A synergistic refrigeration super fabric based on oriented polylactic acid fibers and a preparation method thereof

Abstract

The application discloses a kind of based on poly-lactic acid oriented fiber's synergistic refrigeration super fabric and its preparation method, comprising the following steps: S1, zirconium salt, fumaric acid is uniformly dissolved in solvent, then microwave-ultrasonic wave is cooperated, solvent is removed, dried, high-temperature activation treatment, obtain high reflectivity MOF-801 porous nanocrystal;S2, after porous MOF-801 nanocrystal is uniformly dispersed, hygroscopic salt is impregnated into MOF-801 pore, solvent is removed, dried, obtain MOF-801 confined hygroscopic agent;S3, with poly-lactic acid and MOF-801 confined hygroscopic agent as raw material, by electrospinning technology, based on poly-lactic acid oriented fiber's synergistic refrigeration super fabric is prepared.The super fabric not only has excellent atmospheric water collection performance, high infrared emissivity and high solar reflectivity, but also has biocompatibility, degradability, it is a kind of high-performance synergistic refrigeration material with wide application prospect.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of full-degradation cooling materials, in particular to a synergistic refrigeration super fabric based on polylactic acid oriented fibers and a preparation method thereof. BACKGROUND

[0002] Human thermal comfort is particularly important for mental and physical health. Overheating can cause body temperature dysfunction and disrupt thermal homeostasis, leading to related diseases. To meet the thermal comfort needs of the human body, ventilation and air conditioning systems are used to create an indoor comfortable environment. However, this traditional active cooling system emits greenhouse gases harmful to the environment and consumes a large amount of energy. Seeking an environmentally friendly and low-energy cooling method has become the goal people strive for.

[0003] Radiative cooling can radiate heat to the cold outer space without consuming any non-renewable energy, and wearable fabrics based on passive radiative cooling can effectively reduce health problems caused by high temperatures. Although radiative cooling fabrics have made progress, in high-intensity physical activity and continuous high-temperature environments, single radiative cooling technology is difficult to meet the demand for effective cooling. In addition, most existing radiative cooling fabrics are made of non-degradable polymers, which pose long-term hazards to the environment and living organisms.

[0004] The resolution of water is accompanied by heat release. Passive evaporative cooling using atmospheric water collection materials has a wide application prospect due to its high cooling capacity and environmental friendliness. Metal-organic frameworks (MOFs) have excellent porous structure and high specific surface area, which can efficiently collect water from the atmosphere. Embedding MOF materials into radiative cooling fabrics is expected to achieve the synergistic effect of radiative cooling and evaporative cooling. Although the application of MOFs to fiber fabrics to achieve synergistic passive cooling has great potential, it still faces the following challenges: (1) traditional MOF particles are synthesized by hydrothermal method, with a size of 1-5 μm, and a low Mie scattering efficiency in the visible light range; (2) although MOFs can effectively absorb moisture from the air, their evaporative cooling efficiency needs to be further improved, especially in low humidity environments. SUMMARY

[0005] The purpose of the present application is to prepare a synergistic refrigeration super fabric based on polylactic acid oriented fibers to meet the demand for synergistic passive cooling of radiation and evaporation, and to meet the needs of outdoor workers for high-performance cooling fabrics.

[0006] In order to achieve the above-mentioned purpose, the application provides a kind of based on poly lactic acid oriented fiber's synergistic refrigeration super fabric and its preparation method, by encapsulating hygroscopic salt (HS) in the pore of high refractive MOF-801 porous nanocrystal, obtain MOF-801 confined hygroscopic agent (HS@MOF-801), with poly lactic acid (PLA) and HS@MOF-801 as raw material, PLA / HS@MOF-801 oriented fiber membrane (synergistic refrigeration super fabric) is prepared by electrospinning technology.

