A bicomponent perspiration-type fiber-reinforced phenolic aerogel composite material and a preparation method thereof

Abstract

The present application relates to the technical field of fiber reinforced resin matrix composite, in particular to a two-component sweat type fiber reinforced phenolic aerogel composite material and a preparation method thereof.The method steps include: (1) phenolic resin modification; (2) preparation of phenolic resin pre-gel solution; (3) impregnation of fiber reinforcement; (4) gel curing; (5) drying; (6) inorganic phase change agent filling; (7) organic phase change agent filling.The present application uses heat-acid treated modified phenolic resin as raw material for phenolic aerogel preparation, which can effectively improve the curing crosslinking degree of phenolic resin and refine the skeleton and pore size of aerogel.The present application introduces high phase change enthalpy inorganic phase change agent and organic phase change agent into the pores of phenolic aerogel in turn, and the hierarchical distribution of two-component phase change agent can occur in solid-liquid-gas phase change from outside to inside in high temperature environment, so that it has comprehensive performance of superhigh temperature resistance, long time high efficiency heat insulation and high mechanical strength.

Description

Technical Field

[0001] This invention relates to the field of fiber-reinforced resin-based composite materials, specifically to a bicomponent sweat-inducing fiber-reinforced phenolic aerogel composite material and its preparation method. Background Technology

[0002] Thermally insulating and heat-resistant resin-based composite materials are advanced composite materials composed of high-performance fibers and resin matrices. They maintain high mechanical strength and excellent thermal insulation performance under high-temperature environments. A typical example is high-silica / phenolic composite materials. High-silica / phenolic composite materials use high-silica fibers (SiO2 content ≥96%) as reinforcement and phenolic resin as the matrix. They combine the heat resistance of high-silica fibers with the molding advantages of phenolic resin, exhibiting high strength, toughness, and low thermal conductivity. They are a crucial type of ablation-resistant thermal insulation material in the aerospace field (solid rocket engine nozzles, ramjet engine combustion chambers, etc.). The thermal insulation mechanism of high-silica / phenolic composite materials is as follows: Under high-temperature conditions, the phenolic resin matrix undergoes a pyrolysis reaction, forming a carbonized layer. Pyrolysis gas products are injected into the boundary layer through the carbonized layer, increasing the thermal resistance of external aerodynamic heating to the material's interior, thus creating a thermal blockage effect. However, existing high-silica / phenolic composite materials can only perform short-term (upper limit of working time ~400s) thermal insulation tasks in ultra-high temperature (≥1800℃) environments. The reason is that as the service time increases, the carbonized layer on the material surface gradually extends into the material interior until the entire phenolic resin matrix is ​​converted into dense pyrolytic carbon, which causes the thermal conductivity of the material to increase sharply, making it unable to meet the requirements for long-term and efficient thermal insulation.

[0003] In response, researchers both domestically and internationally have developed a new type of fiber-reinforced resin-based lightweight ablation composite material based on high-silica / phenolic composites. This porous material uses high-silica, quartz, mullite, and carbon fiber preforms as reinforcements and phenolic aerogel as the matrix. Compared to traditional high-silica / phenolic composites with dense structures, fiber-reinforced resin-based lightweight ablation composites feature high porosity and lower thermal conductivity. Furthermore, during long-term high-temperature service, the phenolic aerogel transforms into carbon aerogel (a stacked network structure of nano-carbon particles), thus maintaining good thermal insulation capabilities even during extended service. However, the low density and high porosity also result in generally low mechanical strength, making it difficult to provide thermal insulation under high loads and strong mechanical impacts. Therefore, it is mainly used for high-temperature thermal insulation in specific environments with lower mechanical strength requirements, such as the thermal shielding of reentry vehicles and the windward surface of high-speed aircraft fuselages.

