CN109811426B - Flexible conductive fiber with core-sheath structure and preparation method thereof - Google Patents
Flexible conductive fiber with core-sheath structure and preparation method thereof Download PDFInfo
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Abstract
The invention belongs to the technical field of flexible conductive fibers for wearable electronic equipment and preparation thereof, and particularly relates to a conductive coaxial nanofiber with a core-sheath structure and prepared by wrapping reduced graphene with aramid fibers or polyimide fibers and a preparation method thereof. The invention provides a preparation method of a conductive fiber with a core-sheath structure, which comprises the following steps: 1) preparing a core layer spinning solution; 2) preparing sheath spinning solution; 3) preparing coaxial fibers; 4) high-temperature thermal reduction: obtaining conductive coaxial nano-fibers from the coaxial fibers obtained in the step 3) in a high-temperature thermal reduction mode; namely the conductive fiber with the core-sheath structure. According to the method, graphene oxide is used as a core layer material, and a polymer spun by a high-temperature-resistant and wet method is used as a sheath layer material, so that the graphene oxide of the core layer can be reduced in a high-temperature thermal reduction mode, and the obtained fiber has flexibility and excellent conductivity and mechanical properties.
Description
Technical Field
The invention belongs to the technical field of flexible conductive fibers for wearable electronic equipment and preparation thereof, and particularly relates to a conductive coaxial nanofiber with a core-sheath structure and prepared by wrapping reduced graphene with aramid fibers or polyamide fibers and a preparation method thereof.
Background
In recent years, with the development of science and technology, a new generation of artificial intelligence is rapidly emerging worldwide, and the production and living modes of people are also being deeply changed. As indispensable technical applications in the artificial intelligence era, flexible and wearable intelligent electronic devices are being developed dramatically. Especially in the medical diagnosis field, through the combination of flexible electronic device and spinning technology, can realize possessing the intelligent dress of comprehensive characteristics such as wearable, travelling comfort, and timely feedback to promote wearable intelligent dress system to carry out continuous, noninvasive, real-time and comfortable monitoring to important biological identification sign, provide important clinical relevant information for disease diagnosis, preventive health care and rehabilitation nursing. Meanwhile, the testing of various related physical signs, such as body movement, pulse rate, respiration rate, body temperature, etc., put high demands on the development of flexible sensing electronics. Therefore, there is a need to develop flexible and stretchable micro conductive fibers as an important component of wearable electronic devices to connect and transmit signals. In order to be able to fit on the human body and weave into a textile, the micro conductive fibers should be highly flexible, lightweight, mechanically excellent, and safe and reliable.
For advanced carbon materials such as carbon nanotubes, graphene has unique advantages such as good electrical conductivity, high chemical and thermal stability, relatively low density, and easy functionalization, which gives them great potential in wearable electronic products. But the problems with this are also apparent: firstly, the spinnability is poor, and the single spinning is difficult to prepare into fibers; secondly, even if the carbon fiber can be spun into fiber through some complex process control, the mechanical property, especially the tensile property of the carbon fiber is extremely poor and cannot meet the requirement of practical application; therefore, there is a need to develop a conductive fiber with flexibility to meet the operational requirements of wearable electronic devices.
One method that has been widely adopted to date is to produce fibers of a flexible core-sheath structure (i.e., sheath-core structure) by co-axial spinning. The core layer is an advanced carbon material which endows excellent electric and thermal conductivity, and the sheath layer is a polymer with extremely strong spinnability to provide an isolation protection effect, so that the coaxial fiber has the excellent characteristics of small polymer density, flexibility, chemical corrosion resistance, easiness in molding and processing and the like. On one hand, the polymer of the outer layer enables the carbon material in the inner part to be continuously and smoothly spun, and the polymer serving as the protective sleeve enables the whole fiber to have good flexibility and stretchability; on the other hand, the polymer has excellent electrical insulation performance, so that the conductive core layer can be wrapped and isolated to realize the effects of internal conduction and external insulation; therefore, the whole structure can work normally, safely and effectively, and an effective way is provided for realizing the preparation of the flexible electric wire, the flexible power supply equipment and the integrated multifunctional wearable system.
Because the dispersion performance of the advanced carbon material selected for the core layer is poor, a graphene oxide aqueous solution with good liquid crystal behavior and dispersion performance is generally required to be adopted as the inner-layer spinning solution, when graphene oxide is selected as the core layer material, the inner-layer graphene oxide is difficult to reduce and complicated in conditions under the wrapping isolation of the outer-layer polymer, and the reduction of the inner-layer graphene oxide is difficult to realize, so that the excellent conductivity of the graphene is lost, and therefore, a method needs to be developed, the reduction of the inner-layer graphene oxide can be realized under the condition that the outer-layer structure is not influenced, so that the obtained fiber has flexibility and also has excellent conductivity. In addition, in the fields of high integration level and complex structure of electronic devices such as wearable intelligent clothes, the high requirements on continuous conductivity and mechanical property of conductive fibers are met, the strict requirements on heat resistance and flame retardant property of the fibers in a complex working environment are met, and the requirements of practical use on various aspects of performance need to be met.
