Preparation method of polyimide resin reinforced aerogel
By introducing alcohol-soluble polyimide resin and optimizing the preparation process, a high-strength, low-density polyimide resin-reinforced aerogel was prepared, which solved the problem of insufficient performance of existing aerogels under high temperature and high stress, and realized the efficient application of the material and simplified production.
Patent Information
- Application Number
- CN202511515369.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-10-22
- Publication Date
- 2025-12-19
- Estimated Expiration
- Not applicable · inactive patent
AI Technical Summary
Existing aerogel materials have insufficient performance under high mechanical stress and high temperature conditions. Traditional preparation methods are complex and costly, and problems such as insufficient toughness and high density of single PI systems have not been effectively solved.
A method for preparing polyimide resin-reinforced aerogel was adopted, which involves introducing alcohol-soluble polyimide resin, gradient solvent replacement and low-temperature freeze-drying technology, and monitoring the cross-linking reaction with infrared spectroscopy to prepare a high-strength, low-density porous aerogel.
It significantly improves the tensile strength and thermal stability of aerogels, achieving a balance between lightweight and high strength. It is suitable for applications such as adsorption and catalytic support, and the process is simple, environmentally friendly and efficient.
Smart Images
Figure CN121159931A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of aerogel preparation technology, and more particularly to a method for preparing polyimide resin-reinforced aerogels. Background Technology
[0002] Traditional aerogel materials (such as silica gel and silicon dioxide-based materials) possess advantages such as high specific surface area and low density, but their inherent brittleness, poor flexibility, and limited temperature resistance (typically <300℃) make them unsuitable for applications in aerospace, electronic packaging, and other high-mechanical-stress and high-temperature environments. While pure organic polymer aerogels (such as polyurethane and cellulose derivatives) offer some flexibility, their insufficient thermal stability (thermal decomposition temperature generally below 350℃) and uneven pore size result in weak mechanical properties, further limiting their engineering applications.
[0003] In recent years, polyimide (PI) has attracted much attention due to its excellent high-temperature resistance, superior chemical inertness, and mechanical properties. However, the direct preparation of PI aerogels presents the following problems: ①The precursor polyamic acid (PAA) solution is difficult to form a film and is prone to phase separation; ② The volume shrinks drastically during high-temperature imidization, making it difficult to maintain a porous structure.
[0004] Existing technologies mostly employ supercritical drying or complex template methods, which suffer from high equipment costs, complex processes, and low yields. In addition, single PI systems still have drawbacks such as insufficient toughness and high density. Summary of the Invention
[0005] The purpose of this invention is to address the shortcomings of existing technologies by proposing a method for preparing polyimide resin-reinforced aerogels.
[0006] To achieve the above objectives, the present invention adopts the following technical solution: A method for preparing polyimide resin-reinforced aerogel, wherein the raw material composition of the polyimide resin-reinforced aerogel is as follows: 50 parts of pyromellitic dianhydride, 50 parts of 4,4'-diaminodiphenyl ether, 300 parts of N,N-dimethylformamide, 20-50 parts of alcohol-soluble polyimide resin, 1-5 parts of crosslinking agent, and 0.5-2 parts of catalyst.
[0007] Preferably, the preparation steps include: S1: Preparation of polyamic acid prepolymer; S2: Introducing polyimide resin; S3: Cross-linking reaction; S4: Aging treatment; S5: Solvent displacement; S6: Drying and shaping.
[0008] Preferably, in step S1, the specific method for preparing the polyamic acid prepolymer is as follows: In a three-necked flask equipped with a stirrer, thermometer, and nitrogen protection system, a measured amount of N,N-dimethylformamide was first added. The stirrer was turned on and nitrogen was introduced to purge air from the system. Then, pyromellitic dianhydride was slowly added, controlling the addition rate to avoid local overheating and maintaining the system temperature at 25℃±2℃. After PMDA was completely dissolved, stirring was continued to make the solution homogeneous. Then, 4,4'-diaminodiphenyl ether was added in batches. After the addition was completed, the temperature was raised to 60℃±2℃ and the reaction was carried out at a constant temperature to obtain a polyamic acid prepolymer solution.
