Composite nanofiber membrane with bidirectional thermal management and method of making the same

Abstract

The present application relates to the technical field of textile materials, and particularly relates to a composite nanofiber membrane with bidirectional heat management and a preparation method thereof. The composite nanofiber membrane takes aramid nanofiber membrane as a mechanical support base layer, and a porous polymer fiber layer containing thermochromic microcapsules is compounded as a functional surface layer on the base layer, and ZIF-8 particles are grown on the surface layer. The design makes the fiber membrane become dark at low temperature to enhance solar energy absorption, and turns to light color at high temperature and cooperates with the high infrared emission characteristics of ZIF-8 particles to realize radiation cooling, thereby realizing bidirectional heat regulation function to adjust human thermal comfort. The preparation method provided by the present application can prepare micro-nanofibers with high specific surface area and porous structure by means of electrospinning technology, thereby significantly improving the comfort of wearing. In-situ growth makes the ZIF-8 particles firmly combined with the functional surface layer and not easy to fall off, which is beneficial to long-term use.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of textile materials, in particular to a composite nanofiber membrane with bidirectional thermal management and a preparation method thereof. BACKGROUND

[0002] Passive radiative cooling (PRC) is a technology that does not require external energy input, relying on the optical properties of the material itself and the Earth's atmospheric window to transfer heat from the surface of the object to the low-temperature universe space in the form of infrared radiation, while reflecting as much solar short-wave radiation as possible (to prevent heat absorption and temperature rise), thereby achieving spontaneous cooling of the object in the natural environment. PRC materials can achieve zero-energy cooling by reflecting solar radiation efficiently and enhancing the ability to emit long-wave infrared radiation to the outer space in the atmospheric transparent window. Based on this principle, researchers have developed a variety of materials and structures for achieving daytime radiative cooling, including multilayer photonic crystals, metamaterials, nanoporous polymers, and biomimetic hierarchical fiber assemblies, and have confirmed their excellent cooling performance from both experimental and theoretical aspects.

[0003] However, most traditional radiative cooling materials are limited to single function or static structure. Although they can exhibit good cooling effect in hot environments, they hinder the solar heat gain required by the human body in low-temperature or cold environments, limiting their use comfort in all-weather and all-day conditions. To address this challenge, a dual-mode thermal management material system has emerged, aiming to achieve all-weather self-adaptive regulation of "cooling in hot weather and keeping warm in cold weather".

[0004] Currently, the main strategies for achieving dual-mode regulation include electrochromic devices, mechanically switchable structures (such as flip or louver designs), and fluid regulation systems. However, these methods mostly rely on external energy input or complex driving mechanisms, limiting their applicability and scalability in actual wearable systems. In contrast, thermochromic materials can spontaneously and reversibly change their optical properties in the visible and near-infrared wavelength bands based on environmental temperature without additional energy input, providing an ideal approach for building passive adaptive thermal management systems. However, the radiation regulation ability of thermochromic materials in the mid-infrared wavelength band is relatively weak, making it difficult to achieve efficient radiation cooling, especially in high-temperature environments, which is one of the key factors restricting their widespread application.

[0005] Therefore, it is necessary to effectively combine thermochromic materials with high-emission mid-infrared materials to construct a composite structure that combines adaptive solar regulation and efficient radiation cooling, better meeting the needs of practical applications. SUMMARY

[0006] The present application aims to at least solve one of the technical problems existing in the related art. To this end, a first object of the present application is to provide a preparation method of a composite nanofiber membrane with bidirectional thermal management; and a second object of the present application is to provide a composite nanofiber membrane with bidirectional thermal management.

[0007] To achieve the first object, the technical solution adopted by the present application is as follows:

[0008] The preparation method of the composite nanofiber membrane with bidirectional thermal management comprises the following steps:

[0009] S100, using an aramid spinning organic solution, adopting electrospinning technology I to prepare an aramid nanofiber membrane;

[0010] The main component of the aramid spinning organic solution is poly-m-phenylene isophthalamide, and the solid content of the aramid spinning organic solution is 10wt%-15wt%.

