A radiation-cooled nanofiber membrane composite clothing fabric and its preparation method

Abstract

This application discloses a radiation-cooling nanofiber membrane composite clothing fabric and its preparation method. Using polyvinylidene fluoride-hexafluoropropylene as a matrix and adding nano-silica particles, a P(VDF-HFP / SiO2) composite nanofiber membrane is prepared. The nanofiber membrane of this application achieves enhanced synergistic cooling effect through radiation cooling mechanism and its composite application with clothing fabric. Using vinyl acetate copolymer EVA hot melt adhesive nonwoven fabric as an intermediate layer, the nanofiber membrane and ordinary fabric are composited through a hot-pressing process. The resulting composite material not only exhibits excellent radiation cooling capacity but also enhances moisture absorption and perspiration wicking function by utilizing the unique structural properties of the nanofiber membrane. This ensures that while maintaining excellent breathability, a more effective cooling effect is achieved. Therefore, the radiation-cooling nanofiber membrane and clothing fabric composite material is particularly suitable for producing high-performance clothing, especially for outdoor thermal management and sun protection clothing.

Description

Technical Field

[0001] This invention belongs to the field of textile technology, specifically relating to a radiation-cooled nanofiber membrane composite clothing fabric and its preparation method. Background Technology

[0002] While the economy continues to develop, global energy consumption is showing a year-on-year upward trend, leading to excessive carbon emissions and exacerbated air pollution. These environmental problems have a direct impact on climate change and may trigger frequent extreme heat waves in the coming decades, thus significantly increasing global demand for cooling energy. To address this challenge, passive radiative cooling technology, as an effective and renewable solution, offers a new perspective on alleviating the world's growing cooling needs. Radiative cooling technology has been widely used in energy-efficient buildings, photovoltaic cooling, energy harvesting, and personal thermal management, achieving cooling effects without any external energy input, providing a viable path to solving the global cooling challenge.

[0003] Seeking more efficient and energy-saving solutions has become a research hotspot. By innovatively adjusting the surface and internal structure of textile fibers, it is possible not only to maintain the wearability of textiles, such as their moisture permeability and breathability, but also to utilize the multi-scale disordered porous structure of the fibers to improve the transparency of infrared radiation and the backscattering ability of visible light in the human body. This structural design maximizes the reflection of solar radiation and enhances the dissipation of human body heat radiation, while improving the water absorption and breathability of textiles, thereby effectively achieving personal cooling.

[0004] Although P(VDF-HFP)-based radiation cooling materials have shown potential application value, they still face challenges such as large fiber thickness, poor moisture and air permeability, unstable fiber structure, and low ultraviolet reflectivity. Furthermore, most current processes for preparing porous P(VDF-HFP) nanofiber membranes focus primarily on adsorption and filtration functions, often neglecting the impact of color changes on material properties. For example, existing studies have reported that porous P(VDF-HFP) nanofiber membranes often exhibit a pale yellow color; this color change may adversely affect the material's reflectivity in the ultraviolet-visible wavelength range, thereby reducing the overall cooling effect. Summary of the Invention

[0005] Technical problems to be solved:

[0006] This application addresses the shortcomings of existing technologies by resolving technical issues related to fiber thickness, moisture permeability, fiber structural stability, and ultraviolet reflectivity. It also addresses the technical challenges faced by fabrics in the market regarding cooling functionality and comfort by providing a radiation-cooling nanofiber membrane composite clothing fabric and its preparation method. By controlling the change in fiber color, the reflectivity within the ultraviolet-visible wavelength range is maximized. The addition of silica to the nanofiber membrane not only further enhances the ultraviolet reflectivity of the fiber membrane and strengthens the cooling effect, but also enhances mid-infrared emission, improving radiation cooling efficiency. This effectively addresses the growing cooling demands and provides a highly efficient and environmentally friendly new approach for personal thermal management.

[0007] Technical solution:

[0008] To achieve the above objectives, this application provides the following technical solution:

[0009] A method for preparing a radiation-cooled nanofiber membrane composite clothing fabric includes the following steps:

[0010] Step 1: Polyvinylidene fluoride-co-hexafluoropropylene P(VDF-HFP) is used as the matrix, and nano-SiO2 particles uniformly distributed in the P(VDF-HFP) copolymer are doped to obtain the spinning solution. The P(VDF-HFP) / SiO2 composite nanofiber membrane, i.e. radiation-cooled nanofiber membrane, is prepared from the spinning solution by electrospinning technology.

[0011] Step 2: The P(VDF-HFP) / SiO2 composite nanofiber membrane and clothing fabric are bonded together with EVA hot melt adhesive nonwoven fabric to form a stable composite material, namely radiation-cooled nanofiber membrane composite clothing fabric.

[0012] Furthermore, in the first step, the spinning solution is prepared by dissolving P(VDF-HFP) in a mixed solution of DMF and acetone at 50°C to 60°C.

[0013] The mixture is stirred for 1-2 hours, then nano-SiO2 particles are added, and the mixture is degassed by ultrasonication at 60-100W for 30-60 minutes; the nano-SiO2 particles are hydrophobic silicon dioxide.

