High radiation cooling performance composite fiber membrane PVDF-HFP / PDMS and preparation method thereof

Abstract

The present application belongs to the field of radiation cooling material design, and relates to a high-radiation cooling performance composite fiber membrane PVDF-HFP / PDMS and a preparation method thereof, characterized by preparing a composite fiber membrane with uniform single nanofiber and excellent radiation cooling effect by using a mixed solution of polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP) and polydimethylsiloxane (PDMS). The preparation method has the advantages of simple preparation method, environmental friendliness, large-size preparation, easy scaling, etc., and makes up for the problems of the existing radiation cooling materials, such as insufficient daytime cooling effect, hydrophobicity, poor flexibility, insufficient tensile resistance and the like.

Description

Technical Field

[0001] This invention belongs to the field of radiation cooling materials, specifically relating to a high-radiation cooling performance composite fiber membrane PVDF-HFP / PDMS and its preparation method. Background Technology

[0002] Traditional cooling technologies (such as air conditioners and fans) consume additional energy and further exacerbate greenhouse gas emissions, impacting the sustainable development of human society. In contrast, novel passive radiative cooling technology utilizes the unique selective reflection and emission characteristics of functional materials to radiate their own heat into the cold outer space through an 8-13µm "atmospheric window" via mid-infrared radiation, thus achieving self-cooling. This novel passive cooling technology achieves automatic cooling without consuming additional energy and emits no polluting gases, making it widely applicable in fields such as smart wearable fabrics, building cooling, and biomedicine.

[0003] However, achieving efficient daytime radiative cooling remains a significant challenge. Because materials continuously absorb heat through visible light during the day under solar irradiation, even a few percentage points of solar absorptivity can offset or even exceed the cooling effect from infrared radiation. Therefore, high solar reflectance and mid-infrared emission of radiative functional materials are key to achieving efficient daytime cooling.

[0004] Currently, most passive radiative cooling materials are fabricated on metal mirrors using micro-nano processes such as electron beam lithography and magnetron sputtering to create photonic crystals, multilayer photonic structures, dielectrics, and polymer-polymer dielectric composites. However, these processes still suffer from complexity and high cost. Recently, patent CN110117427A achieved a 95% reflectivity in the 0.3-2.5μm band and a mid-infrared emissivity of 0.93 in the 8-13μm band using a multilayer structure to achieve daytime radiative cooling. However, its implementation and fabrication process are complex, and the cooling efficiency still needs further improvement. Patent CN110330818A describes a radiative cooling nanocomposite with infrared selectivity, but its mid-infrared emissivity in the 8-13μm band is only 0.89-0.92.

[0005] Therefore, current radiative cooling materials still suffer from problems such as high cost, complex manufacturing processes, and the need for further improvement in radiative cooling performance. Furthermore, the overall performance of these materials, such as abrasion resistance, washability, and air permeability, cannot be simultaneously achieved. In summary, a high-performance radiative cooling composite fiber membrane that is easy to manufacture on a large scale at low cost, exhibits excellent cooling performance, and is washable is urgently needed for development. Summary of the Invention

[0006] The purpose of this invention is to provide a method for preparing a composite fiber membrane with high radiative cooling performance, solving the problems of poor daytime cooling effect, high cost, and poor hydrophobicity of radiative cooling materials. This invention aims to reduce material costs, improve radiative cooling effect, and enhance washability, enabling its widespread application in wearable fabrics, building cooling, and other fields.

[0007] The technical solution of this invention is as follows: To achieve the above objectives, this invention is implemented through the following technical solution:

[0008] A high-performance radiative cooling composite fiber membrane, PVDF-HFP / PDMS, and its preparation method are disclosed. The -CF3 groups in PVDF-HFP impart high infrared emissivity in the 8-13 μm wavelength range, as do the Si-O-Si bonds in the PDMS solution. Furthermore, the nanofiber structure fabricated using electrospinning effectively scatters sunlight, resulting in high solar reflectivity. Therefore, the PVDF-HFP / PDMS composite fiber membrane prepared by this method possesses both high infrared emissivity and high solar reflectivity, achieving highly efficient radiative cooling.

