CN114302984B

CN114302984B - Stretchable conductive yarn and method of making the same

Info

Publication number: CN114302984B
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: 2024-05-17
Anticipated expiration: 2041-10-28
Also published as: CN114302984A

Abstract

A stretchable conductive yarn is composed of an elastomeric yarn and silver particles dispersed in and on the elastomeric yarn. The manufacturing method is based on co-thermal drawing of polymer and elastomer and post-loading of silver particles, and belongs to the expandable production technology. The manufacturing method is simple, efficient and cost-effective, while avoiding the use of toxic organic solvents.

Description

Stretchable conductive yarn and method of making the same

Technical Field

The present invention relates generally to a yarn having super stretchability and high conductivity and a method of manufacturing the same.

Background

Wearable electronics play an increasingly important role in human daily life. They are often designed in the form of straps and watches worn on the wrist, footwear worn on the foot, glasses and helmets worn on the head, and products including smart clothing, backpacks, walking sticks and accessories. Typical applications of wearable electronics include sports/health monitoring, positioning, communication, entertainment, electronic payment, etc. According to market statistics, the global wearable electronic product market size in 2020 can reach 312.7 hundred million dollars, which is equivalent to 17.8% increase per year during 2015-2020. Wearable electronics will be a huge market. In addition to functionality, consumer demand for comfort in future wearable electronics will also be increasing. High performance elastic conductive materials as a base component have become a significant impact on further advances in wearable electronics technology.

Yarn, on the other hand, 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. In order to provide comfort and convenience of wear, one of the most important trends in the future of wearable electronics is to integrate electronic devices with garments, or to directly impart electronic functions to garments. Conductive yarns are the basis for electronic textile materials. Therefore, it will play an important role in the future development of high performance wearable electronics. To meet the demand of wearable electronics for large deformation adaptability, such as devices used at the joint sites of the human body, development of high-performance elastic conductive yarns is urgently needed. However, the elastic conductive yarns presently disclosed have at least the following drawbacks: 1. the high stretchability and the electrical conductivity cannot be achieved at the same time; 2. the manufacturing process is not suitable for industrialization; and 3, the manufacturing cost is too high to commercialize.

Disclosure of Invention

The invention discloses a method for manufacturing a stretchable conductive yarn, comprising the following steps: providing a rod consisting of an elastomer which 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 comprised of a first acrylic polymer to produce a first fiber preform; heating and stretching the first fiber preform to produce a first composite fiber having a core-in-core structure; cutting the first composite fiber into a plurality of composite fiber strips; inserting the plurality of composite fiber strips into a second tube comprised of a second acrylic polymer to produce a second fiber preform; heating and stretching the second fiber preform to produce a second composite fiber; immersing the second composite fiber in a glacial acetic acid solution or a formic acid solution to remove the first acrylic polymer and the second acrylic polymer in the second composite fiber to produce a multifilament yarn composed of the elastomer; immersing the multifilament yarn in a silver trifluoroacetate (AgTFA) solution comprising an alcoholic solvent to load silver (Ag) ions in AgTFA solution to the multifilament yarn to produce a Ag ion loaded multifilament yarn; and immersing the multifilament yarn loaded with Ag ions in a reducing agent solution for reducing the Ag ions into Ag particles to generate Ag particles attached to the surface and the inside of the multifilament yarn, thereby generating the stretchable conductive yarn.

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

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

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

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

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

According to certain embodiments, the step of heating and stretching the first fibrous preform comprises a thermal stretching 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 certain embodiments, the second fiber preform is rotated to twist the filaments of the multifilament yarn while the second fiber preform is heated and stretched.

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

According to certain embodiments, the step of heating and stretching the second fibrous preform comprises heat stretching at a temperature of 150 ℃ to 350 ℃.

According to certain embodiments, the step of immersing the second composite fiber in the glacial acetic acid solution or the formic acid solution includes an immersion time of 5 minutes to 30 minutes and an immersion 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 immersing the multifilament yarn in the AgTFA solution comprises an immersion time of 3 minutes to 60 minutes.

According to certain embodiments, the reducing agent of the reducing agent solution is sodium borohydride, phenol, or anti-cyclohaemacid, and the solvent of the reducing agent solution is water or an alcoholic solvent.

