Porous skin-core fiber as well as preparation method and application thereof

Abstract

The invention relates to the technical field of functional fiber material preparation, in particular to a porous skin-core fiber and a fiber microfluid phase separation preparation method and application thereof. According to the method, the fiber is used as a substrate, the fiber is infiltrated in a microfluidic channel filled with a polymer solution which has strong interaction with the fiber and is drawn out, and the anti-Rayleigh instability uniform coating of the surface of the solution microfluidic fiber substrate is realized by utilizing the phenomena of swelling and dissolving of the polymer solution on the fiber substrate and the like. Then, anti-solvent phase separation of the rapidly combined polymer solution is carried out, rapid curing of the microfluid coating is achieved, a porous skin layer structure is formed through phase separation, and finally the porous skin-core structure fiber is prepared. In addition, the skin layer has a neural network-like porous structure with high surface roughness, and the structure has potential application in the fields of friction power generation, sensing, heat insulation and the like. The method generally has the advantages of low cost, easiness in continuous large-scale production, high expansibility and the like, and has a wide application prospect.

Description

Technical Field

[0001] This invention relates to a porous core-sheath fiber, its preparation method, and its application, belonging to the field of functional fiber material preparation technology. Background Technology

[0002] The high performance and functionalization of fibers are the core directions of fiber material development and have significant economic implications for the high-performance fiber material industry. Coating modification of fiber surfaces is the main approach to achieving this goal. However, microfluidic coating manipulation and surface micro / nano fabrication based on fiber substrates face numerous challenges. Microfluidics involves the precise manipulation of small-volume fluids. In the microfluidic process on a one-dimensional fiber surface, a uniform microfluidic film tends to form droplets to minimize its surface energy; this is known as Rayleigh instability. Due to the inhibitory effect of viscosity on fluid dynamics, spinning methods such as melt spinning, which target high-viscosity fluids or melts, can avoid this problem. However, fluid coating, electrospinning, and microfluidic spinning often only allow the use of low-viscosity fluids, making Rayleigh instability difficult to avoid. The resulting fiber with a non-uniform coating exhibiting a periodic spindle structure after curing. However, for functional fibers used in separation, filtration, and thermal insulation applications, their surfaces must have a uniform and continuous functional coating. This means that eliminating the Rayleigh instability of the microfluidic coating on the fiber surface and efficiently converting microfluidics into functional micro / nano structures are crucial challenges that must be overcome in the preparation of functional fibers. At the same time, the coating and fiber substrate usually exhibit weak interfacial interaction, which is another major obstacle limiting the development of functional fibers.

[0003] Previous studies have employed methods to overcome Rayleigh instability in one-dimensional microfluidic spinning. For instance, spatial confinement has proven to be an effective strategy for suppressing Rayleigh instability. However, this suppression is limited to the interior of a finite space. Furthermore, patent CN111534871A proposes a dual-parallel fiber strategy, which effectively reduces the driving force of Rayleigh instability—the Laplace pressure difference—by utilizing the equivalent asymmetry generated by the coated microfluidic using parallel cylindrical fibers, thereby eliminating the Rayleigh instability effect. However, it's important to note that this anti-Rayleigh instability strategy requires a dual-fiber parallel arrangement, which is not applicable to single-fiber applications. Therefore, there is an urgent need to develop a more versatile and economical anti-Rayleigh instability coating strategy for functional coatings on single-fiber surfaces to achieve large-scale controllable preparation and functionalization of core-sheath fibers. Additionally, existing fiber functionalization techniques, such as solution wet spinning combined with phase separation, while capable of producing porous functional fibers, generate numerous structural defects due to their porous structure, making it difficult to balance fiber functionalization and fundamental mechanical properties. This significantly limits the practical large-scale application of functionalized fibers. Therefore, it is essential to develop new processing technologies that can balance functionality and mechanical properties. Summary of the Invention

[0004] The purpose of this invention is to provide a high-strength, high-toughness, multifunctional porous core-sheath fiber and its continuous and large-scale preparation method, so as to solve the two major problems of high-performance fiber processing and functional processing, including the problem of anti-Rayleigh instability of surface low-viscosity fluid coating, and the inherent contradiction between functionalization and mechanical properties.

