US20210189600A1

US20210189600A1 - Conductive fiber and method for fabricating the same

Info

Publication number: US20210189600A1
Application number: US16/721,490
Authority: US
Inventors: Chung-Yang Chuang; Kai-Jen Hsiao; Jing-Wen Tang
Original assignee: Industrial Technology Research Institute ITRI
Current assignee: Industrial Technology Research Institute ITRI
Priority date: 2019-12-19
Filing date: 2019-12-19
Publication date: 2021-06-24

Abstract

A conductive fiber and a method for fabricating the conductive fiber are provided. The method for fabricating the conductive fiber includes the following steps. A first solution is provided, where the first solution includes a spinnable polymer dissolved in a first solvent, wherein the weight ratio of the spinnable polymer to the first solvent is from 5:95 to 20:80. A second solution is provided, wherein the second solution includes a conductive material dispersed in a second solvent, and the weight ratio of the conductive material to the second solvent is from 5:95 to 20:80. The shape of the conductive material is dendritic or snowflake-like. Next, a wet spinning process employing the first solution and the second solution is performed to obtain the conductive fiber.

Description

TECHNICAL FIELD

The disclosure relates to a conductive fiber and a method for fabricating the same.

BACKGROUND

In the textile industry, conductive fibers are the key material for fabricating smart textiles and wearable devices. In general, metal fibers are known as main conventional conductive fibers. They exhibit sufficient strength and rigidity. Since metal fibers have poor elasticity and stretchability, textiles made of metal fibers are uncomfortable to wear.
Conventional fibers used in textiles are comfortable to wear, but they do not conduct electricity, since the chemical structure of conventional fibers does not have conjugating moiety. In order to improve their electrical conductivity, carbon black is used to blend with polymer via extrusion molding to form pellets for spinning. The obtained fiber prepared from the aforementioned process exhibits poor strength due to the excessive amount of carbon black that was added. In addition, due to the phase separation caused by poor compatibility between the carbon black and the polymer, the electrical conductivity of the fiber is hard to improve by simply adding carbon black. Furthermore, in another process for increasing the electrical conductivity of the conventional fiber, a metal layer is formed on the fiber via evaporation or surface chemical deposition to improve the electrical conductivity of the fiber. Since the metal layer exhibits poor stretchability, the fiber is apt to lose electrical conductivity after stretching.
Therefore, a novel conductive fiber and a method for preparing the same are required to solve the aforementioned problems.

SUMMARY

According to embodiments of the disclosure, the disclosure provides a method for fabricating the conductive fiber. The method includes the following steps. A first solution is provided, wherein the first solution includes a spinnable polymer dissolved in a first solvent, wherein the weight ratio of the spinnable polymer to the first solvent is from 5:95 to 20:80. A second solution is provided, wherein the second solution includes a conductive material dispersed in a second solvent, wherein the weight ratio of the conductive material to the second solvent is from 5:95 to 20:80. The shape of the conductive material is dendritic or snowflake-like. Next, the first solution and the second solution are subjected to a wet spinning process, obtaining the conductive fiber.
According to another embodiment of the disclosure, the disclosure provides a conductive fiber. The conductive fiber includes a conductive material and a spinnable polymer, wherein the shape of the conductive material is dendritic or snowflake-like, wherein the weight ratio of the spinnable polymer to the conductive material is from 7:3 to 3:7, based on the total weight of the spinnable polymer and the conductive material.
A detailed description is given in the following embodiments with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 and 2 are schematic diagrams of conductive materials having a dendritic shape according to an embodiment of the disclosure;

FIG. 3 is a schematic diagram of a conductive material having a snowflake-like shape according to an embodiment of the disclosure.

FIG. 4 is a cross-sectional view of a solid conductive fiber according to an embodiment of the disclosure.

FIG. 5 is a cross-sectional view of a hollow conductive fiber according to an embodiment of the disclosure; and

FIG. 6 is a cross-sectional view of a conductive fiber having a core-shell structure according to an embodiment of the disclosure; and

FIG. 7 is a cross-sectional view of a conductive fiber having a core-shell structure according to another embodiment of the disclosure.

