KR101832833B1 - Electrospun fiber bundle using spiral collecting coil and electospinning device of the same - Google Patents

Abstract

A helical collector including a nozzle for discharging a fiber precursor polymer solution, a converging coil positioned at a tip end of the nozzle, and a helical collecting coil spaced apart from the nozzle, And a fiber bundle and a carbon fiber comprising continuously connected and uniaxially aligned formed fibers produced by the electrospinning device.

Description

TECHNICAL FIELD [0001] The present invention relates to an electrospun fiber bundle using a spiral collecting coil and an electrospinning device for the fiber bundle,

The present disclosure relates to an electrospun fiber bundle using a helical collecting coil, and to an electrospinning apparatus for the fiber bundle.

Polyacrylonitrile (PAN), a carbon fiber precursor, has not only high carbon production but also excellent mechanical properties. Some techniques, such as wet spinning and air-gap spinning, can be used to produce carbon fibers including PAN [Liu J, Yue Z, and Fong H .; Small 2009; 5 (5): 536-542.]. The theoretical tensile strength of carbon fibers can be higher than 100 GPa, but commercial carbon fibers (Toray industries, T1000 ^® ) have only achieved ~ 7 GPa due to the diameter of the carbon fibers and the distribution of structural defects in the carbon fibers. Defects are primarily formed in the stabilization and carbonization processes of the PAN fibers to produce carbon fibers [Jalili R, Morshed M, and Ravandi SAH . Journal of Applied Polymer Science 2006; 101 (6): 4350-4357.]. The stabilization process is constituted by "under stretching" oxidation, wherein under " stretching "is performed in order to obtain high temperature durability from the thermoplastic water bath structure, the PAN molecules are aligned along the fiber axis and changed into a ladder- will be. Many studies have investigated means for reducing many types of defects such as internal compression, voids, entanglement, irregular structures, and cracks introduced by sheath-core structures, extensional bubbles, and wide openings . However, fibers with a broad diameter are considered to include un-stretched and / or non-oxidized molecules therein (however, in the case of wide diameter fibers, unstretched and / Or non-oxidized molecules are easily found.

The reduction in the diameter of the carbon fibers produced by wet spinning and air-gap spinning has been shown to reduce the number of defect sites. For example, commercially available T300 and T1000 (Toray Industries) with 7 and 5 탆 diameters have tensile strengths of 3.2 and 7 GPa, respectively. The smaller diameters of the PAN fibers result in less structurally heterogeneous, which is to improve the tensile strength of the carbon fibers in a stabilization and carbonization process referred to as "size-effect ". For this reason, the diameter of the PAN fibers must be further reduced to reach the theoretical tensile strength of the carbon fibers.

Electrospinning is a technique that can be used to reduce the diameter of precursor fibers. Therefore, this is an attractive technique for producing nanofibers containing PAN nanofibers by polymerization.

Twisted precursor fibers can have higher mechanical strength, but it is difficult to stretch polymer molecules along the fiber axis during stabilization under stretching. Without aligning the molecules along the fiber axis, the carbonization of the precursor fibers can not cause high mechanical strength. Various electrospinning technique is a well-aligned nano-been reported to produce a scaled fiber and continuous fiber bundle [Ali U, Zhou Y, Wang X, and Lin T. Journal of the Textile Institute 2012; 103 (1):. 80-88, Pan H, Li L, Hu L, and Cui X. Polymer 2006; 47 (14): 4901-4904.). Typical methods for obtaining well-aligned nanoscale fibers include a grounded collector comprising two aligned electrodes, a rotating disk with sharp edges , A rotating cylinder (Cu wire, Al cylinder), and electrodes having different shapes for the magnetic field. In addition, a variety of methods can be used to produce continuous fiber bundles, for example, by using two metallic needles that are both positive and negative voltage applied and rotating in a water bath have. In particular, water tanks have been used to collect fibers emanating from the surface of water in electrospin, as the methods for aligning the above-mentioned fibers are not likely to produce continuous bundles. However, this can cause cross-contamination within the fiber sample, and may also require higher complexity. The method comprising the two oppositely-charged needles directly produced a continuous twisted radiation. Therefore, in order to improve the mechanical strength of the carbon fiber, the precursor fibers must be aligned along the bundle axis and have a smaller diameter.

The present disclosure seeks to provide an electrospun fiber bundle using a helical collecting coil, and an electrospinning apparatus for the fiber bundle.