[0005] The first technical problem solved by this invention is to develop a core-sheath fiber processing and preparation technology based on a combination of multi-level microfluidics and antisolvent phase separation to address anti-Rayleigh instability.

[0006] The first objective of this invention is to provide a method for preparing porous core-sheath fibers, comprising the following steps:

[0007] S1: Core layer polymer A is prepared by melt spinning as core layer fiber substrate to obtain core layer fiber A. The fiber diameter of core layer fiber A is optimized to be 50-300 μm.

[0008] S2: The core fiber A passes through a secondary microfluidic channel composed of inner and outer coaxial composite layers. The inner microfluidic channel is filled with a continuously supplied solution of the skin polymer B, and the outer microfluidic channel is filled with a continuously supplied antisolvent of the skin polymer B. Through the solid-liquid adhesion and pulling motion of the skin polymer B solution on the surface of the core fiber A, a uniform and controllable skin polymer B solution coating is obtained on the core fiber A substrate. The thickness of this solution coating is optimized to be 1-500 μm.

[0009] S3: The core fiber A coated with the solution of the skin polymer B is rapidly immersed in the second-stage outer microchannel under the external pulling action, that is, the antisolvent bath of the skin polymer B, which induces the solution phase separation of the fluid coating layer on the fiber surface.

[0010] S4: After phase separation, the fibers are heated, dried, and collected to obtain high-strength and tough core-sheath fibers with a porous coating similar to a neural network.

[0011] Using the above technical solution, the secondary microfluidic channel of the present invention consists of two coaxial layers, inner and outer. The inner microchannel of the second stage is filled with a solution of the skin polymer B and connected to a solution pump to ensure a continuous supply of polymer solution. The outer microchannel of the second stage is filled with the antisolvent of the skin polymer B to ensure that the fibers coated with the microfluidic material rapidly undergo phase separation, suppressing Rayleigh instability.

[0012] Preferably, the core polymer A and the skin polymer B can be dissolved in the same solvent, but their molecular chain chemical structures can be the same or different, but preferably the molecular chains have the same chemical structure.

[0013] Preferably, the core polymer A is polyvinylidene fluoride, polymethyl methacrylate, polyacrylonitrile, polyurethane, polyimide, polyvinyl alcohol, or polyvinyl acetate, and the skin polymer B is polyvinylidene fluoride, polymethyl methacrylate, polyacrylonitrile, polyurethane, polyimide, polyvinyl alcohol, or polyvinyl acetate.

[0014] Preferably, the concentration of the skin polymer B is 5wt%-30wt%, and the antisolvent is one or more of saturated sodium chloride aqueous solution, ethanol, and deionized water.

[0015] Preferably, in step S2, the horizontal traction rate of the core fiber A being drawn out of the microchannel is 0.1-1000 cm / s, preferably 1-10 cm / s, the surface temperature of the core fiber A is 10-300℃, the antisolvent phase separation time is 3-60 s, preferably 5-15 s, and the temperature of the antisolvent is 25-80℃.

[0016] Preferably, in step S4, the drying temperature is 60-150℃, the air pressure is between 10Pa and 101kPa, and the drying time is 10-600s.

[0017] The second technical problem solved by this invention is to design and prepare a porous core-sheath fiber, which realizes the micro-nano porous fabrication and functionalization of the sheath structure on the fiber surface, while significantly improving the core-sheath interface strength and the mechanical toughness of the fiber.

[0018] A second objective of this invention is to provide a porous core-sheath fiber prepared by the above method, comprising a sheath and a core, wherein the surface of the core is covered with a sheath, the sheath is a porous structure resembling a neural network, the core is a solid non-porous structure, and there is a fully fused interface transition layer between the sheath and the core, so as to achieve significantly enhanced core-sheath interface interaction and tensile elongation at break.

[0019] Preferably, after the outer layer is peeled off, the surface of the core fiber A has coral island-like protrusions and a surface roughness of 30-100 nm.

[0020] Preferably, the tensile strength and elongation at break of the high-strength core fiber of the neural network porous coating are significantly improved compared with the original core substrate fiber.

