Bionic cellulose-based passive radiation refrigeration material as well as preparation method and application thereof

Abstract

The invention discloses a bionic cellulose-based passive radiation refrigeration material as well as a preparation method and application thereof, and belongs to the crossing field of functional cellulose materials and bionic radiation refrigeration technologies. Cellulose, a modifier, metal salt, an imidazole organic ligand and the like are used as raw materials, natural cellulose from different sources is used as a base material, and the bionic cellulose-based passive radiation refrigeration material is prepared through bionic design and a nanoscale heterojunction in-situ growth process. The preparation method is simple and easy to implement, the reaction condition is mild, the prepared material has excellent optical performance, efficient sunlight reflection and atmospheric window infrared radiation can be achieved, and the remarkable zero-energy-consumption passive cooling effect is achieved; the material has excellent zero-energy-consumption efficient refrigeration performance, excellent environmental durability and excellent sustainable and expanded preparation characteristics, and is light and portable; the prepared material can be applied to multiple scenes and is used for outdoor portable zero-energy-consumption efficient refrigeration.

Description

Technical Field

[0001] This invention belongs to the interdisciplinary field of functional cellulose materials and biomimetic radiation refrigeration technology, specifically involving a cellulose-based passive radiation refrigeration material with a biomimetic pangolin scale multi-scale structure, its large-scale preparation method, and its application. Background Technology

[0002] With global warming and the escalating energy crisis, the demand for portable outdoor thermal management (such as automotive powertrain cooling, wearable cooling systems, and temporary storage and transportation of fresh produce) is becoming increasingly urgent. Traditional compression refrigeration technology relies on high-energy-consuming electricity and is constrained by space, making it difficult to meet the needs of mobile scenarios. Furthermore, its refrigerant emissions impose an environmental burden. Passive radiation cooling (PRC) technology achieves zero-energy cooling by spontaneously reflecting sunlight and efficiently radiating heat to the cold outer space, providing a promising solution for sustainable thermal management. However, the development of current PRC materials faces significant bottlenecks. On the one hand, most materials struggle to simultaneously achieve high-efficiency cooling performance (high solar reflectivity and high infrared emissivity) and excellent outdoor environmental durability (such as hydrophobicity, UV resistance, and antibacterial properties). On the other hand, portability and practicality are insufficient; materials often lack lightweight and flexibility, have poor processability, and cannot meet the demands of dynamic outdoor scenarios for portability and easy deployment. Therefore, developing a new type of PRC material that integrates high-efficiency cooling, excellent environmental resistance, lightweight portability and sustainability is crucial for breaking through the application barriers in dynamic outdoor scenarios such as automotive power equipment, mobile wearables and fresh food cold chain. Summary of the Invention

[0003] The purpose of this invention is to provide a biomimetic cellulose-based passive radiative cooling material with synergistic and efficient optical properties, outdoor environmental durability, and lightweight portability, as well as its preparation method and applications. The preparation method is simple and easily scaled up. The resulting material can be used for portable, high-efficiency outdoor cooling and exhibits good environmental durability.

[0004] To achieve the above objectives, the present invention adopts the following technical solution: A method for preparing a biomimetic cellulose-based passive radiative cooling material includes the following steps: (1) Take 0.25-4 parts by weight of cellulose, 5-30 parts of modifier, 2-50 parts of metal salt, 1-60 parts of imidazole organic ligand, and 5-20 parts of potassium hydroxide or sodium hydroxide for later use; the cellulose is derived from one or more of wood, bamboo fiber, cotton fiber, and hemp fiber; the modifier is one or more of sodium chloroacetate, sodium bromoacetate, sodium tripolyphosphate, citric acid, succinic anhydride, and p-toluenesulfonic acid; the metal salt is silver nitrate, copper nitrate, zinc nitrate, zinc acetate, cobalt nitrate, or ferric chloride; the imidazole organic ligand is 2-methylimidazolium or 1,2-2-methylimidazolium; (2) Place the cellulose raw material in an appropriate amount of water and organic solvent solution, with a volume ratio of water to organic solvent of (1-9):(1-9); then add 5-20 parts of potassium hydroxide or sodium hydroxide, place it in the reaction system, stir at 30-100℃ for 1-6 hours, add 5-30 parts of modifier to the reaction system, stir at 30-80℃ for 1-24 hours; take out the prepared modified cellulose, wash it with ethanol 2-5 times and dry it for later use. (3) Prepare metal salt-organic solvent solutions with a concentration of 5-50 mmol / L using metal salts and organic solvents; prepare imidazole organic ligand solutions with a concentration of 5-50 mmol / L using imidazole organic ligands and organic solvents; (4) Add an appropriate amount of metal salt-organic solvent solution to the container, then put the modified cellulose into the reaction system, stir at 30-100℃ for 1-12 hours, and then hydrothermally treat at 30-80℃ for 5-24 hours; wash the hydrothermally treated cellulose with ethanol or water-ethanol mixture 4 times, and then put it into a system containing an equal volume of metal salt-organic solvent solution and imidazole organic ligand solution, react at 30-80℃ for 4-24 hours, take out the cellulose material, wash it with ethanol 4 times, and then dry it in a vacuum oven at 40-60℃ for 12-24 hours to obtain a multifunctional cellulose-based passive radiation cooling material with a biomimetic structure.

