A method for preparing a flame-retardant hydrophobic aerogel composite by a co-precursor method

Abstract

The application provides a method for preparing a flame-retardant hydrophobic aerogel composite material by a co-precursor method, which comprises the following steps: mixing a water glass solution and phosphoric acid to perform a hydrolysis reaction, so as to obtain an acidic hydrolysis solution; mixing 3-aminopropyl triethoxysilane, water and anhydrous ethanol to perform a hydrolysis reaction, so as to obtain an alkaline hydrolysis solution; mixing the acidic hydrolysis solution and the alkaline hydrolysis solution to perform a reaction, so as to obtain a co-precursor pre-polymer solution; continuously adding the water glass solution, and compounding the water glass solution with a glass fiber felt before gelation, so as to form a silica wet gel composite felt; sealing and aging the silica wet gel composite felt in a precursor solvent, and then performing surface modification on the silica wet gel composite felt in a mixed solution of hexamethyldisiloxane, anhydrous ethanol and hydrochloric acid, and drying, so as to obtain the flame-retardant hydrophobic aerogel composite material. The aerogel has excellent flame retardancy and heat insulation.

Description

Technical Field

[0001] This invention belongs to the field of thermal insulation, green energy-saving and flame-retardant material preparation technology, and particularly relates to a method for preparing flame-retardant hydrophobic aerogel composite materials by a co-precursor method. Background Technology

[0002] Silica aerogel is a high-performance porous material. Its unique three-dimensional network pore structure helps achieve a low density (0.03~0.50 g / cm³). 3 Low thermal conductivity (0.017 W / m·K) and ultra-high specific surface area (500~1200 m²) 2 Aerogels possess excellent properties such as pergola ( / g). These superior properties enable their widespread application in various fields, including building insulation, waste gas adsorption, catalyst carriers, and aerospace. Low-cost and rapid industrial preparation processes are further expanding the application areas of aerogels.

[0003] The most commonly used silica aerogels are hydrophobic, achieved by introducing a large number of organic groups into them. While these organic groups help the aerogel maintain its thermal insulation properties over a long period, they also introduce potential thermal hazards. At high temperatures, these organic groups can pyrolyze, producing flammable gases such as CH4 and CO, posing a certain risk of combustion. As the application range of thermal insulation materials continues to expand, the thermal hazards of aerogel materials are gradually attracting attention.

[0004] Research on the flame retardancy of hydrophobic aerogels has also been initiated. Sanchez-Soto studied the combustion behavior of flame-retardant-modified polyvinyl alcohol (PVOH) / clay composite aerogels, finding that adding ammonium polyphosphate (APP) or Al(OH)3 could reduce the heat release rate (HRR) of the PVOH / clay composite aerogel. Yinfeng Wang et al. replaced trimethylchlorosilane (HMDSO) with dimethylchlorosilane (DMDCS) to modify silica gel, focusing on the thermal hazard assessment of DMDCS-modified silica aerogels (DSA), demonstrating that the total calorific value could be reduced by approximately 12%, providing a potential solution to address the thermal hazards of hydrophobic silica aerogels. Li Zhi et al. used Al(OH)3 and Mg(OH)2 as dopants to reduce the flammability of hydrophobic silica aerogels, demonstrating that the flame retardant effect of Al(OH)3 and Mg(OH)2 is related to their inhibitory effect on the pyrolysis of SA, and that Mg(OH)2 significantly improved the flame retardant properties of silica aerogels.

[0005] Currently, research on suppressing the combustion of SiO2 aerogels can be broadly categorized into two types: physical composite methods and chemical structure optimization design. However, physical composite methods can lead to uneven distribution of flame retardants, easy surface detachment, poor flame retardant effect, and weakened thermal insulation effect. While chemical structure optimization can reduce the fire risk to some extent, it cannot suppress flame combustion. Therefore, there is an urgent need to prepare an aerogel that can effectively suppress the combustion risk while maintaining excellent thermal insulation performance. Summary of the Invention

[0006] In view of this, the purpose of this invention is to provide a method for preparing flame-retardant hydrophobic aerogel composite materials by a co-precursor method, wherein the aerogel composite materials prepared by this method have excellent flame-retardant properties.