[0007] According to the first aspect of the application, a preparation method of a synergistic refrigeration super fabric based on poly lactic acid oriented fiber is provided, comprising the following steps: step S1, dissolving zirconium salt and fumaric acid in a solvent to obtain a mixed solution, carrying out microwave-ultrasonic synergistic reaction, removing the solvent by centrifugation or ultrafiltration technology, and then drying or directly freeze-drying, and then carrying out activation treatment to obtain MOF-801 porous nanocrystals; step S2, dispersing the MOF-801 porous nanocrystals obtained in step S1 in deionized water, impregnating hygroscopic salt into the pores of the MOF-801 porous nanocrystals, removing the solvent (deionized water), and drying to obtain a MOF-801 confined hygroscopic agent; step S3, compounding the MOF-801 confined hygroscopic agent obtained in step S2 and poly lactic acid, and preparing a synergistic refrigeration super fabric based on poly lactic acid oriented fiber by electrospinning technology.

[0008] Preferably, in step S1, the molar ratio of fumaric acid to zirconium salt is 0.1-10; the zirconium salt is one or more of zirconium chloride, zirconium oxychloride, zirconium nitrate, and zirconium acetate, and the concentration of the zirconium salt in the mixed solution is 0.005-1 mol / L.

[0009] Preferably, in step S1, the solvent is one or more of water, dimethylformamide, methylpyrrolidone, ethanol, isobutyl alcohol, n-butyl alcohol, and isopropyl alcohol.

[0010] Preferably, in step S1, the microwave-ultrasonic synergistic reaction has a microwave power of 500-6000 W, an ultrasonic power of 200-1000 W, a reaction temperature of 50-300°C, and a reaction time of 30 seconds-30 minutes; the activation treatment has a temperature of 100-200°C, and the obtained MOF-801 porous nanocrystals have an average diameter of 300-600 nm.

[0011] Preferably, in step S2, the hygroscopic salt is one or more of LiCl, CaCl2, MgCl2, KCl, and NaCl.

[0012] Preferably, the concentration of the MOF-801 porous nanocrystals in deionized water in step S2 is 0.01-1 mol / L, and the mass ratio of the hygroscopic salt to the MOF-801 porous nanocrystals is 0.005-0.4; the time for the impregnation is 20 min-3 h.

[0013] Preferably, the mass ratio of the MOF-801 confined hygroscopic agent to the polylactic acid in step S3 is 00.1-0.9.

[0014] Preferably, the electrospinning technique in step S3 is a melt electrospinning technique or a solution electrospinning technique; the spinning voltage of the melt electrospinning technique is 10-30 kV, the pushing speed is 0.1-10 mL / h, the drum rotation speed is 600 rpm-2000 rpm, and the receiving distance is 5-20 cm; the voltage of the solution electrospinning technique is 10-30 kV, the electrospinning solution consumption rate is 0.1-10 mL / h, the drum rotation speed is 1000 rpm-5000 rpm, and the receiving distance is 15-25 cm.

[0015] To achieve the above-mentioned purpose, according to the second aspect of the present application, the present application further provides a super fabric prepared by the aforementioned preparation method.

[0016] Preferably, the thickness of the super fabric is 200-500 μm, and the average diameter of the fibers is 300-2500 nm.

[0017] The present application has the following advantages: (1) the MOF-801 nanocrystals obtained by the microwave-ultrasonic assisted method have uniform size and regular structure, and have enhanced visible light backscattering characteristics compared with the MOF-801 nanocrystals synthesized by the traditional hydrothermal method; (2) the MOF-801 can provide loading space for the hygroscopic salt and sufficient buffer for the volume change of the hygroscopic salt, and the compounding of the hygroscopic salt makes the MOF-801 nanocrystals have excellent atmospheric water absorption performance in a wide humidity range, and the PLA / CaCl2@MOF-801 oriented fiber membrane can store water in the night or in a high humidity environment and realize evaporation cooling through water desorption in a dry and hot environment; (3) the introduction of the MOF-801 confined hygroscopic agent and the regular arrangement of the polylactic acid fibers make the PLA / CaCl2@MOF-801 oriented fiber membrane have high solar reflectance; (4) the rich chemical bond vibration of the MOF-801 in the atmospheric transparent window range and the ordered arrangement of the polylactic acid molecular chain make the PLA / CaCl2@MOF-801 oriented fiber membrane have high infrared emissivity; (5) the fiber membrane has a hygroscopic capacity of 0.57-0.84 g / g, a maximum evaporation cooling temperature of 9.3-11.6°C, an infrared emissivity of 93.3%-99.6%, a solar reflectance of 90.7%-97.0%, and a maximum outdoor cooling temperature of 9.7-12.3°C.

