Surface aldehyde bamboo powder composite material and preparation method thereof

Abstract

The invention provides a surface hydroformylation bamboo powder composite material, the surface hydroformylation bamboo powder composite material comprises surface hydroformylation bamboo powder particles and amino biomacromolecules, the surfaces of the surface hydroformylation bamboo powder particles are provided with hydroformylation cellulose nanofibers, hydroformylation cellulose nanosheets and hydroformylation lignin, wherein one ends of the aldehyde cellulose nanofibers and the aldehyde cellulose nanosheets are embedded into the bamboo powder particles, and the other ends of the aldehyde cellulose nanofibers and the aldehyde cellulose nanosheets extend freely; and wherein the amino biopolymer, the hydroformylated cellulose nanofiber, the hydroformylated cellulose nanosheet and the hydroformylated lignin form a cross-linked network by hydrogen bonding and covalent binding. The invention further provides a method for preparing the surface aldehyde bamboo powder composite material.

Description

Technical Field

[0001] This invention relates to the field of nanotechnology, specifically to a water-resistant, high-strength surface-aldehyde-modified bamboo powder composite material and its preparation method. Background Technology

[0002] In today's society, people use a large number of non-degradable plastic products in daily life and industrial production, generating hundreds of millions of tons of plastic waste globally every year. Most of this waste is discarded, landfilled, or incinerated, and there is still no efficient, clean, and environmentally friendly method to solve this pollution problem. Therefore, developing and producing next-generation biodegradable polymer materials is an important solution to replace non-degradable plastics.

[0003] However, currently commercialized biodegradable polymers such as PLA and PBAT suffer from drawbacks such as demanding degradation conditions and biotoxic degradation products. Therefore, using purely natural, fully biodegradable, and widely sourced bio-based materials represents a more promising path. Bamboo, as a natural biomass, boasts advantages such as rapid growth, high strength, high cellulose content, and wide planting area, and has been widely used in the preparation of structural materials, such as reconstituted bamboo, bamboo particleboard, and bamboo-plastic composites. Unfortunately, most existing modified bamboo materials use resin adhesives or are compounded with traditional petroleum-based plastics, failing to achieve complete degradation. Furthermore, they are prone to swelling upon contact with water, leading to deterioration of mechanical properties, affecting the material's aesthetics, and significantly reducing product lifespan. Users require frequent cleaning and application of waterproof and mildew-resistant coatings, increasing costs and inconvenience. Therefore, there is an urgent need to develop a high-strength bamboo-based material that is intrinsically water-resistant, fully biodegradable, and does not use any resin adhesives or other non-biodegradable materials. Summary of the Invention

[0004] The technical problem to be solved by this application is how to ensure the water resistance, high strength and biodegradability of the material without adding any waterproof and mildew-proof agents, so as to accelerate the realization of my country's strategic vision of "replacing plastic with bamboo" and broaden the application of bamboo-based composite materials in building materials, transportation construction and other fields.

[0005] Therefore, the purpose of this application is to provide a water-resistant, high-strength surface-aldehyde-based bamboo powder composite material and its preparation method.

[0006] Therefore, this application provides the following implementation scheme.

[0007] In one aspect, this application provides a surface-aldehyde-modified bamboo powder composite material, the surface-aldehyde-modified bamboo powder composite material comprising: surface-aldehyde-modified bamboo powder particles and amino biopolymers.

[0008] The surface of the aldehyde-modified bamboo powder particles contains aldehyde-modified cellulose nanofibers, aldehyde-modified cellulose nanosheets, and aldehyde-modified lignin. One end of each aldehyde-modified cellulose nanofiber and nanosheet is embedded within the bamboo powder particle, while the other end extends freely.

[0009] The amino biopolymer, the aldehyde-modified cellulose nanofiber, the aldehyde-modified cellulose nanosheet, and the aldehyde-modified lignin form a cross-linked network through hydrogen bonding and covalent bonding.

[0010] In some embodiments of this application, the particle size of the surface-aldehyde-modified bamboo powder particles is in the range of 0.1 μm to 500 μm, preferably in the range of 1 μm to 200 μm.

[0011] In some embodiments of this application, the diameter of the aldehyde-modified cellulose nanofibers is in the range of 10 nm to 500 nm, preferably in the range of 15 nm to 200 nm, more preferably in the range of 20 nm to 50 nm; and the thickness of the aldehyde-modified cellulose nanosheets is in the range of 10 nm to 500 nm, preferably in the range of 20 nm to 100 nm.

[0012] In some embodiments of this application, the specific surface area of ​​the surface-aldehyde-modified bamboo powder particles is at least 5 m². 2 / g.

[0013] In some embodiments of this application, the crystallinity of the cellulose in the surface-aldehyde-modified bamboo powder particles is less than 50%.

[0014] In some embodiments of this application, the mass fraction of lignin in the surface-aldehyde-modified bamboo powder particles is greater than 30%.

[0015] In some embodiments of this application, the amino biopolymer is selected from one or more of soy protein isolate, silk fibroin, collagen, keratin, gelatin, and chitosan.

[0016] In some embodiments of this application, the amount of the amino biopolymer is in the range of 0.5% to 8% relative to the weight of the surface-aldehyde-modified bamboo powder particles, preferably in the range of 1% to 6%.

[0017] In some embodiments of this application, in the aldehyde-modified cellulose nanofibers, aldehyde-modified cellulose nanosheets, and aldehyde-modified lignin, the molar ratio of aldehyde groups to hydroxyl groups is in the range of 1% to 20%, preferably in the range of 5% to 20%.

[0018] In another aspect, this application provides a method for preparing the above-mentioned surface-aldehyde-modified bamboo powder composite material, the method comprising the following steps:

[0019] (a) Surface activation treatment of bamboo powder in an activation solution;

[0020] (b) The surface-activated bamboo powder obtained in step (a) is added to an aqueous solution containing an aldehyde oxidizing agent, and then an aldehyde oxidizing reaction is carried out under light-protected heating conditions. After the aldehyde oxidizing reaction is completed, a quencher is added to quench the unreacted aldehyde oxidizing agent.

[0021] (c) The reaction product obtained in step (b) is filtered, washed with water, and then dispersed in water to obtain an aqueous dispersion of aldehyde-modified bamboo powder particles.

[0022] (d) The aqueous dispersion of aldehyde-modified bamboo powder particles obtained in step (c) is mechanically treated and dried to obtain surface-aldehyde-modified bamboo powder particles.

[0023] (e) The surface-aldehyde-modified bamboo powder particles obtained in step (d) are mixed with an aqueous solution of amino biopolymers, and then allowed to stand until a gel is obtained; and

[0024] (f) The gel obtained in step (e) is compressed and molded to obtain the surface-aldehyde-based bamboo powder composite material.

