Fiber having a helical structure and a self-initiated production method thereof

Abstract

The application discloses a kind of fibers with helical structure, and its self-initiated preparation method, which is: high oxidation degree graphene oxide spinning solution is extruded into coagulation bath by spinning head with certain bevel angle, the flow rate difference appears on both sides of spinning solution at outlet due to oblique cut, leading to unstable extrusion, and fiber with one-sided skirt structure is generated at bevel cut.In the process of drying by pulling out coagulation bath, by applying infrared light to one side of the fiber, the fiber spontaneously twists under the joint action of solvent and interfacial tension, and self-twisted graphene oxide fiber is obtained.The self-twisted graphene fiber prepared by one-step method is rich in helical fold, has high elongation, high strength and other characteristics, especially the twisting process is spontaneous, without additional twisting and twisting device, and the twisting degree can be controlled by the bevel angle of the spinning head, the coagulation intensity, the extrusion speed, the take-up speed and the drying intensity, which is flexible and variable.

Description

Technical Field

[0001] This invention relates to the field of macroscopic assembly of nanomaterials, and in particular to a fiber with a helical structure and its self-initiated preparation method. Background Technology

[0002] In 2004, Professors Andre Geim and Kostya Novoselov of the University of Manchester in the UK successfully prepared single-sheet graphene by micromechanically exfoliating highly oriented pyrolytic graphite and discovered a series of unique physical properties, ushering in a new era in the research of two-dimensional nanomaterials. Graphene is a type of graphene composed of sp... 2 Graphene, a monolayer crystalline material composed of hybrid carbon atoms in a two-dimensional periodic hexagonal honeycomb structure, possesses excellent mechanical, electrical, and thermal properties due to its unique two-dimensional layered structure. However, the poor dispersibility of graphene makes assembling sheet-like graphene into macroscopic graphene assemblies a challenge. Graphene oxide, as a derivative of graphene, is highly soluble, making it an excellent material for preparing macroscopic graphene assemblies.

[0003] Graphene fiber, as an emerging carbon fiber assembled from pure graphene, exhibits great potential in flexible capacitors and flexible sensors due to its excellent conductivity. Currently, large-scale production of graphene fiber mainly employs wet spinning, producing fibers with good mechanical, electrical, and thermal properties. However, the resulting graphene fibers are brittle, with an elongation at break typically less than 5%, making them easily broken and severely hindering their application in flexible conductive fields. Therefore, existing technologies typically prepare graphene fibers with a certain degree of helixity by rotating the spinning head or adding an additional twisting step, thereby improving the elongation at break. However, these methods are cumbersome, require complex equipment, and have small production scales. Furthermore, the two-dimensional sheets inside the prepared helical fibers are mainly oriented along the helical direction rather than the fiber axis, making them unable to withstand strong axial tensile forces. Therefore, the prepared fibers often cannot simultaneously achieve both strength and elongation. Summary of the Invention

[0004] The purpose of this invention is to address the shortcomings of the prior art by providing a fiber with a helical structure, composed of two-dimensional sheet materials. It includes a fiber core and a helical rib structure, the helical rib structure surrounding the outer side of the fiber core. The two-dimensional sheet materials constituting the fiber core are oriented axially, while the two-dimensional sheet materials constituting the helical rib structure are oriented parallel to the helical tangent. The two-dimensional sheets of the helical rib structure are continuous with the two-dimensional sheet materials constituting the fiber core. When the fiber is stretched, the fiber core provides strength, and the helical structure provides elongation at break. The two work synergistically to effectively improve elongation while ensuring strength, achieving a balance between high strength and high elongation at break.

[0005] The present invention also provides a method for preparing the above-mentioned fibers, a method for preparing high elongation fibers by self-initiating helices, comprising the following steps:

[0006] (1) A high-oxidation-degree graphene oxide dispersion is prepared as the spinning solution; the carbon-to-oxygen ratio of the high-oxidation-degree graphene oxide is 1.3-2. The spinning solution is extruded into the coagulation bath through the spinning head to form nascent filaments; the spinning head includes a spinning tube with an inner diameter of 80μm-480μm, the spinning tube has a slanted outlet, the spinning solution is extruded into the coagulation bath through the slanted outlet of the spinning tube, the slanted outlet is at an angle of 30°<θ<60° with the axis of the spinning tube; the slanted cut causes a velocity difference on both sides of the spinning solution at the outlet, resulting in unstable coagulation, and fibers with a single-sided skirt structure are generated at the slanted cut. By adjusting the slanted angle of the spinning head and the coagulation bath ratio, the degree of skirt wrinkling can be controlled; generally speaking, the larger the slanted angle and the greater the polarity of the coagulation bath, the greater the skirt wrinkling amplitude. The volume of the highly wrinkled part of the skirt per unit length is greater than that of the fiber main axis, so the amount of solvent contained is greater than that of the fiber main axis.