[0021] Using the above technical solution, the core polymer A and the skin polymer B of the present invention can be the same polymer with the same or different molecular weights and distributions, but the same chemical structure; or, they can be two polymers that can be dissolved in the same solvent and have strong interactions; wherein, the core polymer A and the skin polymer B are preferably at least one of polyvinylidene fluoride (PVDF), polymethyl methacrylate (PMMA), polyacrylonitrile (PAN), polyurethane (PU), polyimide (PI), polyethylene oxide (PEO), polyacrylic acid (PAA), polyvinyl alcohol (PVA), and polyvinyl acetate (PVAc).

[0022] The third objective of this invention is to provide the application of the above-mentioned porous core-sheath fiber in high-performance triboelectric signal output, wherein the triboelectric power generation output voltage reaches more than 80V, which is more than twice that of the original core fiber.

[0023] A fourth objective of this invention is to provide the application of the aforementioned porous core-sheath fiber in thermal insulation fabrics, wherein the thermal conductivity of the fabric is 0.025-0.045 W(m·K). -1 It is far lower than that of traditional fiber comparison samples.

[0024] The beneficial effects of this invention are:

[0025] (1) The porous core-sheath fiber prepared by the present invention has both excellent mechanical properties and the functionality of the sheath, and can realize the multi-scenario application of the core-sheath fiber.

[0026] (2) The microfluidic phase separation control technology on the fiber surface used in this invention has the advantages of high controllability, strong scalability, flexible design, wide applicability, and simple and easy-to-scale method, and is expected to realize the large-scale preparation of functional fibers with different types of core-sheath structure.

[0027] (3) The biomimetic core-sheath structure fiber and its fiber microfluidic phase separation preparation technology disclosed in this invention have achieved a significant improvement in the interface and mechanical properties of the core-sheath fiber, providing a universal solution for the design and preparation of high-strength and tough core-sheath fibers. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the process for preparing porous core-sheath fibers using the homogeneous fiber microfluidic phase separation technology described in Examples 1, 2, 5, and 6 of the present invention.

[0029] Figure 2 This is a schematic diagram of the structure of the two-stage microfluidic channel described in Embodiment 1 of the present invention.

[0030] Figure 3Optical images of the typical homogeneous fiber microfluidic phase separation technology used in Examples 1, 2, and Comparative Examples 1 and 2 of this invention to prepare porous core-sheath fibers resistant to Rayleigh instability and their comparative examples.

[0031] Figure 4 Optical images of porous core-sheath fibers resistant to Rayleigh instability prepared using typical homogeneous fiber microfluidic phase separation technology obtained with different solution concentrations in Example 1 of this invention.

[0032] Figure 5 Optical images of porous core-sheath fibers resistant to Rayleigh instability prepared using typical homogeneous fiber microfluidic phase separation technology obtained at different solution temperatures in Example 1 of this invention.

[0033] Figure 6 Optical images of porous core-sheath fibers resistant to Rayleigh instability prepared using typical homogeneous fiber microfluidic phase separation technology obtained at different fiber stretching rates in Example 1 of this invention.

[0034] Figure 7 These are scanning electron microscope (SEM) images of the surface and cross-section of typical porous core-sheath fibers and their comparative samples prepared in Example 1 and Comparative Example 1 of the present invention.

[0035] Figure 8 These are typical porous core-sheath fiber optical images, SEM images, and stress-strain curves prepared in Examples 5 and 6 of this invention.

[0036] Figure 9 These are optical and SEM microscopic images of the porous spindle fiber controlled by Rayleigh instability prepared in Comparative Example 4 of this invention.

[0037] Figure 10 The image shows the Rayleigh instability-resistant porous core-sheath fiber prepared in Example 3 of this invention and its application in biosignal sensing.

[0038] Figure 11 The porous core-sheath fiber with Rayleigh instability prepared in Example 4 of this invention is applied to thermal insulation fabric. Detailed Implementation

[0039] In order to make the technical means, creative features, objectives and effects achieved by the present invention easier to understand, the present invention is further described below in conjunction with specific implementation methods.

[0040] In the examples and comparative examples, polyvinylidene fluoride (PVDF) was purchased from Arkema (Shanghai) Chemical Co., Ltd., brand name: HSV900; polymethyl methacrylate (PMMA) was purchased from Maclean Biotech Co., Ltd., brand name: P775996; polyvinyl acetate (PVAc) was purchased from Maclean Biotech Co., Ltd., brand name: PB23413; polyurethane (TPU) was purchased from BASF, brand name: 1185A; and the good solvent N,N-dimethylformamide (DMF) was purchased from Sinopharm Group (Shanghai) Co., Ltd.