[0009] Preferably, in step S2, the specific method of introducing the polyimide resin is as follows: The prepared polyamic acid prepolymer solution was cooled to 30℃±2℃, and the pre-prepared alcohol-soluble polyimide resin solution was slowly added while stirring. The mixture was stirred for 2 hours to ensure that the two were fully mixed and formed a stable composite solution.
[0010] Preferably, in step S3, the crosslinking reaction is carried out in the following manner: An appropriate amount of crosslinking agent, ethylenediamine, is added to the composite solution. The amount of ethylenediamine is determined according to the target crosslinking density. Triethylamine is added as a catalyst. After the reaction is completed, a wet gel with a crosslinked structure is obtained.
[0011] Preferably, in step S4, the aging process is specifically performed as follows: The obtained wet gel was allowed to age at room temperature for 24 hours, with the relative humidity of the aging environment controlled at 50%±5%.
[0012] Preferably, in step S5, the solvent replacement method is as follows: DMF in wet gels was removed using a gradient solvent displacement method. First, acetone was used as a transition solvent, and the wet gel was immersed in acetone. Fresh acetone was replaced every 6 hours for a total of 3 displacements. Then, ethanol was used to continue displacing the acetone, and fresh ethanol was replaced every 6 hours for a total of 3 displacements. Finally, the gel was washed 2-3 times with deionized water to remove residual organic solvents and impurities. After each displacement, the container was gently shaken to allow the solvent to fully penetrate into the gel.
[0013] Preferably, in step S6, the specific method of drying and molding is as follows: The wet gel after solvent replacement treatment was placed in a freeze dryer for drying; the freezing temperature was set to -50℃±2℃, the vacuum degree was maintained at 10Pa-50Pa, and the drying time was 72h; after drying, a polyimide resin-reinforced aerogel product was obtained.
[0014] Preferably, in step S2, the solid content of the alcohol-soluble polyimide resin solution is 30%-50%, and the addition rate is controlled at 1 / 3 of the total amount added per hour.
[0015] Preferably, in step S3, the system is heated to 80℃±2℃ during the crosslinking reaction and kept at a constant temperature for 3 hours to ensure the crosslinking reaction proceeds fully; during the reaction, the degree of crosslinking is monitored by sampling and analysis, and the changes in specific functional groups are detected by infrared spectroscopy.
[0016] The beneficial effects of this invention are as follows: 1. This invention significantly improves the tensile strength of the material by introducing alcohol-soluble polyimide resin as a reinforcing phase, while maintaining low density, thus achieving a balance between lightweight and high strength; the resulting aerogel has a high specific surface area and a uniformly distributed three-dimensional porous network, making it suitable for adsorption, catalytic support and other fields.
[0017] 2. This invention employs gradient solvent replacement to effectively remove residual solvent, combined with low-temperature freeze-drying technology to ensure the integrity of the pore structure without collapse; during the crosslinking reaction, the changes in functional groups are monitored in real time using infrared spectroscopy to precisely control the crosslinking density and improve processing quality.
[0018] 3. This invention uses DMF as the initial solvent but ultimately completely replaces it with an aqueous system, reducing the emission of volatile organic compounds; freeze drying has low energy consumption and is suitable for large-scale production. Attached Figure Description
[0019] Figure 1 This is a flowchart of the preparation method of the polyimide resin-reinforced aerogel proposed in this invention. Detailed Implementation
[0020] The technical solution of the present invention will be further described in detail below with reference to specific embodiments.
[0021] Example 1: Preparation method of polyimide resin reinforced aerogel, using the following components:
[0022] Its preparation steps include: S1: Preparation of polyamic acid prepolymer; In a three-necked flask equipped with a stirrer, thermometer, and nitrogen protection system, a measured amount of N,N-dimethylformamide (DMF) was first added. Stirring was started, and nitrogen was introduced to purge air from the system. Then, pyromellitic dianhydride (PMDA) was slowly added, controlling the addition rate to avoid localized overheating and maintaining the system temperature at 25℃±2℃. After the PMDA was completely dissolved, stirring continued for 30 minutes to homogenize the solution. Next, 4,4'-diaminodiphenyl ether (ODA) was added in batches, with 15-minute intervals between each addition. After all additions were completed, the temperature was raised to 60℃±2℃, and the reaction was maintained at this temperature for 4 hours to obtain a polyamic acid prepolymer solution. During this process, the viscosity of the system was closely monitored, and the reaction was stopped when the viscosity reached the set range (80-120 s measured by a Forte 4 cup viscometer).
