Self-assembled forming high-efficiency radiation refrigeration fabric and preparation method thereof

Abstract

The application discloses a self-assembled forming high-efficiency radiation refrigeration fabric and a preparation method thereof. The high-efficiency radiation refrigeration fabric is obtained by introducing calcium vanadinite nanoparticles as inorganic fillers into a polymer matrix by using a sol-gel solution spinning technology, wherein the polymer matrix is formed by polymerization of polyvinyl butyral and polydimethylsilane. The preparation method directly integrates the radiation cooling technology into various applications through the hierarchical multi-level design of the random distribution and the synergistic scattering of the soft fiber and the hard skeleton fiber fabric design. The preparation process is simple, easy to operate, low in preparation cost, high in efficiency and easy for industrialized production. The prepared layered fabric microfiber structure can be cut into any required shape. Moreover, the layered fabric microfiber structure has good radiation refrigeration, flexibility, self-cleaning and mechanical properties, is suitable for various application scenarios and solves the problems of poor radiation refrigeration efficiency, poor cleaning capacity, complex process and application limitation of the existing radiation refrigeration.

Description

Technical Field

[0001] This invention relates to a self-assembled, high-efficiency radiation-cooling fabric and its preparation method, belonging to the field of radiation-cooling materials technology. Background Technology

[0002] Energy consumption and carbon emissions continue to fuel global warming, and prolonged exposure to hot outdoor environments significantly increases the risk of heat stress-related illnesses. Personal thermal management (PTM) technology can control the microclimate of the human body, effectively promoting thermal comfort. However, current PTM designs offer limited cooling in high-temperature environments, and the problem of heat exposure remains unresolved. Furthermore, achieving low-energy production and high economic efficiency simultaneously remains a significant challenge. For outdoor radiative cooling, the most effective method currently is to maximize the reflectivity of fabrics in the solar radiation band, requiring the blocking of sunlight (distributed in the visible and near-infrared range of 0.25–2.5 μm, with a total power density of approximately 1000 W / m²). 2 The energy input of the clothing prevents the surface temperature from rising and consequently increasing the body temperature. Simultaneously, the atmospheric transparency spectral window (ATSW; L~8~13μm) is a promising cooling method to overcome these obstacles. Radiative cooling fibers utilize outer space (approximately 3K) as a natural radiator, radiating heat generated by the Earth's temperature (approximately 300K) into outer space through atmospheric windows (8-13μm), achieving a cooling effect through the synergistic effect of reflection and radiation. Compared to active cooling, this completely passive radiative cooling method requires neither thermal nor electrical energy, reducing electrical energy consumption. The heat radiation from the material continuously flows outward through the window, requiring no external energy input, aligning with China's green development goals and possessing broader application prospects. It is a highly efficient, energy-saving, and environmentally friendly new method. However, existing structures (such as membranes, coatings, and paints) suffer from poor moisture permeability and abrasion resistance at the gas-liquid interface, limiting their application in PTM (partial thermal cooling). Therefore, clothing, as a crucial medium connecting the human body to the external environment, can effectively play a role in daytime heat dissipation.

[0003] In summary, radiation-cooled fabric technology is an innovative technique that utilizes the optical properties of materials to reduce temperature through radiation and reflection. While this technology holds great potential, several challenges remain to be addressed:

[0004] (1) Material selection and cost: High-efficiency radiation cooling materials usually require special nanostructures and composite materials, which are expensive to manufacture and difficult to achieve large-scale commercial production.

[0005] (2) Scope of application and effect: The effect of radiation cooling may vary under different environmental and climatic conditions. How to make it effective in various environments is an important research direction.

[0006] (3) Manufacturing process: Maintaining the uniformity and consistency of radiation cooling materials during large-scale production is a technical challenge that requires improvements in production processes and technologies.

[0007] Solving these problems will help promote the widespread application of radiation-cooled fabric technology, resulting in more significant energy-saving effects. Summary of the Invention

[0008] Objectives of the invention: The first objective of this invention is to provide a self-assembled, high-efficiency radiation cooling fabric; the second objective of this invention is to provide a method for preparing the self-assembled, high-efficiency radiation cooling fabric.

[0009] Technical solution: The present invention discloses a self-assembled high-efficiency radiation cooling fabric, wherein the high-efficiency radiation cooling fabric is obtained by introducing calcium vanadium nanoparticles as inorganic fillers into a polymer matrix using sol-gel solution spinning technology, and the polymer matrix is ​​polymerized from polyvinyl butyral and polydimethylsilane.

