Radiation refrigeration and photo-thermal integrated Janus polylactic acid fiber membrane and preparation method thereof

Abstract

The invention provides a radiation refrigeration and photo-thermal integrated Janus polylactic acid fiber membrane and a preparation method thereof, the method comprises the following steps: step S1, dissolving a silicon source, an alkaline solvent A and deionized water in an alcohol solvent B, and mixing through UV irradiation to obtain a SiO2 suspension; s2, polylactic acid is dissolved in a solvent C, a polylactic acid fiber membrane is prepared through an electric centrifugal spinning technology, then the polylactic acid fiber membrane is soaked in the SiO2 suspension liquid, and a cooling layer fiber membrane is obtained; and S3, dissolving a photo-thermal functional factor, polylactic acid and a dispersing agent in a solvent D to obtain a heating layer spinning solution, preparing heating layer fibers through an electric centrifugal electrostatic spinning technology, and depositing the heating layer fibers on a cooling layer fiber membrane. The Janus polylactic acid fiber membrane prepared by the preparation method disclosed by the invention has cold and hot dual functions, and the temperature adjusting range is widened. The two-way temperature adjusting mechanism can reduce the body surface temperature in a hot environment, heat is generated in a cold environment to meet the heat requirement, and the heat comfort requirement of a human body in different seasons is met.

Description

Technical Field

[0001] The present invention relates to the field of personal thermal management materials, and in particular to a Janus polylactic acid fiber film integrating radiation cooling and photothermal and a preparation method thereof. Background Art

[0002] With the rapid development of science and technology and the surge in the global population, the increasing consumption of natural resources by humans has led to greenhouse gas emissions far exceeding the earth's carrying capacity. At the same time, the reduction of green vegetation and the destruction of the ozone layer have further aggravated global warming, causing the global average temperature to rise year by year. Against this background, the demand for cooling equipment has increased dramatically. However, traditional cooling equipment (such as air conditioners and refrigerators) releases a large amount of greenhouse gases during operation, which not only increases energy consumption, but also causes secondary damage to the environment. Therefore, the development of green and sustainable cooling technology has become the focus of current research.

[0003] Passive radiation cooling technology, as a zero-energy green cooling method, has received widespread attention in recent years. This cooling technology achieves the purpose of cooling by reducing the absorption of sunlight and transferring heat to outer space through infrared reflection. However, a single radiation cooling textile can only achieve passive cooling, and due to the narrow temperature regulation range, it causes unnecessary heat loss in cold environments. With climate change and frequent extreme weather, people are increasingly demanding functional textiles that can dynamically regulate body temperature under different environmental conditions. Passive radiation heating utilizes the photothermal conversion properties of materials, fully absorbs sunlight and converts it into heat energy, and has low infrared emissivity to reduce heat loss. Passive radiation heating is a green heating method with no energy loss, but how to combine it with passive radiation cooling to expand the adjustable temperature range has become the focus and difficulty of current research. Summary of the invention

[0004] The purpose of the present invention is to prepare a fiber membrane with moisture absorption and perspiration removal and a wide temperature regulation range to meet the needs of personal thermal management.

[0005] In order to achieve the above-mentioned purpose, the present invention uses homemade silicon dioxide, photothermal functional factors, and polylactic acid (PLA) as raw materials to provide a Janus polylactic acid fiber membrane integrating radiation cooling and photothermal and a preparation method thereof. According to a first aspect of the present invention, a preparation method of a Janus polylactic acid fiber membrane integrating radiation cooling and photothermal is provided, comprising the following steps: Step S1, preparing SiO2 suspension: dissolving silicon source, alkaline solvent A, and deionized water in alcohol solvent B, and mixing by UV irradiation to obtain a uniform SiO2 suspension; Step S2, preparing a cooling layer fiber membrane: dissolving polylactic acid in solvent C, mixing evenly to obtain a spinning solution; preparing a polylactic acid fiber membrane by electrocentrifugal electrospinning technology; then soaking the polylactic acid fiber membrane in the SiO2 suspension obtained in step S1, repeatedly washing with deionized water after soaking, and drying for 24 hours to obtain a cooling layer fiber membrane with nano-SiO2 directional growth on the fiber surface; Step S3, preparing Janus fiber membrane: dissolving photothermal functional factors, polylactic acid and dispersant in solvent D, obtaining uniform heating layer spinning solution by ultrasound, preparing heating layer fibers by electrocentrifugal electrospinning technology, depositing the heating layer fibers on the cooling layer fiber membrane obtained in step S2, and finally drying the obtained Janus fiber membrane for several hours to obtain a Janus polylactic acid fiber membrane integrating radiant cooling and photothermal.

