A method of reconstituting natural bamboo into high performance bamboo-based materials

Abstract

The application relates to the technical field of bamboo-based material manufacturing, and particularly discloses a method for rebuilding natural bamboo into high-performance bamboo-based material, which has the technical points that natural bamboo is subjected to fiber opening treatment to obtain bamboo fibers, the bamboo fibers are placed in sealed bags, the left and right ends of the sealed bags are provided with air valves, the air valves are connected with a vacuum pump and a pipeline, air and moisture in the sealed bags are removed through vacuum, a high-concentration aluminum ion solution is sucked into the sealed bags, the sealed bags are kept vacuum, the atmospheric pressure is used to compress the sealed bags, the solution is uniformly diffused in the sealed bags, and the bamboo fibers and the aluminum ions are tightly crosslinked in the process. The method can uniformly and tightly combine the bamboo fibers and the aluminum ions, and the aluminum ions can enter the interior of the bamboo fibers under the action of the atmospheric pressure; compared with a physical deposition mode, the method can more tightly combine the bamboo fibers and the aluminum ions, and the scheme is more efficient.

Description

Technical Field

[0001] This invention relates to the field of bamboo-based material manufacturing technology, and more specifically, to a method for reconstructing natural bamboo into high-performance bamboo-based materials. Background Technology

[0002] The vigorous development of modern industry is inseparable from the widespread use of advanced materials. Steel, aluminum, and various alloy materials, due to their high strength, are widely used in aerospace, construction materials, transportation, and other industries. However, these materials suffer from problems such as heavy weight, high cost, and huge carbon emissions. With the implementation of global carbon neutrality policies and the need for sustainable development, related industries are moving towards low energy consumption, low carbon emissions, low cost, and lower material weight. Developing new lightweight, strong, durable, and sustainable advanced materials is therefore crucial. In this context, natural sustainable materials such as bamboo are a viable option for future development and utilization. Global bamboo resources are abundant and widely distributed, with extensive cultivation in various regions worldwide, covering a total area of ​​approximately 36 million hectares. Bamboo grows rapidly, with a peak growth rate of up to one meter per day. The cycle from planting to maturity and harvesting takes as little as three years, compared to the 50-60 years required for timber to mature. Bamboo has a significant growth rate advantage, and once planted, it can be harvested multiple times, resulting in high economic benefits. In addition, bamboo has an excellent carbon sequestration capacity, 1.46 times that of cedar and 1.33 times that of tropical rainforest. According to relevant statistics, the annual carbon sequestration of each hectare of bamboo forest is about 5.1 tons (equivalent to fixing 13.6 tons of carbon dioxide per year). These excellent natural characteristics give bamboo a huge advantage and promising application prospects in the context of carbon neutrality development.

[0003] As a natural material, bamboo's main components are cellulose, lignin, and hemicellulose, with cellulose accounting for approximately 55%, lignin approximately 30%, and hemicellulose approximately 8%. This orderly arrangement of the three components endows bamboo with high mechanical strength. Currently, natural bamboo is used in road and bridge construction, interior furniture decoration, and building construction. Furthermore, bamboo's high mechanical strength lays the foundation for developing advanced bamboo-based composite materials. However, the mechanical properties of natural bamboo have limitations (tensile strength is generally between 100-150 MPa, and bending strength is generally between 50-60 MPa), which is significantly lower than the theoretical mechanical strength of cellulose protofibrils. Natural bamboo is also flammable, a fatal flaw that severely limits the durability and reliability of bamboo-based materials. Therefore, overcoming bamboo's brittleness and improving its strength and flame-retardant properties are necessary steps in preparing advanced bamboo-based materials.

[0004] Natural bamboo fiber lacks specific functionalities, and some materials prepared directly from natural bamboo fiber cannot meet specific functional requirements. To prepare functional materials, existing technologies involve introducing metal ions or other functional elements into bamboo fiber. To improve the flame retardancy of bamboo fiber and its products, aluminum ions can be added to enhance this property. Aluminum ions bind to the hydroxyl, carboxyl, and carbonyl groups of bamboo fiber through ionic cross-linking, thus loading the bamboo fiber and giving it flame-retardant functionality. Currently, the common addition method is physical deposition, which involves spraying a high-concentration aluminum ion solution onto the surface of the bamboo fiber or directly immersing the bamboo fiber in a high-concentration aluminum ion solution, followed by drying and evaporation to remove moisture. The remaining aluminum ions then cross-link with the bamboo fiber. However, in existing technologies, most of the aluminum ions remain on the surface and do not easily penetrate the interior of the bamboo fiber, making it difficult to maintain uniform aluminum ion loading. Furthermore, this method requires a large amount of water, which can severely affect the strength and structure of the bamboo fiber, and evaporating the water is time-consuming and inefficient.

[0005] Therefore, this application proposes a method for reconstructing natural bamboo into high-performance bamboo-based materials to solve the above problems. The method involves tightly cross-linking aluminum ions with bamboo fibers, allowing aluminum ions to enter the bamboo fibers more efficiently and uniformly, thus achieving a tight cross-linking between the two. Summary of the Invention

[0006] The purpose of this invention is to solve the technical problems mentioned in the background section and to provide a method for reconstructing natural bamboo into high-performance bamboo-based materials.

