Waterproof electrospun fibrous fabric

Abstract

This invention discloses a waterproof electrostatic spun fiber fabric, belonging to the field of functional fabric technology. The fabric comprises, from the outside in, a TPU layer, a fabric layer, and a hydrophobically modified chitosan layer. These three layers work together to achieve a balance between functionality and mechanical properties. The hydrophobically modified chitosan in the layer is prepared via a two-step method: first, chitosan is olefinically modified to introduce carbon-carbon double bonds; then, under UV light initiation, catechol groups and long-chain alkyl hydrophobic groups are covalently grafted in a one-step thiol-olefin click chemistry step. The modified product exhibits both strong adhesion and high hydrophobicity. This invention eliminates the need for an additional adhesive gel layer. Through pretreatment of the base fabric and a mild epoxy crosslinking system, strong interlayer adhesion and structural stability are achieved, resulting in a fabric that is both highly waterproof and highly breathable, with excellent wash resistance and anti-swelling properties, making it suitable for various applications including outdoor, sports, and protective applications.

Description

Technical Field

[0001] This invention relates to the field of functional fabric technology, and in particular to a waterproof electrostatic spun fiber fabric. Background Technology

[0002] Electrospinning technology has garnered significant attention in the field of functional fabrics in recent years due to its ability to prepare nanofiber membranes with high specific surface area and high porosity. The fiber membranes formed by electrospinning possess an interconnected three-dimensional porous structure, with pore sizes controllable to sizes smaller than the critical size for capillary permeation of liquid water, while retaining diffusion channels for water vapor molecules. Therefore, while achieving waterproof functionality, they also possess excellent moisture permeability, and are considered one of the effective ways to solve the problem of traditional waterproof fabrics being "waterproof but not breathable."

[0003] However, single-layer electrospun films have significant limitations in practical applications. Since the mechanical strength of the electrospun film mainly depends on the physical overlap between fibers, its tensile and tear properties often fail to meet the daily wear requirements of clothing fabrics, easily leading to damage and peeling. To address this, researchers have attempted to composite electrospun films with traditional woven or knitted fabrics, using the base fabric as the mechanical support layer and the electrospun film as the functional layer to construct a multi-layer composite structure. However, this approach faces new technical challenges: the interfacial bonding between different materials is crucial to the performance of the composite fabric. Existing composite processes often employ adhesive lamination or hot-pressing. The introduction of adhesives can easily clog the pores of the electrospun film, leading to decreased moisture permeability; while simple hot pressing is insufficient to form a strong bond between materials with significant polarity differences, resulting in peeling and bubbling between layers, severely affecting the fabric's washability and lifespan.

[0004] In the selection of materials for functional layers, chitosan, as a natural polymer, has application potential in the field of functional textiles due to its excellent film-forming properties, antibacterial properties, and biocompatibility. However, chitosan molecules are rich in hydroxyl and amino groups, exhibiting strong intrinsic hydrophilicity. When directly used in waterproof fabrics, it easily swells or even dissolves upon contact with water, failing to form a stable waterproof barrier. To address this issue, existing technologies often employ the physical blending of inorganic hydrophobic materials (such as nano-silica and polytetrafluoroethylene microparticles) with chitosan, aiming to impart hydrophobic properties to the composite membrane through filler. However, this blending modification method does not alter the hydrophilic properties of chitosan at the molecular level, resulting in limited improvement in hydrophobic effects. Furthermore, the inorganic filler and chitosan matrix rely solely on physical adsorption for bonding, which can easily lead to precipitation and migration during subsequent spinning or use, resulting in uneven hydrophobic properties, poor washability, and even potential blockage of fiber membrane pores, sacrificing the fabric's moisture permeability. To address this deficiency, researchers have attempted to hydrophobically modify chitosan through chemical modification. However, these traditional chemical modification methods often focus only on improving hydrophobic properties, neglecting the interfacial adhesion between the modified chitosan and the base fabric and other functional layers. This results in insufficient interlayer bonding in the composite fabric, making it difficult to meet the requirements of washability and structural stability in practical applications. These long-standing technical challenges make it difficult for existing chitosan-based waterproof fabrics to simultaneously achieve high waterproofness, high moisture permeability, strong adhesion, and washability, limiting their large-scale application in high-end functional textiles. Developing technical solutions that can overcome these bottlenecks has become an urgent need for the industry. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of existing technologies by proposing a waterproof electrostatic spun fiber fabric.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: a waterproof electrostatic spun fiber fabric, wherein the fabric comprises, from the outside to the inside, a TPU layer, a fabric layer, and a hydrophobic modified chitosan layer.

[0007] Preferably, the TPU layer is a TPU electrospun film.

[0008] Preferably, the hydrophobically modified chitosan layer is a hydrophobically modified chitosan electrospun film, wherein the hydrophobically modified chitosan is a product in which the chitosan backbone is first modified by alkenylation of carbon-carbon double bonds, and then by thiol-alkene click chemistry, in one step covalently grafting catechol groups and long-chain alkyl hydrophobic groups.

[0009] Preferably, the preparation method of the hydrophobically modified chitosan is as follows:

[0010] (1) Add chitosan to dilute acetic acid aqueous solution and stir until dissolved. Then add glycidyl methacrylate and react at room temperature for 4-10 h. Transfer the reaction solution to a dialysis bag and dialyze with deionized water for 12-24 h, changing the dialysate every 8 h. Then freeze-dry under vacuum to obtain alkenylated chitosan. The chemical reaction is shown in the diagram below:

[0011] ;

[0012] The main chain of chitosan is composed of 2-amino-2-deoxy-D-glucose units linked by β-(1,4) glycosidic bonds. Its structure is rich in highly reactive primary and secondary amino groups. In dilute acetic acid aqueous solution, the primary amino groups of chitosan undergo protonation to form ammonium salts, breaking intramolecular and intermolecular hydrogen bonds and achieving uniform dissolution of chitosan in the aqueous phase. After adding glycidyl methacrylate to the system, its molecular structure simultaneously possesses highly reactive epoxy groups and carbon-carbon double bonds that can participate in subsequent click reactions. The nitrogen atoms of the primary amino groups on the chitosan main chain carry lone pairs of electrons. As a strong nucleophile, it attacks the less sterically hindered methylene carbon atom on the epoxy ring of glycidyl methacrylate, initiating a nucleophilic ring-opening reaction of the epoxy ring. After ring opening, the carbon-oxygen bond of the epoxy group breaks, generating secondary amino and hydroxyl groups. Thus, the methacrylate structure with reactive carbon-carbon double bonds is covalently grafted onto the chitosan backbone through stable CN bonds, completing the alkenylation modification of chitosan and introducing sufficient reaction sites for subsequent click chemistry reactions. At the same time, the double bond grafting rate can be controlled by the raw material feed ratio, reserving some unreacted primary amino groups as crosslinking sites in the subsequent fabric preparation process.

