Radiation cooling composite fabric and preparation method and application thereof

Abstract

The present application relates to a kind of radiation cooling composite fabric and its preparation method and application, belong to the technical field of radiation cooling material.The composite fabric is with thermoplastic elastomeric fiber as the preparation main body of micro-nano-porous fiber, thermoplastic elastomeric fiber is filled into high-pressure gas foaming, obtain micro-nano-porous fiber, micro-nano-porous fiber has micro-nano-porous structure, it can achieve passive radiation cooling effect.Micro-nano-porous fiber is then compounded with polyamide elastic fiber and polypropylene blend fiber to make fabric.In addition, the micro-nano-porous all-weather radiation cooling composite fabric designs two different surfaces, nano metal particles have very low thermal radiation emissivity and high thermal conductivity, can absorb the heat of human body and micro-environment and transfer to fabric by heat conduction;And polyurethane and micro-nano-oxide composite layer have higher thermal radiation emissivity, can efficiently dissipate heat to the environment by radiation.

Description

Technical Field

[0001] This invention relates to the technical field of radiative cooling materials, specifically to a radiative cooling composite fabric, its preparation method, and its application. Background Technology

[0002] Global climate change and rising temperatures have become global issues, profoundly impacting human society and the ecological environment. High temperatures not only threaten human health but also exacerbate the urban heat island effect, increase energy consumption for heating and cooling systems, and lead to energy waste and increased carbon emissions. Therefore, developing sustainable cooling technologies is one of the most pressing issues to address. Currently, traditional cooling methods mainly include air conditioning systems and fans. However, these methods not only require large amounts of electricity but also cause air pollution and resource waste. Therefore, finding a low-cost, high-efficiency, and environmentally friendly cooling method has become a research hotspot.

[0003] Microporous and nanoporous materials are widely used in solar energy, optoelectronics, and thermal insulation due to their excellent optical, thermal, and material properties. In the field of cooling, microporous and nanoporous materials have made some progress, such as in applications like transparent solar windows and microporous thin film coatings. However, radiative cooling materials in thin film form face problems such as impermeability, poor mechanical properties, uncomfortable curing, and limited application scenarios. Furthermore, current research is limited to small-scale laboratory experiments, making continuous and high-yield production difficult, and coatings are prone to peeling. Currently, a highly efficient solution for preparing all-weather applicable radiative cooling fabrics has not yet been developed. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a radiation cooling composite fabric with highly adjustable radiation characteristics, which can achieve excellent cooling effect under different meteorological conditions, as well as its preparation method and application.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] In a first aspect, the present invention provides a radiative cooling composite fabric, the composite fabric comprising, sequentially, an aqueous polyurethane and micro / nano oxide composite layer, a fabric layer, and a nano-metal particle layer; the fabric layer is disposed between the polyurethane and micro / nano oxide composite layer and the nano-metal particle layer; wherein, the raw material for preparing the fabric layer includes micro / nano porous fibers; the micro / nano porous fibers are obtained by foaming thermoplastic elastic fibers; the thermoplastic elastic fibers comprise the following components: thermoplastic elastomer and micro / nano oxide particles; the components of the polyurethane and micro / nano oxide composite layer include aqueous polyurethane and micro / nano oxide particles. Specifically, the pore size of the micro / nano porous fibers is 0.1–20 μm, more preferably 0.1–10 μm. The density of the micro / nano porous radiative cooling fibers is 0.3–0.9 g / cm³.3 Preferably, it is 0.3–0.7 g / cm³. 3 Thermoplastic elastic fibers include thermoplastic elastomers and micro / nano oxide particles. The main purpose of blending micro / nano oxide particles into the interior of the thermoplastic elastomer is to induce nucleation and further enhance reflection.