[0014] Furthermore, the mass ratio of nano-SiO2 particles is P(VDF-HFP) = 4-5:100.

[0015] Furthermore, the molar ratio of DMF to acetone in the DMF-acetone mixed solution is DMF:acetone = 6:4.

[0016] Furthermore, the specific preparation method of the P(VDF-HFP) / SiO2 composite nanofiber membrane is as follows:

[0017] S1. Polyvinylidene fluoride-co-hexafluoropropylene P (VDF-HFP) granules were added to a mixed solution of DMF and acetone and magnetically stirred at 50℃~60℃ for 1h~2h to obtain a softened P (VDF-HFP) matrix.

[0018] S2. Nano-SiO2 particles are added to the softened P(VDF-HFP) matrix, and ultrasonic treatment is performed for 30-60 minutes using an ultrasonic disperser at a power of 60-100W to achieve fine crushing of nano-SiO2 particles and degassing of the solution to obtain spinning solution.

[0019] S3. The spinning solution is extruded through the spinneret of the electrospinning process to form a film, thus obtaining a P(VDF-HFP) / SiO2 composite nanofiber membrane.

[0020] Furthermore, the electrospinning process uses a spinning voltage of 12–18 kV, a spinning flow rate of 0.9–1.2 mL / h, and a spinning distance of 12–18 cm.

[0021] Furthermore, the diameter of the fibers in the P(VDF-HFP) / SiO2 composite nanofiber membrane is 100-500 nm.

[0022] Furthermore, the clothing fabric is cotton, polyester, nylon, or a blended fabric.

[0023] Furthermore, the second step involves hot-pressing, with the hot-pressing temperature ranging from 85℃ to 105℃ and the operating pressure from 1.5 to 2.5 kgf / m³. 2 The pressing time is 10-15 seconds.

[0024] This application also discloses radiation-cooled nanofiber membrane composite clothing fabric prepared by any of the above preparation methods.

[0025] Explanation of the principle: The radiation-cooling nanofiber membrane composite clothing fabric of this invention achieves a multi-functional integration of radiation cooling, high breathability, and stain resistance and easy cleaning through a unique material combination and structural design of P(VDF-HFP) / SiO2 nanofiber membrane and EVA hot melt adhesive nonwoven fabric. The P(VDF-HFP) / SiO2 nanofiber membrane utilizes the high reflectivity and optimized mid-infrared radiation capability of SiO2 nanoparticles to effectively reflect sunlight and accelerate body heat dissipation, achieving excellent cooling effect. The porous structure of the EVA hot melt adhesive nonwoven fabric enhances the breathability of the fabric, promotes sweat evaporation, and maintains the stability of the fiber membrane structure, improving durability. In addition, the hydrophobic properties imparted by SiO2 nanoparticles provide the fabric with excellent stain resistance and easy cleaning performance. This innovative sandwich structure design not only effectively utilizes each function, but also achieves an unexpected synergistic performance improvement (1+1>2) through the interaction of materials and structure, greatly enhancing the market competitiveness of the clothing fabric and the user's wearing experience.

[0026] Beneficial effects:

[0027] This application provides a radiation-cooled nanofiber membrane composite clothing fabric and its preparation method, which has the following advantages compared with the prior art:

[0028] 1. This application employs a unique nanofiber membrane composed of SiO2 nanoparticles with radiative cooling properties and a P(VDF-HFP) copolymer matrix with moisture-wicking properties. This allows the radiative cooling nanoparticles to be uniformly distributed within the nanofiber membrane, effectively reflecting sunlight to achieve a significant cooling effect. The moisture-wicking properties of P(VDF-HFP) ensure that the wearer's skin remains dry. This achieves a perfect combination of radiative cooling and moisture-wicking, not only realizing radiative cooling by reflecting sunlight but also further enhancing the cooling effect through moisture absorption and evaporation, thus creating a highly efficient synergistic cooling solution.

[0029] 2. Utilizing synergistic cooling technology, a series of fabrics and garments have been successfully developed. These fabrics and garments not only demonstrate excellent cooling capabilities but also possess moisture-wicking properties, providing wearers with a sweat-wicking, cool, and comfortable wearing experience. The designs of these fabrics and garments take into account the diverse needs of wearers and are suitable for various environments and activities, such as sportswear, outdoor gear, and everyday casual wear, thus meeting the market demand for high-performance, comfortable, breathable fabrics and garments with synergistic cooling capabilities.

[0030] 3. This application further optimizes the structure of the radiation cooling composite fabric. By using EVA hot melt adhesive nonwoven fabric for hot pressing bonding, the overall performance of the fabric is significantly improved. EVA hot melt adhesive nonwoven fabric has the characteristic of low-temperature viscosity, with an operating temperature of 85–105℃, far lower than the dissolution temperature of P(VDF-HFP) nanofiber membrane (120–140℃). This effectively saves energy consumption, reduces production costs, and avoids damage to the nanofiber membrane at high temperatures, ensuring its integrity. EVA hot melt adhesive nonwoven fabric has high breathability, improving the comfort and functionality of the fabric, allowing users to maintain good breathability and coolness during wear. EVA hot melt adhesive nonwoven fabric is not prone to wrinkling or bubbling during hot pressing bonding, ensuring the composite fabric remains flat and aesthetically pleasing during processing and use, while also improving the fabric's durability and service life. Using EVA hot melt adhesive nonwoven fabric as the bonding material for the radiation cooling composite fabric not only outperforms other materials in technical performance but also excels in economy and practicality, comprehensively improving the overall performance of the fabric.