[0023] S2: Introducing polyimide resin; Cool the prepared polyamic acid prepolymer solution to 30℃±2℃, and slowly add the pre-prepared alcohol-soluble polyimide resin solution (solid content 30%-50%) while stirring. Control the addition rate to 1 / 3 of the total amount per hour, and continue stirring for 2 hours to ensure that the two are fully mixed and form a stable composite solution.
[0024] S3: Cross-linking reaction; An appropriate amount of crosslinking agent, ethylenediamine, was added to the composite solution; the amount was determined based on the target crosslinking density. Simultaneously, 0.5-2 parts by mass of triethylamine, a catalyst, were added. The system was heated to 80℃±2℃ and reacted at this temperature for 3 hours to ensure complete crosslinking. During the reaction, the degree of crosslinking was monitored by sampling and analysis, and changes in specific functional groups were detected using infrared spectroscopy. After the reaction, a wet gel with a certain crosslinked structure was obtained.
[0025] S4: Aging treatment; The obtained wet gel was aged at room temperature for 24 hours, with the relative humidity controlled at 50% ± 5%. This further stabilized the gel structure and improved the uniformity and performance stability of the material. The aged wet gel showed increased strength and slight volume shrinkage.
[0026] S5: Solvent displacement; A gradient solvent displacement method was used to remove DMF from the wet gel. First, acetone was used as a transition solvent; the wet gel was immersed in acetone, and fresh acetone was replaced every 6 hours for a total of 3 displacements. Then, ethanol was used to continue displacing the acetone, with fresh ethanol replaced every 6 hours for a total of 3 displacements. Finally, the gel was washed 2-3 times with deionized water to remove residual organic solvents and impurities. After each displacement, the container was gently shaken to ensure the solvent fully penetrated the gel.
[0027] S6: Drying and shaping; The wet gel, after solvent displacement treatment, was placed in a freeze dryer for drying. The freezing temperature was set to -50℃±2℃, the vacuum degree was maintained at 10Pa-50Pa, and the drying time was 72 hours. After drying, a polyimide resin-reinforced aerogel product was obtained. This product has a three-dimensional porous structure with uniform pore size distribution and appears as a pale yellow or brownish-yellow blocky solid.
[0028] Example 2, Preparation method of polyimide resin reinforced aerogel: Weigh the raw materials according to the formula: PMDA 50kg, ODA 50kg, DMF 300kg, alcohol-soluble polyimide resin (solid content 40%) 30kg, ethylenediamine 3kg, triethylamine 1kg.
[0029] The process is carried out in the following steps: First, a polyamic acid prepolymer is prepared. Then, a polyimide resin solution is slowly added to the prepolymer and mixed evenly. Next, a crosslinking agent and a catalyst are added to carry out a crosslinking reaction. After aging treatment, solvent replacement is performed. Finally, the product is obtained by freeze drying.
[0030] The density of the obtained aerogel was measured to be 0.08 g / cm³. 3 Specific surface area is 500m² 2 / g, tensile strength reaches 1.5MPa, and thermal decomposition temperature exceeds 450℃.
[0031] Example 3: The amount of alcohol-soluble polyimide resin in the formulation was adjusted to 50 kg (solid content 30%), while the amounts of other raw materials remained unchanged. The above process steps were repeated for preparation. The resulting aerogel maintained a low density (0.09 g / cm³). 3 Under these conditions, the tensile strength further increased to 2.0 MPa, while the thermal stability also improved, with the thermal decomposition temperature reaching 470℃. This indicates that appropriately increasing the polyimide resin content can effectively improve the performance of the aerogel.
[0032] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.