[0005] Furthermore, in the above-mentioned method for preparing biomimetic cellulose-based passive radiation cooling material, the cellulose raw materials used in step (1) include one or more of cellulose paper and cellulose fibers.

[0006] Furthermore, by using cellulose paper or cellulose fiber as cellulose raw material, multifunctional cellulose-based passive radiation cooling paper or cooling cellulose fiber with biomimetic structure can be prepared. The cooling cellulose fiber is dispersed in an aqueous solution to prepare a suspension, which can be used to coat or spray onto the surface of an object to make a passive radiation cooling coating.

[0007] Preferably, in the above-mentioned method for preparing biomimetic cellulose-based passive radiation cooling material, the organic solvent in steps (2) and (3) is methanol, ethanol, isopropanol or ethyl acetate.

[0008] Preferably, in step (4), an appropriate amount of metal salt-organic solvent solution is added to the container, and the ratio of the volume of the added solution to the mass of cellulose is (5-80) mL: (0.5-20) g. In step (4), the washed cellulose is placed into a system containing equal volumes of metal salt-organic solvent solution and imidazole organic ligand solution, and the ratio of the mass of the added cellulose to the volume of the solution is (5-10) g: (80-100) mL.

[0009] Furthermore, the above-mentioned preparation method of biomimetic cellulose-based passive radiation cooling material also includes step (5): the prepared biomimetic cellulose-based passive radiation cooling material can be placed directly or coated on the surface of the application scenario in the form of lightweight paper or coating, for example, temporary storage or transportation of fruits and vegetables after harvesting on farms, on the surface of automobiles or outdoor electronic devices, on the exterior walls of buildings, etc., for zero-energy high-efficiency cooling of various outdoor facilities.

[0010] On the other hand, the present invention also provides a method for preparing a biomimetic cellulose-based passive radiation cooling material using the above-mentioned method.

[0011] Application of the biomimetic cellulose-based passive radiation cooling material prepared by the preparation method described in this invention as a passive radiation cooling product.

[0012] This invention discloses a cellulose-based high-efficiency portable multifunctional passive radiative cooling material with a biomimetic structure, its preparation method, and its application. Addressing the challenges faced by existing passive radiative cooling materials in terms of comprehensive performance (high cooling efficiency, environmental sustainability, and outdoor durability), this invention innovatively simulates the multi-scale "tough-flexible synergistic" structure of pangolin scales, combining in-situ nucleation growth and sacrificial etching processes to construct a highly efficient optical heterojunction functional layer on a functionalized modified cellulose substrate. The radiative cooling material prepared using this invention exhibits three synergistic superior characteristics: (1) Excellent optical performance: It can achieve efficient solar light reflection and atmospheric window infrared radiation, achieving a significant zero-energy passive cooling effect; (2) Excellent environmental durability: It possesses excellent mechanical strength, flexibility, superhydrophobicity, UV aging resistance, and inherent antibacterial activity, ensuring long-term stable use in complex outdoor environments; (3) Excellent sustainable and scalable preparation characteristics: Using widely available and renewable cellulose as the substrate, it has ultra-lightweight characteristics, is easy to process into different shapes and sizes, and has biodegradability potential. This material breaks through the limitations of traditional passive radiative cooling materials in practical outdoor applications. It is particularly suitable for scenarios requiring portable, efficient, and sustainable thermal management, such as automotive power equipment and temporary storage and transportation of fresh agricultural products, providing an innovative biomass-based solution for zero-energy refrigeration.

[0013] The advantages and beneficial effects of this invention are as follows: 1. The method of this invention uses natural cellulose from different sources as substrates to prepare passive radiation cooling materials through biomimetic design and in-situ growth of nanoscale heterostructures. The reaction conditions are mild, the reagents are low in toxicity, and no precious metals or hazardous chemicals are involved.

