CN111732746B - Aramid nanofiber based laminated composite film, preparation method thereof and recycling method thereof - Google Patents

Aramid nanofiber based laminated composite film, preparation method thereof and recycling method thereof Download PDF

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CN111732746B
CN111732746B CN202010628172.9A CN202010628172A CN111732746B CN 111732746 B CN111732746 B CN 111732746B CN 202010628172 A CN202010628172 A CN 202010628172A CN 111732746 B CN111732746 B CN 111732746B
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aramid
fiber
composite film
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CN111732746A (en
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俞书宏
潘晓锋
高怀岭
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University of Science and Technology of China USTC
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    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J5/00—Manufacture of articles or shaped materials containing macromolecular substances
    • C08J5/18—Manufacture of films or sheets
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B27/00—Layered products comprising a layer of synthetic resin
    • B32B27/12—Layered products comprising a layer of synthetic resin next to a fibrous or filamentary layer
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B27/00—Layered products comprising a layer of synthetic resin
    • B32B27/34—Layered products comprising a layer of synthetic resin comprising polyamides
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
    • C08L77/00—Compositions of polyamides obtained by reactions forming a carboxylic amide link in the main chain; Compositions of derivatives of such polymers
    • C08L77/10—Polyamides derived from aromatically bound amino and carboxyl groups of amino-carboxylic acids or of polyamines and polycarboxylic acids

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Abstract

The invention provides an aramid nano-fiber based composite film, which has a layered structure; the composite film is formed by laminating a plurality of single-layer aramid nano-fiber-based films; the aramid nano-fiber-based film comprises an aramid nano-fiber matrix and an assembly element; the assembly cell includes one or more of an inorganic sheet material, an inorganic wire material, and a polymer. The aramid fiber nanofiber-based composite film provided by the invention has a compact layered structure, a single-layer film is uniform in thickness, and a very small nanoscale uniform interlayer distance is provided, so that the composite film has relatively excellent comprehensive performance. The invention also provides a simple, high-efficiency and easily-scaled preparation method and a recycling method, the prepared aramid nano-fiber based laminated composite film material can be prepared into aramid nano-fiber based composite slurry again, and then the aramid nano-fiber based composite slurry is prepared into the laminated composite film material again by means of a spraying and hot-pressing combined method, so that the repeated recycling of the laminated composite film material is realized.

Description

Aramid nanofiber based laminated composite film, preparation method thereof and recycling method thereof
Technical Field
The invention belongs to the technical field of aramid nano-fiber layered materials, and relates to an aramid nano-fiber based composite film and a preparation method thereof, and a recycling method of the aramid nano-fiber based composite film, in particular to an aramid nano-fiber based layered composite film and a preparation method thereof, and a recycling method of the aramid nano-fiber based layered composite film.
Background
The Aramid fiber is called poly-p-phenylene terephthalamide completely, is Aramid fiber in English, is a novel high-tech synthetic fiber, has excellent performances of ultrahigh tensile strength, high modulus, high temperature resistance, acid and alkali resistance, low density and the like, has the strength of 5-6 times that of a steel wire, the modulus of 2-3 times that of the steel wire or glass fiber, the toughness of 2 times that of the steel wire and the density of only about 1/5 times that of the steel wire, and does not decompose or melt at the temperature of 560 ℃. It has good insulating property and ageing resistance, and has a long life cycle. The invention of aramid fiber is considered as a very important historical process in the material field. Aramid fiber is an important national defense and military material, and besides military application, aramid fiber is widely applied to various aspects of national economy such as aerospace, electromechanics, buildings, automobiles, sports goods and the like as a fiber material with high technical content. The aramid nano-fiber is used as a novel polymer nano-fiber developed in recent years, and not only retains the structural characteristics and excellent mechanical properties and thermal stability of macroscopic aramid fiber; meanwhile, the unique nanoscale morphology of the nano-composite material gives new connotation and excellent characteristics to the nano-composite material. In recent years, the high-performance layered composite film prepared by taking the aramid nano-fiber and other nano-materials as structural units has excellent application prospects in the fields of electrical insulation, heat conduction, electric conduction, composite reinforcement and the like.
Due to the fact that the aramid nano-fiber dimethyl sulfoxide dispersion liquid rapidly gels when meeting water, the existing method for preparing the aramid nano-fiber base laminated composite film mainly comprises a vacuum filtration method and a sol-gel method. In advanced functional materials journal 2019, twenty-ninth volume 1900056 reports that dimethyl sulfoxide dispersion liquid of aramid nano-fibers and boron nitride nanosheets is used as slurry, a proper amount of deionized water is added to form gel, then the gel is re-dispersed into nano assembly units by using a high-speed shearing machine, and then a vacuum filtration method is adopted to prepare the layered composite film material. The mechanical property and the thermal conductivity of the layered composite film material are improved compared with those of a pure aramid nanofiber film. In journal 2020, volume fourteenth 611 of the american chemical society, it is reported that a layered composite film material prepared by using aramid nanofibers and synthetic mica nanosheets as structural units and using a sol-gel-film conversion technique has certain advantages in toughness, dielectric strength and the like compared with other film insulation materials.
However, with the further requirements of the downstream application field on the performance of the aramid nanofiber film, the uniformity and compactness of the layered composite film material prepared by the prior art are relatively poor, so that the performance in unit thickness still needs to be further improved; in addition, although the aramid nano-fiber based laminated composite film with good performance can be obtained by the current preparation method, the problems of large time consumption, low yield and the like exist, the large-scale production is hindered, and the future large-scale production and practical application requirements are still difficult to meet from the practical application perspective.
Therefore, how to design a laminated composite film with higher performance based on aramid nano-fiber and find a more efficient and general method to realize the macro-preparation thereof becomes one of the problems to be solved by a plurality of prospective researchers in the industry.
Disclosure of Invention
In view of the above, the technical problem to be solved by the present invention is to provide an aramid nanofiber-based composite film and a preparation method thereof, and a method for recycling the aramid nanofiber-based composite film, particularly an aramid nanofiber-based laminated composite film and a preparation method thereof. The aramid nano-fiber-based layered composite film provided by the invention has a specific layered structure and composition, has lower uniform interlayer spacing and higher compactness, greatly improves the comprehensive performance of a layered composite film material in unit thickness, is simple in preparation method, mild in condition, easy to operate and low in cost, is suitable for large-scale production, and can better promote the commercial application of the aramid nano-fiber-based layered composite film.
The invention provides an aramid nano-fiber based composite film, which has a layered structure;
the composite film is formed by laminating a plurality of single-layer aramid nano-fiber-based films;
the aramid nano-fiber-based film comprises an aramid nano-fiber matrix and an assembly element;
the assembly cell includes one or more of an inorganic sheet material, an inorganic wire material, and a polymer.
Preferably, the layered structure is a dense layered structure;
the thickness of the single-layer aramid nanofiber-based film is 10-400 nm;
the interlayer spacing between the single-layer aramid nanofiber-based films is 1-10 nm;
the thickness of the aramid fiber nanofiber-based composite film is 5-80 microns;
the number of the layers is 12-8000.
Preferably, the assembly element comprises one or more of natural mineral mica nanosheets, natural mineral mica micron sheets, alumina micron sheets, boron nitride nanosheets, graphene oxide sheets, carbon nanotubes, calcium silicate nanowires, brushite micron sheets and polyvinyl alcohol;
the mass ratio of the aramid nano-fiber matrix to the aramid nano-fiber-based film is 5-90 wt.%;
the diameter of the aramid nano fiber is 5-15 nm;
the length of the aramid nano-fiber is 10-30 mu m.
