A method and equipment for integrated extrusion molding of high-performance nanofiber structural components

Abstract

This invention relates to the field of fiber structural component preparation technology, specifically to a method and equipment for integrated extrusion molding of high-performance nanofiber structural components. The integrated extrusion molding method for high-performance nanofiber structural components of this invention includes the following steps: (1) adding a nanofiber solution to a forced mixing and conveying device, causing the nanofiber solution to be sheared and transformed into a homogenized dispersion in the forced mixing and conveying device, and then injecting the homogenized dispersion into a molding die through an extrusion die under the extrusion pressure provided by the forced mixing and conveying device; (2) immersing the entire molding die in a reconstruction solution, allowing the homogenized dispersion injected into the molding die to exchange solvents with the reconstruction solution, causing the homogenized dispersion to undergo a sol-gel conversion, forming a nanofiber composite gel with a predetermined shape; (3) washing and drying the nanofiber composite gel with the predetermined shape to obtain a nanofiber structural component. This method has fewer steps and less environmental impact.

Description

Technical Field

[0001] This invention relates to the field of fiber structural component manufacturing technology, specifically to an integrated extrusion molding method and equipment for high-performance nanofiber structural components. Background Technology

[0002] High-performance fibers such as PBO and aramid fibers have attracted widespread attention due to their excellent mechanical properties and extremely high decomposition temperatures. As one of the representatives of high-performance fibers, aramid fibers were first synthesized by DuPont in the 1970s. Due to its unique rigid molecular chains and numerous intermolecular hydrogen bonds, aramid fibers possess characteristics such as lightweight, high strength, and high temperature resistance, and have been widely used in the military field. Through wet-processing technology, aramid fibers can be made into high-performance sheet aramid paper materials, and these aramid papers can be further processed through complex processes to produce aramid honeycomb paper with special structural shapes.

[0003] Aramid honeycomb paper (NOMEX honeycomb) is a high-performance biomimetic aramid structural component, composed of interconnected hexagonal units. This honeycomb paper not only inherits the excellent properties of aramid fibers, such as high specific strength, fire resistance, and chemical corrosion resistance, but also possesses unique capabilities such as high vibration absorption and high electromagnetic wave transmittance. Therefore, aramid honeycomb paper plays a crucial role in applications such as aerospace, rail transportation, and military defense, where extremely high lightweight and high-strength properties of materials are required.

[0004] PBO fiber is another representative of high-performance fibers, originally invented by aerodynamics researchers in the U.S. Air Force. Due to its unique molecular structure, PBO fiber possesses excellent strength, modulus, heat resistance, and impact resistance. In 1990, Toyobo Co., Ltd. of Japan purchased PBO patent technology from Dow Chemical Company of the United States, and in 1991, developed PBO fiber using Toyobo's own equipment, significantly increasing its strength and modulus to twice that of PPTA fiber.

[0005] PBO honeycomb paper is a high-performance biomimetic PBO structural component, also composed of hexagonal units. Compared to aramid fibers, PBO fibers have twice the strength and modulus of aramid 1414 fibers, and their decomposition temperature can reach 650°C, superior to the 550°C decomposition temperature of para-aramid. PBO fibers surpass aramid fibers in many performance indicators, especially in high-end applications, where their potential is even more significant.

[0006] Currently, honeycomb paper is mainly prepared using an adhesive stretching method. First, aramid paper and PBO paper are prepared using chopped fibers and chromatography fibers. These papers are then used as raw materials, and the final honeycomb paper product is formed through multiple processes including adhesive coating, hot pressing, edge trimming, stretching, shaping, impregnation, drying, curing, and sheet cutting. However, the above method for preparing honeycomb paper has the following problems:

[0007] 1. Inaccurate structural control: During the stretching process, all honeycomb units are subjected to force and formed simultaneously, making it impossible to precisely control the structural shape of each unit. This can easily lead to some units being overstretched, understretched, or even destroyed, resulting in local defects and affecting the overall strength.

[0008] 2. Performance issues under high temperature: Due to the use of adhesive strips to bond different layers, the adhesive joints may soften and fail under high temperature conditions, affecting the performance of the honeycomb paper under high temperature conditions.

[0009] 3. Shape limitations: The adhesive stretching method can only produce flat honeycomb paper. When applied to curved surfaces or complex spaces, it needs to be spliced ​​or bonded through secondary processing, which cannot fully utilize the strength limit of the honeycomb paper.

