Preparation method of ultrahigh-reflectivity radiation refrigeration fiber membrane

Abstract

The invention discloses a preparation method of an ultrahigh-reflectivity radiation refrigeration fiber membrane, which comprises the following steps: dissolving a polymer in an organic solvent to prepare an electrostatic spinning precursor solution, and adjusting parameters such as the concentration of the electrostatic spinning precursor solution, spinning voltage, spinning distance, roller rotating speed, liquid supply rate, slide rail reciprocating rate and the like to prepare the ultrahigh-reflectivity radiation refrigeration fiber membrane. And preparing the ultrahigh-reflectivity radiation refrigeration fiber membrane with a porous structure, wherein the reflectivity of the ultrahigh-reflectivity radiation refrigeration fiber membrane is greater than 95% at the sunlight wave band of 0.3-2.5 microns. In the dissolving process of the polymer in the organic solvent, the water bath stirring temperature is 20-60 DEG C, the stirring time is 3-6 hours, a bilateral multi-nozzle opposite layout is adopted in electrostatic spinning, the spinning distance is 15-30 cm, the electrostatic spinning voltage is 20-50 kV, the rotating speed of a roller is 400-1000 r / min, the spinning liquid supply rate is 8-30 ml / h, the reciprocating rate of a sliding rail is 3-10 mm / s, and the thickness of the ultrahigh-reflectivity radiation refrigeration fiber membrane is 300-500 microns. The radiation refrigeration film prepared through the method can be prepared in batches, has good flexibility and can be widely applied to the fields of clothes, buildings, equipment and the like.

Description

Technical Field

[0001] The invention relates to the field of radiation cooling technology, and in particular to a radiation cooling fiber membrane with ultra-high reflectivity in the ultraviolet-visible-near infrared full solar spectrum band. Background Art

[0002] Global warming has become one of the major environmental problems and development challenges facing mankind in the 21st century. If urgent action is not taken to reduce greenhouse gas emissions, some areas of the world will no longer be suitable for human habitation by the end of this century. Today, more than 10% of global greenhouse gas emissions come from traditional refrigeration equipment. At present, the number of refrigeration equipment such as air conditioners used in the world has exceeded 3.6 billion, consuming a huge amount of electricity, and the source of electricity still mainly relies on the combustion of fossil fuels, which has led to a continuous increase in greenhouse gas emissions, exacerbating global warming and forming a vicious cycle. In order to break this situation, passive radiation cooling technology came into being.

[0003] Unlike traditional cooling methods, passive radiant cooling technology is a green cooling method that does not require external energy consumption, does not require the use of refrigerants, and has no carbon emissions during use. It has attracted more and more attention, and the corresponding scientific research and technological applications have become one of the focuses of academia and industry in recent years. This technology can effectively reduce the demand for traditional cooling equipment such as fans and air conditioners, and has great application potential in human thermal management.

[0004] An excellent passive radiation cooler should have a sufficiently high reflectivity in the sunlight band (0.3-2.5μm) to reduce the energy absorption of sunlight; in addition, the emissivity in the atmospheric window band (8-13μm) should also be high to achieve energy-free cooling. However, for radiation cooling technology, the key to its daytime cooling performance lies in high reflectivity. Even when the emissivity is 100%, only a few percentage points of sunlight absorption are needed to effectively heat the object, thereby greatly reducing the cooling effect. However, in most studies, the reflectivity is difficult to exceed 95%. Patent CN117822136A discloses the use of an integrated spray gun device for wet blowing to prepare fiber membranes. The preparation method is convenient and fast, and the operation is safe, but the control effect of the fiber membrane micro-nano structure is not good, and the average reflectivity in the sunlight band is below 82%; Patent CN114293366A discloses a radiation cooling fiber membrane doped with titanium oxide particles, which has an average reflectivity of less than 92.3% in the sunlight band, which has certain limitations. Summary of the invention

[0005] In view of the limitation of low reflectivity of current radiant refrigerators, the present invention provides a method for preparing a radiant cooling fiber membrane with ultra-high reflectivity in the entire solar spectrum band of ultraviolet-visible light-near infrared.

