Dual-mode radiant heat management leathernanofabric and method of making

Abstract

The application discloses a kind of bimodal radiation heat management leather-like nanofabric and preparation method thereof.The fabric includes self-bonding heating layer and refrigeration layer by spinning process, and the raw materials of spinning solution of the heating layer include polyurethane, nano conductive carbon black and hydrophobic agent;The raw materials of spinning solution of the refrigeration layer include polyurethane, nano alumina particles and hydrophilic agent.The preparation method is: the spinning solution of heating layer is obtained on the receiving substrate by electrospinning to obtain heating layer fiber membrane;The spinning solution of refrigeration layer is continued to be spun on the obtained heating layer fiber membrane, and the bimodal radiation heat management leather-like nanofabric is obtained.The application provides a kind of breathable bimodal leather-like nanofabric with asymmetric wrinkle photonic microstructure and Janus wetting property, which is prepared by one-step method, and the obtained fabric has asymmetric double-sided wrinkle structure, and has good softness, air permeability, stretchability and other wearability.

Description

TECHNICAL FIELD

[0001] The present application relates to a dual-mode radiative thermal management leather-like nanofabric and a preparation method thereof, and belongs to the technical field of textile products of special yarn raw materials. BACKGROUND

[0002] With the frequent occurrence of global extreme weather events, human thermal regulation is crucial for thermal comfort, health and work efficiency. About 20% of electricity is used for air conditioning and electric fan building and space thermal regulation, which brings huge energy pressure and crisis. Although various thermal management devices have been proposed, such as electric heating wearable devices or thermoelectric devices, they still require additional electricity and are often too bulky to wear. Passive radiative cooling has emerged as a zero-energy and environmentally friendly strategy, which cools objects spontaneously by emitting long-wave infrared (LWIR) radiation and highly reflecting solar radiation (0.25-2.5 μm) through the atmospheric transparent window (8-13 μm). Conversely, passive radiative heating is achieved by high solar absorption and relatively low LWIR emissivity. The key design of radiative cooling and heating materials is to combine the intrinsic properties of materials with structural photonic engineering to achieve selective response to light, thereby controlling the performance of radiative cooling and heating. Currently, a variety of radiative cooling or heating materials have been reported, including nano-photonic structures, hybrid photonic metamaterials, cooling wood, layered porous coatings and radiative cooling or heating fabrics. However, these materials are usually static, used for single cooling or heating, and cannot adapt to changing environments and weather. Therefore, it is very important and challenging to achieve these two contradictory properties in the same material.

[0003] Dual-mode materials freely switch between radiative cooling and heating modes without any energy input, providing an ideal and exciting solution to cope with fluctuating weather. Cui et al. proposed a dual-mode textile obtained by embedding bilayer emitters on a polyethylene (PE) film, where flipping the textile can switch the radiative properties and expand the thermal comfort zone by ~6.5 °C. The dual-mode concept has attracted great attention in the field of building or personal thermal management, but its radiative thermal effects and practical wearability are limited by environmental conditions, such as direct sunlight or outdoor high-temperature environments. Recently, Wang et al. demonstrated a dual-mode porous polymer film, which achieved all-day radiative refrigeration and heating for buildings by phase transition to obtain a porous coating and spray MXene nanosheets on the coating. Currently, most dual-mode materials are achieved by coating non-symmetric photonic structures or emitters on both sides to realize radiative cooling and heating, especially in building thermal regulation. However, these dual-mode materials with non-symmetric spectral response structures often sacrifice high-efficiency thermal regulation performance to achieve dynamic tunability, and are limited by high manufacturing costs and large-scale manufacturing. In addition, little attention has been paid to the breathability, softness, stretchability, and mechanical properties of the materials, resulting in poor wearing experience.

