CN114302984A

CN114302984A - Stretchable conductive yarn and method of making same

Info

Publication number: CN114302984A
Application number: CN202180003441.5A
Authority: CN
Inventors: 马志军; 郑子剑; 庄秋娜
Original assignee: Hong Kong Polytechnic University HKPU
Current assignee: Hong Kong Polytechnic University HKPU
Priority date: 2020-11-02
Filing date: 2021-10-28
Publication date: 2022-04-08
Anticipated expiration: 2041-10-28
Also published as: CN114302984B

Abstract

A stretchable conductive yarn and a method of making the same, the stretchable conductive yarn being comprised of an elastomeric yarn and silver particles dispersed in and on the elastomeric yarn. The manufacturing method is based on co-heating drawing of polymer and elastomer and post-loading of silver particles, and belongs to an extensible production technology. The manufacturing method is simple, efficient and cost-effective, and avoids the use of toxic organic solvents.

Description

Stretchable conductive yarn and method of making same

Technical Field

The present invention generally relates to a yarn having ultra-stretchability and high conductivity and a method for manufacturing the same.

Background

Wearable electronics play an increasingly important role in human daily life. They are typically designed in the form of straps and watches to be worn on the wrist, footwear to be worn on the foot, glasses and helmets to be worn on the head, and products including smart clothing, backpacks, canes and accessories. Typical applications for wearable electronics include sports/fitness monitoring, positioning, communication, entertainment, electronic payment, etc. According to market statistics, the market size of the wearable electronic products in the world can reach $ 312.7 billion in 2020, which is equivalent to 17.8% increase each year in the period of 2015-. Wearable electronics would be a huge market. In addition to functionality, consumer demands for comfort in future wearable electronics will also be higher and higher. High-performance elastic conductive materials as basic components have become a great influence on further development of wearable electronic product technology.

On the other hand, yarn is the basic and most important material for producing garments. Fabrics made from yarns generally have good air and moisture permeability, as well as a soft touch. One of the most important trends in the future development of wearable electronics is to integrate electronic devices with garments, or to directly impart electronic functionality to garments, in order to provide comfort and convenience of wear. The conductive yarn is the basis of the electronic textile material. Therefore, it will play an important role in the future development of high performance wearable electronics. In order to meet the requirement of wearable electronic products on large deformation adaptability, such as devices used at human joint parts, the development of high-performance elastic conductive yarns is urgently needed. However, the elastic conductive yarn disclosed so far has at least the following disadvantages: 1. fail to have both high stretchability and conductivity; 2. the manufacturing process is not suitable for industrialization; and 3, the manufacturing cost is too high to be commercialized.

Disclosure of Invention

The invention discloses a method for manufacturing stretchable conductive yarns, which comprises the following steps: providing a rod composed of an elastomer that is poly (styrene-block-butadiene-block-styrene) (SBS), hydrogenated poly (styrene-block-butadiene-block-styrene)) (SEBS), or Polyurethane (PU); inserting the rod into a first tube composed of a first acrylate polymer to thereby produce a first fiber preform; heating and drawing the first fiber preform to produce a first composite fiber having a core-spun structure; cutting the first composite fiber into a plurality of composite fiber strips; inserting the plurality of composite fiber strands into a second tube comprised of a second acrylate-based polymer to thereby produce a second fiber preform; heating and drawing the second fiber preform to produce a second composite fiber; soaking the second composite fiber in a glacial acetic acid solution or a formic acid solution to remove the first acrylate polymer and the second acrylate polymer in the second composite fiber to generate a multifilament yarn composed of the elastomer; soaking the multifilament yarn in a silver trifluoroacetate (AgTFA) solution comprising an alcohol solvent to load silver (Ag) ions in the AgTFA solution to the multifilament yarn to produce Ag ion-loaded multifilament yarn; and soaking the Ag ion-loaded multifilament yarn in a reducing agent solution for reducing the Ag ions to Ag particles to produce Ag particles attached to the surface and inside of the multifilament yarn, thereby producing the stretchable conductive yarn.

According to certain embodiments, the step of providing a rod comprised of an elastomer comprises preparing the rod by solution casting or hot extrusion of the elastomer.

