Porous thermal insulation material for thermal protection clothing as well as preparation method and application of porous thermal insulation material

Abstract

The invention relates to the technical field of thermal insulation materials for protective clothing, and discloses a porous thermal insulation material for thermal protective clothing and a preparation method and application thereof.The preparation method comprises the following steps that polytetrafluoroethylene and deionized water are mixed and stirred, and polytetrafluoroethylene dispersion liquid is obtained; and uniformly mixing the nano cellulose, the composite heat insulation filler and the polytetrafluoroethylene dispersion liquid, and carrying out freeze drying and heat treatment to obtain the porous heat insulation material. The nano cellulose can be uniformly dispersed among the polytetrafluoroethylene colloidal particles, and a relatively strong interface bonding force is formed among the polytetrafluoroethylene colloidal particles, so that an aerogel structure with a porous structure is formed and is used as a porous thermal insulation material; the nano cellulose is combined with the nano cellulose contained in the composite heat-insulating filler through hydrogen bonds, so that the composite heat-insulating filler is uniformly embedded into the porous heat-insulating material, the porous heat-insulating material with a porous structure inside and a porous gel structure outside is formed, and the heat-insulating property and mechanical property of the porous heat-insulating material are remarkably enhanced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of thermal protective clothing insulation materials, in particular to a porous thermal insulation material for thermal protective clothing and a preparation method and application thereof. BACKGROUND

[0002] Thermal protective clothing is a special clothing for protecting workers in high-temperature environments, which has flame resistance, liquid repellency, no molten droplets during combustion, thermal insulation and high-temperature integrity, and includes four layers of composite structure, namely, an outer layer, a waterproof and breathable layer, a thermal insulation layer and a comfortable layer. The flame-resistant layer is used to block external high-temperature flames, the waterproof and breathable layer is used to prevent the entry of external moisture, the thermal insulation layer is the main thermal barrier to isolate external high heat, and the inner comfortable layer is close to the human skin. The thermal protective clothing with four-layer structure has good thermal protective performance.

[0003] The thermal insulation material required for the thermal insulation layer is the key layer for the thermal protective performance of the thermal protective clothing, and has good mechanical properties, thermal insulation properties and flexibility. The flexible polytetrafluoroethylene and the thermal insulation material are fused at high temperature to form a lightweight thermal insulation material with stable and firm connection. The thermal insulation material is mainly silica aerogel particles, but the silica aerogel particles have poor mechanical properties and are easy to break, which affects the thermal protective performance of the thermal protective clothing. SUMMARY

[0004] TECHNICAL PROBLEM In view of the deficiencies in the prior art, the present application provides a porous thermal insulation material for thermal protective clothing and a preparation method and application thereof, which solves the problem that the thermal insulation material mainly uses silica aerogel particles, but the silica aerogel particles have poor mechanical properties and are easy to break, which affects the thermal protective performance of the thermal protective clothing. TECHNICAL SCHEME

[0005] To achieve the above-mentioned purpose, the present application provides the following technical scheme: A preparation method of a porous thermal insulation material for thermal protective clothing, comprising the following steps: S1, mixing polytetrafluoroethylene and deionized water, stirring to obtain a polytetrafluoroethylene dispersion; S2, uniformly mixing nano-cellulose, composite thermal insulation filler and polytetrafluoroethylene dispersion, and freeze-drying and heat-treating to obtain a porous thermal insulation material; The composite thermal insulation filler is obtained by mixing and reacting silica aerogel particles, methyltrimethoxysilane, nano-cellulose and modified glass fibers; The modified glass fiber is obtained by synthesizing porous carbon nanospheres on the surface of the tannic acid modified glass fiber.

[0006] Further, the composite thermal insulation filler is prepared by the following steps: A1, glass fiber and tannic acid are added into ethanol, stirred at 60-70℃ for 30-40min, cooled to room temperature, filtered, washed, dried, to obtain tannic acid modified glass fiber; A2, polyoxaethylene nonyl phenyl ether, cyclohexane, ammonia, deionized water are mixed, stirred until the solution is clear and transparent, then formaldehyde solution and resorcinol are added, continue to stir, then placed in an autoclave, heated, then add ethanol, ultrasonic, centrifugal, washing, drying, to obtain spherical phenolic resin powder; spherical phenolic resin powder and tannic acid modified glass fiber are added into ethanol, stirred uniformly, heated and stirred until ethanol evaporates, placed in a sintering furnace for sintering, taken out, to obtain modified glass fiber; A3, silica aerogel particles and modified glass fiber are added into ethanol and deionized water, stirred uniformly, then methyltrimethoxysilane is added, stirred and reacted, then nanocellulose is added, continue to stir and react, filtered, washed, dried, to obtain composite thermal insulation filler.

