interfacial reinforcing agent is beneficial to achieving uniform dispersion of the nano-reinforcing phase and the inorganic thermal insulation regulating phase, and also enhances the bonding force between the two and the aerogel matrix. If the content of the interfacial reinforcing agent is too high, it will weaken the bonding force between the two and the aerogel matrix, reducing mechanical properties.

[0039] This invention also provides a method for preparing the high-strength polyimide aerogel composite membrane material according to any one of the above claims, the method comprising the following steps: (1) Functionalized carbon nanomaterials and nano-inorganic oxide fillers are added to an organic solvent and ultrasonically mixed. Then, an interface enhancer is added and stirred to obtain a modified filler dispersion. (2) Add aromatic diamine and aromatic dianhydride to the modified filler dispersion, and react under an inert atmosphere to obtain a modified polyamic acid solution; (3) The modified polyamic acid solution is mixed with a dehydrating agent and a catalyst, and reacted under an inert atmosphere to obtain a modified polyimide sol; (4) The modified polyimide sol is applied to the fabric reinforcement and the sol is impregnated inside the fabric and covers its two surfaces. Then, the high-strength polyimide aerogel composite membrane material is obtained by solvent replacement and supercritical drying.

[0040] In this embodiment of the invention, functionalized carbon nanomaterials and nano-inorganic oxide fillers are first added to an organic solvent and ultrasonically mixed. Then, an interface reinforcing agent is added and stirred to ensure that the interface reinforcing agent is fully grafted onto the surface of the nanofiller, promoting the uniform dispersion of the nanofiller and subsequent chemical bonding. Next, aromatic diamine and aromatic dianhydride are added to the modified filler dispersion and reacted at room temperature (25~30℃) for 5~7 h, so that the active functional groups on the filler surface participate in the reaction, realizing the chemical bonding between the reinforcing phase and the heat-insulating regulating phase and the polyimide matrix. Then, a dehydrating agent and a catalyst are added to carry out a chemical imidization reaction for 10~20 min to form a modified polyimide sol. Finally, the sol is applied to the surface of the fabric reinforcement using a sandwich coating method, so that it fully penetrates the internal pores of the fabric and covers both surfaces. After solvent replacement and drying, a high-strength polyimide aerogel composite membrane material with a sandwich structure is obtained.

[0041] According to some preferred embodiments, in step (1), the organic solvent is N-methylpyrrolidone; the total mass of the functionalized carbon nanomaterials and nano-inorganic oxide fillers accounts for 1 to 4 wt.% of the modified polyamic acid solution (for example, it can be 1 wt.%, 2 wt.%, 3 wt.% or 4 wt.%).

[0042] According to some preferred embodiments, in step (2), the aromatic diamine is at least one of 4,4'-diaminodiphenyl ether or 4,4'-diamino-2,2'-dimethyl-1,1'-biphenyl; the aromatic dianhydride is 3,3',4,4'-biphenyltetracarboxylic dianhydride; preferably, the molar ratio of aromatic diamine to aromatic dianhydride is 1:1.05.

[0043] In this embodiment of the invention, aromatic diamines and aromatic dianhydrides of the aforementioned types are preferably used, and their molar ratio is precisely controlled. This helps to ensure that the aerogel network maintains structural integrity while possessing excellent flexibility. Simultaneously, controlling the content of functionalized carbon nanomaterials and nano-inorganic oxide fillers in the modified polyamic acid solution can enhance the mechanical properties of the skeleton while avoiding agglomeration or decreased flexibility caused by excessive fillers. Thus, the aerogel matrix possesses both high flexibility and low thermal conductivity, and when combined with fabric reinforcement, the aerogel layer of the composite membrane material is less prone to cracking during repeated bending.

[0044] According to some preferred embodiments, in step (3), the dehydrating agent is acetic anhydride and the catalyst is pyridine; preferably, the molar ratio of aromatic dianhydride, catalyst and dehydrating agent is 1:8:8.

[0045] According to some preferred embodiments, the solid content of the modified polyamic acid solution is 7 to 13 wt.% (e.g., 7 wt.%, 10 wt.%, 13 wt.%).

