Preparation method of waterproof and breathable membrane material, waterproof and breathable membrane and waterproof and breathable fabric

Abstract

The application discloses a waterproof and breathable film material preparation method, a waterproof and breathable film and a waterproof and breathable fabric. The preparation method comprises the following steps: S1, preparing a graphene dispersion liquid; S2, respectively taking polylactic acid and cellulose as a base material, adding the graphene dispersion liquid and a bio-based functional additive, and respectively preparing a spinning liquid; S3, in the process of electrospinning, a magnetic field with a strength of 0.5-1.0 T and a direction perpendicular to the spraying direction is applied, a porous nanofiber support layer is first formed, and then a dense nanofiber functional layer is formed, so that a double-layer structure composite fiber film is obtained; and S4, after cross-linking treatment and heat setting, the waterproof and breathable film is obtained. Through the double-layer structure design and the magnetic field, the graphene is induced to arrange in a direction, the obtained film material has a water contact angle of greater than or equal to 142 degrees, a rolling angle of less than or equal to 11 degrees, a moisture permeation of greater than or equal to 6700 g / (m 2 ·24h), a breaking strength of greater than or equal to 6.5 MPa, and an elongation at break of greater than or equal to 46%, and the raw material is degradable, and is suitable for outdoor clothes such as a jacket.

Description

Technical Field

[0001] This invention relates to the field of functional textile materials technology, and more specifically, to a method for preparing a waterproof and breathable membrane material, a waterproof and breathable membrane, and a waterproof and breathable fabric. Background Technology

[0002] The core performance of outdoor clothing such as waterproof jackets lies in their waterproof and breathable properties, which typically rely on functional membrane materials laminated to the inside of the fabric. Traditional waterproof and breathable membranes, such as expanded polytetrafluoroethylene (ePTFE) membranes, while offering excellent performance, involve fluorinated compounds in their manufacturing process, making them difficult to degrade after disposal and thus burdening the environment. Another commonly used type, polyurethane (PU) membranes, are mostly derived from petroleum-based raw materials, similarly facing sustainability challenges.

[0003] Bio-based biodegradable materials (such as polylactic acid (PLA) and cellulose) have attracted attention due to their environmental friendliness. However, existing bio-based membrane materials generally suffer from insufficient mechanical strength and difficulty in balancing waterproof and breathable properties. To improve performance, some studies have attempted to add nanomaterials such as graphene for reinforcement, but they face key technical bottlenecks: First, if the size of graphene does not match the fiber diameter, it can easily lead to fiber breakage or blockage of breathable channels, thereby compromising the membrane's breathability; second, the interfacial compatibility between graphene and the bio-based substrate is poor, making it difficult to form effective stress transfer, resulting in limited reinforcement, and excessive addition can easily cause aggregation, making the membrane material brittle.

[0004] In recent years, some studies have attempted to use magnetic fields to induce the oriented alignment of graphene in polymer matrices to improve the electrical or optical properties of composite materials. For example, Govindaraj et al. (Composites Part B: Engineering, Vol. 306, 2025, p. 112739) reported that graphene sheets could align perpendicular to the magnetic field in a 0.2T static magnetic field and were used for terahertz absorption. However, the graphene used was micrometer-sized sheets (lateral dimension approximately 2.2 μm). If graphene of this size were applied to polymer fibers with diameters of only a few hundred nanometers, the severe size mismatch would lead to fiber breakage, stress concentration, or blockage of interfiber pores.

[0005] Therefore, how to prepare bio-based membrane materials that combine excellent waterproof and breathable properties with mechanical strength is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0006] This invention aims to address the comprehensive technical challenges in existing technologies, including limited reinforcement effects and even damage to fiber structures due to size mismatch between graphene and bio-based nanofibers, and the inability of single-layer membrane structures to synergistically achieve high waterproofness, high moisture permeability, and high mechanical strength. Specifically, the key challenge lies in precisely controlling the size of the graphene nanoparticles to match those of nanofibers with specific diameters, and using a magnetic field to induce their axial orientation within the fibers, while simultaneously distributing them orderly within a bilayer fiber structure. This allows for the simultaneous achievement of excellent superhydrophobic properties and mechanical reinforcement without sacrificing moisture permeability, a critical technical bottleneck that urgently needs to be overcome in this field.

[0007] To address the aforementioned technical problems, in a first aspect, the present invention provides a method for preparing a waterproof and breathable membrane material, comprising the following steps: S1. Preparation of graphene dispersion: Graphene is dispersed in deionized water to obtain graphene dispersion; the thickness of the graphene sheets is 1-5 nm, the lateral dimension is 50-200 nm, and the aspect ratio is 10-200. S2. Preparation of composite spinning solution: Polylactic acid is dissolved in dihydro-L-glucanone, and then the graphene dispersion obtained in step S1 and bio-based functional additives are added and mixed to form the first spinning solution. The graphene concentration in the first spinning solution is 0.01-0.5 mg / mL. Cellulose is mixed with the graphene dispersion obtained in step S1 and bio-based functional additives to form a second spinning solution, wherein the graphene concentration in the second spinning solution is 0.02-3 mg / mL. The mass ratio of polylactic acid to cellulose is 1:2-2:1, and the total amount of graphene added accounts for 0.09%-0.6% of the total mass of polylactic acid and cellulose. S3. Construct a two-layer structure: First, the first spinning solution prepared in step S2 is electrospinned to form a porous nanofiber support layer; then, the second spinning solution prepared in step S2 is electrospinned on the porous nanofiber support layer to form a dense nanofiber functional layer, thereby obtaining a composite fiber membrane with a bilayer structure. During the electrospinning process, a magnetic field is applied to guide the directional alignment of the graphene. The strength of the magnetic field is 0.5-1.0 T, and the direction of the magnetic field is perpendicular to the direction of the spinning solution injection. S4. Post-processing: The composite fiber membrane obtained in step S3 is subjected to cross-linking treatment and heat setting to obtain a waterproof and breathable membrane material.