According to certain embodiments, the first acrylate polymer is polymethyl methacrylate (PMMA) or polyethyl methacrylate and the second acrylate polymer is PMMA or polyethyl methacrylate.

According to certain embodiments, the first acrylate polymer and the second acrylate polymer have the same acrylate polymer.

According to certain embodiments, the first acrylate polymer and the second acrylate polymer have different acrylate polymers.

According to certain embodiments, the elastomer is SBS and the first and second acrylate polymers are PMMA.

According to some embodiments, the step of heating and drawing the first fiber preform includes a hot drawing temperature of 150 ℃ to 350 ℃.

According to certain embodiments, the method further comprises stacking the plurality of composite fiber strips together and inserting the stacked composite fiber strips into the second tube.

According to some embodiments, the second fiber preform is rotated to twist the filaments of the multifilament yarn while being heated and stretched.

According to some embodiments, the second fiber preform is rotated at a speed of 1 to 50 revolutions/cm.

According to some embodiments, the step of heating and drawing the second fiber preform includes a temperature of the hot drawing of 150 ℃ to 350 ℃.

According to certain embodiments, the step of soaking the second composite fiber in a glacial acetic acid solution or a formic acid solution comprises a soaking time of 5 minutes to 30 minutes and a soaking temperature of 25 ℃ to 118 ℃.

According to certain embodiments, the filaments of the multifilament yarn have a diameter of 1 μm to 1000 μm.

According to certain embodiments, the alcoholic solvent is ethanol, methanol, ethylene glycol or propanol.

According to certain embodiments, the step of soaking the multifilament yarn in an AgTFA solution comprises a soaking time of 3 to 60 minutes.

According to certain embodiments, the reducing agent of the reducing agent solution is sodium borohydride, phenol, or ascorbic acid, and the solvent of the reducing agent solution is water or an alcohol solvent.

According to certain embodiments, the step of soaking the Ag ion-loaded multifilament yarn in a reducing agent solution comprises a soaking time of more than 5 minutes.

The invention also discloses a method for making a stretchable conductive yarn comprising: providing a rod composed of an elastomer that is poly (styrene-block-butadiene-block-styrene) (SBS), hydrogenated poly (styrene-block-butadiene-block-styrene)) (SEBS), or Polyurethane (PU); inserting the rod into a tube composed of an acrylic polymer to thereby produce a fiber preform; heating and stretching the fiber preform to produce a composite fiber having a core-spun structure; soaking the composite fiber in a glacial acetic acid solution or a formic acid solution to remove the acrylate polymer in the composite fiber so as to generate a monofilament yarn consisting of the elastomer; soaking the monofilament yarn in a silver trifluoroacetate (AgTFA) solution comprising an alcohol solvent to load silver (Ag) ions in the AgTFA solution to the monofilament yarn to produce Ag ion loaded monofilament yarn; and soaking the Ag ion-loaded monofilament yarn in a reducing agent solution for reducing the Ag ions to Ag particles to produce Ag particles attached to the surface of the monofilament yarn, thereby producing the stretchable conductive yarn.

According to certain embodiments, the acrylate polymer is polymethyl methacrylate (PMMA) or polyethyl methacrylate.

According to some embodiments, the elastomer is SBS and the acrylate polymer is PMMA.

According to some embodiments, the step of heating and drawing the fiber preform includes a hot drawing temperature of 150 ℃ to 350 ℃.

According to certain embodiments, the step of soaking the composite fiber in a glacial acetic acid solution or a formic acid solution comprises a soaking time of 5 minutes to 30 minutes and a soaking temperature of 25 ℃ to 118 ℃.

According to certain embodiments, the filaments of the monofilament yarn have a diameter of 1 μm to 1000 μm.

According to certain embodiments, the step of soaking the monofilament yarn in an AgTFA solution comprises a soaking time of 3 to 60 minutes.

According to certain embodiments, the step of soaking the Ag ion-loaded monofilament yarn in a reducing agent solution comprises a soaking time of more than 5 minutes.

The invention also discloses a stretchable conductive yarn which is manufactured by the method.