[0013] (2) Under nitrogen protection, alkenylated chitosan was added to N,N-dimethylformamide, along with a thiol compound containing catechol, a long-chain alkyl thiol, and a photoinitiator. The reaction was carried out at room temperature for 30-120 min under ultraviolet light irradiation. After the reaction was completed, deionized water was added with stirring. At this time, a solid precipitated out. After standing for 30 min, the solid product was collected by filtration. The solid product was then added to n-hexane and stirred for 1-2 h. After filtration, the obtained solid product was dried to obtain hydrophobically modified chitosan. Taking tetradecanthiol as an example, the chemical reaction is shown below:

[0014] ;

[0015] This step is based on the thiol-olefin click chemistry reaction. In the homogeneous N,N-dimethylformamide system, alkenylated chitosan, catechol-containing thiols, and long-chain alkyl thiols can be completely dissolved, ensuring that the reaction proceeds uniformly at the molecular level. Under ultraviolet light irradiation, the photoinitiator in the system absorbs photon energy and undergoes cleavage, generating highly reactive primary free radicals. These primary free radicals rapidly abstract hydrogen atoms from the thiol groups in the thiol compounds, generating highly reactive sulfur free radicals. These sulfur free radicals have extremely high addition activity and attack the carbon-carbon double bonds grafted onto the chitosan backbone, causing the π-bond of the carbon-carbon double bond to break, forming a stable CS bond with the sulfur free radical, and simultaneously generating a new carbon free radical intermediate. This carbon free radical then continues to abstract thiol hydrogen atoms from another thiol compound in the system, generating a stable alkane structure. Sulfur free radicals are regenerated, thereby initiating a chain addition reaction, which allows the thiol-alkene addition reaction to proceed continuously and efficiently. In this chain reaction process, the catechol-containing mercapto monomer and the long-chain alkyl thiol in the system will simultaneously and indiscriminately undergo free radical addition with the carbon-carbon double bond. Through stable thioether bonds, the mussel-inspired catechol adhesion functional group and the long-chain alkyl hydrophobic group are covalently grafted onto the chitosan molecular chain in one step, simultaneously realizing the hydrophobic modification and interfacial adhesion functionalization of chitosan. This click reaction can be completed rapidly at room temperature and has the characteristics of high reaction efficiency and strong selectivity.

[0016] Preferably, in (1), the chitosan, dilute acetic acid aqueous solution and glycidyl methacrylate are in a weight ratio of 1:25-50:0.1-0.3.

[0017] Preferably, the concentration of the dilute acetic acid aqueous solution in (1) is 1-3 wt%.

[0018] Preferably, the molecular weight cutoff of the dialysis bag in (1) is 3500 Da.

[0019] Preferably, in (2), the alkenylated chitosan, N,N-dimethylformamide, thiol compound containing catechol, long-chain alkyl thiol, photoinitiator, deionized water and n-hexane are in the following weight ratio: 1:15-30:0.08-0.12:0.2-0.4:0.001-0.003:30-40:10-20.

[0020] Preferably, the catechol-containing thiol compound in (2) refers to 2,3-dihydroxyphenylethylthiol.

[0021] Preferably, the long-chain alkyl thiols in (2) refer to one or more of dodecyl mercaptan, tetradecyl mercaptan, hexadecyl mercaptan or octadecyl mercaptan.

[0022] Preferably, the photoinitiator in (2) refers to one of 2-hydroxy-2-methylphenylacetone or 1-hydroxycyclohexylphenyl ketone.

[0023] Preferably, the ultraviolet irradiation conditions in (2) are a wavelength of 365 nm and an irradiation intensity of 500-1000 mW / cm². 2 .

[0024] Furthermore, the present invention also provides a method for preparing a waterproof electrostatic spun fiber fabric, comprising the following steps:

[0025] S1. Thermoplastic polyurethane is dissolved in a mixed solution of N,N-dimethylformamide / tetrahydrofuran to prepare a TPU spinning solution with a concentration of 8-12wt%. The TPU electrospun film is prepared by electrospinning and used as the TPU layer.

[0026] S2. Dissolve hydrophobically modified chitosan in a mixed solution of N,N-dimethylformamide / tetrahydrofuran to prepare a hydrophobically modified chitosan solution with a concentration of 0.1-0.3wt%. Then, immerse the fabric in the solution, process it using an impregnation-rolling process, and then dry it. Finally, bond the TPU layer to one side of the fabric using a hot-pressing method to obtain the fabric layer.

[0027] S3. Dissolve hydrophobically modified chitosan in a mixed solution of N,N-dimethylformamide / tetrahydrofuran to prepare a hydrophobically modified chitosan spinning solution with a concentration of 0.8-1.5wt%. Using the side of the fabric layer without the TPU layer as the receiving surface, prepare a hydrophobically modified chitosan electrospun film by electrospinning, which serves as the hydrophobically modified chitosan layer.

[0028] S4. Spray a crosslinking agent solution onto the hydrophobically modified chitosan layer, let it stand at 30-40℃ for 1-3 hours, and then freeze-dry it to obtain a waterproof electrostatic spun fiber fabric.

[0029] Preferably, the volume ratio of N,N-dimethylformamide to tetrahydrofuran in the N,N-dimethylformamide / tetrahydrofuran mixed solution in S1 is 1:1.

[0030] Preferably, the electrospinning conditions in S1 are: spinning voltage 15-25kV, receiving distance 10-20cm, and single needle injection speed 0.5-2ml / h.

[0031] Preferably, the volume ratio of N,N-dimethylformamide to tetrahydrofuran in the N,N-dimethylformamide / tetrahydrofuran mixed solution in S2 is 1:1.

[0032] Preferably, the fabric in S2 refers to a woven or knitted fabric made of any one of polyester fiber, polyamide fiber, cotton fiber, or viscose fiber.

[0033] More preferably, the fabric in S2 refers to a polyester fiber woven fabric.

