A high-strength polyimide aerogel corrugated paper and preparation method thereof

Abstract

High-strength polyimide aerogel pleated paper and its preparation method. The present invention relates to a low-dimensional polyimide aerogel material and its preparation method. This invention addresses the problem that existing methods cannot produce high-temperature-resistant, high-strength polyimide aerogel pleated paper. The high-strength polyimide aerogel pleated paper is prepared from aromatic diamine, aromatic dianhydride, a catalyst, and a solvent. The preparation method includes: 1. Weighing; 2. Preparing a polyamic acid solution; 3. Preparing a polyimide aerogel; and 4. Preparing the polyimide aerogel pleated paper. The present invention is used for high-strength polyimide aerogel pleated paper and its preparation.

Description

Technical Field

[0001] The invention relates to a polyimide aerogel low-dimensional material and a preparation method thereof. Background Art

[0002] Paper, a low-dimensional, multifunctional material, is widely used in daily life, including wallpaper, wrapping paper, decorative paper, and office paper. A4 paper is an internationally recognized office paper composed of cellulose, hemicellulose, and lignin, and its dimensions are specified by the International Organization for Standardization. Traditional paper made from natural plant fibers suffers from flammability, perhaps its most critical weakness. This not only complicates the preservation of valuable documents but can also cause serious fires, posing a serious threat to human life and property. Therefore, specialized papers are urgently needed in certain fields, such as defense and aerospace, to meet the demands of these environments. Aramid paper, with its unique sheet structure and excellent mechanical, chemical, electrical, and physical properties, has become a revolutionary new material. Aramid paper is currently the fastest-growing specialty chemical fiber paper in the world for high-temperature resistance and insulation. It not only possesses excellent physical and mechanical properties, but also boasts excellent thermal stability, flame retardancy, electrical insulation, and radiation resistance. It is a crucial foundational material in aviation, aerospace, defense, electronics, communications, environmental protection, chemical engineering, and marine development. After years of development, aramid paper has achieved heat resistance exceeding 200°C. As aerospace vehicles develop towards high speed and high performance, they are required to have better mechanical properties, lower density and thermal stability at high temperatures (>300°C). Currently commercialized paper products can no longer meet the high temperature and high strength requirements.

[0003] Polyimides are a class of organic polymers containing an imide ring (-CO-N-CO-) in their backbone. They possess excellent mechanical strength, thermal insulation stability, and anti-friction and anti-wear properties, offering unique advantages as both structural and functional materials. They are currently widely used in demanding applications such as aerospace, the environmental industry, and healthcare. As a member of the high-performance polymer family, polyimides have been formulated into resins, films, fibers, and adhesives for applications in high-temperature filtration, composite materials, and specialized protective equipment. They are known as the "problem solver" in the materials industry. Polyimide aerogels are three-dimensional porous materials composed of cross-linked polymer chains. They combine the excellent properties of polyimide with the outstanding characteristics of aerogels, including lightweight, ultra-low density, high specific surface area, low thermal conductivity, and low dielectric constant. Polyimides can be synthesized using a variety of methods, with the most commonly used method being the reaction of a dianhydride monomer (containing two anhydride groups) with a diamine monomer (containing two amino groups). Due to the wide selection of polyimide raw materials, dianhydrides and diamines, polyimide materials with specific properties can be synthesized based on specific usage conditions. Therefore, polyimide aerogels have the potential to become intermediates for the preparation of paper-like materials. Currently, the highest-performing commercially available polyimide aerogel is the TEEK series. However, its thickness is generally over 5mm, and due to the pre-processing and post-cutting process, the resulting aerogel is thick and has poor surface quality, making it difficult to meet the needs of more advanced applications.

[0004] Wrinkling is a common phenomenon in two-dimensional (2D) materials. Due to their atomic-level thickness, 2D materials typically have relatively low out-of-plane stiffness; when subjected to intermolecular or interfacial interactions, or when their size or mass exceeds a certain critical value, they typically exhibit a wrinkled state. Wrinkles have micro / nanostructures with spatially periodic or non-periodic topologies, which endow the materials with unique acoustic, electrical, optical, mechanical, and biological properties, attracting considerable attention. Compared with flat 2D materials, 2D materials with wrinkled structures exhibit unique advantages in some areas. Wrinkles can greatly improve the flexibility of materials, including bending, twisting, and stretchability. In particular, dynamic wrinkles with adjustable morphology can achieve on-demand regulation of the surface functions and properties of materials. Wrinkles have good stretchability, structural periodicity, and fast response, and have broad application prospects in tunable optical or optoelectronic devices, responsive devices, superhydrophobic coatings, adjustable adhesion, and cell growth templates.

