Ablation / thermal insulation integrated organic silicon hybrid phenolic aerogel composite material, and preparation method and use thereof

Abstract

The application provides an aeroablation / heat insulation integrated organic silicon hybrid phenolic aerogel composite material and a preparation method and application thereof, and belongs to the field of composite materials.The aerogel composite material is prepared by taking fiber felt and hybrid resin as raw materials and through sol-gel and polymerization-induced phase separation.The hybrid phenolic aerogel composite material realizes the aeroablation / heat insulation integrated function in different heat flow environments by means of the pyrolysis mechanism of different fiber felts in different heat flow environments, and has good application prospects as a light thermal protection material, a building fireproof material, a lithium battery fireproof material, and especially a high-speed aircraft thermal protection material.

Description

Technical Field

[0001] This invention belongs to the field of composite materials, specifically relating to an ablation / thermal insulation integrated organosilicon hybrid phenolic aerogel composite material, its preparation method, and its applications. Background Technology

[0002] When spacecraft re-enter the atmosphere, they experience harsh high-temperature environments caused by aerodynamic heating. Therefore, thermal protection systems (TPS) have become a crucial safety guarantee for spacecraft. To meet the urgent need for weight reduction in spacecraft, NASA and other organizations have developed various lightweight TPSs such as AVCOAT, PICA, and SLA over the past thirty years. However, with the gradual development of missions such as deep space exploration, high-speed flight within the atmosphere, and long-duration near-space flights, traditional lightweight TPSs are gradually becoming inadequate for the current demanding service environments. There is an urgent need to modify them to improve their thermal insulation, ablation resistance, and thermal stability to meet the increasingly stringent performance requirements of advanced spacecraft.

[0003] Aerogels, as three-dimensional network structures composed of cross-linked nanoparticles, have attracted increasing attention in thermal control fields such as aerospace due to their advantages such as ultra-low density, high porosity, and low thermal / electrical conductivity. Based on their composition, aerogels can be divided into inorganic aerogels and organic aerogels. With the continuous development of aerospace technology, inorganic aerogels with a temperature resistance not exceeding 700℃ are no longer suitable for use in thermal control systems (TPS) of aircraft operating under extreme environments such as high heat flux and high temperature.

[0004] Therefore, there is an urgent need to develop an organosilicon hybrid phenolic aerogel composite material that integrates ablation and thermal insulation. Summary of the Invention

[0005] The purpose of this invention is to provide an ablation / thermal insulation integrated organosilicon hybrid phenolic aerogel composite material, its preparation method, and its applications.

[0006] This invention provides a fiber felt aerogel composite material, which is a composite material made from fiber felt and hybrid resin.

[0007] Furthermore, the hybrid resin is a hybrid phenolic resin; the fiber felt is a high-silica fiber felt, mullite fiber felt, carbon fiber felt, phenolic fiber felt, or aramid fiber felt.

[0008] Furthermore, the fiber felt is carbon fiber felt; the hybrid phenolic resin is an organosilicon hybrid phenolic resin;

[0009] The organosilicon hybrid phenolic resin is prepared using PMP, 3,3',4,4'-biphenyltetracarboxylic acid dianhydride, (3-aminopropyl)triethoxysilane and phenolic resin as raw materials;

[0010] The PMP was prepared using octaphenylcyclotetrasiloxane, octamethylcyclotetrasiloxane and 1,3-bis(3-aminopropyl)tetramethyldisiloxane as raw materials.

[0011] Furthermore, the preparation method of the PMP includes the following steps:

[0012] Octaphenylcyclotetrasiloxane, octamethylcyclotetrasiloxane, 1,3-bis(3-aminopropyl)tetramethyldisiloxane and a catalyst are mixed, and an inert gas is introduced to react, thus obtaining the product.

[0013] Preferably,

[0014] The catalyst is tetramethylammonium hydroxide;

[0015] And / or, the reaction is carried out at 100-120°C for 1-5 hours, and then the temperature is raised to 150-200°C and held for 0.5-5 hours;

[0016] The mass of the catalyst is 0.5% to 5% of the total mass of octaphenylcyclotetrasiloxane and octamethylcyclotetrasiloxane;

[0017] The molar ratio of the octaphenylcyclotetrasiloxane, octamethylcyclotetrasiloxane, and 1,3-bis(3-aminopropyl)tetramethyldisiloxane is (0.5-3):(7-9.5):2, preferably 1.5:8.5:2.

[0018] Furthermore,

[0019] The molar ratio of the amino group in the PMP to the anhydride in the 3,3',4,4'-biphenyltetracarboxylic acid dianhydride is 1:

[0020] (1~1.1);

[0021] The (3-aminopropyl)triethoxysilane is 20% to 40% mol of amino content in PMP.

[0022] Furthermore, the organosilicon hybrid phenolic resin is prepared by the following method;

[0023] (1) In a solvent, 3,3',4,4'-biphenyltetracarboxylic acid dianhydride and PMP are mixed and reacted;

[0024] (2) After adding (3-aminopropyl)triethoxysilane, the reaction continued to yield PMPA;

[0025] (3) React PMPA with phenolic resin solution to obtain;

[0026] Preferably,

[0027] In step (1), the solvent is tetrahydrofuran;

[0028] And / or, in step (1), the reaction temperature is 30-50°C, the reaction time is 1-5 h; the mass ratio of the solvent to PMP is (1-5):1;

[0029] And / or, in step (2), the temperature of the reaction is 30 to 50°C, and the reaction time is 1 to 5 hours;

[0030] And / or, in step (3), the solvent of the phenolic resin solution is ethanol, wherein the mass ratio of phenolic resin to ethanol is (0.5-1):1, the reaction temperature is 50-110℃, and the reaction time is 0.5-2h.

[0031] The present invention also provides a method for preparing the above-mentioned fiber felt aerogel composite material, wherein the method further comprises the following steps:

[0032] 1) Take the hybrid resin, dissolve it in an organic solvent to obtain a hybrid resin solution with a concentration of 15-25 wt%, and soak the fiber felt in the hybrid resin solution to obtain a fiber felt permeated by the hybrid resin solution.

[0033] 2) The fiber mat permeated with the hybrid resin solution obtained in step 1) is subjected to sol-gel to obtain a wet fiber mat gel.

[0034] 3) Solvent replacement and drying were performed on the wet fiber felt gel to obtain a fiber felt aerogel composite material;

[0035] Preferably, the pressure environment in step 1) is below 0.5 MPa; the organic solvent is ethylene glycol, dimethylformamide, tetrahydrofuran or acetone, preferably ethylene glycol; the solvent used for solvent replacement in step 3) is ethanol, tetrahydrofuran or acetone, preferably ethanol.

[0036] Further, the concentration of the hybrid resin solution in step 1) is 20 wt%;

[0037] The pressure environment is below 0.1 MPa, preferably 0.095 MPa;

[0038] The sol-gel conditions described in step 2) are as follows: maintain the temperature at 100-140℃ for 1-3 hours, at 130-170℃ for 1-3 hours, at 160-200℃ for 1-3 hours, and at 180-220℃ for 1-3 hours.

[0039] Furthermore,

[0040] The sol-gel conditions described in step 1) are: 120℃ for 2 hours, 150℃ for 2 hours, 180℃ for 2 hours, and 200℃ for 1 hour.

[0041] 10. The present invention also provides the use of the above-mentioned fiber felt aerogel composite material in the preparation of ablation-resistant materials and / or heat-insulating materials and / or thermally stable materials.

[0042] Preferably, the ablation-resistant material is an ablation-resistant material used in extreme environments. The extreme environment is defined as an environment with a heat flux density of 1 MW / m³. 2 ~2MW / m 2 environment.