[0006] Preferably, in step S1, the silicon source is one or more of ethyl orthosilicate, methyl orthosilicate, sodium silicate, silicon tetrachloride, and propyl orthosilicate, and the concentration of the silicon source in the SiO2 suspension is 0.01-0.5 mol / L.

[0007] Preferably, in step S1, the alkaline solvent A is one or more of ammonia water, sodium hydroxide, tetramethylammonium hydroxide, ethylenediamine, triethylamine, potassium carbonate, and sodium carbonate, and the pH value of the suspension is adjusted to 7-12.

[0008] Preferably, in step S1, the alcohol solvent B is one or more of methanol, ethanol, isopropanol, ethylene glycol, dimethylformamide, and n-propanol; the UV irradiation time is 5 to 40 minutes, and the irradiation distance is 5 to 30 cm.

[0009] Preferably, the average size of SiO2 in the SiO2 suspension obtained in step S1 is 0.3~1μm.

[0010] Preferably, the solvent C in step S2 is one or more of chloroform, acetone, ethyl acetate, dimethylformamide, dimethylacetamide, ethanol, dichloromethane, and tetrahydrofuran, and the concentration of the polylactic acid in the solvent C in step S2 is 0.1-20 g / L.

[0011] Preferably, the conditions of the electrocentrifugal electrospinning technology in step S2 are: the electrocentrifugal electrospinning liquid consumption rate is 0.5-50 ml / h, the rotation radius is 10-30 cm, the ambient temperature is 10-30° C., and the humidity is 40-90%.

[0012] Preferably, the cooling layer fiber membrane obtained in step S2 has a thickness of 200-500 μm, a fiber diameter of 0.3-2 μm, a porosity of 70-95%, and a SiO2 coverage of the fiber surface of 30-90%.

[0013] Preferably, the photothermal functional factor in step S3 is one or more of carbon nanotubes, boron nitride, polypyrrole, carbon black, graphene, graphene oxide, MXene, and black phosphorus; Preferably, the dispersant in step S3 is one or more of hexadecyltrimethylammonium bromide, sodium dodecyl sulfate, polyethylene glycol, sodium dodecylbenzene sulfonate, and ethyl acetate, and the mass ratio of the dispersant to the photofunctional factor is 1:2 to 1:20.

[0014] Preferably, the solvent D in step S3 is one or more of water, methanol, ethanol, acetone, chloroform, dichloromethane, methylformamide, and ethylacetamide, and the concentration of polylactic acid in solvent C in step S3 is 5-20wt%, and the concentration of graphene oxide in solvent D is 5-20wt%.

[0015] Preferably, the conditions of the electrocentrifugal electrospinning technology in step S3 are: the electrocentrifugal electrospinning liquid consumption rate is 0.5-50 ml / h, the rotation radius is 10-30 cm, the ambient temperature is 10-30° C., and the humidity is 40-90%.

[0016] Preferably, the fiber diameter of the heating layer fiber in step S3 is 0.3-2 μm, the fiber membrane thickness is 50-200 μm, the porosity is 70-95%, and the photothermal functional factor coverage is 30-90%.

[0017] In order to achieve the above object, according to the second aspect of the present invention, the present invention also provides a fiber membrane obtained by the aforementioned preparation method.

