Modified bamboo material, and preparation method and application thereof

Abstract

The application relates to the technical field of bamboo materials, and discloses modified bamboo materials, a preparation method and application thereof, the preparation method of the modified bamboo material comprises the following steps: (1) mixing tetraethyl orthosilicate, a silane coupling agent and anhydrous ethanol, and then adjusting to acidity to obtain a silicon precursor solution; (2) immersing bamboo materials in the silicon precursor solution, and then taking out and drying to obtain mineralized bamboo materials; and (3) carrying out densification treatment on the mineralized bamboo materials to obtain modified bamboo materials. The bamboo materials are subjected to mineralization and densification treatment to improve the rigidity and density of the bamboo materials, reduce vibration response, effectively inhibit vibration, and when the bamboo materials are applied to musical instruments, sound box equipment and the like, sound transmission loss can be more effectively reduced, and acoustic stability can be improved.

Description

Technical Field

[0001] This invention relates to the field of bamboo technology, and in particular to a modified bamboo material, its preparation method, and its application. Background Technology

[0002] Bamboo possesses a unique tissue structure, resulting in significant anisotropy in its permeability. Longitudinally, bamboo's cellular structure is relatively continuous, with tightly packed fiber cells and vessel cells forming a channel-like structure, allowing liquids and nutrients to move rapidly along these longitudinal cellular channels via transpiration. However, radially, bamboo lacks wood rays and other structures. The intercellular connections (simple pits and bordered pits) and the distribution of cell cavities (gradient changes) hinder lateral liquid migration. Furthermore, the presence of numerous fillers such as starch granules within bamboo further impedes liquid migration. Therefore, when modifying bamboo, modifiers must overcome greater resistance to penetrate radially. When considering bamboo for acoustic applications, improving its processability typically requires impurity removal and pore expansion to enhance permeability and improve the migration and loading capacity of modifiers. Currently, delignification treatment is commonly used to loosen the cellular structure, increase the size and number of mesopores, facilitate the entry of nanoparticles, and thus improve loading capacity. However, the cross-sectional stress transmission between bamboo fibers and the matrix is ​​enhanced after delignification treatment, which increases the elastic modulus and vibration transmission, resulting in greater vibration efficiency and making it less effective at suppressing vibration. Therefore, when used in speaker cabinets, it results in large sound transmission loss and poor acoustic stability. Summary of the Invention

[0003] In view of this, the present invention provides a modified bamboo material, its preparation method and application. By mineralizing and densifying the bamboo material to improve its stiffness and density, reduce vibration response, and effectively suppress vibration, when it is applied to musical instruments and speaker equipment, it can more effectively reduce sound transmission loss and improve acoustic stability.

[0004] To achieve the above objectives, the present invention adopts the following technical solution:

[0005] On the one hand, the present invention provides a method for preparing modified bamboo, comprising the following steps:

[0006] (1) Mix tetraethyl orthosilicate, silane coupling agent and anhydrous ethanol and adjust to acidity to obtain silicon precursor solution;

[0007] (2) Immerse the bamboo in the silicon precursor solution, remove it and dry it to obtain mineralized bamboo;

[0008] (3) The mineralized bamboo is densified to obtain modified bamboo.

[0009] Preferably, the molar ratio of tetraethyl orthosilicate, silane coupling agent and anhydrous ethanol is 1:0.1-0.3:4-20.

[0010] Preferably, the silane coupling agent comprises at least one of γ-aminopropyltriethoxysilane (KH-550), γ-aminopropyltrimethoxysilane (KH-551), and γ-(2,3-epoxypropoxy)propyltrimethoxysilane (KH-560).

[0011] Preferably, in step (1), an acidic solution is used to adjust the pH to 3-4.

[0012] Preferably, the acidic solution includes at least one of sulfuric acid solution, hydrochloric acid solution, nitric acid solution, and phosphoric acid solution.

[0013] Preferably, the impregnation is performed under negative pressure for 1-6 hours.

[0014] Preferably, the negative pressure is -0.08 to -0.1 MPa.

[0015] Preferably, the drying process is air drying for 24-40 hours.

[0016] Preferably, after the bamboo is soaked and removed, it is placed inside a wrapping material.

[0017] Preferably, the wrapping material includes one of aluminum foil, polyethylene, nylon, and nonwoven fabric.

[0018] Preferably, the densification process is a hot-pressing densification process.

[0019] Preferably, the hot pressing temperature for the hot pressing densification treatment is 150-180℃, the hot pressing time is 20-30 min, and the pressure is 2-4 MPa.

[0020] Preferably, the compression rate of the mineralized bamboo after the densification treatment is 30-50%.

[0021] On the other hand, the present invention provides a modified bamboo material prepared by the method described in any of the above-mentioned methods.

[0022] Furthermore, the present invention also provides an application of the modified bamboo material prepared by the method described in any one of the above-mentioned methods in musical instruments and sound equipment.