[0011] S200, using a composite spinning solution containing a polymer and thermochromic capsules, adopting electrospinning technology II on the aramid nanofiber membrane to prepare a double-layer composite nanofiber membrane;

[0012] The polymer is selected from aliphatic polyester polymers.

[0013] The mass percentage of the polymer in the composite spinning solution is 8wt%-10wt%, and the mass percentage of the thermochromic capsules is 3wt%-9wt%.

[0014] S300, immersing the double-layer composite nanofiber membrane in a ZIF-8 growth solution, and using in-situ growth technology to grow ZIF-8 particles on the surface layer of the polymer fibers of the double-layer composite nanofiber membrane to obtain a composite nanofiber membrane with bidirectional thermal management.

[0015] The ZIF-8 is zeolitic imidazolate framework-8.

[0016] The temperature of in-situ growth is 15-25℃, and the time of in-situ growth is 6-10h.

[0017] Aramid fiber (main component: poly-m-phenylene isophthalamide) has excellent thermal stability, mechanical strength and flame retardant performance, and is an ideal support substrate; ZIF-8 particles are constructed by in-situ growth, which are firmly combined with polymer fibers and are not easy to fall off, thereby prolonging the service life of the composite nanofiber membrane.

[0018] Preferably, in step S100, the solvent of the aramid spinning organic solution is selected from N,N-dimethylacetamide.

[0019] Preferably, in step S100, the parameters of the electrospinning technique I are set as follows:

[0020] The voltage is 28-30 kV, the receiving distance is 18-20 cm, the spinning speed is 0.1-0.5 mL / h, and the relative humidity is 30%-50%.

[0021] Preferably, in step S200, the aliphatic polyester polymer is selected from one or more of polylactic acid, polycaprolactone, polyhydroxyalkanoate, and polybutylene succinate.

[0022] Preferably, the aliphatic polyester polymer is selected from polylactic acid;

[0023] The preparation of the composite spinning solution containing polylactic acid and thermochromic capsules includes the following steps:

[0024] S210, dissolving polylactic acid in dichloromethane and / or tetrahydrofuran to obtain a polylactic acid solution;

[0025] S220, adding thermochromic capsules to the polylactic acid solution and uniformly distributing the thermochromic capsules in the polylactic acid solution to obtain a composite spinning solution containing polylactic acid and thermochromic capsules.

[0026] Polylactic acid (PLA) as a biodegradable polymer not only has good biocompatibility and spinnability, but its porous structure can further enhance the radiation cooling performance and thermal insulation performance, especially suitable for bidirectional thermal management applications.

[0027] Preferably, in step S200, the particle size of the thermochromic capsules is in the range of 0.5-4.5 μm, and the critical thermochromic temperature is 18-45℃.

[0028] Preferably, in step S200, the parameters of the electrospinning technique II are set as follows:

[0029] The spinning voltage is 16-20 kV, the spinning distance is 18-20 cm, the spinning speed is 0.5-1.5 mL / h, and the relative humidity is 60%-90%.

[0030] Preferably, in step S300, the preparation process of the ZIF-8 growth solution is as follows:

[0031] S310, dissolving zinc acetate and 2-methylimidazole in a polar organic solvent respectively to obtain a zinc acetate solution and a 2-methylimidazole solution;

[0032] The molar ratio of zinc acetate to 2-methylimidazole is 1:2.0-1:2.5.

[0033] S320, the 2-methyl imidazole solution is added to the zinc acetate solution, and after stirring uniformly, an in-situ growth solution of ZIF-8 is obtained.

[0034] Preferably, the polar organic solvent is selected from one or more of methanol, ethanol, isopropanol and N-N dimethylformamide.

[0035] To achieve the second object, the technical scheme adopted by the application is:

[0036] The composite nanofiber membrane with bidirectional thermal management is prepared by using the preparation method of the composite nanofiber membrane with bidirectional thermal management.