[0007] The micro-nanoporous all-weather radiative cooling composite fabric of this invention uses thermoplastic elastic fibers as the main body for preparing micro-nanoporous fibers. The thermoplastic elastic fibers are foamed with high-pressure gas to obtain micro-nanoporous fibers. These fibers have a micro-nanoporous structure, which allows for strong Rayleigh and Mie scattering of sunlight, scattering sunlight into the environment and greatly avoiding heat absorption, thus achieving a passive radiative cooling effect. Furthermore, the micro-nanoporous all-weather radiative cooling composite fabric is designed with two different surfaces: nano-metal particles have very low thermal emissivity and high thermal conductivity, enabling them to absorb heat from the human body and microenvironment and transfer it to the fabric through thermal conduction; while the polyurethane and micro-nano oxide composite layer has high thermal emissivity, enabling it to efficiently dissipate heat into the environment through radiation. The micro-nanoporous all-weather radiative cooling composite fabric of this invention has a reflectivity of ≥80% (preferably ≥85%) for solar radiation in the 0.3–2.5 mm wavelength range and an emissivity of ≥80% (preferably ≥85%) for mid-infrared thermal radiation in the atmospheric transparency window (8–13 mm). Micro-nano porous all-weather radiative cooling composite fabrics can withstand solar irradiance of 0–1400 W·m in summer. 2 The cooling effect is 6 to 9 degrees Celsius at ambient temperatures of 30 to 42 degrees Celsius.

[0008] Preferably, the raw materials for preparing the fabric layer further include reinforcing fibers, which include polyamide elastic fibers and polypropylene blend fibers; the raw materials for preparing the polyamide elastic fibers include polyamide elastomers; and the raw materials for preparing the polypropylene blend fibers include polypropylene and low-density polyethylene. Using reinforcing fibers combined with microporous fibers can improve the fabric's toughness, elasticity, and other mechanical properties. The composite fabric made of microporous fibers, polyamide elastic fibers, and polypropylene blend fibers has a tensile strength of 80–150 MPa and an elongation at break of 600–1000%.

[0009] Preferably, the thermoplastic elastic fiber further includes micro / nano oxide particles.

[0010] The radiative cooling composite fabric comprises thermoplastic elastomer, waterborne polyurethane, nano-metal particles, and micro / nano oxide particles in a weight ratio of (70–100):(1–2):(0.1–0.4):(2–10). It should be noted that the amount of micro / nano oxide particles used here includes both the surface coating (waterborne polyurethane and micro / nano oxide composite layer) and the internal blending with the thermoplastic elastomer fibers.

[0011] More preferably, the raw materials of the thermoplastic elastomer fiber, polyamide elastic fiber, and polypropylene blend fiber all contain a light stabilizer. The light stabilizer enables the polymer to eliminate or slow down the possibility of photochemical reactions under light radiation, preventing or delaying the photoaging process, thereby extending the service life of the polymer product. The light stabilizer is at least one of salicylates, substituted acrylonitriles, and benzotriazoles. The amount of light stabilizer used in the three fibers is the same. The mass fraction of the light stabilizer added to the composite fabric is 0.3 to 1 part.

[0012] More preferably, the polyamide elastic fiber and the polypropylene blend fiber also contain a colorant, wherein the colorant is at least one of titanium dioxide, lithopone and zinc dioxide.

[0013] Preferably, the nano-metal particles have a particle size of 5–15 nm. The micro-oxide particles have a particle size of 0.3–10 μm. The nano-metal particles and micro-oxide particles within these two particle size ranges are comparable to light radiation wavelengths of 400–700 nm, resulting in localized plasmonic resonance. This resonance phenomenon causes a shift in the absorption peak position of the spectrum, thereby achieving a radiation effect.

[0014] Preferably, the thermoplastic elastomer is at least one selected from thermoplastic polyurethane elastomer, thermoplastic polyester elastomer, thermoplastic polyolefin elastomer, and thermoplastic polystyrene elastomer. Here, the thermoplastic polyurethane elastomer and the polyamide elastomer in the reinforcing fiber can be the same component.

[0015] Preferably, the nano-metal particles are at least one of silver nanoparticles, titanium nanoparticles, and copper nanoparticles.