[0031] 4. The radiation-cooling nanofiber membrane of this application has significant advantages over existing fabrics in terms of cooling effect, breathability and moisture permeability, softness and wearing comfort;

[0032] 5. The radiation-cooling nanofiber membrane of this application achieves excellent cooling effect by reflecting visible and infrared light in sunlight and utilizing the infrared radiation mechanism;

[0033] 6. The micro-nano fiber network structure of the radiation-cooling nanofiber membrane of this application gives it excellent breathability, moisture permeability and moisture wicking function, while maintaining a light and soft texture, providing a comfortable wearing experience. This makes the radiation-cooling nanofiber membrane and clothing fabric composite material an ideal choice for producing high-performance clothing, especially suitable for occasions that require optimization and improvement of wearing comfort. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of the cross-sectional structure of the composite fabric of radiation-cooled nanofiber membrane and ordinary polyester fabric in Embodiment 2 of this application;

[0035] Figure 2 This is a schematic diagram illustrating the cooling principle of the radiation-cooled nanofiber membrane composite clothing fabric of this application;

[0036] Explanation of reference numerals in the attached diagram: 1. Radiation-cooled nanofiber membrane, 2. EVA hot melt adhesive nonwoven fabric, 3. Polyester fabric. Detailed Implementation

[0037] This section, with reference to the accompanying drawings, details specific embodiments of this patent application, aiming to provide a clear and comprehensive description of the technical solution. It should be clarified that the embodiments described herein represent only one possible application of this patent and do not represent all possible implementations. Based on the content of this document, those skilled in the art can derive all other potential embodiments covered by this application without any inventive effort. Therefore, these embodiments should all be considered to be within the scope of protection of this patent.

[0038] Example 1

[0039] A method for preparing a radiation-cooled nanofiber membrane composite clothing fabric includes the following steps:

[0040] Step 1: Polyvinylidene fluoride-co-hexafluoropropylene P (VDF-HFP) was used as the matrix, and nano-SiO2 particles uniformly distributed in the P (VDF-HFP) copolymer were doped to obtain the spinning solution. The P (VDF-HFP) / SiO2 composite nanofiber membrane, i.e., radiation-cooled nanofiber membrane, was prepared from the spinning solution by electrospinning technology. Polyvinylidene fluoride-co-hexafluoropropylene P (VDF-HFP) was purchased from Sigma-Aldrich CAS No. 9011-17-0, product number 427160.

[0041] Step 2: The P(VDF-HFP) / SiO2 composite nanofiber membrane and the clothing fabric are bonded together with EVA hot melt adhesive nonwoven fabric to form a stable composite material, namely radiation-cooled nanofiber membrane composite clothing fabric. The EVA hot melt adhesive nonwoven fabric was purchased from Pinghu Zhanpeng Hot Melt Adhesive Film Co., Ltd., ZPME-web001.

[0042] The spinning solution is prepared by dissolving P(VDF-HFP) in a mixed solution of DMF and acetone, stirring and mixing at 50℃~60℃ for 1h~2h, then adding nano-SiO2 particles, and degassing by ultrasonication at 60~100W for 30~60min; the nano-SiO2 particles are hydrophobic silica. In the preparation process, acetone and DMF are used as solvents, which will evaporate during the spinning process. Due to the fine fiber structure and high scattering of the nanofibers formed by PVDF and silica, as well as the color of the material itself, the electrospun film appears white.

[0043] The polyvinylidene fluoride-co-hexafluoropropylene accounts for 10.65% of the spinning solution by mass, and the hydrophobic silica accounts for 0.45% of the spinning solution by mass.

[0044] The molar ratio of DMF to acetone in the DMF-acetone mixed solution is DMF:acetone = 6:4.

[0045] The electrospinning process uses a spinning voltage of 15kV, a spinning flow rate of 1.02mL / h, and a spinning distance of 15cm.

[0046] To enhance the efficiency of radiation-cooling fibers and ensure uniform dispersion of hydrophobic SiO2 nanoparticles in the P(VDF-HFP) copolymer, a P(VDF-HFP) / SiO2 composite nanofiber membrane was prepared by cleverly combining traditional solution preparation methods with electrospinning technology. The specific preparation method is as follows:

[0047] S1. Polyvinylidene fluoride-co-hexafluoropropylene P(VDF-HFP) granules are added to a mixed solution of DMF and acetone, and magnetically stirred at 50℃~60℃ for 1h~2h to obtain a softened P(VDF-HFP) matrix. During this process, the friction between the granules and the solvent, between the granules, and between the granules and the container wall generates heat. With the help of external heating of the instrument, the P(VDF-HFP) copolymer quickly enters the softened state and exhibits strong adhesion properties.

