CN106637568A - Composite conductive fiber and preparation method thereof - Google Patents

Abstract

The invention discloses a composite conductive fiber and a preparation method thereof. The preparation method includes: winding a plurality of single fibers to form the first fiber in a helical shape, and coating the bonding surface of each single fiber with an adhesive during winding, so that these single fibers are firmly bonded , forming a first fiber with a surface having opposite concave portions and relative convex portions extending continuously along the axial direction of the first fiber; adding the first fiber while spinning the conductive material to form the second fiber, so that the first fiber A fiber is uniformly wrapped within the second fiber, thereby forming a composite conductive fiber. The composite conductive fiber of the present invention has a core/protective sheath structure, which is uniform, has excellent electrical conductivity, flexibility and wear resistance, can withstand the irradiation of ultraviolet light, etc. and still maintains excellent characteristics, and can be used as a high-strength, flexible and lightweight fiber. High-quality wires, etc., and its preparation process is simple, can be carried out continuously and automatically, is safe and environmentally friendly, and is suitable for mass production.

Description

Composite conductive fiber and preparation method thereof

technical field

The invention relates to a preparation method of a composite fiber material, in particular to a composite conductive fiber, such as an aramid fiber/carbon nanotube composite fiber and a preparation method thereof.

Background technique

With the development of science and technology and the popularization of electronic equipment, people's requirements for electronic equipment are getting higher and higher, and among them, conductive fibers that are miniature, flexible, lightweight, portable and high-strength are also attracting more and more attention. The conductive fibers currently on the market are mainly metal wires, but they have poor flexibility, are not light, and have low strength. Therefore, high-performance fibers with high strength, flexibility, light weight and electrical conductivity have received extensive attention. Aramid fiber is a high-performance fiber with excellent mechanical properties and heat resistance stability. However, aramid fibers are insulated and non-conductive, and at the same time they are not resistant to ultraviolet light. There is a conjugated system of amides and benzene rings in the aramid fiber structure, which is easy to absorb a large amount under ultraviolet light and cause molecular chain breaks, resulting in yellowing and aging of the fibers. Mechanical properties Decrease gradually, and the service period is short. Moreover, the dense fiber macromolecules are chemically inert, stable in structure, smooth in surface due to the lack of active groups, poor interface adhesion, poor bonding and adhesion with conductive materials, and inability to have electrical conductivity. Good development prospects.

In response to these problems, researchers have developed a variety of methods to modify the conductivity and UV resistance of aramid fibers in recent years. For example, Rice University made aramid/carbon nanotube composite fiber material by first spraying resin on the aramid fiber as an adhesive, and then spraying carbon nanotubes on the fiber with a spray gun. The conductivity reached 65S/cm. After bending and Water cleaning also remains stable, but the carbon nanotubes are unevenly sprayed on the fibers, easy to fall off for a long time, and the process is complicated and difficult to expand. Another example, CN201010128403.6 uses carbon nanotubes as the surface material and epoxy resin as the adhesive to modify the surface of the aramid fibers. The modified fibers obtained have active groups, and the mechanical properties are not affected, but the fiber softness It is greatly reduced, the surface is rough, and the process is complicated. Another example, CN201310575472.5 Soochow University added methoxy groups to the surface of aramid fibers, and then reacted with calcium oxide-doped cerium oxide to react with the fibers to obtain aramid fibers coated with inorganic nanoparticles on the surface. Ultraviolet performance and heat resistance are improved, but the chemical treatment of the fiber causes the mechanical strength of the modified fiber to be greatly reduced, and it has no electrical conductivity.

Contents of the invention

The main purpose of the present invention is to provide a composite conductive fiber and its preparation method to overcome the deficiencies in the prior art.

In order to realize the aforementioned object of the invention, the technical solutions adopted in the present invention include:

An embodiment of the present invention provides a method for preparing a composite conductive fiber, which includes:

Two or more single fibers are wound to form the first fiber with relative concave parts and relative convex parts on the surface, and adhesive is also coated on the bonding surface of at least two single fibers during winding, so that the at least two The single fibers are firmly bonded, and the relative concave portion and the relative convex portion extend continuously along the axial direction of the first fiber;

The first fiber is added while the conductive material is spun to form the second fiber, so that the first fiber is uniformly wrapped in the second fiber, thereby forming a composite conductive fiber.