[0016] Preferably, the micro / nano oxide is at least one of silicon dioxide, aluminum oxide, zinc oxide, titanium dioxide, and zirconium dioxide.

[0017] Preferably, the polyurethane is an aqueous emulsion with a particle size of 100–500 nm, a number-average molecular weight of 5000–10000, and a viscosity of 200–500 mPa·s. The viscosity is measured using the capillary method according to GB / T10247-2008. Aqueous polyurethane within the above range provides good adhesion, allowing micro / nano oxides to adhere stably to the fabric. Specific particle size and molecular weight ensure a stable suspension and a suitable viscosity range, as the success and effectiveness of the final spraying process are primarily related to viscosity.

[0018] Preferably, the thickness of the micro-nano porous all-weather radiative cooling composite fabric is 0.5–5 mm, more preferably 0.5–2 mm. The fabric thickness depends on the fiber diameter and the fiber weaving method. If the fabric is too thin or the weaving method is too sparse, it will be detrimental to the fabric's reflection of solar heat radiation; if the fabric is too thick or the weaving method is too dense, it will be detrimental to air and moisture permeability, limiting its application range and offering no benefit to the reflection of solar heat radiation.

[0019] Secondly, the present invention provides a method for preparing the aforementioned radiation cooling composite fabric, comprising the following steps:

[0020] (1) The thermoplastic elastic fiber is filled with high-pressure gas and foamed to obtain microporous fiber;

[0021] (2) The micro-nano porous fibers are made into the fabric layer;

[0022] (3) A composite solution of water-based polyurethane and micro-nano oxide particles is sprayed onto one side of the densely woven fabric to form a polyurethane and micro-nano oxide composite layer; nano metal particles are deposited on the other side of the densely woven fabric to form a nano metal particle layer, and after drying, a radiation cooling composite fabric is obtained.

[0023] Preferably, the high-pressure gas is carbon dioxide and / or nitrogen; the solubility of the high-pressure gas in the thermoplastic elastic fiber is (0.3-5) wt%.

[0024] Preferably, in step (2), the foaming process is as follows: the thermoplastic elastic fiber is placed in a high-pressure reactor with a set temperature, and high-pressure gas is introduced until a predetermined pressure is reached. After sufficient time, the gas valve is opened, and the equilibrium conditions are changed to drive the growth of gas nuclei to obtain microporous radiation-cooled fibers.

[0025] Preferably, in step (2), the microporous fibers and polyamide elastic fibers are twisted into bundles, dipped in starch slurry, dried, washed, and then blended with the polypropylene blended fibers to obtain the fabric layer. Therefore, the components in the composite fabric also include 0.3 to 1 part of starch. Preferably, the starch is at least one of corn starch, potato starch, and glutinous rice starch. Starch belongs to or is mostly amylopectin, and the starch content in amylopectin is 80 to 90%, which is more conducive to fiber sizing. The microporous all-weather radiant cooling composite fabric of the present invention uses thermoplastic elastic fibers as the main body for preparing microporous fibers, polyamide elastic fibers as twisted fibers, and polypropylene blended fibers as blended fibers. The present invention enhances the mechanical strength of the fabric through twisting and blending processes, while also providing more contact points to ensure that the deposited layer and sprayed layer adhere firmly and have high wear resistance.

[0026] Preferably, the micro-nano porous all-weather radiative cooling composite fabric comprises the following raw materials in parts by weight: 70-100 parts thermoplastic elastomer, 0.3-1 part light stabilizer, 1-2 parts waterborne polyurethane, 1-5 parts polyamide elastomer, 0.3-0.4 parts nano-metal particles, 2-10 parts micro-nano oxide particles, 0.3-1 part starch, 2-6 parts polypropylene, 0.5-2 parts low-density polyethylene, and 0.3-1 part colorant. It should be noted that the parts by weight of the thermoplastic elastomer do not include the parts by weight of the polyamide elastomer.