[0025] In some embodiments of this application, the activation solution in step (a) is selected from aqueous solutions of sodium hydroxide, potassium hydroxide, sodium sulfite, sulfurous acid, sodium chlorite, or hydrogen peroxide.

[0026] In some embodiments of this application, the aldehyde oxidizing agent in step (b) includes sodium periodate.

[0027] In some embodiments of this application, the aqueous solution containing the aldehyde-modifying agent in step (b) further comprises a cellulose protectant, wherein the cellulose protectant is selected from one or more of methanol, ethanol, n-propanol, isopropanol, 1,3-propanediol, and n-butanol.

[0028] In some embodiments of this application, in the reaction system of step (b), the mass ratio of the surface-activated bamboo powder to the total mass of the reaction system is in the range of 5% to 20%, the mass ratio of the cellulose protectant is in the range of 10% to 25%, and the mass ratio of sodium periodate to the surface-activated bamboo powder is in the range of 1:10 to 4:1.

[0029] In some embodiments of this application, the mechanical treatment in step (d) includes one or more of stirring, grinding, ball milling, high-speed shearing, ultrasonic crushing, and high-pressure homogenization.

[0030] In some embodiments of this application, the compression molding pressure in step (f) is in the range of 0.5 MPa to 800 MPa, preferably in the range of 20 MPa to 600 MPa, more preferably in the range of 50 MPa to 200 MPa, and the temperature is in the range of 80°C to 250°C, preferably in the range of 85°C to 210°C, more preferably in the range of 90°C to 160°C.

[0031] The technical solution of the present invention has the following beneficial effects.

[0032] This application provides a water-resistant, high-strength surface-aldehyde-based bamboo powder composite material and its preparation method. The surface-aldehyde-based bamboo powder composite material of this application features green environmental protection, biodegradability, high strength, water resistance, and high hardness. The preparation process of the composite material does not require the addition of any resins or other substances that are difficult to degrade under natural conditions or harmful to the environment as adhesives or hydrophobic coatings, thus making it environmentally friendly. Attached Figure Description

[0033] Figure 1 Transmission electron microscope (TEM) images of surface-aldehyde-modified bamboo powder particles and bamboo powder raw material particles obtained in Example 1 of the preparation of raw materials for this application.

[0034] Figure 2 Infrared spectra of the surface-aldehyde-modified bamboo powder particles and bamboo powder raw materials obtained in Example 1 of the preparation of raw materials of this application.

[0035] Figure 3 X-ray diffraction patterns of surface-aldehyde-modified bamboo powder particles, surface-activated bamboo powder particles, and bamboo powder raw material particles obtained in Example 1 of the preparation of raw materials for this application.

[0036] Figure 4 X-ray photoelectron spectroscopy of the surface-aldehyde-modified bamboo powder particles and bamboo powder raw material particles obtained in Example 1 of the preparation of raw materials for this application.

[0037] Figure 5 Scanning electron microscope (SEM) images of surface-aldehyde-modified bamboo powder particles and bamboo powder raw material particles obtained in Example 1 of the preparation of raw materials for this application.

[0038] Figure 6 Thermogravimetric curves of surface-aldehyde-modified bamboo powder particles and bamboo powder raw material particles obtained in Example 1 of the preparation of raw materials for this application in the temperature range of 30°C to 1000°C under air atmosphere.

[0039] Figure 7 This is a photograph of the surface-aldehyde-based bamboo powder composite material obtained in Example 1 of this application.

[0040] Figure 8This is a SEM image of the fracture section of the surface-aldehyde-modified bamboo powder composite material obtained in Example 1 of this application.

[0041] Figure 9 The three-point bending stress-strain curves and Vickers hardness diagrams of the surface-aldehyde-based bamboo powder composite material obtained in Example 1 of this application in the dry state and after soaking in water for 24 hours are shown.

[0042] Figure 10 The mass gain rate and thickness expansion rate of the surface aldehyde-modified bamboo powder composite material obtained in Example 1 of this application are shown after immersion in water for 24 hours.

[0043] Figure 11 This is a photograph of the surface-aldehyde-based bamboo powder composite material obtained in Example 2 of this application.

[0044] Figure 12 This is a SEM image of the fracture section of the surface-aldehyde-modified bamboo powder composite material obtained in Example 2 of this application.

[0045] Figure 13 The three-point bending stress-strain curves and Vickers hardness diagrams of the surface-aldehyde-based bamboo powder composite material obtained in Example 2 of this application are shown in the dry state and after soaking in water for 24 hours.

[0046] Figure 14 The mass gain rate and thickness expansion rate of the surface aldehyde-modified bamboo powder composite material obtained in Example 2 of this application are shown after soaking in water for 24 hours.

[0047] Figure 15 This is a photograph of the surface-aldehyde-based bamboo powder composite material obtained in Example 3 of this application.

[0048] Figure 16 This is a SEM image of the fracture section of the surface-aldehyde-based bamboo powder composite material obtained in Example 3 of this application.

[0049] Figure 17 The three-point bending stress-strain curves and Vickers hardness diagrams of the surface-aldehyde-based bamboo powder composite material obtained in Example 3 of this application are shown in the dry state and after soaking in water for 24 hours.

[0050] Figure 18 The mass gain rate and thickness expansion rate of the surface aldehyde-modified bamboo powder composite material obtained in Example 3 of this application are shown after soaking in water for 24 hours.

[0051] Figure 19 This is a photograph of the surface-aldehyde-based bamboo powder structural material obtained in Comparative Example 1 of this application.

[0052] Figure 20 This is a SEM image of the fracture cross section of the surface-aldehyde-based bamboo powder structural material obtained in Comparative Example 1 of this application.

[0053] Figure 21 The three-point bending stress-strain curves and Vickers hardness diagrams of the surface-aldehyde-based bamboo powder structural material obtained in Comparative Example 1 of this application are shown in the dry state and after being soaked in water for 24 hours.

[0054] Figure 22 The mass gain rate and thickness expansion rate of the surface aldehyde-based bamboo powder structural material obtained in Comparative Example 1 of this application are shown after immersion in water for 24 hours.

[0055] Figure 23 This is a photograph of the surface-aldehyde-based bamboo powder composite material obtained in Comparative Example 2 of this application.

[0056] Figure 24 This is a SEM image of the fracture cross section of the surface-aldehyde-modified bamboo powder composite material obtained in Comparative Example 2 of this application.

[0057] Figure 25 The three-point bending stress-strain curves and Vickers hardness diagrams of the surface-aldehyde-based bamboo powder composite material obtained in Comparative Example 2 of this application are shown in the dry state and after immersion in water for 24 hours.

[0058] Figure 26 The mass gain and thickness expansion rates of the surface-aldehyde-based bamboo powder composite material obtained in Comparative Example 2 of this application are shown after immersion in water for 24 hours.

[0059] Figure 27 This is a photograph of the surface-activated bamboo powder structural material obtained in Comparative Example 3 of this application.