[0048] S2. Nano-SiO2 particles are added to the softened P(VDF-HFP) matrix, and ultrasonic treatment is performed for 30-60 minutes using an ultrasonic disperser at a power of 60-100W to achieve fine crushing of nano-SiO2 particles and degassing of the solution, resulting in a spinning solution. The surface treatment agent can more effectively treat the nanoparticles locally, significantly reducing the surface energy of the particles and preventing the re-aggregation of hydrophobic SiO2 nanoparticles. The viscous drag force of the P(VDF-HFP) copolymer and the high shear force generated by ultrasound work together to ensure uniform coating between the hydrophobic SiO2 nanoparticles and the P(VDF-HFP) copolymer granules.

[0049] S3. The spinning solution is extruded through the spinneret of an electrospinning process to form a film, thus obtaining a P(VDF-HFP) / SiO2 composite nanofiber membrane. Through the uniform dispersion of hydrophobic SiO2 nanoparticles, the radiation-cooling fiber of this invention can achieve a more uniform radiation-cooling effect, thereby making the cooling performance of the blended yarn products more uniform and stable. Furthermore, the uniform dispersion of hydrophobic SiO2 nanoparticles further smooths the surface of the nanofiber membrane, which is beneficial for improving the reflectivity of sunlight, thereby optimizing the cooling effect of the fabric.

[0050] The clothing fabric is made of cotton, polyester, nylon, or blended fabric.

[0051] A stable composite material is formed by bonding a radiation-cooled nanofiber membrane with a polyester fabric using EVA hot melt adhesive nonwoven fabric. The specific steps are as follows:

[0052] Step 1: Set the temperature of the hot press equipment to 85℃~105℃, and adjust the operating pressure to 1.5~2.5Kgf / m³. 2The pressing time is set to 10-15 seconds;

[0053] Step 2: The radiation-cooled nanofiber membrane 1, EVA hot melt adhesive nonwoven fabric 2, and polyester fabric 3 are stacked in sequence and aligned and fixed on the equipment worktable.

[0054] Step 3: Start the hot pressing equipment and perform hot pressing operation at the set temperature and pressure to fully melt the EVA hot melt adhesive nonwoven fabric 2 and firmly bond it with the radiation cooling nanofiber membrane 1 and polyester fabric 3 to obtain a composite fabric.

[0055] Step 4: Allow the composite fabric to cool naturally to room temperature and conduct a quality inspection to ensure a smooth, wrinkle-free, bubble-free surface and that the adhesive strength and breathability meet the standards. This yields the radiation-cooling nanofiber membrane composite clothing fabric. Clothing made from this fabric offers certain perspiration-wicking, cooling, and comfort benefits.

[0056] Example 2

[0057] A method for preparing a radiation-cooled nanofiber membrane composite clothing fabric includes the following steps:

[0058] Step 1: Polyvinylidene fluoride-co-hexafluoropropylene P(VDF-HFP) (Sigma-Aldrich CAS No. 9011-17-0, Product No. 427160) was used as the matrix, and nano-SiO2 particles uniformly distributed in the P(VDF-HFP) copolymer were doped to obtain the spinning solution. The P(VDF-HFP) / SiO2 composite nanofiber membrane, i.e., radiation-cooled nanofiber membrane, was prepared from the spinning solution by electrospinning technology.

[0059] Step 2: The P(VDF-HFP) / SiO2 composite nanofiber membrane and clothing fabric are bonded together with EVA hot melt adhesive nonwoven fabric to form a stable composite material, namely radiation-cooled nanofiber membrane composite clothing fabric.

[0060] In the first step, the spinning solution is prepared by dissolving P(VDF-HFP) in a mixed solution of DMF and acetone, stirring and mixing at 50℃~60℃ for 1h~2h, then adding nano-SiO2 particles, and degassing by ultrasonication at 60~100W for 30~60min; the nano-SiO2 particles are hydrophobic silica.

[0061] The polyvinylidene fluoride-co-hexafluoropropylene accounts for 10.65% of the spinning solution by mass, and the hydrophobic silica accounts for 0.45% of the spinning solution by mass.

[0062] The molar ratio of DMF to acetone in the DMF-acetone mixed solution is DMF:acetone = 6:4.

[0063] The electrospinning process uses a spinning voltage of 15kV, a spinning flow rate of 0.9mL / h, and a spinning distance of 15cm.

[0064] To enhance the efficiency of radiation-cooling fibers and ensure uniform dispersion of hydrophobic SiO2 nanoparticles in the P(VDF-HFP) copolymer, a P(VDF-HFP) / SiO2 composite nanofiber membrane was prepared by cleverly combining traditional solution preparation methods with electrospinning technology. The specific preparation method is as follows:

[0065] S1. Polyvinylidene fluoride-co-hexafluoropropylene P(VDF-HFP) granules are added to a mixed solution of DMF and acetone, and magnetically stirred at 50℃~60℃ for 1h~2h to obtain a softened P(VDF-HFP) matrix. During this process, the friction between the granules and the solvent, between the granules, and between the granules and the container wall generates heat. With the help of external heating of the instrument, the P(VDF-HFP) copolymer quickly enters the softened state and exhibits strong adhesion properties.