Preferably, the assembly elements are uniformly dispersed and embedded in the aramid nanofiber matrix;
the aramid fiber nanofiber-based composite film is a recyclable aramid fiber nanofiber-based composite film;
the aramid fiber nanofiber-based composite film is prepared by stirring and stripping raw materials with a proton donor-assisted machine, spraying, replacing and hot-pressing.
The invention provides a preparation method of an aramid nano-fiber based composite film, which comprises the following steps:
1) stirring and stripping an aramid fiber raw material, potassium-containing alkali, a proton donor and a solvent to obtain an aramid nanofiber dispersion liquid;
2) shearing and mixing the aramid nano-fiber dispersion liquid obtained in the step and the assembly element to obtain composite slurry;
3) spraying the composite slurry obtained in the step on a substrate to form a single-layer two-phase gel layer, and spraying for multiple times to obtain a composite gel;
4) and (3) immersing the composite gel obtained in the step into water for the first replacement, then drying to form a film, immersing into water again for the second replacement, then drying, and performing hot pressing to obtain the aramid nano-fiber-based composite film.
Preferably, the diameter of the aramid fiber raw material is 5-15 nm;
the length of the aramid fiber raw material is 5-100 cm;
the potassium-containing base comprises potassium hydroxide and/or potassium ethoxide;
the proton donor comprises one or more of water, ethanol, and methanol;
the solvent comprises dimethyl sulfoxide.
Preferably, the concentration of the aramid fiber raw material in the aramid nanofiber dispersion liquid is 5-20 mg/mL;
the mass ratio of the aramid fiber raw material to the potassium-containing alkali is (0.5-2): 1;
the mass ratio of the aramid fiber raw material to the proton donor is (20-80): 1;
the diameter of the aramid nano fiber is 5-15 nm;
the length of the aramid nano-fiber is 10-30 mu m.
Preferably, the rotating speed of stirring and stripping is 100-800 r/min;
the stirring and stripping time is 12-48 h;
the shearing and mixing time is 20-40 min;
the rotating speed of the shearing and mixing is 8000-12000 r/min;
the spraying amount of the spraying is 0.5-12 mL/min;
the substrate includes one or more of a glass substrate, a PET substrate, and a PI substrate.
Preferably, the time for the first replacement is 12-24 h;
forming a composite hydrogel after the first replacement;
the temperature for drying and film forming is 25-80 ℃;
the drying and film forming time is 4-12 h;
the time of the second replacement is 12-24 hours;
forming a water-containing film after the second replacement;
the drying temperature is 25-80 ℃;
the drying time is 4-12 h;
the hot pressing temperature is 80-120 ℃;
the pressure of hot pressing is 5-60 MPa;
and the hot pressing time is 48-96 h.
The invention also provides a method for recycling the aramid nano-fiber-based composite film, which comprises the following steps:
the aramid fiber nano-fiber-based composite film prepared by the aramid fiber nano-fiber-based composite film or the preparation method of any one of the above technical schemes is partially or completely used as an aramid fiber raw material, and the recycling of the aramid fiber nano-fiber-based composite film is realized after the aramid fiber nano-fiber-based composite film is prepared by the preparation method of any one of the above technical schemes.
The invention provides an aramid nano-fiber based composite film, which has a layered structure; the composite film is formed by laminating a plurality of single-layer aramid nano-fiber-based films; the aramid nano-fiber-based film comprises an aramid nano-fiber matrix and an assembly element; the assembly cell includes one or more of an inorganic sheet material, an inorganic wire material, and a polymer. Compared with the prior art, the invention aims at the problems that the structure and the comprehensive performance of the existing aramid nano-fiber-based composite film need to be further improved, and the traditional preparation method has the defects of complex and fussy process, large time consumption, low yield, blockage of large scale and the like.
The invention creatively designs an aramid nano-fiber-based composite film with a special laminated structure, the aramid nano-fiber-based composite film provided by the invention is formed by laminating a plurality of single-layer aramid nano-fiber-based films, and an aramid nano-fiber matrix and a specific assembly element are selected in the single film. More importantly, the aramid nano-fiber-based composite film provided by the invention has a compact layered structure, uniform thickness of a single-layer film, and particularly extremely small and uniform nanoscale interlayer spacing, so that the aramid nano-fiber-based composite film provided by the invention has excellent comprehensive performance.
The invention also provides a corresponding preparation method, so that the aramid nano-fiber-based composite film with the specific laminated structure can be realized, the laminated structure can be realized by spraying through specific raw materials and steps, a solid foundation is laid by combining a specific hot-pressing technology subsequently, residual defects are reduced as far as possible, and finally the high-performance layered composite film material with a compact structure and nanoscale uniform interlayer spacing can be prepared, and the layered composite film material has excellent application prospects in the fields of electrical insulation, heat conduction, electric conduction, composite reinforcement and the like.
The invention provides a simple, efficient and easily-scaled method for preparing a high-performance aramid nano-fiber based laminated composite film material, the prepared aramid nano-fiber based laminated composite film material can be re-prepared into aramid nano-fiber based composite slurry through a proton donor assisted mechanical stirring stripping method, and then the aramid nano-fiber based composite slurry is prepared into a laminated composite film material again by means of a spraying and hot pressing combined method, so that the repeated cyclic utilization of the laminated composite film material can be realized.
The experimental result shows that by means of the compact layered structure design, the tensile strength of the composite film prepared by the invention reaches 200-280 MPa, which is far higher than that of a pure aramid nanofiber film (185 MPa); by virtue of the inherent advantages of the assembly elements, the composite film prepared by the invention realizes multifunctionality, for example, the addition of mica sheets endows the composite film with high resistance performance (165 kV/mm), and the addition of boron nitride sheets endows the composite film with high thermal conductivity (2.5W m)-1K-1) And the addition of the silver wire endows the composite film with high conductivity (4.1M/Sq), and the like.
Drawings
FIG. 1 is a schematic diagram of a route for preparing an aramid nanofiber-based layered composite membrane according to the present invention;
fig. 2 is a transmission electron microscope image of the aramid nanofibers prepared in example 1 of the present invention;
fig. 3 is an atomic force microscope image of natural mica nanoplates prepared in example 1 of the present invention;
FIG. 4 is a diagram showing a two-phase gel of dimethyl sulfoxide and water, a hydrogel after being soaked in water and a layered composite film after being evaporated, which are formed by spraying in example 1 of the present invention;
fig. 5 is a scanning electron microscope photograph of a cross section of the 40 wt.% aramid nanofiber-mica nanosheet layered composite film after hot pressing in example 1 of the present invention;
fig. 6 is a surface scanning electron microscope photograph of a pure aramid nanofiber laminated film prepared in example 3 of the present invention and a surface scanning electron microscope photograph of a 40 wt.% aramid nanofiber-mica nanosheet laminated composite film after hot pressing in example 1;
fig. 7 is the tensile strength of the densified 40 wt.% aramid nanofiber-mica nanosheet layered composite film of example 1 of the present invention and the layered composite film prepared in example 2;
fig. 8 is the dielectric strength of the densified 40 wt.% aramid nanofiber-mica nanosheet layered composite film of example 1 of the present invention and the layered composite film prepared in example 2;
FIG. 9 is a schematic diagram of an automatic spray coating device for use with the present invention;
fig. 10 is a photograph of a 40 wt.% aramid nanofiber-mica sheet layered composite two-phase hydrogel prepared in example 2 of the present invention;
fig. 11 is a cross-sectional scanning electron micrograph of the pure aramid nanofiber laminate film prepared in example 3 of the present invention and a cross-sectional scanning electron micrograph of the 30 wt.% aramid nanofiber-polyvinyl alcohol laminate film in example 4.
Detailed Description
For a further understanding of the invention, reference will now be made to the preferred embodiments of the invention by way of example, and it is to be understood that the description is intended to further illustrate features and advantages of the invention, and not to limit the scope of the claims.