Further, the preparation method includes: twisting and winding more than two single fibers (such as aramid single fibers) to form the first fiber in a helical shape, and twisting and winding more than two single fibers A binder is coated on the bonding surface of the fibers, so that the two or more single fibers are firmly bonded.

The embodiment of the present invention also provides the composite conductive fiber prepared by the method of the present invention.

Embodiments of the present invention also provide a composite conductive fiber, which includes:

A first fiber formed by winding two or more single fibers, the surface of the first fiber has a relatively concave portion and a relative convex portion, and the relatively concave portion and the relative convex portion extend continuously along the axial direction of the first fiber , and the contact surfaces of at least two single fibers are also bonded by an adhesive;

The second fiber formed by spinning the conductive material is wrapped on the surface of the first fiber.

Preferably, the first fiber is a helical fiber formed by twisting and twisting two or more single fibers.

Preferably, the second fiber is a carbon nanotube fiber formed by drawing and spinning a carbon nanotube array.

Compared with the prior art, the present invention winds a plurality of single fibers under the action of a binder to form thick fibers with uneven surfaces, so that these fibers can better fit and adhere to conductive materials such as carbon nanotubes, and then pass When the conductive material is spun into fibers, thick fibers are added to form a composite fiber with a core/protective sheath structure. The composite fiber is uniform, has good conductivity, and can withstand the irradiation of ultraviolet light and the like while still maintaining excellent properties. It also has excellent flexibility and wear resistance, and can be used as a high-strength, flexible and lightweight wire. At the same time, its preparation process is simple, safe and environmentally friendly, and can be continuously automated.

Description of drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings that need to be used in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only These are some embodiments described in the present invention. Those skilled in the art can also obtain other drawings based on these drawings without creative work.

Fig. 1 is a schematic diagram of the spinning preparation process of a continuous aramid fiber/carbon nanotube composite fiber in a typical embodiment of the present invention;

Fig. 2 is a structural representation of a continuous aramid fiber/carbon nanotube composite fiber in a typical embodiment of the present invention;

Fig. 3a-Fig. 3b are the thermal field electron micrographs of the aramid fiber/carbon nanotube array composite fiber obtained by a typical embodiment of the present invention respectively;

Fig. 4a-Fig. 4c are electron micrographs of aramid fibers before and after ultraviolet irradiation in a typical embodiment of the present invention;

Fig. 4d-Fig. 4f are electron micrographs of the aramid fiber/carbon nanotube composite fiber before and after ultraviolet irradiation in a typical embodiment of the present invention.

detailed description

An aspect of the embodiments of the present invention provides a method for preparing a composite conductive fiber, which includes:

Two or more single fibers are wound to form the first fiber with relative concave parts and relative convex parts on the surface, and adhesive is also coated on the bonding surface of at least two single fibers during winding, so that the at least two The single fibers are firmly bonded, and the relative concave portion and the relative convex portion extend continuously along the axial direction of the first fiber;

The first fiber is added while the conductive material is spun to form the second fiber, so that the first fiber is uniformly wrapped in the second fiber, thereby forming a composite conductive fiber.

Further, the single fiber includes any one of aramid single fiber, ultra-high molecular weight polyethylene fiber, poly-p-phenylenebenzobisoxazole (PBO) fiber, glass fiber and carbon fiber, and is not limited thereto.

Further, the conductive material may preferably be selected from any one of black conductive materials such as carbon nanotubes and graphene, and is not limited thereto.

For example, the conductive material may preferably be selected from carbon nanotube arrays or carbon nanotube floating fibers.

In some preferred embodiments, the preparation method may include: twisting two or more single fibers to form the first fiber in a helical shape, and twisting and twisting two or more single fibers Coating adhesive on the bonding surface of the fiber, so that the two or more single fibers are firmly bonded.

Further, the binder includes any one of polyurethane and epoxy resin, but is not limited thereto.