[0006] The method for preparing a super-high reflectivity radiation cooling fiber membrane is as follows: a polymer is dissolved in an organic solvent to prepare an electrospinning precursor solution, and a super-high reflectivity radiation cooling fiber membrane with a porous structure is prepared by reasonably adjusting parameters such as the electrospinning precursor solution concentration, spinning voltage, spinning distance, drum speed, liquid supply rate, and slide rail reciprocating rate. The reflectivity of the super-high reflectivity radiation cooling fiber membrane is greater than 95% in the solar light band of 0.3-2.5 μm. During the preparation process, the spinning time, environmental temperature and humidity, and lighting conditions can also be controlled.

[0007] The present invention discloses a method for preparing an ultra-high reflectivity radiation cooling fiber membrane. The ultra-high reflectivity radiation cooling fiber membrane uses polymers including but not limited to PVDF-HFP (polyvinylidene fluoride hexafluoropropylene), PVDF (polyvinylidene fluoride), PLA (polylactic acid), PEO (polyethylene oxide), PMMA (polymethyl methacrylate), PDMS (polydimethylsiloxane), TPU (polyurethane), PS (polystyrene), POM (polyoxymethylene), PTFE (polytetrafluoroethylene), PVA (polyvinyl alcohol) and other polymer materials. One or more.

[0008] The present invention provides a method for preparing an ultra-high reflectivity radiation cooling fiber membrane, wherein the organic solvent includes but is not limited to one or more organic solvents such as acetone, NN dimethylformamide (DMF), chloroform, tetrahydrofuran and dichloromethane.

[0009] Preferably, the polymer is a fluorine-containing polymer material such as PVDF-HFP, and its mass fraction in the electrospinning precursor solution is 12wt%-16wt%.

[0010] Preferably, the organic solvent is a mixed solution of acetone and NN dimethylformamide, and the mass ratio of acetone to NN dimethylformamide is 1:1.

[0011] Preferably, the water bath stirring temperature during the dissolution process is 20-60° C. and the stirring time is 3-6 h.

[0012] Preferably, the electrospinning adopts a double-sided multi-nozzle opposing layout.

[0013] Preferably, the spinning distance is 15-30 cm.

[0014] Preferably, the electrospinning voltage is 20-50 kV.

[0015] Preferably, the drum rotation speed is 400-1000r / min.

[0016] Preferably, the spinning solution supply rate is 8-30 ml / h.

[0017] Preferably, the reciprocating speed of the slide rail is 3-10 mm / s.

[0018] Preferably, the spinning time is 1-6 hours; and the thickness of the ultra-high reflectivity radiation cooling fiber membrane obtained is 300-500 μm.

[0019] The present invention discloses a method for preparing an ultra-high reflectivity radiation cooling fiber membrane. The ultra-high reflectivity fiber membrane provided can be applied to the fields of clothing, construction, equipment, etc.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] (1) The present invention prepares a porous PVDF-HFP fiber membrane through double-sided multi-nozzle electrospinning technology, and achieves precise control of the macro-micro structure of the fiber membrane by changing the spinning parameters, so that the prepared radiant cooling fiber membrane has an ultra-high reflectivity in the solar light band, which can achieve a better cooling effect.

[0022] (2) The radiant cooling fiber membrane has the advantages of being able to be prepared in batches, low cost, and good performance.

[0023] (3) The radiant cooling fiber membrane has good flexibility and a wide range of applications, and can be applied to clothing, construction, equipment and other fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 The present invention discloses a method for preparing an ultra-high reflectivity radiation cooling fiber membrane, SEM images of the radiation cooling fiber membranes obtained in Examples 1-3, (A) Example 1, (B) Example 2, (C) Example 3.