[0023] This invention provides a modified bamboo material, its preparation method, and its application. Compared with the prior art, its advantages are as follows:

[0024] This invention prepares a silicon precursor solution using tetraethyl orthosilicate, a silane coupling agent, and anhydrous ethanol as raw materials. Bamboo is then impregnated in the silicon precursor solution for mineralization and densification to obtain modified bamboo. Specifically, by impregnating bamboo in the silicon precursor solution, the small-molecule silicon precursor solution easily penetrates the bamboo interior under capillary force, causing in-situ mineralization of the bamboo cell walls to form a nano-silica film. The impregnation process increases the density and mass of the bamboo. Simultaneously, the uniformly distributed silica film binds more tightly to the cell walls, facilitating stress transmission and effectively improving the stiffness of the modified bamboo. The higher density and stiffness reduce vibration response and effectively suppress vibration. Furthermore, when the bamboo is subjected to excited vibration, the nano-silica dissipates vibration energy through friction with the cell walls, resulting in higher damping in the final modified bamboo, further enhancing vibration suppression and improving acoustic stability.

[0025] In addition, musical instruments or speaker equipment made from the modified bamboo of this invention have good sound insulation performance and can effectively avoid resonance overtones, thereby reducing the adverse effects of resonance and sound radiation on sound quality. This not only improves the acoustic performance of the speaker, but also provides new options for the green and high-performance design of speaker materials. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0027] Figure 1 The micropore structure and silicon element distribution of the modified bamboo NTEOS of Example 1 and the modified bamboo DSi of Comparative Example 1 are shown in the diagram.

[0028] Figure 2 Fourier transform infrared spectra of the modified bamboo in Example 1 and Comparative Examples 1-5;

[0029] Figure 3 The diffraction intensity curves and azimuth curves of the modified bamboo in Example 1 and Comparative Examples 1-5 are shown.

[0030] Figure 4 The curves show the changes in water absorption thickness swelling rate (TS) and weight gain rate (WPG) of the modified bamboo in Example 1 and Comparative Examples 1-4 over time.

[0031] Figure 5 Frequency response curves of the speaker side panel, top panel and back panel for Application Example 1 and Application Comparative Examples 1-2;

[0032] Figure 6 The root mean square (RMS) histograms of the vibration response of the speaker side panel, top panel, and back panel for Application Example 1 and Comparative Examples 1-2 are shown.

[0033] Figure 7 The graph shows the test results of the sound insulation performance of the speaker enclosures in Application Example 1 and Comparative Examples 1-2. Detailed Implementation

[0034] The present invention will be described below through specific embodiments. Those skilled in the art will understand that the specific embodiments below are merely illustrative and do not limit the scope of the invention in any way. Furthermore, in the following embodiments, unless otherwise specified, the reagents and equipment used are commercially available. If specific processing conditions and methods are not explicitly described in the later embodiments, conditions and methods known in the art can be used for processing.

[0035] In one aspect of the invention, a method for preparing modified bamboo is provided, comprising the following steps:

[0036] (1) Mix tetraethyl orthosilicate, silane coupling agent and anhydrous ethanol and adjust to acidity to obtain silicon precursor solution;

[0037] (2) Immerse the bamboo in the silicon precursor solution, remove it and dry it to obtain mineralized bamboo;

[0038] (3) The mineralized bamboo is densified to obtain modified bamboo.

[0039] In this invention, tetraethyl orthosilicate, silane coupling agent and anhydrous ethanol are first mixed and adjusted to acidity to obtain a silicon precursor solution.

[0040] In this invention, compared with other silicon-containing substances or organic solvents, tetraethyl orthosilicate has a moderate hydrolysis rate under acidic conditions, which facilitates the control of the sol-gel process; anhydrous ethanol can quickly penetrate the porous structure of bamboo and volatilize efficiently during the drying stage; after adjusting to acidity, the solution contains hydrogen ions, which can break the ethoxy groups in tetraethyl orthosilicate and replace them with hydroxyl groups, thus fully hydrolyzing it into active Si-OH.

[0041] In some embodiments of the present invention, the molar ratio of tetraethyl orthosilicate, silane coupling agent and anhydrous ethanol is 1:0.1-0.3:4-20, specifically 1:0.1:4, 1:0.1:5, 1:0.2:4, 1:0.2:5, etc.

[0042] In some embodiments of the present invention, the silane coupling agent includes at least one of γ-aminopropyltriethoxysilane (KH-550), γ-aminopropyltrimethoxysilane (KH-551), and γ-(2,3-epoxypropoxy)propyltrimethoxysilane (KH-560).