DETAILED DESCRIPTION

The conductive fiber and a method for fabricating the same are described in detail in the following description. In the following detailed description, for purposes of explanation, numerous specific details and embodiments are set forth in order to provide a thorough understanding of the present disclosure. The specific elements and configurations described in the following detailed description are set forth in order to clearly describe the present disclosure. It will be apparent, however, that the exemplary embodiments set forth herein are used merely for the purpose of illustration, and the inventive concept may be embodied in various forms without being limited to those exemplary embodiments. In the drawings, the size, shape, or thickness of some of the elements may be exaggerated and not drawn on scale for illustrative purposes. The disclosure will be described with respect to particular embodiments and with reference to certain drawings but the disclosure is not limited thereto.
The disclosure provides a conductive fiber and a method for fabricating conductive fiber. Since the conductive fiber includes novel conductive materials uniformly dispersed in a spinnable polymer, and since the novel conductive materials, which have specific branched structure, constitute a network structure, not much conductive material needs to be added to give the conductive fiber a low electrical resistance. The novel conductive material can also be used with an elastic polymer, and the combination can be used in a wet spinning process. As a result, a conductive fiber with a solid, hollow or core-shell structure and having electrical conductivity can be prepared. Besides electrical conductivity, the conductive elastic fiber further exhibits improved wearing comfort and reduced electrical resistance.
The disclosure provides a method for fabricating the conductive fiber. The method includes the following steps. A first solution is provided, wherein the first solution includes a spinnable polymer dissolved in a first solvent, wherein the weight ratio of the spinnable polymer to the first solvent is from 5:95 to 20:80 (such as 7:93, 10:90, 12:88, 15:85, or 17:83). A second solution is provided, wherein the second solution includes a conductive material dispersed in a second solvent, wherein the weight ratio of the conductive material to the second solvent is from 5:95 to 20:80 (such as 7:93, 10:90, 12:88, 15:85, or 17:83), and wherein the shape of the conductive material is dendritic or snowflake-like. Next, the first solution and the second solution are subjected to a wet spinning process, obtaining the conductive fiber.
According to embodiments of the disclosure, the conductive material can be metal material.
According to embodiments of the disclosure, the conductive material is a dendritic conductive material or snowflake-like conductive material.
As shown in FIG. 1, the dendritic conductive material 100 of the disclosure is a conductive material having a central stem 1 and a plurality of side branches 3. The side branch forms an acute angle Θ with the central stem, and the acute angle Θ is from 30 degrees to 90 degrees. As shown in FIG. 1, the maximum length of the central stem is defined as the length (L) of the dendritic conductive material, and the maximum width of the conductive material in the direction perpendicular to the central stem is defined as the diameter (D) of the dendritic conductive material. According to embodiments of the disclosure, the dendritic conductive material can have an aspect ratio (i.e. length (L) to diameter (D) ratio (L/D)) is between about from 5 to 15, such as 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, or 15. According to some embodiments of the disclosure, the dendritic conductive material can have a length of 1 μm to 20 μm, and a diameter of 0.3 μm to 5 μm. According to embodiments of the disclosure, as shown in FIG. 2, the dendritic conductive material 100 of the disclosure can have a central stem 1 and a plurality of side branches 3. The dendritic conductive material can further include a plurality of sub-side branches 5. According to embodiments of the disclosure, the sub-side branch 5 can be branched (not shown).
As shown in FIG. 3, the snowflake-like conductive material of the disclosure 200 is a conductive material which has at least one multifurcated branch point 8. According to embodiments of the disclosure, the multifurcated branch point 8 is a tetrafurcated branch point, pentafurcated branch point, or hexafurcated branch point. As shown in FIG. 3, the snowflake-like conductive material of the disclosure 200 can further have a plurality of side branch 9 on the branch 7.
According to embodiments of the disclosure, the conductive material can be a metal or an alloy of the metal, wherein the metal can be gold, silver, copper, aluminum, nickel, or an alloy thereof. For example, the conductive material can be gold, silver, copper, aluminum, nickel, gold-containing alloy, silver-containing alloy, copper-containing alloy, aluminum-containing alloy, nickel-containing alloy, or a combination thereof.
According to embodiments of the disclosure, the weight ratio of the spinnable polymer to the conductive material is from 7:3 to 3:7 (such as 3.5:6.5, 4:6, 5:5, 6:4).
According to embodiments of the disclosure, a solid content of the first solution can be about 5 wt % to 20 wt %; and, a solid content of the second solution can be about 5 wt % to 20 wt %.
According to embodiments of the disclosure, the spinnable polymer can be polyvinyl alcohol, sodium alginate, carboxy methyl cellulose, polyurethane, polyester, styrene-butadiene-styrene resin (SBS), polypropylene (PP) Nitrile butadiene rubber (NBR), or a combination thereof. In addition, According to some embodiments of the disclosure, the spinnable polymer can have a weight average molecular weight of from 10,000 g/mol to 500000 g/mol), such as 50,000 g/mol to 300,000 g/mol. According to embodiments of the disclosure, the first solvent and the second solvent can be the same or different. For example, the first solvent and the second solvent can be independently deionized water, dimethylformamide, dimethylacetamide, dimethylsulfone, tetrahydrofuran, dichloromethane, methylethyl ketone, or chloroform. According to embodiments of the disclosure, the first solvent can be miscible with the second solvent.
According to embodiments of the disclosure, the weight ratio of the first solution to the second solution is from 1:2 to 3:1.
