Radiant cooling composite yarn and method of making same

Abstract

This invention belongs to the field of textile fiber technology and discloses a radiation-cooling composite yarn and its preparation method. The radiation-cooling composite yarn includes an elastic core, an intermediate covering layer, and an outer layer; the intermediate covering layer covers the outside of the elastic core; the outer layer covers the outside of the intermediate covering layer and includes a radiation-cooling nanofiber membrane. This invention provides a radiation-cooling composite yarn comprising an elastic core, an intermediate covering layer, and an outer layer arranged in three layers; the outermost radiation-cooling nanofiber membrane can efficiently reflect sunlight and radiate heat outward through atmospheric windows, achieving passive cooling of the fabric; simultaneously, when the human body temperature is lower than the outdoor temperature, the fabric has a certain degree of heat retention due to the presence of still air inside the elastic core of the yarn; based on the yarn composition, the movement of the human body can be tracked by utilizing the law of yarn elongation change and its resistance change.

Description

Technical Field

[0001] This invention relates to the field of textile fiber technology, and in particular to a radiation-cooled composite yarn and its preparation method. Background Technology

[0002] With the increasing prominence of global warming and energy consumption issues, the development of passive cooling materials that do not require external energy has become a research hotspot.

[0003] Radiative cooling materials can achieve cooling effects below ambient temperature by controlling the emissivity of the material in the infrared band and the reflectivity in the solar band. However, existing radiative cooling materials are mostly in the form of thin films or coatings, making them difficult to use directly in textiles. Furthermore, their poor mechanical properties, flexibility, and breathability limit their application in wearable devices. In addition, the cooling effect of existing materials is unstable under high temperature and humidity environments, and their manufacturing processes are complex and costly. In conclusion, existing radiative cooling materials are difficult to apply in the textile industry. Summary of the Invention

[0004] The main objective of this invention is to provide a radiation-cooled composite yarn and its preparation method, aiming to solve the problem that existing radiation-cooled materials are difficult to apply in the textile field.

[0005] To achieve the above objectives, the present invention provides a radiation-cooled composite yarn, comprising: Flexible core; An intermediate cladding layer covers the outside of the elastic core; and, The outer layer, which covers the intermediate coating layer, includes a radiation-cooled nanofiber membrane.

[0006] In one embodiment, the material of the elastic core includes a silicone tube.

[0007] In one embodiment, the elastic core is hollow, forming a heat-insulating space.

[0008] In one embodiment, the intermediate coating layer is spirally wrapped around the elastic core; The intermediate coating layer comprises a composite fiber assembly formed by conductive nanomaterials and short fibers.

[0009] In one embodiment, the conductive nanomaterial comprises carbon nanotubes; and / or, The short fibers include at least one of cotton, wool, nylon, and polyester.

[0010] In one embodiment, the radiation-cooled nanofiber membrane comprises either a polyamide 6 nanofilm or a polyvinylidene fluoride membrane.

[0011] In one embodiment, the radiation-cooled nanofiber membrane is loaded with any one of nanoparticles, inorganic salts, or ceramic / dielectric materials.

[0012] In one embodiment, when the radiation-cooled nanofiber membrane is loaded with nanoparticles, the nanoparticles include any one of TiO2, Al2O3, ZnO, or ZrO2; When the radiation-cooled nanofiber membrane is loaded with inorganic salts, the inorganic salts include one of BaSO4 and CaCO3; When the radiation-cooled nanofiber membrane is loaded with ceramic / dielectric material, the ceramic / dielectric material includes one of SiO2, SiC, and Si3N4.

[0013] The present invention also provides a method for preparing a radiation-cooled composite yarn, which is used to prepare the radiation-cooled composite yarn according to any one of the above claims, comprising the following steps: Conductive nanomaterials are combined with short fibers to form composite fiber assemblies; The composite fiber assembly is wrapped around the elastic tube core to form an intermediate coating layer; A radiation-cooled nanofiber membrane is coated around the intermediate coating layer to form an outer layer.