[0060] Figure 28 This is a SEM image of the fracture cross section of the surface-activated bamboo powder structural material obtained in Comparative Example 3 of this application.

[0061] Figure 29 The three-point bending stress-strain curves and Vickers hardness diagrams of the surface-activated bamboo powder structural material obtained in Comparative Example 3 of this application are shown in the dry state and after soaking in water for 24 hours.

[0062] Figure 30 The mass gain rate and thickness expansion rate of the surface-activated bamboo powder structural material obtained in Comparative Example 3 of this application are shown after soaking in water for 24 hours. Detailed Implementation

[0063] To further understand the present invention, preferred embodiments of the present invention are described below in conjunction with examples. However, these descriptions are only for further illustrating the specific implementation process and features of the present invention, and are not intended to limit the scope of protection of the present invention.

[0064] To address the issue of poor water resistance in bamboo and the use of large amounts of non-degradable resin adhesives and hydrophobic coatings in existing commercially available bamboo products, this invention provides a water-resistant, high-strength surface-formaldehyde-based bamboo powder composite material and its preparation method.

[0065] In the method of this invention, bamboo powder, a byproduct produced in large quantities during bamboo product processing, undergoes a series of physicochemical treatments to achieve surface aldehyde-based oxidation. This is then combined with amino biopolymers, cross-linked, and hot-pressed to obtain a water-resistant, high-strength composite material. Specifically, the surface of the bamboo powder is activated to expose the cellulose, and then an aldehyde-based oxidation reaction using an aldehyde-based reagent such as sodium periodate converts some of the hydroxyl groups in the cellulose and lignin on the bamboo powder surface into aldehyde groups. Further, mechanical treatment transforms the cellulose into cellulose nanosheets and cellulose nanofibers. Then, amino biopolymers are used to form a cross-linked network with the aldehyde-based lignin and aldehyde-based nanocellulose. Finally, a board forming process further increases the degree of cross-linking of this network, causing the bamboo powder particles to move closer together to form a high-density composite material. This composite material can achieve mechanical properties close to those of a dry state after prolonged immersion in water without adding any resin adhesives. Its bending strength and hardness far exceed those of commonly used plastics and are comparable to bamboo plywood. No resins or other substances that are difficult to degrade under natural conditions or harmful to the environment are added during the production of this composite material as adhesives or hydrophobic coatings. The resulting bamboo-based composite material is characterized by being green and environmentally friendly, biodegradable, high-strength, water-resistant, and high-hardness.

[0066] Unbound by any theoretical constraints, the inventors believe that in the bamboo-based composite material of this invention, the amino-based biopolymers and the aldehyde-based cellulose and lignin extending from the surface-aldehyde-treated bamboo powder form a cross-linked network through the formation of Schiff base, acetal, and hemiacetal structures. By reducing the exposed hydrophilic groups on the surface, the density of the composite material is increased, significantly reducing the interfacial damage effect and water absorption swelling effect caused by water molecule intrusion. Simultaneously, this dense cross-linked network structure results in the surface-aldehyde-treated composite material possessing flexural strength and Vickers hardness far exceeding those of common plastics. This invention utilizes the interfacial construction method of surface aldehyde treatment and amino-based biopolymer composites to obtain a water-resistant, high-strength, high-hardness, and biodegradable bamboo-based composite material.

[0067] 1) Water-resistant, high-strength surface-formaldehyde-based bamboo powder composite material

[0068] This application discloses a surface-aldehyde-modified bamboo powder composite material, which comprises: surface-aldehyde-modified bamboo powder particles and amino biopolymers.

[0069] The surface of the aldehyde-modified bamboo powder particles contains aldehyde-modified cellulose nanofibers, aldehyde-modified cellulose nanosheets, and aldehyde-modified lignin. One end of each aldehyde-modified cellulose nanofiber and nanosheet is embedded within the bamboo powder particle, while the other end extends freely.

[0070] The amino biopolymer, the aldehyde-modified cellulose nanofiber, the aldehyde-modified cellulose nanosheet, and the aldehyde-modified lignin form a cross-linked network through hydrogen bonding and covalent bonding.

[0071] This application presents a surface-aldehyde-based bamboo powder composite material, a high-strength bamboo-based structural material formed by cross-linking aldehyde-based nanocellulose and amino biopolymers. It features biodegradability, high strength, high hardness, and good water resistance. The composite material is obtained from surface-aldehyde-based bamboo powder through amino polymer cross-linking and board molding processes. The surface-aldehyde-based bamboo powder composite material of this application is prepared by pre-gelling and hot-pressing, forming a cross-linked network containing Schiff base, acetal, and hemiacetal structures between the bamboo powder particles, thus completing the composite material preparation without the need for additional resin adhesives or recalcitrant polymer waterproof coatings.

[0072] The term "composite material" refers to a material obtained by combining surface-aldehyde-based bamboo powder with amino biopolymers, where the surface-aldehyde-based bamboo powder is the main stress-bearing phase, and the amino biopolymer is added as an environmentally friendly and biodegradable bamboo powder interfacial crosslinking agent. The surface-aldehyde-based bamboo powder structural material of this application is a composite material.

[0073] The term "resin adhesives and non-degradable polymer waterproof coatings" refers to phenolic resins, urea-formaldehyde resins, epoxy resins, polypropylene, polyethylene, polyvinyl chloride, polystyrene, polyurethane, melamine-formaldehyde resins, acrylic resins, fluoropolymers, and modified asphalt, which are currently widely used in the engineered wood products industry.

[0074] The term "crosslinked network containing Schiff base, acetal, and hemiacetal structures" refers to networks formed by physical entanglement, hydrogen bonds, van der Waals forces, and the interaction between aldehyde-based bamboo powder, aldehyde-based cellulose nanofibers, aldehyde-based cellulose nanosheets, and aldehyde-based lignin, as well as hemiacetals and acetals formed between cellulose aldehyde and hydroxyl groups. It also refers to networks formed by hydrogen bonds, van der Waals forces, and the interaction between aldehyde-based nanocellulose and aldehyde-based lignin and amino biopolymers, as well as Schiff base structures formed between amino and aldehyde groups, and hemiacetals and acetals formed between hydroxyl and aldehyde groups. This complex multi-level crosslinked network involving micron-sized bamboo powder particles, nano-sized cellulose, and amino biopolymers enables the composite material to achieve both high strength and high hardness mechanical properties without the addition of any resin adhesives. The retention of as much lignin as possible, a naturally occurring hydrophobic substance in plant cell walls, contributes to the composite material's water resistance. More importantly, the resulting Schiff base and acetal structures shield the surface hydroxyl groups, forming a highly cross-linked structural material. This transforms the bamboo powder structure from a hydrogen-bonded to a covalent-bonded bonding mode, preventing the adsorption, penetration, and destruction of water molecules. This composite material solves the problem of poor water resistance in traditional bamboo without requiring additional hydrophobic modification or frequent application of hydrophobic coatings. This invention simultaneously addresses the mechanical property degradation and pollution problems caused by the addition of resin adhesives and hydrophobic coatings of recalcitrant polymers, providing a promising alternative material for solving plastic pollution.

