A sustainable cold-feeling nanofiber membrane and a preparation method thereof

Abstract

The application discloses a kind of sustainable cool nanofiber membranes and preparation method thereof.Radiation cooling polymer is dissolved in mixed solvent, and radiation cooling nanofiber membrane is obtained by electrospinning process.Cool nanomaterial is dispersed in solvent, and uniformly dispersed nanomaterial is obtained by ultrasonic treatment, which is deposited on one side of the radiation cooling fiber membrane by spraying process to obtain a sustainable cool nanofiber membrane.The sustainable cool functional nanofiber membrane with two-sided asymmetric heat conduction structure provided by the application blocks the conduction of external heat to the inside with low heat conduction on the outside, and the inside with high heat conduction can quickly transfer the skin heat along the surface, with instant cooling performance, realizing double control of heat source and heat conduction path;At the same time, the internal heat is selectively emitted to outer space in the form of thermal radiation, thereby slowing down the temperature rise of the fiber membrane and continuously maintaining the cool feeling.The preparation process of the application is simple, and no energy is consumed during the sustainable cool process, which is automatic cooling.

Description

TECHNICAL FIELD

[0001] The present application relates to a sustainable cool nanofiber membrane and a preparation method thereof, and belongs to the technical field of functional materials. BACKGROUND

[0002] When people work or exercise in outdoor environments, heat regulation imbalance caused by solar radiation and exercise metabolism can lead to excessive heat stress in the human body, which can cause dizziness and nausea, and even endanger life safety. Textiles with high thermal conductivity can cause the skin surface to lose heat quickly and the temperature to drop instantly when they come into contact with the skin, giving the human body a cool touch. However, in the presence of sunlight, the temperature of the textile will gradually rise, and this coolness will not be sustainable. Textiles that use daytime radiation cooling technology can spontaneously emit infrared radiation from the human body to the cold outer space, while reflecting sunlight, effectively slowing down the warming of the textile caused by solar radiation, thereby maintaining the coolness of the textile for a long time. Therefore, designing a sustainable cool nanofiber membrane has important value in regulating the microclimate of the human body and improving outdoor thermal comfort.

[0003] The sustainable cooling function relies on the support of the high-efficiency thermal conductivity of the material. Chinese invention patents CN116061525A and CN112458563A disclose radiation cooling textile materials with high thermal conductivity by doping thermally conductive fillers in a polymer matrix with low intrinsic thermal conductivity to improve the thermal conductivity of the composite fiber. This strategy relies on a high filler content to build an effective heat conduction path, resulting in low overall thermal conductivity. However, a high filler content can deteriorate the processing performance of the composite fiber and significantly reduce its mechanical properties. Optimizing the filler configuration to build an efficient thermal conduction network in the polymer matrix is crucial for enhancing the thermal conductivity of the composite material, which requires strict selection of thermally conductive materials and careful design of the preparation process to build an efficient thermal conduction network structure (see literature: Chem. Soc. Rev. , 2016, 45 , 3989). Therefore, there is an urgent need for a simple process, high-performance radiation cooling material and processing method to provide textiles with sustainable cooling function. SUMMARY

[0004] The present application provides a sustainable cool nanofiber membrane and a preparation method thereof, which has a simple preparation process and a sustainable cool feeling. The sustainable cooling process does not consume energy and is automatic.

[0005] Janus thermally conductive structure prepared by electrospinning and spraying process can sustain cool nanofiber membrane. The design idea of Janus thermally conductive structure on both sides of the fiber membrane is adopted to build the heterogeneous thermal conductivity of the fiber membrane inside and outside; the low thermal conductivity of the outside side blocks the external heat conduction to the inside; the high thermal conductivity of the inside side can make the skin heat quickly transmit along the surface, has the instantaneous cool performance, and the internal heat is selectively emitted to the outer space in the form of thermal radiation, so that the double control of heat source and heat conduction path is realized. In addition, the nanofiber membrane applying the radiation refrigeration technology can reach 96.4% in solar reflectivity, and has 96.7% of infrared emissivity in the 8-13 micrometer band, so as to slow down the temperature rise of the fiber membrane and sustain the cool feeling. Compared with the single-side weft flat needle cotton fabric, the contact instantaneous cool performance Q max of the nanofiber membrane is twice that of the former. Compared with the fiber membrane without spraying process finishing, the nanofiber membrane with sustainable cool feeling can realize the cool feeling effect of 4.3℃ at most under the condition of 620 W / m 2 of solar irradiation intensity and 36℃ of heating source, and can provide the cool feeling performance for 10 hours in the daytime.

