Patent Publication Number: US-2023158786-A1

Title: Radiative cooling fabrics and products

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a 371 of international PCT patent application PCT/CN2020/101230 filed on Jul. 10, 2020, which claims all benefits accruing under 35 U.S.C. §119 from China Patent Application Nos. 201911086548.1, filed on Nov. 8, 2019, with title of “RADIATIVE COOLING FABRICS AND APPLICATION THEREOF”, and 201911075603.7, filed on Nov. 6, 2019, with title of “RADIATIVE COOLING FUNCTIONAL LAYER, RADIATIVE COOLING FABRICS AND PREPARATION METHOD THEREOF”, in the China National Intellectual Property Administration, the content of which is hereby incorporated by reference. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates to the technical field of radiative cooling, and in particular, to radiative cooling fabrics and products using the same. 
     BACKGROUND 
     There are various sunshade products on the market presently, such as sun visors, outdoor blinds, outdoor hard roller blinds, outdoor soft roller blinds, ceiling curtains, canopy curtains, awnings, car covers, umbrellas, etc. However, the conventional sunshade products usually only have the function of shading and have no cooling effect. With the development of radiative cooling technology, researchers began to study the application of radiative cooling technology in sunshade products in order to introduce an automatic cooling function into the sunshade products. However, there are many practical problems needed to be solved in the combination of fabric and functional layer. 
     SUMMARY 
     Based on this, it is necessary to provide a radiative cooling fabric having shading and automatic cooling functions, which further has a great temperature-lowering effect and has a good wrinkle resistance performance. 
     The present disclosure provides a radiative cooling fabric, comprising a flexible substrate layer and a functional layer stacked in order; the functional layer comprises a first functional layer with a thickness of 10 μm to 200 μm, and the first functional layer comprises a first functional resin and a first functional filler dispersed in the first functional resin; a mass fraction of the first functional filler in the first functional layer is in a range of 1% to 20%, an emissivity of the radiative cooling fabric in a wavelength of 7 μm to 14 μm is not less than 80%, a reflectivity of the radiative cooling fabric in a wavelength of 300 nm to 2500 nm is not less than 80%. An average value of warp recovery angles of the radiative cooling fabric is greater than or equal to 95°, and an average value of the weft recovery angles of the radiative cooling fabric is greater than or equal to 91°. 
     In one embodiment, the first functional filler further comprises a first filler and a second filler, a particle size of the first filler is greater than or equal to 0.01 μm and less than 5 μm, a particle size of the second filler is greater than or equal to 5 μm and less than or equal to 15 μm, a ratio of a mass of the first filler to a mass of the second filler is in a range of 1:4 to 4:1; or the first filler and the second filler are independently selected from cesium tungsten bronze, tin antimony oxide, indium tin oxide, zinc aluminum oxide, silicon dioxide, silicon carbide, titanium dioxide, calcium carbonate, barium sulfate, silicon nitride, or a combination thereof. 
     In one embodiment, the functional layer further comprises a second functional layer, the first functional layer is located on the flexible substrate layer, and the second functional layer is located on a surface of the first functional layer away from the flexible substrate layer; the second functional layer is formed by disposing a second functional filler on the surface of the first functional layer; a thickness of the first functional layer is in a range of 10 μm to 30 μm, and a particle size of the second functional filler is in a range of 1 μm to 40 μm. 
     In one embodiment, a particle size of the second functional filler is 0.5 times to 1.5 times of the thickness of the first functional layer; or an amount of the second functional filler is in a range of 10 g/m 2  to 200 g/m 2 , with respect to an area of a surface of the radiative cooling fabric; or the second functional filler is ceramic powder, titanium white powder, glass microbeads, silicon dioxide, calcium carbonate powder, barium sulfate, talcum powder, zinc sulfate, aluminum silicate, calcium carbonate powder, pearl powder, alumina, zinc oxide, zirconia, cerium oxide, lanthanum oxide, rhodium oxide, magnesium oxide, or a combination thereof. 
     In one embodiment, the functional layer further comprises a third functional layer located on a surface of the second functional layer away from the first functional layer, and the third functional layer comprises a second functional resin, and a thickness of the third functional layer is in a range of 10 μm to 30 μm. 
     In one embodiment, the third functional layer further comprises a third functional filler, the third functional filler is ceramic powder, titanium white powder, glass microbeads, silicon dioxide, calcium carbonate powder, barium sulfate, talcum powder, zinc sulfate, aluminum silicate, calcium carbonate powder, pearl powder, alumina, zinc oxide, zirconia, cerium oxide, lanthanum oxide, rhodium oxide, magnesium oxide, or a combination thereof; and a particle size of the third functional filler is in a range of 4 μm to 20 μm. 
     In one embodiment, the first functional resin and the second functional resin are independently selected from polyimide, cycloolefin polymer, epoxy resin, polyester resin, polyurethane resin, acrylic resin, silicone resin, fluorine resin, or a combination thereof. 
     In one embodiment, a thickness of the flexible substrate layer is in a range of 300 μm to 2 mm; and the flexible substrate layer comprises a fabric layer and a resin coating layer coated on one side or both sides of the fabric layer, a thickness of the resin coating layer is in a range of 1 μm to 20 μm, a material of the fabric layer is polyester, nylon, acrylic, silk, cotton, hemp, or a combination thereof, and a material of the resin coating layer is polyvinyl chloride resin, acrylic resin, epoxy resin, phenol resin, polyurethane resin, or a combination thereof. 
     In one embodiment, further comprising an interfacial agent layer located between the flexible substrate layer and the functional layer, a thickness of the interfacial agent layer is in a range of 1 μm to 20 μm, and a material of the interfacial agent layer is acrylic resin, polyurethane resin, epoxy resin, or a combination thereof. 
     In one embodiment, further comprising a waterproof layer located on a side of the flexible substrate layer away from the functional layer, a thickness of the waterproof layer is in a range of 1 μm to 20 μm, a material of the waterproof layer is acrylic resin, polyurethane resin, epoxy resin, or a combination thereof, and a transmittance of the waterproof layer is greater than or equal to 80% in a wavelength of 400 nm to 700 nm. 
     In one embodiment, further comprising a hydrophobic layer located on a side of the functional layer away from the flexible substrate layer, a thickness of the hydrophobic layer is a range of 1 μm to 20 μm, a material of the hydrophobic layer is fluorine resin, silicone resin, or a combination thereof, nano-scaled silicon dioxide particles are dispersed in the hydrophobic layer, a mass fraction of the silicon dioxide particles in the hydrophobic layer is in a range of 0.5% to 5%, and a transmittance of the hydrophobic layer is greater than or equal to 80% in a wavelength of 7 μm to 14 μm. 
     In one embodiment, further comprising a weather resistant layer located on a side of the functional layer away from the flexible substrate layer, a material of the weather resistant layer is fluorine resin, epoxy resin, polyester resin, polyurethane resin, acrylic resin, silicone resin, or a combination thereof, and a thickness of the weather resistant layer is in a range of 10 μm to 50 μm. 
     The present disclosure provides a product including a part which is made of the radiative cooling fabric. 
     In one embodiment, the product is an umbrella comprising a rod, an umbrella rib and an umbrella cloth which is the part made of the radiative cooling fabric, the umbrella rib is connected to the rod, and the umbrella cloth is supported by the umbrella rib. 
     In one embodiment, the product is a car cover comprising a fixing member and a cover body which is the part made of the radiative cooling fabric, the fixing member is located on the cover body, and the fixing member is configured for fixing the cover body on a car. 
     In one embodiment, the product is a tent comprising a tent frame and a flysheet made of the radiative cooling fabric, and the tent frame is covered by the flysheet. 
     In one embodiment, the product is a hat comprising a hat body made of the radiative cooling fabric, the hat body has a cavity configured for accommodating the head. 
     In one embodiment, the product is a curtain comprising a curtain body made of the radiative cooling fabric, the curtain body is a part of the curtain. 
     In one embodiment, the product is an awning comprising an awning frame and an awning cloth made of the radiative cooling fabric, the awning frame is covered by the awning cloth. 
     In one embodiment, the product is clothing comprising cloth made of the radiative cooling fabric. 
     The radiative cooling fabric provided by this disclosure has excellent shading and radiative cooling effect, and the radiative cooling fabric also has a good wrinkle resistance performance, even if folded repeatedly, the surface of the radiative cooling fabric is not easy to wrinkle. The radiative cooling fabric can be used to make curtains, car covers, tents, awnings, umbrellas, clothing, hats, or other products, so that these products not only have shading functions, but also have good automatic cooling functions. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a schematic diagram of a radiative cooling fabric in one embodiment of the present disclosure. 
         FIG.  2    is a schematic diagram of a radiative cooling fabric in another embodiment of the present disclosure. 
         FIG.  3    is a schematic diagram of a radiative cooling fabric in another embodiment of the present disclosure. 
         FIG.  4    is a schematic diagram of a radiative cooling fabric in another embodiment of the present disclosure. 
         FIG.  5    a schematic diagram of a radiative cooling fabric in another embodiment of the present disclosure. 
         FIG.  6    is a schematic diagram of a radiative cooling fabric in another embodiment of the present disclosure. 
         FIG.  7    is a schematic diagram of a radiative cooling fabric in another embodiment of the present disclosure. 
         FIG.  8    is a schematic diagram of a radiative cooling fabric in another embodiment of the present disclosure. 
         FIG.  9    is a schematic diagram of a radiative cooling fabric in another embodiment of the present disclosure. 
         FIG.  10    is a schematic diagram of an embodiment of an umbrella, in which a part made of the radiative cooling fabric of the present disclosure. 
         FIG.  11    is a schematic diagram of an embodiment of a car cover, in which a part made of the radiative cooling fabric of the present disclosure. 
         FIG.  12    is a cross-section of the fabric shown in  FIG.  11   . 
         FIG.  13    is a schematic diagram of an embodiment of a flysheet made of the radiative cooling fabric of the present disclosure. 
         FIG.  14    is a schematic diagram of a tent frame. 
         FIG.  15    is a schematic diagram of a detachable part of the flysheet made of the radiative cooling fabric of the present disclosure. 
         FIG.  16    is a schematic diagram of a detachable part located on a flysheet. 
         FIG.  17    is a schematic diagram of a detachable part located on an inner tent of a product made of the radiative cooling fabric of the present disclosure. 
         FIG.  18    is a schematic diagram of a power supply located on a detachable part of a product made of the radiative cooling fabric of the present disclosure. 
         FIG.  19    is a circuit diagram of a power supply, a sensor, an alarm, and a controller of a product made of the radiative cooling fabric of the present disclosure. 
         FIG.  20    is a schematic diagram of an embodiment of a hat made of the radiative cooling fabric of the present disclosure. 
         FIG.  21    is an exploded view of the hat shown in  FIG.  20   . 
         FIG.  22    is a schematic diagram of another embodiment of the hat. 
         FIG.  23    is a schematic diagram of another embodiment of the hat. 
         FIG.  24    is a schematic diagram of another embodiment of the hat. 
         FIG.  25    is a schematic diagram of a curtain made of the radiative cooling fabric of the present disclosure. 
         FIG.  26    is a schematic diagram of an awning made of the radiative cooling fabric of the present disclosure. 
         FIG.  27    is a schematic diagram of clothing made of the radiative cooling fabric of the present disclosure. 
         FIG.  28    is a schematic diagram of temperature measurement positions of a stainless-steel display rooms. 
         FIG.  29    is a graph showing the temperature difference of the stainless-steel display rooms shown in  FIG.  28    with a curtain made of the radiative cooling fabric of the present disclosure and with a curtain made of an ordinary sunshade fabric, respectively. 
         FIG.  30    is a schematic diagram of temperature measurement positions of cars. 
         FIG.  31    is a graph showing the temperature difference of the cars shown in  FIG.  30    with a car cover made of the radiative cooling fabric of the present disclosure, with a car cover made of an ordinary fabric, and without a car cover, respectively. 
         FIG.  32    is a schematic diagram of temperature measurement positions of a tent. 
         FIG.  33    is a graph showing the temperature difference of the tents shown in  FIG.  32    with the radiative cooling fabric of the present disclosure and with an ordinary fabric, respectively. 
     