Claims
1. A method for preparing polyimide resin-reinforced aerogel, characterized in that, The specific raw material composition of the polyimide resin-reinforced aerogel is as follows: 50 parts of pyromellitic dianhydride, 50 parts of 4,4'-diaminodiphenyl ether, 300 parts of N,N-dimethylformamide, 20-50 parts of alcohol-soluble polyimide resin, 1-5 parts of crosslinking agent, and 0.5-2 parts of catalyst.
2. The method for preparing polyimide resin-reinforced aerogel according to claim 1, characterized in that, The preparation steps include: S1: Preparation of polyamic acid prepolymer; S2: Introducing polyimide resin; S3: Cross-linking reaction; S4: Aging treatment; S5: Solvent displacement; S6: Drying and shaping.
3. The method for preparing polyimide resin-reinforced aerogel according to claim 2, characterized in that, In S1, the specific method for preparing the polyamic acid prepolymer is as follows: In a three-necked flask equipped with a stirrer, thermometer, and nitrogen protection system, a measured amount of N,N-dimethylformamide was first added. The stirrer was turned on and nitrogen was introduced to purge air from the system. Then, pyromellitic dianhydride was slowly added, controlling the addition rate to avoid local overheating and maintaining the system temperature at 25℃±2℃. After PMDA was completely dissolved, stirring was continued to make the solution homogeneous. Then, 4,4'-diaminodiphenyl ether was added in batches. After the addition was completed, the temperature was raised to 60℃±2℃ and the reaction was carried out at a constant temperature to obtain a polyamic acid prepolymer solution.
4. The method for preparing polyimide resin-reinforced aerogel according to claim 3, characterized in that, In S2, the specific method of introducing polyimide resin is as follows: The prepared polyamic acid prepolymer solution was cooled to 30℃±2℃, and the pre-prepared alcohol-soluble polyimide resin solution was slowly added while stirring. The mixture was stirred for 2 hours to ensure that the two were fully mixed and formed a stable composite solution.
5. The method for preparing polyimide resin-reinforced aerogel according to claim 4, characterized in that, In S3, the specific manner of the crosslinking reaction is as follows: An appropriate amount of crosslinking agent, ethylenediamine, is added to the composite solution. The amount of ethylenediamine is determined according to the target crosslinking density. Triethylamine is added as a catalyst. After the reaction is completed, a wet gel with a crosslinked structure is obtained.
6. The method for preparing polyimide resin-reinforced aerogel according to claim 5, characterized in that, In step S4, the specific method of aging treatment is as follows: The obtained wet gel was allowed to age at room temperature for 24 hours, with the relative humidity of the aging environment controlled at 50%±5%.
7. The method for preparing polyimide resin-reinforced aerogel according to claim 6, characterized in that, In step S5, the specific method of solvent replacement is as follows: DMF in wet gels was removed using a gradient solvent displacement method. First, acetone was used as a transition solvent, and the wet gel was immersed in acetone. Fresh acetone was replaced every 6 hours for a total of 3 displacements. Then, ethanol was used to continue displacing the acetone, and fresh ethanol was replaced every 6 hours for a total of 3 displacements. Finally, the gel was washed 2-3 times with deionized water to remove residual organic solvents and impurities. After each displacement, the container was gently shaken to allow the solvent to fully penetrate into the gel.
8. The method for preparing polyimide resin-reinforced aerogel according to claim 2, characterized in that, In step S6, the specific method of drying and molding is as follows: The wet gel after solvent replacement treatment was placed in a freeze dryer for drying; the freezing temperature was set to -50℃±2℃, the vacuum degree was maintained at 10Pa-50Pa, and the drying time was 72h; after drying, a polyimide resin-reinforced aerogel product was obtained.
9. The method for preparing polyimide resin-reinforced aerogel according to claim 4, characterized in that, In S2, the solid content of the alcohol-soluble polyimide resin solution is 30%-50%, and the addition rate is controlled at 1 / 3 of the total amount added per hour.
10. The method for preparing polyimide resin-reinforced aerogel according to claim 5, characterized in that, In step S3, the system is heated to 80℃±2℃ during the crosslinking reaction and kept at a constant temperature for 3 hours to ensure the crosslinking reaction proceeds fully. During the reaction, the degree of crosslinking is monitored by sampling and analysis, and changes in specific functional groups are detected by infrared spectroscopy.