A washable breathable type radiation refrigeration composite fabric and a preparation method thereof

Abstract

This invention discloses a washable and breathable radiation-cooling composite fabric and its two-step dip-coating preparation method. The first step involves nanoparticle adsorption: the fabric is immersed in an aqueous dispersion of alumina nanoparticles and heated to allow the nanoparticles to adsorb onto the fiber surface. After drying, the alumina composite fabric is obtained. The second step involves polymer coating: the alumina composite fabric is immersed in a mixed solution of polydimethylsiloxane / toluene. After dip-coating and drying curing, a thin layer of polydimethylsiloxane is formed on the fiber surface, resulting in the radiation-cooling composite fabric. This invention features a simple process, high stability, and ease of large-scale production, showing broad application prospects in outdoor personal thermal management and functional clothing.

Description

Technical Field

[0001] This invention relates to the field of functional textiles and passive radiative cooling technology, specifically to a radiative cooling composite fabric with washability, breathability and self-cleaning properties, and its two-step dip-coating preparation method. Background Technology

[0002] With global warming, human thermal comfort has become a challenge. Passive daytime radiative cooling technology achieves cooling by reflecting sunlight (0.3–2.5 μm) and emitting infrared radiation (8–13 μm) into outer space. However, existing radiative cooling fabrics face three major challenges: (1) poor wash fastness: functional particles are easily detached during mechanical washing, resulting in a significant decrease in cooling performance; (2) low wearing comfort: excessively thick polymer coatings often clog fabric pores, causing the fabric to lose its breathability; (3) complex manufacturing process: many high-performance designs rely on complex micro-nano processing, making it difficult to achieve low-cost large-scale mass production. Summary of the Invention

[0003] This invention discloses a radiation-cooling composite fabric with washability, breathability and self-cleaning properties and its two-step dip-coating preparation method, aiming to solve the problems of functional particles being easy to fall off and insufficient water resistance in existing radiation-cooling fabrics.

[0004] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: This invention provides a radiation-cooling composite fabric that combines washability, breathability, and self-cleaning properties. The composite fabric uses a fabric as a substrate. The coating consists of alumina (Al2O3) nanoparticles physically adsorbed on the surface of the fabric fibers and a thin layer of polydimethylsiloxane (PDMS) coating the surface of the particles and fibers.

[0005] Preferably, the alumina nanoparticles have a diameter of approximately 300 nm.

[0006] Preferably, the composite fabric has a solar reflectance of 94% in the 0.3-2.5 μm band and a long-wave infrared emissivity of 95% in the 8-13 μm atmospheric window band.

[0007] Preferably, after 30 standard washing cycles, the radiation-cooling composite fabric maintains a solar reflectivity of over 92% in the 0.3-2.5 μm band and a long-wave infrared emissivity of over 94% in the 8-13 μm atmospheric window band, and its optical and cooling performance retention rate still exceeds 90%.

[0008] Preferably, the composite fabric has an air permeability of 218.3 mm / s and a hydrophobic contact angle of 138°.

[0009] The present invention also provides a method for preparing the above-mentioned radiation-cooling composite fabric, comprising the following steps: Step (1) Nanoparticle adsorption: The fabric is immersed in an aqueous dispersion of alumina nanoparticles and wetted under heating conditions so that the alumina nanoparticles are adsorbed onto the fiber surface. After drying, the alumina composite fabric is obtained.

[0010] Step (2) Polymer coating: The alumina composite fabric obtained in step (1) is immersed in a polydimethylsiloxane (PDMS) / toluene mixed solution. After dip coating and drying curing, a thin layer of polydimethylsiloxane is formed on the fiber surface to obtain a radiation cooling composite fabric.

[0011] In step (1), the mass fraction of the alumina nanoparticle dispersion is 1-3%, preferably 1.8%, the ultrasonic dispersion time is 30 min, the wetting temperature is 65℃, the wetting time is 40 min, and the drying temperature is 60℃.

[0012] In step (2), the polydimethylsiloxane (PDMS) / toluene mixed solution is composed of PDMS prepolymer, curing agent and organic solvent, wherein the mass ratio of PDMS prepolymer to curing agent is 10:1, the organic solvent is toluene, and the mass fraction of PDMS is 2-15%, preferably 3%, the immersion time is 15 min, the drying and curing time is 40 min, and the curing temperature is 80℃.