[0014] 2. The method of this invention produces a multifunctional refrigeration material based on biomimetic design of plants and animals in nature. It has flexibility and mechanical stability. Through in-situ nucleation and template sacrificial etching technology, the nanoscale metal-organic materials and modified cellulose are tightly bonded together, which solves the brittle fracture defect of traditional bio-based radiation refrigeration materials.

[0015] 3. The multifunctional refrigeration material prepared by the method of the present invention integrates environmental durability, including superhydrophobicity, resistance to ultraviolet aging and broad-spectrum antibacterial properties, and has good antibacterial effect against Escherichia coli and Staphylococcus aureus.

[0016] 4. The multifunctional cellulose-based passive radiation cooling material with a biomimetic structure prepared by the method of the present invention has excellent zero-energy-consumption and high-efficiency cooling performance. Through high solar reflectivity and infrared emissivity, it achieves a cooling effect of 21.4℃ lower than the sub-ambient temperature.

[0017] 5. The multifunctional refrigeration material prepared by the method of this invention can be applied in various scenarios in the form of paper or coating, and has the advantage of portable application. When applied to automotive engine cooling, wearable thermal management equipment, temporary storage and transportation of fruit, or building exterior surfaces, it can prevent direct sunlight, reduce internal temperature, extend the service life of instruments, regulate human body temperature to a comfortable range, and extend shelf life, among other effects.

[0018] 6. The cellulose-based radiation cooling material prepared by the method of the present invention has full life-cycle sustainability, with a natural degradation rate of more than 95% within 90 days. Furthermore, the multifunctional cellulose-based radiation cooling material after use is easy to dispose of, and can be directly incinerated or treated as hazardous waste. The incineration residue does not produce harmful substances.

[0019] 7. The biomimetic cellulose-based passive radiation cooling material prepared by the method of the present invention has excellent zero-energy-consumption and high-efficiency cooling performance, outstanding environmental durability, excellent sustainable and scalable preparation characteristics, and is lightweight and portable. Attached Figure Description

[0020] Figure 1 The images show the physical specimen and scanning electron microscope (SEM) image of the zinc-based@modified cellulose high-efficiency portable multifunctional radiation-cooling paper prepared using the method described in Example 1. Figure 1 In the image, part a is the actual object image, and part b is the scanning electron microscope image.

[0021] Figure 2 These are renderings of actual portable applications of zinc-based@modified cellulose high-efficiency portable multifunctional radiation cooling paper; Figure 2Part a shows the application and cooling effect of zinc-based@modified cellulose high-efficiency portable multifunctional radiation cooling paper on the surface of an automobile engine; Part b shows the application and cooling effect of zinc-based@modified cellulose high-efficiency portable multifunctional radiation cooling paper on the human arm; Part c shows the application and cooling effect of zinc-based@modified cellulose high-efficiency portable multifunctional radiation cooling paper in simulated outdoor temporary storage of post-harvest strawberries.

[0022] Figure 3 The image shows the ultralight weight, hydrophobic properties, flexibility, and high mechanical strength of the zinc-based@modified cellulose high-efficiency portable multifunctional radiation cooling paper prepared. Figure 3 Part a shows the ultralightweight properties of the zinc-based@modified cellulose high-efficiency portable multifunctional radiation cooling paper; part b shows the superhydrophobicity of the zinc-based@modified cellulose high-efficiency portable multifunctional radiation cooling paper to methylene blue solution, coffee, milk, and deionized water; part c shows that the zinc-based@modified cellulose high-efficiency portable multifunctional radiation cooling paper can return to its original shape after being double-folded or rolled, indicating its good flexibility; part d shows that a 1cm*4cm piece of zinc-based@modified cellulose high-efficiency portable multifunctional radiation cooling paper can support a 500-gram weight, indicating its good mechanical strength.

[0023] Figure 4 These are schematic diagrams (a) and actual images (b) and electron microscope images (c) of the prepared zinc-based@modified cellulose high-efficiency portable multifunctional radiation cooling paper under ultraviolet accelerated aging test. Figure 4 Part a is a schematic diagram of the accelerated UV aging experiment of zinc-based@modified cellulose high-efficiency portable multifunctional radiation-cooling paper; Part b is an appearance image of the material after the accelerated UV aging experiment of zinc-based@modified cellulose high-efficiency portable multifunctional radiation-cooling paper, as well as an actual image after being rolled, folded or stretched; Part c is a scanning electron microscope image of the material after the accelerated UV aging experiment of zinc-based@modified cellulose high-efficiency portable multifunctional radiation-cooling paper.