According to embodiments of the disclosure, the disclosure provides a conductive fiber. The conductive fiber includes a conductive material and a spinnable polymer, the weight ratio of the spinnable polymer to the conductive material is from 7:3 to 3:7 (such as 3.5:6.5, 4:6, 5:5, or 6:4). When the weight of the spinnable polymer is too low, the conductive material is apt to protrude out from the obtained conductive fiber (i.e. there is no fiber is formed). When the weight of the conductive material is too low, the obtained conductive fiber exhibits low electrical conductively even not conductive. According to embodiments of the disclosure, the conductive fiber of the disclosure can have a fiber fineness from 0.3 mm to 2 mm (such as from 0.3 mm to 1.0 mm, from 0.4 mm to 0.9 mm, or from 0.5 mm to 0.8 mm), and the conductive fiber of the disclosure can have a resistivity about from 9 Ω/cm to 300 Ω/cm.
According to embodiments of the disclosure, FIG. 4 is a cross-sectional view of a conductive fiber 10 according to an embodiment of the disclosure. As shown in FIG. 4, the conductive fiber 10 can be a solid conductive fiber, and the conductive fiber 10 can include a spinnable polymer 12 and a conductive material 14. According to embodiments of the disclosure, the conductive fiber 10 can consist of a spinnable polymer 12 and a conductive material 14. According to embodiments of the disclosure, the weight ratio of the spinnable polymer to the conductive material is from 7:3 to 3:7, (such as 3.5:6.5, 4:6, 5:5, or 6:4).
According to embodiments of the disclosure, the method for fabricating the solid conductive fiber as shown in FIG. 4 can include the following steps. First, the aforementioned first solution and the aforementioned second solution are provided. Next, the first solution is mixed with the second solution, obtaining a third solution, wherein the weight ratio of the first solution to the second solution is from about 1:2 to 3:1. It should be noted that, the first solvent is miscible with the second solvent, and the spinnable polymer should be soluble in the second solvent. Next, a wet spinning process employing the third solution served as a spinning solution is performed, obtaining the solid conductive fiber.
According to embodiments of the disclosure, FIG. 5 is a cross-sectional view of a conductive fiber 10 according to some embodiments of the disclosure. As shown in FIG. 5, the conductive fiber 10 can be a hollow conductive fiber, wherein the hollow conductive fiber includes a hollow portion 11 and a shell portion 13, wherein the shell portion 13 includes a spinnable polymer 12 and a conductive material 14. According to embodiments of the disclosure, the shell portion 13 consists of a spinnable polymer 12 and a conductive material 14. According to embodiments of the disclosure, the volume ratio of the hollow portion 11 to the shell portion 13 can be about 3:1 to 1:3. According to embodiments of the disclosure, the weight ratio of the spinnable polymer and the conductive material is about 1:2 to 3:1, such as 1:1, 1.5:1, 2:1, or 2.5:1.
According to embodiments of the disclosure, the method for fabricating the hollow conductive fiber as shown in FIG. 5 can include the following steps. First, the aforementioned first solution and the aforementioned second solution are provided. Next, the first solution is mixed with the second solution, obtaining a third solution, wherein the weight ratio of the first solution to the second solution is from about 1:2 to 3:1. It should be noted that, the first solvent is miscible with the second solvent, and the spinnable polymer should be soluble in the second solvent. Next, the spinning coagulating bath solution (such as sodium sulfate aqueous solution with a concentration from 1% to 15%, based on the weight of the sodium sulfate aqueous solution) serves as an inner spinning nozzle and the third solution serves as a spinning solution of the outer spinning nozzle. The spinning coagulating bath solution and the third solution are subjected to a wet spinning process via a spinning device with two spinning nozzles, obtaining the hollow conductive fiber.
According to embodiments of the disclosure, FIG. 6 is a cross-sectional view of a conductive fiber 10 according to an embodiment of the disclosure. As shown in FIG. 6, the conductive fiber 10 can be a conductive fiber with a core-shell structure, wherein the core-shell structure consists of a core portion 16 and a shell portion 17. The core portion 16 includes the spinnable polymer 12 and the conductive material 14, and the shell portion 17 includes an elastic polymer 15. According to embodiments of the disclosure, in the core-shell structure of the conductive fiber, the volume ratio of the core portion 16 to the shell portion 17 can be about 3:1 to 1:3.
According to embodiments of the disclosure, the method for fabricating the conductive fiber with a core-shell structure as shown in FIG. 6 can include the following steps. First, the aforementioned first solution and the aforementioned second solution are provided. Next, the first solution with the second solution is mixed, obtaining a third solution, wherein the first solvent is miscible with the second solvent, and the spinnable polymer is dissolved in the second solvent. Next, a fourth solution is provided, wherein the fourth solution includes a elastic polymer dissolved in a third solvent. The third solution serves as a spinning solution of the inner spinning nozzle, and the fourth solution serves as a spinning solution of the outer spinning nozzle. Finally, the third solution and the fourth solution are subjected to a wet spinning process via a spinning device with two spinning nozzles, obtaining the conductive fiber with a core-shell structure. According to other embodiments of the disclosure, the fourth solution includes the aforementioned elastic polymer dissolved in the third solvent, wherein the weight ratio of the elastic polymer to the third solution is from about 5:95 to 20:80 (such as 7:93, 10:90, 12:88, 15:85, or 17:83). According to embodiments of the disclosure, a solid content of the first solution can be about 5 wt % to 20 wt %; a solid content of the second solution can be about 5 wt % to 20 wt %; and, the solid content of the third solution can be about 5 wt % to 20 wt %.
According to other embodiments of the disclosure, as shown in FIG. 7, the conductive fiber 10 can be a conductive fiber with a core-shell structure, wherein the core-shell structure consists of a core portion 16 and a shell portion 17, wherein the core portion 16 includes the elastic polymer 15, and the shell portion 17 includes the spinnable polymer 12 and the conductive material 14.
Below, exemplary embodiments will be described in detail with reference to the accompanying drawings so as to be easily realized by a person having ordinary knowledge in the art. The inventive concept may be embodied in various forms without being limited to the exemplary embodiments set forth herein. Descriptions of well-known parts are omitted for clarity, and like reference numerals refer to like elements throughout.