[0043] This invention provides an integrated ablation / thermal insulation organosilicon hybrid phenolic aerogel composite material, its preparation method, and its applications. First, a PMPI / PR hybrid resin is prepared through anionic ring-opening polymerization and copolymerization. Then, using this hybrid resin as the matrix, three different fiber-felt aerogel composite materials are prepared using carbon fiber felt, high-silica fiber felt, and mullite fiber felt as three-dimensional framework structures through a robust multi-level strategy of sol-gel and polymerization-induced phase separation. This invention generates pores with sizes ranging from 15 nm to 3 μm within the aerogel composite material through polymerization-induced phase separation. Vacuum impregnation fills the internal pores of the fiber felt with the matrix solution. During the subsequent sol-gel process, polymerization-induced phase separation occurs in the hybrid resin, separating the system into a hybrid resin-rich phase and a solvent-rich EG phase. Then, solvent replacement replaces EG with EtOH to reduce capillary pressure during atmospheric pressure drying. Finally, atmospheric pressure drying removes the solvent, yielding the xFPA aerogel composite material with nanoscale pores.

[0044] The fiber-felt aerogel composite material of this invention exhibits excellent thermal stability, mechanical properties, thermal insulation performance, and ablation resistance. Among them, HFPA and MFPA demonstrate superior thermal stability and thermal insulation performance compared to CFPA, with MFPA showing the best thermal stability and HFPA the best thermal insulation performance. CFPA possesses excellent mechanical properties and ablation resistance. This invention achieves integrated ablation / thermal insulation functionality under different heat flux environments, showing promising application prospects as a lightweight thermal protection material, building fireproofing material, lithium battery fireproofing material, and especially as a thermal protection material for high-speed aircraft.

[0045] Obviously, based on the above description of the present invention, and according to common technical knowledge and conventional methods in the field, various other modifications, substitutions or alterations can be made without departing from the basic technical concept of the present invention.

[0046] The following detailed embodiments further illustrate the above-described content of the present invention. However, this should not be construed as limiting the scope of the present invention to the following examples. All technologies implemented based on the above-described content of the present invention fall within the scope of the present invention. Attached Figure Description

[0047] Figure 1 The following are the synthetic routes of the poly(dimethyldiphenylimide)siloxane / phenolic dual-network hybrid resin of the present invention: a is the synthetic route of PMP; b is the synthetic route of PMPA; c is the synthetic route of PMPI / PR hybrid resin.

[0048] Figure 2 The structural characterization results of PMP, PMPA, and hybrid resins of this invention are as follows: a) FTIR spectrum of PMP; b) FTIR spectrum of PMP. 1 H-NMR spectrum; c is the FTIR spectrum of PMPA; d is the FTIR spectrum of hybrid resin and phenolic resin (PR).

[0049] Figure 3 Scanning electron microscopy (SEM) images of PMPI / PR hybrid resins with different phenyl contents: a) S0; b) S5; c) S 15 ;d is S 20 .

[0050] Figure 4 This is a scanning electron microscope image of pure phenolic resin (PR).

[0051] Figure 5 For hybrid resin S 15 AFM and TEM test results: a is S 15 AFM diagram; b is S 15 The HAADF plot.

[0052] Figure 6 TGA results for PMPI / PR hybrid resins with different phenyl contents: a) 800℃, nitrogen; b) 800℃, air; c) Degradation activation energy.

[0053] Figure 7 Optical images of different resins after ablation.

[0054] Figure 8 The following are the results of the ablation resistance study of the PMPI / PR hybrid resin of this invention: a) linear ablation rate of PMPI / PR hybrid resin; b) mass ablation rate of PMPI / PR hybrid resin; c) schematic diagram of the ablation layer; d) thickness distribution of residual resin; e) linear ablation rate distribution; in d and e, x represents the different positions of the sample point on a straight line in the cross-section, starting from one end of the sample cross-section.

[0055] Figure 9 XRD patterns and SEM images of the carbon layers of each resin after ablation are shown below: a) XRD pattern of the carbon layer; b) SEM image of the carbon layer after PR ablation; c) SEM image of the carbon layer after S0 ablation; d) SEM image of the carbon layer after S5 ablation; e) S... 15 SEM images of the carbon layer after ablation; f represents S30 SEM images of the carbon layer after ablation; d' is an enlarged image of the image within the red box in d; e' is an enlarged image of the image within the red box in e; f' is an enlarged image of the image within the red box in f.

[0056] Figure 10 For the preparation and analysis of xFPA in this invention, (a) xFPA preparation process and structural diagram. Original fiber mat: (b) carbon fiber mat; (c) high silica fiber mat; (d) mullite fiber mat. Different types of fiber mat-reinforced aerogels: (e) CFPA; (h) HFPA; (i) MFPA.

[0057] Figure 11 The following are the structural characterization results of the xFPA of this invention: (a) FTIR image of xFPA, (b) XPS image of xFPA, (c) high-resolution scanning C spectrum, and (d) XRD of three fiber felts and their xFPAs.

[0058] Figure 12 SEM images and analysis of xFPA, (af) SEM images of CFPA, HFPA, and MFPA, (go) particle size analysis of xFPA aerogel particles, (jl) adsorption-desorption isotherms of xFPA.

[0059] Figure 13 For mechanical properties, (a) typical stress-strain curves of xFPA in the xy and z directions, (b) typical stress-strain curves of xFPA in the z direction, (c) compressive strength and Young's modulus of xFPA in the xy and z directions, (df): elastic results of cyclic loading-release test of xFPA;

[0060] Figure 14 The results show the thermal stability of xFPA in nitrogen and air. (a): nitrogen, 800°C (b): air, 800°C (c): schematic diagram of butane spray gun.

[0061] Figure 15 Optical images of xFPA after ablation under different heat fluxes and times.

[0062] Figure 16 The height of the ablation pit on the sample after ablation is shown.

[0063] Figure 17 (a)-(f) SEM images of the surface layer after ablation with different heat flows. (g)-(l) SEM images of the pyrolysis layer after ablation with different heat flows.

[0064] Figure 18(a)(d) High-resolution XPS spectra of Si 2p from CFPA, (b)(e) HFPA, (c)(f) MFPA. (g) XRD pattern of the sample surface after ablation. (h) 1MW / m 2 (i)2mw / m 2 Thermal protection mechanisms during the process. Detailed Implementation

[0065] The raw materials and equipment used in this invention are all known products, obtained by purchasing commercially available products.

[0066] The phenolic resin (PR) was purchased from Henan Zhongfan Dongsheng Co., Ltd., item number: A103.

[0067] Octaphenylcyclosiloxane (P4), octamethylcyclosiloxane (D4), (3-aminopropyl)triethoxysilane (APTES), 1,3-bis(3-aminopropyl)tetramethyldisiloxane, and tetramethylammonium hydroxide were purchased from Shanghai Aladdin. 3,3',4,4'-biphenyltetracarboxylic acid dianhydride (BPDA) was purchased from Beijing Forsman. Tetrahydrofuran (THF), anhydrous ethanol (EtOH), and ethylene glycol (EG) were obtained from Shanghai Titan Technology Co., Ltd. (Carbon fiber felt, density: 0.13 g / cm³) 3 Purchased from Shanghai Lishuo Composite Materials Technology Co., Ltd. High silica fiber felt (density: 0.15 g / cm³) 3 Purchased from Nanjing Gaonaite New Materials Co., Ltd. Mullite fiber felt (density: 0.15 g / cm³) 3 (Al2O3: 72%, SiO2: 27.5%) was purchased from Suzhou Felist Materials Technology Co., Ltd.