According to certain embodiments, the step of immersing the Ag ion-loaded multifilament yarn in the reducing agent solution comprises an immersion time of 5 minutes or more.

The invention also discloses a method for manufacturing a stretchable conductive yarn, comprising: providing a rod consisting of an elastomer which 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 produce a fiber preform; heating and stretching the fiber preform to produce a composite fiber having a core-spun structure; immersing the composite fiber in a glacial acetic acid solution or a formic acid solution to remove the acrylic ester polymer in the composite fiber and thereby generate monofilament yarns composed of the elastomer; immersing the monofilament yarn in a silver trifluoroacetate (AgTFA) solution comprising an alcoholic solvent to load silver (Ag) ions in AgTFA solution to the monofilament yarn to produce a Ag ion loaded monofilament yarn; and immersing the monofilament yarn loaded with Ag ions 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 acrylic polymer is polymethyl methacrylate (PMMA) or polyethyl methacrylate.

According to certain embodiments, the elastomer is SBS and the acrylic polymer is PMMA.

According to certain embodiments, the step of heating and stretching the fiber preform comprises a hot stretching temperature of 150 ℃ to 350 ℃.

According to certain embodiments, the step of immersing the composite fiber in the glacial acetic acid solution or the formic acid solution includes an immersion time of 5 minutes to 30 minutes and an immersion temperature of 25 ℃ to 118 ℃.

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

According to certain embodiments, the step of immersing the monofilament yarn in the AgTFA solution comprises immersing for a period of time ranging from 3 minutes to 60 minutes.

According to certain embodiments, the step of immersing the Ag ion-loaded monofilament yarn in the reducing agent solution comprises an immersion time of 5 minutes or more.

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

Drawings

Certain embodiments of the invention are now described with reference to the drawings. It will be appreciated that various changes can be made therein without departing from the scope of the invention as described above.

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

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

Fig. 2B shows an SEM image 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 relaxed (upper) and stretched (lower) states.

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

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

Fig. 2G shows the periodic stretch release at a strain exceeding the critical strain of the Ag-SBS yarns over which the material becomes electrically insulating.

Fig. 3A shows SEM images of Ag-SBS yarns with twist of 0T/cm.

Fig. 3B shows SEM images of Ag-SBS yarns with twist of 4T/cm.

Fig. 3C shows SEM images of Ag-SBS yarns with a twist of 10T/cm.

Fig. 3D shows SEM images of Ag-SBS yarns with filament number 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 of Ag thickness in Ag-SBS yarns treated at different Ag loading cycles.

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

Fig. 4F shows stress-strain curves of Ag-SBS yarns treated via different Ag loading cycles.

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

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

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

Fig. 5A shows an SEM image of fibers prepared from 2 ply Ag-SBS yarns.

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

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

Fig. 5D shows the variation of 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 of single yarn (curve with square marks), 2 ply fiber (curve with loop marks), woven fabric (curve with upper triangle marks) and knitted fabric (curve with lower triangle marks) (R _s refers to resistance when strain is applied, R _s0 refers to resistance in 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 consists of an elastomeric yarn and Ag particles dispersed in and on the elastomeric yarn. The manufacturing method is based on co-thermal drawing of polymer and elastomer and post-loading of silver particles, and belongs to the expandable production technology. In addition, the stretchable conductive yarn produced by the present method may comprise multifilament yarn (i.e., multifilament yarn) or monofilament yarn (i.e., monofilament yarn).

Example 1

The stretchable conductive yarn (Ag-SBS yarn) of this embodiment is composed of SBS yarn and Ag nanoparticles dispersed in and on the surface of the matrix of the SBS yarn and coated on the surface of the SBS filaments thereof. In this embodiment, the SBS yarn is an SBS multifilament yarn composed 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 rod 111 is prepared by solution casting or hot-extruding the SBS mass. Then, the 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 produce the sbs@pmma fiber 122 having a core-spun structure. In step S13, the sbs@pmma fibers 122 are cut into a plurality of sbs@pmma fiber strips 131. In step S14, a plurality of sbs@pmma fiber tapes 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 preform 152 is rotated, and at the same time, the SBS-PMMA fiber preform 152 is heated and drawn by a fiber drawing tower 161 including a furnace 1611 to thereby generate SBS-PMMA fiber 162. In step S17, the SBS-PMMA fibers 162 are soaked in glacial acetic acid 171 to remove PMMA components in the SBS-PMMA composite fibers 162, thereby generating SBS yarns 172 (i.e., SBS multifilament yarns) composed of a plurality of SBS filaments 173. In step S18, the SBS yarn 172 is thread-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 an Ag ion-loaded SBS yarn (Ag ⁺ -SBS yarn 182). In step S19, the Ag ⁺ -SBS multifilament yarn 182 loaded with silver trifluoroacetate is soaked in hydrazine ethanol solution 191 to reduce silver ions into silver particles attached to the surface and inside of the SBS yarn 172, thereby generating the Ag-SBS yarn 100.

