Fiber having spiral structure and method for preparing same under self-initiation

Abstract

A fiber having a spiral structure and a method for preparing same under self-initiation. The method comprises: extruding a graphene oxide spinning solution having a high degree of oxidation into a coagulating bath by means of a spinning head having a certain bevel angle, wherein a bevel cut leads to a difference in flow velocity between two sides of the spinning solution at an outlet, which results in unstable extrusion and the production of a fiber having a single-sided skirt structure. During the processes of pulling out the fiber from the coagulating bath and drying same, infrared illumination is applied to a single side of the fiber, resulting in spontaneous twisting of the fiber under the combined action of a solvent and interfacial tension, and therefore a self-twisting graphene oxide fiber is obtained. The self-twisting graphene fiber prepared by using the method is rich in spiral wrinkles and has the characteristics of high elongation, high strength, etc.; and in particular, the twisting process occurs spontaneously without an additional twisting and throwing device, and the twisting degree can be controlled by means of the bevel angle of the spinning head, the solidification intensity, the extrusion speed, the filament winding speed and the drying intensity, thereby achieving flexibility.

Description

A fiber with a helical structure and a self-initiating preparation method thereof Technical Field

[0001] The present invention relates to the field of nano material macroscopic assembly, in particular to a fiber with a spiral structure and a self-initiating preparation method thereof. Background Art

[0002] In 2004, Professors Andre Geim and Kostya Novoselov of the University of Manchester in the UK successfully prepared single-sheet graphene by micromechanical exfoliation of highly oriented graphite and discovered a series of unique physical properties, which opened a new era in the research of two-dimensional nanomaterials. 2 Graphene, a single-atomic-layer crystalline material composed of hybrid carbon atoms covalently bonded in a two-dimensional periodic hexagonal honeycomb structure, possesses exceptional mechanical, electrical, and thermal properties due to its unique two-dimensional layered structure. However, due to its difficulty in dispersing graphene, assembling graphene flakes into macroscopic graphene assemblies presents a challenge. Graphene oxide, a graphene derivative, is highly soluble, making it an excellent material for preparing graphene macroscopic assemblies.

[0003] As an emerging carbon fiber assembled from pure graphene, graphene fiber has great potential in flexible capacitors and flexible sensors due to its excellent conductivity. Currently, large-scale production of graphene fibers mainly adopts wet spinning, and the prepared graphene fibers have good mechanical, electrical and thermal properties. However, the obtained graphene fibers are brittle materials with an elongation at break usually less than 5%. They are brittle and easy to break, which seriously hinders their application in the field of flexible conductivity. Therefore, the existing technology usually prepares graphene fibers with a certain degree of helicity by rotating the spinning head or adding an additional twisting step, thereby improving the elongation at break of the graphene fibers. However, these methods are cumbersome, the equipment is complex, the production scale is small, and the two-dimensional layers inside the prepared spiral fibers are mainly oriented along the spiral direction rather than the fiber axis, and cannot withstand strong axial tension. Therefore, the prepared fibers often cannot have both strength and elongation.

[0004] Summary of the Invention

[0005] The present invention addresses the deficiencies of the prior art by providing a fiber with a spiral structure, comprising a two-dimensional sheet material; including a fiber core and a spiral rib structure, the spiral rib structure surrounding the outside of the fiber core; the two-dimensional sheet material constituting the fiber core is oriented axially, while the two-dimensional sheet material constituting the spiral rib structure is oriented parallel to the spiral tangent; the two-dimensional sheets of the spiral rib structure are continuous with the two-dimensional sheet material constituting the fiber core. When the fiber is stretched, the fiber core provides strength, and the spiral 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.