[0010] 4. Environmental issues: In order to fill the pores between coarse fibers and optimize load transfer, phenolic resin is used in the impregnation process, which will produce a large amount of toxic and carcinogenic substances such as formaldehyde and phenol, causing serious harm to the environment.

[0011] In conclusion, if a novel method for forming honeycomb paper can be proposed to achieve the efficient preparation of high-quality, irregularly shaped fiber structures, it will be of great significance for improving the shortcomings of existing honeycomb paper applications. Summary of the Invention

[0012] The purpose of this invention is to overcome the defects and shortcomings of the prior art and provide a high-performance nanofiber structural component integrated extrusion molding method. This method mainly solves the problems of easy local unit defects, single molding shape, adhesive failure under high temperature environment, and great hazards in the production process of honeycomb paper prepared by the existing method.

[0013] Another objective of this invention is to provide an integrated extrusion molding equipment for high-performance nanofiber structural parts that implements the above-described method.

[0014] The objective of this invention can be achieved through the following technical solutions:

[0015] A method for integral extrusion molding of high-performance nanofiber structural components includes the following steps:

[0016] (1) The nanofiber solution is added to the forced mixing and conveying device, so that the nanofiber solution is sheared and transformed into a homogenized dispersion in the forced mixing and conveying device. Then, the homogenized dispersion is injected into the molding die through the extrusion die under the extrusion pressure provided by the forced mixing and conveying device.

[0017] (2) Immerse the entire molding mold in the reconstruction solution. The homogenized dispersion injected into the molding mold exchanges solvent with the reconstruction solution, causing the homogenized dispersion to undergo sol-gel conversion and form a nanofiber composite gel with a predetermined shape.

[0018] (3) The nanofiber composite gel with a predetermined shape is washed and dried to obtain a nanofiber structure.

[0019] The nanofiber solution is one of aramid nanofiber solution, aramid nanofiber composite solution, PBO nanofiber solution, and PBO nanofiber composite solution.

[0020] The aramid nanofiber composite solution is a composite solution of aramid nanofiber solution and functional filler; the PBO nanofiber composite solution is a composite solution of PBO nanofiber solution and functional filler.

[0021] The functional filler can be boron nitride nanosheets, graphene, graphene oxide, carbon nanotubes, silica nanoparticles, silver nanoparticles, polyacetylene, aramid short fibers, etc., which have mechanical strength, thermal stability, electrical conductivity, thermal conductivity, or flame retardancy. Aramid nanofiber solution and PBO nanofiber solution are mixed with functional filler to prepare aramid nanofiber composite solution and PBO nanofiber composite solution with specific properties, respectively.

[0022] As a preferred embodiment, in step (1), the molding die is pre-filled with a skeleton structure formed by functional fillers. The functional fillers can be pre-filled in the molding die and the skeleton structure can be pre-formed in the molding die by methods such as drying deposition.

[0023] In step (1), the nanofiber solution is sheared and mixed by the forced mixing and conveying device to form a more uniform and better homogenized dispersion. It has a certain fluidity at a set temperature. The aramid short fiber can be pre-formed into an aramid short fiber skeleton structure in the molding die by methods such as drying and deposition. The fluid nanofiber solution can fill the gaps in the aramid short fiber skeleton structure under the pressure of the device to form a dense structure.

[0024] The reconstruction solutions are of two types. For aramid nanofiber solutions and aramid nanofiber composite solutions, the reconstruction solution uses a proton donor solution with proton-donating capability. Adding a proton donor solution to the aramid nanofiber solution or aramid nanofiber composite solution can reconstruct its molecular chains and form a self-supporting gel with a certain strength. For PBO nanofiber solutions and PBO nanofiber solution composite solutions, the reconstruction solution uses a proton acceptor solution with deprotonating capability. Adding a proton acceptor solution to the PBO nanofiber solution or PBO nanofiber solution composite solution can reconstruct its molecular chains and form a self-supporting gel with a certain strength. By changing the concentration and type of proton donor / proton acceptor solution, nanofiber composite gels with different microstructures can be obtained.