[0018] The technical solution provided by the present application makes the fiber membrane not only have excellent atmospheric water collection performance, high infrared emissivity and high solar reflectivity, but also can realize synergistic passive cooling of radiation and evaporation, and has biocompatibility and degradability, and is a high-performance environment-friendly cooling material with wide application prospect. BRIEF DESCRIPTION OF DRAWINGS

[0019] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed to be used in the embodiments or prior art description will be briefly introduced as follows. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0020] Figure 1 is a method flowchart of the present application.

[0021] Figure 2 is a scanning electron microscope image of CaCl2@MOF-801 in Example 1.

[0022] Figure 3 is a scanning electron microscope image of PLA / CaCl2@MOF-801 oriented fiber membrane in Example 1.

[0023] Figure 4 is an energy dispersive spectrum of PLA / CaCl2@MOF-801 oriented fiber membrane in Example 1. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical solutions and advantages of the present application more clear, the technical solutions of the present application will be described in detail as follows. Obviously, the described embodiments are only some of the embodiments of the present application, not all. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application. The present application will be described in detail below in combination with the embodiments.

[0025] As shown in Figure 1 Example 1 of the present application provides a preparation method of a synergistic refrigeration super fabric based on oriented PLA fiber, which comprises the following steps.

[0026] Step S11, preparation of MOF-801 porous nanocrystals: zirconium oxychloride and fumaric acid are dissolved in dimethylformamide (the concentration of zirconium oxychloride is 0.1 mol / L, and the concentration of fumaric acid is 0.1 mol / L), and after stirring, the mixed solution is placed in a reaction kettle (microwave power is 500 W, ultrasonic power is 600 W, reaction temperature is 120°C, and reaction time is 10 minutes). After the reaction is completed, centrifugation, drying, and activation at a temperature of 120°C, high-reflectivity MOF-801 porous nanocrystals with an average diameter of 330 nm are obtained.

[0027] Step S12, preparation of MOF-801 confined hygroscopic agent (CaCl2@MOF-801): MOF-801 porous nanocrystals (the concentration of MOF-801 is 0.036 mol / L) are uniformly dispersed in deionized water, and a certain amount of CaCl2 (the mass fraction of CaCl2 is 20wt% of the MOF-801 nanocrystals) is added. After stirring, the hygroscopic salt is impregnated into the pores of the MOF-801 (the impregnation time is 20 min), centrifugation, drying, and obtaining MOF-801 confined hygroscopic agent CaCl2@MOF-801.

[0028] Step S13, preparation of PLA / CaCl2@MOF-801 oriented fiber membrane: CaCl2@MOF-801 (the mass ratio of CaCl2@MOF-801 to the added polylactic acid is 0.2) is dissolved in dichloromethane / dimethylformamide (mass ratio 7:3), and after ultrasonic treatment for 30 min, polylactic acid (the concentration of polylactic acid in the solution is 12wt%) is added. After stirring, PLA composite spinning raw material is obtained. Electrospinning is performed at a voltage of 20 kV, a spinning solution consumption rate of 5 mL / h, a cylinder rotation speed of 2000 rpm, a receiving distance of 15 cm, a temperature of 25°C, and a relative humidity of 30%. Finally, the fiber membrane is dried in an oven for 24 h to remove residual organic solvents, and PLA / CaCl2@MOF-801 oriented fiber membrane is obtained, with an average fiber diameter of 540 nm and a fiber membrane thickness of 300 μm.

[0029] Embodiment 2 of the present application provides a preparation method of a synergistic refrigeration super fabric based on polylactic acid oriented fibers, which comprises the following steps.

