Colorful radiation cooling fabric and preparation method thereof

Abstract

The invention discloses a colored radiation cooling fabric and a preparation method thereof, and the colored radiation cooling fabric is prepared by combining a humidity response type cobalt-based complex (CETA) with a flexible polymer base material and adopting an electrostatic spinning process. The cobalt-based complex is generated by a coordination reaction of cobalt chloride hexahydrate and ethanolamine, and endows the fabric with dynamic optical properties. The fabric is changed from color to white in a low-humidity environment to a high-humidity environment, the visible light absorbance is reduced from 0.5 + / -0.05 to 0.2 + / -0.05, the 8-13 [mu] m infrared emissivity in the high-humidity environment reaches 0.90-0.95, and efficient heat dissipation is achieved. The surface temperature of the fabric can be lower than the environment temperature by 5-10 DEG C, air conditioner energy consumption is remarkably reduced, and the fabric is suitable for the fields of buildings, outdoor equipment and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of the preparation of cooling fabrics, and particularly relates to a colored radiative cooling fabric and a preparation method thereof. Background Art

[0002] In recent years, with the intensification of global warming, the demand for cooling functional fabrics in fields such as outdoor activities, high-temperature operations, and building energy conservation has increased significantly. Traditional cooling technologies mainly rely on active refrigeration equipment (such as air-conditioning systems), but problems such as their high energy consumption, high cost, and limited usage scenarios have become increasingly prominent. Passive cooling fabrics, as a solution that does not require external energy input, achieve cooling by reflecting solar radiation or enhancing infrared thermal radiation, and have gradually become a research hotspot. However, the existing cooling fabrics still have the following key problems: (1) The contradiction between the appearance color singularity and the function. Currently, mainstream cooling fabrics (such as white sunshades, light-colored sunscreen clothes) generally adopt light or white designs to improve the solar reflectance (>80%). Although such colors can effectively reduce heat absorption, they have the disadvantages of aesthetic limitations and environmental disharmony.

[0003] (2) Insufficient humidity adaptability. In the outdoor environment, humidity fluctuates frequently (such as rainy days or high-humidity areas). Existing cooling fabrics are prone to problems such as reflectance attenuation and limited infrared emissivity under humid conditions.

[0004] (3) Lack of dynamic environment response ability. Existing fabrics mostly have static functional designs and cannot dynamically adjust optical properties according to environmental changes (such as humidity, temperature). For example, they cannot automatically enhance the infrared emissivity to compensate for the reflectance loss under high humidity. Summary of the Invention

[0005] Embodiments of the present application provide a colored radiative cooling fabric and a preparation method thereof. Through the innovative design of a humidity-responsive cobalt-based complex (CETA), problems such as the single color, strong humidity sensitivity, and insufficient reflectance / emissivity of traditional cooling fabrics are solved, and the unity of dynamic optical performance and efficient thermal management is achieved, providing an energy-saving and environmentally friendly solution for scenarios such as smart buildings, outdoor equipment, and transportation facilities.

[0006] Embodiments of the present application provide a colored radiative cooling fabric, characterized in that it is prepared by modifying a flexible polymer substrate with a cobalt-based complex through an electrospinning process.

[0007] Preferably, the cobalt-based complex is formed by coordinating cobalt chloride hexahydrate and a ligand, and the ligand is ethanolamine.

[0008] Preferably, the visible light absorptivity of the fabric in a high humidity environment of RH60±5% is reduced to 0.1-0.3, while the infrared emissivity is enhanced, specifically 0.90-0.95.

[0009] Preferably, the flexible polymer substrate is PVDF-HFP.

[0010] The present application also provides a method for preparing a colored radiant cooling fabric, which is characterized by comprising the following steps: Step 1: Preparation of cobalt-based complexes Dissolving cobalt chloride hexahydrate in anhydrous ethanol to form a cobalt chloride / ethanol mixed solution; adding ethanolamine for coordination reaction to generate a cobalt-based complex with humidity response characteristics; and obtaining a dehydrated cobalt-based complex CETA powder by drying; Step 2: Preparation of colored radiant cooling fabric The cobalt-based complex CETA powder was combined with a polymer substrate and prepared into a fabric through an electrospinning process.