[0005] However, when using the more mature and environmentally friendly vacuum freeze-drying method to prepare polyimide aerogel pleated paper, there are still problems such as the paper not forming, the paper shrinking and breaking into foaming, the paper warping and curling, and it is difficult to form pleats, which makes it difficult to meet the application needs of special fields. This is mainly due to the limitations of factors such as the structural types, monomer materials, and manufacturing processes that can be used to prepare high-temperature resistant and high-strength polyimide aerogels. The main chain structure currently used is a single thermoplastic structure, and there is no consideration of how to introduce more suitable molecular structural units into the aerogel pleated material to ensure that the structural regularity and dimensional stability are maintained during the paper forming process. It forms a pleated structure with high surface quality. At the same time, there is a lack of consideration of how to consider the molecular structure in the formation of aerogel pleated materials to reduce the quality problems caused by warping, bending, and shrinkage caused by the imidization process. Summary of the Invention

[0006] The present invention aims to solve the problem that the existing method cannot prepare high-temperature resistant and high-strength polyimide aerogel corrugated paper, and further provides a high-strength polyimide aerogel corrugated paper and a preparation method thereof.

[0007] A high-strength polyimide aerogel corrugated paper is prepared from aromatic diamine, aromatic dianhydride, a catalyst and a solvent;

[0008] The molar ratio of the aromatic diamine to the aromatic dianhydride is 1:(0.9-1.2); the molar ratio of the total moles of the aromatic diamine and the aromatic dianhydride to the catalyst is 1:(4-5); the mass ratio of the total mass of the aromatic diamine and the aromatic dianhydride to the solvent is 1:(30-100);

[0009] The aromatic diamine is 4',4'-diaminodiphenyl ether, 4',4'-diaminodiphenylmethane, all-para-triphenyl diether diamine, all-meta-triphenyl diether diamine or 3,3'-dimethyl-4,4'-diaminodiphenylmethane;

[0010] The aromatic dianhydride is 3,3',4,4'-biphenyltetracarboxylic dianhydride or 4',4'-biphenyl ether dianhydride;

[0011] When the aromatic dianhydride is 3,3,4',4'-biphenyltetracarboxylic dianhydride, the repeating unit of the polyimide in the polyimide aerogel corrugated paper is

[0012] The R2 is

[0013] When the aromatic dianhydride is 4',4'-biphenyl ether dianhydride, the repeating unit of the polyimide in the polyimide aerogel corrugated paper is

[0014] The R3 is

[0015]

[0016] A method for preparing high-strength polyimide aerogel corrugated paper is carried out according to the following steps:

[0017] 1. Weigh:

[0018] Weighing aromatic diamine, aromatic dianhydride, catalyst and solvent, dividing the weighed solvent into solvent A and solvent B at a volume ratio of 1:(2-5), and dividing the weighed catalyst into catalyst A and catalyst B at a mass ratio of 1:(2-2.5);

[0019] The molar ratio of the aromatic diamine to the aromatic dianhydride is 1:(0.9-1.2); the molar ratio of the total moles of the aromatic diamine and the aromatic dianhydride to the catalyst is 1:(4-5); the mass ratio of the total mass of the aromatic diamine and the aromatic dianhydride to the solvent is 1:(30-100);

[0020] 2. Preparation of polyamic acid solution:

[0021] Add solvent A to aromatic diamine, stir at a temperature of 40°C to 50°C, add catalyst A during stirring, stir until the aromatic diamine is completely dissolved, then add aromatic dianhydride, catalyst B and solvent B at a temperature of 40°C to 50°C, stir until the aromatic dianhydride is completely dissolved, and then heat at a temperature of 50°C to 65°C with stirring for 2h to 4h to obtain a polyamic acid solution;

[0022] 3. Preparation of polyimide aerogel:

[0023] The polyamic acid solution is poured into a mold and frozen, and then freeze-dried in a vacuum to obtain an anhydrous loose porous aerogel;

[0024] 4. Preparation of polyimide aerogel pleated paper:

[0025] The anhydrous loose porous aerogel is extruded and pretreated to obtain a paper sheet, and the paper sheet is subjected to gradient heating and thermal imidization, and finally cooled to room temperature to obtain the polyimide aerogel corrugated paper.

[0026] The beneficial effects of the present invention are:

[0027] The high-strength polyimide aerogel pleated paper of the present invention utilizes an aromatic diamine containing an ether bond and a single methylene "bridging" group (CXC, where C is a C on the benzene ring and X is a methylene or oxygen atom). Due to the presence of this "bridging" group, the benzene can rotate about the CX axis. Furthermore, when X is a methylene or oxygen atom, the angle between CXC is approximately 110-125°. This angle causes the main chains of the molecules to exhibit a zigzag arrangement when forming a polyamic acid solution. During the paper-forming process, these zigzag molecular chains are stacked layer by layer to form the pleated paper. The polyamic acid repeating units possess high bond energies (20kJ / mol to 40kJ / mol) due to the presence of intermolecular hydrogen bonds (NH···O=C). Furthermore, the presence of high-molecular-weight polyamic acid repeating structural units enables the formation of multiple intermolecular hydrogen bonds.

[0028] In addition, due to the intervention of hinge linkers (-O-, -CO-, -CH2-, etc.), when large rigid units (such as s-BPDA and ODPA) move like soft chains, it is easy to find the excellent orientation of the polyimide chain. The aggregated structure of the originally rigid rod-shaped molecular chains exhibits a liquid crystal state. This is because the rigid chains form an ordered structure, and the ordered structure is small in size. The melting point of the ordered region is very high, which makes it easy to form an orientation. However, for soft chains, which are generally amorphous, the molecular chains slide easily along the molecular axis, making it difficult to form an ordered region. The combination of rigid and soft chains will induce the flexible chains to crystallize, forming a certain ordered structure. However, due to the difference in surface energy of the molecular chains themselves, wrinkles will form during the induction process. This rigidity of polyimide is the simplest indicator of its high glass transition temperature and modulus.

