Preparation method of polyimide aerogel with hierarchical pore structure
By combining chemical preimidation method and salt template method, polyimide aerogel with graded pore structure was prepared, which solved the complexity and high cost of large-scale preparation of polyimide aerogels, achieved high-performance flexibility and thermal insulation effects, and simplified the production process.
Patent Information
- Application Number
- CN202510450185.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-11
- Publication Date
- 2025-07-11
AI Technical Summary
The large-scale preparation of polyimide aerogels faces the problems of complex processes, high costs and insufficient mechanical strength, especially in the drying process, which requires expensive supercritical drying and freeze-drying techniques, and traditional methods lead to structural failure and dimensional shrinkage.
The chemical preimidation method and the salt template method are used to synergize the polyamic acid resin solution through dianhydride and diamine monomer, add chemical imidation reagents and catalysts, and mix them, add salt particles for heat treatment to form a stable crosslinking network structure, and then dry at room temperature to avoid structural damage caused by high-temperature treatment.
The preparation process is simplified, the cost is reduced, and the polyimide aerogel with a graded pore structure is obtained, which has excellent flexibility and structural mechanical strength, effectively blocks heat transfer, and achieves green and large-scale production.
Smart Images
Figure CN120289862A_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of special polymer materials, and particularly relates to a preparation method of a polyimide aerogel with a hierarchical pore structure. Background Art
[0002] Polyimide aerogels combine the excellent thermal stability and chemical stability of polyimide materials with the low density and high specific surface area of aerogel materials, showing good application potential in many fields such as aerospace, energy, and environmental protection. However, the large-scale preparation of polyimide aerogels faces the challenge of complex processes, especially the formation and drying processes of wet gels. Particularly in the drying step, expensive supercritical drying and freeze-drying technologies are usually required to avoid volume shrinkage. In addition, in order to obtain ideal mechanical strength, expensive cross-linking agents usually need to be added, which significantly increases the production cost. Therefore, the complex manufacturing process and low mechanical strength severely limit the large-scale production and wide application of polyimide aerogels. It is of great significance to optimize and explore new synthesis methods and preparation strategies for polyimide aerogels. Summary of the Invention
[0003] This patent proposes an innovative strategy, which synergistically uses the chemical pre-imideization method and the salt template method. A polyamic acid (PAA) resin solution is synthesized using dianhydride and diamine monomers, and then a chemical imideization reagent and a catalyst are added for chemical imideization. Subsequently, salt particles are fully mixed with the PAA solution and heat-treated. This method can form a stable cross-linked network structure at the wet gel stage, and a structurally stable polyimide aerogel can be obtained after desalting and normal temperature drying. During this process, the salt particles provide support for the pores, effectively avoiding pore collapse during the heat treatment process. In addition, since water molecules are released during the chemical imideization process, and water molecules are poor solvents for the PAA resin, they will act as pore-forming agents. As the water molecules accumulate, a microporous structure will appear in the PAA resin matrix. After removing the salt particles, a unique polyimide aerogel with a hierarchical pore structure is formed, whose structural morphology consists of micropores and nanopores on the microporous walls. This hierarchical pore structure can effectively block heat transfer, and at the same time, this hierarchical topological pore structure can effectively eliminate the internal stress caused by impact and bending deformation, making it have excellent flexibility and structural mechanical strength. Additionally, importantly, this method avoids the structural damage to the polyimide aerogel material caused by high-temperature post-treatment in the traditional strategy, effectively improves problems such as high dimensional shrinkage and pore collapse, successfully simplifies the preparation process and reduces the production cost. The technical solution adopted by the present invention is as follows:
[0004] A preparation method of a polyimide aerogel with a hierarchical pore structure, comprising the following steps:
[0005] (1) Add diamine and dianhydride into a polar organic solvent in sequence, dissolve and react fully to obtain a polyamic acid prepolymer solution;
[0006] (2) Add a chemical imidization reagent and a catalyst into the polyamic acid prepolymer solution, stir evenly to obtain a mixed solution;
[0007] (3) Then add salt particles into the above mixed solution, mix fully and pour it into a mold for chemical imidization reaction, and then carry out heat setting;
[0008] (4) Take out the shaped sample from the mold, wash it with water to remove salt particles and dry it to obtain a polyimide aerogel material with a hierarchical pore structure;
[0009] Wherein, the molar ratio of the diamine monomer to the dianhydride monomer is 1: (0.98 - 1.02);
[0010] The addition amounts of the chemical imidization reagent and the catalyst added into the polyamic acid prepolymer solution are in a molar ratio of (1.5 - 2.5): (0.5 - 2.0): 1 to the diamine therein.