[0011] Preferably, the molar ratio of the cobalt chloride hexahydrate to ethanolamine is 1-3:1, preferably 2:1.

[0012] One or more technical solutions provided in the embodiments of the present application have at least the following technical effects: 1. The use of humidity-responsive cobalt-based complexes (CETA) combined with flexible polymers such as PVDF-HFP to prepare colored radiant cooling fabrics using electrospinning technology effectively solves the problems of traditional cooling fabrics such as single color, strong humidity sensitivity, and insufficient reflectivity / emissivity, thereby achieving the unity of dynamic optical performance and efficient thermal management.

[0013] 2. The colorful radiation cooling fabric prepared in the embodiment of the present invention is designed with low-absorption pigments, and the reflectivity in the visible light band is ≥85%, which reduces heat input. The infrared emissivity of the cobalt-based complex CETA is 0.90~0.95 at 8-13 μm, which accelerates the dissipation of heat into outer space. Actual measurements of the fabric show that the surface temperature can be 5-10°C lower than the ambient temperature, significantly reducing the energy consumption of air conditioning.

[0014] 3. The embodiment of the present invention combines the cobalt-based complex CETA with a flexible polymer such as PVDF-HFP through electrospinning technology, giving the fabric light, wearable, and easy-to-process characteristics, and is suitable for the fields of construction, textiles, agriculture, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a reflectivity curve of the fabric in Example 1 of the present application when the ambient humidity is 30%, and the illustration is a real shot of the fabric; Figure 2This is the reflectivity curve of the fabric in Example 1 of this application when the environmental humidity is 60%. The inset is a real - shot picture of the fabric; Figure 3 This is the absorbance curve of cobalt - based complex (CETA) in Example 1 of this application in an ethanol / water mixed solution. Detailed implementation manners

[0016] In the embodiments of this application, by providing a color radiative cooling fabric and its preparation method, through the innovative design of a humidity - responsive cobalt - based complex (CETA), problems such as the single color, strong humidity sensitivity, and insufficient reflectivity / emissivity of traditional cooling fabrics are solved, achieving the unity of dynamic optical properties and efficient thermal management, and providing an energy - saving and environmental - protection solution for scenarios such as smart buildings, outdoor equipment, and transportation facilities.

[0017] The overall idea of the technical solutions in the embodiments of this application to solve the problems is as follows: First, prepare cobalt - based complex (CETA) by oneself. Combine the CETA powder of cobalt - based complex with a polymer substrate (such as PVDF - HFP), and prepare it into a fabric through the electrospinning process. The humidity - responsive characteristics of CETA in the fabric make it present color at low humidity, the visible light absorption rate decreases at high humidity, and at the same time the infrared emissivity increases. Combining the characteristics of high solar - light reflectivity and high infrared emissivity, it ensures continuous cooling in both dry and humid environments, achieving all - weather radiative cooling, and thus solving the problems of single color, strong humidity sensitivity, and insufficient reflectivity / emissivity of traditional cooling fabrics in the prior art.

[0018] To better understand the above - mentioned technical solutions, the above - mentioned technical solutions will be described in detail below in combination with the accompanying drawings of the specification and specific implementation manners. Example 1

[0019] Step 1: Weigh 1.19 g of CoCl2·6H2O powder with a balance. Select anhydrous ethanol as the solvent to dissolve the CoCl2·6H2O powder. The amount of anhydrous ethanol used is 5 ml. Stir with a magnetic stirrer at room temperature for 1 hour to obtain a cobalt chloride / ethanol mixed solution.

[0020] Prepare an ethanolamine solution with 0.153 g of ethanolamine and add it to the mixed solution, and stir at room temperature for 1 hour. Then add 2.5 ml of deionized water to the solution, and stir evenly to obtain a cobalt - based complex CETA solution.

[0021] Place the cobalt - based complex CETA solution in a blast drying oven at 60 °C and dry it for 6 h to obtain CETA powder.

