A fiber membrane with a regulated radiative cooling performance and a preparation method thereof

Abstract

The present application relates to a kind of fiber membrane with the radiation refrigeration performance of regulation and preparation method thereof, wherein the fiber membrane is composed of micro-nano fiber with tensile capacity, the fiber membrane thickness is 10-500 μm;The fiber diameter of the micro-nano fiber is 0.1~25 μm;The micro-nano fiber is high molecular polymer fiber;The solar light transmittance regulation range of the fiber membrane is not less than 40%, and the mid-infrared transmittance regulation range is not less than 50%. Compared with prior art, the fiber membrane in the present application has adjustable transmittance in solar light and mid-infrared two bands simultaneously, when being installed on the upper portion of any existing radiation refrigeration material as wind screen, the refrigeration effect of the radiation refrigeration material can be regulated by regulating the solar light and mid-infrared transmittance.

Description

Technical Field

[0001] This invention relates to the field of radiation cooling technology, and in particular to a fiber membrane with adjustable radiation cooling performance and its preparation method. Background Technology

[0002] In recent years, global warming has exacerbated this phenomenon due to the large amounts of greenhouse gases emitted and waste heat generated by human production and daily life. Frequent high-temperature weather not only increases indoor cooling load and energy consumption of refrigeration equipment but also seriously threatens human survival. During hot seasons or regions, large-scale use of energy-intensive equipment such as air conditioners is necessary to ensure human comfort and health, consuming approximately 15% of global electricity and exacerbating the environmental and energy crisis. Radiative cooling is a passive cooling technology that cools by radiating heat into outer space. This cooling process does not consume any of Earth's energy. Typical radiative cooling materials have high solar reflectivity and high mid-infrared emissivity. However, the optical properties of developed radiative cooling materials are fixed. In cold seasons or at night, the continuous cooling of these materials leads to overcooling, which in turn increases heating energy consumption.

[0003] Currently, radiative cooling materials already possess excellent cooling performance. However, developing dynamic radiative cooling materials with variable optical properties is extremely challenging, significantly increasing costs and manufacturing difficulties. This results in existing dynamic radiative cooling materials still facing significant challenges due to insufficient controllability and high costs. To address these issues, a fiber membrane with tunable transmittance in the sunlight and mid-infrared bands was prepared using electrospinning technology. The fiber membrane exhibits good mechanical properties, and when used as a windscreen attached to any existing radiative cooling material, its cooling effect can be controlled. Summary of the Invention

[0004] The purpose of this invention is to overcome the defects of the prior art by providing a fiber membrane with adjustable radiative cooling performance and its preparation method. The fiber membrane has adjustable transmittance in both sunlight and mid-infrared bands. When it is installed as a wind screen on top of any existing radiative cooling material, the cooling effect of the radiative cooling material can be controlled by adjusting the transmittance of the radiative cooling material in sunlight and mid-infrared.

[0005] The objective of this invention can be achieved through the following technical solutions:

[0006] The first aspect of the present invention provides a fiber membrane with regulated radiative cooling performance, the fiber membrane being composed of micro- and nanofibers with tensile strength, and the thickness of the fiber membrane being 10-500 μm;

[0007] The diameter of the micro / nanofibers is 0.1–25 μm;

[0008] The micro / nanofibers are thermoplastic elastomer polymer fibers;

[0009] The solar transmittance of the fiber membrane is adjustable within a range of not less than 40%, and the mid-infrared transmittance is adjustable within a range of not less than 50%.

[0010] Furthermore, the fiber membrane is formed by electrospinning and depositing a polymer onto the receiver.

[0011] Furthermore, the polymer material in the polymer fiber includes one of polyurethane, ethylene-octene copolymer, butene-styrene thermoplastic elastomer, polyester, and polyolefin.

[0012] Furthermore, when the elongation rates are 0%, 200%, and 400%, the average fiber diameters of the fiber membranes are 15-25 μm, 5-15 μm, and 0.1-5 μm, respectively.

[0013] Furthermore, within the solar spectrum wavelength range of 200–2500 nm, when the elongation of the radiation-cooling fiber membrane varies between 0 and 400%, its average transmittance varies between 20 and 80%.

[0014] Furthermore, within the wavelength range of 3–20 μm, when the elongation of the radiation-cooling fiber membrane varies between 0 and 400%, its average transmittance varies between 20 and 90%.