[0007] This invention provides a method for preparing flame-retardant hydrophobic aerogel composite materials using a co-precursor method, comprising the following steps:

[0008] A water glass solution and phosphoric acid were mixed and hydrolyzed to obtain an acidic hydrolysate; 3-aminopropyltriethoxysilane, water and anhydrous ethanol were mixed and hydrolyzed to obtain an alkaline hydrolysate.

[0009] The acidic hydrolysate and alkaline hydrolysate are mixed and reacted to obtain a co-precursor prepolymer solution. Water glass solution is then added and combined with glass fiber mat before gelation to form a silica wet gel composite mat.

[0010] The silica wet gel composite felt was sealed and aged in a precursor solvent, then surface modified in a mixed solution of hexamethyldisiloxane, anhydrous ethanol and hydrochloric acid, and dried to obtain a flame-retardant hydrophobic aerogel composite material.

[0011] Preferably, the pH value of the acidic hydrolysate is 4.2 to 4.8;

[0012] The pH value of the alkaline hydrolysate is 8.5~9.5.

[0013] Preferably, the water glass solution has a mass fraction of 10-12%.

[0014] Preferably, the volume ratio of the 3-aminopropyltriethoxysilane to the total volume of the 3-aminopropyltriethoxysilane, water, and anhydrous ethanol is 2.5 to 10%.

[0015] Preferably, the pH value of the co-precursor prepolymer solution is 4.5~5.5;

[0016] The pH of the system before gelation is 5.5-6.5 after the addition of water glass solution.

[0017] Preferably, the mass ratio of the co-precursor prepolymer liquid to the glass fiber mat before composite is 2:4~6.

[0018] Preferably, the sealing aging temperature is 20~50℃;

[0019] The sealing aging time is 4~8 hours.

[0020] Preferably, the volume ratio of hexamethyldisiloxane, anhydrous ethanol and hydrochloric acid used for surface modification is 1:1:1.8~2.1.

[0021] Preferably, the surface modification temperature is 50~60℃ and the surface modification time is 2~4h.

[0022] Preferably, the drying is performed by atmospheric pressure staged drying;

[0023] The atmospheric pressure staged drying was carried out at 80℃, 100℃, and 120℃ for 1 h, 1.5 h, and 2 h, respectively.

[0024] This invention provides a method for preparing flame-retardant and hydrophobic aerogel composite materials using a co-precursor method, comprising the following steps: mixing water glass solution and phosphoric acid for hydrolysis to obtain an acidic hydrolysate; mixing 3-aminopropyltriethoxysilane, water, and anhydrous ethanol for hydrolysis to obtain an alkaline hydrolysate; mixing the acidic and alkaline hydrolysates to obtain a co-precursor prepolymer; adding water glass solution and then combining it with glass fiber mat before gelation to form a silica wet gel composite mat; sealing and aging the silica wet gel composite mat in a precursor solvent, then surface modifying it in a mixed solution of hexamethyldisiloxane, anhydrous ethanol, and hydrochloric acid, and drying it to obtain the flame-retardant and hydrophobic aerogel composite material. This invention involves hydrolyzing 3-aminopropyltriethoxysilane to form highly reactive 3-aminopropyltriethoxysilanol, which is then grafted onto the surface of an aerogel. On one hand, the amino group inherent in the 3-aminopropyltriethoxysilanol reacts with subsequent phosphoric acid to generate ammonium phosphate groups, which possess highly efficient flame-retardant properties and can inhibit the combustion performance of hydrophobic aerogels. On the other hand, the 3-aminopropyltriethoxysilanol group itself contains alkyl groups, which can play a role in hydrophobic modification, ensuring the excellent thermal insulation performance of the aerogel, ultimately achieving a balance between thermal insulation and flame-retardant properties of the aerogel.

[0025] This invention completes the surface hydrophobic modification and flame retardant group grafting of silica aerogel in a one-step reaction, simplifying the process and eliminating the two-step process of first hydrophobic modification and then flame retardant doping in the traditional method. The method is simple, convenient and easy to implement. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the process for preparing flame-retardant hydrophobic aerogel composite materials using the co-precursor method of the present invention.

[0027] Figure 2This is a SEM image of the flame-retardant and hydrophobic aerogel composite material SAB-2 prepared in Example 2 of the present invention;

[0028] Figure 3 This is a schematic diagram of the SEM image and hydrophobic angle of the powder in the flame-retardant hydrophobic aerogel composite material SAB-2 prepared in Example 2 of the present invention;

[0029] Figure 4 The image shows the physical product of the flame-retardant and hydrophobic aerogel composite material SAB-2 prepared in Example 2 of this invention.

