Nanofiber membrane with sustainable cold feeling and preparation method thereof

Abstract

The invention discloses a nanofiber membrane with sustainable cold feeling and a preparation method of the nanofiber membrane. The radiation refrigeration polymer is dissolved in a mixed solvent, and the radiation refrigeration nanofiber membrane is obtained by adopting an electrostatic spinning process; the method comprises the following steps: dispersing a cold-feeling nano-material in a solvent, carrying out ultrasonic treatment to obtain a uniformly dispersed nano-material, and depositing the nano-material on the surface of one side of a radiation refrigeration fiber membrane through a spraying process to obtain the nano-fiber membrane with sustainable cold feeling. According to the nanofiber membrane with the sustainable cold feeling function and the asymmetric heat conduction structures on the two sides, the low-heat-conduction outer side prevents external heat from being conducted to the interior, the high-heat-conduction inner side can enable skin heat to be rapidly transmitted in the surface, instant cold feeling performance is achieved, and dual control over a heat source and a heat conduction path is achieved; meanwhile, internal heat is selectively emitted to the outer space in a heat radiation mode, so that temperature rise of the fiber membrane is slowed down, and the cold feeling is continuously kept. The preparation process is simple, energy is not consumed in the sustainable cold feeling process, and automatic cold feeling is achieved.

Description

Technical Field

[0001] The invention relates to a nanofiber membrane with sustainable cooling sensation and a preparation method thereof, belonging to the technical field of functional materials. Background Art

[0002] When people work or exercise in outdoor environments, the imbalance of thermal regulation caused by solar radiation and exercise metabolism can lead to excessive heat stress in the human body, which can cause dizziness and nausea at the mildest and endanger life safety at the worst. The moment textiles with high thermal conductivity come into contact with the skin, they cause rapid loss of heat on the skin surface and an instant drop in temperature, giving the human body a sense of coolness. However, under outdoor sunlight, the temperature of the textiles will gradually increase, and this sense of coolness becomes unsustainable. Textiles that use daytime radiative cooling technology can spontaneously and selectively emit human infrared radiation into the cold outer space, while reflecting sunlight, effectively slowing down the temperature rise of textiles caused by solar radiation, thereby maintaining the long-term sustainability of the coolness of the textiles. Therefore, designing a sustainable cool nanofiber membrane is of great value in regulating the human microclimate and improving outdoor thermal comfort.

[0003] The function of sustainable cooling depends on the support of the material's efficient thermal conductivity. Chinese invention patents CN116061525A and CN112458563A disclose thermally conductive radiant cooling fabric materials, which improve the thermal conductivity of composite fibers by doping thermally conductive fillers into a polymer matrix with low intrinsic thermal conductivity. This strategy relies on a high filler content to construct an effective heat conduction path, resulting in low overall thermal conductivity. Excessive filler content will deteriorate the processing performance of the composite fiber and significantly reduce its mechanical properties. Optimizing the filler configuration to construct an efficient thermal conduction network in the polymer matrix is ​​crucial to enhancing the thermal conductivity of composite materials. It is necessary to strictly screen the thermally conductive materials and carefully design the preparation process to construct an efficient thermal conduction network structure (see literature: Chem. Soc. Rev. , 2016, 45 , 3989). Therefore, there is an urgent need to provide textiles with sustainable cooling function through a simple process, high-performance radiative cooling materials and processing methods. Summary of the invention

[0004] In view of the shortcoming that existing textiles are difficult to achieve sustainable cooling, the present invention provides a nanofiber membrane with a simple preparation process and sustainable cooling and a preparation method thereof. The sustainable cooling process does not consume energy and the cooling is automatic.

[0005] The Janus thermal conductive structure of the nanofiber membrane with sustainable cooling sensation is prepared by electrospinning and spraying process. The design concept of the Janus thermal conductive structure on both sides of the fiber membrane is adopted to construct the heterogeneous thermal conductivity of the fiber membrane inside and outside; the low thermal conductivity outer side blocks the external heat from being conducted to the inside; the high thermal conductivity inner side allows the epidermal heat to be quickly transferred along the surface, with instant cooling performance. At the same time, the internal heat is selectively emitted to outer space in the form of thermal radiation, thereby achieving dual control of the heat source and the heat conduction path. In addition, the nanofiber membrane using radiation cooling technology can achieve a solar reflectivity of 96.4% and an infrared emissivity of 96.7% in the 8-13 micron band, thereby slowing down the temperature rise of the fiber membrane and maintaining a continuous cool feeling. Compared with single-sided plain weft cotton fabric, the nanofiber membrane has an instantaneous cool feeling performance of Q max Compared with the fiber membrane without spraying process, the nanofiber membrane with sustainable cooling sensation is 620 W / m 2 When the intensity of sunlight radiation and the presence of a 36°C heating source are met, the maximum cooling effect of 4.3°C can be achieved, and the cooling performance can be continuously provided for up to 10 hours during the day.