[0030] Step S21, preparation of MOF-801 porous nanocrystals: zirconium acetate and fumaric acid are dissolved in ethanol (the concentration of zirconium oxychloride is 0.5 mol / L, and the concentration of fumaric acid is 0.1 mol / L), and after stirring, the mixed solution is placed in a reaction kettle (microwave power is 800 W, ultrasonic power is 200 W, reaction temperature is 130°C, and reaction time is 5 minutes). After the reaction is completed, freeze-drying, and activation at a temperature of 180°C, high-reflectivity MOF-801 porous nanocrystals with an average diameter of 560 nm are obtained.

[0031] Step S22, preparation of MOF-801 confined hygroscopic agent (LiCl@MOF-801): MOF-801 porous nanocrystals (the concentration of MOF-801 is 0.5 mol / L) are uniformly dispersed in deionized water, a certain amount of LiCl (the mass fraction of LiCl is 20wt% of MOF-801 nanocrystals) is added, stirring to impregnate the hygroscopic salt into the pores of MOF-801 (the impregnation time is 2 h), ultrafiltration, drying, to obtain MOF-801 confined hygroscopic agent LiCl@MOF-801.

[0032] Step S23, preparation of PLA / LiCl@MOF-801 oriented fiber membrane: LiCl@MOF-801, polylactic acid (the mass ratio of LiCl@MOF-801 and polylactic acid is 0.3) are melt blended (the blending time is 13 min, the temperature is 180°C), cooled to room temperature to obtain PLA composite spinning raw material; electrospinning is carried out, the voltage is 20 kV, the push speed is 1 mL / h, the barrel rotation speed is 1000 rpm, the receiving distance is 20 cm, to obtain PLA / LiCl@MOF-801 oriented fiber membrane, the average diameter of the fiber is 1100 nm, and the thickness of the fiber membrane is 300 μm.

[0033] Embodiment 3 of the present application provides a preparation method of a synergistic refrigeration super fabric based on polylactic acid oriented fiber, comprising the following steps.

[0034] Step S31, preparation of MOF-801 porous nanocrystals: zirconium chloride and fumaric acid are dissolved in water (the concentration of zirconium oxychloride is 0.1 mol / L, and the concentration of fumaric acid is 0.4 mol / L), after uniform stirring, the mixed solution is placed into a reaction kettle (microwave power is 1000 W, ultrasonic power is 100 W, reaction temperature is 120°C, and reaction time is 20 minutes), after the reaction is completed, ultrafiltration, drying, and activation at a temperature of 130°C, to obtain high-reflectivity MOF-801 porous nanocrystals, the average diameter of which is 380 nm.

[0035] Step S32, preparation of MOF-801 confined hygroscopic agent (KCl@MOF-801): MOF-801 porous nanocrystals (the concentration of MOF-801 is 0.02 mol / L) are uniformly dispersed in deionized water, a certain amount of KCl (the mass fraction of KCl is 30wt% of MOF-801 nanocrystals) is added, stirring to impregnate the hygroscopic salt into the pores of MOF-801 (the impregnation time is 1 h), centrifugation, drying, to obtain MOF-801 confined hygroscopic agent KCl@MOF-801.

[0036] Step S33, preparing PLA / KCl@MOF-801 oriented fiber membrane: KCl@MOF-801, polylactic acid (the mass ratio of KCl@MOF-801 and polylactic acid is 0.5) are melt blended (the blending time is 10 min, and the temperature is 200°C), and then cooled to room temperature to obtain PLA composite spinning raw material; electrospinning is performed, the voltage is 20 kV, the pushing speed is 3 mL / h, the drum rotating speed is 2000 rpm, and the receiving distance is 15 cm, so as to obtain PLA / KCl@MOF-801 oriented fiber membrane, the average fiber diameter is 1100 nm, and the fiber membrane thickness is 300 μm.

[0037] Embodiment 4 of the present application provides a preparation method of a synergistic refrigeration super fabric based on polylactic acid oriented fiber, which comprises the following steps.