[0007] In the above reaction process, tannic acid contains a large number of phenolic hydroxyl groups, has good adhesion performance, and can adhere to the surface of glass fiber, providing a large number of polar functional groups for glass fiber, to obtain tannic acid modified glass fiber. Cyclohexane as an organic phase, ammonia, deionized water as an aqueous phase, polyoxaethylene nonyl phenyl ether as a surfactant, the hydrophilic group can gather to form a microemulsion, and formaldehyde and resorcinol react in the microemulsion core to form phenolic resin, and then form spherical phenolic resin powder; Further, spherical phenolic resin powder and tannic acid modified glass fiber are mixed in ethanol solvent, tannic acid modified glass fiber contains a large number of polar functional groups, which can combine with spherical phenolic resin powder through hydrogen bond, so that spherical phenolic resin powder is deposited on the surface of tannic acid modified glass fiber, and after high temperature sintering, spherical phenolic resin powder is decomposed to form small size porous carbon nanospheres, realizing the synthesis of small size porous carbon nanospheres on the surface of glass fiber, to obtain modified glass fiber.

[0008] Subsequently in the A3 reaction process, the silicon hydroxyl generated by the hydrolysis of methyltrimethoxysilane can be combined with the hydroxyl on the surface of silica aerogel particles and modified glass fiber through chemical bond, forming an interlaced network porous structure, so that the silica aerogel particles are embedded in the interlaced network porous structure, and the nanocellulose also participates in the reaction due to its large number of hydroxyl groups, forming a three-dimensional network structure, as a composite thermal insulation filler.

[0009] Further, in the A1 step, the mass ratio of glass fiber, tannic acid and ethanol is (2-3):(0.6-0.8):(80-90).

[0010] Further, in step A2, the mass ratio of polyoxyethylene nonylphenyl ether, cyclohexane, ammonia, deionized water, formaldehyde solution, resorcinol and ethanol is (6-7):(20-25):(1-1.2):(1.5-1.7):(0.7-0.9):(0.6-0.8):(20-25).

[0011] Further, in step A2, the mass ratio of the spherical phenolic resin powder, tannic acid-modified glass fiber, and ethanol is (2-2.5):(4.5-5):(80-90).

[0012] Further, in step A3, the mass ratio of the silica aerogel particles, modified glass fiber, ethanol, deionized water, methyltrimethoxysilane and nanocellulose is (1-2):(2.5-3):(70-80):(30-40):(0.5-1):(1.5-1.8).

[0013] Further, in step S1, the stirring rate is 400-450 r / min, and the stirring time is 30-35 min.

[0014] Further, in step S1, the mass ratio of polytetrafluoroethylene to deionized water is (7-9):(36-40).

[0015] Furthermore, in step S2, the freeze-drying temperature is -55℃ and the freeze-drying time is 40-48h.

[0016] Furthermore, in step S2, the heat treatment is carried out in a muffle furnace at a temperature of 380-400°C for a duration of 25-30 minutes.

[0017] Furthermore, the application of a porous thermal insulation material prepared by a method for preparing porous thermal insulation material for thermal protective clothing in thermal protective clothing.

[0018] Beneficial technical effects (1) In the technical solution of the present invention, the glass fiber has a porous structure, which has high temperature resistance and heat insulation performance, and can improve the heat insulation performance of the porous heat insulation material. In addition, the glass fiber is modified with tannic acid, which provides a large number of polar functional groups to the glass fiber, which is conducive to the synthesis of porous carbon nanospheres on the surface of the glass fiber and improves the heat insulation performance. Furthermore, the glass fiber has an excellent aspect ratio and is randomly distributed in the porous heat insulation material, which absorbs and weakens the energy generated by external forces and improves the mechanical properties of the porous heat insulation material.

[0019] (2) In the technical solution of the present invention, small-sized porous carbon nanospheres are synthesized on the surface of glass fiber. On the one hand, the synthesized porous carbon nanospheres have a small porous structure and good thermal insulation performance; and the porous carbon nanospheres have a three-dimensional nano-network structure, which can absorb and weaken the energy generated by external stress, improve the mechanical strength of the porous thermal insulation material, and prevent the nano-silica aerogel from breaking; on the other hand, the glass fiber serves as a carrier for the porous carbon nanospheres, preventing the porous carbon nanospheres from agglomerating in the porous thermal insulation material and affecting the thermal insulation performance of the porous thermal insulation material.