[0018] The beneficial effects of the present invention are: (1) providing a Janus polylactic acid fiber membrane that integrates radiation cooling and photothermal and a preparation method thereof. The fiber membrane can be passively cooled and heated to meet the thermal comfort of the human body; (2) homemade silica is used as the filler of the cooling layer, so that the fiber membrane has excellent radiation cooling performance; (3) graphene oxide has excellent light absorption rate and light conversion ability, so that the fiber membrane exhibits excellent photothermal performance; (4) the fiber membrane cooling layer not only has high infrared emissivity and high solar reflectivity, but also the heating layer can absorb sunlight for photothermal conversion to generate heat, thereby meeting the thermal needs of the human body in a cold environment. The fiber not only has a wide temperature regulation range, but also has excellent performance and a simple preparation process. It is a healthy and safe material with broad application prospects.

[0019] The present invention provides a Janus polylactic acid fiber membrane that integrates radiation cooling and photothermal. In a hot environment, the fiber membrane can effectively reduce the body surface temperature by virtue of its high solar reflectivity and high infrared emissivity; in a cold environment, its heating function can meet the body's demand for heat. This dual-mode design not only breaks through the limitations of traditional radiation cooling textiles, but also realizes an active thermal regulation function. Due to the simple preparation process and excellent performance, it has broad application prospects. It can be used in the field of personal protective clothing. The high infrared emissivity and solar reflectivity of the cooling layer give it a good cooling effect, while the heating layer can meet the body's demand for heat in a cold environment, further ensuring the comfort of the wearer. Due to the simple preparation process and excellent performance, it is a thermal management material with broad prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0021] Figure 1 It is a flow chart of the method of the present invention.

[0022] Figure 2 is a scanning electron microscope image of SiO2 grown on the cooling layer in Example 1.

[0023] Figure 3 This is a scanning electron microscope image of the heating layer fiber membrane in Example 1.

[0024] Figure 4 This is a scanning electron microscope image of the Janus polylactic acid fiber membrane integrating radiative cooling and photothermal in Example 1. DETAILED DESCRIPTION

[0025] To make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be described in detail below. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other implementation methods obtained by ordinary technicians in the field without creative work belong to the scope of protection of the present invention. The present invention will be described in detail below in conjunction with the embodiments.

[0026] like Figure 1 As shown, Example 1 of the present invention provides a method for preparing a Janus polylactic acid fiber film integrating radiation cooling and photothermal, comprising the following steps.

[0027] S11. Prepare SiO2 suspension: dissolve 10 mL of tetraethyl orthosilicate, 15 mL of ammonia water, and 20 mL of deionized water in 120 mL of anhydrous ethanol, adjust the pH value of the mixed solution to 9, irradiate the mixed solution with UV (irradiation time is 10 min, irradiation distance is 10 cm), and after irradiation, stir to obtain a uniform SiO2 suspension (the average size of SiO2 is 700 nm).

[0028] S12. Preparation of cooling layer fiber membrane: dissolve 1 g of polylactic acid in 10 mL of a mixed solvent of dichloromethane and dimethylformamide (7:3), prepare polylactic acid fiber membrane by electrocentrifugal electrospinning (spinning voltage is 20 kv, spinning solution consumption rate is 1.5 mL / h, rotation radius is 10 cm, temperature is 25±2°C, relative humidity is 45±3%), soak the obtained polylactic acid fiber membrane in SiO2 suspension for 20 min, wash it repeatedly with deionized water after soaking, dry the washed fiber membrane for 24 h to obtain a cooling layer fiber membrane (the average fiber diameter is 800 nm, the fiber membrane thickness is 350 μm, the porosity is 85%, and the silica loading rate on the fiber surface is 80%).

