Method for preparing flexible conductive fiber

Abstract

Disclosed in the present invention is a method for preparing a flexible conductive fiber, comprising: immersing a stretched original fiber bundle in a conductive polymer material monomer solution for swelling, taking out the original fiber bundle, wiping the conductive polymer material monomer solution from the surface of the fiber bundle, immersing the fiber bundle in an oxidant solution for polymerization, washing the polymerized fiber bundle by using deionized water, standing for waiting for the residual conductive polymer material monomer to volatilize, and then shrinking the fiber bundle to obtain the flexible conductive fiber. The method of the present invention can improve the breaking strength and elongation at break of the conductive fiber and the conductivity after stretching. The prepared flexible conductive fiber is applicable to preparation of wearable sensors.

Description

A method for preparing flexible conductive fiber Technical Field

[0001] The invention relates to a method for preparing a fiber, in particular to a method for preparing a flexible conductive fiber. Background Art

[0002] Flexible sensors have diverse and flexible structures, which make up for the defects of miniaturization and singularity of traditional sensors. They can quickly and accurately measure and collect special environments and special signals. Currently, flexible sensors are developing towards electronic skin, wearable devices and aerospace, especially wearable devices are developing rapidly.

[0003] Flexible sensors require fibers to be conductive. Conductivity means a resistance below 10⁷ Ω·cm under atmospheric conditions, but conventional fibers are not conductive. Currently, conductive fibers are categorized as follows: conductive metal fibers, metal compound-based conductive fibers, carbon black-based conductive fibers, and conductive polymer fibers. Because the conjugated structure in the backbone of polyaniline and polypyrrole makes the molecular chains rigid and insoluble, they are difficult to spin directly into fibers. Therefore, conductive polymer fibers are made by polymerizing conductive polymers such as aniline and pyrrole onto the fiber surface.

[0004] However, due to the influence of polyaniline and polypyrrole on the surface, the breaking strength and elongation of conductive polymer fibers are relatively low, and the conductivity will decrease significantly after the fiber is stretched, which affects its application in the field of conductive functional textiles. Summary of the Invention

[0005] In response to the above technical requirements, the present invention provides a method for preparing flexible conductive fibers, which improves the breaking strength and elongation at break of the conductive fibers as well as the conductivity after stretching.

[0006] The technical solution of the present invention is as follows: a method for preparing flexible conductive fibers, wherein the original fiber bundle is kept in a stretched state and a conductive polymer material is polymerized on the surface by chemical oxidation to obtain the flexible conductive fibers.

[0007] Furthermore, the maintaining of the original fiber bundle in a stretched state is to stretch the original fiber bundle by 10% to 25%.

[0008] Furthermore, the specific steps of maintaining the original fiber bundle in a stretched state and polymerizing the conductive polymer material on the surface include: immersing the stretched original fiber bundle in the conductive polymer material monomer solution to swell, then taking out the original fiber bundle and wiping the conductive polymer material monomer solution on the surface of the fiber bundle, and then immersing it in an oxidant solution for polymerization, washing the polymerized fiber bundle with deionized water, and letting it stand to wait for the residual conductive polymer material monomer to evaporate, and then shrinking the fiber bundle.

[0009] Furthermore, the swelling time of the original fiber bundle in the conductive polymer material monomer solution is 10 to 30 minutes.

[0010] Furthermore, the original fiber bundle is TPU fiber prepared by centrifugal spinning.

[0011] Furthermore, the rotation speed during centrifugal spinning is set to 1000-4000 r / min.

[0012] Furthermore, during the centrifugal spinning, the receiving distance of the centrifugal spinning is 8 to 10 cm.

[0013] Furthermore, the conductive polymer material is polypyrrole or polyaniline.

[0014] Furthermore, the oxidant solution is a 1-3 mol / L ammonium persulfate solution.