[0068] Example 1: Preparation of the aerogel composite material of the present invention

[0069] I. Experimental Methods

[0070] (I) Matrix material for preparing the aerogel composite material of the present invention

[0071] 1. Synthesis of PMP with different phenyl contents

[0072] PMP is synthesized by anionic ring-opening polymerization of D4, P4, and 1,3-bis(3-aminopropyl)tetramethyldisiloxane under the catalysis of tetramethylammonium hydroxide. Specifically, D4, P4, the end-capping agent 1,3-bis(3-aminopropyl)tetramethyldisiloxane, and tetramethylammonium hydroxide (TMAOH) are added to a three-necked flask. First, a vacuum is drawn at 60°C to remove water from the system. Then, nitrogen gas is introduced to restore the system to atmospheric pressure, and the reaction is carried out at 120°C for 2.5 h. Next, the temperature of the system is raised to 150°C and maintained for 0.5 h, during which the catalyst tetramethylammonium hydroxide decomposes into trimethylamine and methanol. Finally, the system is evacuated to remove unreacted monomers, trimethylamine, and methanol, yielding a colorless, transparent, viscous liquid, which is PMP. The raw material formulations for synthesizing PMP with different phenyl contents are shown in Table 1. The amount of the catalyst tetramethylammonium hydroxide is 0.5 wt% of the total mass of P4 and D4. In Table 1, PMP0 indicates that the molar content of phenyl in the synthesized PMP is 0%, PMP5 indicates that the molar content of phenyl in the synthesized PMP is 5%, and PMP 15 This indicates that the molar content of phenyl in the synthesized PMP is 15%. 30 This indicates that the molar content of phenyl in the synthesized PMP is 30%.

[0073] Table 1. Raw material formulations for synthesizing PMPs with different phenyl contents

[0074]

[0075] 2. Synthesis of PMPA with different phenyl contents

[0076] Under a nitrogen atmosphere, a THF solution containing 50 wt% PMP was added dropwise to a three-necked flask containing BPDA (the molar ratio of amino group in PMP to anhydride in BPDA was 1:1.05) and tetrahydrofuran (THF, the mass ratio of THF to PMP was 1:1). The reaction was carried out at 35 °C for 2.5 h to ensure that the molecular chain was capped by excess anhydride. Then, the capping agent APTES (20 mol% of the amino group in PMP) was added, and the reaction was continued for 1 h to obtain a transparent, viscous PMPA. The synthetic route of PMPA is as follows: Figure 1 As shown in b). PMPA with different phenyl contents was prepared using PMP with different phenyl contents, and named PMPA0, PMPA5, and PMPA6 respectively. 15 PMPA 30 .

[0077] 3. Synthesis of PMPI / PR hybrid resins with different phenyl contents

[0078] PMPA was added to an anhydrous ethanol solution containing 50 wt% PR (PR to anhydrous ethanol mass ratio of 1:1), and the mass ratio of PMPA to PR was 1:2. The reaction was carried out at 80℃ for 1 h, followed by vacuum removal at 90℃ to remove the solvent, yielding a pale yellow powder of organosilicon hybrid phenolic resin. Different pale yellow powders were prepared using PMPA with different phenyl contents and named P0, P5, and P6, respectively. 15 P 30 .

[0079] The hybrid resin was cured and imidized by hot pressing to obtain the PMPI / PR hybrid resin. The curing and imidization program was as follows: 120℃ for 0.5 h, 160℃ for 1 h, 180℃ for 2 h, and 200℃ for 2 h sequentially. PMPI / PR hybrid resins with different phenyl contents were prepared using PMPA with different phenyl contents and named S0, S5, and S6, respectively. 15 S 30 .

[0080] (II) Preparation of the aerogel composite material (xFPA) of the present invention

[0081] First, P 15 A 20 wt% ethylene glycol (EG) solution (matrix impregnation solution) was prepared, and different fiber felts were immersed in this solution, wherein P 15 A 20wt% ethylene glycol solution was prepared and mixed with different fiber mats at a volume ratio of 1:1. The matrix impregnation solution was sufficient to penetrate the fiber mats. The mats were impregnated under a vacuum of 0.095 MPa for 0.5 h to ensure the hybrid resin solution fully penetrated into the fiber mats. The impregnated fiber mats were then transferred to a hydrothermal reactor and subjected to sol-gel processes at 120℃ / 2h + 150℃ / 2h + 180℃ / 2h + 200℃ / 1h to obtain different wet gels.

[0082] The wet gel was placed in ethanol (EtOH) for solvent replacement, with the solution being changed every 12 hours for 3 days. Finally, the replaced wet gel was dried in air at 30°C and normal pressure for 48 hours to obtain the aerogel composite material of the present invention.

[0083] Depending on the type of fiber felt, the resulting composite material xFPA was named CFPA (carbon fiber felt aerogel composite), with a density of 0.28 g / cm³. 3 HFPA (high silica fiber felt aerogel composite material) with a density of 0.32 g / cm³. 3 MFPA (mullite fiber felt aerogel composite material) with a density of 0.35 g / cm³. 3 .

[0084] (III) Investigation of the aerogel composite material xFPA of the present invention

[0085] xFPA aerogel composites are prepared using a robust, multi-level strategy involving sol-gel and polymerization-induced phase separation. This polymerization-induced phase separation allows for the creation of pores with sizes ranging from 15 nm to 3 μm within the aerogel composite. Figure 10 As shown in Figure a, vacuum impregnation fills the internal pores of the fiber felt with a matrix solution. During the subsequent sol-gel process, the hybrid resin undergoes polymerization-induced phase separation, resulting in a system rich in both the hybrid resin and solvent-rich ethylene glycol. Then, EG is replaced with ethanol via solvent displacement to reduce capillary pressure during atmospheric drying. Finally, the solvent is removed by atmospheric drying, yielding an xFPA aerogel composite material with nanoscale pores.

[0086] like Figure 10 b~ Figure 10 As shown in d, the xFPA aerogel composite material exhibits good processability and can be used to fabricate large-size components in practical applications. Hybrid resin aerogel particles uniformly fill the voids within the fiber felt and grow on the fiber surface. Figure 10 e~ Figure 10 f).

[0087] In xFPA aerogel composites, these interconnected pore structures endow them with lightweight and excellent thermal insulation properties.

[0088] The following experimental examples demonstrate the beneficial effects of the present invention.

[0089] Experimental Example 1: Structural Characterization of PMP and PMPI / PR Hybrid Resins with Different Phenyl Content

[0090] 1. Experimental Methods

[0091] Fourier transform infrared spectroscopy (FTIR) was used to analyze PMP0, PMP5, and PMP prepared according to the method described in Example 1. 15 PMP 30 PMPA0, PMPA5, PMPA 15 PMPA 30 S0, S5, S 15 S 30 The test was performed using pure phenolic resin (PR); 1H NMR spectroscopy was employed. 1 H-NMR spectroscopy was used to analyze PMP0, PMP5, and PMP prepared according to the method described in Example 1. 15 and PMP 30 Conduct testing.

[0092] FTIR detection conditions: at room temperature, performed on a Nicolet IS50 spectrometer.

[0093] 1 H-NMR detection conditions: The sample was dissolved in CDCl3 and the analysis was performed on a Bruker AVIII HD 400MHz spectrometer.