[0013] Compared with the prior art, the present invention has the following beneficial effects: 1. The composite fabric of the present invention, through the construction of a hierarchical micro / nano structure, exhibits 94% reflectivity in the solar spectrum (0.3–2.5 μm) and 95% emissivity in the atmospheric window band (8–13 μm), with a wavelength of 910 W / m². 2 Radiation cooling of 8.5°C was achieved under irradiation.

[0014] 2. This invention employs a two-step dip-coating preparation method, using PDMS diluted with toluene to coat nanoparticles and fibers, firmly fixing alumina nanoparticles onto the fibers, so that the fabric can still maintain more than 90% of its radiative cooling performance after 30 standard washes, exhibiting good wash durability.

[0015] 3. The radiation cooling composite fabric of the present invention improves the cooling performance while retaining the pore structure between the original fabric fibers. The air permeability of the composite fabric is measured to be maintained at 218.3 mm / s (more than 90% of the original fabric), thus taking into account the wearing comfort.

[0016] 4. This invention utilizes the low surface energy characteristics of PDMS and the surface roughness generated by Al2O3 nanoparticles to give the fabric a static water contact angle of 138°, exhibiting good hydrophobic self-cleaning function, which is beneficial to improving the stability of the fabric in outdoor environments.

[0017] 5. The preparation process used in this invention is simple, highly stable, and easy to mass-produce, and has broad application prospects in the field of outdoor personal thermal management and functional clothing. Attached Figure Description

[0018] Figure 1 This is a scanning electron microscope image of the original fabric in Embodiment 1 of the present invention.

[0019] Figure 2 This is a scanning electron microscope image of a typical composite fabric with specific proportions in Example 1 of the present invention.

[0020] Figure 3 The image shows the reflectance curves of alumina composite fabrics obtained under different mass fractions of alumina nanoparticle dispersions in Example 2 of this invention.

[0021] Figure 4 The image shows a comparison of the solar reflectance of the radiation-cooled composite fabrics obtained under different PDMS / toluene mixed solution mass fractions in Example 2 of this invention in the 0.3–2.5 μm wavelength band.

[0022] Figure 5 The image shows the long-wave infrared emissivity spectrum of the radiation-cooled composite fabric obtained under different PDMS / toluene mixed solution mass fractions in Example 2 of this invention in the 8–13 μm atmospheric window band.

[0023] Figure 6 This is the outdoor radiative cooling performance testing device in Embodiment 2 of the present invention.

[0024] Figure 7 This is a temperature curve diagram of different radiation-cooled composite fabrics in Embodiment 2 of the present invention.

[0025] Figure 8 This is a graph showing the net cooling power curve of the typical ratio composite fabric in Example 2 of the present invention in outdoor testing.

[0026] Figure 9 This is a comparison chart of the reflectance of a typical composite fabric with specific proportions in Example 3 of the present invention before and after 30 standard washing cycles.

[0027] Figure 10 This is a comparison chart of the emissivity of the typical compound fabric in Example 3 of the present invention before and after 30 standard washing cycles.

[0028] Figure 11This is a comparison of the surface morphology of the typical composite fabric in Example 3 of the present invention before and after 30 standard washing cycles.

[0029] Figure 12 The figure shows the air permeability test results of a typical composite fabric in Example 4 of this invention.

[0030] Figure 13 This is a graph showing the hydrophobic angle test results of a typical composite fabric in Example 4 of the present invention. Detailed Implementation

[0031] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

[0032] This invention discloses a radiation-cooling composite fabric with washability, breathability, and self-cleaning properties, and its two-step dip-coating preparation method, aiming to solve the problems of easy detachment of functional particles and insufficient washability in existing radiation-cooling fabrics. First, the fabric is immersed in an aqueous dispersion of alumina nanoparticles (Al2O3, approximately 300 nm in diameter) at a mass fraction of approximately 1-3% for about 40 minutes at 65°C, allowing the particles to be fully adsorbed onto the fiber surface. Then, the fabric is immersed in a mixed solution of polydimethylsiloxane (PDMS) / toluene at a mass fraction of approximately 2-15%, followed by dip-coating and drying to form a PDMS thin layer, which coats and fixes the Al2O3 nanoparticles while maintaining the original porous structure of the fabric. The resulting composite fabric has a solar reflectance of 94% and a long-wave infrared emissivity of 95%, with a wavelength of 910 W / m². 2 Under solar irradiation, it can achieve radiative cooling of 8.5 °C, with an average net cooling power of 92.1 W / m². After 30 standard washes, its optical and cooling properties retain over 90%. Furthermore, the fabric maintains a high air permeability of 218.3 mm / s and possesses self-cleaning properties with a 138° hydrophobic contact angle. This invention features a simple process, high stability, and ease of large-scale production, showing broad application prospects in outdoor personal thermal management and functional clothing.