[0075] The amino biopolymer in the surface-aldehyde-modified bamboo powder composite material of the present invention can be a mechanically activated amino biopolymer. The amino biopolymer can be selected from one or more of soy protein isolate, silk fibroin, collagen, keratin, gelatin, and chitosan. The amount of amino biopolymer added relative to the mass of the surface-aldehyde-modified bamboo powder particles ranges from 0.5% to 8%, preferably from 1% to 6%. The amino biopolymer acts as a crosslinking agent in the present invention, optimizing the mechanical properties of the material within a certain range while ensuring its water resistance. However, excessive addition will lead to a decrease in the mechanical properties and loss of water resistance.

[0076] Therefore, the surface-aldehyde-modified bamboo powder composite material is mainly obtained by molding surface-aldehyde-modified bamboo powder particles. The surface-aldehyde-modified bamboo powder particles account for more than 50% of the total mass of the composite material system, preferably more than 75%, and more preferably more than 95%.

[0077] In the surface-aldehyde-modified bamboo powder composite material of the present invention, the surface-aldehyde-modified bamboo powder can be directly formed into a structural material through a board molding process, utilizing the interaction between aldehyde-modified lignin, aldehyde-modified cellulose nanofibers, and aldehyde-modified cellulose nanosheets at the bamboo powder surface interface. An amino-based biopolymer crosslinking agent is added to form a high-performance structural material. The present invention obtains a biodegradable, high-strength, high-hardness, and water-resistant structural material without the need for any additional flame retardants or recalcitrant polymers. The preparation method of the present invention is also lower in cost and more environmentally friendly.

[0078] In the surface-aldehyde-modified bamboo powder composite material of the present invention, a strong interfacial structure can be formed on the surface of the surface-aldehyde-modified bamboo powder particles, consisting of a cross-linked network of aldehyde-modified lignin, aldehyde-modified cellulose nanofibers, and aldehyde-modified cellulose nanosheets with amino biopolymers. This results in the surface-aldehyde-modified bamboo powder composite material possessing the following properties:

[0079] i) The bending strength in all directions reaches more than 100 MPa;

[0080] ii) Vickers hardness value above 45;

[0081] iii) Flexural modulus above 5 GPa;

[0082] iv) The density of the surface-formaldehyde-based bamboo powder composite material is greater than 0.9 g / cm³. 3 ;

[0083] v) After the surface-aldehyde-based bamboo powder composite material is immersed in deionized water for 24 hours, the retention rate of Vickers hardness and flexural strength is at least 70%;

[0084] vi) After the surface-aldehyde-based bamboo powder composite material is soaked in deionized water for 24 hours, the mass increase rate is less than 1% and the thickness expansion rate is less than 5%.

[0085] vii) The surface-formaldehyde-based bamboo powder composite material, when tested by a dynamic mechanical thermal analyzer under double cantilever beam loading mode, maintains a storage modulus above 1 GPa at temperatures ranging from 25°C to 160°C.

[0086] viii) The surface-formaldehyde-based bamboo powder composite material described above can be softened and degraded by soaking in alkaline aqueous solution (pH greater than 9) or acidic aqueous solution (pH less than 4). The decomposition products can be directly buried in the soil for further composting treatment to achieve a degradation rate of more than 80%.

[0087] 2) Preparation method of surface-aldehyde-modified bamboo powder composite material

[0088] This disclosure also discloses a method for preparing the above-mentioned surface-aldehyde-modified bamboo powder composite material, the method comprising the following steps:

[0089] (a) Surface activation treatment of bamboo powder in an activation solution;

[0090] (b) The surface-activated bamboo powder obtained in step (a) is added to an aqueous solution containing an aldehyde oxidizing agent, and then an aldehyde oxidizing reaction is carried out under light-protected heating conditions. After the aldehyde oxidizing reaction is completed, a quencher is added to quench the unreacted aldehyde oxidizing agent.

[0091] (c) The reaction product obtained in step (b) is filtered, washed with water, and then dispersed in water to obtain an aqueous dispersion of aldehyde-modified bamboo powder particles.

[0092] (d) The aqueous dispersion of aldehyde-modified bamboo powder particles obtained in step (c) is mechanically treated and dried to obtain surface-aldehyde-modified bamboo powder particles.

[0093] (e) The surface-aldehyde-modified bamboo powder particles obtained in step (d) are mixed with an aqueous solution of amino biopolymers, and then allowed to stand until a gel is obtained; and

[0094] (f) The gel obtained in step (e) is compressed and molded to obtain the surface-aldehyde-based bamboo powder composite material.

[0095] The surface-aldehyde-modified bamboo powder particles in this application are bamboo powder micron particles with a large number of cellulose nanofibers or cellulose nanosheets embedded in the particle interior at one end and freely extended at the other end on the surface. Some of the hydroxyl groups on the cellulose nanofibers and cellulose nanosheets have been converted into aldehyde groups. The aromatic structure of the lignin molecules on the surface of the surface-aldehyde-modified bamboo powder produces some ortho-quinone structures under the oxidation of the aldehyde-modifying reagent, and the aliphatic side chain hydroxyl groups of the lignin molecules have been partially oxidized into aldehyde groups.

[0096] In this application, the bamboo powder raw material includes, but is not limited to, powder obtained by crushing and grinding the stems of plants of the Poaceae family and Bambusa genus such as Moso bamboo, Nan bamboo, Giant dragon bamboo, Ci bamboo, Arrow bamboo, Yellow bamboo, Green skin bamboo, Tea bamboo, and Arrow Ci bamboo. The fineness of the powder is preferably 30 to 2000 mesh, more preferably 80 to 500 mesh, and the cellulose content should be greater than 30%.

[0097] The particle size of the surface-aldehyde-modified bamboo powder particles is preferably 0.1 to 500 micrometers, more preferably 1 to 200 micrometers. The cellulose content of the surface-aldehyde-modified bamboo powder particles is preferably 30% to 85%, more preferably 40% to 65%. The lignin content of the surface-aldehyde-modified bamboo powder is preferably 15% to 35%, more preferably 15% to 25%.

[0098] In this application, the term "surface aldehyde-modified" refers to the microscopic chemical structure of aldehyde-modified cellulose and aldehyde-modified lignin on the surface of bamboo powder. Specifically, it refers to the exposure of lignin and cellulose nanofibers and cellulose nanosheets on the surface of bamboo powder, wherein some of the hydroxyl groups in the lignin, cellulose nanofibers, and cellulose nanosheets have been converted into aldehyde groups. Preferably, the molar ratio of aldehyde groups to hydroxyl groups is 1% to 20%, more preferably 5% to 20%. The diameter of the exposed aldehyde-modified cellulose nanofibers in the surface-aldehyde-modified bamboo powder can be less than 500 nm, preferably less than 200 nm, more preferably less than 50 nm. The thickness of the aldehyde-modified cellulose nanosheets can be less than 500 nm, preferably less than 200 nm, more preferably less than 100 nm.