    
    
     In the drawings,  11  represents a flexible substrate layer;  12  represents a functional layer;  13  represents an interfacial agent layer;  14  represents a waterproof layer;  15  represents a hydrophobic layer;  16  represents a weather resistant layer;  121  represents a first functional layer;  122  represents a second functional layer;  123  represents a third functional layer;  124  represents a first functional filler;  125  represents a second functional filler;  126  represents a third functional filler;  20  represents an umbrella;  21  represents an umbrella cloth;  22  represents an umbrella rib;  23  represents a rod;  30  represents a car cover;  31  represents a cover body;  32  represents a fixing member;  321  represents a magnetic attraction layer;  322  represents a magnetic body;  40  represents a tent ;  41  represents a flysheet;  42  represents a tent frame;  43  represents an inner tent;  44  represents a detachable part;  45  represents a power supply;  46  represents a sensor;  47  represents an alarm;  48  represents a controller;  49  represents a door body;  50  represents a hat;  51  represents a hat body;  511  represents a vent;  52  represents a curtain;  521  represents a mounting plate;  5211  represents a mounting hole;  522  represents a curtain body;  53  represents a storage bag;  54  represents a cooling bag;  60  represents a curtain;  70  represents an awning;  71  represents an awning frame;  72  represents an awning cloth;  80  represents a clothing;  81  represents cloth. 
     DETAILED DESCRIPTION 
     The technical proposals of the embodiments of the present disclosure will be clearly and completely described below by combining with drawings. It is obvious that the described embodiments are only a part and not all of the embodiments of the present disclosure. All other embodiments obtained by one skilled in the art based on the embodiments of the present disclosure without any creative efforts are within the scope of the present disclosure. 
     The present disclosure provides a radiative cooling fabric. The radiative cooling fabric can include a flexible substrate layer  11  and a functional layer  12  stacked on top of one another. The functional layer  12  can be configured for reflecting sunlight and reducing the temperature automatically. 
     As shown in  FIG.  1   , an embodiment of the present disclosure provides a radiative cooling fabric. A functional layer  12  can include a first functional layer  121 . The first functional layer  121  can include a first functional resin and a first functional filler  124 , and the first functional filler  124  can be dispersed in the first functional resin. 
     The reflection performance and the automatic cooling performance of the functional layer  12  can be affected by both the first functional resin and the first functional filler  124  of the first functional layer  121 . The thicker the first functional layer  121  is, the better the reflection performance and the automatic cooling performance are. The more the content of the first functional filler  124  is, the better the reflection performance and the automatic cooling performance are. However, it was found that if the thickness of the first functional layer  121  is too thick or the content of the first functional filler  124  is too much, the wrinkle resistance of the radiative cooling fabric will get worse. Especially after many times of folding, the surface of the radiative cooling fabric will have many wrinkles, which will affect the appearance and the performance of the radiative cooling fabric. However, if the thickness of the first functional layer  121  is too thin or the content of the first functional filler  124  is insufficient, the reflection performance and the automatic cooling performance of the radiative cooling fabric will get worse. 
     To balance these two properties of the radiative cooling fabric, it was found that when a thickness of the first function layer  121  is in a range of 10 μm to 200 μm, and a mass fraction of the first functional filler  124  in the first functional layer  121  is in a range of 1% to 20%, the emissivity of the first functional layer  121  in the wavelength of 7 μm to 14 μm can be not less than 80%, and the reflectivity of the first functional layer  121  in the wavelength of 300 nm to 2500 nm can be not less than 80%. Additionally, the radiative cooling fabric can also have good wrinkle resistance. 
     Specifically, the wrinkle resistance of the radiative cooling fabric can be characterized by a fold recovery angle, an average value of a warp recovery angle can be greater than or equal to 95°, and an average value of a weft recovery angle can be greater than or equal to 91°. 
     In one or more embodiment(s), when a thickness of the flexible substrate layer  11  is in a range of 300 μm to 2 mm, and a mass fraction of the first functional filler  124  of the first functional layer  121  is in a range of 8% to 20%, the average value of the warp recovery angle can be greater than or equal to 98°, and the average value of the weft recovery angle can be greater than or equal to 93°. 
     The first functional filler  124  can include a first filler and a second filler. A particle size of the first filler can be greater than or equal to 0.01 μm and less than 5 μm. A particle size of the second filler can be greater than or equal to 5 μm and less than or equal to 15 μm. A ratio of a mass of the first filler to a mass of the second filler can be in a range of 1:4 to 4:1. 
     Both the first filler and the second filler can emit infrared rays in the wavelength of the atmospheric window (in a range of 7 μm to 14 μm), thereby achieving effectively radiative cooling. Additionally, the first filler with small particle size can reflect sunlight better (in a range of 300 nm to 2500 nm), and the second filler with large particle size can further increase the reflectivity of sunlight in the first functional layer  121 . So, the first functional filler  124  with a combination of different particle sizes can reflect sunlight better, thereby improving the reflection and heat insulation effect of the radiative cooling fabric. 
     In one or more embodiment, the first filler and the second filler can be independently selected from cesium tungsten bronze, tin antimony oxide, indium tin oxide, zinc aluminum oxide, silicon dioxide, silicon carbide, titanium dioxide, calcium carbonate, barium sulfate, silicon nitride, or a combination thereof. 
     In one or more embodiment, the first functional layer  121  can also include an additive dispersed in the resin substrate layer. The additive can be but not limited to dispersants, defoamer, wetting agent, preservative, film-forming additive, thickener, or a combination thereof. 
     It should be noted that a number of the first functional layer  121  is not limited and can be one layer or multiple layers. 
     As shown in  FIG.  2   , another embodiment of the present disclosure provides a radiative cooling fabric. The functional layer  12  in this embodiment can further include a second functional layer  122 . The first functional layer  121  can be located on the flexible substrate layer  11 , and the second functional layer  122  can be located on a surface of the first functional layer  121  away from the flexible substrate layer  11 . The second functional layer  122  can be formed by disposing a second functional filler  125  on the surface of the first functional layer  121 . The second functional filler  125  can be bonded to the first functional layer  121 . A thickness of the first functional layer  121  can be in a range of 10 μm to 30 μm. A particle size of the second functional filler  125  can be in a range of 1 μm to 40 μm. 
     In one or more embodiment, a particle size of the second functional filler  125  can be 0.5 times to 1.5 times of a thickness of the first functional layer  121 . An amount of the second functional filler  125  can be in a range of 10 g/m 2  to 200 g/m 2 , with respect to an area of a surface of the radiative cooling fabric. 
     The second functional filler  125  can be configured for increasing the reflectivity of the functional layer  12  in the wavelength of 300 nm to 2500 nm. The second functional filler  125  can be ceramic powder, titanium white powder, glass microbeads, silicon dioxide, calcium carbonate powder, barium sulfate, talcum powder, zinc sulfate, aluminum silicate, calcium carbonate powder, pearl powder, alumina, zinc oxide, zirconia, cerium oxide, lanthanum oxide, rhodium oxide, magnesium oxide, or a combination thereof. The second functional filler  125  can preferably have a shape of spherical or ellipsoidal. 
     Coating the second functional filler  125  on the first functional layer  121  can greatly increase the reflectivity of the functional layer  12 , thereby improving the radiative cooling efficiency of the functional layer  12  during daytime, and then a thickness of the functional layer  12  can be further reduced. The functional layer  12  can have a reflectivity greater than 88% in the wavelength of 300 nm to 2500 nm and an emissivity greater than 90% in the wavelength of 7 μm to 14 μm with a thickness no more than 50 μm. Disposing the second functional filler  125  on the first functional layer  121  is beneficial to obtain a radiative cooling fabric with better flexibility and higher radiative cooling effect. 
     It should be noted that the second functional filler  125  is disposed on the surface of the first functional layer  121  in a single layer to form the second functional layer  122 . That is, all the second functional filler  125  can be bonded to the first functional layer  121 , the second functional filler  125  does not stack with each other. So, the thickness of the second functional layer  122  can be less than or equal to the particle size of the second functional filler  125 . 
     Specifically, the present disclosure further provides a preparation method of the functional layer  12 , which includes the following steps. 
     S 1 , forming a first functional layer  121  on a flexible substrate layer  11 , and spraying a second functional filler  125  evenly onto a surface of the first functional layer  121  before the first functional layer  121  is dried or cured; and 
     S 2 , drying or curing the first functional layer  121 , so that the second functional filler  125  is bonded to the first functional layer  121  to form a second functional layer  122 . 
     It should be noted that the term “curing” in the specification and claims of the present disclosure can be but not limited to heat curing, light curing, natural drying, etc., the first functional layer  121  can be prepared by scraping, rolling, spraying, brushing, and the like, and the second functional filler  125  can be atomized by a pneumatic spray device and then sprayed evenly onto the surface of the first functional layer  121 . 
     As shown in  FIG.  3   , another embodiment of the present disclosure provides a radiative cooling fabric. On the basis of the embodiment of  FIG.  2   , the functional layer  12  in this embodiment can further include a third functional layer  123 . The third functional layer  123  can be located on a surface of the second functional layer  122  away from the first functional layer  121 . The third functional layer  123  can include a second functional resin. A thickness of the third functional layer  123  can be in a range of 10 μm to 30 μm. 
     It should be noted that since the second functional layer  122  is formed by disposing the second functional filler  125 , there can be a gap between the two adjacent second functional filler  125 . The third functional resin of the third functional layer  123  can fill the gap and be bonded to the first functional layer  121 . 