[0046] In this embodiment of the invention, by controlling the solid content of the modified polyamic acid solution within a suitable range, it is not only beneficial for the sol to fully penetrate the internal pores of the fabric reinforcement fibers to form a continuous and interconnected matrix network, but also beneficial for ensuring the good flexibility of the aerogel matrix.

[0047] According to some preferred embodiments, in step (4), before applying the modified polyimide sol to the fabric reinforcement, the fabric reinforcement is further pretreated by sequentially immersing it in a solvent and a modified solution; the solvent is ethanol; the modified solution is obtained by mixing ethanol, water, glacial acetic acid and a silane coupling agent; wherein the concentration of the silane coupling agent is 0.5~1.5 wt.% (for example, it can be 0.5 wt.%, 0.8 wt.%, 1.0 wt.%, 1.2 wt.% or 1.5 wt.%).

[0048] In this embodiment of the invention, before applying the modified polyimide sol to the surface of the fabric reinforcement, the fabric reinforcement is first soaked in ethanol for 10-12 hours to wash away impurities on the fabric surface; then, ethanol and water are mixed at a volume ratio of 95:5, and glacial acetic acid is added to adjust the pH value to 4.5-5.5. Subsequently, a silane coupling agent (preferably 3-aminopropyltriethoxysilane) is slowly added under stirring to form a modified solution of suitable concentration; the washed fabric reinforcement is then soaked in the above modified solution at room temperature for 6-8 hours to allow the coupling agent molecules to be fully grafted onto the fiber surface; then, it is rinsed twice with ethanol to remove excess ungrafted coupling agent, and dried in an oven at 95-105°C for 1-2 hours to obtain the pretreated fabric. The chemical groups introduced on the surface of the pretreated fabric can chemically bond with the chemical groups in the subsequently applied modified polyimide sol. This not only facilitates the uniform impregnation and firm adhesion of the modified polyimide sol inside the fabric, but also avoids cracking, delamination, or interfacial peeling during subsequent solvent replacement and supercritical drying processes.

[0049] According to some preferred embodiments, in step (4), the composite method is as follows: the modified polyimide sol is poured onto a glass plate and spread out on an adjustable coating machine to form a uniform bottom layer sol; a layer of fabric reinforcement is laid flat on the bottom layer sol, and then the modified polyimide sol is poured onto the fabric reinforcement and spread out again in the adjustable coating machine, so that the sol penetrates from top to bottom and immerses in the internal pores of the fabric, and simultaneously covers the upper and lower surfaces of the fabric; preferably, the coating speed of the adjustable coating machine is 25~35 mm / s (for example, it can be 25 mm / s, 30 mm / s or 35 mm / s).

[0050] According to some preferred embodiments, the thickness of the composite membrane material is 0.15 to 1 mm (for example, it can be 0.15 mm, 0.2 mm, 0.5 mm, 0.6 mm, 0.8 mm or 1 mm).

[0051] Traditional impregnation methods often result in uneven aerogel distribution along the fabric thickness direction, with a thinner upper layer and a thicker lower layer, and poor continuity of the aerogel layer on the same surface. Single-sided coating methods tend to lead to weak interfacial bonding and delamination after drying. In this invention, a sandwich-style composite method is employed, applying modified polyimide sol to both the upper and lower surfaces of the fabric reinforcement. This allows the sol to fully and uniformly wet the pores between fibers, forming a fully encapsulated structure of the fabric reinforcement. This allows for separate control of the aerogel layer thickness on the upper and lower surfaces, ensuring relative uniformity and good continuity, preventing defects such as bubbles or exposed reinforcement. Furthermore, the bidirectional penetration of the sol from top to bottom completely encapsulates the fibers with the aerogel matrix, resulting in stronger interfacial bonding and reducing the likelihood of cracking or delamination during subsequent solvent replacement and supercritical drying. Consequently, the prepared polyimide aerogel composite membrane material achieves a strong, integrated bond, significantly enhancing its tensile strength while maintaining its lightweight and high-efficiency thermal insulation properties.

[0052] According to some preferred embodiments, in step (4), the replacement solvent is anhydrous ethanol, which is replaced every 12 h at room temperature for 4 times; the supercritical drying is supercritical carbon dioxide drying, with a drying pressure of 7.4~8.4 MPa (for example, 7.4 MPa, 7.5 MPa, 7.8 MPa, 8.0 MPa, 8.2 MPa or 8.4 MPa), a temperature of 36~48℃ (for example, 36℃, 40℃, 42℃, 45℃ or 48℃), and a time of 2~4 h (for example, 2 h, 3 h or 4 h).