[0033] Example 1: Standard preparation and microstructure characterization of composite fabrics This embodiment provides a preparation process for composite fabrics with typical formulations, and the specific steps are as follows: Nanoparticle adsorption: A 1.8% (w / w) aqueous dispersion of alumina (Al2O3, approximately 300 nm in diameter) was prepared. The fabric was immersed in the dispersion and sonicated for 30 min, followed by immersion in a 65 °C water bath for 40 min, and then removed and dried at 60 °C.

[0034] Polymer coating: The above alumina composite fabric is immersed in a 3% (w / w) polydimethylsiloxane (PDMS) / toluene mixed solution for 15 min, removed and left to stand for 5 min, and then cured at 80 °C for 40 min to obtain the final radiation cooling composite fabric.

[0035] The microstructure of the fabric was observed using a scanning electron microscope. Figure 1 The original fabric fiber surface is smooth. Figure 2 In preparing the composite fabric with a typical ratio for this embodiment, it can be observed that the fiber surface is uniformly covered by Al2O3 nanoparticles, and the particles are coated with a thin PDMS film, forming a stable hierarchical micro / nano structure. This structure not only preserves the natural gaps between fibers, but also lays the structural foundation for subsequent optical performance and durability.

[0036] Example 2: Optical and Radiative Cooling Properties of Composite Fabrics This embodiment first investigated the solar reflectance of alumina composite fabrics obtained by treating aqueous dispersions of 1-3% (w / w) Al₂O₃ nanoparticles. Following the preparation method in the first step of Example 1, aqueous solutions of alumina nanoparticles with different (w / w) fractions were prepared to obtain alumina composite fabrics. The optical properties of the different alumina composite fabric samples were then characterized, such as… Figure 3 As shown.

[0037] This embodiment further investigated the reflectance and emissivity of alumina composite fabrics immersed in a 2-15% (w / w) polydimethylsiloxane (PDMS) / toluene mixed solution. Following the preparation method in step two of Example 1, a coating treatment was performed in the PDMS / toluene mixed solution to obtain the radiation-cooled composite fabric. The solar reflectance (0.3–2.5 μm) and long-wave infrared emissivity (8–13 μm) of the different radiation-cooled composite fabric samples were characterized.

[0038] (1) Changes in reflectivity: such as Figure 4 As shown, the solar reflectance of the fabric gradually decreases with increasing PDMS concentration. Especially when the concentration exceeds 5 wt%, the reflectance drops significantly due to the change in interfacial scattering conditions on the fiber surface caused by the thickening of the PDMS coating.

[0039] (2) Emissivity variation: such as Figure 5 As shown, with the increase of PDMS concentration, the long-wave infrared emissivity of the fabric in the atmospheric window band increases due to the increase in the vibration intensity of Si-O-Si molecular bonds.

[0040] In addition, this embodiment uses the following... Figure 6The outdoor radiative cooling performance testing device shown monitors the temperature change curve of the composite fabric in real time under natural sunlight irradiation (solar irradiance approximately 910 W / m²). The temperature test results are as follows: Figure 7 As shown, the composite fabric exhibits a surface temperature lower than the ambient temperature, with the maximum temperature drop of the typical composite fabric reaching 8.5 °C.

[0041] After comparing the temperatures of samples with different ratios, a typical composite fabric with a specific ratio was selected for refrigeration power testing. The net refrigeration power was determined using the feedback heating compensation method. The results are as follows: Figure 8 As shown, the average net cooling power of the composite fabric reaches 92.1 W / m².

[0042] Based on the combined results of reflectivity, emissivity, and radiative cooling performance, the sample corresponding to the aqueous dispersion of alumina nanoparticles with a mass fraction of 1.8% and the mixed solution of PDMS / toluene with a mass fraction of 3% exhibited better overall performance. Therefore, it was selected as a typical sample ratio for subsequent tests on washability, air permeability, and hydrophobicity.

[0043] Example 3: Verification of Washing Durability and Structural Stability This embodiment evaluates the long-term stability of a typical blend of composite fabrics using a standard household washing cycle.