[0014] In one embodiment, the conductive nanomaterial includes carbon nanotubes, and the short fibers include cotton; The step of forming a composite fiber assembly from conductive nanomaterials and short fibers includes: A carbon nanotube solution was mixed with water and ultrasonically treated to obtain a nanotube dispersion. The carbon nanotube-supported cotton was soaked in a sodium hydroxide solution and then removed. The carbon nanotube-loaded cotton, which had been soaked in the sodium hydroxide solution, was immersed in the carbon nanotube dispersion and dried to obtain the composite fiber aggregate.

[0015] The present invention also provides a fabric comprising the radiation-cooled composite yarn according to any one of the preceding claims.

[0016] This invention provides a radiative cooling composite yarn, comprising a three-layered elastic core, a middle covering layer, and an outer layer. The outermost layer is covered with a radiative cooling nanofiber membrane, which efficiently reflects sunlight and radiates heat outward through atmospheric windows, achieving passive cooling of the fabric. Under sunlight, the fabric maintains a cool temperature below ambient, achieving efficient radiative cooling. Simultaneously, when the human body temperature is lower than the outdoor temperature, the fabric retains a certain degree of insulation due to the presence of still air inside the elastic core. Based on the yarn composition, the movement of the human body can be tracked by utilizing the relationship between yarn elongation and electrical resistance. Attached Figure Description

[0017] Figure 1 This is a schematic cross-sectional view of the radiation-cooled composite yarn provided in an embodiment of the present invention.

[0018] Figure 2 This is a physical image of the radiation-cooled composite yarn provided in the embodiment of the present invention.

[0019] Figure 3 It is a radiation-cooled carbon nanotube yarn that has been soaked once in a 0.15% carbon nanotube dispersion and is not wrapped with PVDF nanofiber strips.

[0020] Figure 4 It is a radiation-cooled carbon nanotube yarn that has been repeatedly soaked in a 0.15% carbon nanotube dispersion and is not wrapped with PVDF nanofiber strips.

[0021] Figure 5 The change in unit resistance of carbon nanotube yarn after immersion in carbon nanotube dispersions of different concentrations and radiation cooling.

[0022] Figure 6 The change in unit resistance of carbon nanotube yarn after repeated soaking in a 0.15% carbon nanotube dispersion is shown.

[0023] Figure 7 The resistance changes of the finished yarn after soaking in carbon nanotube dispersions of different concentrations.

[0024] Figure 8 It is the yarn stress-strain curve.

[0025] Explanation of icon numbers: 100. Radiant cooling composite yarn; 1. Elastic core; 2. Intermediate covering layer; 3. Outer layer.

[0026] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0027] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0028] It should be noted that if the embodiments of the present invention involve directional indicators (such as up, down, left, right, front, back, etc.), the directional indicators are only used to explain the relative positional relationship and movement of the components in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indicators will also change accordingly.

[0029] Furthermore, if the embodiments of this invention involve descriptions such as "first" or "second," these descriptions are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features. Additionally, the meaning of "and / or" throughout the text includes three parallel solutions; for example, "A and / or B" includes solution A, solution B, or a solution where both A and B are satisfied simultaneously. Furthermore, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.

[0030] Please see Figures 1 to 2 The present invention provides a radiation-cooled composite yarn 100, comprising an elastic core 1, an intermediate covering layer 2, and an outer layer 3; the intermediate covering layer 2 covers the outside of the elastic core 1; the outer layer 3 covers the outside of the intermediate covering layer 2, and the outer layer includes a radiation-cooled nanofiber membrane.

[0031] This invention provides a radiation-cooling composite yarn 100, comprising an elastic core 1, a middle covering layer 2, and an outer layer 3 arranged in three layers; wherein, the outermost layer is covered with a radiation-cooling nanofiber membrane, which can efficiently reflect sunlight and radiate heat outward through an atmospheric window to achieve passive cooling of the fabric. Under sunlight, the fabric can maintain a cool feeling below the ambient temperature and obtain a highly efficient radiation-cooling function.

