Flexible nylon yarn composite fiber membrane with heat and humidity management function and preparation method of flexible nylon yarn composite fiber membrane

Abstract

The invention discloses a flexible nylon yarn composite fiber membrane with a heat and humidity management function and a preparation method of the flexible nylon yarn composite fiber membrane, and belongs to the technical field of radiation cooling heat and humidity management materials. According to the preparation method, a silk fibroin (SF) solution and a nylon 66 (PA66) solution are mixed according to a certain proportion to prepare a precursor solution, and the PA66-SF composite fiber membrane is prepared by adopting an electrostatic spinning process. By introducing the PA66, the defect that the reflectivity of an ultraviolet region of an SF fiber membrane is low due to the inherent absorption characteristic of protein is effectively improved, the mechanical property of the SF fiber membrane can be remarkably improved, and the fiber membrane has excellent dry flexibility and wet stability. The preparation method provided by the invention is simple and convenient to operate, and the prepared flexible fiber membrane material has a temperature-humidity collaborative management function and is wide in application prospect.

Description

Technical Field

[0001] The invention relates to a flexible nylon silk composite fiber membrane with heat and moisture management functions and a preparation method thereof, belonging to the field of radiation cooling heat and moisture management materials. Background Art

[0002] With the development of society and the continuous advancement of industrialization, technology, while bringing convenience to humanity, has also brought about a series of byproducts such as global warming and energy shortages. Extreme heat can have multi-system and multi-level negative impacts on human health, especially threatening the health and safety of vulnerable groups. Traditional electric-driven refrigeration technologies, such as air conditioners, rely on electric compressors, which consume large amounts of electricity and emit large amounts of greenhouse gases and harmful gases, exacerbating the greenhouse effect and air pollution. The growing contradiction between the demand for cooling energy and the need to implement energy conservation and emission reduction policies has become a prominent issue that needs to be addressed in the 21st century.

[0003] Radiative cooling is a novel cooling technology that boasts zero energy consumption, efficient heat dissipation, and environmental friendliness. It utilizes atmospheric windows to dissipate heat into space through radiation, while simultaneously reducing heat input through high solar reflectivity. Conventional radiative cooling textiles primarily utilize non-renewable, non-degradable, petroleum-based synthetic polymers, such as PVDF and PU, as their matrix materials. Their inherent hydrophobicity limits their sweat management capabilities (see ACS Appl. Mater. 2024, 2024). 16, 16778 −16787 In recent years, silk fibroin extracted from silk has attracted extensive research interest in the fields of radiative cooling and sweat management due to its excellent renewability, biodegradability, and hygroscopicity. The prior art reports a stretchable silk fibroin nanofiber textile with efficient passive personal thermal management developed by optimizing the nanofiber diameter (see reference: Chem. Eng. J. 2023, 466, 143127 However, the intrinsic absorption of proteins in the ultraviolet region inevitably weakens their full solar spectrum reflectivity (see reference: Nat. Nanotechnol. 2021, 16, 1342-1348 ), while untreated regenerated silk fibroin fiber membranes have defects such as flexibility, mechanical brittleness and poor stability when in contact with water, which restricts their practical application in radiative cooling and sweat management. Summary of the Invention

[0004] In response to the shortcomings of existing silk fibroin fiber membranes in terms of poor reflective performance and mechanical properties in the ultraviolet band, the present invention provides a flexible nylon silk fibroin composite fiber membrane and a preparation method thereof that can effectively improve the reflective performance of the fiber membrane in the ultraviolet band, meet the requirements of efficient radiation cooling, and improve the mechanical properties of the fiber membrane so that it has excellent flexibility in a dry state and can still maintain stable mechanical strength in a wet state, thereby meeting the application requirements of sweat management.

[0005] To achieve the above-mentioned object of the invention, the technical solution adopted by the present invention is to provide a method for preparing a flexible nylon silk composite fiber membrane with heat and moisture management function, comprising the following steps: 1. Preparation of Nylon 66-Silk Fibroin Composite Precursor Solution Silk fibroin powder (denoted as SF) and sodium lauryl sulfate are dispersed in hexafluoroisopropanol, with the sodium lauryl sulfate accounting for 3% to 7% of the mass of SF. After stirring evenly, formic acid is added, with the volume ratio of hexafluoroisopropanol to formic acid being 1:1 to 1:2, to obtain an SF solution with a mass percentage concentration of 8 to 12% of SF. Nylon 66 (referred to as PA66) is pelletized and dissolved in hexafluoroisopropanol or formic acid to obtain a solution with a PA66 mass percentage concentration of 10 to 15%; Slowly add the PA66 solution to the SF solution at a volume ratio of 3:6 to 3:10. After continuous stirring and standing, a stable PA66-SF composite precursor solution is obtained. 2. Preparation of Nylon 66-Silk Fibroin Composite Fiber Membrane The PA66-SF composite precursor solution obtained in step 1 is subjected to an electrospinning process to prepare a flexible nylon silk composite fiber membrane with heat and moisture management functions.

