Preparation method of structure-reinforced nanofibril aramid electrothermal film

Abstract

The application discloses a preparation method of a structure-reinforced nanomeric aramid electric heating film. The preparation method is as follows: mixing two-dimensional nanometer sheets of montmorillonite dispersed in dimethyl sulfoxide and TEMPO-oxidized nanocellulose with a nanomeric aramid dispersion, then performing ultrasonic treatment on the mixed solution after protonating the nanomeric aramid. After forming a composite gel by vacuum suction filtration, a layer of silver nanowires is secondarily filtered on the surface of the composite gel, and then the composite gel is subjected to hot-pressing treatment to obtain a high-strength electric heating film. The structure-reinforced nanomeric aramid electric heating film has high strength, the maximum tensile force of which can reach 488.48 MPa, the Young's modulus of which can reach 11.79 GPa, and the toughness of which can reach 52.74 MJ / m 3 . In addition to excellent electric heating performance, the film also has good durability, and the folding resistance of the film can reach 117145 times. The application provides a thought for the development of high-strength and high-performance electric heating materials.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of nanomaterials, and particularly relates to a preparation method of a structure-enhanced nanomylon electric heating film. BACKGROUND

[0002] Nanomylon is a kind of nanoscale synthetic fiber material with high aspect ratio and high strength, which is prepared by using para-aramid fiber as raw material and through a DMSO / KOH system. The surface of nanomylon has a large number of amide groups, which can form a large number of hydrogen bonds among each other, and is used for preparing high-performance thin film materials. However, due to the weak electronegativity of carbonyl and imino groups, the hydrogen bonds formed by the nanomylon fiber network itself are still too weak to truly play the excellent physical properties of nanomylon at the macro material level. Preparing a composite material is a good strategy to improve the strength of the main material, but due to the high strength, high aspect ratio and chemical inertness of nanomylon itself, the strength, dispersibility and surface chemical properties of the introduced material are also required to be high. At the same time, in order to maintain the excellent thermal stability and self-extinguishing property of nanomylon, the introduced material also needs to have good thermal stability. For the introduced material with poor thermal stability, the amount thereof should be as small as possible to maintain the heat resistance of nanomylon.

[0003] The development of today's society has higher and higher requirements for the performance of flexible electronic devices. However, due to the lack of functional groups on the surface of many conductive materials, the excessive introduction of them into the main strength material often leads to a serious decline in the strength of the final material. Therefore, there is a problem that functionality and strength often cannot be considered together, and the material with good conductive performance often has poor mechanical properties. Therefore, special methods are needed to functionalize the high-strength thin film. SUMMARY

[0004] In order to overcome the shortcomings and deficiencies of the prior art, the purpose of the present application is to provide a preparation method of a structure-enhanced nanomylon electric heating film.

[0005] The purpose of the present application is achieved by the following technical solutions:

[0006] A preparation method of a structure-enhanced nanomylon electric heating film, comprising the following steps:

[0007] (1) dispersing para-aramid short fibers in dimethyl sulfoxide (DMSO) and adding KOH, and stirring for a period of time to obtain a nanomylon dispersion;

[0008] (2) dispersing and exfoliating montmorillonite nanosheets by ultrasonic method, and preparing nanocellulose by TEMPO oxidation method;

[0009] (3) synthesizing and preparing silver nanowires by polyol method;

[0010] (4) dispersing the montmorillonite nanosheet and nanocellulose prepared in step (2) in dimethyl sulfoxide, and then mixing the same with the nanofiber dispersion prepared in step (1); then adding deionized water to the mixed solution to protonate the nanofiber, and dispersing the nanofiber flocculation by high-speed shearing treatment to obtain a mixed solution;

[0011] (5) ultrasonic treating the mixed solution obtained in step (4), and then obtaining a nanofiber composite hydrogel by vacuum filtration; then adding the silver nanowire dispersion prepared in step (3) into the filter, and obtaining a nanofiber / silver nanowire composite hydrogel after the filtration is completed;

[0012] (6) heat pressing the nanofiber / silver nanowire composite hydrogel to finally obtain a structure-reinforced nanofiber electrothermal film.

