阅读说明：本技术 弹性皮芯纤维及其制备方法 (Elastic sheath-core fiber and preparation method thereof ) 是由 韦炜 王栋 汤清伦 严坤 李沐芳 于 2021-09-15 设计创作，主要内容包括：本发明提供了一种弹性皮芯纤维及其制备方法。该制备方法通过对预拉伸状态的长丝进行皮层包裹,释放应力后,能够形成特殊的三维螺旋结构,显著提高了纤维的可拉伸性能。尤其是采用横截面为非对称结构的长丝和具有弹性的成膜物质进行包裹,能够在皮层表面形成粗糙的褶皱和多孔结构,提高表面形貌的粗糙度。进一步在其表面制备导电等功能层,功能层的附着牢度较高,纤维的拉伸导电性也显著提高,可很好地用于可穿戴电子设备。(The invention provides an elastic sheath-core fiber and a preparation method thereof. According to the preparation method, the skin layer of the filaments in the pre-stretched state is wrapped, and after stress is released, a special three-dimensional spiral structure can be formed, so that the stretchability of the fiber is remarkably improved. Especially, filaments with asymmetric cross sections and elastic film-forming substances are used for wrapping, so that rough wrinkles and porous structures can be formed on the surface of the skin layer, and the roughness of the surface appearance is improved. And further, functional layers such as electric conduction and the like are prepared on the surface of the fiber, the adhesion fastness of the functional layers is higher, the tensile conductivity of the fiber is also obviously improved, and the fiber can be well used for wearable electronic equipment.)

1. A preparation method of elastic sheath-core fiber is characterized by comprising the following steps:

s1, carrying out pre-drafting on a core layer filament according to a preset drafting ratio;

s2, preparing a cortex solution;

and S3, coating the surface layer solution on the surface of the core layer filament subjected to the pre-drafting through a solid-liquid microfluid coating technology, curing to form a film, and then releasing the pre-drafting stress of the core layer filament to obtain the elastic skin-core fiber.

2. The method of claim 1, wherein in step S1, the core filaments are elastic filaments with asymmetric cross-section.

3. The method of claim 2, wherein the elastic filament is a filament bundle consisting of a plurality of filaments, and the plurality of filaments are pressed against each other when pre-drafted, such that the cross section of the elastic filament has an asymmetric structure; the material of the elastic filament includes but is not limited to one or more of polyurethane, polyether ester, polyolefin and rubber.

4. The method of claim 1, wherein in step S1, the predetermined draft ratio is 0% to 1200%.

5. The method of claim 1, wherein in step S2, the solvent of the sheath solution is a mixed solvent composed of a plurality of solvents with different volatilization rates, and is used for generating a porous structure during the curing process; the cortex solution comprises an elastic film-forming substance.

6. The method for preparing the elastic sheath-core fiber according to claim 5, wherein the film-forming material in the sheath solution includes but is not limited to one or more of SBS, PU, PVP; the cortex solution also comprises a functional material, wherein the functional material is one or more of a conductive material, a magnetic material and a sensing material.

7. The method of making an elastic core-sheath fiber according to any one of claims 1 to 6, wherein in step S3, the microfluidic coating encapsulation technique in solid-liquid form comprises the steps of: drawing the core layer filaments from an inner layer channel of a microfluid control device after the pre-drawing; and extruding the skin layer solution from an outer layer channel of the microfluid control device, converging the skin layer solution with the pre-drafted core layer filament at an outlet, coating the surface of the core layer filament, and curing to form a film after the solvent is volatilized.

8. The method of claim 7, wherein the cross-section of the inner and outer channels of the microfluidic control device is an eccentric circular structure.

9. The method of making an elastic sheath-core fiber according to any one of claims 1 to 8, further comprising: and preparing a layer of conductive material on the surface of the elastic sheath-core fiber.

10. An elastic sheath-core fiber, characterized by being produced by the production method according to any one of claims 1 to 9.

Technical Field

The invention relates to the technical field of composite fiber preparation, in particular to an elastic sheath-core fiber and a preparation method thereof.

Background

With the development of the science and technology society, wearable flexible electronic equipment gradually enters the lives of people, and becomes an indispensable part for human life and science and technology development. When the conventional conductive fiber is practically used, the deformation amount is generally limited by materials or structures, so that the ductility and the flexibility of the product are poor, and the requirement of a large-size transformer cannot be met. Especially, when the deformation is large, the conductive path in the conductive fiber is damaged, and the device is failed or even damaged.

The flexible stretchable conductive fiber is used as an ideal preparation material for wearable flexible electronic equipment, can meet various deformation requirements such as bending and stretching in the using process, realizes the flexibility of devices such as information acquisition, transmission and energy storage, and is widely concerned by researchers. Therefore, the research and development of the flexible and stretchable conductive fiber have important significance.