[0006] The technical scheme for realizing the purpose of the application provides a preparation method of a nanofiber membrane with sustainable cool feeling, comprising the following steps:

[0007] (1) The radiation refrigeration polymer is added to the mixed solvent, the radiation refrigeration polymer comprises cellulose acetate and polyethylene oxide in a mass ratio of 10:1-10:6, the mixed solvent comprises acetone and N,N-dimethylformamide in a mass ratio of 1:1-1:9, and the mass ratio of the radiation refrigeration polymer to the mixed solvent is 1:5.6-1:9; the radiation refrigeration polymer is completely dissolved under the condition of magnetic stirring to obtain a spinning solution;

[0008] (2) The spinning solution obtained in the step (1) is subjected to an electrospinning process to obtain a radiation refrigeration nanofiber membrane on a receiving plate;

[0009] (3) The cool nanomaterial is dispersed in a mixed solution, the mass ratio of the cool nanomaterial to the mixed solution is 1:70-1:100; the cool nanomaterial is boron nitride nanoparticles, and the mixed solution comprises N,N-dimethylformamide and isopropyl alcohol in a mass ratio of 10:2-10:4; the cool nanomaterial is uniformly dispersed by ultrasonic treatment to obtain a dispersion liquid;

[0010] (4) The dispersion liquid obtained in the step (3) is sprayed on one side surface of the radiation refrigeration nanofiber membrane by a spraying process to obtain a nanofiber membrane with sustainable cool feeling.

[0011] The preparation method of the sustainable cool nanofiber film comprises the following steps: adding boron nitride, isopropyl alcohol and ball milling beads in a mass ratio of 1:30-60:5-20 into a ball milling tank for ball milling treatment to obtain a dispersion liquid, and then performing ultrasonic treatment, centrifugal treatment and vacuum drying treatment to obtain boron nitride nanoparticles.

[0012] The process conditions of the electrospinning are as follows: the inner diameter of the spinning nozzle is 0.42-0.84 mm, the advancing speed of the injector 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 DEG C, and the humidity is 40-45%; the process conditions of the spraying are as follows: the advancing speed of the injector of the spraying gun is 2.5-5 ml / min, and the spraying amount is 0.05-0.1 ml / cm 2 .

[0013] The technical scheme further comprises a sustainable cool nanofiber film obtained by the preparation method.

[0014] The sustainable cool nanofiber film has a diameter of 200-600 nm, an instantaneous cool feeling performance Q max value of 0.164-0.270, an average solar reflectivity of 85.7%-96.4%, and an infrared emissivity in the range of 8-13 microns of 76.8-96.7.

[0015] Compared with single-side weft plain cotton fabric, the sustainable cool nanofiber film has an instantaneous cool feeling performance Q max value of twice that of the former; compared with the fiber film without the spraying process finishing, the sustainable cool nanofiber film can achieve a cool feeling effect of 4.3 DEG C at most in the presence of 620 W / m 2 solar irradiation intensity and a 36 DEG C heating source, and can continuously provide cool feeling performance for 10 hours in the daytime.

[0016] The application proposes a construction idea combining two strategies of screening of heat-conducting materials and careful design of preparation process, to obtain a sustainable cool nanofiber membrane, and the invention principle is that: the high aspect ratio of the flaky filler helps to form phonon heat conduction channels when the fillers are overlapped, thereby improving the heat conduction efficiency. Boron nitride nanosheet (BNNS) is a two-dimensional flaky material with high aspect ratio, and its thermal conductivity is as high as 600 W / (m*K), which shows the potential as an ideal heat-conducting filler. The application realizes the effective loading of the filler on the polymer interface by using a spraying process, and easily realizes the design of the Janus heat-conducting structure on both sides of the fiber membrane. At the same time, this non-internal type of heat-conducting finishing method effectively prevents the external heat from being conducted to the inside by relying on the low thermal conductivity of the polymer on the external environment side, thereby reducing the input of external heat. By using the spraying process to construct an in-plane continuous heat-conduction network on the fiber membrane (skin side) interface, the boron nitride nanosheet (BNNS) with high aspect ratio is closely connected between each other to form a directional phonon heat conduction channel. This structural feature realizes the continuous heat-conduction network of the composite material in the in-plane direction, greatly improves the utilization efficiency of the filler, and endows the fiber membrane with instantaneous cool performance, and the cool performance Q max value of the nanofiber membrane can reach 0.270.