[0004] With the continuous advancement of my country's aerospace technology, aircraft are gradually developing towards higher speeds, longer service lives, and more complex mission conditions. This places increasingly stringent and diverse demands on the high-temperature resistance, long-term thermal insulation, and mechanical strength of thermal protection materials. Resolving the inherent conflict between strength and thermal insulation in existing high-temperature resistant insulation materials, and developing new thermal protection materials with ultra-high temperature resistance, longer service life, higher thermal insulation efficiency, and higher load-bearing capacity, has become a crucial technological breakthrough necessary to support the development of my country's high-speed aircraft. Summary of the Invention

[0005] To address the aforementioned problems, this invention provides a bicomponent sweating fiber-reinforced phenolic aerogel composite material and its preparation method. The resulting composite material possesses comprehensive properties such as ultra-high temperature resistance, long-term high-efficiency thermal insulation, and high mechanical strength, and is expected to be applied to the thermal protection system of next-generation high-speed aircraft.

[0006] This invention proposes a method for preparing a bicomponent sweat-inducing fiber-reinforced phenolic aerogel composite material, comprising the following steps:

[0007] (1) Phenolic resin modification: Phenolic resin and solvent are mixed, and acid treatment agent is added to react and obtain a modified phenolic resin mixed solution;

[0008] (2) Preparation of phenolic resin pregel solution: Mix the modified phenolic resin mixed solution, pore-forming agent and curing agent to obtain phenolic resin pregel solution;

[0009] (3) Impregnating fiber reinforcement: Phenolic resin pregel solution is injected into a mold containing fiber reinforcement, and vacuum pressure is maintained to ensure that the pregel solution fully impregnates the fiber reinforcement;

[0010] (4) Gel curing: The mold containing the fiber reinforcement obtained in step (3) is heated and kept at a constant temperature to obtain the fiber-reinforced phenolic wet gel composite material;

[0011] (5) Drying: The fiber-reinforced phenolic wet gel composite material obtained in step (4) is dried to obtain the fiber-reinforced phenolic aerogel composite material;

[0012] (6) Inorganic phase change agent filling: The composite material obtained in step (5) is immersed in a saturated solution of inorganic phase change agent, and after vacuum pressure is maintained, it is taken out and dried to obtain fiber-reinforced phenolic aerogel composite material filled with inorganic phase change agent.

[0013] (7) Organic phase change agent filling: The composite material obtained in step (6) is immersed in the molten pool of organic phase change agent, and after vacuum pressure holding, it is taken out and cooled to obtain a bicomponent sweating fiber-reinforced phenolic aerogel composite material.

[0014] Further, in step (1), the phenolic resin is a linear thermosetting phenolic resin, and the grade of the linear thermosetting phenolic resin is one or more of 2124, 2127, 2130, 2124 and 2132; the solvent is one or more of ethanol, methanol, ethylene glycol, isopropanol and glycerol; and the acid treatment agent is one or more of hydrochloric acid, sulfuric acid, formic acid, acetic acid, oxalic acid and citric acid.

[0015] The mass ratio of phenolic resin to solvent is 1:(1~3), and the acid treatment agent accounts for 0.1~1.5% of the total mass of phenolic resin and solvent; the reaction temperature is 50~120℃, and the reaction time is 0.5~3h.

[0016] Further, in step (2), the pore-forming agent is one or more of acetone, methanol, dimethylformamide, ethanol, ethylene glycol, ethylene glycol monoethyl ether, isopropanol and glycerol, and the curing agent is one or more of paraformaldehyde, benzenesulfonyl chloride, hexamethylenetetramine, p-hydroxybenzenesulfonic acid and p-toluenesulfonic acid.

[0017] The mass ratio of the modified phenolic resin mixture to the pore-forming agent is 1:(0.1~20), and the curing agent accounts for 1~10% of the total mass of the modified phenolic resin mixture and the pore-forming agent.

[0018] Further, in step (3), the fiber reinforcement is one or more of high silica fiber, quartz fiber, mullite fiber, alumina fiber, zirconium oxide fiber and carbon fiber; the volume of the phenolic resin pregel solution is 1.5 to 3 times the volume of the fiber reinforcement; the vacuum degree during the vacuum pressure holding process is -0.08 to -0.1 MPa, and the pressure holding time is 10 to 48 hours.