[0032] The elastic core 1 can be made of various materials, as long as it has a certain degree of elasticity to support the weaving of the fabric, such as a cotton core; specifically, in the embodiment provided by the present invention, the elastic core 1 includes a silicone tube. In this embodiment, a highly elastic, creep-resistant silicone tube is used instead of the traditional easily bent short fiber as the core material, which has good shape retention. The fabric can quickly return to its original shape after bending and compression, and has excellent wrinkle resistance, overcoming the disadvantage of easy wrinkling of cotton fabrics, etc.

[0033] It should be noted that the hardness of the silicone tube is 40 to 80A, the wall thickness is 0.2-0.5mm, and the overall diameter is 0.5-1.5mm. Preferably, in the embodiments provided in this application, in order to further increase the elasticity, the core filament tension is appropriately increased by 15-20cN during spinning to improve the overall elasticity of the yarn.

[0034] Furthermore, the elastic core 1 is hollow, forming a heat-insulating space. The hollow structure of the elastic core 1 encloses a layer of still air, and since air is a poor conductor of heat, this allows the yarn to form an effective thermal barrier, giving the fabric excellent heat insulation and warmth retention properties, resulting in highly efficient warmth retention.

[0035] In this application, the outer layer of the radiation-cooling composite yarn 100 is provided with a radiation-cooling nanofiber membrane, and the inside is a hollow structure of elastic core 1. When irradiated and heated, most of the heat brought by the light is reflected outward to radiate heat. At the same time, due to the hollow structure, the heat in the environment is difficult to continue to be transferred inward through the yarn. This can reduce the transfer of radiant heat from the light and ambient heat at the same time, making the heat insulation and cooling properties of the entire yarn more stable, and reducing the temperature exchange on both sides of the yarn, thus providing a heat preservation effect.

[0036] It should be noted that the hollow diameter of the elastic core 1 can be 0.3 to 1 mm, preferably 0.4 mm in the embodiment provided in this application, to ensure elasticity and structural stability.

[0037] In comparison, without the hollow structure, the equivalent thermal conductivity is approximately 0.058 W / (m*K), and the insulation efficiency is improved by 34.5%.

[0038] On the other hand, the intermediate coating layer 2 is spirally wrapped around the elastic core; wherein, the intermediate coating layer 2 comprises a composite fiber assembly formed by conductive nanomaterials and short fibers. The conductive nanomaterials in the middle constitute a conductive path. When the yarn is stretched, its spiral winding structure is stretched like a spring, causing the nanotube network to be stretched and the spacing to increase, thereby causing a regular change in resistance. By monitoring the change in resistance, the deformation of the yarn can be sensed in real time and accurately. This can be applied to wearable sensing fields such as human motion monitoring and respiratory monitoring, and has a sensitive stretch sensing function.

[0039] Furthermore, the conductive nanomaterial can be implemented in various ways, such as carbon nanotubes, silver nanowires, graphene, or carbon nanotubes and silver nanowires combined in a ratio of 1:2 to 1:5. In this application, the conductive nanomaterial includes carbon nanotubes.

[0040] It should be noted that the resistance of carbon nanotubes changes with temperature. Therefore, under continuous light and heat, carbon nanotubes can also detect the temperature changes of yarn. Their resistance decreases as the temperature rises, unlike the local fluctuations caused by movement. By monitoring the linear change in the overall resistance of the yarn, the ambient temperature of the yarn can be determined. This allows for linkage with external auxiliary equipment to provide active cooling or temperature alerts in addition to passive cooling of the yarn, making it suitable for a wider range of applications.

[0041] In addition, the short fibers can be made of a variety of materials, including at least one of cotton, wool, nylon and polyester.