[0011] Preferably, in (1): the monomer of the dianhydride is one of pyromellitic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 3,3',4,4-benzophenone tetracarboxylic dianhydride, 4,4'-diphenylether dianhydride, 4,4-(hexafluoroisopropylidene) diphthalic anhydride;
[0012] The monomer of the diamine is one or a mixture of several of diaminodiphenylmethane, p-phenylenediamine, 2-trifluoromethyl-4,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl sulfone, etc.; the chemical imidization reagent is one of acetic anhydride and propionic anhydride, and the catalyst is one or a combination of several of pyridine, triethylamine, quinoline, and isoquinoline;
[0013] The polar organic solvent is one of N,N-dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone.
[0014] Preferably, in (1) and (2): the solid content of the polyamic acid prepolymer in the polyamic acid prepolymer solution is 5wt% - 30wt%.
[0015] Preferably, in (3): the salt particles are water-soluble salt substances, and the particle size of the salt particles of the salt substances is 100μm - 1000μm;
[0016] The salt substances are one of sodium chloride, potassium chloride, sodium sulfate, and ferric chloride;
[0017] The salt substance is preferably sodium chloride particles.
[0018] Preferably, in (3): the chemical imidization temperature is between 40°C and 80°C, and the time is 2 to 6 hours.
[0019] Preferably, in (3): the heat setting process is at 100°C to 180°C, and the time is 2 to 4 hours.
[0020] Preferably, the microstructure of the prepared polyimide aerogel material with a hierarchical pore structure includes micron-sized pores and nano-sized pore structures on the pore walls of the micron-sized pores;
[0021] The micron-sized pore structure and the nano-sized pore structure together constitute a hierarchical pore structure.
[0022] Preferably, the aperture of the micron-sized pores is 100μm to 1000μm.
[0023] Preferably, the aperture of the nano-sized pores is 50nm to 20μm.
[0024] Preferably, the prepared polyimide aerogel material with a hierarchical pore structure is applied to the fields of shock absorption and thermal insulation materials.
[0025] Compared with the prior art, the beneficial effects achieved by the present invention are as follows:
[0026] (1) Outstanding thermal insulation performance and flexibility: This patent uses the chemical imidization method combined with the salt template method to prepare a polyimide aerogel with a hierarchical pore structure. The structural morphology of the prepared polyimide aerogel with a hierarchical pore structure is a hierarchical pore structure composed of micropores and nanopores on the micropore walls. This hierarchical pore structure can effectively block heat transfer, and the thermal conductivity at room temperature can reach 0.026 W / (m·K), and the overall is between 0.026 - 0.030 W / (m·K). At the same time, this hierarchical topological structure can effectively eliminate the internal stress caused by impact and bending deformation, making it have excellent structural flexibility and mechanical strength.
[0027] (2) Extremely low dimensional shrinkage rate: The dimensional shrinkage of polyimide aerogel mainly occurs in the imidization stage. Especially, conventional high-temperature thermal imidization will cause obvious dimensional shrinkage. In the method adopted in this patent, imidization is completed under the spatial support of the salt template, so no obvious dimensional shrinkage occurs during imidization, and the overall dimensional shrinkage rate < 10%. And in the subsequent water removal and free heat treatment stages, imidization has been basically completed, so this study effectively avoids the significant volume shrinkage phenomenon. This method avoids the structural damage to the pores of polyimide aerogel caused by high-temperature post-treatment in traditional strategies, and effectively improves the problems of high dimensional shrinkage and pore collapse.
[0028] (3) Facilitate green and large-scale preparation: Compared with the supercritical drying method and freeze-drying method used in the processing and preparation of traditional polyimide aerogel materials, the preparation process has been successfully simplified, the production cost has been reduced, and the green preparation of high-performance polyimide aerogels has been achieved. Description of the Drawings
[0029] Figure 1 Electron microscope image of the polyimide aerogel with a hierarchical pore structure prepared in Example 2;
[0030] Figure 2 Electron microscope image of the polyimide aerogel with a hierarchical pore structure prepared in Example 2;
[0031] Figure 3 Infrared image of the polyimide aerogel material with a hierarchical pore structure prepared in Example 3.