[0066] S2. Nano-SiO2 particles are added to the softened P(VDF-HFP) matrix, and ultrasonic treatment is performed for 30-60 minutes using an ultrasonic disperser at a power of 60-100W to achieve fine crushing of nano-SiO2 particles and degassing of the solution, resulting in a spinning solution. The surface treatment agent can more effectively treat the nanoparticles locally, significantly reducing the surface energy of the particles and preventing the re-aggregation of hydrophobic SiO2 nanoparticles. The viscous drag force of the P(VDF-HFP) copolymer and the high shear force generated by ultrasound work together to ensure uniform coating between the hydrophobic SiO2 nanoparticles and the P(VDF-HFP) copolymer granules.

[0067] S3. The spinning solution is extruded through the spinneret of an electrospinning process to form a film, thus obtaining a P(VDF-HFP) / SiO2 composite nanofiber membrane. Through the uniform dispersion of hydrophobic SiO2 nanoparticles, the radiation-cooling fiber of this invention can achieve a more uniform radiation-cooling effect, thereby making the cooling performance of the blended yarn products more uniform and stable. Furthermore, the uniform dispersion of hydrophobic SiO2 nanoparticles further smooths the surface of the nanofiber membrane, which is beneficial for improving the reflectivity of sunlight, thereby optimizing the cooling effect of the fabric.

[0068] The garment is made of polyester.

[0069] A stable composite material is formed by bonding a radiation-cooled nanofiber membrane with a polyester fabric using EVA hot melt adhesive nonwoven fabric. The specific steps are as follows:

[0070] Step 1: Set the temperature of the hot press equipment to 85℃~105℃, and adjust the operating pressure to 1.5~2.5Kgf / m³. 2The pressing time is set to 10-15 seconds;

[0071] Step 2: The radiation-cooled nanofiber membrane 1, EVA hot melt adhesive nonwoven fabric 2, and polyester fabric 3 are stacked in sequence and aligned and fixed on the equipment worktable.

[0072] Step 3: Start the hot pressing equipment and perform hot pressing operation at the set temperature and pressure to fully melt the EVA hot melt adhesive nonwoven fabric 2 and firmly bond it with the radiation cooling nanofiber membrane 1 and polyester fabric 3 to obtain a composite fabric.

[0073] Step 4: Allow the composite fabric to cool naturally to room temperature and conduct a quality inspection to ensure that the surface is smooth and wrinkle-free, bubble-free, and that the bonding strength and breathability meet the standards. This yields the radiation-cooled nanofiber membrane composite clothing fabric.

[0074] Clothing made from radiation-cooled nanofiber membrane composite fabric has certain effects of sweat-wicking, cooling, and comfort.

[0075] This patent embodiment introduces a unique design for a radiation-cooling nanofiber membrane. This design effectively achieves heat emission by reflecting visible and infrared light from sunlight and utilizing the mechanism of infrared radiation to penetrate the atmosphere through an atmospheric window (8μm–13μm wavelength band), thereby promoting cooling. This radiation-cooling nanofiber membrane is composed of a P(VDF-HFP) copolymer matrix in which SiO2 nanoparticles are uniformly distributed, forming a P(VDF-HFP) / SiO2 nanofiber membrane. Figure 1 The illustrated radiative cooling principle demonstrates the process when the full spectrum of sunlight shines on the surface of a P(VDF-HFP) / SiO2 nanofiber membrane. This nanofiber membrane effectively reflects a portion of this light, including visible and infrared light. Through a specific atmospheric window (8μm–13μm wavelength), the membrane can emit heat in the mid-infrared frequency band, penetrating the atmosphere and achieving excellent radiative cooling. This invention, through ingenious material design and structural optimization, enables the P(VDF-HFP) / SiO2 nanofiber membrane to not only excel in reflecting sunlight but also effectively emit heat through a unique infrared radiation mechanism, providing an innovative solution for efficient cooling.

[0076] By utilizing the unique structural properties of nanofiber membranes, this invention significantly enhances the moisture-wicking capacity of fabrics. The nanofiber membrane employs a fine micro-nano-scale fiber network structure with an extremely high surface area and unique porosity, providing ideal channels for the absorption and transport of water molecules. When the wearer engages in high-intensity activity and sweats, these micro-nano-scale fibers rapidly absorb and disperse sweat, releasing it outwards through the pores between the fibers. Furthermore, this nanofiber membrane structure effectively prevents sweat accumulation on the skin surface while maintaining good breathability, thereby reducing skin dampness and discomfort. This nanofiber membrane, while improving moisture-wicking efficiency, also maintains a lightweight and soft texture, ensuring wearing comfort. Through optimization of the moisture-wicking performance of the nanofiber membrane, this invention is suitable not only for wear in high-temperature environments but also for use in sports and outdoor activities, providing the wearer with a lasting dry and comfortable experience. This nanofiber membrane, combining highly efficient moisture wicking with a comfortable wearing experience, demonstrates the breakthrough and application potential of this invention in fabric technology innovation.