[0024] Figure 5 It is a zinc-based, modified cellulose, high-efficiency, portable, multifunctional radiation-cooling paper for Escherichia coli (E. coli). E. coli ) and Staphylococcus aureus ( S. aureus (Image showing the size of the inhibition zone.)

[0025] Figure 6 This is an image showing the effect of zinc-based@modified cellulose high-efficiency portable multifunctional radiative cooling paper in outdoor radiative cooling applications. Detailed Implementation

[0026] The present invention will now be described in further detail with reference to the embodiments and accompanying drawings. Unless otherwise specified, the materials, reagents, etc. used in the following embodiments are commercially available.

[0027] The following methods can be used to prepare lightweight, environmentally durable, and highly efficient cellulose-based passive radiation cooling paper or cellulose-based radiation cooling coating. Example 1

[0028] A method for preparing a biomimetic cellulose-based passive radiative cooling material includes the following steps: (1) Take 0.5 parts of bamboo pulp cellulose paper, 10 parts of modifier, 20 parts of metal salt, 10 parts of imidazole organic ligand, and 10 parts of sodium hydroxide by weight; the modifier is sodium chloroacetate; the metal salt is zinc nitrate; and the imidazole organic ligand is 2-methylimidazole. (2) Immerse bamboo pulp cellulose paper in a certain amount of water and isopropanol mixture, with a volume ratio of water to isopropanol of 4:6; then add 10 parts of sodium hydroxide, stir at 80°C for 2 hours, add 10 parts of sodium chloroacetate to the reaction system, and stir at 40°C for 8 hours; take out the modified cellulose paper, wash it with ethanol 4 times, and dry it to obtain modified bamboo pulp cellulose paper.

[0029] (3) Prepare a 5 mmol / L metal salt-organic solvent solution using a metal salt and an organic solvent, and prepare an 8 mmol / L imidazole organic ligand solution using an imidazole organic ligand and an organic solvent, wherein the organic solvent is isopropanol; (4) Add a metal salt-organic solvent solution to the container. The ratio of the volume of the added solution to the mass of the bamboo pulp cellulose paper is 20 mL: 1 g. Then add the modified bamboo pulp cellulose paper, stir at 60°C for 1 hour, and then hydrothermally treat at 60°C for 12 hours. Take out the hydrothermally treated cellulose paper, wash it 4 times with a water-ethanol mixture, and then put it into a system containing an equal volume of metal salt-organic solvent solution and imidazole organic ligand solution. The ratio of the mass of the added cellulose paper to the volume of the solution is 6 g: 150 mL. React at 80°C for 12 hours. Take out the cellulose paper, wash it 4 times with ethanol, and then dry it in a vacuum oven at 60°C for 24 hours to obtain a multifunctional cellulose-based passive radiation cooling paper with a biomimetic structure, namely: zinc-based@modified cellulose high-efficiency portable multifunctional radiation cooling paper. The actual picture and scanning electron microscope image of the obtained radiation cooling paper are shown in [reference needed]. Figure 1 .

[0030] (5) Cut the prepared multifunctional cellulose-based passive radiation cooling paper with high efficiency radiation cooling into a suitable shape so that it can be placed on a car engine and made into a multifunctional outdoor power device cooling paper. Example 2

[0031] A method for preparing a biomimetic cellulose-based passive radiative cooling material includes the following steps: (1) Take 0.6 parts by weight of wood pulp cellulose paper, 15 parts of modifier, 12 parts of metal salt, 6 parts of imidazole organic ligand, and 10 parts of sodium hydroxide; the modifier is sodium bromoacetate; the metal salt is silver nitrate; the imidazole organic ligand is 1,2-2-methylimidazolium. (2) Immerse the wood pulp cellulose paper in a certain amount of water and ethanol mixture, with a volume ratio of 5:5; then add 10 parts of sodium hydroxide, stir at 30°C for 6 hours, add 15 parts of sodium bromoacetate to the reaction system, stir at 70°C for 6 hours; take out the modified cellulose paper, wash it with ethanol 4 times, and dry it to obtain the modified wood pulp cellulose paper.