[0029] The synergistic effects of multiple intermolecular hydrogen bonds, p-π conjugation, π-π stacking, and layered main chain molecular stacking provide further possibilities for self-organization. Furthermore, the use of aromatic diamines and dianhydrides, along with the introduction of benzene ring groups into the molecular backbone, allows for molecular chain stacking and higher-order assembly, resulting in high strength. The preparation method employs an aromatic diamine containing an ether bond and a single methylene "bridging" group (CXC, where C is a C on the benzene ring and X is a methylene or oxygen atom). This bridging group allows for rotation of the benzene around the CX axis. Theoretically, the resulting polyimide aerogel should be flexible, with reduced thermal stability and Tg. However, the synergistic effects of multiple intermolecular hydrogen bonds, p-π conjugation, π-π stacking, and layered main chain molecular stacking modulate strength. Surprisingly, this synergistic effect of layered main chain molecular stacking significantly enhances paper strength, properties not achieved or mentioned in related literature and patents.

[0030] In addition, the main chain structures used in the present invention are all aromatic ring structures, which have extremely good thermal and oxygen stability and bulk strength, and have the best bulk performance among current paper products, laying the foundation for paper products to be used as high-performance special functional materials for aerospace.

[0031] In addition, the preparation method of the present invention is different from other preparation methods in that it has the following characteristics:

[0032] (1) The operation process is simple and does not require the multi-step pretreatment (pulping, beating, filling, cutting, etc.) required for the preparation of ordinary paper (A4 paper, kraft paper);

[0033] (2) No need to introduce functional fillers. The preparation process of special high-strength paper often requires the introduction of some functional fillers (carbon fiber, glass fiber, talc, etc.). In addition, the introduction of fillers will cause serious water pollution and waste disposal problems;

[0034] (3) Water is used as the solvent during the preparation process, and no organic solvent is required for in-situ polymerization, and no multi-step chemical treatment is involved;

[0035] (4) Instead of using supercritical carbon dioxide drying and chemical drying to obtain PI aerogel, a simple, cheap, green and safe freeze-drying technology was used; and in the process from polyamic acid to polyimide, thermal imidization was selected instead of chemical imidization.

[0036] In summary, the process of this method is easy to control and is mainly suitable for the treatment of small batches of aqueous solutions. The most important thing is that it saves time and effort, and is environmentally friendly and green. It can produce high-strength corrugated specialty paper with no warping or curling, regular structure and stable dimensions. The highest room temperature tensile strength can reach 220MPa, and the high-temperature tensile strength can reach 46MPa. These values ​​are far higher than those of similar polyimide paper (139MPa), and it has good application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 This is a physical picture of the polyimide aerogel corrugated paper prepared in Example 1;

[0038] Figure 2 This is a scanning electron microscope image of the cross section of the polyimide aerogel corrugated paper prepared in Example 1;

[0039] Figure 3 This is a surface scanning electron microscope image of the polyimide aerogel corrugated paper prepared in Example 1;

[0040] Figure 4 This is the infrared spectrum of the polyimide aerogel corrugated paper prepared in Example 1. DETAILED DESCRIPTION

[0041] Specific embodiment 1: A high-strength polyimide aerogel corrugated paper of this embodiment is prepared from aromatic diamine, aromatic dianhydride, catalyst and solvent;

[0042] The molar ratio of the aromatic diamine to the aromatic dianhydride is 1:(0.9-1.2); the molar ratio of the total moles of the aromatic diamine and the aromatic dianhydride to the catalyst is 1:(4-5); the mass ratio of the total mass of the aromatic diamine and the aromatic dianhydride to the solvent is 1:(30-100);

[0043] The aromatic diamine is 4',4'-diaminodiphenyl ether, 4',4'-diaminodiphenylmethane, all-para-triphenyl diether diamine, all-meta-triphenyl diether diamine or 3,3'-dimethyl-4,4'-diaminodiphenylmethane;

[0044] The aromatic dianhydride is 3,3',4,4'-biphenyltetracarboxylic dianhydride or 4',4'-biphenyl ether dianhydride;

[0045] When the aromatic dianhydride is 3,3,4',4'-biphenyltetracarboxylic dianhydride, the repeating unit of the polyimide in the polyimide aerogel corrugated paper is

[0046] The R2 is

[0047]

[0048] When the aromatic dianhydride is 4',4'-biphenyl ether dianhydride, the repeating unit of the polyimide in the polyimide aerogel corrugated paper is

[0049] The R3 is

[0050] The 4',4'-diaminodiphenyl ether described in this specific embodiment is abbreviated as ODA, the 4',4'-diaminodiphenylmethane described is abbreviated as MDA, the all-para-triphenyl diether diamine described is abbreviated as 1,3,4-APB, the all-meta-triphenyl diether diamine described is abbreviated as 1,3,3-APB, the 3,3'-dimethyl-4,4'-diaminodiphenylmethane described is abbreviated as DMMDA; the 3,3',4,4'-biphenyltetracarboxylic dianhydride described is abbreviated as s-BPDA, and the 4',4'-biphenyl ether dianhydride described is abbreviated as ODPA.