[0043] In some embodiments of the present invention, in step (1), an acidic solution is used to adjust the pH to 3-4, specifically to pH 4, 3.8, 3.6, 3.4, 3.2, and 3. The acidic solution includes at least one of sulfuric acid solution, hydrochloric acid solution, nitric acid solution, and phosphoric acid solution. Under acidic conditions, the hydrolysis rate is faster than the condensation rate, forming a linear or branched SiO2 network, which is beneficial for impregnation or coating of bamboo.

[0044] In this invention, after obtaining the silicon precursor solution, bamboo is immersed in the silicon precursor solution, removed and dried to obtain mineralized bamboo.

[0045] This invention involves immersing bamboo in a silicon precursor solution. The small-molecule silicon precursor solution easily penetrates the bamboo interior under capillary action, causing in-situ mineralization of the bamboo cell walls to form a nano-silica film. The immersion process increases the density and mass of the bamboo. At the same time, the uniformly distributed silica film binds more tightly to the cell walls, which helps stress transmission and effectively improves the stiffness of the modified bamboo. The higher density and stiffness reduce vibration response and effectively suppress vibration. In addition, when the bamboo is subjected to excited vibration, the nano-silica dissipates vibration energy through friction with the cell walls, resulting in higher damping of the final modified bamboo, which is more conducive to suppressing vibration and improving acoustic stability.

[0046] In some embodiments of the present invention, the impregnation is carried out under negative pressure for 1-6 hours, specifically 6 hours, 4 hours, 2 hours and 1 hour, etc.; the pressure of the negative pressure is -0.08 to -0.1 MPa, specifically -0.08 MPa, -0.09 MPa and -0.1 MPa, etc., and the impregnation process can be carried out in a vacuum tank, for example. Impregnation under negative pressure can promote better penetration of the silicon precursor solution into the interior of the bamboo.

[0047] In some embodiments of the present invention, the drying process is air drying for 24-40 hours, specifically 24 hours, 28 hours, 32 hours, 36 hours, and 40 hours. Air drying can preserve the natural properties of bamboo to the greatest extent and avoid microcracks caused by rapid shrinkage of cell walls; at the same time, the tetraethyl orthosilicate-silane system of the present invention is more likely to complete the gradual condensation to form a uniform SiO2 network during the air drying process.

[0048] In some embodiments of the present invention, after the bamboo is impregnated and removed, it is placed inside a wrapping material. This physical barrier slows down the rapid evaporation of moisture from the bamboo surface, allowing internal moisture to gradually migrate outwards and preventing stress cracking caused by uneven drying. The wrapping material includes one of aluminum foil, polyethylene, nylon, and non-woven fabric. For example, when the wrapping material is aluminum foil, it can be treated to have ventilation holes. Wrapping the bamboo allows the silicon precursor solution adhering to the bamboo surface to further penetrate into the bamboo, and the residual silicon precursor solution on the surface forms a silicon film on the bamboo surface.

[0049] In some embodiments of the present invention, in order to facilitate the application of bamboo, the bamboo is treated to be flat before impregnation, and after cleaning and drying, flattened bamboo is obtained. The methods for flattening bamboo mainly include steaming and softening followed by pressing, pressing with heavy objects, and flattening by mechanical processing. The present invention does not impose special limitations on the method of flattening bamboo or the cleaning and drying process, and can be adjusted according to the actual situation.

[0050] In this invention, after obtaining mineralized bamboo, the mineralized bamboo is subjected to densification treatment to obtain modified bamboo.

[0051] In some embodiments of the present invention, the densification treatment is a hot-press densification treatment. The hot-pressing temperature of the hot-press densification treatment is 150-180°C, specifically 180°C, 170°C, 160°C, and 150°C, etc. The hot-pressing time is 20-30 min, specifically 30 min, 28 min, 25 min, and 20 min, etc. The pressure is 2-4 MPa, specifically 2 MPa, 2.5 MPa, 3 MPa, 3.5 MPa, and 4 MPa, etc.

[0052] In some embodiments of the present invention, the compression rate of the mineralized bamboo after the densification treatment is 30-50%, specifically 30%, 35%, 40%, 45%, and 50%. Different compression rates affect the mechanical properties, weather resistance, water absorption, and microstructure of the bamboo, and can be adjusted according to actual needs during actual operation.

[0053] In some embodiments of the present invention, the hot pressing densification process is carried out in a hot press. After the hot pressing process is completed, the material is cooled at room temperature. Preferably, a certain pressure is maintained during cooling, which helps to stabilize the bamboo material's shape and densification structure. The pressure value maintained during cooling is not specifically limited and can be adjusted according to the actual situation.

[0054] In some specific embodiments of the present invention, the densification treatment may involve placing the mineralized bamboo in a hot press (pressure value of 2MPa) preheated to 180°C and compressing it to 8mm for 30 minutes, and then cold pressing it at room temperature for 30 minutes. At this time, the compression rate of the mineralized bamboo is about 30%.