In some preferred embodiments, the preparation method may include: after the first fiber is uniformly wrapped in the second fiber, further densifying the formed composite fiber, thereby forming the Composite conductive fibers.

For example, the preparation method may further include: contacting the composite fiber with a densification agent, so as to realize the densification treatment of the composite fiber.

Preferably, the preparation method includes: soaking the composite fiber with a densification agent, so as to realize the densification treatment of the composite fiber.

Wherein, the densification agent may include water or polar organic solvents such as ethanol and ethylene glycol, preferably ethanol or ethylene glycol. In addition, the densification agent may also be a solution using water, ethanol, ethylene glycol, etc. as a solvent, and a resin material such as PVA as a solute, but is not limited thereto.

An aspect of the embodiments of the present invention provides composite conductive fibers prepared by any one of the methods described herein.

An aspect of the embodiments of the present invention provides a composite conductive fiber, which includes:

A first fiber formed by winding two or more single fibers, the surface of the first fiber has a relatively concave portion and a relative convex portion, and the relatively concave portion and the relative convex portion extend continuously along the axial direction of the first fiber , and the contact surfaces of at least two single fibers are also bonded by an adhesive;

The second fiber formed by spinning the conductive material is wrapped on the surface of the first fiber.

More preferably, the first fiber is a helical aramid fiber formed by twisting two or more aramid single fibers.

Further, the first fiber is a helical fiber formed by twisting and winding more than two single fibers.

Wherein, the single fiber includes any one or more combinations of aramid single fiber, ultra-high molecular weight polyethylene fiber, poly-p-phenylene benzobisoxazole (PBO) fiber, glass fiber and carbon fiber, and not limited to this.

Further, the conductive material includes carbon nanotubes and/or graphene, etc., and is not limited thereto. Preferably, the conductive material includes carbon nanotube arrays or carbon nanotube floating fibers. Further preferably, the second fiber is a carbon nanotube fiber formed by drawing and spinning a carbon nanotube array.

Further, the adhesive includes any one or a combination of polyurethane, epoxy resin and the like.

Preferably, the composite conductive fiber is also processed by the densification method in the aforementioned preparation method.

Further, the electrical conductivity of the composite conductive fiber is above 1×10 ⁴ S/m, and the breaking strength is above 1769 MPa.

In the foregoing embodiments of the present invention, by first pretreating the single fiber (such as aramid fiber), for example, a plurality of single fibers are twisted and wound into a helical fiber (can be named as a thick fiber) on a spinning machine, And while twisting and winding the single fiber, apply a binder such as polyurethane glue (it can be excessive, so as to facilitate the cooperation with the densification agent in the subsequent densification process, and promote the bonding of the conductive material and the thick fiber) , after drying and solidification, a plurality of single fibers are evenly entwined to form rough fibers with tightly combined concave and convex surfaces. Such thick fibers with grooves and convex grooves on the surface can be better wrapped and fitted by carbon nanotubes because of their larger contact surface. The addition of the binder can not only make the single fibers more firmly bonded, but also significantly enhance the tensile properties of the thick fibers formed, especially their breaking strength and elongation at break, and further make Conductive materials such as carbon nanotubes and graphene are more firmly bonded to the surface of thick fibers. Referring to Fig. 1 and Fig. 2, then the conductive material (such as carbon nanotube array) is stretched, twisted and spun, and the aforementioned thick fiber is added, the thick fiber can be wrapped in the composite fiber evenly and obediently, and then passed through ethanol/ethyl alcohol Diol droplets etc. densify the composite fiber to obtain a composite conductive fiber with a "core-spun yarn" structure (such as aramid fiber/carbon nanotube composite fiber). Among them, as mentioned above, due to the coarsening of the roughness of the aramid fiber pretreatment, and the carbon nanotubes themselves have a large specific surface area, and further densification of the composite fiber by ethanol, etc., one can make the conductive The materials can be more densely assembled, and the second can make the above-mentioned thick fibers and conductive materials such as carbon nanotubes better composite (so that the two can be better combined by physical effects such as adsorption, and the two can also be restored. It can be bonded by the aforementioned resin materials, etc.), so that the fibers (such as aramid fibers) with smooth and stable surfaces that are not easy to compound can be wrapped by conductive materials such as carbon nanotubes to form a core/protective sheath structure. Among them, the wrapping layer formed by conductive materials such as carbon nanotubes can not only enhance the conductivity of the composite fiber, but also can be used as a protective layer to enhance the UV resistance and anti-aging performance of the composite fiber. In addition, it also helps to greatly improve the mechanical properties of the composite fiber. performance.