[0034] Preferably, the impregnation-rolling process in S2 is as follows: room temperature impregnation for 30-60 minutes, and the roll-off rate is controlled at 60-80%.

[0035] Preferably, the hot pressing temperature in S2 is 80-110℃, the pressure is 0.2-0.5MPa, and the time is 10-20s.

[0036] Preferably, the volume ratio of N,N-dimethylformamide to tetrahydrofuran in the N,N-dimethylformamide / tetrahydrofuran mixed solution in S3 is 3:7-5:5.

[0037] Preferably, the electrospinning conditions in S3 are: spinning voltage 12-20kV, receiving distance 8-15cm, and single needle injection speed 0.3-2ml / h.

[0038] Preferably, the crosslinking agent solution in S4 refers to an ethanol / water mixture of glycerol triglycidyl ether, with a concentration of 1-3 wt%, pH=8.0-9.0, and a spraying rate of 50-200 g / m³. 2 The volume ratio of ethanol to water in the ethanol / water mixed solution is 7:3-9:1.

[0039] Preferably, the mechanism of action of the waterproof electrostatic spun fiber fabric in this invention is explained as follows:

[0040] The fabric of this invention adopts a three-layer composite structure design from the outside to the inside: a TPU layer, a fabric layer, and a hydrophobic modified chitosan layer. The middle fabric layer serves as a mechanical support skeleton, providing the entire fabric with excellent mechanical properties such as tensile strength, bending strength, and tear resistance, adapting to the mechanical needs of garment processing and daily wear. At the same time, the membranes formed by electrospinning on both the inner and outer sides achieve functional zoning and structural synergy through the base fabric, avoiding the problems of insufficient mechanical properties and easy damage of single-layer spun membranes, and also solving the industry pain point of functional conflicts between layers after multi-layer membrane composites. The outer TPU electrospinned membrane itself has good waterproofness, flexibility, and weather resistance. As the outermost layer of the fabric, it can block the intrusion of liquid water, dust, and other substances from the external environment. At the same time, its own electrospinned porous structure retains basic water vapor permeability, does not hinder the outward expulsion of human sweat vapor, and can also provide physical protection for the inner functional layers, reducing the damage to the core functional layers caused by friction and bending during daily wear.

[0041] The realization of the fabric's core functions relies on the molecular structure design of hydrophobically modified chitosan and the structural control of electrospinning. By simultaneously covalently grafting long-chain alkyl hydrophobic groups onto the chitosan molecular chain through thiol-ene click chemistry, the surface energy of chitosan is significantly reduced, overcoming the strong hydrophilicity inherent in chitosan due to its numerous hydroxyl and amino groups. This achieves the intrinsic hydrophobicity of the chitosan matrix. After electrospinning, the rough microscopic surface formed by the interwoven nanofibers combines with the material's inherently low surface energy to synergistically construct a superhydrophobic interface, allowing liquid water to form spherical droplets that roll off the fabric surface, achieving excellent liquid water barrier properties. Simultaneously grafted catechol groups, based on the biomimetic adhesion mechanism of mussels, can achieve strong interfacial bonding with the base fabric fibers and TPU film through multiple forces such as hydrogen bonds, covalent bonds, π-π stacking, and mechanical interlocking. This solves the problem of easy peeling and delamination between different material layers at the molecular level, while eliminating the need for an additional adhesive gel layer, thus avoiding the defects of adhesive layers clogging pores and sacrificing fabric moisture permeability. In achieving strong interfacial adhesion, this invention employs a pre-treatment process of impregnating and rolling the base fabric. This allows a low-concentration hydrophobic modified chitosan solution to fully penetrate the gaps between the base fabric fibers and the surface of individual fibers. After drying, the modified chitosan forms a uniform coating layer on the surface of the base fabric fibers and a nanoscale anchoring structure in the fiber gaps. This provides sufficient adhesion sites for the hot-pressing adhesion of the outer TPU film, enabling the TPU and the base fabric to achieve strong adhesion through the catechol groups of the modified chitosan during low-temperature hot pressing. It also lays the interfacial foundation for the in-situ composite of the inner hydrophobic modified chitosan electrospun film. During the electrospinning process of preparing hydrophobic modified chitosan layers, the solvent in the spinning solution slightly swells the modified chitosan pre-coated on the base fabric surface, causing the newly deposited nanofibers to become molecularly entangled with the modified chitosan on the base fabric surface. Subsequently, through cross-linking reactions, covalent bonds are further formed, achieving molecular-level integration between the spun film and the base fabric. This avoids the problems of interlayer interface cracking and peeling, and significantly improves the washability and bending resistance of the fabric.

[0042] The balance between waterproof and breathable properties of the fabric is achieved through a three-layer structure with synergistic material properties. Regarding liquid water barrier, both the outer TPU electrospun membrane and the inner hydrophobic modified chitosan electrospun membrane are three-dimensional porous networks formed by interwoven nanofibers. Their pore sizes are smaller than the capillary penetration critical size of liquid water. Combined with the hydrophobic properties of modified chitosan, a double waterproof barrier is formed, significantly improving the fabric's hydrostatic pressure performance and effectively preventing the intrusion of external liquid water. Regarding water vapor permeability, the nanofiber membrane formed by electrospinning possesses high porosity and an interconnected three-dimensional pore structure, providing continuous channels for the diffusion and transmission of human sweat vapor. Simultaneously, the small amount of hydrophilic groups remaining on the chitosan molecular chain and the soft segment structure of TPU itself can promote rapid water vapor permeation through an adsorption-diffusion-desorption mechanism. The interconnected pores of the three layers do not form a barrier to water vapor transmission, ultimately achieving a balance between high waterproofness and high breathability, resolving the contradiction of traditional waterproof fabrics being "waterproof but not breathable, breathable but not waterproof."

[0043] The long-term stability of the fabric's performance relies on a mild epoxy crosslinking curing system. This invention reserves some primary amino groups on the chitosan molecular chain during the alkenylation modification stage as sites for crosslinking reactions. The subsequently sprayed crosslinking agent, under mild, weakly alkaline conditions, undergoes a highly efficient nucleophilic ring-opening reaction with the primary amino groups. The two active hydrogens of a single primary amino group can combine with epoxy groups, forming a stable covalent crosslinking network between the modified chitosan molecular chains. This transforms the electrospun nanofibers from a physically stacked structure into a covalently bonded whole, preventing chitosan from swelling and dissolving in humid environments, significantly improving the fabric's anti-swelling and water resistance. It also further strengthens the interlayer bonding force, reducing the loss of functional groups and fiber structure damage during washing and bending, ensuring that the fabric's waterproof and adhesive properties remain stable even after long-term use and multiple washes. Meanwhile, the cross-linking reaction can be carried out at room temperature, and the process of spinning and setting before cross-linking will not destroy the nanoporous structure formed by electrospinning, perfectly preserving the original high porosity and high moisture permeability of the fabric, and achieving simultaneous improvement in structural stability and functional stability.

