Janus knitted fabric with radiation refrigeration and one-way moisture conduction functions as well as preparation method and application of Janus knitted fabric

Abstract

The invention provides a method for directionally constructing a micro-nano porous structure between fibers of a fabric so as to enhance the radiation cooling performance of the cotton fabric. In particular to a Janus knitted fabric with radiation refrigeration and one-way moisture conduction functions and a preparation method and application thereof, the front side of the Janus knitted fabric is hydrophilic cotton yarns, and the back side of the Janus knitted fabric is synthetic fibers; after weaving is completed, the reverse side of the Janus knitted fabric is coated with a polymer solution containing inorganic micro-nano particles, and the distance gt of the synthetic fibers is regulated and controlled; the diameter of the inorganic micro-nano particles and the spacing of the synthetic fibers are gt The polymer solution is directionally distributed to the cotton yarn layer due to the spacing of the hydrophilic cotton fibers, and then a micro-nano porous structure is formed among the cotton fibers through non-solvent induced phase separation. According to the Janus knitted fabric prepared by the invention, a micro-nano porous structure is formed in situ between cotton fibers, the surface texture and macrostructure characteristics of the fabric are not influenced, the original hand feeling and hydrophilicity of the fabric are kept, and the Janus knitted fabric has an excellent radiation cooling function.

Description

Technical Field

[0001] This invention belongs to the field of functional fabrics, and specifically relates to a Janus knitted fabric with radiative cooling and unidirectional moisture-wicking functions, its preparation method, and its application. Background Technology

[0002] Passive radiation cooling coated textiles are mainly produced by dipping, spraying and other methods on the basis of existing textiles. The coating often completely covers the structure and texture of the fabric itself, losing the original style, breathability and softness of the fabric.

[0003] Janus structural materials have shown unique advantages in the field of smart textiles due to their asymmetric functional design. By constructing hydrophilic / hydrophobic double-sided structures, they can achieve targeted sweat management. However, few studies have utilized the unidirectional moisture-wicking effect to regulate the morphology and structure of coatings.

[0004] CN202510747206.9 discloses a Janus cotton fabric with radiation cooling and antibacterial functions and its preparation method. The method involves growing a biomimetic silica nanosheath layer in situ on the surface of cotton fibers using a controllable sol-gel method, introducing high-refractive-index nanoparticles to construct a dual-scale photonic crystal structure, utilizing the plasma resonance effect to enhance solar spectrum reflection, and using biomacromolecule self-assembly technology to modify the hydrophilic interface to form a superhydrophilic antibacterial layer. A superhydrophobic interface is then constructed on one side of the fabric through precise spraying, ultimately forming a Janus structure with an asymmetric wetting gradient.

[0005] CN202510528867.2 discloses a radiation-cooling self-cleaning coated fabric and its preparation method. TPU and PVDF are used as matrices, and nano-sized hydrophobic SiO2 particles are added to prepare SiO2@TPU / PVDF coating liquid. The coating liquid is uniformly loaded onto the fabric surface using a doctor blade coating machine to form a coated fabric that exhibits excellent radiation-cooling capability.

[0006] CN113136724A discloses a radiation cooling fabric, which is prepared by impregnating silk fabric with nano-alumina hydrosol. After drying, the nano-alumina particles are attached to the fibers. The particles with high refractive index are superimposed on the fibers to improve the fabric's reflectivity, thereby achieving a cooling effect of 3.6 ℃ lower than room temperature under sunlight.

[0007] CN117947632A discloses a fabric with humidity and heat regulation function, its preparation method and application, including the following steps: patterning a polymer template solution on the surface of a fabric substrate to obtain a patterned substrate; impregnating and curing the patterned substrate with a mixed solution including metal nanoparticles and adhesive to load the metal nanomaterials onto the surface of the patterned substrate; removing the cured pattern to obtain a fabric with humidity and heat regulation function.

[0008] The current research process for passive radiation cooling coated textiles mainly faces the following problems:

[0009] (1) The coating constructed by the scraping method accumulates on the original fabric surface. The thicker coating has completely changed the original morphology, surface properties, hand feel and other characteristics of the fabric.

[0010] (2) The coating constructed by the impregnation method is distributed indiscriminately on the surface and inner layer of the fabric. If the load is too high, it is easier for the fabric to lose its original softness, breathability and elasticity.