[0007] The above-mentioned objective of the present invention is achieved as follows: A method for reconstructing natural bamboo into a high-performance bamboo-based material includes the following steps: S1. Fiber splitting treatment of natural bamboo: A fiber splitting system is constructed using hydrogen peroxide solution and ozone gas to oxidize some of the lignin and hemicellulose in natural bamboo and break the internal lignin hydrogen bond network to obtain dispersed bamboo fibers. S2. Arrange the bamboo fibers processed in step S1 neatly into a specific sealed bag. There are air valves on both the left and right ends of the sealed bag, namely valve A and valve B. Connect valve A to a vacuum pump and valve B to a conduit. Place the other end of the conduit into a high-concentration aluminum ion solution. Then keep valves A and B closed. S3. Turn on the vacuum pump and open valve A to fully remove the gas and excess moisture from the sealed bag, and maintain the vacuum for 5 minutes. S4. Slowly open valve B to allow the high-concentration aluminum ion solution to enter the sealed bag. After fully opening valve B, the solution will quickly enter the sealed bag and combine with the bamboo fiber. Once the measured amount of solution has entered the sealed bag, close valve B. Under the action of the vacuum pump, the solution gradually permeates towards valve A, with valve A at the top and valve B at the bottom, so that the solution permeates evenly into every corner of the bamboo fiber. S5. Once bubbles or solution are observed at valve A, immediately close valve A to keep the sealed bag in a vacuum state. Use atmospheric pressure to make the aluminum ion solution evenly distributed in the sealed bag and evenly cross-linked with the bamboo fiber. That is, the aluminum ions enter the gaps in the bamboo fiber, making the two tightly cross-linked. S6. Place the sealed bag in a cool, ventilated place and maintain the vacuum condition for 10 hours.

[0008] Furthermore, it also includes: orthogonally arranging the bamboo fibers after ion crosslinking in step S6 and then hot-pressing them to make the cellulose of the bamboo fibers highly compact and reinforced to form an "ionic bond-hydrogen bond" network structure, thereby reconstructing a high-performance bamboo-based material.

[0009] Furthermore, the fiber opening process in step S1 specifically includes the following steps: 1) Remove the green and yellow parts of the natural bamboo and cut it into strips; 2) Prepare a hydrogen peroxide solution and immerse the treated bamboo strips in the hydrogen peroxide solution. Heat and introduce ozone gas to start the oxidation reaction. After the oxidation treatment time is up, take out the softened bamboo fibers, rinse them repeatedly in deionized water, flatten them with a roller, disperse them in water, and then dry them to obtain dispersed bamboo fibers.

[0010] Furthermore, the vacuum level in step S3 is 0.08 MPa.

[0011] Compared with the prior art, the present invention has the following beneficial effects: 1. The solution of the present invention enables bamboo fiber and aluminum ions to be uniformly and tightly bonded, and aluminum ions can enter the interior of bamboo fiber under atmospheric pressure. Compared with physical deposition, the method of the present invention can make the two bond more tightly, and the solution of the present invention is more efficient in operation. 2. The method of this invention reconstructs natural bamboo into high-performance bamboo-based materials, achieving a major breakthrough in terms of lightweight and high strength. The bamboo-based materials obtained by the method of this invention have a density of only 0.83, similar to that of natural bamboo (0.76), and far lower than that of high-density bamboo steel (1.63). Furthermore, the reconstructed natural bamboo exhibits excellent weather resistance and stability. The reconstruction method of this invention provides a feasible approach for the efficient utilization of global bamboo resources and the development of lightweight and high-strength composite materials. Attached Figure Description

[0012] Figure 1 This is a schematic diagram of the sealed bag in an embodiment of the present invention; Figure 2 This is a schematic diagram of cross-linked ions in an embodiment of the present invention; Figure 3 These are the X-ray diffraction (XRD) patterns of natural bamboo, dispersed bamboo fiber, and reconstituted bamboo in embodiments of the present invention; Figure 4 The SAXS patterns of natural bamboo, open-fiber bamboo, and reconstructed bamboo in the embodiments of the present invention are shown in the following: (a, b, and c are natural bamboo, open-fiber bamboo, and reconstructed bamboo, respectively). Figure 5 This is a comparison of the density and tensile strength of reconstructed bamboo and bamboo fiber-based polymer materials in the embodiments of the present invention; Figure 6 This is a comparison of the specific strength of reconstructed bamboo and metal alloy materials in the embodiments of the present invention; Figure 7 The bending strength of reconstructed bamboo and natural bamboo in the L and T directions in the embodiments of the present invention; Figure 8 This is a comparison of the impact toughness of reconstructed bamboo and natural bamboo in the embodiments of the present invention; Figure 9 This is a comparison of the compressive strength of reconstructed bamboo and natural bamboo in the embodiments of the present invention; Figure 10 This refers to the puncture resistance of the reconstructed bamboo in this embodiment of the invention; Figure 11 The limiting oxygen index and ignition time of reconstructed bamboo and natural bamboo in the embodiments of the present invention; Figure 12 This is a thermogravimetric analysis of reconstructed bamboo and natural bamboo in the embodiments of the present invention; Figure 13 This is a comparison of the heat release rate (HRR) between reconstructed bamboo and natural bamboo in the embodiments of the present invention; Figure 14 This is a comparison of the total heat release (THR) of reconstructed bamboo and natural bamboo in the embodiments of the present invention; Figure 15 This is a comparison of the effective heat of combustion (EHC) between reconstructed bamboo and natural bamboo in the embodiments of the present invention; Figure 16 This is a comparison of the total smoke emissions (TSP) of reconstructed bamboo and natural bamboo in the embodiments of the present invention; Figure 17 The water resistance of reconstructed bamboo, natural bamboo, and surface-modified reconstructed bamboo in the embodiments of the present invention is as follows. Detailed Implementation