At present, people mainly adopt the conventional coating or composite spinning method to blend conductive substances and fiber-forming polymers and prepare elastic conductive fibers by melt spinning, wet spinning and other methods for the research of flexible stretchable conductive fibers. The defects of complex process, poor performance stability, single structure, thick fiber and the like exist, and the practical application of the stretchable conductive fiber is limited.

In view of the above, there is a need for an improved elastic sheath-core fiber and a flexible stretchable conductive fiber based thereon to solve the above problems.

Disclosure of Invention

In order to overcome the defects of the prior art, the invention aims to provide an elastic sheath-core fiber and a preparation method thereof. According to the invention, the skin layer of the filaments in a pre-stretched state is wrapped, and after stress is released, a special three-dimensional spiral porous structure can be formed, so that the stretchability of the fiber and the richness of the surface appearance are obviously improved. Further, functional layers such as electric conduction and the like are prepared on the surface of the fiber, so that the tensile conductivity of the fiber is remarkably improved, and the fiber can be well used for wearable electronic equipment.

In order to achieve the above object, the present invention provides a method for preparing an elastic sheath-core fiber, comprising the steps of:

s1, carrying out pre-drafting on a core layer filament according to a preset drafting ratio;

s2, preparing a cortex solution;

and S3, coating the surface layer solution on the surface of the core layer filament subjected to the pre-drafting through a solid-liquid microfluid coating technology, curing to form a film, and then releasing the pre-drafting stress of the core layer filament to obtain the elastic skin-core fiber.

As a further improvement of the present invention, in step S1, the core layer filaments are elastic filaments with an asymmetric structure in cross section.

As a further improvement of the invention, the elastic filament is a filament bundle consisting of a plurality of monofilaments, and when the elastic filament is pre-drafted, the monofilaments are mutually pressed, so that the cross section of the elastic filament is in an asymmetric structure.

As a further improvement of the invention, the material of the elastic filament includes but is not limited to one or more of polyurethane, polyether ester, polyolefin and rubber.

As a further improvement of the present invention, in step S1, the preset draft ratio is 0% to 1200%.

As a further improvement of the present invention, in step S2, the solvent of the skin layer solution is a mixed solvent composed of a plurality of solvents with different volatilization rates, and is used for generating a porous structure during the curing process.

As a further improvement of the present invention, in step S2, the skin layer solution includes an elastic film-forming substance.

As a further improvement of the invention, the film-forming material in the skin layer solution includes but is not limited to one or more of SBS, PU and PVP.

As a further improvement of the invention, the cortex layer solution also comprises functional materials.

As a further improvement of the invention, the functional material is one or more of a conductive material, a magnetic material and a sensing material.

As a further improvement of the present invention, in step S3, the microfluidic coating encapsulation technique in solid-liquid form includes the following steps: drawing the core layer filaments from an inner layer channel of a microfluid control device after the pre-drawing; and extruding the skin layer solution from an outer layer channel of the microfluid control device, converging the skin layer solution with the pre-drafted core layer filament at an outlet, coating the surface of the core layer filament, and curing to form a film after the solvent is volatilized.

As a further improvement of the invention, the cross section of the inner layer channel and the outer layer channel of the microfluidic control device is of an eccentric circle structure.

As a further improvement of the present invention, the preparation method further comprises: and preparing a layer of conductive material on the surface of the elastic sheath-core fiber.

As a further improvement of the invention, the conductive material on the surface of the elastic sheath-core fiber is prepared by magnetron sputtering.

In order to achieve the aim, the invention provides an elastic sheath-core fiber prepared by the preparation method.

The invention has the beneficial effects that:

1. the invention provides a preparation method of elastic sheath-core fiber, which is characterized in that a polymer with certain film-forming property is used as a sheath material, a pre-stretched elastic filament is used as a core material, and the prestress of the elastic fiber filament is released after the sheath material is cured, so that the novel elastic sheath-core composite fiber with a three-dimensional spiral structure is prepared. The elastic sheath-core composite fiber with the spiral structure has good flexibility and stretchability, and can be used for preparing flexible and stretchable devices. By regulating and controlling the composition of the cortical solvent and the curing environment, a microporous structure can be formed on the surface of the fiber, so that the surface roughness of the fiber is improved, and the combination of functional substances such as electric conduction and the like and the fiber is facilitated.