[0032] The technical solutions in the embodiments of the present invention will be described below. Detailed Embodiments
[0033] A preparation method of a polyimide aerogel with a hierarchical pore structure, comprising the following steps:
[0034] (1) Add diamine and dianhydride to a polar organic solvent in sequence, dissolve and react fully to obtain a polyamic acid prepolymer solution;
[0035] (2) Add a chemical imidization reagent and a catalyst to the polyamic acid prepolymer solution, stir evenly to obtain a mixed solution;
[0036] (3) Then add salt particles to the above mixed solution, fully mix and pour it into a mold for chemical imidization reaction, and then perform heat setting;
[0037] (4) Take out the shaped sample from the mold, wash it with water to remove salt particles and dry it to obtain a polyimide aerogel material with a multi-stage pore structure;
[0038] Wherein, the molar ratio of the diamine monomer to the dianhydride monomer is 1:(0.98 - 1.02);
[0039] The addition amounts of the chemical imidization reagent and the catalyst added to the polyamic acid prepolymer solution and the molar ratio of diamine therein are (1.5 - 2.5):(0.5 - 2.0):1.
[0040] In the present application, the monomer of the dianhydride is one of pyromellitic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 3,3',4,4'-benzophenone tetracarboxylic dianhydride, 4,4'-oxydiphthalic dianhydride, 4,4'-(hexafluoroisopropylidene)diphthalic anhydride;
[0041] The monomer of the diamine is one or a mixture of several of diaminodiphenylmethane, p-phenylenediamine, 2-(trifluoromethyl)-4,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl sulfone, etc.; the chemical imidization reagent is one of acetic anhydride and propionic anhydride, and the catalyst is one or a combination of several of pyridine, triethylamine, quinoline, and isoquinoline;
[0042] The polar organic solvent is one of N,N-dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone.
[0043] In the present application, in (1) and (2): the solid content of the polyamic acid prepolymer in the polyamic acid prepolymer solution is 5 wt% to 30 wt%.
[0044] In the present application, in (3): the salt particles are water-soluble salt substances, and the particle size of the salt particles of the salt substances is 100 μm to 1000 μm;
[0045] The salt substances are one of sodium chloride, potassium chloride, sodium sulfate, ferric chloride, etc.;
[0046] The salt substances are preferably sodium chloride particles.
[0047] In the present application, in (3): the chemical imidization temperature is between 40 °C and 80 °C, and the time is 2 to 6 hours.
[0048] In the present application, in (3): the heat setting process is at 100 °C to 180 °C, and the time is 2 to 4 hours.
[0049] In the present application, the microstructure of the prepared polyimide aerogel material with a hierarchical pore structure includes micron-sized pores and nano-sized pore structures on the pore walls of the micron-sized pores;
[0050] The micron-sized pore structure and the nano-sized pore structure together constitute a hierarchical pore structure.
[0051] In the present application, the pore diameter of the micron-sized pores is 100 μm to 1000 μm.
[0052] In the present application, the pore diameter of the nano-sized pores is 50 nm to 20 μm.
[0053] In this application, the prepared polyimide aerogel material with a hierarchical pore structure is applied to the fields of shock absorption and thermal insulation materials.
[0054] It should be noted that: the polyimide aerogel material with a hierarchical pore structure described in this application includes but is not limited to being applied to the fields of shock absorption and thermal insulation materials.
[0055] The following further illustrates this application in combination with the following embodiments
[0056] Example 1
[0057] Weigh 8.88 g of 4,4'-(hexafluoroisopropylidene)diphthalic anhydride, add 58 g of N,N-dimethylformamide solution, and then add 5.64 g of 4,4'-methylenebis(2-methyl-6-ethylaniline) in batches. After fully reacting in a cold water bath, a homogeneous polyamic acid resin solution is obtained. Take the polyamic acid resin solution, add 2.5 g of the catalyst isoquinoline and 4.2 g of the chemical imidization reagent acetic anhydride. After fully mixing, add sodium chloride salt particles with an average particle size of 100 μm until it is completely infiltrated by the resin. Place it in a petri dish and heat it at 60 °C for 2 h for chemical imidization, and then perform heat setting. The heat setting process is 120 °C / 2 h. Soak the heat-set sample in water to remove salt. After the salt is completely removed, dry it at 80 °C for 2 h to obtain a polyimide aerogel with a hierarchical pore structure.