The composite conductive fiber of the present invention not only has a uniform and smooth appearance, but also has a conductivity of more than 1×10 ⁴ S/m, and at the same time maintains good mechanical strength, flexibility and heat resistance, and greatly improves the resistance to ultraviolet light. , The composite effect of conductive material and aramid fiber is very stable, not easy to fall off, and can be used as high-strength, flexible and lightweight wire. Moreover, the preparation process of the present invention is simple and easy to operate, and can be carried out continuously and automatically. At the same time, the raw materials used are all safe and non-toxic, cheap and environmentally friendly, and suitable for mass production.

Those skilled in the art can refer to the content of this article to appropriately improve the process parameters to achieve. In particular, it should be pointed out that all similar replacements and modifications are obvious to those skilled in the art, and they are all considered to be included in the present invention. The application of the present invention has been described through the preferred embodiments, and the relevant personnel can obviously make changes or appropriate changes and combinations to the application described herein without departing from the content, spirit and scope of the present invention to realize and apply the technology of the present invention .

In order to further understand the present invention, the present invention will be described in detail below in conjunction with examples.

The preparation process of a kind of aramid fiber/carbon nanotube array composite fiber involved in this embodiment comprises the following steps:

1) Separation of aramid single fiber: take aramid yarn, separate a single aramid fiber (about 12 μm in diameter), separate it for 10 m, and wind the single fiber onto a transparent tube shaft. Two groups of aramid monofilaments can be separated.

2) Aramid winding: Place the two sets of tube shafts wrapped with aramid single fiber into different positions of the same iron bar, and the tube shafts meet at 3cm, fix on the spinning machine, and pull out two tube shafts from the two tube shafts at the same time The fiber is twisted and wound into a helical fiber, and the twisting speed is 700 cycles/min to obtain two twisted fibers, which are marked as thick aramid fiber.

3) Aramid fiber bonding: Due to the smooth surface of the aramid fiber, the two fibers cannot be bonded and fixed. It is necessary to apply polyurethane glue while twisting and winding. Observe the operation under a microscope and use a fine brush head on the bonding surface of the two single fibers Brush evenly with polyurethane with a thickness of 1 μm. Afterwards, let it dry naturally at room temperature for 2 hours, and the polyurethane glue will dry and solidify, so that the aramid fibers can be bonded and adhered firmly. Glue is only applied on the contact surface, and two fiber monofilaments are evenly wound, which can form thick aramid fibers with tightly combined concave and convex surfaces. Another spool is used to collect the coarse aramid fibers.

4) Fixing of the spinning device: insert the tube shaft wrapped with thick aramid fibers into the iron bar, the tube shaft can rotate in the iron bar, and the iron bar is fixed on the stand 1; the silicon wafer with the carbon nanotube array It is fixed on the platform 2, and the platform 1 is located at the front and upper part of the platform 2; the spinning machine places the collection tube axis and keeps the same level with the silicon wafer.

5) Carbon nanotube array stretching: Measure a carbon nanotube array with a width of 2 cm, use a blade to scrape the film of the array, and stretch the drawn carbon nanotube array film to a certain length and fix it on the shaft of the collecting tube.

6) Aramid fiber introduction: The vertical distance between the thick aramid fiber on the iron bar of platform 1 and the carbon nanotube array is 1 cm, and the drawn thick aramid fiber is also fixed on the same position of the carbon nanotube array collection tube axis, and kept thick. Aramid fibers are located in the middle of the carbon nanotube array stretched film.