[0019] Furthermore, in step (4), the temperature of the heat preservation is 60~200℃ and the heat preservation time is 1~72h.

[0020] Furthermore, in step (5), the drying temperature is 50~150℃ and the drying time is 10~100h.

[0021] Further, in step (6), the inorganic phase change agent is one or more of sodium chloride, potassium chloride, calcium nitrate tetrahydrate, calcium chloride hexahydrate, and magnesium chloride hexahydrate;

[0022] The vacuum degree of the vacuum holding is -0.08 to -0.1 MPa, and the holding time is 10 to 48 hours.

[0023] The drying temperature is 100~120℃, and the drying time is 12~24h.

[0024] Further, in step (7), the organic phase change agent is one or more of stearic acid, pentaerythritol, xylitol, polyethylene glycol, neopentyl glycol, erythritol, and paraffin.

[0025] The vacuum degree of the vacuum holding is -0.08 to -0.1 MPa, and the holding time is 10 to 48 hours.

[0026] A bicomponent sweat-inducing fiber-reinforced phenolic aerogel composite material prepared according to the above-described method has a density ≤1.45 g / cm³. 3 The tensile strength is ≥308MPa, the flexural strength is ≥169MPa, and the tensile strength is ≥92MPa. The thermal insulation performance of the 13mm thick composite material was tested by oxyacetylene flame ablation method. The back temperature peak was ≤309℃ after heating for 600s at a surface temperature of 1850℃ at the hot end.

[0027] The effects and advantages of this invention are as follows:

[0028] 1. This invention uses hot acid-treated modified phenolic resin as raw material to prepare phenolic aerogel. On the one hand, it can effectively improve the curing and crosslinking degree of phenolic resin and significantly improve the mechanical strength of the phenolic aerogel skeleton; on the other hand, it can effectively refine the skeleton and pore size of the aerogel, so that the prepared phenolic aerogel exhibits mesoporous (average pore size: 40nm) network structure characteristics, which can significantly reduce the gaseous, solid and radiative heat conduction of the material.

[0029] 2. This invention uses a high-strength, mesoporous network phenolic aerogel composite material as the base, and sequentially introduces an inorganic phase change agent (high-temperature phase change) and an organic phase change agent (medium-temperature phase change) with high phase change enthalpy into the pores of the phenolic aerogel. The hierarchically distributed binary phase change agent can undergo solid-liquid-gas phase change "from the outside to the inside" under high temperature conditions, thereby endowing the material with the ability to efficiently dissipate heat over a wide temperature range, giving it comprehensive properties such as resistance to ultra-high temperature, long-term efficient heat insulation and high mechanical strength. Attached Figure Description

[0030] Figure 1 This is a flowchart illustrating the preparation process of the bicomponent sweating fiber-reinforced phenolic aerogel composite material of the present invention.

[0031] Figure 2 Electron micrographs of the fiber-reinforced phenolic aerogel composites prepared in Comparative Example 1 and Example 3. Figure 2 (a) in the text is Comparative Example 1; Figure 2 (b) in the example is Example 3.

[0032] Figure 3 Mercury porosimetry pore size distribution curves of the fiber-reinforced phenolic aerogel composites prepared in Comparative Example 1 and Example 3.

[0033] Figure 4 The temperature rise curves on the back side of the composite materials in Comparative Examples 4, 5 and 3 during the high-temperature thermal insulation performance test are shown.

[0034] Figure 5 This invention relates to a method for constructing a bicomponent sweating-type high-silica / phenolic aerogel composite material.

[0035] Figure 6 This invention relates to a mechanism for efficient heat dissipation over a wide temperature range in the bicomponent sweating high-silica / phenolic aerogel composite material during high-temperature service. Detailed Implementation

[0036] 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. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. The following embodiments are composite materials with different properties prepared according to different raw materials and proportions.