[0041] Example 1

[0042] (1) PVDF fibers with a diameter of 100 μm were prepared as the core layer under the processing conditions of a twin-screw extruder with a rotation speed of 2 rpm / s and a traction rate of 20 cm / s.

[0043] (2) Prepare a homogeneous PVDF solution using DMF as solvent, wherein the mass fraction of PVDF is 10 wt%;

[0044] (3) Fix one end of the PVDF fiber obtained in step (1) onto the winding and collecting roller, and then inject the PVDF solution obtained in step (2) into the microfluidic channel of the PVDF solution. Control the traction speed of the PVDF core fiber to 2.5 cm / s through the winding and collecting roller device, so that it is drawn out of the PVDF solution at a uniform speed and smoothly, and quickly enters the outer microfluidic channel filled with antisolvent. Then continue to carry out subsequent phase separation in a 25℃ deionized water bath for 1 min.

[0045] (4) The fiber obtained in step (3) is pulled forward and dried with an infrared lamp for 30 seconds to obtain porous core-sheath fiber NSF-100.

[0046] refer to Figure 2 This two-stage microfluidic channel consists of inner and outer stages. The inner channel is filled with a solution of the skin polymer B and connected to a solution pump to ensure a continuous supply of polymer solution. The outer channel is filled with the antisolvent of the skin polymer B to ensure that the microfluidically coated fibers immediately enter the phase separation tank and react with the antisolvent; Figure 2 It can be seen that the structural design of the two-stage microfluidic channel provides a key control method for the rapid solidification of phase-separated surfaces.

[0047] refer to Figure 4 As the temperature of the microfluidic solution increases, the time for Rayleigh instability to occur is delayed.

[0048] refer to Figure 5As the concentration of the microfluidic solution increases and the fiber traction rate decreases, the time of Rayleigh instability is delayed. The above provides a reference technical standard for the preparation of core-sheath fibers by homogeneous microfluidic phase separation.

[0049] refer to Figure 6 The homogeneous structure design gives the core-skin interface strong mechanical anchoring, resulting in interfacial interdiffusion and co-crystallization.

[0050] Example 2

[0051] (1) PVDF fibers with a diameter of 300 μm were prepared under the processing conditions of a twin-screw extruder with a rotation speed of 2 rpm / s and a traction rate of 10 cm / s.

[0052] (2) PVDF fibers with a diameter of 100 μm were prepared as the core layer under the processing conditions of a twin-screw extruder with a rotation speed of 2 rpm / s and a traction rate of 20 cm / s.

[0053] (3) Prepare a homogeneous PVDF solution using DMF as solvent, wherein the mass fraction of PVDF is 10 wt%;

[0054] (4) Fix one end of the PVDF fiber obtained in step (1) onto the winding and collecting roller, and then inject the PVDF solution obtained in step (2) into the inner microfluidic channel of the PVDF solution. Control the traction speed of the PVDF core fiber to 2.5 cm / s through the winding and collecting roller device, so that it is drawn out of the PVDF solution at a uniform speed and smoothly, and quickly enters the outer microfluidic channel filled with antisolvent. Then continue to carry out subsequent phase separation in a 25°C deionized water bath for 1 min.

[0055] (5) The fiber obtained in step (3) is further pulled forward and dried with an infrared lamp for 30 seconds to obtain porous core-sheath fiber NSF-300.

[0056] Example 3

[0057] (1) The porous core-sheath fiber with anti-Rayleigh instability prepared in Example 1 was woven into a fabric of 2cm×2cm.

[0058] (2) Nitrile rubber and the Rayleigh instability resistant porous core fiber obtained in step (1) are used as the positive and negative electrode materials of the nano-triboelectric generator, respectively, and a copper sheet with a measurement size of 2×2cm is attached to each of them to establish a connection with the electricity meter.

[0059] (3) Fix the nano-triboelectric generator obtained in step (2) onto human skin, and output different voltage signal values ​​through the pressure generated by different human movements.