[0053] In summary, the polyimide aerogel composite membrane material prepared by this invention possesses flexibility, thermal insulation, and excellent mechanical properties, and can be manufactured in various sizes to meet different needs. Furthermore, the preparation method of this invention is simple and highly designable; by adjusting the fabric type, aerogel monomer type, the ratio of nano-reinforcing phase and inorganic thermal insulation adjusting phase, and the material thickness, the mechanical and thermal insulation properties of the material can be optimized, thereby meeting the application requirements of lightweight, high-strength, and thermally insulating materials in aerospace and other fields.

[0054] To more clearly illustrate the technical solution and advantages of the present invention, the following examples provide a detailed description of a high-strength polyimide aerogel composite membrane material and its preparation method. In the following examples, reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained commercially.

[0055] Example 1: (1) The fabric reinforcement (area density of 230 g / m²) 2The plain weave para-aramid fabric was washed by immersing it in a solvent (anhydrous ethanol) for 12 h; ethanol and deionized water were mixed at a volume ratio of 95:5, the pH was adjusted to 4.5 with glacial acetic acid, and a silane coupling agent (3-aminopropyltriethoxysilane) was slowly added under stirring to prepare a modified solution with a concentration of 1 wt.%; the washed fabric reinforcement was immersed in the modified solution for 6 h at room temperature, then rinsed twice with ethanol, and dried in an oven at 100 °C for 1.5 h to obtain the pretreated fabric reinforcement; Functionalized carbon nanomaterials (carboxylated carbon nanotubes) and nano-inorganic oxide fillers (nano-silica with a particle size of 15 nm) at a mass ratio of 1.5:1 were added to an organic solvent (N-methylpyrrolidone) and ultrasonically mixed for 1 h. Then, an interface enhancer (3-aminopropyltriethoxysilane) was added and stirred for 30 min to obtain a modified filler dispersion. The amount of interface enhancer added was 20 wt.% of the nano-inorganic oxide filler. (2) Under a nitrogen atmosphere and with stirring at 350 r / min, aromatic diamine (4,4'-diaminodiphenyl ether) and aromatic dianhydride (3,3',4,4'-biphenyltetracarboxylic dianhydride) were added to the above modified filler dispersion at a molar ratio of 1:1.05, and reacted at room temperature (25°C) for 6 h to obtain a modified polyamic acid solution with a solid content of 10 wt.%; the total mass of functionalized carbon nanomaterials and nano-inorganic oxide fillers accounted for 3 wt.% of the modified polyamic acid solution. (3) Continue to add dehydrating agent (acetic anhydride) and catalyst (pyridine) to the modified polyamic acid solution under nitrogen atmosphere, mix well, and react at room temperature (25°C) for 10 min to obtain modified polyimide sol; wherein the molar ratio of aromatic diammonium, catalyst and dehydrating agent is 1:8:8; (4) Pour a portion of the modified polyimide sol onto a glass plate and spread it on an adjustable coating machine to form a uniform bottom layer sol. Spread a layer of pretreated fabric reinforcement on the bottom layer sol and gently press it to ensure that the fabric and the modified polyimide sol are in complete contact without air bubbles. Pour the remaining modified polyimide sol onto the fabric surface and spread it again in an adjustable coating machine at a coating speed of 30 mm / s to allow the sol to penetrate from top to bottom and into the internal pores of the fabric, while simultaneously covering the upper and lower surfaces of the fabric. After aging the obtained fabric-reinforced wet gel on a glass plate for 12 h, replace the solvent with anhydrous ethanol and soak for three days, changing the solvent every 12 h. Finally, place the fabric-reinforced wet gel in a supercritical drying kettle and dry it for 3 h at 7.8 MPa and 40 ℃ to obtain a high-strength polyimide aerogel composite membrane material with a thickness of 0.6 mm.

[0056] The high-strength polyimide aerogel composite membrane material prepared in this embodiment exhibits excellent flexibility, without interfacial delamination after multiple bending, and has a thermal conductivity of 29.62 mW·m. -1 ·K -1 The tensile strength is 391.2 MPa and the elongation at break is 12.71%.