Drawings

Certain embodiments of the invention will now be described by way of the accompanying drawings. It will be appreciated that various changes can be made without departing from the scope of the invention as described above.

Fig. 1 illustrates a method of making stretchable conductive yarns (Ag-SBS yarns) according to certain embodiments of the present invention.

Fig. 2A shows a photograph of Ag-SBS yarn.

Fig. 2B shows SEM images of Ag-SBS yarns.

Fig. 2C shows an SEM image of a cross section of an Ag-SBS yarn.

Fig. 2D shows photographs of Ag-SBS yarns in a relaxed state (top) and a stretched state (bottom).

Fig. 2E shows the stress-strain curve of Ag-SBS yarns.

Fig. 2F shows the resistance of Ag-SBS yarn as a function of applied strain.

Figure 2G shows the cyclic tensile release at strains above the critical strain of Ag-SBS yarns, above which the material becomes electrically insulating.

FIG. 3A shows an SEM image of an Ag-SBS yarn with a twist of 0T/cm.

FIG. 3B shows an SEM image of an Ag-SBS yarn with a twist of 4T/cm.

FIG. 3C shows an SEM image of an Ag-SBS yarn with a twist of 10T/cm.

Fig. 3D shows an SEM image of an Ag-SBS yarn with a filament number of 1.

Fig. 3E shows an SEM image of an Ag-SBS yarn with a filament count of 87.

Fig. 3F shows an SEM image of an Ag-SBS yarn with filament number 217.

Fig. 4A shows SEM images of Ag-SBS yarns treated by 1 cycle of Ag loading.

Fig. 4B shows SEM images of Ag-SBS yarns treated by 7 cycles of Ag loading.

Fig. 4C shows SEM images of Ag-SBS yarns treated by 15 cycles of Ag loading.

Fig. 4D shows the variation in Ag thickness in Ag-SBS yarns treated at different Ag loading periods.

Fig. 4E shows the variation in Ag mass ratio in Ag-SBS yarns treated at different Ag loading periods.

Fig. 4F shows the stress-strain curves of Ag-SBS yarns treated through different Ag loading periods.

Fig. 4G shows the "strain at break" and modulus of Ag-SBS yarns as a function of treatment cycle used to load Ag.

Fig. 4H shows the resistance change of Ag-SBS yarns treated through different Ag loading periods as the applied strain increases.

Fig. 4I shows the change in conductivity and critical strain (above which the yarn suddenly becomes insulating) of an Ag-SBS yarn using an Ag loading period as a variable.

Fig. 5A shows an SEM image of a fiber made from a 2 ply Ag-SBS yarn.

Fig. 5B shows a photograph and SEM image of a fabric prepared by weaving Ag-SBS yarns (inset).

Fig. 5C shows a photograph and SEM image of a fabric prepared by knitting Ag-SBS yarns (inset).

Fig. 5D shows the change in stress-strain curves for single yarns, 2 ply fibers, woven fabrics, and knitted fabrics.

FIG. 5E shows the change in the relative resistance-strain curves (R) for a single yarn (curve with square marks), a 2-ply fiber (curve with loop marks), a woven fabric (curve with upper triangular marks), and a knitted fabric (curve with lower triangular marks)_sMeans thatResistance when strain is applied, R_s0Refers to resistance in a relaxed state).

Fig. 5F shows the critical strain for different samples.

Detailed Description

The invention provides a stretchable conductive yarn and a manufacturing method thereof. The stretchable conductive yarn is composed of an elastomeric yarn and Ag particles dispersed in and on the elastomeric yarn. The manufacturing method is based on co-heating drawing of polymer and elastomer and post-loading of silver particles, and belongs to an extensible production technology. Furthermore, the stretchable conductive yarns produced by the present process may comprise multifilament yarns (i.e., multifilament yarns) or monofilament yarns (i.e., monofilament yarns).