Disclosure of Invention
In order to overcome the defects, the invention provides a preparation method of a conductive fiber with a core-sheath structure, which takes graphene oxide as a core layer material and a polymer spun by a high-temperature-resistant and wet method as a sheath layer material, so that the graphene oxide of the core layer can be reduced in a high-temperature thermal reduction mode, and the obtained fiber has flexibility and excellent conductivity and mechanical properties.
The technical scheme of the invention is as follows:
the first technical problem to be solved by the present invention is to provide a method for preparing a conductive fiber with a core-sheath structure, wherein the method comprises the following steps:
1) preparing a core layer spinning solution: uniformly mixing a graphene oxide aqueous solution with other conductive fillers to prepare a suspension or a graphene oxide aqueous solution serving as a core layer spinning solution;
2) preparing a sheath spinning solution: uniformly mixing the aramid nano-fiber or polyimide precursor and a solvent to obtain a sheath spinning solution;
3) preparing a coaxial fiber: preparing a coaxial fiber with a core-sheath structure, in which aramid fiber or polyamide wraps graphene oxide, by a coaxial wet spinning process from the core layer spinning solution and the sheath layer spinning solution;
4) high-temperature thermal reduction: obtaining conductive coaxial nano-fibers from the coaxial fibers obtained in the step 3) in a high-temperature thermal reduction mode; namely the conductive fiber with the core-sheath structure.
Further, in the step 1), the concentration of the graphene oxide aqueous solution is suitable for spinning; preferably, the concentration of the graphene oxide aqueous solution is 10mg/ml to 30 mg/ml.
Further, in the step 1), the mass ratio of the graphene oxide to other conductive fillers is as follows: 1: 0.1 to 1.
Further, in the step 1), the method for uniformly mixing the graphene oxide aqueous solution and other conductive fillers to prepare the suspension comprises the following steps: adding other conductive nano fillers into the graphene oxide aqueous solution, and stirring and ultrasonically dispersing for 10-20 min; then, freeze-drying to obtain a mixed solution with a required concentration; then stirring and defoaming to obtain a uniformly mixed suspension.
Further, in step 1), the other conductive fillers include, but are not limited to: graphene materials (including graphene nanoplatelets and reduced graphene oxide), carbon nanotubes, expanded graphite, silver nanowires, copper nanowires, or silver nanoplatelets.
Further, in the step 2), the solvent is dimethyl sulfoxide (DMSO), acetone, N-Dimethylformamide (DMF), Dimethylacetamide (DMAC), or N-methylpyrrolidone (NMP).
Further, in the step 2), the concentration of the sheath spinning solution is 1-8 wt%.
Further, in the step 2), the sheath spinning solution is prepared by the following method: dissolving aramid fiber or polyamide acid completely by magnetic stirring or mechanical stirring to obtain sheath spinning solution; preferably, the dissolution can be accelerated by heating in a water bath at 30-60 ℃.
Further, in the step 3), the wet spinning process comprises: and respectively taking a proper amount of the core layer spinning solution and the sheath layer spinning solution by using an injector, connecting a coaxial spinning needle, then carrying out wet spinning by controlling different propelling speeds, and finally collecting and drying the spun fiber to obtain the aramid fiber or polyamide-coated graphene oxide coaxial fiber with the core-sheath structure.
Further, in the step 4), the temperature of the high-temperature thermal reduction is 200-300 ℃, the reduction time is 1-3 hours, and the reduction is carried out under the protection of inert atmosphere in order to avoid oxidizing the aramid nano-fiber at high temperature.
The second technical problem to be solved by the invention is to provide a conductive fiber with a core-sheath structure, wherein the conductive fiber is prepared by adopting the method.
The sheath layer material of the conductive fiber is aramid nanofiber or polyamide fiber, and the core layer material of the conductive fiber is reduced graphene oxide or a mixture of the reduced graphene oxide and other conductive fillers.
The invention has the beneficial effects that:
the invention improves the existing coaxial fiber system, and realizes that when the core layer material is graphene oxide, the graphene oxide of the core layer can be endowed with and improve the overall conductivity of the conductive fiber by a high-temperature thermal reduction mode and doping other conductive substances; the method is simple to operate, the parameters are easy to control, and the fiber with excellent conductivity and mechanical property can be stably and continuously spun, so that the method has important practical significance; in addition, the invention also has the following advantages:
1. according to the invention, the excellent characteristics of the core graphene and the sheath aramid nanofiber are closely combined through coaxial spinning, and the outer aramid nanofiber protective sleeve endows the fibers with good mechanical properties and superior heat resistance and flame retardance under the condition of not influencing the conductive property of the core layer, so that the flexible conductive coaxial nanofiber is prepared, and an effective way is provided for realizing the preparation of a flexible wire and a flexible power supply device and finally integrating a multifunctional wearable system.