2. According to the preparation method of the elastic sheath-core fiber, the elastic filament with the asymmetric cross section is preferably used as the core layer material and the elastic film forming substance is preferably used as the sheath layer material, the core layer filament is wrapped by the sheath layer material in the pre-drafting state, the stress can be released along with the elastic core filament, a microscopic three-dimensional spiral structure is easier to form, and the regularity and the controllability of the spiral structure are high; meanwhile, the surface also forms a fold and micropore structure, so that the richness of the surface appearance of the fiber is obviously improved, and an effective way is provided for further modifying the surface.

3. According to the preparation method of the elastic sheath-core fiber provided by the invention, the functional material is added into the sheath layer, or a layer of functional material, such as a conductive material, is prepared on the surface of the prepared elastic sheath-core fiber, so that the conductive fiber with good tensile cycle performance can be obtained, and the resistance change rate is only 6% under the 150% drafting condition. Therefore, the flexible wire can be applied to wearable electronic equipment as a flexible wire.

4. The preparation method of the elastic sheath-core fiber provided by the invention adopts a solid-liquid microfluid coating technology to coat the sheath, and the elastic fiber filament of the core layer material is always kept in a pre-drafting state when entering a chip channel; the micro-fluidic chip can accurately regulate and control the flow of the cortical solution, so that the preparation is kept balanced, and the uniformity of a fiber structure is ensured. After the skin layer solution is extruded from the tail end of the chip channel, the phenomenon of extrusion swelling can be caused, and the core wire can be better wrapped. Therefore, the composite elastic sheath-core fiber with the surface having the multilevel structure is prepared by the one-step method, the bonding fastness of the sheath layer and the core layer is high, and the preparation method has the advantages of simplicity, rapidness, no pollution to the environment, and no waste liquid generation compared with a wet spinning method.

Drawings

FIG. 1 is a schematic representation of the microfluidic coating technology preparation of elastic sheath-core fibers.

Fig. 2 is a schematic diagram of a C-shaped structure of the microfluidic chip.

FIG. 3 is a schematic representation of sample preparation during sputtering of elastic sheath-core fibers.

FIG. 4 is an infrared spectrum of SBS, PU and SBS/PU.

FIG. 5 is an electron micrograph of a PU filament bundle of example 1.

FIG. 6 is SBS prepared in example 1₁₅/PU₃₀₀Electron microscope images of the sheath-core composite elastic fiber at different magnifications.

FIG. 7 is a SBS prepared in example 1₁₅/PU₃₀₀The sheath-core composite elastic fiber has a 30 th cycle stress-strain curve under the condition of constant elongation of 400%.

FIG. 8 is a Cu/SBS prepared in example 1₁₅/PU₃₀₀The cycle stretch conductivity curve of the composite conductive fiber under different tensile strains.

FIG. 9 is a Cu/SBS prepared in example 1₁₅/PU₃₀₀The resistance change curve of the composite conductive fiber in the finger joint bending process.

FIG. 10 is a Cu/SBS prepared in example 1₁₅/PU₃₀₀The composite conductive fiber is connected into the LED demonstration circuit, and the lighting condition of the LED lamp is a real object diagram in the stretching process.

FIG. 11 is the SBS prepared in example 2₂₅/PU₂₀₀Electron microscope images of the sheath-core composite elastic fiber at different magnifications.

FIG. 12 is SBS prepared according to example 2₂₅/PU₂₀₀The sheath-core composite elastic fiber has a 30 th cycle stress-strain curve under the condition of constant elongation of 400%.

FIG. 13 is SBS prepared in example 3₁₅/PU₀Electron microscope images of the sheath-core composite elastic fiber at different magnifications.

FIG. 14 is SBS prepared in example 4₁₅/PU₄₀₀Electron microscope images of the sheath-core composite elastic fiber at different magnifications.

FIG. 15 is SBS prepared according to example 4₁₅/PU₄₀₀The sheath-core composite elastic fiber has a 30 th cycle stress-strain curve under the condition of constant elongation of 400%.

FIG. 16 is SBS prepared in example 5₁₅/PU₂₀₀Electron microscope images of the sheath-core composite elastic fiber at different magnifications.

FIG. 17 shows PVP prepared in example 6₁₅/PU₂₀₀Electron microscope images of the sheath-core composite elastic fiber at different magnifications.

FIG. 18 is SBS prepared according to example 7₁₅/PU₂₀₀Electron microscope images of the sheath-core composite elastic fiber at different magnifications.

FIG. 19 is a SBS prepared according to example 8₁₅/PU₂₀₀Electron microscope images of the sheath-core composite elastic fiber at different magnifications.

FIG. 20 is SBS prepared according to example 9₁₅/PET₂₀₀Sheath-core composite elastic fiberElectron micrographs at the same magnification.

FIG. 21 is a schematic structural diagram of an apparatus for preparing an elastic sheath-core fiber based on a microfluidic coating technology according to the present invention.