[0010] The method for preparing the self-assembled high-efficiency radiation cooling fabric of the present invention includes the following steps:

[0011] (1) Dissolve calcium hydroxide and aluminum sulfate in water, adjust the pH to fully hydrate them, and obtain calcium vanadium granules (AFt);

[0012] (2) Dissolve polyvinyl butyral (PVB) in ethanol to obtain a polyvinyl butyral ethanol solution, add calcium vanadium particles and polydimethylsilane (PDMS), stir thoroughly to obtain a spinning precursor solution.

[0013] (3) The spinning precursor solution is fed into an air-jet spinning machine and blown with compressed air-assisted microcurrent to form high-efficiency radiation cooling fiber. The high-efficiency radiation cooling fiber is collected with a polytetrafluoroethylene (PTFE) membrane to obtain a high-efficiency radiation cooling fabric.

[0014] Further, in step (1), the molar ratio of calcium hydroxide to aluminum sulfate is 4-8:1, preferably 6:1, and Na(OH)2 is added to adjust the pH to 11.

[0015] Furthermore, in step (1), the particle size of the calcium vanadate particles is 0.3-2 μm.

[0016] Furthermore, in step (2), the mass ratio of calcium vanadate particles, polydimethylsilane and polyvinyl butyral is 1-6:4:4, preferably 6:4:4.

[0017] Furthermore, in step (2), the concentration of the polyvinyl butyral ethanol solution is 6-30 wt%.

[0018] Furthermore, in step (2), polyvinyl butyral (PVB) is dissolved in ethanol at 40-100°C.

[0019] Furthermore, in step (3), the flow rate of the spinning precursor solution into the air-jet spinning machine is 5-80 mL·h. -1 .

[0020] Furthermore, in step (3), the compressed air pressure is above 0.64 MPa.

[0021] Furthermore, in step (3), the voltage obtained from the microcurrent is approximately 0.01-0.1 kV.

[0022] Furthermore, in step (3), the moving speed of the high-efficiency radiation cooling fiber collected by the polytetrafluoroethylene (PTFE) membrane is 5-100 mm / min.

[0023] Furthermore, in step (3), when collecting the high-efficiency radiation cooling fiber with a polytetrafluoroethylene (PTFE) membrane, it is collected at a distance of 20-80 cm from the nozzle of the air-jet spinning machine.

[0024] Furthermore, in step (3), the diameter of the high-efficiency radiation cooling fiber is 0.2-2 μm.

[0025] Furthermore, in step (3), the thickness of the radiation cooling fabric is 0.01-3 mm.

[0026] This invention relates to a highly efficient radiation-cooling fabric, obtained by introducing calcium vanadium nanoparticles as inorganic fillers into a polymer matrix using sol-gel solution spinning technology. The polymer matrix is ​​composed of polyvinyl butyral and polydimethylsilane. The preparation method of this invention is simple, easy to operate, low in cost, and highly efficient, making it suitable for industrial production. The prepared layered fabric is composed of microfibers and can be cut into any desired shape. It also possesses excellent radiation cooling, flexibility, self-cleaning properties, and mechanical properties, making it suitable for various applications and solving the problems of poor efficiency, poor cleaning ability, complex processes, and limited applications in existing radiation cooling methods. This invention effectively reduces the preparation process and cost, is simple, and directly integrates radiation cooling technology into various applications through a multi-layered, multi-level random distribution design and a fiber fabric design with synergistic scattering of soft fibers and a rigid skeleton. It designs a multi-layered fabric of self-assembled composite micro / nano fibers. Simultaneously, the fabric effectively exhibits color-compatible radiation cooling, provides necessary breathability, self-cleaning properties, and robust mechanical properties, and is more easily compatible with commercial fabrics. Supported by comprehensive analysis of heat transfer between practical applications and the environment, selective spectral design for textiles introduces an innovative and effective solution for passive cooling in order to combat the urban heat island effect, and also opens up horizons for future applications of radiative cooling fabrics.

[0027] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages:

[0028] (1) This method uses a small amount of raw materials, has a simple mixing ratio, and is widely available. It is also simple to operate and easy to apply in practice.

[0029] (2) The molding process of this method adopts air spinning and electrospinning in synergy, which maintains the characteristics of fiber molding rate and good dispersion.

[0030] (3) This method is economical to produce fabrics with the highest reflectivity and emissivity in the industry, and has an effective cooling effect.

[0031] (4) The fabric formed by this method is superhydrophobic and can achieve self-cleaning. Attached Figure Description

[0032] Figure 1 The image shows the molding effect of the radiation-cooling fabric prepared in Example 1.