[0015] The advantages of the present invention compared with the prior art are:

[0016] Conductive fibers with a wrinkled conductive layer on the surface are obtained by pre-stretching the fiber bundle and then polymerizing the conductive polymer material. The conductive fiber has a resistance of less than 10 7 Ω·cm, the breaking elongation and breaking strength can reach up to 169% and 9.5% respectively, which are 20% and 42% higher than those of the conductive fiber without stretching polymerization. In addition, the resistance change rate of the finished flexible conductive fiber is small when stretched, and it can be used to prepare wearable sensors. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] FIG1 is an electron microscope image of the flexible conductive fiber prepared in Example 1.

[0018] FIG2 shows the resistance of the flexible conductive fiber prepared in Example 1 at different stretching lengths. DETAILED DESCRIPTION

[0019] The present invention will be further described below with reference to the examples, but are not intended to limit the present invention.

[0020] Example 1

[0021] TPU (polyurethane) is dissolved in a mixture of tetrahydrofuran (THF) and N-dimethylformamide (DMF) with a TPU concentration of 13.5-23.5%, a DMF:THF ratio of 1:1-1:3, and a stirring time of 3-6 hours at a stirring temperature of 35-55°C to prepare a TPU spinning solution. After the TPU spinning solution is prepared, a raw fiber bundle is prepared by a centrifugal spinning process. During the centrifugal spinning process, the needle head model is selected as No. 19, the roller receiving distance is 8 cm, and the rotation speed is set to 1000 r / min.

[0022] The original fiber bundle was washed and dried with deionized water, then kept stretched 10%, immersed in pyrrole to swell for 10 minutes, the fiber bundle was taken out, the pyrrole solution on the surface of the fiber bundle was wiped with dust-free paper, and immersed in 2 mol / L ammonium persulfate (APS, acidic solution: pH = 1) solution for polymerization. After the polymerized fiber bundle was washed with deionized water and left to stand for the volatilization of the residual pyrrole in the fiber, the fiber bundle shrank to obtain a flexible conductive fiber with a wrinkled surface. The electron microscope image of the flexible conductive fiber is shown in Figure 1. It can be seen that the fiber has a wrinkled outer surface.

[0023] Example 2

[0024] The original fiber bundle of Example 1 was washed and dried with deionized water, then stretched by 15% and immersed in pyrrole to swell for 10 minutes. The fiber bundle was removed, the pyrrole solution on the surface of the fiber bundle was wiped with dust-free paper, and then immersed in a 2 mol / L ammonium persulfate (APS, acidic solution: pH = 1) solution for polymerization. After the polymerized fiber bundle was washed with deionized water and allowed to stand for the volatilization of the residual pyrrole in the fiber, the fiber bundle shrank to obtain a flexible conductive fiber with a wrinkled surface.

[0025] Example 3

[0026] The original fiber bundle of Example 1 was washed and dried with deionized water, then stretched by 20% and immersed in pyrrole to swell for 10 minutes. The fiber bundle was removed, the pyrrole solution on the surface of the fiber bundle was wiped with dust-free paper, and then immersed in a 2 mol / L ammonium persulfate (APS, acidic solution: pH = 1) solution for polymerization. After the polymerized fiber bundle was washed with deionized water and allowed to stand for the volatilization of the residual pyrrole in the fiber, the fiber bundle shrank to obtain a flexible conductive fiber with a wrinkled surface.

[0027] Example 4

[0028] The original fiber bundle of Example 1 was washed and dried with deionized water, then maintained at a 25% stretch and immersed in pyrrole to swell for 10 minutes. The fiber bundle was removed, the pyrrole solution on the surface of the fiber bundle was wiped with dust-free paper, and then immersed in a 2 mol / L ammonium persulfate (APS, acidic solution: pH = 1) solution for polymerization. After the polymerized fiber bundle was washed with deionized water and allowed to stand for the volatilization of the residual pyrrole in the fiber, the fiber bundle shrank to obtain a flexible conductive fiber with a wrinkled surface.