[0007] (2) The nascent filament is drawn into a heated environment, causing the solvent to evaporate and the fiber to self-initiate a spiral, resulting in a high elongation fiber. During the solvent evaporation process, the difference in solvent content between the fiber spindle and the skirt leads to a difference in evaporation rate, resulting in asymmetric shrinkage. This causes the fiber spindle to twist, and the skirt wraps around the spindle in a spiral manner. This self-initiated spiral process causes the graphene core sheet to be oriented along the fiber axis, and the two-dimensional sheet material of the spiral rib structure to be oriented perpendicular to the spiral tangent. Since there is a continuous transition from the fiber spindle to the two-dimensional sheet of the skirt, the two-dimensional sheet of the spiral rib structure formed by the self-initiated spiral and the two-dimensional sheet material constituting the fiber core are in a continuous transition.

[0008] Graphene oxide fibers exhibit an extrusion swell effect (the higher the oxidation degree, the more pronounced the swell effect). In existing technologies, to obtain high-strength graphene fibers, low-oxidation, flat-exit spindle heads are used to ensure uniform extrusion and fiber cross-section. However, for high-toughness graphene fibers, current methods involve spindle head rotation or post-twisting. This application creatively employs a slanted exit, extruding graphene oxide dispersions with high oxygen content (3 mg / g-8 mg / g) to construct skirts, combined with drying-initiated self-helical processes, resulting in high-strength and high-elongation-at-break graphene fibers with unexpected technical advantages.

[0009] In some embodiments of the present invention, since the self-initiated spiral process is mainly dominated by the solvent evaporation rate and the rate difference, a fast evaporation rate and a large rate difference are conducive to the formation of the spiral. Therefore, an organic system is specifically selected, and the high-oxidation-degree graphene oxide dispersant is N,N-dimethylformamide, dimethyl sulfoxide, ethylene glycol, pyridine, N-methylpyrrolidone, tetrahydrofuran, acetone, acetic acid, etc.

[0010] In some embodiments of the present invention, the coagulation bath is a mixture of one or more of ethyl acetate, dichloromethane, methanol, acetone, n-hexane, isopropanol, etc., in different proportions.

[0011] In some embodiments of the present invention, the temperature of the thermal environment is above 20 degrees Celsius, and those skilled in the art can select the appropriate evaporation temperature according to the solvent actually used. Furthermore, the degree of fiber spiral can be controlled by adjusting the winding speed and temperature; the slower the winding speed and the higher the temperature, the more intense the drying, the higher the degree of spiral wrinkles, and the higher the breaking elongation.

[0012] In some preferred embodiments of the present invention, the high-oxidation-degree graphene oxide dispersant further includes a polymer, which accounts for 30%-50% of the solute mass; the polymer is polyvinyl alcohol or polyethylene oxide. The addition of polyvinyl alcohol or polyethylene oxide can further improve fiber strength, and the incorporation of the polymer does not affect the formation of the helix.

[0013] Furthermore, the extrusion speed of the spinning solution in step 2 is 0.01 ml / min-0.10 ml / min, which has a good internal spiral effect.

[0014] In some preferred embodiments of the present invention, the graphene oxide fibers obtained in step 2 are further reduced to obtain reduced graphene oxide fibers with high elongation and high strength.

[0015] Typically, the reduction is either chemical or thermal. Generally, chemical reduction can use acetic acid, hydroiodic acid, trifluoroacetic acid, hydrazine hydrate, vitamin C, or mixtures thereof; thermal reduction typically occurs at temperatures between 100 and 3000°C. Those skilled in the art will understand that thermal reduction should be carried out in an oxygen-free environment, including but not limited to an inert gas atmosphere or under vacuum conditions.