Example 1

The stretchable conductive yarn of this example (Ag-SBS yarn) consists of SBS yarn and Ag nanoparticles dispersed in the matrix and on the surface of the SBS yarn and coated on the surface of its SBS filaments. In this embodiment, the SBS yarn is a SBS multifilament yarn consisting of a plurality of SBS filaments. The Ag-SBS yarn 100 is manufactured according to the steps of the method shown in fig. 1. In step S11, the SBS bar 111 is prepared by solution casting or hot extruding the SBS material. Then, an SBS rod 111 is inserted into the hollow PMMA tube 112, thereby producing an SBS @ PMMA fiber preform 113 having a clad structure. In step S12, the SBS @ PMMA fiber preform 113 is heated and drawn by the fiber drawing tower 121 including the furnace 1211 to thereby generate the SBS @ PMMA fiber 122 having a cored structure. In step S13, the SBS @ PMMA fibers 122 are cut into a plurality of SBS @ PMMA fiber strands 131. In step S14, a plurality of SBS @ PMMA fiber strips 131 are stacked into a fiber rod 141. In step S15, the fiber rod 141 is inserted into another hollow PMMA tube 151, thereby generating a cylindrical SBS-PMMA fiber preform 152. In step S16, the SBS-PMMA fiber is rotated to be prefabricatedThe rod 152, and simultaneously the SBS-PMMA fiber preform 152 is heated and drawn by a fiber drawing tower 161 including a furnace 1611 to generate SBS-PMMA fibers 162. In step S17, the SBS-PMMA fiber 162 is soaked in glacial acetic acid 171 to remove the PMMA component of the SBS-PMMA composite fiber 162, thereby generating the SBS yarn 172 (i.e., SBS multifilament yarn) composed of a plurality of SBS filaments 173. In step S18, the SBS yarn 172 thread is soaked in a silver trifluoroacetate (AgTFA) solution 181 in ethanol as a solvent to load silver precursors including silver ions into the matrix of the SBS yarn 172, thereby generating Ag ion-loaded SBS yarn (Ag⁺-SBS yarns 182). In step S19, Ag loaded with silver trifluoroacetate⁺The SBS multifilament yarn 182 is soaked in a hydrazine ethanol solution 191 to reduce silver ions to silver particles attached to the surface and inside of the SBS yarn 172, thereby producing the Ag-SBS yarn 100.

Details of the manufacture of example 1

Materials: poly (styrene-block-butadiene-block-styrene) (SBS) powder with a styrene/butadiene mass ratio of 40/60 is provided. A polymethyl methacrylate (PMMA) hollow tube with adjustable diameter and wall thickness is provided. Ethylene, glacial acetic acid, Dichloroethane (DCE) of 99% purity and hydrazine hydrate of 80% purity are provided. Silver trifluoroacetate is provided.

Manufacturing of SBS @ PMMA fiber preform with core-spun layer structure: first, SBS bars were prepared using SBS powder. SBS powder is dissolved in DCE at the appropriate concentration. The SBS solution was then poured into a Teflon (Teflon) mold and placed to evaporate the solvent. And after complete drying, obtaining a layer of SBS thick film at the bottom of the Teflon mold, and stripping the SBS thick film. The SBS thick film was rolled into a rod (used as a cladding for a composite fiber preform) with a diameter slightly smaller than the inner diameter of the PMMA tube. In addition to the cast manufacturing method, the SBS bars can also be hot extruded using a co-rotating twin screw extruder. The SBS @ PMMA fiber preform was obtained by inserting a SBS rod into a PMMA tube.

Thermal drawing of SBS @ PMMA fibers: the SBS @ PMMA fiber preform is fixed through a steel sleeve connected to a servo motor. And a motor with a prefabricated rod is arranged on the wire drawing tower to draw the SBS @ PMMA fiber. During the fiber drawing process, the furnace temperature is gradually increased until the preform is softened and elongated. The feeding speed of the prefabricated rod and the drawing speed of the fiber are accurately adjusted to ensure smooth drawing of the fiber and control the diameter of the fiber. The temperature of the drawn fiber was set to about 255 ℃. To make an SBS yarn, the obtained SBS @ PMMA fibers are cut into strips of shorter length SBS @ PMMA and stacked together to form a cylindrical rod with a diameter slightly smaller than the inner diameter of the PMMA tube. A cylindrical rod of stacked fiber strips is inserted into a PMMA tube to obtain a preform for drawing SBS-PMMA fibers (which include SBS filaments). The feeding speed of the prefabricated rod and the drawing speed of the fiber are accurately adjusted to ensure smooth drawing of the fiber and control the diameter of the fiber. Upon drawing, the preform is rotated to twist the SBS-PMMA fiber.