EXAMPLES

Preparation of Dendritic Silver Powder
0.1-0.6 wt % parts by weight of silver nitrate (commercially available from Sigma-Aldrich) and 1-5 wt % parts by weight of nitric acid (commercially available from Sigma-Aldrich) were dissolved in deionized water, obtaining a solution. 0.02-0.2 wt % parts by weight of polyvinylpyrrolidone (commercially available from Sigma-Aldrich) was added to the aforementioned solution. After stirring, the aforementioned solution was disposed in an electrochemical deposition equipment, at a current density of 4 ASD. Herein, ITO (Indium tin oxide) glass was used as a working electrode, Ag—AgCl was used as reference electrode, platinum (Pt) was used as counter electrode. After deposition for 5-15 minutes, dendritic silver powder (with a diameter of about 0.5-2 μm, and a length of about 5-20 μm) was obtained.

Preparation of Conductive Fiber

Example 1

Polyvinyl alcohol (with a trade number of BF-24) and waterborne polyurethane (with a trade number of Paramillion AF36) were dissolved in deionized water, obtaining a first solution (with a solid content of 12 wt %, based on the total weight of water, polyvinyl alcohol, and waterborne polyurethane) (wherein the weight ratio of polyvinyl alcohol to waterborne polyurethane was 9:1). In addition, the dendritic silver powder (serving as a conductive material) was dispersed in deionized water, obtaining a second solution (the weight ratio of the conductive material to the water was 20:80). Next, the first solution was added to the second solution (wherein the weight ratio of the first solution to the second solution was 5:5). Next, after stirring at 50° C. for 120 minutes (with a stirring rate of 100 rpm), the dendritic silver powder was fully dispersed in the aforementioned first solution, obtaining a third solution. Next, the third solution was subjected to a wet spinning process via a spinning device, obtaining solid Conductive fiber (1). The spinning process was performed under the following conditions: the spinning nozzle had a diameter of 1.0 mm; the spinning temperature was about 50° C.; the spinning nozzle had a liquid flow speed of 3 cc/min; the spinning speed of the spinning process was 1 m/min; sodium sulfate aqueous solution (5%) served as the coagulating bath; and, the temperature of the coagulating bath was 25° C. Next, the fiber fineness of Conductive fiber (1) was measured with a scanning electron microscope (JEOL JSM-6480), and the resistance of Conductive fiber (1) was measured using a resistance meter (RM3544, made by Hioki Co., Ltd.). The results are shown in Table 1.

Example 2

Polyvinyl alcohol (with a trade number of BF-24) and waterborne polyurethane (with a trade number of Paramillion AF36) were dissolved in deionized water, obtaining a first solution (with a solid content of 12 wt % u, based on the total weight of water, polyvinyl alcohol, and waterborne polyurethane) (wherein the weight ratio of polyvinyl alcohol to waterborne polyurethane was 9:1). In addition, the dendritic silver powder (serving as a conductive material) was dispersed in deionized water, obtaining a second solution (the weight ratio of the conductive material to water was 20:80). Next, the first solution was added to the second solution (wherein the weight ratio of the first solution to the second solution was 5:5). Next, after stirring at 50° C. for 120 minutes (with a stirring rate of 100 rpm), the dendritic silver powder was fully dispersed in the aforementioned first solution, obtaining a third solution. Polyurethane (serving as an elastic polymer) (fabricated by Formosa Asahi spandex, with a trade number of Roica) was dissolved in N,N-dimethyl acetamide, obtaining a fourth solution (with a solid content of 15 wt %). Next, the third solution was used as a spinning solution of the inner spinning nozzle, and the fourth solution was used as a spinning solution of the outer spinning nozzle. The third solution and the fourth solution were subjected to a wet spinning process via a spinning device with two spinning nozzles, obtaining Conductive fiber (2) with a core-shell structure (wherein waterborne polyurethane/polyvinyl alcohol/dendritic silver powder composed the core portion, and the polyurethane composed the shell portion). The spinning process was performed under the following conditions: the inner spinning nozzle had a diameter of 0.6 mm; the outer spinning nozzle had a diameter of 1.0 mm; the spinning temperature was about 50° C.; the inner spinning nozzle had a liquid flow speed of 3.6 cc/min; the outer spinning nozzle had a liquid flow speed of 2.4 cc/min; the spinning speed of the spinning process was 1 m/min; sodium sulfate aqueous solution (5%) served as the coagulating bath; and, the temperature of the coagulating bath was 25° C. Next, the fiber fineness of Conductive fiber (2) was measured with a scanning electron microscope (JEOL JSM-6480), and the resistance of Conductive fiber (2) was measured using a resistance meter (RM3544, made by Hioki Co., Ltd.). The results are shown in Table 1.