[0055] Understandably, densification treatment disrupts the natural pores and channels inside bamboo, reducing the propagation path of sound waves and thus effectively improving low-frequency sound insulation. This allows bamboo to be transformed from a material that easily resonates in musical instruments into a material that does not easily resonate and vibrates, has good acoustic stability, and obtains acoustic vibration characteristics similar to those of high-quality solid wood.

[0056] On the other hand, the present invention provides a modified bamboo material prepared by the method described in any of the above-mentioned methods.

[0057] Furthermore, the present invention also provides an application of the modified bamboo material prepared by the method described in any one of the above-mentioned methods in musical instruments and sound equipment.

[0058] The technical solutions of this invention will be clearly and completely described below with reference to specific embodiments. The embodiments of this application are only examples, and all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0059] It should be noted that the flattened bamboo in the following examples and comparative examples was taken from the same bamboo material, and the compression rate of the densification process was 30%.

[0060] Example 1

[0061] This embodiment provides a method for preparing modified bamboo, the specific steps of which are as follows:

[0062] (1) Tetraethyl orthosilicate (TEOS, chromatographic grade, Shanghai Maclean Biochemical Technology Co., Ltd.), γ-aminopropyltriethoxysilane (KH550) and anhydrous ethanol (analytical grade, Anaiji Chemical) were mixed in a molar ratio of 1:4:0.1, and then hydrochloric acid was added to adjust the pH value to 4 to obtain a silicon precursor solution; flattened bamboo was immersed in the silicon precursor solution and immersed in a vacuum tank of -1MPa for 6 hours under negative pressure. After immersion, it was wrapped with aluminum foil and left to stand at room temperature and air-dried for 1 day to obtain mineralized bamboo.

[0063] (2) The mineralized bamboo was hot-pressed for 30 minutes to 8 mm in a hot press with a pressure of 2 MPa and a temperature of 180°C, and then cold-pressed at room temperature for 30 minutes to obtain modified bamboo, hereinafter referred to as NTEOS.

[0064] Comparative Example 1

[0065] This comparative example provides a method for preparing modified bamboo, the specific steps of which are as follows:

[0066] (1) Sodium hydroxide (analytical grade, Sinopharm Chemical Reagent Co., Ltd.) and anhydrous sodium sulfite (analytical grade, Tianjin Damao Chemical Reagent Factory) were mixed in a molar ratio of 2.5:0.4 to obtain an alkaline solution. Clean and dry flat bamboo was immersed in the alkaline solution and treated in a boiling water bath for 8 hours. Then, it was rinsed with deionized water to remove residual chemical reagents and obtain delignified bamboo.

[0067] (2) Nano silica particles with a particle size of 15 nm and a mass fraction of 2% (Shanghai Maclean Biochemical Technology Co., Ltd.) were ultrasonically dispersed in pure water for 30 min to obtain a suspension. Then, the delignified bamboo was immersed in the suspension and impregnated in a vacuum tank of -1 MPa for 6 h under negative pressure. After impregnation, the bamboo was wrapped in aluminum foil and left to stand at room temperature. It was then air-dried for 1 day to obtain mineralized bamboo.

[0068] (3) The mineralized bamboo was hot-pressed for 30 minutes to 8 mm in a hot press with a pressure of 2 MPa and a temperature of 180°C, and then cold-pressed for 30 minutes at room temperature to obtain modified bamboo, hereinafter referred to as DSi.

[0069] like Figure 1 The image shows the micropore structure and silicon distribution of the modified bamboo NTEOS from Example 1 and the modified bamboo DSi from Comparative Example 1. Figure 1 A and Figure 1 D represents the micropore structure of NTEOS and DSi, respectively. Figure 1 B and Figure 1 E are respectively Figure 1 A and Figure 1 The magnified image of D shows that the thin-walled cells and vascular bundles in the bamboo cross-section are clearly crushed and deformed. The effect of compression densification on DSi bamboo after delignification treatment is more obvious, and the volume compression rate of thin-walled cells is greater. Under the same degree of densification, the vascular bundles such as vessels and sieves in DSi bamboo after delignification treatment are compressed and deformed, and wrinkles are produced. The interlocking of fiber cells with thin-walled cells forms a mechanical interlocking structure, which increases the elastic modulus of the modified bamboo and is not conducive to vibration suppression.

[0070] Figure 1 C and Figure 1F represents the silicon element distribution of mineralized bamboo in Example 1 and Comparative Example 1, respectively. As can be seen from the figure, after impregnation treatment, the mineralized bamboo in Comparative Example 1, after being impregnated with nano-silica suspension, has independent spherical silica particles on its cell walls, which are relatively dispersed. Therefore, it has little impact on mechanical properties and water absorption thickness swelling rate. In Example 1, the silicon precursor solution can uniformly penetrate into the bamboo and hydrolyze inside the bamboo. A uniform nano-silica film is generated in situ on the cell walls of the bamboo. Most of the pores are covered and blocked by the film, which reduces the water absorption thickness swelling rate of NTEOS and thus improves the stability of the modified bamboo.