[0017] Compared with the modern technology, the application has the beneficial effects that:

[0018] 1. The application uses radiation cooling polymers cellulose acetate, polyethylene oxide and cool nanomaterial boron nitride as raw materials, and uses an electrospinning process to prepare a radiation cooling fiber membrane with high efficiency of solar reflection and infrared emission performance, and then uses a spraying method to uniformly load the cool nanomaterial on the radiation cooling fiber membrane. The nanofiber membrane has radiation cooling and cool functions, and a sustainable cool nanofiber membrane is obtained.

[0019] 2. The application provides a preparation method of a sustainable cool nanofiber membrane, and the preparation process is simple, and no energy is consumed in the sustainable cool process, and the cool function is automatic. DETAILED DESCRIPTION

[0020] Figure 1 The electron microscope graph of the sustainable cool nanofiber membrane prepared in Example 1 of the application, (a) is the SEM graph of one side of the nanofiber membrane without spraying boron nitride, and (b) is the SEM graph of one side of the nanofiber membrane sprayed with boron nitride.

[0021] Figure 2 The reflectivity curve graph of the sustainable cool nanofiber membrane prepared in Example 1 of the application to different wave bands of sunlight.

[0022] Figure 3 The mid-infrared emissivity of the sustainable cool nanofiber membrane prepared in Example 1 of the application.

[0023] Figure 4 Instantaneous sensory performance Q of single-sided weft flat needle cotton fabric and the sustainable cool nanofiber membrane prepared in Example 1 max The contrast chart of the values. DETAILED DESCRIPTION

[0024] The technical solutions of the present application will be further described below in combination with the drawings and examples. Example 1

[0025] 1 g of cellulose acetate, 0.1 g of polyethylene oxide, and a mixed solvent of acetone and N,N-dimethylformamide (mass ratio 1:1) were added, the mass ratio of polymer to solvent was 1:9, and the polymer was completely dissolved by magnetic stirring at room temperature for 3 h to obtain a spinning solution;

[0026] The spinning solution was sucked into a 5 ml syringe 1 and fixed on a push pump for electrospinning. A spinning nozzle with a diameter of 0.84 mm was used, the push speed of the syringe was set to 0.5 ml / h, the receiving distance was 10 cm, and the spinning was carried out under the conditions of voltage 10 kV, temperature 25 ℃, and humidity 40%. With the volatilization of the solvent, a radiative cooling nanofiber membrane was obtained on the receiving plate.

[0027] 1 g of boron nitride, isopropyl alcohol, and ball milling beads (mass ratio 1:30:5) were added together into a ball milling tank, and ball milling was carried out at 400 rpm for 2 h. Then, the dispersion was ultrasonically treated for 1 h, followed by centrifugation at 3000 rpm for 10 min, taking the supernatant, and centrifugation at 10000 rpm for 30 min, and placing in a vacuum oven at 60 ℃ for drying for 12 h.

[0028] 0.1 g of dried boron nitride was dispersed in a mixed solution of N,N-dimethylformamide and isopropyl alcohol (mass ratio 10:2), and the mass ratio of cool nanomaterial to mixed solvent was 1:100. The nanomaterial was uniformly dispersed by ultrasonic treatment for 0.5 h to obtain a dispersion.

[0029] The dispersion was sucked into a 2 ml spray gun, and the push speed of the syringe was set to 2.5 ml / min for spraying on one side of the surface of the radiative cooling nanofiber membrane, and the spraying amount was 0.02 ml / cm 2 , to obtain a sustainable cool nanofiber membrane.

[0030] Referring to the drawings Figure 1, (a) is an SEM image of the radiation refrigeration nanofiber film prepared in the embodiment, and it can be seen that nanofibers with a diameter of 300 nm to 600 nm are successfully prepared by electrospinning; (b) is an SEM image of the side of the nanofiber film prepared in the embodiment sprayed with boron nitride, and it can be seen that the boron nitride is uniformly distributed on the fiber film and stacked with each other by the spraying process.