[0033] Figure 2 The reflectance and emissivity diagrams are for the radiation-cooled fabric prepared in Example 1.

[0034] Figure 3 The contact angle diagram of the radiation-cooled fabric prepared in Example 1;

[0035] Figure 4 The mechanical properties of the radiation-cooled fabric prepared in Example 1 are shown in the diagram.

[0036] Figure 5 The afternoon temperature change curve of the radiation-cooled fabric prepared in Example 1;

[0037] Figure 6 Scanning electron microscope images of the radiation-cooled fabrics prepared in Example 1 and Comparative Example 1;

[0038] Figure 7 Scattering simulation diagrams for different fiber diameters at different wavelengths;

[0039] Figure 8 The diagram shows the refractive index and extinction coefficient of pervanadium.

[0040] Figure 9 Reflectance diagrams for different calcium vanadate solid contents. Detailed Implementation

[0041] The technical solution of the present invention will be further described below with reference to the accompanying drawings.

[0042] The following materials were used in the experiment: polyvinyl butyral (Aladdin), calcium hydroxide (analytical grade, Sinopharm), aluminum sulfate octahydrate (analytical grade, Sinopharm), polydimethylsilane (Aladdin), and polytetrafluoroethylene membrane (Longfa Materials Co., Ltd., 50 micrometers thick).

[0043] The air-jet spinning machine (X100AHC air-jet spinning platform) was provided by Xianning Youwei Co., Ltd.

[0044] Reflectivity was measured using a Lambda 750s (PerkinElmer, USA) integrating sphere. A high-reflectivity barium sulfate (BaSO4) pellet was used as the test background, and the test wavelength λ ranged from 0.2 to 2.5 μm.

[0045] The actual cooling effect of the fabric is measured using a TP700 multi-channel data logger, with the thermocouple tightly attached to the inside of the material.

[0046] The surface properties of fibers were studied using a fully automated video micro-contact angle measuring instrument, model JJY-82BKruss DSA. Under 25°C conditions, the contact angle (CA) of samples was measured using a static drop technique on a solid surface. The measurement range was from 0 to 180°, with an angle measurement error of ±0.5°. Fibers were spun onto a glass slide, and then water droplets were added to the slide. The hydrophobic angle was observed using an adjustable backlight plane parallel light source.

[0047] Example 1

[0048] (1) Add 0.2223g of calcium hydroxide and 0.3332g of aluminum sulfate octahydrate in a molar ratio of 6:1 to 50mL of water to dissolve. Add Na(OH)2 to adjust the pH to 11. Stir thoroughly to fully hydrate the precipitate. Filter the precipitate and grind it with a ball mill to obtain calcium vanadium (AFt) particles with an average particle size of 0.6μm.

[0049] (2) PVB is dissolved in ethanol at 40°C to prepare a PVB ethanol solution with a PVB concentration of 9wt%. Then, Aft particles and PDMS are added. The mass ratio of Aft:PDMS:PVB is 6:4:4. The mixture is stirred with magnetic force to make a white spinning precursor solution.

[0050] (3) Use a peristaltic pump at a rate of 40 mL·h -1 The propulsion speed drives the spinning precursor solution into the air-jet spinning machine. Compressed air is used at a gas pressure of ~0.64 MPa, assisted by a microcurrent of 0.01 kV to blow fibers (fiber diameter 0.2 μm-2 μm). The fibers are collected using a PTFE membrane at a moving speed of 50 mm / min at a distance of approximately 50 cm from the nozzle of the air-jet spinning machine. Figure 1 A 1.5 x 10 meter radiation-cooling fabric with a thickness of 3 mm was obtained through an industrial molding process.

[0051] The prepared radiation-cooled fabric was cut into target shapes of 5cm x 5cm. Its reflectance and emissivity were measured using a UV-Vis-NIR spectrophotometer (PerkinElmer, USA) and a Fourier transform infrared spectrometer (Nicolet IS50, Thermo Fisher Scientific, USA). The testing procedure was referenced from Shaoning Z, Sijie P, Minyu S, et al. Hierarchical-morphology metafabric for scalable passive daytimeradiative cooling.[J]. Science (New York, NY), 2021, 373(6555):692-696. The results are as follows. Figure 2 As shown.

[0052] Figure 2 The image shows the reflectance and emissivity of the radiation-cooled fabric prepared in Example 1. The reference background was high-reflectivity barium sulfate (BaSO4), and the test wavelength λ ranged from 200 to 2500 nm. Figure 2 The data was calculated using Matlab interpolation, and the total reflectivity was 98.8% and the total emissivity was 98.6%, making it the best performing comprehensive radiation cooling fabric in the industry to date.

