Wood fiber / mxene composite material and preparation method and application thereof

Abstract

The application discloses a kind of wood fiber / MXene composite material and its preparation method and application, belong to electromagnetic shielding material technical field.The modified wood fiber of removing lignin and hemicellulose is mixed with biomass adhesive, sprays aniline monomer solution, pre-presses, sprays oxidizing solution, cold-presses, and aniline occurs oxidation polymerization and generates polyaniline with conductivity and electromagnetic shielding performance, and is loaded on the surface of modified wood fiber to form conductive network, to obtain blank, the blank is hot-pressed, and biomass adhesive occurs esterification crosslinking and forms three-dimensional crosslinking network, while modified wood fiber and biomass adhesive produce hydrogen bond combination, to obtain wood fiber preform plate;MXene nanosheet solution is coated on the surface of the wood fiber preform plate, MXene nanosheet is closely combined with polyaniline by electrostatic adsorption and π-π conjugation effect, and forms interwoven conductive network, effectively improves the conductivity of composite material.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electromagnetic shielding materials, and particularly relates to a wood fiber / MXene composite material and a preparation method and application thereof. BACKGROUND

[0002] With the rapid development of modern science and technology, higher requirements are put forward for the performance of materials in various fields, especially in electronic devices, communication equipment and national defense industry, and electromagnetic shielding materials have become a crucial part. Traditional electromagnetic shielding materials such as metal materials have good shielding effect, but their processing cost is high, the weight is large, the corrosion is strong, and the environmental impact is large. Although carbon-based materials and polymer materials are light, their electromagnetic shielding performance is limited, and it is difficult to meet the demand of high-performance electromagnetic shielding. Therefore, how to develop a new type of material with light weight, environmental protection, good electromagnetic shielding performance has become the focus of research.

[0003] In recent years, biomass materials such as wood fiber, bamboo powder and straw have gradually been applied in the field of electromagnetic shielding materials due to their advantages of being renewable, environmentally friendly, light weight, and wide resource base and good mechanical properties. However, the poor electrical conductivity of biomass materials limits their application in the field of electronic information due to the weak electromagnetic shielding performance of wood. SUMMARY

[0004] The present application provides a wood fiber / MXene composite material and a preparation method and application thereof, which effectively solves the technical problem of insufficient electromagnetic shielding performance of biomass materials in the prior art. The present application combines MXene nanosheets with biomass fibers to endow the composite material with excellent electromagnetic shielding performance. The density of the composite material is 0.8 g / cm 3 ~1.2 g / cm 3 , the tensile strength is not less than 50 MPa, the shielding effectiveness is more than 50 dB in the frequency range of 8.2 GHz to 12.4 GHz, and can reach 47 dB to 58 dB; and the preparation cost is low and easy to industrialize.

[0005] The first object of the present application is to provide a preparation method of a wood fiber / MXene composite material, comprising the following steps:

[0006] The wood fiber is crushed, and the lignin and hemicellulose in the wood fiber are removed to obtain modified wood fiber.

[0007] Mix the modified wood fiber with the biomass adhesive, spray the aniline monomer solution in a stirring state, pre-press, spray the oxidizing solution, cold-press, the aniline undergoes oxidative polymerization under the action of the oxidizing solution to generate polyaniline, and is loaded on the surface of the modified wood fiber by hydrogen bonding to obtain a blank, hot-press the blank, the biomass adhesive undergoes esterification crosslinking to form a three-dimensional crosslinking network, and the modified wood fiber and the biomass adhesive are combined by hydrogen bonding to obtain a wood fiber preform board.

[0008] Coat the MXene nanosheet solution on the surface of the wood fiber preform board, and the MXene nanosheet and the polyaniline generate electrostatic adsorption and π-π conjugation to obtain a wood fiber / MXene composite material.

[0009] As a preferred embodiment, the preparation method of the biomass adhesive is to mix 4-25 parts by mass of a sugar, 12-70 parts of an organic acid, and 4-27 parts of distilled water, stir at 90-100°C at a speed of 200-300 r / min for 1-2 h, add 5-31 parts of defatted protein powder, stir uniformly, and cool to room temperature to obtain the biomass adhesive.

[0010] As a preferred embodiment, the mass ratio of the modified wood fiber to the biomass adhesive is 1:2.8-3.8.

[0011] As a preferred embodiment, the aniline monomer solution is a hydrochloric acid solution of aniline with a concentration of 0.5 mg / mL-2.0 mg / mL, and the use amount ratio of the modified wood fiber to the aniline monomer solution is 1 g:0.5 mL-2 mL.

[0012] As a preferred embodiment, the oxidizing solution is a hydrochloric acid solution of potassium permanganate with a concentration of 0.8 g / mL-1.3 g / mL, and the volume ratio of the aniline monomer solution to the oxidizing solution is 1:0.5-1.5.

[0013] As a preferred embodiment, the concentration of the MXene nanosheet solution is 1 mg / mL-5 mg / mL, and the coating thickness of the MXene nanosheet is 10 μm-50 μm.

[0014] As a preferred embodiment, the cold-pressing is cold-pressing at -5°C-0°C and 1 MPa-5 MPa for 30 min, and the hot-pressing is heating the blank to 140°C-165°C at a rate of 5-10°C / min, increasing the pressure to 3-7 MPa at a rate of 1 MPa / min-2 MPa / min, and hot-pressing for 18-25 min, and after hot-pressing, releasing the pressure to normal pressure in 4 min-6 min.

[0015] As a preferred embodiment, the modified wood fiber is specifically: after the wood fiber is crushed, the crushed wood fiber is immersed in a mixed solution of 2.5 mol / L NaOH and 0.4 mol / L Na2SO3 according to a mass-volume ratio of 1g:15-30mL, boiled for 5-7h, rinsed with distilled water, and then boiled in 2.5 mol / L H2O2 solution again according to a dosage ratio of wood fiber to H2O2 solution of 1g:20-30mL for 2-3h, so as to remove lignin and hemicellulose.