[0008] By adopting the above technical solution: Firstly, this invention limits the lateral dimension and aspect ratio of the graphene to a specific value, enabling it to embed within the fiber without disrupting fiber continuity while providing sufficient interfacial contact area. If the graphene is too large, it will protrude from the fiber surface, causing stress concentration and fiber breakage; if the size is too small, it cannot form a stress transmission network across the fiber.

[0009] Secondly, under the premise of the above-mentioned size matching, a magnetic field of 0.5-1.0T perpendicular to the spraying direction is applied to induce the graphene sheets to align along the fiber axis, forming a continuous stress transmission channel. At the same time, the edge of the sheet constructs an ordered micro-nano rough structure on the fiber surface, improving the hydrophobic angle.

[0010] Thirdly, the support layer ensures efficient water vapor transmission, the functional layer achieves water permeability resistance, and the size of graphene is just between the pore sizes of the two layers, allowing it to be evenly distributed in the two layers without blocking the air permeability channels.

[0011] Furthermore, the specific preparation steps of the graphene dispersion in step S1 are as follows: Graphene was added to deionized water, and a bio-based surfactant was added as a dispersant. The amount of the dispersant was 5 times the mass of the graphene. The mixture was dispersed at 20-30°C and under high-frequency ultrasound at 40 kHz for 50 minutes to obtain a graphene dispersion. The bio-based surfactant is sodium alginate or chitosan.

[0012] Furthermore, the graphene is selected from graphene oxide (GO) and / or reduced graphene oxide (rGO).

[0013] Furthermore, the graphene undergoes surface modification through hydroxylation or carboxylation.

[0014] Further, in step S2, the cellulose is subjected to TEMPO oxidation treatment, and its surface carboxyl content is 1.2-1.5 mmol / g; the polylactic acid has a melt index of 5-15 g / 10min.

[0015] Further, in step S2, the bio-based functional additive includes a bio-based plasticizer and / or a crosslinking agent; when both plasticizer and crosslinking agent are included, their mass ratio is 10:1 to 20:1; the bio-based plasticizer is glycerol or tributyl citrate, and the crosslinking agent is a silane coupling agent or calcium chloride.

[0016] Furthermore, in step S3, The spinning parameters of the first spinning solution are: voltage 12-18 kV, receiving distance 10-15 cm, injection speed 1-1.5 mL / h, to spin a porous nanofiber support layer with a porosity of 70%-85%. The spinning parameters of the second spinning solution are: voltage 10-15 kV, receiving distance 8-12 cm, injection speed 0.3-0.8 mL / h, to spin a dense nanofiber functional layer with a porosity of 40%-60%.

[0017] Furthermore, in step S4, The crosslinking treatment involves immersing the composite fiber membrane in a 0.1-0.5 mol / L calcium chloride solution for 10-30 minutes; the heat setting is a gradient heat setting, which involves holding the membrane at 30°C, 50°C, and 70°C for 30 minutes each.

[0018] In a second aspect, the present invention provides a waterproof and breathable membrane material, which is prepared by any of the above-described preparation methods and includes a dense nanofiber functional layer and a porous nanofiber support layer.

[0019] Furthermore, the dense nanofiber functional layer has a fiber diameter of 50-200 nm and a pore size between fibers of 50-100 nm; the porous nanofiber support layer has a fiber diameter of 200-500 nm and a pore size between fibers of 1-3 μm.

[0020] Furthermore, the waterproof and breathable membrane material has a water contact angle ≥142°, a roll-off angle ≤11°, a moisture permeability ≥6700g / (m2·24h), a tensile strength ≥6.5 MPa, and an elongation at break ≥46%.

[0021] Thirdly, the present invention also provides a waterproof and breathable fabric, comprising a fabric substrate and the aforementioned waterproof and breathable membrane material laminated onto the fabric substrate. Specifically, the waterproof and breathable membrane material can be bonded to the fabric substrate by hot-pressing or by needle and thread sewing; the parameters for hot-pressing are: temperature 80-120℃, pressure 0.5-2MPa, and time 10-30s; the fabric substrate is made of natural fibers and / or synthetic fibers, preferably a fabric made of at least one of cotton fibers, polyester fibers, or bio-based fibers.