[0051] The beneficial effects of this specific embodiment are:

[0052] The high-strength polyimide aerogel pleated paper of this specific embodiment uses an aromatic diamine containing an ether bond and a single methylene "bridging" group (CXC, where C is a C on the benzene ring and X is a methylene or oxygen atom). Due to the presence of this "bridging" group, the benzene can rotate around the CX axis. When X is a methylene or oxygen atom, the angle between CXC is approximately 110-125°. It is precisely because of this angle that the main chain of the molecules exhibits a zigzag arrangement when forming a polyamic acid solution. During the paper forming process, these zigzag molecular chains are stacked layer by layer to form the pleated paper. Among them, the polyamic acid repeating unit has a high bond energy (20kJ / mol to 40kJ / mol) due to the intermolecular hydrogen bond containing NH···O=C. At the same time, the presence of the high molecular weight polyamic acid repeating structural unit can form multiple intermolecular hydrogen bonds.

[0053] In addition, due to the intervention of hinge linkers (-O-, -CO-, -CH2-, etc.), when large rigid units (such as s-BPDA and ODPA) move like soft chains, it is easy to find the excellent orientation of the polyimide chain. The aggregated structure of the originally rigid rod-shaped molecular chains exhibits a liquid crystal state. This is because the rigid chains form an ordered structure, and the ordered structure is small in size. The melting point of the ordered region is very high, which makes it easy to form an orientation. However, for soft chains, which are generally amorphous, the molecular chains slide easily along the molecular axis, making it difficult to form an ordered region. The combination of rigid and soft chains will induce the flexible chains to crystallize, forming a certain ordered structure. However, due to the difference in surface energy of the molecular chains themselves, wrinkles will form during the induction process. This rigidity of polyimide is the simplest indicator of its high glass transition temperature and modulus.

[0054] The synergistic effects of multiple intermolecular hydrogen bonds, p-π conjugation, π-π stacking, and layered main chain molecular stacking provide further possibilities for self-organization. Furthermore, the use of aromatic diamines and dianhydrides, along with the introduction of benzene ring groups into the molecular backbone, allows for molecular chain stacking and higher-order assembly, resulting in high strength. The preparation method employs an aromatic diamine containing an ether bond and a single methylene "bridging" group (CXC, where C is a C on the benzene ring and X is a methylene or oxygen atom). This bridging group allows for rotation of the benzene around the CX axis. Theoretically, the resulting polyimide aerogel should be flexible, with reduced thermal stability and Tg. However, the synergistic effects of multiple intermolecular hydrogen bonds, p-π conjugation, π-π stacking, and layered main chain molecular stacking modulate strength. Surprisingly, this synergistic effect of layered main chain molecular stacking significantly enhances paper strength, properties not achieved or mentioned in related literature and patents.

[0055] In addition, the main chain structures used in this specific embodiment are all aromatic ring structures, which have extremely good thermal and oxygen stability and bulk strength, and have the best bulk performance among current paper products, laying the foundation for paper products to be used as high-performance special functional materials for aerospace.

[0056] In addition, the preparation method of this embodiment is different from other preparation methods in that it has the following characteristics:

[0057] (5) The operation process is simple and does not require the multi-step pretreatment (pulping, beating, filling, cutting, etc.) required for the preparation of ordinary paper (A4 paper, kraft paper);

[0058] (6) No need to introduce functional fillers. The preparation process of special high-strength paper often requires the introduction of some functional fillers (carbon fiber, glass fiber, talc, etc.). In addition, the introduction of fillers will cause serious water pollution and waste disposal problems;

[0059] (7) Water is used as the solvent during the preparation process, and there is no need to use organic solvents as solvents for in-situ polymerization, and no multi-step chemical treatment is involved;

[0060] (8) Instead of using supercritical carbon dioxide drying and chemical drying to obtain PI aerogel, a simple, cheap, green and safe freeze-drying technology was used; and in the process from polyamic acid to polyimide, thermal imidization was selected instead of chemical imidization.

[0061] In summary, the process of this method is easy to control and is mainly suitable for the treatment of small batches of aqueous solutions. The most important thing is that it saves time and effort, and is environmentally friendly and green. It can produce high-strength corrugated specialty paper with no warping or curling, regular structure and stable dimensions. The highest room temperature tensile strength can reach 220MPa, and the high-temperature tensile strength can reach 46MPa. These values ​​are far higher than those of similar polyimide paper (139MPa), and it has good application prospects.

[0062] Specific embodiment 2: This embodiment differs from specific embodiment 1 in that the catalyst is triethylamine. Other aspects are the same as specific embodiment 1.

[0063] Specific embodiment 3: This embodiment differs from specific embodiment 1 or 2 in that the solvent is water. Other aspects are the same as specific embodiment 1 or 2.