7) Composite wrapping: Turn on the textile machine, adjust the twisting speed to 777 cycles/min, and the carbon nanotube array film can evenly wrap the aramid fibers; adjust the forward speed to 7 cycles/min, draw the absolute ethanol solution into the needle tube, When the carbon nanotube array wraps the aramid fiber to form a composite fiber, the needle tube extrudes ethanol, so that the composite fiber passes through the ethanol droplet and infiltrates the fiber to complete the densification process. In this way, the twisted aramid fiber/carbon nanotube array composite fiber can be collected by the collecting tube axis. Set the twisting speed and forward speed, and collect the composite fibers continuously and automatically.

In this embodiment, the diameter, electrical conductivity, and tensile strength of the spun composite fiber can be adjusted by controlling the width of the scraping film of the carbon nanotube array, the collection speed of the composite fiber, and the twisting speed. And the densification of ethanol is because the carbon nanotubes will be infiltrated by the organic solvent. When the carbon nanotube array fiber passes through the organic solvent droplet, under the action of the surface tension of the droplet, the droplet squeezes the fiber and the fiber diameter shrinks; the liquid After evaporation, surface tension further tensions the fibers, completing densification. The composite fiber is impregnated with ethanol organic solvent to make the fiber dense, increase the composite effect of the two fibers, and improve the mechanical strength of the fiber.

Observing the aramid fiber/carbon nanotube array composite fiber obtained in this embodiment under a thermal field electron microscope, it can be seen that the carbon nanotube array completely wraps the aramid fiber and wraps it evenly and has the same thickness (see Fig. 3a-Fig. 3b ), and two aramid monofilaments are wound to form a rough aramid fiber with a concave-convex surface, which can fit more firmly with the carbon nanotube array. The carbon nanotubes completely wrap the aramid fiber like a "coat", so that the core aramid fiber will not be damaged by ultraviolet rays, and the ultraviolet resistance is guaranteed.

For example, use a high-power ultraviolet lamp to irradiate the aramid fiber and composite fiber of this embodiment at close range for 2 hours under the same conditions. After only 2 hours of irradiation, it can be seen that the tensile strength of the aramid fiber has decreased by 27.28%. After 4 hours of irradiation, the aramid fiber The mechanical strength of the aramid fiber decreased by 31.48%, and the structural deformation of the aramid fiber was obvious after being exposed to ultraviolet light under the electron microscope (see Fig. 4a-Fig. 4c).

As for the composite fiber, because the black material of the outer layer of carbon nanotubes can absorb ultraviolet rays, the inner aramid fiber is protected from ultraviolet rays, and the mechanical strength does not decrease, so that the carbon nanotubes have played a good role in protecting the aramid against ultraviolet rays. effect (see Figure 4d-Figure 4f).

The diameter of the composite fiber in this embodiment is about 21.28 μm, the electrical conductivity can reach 4.6×10 ⁴ S/m, the breaking strength is about 1769 MPa, and the wear resistance is good. Compared with the existing modified conductive aramid fiber Fiber has been greatly improved.

In addition, two sections of the composite fiber of this example were taken and placed in NaOH solution with a concentration of about 1mol/L and soaked in distilled water for 12 days. After 12 days, the sample was taken out, and it was found that the composite fiber did not fall off, and was still wrapped tightly and completely, and the composite effect was far superior. It is far superior to the existing composite aramid fiber formed by dry-spraying carbon nanotube powder, which is enough to prove that the performance of the composite fiber is stable.

In summary, the aramid fiber/carbon nanotube array composite fiber of this example has multiple advantages such as excellent composite effect, high stability, good UV resistance, greatly improved surface activity, high electrical conductivity, etc., and the preparation process is simple, and can be Continuously automated mass production.

As a comparison, the inventors of this case also prepared another composite fiber by referring to the process of the foregoing examples, but in step (3), the operation of coating glue on the contact surface of the single fiber was omitted. The electrical conductivity, tensile strength, and UV resistance of the composite fiber obtained in the comparative example were tested by using the aforementioned test method, and the results showed that the performance of the composite fiber was far inferior to that of the composite fiber obtained in the example. The composite fiber of this comparative example is soaked with the NaOH solution of 1mol/L with concentration again, when soaking to the 6th day, this composite fiber appears obvious expansion, when to the 12th day, black sediment can be seen in the solution, to this The black precipitate was determined to be carbon nanotubes.