2. Compared with the traditional coaxial fiber, the core layer spinning solution of the coaxial nanofiber is a graphene oxide aqueous solution, has good dispersibility and spinnability, can assist in dispersing other conductive nano fillers to enhance the conductive effect, and can be easily reduced into graphene with good conductive performance in different modes.
3. The aramid nanofiber adopted by the sheath layer can bear the tolerance temperature of more than 200 ℃, so that the problem that the traditional coaxial structure is difficult to realize chemical reduction due to the fact that the sheath layer is used for isolating and wrapping the graphene oxide of the core layer is solved, the graphene oxide can be subjected to high-temperature thermal reduction, and the obtained conductive fiber has excellent thermal conductivity and mechanical property.
4. The invention relates to a preparation method of aramid fiber-coated graphene coaxial nanofiber, which can adjust the thickness of a core-sheath layer by adjusting the concentration and spinning rate ratio of a core-sheath layer spinning solution, thereby realizing the regulation and control of the mechanical property and the electric conductivity of the coaxial fiber, and controlling the electric conductivity according to the type and the amount of added conductive nano filler.
Description of the drawings:
FIG. 1 is a schematic representation of the coaxial spinning process of the present invention and a photograph of the coaxial fibers produced.
FIG. 2a, FIG. 2c and FIG. 2d are polarization microscope photographs of the shrinkage process of the ANF @ GO coaxial fiber obtained in comparative example 1, wherein FIG. 2a is the 0min state, FIG. 2c is the 3min state, and FIG. 2d is the 6min state; FIG. 2b is a polarizing microscope photograph of the coaxial fibers of ANF @ GO-GNPs obtained in example 1.
FIGS. 3a and 3c are scanning electron micrographs of sections of the ANF @20GO coaxial fiber obtained in comparative example 1, with the lower image being a partial magnification of the upper image; FIGS. 3b and 3d are scanning electron micrographs of cross sections of the coaxial fibers of ANF @20GO-5GNPs obtained in example 1, with the lower image being a partial magnification of the upper image.
Detailed Description
According to the invention, the excellent characteristics of the core layer graphene oxide and the sheath aramid nanofiber are closely combined through coaxial spinning, wherein the graphene oxide of the core layer has good dispersibility and spinnability, so that other conductive nano fillers can be dispersed in an auxiliary manner to enhance the conductive effect, and the graphene oxide is further reduced into graphene with good conductive performance through a simple process; the aramid nano-fiber or polyamide protective sleeve on the outer layer endows the fiber with good mechanical property and flame retardance and can bear the tolerance temperature of more than 200 ℃, so that the graphene oxide on the inner layer can be subjected to high-temperature thermal reduction, and the problem that the traditional coaxial structure is difficult to realize chemical reduction due to the fact that the sheath layer is used for isolating and wrapping the graphene oxide on the core layer is solved; the flexible conductive coaxial nanofiber is prepared, and an effective way is provided for the preparation of a flexible wire, flexible power supply equipment and finally an integrated multifunctional wearable system.
According to the invention, the aramid nano fiber or polyamide fiber is selected as the sheath material, because the aramid nano fiber or polyamide fiber has excellent mechanical properties, the durability of the coaxial structure is ensured, and the aramid nano fiber or polyamide fiber can bear the tolerance temperature of more than 200 ℃, so that the graphene oxide can be subjected to high-temperature thermal reduction, and the aramid nano fiber or polyamide fiber has the advantage of good flame retardant property and has higher safety when being used as a protective layer of a flexible wire; the core layer of the conductive fiber is reduced graphene oxide and is doped with other nano-fillers with excellent conductivity coefficient, the GO aqueous solution is selected as the inner-layer spinning solution according to the good dispersibility and liquid crystal behavior of the GO aqueous solution to endow the GO aqueous solution with better spinning performance, and the GO aqueous solution can be easily reduced into the reduced graphene oxide by adopting a high-temperature thermal reduction mode so that the reduced graphene oxide has conductivity; in addition, the invention can also assist in dispersing other nano conductive fillers except graphene, thereby further improving the overall conductivity coefficient of the fiber.
The present invention is further illustrated by the following examples, which should be construed as merely illustrative, and not limitative of the remainder of the disclosure in any way whatsoever.