All of the starting materials of the present invention, without particular limitation as to their source, may be purchased commercially or prepared according to conventional methods well known to those skilled in the art.
All the raw materials of the invention are not particularly limited in purity, and the invention preferably adopts the conventional purity used in the field of analytically pure or aramid nanofiber film materials.
The invention provides an aramid nano-fiber based composite film, which has a layered structure;
the composite film is formed by laminating a plurality of single-layer aramid nano-fiber-based films;
the aramid nano-fiber-based film comprises an aramid nano-fiber matrix and an assembly element;
the assembly cell includes one or more of an inorganic sheet material, an inorganic wire material, and a polymer.
The specific structure of the layered structure is not particularly limited in principle, and a person skilled in the art can select and adjust the layered structure according to the actual application condition, the product requirement and the quality requirement.
The specific parameters of the single-layer aramid nanofiber-based film are not particularly limited in principle, and a person skilled in the art can select and adjust the specific parameters according to actual application conditions, product requirements and quality requirements, the specific structure, composition and morphology of the composite material are better guaranteed, the specific film interlayer spacing is lower and uniform, the compactness is higher, the comprehensive performance of the composite film is further improved, the preparation process is simplified, and the thickness of the single-layer aramid nanofiber-based film is preferably 10-400 nm, more preferably 50-350 nm, more preferably 100-300 nm, and more preferably 150-250 nm.
The interlayer spacing between the single-layer films of the composite film is not particularly limited in principle, and can be selected and adjusted by a person skilled in the art according to actual application conditions, product requirements and quality requirements, the specific structure, composition and morphology of the composite material are better guaranteed, the specific film interlayer spacing is lower and uniform, the compactness is higher, the comprehensive performance of the composite film is further improved, the preparation process is simplified, and the interlayer spacing between the single-layer aramid nanofiber-based films is preferably 1-10 nm, more preferably 3-8 nm, and more preferably 5-6 nm.
The thickness of the aramid nano-fiber based composite film is not particularly limited in principle, and can be selected and adjusted by a person skilled in the art according to actual application conditions, product requirements and quality requirements, the specific structure, composition and morphology of the composite material are better guaranteed, the specific lower and uniform film interlayer spacing and higher compactness are achieved, the comprehensive performance of the composite film is further improved, and the preparation process is simplified, wherein the thickness of the aramid nano-fiber based composite film is preferably 5-80 micrometers, more preferably 15-70 micrometers, more preferably 25-60 micrometers, and more preferably 35-50 micrometers.
The number of the single-layer aramid nanofiber-based film in the composite film is not particularly limited in principle, and can be selected and adjusted by a person skilled in the art according to actual application conditions, product requirements and quality requirements.
The invention is not particularly limited in principle to the specific type of the assembly element, and the skilled in the art can select and adjust the assembly element according to the actual application condition, the product requirement and the quality requirement, in order to better ensure the specific structure, composition and morphology of the composite material, specifically lower and uniform interlayer spacing of the film and higher compactness, further improve the comprehensive performance of the composite film and simplify the preparation process, the assembly element preferably comprises one or more of natural mineral mica nanosheets, natural mineral mica micron sheets, aluminum oxide micron sheets, boron nitride nanosheets, graphene oxide sheets, carbon nanotubes, calcium silicate nanowires, brushite micron sheets and polyvinyl alcohol, and more preferably comprises one or more of natural mineral mica nanosheets, natural mineral mica micron sheets, aluminum oxide micron sheets, boron nitride nanosheets, graphene oxide sheets, carbon nanotubes, calcium carbonate nanotubes, brushite micron sheets and polyvinyl alcohol, Calcium silicate nanowires, brushite nanoplatelets, or polyvinyl alcohol.
The content of the aramid nanofiber matrix is not particularly limited in principle, and can be selected and adjusted by a person skilled in the art according to actual application conditions, product requirements and quality requirements, the specific structure, composition and morphology of the composite material, the specific lower and uniform film interlayer spacing and higher compactness are better ensured, the comprehensive performance of the composite film is further improved, and the preparation process is simplified, wherein the mass ratio of the aramid nanofiber matrix to the aramid nanofiber-based film is preferably 5 wt.% to 90 wt.%, more preferably 15 wt.% to 80 wt.%, more preferably 25 wt.% to 70 wt.%, more preferably 35 wt.% to 60 wt.%, and more preferably 45 wt.% to 50 wt.%.
The diameter of the aramid nano fiber in the single-layer aramid nano fiber-based film is not particularly limited in principle, and can be selected and adjusted by a person skilled in the art according to the actual application condition, the product requirement and the quality requirement, the composite material disclosed by the invention has the advantages that the specific structure, composition and appearance, the specific lower and uniform film interlayer spacing and higher compactness of the composite material are better ensured, the comprehensive performance of the composite film is further improved, the preparation process is simplified, and the diameter of the aramid nano fiber is preferably 5-15 nm, more preferably 7-13 nm, and more preferably 9-11 nm.
The length of the aramid nano-fiber in the single-layer aramid nano-fiber-based film is not particularly limited in principle, and can be selected and adjusted by a person skilled in the art according to the actual application condition, the product requirement and the quality requirement, the specific structure, composition and morphology of the composite material, the specific lower and uniform film interlayer spacing and higher compactness are better ensured, the comprehensive performance of the composite film is further improved, the preparation process is simplified, and the length of the aramid nano-fiber is preferably 10-30 micrometers, more preferably 13-27 micrometers, more preferably 16-24 micrometers, and more preferably 19-21 micrometers.
The invention has no special limitation on the specific shape of the single-layer aramid nano-fiber-based film in principle, and a person skilled in the art can select and adjust the shape according to the actual application condition, the product requirement and the quality requirement.
The invention has no special limitation on the service performance of the aramid nano-fiber-based composite film in principle, and a person skilled in the art can select and adjust the composite film according to the actual application condition, the product requirement and the quality requirement.
The invention provides an aramid nanofiber-based composite film in the steps, the specific morphology of the aramid nanofiber-based composite film is not particularly limited in principle, and a person skilled in the art can select and adjust the film according to the actual application condition, the product requirement and the quality requirement.
The invention has no special restriction on the preparation route of the aramid nano-fiber based composite film in principle, and a person skilled in the art can select and adjust the aramid nano-fiber based composite film according to the actual application condition, the product requirement and the quality requirement.
The invention also provides a preparation method of the aramid nano-fiber-based composite film, which comprises the following steps:
1) stirring and stripping an aramid fiber raw material, potassium-containing alkali, a proton donor and a solvent to obtain an aramid nanofiber dispersion liquid;
2) shearing and mixing the aramid nano-fiber dispersion liquid obtained in the step and the assembly element to obtain composite slurry;
3) spraying the composite slurry obtained in the step on a substrate to form a single-layer two-phase gel layer, and spraying for multiple times to obtain a composite gel;
4) and (3) immersing the composite gel obtained in the step into water for the first replacement, then drying to form a film, immersing into water again for the second replacement, then drying, and performing hot pressing to obtain the aramid nano-fiber-based composite film.
The structure, composition and parameters of the aramid nano-fiber-based composite film and the corresponding preferred principle can be corresponding to the structure, composition and parameters of the aramid nano-fiber-based composite film and the corresponding preferred principle, and are not described in detail herein.
Firstly, stirring and stripping an aramid fiber raw material, potassium-containing alkali, a proton donor and a solvent to obtain an aramid nanofiber dispersion liquid.