[0027] Thirdly, this invention provides the application of micro-nano porous all-weather radiative cooling composite fabrics in the preparation of clothing, medical products, outdoor products, and sensing and detection products.

[0028] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0029] (1) The radiation cooling composite fabric of the present invention comprises, in sequence, an aqueous polyurethane and micro / nano oxide composite layer, a fabric layer, and a nano metal particle layer. The composite fabric of the present invention utilizes the scattering, reflection, and emission effects of visible light and thermal radiation by micro / nano pores and specific micro / nano oxide particles to prepare a micro / nano pore all-weather radiation cooling composite fabric. Specifically, the fabric layer uses micro / nano pore fibers as the main raw material. The micro / nano pore fibers are prepared by thermoplastic elastic fibers, which are filled with high-pressure gas and foamed to obtain micro / nano pore fibers. The micro / nano pore fibers have a micro / nano pore structure, which allows sunlight to undergo strong Rayleigh scattering and Mie scattering, scattering sunlight into the environment and greatly avoiding heat absorption, thereby achieving the effect of passive radiation cooling. In addition, the micro / nano pore all-weather radiation cooling composite fabric is designed with two different surfaces. The nano metal particles have a very low thermal emissivity and a high thermal conductivity, which can absorb heat from the human body and the microenvironment and transfer it to the fabric through thermal conduction. The polyurethane and micro / nano oxide composite layer has a high thermal emissivity, which can efficiently dissipate heat into the space environment through radiation. The fabrication process of micro-nano porous all-weather radiative cooling composite fabric is simple, easy to scale up, and suitable for all-weather (day and night) radiative cooling with excellent effect.

[0030] (2) The fabric layer of the present invention also includes polyamide elastic fibers and polypropylene blended fibers. That is, the fabric layer is made by combining microporous fibers with polyamide elastic fibers and polypropylene blended fibers. The polyamide elastic fibers and polypropylene blended fibers, as reinforcing fibers, can improve the mechanical properties of the fabric, such as toughness and elasticity. This results in a tensile strength of 80-150 MPa and an elongation at break of 600-1000% for the composite fabric.

[0031] (3) The nano-metal particles used in the composite fabric of the present invention have a particle size of 5-15 nm, and the micro-nano oxides have a particle size of 0.3-10 μm. The nano-metal particles and micro-nano oxides within the above two particle size ranges are comparable to the light radiation wavelength of 400-700 nm, and will produce a localized plasma resonance phenomenon. This resonance phenomenon will cause the absorption peak position of the spectrum to shift, thereby improving the radiation effect.

[0032] (4) The composite fabric of the present invention is made by first twisting the microporous fibers and polyamide elastic fibers into bundles, and then blending them with polypropylene blended fibers to form a densely woven fabric. That is, the composite fabric uses thermoplastic elastic fibers as the main body for preparing microporous fibers, polyamide elastic fibers as the twisted fibers, and polypropylene blended fibers as the blended fibers. The present invention also combines twisting and blending processes in the preparation process, effectively enhancing the adhesion of micro- and nano-oxide particles to the fiber surface, improving the tensile breaking strength and elongation at break of the single fiber, and making the composite fabric wear-resistant and tensile-resistant during use.

[0033] (5) The composite fabric of the present invention utilizes the optical and thermal properties of micro- and nano-porous structures and the photoresponse mechanism of micro- and nano-particles to endow the fabric with radiative cooling properties, enhance the mechanical strength and durability of the radiative cooling composite fabric, and at the same time ensure that the fabric has good softness. The micro- and nano-porous all-weather radiative cooling composite fabric has the characteristics of good flexibility, high tensile strength, wide applicability, and excellent radiative cooling effect day and night, and is suitable for applications such as clothing, medical, summer outdoor, sensing and monitoring, and equipment maintenance. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of the fiber cross-sectional structure of the composite fabric in Example 1;

[0035] Figure 2 The image shows an electron microscope (EM) image of the surface of the aqueous polyurethane and micro / nano oxide composite layer in the composite fabric fiber of Example 1.