[0037] The one or more technical solutions in the embodiments of the application have at least one of the following technical effects:

[0038] The composite nanofiber membrane with bidirectional thermal management provided by the application takes aramid nanofiber membrane as a mechanical support base layer, composites a porous polymer fiber layer containing thermochromic microcapsules on the base layer, takes the porous polymer fiber layer as a functional surface layer, and in-situ grows ZIF-8 particles on the surface of the polymer fiber. This design not only realizes self-adaptive adjustment of the sunlight spectrum by means of the thermochromic microcapsules, but also strengthens the radiation cooling efficiency by means of the high mid-infrared emissivity of the ZIF-8 particles, and the two work together to automatically adjust the thermal comfort of the human body under different environmental temperature conditions, and effectively realize zero-energy-consumption, self-adaptive and bidirectional high-efficiency thermal management.

[0039] The preparation method of the composite nanofiber membrane with bidirectional thermal management provided by the application can prepare micro-nanofibers with high specific surface area and porous structure by means of electrospinning technology, thereby significantly improving the comfort and thermal-humidity management performance of wearing.

[0040] Meanwhile, the thermochromic capsules are directly dispersed in the spinning solution to achieve secondary packaging, which effectively avoids the leakage problem of the thermochromic capsules during use.

[0041] In terms of raw material selection, aramid (main component: poly-m-phenylene isophthalamide) has excellent thermal stability, mechanical strength and flame retardant performance, and is an ideal support base material.

[0042] The mass concentration design of the thermochromic microcapsules (TCMCs) in the functional surface layer avoids the problems of fiber forming difficulty and mechanical performance reduction caused by excessive fillers, and at the same time ensures that the surface layer has excellent optical response characteristics.

[0043] The zeolitic imidazolate framework structure material-8 (ZIF-8) particles formed in an in-situ growth manner are combined with polylactic acid (PLA) fibers firmly and are not easy to fall off, and can prolong the service life of the composite nanofiber membrane with bidirectional thermal management function.

[0044] Additional aspects and advantages of the present application will be made apparent from the following description. BRIEF DESCRIPTION OF DRAWINGS

[0045] Figure 1 is a scanning electron microscope image of the aramid nanofiber membrane provided by the embodiment 1 of the present application.

[0046] Figure 2 is a scanning electron microscope image of the double-layer composite nanofiber membrane provided by the embodiment 1 of the present application.

[0047] Figure 3 is a surface temperature change curve diagram of the composite nanofiber membrane with bidirectional thermal management provided by different embodiments provided by the test example of the present application under 1KW·m -2 light intensity.

[0048] Figure 4 is a temperature change curve of the composite nanofiber membrane with bidirectional thermal management provided by different embodiments provided by the test example of the present application in winter outdoor. DETAILED DESCRIPTION

[0049] In order to make the objects, technical solutions and advantages of the present application clearer, the technical solutions in the present application will be described clearly and completely below in combination with specific embodiments. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the present application. The following embodiments are used to illustrate the present application, but cannot be used to limit the scope of the present application.

[0050] In the following embodiments, the experimental methods used are conventional methods, and the used materials, reagents, etc. are obtained from commercial channels, unless otherwise specified, according to the techniques or conditions described in the literature in the art or according to the product instructions.

[0051] The aramid spinning solution with a solid content of 12wt% is prepared as follows:

[0052] Dimethylacetamide (DMAc) (2.5g) is added to the meta-aramid stock solution (20wt% poly-m-phenylene isophthalamide dimethylacetamide solution) (3.75g), and the mixture is stirred thoroughly to obtain the aramid spinning solution with a solid content of 12wt%.

[0053] A ZIF-8 growth solution was prepared as follows:

[0054] Zn(Ac)2(0.501 g) was dissolved in methanol (40 mL) to obtain a Zn(Ac)2solution;

[0055] 2-methylimidazole (0.526 g) was dissolved in methanol (40 mL) to obtain a 2-methylimidazole solution;

[0056] The Zn(Ac)2solution was added dropwise to the 2-methylimidazole solution, and stirred uniformly to obtain a ZIF-8 growth solution with a molar ratio of Zn(Ac)2to 2-methylimidazole of 1:2.37.

[0057] Example 1

[0058] PLA (1.24 g) particles were added to a mixed solvent (12.54 g) of dichloromethane (DCM) and tetrahydrofuran (THF) with a volume ratio of 4:1, and stirred until completely dissolved to obtain a 9wt% PLA solution; then TCMCs (0.80 g) were added to the PLA solution, with a mass ratio of 6wt%, and the TCMCs were uniformly dispersed by stirring and ultrasonic treatment to obtain a PLA / TCMCs composite spinning solution.