[0022] Step 2: Weigh 3 g of dried PVDF-HFP powder on a balance, and use N-N-dimethylformamide as a solvent to dissolve it to prepare a spinning solution, in which the mass fraction of PVDF-HFP is 15%. Then, 0.5 g of cobalt-based complex CETA powder is dissolved in 1 ml of anhydrous ethanol, and the solution is added to the PVDF-HFP spinning solution. A magnetic stirrer is used to stir at room temperature for 24 hours to obtain a PVDF-HFP / CETA electrospinning mixed solution. Move the prepared spinning solution to the operating table for electrospinning. The spinning voltage is set to 18 kV, the push speed is set to 0.005 mm / s, the spinning distance is 12 cm, the spinning time is 24 h, the temperature is 25±2°C, the relative humidity is 40±5%, the inner diameter of the needle is 0.6 mm, and the rotating drum of the collector is rotated at a speed of 300 rpm. After the spinning is completed, a colored radiation cooling fabric modified with cobalt-based complex CETA is obtained①.

[0023] The reflectivity performance of the colored radiant cooling fabric① was tested. Please refer to Figures 1 to 2 , Figure 1 This is the reflectivity curve of the fabric when the ambient humidity is 30%, and the inset is a real picture of the fabric. Figure 2 This is the reflectivity curve of the fabric when the ambient humidity is 60%, and the inset is a real picture of the fabric.

[0024] Figure 1 and Figure 2 The reflectivity curve results show that due to the reduced absorbance of the cobalt-based complex CETA in a high humidity environment, the appearance of the fabric changes from color to white, and the reflectivity in the visible light band is greatly improved. When the ambient humidity increases from 30% to 60%, the visible light reflectivity can be increased by more than 5%, and the reflectivity is ≥85%, which can improve the radiation cooling performance of the fabric.

[0025] The infrared emissivity of colored radiant cooling fabric① was tested according to the commonly used infrared emissivity test standard ASTM E408, with wavelength range: 8-13 μm (atmospheric window band), temperature: 25±1°C; relative humidity: RH30±5% (simulating low humidity environment) and RH60±5% (simulating high humidity environment). The test results show that under low humidity (RH30±5%), the infrared emissivity of the 8-13 μm band is 0.85~0.90; under high humidity (RH60±5%), the emissivity increases to 0.90~0.95, with an increase of ≥5%.

[0026] Please refer to Figure 3, 0.1 g of cobalt-based complex CETA powder in Example 1 was dissolved in 10 ml of absolute ethanol, and 1 ml of deionized water was added to the solution. The absorbance of the mixed solution in the visible light band was measured. The test results showed that at low humidity (RH30±5%), the average absorbance of the material in the 400 - 700 nm band was 0.4 - 0.6, and at high humidity (RH60±5%), the absorbance decreased to 0.1 - 0.3, with a decrease of ≥50%.

[0027] Figure 3 The results showed that in the presence of water molecules, the absorption peak of the cobalt-based complex CETA in the visible light band weakened, and the absorbance decreased significantly. The decrease in absorbance indicated that CETA reduced the absorption of visible light when the humidity increased, thereby enhancing the reflectivity. It had the characteristics of dynamic spectral response.

[0028] Further humidity response tests were carried out on the cobalt-based complex CETA. The results showed that when the ambient humidity changed from 30% to 60% at a humidity change rate of 5% RH / min, the response time was 30 seconds. The absorbance of the material in the visible light band decreased from 0.5±0.05 to 0.2±0.05, and at the same time, the infrared emissivity increased from 0.90 to 0.95, meeting the requirements of dynamic regulation.

[0029] The technical solutions in the embodiments of the present application at least have the following technical effects: (1) The color radiative cooling fabric prepared in the embodiment of the present invention can achieve self-adaptive adjustment of color and radiative properties due to the cobalt-based complex (CETA) responding to humidity changes through chemical bond recombination. It is mainly manifested that the fabric presents color in a low-humidity environment, has few absorption peaks in the visible light band, and the reflectivity ≥85%. In a high-humidity environment, the visible light absorption rate decreases (the reflectivity increases to ≥90%), and at the same time, the infrared emissivity increases.

[0030] (2) The color radiative cooling fabric prepared in the embodiment of the present invention is designed with low-absorption pigments, and the reflectivity in the visible light band ≥85%, reducing heat input. The infrared emissivity of the cobalt-based complex CETA in the 8 - 13 μm range can be increased by more than 5% in high humidity compared to low humidity, accelerating the dissipation of heat into outer space, enabling the surface temperature to be 5 - 10℃ lower than the ambient temperature, and the measured air-conditioning energy consumption is reduced by 20% - 30%.