     A thickness of the third functional layer  123  can be greater than or equal to the particle size of the second functional filler  125 , so that the third functional layer  123  can fully cover the second functional filler  125  and bond to the second functional filler  125 . 
     Specifically, the preparation method of the functional layer  12  can further include forming and curing a third functional layer  123  on a surface of the second functional layer  122 . 
     As shown in  FIG.  4   , another embodiment of the present disclosure provides a radiative cooling fabric. Different from the structure shown in  FIG.  3   , a thickness of the third functional layer  123  in this embodiment can be less than the particle size of the second functional filler  125 , therefore, part of the second functional filler  125  can protrude from a surface of the third functional layer  123 . 
     As shown in  FIG.  5   , another embodiment of the present disclosure provides a radiative cooling fabric. On the basis of the embodiments of  FIG.  3    and  FIG.  4   , the third functional layer  123  in this embodiment can further include a third functional filler  126  dispersed in the second functional resin. The third functional filler  126  can be a filler with a high emissivity in the wavelength of 7 μm to 14 μm and a high reflectivity in the wavelength of 300 nm to 2500 nm to further improve the radiative cooling effect of the functional layer  12 . 
     In one or more embodiment, the third functional filler  126  can be ceramic powder, titanium white powder, glass microbeads, silicon dioxide, calcium carbonate powder, barium sulfate, talcum powder, zinc sulfate, aluminum silicate, calcium carbonate powder, pearl powder, alumina, zinc oxide, zirconia, cerium oxide, lanthanum oxide, rhodium oxide, magnesium oxide, or a combination thereof. A particle size of the third functional filler  126  can be in a range of 4 μm to 20 μm. 
     Due to the arrangement of the second functional layer  122  and the third functional layer  123 , the radiative cooling effect of the functional layer  12  can be improved, and the thickness of the functional layer  12  can be further reduced (basically no more than 100 μm), so that the radiative cooling fabric can have better radiative cooling effect and wrinkle resistance, meanwhile, the cost can be reduced. 
     The radiative cooling function of the resin should be considered, so that the functional layer  12  can achieve the radiative cooling effect due to the resin and the functional filler together. In the embodiments of  FIG.  1    to  FIG.  5   , the first functional resin and the second functional resin can be independently selected from polyimide, cycloolefin polymer, epoxy resin, polyester resin, polyurethane resin, acrylic resin, silicone resin, fluorine resin, or a combination thereof. 
     In one or more embodiment, the flexible substrate layer  11  can include a fabric layer and a resin coating layer coated on one side or both sides of the fabric layer. A thickness of the resin coating layer can be in a range of 1μm to 20 μm. A material of the fabric layer can include polyester, nylon, acrylic, silk, cotton, hemp, or a combination thereof. A material of the resin coating layer can include polyvinyl chloride resin, acrylic resin, epoxy resin, phenol resin, polyurethane resin, or a combination thereof. 
     As shown in  FIG.  6   , another embodiment of the present disclosure provides a radiative cooling fabric. On the basis of the embodiments of  FIG.  1    to  FIG.  5   , an interfacial agent layer  13  can be located between the flexible substrate layer  11  and the functional layer  12 . A thickness of the interfacial agent layer  13  can be in a range of 1μm to 20 μm, and a material of the interfacial agent layer  13  can include acrylic resin, polyurethane resin, epoxy resin, or a combination thereof. The interfacial agent layer  13  can be configured for improving the adhesion of the functional layer  12  on the flexible substrate layer  11 , and the interfacial agent layer  13  can also be waterproof. 
     As shown in  FIG.  7   , another embodiment of the present disclosure provides a radiative cooling fabric. On the basis of the embodiments of  FIG.  1    to  FIG.  6   , a waterproof layer  14  can be located on a side of the flexible substrate layer  11  away from the functional layer  12 . A thickness of the waterproof layer  14  can be in a range of 1 μm to 20 μm, and a material of the waterproof layer  14  can include acrylic resin, polyurethane resin, epoxy resin, or a combination thereof. The waterproof layer  14  can have a transmittance greater than or equal to 80% in the wavelength of 400 nm to 700 nm. The waterproof layer  14  can have a high light transmittance, and basically cannot block the pattern on the inner surface of the flexible substrate layer  11 . 
     As shown in  FIG.  8   , another embodiment of the present disclosure provides a radiative cooling fabric. On the basis of the embodiments of  FIG.  1    to  FIG.  7   , a hydrophobic layer  15  can be located on a side of the functional layer  12  away from the flexible substrate layer  11 . A material of the hydrophobic layer  15  can include fluorine resin, silicone resin, or a combination thereof. Furthermore, nano-scaled silicon dioxide particles can be dispersed in the hydrophobic layer  15 . A mass fraction of the silicon dioxide particles in the hydrophobic layer  15  can be in a range of 0.5% to 5%, and a particle size of silicon dioxide particles can be in a range of 0.5 nm to 20 nm. The silicon dioxide particles can further improve a hydrophobic performance of the hydrophobic layer  15 , so that a contact angle of the hydrophobic layer  15  can be greater than 110°. A thickness of the hydrophobic layer  15  can be in a range of 1 μm to 20 μm. The hydrophobic layer  15  can have a transmittance greater than or equal to 80% in the infrared wavelength of 7 μm to 14 μm, so that the hydrophobic layer  15  basically cannot affect the radiative cooling effect of the functional layer  12 . 
     As shown in  FIG.  9   , another embodiment of the present disclosure provides a radiative cooling fabric. On the basis of the embodiments of  FIG.  1    to  FIG.  7   , a weather resistant layer  16  can be located on a side of the functional layer  12  away from the flexible substrate layer  11 . A material of the weather resistant layer  16  can include fluorine resin, epoxy resin, polyester resin, polyurethane resin, acrylic resin, silicone resin, or a combination thereof, and a thickness of the weather resistant layer  16  can be in a range of 10 μm to 50 μm. 
     Therefore, the radiative cooling fabric provided by the present disclosure can have excellent shading and radiative cooling effect and wrinkle resistance performance. Even if folded repeatedly, the surface of the radiative cooling fabric is not easy to wrinkle. 
     The present disclosure further provides a product using the radiative cooling fabric. The product can include curtains, car covers, tents, awnings, umbrellas, clothing, hats, etc. These products not only have shading function, but also have good automatic cooling effect. 
     As shown in  FIG.  10   , one embodiment of the present disclosure provides a product made of the radiative cooling fabric of the present disclosure. The product is an umbrella  20  including a rod  23 , an umbrella rib  22 , and an umbrella cloth  21  made of the radiative cooling fabric. The umbrella rib  22  is connected to the rod  23 , and the umbrella cloth  21  is supported by the umbrella rib  22 . When sunlight irradiates the umbrella cloth  21 , the functional layer  12  of the umbrella cloth  21  can reflect the sunlight to prevent the umbrella cloth  21  from accumulating excessive heat. The umbrella cloth  21  can also emit the heat on the umbrella cloth  21  and in the inner space of the umbrella  20  through an atmospheric window in a form of infrared radiation, so as to achieve cooling without energy consumption and improve user&#39;s comfort. Moreover, the umbrella cloth  21  has excellent wrinkle resistance performance; the umbrella cloth  21  is not easy to wrinkle even if folded repeatedly. 
     It should be noted that the term “inner space of the umbrella  20 ” in the specification and claims of the present disclosure refers to a space away from the sunlight when the umbrella  20  is in use. 
     In one or more embodiment(s), the umbrella  20  can further include a solar panel and a fan. The solar panel is electrically connected to the fan. The fan is located on the rod  23  and inside the umbrella cloth  21 , and the solar panel is located on the rod  23  and outside the umbrella cloth  21 . When sunlight irradiates the solar panels, the solar panels can absorb sunlight and convert the solar energy into electric energy directly or indirectly through photoelectric effect or photochemical effect, so as to provide the electric energy needed for the fans. When the fan is running, it can blow the cold air inside the umbrella cloth  21  to the user, which can increase the air velocity, exchange heat, reduce temperature, and further improve user comfort. 
     In one or more embodiment, one end of the rod  23  is outside the umbrella cloth  21 . A solar panel interface is located on the end. The solar panel interface and the fan are connected through a wire. It should be noted that a fan interface is located on a middle part of the rod  23 , the rod  23  has a hollow structure, and the wire passes through the hollowed rod  23 . One end of the wire is connected to the solar panel interface, and the other end of the wire is connected to the fan interface. Through the hidden wire accidents caused by broken wires can be avoided, and the umbrella  20  can keep clean and be convenient to use. 
     It should be noted that the solar panel can be mounted rotationally on the rod  23  and outside the umbrella cloth  21 , and the fan can be mounted rotationally on the rod  23  and inside the umbrella cloth  21 . This can adjust the direction of the solar panel and the fan according to needs, so that the practicality is increased. 
     As shown in  FIG.  11    and  FIG.  12   , one embodiment of the present disclosure provides a product made of the radiative cooling fabric of the present disclosure. The product is a car cover  30  including a fixing member  32  and a cover body  31  made of the radiative cooling fabric. The fixing member  32  is provided on the cover body  31 . The fixing member  32  is configured for fixing the cover body  31  on a car. Thus, the cover body  31  can be fixed and closely attached to the surface of a car. On one hand, heat outside the car can be effectively prevented from entering the car by convection and heat transfer; on the other hand, when sunlight irradiates the cover body  31 , the functional layer  12  of the cover body  31  can reflect the sunlight to prevent the cover body  31  from accumulating excessive heat. The cover body  31  can also emit the heat on the cover body  31  and in the inner space of the car through an atmospheric window in a form of infrared radiation, so as to achieve cooling without energy consumption and improve user comfort. Moreover, the cover body  31  has excellent wrinkle resistance performance. The cover body  31  is not easy to wrinkle even if folded repeatedly. 
     In one or more embodiment, the fixing member  32  can further include a magnetic attraction layer  321  stacked between the flexible substrate layer  11  and the functional layer  12 . With the magnetic attraction layer  321 , the cover body  31  can be closely attached to the surface of a car to prevent the cover body  31  from being blown away by strong winds. Moreover, since the cover body  31  is closely attached to the surface of the car, the air between the cover body  31  and the car surface can be reduced, which can avoid damage to the car surface caused by the cover body  31  hitting the car surface under strong winds. 