[0037] Example 1:

[0038] The preparation process of the bicomponent sweating fiber-reinforced phenolic aerogel composite material in this embodiment is as follows: Figure 1 As shown, specifically:

[0039] (1) Phenolic resin and ethylene glycol are mixed and stirred evenly in a mass ratio of 1:1.5. Hydrochloric acid (concentration: 1mol / L) with a mass ratio of 0.5% (total mass of phenolic resin and ethylene glycol) is added for hot acid treatment at a heating temperature of 60℃ and a holding time of 1h to obtain a modified phenolic resin mixed solution.

[0040] (2) Mix the modified phenolic resin mixture and ethanol at a mass ratio of 1:2, add 2% p-hydroxybenzenesulfonic acid (total mass of modified phenolic resin mixture and ethanol), and stir at room temperature for 2 hours to obtain a phenolic resin pregel solution.

[0041] (3) Inject the phenolic resin pregel solution into the needle-punched high-silica fiber reinforcement (purchased from Jiangsu Tianniao High-Tech Co., Ltd., the density of the reinforcement is 0.6 g / cm³). 3A polytetrafluoroethylene mold (150mm × 150mm × 20mm) with mold dimensions of 160mm × 160mm × 50mm was used to completely immerse the high-silica fiber reinforcement in a phenolic resin pregel solution under vacuum pressure. To ensure that the liquid level of the phenolic resin pregel solution remained above the high-silica fiber reinforcement throughout the entire pressure holding process, the volume of the phenolic resin pregel solution was set to 1.5 times the volume of the high-silica fiber reinforcement. The vacuum degree during the vacuum pressure holding process was -0.09MPa (gauge pressure), and the pressure holding time was 24 hours to allow the phenolic resin pregel solution to fully wet the fiber reinforcement.

[0042] (4) Place the mold containing the fiber reinforcement into a heating furnace, heat it to 100°C, and keep it at that temperature for 20 hours to allow the phenolic resin pregel solution in the high silica fiber reinforcement to gel and solidify, thereby obtaining the fiber-reinforced phenolic wet gel composite material.

[0043] (5) Demold the fiber-reinforced phenolic wet gel composite material and dry it in a drying oven at 100°C and normal pressure for 24 hours to obtain the fiber-reinforced phenolic aerogel composite material.

[0044] (6) The fiber-reinforced phenolic aerogel composite material was immersed in a saturated aqueous solution of potassium chloride under vacuum impregnation at a vacuum degree of -0.09 MPa. After vacuum pressure was maintained for 24 hours, the composite material was removed and placed in an oven to dry at 100°C for 24 hours to obtain a fiber-reinforced phenolic aerogel composite material filled with inorganic phase change agent.

[0045] (7) The fiber-reinforced phenolic aerogel composite material filled with inorganic phase change agent was immersed in the erythritol melt pool (erythritol was heated at 150°C for 2 hours to melt) for vacuum impregnation. The vacuum degree was -0.09MPa. After vacuum pressure was maintained for 24 hours, it was taken out and naturally cooled to room temperature to obtain the fiber-reinforced phenolic aerogel composite material filled with inorganic and organic phase change agent (bicomponent sweating agent), namely: bicomponent sweating type fiber-reinforced phenolic aerogel composite material.

[0046] Example 2:

[0047] (1) Phenolic resin and ethanol are mixed and stirred evenly in a mass ratio of 1:1.8. Then, sulfuric acid (concentration: 1mol / L) with a mass ratio of 0.3% (total mass of phenolic resin and ethanol) is added for hot acid treatment at a temperature of 50℃ for 1.5h to obtain a modified phenolic resin mixed solution.

[0048] (2) Mix the modified phenolic resin mixture and isopropanol in a mass ratio of 1:2, add p-toluenesulfonic acid with a mass ratio of 4% (total mass of the modified phenolic resin mixture and isopropanol), and stir until homogeneous to obtain a phenolic resin pregel solution.

[0049] (3) Inject the phenolic resin pregel solution into the needle-punched mullite fiber reinforcement (purchased from Jiangsu Tianniao High-Tech Co., Ltd., the density of the reinforcement is 0.6 g / cm³). 3 The high-silica fiber reinforcement was completely immersed in a phenolic resin pregel solution under vacuum pressure. The volume of the phenolic resin pregel solution was set to 1.5 times the volume of the mullite fiber reinforcement. The vacuum degree during the vacuum pressure process was -0.09 MPa, and the pressure holding time was 24 hours, so that the phenolic resin pregel solution could fully wet the fiber reinforcement.

