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

Abstract

The invention discloses a wood fiber / MXene composite material and a preparation method and application thereof, and belongs to the technical field of electromagnetic shielding materials. Modified wood fibers without lignin and hemicellulose are mixed with a biomass adhesive, an aniline monomer solution is sprayed, pre-pressing is conducted, an oxidation solution is sprayed, cold pressing is conducted, aniline is subjected to an oxidation polymerization reaction to generate polyaniline with electrical conductivity and electromagnetic shielding performance, the polyaniline is loaded on the surfaces of the modified wood fibers to form a conductive network, and a blank is obtained; the blank is subjected to hot pressing, the biomass adhesive is subjected to esterification crosslinking to form a three-dimensional crosslinking network, meanwhile, the modified wood fibers and the biomass adhesive generate hydrogen bonding, and a wood fiber prefabricated slab is obtained; the surface of the wood fiber prefabricated slab is coated with an MXene nanosheet solution, MXene nanosheets and polyaniline are tightly combined through electrostatic adsorption and pi-pi conjugation to form an interlaced conductive network, and the conductivity of the composite material is effectively improved.

Description

Technical Field

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

[0002] With the rapid development of modern technology, higher requirements are put forward for the performance of materials in various fields. Especially in electronic devices, communication equipment, and the national defense industry, electromagnetic shielding materials have become a crucial part. Traditional electromagnetic shielding materials such as metal materials have good shielding effects, but they have high processing costs, large weights, strong corrosiveness, and greater environmental impacts. Although carbon-based materials and polymer materials are lightweight, their electromagnetic shielding performance is limited and it is difficult to meet the requirements of high-performance electromagnetic shielding. Therefore, how to develop new materials with lightweight, environmental friendliness, and good electromagnetic shielding performance has become the focus of research.

[0003] In recent years, biomass materials such as wood fibers, bamboo powders, and straws have gradually been applied to the field of electromagnetic shielding materials due to their advantages such as being renewable, environmentally friendly, lightweight, having a wide resource base, and good mechanical properties. However, the electrical conductivity of biomass materials is poor, and the weak electromagnetic shielding performance of wood limits its application in the field of electronic information. Summary of the Invention

[0004] The present invention provides a wood fiber / MXene composite material, a preparation method thereof, and an application thereof, effectively solving the technical problem of insufficient electromagnetic shielding performance existing in the use of biomass materials in the prior art. The present invention composites MXene nanosheets with biomass fibers, endowing 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, and the shielding effectiveness exceeds 50 dB in the frequency range of 8.2 GHz to 12.4 GHz, reaching 47 dB to 58 dB; and the preparation cost is low and it is easy to industrialize production.

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

[0006] Crush the wood fibers, remove the lignin and hemicellulose in the wood fibers to obtain modified wood fibers.

[0007] Mix the modified wood fibers with the biomass adhesive, spray the aniline monomer solution under stirring, pre-press, spray the oxidation solution, cold-press. Aniline undergoes an oxidative polymerization reaction under the action of the oxidation solution to form polyaniline, which is loaded on the surface of the modified wood fibers by hydrogen bonding to obtain a blank. Hot-press the blank, the biomass adhesive undergoes esterification cross-linking to form a three-dimensional cross-linked network, and at the same time, hydrogen bonding occurs between the modified wood fibers and the biomass adhesive to obtain a wood fiber prefabricated board.

[0008] Coat the surface of the wood fiber prefabricated board with the MXene nanosheet solution. Electrostatic adsorption and π-π conjugation occur between the MXene nanosheets and the polyaniline 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 saccharides, 12-70 parts of organic acids and 4-27 parts of distilled water, stir at a speed of 200-300 r / min at 90-100 °C for 1-2 h, add 5-31 parts of deproteinized powder, stir evenly, and cool to room temperature to obtain it.

[0010] As a preferred embodiment, the mass ratio of the modified wood fibers 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 dosage ratio of the modified wood fibers to the aniline monomer solution is 1 g:0.5 mL - 2 mL.

[0012] As a preferred embodiment, the oxidation 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 oxidation 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 nanosheets is 10 μm - 50 μm.

[0014] As a preferred embodiment, the cold pressing is: cold pressing and forming for 30 min under the conditions of -5 °C - 0 °C and 1 MPa - 5 MPa; 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, hot pressing and forming for 18 - 25 min. After hot pressing, depressurize to normal pressure in 4 - 6 min.

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

[0016] As a preferred embodiment, the wood fiber is at least one of tree fiber, shrub fiber and vine fiber; the saccharide 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; the deproteinized powder is at least one of defatted soy protein powder, defatted corn protein powder and cottonseed protein powder.

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

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

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0020] The present invention provides a method for preparing a wood fiber / MXene composite material. First, the wood fibers are crushed, and then the lignin and hemicellulose in the wood fibers are removed to obtain modified wood fibers. The modified wood fibers are mixed with a biomass adhesive, and an aniline monomer solution is sprayed under stirring, followed by pre-pressing, spraying an oxidizing solution, and cold pressing. Under the action of the oxidizing solution, aniline undergoes oxidative polymerization to form polyaniline, which is loaded on the surface of the modified wood fibers by hydrogen bonding to obtain a blank. Since polyaniline has good electrical conductivity and electromagnetic shielding performance, a conductive network is formed on the wood fibers, endowing the composite material with electromagnetic shielding performance. At the same time, the combination of polyaniline and wood fibers can improve the interfacial interaction between the wood fibers and the subsequently coated MXene nanosheets, which is beneficial to the transmission of electrons in the composite material and further enhances 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, hydrogen bonding occurs between the modified wood fibers and the biomass adhesive to obtain a wood fiber prefabricated board. The MXene nanosheet solution is coated on the surface of the wood fiber prefabricated board to obtain a wood fiber / MXene composite material. The MXene nanosheets and polyaniline are tightly combined through electrostatic adsorption and π-π conjugation to form an interwoven conductive network, effectively improving the electrical conductivity of the composite material.