[0006] The present invention also provides a method for preparing the above-mentioned fiber, a method for preparing a high-elongation fiber by self-initiating spiral, comprising the following steps:

[0007] (1) A highly oxidized graphene oxide dispersion is prepared as a spinning solution; the carbon-oxygen ratio of the highly oxidized graphene oxide is 1.3-2, and the spinning solution is squeezed into a coagulation bath through a spinning head to form a primary fiber; the spinning head includes a spinning tube with an inner diameter of 80 μm-480 μm, the spinning tube having an oblique cut outlet, and the spinning solution is extruded into the coagulation bath through the oblique cut outlet of the spinning tube, wherein the oblique cut outlet is at an angle of 30°<θ<60° to the axis of the spinning tube; the oblique cut causes a flow velocity difference on both sides of the spinning solution at the outlet, resulting in unstable coagulation, and producing a fiber with a single-sided skirt structure at the oblique cut. The degree of wrinkling of the skirt can be controlled by adjusting the bevel angle of the spinning head and the coagulation bath ratio; generally speaking, the larger the bevel angle, the greater the polarity of the coagulation bath, and the greater the amplitude of the skirt wrinkling. The volume of the highly wrinkled portion of the skirt is larger than the main axis of the fiber per unit length, and therefore the amount of solvent contained is larger than the main axis of the fiber.

[0008] (2) Pulling the spun silk into a hot environment causes the solvent to evaporate, and the fiber self-initiates a spiral to obtain a high-elongation fiber. During the solvent volatilization process, the difference in the amount of solvent contained in the fiber main shaft and the skirt leads to a difference in the volatilization rate, which in turn causes asymmetric contraction, causing the fiber main shaft to drive the skirt to twist, and the skirt is wound around the main shaft in a spiral manner. This self-initiated spiral process causes the core layer graphene sheet to be oriented along the fiber axis, and the two-dimensional sheet material of the spiral rib structure is oriented perpendicular to the spiral tangent direction. Since the two-dimensional sheet from the fiber main shaft to the skirt is in a continuous transition, the two-dimensional sheet of the spiral rib structure formed by the self-initiated spiral is in a continuous transition with the two-dimensional sheet material constituting the fiber core.

[0009] Graphene oxide fiber has an extrusion swelling effect (the higher the degree of oxidation, the more obvious the swelling effect). In the prior art, in order to obtain high-strength graphene fibers, a spinning head with a low degree of oxidation and a flat outlet is used to ensure uniform extrusion and uniform fiber cross-section. When making high-toughness graphene fibers, the spinning head rotation or post-twisting process is currently used. The present application creatively adopts a beveled outlet to extrude a graphene oxide dispersion with a high oxygen content and a concentration of 3mg / g-8mg / g to construct a skirt, and combines the drying-induced self-spiral to obtain high-strength and high-elongation-at-break graphene fibers with unexpected technical effects.

[0010] In certain embodiments of the present invention, since the spiral self-initiation process is mainly dominated by the solvent volatilization rate and rate difference, a fast volatilization rate and a large rate difference are conducive to the formation of the spiral. Therefore, an organic system is specially selected, and the highly oxidized graphene oxide dispersant is N,N-dimethylformamide, dimethyl sulfoxide, ethylene glycol, pyridine, N-methylpyrrolidone, tetrahydrofuran, acetone, acetic acid, etc.

[0011] In certain embodiments of the present invention, the coagulation bath is a mixed solution of one or more of ethyl acetate, dichloromethane, methanol, acetone, n-hexane, isopropanol, etc. in different proportions.

[0012] In certain embodiments of the present invention, the temperature of the thermal environment is above 20 degrees Celsius. Those skilled in the art can select a corresponding volatilization temperature based on the actual solvent used. Furthermore, the degree of fiber helicity 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 helicity of the spiral folds, and the higher the elongation at break.

[0013] In certain preferred embodiments of the present invention, the highly oxidized graphene oxide dispersant further includes a polymer, with the polymer comprising 30% to 50% of the solute mass; the polymer is polyvinyl alcohol or polyethylene oxide. The addition of polyvinyl alcohol or polyethylene oxide can further enhance fiber strength, and the inclusion of the polymer does not affect helical formation.

[0014] Furthermore, the spinning solution extrusion speed in step 2 is 0.01 ml / min-0.10 ml / min, which has a good inner spiral effect.

[0015] 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.

