Light heat insulation fabric and preparation method thereof

Abstract

The invention belongs to the technical field of functional textile material and nano material preparation processes and thermal protection engineering, and particularly relates to a light thermal insulation fabric and a preparation method thereof. The invention aims to solve the problem that the light weight, high heat insulation and other properties of the current fabric restrict each other. The preparation method comprises the following steps: carrying out fiber forming and chemical imidization on a polyamide acid precursor liquid in a coagulating bath containing an imidization reagent by utilizing wet spinning, carrying out supercritical drying to obtain modified polyimide aerogel composite fibers, blending the modified polyimide aerogel composite fibers with a thermoplastic polymer, and carrying out electrostatic spinning by adding a placeholder to prepare a porous flexible substrate layer; a thermal insulation layer is constructed on the surface of a substrate fiber in an in-situ growth manner through a solvothermal method, and a silane coupling agent and an epoxy modifier are adopted for alternate interface treatment, so that the problem of performance balance is effectively solved.

Description

Technical Field

[0001] This invention belongs to the field of functional textile materials, nanomaterial preparation processes and thermal protection engineering technology, specifically relating to a lightweight heat-insulating fabric and its preparation method. Background Technology

[0002] As humanity accelerates its exploration of extreme environments and demands for greater comfort in personal thermal protection equipment, the development of novel thermal insulation materials that combine lightweight, thinness, warmth, and strength has become a research hotspot in materials science. Heat transfer primarily occurs through three mechanisms: conduction, convection, and radiation. Traditional thermal insulation materials, such as natural fibers like cotton, wool, and down (CN117005086A), mainly rely on static air layers between fibers for insulation. While they offer a pleasant feel and moderate warmth, in extremely cold environments, achieving sufficient insulation often requires significantly increased thickness, resulting in bulky equipment and restricting user mobility. Furthermore, when ambient wind speeds are high or humidity increases, convective heat loss and moisture conduction in these materials increase dramatically, leading to a significant decrease in insulation performance.

[0003] While synthetic fibers such as polyester hollow fibers and microfibers have made progress in lightweighting, their micropore sizes remain at the micrometer level, failing to effectively suppress the Brownian motion of gas molecules, resulting in a gas-phase thermal conductivity that is difficult to exceed the limits of air. Furthermore, these organic fiber materials are typically transparent to infrared thermal radiation; under high-temperature heat sources, radiative heat transfer becomes the dominant mechanism, leading to protective failure. Aerogels, especially polyimide (PI) aerogels, are considered the best candidates for thermal insulation among solid materials due to their unique nanoporous structure, extremely high porosity, and extremely low density. However, applying PI aerogels to flexible fabrics faces significant technical challenges: the aerogel skeleton is extremely thin, and the node connections are fragile. Traditional PI aerogels are prone to skeleton breakage when bent, stretched, or compressed, making them unable to withstand the dynamic deformation during textile weaving, cutting, and wearing. To address the brittleness issue, aerogel powder is often combined with fibers. However, simple physical filling or adhesive bonding can lead to weak bonding between aerogel particles and the fiber matrix, resulting in a large amount of particles falling off after washing. Furthermore, adhesives can clog the pores of the aerogel, significantly reducing its thermal insulation performance.

[0004] Several technical approaches have been proposed to improve the performance of lightweight thermal insulation fabrics. For example, electrospinning can prepare nanofiber membranes with high specific surface area. Although nanofibers can separate air, the porosity and pore size distribution of conventional electrospun membranes are difficult to reach the level of aerogels. Another example is magnetron sputtering, which can prepare metal or oxide films that reflect infrared radiation. However, depositing rigid inorganic films on a loose, porous, flexible substrate can easily lead to stress mismatch and subsequent film cracking.

[0005] In summary, existing technologies still have considerable room for improvement in terms of the functional balance of thermal insulation fabrics, and there is an urgent need for a new method for preparing a thermal insulation fabric that is lightweight, highly insulating, strong, and flexible. Summary of the Invention

[0006] This invention provides a lightweight thermal insulation fabric and its preparation method, aiming to break down the performance barriers between lightweight, high thermal insulation, and strong flexibility. Through multi-scale structural design and interface engineering, this invention effectively overcomes the mutual constraints between these properties, obtaining a thermal insulation fabric with excellent overall performance.

[0007] The specific technical solution is as follows: A lightweight thermal insulation fabric and its preparation method are as follows: S1: Preparation of composite fibers.

[0008] S11: Dissolve p-phenylenediamine in an appropriate amount of N,N-dimethylacetamide solvent, cool in an ice-water bath, add 3,3′,4,4′-biphenyltetracarboxylic dianhydride while stirring, filter, and degas to obtain polyamic acid spinning solution.