[0013] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0014] The implementation of the present invention will be described in detail below with reference to specific embodiments.

[0015] Reference Figures 1-17 The image shows a preferred embodiment of the present invention.

[0016] Example: An embodiment of the present invention provides a method for reconstructing natural bamboo into a high-performance bamboo-based material. This method uses atmospheric pressure to force aluminum ions into the interior of bamboo fibers, causing them to be tightly cross-linked together.

[0017] The equipment and materials required in the method of this invention include: vacuum pump, conduit, sealing bag, etc.

[0018] The system mechanism in the method of this invention is as follows: a vacuum-permeation system is used to tightly crosslink bamboo fiber with aluminum ions. Atmospheric pressure is used to force aluminum ions from the outside of the bamboo fiber into its interior, so that they diffuse evenly and combine with various groups on the surface of the bamboo fiber.

[0019] The process of this invention is as follows: Natural bamboo is split to obtain bamboo fibers; the bamboo fibers are placed in a sealed bag with valves at both ends. These valves are connected to a vacuum pump and a conduit. Air and moisture are removed from the sealed bag through vacuum, and a high-concentration aluminum ion solution is drawn into the sealed bag. The vacuum inside the sealed bag is then maintained, and atmospheric pressure is used to compress it, causing the solution to diffuse evenly within the bag. During this process, the bamboo fibers and aluminum ions are tightly cross-linked. The cross-linked fibers are then orthogonally arranged and hot-pressed to ensure a highly compact arrangement of cellulose fibers and enhance the "ionic-hydrogen bond" network, ultimately reconstructing a super-strong bamboo-based material.

[0020] The specific implementation of the present invention is as follows: The processed bamboo fibers are neatly arranged into specific sealed bags (such as...). Figure 1As shown, the sealed bag has valves (Valve A and Valve B) at both ends. Connect Valve A to a vacuum pump and Valve B to a conduit. Place the other end of the conduit into a high-concentration aluminum ion solution. After filling with bamboo fiber and connecting the conduit, keep Valves A and B closed. First, turn on the vacuum pump and open Valve A to fully remove gas and excess moisture from the sealed bag, maintaining a vacuum of 0.08 MPa for 5 minutes. Second, open Valve B to allow the high-concentration aluminum ion solution to enter the sealed bag. Open the valve slowly; once fully open, the solution will quickly enter the sealed bag and combine with the bamboo fiber. Once a measured amount of solution has entered the sealed bag, close Valve B. Under the action of the vacuum pump, the solution will gradually permeate towards Valve A, with Valve A above and Valve B below, ensuring the solution evenly permeates every corner of the bamboo fiber. Third, upon observing bubbles or solution appearing at valve A, immediately close valve A to maintain a vacuum state in the sealed bag. Atmospheric pressure allows the aluminum ion solution to evenly distribute throughout the sealed bag, cross-linking with the bamboo fibers. During this process, aluminum ions enter the gaps in the bamboo fibers, resulting in a tight cross-linking. Fourth, place the sealed bag in a cool, ventilated place, maintaining the vacuum condition for 10 hours. Ideally, after these ions have cross-linked (e.g., ... Figure 2 The fibers (as shown) are orthogonally arranged and then hot-pressed to make the cellulose highly compact and enhance the effect of the "ionic bond-hydrogen bond" network, ultimately rebuilding super-strong bamboo.

[0021] The following is a further detailed description of the embodiments of the present invention and their progressive significance: I. The fiber opening mechanism adopted in this invention The internal structure of natural bamboo is mainly composed of rigid fiber bundles and thin-walled cells, exhibiting a porous structure in cross-section. The fiber bundles are arranged highly parallel to their growth direction, while the thin-walled cells are parallel or perpendicular to the growth direction. These fiber bundles and thin-walled cells adhere to each other through a low-strength polymer matrix composed of lignin and hemicellulose. In other words, within the natural bamboo fiber, cellulose is encapsulated by lignin and hemicellulose, primarily connected by hydrogen bonds, forming a lignin-hydrogen bond network. However, due to the inherent brittleness of this lignin-hydrogen bond network, the inefficient load transfer caused by weak interfacial interactions between the hard and thin-walled cells in natural bamboo, and the presence of numerous defects, the mechanical properties of natural bamboo face a bottleneck, significantly lower than the theoretical mechanical strength of cellulose protofibrils. After the natural bamboo is split into fibers, the pore walls of the bamboo fibers become thinner, resulting in a more porous structure. Some of the original lignin is removed, and the lignin-hydrogen bond structure is disrupted. After drying, the overall porous structure and fiber bundle arrangement of the dispersed bamboo fibers remain intact.