[0044] Compared with the prior art, the beneficial effects of the present invention are:

[0045] 1. This invention achieves one-step bifunctional modification of chitosan through thiol-olefin click chemistry, simultaneously covalently grafting catechol adhesion groups and long-chain alkyl hydrophobic groups, endowing chitosan with intrinsic hydrophobic properties and strong interfacial adhesion at the molecular level. It completely eliminates the inorganic fillers in physical blending, avoiding the defects of filler agglomeration, shedding, and matrix swelling and collapse. At the same time, it solves the problems of poor selectivity and single function of conventional chemical modification reactions, allowing chitosan-based fabrics to have both superhydrophobic properties and stable interfacial bonding, providing high-quality bio-based raw materials for high-end functional fabrics.

[0046] 2. This invention eliminates the need for an additional adhesive gel layer. Relying on the multiple adhesion mechanisms of catechol groups and the base fabric impregnation-rolling pretreatment process, modified chitosan forms a coating layer and nano-anchoring structure on the surface of the base fabric fibers. Combined with the molecular chain entanglement during electrospinning and subsequent cross-linking consolidation, molecular-level integrated bonding of the spinning film, base fabric, and TPU layer is achieved. This solves the pain points of easy peeling and delamination between composite fabric layers, while avoiding the problems of adhesive gel layer clogging pores and sacrificing moisture permeability, thus achieving both strong adhesion and high moisture permeability.

[0047] 3. This invention reacts the primary amines reserved in the alkenylation stage with a multi-element epoxy crosslinking agent to form a stable covalent crosslinking network under mild conditions, transforming the physical stacking structure of nanofibers into a covalently connected whole. This significantly improves the fabric's anti-swelling and washability, avoids performance degradation in humid environments, and does not damage the nanoporous structure formed by electrospinning, perfectly preserving high porosity and moisture-permeable channels, thus achieving a simultaneous improvement in structural and functional stability.

[0048] 4. This invention achieves a balance between high waterproofness and high moisture permeability through the pore design and material optimization of a three-layer composite structure. The double hydrophobic barrier effectively blocks the intrusion of external liquid water, and the interconnected nanopores provide a continuous path for water vapor transmission. At the same time, the combination of the hydrophilic-hydrophobic balance mechanism of chitosan and TPU solves the contradiction of traditional waterproof fabrics being "waterproof but not breathable, breathable but not waterproof". The fabric also has excellent mechanical properties, meets the standards of high-end textile products, and is suitable for various applications such as outdoor, sports, and protection. Detailed Implementation

[0049] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with existing known technologies. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0050] Preparation Example 1: The specific preparation method of hydrophobically modified chitosan includes the following steps:

[0051] (1) Add 100g of chitosan to 2.5kg of 1wt% dilute acetic acid aqueous solution and stir until dissolved. Then add 10g of glycidyl methacrylate and react at room temperature for 4h. Transfer the reaction solution to a dialysis bag with a molecular weight cutoff of 3500Da and dialyze with deionized water for 12h. Change the dialysate every 8h. Then freeze dry under vacuum to obtain alkenylated chitosan.

[0052] (2) Under nitrogen protection, 100g of alkenylated chitosan was added to 1.5kg of N,N-dimethylformamide, along with 8g of 2,3-dihydroxyphenylethanethiol, 20g of dodecyl mercaptan, and 0.1g of 2-hydroxy-2-methylphenylacetone. The mixture was then subjected to a light intensity of 500mW / cm at a wavelength of 365nm. 2 Under ultraviolet light irradiation, the reaction was carried out at room temperature for 30 minutes. After the reaction was completed, 3 kg of deionized water was added with stirring. At this time, a solid was precipitated. After standing for 30 minutes, the solid product was collected by filtration. Then, the solid product was added to 1 kg of n-hexane, stirred for 1 hour, filtered, and the obtained solid product was dried to obtain hydrophobic modified chitosan.

[0053] Preparation Example 2: A specific method for preparing hydrophobically modified chitosan, including the following steps:

[0054] (1) Add 100g of chitosan to 4kg of 2wt% dilute acetic acid aqueous solution and stir until dissolved. Then add 20g of glycidyl methacrylate and react at room temperature for 6h. Transfer the reaction solution to a dialysis bag with a molecular weight cutoff of 3500Da and dialyze with deionized water for 18h. Change the dialysate every 8h. Then freeze dry under vacuum to obtain alkenylated chitosan.

[0055] (2) Under nitrogen protection, 100g of alkenylated chitosan was added to 2.5kg of N,N-dimethylformamide, along with 10g of 2,3-dihydroxyphenylethanethiol, 30g of tetradecyl mercaptan, and 0.2g of 2-hydroxy-2-methylphenylacetone. The mixture was then subjected to a light intensity of 800mW / cm at a wavelength of 365nm. 2 Under ultraviolet light irradiation, the reaction was carried out at room temperature for 60 minutes. After the reaction was completed, 3.5 kg of deionized water was added with stirring. At this time, a solid was precipitated. After standing for 30 minutes, the solid product was collected by filtration. Then, the solid product was added to 1.5 kg of n-hexane and stirred for 1.5 h. After filtration, the obtained solid product was dried to obtain hydrophobic modified chitosan.

[0056] Preparation Example 3: The specific preparation method of hydrophobically modified chitosan includes the following steps:

[0057] (1) Add 100g of chitosan to 5kg of 3wt% dilute acetic acid aqueous solution and stir until dissolved. Then add 30g of glycidyl methacrylate and react at room temperature for 10h. Transfer the reaction solution to a dialysis bag with a molecular weight cutoff of 3500Da and dialyze with deionized water for 24h. Change the dialysate every 8h. Then freeze dry under vacuum to obtain alkenylated chitosan.