[0020] (3) In the technical solution of the present invention, silica aerogel particles, methyltrimethoxysilane, nanocellulose and modified glass fiber are mixed and reacted. On the one hand, methyltrimethoxysilane can form a cross-linked network porous structure with silica aerogel particles and modified glass fiber, which can improve the thermal insulation performance of porous thermal insulation material. The cross-linked network structure can improve the mechanical strength of porous thermal insulation material. On the other hand, nanocellulose contains a large number of hydroxyl groups and can also participate in the reaction to form a three-dimensional network structure, which can significantly enhance the thermal insulation performance.

[0021] (4) In the technical solution of this invention, nanocellulose, composite heat-insulating filler, and polytetrafluoroethylene dispersion are mixed evenly, and then freeze-dried and heat-treated to obtain a porous heat-insulating material. On the one hand, nanocellulose can be evenly dispersed between polytetrafluoroethylene particles, and a strong interfacial bonding force is formed between the polytetrafluoroethylene particles to form a porous aerogel structure, which serves as a porous heat-insulating material. On the other hand, nanocellulose and the nanocellulose contained in the composite heat-insulating filler are bonded by hydrogen bonds, so that the composite heat-insulating filler is evenly embedded in the porous heat-insulating material, forming a porous heat-insulating material with a porous internal structure and a porous gel external structure, which significantly enhances the heat insulation performance and mechanical properties of the porous heat-insulating material. Detailed Implementation To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are described clearly and completely. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] The raw materials used in the embodiments of this invention are shown below, and all reagents used are analytical grade.

[0023] The polytetrafluoroethylene (PTFE) was in powder form, with product number P875334 and a particle size of 0.1 μm, and was purchased from Shanghai Maclean Biochemical Technology Co., Ltd.

[0024] The nanocellulose, catalog number C699137, with a diameter of 20nm, was purchased from Shanghai Maclean Biochemical Technology Co., Ltd.

[0025] The glass fiber has a diameter of 1μm and a length of 10μm.

[0026] The silica aerogel particles have a diameter of 50 nm. Example

[0027] A method for preparing a porous thermal insulation material for thermal protective clothing includes the following steps: S1. Mix polytetrafluoroethylene (PTFE) and deionized water, and stir to obtain a PTFE dispersion; the stirring rate is 400 r / min, and the stirring time is 30 min; the mass ratio of PTFE to deionized water is 7:36. S2. Nanocellulose, composite heat insulation filler and polytetrafluoroethylene dispersion are mixed evenly, and then freeze-dried and heat-treated to obtain porous heat insulation material; the freeze-drying temperature is -55℃ and the freeze-drying time is 40h; the heat treatment is carried out in a muffle furnace at a temperature of 380℃ and a time of 25min.

[0028] The composite thermal insulation filler is prepared by the following steps: A1. Glass fiber and tannic acid were added to ethanol, stirred at 60°C for 30 min, cooled to room temperature, filtered, washed three times with deionized water, and dried in an oven at 70°C for 10 min to obtain tannic acid-modified glass fiber; the mass ratio of glass fiber, tannic acid and ethanol was 2:0.6:80. A2. Polyoxyethylene nonylphenyl ether, cyclohexane, ammonia, and deionized water were mixed and stirred at 50°C until the solution was clear and transparent. Then, a 36% formaldehyde solution and resorcinol were added, and stirring was continued for 24 hours. The mixture was then placed in a hydrothermal reactor and heated at 120°C for 24 hours. Ethanol was added, and the mixture was sonicated at 40 kHz for 10 minutes and centrifuged at 5000 r / min to collect the precipitate. The precipitate was washed three times with deionized water and dried in a 70°C oven for 10 minutes to obtain spherical phenolic resin powder. The mass ratio of polyoxyethylene nonylphenyl ether, cyclohexane, ammonia, deionized water, formaldehyde solution, resorcinol, and ethanol was 6:20:1:1.5:0.7:0.6:20. Spherical phenolic resin powder and tannic acid-modified glass fiber were added to ethanol and stirred evenly. The mixture was stirred at 90°C until the ethanol evaporated. The mixture was then placed in a sintering furnace and sintered at 250°C for 30 min. The temperature was then increased to 800°C at a rate of 5°C / min and sintered for 3 h to obtain modified glass fiber. The mass ratio of spherical phenolic resin powder, tannic acid-modified glass fiber and ethanol was 2:4.5:80. A3. Add silica aerogel particles and modified glass fiber to ethanol and deionized water, stir evenly, add methyltrimethoxysilane, stir and react at 75℃ for 30 min, add nanocellulose, continue stirring and react for 30 min, filter, wash three times with deionized water, and dry in an oven at 70℃ for 10 min to obtain composite thermal insulation filler; the mass ratio of silica aerogel particles, modified glass fiber, ethanol, deionized water, methyltrimethoxysilane and nanocellulose is 1:2.5:70:30:0.5:1.5. Example