     It should be noted that the cover body  31  can also be fixed and closely attached to the surface of a car with an electrostatic attraction layer, an adhesive layer, or a vacuum attraction layer. 
     In one or more embodiment, a thickness of the magnetic attraction layer  321  can be in a range of 7 μm to 12 μm, so that the car cover  30  can be fixed and closely attached to the surface of a car, and can also be easily removed from the car. 
     In one or more embodiment, the fixing member  32  can further include a magnetic body  322  located at an edge of the cover body  31 . Specifically, the magnetic body  322  can be a magnetic strip arranged at intervals at the edge of the cover body  31 ; or the magnetic body  322  can be a soft magnetic strip surrounded at the edge of the cover body  31 . The cover body  31  can be firmly attracted to the car body with the magnetic body  322 . 
     In one or more embodiment, the fixing member  32  can be a connecting belt and/or a hook. When the fixing member  32  is a connecting belt, one end of the connecting belt is located on the cover body  31 , and the other end of the connecting belt is used to detachably connect the wheel. Specifically, a hook is provided at one end of the connecting belt away from the cover body  31 , and the connecting belt can be connected to the wheel with the hook. Alternatively, a fastening (such as Velcro) is provided at one end of the connecting belt away from the cover body  31 , and the connecting belt can be connected to the wheel with the fastening. It can be understood that the connecting belt can also be fastened to the wheel. The car cover  30  can be firmly fixed on the car with the connecting belt to prevent the car cover  30  from being blown away by strong winds. When the hook is provided at an end of the connecting belt away from the cover body  31 , the connecting belt can also be connected to a lower edge of the car or a rearview mirror with the hook. When the fastening is provided on the end of the connecting belt away from the car cover  31 , the connecting belt can also be connected to the rearview mirror of the car with the fastening. It can be understood that the connecting belt can also be directly fastened to the rearview mirror. It can be understood that the way in which the end of the connecting belt away from the cover body  31  is connected to the cover body  31  can be selected according to the actual demand 
     It should be noted that if the car cover  30  is a half cover, the car cover  30  can be laid on the surface of the cab and trunk during use, and a circle of magnets can be placed at the edge of the car cover  30 , so that the car cover  30  can be close to the car surface. And if the car cover  30  is a full cover, the car cover  30  can be laid on the entire surface of the car, and magnets can be placed at a position of the car cover  30  corresponding to the door. 
     As shown in  FIG.  13    to  FIG.  19   , one embodiment of the present disclosure provides a product made of the radiative cooling fabric of the present disclosure. The product is a tent  40  including a tent frame  42  and a flysheet  41  made of the radiative cooling fabric. An outer side of the tent frame  42  is covered with the flysheet  41 . When sunlight irradiates the flysheet  41 , the functional layer  12  of the flysheet  41  can reflect the sunlight to prevent the flysheet  41  from accumulating excessive heat. The flysheet  41  can also emit the heat on the cover body  31  and in the inner space of the tent  40  through an atmospheric window in a form of infrared radiation, so as to achieve cooling without energy consumption and improve user comfort. Moreover, the flysheet  41  has excellent wrinkle resistance performance The flysheet  41  is not easy to wrinkle even if folded repeatedly. 
     It should be noted that the term “inner space of the tent  40 ” in the specification and claims of the present disclosure refers to a space away from the outdoors when the tent  40  is in use. 
     In one or more embodiment, the tent  40  can further include an inner tent  43  and a bottom tent. The inner tent  43  is located on the inner side of the flysheet  41 , and the bottom tent is located at the bottom of the inner tent  43 , and the inner tent  43  is connected to the tent frame  42 . Generally, the inner tent  43  is hoisted to the tent frame  42  by ropes, buckles, etc., and the flysheet  41  is covered on the tent frame  42  so that there is a certain gap between the inner tent  43  and the flysheet  41 . A closed space can be formed by providing an inner tent  43  inside the flysheet  41  and a bottom tent at the bottom of the inner tent  43 , which can keep heat well and prevent mosquitoes. It can be understood that the inner tent  43  and the flysheet  41  can also be connected by stitching or pasting, and then place the inner tent  43  and the flysheet  41  together on the tent frame  42  to facilitate the folding or opening of the tent  40 . 
     In one or more embodiment, the inner tent  43  can be made of polyester oxford cloth, which makes the tent  40  reliable, windproof, rainproof, and sun proof, so as to meet the requirements of the ordinary outdoor tent  40 . It can be understood that the inner tent  43  can also be made of mesh cloth, such as B 3  mesh cloth. The mesh cloth has good air permeability and light weight, and is convenient for storage and carrying. Additionally, the mesh cloth can also make the tent  40  have air permeability and anti-mosquito functions. 
     In one or more embodiment, the tent  40  can further include a detachable part  44 . The detachable part  44  can be detachably connected to the flysheet  41  or to a part of the inner tent  43  exposed to the flysheet  41 . The detachable part  44  can be located at the position of a dome structure of the tent  40 , and a planar shape of the detachable part  44  can be a square. 
     In one or more embodiment, the detachable part  44  can be made of the radiative cooling fabric. A radiative cooling effect of the tent  40  can be enhanced with the detachable part  44 . Additionally, the detachable part  44  is flexible to use and easy to replace. 
     In one or more embodiment, the detachable part  44  can be detachably connected to the flysheet  41  by zippers, Velcro, buttons, knots, etc., or detachably connected to the part of the inner tent  43  exposed to the flysheet  41 . 
     In one or more embodiment, the tent  40  can further include a door body  49 , a side of the flysheet  41  has an opening, and the door body  49  is located at the opening. Specifically, the door body  49  can be shaded in a form of a roller blind or in the form of a flip to facilitate entering and exiting the tent. It can be understood that the door body  49  can also include a window body. 
     In one or more embodiment, the tent  40  can further include a power supply  45 , a sensor  46 , an alarm  47 , and a controller  48 . The sensor  46 , the alarm  47 , and the controller  48  are respectively electrically connected to the power supply  45 . The controller  48  is electrically connected to the sensor  46  and the alarm  47  to meet the multi-functional requirements of the tent  40 . In this embodiment, the power supply  45  is a solar flexible battery located on the outer surface of the tent  40 . 
     In one or more embodiment, the sensor  46  can be a temperature sensor  46 , a distance sensor  46 , a smoke sensor  46 , or a combination thereof. The temperature sensor  46  can monitor temperature of the tent  40  to sense the actual temperature inside the tent  40  in real time; the distance sensor  46  can detect whether there is a beast or other objects approaching the tent  40 ; the smoke sensor  46  can detect whether a fire occurs inside or outside the tent  40 . And the alarm  47  can give an alarm in the form of sound and/or light to remind the persons in the tent  40  of a danger or to scare away wild animals. 
     As shown in  FIG.  20    to  FIG.  24   , one embodiment of the present disclosure provides a product made of the radiative cooling fabric of the present disclosure. The product is a hat  50  including a hat body  51  made of the radiative cooling fabric. The hat body  51  can be a cavity configured for accommodating a head. When sunlight irradiates the hat body  51 , the functional layer  12  of the hat body  51  can reflect the sunlight to prevent the hat body  51  from accumulating excessive heat. The functional layer  12  can also emit the heat on the surface of the hat body  51  and in the inner space of the cavity through an atmospheric window in a form of infrared radiation, so as to achieve cooling without energy consumption and improve user comfort. Moreover, the hat body  51  has excellent wrinkle resistance performance The hat body  51  is not easy to wrinkle even if folded repeatedly. 
     In one or more embodiment, at least one vent  511  is formed on the hat body  51 . The vent  511  can extend from the inner wall of the cavity to the outer wall of the cavity. If there are more than one vents  511 , the vents  511  can be arranged oppositely. The heat in the inner space of the cavity can be dissipated to the external environment with the vent  511 , so as to realize air circulation in the inner space of the cavity and further reduce the temperature of the inner space of the cavity. 
     In one or more embodiment, the hat  50  can further include a curtain  52  located at the opening of the cavity. When in use, the curtain  52  hangs on the neck of the user to avoid direct sunlight and sunburn on the neck. The curtain  52  is made of the radiative cooling fabric. When sunlight irradiates the curtain  52 , the functional layer  12  of the curtain  52  can reflect the sunlight to prevent the curtain  52  from accumulating excessive heat. The functional layer  12  can also emit the heat on the surface of the curtain  52  through an atmospheric window in a form of infrared radiation, so as to achieve cooling without energy consumption and improve user comfort. Moreover, the curtain  52  has excellent wrinkle resistance performance. The curtain  52  is not easy to wrinkle even if folded repeatedly. The curtain  52  can be folded according to requirements, which is convenient for storage and carrying. 
     In one or more embodiment(s), the curtain  52  can further include a mounting plate  521  and a curtain body  522  located on an edge of the mounting plate  521 . The mounting plate  521  is provided with a mounting hole  5211  adapted to the hat  50 . When in use, the mounting plate  521  is clamped on the top of the hat  50  by the mounting hole  5211 , which is easy to assemble and disassemble. 
     In one or more embodiment(s), the hat  50  can further include a storage bag  53  provided in the curtain  52 . The storage bag  53  located on a surface of the curtain  52  can store a folded curtain  52 , which is convenient for storage and portability 
     In one or more embodiment(s), the hat  50  can further include a cooling bag  54  located on an inner surface of the hat  50  corresponding to a position of the user&#39;s back head. Specifically, the cooling bag  54  can be detachably located on the inner surface of the hat  50  with a buckle, a zipper, or the like. Ice cubes, ice packs or other phase change substances can be added into the cooling bag  54  to cool the head. The melting and evaporation of the ice cubes, ice packs or other phase change substances can absorb the heat of the head and cool the head for a long time. It can be understood that even if the ice cubes, ice packs or other phase change materials are not put in, the cooling bag  54  can still reduce the heat generated by solar radiation, because the neck is covered by the cooling bag  54 . 