[0021] The biomass adhesive used in the present invention is made of 4-25 parts by mass of sugars, 12-70 parts of organic acids, 4-27 parts of distilled water, and 5-31 parts of deproteinized powder. The sugars, organic acids, and deproteinized powder synergistically form a stable adhesive system. The sugars and organic acids undergo an esterification reaction during heating and stirring, increasing the viscosity and stability of the adhesive. The sugars and deproteinized powder have good compatibility with the wood fibers. The deproteinized powder interacts with the hydroxyl groups on the surface of the wood fibers through hydrogen bonds and van der Waals forces, enhancing the binding force between the adhesive and the wood fibers, ensuring good mechanical properties of the wood fiber prefabricated board, providing a basic support for the improvement of the overall performance, and providing a stable structural basis for the subsequent coating of the MXene nanosheet solution.

[0022] In the present invention, aniline monomers are polymerized on the surface of wood fibers. During the electromagnetic shielding process, good synergistic effects between polyaniline and MXene nanosheets are achieved, endowing the material with excellent electromagnetic shielding performance. Especially in the frequency range of 8.2-12.4 GHz, the shielding effectiveness exceeds 50 dB. By introducing MXene nanosheets, not only the electrical conductivity of the composite material is improved, but also the material is provided with anti-mildew characteristics, extending the service life of the material. The preparation process of the present invention is simple, and there is no glue or formaldehyde in the preparation process, meeting the requirements of green environmental protection and enabling large-scale industrial production. Description of the Drawings

[0023] Figure 1 It is a flowchart for the preparation of the wood fiber / MXene composite material in Example 1 of the present invention.

[0024] Figure 2 SEM image of the aniline-polymerized wood fiber matrix in Example 1 of the present invention.

[0025] Figure 3 Electromagnetic efficiency diagram of the wood fiber / MXene composite materials in Examples 1 to 5 of the present invention.

[0026] Figure 4 SEM comparison diagram of the wood fiber / MXene composite materials in Examples 1 and 4 of the present invention. Among them, in Figures (a), (c), and (e), the coating thickness is 10 μm, Figure (a) is 500 μm, Figure (c) is 5 μm, and Figure (e) is 500 nm; in Figures (b), (d), and (f), the coating thickness is 50 μm, Figure (b) is 500 μm, Figure (d) is 5 μm, and Figure (f) is 500 nm. Detailed implementation manners

[0027] In order to enable those skilled in the art to better understand and implement the technical solution of the present invention, the present invention will be further described below in conjunction with specific embodiments and the accompanying drawings. However, the specific embodiments cited shall not be construed as limiting the present invention. The following test methods and detection methods are all conventional methods unless otherwise specified; the reagents and raw materials are all commercially available unless otherwise specified.

[0028] In view of the technical problems mentioned in the background art of the present invention: the poor conductivity of biomass materials and the weak electromagnetic shielding performance of wood limit its application in the field of electronic information, the present invention provides a wood fiber / MXene composite material, its preparation method and application.

[0029] The technical solution of the present invention will be analyzed and described in detail below.

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

[0031] Crush the wood fiber, remove lignin and hemicellulose in the wood fiber to obtain modified wood fiber.

[0032] Mix the modified wood fiber with a biomass adhesive, spray an aniline monomer solution under stirring, and pre-press. Through pre-pressing, the material density is increased and the interlayer porosity of the material is reduced to prepare for subsequent hot pressing. After pre-pressing, spray an oxidizing solution and cold-press. Aniline undergoes an oxidation polymerization reaction 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. Hot-press the blank, and the biomass adhesive undergoes esterification cross-linking to form a three-dimensional cross-linked network. At the same time, hydrogen bonding occurs between the modified wood fiber and the biomass adhesive to obtain a wood fiber prefabricated board.

[0033] Coat the surface of the wood fiber preform with the MXene nanosheet solution. The MXene nanosheets and polyaniline undergo electrostatic adsorption and π-π conjugation to obtain a wood fiber / MXene composite material.

[0034] In the above technical solution, due to the good conductivity and electromagnetic shielding performance of polyaniline, a conductive network is formed on the wood fibers, endowing the composite material with electromagnetic shielding performance. At the same time, the combination of polyaniline and wood fibers can improve the interfacial interaction between the wood fibers and the subsequently coated MXene nanosheets, which is beneficial to the transmission of electrons in the composite material and further enhances the electromagnetic shielding performance. The MXene nanosheets and polyaniline are tightly combined through electrostatic adsorption and π-π conjugation to form an intertwined conductive network, effectively improving the conductivity of the composite material.