[0029] A method for preparing a porous thermal insulation material for thermal protective clothing includes the following steps: S1. Mix polytetrafluoroethylene (PTFE) and deionized water, and stir to obtain a PTFE dispersion; the stirring rate is 430 r / min, and the stirring time is 33 min; the mass ratio of PTFE to deionized water is 8:38. S2. Nanocellulose, composite heat insulation filler and polytetrafluoroethylene dispersion are mixed evenly, and then freeze-dried and heat-treated to obtain porous heat insulation material; the freeze-drying temperature is -55℃ and the freeze-drying time is 44h; the heat treatment is carried out in a muffle furnace at a temperature of 390℃ and a time of 28min.

[0030] The composite thermal insulation filler is prepared by the following steps: A1. Glass fiber and tannic acid were added to ethanol and stirred at 65°C for 35 min. After cooling to room temperature, the mixture was filtered, washed three times with deionized water, and dried in an oven at 70°C for 10 min to obtain tannic acid-modified glass fiber. The mass ratio of glass fiber, tannic acid, and ethanol was 2.5:0.7:85. A2. Polyoxyethylene nonylphenyl ether, cyclohexane, ammonia, and deionized water were mixed and stirred at 50°C until the solution was clear and transparent. Then, a 36% formaldehyde solution and resorcinol were added, and stirring was continued for 24 hours. The mixture was then placed in a hydrothermal reactor and heated at 120°C for 24 hours. Ethanol was added, and the mixture was sonicated at 40 kHz for 10 minutes and centrifuged at 5000 r / min to collect the precipitate. The precipitate was washed three times with deionized water and dried in a 70°C oven for 10 minutes to obtain spherical phenolic resin powder. The mass ratio of polyoxyethylene nonylphenyl ether, cyclohexane, ammonia, deionized water, formaldehyde solution, resorcinol, and ethanol was 6.5:23:1.1:1.6:0.8:0.7:23. Spherical phenolic resin powder and tannic acid-modified glass fiber were added to ethanol and stirred evenly. The mixture was stirred at 90°C until the ethanol evaporated. The mixture was then placed in a sintering furnace and sintered at 250°C for 30 min. The temperature was then increased to 800°C at a rate of 5°C / min and sintered for 3 h to obtain modified glass fiber. The mass ratio of spherical phenolic resin powder, tannic acid-modified glass fiber and ethanol was 2.3:4.7:85. A3. Add silica aerogel particles and modified glass fiber to ethanol and deionized water, stir evenly, add methyltrimethoxysilane, stir and react at 75℃ for 30 min, add nanocellulose, continue stirring and react for 30 min, filter, wash three times with deionized water, and dry in an oven at 70℃ for 10 min to obtain composite thermal insulation filler; the mass ratio of silica aerogel particles, modified glass fiber, ethanol, deionized water, methyltrimethoxysilane and nanocellulose is 1.5:2.8:75:35:0.8:1.7. Example

[0031] A method for preparing a porous thermal insulation material for thermal protective clothing includes the following steps: S1. Mix polytetrafluoroethylene (PTFE) and deionized water, and stir to obtain a PTFE dispersion; the stirring rate is 450 r / min, and the stirring time is 35 min; the mass ratio of PTFE to deionized water is 9:40. S2. Nanocellulose, composite heat insulation filler and polytetrafluoroethylene dispersion are mixed evenly, and then freeze-dried and heat-treated to obtain porous heat insulation material; the freeze-drying temperature is -55℃ and the freeze-drying time is 48h; the heat treatment is carried out in a muffle furnace at a temperature of 400℃ and a time of 30min.