[0030] Figure 5 The N2 adsorption-desorption curves of the aerogel composite materials prepared in the embodiments and comparative examples of the present invention are shown.

[0031] Figure 6 The graph shows the total heat release curves of the aerogel composite materials prepared in the embodiments and comparative examples of the present invention in the cone mass experiment. Detailed Implementation

[0032] This invention provides a method for preparing flame-retardant hydrophobic aerogel composite materials using a co-precursor method, comprising the following steps:

[0033] A water glass solution and phosphoric acid were mixed and hydrolyzed to obtain an acidic hydrolysate; 3-aminopropyltriethoxysilane, water and anhydrous ethanol were mixed and hydrolyzed to obtain an alkaline hydrolysate.

[0034] The acidic hydrolysate and alkaline hydrolysate are mixed and reacted to obtain a co-precursor prepolymer solution. Water glass solution is then added and combined with glass fiber mat before gelation to form a silica wet gel composite mat.

[0035] The silica wet gel composite felt was sealed and aged in a precursor solvent, then surface modified in a mixed solution of hexamethyldisiloxane, anhydrous ethanol and hydrochloric acid, and dried to obtain a flame-retardant hydrophobic aerogel composite material.

[0036] This invention prepares a novel flame-retardant gel by in-situ chemical grafting. The dihydrogen phosphate group is grafted into the silica polymer network through the chemical bond of 3-aminopropyltriethoxysilane, which significantly improves the flame retardant efficiency. While maintaining its excellent properties, the synthesis is simple, green and energy-saving, and easy to operate.

[0037] This invention involves mixing a water glass solution and phosphoric acid to undergo a hydrolysis reaction, yielding an acidic hydrolysate. The water glass solution used in this invention has a mass fraction of 10-12%; preferably, it is prepared by diluting 34% water glass with water; the volume ratio of 34% water glass to water is 1:3. This invention preferably uses 85% phosphoric acid. Preferably, the diluted water glass solution is added to the phosphoric acid; preferably, the acidic hydrolysis is carried out under magnetic stirring.

[0038] The reactions involved in the preparation of the acidic hydrolysate are as follows:

[0039]

[0040]

[0041] The pH value of the acidic hydrolysate prepared by this invention is controlled at 4.2~4.8; specifically, it can be 4.2, 4.3, 4.4, 4.5, 4.6, 4.7 or 4.8.

[0042] In this invention, 3-aminopropyltriethoxysilane, water, and anhydrous ethanol are mixed and hydrolyzed to obtain an alkaline hydrolysate.

[0043] In this invention, the volume ratio of the 3-aminopropyltriethoxysilane to the total volume of the 3-aminopropyltriethoxysilane, water, and anhydrous ethanol is 2.5% to 10%; specifically, the volume ratio is 2.5%, 3.0%, 3.5%, 4.0%, 4.5%, 5.0%, 5.5%, 6.0%, 6.5%, 7.0%, 7.5%, 8.0%, 8.5%, 9.0%, 9.5%, or 10%. The volume ratio of water to anhydrous ethanol is 1:1.

[0044] In this invention, the hydrolysis reaction is carried out by mixing 3-aminopropyltriethoxysilane, water, and anhydrous ethanol at room temperature, preferably 15-30°C. The pH of the alkaline hydrolysate is 8.5-9.5; specifically, it can be 8.5, 8.6, 8.7, 8.8, 8.9, 9.0, 9.1, 9.2, 9.3, 9.4, or 9.5.

[0045] After obtaining the acidic hydrolysate and the alkaline hydrolysate, the present invention mixes and reacts the acidic hydrolysate and the alkaline hydrolysate to obtain a co-precursor prepolymer solution, and then adds water glass solution to combine it with glass fiber mat before gelation to form a silica wet gel composite mat.

[0046] The reaction carried out after mixing the acidic hydrolysate and the alkaline hydrolysate in this invention is as follows:

[0047]

[0048]

[0049] The pH value of the prepolymer solution of the co-precursor prepared by the present invention is 4.5~5.5; specifically, it can be 4.5, 4.6, 4.7, 4.8, 4.9, 5.0, 5.1, 5.2, 5.3, 5.4 or 5.5.