[0016] Typically, the reduction is chemical reduction or thermal reduction. Generally, chemical reduction can be performed using acetic acid, hydroiodic acid, trifluoroacetic acid, hydrazine hydrate, vitamin C, or mixtures thereof; thermal reduction generally involves a temperature between 100°C and 3000°C. Those skilled in the art will appreciate that thermal reduction should be performed in an oxygen-free environment, including but not limited to an inert gas atmosphere or under vacuum conditions.

[0017] 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 spun yarn. The non-uniform thermal environment can aggravate the difference in solvent evaporation rate and further enhance the degree of spirality.

[0018] In certain embodiments of the present invention, the following scheme is specifically adopted: a continuous preparation method of graphene fibers with a spiral wrinkle microstructure includes the following steps:

[0019] (1) Highly oxidized graphene oxide with a carbon-oxygen ratio of 1.3-2 is configured into a graphene oxide spinning solution with a concentration of 3 mg / g-8 mg / g, or 30%-50% ultra-high molecular weight polyvinyl alcohol or polyethylene oxide is added and mixed uniformly to form a composite spinning solution.

[0020] (2) The spinning solution prepared in step 1 is extruded into a coagulation bath through an obliquely cut spinning head. Due to the asymmetry of the cross section of the spinning head, a flow rate difference occurs on both sides of the extrusion port of the spinning solution, resulting in unstable coagulation and a wavy skirt.

[0021] (3) The fully solidified fiber is pulled out for drying and infrared light is applied on one side, causing the fiber to twist spontaneously under the combined effects of the solvent and interfacial tension. The drying time and intensity of the drying 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 helicity of the spiral folds, and the higher the elongation at break.

[0022] (4) The graphene oxide fiber obtained in step 3 is further sent into a reduction bath for in-situ chemical reduction to obtain reduced graphene oxide or reduced graphene oxide composite fiber.

[0023] (5) The reduced graphene oxide fiber obtained in step 4 is continuously fed into a thermal reduction drum for thermal reduction, and the resulting fibers are collected to obtain graphene fibers or graphene composite fibers having a spiral wrinkled microstructure.

[0024] Furthermore, the infrared light in step 3 is 250W infrared lamps, the number of which is 1-3, and the distance between the infrared light and the fiber is fixed in the range of 5-10 cm. The winding speed is 0.5 m / min-3 m / min.

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

[0026] Furthermore, the temperature of the high-temperature heat reduction cylinder in step 5 is 100°C-350°C.

[0027] The beneficial effects of the present invention are as follows: through the method of beveling the spinning head, the present invention causes the fiber to undergo unstable coagulation at the spinning head outlet, generating initial helicity. During the subsequent drying process, an infrared light source is applied unilaterally, causing unstable drying and shrinkage on both sides of the fiber, intensifying the degree of spiral wrinkles. No subsequent additional twisting process is required, achieving a one-step method for preparing graphene fibers with spiral wrinkle microstructures. Through subsequent in-situ chemical reduction and thermal reduction, the twisted graphene fibers obtained have the characteristics of high strength, high conductivity, high elongation, and are also resistant to ultraviolet and infrared light. They can be widely used in flexible sensing, flexible conductive wearables, flexible stretchable devices and other fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 is a schematic diagram of the one-step process for preparing graphene fibers with spiral wrinkled microstructures (including a schematic diagram of an oblique needle).

[0029] Figure 2 is a SEM image of graphene fiber with spiral wrinkle microstructure.

[0030] Figure 3 shows the tensile strain curve of graphene and ultra-high molecular weight polyethylene oxide composite spiral wrinkled microstructured fibers. DETAILED DESCRIPTION

[0031] The present invention is described in detail below through examples. These examples are only used to further illustrate the present invention and cannot be understood as limiting the scope of protection of the present invention. Those skilled in the art may make some non-essential changes and adjustments based on the contents of the above invention, which all fall within the scope of protection of the present invention.