[0032] The composite thermal insulation filler is prepared by the following steps: A1. Glass fiber and tannic acid were added to ethanol and stirred at 70°C for 40 min. After cooling to room temperature, the mixture was filtered, washed three times with deionized water, and dried in an oven at 70°C for 10 min to obtain tannic acid-modified glass fiber. The mass ratio of glass fiber, tannic acid and ethanol was 3:0.8:90. A2. Polyoxyethylene nonylphenyl ether, cyclohexane, ammonia, and deionized water were mixed and stirred at 50°C until the solution was clear and transparent. Then, a 36% formaldehyde solution and resorcinol were added, and stirring was continued for 24 hours. The mixture was then placed in a hydrothermal reactor and heated at 120°C for 24 hours. Ethanol was added, and the mixture was sonicated at 40 kHz for 10 minutes and centrifuged at 5000 r / min to collect the precipitate. The precipitate was washed three times with deionized water and dried in an oven at 70°C for 10 minutes to obtain spherical phenolic resin powder. The mass ratio of polyoxyethylene nonylphenyl ether, cyclohexane, ammonia, deionized water, formaldehyde solution, resorcinol, and ethanol was 7:25:1.2:1.7:0.9:0.8:25. Spherical phenolic resin powder and tannic acid-modified glass fiber were added to ethanol and stirred evenly. The mixture was stirred at 90°C until the ethanol evaporated. The mixture was then placed in a sintering furnace and sintered at 250°C for 30 min. The temperature was then increased to 800°C at a rate of 5°C / min and sintered for 3 h to obtain modified glass fiber. The mass ratio of spherical phenolic resin powder, tannic acid-modified glass fiber and ethanol was 2.5:5:90. A3. Add silica aerogel particles and modified glass fiber to ethanol and deionized water, stir evenly, add methyltrimethoxysilane, stir and react at 75℃ for 30 min, add nanocellulose, continue stirring and react for 30 min, filter, wash three times with deionized water, and dry in an oven at 70℃ for 10 min to obtain composite thermal insulation filler; the mass ratio of silica aerogel particles, modified glass fiber, ethanol, deionized water, methyltrimethoxysilane and nanocellulose is 2:3:80:40:1:1.8.

[0033] Comparative Example 1 The only difference between this comparative example and Example 3 is the preparation of the composite thermal insulation filler, as detailed below: The composite thermal insulation filler is prepared by the following steps: A1. Polyoxyethylene nonylphenyl ether, cyclohexane, ammonia, and deionized water were mixed and stirred at 50°C until the solution was clear and transparent. Then, a 36% formaldehyde solution and resorcinol were added, and stirring was continued for 24 hours. The mixture was then placed in a hydrothermal reactor and heated at 120°C for 24 hours. Ethanol was added, and the mixture was sonicated at 40 kHz for 10 minutes. The precipitate was collected by centrifugation at 5000 r / min. The precipitate was washed three times with deionized water and dried in an oven at 70°C for 10 minutes to obtain spherical phenolic resin powder. The mass ratio of polyoxyethylene nonylphenyl ether, cyclohexane, ammonia, deionized water, formaldehyde solution, resorcinol, and ethanol was 7:25:1.2:1.7:0.9:0.8:25. Spherical phenolic resin powder and glass fiber were added to ethanol and stirred evenly. The mixture was stirred at 90°C until the ethanol evaporated. The mixture was then placed in a sintering furnace and sintered at 250°C for 30 min. The temperature was then increased to 800°C at a rate of 5°C / min and sintered for 3 h to obtain modified glass fiber. The mass ratio of spherical phenolic resin powder, glass fiber and ethanol was 2.5:5:90. A2. Add silica aerogel particles and modified glass fiber to ethanol and deionized water, stir evenly, add methyltrimethoxysilane, stir and react at 75℃ for 30 min, add nanocellulose, continue stirring and react for 30 min, filter, wash three times with deionized water, and dry in an oven at 70℃ for 10 min to obtain composite thermal insulation filler; the mass ratio of silica aerogel particles, modified glass fiber, ethanol, deionized water, methyltrimethoxysilane and nanocellulose is 2:3:80:40:1:1.8.