[0013] Preferably, the concentration of the nanofiber dispersion in step (1) is 2-4 mg / L, and the stirring time is 5-7 days.

[0014] Preferably, in step (1), the para-aramid short-cut fiber is 1 part by mass, the dimethyl sulfoxide is 250-500 parts by volume, and the KOH is 1.5-3.0 parts by mass.

[0015] Preferably, the specific steps for preparing the montmorillonite nanosheet in step (2) are as follows: dispersing the montmorillonite powder into water at a concentration of 0.5-1.0 wt%, and then ultrasonic treating the same by using an ultrasonic cell disruptor at a power of 800 W for 5-10 min, and then standing for 24 h; then discarding the lower sediment and leaving the upper suspension to finally obtain a montmorillonite nanosheet suspension; the thickness of the montmorillonite nanosheet is 1-3 nm, and the length-diameter ratio is 100-700.

[0016] Preferably, the specific steps for preparing the nanocellulose by TEMPO oxidation in step (2) are as follows: dispersing the bleached coniferous wood pulp into water, adding 2,2,6,6-tetramethylpiperidine N-oxide and sodium bromide, and stirring to disperse uniformly; then adding sodium hypochlorite solution to perform TEMPO oxidation reaction, and maintaining the pH of the suspension at 10-10.5; after the reaction is completed, the suspension is filtered and washed by centrifugation until the pH of the filtrate reaches neutral; and the treated suspension is subjected to fine fiberization treatment by a micro-jet homogenizer to finally obtain TEMPO-oxidized nanocellulose.

[0017] Further, the nanocellulose preparation of step (2) is specifically as follows: 10 g bleached coniferous pulp is dispersed in 1000 mL water, 160 mg 2, 2, 6, 6-tetramethylpiperidine N-oxide, 1 g sodium bromide are added, and stirred to be uniformly dispersed; then sodium hypochlorite solution is added to perform TEMPO oxidation reaction, and the pH of the suspension is maintained at 10-10.5; after the reaction is completed, the suspension is filtered and washed by centrifugation until the pH of the filtrate reaches neutral; the treated suspension is subjected to fibrillation treatment by a microfluidizer, and finally TEMPO-oxidized nanocellulose is obtained.

[0018] Further preferably, in the fibrillation treatment by the microfluidizer, the homogenization pore size is 87-400 μm, the homogenization pressure is 69-172 MPa, the homogenization suspension concentration is 0.2-1.5%, and the homogenization frequency is 2-10 times.

[0019] Further preferably, in the fibrillation treatment by the microfluidizer, the optimal homogenization pore size is 200 μm, the homogenization pressure is 138 MPa, the homogenization suspension concentration is 0.4-0.8%, and the homogenization frequency is 4-16 times.

[0020] Preferably, the TEMPO-oxidized nanocellulose of step (2) has a final carboxyl content of 0.8-1.5 mmol / g.

[0021] Preferably, the polyol method for synthesizing silver nanowires of step (3) is specifically as follows: first, 1.0 g silver nitrate dissolved in ethylene glycol is added to a reaction vessel, heated at 140°C for 30 min; then, 2.0 g polyvinylpyrrolidone and 0.01 g copper chloride dihydrate dissolved in ethylene glycol are added to the reaction vessel, and reacted at 140°C for 1.5 h under nitrogen atmosphere; subsequently, the synthesized product is washed several times by centrifugation using ethanol and water, and the silver nanowires are dispersed in water to obtain a water dispersion thereof. The obtained silver nanowires have a diameter of 60-110 nm and an aspect ratio of 200-550.

[0022] Preferably, the mass ratio of the montmorillonite nanosheet and the nanocellulose in the structure-reinforced nanofiber aramid electrothermal film of step (4) is 0.5-5.0 wt% and 1.0-5.0 wt%, respectively.

[0023] Preferably, the rotation speed of the high-speed shearing treatment of step (4) is 40000-50000 r / min, more preferably 43000 r / min.