[0029] S13, preparation of Janus fiber membrane: 1g of graphene oxide and 0.5g of sodium dodecylbenzene sulfonate as dispersants were dissolved in 10mL of dimethylformamide, and 1g of polylactic acid was added to the solution after ultrasonication for 30min, and mixed evenly to obtain a heating layer spinning solution. The cooling layer prepared in step S12 was used as the substrate, and the heating fiber was deposited on the cooling fiber membrane by electrocentrifugal electrospinning (voltage of 20kV, spinning solution consumption rate of 1.5mL / h, rotation radius of 10cm, temperature of 25±2℃, relative humidity of 45±3%) to obtain a heating layer in the fiber membrane (the average diameter of the heating layer fiber was 500nm, the thickness of the fiber membrane was 150μm, the porosity was 80%, and the coverage of graphene oxide on the fiber membrane was 80%). Finally, the fiber membrane was dried for 24h to remove the residual solvent to obtain a Janus polylactic acid fiber membrane integrating radiative cooling and photothermal.

[0030] Embodiment 2 of the present invention provides a method for preparing a Janus polylactic acid fiber membrane integrating radiation cooling and photothermal, comprising the following steps.

[0031] S21. Prepare SiO2 suspension: dissolve 10 mL of methyl orthosilicate, 15 mL of sodium hydroxide and 15 mL of deionized water in 120 mL of anhydrous ethanol, adjust the pH value of the mixture to 10, irradiate the mixture with UV (irradiation time is 15 min, irradiation distance is 15 cm), and after irradiation, stir to obtain a uniform SiO2 suspension (average size of SiO2 is 800 nm).

[0032] S22. Preparation of cooling layer fiber membrane: 1.2 g of polylactic acid was dissolved in 10 mL of a mixed solvent of dichloromethane and dimethylformamide (7:3), and polylactic acid fiber membrane was prepared by electrocentrifugal electrospinning (spinning voltage was 20 kV, spinning solution consumption rate was 2 mL / h, rotation radius was 15 cm, temperature was 25±2°C, relative humidity was 45±3%), and the obtained polylactic acid fiber membrane was immersed in SiO2 suspension for 10 min. After immersion, it was repeatedly washed with deionized water, and the washed fiber membrane was dried for 24 h to obtain a cooling layer fiber membrane (the average fiber diameter was 700 nm, the fiber membrane thickness was 400 μm, the porosity was 90%, and the silica loading rate on the fiber surface was 75%).

[0033] S23, preparation of Janus fiber membrane: 1.2g of graphene oxide and 0.6g of hexadecyltrimethylammonium bromide as dispersants were dissolved in 10mL of dimethylformamide, and 1.2g of polylactic acid was added to the solution after ultrasonic treatment for 30min, and mixed evenly to obtain a heating layer spinning solution. The cooling layer fiber membrane prepared in step S22 was used as the substrate, and the heating fiber was deposited on the cooling fiber membrane by electrocentrifugal electrospinning (voltage of 22kV, spinning solution consumption rate of 2mL / h, rotation radius of 15cm, temperature of 25±2℃, relative humidity of 45±3%) to obtain a heating layer in the fiber membrane (the average diameter of the heating layer fiber was 600nm, the thickness of the fiber membrane was 120μm, the porosity was 90%, and the coverage of graphene oxide on the fiber membrane was 85%). Finally, the fiber membrane was dried for 24h to remove the residual solvent to obtain a Janus polylactic acid fiber membrane integrating radiative cooling and photothermal.

[0034] Embodiment 3 of the present invention provides a method for preparing a Janus polylactic acid fiber membrane integrating radiation cooling and photothermal treatment, comprising the following steps.

[0035] S31. Prepare SiO2 suspension: dissolve 10 mL of propyl orthosilicate, 10 mL of ammonia water, and 15 mL of deionized water in 120 mL of anhydrous ethanol, adjust the pH value of the mixed solution to 8, and irradiate the mixed solution with UV (irradiation time is 20 min, irradiation distance is 20 cm). After irradiation, stir to obtain a uniform SiO2 suspension (the average size of SiO2 is 550 nm).