[0050] In this invention, the pH value of the system after adding water glass solution and before gelation is preferably controlled to be 5.5~6.5; specifically, it can be 5.5, 5.6, 5.7, 5.8, 5.9, 6.0, 6.1, 6.2, 6.3, 6.4 or 6.5.

[0051] In this invention, the mass ratio of the co-precursor prepolymer liquid to the glass fiber mat before composite is 2:4~6; specifically, it can be 2:4, 2:4.5, 2:5, 2:5.5 or 2:6.

[0052] After obtaining the silica wet gel composite felt, the present invention seals and ages the silica wet gel composite felt in a precursor solvent, then performs surface modification in a mixed solution of hexamethyldisiloxane, anhydrous ethanol and hydrochloric acid, and dries it to obtain a flame-retardant hydrophobic aerogel composite material.

[0053] In this invention, the sealing aging temperature is 20~50℃; the sealing aging time is 4~8h, specifically 4h, 5h, 6h, 7h or 8h.

[0054] In this invention, the volume ratio of hexamethyldisiloxane, anhydrous ethanol and hydrochloric acid used for surface modification is 1:1:1.8~2.1; specifically, it can be 1:1:1.8, 1:1:1.9, 1:1:2.0 or 1:1:2.1.

[0055] The surface modification in this invention involves the following reactions:

[0056]

[0057] In this invention, the surface modification temperature is 50~60℃, specifically 50℃, 51℃, 52℃, 63℃, 54℃, 55℃, 56℃, 57℃, 58℃, 59℃, or 60℃; the surface modification time is 2~4 hours, specifically 2 hours, 2.5 hours, 3 hours, 3.5 hours, or 4 hours. The surface modification temperature is preferably achieved using a water bath heating method.

[0058] In this invention, the drying is atmospheric pressure staged drying; atmospheric pressure staged drying is drying at 80℃, 100℃ and 120℃ for 1h, 1.5h and 2h respectively.

[0059] The flame-retardant and hydrophobic aerogel composite material prepared by the co-precursor method of the present invention is obtained by the preparation method described in the above technical solution.

[0060] This invention uses 3-aminopropyltriethoxysilane and water glass as co-precursors, and prepares the aerogel by modification via a sol-gel method followed by drying under normal pressure. This method can retain the excellent thermal insulation properties of hydrophobic silica aerogel to the greatest extent. The aerogel has a thermal conductivity of 0.020~0.022 W / m·K, a porosity of 95~97%, and a density of 0.090~0.109 g / cm³. 3 Specific surface area is 750~1500 m² 2 / g.

[0061] To further illustrate the present invention, the following detailed description, in conjunction with embodiments, of a method for preparing flame-retardant hydrophobic aerogel composite materials using a co-precursor method, should not be construed as limiting the scope of protection of the present invention.

[0062] Comparative Example

[0063] Preparation of flame-retardant hydrophobic aerogel composites with 0% volume fraction of 3-aminopropyltriethoxysilane in the co-precursor prepolymer solution

[0064] (1) Preparation of precursor fluids

[0065] The diluted water glass solution was added to a beaker containing 2 mL of phosphoric acid and stirred magnetically to control the pH value to 4.5, resulting in an acidic hydrolysate. 10 mL of a 1:1 mixture of anhydrous ethanol and water was taken as the precursor preparation solution.

[0066] (2) Preparation of sol and composite by co-precursor method

[0067] The acidic hydrolysate and the precursor preparation solution are mixed and reacted to obtain a co-precursor prepolymer solution. The pH of the prepolymer solution is controlled at 5. A diluted water glass solution is added until the pH value is 6. Before gelation, it is compounded with glass fiber mat at a compound mass ratio of 2:5 to form a silica wet gel composite mat.

[0068] (3) Aging and Modification

[0069] The silica wet gel composite felt was sealed and aged in a precursor solvent for 5 hours, and then surface modified for 3 hours in a mixed solution of hexamethyldisiloxane, anhydrous ethanol and hydrochloric acid in a volume ratio of 1:1:2.