However, the problems to be solved by the present invention are not limited to the above-mentioned problems, and other problems not mentioned can be clearly understood by those skilled in the art from the following description.

According to a first aspect of the present invention, there is provided a fiber precursor polymer solution comprising: a nozzle for discharging a fiber precursor polymer solution; A converging coil positioned at a tip end of the nozzle; And a helical collector including a helical collecting coil spaced apart from the nozzle. ≪ Desc / Clms Page number 2 >

The second aspect of the present application provides a fiber bundle comprising fibers formed continuously and uniaxially aligned.

The third aspect of the present application provides a carbon fiber formed by using a bundle of fibers comprising sequentially connected uniaxially aligned fibers according to the second aspect of the present application as precursor fibers.

The electrospinning apparatus of the fiber bundle according to an embodiment of the present invention includes a helical collector including a helical collecting coil so that the fiber precursor polymer solution discharged from the tip of the nozzle is transferred to the web web ) In the form of a thin sheet on the entrance face of the helical collecting coil and withdrawing the deposited fibrous web to obtain a fiber bundle comprising successively uniaxially aligned fibers.

Continuous and aligned polymeric fibers (nanofibers) having a diameter of about 250 nm can be obtained using optimal experimental conditions according to one embodiment herein.

In one embodiment of the invention, to obtain fiber bundles of various diameters, spiral collecting coils having various gap sizes were experimented, and as a result, by adjusting the spacing distance of the spiral collecting coils, (Nanofibers) of the diameter of the web to obtain bundles of various diameters that can be used for a wide variety of applications (e. G., Carbon fiber applications and use of carbon bundles). A bundle of diameters corresponding to about 30 [mu] m to about 120 [mu] m is obtained when the spacing between the coils of the helical collecting coil is about 15 mm, about 20 mm, about 25 mm, about 30 mm. The spiral collector at a distance of about 20 mm produced about 90 urn bundles, which are considered to be best aligned among all fiber bundles, which have high strength and elongation rates of about 12.6 MPa and about 62.6%, respectively.

The fiber bundle in accordance with one embodiment herein may be formed using nanofibers having a diameter of from about 10 nm to about 800 nm to have a diameter of from about 1 [mu] m to about 500 [mu] m, wherein the fiber bundle is a carbon fiber precursor fiber Can be used.

Figures 1 (a) to 1 (d) illustrate, in an embodiment of the present application, a schematic view of an electrospinning system, (b) an image of fibers emitted to a spiral collector, (c) fibers aligned from a spiral collector, (D) an SEM image of the recovered fiber bundle.
Figures 2 (a) -2 (d) illustrate an embodiment of the present invention in which (a) an image of the electrospinning process taken at the collector tip with a high speed camera, (b) a schematic view of a spiral collector, And an image of the second spirally deposited fiber, and (d) a SEM image of the fibers aligned between the first spiral and the second spiral.
3 (a) to 3 (g) are graphs showing a collector schematic diagram and a collector distance of the collector system in the embodiment of the present invention, (b) a graph of distance calculation every 1/4 of the first spiral, , (c) to (g) are the electric field simulations according to the spiral spacing distance.
4A-4D are high-speed camera images and schematic views of electrospinning on a spiral collector according to a spiral spacing distance, in one embodiment of the present application: (a) without rotation and (b) (C) a schematic diagram of the net force along the spiral distance, and (d) a schematic and image showing the effect of rotation on the deposition behavior of the PAN nanofibers in the spiral collector.
Figures 5 (a) - (f) show, in an embodiment of the present invention, a cross-sectional view of an embodiment of the present invention, wherein (a) 15 mm, (E) a graph of fiber and bundle diameter along a linear spacing distance, and (f) a force-tension relationship of the bundle according to the bundle diameter.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily carry out the present invention. It should be understood, however, that the present invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. In the drawings, the same reference numbers are used throughout the specification to refer to the same or like parts.

Throughout this specification, when a part is referred to as being "connected" to another part, it is not limited to a case where it is "directly connected" but also includes the case where it is "electrically connected" do.

Throughout this specification, when a member is " on " another member, it includes not only when the member is in contact with the other member, but also when there is another member between the two members.