[0025] Figure 2 The present invention discloses a method for preparing an ultra-high reflectivity radiation cooling fiber membrane, and the fiber diameter distribution and pore size diagram of the radiation cooling fiber membrane obtained in Example 2, (A) fiber diameter, (B) pore size. DETAILED DESCRIPTION

[0026] In order to make the advantageous features and purposes of the present invention more obvious and understandable, the technical solutions in the embodiments, comparative examples and experimental examples of the present invention are clearly and completely described below. Obviously, the described embodiments, comparative examples and experimental examples are only part of the embodiments, comparative examples and experimental examples of the present invention, but not all. Based on the embodiments, comparative examples and experimental examples in the present invention, all other embodiments, comparative examples and experimental examples obtained by those skilled in the art without creative work are within the scope of protection of the present disclosure.

[0027] Example 1

[0028] The present invention provides a method for preparing an ultra-high reflectivity radiative cooling fiber membrane, and the specific preparation steps are as follows: (1) Preparation of 12wt% PVDF-HFP spinning solution: 16.8g PVDF-HFP is dispersed in a mixed solvent of 123.2g acetone and DMF (wherein the mass ratio of acetone to DMF is 1:1), and stirred in a 50°C water bath for 3 hours until completely dissolved, to obtain 140g of a spinning solution with a concentration of 12wt%.

[0029] (2) Electrospinning: The spinning solution in step (1) of this embodiment is poured into a syringe with a needle specification of 20G; the spinning voltage is 30kV; the roller speed is 700r / min; the spinning distance is 30cm; the spinning liquid supply rate is 12ml / h; and a 500μm radiation cooling fiber membrane sample is obtained.

[0030] Example 2

[0031] (1) Preparation of 16 wt% PVDF-HFP spinning solution: 19.2 g PVDF-HFP was dispersed in 100.8 g of a mixed solvent of acetone and DMF (wherein the mass ratio of acetone to DMF was 1:1) and stirred in a 50°C water bath for 3 hours until completely dissolved, to obtain 120 g of a spinning solution with a concentration of 16 wt%.

[0032] (2) Electrospinning: The spinning solution in step (1) of this embodiment was poured into a syringe with a needle specification of 20G; the spinning voltage was 30 kV; the roller speed was 700 r / min; the spinning distance was 30 cm; the spinning liquid supply rate was 20 ml / h; and a 500 μm radiation cooling fiber membrane sample was obtained.

[0033] Example 3

[0034] (1) Preparation of 20 wt% PVDF-HFP spinning solution: 20 g PVDF-HFP was dispersed in 80 g of a mixed solvent of acetone and DMF (wherein the mass ratio of acetone to DMF was 1:1), and stirred in a 50°C water bath for 3 hours until completely dissolved, to obtain 100 g of a spinning solution with a concentration of 20 wt%.

[0035] (2) Electrospinning: The spinning solution in step (1) of this embodiment was poured into a syringe with a needle specification of 20G; the spinning voltage was 30 kV; the roller speed was 700 r / min; the spinning distance was 30 cm; the spinning liquid supply rate was 26 ml / h; and a 500 μm radiation cooling fiber membrane sample was obtained.

[0036] Comparative Example 1

[0037] The preparation method of the radiation cooling film provided in this comparative example is basically the same as that of Example 1, except that 112 g of a spinning solution with a concentration of 12 wt % is prepared and spun to obtain a 400 μm radiation cooling fiber film sample.

[0038] Comparative Example 2

[0039] The preparation method of the radiation cooling film provided in this comparative example is basically the same as that of Example 1, except that 84 g of a spinning solution with a concentration of 12 wt % is prepared and spun to obtain a 300 μm radiation cooling fiber film sample.

[0040] Comparative Example 3

[0041] The preparation method of the radiation cooling film provided in this comparative example is basically the same as that of Example 1, except that 56 g of a spinning solution with a concentration of 12 wt % is prepared and spun to obtain a 200 μm radiation cooling fiber film sample.

[0042] Comparative Example 4

[0043] The preparation method of the radiation cooling film provided in this comparative example is basically the same as that of Example 1, except that 28 g of a spinning solution with a concentration of 12 wt % is prepared and spun to obtain a 100 μm radiation cooling fiber film sample.

