CN113981670A - Flexible and stretchable electromagnetic shielding fiber film and preparation method thereof - Google Patents
Flexible and stretchable electromagnetic shielding fiber film and preparation method thereof Download PDFInfo
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Abstract
The invention discloses a flexible stretchable electromagnetic shielding fiber film and a preparation method thereof, wherein the method comprises the following steps: firstly, preparing a PU fiber film by an electrostatic spinning technology; secondly, embedding and crosslinking carbon nanotubes on the surface of the PU fiber film by using the PU fiber film as a substrate through an ultrasonic cavitation load process to obtain a PU/CNTs fiber film; and finally, carrying out a post-treatment process of reducing silver nanoparticles by a solution method on the PU/CNTs fiber film to prepare the PU/CNTs/AgNPs composite fiber film so as to improve the electromagnetic shielding efficiency of the PU/CNTs/AgNPs composite fiber film. The flexible and stretchable electromagnetic shielding fiber film prepared by the invention utilizes the carbon nano tube and the nano silver to modify the electrostatic spinning PU fiber film, can effectively shield electromagnetic interference, and has the outstanding advantages of high stretching rate, good conductivity, light weight and the like. Has wide application prospect in the field of electromagnetic shielding of flexible electronics, wearable devices and the like.
Description
Technical Field
The invention relates to the field of electromagnetic protection of wearable devices and electronic communication equipment, in particular to a flexible and stretchable electromagnetic shielding fiber film and a preparation method thereof.
Background
With the advent of the 5G era, pollution caused by electromagnetic wave radiation has also received increasing attention. At present, the main approach for eliminating the negative effect of electromagnetic waves is to protect the protected object by preparing electromagnetic shielding materials, and the current widely used metallic electromagnetic shielding materials based on the principle of electromagnetic wave reflection cause the electronic information equipment module to be huge and heavy due to the defects of large density, high cost, low specific efficiency and the like, and can not meet the requirements of modern electronic equipment on light weight, intellectualization, flexibility and miniaturization. Therefore, the development of novel electromagnetic shielding materials with light weight, flexibility and high performance has become an urgent need in the field of modern electronic technology.
The polymer micro-nano fiber film prepared based on the electrostatic spinning technology has the advantages of light weight, flexibility, large specific surface area, high porosity and the like, and is an ideal template for developing a new generation of electromagnetic shielding films. In order to make the electrospun polymer fiber have excellent conductivity and thus improve the electromagnetic shielding effect, the polymer fiber is usually carbonized by a high temperature process in the conventional process. However, the high-temperature treatment method has the defects of complex process, high cost and the like, reduces the flexibility of the polymer fiber, and seriously restricts the application and popularization of the process method.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provide a flexible stretchable electromagnetic shielding fiber film and a preparation method thereof, so as to solve the problem that the existing polymer micro-nano fiber film is difficult to have high flexibility and excellent conductivity.
The purpose of the invention is realized by at least one of the following technical solutions.
The utility model provides a flexible tensile electromagnetic shield fiber film, includes Polyurethane (PU) fiber film, load Carbon Nanotube (CNTs) in the PU fiber film, PU fiber film is electrostatic spinning film.
Preferably, the PU fiber film loaded with carbon nanotubes is covered with silver nanoparticles (AgNPs).
The invention also provides a method for preparing the flexible stretchable electromagnetic shielding fiber film, which comprises the following steps:
preparing a PU fiber film by an electrostatic spinning method;
the PU fiber film is used as a flexible stretchable substrate, and the carbon nano tubes are embedded and crosslinked on the surface of the PU fiber through an ultrasonic cavitation load process to obtain the PU/CNTs fiber film, wherein the PU/CNTs fiber film is a flexible stretchable electromagnetic shielding fiber film.
Preferably, when the PU fiber film is prepared by an electrostatic spinning method, the PU solution with the mass fraction of 25-35% is adopted as the electrostatic spinning precursor solution, and the mixed solution of dimethyl formamide and acetone is adopted as the solvent of the electrostatic spinning precursor solution.