Throughout this specification, when an element is referred to as " including " an element, it is understood that the element may include other elements as well, without departing from the other elements unless specifically stated otherwise. The terms " about ", " substantially ", etc. used to the extent that they are used throughout the specification are intended to be taken to mean the approximation of the manufacturing and material tolerances inherent in the stated sense, Accurate or absolute numbers are used to help prevent unauthorized exploitation by unauthorized intruders of the referenced disclosure. The word " step (or step) " or " step " used to the extent that it is used throughout the specification does not mean " step for.

Throughout this specification, the term " combination (s) thereof " included in the expression of the machine form means a mixture or combination of one or more elements selected from the group consisting of the constituents described in the expression of the form of a marker, Quot; means at least one selected from the group consisting of the above-mentioned elements.

Throughout this specification, the description of "A and / or B" means "A or B, or A and B".

Hereinafter, embodiments and examples of the present invention will be described in detail with reference to the accompanying drawings. However, the present invention is not limited to these embodiments and examples and drawings.

According to a first aspect of the present invention, there is provided a fiber precursor polymer solution comprising: a nozzle for discharging a fiber precursor polymer solution; A converging coil positioned at a tip end of the nozzle; And a helical collector including a helical collecting coil spaced apart from the nozzle. ≪ Desc / Clms Page number 2 >

In one embodiment of the invention, a spinner may be attached to one side of the helical collector to rotate the helical collector.

In one embodiment of the invention, the distance between the nozzle and the helical collector may be from about 1 cm to about 20 cm, but is not limited thereto. For example, the distance between the nozzle and the spiral collector may range from about 1 cm to about 20 cm, from about 5 cm to about 20 cm, from about 10 cm to about 20 cm, from about 15 cm to about 20 cm, from about 1 cm to about 15 cm, from about 1 cm to about 10 cm, or from about 1 cm to about 5 cm.

In one embodiment of the invention, the electrospinning device of the fiber bundle may further comprise a drum. The drum may further comprise a collection of fiber bundles.

In one embodiment of the invention, the drum may include, but is not limited to, a copper rod.

In one embodiment of the present invention, a fiber web formed by discharging the fiber precursor polymer solution from the tip of the nozzle and passing through the condensing coil is deposited on an entrance surface of the spiral collecting coil, And then withdrawing the deposited fibrous web to obtain a bundle of fibers comprising successively uniaxially (one axis) aligned fibers.

Specifically, in one embodiment of the present invention, during the electrospinning, the nozzle and the converging coil are positively charged by applying a voltage, and the nanofibers electrospun from the positively charged nozzle form a spiral The nanofibers are deposited on the helical collector as an aligned nanofiber web in the form of a thin sheet is formed on the entrance face of the collecting coil, i. E. The entrance face of the first coil of the helical collecting coil. The deposited nanofiber web may be drawn and rolled into the drum to obtain a bundle of fibers comprising continuously aligned nanofibers, wherein the deposition of the nanofiber web and the nanofiber drawing are simultaneously < RTI ID = 0.0 > .

In one embodiment of the invention, the spiral collector and the drum may be rotating in opposite directions. A nanofiber web is deposited on the helical collector coil of the spiral collector while the spiral collector and the drum are simultaneously rotated in opposite directions and the deposited nanofiber web is pulled out and wound on the drum to obtain the fiber bundle .

In one embodiment of the present invention, the fiber precursor polymer solution may include, but is not limited to, a polymer material and a solvent.

In one embodiment of the present invention, the fiber precursor polymer is selected from the group consisting of polyacrylonitrile (PAN), cellulose, polyvinylidene fluoride (PVDF), poly (methyl methacrylate ), PMMA, polytetrafluoroethylene (PTFE), polysulfone (PSU), polyimide (PI), and combinations thereof. However, But may not be limited thereto.

In one embodiment herein, the solvent is selected from the group consisting of N, N-dimethylformamide, ethyl acetate, tetrahydrofuran (THF), dichloromethane, acetone, acetonitrile , MeCN), dimethyl sulfoxide (DMSO), acetic acid, n-butanol, isopropanol, ethanol, methanol, water, and combinations thereof But it is not limited thereto.

In one embodiment of the invention, the converging coil and the spiral collecting coil each comprise a wire comprising independently selected from the group consisting of copper, iron, nickel, aluminum, zinc, and combinations thereof But may not be limited thereto.