[0064] Specific embodiment 4: This embodiment provides a method for preparing high-strength polyimide aerogel corrugated paper, which is characterized by being carried out in the following steps:

[0065] 1. Weigh:

[0066] Weighing aromatic diamine, aromatic dianhydride, catalyst and solvent, dividing the weighed solvent into solvent A and solvent B at a volume ratio of 1:(2-5), and dividing the weighed catalyst into catalyst A and catalyst B at a mass ratio of 1:(2-2.5);

[0067] The molar ratio of the aromatic diamine to the aromatic dianhydride is 1:(0.9-1.2); the molar ratio of the total moles of the aromatic diamine and the aromatic dianhydride to the catalyst is 1:(4-5); the mass ratio of the total mass of the aromatic diamine and the aromatic dianhydride to the solvent is 1:(30-100);

[0068] 2. Preparation of polyamic acid solution:

[0069] Add solvent A to aromatic diamine, stir at a temperature of 40°C to 50°C, add catalyst A during stirring, stir until the aromatic diamine is completely dissolved, then add aromatic dianhydride, catalyst B and solvent B at a temperature of 40°C to 50°C, stir until the aromatic dianhydride is completely dissolved, and then heat at a temperature of 50°C to 65°C with stirring for 2h to 4h to obtain a polyamic acid solution;

[0070] 3. Preparation of polyimide aerogel:

[0071] The polyamic acid solution is poured into a mold and frozen, and then freeze-dried in a vacuum to obtain an anhydrous loose porous aerogel;

[0072] 4. Preparation of polyimide aerogel pleated paper:

[0073] The anhydrous loose porous aerogel is extruded and pretreated to obtain a paper sheet, and the paper sheet is subjected to gradient heating and thermal imidization, and finally cooled to room temperature to obtain the polyimide aerogel corrugated paper.

[0074] Specific embodiment 5: This embodiment differs from specific embodiment 4 in that the solid content of the polyamic acid solution prepared in step 2 is 1% to 5%. Other aspects are the same as specific embodiment 4.

[0075] Specific embodiment 6: This embodiment differs from either specific embodiment 4 or 5 in that, in step 3, the polyamic acid solution is poured into a mold, frozen at a temperature of -20°C to -25°C for 1 to 2 hours, and then vacuum-dried at a temperature of -20°C to -25°C for 24 to 36 hours. Otherwise, the same as specific embodiment 4 or 5.

[0076] Specific embodiment 7: This embodiment differs from any one of specific embodiments 4 to 6 in that the thickness of the anhydrous loose porous aerogel prepared in step 3 is 2 mm to 3 mm. Other aspects are the same as specific embodiments 4 to 6.

[0077] Specific embodiment eight: This embodiment differs from any one of specific embodiments four to seven in that in step four, a laminator is used to pre-extrusion-treat the anhydrous loose porous aerogel to obtain a paper sheet. The rest is the same as specific embodiments six or four to seven.

[0078] Specific embodiment 9: This embodiment differs from any one of specific embodiments 4 to 8 in that the thickness of the paper sheet in step 4 is 30 μm to 40 μm. Other aspects are the same as specific embodiments 4 to 8.

[0079] Specific embodiment ten: This embodiment differs from specific embodiments four to eight in that the gradient temperature rise thermal imidization described in step four is specifically carried out according to the following steps: ① Raise the temperature to 80℃~100℃ at a heating rate of 1℃ / min~10℃ / min, and keep the temperature at 80℃~100℃ for 50min~80min; ② Raise the temperature from 80℃~100℃ to 180℃~200℃ at a heating rate of 1℃ / min~10℃ / min, and keep the temperature at 180℃~200℃ for 50min~80min; ℃, and keep warm for 60 minutes to 70 minutes; ③ Raise the temperature from 180℃ to 200℃ to 280℃ to 300℃ at a heating rate of 1℃ / min to 10℃ / min, and keep warm at 280℃ to 300℃ for 60 minutes to 70 minutes; ④ Raise the temperature from 280℃ to 300℃ to 380℃ to 400℃ at a heating rate of 1℃ / min to 10℃ / min, and keep warm at 380℃ to 400℃ for 60 minutes to 70 minutes. Other steps are the same as those in Specific Embodiments 4 to 8.

[0080] The following examples are used to verify the beneficial effects of the present invention:

[0081] Example 1:

[0082] A high-strength polyimide aerogel corrugated paper is prepared from aromatic diamine, aromatic dianhydride, a catalyst and a solvent;

[0083] The molar ratio of the aromatic diamine to the aromatic dianhydride is 1:1; the molar ratio of the total moles of the aromatic diamine and the aromatic dianhydride to the catalyst is 1:4.5; the mass ratio of the total mass of the aromatic diamine and the aromatic dianhydride to the solvent is 1:100;

[0084] The aromatic diamine is 4',4'-diaminodiphenyl ether;

[0085] The aromatic dianhydride is 3,3',4,4'-biphenyltetracarboxylic dianhydride;

[0086] The repeating unit of polyimide in the polyimide aerogel corrugated paper is

[0087] The R2 is

[0088] The catalyst is triethylamine;

[0089] The solvent is water.