[0015] A second aspect of the present invention provides a method for preparing a fiber membrane with regulated radiative cooling performance as described above, comprising the following steps:

[0016] S1. Mix the polymer and organic solvent and stir until completely dissolved to form a spinning solution;

[0017] S2. The spinning solution is injected into the syringe of the electrospinning machine and sprayed out to form fibers. The fibers accumulate on the receiver to form the fiber membrane. The fiber membrane is dried under ventilation conditions for 2 to 48 hours to obtain a fiber membrane with regulated radiative cooling performance.

[0018] Furthermore, the organic solvent is selected from one or a combination of solvents such as tetrahydrofuran, chloroform, toluene, cyclohexane, n-hexane, ethyl acetate, butyl acetate, xylene, and carbon tetrachloride.

[0019] Further, in S1, the mass ratio of the polymer to the organic solvent is (0.1 to 1):1.

[0020] Furthermore, in S2, the electrospinning uses a voltage of 5–25 kV, a feed speed of 0.0005–0.1 mm / s, a distance of 5–30 cm, and a syringe needle size of 17–22.

[0021] More preferably, in S2, the voltage used for electrospinning is 20-25kV, the feed speed is 0.005-0.1mm / s, the distance is 20cm, and the syringe needle is No. 18.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] 1) This invention proposes an effective method for preparing fiber membranes with regulated radiative cooling performance. Compared with existing technologies, this method has the advantages of simplicity, environmental friendliness, and energy saving and emission reduction. The fabric has a wide range of regulated transmittance in both sunlight and mid-infrared bands, exhibiting excellent regulation of the cooling effect of radiative cooling materials; it overcomes the defect of fixed optical properties in traditional radiative cooling materials, and can effectively reduce the increased heating energy consumption caused by excessive cooling in cold seasons or at night.

[0024] 2) Furthermore, the fiber membrane prepared by this invention also exhibits excellent tensile properties and cycle stability. This invention provides a novel method for dynamic radiative cooling, which, when combined with radiative cooling materials, enables dynamic radiative cooling in low-temperature environments. This technology has potential economic value and social benefits. Attached Figure Description

[0025] Figure 1 This is a photograph of the fiber membrane used in this invention.

[0026] Figure 2 These are optical photographs and SEM images of the fiber membrane in this invention at different stretching rates;

[0027] Figure 3 This is a tensile test diagram of the fiber membrane fracture in this invention;

[0028] Figure 4 This is a diagram of the cyclic tensile test of the fiber membrane in this invention;

[0029] Figure 5 The images show the solar and mid-infrared transmittance spectra of the fiber membrane in this invention at different stretching rates.

[0030] Figure 6 This is a temperature comparison between the fiber membrane in the present invention in a cooling state during the day and a traditional radiative cooling material;

[0031] Figure 7 This is a temperature comparison between the fiber membrane of the present invention in a non-cooled state at night and a traditional radiative cooling material. Detailed Implementation

[0032] This invention belongs to the field of radiative cooling technology, specifically relating to a fiber membrane with adjustable radiative cooling performance and its preparation method. The fiber membrane is assembled from stretchable nanofibers. The fiber membrane possesses adjustable transmittance in both sunlight and mid-infrared bands. When used as a windscreen on top of any existing radiative cooling material, its cooling effect can be controlled by adjusting the transmittance of the radiative cooling material in sunlight and mid-infrared. The fiber membrane has a breaking tensile strength greater than 500%, maintains its original tensile properties after cyclic stretching, and exhibits high mechanical strength. The fiber membrane effectively solves the overcooling problem caused by continuous cooling of radiative cooling materials at low temperatures. Combining this fiber membrane with radiative cooling materials achieves dynamic control of the cooling effect. Furthermore, the preparation method of this fiber membrane is simple and environmentally friendly. Addressing the overcooling problem caused by continuous cooling of traditional radiative cooling materials at low temperatures, this invention provides a method for achieving dynamic radiative cooling by adjusting the transmittance of the radiative cooling material in sunlight and mid-infrared.

[0033] The fiber membrane for regulating radiative cooling performance in this invention is composed of micro- and nanofibers with tensile strength.

[0034] In specific implementation, the fiber membrane has a thickness of 10-500 μm and a high tensile strength.

[0035] In specific implementation, the solar transmittance of the fiber membrane is controlled within a range of not less than 40%, and the mid-infrared transmittance is controlled within a range of not less than 50%.