[0071] Comparative Example 2

[0072] This comparative example provides a method for preparing modified bamboo, the specific steps of which are as follows:

[0073] (1) Sodium hydroxide (analytical grade, Sinopharm Chemical Reagent Co., Ltd.) and anhydrous sodium sulfite (analytical grade, Tianjin Damao Chemical Reagent Factory) were mixed in a molar ratio of 2.5:0.4 to obtain an alkaline solution. Clean and dry flat bamboo was immersed in the alkaline solution and treated in a boiling water bath for 8 hours. Then, it was rinsed with deionized water to remove residual chemical reagents and obtain delignified bamboo.

[0074] (2) Tetraethyl orthosilicate (TEOS, chromatographic grade, Shanghai Maclean Biochemical Technology Co., Ltd.), γ-aminopropyltriethoxysilane (KH550) and anhydrous ethanol (analytical grade, Anaiji Chemical) were mixed in a molar ratio of 1:4:0.1, and then hydrochloric acid was added to adjust the pH value to 4 to obtain a silicon precursor solution; the delignified bamboo was immersed in the silicon precursor solution and immersed in a vacuum tank at -1MPa for 6 hours under negative pressure. After immersion, it was wrapped with aluminum foil and left to stand at room temperature for 1 day to air dry to obtain mineralized bamboo.

[0075] (3) The mineralized bamboo was hot-pressed for 30 minutes to 8 mm in a hot press with a pressure of 2 MPa and a temperature of 180°C, and then cold-pressed for 30 minutes at room temperature to obtain modified bamboo, hereinafter referred to as DTEOS.

[0076] Comparative Example 3

[0077] This comparative example provides a method for preparing modified bamboo, the specific steps of which are as follows:

[0078] (1) Nano silica particles with a particle size of 15 nm and a mass fraction of 2% (Shanghai Maclean Biochemical Technology Co., Ltd.) were ultrasonically dispersed in pure water for 30 min to obtain a suspension. Then, clean and dry flat bamboo was immersed in the suspension and immersed in a vacuum tank of -1 MPa for 6 h under negative pressure. After immersion, the bamboo was wrapped in aluminum foil and left to stand at room temperature. It was then air-dried for 1 day to obtain mineralized bamboo.

[0079] (2) The mineralized bamboo was hot-pressed for 30 minutes to 8 mm in a hot press with a pressure of 2 MPa and a temperature of 180°C, and then cold-pressed for 30 minutes at room temperature to obtain modified bamboo, hereinafter referred to as NSi.

[0080] Comparative Example 4

[0081] This comparative example provides a method for preparing modified bamboo, the specific steps of which are as follows: flattened bamboo is hot-pressed in a hot press with a pressure of 2MPa and a temperature of 180℃ for 30 minutes to 8mm, and then cold-pressed at room temperature for 30 minutes to obtain modified bamboo, hereinafter referred to as D8.5.

[0082] Comparative Example 5

[0083] This comparative example provides a method for preparing modified bamboo, the specific steps of which are as follows:

[0084] (1) Sodium hydroxide (analytical grade, Sinopharm Chemical Reagent Co., Ltd.) and anhydrous sodium sulfite (analytical grade, Tianjin Damao Chemical Reagent Factory) were mixed in a molar ratio of 2.5:0.4 to obtain an alkaline solution. Clean and dry flat bamboo was immersed in the alkaline solution and treated in a boiling water bath for 8 hours. Then, it was rinsed with deionized water to remove residual chemical reagents and obtain delignified bamboo.

[0085] (2) The bamboo treated with delignification was hot-pressed for 30 minutes to 8 mm in a hot press with a pressure of 2 MPa and a temperature of 180°C, and then cold-pressed for 30 minutes at room temperature to obtain modified bamboo, hereinafter referred to as De.

[0086] The chemical composition, microstructure, acoustic properties, mechanical properties, and water absorption thickness swelling rate of the modified bamboo materials in Example 1 and Comparative Examples 1-5 were analyzed below.