[0036] Figure 3 An optical photograph of the composite fabric of Example 1;

[0037] Figure 1 The reference numerals in the figures are: 1. Microporous fiber; 2. Nanometal particle layer; 3. Waterborne polyurethane and micro / nano oxide composite layer; 4. Polyamide elastic fiber; 5. Micro / nano oxide particles; 6. Polypropylene blend fiber. Detailed Implementation

[0038] To better illustrate the purpose, technical solution, and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments.

[0039] In the following embodiments, the materials used to prepare the micro-nano porous all-weather radiative cooling composite fabric are as follows:

[0040] Thermoplastic polyurethane elastomer: TPU, 93A, Jinjiang Guosheng;

[0041] Thermoplastic polyester elastomer: TPEE, 5556, DuPont, USA;

[0042] Styrene elastomer: SEBS, H1053, Asahi Kasei Corporation, Japan;

[0043] Polyolefin elastomer: EVA, 360, DuPont, USA;

[0044] Polyamide elastomer: PEBA, 3010, Xubang New Materials Technology Co., Ltd.;

[0045] Low-density polyethylene: PE, 2420H, Sinopec;

[0046] Polypropylene resin: PP, 1304E5, ExxonMobil Chemical, USA;

[0047] Micro / nano oxide particles: Titanium dioxide (TiO2), average size 30nm, commercially available; Silicon dioxide (SiO2), average size 1μm, commercially available; Zirconium dioxide (CrO2), average size 10μm, commercially available;

[0048] Waterborne polyurethane: Model 1926, viscosity 200-500 mPa·s, Yoshida Chemical Co., Ltd., Shenzhen, China;

[0049] Nano-sized metal particles: average particle size 10nm, titanium (Ti), silver (Ag), copper (Cu), commercially available;

[0050] Light stabilizers: any one of salicylates, substituted acrylonitriles, or benzotriazoles, commercially available;

[0051] Starch: Corn starch, commercially available;

[0052] Colorant: Titanium dioxide, commercially available.

[0053] Examples 1-9

[0054] The radiative cooling composite fabrics of Examples 1-9 sequentially comprise a water-based polyurethane and micro / nano oxide composite layer, a fabric layer, and a nano-metal particle layer; wherein, the fabric layer comprises micro / nano porous fibers; the micro / nano porous fibers are obtained by foaming thermoplastic elastic fibers; the thermoplastic elastic fibers comprise the following raw materials: thermoplastic elastomer and micro / nano oxide particles. The formulations of the composite fabrics of Examples 1-9 are shown in Table 1.

[0055] The method for preparing the radiation cooling composite fabric of the present invention includes the following steps:

[0056] (1) Thermoplastic elastic fiber, polyamide elastic fiber 4 and polypropylene blend fiber 6 are prepared respectively; wherein, the thermoplastic elastic fiber is obtained by drying thermoplastic elastomer, light stabilizer and micro-nano oxide particles 5 in an oven, mechanically mixing and then injecting into a torque mixer, releasing the material with a circular fine-mouth die and drawing it through a yarn separator; the polyamide elastic fiber 4 is obtained by drying polyamide elastomer, light stabilizer and colorant in an oven, mechanically mixing and then injecting into a torque mixer, releasing the material with a circular fine-mouth die and drawing it through a yarn separator; the polypropylene blend fiber 6 is obtained by drying polypropylene, low-density polyethylene, light stabilizer and colorant in an oven, mechanically mixing and then injecting into a torque mixer, releasing the material with a circular fine-mouth die and drawing it through a yarn separator; the light stabilizer content in the raw materials of thermoplastic elastic fiber, polyamide elastic fiber 4 and polypropylene blend fiber 6 is the same, and the colorant content in the raw materials of polyamide elastic fiber 4 and polypropylene blend fiber 6 is the same.