Preferably, when the PU fiber film is prepared by an electrostatic spinning method, the electrostatic spinning working voltage is 10-15 kV, the distance from a spinning nozzle to a fiber receiving device is 10-20 cm, and the feeding speed of an injector is 0.1-100 mL/h.
Preferably, when the PU/CNTs fiber film is obtained by embedding and crosslinking carbon nano tubes on the surface of PU fibers through an ultrasonic cavitation load process, the power of an ultrasonic vibrator is 320-350W, the frequency of ultrasonic waves is 20kHz, the time length of single ultrasonic cavitation load is 5min, the duty ratio of ultrasonic action is 1:2, and the time of ultrasonic action and the interruption time are 5s and 10s respectively.
Preferably, when the PU/CNTs fiber film is obtained by embedding and crosslinking carbon nanotubes on the surface of PU fibers through an ultrasonic cavitation load process, 40-60 mg of sodium dodecyl benzene sulfonate and 40-60 mg of carbon nanotubes are added into 100mL of deionized water in the adopted carbon nanotube suspension, and the length of the carbon nanotubes is 5-30 mu m.
Preferably, silver nanoparticles are attached to the PU/CNTs fiber film through a solution reduction method to obtain the PU/CNTs/AgNPs composite fiber film, and the PU/CNTs/AgNPs composite fiber film is a flexible and stretchable electromagnetic shielding fiber film.
Preferably, the process of attaching silver nanoparticles to the PU/CNTs film by a solution reduction method comprises:
primary soaking: soaking the PU/CNTs fiber film in a silver precursor solution for 40-80 min, and then drying in a vacuum environment;
secondary soaking: soaking the dried PU/CNTs fiber film in a silver reducing agent solution for 20-40 min, then washing away the reducing agent on the PU/CNTs fiber film by deionized water, and drying in a vacuum environment;
repeating the process from one soaking to the second soaking for a plurality of times to obtain the PU/CNTs/AgNPs composite fiber film.
Preferably:
during primary soaking, the adopted silver precursor solution is an ethanol solution of silver trifluoroacetate with solute mass percent of 10-20%, the drying temperature is 40-50 ℃, and the drying time is 10-20 min;
during secondary soaking, the adopted silver reducing agent solution is an L-ascorbic acid deionized water solution with the concentration of 15-25 mg/mL, the drying temperature is 40-50 ℃, and the drying time is 10-20 min;
the number of times from the primary soaking to the secondary soaking is 3-8.
The invention has the following beneficial effects:
the flexible stretchable electromagnetic shielding fiber film takes the PU fiber film prepared by electrostatic spinning as a flexible stretchable substrate, and the substrate has the characteristics of light weight, flexibility, stretchability and high porosity and can provide a multiple reflection interface for electromagnetic shielding. The carbon nano tubes are loaded in the PU fiber film, the PU fiber in the PU fiber film is directly endowed with conductivity by virtue of the carbon nano tubes, the flexibility of the PU fiber film is enhanced, the breaking strength is greatly improved, and both flexibility and high-efficiency functionalization are considered. In conclusion, the flexible and stretchable electromagnetic shielding fiber film has the characteristics of high flexibility, strong stretchability and excellent conductivity.
Drawings
FIG. 1 is a schematic diagram of the present invention for preparing PU fiber film by electrostatic spinning technology, wherein E is high voltage electrostatic field, and F is electrostatic field stretching force.
FIG. 2 is a schematic diagram of an ultrasonic cavitation load process platform employed in the present invention.
FIG. 3 is an SEM image of an electrospun PU fiber film prepared by an example of the present invention.
FIG. 4 is an SEM image of a PU/CNTs fiber film prepared by the embodiment of the invention.
Fig. 5(a) and fig. 5(b) are a schematic structural diagram and an SEM image of the flexible and stretchable PU/CNTs/AgNPs composite fiber film prepared in the embodiment of the present invention, respectively.