[0077] In this embodiment of the invention, we focus on the compatibility between the Si-O-Si bond vibration absorption peak in SiO2 and the atmospheric window band, a characteristic that significantly enhances the emissivity in the mid-infrared band. Therefore, the mass percentage of SiO2 nanoparticles in the radiation-cooling fiber directly affects the radiation-cooling effect. It is important to note that if the content of hydrophobic SiO2 nanoparticles is too high, it will cause excessive agglomeration of nanoparticles during spinning. To optimize this effect and ensure maximum radiation-cooling performance, in this embodiment, we specifically selected a mass percentage of hydrophobic silica in the radiation-cooling fiber of 0.45% to 1.75%. Simultaneously, to ensure that the P(VDF-HFP) / SiO2 nanofiber membrane has excellent radiation-cooling effect and stable solar reflectivity, the mass percentage of P(VDF-HFP) is set between 10.50% and 10.75%. This configuration not only ensures the high efficiency of the radiation-cooling fiber but also helps maintain the overall stability and performance of the fiber membrane.

[0078] Example 3

[0079] A method for preparing a radiation-cooled nanofiber membrane composite clothing fabric includes the following steps:

[0080] Step 1: Polyvinylidene fluoride-co-hexafluoropropylene P(VDF-HFP) (Sigma-Aldrich CAS No. 9011-17-0, Product No. 427160) was used as the matrix, and nano-SiO2 particles uniformly distributed in the P(VDF-HFP) copolymer were doped to obtain the spinning solution. The P(VDF-HFP) / SiO2 composite nanofiber membrane, i.e., radiation-cooled nanofiber membrane, was prepared from the spinning solution by electrospinning technology.

[0081] Step 2: The P(VDF-HFP) / SiO2 composite nanofiber membrane and the clothing fabric are combined with EVA hot melt adhesive nonwoven fabric (Pinghu Zhanpeng Hot Melt Adhesive Film Co., Ltd., ZPME-web001) to form a stable composite material, namely radiation-cooled nanofiber membrane composite clothing fabric.

[0082] The spinning solution is prepared by dissolving P(VDF-HFP) in a mixed solution of DMF and acetone, stirring and mixing at 50℃~60℃ for 1h~2h, then adding nano-SiO2 particles, and degassing by ultrasonication at 60~100W for 30~60min; the nano-SiO2 particles are hydrophobic silica.

[0083] The polyvinylidene fluoride-co-hexafluoropropylene accounts for 10.65% of the spinning solution by mass, and the hydrophobic silica accounts for 0.45% of the spinning solution by mass.

[0084] The molar ratio of DMF to acetone in the DMF-acetone mixed solution is DMF:acetone = 6:4.

[0085] The electrospinning process uses a spinning voltage of 15kV, a spinning flow rate of 1.2mL / h, and a spinning distance of 15cm.

[0086] To enhance the efficiency of radiation-cooling fibers and ensure uniform dispersion of hydrophobic SiO2 nanoparticles in the P(VDF-HFP) copolymer, a P(VDF-HFP) / SiO2 composite nanofiber membrane was prepared by cleverly combining traditional solution preparation methods with electrospinning technology. The specific preparation method is as follows:

[0087] S1. Polyvinylidene fluoride-co-hexafluoropropylene P(VDF-HFP) granules are added to a mixed solution of DMF and acetone, and magnetically stirred at 50℃~60℃ for 1h~2h to obtain a softened P(VDF-HFP) matrix. During this process, the friction between the granules and the solvent, between the granules, and between the granules and the container wall generates heat. With the help of external heating of the instrument, the P(VDF-HFP) copolymer quickly enters the softened state and exhibits strong adhesion properties.

[0088] S2. Nano-SiO2 particles are added to the softened P(VDF-HFP) matrix, and ultrasonic treatment is performed for 30-60 minutes using an ultrasonic disperser at a power of 60-100W to achieve fine crushing of nano-SiO2 particles and degassing of the solution, resulting in a spinning solution. The surface treatment agent can more effectively treat the nanoparticles locally, significantly reducing the surface energy of the particles and preventing the re-aggregation of hydrophobic SiO2 nanoparticles. The viscous drag force of the P(VDF-HFP) copolymer and the high shear force generated by ultrasound work together to ensure uniform coating between the hydrophobic SiO2 nanoparticles and the P(VDF-HFP) copolymer granules.

[0089] S3. The spinning solution is extruded through the spinneret of an electrospinning process to form a film, thus obtaining a P(VDF-HFP) / SiO2 composite nanofiber membrane. Through the uniform dispersion of hydrophobic SiO2 nanoparticles, the radiation-cooling fiber of this invention can achieve a more uniform radiation-cooling effect, thereby making the cooling performance of the blended yarn products more uniform and stable. Furthermore, the uniform dispersion of hydrophobic SiO2 nanoparticles further smooths the surface of the nanofiber membrane, which is beneficial for improving the reflectivity of sunlight, thereby optimizing the cooling effect of the fabric.

