阅读说明：本技术 一种辐射制冷膜 (Radiation refrigeration film ) 是由 朱斌 李朵 朱嘉 于 2020-06-09 设计创作，主要内容包括：本发明公开了一种选择性发射辐射制冷膜,具体设计了一种通过微观结构设计提高薄膜对0.3-2.5μm波长太阳光的反射,通过特殊分子结构实现薄膜在8-13μm“大气窗口”波段选择性发射,即在中红外波段,仅在8-13μm波段具有尽可能高的发射率,而在其他中红外波段发射率尽可能低,从而获得近理想的高效辐射制冷薄膜的方法。该方法制备辐射制冷膜高效易行,且适用于大规模生产。(The invention discloses a refrigeration film capable of selectively emitting radiation, and particularly designs a method for improving the reflection of the film to sunlight with the wavelength of 0.3-2.5 mu m through microstructure design and realizing the selective emission of the film in an atmospheric window waveband of 8-13 mu m through a special molecular structure, namely in a middle infrared waveband, the film only has the emissivity as high as possible in the waveband of 8-13 mu m, and the emissivity is as low as possible in other middle infrared wavebands, so that the ideal high-efficiency radiation refrigeration film is obtained. The method for preparing the radiation refrigeration film is efficient and easy to implement, and is suitable for large-scale production.)

1. A radiation refrigerating film, characterized in that it comprises a polymeric material having an emission property higher than 80% in the infrared 8-13 μm band, said film having a pore structure with 5-10 μm micropores inside.

2. A radiation refrigerating film according to claim 1 wherein said polymeric material comprises PEO, PP.

3. The radiation refrigeration film as claimed in claim 2, wherein the preparation method of the radiation refrigeration film comprises an electrospinning method, an extrusion molding method with a pore-forming agent added, and a tape casting method.

4. The radiation refrigerating film as claimed in claim 3, wherein said electrospinning method is prepared as follows:

(1) dissolving the polymer material to obtain 5-10 wt% of spinning solution;

(2) injecting the spinning solution in the step (1) into an injector, and extruding the solution to perform electrostatic spinning to obtain nano fibers;

(3) collecting the nanofiber spun in the step (2) by using a roller collector to obtain the nanofiber membrane.

5. The radiation refrigerating film as claimed in claim 4, wherein the pushing speed of the electrostatic spinning is 2mL/h, the needle of the electrostatic spinning is a 20-gauge needle, the voltage of the electrostatic spinning is 22kV, and the spinning distance of the electrostatic spinning is 15 cm.

6. The radiation refrigerating film as claimed in claim 4 or 5, wherein a drum rotation speed of the drum collector is 500 rpm.

Technical Field

The invention belongs to a radiation refrigeration material, and particularly relates to a selective radiation-emitting refrigeration film.

Technical Field

Along with the change of the earth climate, the social consensus is formed by saving energy and reducing carbon emission. And the energy consumed by refrigeration of air conditioners and the like accounts for about 15% of the total electricity consumption in the world every year, so that the research and development of passive refrigeration technology without energy consumption are extremely important for energy conservation and emission reduction. The fiber membrane prepared by the existing melt-blown method and other methods is widely applied to the aspects of air filtration, clothing cloth and the like, but when the fiber membrane is used in outdoor high-temperature environment, the traditional fiber membrane cannot realize temperature reduction, so that the realization of the dynamic refrigeration fiber membrane without energy consumption is still a challenge. Radiation refrigeration is a refrigeration technology for realizing cooling by radiating heat to cold outer space spontaneously, the earth atmosphere has different transmittances to electromagnetic waves with different wavelengths, wherein the transmittance to the electromagnetic waves with a wave band of 8-13 mu m is extremely high, namely an 'atmospheric window'. Therefore, the material has the emissivity as high as possible in 8-13 mu m and the reflectivity as high as possible in the wave bands except 8-13 mu m, particularly in the solar spectrum wave band of 0.3-2.5 mu m by regulating and controlling the spectral properties of the material, so that the material has excellent radiation refrigeration effect, thereby realizing passive refrigeration with zero power consumption, no refrigerant and zero emission, and theoretically, the refrigeration power can reach 150W/m². Therefore, the development of radiation refrigeration, a green passive refrigeration technology, can save a large amount of energy and can relieve the problems of environmental pollution, greenhouse effect and the like caused by the traditional refrigeration means.

The traditional refrigeration mode such as air conditioning refrigeration needs to consume a large amount of energy, and the greenhouse effect is intensified. In addition, the radiation refrigeration materials reported in recent years, although exhibiting good refrigeration power, have limited their radiation refrigeration performance due to the low reflectivity of the materials outside of 8-13 μm; the selective emission radiation refrigeration material based on the photonic crystal has high emissivity at 8-13 mu m through spectral design, and has high reflectivity beyond 8-13 mu m, although the material has excellent radiation refrigeration performance, the material has complex preparation process and high production cost, and is difficult to realize large-scale preparation.