[0029] Example 5

[0030] The original fiber bundle of Example 1 was washed and dried with deionized water, then stretched by 35% and immersed in pyrrole to swell for 10 minutes. The fiber bundle was removed, the pyrrole solution on the surface of the fiber bundle was wiped with dust-free paper, and then immersed in a 2 mol / L ammonium persulfate (APS, acidic solution: pH = 1) solution for polymerization. After the polymerized fiber bundle was washed with deionized water and allowed to stand for the volatilization of the residual pyrrole in the fiber, the fiber bundle shrank to obtain a flexible conductive fiber with a wrinkled surface.

[0031] Example 6

[0032] The original fiber bundle of Example 1 was washed and dried with deionized water, then stretched by 5%, immersed in pyrrole to swell for 10 minutes, and the fiber bundle was removed. The pyrrole solution on the surface of the fiber bundle was wiped with dust-free paper, and then immersed in a 2 mol / L ammonium persulfate (APS, acidic solution: pH = 1) solution for polymerization. After the polymerized fiber bundle was washed with deionized water and allowed to stand for the volatilization of the residual pyrrole in the fiber, the fiber bundle shrank to obtain a flexible conductive fiber with a wrinkled surface.

[0033] Example 7

[0034] The TPU spinning solution of Example 1 was used to prepare a raw fiber bundle by centrifugal spinning. During the centrifugal spinning process, the model of the spinning needle was selected to be No. 20, the receiving distance of the roller was 10 cm, and the rotation speed was set to 2000 r / min.

[0035] The original fiber bundle was washed and dried with deionized water, then stretched 10% and immersed in pyrrole to swell for 10 minutes. The fiber bundle was removed, the pyrrole solution on the fiber bundle surface was wiped with dust-free paper, and then immersed in a 2 mol / L ammonium persulfate (APS, acidic solution: pH = 1) solution for polymerization. The polymerized fiber bundle was washed with deionized water and allowed to stand for the evaporation of the residual pyrrole in the fiber. The fiber bundle then shrank, resulting in a flexible conductive fiber with a wrinkled surface.

[0036] Example 8

[0037] The TPU spinning solution of Example 1 was used to prepare a raw fiber bundle by centrifugal spinning. During the centrifugal spinning process, the model of the spinning needle was selected to be No. 22, the receiving distance of the roller was 10 cm, and the rotation speed was set to 4000 r / min.

[0038] The original fiber bundle was washed and dried with deionized water, then stretched 10% and immersed in pyrrole to swell for 10 minutes. The fiber bundle was removed, the pyrrole solution on the fiber bundle surface was wiped with dust-free paper, and then immersed in a 2 mol / L ammonium persulfate (APS, acidic solution: pH = 1) solution for polymerization. The polymerized fiber bundle was washed with deionized water and allowed to stand for the evaporation of the residual pyrrole in the fiber. The fiber bundle then shrank, resulting in a flexible conductive fiber with a wrinkled surface.

[0039] Example 9

[0040] The TPU spinning solution of Example 1 was used to prepare a raw fiber bundle by centrifugal spinning. During the centrifugal spinning process, the model of the spinning needle was selected to be No. 20, the receiving distance of the roller was 10 cm, and the rotation speed was set to 2000 r / min.

[0041] The raw fiber bundle was washed and dried with deionized water, then stretched 10% and immersed in pyrrole to swell for 20 minutes. The fiber bundle was removed, the pyrrole solution on the fiber bundle surface was wiped with dust-free paper, and then immersed in a 1 mol / L ammonium persulfate (APS, acidic solution: pH = 1) solution for polymerization. The polymerized fiber bundle was washed with deionized water and allowed to stand for the evaporation of the residual pyrrole in the fiber. The fiber bundle then shrank, resulting in a flexible conductive fiber with a wrinkled surface.