[0057] Example 2: Example 2 is basically the same as Example 1, except that in step (1), the fabric reinforcement used has an areal density of 200 g / m². 2 Plain-weave poly(p-phenylenebenzodioxazole) fiber (PBO) fabric.

[0058] The high-strength polyimide aerogel composite membrane material prepared in this embodiment exhibits excellent flexibility, without interfacial delamination after multiple bending, and has a thermal conductivity of 33.52 mW·m. -1 ·K -1 The tensile strength is 460.5 MPa and the elongation at break is 5.12%.

[0059] Example 3: Example 3 is basically the same as Example 1, except that in step (1), the fabric reinforcement used has an areal density of 210 g / m². 2 The thickness of the high-strength polyimide aerogel composite membrane material obtained in step (4) is 0.15 mm, and the glass fiber cloth with plain weave structure is also 0.15 mm.

[0060] The high-strength polyimide aerogel composite membrane material prepared in this embodiment exhibits excellent flexibility, without interfacial delamination after multiple bending, and has a thermal conductivity of 35.01 mW·m. -1 ·K -1 The tensile strength is 165.9 MPa and the elongation at break is 3.19%.

[0061] Example 4: Example 4 is basically the same as Example 1, except that in step (2), the aromatic diamine is replaced with the same proportion of 4,4'-diamino-2,2'-dimethyl-1,1'-biphenyl.

[0062] The high-strength polyimide aerogel composite membrane material prepared in this embodiment exhibits excellent flexibility, without interfacial delamination after multiple bending, and has a thermal conductivity of 34.11 mW·m. -1 ·K -1 The tensile strength is 371.6 MPa and the elongation at break is 12.25%.

[0063] Example 5: Example 5 is basically the same as Example 1, except that: in step (1), the mass ratio of functionalized carbon nanomaterials and nano-inorganic oxide fillers is 0.5:1; in step (2), under nitrogen atmosphere and stirring at a speed of 350 r / min, aromatic diamine (4,4'-diaminodiphenyl ether and 4,4'-diamino-2,2'-dimethyl-1,1'-biphenyl in a molar ratio of 1:1) is added to the above modified filler dispersion, and then aromatic dianhydride (3,3',4,4'-biphenyltetracarboxylic dianhydride) is added and reacted at room temperature (25°C) for 6 h to obtain a modified polyamic acid solution with a solid content of 10 wt.%; wherein, the molar ratio of aromatic diamine and aromatic dianhydride is 1:1.05.

[0064] The high-strength polyimide aerogel composite membrane material prepared in this embodiment exhibits excellent flexibility, without interfacial delamination after multiple bending, and has a thermal conductivity of 33.06 mW·m. -1 ·K -1 The tensile strength is 380.2 MPa and the elongation at break is 12.53%.

[0065] Example 6: Example 6 is basically the same as Example 1, except that: in step (1), the mass ratio of functionalized carbon nanomaterials and nano-inorganic oxide fillers is 1:1; in step (2), the solid content of the modified polyamic acid solution is 7 wt.%; and in step (4), the thickness of the high-strength polyimide aerogel composite membrane material is 0.8 mm.

[0066] The high-strength polyimide aerogel composite membrane material prepared in this embodiment exhibits excellent flexibility, without interfacial delamination after multiple bending, and has a thermal conductivity of 30.92 mW·m. -1 ·K -1 The tensile strength is 349.4 MPa and the elongation at break is 12.39%.

[0067] Example 7: Example 7 is basically the same as Example 1, except that: in step (1), the mass ratio of functionalized carbon nanomaterials and nano-inorganic oxide fillers is 0.5:1; in step (2), the solid content of the modified polyamic acid solution is 13 wt.%; and in step (4), the thickness of the high-strength polyimide aerogel composite membrane material is 0.8 mm.

[0068] The high-strength polyimide aerogel composite membrane material prepared in this embodiment has a thermal conductivity of 30.08 mW·m. -1 ·K -1 The tensile strength is 359.3 MPa and the elongation at break is 11.42%.

[0069] Example 8: Example 8 is basically the same as Example 1, except that in step (1), the mass ratio of functionalized carbon nanomaterials and nano-inorganic oxide fillers is 2:1.