[0004] It is well known that the skin of humans, animals, and insects has a dual role: one is to resist the cold and hot stimulation from the outside world, and the other is to regulate body temperature by heat dissipation and insulation. For example, human skin has a wrinkled microstructure in the epidermis layer, which is not only an important organ for heat dissipation, but also an ideal infrared emitter. In addition, human skin has outstanding breathability, stretchability, and flexibility. Through coating or impregnation processes, a biomimetic skin radiative cooling coating fabric with photonic wrinkled microstructure has been proposed. However, in a complex and variable environment, clothing as the “second layer of skin” of the human body not only plays a crucial role in regulating the heat transfer between the human skin and the outside environment, but also needs certain extensibility, breathability, softness, and aesthetic appearance. Therefore, there is an urgent need to develop a new type of textile with high-efficiency thermal management, skin characteristics, and special appearance through a simple and scalable preparation process.

[0005] Based on the human-clothing-environment system, we report a dual-mode "leather-like" nanotextile (LNT) with high-efficiency radiative cooling and heating performance, double-sided corrugated texture, Janus wettability, air permeability, softness, and stretchability. The LNT is fabricated by using a scalable electrospinning technique with low-cost materials to deposit polyurethane fiber membranes with gradient wettability and asymmetric optical structure layer by layer. The hydrophobic heating layer with photothermal effect is seamlessly bonded with the cooling layer integrated with embedded particle networks, constructing Janus wettability, double-sided leather-like texture, and switchable cooling and heating dual modes. In the cooling mode, the skin-like corrugated structure not only improves the solar reflectance (R ≈ 94.8%) and LWIR emissivity (ε ≈ 95.0%) of the material, but also enhances the sweat-wicking performance and mechanical properties. When the LNT is turned over, the heating mode with the cowhide-like corrugated structure has a higher solar absorptance (A ≈ 95.3%). This radiative property realizes a wider thermal management area (44.1℃), which is superior to that of commercial textiles (15.8℃). In addition, practical wearing tests show that the clothing made of LNT can provide a more comfortable microenvironment for the human body, with a temperature reduction / increase of 1.6-8.0℃ / 1.0-7.1℃ compared with ordinary textiles. This study opens up new possibilities for the development of sustainable all-weather intelligent clothing. SUMMARY

[0006] The technical problem solved by the present application is to develop a breathable dual-mode leather-like nanofabric with heating and refrigeration functions based on one-step electrospinning technology.

[0007] To solve the above problems, the present application provides a dual-mode radiative thermal management leather-like nanofabric, which comprises a heating layer and a refrigeration layer compounded by a spinning process, the raw materials of the spinning solution of the heating layer include polyurethane (PU), nano-conductive carbon black (CB), and a hydrophobic agent (FA); the raw materials of the spinning solution of the refrigeration layer include PU, nano-alumina particles (Al2O3), and a hydrophilic agent (TF).

[0008] Preferably, the polyurethane contained in the heating layer and the refrigeration layer is bio-based PU or ordinary PU; the polyurethane contained in the heating layer and the refrigeration layer is the same or different.

[0009] Preferably, the particle size of the nano-conductive carbon black is 30-45 nm; the particle size of the nano-alumina particles is 300-500 nm.

[0010] Preferably, the hydrophobic agent is a fluorine-containing hydrophobic agent (FA), preferably a fluorine-containing acrylate; the hydrophilic agent uses a non-woven fabric hydrophilic agent.

[0011] Preferably, the solvent used in the spinning solution of the heating layer and the refrigeration layer is a mixture of N,N-dimethylformamide (DMF) and acetone (AC).

[0012] More preferably, the ratio of the spinning solution of the heating layer is that the solvent is a mixture of N,N-dimethylformamide and acetone with a mass ratio of 7:3, and the adding amount of polyurethane, nano conductive carbon black and hydrophobic agent is 18-19%, 3-4% and 0.5-1.5% respectively based on the mass of the solution; the ratio of the spinning solution of the refrigeration layer is that the solvent is a mixture of N,N-dimethylformamide and acetone with a mass ratio of 4:6, and the adding amount of polyurethane, nano alumina particles and hydrophilic agent is 8-12%, 8-12% and 3-5% respectively based on the mass of the solution.