[0016] In some preferred embodiments of the present invention, the thermal environment in step 2 is a non-uniform thermal environment, wherein the heat source is located on one side of the nascent filament. The non-uniform thermal environment can exacerbate the difference in solvent evaporation rates, further enhancing the spiral structure.

[0017] In some embodiments of the present invention, the following scheme is specifically adopted: a continuous preparation method of graphene fibers with helical pleated microstructures, comprising the following processes:

[0018] (1) Prepare graphene oxide with a carbon-oxygen ratio of 1.3-2 into a graphene oxide spinning solution with a concentration of 3mg / g-8mg / g, or add 30%-50% of ultra-high molecular weight polyvinyl alcohol or polyethylene oxide and mix evenly to prepare a composite spinning solution.

[0019] (2) The spinning solution prepared in step 1 is extruded into the coagulation bath through the obliquely cut spinning head. Due to the asymmetry of the cutting surface of the spinning head, the spinning solution has a flow rate difference on both sides of the extrusion port, resulting in unstable coagulation and producing a wavy skirt.

[0020] (3) After the fibers have been fully solidified, they are pulled out and dried. Infrared light is applied to one side, causing the fibers to twist spontaneously under the combined action of solvent and interfacial tension. The drying time and intensity are controlled by adjusting the winding speed and the number of infrared lamps. The slower the winding speed and the more infrared lamps, the more intense the drying, the higher the helix degree of the spiral pleats, and the higher the breaking elongation.

[0021] (4) The graphene oxide fibers obtained in step 3 are further fed into a reduction bath for in-situ chemical reduction to obtain reduced graphene oxide or reduced graphene oxide composite fibers.

[0022] (5) The reduced graphene oxide fibers obtained in step 4 are further fed into the thermal reduction chamber for thermal reduction.

[0023] The fibers are collected to obtain graphene fibers or graphene composite fibers with a spiral pleated microstructure.

[0024] Furthermore, the infrared illumination mentioned in step 3 uses 1-3 infrared lamps with a power of 250W, and the distance between the infrared light and the fiber is fixed within the range of 5-10cm. The winding speed is 0.5m / min-3m / min.

[0025] Furthermore, the reducing bath described in step 4 is a reducing bath containing acetic acid, hydroiodic acid, trifluoroacetic acid, hydrazine hydrate, vitamin C, or a mixture thereof.

[0026] Furthermore, the temperature of the high-temperature thermal reduction cylinder described in step 5 is 100℃-350℃.

[0027] The beneficial effects of this invention are as follows: By using a slanted cutting method at the spinning head, the fiber undergoes unstable solidification at the spinning head exit, generating an initial helical structure. During the subsequent drying process, an infrared light source is applied to one side, causing unstable drying shrinkage on both sides of the fiber, further intensifying the helical wrinkles. This eliminates the need for subsequent additional twisting, achieving a one-step preparation of graphene fibers with helical wrinkled microstructures. Through subsequent in-situ chemical reduction and thermal reduction, the resulting twisted graphene fibers possess high strength, high conductivity, and high elongation, while also exhibiting UV and infrared resistance. They can be widely applied in fields such as flexible sensing, flexible conductive wearables, and flexible tensile devices. Attached Figure Description

[0028] Figure 1 A schematic diagram of the one-step process for preparing helical pleated microstructures of graphene fibers (including a schematic diagram of the oblique cutting needle).

[0029] Figure 2 This is a SEM image of graphene fibers with a spiral folded microstructure.

[0030] Figure 3 The tensile strain curves are for graphene and ultra-high molecular weight polyethylene composite spiral pleated microstructure fibers. Detailed Implementation

[0031] The present invention will be specifically described below through embodiments. These embodiments are only used to further illustrate the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-essential changes and adjustments made by those skilled in the art based on the above-described invention shall fall within the scope of protection of the present invention.

[0032] Example 1:

[0033] (1) High-oxidation graphene with a carbon-to-oxygen ratio of 1.6 was added to N-methylpyrrolidone to obtain a spinning solution with a graphene oxide concentration of 3 mg / g. The solution was loaded into a 5 ml syringe and pushed at a speed of 0.03 ml / min. It was then squeezed into a hexane coagulation bath through a spinning head with a 30° bevel angle and an 80 μm aperture.

[0034] (2) The fiber produces initial spiral folds at the obliquely cut spinning head. After sufficient solidification, it is pulled out of the coagulation bath and dried.