Example 3

Polyvinyl alcohol (with a trade number of BF-24) and waterborne polyurethane (with a trade number of Paramillion AF36) were dissolved in deionized water, obtaining a first solution (with a solid content of 12 wt %, based on the total weight of water, polyvinyl alcohol, and waterborne polyurethane) (wherein the weight ratio of polyvinyl alcohol to waterborne polyurethane was 9:1). In addition, the dendritic silver powder (serving as a conductive material) was dispersed in deionized water, obtaining a second solution (the weight ratio of the conductive material to the water was 20:80). Next, the first solution was added to the second solution (wherein the weight ratio of the first solution to the second solution was 5:5). Next, after stirring at 50° C. for 120 minutes (with a stirring rate of 100 rpm), the dendritic silver powder was fully dispersed in the aforementioned first solution, obtaining a third solution. Next, the third solution was used as a spinning solution of the inner spinning nozzle, and sodium sulfate aqueous solution (5%) was used as a spinning solution of the outer spinning nozzle. The third solution and the sodium sulfate aqueous solution were subjected to a wet spinning process via a spinning device with two spinning nozzles, obtaining hollow Conductive fiber (3). The spinning process was performed under the following conditions: the inner spinning nozzle had a diameter of 1.0 mm; the outer spinning nozzle had a diameter of 1.9 mm; the spinning temperature was about 50° C.; the inner spinning nozzle had a liquid flow speed of 0.6 cc/min; the outer spinning nozzle had a liquid flow speed of 2.1 cc/min; the spinning speed of the spinning process was 15 m/min; sodium sulfate aqueous solution (5%) served as the coagulating bath; and, the temperature of the coagulating bath was 25° C. Next, the fiber fineness of Conductive fiber (3) was measured with a scanning electron microscope (JEOL JSM-6480), and the resistance of Conductive fiber (3) was measured using a resistance meter (RM3544, made by Hioki Co., Ltd.). The results are shown in Table 1.

Example 4

Polyvinyl alcohol (with a trade number of BF-24) and waterborne polyurethane (with a trade number of Paramillion AF36) were dissolved in deionized water, obtaining a first solution (with a solid content of 12 wt %, based on the total weight of water, polyvinyl alcohol, and waterborne polyurethane) (wherein the weight ratio of polyvinyl alcohol to waterborne polyurethane was 9:1). In addition, the dendritic silver powder (serving as a conductive material) was dispersed in deionized water, obtaining a second solution (the weight ratio of the conductive material to the water was 20:80). Next, the first solution was added to the second solution (the weight ratio of the first solution to the second solution was 4:6). Next, after stirring at 50° C. for 120 minutes (with a stirring rate of 100 rpm), the dendritic silver powder was fully dispersed in the aforementioned first solution, obtaining a third solution. Polyurethane (serving as elastic polymer) (fabricated by Formosa Asahi spandex, with a trade number of Roica) was dissolved in N,N-dimethyl acetamide, obtaining a fourth solution (the weight ratio of polyurethane to dimethylacetamide was 15:85). Next, the third solution was used as a spinning solution of the inner spinning nozzle, and the fourth solution was used as a spinning solution of the outer spinning nozzle. The third solution and the fourth solution were subjected to a wet spinning process via a spinning device with two spinning nozzles, obtaining Conductive fiber (4) with a core-shell structure (wherein waterborne polyurethane/polyvinyl alcohol/dendritic silver powder composed the core portion, and the polyurethane composed the shell portion). The spinning process was performed under the following conditions: the inner spinning nozzle had a diameter of 1.0 mm; the outer spinning nozzle had a diameter of 0.6 mm; the spinning temperature was about 50° C.; the inner spinning nozzle had a liquid flow speed of 3.6 cc/min; the outer spinning nozzle had a liquid flow speed of 2.4 cc/min; the spinning speed of the spinning process was 1 m/min; sodium sulfate aqueous solution (5%) served as the coagulating bath; and, the temperature of the coagulating bath was 25° C. Next, the fiber fineness of Conductive fiber (4) was measured with a scanning electron microscope (JEOL JSM-6480), and the resistance of Conductive fiber (4) was measured using a resistance meter (RM3544, made by Hioki Co., Ltd.). The results are shown in Table 1.

Example 5

Polyvinyl alcohol (with a trade number of BF-24) was dissolved in deionized water, obtaining a first solution (the weight ratio of polyvinyl alcohol to water was 12:88). In addition, the dendritic silver powder (serving as a conductive material) was dispersed in deionized water, obtaining a second solution (the weight ratio of the conductive material to the water was 20:80). Next, the first solution was added to the second solution (wherein the weight ratio of the first solution to the second solution was 5:5). Next, after stirring at 50° C. for 120 minutes (with a stirring rate of 100 rpm), the dendritic silver powder was fully dispersed in the aforementioned first solution, obtaining a third solution. The third solution was used as a spinning solution of the spinning nozzle. Next, the third solution serving as a spinning solution was subjected to a wet spinning process via a spinning device, obtaining solid conductive fiber (5). The spinning process was performed under the following conditions: the spinning nozzle had a diameter of 1.0 mm; the spinning temperature was about 50° C.; the spinning nozzle had a liquid flow speed of 3.0 cc/min; the spinning speed of the spinning process was 1 m/min; sodium sulfate aqueous solution (5%) served as the coagulating bath; and, the temperature of the coagulating bath was 25° C. Next, the fiber fineness of Conductive fiber (5) was measured with a scanning electron microscope (JEOL JSM-6480), and the resistance of Conductive fiber (5) was measured using a resistance meter (RM3544, made by Hioki Co., Ltd.). The results are shown in Table 1.