[0022] The advanced fiber-opening treatment system designed in this embodiment of the invention mainly relies on hydrogen peroxide (H2O2) and ozone (O3). Hydrogen peroxide (H2O2) penetrates into the interior of natural bamboo through its porous structure, decomposing free radicals that attack lignin and hemicellulose, ultimately leading to lignin oxidation and depolymerization and hemicellulose degradation. During this process, ozone (O3) not only provides an oxygen-rich environment for the reaction but also reacts with water to continuously generate hydrogen peroxide (H2O2), thereby continuously enhancing the oxidation of lignin and hemicellulose in bamboo by hydrogen peroxide (H2O2). Because lignin and hemicellulose are wrapped around the outer layer of cellulose and the cellulose is relatively tightly packed and has a higher degree of crystallinity, the inner cellulose layer is not easily penetrated and destroyed by hydrogen peroxide (H2O2). Based on this characteristic, this application further controls various reaction conditions (temperature, time, concentration, etc.) in the fiber-opening system to achieve the goal of partially removing the lignin and hemicellulose on the outer layer of cellulose without destroying the structure of the cellulose itself. After being processed by an advanced fiber-opening system, the original lignin hydrogen bond network of bamboo fiber is broken, and the interaction between cellulose fibers is very weak. After light rolling and drying, open-fiber bamboo can be obtained.

[0023] Chemical composition analysis of natural bamboo and bamboo shavings showed that bamboo shavings had significantly lower lignin and hemicellulose content compared to natural bamboo, at only 9.3% and 4.8% respectively, while the cellulose content increased to 78.1%. Fourier transform infrared spectroscopy (FT-IR) analysis indicated that the lignin content of bamboo shavings was higher at 1590, 1501, and 1452 cm⁻¹. -1 The characteristic peaks (aromatic skeletal vibrations) in the isotropic bands show a significant decrease, while the CH and CO in cellulose, as well as the -COC on the pyran ring and glycosidic bond, are at 1376, 1062, and 890 cm⁻¹, respectively. -1 The characteristic peaks at the corresponding wavelengths showed no significant difference. The X-ray diffraction (XRD) pattern corresponds to crystalline natural cellulose I (2θ = 22.8°), indicating that the cellulose structure was not destroyed after fiber splitting. Furthermore, since cellulose has a higher crystallinity than lignin and hemicellulose, the crystallinity of split bamboo is higher than that of natural bamboo. In the implementation of this application, mechanical tests were conducted on split bamboo of different widths. Thanks to the removal of the lignin hydrogen bond network and the complete preservation of the cellulose structure, the split bamboo fibers not only exhibited excellent tensile properties but also demonstrated superior toughness. To further enhance the processing performance and expand the application scope of split bamboo, this application incorporates a deep crosslinking system to modify the functional groups on the cellulose surface and strengthen the intercellulose bonds, as described below.

[0024] II. Design of "Ionic Bond-Hydrogen Bond Network" Hydrogen bonding is an important intermolecular force in cellulose, mainly formed by hydrogen bonds between hydroxyl oxygen atoms and hydroxyl hydrogen atoms of adjacent molecules. The hydrogen-bonded structure of cellulose creates mutual attraction between cellulose molecules, resulting in the crystalline structure of cellulose. Ionic bonds are far stronger than hydrogen bonds. This application analyzed the hydrogen and ionic bonds between fibers using simulation calculations (MD), and the results show that the forces between surface ions are stronger. The formation mechanism of ionic bonds between cellulose molecules is (based on Al...) 3+ (Taking hydroxyl groups as an example): Hydrated Al ions undergo a proton transfer reaction with water, i.e., hydrolysis, which generates a complex with hydroxyl groups as ligands. The oxygen atoms of the two hydroxyl groups coordinate with a metal ion simultaneously, forming a stable bridging 3D network structure. This structure gives the ionic bonds high strength and stability.

[0025] Cellulose is produced by the β-transfer of glucose monomers. 1，4 Cellulose is a polymer linked by glycosidic bonds, and its surface is rich in hydroxyl groups. The fiber-opening system removes components coating the outer layer of cellulose, widening the spaces between cellulose fibers and allowing metal ions to enter, essentially creating an ion channel within the cellulose. On both sides of this channel are numerous hydroxyl groups, as well as active functional groups such as carboxyl, carbonyl, and aldehyde groups formed by oxidation with hydrogen peroxide (H₂O₂). These groups provide a large number of coordination sites for metal ions. In this deeply cross-linked system, aluminum ions (Al₂O₃)... 3+ ) will enter these ion channels through Brownian motion. This application further utilizes vacuum permeation to target aluminum ions (Al) 3+ Transport of aluminum ions (Al) in the channel to facilitate their transport. 3+ ) and the groups in the channel undergo deep cross-linking. Under the influence of electronegativity, these groups and aluminum ions (Al) 3+ Aluminum ions (Al) coordinate to form ionic bonds, which then fill the channels. The feasibility of this crosslinking mechanism was confirmed by analyzing the Zeta potential during fiber opening and XPS analysis of bamboo fibers after deep crosslinking. In summary, the deep crosslinking system promotes the formation of ionic bonds by aluminum ions (Al). 3+ ) effectively enters the spaces between cellulose molecules and generates strong coordination with them. With the help of these forces, cellulose reacts with aluminum ions (Al ions). 3+ The bonds between cellulose molecules and between cellulose molecules are stronger, and the deep cross-linking system provides the basis for the reconstruction of super-strong bamboo with ionic-hydrogen bond network structure in this application.