[0006] The present invention discloses a method for preparing a flexible nylon silk composite fiber membrane with heat and moisture management functions, which comprises the following steps: using 0.02-0.03 wt% of Na2CO3 and 0.05-0.08 wt% of NaHCO3 as a composite degumming agent, degumming silk at a bath ratio of 40-60:1 to obtain silk fibroin fibers; dissolving the degummed and dried silk fibroin fibers in a 9.3 mol / L lithium bromide solution at a bath ratio of 10-12:1, and filtering the obtained silk solution after dialysis to obtain a clarified silk solution; and obtaining silk fibroin powder after freeze-drying and grinding.

[0007] The electrospinning process employed in the present invention includes the following process conditions: a high-voltage electrostatic discharge (ESD) range of 10 to 16 kV, a syringe pump flow rate of 0.8 to 1.5 ml / h, a drum-type receiving device with a receiving distance of 12 to 18 cm and a drum speed of 100 to 200 rpm. The resulting PA66-SF fiber membrane is then dried in an oven at 40 to 60°C.

[0008] The technical solution of the present invention also includes a flexible nylon silk composite fiber membrane with heat and moisture management function obtained according to the above preparation method.

[0009] The principle behind this invention is that silk fibroin exhibits high emissivity in the 8-13μm atmospheric window band due to the strong vibrational coupling of chemical bonds such as CN, NH, and O=C-OH. By optimizing the ratio of PA66 and SF, the PA66-SF fiber membrane exhibits excellent full-band reflectivity, providing an ideal material platform for achieving efficient passive radiative cooling. Conventional SF fiber membranes are prone to swelling and transparency upon contact with water, severely impacting their stability in use. This invention introduces PA66, forming hydrogen bonds between the carbonyl groups of SF and the amino groups of PA66. The resulting PA66-SF hydrogen bond double network structure effectively transfers stress along the polymer chain and disperses it throughout the entire network structure, significantly improving the fiber membrane's flexibility and wet stability. Furthermore, the fiber membrane's efficient water absorption and evaporation properties give it broad potential for application in regulating human thermal and moisture comfort.

[0010] Compared with the prior art, the present invention has the following beneficial effects: 1. The present invention provides a new type of heat and moisture management flexible silk protein-based fiber membrane. The fiber membrane is compounded with PA66, which has low UV absorption and can form a hydrogen bond network with silk protein, effectively compensating for the high absorption characteristics and poor mechanical properties of pure silk fibroin materials in the ultraviolet band, and providing new ideas for the development of high-performance heat and moisture management flexible materials.

[0011] 2. The fiber membrane provided by the present invention has excellent radiative cooling and sweat management properties. The average reflectivity of the PA66-SF fiber membrane in the solar spectrum range is as high as 93.82%, and the difference in reflectivity between the full band and the ultraviolet region is only 1.98, which is significantly better than the pure SF fiber membrane (difference 5.57). Outdoor measurements show that compared with bare skin, PET and Silk, they achieve cooling advantages of 17.47°C, 9.21°C and 6.93°C respectively. In terms of mechanical properties, the tensile strength of the fiber membrane reaches 5.95 MPa, the elongation at break is 11.54%, and the toughness index is 0.41, which are all improved compared to the pure SF membrane. This material has excellent moisture regulation ability and realizes dynamic thermal management by quickly absorbing sweat and promoting evaporative heat dissipation.