[0090] The method for preparing the high-strength polyimide aerogel corrugated paper is carried out according to the following steps:

[0091] 1. Weigh:

[0092] Weighing aromatic diamine, aromatic dianhydride, catalyst and solvent, dividing the weighed solvent into solvent A and solvent B at a volume ratio of 1:2, and dividing the weighed catalyst into catalyst A and catalyst B at a mass ratio of 1:2;

[0093] 2. Preparation of polyamic acid solution:

[0094] Solvent A was added to aromatic diamine, and the mixture was stirred at 45°C. Catalyst A was added during the stirring process, and the mixture was stirred until the aromatic diamine was completely dissolved. Then, aromatic dianhydride, catalyst B, and solvent B were added at 45°C, and the mixture was stirred until the aromatic dianhydride was completely dissolved. The mixture was then heated at 55°C with stirring for 4 hours to obtain a polyamic acid solution.

[0095] The solid content of the polyamic acid solution is 1%;

[0096] 3. Preparation of polyimide aerogel:

[0097] The polyamic acid solution was poured into a mold, frozen at -20°C for 1 hour, and then vacuum dried at -20°C for 36 hours to obtain an anhydrous loose porous aerogel.

[0098] The anhydrous loose porous aerogel has a thickness of 3 mm and a size of 8 cm × 8 cm;

[0099] 4. Preparation of polyimide aerogel pleated paper:

[0100] Using a laminator, the water-free loose porous aerogel is extruded and pre-treated to obtain a paper sheet, which is then subjected to gradient heating for thermal imidization and finally cooled to room temperature to obtain polyimide aerogel corrugated paper;

[0101] The thickness of the paper sheet is 35 μm;

[0102] The gradient temperature rise thermal imidization is specifically carried out according to the following steps: ① heating to 100°C at a heating rate of 10°C / min, and keeping the temperature at 100°C for 60 minutes; ② heating from 100°C to 200°C at a heating rate of 10°C / min, and keeping the temperature at 200°C for 60 minutes; ③ heating from 200°C to 300°C at a heating rate of 10°C / min, and keeping the temperature at 300°C for 60 minutes; ④ heating from 300°C to 400°C at a heating rate of 10°C / min, and keeping the temperature at 400°C for 60 minutes.

[0103] The mold described in step three is a homemade mold, with aluminum as the base plate and thin rubber strips for limiting.

[0104] Example 2: This example is different from Example 1 in that the aromatic diamine is 4',4'-diaminodiphenyl ether; the aromatic dianhydride is 4',4'-biphenyl ether dianhydride; the repeating unit of the polyimide in the polyimide aerogel corrugated paper is The R3 is The rest is the same as that of the first embodiment.

[0105] Example 3: This example differs from Example 1 in that the mass ratio of the total mass of the aromatic diamine and aromatic dianhydride to the solvent is 1:30; the aromatic diamine is 4',4'-diaminodiphenylmethane; the aromatic dianhydride is 3,3',4,4'-biphenyltetracarboxylic dianhydride; and the repeating unit of the polyimide in the polyimide aerogel corrugated paper is The R2 is The solid content of the polyamic acid solution prepared in step 2 is 3%. Other steps are the same as those in Example 1.

[0106] Example 4: This example differs from Example 1 in that the mass ratio of the total mass of the aromatic diamine and aromatic dianhydride to the solvent is 1:30; the aromatic diamine is 3,3'-dimethyl-4,4'-diaminodiphenylmethane; the aromatic dianhydride is 4',4'-diphenyl ether dianhydride; the repeating unit of the polyimide in the polyimide aerogel corrugated paper is The R3 is The solid content of the polyamic acid solution prepared in step 2 is 3%. Other steps are the same as those in Example 1.

[0107] Example 5: This example differs from Example 2 in that the molar ratio of the aromatic diamine to the aromatic dianhydride is 1:1.02; the mass ratio of the total mass of the aromatic diamine and aromatic dianhydride to the solvent is 1:60; and the solid content of the polyamic acid solution prepared in step 2 is 2%. Other steps are the same as in Example 2.

[0108] Example 6: This example differs from Example 3 in that the molar ratio of the total moles of the aromatic diamine and aromatic dianhydride to the catalyst is 1:4.8; the mass ratio of the total mass of the aromatic diamine and aromatic dianhydride to the solvent is 1:60; and the solid content of the polyamic acid solution prepared in step 2 is 2%. Other steps are the same as those in Example 3.

[0109] Comparative Experiment 1: The difference between this embodiment and the first embodiment is that the aromatic diamine is replaced by 1,4-cyclohexanediamine (HPDA); the repeating unit of the polyimide in the polyimide aerogel corrugated paper is The solid content of the polyamic acid solution prepared in step 2 is 2%. Other steps are the same as those in Example 1.

[0110] Comparative Experiment 2: The difference between this embodiment and the first embodiment is that the aromatic dianhydride is replaced by 4,4'-(hexafluoroisopropylene) diphthalic anhydride; the repeating unit of the polyimide in the polyimide aerogel corrugated paper is The solid content of the polyamic acid solution prepared in step 2 is 2%. Other steps are the same as those in Example 1.

[0111] Table 1 Examples and comparative experimental components

[0112]

[0113] The polyimide aerogel corrugated papers prepared in Examples 1 to 6 and Comparative Experiments 1 to 2 were subjected to the following tests:

[0114] Glass transition temperature: tested using differential scanning calorimetry (DSC) with a heating rate of 10°C / min.