[0026] III. Reconstruction with Super Strong Bamboo In this application, a deep cross-linking strategy is used to combine numerous aluminum ions (Al... 3+ After the introduction of ion channels, these aluminum ions (Al) 3+The bamboo fibers not only fill the channels but also cross-link with the abundant functional groups within them. However, due to the relatively loose structural characteristics and the presence of extensive ion channels, the bond energy formed at this stage is not strong enough to provide strong support. This application divides the deeply cross-linked bamboo fibers into several batches of identical blanks, stacks them in a cross-shaped pattern, and then places them in a mold for hot pressing. Thus, this application completes all the reconstruction steps for ultra-strong rebuilding bamboo, which has significant advantages over bamboo steel, bamboo plywood, stainless steel, and concrete in terms of strength, lightweight, sustainability, energy efficiency, and cost.

[0027] In this process, the dispersed cellulose material is integrated and arranged together, the spacing between the cellulose fibers is reduced, and the bonding between the fibers becomes tighter. Previously existing ion channels are compressed, the channels become smaller, and the aluminum ions (Al) within the channels... 3+ The closer proximity of the ionic and hydrogen bonds to the functional groups enhances electronegativity and strengthens ionic bond energies. Simultaneously, the hydrogen bonding between the functional groups is further strengthened, forming a powerful "ionic-hydrogen bond network" through a neat and dense arrangement. With the formation of this network structure, the proposed method reconstructs "super-strong reconstructed bamboo" (a bamboo-based material prepared by this method). Benefiting from the uniform structure of the ionic-hydrogen bond network, the super-strong reconstructed bamboo exhibits almost no difference in mechanical properties along the L and T directions. Furthermore, due to the strong support and linkage provided by the ionic-hydrogen bond network to cellulose, the "super-strong reconstructed bamboo" achieves superior mechanical properties without requiring a highly dense structure. Therefore, during hot pressing, the pressure is only 5 MPa and the time is only 2 hours. Moreover, the absence of binders eliminates the need for a high-temperature liquid-solid transition, and the hot pressing temperature is set at only 70 ºC. Thus, the lower temperature, lower pressure, and shorter time provide significant advantages for industrial production in terms of energy efficiency, cost, and safety. The bamboo-based material prepared by the method of this application has a density of only 0.83, compared to 1.6 for high-density bamboo. The bamboo-based material prepared by the method of this application can reduce the weight by about 50% under the same volume conditions. This characteristic makes it a major breakthrough in lightweighting. Compared with other structural materials, such as bamboo steel, fiberglass, and stainless steel, its advantages are more obvious.

[0028] IV. Strengthening Mechanisms In the process of opening natural bamboo fibers according to the embodiments of this application, most of the amorphous hemicellulose, lignin, pectin and waxy substances covering the outer surface of bamboo fibers are removed. Compared with natural bamboo, the hydroxyl groups exposed on the fiber surface of opened bamboo are more uniform and the crystallinity is higher. The crystallinity of reconstructed bamboo fibers is further improved compared with that of opened bamboo. Figure 3Furthermore, the small-angle X-ray scattering (SAXS) pattern indicates that the reconstructed bamboo exhibits excellent cellulose arrangement. Figure 4 ).

[0029] Another characteristic of bamboo fiber is its large aspect ratio (200~400), exhibiting a significantly higher aspect ratio and a large interfacial area. In the presence of aluminum ions (Al... 3+ Once the aluminum ions enter the interior of the bamboo, they enhance the bonding between these fibrils through electrostatic interactions and the ionic bonds formed between the cellulose fibers. This may be due to the aluminum ions (Al2O3). 3+ The metal ions modify the bond energy between cellulose fibers. The 3D network cross-linking structure formed by these metal ions promotes the formation of hydrogen bonds between cellulose fibers and maintains a large interfacial area. Furthermore, the entry of these metal ions resists the capillary forces of bamboo fibers. These measures result in good arrangement between cellulose fibers, allowing the split bamboo to form stronger energy bonds, including ionic bonds, hydrogen bonds, and van der Waals forces, after hot pressing. The molecular locking effect generated by the "ionic-hydrogen bond network" between cellulose fibers gives the reconstructed bamboo strong mechanical properties and stability.