[0053] The surface properties of fibers were studied using a fully automated video micro-contact angle measuring instrument, model JJY-82BKruss DSA. At 25°C, the contact angle (CA) of the samples was measured using a static drop technique on the surface of a radiation-cooled fabric. The measurement range was from 0 to 180°, with an angle measurement error of ±0.5°. The fibers were spun onto a glass slide, and then water droplets were added to the radiation-cooled fabric sheet. The hydrophobic angle was observed using an adjustable backlight plane parallel light source. The results are as follows: Figure 3 As shown. By Figure 3 As can be seen, the contact angle of the radiation-cooled fabric prepared in this embodiment is 162.4°, indicating that water droplets can gradually remove dust from the material surface.

[0054] The test sample of the radiation-cooled fabric was clamped at both ends onto the upper and lower grips of a multifunctional electronic fabric tensile tester, with a spacing of 10 cm. The sample was stretched until it broke under stress. The same method was used to test reference samples (aluminum foil, cotton, and linen) one by one to obtain the breaking strength and elongation at break of different fabrics. The results are as follows: Figure 4 As shown. By Figure 4 It can be seen that the tensile strength of the radiation cooling fabric prepared in this embodiment is comparable to that of commercial fabrics.

[0055] Comparative Example 1

[0056] The preparation of the radiation-cooled fabric is the same as in Example 1, except that in step (3), the multi-axis needle of the air-jet spinning machine is connected to a peristaltic pump and inserted into the solution tank, and the peristaltic pump is used to spray the solution at a rate of 40 mL·h. -1 The propulsion speed drives the spinning precursor solution into the spinning machine. Fibers (0.2μm-2μm in diameter) are blown using only compressed air at a gas pressure of ~0.64 MPa, and collected at a moving speed of 50 mm / min using a PTFE membrane at a distance of approximately 50 cm from the nozzle of the air-jet spinning machine. A radiation-cooled fabric with a thickness of 3 mm is obtained.

[0057] Cooling effect test using TP700 multi-channel data logger: The TP700 multi-channel data logger body is constructed of low thermal conductivity polystyrene foam (EPS), with a high-reflectivity aluminum foil layered on the exterior to reduce heating from external light. An aerogel felt and aluminum foil are placed beneath the fiber layer to ensure insulation, thus negligible heat conduction and convection between the environment and the cooling fibers. The fiber surface is covered with a polyethylene (PE) film to reduce air convection and heat loss, focusing only on absorption of radiation from the sun and environment. The composite fiber is located on the polystyrene foam surface, with an opening area of ​​10cm × 15cm, and the cooling space is above the fiber. The experiment mainly measured and recorded the temperature of the back of the radiative cooling fiber and the ambient air. Results are as follows: Figure 5 As shown. Figure 5 The graphs show the afternoon temperature changes of the radiation-cooled fabrics prepared in Comparative Example 1 and Example 1, where (a) is a graph of the air-spun fibers in Comparative Example 1, and (b) is a graph of the air-spun and electrospun fibers in Example 1. Figure 5 As can be seen, by measuring the temperature difference between the radiation-cooling fabrics prepared in Example 1 and Comparative Example 1 and the ambient temperature, the radiation-cooling fabric prepared in Example 1 was at most 12.5°C lower than the ambient temperature during the test period, demonstrating a good radiation-cooling effect.

[0058] Scanning electron microscopy analysis was performed on the radiation-cooling fabric prepared in this comparative example and the radiation-cooling fabric prepared in Example 1. The results are as follows: Figure 6 As shown. Figure 6 Scanning electron microscope (SEM) images of the radiation-cooled fabrics prepared in Example 1 and Comparative Example 1, wherein (a) is the air-spun fiber of Comparative Example 1 and (b) is the fiber formed by a mixture of air spinning and electrospinning in Example 1. Figure 6 As can be seen, at the same magnification, compared with the simple air spinning of Comparative Example 1, Example 1 uses a mixture of air spinning and electrospinning to ensure good fiber dispersion and prevents the fibers from sticking together and forming coarse fibers, which would affect the scattering effect.

[0059] Example 2

[0060] The scattering of different fiber diameters at different wavelengths was simulated using FDTD software. The results... Figure 7 As shown. By Figure 7 It can be observed that the finer the fiber, the better the scattering effect of visible light. Figure 6 Correspondingly, this affects the overall reflection effect.