[0035] To increase the interaction force between wood fibers and the internal binding force of the composite material, thereby achieving excellent electromagnetic shielding performance of the composite material, the preparation method of the biomass adhesive is to mix 4 - 25 parts by mass of sugars, 12 - 70 parts by mass of organic acids, and 4 - 27 parts by mass of distilled water, stir at a speed of 200 - 300 r / min at 90 - 100 °C for 1 - 2 h, add 5 - 31 parts by mass of deproteinized powder, stir evenly, and cool to room temperature. According to a mass ratio of 1:2.8 - 3.8, add the biomass adhesive to the modified wood fibers. During preparation, the sugars, organic acids, and deproteinized powder synergistically form a stable adhesive system. The sugars and organic acids undergo an esterification reaction during heating and stirring, increasing the viscosity and stability of the adhesive. The deproteinized powder interacts with functional groups such as hydroxyl groups on the surface of the wood fibers through hydrogen bonds and van der Waals forces, enhancing the binding force between the adhesive and the wood fibers, enabling the wood fiber preform to have a certain mechanical strength, and providing a stable structural basis for subsequent coating with the MXene nanosheet solution. Different ratios of sugars, organic acids, and deproteinized powder affect the bonding performance and stability. The sugars and deproteinized powder have good compatibility with the wood fibers, ensuring the mechanical properties of the preform and providing a basic support for the improvement of the overall performance.

[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 dosage ratio of the modified wood fiber to the aniline monomer solution is 1 g: 0.5 to 2 mL. The oxidation solution is a hydrochloric acid solution of potassium permanganate with a concentration of 0.8 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 and the hydrochloric acid solution are mixed and stirred to form an aniline monomer solution, and potassium permanganate is dissolved in the hydrochloric acid solution to form an oxidation solution. In an acidic environment, potassium permanganate has strong oxidizing properties, which promotes the polymerization reaction of aniline monomers to generate polyaniline. Polyaniline has good electrical conductivity and electromagnetic shielding performance, forms a conductive network on the wood fiber, and imparts electromagnetic shielding performance to the composite material. Hydrochloric acid can provide a relatively stable and moderate acidic environment, which is helpful for the dissolution of aniline and subsequent oxidation polymerization reactions. Moreover, the chloride ions in hydrochloric acid are small in volume and have good solubility, and enter the molecular chain of polyaniline during the polymerization process of aniline, thereby improving the electrical conductivity of polyaniline. In addition, hydrochloric acid is widely sourced, relatively inexpensive, and easy to obtain and use. In contrast, some other strong acids may have stronger corrosiveness and danger, which not only increases the operation risk but also raises the requirements for equipment, and is not conducive to large-scale production. The combination of polyaniline and wood fiber can improve the interfacial interaction between the wood fiber and the subsequently coated MXene nanosheets, which is beneficial to the transmission of electrons in the composite material and further enhances 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 production amount and performance of polyaniline. The preparation of both polyaniline and the adhesive is in an acidic environment, and they produce a synergistic effect, enhancing the overall effect.

[0037] In order to further improve the electrical 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 nanosheets is 10 μm to 50 μm. The concentration and coating thickness of the MXene nanosheet solution affect the electrical conductivity and electromagnetic shielding effect of the composite material. Both polyaniline and MXene nanosheets have good electrical conductivity, and they form an intertwined conductive network in the composite material, effectively improving the electrical conductivity of the composite material.

[0038] To further improve the internal bonding force of the composite material and achieve a better electromagnetic shielding effect, the cold pressing is as follows: cold pressing and forming for 30 min under the conditions of -5°C to 0°C and 1 MPa to 5 MPa; the conditions for the oxidative polymerization reaction of aniline monomers need to be below 0°C, and the range of -5 to 0°C is optimal. The hot pressing is as follows: heating the blank to 140°C to 165°C at a rate of 5 to 10°C / min, increasing the pressure to 3 to 7 MPa at a rate of 1 MPa / min to 2 MPa / min, hot pressing and forming for 18 to 25 min to achieve the curing of the adhesive, further forming the composite material, and under the action of a greater pressure, the physical densification and chemical bonding of the material are synergistically enhanced. After hot pressing, the pressure is released to atmospheric pressure within 4 min to 6 min. When the temperature is between 140°C and 165°C, if the temperature is lower than 140°C, it will cause incomplete curing of the adhesive, and if the temperature is higher than 165°C, it will cause carbonization of the wood fibers. During hot pressing, the pressure is increased to 3 MPa to 7 MPa at a rate of 1 MPa / min to 2 MPa / min to avoid material delamination caused by sudden pressure changes.

[0039] It should be noted that the following interactions will occur among the raw materials during the hot pressing process of the composite material:

[0040] Esterification crosslinking of the biomass adhesive: Under the action of the temperature and pressure during hot pressing, the acid groups in the adhesive further react with the hydroxyl components in the saccharides to undergo an esterification crosslinking reaction to form ester bonds. This crosslinked structure helps to enhance the network structure of the adhesive itself and improve its bonding performance. For example, citric acid (-COOH) in the adhesive reacts with sucrose (-OH) at 140°C to 165°C to generate sucrose citrate ester, forming a three-dimensional crosslinked network.

[0041] Interface hydrogen bond interaction between 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, 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, hydrogen bonds are formed between the polar groups on the polyaniline molecular chain and the hydroxyl groups on the surface of the wood fibers as well as the polar groups in the adhesive, increasing the interaction force between them; on the other hand, under the action of stirring by a kneader and cold pressing, polyaniline is intertwined with the fiber matrix through physical entanglement and other methods, further enhancing the bonding strength between the fiber matrix and polyaniline and improving the performance of the composite material.