[0006] The technical solution to achieve the purpose of the present invention is to provide a method for preparing a nanofiber membrane with a continuous cooling sensation, comprising the following steps: (1) adding a radiation cooling polymer to a mixed solvent, wherein the radiation cooling polymer comprises cellulose acetate and polyethylene oxide in a molar ratio of 10:1 to 10:6, and the mixed solvent comprises acetone and N,N-dimethylformamide in a mass ratio of 1:1 to 1:9, and the mass ratio of the radiation cooling polymer to the mixed solvent is 1:5.6 to 1:9; applying magnetic stirring until the radiation cooling polymer is completely dissolved to obtain a spinning solution; (2) using the spinning solution obtained in step (1) through an electrospinning process to obtain a radiation cooling nanofiber membrane on a receiving plate; (3) dispersing a cold-sensing nanomaterial in a mixed solution, wherein the mass ratio of the cold-sensing nanomaterial to the mixed solution is 1:70 to 1:100; the cold-sensing nanomaterial is boron nitride nanoparticles, and the mixed solution comprises N,N-dimethylformamide and isopropanol in a mass ratio of 10:2 to 10:4; performing ultrasonic treatment until the cold-sensing nanomaterial is uniformly dispersed to obtain a dispersion; (4) The dispersion obtained in step (3) is sprayed onto the surface of one side of the radiant cooling nanofiber membrane by a spraying process to obtain a nanofiber membrane with a sustainable cooling sensation.

[0007] The method for preparing the nanofiber membrane with sustainable cooling sensation of the present invention comprises adding boron nitride, isopropyl alcohol and ball milling beads into a ball mill at a mass ratio of 1:30-60:5-20 for ball milling to obtain a dispersion, and then subjecting the dispersion to ultrasonic, centrifugal and vacuum drying treatment to obtain boron nitride nanoparticles.

[0008] The process conditions of the electrospinning of the present invention are as follows: the inner diameter of the spinning nozzle is 0.42-0.84 mm, the propulsion speed of the syringe is 0.5-1.5 ml / h, and the receiving distance is 10-20 cm; the spinning voltage is 10-25 kV, the temperature is 25-30 ° C, and the humidity is 40-45%; the process conditions of the spraying are as follows: the propulsion speed of the spray gun syringe is 2.5-5 ml / min, and the spraying amount is 0.05-0.1 ml / cm 2 .

[0009] The technical solution of the present invention also includes a nanofiber membrane with sustainable cooling sensation obtained by the above preparation method.

[0010] The nanofiber membrane with a sustainable cooling sensation of the present invention has a diameter of 200-600 nm and a cooling sensation performance of Q max The value is 0.164~0.270; the average reflectivity of sunlight is 85.7%~96.4%, and the infrared emissivity in the range of 8~13 microns is 76.8~96.7.

[0011] The nanofiber membrane with sustainable cooling sensation prepared by the present invention has a cooling sensation performance of Q100 at the instant of contact compared with the single-sided plain weft cotton fabric. max The value is twice that of the former; compared with the fiber membrane without spraying process, the nanofiber membrane with sustainable cooling sensation is 620 W / m 2 When the intensity of sunlight radiation and the presence of a 36°C heating source are met, the maximum cooling effect of 4.3°C can be achieved, and the cooling performance can be continuously provided for up to 10 hours during the day.

[0012] The present invention proposes a construction idea that combines the two strategies of screening thermal conductive materials and carefully designing the preparation process to obtain a nanofiber membrane with sustainable cooling sensation. The invention principle is that the effective area of ​​the sheet filler when overlapping each other due to its high aspect ratio is conducive to the formation of phonon heat conduction channels, thereby improving the heat conduction efficiency. Boron nitride nanosheets (BNNS) are two-dimensional sheet materials with a high aspect ratio, and their thermal conductivity coefficient is as high as 600 W / (m·K), showing the potential as an ideal thermal conductive filler. The present invention adopts a spraying process to realize the effective loading of fillers on the polymer interface, and easily realizes the asymmetric (Janus) thermal conductive structure design on both sides of the fiber membrane. At the same time, this non-internal load thermal conductive finishing method, the external environment side relies on the low thermal conductivity of the polymer to effectively prevent the external heat from being conducted to the inside, reducing the input of external heat. Through the spraying process, a continuous thermal conductive network is constructed on the interface of the fiber membrane (skin side), in which the boron nitride nanosheets (BNNS) with a high aspect ratio are closely connected to each other to form a directional arrangement of phonon heat conduction channels. This structural feature realizes a continuous heat conduction network in the in-plane direction of the composite material, greatly improving the utilization efficiency of the filler and giving the fiber membrane instantaneous cooling performance. max The value can reach 0.270.