[0042] In this embodiment, the short fiber is cotton, which has a certain degree of hygroscopicity. When the air moisture content changes, the resistance of the carbon nanotube network can be adjusted by expansion / contraction, so that the yarn has the dual parameter sensing function of temperature and humidity strain. This works in synergy with the "high temperature and high humidity environment cooling stability" of the outer radiation cooling film. When the humidity increases, the cotton fiber absorbs moisture and expands, the spacing between the carbon nanotubes increases, and the change in resistance can reflect the ambient humidity.

[0043] In a specific embodiment of the present invention, the elastic core 1 is a silicone tube, and the intermediate coating layer 2 is a composite fiber assembly formed by conductive nanomaterials and short fibers. The intermediate coating layer 2 can be wrapped around the outside of the elastic core 1 in various ways, such as single-layer spiral winding, double-layer bidirectional spiral winding, double-layer unidirectional spiral winding, etc. In this embodiment, single-layer spiral winding is used, and the winding density of the intermediate coating layer 2 is 10-30 turns / cm (where the pitch is 0.33mm to 1mm and the helix angle is 30° to 60°).

[0044] The intermediate coating layer 2 comprises a composite fiber assembly formed by conductive nanomaterials and short fibers. In the intermediate coating layer 2, the mass ratio of the conductive nanomaterials to the short fibers is 1:10 to 1:100, which ensures the continuity of the conductive pathway and the flexibility of the yarn.

[0045] In this embodiment, the radiation-cooled nanofiber membrane includes either a polyamide 6 nanofiber membrane or a polyvinylidene fluoride membrane.

[0046] When the material of the radiation-cooling nanofiber membrane includes polyvinylidene fluoride (PVDF), based on the triboelectric and electrostatic induction effects, charge transfer occurs between the outer PVDF (a strongly negatively charged material) and the inner (a strongly positively charged material) layer when they come into contact and separate (e.g., under impact, friction, or vibration), generating an electric current. This can convert everyday mechanical energy (such as human movement) into electrical energy to power microelectronic devices, enabling self-powered wearable systems and achieving triboelectric nanogenerator functionality.

[0047] Similarly, polyamide 6 nanofilms can achieve the same function.

[0048] In the embodiments provided by the present invention, the thickness of the nanofiber membrane is 10μm to 200μm, the pore size is 0.1μm to 5μm, the solar reflectivity is ≥90%, and the infrared emissivity is ≥90%, thereby ensuring that the radiation-cooling nanofiber membrane can generate sufficient current, while reducing the impact on the elastic core 1 and the intermediate coating layer 2.

[0049] In addition, there are various ways to coat the nanofiber membrane 3 onto the intermediate coating layer 2, such as single-layer spiral winding coating, double-layer bidirectional spiral coating, double-layer unidirectional spiral coating, etc. In this embodiment, single-layer spiral winding coating is used.

[0050] The simultaneous installation of the radiation-cooling nanofiber membrane and the hollow structure enhances the yarn's insulation, preventing continuous high-temperature heating that could reduce cooling efficiency. Furthermore, the yarn's sides facing and away from the high-temperature environment are physically isolated, facilitating the distinction between the inner and outer sides and ensuring the accuracy of sensing and detection functions in the intermediate coating layer, such as motion deformation detection.

[0051] It should be noted that, in the embodiments provided by this invention, the three-layer composite structure can simultaneously achieve multifunctional integration of "radiative cooling + tensile sensing + mechanical elasticity". In addition to providing a cooling effect, polyvinylidene fluoride can also provide electrical energy to carbon nanotubes, enabling energy-free sensing. This facilitates the integration of passive cooling and active sensing. Furthermore, the hollow structure ensures the mechanical properties of the yarn while isolating it from temperature transfer caused by ambient temperature, thereby expanding the yarn's applicability.

[0052] Furthermore, the radiation-cooled nanofiber membrane is loaded with any one of nanoparticles, inorganic salts, or ceramic / dielectric materials. In this embodiment, the nanoparticles can achieve an antibacterial effect, and the carbon nanotube network in the intermediate layer can enhance the release of ions from the nanoparticles through a weak current, such as a μA-level current generated by triboelectric charging, further improving the antibacterial durability.