[0032] (3) Prepare a 6 mmol / L metal salt-organic solvent solution using a metal salt and an organic solvent, and prepare a 10 mmol / L imidazole organic ligand solution using an imidazole organic ligand and an organic solvent, wherein the organic solvent is isopropanol; (4) Add a metal salt-organic solvent solution to the container. The volume ratio of the added solution to the mass of the wood pulp cellulose paper is 20 mL: 1 g. Then add the modified wood pulp cellulose paper, stir at 70 °C for 2 hours, and then hydrothermally treat at 70 °C for 10 hours. Take out the hydrothermally treated cellulose paper, wash it 4 times with a water-ethanol mixture, and then put it into a system containing an equal volume of metal salt-organic solvent solution and imidazole organic ligand solution. The mass ratio of the added cellulose paper to the volume of the solution is 5 g: 60 mL. React at 40 °C for 10 hours. Take out the cellulose paper, wash it 4 times with ethanol, and then dry it in a vacuum oven at 40 °C for 24 hours to obtain a multifunctional cellulose-based passive radiation refrigeration paper with a biomimetic structure.

[0033] (5) Cut the prepared multifunctional cellulose-based passive radiation cooling paper with high efficiency radiation cooling into a suitable shape for easy use in human body thermal management and make it into a multifunctional portable human body thermal management cooling paper. Example 3

[0034] A method for preparing a biomimetic cellulose-based passive radiative cooling material includes the following steps: (1) Take 1.5 parts by weight of sugarcane bagasse cellulose paper, 8 parts of modifier, 15 parts of metal salt, 6 parts of imidazole organic ligand, and 8 parts of sodium hydroxide; the modifier is succinic anhydride; the metal salt is zinc acetate; the imidazole organic ligand is 1,2-2-methylimidazolium. (2) Immerse the bagasse cellulose paper in a certain amount of water and ethyl acetate mixture, with a volume ratio of water to ethyl acetate of 4:6; then add 8 parts of sodium hydroxide, stir at 30°C for 5.5 hours, add 8 parts of succinic anhydride to the reaction system, stir at 60°C for 8 hours; take out the modified cellulose paper, wash it 3 times with ethanol, and dry it to obtain the modified bagasse cellulose paper.

[0035] (3) Prepare an 8 mmol / L metal salt-organic solvent solution using a metal salt and an organic solvent, and prepare a 12 mmol / L imidazole organic ligand solution using an imidazole organic ligand and an organic solvent, wherein the organic solvent is isopropanol; (4) Add a metal salt-organic solvent solution to the container. The volume ratio of the added solution to the mass of the bagasse cellulose paper is 20 mL: 1 g. Then add the modified bagasse cellulose paper, stir at 60°C for 5 hours, and then hydrothermally treat at 60°C for 5 hours. Take out the hydrothermally treated cellulose paper, wash it with ethanol 4 times, and then put it into a system containing an equal volume of metal salt-organic solvent solution and imidazole organic ligand solution. The mass ratio of the added cellulose paper to the volume of the solution is 6 g: 150 mL. React at 60°C for 6 hours. Take out the cellulose paper, wash it with ethanol 4 times, and then dry it in a vacuum oven at 60°C for 24 hours to obtain a multifunctional cellulose-based passive radiation cooling paper with a biomimetic structure.

[0036] (5) Cut the prepared multifunctional cellulose-based passive radiation cooling paper with high efficiency radiation cooling into a suitable shape and stick it around the fruit temporary storage or transport box to make multifunctional cooling packaging paper. Example 4

[0037] A method for preparing a biomimetic cellulose-based passive radiative cooling material includes the following steps: (1) Take 1.5 parts by weight of cellulose fiber, 18 parts of modifier, 9 parts of metal salt, 15 parts of imidazole organic ligand, and 6 parts of sodium hydroxide; the modifier is citric acid; the metal salt is zinc acetate; and the imidazole organic ligand is 2-methylimidazole. (2) Immerse the cellulose fiber in a certain amount of water and methanol mixture, with a volume ratio of water to methanol of 7:3; then add 6 parts of sodium hydroxide, stir at 30°C for 5 hours, add 18 parts of citric acid to the reaction system, and stir at 40°C for 1 hour; take out the modified cellulose fiber, wash it with ethanol 4 times, and obtain the modified cellulose fiber aqueous dispersion.