[0035] (3) Place a 250W infrared lamp 15cm away from one side of the fiber to make the drying temperature of the fiber about 20 degrees Celsius. Under the irradiation of the drying light source on one side, the fiber undergoes asymmetrical shrinkage on the side with the light source and the side without the light source, which leads to increased helicity and obtains graphene oxide fiber with a helical fold microstructure;

[0036] (4) The graphene oxide fibers obtained in step 3 are sent into a reduction bath of HI and trifluoroacetic acid in a ratio of 1:6 for chemical reduction, and the fibers are collected to obtain reduced graphene oxide fibers.

[0037] (5) The reduced graphene oxide fibers obtained in step 4 are further fed into a thermal reduction chamber for thermal reduction at a temperature of 300℃. Finally, twisted graphene fibers are obtained. The helical folds are left-handed, with a pitch of 30 μm, a strength of up to 567 MPa, an elongation at break of 20%, and an electrical conductivity of 1.21 × 10⁻⁶. 6 .

[0038] When the spinneret slant angle in this embodiment is changed to 45° and the extrusion speed is changed to 0.1 ml / min, the resulting spiral-pleated microstructured graphene fiber has a pitch of 22 μm, a strength of 531 MPa, an elongation at break of 24%, and an electrical conductivity of 1.22 × 10⁻⁶. 6 .

[0039] When the spinneret slant angle in this embodiment is changed to 60° and the extrusion speed is changed to 0.1 ml / min, the resulting spiral-pleated microstructured graphene fiber has a pitch of 16 micrometers, a fiber strength of 509 MPa, a breaking elongation of 28%, and an electrical conductivity of 1.20 × 10⁻⁶. 6 S / m.

[0040] When the take-up speed in this embodiment was changed to 1.8 m / min, the resulting spiral-pleated microstructured graphene fiber had a pitch of 33 μm, a strength of 589 MPa, an elongation at break of 17%, and an electrical conductivity of 1.23 × 10⁻⁶. 6 S / m.

[0041] When the coagulation bath in this example was changed to a 1:1 mixture of ethyl acetate and ethanol, the resulting spiral-pleated microstructured graphene fibers had a pitch of 32 μm, a strength of 536 MPa, an elongation at break of 15%, and an electrical conductivity of 1.19 × 10⁻⁶. 6 S / m.

[0042] When the graphene oxide concentration in this embodiment is 8 mg / g, the resulting spiral-pleated microstructured graphene fibers have a pitch of 18 μm, a strength of 536 MPa, an elongation at break of 25%, and an electrical conductivity of 1.20 × 10⁻⁶. 6 S / m.

[0043] When graphene oxide with a carbon-to-oxygen ratio of 2 was selected in this embodiment, the resulting helical pleated microstructure graphene fibers had a pitch of 21 μm, a strength of 492 MPa, an elongation at break of 23%, and an electrical conductivity of 0.89 × 10⁻⁶. 6 S / m.

[0044] When three infrared lamps were used for drying in this embodiment, and the lamps were located on the same side of the fiber, the resulting spiral-pleated microstructured graphene fiber had a pitch of 19 μm, a strength of 492 MPa, an elongation at break of 27%, and an electrical conductivity of 1.25 × 10⁻⁶. 6 S / m.

[0045] Example 2:

[0046] (1) A composite spinning solution of N,N-dimethylformamide phase with a mass ratio of 1:1 and a total concentration of 5 mg / g was prepared using graphene with a carbon-oxygen ratio of 1.8 and ultra-high molecular weight polyvinyl alcohol. The solution was loaded into a 5 ml syringe and squeezed into an ethyl acetate coagulation bath through a spinning head with a 45° oblique angle and a pore size of 340 μm.

[0047] (2) The fiber produces initial spiral folds at the obliquely cut spinning head. After sufficient solidification, it is pulled out of the coagulation bath and dried at a speed of 2m / min.

[0048] (3) Place an infrared lamp with a power of 250w at a distance of 10cm from one side of the fiber. Under the irradiation of a dry light source on one side, the fiber undergoes asymmetrical shrinkage on the side with the light source applied and the side without the light source applied, resulting in increased helicity and obtaining graphene oxide fiber with a highly helical folded microstructure.