[0099] In this application, the activation solution is a solution system capable of oxidatively decomposing or hydrolyzing lignin and hemicellulose. Its function is to expose more cellulose and lignin on the surface of bamboo powder to participate in the aldehyde oxidation reaction, reduce the molecular weight of surface lignin, and thus lower the glass transition temperature of lignin. Preferably, the activation solution can be selected from one or more of the following: sodium hydroxide aqueous solution, potassium hydroxide aqueous solution, sodium sulfite aqueous solution, sulfurous acid aqueous solution, sodium chlorite aqueous solution, hydrogen peroxide aqueous solution, sodium hydroxide-sodium sulfite aqueous solution, sodium chlorite-acetic acid aqueous solution, hydrogen peroxide-acetic acid aqueous solution, phosphoric acid aqueous solution, and sulfuric acid aqueous solution, more preferably sodium hydroxide aqueous solution and sodium hydroxide-sodium sulfite aqueous solution. The activation solution can also be a eutectic solvent such as choline chloride-lactic acid or choline chloride-oxalic acid, or a solvent capable of dissolving biomolecules such as acetone. Preferably, the mass concentration of the activation solution can be 1% to 50%, and the activation reaction time can be 1 to 120 hours, preferably 3 to 80 hours, more preferably 3 to 50 hours. The surface activation temperature can be 10 to 120°C, preferably 30 to 120°C, and more preferably 50 to 100°C.

[0100] In this application, the aldehyde-modifying agent includes sodium periodate. The aqueous solution containing the aldehyde-modifying agent can be prepared by combining sodium periodate, a cellulose protectant, and water. Specifically, for this reaction system, the surface-activated bamboo powder particles account for 5% to 20% of the total mass of the system, preferably 10% to 20%; the mass ratio of sodium periodate to surface-activated bamboo powder is 1:10 to 4:1, preferably 1:1 to 2:1; the cellulose protectant accounts for 10% to 25% of the total mass of the reaction system, preferably 10% to 20%. The cellulose protectant can be selected from one or more of methanol, ethanol, n-propanol, isopropanol, 1,3-propanediol, and n-butanol. The remaining component is water.

[0101] In this application, the aldehyde oxidization reaction is a reaction in which the C2-C3 covalent bonds on the glycosylated structural units of cellulose are broken by the oxidation of sodium periodate, and the attached hydroxyl groups are oxidized to aldehyde groups. The reaction temperature of the aldehyde oxidization reaction is preferably from 10°C to 80°C, and the reaction time is preferably from 30 minutes to 1440 minutes, more preferably from 120 minutes to 720 minutes, and even more preferably from 240 minutes to 720 minutes.

[0102] In this application, the mechanical processing method may include one or more of stirring, grinding, ball milling, high-speed shearing, ultrasonic crushing and high-pressure homogenization, and the mechanical processing time may be from 10 minutes to 60 minutes.

[0103] In this application, the drying method is preferably one or more of freeze drying, atmospheric pressure drying, high temperature drying, and reduced pressure high temperature drying, with freeze drying being the most preferred.

[0104] In this application, before mixing with surface-aldehyde-modified bamboo powder particles, the amino biopolymer can be mechanically activated to expose more characteristic functional groups and thus exhibit higher chemical reactivity with the surface-aldehyde-modified bamboo powder particles. Specifically, mechanical activation may include the following steps: adjusting the pH of the solvent water according to the solubility characteristics of the amino biopolymer, adding the amino biopolymer, and after stirring and sonicating to ensure complete dissolution, mechanically activating the solution. The preferred mechanical treatment methods are one or more of stirring, grinding, ball milling, high-pressure homogenization, high-speed shearing, and ultrasonic crushing, more preferably ultrasonic crushing or high-speed shearing.

[0105] The amino biopolymer can be selected from one or more of soy protein isolate, silk fibroin, collagen, keratin, gelatin, and chitosan. The amount of amino biopolymer added is 0.5% to 8% relative to the mass of the surface-aldehyde-treated bamboo powder, preferably 1% to 6%, and more preferably 5%.

[0106] In the method for preparing surface-aldehyde-modified bamboo powder composite material of this application, surface-aldehyde-modified bamboo powder particles are first added to an aqueous solution containing mechanically activated amino biopolymers and heated to gel. The aldehyde-modified nanocellulose and aldehyde-modified lignin on the surface and between the bamboo powder particles approach each other and form covalent bonds under the cross-linking effect of the amino biopolymers. Then, the moisture is removed by a drying and molding process, and the bamboo powder particles approach each other, resulting in stronger hydrogen bonds, van der Waals forces, covalent bonds and other interactions at the interface of the bamboo powder particles. Finally, a biodegradable, high-strength, high-hardness and water-resistant structural material is obtained.

[0107] In a specific example, the drying and forming process is one or more of the conventional drying and forming processes such as compression, hot pressing, vacuum drying, and natural drying.

[0108] Compression molding involves compression within a mold, the mold being selected from commonly used molding processes such as stainless steel, aluminum alloy, and graphite molds, with no restrictions on the shape or size of the mold. In the compression molding process, the pressure can range from 0.5 MPa to 800 MPa, preferably from 20 MPa to 600 MPa, more preferably from 50 MPa to 200 MPa, and the temperature can range from 80°C to 250°C, preferably from 85°C to 210°C, and more preferably from 90°C to 160°C.

[0109] In summary, this invention provides a water-resistant, high-strength surface-aldehyde-modified bamboo powder composite material and its preparation method. According to the method of this invention, surface-aldehyde-modified bamboo powder particles with aldehyde-modified cellulose nanofibers, aldehyde-modified cellulose nanosheets, and aldehyde-modified lignin on their surface can be prepared. By blending and crosslinking this surface-aldehyde-modified bamboo powder with amino biopolymers and using a board manufacturing process, a dense composite material with a covalently crosslinked network of aldehyde-modified cellulose nanofibers, aldehyde-modified lignin, and amino biopolymers on the surface interface of the bamboo powder particles can be obtained. This multi-scale crosslinked network structure allows the material to fully disperse stress during loading, achieving high strength and high hardness mechanical properties. The covalently crosslinked network formed by the reaction of aldehyde groups with hydroxyl and amino groups shields or consumes hydrophilic hydroxyl groups, inhibiting the adsorption, diffusion, and penetration of water molecules, thus maintaining most of the mechanical properties even under high humidity environments or after prolonged immersion in water. Furthermore, since this composite material does not contain any additional resin adhesives or recalcitrant polymer hydrophobic coatings, it can fully degrade in alkaline aqueous solutions and composting treatments, and does not produce any toxic or harmful gases during normal use. The production process is environmentally friendly, simple, and efficient. The composite material provided by this invention outperforms most commercially available plastics, resins, bamboo-plastic composites, and reconstituted bamboo in terms of mechanical properties, water resistance, and degradation ability, demonstrating strong competitiveness and application potential.