Example 6

Polyvinyl alcohol (with a trade number of BF-24) and waterborne polyurethane (with a trade number of Paramillion AF36) were dissolved in deionized water, obtaining a first solution (with a solid content of 12 wt %, based on the total weight of water, polyvinyl alcohol, and waterborne polyurethane) (wherein the weight ratio of polyvinyl alcohol to waterborne polyurethane was 9:1). In addition, the dendritic silver powder (serving as a conductive material) was dispersed in deionized water, obtaining a second solution (the weight ratio of the conductive material to the water was 20:80). Next, the first solution was added to the second solution (the weight ratio of the first solution to the second solution was 3.5:6.5). Next, after stirring at 50° C. for 120 minutes (with a stirring rate of 100 rpm), the dendritic silver powder was fully dispersed in the aforementioned first solution, obtaining a third solution. The third solution was used as a spinning solution of the spinning nozzle. Next, the third solution serving as a spinning solution was subjected to a wet spinning process via a spinning device, obtaining solid conductive fiber (6). The spinning process was performed under the following conditions: the spinning nozzle had a diameter of 1.0 mm; the spinning temperature was about 50° C.; the spinning nozzle had a liquid flow speed of 3.0 cc/min; the spinning speed of the spinning process was 1 m/min sodium sulfate aqueous solution (5%) served as the coagulating bath; and, the temperature of the coagulating bath was 25° C. Next, the fiber fineness of Conductive fiber (6) was measured with a scanning electron microscope (JEOL JSM-6480), and the resistance of Conductive fiber (6) was measured using a resistance meter (RM3544, made by Hioki Co., Ltd.). The results are shown in Table 1.

Comparative Example 1

Polyvinyl alcohol (with a trade number of BF-24) and (with a trade number of Paramillion AF36) were dissolved in deionized water, obtaining a first solution (with a solid content of 12 wt %, based on the total weight of water, polyvinyl alcohol, and waterorne polyurethane) (wherein the weight ratio of polyvinyl alcohol to waterborne polyurethane was 9:1). In addition, flake-like silver powder (serving as a conductive material) (fabricated by AgPro technology Inc., with a trade number of SYP981) (having a diameter of 50:9 μm) was dispersed in deionized water, obtaining a second solution (the weight ratio of the conductive material to the water was 20:80). Next, the first solution was added to the second solution (wherein the weight ratio of the first solution to the second solution was 5:5). Next, after stirring at 50° C. for 120 minutes (with a stirring rate of 100 rpm), the dendritic silver powder was fully dispersed in the aforementioned first solution, obtaining a third solution. The third solution was used as a spinning solution of the spinning nozzle. Next, the third solution serving as a spinning solution was subjected to a wet spinning process via a spinning device, obtaining solid conductive fiber (7). The spinning process was performed under the following conditions: the spinning nozzle had a diameter of 1.0 mm; the spinning temperature was about 50° C.; the spinning nozzle had a liquid flow speed of 3.0 cc/min; the spinning speed of the spinning process was 1 m/min sodium sulfate aqueous solution (5%) served as the coagulating bath; and, the temperature of the coagulating bath was 25° C. Next, the fiber fineness of Conductive fiber (7) was measured with a scanning electron microscope (JEOL JSM-6480), and the resistance of Conductive fiber (7) was measured using a resistance meter (RM3544, made by Hioki Co., Ltd.). The results are shown in Table 1.

Comparative Example 2

Polyvinyl alcohol (with a trade number of BF-24) and waterborne polyurethane (with a trade number of Paramillion AF36) were dissolved in deionized water, obtaining a first solution (with a solid content of 12 wt %, based on the total weight of water, polyvinyl alcohol, and waterborne polyurethane) (wherein the weight ratio of polyvinyl alcohol to waterborne polyurethane was 9:1). In addition, nano silver wire (serving as a conductive material) (having a diameter of 60 nm, and a length of 22 μm) was dispersed in deionized water, obtaining a second solution (the weight ratio of the conductive material to the water was 20:80). Next, the first solution was added to the second solution (wherein the weight ratio of the first solution to the second solution was 5:5). Next, after stirring at 50° C. for 120 minutes (with a stirring rate of 100 rpm), the silver nanowire was fully dispersed in the aforementioned first solution, obtaining a third solution. The third solution was used as a spinning solution of the spinning nozzle. Next, the third solution serving as a spinning solution was subjected to a wet spinning process via a spinning device, obtaining solid conductive fiber (8). The spinning process was performed under the following conditions: the spinning nozzle had a diameter of 1.0 mm; the spinning temperature was about 50° C.; the spinning nozzle had a liquid flow speed of 3.0 cc/min; the spinning speed of the spinning process was 1 m/min; sodium sulfate aqueous solution (5%) served as the coagulating bath; and, the temperature of the coagulating bath was 25° C. Next, the fiber fineness of Conductive fiber (8) was measured with a scanning electron microscope (JEOL JSM-6480), and the resistance of Conductive fiber (8) was measured using a resistance meter (RM3544, made by Hioki Co., Ltd.). The results are shown in Table 1.