[0060] Depend on Figure 9It is known that porous core-sheath fibers resistant to Rayleigh instability have excellent electrical output performance and can accurately output different signals according to different human body movements.

[0061] Example 4

[0062] (1) The porous core-sheath fiber with anti-Rayleigh instability prepared in Example 1 was woven into a fabric of 2cm×2cm.

[0063] (2) Place the core-sheath fiber fabric obtained in step (1) on a constant temperature heating table, the temperature of which is set to 40°C.

[0064] (3) After the fabric obtained in step (1) is placed on the hot table for 60 seconds, a thermal image is taken by a thermal imager at a working distance of 40 cm to characterize its thermal insulation performance.

[0065] Depend on Figure 9 It can be seen that porous core-sheath fibers with Rayleigh instability resistance have better thermal insulation performance than commercial wool.

[0066] Example 5

[0067] (1) TPU fibers with a diameter of 100 μm were prepared under the processing conditions of a twin-screw extruder with a rotation speed of 20 rpm / s and a traction rate of 10 cm / s.

[0068] (2) Prepare a homogeneous TPU solution with DMF as solvent, wherein the mass fraction of TPU is 20 wt%;

[0069] (3) Fix one end of the TPU fiber obtained in step (1) onto the winding and collecting roller, and then inject the TPU solution obtained in step (2) into the inner microfluidic channel. Using a traction winding device, the TPU fiber is uniformly and smoothly extracted from the TPU solution along the axial direction of the TPU fiber at a traction rate of 2.5 cm / s, and TPU fiber coated with a microfluidic coating of a TPU solution with a mass fraction of 20 wt% is obtained.

[0070] (4) The TPU fibers coated with a microfluidic liquid film of a TPU solution with a mass fraction of 20 wt% obtained in step (3) are further pulled forward and enter the outer microfluidic channel filled with antisolvent. Phase separation is carried out in deionized water at 25°C for 1 min to form a porous coating.

[0071] (5) The fiber obtained in step (4) is pulled forward and dried with an infrared lamp for 30 seconds to obtain porous core-sheath fiber TPU@TPU-100.

[0072] Example 6

[0073] (1) PVAc fibers with a diameter of 100 μm were prepared under the processing conditions of a twin-screw extruder with a rotation speed of 20 rpm / s and a traction rate of 8.4 cm / s.

[0074] (2) Prepare a homogeneous PVAc solution with DMF as solvent, wherein the mass fraction of PVAc is 30 wt%;

[0075] (3) Fix one end of the PVAc fiber obtained in step (1) onto the winding and collecting roller, and then inject the PVAc solution obtained in step (2) into the inner microfluidic channel. Using a traction winding device, the PVAc fiber is uniformly and smoothly extracted from the PVAc solution at a traction rate of 2.5 cm / s along the axial direction of the PVAc fiber to obtain the PVAc fiber coated with a microfluidic coating of a PVAc solution with a mass fraction of 30 wt%.

[0076] (4) The PVAc fiber coated with a microfluidic liquid film of a PVAc solution with a mass fraction of 30wt% obtained in step (3) is further pulled forward and enters the outer microfluidic channel filled with antisolvent. Phase separation is carried out in deionized water at 25℃ for 1 min to form a porous coating.

[0077] (5) The fiber obtained in step (4) is pulled forward and dried with an infrared lamp for 30 seconds to obtain porous core-sheath fiber PVAc@PVAc-100.

[0078] Comparative Example 1

[0079] (1) Prepare a homogeneous solution of polyvinylidene fluoride (PVDF) in N,N-dimethylformamide (DMF) as solvent, wherein the mass fraction of PVDF is 10 wt%.

[0080] (2) Fix one end of a nylon fiber with a diameter of 100 μm on a winding and collecting roller, and then inject a PVDF solution with a mass fraction of 10 wt% obtained in step (1) into a microfluidic channel. The nylon fiber is uniformly and smoothly extracted from the PVDF solution at a stretching rate of 2.5 cm / s by a traction winding device to obtain a nylon fiber coated with a microfluidic liquid film of a PVDF solution with a mass fraction of 10 wt%.