[0025] The solvent exchange between the homogenized dispersion and the reconstituted solution is performed after step (1) or simultaneously with step (1). In step (2), the solvent exchange process can be completed by transferring the molding die to the reconstituted solution after extrusion, or by directly extruding the solution into the molding die that has been immersed in the reconstituted solution.

[0026] An integrated extrusion molding equipment for high-performance nanofiber structural components is provided for implementing the integrated extrusion molding method for high-performance nanofiber structural components of the present invention. The equipment includes a forced mixing and conveying device, an extrusion die, and a molding die. The input end of the forced mixing and conveying device is provided with a feed port. The extrusion die is fixedly installed at the output end of the forced mixing and conveying device and is connected to the molding die through a pipeline.

[0027] The forced mixing and conveying device can be a mixing and conveying system formed by a positive displacement pump and a mixer, a multi-rotor mixing and conveying system, or a single-rotor mixing and conveying system.

[0028] The forced mixing conveying device is a mechanism with positive displacement conveying capability. It can be achieved by using a mixing conveying system that combines a positive displacement pump and a mixer, or by using a multi-rotor mixing conveying system or a single-rotor mixing conveying system that has both conveying and mixing functions. By selecting different types of mixing conveying systems and changing the extrusion speed and extrusion pressure of the mixing conveying system, different mold filling speeds and filling effects can be achieved.

[0029] The positive displacement pump can be a reciprocating pump, diaphragm pump, gear pump, screw pump, plunger pump, or vane pump; the mixer can be a dynamic mixer or a static mixer, the dynamic mixer including a multi-stage rotating mechanism, and the static mixer consisting of multi-stage mixing channels. By using different types of positive displacement pumps and mixers, and by adjusting the mixer's rotation speed and mixing stages, uniform dispersion of packing systems with different concentrations and functions can be achieved.

[0030] Select a suitable mixing and conveying system as the forced mixing and conveying device based on specific application requirements, material properties, and expected product performance.

[0031] The extrusion die can be a single-flow-path extrusion die or a multi-flow-path extrusion die.

[0032] The extrusion die head is provided with multiple discharge ports, the molding die is provided with a feed port, the number of discharge ports corresponds to the number of feed ports, and the discharge ports are connected to the feed ports through pipelines.

[0033] By changing the number of feed inlets and outlets, simultaneous extrusion in multiple directions can be achieved.

[0034] The molding die includes a mold cavity and a cover plate, both of which are provided with porous structures. These porous structures facilitate solvent exchange between the nanofiber solution and the reconstructed solution.

[0035] The mold cavity contains multiple hollow filling pillars. The hollow structure increases the dissolution and exchange area between the nanofiber solution and the reconstructed solution.

[0036] By changing the cross-sectional shape, spatial shape, and distance between adjacent filler columns, fiber structural components with different pore structures and pore densities can be prepared.

[0037] Furthermore, by designing special curved molds and changing the density or shape of the filling columns in different mold areas, fiber structural components with complex spatial topologies can be produced.

[0038] As a preferred embodiment, both the forced mixing conveyor and the extrusion die are equipped with temperature control devices; the forced mixing conveyor and the extrusion die are connected by flanges; the discharge port of the extrusion die is connected to the pipeline, and the pipeline is connected to the inlet of the molding die by clamps, and the clamp connections are sealed with rubber rings.

[0039] The principle of this invention lies in the following: Nanofibers prepared by the deprotonation method exist in the form of a polyanionic solution, with amide hydrogen missing from their molecular chains. Adding a proton donor to the nanofiber solution causes structural reconstruction of its molecular chains. At this point, intermolecular hydrogen bonds are formed between the restored nanofibers, leading to cross-linking and stacking, ultimately forming a gel-like product with a microscopic three-dimensional network structure. Utilizing this sol-gel conversion principle, the efficient fabrication of complex fibrous structures can be achieved.

[0040] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0041] 1. The high-performance nanofiber structural component integrated extrusion molding method of the present invention utilizes the solution filling principle for preparation. By controlling the structure of the filling column in the mold, precise control of the structure of a single hexagonal unit can be achieved, which is beneficial to forming fiber honeycomb paper with uniform size and structure and few unit defects.

[0042] 2. The high-performance nanofiber structural component integrated extrusion molding method of the present invention is based on the sol-gel conversion method, which can directly form an integrated fiber honeycomb paper with a predetermined shape without additional shaping or bonding. The preparation process is simple and the structural strength is consistent at high temperature.