[0090] The clothing fabric is made of cotton, polyester, nylon, or blended fabric.

[0091] A stable composite material is formed by bonding a radiation-cooled nanofiber membrane with a polyester fabric using EVA hot melt adhesive nonwoven fabric. The specific steps are as follows:

[0092] Step 1: Set the temperature of the hot press equipment to 85℃~105℃, and adjust the operating pressure to 1.5~2.5Kgf / m³. 2 The pressing time is set to 10-15 seconds;

[0093] Step 2: The radiation-cooled nanofiber membrane 1, EVA hot melt adhesive nonwoven fabric 2, and polyester fabric 3 are stacked in sequence and aligned and fixed on the equipment worktable.

[0094] Step 3: Start the hot pressing equipment and perform hot pressing operation at the set temperature and pressure to fully melt the EVA hot melt adhesive nonwoven fabric 2 and firmly bond it with the radiation cooling nanofiber membrane 1 and polyester fabric 3 to obtain a composite fabric.

[0095] Step 4: Allow the composite fabric to cool naturally to room temperature and conduct a quality inspection to ensure a smooth, wrinkle-free, bubble-free surface and that the adhesive strength and breathability meet the standards. This yields the radiation-cooling nanofiber membrane composite clothing fabric. Clothing made from this fabric offers certain perspiration-wicking, cooling, and comfort benefits.

[0096] Comparative Example 1

[0097] A common white polyester plain weave fabric, which is also the base fabric. This fabric has a relatively loose structure, excellent breathability, and limited radiative cooling capacity.

[0098] Comparative Example 2

[0099] The difference from Example 1 is that P(VDF-HFP) accounts for 10.70% of the spinning solution by mass, and hydrophobic silica accounts for 0% of the spinning solution by mass.

[0100] Comparative Example 3

[0101] The difference from Example 2 is that P(VDF-HFP) accounts for 10.60% of the spinning solution by mass, and hydrophobic silica accounts for 0.90% of the spinning solution by mass.

[0102] Comparative Example 4

[0103] The difference from Example 2 is that P(VDF-HFP) accounts for 10.55% of the spinning solution by mass, and hydrophobic silica accounts for 1.30% of the spinning solution by mass.

[0104] Comparative Example 5

[0105] The difference from Example 2 is that P(VDF-HFP) accounts for 10.50% of the spinning solution by mass, and hydrophobic silica accounts for 1.75% of the spinning solution by mass.

[0106] The synergistic cooling functional fabrics in Examples 1-3 and Comparative Examples 1-5 were tested for radiative cooling performance and breathability. The results are shown in Table 1. The testing conditions for radiative cooling performance, breathability, and hydrophobicity were: ambient temperature 30℃, convective heat transfer coefficient 10W / m². 2 *K, atmospheric mass AM1.6, atmospheric pressure 100Pa. The test method for radiative cooling performance is an outdoor daytime cooling test; the test index is the temperature difference, and the smaller the value, the better the effect. The test method for breathability performance is the standard test method for the gas permeability of materials; the test index is the air permeability rate, and the higher the air permeability rate, the better the fabric's breathability and thermal comfort. The test standard for hydrophobic performance is the contact angle; the larger the contact angle, the better the hydrophobic performance and the better the stain resistance.

[0107] Table 1

[0108]

[0109] As shown in Table 1, the fabric of Example 1 was made of radiation-cooled nanofiber membrane composite ordinary polyester fabric, which achieved better radiation-cooling effect and stain resistance.

[0110] Compared to Example 1, Examples 2 and 3 showed poorer radiative cooling effects. This is because different spinning flow rates significantly affect the morphology and quality of the fibers. Excessive flow rate increases the amount of polymer solution sprayed, resulting in larger fiber diameters; conversely, insufficient flow rate reduces the amount of polymer solution sprayed, leading to smaller fiber diameters. Furthermore, excessively high flow rates prevent the sprayed fibers from being fully stretched under the electric field, easily causing fiber entanglement or adhesion; while excessively low flow rates may result in uneven fiber accumulation on the collector, affecting the uniformity and performance of the final product. The radiative cooling effect was optimal when the spinning flow rate was 1.02 mL / h.

[0111] Compared to Comparative Example 1, Comparative Example 2 showed a slight improvement in radiative cooling effect, but this improvement was not significant. Meanwhile, the breathability and hydrophobicity properties changed noticeably. This is because the unique microstructure and material properties of the P(VDF-HFP) nanofiber membrane effectively reflect and scatter infrared rays from sunlight, thereby reducing the surface temperature of the clothing. Furthermore, the nanofiber material can be designed to be highly hydrophobic through its surface properties, helping the fabric resist moisture and stains more effectively. However, the presence of the membrane may partially block the pores, reducing airflow and slightly affecting breathability, but it still meets and exceeds the standard clothing breathability (700 mm / s).