[0009] S12: Add acetic anhydride and triethylamine to acetone, stir, and cool to room temperature to obtain a coagulation bath.

[0010] S13: The polyamic acid spinning solution prepared in S11 is spun into the coagulation bath prepared in S12, left to stand for 10 minutes, then stretched, soaked, supercritical dried, and chopped to obtain modified polyimide-aerogel composite fibers.

[0011] S2: Prepare a flexible substrate layer.

[0012] S21: Add thermoplastic polyurethane to a mixed solvent of N,N-dimethylformamide and tetrahydrofuran in a volume ratio of 1:1, stir, and obtain a core layer solution; add the modified polyimide-aerogel composite fiber prepared in S13 to a mixed solvent of N,N-dimethylformamide and tetrahydrofuran in a volume ratio of 1:1, shear emulsify, then add sodium chloride crystal powder, stir at low speed, and let stand to degas, and obtain a sheath layer solution.

[0013] S22: The core layer solution and sheath layer solution prepared in S21 are spun into a composite fiber nonwoven fabric through a coaxial nozzle, and then placed in deionized water at a temperature of 50°C, stirred, and dried to obtain a flexible base layer.

[0014] S3: Preparation of the thermal insulation functional layer.

[0015] S31: The flexible substrate prepared in S22 is immersed in anhydrous ethanol for wetting, and then transferred to deionized water to displace the ethanol, thus obtaining a pretreated flexible substrate.

[0016] S32: Add 2-methylimidazole and carboxylated nanocellulose to a 1:1 volume ratio of methanol and water, stir, sonicate, then add zinc nitrate solution and continue stirring to obtain a mixed precursor solution.

[0017] S33: The pretreated flexible substrate layer prepared in S31 is immersed in the mixed precursor solution prepared in S32, heated to react, cooled to room temperature, washed, replaced, and dried with supercritical CO2 to obtain a functional substrate with a heat insulation layer.

[0018] S4: Interface enhancement processing.

[0019] S41: Immerse the functional substrate of the heat insulation layer prepared in S33 in KH-550 solution for 15 min, and then heat treat it at 80℃ for 15 min to obtain the pre-cured material.

[0020] S42: Immerse the pre-cured material prepared in S41 in a polyethylene glycol diglycidyl ether solution for 20 min, and then heat-treat it at 100°C for 30 min.

[0021] S43: Repeat steps S41 and S42 1 to 3 times, and then treat at 85°C for 60 minutes to obtain the fabric with reinforced interface.

[0022] Furthermore, the p-phenylenediamine described in S11 has a molar ratio of 1:1 to 3,3′,4,4′-biphenyltetracarboxylic dianhydride.

[0023] The polyamic acid spinning solution described in S11 has a solid content of 6-12%.

[0024] The coagulation bath described in S12 contains acetic anhydride with a mass concentration of 10-30% and triethylamine with a volume concentration of 5-15%.

[0025] The soaking described in S13 uses ethanol and deionized water, and is performed 5 to 8 times.

[0026] The supercritical drying described in S13 has the following parameter settings: the drying medium is CO2, the temperature is 40℃, and the pressure is 10MPa.

[0027] Furthermore, the stirring described in S21 has the following parameter settings: temperature 50-60℃, rotation speed 300-600rpm, and duration 2-6h.

[0028] The shear emulsification described in S21 has the following parameters: rotation speed 9000-11000 rpm, duration 10-20 min.

[0029] The low-speed stirring described in S21 has the following parameters: rotation speed 100-300 rpm, duration 1-2 h.

[0030] The thermoplastic polyurethane described in S21 comprises 70-90% of the effective solid mass in the core layer solution and the sheath solution, the modified polyimide-aerogel composite fiber comprises 10-30% of the effective solid mass in the core layer solution and the sheath solution, and the sodium chloride crystal powder comprises 10-30% of the total mass of the core layer solution and the sheath solution.

[0031] The spinning parameters described in S22 are as follows: core layer advance speed 0.1-1 mL / h, sheath layer advance speed 0.5-3 mL / h, working voltage 15-25 kV, receiving distance 12-20 cm, temperature 20-30 °C, and relative humidity 40%.

[0032] The drying process described in S22 has the following parameters: temperature 60-80℃, duration 12-24h.

[0033] Furthermore, the 2-methylimidazole described in S32 has a molar ratio of 4:1 to 8:1 with zinc nitrate.

[0034] The carboxylated nanocellulose described in S32 has a mass ratio of 1:5 to 1:20 with zinc nitrate.

[0035] The heating reaction described in S33 has the following parameters: temperature 60-70℃, duration 4-12h.

[0036] The replacement described in S33 involves sequentially immersing the sample in ethanol solutions with concentration gradients of 50%, 75%, 95%, and 100%.