[0011] (3) The coating constructed by the template method requires a patterning step and the application of adhesive, which has a negative impact on the feel and style of the fabric;

[0012] (4) The coating distributed on the surface of the fabric is prone to friction with the outside world, and is easy to rub off, resulting in poor durability. Summary of the Invention

[0013] The technical problem to be solved by the present invention is to provide a Janus knitted fabric with radiative cooling and unidirectional moisture-wicking functions, as well as its preparation method and application, so as to overcome the negative impact of the coating constructed by the prior art on the surface properties and hand feel of the fabric, as well as the defects of the coating being easy to rub off and having poor durability.

[0014] This invention provides a Janus knitted fabric with radiative cooling and unidirectional moisture-wicking functions. The front side of the Janus knitted fabric is hydrophilic cotton yarn, and the reverse side is synthetic fiber. After weaving, the reverse side of the Janus knitted fabric is coated with a polymer solution containing inorganic micro-nano particles. By adjusting the spacing between synthetic fibers to be greater than the diameter of inorganic micro-nano particles and greater than the spacing between cotton fibers in the hydrophilic cotton yarn, a micro-nano porous structure is formed between the fibers of the hydrophilic cotton yarn after non-solvent-induced phase separation.

[0015] Preferably, the synthetic fiber is any one of polyester, nylon, polyethylene, and polypropylene; the spacing between the synthetic fibers is 8~15 μm.

[0016] Preferably, the polymer is any one of polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP), polyacrylonitrile (PAN), and cellulose acetate (CA).

[0017] Preferably, the inorganic micro / nanoparticles include at least one of SiO2, ZnO, and TiO2, with a diameter of 0.3~8 μm.

[0018] Preferably, the inorganic micro / nano particles in the polymer solution have a mass fraction of 3-15 wt%, and the polymer has a mass fraction of 5-15 wt%.

[0019] This invention provides a method for preparing Janus knitted fabric with radiative cooling and unidirectional moisture-wicking functions, comprising the following steps:

[0020] (1) Using hydrophilic cotton yarn as the hydrophilic front and synthetic fiber as the hydrophobic back, a knitted base fabric with opposite front and back sides is prepared by knitting;

[0021] (2) The polymer and inorganic micro / nanoparticles are uniformly dispersed in an organic solvent to obtain a polymer solution containing inorganic micro / nanoparticles;

[0022] (3) The polymer solution containing inorganic micro-nano particles obtained in step (2) is uniformly coated on the reverse side of the knitted fabric base and left to stand, so that the polymer solution diffuses and penetrates into the front side of the knitted fabric base along the capillary between the fibers, wherein the inorganic micro-nano particles are transferred to the hydrophilic cotton yarn layer as the solution penetrates.

[0023] (4) After step (3) the knitted fabric base fabric is left to stand with the reverse side facing up, it is soaked in a non-solvent coagulation bath to solidify, so that the polymer solution is separated in situ between the hydrophilic cotton yarns. After drying, a micro-nano porous structure is formed, thereby obtaining Janus knitted fabric with radiation cooling and one-way moisture-wicking functions.

[0024] Preferably, the knitting structure in step (1) is either a yarn-filled structure or an air-layer composite structure.

[0025] Preferably, the hydrophilic cotton yarn in step (1) is spun by any one of ring spinning, compact spinning, Siro spinning, or vortex spinning, and the twist coefficient of the hydrophilic cotton yarn is 3.2 to 4.0.

[0026] Preferably, the organic solvent in step (2) is at least one of N,N-dimethylformamide (DMF), dimethylacetamide (DMAc), dimethyl sulfoxide (DMSO), or acetone.

[0027] Preferably, the dispersion in step (2) is specifically carried out by magnetic stirring for 4 to 6 hours at a temperature of 50 to 70 ℃ and a stirring speed of 300 to 800 r / min.

[0028] Preferably, the amount of the mixed solution applied in step (3) is 30~100 g / m 2 The settling time is 1 to 5 minutes.

[0029] Preferably, the non-solvent coagulation bath in step (4) is at least one of deionized water or anhydrous ethanol.

[0030] Preferably, the drying temperature in step (4) is 50~80 ℃ and the time is 5~20 min.

[0031] The present invention also provides an application of the above-mentioned Janus knitted fabric with radiative cooling and unidirectional moisture-wicking functions in functional fabrics.