Fig. 6 is a schematic flow chart of preparing a flexible stretchable electromagnetic shielding fiber film according to an embodiment of the invention.
FIG. 7 is a data chart of the conductivity of the flexible and stretchable PU/CNTs/AgNPs composite fiber film prepared by the embodiment of the invention changing with the mechanical bending effect.
FIG. 8 is an electromagnetic shielding effectiveness chart of the PU/CNTs/AgNPs composite fiber film prepared by the embodiment of the invention, wherein PU/CNTs/AgNPs-2, PU/CNTs/AgNPs-4 and PU/CNTs/AgNPs-6 are samples of silver nanoparticles which are reduced and loaded for 2 times, 4 times and 6 times respectively.
The method comprises the following steps of 1-electrostatic spinning precursor liquid, 2-spinning nozzle, 3-fiber receiving device, 4-injection pump, 5-injector, 6-high voltage power supply, 7-computer, 8-signal acquisition system, 9-temperature sensor, 10-sound pressure sensor, 11-ultrasonic generator, 12-ultrasonic vibrator, 13-water bath device, 14-precision displacement platform, 15-PU fiber film, 16-CNTs embedded and crosslinked on the surface of the fiber, and 17-reduced AgNPs.
Detailed Description
The invention is described in further detail below with reference to the following figures and specific examples:
the invention provides a preparation method of a flexible stretchable electromagnetic shielding fiber film, which comprises the following steps:
firstly, preparing a precursor solution by using a PU polymer, and preparing a PU fiber film by using an electrostatic spinning technology;
secondly, embedding and crosslinking CNTs on the surface of the PU fiber by using the prepared PU fiber film as a substrate through an ultrasonic cavitation load process to prepare a PU/CNTs fiber film;
and finally, carrying out a post-treatment process of reducing AgNPs by a solution method on the PU/CNTs fiber film to prepare the PU/CNTs/AgNPs composite fiber film, and further improving the electromagnetic shielding efficiency of the PU/CNTs/AgNPs composite fiber film.
Referring to fig. 1, the device used in the invention for preparing PU fiber film by electrostatic spinning technology mainly comprises a spinneret 2, a fiber receiving device 3, an injection pump 4, an injector 5 and a high voltage power supply 6;
wherein the injection pump 4 is connected with an injector 5, the spinning nozzle 2 is connected with the injector 5, and the electrostatic spinning precursor solution 1 is filled in the injector 5; the anode of the high-voltage power supply 6 is connected with the spinning nozzle 2, and the cathode of the high-voltage power supply 6 is connected with the fiber receiving device 3; the spinneret 2 is arranged at the left side of the fiber receiving device 3, and an electrostatic field is formed between the spinneret 2 and the fiber receiving device 3; by adjusting the flow rate of the injection pump 4, the precursor liquid 1 can be ejected from the spinneret 2 by the electrostatic force to form nanofibers.
As a preferred embodiment of the present invention, the PU electrospun fiber film is prepared by an electrospinning process. Under electrostatic spinning in-process strong electric field and electrostatic stretching effect, make PU highly tensile fibre pad, in addition, through adjusting high voltage power supply 6's operating voltage, spinning jet 2 to the distance of fibre receiving arrangement 3, the feed rate of syringe 5, can regulate and control the diameter of spinning fibre and the thickness of fibre membrane, the electrostatic spinning parameter is as follows: the working voltage of the high-voltage power supply 6 is 10-15 kV, the distance between the spinning nozzle 2 and the fiber receiving device 3 is 10-20 cm, the electrostatic spinning precursor liquid can be sprayed out from the spinning nozzle 2 through an electric field formed between the spinning nozzle 2 and the fiber receiving device 3, and the feeding speed of the injector 5 is set to be 0.1-100 mL/h.