[0037] Furthermore, the KH-550 solution described in S41 has a mass concentration of 1%.

[0038] The polyethylene glycol diglycidyl ether solution described in S42 has a mass concentration of 5%.

[0039] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention extends the heat conduction path through a hierarchical porous structure, achieving a balance between ultra-low thermal conductivity and lightweight properties.

[0040] 2. This invention solves the interfacial compatibility problem at the molecular level through interface strengthening technology, constructs a fiber network, and improves tensile strength. Attached Figure Description

[0041] Figure 1 This is a flowchart of the manufacturing process for a lightweight thermal insulation fabric.

[0042] Figure 2 This is the FTIR image of the composite fiber prepared in S1 of Example 1.

[0043] Figure 3This is a comparison chart of the areal density and thermal conductivity of the fabrics finally prepared in Examples 1-4 and Comparative Examples 1-3. Detailed Implementation

[0044] The following embodiments further explain and illustrate the technical solutions of the present invention. It should be specifically noted that each specific embodiment is a concretization and explanation of the technical solution and should not be considered as a limitation on the scope of protection of the present invention. Those skilled in the art still have the right to modify the technical solutions of these embodiments and make equivalent substitutions for some or all of the technical features, and these modifications or substitutions do not change the essence of the corresponding technical solutions, nor do they cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions described in the present invention.

[0045] This invention proposes a lightweight thermal insulation fabric and its preparation method. A high-performance composite fabric with a multi-level structure is prepared through coupled wet spinning to construct the skeleton, electrospinning, in-situ growth, interfacial chemical toughening, and magnetron sputtering radiation blocking. (See attached diagram) Figure 1 The diagram shows a method for preparing a lightweight thermal insulation fabric, the detailed technical solution of which is as follows: 1. Preparation of composite fibers p-Phenylenediamine was dissolved in an appropriate amount of N,N-dimethylacetamide solvent, cooled in an ice-water bath, and 3,3′,4,4′-biphenyltetracarboxylic dianhydride was added while stirring. The mixture was filtered and degassed to obtain a polyamic acid spinning solution. Acetic anhydride and triethylamine were added to acetone, stirred, and cooled to room temperature to obtain a coagulation bath. The polyamic acid spinning solution was spun into the coagulation bath, stretched, soaked, and supercritical dried to obtain modified polyimide-aerogel composite fibers.

[0046] Polyamic acid (PAA) is extruded into a coagulation bath containing a chemical imidizing agent. During fiber coagulation, a chemical imidization reaction occurs (acetic anhydride dehydration and triethylamine catalysis directly convert the amyl acid structure on the PAA molecular chain into a polyimide structure during coagulation). The solvent in the gel fiber is removed by supercritical CO2 drying under conditions of no liquid phase surface tension, thus completely preserving its internal three-dimensional nanoporous network and obtaining low-density, high-porosity aerogel fibers.

[0047] 2. Preparation of flexible substrate layer Thermoplastic polyurethane was added to a 1:1 volume ratio of N,N-dimethylformamide and tetrahydrofuran mixed solvent and stirred to obtain a core layer solution. Modified polyimide-aerogel composite fibers were added to the 1:1 volume ratio of N,N-dimethylformamide and tetrahydrofuran mixed solvent, sheared and emulsified, and then sodium chloride crystal powder was added. The mixture was stirred at low speed and allowed to stand to degas, resulting in a sheath layer solution. The core layer solution and sheath layer solution were spun into a composite fiber nonwoven fabric through a coaxial nozzle, and then placed in deionized water at 50°C, stirred, and dried to obtain a flexible base layer.

[0048] The spinning solution containing chopped aerogel fibers and a polymer matrix is ​​stretched and solidified under a high-voltage electric field to form a three-dimensional network of interconnected ultrafine fibers, providing basic flexibility and strength. A water-soluble site-filler (NaCl) is uniformly dispersed in the spinning solution. After spinning into fabric, the site-filler is dissolved and removed by a water bath treatment. This creates additional micron-sized through-pores within the dense electrospun fiber network. These macropores not only reduce the areal density of the material but also improve its softness and breathability, and provide a larger specific surface area and anchoring points for the in-situ growth of subsequent functional layers.

[0049] 3. Preparation of the thermal insulation functional layer The flexible substrate was wetted in anhydrous ethanol and then transferred to deionized water to displace the ethanol, resulting in a pretreated flexible substrate. 2-methylimidazole and carboxylated nanocellulose were added to a 1:1 volume ratio of methanol and water, stirred, and sonicated. Zinc nitrate solution was then added and stirring was continued to obtain a mixed precursor solution. The pretreated flexible substrate was immersed in the mixed precursor solution, heated to react, cooled to room temperature, washed, displaced, and dried with supercritical CO2 to obtain a functional substrate with a heat insulation layer.