Comparative Example 3

Polyvinyl alcohol (with a trade number of BF-24) and waterborne polyurethane (serving as elastic polymer) (with a trade number of Paramillion AF36) were dissolved in deionized water (wherein the weight ratio of polyvinyl alcohol to waterborne polyurethane was 9:1), obtaining a first solution (with a solid content of 12 wt %, based on the total weight of water, polyvinyl alcohol, and waterborne polyurethane) (wherein the weight ratio of polyvinyl alcohol to waterborne polyurethane was 9:1). In addition, the dendritic silver powder was dispersed in deionized water, obtaining a second solution (the weight ratio of the conductive material to the water was 20:80). Next, the first solution was added to the second solution (the weight ratio of the first solution to the second solution was 8:2). Next, after stirring at 50° C. for 120 minutes (with a stirring rate of 100 rpm), the dendritic silver powder was fully dispersed in the aforementioned first solution, obtaining a third solution. The third solution was used as a spinning solution of the spinning nozzle. Next, the third solution serving as a spinning solution was subjected to a wet spinning process via a spinning device, obtaining solid conductive fiber (9). The spinning process was performed under the following conditions: the spinning nozzle had a diameter of 1.0 mm; the spinning temperature was about 50° C.; the spinning nozzle had a liquid flow speed of 3.0 cc/min; the spinning speed of the spinning process was 1 m/min; sodium sulfate aqueous solution (5%) served as the coagulating bath; and, the temperature of the coagulating bath was 25° C. Next, the fiber fineness of Conductive fiber (9) was measured with a scanning electron microscope (JEOL JSM-6480), and the resistance of Conductive fiber (9) was measured using a resistance meter (RM3544, made by Hioki Co., Ltd.). The results are shown in Table 1.

Comparative Example 4

Polyvinyl alcohol (with a trade number of BF-24) and waterborne polyurethane (with a trade number of Paramillion AF36) were dissolved in deionized water, obtaining a first solution (with a solid content of 12 wt % c, based on the total weight of water, polyvinyl alcohol, and waterborne polyurethane) (wherein the weight ratio of polyvinyl alcohol to waterborne polyurethane was 9:1). In addition, the dendritic silver powder was dispersed in deionized water, obtaining a second solution (the weight ratio of the conductive material to the water was 20:80). Next, the first solution was added to the second solution (the weight ratio of the first solution to the second solution was 2.5:7.5). Next, after stirring at 50° C. for 120 minutes (with a stirring rate of 100 rpm), a mixed solution was obtained. The obtained mixed solution showed a partial aggregation state, and the solution had dendritic silver powder precipitated out. A resulting phase separation was observed. Thus, it was impossible to perform spinning processing with the mixed solution. Next, the fiber fineness of Conductive fiber (10) was measured with a scanning electron microscope (JEOL JSM-6480), and the resistance of Conductive fiber (10) was measured using a resistance meter (RM3544, made by Hioki Co., Ltd.). The results are shown in Table 1.

TABLE 1

Example/	polymer/	fiber
conductive	conductive	fineness		conductive
fiber	material	(mm)	resistance(Ω/cm)	material

(1)	5/5	0.70	129.6	dendritic
				silver powder
(2)	5/5	0.98	110.6	dendritic
				silver powder
(3)	5/5	0.85	74.0	dendritic
				silver powder
(4)	4/6	1.55	9.9	dendritic
				silver powder
(5)	5/5	0.72	132.1	dendritic
				silver powder
(6)	3.5/6.5	0.75	27.9	dendritic
				silver powder

Comparative
Example/	polymer/	fiber
conductive	conductive	fineness	resistivity	conductive
fiber	material	(mm)	(Ω/cm)	material

Comparative
	5/5	0.75	159.8	flake-like
Example 1/(7)				silver powder
Comparative
	5/5	0.33	292.0	silver
Example 2/(8)				nano wire
Comparative
	8/2	0.70	>106	dendritic
Example 3/(9)				silver powder
Comparative	2.5/7.5	ND	ND	dendritic
Example 4/(10)				silver powder

The method for fabricating the conductive fiber of the disclosure employs conductive materials with a specific shape (such as a dendritic or snowflake-like shape). Since the conductive materials can be uniformly dispersed in the spinnable polymer, and since the conductive materials with a specific branched structure constitute a network structure, the conductive fiber has low electrical resistance. As a result, not much conductive material needs to be added to give the conductive fiber good electrical characteristics. The conductive material of the disclosure can also be used with an elastic polymer for preparing a solid conductive fiber, a hollow conductive fiber, or a conductive fiber with a core-shell structure.
Accordingly, in comparison with conventional conductive materials (such as flake-like silver powder or nano silver wire), the electrically conductive path composed by the dendritic silver powder exhibits great conductivity due to the multiple contact points. In addition, since the multiple contact points do not damage easily after washing, the conductive fiber exhibits high laundry resistance. Furthermore, conventional conductive fibers are apt to lose their electrical conductivity after stretching since the touch point is damaged. In contrast, since the conductive fiber including dendritic silver powders has a large number of contact points and exhibits high damage tolerance, the conductive fiber of the disclosure can maintain better conductive properties. Therefore, the conductive fibers made of dendritic silver powder have the advantages of high wearing comfort and low resistance when wearing.
It will be clear that various modifications and variations can be made to the disclosed methods and materials. It is intended that the specification and examples be considered as exemplary only, with the true scope of the disclosure being indicated by the following claims and their equivalents.