The diameter of the aramid fiber raw material is not particularly limited in principle, and can be selected and adjusted by a person skilled in the art according to the actual application condition, the product requirement and the quality requirement, the specific structure, composition and morphology of the composite material, the specific lower and uniform film interlayer spacing and higher compactness are better ensured, the comprehensive performance of the composite film is further improved, the preparation process is simplified, and the diameter of the aramid fiber raw material is preferably 5-15 nm, more preferably 7-13 nm, and more preferably 9-11 nm.
The length of the aramid fiber raw material is not particularly limited in principle, and can be selected and adjusted by a person skilled in the art according to the actual application condition, the product requirement and the quality requirement, the specific structure, composition and morphology of the composite material, the specific lower and uniform film interlayer spacing and higher compactness are better ensured, the comprehensive performance of the composite film is further improved, the preparation process is simplified, and the length of the aramid fiber raw material is preferably 5-100 cm, more preferably 25-80 cm, and more preferably 45-60 cm.
The specific selection of the potassium-containing alkali is not particularly limited in principle, and can be selected and adjusted by a person skilled in the art according to the actual application condition, the product requirement and the quality requirement.
The specific choice of the proton donor is not particularly limited in principle, and can be selected and adjusted by a person skilled in the art according to the actual application situation, the product requirements and the quality requirements.
The specific selection of the solvent is not particularly limited in principle, and a person skilled in the art can select and adjust the solvent according to the actual application condition, the product requirement and the quality requirement.
The concentration of the aramid fiber raw material in the aramid fiber nano-fiber dispersion liquid is not particularly limited in principle, and can be selected and adjusted by a person skilled in the art according to actual application conditions, product requirements and quality requirements.
The mass ratio of the aramid fiber raw material to the potassium-containing alkali is not particularly limited in principle, and can be selected and adjusted by a person skilled in the art according to actual application conditions, product requirements and quality requirements, the specific structure, composition and morphology of the composite material, the specific lower and uniform film interlayer spacing and higher compactness are better ensured, the comprehensive performance of the composite film is further improved, the preparation process is simplified, and the mass ratio of the aramid fiber raw material to the potassium-containing alkali is preferably (0.5-2): 1, more preferably (0.8 to 1.7): 1, more preferably (1.1 to 1.4): 1.
in the invention, the mass ratio of the aramid fiber raw material to the proton donor is not particularly limited in principle, and can be selected and adjusted by a person skilled in the art according to actual application conditions, product requirements and quality requirements, in order to better ensure the specific structure, composition and morphology of the composite material, specifically lower and uniform film interlayer spacing and higher compactness, further improve the comprehensive performance of the composite film and simplify the preparation process, the mass ratio of the aramid fiber raw material to the proton donor is preferably (20-80): 1, more preferably (30 to 70): 1, more preferably (40 to 60): 1.
the diameter of the aramid nano-fiber in the aramid nano-fiber dispersion liquid is not particularly limited in principle, and can be selected and adjusted by a person skilled in the art according to actual application conditions, product requirements and quality requirements, the specific structure, composition and morphology of the composite material are better guaranteed, the specific lower and uniform film interlayer spacing and higher compactness are achieved, the comprehensive performance of the composite film is further improved, the preparation process is simplified, and the diameter of the aramid nano-fiber is preferably 5-15 nm, more preferably 7-13 nm, and more preferably 9-11 nm.
The invention has no special limitation on the length of the aramid nano-fiber in the aramid nano-fiber dispersion liquid in principle, and a person skilled in the art can select and adjust the length according to the actual application condition, the product requirement and the quality requirement, in order to better ensure the specific structure, the composition and the morphology of the composite material, specifically lower and uniform film interlayer spacing and higher compactness, further improve the comprehensive performance of the composite film and simplify the preparation process, the length of the aramid nano-fiber is preferably 10-30 μm, more preferably 13-27 μm, more preferably 16-24 μm, and more preferably 19-21 μm.
The rotating speed of stirring and stripping is not particularly limited in principle, and can be selected and adjusted by a person skilled in the art according to the actual application condition, the product requirement and the quality requirement, the specific structure, composition and morphology of the composite material, the specific lower and uniform film interlayer spacing and higher compactness are better ensured, the comprehensive performance of the composite film is further improved, the preparation process is simplified, and the rotating speed of stirring and stripping is preferably 100-800 r/min, more preferably 200-700 r/min, more preferably 300-600 r/min, and more preferably 400-500 r/min.
The stirring and stripping time is not particularly limited in principle, and can be selected and adjusted by a person skilled in the art according to the actual application condition, the product requirement and the quality requirement, the specific structure, composition and morphology of the composite material, the specific lower and uniform film interlayer spacing and higher compactness are better ensured, the comprehensive performance of the composite film is further improved, the preparation process is simplified, and the stirring and stripping time is preferably 12-48 hours, more preferably 18-42 hours, and more preferably 24-36 hours. .
The invention has no special limitation on other conditions of stirring and stripping in principle, and a person skilled in the art can select and adjust the conditions according to the actual application condition, the product requirement and the quality requirement, in order to better ensure the specific structure, composition and morphology of the composite material, particularly lower and uniform interlayer spacing of the film and higher compactness, further improve the comprehensive performance of the composite film and simplify the preparation process, wherein the stirring temperature is normal temperature, preferably 20-30 ℃, more preferably 22-28 ℃, and more preferably 24-26 ℃. After stirring and stripping, the aramid fiber dissolving solution is obtained after the fibers are completely dissolved and weighed for later use.
The invention is a complete and refined integral preparation process, better ensures the specific structure, composition and appearance of the composite material, specifically lower and uniform film interlayer spacing and higher compactness, further improves the comprehensive performance of the composite film, and simplifies the preparation process, and the steps can be specifically as follows:
the aramid fiber is cut short by using a scalpel, then the aramid fiber and potassium hydroxide are sequentially put into a dimethyl sulfoxide solution, finally a proton donor is added into the solution, and then strong shearing force is provided through mechanical stirring to obtain the aramid nanofiber.
The invention particularly adopts the proton donor, thereby greatly improving the deprotonation speed of the aramid fiber, simultaneously being beneficial to inhibiting the reduction of the molecular weight of the aramid nanofiber and laying a foundation for forming a uniform and compact aramid nanofiber based laminated composite film subsequently.
The aramid nano-fiber dispersion liquid and the assembly element obtained in the step are sheared and mixed to obtain the composite slurry.
The invention has no particular limitation on the mode and condition of shearing and mixing in principle, and a person skilled in the art can select and adjust the mode and condition according to the actual application condition, the product requirement and the quality requirement. The temperature of the mechanical shearing is normal temperature, preferably 20-30 ℃, more preferably 22-28 ℃, and more preferably 24-26 ℃. The shearing time is preferably 20-40 min, more preferably 22-38 min, more preferably 25-35 min, and more preferably 28-32 min. The shearing rotating speed is preferably 8000-12000 r/min, more preferably 8500-11500 r/min, more preferably 9000-11000 r/min, and more preferably 9500-10500 r/min.
The invention is a complete and refined integral preparation process, better ensures the specific structure, composition and appearance of the composite material, specifically lower and uniform film interlayer spacing and higher compactness, further improves the comprehensive performance of the composite film, and simplifies the preparation process, and the steps can be specifically as follows: the method comprises the steps of dispersing an inorganic unit in dimethyl sulfoxide, dissolving an organic matter in the dimethyl sulfoxide to obtain a dispersion liquid of an assembly unit, and mixing a suspension or a solution of the assembly unit with an aramid fiber dissolving liquid to obtain an assembly unit-aramid nanofiber dispersion liquid, namely composite slurry. More specifically, the assembly unit dispersion liquid or solution is added into the aramid fiber dissolving liquid, and then the uniform assembly unit-aramid nanofiber dispersion liquid, namely the uniform composite slurry, is obtained through mechanical shearing.