[0032] Example 1:

[0033] (1) Highly oxidized graphene with a carbon-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 through a spinning head with a bevel angle of 30° and an aperture of 80 μm into a n-hexane coagulation bath;

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

[0035] (3) A 250W infrared lamp was placed 15 cm away from one side of the fiber, so that the drying temperature at the fiber was about 20 degrees Celsius. Under the irradiation of the unilateral drying light source, the fiber contracted asymmetrically between the side with the light source and the side without the light source, resulting in increased helicity, and obtaining graphene oxide fibers with a spiral wrinkled microstructure;

[0036] (4) sending the graphene oxide fiber obtained in step 3 into a reduction bath of 1:6 HI and trifluoroacetic acid for chemical reduction, and collecting the reduced graphene oxide fiber;

[0037] (5) The reduced graphene oxide fiber obtained in step 4 is further fed into a thermal reduction drum for thermal reduction at a temperature of 300°C. Finally, a twisted graphene fiber is obtained. The spiral folds are left-handed, with a pitch of 30 μm, a strength of 567 MPa, an elongation at break of 20%, and a conductivity of 1.21×10 6 .

[0038] When the bevel angle of the spinning head in this embodiment is changed to 45° and the extrusion speed is changed to 0.1 ml / min, the obtained spiral wrinkled microstructured graphene fiber has a pitch of 22 μm, a strength of 531 MPa, an elongation at break of 24%, and a conductivity of 1.22×10 6 .

[0039] When the bevel angle of the spinning head in this embodiment is changed to 60° and the extrusion speed is changed to 0.1 ml / min, the obtained spiral wrinkled microstructured graphene fiber has a pitch of 16 μm, a fiber strength of 509 MPa, an elongation at break of 28%, and a conductivity of 1.20×10 6 S / m.

[0040] When the winding speed in this embodiment is changed to 1.8 m / min, the obtained spiral wrinkled microstructured graphene fiber has a pitch of 33 μm, a strength of 589 MPa, an elongation at break of 17%, and a conductivity of 1.23×10 6 S / m.

[0041] When the coagulation bath in this embodiment is changed to a 1:1 mixture of ethyl acetate and ethanol, the obtained spiral wrinkled microstructured graphene fiber has a pitch of 32 μm, a strength of 536 MPa, an elongation at break of 15%, and a conductivity of 1.19×10 6 S / m.

[0042] When the graphene oxide concentration in this embodiment is 8 mg / g, the obtained spiral wrinkled microstructured graphene fiber has a pitch of 18 μm, a strength of 536 MPa, an elongation at break of 25%, and a conductivity of 1.20×10 6 S / m.

[0043] When graphene oxide with a carbon-oxygen ratio of 2 is used in this embodiment, the obtained spiral wrinkled microstructured graphene fiber has a pitch of 21 μm, a strength of 492 MPa, an elongation at break of 23%, and a conductivity of 0.89×10 6 S / m.

[0044] When three infrared lamps are used for drying in this embodiment, and the infrared lamps are located on the same side of the fiber, the obtained spiral wrinkled microstructured graphene fiber has a pitch of 19 μm, a strength of 492 MPa, an elongation at break of 27%, and a conductivity of 1.25×10 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 highly oxidized 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 extruded into an ethyl acetate coagulation bath through a spinning head with a bevel angle of 45° and a pore size of 340 μm.

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

[0048] (3) A 250W infrared lamp was placed 10 cm away from one side of the fiber. Under the irradiation of a single-sided dry light source, the fiber contracted asymmetrically between the side with the light source and the side without the light source, resulting in an increase in the helicity, and a graphene oxide fiber with a highly spiral wrinkled microstructure was obtained.

[0049] (4) sending the graphene oxide fiber obtained in step 3 into a reducing bath with a HI:trifluoroacetic acid ratio of 1:3 for chemical reduction, and collecting the reduced graphene oxide fiber;

[0050] (5) The reduced graphene oxide fiber obtained in step 4 is further fed into the thermal reduction drum for thermal reduction. Finally, a graphene composite fiber with a spiral wrinkle microstructure is obtained. The spiral wrinkles 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 5 S / m.