[0110] Example

[0111] To further understand the present invention, the following detailed description of the surface-aldehyde-based bamboo powder composite material provided by the present invention is provided in conjunction with the embodiments. The scope of protection of the present invention is not limited by the following embodiments.

[0112] The reagents used in the following examples are all commercially available and were used directly without any special treatment.

[0113] Performance testing methods

[0114] The infrared spectra of the surface-aldehyde-modified bamboo powder and bamboo powder raw materials mentioned in this specification were obtained by sample preparation using the KBr pellet method well known in the art.

[0115] The crystallinity mentioned in this specification is calculated by subtracting the contrast at 2θ=18 from the contrast at 2θ=22.7 in the XRD pattern and then dividing by the contrast at 2θ=22.7.

[0116] The X-ray photoelectron spectra of surface-aldehyde-modified bamboo powder and bamboo powder raw materials mentioned in this specification were measured using an Al Kα X-ray source with a Thermo Scientific X-ray photoelectron spectrometer.

[0117] The three-point bending stress-strain curves mentioned in this specification were measured at room temperature using an Instron 5565 A universal testing machine with a bending fixture span of 12.5 mm and sample dimensions of approximately 25 mm × 3 mm × 2.5 mm.

[0118] The Vickers hardness mentioned in this specification is measured at room temperature using a Vickers hardness tester and its associated diamond pyramid indenter.

[0119] The mass gain rate mentioned in this specification is calculated by fully immersing a composite material with dimensions of approximately 25 mm × 10 mm × 2 mm in about 200 mL of tap water, periodically removing it and drying the surface moisture, measuring its mass before immersion and after a certain immersion time, and then using the formula "mass gain rate = 100% × (mass before immersion - mass after immersion) / mass before immersion".

[0120] The thickness expansion rate mentioned in this specification is calculated by completely immersing a composite material of approximately 25 mm × 10 mm × 2 mm in approximately 200 mL of tap water, periodically removing it and drying the surface moisture, measuring its thickness before and after immersion, and then using the formula "thickness expansion rate = 100% × (thickness before immersion - thickness after immersion) / thickness before immersion".

[0121] First, an example of preparing surface-aldehyde-modified bamboo powder particles, which serve as the basic unit of the structural material described in this invention, is provided. The resulting surface-aldehyde-modified bamboo powder particles will be used to prepare the composite material in the example.

[0122] Example 1 of raw material preparation

[0123] A) Add 200 g of bamboo powder with a particle size of 80 mesh to 2 L of 1 mol / L sodium hydroxide aqueous solution, stir in a water bath at 80℃ for 2 hours to complete the surface activation step;

[0124] B) The surface-activated bamboo powder particles were thoroughly washed with deionized water until the pH of the filtrate was equal to 7. The filtrate was then added to a 2L aldehyde oxidizing reagent solution containing 250mL of 1,3-propanediol and 100g of sodium periodate. The reaction vessel was covered with aluminum foil to protect it from light. The reaction was carried out for 5 hours under water bath heating and stirring at 45°C. Then, 150mL of ethylene glycol was added and the reaction was continued for 1 hour under the same water bath heating and stirring conditions. The reaction mixture was washed with deionized water until the pH of the filtrate was equal to 7 to obtain the reaction product.

[0125] C) The reaction product was dispersed in 3L of deionized water. The dispersion was processed 10 times with a mill at 3000 rpm. The dispersion was then freeze-dried to obtain surface-aldehyde-modified bamboo powder particles.

[0126] Figure 1 The images show transmission electron microscopy (TEM) images of the obtained surface-aldehyde-modified bamboo powder particles and the raw bamboo powder particles. As can be seen from the images, the surface of the obtained surface-aldehyde-modified bamboo powder particles is uniformly distributed with cellulose nanofibers and cellulose nanosheets, while the surface of the untreated bamboo powder has a smooth surface. The diameter of the nanofibers and the thickness of the nanosheets range from 5 to 50 nanometers.

[0127] Figure 2 The infrared spectra of the obtained surface-aldehyde-modified bamboo powder particles and bamboo powder raw materials are shown in the figure. The surface-aldehyde-modified bamboo powder at 885 cm⁻¹... -1 The presence of a distinct hemiacetal structure absorption peak is due to the reaction of the aldehyde groups on the aldehyde-modified cellulose on the surface of bamboo powder with the hydroxyl groups on other cellulose molecules to form a hemiacetal, which prevents it from showing a distinct aldehyde peak.

[0128] Figure 3 The X-ray diffraction patterns are shown for the obtained surface-aldehyde-modified bamboo powder particles, surface-activated bamboo powder particles, and bamboo powder raw materials. After surface activation treatment to remove some amorphous lignin and hemicellulose, the crystallinity of the surface-activated bamboo powder was improved. However, the sodium periodate oxidation reaction destroyed the crystalline structure of bamboo powder cellulose maintained by hydrogen bonds, resulting in a rapid decrease in its crystallinity. This can be seen as a testament to the successful conduct of the sodium periodate oxidation reaction.

[0129] Figure 4 The X-ray photoelectron spectra of the obtained surface-aldehyde-modified bamboo powder particles and bamboo powder raw materials are shown. After fitting and peak separation, it can be seen that the C=O structure of the surface-aldehyde-modified bamboo powder is significantly increased.

[0130] Figure 5 SEM images of the obtained surface-aldehyde-modified bamboo powder particles and bamboo powder raw materials.

[0131] Figure 6Thermogravimetric curves of the obtained surface-aldehyde-modified bamboo powder particles and bamboo powder raw materials in air atmosphere within a temperature range of 30℃ to 1000℃.

[0132] Example 2 of raw material preparation

[0133] A) Add 200 g of bamboo powder with a particle size of 200 mesh to 2 L of 1 mol / L potassium hydroxide aqueous solution, stir in a water bath at 80°C for 4 hours to complete the surface activation step;

[0134] B) The surface-activated bamboo powder particles were thoroughly washed with deionized water until the pH of the filtrate was equal to 7. The filtrate was then added to a 2L aldehyde hydration reagent solution containing 250mL n-propanol and 200g sodium periodate. The reaction vessel was covered with aluminum foil to protect it from light. The reaction was carried out for 4 hours under water bath heating and stirring at 60°C. Then, 150mL ethylene glycol was added and the reaction was continued for 1 hour under the same water bath heating and stirring conditions. The reaction mixture was washed with deionized water until the pH of the filtrate was equal to 7 to obtain the reaction product.