[0034] Comparative Example 2 The only difference between this comparative example and Example 3 is the preparation of the composite thermal insulation filler, as detailed below: The composite thermal insulation filler is prepared by the following steps: A1. Glass fiber and tannic acid were added to ethanol and stirred at 70°C for 40 min. After cooling to room temperature, the mixture was filtered, washed three times with deionized water, and dried in an oven at 70°C for 10 min to obtain tannic acid-modified glass fiber. The mass ratio of glass fiber, tannic acid and ethanol was 3:0.8:90. A2. Add silica aerogel particles and tannic acid-modified glass fibers to ethanol and deionized water, stir evenly, add methyltrimethoxysilane, stir and react at 75℃ for 30 min, add nanocellulose, continue stirring and react for 30 min, filter, wash three times with deionized water, and dry in an oven at 70℃ for 10 min to obtain composite thermal insulation filler; the mass ratio of silica aerogel particles, tannic acid-modified glass fibers, ethanol, deionized water, methyltrimethoxysilane and nanocellulose is 2:3:80:40:1:1.8.

[0035] Comparative Example 3 The only difference between this comparative example and Example 3 is the preparation of the composite thermal insulation filler, as detailed below: The composite thermal insulation filler is prepared by the following steps: A1. Glass fiber and tannic acid were added to ethanol and stirred at 70°C for 40 min. After cooling to room temperature, the mixture was filtered, washed three times with deionized water, and dried in an oven at 70°C for 10 min to obtain tannic acid-modified glass fiber. The mass ratio of glass fiber, tannic acid and ethanol was 3:0.8:90. A2. Polyoxyethylene nonylphenyl ether, cyclohexane, ammonia, and deionized water were mixed and stirred at 50°C until the solution was clear and transparent. Then, a 36% formaldehyde solution and resorcinol were added, and stirring was continued for 24 hours. The mixture was then placed in a hydrothermal reactor and heated at 120°C for 24 hours. Ethanol was added, and the mixture was sonicated at 40 kHz for 10 minutes and centrifuged at 5000 r / min to collect the precipitate. The precipitate was washed three times with deionized water and dried in an oven at 70°C for 10 minutes to obtain spherical phenolic resin powder. The mass ratio of polyoxyethylene nonylphenyl ether, cyclohexane, ammonia, deionized water, formaldehyde solution, resorcinol, and ethanol was 7:25:1.2:1.7:0.9:0.8:25. Spherical phenolic resin powder and tannic acid-modified glass fiber were added to ethanol and stirred evenly. The mixture was stirred at 90°C until the ethanol evaporated. The mixture was then placed in a sintering furnace and sintered at 250°C for 30 min. The temperature was then increased to 800°C at a rate of 5°C / min and sintered for 3 h to obtain modified glass fiber. The mass ratio of spherical phenolic resin powder, tannic acid-modified glass fiber and ethanol was 2.5:5:90. A3. Add silica aerogel particles and modified glass fiber to ethanol and deionized water, stir evenly, add nanocellulose, stir and react at 75℃ for 30 min, filter, wash three times with deionized water, and dry in an oven at 70℃ for 10 min to obtain composite thermal insulation filler; the mass ratio of silica aerogel particles, modified glass fiber, ethanol, deionized water and nanocellulose is 2:4:80:40:1.8.

[0036] Comparative Example 4 The only difference between this comparative example and Example 3 is the preparation of the composite thermal insulation filler, as detailed below: The composite thermal insulation filler is prepared by the following steps: A1. Glass fiber and tannic acid were added to ethanol and stirred at 70°C for 40 min. After cooling to room temperature, the mixture was filtered, washed three times with deionized water, and dried in an oven at 70°C for 10 min to obtain tannic acid-modified glass fiber. The mass ratio of glass fiber, tannic acid and ethanol was 3:0.8:90. A2. Polyoxyethylene nonylphenyl ether, cyclohexane, ammonia, and deionized water were mixed and stirred at 50°C until the solution was clear and transparent. Then, a 36% formaldehyde solution and resorcinol were added, and stirring was continued for 24 hours. The mixture was then placed in a hydrothermal reactor and heated at 120°C for 24 hours. Ethanol was added, and the mixture was sonicated at 40 kHz for 10 minutes and centrifuged at 5000 r / min to collect the precipitate. The precipitate was washed three times with deionized water and dried in an oven at 70°C for 10 minutes to obtain spherical phenolic resin powder. The mass ratio of polyoxyethylene nonylphenyl ether, cyclohexane, ammonia, deionized water, formaldehyde solution, resorcinol, and ethanol was 7:25:1.2:1.7:0.9:0.8:25. Spherical phenolic resin powder and tannic acid-modified glass fiber were added to ethanol and stirred evenly. The mixture was stirred at 90°C until the ethanol evaporated. The mixture was then placed in a sintering furnace and sintered at 250°C for 30 min. The temperature was then increased to 800°C at a rate of 5°C / min and sintered for 3 h to obtain modified glass fiber. The mass ratio of spherical phenolic resin powder, tannic acid-modified glass fiber and ethanol was 2.5:5:90. A3. Add silica aerogel particles and modified glass fiber to ethanol and deionized water, stir evenly, add methyltrimethoxysilane, stir and react at 75℃ for 30 min, filter, wash three times with deionized water, and dry in an oven at 70℃ for 10 min to obtain composite thermal insulation filler; the mass ratio of silica aerogel particles, modified glass fiber, ethanol, deionized water and methyltrimethoxysilane is 2:4.8:80:40:1.