Example 1
(1) Preparing large-lamellar GO by adopting an improved Hummers method, and then removing redundant acid and non-peeled expanded graphite by centrifuging to obtain a GO aqueous solution; then centrifuging for 30min through 12000rad/min to obtain a GO water solution with the concentration of 20 mg/ml;
(2) taking 20ml of GO solution with the solubility, adding 100mg of GNPs, stirring and ultrasonically dispersing for 15min, further mixing for 3min in an AR-100 stirring defoaming machine, and defoaming for 1min to obtain a uniformly mixed suspension as a core layer spinning solution;
(3) respectively weighing 6.73g of Kevlar 49 and KOH into 300ml of DMSO, stirring and dissolving for two weeks at room temperature after sealing, then further centrifuging for 5 minutes at 8000rad/min to remove undissolved KOH in the suspension, and preparing an ANF/DMSO solution with the solubility of 2 wt% to be used as a sheath spinning solution;
(4) respectively taking appropriate amount of the core layer spinning solution and the sheath layer spinning solution obtained in the steps (2) and (3) by using an injector, connecting a coaxial spinning needle (the inner diameter is 0.26mm, the outer diameter is 0.86mm), then carrying out wet spinning by controlling the flow rate of the outer layer spinning solution to be 4ml/h and the flow rate of the inner layer spinning solution to be 6ml/h, winding the spun fiber after the fiber is solidified by a coagulating bath of a mixed solution of 5 wt% glacial acetic acid acetone and water (1:1, v/v), drying the fiber at room temperature for 12h, and then placing the fiber in an oven at 60 ℃ for drying for 1 h;
(5) and (4) putting the dried coaxial nano fibers in the step (4) into a tubular furnace for high-temperature thermal reduction, wherein the reduction condition is that the coaxial nano fibers are heated for 2 hours at 215 ℃ in a nitrogen atmosphere.
Example 2
(1) Preparing large-lamellar GO by adopting an improved Hummers method, and then removing redundant acid and non-peeled expanded graphite by centrifuging to obtain a GO aqueous solution; then centrifuging for 30min through 12000rad/min to obtain a GO solution with the concentration of 20 mg/ml;
(2) taking 20ml of GO solution with the solubility, adding 200mg of GNPs, stirring and ultrasonically dispersing for 15min, further mixing for 3min in an AR-100 stirring defoaming machine, and defoaming for 1min to obtain a uniformly mixed suspension as a core layer spinning solution;
(3) respectively weighing 6.73g of Kevlar 49 and KOH into 300ml of DMSO, stirring and dissolving for two weeks at room temperature after sealing, then further centrifuging for 5 minutes at 8000rad/min to remove undissolved KOH in the suspension, and preparing an ANF/DMSO solution with the solubility of 2 wt% to be used as a sheath spinning solution;
(4) respectively taking appropriate amount of the core layer spinning solution and the sheath layer spinning solution obtained in the steps (2) and (3) by using an injector, connecting a coaxial spinning needle (the inner diameter is 0.26mm, the outer diameter is 0.86mm), then carrying out wet spinning by controlling the flow rate of the outer layer spinning solution to be 4ml/h and the flow rate of the inner layer spinning solution to be 6ml/h, winding the spun fiber after the fiber is solidified by a coagulating bath of a mixed solution of 5 wt% glacial acetic acid acetone and water (1:1, v/v), drying the fiber at room temperature for 12h, and then placing the fiber in an oven at 60 ℃ for drying for 1 h;
(5) and (4) putting the dried coaxial nano fibers in the step (4) into a tubular furnace for high-temperature thermal reduction, wherein the reduction condition is that the coaxial nano fibers are heated for 2 hours at 215 ℃ in a nitrogen atmosphere.
Comparative example 1 no addition of GNPs
(1) Preparing large-lamellar GO by adopting an improved Hummers method, and then removing redundant acid and non-peeled expanded graphite by centrifuging to obtain a GO aqueous solution; then centrifuging for 30min through 12000rad/min to obtain a GO solution with the concentration of 20 mg/ml;
(2) respectively weighing 6.73g of Kevlar 49 and KOH into 300ml of DMSO, stirring and dissolving for two weeks at room temperature after sealing, then further centrifuging for 5 minutes at 8000rad/min to remove undissolved KOH in the suspension, and preparing an ANF/DMSO solution with the solubility of 2 wt% to be used as a sheath spinning solution;
(3) respectively taking appropriate amount of the core layer spinning solution and the sheath layer spinning solution obtained in the steps (2) and (3) by using an injector, connecting a coaxial spinning needle (the inner diameter is 0.26mm, the outer diameter is 0.86mm), then carrying out wet spinning by controlling the flow rate of the outer layer spinning solution to be 4ml/h and the flow rate of the inner layer spinning solution to be 6ml/h, winding the spun fiber after the fiber is solidified by a coagulating bath of a mixed solution of 5 wt% glacial acetic acid acetone and water (1:1, v/v), drying the fiber at room temperature for 12h, and then placing the fiber in an oven at 60 ℃ for drying for 1 h;
(4) and (4) putting the dried coaxial nano fibers in the step (4) into a tubular furnace for high-temperature thermal reduction, wherein the reduction condition is that the coaxial nano fibers are heated for 2 hours at 215 ℃ in a nitrogen atmosphere.
Table 1 shows the results of conducting property and mechanical property tests of the conductive fibers obtained in example 1, example 2 and comparative example 1.