[0050] Under hydrothermal conditions, zinc ions preferentially bind to negatively charged sites (such as carboxyl groups) on the surface of carboxylated cellulose nanofibers, forming initial nucleation sites. Subsequently, 2-methylimidazole diffuses to these sites and undergoes a coordination reaction with zinc ions, directly growing ZIF-8 crystals in situ on the fiber surface. Simultaneously, the carboxylated cellulose nanofibers not only serve as templates for dispersing and anchoring ZIF-8, but also form a three-dimensional nanofiber network after drying. Ultimately, a dual-composite porous structure is formed on the substrate fiber surface, where "ZIF-8 nanocrystals" are embedded in a "cellulose aerogel network." This structure achieves highly efficient thermal insulation through a dual mechanism of effectively scattering infrared radiation and restricting air convection.

[0051] Interface enhancement processing The functional substrate of the heat insulation layer is immersed in KH-550 solution and then heat-treated to obtain a pre-cured material; the pre-cured material is immersed in polyethylene glycol diglycidyl ether and then heat-treated; the above steps are repeated, and then the material is treated at 85°C to obtain the fabric with interface reinforcement.

[0052] The silane coupling agent (KH-550) undergoes dehydration condensation with the hydroxyl groups on the surface of the substrate polyimide fiber, the thermal insulation layer ZIF-8@cellulose composite aerogel (rich in hydroxyl and carboxyl groups), and the cellulose nanofibers, forming strong Si-OC covalent bonds. Simultaneously, the amino group (-NH2) at the other end of KH-550 is exposed as an active reaction site. The epoxy groups at both ends of the polyethylene glycol diglycidyl ether (PEGDE) molecule undergo ring-opening addition reactions with the KH-550 amino group anchored at the interface, forming strong CN covalent bonds. The long-chain flexible structure of PEGDE effectively transfers and disperses stress between crosslinking points. Upon a second immersion in the KH-550 solution, its amino groups can continue to react with unreacted epoxy or hydroxyl groups on the previous PEGDE chain, thereby continuously increasing the crosslinking density and thickness of the interfacial layer. Ultimately, a three-dimensional interpenetrating network consisting of a rigid covalent backbone and a flexible hydrogen bond network is formed in the interfacial region. This network can efficiently transfer stress, prevent crack propagation, and resist interlaminar shear forces caused by temperature changes or repeated bending.

[0053] Example 1 A method for preparing a lightweight thermal insulation fabric is as follows: Table 1 Main Raw Materials S1: Preparation of composite fibers.

[0054] S11: Dissolve p-phenylenediamine in an appropriate amount of N,N-dimethylacetamide solvent, cool in an ice-water bath, and add 3,3′,4,4′-biphenyltetracarboxylic dianhydride while stirring. Filter and degas to obtain a polyamic acid spinning solution with a solid content of 9%. The molar ratio of p-phenylenediamine to 3,3′,4,4′-biphenyltetracarboxylic dianhydride is 1:1.

[0055] S12: Acetic anhydride and triethylamine are added to acetone, stirred, and cooled to room temperature to obtain a coagulation bath. The acetic anhydride concentration is 20% by mass, and the triethylamine concentration is 10% by volume.

[0056] S13: The polyamic acid spinning solution prepared in S11 was spun into the coagulation bath prepared in S12, held for 10 minutes, then stretched, soaked, supercritical dried, and chopped to obtain modified polyimide-aerogel composite fibers. The soaking was performed using ethanol and deionized water seven times. The supercritical drying parameters were set as follows: drying medium: CO2; temperature: 40℃; pressure: 10MPa.

[0057] S2: Prepare a flexible substrate layer.

[0058] S21: Thermoplastic polyurethane was added to a 1:1 volume ratio of N,N-dimethylformamide and tetrahydrofuran mixed solvent and stirred to obtain a core layer solution. The modified polyimide-aerogel composite fiber prepared in S13 was added to a 1:1 volume ratio of N,N-dimethylformamide and tetrahydrofuran mixed solvent, sheared and emulsified, and then sodium chloride crystal powder was added. The mixture was stirred at low speed and allowed to stand to remove bubbles to obtain a sheath layer solution. The stirring parameters were set as follows: temperature 55℃, rotation speed 450 rpm, duration 4 h; shear emulsification parameters were set as follows: rotation speed 10000 rpm, duration 15 min; low-speed stirring parameters were set as follows: rotation speed 200 rpm, duration 1.5 h; thermoplastic polyurethane accounted for 80% of the effective solid mass of the core layer solution and sheath layer solution, modified polyimide-aerogel composite fiber accounted for 20% of the effective solid mass of the core layer solution and sheath layer solution, and sodium chloride crystal powder accounted for 20% of the total mass of the core layer solution and sheath layer solution.