[0037] The porous thermal insulation materials prepared in Examples 1-3 and Comparative Examples 1-4 are now being tested.

[0038] The thermal conductivity and thermal diffusivity of the porous insulation material prepared above were tested using a HotDisk instrument (TPS2500S).

[0039] According to ASTM D1621 standard, the compressive properties of the porous thermal insulation material prepared above were tested using a universal testing machine (CMT-4104). The sample size was 30mm × 30mm × 10mm, and the compression rate was 0.5mm / min.

[0040] The results are shown in Table 1.

[0041] Table 1 Performance testing of porous thermal insulation materials prepared in Examples 1-3 and Comparative Examples 1-4 Item Thermal conductivity (W / m-k) Thermal diffusivity (mm2 / s) 2 / s) Compression strength / kPa Strain recovery rate / % Example 1 0.0271 0.056 15.7 89.9 Example 2 0.0223 0.051 16.8 91.2 Example 3 0.0285 0.058 15.1 89.3 Comparative Example 1 0.0357 0.133 12.5 70.7 Comparative Example 2 0.0459 0.295 10.7 63.2 Comparative Example 3 0.4114 0.230 11.2 66.4 Comparative Example 4 0.328 0.117 13.8 73.1 As can be seen from the data in Table 1, the porous thermal insulation materials prepared in Examples 1-3 have high thermal insulation performance.

[0042] Comparative Example 1 showed that replacing the tannic acid-modified glass fiber with a composite thermal insulation filler prepared from glass fiber and adding it to a porous thermal insulation material resulted in a decrease in its thermal insulation performance. This demonstrates that modifying glass fiber with tannic acid provides a large number of polar functional groups to the glass fiber, which is beneficial for the synthesis of porous carbon nanospheres on the surface of the glass fiber, thereby improving the thermal insulation performance. Furthermore, the glass fiber acts as a carrier for the porous carbon nanospheres, preventing them from agglomerating in the porous thermal insulation material and affecting its thermal insulation performance. In addition, the porous carbon nanospheres have a three-dimensional nano-network structure, which can absorb and weaken the energy generated by external stress, improve the mechanical strength of the porous thermal insulation material, and prevent the breakage of nano-silica aerogel.

[0043] Comparative Example 2 showed that when the modified glass fiber was replaced with tannic acid-modified glass fiber, the composite thermal insulation filler was added to the porous thermal insulation material, and its thermal insulation performance decreased. This proves that the synthesis of small-sized porous carbon nanospheres on the surface of glass fiber has the following advantages: Firstly, the synthesized porous carbon nanospheres have a smaller porous structure and better thermal insulation performance. Secondly, the porous carbon nanospheres have a three-dimensional nano-network structure, which can absorb and reduce the energy generated by external stress, improve the mechanical strength of the porous thermal insulation material, and prevent the nano-silica aerogel from breaking.

[0044] Comparative Example 3 showed that when methyltrimethoxysilane was replaced by modified glass fiber with an equal mass of composite thermal insulation filler and added to porous thermal insulation material, its thermal insulation performance decreased. This demonstrates that methyltrimethoxysilane can form a cross-linked network porous structure with silica aerogel particles and modified glass fiber, thereby improving the thermal insulation performance of porous thermal insulation material. Furthermore, the cross-linked network structure can improve the mechanical strength of porous thermal insulation material.