[0050] (4) Place the mold containing the fiber reinforcement into a heating furnace, heat it to 100°C, and keep it at that temperature for 20 hours to allow the phenolic resin pregel solution in the mullite fiber reinforcement to gel and solidify, thereby obtaining the fiber-reinforced phenolic wet gel composite material.

[0051] (5) Demold the fiber-reinforced phenolic wet gel composite material and dry it in a drying oven at 100°C and normal pressure for 24 hours to obtain the fiber-reinforced phenolic aerogel composite material.

[0052] (6) The fiber-reinforced phenolic aerogel composite material was immersed in a saturated aqueous solution of potassium chloride under vacuum impregnation at a vacuum degree of -0.09 MPa. After vacuum pressure was maintained for 24 hours, the composite material was removed and placed in an oven to dry at 100°C for 24 hours to obtain a fiber-reinforced phenolic aerogel composite material filled with inorganic phase change agent.

[0053] (7) The fiber-reinforced phenolic aerogel composite material filled with inorganic phase change agent was immersed in a polyethylene glycol melt pool (polyethylene glycol was heated at 100°C for 2 hours to melt) for vacuum impregnation. The vacuum degree was -0.09MPa. After vacuum pressure was maintained for 24 hours, it was taken out and naturally cooled to room temperature to obtain the fiber-reinforced phenolic aerogel composite material filled with inorganic and organic phase change agent (bicomponent), namely: bicomponent sweating fiber-reinforced phenolic aerogel composite material.

[0054] Example 3:

[0055] (1) Phenolic resin and ethylene glycol are mixed and stirred evenly in a mass ratio of 1:1.5. Citric acid with a mass ratio of 0.4% (total mass of phenolic resin and ethylene glycol) is added for hot acid treatment at a temperature of 60°C for 1 hour to obtain a modified phenolic resin mixed solution.

[0056] (2) Mix the modified phenolic resin mixture and ethanol in a mass ratio of 1:2, add 2% p-hydroxybenzenesulfonic acid (total mass of modified phenolic resin mixture and ethanol), and stir until homogeneous to obtain a phenolic resin pregel solution.

[0057] (3) Inject the phenolic resin pregel solution into a high-silica fiber reinforcement with a needle-punched structure (the density of the reinforcement is 0.6 g / cm³). 3 In a polytetrafluoroethylene mold with dimensions of 150mm×150mm×20mm (mold size 160mm×160mm×50mm), the volume of the phenolic resin pregel solution is set to be 1.5 times the volume of the high silica fiber reinforcement. The vacuum degree during the vacuum holding process is -0.09MPa, and the holding time is 24h, so as to allow the phenolic resin pregel solution to fully impregnate the fiber reinforcement.

[0058] (4) Place the mold containing the fiber reinforcement into a heating furnace, heat it to 100°C, and keep it at that temperature for 20 hours to allow the phenolic resin pregel solution in the high silica fiber reinforcement to gel and solidify, thereby obtaining the fiber-reinforced phenolic wet gel composite material.

[0059] (5) Demold the fiber-reinforced phenolic wet gel composite material and dry it in a drying oven at 100°C and normal pressure for 24 hours to obtain the fiber-reinforced phenolic aerogel composite material.

[0060] (6) The fiber-reinforced phenolic aerogel composite material was immersed in a saturated sodium chloride aqueous solution for vacuum impregnation at a vacuum degree of -0.09 MPa. After vacuum pressure was maintained for 24 hours, the composite material was removed and placed in an oven to dry at 100°C for 24 hours to obtain the fiber-reinforced phenolic aerogel composite material filled with inorganic phase change agent.