Details of the manufacture of example 1

Materials: poly (styrene-block-butadiene-block-styrene) (SBS) powder having 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, 99% pure ethylene Dichloride (DCE) and 80% pure hydrazine hydrate are provided. Silver trifluoroacetate is provided.

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

Thermal stretching of SBS@PMMA fibers: the SBS@PMMA fiber preform is fixed through a steel sleeve connected to a servo motor. The motor with the preform is mounted on a drawing tower to draw out 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 preform 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 ℃. For the manufacture of SBS yarns, the obtained sbs@pmma fibers were cut into short length sbs@pmma fiber strips and stacked together to form a cylindrical rod with a diameter slightly smaller than the inner diameter of the PMMA tube. Cylindrical rods, in which fiber rods are stacked, are inserted into the PMMA tube to obtain a preform for drawing SBS-PMMA fibers, which contain a plurality of SBS filaments. The feeding speed of the preform and the drawing speed of the fiber are accurately adjusted to ensure smooth drawing of the fiber and control the diameter of the fiber. At the time of drawing, the preform is rotated to twist the SBS-PMMA fiber.

Preparation of SBS yarns: the SBS-PMMA fiber obtained in the above steps is soaked in glacial acetic acid to remove PMMA components. 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 the removal of PMMA. The soaking temperature is preferably in the range of room temperature to 60 ℃. After soaking, the resulting SBS yarn was rinsed with fresh glacial acetic acid to remove residual PMMA. And finally, naturally drying the SBS yarns in air.

Loading of Ag nanoparticles: silver trifluoroacetate was dissolved in ethylene at a concentration of 0.1-1 g/mL. The dried SBS yarn was soaked in the above solution for about 5 minutes, then removed and naturally dried. The dried yarn was then soaked in an ethanol solution of hydrazine. Typical soaking times are not less than 5 minutes. Afterwards, the Ag-SBS yarns were 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, resulting in final stretchable and conductive Ag-SBS yarns.

Characterization of Ag-SBS yarns: the mechanical properties of SBS yarns and Ag-SBS yarns were studied using an Instron 5944 universal tester. The SBS yarn or Ag-SBS yarn with the length of 5cm is fixed on a machine, and two ends are beaten by a pair of clapping plates. After setting the test parameters, the sample is stretched. The change in tensile stress as a function of tensile strain is monitored. The Young's modulus of the yarn was calculated by software from the stress-strain curve. The microscopic morphology of the Ag-SBS yarns was observed by scanning electron microscopy (SEM, hitachi TM3000 bench microscope). A homemade device consisting of a Keithley 2400 source meter and Zolix moving plate was used to study the electrical properties of Ag-SBS yarns. Both ends of the Ag-SBS yarn were fixed to a pair of clapper plates of Zolix moving plates. Two pairs of electrodes of the Keithley 2400 source were attached to both ends of the film. The change in sheet resistance is automatically recorded by the computer during the stretching of the film by the Zolix moving plate.