TABLE 1 conductivity and mechanical Properties test results for ANF @20rGO fibers after addition of different levels
| Example 1 | Example 2 | Comparative example 1 | |
| Conductivity (S/m) | 10751.12 | 14974.67 | 577.87 |
| Tensile Strength (MPa) | 323.68 | 320.95 | 336.84 |
| Elongation at Break (%) | 7.21 | 6.94 | 10.13 |
Example 3
(1) Preparing large-lamellar GO by adopting an improved Hummers method, and then removing redundant acid and non-peeled expanded graphite by centrifuging to obtain a GO aqueous solution; then centrifuging for 30min through 10000rad/min to obtain GO solution with the concentration of 15 mg/ml;
(2) taking 20ml of GO solution with the solubility, adding 100mg of GNPs, stirring and ultrasonically dispersing for 15min, further mixing for 3min in an AR-100 stirring defoaming machine, and defoaming for 1min to obtain a uniformly mixed suspension as a core layer spinning solution;
(3) respectively weighing 6.73g of Kevlar 49 and KOH into 300ml of DMSO, stirring and dissolving for two weeks at room temperature after sealing, then further centrifuging for 5 minutes at 8000rad/min to remove undissolved KOH in the suspension, and preparing an ANF/DMSO solution with the solubility of 2 wt% to be used as a sheath spinning solution;
(4) respectively taking appropriate amount of the core layer spinning solution and the sheath layer spinning solution obtained in the steps (2) and (3) by using an injector, connecting a coaxial spinning needle (the inner diameter is 0.26mm, the outer diameter is 0.86mm), then carrying out wet spinning by controlling the flow rate of the outer layer spinning solution to be 4ml/h and the flow rate of the inner layer spinning solution to be 6ml/h, winding the spun fiber after the fiber is solidified by a coagulating bath of a mixed solution of 5 wt% glacial acetic acid acetone and water (1:1, v/v), drying the fiber at room temperature for 12h, and then placing the fiber in an oven at 60 ℃ for drying for 1 h;
(5) and (4) putting the dried coaxial nano fibers in the step (4) into a tubular furnace for high-temperature thermal reduction, wherein the reduction condition is that the coaxial nano fibers are heated for 2 hours at 215 ℃ in a nitrogen atmosphere.
Example 4
(1) Preparing large-lamellar GO by adopting an improved Hummers method, and then removing redundant acid and non-peeled expanded graphite by centrifuging to obtain a GO aqueous solution; then centrifuging for 30min through 10000rad/min to obtain GO solution with the concentration of 15 mg/ml;
(2) taking 20ml of GO solution with the solubility, adding 200mg of GNPs, stirring and ultrasonically dispersing for 15min, further mixing for 3min in an AR-100 stirring defoaming machine, and defoaming for 1min to obtain a uniformly mixed suspension as a core layer spinning solution;
(3) respectively weighing 6.73g of Kevlar 49 and KOH into 300ml of DMSO, stirring and dissolving for two weeks at room temperature after sealing, then further centrifuging for 5 minutes at 8000rad/min to remove undissolved KOH in the suspension, and preparing an ANF/DMSO solution with the solubility of 2 wt% to be used as a sheath spinning solution;
(4) respectively taking appropriate amount of the core layer spinning solution and the sheath layer spinning solution obtained in the steps (2) and (3) by using an injector, connecting a coaxial spinning needle (the inner diameter is 0.26mm, the outer diameter is 0.86mm), then carrying out wet spinning by controlling the flow rate of the outer layer spinning solution to be 4ml/h and the flow rate of the inner layer spinning solution to be 6ml/h, winding the spun fiber after the fiber is solidified by a coagulating bath of a mixed solution of 5 wt% glacial acetic acid acetone and water (1:1, v/v), drying the fiber at room temperature for 12h, and then placing the fiber in an oven at 60 ℃ for drying for 1 h;
(5) and (4) putting the dried coaxial nano fibers in the step (4) into a tubular furnace for high-temperature thermal reduction, wherein the reduction condition is that the coaxial nano fibers are heated for 2 hours at 215 ℃ in a nitrogen atmosphere.
Comparative example 2
(1) Preparing large-lamellar GO by adopting an improved Hummers method, and then removing redundant acid and non-peeled expanded graphite by centrifuging to obtain a GO aqueous solution; then centrifuging for 30min through 10000rad/min to obtain GO solution with the concentration of 15 mg/ml;
(2) respectively weighing 6.73g of Kevlar 49 and KOH into 300ml of DMSO, stirring and dissolving for two weeks at room temperature after sealing, then further centrifuging for 5 minutes at 8000rad/min to remove undissolved KOH in the suspension, and preparing an ANF/DMSO solution with the solubility of 2 wt% to be used as a sheath spinning solution;
(3) respectively taking appropriate amount of the core layer spinning solution and the sheath layer spinning solution obtained in the steps (2) and (3) by using an injector, connecting a coaxial spinning needle (the inner diameter is 0.26mm, the outer diameter is 0.86mm), then carrying out wet spinning by controlling the flow rate of the outer layer spinning solution to be 4ml/h and the flow rate of the inner layer spinning solution to be 6ml/h, winding the spun fiber after the fiber is solidified by a coagulating bath of a mixed solution of 5 wt% glacial acetic acid acetone and water (1:1, v/v), drying the fiber at room temperature for 12h, and then placing the fiber in an oven at 60 ℃ for drying for 1 h;
(4) and (4) putting the dried coaxial nano fibers in the step (3) into a tubular furnace for high-temperature thermal reduction, wherein the reduction condition is that the coaxial nano fibers are heated for 2 hours at 215 ℃ in a nitrogen atmosphere. Table 2 shows the results of conducting property and mechanical property tests of the conductive fibers obtained in examples 3 and 4 and comparative example 2.