In the figure, 1-core layer filament; 11-cortex solution; 12-sheath-core composite fiber; 13-elastic sheath-core fiber with three-dimensional spiral structure; 14-acrylic frame;

2-a pressure controller; 3-a first guide wheel; 4-a second guide wheel; 5-a microfluidic chip; 6-liquid injector; 7-a heating and curing device; 7-1-infrared heating lamps; 7-2-temperature sensor; 8-a temperature controller; 9-a reduction gear; 10-a spooling device; 11-platform support.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in detail below with reference to specific embodiments.

It should be noted that, in order to avoid obscuring the present invention with unnecessary details, only the structures and/or processing steps closely related to the scheme of the present invention are shown in the specific embodiments, and other details not closely related to the present invention are omitted.

In addition, it is also to be noted that the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus.

The preparation method of the elastic sheath-core fiber provided by the invention comprises the following steps:

s1, carrying out pre-drafting on a core layer filament 1 according to a preset drafting ratio;

s2, preparing a cortex solution 11;

and S3, coating the surface layer solution 11 on the surface of the core layer filament 1 subjected to the pre-drafting through a solid-liquid microfluid coating technology to be cured into a film, and then releasing the pre-drafting stress of the core layer filament 1 to obtain the elastic sheath-core fiber.

By adopting the technical scheme, the novel three-dimensional spiral-structure elastic skin-core composite fiber 13 which is different from the conventional single linear elastic fiber is prepared by taking a polymer with certain film-forming property as a skin layer material and taking a pre-stretched elastic filament as a core layer material and regulating and controlling a spinning process. The elastic sheath-core composite fiber 13 with the spiral structure has good flexibility and stretchability, is simple in preparation process and high in repeatability, and can be used for preparing flexible and stretchable devices.

In step S1, the core filaments 1 are preferably elastic filaments with an asymmetric cross-section. The experimental result of the invention shows that the elastic filament with the asymmetric structure is wrapped by the skin layer material in the pre-drafting state, and after the stress is released, a microscopic three-dimensional spiral structure is easier to form, and the regularity and the controllability of the spiral structure are high.

Preferably, the elastic filament is a filament bundle consisting of several filaments (e.g. 6-20, preferably 8, 10, 12), which are pressed against each other when pre-drawn, so that the elastic filament has an asymmetric cross-section. The diameter of the monofilament is 0.5-100 mu m, and the cross section is preferably regular round; the fineness of the elastic filament is 40-140D, and the elastic filament is in an asymmetric structure on the cross section.

The material of the elastic filament includes but is not limited to one or more of polyurethane, polyether ester, polyolefin and rubber, and preferably polyurethane filament or rubber filament or composite filament thereof. The preset drafting ratio is 0% -1200%, preferably 100% -1000%, more preferably 100% -600%, more preferably 200% -400%, and in practical application, the drafting ratio can be adjusted according to the core filament performance and the required performance of the sheath-core fiber. Through carrying out different degrees of preliminary draft to the elasticity filament, can regulate and control the helical structure of elasticity skin-core combined fiber, such as helix angle etc..

In step S2, the solvent of the skin layer solution 11 is preferably a mixed solvent composed of a plurality of solvents having different volatilization rates, and is used to generate a porous structure during the curing process. Such as toluene/ethyl acetate, toluene/acetone, ethanol/acetone and the like, and the solvent is volatilized in a gradient manner in the solidification process to generate a phase separation process, so that a microporous structure is formed on the surface of the fiber, the fiber has larger surface roughness, and the combination of functional substances such as electric conduction and the like and the fiber is facilitated. In the process, parameters such as the concentration (15-25%), the ambient temperature (20-40 ℃), the humidity (40-60%) and the like of the skin layer material can be adjusted and controlled, and then the spiral structure and the surface appearance of the composite fiber can be adjusted and controlled.

In step S2, the film-forming substance in the skin layer solution 11 is selected from PVP (polyvinylpyrrolidone), SBS (styrene-butadiene-styrene block copolymer), PU, etc., and the elastic film-forming substance is preferably included in the skin layer solution 11. The film-forming material includes but is not limited to SBS and PU. The film forming material is selected, so that the stress can be released along with the elastic core wire, and the surface appearance with a fold structure and a porous structure can be formed. Through proper matching of the elastic materials of the skin layer and the core layer, the skin-core fiber with rich surface appearance and good stretchability (namely, the skin layer material has high bonding fastness and is not easy to damage) can be obtained.