Claims

What is claimed is:

1. A method for fabricating a conductive fiber, comprising:

providing a first solution, wherein the first solution comprises a spinnable polymer dissolved in a first solvent, wherein the weight ratio of the spinnable polymer to the first solvent is from 5:95 to 20:80;

providing a second solution, wherein the second solution comprises a conductive material dispersed in a second solvent, wherein the weight ratio of the conductive material to the second solvent is from 5:95 to 20:80, and wherein the shape of the conductive material is dendritic or snowflake-like; and

subjecting the first solution and the second solution to a wet spinning process, obtaining the conductive fiber.

2. The method for fabricating the conductive fiber as claimed in claim 1, wherein the conductive material is gold, silver, copper, aluminum, nickel or a combination thereof.

3. The method for fabricating the conductive fiber as claimed in claim 1, wherein the weight ratio of the spinnable polymer to the conductive material is from 7:3 to 3:7.

4. The method for fabricating the conductive fiber as claimed in claim 1, wherein the conductive material has an aspect ratio between 5 and 15.

5. The method for fabricating the conductive fiber as claimed in claim 1, wherein the spinnable polymer is polyvinyl alcohol, sodium alginate, carboxy methyl cellulose, polyurethane, polyester, styrene-butadiene-styrene resin (SBS), polypropylene (PP), Nitrile butadiene rubber (NBR), or a combination thereof.

6. The method for fabricating the conductive fiber as claimed in claim 1, wherein the first solvent and the second solvent are independently deionized water, dimethylformamide, dimethylacetamide, dimethylsulfone, tetrahydrofuran, dichloromethane, methylethyl ketone, or chloroform.

7. The method for fabricating the conductive fiber as claimed in claim 1, wherein the weight ratio of the first solution to the second solution is from 1:2 to 3:1.

8. The method for fabricating the conductive fiber as claimed in claim 1, wherein the steps of subjecting the first solution and the second solution to a wet spinning process comprise:

mixing the first solution with the second solution, obtaining a third solution, wherein the first solvent is miscible with the second solvent, and the spinnable polymer is dissolved in the second solvent; and

subjecting the third solution serving as a spinning solution to a wet spinning process.

9. The method for fabricating the conductive fiber as claimed in claim 1, wherein the steps of subjecting the first solution and the second solution to a wet spinning process comprise:

subjecting a spinning coagulating bath solution serving as a spinning solution of the inner spinning nozzle and the third solution serving as a spinning solution of the outer spinning nozzle to a wet spinning process via a spinning device with two spinning nozzles.

10. The method for fabricating the conductive fiber as claimed in claim 1, wherein the steps of subjecting the first solution and the second solution to a wet spinning process comprise:

mixing the first solution with the second solution, obtaining a third solution, wherein the first solvent is miscible with the second solvent, and the spinnable polymer is dissolved in the second solvent;

providing a fourth solution, wherein the fourth solution comprises a elastic polymer dissolved in a third solvent; and

subjecting the third solution serving as a spinning solution of the inner spinning nozzle and the fourth solution serving as a spinning solution of the outer spinning nozzle to a wet spinning process via a spinning device with two spinning nozzles.

11. The method for fabricating the conductive fiber as claimed in claim 10, wherein the weight ratio of the elastic polymer to the third solvent is from 5:95 to 20:80.

12. The method for fabricating the conductive fiber claimed in claim 11, wherein the elastic polymer is polyurethane, styrene-butadiene-styrene resin (SBS), polypropylene (PP) Nitrile butadiene rubber (NBR), or a combination thereof.

13. A conductive fiber, comprising:

a conductive material and a spinnable polymer, wherein the shape of the conductive material is dendritic or snowflake-like, wherein the weight ratio of the spinnable polymer to the conductive material is from 7:3 to 3:7, based on the total weight of the spinnable polymer and the conductive material.

14. The conductive fiber as claimed in claim 13, wherein the conductive material comprises gold, silver, copper, aluminum, nickel or a combination thereof.

15. The conductive fiber as claimed in claim 13, wherein the conductive material has an aspect ratio between 5 and 15.

16. The conductive fiber as claimed in claim 13, wherein the spinnable polymer is polyvinyl alcohol, sodium alginate, carboxy methyl cellulose, polyurethane, polyester, styrene-butadiene-styrene resin (SBS), polypropylene (PP) Nitrile butadiene rubber (NBR), or a combination thereof.

17. The conductive fiber as claimed in claim 13, wherein the conductive fiber is a solid conductive fiber.

18. The conductive fiber as claimed in claim 13, wherein the conductive fiber is a hollow conductive fiber.

19. The conductive fiber as claimed in claim 13, wherein the conductive fiber further comprises an elastic polymer.

20. The conductive fiber as claimed in claim 19, wherein the conductive fiber is a conductive fiber with a core-shell structure, wherein the core-shell structure consists of a core portion and a shell portion, wherein the core portion comprises the spinnable polymer and the conductive material, and the shell portion comprises the elastic polymer.