[0024] Preferably, the amount of the silver nanowires of step (5) is 0.1-1.0 g / m 2 (0.1-1.0 grams per square meter of nanofiber aramid composite hydrogel).

[0025] Preferably, the temperature of the hot pressing in step (6) is 60-120℃, and the time is 12-36h.

[0026] Compared with the prior art, the present application has the following advantages and beneficial effects:

[0027] (1) The present application uses montmorillonite nanosheets to improve the structural strength and stress transfer efficiency of the nanofibril network. First, the surface of the montmorillonite nanosheet has abundant hydroxyl groups, which can form a large number of hydrogen bonds with the nanofibril and have good interfacial bonding force with the nanofibril. Second, due to the high strength and high aspect ratio of the montmorillonite nanosheet, after being combined with the nanofibril, it can act as a stress transfer medium to more evenly disperse the stress received by the nanofibril network as a whole. Third, when the nanofibril network is about to cause stress concentration under the action of stress, the presence of the montmorillonite nanosheet can delay the expansion of the crack and prevent the occurrence of stress concentration, thereby maintaining the overall stability of the fiber network and allowing the nanofibril network to withstand external stress to the greatest extent.

[0028] (2) The present application introduces small-sized TEMPO-oxidized nanocellulose into the nanofibril network while using montmorillonite nanosheets to reinforce the nanofibril network. On the one hand, the surface of the TEMPO-oxidized nanocellulose has abundant carboxyl and hydroxyl groups, which can form strong interfacial bonding with the nanofibril and the montmorillonite nanosheet, thereby further improving the cohesion of the overall fiber network. On the other hand, the small size of the TEMPO-oxidized nanocellulose can well fill the gaps in the fiber network, thereby improving the density of the nanofibril film and reducing the stress concentration phenomenon caused by the gaps when the nanofibril film is subjected to stress.

[0029] (3) The present application uses montmorillonite nanosheets and TEMPO-oxidized nanocellulose to synergistically reinforce the nanofibril, and introduces high-aspect-ratio and high-conductivity silver nanowires as a conductive layer on the surface of the nanofibril to endow the film with electrical heating performance, thereby ultimately obtaining an ultra-high-strength electrothermal film. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 Tensile stress-strain curve of the nanofibril composite film.

[0031] Figure 2 Surface temperature of the film of Example 3 under different voltages.

[0032] Figure 3 Surface temperature of the film of Example 4 under different voltages.

[0033] Figure 4 Thermogravimetric curve of the nanofibril composite film.

[0034] Figure 5The nanofibril composite film after being burned for 2 seconds using an alcohol lamp. DETAILED DESCRIPTION

[0035] The application will be further described in connection with the following examples and drawings, but the embodiments of the application are not limited thereto.

[0036] The para-aramid short-cut fibers used in the embodiments of the application are Kevlar 49 of the U.S. DuPont Company, and the bleached conifer pulp, montmorillonite and other medicines can be directly purchased from the market.

[0037] Example 1

[0038] The preparation method of the pure nanofibril film in the embodiment is as follows:

[0039] (1) 1 g of para-aramid short-cut fibers is dispersed in 500 mL of DMSO, 1.5 g of KOH is added, and continuous stirring is performed for 7 days to obtain a nanofibril dispersion with a concentration of 2 mg / L.

[0040] (2) 100 mL of DMSO is added to 132.47 mL of the nanofibril dispersion. Then, 132.47 mL of deionized water is added to protonate the nanofibril, and then the solution is sheared at a speed of 40000 r / min for 5 min.

[0041] (3) The solution is ultrasonically treated at a power of 800 W for 5 min, and then nanofibril hydrogel is obtained by vacuum filtration. 100 mL of deionized water is added to the filter, and the nanofibril hydrogel is washed by filtration to remove residual DMSO and KOH therein.

[0042] (4) The nanofibril hydrogel is hot-pressed at 80°C for 24 hours to finally obtain a pure nanofibril film.