[0022] Compared with the prior art, the above-mentioned technical solution of the present invention produces a non-obvious synergistic effect: The precisely sized graphene sheets are perfectly embedded within the nanofibers, avoiding both stress concentration caused by protrusion from the fiber surface and inability to form effective bridging due to their small size; this is the material basis for achieving effective magnetic field induction and mechanical enhancement. Simultaneously, a magnetic field perpendicular to the jetting direction is applied during electrospinning, guiding the graphene to align along the fiber axis. This directional alignment forms stress transmission channels along the fiber direction in the support layer, significantly improving breaking strength and elongation; in the functional layer, it creates oriented micro-nano rough structures at the edges of the graphene sheets on the fiber surface, raising the water contact angle to a superhydrophobic level (≥142°). Without a magnetic field or a bilayer structure, neither of these effects can be achieved simultaneously. Detailed Implementation

[0023] To enable those skilled in the art to better understand the technical solutions of the present invention, the present invention will be further described below in conjunction with embodiments. The described embodiments are specific implementations of some aspects of the present invention, and are not intended to limit the scope of protection of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0024] This invention provides a method for preparing a waterproof and breathable membrane material, as well as a waterproof and breathable membrane obtained by the method and a waterproof and breathable fabric containing the membrane. This technical solution constructs a two-layer structure of "porous nanofiber support layer + dense nanofiber functional layer," combined with magnetic field-induced directional alignment of graphene of specific sizes, bio-based fully degradable raw materials, and post-processing strengthening technology, synergistically achieving high moisture permeability, superhydrophobic properties, and excellent mechanical properties of the membrane material.

[0025] All performance indicators of this invention were tested according to the following standards or methods: Water contact angle and roll-off angle: Using a contact angle meter (Krüss DSA100), 2 μL of deionized water was dropped onto the sample surface at room temperature, and the static water contact angle was measured; then the sample was tilted, and the angle at which the droplet began to roll was recorded as the roll-off angle. Five different locations were tested for each sample, and the average value was taken.

[0026] Moisture permeability (water vapor transmission rate): Tested using the hygroscopic method. The sample was placed in a constant temperature and humidity chamber at 38℃ and 90% relative humidity for 24 hours. The moisture permeability was obtained by calculating the mass of water vapor passing through the sample per unit area and per unit time. The results are expressed in g / (m²). 2 ·24h) indicates.

[0027] Breaking strength and elongation at break: The sample was cut into long strip specimens (10 mm wide, 50 mm gauge length), and stretched using a universal testing machine at a tensile speed of 50 mm / min. The maximum breaking force (converted to breaking strength, unit MPa) and the elongation at break (%) were recorded.

[0028] Porosity: Calculated by weighing. The formula is: Porosity (%) = (1 - apparent density / skeletal density) × 100%. The apparent density is obtained from the sample mass and geometric volume (area × thickness), and the skeletal density is determined by the specific gravity bottle method.

[0029] Fiber diameter and pore size: The cross-section and surface morphology of the samples were photographed using a scanning electron microscope (SEM). The diameter of at least 50 fibers and the size of 50 pores were statistically determined using ImageJ software.

[0030] Degradation performance: The samples were buried in standard soil (pH 6.5-7.5, humidity 50%-60%, temperature 25℃), and after 180 days, they were taken out, washed with deionized water, dried, weighed, and the mass loss rate was calculated.

[0031] Peel strength (composite fabric): The composite fabric is cut to the specified size and subjected to a 90° peel test using a universal testing machine at a peel speed of 100 mm / min. The average peel force is recorded and divided by the sample width to obtain the peel strength, in N / cm.

[0032] Hydrostatic pressure resistance: Using a hydrostatic pressure tester, apply water pressure to the sample at a specified pressurization rate and record the pressure value when the third water droplet appears, in mmH2O.

[0033] Washing durability: The sample was placed in a household washing machine and washed according to the standard washing program (water temperature 40℃, washing time 30 min, rinsing 3 times, spin speed 800 rpm). After each wash, the sample was air-dried naturally. The performance test was conducted after repeating the specified number of times.

[0034] [Preparation Example] The following preparation examples are used to prepare the substrate and graphene dispersion required by this invention. The amount of material fed in each preparation example can be appropriately increased according to actual needs, as long as the key parameters of the obtained product (such as the carboxyl content of the treated cellulose of 1.2-1.5 mmol / g, the melt index of the treated polylactic acid of 5-15 g / 10min, the graphene concentration and sheet size, etc.) meet the requirements.

[0035] Preparation Example 1: Preparation of Cellulose Nanofibers (CNF) A suitable amount of natural cotton cellulose was weighed and placed in a sodium chlorite-glacial acetic acid system for delignification treatment at 80°C for 4 hours. Subsequently, TEMPO oxidation treatment was performed (TEMPO / NaBr / NaClO system, pH 10-11, reaction at room temperature for 3 hours). After centrifugation, washing, and freeze-drying, cellulose nanofibers (CNFs) with adjustable surface carboxyl content were obtained. By controlling the TEMPO oxidation reaction time or reagent ratio, the following two specifications of CNFs were prepared: CNF-A: Surface carboxyl content is 1.2 mmol / g.

[0036] CNF-B: The surface carboxyl content is 1.5 mmol / g.