[0058] The thermal conductivity of the hierarchical pore structure polyimide aerogel prepared in this example is 0.028 W / (m·K), and the density of the polyimide aerogel prepared by this method is 0.043 g / cm 3 。
[0059] Example 2
[0060] Weigh 6 g of 3,3',4,4'-biphenyltetracarboxylic dianhydride, add 115 g of N,N-dimethylformamide solution, and then add 4 g of 4,4'-diaminodiphenyl ether in batches. After fully reacting in a cold water bath, a homogeneous polyamic acid resin solution is obtained. Take the polyamic acid resin solution, add 2.5 g of the catalyst triethylamine and 4.2 g of the chemical imidization reagent acetic anhydride. After fully mixing, add sodium chloride salt particles with an average particle size of 200 μm until it is completely infiltrated by the resin. Place it in a petri dish for heat setting. The heat setting process is 150 °C / 2 h. Soak the heat-set sample in water to remove salt. After the salt is completely removed, dry it at room temperature to obtain a polyimide aerogel with a hierarchical pore structure.
[0061] The thermal conductivity of the hierarchical pore structure polyimide aerogel prepared in this example is 0.026 W / (m·K), and the density is 0.037 g / cm 3 , Figure 1 andFigure 2 The electron microscope image of the hierarchical pore structure polyimide aerogel prepared in this example. Figure 1 The electron microscope image of the polyimide aerogel with a hierarchical pore structure prepared in this example. It can be seen from Figure 1 that the large square pores in the figure are micropores, and the upper surface of the micropore wall is rough and uneven, with finer nanoscale pores, jointly constituting a hierarchical pore structure. Figure 2 It is an enlarged view of the local micropore wall. It is further proved from Figure 2 that the upper surface of the micropore wall has finer nanoscale pores, making the whole structure show a three-dimensional network characteristic.
[0062] Example 3
[0063] Weigh 6.6 g of 3,3',4,4'-benzophenone tetracarboxylic dianhydride, add 43 g of N,N-dimethylacetamide solution, and then add 4 g of 4,4'-diaminodiphenyl ether in batches. After fully reacting in a cold water bath, a uniform polyamic acid resin solution is obtained. Take the polyamic acid resin solution, add 1.5 g of the catalyst quinoline and 4.5 g of the chemical imidization reagent acetic anhydride. After fully mixing, add potassium chloride salt particles with an average particle size of 200 μm until it is completely infiltrated by the resin. Place it in a petri dish for heat setting, and the heat setting process is 150 °C / 2 h. Soak the sample after heat setting in water to remove salt. After the salt is completely removed, dry it at 60 °C / 2 h to obtain a polyimide aerogel with a hierarchical pore structure.
[0064] The thermal conductivity of the hierarchical pore structure polyimide aerogel prepared in this example is 0.028 W / (m·K), and the density is 0.035 g / cm 3 . Figure 3 It is the infrared image of the polyimide aerogel material with a hierarchical pore structure prepared in this example. It can be found from the figure that the absorption peak in the range of 1700 cm -1 -1800 cm -1 is usually related to the stretching vibration of the carbonyl C=O. In the polyimide structure, the carbonyl group on the imide ring will produce a characteristic absorption in this region. At the same time, the stretching vibration peak of the C-N bond on the imide ring is at 1360 cm -1 , thus proving the existence of polyimide.
[0065] Example 4
[0066] Weigh 6.6 g of 3,3',4,4'-benzophenone tetracarboxylic dianhydride, add 43 g of N,N-dimethylformamide solution, and then add 4 g of 4,4'-diaminodiphenyl ether in batches. After fully reacting in a cold water bath, a uniform polyamic acid resin solution is obtained. Take the polyamic acid resin solution, add 1.6 g of catalyst triethylamine and 5.2 g of chemical imidization reagent propionic anhydride. After fully mixing, add sodium chloride salt particles with an average particle size of 500 μm until they are completely infiltrated by the resin. Place them in a petri dish for heat setting, and the heat setting process is 120 °C / 2 h. Soak the heat-set sample in water to remove salt, and after the salt is completely removed, dry it at 100 °C / 2 h to obtain a polyimide aerogel with a hierarchical pore structure.
[0067] The thermal conductivity of the hierarchical pore structure polyimide aerogel prepared in this example is 0.026 W / (m·K), and the density of the polyimide aerogel prepared by this method is 0.046 g / cm 3 .