[0016] As a preferred embodiment, the wood fiber is at least one of tree fiber, shrub fiber and liana fiber; the sugar is at least one of sucrose, maltose and lactose; the organic acid is at least one of citric acid, malic acid, grape acid, oxalic acid and acetic acid; and the defatted protein powder is at least one of defatted soybean protein powder, defatted corn protein powder and cottonseed protein powder.

[0017] A second object of the present application is to provide a wood fiber / MXene composite material prepared by the above preparation method.

[0018] A third object of the present application is to provide an application of the above wood fiber / MXene composite material in electromagnetic shielding.

[0019] Compared with the prior art, the present application has the following beneficial effects:

[0020] The present application provides a preparation method of a wood fiber / MXene composite material. First, wood fiber is crushed, and then lignin and hemicellulose in the wood fiber are removed to obtain modified wood fiber. The modified wood fiber is mixed with a biomass adhesive, and aniline monomer solution is sprayed under stirring. Pre-pressing, spraying of an oxidizing solution, and cold pressing are performed. Aniline undergoes oxidative polymerization under the action of the oxidizing solution to generate polyaniline, which is loaded on the surface of the modified wood fiber by hydrogen bonding to obtain a blank. Since polyaniline has good electrical conductivity and electromagnetic shielding performance, it forms a conductive network on the wood fiber, giving the composite material electromagnetic shielding performance. At the same time, the combination of polyaniline and wood fiber can improve the interfacial interaction between wood fiber and subsequently coated MXene nanosheets, which is conducive to the transmission of electrons in the composite material, further improving the electromagnetic shielding performance. The blank is hot-pressed, and the biomass adhesive undergoes esterification crosslinking to form a three-dimensional crosslinked network. At the same time, the modified wood fiber and the biomass adhesive are combined by hydrogen bonding to obtain a wood fiber preform. MXene nanosheet solution is coated on the surface of the wood fiber preform to obtain a wood fiber / MXene composite material. MXene nanosheets and polyaniline are tightly combined through electrostatic adsorption and π-π conjugation to form a conductive network that interweaves with each other, effectively improving the electrical conductivity of the composite material.

[0021] The biomass adhesive adopted by the present application is prepared from 4-25 parts by mass of saccharides, 12-70 parts of organic acid, 4-27 parts of distilled water and 5-31 parts of defatted protein powder. The saccharides, the organic acid and the defatted protein powder cooperatively form a stable adhesive system, the saccharides and the organic acid undergo esterification reaction in the heating and stirring process, thereby increasing the viscosity and stability of the adhesive; the saccharides and the defatted protein powder have good compatibility with wood fibers, the defatted protein powder interacts with the hydroxyl groups on the surface of the wood fibers through hydrogen bonds and van der Waals force, thereby enhancing the bonding force between the adhesive and the wood fibers and ensuring good mechanical properties of the wood fiber preform plate, providing a basic support for improving the overall performance and providing a stable structural basis for subsequent coating of the MXene nanosheet solution.

[0022] In the electromagnetic shielding process, the present application polymerizes aniline monomers on the surface of wood fibers, realizes good synergistic effect of polyaniline and MXene nanosheets, and endows the material with excellent electromagnetic shielding performance, especially in the frequency range of 8.2-12.4 GHz, the shielding effectiveness is more than 50 dB. By introducing the MXene nanosheet, not only the conductivity of the composite material is improved, but also the material is provided with anti-mildew property, thereby prolonging the service life of the material. The preparation process of the present application is simple, the preparation process is glue-free and formaldehyde-free, meets the green environmental protection requirements, and can realize large-scale industrial production. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 The preparation flow chart of the wood fiber / MXene composite material of the present application embodiment 1.

[0024] Figure 2 The SEM graph of the aniline polymerized wood fiber matrix in the present application embodiment 1.

[0025] Figure 3 The electromagnetic efficiency graph of the wood fiber / MXene composite material of the present application embodiment 1-embodiment 5.

[0026] Figure 4 The SEM comparison graph of the wood fiber / MXene composite material of the present application embodiment 1 and embodiment 4, wherein the (a) graph, the (c) graph and the (e) graph are coated with a thickness of 10 microns, the (a) graph is 500 microns, the (c) graph is 5 microns, and the (e) graph is 500 nanometers; the (b) graph, the (d) graph and the (f) graph are coated with a thickness of 50 microns, the (b) graph is 500 microns, the (d) graph is 5 microns, and the (f) graph is 500 nanometers. DETAILED DESCRIPTION

[0027] In order for those skilled in the art to better understand the technical solutions of the present application and to implement them, the present application will be further described below in conjunction with specific examples and drawings, but the examples are not limiting of the present application. The following test methods and detection methods are conventional methods unless otherwise specified; the reagents and raw materials are commercially available unless otherwise specified.

[0028] In view of the technical problem of the poor electrical conductivity of biomass materials and the weak electromagnetic shielding performance of wood limiting the application of wood in the electronic information field mentioned in the background of the present application, the present application provides a wood fiber / MXene composite material and a preparation method and application thereof.

[0029] The technical solutions of the present application will be described in detail below.

[0030] The present application first provides a preparation method of a wood fiber / MXene composite material, comprising the following steps:

[0031] The wood fibers are crushed, and lignin and hemicellulose in the wood fibers are removed to obtain modified wood fibers.

[0032] The modified wood fibers are mixed with a biomass adhesive, and an aniline monomer solution is sprayed in a stirring state, pre-pressed, and through pre-pressing, the material density is improved, and the material layer porosity is reduced to prepare for subsequent hot-pressing, and after pre-pressing, an oxidizing solution is sprayed, and cold-pressed, and the aniline undergoes an oxidative polymerization reaction under the action of the oxidizing solution to generate polyaniline, and is loaded on the surface of the modified wood fibers by hydrogen bonding to obtain a blank, and the blank is hot-pressed, the biomass adhesive undergoes esterification crosslinking to form a three-dimensional crosslinking network, and at the same time, the modified wood fibers and the biomass adhesive are combined by hydrogen bonding to obtain a wood fiber preform board.