[0030] This application conducted a series of evaluations on the mechanical properties of reconstructed bamboo. First, the tensile strength and density of reconstructed bamboo were compared with those of hot-pressed bamboo and bamboo-based polymer composites. The results showed that ( Figure 5 Reconstructed bamboo exhibits stronger tensile properties compared to these high-molecular bamboo-based composites under lower density conditions. Further comparisons are made with traditional metal alloys and recently emerging structural materials such as bamboo-steel and bamboo plywood. Figure 6 Reconstructed bamboo has a significant advantage in specific strength, and the invention presented in this application represents a major breakthrough in its lightweight and high-strength characteristics. The tensile properties of reconstructed bamboo fibers are significantly improved compared to natural bamboo, increasing from 120 MPa to 631 MPa, a performance exceeding that of most bamboo-based fiber composites. Bending strength is another crucial indicator for engineering structural materials; through the reconstruction process, the bending strength of natural bamboo is increased from 108 MPa to 353 MPa, an increase of approximately 3.3 times. Figure 7 The dimensions of natural bamboo and reconstructed bamboo in the test were 300 mm × 7 mm × 1 mm, which is excellent. Furthermore, the reconstructed bamboo also exhibited good stability after multiple bending tests, mainly due to the replacement of the brittle natural lignin network by the "ionic-hydrogen bond network." This important network substitution effect is further reflected in the impact toughness of the reconstructed bamboo, which increased from 2.9 to 8.3 J / cm² compared to natural bamboo. 2 It increased by nearly 3 times. Figure 8This gives bamboo, which is already quite strong, even better toughness, providing a foundation for the multi-faceted shaping and application of bamboo. The bamboo used for impact toughness testing had a length, width, and thickness of 50 mm × 10 mm × 5 mm. When testing the compressive strength of bamboo, it was found that reconstructed bamboo had stronger compressive strength and longer displacement characteristics than natural bamboo. With a load limit of 30 kN, a load was applied perpendicular to the fiber alignment direction to reconstructed bamboo measuring 20 mm × 20 mm × 20 mm. The test results showed that the compressive strength of the reconstructed bamboo was 64 MPa, which is approximately 52% higher than the 42 MPa of natural bamboo. Figure 9 Furthermore, under the same loading conditions, reconstructed bamboo exhibits greater displacement and a longer testing duration compared to natural bamboo. This indicates that natural bamboo is more easily cracked or broken, while reconstructed bamboo demonstrates stronger overall stability. Similarly, when a 30 kN load is applied parallel to the fiber alignment direction, the compressive strength of reconstructed bamboo is significantly higher than that of natural bamboo. Puncture force is also an important indicator for evaluating mechanical strength. A puncture resistance test was conducted on 10 mm thick reconstructed bamboo. At a puncture depth of approximately 30% of the overall thickness, a maximum puncture force of 538 N was obtained. Figure 10 This may be because, under the influence of the puncture force, the fibers of the reconstructed bamboo are broken in some areas, which destroys the stable network structure and reduces its stability. Even after being completely penetrated, the puncture resistance of the reconstructed bamboo can still maintain a good level.

[0031] V. Improved weather resistance Durability is one of the essential properties of advanced structural materials. This application evaluated the performance of reconstructed bamboo in terms of thermal stability, flame retardancy, water resistance, and UV resistance. Compared with natural bamboo, the LOI index of reconstructed bamboo increased from 25% to 35%, and the ignition time of reconstructed bamboo increased from 49 s to 63 s. Figure 11 The significant improvement in these two properties indicates that reconstructed bamboo is more difficult to burn. Thermogravimetric analysis (TG) and thermogravimetric analysis (DTG) results for natural bamboo, open-fiber bamboo, and reconstructed bamboo show that ( Figure 12 Under the primary mass loss temperature range of 220–300 °C, split bamboo exhibits lower mass loss compared to natural bamboo. This is mainly because lignin and hemicellulose are partially removed from split bamboo, resulting in a higher cellulose content. The higher crystallinity of the cellulose provides split bamboo with more stable properties. Reconstructed bamboo, after hot pressing, has even higher fiber crystallinity, a more orderly and dense arrangement, and greater stability, thus exhibiting the lowest mass loss.

[0032] This application further evaluates the performance of reconstructed bamboo during combustion. Compared with natural bamboo, reconstructed bamboo shows a significant decrease in heat release rate (HRR), total heat release (THR), effective heat of combustion (EHC), smoke release (TSP), and smoke release rate (TSR) during combustion. Its flame retardant properties far exceed those of bamboo fiber-based polymers.

[0033] Analyzing the performance of reconstructed bamboo 300 s and 600 s before the fire, at 300 s, the HRR of reconstructed bamboo was nearly 3.5 times lower than that of natural bamboo. Figure 13 Correspondingly, the THR at this time decreased from 31.1 to 15.2 MJ / m 2 Between 300 and 600 seconds, the HRR of reconstructed bamboo remained very stable, while the HRR of natural bamboo continued to rise. This resulted in the natural bamboo having a HRR 2.4 times higher than that of reconstructed bamboo at 600 seconds. Figure 14 The EHC data further illustrates the low heat release properties of reconstructed bamboo; at 300 s and 600 s, the effective heat release of reconstructed bamboo is approximately 3.1 times lower than that of natural bamboo. Figure 15 In other words, burning the same mass of reconstructed bamboo releases less heat. This is thanks to the fact that this invention removes most of the high-calorific-value components, namely lignin, during the fiber-opening process, resulting in a significant improvement in the heat release of reconstructed bamboo.