Table 2 conductivity and mechanical property test results of ANF @15rGO fibers after different contents are added
| Example 3 | Example 4 | Comparative example 2 | |
| Conductivity (S/m) | 3826.19 | 5848.33 | 233.21 |
| Tensile Strength (MPa) | 323.68 | 320.95 | 345.21 |
| Elongation at Break (%) | 7.90 | 7.76 | 10.03 |
Example 5
(1) Preparing large-lamellar GO by adopting an improved Hummers method, and then removing redundant acid and non-peeled expanded graphite by centrifuging to obtain a GO aqueous solution; then centrifuging for 10min at 8000rad/min to obtain a GO solution with the concentration of 10 mg/ml;
(2) taking 20ml of GO solution with the solubility, adding 100mg of GNPs, stirring and ultrasonically dispersing for 15min, further mixing for 3min in an AR-100 stirring defoaming machine, and defoaming for 1min to obtain a uniformly mixed suspension as a core layer spinning solution;
(3) respectively weighing 6.73g of Kevlar 49 and KOH into 300ml of DMSO, stirring and dissolving for two weeks at room temperature after sealing, then further centrifuging for 5 minutes at 8000rad/min to remove undissolved KOH in the suspension, and preparing an ANF/DMSO solution with the solubility of 2 wt% to be used as a sheath spinning solution;
(4) respectively taking appropriate amount of the core layer spinning solution and the sheath layer spinning solution obtained in the steps (2) and (3) by using an injector, connecting a coaxial spinning needle (the inner diameter is 0.26mm, the outer diameter is 0.86mm), then carrying out wet spinning by controlling the flow rate of the outer layer spinning solution to be 4ml/h and the flow rate of the inner layer spinning solution to be 6ml/h, winding the spun fiber after the fiber is solidified by a coagulating bath of a mixed solution of 5 wt% glacial acetic acid acetone and water (1:1, v/v), drying the fiber at room temperature for 12h, and then placing the fiber in an oven at 60 ℃ for drying for 1 h;
(5) and (4) putting the dried coaxial nano fibers in the step (4) into a tubular furnace for high-temperature thermal reduction, wherein the reduction condition is that the coaxial nano fibers are heated for 2 hours at 215 ℃ in a nitrogen atmosphere.
Example 6
(1) Large-lamellar GO is prepared by a modified Hummers method, and then excess acid and unexfoliated expanded graphite are removed by centrifugation to obtain an aqueous GO solution. Then centrifuging for 10min at 8000rad/min to obtain a GO solution with the concentration of 10 mg/ml;
(2) taking 20ml of GO solution with the solubility, adding 200mg of GNPs, stirring and ultrasonically dispersing for 15min, further mixing for 3min in an AR-100 stirring defoaming machine, and defoaming for 1min to obtain a uniformly mixed suspension as a core layer spinning solution;
(3) respectively weighing 6.73g of Kevlar 49 and KOH into 300ml of DMSO, stirring and dissolving for two weeks at room temperature after sealing, then further centrifuging for 5 minutes at 8000rad/min to remove undissolved KOH in the suspension, and preparing an ANF/DMSO solution with the solubility of 2 wt% to be used as a sheath spinning solution;
(4) respectively taking appropriate amount of the core layer spinning solution and the sheath layer spinning solution obtained in the steps (2) and (3) by using an injector, connecting a coaxial spinning needle (the inner diameter is 0.26mm, the outer diameter is 0.86mm), then carrying out wet spinning by controlling the flow rate of the outer layer spinning solution to be 4ml/h and the flow rate of the inner layer spinning solution to be 6ml/h, winding the spun fiber after the fiber is solidified by a coagulating bath of a mixed solution of 5 wt% glacial acetic acid acetone and water (1:1, v/v), drying the fiber at room temperature for 12h, and then placing the fiber in an oven at 60 ℃ for drying for 1 h;
(5) and (4) putting the dried coaxial nano fibers in the step (4) into a tubular furnace for high-temperature thermal reduction, wherein the reduction condition is that the coaxial nano fibers are heated for 2 hours at 215 ℃ in a nitrogen atmosphere.