[0049] (4) The graphene oxide fibers obtained in step 3 are sent into a reduction bath with a ratio of HI:trifluoroacetic acid of 1:3 for chemical reduction, and the fibers are filament-wound to obtain reduced graphene oxide fibers.

[0050] (5) The reduced graphene oxide fibers obtained in step 4 are further fed into a thermal reduction chamber for thermal reduction. Finally, graphene composite fibers with a helical pleated microstructure are obtained. The helical pleats are left-handed, with a pitch of 14 μm, a strength of up to 920 MPa, and an elongation at break of 30%. The electrical conductivity is 3.24 × 10⁻⁶. 5 S / m.

[0051] Example 3:

[0052] (6) Prepare a composite spinning solution of N,N-dimethylformamide phase with a mass ratio of 3:7 and a total concentration of 8 mg / g using graphene with a carbon-oxygen ratio of 1.3 and a high degree of oxidation and ultra-high molecular weight polyethylene oxide. Put the solution into a 5 ml syringe and squeeze it into an ethyl acetate coagulation bath through a spinning head with a 30° oblique angle and a pore size of 480 μm.

[0053] (7) The fiber produces preliminary spiral folds at the obliquely cut spinning head. After sufficient solidification, it is pulled out of the coagulation bath and dried at a speed of 2m / min.

[0054] (8) Place an infrared lamp with a power of 250w at a distance of 10cm from one side of the fiber. Under the irradiation of a dry light source on one side, the fiber undergoes asymmetrical shrinkage on the side with the light source applied and the side without the light source applied, resulting in increased helicity and obtaining graphene oxide composite fiber with a highly helical folded microstructure.

[0055] (9) The graphene oxide composite fiber obtained in step 3 is sent into a hydrazine hydrate reduction bath for chemical reduction, and the fiber is collected to obtain reduced graphene oxide composite fiber.

[0056] (10) The reduced graphene oxide fibers obtained in step 4 are further fed into a thermal reduction chamber for thermal reduction. Finally, helical wrinkled microstructured graphene composite fibers are obtained. The helical structure is left-handed, with a pitch of 12 μm, a strength of up to 1060 MPa, and an elongation at break of 35%. The electrical conductivity is 4.58 × 10⁻⁶. 5 S / m.

Claims

1. A method of making high elongation fibers from self-initiating helices, characterized by, The method comprises the following steps: (1) configuring a high-oxidation graphene oxide dispersion as a spinning solution; the carbon-oxygen ratio of the high-oxidation graphene oxide is 1.3-2; the spinning solution is extruded into a coagulation bath through a spinning head to form a nascent fiber; the spinning head comprises a spinning tube with an inner diameter of 80-480 μm, and the spinning tube has a bevelled outlet; the spinning solution is extruded to the coagulation bath through the bevelled outlet of the spinning tube, and the bevelled outlet is bevelled at an angle of 30°<θ<60° with respect to the axial direction of the spinning tube; (2) the nascent fiber is drawn into a hot environment to volatilize the solvent and self-initiate a spiral to obtain a high-elongation fiber.

2. The method of claim 1, wherein, The high-oxidation graphene oxide dispersion comprises N, N-dimethylformamide, dimethyl sulfoxide, ethylene glycol, pyridine, N-methyl pyrrolidone, tetrahydrofuran, acetone, and acetic acid.

3. The method of claim 1, wherein, The coagulation bath is a mixed solution of one or more of ethyl acetate, dichloromethane, methanol, acetone, n-hexane, and isopropyl alcohol in different proportions.

4. The method of claim 1, wherein, The temperature of the hot environment is above 20°C.

5. The method of claim 1, wherein, The high-oxidation graphene oxide dispersion further comprises a high-molecular polymer, and the high-molecular polymer accounts for 30%-50% of the mass of the solute; the high-molecular polymer is polyvinyl alcohol or polyethylene oxide.

6. The method of claim 1, wherein, The high-elongation fiber obtained in step 2 is reduced to obtain a high-elongation and high-strength reduced graphene oxide fiber.

7. The method of claim 6, wherein, The reduction is chemical reduction or thermal reduction.

8. The method of claim 1, wherein, The extrusion speed of the spinning solution in step 1 is 0.01-0.10 ml / min.

9. The method of claim 1, wherein, The hot environment in step 2 is a non-uniform hot environment, and the heat source is located on one side of the nascent fiber.

10. A high-elongation fiber prepared by the method of claim 1.

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