[0043] 3. The high-performance nanofiber structural component integrated extrusion molding equipment of the present invention can design molds according to actual scenarios and directly produce fiber structural components with complex spatial structures without splicing or secondary processing. Based on the actual stress distribution of the structural component, the local density of the filling columns in the mold can be changed to achieve local reinforcement of high stress areas, making the strength design of the entire fiber structural component more balanced.

[0044] 4. The high-performance nanofiber structural component integrated extrusion molding method of the present invention produces fiber structural components with high density and good load transfer performance. It does not require impregnation reinforcement, has less pollution, and its micro-pore structure can be controlled by different reconstruction methods, which is beneficial for loading different functional fillers.

[0045] The integrated extrusion molding method for high-performance nanofiber structural parts provided by this invention has the advantages of fewer processes and less environmental hazard. The proposed integrated extrusion molding equipment for nanofiber structural parts has a simple structure and wide applicability, and can realize the efficient preparation of functional nanofiber structural parts with complex spatial structures. Attached Figure Description

[0046] Figure 1 This is a schematic diagram of the overall structure of the integrated extrusion molding equipment for nanofiber structural components in Embodiment 1 of the present invention;

[0047] Figure 2 This is a schematic diagram of the sol-gel conversion and drying steps in the integrated extrusion molding method for nanofiber structural parts of the present invention;

[0048] Figure 3 This is a schematic diagram of the static mixer in Embodiment 1 of the present invention;

[0049] Figure 4 This is a schematic diagram of the structure of aramid honeycomb paper with a uniform hexagonal structure in Embodiment 1 of the present invention;

[0050] Figure 5 This is a cross-sectional view of the aramid honeycomb paper with a uniform hexagonal structure in Embodiment 1 of the present invention;

[0051] Figure 6 This is a schematic diagram of the overall structure of the integrated extrusion molding equipment for nanofiber structural components in Embodiment 3 of the present invention;

[0052] Figure 7 This is a schematic diagram of the structure of aramid honeycomb paper with the same density in Embodiment 3 of the present invention;

[0053] Figure 8 This is a cross-sectional view of aramid honeycomb paper with the same density in Embodiment 3 of the present invention;

[0054] Figure 9 This is a schematic diagram of the dynamic mixer in Embodiment 4 of the present invention;

[0055] Figure 10 This is a schematic diagram of the process of simultaneous multi-directional extrusion filling by a multi-channel extrusion die head with multiple discharge ports in Embodiment 4 of the present invention.

[0056] Figure 11 This is a schematic diagram of the aramid honeycomb paper with a spatial topology in Embodiment 4 of the present invention;

[0057] Figure 12 This is a cross-sectional view of the aramid honeycomb paper with a spatial topology in Embodiment 4 of the present invention;

[0058] Wherein: 1: push rod, 2: positive displacement pump, 3: hopper, 4: mixer, 5: temperature control device, 6: extrusion die head, 7: pipeline, 8: mold cavity, 9: cover plate, 10: barrel, 11: rotor, 12: first extrusion direction, 13: second extrusion direction, 14: third extrusion direction, 15: fourth extrusion direction. Detailed Implementation

[0059] The present invention will be further described in detail below with reference to the embodiments and accompanying drawings, but the embodiments of the present invention are not limited thereto.

[0060] Example 1

[0061] like Figure 1 and Figure 2 As shown, a method for integral extrusion molding of high-performance nanofiber structural components mainly includes the following steps:

[0062] (1) First, a pure aramid nanofiber solution with a mass concentration of 1.5wt% is added to the cavity of the push rod plunger pump through the hopper. After the cavity of the push rod plunger pump is filled with the pure aramid nanofiber solution, the push rod is started to push the pure aramid nanofiber solution through the SK type static mixer with a single flow channel twist angle of 120 degrees and a flow channel number of 4 at a speed of 8mm / s under the conditions of extrusion pressure of 3.5MPa and extrusion temperature of 60℃. Then, it is injected into the planar honeycomb mold through the pipeline through the single flow path extrusion die head, so that the mold cavity is completely filled.

[0063] The planar honeycomb mold has a porous structure with a pore size of 150 micrometers; and the mold is equipped with filling columns with a cross-sectional angle of 120 degrees and a gap of 1.6 mm between adjacent filling columns.