[0043] Example 2

[0044] The preparation method of the structure-reinforced nanofibril composite film in the embodiment is as follows:

[0045] (1) 1 g of para-aramid short-cut fibers is dispersed in 500 mL of DMSO, 1.5 g of KOH is added, and continuous stirring is performed for 7 days to obtain a nanofibril dispersion with a concentration of 2 mg / L.

[0046] (2) The montmorillonite powder is dispersed into water at a concentration of 1.0 wt%, and then ultrasonically treated for 10 min using an ultrasonic cell disruptor, and then left to stand for 24 h. Then, the lower precipitate is discarded, and the upper suspension is left to finally obtain a montmorillonite nanosheet suspension. The average thickness of the montmorillonite nanosheet is 2.3 nm, and the average length-diameter ratio is 69.0.

[0047] (3) 10 g of absolutely dry bleached coniferous wood pulp was dispersed in 1 L of ionized water, 160 mg of 2,2,6,6-tetramethylpiperidine N-oxide, 1 g of sodium bromide were added, and the dispersion was stirred until uniform. Then, 75 mmol of sodium hypochlorite solution was added to perform TEMPO oxidation reaction, and the pH of the suspension was kept stable at 10-10.5. After the reaction was completed, the suspension was filtered by centrifugation and washed until the pH of the filtrate reached neutral. The treated suspension was fine-fiberized at a concentration of 0.8 wt% using a microfluidizer homogenizer, using a 200 μm aperture, at a pressure of 138 MPa for 8 times, and finally TEMPO-oxidized nanocellulose was obtained, with a carboxyl content of 1.15 mmol / g.

[0048] (4) 0.99 mg of absolutely dry montmorillonite nanosheet and 0.66 mg of absolutely dry TEMPO-oxidized nanocellulose were weighed and dispersed in 100 mL of DMSO, and then 132.14 mL of nanofibril dispersion was measured and mixed with the montmorillonite nanosheet / nanocellulose suspension. Then, 132.14 mL of deionized water was added to protonate the nanofibril, and then the solution was sheared at a rotation speed of 40,000 r / min for 5 min.

[0049] (5) The sheared solution was ultrasonically treated at a power of 800 W for 5 min, and then a nanofibril composite hydrogel was obtained by vacuum filtration. 100 mL of deionized water was added to the filter, and the composite hydrogel was washed by filtration to remove residual DMSO and KOH, and to convert the carboxyl group from sodium carboxylate to carboxylic acid form.

[0050] (6) The nanocellulose / nanofibril composite hydrogel was hot-pressed at 80°C for 24 hours, and finally a structure-reinforced nanofibril composite film was obtained.

[0051] Example 3

[0052] The preparation method of the structure-reinforced nanofibril electrothermal film in this embodiment is as follows:

[0053] (1) 1 g of p-aramid short-cut fiber was dispersed in 500 mL of DMSO, 1.5 g of KOH was added, and continuous stirring was performed for 7 days to obtain a nanofibril dispersion with a concentration of 2 mg / L.

[0054] (2) Montmorillonite powder was dispersed in water at a concentration of 1.0 wt%, and then ultrasonically treated using an ultrasonic cell disruptor for 10 min, and then left to stand for 24 h. Then, the lower precipitate was discarded, and the upper suspension was left to obtain a montmorillonite nanosheet suspension. The average thickness of the montmorillonite nanosheet was 2.3 nm, and the average length-diameter ratio was 69.0.

[0055] (3) 10 g of absolutely dry bleached coniferous wood pulp was dispersed in 1 L of ionized water, 160 mg of 2,2,6,6-tetramethylpiperidine N-oxide, 1 g of sodium bromide were added, and the dispersion was stirred until uniform. Then, 75 mmol of sodium hypochlorite solution was added to perform TEMPO oxidation, and the pH of the suspension was maintained at 10-10.5. After the reaction was completed, the suspension was filtered by centrifugation and washed until the pH of the filtrate reached neutral. The treated suspension was fine-fiberized at a concentration of 0.8 wt% using a microfluidizer, using a 200 μm aperture, at a pressure of 138 MPa for 8 times, and finally TEMPO-oxidized nanocellulose was obtained, which had a carboxyl group content of 1.15 mmol / g.