[0044] Composite fabrics are placed in a washing tank for multiple cycles of washing. For example... Figure 9 and Figure 10 As shown, after 30 standard washing cycles, its solar reflectance remains at 92%, its long-wave infrared emissivity remains at 94%, and its optical and cooling performance retention rates both exceed 90%.

[0045] pass Figure 11 The electron microscopy images clearly show that, due to the PDMS coating effect, the alumina nanoparticles are still tightly attached to the surface of the washed fiber, and no obvious detachment phenomenon is observed, which proves that the composite coating prepared by the two-step dip-coating method of the present invention has extremely high mechanical stability.

[0046] Example 4: Wearing Comfort and Self-Cleaning Function Test This embodiment further demonstrates the practicality of typical ratio composite fabrics as wearable textiles.

[0047] Breathability: such as Figure 12 As shown, using the GB / T 5453 standard test, the air permeability of the composite fabric was measured to be 218.3 mm / s, maintaining more than 90% of the original fabric. This proves that the low-viscosity PDMS diluted with toluene only coats a single fiber and does not clog the original pores of the fabric, ensuring excellent air permeability.

[0048] Self-cleaning performance: Figure 13 The hydrophobicity test of the fabric was demonstrated. Due to the synergistic effect of the low surface energy of PDMS and the rough surface constructed by nanoparticles, the static water contact angle (WCA) of the composite fabric reached 138°. Droplets formed spherical shapes on the fabric surface and rolled off very easily, effectively removing dust and dirt, exhibiting significant self-cleaning and stain-repellent properties.

[0049] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural modifications made based on the description and drawings of the present invention, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A washable and breathable radiation-cooling composite fabric, characterized in that, The composite fabric uses fabric as a base, and the coating consists of alumina nanoparticles physically adsorbed on the surface of the fabric fibers and a thin layer of polydimethylsiloxane coating the surface of the particles and fibers.

2. The radiation-cooling composite fabric according to claim 1, characterized in that, The alumina nanoparticles have an average particle size of approximately 300 nm.

3. The radiation-cooling composite fabric according to claim 1, characterized in that, After undergoing 30 standard washing cycles, the composite fabric maintains a solar reflectance of over 92% in the 0.3-2.5 μm band and a long-wave infrared emissivity of over 94% in the 8-13 μm atmospheric window band, while retaining over 90% of its optical and cooling properties.

4. The radiation-cooling composite fabric according to claim 1, characterized in that, The composite fabric has hydrophobic and self-cleaning properties, with a static water contact angle of not less than 135° and an air permeability of not less than 200 mm / s under a pressure of 100 Pa.

5. The radiation-cooling composite fabric according to claim 4, characterized in that, The composite fabric has an air permeability of 218.3 mm / s and a hydrophobic contact angle of 138°.

6. A method for preparing the radiation-cooled composite fabric according to any one of claims 1-5, characterized in that, Includes the following steps: Step (1) Nanoparticle adsorption: The fabric is immersed in an aqueous dispersion of alumina nanoparticles and wetted under heating conditions so that the alumina nanoparticles are adsorbed on the fiber surface. After drying, the alumina composite fabric is obtained. Step (2) Polymer coating: The alumina composite fabric obtained in step (1) is immersed in a polydimethylsiloxane / toluene mixed solution. After immersion coating and drying curing, a thin layer of polydimethylsiloxane is formed on the fiber surface to obtain a radiation cooling composite fabric.

7. The preparation method according to claim 6, characterized in that, In step (1), the mass fraction of the alumina nanoparticle dispersion is 1-3%, the ultrasonic dispersion time is 30 min, the wetting temperature is 65℃, the wetting time is 40 min, and the drying temperature is 60℃.

8. The preparation method according to claim 6, characterized in that, In step (2), the polydimethylsiloxane / toluene mixed solution is composed of polydimethylsiloxane prepolymer, curing agent and organic solvent, wherein the mass ratio of polydimethylsiloxane prepolymer to curing agent is 10:1, the organic solvent is toluene, the mass fraction of polydimethylsiloxane is 2-15%, the immersion time is 15 min, the drying and curing time is 40 min, and the curing temperature is 80℃.

9. The preparation method according to claim 8, characterized in that, The dilution effect of the organic solvent toluene causes polydimethylsiloxane to form a discontinuous and dense coating layer on the surface of the fabric fibers, thereby fixing the alumina nanoparticles and preserving the original pore structure of the fabric.

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