[0038] (3) Prepare a 15 mmol / L metal salt-organic solvent solution using a metal salt and an organic solvent, and prepare a 9 mmol / L imidazole organic ligand solution using an imidazole organic ligand and an organic solvent, wherein the organic solvent is methanol; (4) Add a metal salt-organic solvent solution to the container, with the volume of the solution added being 40 mL: 5 g of cellulose fiber. Then add the modified cellulose fiber aqueous dispersion, stir at 60 °C for 2 hours, heat-treat at 40 °C for 5 hours, and then hydrothermally treat at 80 °C for 5 hours. Wash the hydrothermally treated cellulose fiber four times with ethanol solvent, and then put it into a system containing an equal volume of metal salt-organic solvent solution and imidazole organic ligand solution, with the mass ratio of the added cellulose fiber to the volume of the solution being 2 g: 120 mL. React at 40 °C for 5 hours, remove the cellulose fiber, wash it four times with ethanol, and then dry it in a vacuum oven at 60 °C for 24 hours to obtain a multifunctional cellulose-based passive radiation cooling cellulose fiber with a biomimetic structure.

[0039] (5) Disperse the obtained multifunctional cellulose fiber with high efficiency radiation cooling in an aqueous solution to prepare a suspension, which is used to coat or spray on the surface of fruit and vegetable or food packaging to make a multifunctional cellulose-based radiation cooling coating. Example 5

[0040] A method for preparing a biomimetic cellulose-based passive radiative cooling material includes the following steps: (1) Take 1.4 parts of cellulose fiber, 30 parts of modifier, 14 parts of metal salt, 8 parts of imidazole organic ligand, and 15 parts of sodium hydroxide by weight; the modifier is succinic anhydride; the metal salt is cobalt nitrate; the imidazole organic ligand is 1,2-2-methylimidazolium. (2) Immerse the cellulose fiber in a certain amount of water and ethanol mixture, with a volume ratio of water to ethanol of 6:4; then add 15 parts of sodium hydroxide, stir at 80°C for 1.5 hours, add 30 parts of succinic anhydride to the reaction system, and react at 30°C for 10 hours; take out the modified cellulose fiber, wash it with ethanol 4 times, and obtain the modified cellulose fiber aqueous dispersion.

[0041] (3) Prepare a 30 mmol / L metal salt-organic solvent solution using a metal salt and an organic solvent, and prepare a 10 mmol / L imidazole organic ligand solution using an imidazole organic ligand and an organic solvent, wherein the organic solvent is ethanol; (4) Add a metal salt-organic solvent solution to the container. The volume ratio of the added solution to the mass of the cellulose fiber is 15 mL: 1 g. Then add the modified cellulose fiber aqueous dispersion, stir at 40 °C for 6 hours, and then hydrothermally treat at 60 °C for 6 hours. Wash the hydrothermally treated cellulose fiber with ethanol 4 times, and then put it into a system containing an equal volume of metal salt-organic solvent solution and imidazole organic ligand solution. The mass ratio of the added cellulose fiber to the volume of the solution is 5 g: 80 mL. React at 60 °C for 4 hours. Take out the cellulose fiber, wash it with ethanol 4 times, and then dry it in a vacuum oven at 60 °C for 24 hours to obtain a multifunctional cellulose-based passive radiation cooling cellulose fiber with a biomimetic structure.

[0042] (5) Disperse the obtained multifunctional cellulose fiber with high efficiency radiation cooling in an aqueous solution to prepare a suspension for coating or spraying on the surface of building materials, outdoor electronic equipment and other outdoor equipment that is prone to aging and requires cooling, to make an outdoor portable multifunctional cellulose-based radiation cooling coating. Example 6

[0043] Performance test of the biomimetic cellulose-based passive radiation cooling material of this invention I. Cooling effect test in different scenarios The zinc-based@modified cellulose high-efficiency portable multifunctional radiation cooling paper prepared in Example 1 was applied to different scenarios for cooling effect testing. Testing method: An infrared thermal imager was used to measure the temperature of the material surface and the environment. The material was placed on different object surfaces, and after waiting 3 minutes, the surface temperature of the material was recorded using a thermal imager.

[0044] The following are examples of practical portable application scenarios for zinc-based modified cellulose high-efficiency portable multifunctional radiation cooling paper. Figure 2 As shown. Figure 2 Part a shows the application and cooling effect of zinc-based@modified cellulose high-efficiency portable multifunctional radiation cooling paper on the surface of an automobile engine; Part b shows the application and cooling effect of zinc-based@modified cellulose high-efficiency portable multifunctional radiation cooling paper on the human arm; Part c shows the application and cooling effect of zinc-based@modified cellulose high-efficiency portable multifunctional radiation cooling paper in simulated outdoor temporary storage of post-harvest strawberries.

[0045] from Figure 2 As can be seen, the zinc-based@modified cellulose high-efficiency portable multifunctional radiation cooling paper prepared by the present invention can effectively reduce the temperature of the object surface. The product of the present invention has a very good zero-energy high-efficiency cooling effect, and is lightweight and portable, which can be used for outdoor portable high-efficiency cooling and can be applied to a variety of scenarios.