[0068] Example 5
[0069] Weigh 2.94 g of 3,3',4,4'-biphenyltetracarboxylic dianhydride, add 117 g of N,N-dimethylformamide solution, and then add 4 g of 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl in batches. After fully reacting in a cold water bath, a uniform polyamic acid resin solution is obtained. Take the polyamic acid resin solution, add 1.3 g of catalyst isoquinoline and 3.2 g of chemical imidization reagent acetic anhydride. After fully mixing, add sodium chloride salt particles with an average particle size of 800 μm until they are completely infiltrated by the resin. Place them in a petri dish for heat setting, and the heat setting process is 150 °C / 2 h. Soak the heat-set sample in water to remove salt, and after the salt is completely removed, dry it at 80 °C / 2 h to obtain a polyimide aerogel with a hierarchical pore structure.
[0070] The thermal conductivity of the hierarchical pore structure polyimide aerogel prepared in this example is 0.03 W / (m·K), and the density of the polyimide aerogel prepared by this method is 0.042 g / cm 3 .
[0071] The above examples are used to help understand the method and its core idea of the present invention, and are not limitations on the content of the invention. Without departing from the principle of the present invention, local improvements and modifications to the present invention also fall within the protection scope of the claims of the present invention.
Claims
1. A preparation method of a polyimide aerogel with a hierarchical pore structure, characterized in that, It includes the following steps: (1) Add diamine and dianhydride into a polar organic solvent in sequence, dissolve and react fully to obtain a polyamic acid prepolymer solution; (2) Add a chemical imidization reagent and a catalyst into the polyamic acid prepolymer solution, stir evenly to obtain a mixed solution; (3) Then add salt particles into the above-mentioned mixed solution, mix fully and pour it into a mold for chemical imidization reaction, and then perform heat setting; (4) Take out the shaped sample from the mold, wash it with water to remove salt particles and dry it to obtain a polyimide aerogel material with a hierarchical pore structure; Among them, the molar ratio of the diamine monomer to the dianhydride monomer is 1:(0.98 - 1.02); The addition amounts of the chemical imidization reagent and the catalyst added into the polyamic acid prepolymer solution and the molar ratio of diamine therein are (1.5 - 2.5):(0.5 - 2.0):
1.
2. The preparation method of a polyimide aerogel with a hierarchical pore structure according to claim 1, wherein, In (1): The dianhydride monomer is one of pyromellitic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 3,3',4,4-benzophenone tetracarboxylic dianhydride, 4,4'-diphenylether dianhydride, 4,4-(hexafluoroisopropylidene) diphthalic anhydride; The diamine monomer is one or a mixture of several of diaminodiphenylmethane, p-phenylenediamine, 2-trifluoromethyl-4,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl sulfone; The chemical imidization reagent is one of acetic anhydride and propionic anhydride, and the catalyst is one or a combination of several of pyridine, triethylamine, quinoline, and isoquinoline; The polar organic solvent is one of N,N-dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone.
3. The preparation method of a polyimide aerogel with a hierarchical pore structure according to claim 1, characterized in that, In (1) and (2): The solid content of the polyamic acid prepolymer in the polyamic acid prepolymer solution is 5wt% - 30wt%.
4. The preparation method of a polyimide aerogel with a hierarchical pore structure according to claim 1, characterized in that, In (3): The salt particles are water-soluble salt substances, and the size of the salt particles is 100μm - 1000μm; The salt particles are one of sodium chloride, potassium chloride, sodium sulfate, and ferric chloride; The salt particles are preferably sodium chloride particles.
5. The preparation method of a polyimide aerogel with a hierarchical pore structure according to claim 1, characterized in that, In (3): The chemical imidization temperature is between 40°C and 80°C, and the time is 2 - 6 hours.
6. The preparation method of a polyimide aerogel with a hierarchical pore structure according to claim 1, characterized in that, In (3): The heat setting process is at 100°C - 180°C, and the time is 2 - 4 hours.
7. A method for preparing a polyimide aerogel with a hierarchical pore structure according to any one of claims 1 to 6, characterized in that, The microstructure of the prepared polyimide aerogel material with a hierarchical pore structure includes micron-sized pores and nano-sized pore structures on the pore walls of the micron-sized pores; The micron-sized pore structure and the nano-sized pore structure together constitute a hierarchical pore structure.
8. The preparation method of a polyimide aerogel with a hierarchical pore structure according to claim 7, characterized in that, The aperture of the micron-sized pores is 100μm - 1000μm.
9. The preparation method of a polyimide aerogel with a hierarchical pore structure according to claim 7, characterized in that, The aperture of the nano-sized pores is 50nm - 20μm.
10. The preparation method of a polyimide aerogel with a hierarchical pore structure according to any one of claims 1 to 6, characterized in that, The prepared polyimide aerogel material with a hierarchical pore structure is applied to the fields of shock absorption and thermal insulation materials.