[0043] Synergistic mechanism between MXene nanosheets and polyaniline: The two-dimensional layer plane of MXene and the benzene ring of polyaniline enhance electron transport through π-π stacking. At the same time, surface functional groups form hydrogen bonds with polyaniline segments. Secondly, the surface of MXene is negatively charged, while polyaniline is positively charged in the doped state, and the two can achieve close composite through electrostatic attraction. Moreover, the two-dimensional sheets of MXene are intertwined with the fibrous structure of polyaniline to form a three-dimensional conductive path, and through the multiple reflection-absorption mechanism, the electromagnetic shielding efficiency of the composite material can be significantly improved.

[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 1 g: 15 - 30 mL, the crushed wood fibers are immersed in a mixed solution of 2.5 mol / L NaOH and 0.4 mol / L Na 2 SO 3 , boiled for 5 - 7 h, rinsed with distilled water, and then according to the dosage ratio of wood fiber to H 2 O 2 solution of 1 g: 20 - 30 mL, boiled again in 2.5 mol / L H 2 O 2 solution for 2 - 3 h to remove lignin and hemicellulose to obtain.

[0045] It should be noted that the wood fibers used in the present invention are at least one of tree fibers, shrub fibers and vine plant fibers; the saccharides are at least one of sucrose, maltose and lactose; the organic acids are at least one of citric acid, malic acid, gluconic acid, oxalic acid and acetic acid; the deproteinized powder is at least one of defatted soy protein powder, defatted corn protein powder and cottonseed protein powder.

[0046] The technical effects of the present invention will be described below 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 Figure 1 shown, including the following steps:

[0049] (1) Wood fiber treatment: Crush and sieve tree fibers to obtain tree fibers with a length within 5 mm and a diameter within 0.2 mm. According to the dosage ratio of 1 g: 30 mL, immerse the sieved tree fibers in a mixed solution of 2.5 mol / L NaOH and 0.4 mol / L Na 2 SO 3 , boil for 7 h, rinse with distilled water, and then according to the dosage ratio of wood fiber to H 2 O 2 solution of 1 g: 30 mL, in 2.5 mol / L H2 O 2 The solution was boiled again for 3 h to remove lignin and hemicellulose. After being washed with deionized water, it was placed in an oven at 110 °C and dried for 8 h to obtain modified arbor fibers.

[0050] (2) Preparation of biomass adhesive: Weigh 80 g of sucrose, 240 g of citric acid, and 80 g of distilled water, put them into a beaker and stir evenly. Stir at 100 °C at a speed of 250 r / min for 2 h. During the stirring process, gradually add 90 g of defatted soy protein powder. After the reaction ends, cool the mixture to room temperature to obtain the biomass adhesive.

[0051] (3) Preparation of polymer conductive solution: Prepare two portions of hydrochloric acid solution with a concentration of 1 mol / L. Weigh 51 g of aniline and put it into one portion of the hydrochloric acid solution and stir evenly to make the aniline solution fully mixed, obtaining an aniline monomer solution with a concentration of 1.1 mg / mL; Add potassium permanganate to the other portion of the hydrochloric acid solution and stir evenly to adjust the concentration of potassium permanganate to 1 g / mL to obtain the oxidation solution.

[0052] (4) Pre-pressing: According to a mass ratio of 1:2.8, uniformly stir the biomass adhesive and modified arbor fibers in a kneader at a rotation speed of 35 r / min. According to the dosage ratio of 1 g of modified arbor fibers to 1.2 mL of aniline monomer solution, evenly spray the aniline monomer solution through a spray gun. After stirring for 30 min, lay the material well in a pre-pressing molding machine. According to a volume ratio of 1:1.1 of aniline monomer solution to oxidation solution, evenly spray the oxidation solution through a spray gun. After the oxidation solution spraying is completed, control the temperature at 0 °C and cold press for 30 min under a pressure of 2 MPa to make the aniline monomer fully polymerize on the material to obtain a blank.

[0053] (5) Molding: Place the blank in a hot-pressing molding machine. Under the conditions of a hot-pressing temperature of 150 °C, a hot-pressing pressure of 5 MPa, and a hot-pressing time of 20 min, the thickness of the hot-pressing plate is 0.5 mm. After observing that there is no obvious water vapor discharge, release the pressure for 6 min to obtain a wood fiber prefabricated board.

[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 prefabricated board. After drying, obtain a wood fiber / MXene electromagnetic shielding composite material. The coating thickness of the MXene nanosheets is 50 μm, and the shielding effectiveness of the wood fiber / MXene electromagnetic shielding composite material is 57 dB at 8.2 - 12.4 GHz.

[0055] Example 2

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

[0057] (1) Wood fiber treatment: Crush and sieve shrub fibers to obtain shrub fibers with a length within 5 mm and a diameter within 0.2 mm. According to the dosage ratio of 1 g:25 mL, boil the sieved shrub fibers in a mixed solution of 2.5 mol / L NaOH and 0.4 mol / L Na 2 SO 3 for 7 h, rinse with distilled water, and then according to the dosage ratio of shrub fiber to H 2 O 2 solution of 1 g:30 mL, boil in 2.5 mol / L H 2 O 2 solution for another 3 h to remove lignin and hemicellulose. After washing with deionized water, place it in an oven at 110 °C and dry for 8 h to obtain modified shrub fibers.

[0058] (2) Preparation of biomass adhesive: Weigh 65 g of maltose, 175 g of malic acid, and 70 g of distilled water, put them into a beaker and stir evenly. Stir at 100 °C and a speed of 250 r / min for 2 h. During the stirring process, gradually add 90 g of defatted corn protein powder. After the reaction ends, cool the mixture to room temperature to obtain the biomass adhesive.