[0058] (2) Under nitrogen protection, 100g of alkenylated chitosan was added to 3kg of N,N-dimethylformamide, along with 12g of 2,3-dihydroxyphenylethanethiol, 40g of hexadecyl mercaptan, and 0.3g of 1-hydroxycyclohexylphenyl ketone. The mixture was then subjected to a light intensity of 1000mW / cm at a wavelength of 365nm. 2 Under ultraviolet light irradiation, the reaction was carried out at room temperature for 120 min. After the reaction was completed, 4 kg of deionized water was added with stirring. At this time, a solid was precipitated. After standing for 30 min, the solid product was collected by filtration. Then, the solid product was added to 2 kg of n-hexane, stirred for 2 h, filtered, and the obtained solid product was dried to obtain hydrophobic modified chitosan.

[0059] Preparation Example 4: The difference between Preparation Example 4 and Preparation Example 2 is that tetradecanthiol is replaced with octadecylthiol, while the other steps remain unchanged.

[0060] Comparative Preparation Example 1: The difference between Comparative Preparation Example 1 and Preparation Example 2 is that tetradecanthiol is replaced with 1-decanethiol, while the other steps remain unchanged.

[0061] Comparative Preparation Example 2: The difference between Comparative Preparation Example 2 and Preparation Example 2 is that tetradecanthiol is replaced with n-octylthiol, while the other steps remain unchanged.

[0062] Comparative Preparation Example 3: The difference between Comparative Preparation Example 3 and Preparation Example 2 is that 2,3-dihydroxyphenylethylthiol is not added in step (2), while the other steps remain unchanged.

[0063] Comparative preparation example 4: The difference between comparative preparation example 4 and preparation example 2 is that tetradecyl mercaptan is not added in step (2), while the other steps remain unchanged.

[0064] Example 1: A specific method for preparing a waterproof electrostatic spun fiber fabric, comprising the following steps:

[0065] S1. Thermoplastic polyurethane was dissolved in a mixed solution of N,N-dimethylformamide / tetrahydrofuran (the volume ratio of N,N-dimethylformamide and tetrahydrofuran was 1:1) to prepare a TPU spinning solution with a concentration of 8wt%. Electrospinning was performed with a spinning voltage of 15kV, a receiving distance of 10cm, and a single needle injection speed of 0.5ml / h to prepare a TPU electrospun film, which served as the TPU layer.

[0066] S2. The hydrophobic modified chitosan prepared according to Preparation Example 1 was dissolved in a mixed solution of N,N-dimethylformamide / tetrahydrofuran (the volume ratio of N,N-dimethylformamide and tetrahydrofuran was 1:1) to prepare a hydrophobic modified chitosan solution with a concentration of 0.1wt%. Then, the polyester fiber woven fabric was immersed in the solution and treated by an impregnation-rolling process (immersion at room temperature for 30 min, with the roll-off rate controlled at 60%) and dried. The TPU layer was then bonded to one side of the fabric by hot pressing (temperature of 80℃, pressure of 0.2MPa, time of 10s) to obtain the fabric layer.

[0067] S3. The hydrophobic modified chitosan prepared according to Preparation Example 1 was dissolved in a mixed solution of N,N-dimethylformamide / tetrahydrofuran (the volume ratio of N,N-dimethylformamide and tetrahydrofuran was 3:7) to prepare a hydrophobic modified chitosan spinning solution with a concentration of 0.8wt%. The side of the fabric layer without the TPU layer was used as the receiving surface. Electrospinning was performed with a spinning voltage of 12kV, a receiving distance of 8cm, and a single needle injection speed of 0.3ml / h to prepare a hydrophobic modified chitosan electrospun film as the hydrophobic modified chitosan layer.

[0068] S4. Apply 50 g / m² of the hydrophobically modified chitosan layer. 2 The spraying concentration was 1 wt%, and the pH was 8.0-9.0. The solution of glycerol triglycidyl ether in ethanol / water (volume ratio of ethanol to water was 7:3) was sprayed. After standing at 30°C for 1 hour, the solution was freeze-dried to obtain waterproof electrostatic spun fiber fabric.

[0069] Example 2: A specific method for preparing a waterproof electrostatic spun fiber fabric, comprising the following steps:

[0070] S1. Thermoplastic polyurethane was dissolved in a mixed solution of N,N-dimethylformamide and tetrahydrofuran (the volume ratio of N,N-dimethylformamide and tetrahydrofuran was 1:1) to prepare a TPU spinning solution with a concentration of 10wt%. Electrospinning was performed with a spinning voltage of 20kV, a receiving distance of 15cm, and a single needle injection speed of 1.2ml / h to prepare a TPU electrospun film, which served as the TPU layer.

[0071] S2. The hydrophobic modified chitosan prepared according to Preparation Example 2 was dissolved in a mixed solution of N,N-dimethylformamide / tetrahydrofuran (the volume ratio of N,N-dimethylformamide and tetrahydrofuran was 1:1) to prepare a hydrophobic modified chitosan solution with a concentration of 0.2wt%. Then, the polyester fiber woven fabric was immersed in the solution and treated by an impregnation-rolling process (immersion at room temperature for 45 min, with the roll-off rate controlled at 70%) and dried. The TPU layer was then bonded to one side of the fabric by hot pressing (temperature of 95℃, pressure of 0.3MPa, time of 15s) to obtain the fabric layer.

[0072] S3. The hydrophobic modified chitosan prepared according to Preparation Example 2 was dissolved in a mixed solution of N,N-dimethylformamide / tetrahydrofuran (the volume ratio of N,N-dimethylformamide and tetrahydrofuran was 4:6) to prepare a hydrophobic modified chitosan spinning solution with a concentration of 1.2wt%. The side of the fabric layer without the TPU layer was used as the receiving surface. Electrospinning was performed with a spinning voltage of 15kV, a receiving distance of 12cm, and a single needle injection speed of 1.2ml / h to prepare a hydrophobic modified chitosan electrospun film as the hydrophobic modified chitosan layer.

[0073] S4. Apply 120 g / m² of the hydrophobically modified chitosan layer. 2 The spraying concentration was 2wt%, and the pH was 8.0-9.0. The solution of glycerol triglycidyl ether in ethanol / water (volume ratio of ethanol to water was 8:2) was sprayed. After standing at 35℃ for 2 hours, the solution was freeze-dried to obtain waterproof electrostatic spun fiber fabric.