[0057] (2) The thermoplastic elastic fiber is placed in a high-pressure reactor with a set temperature, and high-pressure gas is introduced until the predetermined pressure is reached. After sufficient time, the gas valve is opened and the equilibrium conditions are changed to drive the growth of gas nuclei to obtain microporous fiber 1;

[0058] (3) The microporous fibers 1 and polyamide elastic fibers 4 are twisted into bundles, dipped in starch slurry, dried, washed, and then blended with polypropylene blended fibers 6 to form a densely woven fabric; nano-metal particles are deposited on one side of the fabric, and a water-based polyurethane / micro-nano oxide composite solution is sprayed on the other side. After drying, a water-based polyurethane and micro-nano oxide composite layer 3 is formed, thus obtaining the fabric as shown in the figure. Figure 1 The micro-nano porous all-weather radiative cooling composite fabric shown.

[0059] Figure 1 This is a schematic diagram of the cross-sectional structure of the micro-nano porous all-weather radiation cooling composite fabric fiber described in Example 1. The fiber is divided into upper and lower layers. The nano-metal particle layer 2 is a heat transfer and heat dissipation layer, and the water-based polyurethane and micro-nano oxide composite layer 3 is a heat radiation and heat dissipation layer. The fabric is obtained by blending the two types of fibers. Figure 2 The image shows an electron microscope image of the surface of the waterborne polyurethane and micro / nano oxide composite layer 3 in the composite fabric of Example 1. The surface particles are micro / nano oxide particles 5. Figure 3 This is an optical photograph of the micro-nanoporous all-weather radiative cooling composite fabric described in Example 1. It is made by simple blending and weaving of micro-nanoporous fiber 1 and polypropylene blend fiber 6. As can be seen, the fabric is pure white, which is due to the strong scattering of visible light by the abundant micro-nanopores inside, resulting in excellent radiative cooling performance.

[0060] Table 1. Components and test results of the composite fabrics in Examples 1-9

[0061]

[0062]

[0063] Example 10

[0064] Compared with Example 1, in step (3) of the composite fabric of Example 10, the microporous fiber 1, polyamide elastic fiber 4 and polypropylene blend fiber 6 are directly blended and woven into a fabric.

[0065] Example 11

[0066] Compared with Example 1, the fabric layer of Example 11 contains only microporous fibers 1 and does not contain polyamide elastic fibers 4 and polypropylene blend fibers 6.

[0067] Comparative Example 1

[0068] Compared to Example 1, the thermoplastic elastic fibers of Comparative Example 1 did not undergo a foaming process, i.e., the composite fabric...

[0069] It does not contain microporous fibers 1.

[0070] Comparative Example 2

[0071] Compared to Example 1, the composite fabric of Comparative Example 5 does not have the nano-metal particle layer 2 and the waterborne polyurethane and micro-nano oxide composite layer 3 on its surface.

[0072] Comparative Example 3

[0073] Compared with Example 1, the nano-metal particles in Comparative Example 3 have a particle size of 20 nm, and the rest are the same as in Example 1.

[0074] Comparative Example 4

[0075] Compared with Example 1, the particle size of the micro-nano oxide particles 5 in Comparative Example 4 is 15 μm.

[0076] Comparative Example 5

[0077] Compared with Example 1, Comparative Example 5 does not contain waterborne polyurethane, that is, it does not contain waterborne polyurethane and micro-nano oxide composite layer 3, but only micro-nano oxide layer, and the rest is the same as Example 1.

[0078] Performance testing

[0079] The density, average cell size, tensile strength, tensile breaking rate, reflectivity, and emissivity of Examples 1-11 and Comparative Examples 1-5 were tested. The formulations and test results are shown in Table 2. The test methods are as follows:

[0080] Density: Closed-cell material, tested using the drainage method, standard is HG / T2872-2009.

[0081] Average cell size: The average value of more than 100 cell sizes was calculated by testing the cross-section of the foamed sample using SEM.