[0013] Compared with modern technology, the beneficial effects of the present invention are: 1. The present invention uses the radiation cooling polymer cellulose acetate, polyethylene oxide and the cold-sensing nanomaterial boron nitride as raw materials, adopts the electrospinning process to prepare a radiation cooling fiber membrane with high-efficiency sunlight reflection and infrared emission performance, and then adopts the spraying method to evenly load the cold-sensing nanomaterial onto the radiation cooling fiber membrane. The nanofiber membrane has both radiation cooling and cold-sensing functions, and a nanofiber membrane with sustainable cold feeling is obtained.

[0014] 2. The present invention provides a method for preparing a nanofiber membrane with sustainable cooling sensation. The preparation process is simple, no energy is consumed during the sustainable cooling sensation, and the cooling sensation is automatic. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 These are electron microscope images of the nanofiber membrane with sustainable cooling sensation prepared in Example 1 of the present invention, (a) is a SEM image of the side of the nanofiber membrane that is not sprayed with boron nitride, and (b) is a SEM image of the side of the nanofiber membrane that is sprayed with boron nitride.

[0016] Figure 2 This is a graph showing the reflectivity of the sustainable cooling nanofiber membrane prepared in Example 1 of the present invention to sunlight of different wavelengths.

[0017] Figure 3 The mid-infrared emissivity of the nanofiber membrane with sustainable cooling sensation prepared in Example 1 of the present invention.

[0018] Figure 4 The instantaneous cooling performance Q of the single-sided plain-knit cotton fabric in contact with the sustainable cooling nanofiber membrane prepared in Example 1 is max Comparison chart of values. DETAILED DESCRIPTION

[0019] The technical solution of the present invention is further described below in conjunction with the accompanying drawings and embodiments. Example 1

[0020] 1 g of cellulose acetate and 0.1 g of polyethylene oxide were added to a mixed solvent of acetone and N,N-dimethylformamide (mass ratio of 1:1), with the mass ratio of polymer to solvent being 1:9, and stirred at room temperature for 3 h using a magnetic stirrer until the polymer was completely dissolved to obtain a spinning solution; 5 ml of spinning solution was sucked into syringe 1 and fixed on the propulsion pump for electrospinning. A spinning nozzle with a diameter of 0.84 mm was used, the propulsion speed of the syringe was set to 0.5 ml / h, the receiving distance was 10 cm, and spinning was performed under the conditions of voltage 10 kV, temperature 25 ℃, and humidity 40%. As the solvent evaporated, a radiation cooling nanofiber membrane was obtained on the receiving plate.

[0021] 1 g of boron nitride, isopropanol and ball milling beads (mass ratio of 1:30:5) were added into a ball mill and ball milled at 400 rpm for 2 h. Subsequently, the dispersion was ultrasonicated for 1 h and then centrifuged at 3000 rpm for 10 min. The supernatant was taken and centrifuged at 10000 rpm for 30 min, and then dried in a vacuum oven at 60°C for 12 h.

[0022] Take 0.1 g of dried boron nitride and disperse it in a mixed solution of N,N-dimethylformamide and isopropanol (mass ratio is 10:2), and the mass ratio of the cold-sensitive nanomaterial to the mixed solvent is 1: 100. Ultrasonicate for 0.5 h until the nanomaterial is evenly dispersed to obtain a dispersion.

[0023] Aspirate 2 ml of the dispersion into the spray gun, set the syringe propulsion speed to 2.5 ml / min and spray it on the surface of one side of the radiation cooling nanofiber membrane. The spraying amount is 0.02 ml / cm 2 , and obtain a nanofiber membrane with sustainable cooling sensation.

[0024] See attached Figure 1 , (a) is a SEM image of the radiative cooling nanofiber membrane prepared in this embodiment. It can be seen that nanofibers of 300 nm to 600 nm are successfully prepared by electrospinning; (b) is a SEM image of the side of the nanofiber membrane sprayed with boron nitride prepared in this embodiment. It can be seen that through the spraying process, boron nitride is evenly distributed on the fiber membrane and stacked on each other.

[0025] See attached Figure 2 , is the reflectivity of the sustainable cooling nanofiber membrane prepared in this embodiment to sunlight of different wavelengths, and the sunlight reflectivity is 96.4%.