[0070] The high-strength polyimide aerogel composite membrane material prepared in this embodiment has a thermal conductivity of 32.14 mW·m. -1 ·K -1 The tensile strength is 385.9 MPa and the elongation at break is 12.01%.

[0071] Example 9: Example 9 is basically the same as Example 1, except that in step (1), the total mass of functionalized carbon nanomaterials and nano-inorganic oxide fillers accounts for 5 wt.% of the modified polyamic acid solution.

[0072] The high-strength polyimide aerogel composite membrane material prepared in this embodiment has a thermal conductivity of 34.11 mW·m. -1 ·K -1 It has a tensile strength of 362.9 MPa and an elongation at break of 11.59%, but after repeated bending, the aerogel layer cracks and delaminates at the interface with the fabric reinforcement.

[0073] Example 10: Example 10 is basically the same as Example 1, except that in step (1), only ethanol is used to wash the fabric reinforcement and it is dried in an oven at 60°C for 6 hours to obtain the pretreated fabric reinforcement.

[0074] The high-strength polyimide aerogel composite membrane material prepared in this embodiment exhibits excellent flexibility and a thermal conductivity of 29.84 mW·m. -1 ·K -1 It has a tensile strength of 389.1 MPa and an elongation at break of 10.87%, but after repeated bending, the aerogel layer and the fabric reinforcement undergo interfacial delamination.

[0075] Comparative Example 1: Comparative Example 1 is basically the same as Example 1, except that: the fabric reinforcement in steps (1) and (4) is removed; in step (4), the modified polyimide sol is placed in an adjustable coating machine with a coating speed of 30 mm / s and a coating thickness of 1 mm to obtain a modified polyimide wet gel film; the obtained wet gel film is then aged on a glass plate for 12 h, and then solvent is replaced with anhydrous ethanol for three days, with the solvent being replaced every 12 h; finally, the polyimide wet gel film is placed in a supercritical drying kettle and dried at 7.8 MPa and 40℃ for 3 h to obtain a polyimide aerogel composite membrane material.

[0076] The thermal conductivity of the polyimide aerogel film prepared in this comparative example is 23.71 mW·m.-1 ·K -1 The tensile strength is 5.9 MPa and the elongation at break is 15.23%.

[0077] Comparative Example 2: Comparative Example 2 is basically the same as Example 4, except that: the fabric reinforcement in steps (1) and (4) is removed; in step (4), the modified polyimide sol is placed in an adjustable coating machine with a coating speed of 30 mm / s and a coating thickness of 1 mm to obtain a modified polyimide wet gel film; the obtained wet gel film is then aged on a glass plate for 12 h, and then solvent is replaced with anhydrous ethanol for three days, with the solvent being replaced every 12 h; finally, the fabric-reinforced wet gel is placed in a supercritical drying kettle and dried at 7.8 MPa and 40 °C for 3 h to obtain a polyimide aerogel composite membrane material.

[0078] The thermal conductivity of the polyimide aerogel film prepared in this comparative example is 32.66 mW·m. -1 ·K -1 The tensile strength is 8.8 MPa and the elongation at break is 26.52%. Due to the lack of fabric reinforcement, the mechanical strength is low and cracks appear after repeated bending.

[0079] Comparative Example 3: Comparative Example 3 is basically the same as Example 5, except that: the fabric reinforcement in steps (1) and (4) is removed; in step (4), the modified polyimide sol is placed in an adjustable coating machine with a coating speed of 30 mm / s and a coating thickness of 1 mm to obtain a modified polyimide wet gel film; the obtained wet gel film is then aged on a glass plate for 12 h, and then solvent is replaced with anhydrous ethanol for three days, with the solvent being replaced every 12 h; finally, the fabric-reinforced wet gel is placed in a supercritical drying kettle and dried at 7.8 MPa and 40 °C for 3 h to obtain a polyimide aerogel composite membrane material.

[0080] The thermal conductivity of the polyimide aerogel film prepared in this comparative example is 28.26 mW·m. -1 ·K -1 The tensile strength is 7.4 MPa and the elongation at break is 15.37%. Due to the lack of fabric reinforcement, the mechanical strength is low.