Preparation of SBS yarn: and soaking the SBS-PMMA fiber obtained in the step in glacial acetic acid to remove the PMMA component. Typically, the soaking time is in the range of 5 to 30 minutes, depending on the temperature of the soaking solution. Higher temperatures are beneficial to accelerate PMMA removal. The soaking temperature is preferably in the range of room temperature to 60 ℃. After soaking, the resulting SBS yarns were rinsed with fresh glacial acetic acid to remove residual PMMA. Finally, the SBS yarns were naturally dried in air.

Loading Ag nano particles: silver trifluoroacetate was dissolved in ethylene at a concentration of 0.1-1 g/mL. And soaking the dried SBS yarns in the solution for about 5 minutes, taking out, and naturally airing. The dried yarn was then soaked in an ethanol solution of hydrazine. Typical soaking times are not less than 5 minutes. Thereafter, the Ag-SBS yarn was taken out and soaked in fresh ethylene for not less than 10 minutes to remove the remaining hydrazine, and then left to dry in air to obtain a final stretchable and conductive Ag-SBS yarn.

Characterization of Ag-SBS yarns: the mechanical properties of the SBS yarn and Ag-SBS yarn were investigated using an Instron 5944 universal tester. SBS yarn or Ag-SBS yarn with length of 5cm is fixed on the machine, and two ends are flapped by a pair of clappers. After setting the test parameters, the sample was stretched. The variation of tensile stress as a function of tensile strain was monitored. The young's modulus of the yarn was calculated from the stress-strain curve by the software. The microscopic morphology of the Ag-SBS yarn was observed by scanning electron microscopy (SEM, Hitachi (TM) 3000 bench microscope). A homemade device consisting of a Keithley 2400 source meter and a Zolix moving plate was used to study the electrical properties of Ag-SBS yarns. Both ends of the Ag-SBS yarn were fixed on a pair of clappers of a Zolix moving plate. Two pairs of electrodes from a Keithley 2400 source were attached to both ends of the membrane. The change in film resistance during stretching of the film by the Zolix moving plate was automatically recorded by the computer.

Existing strategies for preparing stretchable conductive fibers, wires and yarns mainly include the following types: (1) spinning a mixture of natural or chemical synthetic fibers and metal fibers into a composite yarn; (2) coating the elastomeric fiber or yarn with a metal or carbon material by dip coating, physical deposition or chemical reaction; (3) metal wires or carbon fibers are wound on the elastomer core fibers to form composite fibers. Sometimes, an additional protective shell is coated on the outside for protection; (4) twisting the carbon nanotube fibers to achieve stretchability; (5) dispersing conductive fillers including metal nanowires, metal nanoflakes, metal nanoparticles, metal nanoflowers, carbon nanotubes, carbon black, graphene, or conductive polymers in a matrix of the elastic fibers or yarns. Of all the above strategies, only the first and second strategies have been successfully used in the manufacture of commercial products. However, the conductive yarns prepared by these methods have only low stretchability (typically less than 50% strain). The third strategy and the fourth strategy are complicated and difficult to implement, and are not suitable for industrial production. The last strategy is simple and efficient, and is suitable for various conductive additives and elastomers. Furthermore, this strategy can achieve both extremely high stretchability and electrical conductivity. Therefore, the last strategy is very promising for industrial applications. To prepare elastic conductive fibers/wires/yarns by this strategy, the conductive filler is first dispersed in an elastomer solution and then the fiber or yarn is made by wet spinning. PSS as conductive filler by this strategy has been used to make stretchable and conductive yarns. However, neither the conductivity (5.4S/cm) nor the stretchability (. about.400% strain) achieved was high. The invention provides a novel manufacturing method of stretchable conductive yarn based on a fifth strategy. The present yarn manufacturing process is, however, quite different from previously reported processes. As shown in fig. 1, the present method has at least 3 advantages over previously reported methods: (1) no toxic organic solvent is used. For wet spinning of elastomeric fibers or yarns, toxic organic solvents, such as Dimethylformamide (DMF), DMSO (dimethyl sulfoxide), Tetrahydrofuran (THF), Dichloroethane (DCE) or toluene, must be used to prepare the elastomer solution. However, the process of manufacturing the SBS-PMMA fiber by the present method is a completely dry process, and glacial acetic acid (or formic acid) for removing PMMA is a non-toxic weak acid. (2) The diameter, twist and filament number of the yarn are easy to control. The diameter of the yarn can be adjusted by varying the draw speed of the SBS-PMMA fibers. The twist can be adjusted by changing the rotational speed of the servo motor holding the preform, while the number of filaments can be changed by changing the number of SBS @ PMMA fiber strips stacked in the preform. (3) Conductive fillers are easily loaded. The loading of the conductive filler in the elastomeric fiber or yarn prepared by wet spinning in most reported processes is carried out by dispersing the conductive filler in an elastomer solution. Homogeneous conductive filler and elastomer suspensions that achieve high dispersibility and long-term stability are technically challenging. Loading Ag in the present process is achieved by soaking SBS yarns in an ethanol solution of silver trifluoroacetate and subsequent reduction. This method is very simple and effective. Therefore, the manufacturing method of the stretchable conductive yarn proposed by the present invention is very promising in industrial applications.