[0042] Example 10

[0043] The TPU spinning solution of Example 1 was used to prepare a raw fiber bundle by centrifugal spinning. During the centrifugal spinning process, the model of the spinning needle was selected to be No. 20, the receiving distance of the roller was 10 cm, and the rotation speed was set to 2000 r / min.

[0044] The raw fiber bundle was washed and dried with deionized water, then stretched 10% and immersed in pyrrole to swell for 30 minutes. The fiber bundle was removed, the pyrrole solution on the fiber bundle surface was wiped with dust-free paper, and then immersed in a 3 mol / L ammonium persulfate (APS, acidic solution: pH = 1) solution for polymerization. The polymerized fiber bundle was washed with deionized water and allowed to stand for the evaporation of the residual pyrrole in the fiber. The fiber bundle then shrank, resulting in a flexible conductive fiber with a wrinkled surface.

[0045] Example 11

[0046] The TPU spinning solution of Example 1 was used to prepare a raw fiber bundle by centrifugal spinning. During the centrifugal spinning process, the model of the spinning needle was selected to be No. 20, the receiving distance of the roller was 10 cm, and the rotation speed was set to 2000 r / min.

[0047] The raw fiber bundle was washed and dried with deionized water. Then, while stretched 10%, it was immersed in a solution of aniline and pentasulfosalicylic acid in a mass ratio of 1:1.5 to swell for 10 minutes. The fiber bundle was removed, its surface wiped clean with dust-free paper, and then immersed in a 2 mol / L ammonium persulfate (APS, acidic solution: pH = 1) solution for polymerization. The polymerized fiber bundle was rinsed with deionized water and allowed to stand for evaporation of the residual aniline solution within the fiber. The fiber bundle then contracted, resulting in a flexible conductive fiber with a wrinkled surface.

[0048] Example 12

[0049] The TPU spinning solution of Example 1 was used to prepare a raw fiber bundle by an electrospinning process. The raw fiber bundle was washed and dried with deionized water, then maintained in a 10% stretched state, immersed in pyrrole to swell for 10 minutes, and the fiber bundle was taken out. The pyrrole solution on the surface of the fiber bundle was wiped with dust-free paper, and then immersed in a 2 mol / L ammonium persulfate (APS, acidic solution: pH = 1) solution for polymerization. After the polymerized fiber bundle was washed with deionized water and allowed to stand for the volatilization of the residual pyrrole in the fiber, the fiber bundle shrank to obtain a flexible conductive fiber with a wrinkled surface.

[0050] Comparative Example 1

[0051] The TPU spinning solution of Example 1 was used to prepare a raw fiber bundle by centrifugal spinning. During the centrifugal spinning process, the model of the spinning needle was selected to be No. 20, the receiving distance of the roller was 10 cm, and the rotation speed was set to 2000 r / min.

[0052] The raw fiber bundle was washed and dried with deionized water, then immersed in pyrrole to swell for 30 minutes. The fiber bundle was removed, the pyrrole solution on the fiber bundle surface was wiped with dust-free paper, and then immersed in 3 mol / L ammonium persulfate (APS, acidic solution: pH = 1) solution for polymerization. The polymerized fiber bundle was washed with deionized water and allowed to stand for the residual pyrrole in the fiber to evaporate. The fiber bundle then shrank to obtain a flexible conductive fiber.

[0053] Comparative Example 2

[0054] The TPU spinning solution of Example 1 was used to prepare a raw fiber bundle by centrifugal spinning. During the centrifugal spinning process, the model of the spinning needle was selected to be No. 19, the receiving distance of the roller was 8 cm, and the rotation speed was set to 1000 r / min.