[0031] Referring to the accompanying drawings Figure 2 The reflectivity of the sustainable cool nanofiber film prepared in the embodiment to different wave bands of sunlight is 96.4%.

[0032] Referring to the accompanying drawings Figure 3 The infrared emissivity of the sustainable cool nanofiber film prepared in the embodiment is 96.7% in the range of 8 to 13 microns.

[0033] Referring to the accompanying drawings Figure 4 The Q max value of the single-side weft flat needle cotton fabric and the sustainable cool nanofiber film prepared in the embodiment is compared in the graph; it can be seen from the graph that Figure 4 the Q max value of the single-side weft flat needle cotton fabric is 0.135, and the Q max value of the sustainable cool nanofiber film is 0.270. Embodiment 2

[0034] 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 1:3), and the mass ratio of the polymer to the solvent was 1:7.5. The polymer was completely dissolved by magnetic stirring at room temperature for 4 h, and a spinning solution was obtained;

[0035] The spinning solution was sucked into a 5 ml syringe 1, and electrospinning was performed by fixing it on a push pump. A spinning nozzle with a diameter of 0.84 mm was used, the push speed of the syringe was set to 1 ml / h, the receiving distance was 12 cm, and the spinning was performed under the conditions of a voltage of 15 kV, a temperature of 25°C, and a humidity of 45%. As the solvent volatilized, a radiation refrigeration nanofiber film was obtained on the receiving plate.

[0036] 2 g of boron nitride, isopropyl alcohol and ball milling beads (mass ratio 1:40:10) were added to a ball milling tank, and ball milling was performed at 400 rpm for 5 h. Then, the dispersion was ultrasonically treated for 2 h, followed by centrifugation at a speed of 3000 rpm for 10 min, and the upper clear liquid was taken and centrifuged at a speed of 10000 rpm for 30 min, and then placed in a vacuum oven at 60°C for drying for 12 h.

[0037] Take the dried boron nitride 0.1 g dispersed in N,N-dimethylformamide and isopropanol (mass ratio 10:2.5) mixed solution, cold nanometer material and mixed solvent mass ratio is 1:85. Ultrasonic 0.5 h until the nanometer material is uniformly dispersed, to get the dispersion.

[0038] The dispersion is sucked into 5 ml to the spray gun, the injection speed of the injector is set to 3 ml / min, and the surface of the radiation cooling nanofiber membrane is sprayed, and the spraying amount is 0.05ml / cm 2 Sustainable cooling nanofiber membrane is obtained. Example 3

[0039] 1 g of cellulose acetate, 0.4 g of polyethylene oxide is added to the mixed solvent of acetone and N,N-dimethylformamide (mass ratio 1:6), the mass ratio of polymer to solvent is 1:6.5, and the polymer is completely dissolved by magnetic stirrer at room temperature for 4 h, to get the spinning solution;

[0040] The spinning solution is sucked into 5 ml to the injector 1, and is fixed on the push pump for electrospinning. The spinning nozzle with a diameter of 0.42 mm is used, the injection speed of the injector is set to 1.2 ml / h, the receiving distance is 15 cm, and the spinning is carried out under the conditions of voltage 18 kV, temperature 30℃, humidity 40%. With the volatilization of the solvent, the radiation cooling nanofiber membrane is obtained on the receiving plate.

[0041] 3 g of boron nitride, isopropanol and ball milling beads (mass ratio 1:50:15) are added to the ball milling tank, and ball milling is carried out at 400 rpm for 8 h; then, the dispersion is ultrasonic for 3 h, followed by centrifugation at 3000 rpm for 10 min, taking the supernatant, centrifugation at 10000 rpm for 30 min, and placing in 60℃ vacuum oven for drying for 12 h.

[0042] Take the dried boron nitride 0.1 g dispersed in N,N-dimethylformamide and isopropanol (mass ratio 10:3) mixed solution, cold nanometer material and mixed solvent mass ratio is 1:75. Ultrasonic 0.5 h until the nanometer material is uniformly dispersed, to get the dispersion.