[0081] (3) The nylon fiber coated with a microfluidic liquid film of a PVDF solution with a mass fraction of 10 wt% obtained in step (2) is stretched forward and entered into a water bath phase separation tank. Phase separation is carried out in deionized water at 25°C for 1 min to form a porous coating.

[0082] (4) The coated fiber obtained in step (3) is further pulled forward and dried with an infrared lamp for 30 seconds to obtain porous spindle fiber PVDF@Nlyon-100.

[0083] Comparative Example 2

[0084] (1) Prepare a homogeneous solution of polyvinylidene fluoride (PVDF) in N,N-dimethylformamide (DMF) as solvent, wherein the mass fraction of PVDF is 10 wt%.

[0085] (2) Fix one end of a nylon fiber with a diameter of 300 μm on a winding and collecting roller, and then inject a PVDF solution with a mass fraction of 10 wt% obtained in step (1) into a microfluidic channel. The nylon fiber is uniformly and smoothly extracted from the PVDF solution at a stretching rate of 2.5 cm / s by a traction winding device to obtain a nylon fiber coated with a microfluidic liquid film of a PVDF solution with a mass fraction of 10 wt%.

[0086] (3) The nylon fiber coated with a microfluidic liquid film of a PVDF solution with a mass fraction of 10 wt% obtained in step (2) is stretched forward and entered into a water bath phase separation tank. Phase separation is carried out in deionized water at 25°C for 1 min to form a porous coating.

[0087] (4) The coated fiber obtained in step (3) is further pulled forward and dried with an infrared lamp for 30 seconds to obtain porous spindle core fiber PVDF@Nlyon-300.

[0088] Comparative Example 3

[0089] (1) Prepare a homogeneous solution of polymethyl methacrylate (PMMA) in N,N-dimethylformamide (DMF) solvent, wherein the mass fraction of PMMA is 15 wt%;

[0090] (2) Fix one end of a nylon fiber with a diameter of 100 μm on a winding and collecting roller, and then inject a PMMA solution with a mass fraction of 15 wt% obtained in step (1) into a microfluidic channel. The nylon fiber is then uniformly and smoothly extracted from the PMMA solution at a stretching rate of 2.5 cm / s along the axial direction of the nylon fiber by a traction winding device, so as to obtain a nylon fiber coated with a microfluidic liquid film of a PMMA solution with a mass fraction of 15 wt%.

[0091] (3) The nylon fiber coated with a microfluidic liquid film of PMMA solution with a mass fraction of 15 wt% obtained in step (2) is stretched forward and entered into a phase separation tank. Phase separation is carried out in deionized water at 25°C for 1 min to form a porous coating.

[0092] (4) The coated fiber obtained in step (3) is further pulled forward and dried with an infrared lamp for 30 seconds to obtain porous spindle core fiber PMMA@Nylon-100.

[0093] Comparative Example 4

[0094] PVDF fibers with a diameter of 100 μm were prepared under the processing conditions of a twin-screw extruder with a rotation speed of 2 rpm / s and a traction rate of 20 cm / s.

[0095] refer to Figure 8 Homogeneous structural design cannot completely overcome Rayleigh instability. It needs to work together with two-stage microchannels to achieve the preparation of porous uniform coated fibers that resist Rayleigh instability.

[0096] Comparative Example 5

[0097] PVDF fibers with a diameter of 300 μm were prepared under the processing conditions of a twin-screw extruder with a rotation speed of 2 rpm / s and a traction rate of 10 cm / s.

[0098] Comparative Example 6

[0099] (1) PVDF fibers with a diameter of 100 μm were prepared under the processing conditions of a twin-screw extruder with a rotation speed of 2 rpm / s and a traction rate of 20 cm / s.

[0100] (2) Prepare a homogeneous PVDF solution with DMF as solvent, wherein the mass fraction of PVDF is 10 wt%;

[0101] (3) Fix one end of the PVDF fiber obtained in step (1) onto the winding and collecting roller, and then use a traction winding device to uniformly and smoothly extract the PVDF fiber from the PVDF solution at a traction rate of 2.5 cm / s to obtain PVDF fiber coated with a microfluidic coating of a PVDF solution with a mass fraction of 10 wt%.

[0102] (4) The PVDF fiber coated with the periodic spindle knot microfluidic obtained in step (3) is further pulled forward and subjected to phase separation in deionized water at 25°C for 1 minute to form a porous spindle knot.