The existing preparation strategies for 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 fibers or yarns with a metal or carbon material by dip coating, physical deposition or chemical reaction; (3) And winding metal wires or carbon fibers on the elastomer core fibers to form the 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 filler, including metal nanowires, metal nanoflakes, metal nanoparticles, metal nanoflowers, carbon nanotubes, carbon black, graphene or conductive polymers, in a matrix of elastic fibers or yarns. Of all the above strategies, only the first strategy and the second strategy have been successfully used for the manufacture of commercial products. However, the conductive yarns made by these methods have only low stretchability (typically less than 50% strain). The third strategy and the fourth strategy are cumbersome 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 very high stretchability and electrical conductivity. Thus, the last strategy is very promising for industrial applications. To prepare an elastic conductive fiber/wire/yarn by this strategy, the conductive filler is first dispersed in an elastomer solution and then the fiber or yarn is made by wet spinning. The current use of PEDOT: PSS as conductive filler creates a stretchable and conductive yarn by this strategy. However, both the conductivity (5.4S/cm) and the stretchability (400% strain) achieved were not high. The invention provides a new manufacturing method of a stretchable conductive yarn based on a fifth strategy. However, the present yarn manufacturing process is quite different from the previously reported process. As shown in fig. 1, the present method has at least 3 advantages over the previously reported methods: (1) no toxic organic solvents are used. For wet spinning of elastomeric fibers or yarns, it is necessary to use toxic organic solvents such as Dimethylformamide (DMF), DMSO (dimethyl sulfoxide), tetrahydrofuran (THF), dichloroethane (DCE), or toluene to prepare the elastomeric solution. However, the process of manufacturing SBS-PMMA fiber by the present method is a completely dry process, and glacial acetic acid (or formic acid) for removing PMMA is a nontoxic weak acid. (2) easy control of yarn diameter, twist and filament count. The diameter of the yarn can be adjusted by changing the drawing speed of the SBS-PMMA fiber. The twist can be adjusted by varying the rotational speed of the servo motor holding the preform, while the filament count can be varied by varying the number of sbs@pmma fiber rods stacked in the preform. (3) the conductive filler is easy to load. The loading of the conductive filler in the elastomeric fibers or yarns prepared by wet spinning in most of the reported processes is performed by dispersing the conductive filler in the elastomeric solution. Achieving a homogeneous conductive filler and elastomer suspension with high dispersibility and long term stability is technically challenging. The loading of Ag in the present process is achieved by immersing the SBS yarn in an ethanol solution of silver trifluoroacetate and subsequent reduction. This method is very simple and efficient. Therefore, the manufacturing method of the stretchable conductive yarn provided by the invention is very promising in industrial application.

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

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

The Ag-SBS yarns are mechanically strong enough to be post-treated, such as ply-twisted, braided and knitted, to make various textiles. As proof of concept, 2 ply fibers, woven fabrics and knit fabrics were produced (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 woven fabric exhibited higher stretchability (fig. 5D). On the other hand, the electromechanical properties of woven fabrics are almost the same as single yarns, while the critical strain of two ply fiber and knitted fabrics is much higher (fig. 5E and 5F).

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

The present disclosure provides for the manufacture of SBS-PMMA fibers by hot drawing on a fiber drawing 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 the 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.

Because SBS cannot be directly processed into fibers or yarns by hot drawing, SBS fibers or yarns are typically 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 thermally drawn into fibers, is used to coat and guide the thermal drawing of SBS. And removing PMMA components in the SBS-PMMA composite fiber after the hot drawing to prepare the SBS fiber or yarn. The loading of silver nanoparticles can be achieved by post-soaking and reduction. Thus, the present invention solves the problem of unavoidable use of toxic organic solvents in SBS fiber or yarn wet spinning.

The fusion of soft wearable electronics with apparel is a necessary trend in the future of wearable electronics development. Highly stretchable conductive fibers or yarns are commercially available as an important component of flexible electronic devices. The manufacturing method of the super-elastic conductive yarn provided by the invention is simple, efficient and cost-effective. The method can avoid the use of toxic organic solvents which are indispensable in the wet spinning manufacturing process. Thus, the present method is very promising in industrial applications.

The invention can be applied to antistatic gloves, electromagnetic shielding clothing, medical or sports monitoring, wearable electronic products or soft 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 for elements thereof 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 which is poly (styrene-block-butadiene-block-styrene), hydrogenated poly (styrene-block-butadiene-block-styrene) or polyurethane;

inserting the rod into a first tube comprised of a first acrylic polymer to produce a first fiber preform;

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

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

inserting the plurality of composite fiber strips into a second tube comprised of a second acrylic polymer to produce a second fiber preform;

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

immersing the second composite fiber in a glacial acetic acid solution or a formic acid solution to remove the first acrylic polymer and the second acrylic polymer in the second composite fiber to produce a multifilament yarn composed of the elastomer;

Immersing the multifilament yarn in a silver trifluoroacetate solution comprising an alcoholic solvent to load silver ions in the silver trifluoroacetate solution to the multifilament yarn to produce a silver ion loaded multifilament yarn; and

Immersing the multifilament yarn loaded with silver ions in a reducing agent solution for reducing the silver ions to silver particles to generate silver particles attached to the surface and the inside of the multifilament yarn, thereby generating the stretchable conductive yarn;

The first acrylic polymer is polymethyl methacrylate or polyethyl methacrylate, and the second acrylic polymer is polymethyl methacrylate or polyethyl methacrylate.