[0059] S22: The core layer solution and sheath layer solution prepared in S21 are spun into a composite fiber nonwoven fabric using a coaxial nozzle. The fabric is then placed in deionized water at 50℃, stirred, and dried to obtain a flexible base layer. The spinning parameters are set as follows: core layer feed rate 0.5 mL / h, sheath layer feed rate 1.8 mL / h, operating voltage 20 kV, receiving distance 16 cm, temperature 25℃, and relative humidity 40%.

[0060] S3: Preparation of the thermal insulation functional layer.

[0061] S31: The flexible substrate prepared in S22 is immersed in anhydrous ethanol for wetting, and then transferred to deionized water to displace the ethanol, thus obtaining a pretreated flexible substrate.

[0062] S32: 2-Methylimidazole and carboxylated nanocellulose were added to a 1:1 volume ratio of methanol and water, stirred, and sonicated. Then, zinc nitrate solution was added, and stirring was continued to obtain a mixed precursor solution. The molar ratio of 2-methylimidazole to zinc nitrate was 6:1; the mass ratio of carboxylated nanocellulose to zinc nitrate was 1:13.

[0063] S33: The pretreated flexible substrate layer prepared in S31 was immersed in the mixed precursor solution prepared in S32, heated to react, cooled to room temperature, washed, and then subjected to displacement by sequential immersion in ethanol solutions with concentration gradients of 50%, 75%, 95%, and 100%. Supercritical CO2 drying was then performed to obtain a functional substrate with a heat-insulating layer. The heating reaction parameters were set as follows: temperature 65℃, duration 8 hours.

[0064] S4: Interface enhancement processing.

[0065] S41: Immerse the functional substrate of the heat insulation layer prepared in S33 into a 1% KH-550 solution for 15 minutes, and then heat treat it at 80°C for 15 minutes to obtain a pre-cured material.

[0066] S42: Immerse the pre-cured material prepared in S41 in a 5% (w / w) polyethylene glycol diglycidyl ether solution for 20 min, and then heat-treat it at 100°C for 30 min.

[0067] S43: Repeat steps S41 and S42 twice, then treat at 85°C for 60 minutes to obtain the fabric with reinforced interface.

[0068] Example 2 The composition and preparation process are the same as in Example 1, except that: In the preparation process, the polyamic acid spinning solution in S11 has a solid content of 6%, and the other components are the same.

[0069] In the S12 coagulation bath of the preparation process, the mass concentration of acetic anhydride is 10%, the volume concentration of triethylamine is 5%, and other components are the same.

[0070] In the preparation process, S13 is soaked in ethanol and deionized water, and the soaking is repeated 5 times. The other steps are the same.

[0071] In step S21 of the preparation process, the stirring parameters are set as follows: temperature 50℃, rotation speed 300rpm, duration 2h; shear emulsification parameters are set as follows: rotation speed 9000rpm, duration 20min; low-speed stirring parameters are set as follows: rotation speed 100rpm, duration 1h, and other steps are the same.

[0072] In step S21 of the preparation process, the thermoplastic polyurethane accounts for 70% of the effective solid mass of the core layer solution and the sheath solution, the modified polyimide-aerogel composite fiber accounts for 30% of the effective solid mass of the core layer solution and the sheath solution, and the sodium chloride crystal powder accounts for 10-30% of the total mass of the core layer solution and the sheath solution, with the other components being the same.

[0073] In the S22 process of preparation, the spinning parameters are set as follows: core layer advance speed 0.1 mL / h, sheath layer advance speed 0.5 mL / h, working voltage 15 kV, receiving distance 12 cm, temperature 20 ℃, and other steps are the same.

[0074] In the preparation process S32, the molar ratio of 2-methylimidazole to zinc nitrate is 1:1; the mass ratio of carboxylated nanocellulose to zinc nitrate is 1:5, and other components are the same.

[0075] The heating reaction parameters in step S33 of the preparation process are set as follows: temperature 60℃, duration 4h, and other steps are the same.

[0076] In step S43 of the preparation process, steps S41 and S42 are executed cyclically once, and the other steps are the same.

[0077] Example 3 The composition and preparation process are the same as in Example 1, except that: In the preparation process, the polyamic acid spinning solution in S11 has a solid content of 12%, and the other components are the same.

[0078] In the S12 coagulation bath of the preparation process, the mass concentration of acetic anhydride is 30%, the volume concentration of triethylamine is 15%, and other components are the same.

[0079] In the preparation process, S13 is soaked in ethanol and deionized water, and the soaking is repeated 8 times. The other steps are the same.