[0013] The application also provides a preparation method of the above-mentioned dual-mode radiation heat management type leather-like nanofabric, which comprises the following steps:

[0014] Step 1): preparing a spinning solution of the heating layer, and obtaining a heating layer fiber membrane by electrospinning the spinning solution of the heating layer on a receiving substrate;

[0015] Step 2): preparing a spinning solution of the refrigeration layer, and continuing to spin on the obtained heating layer fiber membrane to obtain the dual-mode radiation heat management type leather-like nanofabric.

[0016] Preferably, the process parameters of electrospinning in step 1) are that the temperature is 24-26℃, the relative humidity is 90-95%, the voltage is 28-32kV, the perfusion speed is 2.8-3.2mL / h, the distance between the needle tube and the receiver is 25-30cm, the roller speed is 60-70rmp, and the receiving substrate is oil gloss paper.

[0017] Preferably, the process parameters of spinning in step 2) are that the temperature is 24-26℃, the relative humidity is 90-95%, the voltage is 24-26kV, the perfusion speed is 0.8-1mL / h, the distance between the needle tube and the receiver is 25-30cm, and the roller speed is 60-70rmp.

[0018] The application provides a breathable dual-mode leather-like nanofabric with asymmetric pleated photonic microstructure and Janus wettability, which is prepared by one-step method.

[0019] The application provides a breathable dual-mode leather-like nanofabric with asymmetric pleated photonic microstructure and Janus wettability, which is prepared by one-step method.

[0020] The raw materials used in the present application, PU polymer as the main material of the fiber, CB has the photo-thermal effect, can realize the sunlight heating, FA as the hydrophobic agent, the construction of the relatively loose hydrophobic layer. Al2O3 has excellent optical properties, mainly to achieve sunlight reflection, TF hydrophilic agent, help to form the fiber welding network and wrinkle. Refrigeration layer: the wrinkle microstructure with skin-like wrinkles, these microstructures are built by the welded fiber network, the fiber is embedded with nano Al2O3 particles, the fiber layer is relatively dense, and the fiber diameter is about 0.55 μm.

[0021] The forming mechanism of the present application: the skin-like wrinkle structure and the welded fiber network formed in the refrigeration layer are due to the addition of the hydrophilic agent TF, which contains multiple ether oxygen groups and hydroxyl groups. During electrospinning, when the hydrophilic solution jet is exposed to air, these groups can interact with water molecules through hydrogen bonds, allowing the PU chain to be surrounded by water molecules in the environment. Therefore, during the stretching and solidification of the nanofiber, a dilute solution will be generated around the jet. According to the Kelvin equation, dilute solution vapor is more likely to condense at larger interfacial curvatures than at fiber junctions, resulting in local dissolution and physical crosslinking of the nanofiber at the junctions, forming a welded fiber network. During electrospinning, the random stacking of nanofibers leads to various welding methods and condensation at larger interfacial curvatures, forming a texture similar to skin wrinkles after a certain accumulation of fibers. In addition, due to the presence of multiple hydrogen bonds in the nanofiber, the stacking structure between the layers becomes relatively dense.

[0022] The heating layer in the obtained fabric has a texture similar to cowhide, with wrinkles of different depths, interconnected grooves, and intersecting patterns, showing a unique texture. The heating fiber layer is relatively loose, with a fiber diameter of about 1.36 μm.

[0023] Compared with the cooling layer, the heating layer has a looser and thinner fiber structure, which makes it more prone to deformation when it shrinks. The reason for the loose structure of the heating layer is the rapid evaporation of the solvent and the few hydrogen bonds between the fibers. Due to the PU matrix, these elastic fibers are in a straight stretched state on the receiver, thus giving the fiber membrane a certain elastic force (Fe) and storing appropriate internal stress (Ft) in the fibers. According to the law of conservation of energy and the inherent properties of PU-based fibers, when the fiber membrane is removed from the receiver, Ft will be released, generating a shrinkage force (Fs), which causes the relatively thin and loose heating layer to deform and be pulled upwards under the synergistic action of these forces, resulting in various depths of wrinkles and intersecting grooves on the heating side, similar to the texture of cowhide.