[0061] (7) The fiber-reinforced phenolic aerogel composite material filled with inorganic phase change agent was immersed in a neopentyl glycol melt pool (the neopentyl glycol was heated at 150°C for 2 hours to melt) for vacuum impregnation. The vacuum degree was -0.09 MPa. After vacuum pressure was maintained for 24 hours, it was taken out and naturally cooled to room temperature to obtain the fiber-reinforced phenolic aerogel composite material filled with inorganic and organic phase change agents (bicomponents), namely: bicomponent sweating fiber-reinforced phenolic aerogel composite material.

[0062] Comparative Example 1:

[0063] The only difference between Comparative Example 1 and Example 3 is that unmodified phenolic resin was used to prepare the composite material; other preparation parameters were the same as in Example 3.

[0064] Comparative Example 2:

[0065] The difference between Comparative Example 2 and Example 3 is that the inorganic phase change agent (i.e., sodium chloride) was not filled, but only the organic phase change agent (i.e., neopentyl glycol) was filled. Other preparation parameters were the same as in Example 3.

[0066] Comparative Example 3:

[0067] The difference between Comparative Example 3 and Example 3 is that neither Comparative Example 3 was filled with an inorganic phase change agent (i.e., sodium chloride) nor an organic phase change agent (i.e., neopentyl glycol). Other preparation parameters were the same as in Example 3.

[0068] Comparative Example 4:

[0069] The traditional commercially available density is 1.00 g / cm³. 3 The high-silica / phenolic heat-resistant composite material is made by molding process and has the characteristics of being lightweight and high-strength.

[0070] Comparative Example 5:

[0071] The traditional commercially available density is 1.50 g / cm³. 3 The high-silica / phenolic heat-resistant composite material is made by molding process and has the characteristics of being lightweight and high-strength.

[0072] The pore structure of the composite material was analyzed using scanning electron microscopy and mercury porosimetry. The compressive strength, flexural strength, and tensile strength of the composite material were tested according to the national standard GB / T34336-2017 "Nanoporous Aerogel Composite Thermal Insulation Products". The high-temperature thermal insulation performance of the composite material was tested according to the national standard GJB 323B-2018 "Ablation Test Methods for Ablation Materials". The high-temperature thermal insulation performance test was conducted as follows: 1) The sample was cut into thermal insulation composite material test pieces with dimensions of 40mm×40mm×13mm; 2) The thermal insulation composite material test pieces were placed between a 4mm thick C / SiC ceramic matrix composite heat shield (dimensions: 50mm×50mm×4mm) and a 5mm thick stainless steel plate (dimensions: 50mm×50mm×5mm); 3) An oxyacetylene flame was vertically sprayed onto the ceramic matrix composite heat shield, and the back temperature rise of the thermal insulation composite flat plate test piece was tested at a surface temperature of 1850℃ at the hot end of the ceramic matrix composite heat shield, with a total heating time of 600s; 4) The back temperature rise curve of the thermal insulation composite material test piece during the test was recorded, and its high-temperature thermal insulation performance was evaluated by comparing the back temperature peak values ​​of different thermal insulation composite material test pieces at 600s. The test results are shown in Table 1.

[0073] Table 1. Comparison of density, mechanical strength, and peak back temperature of different samples.

[0074]

[0075] As shown in Table 1, the composite material obtained by this invention possesses both high mechanical strength and superior high-temperature thermal insulation performance. Examples 3 and 1 demonstrate that the advantages of using modified phenolic resin to prepare aerogels are: firstly, it effectively improves the curing and crosslinking degree of the phenolic resin, significantly enhancing the mechanical strength of the phenolic aerogel skeleton (e.g., compressive strength increased from 146 MPa to 325 MPa); secondly, it effectively refines the aerogel skeleton and pore size (e.g., ...). Figure 2 As shown), the prepared phenolic aerogel exhibits a mesoporous (average pore size: 40 nm) network structure (as shown). Figure 3 As shown in Example 2, the gaseous, solid, and radiative heat conduction of the material is significantly reduced (back temperature peak decreases from 396℃ to 306℃). Comparative Example 2 shows that the composite material obtained by filling with a single-component phase change agent also has high mechanical strength, but its back temperature peak (385℃) is higher than that of the composite material obtained by filling with a two-component phase change agent (Examples 1, 2, and 3). Comparative Example 3 shows that the composite material without phase change agent not only has significantly lower mechanical strength but also a significantly higher back temperature peak (461℃). Therefore, filling with a phase change agent can effectively improve the mechanical strength of the aerogel skeleton and significantly improve the thermal insulation performance of the composite material.