[0094] 2. Experimental Results

[0095] Figure 2 (a) and 2(b) give the FTIR and FTIR of PMPs with different phenyl contents. 1 H-NMR results. Figure 2 (a) 3380~3310cm -1 The absorption peak corresponds to the NH stretching vibration of the terminal amino group in the PMP molecular chain. The peaks are located in the range of 3067–3007 cm⁻¹. -1 The peaks near the phenyl group represent the CH stretching vibrations on the benzene ring, which increase with increasing phenyl content. (1132–1009 cm⁻¹) -1 The broad peaks in the vicinity correspond to the Si-O-Si backbone in the molecular chain. Figure 2 In (b), the chemical shift at 0.1 ppm corresponds to the characteristic absorption peak of the side methyl group in PMP, and the multiple peaks between 7.0 and 8.0 ppm correspond to the characteristic absorption peak of H on the benzene ring. The characteristic absorption peak of the amino group is located at 1.4 ppm, which coincides with the -C-CH2-C- in 1,3-bis(3-aminopropyl)tetramethyldisiloxane. 1 The integral areas of characteristic absorption peaks of different functional groups in the H-NMR spectra were used to calculate the phenyl and amino content in PMPs with different phenyl contents, and the results are shown in Table 2. In addition, the molecular weight data of various PMPs with different phenyl contents are also listed in Table 2.

[0096] Table 2. Content of phenyl and amino groups in PMP and molecular weight of PMP

[0097]

[0098] Figure 2 In (c), at 1644cm -1 The amide I band appears at 1574 cm⁻¹, representing the C=O stretching vibration in ammonium acids. -1 The NH-angle vibration at this point corresponds to the "cyclic breathing" mode found in aromatic amines, belonging to the amide II band. This evidence indicates that amide acids have been successfully introduced into PMPA. The FTIR spectra of the cured and imidized hybrid resins are shown below. Figure 2 As shown in (d). The hybrid resin at 1775 cm⁻¹ -1 and 1716cm -1 Absorption peaks appeared nearby for both asymmetric and symmetric C=O stretching of the imide group. (1390 cm⁻¹) -1The peak at 970 cm⁻¹ represents the CN stretching vibration in the imide group. -1 The nearby peaks belong to the Si-O-ph structure, indicating that the ethoxy group at the end of the PMPI molecular chain successfully reacted with the hydroxyl group in PR, promoting the construction of the three-dimensional cross-linked network structure.

[0099] Experimental Example 2: Microstructure of PMPI / PR hybrid resins with different phenyl contents

[0100] 1. Experimental Methods

[0101] S0, S5, and S2 prepared according to the method described in Example 1 were analyzed using SEM. 15 S 30 The pure phenolic resin (PR) was analyzed and subjected to EDS analysis. AFM and TEM were used to analyze the S... 15 Conduct testing.

[0102] SEM detection conditions: After the sample was fractured in liquid nitrogen, it was observed using a Hitachi Co. S-4800 electron microscope at an accelerating voltage of 15kV.

[0103] AFM testing conditions: Use the tapping mode on the Bruker Dimension ICON to observe the sample cross-section.

[0104] TEM detection conditions: The resin sections were stained with phosphotungstic acid and then observed on a Talos F200S G2.

[0105] 2. Experimental Results

[0106] Figure 3 These are SEM images of cross-sections of hybrid resins with different phenyl contents. Figure 4 This is a SEM image of the cross-section of pure PR. EDS analysis shows that silicone resins with different phenyl contents exhibit uniform distribution within the PR matrix, without significant phase separation behavior. This indicates that introducing ethoxy, imide rings, and phenyl groups into the silicone segments can significantly improve their compatibility with PR, thereby avoiding the formation of island-type phase structures. To further accurately characterize the phase structure of the hybrid resin, S was selected... 15 AFM and TEM tests were performed.

[0107] Figure 5 (a) is using AFM's tap mode on S 15 Results of cross-sectional testing. Based on the different interactions between the probe and the PMPI soft chain and the PR hard chain, the hybrid resin exhibits a bicontinuous structure with a bright-dark distribution in the phase diagram. Figure 5 (b) is S 15The HAADF plot shows that the black portion represents PMPI. It can be seen that PMPI exhibits a nanoscale co-continuous distribution in the matrix, similar to AFM. These results indicate that S... 15 It exhibits a nanoscale dual continuous network microstructure.

[0108] Experimental Example 3: Thermal Performance Study

[0109] 1. Experimental Methods

[0110] S0, S5, and S prepared according to the method described in Example 1 15 S 30 Thermogravimetric analysis (TGA) was performed on pure phenolic resin (PR).

[0111] TGA testing conditions: Tested on a NETZSCH STA 449F3 at a heating rate of 10℃ / min.

[0112] 2. Experimental Results

[0113] To evaluate the effect of PMPI introduction on the thermal stability of the hybrid resin, the thermal degradation behavior of the hybrid resin of this invention under nitrogen and air atmospheres was studied using TGA. The results are as follows: Figure 6 As shown. Characteristic data of resin thermal degradation and heat resistance index are listed in Table 3. Under nitrogen atmosphere, S0~S 30 The residual weight at 800℃ showed little difference, remaining at 47%, a decrease compared to pure PR. This may be because the introduction of PMPI disrupted the three-dimensional network structure of PR, reducing the degree of crosslinking. In air, at 250–350℃, S0, S5, and S... 15 The thermal residual weight increased, which may be due to the ceramization reaction of the PMPI segments, generating SiO2 and causing the weight gain. At 800℃, S0~S 15 The thermal residual weight of PMPI is around 10%, significantly higher than that of pure PR (1.9%). This is because PMPI forms a dense SiO2 protective layer under high temperature and oxygen-containing atmosphere, which to some extent delays the thermal decomposition and oxidation of the PR matrix.

[0114] The degradation activation energy E of all samples was calculated using the Friedmann method at a heating rate of 10 °C / min. a(The Friedman method follows the method described in the literature, Paik P, Kar KK. Thermal degradation kinetics and estimation of lifetime of polyethylene particles: Effects of particlesize. Materials Chemistry and Physics. 2009; 113(2-3):953-61.), and the results are as follows. Figure 6 As shown in (c). S0 (16.71 kJ / mol), S5 (17.29 kJ / mol), S 15 The Ea of S (16.08 kJ / mol) is higher than that of pure PR (11.76 kJ / mol). However, S 30 Ea showed a significant decrease. S0~S 15 The higher degradation activation energy is mainly attributed to the introduction of high-energy Si-O-Si bonds (446 kJ / mol) into the matrix by the addition of PMPI molecular chains, which is much higher than that of C-C (358 kJ / mol) and CO (384 kJ / mol). Simultaneously, the introduced phenyl groups can inhibit the decomposition of Si-O-Si bonds, thereby increasing the degradation activation energy of the hybrid resin. However, when the phenyl content is too high (S... 30 The significant steric hindrance of PMPI hinders the chemical bonding and entanglement of PMPI and PR molecular chains, greatly disrupting the three-dimensional network structure and resulting in a lower degradation activation energy. These results suggest that introducing an appropriate amount of phenyl groups into PMPI should inhibit the thermal degradation of the hybrid resin.

[0115] Table 3. Characteristic thermal data of degradation

[0116]

[0117] T 5％ and T 30％ These are the decomposition temperatures corresponding to 5% and 30% weight loss, respectively. * T Heat-resistance index =0.49×[T 5％ +0.6×(T 30％ -T 5％ )).

[0118] Experimental Example 4: Ablation Resistance of PMPI / PR Hybrid Resin

[0119] 1. Experimental Methods

[0120] S0, S5, and S prepared according to the method described in Example 1 15 S 30The ablation resistance of pure phenolic resin (PR) was tested.