The skin layer solution 11 also includes functional materials. By adding a proper amount of functional materials into the cortex solution 11, the functional materials and the cortex film-forming substance are coated on the surface of the elastic core filament together, so that the functional elastic sheath-core fiber is obtained. For example, the functional material is one or more of a conductive material, a magnetic material, and a sensing material (e.g., a temperature and humidity sensing material, a pressure sensitive material, a photosensitive material, etc.). Therefore, the elastic sheath-core fiber with conductivity or magnetism can be obtained, the elastic sheath-core fiber with good tensile conductivity or magnetism can be used as a flexible stretchable wire to be applied to intelligent wearable electronic equipment.

In step S3, the device based on the microfluidic coating technology adopted by the microfluidic coating technology in solid-liquid form is shown in fig. 21, and includes a microfluidic control device and a filament drawing device, a chip of the microfluidic control device includes at least two coaxial C-shaped channels (i.e., an inscribed eccentric circular structure (such as the C-shaped structure shown in fig. 3), and after a skin layer solution is extruded from a terminal, the skin layer solution may swell, and after the C-shaped port swells, the skin layer solution can be better wrapped on a core filament); and the filament drafting device drafts the core layer filaments from the inner layer channel to an outlet, and the skin layer microfluid solution is extruded from the outer layer channel and converged with the core layer filaments, so that solid-liquid coating based on the microfluid coating technology is realized, and the skin-core fiber is obtained.

Drawing the core layer filament 1 after the pre-drawing from an inner layer channel of a microfluid control device; extruding the skin layer solution 11 from an outer layer channel of the microfluid control device, converging the skin layer solution with the core layer filaments after pre-drafting at an outlet, coating the surface of the core layer filaments, and curing to form a film after the solvent is volatilized; then stretching the graphene into graphene dispersion liquid, and swelling and coating the graphene dispersion liquid; and finally releasing the stress. By the operation, the elastic fiber filament of the core layer material is always kept in a pre-drafting state when entering the chip channel; the micro-fluidic chip can accurately regulate and control the flow of the cortical solution, so that the preparation is kept balanced, and the uniformity of a fiber structure is ensured. Releasing the pre-drafting stress, and naturally retracting the elastic filaments to prepare the elastic sheath-core fiber with the three-dimensional spiral structure.

The filament drafting device comprises a pressure controller 2, a speed reducer 9, a first guide wheel 3 and a second guide wheel 4; the pressure controller 2 and the first guide wheel 3 are arranged at a position before the channel inlet of the chip, and the speed reducer 9 and the second guide wheel 4 are arranged at a position after the channel outlet of the chip; the core layer filament 1 is led out from the pressure controller 2, led in from the inlet of the core layer channel of the chip through the first guide wheel 3, led out from the outlet and pulled to the speed reducer 9 through the second guide wheel 4; the pressure controller 2 applies pressure to the core filament 1 and the speed reducer 9 applies a drawing force to the core filament 1. The pressure controller 2 is matched with a speed reducing device 9, wherein the speed reducing device 9 is provided with a motor as a driving device, and the pressure controller 2 is not provided with the motor and only provides pressure as a driven device.

In particular, the pressure controller 2 is arranged on the platform support, and the channels of the microfluidic chip 5 are arranged vertically and horizontally, so that the core layer filaments 1 are stretched out vertically to the horizontal plane and are conveyed to the speed reducer through the second guide wheel 4 in parallel with the horizontal plane. So set up, can make cortex solution under gravity and surface tension effect, at exit diffusion, flow downwards, the cortex solution of exit is taken away by the core layer filament 1 in the continuous motion, and the cortex solution wraps up on 1 surface of core layer filament after 1 surface flow solidification of core layer filament. Compared with horizontal stretching, the uniformity of the skin layer coating can be improved.

The device for preparing the sheath-core fiber based on the microfluid coating technology further comprises a heating and curing device 7, wherein the heating and curing device 7 is arranged at the outlet end of the channel of the chip and is used for accelerating the curing of the sheath solution. The cortex solution is injected into the microfluidic chip 5 through a liquid extrusion device (a liquid injector 6) and a connecting conduit, the liquid injector 6 can also be a dual-channel or multi-channel injector, and multiple polymer components are filled in multiple liquid injectors so as to realize the requirements that the prepared fiber contains multiple components and multiple functions.

Specifically, the heating and curing device 7 comprises an infrared heating lamp 7-1 and a temperature sensor 7-2, wherein the infrared heating lamp 7-1 and the temperature sensor 7-2 are connected with a temperature controller 8, so that the intelligent control of the temperature is realized. The infrared heating lamp 7-1 may be replaced with an ultraviolet heating curing lamp.

In some embodiments, the apparatus for preparing core-sheath fiber based on microfluid coating technology of the present invention further comprises a winding device 10 having a speed difference with the speed reduction device 9 for performing the packing winding of the obtained core-sheath fiber in a crimped state.