[0037] Preparation Example 2: Pretreatment of Polylactic Acid (PLA) Polylactic acid (PLA) with a molecular weight of 100,000-150,000 was selected and thermally degraded at 180℃ for different times to adjust its melt index to the desired range. Two specifications of PLA were then prepared: PLA-A: Melt index is 5 g / 10min (190℃, 2.16kg).

[0038] PLA-B: Melt index is 12 g / 10min (190℃, 2.16kg).

[0039] PLA-C: Melt index is 15 g / 10min (190℃, 2.16kg).

[0040] Preparation Example 3: Preparation of Graphene Dispersion Graphene with a sheet thickness of 1-5 nm, a lateral dimension of 50-100 nm, and an aspect ratio of 10-200 (including graphene oxide GO, reduced graphene oxide rGO, hydroxylated graphene oxide GO-OH, etc.) is selected as the reinforcing component.

[0041] The following general method is used to prepare the graphene dispersion: graphene and bio-based surfactant (chitosan or sodium alginate with a degree of deacetylation ≥90%) are mixed at a mass ratio of 1:5, deionized water is added, and the dispersion is carried out at 20-30℃ and 40kHz high-frequency ultrasound for 50 minutes to obtain the desired concentration of graphene dispersion.

[0042] The following dispersions were prepared in various specifications: GO dispersion - 0.3: GO was used at a concentration of 0.3 mg / mL; GO dispersion-1.0: GO was used at a concentration of 1.0 mg / mL; GO dispersion-1.2: GO was used at a concentration of 1.2 mg / mL; rGO dispersion-0.1: rGO was used at a concentration of 0.1 mg / mL; rGO dispersion-2.0: rGO was used at a concentration of 2.0 mg / mL; GO-OH dispersion-2.0: GO-OH was used at a concentration of 2.0 mg / mL; GO-OH dispersion-3.0: GO-OH was used at a concentration of 3.0 mg / mL.

[0043] Dynamic light scattering tests showed that the average hydrated particle size of graphene in the above dispersion was 100-150 nm, the Zeta potential was ≤-30 mV, and the dispersion stability was good.

[0044] The following examples use the substrate and graphene dispersion obtained in the preparation example to prepare a composite spinning solution in a certain proportion, and prepare a waterproof and breathable membrane material by electrospinning and post-treatment. Example 1

[0045] Raw material selection: 3.70 g of CNF-B (carboxyl content 1.5 mmol / g) from Preparation Example 1, 7.41 g of PLA-B (melt index 12 g / 10 min) from Preparation Example 2, and 30 mL of GO dispersion-1.0 (concentration 1.0 mg / mL) from Preparation Example 3 were used. The bio-based functional additives were tributyl citrate (TBC) and silane coupling agent KH550, with a mass ratio of 15:1. The total mass of the core substrate (CNF+PLA) was 11.11 g, the total amount of graphene added accounted for 0.27% (i.e., 0.03 g) of the core substrate mass, and the total amount of bio-based functional additives added accounted for 13.5% of the core substrate mass. The volume ratio of the graphene dispersion used to prepare the first and second spinning solutions was 3:7 (i.e., 9 mL for the first spinning solution and 21 mL for the second spinning solution).

[0046] Preparation of spinning solution: First spinning solution (PLA-based, used as the support layer): Dissolve 7.41 g PLA in dihydro-L-glucanone (Cyrene™) at room temperature with stirring, heating if necessary; add 9 mL GO dispersion-1.0, 0.70 g TBC and 0.047 g KH550, and add Cyrene solvent to a total volume of 300 mL to obtain a first spinning solution with PLA concentration of 2.5% (w / v) and graphene concentration of 0.03 mg / mL.

[0047] Second spinning solution (cellulose-based, for functional layer): Add 3.70 g CNF-B to 21 mL GO dispersion-1.0 and stir until uniformly dispersed. Add 0.75 g TBC and 0.053 g KH550, and add deionized water to a total volume of 150 mL to obtain a second spinning solution with CNF concentration of 2.5% (w / v) and graphene concentration of 0.14 mg / mL.

[0048] Construct a two-layer structure: A two-step electrospinning process is employed, during which a 0.5 T magnetic field is applied, with the direction of the magnetic field perpendicular to the direction of the spinning solution injection. The magnetic field is generated by a pair of permanent magnets symmetrically positioned between the spinning nozzle and the receiver, with the magnetic field lines perpendicular to the line connecting the nozzle and the receiver, and the magnetic field covers the entire spinning area.

[0049] First, a porous nanofiber support layer was formed by electrospinning a first spinning solution using a multi-nozzle array. The spinning parameters were: voltage 12 kV, receiving distance 10 cm, injection rate 1 mL / h, and spinning time 2 hours. The resulting fibers had a diameter of 350 ± 50 nm, a pore size of 2 ± 0.5 μm, and a porosity of 78%. Then, a dense nanofiber functional layer was formed on the surface of the support layer by electrospinning a second spinning solution using a single nozzle. The spinning parameters were: voltage 10 kV, receiving distance 8 cm, injection rate 0.3 mL / h, and spinning time 1.5 hours. The resulting fibers had a diameter of 120 ± 30 nm, a pore size of 75 ± 15 nm, and a porosity of 55%.