By adopting the method provided by the invention, the continuous super-drawing conductive yarn can be efficiently manufactured. Fig. 2A shows a photograph of a roll of Ag-SBS yarn with a total length of about 500 m. The Ag-SBS yarns consisted of 87 SBS filaments with a diameter of about 10 μm (fig. 2B). Silver nanoparticles were dispersed on the surface and inside of the yarn (fig. 2C). The Ag-SBS yarns have high stretchability (fig. 2D). It can be stretched to more than 15 times its original length before mechanical failure (fig. 2E). Its resistance increases rapidly with increasing applied strain and becomes insulating at strains above 148%. As the strain is released, it conducts again at about 145% strain (fig. 2F). The conductivity of the Ag-SBS yarns can be maintained after repeated stretching and releasing (fig. 2G). The final Ag-SBS yarn twist can be flexibly adjusted by changing the rotational speed of the servo motor holding the preform (while the feed rate to the preform and the fiber draw rate are fixed) (fig. 3A-3C). The present invention demonstrates the fabrication of Ag-SBS yarns with different filament counts by simply varying the number of SBS @ PMMA fiber strands stacked in the preform (fig. 3D-3F).

The mechanical, electrical and electromechanical properties of Ag-SBS yarns can be tuned by varying the process cycle used to load the Ag nanoparticles. The stretchability and flexibility of Ag-SBS yarns decreases with increasing Ag loading treatment period (fig. 4F and 4G), while the conductivity changes inversely (curve with square marks in fig. 4I). The change in yarn critical strain is not monotonic with increasing loading period (circled curves in fig. 4H and 4I). The sample treated with 5 cycles showed the highest critical strain. The conductivity of this sample was about 2536S/cm, which is high enough for a large number of applications. Thus, for different applications, the present method can adjust the mechanical, electrical and electromechanical properties of Ag-SBS yarns, with the balance achieved only by varying the treatment period for loading Ag nanoparticles.

The mechanical strength of Ag-SBS yarns is sufficient for post-processing, such as plying, weaving, and knitting, to make various textiles. As proof of concept, 2-ply fibers, woven fabrics, and knitted fabrics were manufactured (fig. 5A-5C). The stretchability of the 2-ply fiber and the woven fabric was only slightly reduced compared to the single Ag-SBS yarn, while the knitted fabric showed higher stretchability (fig. 5D). On the other hand, the electromechanical properties of the woven fabric are almost the same as for single yarns, while the critical strain is much higher for the two-ply fibers and the knitted fabric (fig. 5E and 5F).