[0115] 5% thermal weight loss temperature: The test was performed using a thermal gravimetric analyzer (TGA). Heating rate: 10°C / min; test atmosphere: air.

[0116] Carbon residue rate at 800°C: Tested using a thermogravimetric analyzer (TGA). Heating rate: 10°C / min; Test atmosphere: nitrogen.

[0117] Tensile Strength: The test was conducted using a large-capacity dynamic mechanical analyzer (DMA 3200) for room temperature and high temperature tensile tests. The DMA 3200 used a tensile fixture in dynamic mode. The specimens were 3-5 mm wide, 2-3 cm long, and 0.03-0.05 mm thick. Three specimens were used for each test. The tests were conducted at different temperatures (room temperature and 300°C) at a tensile speed of 2 mm / min. The strength was calculated using the formula: σ = F / S, where σ is the strength, F is the maximum force in the specimen during tension, and S is the original cross-sectional area of ​​the specimen.

[0118] Storage modulus: The test was performed using a dynamic mechanical analyzer (DMA). The heating rate was 5°C / min and the test atmosphere was air.

[0119] Limiting oxygen index: The test was performed using an oxygen index meter (SS-1005, Yihai Datong Instrument Equipment Co., Ltd., Shenyang, China) according to the test method of GBT2406-2009. The sample size was 120×50×0.05 mm.

[0120] Water absorption: The determination was carried out using an analytical electronic balance (Sartorius, Germany) according to the calculation formula: water absorption = (wet weight - dry weight) / dry weight × 100%, where wet weight refers to the mass obtained after the paper is immersed in ultrapure water for 24 h.

[0121] Elongation: An electronic universal material testing machine (USA, INSTRON 5969) was used with a tensile speed of 2 mm / min. Elongation was calculated according to the formula: (L2-L1) / L1×100%, where L1 is the length of the paper before stress and L2 is the length of the paper after stress.

[0122] Shrinkage: The test was conducted using a Puyun PY-H801B microcomputer horizontal paper shrinkage tester (Puyun Electronics Co., Ltd., Shenzhen, China). The paper was immersed in ultrapure water at 25°C for 24 hours and then removed from the water. The relative change in size after air-drying was calculated and expressed as a percentage of the original sample size.

[0123] Roughness: The test was performed using a surface roughness measuring instrument (Weifang Huaqi Instrument Co., Ltd., China).

[0124] Contact angle: A contact angle meter (Krues, Germany) was used, and the test liquid was ultrapure water.

[0125] Density: The density of the aerogel paper sample was measured using an electronic density meter (WLD-120E, China Co., Ltd.).

[0126] Air permeability: The test was performed using a paper air permeability tester (Jinan Saicheng Electronic Technology Co., Ltd., China).

[0127] Folding resistance: The test was conducted using a paper folding resistance tester (Jinan Sanquan Zhongshi Experimental Instrument Co., Ltd., China). Test parameters: At room temperature, a piece of paper cut into 5 cm × 1 cm was folded back and forth until the paper broke.

[0128] Moisture content: The test adopts an analytical electronic balance (Sartorius, Germany) and a drying method, that is, several samples are taken from different parts, about 50g of the sample is weighed on a balance, and the pieces are torn into pieces and placed in an oven to dry to constant weight to calculate the moisture content.

[0129] Smoothness: The test was performed using a paper smoothness tester (Jinan Sanquan Zhongshi Experimental Instrument Co., Ltd., China).

[0130] Table 2 Properties of pleated paper

[0131]

[0132]

[0133] Comparative experiments show that not using aromatic diamines containing ether bonds and single methylene bridge groups, and not using π-π or p-π effects (specific fully aromatic structures composed of rigid rod-like structures), will result in the formed polyimide aerogel paper having low strength and even being difficult to form.

[0134] Examples 1 to 6 can all provide high-strength polyimide aerogel corrugated paper.

[0135] At the same time, Examples 1, 4, and 6 have higher room temperature and high temperature (300°C) tensile strengths due to the multiple π-π and p-π interactions in the molecular main chain, the mutual combination of rigid chains and flexible chains, and the formation of crystallization-induced ordered regions. The highest room temperature tensile strength can reach 220 MPa, which is far higher than that of similar polyimide paper (139 MPa), and has good application prospects.

[0136] Figure 1 This is a physical picture of the polyimide aerogel corrugated paper prepared in Example 1; as can be seen from the figure, the polyimide aerogel corrugated paper was successfully synthesized, the paper has no warping or curling, and has a regular structure and stable dimensions.

[0137] Figure 2 This is a scanning electron microscope image of the cross section of the polyimide aerogel corrugated paper prepared in Example 1. As can be seen from the figure, the paper prepared in this example also forms corrugations in the internal single layer at the micron scale, with many interlayer binding sites and strong binding force.

[0138] Figure 3 This is a surface scanning electron microscope image of the polyimide aerogel corrugated paper prepared in Example 1. As can be seen from the image, the paper prepared in this example also has corrugations formed on the surface at the micrometer scale.

[0139] Figure 4 This is an infrared spectrum of the polyimide aerogel corrugated paper prepared in Example 1. As can be seen from the figure, there is absorption at the characteristic peak of polyimide, indicating that the paper prepared in this example is successfully synthesized in terms of molecular structure.