In one embodiment of the invention, the distance between the coils of the helical collecting coil may be from about 5 mm to about 30 mm, but is not limited thereto. For example, from about 5 mm to about 30 mm, from about 10 mm to about 30 mm, from about 15 mm to about 30 mm, from about 20 mm to about 30 mm, from about 25 mm to about 30 mm, mm, from about 5 mm to about 20 mm, from about 5 mm to about 15 mm, or from about 5 mm to about 10 mm.

In one embodiment of the present invention, the diameter of the fibers forming the fiber bundle may be from about 10 nm to about 800 nm, but may not be limited thereto. For example, the diameter of the fibers can be from about 10 nm to about 800 nm, from about 10 nm to about 700 nm, from about 10 nm to about 600 nm, from about 10 nm to about 500 nm, from about 10 nm to about 400 nm, From about 10 nm to about 300 nm, from about 10 nm to about 200 nm, from about 10 nm to about 100 nm, from about 200 nm to about 300 nm, from about 100 nm to about 800 nm, from about 200 nm to about 800 nm, From about 500 nm to about 800 nm, from about 800 nm, from about 400 nm to about 800 nm, from about 500 nm to about 800 nm, from about 600 nm to about 800 nm, or from about 700 nm to about 800 nm .

In one embodiment of the invention, the diameter of the fiber bundle may be from about 1 [mu] m to about 500 [mu] m, but is not limited thereto. For example, the diameter of the fiber bundle may range from about 1 micron to about 500 microns, from about 1 micron to about 400 microns, from about 1 micron to about 300 microns, from about 1 micron to about 200 microns, from about 1 micron to about 100 microns, From about 50 microns to about 500 microns, from about 200 microns to about 500 microns, from about 300 microns to about 500 microns, or from about 100 microns to about 500 microns, from about 1 micron to about 50 microns, from about 30 microns to about 120 microns, But it may be, but not limited to, 400 탆 to about 500 탆.

The second aspect of the present application provides a fiber bundle comprising fibers formed continuously and uniaxially aligned.

The fiber bundle may be produced by an electrospinning device of the fiber bundle of the first aspect of the present application, and a detailed description of the parts overlapping with the first aspect of the present application is omitted. However, the description of the first aspect of the present invention The contents can be equally applied even if the description is omitted from the second aspect.

In one embodiment of the invention, the fibers are selected from the group consisting of polyacrylonitrile (PAN), cellulose, polyvinylidene fluoride (PVDF), poly (methyl methacrylate) (PMMA), polytetrafluoroethylene (PTFE), polysulfone (PSU), polyimide (PI), and combinations thereof. .

In one embodiment of the invention, the diameter of the fibers forming the fiber bundle may be from about 10 nm to about 800 nm, but may not be limited thereto. For example, the diameter of the fibers can be from about 10 nm to about 800 nm, from about 10 nm to about 700 nm, from about 10 nm to about 600 nm, from about 10 nm to about 500 nm, from about 10 nm to about 400 nm, From about 10 nm to about 300 nm, from about 10 nm to about 200 nm, from about 10 nm to about 100 nm, from about 200 nm to about 300 nm, from about 100 nm to about 800 nm, from about 200 nm to about 800 nm, From about 500 nm to about 800 nm, from about 800 nm, from about 400 nm to about 800 nm, from about 500 nm to about 800 nm, from about 600 nm to about 800 nm, or from about 700 nm to about 800 nm .

In one embodiment of the invention, the diameter of the fiber bundle may be from about 1 [mu] m to about 500 [mu] m, but is not limited thereto. For example, the diameter of the fiber bundle may range from about 1 micron to about 500 microns, from about 1 micron to about 400 microns, from about 1 micron to about 300 microns, from about 1 micron to about 200 microns, from about 1 micron to about 100 microns, From about 50 microns to about 500 microns, from about 200 microns to about 500 microns, from about 300 microns to about 500 microns, or from about 100 microns to about 500 microns, from about 1 micron to about 50 microns, from about 30 microns to about 120 microns, But it may be, but not limited to, 400 탆 to about 500 탆.

The third aspect of the present application provides a carbon fiber formed by using a bundle of fibers comprising sequentially connected uniaxially aligned fibers according to the second aspect of the present application as precursor fibers.

Although a detailed description of the parts overlapping with the first and second aspects of the present application is omitted, the description of the first and second aspects of the present application may be applied equally to the third aspect of the present invention.