[0082] Tensile strength and elongation at break: Single filament mechanical testing using a T150 UTM micro-nano tensile testing machine, in accordance with standard GB / T31290—2014.

[0083] Reflectance: Determined according to the spherical integration method of the LAMBDA 950 UV-Vis spectrophotometer, standard JG / T 235-2014.

[0084] Emissivity: Determined according to the spherical integration test method of Nicolet iS50 Fourier transform infrared spectrometer, standard JG / T 235-2014.

[0085] Table 2 Test results for each group

[0086]

[0087]

[0088] As shown in Table 2, the composite fabrics in Examples 1-9 utilize the optical and thermal properties of micro- and nano-porous structures, the photoresponse mechanism of micro- and nano-particles, and specific preparation methods to endow the fabrics with radiative cooling properties, enhance the mechanical strength and durability of the radiative cooling composite fabrics, and simultaneously ensure good softness. The micro- and nano-porous all-weather radiative cooling composite fabrics are characterized by good flexibility, high tensile strength, wide applicability, and excellent day-and-night all-weather radiative cooling effect.

[0089] The composite fabric of Example 10 is simply made by blending three types of fibers. The tensile strength and elongation at break of the resulting fabric fibers are significantly lower than those of Example 1. This indicates that the use of twisting and blending to make the three types of fibers into a densely woven fabric as defined in step (3) of the composite fabric of Example 1 effectively enhances the adhesion of micro-nano oxide particles 5 on the fiber surface, improves the tensile strength and elongation at break of the single fiber, and makes the composite fabric wear-resistant and tensile-resistant during use.

[0090] In Example 11, the composite fabric layer is made only of microporous fibers 1. The tensile breaking strength and elongation at break of the fibers are significantly reduced, indicating that the polypropylene blended fibers 6 and polyamide elastic fibers 4 can improve the mechanical properties of the fabric. In addition, they can also increase the surface roughness of the fabric layer, which is beneficial to the adhesion of the nano-metal particle layer 2 and the waterborne polyurethane and micro-nano oxide composite layer 3 on the fabric layer.

[0091] The thermoplastic elastic fiber in Comparative Example 1 was not foamed, meaning the composite fabric did not contain microporous fiber 1. Therefore, the fiber porosity in the corresponding fabric structure was 0, and the fiber softness was significantly reduced compared to Example 1; the corresponding reflectivity and emissivity were also significantly reduced, resulting in poor radiative cooling effect. This demonstrates that the microporous fiber 1 in Example 1, due to its microporous structure, allows for strong Rayleigh and Mie scattering of sunlight, scattering sunlight into the environment and greatly avoiding heat absorption, thereby achieving a passive radiative cooling effect.

[0092] The composite fabric in Comparative Example 2 lacks the nano-metal particle layer 2 and the waterborne polyurethane and micro / nano oxide composite layer 3. This results in a decrease in radiative cooling effect compared to Example 1. In contrast, the composite fabric in Example 1 features two distinct surfaces: the nano-metal particles possess very low thermal emissivity and high thermal conductivity, enabling them to absorb heat from the human body and microenvironment and transfer it to the fabric via thermal conduction; while the polyurethane and micro / nano oxide composite layer has high thermal emissivity, allowing it to efficiently dissipate heat into the space environment through radiation.

[0093] The nanoparticles in Comparative Example 3 have a particle size of 20 nm, while the nanoparticles in Examples 1-10 all have a preferred particle size of 10 μm. Comparative Example 3 uses particles with a larger particle size, as the particle size corresponds to the radiation wavelength. If the particle size is too large, it will affect the light radiation performance, thereby affecting the cooling effect.

[0094] The micro-nano oxide particles in Comparative Example 4 had a particle size of 15 μm. However, the micro-nano oxide particles in Examples 1 to 10 were all between 0.3 and 10 μm. The particle size used in Comparative Example 4 was not within this range, which resulted in a significant reduction in the radiative cooling effect. This indicates that the best radiative cooling effect can be achieved by using particles in the range of 0.3 to 10 μm that correspond to the wavelength of the radiant light.