[0053] Specifically, the nanoparticles include any one of TiO2, Al2O3, ZnO, or ZrO2; the inorganic salt includes one of BaSO4 and CaCO3; and the ceramic / dielectric material includes one of SiO2, SiC, and Si3N4.

[0054] On the other hand, the radiation-cooling nanofiber membrane is spirally wrapped around the outer side of the intermediate coating layer; wherein, the winding angle of the radiation-cooling nanofiber membrane increases from both ends of the yarn towards the middle.

[0055] Small-angle wrapping at both ends (15-30°) enhances the structural stability of the yarn during stretching (increasing the breaking elongation by 15%), while large-angle wrapping in the middle (45-60°) reduces the pulling and wrinkling of the radiation cooling film, ensuring the film layer is flat to maintain high reflectivity (>90%). The gradient angle design improves the synchronization between the spiral structure of the middle coating layer and the deformation of the outer film, avoiding the "false strain" signal of the carbon nanotube network caused by excessive stretching of the outer film (traditional equal-angle wrapping is prone to sensing errors due to the breakage of the outer film).

[0056] In the embodiments provided by the present invention, the linearity (R²) of the sensing signal of the yarn is improved from 0.92 to 0.98 in the 50% strain cycle test, and the reflectivity of the outer film is reduced by <2% (compared to >8% for traditional equal-angle wrapping).

[0057] Based on the above-mentioned radiation-cooled composite yarn, the present invention provides a method for preparing radiation-cooled composite yarn, comprising the following steps: S10. Conductive nanomaterials and short fibers are combined to form a composite fiber assembly; S20. The composite fiber assembly is wrapped around the elastic core to form an intermediate coating layer; S30. A radiation-cooled nanofiber membrane is coated around the intermediate coating layer to form an outer layer.

[0058] Specifically, the conductive nanomaterial includes carbon nanotubes, and the short fibers include cotton; Step S10 includes: S11. The carbon nanotube solution is mixed with water and ultrasonically treated to obtain a nanotube dispersion; S12. Soak the carbon nanotube-supported cotton in sodium hydroxide solution and then remove it; The concentration of the sodium hydroxide solution is 0.4% to 2%, and the soaking time is 60 min to 120 min, in order to ensure the subsequent carbon nanotube loading efficiency.

[0059] S13. The carbon nanotube-supported cotton that has been soaked in the sodium hydroxide solution is immersed in the carbon nanotube dispersion and dried to obtain the composite fiber aggregate.

[0060] Based on the above-mentioned radiation-cooling composite yarn, the present invention also provides a fabric that includes all the technical features of the above-mentioned radiation-cooling composite yarn, and therefore also has the technical effects brought about by all the above-mentioned technical features, which will not be described in detail here.

[0061] Based on the aforementioned radiation-cooled composite yarn, this invention provides a specific embodiment.

[0062] In Example 1, radiation-cooled carbon nanotube yarn was prepared using a friction spinning process.

[0063] 50g of carbon nanotubes were dispersed in 950g of deionized water and ultrasonically treated for 2 hours to obtain a uniform dispersion. The carbon nanotube-supported cotton, which had been soaked in sodium hydroxide solution, was then impregnated with the dispersion and dried. A composite yarn with silicone tube core yarn and carbon nanotube-loaded cotton body yarn was produced by friction spinning process. Radiation-cooled carbon nanotube yarns were obtained by wrapping PVDF nanofiber strips.

[0064] Please refer to Figure 3 The yarn is a radiation-cooled carbon nanotube yarn that has not been wrapped with PVDF nanofiber strips after friction spinning and has only been soaked once in a carbon nanotube dispersion with a concentration of 0.15%.

[0065] Please see Figure 4 It is a radiation-cooled carbon nanotube yarn that has been repeatedly soaked in a carbon nanotube dispersion with a concentration of 0.15% and has not been wrapped with PVDF nanofiber strips.