[0034] Smoke produced during fires often seriously endangers human lives; therefore, smoke release is a crucial indicator for evaluating the flame-retardant performance of materials. The "ion-hydrogen bond network" designed in this invention reduces smoke release from reconstructed bamboo, and aluminum ions (Al...)... 3+ The presence of cellulose fibers promotes cellulose carbonization, thus inhibiting smoke generation and insulating against heat transfer. Therefore, in a short period, the smoke emission from reconstructed bamboo is approximately 3.4 times lower than that from natural bamboo. Figure 16 The value decreased from 0.75 to 0.22 m. 2 (Sample size is 10 x 10 x 1 cm).

[0035] Water vapor resistance is also an important indicator of material stability. This application conducted water resistance tests on natural bamboo, reconstructed bamboo, and surface-treated reconstructed bamboo. The humidity chamber was set to 20 °C and 95% RH. Cut samples with dimensions of approximately 50 mm x 10 mm x 10 mm were placed in the humidity chamber, and the mass of the samples was recorded at intervals. The results showed that natural bamboo possesses a certain degree of water resistance due to the presence of hydrophobic components such as wax on its surface. During the reconstruction process, these hydrophobic components are removed, and cellulose is highly hydrophilic. Therefore, the water resistance of reconstructed bamboo decreased compared to natural bamboo. Under the same conditions, the moisture content of reconstructed bamboo increased by 4% compared to natural bamboo. Figure 17 Then, this application utilizes a thin-coat spraying treatment commonly used in the board industry to improve this situation. The water resistance of the reconstructed bamboo after surface treatment is greatly improved. After being placed in a humidity chamber for 120 hours, its moisture content increases very little, almost identical to its original state before being placed in the humidity chamber.

[0036] The properties of UV resistance also have a certain impact on the stability of the material. In this application, the reconstructed bamboo sample was placed in a UV aging chamber for 30 days of UV aging. After being taken out, it was found that there was no obvious color change on the surface of the material. Furthermore, mechanical property tests were conducted on it, and the results showed that the surface performance was basically unaffected after UV aging.

[0037] This invention utilizes a reconstruction process to design and manufacture lightweight, high-strength, and durable bamboo fiber-based structural materials from natural bamboo. The process involves pretreatment with H₂O₂ and O₃, followed by fiber splitting of the natural bamboo, the introduction of aluminum ions to rebuild an ionic-hydrogen bond network, and further strengthening this network through hot pressing to obtain reconstructed bamboo. Thanks to this strong ionic-hydrogen bond network, while maintaining a similar density to natural bamboo (reconstructed bamboo ~0.83, natural bamboo ~0.76), it achieves a tensile strength of 631 MPa and a flexural strength of 353 MPa. This strength far exceeds that of commercially available bamboo plywood, and its lightweight and high-strength properties far surpass some metal alloys, while also exhibiting good durability. This bamboo-based composite material has the potential to replace traditional non-renewable structural materials (such as metal alloys, glass fibers, and plastics). The proposed reconstruction process is scalable, providing a new avenue for the efficient utilization of other lignocellulosic materials and the development of related industries.

[0038] It is worth noting that the methods, materials, and characterization of the above-described embodiments of the present invention are described below: 1. Materials and Supplies: Natural bamboo was purchased from Hunan, China. The bamboo was cleaned of the outer green and inner yellow layers and cut into strips measuring 150×30×7 mm in length, width, and thickness. A bamboo roller was purchased from BAOPIN INTERNATIONAL PRECISION INSTRUMEN, an ozone generator from Nanjing Wohuan Technology Co., Ltd., and high-purity oxygen (O2) from Chengdu Heping Gas Co., Ltd. Sodium hydroxide (NaOH, >96%) and aluminum sulfate (Al2(SO4)3, >97%) were provided by Shanghai Aladdin Reagent. Hydrogen peroxide (H2O2, 30%) was purchased from Shudu Chemical Reagent. Deionized water prepared in the laboratory was used for bamboo processing.

[0039] 2. Method: The manufacturing process of "Super Strong Reconstructed Bamboo" mainly involves three steps: "fiber opening - cross-linking - reconstruction". First, the fiber opening process involves immersing bamboo strips in a 30 wt% H2O2 solution, raising the solution temperature to 80 ºC, and introducing ozone gas (flow rate 2 L / min, ozone concentration 80 mg / L). After 4.5 h, the heating and ozone gas are turned off. This step partially removes lignin and hemicellulose, and the fibers are dispersed by mechanical rolling and water. The dispersed fibers are washed with deionized water, then transferred to a 0.1 mol / L NaOH solution for 2 h to neutralize the acidity, washed again with deionized water, and then transferred to a 10 wt% Al2(SO4)3 solution, with the temperature raised to 70 ºC and maintained for 4 h. After drying, the dried bamboo fibers are placed in a specially designed sealed bag. Valves are attached to both ends of the bag, and tubing can be connected to these valves. First, close one valve and connect the other valve to the tubing and then to a vacuum pump. Degas the bag for 10 minutes to remove excess air and moisture. Once the vacuum level in the bag stabilizes at 0.08 MPa, connect the other valve to the tubing, and then place the other end of the tubing into an aluminum ion-rich environment (Al). 3+ In a solution containing [missing information], the valve is opened to allow the solution to enter a sealed bag under atmospheric pressure, and the sealed bag is kept under vacuum for 2 hours. After removal, bamboo fibers are orthogonally laid in a mold and formed using hot pressing at a pressure of 5 MPa, a temperature of 70 ºC, and a pressing time of 4 hours.