[0074] Example 3: A specific method for preparing a waterproof electrostatic spun fiber fabric, comprising the following steps:

[0075] S1. Thermoplastic polyurethane was dissolved in a mixed solution of N,N-dimethylformamide / tetrahydrofuran (the volume ratio of N,N-dimethylformamide and tetrahydrofuran was 1:1) to prepare a TPU spinning solution with a concentration of 12wt%. Electrospinning was performed with a spinning voltage of 25kV, a receiving distance of 20cm, and a single needle injection speed of 2ml / h to prepare a TPU electrospun film, which served as the TPU layer.

[0076] S2. The hydrophobic modified chitosan prepared according to Preparation Example 3 was dissolved in a mixed solution of N,N-dimethylformamide / tetrahydrofuran (the volume ratio of N,N-dimethylformamide and tetrahydrofuran was 1:1) to prepare a hydrophobic modified chitosan solution with a concentration of 0.3wt%. Then, the polyester fiber woven fabric was immersed in the solution and treated with an impregnation-rolling process (immersion at room temperature for 60 min, with the roll-off rate controlled at 80%) and dried. The TPU layer was then bonded to one side of the fabric by hot pressing (temperature of 110℃, pressure of 0.5MPa, time of 20s) to obtain the fabric layer.

[0077] S3. The hydrophobic modified chitosan prepared according to Preparation Example 3 was dissolved in a mixed solution of N,N-dimethylformamide / tetrahydrofuran (the volume ratio of N,N-dimethylformamide and tetrahydrofuran was 5:5) to prepare a hydrophobic modified chitosan spinning solution with a concentration of 1.5wt%. The side of the fabric layer without the TPU layer was used as the receiving surface. Electrospinning was performed with a spinning voltage of 20kV, a receiving distance of 15cm, and a single needle injection speed of 2ml / h to prepare a hydrophobic modified chitosan electrospun film as the hydrophobic modified chitosan layer.

[0078] S4. Apply 200 g / m² of the hydrophobically modified chitosan layer. 2 A 3wt% ethanol / water mixture of glycerol triglycidyl ether (ethanol to water volume ratio of 9:1) with a pH of 8.0-9.0 was sprayed and allowed to stand for 3 hours at 40℃ before being freeze-dried to obtain a waterproof electrostatic spun fiber fabric.

[0079] Example 4: The difference between Example 4 and Example 2 is that the hydrophobic modified chitosan prepared according to Preparation Example 2 is replaced with the hydrophobic modified chitosan prepared according to Preparation Example 4.

[0080] Comparative Example 1: The difference between Comparative Example 1 and Example 2 is that the hydrophobic modified chitosan prepared according to Preparation Example 2 is replaced with the hydrophobic modified chitosan prepared according to Comparative Preparation Example 1.

[0081] Comparative Example 2: The difference between Comparative Example 2 and Example 2 is that the hydrophobic modified chitosan prepared according to Preparation Example 2 is replaced with the hydrophobic modified chitosan prepared according to Comparative Preparation Example 2.

[0082] Comparative Example 3: The difference between Comparative Example 3 and Example 2 is that the hydrophobic modified chitosan prepared according to Preparation Example 2 is replaced with the hydrophobic modified chitosan prepared according to Comparative Preparation Example 3.

[0083] Comparative Example 4: The difference between Comparative Example 4 and Example 2 is that the hydrophobic modified chitosan prepared according to Preparation Example 2 is replaced with the hydrophobic modified chitosan prepared according to Comparative Preparation Example 4.

[0084] Comparative Example 5: The difference between Comparative Example 5 and Example 2 is that the part in step S2 where the fabric is soaked in the hydrophobic modified chitosan solution is omitted. The modified step S2 is: "The TPU layer is bonded to one side of the fabric by hot pressing (temperature is 110°C, pressure is 0.5MPa, time is 20s) to obtain the fabric layer". The other steps remain unchanged.

[0085] Comparative Example 6: The difference between Comparative Example 6 and Example 2 is that step S4 is omitted. In step S3, after the hydrophobic modified chitosan electrospun film is prepared as the hydrophobic modified chitosan layer, it is directly freeze-dried to obtain the waterproof electrospun fiber fabric.

[0086] Performance testing:

[0087] The fabrics prepared in Examples 1-4 and Comparative Examples 1-6 were subjected to system performance tests according to the following standards:

[0088] Hydrostatic pressure: GB / T 4744-2013 "Test and evaluation of water resistance of textiles - hydrostatic pressure method";

[0089] Water contact angle: Using a contact angle meter, five different sites on the hydrophobic modified chitosan layer of the fabric surface were measured, and the average value was taken.

[0090] Moisture permeability: GB / T 12704.2-2009 "Textiles - Test methods for moisture permeability of fabrics - Part 2: Evaporation method";

[0091] Interlayer peel strength: GB / T 2791-1995 "Test method for T peel strength of adhesives", testing the T peel strength between the fabric layer and the hydrophobic modified chitosan layer;

[0092] Washability: GB / T 8629-2001 5A washing program, after 20 washes, test the hydrostatic pressure and calculate the retention rate;

[0093] Anti-swelling rate: The fabric was cut into 2cm×2cm samples, and the initial mass (m0) was measured. After soaking in deionized water for 24 hours, the surface moisture was dried and the mass (m1) was measured. The calculation formula is: (m1-m0) / m0×100%;

[0094] Tensile strength: GB / T 3923.1-2013 "Textiles - Tensile properties of fabrics - Part 1: Determination of breaking strength and elongation at break - Strip method";

[0095] Tear strength: GB / T 3917.1-2009 "Textiles - Tear properties of fabrics - Part 1: Determination of tear strength - Impact pendulum method";

[0096] Yellowing grade: GB / T 29731-2013 "Textiles - Tests for color fastness to artificial light: Xenon arc", after 72 hours of UVB irradiation, the grade is rated according to the standard (Grade 1: no yellowing, Grade 5: severe yellowing).

[0097] High humidity tack: After being placed in an environment of 35℃ and 90% RH for 24 hours, the surface tack is evaluated by touch (Level 1: no tack, Level 3: slightly tacky, Level 5: severely tacky).

[0098] The performance test results are shown in Table 1.

[0099] Table 1 Performance Test Results

[0100]

[0101] Data Analysis:

[0102] As can be seen from the performance test data in Table 1, the waterproof electrospun fiber fabrics prepared by the technical solution of the present invention in Examples 1-4 all exhibit excellent waterproof, breathable, interfacial adhesion and structural stability performance. Among them, Example 2 has the most outstanding comprehensive performance, with excellent mechanical properties and long-term use stability.