[0056] (4) 1.0 g of silver nitrate dissolved in ethylene glycol was added to a three-necked flask, and heated at 140°C for 30 min. Then, 2.0 g of polyvinylpyrrolidone and 0.01 g of copper chloride dihydrate dissolved in ethylene glycol were slowly added to the three-necked flask, and reacted at 140°C for 1.5 h under nitrogen atmosphere. Subsequently, the synthesized product was washed several times by centrifugation using ethanol and water, and the silver nanowires were dispersed in water to obtain a water dispersion thereof. The obtained silver nanowires had a diameter of 84.2 nm and an aspect ratio of 289.0.

[0057] (5) 0.99 mg of absolutely dry montmorillonite nanosheet and 0.66 mg of absolutely dry TEMPO-oxidized nanocellulose were weighed and dispersed in 100 mL of DMSO, and then 132.14 mL of nanofibril dispersion was measured and mixed with the montmorillonite nanosheet / nanocellulose suspension. Then, 132.14 mL of deionized water was added to protonate the nanofibril, and then the solution was sheared at a rotation speed of 40,000 rpm for 5 min.

[0058] (6) The sheared solution was ultrasonically treated at a power of 800 W for 5 min, and then a nanofibril composite hydrogel was obtained by vacuum filtration. 0.88 mg of absolutely dry silver nanowires was weighed and dispersed in 100 mL of deionized water, and then poured into a filter for filtration until the silver nanowires were formed on the surface of the hydrogel.

[0059] (7) The nanofibril composite hydrogel was hot-pressed at 80°C for 24 hours, and finally a structure-reinforced nanofibril electrothermal film was obtained, in which the content of silver nanowires was 0.2 g / m 2 .

[0060] Example 4

[0061] The preparation method of the structure-reinforced nanofibril electrothermal film in this example is as follows:

[0062] (1) 1 g para-aramid short-cut fibers were dispersed in 500 mL DMSO, 1.5 g KOH was added, and continuous stirring was carried out for 7 days to obtain a nanometer aramid dispersion with a concentration of 2 mg / L.

[0063] (2) Montmorillonite powder was dispersed in water at a concentration of 1.0 wt%, and then ultrasonically treated for 10 min using an ultrasonic cell crusher. After standing for 24 h, the lower precipitate was discarded, and the upper suspension was left to obtain a montmorillonite nanosheet suspension. The average thickness of the montmorillonite nanosheet was 2.3 nm, and the average length-diameter ratio was 69.0.

[0064] (3) 10 g of absolutely dry bleached coniferous wood pulp was dispersed in 1 L of ionized water, 160 mg of 2,2,6,6-tetramethylpiperidine N-oxide, and 1 g of sodium bromide were added and stirred to disperse uniformly. Then, 75 mmol of sodium hypochlorite solution was added to carry out TEMPO oxidation reaction, and the pH of the suspension was kept stable at 10-10.5. After the reaction was completed, the suspension was filtered and washed by centrifugation until the pH of the filtrate reached neutral. The treated suspension was fine-fibered at a concentration of 0.8 wt% using a micro-jet homogenizer, using a 200 μm aperture, and homogenized 8 times at a pressure of 138 MPa to finally obtain TEMPO-oxidized nanocellulose with a carboxyl content of 1.15 mmol / g.

[0065] (4) 1.0 g of silver nitrate dissolved in ethylene glycol was added to a three-necked flask, heated at 140°C for 30 min. Then, 2.0 g of polyvinylpyrrolidone and 0.01 g of copper chloride dihydrate dissolved in ethylene glycol were slowly added to the three-necked flask, and reacted at 140°C for 1.5 h under nitrogen atmosphere. The product was then washed several times by centrifugation using ethanol and water, and the silver nanowires were dispersed in water to obtain a water dispersion thereof. The obtained silver nanowires had a diameter of 84.2 nm and a length-diameter ratio of 289.0.