[0031] (3) In the embodiment of the present invention, the cobalt-based complex CETA is combined with a flexible polymer such as PVDF-HFP through electrospinning technology, endowing the fabric with the characteristics of light weight, wearable, and easy processing, and is applicable to fields such as architecture, textiles, and agriculture. Example 2

[0032] The amount of ethanolamine in Example 1 was changed from 0.153 g to 0.305 g, and the remaining steps, including the detection conditions, were the same as those in Example 1. The prepared cobalt-based complex CETA was incompletely coordinated. Due to the unstable structure, the humidity response sensitivity decreased. At RH 30% - 60%, the response speed was 45 - 60 seconds, and the increase in reflectivity / emissivity decreased accordingly. The increase in emissivity at high humidity was 2%. Moreover, the excessive ethanolamine affected the compatibility of the polymer substrate, and it was necessary to compensate by adjusting the electrospinning parameters. Example 3

[0033] The amount of ethanolamine in Example 1 was changed from 0.153 g to 0.102 g, and the remaining steps, including the detection conditions, were the same as those in Example 1. The prepared cobalt-based complex CETA had some Co 2+ not completely coordinated, with residual free CoCl2. The infrared emissivity was higher at high humidity, between 0.92 and 0.96. However, at low humidity, the uncoordinated Co 2+ might cause uneven color and poor color stability. Example 4

[0034] The amount of ethanolamine in Example 1 was changed from 0.153 g to 0.061 g, and the remaining steps, including the detection conditions, were the same as those in Example 1. A mixed solution was prepared, but the cobalt-based complex CETA solution could not be made. This was mainly because the ethanolamine was severely insufficient, and Co 2+ mainly existed in the hydrated form ([Co(H2O)6] 2+ ), the formation rate of CETA was low, and the uncoordinated Co 2+ increased the visible light absorption and decreased the reflectivity. Due to the low content of CETA, the increase in infrared emissivity at high humidity was also limited, with basically no increase.

[0035] Generally speaking, the fabric made in Example 1 of this application has the best performance, which can meet the requirements of color aesthetics, respond to humidity changes, and achieve the adaptive adjustment of color and radiation performance.

[0036] Although the preferred embodiments of the present invention have been described, those skilled in the art can make additional changes and modifications once they know the basic creative concept. Therefore, the appended claims are intended to be construed to include the preferred embodiments as well as all changes and modifications falling within the scope of the present invention.

[0037] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalent technologies, the present invention is also intended to include these changes and modifications.

Claims

1. A colored radiation cooling fabric, characterized in that: The flexible polymer substrate is modified by using a cobalt-based complex and prepared by an electrostatic spinning process.

2. The colored radiant cooling fabric according to claim 1, characterized in that: The cobalt-based complex is formed by coordinating cobalt chloride hexahydrate and a coordinating agent, wherein the coordinating agent is ethanolamine.

3. The colored radiant cooling fabric according to claim 1, characterized in that: The visible light absorptivity of the fabric in a high humidity environment of RH60±5% is reduced to 0.1-0.3, while the 8-13 μm infrared emissivity is enhanced, specifically 0.90-0.

95.

4. The colored radiant cooling fabric according to claim 1, characterized in that: The flexible polymer substrate is PVDF-HFP.

5. The method for preparing the colored radiant cooling fabric according to any one of claims 1 to 4, characterized in that: The following steps are involved: Step 1: Preparation of cobalt-based complexes Dissolving cobalt chloride hexahydrate in anhydrous ethanol to form a cobalt chloride / ethanol mixed solution; adding ethanolamine for coordination reaction to generate a cobalt-based complex with humidity response characteristics; and obtaining a dehydrated cobalt-based complex CETA powder by drying; Step 2: Preparation of colored radiant cooling fabric The cobalt-based complex CETA powder was combined with a polymer substrate and prepared into a fabric through an electrospinning process.

6. The preparation method according to claim 5, characterized in that: The molar ratio of the cobalt chloride hexahydrate to ethanolamine is 1-3:1, preferably 2:1.

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