[0040] 3. Characterization: (1) The surface and cross-sectional morphology of the samples were observed using SEM (Thermo Scientific Apros2, USA). The contents of lignin, cellulose and hemicellulose in the samples were determined according to NREL standards.

[0041] (2) This invention uses XRD (Bruker D8 advance, Germany) at 4° min within the range of 5°~80°. -1The crystal structure of the sample was scanned and used to analyze the crystallinity of the cellulose in the sample.

[0042] (3) The present invention uses RAMAN (Thermo Fisher Scientific Dxr2xi) to observe the changes and distribution of lignin content in the samples.

[0043] (4) The present invention uses XRM (German ZEISS Xradia615 Versa) to scan the internal structural changes of the sample and simulates and analyzes the wall thickness of the bamboo fiber pores.

[0044] (5) This invention uses MD (LAMMPS) simulation analysis to analyze the strength of hydrogen bond network in natural bamboo and the strength of "ionic bond-hydrogen bond" network after reconstruction, and compares them.

[0045] (6) The present invention uses TG (German NETZSCH TG 209F1) to measure the mass loss of the sample at 50 ºC-800 ºC, and further analyzes the temperature range in which the maximum heat loss rate is located.

[0046] (7) The present invention uses a critical oxygen measuring instrument (China TTech-GBT2406-1) to determine the ignition time of the sample with reference to the UL-94 method and evaluate the flame retardancy level.

[0047] (8) The present invention uses a cone calorimeter (FTT I-CONE, USA, in accordance with ISO5660-1 standard) to analyze the heat release rate and smoke release rate of the sample.

[0048] (9) The present invention uses a water vapor aging chamber (China ESPEC SETH-Z-032L) to test the water resistance of the material.

[0049] (10) The present invention uses a pendulum impact testing machine (China GT-7045-MDH) to test the impact toughness of the sample.

[0050] (11) The present invention uses an electronic testing system (US MTS E45.105) to test the puncture resistance of the sample.

[0051] (12) The present invention uses a universal mechanical testing system (INSTRON 68TM-30, USA) to test the tensile strength, bending strength and compressive strength of the sample.

[0052] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for reconstructing natural bamboo into high-performance bamboo-based materials, characterized in that, Includes the following steps: S1. Fiber splitting treatment of natural bamboo: A fiber splitting system is constructed using hydrogen peroxide solution and ozone gas to oxidize some of the lignin and hemicellulose in natural bamboo and break the internal lignin hydrogen bond network to obtain dispersed bamboo fibers. S2. Arrange the bamboo fibers processed in step S1 neatly into a specific sealed bag. There are air valves on both the left and right ends of the sealed bag, namely valve A and valve B. Connect valve A to a vacuum pump and valve B to a conduit. Place the other end of the conduit into a high-concentration aluminum ion solution. Then keep valves A and B closed. S3. Turn on the vacuum pump and open valve A to fully remove the gas and excess moisture from the sealed bag, and maintain the vacuum for 5 minutes. S4. Slowly open valve B to allow the high-concentration aluminum ion solution to enter the sealed bag. After fully opening valve B, the solution will quickly enter the sealed bag and combine with the bamboo fiber. Once the measured amount of solution has entered the sealed bag, close valve B. Under the action of the vacuum pump, the solution gradually permeates towards valve A, with valve A at the top and valve B at the bottom, so that the solution permeates evenly into every corner of the bamboo fiber. S5. Once bubbles or solution are observed at valve A, immediately close valve A to keep the sealed bag in a vacuum state. Use atmospheric pressure to make the aluminum ion solution evenly distributed in the sealed bag and evenly cross-linked with the bamboo fiber. That is, the aluminum ions enter the gaps in the bamboo fiber, making the two tightly cross-linked. S6. Place the sealed bag in a cool, ventilated place and maintain the vacuum condition for 10 hours.

2. The method for reconstructing natural bamboo into high-performance bamboo-based materials according to claim 1, characterized in that, Also includes: After the bamboo fibers that have undergone ion crosslinking in step S6 are orthogonally arranged, they are hot-pressed to make the cellulose of the bamboo fibers highly compact and reinforced to form an "ionic bond-hydrogen bond" network structure, thus reconstructing a high-performance bamboo-based material.

3. The method for reconstructing natural bamboo into a high-performance bamboo-based material according to claim 1, characterized in that, The fiber opening process in step S1 specifically includes the following steps: 1) Remove the green and yellow parts of the natural bamboo and cut it into strips; 2) Prepare a hydrogen peroxide solution and immerse the treated bamboo strips in the hydrogen peroxide solution. Heat and introduce ozone gas to start the oxidation reaction. After the oxidation treatment time is up, take out the softened bamboo fibers, rinse them repeatedly in deionized water, flatten them with a roller, disperse them in water, and then dry them to obtain dispersed bamboo fibers.

4. The method for reconstructing natural bamboo into a high-performance bamboo-based material according to claim 1, characterized in that, The vacuum level in step S3 is 0.08 MPa.

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