The composite slurry obtained in the step is sprayed on a substrate to form a single-layer two-phase gel layer, and the composite gel is obtained after multiple spraying.
The spraying amount of the spraying is not particularly limited in principle, and can be selected and adjusted by a person skilled in the art according to the actual application condition, the product requirement and the quality requirement, the specific structure, composition and morphology of the composite material, the specific lower and uniform film interlayer spacing and higher compactness are better ensured, the comprehensive performance of the composite film is further improved, the preparation process is simplified, and the spraying amount of the spraying is preferably 0.5-12 mL/min, more preferably 2-9 mL/min, and more preferably 4-8 mL/min.
The specific selection of the substrate is not particularly limited in principle, and those skilled in the art can select and adjust the substrate according to the actual application situation, the product requirements and the quality requirements, and the substrate preferably comprises one or more of a glass substrate, a PET substrate and a PI substrate, more preferably a glass substrate, a PET substrate or a PI substrate, in order to better ensure the specific structure, composition and morphology of the composite material, specifically lower and uniform interlayer spacing of the film and higher compactness, further improve the comprehensive performance of the composite film and simplify the preparation process.
The invention is a complete and refined integral preparation process, better ensures the specific structure, composition and appearance of the composite material, specifically lower and uniform film interlayer spacing and higher compactness, further improves the comprehensive performance of the composite film, and simplifies the preparation process, and the steps can be specifically as follows: after the composite slurry is obtained, spraying the composite slurry on the surface of a glass substrate, wherein in the process, atomized droplets of the aramid nano-fiber rapidly gelatinize by absorbing water vapor in the air, so that the atomized droplets of the aramid nano-fiber are deposited on the glass substrate to form a dimethyl sulfoxide and water two-phase gel layer, then, soaking the gel in water to replace the dimethyl sulfoxide to form hydrogel, and then, evaporating and drying the hydrogel to form a film.
Specifically, the distance between the spray gun used for spraying and the substrate is preferably 15-25 cm; more preferably 18-22 cm; most preferably 20 cm. The spraying speed is preferably 7 mL/min. The specific process of single spraying in the multiple spraying is as follows: continuously spraying on the glass substrate. Continuously spraying 5-20 mg/mL of aramid nano-fiber composite dispersion liquid for 10-30 min to form a dimethyl sulfoxide and water two-phase gel layer on the surface of the glass substrate.
In the invention, the automatic spraying device comprises a high-pressure airless sprayer, a mechanical arm and a spray gun.
The high-pressure airless sprayer automatically conveys slurry to the spray gun, the spray amount is controlled by the spray gun, and the spray range is controlled by the mechanical arm. The invention has no special requirements on the spraying speed and concentration, and can ensure that the uniform dimethyl sulfoxide and water two-phase hydrogel is formed.
The method of spray assembly of the present invention is not limited and is well known to those skilled in the art.
Compared with other methods, the method for preparing the layered film material by using the spraying technology has higher speed; time can be saved considerably.
Finally, the composite gel obtained in the step is immersed in water for the first replacement, then is dried to form a film, is immersed in water again for the second replacement, is dried, and is hot-pressed to obtain the aramid nanofiber-based composite film.
The time of the first replacement is not particularly limited in principle, and can be selected and adjusted by a person skilled in the art according to the actual application situation, the product requirements and the quality requirements, the specific structure, composition and morphology of the composite material, the specific lower and uniform film interlayer spacing and the higher compactness are better ensured, the comprehensive performance of the composite film is further improved, the preparation process is simplified, and the time of the first replacement is preferably 12-24 hours, more preferably 14-22 hours, and more preferably 16-20 hours.
The invention is a complete and refined integral preparation process, better ensures the specific structure, composition and appearance of the composite material, specifically lower and uniform interlayer spacing of the film and higher compactness, further improves the comprehensive performance of the composite film, simplifies the preparation process, and forms composite hydrogel after the composite gel is replaced for the first time in deionized water, namely the hydrogel is formed.
The temperature of the dry film-forming is not particularly limited in principle, and can be selected and adjusted by a person skilled in the art according to the actual application condition, the product requirement and the quality requirement, the specific structure, composition and morphology of the composite material, the specific lower and uniform film interlayer spacing and higher compactness are better ensured, the comprehensive performance of the composite film is further improved, the preparation process is simplified, and the temperature of the dry film-forming is preferably 25-80 ℃, more preferably 35-70 ℃, and more preferably 45-60 ℃.
The drying and film-forming time is not particularly limited in principle, and can be selected and adjusted by a person skilled in the art according to the actual application condition, the product requirement and the quality requirement, the specific structure, composition and morphology of the composite material, the specific lower and uniform film interlayer spacing and the specific higher compactness are better ensured, the comprehensive performance of the composite film is further improved, the preparation process is simplified, and the drying and film-forming time is preferably 4-12 hours, more preferably 5-11 hours, more preferably 6-10 hours, and more preferably 7-9 hours.
The time of the second replacement is not particularly limited in principle, and can be selected and adjusted by a person skilled in the art according to the actual application situation, the product requirements and the quality requirements, the specific structure, composition and morphology of the composite material, the specific lower and uniform film interlayer spacing and the higher compactness are better ensured, the comprehensive performance of the composite film is further improved, the preparation process is simplified, and the time of the second replacement is preferably 12-24 hours, more preferably 14-22 hours, and more preferably 16-20 hours.
The invention is a complete and refined integral preparation process, better ensures the specific structure, composition and appearance of the composite material, particularly lower and uniform interlayer spacing of the film and higher compactness, further improves the comprehensive performance of the composite film, simplifies the preparation process, and forms the water-containing film after the hydrogel is replaced for the second time in deionized water.
The drying temperature is not particularly limited in principle, and can be selected and adjusted by a person skilled in the art according to the actual application condition, the product requirement and the quality requirement, in order to better ensure the specific structure, composition and morphology of the composite material, particularly lower and uniform interlayer spacing of the film and higher compactness, further improve the comprehensive performance of the composite film and simplify the preparation process, wherein the drying temperature is preferably 25-80 ℃, more preferably 35-70 ℃, and more preferably 45-60 ℃.
The drying time is not particularly limited in principle, and can be selected and adjusted by a person skilled in the art according to the actual application condition, the product requirement and the quality requirement, the specific structure, composition and morphology of the composite material, the specific lower and uniform film interlayer spacing and higher compactness are better ensured, the comprehensive performance of the composite film is further improved, the preparation process is simplified, and the drying time is preferably 4-12 hours, more preferably 5-11 hours, more preferably 6-10 hours, and more preferably 7-9 hours.
The hot pressing temperature is not particularly limited in principle, and can be selected and adjusted by a person skilled in the art according to actual application conditions, product requirements and quality requirements, the specific structure, composition and morphology of the composite material, the specific lower and uniform film interlayer spacing and higher compactness are better ensured, the comprehensive performance of the composite film is further improved, the preparation process is simplified, and the hot pressing temperature is preferably 80-120 ℃, more preferably 85-115 ℃, more preferably 90-110 ℃, and more preferably 95-105 ℃.
The hot pressing pressure is not particularly limited in principle, and can be selected and adjusted by a person skilled in the art according to the actual application condition, the product requirement and the quality requirement, the specific structure, composition and morphology of the composite material, the specific lower and uniform film interlayer spacing and the higher compactness are better ensured, the comprehensive performance of the composite film is further improved, the preparation process is simplified, and the hot pressing pressure is preferably 5-60 MPa, more preferably 15-50 MPa, and more preferably 25-40 MPa.