[0032] Preferably, the application includes, but is not limited to, outdoor clothing, sportswear, sun-protective clothing, or see-through clothing.

[0033] This invention enhances the radiative cooling performance of cotton knitted fabrics by creating micro / nano structures between fibers. Specifically, a polymer solution containing inorganic micro / nano particles is applied to the hydrophobic side of a unidirectional moisture-wicking fabric. By adjusting the fiber spacing of the fabric, ensuring that the spacing between synthetic fibers on the hydrophobic side is greater than the diameter of the inorganic micro / nano particles, and the spacing between synthetic fibers is greater than the spacing between cotton fibers in the hydrophilic cotton yarn, the liquid spreads along the fabric surface and diffuses along the fabric thickness direction. The capillary action between the fibers ensures uniform diffusion of the polymer solution. The twisting structure of the hydrophilic cotton yarn traps the inorganic micro / nano particles, preventing the polymer solution from accumulating on the fabric surface and preventing the inorganic micro / nano particles from escaping the fabric. Then, through non-solvent-induced phase separation, the polymer between the hydrophilic cotton yarns forms a micro / nano porous structure in situ.

[0034] Beneficial effects

[0035] (1) The present invention forms a micro-nano porous structure between cotton yarns, which does not cover the surface texture of the fabric, does not affect the macroscopic structure of the fabric, and maintains the original fluffy shape, hand feel and hydrophilicity of the fiber.

[0036] (2) In this invention, the porous structure is between the cotton yarn fibers and does not protrude from the fabric surface. It is not easy to come into contact with the outside world during use, and has better durability.

[0037] (3) This invention utilizes the wicking-one-way moisture-wicking effect to promote the polymer solution to penetrate from the hydrophobic bottom to the hydrophilic front, and diffuse from the inside to the outside of the cotton yarn, so as to realize the directional deposition of polymer in the fabric structure, effectively avoiding the significant increase in thickness caused by the enrichment of surface materials.

[0038] (4) The Janus knitted fabric of this invention has a maximum solar reflectance of >85% and a solar weighted average reflectance of 5%, which has excellent radiation cooling function. Attached Figure Description

[0039] Figure 1 The image shows a scanning electron microscope (SEM) image (300 μm) of Janus knitted fabric I from Example 1.

[0040] Figure 2 The images are scanning electron microscope (SEM) images of Janus knitted fabric I (left) in Example 1 and Janus knitted fabric II (right) in Comparative Example 1.

[0041] Figure 3This is a scanning electron microscope image of the cotton side of Janus knitted fabric I in Example 1.

[0042] Figure 4 This is a scanning electron microscope image of the cotton side of Janus knitted fabric II in Comparative Example 1.

[0043] Figure 5 This is a graph showing the change in optical properties of the fabric before and after the coating of polyester in Example 1. Detailed Implementation

[0044] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0045] This invention utilizes a unidirectional moisture-wicking effect to apply a coating from the hydrophobic side of the fabric. This allows a polymer solution containing inorganic micro / nano ions to be directionally transported along the fabric's thickness, controlling the directional diffusion and deposition of the solution onto the subsurface layer of the fabric's surface fibers, distributing it between the fibers. The design objectives of the polymer solution containing inorganic micro / nano ions are: 1) good phase separation and pore-forming characteristics; 2) good directional diffusion capability; and 3) targeted phase separation and pore formation. After applying the polymer solution using this method, there is no deposition on the surface fibers of the fabric, preserving the fabric's surface feel and making the coating more wear-resistant. The micro / nano coating is constructed between the fibers in the subsurface layer, enhancing the fabric's solar reflectivity. During wear, there is no polymer deposition on the surface of the skin-contact fibers, resulting in a more skin-friendly and comfortable feel.

[0046] Example 1

[0047] This embodiment provides a Janus knitted fabric with radiative cooling and one-way moisture-wicking functions, the preparation method of which includes the following steps:

[0048] (1) Preparation of knitted base fabric

[0049] An air-layer composite structure is woven using 50S compact Siro-spun cotton yarn (hydrophilic cotton yarn) and 100D / 72F polyester yarn (synthetic fiber). The upper needle plate has all needles exiting, and the polyester yarn is used to knit the reverse side of the fabric. The lower needle cylinder has all needles exiting, and the cotton yarn is used to knit the right side of the fabric. The cotton yarn is knitted into loops to connect the upper and lower needle plates. The twist coefficient of the cotton yarn is 3.2, the fiber spacing of the cotton yarn is 4~9 μm, and the fiber spacing of the polyester yarn is 10~12 μm, thus obtaining a knitted base fabric.