[0059] (3) Preparation of polymer conductive solution: Prepare two portions of hydrochloric acid solution with a concentration of 1 mol / L. Weigh 36 g of aniline solution and put it into one portion of the hydrochloric acid solution and stir evenly to make the aniline solution fully mixed to obtain an aniline monomer solution with a concentration of 0.5 mg / mL; add potassium permanganate to the other portion of the hydrochloric acid solution and stir evenly to adjust the concentration of potassium permanganate to 0.8 g / mL to obtain the oxidation solution.

[0060] (4) Pre-pressing: According to the mass ratio of 1:3.1, evenly stir the biomass adhesive and modified shrub fibers in a kneader at a rotation speed of 35 r / min. According to the dosage ratio of modified shrub fiber to aniline monomer solution of 1 g:2 mL, evenly spray the aniline monomer solution through a spray gun. After stirring for 30 min, spread the material in a pre-pressing machine. According to the volume ratio of aniline monomer solution to oxidation solution of 1:1.5, evenly spray the oxidation solution through a spray gun. After the oxidation solution spraying is completed, control the temperature at 0 °C and cold press for 30 min under a pressure of 2 MPa to make the aniline monomer fully polymerize on the material to obtain a blank.

[0061] (5) Molding: Place the blank in a hot-pressing machine. Under the conditions of a hot-pressing temperature of 150 °C, a hot-pressing pressure of 5 MPa, and a hot-pressing time of 18 min, the thickness of the hot-pressing plate is 0.5 mm. After observing that there is no obvious water vapor discharge, relieve the pressure for 5 min to obtain a wood fiber prefabricated board.

[0062] (6) Preparation of composite material: Brush the MXene nanosheet solution with a concentration of 2 mg / mL onto the surface of the wood fiber prefabricated board. After drying, a wood fiber / MXene electromagnetic shielding composite material is obtained. The coating thickness of the MXene nanosheets is 20 μm, and the shielding effectiveness of the wood fiber / MXene electromagnetic shielding composite material is 52 dB at 8.2 - 12.4 GHz.

[0063] Example 3

[0064] A preparation method of a wood fiber / MXene composite material, comprising the following steps:

[0065] (1) Wood fiber treatment: Crush and sieve the vine plant fibers to obtain vine plant fibers with a length within 5 mm and a diameter within 0.2 mm. According to the dosage ratio of 1 g:25 mL, place the sieved vine plant fibers in a mixed solution of 2.5 mol / L NaOH and 0.4 mol / L Na 2 SO 3 and boil for 6 h. Rinse with distilled water, and then according to the dosage ratio of vine plant fibers to H 2 O 2 solution of 1 g:25 mL, boil again in 2.5 mol / L H 2 O 2 solution for 2.5 h to remove lignin and hemicellulose. After washing with deionized water, place it in an oven at 110 °C and dry for 7 h to obtain modified vine plant fibers.

[0066] (2) Preparation of biomass adhesive: Weigh 250 g of lactose, 700 g of acetic acid, and 270 g of distilled water, put them into a beaker and stir evenly. Stir at 90 °C at a speed of 250 r / min for 1 h. During the stirring process, gradually add 290 g of defatted corn protein powder. After the reaction ends, cool the mixture to room temperature to obtain the 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 the 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 the hydrochloric acid solution and stir evenly to adjust the concentration of potassium permanganate to 1.3 g / mL to obtain the oxidation solution.

[0068] (4) Pre - pressing: Biomass adhesive and modified liana fiber are evenly stirred in a kneader at a rotation speed of 35 r / min according to a mass ratio of 1:3.0. According to the dosage ratio of modified liana fiber to aniline monomer solution of 1 g:0.8 mL, aniline monomer solution is evenly sprayed through a spray gun. After stirring for 30 min, the material is laid in a pre - pressing molding machine. According to the volume ratio of aniline monomer solution to oxidation liquid of 1:0.7, the oxidation liquid is evenly sprayed through a spray gun. After the spraying of the oxidation liquid is completed, the temperature is controlled at 0 °C, and cold pressing is carried out at a pressure of 2 MPa for 30 min to make the aniline monomer fully polymerize on the material to obtain a blank.

[0069] (5) Molding: The blank is placed in a hot - pressing molding machine. Under the conditions of a hot - pressing temperature of 150 °C, a hot - pressing pressure of 5 MPa, and a hot - pressing time of 20 min, the thickness of the hot - pressing plate is 0.5 mm. After observing that there is no obvious water vapor discharge, the pressure is relieved for 4 min to obtain a wood fiber pre - fabricated board.

[0070] (6) Preparation of composite material: A solution of MXene nanosheets with a concentration of 5 mg / mL is brushed onto the surface of the wood fiber pre - fabricated board. After drying, a wood fiber / MXene electromagnetic shielding composite material is obtained. The coating thickness of the MXene nanosheets is 30 μm, and the shielding effectiveness of the wood fiber / MXene electromagnetic shielding composite material is 54 dB in the range of 8.2 - 12.4 GHz.

[0071] Example 4

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

[0073] (1) Wood fiber treatment: Arbor fibers are crushed and sieved to obtain arbor fibers with a length within 5 mm and a diameter within 0.2 mm. According to the dosage ratio of 1 g:20 mL, the sieved arbor fibers are boiled in a mixed solution of 2.5 mol / L NaOH and 0.4 mol / L Na 2 SO 3 for 6 h, rinsed with distilled water, and then according to the dosage ratio of arbor fiber to H 2 O 2 solution of 1 g:25 mL, boiled again in 2.5 mol / L H 2 O 2 solution for 2.5 h to remove lignin and hemicellulose. After being washed with deionized water, it is placed in an oven at 110 °C and dried for 7 h to obtain modified arbor fibers.