As a preferred embodiment of the invention, the PU is adopted to prepare the electrospinning precursor liquid, the material has good flexibility characteristics and thermoplastic properties, and the electrospinning fiber structure with high ductility can be prepared. The method for preparing the electrostatic spinning precursor solution by using PU comprises the following steps: dissolving PU particles in a solvent which is a mixed solution of dimethylformamide and acetone in a mass ratio of 1:1 to obtain an electrostatic spinning precursor solution with the PU mass fraction of 25-35%.
Referring to fig. 2, the device adopted for embedding and crosslinking CNTs into a PU electrospun fiber film by an ultrasonic cavitation load process mainly comprises a computer 7, a signal acquisition system 8, a temperature sensor 9, a sound pressure sensor 10, an ultrasonic generator 11, an ultrasonic vibrator 12, a water bath device 13 and a precision displacement platform 14;
the ultrasonic generator 11 is connected with the ultrasonic vibrator 12, the CNTs suspension is filled in the water bath device 13, and the ultrasonic vibrator 12 is placed in the CNTs suspension to realize power input; the temperature sensor 10 and the sound pressure sensor 11 are used for detecting temperature and sound pressure signals in the ultrasonic cavitation load process; the signal acquisition system 8 is connected with the computer 7 and is used for acquiring and displaying the sensing signals in real time; in the ultrasonic cavitation load process, in order to conveniently adjust the intensity of the ultrasonic cavitation load effect, a sample is placed on the precise displacement platform 14, the distance between the sample and the ultrasonic vibrator 12 is adjusted by adjusting the height of the precise displacement platform 14, and the effective distance between the ultrasonic vibrator 12 and the sample is adjusted to be 0.5-50 mm; by adjusting the parameters and processing time of the ultrasonic generator 11, the CNTs can be anchored on the PU fiber film under the action of transient high temperature (above 5000K), high pressure (100MPa), shock waves and micro-jet generated by the ultrasonic cavitation effect.
As a preferred embodiment of the invention, when the PU/CNTs fiber film is prepared by the ultrasonic cavitation load CNTs process, CNTs suspension is taken as a raw material, under the action of high-power ultrasonic waves, cavitation bubbles are generated in the CNTs suspension, and the cavitation bubbles are accompanied with the action of micro jet and shock waves when collapsing in an ultrasonic field. These microjets and shock waves generate high temperatures and pressures that cause the CNTs to sinter, pushing the CNTs at very high velocities towards the nanofiber surface. When the CNTs moving rapidly collide with the nanofiber surface, interfacial collision between the CNTs and the nanofibers occurs, the electrospun PU nanofibers may be partially softened or even melted at the impact site, and then the CNTs may be uniformly anchored on the electrospun PU fiber film. The CNTs have excellent physical properties, so that the electrostatic spinning PU fiber film has excellent conductivity, the recoverable tensile rate reaches 250%, the breaking strength is enhanced by 4 times, and the flexibility is enhanced by 20%. The technological parameters of the ultrasonic cavitation load CNTs are as follows: the power of the ultrasonic vibrator 12 is 320-350 w, the frequency of the ultrasonic wave is 20kHz, the time length of single ultrasonic cavitation is 5min, and the ultrasonic cavitation loading process is repeated for 6 times to realize the efficient loading of the CNTs. In order to suppress the melting of the PU fiber at a high temperature induced by ultrasonic cavitation, the ultrasonic action duty ratio was set to 1:2, i.e., the ultrasonic action time and the interruption time were 5s and 10s, respectively, and the temperature of the water bath device 13 was set to 50 ℃. The preparation method of the CNTs suspension comprises the following steps: adding a proper amount of sodium dodecyl benzene sulfonate into a certain amount of deionized water as a solvent, weighing a certain amount of long CNTs powder with the carbon nanotube length of 5-30 mu m, and dispersing the long CNTs powder in the solvent through low-power ultrasonic treatment. Wherein the ultrasonic power for dispersing the suspension is 120W, and 40-60 mg of sodium dodecyl benzene sulfonate and 40-60 mg of CNTs powder are added into 100mL of deionized water.