[0080] In step S21 of the preparation process, the stirring parameters are set as follows: temperature 60℃, rotation speed 600rpm, duration 6h; shear emulsification parameters are set as follows: rotation speed 11000rpm, duration 10min; low-speed stirring parameters are set as follows: rotation speed 300rpm, duration 2h, and other steps are the same.

[0081] In step S21 of the preparation process, the thermoplastic polyurethane accounts for 90% of the effective solid mass of the core layer solution and the sheath solution, the modified polyimide-aerogel composite fiber accounts for 30% of the effective solid mass of the core layer solution and the sheath solution, and the sodium chloride crystal powder accounts for 10-30% of the total mass of the core layer solution and the sheath solution, with the other components being the same.

[0082] In the S22 process of preparation, the spinning parameters are set as follows: core layer advance speed 1 mL / h, sheath layer advance speed 3 mL / h, working voltage 25 kV, receiving distance 20 cm, temperature 30 ℃, and other steps are the same.

[0083] In the preparation process S32, the molar ratio of 2-methylimidazole to zinc nitrate is 8:1; the mass ratio of carboxylated nanocellulose to zinc nitrate is 1:20, and other components are the same.

[0084] The heating reaction parameters in step S33 of the preparation process are set as follows: temperature 70℃, duration 12h, and other steps are the same.

[0085] In step S43 of the preparation process, steps S41 and S42 are executed cyclically for a total of 3 times, while other steps are the same.

[0086] Example 4 The composition and preparation process are the same as in Example 1, except that: In the preparation process, the polyamic acid spinning solution in S11 has a solid content of 11%, and the other components are the same.

[0087] In the S12 coagulation bath of the preparation process, the mass concentration of acetic anhydride was 18%, the volume concentration of triethylamine was 7%, and other components were the same.

[0088] In step S13 of the preparation process, ethanol and deionized water are used for soaking, and the soaking is repeated 6 times. The other steps are the same.

[0089] In step S21 of the preparation process, the stirring parameters were set as follows: temperature 52℃, rotation speed 400rpm, duration 5h; shear emulsification parameters were set as follows: rotation speed 10500rpm, duration 17min; low-speed stirring parameters were set as follows: rotation speed 140rpm, duration 1.8h, and other steps were the same.

[0090] In step S21 of the preparation process, the thermoplastic polyurethane accounts for 75% of the effective solid mass of the core layer solution and the sheath solution, the modified polyimide-aerogel composite fiber accounts for 25% of the effective solid mass of the core layer solution and the sheath solution, and the sodium chloride crystal powder accounts for 15% of the total mass of the core layer solution and the sheath solution, with the other components being the same.

[0091] The spinning parameters in S22 of the preparation process are set as follows: core layer advance speed 0.8 mL / h, sheath layer advance speed 1.9 mL / h, working voltage 18 kV, receiving distance 18 cm, temperature 28 ℃, and other steps are the same.

[0092] In the preparation process S32, the molar ratio of 2-methylimidazole to zinc nitrate is 7:1; the mass ratio of carboxylated nanocellulose to zinc nitrate is 1:14, and other components are the same.

[0093] The heating reaction parameters in step S33 of the preparation process are set as follows: temperature 62℃, duration 10h, and other steps are the same.

[0094] Comparative Example 1 The composition and preparation process are the same as in Example 1, except that: In step S2 of the preparation process, no NaCl site-filling agent is added; the other steps are the same.

[0095] Comparative Example 2 The composition and preparation process are the same as in Example 1, except that: The interface strengthening step in step S4 of the preparation process is removed, while the other steps remain the same.

[0096] Comparative Example 3 Silica aerogel mat (3 mm thick, 0.15 g / cm³) was used. 3 It is sandwiched between two layers of flame-retardant fabric (aramid 1313 woven fabric) and bonded together using a flame bonding machine through a low-melting-point fiber web.

[0097] Samples of the modified polyimide-aerogel composite fiber prepared in Example 1 (S1) were taken for FTIR testing: 0.2g of fiber was thoroughly dried under an infrared lamp, then ground together with 20g of dried potassium bromide powder, and 0.2g of the mixture was pressed into a transparent sheet for Fourier transform infrared spectroscopy (4cm resolution). -1 (64 scans) Figure 2 As shown, at 1770cm -1 and 1375cm -1 Nearby, distinct imine characteristic peaks appeared.

[0098] Based on Examples 1-4 and Comparative Examples 1-3, samples of the finally prepared fabric were taken for areal density testing: the samples were placed in an environment of 23°C and 50% relative humidity for 24 hours, and then the fabric was cut into (100mm×100mm) pieces, weighed, and the mass per unit area was calculated. Five sets of measurements were taken and the average value was taken.