Claims

1. A high-strength polyimide aerogel corrugated paper, characterized in that It is prepared from aromatic diamine, aromatic dianhydride, catalyst and solvent; The molar ratio of the aromatic diamine to the aromatic dianhydride is 1:(0.9-1.2); the molar ratio of the total moles of the aromatic diamine and the aromatic dianhydride to the catalyst is 1:(4-5); the mass ratio of the total mass of the aromatic diamine and the aromatic dianhydride to the solvent is 1:(30-100); The aromatic diamine is 4',4'-diaminodiphenyl ether, 4',4'-diaminodiphenylmethane, all-para-triphenyl diether diamine, all-meta-triphenyl diether diamine or 3,3'-dimethyl-4,4'-diaminodiphenylmethane; The aromatic dianhydride is 3,3',4,4'-biphenyltetracarboxylic dianhydride or 4',4'-biphenyl ether dianhydride; When the aromatic dianhydride is 3,3,4',4'-biphenyltetracarboxylic dianhydride, the repeating unit of the polyimide in the polyimide aerogel corrugated paper is ; The R2 is 、 、 、 or ; When the aromatic dianhydride is 4',4'-biphenyl ether dianhydride, the repeating unit of the polyimide in the polyimide aerogel corrugated paper is ; The R3 is 、 、 、 or .

2. The high-strength polyimide aerogel corrugated paper according to claim 1, characterized in that The catalyst is triethylamine.

3. The high-strength polyimide aerogel corrugated paper according to claim 1, characterized in that The solvent is water.

4. The method for preparing a high-strength polyimide aerogel corrugated paper according to claim 1, characterized in that It is carried out in the following steps:

1. Weigh: Weighing aromatic diamine, aromatic dianhydride, catalyst and solvent, dividing the weighed solvent into solvent A and solvent B at a volume ratio of 1:(2-5), and dividing the weighed catalyst into catalyst A and catalyst B at a mass ratio of 1:(2-2.5); The molar ratio of the aromatic diamine to the aromatic dianhydride is 1:(0.9-1.2); the molar ratio of the total moles of the aromatic diamine and the aromatic dianhydride to the catalyst is 1:(4-5); the mass ratio of the total mass of the aromatic diamine and the aromatic dianhydride to the solvent is 1:(30-100); 2. Preparation of polyamic acid solution: Add solvent A to aromatic diamine, stir at a temperature of 40°C to 50°C, add catalyst A during stirring, and stir until the aromatic diamine is completely dissolved, then add aromatic dianhydride, catalyst B and solvent B at a temperature of 40°C to 50°C, stir until the aromatic dianhydride is completely dissolved, and then heat at a temperature of 50°C to 65°C with stirring for 2h to 4h to obtain a polyamic acid solution; 3. Preparation of polyimide aerogel: The polyamic acid solution is poured into a mold and frozen, and then freeze-dried in a vacuum to obtain an anhydrous loose porous aerogel; 4. Preparation of polyimide aerogel pleated paper: The anhydrous loose porous aerogel is extruded and pretreated to obtain a paper sheet, and the paper sheet is subjected to gradient heating and thermal imidization, and finally cooled to room temperature to obtain the polyimide aerogel corrugated paper.

5. The method for preparing high-strength polyimide aerogel corrugated paper according to claim 4, characterized in that The solid content of the polyamic acid solution prepared in step 2 is 1% to 5%.

6. The method for preparing high-strength polyimide aerogel corrugated paper according to claim 4, characterized in that In step 3, the polyamic acid solution is poured into a mold, frozen at a temperature of -20°C to -25°C for 1 hour to 2 hours, and then vacuum-dried at a temperature of -20°C to -25°C for 24 hours to 36 hours.

7. The method for preparing high-strength polyimide aerogel corrugated paper according to claim 4, characterized in that The anhydrous loose porous aerogel prepared in step 3 has a thickness of 2 mm to 3 mm.

8. The method for preparing high-strength polyimide aerogel corrugated paper according to claim 4, characterized in that Step 4: Using a film press, the anhydrous loose porous aerogel is subjected to extrusion pretreatment to obtain a paper sheet.

9. The method for preparing high-strength polyimide aerogel corrugated paper according to claim 8, characterized in that The thickness of the paper sheet described in step 4 is 30 μm to 40 μm.

10. The method for preparing high-strength polyimide aerogel corrugated paper according to claim 4, characterized in that The gradient temperature rise thermal imidization described in step 4 is specifically carried out according to the following steps: ① heating to 80℃~100℃ at a heating rate of 1℃ / min~10℃ / min, and keeping the temperature at 80℃~100℃ for 50min~80min; ② heating from 80℃~100℃ to 180℃~200℃ at a heating rate of 1℃ / min~10℃ / min, and keeping the temperature at 180℃~200℃ for 60min~70min; 0min; ③ Raise the temperature from 180℃~200℃ to 280℃~300℃ at a heating rate of 1℃ / min~10℃ / min, and keep it at 280℃~300℃ for 60min~70min; ④ Raise the temperature from 280℃~300℃ to 380℃~400℃ at a heating rate of 1℃ / min~10℃ / min, and keep it at 380℃~400℃ for 60min~70min.

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