[0038] Step S41, preparing MOF-801 porous nanocrystals: zirconium oxychloride and fumaric acid are dissolved in dimethylformamide (the concentration of zirconium oxychloride is 0.2 mol / L, and the concentration of fumaric acid is 0.05 mol / L), the mixed solution is placed into a reaction kettle after uniform stirring (the microwave power is 500 W, the ultrasonic power is 800 W, the reaction temperature is 130°C, and the reaction time is 10 min), centrifugation is performed after the reaction is completed, drying is performed, and activation is performed at a temperature of 150°C, so as to obtain high-reflectivity MOF-801 porous nanocrystals, and the average diameter is 430 nm.

[0039] Step S42, preparing MOF-801 confined hygroscopic agent (CaCl2@MOF-801): MOF-801 porous nanocrystals (the concentration of MOF-801 is 0.036 mol / L) are uniformly dispersed in deionized water, a certain amount of CaCl2 (the mass fraction of CaCl2 is 50wt% of the MOF-801 nanocrystals) is added, stirring is performed to impregnate the hygroscopic salt into the pores of the MOF-801 (the impregnation time is 40 min), and freeze-drying is performed, so as to obtain MOF-801 confined hygroscopic agent CaCl2@MOF-801.

[0040] Step S43, preparing PLA / CaCl2@MOF-801 oriented fiber membrane: CaCl2@MOF-801 (the mass ratio of CaCl2@MOF-801 and polylactic acid to be added is 0.5) is dissolved in dichloromethane, polylactic acid (the concentration of polylactic acid in the solution is 10wt%) is added after ultrasonic treatment for 30 min, and uniform stirring is performed to obtain PLA composite spinning raw material; electrospinning is performed, the voltage is 30 kV, the pushing speed is 8 mL / h, the drum rotating speed is 2000 rpm, and the receiving distance is 15 cm, so as to obtain PLA / CaCl2@MOF-801 oriented fiber membrane, the average fiber diameter is 610 nm, and the fiber membrane thickness is 400 μm.

[0041] Comparative Example 1 of this invention provides a method for preparing a synergistic cooling superfabric based on polylactic acid (PLA) oriented fibers, which basically adopts the method of Example 1 to prepare PLA fiber membranes. The difference is that the PLA fibers in this example are non-oriented and the fibers are randomly distributed. Specifically, zirconium oxychloride and fumaric acid were dissolved in dimethylformamide (zirconia concentration was 0.1 mol / L, fumaric acid concentration was 0.1 mol / L), stirred until homogeneous, and then placed in a reaction vessel (microwave power was 500 W, ultrasonic power was 600 W, reaction temperature was 120℃, reaction time was 10 minutes). After the reaction, the mixture was dried and activated at 120°C to obtain high-reflectivity MOF-801 porous nanocrystals with an average diameter of 330 nm. The MOF-801 porous nanocrystals (MOF-801 concentration was 0.036 mol / L) were uniformly dispersed in deionized water, and a certain amount of CaCl2 (CaCl2 mass fraction was 20 wt% of MOF-801 nanocrystals) was added. The mixture was stirred to impregnate the hygroscopic salt into the pores of MOF-801 (impregnation time was 20 min). After centrifugation, washing, and drying, the MOF-801-confined hygroscopic agent CaCl2@MOF-801 was obtained. CaCl2@MOF-801 (the mass ratio of CaCl2@MOF-801 to the polylactic acid to be added is 0.2) was dissolved in dichloromethane / dimethylformamide (mass ratio 7:3), and after sonication for 30 min, polylactic acid (the concentration of polylactic acid in the solution is 12 wt%) was added and stirred evenly to obtain PLA composite spinning raw material; electrospinning was performed at a voltage of 20 kV, a spinning solution consumption rate of 5 mL / h, a drum rotation speed of 500 rpm, a receiving distance of 15 cm, a temperature of 25℃, and a relative humidity of 30%, to obtain a PLA / CaCl2@MOF-801 non-oriented fiber membrane with an average fiber diameter of 825 nm and a fiber membrane thickness of 300 μm.