[0066] (5) 0.99 mg of absolutely dry montmorillonite nanosheet and 0.66 mg of absolutely dry TEMPO-oxidized nanocellulose were weighed and dispersed in 100 mL of DMSO, and then 132.14 mL of nanometer aramid dispersion was measured and mixed with the montmorillonite nanosheet / nanocellulose suspension. Then, 132.14 mL of deionized water was added to protonate the nanometer aramid, and then the solution was sheared at a speed of 40,000 r / min for 5 min.

[0067] (6) The sheared solution was ultrasonically treated at a power of 800 W for 5 min, and then a nanometer aramid composite hydrogel was obtained by vacuum filtration. 1.77 mg of absolutely dry silver nanowires was weighed and dispersed in 100 mL of deionized water, and then poured into the filter for filtration until the silver nanowires were formed on the surface of the hydrogel.

[0068] (7) The nano aramid composite hydrogel is hot-pressed at 80°C for 24 hours to obtain a structure-reinforced nano aramid electrothermal film, wherein the content of silver nanowires is 0.4 g / m 2 .

[0069] The mechanical properties of the films prepared in Examples 1-4 were detected. Example 1 is a pure nano aramid film, Example 2 is a structure-reinforced nano aramid film without electrically conductive ability, and Examples 3-4 are structure-reinforced nano aramid electrothermal films with good electric heating performance. The electrothermal films were cut into 15 mm x 25 mm size, a DC power supply was used to provide voltage, and an infrared camera was used to observe and record the electrothermal temperature of the films. The films were cut into 5 mm x 50 mm strips, and a universal mechanical testing machine was used to test the tensile mechanical properties of the samples. The films were cut into 15 mm x 50 mm strips, and a MIT folding resistance tester was used to test their folding resistance. Each group of samples was repeated at least 5 times, and the average value was taken. The average test results are shown in Table 1. The results are shown in Figure 1 . The electric heating performance of Examples 3 and 4 was tested, and the results are shown in Figure 2 and 3 . The thermal stability of the films prepared in Examples 1-4 was detected, and the thermogravimetric results are shown in Figure 4 . The films prepared in Examples 1, 2 and 3 were burned for 2s respectively using an alcohol lamp, and the self-extinguishing results are shown in Figure 5 .

[0070] Table 1. Mechanical test results of a high-strength nano cellulose-nano aramid composite film

[0071]

[0072] As shown in Table 1 and Figure 1 , the maximum tensile force of the pure nano aramid film in Example 1 was 222.10 ± 13.29 MPa, the Young's modulus was 5.43 ± 0.11 GPa, and the toughness was 19.85 ± 1.44 MJ / m 3 . Due to the high strength and high aspect ratio of nano aramid, the folding resistance reached 34538 ± 9512 times. After the introduction of montmorillonite nanosheets and nano cellulose (Example 2), the tensile properties were greatly improved, the maximum tensile force was 484.58 ± 12.03 MPa, the Young's modulus was 11.35 ± 0.42 GPa, and the toughness was 53.70 ± 4.49 MJ / m 3 . And the structure-reinforced nano aramid fiber network gave it very high folding resistance, and the folding number reached 129181 ± 6420.

[0073] As Figure 2 and Figure 3As shown, the structure-reinforced aramid nanofiber electrothermal film with the introduction of silver nanowires exhibits excellent electrothermal performance, with its heat generation temperature strictly corresponding to the input voltage, and it reaches a stable temperature in just 15 seconds. Furthermore, this electrothermal film also possesses extremely high mechanical properties, at 0.2 g / m². 2 When silver nanowires were used, the maximum tensile strength was 488.48±13.54 MPa, the Young's modulus was 11.79±0.39 GPa, and the toughness was 52.74±2.76 MJ / m. 3 Its flexural strength is 117145±5237 cycles.

[0074] like Figure 4 and Figure 5 As shown, this structure-enhanced nano-aramid electrothermal film possesses excellent thermal stability and self-extinguishing properties, which are crucial for electrothermal materials.