[0050] (2) Preparation of polymer solutions containing inorganic micro and nanoparticles

[0051] Acetone and N,N-dimethylformamide were mixed at a mass ratio of 3:7 to prepare a composite solvent. 2.0 g of polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP) (Mw~400000) and 1.6 g of mesoporous SiO2 (8 μm) were added to 40 g of the composite solvent and stirred continuously at 400 rpm / min for 2 h at room temperature to obtain a mixed solution with a polymer content of 5 wt% and an inorganic micro / nano particle content of 4 wt%.

[0052] (3) Scraping

[0053] The knitted fabric base was fixed on a coating machine, and a 200 μm coating rod was used to uniformly coat the reverse side of the knitted fabric base with the mixed solution at a certain speed. The coated knitted fabric was then immersed in water with the reverse side facing up for phase separation. After phase separation was completed in 5 minutes, the knitted fabric was removed and dried in a 60°C oven for 30 minutes to finally obtain Janus knitted fabric I based on solvent-inducing phase separation.

[0054] Comparative Example 1

[0055] Comparative Example 1 provides a Janus knitted fabric, the preparation method of which is the same as in Example 1, except that: in step (3), the mixed solution is uniformly coated on the front side (cotton side) of the knitted fabric base, and the coated knitted fabric is kept with the front side facing up and placed in water for phase separation. Janus knitted fabric II is obtained.

[0056] The Janus knitted fabric prepared above was characterized.

[0057] (1) Morphological changes and electron micrographs of Janus knitted fabrics

[0058] The morphology of Janus knitted fabric I prepared in Example 1, obtained by scraping the coating from the polyester surface (bottom surface), is as follows. Figure 1 (300 μm) Figure 2 As shown on the left, the fabric retains a clear fiber texture and original pore structure, with no polymer accumulation, maintaining the fabric's inherent breathability and skin-friendly properties; in contrast, as Figure 2 As shown on the right, the Janus knitted fabric II prepared by directly coating the cotton surface in Comparative Example 1 has a blurred surface texture and excessively filled pores, which destroys the integrity of the original structure of the fabric.

[0059] Figure 3 This shows the cotton surface morphology of Janus knitted fabric I in Example 1. After scraping the bottom layer, the surface structure of the cotton fabric is clear, with no polymer coverage. The polymer was successfully conducted from the bottom layer to the cotton layer, and a phase-separated coating was formed between the fibers, exhibiting a porous structure with a pore size ranging from 0.36 to 7.07 μm. SiO2 nanoparticles are embedded in the porous structure to form a multi-level microporous structure, enhancing light scattering and reflection properties.

[0060] Comparative Example 1: The polymer was applied directly to the cotton surface and accumulated to cover the fabric surface. Figure 4 The phase separation effect is poor, the pore density is low, which affects the appearance of the fabric and damages the fabric's breathability. Moreover, the coating floats on the fabric surface and is easily peeled off by external forces, reducing the coating's abrasion resistance and durability.

[0061] (2) Variations in the morphology of Janus knitted fabric and changes in fabric thickness as shown in electron micrographs

[0062] Table 1 shows the changes in fabric thickness before and after coating preparation. From the fabric thickness data in Table 1, it can be observed that after coating treatment using the directional induced deposition process in Example 1, the overall fabric thickness change is relatively small. In contrast, in Comparative Example 1, the coating treatment is applied directly to the cotton surface, and the polymer easily encapsulates the fibers in the cotton layer (…). Figure 4 This will cause the fabric thickness to increase even more.

[0063] Table 1. Thickness of the knitted fabric base, Janus knitted fabric I in Example 1, and Janus knitted fabric II in Comparative Example 1

[0064]

[0065] The coating utilizes the wicking-one-way moisture-wicking effect to promote the penetration of the polymer solution from the polyester bottom layer to the cotton layer, and then diffuses from the inside out in the cotton layer, achieving directional deposition of the polymer inside the fabric structure. This effectively avoids a significant increase in thickness caused by the enrichment of surface materials, and while maintaining the original structural characteristics of the fabric, it achieves the uniform construction of a radiation cooling coating in the middle of the fabric.