[0074] (2) Preparation of biomass adhesive: Weigh 40 g of sucrose, 120 g of citric acid, and 40 g of distilled water, put them into a beaker and stir evenly. Stir at 90 °C at a speed of 250 r / min for 1 h. During the stirring process, gradually add 50 g of defatted soy protein powder. After the reaction is completed, cool the mixture to room temperature to obtain the biomass adhesive.

[0075] (3) Preparation of polymer conductive solution: Prepare two portions of hydrochloric acid solution with a concentration of 1 mol / L. Weigh 28 g of aniline solution and put it into one portion of the hydrochloric acid solution and stir evenly to make the aniline solution fully mixed, obtaining an aniline monomer solution with a concentration of 0.8 mg / mL; add potassium permanganate to the other portion of the hydrochloric acid solution and stir evenly to adjust the concentration of potassium permanganate to 0.9 g / mL to obtain the oxidation solution.

[0076] (4) Pre-pressing: According to the mass ratio of 1:3.8, evenly stir the biomass adhesive and modified arbor fiber in a kneader at a speed of 35 r / min. According to the dosage ratio of 1 g of modified arbor fiber to 1.5 mL of aniline monomer solution, evenly spray the aniline monomer solution through a spray gun. After stirring for 30 min, spread the material well in a pre-pressing machine. According to the volume ratio of 1:1.2 of aniline monomer solution to oxidation solution, evenly spray the oxidation solution through a spray gun. After the spraying of the oxidation solution is completed, control the temperature at 0 °C and cold press for 30 min under a pressure of 2 MPa to make the aniline monomer fully polymerize on the material to obtain the blank.

[0077] (5) Forming: Place the blank in a hot-pressing machine. Under the conditions of a hot-pressing temperature of 150 °C, a hot-pressing pressure of 5 MPa, and a hot-pressing time of 18 min, the thickness of the hot-pressing plate is 0.5 mm. After observing that there is no obvious water vapor discharge, release the pressure for 5 min to obtain the wood fiber prefabricated board.

[0078] (6) Preparation of composite material: Brush the MXene nanosheet solution with a concentration of 1 mg / mL onto the surface of the wood fiber prefabricated board. After drying, obtain the wood fiber / MXene electromagnetic shielding composite material. The coating thickness of the MXene nanosheets is 10 μm, and the shielding effectiveness of the wood fiber / MXene electromagnetic shielding composite material is 50 dB at 8.2 - 12.4 GHz.

[0079] Example 5

[0080] A preparation method of a wood fiber / MXene composite material, comprising the following steps:

[0081] (1) Wood fiber treatment: Crush and sieve the vine plant fiber to obtain vine plant fiber with a length within 5 mm and a diameter within 0.2 mm. According to the dosage ratio of 1 g:15 mL, put the sieved vine plant fiber into 2.5 mol / L NaOH and 0.4 mol / L Na 2 SO 3in a mixed solution and boiled for 5 h, rinsed with distilled water, and then according to the dosage ratio of liana fiber to H 2 O 2 solution of 1 g:20 mL, in 2.5 mol / L H 2 O 2 solution and boiled again for 2 h to remove lignin and hemicellulose. After washing with deionized water, it was placed in an oven at 110 °C and dried for 6 h to make it dry, and the modified liana fiber was obtained.

[0082] (2) Preparation of biomass adhesive: Weigh 200 g of lactose, 600 g of acetic acid, and 200 g of distilled water, put them into a beaker and stir evenly. Stir at 95 °C at a speed of 250 r / min for 1.5 h. During the stirring process, gradually add 250 g of defatted corn protein powder. After the reaction, cool the mixture to room temperature to obtain the biomass adhesive.

[0083] (3) Preparation of polymer conductive solution: Prepare two portions of hydrochloric acid solution with a concentration of 1 mol / L. Weigh 155 g of aniline and put it into one portion of the hydrochloric acid solution and stir evenly to make the aniline solution fully mixed to obtain an aniline monomer solution with a concentration of 2.0 mg / mL; add potassium permanganate to the other portion of the hydrochloric acid solution and stir evenly to adjust the concentration of potassium permanganate to 1.1 g / mL to obtain the oxidation solution.

[0084] (4) Pre-pressing: According to the mass ratio of 1:2.8, the biomass adhesive and the modified liana fiber were evenly stirred in a kneader at a rotation speed of 35 r / min. According to the dosage ratio of the modified liana fiber to the aniline monomer solution of 1 g:0.5 mL, the aniline monomer solution was evenly sprayed through a spray gun. After stirring for 30 min, the material was laid in a pre-pressing molding machine. According to the volume ratio of the aniline monomer solution to the oxidation solution of 1:0.5, the oxidation solution was evenly sprayed through a spray gun. After the spraying of the oxidation solution was completed, control the temperature at 0 °C and cold press for 30 min under a pressure of 2 MPa to make the aniline monomer fully polymerize on the material to obtain a blank.

[0085] (5) Molding: Place the blank in a hot-pressing molding machine. Under the conditions of a hot-pressing temperature of 150 °C, a hot-pressing pressure of 5 MPa, and a hot-pressing time of 25 min, the thickness of the hot-pressing plate is 0.5 mm. After observing that there is no obvious water vapor discharge, release the pressure for 5 min to obtain a wood fiber prefabricated board.