[0103] Example 2 exhibits the best waterproof performance, likely because it uses hydrophobically modified chitosan grafted with a long-chain alkyl group of 14-carbon tetradecanthiol. This carbon chain length reduces the surface energy of the chitosan molecules. Combined with the rough nanofiber micro-surface formed by electrospinning, it synergistically constructs a hydrophobic interface, making it difficult for liquid water to adhere and penetrate. At the same time, the outer TPU electrospun membrane and the inner hydrophobically modified chitosan spun membrane form a double waterproof barrier. Their nanoscale pore size is smaller than the critical size for capillary penetration of liquid water, further blocking the intrusion path of liquid water. Combined with the optimal spinning solution concentration and electrospinning parameters, the waterproof structure becomes more dense and stable. The waterproof performance of each comparative example was inferior to that of Example 2: In Comparative Examples 1 and 2, the spatial shielding effect of the hydrophobic groups was weakened and the surface energy of the molecules was increased due to the replacement of tetradecyl mercaptan with long-chain alkyl mercaptan with shorter carbon chains, resulting in a loss of superhydrophobic effect and a decrease in waterproof performance; In Comparative Example 4, since no long-chain alkyl mercaptan was added, the chitosan molecular chain retained a large number of hydrophilic groups such as hydroxyl and amino groups, which could not form an effective hydrophobic barrier, and the waterproof performance was completely ineffective; Although Comparative Examples 3, 5 and 6 retained long-chain hydrophobic groups, the lack of catechol groups, pretreatment of the base fabric impregnation or cross-linking steps affected the integrity of the waterproof structure, and the waterproof performance was slightly lower than that of Example 2.

[0104] Example 2 exhibits the highest interlayer peel strength and the strongest interlayer bonding. This may be because the modified chitosan used in it is simultaneously grafted with mussel-inspired catechol groups. These groups can become the core bridge for interfacial adhesion through multiple forces such as hydrogen bonds, covalent bonds, π-π stacking, and mechanical interlocking. At the same time, the base fabric impregnation-rolling pretreatment process allows the modified chitosan to fully penetrate into the fiber gaps of the base fabric and form a coating layer and nano-anchoring structure. During the subsequent electrospinning process, the spinning solution solvent slightly swells the modified chitosan on the surface of the base fabric, causing the newly deposited nanofibers to undergo molecular chain entanglement with the modified chitosan on the base fabric surface. Then, through cross-linking reaction, covalent bonds are formed to consolidate the bond, ultimately achieving a molecular-level integrated interface. The interlayer peel strength of each comparative example was lower than that of Example 2: Comparative Example 3 lost its core adhesion effect due to the absence of added catechol groups, and the interlayer bond was only physical contact, resulting in a significant reduction in peel strength; Comparative Example 5 omitted the base fabric impregnation pretreatment step, and without the anchoring and coating effect of modified chitosan, the TPU film, spun film and base fabric were only physically bonded by hot pressing, resulting in extremely weak interlayer bonding force; Although the other comparative examples retained the catechol groups and pretreatment process, the interlayer adhesion performance was slightly inferior to that of Example 2 because the hydrophobic chain length or process parameters were not optimally matched.

[0105] Example 2 exhibits the best long-term stability, washability, and swelling resistance. This is likely due to its scientifically designed crosslinking system: the primary amino groups reserved during the alkenylation modification stage undergo a highly efficient nucleophilic ring-opening reaction with the crosslinking agent under weakly alkaline conditions. The two active hydrogens of a single primary amino group combine with the epoxy group to form a stable covalent crosslinking network between the modified chitosan molecular chains. This transforms the nanofibers formed by electrospinning from a physically stacked structure into a covalently bonded whole, preventing chitosan from swelling and dissolving in a humid environment and strengthening the interlayer bonding force, allowing the performance to remain stable after multiple washes. At the same time, the process of spinning and shaping before crosslinking perfectly preserves the nanoporous structure and does not disrupt the waterproof and breathable balance. The long-term stability of each comparative example was not as good as that of Example 2: Comparative Example 6 omitted the cross-linking and curing process, and without the binding of the cross-linking network, the nanofibers were only physically stacked, which easily loosened and swelled in washing and humid environments, resulting in a significant decrease in washability and anti-swelling rate; Comparative Examples 3 and 5 had weak interlayer bonding forces, and the interlayers were easily loosened and delaminated during washing, resulting in a significant decrease in washability; Comparative Example 4 had strong hydrophilicity, and was easy to absorb water and swell, resulting in significant performance degradation during long-term use; Although Comparative Examples 1 and 2 had complete cross-linking systems, the insufficient length of the hydrophobic chains indirectly affected the structural stability, and the long-term performance was slightly lower than that of Example 2.

[0106] Example 2 achieves a balance between moisture permeability and mechanical properties. On one hand, the nanofiber membrane formed by electrospinning possesses high porosity and an interconnected three-dimensional pore structure, providing continuous channels for the transmission of human sweat vapor. Simultaneously, the small amount of hydrophilic groups remaining in chitosan synergistically interacts with the TPU soft segment structure, promoting rapid water vapor penetration through an adsorption-diffusion-desorption mechanism, thus achieving high moisture permeability. On the other hand, the base fabric in the three-layer composite structure provides basic support as a mechanical skeleton, and the cross-linked network further enhances the inter-fiber bonding force, allowing tensile strength and tear strength to reach optimal levels. The relevant properties of each comparative example are inferior to Example 2: Comparative Example 4, due to its strong hydrophilicity, has a slightly increased moisture permeability but no practical application value (waterproof function fails); Comparative Example 6, due to the lack of cross-linked network reinforcement, has significantly weakened mechanical properties; Comparative Examples 3 and 5, due to weak interlayer bonding and poor overall stress synergy, have their mechanical properties somewhat affected; Comparative Examples 1 and 2, due to suboptimal hydrophobic chain length or process parameters, have slightly inferior moisture permeability and mechanical properties compared to Example 2.

[0107] Example 2 exhibits excellent appearance stability and user experience. The spatial shielding effect of the hydrophobic groups prevents the exposure of hydrophilic groups, resulting in a non-sticky surface even in high humidity environments and a comfortable wearing experience. Among the comparative examples, only Comparative Example 4, due to the lack of grafted long-chain hydrophobic groups and the strong hydrophilicity of chitosan, exhibits slight stickiness on the surface under high humidity environments, affecting the user experience. Although the other comparative examples maintain the same appearance and stickiness as Example 2, their overall performance is still inferior to Example 2 because their core functional indicators (waterproofing, adhesion, and stability) are not optimal.