[0033] The MXene nanosheet solution is coated on the surface of the wood fiber preform board, the MXene nanosheet and the polyaniline produce electrostatic adsorption and π-π conjugation effect to obtain a wood fiber / MXene composite material.

[0034] In the above technical solution, the polyaniline has good electrical conductivity and electromagnetic shielding performance, forms a conductive network on the wood fibers, and endows the composite material with electromagnetic shielding performance. At the same time, the combination of polyaniline and wood fibers can improve the interfacial interaction between wood fibers and the subsequently coated MXene nanosheets, which is conducive to the transmission of electrons in the composite material, and further improves the electromagnetic shielding performance. The MXene nanosheet and the polyaniline are tightly combined through electrostatic adsorption and π-π conjugation effect to form a mutually interwoven conductive network, which effectively improves the electrical conductivity of the composite material.

[0035] In order to improve the interaction force between wood fibers, improve the bonding force in the composite material, and realize the excellent electromagnetic shielding performance of the composite material, the preparation method of the biomass adhesive is mixing 4-25 parts by mass of sugar, 12-70 parts of organic acid and 4-27 parts of distilled water, stirring at 90-100 DEG C and 200-300 r / min for 1-2 h, adding 5-31 parts of defatted protein powder, stirring uniformly, cooling to room temperature, and adding biomass adhesive to the modified wood fiber according to the mass ratio of 1:2.8-3.8. During preparation, sugar, organic acid and defatted protein powder form a stable adhesive system, sugar and organic acid occur esterification reaction during heating and stirring process, increase the viscosity and stability of the adhesive; defatted protein powder interacts with the functional groups such as hydroxyl groups on the surface of wood fiber through hydrogen bond and van der waals force, enhances the bonding force of the adhesive and wood fiber, and makes the wood fiber preform plate have certain mechanical strength, providing stable structure basis for subsequent coating of MXene nanosheet solution. Different proportions of sugar, organic acid and defatted protein powder affect the bonding performance and stability, sugar and defatted protein powder have good compatibility with wood fiber, ensure the mechanical performance of the preform plate, and provide basic support for overall performance improvement.

[0036] In order to further improve the electromagnetic shielding performance of the composite material, the aniline monomer solution is a hydrochloric acid solution of aniline with a concentration of 0.5 mg / mL to 2.0 mg / mL, and the use ratio of the modified wood fiber to the aniline monomer solution is 1 g:0.5 mL to 2 mL. The oxidation solution is a hydrochloric acid solution of potassium permanganate with a concentration of 0.8 g / mL to 1.3 g / mL, and the volume ratio of the aniline monomer solution to the oxidation solution is 1:0.5 to 1.5. As a precursor of the conductive polymer, the aniline solution is mixed with the hydrochloric acid solution to form the aniline monomer solution, and the potassium permanganate is dissolved in the hydrochloric acid solution to form the oxidation solution. In an acidic environment, the potassium permanganate has strong oxidizing properties, which promotes the polymerization of the aniline monomer to generate polyaniline. Polyaniline has good conductivity and electromagnetic shielding performance, and forms a conductive network on the wood fiber, which gives the composite material electromagnetic shielding performance. Hydrochloric acid can provide a relatively stable and moderate acidic environment, which helps the dissolution of aniline and the subsequent oxidation polymerization reaction. Moreover, the chloride ions in hydrochloric acid have small volume and good solubility, which enter the molecular chain of polyaniline during the polymerization of aniline, thereby improving the conductivity of polyaniline. Moreover, hydrochloric acid is widely available and relatively inexpensive, which is easy to obtain and use. Compared with some other strong acids, some other strong acids may have stronger corrosiveness and danger, which not only increases the operation risk, but also increases the requirements for equipment, which is not conducive to large-scale production. The combination of polyaniline and wood fiber can improve the interfacial interaction between wood fiber and the subsequently coated MXene nanosheets, which is conducive to the transmission of electrons in the composite material, and further improves the electromagnetic shielding performance. The mass ratio of aniline to hydrochloric acid in the aniline monomer solution and the concentration of potassium permanganate in the oxidation solution determine the amount and performance of polyaniline. Both the preparation of polyaniline and the adhesive are in an acidic environment, and the two have a synergistic effect, which enhances the overall effect.

[0037] In order to further improve the conductivity of the composite material, the concentration of the MXene nanosheet solution is 1 mg / mL to 5 mg / mL, and the coating thickness of the MXene nanosheet is 10 μm to 50 μm. The concentration of the MXene nanosheet solution and the coating thickness affect the conductivity and electromagnetic shielding effect of the composite material. Both polyaniline and MXene nanosheet have good conductivity, and the two form an interwoven conductive network in the composite material, which effectively improves the conductivity of the composite material.

[0038] To further improve the internal bonding force of the composite material and achieve better electromagnetic shielding effect, the cold pressing is performed at -5°C to 0°C and 1 MPa to 5 MPa for 30 min; the oxidation polymerization reaction of the aniline monomer needs to be performed below 0°C, and is best performed at -5°C to 0°C. The hot pressing is performed by heating the blank to 140°C to 165°C at a rate of 5°C / min to 10°C / min, increasing the pressure to 3 MPa to 7 MPa at a rate of 1 MPa / min to 2 MPa / min, and hot pressing for 18 min to 25 min to achieve curing of the adhesive and further forming of the composite material, and under the action of greater pressure, the physical densification and chemical bonding of the material are synergistically enhanced, and after hot pressing, the pressure is released to normal pressure in 4 min to 6 min. The temperature is between 140°C and 165°C, and if the temperature is lower than 140°C, the adhesive may not be completely cured, and if the temperature is higher than 165°C, the wood fibers may be carbonized. During hot pressing, the pressure is increased to 3 MPa to 7 MPa at a rate of 1 MPa / min to 2 MPa / min, so as to avoid sudden change of pressure and cause delamination of the material.