As a preferred embodiment of the invention, the post-treatment process of the PU/CNTs fiber film adopts a solution reduction method to uniformly attach AgNPs on the PU/CNTs fiber film to prepare the PU/CNTs/AgNPs composite fiber film, thereby achieving the purpose of reducing resistance and enhancing conductivity, and retaining high flexibility, light weight and excellent electromechanical properties.
The process for loading AgNPs by using the solution reduction method comprises the key process steps of:
firstly, putting a PU/CNTs fiber film into a silver precursor solution for soaking, and then putting the film into an oven for drying in a vacuum environment;
secondly, soaking the dried film in a silver reducing agent solution for a period of time, washing away the residual reducing agent on the film by deionized water, and then drying the film in an oven in a vacuum environment;
and finally, repeating the steps for 3-8 times, so that more AgNPs uniformly cover the surface of the PU/CNTs fiber film, and obtaining the PU/CNTs/AgNPs composite fiber film.
The adopted silver reducing agent solution is L-ascorbic acid with the concentration of 15-25 mg/mL, and the solvent adopts deionized water; the soaking time in the step is 20-40 min; controlling the temperature of the oven to be 40 ℃; the drying time was 30 min.
As a preferred embodiment of the invention, when the PU/CNTs/AgNPs composite fiber film is prepared by a silver reduction process, the PU/CNTs fiber film is soaked in a silver precursor solution for 40-80 min, and is taken out and dried for 10min in a vacuum environment at 40 ℃. And then, soaking the dried film in a silver reducing agent solution for 30min, and reducing the silver precursor absorbed in the PU/CNTs fiber film into a silver simple substance to be attached to the fiber film. Finally, the residual reducing agent on the film is washed away by deionized water and dried for 30min in a vacuum environment at 40 ℃. The silver simple substance is uniformly fixed on the PU/CNTs fiber film through continuous and multiple adsorption-drying processes. In the process of increasing the times of reducing the AgNPs from 0 to 6, the sheet resistance is rapidly reduced from 200 omega/□ to 25 omega/□, and the conductivity and the electromagnetic shielding performance of the material are well enhanced. The preparation method of the silver precursor solution comprises the following steps: and (2) taking ethanol as a solvent, and dissolving silver trifluoroacetate crystal powder with a certain mass into the solvent to obtain a silver precursor solution with the mass fraction of silver trifluoroacetate being 15%. The preparation method of the silver reducing agent solution comprises the following steps: deionized water is used as a solvent, and L-ascorbic acid with certain mass is dissolved in the solvent to obtain a reducing agent solution with the concentration of 20 mg/mL.
The scheme shows that the invention has the following advantages and effects:
(1) when the flexible stretchable electromagnetic shielding fiber film is prepared, the PU fiber film which is light, flexible, stretchable and high in porosity is successfully prepared by utilizing an electrostatic spinning process, and a multiple reflection interface is provided for electromagnetic shielding.
(2) When the flexible and stretchable electromagnetic shielding fiber film is prepared, a class of ultrasonic cavitation load process is provided, the surface material of the fiber is damaged and softened based on cavitation, and the CNTs are embedded and crosslinked on the surface of the PU fiber in situ. The electrical conductivity of the PU fiber is directly endowed by virtue of the CNTs, the flexibility of the PU fiber film is enhanced, the fracture strength is greatly improved, and both the flexibility and the high-efficiency functionalization are considered. Compared with the traditional process, the method has the advantages of high material utilization rate, large-area manufacturing, simplicity, high efficiency, low temperature, greenness, reliability, controllability and the like.
(3) When the flexible and stretchable electromagnetic shielding fiber film is prepared, the post-treatment process of AgNPs is reduced by a solution method, so that the conductivity of the film is further improved, and the composite fiber film with high conductivity, excellent mechanical stretching performance, excellent electromechanical comprehensive performance and good shielding performance is obtained.