The hot pressing time is not particularly limited in principle, and can be selected and adjusted by a person skilled in the art according to the actual application condition, the product requirement and the quality requirement, in order to better ensure the specific structure, composition and morphology of the composite material, particularly lower and uniform film interlayer spacing and higher compactness, further improve the comprehensive performance of the composite film and simplify the preparation process, the hot pressing time is preferably 48-96 hours, more preferably 58-86 hours, and more preferably 68-76 hours.
The method comprises the steps of immersing the formed two-phase gel in water for 12-24 hours to displace dimethyl sulfoxide to form hydrogel, drying the hydrogel at 25-80 ℃ to form a film, displacing again, drying, and hot-pressing to form the aramid nano-fiber-based composite film. The present invention employs further displacement followed by drying and then hot pressing to densify the film.
The composite gel is immersed in water for the first replacement to replace dimethyl sulfoxide in the composite gel, the aramid nano-fiber is protonated, then the composite gel is dried to form a film, and is immersed again for the second replacement to fully replace the dimethyl sulfoxide in the film and further protonate the aramid nano-fiber, the previous molecular structure is recovered, and then the composite gel is dried and hot-pressed to obtain the compact aramid nano-fiber based composite film. The invention adopts proton donor and combines two-step replacement steps, so that the composite film can be further densified through hot pressing without being crushed, the shape of a single film can be kept, and an effective layer structure and a more compact interlayer spacing are formed.
The steps of the invention provide a preparation method of an aramid nano-fiber based laminated composite film, which is a complete and refined integral preparation process, better ensures the specific structure, composition and appearance of the composite material, and particularly has lower and uniform film interlayer spacing and higher compactness, further improves the comprehensive performance of the composite film, simplifies the preparation process, and the preparation process can specifically comprise the following steps:
(1) in a solvent, stirring and stripping aramid fibers by using a proton donor assisted machine to obtain an aramid nanofiber dissolving solution;
(2) compounding an inorganic sheet material, an inorganic wire material or a polymer and other assembly elements with aramid nano-fibers according to a certain proportion, and obtaining uniform composite slurry through high-speed shearing; the solvent used is dimethyl sulfoxide;
(3) spraying the composite slurry on the surface of a glass substrate, wherein in the process, atomized droplets of the aramid nano-fibers are quickly gelatinized by absorbing water vapor in the air, so that the atomized droplets are deposited on the glass substrate to form a dimethyl sulfoxide and water two-phase gel layer, then, soaking the gel in water to displace the dimethyl sulfoxide to form hydrogel, evaporating and drying the hydrogel to form a film, soaking the gel in water again to displace the dimethyl sulfoxide and protonate the aramid nano-fibers, and then, drying the film to form the film;
in the invention, the aramid nano-fiber-based composite slurry forms dimethyl sulfoxide and water two-phase gel on the surface of the substrate by absorbing water vapor in air by means of a spraying technology, or the slurry is amplified by automatic spraying to prepare the gel. Wherein, automatic spraying device includes high-pressure airless sprayer, arm and spray gun. The high-pressure airless sprayer automatically conveys the slurry to the spray gun, the spray amount is controlled by the spray gun, and the spray range is controlled by the mechanical arm.
(4) Finally, the aramid fiber nano-fiber-based composite film is formed by hot pressing, the structure is compact by means of the hot pressing technology, and the residual defects are reduced as much as possible, so that the high-performance layered composite film material is obtained.
Referring to fig. 1, fig. 1 is a schematic diagram of a route for preparing an aramid nanofiber-based layered composite membrane provided by the invention.
The invention also provides a method for recycling the aramid nano-fiber-based composite film, which comprises the following steps:
the aramid fiber nano-fiber-based composite film prepared by the aramid fiber nano-fiber-based composite film or the preparation method of any one of the technical schemes is partially or completely used as an aramid fiber raw material, and the recycling of the aramid fiber nano-fiber-based composite film is realized after the aramid fiber nano-fiber-based composite film is prepared by the preparation method of any one of the technical schemes.
According to the invention, the laminated composite film material can be prepared into the aramid nano-fiber-based composite slurry again by a proton donor assisted mechanical stirring stripping method, and then the laminated composite film material is prepared again by a spraying and hot pressing combined method, so that the laminated composite film material can be recycled for multiple times.
The steps of the invention provide an aramid nano-fiber based laminated composite film, a preparation method thereof and a recycling method of the aramid nano-fiber based laminated composite film. The invention designs an aramid nano-fiber based composite film with a special laminated structure, the aramid nano-fiber based composite film provided by the invention is formed by laminating a plurality of single-layer aramid nano-fiber based films, and an aramid nano-fiber matrix and a specific assembly element are selected in a single film. More importantly, the aramid nano-fiber-based composite film provided by the invention has a compact layered structure, uniform thickness of a single-layer film, and particularly extremely small and uniform nanoscale interlayer spacing, so that the aramid nano-fiber-based composite film provided by the invention has excellent comprehensive performance.
The invention also provides a corresponding preparation method, so that the aramid nano-fiber-based composite film with the specific laminated structure can be realized, the laminated structure can be realized by spraying through specific raw materials and steps, a solid foundation is laid by combining a specific hot-pressing technology subsequently, residual defects are reduced as far as possible, and finally the high-performance layered composite film material with a compact structure and nanoscale uniform interlayer spacing can be prepared, and the layered composite film material has excellent application prospects in the fields of electrical insulation, heat conduction, electric conduction, composite reinforcement and the like.
The invention provides a simple, efficient and easily-scaled method for preparing a high-performance aramid nano-fiber based laminated composite film material, the prepared aramid nano-fiber based laminated composite film material can be re-prepared into aramid nano-fiber based composite slurry through a proton donor assisted mechanical stirring stripping method, and then the aramid nano-fiber based composite slurry is prepared into a laminated composite film material again by means of a spraying and hot pressing combined method, so that the repeated cyclic utilization of the laminated composite film material can be realized.
The experimental result shows that by means of the compact layered structure design, the tensile strength of the composite film prepared by the invention reaches 200-280 MPa, which is far higher than that of a pure aramid nanofiber film (185 MPa); by virtue of the inherent advantages of the assembly elements, the composite film prepared by the invention realizes multifunctionality, for example, the addition of mica sheets endows the composite film with high resistance performance (165 kV/mm), and the addition of boron nitride sheets endows the composite film with high thermal conductivity (2.5W m)-1K-1) And the addition of the silver wire endows the composite film with high conductivity (4.1M/Sq), and the like. And after the aramid nano fiber-natural mica nanosheet composite film is prepared through the second circulation, the tensile strength is 220MPa, the breakdown resistance is 160kV/mm, and the tensile strength is still far higher than that of a pure aramid nano fiber film.
For further illustration of the present invention, the following will describe in detail the aramid nanofiber-based composite film and the preparation method thereof, and the recycling method of the aramid nanofiber-based composite film provided by the present invention with reference to the following examples, but it should be understood that these examples are implemented on the premise of the technical solution of the present invention, and the detailed implementation manner and the specific operation process are given, which are only for further illustration of the features and advantages of the present invention, but not for limitation of the claims of the present invention, and the protection scope of the present invention is not limited to the following examples.
Example 1
Preparing an aramid nanofiber-natural mica nanosheet layered composite film material:
a. and (3) preparation of dispersed aramid nano fibers: weighing 20g of commercial aramid fiber, adding the aramid fiber into a mixed solution of 2L of dimethyl sulfoxide, 20g of potassium hydroxide and 40mL of water, and mechanically stirring for 48 hours to form a uniform aramid nanofiber dispersion solution.
The aramid nanofiber dispersion prepared in example 1 of the present invention was characterized.
Referring to fig. 2, fig. 2 is a transmission electron microscope image of the aramid nanofibers prepared in example 1 of the present invention.