Disclosure of Invention

In order to improve the radiation refrigeration performance of fiber products under outdoor conditions, the invention aims to provide a radiation refrigeration film capable of selectively emitting, which realizes selective emission through molecular structure screening, namely, the film has selective high emission only in an infrared band of 8-13 mu m, the emissivity of the film is as low as possible in other middle infrared bands, and the film can realize the reflectivity of a sunlight band of 0.3-2.5 mu m up to 96 percent through microstructure design, thereby realizing the high-performance radiation refrigeration material capable of selectively emitting infrared rays and being prepared in a large scale for the first time, realizing the radiation refrigeration performance lower than room temperature and greatly improving the cooling effect of the fiber material.

In order to achieve the above object, the present invention provides a radiation refrigerating film comprising a polymer material having polymer molecules with selective emittance in the mid-infrared band of 8-13 μm, the emittance being higher than 80%, and a pore structure having 5-10 μm micropores inside the radiation refrigerating film such that the reflectivity in the 0.3-2.5 μm band of sunlight is higher than 90%.

Preferably, the polymeric material comprises PEO, PP.

Preferably, the preparation method of the radiation refrigeration film comprises electrostatic spinning, extrusion molding by adding pore-forming agent and tape casting molding.

Preferably, the preparation method of the electrostatic spinning comprises the following steps:

(1) dissolving a polymer material to obtain a spinning solution with the weight percent of 5-10 percent;

(2) injecting the spinning solution in the step (1) into an injector, and extruding the solution to perform electrostatic spinning to obtain nano fibers;

(3) collecting the nanofiber spun in the step (2) by using a roller collector to obtain the nanofiber membrane.

Preferably, the pushing speed of the electrostatic spinning is 2mL/h, the needle of the electrostatic spinning is a No. 20 needle, the voltage of the electrostatic spinning is 22kV, and the spinning distance of the electrostatic spinning is 15 cm.

Preferably, the drum rotation speed of the drum-type collector is 500 rpm.

Has the advantages that:

in the radiation refrigeration film, the adopted polymer material has high emission selectivity in an infrared band, the emissivity of the polymer material in an 8-13 mu m range is 82%, the reflectivity of the radiation refrigeration film prepared by electrostatic spinning in a sunlight band reaches 96%, and the temperature of the prepared radiation refrigeration film in the sunlight can be about 5 ℃ lower than the ambient temperature. Meanwhile, under the influence of no sunlight, the temperature of the radiation refrigeration material can be reduced by about 3 ℃ compared with the common radiation refrigeration material without selective infrared emission, and the temperature of the radiation refrigeration material is reduced by 7 ℃ compared with the environment.

Drawings

Fig. 1 is a solar waveband reflection test pattern of the radiation refrigeration film of the embodiment 1 of the invention.

FIG. 2 is an infrared emission test spectrum of the irradiated refrigeration film of example 1 of the present invention.

FIG. 3 is a SEM image of the microstructure of the irradiated refrigeration film of example 1 of the present invention.

Fig. 4 is the daytime radiation refrigeration performance of the radiation refrigeration film of example 1 of the present invention.

Fig. 5 is a comparison of the performance test of the radiation refrigeration film of the example 1 of the invention and the performance test of the common non-selective radiation refrigeration material (control group).

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings of the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Example 1

The radiation refrigeration film is obtained by an electrostatic spinning technology, and the specific preparation method is as follows:

(1) firstly, 40g of PEO particles are dissolved in 458mL of acetonitrile, and the mixture is magnetically stirred for 8 hours at 100 ℃ to obtain a spinning solution with the mass fraction of 10 wt%;

(2) injecting the spinning solution obtained in the step (1) into an injector, extruding the solution at a push speed of 2mL/h for electrostatic spinning, wherein an electrostatic spinning needle is a No. 20 needle, the voltage is 22kV, and the spinning distance is 15 cm;

(3) collecting the nanofiber spun in the step (2) by using a roller collector, wherein the rotating speed of the roller is 500rpm, and obtaining a radiation refrigeration film with the thickness of about 500 mu m after 12 hours.

The test method comprises the following steps:

A. the reflectivity of the radiation-cooled film obtained by the electrospinning technique was measured using a UV-vis-nir spectrophotometer (UV3600, shimadzu) equipped with an integrating sphere model (ISR-3100), and fig. 1 shows the measurement results.