[0036] In specific implementation, the preparation method of the fiber membrane for regulating radiative cooling performance includes the following steps:

[0037] a) Mix the polymer and organic solvent in a certain mass ratio and stir until completely dissolved to form a spinning solution;

[0038] b) The spinning solution is injected into the syringe of an electrospinning machine and sprayed out under certain conditions to form fibers; the fibers accumulate on the receiver to form the fiber membrane; the fiber membrane is dried under ventilated conditions for 2 to 48 hours to obtain the fiber membrane.

[0039] In specific implementation, the mass ratio of the thermoplastic elastomer polymer to the organic solvent in step a) is (0.1~1):1.

[0040] In specific implementation, the thermoplastic elastomer polymer mentioned in step a) is used as the raw material, wherein the polymer can be polyurethane, ethylene-octene copolymer, butene-styrene thermoplastic elastomer, polyester and polyolefin, etc.

[0041] In specific implementation, the organic solvent mentioned in step a) is used to dissolve the polymer. The organic solvent may be one or a combination of multiple solvents, such as tetrahydrofuran, chloroform, toluene, cyclohexane, n-hexane, ethyl acetate, butyl acetate, xylene, and carbon tetrachloride.

[0042] In specific implementation, the certain conditions mentioned in step a) include an electrospinning voltage of 5–25 kV, a feed speed of 0.0005–0.1 mm / s, a distance of 5–30 cm, and a syringe needle size of 17–22. Preferably, the electrospinning voltage is 20–25 kV, the feed speed is 0.005–0.1 mm / s, the distance is 20 cm, and the syringe needle size is 18.

[0043] In specific implementation, the fiber diameter of the fiber membrane is 0.1 to 25 μm.

[0044] The present invention has the following main technological innovations:

[0045] (1) In view of the problem of overcooling of existing radiation cooling materials, the present invention combines a fiber membrane with adjustable transmittance of sunlight and mid-infrared light with radiation cooling materials, which has the advantages of low cost and scalable manufacturing.

[0046] (2) In view of the problems of high cost and high development difficulty of existing dynamic radiation cooling materials, this invention proposes a method for preparing fiber membranes with controlled radiation cooling performance by simple electrospinning.

[0047] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. Any preparation methods, materials, structures, or compositional ratios not explicitly described in this technical solution are considered common technical features disclosed in the prior art.

[0048] Unless otherwise specified, the terms used herein (including technical terms) shall be interpreted as having the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. It will also be understood that the terms used herein shall be interpreted as having the same meaning as they have in the context of this specification and related art, and shall not be interpreted in an idealized or excessive manner, unless specifically defined herein.

[0049] Example 1

[0050] This embodiment prepares a fiber membrane 1 with regulated radiative cooling performance, including the following steps:

[0051] a) Butene-styrene thermoplastic elastomer SEBS was completely dissolved in tetrahydrofuran and stirred for 2 hours to obtain a spinning solution with a concentration of 30 wt%.

[0052] b) The spinning solution from step a) is transferred to a syringe, and a fiber membrane is prepared by electrospinning. The syringe needle is No. 18, the spinning voltage is 25kV, the advance speed is 0.01mm / s, and the distance is 20cm. The spinning solution is ejected under the action of an electric field, and the solvent in the fiber evaporates rapidly in the air and falls onto the receiving substrate to form fiber membrane 1, which regulates the radiation cooling performance. The actual fiber membrane is shown in Figure 1. Figure 1 As shown.

[0053] Example 2

[0054] This embodiment prepares a fiber membrane 2 with regulated radiative cooling performance, including the following steps:

[0055] a) Butene-styrene thermoplastic elastomer SEBS was added to a mixed solution of tetrahydrofuran and toluene, and stirred for 2 hours to obtain a spinning solution with a concentration of 30 wt%.

[0056] b) The spinning solution from step a) is transferred to a syringe, and a fiber membrane is prepared by electrospinning. The syringe needle is No. 18, the spinning voltage is 20kV, the advance speed is 0.005mm / s, and the distance is 20cm. The spinning solution is ejected under the action of an electric field, and the solvent in the fiber evaporates rapidly in the air and falls onto the receiving substrate to form a fiber membrane 2 that regulates the radiation cooling performance.

[0057] Verification Example 1

[0058] This verification example tested the optical properties of the fiber membrane with modulated radiative cooling performance prepared in Example 1.

[0059] a) Characterizing the microstructure of fiber membrane 1:

[0060] The microstructure of the fiber membrane at different stretching ratios was observed using field emission scanning electron microscopy, such as... Figure 2 As shown, the fiber membrane 1 is composed of multiple fibers, and the fiber diameter is related to the elongation. When the elongation is 0%, 200%, and 400%, the average fiber diameter of the fiber membrane 1 is 15.4, 7.1, and 4.7 μm, respectively.