2. The method of claim 1, wherein the step of providing a rod composed 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 acrylic polymer and the second acrylic polymer have the same acrylic polymer.

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

5. The method of claim 1, wherein the elastomer is poly (styrene-block-butadiene-block-styrene), and the first and second acrylic polymers are polymethyl methacrylate.

6. The method of claim 1, wherein the step of heating and stretching the first fiber preform comprises a thermal stretching temperature of 150 ℃ to 350 ℃.

7. 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.

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

9. The method of claim 8, wherein the speed at which the second fiber preform is rotated is 1 to 50 revolutions/cm.

10. The method of claim 1, wherein the step of heating and stretching the second fiber preform comprises a temperature of 150 ℃ to 350 ℃ for hot stretching.

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

12. The method of claim 1, wherein the filaments of the multifilament yarn have a diameter of 1 μm to 1000 μm.

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

14. The method of claim 1, wherein the step of immersing the multifilament yarn in the silver trifluoroacetate solution comprises an immersion time of 3 minutes to 60 minutes.

15. The method of claim 1, wherein the reducing agent of the reducing agent solution is sodium borohydride, phenol, or anti-cyclic acid, and the solvent of the reducing agent solution is water or an alcohol solvent.

16. The method of claim 1, wherein the step of immersing the silver ion loaded multifilament yarn in the reducing agent solution comprises an immersion time of 5 minutes or more.

17. A stretchable electrically conductive yarn made by the method of any one of claims 1-16.

18. A method for making a stretchable conductive yarn comprising:

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

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

Immersing the composite fiber in a glacial acetic acid solution or a formic acid solution to remove the acrylic ester polymer in the composite fiber and thereby generate monofilament yarns composed of the elastomer;

Immersing the monofilament yarn in a silver trifluoroacetate solution comprising an alcoholic solvent to load silver ions in the silver trifluoroacetate solution to the monofilament yarn to produce a silver ion loaded monofilament yarn; and

Immersing the monofilament yarn loaded with silver ions in a reducing agent solution for reducing the silver ions to silver particles to produce silver particles attached to the surface of the monofilament yarn, thereby producing the stretchable conductive yarn;

wherein the acrylic polymer is polymethyl methacrylate or polyethyl methacrylate.

19. The method of claim 18, wherein the step of providing a rod composed of an elastomer comprises preparing the rod by solution casting or hot extrusion of the elastomer.

20. The method of claim 18, wherein the elastomer is poly (styrene-block-butadiene-block-styrene) and the acrylic polymer is polymethyl methacrylate.

21. The method of claim 18, wherein the step of heating and stretching the fiber preform comprises a hot stretching temperature of 150 ℃ to 350 ℃.

22. The method of claim 18, wherein the step of immersing the composite fiber in the glacial acetic acid solution or the formic acid solution includes an immersion time of 5 minutes to 30 minutes and an immersion temperature of 25 ℃ to 118 ℃.

23. A method according to claim 18, wherein the filaments of the monofilament yarn have a diameter of 1 μm to 1000 μm.

24. The method of claim 18, wherein the alcoholic solvent is ethanol, methanol, ethylene glycol, or propanol.

25. The method of claim 18 wherein the step of immersing the monofilament yarn in the silver trifluoroacetate solution comprises an immersion time of from 3 minutes to 60 minutes.

26. The method of claim 18, wherein the reducing agent of the reducing agent solution is sodium borohydride, phenol, or anti-cyclic acid, and the solvent of the reducing agent solution is water or an alcoholic solvent.

27. The method of claim 18, wherein the step of immersing the silver ion loaded monofilament yarn in the reducing agent solution comprises an immersion time of 5 minutes or more.

28. A stretchable electrically conductive yarn made by the method of any one of claims 18-27.