     In one or more embodiment(s), the hat  50  can further include pigments dispersed in the functional layer  12 . Specifically, the pigment can be dispersed in the first functional layer  121 , the second functional layer  122 , or the third functional layer  123 . By adding the pigment in the functional layer  12 , it is convenient to classify the hats  50 , and it is also convenient for users to identify their own hats  50 . 
     As shown in  FIG.  25   , one embodiment of the present disclosure provides a product made of the radiative cooling fabric of the present disclosure. The product is a curtain  60  including a curtain body made of the radiative cooling fabric. The curtain body forms a part of the curtain  60 . When sunlight irradiates the curtain body, the functional layer  12  of the curtain body can reflect the sunlight to prevent the curtain body from accumulating excessive heat. The functional layer  12  can also emit the heat on the surface of the curtain body and in the inner space of a building through an atmospheric window in a form of infrared radiation, so as to achieve cooling without energy consumption and improve user comfort. Moreover, the curtain body has excellent wrinkle resistance performance. The curtain body is not easy to wrinkle even if folded repeatedly. The curtain body can be folded according to requirements, which is convenient for storage and carrying. 
     As shown in  FIG.  26   , one embodiment of the present disclosure provides a product made of the radiative cooling fabric of the present disclosure. The product is an awning  70  including an awning frame  71  and an awning cloth  72  made of the radiative cooling fabric. The awning frame  71  is covered by the awning cloth  72 . When sunlight irradiates the awning cloth  72 , the functional layer  12  of the awning cloth  72  can reflect the sunlight to prevent the awning cloth  72  from accumulating excessive heat. The functional layer  12  can also emit the heat on the surface of the awning cloth  72  and in the inner space of the awning  70  through an atmospheric window in a form of infrared radiation, so as to achieve cooling without energy consumption and improve user comfort. Moreover, the awning cloth  72  has excellent wrinkle resistance performance The awning cloth  72  is not easy to wrinkle even if folded repeatedly. 
     It should be noted that the term “inner space of the awning  70 ” in the specification and claims of the present disclosure refers to a space away from the sunlight when the awning  70  is in use. 
     As shown in  FIG.  27   , one embodiment of the present disclosure provides a product made of the radiative cooling fabric of the present disclosure. The product is clothing  80  including cloth  81  made of the radiative cooling fabric. Specifically, the cloth  81  can be chest cloth, back cloth, shoulder cloth, etc. When sunlight irradiates the cloth  81 , the functional layer  12  of the cloth  81  can reflect the sunlight to prevent the cloth  81  from accumulating excessive heat. The functional layer  12  can also emit the heat on the surface of cloth  81  and in the inner space of the clothing  80  (such as human body) through an atmospheric window in a form of infrared radiation, so as to achieve cooling without energy consumption and improve user&#39;s comfort. Moreover, the cloth  81  has excellent wrinkle resistance performance. The cloth  81  is not easy to wrinkle even if folded repeatedly. 
     Embodiment 1 
     A radiative cooling fabric is provided. The radiative cooling fabric includes a waterproof layer, a flexible substrate layer, an interfacial agent layer, a first functional layer, and a hydrophobic layer stacked in order. The waterproof layer is an acrylic resin with a thickness of 10 μm. The flexible substrate layer is a polyester fabric with a thickness of 1 mm The interfacial agent layer is a polyurethane resin with a thickness of 10 μm. A thickness of the first functional layer is 30 μm, and the first functional layer includes 85 wt % epoxy resin and 10 wt % titanium dioxide (with a particle size of 5 μm), 3 wt % silicon nitride (with a particle size of 1 μm), and 2 wt % additive. The hydrophobic layer is a fluorine resin with a thickness of 10 μm. 
     Embodiment 2 
     A radiative cooling fabric is provided. The radiative cooling fabric includes a waterproof layer, a flexible substrate layer, a first functional layer, and a hydrophobic layer stacked in order. The waterproof layer is a polyurethane resin with a thickness of 20 μm. The flexible substrate layer is a polyester fabric with a thickness of 1 mm A thickness of the first functional layer is 60 μm, and the first functional layer includes 88 wt % polyimide, 5 wt % calcium carbonate (with a particle size of 3 μm), 3 wt % silicon dioxide (with a particle size of 5 μm), and 4wt % additive. The hydrophobic layer is a fluorine resin with a thickness of 10 μm. 
     Embodiment 3 
     A radiative cooling fabric is provided. The radiative cooling fabric includes a flexible substrate layer, an interfacial agent layer, a first functional layer, and a hydrophobic layer stacked in order. The flexible substrate layer is a polyester fabric with a thickness of 1 mm The interfacial agent layer is an epoxy resin with a thickness of 20 μm. A thickness of the first functional layer is 10 μm, and the first functional layer includes 80 wt % cycloolefin polymer, 9 wt % barium sulfate (with a particle size of 2 μm), 9 wt % silicon carbide (with a particle size of 7 μm), and 2 wt % additive. The hydrophobic layer is a silicone resin with a thickness of 20 μm. 
     Embodiment 4 
     A radiative cooling fabric is provided. The radiative cooling fabric includes a flexible substrate layer and a first functional layer stacked in order. The flexible substrate layer is a polyester fabric with a thickness of 1 mm A thickness of the first functional layer is 200 μm, and the first functional layer includes 76 wt % polyester resin, 10 wt % zinc aluminum oxide (with a particle size of 1 μm), 10 wt % silicon dioxide (with a particle size of 8 μm), and 4 wt % additive. 
     Embodiment 5 
     A radiative cooling fabric is provided. The radiative cooling fabric includes a flexible substrate layer and a first functional layer stacked in order. The flexible substrate layer is a cotton fabric with a thickness of 2 mm A thickness of the first functional layer is 150 μm, and the first functional layer includes 80 wt % polyurethane resin, 6 wt % indium tin oxide (with a particle size of 0.01 μm), 12 wt % titanium dioxide (with a particle size of 6 μm) and 2 wt % additive. 
     Embodiment 6 
     A radiative cooling fabric is provided. The radiative cooling fabric includes a flexible substrate layer and a first functional layer stacked in order. The flexible substrate layer is a nylon fabric with a thickness of 0.3 mm. A thickness of the first functional layer is 100 μm. The first functional layer includes 90 wt % acrylic resin, 4 wt % indium tin oxide (with a particle size of 3 μm), 4 wt % calcium carbonate (with a particle size of 15 μm) and 2 wt % additive. 
     Embodiment 7 
     A radiative cooling fabric is provided. The radiative cooling fabric includes a flexible substrate layer and a first functional layer stacked in order. The flexible substrate layer includes a polyester fabric with a thickness of 0.5 mm and a polyvinyl chloride resin coated on both sides of the polyester fabric. A thickness of a polyvinyl chloride resin layer is 20 μm. A thickness of the first functional layer is 80 μm. The first functional layer includes 88 wt % silicone resin, 8 wt % cesium tungsten bronze (with a particle size of 2 μm), 3wt % silicon nitride (with a particle size of 10 μm), and 1 wt % additive. 
     Embodiment 8 
     A radiative cooling fabric is provided. The radiative cooling fabric includes a flexible substrate layer and a first functional layer stacked in order. The flexible substrate layer includes a polyester fabric with a thickness of 0.5 mm and a polyurethane resin coated on both sides of the polyester fabric. A thickness of a polyurethane resin layer is 20 μm. A thickness of the first functional layer is 120 μm, The first functional layer includes 85 wt % acrylic resin,  6  wt % barium sulfate (with a particle size of 3 μm), 6 wt % calcium carbonate (with a particle size of 15 μm) and 3 wt % additive. 
     Embodiment 9 
     A radiative cooling fabric is provided. The radiative cooling fabric includes a flexible substrate layer and a first functional layer stacked in order. The flexible substrate layer includes a polyester fabric with a thickness of 1 mm A thickness of the first functional layer is 100 μm. The first functional layer includes 90 wt % silicone resin, 5 wt % titanium dioxide (with a particle size of 2 μm), 3 wt % calcium carbonate (with a particle size of 10 μm) and 2 wt % additive. 
     Comparative Embodiment 1 
     A radiative cooling fabric is provided. The radiative cooling fabric includes a flexible substrate layer and a first functional layer stacked in order. The flexible substrate layer includes a polyester fabric with a thickness of 1 mm A thickness of the first functional layer is 250 μm. The first functional layer includes 90 wt % silicone resin, 5 wt % titanium dioxide (with a particle of 2 μm), 3 wt % calcium carbonate (with a particle of 10 μm), and 2 wt % additive. 
     Comparative Embodiment 2 
     A radiative cooling fabric is provided. The radiative cooling fabric includes a flexible substrate layer and a functional layer stacked in order. The flexible substrate layer includes a polyester fabric with a thickness of 1 mm A thickness of the functional layer is 5 μm. The functional layer includes 70 wt % silicone resin, 14 wt % titanium dioxide (with a particle of 2 μm), 14 wt % calcium carbonate (with a particle of 10 μm), and 2 wt % additive. 
     Comparative Embodiment 3 
     A radiative cooling fabric is provided. The radiative cooling fabric includes a waterproof layer, a flexible substrate layer, an interfacial agent layer, a functional layer, and a hydrophobic layer stacked in order. The waterproof layer is an acrylic resin with a thickness of 25 μm. The flexible substrate layer is a polyester fabric with a thickness of 1 mm The interfacial agent layer is a polyurethane resin with a thickness of 25 μm. A thickness of the functional layer is 200 μm, and the functional layer includes 85wt % epoxy resin, 10 wt % titanium dioxide (with a particle size of 5 μm), 3 wt % silicon nitride (with a particle size of 1 μm) and 2wt % other additive. The hydrophobic layer is a fluorine resin with a thickness of 25 μm. 
     A reflectivity of the radiative cooling fabric in the above embodiments and comparative embodiments in the wavelength of 300 nm to 2500 nm and an emissivity of the radiative cooling fabric in the above embodiments and comparative embodiments in the wavelength of 7 μm to 14 μm are tested. The test results are shown in Table 1. 
     The wrinkle resistance of the radiative cooling fabric of the above embodiments and comparative embodiments are tested. The wrinkle recovery performance of the fabric is tested according to GB/T3819-1997 standard. Before cutting the sample, locating the sample in a standard condition (with a temperature of 20±3 degrees centigrade and a relative humidity of 65±5%) for 24 hours; marking the warp and weft in the fabric by a fabric wrinkle elasticity tester (model YG(B)541D, made in China); cutting a piece of 40 mm×15 mm sample with a shape of “convex” along the width direction of the sample and 5 cm away from the edge of the fabric; folding the sample in half according to the standard and standing for 1 minute under a pressure of 10 N; measuring the elastic angle of the sample (5 minutes after the force is released) by the fabric wrinkle elasticity tester; and obtaining an average value by measuring 5 times in warp direction and weft direction respectively. The larger the wrinkle recovery angle, the better the wrinkle resistance of the fabric. The test results are shown in Table 1. 
     