(4) The technical means for preparing the flexible and stretchable electromagnetic shielding fiber film is simple and easy to implement, and is convenient to popularize and apply.
Example (b):
weighing 3gPU particles as raw materials, placing the raw materials in a mixed solution of 5g of dimethylformamide and 5g of acetone, fully stirring until PU is completely dissolved to obtain 30 wt% of PU electrostatic spinning precursor solution, and transferring the prepared electrostatic spinning precursor solution 1 to an injector 5;
fixing an injector 5 on an objective table of an injection pump 4, installing a spinneret 2 on the injector 5, pushing a piston of the injector 5 to convey electrostatic spinning precursor liquid to the spinneret 2 through the injection pump 4, and setting the output speed of the injection pump 4 to be 1 mL/h;
connecting the positive electrode and the negative electrode of a high-voltage power supply 6 to the spinning nozzle 2 and the fiber receiving device 3 respectively, and grounding the fiber receiving device 3;
adjusting the position of the fiber receiving device 3 to ensure that the distance between the fiber receiving device 3 and the spinneret 2 is 15cm, and the center of the fiber receiving device 3 is opposite to the spinneret 2, so that the spinning jet flow is completely collected in the fiber receiving device 3;
setting the output voltage of the high-voltage power supply 6 to be 12kV, turning on the high-voltage power supply 6 and the injection pump 4, and carrying out electrostatic spinning for 2 hours;
after spinning is finished, the high-voltage power supply 6 and the injection pump 4 are closed, the PU electrostatic spinning fiber film is peeled from the fiber receiving device 3, the fiber film is dried on a hot plate at 50 ℃ for more than 12 hours, the solvent which is not completely volatilized is removed, and finally the fiber film is stored in a drying oven, as shown in figure 3, the diameter of the PU fiber is about 800 nm;
adding 50mg of sodium dodecyl benzene sulfonate into 100mL of deionized water, fully stirring to obtain a solvent, weighing 50mg of long CNTs powder with the carbon nanotube length of 5-30 mu m, dispersing in the solvent, carrying out 120W low-power ultrasonic treatment for 1 hour, standing to obtain a CNTs suspension, and transferring the prepared CNTs suspension into a water bath device 13;
connecting an ultrasonic generator 11 with an ultrasonic vibrator 12, placing the ultrasonic vibrator 12 in a CNTs suspension, controlling parameters of ultrasonic waves in an ultrasonic cavitation load process through the ultrasonic generator 11, setting the power of the ultrasonic vibrator 12 to be 350W, the frequency of the ultrasonic waves to be 20kHz, the time of loading the CNTs by single ultrasonic cavitation to be 5min, setting the ultrasonic action duty ratio to be 1:2, namely the ultrasonic action time and the interruption time to be 5s and 10s respectively, and simultaneously controlling the temperature of a water bath device 13 to be 50 ℃;
placing the prepared PU electrostatic spinning fiber film on a precision displacement platform 14, and adjusting the height of the precision displacement platform 14 to enable the effective distance between the placement position of the PU electrostatic spinning fiber film and an ultrasonic vibrator to be 1 mm;
connecting a temperature sensor 9 and a sound pressure sensor 10 with a signal acquisition system 8, and connecting the temperature and sound signal acquisition system 8 with a computer 7, and detecting the state parameters of the ultrasonic cavitation effect in real time, in situ and on line;
starting the ultrasonic generator 11, carrying out an ultrasonic cavitation load process, and repeating the ultrasonic cavitation load process for 6 times, wherein the total ultrasonic cavitation time is 30 min;
after the ultrasonic cavitation load process is finished, the ultrasonic generator is closed, the PU/CNTs fiber film is taken out from the CNTs suspension, and the film is dried, as shown in figure 4, the CNTs are successfully anchored on the surface of the PU fiber, and a corresponding conductive path is formed;
preparing silver precursor solution by adopting silver trifluoroacetate, and dissolving 3g of silver trifluoroacetate crystal powder in 20g of ethanol to obtain 15 wt% of silver precursor solution;
putting the prepared PU/CNTs fiber film into a silver precursor solution to be soaked for 60min, and then putting the solution into an oven to be dried in vacuum for 10min at 40 ℃;
preparing a silver reducing agent solution by adopting L-ascorbic acid, and dissolving 2g of the L-ascorbic acid in 100mL of deionized water to obtain a silver reducing agent solution with the concentration of the L-ascorbic acid being 20 mg/mL;
and (2) soaking the dried film in a silver reducing agent solution for 30min, reducing silver precursors absorbed in the fiber film into silver simple substances to be attached to the micro-nano fibers, then washing away the residual reducing agent on the film by using deionized water, putting the film in an oven, drying the film for 30min at 40 ℃ in vacuum, repeating the adsorption-reduction process for 6 times, and enabling the reduced AgNPs 17 to uniformly cover the PU fiber film 15 and the CNTs 16 embedded and crosslinked on the fiber surface, as shown in fig. 5(a), thus obtaining the flexible and stretchable electromagnetic shielding fiber film, as shown in fig. 5 (b).