[0046] II. Testing of ultralightweight properties, hydrophobicity, flexibility, and mechanical strength. The ultralight weight, hydrophobicity, flexibility, and mechanical strength of the zinc-based@modified cellulose high-efficiency portable multifunctional radiation cooling paper prepared in Example 1 were tested.

[0047] The ultra-lightweight, hydrophobic, flexible, and high mechanical strength properties of zinc-based@modified cellulose high-efficiency portable multifunctional radiation cooling paper can be found in the product image. Figure 3 . Figure 3 Part a shows the ultralightweight properties of the zinc-based@modified cellulose high-efficiency portable multifunctional radiation cooling paper; part b shows the superhydrophobicity of the zinc-based@modified cellulose high-efficiency portable multifunctional radiation cooling paper to methylene blue solution, coffee, milk, and deionized water; part c shows that the zinc-based@modified cellulose high-efficiency portable multifunctional radiation cooling paper can return to its original shape after being double-folded or rolled, indicating its good flexibility; part d shows that a 1cm*4cm piece of zinc-based@modified cellulose high-efficiency portable multifunctional radiation cooling paper can support a 500-gram weight, indicating its good mechanical strength.

[0048] from Figure 3 As can be seen from the above, the zinc-based@modified cellulose high-efficiency portable multifunctional radiation cooling paper prepared by this invention has ultra-lightweight properties, superhydrophobicity, good flexibility and good mechanical strength properties.

[0049] III. Accelerated UV Aging Test The zinc-based@modified cellulose high-efficiency portable multifunctional radiation-cooling paper prepared in Example 1 was subjected to accelerated UV aging test. The accelerated UV aging test method involved a 24-hour accelerated UV aging test at a distance of 10 cm from a 500 W mercury lamp.

[0050] Schematic diagram (a) and actual image (b) and electron microscope image (c) of accelerated UV aging test of zinc-based@modified cellulose high-efficiency portable multifunctional radiation cooling paper are shown below. Figure 4 . Figure 4 Part a of the diagram is a schematic diagram of the accelerated UV aging experiment of zinc-based@modified cellulose high-efficiency portable multifunctional radiation-cooling paper; Part b is an appearance image of the material after the accelerated UV aging experiment, as well as actual images after being rolled, folded, or stretched; Part c is a scanning electron microscope image of the material after the accelerated UV aging experiment. Figure 4 As can be seen, the radiation cooling paper prepared by this invention has excellent resistance to ultraviolet aging.

[0051] IV. Antibacterial Test The zinc-based@modified cellulose high-efficiency portable multifunctional radiation cooling paper prepared in Example 1 was subjected to an antibacterial test. Antibacterial test method: The material was placed on a solid petri dish and incubated in an incubator for 12 hours, and the inhibition zone was photographed.

[0052] Zinc-based modified cellulose high-efficiency portable multifunctional radiation cooling paper for Escherichia coli ( E. coli ) and Staphylococcus aureus ( S. aureus See the diagram for the size of the inhibition zone. Figure 5 .from Figure 5 As can be seen, the radiation cooling paper prepared by this invention has excellent antibacterial properties and good antibacterial effect against both Escherichia coli and Staphylococcus aureus.

[0053] V. Outdoor Radiant Cooling Application Effect Test The zinc-based@modified cellulose high-efficiency portable multifunctional radiative cooling paper prepared in Example 1 was tested for its outdoor radiative cooling effect. Test method: The outdoor test site was located in Nanning, China (22.50°N, 108.68°E). The custom-made device used for the outdoor test was made of polystyrene foam with an open window at the top, which was covered by the test sample to form a closed space. A porous polyethylene film was placed on top of the sample to reduce heat convection between the interior and exterior. All other surfaces of the device were covered with aluminum foil to avoid absorbing solar radiation. During the outdoor test, the device was directly exposed to sunlight. The sample thickness used for the outdoor radiative cooling test was 200 µm. The internal temperature of the device and the external ambient temperature were recorded using a temperature sensor (TESTO 176 T4 digital thermometer). The solar radiation intensity during the test was recorded using a solar radiometer (TES-1333R solar power meter).

[0054] See the image showing the outdoor application effect of zinc-based modified cellulose high-efficiency portable multifunctional radiative cooling paper. Figure 6 .from Figure 6 As can be seen, the zinc-based@modified cellulose high-efficiency portable multifunctional radiation cooling paper prepared by this invention has excellent zero-energy high-efficiency cooling performance. Through high solar reflectivity and infrared emissivity, it can achieve a cooling effect of 21.4℃ lower than the sub-ambient temperature.