       
         
           
               
               
               
               
               
             
               
                 TABLE 1 
               
               
                   
               
               
                   
                 Reflectivity in  
                 Emissivity in 
                 Average  
                 Average 
               
               
                   
                 the  
                 the  
                 value of 
                 value of  
               
               
                   
                 avelength 
                 wavelength 
                 warp  
                 weft  
               
               
                   
                 of 300 nm to 
                 of 7 μm to 
                 recovery 
                 recovery  
               
               
                 Embodiment 
                 2500 nm 
                 14 μm 
                 angle 
                 angle 
               
               
                   
               
             
            
               
                 Embodiment 1 
                 86% 
                 87% 
                 104.4° 
                 100.4° 
               
               
                 Embodiment 2 
                 88% 
                 89% 
                 103.9° 
                 100.2° 
               
               
                 Embodiment 3 
                 82% 
                 83% 
                 104.7° 
                 101.2° 
               
               
                 Embodiment 4 
                 93% 
                 94% 
                  98.4° 
                  93.7° 
               
               
                 Embodiment 5 
                 92% 
                 94% 
                 100.7° 
                  98.0° 
               
               
                 Embodiment 6 
                 92% 
                 93% 
                 102.8° 
                  99.3° 
               
               
                 Embodiment 7 
                 90% 
                 91% 
                 103.2° 
                  99.8° 
               
               
                 Embodiment 8 
                 92% 
                 93% 
                 101.5° 
                  98.5° 
               
               
                 Embodiment 9 
                 92% 
                 93% 
                 102.6° 
                  99.2° 
               
               
                 Comparative 
                 92% 
                 93% 
                  89.2° 
                  84.3° 
               
               
                 embodiment 1 
                   
                   
                   
                   
               
               
                 Comparative 
                 69% 
                 72% 
                  93.5° 
                  90.4° 
               
               
                 embodiment 2 
                   
                   
                   
                   
               
               
                 Comparative 
                 93% 
                 93% 
                  90.7° 
                  84.8° 
               
               
                 embodiment 3 
               
               
                   
               
            
           
         
       
     
     It can be seen from the recovery angle of the embodiment 9 and the comparative embodiment 1, when the thickness of the functional layer exceeds 200 μm, the wrinkle resistance of the fabric is significantly reduced, while the reflectivity and emissivity of the functional layer tend to be stable with the increase of the thickness. That is, when the thickness of the functional layer reaches about 200 μm, increasing the thickness of the functional layer will not improve the reflection and radiative cooling performance of the functional layer, but will make the wrinkle resistance of the fabric worse. 
     It can be seen from the recovery angle of the embodiment 9 and the comparative embodiment 2, when the filler in the functional layer exceeds 20%, even if the thickness of the functional layer is thin, the wrinkle resistance of the fabric will get worse. 
     It can be seen from the recovery angle of the embodiment 1 and the comparative embodiment 3, when the thickness of each layer in the radiative cooling fabric exceeds a certain value, the wrinkle resistance of the fabric will get worse. 
     The present disclosure further provides an application case of the radiative cooling fabric. 
     As shown in  FIG.  28   , a stainless-steel display room A is provided with a length of 5 meters, a width of 4 meters, and a height of 3 meters. One wall of the display room has a glass window with a size of 2.5 m×2 m. A radiative cooling fabric of the embodiment of  FIG.  6    is located on the inside of the glass windows of the display room A. An area of the radiative cooling fabric is 5 m 2 . The display room A is placed in an open outdoor place, and a thermocouple with a data logger is used to measure and record the temperature change at a temperature measurement position bl in the middle of the display room A, The temperature change is shown in curve b of  FIG.  29   . 
     A stainless steel display room B is provided. The material, size, structure and shape of the display room B and the display room A are the same. The difference is that the glass window of the display room B is equipped with an ordinary shading curtain (polyester fabric with a thickness of 1 mm). An area of the shading curtain is 5 m 2 . Place the display room B in a place same as the environment of the display room A, and a thermocouple with a data logger is used to measure and record the temperature change at a temperature measurement position al in the middle of the display room B. The temperature change is shown in curve a of  FIG.  29   . 
     While measuring the temperature change of display room A and display room B, an outdoor ambient temperature and solar radiative intensity are also measured at the same time. The ambient temperature is shown in curve c of  FIG.  29   , and the solar radiative intensity is shown in curve d of  FIG.  29   . It can be seen from the curves in  FIG.  29   , in the same period of time, the temperature in display room B can be up to 20 degrees centigrade higher than that of the outdoor, while the temperature in display room A can be up to 6 degrees centigrade lower than the that in display room B, which shows that the radiative cooling fabric has a good automatic cooling effect. The radiative cooling fabric can reduce the indoor temperature and improve indoor comfort. Additionally, the radiative cooling fabric is energy-saving and environmentally friendly. 
     Another application case of the radiative cooling fabric is provided. 
     As shown in  FIG.  30   , three cars C, D, and E of the same brand and model are provided. The three cars are parked in the same environment. Car C is covered with a car cover which is made of an ordinary fabric (polyester fabric with a thickness of 1 mm). Car D is covered with a car cover made of the radiative cooling fabric of the embodiment of  FIG.  8   . And car E does not have any car cover. Temperature measurement positions e 1 , g 1 , and f 1  are set in the middle of the cabs of the cars C, D, and E respectively. A thermocouple with a data logger is used to measure and record the temperature changes of each temperature measurement position. The measurement results are shown in curves e.g., and f of  FIG.  31   . While measuring the temperature changes inside the cars, an outdoor ambient temperature and solar radiative intensity are also measured at the same time. The ambient temperature is shown in curve h of  FIG.  31   , and the solar radiative intensity is shown in curve j of  FIG.  31   . It can be seen from the curves in  FIG.  31   , the temperature of the car with a car cover made of radiative cooling fabric is the lowest. In the same period of time, the maximum temperature difference between D and C can reach 20 degrees centigrade, and the maximum temperature difference between D and E can reach 30 degrees centigrade, which shows that the car cover made of a radiative cooling fabric can greatly reduce the temperature of the car and solve the problem of high temperature inside the car under sunlight, so as to extend the life of the car, improve the safety, and increase the comfort. 
     Another application case of the radiative cooling fabric is provided. 
     As shown in  FIG.  32   , tent H and tent J of the same size, shape and style are provided. A flysheet of the tent H is made of a radiative cooling fabric of the embodiment of  FIG.  9   , and a flysheet of the tent J is made of ordinary fabric (polyester fabric with a thickness of 1 mm).The tent H and tent J are located in the same environment. Temperature measurement positions ml and kl are set in the middle of the tent H and tent J, respectively. The temperature changes at the positions ml and kl are measured and the results are shown in curves m and k of  FIG.  33   . While measuring the temperature changes inside the tents, an outdoor ambient temperature and solar radiative intensity are also measured at the same time. The ambient temperature is shown in curve n of  FIG.  33   , and the solar radiative intensity is shown in curve p of  FIG.  33   . It can be seen from the curves in  FIG.  33   , in the same period of time, the maximum temperature difference between H and J can reach 20 degrees centigrade, which shows that the tent made of a radiative cooling fabric has a good automatic cooling effect. The radiative cooling fabric can reduce the internal temperature of the tent and improve comfort. 