[0024] The simple and scalable preparation of the present application constructs a unique double-sided wrinkle structure and Janus wetting gradient, develops a breathable, soft, and elastic leather-like nanofabric, and simultaneously has efficient radiation cooling and heating performance. Attached Figure Description

[0025] Figure 1 A photograph of the fabric prepared according to the present invention;

[0026] Figure 2 These are electron microscope comparison images of different proportions of the cooling layer in Example 1;

[0027] Figure 3 These are electron microscope comparison images of different proportions of the heating layer in Example 1;

[0028] Figure 4 This is molecular simulation data of the interaction between water molecules and surrounding molecules in Example 1;

[0029] Figure 5 This is a graph showing the data on the softness of the fabric obtained in Example 1;

[0030] Figure 6 This is a graph showing the air permeability data of the fabric obtained in Example 1. Detailed Implementation

[0031] To make the present invention more apparent and understandable, preferred embodiments are described in detail below with reference to the accompanying drawings.

[0032] Example 1

[0033] A method for preparing a dual-mode radiative heat management type of leather nanofiber fabric:

[0034] Step 1): Preparation of spinning solution A for the heating layer: The solvent is a mixture of N,N-dimethylformamide and acetone in a weight ratio of 7:3. Based on the solution mass, add 18% polyurethane (Huntsman, model A85 P4394), 10% nano alumina particles (particle size 300-500nm), 3% nano conductive carbon black (particle size 30-45nm), and 1% hydrophobic agent (Suzhou Zhiyuan New Science Chemical Co., Ltd., model M-401N), stir evenly, and set aside for use.

[0035] Step 2): The spinning solution of the heating layer is electrospun on the receiving substrate to obtain a fiber membrane of the heating layer. The process parameters of electrospinning are: 24℃, relative humidity 90%, voltage 30kV, injection rate 3mL / h, needle-to-receiver distance 25-30cm, roller speed 60rpm, and the receiving substrate is glossy paper.

[0036] Step 3): preparing the spinning solution B of the refrigeration layer: using a mixture of N,N-dimethylformamide and acetone in a weight ratio of 4:6 as the solvent, adding 10% polyurethane (Huntsman, model A85 P4394), 10% nano-alumina particles (particle size 300-500 nm), and 4% hydrophilic agent TF-629B based on the mass of the solution, stirring uniformly, and waiting for use; the volume ratio of the spinning solution A to the spinning solution B is about 4:15;

[0037] Step 4): continuing spinning on the obtained heating layer fiber membrane, to obtain a double-mode radiation heat management type leather nanofabric, and the process parameters of the spinning are as follows: 24℃, relative humidity 90%, voltage 25kV, perfusion speed 0.8mL / h, needle tube and receiver distance 25cm, and roller speed 60rmp.

[0038] From Figure 2 , 3 It can be seen that the obtained fabric has an anisotropic double-sided wrinkle structure.

[0039] In order to further illustrate the influence of TF on the formation of the cooling side wrinkle microstructure, the present application carries out molecular dynamics (MD) simulation to study the interaction between water molecules and the molecules on the surface of the cooling nanofiber in the electrospinning process. The MS software is used to carry out simulation under the conditions of 90% RH and 24℃, and the influence of TF on the structure formation in the electrospinning process is discussed. The MD result proves that the hydrophilic groups of TF quickly capture the water molecules in the air and adsorb them to the surface of the nanofiber and the inside of the fiber network.

[0040] The present application also analyzes the interaction between the water molecules and the surrounding molecules. As described before, the water molecules are distributed around the nanofiber and form hydrogen bonds with it. During the experiment, it can be observed that the total number of hydrogen bonds in the simulation system sharply increases within 20ps of simulation time and then tends to be stable (as shown in Figure 4 Therefore, the invading water molecules exist throughout the electrospinning process, dilute the solvent, and then form a welded fiber network.

[0041] It is just due to the differentiation of the two layers of fibers that the double-sided wrinkle texture is formed. In the process of stretching, the texture on the side of the refrigeration will change with the change of the stretching stress, and the texture still exists after a certain stress, and the texture returns to the initial texture after the stress is removed. The texture on the side of the heating will disappear after a certain stretching, and the texture returns to the initial texture after the stress is removed.