[0036] S32. Preparation of cooling fiber membrane: 1.5 g of polylactic acid was dissolved in 10 mL of a mixed solvent of dichloromethane and dimethylformamide (7:3), and polylactic acid fiber membrane was prepared by electrocentrifugal electrospinning (spinning voltage was 20 kv, spinning solution consumption rate was 1.5 mL / h, rotation radius was 20 cm, temperature was 25±2°C, relative humidity was 45±3%), and the obtained polylactic acid fiber membrane was immersed in SiO2 suspension for 30 min. After immersion, it was repeatedly washed with deionized water, and the washed fiber membrane was dried for 24 h to obtain a cooling layer fiber membrane (the average fiber diameter was 800 nm, the fiber membrane thickness was 350 μm, the porosity was 85%, and the silica loading rate on the fiber surface was 85%).

[0037] S33, prepare Janus fiber membrane: 1.5g of graphene oxide and 5mL of ethyl acetate as dispersant are dissolved in 10mL of dimethylformamide, and 1.5g of polylactic acid is added to the solution after ultrasonication for 30min, and mixed evenly to obtain a heating layer spinning solution. With the cooling layer prepared in step S32 as the substrate, the heating fiber is deposited on the cooling fiber membrane by electrocentrifugal electrospinning (voltage is 20kV, spinning solution consumption rate is 1.5mL / h, rotation radius is 20cm, temperature is 25±2℃, relative humidity is 45±3%) to obtain a heating layer in the fiber membrane (the average diameter of the heating layer fiber is 500nm, the thickness of the fiber membrane is 150μm, the porosity is 85%, and the coverage of graphene oxide is 70%). Finally, the obtained fiber membrane is dried for 24h to remove the residual solvent to obtain a Janus polylactic acid fiber membrane integrating radiative cooling and photothermal.

[0038] Embodiment 4 of the present invention provides a method for preparing a polylactic acid fiber film with moisture absorption and perspiration removal and active thermal management, comprising the following steps.

[0039] S41. Prepare SiO2 suspension: dissolve 10 mL of tetraethyl orthosilicate, 15 mL of sodium carbonate and 15 mL of deionized water in 120 mL of anhydrous ethanol, adjust the pH value of the mixture to 8, irradiate the mixture with UV (irradiation time is 25 min, irradiation distance is 25 cm), and after irradiation, stir to obtain a uniform SiO2 suspension (average size of SiO2 is 500 nm).

[0040] S42. Preparation of cooling fiber membrane: 0.8 g of polylactic acid was dissolved in 10 mL of a mixed solvent of dichloromethane and dimethylformamide (7:3), and polylactic acid fiber membrane was prepared by electrocentrifugal electrospinning (spinning voltage was 20 kv, spinning solution consumption rate was 1 mL / h, rotation radius was 25 cm, temperature was 25±2°C, relative humidity was 45±3%), and the obtained polylactic acid fiber membrane was immersed in SiO2 suspension for 40 min. After immersion, it was repeatedly washed with deionized water, and the washed fiber membrane was dried for 24 h to obtain a cooling layer fiber membrane (the average fiber diameter was 450 nm, the fiber membrane thickness was 350 μm, the porosity was 82%, and the silica loading rate on the fiber surface was 90%).

[0041] S43, prepare Janus fiber membrane: 0.8g of graphene oxide and 0.1g of sodium dodecylbenzene sulfate as dispersants are dissolved in 10mL of dimethylformamide, and 0.8g of polylactic acid is added to the solution after ultrasonic treatment for 30min, and mixed evenly to obtain a heating layer spinning solution. With the cooling layer prepared in step S42 as the substrate, the heating fiber is deposited on the cooling fiber membrane by electrocentrifugal electrospinning (voltage is 20kV, spinning solution consumption rate is 1mL / h, rotation radius is 25cm, temperature is 25±2℃, relative humidity is 45±3%) to obtain a heating layer in the fiber membrane (the average diameter of the heating layer fiber is 450nm, the thickness of the fiber membrane is 150μm, the porosity is 82%, and the loading rate of graphene oxide is 90%). Finally, the obtained fiber membrane is dried for 24h to obtain a Janus polylactic acid fiber membrane integrating radiative cooling and photothermal.