[0043] The dispersion is sucked into 8 ml to the spray gun, the injection speed of the injector is set to 3 ml / min, and the surface of the radiation cooling nanofiber membrane is sprayed, and the spraying amount is 0.08ml / cm 2 Sustainable cooling nanofiber membrane is obtained. Example 4

[0044] 1 g of cellulose acetate, 0.6 g of polyethylene oxide added to a mixed solvent of acetone and N, N-dimethylformamide (mass ratio 1:1), the mass ratio of polymer to solvent was 1:5.6, stirred by a magnetic stirrer at room temperature for 5 h, and the polymer was completely dissolved to obtain a spinning solution;

[0045] The spinning solution was sucked into a 5 ml syringe 1 and fixed on a push pump for electrospinning. A spinning nozzle with a diameter of 0.42 mm was used, the push speed of the syringe was set to 1.5 ml / h, the receiving distance was 20 cm, and the spinning was carried out under the conditions of voltage 25 kV, temperature 30℃, humidity 40%. With the volatilization of the solvent, the radiative cooling nanofiber membrane was obtained on the receiving plate.

[0046] 4 g of boron nitride, isopropyl alcohol and ball milling beads (mass ratio 1:60:20) were added to a ball milling tank, and ball milling was carried out at 400 rpm for 12 h; the dispersion was ultrasonically treated for 4 h, centrifuged at 3000 rpm for 10 min, the upper clear liquid was taken, centrifuged at 10000 rpm for 30 min, and placed in a vacuum oven at 60℃ for drying for 12 h.

[0047] 0.1 g of dried boron nitride was dispersed in a mixed solution of N, N-dimethylformamide and isopropyl alcohol (mass ratio 10:4), the mass ratio of cold-sensing nanomaterial to mixed solvent was 1:70. Ultrasonic treatment for 1 h until the nanomaterial was uniformly dispersed to obtain a dispersion.

[0048] The dispersion was sucked into a 10 ml spray gun, the push speed of the syringe was set to 5 ml / min, and the radiative cooling nanofiber membrane was sprayed on one side of the surface, the spraying amount was 0.1 ml / cm 2 , and a sustainable cold-sensing nanofiber membrane was obtained.

Claims

1. A method of preparing a sustainable cold-feeling nanofiber membrane, characterized by It comprises the following steps: (1) adding a radiation cooling polymer into a mixed solvent, the radiation cooling polymer comprising cellulose acetate and polyethylene oxide in a molar ratio of 10:1-10:6, the mixed solvent comprising acetone and N,N-dimethylformamide in a mass ratio of 1:1-1:9, the mass ratio of the radiation cooling polymer to the mixed solvent being 1:5.6-1:9, and magnetically stirring until the radiation cooling polymer is completely dissolved to obtain a spinning solution; (2) obtaining a radiation cooling nanofiber membrane on a receiving plate by using an electrostatic spinning process on the spinning solution obtained in step (1); (3) dispersing a cold-sensing nanomaterial in a mixed solution, the mass ratio of the cold-sensing nanomaterial to the mixed solution being 1:70-1:100, the cold-sensing nanomaterial being boron nitride nanoparticles, and the mixed solution comprising N,N-dimethylformamide and isopropanol in a mass ratio of 10:2-10:4; ultrasonic treatment is performed until the cold-sensing nanomaterial is uniformly dispersed to obtain a dispersion liquid; (4) spraying the dispersion liquid obtained in step (3) on one side of the radiation cooling nanofiber membrane by using a spraying process to obtain a sustainable cold-sensing nanofiber membrane.

2. The method of claim 1, wherein: The boron nitride, isopropanol and ball milling beads are added into a ball milling tank in a mass ratio of 1:30-60:5-20 for ball milling treatment to obtain a dispersion liquid, and then the dispersion liquid is subjected to ultrasonic treatment, centrifugal treatment and vacuum drying treatment to obtain boron nitride nanoparticles.

3. The method of claim 1, wherein the method is characterized by: The process conditions of the electrostatic spinning are as follows: the inner diameter of a spinning nozzle is 0.42-0.84 mm, the injection speed of a 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 ℃, and the humidity is 40-45%.

4. The method of claim 1, wherein the method is characterized by: The process conditions for the spraying are that the injection speed of the spray gun injector is 2.5 ~ 5 ml / min, and the spraying amount is 0.05 ~ 0.1 ml / cm 2 .

5. A sustainable cold-sensing nanofiber membrane prepared by the method according to claim 1.

6. The sustainable cold-feeling nanofiber membrane according to claim 5, characterized in that: The diameter of the nanofiber is 200-600 nm; the contact instant olfactory performance Q of the nanofiber membrane is 0.164-0.270 max The average solar reflectivity 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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