[0042] Figure 5 The softness of the leather fabric obtained in Example 1 is greatly improved compared with cotton fabric and commercially available leather.

[0043] Figure 6 Data chart of air permeability (test standard GB / T 5453-1997) of the leather fabric obtained in Example 1.

[0044] Example 2

[0045] The difference between this example and Example 1 is that the polyurethane is replaced by bio-based polyurethane, and other parameters are the same. Compared with non-bio-based polyurethane, the softness and air permeability of bio-based polyurethane are relatively close, but bio-based air permeable double-mode leather-like nanofabric can be realized, which is more environmentally friendly.

Claims

1. A dual mode radiative thermal management class leather nanofabric comprising a heating layer and a refrigeration layer self-bonded through a spinning process, characterized in that, The raw material of the spinning solution of the heating layer comprises polyurethane, nano conductive carbon black and hydrophobic agent; the raw material of the spinning solution of the refrigeration layer comprises polyurethane, nano aluminum oxide particles and hydrophilic agent.

2. The dual mode radiant thermal management leatherscale nanofabric of claim 1, wherein, The polyurethane contained in the heating layer and the refrigeration layer is bio-based polyurethane or non-bio-based polyurethane; the polyurethane contained in the heating layer and the refrigeration layer is the same or different.

3. The dual mode radiant thermal management leathernet nanofabric of claim 1, wherein, The particle size of the nano conductive carbon black is 30-45 nm; the particle size of the nano aluminum oxide particles is 300-500 nm.

4. The dual mode radiant thermal management leathernet nanofabric of claim 1, wherein, The hydrophobic agent is a fluorine-containing hydrophobic agent; the hydrophilic agent uses a non-woven fabric hydrophilic agent.

5. The dual mode radiant thermal management leathernet nanofabric of claim 1, wherein, The solvent used in the spinning solution of the heating layer and the refrigeration layer is a mixture of N,N-dimethylformamide and acetone.

6. The dual mode radiant thermal management leatherscapes nanofabric of claim 5, wherein, The ratio of the spinning solution of the heating layer is that the solvent is a mixture of N,N-dimethylformamide and acetone with a mass ratio of 7:3, the adding amount of polyurethane, nano conductive carbon black and hydrophobic agent is 18-19%, 3-4% and 0.5-1.5% respectively based on the mass of the solution; the ratio of the spinning solution of the refrigeration layer is that the solvent is a mixture of N,N-dimethylformamide and acetone with a mass ratio of 4:6, the adding amount of polyurethane, nano aluminum oxide particles and hydrophilic agent is 8-12%, 8-12% and 3-5% respectively based on the mass of the solution.

7. The method of producing dual mode radiant heat management leatherskin nanofabrics according to any one of claims 1-6, characterized in that, The method comprises the following steps: Step 1): preparing a spinning solution of the heating layer, and obtaining a heating layer fiber membrane by electrospinning the spinning solution of the heating layer on a receiving substrate; Step 2): preparing a spinning solution of the refrigeration layer, and continuing to spin on the obtained heating layer fiber membrane to obtain a dual-mode radiation heat management type leather nanofabric.

8. The method of claim 7, wherein the dual-mode radiant heat management nanofabricated leather is prepared by the steps of: The process parameters of the electrospinning in step 1) are that the temperature is 24-26℃, the relative humidity is 90-95%, the voltage is 28-32kV, the perfusion speed is 2.8-3.2mL / h, the distance between the needle tube and the receiver is 25-30cm, the roller speed is 60-70rmp, and the receiving substrate uses glossy paper.

9. The method of claim 7, wherein the dual-mode radiant heat management nanofabricated leather is prepared by the steps of: The process parameters of the spinning in step 2) are that the temperature is 24-26℃, the relative humidity is 90-95%, the voltage is 24-26kV, the perfusion speed is 0.8-1mL / h, the distance between the needle tube and the receiver is 25-30cm, and the roller speed is 60-70rmp.

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