[0112] Compared to Example 1, Comparative Example 2 exhibits inferior radiative cooling and moisture permeability. Although both examples use polyester fabric as the supporting material and are composited with a nanofiber membrane composed of P(VDF-HFP) and SiO2, Example 1 effectively enhances the fabric's emissivity in the atmospheric window band (8μm–13μm) by incorporating SiO2 nanoparticles into the nanofiber membrane. The Si-O-Si bond vibration absorption peak of the SiO2 nanoparticles matches this band, thereby improving the radiative cooling effect. In contrast, while Comparative Example 2 also uses a P(VDF-HFP) nanofiber membrane, it does not incorporate SiO2 nanoparticles, thus resulting in inferior radiative cooling performance compared to Example 1. Furthermore, the addition of SiO2 may also improve the fabric's breathability, making Example 1 superior in terms of breathability as well.

[0113] Compared to Example 1, the radiative cooling effect of Comparative Examples 3, 4, and 5 was weakened. Increasing the SiO2 content altered the optical properties of the nanofiber membrane, particularly its emissivity in the atmospheric window band. Inhomogeneous SiO2 distribution or particle size can lead to decreased emissivity, thereby reducing the radiative cooling effect. Simultaneously, a higher SiO2 content enhances the thermal conductivity of the nanofiber membrane, resulting in increased heat transfer efficiency within the material and reduced heat radiated from the surface to the external environment.

[0114] The foregoing description has fully disclosed the specific embodiments of the present invention. It should be noted that any modifications made to the specific embodiments of the present invention by those skilled in the art do not depart from the scope of the claims. Accordingly, the scope of the claims is not limited to the foregoing specific embodiments.

Claims

1. A method for preparing a radiation-cooled nanofiber membrane composite clothing fabric, characterized in that, The steps are as follows: Step 1: Polyvinylidene fluoride-co-hexafluoropropylene P(VDF-HFP) is used as the matrix, and nano-SiO2 particles uniformly distributed in the P(VDF-HFP) copolymer are doped to obtain the spinning solution. The P(VDF-HFP) / SiO2 composite nanofiber membrane, i.e. radiation-cooled nanofiber membrane, is prepared from the spinning solution by electrospinning technology. Step 2: The P(VDF-HFP) / SiO2 composite nanofiber membrane is combined with the clothing fabric through EVA hot melt adhesive nonwoven fabric to form a stable composite material, namely radiation-cooled nanofiber membrane composite clothing fabric. The EVA hot melt adhesive nonwoven fabric has a porous structure. In the first step, the spinning solution is prepared by dissolving P(VDF-HFP) in a mixed solution of DMF and acetone, stirring and mixing at 50℃~60℃ for 1h~2h, then adding nano-SiO2 particles, and degassing by ultrasonication at 60~100W for 30~60min; the nano-SiO2 particles are hydrophobic silica, and the mass ratio of nano-SiO2 particles:P(VDF-HFP) is 4-5:

100. In the second step, the P(VDF-HFP) / SiO2 composite nanofiber membrane and the garment fabric are combined into a sandwich structure by hot pressing process with EVA hot melt glue non-woven fabric as the intermediate layer, the combination in the second step is hot pressing combination, the hot pressing temperature of the hot pressing combination process is 85-105℃, which is lower than the dissolution temperature 120-140℃ of the P(VDF-HFP) nanofiber membrane, the operating pressure is 1.5-2.5Kgf / m 2 , and the pressing time is 10-15s.

2. The method for preparing the radiation-cooled nanofiber membrane composite clothing fabric according to claim 1, characterized in that: The molar ratio of DMF to acetone in the DMF-acetone mixed solution is DMF:acetone = 6:

4.

3. The method for preparing radiation-cooled nanofiber membrane composite clothing fabric according to claim 2, characterized in that, The specific preparation method of P(VDF-HFP) / SiO2 composite nanofiber membrane is as follows: S1. Polyvinylidene fluoride-co-hexafluoropropylene P (VDF-HFP) granules were added to a mixed solution of DMF and acetone and magnetically stirred at 50℃~60℃ for 1h~2h to obtain a softened P (VDF-HFP) matrix. S2. Nano-SiO2 particles are added to the softened P(VDF-HFP) matrix, and ultrasonic treatment is performed for 30-60 minutes using an ultrasonic disperser at a power of 60-100W to achieve fine crushing of nano-SiO2 particles and degassing of the solution to obtain spinning solution. S3. The spinning solution is extruded through the spinneret of the electrospinning process to form a film, thus obtaining a P(VDF-HFP) / SiO2 composite nanofiber membrane.

4. The method for preparing the radiation-cooled nanofiber membrane composite clothing fabric according to claim 3, characterized in that: The electrospinning process uses a spinning voltage of 12–18 kV, a spinning flow rate of 0.9–1.2 mL / h, and a spinning distance of 12–18 cm.

5. The method for preparing radiation-cooled nanofiber membrane composite clothing fabric according to claim 1, characterized in that: The diameter of the fibers in the P(VDF-HFP) / SiO2 composite nanofiber membrane is 100-500 nm.

6. The method for preparing radiation-cooled nanofiber membrane composite clothing fabric according to claim 1, characterized in that: The clothing fabric is made of cotton, polyester, nylon, or blended fabric.

7. A radiation-cooled nanofiber membrane composite garment fabric prepared by the preparation method according to any one of claims 1-6.

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