In one embodiment of the invention, the fiber bundle can be stabilized and carbonized using precursor fibers to form carbon fibers. The stabilization step is constituted by " under stretching "oxidation, and under" stretching "is performed in order to obtain a high temperature durability from the thermoplastic water tank structure. The fiber molecule (for example, polyacrylonitrile) Is aligned along the fiber axis and the polymer is cyclized.

Conventional wide diameter fibers can contain stabilized and carbonized defects by including un-stretched and / or non-oxidized molecules therein. However, in one embodiment herein, fiber bundles formed from continuously connected uniaxially aligned fibers have a small diameter of about 1 [mu] m to about 500 [mu] m, so that stabilization and carbonization defects for carbon fiber formation .

Hereinafter, embodiments of the present invention will be described in detail. However, the present invention is not limited thereto.

[Example]

≪ Preparation of electrospinning and fiber bundles >

Polyacrylonitrile (PAN, average molecular weight 150,000) and N, N-dimethylformamide (DMF) were purchased from Signa-Aldrich Korea Co., Ltd.

The electrospinning device consists of a converging lens (Nano NC Co. Ltd.) that includes a positive-charged needle nozzle and a high-voltage DC output supply. The helical collector ground was attached to a rotating winder at 800 rpm. A schematic view of the electrospinning device is shown in Fig. 1 (a). The converging coil of the converging lens and the helical collecting coil of the collector were made from Cu wire having a diameter of 1.5 mm. The converging coil was manufactured by winding a copper wire over a cylindrical stainless steel tool. The coils were rotated twice and the spacing distance between the copper wires was 10 mm. In the spiral collecting coil, the copper wire was manufactured by winding copper wire in a cone-shaped stainless steel structure, and the number of revolutions was determined according to the spacing distance. The spiral collector was attached to a rotating winder positioned in front of the nozzle at a distance of 10 cm at an angle of 45 °. The converging coil was positioned around the tip, and the optimum position was 10 mm behind.

During electrospinning, the nozzle and the converging coil were positively charged by applying at 25 kV, and the collector was grounded. The nanofibers electrospun from the positively charged nozzle were deposited on the helical collector as an aligned nanofiber web was formed at the entrance of the helical coil. Continuous, aligned nanofiber bundles were created simultaneously during electrospinning in the spiral collector as they were recovered from the nanofiber web. A copper rod insulated by teflon was used to attach the aligned nanofiber bundles and then the aligned nanofiber bundles were recovered as they slowly moved to the copper rod (drum). The recovered fiber bundle was wound on a polyvinylidene fluoride (PVDF) drum by using a DC motor.

<Characteristic Analysis of Fiber Bundle>

A scanning electron microscope (SEM) (JEOL, JSM-7401F) was used to observe the recovered fibers and the average diameter of the fibers and bundles was calculated from the SEM image using image analysis software (Gwyddion). At least 40 fibers were measured to calculate the average fiber diameter. Three-dimensional equipotential lines were simulated to measure how well-aligned fibers were collected in a helical collecting coil using a commercial 3D simulation program (Opera 3D, version 16). The magnetic field lines perpendicular to the equipotential lines affect the negatively charged polymer fibers and the polymer fiber jets are attracted towards the grounded spiral collecting coil by a macroscopic magnetic field. The behavior of the fibers was observed by photographing the spiral collecting coils using a high-speed camera (IDTvision, X-stream ^TM XS-4) during the collection process. The high-speed camera was positioned in front of the helical collector at a distance of 30 mm, and a 4,000-image was recorded at 1 second at 5000 fps. Each fiber bundle had a length of about 30 mm. And both ends of the bundle were secured by a double-sided tape and covered by a slide glass to create a handle for testing mechanical specifications. The test length was 20 mm long. The mechanical specification was measured using a pull-push gauge (JISC, JSV-H1000-HF1) and the fiber bundle pulled at a rate of 10 mm / min.

<Characteristic analysis of fiber bundle>

The aligned, continuous fiber bundle can be easily fabricated using an electrospinning system in which the shape of the collector shown in FIG. 1 has a novel design. Figure 1 (a) shows a schematic of an electrospinning process for continuous and aligned fiber bundles, in which a Cu wire wound around the tips of the needles is installed to provide a converging lens with the same voltage applied to the needles . The converging lens causes more fibers to reach the collector by focusing on the magnetic field.