[0050] Post-treatment: The spun double-layer composite fiber membrane was immersed in 0.1 mol / L CaCl2 solution for 30 minutes for cross-linking treatment. After removal, it was washed three times with deionized water and air-dried naturally. Then, gradient heat setting was performed: the membrane was successively heated at 30℃, 50℃, and 70℃ for 30 minutes each to obtain the waterproof and breathable membrane material.

[0051] The performance of the prepared waterproof and breathable membrane material was tested, and the results are shown in Table 1. Example 2

[0052] Raw material selection: Cellulose was replaced with CNF-A (carboxyl content 1.2 mmol / g) 5.56 g, and PLA was replaced with PLA-A (melt index 5 g / 10min) 5.56 g, i.e., the mass ratio of cellulose to PLA was adjusted to 1:1. The graphene dispersion was replaced with rGO dispersion-2.0 (concentration 2.0 mg / mL), with a volume of 30 mL. Bio-based functional additives were replaced with glycerol and calcium chloride, with a mass ratio of 12.5:1. The total mass of the core substrate was 11.12 g, and the total amount of graphene added accounted for 0.54% (i.e., 0.06 g) of the core substrate mass. The first spinning solution used 9 mL of rGO dispersion, and the second spinning solution used 21 mL of rGO dispersion.

[0053] Preparation of spinning solution: First spinning solution: Take 5.56 g of PLA, add 9 mL of rGO dispersion-2.0, 0.69 g of glycerol, and 0.06 g of calcium chloride, and add Cyrene to 250 mL to obtain a PLA concentration of approximately 2.2% (w / v) and a graphene concentration of approximately 0.072 mg / mL.

[0054] Second spinning solution: Take 5.56 g of CNF-A, add 21 mL of rGO dispersion-2.0, 0.69 g of glycerol, and 0.06 g of calcium chloride, and add water to 200 mL to obtain a CNF concentration of about 2.8% (w / v) and a graphene concentration of about 0.21 mg / mL.

[0055] Construct a double-layer structure: the magnetic field strength is adjusted to 0.8 T, and the other spinning parameters are the same as in Example 1.

[0056] Post-treatment: The cross-linking treatment was changed to soaking in 0.3 mol / L CaCl2 solution for 20 minutes, and gradient heat setting was the same as in Example 1.

[0057] The performance of the prepared waterproof and breathable membrane material was tested, and the results are shown in Table 1. Example 3

[0058] Raw material selection: Cellulose was replaced with CNF-B 7.41 g, and PLA was replaced with PLA-C (melt index 15 g / 10min) 3.70 g, i.e., the cellulose to PLA mass ratio was adjusted to 2:1. The graphene dispersion was replaced with rGO dispersion-0.1 (concentration 0.1 mg / mL), used in 100 mL. The bio-based functional additives remained TBC and KH550, with a mass ratio of 15:1. The total mass of the core substrate was 11.11 g, and the total amount of graphene added accounted for 0.09% (i.e., 0.01 g) of the core substrate mass. The first spinning solution used 30 mL of rGO dispersion, and the second spinning solution used 70 mL of rGO dispersion.

[0059] Preparation of spinning solution: First spinning solution: Take 3.70 g of PLA, add 30 mL of rGO dispersion-0.1, 0.35 g of TBC, and 0.023 g of KH550, and add Cyrene to 150 mL to obtain a PLA concentration of about 2.5% (w / v) and a graphene concentration of about 0.02 mg / mL.

[0060] Second spinning solution: Take 7.41 g CNF-B, add 70 mL rGO dispersion-0.1, 1.05 g TBC, and 0.07 g KH550, and add water to 250 mL to obtain CNF concentration of about 3.0% (w / v) and graphene concentration of about 0.028 mg / mL.

[0061] A two-layer structure was constructed: the magnetic field strength was adjusted to 1.0 T; the spinning parameters of the support layer were adjusted to 18 kV voltage, 15 cm receiving distance, and 1.5 mL / h injection speed; the spinning parameters of the functional layer were adjusted to 15 kV voltage, 12 cm receiving distance, and 0.8 mL / h injection speed.

[0062] Post-treatment: The cross-linking treatment was changed to soaking in 0.5 mol / L CaCl2 solution for 10 minutes, and gradient heat setting was the same as in Example 1.

[0063] The performance of the prepared waterproof and breathable membrane material was tested, and the results are shown in Table 1. Example 4

[0064] Raw material selection: Cellulose was replaced with CNF-A 4.07 g, and PLA was replaced with PLA-B 8.15 g, i.e., the mass ratio of cellulose to PLA was 1:2. Graphene dispersion: 10 mL of GO-OH dispersion-2.0 (concentration 2.0 mg / mL) was used for the first spinning solution, and 16.7 mL of GO-OH dispersion-3.0 (concentration 3.0 mg / mL) was used for the second spinning solution. The mass ratio of TBC to KH550 in the bio-based functional additives was adjusted to 10:1. The total mass of the core substrate was 12.22 g. The total amount of graphene added was approximately 0.070 g, accounting for 0.57% of the mass of the core substrate.