[0086] (6) Preparation of composite material: Brush the MXene nanosheet solution with a concentration of 4 mg / mL on the surface of the wood fiber prefabricated board. After drying, a wood fiber / MXene electromagnetic shielding composite material is obtained. The coating thickness of the MXene nanosheets is 40 μm, and the shielding effectiveness of the wood fiber / MXene electromagnetic shielding composite material is 55 dB in the range of 8.2 - 12.4 GHz.

[0087] To further illustrate the technical effects of the present invention, the present invention also sets up a comparative example as follows:

[0088] Comparative Example 1

[0089] Compared with Example 1, the difference is that the MXene nanosheet solution is not brushed.

[0090] A preparation method of a wood fiber prefabricated board includes the following steps:

[0091] (1) Wood fiber treatment: Crushing and sieving arbor fibers to obtain arbor fibers with a length within 5 mm and a diameter within 0.2 mm. According to the dosage ratio of 1 g:30 mL, the sieved arbor fibers are boiled in a mixed solution of 2.5 mol / L NaOH and 0.4 mol / L Na 2 SO 3 for 7 h, rinsed with distilled water, and then according to the dosage ratio of wood fiber to H 2 O 2 solution of 1 g:30 mL, boiled again in 2.5 mol / L H 2 O 2 solution for 3 h to remove lignin and hemicellulose. After washing with deionized water, it is placed in an oven at 110°C and dried for 6 - 8 h to obtain modified arbor fibers.

[0092] (2) Preparation of biomass adhesive: Weigh 80 g of sucrose, 240 g of citric acid, and 80 g of distilled water, put them into a beaker and stir evenly. Stir at 100°C at a speed of 250 r / min for 2 h. During the stirring process, gradually add 90 g of defatted soy protein powder. After the reaction ends, cool the mixture to room temperature to obtain a biomass adhesive.

[0093] (3) Preparation of polymer conductive solution: Prepare two portions of hydrochloric acid solution with a concentration of 1 mol / L. Weigh 51 g of aniline and put it into one portion of the hydrochloric acid solution and stir evenly to make the aniline solution fully mixed to obtain an aniline monomer solution with a concentration of 1.1 mg / mL; add potassium permanganate to the other portion of the hydrochloric acid solution and stir evenly to adjust the concentration of potassium permanganate to 1 g / mL to obtain an oxidation solution.

[0094] (4) Pre-pressing: According to the mass ratio of 1:2.8, uniformly stir the biomass adhesive and modified arbor fibers in a kneader at a rotation speed of 35 r / min. According to the dosage ratio of modified arbor fibers to aniline monomer solution of 1 g:1.2 mL, evenly spray the aniline monomer solution through a spray gun. After stirring for 30 min, spread the material in a pre-pressing molding machine. According to the volume ratio of aniline monomer solution to oxidation solution of 1:1.1, evenly spray the oxidation solution through a spray gun. After the oxidation solution spraying is completed, control the temperature at 0°C and cold press at a pressure of 2 MPa for 30 min to make the aniline monomer fully polymerize on the material to obtain a blank.

[0095] (5) Molding: Place the blank in a hot press molding machine. Under the conditions of a hot pressing temperature of 150 °C, a hot pressing pressure of 5 MPa, and a hot pressing time of 20 min, the thickness of the hot pressing plate is 0.5 mm. After observing that there is no obvious water vapor discharge, release the pressure for 6 min to obtain a wood fiber prefabricated board.

[0096] The electromagnetic shielding effectiveness of the above wood fiber prefabricated board is 38 dB in the frequency range of 8.2 - 12.4 GHz.

[0097] Comparative Example 2

[0098] The difference from Example 1 is that the cold pressing process is not carried out, and after directly mixing the modified wood fiber and the biomass adhesive, hot pressing molding is carried out.

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

[0100] (1) Wood fiber treatment: Crush and sieve the arbor fiber to obtain arbor fiber with a length within 5 mm and a diameter within 0.2 mm. According to the dosage ratio of 1 g:30 mL, place the sieved arbor fiber in a mixed solution of 2.5 mol / L NaOH and 0.4 mol / L Na 2 SO 3 and boil for 7 h, rinse with distilled water, and then according to the dosage ratio of wood fiber to H 2 O 2 solution of 1 g:30 mL, boil in 2.5 mol / L H 2 O 2 solution for another 3 h to remove lignin and hemicellulose. After washing with deionized water, place it in an oven at 110 °C and dry for 8 h to make it dry, obtaining modified arbor fiber.

[0101] (2) Preparation of biomass adhesive: Weigh 80 g of sucrose, 240 g of citric acid, and 80 g of distilled water, put them into a beaker and stir evenly. At 100 °C, stir at a speed of 250 r / min for 2 h. During the stirring process, gradually add 90 g of defatted soy protein powder. After the reaction ends, cool the mixture to room temperature to obtain the biomass adhesive.

[0102] (3) Preparation of polymer conductive solution: Prepare two portions of hydrochloric acid solution with a concentration of 1 mol / L. Weigh 51 g of aniline and put it into one portion of the hydrochloric acid solution and stir evenly to make the aniline solution completely mixed, obtaining an aniline monomer solution with a concentration of 1.1 mg / mL; add potassium permanganate to the other portion of the hydrochloric acid solution and stir evenly to adjust the concentration of potassium permanganate to 1 g / mL to obtain the oxidation solution.