Comparative example 3
(1) Preparing large-lamellar GO by adopting an improved Hummers method, and then removing redundant acid and non-peeled expanded graphite by centrifuging to obtain a GO aqueous solution; then centrifuging for 10min at 8000rad/min to obtain a GO solution with the concentration of 10 mg/ml;
(2) respectively weighing 6.73g of Kevlar 49 and KOH into 300ml of DMSO, stirring and dissolving for two weeks at room temperature after sealing, then further centrifuging for 5 minutes at 8000rad/min to remove undissolved KOH in the suspension, and preparing an ANF/DMSO solution with the solubility of 2 wt% to be used as a sheath spinning solution;
(3) respectively taking appropriate amount of the core layer spinning solution and the sheath layer spinning solution obtained in the steps (2) and (3) by using an injector, connecting a coaxial spinning needle (the inner diameter is 0.26mm, the outer diameter is 0.86mm), then carrying out wet spinning by controlling the flow rate of the outer layer spinning solution to be 4ml/h and the flow rate of the inner layer spinning solution to be 6ml/h, winding the spun fiber after the fiber is solidified by a coagulating bath of a mixed solution of 5 wt% glacial acetic acid acetone and water (1:1, v/v), drying the fiber at room temperature for 12h, and then placing the fiber in an oven at 60 ℃ for drying for 1 h;
(4) and (4) putting the dried coaxial nano fibers in the step (3) into a tubular furnace for high-temperature thermal reduction, wherein the reduction condition is that the coaxial nano fibers are heated for 2 hours at 215 ℃ in a nitrogen atmosphere.
Table 3 shows the results of conducting property and mechanical property tests of the conductive fibers obtained in example 5, example 6 and comparative example 3.
TABLE 3 conductivity and mechanical Properties test results for ANF @10rGO fibers after addition of different levels
| Example 5 | Example 6 | Comparative example 3 | |
| Conductivity (S/m) | 745.34 | 1731.52 | 33.08 |
| Tensile Strength (MPa) | 301.28 | 292.32 | 319.65 |
| Elongation at Break (%) | 7.89 | 6.76 | 10.95 |
Combining the data from tables 1-3, one can see that: the ANF @ rGO coaxial nano-fiber prepared by the invention can be reduced at 215 ℃, so that the ANF @ rGO coaxial nano-fiber has better conductivity, and meanwhile, the fiber still keeps good mechanical properties including excellent strength and toughness, and can meet the requirements of textiles on the mechanical properties of the fiber. By comparing data of different examples and comparative examples, the conductivity of the fiber is related to the concentration of GO and the content of the added GNPs, when the concentration of GO is higher and the content of the added GNPs is higher, the conductivity can be obviously improved, and although part of mechanical properties can be lost, the conductivity is quite excellent, and the fiber wire with high flexibility and high conductivity can be successfully prepared on the surface by the method provided by the invention.
FIG. 1 is a schematic diagram of the coaxial spinning process of the present invention and a photograph of the coaxial fibers produced; the method comprises the steps of selecting a mixed solution of graphene nanosheets dispersed in a graphene oxide aqueous solution as an inner layer spinning solution, spinning coaxial fibers of a core-sheath structure through a needle head of a coaxial structure, putting a spinning opening into a coagulating bath of an acetone/water (1; 1v/v) solution containing 5 w% of glacial acetic acid, and then rapidly coagulating to form coaxial fibers of GO/GNPs wrapped by ANF, wherein the outer layer transparent core-sheath structure is successfully designed as seen from a picture of the fibers in the upper figure; in addition, the fiber has good spinning performance, can realize continuous and uninterrupted spinning and winding under well-adjusted proper process conditions, and shows the potential of large-scale production of multifunctional core-sheath fibers.
FIG. 2 is a photograph taken by a polarizing microscope of the shrinkage process of the coaxial fibers obtained in comparative example 1 and example 1, wherein the microstructures of the individual fibers ANF @ GO and ANF @ GO-GNPs and the solidification process of the individual fibers ANF @ GO are observed under the polarizing microscope, and the fibers having coaxial structures with different morphologies of the inner and outer layers are more clearly seen from the photograph; the GO fibers of the core layer have liquid crystal behaviors, so that bright schlieren textures are shown under a polarizing microscope; after GNPs are added, GNPs in a randomly dispersed state partially block the bright gloss produced by GO, and some black speck pattern 2(b) appears in the image; furthermore, as can be seen from the drying shrinkage process (fig. 2a-c-d), the inner GO is wrapped by the outer aramid layer, the drying process is slow, so bright gloss is still maintained, and the outer ANF polymer protective sheath shrinks continuously, thereby wrapping the inner graphene oxide fiber tightly.