An air exhaust device can be arranged in the spinning device, so that the whole preparation process is carried out in a safe ventilation environment.

The method comprises the following steps: drawing the core layer filament 1 subjected to the pre-drawing from an inner layer channel of a microfluid control device; and extruding the skin layer solution 11 from an outer layer channel of the microfluid control device, converging the skin layer solution and the pre-drafted core layer filament 1 at an outlet, coating the surface of the core layer filament, and curing to form a film after the solvent is volatilized. By the operation, the elastic fiber filament of the core layer material is always kept in a pre-drafting state when entering the chip channel; the micro-fluidic chip can accurately regulate and control the flow of the cortical solution 11, so that the preparation is kept balanced, and the uniformity of a fiber structure is ensured.

Specifically, referring to fig. 1, by using a microfluidic coating technology, through a microfluidic chip channel design, a polymer solution with a certain film-forming property is used as a skin layer to wrap the surface of an elastic filament of a pre-stretched core layer, and at a chip outlet, the polymer solution wrapped on the surface of the elastic filament is rapidly cured to form a film, so as to obtain a skin-core composite fiber 12; and then releasing the pre-drafting stress, and naturally retracting the elastic filament to prepare the elastic sheath-core fiber 13 with the three-dimensional spiral structure.

The polymer solution is injected into an outer channel of the micro-fluid control device by an injection pump and is converged with the elastic filament at an outlet, the polymer solution starts to diffuse and flow downwards at the outlet due to gravity and surface tension, the polymer solution at the outlet is taken away by the elastic filament in continuous motion, and the polymer solution is coated on the surface of PU after flowing and curing on the surface of the PU filament. Due to the rapid volatilization of the solvent, the polymer solution is rapidly solidified into a film on the surface of the elastic filament to form the composite elastic fiber with a skin-core structure. The flow of the polymer solution and the winding speed of the elastic filament are regulated and controlled to reach a dynamic balance state, so that continuous preparation is realized. Due to the difference of the retraction rates of the inner layer material and the outer layer material, after the pre-drawn PU releases the tensile stress, the fiber retracts to a stable state, and the composite fiber forms a three-dimensional spiral structure.

The preparation method further comprises the following steps: and preparing a layer of conductive material on the surface of the elastic sheath-core fiber. The conductive material on the surface of the elastic sheath-core fiber is preferably prepared by magnetron sputtering.

The composite fiber with the spiral structure is used as a flexible substrate, and a layer of composite nano conductive layer is prepared on the surface of the fiber through magnetron sputtering, so that the flexible stretchable composite conductive fiber with the three-dimensional spiral structure is obtained. The conductive fiber prepared by the method has the advantages of thin diameter, rich surface structure and good tensile conductive stability.

Because the composite elastic fiber belongs to a three-dimensional spiral structure, the front and back surfaces of the composite elastic fiber need to be sputtered so that the composite elastic fiber base material can be uniformly conductive. As shown in fig. 3, the composite elastic fiber is fixed on the cut hollow acrylic frame 14, the acrylic frame 14 is fixed on a sample table, and after the single-side sputtering is finished, the acrylic plate is turned over to perform the reverse-side sputtering coating.

Example 1

A preparation method of elastic sheath-core fiber comprises the following steps:

(1) preparing a cortex solution: preparing a mixed solvent with the mixing ratio of 3:1 from ethyl acetate and toluene for later use. Weighing a proper amount of SBS master batch, slowly adding the SBS master batch into the mixed solvent, magnetically stirring for 12 hours at normal temperature until SBS particles are completely dissolved, preparing SBS solution with the mass fraction of 15%, and enabling the solution to be clear and transparent.

(2) The core material is selected from 140D PU filament, and the pre-drafting is 300%.

(3) By utilizing a microfluid coating technology and through a microfluidic chip channel design, an SBS solution is taken as a skin layer and is wrapped on the surface of a core layer PU filament subjected to pre-drawing, the SBS solution wrapped on the surface of the PU filament is rapidly solidified to form a film at a chip outlet, then the pre-drawing stress is released, and the PU fiber naturally retracts to prepare the SBS/PU skin-core composite elastic fiber with a three-dimensional spiral structure. (curing ambient temperature 20 ℃ C., relative humidity 40%)

Please refer to FIG. 4, which shows 699cm from the infrared spectrogram^-1The position is a benzene ring monosubstituted vibration absorption peak of polystyrene, which is 966cm^-1Where is the flexural vibration absorption peak of C-H on the C ═ C group of the butadiene. As can be seen from the figure, 699cm in the infrared spectrogram of SBS/PU^-1、966cm^-1The infrared characteristic peak which is peculiar to SBS appears. Meanwhile, 1736cm in the infrared spectrogram of PU^-1The peak sum of the C-O stretching vibration characteristic peak appeared at the position of 3332cm^-1The appearance of the characteristic peak of the N-H stretching vibration completely disappears in an infrared spectrogram of SBS/PU, which shows that the core layer PU filament is completely wrapped by the sheath SBS in the SBS/PU sheath-core composite elastic fiber, and shows that the SBS/PU sheath-core composite fiber prepared by the method has stable structure and no core leakage phenomenon.