As can be seen from fig. 2, the diameter of the aramid nanofibers is about 11 nm.
b. Preparation of natural mica nanosheets: 50g of natural mica powder is put into a heating device and heated to 800 ℃ at the heating rate of 10 ℃/min and then is kept warm for 1 h; then, 30g of calcined mica powder is put into 500mL of 6mol/L nitric acid solution to react for 6 hours at the temperature of 95 ℃; further adding 30g of acid-leached mica powder into 500mL of sodium chloride solution with the mass concentration of 40 wt.% to react for 6h at the temperature of 95 ℃, and then adding 5g of sodium-modified mica powder and 20g of hexadecyl trimethyl ammonium chloride into 500mL of deionized water to react for 24h at the temperature of 80 ℃; the ultrasonic crushing step comprises the steps of dispersing 10g of intercalated mica powder in 500mL of ethanol, ultrasonically crushing by 665W, centrifuging for 10min at 3000r/min every 0.5h, collecting upper-layer suspension to obtain mica nanosheets, centrifuging the mica nanosheets in the ethanol for 20min at 10000r/min, collecting samples, washing the samples for multiple times by using dimethyl sulfoxide, and dispersing in the dimethyl sulfoxide to prepare mica suspension with the concentration of 20 mg/mL.
The natural mica nanosheet prepared in example 1 of the present invention was characterized.
Referring to fig. 3, fig. 3 is an atomic force microscope image of natural mica nanoplates prepared in example 1 of the present invention.
As can be seen from fig. 3, the thickness of the natural mica nanosheet is about 1 nm.
c. Aramid nanofiber-natural mica nanosheet composite film: after the mica nanosheet dispersion liquid is added into the aramid fiber dissolving liquid, a mechanical shearing machine is used for shearing for 30min under the condition of 10000r/min to form a uniform dispersion liquid, and the mass content of the mica nanosheets in the mica nanosheet-aramid fiber dispersing liquid is 40 wt.%. Forming gel on the surface of the glass substrate by means of a spraying technology, then putting the gel into deionized water for soaking for 12 hours, and then drying for 48 hours under the normal temperature condition to obtain the composite film. And further soaking in deionized water for 12h, drying at normal temperature for 48h, and continuously treating the composite film for 72h at 120 ℃ and 30MPa by using a tablet press to finally obtain the compact layered composite film material.
The aramid nanofiber-natural mica nanosheet composite film prepared in example 1 of the present invention is characterized.
Referring to fig. 4, fig. 4 is a view showing a laminated composite film formed by spraying two-phase gel of dimethyl sulfoxide and water, a hydrogel soaked in water and an evaporated film in example 1 of the present invention.
Referring to fig. 5, fig. 5 is a cross-sectional scanning electron microscope photograph of the 40 wt.% aramid nanofiber-mica nanosheet layered composite film after hot pressing in example 1 of the present invention.
As can be seen from FIG. 5, the composite film prepared by the present invention has a uniform and dense layered structure, and the interlayer distance after hot pressing is about 1 nm.
Referring to fig. 6, fig. 6 is a surface scanning electron microscope photograph of the pure aramid nanofiber layered film prepared in example 3 of the present invention and a surface scanning electron microscope photograph of the 40 wt.% aramid nanofiber-mica nanosheet layered composite film after hot pressing in example 1.
As can be seen from FIG. 6, the aramid nanofibers and mica nanosheets on the surface of the composite film are uniformly distributed.
The performance of the aramid nanofiber-natural mica nanosheet composite film prepared in the embodiment 1 of the invention is detected.
Referring to fig. 7, fig. 7 is the tensile strength of the densified 40 wt.% aramid nanofiber-mica nanosheet layered composite film of example 1 and the layered composite film prepared in example 2 of the present invention.
Referring to fig. 8, fig. 8 is the dielectric strength of the 40 wt.% aramid nanofiber-mica nanosheet layered composite film densified in example 1 of the present invention and the layered composite film prepared in example 2.
The tensile mechanics and breakdown voltage tests of the laminated composite film show that the tensile strength and the dielectric strength of the material are 260MPa and 165kV/mm respectively.
d. And (c) preparing the composite nano slurry by taking the layered composite film as a raw material according to the step a, preparing the layered composite film again according to the step c, and testing that the tensile strength of the layered composite film is 220MPa and the dielectric strength is 160 kV/mm. After the secondary preparation, the performance is basically kept stable, which shows that the invention can realize the recycling of the aramid nano-fiber-based composite film.
Example 2
Preparing an aramid nanofiber-natural mica micron sheet composite film material:
a. aramid nanofibers were prepared as in example 1.
b. Adding 26 mica micron sheets into 40mL of dimethyl sulfoxide, fully vibrating to uniformly disperse the mica micron sheets, then adding the mica micron sheets into 4L of 10mg/mL aramid nano fibers, and sealing and stirring to uniformly disperse the aramid nano fibers.
c. The tube of the automatic spraying machine is connected to the composite slurry, spraying is carried out by the automatic spraying machine, the spraying range is controlled by a mechanical arm, (the device is shown as figure 9), 4L of slurry is sprayed on a 40-by-40 glass substrate within 30min, and the two-phase hydrogel of dimethyl sulfoxide and water is obtained.
Referring to fig. 9, fig. 9 is a schematic diagram of an automatic coating apparatus used in the present invention.
Referring to fig. 10, fig. 10 is a photograph of a 40 wt.% aramid nanofiber-mica sheet layered composite two-phase hydrogel prepared in example 2 of the present invention.
The performance of the composite film of aramid nanofibers and natural mica micro-flakes prepared in example 2 of the present invention was tested.
Referring to fig. 7, fig. 7 is the tensile strength of the densified 40 wt.% aramid nanofiber-mica nanosheet layered composite film of example 1 and the layered composite film prepared in example 2 of the present invention.
Referring to fig. 8, fig. 8 is the dielectric strength of the 40 wt.% aramid nanofiber-mica nanosheet layered composite film densified in example 1 of the present invention and the layered composite film prepared in example 2.
The test shows that the tensile strength of the laminated composite film is 195MPa and the dielectric strength is 126 kV/mm.
Example 3
Preparing an aramid nano-fiber film material:
a. aramid nanofibers were prepared as in example 1.
b. The layered composite film was prepared as in example 1.
The pure aramid nanofiber layered film prepared in example 3 of the present invention was characterized.
Referring to fig. 6, fig. 6 is a surface scanning electron microscope photograph of the pure aramid nanofiber layered film prepared in example 3 of the present invention and a surface scanning electron microscope photograph of the 40 wt.% aramid nanofiber-mica nanosheet layered composite film after hot pressing in example 1.
As can be seen from fig. 6, the fiber distribution on the surface of the pure aramid nanofiber film is very uniform.
The performance of the pure aramid nanofiber laminated film prepared in the embodiment 3 of the invention is detected.
The test shows that the tensile strength of the laminated film is 185MPa, and the dielectric strength is 103 kV/mm.
Example 4
Preparing an aramid nano fiber-polyvinyl alcohol composite film material:
a. aramid nanofibers were prepared as in example 1.
b. Adding 2g of polyvinyl alcohol into 98mL of dimethyl sulfoxide, heating to dissolve the polyvinyl alcohol, then adding the polyvinyl alcohol into 10mg/mL of aramid nano-fiber to prepare composite slurry of 30 wt.% of polyvinyl alcohol, and heating, sealing and stirring to uniformly disperse the polyvinyl alcohol.
c. The layered composite film was prepared as in example 1.
The aramid nanofiber-polyvinyl alcohol composite film prepared in example 4 of the present invention was characterized.
Referring to fig. 6, fig. 6 is a surface scanning electron microscope photograph of the pure aramid nanofiber layered film prepared in example 3 of the present invention and a surface scanning electron microscope photograph of the 40 wt.% aramid nanofiber-mica nanosheet layered composite film after hot pressing in example 1.