[0099] Based on Examples 1-4 and Comparative Examples 1-3, samples of the finally prepared fabric were taken for thermal conductivity testing: the fabric was folded into a flat sample with a thickness of 3 mm, and then placed in an environment of 23°C and 50% relative humidity for 24 hours for testing. The test was conducted three times at different locations, and the average value was taken, referring to the standard GB / T 10297-2015 "Determination of Thermal Conductivity of Non-metallic Solid Materials - Hot Wire Method".

[0100] Based on Examples 1-4 and Comparative Examples 1-3, samples of the finally prepared fabric were taken and subjected to tensile strength tests: the samples were placed in an environment of 23°C and 50% relative humidity for 24 hours, cut into rectangular strips (150 mm long and 10 mm wide), and the width and thickness were measured at 5 points in the middle of the sample. The average value was taken to calculate the cross-sectional area. The test speed was 100 mm / min.

[0101] The specific test results are shown in Table 2. Figure 2 , Figure 3 As shown: Table 2 Comparison of core performance of Examples 1-4 and Comparative Examples 1-3 The comparison results above show that Example 1 has the best overall performance. Its unique multi-level porous structure results in extremely low thermal conductivity. The low-density aerogel fibers and electrospun microfibers result in low areal density. With TPU as the main elastomer, it provides excellent elastic recovery and flexibility. The modified polyimide composite fiber acts as a rigid reinforcement unit to improve tensile strength. This indicates that Example 1 successfully solves the inherent mutual constraint between lightweight, high thermal insulation, and strong flexibility in current fabrics. The overall performance of Examples 2 to 4 is slightly lower than that of Example 1, but still maintains a high level. This shows that it still achieves excellent performance balance under a wide range of parameter variations. Comparative Example 1 does not add a placebo and lacks in-situ growth, resulting in a sharp increase in thermal conductivity and the worst thermal insulation performance. Comparative Example 2 has low tensile strength because the interlayer is only physically wrapped and there is no interface reinforcement. Comparative Example 3 has extremely low thermal conductivity due to the nanopores of the silica aerogel itself, resulting in the best thermal insulation performance. However, it is essentially a rigid and brittle porous block with high density and easy powder shedding, which completely fails to meet the requirements of flexible wearable fabrics.

[0102] In summary, it is clear from the above embodiments and comparative examples that the lightweight thermal insulation fabric provided by the present invention significantly outperforms traditional solutions in achieving a balance between lightweight, high thermal insulation, and strong flexibility. This is attributed to the use of porous aerogel fibers to solve the thermal insulation problem, the use of electrospun TPU networks to solve the lightweight and flexible problem, and the use of a refined interface strengthening process to firmly combine the two to solve the strength problem, thereby achieving a unity of multiple contradictory properties.

Claims

1. A method for preparing a lightweight thermal insulation fabric, comprising substrate preparation, functional layer preparation, and post-treatment, characterized in that: The substrate preparation involves preparing a composite fiber substrate by coaxial electrospinning of polyimide-aerogel composite fibers and thermoplastic polyurethane, with sodium chloride added as a site-filling agent to form a porous structure. The functional layer preparation involves pretreating the composite fiber substrate with ethanol and then preparing ZIF-8 nanocrystals in situ on the fiber surface to obtain a functional substrate. The post-treatment involves immersing the functional substrate in a KH-550 solution for pre-curing, followed by immersion in polyethylene glycol diglycidyl ether to complete chemical cross-linking.