[0121] Test method for ablation resistance: According to GJB 323A-1996, using the ZR-323A oxyacetylene ablation machine from Xi'an Zhirui Company, at 4MW / m 2 Ablation under hot flow for 30 seconds.

[0122] 2. Experimental Results

[0123] Using a heat flux of 4MW / m 2 The ablation resistance of the hybrid resin of this invention was tested using an oxyacetylene flame. Optical images of the ablated hybrid resin are shown below. Figure 7 As shown. Figure 8 (a) and (b) show the linear ablation rate (LAR) and mass ablation rate (MAR) of the resin. With the gradual increase of phenyl content, the linear ablation rate of the hybrid resin gradually decreases, and its ablation resistance improves. 15 The linear ablation rate was the lowest (0.055 mm / s), a decrease of 74.4% compared to pure PR (0.21 mm / s). However, with further increases in phenyl content, the linear ablation rate of the hybrid resin increased, and its ablation resistance decreased. Regarding the mass ablation rate, S... 15The ablation rate of the treated tissue (0.055 g / s) decreased by approximately 15.1% compared to pure PR (0.067 g / s). Compared with PR composites incorporating tetrasilanol octaphenyl POSS (T-POSS) (Niu Z, Li G, Ma X, et al. Synergetic effect of O-POSS and T-POSS to enhance ablative resistant of phenolic-based silica fiber composites via strong interphase strength and ceramic formation[J]. Composites Part A: Applied Science and Manufacturing, 2022, 155: 106855.) and carbon nanotubes (CNTs) (Wang ZJ, Kwon DJ, Gu GY, et al. Ablative and mechanical evaluation of CNT / phenolic composites by thermal and microstructural analyses[J]. Composites Part B: Engineering, 2014, 60: 597-602.) (LAR values ​​are 0.100 mm / s and 0.130 mm / s, respectively), S 15 The LAR value decreased significantly, and the ablation resistance was significantly improved.

[0124] The PR, S0, and S values ​​of the sample were measured using a 3D profilometer. 15 The residual thickness after ablation was calculated, and the thickness difference at each location before and after ablation was divided by the ablation time to obtain the LAR at the corresponding point. Figure 8 In (d), the ablated PR and S 15 Compared to S0, the thickness of the ablation edge region increased significantly, while S0 did not show a significant increase in thickness at the ablation edge region. In the central ablation region where the flame was most intense, S0 and S... f Compared to PR, there was no significant reduction in thickness. For example... Figure 8 As shown in (e), the introduction of an appropriate amount of phenyl group makes S 15 Compared to S0 and PR, the LAR at all points remains at a low level, with a maximum LAR of only 0.055 mm / s, approximately one-quarter that of pure PR (0.21 mm / s). In summary, the hybrid resin of this invention can effectively resist the erosion of high-heat-flux flames and is expected to withstand more demanding service environments in the future.

[0125] The carbon layers of each resin after ablation were characterized by XRD to confirm their composition. The results are as follows: Figure 9 As shown in (a), the diffraction peak observed near 23.6° corresponds to amorphous SiO2. The peaks appearing near 35.3°, 59.9°, and 71.7° belong to the (1 1 1), (2 2 0), and (3 1 1) diffraction planes of SiC, respectively, matching the cubic structure of β-SiC. In addition, a small shoulder peak appears to the left of the (1 1 1) peak, which is a stacking fault formed by SiC grain growth during ablation. The diffraction peaks located at 2θ = 25.7° and 43.1° belong to the (002) and (100) reflections of graphite, indicating that the PR matrix underwent graphitization during ablation.

[0126] Figure 9 (b)~ Figure 9 In (f), XRD and EDS mapping results show that, compared with the pure PR smooth carbon layer, S0~S 30 The carbon layer is covered with a SiO2 / SiC composite ceramic protective layer, which helps enhance the hybrid resin's ability to withstand the impact of high-speed oxygen-containing hot airflow. Compared to S5~S 30 The carbon layer of S0 is covered with a large number of large-diameter SiO2 spheres. This is likely because the liquid SiO2 generated on the surface of the S0 carbon layer during ablation is not very resistant to the high-speed, high-pressure oxyacetylene flame, causing it to flow towards the original layer along with the hot air. These washed-down molten SiO2 undergo nucleation and growth on the side of the carbon layer, and after ablation, as the temperature decreases, the surface tension of the SiO2 increases, gradually cooling and forming spheres. For S5 to S... 30 Enlarge the area within the red frame, as shown below. Figure 9 (d')~ Figure 9 As shown in (f'), the diameter of the SiO2 spheres on the side of the carbon layer is significantly reduced. This may be related to the fact that the introduced phenyl group helps to increase the viscosity of the SiO2 liquid film, thereby enhancing its ability to resist the impact of hot airflow.

[0127] The above experimental results show that the PMPI / PR hybrid resin of the present invention has good ablation resistance, wherein S 15 It has the best resistance to ablation.

[0128] Experimental Example 5: Chemical and Microstructure of the xFPA of the present invention

[0129] 1. FTIR analysis of xFPA in this invention

[0130] Figure 11 a shows the FTIR plot of xFPA. Hybrid resin particles in xPFA at 1775 cm⁻¹ -1and 1716cm -1 Absorption peaks appeared nearby for both asymmetric and symmetric C=O stretching of the imide group. (1390 cm⁻¹) -1 The peak at the peak represents the C=N stretching vibration in the imide group. All xFPA aerogel composites exhibit similar FTIR curves, indicating that their internal PMPI / PR hybrid resin aerogels have similar chemical structures.

[0131] 2. XPS analysis of xFPA in this invention

[0132] The chemical state of xFPA was further analyzed using XPS. Figure 11 b. It can be seen that all xFPAs contain C, O, and Si elements. Furthermore, MFPAs also contain Al, corresponding to the Al₂O₃ component. Figure 11 In the high-resolution scanning C-spectrum of CFPA, taking CFPA as an example, the C 1s peaks at 284.44, 284.89, 286.08, 287.33, and 291.43 eV represent C-Si, C=C, CO, CN, and C=O, respectively. C-Si originates from the Si-CH3 in the PMPI backbone, C=C corresponds to the benzene ring structure in the hybrid resin, and CO belongs to the -CH2-O-CH2- structure in PR. CN and C=O originate from the imide ring in the hybrid resin.

[0133] Figure 11 Figure d shows the XRD patterns of three fiber felts and their xFPAs. In CFPA, the peaks at 25.5° and 42.5° correspond to the (002) and (100) planes of graphite in the carbon fiber felt, respectively. In HFPA, the broad peak near 22.2° represents amorphous SiO2. In addition, compared to the high-silica fiber felt, HFPA shows peaks near 38.4°, 44.5°, 64.8°, and 77.9°, which may be the corresponding peaks of the hybrid resin. In MFPA, the peaks near 20.0° and 67.0° represent SiO2, and the five peaks at 32.5°, 37.2°, 39.6°, 45.6°, and 66.9° correspond to the (220), (311), (222), (400), and (440) planes of low-crystallinity Al2O3.

[0134] 3. SEM images of xFPA of the present invention

[0135] Figure 12 a~ Figure 12 f shows the SEM image of xFPA. From Figure 12As can be seen from a to c, almost no aerogel particles adhere to the surface of the carbon fiber, while a large number of aerogel particles aggregate and grow on the surfaces of the high-silica fiber and mullite fiber. This may be related to the fact that the latter two can form hydrogen bonds with the hybrid resin. Furthermore, from... Figure 12 As can be observed from d to f, all aerogel composites exhibit similar bicontinuous and permeable structures. These aerogel networks possess a submicron-scale bicontinuous framework composed of grape-like aggregates of nanoscale PMPI / PR hybrid resin particles. Between these frameworks, mesoporous and macroporous structures are formed, laying the foundation for the lightweight and thermal insulation properties of xFPA. The particle size of the aerogel particles in the SEM was calculated (…). Figure 12 g~ Figure 12 i) The results showed that the aerogel particle size in CFPA, MFPA and HFPA increased from 0.113 μm to 0.162 μm, which may be related to the material composition of the fiber mat. Figure 12 j~ Figure 12 l shows the adsorption-desorption isotherm of xFPA aerogel composite material.