[0070] (4) Drying

[0071] The modified composite felt was subjected to staged drying under normal pressure, and dried at oven temperatures of 80℃, 100℃, and 120℃ for 1 h, 1.5 h, and 2 h, respectively, to obtain a comparative sample of hydrophobic aerogel composite material, denoted as SAB-0. The physicochemical parameters of SAB-0 aerogel are shown in Table 1:

[0072] Table 1

[0073]

[0074] Example 1

[0075] Flame-retardant and hydrophobic aerogel composite material with 2.5% volume fraction of 3-aminopropyltriethoxysilane in the co-precursor prepolymer solution was prepared.

[0076] (1) Preparation of precursor fluids

[0077] The diluted water glass solution was added to a beaker containing 2 mL of phosphoric acid and stirred magnetically to control the pH value to 4.5, resulting in an acidic hydrolysate. 250 μL of 3-aminopropyltriethoxysilane, water, and anhydrous ethanol were mixed to prepare 10 mL of solution, with the volume ratio of water to anhydrous ethanol being 1:1. The mixture was then placed in a beaker to carry out the hydrolysis reaction, resulting in an alkaline hydrolysate.

[0078] (2) Preparation of sol and composite by co-precursor method

[0079] The acidic hydrolysate and alkaline hydrolysate are mixed and reacted to obtain a co-precursor prepolymer solution. The pH of the prepolymer solution is controlled at 5. Diluted water glass solution is added until the pH value is 6. Before gelation, it is compounded with glass fiber mat at a compound mass ratio of 2:5 to form silica wet gel composite mat.

[0080] (3) Aging and Modification

[0081] The silica wet gel composite felt was sealed and aged in a precursor solvent for 5 hours, and then surface modified for 3 hours in a mixed solution of hexamethyldisiloxane, anhydrous ethanol and hydrochloric acid in a volume ratio of 1:1:2.

[0082] (4) Drying

[0083] The modified composite felt was subjected to staged drying under normal pressure, and dried at oven temperatures of 80℃, 100℃, and 120℃ for 1 h, 1.5 h, and 2 h, respectively, to obtain a flame-retardant hydrophobic aerogel composite material, denoted as SAB-1. The physicochemical parameters of SAB-1 aerogel are shown in Table 2:

[0084] Table 2

[0085]

[0086] Example 2

[0087] Preparation of flame-retardant and hydrophobic aerogel composites with 5% by mass of 3-aminopropyltriethoxysilane in the co-precursor prepolymer solution

[0088] (1) Preparation of precursor fluid

[0089] The diluted water glass solution was added to a beaker containing 2 mL of phosphoric acid and stirred magnetically to control the pH value to 4.5, resulting in an acidic hydrolysate. 250 μL of 3-aminopropyltriethoxysilane, water, and anhydrous ethanol were mixed to prepare 10 mL of solution, with the volume ratio of water to anhydrous ethanol being 1:1. The mixture was then placed in a beaker to carry out the hydrolysis reaction, resulting in an alkaline hydrolysate.

[0090] (2) Preparation of sol and composite materials using the co-precursor method

[0091] The acidic hydrolysate and alkaline hydrolysate are mixed and reacted to obtain a co-precursor prepolymer solution. The pH of the prepolymer solution is controlled at 5. Diluted water glass solution is added until the pH value is 6. Before gelation, it is compounded with glass fiber mat at a compound mass ratio of 2:5 to form silica wet gel composite mat.

[0092] (3) Aging and Modification

[0093] The silica wet gel composite felt was sealed and aged in a precursor solvent for 5 hours, and then surface modified for 3 hours in a mixed solution of hexamethyldisiloxane, anhydrous ethanol and hydrochloric acid in a volume ratio of 1:1:2.

[0094] (4) Drying

[0095] The modified composite felt was subjected to staged drying under normal pressure, and dried at oven temperatures of 80℃, 100℃, and 120℃ for 1 h, 1.5 h, and 2 h, respectively, to obtain a flame-retardant hydrophobic aerogel composite material, denoted as SAB-2. The physicochemical parameters of SAB-2 aerogel are shown in Table 3.

[0096] Table 3

[0097]

[0098] Figure 2 SEM image of SAB-2 aerogel composite material; Figure 3 This is a SEM image of powder in SAB-2 aerogel. Figure 2 The enlarged view shows that the hydrophobic angle of SAB-2 is 112°.