[0066] Please see Figures 5 to 8 This invention provides the effect of unit resistance change and stress-strain images of radiation-cooled carbon nanotube yarn under different experimental conditions.

[0067] The radiation-cooled carbon nanotube yarn, formed by core-yarn wrapping, has a linear density of 150-300 tex, a breaking strength ≥1.5 cN / dtex, a breaking elongation of 10%-25%, a core diameter of 7-400 μm, a sheath diameter of 50-800 μm, an electrical conductivity ≥100 S / cm, and a thermal conductivity ≥200 W / (m*K). The density of the radiation-cooled yarn is 0.7-1.8 g / cm³. 3 The overall porosity is 40%-60%.

[0068] The above are merely preferred embodiments of the present invention and do not limit the scope of the patent. Any equivalent structural or procedural transformations made based on the description and drawings of the present invention, or direct or indirect applications in other related technical fields, are similarly included within the scope of patent protection of the present invention.

Claims

1. A radiation-cooled composite yarn, characterized in that, include: Flexible core; An intermediate coating layer covers the outside of the elastic core; as well as, The outer layer, which covers the intermediate coating layer, includes a radiation-cooled nanofiber membrane.

2. The radiation-cooled composite yarn according to claim 1, characterized in that, The elastic core is hollow, forming a heat-insulating space.

3. The radiation-cooled composite yarn according to claim 1, characterized in that, The intermediate coating layer is spirally wrapped around the elastic core; The intermediate coating layer comprises a fiber aggregate formed of conductive nanomaterials and short fibers.

4. The radiation-cooled composite yarn according to claim 3, characterized in that, The conductive nanomaterials include carbon nanotubes; and / or, The short fibers include at least one of cotton, wool, nylon, and polyester.

5. The radiation-cooled composite yarn according to claim 1, characterized in that, The radiation-cooled nanofiber membrane includes either a polyamide 6 nanofiber membrane or a polyvinylidene fluoride membrane.

6. The radiation-cooled composite yarn according to claim 5, characterized in that, The radiation-cooled nanofiber membrane is loaded with any one of nanoparticles, inorganic salts, or ceramic / dielectric materials.

7. The radiation-cooled composite yarn according to claim 6, characterized in that, When the radiation-cooled nanofiber membrane is loaded with nanoparticles, the nanoparticles include any one of TiO2, Al2O3, ZnO or ZrO2; When the radiation-cooled nanofiber membrane is loaded with inorganic salts, the inorganic salts include one of BaSO4 and CaCO3; When the radiation-cooled nanofiber membrane is loaded with ceramic / dielectric material, the ceramic / dielectric material includes one of SiO2, SiC, and Si3N4.

8. The radiation-cooled composite yarn according to claim 1, characterized in that, The radiation-cooling nanofiber membrane is spirally wrapped around the intermediate coating layer; The winding angle of the radiation-cooled nanofiber membrane increases from both ends of the yarn toward the middle.

9. A method for preparing a radiation-cooled composite yarn, used to prepare the radiation-cooled composite yarn according to any one of claims 1 to 4, characterized in that, Includes the following steps: Conductive nanomaterials are combined with short fibers to form composite fiber assemblies; The composite fiber assembly is wrapped around the elastic tube core to form an intermediate coating layer; A radiation-cooled nanofiber membrane is coated around the intermediate coating layer to form an outer layer.

10. The method for preparing radiation-cooled composite yarn according to claim 9, characterized in that, The conductive nanomaterial includes carbon nanotubes, and the short fibers include cotton. The step of forming a composite fiber assembly from conductive nanomaterials and short fibers includes: A carbon nanotube solution was mixed with water and ultrasonically treated to obtain a nanotube dispersion. The carbon nanotube-supported cotton was soaked in a sodium hydroxide solution and then removed. The carbon nanotube-loaded cotton, which had been soaked in the sodium hydroxide solution, was immersed in the carbon nanotube dispersion and dried to obtain the composite fiber aggregate.

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