[0042] Comparative Example 1 of the present invention is based on the fiber membrane prepared in Example 1, except that in this example, silica will not be grown on the cooling layer fiber membrane. Specifically, step S11 is omitted, and the cooling fiber membrane is directly prepared. 1g of polylactic acid is dissolved in 10mL of a mixed solvent of dichloromethane and dimethylformamide (7:3), and a polylactic acid fiber membrane is prepared by electrocentrifugal electrospinning (spinning voltage is 20kv, spinning solution consumption rate is 1.5mL / h, rotation radius is 10cm, temperature is 25±2℃, relative humidity is 45±3%), and the obtained fiber membrane is dried for 24h to obtain a cooling layer fiber membrane without silica growth (the average fiber diameter is 800nm, the fiber membrane thickness is 350μm, and the porosity is 85%). The parameters of the subsequent steps remain unchanged.

[0043] Comparative Example 2 of the present invention is based on the fiber membrane prepared in Example 1, except that the cooling layer will not be prepared in this example. Specifically, steps S11 and S12 are omitted, and the heating fiber membrane is directly prepared. Preparation of the heating fiber membrane: 1g of graphene oxide and 0.5g of sodium dodecylbenzene sulfonate are dissolved in 10mL of dimethylformamide as a dispersant, and 1g of polylactic acid is added to the solution after ultrasonication for 30min, and mixed evenly to obtain a heating layer spinning solution. The heating fiber is deposited on the cooling fiber membrane by electrocentrifugal electrospinning (voltage of 20kV, spinning solution consumption rate of 1.5mL / h, rotation radius of 10cm, temperature of 25±2℃, relative humidity of 45±3%) to obtain a heating layer in the fiber membrane (the average diameter of the heating layer fiber is 500nm, the thickness of the fiber membrane is 150μm, the porosity is 80%, and the coverage of graphene oxide on the fiber membrane is 80%), and finally the fiber membrane is dried for 24h to remove the residual solvent. The remaining parameters and steps remain the same.

[0044] Structural characterization and performance testing.

[0045] Scanning electron microscope observation: The microstructure of the heating layer fiber membrane, cooling layer fiber membrane and Janus polylactic acid fiber membrane was observed by field emission scanning electron microscope (model SU8220, HITACHI) ( Figure 2 , Figure 3 , Figure 4 ).

[0046] Solar reflectivity test: A UV-visible-near infrared spectrophotometer (model UV-3600, Shimadzu) was used to measure the reflectivity of the fiber membrane at the atmospheric window wavelength of 0.3~2.5μm.

[0047] Infrared emissivity test: The infrared reflectivity and transmittance of the fiber membrane at a wavelength of 8-13 μm were measured using an FTIR spectrometer (model NEXUS-670, Thermo Fisher) equipped with a diffuse gold integrating sphere (PIKE Technologies). Infrared emissivity = 1-reflectivity-transmittance.

[0048] Outdoor cooling performance test: The cooling performance of the fiber membrane was measured outdoors (10:00~16:00, September 27, 2024, Xuzhou). The simulated skin (insulating foam wrapped in aluminum foil) was heated using a silicone rubber heating plate and the temperature was maintained at 37°C. A K-type thermocouple (model YET-640X, Dickway) was used to record the temperature difference between the cooling layer fiber membrane and the exposed simulated skin.

[0049] Outdoor heating performance test: The heating performance of the fiber membrane was measured outdoors (10:00~16:00, September 28, 2024, Xuzhou), and a K-type thermocouple (model YET-640X, Dickway) was used to record the temperature difference between the heating layer fiber membrane and the exposed simulated skin.

[0050] Experimental results: Figure 1 This is the invention flow chart of this experiment Figure 2 is a scanning electron microscope image of the cooling layer fiber membrane in Example 1.