[0026] See attached Figure 3 The nanofiber membrane with sustainable cooling sensation prepared in this embodiment has an infrared emissivity of 96.7% at 8 to 13 microns.

[0027] See attached Figure 4 , is the instantaneous cool feeling performance Q of the single-sided plain weft cotton fabric in contact with the sustainable cool feeling nanofiber membrane prepared in this embodiment max Comparison chart of values; Figure 4 It can be seen that single-sided plain weft cotton fabric Q max The value is 0.135, the nanofiber membrane with sustainable cooling Q max The value is 0.270. Example 2

[0028] 1 g of cellulose acetate and 0.6 g of polyethylene oxide were added to a mixed solvent of acetone and N,N-dimethylformamide (mass ratio of 1:3), with the mass ratio of polymer to solvent being 1:7.5, and stirred at room temperature for 4 h using a magnetic stirrer until the polymer was completely dissolved to obtain a spinning solution; 5 ml of spinning solution was sucked into syringe 1 and fixed on the propulsion pump for electrospinning. A spinning nozzle with a diameter of 0.84 mm was used, the propulsion speed of the syringe was set to 1 ml / h, the receiving distance was 12 cm, and spinning was performed under the conditions of voltage 15 kV, temperature 25°C, and humidity 45%. As the solvent evaporated, a radiation cooling nanofiber membrane was obtained on the receiving plate.

[0029] 2 g of boron nitride, isopropanol and ball milling beads (mass ratio of 1:40:10) were added to a ball mill and ball milled at 400 rpm for 5 h. Subsequently, the dispersion was ultrasonicated for 2 h and then centrifuged at 3000 rpm for 10 min. The supernatant was taken and centrifuged at 10000 rpm for 30 min and dried in a vacuum oven at 60°C for 12 h.

[0030] 0.1 g of dried boron nitride was dispersed in a mixed solution of N,N-dimethylformamide and isopropanol (mass ratio was 10:2.5), and the mass ratio of the cold-sensitive nanomaterial to the mixed solvent was 1:85. Ultrasonic treatment was performed for 0.5 h until the nanomaterial was evenly dispersed to obtain a dispersion.

[0031] Aspirate 5 ml of the dispersion into the spray gun, set the syringe propulsion speed to 3 ml / min and spray it on the surface of one side of the radiation cooling nanofiber membrane. The spraying amount is 0.05 ml / cm 2 A nanofiber membrane with sustainable cooling sensation is obtained. Example 3

[0032] 1 g of cellulose acetate and 0.4 g of polyethylene oxide were added to a mixed solvent of acetone and N,N-dimethylformamide (mass ratio of 1:6), with the mass ratio of polymer to solvent being 1:6.5, and stirred at room temperature for 4 h using a magnetic stirrer until the polymer was completely dissolved to obtain a spinning solution; 5 ml of spinning solution was sucked into syringe 1 and fixed on the propulsion pump for electrospinning. A spinning nozzle with a diameter of 0.42 mm was used, the propulsion speed of the syringe was set to 1.2 ml / h, the receiving distance was 15 cm, and spinning was performed under the conditions of voltage 18 kV, temperature 30 ℃, and humidity 40%. As the solvent evaporated, a radiation cooling nanofiber membrane was obtained on the receiving plate.

[0033] 3 g of boron nitride, isopropanol and ball milling beads (mass ratio of 1:50:15) were added to a ball mill and ball milled at 400 rpm for 8 h. Subsequently, the dispersion was ultrasonicated for 3 h and then centrifuged at 3000 rpm for 10 min. The supernatant was taken and centrifuged at 10000 rpm for 30 min and dried in a vacuum oven at 60°C for 12 h.

[0034] Take 0.1 g of dried boron nitride and disperse it in a mixed solution of N,N-dimethylformamide and isopropanol (mass ratio is 10:3), and the mass ratio of the cold-sensitive nanomaterial to the mixed solvent is 1:75. Ultrasonicate for 0.5 h until the nanomaterial is evenly dispersed to obtain a dispersion.