[0087] 1. Chemical composition analysis

[0088] like Figure 2 The figure shows the Fourier transform infrared spectra of the modified bamboo in Example 1 and Comparative Examples 1-5. In the figure, 3425 cm⁻¹... -1 The broad peak at 1508 cm⁻¹ is related to the stretching vibration of hydroxyl groups. Because delignification removes some hemicellulose and lignin, the relative surface area of ​​the cellulose microfibrils increases, exposing more hydroxyl groups and enhancing the hydroxyl peak. This helps form additional intermolecular / internal hydrogen bonds during subsequent compression compaction. However, the increased exposure of hydrophilic groups also increases the hydrophilicity of bamboo. -1 The peaks on the left and right correspond to the vibrations of the lignin aromatic ring skeleton (C=C), 1735 cm⁻¹ -1 The peak at 1250 cm⁻¹ corresponds to the C=O stretching vibration of the lignin ester group and carbonyl group. -1The peaks at this location correspond to the CO vibrations of lignin. The decrease in the intensity of these peaks indicates that lignin has been removed from DTEOS, DSi, and De. Delignification treatment increases the porosity of bamboo, which facilitates the impregnation, filling, and stable deposition of nanoparticles such as silica. Silane-related absorption peaks, such as the tensile vibrations of Si-OC and the asymmetric tensile vibrations of Si-O-Si, are observed at 1200 cm⁻¹. -1 Up to 850cm -1 Within this range, the absorption peaks associated with cellulose overlap, making accurate differentiation difficult. After impregnation with the silicon precursor solution, the peak at 1045 cm⁻¹ is significantly higher. -1 The peak position shifted to 1057cm -1 Furthermore, compared to DSi and De without impregnation and mineralization treatment, its peak intensity is higher than 3425 cm⁻¹. -1 A broad hydroxyl-related peak at 460 cm⁻¹, in addition, at 460 cm⁻¹ -1 The peak at this point is related to the bending vibration of Si-O-Si. It can be seen that the peak intensity of bamboo after being modified by impregnation with silicon precursor solution and silica suspension increases at this point, indicating that silica is impregnated and deposited in bamboo.

[0089] 2. Microstructure analysis

[0090] like Figure 3 As shown, the diffraction intensity curves of the modified bamboo in Example 1 and Comparative Examples 1-5 are presented. Figure 3 A) and azimuth curve ( Figure 3 B), Figure 3 Each curve in A shows a typical cellulose Iβ crystal pattern, with the 16° diffraction peak formed by (101). The peaks at 22° and 34° are obtained by superimposing the diffraction peaks of the crystal planes, and the peaks at 22° and 34° are the diffraction peaks of the (002) and (004) crystal planes, respectively. The modification treatment did not change the crystal form of bamboo cellulose.

[0091] The relative crystallinity and microfibril angle of the modified bamboo in Example 1 and Comparative Examples 1-5 were calculated using the Segal method in this invention. The results are shown in Table 1.

[0092] Table 1. Results of relative crystallinity and microfibril angle determination of modified bamboo.

[0093]

[0094] As shown in Table 1, compared to D8.5 without TEOS impregnation, the relative crystallinity of NTEOS and DTEOS decreased. This is due to the expansion of the amorphous region volume, the low crystallinity of the silica gel generated by TEOS hydrolysis, and the decrease in the intensity of diffraction peaks caused by the increase of amorphous components on the cell wall. The decrease in crystallinity indicates that TEOS exists in the cell wall. In addition, after delignification treatment, the hemicellulose and some amorphous cellulose of flattened bamboo were effectively removed, and the proportion of cellulose crystalline regions increased relatively. Therefore, the relative cellulose content of DSi, DTEOS, and De was higher than that of the undelignified sample, and correspondingly, the relative crystallinity was also higher. Table 1 also shows that the microfibril angle of NTEOS was only slightly larger than that of D8.5, indicating that the modification treatment did not significantly affect the structural stability of the fiber cell wall microfibrils, and the microfibrils were still highly aligned at a certain angle along the axis.

[0095] 3. Acoustic performance analysis

[0096] The first three natural frequencies and first-order transfer function of the modified bamboo materials in Example 1 and Comparative Examples 1-3 and 5 were measured in this invention, and the results are shown in Table 2. The natural frequency of a material refers to the inherent vibration frequency of the material when it is not subjected to external forces. Generally, the higher the stiffness of a material, the higher its natural frequency. However, when the density of a material is higher, its mass is greater, and under the same stiffness conditions, the vibration frequency will decrease.

[0097] Table 2. Results of determination of the first three natural frequencies and first-order transfer function of modified bamboo.

[0098] Note: The data in the table are in the form A(b), where A is the mean and b is the standard deviation.

[0099] As shown in Table 2, the first-order natural frequencies of the modified bamboo treated by different methods are not significantly different. The first-order natural frequency of NTEOS modified bamboo in Example 1 is 1011.7 Hz, slightly lower than other materials. Compared with NTEOS (2665.04 Hz) and NSi (2868.42 Hz), the second-order natural frequencies of DTEOS, De, and DSi decrease to 1600-1750 Hz, and the spacing between the resonance peaks narrows, indicating that they are more prone to resonance in the low-to-mid frequency range. Furthermore, Table 2 shows the first-order resonance peak transfer function values ​​of NTEOS, DSi, NSi, DTEOS, and De. NTEOS has the lowest first-order resonance peak transfer function value. A lower resonance peak transfer function value indicates a smaller response when the material vibrates, meaning it can suppress vibration. This demonstrates that the modified bamboo of this invention has a smaller response when vibrating and can better suppress vibration.