[0059] The TCMCs were prepared according to the method disclosed in Example 1 of patent CN110964498A, had an average diameter of 1.8 μm, and had a critical thermochromic temperature range of 25-35°C.

[0060] An aramid nanofiber membrane was prepared using an aramid spinning solution with a solid content of 12wt% by electrospinning technology; the parameters of the electrospinning were set as follows:

[0061] The spinning voltage was 30 kV, the receiving distance was 18 cm, the spinning speed was 0.3 mL / h, and the relative humidity was controlled in the range of 35%-45%.

[0062] The scanning electron microscope image of the aramid nanofiber membrane is shown in Figure 1 As can be seen from the image, the aramid nanofiber membrane is a network structure of micro-nanofibers, with a large number of ultrafine fibers randomly interwoven and stacked to form a high-porosity network membrane; the random arrangement of the fibers allows the aramid nanofiber membrane to have high specific surface area, flexibility and porosity at the same time.

[0063] The PLA / TCMCs composite spinning solution prepared in the foregoing was electrospun on the aramid nanofiber membrane to obtain a double-layer composite nanofiber membrane (the aramid nanofiber membrane as a mechanical support base layer and the porous PLA fiber layer containing the thermochromic microcapsules as a functional surface layer); wherein the electrospinning parameters were set as follows:

[0064] The spinning voltage was 18 kV, the spinning distance was 18 cm, the spinning speed was 1.0 mL / h, and the relative humidity was controlled in the range of 70% to 80%.

[0065] The double-layer composite nanofiber membrane was soaked in the ZIF-8 growth solution for 8 h, cleaned with methanol and dried to obtain a composite nanofiber membrane with a thermochromic microcapsule mass content of 6% and bidirectional heat management, the scanning electron microscope image of which is shown in Figure 2 From the image, it can be seen that a large number of ZIF-8 particles are loaded on the surface layer of the double-layer composite nanofiber membrane.

[0066] Example 2

[0067] Except that the amount of TCMCs in Example 1 was replaced by 12.4 g, the rest of the process was the same as Example 1 to obtain a composite nanofiber membrane with a thermochromic microcapsule mass content of 9% and bidirectional heat management.

[0068] Example 3

[0069] Except that the amount of TCMCs in Example 1 was replaced by 0.39 g, the rest of the process was the same as Example 1 to obtain a composite nanofiber membrane with a thermochromic microcapsule mass content of 3% and bidirectional heat management.

[0070] Test Example

[0071] The composite nanofiber membranes with bidirectional heat management provided by Example 1, Example 2 and Example 3 were irradiated under simulated sunlight (intensity of 1 kW·m -2 ), and the light-heat absorption of the composite nanofiber membranes with bidirectional heat management was as shown in Figure 3 From the image, it can be seen that the steady-state equilibrium temperatures of the three examples are 56.2℃, 57.7℃ and 55.8℃, respectively, and the steady-state temperatures of the three examples are concentrated in the range of 55.8℃ to 57.7℃.

[0072] In order to investigate the light-heat conversion performance in a low-temperature environment, outdoor field tests were carried out during the day (5 pm) in winter. The test results showed that it could quickly produce a thermal response under residual solar radiation, as shown in Figure 4 The temperatures of the composite nanofiber membranes with bidirectional heat management provided by Example 1, Example 2 and Example 3 reached 28.1℃, 31.6℃ and 26.0℃, respectively, at the 97th second after the start of the test.

[0073] Figure 3 and Figure 4 The results show that the composite nanofiber membrane provided by the application has bidirectional thermal management performance, in a low-temperature / weak-light environment, its dark state can realize rapid light-heat conversion, and the steady-state temperature can reach above 55 DEG C; in a high-temperature environment, its light state can effectively reflect sunlight and strengthen mid-infrared emission, and active cooling is realized.