[0064] (2) Subsequently, the planar honeycomb mold was removed and immersed in an acetic acid solution with a volume concentration of 40 vol% (e.g. Figure 5 As shown in the figure, the pure aramid nanofiber solution is subjected to solvent exchange with the acetic acid solution, and left to stand for a certain period of time until the reconstruction is completed;

[0065] (3) Finally, rinse the flat honeycomb mold in clean water and dry it in an oven at a certain temperature before taking it out.

[0066] In this embodiment, the high-performance nanofiber structural component integrated extrusion molding equipment implementing the above method includes a forced mixing and conveying device, an extrusion die 6, and a molding die. The forced mixing and conveying device adopts a mixing and conveying system formed by a positive displacement pump 2 and a mixer 4. The positive displacement pump is a push rod type plunger pump, and a push rod 1 is concentrically installed in the cavity of the positive displacement pump. The two can move relative to each other. The input end of the positive displacement pump is provided with a feed port, and a hopper 3 is installed on the feed port; Figure 3 As shown, the mixer is a static mixer composed of multi-stage mixing channels, installed after the positive displacement pump and connected by bolts; the extrusion die head is fixedly installed at the output end of the static mixer and connected to the molding die through a pipeline; the molding die includes a mold cavity 8 and a cover plate 9, the cover plate and the mold cavity are joined to form a closed extrusion cavity space, and both the mold cavity and the cover plate are provided with a porous structure; the temperature control device 5 is distributed on the positive displacement pump, the mixer and the extrusion die head to maintain the extrusion temperature.

[0067] In this embodiment, a pure aramid nanofiber solution is used as the nanofiber solution, and its mass concentration is 1-2.5 wt%, preferably 1.5 wt%.

[0068] A push rod type plunger pump is used as the injection pressure source, wherein the push rod speed is 0.5-20mm / s, with a preferred value of 8mm / s, and the injection pressure in the pressure device cavity is 2.3-5.5MPa, with a preferred value of 3.5MPa.

[0069] The mixer uses, for example Figure 4 The SK-type static mixer shown mixes nanofiber solutions by using its reverse-twisting flow channels to achieve thorough mixing. The twist angle of a single flow channel is 90-180 degrees, with a preferred value of 120 degrees, and the number of flow channel stages is 2-10, with a preferred value of 4 stages.

[0070] The temperature control device uses thermocouples, and the extrusion temperature is 30-120℃, with a preferred value of 50-70℃.

[0071] An acetic acid solution with proton-donating capability is used as the reconstruction solution, with a volume concentration of 15-80 vol%, preferably 30-50 vol%.

[0072] A planar honeycomb mold is used as the molding die for extrusion molding. The mold cavity and cover plate are provided with a porous structure to realize solvent exchange. The pore size is 20-310 micrometers, with a preferred value of 120-180 micrometers.

[0073] The filling pillars distributed inside the mold cavity have a uniform cross-sectional size in the height direction. The cross-section is hexagonal, and the angle of each corner varies from 30 to 150 degrees, with a preferred value of 120 degrees. The gap between adjacent filling pillars is 0.4-5 mm, with a preferred value of 1.6 mm.

[0074] like Figure 4 and Figure 5 As shown, using the above method and equipment, aramid honeycomb paper with a uniform hexagonal structure can be prepared quickly and in an integrated manner, with a bulk density of 20-70 kg / m3 and a hexagonal plane compressive strength of 172-200 MPa.

[0075] Example 2

[0076] Compared with Example 1, the difference is that the nanofiber solution used is a PBO nanofiber solution, and the reconstruction solution uses a proton acceptor solution with deprotonation capability.

[0077] A method for integral extrusion molding of high-performance nanofiber structural components mainly includes the following steps:

[0078] (1) First, a pure PBO nanofiber solution with a mass concentration of 1.5wt% is added to the cavity of the push rod plunger pump through the hopper. After the cavity of the push rod plunger pump is filled with pure aramid nanofiber solution, the push rod is started to push the pure PBO nanofiber solution through the SK type static mixer with a single flow channel twist angle of 120 degrees and a flow channel number of 4 at a speed of 8mm / s under the conditions of extrusion pressure of 3.5MPa and extrusion temperature of 60℃. Then, it is injected into the planar honeycomb mold through the pipeline through the single flow path extrusion die head so that the mold cavity is completely filled.