[0136] According to IUPAC classification, all samples exhibited typical Type IV isotherms and an H3 hysteresis loop at high relative pressure caused by capillary condensation, indicating the presence of mesopores and macropores within the composite material. Pore size distribution ( Figure 12 j~ Figure 12 The attached figure (Figure 1) shows that the pore size of the xFPA aerogel composite material is mostly concentrated in the range of 20-40 nm, indicating that mesopores are the main component. The results of the BET surface area, pore surface area, and pore volume measured by the specific surface area assay are listed in Table 4. Table 4 shows that the ratio of mesopore volume to total pore volume in xFPA is 92%–95%, further indicating that the pores in the xFPA aerogel composite material are mainly mesopores.

[0137] Table 4 shows the correlation results of BET surface area, pore surface area, and pore volume of the xFPA of this invention.

[0138]

[0139] Note: S BET :BET surface area; S mic : Micropore surface area; S meso: Cumulative desorption surface area for pore sizes ranging from 1.7 to 300 nm; V mic : Micropore volume; V mesoCumulative desorption volume for pore sizes ranging from 1.7 to 300 nm; V total Total pore volume calculated at a relative pressure of 0.99.

[0140] Experimental results show that aerogel composites with nanoscale pore sizes were successfully synthesized through a multi-level robust strategy involving sol-gel and polymerization-induced phase separation. These abundant nanoscale pores endow the material with excellent thermal insulation properties.

[0141] Experimental Example 6: Investigation of the mechanical properties and thermal stability of the xFPA of the present invention

[0142] 1. Investigation into the mechanical properties of the xFPA of this invention

[0143] The xFPA of this invention was fabricated into 10*10*10mm cubes, and the mechanical properties of all xFPA aerogel composites were evaluated using a universal testing machine with a loading speed of 0.2mm / min. The results are as follows: Figure 13 As shown, the xy direction refers to the horizontal direction of the fiber felt, and the z direction refers to the direction perpendicular to the horizontal plane.

[0144] Figure 13 a and Figure 13 b shows the typical stress-strain curves of these aerogel composites in the xy and z directions, both exhibiting the typical nonlinear upward-convex compressive response of porous materials. The compression process of aerogel composites can be divided into three stages. The first stage is the linear elastic stage, in which the pore structure in the aerogel composite can recover after stress relief, achieving 100% volume recovery. The second stage is the yielding stage, where the curve shows a nonlinear rise. In the xy direction, pore collapse and irreversible fiber yielding occur in the aerogel composite, while in the z direction, the aerogel composite can withstand more than 35% compression without catastrophic collapse. Finally, in the compaction stage, the aerogel composite is gradually compacted in both the xy and z directions, eventually causing irreversible damage.

[0145] Figure 13 c shows the compressive strength and Young's modulus of xFPA in the xy and z directions. It can be seen that CFPA exhibits the highest compressive strength and Young's modulus in both the xy and z directions, demonstrating the excellent reinforcing effect of carbon fiber mat on the mechanical properties of aerogels.

[0146] Simultaneously, cyclic loading-release tests were conducted on all xFPAs to study the elasticity of the aerogel composites, and the results are as follows: Figure 13 d~ Figure 13As shown in f, CFPA is slightly inferior to HFPA and MFPA in terms of elasticity. After ten cycles, CFPA recovers only 92% of its initial size, while HFPA and MFPA recover 94%. Furthermore, CFPA retains only 85% of its initial maximum compressive strength, while HFPA and MFPA retain 94% of their initial maximum compressive strength.

[0147] 2. Investigation into the thermal stability and insulation performance of the xFPA of this invention

[0148] The thermal stability of all xFPA aerogel composites in nitrogen and air was tested, and the results are as follows: Figure 14 As shown, optical images of xFPA after ablation under different heat fluxes and times are as follows: Figure 15 As shown, all xFPAs exhibited similar DTG curves regardless of whether they were in nitrogen or air, consistent with the common pyrolysis process of PR aerogels. Weight loss between room temperature and 300°C was primarily due to the removal of small molecules such as adsorbed water. Between 300 and 600°C, the weight loss was mainly due to the vigorous thermal decomposition of the hybrid resin. At 800°C in air, the thermal residual weight of CFPA was 46%, lower than that of HFPA (51%) and MFPA (58%), indicating that HFPA and MFPA are significantly superior to CFPA in terms of thermal stability.

[0149] In addition, the present invention also uses a Hot Disk thermal constant analyzer to test the thermal conductivity of CFPA, HFPA and MFPA. The thermal conductivity of CFPA, HFPA and MFPA are 0.0733, 0.05394 and 0.06396 respectively. HFPA has the best thermal conductivity, which is significantly lower than that of CFPA and MFPA.

[0150] Experimental results show that the thermal stability and thermal insulation performance of HFPA and MFPA prepared by this invention are better than those of CFPA. Among them, MFPA has the best thermal stability and HFPA has the best thermal insulation performance.

[0151] Experimental Example 7: Ablation Performance of the xFPA of the Present Invention

[0152] 1. Ablation experiments and results of the xFPA of this invention

[0153] xFPA aerogel composites at heat flux densities of 1 MW / m 2 and 2MW / m 2 The ablation behavior under an oxyacetylene flame was studied. The morphology and ablation rate after ablation are shown in the following figures. Figure 16 As shown.

[0154] It can be seen that at 1MW / m 2As the ablation time increased, the surfaces of all xFPAs did not show significant changes and the conditions were similar: the ablation center was covered by a layer of gray material, while the ablation edges appeared black and charred.

[0155] When the heat flux density increases to 2MW / m 2 After 30 seconds of ablation, the various xFPAs exhibited distinctly different ablation morphologies. In the ablation center of the CFPA, the fibrous skeleton structure and the pores created by the overflow of pyrolysis gases during ablation were clearly visible. The ablation center of the HFPA was covered with white and grayish-green material, exhibiting a wave-like morphology.

[0156] 2. Analysis of 3D profilometry results of ablation experiments using the xFPA of this invention

[0157] The surface undulations of the ablation of samples under different heat flows and ablation times were characterized using a 3D profilometer, and plotted on [the graph / plotting method]. Figure 17 In the middle. At 1MW / m 2 Under heat flux, with prolonged ablation time, CFPA and MFPA showed slight indentation at the ablation center. In contrast, HFPA exhibited significant expansion at the ablation center. At 2MW / m 2 After 30 seconds of ablation under hot flux, all xFPAs showed significant ablation retreat, with the MFPA exhibiting the most pronounced retreat. For all xFPAs at 1 MW / m... 2 Lower ablation 30s and 90s, 2MW / m 2 The linear ablation rate and mass ablation rate after 30 s of ablation were calculated, and the results are shown in Table 5. When the heat flux density is relatively low (1 MW / m³), 2 HFPA exhibited a superior linear ablation rate, but its mass ablation rate was significantly higher than that of CFPA and MFPA. With increasing heat flux density (2MW / m²), 2 In comparison, the line ablation rates of HFPA and MFPA both showed a significant increase, while CFPA showed only a slight increase. Therefore, overall, CFPA is more adaptable to various ablation environments.