[0081] Comparative Example 4: Comparative Example 4 is basically the same as Example 1, except that: in step (1), only the fabric reinforcement is pretreated and no functionalized carbon nanomaterials and nano-inorganic oxide fillers are added; in step (2), under nitrogen atmosphere and stirring at a speed of 350 r / min, aromatic diamine (4,4'-diaminodiphenyl ether) and aromatic dianhydride (3,3',4,4'-biphenyltetracarboxylic dianhydride) are added to an organic solvent (N-methylpyrrolidone) at a molar ratio of 1:1.05 and reacted at room temperature (25°C) for 6 h to obtain a polyamic acid solution with a solid content of 10 wt.%.

[0082] The high-strength polyimide aerogel composite membrane material prepared in this comparative example has a thermal conductivity of 29.12 mW·m. -1 ·K -1 The tensile strength is 380.8 MPa and the elongation at break is 12.71%.

[0083] Comparative Example 5: Comparative Example 5 is basically the same as Example 1, except that in step (1), the functionalized carbon nanomaterial (carboxylated carbon nanotubes) is added to an organic solvent (N-methylpyrrolidone) and ultrasonically mixed for 1 h, and then the interface enhancer (3-aminopropyltriethoxysilane) is added and stirred for 30 min to obtain a modified filler dispersion; wherein, the amount of interface enhancer added is 20 wt. of the functionalized carbon nanomaterial.

[0084] The thermal conductivity of the polyimide aerogel composite membrane material prepared in this comparative example is 34.52 mW·m. -1 ·K -1 The tensile strength is 389.3 MPa and the elongation at break is 12.11%.

[0085] Comparative Example 6: Comparative Example 6 is basically the same as Example 1, except that in step (1), the inorganic oxide filler (nano silica with a particle size of 15 nm) is added to an organic solvent (N-methylpyrrolidone) and ultrasonically mixed for 1 h, and then the interface enhancer (3-aminopropyltriethoxysilane) is added and stirred for 30 min to obtain a modified filler dispersion; wherein, the amount of interface enhancer added is 20 wt. of the inorganic oxide filler.

[0086] The high-strength polyimide aerogel composite membrane material prepared in this comparative example has a thermal conductivity of 28.68 mW·m. -1 ·K -1 The tensile strength is 373.9 MPa and the elongation at break is 11.08%.

[0087] Comparative Example 7: Comparative Example 7 is basically the same as Comparative Example 4, except that in step (4), a layer of pretreated fabric reinforcement is laid flat on a glass plate, the modified polyimide sol is poured onto the fabric surface, and it is spread in an adjustable coating machine at a coating speed of 30 mm / s so that the sol can penetrate from top to bottom and immerse itself in the internal pores of the fabric. After aging the obtained fabric reinforcement wet gel on a glass plate for 12 h, it is soaked for three days with anhydrous ethanol as the solvent and the solvent is changed every 12 h. Finally, the fabric reinforcement wet gel is placed in a supercritical drying kettle and dried for 3 h at 7.8 MPa and 40 ℃. After drying, the aerogel matrix and the fabric reinforcement undergo interfacial debonding, the aerogel layer peels off from the fabric surface, the material loses its structural integrity, and subsequent mechanical and thermal insulation performance tests cannot be performed.

[0088] The performance of the high-strength polyimide aerogel composite membrane material samples provided in the examples and comparative examples was tested, and the test results are shown in Table 1 below: Thermal conductivity: The transient planar heat source (heat plate) method was adopted, and the test standard referred to "Determination of thermal conductivity and thermal diffusivity of plastics - Part 2: Transient planar heat source (heat plate) method GB / T 42919.2-2025"; Tensile strength and elongation at break: tested using a universal testing machine, with the testing standard referring to "Test Method for Tensile Properties of Fiber Reinforced Plastics GB / T 1447-2005".

[0089] Table 1 From Table 1 and Figures 1 to 2 As can be seen from the present invention, the polyimide aerogel composite membrane material prepared in the embodiments of the present invention has both flexibility, thermal insulation and excellent mechanical properties.