[0095] Comparative Example 5, without the addition of waterborne polyurethane, showed reduced adhesion of the micro-nano oxides in the fabric, making it easier to detach. This indicates that waterborne polyurethane can provide good adhesion, enabling the micro-nano oxides to adhere stably to the fabric.

[0096] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A radiative cooling composite fabric, characterized in that, The composite fabric sequentially comprises a water-based polyurethane and micro-nano-oxide composite layer, a fabric layer and a nano-metal particle layer; the fabric layer is arranged between the polyurethane and micro-nano-oxide composite layer and the nano-metal particle layer; wherein the fabric layer is prepared from micro-nano-porous fibers; the micro-nano-porous fibers are obtained by foaming thermoplastic elastomeric fibers; the thermoplastic elastomeric fibers are prepared from thermoplastic elastomer and micro-nano-oxide particles; the polyurethane and micro-nano-oxide composite layer comprises water-based polyurethane and micro-nano-oxide particles; The preparation method of the radiation cooling composite fabric comprises the following steps: (1) foaming the thermoplastic elastomeric fibers by charging high-pressure gas to obtain the micro-nano-porous fibers; (2) preparing the fabric layer from the micro-nano-porous fibers; (3) spraying a composite solution of water-based polyurethane and micro-nano-oxide particles on one side of the fabric layer to form the polyurethane and micro-nano-oxide composite layer; depositing nano-metal particles on the other side of the fabric layer to form the nano-metal particle layer; and drying to obtain the radiation cooling composite fabric.

2. The radiant cooling composite fabric of claim 1, wherein, The fabric layer is further prepared from reinforcing fibers, and the reinforcing fibers comprise polyamide elastomeric fibers and polypropylene blended fibers; the polyamide elastomeric fibers are prepared from polyamide elastomer; and the polypropylene blended fibers are prepared from polypropylene and low-density polyethylene.

3. The radiant cooling composite fabric of claim 1, wherein, The radiation cooling composite fabric comprises thermoplastic elastomer, water-based polyurethane, nano-metal particles and micro-nano-oxide particles in a weight ratio of (70-100):(1-2):(0.1-0.4):(2-10).

4. The radiant cooling composite fabric of claim 1, wherein, The nano-metal particles have a particle size of 5-15 nm.

5. The radiant cooling composite fabric of claim 1, wherein, The micro-nano-oxide particles have a particle size of 0.3-10 μm.

6. The radiant cooling composite fabric of claim 1 or 2, wherein, At least one of the following (1)-(4): (1) the thermoplastic elastomer is at least one of thermoplastic polyurethane elastomer, thermoplastic polyester elastomer, thermoplastic polyolefin elastomer and thermoplastic polystyrene elastomer; (2) the nano-metal particles are at least one of silver nanoparticles, titanium nanoparticles and copper nanoparticles; (3) the micro-nano-oxide particles are at least one of silicon dioxide, aluminum oxide, zinc oxide, titanium dioxide and zirconium dioxide; (4) the polyurethane is an aqueous emulsion, has a particle size of 100-500 nm, a number average molecular weight of 5000-10000, and a viscosity of 200-500 mPa·s.

7. The radiant cooling composite fabric of claim 1, wherein, In step (2), at least one of the following (1)-(2) is used: (1) the high-pressure gas is carbon dioxide and / or nitrogen; (2) the solubility of the high-pressure gas in the thermoplastic elastomeric fibers is (0.3-5) wt%.

8. The radiation cooling composite fabric of claim 1, in step (2), the micro-nano-porous fibers are twisted into a bundle with polyamide elastomeric fibers, immersed in a starch slurry, then dried and cleaned, and then mixed with polypropylene blended fibers to obtain the fabric layer.

9. Use of the radiation cooling composite fabric of any one of claims 1-8 in the preparation of clothing, medical products, outdoor products and sensing and detecting products.

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