B. The emissivity of the radiation refrigeration film obtained by implementing the electrospinning technology was tested by using fourier transform infrared (FT-IR) spectrometer (Nicolet IS50, thermo fisher) and gold integrating sphere (intersatir MIR, Pike) and mercury cadmium telluride detector, and fig. 2 shows the test results.

C. The radiation refrigeration film obtained by implementing the electrostatic spinning technology is subjected to a microscopic morphology test, fig. 3 is an SEM image of the test, an instrument used is Zeiss Sigma VP, and fig. 3 is a test result.

D. The method comprises the steps of carrying out temperature test on a radiation refrigeration film obtained by implementing an electrostatic spinning technology, respectively placing temperature testers below the radiation refrigeration film and in the air, recording the air temperature and the temperature below the radiation refrigeration film, wherein the lower the temperature is, the better the refrigeration effect is represented, and the used instrument is a thermocouple of K-type and Omega.

E. The radiation refrigeration film obtained by implementing the electrostatic spinning technology and a common non-selective emission radiation refrigeration material (a control group) are subjected to temperature test, temperature testers are respectively placed below the radiation refrigeration film and the non-selective radiation refrigeration material and in the air, the air temperature and the temperatures below the radiation refrigeration film and the non-selective radiation refrigeration material are recorded, the lower the temperature is, the better the refrigeration effect is, and the used instrument is a thermocouple of K-type and Omega.

And (4) testing and analyzing results:

PEO has high selectivity and high emissivity in a wave band of 8-13 mu m because the internal molecular composition of PEO only contains C-C, C-O and C-H with selective vibration peaks in the wave band of 8-13 mu m, and can emit energy to the outer space in a heat radiation mode through an 'atmospheric window' without absorbing heat radiation energy from other wave bands except the 'atmospheric window', and finally achieves passive cooling. Meanwhile, the nano-fiber is prepared by the electrostatic spinning technology, and the prepared radiation refrigeration film has higher reflectivity at a 0.3-2.5 mu m wave band of sunlight due to holes with the size of about 5 mu m in the nano-fiber. The spectrum test is carried out, the lower curve in figure 1 represents the radiation energy spectrum of the sunlight, the upper curve represents the reflectivity of the radiation refrigerating film, and the average value is 96%; the lower curve in fig. 2 represents the atmospheric transmittance, and the upper infrared absorption curve shows that the infrared emissivity reaches 82% at 8-13 μm.

The SEM image of FIG. 3 shows the micro-morphology of the radiation refrigeration film obtained by implementing the electrostatic spinning technology, and it can be seen that the diameter of the nano-fiber is about 500nm, and the pore diameter of the internal pore is 5-10 μm.

The temperature tester is placed under the radiation refrigeration membrane and in the air, and the air temperature and the temperature under the radiation refrigeration membrane are recorded, wherein the lower the temperature is, the better the refrigeration effect is. Fig. 4 shows that the temperature of the radiation refrigeration film obtained by implementing the electrostatic spinning technology is tested in the daytime, and shows that the temperature of the radiation refrigeration film in the sunlight can be lower than the room temperature by about 5 ℃, which illustrates that the radiation refrigeration film with selective infrared emission can indeed realize the radiation refrigeration effect lower than the room temperature in the sun; fig. 5 is a comparison of the cooling performance test of the radiation refrigeration film of the present invention and a common non-selective radiation refrigeration material (control group), and the comparison shows that the film prepared by the electrospinning technique can be cooled to a lower temperature, which illustrates that the radiation refrigeration film with selective infrared emission of the present invention has better refrigeration performance than the radiation refrigeration material without selective infrared emission reported before.

Example 2

The radiation refrigeration film is obtained by a tape casting technology, and the preparation method comprises the following specific steps:

(1) firstly, carrying out ball milling on 18g of PEO, 3g of PAN and 100mL of acetone on a ball mill for 4 hours to obtain a uniformly mixed solution;

(2) pouring the solution in the step (1) on a glass plate, and coating by using a scraper;

(3) and (3) putting the glass plate coated with the solution in the step (2) into a vacuum drying oven, and drying for 6 hours at 50 ℃ to obtain the radiation refrigerating film with the thickness of 50 microns.

Example 3

The radiation refrigeration film is obtained by adding a foaming agent extrusion molding technology, and the preparation method comprises the following specific steps:

(1) firstly, 40g of PEO particles and 0.04g of azo foaming agent are uniformly mixed to obtain a mixture;

(2) and (2) adding the mixture obtained in the step (1) into a screw extruder for extrusion, decomposing the azo foaming agent in the screw to generate bubbles, and overflowing the bubbles to form micropores in the film in the process of extruding the PEO film so as to obtain the radiation refrigeration film with the thickness of 500 mu m.