[0039] It should be noted that the following interactions may occur between the raw materials in the composite material during hot pressing:

[0040] Esterification cross-linking of the biomass adhesive: under the action of temperature and pressure during hot pressing, the acid in the adhesive and the hydroxyl component in the sugar further undergo esterification cross-linking reaction to form ester bonds, and such cross-linking structure helps to enhance the network structure of the adhesive itself and improve its bonding performance. For example, the esterification reaction of citric acid (-COOH) in the adhesive and sucrose (-OH) occurs at 140°C to 165°C to generate sucrose citrate ester and form a three-dimensional cross-linking network.

[0041] Interfacial hydrogen bonding between the wood fibers and the biomass adhesive: during hot pressing, hydrogen bonds are formed between the polar groups in the adhesive and the hydroxyl groups on the surface of the wood fibers, thereby enhancing the interfacial bonding force between the wood fibers and the adhesive.

[0042] Interaction between polyaniline and the fiber matrix: on the one hand, during cold pressing, the polar groups on the molecular chain of polyaniline form hydrogen bonds with the hydroxyl groups on the surface of the wood fibers and the polar groups in the adhesive, thereby increasing the interaction force between them; on the other hand, through the action of the kneader and cold pressing, polyaniline is intertwined with the fiber matrix through physical winding and the like, thereby further enhancing the bonding strength between the fiber matrix and polyaniline and improving the performance of the composite material.

[0043] The synergistic mechanism of MXene nanoplate and polyaniline: the two-dimensional layer plane of MXene and the benzene ring of polyaniline are enhanced by pi-pi stacking to enhance electron transmission, and the surface functional groups and polyaniline segments form hydrogen bonds. Secondly, the surface of MXene is negatively charged, while polyaniline is positively charged in the doped state, and the two can be closely combined through electrostatic attraction. And the two-dimensional sheet layer of MXene and the fibrous structure of polyaniline interweave to form a three-dimensional conductive path, which can significantly improve the electromagnetic shielding efficiency of the composite material through multiple reflection-absorption mechanisms.

[0044] In order to remove lignin and hemicellulose from wood fibers, the modified wood fibers are specifically: after the wood fibers are crushed, according to the mass-volume ratio of 1g:15-30mL, the crushed wood fibers are immersed in a mixed solution of 2.5mol / L NaOH and 0.4mol / L Na2SO3, boiled for 5-7h, rinsed with distilled water, and then according to the dosage ratio of wood fibers to H2O2 solution 1g:20-30mL, boiled in 2.5mol / L H2O2 solution for 2-3h to remove lignin and hemicellulose.

[0045] It should be noted that the wood fibers used in the present application are at least one of tree fibers, shrub fibers and liana fibers; the sugar is at least one of sucrose, maltose and lactose; the organic acid is at least one of citric acid, malic acid, grape acid, oxalic acid and acetic acid; and the defatted protein powder is at least one of defatted soybean protein powder, defatted corn protein powder and cottonseed protein powder.

[0046] The technical effects of the present application will be described below in conjunction with specific examples and comparative examples.

[0047] Example 1

[0048] A preparation method of a wood fiber / MXene composite material, the preparation process is as shown in Figure 1 The preparation method comprises the following steps:

[0049] (1) Wood fiber treatment: the tree fibers are crushed and sieved to obtain tree fibers with a length of less than 5mm and a diameter of less than 0.2mm, according to the dosage ratio of 1g:30mL, the sieved tree fibers are boiled in a mixed solution of 2.5mol / L NaOH and 0.4mol / L Na2SO3 for 7h, rinsed with distilled water, and then according to the dosage ratio of wood fibers to H2O2 solution 1g:30mL, boiled in 2.5mol / L H2O2 solution for 3h to remove lignin and hemicellulose, and then washed with deionized water and dried in an oven at 110℃ for 8h to obtain modified tree fibers.

[0050] (2) Biomass adhesive preparation: Take 80 g of sucrose, 240 g of citric acid, and 80 g of distilled water, mix them in a beaker, and stir at 100℃ and 250 r / min for 2 hours. During the stirring process, gradually add 90 g of defatted soybean protein powder. After the reaction is completed, cool the mixture to room temperature to obtain the biomass adhesive.

[0051] (3) Preparation of high molecular conductive solution: Prepare two 1 mol / L hydrochloric acid solutions. Take 51 g of aniline and add it to one of the hydrochloric acid solutions and stir until the aniline solution is fully mixed to obtain a 1.1 mg / mL aniline monomer solution. Add potassium permanganate to the other hydrochloric acid solution and stir until the concentration of potassium permanganate is 1 g / mL to obtain an oxidizing solution.

[0052] (4) Pre-pressing: Mix the biomass adhesive and modified tree fibers in a kneader at a mass ratio of 1:2.8 and a stirring speed of 35 r / min. Spray the aniline monomer solution uniformly through a spray gun at a dosage ratio of 1 g of modified tree fibers to 1.2 mL of aniline monomer solution. After stirring for 30 minutes, place the material in a pre-pressing machine and spray the oxidizing solution uniformly through a spray gun at a volume ratio of 1:1.1. After the oxidizing solution is sprayed, control the temperature at 0℃ and the pressure at 2 MPa for 30 minutes to allow the aniline monomer to fully polymerize on the material to obtain a blank.

[0053] (5) Forming: Place the blank in a hot-pressing machine and hot-press at a temperature of 150℃, a pressure of 5 MPa, a hot-pressing time of 20 minutes, and a hot-pressing plate thickness of 0.5 mm. After observing that there is no obvious water vapor discharge, release the pressure for 6 minutes to obtain a wood fiber preform.

[0054] (6) Preparation of composite material: Brush the MXene nanosheet solution with a concentration of 3 mg / mL onto the surface of the wood fiber preform and dry to obtain a wood fiber / MXene electromagnetic shielding composite material. The MXene nanosheet coating thickness is 50 μm, and the wood fiber / MXene electromagnetic shielding composite material has a shielding effectiveness of 57 dB at 8.2-12.4 GHz.