[0061] Example 3

[0062] The preparation process is the same as in Example 1, except that in step (2), the mass ratio of AFt:PDMS:PVB is 1:4:4, 1:1.5:1.5, 1:1:1, 1.6:1:1, and 1.7:1:1, respectively, and three groups of radiation cooling fabrics with a thickness of 3 mm are prepared. When the mass ratio of AFt:PDMS:PVB is 1.6:1:1, the content of ettringite is too high. When the mass ratio of AFt:PDMS:PVB is 1.7:1:1, the needle blockage phenomenon occurs during the spinning process, and the fibers are not formed, resulting in poor effect.

[0063] The refractive index and extinction coefficient of the calcium vanadate prepared in step (1) of Example 1 were tested, and the results are as follows: Figure 8 As shown. Figure 8 The refractive and extinction coefficients of vanadate are given by... Figure 8As can be seen, ettringite exhibits an extinction coefficient in the ultraviolet-visible-near-infrared range of 0.3μm-2.5μm, indicating almost no light absorption and thus a higher potential for increasing reflectivity. This is also why ettringite is used as a fiber filler.

[0064] The reflectance of the three groups of radiation-cooled fabrics prepared in this embodiment was compared with the reflectance obtained in Example 1. If... Figure 9 As shown. By Figure 9 It can be seen that the reflectances of AFt:PDMS:PVB at mass ratios of 1:4:4 (calcium vanadate solid content 20%), 1:1.5:1.5 (calcium vanadate solid content 40%), and 1:1:1 (calcium vanadate solid content 50%) are 94.52%, 95.12%, and 97.21%, respectively. In Example 1, the fabric has the highest reflectance of 98.8% when the mass ratio is 1.5:1:1 (calcium vanadate solid content 60%). That is, as the content of calcium vanadate increases, the comprehensive reflectance of the fabric in the ultraviolet-visible-mid-infrared range increases. This is because calcium vanadate has many hydroxyl groups, which are easy to combine with organic matter, thereby achieving multiple fillings of medium particles, improving the scattering effect, and thus achieving high reflectance.

[0065] Of course, the above description is not intended to limit the present invention, and the present invention is not limited to the examples given above. Any changes, modifications, additions or substitutions made by those skilled in the art within the scope of the present invention should also fall within the protection scope of the present invention.

Claims

1. A method for preparing a self-assembled, high-efficiency radiation-cooling fabric, characterized in that, Includes the following steps: (1) Dissolve calcium hydroxide and aluminum sulfate octadecahydrate in water, adjust the pH to fully hydrate them, filter, grind, and obtain calcium vanadium stone particles; (2) Dissolve polyvinyl butyral in ethanol to obtain a polyvinyl butyral ethanol solution, add calcium vanadium particles and polydimethylsilane, stir thoroughly to obtain a spinning precursor solution. The concentration of the polyvinyl butyral ethanol solution is 6-30 wt%, and the mass ratio of calcium vanadium particles, polydimethylsilane and polyvinyl butyral is 1-6:4:

4. (3) The spinning precursor solution is fed into an air-jet spinning machine and blown with compressed air-assisted microcurrent to form high-efficiency radiation-cooling fiber. The high-efficiency radiation-cooling fiber is collected with a PTFE membrane to obtain a high-efficiency radiation-cooling fabric.

2. The preparation method according to claim 1, characterized in that, In step (1), the molar ratio of calcium hydroxide to aluminum sulfate octadecahydrate is 4-8:1, and NaOH is added to adjust the pH to 11.

3. The preparation method according to claim 1, characterized in that, In step (2), polyvinyl butyral is dissolved in ethanol at 40-100℃.

4. The preparation method according to claim 1, characterized in that, In step (3), the flow rate of the spinning precursor solution into the air-jet spinning machine is 5-80 mL·h. −1 .

5. The preparation method according to claim 1, characterized in that, In step (3), the compressed air pressure is above 0.64 MPa.

6. The preparation method according to claim 1, characterized in that, In step (3), the voltage of the microcurrent is 0.01-0.1kV.

7. The preparation method according to claim 1, characterized in that, In step (3), the moving speed of the PTFE membrane for collecting the high-efficiency radiation cooling fiber is 5-100 mm / min. When collecting the high-efficiency radiation cooling fiber with the PTFE membrane, it is collected at a distance of 20-80 cm from the nozzle of the air-jet spinning machine.

8. The preparation method according to claim 1, characterized in that, In step (3), the diameter of the high-efficiency radiation cooling fiber is 0.2-2 μm and the thickness of the radiation cooling fabric is 0.01-3 mm.

9. A self-assembled, high-efficiency radiation-cooling fabric obtained by the preparation method according to any one of claims 1-8.

Images