[0103] (5) The fiber obtained in step (4) is further pulled forward and dried with an infrared lamp for 30 seconds to obtain porous spindle core fiber PVDF@PVDF-100.

[0104] Test Example 1

[0105] Optical images of the products obtained in Example 1, Example 2, Comparative Example 1, and Comparative Example 2 were compared. Figure 3 It is known that the structural design of homogeneous fibers greatly delays the time of instability of the microfluidic liquid film, providing a sufficiently long processing window for the phase separation and solidification process.

[0106] Test Example 2

[0107] The typical porous core-sheath fibers prepared in Examples 5 and 6 were compared using optical images, SEM images, and their stress-strain curves. Figure 7 It can be seen that the homogeneous fiber microfluidic phase separation technology has good scalability and enhances mechanical properties for different systems.

[0108] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or basic characteristics. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

[0109] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A porous core-sheath fiber and its preparation method, characterized in that, Includes the following steps: S1: Core layer polymer A is prepared by melt spinning as core layer fiber substrate to obtain core layer fiber A, wherein the fiber diameter of core layer fiber A is 50-300μm; S2: The core fiber A passes through a secondary microfluidic channel composed of inner and outer coaxial composite layers. The inner microfluidic channel is filled with a continuously supplied solution of the skin polymer B, and the outer microfluidic channel is filled with a continuously supplied antisolvent of the skin polymer B. A uniform and controllable skin polymer B solution coating with a thickness of 1-500 μm is obtained on the core fiber A substrate. S3: The core fiber A coated with the solution of the skin polymer B is rapidly immersed in the second-stage outer microchannel under the external pulling action, that is, the antisolvent bath of the skin polymer B, which induces the solution phase separation of the fluid coating layer on the fiber surface. S4: After phase separation, the fibers are heated, dried, and collected to obtain high-strength and tough core-sheath fibers with a porous coating similar to a neural network.

2. The method for preparing porous core-sheath fiber as described in claim 1, characterized in that, The core polymer A and the skin polymer B are dissolved in the same solvent, and their molecular chain chemical structures may be the same or different.

3. The method for preparing porous core-sheath fiber as described in claim 1, characterized in that, The core polymer A is polyvinylidene fluoride, polymethyl methacrylate, polyacrylonitrile, polyurethane, polyimide, polyvinyl alcohol, or polyvinyl acetate, and the skin polymer B is polyvinylidene fluoride, polymethyl methacrylate, polyacrylonitrile, polyurethane, polyimide, polyvinyl alcohol, or polyvinyl acetate.

4. The method for preparing porous core-sheath fiber as described in claim 1, characterized in that, The concentration of the skin polymer B is 5wt%-30wt%, and the antisolvent is one or more of saturated sodium chloride aqueous solution, ethanol, and deionized water.

5. The method for preparing porous core-sheath fiber as described in claim 1, characterized in that, In step S2, the horizontal traction rate of the core fiber A being extracted from the microchannel is 0.1-1000 cm / s, the surface temperature of the core fiber A is 10-300℃, the antisolvent phase separation time is 3-60 s, and the temperature of the antisolvent is 25-80℃.

6. The method for preparing porous core-sheath fiber as described in claim 1, characterized in that, In step S4, the drying temperature is 60-150℃, the air pressure is between 10Pa and 101kPa, and the drying time is 10-600s.

7. The method for preparing porous core-sheath fiber as described in claim 1, characterized in that, The high-strength, high-toughness core-sheath fibers of the neural network-like porous coating have an average pore size of 0.01-3 μm.

8. A porous core-sheath fiber prepared by the method according to any one of claims 1-7, characterized in that, It includes a cortex and a core layer. The cortex is a porous structure similar to a neural network, and the core layer is a solid, non-porous structure. There is a fully integrated interface transition layer between the cortex and the core layer.

9. The application of the porous core-sheath fiber as described in claim 8 in high-performance triboelectric signal output, characterized in that, The output voltage of the triboelectric generator reaches over 80V.

10. The application of the porous core-sheath fiber as described in claim 8 in thermal insulation fabrics, characterized in that, The thermal conductivity of the fabric is 0.025-0.045 W / (m·K). -1 .

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