[0045] Comparative Example 4 showed that when a composite thermal insulation filler prepared by replacing nanocellulose with modified glass fiber was added to a porous thermal insulation material, its thermal insulation performance decreased. This demonstrates that nanocellulose, containing a large number of hydroxyl groups, can also participate in the reaction, forming a three-dimensional network structure that significantly enhances thermal insulation performance. Furthermore, nanocellulose and the nanocellulose contained in the composite thermal insulation filler are bonded through hydrogen bonds, allowing the composite thermal insulation filler to be uniformly embedded in the porous thermal insulation material. This results in a porous thermal insulation material with a porous internal structure and a porous gel external structure, significantly enhancing the thermal insulation and mechanical properties of the porous thermal insulation material.

[0046] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0047] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

[0048] Those skilled in the art should understand that the above descriptions are merely several specific embodiments of the present invention, and not all embodiments.

Claims

1. A method for preparing a porous thermal insulation material for thermal protective clothing, characterized in that, Includes the following steps: S1. Mix polytetrafluoroethylene and deionized water and stir to obtain a polytetrafluoroethylene dispersion; S2. Mix nanocellulose, composite thermal insulation filler and polytetrafluoroethylene dispersion evenly, and then freeze-dry and heat-treat to obtain porous thermal insulation material; The composite thermal insulation filler is obtained by mixing and reacting silica aerogel particles, methyltrimethoxysilane, nanocellulose and modified glass fiber. Modified glass fiber is obtained by synthesizing porous carbon nanospheres on the surface of glass fiber modified with tannic acid.

2. The method for preparing a porous thermal insulation material for thermal protective clothing according to claim 1, characterized in that, The composite thermal insulation filler is prepared by the following steps: A1. Add glass fiber and tannic acid to ethanol, stir at 60-70℃ for 30-40 min, cool to room temperature, filter, wash and dry to obtain tannic acid modified glass fiber. A2. Mix polyoxyethylene nonylphenyl ether, cyclohexane, ammonia, and deionized water, and stir until the solution is clear and transparent. Then add formaldehyde solution and resorcinol, continue stirring, place in a hydrothermal reactor, heat, add ethanol, and after sonication, centrifugation, washing, and drying, obtain spherical phenolic resin powder. Spherical phenolic resin powder and tannic acid-modified glass fiber were added to ethanol, stirred evenly, heated and stirred until the ethanol evaporated, placed in a sintering furnace for sintering, and then removed to obtain modified glass fiber. A3. Add silica aerogel particles and modified glass fiber to ethanol and deionized water, stir evenly, add methyltrimethoxysilane, stir to react, add nanocellulose, continue stirring to react, filter, wash, and dry to obtain composite thermal insulation filler.

3. The method for preparing a porous thermal insulation material for thermal protective clothing according to claim 2, characterized in that, In step A1, the mass ratio of glass fiber, tannic acid and ethanol is (2-3):(0.6-0.8):(80-90).

4. The method for preparing a porous thermal insulation material for thermal protective clothing according to claim 2, characterized in that, In step A2, the mass ratio of polyoxyethylene nonylphenyl ether, cyclohexane, ammonia, deionized water, formaldehyde solution, resorcinol and ethanol is (6-7):(20-25):(1-1.2):(1.5-1.7):(0.7-0.9):(0.6-0.8):(20-25); In step A2, the mass ratio of the spherical phenolic resin powder, tannic acid-modified glass fiber, and ethanol is (2-2.5):(4.5-5):(80-90).

5. The method for preparing a porous thermal insulation material for thermal protective clothing according to claim 2, characterized in that, In step A3, the mass ratio of the silica aerogel particles, modified glass fiber, ethanol, deionized water, methyltrimethoxysilane and nanocellulose is (1-2):(2.5-3):(70-80):(30-40):(0.5-1):(1.5-1.8).

6. The method for preparing a porous thermal insulation material for thermal protective clothing according to claim 1, characterized in that, In step S1, the stirring rate is 400-450 r / min and the stirring time is 30-35 min; In step S1, the mass ratio of polytetrafluoroethylene to deionized water is (7-9):(36-40).

7. The method for preparing a porous thermal insulation material for thermal protective clothing according to claim 1, characterized in that, In step S2, the freeze-drying temperature is -55℃ and the freeze-drying time is 40-48h.

8. The method for preparing a porous thermal insulation material for thermal protective clothing according to claim 1, characterized in that, In step S2, the heat treatment is carried out in a muffle furnace at a temperature of 380-400°C for 25-30 minutes.

9. A porous thermal insulation material prepared by the method for preparing the porous thermal insulation material for thermal protective clothing according to any one of claims 1-8.

10. The application of the porous thermal insulation material of claim 9 in thermal protective clothing.