     Embodiment 10 
     A method for preparing a radiative cooling fabric is provided including following steps: 
     providing a flexible substrate layer, which includes a polyester fabric and polyvinyl chloride resin layers coated on both sides of the polyester fabric, a thickness of the polyester fabric is 1 mm, and a thickness of each polyvinyl chloride resin layer is 10 μm; 
     coating a PET resin with a thickness of 20 μm on the flexible substrate layer, spraying a layer of titanium white powders with an average particle size of 10 μm on a surface of the PET resin before the PET resin is dried, and drying the PET resin to obtain a first function layer and a second functional layer; and 
     coating a PET resin with a thickness of 20 μm on the titanium white powders, and drying the PET resin to obtain a third functional layer. 
     Embodiment 11 
     A method for preparing a radiative cooling fabric is provided including the following steps: 
     providing a flexible substrate layer, which includes a polyester fabric and polyvinyl chloride resin layers coated on both sides of the polyester fabric, a thickness of the polyester fabric is 1 mm, and a thickness of each polyvinyl chloride resin layer is 10 μm; 
     coating a polyacrylic acid (PAA) resin with a thickness of 20 μm on the flexible substrate layer, spraying a layer of talcum powders with an average particle size of 20 μm on a surface of the polyacrylic acid (PAA) before the polyacrylic acid (PAA) resin is dried, and drying the polyacrylic acid (PAA) resin to obtain a first function layer and a second functional layer; and 
     coating a polyacrylic acid (PAA) resin with a thickness of 10 μm on the talcum powders, and drying the polyacrylic acid (PAA) resin to obtain a third functional layer. 
     Embodiment 12 
     A method for preparing a radiative cooling fabric is provided including the following steps: 
     providing a flexible substrate layer, which includes a polyester fabric and polyvinyl chloride resin layers coated on both sides of the polyester fabric, a thickness of the polyester fabric is 1 mm, and a thickness of each polyvinyl chloride resin layer is 10 μm; 
     coating a polyurethane resin with a thickness of 20 μm on the flexible substrate layer, spraying a layer of silicon dioxide powders with an average particle size of 30 μm on a surface of the polyurethane resin before the polyurethane resin is dried, and drying the polyurethane resin to obtain a first function layer and a second functional layer; and 
     coating a polyurethane resin with a thickness of 10 μm on the silicon dioxide powders, and drying the polyurethane resin to obtain a third functional layer. 
     Embodiment 13 
     Providing a flexible substrate layer, which includes a polyester fabric and polyvinyl chloride resin layers coated on both sides of the polyester fabric, a thickness of the polyester fabric is 1 mm, and a thickness of each polyvinyl chloride resin layer is 10 μm; 
     coating a PET resin with a thickness of 20 μm on the flexible substrate layer, wherein the PET resin layer is mixed with 10% by volume of silicon dioxide with an average particle size of 10 μm, spraying a layer of titanium white powders with an average particle size of 30 μm on a surface of the PET resin before the PET resin is dried, and drying the PET resin to obtain a first function layer and a second functional layer; and 
     coating a PET resin with a thickness of 10 μm on the titanium white powders, wherein the PET resin layer is mixed with 5% by volume of silicon dioxide with an average particle size of 6 μm, drying the PET resin to obtain a third functional layer. 
     Embodiment 14 
     Providing a flexible substrate layer, which includes a polyester fabric and polyvinyl chloride resin layers coated on both sides of the polyester fabric, a thickness of the polyester fabric is 1 mm, and a thickness of each polyvinyl chloride resin layer is 10 μm; 
     coating a PET resin with a thickness of 20 μm on the flexible substrate layer, wherein the PET resin layer is mixed with 15% by volume of titanium white powders with an average particle size of 10 μm, spraying a layer of silicon dioxide powders with an average particle size of 30 μm on a surface of the PET resin before the PET resin is dried, and drying the PET resin to obtain a first function layer and a second functional layer; and 
     coating a PET resin with a thickness of 10 μm on the silicon dioxide powders, wherein the PET resin layer is mixed with 12% by volume of pearl powders, drying the PET resin to obtain a third functional layer. 
     Comparative Embodiment 4 
     A method for preparing a radiative cooling fabric is provided including the following steps: 
     providing a flexible substrate layer, which includes a polyester fabric and polyvinyl chloride resin layers coated on both sides of the polyester fabric, a thickness of the polyester fabric is 1 mm, and a thickness of each polyvinyl chloride resin layer is 10 μm; 
     coating a PET resin with a thickness of 50 μm on the flexible substrate layer, wherein the PET resin is mixed with 30% by mass of silicon dioxide with an average particle size of 10 μm; and 
     drying the PET resin. 
     Comparative Embodiment 5 
     A method for preparing a radiative cooling fabric is provided including the following steps: 
     providing a flexible substrate layer, which includes a polyester fabric and polyvinyl chloride resin layers coated on both sides of the polyester fabric, a thickness of the polyester fabric is 1 mm, and a thickness of each polyvinyl chloride resin layer is 10 μm; 
     coating a polyurethane resin with a thickness of 100 μm on the flexible substrate layer, wherein the polyurethane resin is mixed with 25% by mass of titanium white powders with an average particle size of 10 μm; and 
     drying the polyurethane resin. 
     Comparative Embodiment 6 
     A method for preparing a radiative cooling fabric is provided including the following steps: 
     providing a flexible substrate layer, which includes a polyester fabric and polyvinyl chloride resin layers coated on both sides of the polyester fabric, a thickness of the polyester fabric is 1 mm, and a thickness of each polyvinyl chloride resin layer is 10 μm; 
     coating a polyurethane resin with a thickness of 20 μm on the flexible substrate layer and drying, and coating an aluminum oxide layer with a thickness of 20 nm on a surface of the polyurethane resin layer by a magnetron sputtering method; and 
     coating a polyurethane resin with a thickness of 10 μm on the aluminum oxide layer, wherein the polyurethane resin layer is mixed with 5% by volume of silicon dioxide with an average particle size of 6 μm, and then drying the polyurethane resin. 
     Comparative Embodiment 7 
     A method for preparing a radiative cooling fabric is provided including the following steps: 
     providing a flexible substrate layer, which includes a polyester fabric and polyvinyl chloride resin layers coated on both sides of the polyester fabric, a thickness of the polyester fabric is 1 mm, and a thickness of each polyvinyl chloride resin layer is 10 μm; 
     coating a polyurethane resin with a thickness of 20 μm on the flexible substrate layer and drying, and coating aluminum oxide layers on a surface of the polyurethane resin layer by a magnetron sputtering method, wherein a thickness of each aluminum oxide layer is 20 nm, and a number of the aluminum oxide layers is 10; and 
     coating a polyurethane resin with a thickness of 10 μm on the aluminum oxide layers, wherein the polyurethane resin layer is mixed with 5% by volume of silicon dioxide with an average particle size of 6 μm, and then drying the polyurethane resin. 
     Comparative Embodiment 8 
     A method for preparing a radiative cooling fabric is provided including the following steps: 
     providing a flexible substrate layer, which includes a polyester fabric and polyvinyl chloride resin layers coated on both sides of the polyester fabric, a thickness of the polyester fabric is 1 mm, and a thickness of each polyvinyl chloride resin layer is 10 μm; 
     coating a polyurethane resin with a thickness of 20 μm on the flexible substrate layer and drying, wherein the polyurethane resin layer is mixed with 15% by volume of titanium white powder with an average particle size of 10 μm, and coating aluminum oxide layers on a surface of the polyurethane resin layer by a magnetron sputtering method, wherein a thickness of each aluminum oxide layer is 20 nm, and a number of the aluminum oxide layers is 10; and 
     coating a polyurethane resin with a thickness of 10 μm on the aluminum oxide layers, wherein the polyurethane resin layer is mixed with 5% by volume of silicon dioxide with an average particle size of 6 μm, and then drying the polyurethane resin. 
     An emissivity of the radiative cooling fabric in the above embodiments and comparative embodiments in the wavelength of 7 μm to 14 μm and a reflectivity of the radiative cooling fabric in the above embodiments and comparative embodiments in the wavelength of 300 nm to 2500 nm are tested. The test results are shown in Table 2. 
     