Referring to FIG. 5, it can be seen that the core PU filaments are filament bundles consisting of 12 filaments, the PU filaments have a diameter of about 43 μm and a regular circular cross-section. The 12 monofilaments are closely arranged in space and present irregular shapes. As can be seen from b in fig. 5, the diameter of the filaments of the PU filaments in the SBS/PU composite elastic fiber is slightly reduced due to the pre-drawing, and the filaments of the PU filament bundle are pressed against each other due to the drawing force, and finally assume an approximately trapezoidal arrangement, and due to the asymmetric structural arrangement, the final SBS/PU composite elastic fiber is retracted, and then deformed and twisted in space, thereby assuming a three-dimensional spiral structure in a natural state. In fig. 5, c is a partial enlarged view, it can be observed that the SBS in the skin layer is tightly bonded to the PU in the core layer, which indicates that the two materials have strong bonding force and certain structural stability. In addition, dense micropores are observed on the surface of the fiber due to phase separation of the SBS solution during curing.

Referring to fig. 6, it can be seen that the SBS/PU sheath-core composite elastic fiber has a uniform three-dimensional spiral structure and uniform wrinkles on the surface thereof, because the SBS material of the outer layer is a flexible elastic material, and after releasing the pre-strain, the sheath material is extruded, so that the wrinkle structure is formed on the surface of the composite fiber. Meanwhile, the surface of the fiber sample also has a uniform and compact micropore structure, which is probably because the solvents of ethyl acetate and toluene in the SBS solution of the cortex layer volatilize at a high speed, so that the temperature change is brought, and thermally induced phase separation is generated, so that micropores are formed on the surface of the fiber.

FIG. 7 is SBS_x/PU_y(x represents SBS concentration, y represents pre-drawing proportion of PU) under the condition that the elastic recovery performance of the composite elastic fiber is fixed and extended by 400%, the 30 th cycle stress-strain curve. The SBS/PU composite elastic fiber with the spiral structure has smaller energy loss ring and better elastic recovery performance. On the stress-strain curve of the SBS/PU composite elastic fiber, partial stress peaks appear, which correspond to the change of each micropore and wrinkle on the surface of the fiber during the stretching process.

Application test

And (3) selecting a copper target with the purity of 99.99% to sputter a layer of conductive copper layer on the surface of the prepared SBS/PU skin-core composite elastic fiber, wherein the magnetron sputtering technological parameters are the sputtering time of 1800s, the sputtering pressure of 0.5Pa and the sputtering power of 80W.

Referring to FIG. 8, it can be seen that Cu/SBS₁₅/PU₃₀₀The strain of the composite conductive fiber is below 100%, the curve change trend is mild, and after 500 times of circulation, the resistance is cyclically stretchedThe stability is better. At the strain of 150%, the resistance change of the composite conductive fiber is relatively stable in the first 200 times of stretching, the cyclic stretching is continued, cracks are formed on the surface of the conductive layer, the resistance is slightly increased, the cracks are formed in the later stretching but the influence is small, so that the resistance change tends to be smooth, and after the cyclic stretching is performed for 500 times, the delta R/R is 0.087. When the strain exceeds 200%, Cu/SBS₁₅/PU₃₀₀The conductive layer on the surface of the composite conductive fiber is broken, and the fiber is not conductive.

Referring to FIG. 9, a Cu/SBS segment is selected₁₅/PU₃₀₀The two ends of the composite conductive fiber are attached and fixed at the finger joint, and the resistance change condition of the composite conductive fiber is observed in the bending process of the finger joint. When the finger joint is bent at different angles, the resistance stability is good. The conductive fiber has a resistance change rate of about 6% when the finger is bent at an angle of 90 °.

Referring to FIG. 10, a 2cm cut of Cu/SBS is shown₁₅/PU₃₀₀The composite conductive fiber is connected into the LED demonstration circuit, and the wire replacement performance of the elastic composite conductive fiber is represented by observing the lighting condition of the LED lamp in the stretching process. It can be seen that a single conductive fiber prepared by the experiment can light one LED bulb, and the LED bulb is always kept in a lighting state in the stretching process. When the conductive fiber is stretched, the conductivity of the conductive fiber is changed but not greatly, so that the LED bulb is kept in a lighting state, and the brightness of the bulb is hardly changed. The prepared conductive fiber has good conductivity and can be used as an elastic stretchable wire in future wearable flexible devices.