[0158] Table 5 shows the linear ablation rate and mass ablation rate of xFPA under different conditions.

[0159]

[0160] Note: LAR line ablation rate, MAR mass ablation rate.

[0161] 3. Characterization and testing of the ablation experimental surface layer and pyrolysis layer of the xFPA of this invention.

[0162] Based on the macroscopic ablation behavior analysis, this invention further delves into the three-dimensional skeletal support effect of different fiber mats under different heat flows, specifically at 1MW / m². 2 and 2MW / m 2 After 30 seconds of ablation, the surface layer and pyrolysis layer of the sample were characterized by corresponding tests, and the results are as follows: Figure 17 As shown. Figure 17 a- Figure 17 c shows that at 1MW / m 2 The surface microstructure of xFPA was observed after 30 seconds of ablation. It can be seen that the surfaces of CFPA, HFPA, and MFPA are all covered by a continuous and dense protective film. According to EDS Mapping... Figure 17 a- Figure 17 c) and XRD Figure 18 As a result of g), this protective film should be a mixed ceramic layer of SiO2 and SiC, which may be due to the in-situ ceramicization of the hybrid resin matrix during the ablation process. This ceramic layer has radiative heat dissipation and a low oxygen diffusion coefficient. At the same time, under low heat flux temperatures, the high silica fiber felt and mullite fiber felt do not melt or only partially melt, and still have excellent three-dimensional skeleton support capabilities. Together, they resist the erosion of high-temperature oxygen-containing hot airflow. Figure 17 g- Figure 17 i then showed 1MW / m 2 The pyrolysis layer of the composite material under heat flux. After pyrolysis, the hybrid resin matrix forms a thin C / Si composite layer covering the fiber surface, which can prevent the fibers from contacting the high-temperature gas flow to a certain extent. In addition, the aerogel particles in the fiber gaps, due to active pyrolysis, continuously generate pyrolysis gases that can provide internal pressure, thereby further preventing oxygen penetration. Meanwhile, the nanoscale porous structure in the original layer of the composite material remains intact, giving xFPA excellent thermal insulation capabilities. Therefore, under low heat flux, CFPA, HFPA, and MFPA all exhibit excellent thermal protection capabilities. Figure 18 h illustrates the changes that occur in the fiber mat and resin matrix of the aerogel composite under low heat flux. Change description: Under low heat flux (1MW / m²), 2 Because the temperature (1800℃) and mechanical ablation ability of the oxyacetylene flame are both at a relatively low level, none of the three types of fiber felts will melt. Simultaneously, the SiO2 and SiC composite ceramic layer generated after the in-situ ceramization of the hybrid resin matrix can cover the surface of the fiber felt, playing a role in radiative heat dissipation and oxygen isolation. The gas generated in the pyrolysis layer of the aerogel composite material can provide internal pressure, thereby preventing oxygen penetration, while the nanoscale porous structure in the original layer has excellent thermal insulation capabilities.

[0163] As the heat flux density increases, the surface morphology of xFPA also changes significantly. Figure 17 d- Figure 17 f shows that at 2MW / m 2 The condition of the xFPA surface layer after 30 seconds of ablation under thermal flux. Compared to 1MW / m 2 2MW / m 2 The oxyacetylene flame possesses stronger mechanical ablation capabilities and higher temperatures. Therefore, in the surface layer of CFPA, most of the SiO2 and SiC generated by the ceramization of the hybrid resin matrix are blown away by the oxyacetylene flame, leaving only a three-dimensional network structure composed of carbon fibers. A magnified view of a single fiber and EDS mapping tests were performed, and the results are as follows... Figure 17 As shown in the inset diagram of d, the fiber surface contains a relatively high amount of Si. The HFPA surface exhibits a relatively smooth SiO2 liquid film formed after the high-silica fibers melt and cool, with some pores caused by the overflow of pyrolysis gases. The MFPA surface is scattered with mixed Al2O3 and SiO2 microspheres remaining after being subjected to high-temperature, high-speed oxyacetylene flame erosion, which is consistent with... Figure 17 c forms a stark contrast. Combined with Figure 16 d, can be found at 2MW / m 2 Under heat flux, high-silica fiber felt and mullite fiber felt melt, losing the unique three-dimensional skeletal support of the fiber felt and thus failing to provide the aerogel composite with good resistance to oxyacetylene flame erosion, resulting in a significant decrease in its thermal radii (LAR). In contrast, carbon fiber felt has excellent skeletal support, giving the aerogel composite good thermal protection capabilities. Figure 17 j~ Figure 17 l shows the situation of the pyrolysis layer, which is compared with 1MW / m 2 The situation of the pyrolysis layer after 30 seconds of ablation is similar.

[0164] To further characterize the surface composition of the ablation-treated aerogel composite, XPS and XRD tests were performed. Figure 18 (a)-(f) show the high-resolution scanning spectra of Si 2p on the surface of the three aerogel composites after ablation with different thermal fluxes. The Si 2p peaks are concentrated at 101.7 and 103.6 eV. Figure 18 (a)); 102.1, 103.6 eV ( Figure 18 (d)); 101.7, 103.1 eV ( Figure 18 b); 101.7, 103.2 eV ( Figure 18 (e)); 101.7, 102.8 eV ( Figure 18 (c)); 101.7, 103.4 eV ( Figure 18 f). These correspond to SiC and SiO2, respectively, which are generated by the pyrolysis of hybrid resin particles during ablation. Figure 18(g) shows the XRD pattern of the sample surface. No SiO2 peak was detected in the CFPA, which may be due to the low CFPA content or its amorphous state. At 2MW / m²... 2 At that time, neither CFPA nor HFPA showed a SiC peak.

[0165] like Figure 18 As shown in h, under low heat flux (1MW / m 2 Because the temperature (1800℃) and mechanical ablation ability of the oxyacetylene flame are both at a relatively low level, none of the three types of fiber felts will melt. Simultaneously, the SiO2 and SiC composite ceramic layer generated after the in-situ ceramization of the hybrid resin matrix can cover the surface of the fiber felt, playing a role in radiative heat dissipation and oxygen isolation. The gas generated in the pyrolysis layer of the aerogel composite material can provide internal pressure, thereby preventing oxygen penetration, while the nanoscale porous structure in the original layer has excellent thermal insulation capabilities.

[0166] like Figure 18 As shown in i, with the increase of heat flux (2MW / m 2 In oxyacetylene flames, the temperature (2300℃) and mechanical ablation capacity increase significantly. Under these conditions, high-silica fibers and mullite fibers melt and lose their three-dimensional skeletal support. Furthermore, the molten SiO2 and SiO2 / Al2O3 cannot effectively resist the mechanical ablation of the oxyacetylene flame, leading to a significant decrease in the thermal elasticity (LAR) of the aerogel composite. In contrast, carbon fiber felt retains good morphological retention during ablation, maintaining its three-dimensional skeletal support. Simultaneously, the SiO2 and SiC formed by the ceramicization of the hybrid resin adhere to the carbon fibers, further enhancing their oxidation resistance and maximizing the preservation of the aerogel composite's shape and thermal insulation capabilities. This invention discloses an integrated ablation / thermal insulation organosilicon hybrid phenolic aerogel composite material, its preparation method, and its applications. First, a PMPI / PR hybrid resin is prepared through anionic ring-opening polymerization and copolymerization. Then, using this hybrid resin as the matrix, three different fiber felt aerogel composite materials are prepared using carbon fiber felt, high-silica fiber felt, and mullite fiber felt as three-dimensional framework structures through a robust multi-level strategy of sol-gel and polymerization-induced phase separation. This invention generates pores with sizes ranging from 15 nm to 3 μm within the aerogel composite material through polymerization-induced phase separation. Vacuum impregnation fills the internal pores of the fiber felt with the matrix solution. During the subsequent sol-gel process, polymerization-induced phase separation occurs in the hybrid resin, separating the system into a phase rich in hybrid resin and a phase rich in solvent EG. Then, solvent replacement replaces EG with EtOH to reduce capillary pressure during atmospheric drying. Finally, atmospheric drying removes the solvent, yielding the xFPA aerogel composite material with nanoscale pores. In particular, the carbon fiber felt aerogel composite material exhibits high pore size at 2 MW / m³. 2Under a 30s heat flow environment, the three-dimensional skeleton maintained its supporting function, and the carbon fiber felt aerogel composite material had superior shape retention and thermal insulation capabilities.