[0066] Experimental results show that coating from the hydrophobic side effectively guides the polymer to form a porous structure in the fiber gaps, without changing the overall fabric thickness, which is significantly superior to coating directly from the cotton surface. The coating preparation method based on the unidirectional moisture-wicking effect demonstrates good rationality and universality.

[0067] (3) Changes in the optical properties of the fabric

[0068] After coating the hydrophobic side with a polymer solution containing inorganic micro- and nano-particles, the solar reflectance of Janus knitted fabric increases by an average of 5%, with a maximum reflectance of >85% and a weighted average reflectance of 80.5%, demonstrating excellent radiative cooling capabilities.

Claims

1. A Janus knitted fabric with radiative cooling and unidirectional moisture-wicking functions, characterized in that, The Janus knitted fabric has a hydrophilic cotton yarn on the front and a synthetic fiber on the back. After weaving, the reverse side of the Janus knitted fabric is coated with a polymer solution containing inorganic micro-nano particles. By adjusting the spacing between synthetic fibers to be greater than the diameter of inorganic micro-nano particles and greater than the spacing between cotton fibers in the hydrophilic cotton yarn, a micro-nano porous structure is formed between the fibers of the hydrophilic cotton yarn after non-solvent-induced phase separation.

2. The Janus knitted fabric with radiative cooling and unidirectional moisture-wicking functions according to claim 1, characterized in that, The synthetic fiber is any one of polyester, nylon, polyethylene, and polypropylene.

3. The Janus knitted fabric with radiative cooling and unidirectional moisture-wicking functions according to claim 1, characterized in that, The polymer is any one of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, polyacrylonitrile, and cellulose acetate; the inorganic micro-nano particles include at least one of SiO2, ZnO, and TiO2; the mass fraction of inorganic micro-nano particles in the polymer solution is 3-15 wt%, and the mass fraction of the polymer is 5-15 wt%.

4. The Janus knitted fabric with radiative cooling and unidirectional moisture-wicking functions according to claim 1, characterized in that, The spacing between the synthetic fibers is 8~15 μm; the diameter of the inorganic micro / nanoparticles is 0.3~8 μm; and the twist coefficient of the hydrophilic cotton yarn is 3.2~4.

0.

5. A method for preparing Janus knitted fabric with radiative cooling and unidirectional moisture-wicking functions as described in any one of claims 1 to 4, comprising the following steps: (1) Using hydrophilic cotton yarn as the hydrophilic front and synthetic fiber as the hydrophobic back, a knitted base fabric with opposite front and back sides is prepared by knitting; (2) The polymer and inorganic micro / nanoparticles are uniformly dispersed in an organic solvent to obtain a polymer solution containing inorganic micro / nanoparticles; (3) The polymer solution containing inorganic micro-nano particles obtained in step (2) is uniformly coated on the reverse side of the knitted fabric base and left to stand; (4) After step (3) the knitted fabric base fabric is left to stand with the reverse side facing up, it is soaked in a non-solvent coagulation bath to solidify, so that the polymer solution is separated in situ between the cotton fibers of the hydrophilic cotton yarn. After drying, a micro-nano porous structure is formed, thereby obtaining Janus knitted fabric with radiation cooling and unidirectional moisture-wicking functions.

6. The preparation method according to claim 5, characterized in that, In step (1), the knitting structure can be either a yarn-filled structure or an air-layer composite structure.

7. The preparation method according to claim 5, characterized in that, The organic solvent in step (2) is at least one of N,N-dimethylformamide, dimethylacetamide, dimethyl sulfoxide, or acetone; the dispersion is specifically carried out by magnetic stirring for 4 to 6 hours at a temperature of 50 to 70 °C and a stirring speed of 300 to 800 r / min.

8. The preparation method according to claim 5, characterized in that, The amount of the mixed solution applied in step (3) is 30~100 g / m 2 The settling time is 1 to 5 minutes.

9. The preparation method according to claim 5, characterized in that, In step (4), the non-solvent coagulation bath is at least one of deionized water or anhydrous ethanol; the drying temperature is 50~80 ℃ and the time is 5~20 min.

10. The application of Janus knitted fabric with radiative cooling and unidirectional moisture-wicking functions as described in any one of claims 1 to 4 in functional fabrics.

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