[0099] Example 3

[0100] Preparation of flame-retardant and hydrophobic aerogel composites with 7.5% by mass of 3-aminopropyltriethoxysilane in the co-precursor prepolymer solution:

[0101] (1) Preparation of precursor fluids

[0102] The diluted water glass solution was added to a beaker containing 2 mL of phosphoric acid and stirred magnetically to control the pH value to 4.5, resulting in an acidic hydrolysate. 250 μL of 3-aminopropyltriethoxysilane, water, and anhydrous ethanol were mixed to prepare 10 mL of solution, with the volume ratio of water to anhydrous ethanol being 1:1. The mixture was then placed in a beaker to carry out the hydrolysis reaction, resulting in an alkaline hydrolysate.

[0103] (2) Preparation of sol and composite by co-precursor method

[0104] The acidic hydrolysate and alkaline hydrolysate are mixed and reacted to obtain a co-precursor prepolymer solution. The pH of the prepolymer solution is controlled at 5, and diluted water glass solution is added until the pH value is 6. Before gelation, it is compounded with glass fiber mat at a compound mass ratio of 2:5 to form silica wet gel composite mat.

[0105] (3) Aging and Modification

[0106] The silica wet gel composite felt was sealed and aged in a precursor solvent for 5 hours, and then surface modified for 3 hours in a mixed solution of hexamethyldisiloxane, anhydrous ethanol and hydrochloric acid in a volume ratio of 1:1:2.

[0107] (4) Drying

[0108] The modified composite felt was subjected to staged drying under normal pressure, and dried at oven temperatures of 80℃, 100℃, and 120℃ for 1 h, 1.5 h, and 2 h, respectively, to obtain a flame-retardant hydrophobic aerogel composite material, denoted as SAB-3. The physicochemical parameters of SAB-3 aerogel are shown in Table 4.

[0109] Table 4

[0110]

[0111] Example 4

[0112] Preparation of flame-retardant and hydrophobic aerogel composites with 10% by mass of 3-aminopropyltriethoxysilane in the co-precursor prepolymer solution

[0113] (1) Preparation of precursor fluids

[0114] The diluted water glass solution was added to a beaker containing 2 mL of phosphoric acid and stirred magnetically to control the pH value to 4.5, resulting in an acidic hydrolysate. 250 μL of 3-aminopropyltriethoxysilane, water, and anhydrous ethanol were mixed to prepare 10 mL of solution, with the volume ratio of water to anhydrous ethanol being 1:1. The mixture was then placed in a beaker to carry out the hydrolysis reaction, resulting in an alkaline hydrolysate.

[0115] (2) Preparation of sol and composite by co-precursor method

[0116] The acidic hydrolysate and alkaline hydrolysate are mixed and reacted to obtain a co-precursor prepolymer solution. The pH of the prepolymer solution is controlled at 5. Diluted water glass solution is added until the pH value is 6. Before gelation, it is compounded with glass fiber mat at a compound mass ratio of 2:5 to form silica wet gel composite mat.

[0117] (3) Aging and Modification

[0118] The silica wet gel composite felt was sealed and aged in a precursor solvent for 5 hours, and then surface modified for 3 hours in a mixed solution of hexamethyldisiloxane, anhydrous ethanol and hydrochloric acid in a volume ratio of 1:1:2.

[0119] (4) Drying

[0120] The modified composite felt was subjected to staged drying under normal pressure, and dried at oven temperatures of 80℃, 100℃, and 120℃ for 1 h, 1.5 h, and 2 h, respectively, to obtain a flame-retardant hydrophobic aerogel composite material, denoted as SAB-4. The physicochemical parameters of SAB-4 aerogel are shown in Table 5.

[0121] Table 5

[0122]

[0123] The present invention conducted N2 adsorption-desorption tests on the aerogel composite materials prepared in Examples 1-4 and the comparative examples, see [see details]. Figure 5 Silica aerogel is a nanoporous material, and its overall structure can be characterized by N2 desorption and adsorption isotherms; according to the BDDT (Brunauer, Deming, Deming, and Teller) classification system, Figure 5 All curves represent type IV isotherms, indicating that despite the high APTES content of up to 10% in the sample, the main pore structure in the aerogel remains mesoporous.