[0055] Example 2

[0056] A method for preparing a wood fiber / MXene composite material, comprising the following steps:

[0057] (1) Wood fiber treatment: the shrub fiber is crushed and sieved to obtain shrub fiber with a length of less than 5 mm and a diameter of less than 0.2 mm, and the sieved shrub fiber is boiled in a mixed solution of 2.5 mol / L NaOH and 0.4 mol / L Na2SO3 for 7 h at a dosage ratio of 1 g:25 mL, and then rinsed with distilled water, and then boiled in a 2.5 mol / L H2O2 solution again for 3 h at a dosage ratio of 1 g:30 mL, so as to remove lignin and hemicellulose, and then washed with deionized water and dried in an oven at 110°C for 8 h to obtain modified shrub fiber.

[0058] (2) Biomass adhesive preparation: 65 g of maltose, 175 g of malic acid and 70 g of distilled water are weighed and placed in a beaker and stirred uniformly at 100°C and 250 r / min for 2 h, and during the stirring process, 90 g of defatted corn protein powder is gradually added, and after the reaction is completed, the mixture is cooled to room temperature to obtain a biomass adhesive.

[0059] (3) Preparation of a high-molecular conductive solution: two portions of a 1 mol / L hydrochloric acid solution are prepared, 36 g of aniline solution is weighed and placed in one portion of the hydrochloric acid solution and stirred uniformly to completely mix the aniline solution, to obtain an aniline monomer solution with a concentration of 0.5 mg / mL; and the other portion of the hydrochloric acid solution is stirred uniformly with potassium permanganate to adjust the concentration of the potassium permanganate to 0.8 g / mL to obtain an oxidizing solution.

[0060] (4) Pre-pressing: the biomass adhesive and the modified shrub fiber are uniformly stirred in a kneader at a mass ratio of 1:3.1 and a rotation speed of 35 r / min, the aniline monomer solution is uniformly sprayed through a spray gun at a dosage ratio of 1 g:2 mL, and after stirring for 30 min, the material is laid in a pre-pressing machine, and the oxidizing solution is uniformly sprayed through a spray gun at a volume ratio of 1:1.5. After the spraying of the oxidizing solution is completed, the temperature is controlled at 0°C, and the material is cold-pressed at a pressure of 2 MPa for 30 min to allow the aniline monomer to fully polymerize on the material to obtain a blank.

[0061] (5) Forming: the blank is placed in a hot-pressing machine, and hot-pressing is performed at a hot-pressing temperature of 150°C, a hot-pressing pressure of 5 MPa, a hot-pressing time of 18 min and a hot-pressing plate thickness of 0.5 mm. After no obvious water vapor is observed, the pressure is released for 5 min to obtain a wood fiber preform.

[0062] (6) Preparation of composite material: A 2 mg / mL MXene nanosheet solution was brushed onto the surface of the wood fiber prefabricated board. After drying, a wood fiber / MXene electromagnetic shielding composite material was obtained. The MXene nanosheet coating thickness was 20 μm. The shielding effectiveness of the wood fiber / MXene electromagnetic shielding composite material was 52 dB in the range of 8.2 to 12.4 GHz.

[0063] Example 3

[0064] A method for preparing a wood fiber / MXene composite material includes the following steps:

[0065] (1) Wood fiber treatment: The vine plant fiber was crushed and sieved to obtain vine plant fiber with a length of less than 5 mm and a diameter of less than 0.2 mm. The sieved vine plant fiber was boiled in a mixed solution of 2.5 mol / L NaOH and 0.4 mol / L Na2SO3 for 6 h according to the dosage ratio of 1 g: 25 mL. After rinsing with distilled water, it was boiled again in 2.5 mol / L H2O2 solution for 2.5 h according to the dosage ratio of vine plant fiber to H2O2 solution of 1 g: 25 mL to remove lignin and hemicellulose. After washing with deionized water, it was placed in an oven at 110℃ and dried for 7 h to obtain modified vine plant fiber.

[0066] (2) Preparation of biomass adhesive: Weigh 250g of lactose, 700g of acetic acid and 270g of distilled water, put them into a beaker and stir evenly. Stir at 90℃ and 250r / min for 1h. During the stirring process, gradually add 290g of defatted corn gluten powder. After the reaction is completed, cool the mixture to room temperature to obtain biomass adhesive.

[0067] (3) Preparation of polymer conductive solution: Prepare two portions of hydrochloric acid solution with a concentration of 1 mol / L. Weigh 65 g of aniline and put it into one portion of hydrochloric acid solution and stir evenly to make the aniline solution completely mixed to obtain an aniline monomer solution with a concentration of 1.7 mg / mL. Add potassium permanganate to the other portion of hydrochloric acid solution and stir evenly. Adjust the concentration of potassium permanganate to 1.3 g / mL to obtain an oxidizing solution.

[0068] (4) Pre-compression: The biomass adhesive and modified vine fiber are uniformly stirred in a kneader at a speed of 35 r / min at a mass ratio of 1:3.0. The aniline monomer solution is evenly sprayed through a spray gun at a volume ratio of 1 g:0.8 mL of modified vine fiber to aniline monomer solution. After stirring for 30 min, the material is laid out in a pre-compression molding machine. The oxidizing liquid is evenly sprayed in through a spray gun at a volume ratio of 1:0.7 of aniline monomer solution to oxidizing liquid. After the oxidizing liquid is sprayed, the material is cold-pressed at 0℃ and 2 MPa for 30 min to allow the aniline monomer to fully polymerize on the material and obtain the blank.

[0069] (5) Molding: The blank is placed in a hot press molding machine, and the hot pressing temperature is 150℃, the hot pressing pressure is 5MPa, the hot pressing time is 20min, and the hot pressing plate thickness is 0.5mm. After observing that there is no obvious water vapor discharge, the pressure is released for 4min, and a wood fiber preform plate is obtained.

[0070] (6) Composite material preparation: A MXene nanosheet solution with a concentration of 5mg / mL is brushed onto the surface of the wood fiber preform plate, and after drying, a wood fiber / MXene electromagnetic shielding composite material is obtained, with a MXene nanosheet coating thickness of 30μm. The wood fiber / MXene electromagnetic shielding composite material has a shielding effectiveness of 54dB at 8.2~12.4GHz.