[0100] In addition, the acoustic vibration characteristic parameters of the modified bamboo materials of Example 1 and Comparative Examples 1-3 and 5 were measured in this invention, and the results are shown in Table 3.

[0101] Table 3. Results of acoustic vibration characteristics measurement of modified bamboo.

[0102]

[0103]

[0104] Note: The data in the table are in the form A(b), where A is the mean and b is the standard deviation.

[0105] As shown in Table 3, the specific dynamic modulus of elasticity (E / ρ) of NTEOS is 38.7% lower than that of DSi, and also lower than that of delignified modified bamboo materials DTEOS and De. Since the vibration efficiency of the material decreases with decreasing specific dynamic modulus of elasticity, it indicates that the vibration efficiency of the modified bamboo material NTEOS of this invention is relatively low, which is more conducive to suppressing vibration. Sound conversion efficiency is the conversion efficiency during the vibration process of a material. Wood with a higher sound conversion efficiency is better able to convert vibration into sound radiation, thus making it suitable for making resonator boxes for musical instruments. Among them, NTEOS has the lowest sound conversion efficiency, which helps to prevent the vibration of the speaker cabinet when used to make speaker boxes and other equipment. Acoustic impedance, sound radiation quality constant, and the conversion of vibration energy into sound energy are related. The smaller the sound radiation quality constant, the lower the loudness of the sound radiation. NTEOS has the smallest sound radiation quality constant, mainly because the sound radiation quality constant is negatively correlated with density. The silica impregnated in the bamboo fails to play a role in transmitting vibration, but instead increases the specific gravity of the bamboo, thus reducing the sound radiation quality constant and helping to suppress vibration. A higher acoustic impedance indicates increased energy consumption during vibration transmission. Acoustic impedance increases with material density; compression compaction increases the density of bamboo, resulting in an NTEOS acoustic impedance of 3.797 × 10⁻⁶. 6 kg·s -1 ·m 2 The increased difference in acoustic impedance with air leads to greater vibration loss at the interface between NTEOS and air, which helps reduce sound radiation. Due to the presence of internal friction, the vibrational energy generated during material vibration is converted into internal energy dissipation. This ability is characterized by the loss tangent, with NTEOS exhibiting the highest loss tangent, indicating that NTEOS is more effective at converting vibrational energy into heat dissipation, thus more effectively suppressing vibration.

[0106] 4. Mechanical property analysis

[0107] The mechanical properties of the modified bamboo in Example 1 and Comparative Examples 1-3 and 5 were measured in this invention, and the results are shown in Table 4.

[0108] Table 4. Results of Mechanical Property Testing of Modified Bamboo

[0109]

[0110] As can be seen from Table 4, the bending strength and bending modulus of Example 1 and Comparative Examples 1-3 and 5 are higher than those of natural flattened bamboo. Furthermore, NTEOS exhibits the highest bending strength and a relatively high bending modulus. Since Example 1 did not employ a lignin removal process, its energy consumption is also relatively lower. In other words, the modified bamboo NTEOS prepared by this invention possesses excellent mechanical properties.

[0111] It should be noted that NTEOS exhibits the highest flexural strength. This is because the silicon precursor solution has better permeability, allowing TEOS to penetrate more easily into the cell walls and cavities of bamboo. Under mild conditions, it undergoes hydrolysis, resulting in in-situ generated nano-silica particles that chemically cross-link with bamboo components such as cellulose, forming a strong bond. Simultaneously, these in-situ generated nanoparticles effectively fill the tiny pores inside the bamboo and the cracks and defects generated during the flattening process, enhancing the structural integrity of the bamboo. Furthermore, TEOS forms a uniformly distributed thin film-like modified layer inside the bamboo, which can disperse stress over a wider area under external force, reducing stress concentration and preventing cell wall deformation and damage. The contribution of nano-silica impregnation modification to bamboo strength is limited. This is because the physical deposition has poor dispersion and insufficient bonding with bamboo. Nano-silica particles penetrate into the cell cavities of bamboo through water channels and are physically deposited, resulting in a relatively dispersed distribution within the bamboo. This prevents the formation of a uniform and continuous modified layer like that of TEOS modification, limiting its support for the bamboo cell walls and making it difficult to effectively transfer and distribute stress throughout the bamboo structure. At the same time, the bonding force between the physically deposited silica particles and bamboo components is relatively weak. When bamboo is subjected to external forces, the nanoparticles may slip relative to the bamboo matrix, limiting the effect of nano-silica on improving the strength of bamboo.

[0112] 5. Analysis of water absorption thickness expansion rate

[0113] This invention measured the changes in water absorption thickness swelling rate and weight gain rate of modified bamboo materials in Example 1 and Comparative Examples 1-4 with immersion time. The results are shown in [reference needed]. Figure 4 .