In addition, the inventors of this case also used conductive materials such as graphene to replace the carbon nanotubes in the foregoing examples, and used ultra-high molecular weight polyethylene fibers, poly-p-phenylenebenzobisoxazole (PBO) fibers, glass fibers, and carbon fibers, etc. Instead of the aforementioned aramid fibers, a series of other composite conductive fibers were prepared, and the properties of these composite conductive fibers were also tested. The results showed that these composite conductive fibers were uniform and conductive. Good resistance, excellent resistance to ultraviolet light, high flexibility and wear resistance.

Finally, it should also be noted that the term "comprises", "comprises" or any other variation thereof is intended to cover a non-exclusive inclusion such that a process, method, article or apparatus comprising a set of elements includes not only those elements, but also Other elements not expressly listed, or inherent to the process, method, article, or apparatus are also included.

Claims (10)

1. A preparation method for composite conductive fibers, characterized in that it comprises: Two or more single fibers are wound to form the first fiber with relative concave parts and relative convex parts on the surface, and adhesive is also coated on the bonding surface of at least two single fibers during winding, so that the at least two The single fibers are firmly bonded, and the relative concave portion and the relative convex portion extend continuously along the axial direction of the first fiber; The first fiber is added while the conductive material is spun to form the second fiber, so that the first fiber is uniformly wrapped in the second fiber, thereby forming a composite conductive fiber. 2. preparation method according to claim 1, is characterized in that: described monofilament comprises aramid monofilament, ultrahigh molecular weight polyethylene fiber, polyparaphenylene benzobisoxazole (PBO) fiber, glass fiber and Any kind of carbon fiber. 3. The preparation method according to claim 1, characterized in that: the conductive material comprises carbon nanotubes and/or graphene; preferably, the conductive material comprises carbon nanotube arrays or carbon nanotube floating fibers. 4. preparation method according to claim 1, is characterized in that, The preparation method includes: during the process of winding the two or more single fibers to form the first fiber, also using a binder to adhere and combine the two or more single fibers; Preferably, the preparation method further includes: twisting two or more single fibers to form the first helical fiber, and coating the joint surface of the two or more single fibers during twisting and winding A binder, so that the two or more single fibers are firmly bonded; Preferably, the binder includes any one of polyurethane and epoxy resin. 5. preparation method according to claim 1, is characterized in that, The preparation method includes: after the first fiber is uniformly wrapped in the second fiber, further densifying the formed composite fiber, thereby forming the composite conductive fiber; Preferably, the preparation method includes: contacting the composite fiber with a densification agent, so as to realize the densification treatment of the composite fiber; Preferably, the preparation method includes: soaking the composite fiber with a densification agent, so as to realize the densification treatment of the composite fiber; Preferably, the densification agent comprises ethanol and/or ethylene glycol. 6. The composite conductive fiber prepared by the method according to any one of claims 1-5. 7. A composite conductive fiber, characterized in that it comprises: A first fiber formed by winding two or more single fibers, the surface of the first fiber has a relatively concave portion and a relative convex portion, and the relatively concave portion and the relative convex portion extend continuously along the axial direction of the first fiber , and the contact surfaces of at least two single fibers are also bonded by an adhesive; The second fiber formed by spinning the conductive material is wrapped on the surface of the first fiber. 8. The composite conductive fiber according to claim 7, characterized in that: the first fiber is a helical fiber formed by twisting and winding more than two single fibers; preferably, the single fibers include aramid fibers Any one of single fiber, ultra-high molecular weight polyethylene fiber, poly-p-phenylene benzobisoxazole (PBO) fiber, glass fiber and carbon fiber; and/or, the conductive material includes carbon nanotubes and/or graphite Preferably, the conductive material includes a carbon nanotube array or a carbon nanotube floating fiber; preferably, the second fiber is a carbon nanotube fiber formed by stretching and spinning a carbon nanotube array. 9. The composite conductive fiber according to claim 7, characterized in that: the binder comprises any one of polyurethane and epoxy resin. 10. The composite conductive fiber according to any one of claims 7-9, characterized in that: the electrical conductivity of the composite conductive fiber is above 1×10 ⁴ S/m, and the breaking strength is above 1769 MPa.