[0051] Figure 3 This is a scanning electron microscope image of the heating layer fiber membrane in Example 1.

[0052] Figure 4 This is a scanning electron microscope image of the Janus polylactic acid fiber membrane integrating radiative cooling and photothermal in Example 1.

[0053] Table 1 compares the test results of the average solar reflectance, average infrared emissivity, radiation cooling temperature, and outdoor heating temperature of the fiber membranes obtained in the embodiment and the comparative example.

[0054] Table 1

[0055] Examples 1 to 4 all have high solar reflectivity (average solar reflectivity is > 94%). This is mainly because the complex fiber network prolongs the propagation path of sunlight in the fiber and increases the number of light reflections. In addition, thanks to the directionally grown silica on the cooling layer, the reflectivity of sunlight is excellent, which enhances the scattering of light. Comparative Example 1 shows a lower solar emissivity of only 75.8%, which further verifies the excellent light reflectivity of silica; the solar emissivity of Comparative Example 2 is only 8.9%, which shows a higher light absorption rate.

[0056] Compared with comparative example 1, examples 1 to 4 have higher infrared emissivity (96.6% to 97.3%), which is due to the fixed growth of silica on the surface of the fiber film cooling layer. Silica has abundant chemical bonds in the infrared band and produces strong vibration absorption, thereby improving the infrared emissivity. The infrared emissivity of comparative example 2 is only 8.3%, which reduces heat loss.

[0057] During the outdoor refrigeration test, compared with Comparative Example 1, the cooling layer fiber membranes of Examples 1 to 4 exhibited better radiative cooling performance (cooling temperature: 9.3~10.1°C), which was due to the high infrared emission and high solar reflectivity of the directionally grown silica on the surface of the fiber membrane, as well as the complex fiber network structure obtained by electrocentrifugal spinning.

[0058] During the outdoor heating temperature test, the heating layer fiber membranes of Examples 1 to 4 exhibited good photothermal effects, which was due to the fact that graphene oxide contained abundant oxygen-containing functional groups, which expanded the light absorption range of graphene oxide. In addition, graphene oxide had high light absorption rate and high light-to-heat conversion efficiency, and could convert the absorbed light energy into heat energy.

[0059] This shows that the technical solution proposed in the present invention enables the cooling fiber membrane to have excellent radiation cooling effect and excellent light-to-heat conversion function, ensuring the thermal comfort of the human body in both cold and hot environments. This is likely due to: (1) The high emissivity of silica in the mid-infrared band and the high reflectivity of sunlight give the fiber membrane excellent radiation cooling performance; (2) The complex fiber network and the directional growth of silica on the fiber surface enhance Mie scattering and improve the cooling performance; (3) The excellent light absorption rate and light-to-heat conversion performance of graphene oxide provide heat in cold environments to achieve thermal comfort for the human body; (4) The Janus polylactic acid fiber membrane that integrates radiation cooling and light-to-heat can perform thermal management.

[0060] The present invention relates to a Janus polylactic acid fiber membrane integrating radiation cooling and light and heat and a preparation process thereof. The technical solution adopted by the present invention has a variety of implementation methods and approaches, and the above is only a preferred implementation method of the present invention. It should be pointed out that a person of ordinary skill in the art can make various improvements and optimizations to the present invention without departing from the basic principles of the present invention, and these improvements and optimizations should be included in the protection scope of the present invention. In addition, each component not described in detail in this embodiment can be implemented with the aid of existing technology.