[0044] Comparative Example 5

[0045] The preparation method of the radiation cooling film provided in this comparative example is basically the same as that of Example 2, except that 96 g of a spinning solution with a concentration of 16 wt % is prepared and spun to obtain a 400 μm radiation cooling fiber film sample.

[0046] Comparative Example 6

[0047] The preparation method of the radiation cooling film provided in this comparative example is basically the same as that of Example 2, except that 72 g of a spinning solution with a concentration of 16 wt % is prepared and spun to obtain a 300 μm radiation cooling fiber film sample.

[0048] Comparative Example 7

[0049] The preparation method of the radiation cooling film provided in this comparative example is basically the same as that of Example 2, except that 48 g of a spinning solution with a concentration of 16 wt % is prepared and spun to obtain a 200 μm radiation cooling fiber film sample.

[0050] Comparative Example 8

[0051] The preparation method of the radiation cooling film provided in this comparative example is basically the same as that of Example 2, except that 24 g of a spinning solution with a concentration of 16 wt % is prepared and spun to obtain a 100 μm radiation cooling fiber film sample.

[0052] Comparative Example 9

[0053] The preparation method of the radiation cooling film provided in this comparative example is basically the same as that of Example 3, except that 80 g of a spinning solution with a concentration of 20 wt % is prepared and spun to obtain a 400 μm radiation cooling fiber film sample.

[0054] Comparative Example 10

[0055] The preparation method of the radiation cooling film provided in this comparative example is basically the same as that of Example 3, except that 60 g of a spinning solution with a concentration of 20 wt % is prepared and spun to obtain a 300 μm radiation cooling fiber film sample.

[0056] Comparative Example 11

[0057] The preparation method of the radiation cooling film provided in this comparative example is basically the same as that of Example 3, except that 40 g of a spinning solution with a concentration of 20 wt % is prepared and spun to obtain a 200 μm radiation cooling fiber film sample.

[0058] Comparative Example 12

[0059] The preparation method of the radiation cooling film provided in this comparative example is basically the same as that of Example 3, except that 20 g of a spinning solution with a concentration of 20 wt % is prepared and spun to obtain a 100 μm radiation cooling fiber film sample.

[0060] Experimental Example 1

[0061] After the sample surface was treated with gold spraying, the surface morphology of the radiation cooling fiber membrane obtained in Examples 1-3 was characterized by a field emission scanning electron microscope (Hitachi S4700). The SEM images are shown in the attached figure. Figure 1 As shown in (A)-(C).

[0062] Image-J image analysis software was used to measure the fiber diameter of the SEM image, and the fiber diameter distribution of the three PVDF-HFP mass fraction samples was statistically analyzed. The average fiber diameters of the fiber membranes obtained in Examples 1-3 were 0.35±0.11μm, 0.57±0.15μm, and 1.05±0.17μm, respectively. The fiber diameter distribution and pore size distribution of Example 2 are shown in Figure 2 (A) and Figure 2 (B) shown.

[0063] The pore size of the fiber membrane was tested using a capillary pore size analyzer, and the pore size distribution of three mass fraction PVDF-HFP samples was statistically analyzed. The average pore sizes of the fiber membranes obtained in Examples 1-3 were 0.65±0.23 μm, 0.71±0.15 μm, and 0.95±0.61 μm, respectively.

[0064] Experimental Example 2

[0065] The radiation cooling fiber membranes prepared in each embodiment and the radiation cooling fiber membranes prepared in each comparative example were subjected to the following performance tests.

[0066] The reflectance spectra of the radiative cooling fiber membrane samples prepared in each embodiment and comparative example in the solar light band (0.3-2.5 μm) were tested by using an ultraviolet-visible-near-infrared spectrophotometer (UV-VIS-NIR) equipped with a BaSO4 integrating sphere.

[0067] The emissivity spectra of the radiative cooling fiber membrane samples prepared in each embodiment and comparative example in the atmospheric window band (8-13 μm) were tested by using a Fourier transform infrared spectrometer (Nicolet iS50) equipped with a gold integrating sphere.

[0068] The reflectivity and emissivity test results were weighted averaged and the results are shown in Table 1.