[0065] Preparation of spinning solution: First spinning solution: Take 8.15 g of PLA, add 10 mL of GO-OH dispersion-2.0, 0.75 g of TBC, and 0.08 g of KH550, and add Cyrene to 330 mL to obtain a graphene concentration of about 0.06 mg / mL.

[0066] Second spinning solution: Take 4.07 g CNF-A, add 16.7 mL GO-OH dispersion-3.0, 0.75 g TBC, and 0.08 g KH550, and add water to 160 mL to obtain a graphene concentration of about 0.31 mg / mL.

[0067] Construct a double-layer structure: the magnetic field strength is adjusted to 0.6 T, and the other spinning parameters are the same as in Example 1.

[0068] Post-treatment: Same as in Example 1 (soaking in 0.1 mol / L CaCl2 for 30 minutes).

[0069] The performance of the prepared waterproof and breathable membrane material was tested, and the results are shown in Table 1. Example 5

[0070] Raw material selection: Cellulose was replaced with CNF-B 4.07 g, and PLA was replaced with PLA-B 8.15 g, i.e., the mass ratio of cellulose to PLA was 1:2. Graphene dispersion: 48 mL of GO dispersion-0.3 (concentration 0.3 mg / mL) was used in the first spinning solution, and 30.5 mL of GO dispersion-1.2 (concentration 1.2 mg / mL) was used in the second spinning solution. The mass ratio of TBC to KH550 in the bio-based functional additives remained at 15:1. The total mass of the core substrate was 12.22 g. The total amount of graphene added was approximately 0.051 g, accounting for 0.42% of the mass of the core substrate.

[0071] Preparation of spinning solution: First spinning solution: Take 8.15 g of PLA, add 48 mL of GO dispersion-0.3, 0.84 g of TBC, and 0.056 g of KH550, and add Cyrene to 330 mL to obtain a graphene concentration of approximately 0.044 mg / mL.

[0072] Second spinning solution: Take 4.07 g CNF-B, add 30.5 mL GO dispersion-1.2, 0.84 g TBC, and 0.056 g KH550, and add water to 160 mL to obtain a graphene concentration of approximately 0.23 mg / mL.

[0073] A two-layer structure was constructed: the magnetic field strength was adjusted to 0.7 T; the porosity of the support layer was adjusted to 85%; and the fiber diameter and porosity of the functional layer were adjusted to 200 nm and 40%, respectively. Specific spinning parameters were: support layer voltage 16 kV, receiving distance 13 cm, and injection speed 1.2 mL / h; functional layer voltage 12 kV, receiving distance 10 cm, and injection speed 0.5 mL / h.

[0074] Post-processing: Same as in Example 1.

[0075] The performance of the prepared waterproof and breathable membrane material was tested, and the results are shown in Table 1.

[0076] Table 1 - Performance Test Results

[0077] As can be seen from the data in Table 1: The waterproof and breathable membranes prepared in the various embodiments of this invention exhibit excellent comprehensive performance, with a water contact angle ≥142°, moisture permeability ≥6700g / (m²·24h), and tensile strength ≥6.5 MPa. Comparative analysis shows that GO-type graphene (Examples 1 and 5) has higher hydrophobicity and moisture permeability than rGO (Examples 2 and 3), while GO-OH (Example 4) provides the highest tensile strength (11.0 MPa) and degradation rate (94%). The optimal window for graphene addition is 0.27%~0.42%. A PLA:CNF ratio of 2:1 is beneficial for improving strength and moisture permeability, while increasing the CNF ratio or adding glycerol can improve flexibility (the elongation at break in Example 2 reached 80%). The magnetic field strength needs to be matched with the type of graphene; 0.5~0.7T is sufficient for the GO system, while rGO requires 0.8~1.0T compensation. In summary, Example 5 (GO, 0.42%, PLA:CNF=2:1, 0.7T) achieves the best balance between moisture permeability, hydrophobicity, and mechanical properties, and is the preferred embodiment.

[0078] [Comparison Example] The following comparative examples are used to illustrate the technical effects of the key features of the present invention. Unless otherwise specified, the raw materials and processes used in each comparative example are the same as in Example 1.

[0079] Compare with Example 1 Using the exact same raw material formulation and preparation process as Example 1, the only difference was that no magnetic field was applied during the electrospinning process. The results showed that without a magnetic field, the graphene sheets were randomly distributed within the fibers, failing to form a continuous stress transfer network along the fiber axis, and the micro-nano roughness of the fiber surface was insufficient. The resulting membrane material had a water contact angle of only 132° and a roll-off angle of 15°, indicating a significant decrease in hydrophobicity. Although the moisture permeability reached 12300 g / (m²·24h), the tensile strength was only 5.7 MPa, and the elongation at break was 43%. Compared to Example 1, the fiber structure was more porous without a magnetic field. Although the moisture permeability was slightly improved, the hydrophobicity and mechanical properties decreased significantly, indicating that magnetic field-induced directional alignment of graphene is crucial for enhancing mechanical properties and superhydrophobic characteristics.