Claims

1. A method for preparing a biomimetic cellulose-based passive radiative cooling material, characterized in that, Includes the following steps: (1) Take 0.25-4 parts by weight of cellulose, 5-30 parts of modifier, 2-50 parts of metal salt, 1-60 parts of imidazole organic ligand, and 5-20 parts of potassium hydroxide or sodium hydroxide for later use; the cellulose is derived from one or more of wood, bamboo fiber, cotton fiber, and hemp fiber; the modifier is one or more of sodium chloroacetate, sodium bromoacetate, sodium tripolyphosphate, citric acid, succinic anhydride, and p-toluenesulfonic acid; the metal salt is silver nitrate, copper nitrate, zinc nitrate, zinc acetate, cobalt nitrate, or ferric chloride; the imidazole organic ligand is 2-methylimidazolium or 1,2-2-methylimidazolium; (2) Place the cellulose raw material in an appropriate amount of water and organic solvent solution, with a volume ratio of water to organic solvent of (1-9):(1-9); then add 5-20 parts of potassium hydroxide or sodium hydroxide, place it in the reaction system, stir at 30-100℃ for 1-6 hours, add 5-30 parts of modifier to the reaction system, stir at 30-80℃ for 1-24 hours; take out the prepared modified cellulose, wash it with ethanol 2-5 times and dry it for later use. (3) Prepare metal salt-organic solvent solutions with a concentration of 5-50 mmol / L using metal salts and organic solvents; prepare imidazole organic ligand solutions with a concentration of 5-50 mmol / L using imidazole organic ligands and organic solvents; (4) Add an appropriate amount of metal salt-organic solvent solution to the container, then put the modified cellulose into the reaction system, stir at 30-100℃ for 1-12 hours, and then hydrothermally treat at 30-80℃ for 5-24 hours; wash the hydrothermally treated cellulose with ethanol or water-ethanol mixture 4 times, and then put it into a system containing an equal volume of metal salt-organic solvent solution and imidazole organic ligand solution, react at 30-80℃ for 4-24 hours, take out the cellulose material, wash it with ethanol 4 times, and then dry it in a vacuum oven at 40-60℃ for 12-24 hours to obtain a multifunctional cellulose-based passive radiation cooling material with a biomimetic structure.

2. The preparation method of the biomimetic cellulose-based passive radiative cooling material according to claim 1, characterized in that, In step (1), the cellulose raw materials used include one or more of cellulose paper and cellulose fibers.

3. The method for preparing the biomimetic cellulose-based passive radiative cooling material according to claim 2, characterized in that, Using cellulose paper or cellulose fiber as cellulose raw material, multifunctional cellulose-based passive radiation cooling paper or cooling cellulose fiber with biomimetic structure can be prepared. The cooling cellulose fiber is dispersed in an aqueous solution to prepare a suspension, which can be used to coat or spray on the surface of an object to make a passive radiation cooling coating.

4. The method for preparing the biomimetic cellulose-based passive radiative cooling material according to claim 1, characterized in that, In steps (2) and (3), the organic solvent is methanol, ethanol, isopropanol or ethyl acetate.

5. The method for preparing the biomimetic cellulose-based passive radiative cooling material according to claim 1, characterized in that, In step (4), an appropriate amount of metal salt-organic solvent solution is added to the container. The ratio of the volume of the added solution to the mass of cellulose is (5-80) mL: (0.5-20) g.

6. The method for preparing the biomimetic cellulose-based passive radiative cooling material according to claim 1, characterized in that, In step (4), the washed cellulose is placed into a system containing an equal volume of metal salt-organic solvent solution and imidazole organic ligand solution. The ratio of the mass of cellulose to the volume of the solution is (5-10) g: (80-100) mL.

7. The method for preparing the biomimetic cellulose-based passive radiative cooling material according to claim 1, characterized in that, It also includes step (5): The prepared biomimetic cellulose-based passive radiation cooling material can be placed directly on the surface of a material or coated in the form of lightweight paper or coating, depending on the needs of the application scenario, for zero-energy high-efficiency cooling of various outdoor facilities.

8. A biomimetic cellulose-based passive radiative cooling material, characterized in that, It is prepared by the preparation method described in any one of claims 1-7.

9. The application of the biomimetic cellulose-based passive radiation cooling material prepared by the preparation method according to any one of claims 1-7 in the use of or preparation of passive radiation cooling products.

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