[0042] Comparative Example 2 of this invention provides a method for preparing a synergistic cooling superfabric based on polylactic acid (PLA) oriented fibers, which basically adopts the method of Example 4 to prepare PLA fiber membranes. The difference is that this example does not use MOF-801-confined hygroscopic agent to modify the PLA fibers. Specifically, PLA is dissolved in dichloromethane (PLA concentration in solution is 10 wt%), stirred evenly to obtain PLA spinning raw material; electrospinning is performed at a voltage of 30 kV, a feed speed of 8 mL / h, a drum rotation speed of 2000 rpm, and a receiving distance of 15 cm to obtain a pure PLA oriented fiber membrane with an average fiber diameter of 570 nm and a membrane thickness of 400 μm.

[0043] The present application provides a preparation method of a synergistic refrigeration super fabric based on polylactic acid non-oriented fibers. The PLA fiber film is prepared by the method of Comparative Example 2. The difference is that the PLA fibers of the fiber film in this example are non-oriented, and the fibers are randomly distributed. Specifically, polylactic acid is dissolved in dichloromethane (the concentration of polylactic acid in the solution is 10wt %), and stirred uniformly to obtain PLA spinning raw material; electrospinning is performed, the voltage is 30 kV, the pushing speed is 8 mL / h, the cylinder rotation speed is 300 rpm, and the receiving distance is 15 cm, to obtain a pure PLA non-oriented fiber film, the average diameter of the fibers is 800 nm, and the thickness of the fiber film is 350 pm.

[0044] The structural characterization and performance test are as follows.

[0045] Scanning electron microscope observation: The microstructure of the Janus polylactic acid cooling temperature fiber film is observed by a field emission scanning electron microscope (model SU8220, HITACHI) Figure 2 , Figure 3 ).

[0046] Solar reflectance test: The reflectance of the fiber film at 300-2500 nm is measured by using an ultraviolet-visible-near infrared spectrophotometer (model UV-3600, Shimadzu).

[0047] Infrared reflectance test: The infrared reflectance and transmittance of the fiber film at 8-13 pm are measured by using an FTIR spectrometer (model NEXUS-670, Thermo Fisher) equipped with a diffuse gold integrating sphere (PIKE Technologies).

[0048] Moisture absorption performance test: Before the test, the fiber film is placed in an environment with a relative humidity of 20%RH and a temperature of 40°C for 12 h, and then weighed. After that, the fiber film is placed in an environmental simulation chamber and weighed at regular intervals. The moisture absorption capacity of the fiber film is evaluated by the change in mass, and the moisture absorption amount of the fiber film is defined as the mass difference before and after the test.

[0049] Evaporative cooling performance test: After the fiber film is placed in an environment with a relative humidity of 80%RH and a temperature of 25°C and an environment with a relative humidity of 20%RH and a temperature of 40°C for 12 h respectively, a heat flux density of 500 W / m 2 The fiber film is heated by a heating table, and the temperature change of the surface of the fiber film is recorded by an infrared thermal imager (model 345GT, FOTRIC). The maximum evaporative cooling temperature of the fiber film is defined as the maximum temperature difference between the wet fiber film and the dry fiber film.

[0050] Radiative cooling performance test: The radiative cooling performance of the fiber film was measured outdoors (11:00-13:00, October 20, 2024, Xuzhou), a silicon rubber heating plate was used to heat the simulated skin (insulating foam wrapped with aluminum foil), and the temperature was maintained at 37°C. The temperature difference between the lower side of the fiber film and the bare simulated skin was recorded using a K-type thermocouple (model YET-640X, Dickvi).

[0051] The experimental results are as follows.

[0052] As shown in Figure 2 , the CaCl2@MOF-801 nanocrystals synthesized in Example 1 are regular in structure and have an octahedral morphology, with an average diameter of 330 nm. Figure 2 The scanning electron microscope image of the PLA / CaCl2@MOF-801 fiber film prepared by electrospinning technology shows that the PLA fibers are arranged in an oriented manner, and the CaCl2@MOF-801 nanocrystals are uniformly distributed inside and on the surface of the PLA fibers. Figure 4 The energy dispersive spectrum of the PLA / CaCl2@MOF-801 fiber film shows that Zr, Ca, and Cl elements are widely arranged, verifying the uniform arrangement of CaCl2@MOF-801 nanocrystals in the PLA fibers and further proving that the hygroscopic salt CaCl2 is immersed in the MOF-801 pores.