Compared with the existing manufacturing method of the super-elastic conductive fiber and the yarn, the method is environment-friendly, can flexibly adjust the geometric property, the mechanical property and the electrical property of the yarn, and is simple and efficient in loading the conductive filler. The super-elastic, highly conductive yarn produced by the present method can be further processed into various textiles, such as 2-ply fibers, woven fabrics, and knitted fabrics.

The present disclosure provides for the manufacture of SBS-PMMA fibers by hot drawing on a fiber draw tower, where SBS-PMMA fibers comprising a plurality of SBS cores, i.e., fibers comprising a plurality of elastomeric filaments, are manufactured by hot drawing. Certain embodiments of the present disclosure include adjusting twist and filament count simply by varying the rotational speed of the preform and the number of SBS @ PMMA fiber strips stacked in the preform.

Since SBS cannot be directly processed into fibers or yarns by hot drawing, SBS fibers or yarns are generally manufactured by wet spinning, and it is inevitable to use toxic organic solvents to prepare SBS solutions. In the present invention, PMMA, which is an inexpensive polymer that is easily hot drawn into fibers, is used to coat SBS and to guide the hot drawing of SBS. And removing the PMMA component in the SBS-PMMA composite fiber after hot drawing to prepare the SBS fiber or yarn. The loading of the silver nanoparticles can be achieved by post-soaking and reduction. Therefore, the present invention solves the problem of unavoidably using toxic organic solvents in the wet spinning of SBS fibers or yarns.

The integration of flexible wearable electronics and clothing is a necessary trend for the development of wearable electronics in the future. Highly stretchable conductive fibers or yarns are commercialized as an important component of soft electronic devices. The manufacturing method of the super-elastic conductive yarn is simple, efficient and high in cost benefit. The method can avoid the use of toxic organic solvents which are essential in the wet spinning manufacturing process. Therefore, the method has great prospect in industrial application.

The invention can be applied to antistatic gloves, electromagnetic shielding clothes, medical treatment or motion monitoring, wearable electronic products or flexible robots. The invention can be applied to the clothing industry, fashion industry, medical industry or electronic industry.

While the invention has been described with reference to specific embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from its scope. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed, but that the invention will include all embodiments falling within the scope of the appended claims.

Claims

1. A method for making a stretchable conductive yarn, comprising:

providing a rod composed of an elastomer that is poly (styrene-block-butadiene-block-styrene) (SBS), hydrogenated poly (styrene-block-butadiene-block-styrene)) (SEBS), or Polyurethane (PU);

inserting the rod into a first tube composed of a first acrylate polymer to thereby produce a first fiber preform;

heating and drawing the first fiber preform to produce a first composite fiber having a core-spun structure;

cutting the first composite fiber into a plurality of composite fiber strips;

inserting the plurality of composite fiber strands into a second tube comprised of a second acrylate-based polymer to thereby produce a second fiber preform;

heating and drawing the second fiber preform to produce a second composite fiber;

soaking the second composite fiber in a glacial acetic acid solution or a formic acid solution to remove the first acrylate polymer and the second acrylate polymer in the second composite fiber to generate a multifilament yarn composed of the elastomer;

soaking the multifilament yarn in a silver trifluoroacetate (AgTFA) solution comprising an alcohol solvent to load silver (Ag) ions in the AgTFA solution to the multifilament yarn to produce Ag ion-loaded multifilament yarn; and

the Ag ion-loaded multifilament yarn is soaked in a reducing agent solution for reducing the Ag ions to Ag particles to produce Ag particles attached to the surface and inside of the multifilament yarn, thereby producing the stretchable conductive yarn.

2. The method of claim 1, wherein the step of providing a rod comprised of an elastomer comprises preparing the rod by solution casting or hot extrusion of the elastomer.

3. The method of claim 1, wherein the first acrylate polymer is polymethyl methacrylate (PMMA) or polyethyl methacrylate and the second acrylate polymer is PMMA or polyethyl methacrylate.

4. The method of claim 1, wherein the first acrylate polymer and the second acrylate polymer have the same acrylate polymer.

5. The method of claim 1, wherein the first acrylate polymer and the second acrylate polymer have different acrylate polymers.