[0071] Example 4

[0072] A method for preparing a wood fiber / MXene composite material, comprising the following steps:

[0073] (1) Wood fiber treatment: The arbor fiber is crushed and sieved to obtain arbor fiber with a length of less than 5mm and a diameter of less than 0.2mm. The sieved arbor fiber is boiled in a mixed solution of 2.5mol / L NaOH and 0.4mol / L Na2SO3 for 6h at a dosage ratio of 1g:20mL. It is then rinsed with distilled water, and then boiled in a 2.5mol / L H2O2 solution for 2.5h at a dosage ratio of 1g:25mL. The lignin and hemicellulose are removed, and the modified arbor fiber is dried in an oven at 110℃ for 7h.

[0074] (2) Biomass adhesive preparation: Weigh 40g of sucrose, 120g of citric acid, and 40g of distilled water, and place them in a beaker and stir until uniform. Stir at 250r / min for 1h at 90℃. During the stirring process, gradually add 50g of defatted soybean protein powder. After the reaction is complete, cool the mixture to room temperature to obtain a biomass adhesive.

[0075] (3) Preparation of a polymer conductive solution: Prepare two 1mol / L hydrochloric acid solutions. Weigh 28g of aniline solution and place it in one of the hydrochloric acid solutions and stir until uniform. This gives an aniline monomer solution with a concentration of 0.8mg / mL. For the other hydrochloric acid solution, add potassium permanganate and stir until uniform. Adjust the concentration of the potassium permanganate to 0.9g / mL to obtain an oxidizing solution.

[0076] (4) Pre-pressing: Biomass adhesive and modified arbor fiber were uniformly stirred in a kneader at a speed of 35 r / min according to a mass ratio of 1:3.8. Aniline monomer solution was uniformly sprayed by a spray gun according to a dosage ratio of 1 g:1.5 mL of modified arbor fiber to aniline monomer solution. After stirring for 30 min, the material was laid in a pre-pressing machine. Oxidizing solution was uniformly sprayed by a spray gun according to a volume ratio of 1:1.2 of aniline monomer solution to oxidizing solution. After the spraying of the oxidizing solution was completed, the temperature was controlled at 0 ℃, and the material was cold-pressed at a pressure of 2 MPa for 30 min to make the aniline monomer fully polymerize on the material to obtain a blank.

[0077] (5) Forming: The blank was placed in a hot-pressing machine. Hot-pressing was performed at a hot-pressing temperature of 150 ℃, a hot-pressing pressure of 5 MPa, a hot-pressing time of 18 min, and a hot-pressing plate thickness of 0.5 mm. After no obvious water vapor was observed, the pressure was released for 5 min to obtain a wood fiber preform.

[0078] (6) Composite material preparation: MXene nanosheet solution with a concentration of 1 mg / mL was brushed onto the surface of the wood fiber preform. After drying, a wood fiber / MXene electromagnetic shielding composite material was obtained. The MXene nanosheet coating thickness was 10 μm. The wood fiber / MXene electromagnetic shielding composite material had a shielding effectiveness of 50 dB at 8.2-12.4 GHz.

[0079] Example 5

[0080] A method for preparing a wood fiber / MXene composite material includes the following steps:

[0081] (1) Wood fiber treatment: The vine fiber was crushed and sieved to obtain vine fiber with a length of less than 5 mm and a diameter of less than 0.2 mm. The sieved vine fiber was boiled in a mixed solution of 2.5 mol / L NaOH and 0.4 mol / L Na2SO3 for 5 h according to a dosage ratio of 1 g:15 mL. The vine fiber was rinsed with distilled water and then boiled in a 2.5 mol / L H2O2 solution for 2 h according to a dosage ratio of 1 g:20 mL. Lignin and hemicellulose were removed. After washing with deionized water, the modified vine fiber was dried in an oven at 110 ℃ for 6 h to obtain modified vine fiber.

[0082] (2) Biomass adhesive preparation: 200 g of lactose, 600 g of acetic acid, and 200 g of distilled water were placed in a beaker and stirred uniformly. The mixture was stirred at 95 ℃ and a speed of 250 r / min for 1.5 h. During the stirring process, 250 g of defatted corn gluten meal was gradually added. After the reaction was completed, the mixture was cooled to room temperature to obtain a biomass adhesive.

[0083] (3) Preparation of a polymer conductive solution: two portions of a hydrochloric acid solution with a concentration of 1 mol / L were prepared, 155 g of aniline was weighed and placed in one portion of the hydrochloric acid solution and stirred until the aniline solution was completely mixed to obtain an aniline monomer solution with a concentration of 2.0 mg / mL; the other portion of the hydrochloric acid solution was stirred with potassium permanganate until the concentration of the potassium permanganate was 1.1 g / mL to obtain an oxidizing solution.

[0084] (4) Pre-pressing: biomass adhesive and modified liana fiber were uniformly stirred in a kneader at a speed of 35 r / min according to a mass ratio of 1:2.8, aniline monomer solution was uniformly sprayed by a spray gun according to a dosage ratio of 1 g of modified liana fiber to 0.5 mL of aniline monomer solution, and the material was uniformly laid in a pre-pressing machine after stirring for 30 min, and the oxidizing solution was uniformly sprayed by a spray gun according to a volume ratio of 1:0.5. After the spraying of the oxidizing solution was completed, the temperature was controlled at 0℃, and the material was cold-pressed at a pressure of 2 MPa for 30 min to allow the aniline monomer to fully polymerize on the material to obtain a blank.

[0085] (5) Forming: the blank was placed in a hot-pressing machine, and hot-pressing was performed at a hot-pressing temperature of 150℃, a hot-pressing pressure of 5 MPa, a hot-pressing time of 25 min, and a hot-pressing plate thickness of 0.5 mm. After no obvious water vapor was observed, the pressure was released for 5 min to obtain a wood fiber preform.

[0086] (6) Preparation of a composite material: a MXene nanosheet solution with a concentration of 4 mg / mL was brushed onto the surface of the wood fiber preform, and a wood fiber / MXene electromagnetic shielding composite material was obtained after drying. The thickness of the MXene nanosheet coating was 40 μm, and the wood fiber / MXene electromagnetic shielding composite material had a shielding effectiveness of 55 dB at 8.2-12.4 GHz.