[0135] C) Disperse the reaction product in 3L of deionized water, process it with a high-speed shear machine at 10,000 rpm for 30 minutes, and freeze-dry the dispersion to obtain surface-aldehyde-modified bamboo powder particles.

[0136] Example 3 of raw material preparation

[0137] A) Add 200 g of bamboo powder with a particle size of 500 mesh to 2 L of 2 mol / L potassium hydroxide aqueous solution, and stir in a water bath at 80°C for 1.5 hours to complete the surface activation step;

[0138] B) The surface-activated bamboo powder particles were thoroughly washed with deionized water until the pH of the filtrate was equal to 7. The filtrate was then added to a 2L aldehyde hydration reagent solution containing 250mL isopropanol and 100g sodium periodate. The reaction vessel was covered with aluminum foil to protect it from light. The reaction was carried out for 12 hours under water bath heating and stirring at 60°C. Then, 150mL ethylene glycol was added and the reaction was continued for 1 hour under the same water bath heating and stirring conditions. The reaction mixture was washed with deionized water until the pH of the filtrate was equal to 7 to obtain the reaction product.

[0139] C) Disperse the reaction product in 3L of deionized water, treat the aqueous dispersion of the above reaction product with a 600W ultrasonic crusher for 2 hours, and freeze-dry the dispersion to obtain surface aldehyde-modified bamboo powder particles.

[0140] The following are examples of the composite material of the present invention:

[0141] Example 1

[0142] A) Mix 10 g of surface-aldehyde-modified bamboo powder particles with mechanically activated soy protein isolate aqueous solution (net content of amino biopolymer is 0.5 g), use a mechanical stirrer to stir the mixture at 300 rpm at 60°C for 60 minutes, and then let it stand for 12 hours to complete gelation;

[0143] B) Place the gel obtained in step A) into a container with a size of 6*6 cm. 2 In a stainless steel mold, after most of the moisture is removed by extrusion, a positive pressure of 100 MPa is applied to the mold head at 100°C and maintained for 6 hours. After demolding, the composite material is cut and polished to obtain a plate-shaped composite material.

[0144] Figure 7 The image shows a photograph of the obtained surface-aldehyde-modified bamboo powder composite material. As can be seen from the image, the composite material is hard and smooth, with no obvious surface defects, and a density of 1.24 g / cm³. 3

[0145] Figure 8 The image shows the SEM image of the fracture cross section of the obtained surface-aldehyde-modified bamboo powder composite material.

[0146] Figure 9 The three-point bending stress-strain curves and Vickers hardness diagrams of the obtained surface aldehyde-modified bamboo powder composite material in the dry state and after soaking in water for 24 hours are shown.

[0147] Figure 10 The mass gain and thickness expansion rate of the obtained surface-aldehyde-modified bamboo powder composite material after immersion in water for 24 hours are shown.

[0148] Example 2

[0149] A) Mix 10 g of surface-aldehyde-modified bamboo powder particles with mechanically activated gelatin aqueous solution (net content of amino biopolymer is 0.5 g), stir the mixture at 300 rpm at 60°C for 90 minutes using a mechanical stirrer, and then let it stand for 12 hours to complete gelation.

[0150] B) Place the gel obtained in step A) into a container with a size of 6*6 cm. 2 In a stainless steel mold, after most of the moisture is removed by extrusion, a positive pressure of 50 MPa is applied to the mold head at 80°C and maintained for 6 hours. After demolding, the composite material is cut and polished to obtain a plate-shaped composite material.

[0151] Figure 11 The image shows a photograph of the obtained surface-aldehyde-modified bamboo powder composite material. As can be seen from the image, the composite material is hard and smooth, with no obvious surface defects, and a density of 1.29 g / cm³. 3

[0152] Figure 12The image shows the SEM image of the fracture section of the obtained surface-aldehyde-modified bamboo powder composite material.

[0153] Figure 13 The three-point bending stress-strain curves and Vickers hardness diagrams of the obtained surface aldehyde-modified bamboo powder composite material in the dry state and after soaking in water for 24 hours are shown.

[0154] Figure 14 The mass gain and thickness expansion rate of the obtained surface-aldehyde-modified bamboo powder composite material after immersion in water for 24 hours are shown.

[0155] Example 3

[0156] A) Mix 10 g of surface-aldehyde-modified bamboo powder particles with mechanically activated protonated chitosan aqueous solution (net content of amino biopolymer is 0.2 g), stir the mixture at 300 rpm at 70°C for 120 minutes using a mechanical stirrer, and then let it stand for 12 hours to complete gelation.

[0157] B) Place the gel obtained in step A) into a container with a size of 6*6 cm. 2 In a stainless steel mold, after most of the moisture is removed by extrusion, a positive pressure of 200 MPa is applied to the mold head at 120°C and maintained for 6 hours. After demolding, the composite material is cut and polished to obtain a plate-shaped composite material.

[0158] Figure 15 This is a photograph of the obtained surface-aldehyde-modified bamboo powder composite material. As can be seen from the image, the composite material is hard and smooth, with no obvious surface defects, and a density of 1.28 g / cm³. 3

[0159] Figure 16 The image shows the SEM image of the fracture section of the obtained surface-aldehyde-modified bamboo powder composite material.

[0160] Figure 17 The three-point bending stress-strain curves and Vickers hardness diagrams of the obtained surface aldehyde-modified bamboo powder composite material in the dry state and after soaking in water for 24 hours are shown.

[0161] Figure 18 The mass gain and thickness expansion rate of the obtained surface-aldehyde-modified bamboo powder composite material after immersion in water for 24 hours are shown.

[0162] Comparative Example 1

[0163] A) Place 11 g of surface-aldehyde-modified bamboo powder granules directly into a 6*6 cm container. 2 In a stainless steel mold, after most of the moisture is removed by squeezing, a positive pressure of 100 MPa is applied to the mold head at 100°C and maintained for 6 hours. After demolding, the material is cut and polished to obtain a surface-formaldehyde-based bamboo powder structural material.

[0164] Figure 19 The image shows a photograph of the obtained surface-aldehyde-modified bamboo powder structural material. As can be seen from the image, the structural material is hard and smooth, with no obvious surface defects, and a density of 1.26 g / cm³. 3

[0165] Figure 20 The image shows the SEM image of the fracture cross section of the obtained surface-aldehyde-modified bamboo powder structural material.

[0166] Figure 21 The three-point bending stress-strain curves and Vickers hardness diagrams of the obtained surface aldehyde-based bamboo powder structural material in the dry state and after soaking in water for 24 hours are shown.

[0167] Figure 22 The mass gain and thickness expansion rates of the obtained surface-aldehyde-based bamboo powder structural material after immersion in water for 24 hours are shown.