[0069] Table 1 Weighted average reflectivity and emissivity

[0070]

[0071]

[0072] It can be seen from Table 1 that the radiation cooling performance of the sample in Example 2 is more advantageous than that of other examples and comparative examples.

[0073] Experimental Example 3 Daytime cooling performance test.

[0074] The cooling performance of the prepared fiber membrane was tested using a radiation cooling temperature measuring device. Continuous outdoor temperature measurement was conducted for 4 hours (10:00-14:00) at Beijing University of Chemical Technology on October 2, 2024. Under an average solar radiation power of 820W / m 2 Under the conditions of , the cooling effects of Example 2, Comparative Example 2, Comparative Example 4 and a white cloth with a thickness of 500μm were tested. The white cloth had an average temperature rise of 3.9℃, the average cooling temperature of the radiation cooling fiber membrane with an average thickness of only 100μm could reach 4.9℃; the average cooling temperature of the radiation cooling fiber membrane with an average thickness of 300μm could reach 8.4℃; the average cooling temperature of the radiation cooling fiber membrane with a thickness of 500μm could reach 10.3℃.

[0075] Experimental Example 4 is an infrared thermal imaging test.

[0076] The temperature changes of Example 2, Comparative Example 2, Comparative Example 4 and a white cloth with a thickness of 500 μm wrapped in a stainless steel box and on the surface of human skin were compared and measured by an infrared thermal imager. The results are shown in Table 1 and Table 2 respectively.

[0077] Table 2 Surface temperature change of stainless steel box

[0078]

[0079] Table 3 Changes in human skin surface temperature

[0080]

[0081] Whether covered on the surface of an iron box or on the surface of human skin, the temperature of the radiant cooling fiber membrane is lower than that of the white cloth, indicating that the ultra-high reflectivity radiant cooling fiber membrane of the present invention has excellent performance and can be used for spontaneous cooling with zero energy consumption and zero carbon emissions in the fields of construction, equipment, and clothing.

[0082] The present invention prepares a radiation cooling fiber membrane with ultra-high reflectivity (up to 99.39%) by regulating the thickness of the fiber membrane and the micro-nano structure using an electrostatic spinning method.

Claims

1. A method for preparing an ultra-high reflectivity radiation cooling fiber membrane, wherein a polymer is dissolved in an organic solvent to prepare an electrospinning precursor solution, and an ultra-high reflectivity radiation cooling fiber membrane having a porous structure is prepared by adjusting the concentration of the electrospinning precursor solution, the spinning voltage, the spinning distance, the drum speed, the liquid supply rate and the slide rail reciprocating rate, wherein: The reflectivity of the ultra-high reflectivity radiation cooling fiber membrane is greater than 95% in the solar light band of 0.3-2.5μm; the polymer includes one or more of PVDF-HFP, PVDF, PLA, PEO, PMMA, PDMS, TPU, PS, POM, PTFE or PVA, and the organic solvent includes one or more of acetone, NN dimethylformamide, chloroform, tetrahydrofuran and dichloromethane; during the dissolution of the polymer in the organic solvent, the water bath stirring temperature is 20-60°C and the stirring time is 3-6h, the electrospinning adopts a double-sided multi-nozzle opposed layout, the spinning distance is 15-30cm, the electrospinning voltage is 20-50kV, the drum speed is 400-1000r / min, the spinning liquid supply rate is 8-30ml / h, the slide rail reciprocating rate is 3-10mm / s, and the thickness of the ultra-high reflectivity radiation cooling fiber membrane is 300-500μm.

2. The method for preparing the ultra-high reflectivity radiation cooling fiber membrane according to claim 1, characterized in that: The polymer is a fluorine-containing high molecular material such as PVDF-HFP, and its mass fraction in the electrostatic spinning precursor solution is 12wt%-16wt%.

3. The method for preparing a super-high reflectivity radiation cooling fiber membrane according to claim 1, characterized in that: The organic solvent is a mixed solution of acetone and NN dimethylformamide, and the mass ratio of acetone to NN dimethylformamide is 1:1.

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