[0080] Compare with Example 2 Using the same raw material formulation as in Example 1, but only the support layer was spun without preparing the dense nanofiber functional layer, a single-layer porous fiber membrane was finally obtained. Test results showed that the water contact angle of this single-layer membrane was only 120°, the roll-off angle was as high as 23°, and its waterproof performance was poor; the moisture permeability was 12900 g / (m²·24h), the tensile strength was only 2.5 MPa, and the elongation at break was 80%. This indicates that a single-layer structure cannot simultaneously achieve both high waterproof performance and high breathability.

[0081] Compare with Example 3 The process was basically the same as in Example 1, but the amount of graphene added was increased to 1.2 wt% of the core substrate mass, exceeding the 0.09%-0.6% range defined in this invention. Significant graphene agglomeration was observed during spinning, resulting in nozzle clogging and bead-like defects in the resulting fibers. The final membrane material had a water contact angle of 136°, a roll-off angle of 11°, a moisture permeability of 9500 g / (m²·24h), a tensile strength reduced to 4.3 MPa, and an elongation at break of only 33%. Excessive graphene not only failed to further strengthen the material but also caused pore blockage and stress concentration due to agglomeration, leading to a comprehensive deterioration of all properties.

[0082] Compare with Example 4 The same process as in Example 1 was used, but commercial graphene with a lateral dimension of approximately 500 nm and an aspect ratio of only 100 was selected. This size is significantly different from the 50-200 nm lateral dimension specified in this invention. In the resulting membrane material, the graphene sheets protrude from the fiber surface, disrupting the continuity and uniformity of the fibers. The test results were: water contact angle 127°, roll-off angle 17°, moisture permeability 11600 g / (m²·24h), tensile strength 5.2 MPa, and elongation at break 45%. Compared with Example 1, both hydrophobicity and mechanical properties decreased significantly, demonstrating that the lateral dimension and aspect ratio of graphene must match the fiber diameter to effectively embed into the fiber and exert a reinforcing effect.

[0083] Compare with Example 5 The same formulation and spinning process as in Example 1 were used, but the calcium chloride solution crosslinking treatment was omitted in the post-treatment stage; only gradient heat setting was performed. The initial tensile strength of the resulting membrane material was 6.7 MPa, and the elongation at break was 45%. After washing the material five times according to the standard washing procedure, the tensile strength dropped sharply to 3.1 MPa, indicating significantly insufficient mechanical durability. This demonstrates that crosslinking treatment is a necessary step to stabilize the fiber network structure and ensure the membrane material maintains mechanical stability in practical use.

[0084] [Application Example] This application example aims to verify the compatibility of the waterproof and breathable membrane material prepared by the present invention with different types of fabric substrates, as well as the robustness of the hot-pressing composite process parameters.

[0085] The waterproof and breathable membrane material prepared in Example 5 was selected as the composite membrane. Three representative fabric substrates were selected: Substrate A is pure cotton plain weave woven fabric (weight 130 g / m²). Substrate B is nylon 6 taffeta (45 g / m², commonly used as the outer layer fabric of rain jackets). Substrate C is polylactic acid filament knitted fabric (weight 110 g / m²).

[0086] The membrane material was hot-pressed onto substrates A, B, and C, respectively. Each substrate was laminated using three boundary conditions and one set of center conditions. Condition I is a temperature of 80℃, a pressure of 0.5 MPa, and a time of 10 s; Condition II is a temperature of 100℃, a pressure of 1.2 MPa, and a time of 20 s; Condition III is a temperature of 120℃, a pressure of 2.0 MPa, and a time of 30 s.

[0087] After lamination, the samples were placed in a standard environment (temperature 23±2℃, relative humidity 50±5%) for 24 hours before performance testing. The peel strength and hydrostatic pressure resistance of the composite fabric were tested, with five samples tested for each sample and the average value taken. The results are shown in Table 2.

[0088] Table 2 - Performance of Composite Fabrics Based on Different Substrates Under Different Composite Conditions

[0089] Results Analysis: As shown in Table 2, peel strength and hydrostatic pressure resistance both increased with increasing composite temperature, pressure, and time. However, excessively high conditions (Condition III) could cause wrinkles or a hardened feel in some substrates (especially cotton and PLA knitted fabrics). Condition II (100℃, 1.2 MPa, 20 s) achieved good peel strength (5.3~7.6 N / cm) and hydrostatic pressure resistance (9800~11200 mmH2O) on all three substrates, with uniform appearance and moderate feel. Therefore, Condition II is the recommended composite process.

[0090] Each composite fabric prepared under condition II was selected, and its moisture permeability was tested and compared with that of the individual membrane material prepared in Example 5. The moisture permeability was tested using the same standard, and the results are shown in Table 3.

[0091] Table 3 - Comparison of moisture permeability before and after composite treatment

[0092] Results analysis: The moisture permeability of the composite fabric decreased compared to the original membrane material, due to the presence of mass transfer resistance in the fabric substrate. However, the moisture permeability of all composite fabrics remained at 6200 g / (m²). 2 • 24h or more, meeting the requirements of the current GB / T 32614-2023 "Outdoor Sports Clothing and Rain Jackets" as a Class I product with a moisture permeability of ≥6000 g / (m²). 2 The requirement of 24h indicates that the membrane materials of the present invention still maintain excellent water vapor permeability after lamination. Among them, PLA knitted composite fabric has the highest moisture permeability because it has a bio-based porous structure and good compatibility with membrane materials; cotton fabric has the lowest moisture permeability because cotton fibers may partially block mass transfer channels after absorbing moisture and expanding.