[0079] (2) Subsequently, the planar honeycomb mold was removed and immersed in an isopropanol solution with a volume concentration of 45 vol% (e.g. Figure 5 As shown in the figure, the pure PBO nanofiber solution is subjected to solvent exchange with the isopropanol solution, and then left to stand for a certain period of time until the reconstruction is completed.

[0080] (3) Finally, rinse the flat honeycomb mold in clean water and dry it in an oven at a certain temperature before taking it out.

[0081] In this embodiment, a pure PBO nanofiber solution is used as the nanofiber solution, with a mass concentration of 1-2.5 wt%, preferably 1.5 wt%.

[0082] An isopropanol solution with deprotonating ability is used as the reconstruction solution, with a volume concentration of 15-80 vol%, preferably 30-50 vol%.

[0083] Using the above methods and equipment, PBO honeycomb paper with a uniform hexagonal structure can be rapidly and integrally prepared, such as... Figure 5 As shown, its bulk density is 45-70 kg / m3, and its hexagonal plane compressive strength is 200-250 MPa.

[0084] The parts not mentioned in this embodiment are the same as in Embodiment 1.

[0085] Example 3

[0086] Compared with Example 1, the differences are as follows: the nanofiber solution is an aramid nanofiber composite solution that is a mixture of aramid nanofiber solution and functional filler; the forced mixing and conveying device adopts a dual-rotor mixing and conveying system; and the molding die adopts a honeycomb mold with different local densities.

[0087] A method for integral extrusion molding of high-performance nanofiber structural components mainly includes the following steps:

[0088] (1) First, the aramid nanofiber solution with a mass concentration of 1wt% and the boron nitride nanosheets are mixed to form an aramid nanofiber composite solution. The aramid nanofiber solution is added to the cavity of the dual rotor mixing and conveying system through the hopper. After the cavity of the dual rotor mixing and conveying system is filled with the aramid nanofiber composite solution, the rotor is started. The rotor runs at a speed of 500rpm, so that the aramid nanofiber solution is fully mixed with the boron nitride nanosheets under the action of the dual rotor. At the same time, the aramid nanofiber composite solution is pushed through the SK type static mixer with a single flow channel twist angle of 120 degrees and a flow channel number of 4 stages at a speed of 8mm / s under the conditions of extrusion pressure of 22MPa and extrusion temperature of 50℃. Then, it is injected into the honeycomb mold with different local densities through the single flow path extrusion die head and the pipeline, so that the mold cavity is completely filled.

[0089] Among them, the honeycomb mold with different local densities has a porous structure with a pore size of 150 micrometers; and the mold is equipped with filling columns with a regular hexagonal cross-section, and the gap between adjacent filling columns is divided into three levels: 4mm, 2mm, and 1mm.

[0090] (2) Subsequently, the honeycomb molds with different densities in certain areas were removed and immersed in an acetic acid solution with a volume concentration of 40 vol% (e.g. Figure 5 As shown in the figure, the aramid nanofiber composite solution is subjected to solvent exchange with the acetic acid solution, and then left to stand for a certain period of time until the reconstruction is completed;

[0091] (3) Finally, rinse the honeycomb molds with different densities in clean water and dry them in an oven at a certain temperature before taking them out.

[0092] In this embodiment, the integrated extrusion molding equipment for high-performance nanofiber structural parts implementing the above method includes a forced mixing and conveying device, an extrusion die, and a molding die, such as... Figure 6 As shown, the forced mixing and conveying device adopts a multi-rotor mixing and conveying system, which is a dual-rotor mixing and conveying system composed of two meshing rotors 11 and a material cylinder 10. The two rotors can move relative to each other. The input end of the material cylinder is provided with a feed inlet, and a hopper is installed on the feed inlet. The extrusion die head is fixedly installed at the output end of the material cylinder and connected to the molding die through a pipeline. The molding die includes a mold cavity and a cover plate. The cover plate and the mold cavity are joined to form a closed extrusion cavity space. Both the mold cavity and the cover plate are provided with a porous structure. Temperature control devices are distributed on the material cylinder and the extrusion die head to maintain the extrusion temperature.

[0093] In this embodiment, an aramid nanofiber composite solution, which is a mixture of aramid nanofiber solution and boron nitride nanosheets, is used as the nanofiber solution. The mass concentration of the aramid nanofiber solution is 1.5-2 wt%, preferably 1 wt%.