[0055] The raw fiber bundle was washed and dried with deionized water, then immersed in pyrrole to swell for 10 minutes. The fiber bundle was removed, the pyrrole solution on the fiber bundle surface was wiped with dust-free paper, and then immersed in 2 mol / L ammonium persulfate (APS, acidic solution: pH = 1) solution for polymerization. The polymerized fiber bundle was washed with deionized water and allowed to stand for the residual pyrrole in the fiber to evaporate. The fiber bundle then shrank to obtain a flexible conductive fiber.

[0056] The flexible conductive fibers prepared in the above embodiments and comparative examples were tested for elongation at break and breaking strength in accordance with the Chinese national standard GB / T 3916-2007 "Test method for fiber strength." The fiber resistance was tested in accordance with the Chinese national standard GB / T 11017-2002 "Constant current method for determining the electrical conductivity of chemical fibers." The resistance values ​​were compared when the fiber was at its original length of 10 cm and when it was stretched by 5%. The results are shown in Table 1.

[0057] Table 1 Test results of elongation at break, breaking strength and fiber resistance of each embodiment and comparative example

[0058] In addition, the flexible conductive fiber prepared in Example 1 was stretched to different degrees, and the fiber resistance was tested. The resistance change is shown in FIG2 .

[0059] The test results of the above examples and comparative examples show that stretching during the polymerization of the conductive material affects the change in the fiber's resistance and mechanical properties. In Example 1, when the conductive material was stretched to 10%, the elongation at break was 11.5%, and the breaking strength was 169 cN / dTex. The elongation at break and the breaking strength of the conductive fiber were 20% and 42% higher, respectively, than those of the unstretched fiber. In Example 10, when compared to Comparative Example 1, the elongation at break and the breaking strength of the conductive fiber were 18% and 36% higher, respectively, than those of the unstretched fiber. The resistance change of the finished fiber, which was not stretched during the preparation process, increased significantly during stretching. When the elongation was low (5%), the elongation at break was low, at 11.1%. In this case, less pyrrole was polymerized, resulting in a slightly higher resistance of 9.07 MΩ. When the stretching was high (35%), the elongation at break was low, at 11.3%, and the breaking strength was poor, at 128 cN / dTex. In this case, excessive pyrrole was polymerized, damaging the fiber's surface structure and affecting its performance. Changing the needle size, receiving distance, polymerization time, and concentration had minimal effects on the fiber's elongation at break, breaking strength, and electrical resistance. Example 12 shows that, under the same stretching conditions, the resistance of electrospun fibers is higher than that of centrifugal spinning. This is because the fibers produced by electrospinning are denser, preventing them from fully reacting with pyrrole, resulting in a higher resistance even under the same stretching conditions.

Claims

1. A preparation method of a flexible conductive fiber, characterized in that, The original fiber bundle is kept in a stretched state, and a conductive polymer material is polymerized on the surface by a chemical oxidation method to obtain the flexible conductive fiber. The conductive polymer material is polypyrrole or polyaniline. The specific steps include: stretching the original fiber bundle by 10% to 25% and immersing it in the monomer solution of the conductive polymer material for swelling, then taking out the original fiber bundle and wiping the monomer solution of the conductive polymer material on the surface of the fiber bundle, and then immersing it in an oxidant solution for polymerization. After the polymerized fiber bundle is washed with deionized water and left standing until the residual monomer of the conductive polymer material volatilizes, the fiber bundle is shrunk. The original fiber bundle is a TPU fiber prepared by centrifugal spinning, and the receiving distance of centrifugal spinning during centrifugal spinning is 8 to 10 cm.

2. The preparation method of the flexible conductive fiber according to claim 1, characterized in that, The swelling time of the original fiber bundle in the monomer solution of the conductive polymer material is 10 to 30 minutes.

3. The preparation method of the flexible conductive fiber according to claim 1, wherein, The rotation speed during centrifugal spinning is set to 1000 to 4000 r / min.

4. The preparation method of the flexible conductive fiber according to claim 1, characterized in that The oxidant solution is a 1 to 3 mol / L ammonium persulfate solution.

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