[0093] This application example demonstrates that the waterproof and breathable membrane material prepared by this invention can be firmly bonded to various fabric substrates such as natural fibers (cotton), synthetic fibers (nylon), and bio-based fibers (PLA) through hot pressing, and can achieve good composite strength and waterproof performance within a limited range of process parameters. The bonded fabric still maintains high moisture permeability, meeting the practical needs of outdoor clothing such as rain jackets.

[0094] The above are all preferred embodiments of this application and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A method for preparing a waterproof and breathable membrane material, characterized in that, Includes the following steps: S1. Preparation of graphene dispersion: Graphene is dispersed in deionized water to obtain a graphene dispersion; the graphene sheet thickness is 1-5 nm, the lateral dimension is 50-200 nm, and the aspect ratio is 10-200; the specific preparation steps of the graphene dispersion in step S1 are as follows: Graphene was added to deionized water, and a bio-based surfactant was added as a dispersant. The amount of the dispersant was 5 times the mass of the graphene. The mixture was dispersed at 20-30°C and under high-frequency ultrasound at 40 kHz for 50 minutes to obtain a graphene dispersion. The bio-based surfactant was sodium alginate or chitosan. S2. Preparation of composite spinning solution: Polylactic acid is dissolved in dihydro-L-glucanone, and then the graphene dispersion obtained in step S1 and bio-based functional additives are added and mixed to form the first spinning solution. The graphene concentration in the first spinning solution is 0.01-0.5 mg / mL. Cellulose is mixed with the graphene dispersion obtained in step S1 and bio-based functional additives to form a second spinning solution, wherein the graphene concentration in the second spinning solution is 0.02-3 mg / mL. The mass ratio of polylactic acid to cellulose is 1:2-2:1, and the total amount of graphene added accounts for 0.09%-0.6% of the total mass of polylactic acid and cellulose. S3. Construct a two-layer structure: First, the first spinning solution prepared in step S2 is electrospun to form a porous nanofiber support layer. The spinning parameters of the first spinning solution are: voltage 12-18 kV, receiving distance 10-15 cm, injection speed 1-1.5 mL / h, and a porous nanofiber support layer with a porosity of 70%-85% is formed. Then, on the porous nanofiber support layer, the second spinning solution prepared in step S2 is electrospun to form a dense nanofiber functional layer, thereby obtaining a composite fiber membrane with a bilayer structure; the spinning parameters of the second spinning solution are: voltage 10-15 kV, receiving distance 8-12 cm, injection speed 0.3-0.8 mL / h, and a dense nanofiber functional layer with a porosity of 40%-60% is spun. During the electrospinning process, a magnetic field is applied to guide the directional alignment of the graphene. The strength of the magnetic field is 0.5-1.0 T, and the direction of the magnetic field is perpendicular to the direction of the spinning solution injection. S4. Post-processing: The composite fiber membrane obtained in step S3 is subjected to cross-linking treatment and heat setting to obtain a waterproof and breathable membrane material.

2. The preparation method according to claim 1, characterized in that: In step S2, the cellulose is subjected to TEMPO oxidation treatment, and its surface carboxyl content is 1.2-1.5 mmol / g; the polylactic acid has a melt index of 5-15 g / 10min.

3. The preparation method according to claim 1, characterized in that: In step S2, the bio-based functional additive includes a bio-based plasticizer and / or a crosslinking agent; when both plasticizer and crosslinking agent are included, their mass ratio is 10:1 to 20:1; the bio-based plasticizer is glycerol or tributyl citrate, and the crosslinking agent is a silane coupling agent or calcium chloride.

4. The preparation method according to claim 1, characterized in that: In step S4, The crosslinking treatment involves immersing the composite fiber membrane in a 0.1-0.5 mol / L calcium chloride solution for 10-30 minutes; the heat setting is a gradient heat setting, which involves holding the membrane at 30°C, 50°C, and 70°C for 30 minutes each.

5. A waterproof and breathable membrane material, characterized in that: Prepared by the preparation method according to any one of claims 1-4, comprising a dense nanofiber functional layer and a porous nanofiber support layer.

6. The waterproof and breathable membrane material according to claim 5, characterized in that: The dense nanofiber functional layer has a fiber diameter of 50-200 nm and a pore size of 50-100 nm; the porous nanofiber support layer has a fiber diameter of 200-500 nm and a pore size of 1-3 μm.

7. The waterproof and breathable membrane material according to claim 6, characterized in that: The waterproof and breathable membrane material has a water contact angle ≥142°, a roll-off angle ≤11°, and a moisture permeability ≥6700 g / (m²). 2 • 24h), breaking strength ≥ 6.5MPa, breaking elongation ≥ 46%.

8. A waterproof and breathable fabric, characterized in that, It includes a fabric substrate and a waterproof and breathable membrane material as described in any one of claims 5-7, laminated onto the fabric substrate.

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