[0075] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A method for preparing a structure-reinforced nano-aramid electrothermal film, characterized in that, Includes the following steps: (1) Disperse para-aramid short fibers in dimethyl sulfoxide, add KOH, and stir to obtain nano-aramid dispersion; (2) Montmorillonite nanosheets were dispersed and exfoliated by ultrasonic method, and nanocellulose was prepared by TEMPO oxidation method; the aspect ratio of the montmorillonite nanosheets was 100-700; the final carboxyl content of the TEMPO oxidized nanocellulose was 0.8-1.5 mmol / g. (3) Silver nanowires were prepared by using the polyol method; (4) Take the montmorillonite nanosheets and nanocellulose obtained in step (2) and disperse them in dimethyl sulfoxide, and then mix them with the nanoaramid dispersion obtained in step (1). Then, deionized water was added to the mixed solution to protonate the nano-aramid fibers, and the nano-aramid flocs were dispersed by high-speed shearing to obtain the mixed solution. (5) The mixed solution obtained in step (4) is ultrasonically treated, and then the nano-aramid composite hydrogel is obtained by vacuum filtration; then the silver nanowire dispersion prepared in step (3) is added to the filter, and the nano-aramid / silver nanowire composite hydrogel is obtained after filtration; the amount of silver nanowires used is 0.1-1.0 g / m 2 ; (6) The nano-aramid / silver nanowire composite hydrogel is hot-pressed to finally obtain a structure-reinforced nano-aramid electrothermal film; the montmorillonite nanosheets and nanocellulose account for 0.5-5.0 wt% and 1.0-5.0 wt% of the structure-reinforced nano-aramid electrothermal film, respectively.

2. The method for preparing the structure-reinforced nano-aramid electrothermal film according to claim 1, characterized in that: In step (1), the concentration of the nano-aramid dispersion is 2-4 mg / L, and the stirring time is 5-7 days.

3. The method for preparing the structure-reinforced nano-aramid electrothermal film according to claim 1, characterized in that: In step (1), the amount of para-aramid short-cut fiber is 1 part by mass, the amount of dimethyl sulfoxide is 250-500 parts by volume, and the amount of KOH is 1.5-3.0 parts by mass.

4. The method for preparing the structure-reinforced nano-aramid electrothermal film according to claim 1, characterized in that: The specific steps for preparing nanocellulose by TEMPO oxidation in step (2) are as follows: bleached softwood pulp is dispersed in water, and 2,2,6,6-tetramethylpiperidine nitrogen oxides and sodium bromide are added and stirred until evenly dispersed; then sodium hypochlorite solution is added to carry out the TEMPO oxidation reaction, and the pH of the suspension is maintained at 10-10.5; after the reaction, the suspension is washed by centrifugation and filtration until the pH of the filtrate reaches neutral; the treated suspension is finely fiberized by microfluidic homogenizer to finally obtain TEMPO-oxidized nanocellulose.

5. The method for preparing the structure-reinforced nano-aramid electrothermal film according to claim 4, characterized in that: In the microfluidic homogenizer fine fiberization process, the homogenization pore size is 87-400μm, the homogenization pressure is 69-172MPa, the homogenization suspension concentration is 0.2-1.5wt%, and the homogenization times are 2-10 times.

6. The method for preparing the structure-reinforced nano-aramid electrothermal film according to claim 1, characterized in that: The specific steps for synthesizing silver nanowires using the polyol method described in step (3) are as follows: First, silver nitrate dissolved in ethylene glycol is added to the reaction vessel and heated at 140°C for 30 min; then, ethylene glycol containing dissolved polyvinylpyrrolidone and copper chloride dihydrate is added to the reaction vessel and reacted at 140°C for 1.5 h under nitrogen atmosphere; subsequently, the synthesized product is washed several times by centrifugation with ethanol and water to disperse the silver nanowires in water and obtain its aqueous dispersion.

7. The method for preparing the structure-reinforced nano-aramid electrothermal film according to claim 1, characterized in that: The hot pressing temperature in step (6) is 60-120℃, and the time is 12-36h.

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