[0090] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A high-strength polyimide aerogel composite membrane material, characterized in that, The composite membrane material comprises an integrally formed modified polyimide aerogel matrix and a fabric reinforcement; wherein the modified polyimide aerogel matrix continuously fills the internal pores of the fabric reinforcement and extends to the two opposite surfaces of the fabric reinforcement, forming an upper surface layer and a lower surface layer, respectively, to form a sandwich composite membrane structure in which the upper and lower aerogel surface layers are interspersed with the fabric reinforcement.

2. The composite membrane material according to claim 1, characterized in that, The fabric reinforcement is one of poly(p-phenylenebenzodioxazole) fiber fabric, aramid fabric, or glass fiber cloth; and / or... The areal density of the fabric reinforcement is 200~230 g / m³. 2 .

3. The composite membrane material according to claim 1, characterized in that, The modified polyimide aerogel matrix contains a dispersed nano-reinforcing phase, an inorganic thermal insulation regulating phase, and an interface reinforcing agent; The nano-reinforcing phase includes functionalized carbon nanomaterials, preferably carboxylated carbon nanotubes; the inorganic heat-insulating regulating phase includes nano-inorganic oxide fillers, preferably nano-silica. The interface enhancer includes a silane coupling agent, preferably 3-aminopropyltriethoxysilane.

4. The composite membrane material according to claim 3, characterized in that, The carboxylated carbon nanotubes have an inner diameter of 5-10 nm, an outer diameter of 10-20 nm, a length of 10-30 μm, and a carboxyl content of 1.2 wt.%; and / or, The particle size of the nano-silica is 10~20 nm.

5. The composite membrane material according to claim 3, characterized in that, The mass ratio of the nano-reinforcing phase to the inorganic thermal insulation regulating phase is (0.5~1.5):1; Preferably, the amount of interface reinforcing agent added is 10~20 wt.% of the inorganic heat-insulating conditioning phase.

6. A method for preparing a high-strength polyimide aerogel composite membrane material, characterized in that, The preparation method includes the following steps: (1) Functionalized carbon nanomaterials and nano-inorganic oxide fillers are added to an organic solvent and ultrasonically mixed. Then, an interface enhancer is added and stirred to obtain a modified filler dispersion. (2) Add aromatic diamine and aromatic dianhydride to the modified filler dispersion, and react under an inert atmosphere to obtain a modified polyamic acid solution; (3) The modified polyamic acid solution is mixed with a dehydrating agent and a catalyst, and reacted under an inert atmosphere to obtain a modified polyimide sol; (4) The modified polyimide sol is applied to the fabric reinforcement by the sandwich composite method, and the sol is impregnated inside the fabric and covers its two surfaces. Then, the high-strength polyimide aerogel composite membrane material is obtained by solvent replacement and supercritical drying.

7. The preparation method according to claim 6, characterized in that, In step (1), the organic solvent is N-methylpyrrolidone; and / or, The total mass of functionalized carbon nanomaterials and nano-inorganic oxide fillers accounts for 1-4 wt.% of the modified polyamic acid solution.

8. The preparation method according to claim 6, characterized in that, In step (2), the aromatic diamine is at least one of 4,4'-diaminodiphenyl ether or 4,4'-diamino-2,2'-dimethyl-1,1'-biphenyl; the aromatic dianhydride is 3,3',4,4'-biphenyltetracarboxylic dianhydride; preferably, the molar ratio of aromatic diamine to aromatic dianhydride is 1:1.05; and / or, In step (3), the dehydrating agent is acetic anhydride and the catalyst is pyridine; preferably, the molar ratio of aromatic dianhydride, catalyst and dehydrating agent is 1:8:

8.

9. The preparation method according to claim 6, characterized in that, In step (4), before applying the modified polyimide sol to the fabric reinforcement, the step further includes a pretreatment step of immersing the fabric reinforcement in a solvent and a modified solution in sequence. The solvent is ethanol; the modified solution is obtained by mixing ethanol, water, glacial acetic acid and silane coupling agent; wherein the concentration of the silane coupling agent is 0.5~1.5 wt.%.

10. The preparation method according to claim 6, characterized in that, In step (4), the replacement solvent is anhydrous ethanol, which is replaced every 12 hours at room temperature, for a total of 4 replacements; and / or, The supercritical drying is supercritical carbon dioxide drying, with a drying pressure of 7.4~8.4 MPa, a temperature of 36~48℃, and a time of 2~4 h.

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