[0053] Table 1 compares the test results of the hygroscopic amount, average infrared emissivity, average solar reflectivity, maximum evaporative cooling temperature, maximum outdoor cooling temperature, and tensile strength of the PLA fiber films obtained in the examples and comparative examples.

[0054] Table 1

[0055] Item Group Moisture absorption (g / g) Average infrared emissivity (%) Average solar reflectance (%) Maximum evaporative cooling temperature (°C) Maximum outdoor cooling temperature (°C) Example 1 0.61 99.6 94.7 10.2 10.1 Example 2 0.84 98.3 94.2 11.6 11.4 Example 3 0.57 97.0 95.5 9.7 10.8 Example 4 0.66 96.4 97.0 10.6 12.3 Comparative Example 1 0.59 93.3 90.7 9.3 9.7 Comparative Example 2 - 75.1 81.3 2.3 5.4 Comparative Example 3 - 71.0 79.4 2.1 3.6

[0056] Compared to Comparative Examples 2 and 3 (without hygroscopic ability), Examples 1-4 and Comparative Example 1 have hygroscopic properties (hygroscopic amount of 0.57-0.84 g / g), because the introduction of the MOF-801 confined hygroscopic agent enables the PLA fiber film to have adsorption ability for water molecules. The MOF-801 nanocrystals have a large number of pores inside, which can realize the adsorption and desorption of water molecules, and the combination of the hygroscopic salt enables the MOF-801 nanocrystals to have excellent atmospheric water absorption performance in a wide humidity range.

[0057] Examples 1-4 all have a higher average infrared emissivity (96.4%-99.6%), because the rich chemical bond (COO- bond, C-H bond, O-H bond) vibration in MOF-801 greatly enhances the infrared light emission of the fiber film. Compared with Example 1, the infrared emissivity of Comparative Example 1 is slightly lower (93.3%), because the orientation of the PLA fiber enhances the vibration of the chemical bond (C=O bond) in the 8-13 μm wave band and the absorption peak intensity of the microstructure beta phase is enhanced.

[0058] Examples 1-4 all have a higher average solar reflectivity (94.2%-97.0%), which is due to the introduction of the optically optimized MOF-801 nanocrystals and the directional arrangement of the PLA nanofibers, which enhances the scattering efficiency of the PLA fiber film. The average solar reflectivity of Comparative Example 1 is 90.7%, which is slightly lower than Examples 1-4, because the randomly arranged PLA fibers have a larger pore size distribution, causing multiple scattering and absorption of light. The PLA fiber films in Comparative Examples 2 (79.4%) and 3 (81.3%) are not modified with nanocrystals, and exhibit the lowest average solar reflectivity.

[0059] Examples 1-4 exhibit good evaporative cooling performance (maximum evaporative cooling temperature: 9.7-11.6°C), which is due to their excellent moisture absorption performance. The radiative cooling performance of Comparative Examples 2 and 3 is poor, with cooling temperatures of 2.3°C and 2.1°C, respectively.

[0060] Examples 1-4 exhibit good radiative cooling performance (maximum outdoor cooling temperature: 10.1-12.3°C), which is due to their high infrared emissivity and high solar reflectivity. The radiative cooling performance of Comparative Example 1 is slightly lower than Examples 1-4 (maximum outdoor cooling temperature: 9.3), and the radiative cooling performance of Comparative Examples 2 and 3 is the worst, with maximum outdoor cooling temperatures of 2.4°C and 6.3°C, respectively.

[0061] Thus, the technical solution proposed by the present application enables the PLA / HS@MOF-801 oriented fiber film to have excellent synergistic passive cooling effect and excellent mechanical properties.