[0168] Comparative Example 2

[0169] A) Mix 10 g of surface-aldehyde-modified bamboo powder with mechanically activated soy protein isolate aqueous solution (net content of amino biopolymer is 1 g), and stir the mixture at 300 rpm at 50°C for 120 minutes using a mechanical stirrer. Then let it stand for 12 hours to complete gelation.

[0170] B) Place the gel obtained in step A) into a container with a size of 6*6 cm. 2 In a stainless steel mold, after most of the moisture is removed by extrusion, a positive pressure of 100 MPa is applied to the mold head at 100°C and maintained for 6 hours. After demolding, the composite material is cut and polished to obtain a plate-shaped composite material.

[0171] Figure 23 This is a photograph of the obtained surface-aldehyde-modified bamboo powder composite material. As can be seen from the image, the composite material is hard and smooth, with no obvious surface defects, and a density of 1.09 g / cm³. 3

[0172] Figure 24 The image shows the SEM image of the fracture section of the obtained surface-aldehyde-modified bamboo powder composite material.

[0173] Figure 25 The three-point bending stress-strain curves and Vickers hardness diagrams of the obtained surface aldehyde-modified bamboo powder composite material in the dry state and after soaking in water for 24 hours are shown.

[0174] Figure 26 The mass gain and thickness expansion rate of the obtained surface-aldehyde-modified bamboo powder composite material after immersion in water for 24 hours are shown.

[0175] Comparative Example 3

[0176] A) Add 12 g of surface-activated bamboo powder directly to a 6*6 cm sample. 2 In a stainless steel mold, a positive pressure of 120 MPa is applied to the mold head at 150°C and maintained for 8 hours. After demolding, the material is cut and polished to obtain a plate-shaped structure.

[0177] Figure 27 The image shows a photograph of the obtained surface-activated bamboo powder structural material. As can be seen from the image, the structural material is hard and smooth, with no obvious surface defects, and a density of 1.18 g / cm³. 3

[0178] Figure 28 The image shows the SEM image of the fracture cross section of the obtained surface-activated bamboo powder structural material.

[0179] Figure 29 The three-point bending stress-strain curves and Vickers hardness diagrams of the obtained surface-activated bamboo powder structural material in the dry state and after soaking in water for 24 hours are shown.

[0180] Figure 30 The mass gain and thickness expansion rates of the obtained surface-activated bamboo powder structural material after immersion in water for 24 hours are shown.

[0181] The experimental results from the above examples and comparative examples show that the flexural strength of the surface-aldehyde-based bamboo powder composite materials in Examples 1-3 is greater than 120 MPa both before and after immersion in deionized water, and there is no significant decrease before and after immersion; while the flexural strength of the structural materials in Comparative Examples 1-3 decreases significantly after immersion. The Vickers hardness of the surface-aldehyde-based bamboo powder composite materials in Examples 1-3 is all above 50, and only decreases slightly after immersion in deionized water, while the Vickers hardness of the structural materials in Comparative Examples 1-3 decreases significantly after immersion. The surface-aldehyde-based bamboo powder composite materials in Examples 1-3 exhibit very low mass gain and thickness expansion rates after immersion in deionized water, indicating excellent water resistance.

[0182] It should be understood that the above description is merely a specific embodiment of the present invention, and the present invention is not limited thereto. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A surface aldehyde groupated bamboo powder composite material, characterized in that, The surface aldehyde group-modified bamboo powder composite comprises surface aldehyde group-modified bamboo powder particles and an amino biopolymer, wherein the surface aldehyde group-modified bamboo powder particles have aldehyde group-modified cellulose nanofibers, aldehyde group-modified cellulose nanosheets, and aldehyde group-modified lignin on their surfaces, wherein one end of the aldehyde group-modified cellulose nanofibers and the aldehyde group-modified cellulose nanosheets is embedded in the bamboo powder particles, and the other end is freely stretched; and wherein the amino biopolymer, the aldehyde group-modified cellulose nanofibers, the aldehyde group-modified cellulose nanosheets, and the aldehyde group-modified lignin form a crosslinked network through hydrogen bonding and covalent bonding.

2. The surface- aldehyde -functionalized bamboo flour composite of claim 1, wherein, The particle size of the surface aldehyde group-modified bamboo powder particles is in the range of 0.1 μm to 500 μm.

3. The surface- aldehyde -functionalized bamboo flour composite of claim 1, wherein, The diameter of the aldehyde group-modified cellulose nanofibers is in the range of 10 nm to 500 nm, and the thickness of the aldehyde group-modified cellulose nanosheets is in the range of 10 nm to 500 nm.

4. The surface- aldehyde -functionalized bamboo flour composite of claim 1, wherein, The amino biopolymer is selected from one or more of soybean protein isolate, silk fibroin, collagen, keratin, gelatin, and chitosan.

5. The surface- aldehyde -functionalized bamboo flour composite of claim 1, wherein, The amount of the amino biopolymer is in the range of 0.5% to 8% relative to the weight of the surface aldehyde group-modified bamboo powder particles.

6. The surface- aldehyde -functionalized bamboo flour composite of claim 1, wherein, In the aldehyde group-modified cellulose nanofibers, aldehyde group-modified cellulose nanosheets, and aldehyde group-modified lignin, the molar ratio of aldehyde groups to hydroxyl groups is in the range of 1% to 20%.

7. A method of preparing the surface aldehyde groupated bamboo powder composite material according to any one of claims 1 to 6, characterized in that, The method comprises the following steps: (a) surface activation treatment of bamboo powder in an activation solution; (b) adding the surface-activated bamboo powder obtained in step (a) to an aqueous solution containing an aldehyde group-modifying agent, then performing an aldehyde group-modification reaction under light-avoiding heating conditions, and adding a quenching agent to quench unreacted aldehyde group-modifying agent after the aldehyde group-modification reaction is completed; (c) filtering the reaction product obtained in step (b), washing with water, then dispersing in water to obtain an aqueous dispersion of aldehyde group-modified bamboo powder particles; (d) mechanical treatment and drying of the aqueous dispersion of aldehyde group-modified bamboo powder particles obtained in step (c) to obtain surface aldehyde group-modified bamboo powder particles; (e) mixing the surface aldehyde group-modified bamboo powder particles obtained in step (d) with an aqueous solution of an amino biopolymer, then standing to obtain a gel; and (f) compression molding of the gel obtained in step (e) to obtain the surface aldehyde group-modified bamboo powder composite.

8. The method of claim 7, wherein, The activation solution in step (a) is selected from an aqueous sodium hydroxide solution, an aqueous potassium hydroxide solution, an aqueous sodium sulfite solution, an aqueous sulfurous acid solution, an aqueous sodium chlorite solution, or an aqueous hydrogen peroxide solution.

9. The method of claim 7, wherein, The aldehyde group-modifying agent in step (b) includes sodium periodate.

10. The method of claim 7, wherein, The pressure in the compression molding in step (f) is in the range of 0.5 MPa to 800 MPa, and the temperature is in the range of 80°C to 250°C.

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