[0061] b) Test the transmittance of fiber membrane 1 in the solar radiation band:

[0062] The transmittance spectrum of fiber membrane 1 in the solar spectrum of 200–2500 nm was measured using a UV-Vis-NIR spectrophotometer (Lambda 1050, PerkinElmer). Figure 5 As shown, when the elongation of the radiation-cooling fiber membrane 1 varies between 0 and 400%, its average transmittance in the solar band dynamically changes between 20.5% and 75.3%.

[0063] c) Test the transmittance of fiber membrane 1 in the mid-infrared band:

[0064] The transmittance spectrum of fiber membrane 1 in the wavelength range of 3–20 μm was measured using an integrating sphere Fourier transform infrared spectrometer (Nicolet 6700, Thermo Scientific). Figure 5 As shown, when the elongation of the radiation-cooled fiber membrane 1 varies between 0 and 400%, the average transmittance in the infrared band varies between 21.2% and 85.6%.

[0065] The above tests show that the transmittance of the fiber membrane used to regulate radiative cooling performance can dynamically change between 20.5% and 75.3% in the solar band, and between 21.2% and 85.6% in the mid-infrared band. This indicates that placing the fiber membrane above the radiative cooling material can control the radiative heat transfer of the radiative cooling material through stretching.

[0066] d) Test the mechanical properties of fiber membrane 1:

[0067] A 2cm wide strip is cut from the fiber membrane 1 that regulates radiative cooling performance, and the initial length of the strip is measured to be 5cm. The strip is then stretched to its maximum extent until it is about to break, such as... Figure 3 As shown, the tensile strength at break of fiber membrane 1 reached 500%. Furthermore, the fiber membrane underwent 100 cycles of tensile testing. Figure 4 The tensile properties of the fiber membrane did not decrease significantly after cyclic stretching, indicating that the fiber membrane has excellent mechanical properties.

[0068] e) Test the effect of fiber membrane 1 on the temperature regulation of radiation cooling:

[0069] Temperature testing of the radiative cooling material was conducted using two 40×40×20cm acrylic measuring chambers. Each chamber had a solar reflective film on the outside and an 8×8cm window at the top. A polyethylene film or the prepared fiber membrane 1 was placed in the window of each chamber, respectively. The polyethylene film served as a control. The radiative cooling material was placed on a polystyrene foam support inside the measuring chamber, 2cm from the window. The top of the measuring chamber faced the sky. The temperature of the radiative cooling material was recorded during the test using thermocouples with a temperature uncertainty of 0.1℃. (See also...) Figure 6 and Figure 7 The test results showed that during the day, the temperature of the radiative cooling material under the window covered by the fiber membrane 1 with a tensile strength of 400% was 0.3℃ lower than that of the control sample; at night, the temperature of the radiative cooling material under the fiber membrane 1 with a tensile strength of 0% was 3.3℃ higher than that of the control sample. This indicates that the radiative cooling material has an excellent regulatory effect on the cooling effect.

[0070] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A fiber membrane with modulated radiative cooling performance, characterized in that, The fiber membrane is composed of stretchable butene-styrene thermoplastic elastomer fibers, the thickness of the fiber membrane is 10-500 μm, and the fiber diameter of the butene-styrene thermoplastic elastomer fibers is 0.1-25 μm; When in use, the fiber membrane covers the radiative cooling material, forming a transmittance control layer between the external environment and the radiative cooling material. By controlling the transmittance of sunlight and the transmittance of mid-infrared light, the solar light input and mid-infrared thermal radiation output of the radiative cooling material are controlled. When the elongation of the fiber membrane changes from 0% to 400%, the average fiber diameter of the butene-styrene thermoplastic elastomer fiber decreases from 15.4 μm to 4.7 μm; When the elongation of the fiber membrane changes from 0% to 400%, its transmittance in the solar band can dynamically change between 20.5% and 75.3%, and its transmittance in the mid-infrared band can change between 21.2% and 85.6%.

2. The fiber membrane with regulated radiative cooling performance according to claim 1, characterized in that, The tensile strength of the fiber membrane reaches 500%; when the tensile strength of the fiber membrane is 0%, 200% and 400% respectively, the average fiber diameter of the butene-styrene thermoplastic elastomer fiber is 15.4 μm, 7.1 μm and 4.7 μm respectively.

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