[0167] The fiber-felt aerogel composite material of this invention exhibits excellent thermal stability, mechanical properties, thermal insulation performance, and ablation resistance. Among them, HFPA and MFPA demonstrate superior thermal stability and thermal insulation performance compared to CFPA, with MFPA showing the best thermal stability and HFPA the best thermal insulation performance. CFPA possesses excellent mechanical properties and ablation resistance. This invention achieves integrated ablation / thermal insulation functionality under different heat flux environments, making it suitable as a lightweight thermal protection material, building fireproofing material, lithium battery fireproofing material, and particularly promising for application as a thermal protection material for high-speed aircraft.

Claims

1. A fiber-felt aerogel composite material, characterized in that, It is a composite material made from fiber felt and hybrid resin as raw materials according to the following method: 1) Take the hybrid resin, dissolve it in an organic solvent to obtain a hybrid resin solution with a concentration of 15-25 wt%, and soak the fiber felt in the hybrid resin solution to obtain a fiber felt permeated by the hybrid resin solution. 2) The fiber mat permeated with the hybrid resin solution obtained in step 1) is subjected to sol-gel to obtain a wet fiber mat gel. 3) Solvent replacement and drying of the wet fiber felt gel yields a fiber felt aerogel composite material; The fiber felt is carbon fiber felt; the hybrid resin is organosilicon hybrid phenolic resin; The organosilicon hybrid phenolic resin is prepared by the following method; (1) In a solvent, 3,3',4,4'-biphenyltetracarboxylic acid dianhydride and PMP are mixed and reacted; (2) After adding (3-aminopropyl)triethoxysilane, the reaction continued to yield PMPA; (3) React PMPA with phenolic resin solution to obtain; The PMP was prepared using octaphenylcyclotetrasiloxane, octamethylcyclotetrasiloxane and 1,3-bis(3-aminopropyl)tetramethyldisiloxane as raw materials.

2. The fiber-felt aerogel composite material according to claim 1, characterized in that, The preparation method of the PMP includes the following steps: Octaphenylcyclotetrasiloxane, octamethylcyclotetrasiloxane, 1,3-bis(3-aminopropyl)tetramethyldisiloxane and a catalyst are mixed, and an inert gas is introduced to react, thus obtaining the product.

3. The fiber-felt aerogel composite material according to claim 2, characterized in that, The catalyst is tetramethylammonium hydroxide.

4. The fiber-felt aerogel composite material according to claim 2, characterized in that, The reaction is carried out at 100~120℃ for 1~5 hours, and then the temperature is raised to 150~200℃ and held for 0.5~5 hours.

5. The fiber felt aerogel composite material according to claim 2, characterized in that, The mass of the catalyst is 0.5% to 5% of the total mass of octaphenylcyclotetrasiloxane and octamethylcyclotetrasiloxane.

6. The fiber-felt aerogel composite material according to claim 2, characterized in that, The molar ratio of the octaphenylcyclotetrasiloxane, octamethylcyclotetrasiloxane and 1,3-bis(3-aminopropyl)tetramethyldisiloxane is (0.5~3):(7~9.5):

2.

7. The fiber-felt aerogel composite material according to claim 6, characterized in that, The molar ratio of the octaphenylcyclotetrasiloxane, octamethylcyclotetrasiloxane, and 1,3-bis(3-aminopropyl)tetramethyldisiloxane is 1.5:8.5:

2.

8. The fiber-felt aerogel composite material according to claim 1, characterized in that, The molar ratio of the amino group in the PMP to the anhydride in the 3,3',4,4'-biphenyltetracarboxylic acid dianhydride is 1:(1~1.1). The (3-aminopropyl)triethoxysilane is 20%~40% mol of amino content in PMP.

9. The fiber-felt aerogel composite material according to any one of claims 1-8, characterized in that, The organosilicon hybrid phenolic resin is prepared by the following method; (1) In a solvent, 3,3',4,4'-biphenyltetracarboxylic acid dianhydride and PMP are mixed and reacted; (2) After adding (3-aminopropyl)triethoxysilane, the reaction continued to yield PMPA; (3) React PMPA with phenolic resin solution to obtain the product.

10. The fiber-felt aerogel composite material according to claim 9, characterized in that, In step (1), the solvent is tetrahydrofuran; And / or, in step (1), the reaction temperature is 30~50℃, the reaction time is 1~5h; the mass ratio of the solvent to PMP is (1~5):1; And / or, in step (2), the temperature of the reaction is 30~50℃ and the reaction time is 1~5h; And / or, in step (3), the solvent of the phenolic resin solution is ethanol, wherein the mass ratio of phenolic resin to ethanol is (0.5-1):1, the reaction temperature is 50~110℃, and the reaction time is 0.5-2h.

11. A method for preparing the fiber felt aerogel composite material according to any one of claims 1-10, characterized in that, The method includes the following steps: 1) Take the hybrid resin, dissolve it in an organic solvent to obtain a hybrid resin solution with a concentration of 15-25 wt%, and soak the fiber felt in the hybrid resin solution to obtain a fiber felt permeated by the hybrid resin solution. 2) The fiber mat permeated with the hybrid resin solution obtained in step 1) is subjected to sol-gel to obtain a wet fiber mat gel. 3) The wet fiber felt gel was solvent-displaced and dried to obtain a fiber felt aerogel composite material.

12. The method according to claim 11, characterized in that, In step 1), the pressure environment is below 0.5 MPa; the organic solvent is ethylene glycol, dimethylformamide, tetrahydrofuran, or acetone; in step 3), the solvent used for solvent replacement is ethanol, tetrahydrofuran, or acetone.

13. The method according to claim 12, characterized in that, The organic solvent mentioned in step 1) is ethylene glycol.

14. The method according to claim 12, characterized in that, Step 3) The solvent used for solvent replacement is ethanol.

15. The method according to claim 11 or 12, characterized in that, The concentration of the hybrid resin solution mentioned in step 1) is 20 wt%; The pressure environment in step 1) is below 0.1 MPa; The sol-gel conditions described in step 2) are as follows: maintain the temperature at 100-140℃ for 1-3 h, 130-170℃ for 1-3 h, 160-200℃ for 1-3 h, and 180-220℃ for 1-3 h.

16. The method according to claim 15, characterized in that, The pressure environment is 0.095 MPa.

17. The method according to claim 15, characterized in that, The sol-gel conditions described in step 1) are as follows: keep at 120℃ for 2 hours, 150℃ for 2 hours, 180℃ for 2 hours, and 200℃ for 1 hour.

18. Use of the fiber felt aerogel composite material according to any one of claims 1-10 in the preparation of ablation-resistant materials and / or thermal insulation materials and / or thermally stable materials.

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