2. The method for preparing the lightweight heat-insulating fabric according to claim 1, characterized in that, Includes the following steps: S1: Preparation of composite fibers; S11: Dissolve p-phenylenediamine in an appropriate amount of N,N-dimethylacetamide solvent, cool in an ice-water bath, add 3,3′,4,4′-biphenyltetracarboxylic dianhydride while stirring, filter, degas, and obtain polyamic acid spinning solution; S12: Add acetic anhydride and triethylamine to acetone, stir, and cool to room temperature to obtain a coagulation bath; S13: The polyamic acid spinning solution prepared in S11 is spun into the coagulation bath prepared in S12, left to stand for 10 minutes, then stretched, soaked, supercritical dried, and chopped to obtain modified polyimide-aerogel composite fiber. S2: Fabrication of a flexible substrate layer; S21: Add thermoplastic polyurethane to a mixed solvent of N,N-dimethylformamide and tetrahydrofuran in a volume ratio of 1:1, stir, and obtain a core layer solution; add the modified polyimide-aerogel composite fiber prepared in S13 to a mixed solvent of N,N-dimethylformamide and tetrahydrofuran in a volume ratio of 1:1, shear emulsify, then add sodium chloride crystal powder, stir at low speed, and let stand to degas, to obtain a sheath layer solution; S22: The core layer solution and sheath layer solution prepared in S21 are spun into a composite fiber nonwoven fabric through a coaxial nozzle, and then placed in deionized water at a temperature of 50°C, stirred, and dried to obtain a flexible base layer. S3: Preparation of the thermal insulation functional layer; S31: The flexible substrate prepared in S22 is immersed in anhydrous ethanol for wetting, and then transferred to deionized water to displace the ethanol, thus obtaining a pretreated flexible substrate. S32: Add 2-methylimidazole and carboxylated nanocellulose to a 1:1 volume ratio of methanol and water, stir, sonicate, then add zinc nitrate solution and continue stirring to obtain a mixed precursor solution; S33: The pretreated flexible substrate layer prepared in S31 is immersed in the mixed precursor liquid prepared in S32, heated to react, cooled to room temperature, washed, replaced, and dried with supercritical CO2 to obtain a functional substrate with a heat insulation layer. S4: Interface enhancement processing; S41: Immerse the functional substrate of the heat insulation layer prepared in S33 in KH-550 solution for 15 min, and then heat treat it at 80℃ for 15 min to obtain the pre-cured material; S42: Immerse the pre-cured material prepared in S41 in a polyethylene glycol diglycidyl ether solution for 20 min, and then heat-treat it at 100°C for 30 min; S43: Repeat steps S41 and S42 1 to 3 times, and then treat at 85°C for 60 minutes to obtain the fabric with reinforced interface.

3. The method for preparing a lightweight heat-insulating fabric according to claim 2, characterized in that: The p-phenylenediamine described in S11 has a molar ratio of 1:1 to 3,3′,4,4′-biphenyltetracarboxylic dianhydride. The polyamic acid spinning solution described in S11 has a solid content of 6-12%. The coagulation bath described in S12 contains acetic anhydride with a mass concentration of 10-30% and triethylamine with a volume concentration of 5-15%.

4. The method for preparing a lightweight heat-insulating fabric according to claim 2, characterized in that: The soaking described in S13 uses ethanol and deionized water, and is performed 5 to 8 times. The supercritical drying described in S13 has the following parameter settings: the drying medium is CO2, the temperature is 40℃, and the pressure is 10MPa.

5. The method for preparing a lightweight heat-insulating fabric according to claim 2, characterized in that: The stirring described in S21 has the following parameters: temperature 50-60℃, speed 300-600rpm, and duration 2-6h. The shear emulsification described in S21 has the following parameter settings: rotation speed 9000~11000rpm, duration 10~20min; The low-speed stirring described in S21 has the following parameter settings: rotation speed 100-300 rpm, duration 1-2 h; The thermoplastic polyurethane described in S21 comprises 70-90% of the effective solid mass in the core layer solution and the sheath solution, the modified polyimide-aerogel composite fiber comprises 10-30% of the effective solid mass in the core layer solution and the sheath solution, and the sodium chloride crystal powder comprises 10-30% of the total mass of the core layer solution and the sheath solution. The spinning parameters described in S22 are as follows: core layer advance speed 0.1-1 mL / h, sheath layer advance speed 0.5-3 mL / h, working voltage 15-25 kV, receiving distance 12-20 cm, temperature 20-30 °C, and relative humidity 40%.

6. The method for preparing a lightweight thermal insulation fabric according to claim 2, characterized in that: The spinning parameters described in S22 are as follows: core layer advance speed 0.1-1 mL / h, sheath layer advance speed 0.5-3 mL / h, operating voltage 15-25 kV, receiving distance 12-20 cm, temperature 20-30 °C, and relative humidity 40%. The drying process described in S22 has the following parameters: temperature 60-80℃, duration 12-24h.

7. The method for preparing a lightweight heat-insulating fabric according to claim 2, characterized in that: The 2-methylimidazole described in S32 has a molar ratio of 4:1 to 8:1 with zinc nitrate. The carboxylated nanocellulose described in S32 has a mass ratio of 1:5 to 1:20 with zinc nitrate.

8. The method for preparing a lightweight heat-insulating fabric according to claim 2, characterized in that: The heating reaction described in S33 has the following parameter settings: temperature 60-70℃, duration 4-12h; The replacement described in S33 involves sequentially immersing the sample in ethanol solutions with concentration gradients of 50%, 75%, 95%, and 100%.

9. The method for preparing a lightweight thermal insulation fabric according to claim 2, characterized in that: The KH-550 solution described in S41 has a mass concentration of 1%. The polyethylene glycol diglycidyl ether solution described in S42 has a mass concentration of 5%.

10. The lightweight thermal insulation fabric prepared by the method according to claims 1-9, characterized in that: The lightweight thermal insulation fabric has a thermal conductivity of ≤0.045W / m·K and a tensile strength of ≥25MPa.

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