       
         
           
               
               
               
               
               
             
               
                 TABLE 2 
               
               
                   
               
               
                   
                 Emissivity in the 
                 Reflectivity in the 
                 Average value 
                 Average value of 
               
               
                   
                 wavelength of 7 
                 wavelength of 
                 of warp 
                 weft recovery 
               
               
                 Embodiment 
                 μm to 14 μm 
                 300 nm to 2500 nm 
                 recovery angle 
                 angle 
               
               
                   
               
             
            
               
                 Embodiment 
                 91.1% 
                 89.2% 
                 125.1° 
                 124.2° 
               
               
                 10 
                   
                   
                   
                   
               
               
                 Embodiment 
                 92.4% 
                 90.2% 
                 127.5° 
                 125.2° 
               
               
                 11 
                   
                   
                   
                   
               
               
                 Embodiment 
                 92.7% 
                 93.5% 
                 123.2° 
                 121.5° 
               
               
                 12 
                   
                   
                   
                   
               
               
                 Embodiment 
                 93.6% 
                 93.8% 
                  122.° 
                 120.8° 
               
               
                 13 
                   
                   
                   
                   
               
               
                 Embodiment 
                 93.9% 
                 93.4% 
                 119.9° 
                 117.7° 
               
               
                 14 
                   
                   
                   
                   
               
               
                 Comparative 
                 78.2% 
                 75.1% 
                  91.4° 
                  91.0° 
               
               
                 embodiment 4 
                   
                   
                   
                   
               
               
                 Comparative 
                 79.5% 
                 76.6% 
                  92.8° 
                  92.5° 
               
               
                 embodiment 5 
                   
                   
                   
                   
               
               
                 Comparative 
                 85.1% 
                 78.9% 
                  93.5° 
                  92.1° 
               
               
                 embodiment 6 
                   
                   
                   
                   
               
               
                 Comparative 
                 85.6% 
                 87.0% 
                  92.6° 
                  91.7° 
               
               
                 embodiment 7 
                   
                   
                   
                   
               
               
                 Comparative 
                 89.7% 
                 88.5% 
                  92.0° 
                  90.7° 
               
               
                 embodiment 8 
               
               
                   
               
            
           
         
       
     
     In the foregoing embodiments, the descriptions of the various embodiments are different, and the parts that are not described in detail in a certain embodiment may be referred to the related descriptions of other embodiments. 
     The above embodiments are only used to explain the technical solutions of the present disclosure and are not limited thereto. Those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or some technical features are equivalently substituted; and these modifications or substitutions do not detract from the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present disclosure.