[0035] Aspirate 8 ml of the dispersion into the spray gun, set the syringe propulsion speed to 3 ml / min and spray it on the surface of one side of the radiation cooling nanofiber membrane. The spraying amount is 0.08 ml / cm 2 , and obtain a nanofiber membrane with sustainable cooling sensation. Example 4

[0036] 1 g of cellulose acetate and 0.6 g of polyethylene oxide were added to a mixed solvent of acetone and N,N-dimethylformamide (mass ratio of 1:1), with the mass ratio of polymer to solvent being 1:5.6, and stirred at room temperature for 5 h using a magnetic stirrer until the polymer was completely dissolved to obtain a spinning solution; 5 ml of spinning solution was sucked into syringe 1 and fixed on the propulsion pump for electrospinning. A spinning nozzle with a diameter of 0.42 mm was used, the propulsion speed of the syringe was set to 1.5 ml / h, the receiving distance was 20 cm, and spinning was performed under the conditions of voltage 25 kV, temperature 30 ℃, and humidity 40%. As the solvent evaporated, a radiation cooling nanofiber membrane was obtained on the receiving plate.

[0037] 4 g of boron nitride, isopropanol and ball milling beads (mass ratio of 1:60:20) were added into a ball mill and ball milled at 400 rpm for 12 h. The dispersion was ultrasonically treated for 4 h and centrifuged at 3000 rpm for 10 min. The supernatant was taken and centrifuged at 10000 rpm for 30 min, and then dried in a vacuum oven at 60°C for 12 h.

[0038] 0.1 g of dried boron nitride was dispersed in a mixed solution of N,N-dimethylformamide and isopropanol (mass ratio was 10:4), and the mass ratio of the cold-sensitive nanomaterial to the mixed solvent was 1:70. Ultrasonic treatment was performed for 1 h until the nanomaterial was evenly dispersed to obtain a dispersion.

[0039] Aspirate 10 ml of the dispersion into the spray gun, set the syringe propulsion speed to 5 ml / min and spray it on the surface of one side of the radiation cooling nanofiber membrane. The spraying amount is 0.1 ml / cm 2 , a nanofiber membrane with sustainable cooling sensation is obtained.

Claims

1. A method for preparing a nanofiber membrane with a sustainable cooling sensation, characterized in that The following steps are involved: (1) adding a radiation cooling polymer to a mixed solvent, wherein the radiation cooling polymer comprises cellulose acetate and polyethylene oxide in a molar ratio of 10:1 to 10:6, and the mixed solvent comprises acetone and N,N-dimethylformamide in a mass ratio of 1:1 to 1:9, and the mass ratio of the radiation cooling polymer to the mixed solvent is 1:5.6 to 1:9; applying magnetic stirring until the radiation cooling polymer is completely dissolved to obtain a spinning solution; (2) using the spinning solution obtained in step (1) through an electrospinning process to obtain a radiation cooling nanofiber membrane on a receiving plate; (3) dispersing a cold-sensing nanomaterial in a mixed solution, wherein the mass ratio of the cold-sensing nanomaterial to the mixed solution is 1:70 to 1:100; the cold-sensing nanomaterial is boron nitride nanoparticles, and the mixed solution comprises N,N-dimethylformamide and isopropanol in a mass ratio of 10:2 to 10:4; performing ultrasonic treatment until the cold-sensing nanomaterial is uniformly dispersed to obtain a dispersion; (4) The dispersion obtained in step (3) is sprayed onto the surface of one side of the radiant cooling nanofiber membrane by a spraying process to obtain a nanofiber membrane with a sustainable cooling sensation.

2. The method for preparing a nanofiber membrane with a sustainable cool sensation according to claim 1, characterized in that: Boron nitride, isopropanol and ball milling beads are added into a ball milling jar at a mass ratio of 1:30-60:5-20 for ball milling to obtain a dispersion, which is then subjected to ultrasonic, centrifugal and vacuum drying treatments to obtain boron nitride nanoparticles.

3. The method for preparing a nanofiber membrane with sustainable cooling sensation according to claim 1, characterized in that: The electrospinning process conditions are as follows: the inner diameter of the spinning nozzle is 0.42-0.84 mm, the propulsion speed of the syringe is 0.5-1.5 ml / h, the receiving distance is 10-20 cm, the spinning voltage is 10-25 kV, the temperature is 25-30°C, and the humidity is 40-45%.

4. The method for preparing a nanofiber membrane with sustainable cooling sensation according to claim 1, characterized in that: The process conditions of the spraying are that the propulsion speed of the spray gun syringe is 2.5 ~ 5 ml / min, and the spraying amount is 0.05 ~ 0.1 ml / cm 2 .

5. A nanofiber membrane with a sustainable cool feeling obtained by the preparation method of claim 1.

6. The nanofiber membrane with sustainable cooling sensation according to claim 5, characterized in that: The diameter of the nanofiber is 200-600 nm; the nanofiber membrane has a cooling performance of Q max The value is 0.164~0.270; the average reflectivity of sunlight is 85.7%~96.4%, and the infrared emissivity in the range of 8~13 microns is 76.8~96.7.

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