[0087] In order to further illustrate the technical effects of the present application, the present application also provides a comparative example, as follows:

[0088] Comparative Example 1

[0089] Compared with Example 1, the difference lies in that no MXene nanosheet solution is brushed.

[0090] A preparation method of a wood fiber preform, comprising the following steps:

[0091] (1) Wood fiber treatment: the arbor fiber was crushed and sieved to obtain arbor fiber with length less than 5 mm and diameter less than 0.2 mm, the sieved arbor fiber was boiled in a mixed solution of 2.5 mol / L NaOH and 0.4 mol / L Na2SO3 for 7 h at a dosage ratio of 1 g:30 mL, and then rinsed with distilled water, and boiled again in a 2.5 mol / L H2O2 solution for 3 h at a dosage ratio of 1 g:30 mL, so as to remove lignin and hemicellulose, and then washed with deionized water and dried in an oven at 110°C for 6-8 h to obtain modified arbor fiber.

[0092] (2) Biomass adhesive preparation: 80 g of sucrose and 240 g of citric acid were weighed and put into a beaker, and 80 g of distilled water was added and stirred uniformly at 100°C and 250 r / min for 2 h, during which 90 g of defatted soybean protein powder was gradually added, and after the reaction was completed, the mixture was cooled to room temperature to obtain a biomass adhesive.

[0093] (3) Preparation of a polymer conductive solution: two portions of 1 mol / L hydrochloric acid solution were prepared, 51 g of aniline was weighed and put into one portion of the hydrochloric acid solution and stirred uniformly to completely mix the aniline solution to obtain an aniline monomer solution with a concentration of 1.1 mg / mL; the other portion of the hydrochloric acid solution was added with potassium permanganate and stirred uniformly to adjust the concentration of the potassium permanganate to 1 g / mL to obtain an oxidizing solution.

[0094] (4) Pre-pressing: the biomass adhesive and the modified arbor fiber were uniformly stirred in a kneader at a mass ratio of 1:2.8 and a rotation speed of 35 r / min, the aniline monomer solution was uniformly sprayed through a spray gun at a dosage ratio of 1 g:1.2 mL, and after stirring for 30 min, the material was laid in a pre-pressing machine, the oxidizing solution was uniformly sprayed through a spray gun at a volume ratio of 1:1.1, after the spraying of the oxidizing solution was completed, the temperature was controlled at 0°C and the pressure was controlled at 2 MPa for cold pressing for 30 min, so that the aniline monomer was fully polymerized on the material to obtain a blank.

[0095] (5) Forming: the blank was placed in a hot-pressing machine, and hot-pressing was performed at a hot-pressing temperature of 150°C, a hot-pressing pressure of 5 MPa, a hot-pressing time of 20 min, and a hot-pressing plate thickness of 0.5 mm. After no obvious water vapor was observed, the pressure was released for 6 min to obtain a wood fiber preform.

[0096] The electromagnetic shielding effectiveness of the wood fiber preform in the frequency range of 8.2-12.4 GHz was 38 dB.

[0097] Comparative Example 2

[0098] The difference from example 1 is that the cold pressing process is not carried out, and the modified wood fiber and biomass adhesive are mixed directly and then hot pressed to form.

[0099] A preparation method of a wood fiber / MXene composite material, the preparation process is as shown in Figure 1 The preparation process is as shown in the figure, and comprises the following steps:

[0100] (1) Wood fiber treatment: pulverize and sieve the arbor fiber to obtain arbor fiber with a length of less than 5 mm and a diameter of less than 0.2 mm, and then boil the sieved arbor fiber in a mixed solution of 2.5 mol / L NaOH and 0.4 mol / L Na2SO3 for 7 h at a dosage ratio of 1 g:30 mL, rinse with distilled water, and then boil the arbor fiber in a 2.5 mol / L H2O2 solution again for 3 h at a dosage ratio of 1 g:30 mL, so as to remove lignin and hemicellulose, and then clean the arbor fiber with deionized water and dry it in an oven at 110°C for 8 h to obtain modified arbor fiber.

[0101] (2) Biomass adhesive preparation: weigh 80 g of sucrose, 240 g of citric acid, and 80 g of distilled water, put them into a beaker, stir uniformly, and stir at a speed of 250 r / min at 100°C for 2 h, during the stirring process, gradually add 90 g of defatted soybean protein powder, after the reaction is completed, cool the mixture to room temperature to obtain the biomass adhesive.

[0102] (3) Preparation of a high-molecular conductive solution: prepare two portions of 1 mol / L hydrochloric acid solution, weigh 51 g of aniline and put it into one portion of the hydrochloric acid solution to stir uniformly, so that the aniline solution is completely mixed, to obtain an aniline monomer solution with a concentration of 1.1 mg / mL; the other portion of the hydrochloric acid solution is stirred uniformly with potassium permanganate, and the concentration of the potassium permanganate is adjusted to 1 g / mL to obtain an oxidizing solution.

[0103] (4) Pre-pressing: according to a mass ratio of 1:2.8, the biomass adhesive and the modified arbor fiber are uniformly stirred in a kneader at a rotating speed of 35 r / min, according to a dosage ratio of 1 g:1.2 mL of the modified arbor fiber and the aniline monomer solution, the aniline monomer solution is uniformly sprayed through a spray gun, after stirring for 30 min, the material is well laid in a pre-pressing machine, according to a volume ratio of 1:1.1 of the aniline monomer solution and the oxidizing solution, the oxidizing solution is uniformly sprayed through a spray gun, and after the spraying of the oxidizing solution is completed, a blank is obtained.

[0104] (5) Forming: the blank is placed in a hot-pressing machine, and hot-pressing is performed at a hot-pressing temperature of 150°C, a hot-pressing pressure of 5 MPa, a hot-pressing time of 20 min, and a hot-pressing plate thickness of 0.5 mm. After observing that no obvious water vapor is discharged, the pressure is released for 6 min to obtain a wood fiber preform plate.