Figure 1 (b) shows the shape of the spiral collector and the formation of the aligned continuous fiber bundle. Electrospun jet was deposited at the entrance face of the spiral collector by forming an aligned web, and the web was recovered by a DC motor. Figures 1 (b) and 1 (c) show the deposited web and recovered web, respectively, and the aligned fiber web was easily obtained as a fiber bundle (Figure 1 (c)). The SEM image in Figure 1 (d) shows that a well-aligned, continuous fiber bundle was produced with an optimum fiber diameter of approximately 200-300 nm.

As shown in Figs. 2 (a) to 2 (c), the deposition process was observed during formation of the helical collecting coil using a high-speed camera for capturing the behavior of the electrospun jet. The image and video indicate that a positively-charged electrospun jet is pulled toward each position of the grounded spiral collector with a high voltage output supply. 2 (a) to 2 (c), the image shows that the electrospun jet is attached to the tip edge and deposited on the wires of the helical collector. As shown in Fig. 2 (a), the collected fibers were unfolded and cracked in many spread directions from the tip edges of the spiral collectors. The resultant image shows that the entrance surface of the helical collector is covered by the unfolded fibers. However, as shown in Figures 2 (c) and 2 (d), on the side of the helical collector, the fibers are aligned, but they can not be used in the manufacturing process because they are not continuously connected to each other. Therefore, fiber deposition must be induced at the entrance face of the helical collector to obtain a continuous aligned fiber bundle. As shown in Figures 2 (c) and 2 (d), most of the fibers were aligned in a vertical direction to the copper wire. However, some fibers were partially tilted in the longitudinal direction of the copper wire. Since the fibers are deposited on the surface of the planar collector, they are firmly attached to the copper wire as they are deposited. Therefore, the fibers must be deposited in a direction perpendicular to the copper wires to reduce the contact area for the successively aligned fiber bundles.

Many researchers have used two-dimensional magnetic field simulations to predict the morphology or orientation of the electrospun fiber. This is because when the electrospun fiber is released from the needle, it is attracted by electrostatic force. Here, the three-dimensional equipotential line was simulated to measure how the electrospinning process is affected by the electric field, which can be considered as connected through the viscoelastic element with a string of positively-charged elements, It is strongly related whether the irradiated fiber is deposited on the collector.

A schematic view of the spiral collector system is shown in Fig. 3 (a). The first cycle portion of the helical collecting coil is divided by one quarter (pi, 2 pi, pi / 2 and 3 pi / 2) and L1, L2, L3 and L4 represent the working distance for each quarter It was used for betting. Also, we calculated the distance between the tip of the needle and the spiral collector portion by the following equation (1).

[Formula 1]

To understand the effect of the spiral spacing distance, the spacing distance was increased from 5 mm to 30 mm at 5 mm intervals. We have not considered the spiral wire beyond the third cycle because some fibers are attached to the collector. As shown in Fig. 3 (b), the results show that L1, L2, L3, and L4 increase with increasing spiral spacing distance. In the area between the spacing distances of 20 mm and 30 mm, the working distance to L2 and L3 was reversed and L2 began to increase more than L3. As shown in FIGS. 3 (c) to 3 (g), these results were used to perform simulations of three-dimensional equipotential lines according to the spacing distance of the helical coils in order to confirm the influence of the spiral spacing distance. The 25 kV potential was applied to the needle and coil, and the collector was grounded. Here, 5 mm is regarded as the narrowest spacing distance in the helical collector. The spacing distance was increased from 5 mm to 30 mm at 5 mm intervals. As shown in Fig. 3 (c), the cone-shaped collector can be regarded as a helical collector with a 0-spacing distance. As shown in FIGS. 3 (d) to 3 (g), the equipotential lines are concentrated at the corners of such collectors, and the density of the equipotential lines at the corners changes with increasing spacing distance of the helical collectors. The simulation results indicate that the spacing distance of the helical collector is short, and the authors predicted that almost all electrospun fibers would be deposited in a vertical direction between the first and second cycles of the helical wire. This is because the second cycle of the helical wire is close enough for the jet ejected to the electric field at the edge to be attracted. As the working distance increases, the electrical attraction due to the negatively charged spiral collector will decrease, because the intensity of the electric field is inversely proportional to distance (E = V / d [v / m]).