[0076] Figure 4 The image shows the back-side temperature rise curves of the thermal insulation composite material specimens in Examples 3, 4, and 5 during oxyacetylene flame heating. Figure 4 As can be seen, in Comparative Example 4, the back-side temperature rise curve of the traditional commercially available high-silica / phenolic heat-insulating composite material reached the inflection point at 270s, with a corresponding back-side temperature peak of 400℃. In Comparative Example 5, although the back-side temperature rise curve of the traditional commercially available high-silica / phenolic heat-insulating composite material only reached the inflection point at 370s, the corresponding back-side temperature peak was as high as 490℃. In contrast, the bicomponent sweating fiber-reinforced phenolic aerogel composite material prepared in this invention exhibited a significantly lower back-side temperature rise rate than the traditional commercially available silica / phenolic composite material during the test. This is attributed to its mesoporous network structure (significantly reducing gaseous, solid, and radiative heat conduction of the material) and its wide-temperature-range high-efficiency heat dissipation capability (solid-liquid-gas phase change heat absorption of the phase change agent), which gives it excellent ultra-high temperature long-term heat insulation performance. Among them, the back temperature peak of the bicomponent sweating fiber-reinforced phenolic aerogel composite material was only 306℃ at a heating time of 600s, while the back temperature peaks of the two traditional commercially available silicon / phenolic heat-resistant composite materials were as high as 527℃ and 547℃, respectively.

[0077] Figure 5This invention showcases the unique features and innovations of the material prepared according to this invention. The unique features and innovations of this invention are: obtaining a high-strength, mesoporous network phenolic aerogel through phenolic resin modification; introducing an inorganic phase change agent (high-temperature phase change) into the inner layer of the aerogel pore wall via solution impregnation; and introducing an organic phase change agent (medium-temperature phase change) into the outer layer of the aerogel pore wall via melting and absorption. Figure 6 This invention demonstrates the mechanism by which the bicomponent sweating high-silica / phenolic aerogel composite material of the present invention dissipates heat efficiently over a wide temperature range during high-temperature service. The aforementioned hierarchically distributed bicomponent phase change agent can undergo solid-liquid-gas phase change sequentially "from the outside to the inside" under high-temperature conditions, endowing the material with the ability to dissipate heat efficiently over a wide temperature range. This significantly improves its long-term thermal insulation performance under ultra-high temperature conditions while maintaining excellent mechanical strength.

Claims

1. A method for preparing a bicomponent sweat-inducing fiber-reinforced phenolic aerogel composite material, characterized in that: Includes the following steps: (1) Phenolic resin modification: Phenolic resin and solvent are mixed, and an acid treatment agent is added to react and obtain a modified phenolic resin mixed solution; the phenolic resin is a linear thermosetting phenolic resin, and the grade of the linear thermosetting phenolic resin is one or more of 2124, 2127, 2130, 2124 and 2132; the solvent is one or more of ethanol, methanol, ethylene glycol, isopropanol and glycerol; and the acid treatment agent is one or more of hydrochloric acid, sulfuric acid, formic acid, acetic acid, oxalic acid and citric acid. The mass ratio of phenolic resin to solvent is 1:(1~3), and the acid treatment agent accounts for 0.1~1.5% of the total mass of phenolic resin and solvent; the reaction temperature is 50~120℃, and the reaction time is 0.5~3h; (2) Preparation of phenolic resin pregel solution: Mix the modified phenolic resin mixed solution, pore-forming agent and curing agent to obtain phenolic resin pregel solution; (3) Impregnating fiber reinforcement: Phenolic resin pregel solution is injected into a mold containing fiber reinforcement, and vacuum pressure is maintained to ensure that the pregel solution fully impregnates the fiber reinforcement; (4) Gel curing: The mold containing the fiber reinforcement obtained in step (3) is heated and kept at a constant temperature to obtain the fiber-reinforced phenolic wet gel composite material; (5) Drying: The fiber-reinforced phenolic wet gel composite material obtained in step (4) is dried to obtain the fiber-reinforced phenolic aerogel composite material; (6) Inorganic phase change agent filling: The composite material obtained in step (5) is immersed in a saturated solution of inorganic phase change agent, and after vacuum pressure is maintained, it is taken out and dried to obtain fiber-reinforced phenolic aerogel composite material filled with inorganic phase change agent. (7) Organic phase change agent filling: The composite material obtained in step (6) is immersed in the molten pool of organic phase change agent, and after vacuum pressure holding, it is taken out and cooled to obtain a bicomponent sweating fiber-reinforced phenolic aerogel composite material.