Example 2

Compared with the examples, the difference of the preparation method of the elastic sheath-core fiber is that the mass fraction of SBS is 25 percent, and the pre-drafting of PU is 200 percent. The rest is substantially the same as that of embodiment 1, and will not be described herein.

Referring to FIG. 11, it can be seen that SBS₂₅/PU₂₀₀The micropores are hardly observed on the surface of the composite elastic fiber. This is probably due to the reduced solvent content and the rich solvent content of the cortical SBS solutionThe volume of the phase-collected is reduced relative to the total volume, and finally a small number of micropores are formed on the surface of the fiber.

The composite elastic fiber produced under this condition has a large residual strain although the energy loss is small.

Example 3

A method for preparing elastic sheath-core fiber, compared with the examples, the difference is that the pre-drafting of PU is 0%. The rest is substantially the same as that of embodiment 1, and will not be described herein.

Referring to fig. 13, it can be seen that the fiber surface still has micropores but almost no spiral structure. Indicating that the core wire is not pre-stretched and the regular helical structure of the invention cannot be obtained.

Example 4

A method of making an elastic sheath-core fiber, except that the pre-draw of PU is 400%, as compared to the examples. The rest is substantially the same as that of embodiment 1, and will not be described herein.

Referring to fig. 14 and 15, it can be seen that pre-draft of 400% also resulted in a helical structure of elastic sheath-core fiber with better cyclic stretch performance.

Example 5

Compared with the examples, the difference of the preparation method of the elastic sheath-core fiber is that the solvent is only ethyl acetate, and the PU pre-drafting is 200%. The rest is substantially the same as that of embodiment 1, and will not be described herein.

Referring to FIG. 16, an elastic fiber can be formed in a three-dimensional spiral and pleated structure, but with substantially no cell structure on the surface of the fiber.

Example 6

Compared with the examples, the difference of the preparation method of the elastic sheath-core fiber is that the sheath material is 15 percent of PVP solution by mass fraction, and the PU pre-drafting is 200 percent. The rest is substantially the same as that of embodiment 1, and will not be described herein.

Referring to fig. 17, it can be seen that the fibers can form a three-dimensional spiral structure, but have smooth surfaces without wrinkles and a microporous structure. The elastic film forming material is adopted in the skin layer, and the skin layer and the core layer can release stress together, so that a fold and a porous structure are generated, the improvement of the abundance of the surface appearance of the fiber is facilitated, and an effective way is provided for further function modification of the surface.

Example 7

Compared with the embodiment, the preparation method of the elastic sheath-core fiber is different in that the curing temperature is 30 ℃, the relative humidity is 60 percent, and the PU pre-drafting is 200 percent. The rest is substantially the same as that of embodiment 1, and will not be described herein.

Referring to fig. 18, it can be seen that the fiber can form a three-dimensional spiral structure, but the micropores on the surface of the fiber are closely arranged. The curing temperature or humidity can be regulated and controlled, so that the surface appearance of the fiber can be regulated and controlled.

Example 8

Compared with the embodiment, the preparation method of the elastic sheath-core fiber is different in that dipping is adopted instead of spinning in a microfluidic chip. The rest is substantially the same as that of embodiment 1, and will not be described herein.

Referring to fig. 19, it can be seen that the SBS on the surface of the fiber is excessively wrapped, resulting in insignificant spiral and micropore structures.

Example 9

Compared with the examples, the preparation method of the elastic sheath-core fiber is different in that the core material is non-elastic PET (polyethylene terephthalate) filament. The rest is substantially the same as that of embodiment 1, and will not be described herein.

Referring to fig. 20, it can be seen that the fibers have no elasticity, cannot form a three-dimensional spiral structure, and the uniformity of the skin layer is significantly reduced.

In conclusion, the elastic sheath-core fiber provided by the invention can form a special three-dimensional spiral structure after releasing stress by sheath wrapping the filaments in a pre-stretched state, and the stretchability of the fiber is remarkably improved. Especially, filaments with asymmetric cross sections and elastic film-forming substances are adopted for wrapping, so that rough wrinkles and porous structures can be formed on the surface of the skin layer, and the richness of the surface appearance is improved. And further, functional layers such as electric conduction and the like are prepared on the surface of the fiber, the adhesion fastness of the functional layers is higher, the tensile conductivity of the fiber is also obviously improved, and the fiber can be well used for wearable electronic equipment.

Although the present invention has been described in detail with reference to the preferred embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the spirit and scope of the present invention.