[0009] This invention involves dissolving PVDF-HFP powder in an organic solvent and then mixing it with PDMS to prepare a PVDF-HFP / PDMS composite solution. Finally, an electrospinning method is used to obtain a high-radiative cooling composite fiber membrane, PVDF-HFP / PDMS. The specific steps are as follows:

[0010] (1) Dissolve an appropriate amount of PVDF-HFP powder in an organic solvent by heating in a water bath to obtain a PVDF-HFP solution;

[0011] (2) Mix the above PVDF-HFP solution with PDMS evenly and stir at room temperature for 30 min to obtain PVDF-HFP / PDMS mixture.

[0012] (3) The above PVDF-HFP / PDMS mixture was used to obtain the composite fiber membrane PVDF-HFP / PDMS by electrospinning.

[0013] Furthermore, in step (1), the organic solvent used is a mixed solution of acetone and N,N-dimethylformamide (DMF) in a mass ratio of 1:1;

[0014] Furthermore, in step (1), the solid content of the PVDF-HFP solution used is 20 wt%.

[0015] Preferably, in step (1), the reaction temperature is 40-50℃ and the reaction time is 5h.

[0016] Furthermore, in step (2), the mass ratio of PVDF-HFP solution to PDMS is 9:1;

[0017] Furthermore, in step (3), the ambient temperature for electrospinning is 25-45℃, the voltage is 18-25kV, the feeding speed is 1-10mL / h, the distance between the needle and the receiver roller is 5-15cm, the rotation speed of the roller is 200rpm, and the spinning time is 5-30h.

[0018] Preferably, in step (3), the ambient temperature for electrospinning is 40℃, the voltage is 20kV, the feeding speed is 2mL / h, the distance between the needle and the receiver roller is 12cm, the rotation speed of the roller is 200rpm, and the spinning time is 15h.

[0019] Beneficial effects:

[0020] (1) This invention proposes a new method for preparing radiation cooling composite fiber membranes.

[0021] (2) Excellent performance: Excellent daytime and nighttime radiative cooling performance, with an average solar reflectance of up to 98.86% in the 0.3-2.5μm band and an average mid-infrared emissivity of up to 0.967 in the 8-13μm "atmospheric window" band, achieving 738W / m² during the day. 2 Under sunlight, the temperature can drop by up to 6.4℃, and under no-sunlight conditions at night, the average temperature drop is 7.1℃.

[0022] (3) Compared with other methods, this preparation method has the following advantages:

[0023] ① The preparation process is simple, easy to operate, and highly reproducible;

[0024] ②Environmentally friendly, with no pollutants generated during the preparation process;

[0025] ③ It can be manufactured in large sizes at a low cost, and has good prospects for industrial application;

[0026] ④ The resulting product has the advantages of high reflectivity in the ultraviolet-visible-near infrared wide band, high emissivity in the mid-infrared, tensile strength, water resistance, and high flexibility.

[0027] (4) This invention provides a new method for low-cost, large-scale preparation of radiation cooling films, and provides a new technical approach for zero-energy cooling of buildings, high-power electronic devices, wearable fabrics, etc. Attached image description:

[0028] Figure 1 This is a photograph of the product of Example 1.

[0029] Figure 2 This is a SEM image of the product from Example 1.

[0030] Figure 3 The spectrum of the product of Example 1 in the range of 0.3-15 μm is shown.

[0031] Figure 4 This is a temperature curve of the product from Example 1 measured outdoors.

[0032] Figure 5 The image shows the contact angle test result of the product from Example 1. Detailed implementation method:

[0033] The specific implementation method for preparing the material in this invention is as follows:

[0034] Example 1: 6g of PVDF-HFP powder was dissolved in a mixed solvent of acetone and DMF, with each acetone and DMF weighing 12g. The mixture was stirred and heated in a water bath at 45°C for 5 hours. Then, the mixture was mixed with 3.3g of PDMS and stirred at room temperature for 30 minutes to obtain PVDF-HFP / PDMS, which was then used for electrospinning. The spinning temperature was adjusted to 40°C, the voltage to 20kV, the needle and roller distance to 12cm, the roller speed to 200rpm, the feed rate to 2mL / h, and the spinning time to 15 hours, finally yielding the composite fiber membrane PVDF-HFP / PDMS. Figure 1 The image shows a physical picture of the product; the film is white. Figure 2 The image shows a SEM image of the composite fiber membrane PVDF-HFP / PDMS. As can be seen from the image, PVDF-HFP / PDMS were successfully mixed after co-spun without phase separation, forming a uniform and single fiber membrane with a fiber diameter of approximately 200 nm. Figure 3 This is the spectrum of the composite fiber membrane PVDF-HFP / PDMS in the 0.3-15 μm range. It can be seen that the fiber membrane has a high reflectance of 98.86% in the 0.3-2.5 μm band; simultaneously, the product has a mid-infrared emissivity of 0.967 in the 8-13 μm band. From... Figure 4 The outdoor test results show that, compared with the ambient temperature, at 738W / m 2 Under sunlight, PVDF-HFP / PDMS can achieve a cooling effect of 6.4℃; and at night when there is no sunlight, it can achieve a cooling effect of about 7.1℃. Figure 5 The contact angle test results show that the product has a contact angle of 116.5°, indicating hydrophobic properties.

[0035] Example 2

[0036] The mass of the PDMS solution was 7.5 g, and other conditions were the same as in Example 1, ultimately yielding the composite fiber membrane PVDF-HFP / PDMS-2. The obtained product exhibited a high reflectance of 89.88% in the 0.3-2.5 μm wavelength range; simultaneously, it possessed a mid-infrared emissivity of 0.972 in the 8-13 μm wavelength range. Outdoor measurements showed that, compared to ambient temperature, at 800 W / m²... 2 Under sunlight, PVDF-HFP / PDMS-2 can achieve a cooling effect of 5.1℃; and when there is no sunlight at night, it can achieve a cooling effect of about 7.2℃.

[0037] Example 3

[0038] The mass of the PDMS solution was 2g, and other conditions were the same as in Example 1, ultimately yielding the composite fiber membrane PVDF-HFP / PDMS-3. The obtained product exhibited a high reflectance of 99.01% in the 0.3-2.5μm wavelength range; simultaneously, it possessed a mid-infrared emissivity of 0.960 in the 8-13μm wavelength range. Outdoor measurements showed that, compared to ambient temperature, at 800W / m²... 2 Under solar radiation, PVDF-HFP / PDMS can achieve a cooling effect of 6.1℃; and when there is no sunlight at night, it can achieve a cooling effect of about 6.9℃.

[0039] Example 4

[0040] The PDMS solution was 0 g in mass, and other conditions were the same as in Example 1 to prepare the PVDF-HFP fiber membrane. The obtained product exhibited a high reflectance of 99.38% in the 0.3-2.5 μm wavelength range; simultaneously, the product had a mid-infrared emissivity of 0.957 in the 8-13 μm wavelength range. Outdoor measurements showed that, compared to ambient temperature, at 800 W / m²... 2 Under solar radiation, PVDF-HFP / PDMS can achieve a cooling effect of 5.5℃; and when there is no sunlight at night, it can achieve a cooling effect of about 6.1℃.

Claims

1. A method for preparing a high-radiative cooling composite fiber membrane PVDF-HFP / PDMS, characterized in that, 6g of PVDF-HFP powder was dissolved in a mixed solvent of acetone and DMF, wherein the mass of each acetone and DMF was 12g. The mixture was stirred and heated in a water bath at 45°C for 5h. Then, the mixture was mixed with 3.3g of PDMS and stirred at room temperature for 30min to obtain PVDF-HFP / PDMS, which was then used for electrospinning. The spinning temperature was adjusted to 40°C, the voltage to 20kV, the needle and roller distance to 12cm, the roller speed to 200rpm, the feed rate to 2mL / h, and the spinning time to 15h, finally obtaining the composite fiber membrane PVDF-HFP / PDMS. The composite fiber membrane exhibits a high reflectivity of 98.86% in the 0.3-2.5μm wavelength range and a mid-infrared emissivity of 0.967 in the 8-13μm wavelength range; compared to ambient temperature, it has a high reflectivity of 738 W / m 2 Under solar radiation, PVDF-HFP / PDMS can achieve a cooling effect of 6.4℃; at night when there is no sunlight, it can achieve a cooling effect of about 7.1℃.

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