[0124] The total heat release value of the composite materials prepared in Examples 1-4 and the comparative example was tested by cone-scale experiments. The results are shown in the figure. Figure 6 ;from Figure 6 It can be seen that the THR of the sample decreases significantly with the increase of APTES content. When the doping content exceeds 5%, the THR of the sample shows a significant decreasing trend. Figure 6 As shown, it can be concluded that APTES has a significant inhibitory effect on the combustion of silica aerogel. The reduction rate of THR in the samples is positively correlated with the APTES content; from a content of 2.5% to 10%, the THR increases significantly from 23.1% to 69.2%.

[0125] As can be seen from the above embodiments, the present invention provides a method for preparing flame-retardant hydrophobic aerogel composite materials using a co-precursor method, comprising the following steps: mixing water glass solution and phosphoric acid for hydrolysis reaction to obtain an acidic hydrolysate; mixing 3-aminopropyltriethoxysilane, water, and anhydrous ethanol for hydrolysis reaction to obtain an alkaline hydrolysate; mixing the acidic hydrolysate and the alkaline hydrolysate for reaction to obtain a co-precursor prepolymer solution; continuing to add water glass solution and combining it with glass fiber mat before gelation to form a silica wet gel composite mat; sealing and aging the silica wet gel composite mat in a precursor solvent, then performing surface modification in a mixed solution of hexamethyldisiloxane, anhydrous ethanol, and hydrochloric acid, and drying to obtain a flame-retardant hydrophobic aerogel composite material. This invention involves hydrolyzing 3-aminopropyltriethoxysilane to form highly reactive 3-aminopropyltriethoxysilanol, which is then grafted onto the surface of an aerogel. On one hand, the amino group inherent in the 3-aminopropyltriethoxysilanol reacts with subsequent phosphoric acid to generate ammonium phosphate groups, which possess highly efficient flame-retardant properties and can inhibit the combustion of hydrophobic aerogels. Experimental results show that the aerogel has a thermal conductivity of 0.020–0.022 W / m·K, a porosity of 95–97%, and a density of 0.090–0.109 g / cm³. 3 Specific surface area is 750~1500 m² 2 / g, the total heat release from the cone mass test is 3.25 MJ·m -2 Gradually decreased to 1.12 MJ·m -2 .

[0126] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a flame-retardant hydrophobic aerogel composite material by a co-precursor method, comprising the following steps: mixing a water glass solution and phosphoric acid to perform a hydrolysis reaction, to obtain an acidic hydrolysis solution, the pH value of the acidic hydrolysis solution being 4.2-4.8; mixing 3-aminopropyl triethoxysilane, water and anhydrous ethanol to perform a hydrolysis reaction, to obtain an alkaline hydrolysis solution, the pH value of the alkaline hydrolysis solution being 8.5-9.5; the volume ratio of the 3-aminopropyl triethoxysilane to the total volume of the 3-aminopropyl triethoxysilane, water and anhydrous ethanol being 2.5-10%; the mass fraction of the water glass solution being 10-12%; mixing the acidic hydrolysis solution and the alkaline hydrolysis solution to perform a reaction, to obtain a co-precursor pre-polymer solution, the pH value of the co-precursor pre-polymer solution being 4.5-5.5; continuously adding a water glass solution, the pH value of the system before gelation being 5.5-6.5 after adding the water glass solution, and being combined with a glass fiber felt before gelation, to form a silica wet gel composite felt; sealing and aging the silica wet gel composite felt in a precursor solvent, and then performing a surface modification in a mixed solution of hexamethyldisiloxane, anhydrous ethanol and hydrochloric acid, and drying, to obtain the flame-retardant hydrophobic aerogel composite material. The sealing and aging temperature is 20-50℃, and the sealing and aging time is 4-8h.

2. The method of claim 1, wherein, The mass ratio of the co-precursor pre-polymer solution to the glass fiber felt before being combined is 2:4-6.

3. The method of claim 1, wherein, The volume ratio of hexamethyldisiloxane, anhydrous ethanol and hydrochloric acid used for the surface modification is 1:1:1.8-2.

1.

4. The method of claim 1, wherein, The surface modification temperature is 50-60℃, and the surface modification time is 2-4h.

5. The method of claim 1, wherein, The drying is normal pressure staged drying. The normal pressure staged drying is drying at 80℃, 100℃ and 120℃ for 1h, 1.5h and 2h, respectively.

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