[0108] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A waterproof electrostatic spun fiber fabric, characterized in that, The fabric comprises, from the outside to the inside, a TPU layer, a fabric layer, and a hydrophobically modified chitosan layer. The TPU layer is a TPU electrospun film; The hydrophobically modified chitosan layer is a hydrophobically modified chitosan electrospun film, wherein the hydrophobically modified chitosan is a product in which the chitosan backbone is first modified by alkenylation of carbon-carbon double bonds, and then by thiol-alkene click chemistry, in one step covalently grafting catechol groups and long-chain alkyl hydrophobic groups. The preparation method of the hydrophobically modified chitosan is as follows: (1) Add chitosan to dilute acetic acid aqueous solution and stir until dissolved. Then add glycidyl methacrylate and react at room temperature for 4-10 hours. Transfer the reaction solution to a dialysis bag and dialyze with deionized water for 12-24 hours. Change the dialysis solution every 8 hours. Then freeze dry under vacuum to obtain alkenylated chitosan. (2) Under nitrogen protection, alkenylated chitosan was added to N,N-dimethylformamide, along with a thiol compound containing catechol, a long-chain alkyl thiol, and a photoinitiator. The reaction was carried out at room temperature for 30-120 min under ultraviolet light irradiation. After the reaction was completed, deionized water was added under stirring. At this time, a solid was precipitated. After standing for 30 min, the solid product was collected by filtration. The solid product was then added to n-hexane and stirred for 1-2 h. After filtration, the obtained solid product was dried to obtain hydrophobic modified chitosan. The thiol compound containing catechol refers to 2,3-dihydroxyphenylethylthiol; The long-chain alkyl thiols refer to one or more of dodecyl mercaptan, tetradecyl mercaptan, hexadecyl mercaptan, or octadecyl mercaptan.

2. The waterproof electrostatic spun fiber fabric according to claim 1, characterized in that, In (1), the chitosan, dilute acetic acid aqueous solution and glycidyl methacrylate are in a weight ratio of 1:25-50:0.1-0.

3.

3. The waterproof electrostatic spun fiber fabric according to claim 1, characterized in that, The concentration of the dilute acetic acid aqueous solution in (1) is 1-3 wt%; the molecular weight cutoff of the dialysis bag is 3500 Da.

4. The waterproof electrostatic spun fiber fabric according to claim 1, characterized in that, In (2), the alkenylated chitosan, N,N-dimethylformamide, thiols containing catechol, long-chain alkyl thiols, photoinitiator, deionized water and n-hexane are in the following weight ratio: 1:15-30:0.08-0.12:0.2-0.4:0.001-0.003:30-40:10-20.

5. The waterproof electrostatic spun fiber fabric according to claim 1, characterized in that, The photoinitiator in (2) refers to either 2-hydroxy-2-methylphenylacetone or 1-hydroxycyclohexylphenyl ketone; the ultraviolet irradiation conditions are a wavelength of 365 nm and an irradiation intensity of 500-1000 mW / cm². 2 .

6. The method for preparing waterproof electrostatic spun fiber fabric according to any one of claims 1-5, characterized in that, Includes the following steps: S1. Thermoplastic polyurethane is dissolved in a mixed solution of N,N-dimethylformamide / tetrahydrofuran to prepare a TPU spinning solution with a concentration of 8-12wt%. The TPU electrospun film is prepared by electrospinning and used as the TPU layer. S2. Dissolve hydrophobically modified chitosan in a mixed solution of N,N-dimethylformamide / tetrahydrofuran to prepare a hydrophobically modified chitosan solution with a concentration of 0.1-0.3wt%. Then, immerse the fabric in the solution, process it using an impregnation-rolling process, and then dry it. Finally, bond the TPU layer to one side of the fabric using a hot-pressing method to obtain the fabric layer. S3. Dissolve hydrophobically modified chitosan in a mixed solution of N,N-dimethylformamide / tetrahydrofuran to prepare a hydrophobically modified chitosan spinning solution with a concentration of 0.8-1.5wt%. Using the side of the fabric layer without the TPU layer as the receiving surface, prepare a hydrophobically modified chitosan electrospun film by electrospinning, which serves as the hydrophobically modified chitosan layer. S4. Spray a crosslinking agent solution onto the hydrophobically modified chitosan layer, let it stand at 30-40℃ for 1-3 hours, and then freeze-dry it to obtain a waterproof electrostatic spun fiber fabric.

7. The method for preparing waterproof electrostatic spun fiber fabric according to claim 6, characterized in that, In the S1 N,N-dimethylformamide / tetrahydrofuran mixed solution, the volume ratio of N,N-dimethylformamide and tetrahydrofuran is 1:1; the electrospinning conditions are: spinning voltage 15-25kV, receiving distance 10-20cm, and single needle injection speed 0.5-2ml / h.

8. The method for preparing waterproof electrostatic spun fiber fabric according to claim 6, characterized in that, The volume ratio of N,N-dimethylformamide to tetrahydrofuran in the N,N-dimethylformamide / tetrahydrofuran mixed solution in S2 is 1:1; the fabric refers to woven or knitted fabric made of any one of polyester fiber, polyamide fiber, cotton fiber, or viscose fiber; the impregnation-rolling process is as follows: impregnation at room temperature for 30-60 minutes, with the roll-off rate controlled at 60-80%; the hot pressing temperature is 80-110℃, the pressure is 0.2-0.5MPa, and the time is 10-20s.

9. The method for preparing waterproof electrostatic spun fiber fabric according to claim 6, characterized in that, In the S3 solution, the volume ratio of N,N-dimethylformamide to tetrahydrofuran is 3:7-5:5; the electrospinning conditions are: spinning voltage 12-20kV, receiving distance 8-15cm, and single needle injection speed 0.3-2ml / h.

10. The method for preparing waterproof electrostatic spun fiber fabric according to claim 6, characterized in that, The crosslinking agent solution in S4 refers to an ethanol / water mixture of glycerol triglycidyl ether, with a concentration of 1-3 wt%, pH=8.0-9.0, and a spraying rate of 50-200 g / m³. 2 The volume ratio of ethanol to water in the ethanol / water mixed solution is 7:3-9:1.

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