Electrospinning is performed on their spiral collectors depending on the spacing distance. The PAN (10 wt%) / DMF solution was electrospun to the spiral collector for 1 min at 25 kV as the collector rotated and rotated, as shown in Figures 4 (a) and 4 (b), respectively. As the spacing distance of the helical coils increased, the direction of deposition of the PAN fibers changed from the inside to the inlet of the linear collector, and the web shape of the deposited fibers also changed. When the spacing distance is less than 10 mm, the electrospun fiber is deposited inside the collector like a cone-shaped collector.

Other deposition cases are divided into three cases depending on the distance of the spiral gap. The deposition cases are strongly related to the direction of electrical attraction and net force. FIG. 4 (c) shows the intensity of the electric field for the three cases, and the direction of the vector in the elemental view is described and shown. Figure 4 (d) shows a schematic representation of the effect and shape of rotation of the fibers deposited on the helical collector. As shown at the top of the (c) of Figure 4, the first case (L3> L2), the electrical force (F ₂₎ is vertically between the first cycle and the second cycle of the attracted helical wire strongly to the radiated fibers the electric It was caused by the electric field. In this case, the spacing distance was 10 mm to 20 mm. As shown at the top of Figure 4 (d), the electrospun fiber was drawn between the first and second cycles of the helical wire, and as shown in Figures 5 (a) and 5 (b) The fibers were well-aligned. As shown in the middle of FIG. 4 (c), in the second case (L3 L2) with an interval distance of 25 mm, the electrosurfacted jet is applied to the electric attraction F ₁ As well as by F ₂ generated in the second cycle of the helical wire. Therefore, as shown in FIG. 4 (d) and FIG. 5 (c), this was possible in the case of electroluminescent fibers that spread across the entrance face of the collector and were not well-aligned. In the third case (L3 &lt; L2), almost all of the fibers were deposited along the first cycle of the helical wire. As shown in the lower part of FIG. 4 (c), the electrospun jet was affected by the strong electric field of the first cycle of the helical wire rather than the weak electric field of the second cycle of the helical wire. As shown at the bottom of Figures 4 (d) and 5 (d), this case had a spiral spacing of 30-mm, and therefore the electrospun PAN fibers were only deposited on the first linear wire, Order than the first case. In the absence of rotation in the collector, the fibers were deposited on the collector without closure of the inlet surface, and if there was a rotation, the fibers covered the collector inlet surface, as shown in Figures 4 (a) and 4 (b) As shown in FIG. In the present application, we have found that by comparing the differences of the linear collector with the presence or absence of rotation in the collector, the fibers are most strongly attached to the magnetic field point and spread along the changed point due to rotation. These stretched fibers were used to form fibers that were aligned with edge blades or rotating cylinders.

As the fiber bundles were recovered from the nanofiber webs, the present inventors were able to obtain aligned and continuous fiber bundles and were able to infer the amount of fibers produced according to the spiral distance. Closure of the inlet surface changed the amount of fibers deposited on the spiral collector and, as shown in Figures 5 (a) - (d), this affected the fiber bundle diameter, Observed in the image. The average diameter of the fibers and bundles is shown in Figure 5 (e). When the spacing distance of the helical coils was 15 mm, 20 mm, 25 mm, and 30 mm, the average bundle diameters obtained were 30 μm, 90 μm, 120 μm, and 105 μm, respectively. The diameter of the fiber bundle was increased to about 25 mm, and the amount of deposited and recovered fiber was also increased. At a spiral spacing distance of 25 mm, the two directional electric fields (F ₁ and F ₂ ) equilibrium pulls a lot of fibers toward the collector entrance surface. As shown in the SEM image of FIG. 5 (c), as a result of the electric field equilibrium, the diameter of the bundle increased to about 120 μm, while the bundle alignment was lost.

On the other hand, as shown in the SEM image of FIG. 5 (d), when the spiral spacing distance was 30 mm, the electrospun fiber was deposited in the first cycle of the helical wire and the diameter of the fiber bundle was reduced Because it did not affect the electric field of the second cycle of the helical wire. In such a case, the fiber bundles are discontinuous and exhibit low throughput due to their strong adhesion. Therefore, the equilibrium of the electric field needs to be maintained, since it ensures the optimal design of the spiral collector to obtain continuous and aligned fibers from the spiral collector.