In the above scheme of this embodiment, in the preparation process of the flexible stretchable electromagnetic shielding fiber film, the electrostatic spinning process is first utilized to successfully prepare the light, flexible, stretchable and high-porosity PU fiber film, the electrostatic spinning PU fiber film has a large specific surface area and a three-dimensional network structure, and electromagnetic waves can be reflected in the electrostatic spinning PU fiber film for multiple times, so that the electromagnetic shielding effectiveness (EMI SE) is improved. The electromagnetic shielding effectiveness of the conductive polymer composite material depends on the conductivity of the conductive polymer composite material to a great extent, so that a class of ultrasonic cavitation load process is developed, the embedding and crosslinking of CNTs on the surface of PU fibers are realized, and the conductivity is directly endowed to the PU fibers by virtue of the CNTs. And finally, through a process of loading AgNPs by a solution reduction method, the AgNPs are uniformly covered on the surface of the PU/CNTs fiber film, the conductivity and the electromagnetic shielding performance of the film are further improved, and the whole preparation process of the PU/CNTs/AgNPs composite fiber film is shown in FIG. 6. The prepared PU/CNTs/AgNPs composite fiber film has excellent conductivity, mechanical tensile property and excellent dynamic tolerance, as shown in figure 7, after 1000 times of mechanical bending action, the conductivity of the sheet is reduced by about 3 percent, and long-term electromagnetic shielding guarantee can be provided. In addition, the prepared flexible stretchable electromagnetic shielding film shows good electromagnetic shielding effectiveness (EMI SE). In the technical process of loading AgNPs by a solution reduction method, the average EMI SE of the PU/CNTs/AgNPs-6 composite fiber film prepared after the silver nanoparticles are loaded for 6 times is reduced and the bandwidth of 8.2-12.4GHz exceeds 13.9dB, as shown in figure 8.
In conclusion, the flexible and stretchable electromagnetic shielding fiber film prepared by the invention utilizes the carbon nano tube and the nano silver to modify the electrostatic spinning PU fiber film, can effectively shield electromagnetic interference, and has the outstanding advantages of high stretching rate, good conductivity, light weight and the like. Has wide application prospect in the field of electromagnetic shielding of flexible electronics, wearable devices and the like.
Although the present invention has been described in detail with reference to the above embodiments, it should be understood by those skilled in the art that: modifications and equivalents may be made thereto without departing from the spirit and scope of the invention and it is intended to cover in the claims the invention as defined in the appended claims.
Claims (10)
1. The flexible stretchable electromagnetic shielding fiber film is characterized by comprising a PU fiber film, wherein carbon nano tubes are loaded in the PU fiber film, and the PU fiber film is an electrostatic spinning film.
2. A flexible stretchable electromagnetic shielding fiber film according to claim 1, wherein the PU fiber film loaded with carbon nanotubes is covered with silver nanoparticles.