6. The method of claim 1, wherein the elastomer is SBS and the first and second acrylate polymers are PMMA.

7. The method according to claim 1, wherein the step of heating and drawing the first fiber preform includes a thermal drawing temperature of 150 ℃ to 350 ℃.

8. The method of claim 1, further comprising stacking the plurality of composite fiber strips together and inserting the stacked composite fiber strips into the second tube.

9. The method according to claim 1, wherein the second fiber preform is rotated to twist the filaments of the multifilament yarn while being heated and stretched.

10. The method of claim 9, wherein the second fiber preform is rotated at a speed of 1 to 50 revolutions/cm.

11. The method according to claim 1, wherein the step of heating and drawing the second fiber preform includes a temperature of the hot drawing of 150 ℃ to 350 ℃.

12. The method of claim 1, wherein the step of soaking the second composite fiber in a glacial acetic acid solution or a formic acid solution comprises a soaking time of 5 minutes to 30 minutes and a soaking temperature of 25 ℃ to 118 ℃.

13. A process according to claim 1, wherein the filaments of the multifilament yarn have a diameter of 1 to 1000 μ η ι.

14. The method of claim 1, wherein the alcoholic solvent is ethanol, methanol, ethylene glycol or propanol.

15. The method according to claim 1, wherein the step of soaking the multifilament yarn in an AgTFA solution comprises a soaking time of 3 to 60 minutes.

16. The method according to claim 1, wherein the reducing agent of the reducing agent solution is sodium borohydride, phenol or ascorbic acid, and the solvent of the reducing agent solution is water or an alcohol solvent.

17. The method according to claim 1, wherein the step of soaking the Ag ion-loaded multifilament yarn in a reducing agent solution comprises a soaking time of 5 minutes or more.

18. A stretchable conductive yarn made by the method of any of claims 1-17.

19. A method for making a stretchable conductive yarn, comprising:

inserting the rod into a tube composed of an acrylic polymer to thereby produce a fiber preform;

heating and stretching the fiber preform to produce a composite fiber having a core-spun structure;

soaking the composite fiber in a glacial acetic acid solution or a formic acid solution to remove the acrylate polymer in the composite fiber so as to generate a monofilament yarn consisting of the elastomer;

soaking the monofilament yarn in a silver trifluoroacetate (AgTFA) solution comprising an alcohol solvent to load silver (Ag) ions in the AgTFA solution to the monofilament yarn to produce Ag ion loaded monofilament yarn; and

immersing the Ag ion-loaded monofilament yarn in a reducing agent solution for reducing the Ag ions to Ag particles to produce Ag particles attached to the surface of the monofilament yarn, thereby producing the stretchable electrically conductive yarn.

20. The method of claim 19, wherein the step of providing a rod comprised of an elastomer comprises preparing the rod by solution casting or hot extrusion of the elastomer.

21. The method of claim 19, wherein the acrylate polymer is Polymethylmethacrylate (PMMA) or polyethylmethacrylate.

22. The method of claim 19, wherein the elastomer is SBS and the acrylate polymer is PMMA.

23. The method of claim 19, wherein the step of heating and drawing the fiber preform comprises a thermal drawing temperature of 150 ℃ to 350 ℃.

24. The method of claim 19, wherein the step of soaking the composite fiber in a glacial acetic acid solution or a formic acid solution comprises a soaking time of 5 minutes to 30 minutes and a soaking temperature of 25 ℃ to 118 ℃.

25. A process as claimed in claim 19, in which the filaments of the monofilament yarn have a diameter of from 1 to 1000 μm.

26. The method of claim 19, wherein the alcoholic solvent is ethanol, methanol, ethylene glycol or propanol.

27. The method according to claim 19, wherein the step of soaking the monofilament yarn in an AgTFA solution comprises a soaking time of 3 to 60 minutes.

28. The method of claim 19, wherein the reducing agent of the reducing agent solution is sodium borohydride, phenol, or ascorbic acid, and the solvent of the reducing agent solution is water or an alcohol solvent.

29. The method according to claim 19, wherein the step of soaking the Ag ion-loaded monofilament yarn in a reducing agent solution comprises a soaking time of 5 minutes or more.

30. A stretchable conductive yarn made by the method of any of claims 19-29.