In order to measure the mechanical properties of the fiber bundle prior to the stabilization process, a tensile test was performed as shown in Figure 5 (f) and Table 1 below. Breaking force and elongation were measured according to the distance distance, and tensile test results showed that the range of breaking force and elongation was 13 to 80 mN and 18.4 to 62.6%, respectively. Bundles with a diameter of 90 μm required the highest destructive force and elongation, and bundles with a diameter greater than 90 μm were destroyed at lower forces, even bundles consisting of very large amounts of fibers. As shown in the SEM image of Figs. 5 (a) to 5 (d), the loss of alignment is the reason for the lower destructive force.

[Table 1]

Previous studies have shown that the tip of an electrospun jet generally exhibits flexural instability, and more bending, winding, helical and looping paths can be observed as the distance reaches an increase. As indicated above, the increase in the spacing distance also causes an increase in the distance over which the electrospun jet must reach. Therefore, as shown in Fig. 5 (f), the bundle consists of warp, hoop, spiral and roofing fibers, and the breaking force of such a bundle is reduced. Further, the tensile strength is calculated depending on the cross-sectional area of the bundle, as shown in Table 1 above. The 90 [mu] m bundle requires a breaking force and tensile strength of about 80 mN and about 12.6 MPa. These mechanical strength values are found to be reasonable values when compared with the results obtained in other studies. The breaking strength and tensile modulus of the 13 wt% PAN nanofibers were about 1 N and about 30% after ironing between two teflon-coated fabrics (low set temperature of about 100 ° C) and heat treatment. The tensile strength of the nanofiber mat with 10 wt% PAN concentration was 10.89 MPa after heat treatment at 220 캜 for 30 min.

One embodiment of the present application has obtained continuous and aligned PAN polymer fibers having a diameter of about 250 nm using optimal experimental conditions. The fibers deposited near the entrance face of the helical collector were aligned and the fibers were recovered. These phenomena have been studied by performing calculations on the distribution of the equipotential lines and the distance between the needle and the position of the helical coil. To obtain bundles of various diameters, several gap sizes were tested on a helical collecting coil. As a result, by adjusting the spacing distance of the spiral collecting coils, bundles of various diameters have been obtained that can be used for a wide variety of applications (e.g., carbon fiber applications and use of carbon bundles). Bundles of diameters corresponding to 30 to 120 占 퐉 were obtained when the gap sizes of the helical coils were 15 mm, 20 mm, 25 mm, and 30 mm. The spiral collector at 20 mm distance produced a 90 μm bundle, which is considered to be the best aligned among all fiber bundles, with strength and elongation of about 12.6 MPa and about 62.6%, respectively. In order to produce aligned and continuous fiber bundles using the spiral collector, it is necessary to optimize the design of the spiral collector to maintain the equilibrium of the electric field.

It will be understood by those of ordinary skill in the art that the foregoing description of the embodiments is for illustrative purposes and that those skilled in the art can easily modify the invention without departing from the spirit or essential characteristics thereof. It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive. For example, each component described as a single entity may be distributed and implemented, and components described as being distributed may also be implemented in a combined form.

The scope of the present invention is defined by the appended claims rather than the detailed description, and all changes or modifications derived from the meaning and scope of the claims and their equivalents should be construed as being included within the scope of the present invention.

Claims (13)

A nozzle for discharging the fiber precursor polymer solution;
A converging coil positioned at a tip end of the nozzle; And
A spiral collector including a helical collecting coil spaced apart from the nozzle,
And an optical fiber bundle.
The method according to claim 1,
A fiber web formed by passing the fiber precursor polymer solution from the tip of the nozzle and passing through the converging coil is deposited on the inlet face of the helical collecting coil and is withdrawed by the deposited fiber web Wherein the fiber bundle is obtained by successively uniaxially aligned fibers.
3. The method of claim 2,
Further comprising a drum for collecting the fiber bundle.
The method according to claim 1,
Wherein the fiber precursor polymer solution comprises a fiber precursor polymer material and a solvent.
The method according to claim 1,
Wherein the converging coil and the spiral collecting coil each comprise a wire that is independently selected from the group consisting of copper, iron, nickel, aluminum, zinc, and combinations thereof. Device.
The method according to claim 1,
Wherein a distance between the coils of the helical collecting coil is 5 mm to 30 mm.
The method according to claim 1,
Wherein the diameter of the fibers is from 10 nm to 800 nm.
The method according to claim 1,
Wherein the diameter of the fiber bundle is from 1 [mu] m to 500 [mu] m.
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