[0062] The present application provides a synergistic refrigeration super fabric based on oriented poly-lactic acid fibers and a preparation method thereof. There are many methods and approaches to realize this technical solution, and the above description is only the preferred embodiment of the present application. It should be noted that for ordinary technical personnel in this technical field, without departing from the principle of the present application, several improvements and refinements can be made, which should also be considered as the protection scope of the present application. The components not explicitly described in the present embodiment can be realized by existing technology.

Claims

1. A method for preparing a synergistic refrigeration super fabric based on oriented polylactic acid fibers, characterized by, The method comprises the following steps: Step S1, dissolving zirconium salt and fumaric acid in a solvent to obtain a mixed solution, performing microwave-ultrasonic synergistic reaction on the mixed solution, removing the solvent, drying, and activating to obtain MOF-801 porous nanocrystals; Step S2, dispersing the MOF-801 porous nanocrystals obtained in step S1 in deionized water, impregnating hygroscopic salt into the pores of the MOF-801 porous nanocrystals, removing the deionized water, and drying to obtain MOF-801 confined hygroscopic agent; Step S3, compounding polylactic acid and the MOF-801 confined hygroscopic agent obtained in step S2, and preparing polylactic acid oriented fiber based synergistic refrigeration super fabric by electrospinning technology.

2. The method for preparing a synergistic refrigeration polylactic acid oriented fiber-based super fabric according to claim 1, characterized in that, In step S1, the molar ratio of fumaric acid to zirconium salt is 0.1-10; the zirconium salt is one or more of zirconium chloride, zirconium oxychloride, zirconium nitrate, and zirconium acetate, and the concentration of the zirconium salt in the mixed solution is 0.005-1 mol / L.

3. The method for preparing the synergistic cooling superfabric based on polylactic acid oriented fibers according to claim 1, characterized in that, In step S1, the solvent is one or more of water, dimethylformamide, methylpyrrolidone, ethanol, isobutyl alcohol, n-butyl alcohol, and isopropyl alcohol.

4. The method for preparing the synergistic cooling superfabric based on polylactic acid oriented fibers according to claim 1, characterized in that, In step S1, the microwave-ultrasonic synergistic reaction has a microwave power of 500-6000 W, an ultrasonic power of 200-1000 W, a reaction temperature of 50-300°C, and a reaction time of 30 seconds-30 minutes; the activation treatment has a temperature of 100-200°C, and the obtained MOF-801 porous nanocrystals have an average diameter of 300-600 nm.

5. The method for preparing the synergistic cooling superfabric based on polylactic acid oriented fibers according to claim 1, characterized in that, In step S2, the hygroscopic salt is one or more of LiCl, CaCl2, MgCl2, KCl, and NaCl.

6. The method for preparing the synergistic cooling superfabric based on polylactic acid oriented fibers according to claim 1, characterized in that, In step S2, the concentration of the MOF-801 porous nanocrystals in the deionized water is 0.01-1 mol / L, the mass ratio of the hygroscopic salt to the MOF-801 porous nanocrystals is 0.005-0.4, and the impregnation time is 20 minutes-3 hours.

7. The method for preparing the synergistic cooling superfabric based on polylactic acid oriented fibers according to claim 1, characterized in that, In step S3, the mass ratio of the MOF-801 confined hygroscopic agent to the polylactic acid is 00.1-0.

9.

8. The method for preparing the synergistic cooling superfabric based on polylactic acid oriented fibers according to claim 1, characterized in that, The electrospinning technology is melt electrospinning technology or solution electrospinning technology. In the melt electrospinning technology, the spinning voltage is 10-30 kV, the advancing speed is 0.1-10 mL / h, the drum rotation speed is 600 rpm-2000 rpm, and the receiving distance is 5-20 cm; in the solution electrospinning technology, the voltage is 10-30 kV, the electrospinning solution consumption rate is 0.1-10 mL / h, the drum rotation speed is 1000 rpm-5000 rpm, and the receiving distance is 15-25 cm.

9. A super fabric prepared by the method for preparing a polylactic acid oriented fiber based synergistic refrigeration super fabric according to any one of claims 1-8.

10. The super fabric of claim 9, wherein, The super fabric has a thickness of 200-500 μm and an average fiber diameter of 300-2500 nm.

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