[0105] (6) Preparation of the composite material: a MXene nanosheet solution with a concentration of 3 mg / mL is brushed on the surface of a wood fiber preform plate, and after drying, a wood fiber / MXene electromagnetic shielding composite material is obtained, the MXene nanosheet coating thickness is 50 mu m, and the wood fiber / MXene electromagnetic shielding composite material has a shielding effectiveness of 42 dB at 8.2-12.4 GHz.

[0106] The morphology and electromagnetic shielding performance of the wood fiber / MXene composite material prepared in the embodiment of the application are characterized and analyzed, and the specific results are as follows:

[0107] Figure 2 The SEM image of the polyaniline polymerized wood fiber matrix in Example 1 of the application is shown in Figure 1. Figure 2 It can be seen that a continuous polyaniline coating layer is clearly visible on the modified wood fiber, indicating that aniline is successfully loaded on the fiber surface through oxidative polymerization, without obvious interface defects, and the two are closely combined to form an interwoven network with the wood fiber.

[0108] Figure 3 The electromagnetic effectiveness diagram of the wood fiber / MXene composite material in Example 1-Example 5 of the application is shown in Figure 2. Figure 3 It can be seen that in the range of 8.2-12.4 GHz (X-band), the shielding effectiveness (SE) of all examples is more than 47 dB, with a maximum of 58 dB (Example 1).

[0109] Figure 4 The SEM comparison diagram of the wood fiber / MXene composite material obtained by brushing the MXene nanosheet solution of the application on the wood fiber preform plate in different thicknesses is shown in Figure 3, wherein (a), (c) and (e) are the effect of a coating thickness of 10 mu m, there are local uncovered areas on the surface of the wood fiber preform plate, and the lamellas are dispersedly distributed, which will lead to discontinuous conductive network. (b), (d) and (f) are the effect of a coating thickness of 50 mu m, forming a dense layered structure, which is closely combined with the polyaniline layer through pi-pi conjugation and electrostatic adsorption, significantly improving the surface conductivity of the composite material. As can be seen from (b), (d) and (f), when the coating thickness is 50 mu m, the "brick-mud" lamella stacking structure is formed on the surface of the composite material, significantly enhancing the electromagnetic wave multiple reflection and absorption capacity, and effectively improving the electromagnetic shielding effectiveness of the composite material.

[0110] Obviously, those skilled in the art can make various modifications and variations to the application without departing from the spirit and scope of the application. Thus, if these modifications and variations of the application fall within the scope of the claims of the application and their equivalent technologies, the application also intends to include these modifications and variations.

Claims

1. A method for preparing a wood fiber / MXene composite material, characterized in that, Includes the following steps: Wood fibers are pulverized to remove lignin and hemicellulose, thus obtaining modified wood fibers. Modified wood fibers are mixed with biomass adhesives, and an aniline monomer solution is sprayed while stirring. The mixture is then pre-pressed, sprayed with an oxidizing liquid, and cold-pressed. Under the action of the oxidizing liquid, aniline undergoes an oxidative polymerization reaction to generate polyaniline, which is then loaded onto the surface of the modified wood fibers through hydrogen bonding to obtain a preform. The preform is then hot-pressed, and the biomass adhesive undergoes esterification and cross-linking to form a three-dimensional cross-linked network. At the same time, the modified wood fibers and the biomass adhesive form hydrogen bonds to obtain a wood fiber precast board. MXene nanosheet solution was coated onto the surface of the wood fiber prefabricated board. MXene nanosheets and polyaniline underwent electrostatic adsorption and π-π conjugation to obtain a wood fiber / MXene composite material. The cold pressing is performed by cold pressing at -5℃ to 0℃ and 1MPa to 5MPa for 30 minutes; the hot pressing is performed by heating the billet to 140℃ to 165℃ at a rate of 5 to 10℃ / min, pressing it to 3 to 7MPa at a rate of 1MPa / min to 2MPa / min, hot pressing for 18 to 25 minutes, and then releasing the pressure to atmospheric pressure in 4 to 6 minutes after hot pressing. The concentration of the MXene nanosheet solution is 1 mg / mL to 5 mg / mL; the coating thickness of the MXene nanosheets is 10 μm to 50 μm. The preparation method of the biomass adhesive is as follows: 4-25 parts by weight of sugar, 12-70 parts by weight of organic acid and 4-27 parts by weight of distilled water are mixed and stirred at 90-100℃ and 200-300 r / min for 1-2 hours. Then, 5-31 parts by weight of defatted protein powder are added, stirred evenly, and cooled to room temperature to obtain the final product. The mass ratio of the modified wood fiber to the biomass adhesive is 1:2.8~3.

8.

2. The preparation method according to claim 1, characterized in that, The aniline monomer solution is a hydrochloric acid solution of aniline with a concentration of 0.5 mg / mL to 2.0 mg / mL, and the volume ratio of the modified wood fiber to the aniline monomer solution is 1 g: 0.5 mL to 2 mL; the oxidation solution is a hydrochloric acid solution of potassium permanganate with a concentration of 0.8 g / mL to 1.3 g / mL, and the volume ratio of the aniline monomer solution to the oxidation solution is 1: 0.5 to 1.

5.

3. The preparation method according to claim 1, characterized in that, The modified wood fiber is specifically prepared by: crushing the wood fiber, boiling it in a mixed solution of NaOH and Na2SO3 for 5-7 hours, rinsing it with distilled water, and then boiling it again in H2O2 solution for 2-3 hours to remove lignin and hemicellulose.

4. The preparation method according to claim 1, characterized in that, The wood fiber is at least one of tree fiber, shrub fiber, and vine fiber; the sugar is at least one of sucrose, maltose, and lactose; the organic acid is at least one of citric acid, malic acid, gluconic acid, oxalic acid, and acetic acid; and the defatted protein powder is at least one of defatted soybean protein powder, defatted corn protein powder, and cottonseed protein powder.

5. A wood fiber / MXene composite material prepared by the preparation method according to any one of claims 1 to 4.

6. The application of the wood fiber / MXene composite material according to claim 5 in electromagnetic shielding.

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