[0094] A dual-rotor mixing and conveying system consisting of two meshing rotors and a material cylinder is used as the source of extrusion pressure, which simultaneously realizes extrusion pressure and mixing. The rotor speed is 100-1000 rpm, preferably 500 rpm, and the extrusion pressure in the pressure device cavity is 4.3-50 MPa, preferably 17.7-28 MPa.

[0095] The temperature control device uses thermocouples, and the extrusion temperature is 30-90℃, with a preferred value of 40-60℃.

[0096] An acetic acid solution with proton-donating capability is used as the reconstruction solution, with a volume concentration of 15-80 vol%, preferably 30-50 vol%.

[0097] Using honeycomb molds with different local densities as extrusion molding molds, the cross-section of the filling columns inside the mold cavity is a regular hexagon, and the gap between adjacent filling columns is divided into three levels: 4mm, 2mm, and 1mm. Hexagonal units with different thicknesses can be formed on the same sheet of aramid-boron nitride nano-honeycomb paper.

[0098] like Figure 7 and Figure 8 As shown, using the above method and equipment, aramid-boron nitride nanocellular paper with high thermal conductivity and varying local thicknesses can be rapidly and integrally prepared, with an in-plane thermal conductivity of 1.8-4.1 W / (m•K).

[0099] The parts not mentioned in this embodiment are the same as in Embodiment 1.

[0100] Example 4

[0101] Compared with Example 1, the differences are as follows: the mixer adopts a dynamic mixer including a multi-stage rotating mechanism, the extrusion die adopts a multi-channel extrusion die with multiple discharge ports, the molding die adopts a honeycomb mold with a spatial topology, and the reconstruction solution adopts a formic acid solution.

[0102] A method for integral extrusion molding of high-performance nanofiber structural components mainly includes the following steps:

[0103] (1) First, a pure aramid nanofiber solution with a mass concentration of 2.5wt% is added to the cavity of the push rod plunger pump through the hopper. After the cavity of the push rod plunger pump is filled with the pure aramid nanofiber solution, the push rod is started to push the pure aramid nanofiber solution to pass through a multi-stage dynamic mixer with a mixing speed of 4500rpm and a mixing stage of 2 stages under the conditions of extrusion pressure of 3.5MPa and extrusion temperature of 70℃. Then, it is injected into a honeycomb mold with a spatial topology through a multi-flow extrusion die head and a pipeline, so that the mold cavity is completely filled.

[0104] The honeycomb mold with spatial topology is designed based on the current aircraft radome profile; the mold has a pore structure with a pore size of 150 micrometers, and infill pillars with a regular hexagonal cross-section are set inside the mold, with a gap of 1.6 mm between adjacent infill pillars, and the thickness of the mold cavity is 12 mm; the mold has feed ports on all four sides, and simultaneous extrusion in the first extrusion direction 12, the second extrusion direction 13, the third extrusion direction 14, and the fourth extrusion direction 15 is achieved through a multi-flow extrusion die head (e.g., ...). Figure 10 (as shown)

[0105] (2) Then the honeycomb mold with spatial topology was removed and immersed in a formic acid solution with a volume concentration of 48 vol% to allow solvent exchange between the pure aramid nanofiber solution and the formic acid solution. The solution was left to stand for a certain period of time until reconstruction was completed.

[0106] (3) Finally, the honeycomb mold with spatial topology is rinsed clean in water and dried in an oven at a certain temperature before being taken out.

[0107] like Figure 1 As shown, in this embodiment, the high-performance nanofiber structural component integrated extrusion molding equipment implementing the above method includes a forced mixing and conveying device, an extrusion die, and a molding die. The forced mixing and conveying device adopts a mixing and conveying system formed by a positive displacement pump and a mixer. The positive displacement pump is a push rod type plunger pump, and a push rod is concentrically installed in the cavity of the positive displacement pump. The two can move relative to each other. The input end of the positive displacement pump is provided with a feed port, and a hopper is installed on the feed port; as Figure 9 As shown, the mixer is a dynamic mixer with a multi-stage rotating mechanism, installed after the positive displacement pump and connected by bolts; the extrusion die head is fixedly installed at the output end of the dynamic mixer and connected to the molding die through a pipeline; the molding die includes a mold cavity and a cover plate, the cover plate and the mold cavity are joined to form a closed extrusion cavity space, and both the mold cavity and the cover plate are provided with a porous structure; temperature control devices are distributed on the positive displacement pump, the mixer and the extrusion die head to maintain the extrusion temperature.