Claims

1. A method for preparing a Janus polylactic acid fiber membrane integrating radiation cooling and light-heat, characterized in that: The following steps are involved: Step S1, preparing SiO2 suspension: dissolving silicon source, alkaline solvent A and deionized water in alcohol solvent B, and reacting by UV irradiation to obtain SiO2 suspension; Step S2, preparing a cooling layer fiber membrane: dissolving polylactic acid in solvent C, preparing a polylactic acid fiber membrane by electrocentrifugal electrospinning technology, and then soaking the polylactic acid fiber membrane in the SiO2 suspension obtained in step S1 to prepare a cooling layer fiber membrane with nano-SiO2 directional growth on the fiber surface; Step S3, preparing Janus fiber membrane: dissolving photothermal functional factors, polylactic acid, and dispersant in solvent D to obtain a heating layer spinning solution, and then preparing a heating layer fiber by electrocentrifugal electrospinning technology, and depositing the heating layer fiber on the cooling layer fiber membrane obtained in step S2 to prepare a Janus polylactic acid fiber membrane integrating radiant cooling and photothermal.

2. The method for preparing the Janus polylactic acid fiber membrane integrating radiation cooling and light-heat according to claim 1, characterized in that: The silicon source in step S1 is one or more of ethyl orthosilicate, methyl orthosilicate, sodium silicate, silicon tetrachloride, and propyl orthosilicate, and the concentration of the silicon source in the SiO2 suspension is 0.01-0.5 mol / L.

3. The method for preparing the Janus polylactic acid fiber membrane integrating radiation cooling and light-heat according to claim 1, characterized in that: The alkaline solvent A in step S1 is one or more of ammonia water, sodium hydroxide, tetramethylammonium hydroxide, ethylenediamine, triethylamine, potassium carbonate, and sodium carbonate; the pH value of the suspension in step S1 is 7-12.

4. The method for preparing the Janus polylactic acid fiber membrane integrating radiation cooling and light-heat according to claim 1, characterized in that: The alcohol solvent B in step S1 is one or more of methanol, ethanol, isopropanol, ethylene glycol, dimethylformamide, and n-propanol; the conditions for the UV irradiation reaction are that the irradiation time is 5 to 40 minutes and the irradiation distance is 5 to 30 cm.

5. The method for preparing the Janus polylactic acid fiber membrane integrating radiation cooling and light-heat according to claim 1, characterized in that: The solvent C in step S2 is one or more of chloroform, acetone, ethyl acetate, dimethylformamide, dimethylacetamide, ethanol, dichloromethane, and tetrahydrofuran, and the concentration range of the polylactic acid in the solvent C in step S2 is 5-20wt%.

6. The method for preparing the Janus polylactic acid fiber membrane integrating radiation cooling and light-heat according to claim 1, characterized in that: The conditions of the electrocentrifugal electrospinning technology in step S2 and step S3 are that the electrocentrifugal electrospinning liquid consumption rate is 0.5-50 ml / h, the rotation radius is 10-30 cm, the ambient temperature is 10-30° C., and the humidity is 40-90%.

7. The method for preparing the Janus polylactic acid fiber membrane integrating radiation cooling and light-heat according to claim 1, characterized in that: The photothermal functional factor described in step S3 is one or more of carbon nanotubes, boron nitride, polypyrrole, carbon black, graphene, graphene oxide, MXene, and black phosphorus.

8. The method for preparing the Janus polylactic acid fiber membrane integrating radiation cooling and light-heat according to claim 1, characterized in that: The dispersant in step S3 is one or more of hexadecyltrimethylammonium bromide, sodium dodecyl sulfate, polyethylene glycol, sodium dodecylbenzene sulfonate, and ethyl acetate; the mass ratio of the dispersant to the photothermal functional factor is 1:2 to 1:

20.

9. The method for preparing the Janus polylactic acid fiber membrane integrating radiation cooling and light-heat according to claim 1, characterized in that: The solvent D in step S3 is one or more of water, methanol, ethanol, acetone, chloroform, dichloromethane, methylformamide, and ethylacetamide. The concentration range of the polylactic acid in the solvent D in step S3 is 5-20wt%, and the concentration of the photothermal functional factor in the solvent D is 5-20wt%.

10. A fiber membrane prepared by the method for preparing a Janus polylactic acid fiber membrane integrating radiation cooling and photothermal energy according to any one of claims 1 to 9.

Images