[0012] 3. Compared with traditional silk fibroin fiber membranes, the composite fiber membrane provided by the present invention has improved reflectivity in the ultraviolet band, can efficiently reflect solar radiation, and meet the performance requirements of high-efficiency radiation cooling materials; the fiber membrane can still maintain stable mechanical properties in a humid environment, avoiding rapid shrinkage due to water absorption, and can return to a dry state under room temperature drying conditions, showing good environmental adaptability; the tensile strength and toughness of the fiber membrane are significantly improved, while maintaining mechanical strength while having higher flexibility, broadening its application potential in the field of heat and moisture management. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 This is a SEM image of the composite fiber membrane prepared in Example 1 of the present invention; Figure 2 The stress-strain diagrams of the composite fiber membrane prepared in Example 1 of the present invention and the comparative example; Figure 3 The infrared fitting diagrams of the composite fiber membrane prepared in Example 1 of the present invention and the comparative example; Figure 4 The reflection spectrum curves of the composite fiber membrane prepared in Example 1 of the present invention and the comparative example in the 0.3-2.5 μm band and the outdoor cooling test results are shown; Figure 5 This is a graph showing the contact angle test results of the composite fiber membrane prepared in Example 1 of the present invention; Figure 6 This is a graph showing the results of an indoor simulated sweat evaporation test of the composite fiber membrane prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0014] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0015] Example 1: 20g of raw silk was degummed in 1L of boiling deionized water containing 0.75g of NaHCO₃ and 0.25g of Na₂CO₃ for 30 minutes each, repeated three times. After thorough washing, the degummed silk was dried at 40°C. 10g of degummed silk was dissolved in 100mL of 9.3M LiBr solution and heated at 60°C for 4 hours. After complete dissolution, the silk was transferred to a 3500Da dialysis bag and dialyzed for 3 days to remove salt. The dialyzate was centrifuged at 8000rpm for 20 minutes and filtered through 250- and 350-mesh nylon filters to obtain a clear solution. The solution was freeze-dried and ground to produce a white silk fibroin (SF) powder.

[0016] Dissolve 1.4g of SF powder and 0.05g of sodium lauryl sulfate in 7mL of hexafluoroisopropanol. Stir at room temperature for 1 hour, then add 7mL of formic acid and continue stirring for 4 hours to prepare an SF solution. Simultaneously, dissolve 0.72g of PA66 pellets in 6mL of hexafluoroisopropanol and stir for 3 hours to prepare a PA66 solution. The two solutions are mixed, stirred for 4 hours, and then allowed to stand overnight to obtain a homogeneous PA66-SF spinning solution.

[0017] The electrospinning process was used with a voltage of 15 kV, a feed rate of 1 mL / h, a spinning distance of 12 cm, a drum speed of 200 rpm, and continuous spinning for 5 hours. The resulting fiber membrane was dried at 40°C to obtain a PA66-SF composite fiber membrane. The comparative SF fiber membrane was prepared using the same spinning process.

[0018] See attached Figure 1 , which is the SEM image of the PA66-SF composite fiber membrane prepared in this example, it can be seen that the fiber membrane has good morphological characteristics and no beading or fiber adhesion.

[0019] See attached Figure 2 , which is the stress-strain curve of the PA66-SF composite fiber membrane prepared in this embodiment and the comparative example SF fiber membrane, Figure 2 The comparison results show that the dry flexibility of the fiber membrane is significantly improved by introducing PA66.

[0020] See attached Figure 3 Figure a is the infrared fitting curve of the comparative SF fiber membrane prepared in this embodiment, and Figure b is the infrared fitting curve of the PA66-SF composite fiber membrane prepared in this embodiment. The comparison results show that the silk fibroin fiber mainly exhibits amorphous structural characteristics. When compounded with nylon 66, the β-folding content is significantly increased, while the proportion of random coil and α-helix is ​​correspondingly reduced, which provides a theoretical explanation for the improvement of the mechanical properties of the fiber membrane.

[0021] See attached Figure 4 Figure a is a reflection spectrum curve of the PA66-SF composite fiber membrane prepared in this embodiment and the comparative SF fiber membrane in the range of 0.3~2.5μm. The average reflectivity of the PA66-SF composite fiber membrane in the ultraviolet region is 91.84%, and the average reflectivity of the entire band is 93.82%; Figure b is the outdoor test results of the PA66-SF composite fiber membrane prepared in this embodiment. It can be seen that the radiation cooling of PA66-SF reaches 17.47℃ compared with the bare skin, and the cooling is 9.21℃ and 6.93℃ compared with PET and Silk, respectively.

[0022] See attached Figure 5 , which is the contact angle diagram of the PA66-SF composite fiber membrane prepared in this example, it can be seen that PA66-SF has excellent hydrophilicity.

[0023] See attached Figure 6 , which is the indoor simulated sweat evaporation test result of the PA66-SF composite fiber membrane prepared in this example. It can be seen that the composite fiber membrane can absorb moisture and return to the initial temperature after complete evaporation due to its efficient moisture absorption and evaporation characteristics, confirming the application potential of the composite fiber membrane in regulating human thermal and moisture comfort.