[0051] Example 3:

[0052] (6) A N,N-dimethylformamide composite spinning solution with a mass ratio of 3:7 and a total concentration of 8 mg / g was prepared using highly oxidized graphene with a carbon-oxygen ratio of 1.3 and ultra-high molecular weight polyethylene oxide. The solution was loaded into a 5 ml syringe and extruded into an ethyl acetate coagulation bath through a spinning head with a bevel angle of 30° and a pore size of 480 μm.

[0053] (7) The fiber produces initial spiral wrinkles at the oblique spinning head. After sufficient coagulation, it is pulled out from the coagulation bath and dried at a pulling speed of 2 m / min.

[0054] (8) An infrared lamp with a power of 250W was placed 10 cm away from one side of the fiber. Under the irradiation of a single-sided dry light source, the fiber contracted asymmetrically with the side where the light source was applied and the side where the light source was not applied, resulting in an increase in the helicity, thereby obtaining a graphene oxide composite fiber with a highly spiral wrinkled microstructure.

[0055] (9) sending the graphene oxide composite fiber obtained in step 3 into a hydrazine hydrate reduction bath for chemical reduction, and collecting the reduced graphene oxide composite fiber;

[0056] (10) The reduced graphene oxide fiber obtained in step 4 is further fed into a thermal reduction drum for thermal reduction. Finally, a spiral wrinkled microstructured graphene composite fiber is obtained. The spiral 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 5 S / m.

Claims

1. A fiber with a helical structure, characterized in that, It is composed of two-dimensional sheet materials; it includes a fiber core and a helical rib structure, and the helical rib structure surrounds the outside of the fiber core; the two-dimensional sheet materials forming the fiber core are axially oriented, and the two-dimensional sheet materials forming the helical rib structure are oriented parallel to the helical tangent direction; the two-dimensional sheet of the helical rib structure and the two-dimensional sheet materials forming the fiber core show a continuous transition.

2. A method for preparing high-elongation fibers by self-initiated spiral, characterized in that, It includes the following process: (1) Prepare a graphene oxide dispersion with a high degree of oxidation as the spinning solution; the carbon-oxygen ratio of the graphene oxide with a high degree of oxidation is 1.3 - 2. The spinning solution is extruded into a coagulation bath through a spinneret to form a nascent fiber; the spinneret includes a spinning tube with an inner diameter of 80 μm - 480 μm, and the spinning tube has an inclined cut outlet. The spinning solution is extruded to the coagulation bath at the inclined cut outlet of the spinning tube, and the inclination of the inclined cut outlet forms an angle of 30° < θ < 60° with the axis of the spinning tube; (2) The nascent fiber is drawn to a hot environment so that the solvent volatilizes and the fiber self-induces helix to obtain a fiber with a high elongation rate.

3. The method according to claim 2, wherein The dispersant for graphene oxide with a high degree of oxidation is N,N-dimethylformamide, dimethyl sulfoxide, ethylene glycol, pyridine, N-methylpyrrolidone, tetrahydrofuran, acetone, acetic acid, etc.

4. The method according to claim 2, wherein The coagulation bath is a mixed solution of one or several of ethyl acetate, dichloromethane, methanol, acetone, n-hexane, isopropanol, etc. in different proportions.

5. The method according to claim 2, characterized in that, The temperature of the hot environment is above 20 degrees Celsius.

6. The method according to claim 2, wherein The dispersant for graphene oxide with a high degree of oxidation also includes a polymer, and the polymer accounts for 30% - 50% of the solute mass; the polymer is polyvinyl alcohol or polyethylene oxide.

7. The method according to claim 2, characterized in that, It also includes reducing the graphene oxide fiber obtained in step 2 to obtain a reduced graphene oxide fiber with a high elongation rate and high strength.

8. The method according to claim 2, characterized in that, The reduction is chemical reduction or thermal reduction.

9. The method according to claim 2, characterized in that, The extrusion speed of the spinning solution in step 2 is 0.01 ml / min - 0.10 ml / min.

10. The preparation method according to claims 2-9, characterized in that, The hot environment in step 2 is an uneven hot environment, and the heat source is located on one side of the nascent fiber.

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