Referring to fig. 11, fig. 11 is a cross-sectional scanning electron micrograph of the pure aramid nanofiber laminated film prepared in example 3 of the present invention and a cross-sectional scanning electron micrograph of the 30 wt.% aramid nanofiber-polyvinyl alcohol laminated composite film in example 4.
As can be seen from fig. 11, the microstructure of the aramid nanofiber-polyvinyl alcohol film prepared by spraying is a layered structure.
The performance of the aramid nanofiber-polyvinyl alcohol composite film prepared in the embodiment 4 of the invention is detected.
The test shows that the tensile strength of the laminated composite film is 265 MPa.
Example 5
Preparing an aramid nano-fiber-boron nitride micron sheet composite film material:
a. aramid nanofibers were prepared as in example 1.
b. Adding 1g of boron nitride into 50mL of dimethyl sulfoxide, stirring and shaking to uniformly disperse the boron nitride, then adding the boron nitride into 10mg/mL of aramid nano-fiber to prepare composite slurry of 40 wt.% of boron nitride, and sealing and stirring to uniformly disperse the boron nitride.
c. The layered composite film was prepared as in example 1.
The performance of the aramid nanofiber-boron nitride micron sheet composite film prepared in the embodiment 5 of the invention is detected.
The test shows that the tensile strength of the laminated composite film is 221MPa, and the thermal conductivity is 2.5W m-1K-1。
Example 6
Preparing an aramid nanofiber-silver nanowire composite film material:
a. aramid nanofibers were prepared as in example 1.
b. A certain amount of silver nanowire water dispersion is subjected to 10000 r/min; the centrifugation time is 15min, the number of times of washing with dimethyl sulfoxide is 2-3, finally 2% of silver nanowire dimethyl sulfoxide dispersion liquid is prepared, then the silver nanowire dimethyl sulfoxide dispersion liquid is added into 10mg/mL of aramid nano fiber to prepare 40 wt% of silver nanowire composite slurry, and the composite slurry is sealed and stirred to be uniformly dispersed.
c. The layered composite film was prepared as in example 1.
The aramid nanofiber-silver nanowire composite film prepared in example 6 of the present invention was subjected to performance testing.
The test shows that the tensile strength of the laminated composite film is 270MPa, and the resistance is 4.1M/Sq.
The aramid nanofiber-based laminated composite film and the preparation method thereof and the recycling method of the aramid nanofiber-based laminated composite film provided by the invention are described in detail, and the principle and the implementation mode of the invention are explained by applying specific examples, and the description of the examples is only used for helping to understand the method and the core idea of the invention, including the best mode, and also for enabling any person skilled in the art to practice the invention, including making and using any device or system and implementing any combined method. It should be noted that, for those skilled in the art, it is possible to make various improvements and modifications to the present invention without departing from the principle of the present invention, and those improvements and modifications also fall within the scope of the claims of the present invention. The scope of the invention is defined by the claims and may include other embodiments that occur to those skilled in the art. Such other embodiments are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.

Claims (9)

1. The aramid nanofiber-based composite film is characterized in that the composite film has a layered structure;
the layered structure is a compact layered structure;
the composite film is formed by laminating a plurality of single-layer aramid nano-fiber-based films;
the thickness of the single-layer aramid nanofiber-based film is 10-400 nm;
the interlayer spacing between the single-layer aramid nanofiber-based films is 1-10 nm;
the thickness of the aramid fiber nanofiber-based composite film is 5-80 microns;
the number of the layers is 12-8000;
the aramid nano-fiber-based film comprises an aramid nano-fiber matrix and an assembly element;
the assembly cell includes one or more of an inorganic sheet material, an inorganic wire material, and a polymer.
2. The composite film of claim 1, wherein the assembly elements comprise one or more of natural mineral mica nanoplatelets, natural mineral mica microsheets, alumina microsheets, boron nitride nanoplatelets, graphene oxide sheets, carbon nanotubes, calcium silicate nanowires, brushite microsheets, and polyvinyl alcohol;
the mass ratio of the aramid nano-fiber matrix to the aramid nano-fiber-based film is 5-90 wt.%;
the diameter of the aramid nano fiber is 5-15 nm;
the length of the aramid nano-fiber is 10-30 mu m.
3. The composite film of claim 1, wherein the assembly elements are uniformly dispersed embedded in the aramid nanofiber matrix;
the aramid fiber nanofiber-based composite film is a recyclable aramid fiber nanofiber-based composite film;
the aramid fiber nanofiber-based composite film is prepared by stirring and stripping raw materials with a proton donor-assisted machine, spraying, replacing and hot-pressing.
4. The preparation method of the aramid nanofiber-based composite film is characterized by comprising the following steps of:
1) stirring and stripping an aramid fiber raw material, potassium-containing alkali, a proton donor and a solvent to obtain an aramid nanofiber dispersion liquid;
2) shearing and mixing the aramid nano-fiber dispersion liquid obtained in the step and the assembly element to obtain composite slurry;
3) spraying the composite slurry obtained in the step on a substrate to form a single-layer two-phase gel layer, and spraying for multiple times to obtain a composite gel;
4) and (3) immersing the composite gel obtained in the step into water for the first replacement, then drying to form a film, immersing into water again for the second replacement, then drying, and performing hot pressing to obtain the aramid nano-fiber-based composite film.
5. The preparation method according to claim 4, wherein the diameter of the aramid fiber raw material is 5-15 nm;
the length of the aramid fiber raw material is 5-100 cm;
the potassium-containing base comprises potassium hydroxide and/or potassium ethoxide;
the proton donor comprises one or more of water, ethanol, and methanol;
the solvent comprises dimethyl sulfoxide.
6. The preparation method of claim 4, wherein the concentration of the aramid fiber raw material in the aramid nanofiber dispersion liquid is 5-20 mg/mL;
the mass ratio of the aramid fiber raw material to the potassium-containing alkali is (0.5-2): 1;
the mass ratio of the aramid fiber raw material to the proton donor is (20-80): 1;
the diameter of the aramid nano fiber is 5-15 nm;
the length of the aramid nano-fiber is 10-30 mu m.
7. The preparation method according to claim 4, wherein the rotation speed of stirring stripping is 100-800 r/min;
the stirring and stripping time is 12-48 h;
the shearing and mixing time is 20-40 min;
the rotating speed of the shearing and mixing is 8000-12000 r/min;
the spraying amount of the spraying is 0.5-12 mL/min;
the substrate includes one or more of a glass substrate, a PET substrate, and a PI substrate.
8. The preparation method according to claim 4, wherein the time for the first replacement is 12-24 h;
forming a composite hydrogel after the first replacement;
the temperature for drying and film forming is 25-80 ℃;
the drying and film forming time is 4-12 h;
the time of the second replacement is 12-24 hours;
forming a water-containing film after the second replacement;
the drying temperature is 25-80 ℃;
the drying time is 4-12 h;
the hot pressing temperature is 80-120 ℃;
the pressure of hot pressing is 5-60 MPa;
and the hot pressing time is 48-96 h.
9. A method for recycling an aramid nanofiber-based composite film is characterized by comprising the following steps:
the aramid nano-fiber-based composite film prepared by using the aramid nano-fiber-based composite film of any one of claims 1 to 3 or the aramid nano-fiber-based composite film prepared by using the preparation method of any one of claims 4 to 8, wherein a part or all of the aramid nano-fiber-based composite film is used as an aramid fiber raw material, and the aramid nano-fiber-based composite film is prepared by using the preparation method of any one of claims 4 to 8, so that the recycling of the aramid nano-fiber-based composite film is realized.
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