[0024] Example 2: 1.2g of SF powder and 0.06g of sodium lauryl sulfate were dissolved in 6mL of hexafluoroisopropanol and stirred at room temperature for 1 hour. Afterwards, 6mL of formic acid was added and stirred for another 4 hours to prepare an SF solution. Simultaneously, 0.96g of PA66 pellets were dissolved in 8mL of hexafluoroisopropanol and stirred for 3 hours to prepare a PA66 solution. The mixture was stirred for 4 hours and then allowed to stand overnight to obtain a homogeneous PA66-SF spinning solution. The electrospinning process was performed at a voltage of 15kV, a feed rate of 1mL / h, a spinning distance of 12cm, and a drum speed of 200rpm for 5 hours. The resulting fiber membrane was then dried at 40°C to obtain a PA66-SF fiber membrane.

[0025] Example 3: 1.6g of SF powder and 0.08g of sodium lauryl sulfate were dissolved in 8mL of hexafluoroisopropanol and stirred at room temperature for 1 hour. 8mL of formic acid was added and stirred for another 4 hours to prepare an SF solution. Simultaneously, 0.48g of PA66 pellets were dissolved in 46mL of hexafluoroisopropanol and stirred for 3 hours to prepare a PA66 solution. The mixture was stirred for 4 hours and then allowed to stand overnight to obtain a homogeneous PA66-SF spinning solution. The electrospinning process was performed at a voltage of 15kV, a feed rate of 1mL / h, a spinning distance of 12cm, and a drum speed of 200rpm for 5 hours. The resulting fiber membrane was then dried at 40°C to obtain a PA66-SF fiber membrane.

[0026] Example 4: 1.8g of SF powder and 0.09g of sodium lauryl sulfate were dissolved in 9mL of hexafluoroisopropanol and stirred at room temperature for 1 hour. Afterwards, 9mL of formic acid was added and stirred for another 4 hours to prepare an SF solution. Simultaneously, 0.24g of PA66 pellets were dissolved in 2mL of hexafluoroisopropanol and stirred for 3 hours to prepare a PA66 solution. The mixture was stirred for 4 hours and then allowed to stand overnight to obtain a homogeneous PA66-SF spinning solution. The electrospinning process was performed at a voltage of 15kV, a feed rate of 1mL / h, a spinning distance of 12cm, and a drum speed of 200rpm for 5 hours. The resulting fiber membrane was then dried at 40°C to obtain a PA66-SF fiber membrane.

Claims

1. A method for preparing a flexible nylon silk composite fiber membrane with heat and moisture management function, characterized in that The following steps are involved: (1) Preparation of nylon 66-silk fibroin composite precursor solution Silk fibroin powder (denoted as SF) and sodium lauryl sulfate are dispersed in hexafluoroisopropanol, with the sodium lauryl sulfate accounting for 3% to 7% of the mass of SF. After stirring evenly, formic acid is added, with the volume ratio of hexafluoroisopropanol to formic acid being 1:1 to 1:2, to obtain an SF solution with a mass percentage concentration of 8 to 12% of SF. Nylon 66 (referred to as PA66) is pelletized and dissolved in hexafluoroisopropanol or formic acid to obtain a solution with a PA66 mass percentage concentration of 10 to 15%; Slowly add the PA66 solution to the SF solution at a volume ratio of 3:6 to 3:

10. After continuous stirring and standing, a stable PA66-SF composite precursor solution is obtained. (2) Preparation of nylon 66-silk fibroin composite fiber membrane The PA66-SF composite precursor solution obtained in step (1) is subjected to an electrospinning process to prepare a flexible nylon silk composite fiber membrane with heat and moisture management functions.

2. The method for preparing a flexible nylon silk composite fiber membrane with heat and moisture management function according to claim 1, characterized in that: The method comprises the following steps: degumming silk with 0.02-0.03 wt% of Na2CO3 and 0.05-0.08 wt% of NaHCO3 as a composite degumming agent at a bath ratio of 40-60:1 to obtain silk fibroin fibers; dissolving the degummed and dried silk fibroin fibers in a 9.3 mol / L lithium bromide solution at a bath ratio of 10-12:1; filtering the obtained fibroin solution after dialysis to obtain a clarified fibroin solution; After freeze-drying and grinding, silk fibroin powder is obtained.

3. The method for preparing a flexible nylon silk composite fiber membrane with heat and moisture management function according to claim 1, characterized in that: The electrospinning process has a high-voltage electrostatic adjustment range of 10 to 16 kV, an injection pump flow rate of 0.8 to 1.5 ml / h, a drum-type receiving device, a receiving distance of 12 to 18 cm, and a drum speed of 100 to 200 r / min.

4. The method for preparing a flexible nylon silk composite fiber membrane with heat and moisture management function according to claim 1, characterized in that: The obtained PA66-SF fiber membrane is dried in an oven at a temperature of 40 to 60°C.

5. A flexible nylon silk composite fiber membrane with heat and moisture management function obtained by the preparation method of claim 1.

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