[0074] Finally, it should be noted that: the above examples are only used to illustrate the technical solutions of the present application, but not to limit it; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing examples, or make equivalent replacement for part of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for preparing a composite nanofiber membrane with bidirectional thermal management, characterized in that, It comprises the following steps: S100, using aramid spinning organic solution, electrospinning technology I is used to prepare aramid nanofiber membrane; Wherein, the main component of the aramid spinning organic solution is poly-m-phenylene isophthalamide, and the solid content of the aramid spinning organic solution is 10wt%-15wt%; S200, using a composite spinning solution containing polymer and thermochromic capsules, electrospinning technology II is used on the aramid nanofiber membrane to prepare a double-layer composite nanofiber membrane; Wherein, the polymer is selected from aliphatic polyester polymers; The mass percentage of the polymer in the composite spinning solution is 8wt%-10wt%, and the mass percentage of the thermochromic capsule is 3wt%-9wt%. S300, immerse the double-layer composite nanofiber membrane in the ZIF-8 growth solution, and use in-situ growth technology to grow ZIF-8 particles on the surface of the polymer fiber of the double-layer composite nanofiber membrane, to obtain a composite nanofiber membrane with bidirectional thermal management; Wherein, ZIF-8 is zeolite imidazolate framework-8; The temperature of in-situ growth is 15-25℃, and the time of in-situ growth is 6-10h.

2. The method of claim 1, wherein the composite nanofiber membrane having bidirectional thermal management is prepared by the steps of: In step S100, the solvent of the aramid spinning organic solution is selected from N,N-dimethylacetamide.

3. The method of claim 1, wherein the composite nanofiber membrane having bidirectional thermal management is prepared by the steps of: In step S100, the parameters of the electrospinning technology I are set as follows: The voltage is 28-30kV, the receiving distance is 18-20cm, the spinning speed is 0.1-0.5mL / h, and the relative humidity is 30%-50%.

4. The method of claim 1, wherein the composite nanofiber membrane having bidirectional thermal management is prepared by the steps of: In step S200, the aliphatic polyester polymer is selected from one or more of polylactic acid, polycaprolactone, polyhydroxyalkanoate and polybutylene succinate.

5. The method of claim 4, wherein the composite nanofiber membrane having bidirectional thermal management is prepared by the steps of: The aliphatic polyester polymer is selected from polylactic acid; The preparation of the composite spinning solution containing polylactic acid and thermochromic capsules comprises the following steps: S210, dissolve polylactic acid in dichloromethane and / or tetrahydrofuran to obtain a polylactic acid solution; S220, add thermochromic capsules to the polylactic acid solution, and make the thermochromic capsules uniformly distributed in the polylactic acid solution to obtain a composite spinning solution containing polylactic acid and thermochromic capsules.

6. The method of claim 1, wherein the composite nanofiber membrane having bidirectional thermal management is prepared by the steps of: In step S200, the particle size of the thermochromic capsule is 0.5-4.5μm, and the critical thermochromic temperature is 18-45℃.

7. The method for preparing the composite nanofiber membrane with bidirectional thermal management as described in claim 1, characterized in that, In step S200, the parameters of the electrospinning technology II are set as follows: The spinning voltage is 16-20kV, the spinning distance is 18-20cm, the spinning speed is 0.5-1.5mL / h, and the relative humidity is 60%-90%.

8. The method of claim 1, wherein the composite nanofiber membrane having bidirectional thermal management is prepared by the steps of: In step S300, the preparation process of the ZIF-8 growth solution is as follows: S310, dissolve zinc acetate and 2-methylimidazole in a polar organic solvent respectively to obtain a zinc acetate solution and a 2-methylimidazole solution; Wherein, the molar ratio of zinc acetate to 2-methylimidazole is 1:2.0-1:2.5; S320, add the 2-methylimidazole solution to the zinc acetate solution, stir uniformly, and obtain the in-situ growth solution of ZIF-8.

9. The method for preparing the composite nanofiber membrane with bidirectional thermal management as described in claim 8, characterized in that, The polar organic solvent is selected from one or more of methanol, ethanol, isopropanol and N-N dimethylformamide.

10. A composite nanofiber membrane with bidirectional thermal management, characterized in that, The composite nanofiber membrane with bidirectional thermal management is prepared by the method according to any one of claims 1 to 9. The composite nanofiber membrane with bidirectional thermal management is prepared by the method according to any one of claims 1 to 9.

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