[0108] In this embodiment, a pure aramid nanofiber solution is used as the nanofiber solution, with a mass concentration of 1.5-4 wt%, preferably 2.5 wt%.

[0109] The mixer uses a multi-stage dynamic mixer to mix the nanofiber solution. The solution is fully mixed through its multi-stage rotation mechanism. The mixing speed is 3000-6000 rpm, with a selected value of 4000-5000 rpm. The number of mixing stages is 1-4, with a preferred value of 2 stages.

[0110] The temperature control device uses thermocouples, and the extrusion temperature is 50-110℃, with a preferred value of 62-77℃.

[0111] Formic acid solution with proton-donating capability is used as the reconstruction solution, with a volume concentration of 30-70 vol%, preferably 40-55 vol%.

[0112] A honeycomb mold with a spatial topology is used as the molding die for extrusion molding, and the thickness of the mold cavity is 5-30mm, with a preferred value of 12mm.

[0113] like Figure 11 and Figure 12 As shown, using the above method and equipment, aramid honeycomb paper with a spatial topology can be prepared quickly and in an integrated manner.

[0114] The parts not mentioned in this embodiment are the same as in Embodiment 1.

[0115] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A method for integral extrusion molding of high-performance nanofiber structural components, characterized in that, Includes the following steps: (1) The nanofiber solution is added to the forced mixing and conveying device, so that the nanofiber solution is sheared and transformed into a homogenized dispersion in the forced mixing and conveying device. Then, the homogenized dispersion is injected into the molding die through the extrusion die under the extrusion pressure provided by the forced mixing and conveying device. The nanofiber solution is one of aramid nanofiber solution, aramid nanofiber composite solution, PBO nanofiber solution and PBO nanofiber composite solution; The molding die includes a mold cavity and a cover plate. Both the mold cavity and the cover plate are provided with a porous structure, and the size of the pores is from 20μm to 310μm. The mold cavity contains multiple filling pillars, which are hollow and the gap between adjacent filling pillars is 0.4 mm to 5 mm. The molding die is pre-filled with a skeleton structure formed by functional fillers; (2) Immerse the entire molding mold in the reconstruction solution. The homogenized dispersion injected into the molding mold exchanges solvent with the reconstruction solution, causing the homogenized dispersion to undergo sol-gel conversion and form a nanofiber composite gel with a predetermined shape. Specifically, for aramid nanofiber solutions and aramid nanofiber composite solutions, the reconstructed solution uses a proton donor solution with proton supply capability; for PBO nanofiber solutions and PBO nanofiber composite solutions, the reconstructed solution uses a proton acceptor solution with deprotonation capability. (3) The nanofiber composite gel with a predetermined shape is washed and dried to obtain a nanofiber structure.

2. A high-performance nanofiber structural component integrated extrusion molding equipment, implementing the high-performance nanofiber structural component integrated extrusion molding method as described in claim 1, characterized in that, It includes a forced mixing conveyor, an extrusion die, and a molding die. The input end of the forced mixing conveyor is equipped with a feed port, and the extrusion die is fixedly installed at the output end of the forced mixing conveyor and connected to the molding die through a pipeline.

3. The integrated extrusion molding equipment for high-performance nanofiber structural parts according to claim 2, characterized in that, The forced mixing and conveying device adopts a mixing and conveying system formed by a positive displacement pump and a mixer, a multi-rotor mixing and conveying system, or a single-rotor mixing and conveying system.

4. The integrated extrusion molding equipment for high-performance nanofiber structural parts according to claim 3, characterized in that, The positive displacement pump is a reciprocating pump, diaphragm pump, gear pump, screw pump, plunger pump, or vane pump; the mixer is a dynamic mixer or a static mixer, the dynamic mixer includes a multi-stage rotating mechanism, and the static mixer consists of a multi-stage mixing channel.

5. The integrated extrusion molding equipment for high-performance nanofiber structural components according to claim 2, characterized in that, The extrusion die head can be a single-flow-path extrusion die head or a multi-flow-path extrusion die head.

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