3. A preparation method of a flexible stretchable electromagnetic shielding fiber film is characterized by comprising the following steps:
preparing a PU fiber film by an electrostatic spinning method;
the PU fiber film is used as a flexible stretchable substrate, and the carbon nano tubes are embedded and crosslinked on the surface of the PU fiber through an ultrasonic cavitation load process to obtain the PU/CNTs fiber film, wherein the PU/CNTs fiber film is a flexible stretchable electromagnetic shielding fiber film.
4. The method for preparing the flexible and stretchable electromagnetic shielding fiber film according to claim 3, characterized in that when the PU fiber film is prepared by an electrostatic spinning method, the PU solution with the mass fraction of 25-35% is adopted as the electrostatic spinning precursor solution, and the mixed solution of dimethyl formamide and acetone is adopted as the solvent of the electrostatic spinning precursor solution.
5. The method for preparing the flexible and stretchable electromagnetic shielding fiber film according to claim 3 or 4, wherein when the PU fiber film is prepared by the electrostatic spinning method, the electrostatic spinning working voltage (6) is 10-15 kV, the distance from the spinning nozzle (2) to the fiber receiving device (3) is 10-20 cm, and the feeding rate of the injector (5) is 0.1-100 mL/h.
6. The preparation method of the flexible stretchable electromagnetic shielding fiber film according to claim 3, characterized in that when the PU/CNTs fiber film is obtained by embedding and crosslinking carbon nanotubes on the surface of PU fibers through an ultrasonic cavitation load process, the power of an ultrasonic vibrator (12) is 320-350W, the frequency of ultrasonic waves is 20kHz, the time length of single ultrasonic cavitation load is 5min, and the duty ratio of ultrasonic action is 1:2, wherein the time of ultrasonic action and the time of interruption are respectively 5s and 10 s.
7. The preparation method of the flexible stretchable electromagnetic shielding fiber film according to claim 6, characterized in that when the PU/CNTs fiber film is obtained by embedding and crosslinking carbon nanotubes on the surface of PU fibers through an ultrasonic cavitation load process, 40-60 mg of sodium dodecyl benzene sulfonate and 40-60 mg of carbon nanotubes are added to 100mL of deionized water in an adopted carbon nanotube suspension, and the length of the carbon nanotubes is 5-30 μm.
8. The preparation method of the flexible stretchable electromagnetic shielding fiber film according to claim 3, characterized in that silver nanoparticles are attached to the PU/CNTs fiber film by a solution reduction method to obtain the PU/CNTs/AgNPs composite fiber film, wherein the PU/CNTs/AgNPs composite fiber film is the flexible stretchable electromagnetic shielding fiber film.
9. The method for preparing the flexible and stretchable electromagnetic shielding fiber film according to claim 8, wherein the process of attaching silver nanoparticles to the PU/CNTs fiber film by a solution reduction method comprises the following steps:
primary soaking: soaking the PU/CNTs fiber film in a silver precursor solution for 40-80 min, and then drying in a vacuum environment;
secondary soaking: soaking the dried PU/CNTs fiber film in a silver reducing agent solution for 20-40 min, then washing away the reducing agent on the PU/CNTs fiber film by deionized water, and drying in a vacuum environment;
repeating the process from one soaking to the second soaking for a plurality of times to obtain the PU/CNTs/AgNPs composite fiber film.
10. The method of claim 9 for making a flexible stretchable electromagnetic shielding fiber film, wherein:
during primary soaking, the adopted silver precursor solution is an ethanol solution of silver trifluoroacetate with solute mass percent of 10-20%, the drying temperature is 40-50 ℃, and the drying time is 10-20 min;
during secondary soaking, the adopted silver reducing agent solution is an L-ascorbic acid deionized water solution with the concentration of 15-25 mg/mL, the drying temperature is 40-50 ℃, and the drying time is 10-20 min;
the number of times from the primary soaking to the secondary soaking is 3-8.
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