2. The preparation method of the bicomponent sweat-inducing fiber-reinforced phenolic aerogel composite material according to claim 1, characterized in that: In step (2), the pore-forming agent is one or more of acetone, methanol, dimethylformamide, ethanol, ethylene glycol, ethylene glycol monoethyl ether, isopropanol and glycerol, and the curing agent is one or more of paraformaldehyde, benzenesulfonyl chloride, hexamethylenetetramine, p-hydroxybenzenesulfonic acid and p-toluenesulfonic acid. The mass ratio of the modified phenolic resin mixture to the pore-forming agent is 1:(0.1~20), and the curing agent accounts for 1~10% of the total mass of the modified phenolic resin mixture and the pore-forming agent.

3. The preparation method of the bicomponent sweat-inducing fiber-reinforced phenolic aerogel composite material according to claim 1, characterized in that: In step (3), the fiber reinforcement is one or more of the following: high silica fiber, quartz fiber, mullite fiber, alumina fiber, zirconium oxide fiber, and carbon fiber; the volume of the phenolic resin pregel solution is 1.5 to 3 times the volume of the fiber reinforcement; the vacuum degree during the vacuum pressure holding process is -0.08 to -0.1 MPa, and the pressure holding time is 10 to 48 hours.

4. The preparation method of the bicomponent sweating fiber-reinforced phenolic aerogel composite material according to claim 1, characterized in that: In step (4), the temperature for heat preservation is 60~200℃ and the heat preservation time is 1~72h.

5. The preparation method of the bicomponent sweat-inducing fiber-reinforced phenolic aerogel composite material according to claim 1, characterized in that: In step (5), the drying temperature is 50~150℃ and the drying time is 10~100h.

6. The preparation method of the bicomponent sweat-inducing fiber-reinforced phenolic aerogel composite material according to claim 1, characterized in that: In step (6), the inorganic phase change agent is one or more of sodium chloride, potassium chloride, calcium nitrate tetrahydrate, calcium chloride hexahydrate, and magnesium chloride hexahydrate; The vacuum degree of the vacuum holding is -0.08 to -0.1 MPa, and the holding time is 10 to 48 hours. The drying temperature is 100~120℃, and the drying time is 12~24h.

7. The preparation method of the bicomponent sweat-inducing fiber-reinforced phenolic aerogel composite material according to claim 1, characterized in that: In step (7), the organic phase change agent is one or more of stearic acid, pentaerythritol, xylitol, polyethylene glycol, neopentyl glycol, erythritol, and paraffin. The vacuum degree of the vacuum holding is -0.08 to -0.1 MPa, and the holding time is 10 to 48 hours.

8. A bicomponent sweating fiber-reinforced phenolic aerogel composite material prepared by the preparation method of any one of claims 1-7, characterized in that: The density of the aforementioned bicomponent sweat-inducing fiber-reinforced phenolic aerogel composite material is ≤1.45 g / cm³. 3 The tensile strength is ≥308MPa, the flexural strength is ≥169MPa, and the tensile strength is ≥92MPa. The thermal insulation performance of the 13mm thick composite material was tested by oxyacetylene flame ablation method. The back temperature peak was ≤309℃ after heating for 600s at a surface temperature of 1850℃ at the hot end.

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