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

[0104] (5) Molding: The blank is placed in a hot - pressing machine. Under the conditions of a hot - pressing temperature of 150 °C, a hot - pressing pressure of 5 MPa, and a hot - pressing time of 20 min, the thickness of the hot - pressing plate is 0.5 mm. After observing that there is no obvious water vapor discharge, the pressure is relieved for 6 min, and a wood fiber pre - fabricated board is obtained.

[0105] (6) Preparation of composite material: A solution of MXene nanosheets with a concentration of 3 mg / mL is brush - coated on the surface of the wood fiber pre - fabricated board. After drying, a wood fiber / MXene electromagnetic shielding composite material is obtained. The coating thickness of MXene nanosheets is 50 μm, and the shielding effectiveness of the wood fiber / MXene electromagnetic shielding composite material is 42 dB in the range of 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 present invention are characterized and analyzed. The specific results are as follows:

[0107] Figure 2 This is the SEM image of the aniline - polymerized wood fiber matrix in Example 1 of the present invention. It can be seen from Figure 2 that a continuous coating layer of polyaniline is clearly visible on the modified wood fiber, indicating that aniline is successfully loaded on the fiber surface through an oxidative polymerization reaction, there are no obvious interfacial defects, the two are closely combined, and an intertwined network is formed with the wood fiber.

[0108] Figure 3 This is the electromagnetic effectiveness image of the wood fiber / MXene composite materials in Examples 1 - 5 of the present invention. It can be seen from Figure 3 that in the range of 8.2 - 12.4 GHz (X - band), the shielding effectiveness (SE) of all examples exceeds 47 dB, and the highest reaches 58 dB (Example 1).

[0109] Figure 4SEM comparison diagrams of the wood fiber / MXene composite material obtained by coating the MXene nanosheet solution of the present invention on a wood fiber prefabricated board in different coating thicknesses. Among them, the effects of the coating thickness of 10 μm are shown in Figures (a), (c), and (e). There are local uncovered areas on the surface of the wood fiber prefabricated board, and the sheets are dispersed, which will lead to discontinuous conductive networks. The effects of the coating thickness of 50 μm are shown in Figures (b), (d), and (f). A dense layered structure is formed, which is tightly combined with the polyaniline layer through π-π conjugation and electrostatic adsorption, significantly improving the surface conductivity of the composite material. It can be seen from Figures (b), (d), and (f) that when the coating thickness is 50 μm, a "brick-mortar" sheet stacking structure is formed on the surface of the composite material, significantly enhancing the multiple reflection and absorption capabilities of electromagnetic waves and effectively improving the electromagnetic shielding efficiency of the composite material.

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

Claims

1. A method for preparing a wood fiber / MXene composite material, characterized in that: The following steps are involved: The wood fibers are crushed to remove lignin and hemicellulose from the wood fibers to obtain modified wood fibers; The modified wood fiber and the biomass adhesive are mixed, and an aniline monomer solution is sprayed in a stirring state, pre-pressed, and an oxidizing liquid is sprayed, and cold pressed, and the aniline undergoes an oxidative polymerization reaction under the action of the oxidizing liquid to generate polyaniline, and is loaded on the surface of the modified wood fiber by hydrogen bonding to obtain a blank, and the blank is hot-pressed, and the biomass adhesive undergoes esterification cross-linking to form a three-dimensional cross-linked network, and at the same time, the modified wood fiber and the biomass adhesive are hydrogen-bonded to obtain a wood fiber prefabricated board; The MXene nanosheet solution is coated on the surface of the wood fiber prefabricated board, and the MXene nanosheet and polyaniline produce electrostatic adsorption and π-π conjugation to obtain a wood fiber / MXene composite material.

2. The preparation method according to claim 1, characterized in that: The preparation method of the biomass adhesive comprises the following steps of mixing 4 to 25 parts by mass of sugar, 12 to 70 parts by mass of organic acid and 4 to 27 parts by mass of distilled water, stirring at 90 to 100° C. and a speed of 200 to 300 r / min for 1 to 2 hours, adding 5 to 31 parts of defatted protein powder, stirring evenly, and cooling to room temperature.

3. The preparation method according to claim 2, characterized in that: The mass ratio of the modified wood fiber to the biomass adhesive is 1:2.8-3.

8.

4. 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 dosage ratio of the modified wood fiber to the aniline monomer solution is 1 g:0.5 mL to 2 mL; the oxidizing liquid 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 oxidizing liquid is 1:0.5 to 1.

5.

5. The preparation method according to claim 1, characterized in that: 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.

6. The preparation method according to claim 1, characterized in that: The cold pressing comprises: cold pressing for 30 minutes at -5°C to 0°C and 1MPa to 5MPa; the hot pressing comprises: heating the blank to 140°C to 165°C at a rate of 5 to 10°C / min, increasing the pressure to 3 to 7MPa at a rate of 1MPa / min to 2MPa / min, hot pressing for 18 to 25 minutes, and after hot pressing, releasing the pressure to normal pressure within 4 to 6 minutes.

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

8. The preparation method according to claim 2, 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; the defatted protein powder is at least one of defatted soy protein powder, defatted corn protein powder and cottonseed protein powder.

9. A wood fiber / MXene composite material prepared by the preparation method according to any one of claims 1 to 8.

10. Use of the wood fiber / MXene composite material according to claim 9 in electromagnetic shielding.

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