FIGS. 3a and 3c are scanning electron micrographs of sections of the ANF @20GO coaxial fiber obtained in comparative example 1, with the lower image being a partial magnification of the upper image; FIGS. 3b and 3d are scanning electron micrographs of cross sections of the coaxial fibers of ANF @20GO-5GNPs obtained in example 1, the lower image being a partial enlargement of the upper image; as can be seen from the figure, the cross section of the fiber obtained by the invention shows a remarkable sheath-core structure (sheath-core structure) in an SEM image, and the skin layer formed by the outer layer of the ANF fiber is more compact, so that a protective layer of GO is provided, and the overall mechanical behavior of the fiber is remarkably improved; while the core GO is characterized by a compact layered structure with dentate curvature, similar to the oriented structure of pure graphene oxide fibers (fig. 3 c); because the aqueous solution of the graphene oxide has the same solidification effect on the ANF/DMSO system, the outer layer and the inner layer of the ANF at the outer layer are simultaneously solidified in the spinning process to cause separation from the graphene of the core layer, so that the minimum interface interaction exists between the core part and the sheath part, and GO can be automatically sealed during wet spinning, thereby preventing the mutual interface permeation and avoiding the massive sacrifice of conductivity; after the GNPs are doped, due to the good dispersion effect of the graphene oxide aqueous solution, the graphene nanoplatelets are uniformly dispersed in the core layer, the lap joint of the conductive network is enhanced, and the graphene nanoplatelets can be found in a scanning electron microscope image (fig. 3d) of the enlarged core layer.
Claims (12)
1. A preparation method of a conductive fiber with a core-sheath structure is characterized by comprising the following steps:
1) preparing a core layer spinning solution: uniformly mixing a graphene oxide aqueous solution with other conductive fillers to prepare a suspension or a graphene oxide aqueous solution serving as a core layer spinning solution;
2) preparing a sheath spinning solution: uniformly mixing the aramid nano-fiber or polyimide precursor and a solvent to obtain a sheath spinning solution;
3) preparing a coaxial fiber: preparing a coaxial fiber with a core-sheath structure, in which aramid fiber or polyimide wraps graphene oxide, by a coaxial wet spinning process from the core layer spinning solution and the sheath layer spinning solution;
4) high-temperature thermal reduction: obtaining conductive coaxial nano fibers, namely conductive fibers with a core-sheath structure, from the coaxial fibers obtained in the step 3) in a high-temperature thermal reduction mode; wherein the temperature of the high-temperature thermal reduction is 200-300 ℃, the reduction time is 1-3 h, and the reduction is carried out under the protection of inert atmosphere.
2. The method for preparing the conductive fiber having the core-sheath structure according to claim 1, wherein in the step 1), the concentration of the graphene oxide aqueous solution is suitable for spinning.
3. The method of manufacturing a conductive fiber having a core-sheath structure according to claim 1, wherein the concentration of the aqueous graphene oxide solution is 10mg/ml to 30 mg/ml.
4. The method for preparing the conductive fiber with the core-sheath structure according to claim 2, wherein in the step 1), the mass ratio of the graphene oxide to the other conductive fillers is: 1: 0.1 to 1.
5. The method for preparing the conductive fiber with the core-sheath structure according to any one of claims 1 to 3, wherein in the step 1), the method for uniformly mixing the graphene oxide aqueous solution and other conductive fillers to prepare the suspension comprises the following steps: adding other conductive nano fillers into the graphene oxide aqueous solution, and stirring and ultrasonically dispersing for 10-20 min; then, freeze-drying to obtain a mixed solution with a required concentration; then stirring and defoaming to obtain a uniformly mixed suspension.
6. The method for preparing the conductive fiber with the core-sheath structure according to any one of claims 1 to 4, wherein the other conductive fillers in the step 1) include: at least one of a graphene material, a carbon nanotube, expanded graphite, a silver nanowire, a copper nanowire or a silver nanosheet.
7. The method for preparing the conductive fiber with the core-sheath structure according to any one of claims 1 to 4, wherein in the step 2), the solvent is dimethyl sulfoxide, acetone, N-dimethylformamide, dimethylacetamide or N-methylpyrrolidone.
8. The method for preparing the conductive fiber with the core-sheath structure according to claim 7, wherein in the step 2), the concentration of the sheath spinning solution is 1 to 8 wt%.
9. The method for preparing the conductive fiber with the core-sheath structure according to any one of claims 1 to 4, wherein in the step 2), the sheath spinning solution is prepared by adopting the following method: and (3) completely dissolving the aramid nano-fiber or polyimide precursor by magnetic stirring or mechanical stirring to obtain the sheath spinning solution.
10. The method for preparing the conductive fiber with the core-sheath structure according to any one of claims 1 to 4, wherein in the step 3), the wet spinning process comprises: and respectively taking a proper amount of the core layer spinning solution and the sheath layer spinning solution by using an injector, connecting a coaxial spinning needle, then carrying out wet spinning by controlling different propelling speeds, and finally collecting and drying the spun fiber to obtain the aramid fiber or polyimide-coated graphene oxide coaxial fiber with the core-sheath structure.
11. An electrically conductive fiber having a core-sheath structure, characterized in that the electrically conductive fiber is produced by the production method according to any one of claims 1 to 10.
12. The conductive fiber with the core-sheath structure of claim 11, wherein the sheath material of the conductive fiber is aramid nanofiber or polyimide fiber, and the core material of the conductive fiber is reduced graphene oxide or a mixture of reduced graphene oxide and other conductive fillers.
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