[0114] like Figure 4Figures A and 4B show the curves of water absorption thickness swelling rate (TS) and weight gain rate (WPG) of the modified bamboo materials in Example 1 and Comparative Examples 1-4, respectively, over time. As can be seen from the figures, at room temperature, in the early stage of impregnation, the TS and WPG of each modified bamboo material increased rapidly, and then gradually leveled off. After 24 hours of impregnation, the water absorption thickness swelling rates of NTEOS, NSi, and D8.5 were 5.62%, 6.92%, and 7.37%, respectively. After impregnation, the hydrolysis product of TEOS, orthosilicic acid, is unstable at room temperature and further decomposes into metasilicic acid and amorphous silica particles, forming a silica film on the cell wall. This film blocks the cell pits and cracks caused by hot pressing, reducing the channels for water. Simultaneously, the hydrophilic hydroxyl groups in the bamboo are covered and shielded by the silica film, or undergo condensation reactions to form siloxane bonds, further reducing its ability to adsorb water molecules. Under this dual effect, the water absorption thickness swelling rate of NTEOS is reduced. For NSi, the impregnated nano-silica particles can physically fill and block vascular tissues such as vessels and sieves, resulting in a low thickness expansion rate after 24 hours. The TS (transformation time) of DTEOS and DSi after delignification treatment were 15.92% and 14.93% respectively after 24 hours of immersion. This is because delignification treatment disrupts the structure of the middle lamina and cell corners, increasing the number and size of mesopores, making it easier for water molecules to enter.

[0115] Furthermore, considering the changes in TS and WPG over time, the undelignified modified bamboo maintained a slow growth rate for the first 120 hours, while the delignified modified bamboo showed a steady increase in weight and thickness after only 40 hours of immersion. This is because the approximately 30% compression rate and the deposited silica were insufficient to fill and block these pores, leading to rapid water penetration into the bamboo. After about 150 hours, the weight gain and thickness expansion rate of all materials no longer showed significant changes. The thickness expansion rate of NTEOS was 14.44%, which was lower than that of D8.5 (16.40%) which was only compressed and compacted. The weight gain rate also showed a similar trend, indicating that TEOS modification effectively reduced the water absorption thickness expansion rate of bamboo.

[0116] Application Example 1

[0117] This application example provides a speaker made from the modified bamboo material NTEOS of Example 1.

[0118] Application Comparative Example 1

[0119] This application provides a comparative example of a speaker made of commercially available medium-density fiberboard (MDF density 650 kg / m³). 3 ) is the raw material.

[0120] Application Comparative Example 2

[0121] This application provides a comparative example of a speaker made of commercially available acrylonitrile-styrene-butadiene copolymer sheet (ABS, density 1050 kg / m³). 3 ) is the raw material.

[0122] The thickness of the raw materials in Application Example 1 and Comparative Examples 1-2 above is 8±0.1mm, the specifications of the manufactured speakers are 160mm(L)×160mm(W)×8mm(T), and the speaker manufacturing process is the same.

[0123] It should be noted that, in order to evaluate the influence of the cabinet material on the frequency response function and mode shape of the speaker, a simple sealed cabinet design was adopted, with openings on two sides to place the speaker and lead wires, and the cabinet surfaces were sealed with silicone sealant. Apart from the difference in cabinet material, the three types of speakers are not significantly different.

[0124] The present invention analyzes the spectral characteristics, vibration response, and sound insulation performance of the speaker enclosure.

[0125] 1. Spectral Characteristics Analysis

[0126] The first three resonant peak frequencies of each side of the speaker enclosure were tested in the corresponding use case 1 and application comparison examples 1-2. The results are shown in Table 5.

[0127] Table 5. Results of frequency measurements of the first three resonant peaks on each side of the speaker enclosure.

[0128]

[0129] Note: The third-order resonant peak frequency of the NTEOS enclosure is much higher than 600Hz, so it will not be analyzed.

[0130] As shown in Table 5, the speaker panels made using the modified bamboo NTEOS material of this invention have higher natural frequencies. The natural frequency (peak position of the resonance peak) of a material is mainly determined by its elastic modulus and density. Materials with higher elastic modulus are less prone to bending deformation under external force, thus having higher natural frequencies. That is, the bamboo material of this invention, after mineralization and densification treatment, has a high elastic modulus, and its natural frequency also increases accordingly, resulting in poorer vibration suppression. In addition, in the frequency band below 550Hz, the number of resonance peaks in each panel of the speaker panel made using the modified bamboo NTEOS material of this invention is less than or equal to 2, while the number of resonance peaks in each panel of the speaker panel made using ABS and MDF materials is ≥2. The fewer resonance peaks can effectively avoid resonance overtones in the cabinet.

[0131] The present invention also tested the vibration frequency response of each side of the speaker enclosure corresponding to Use Case 1 and Application Comparison Examples 1-2, and the results are shown in [reference]. Figure 5 .

[0132] like Figure 5 The figures show the frequency response curves of the speaker cabinet side panel (A), top panel (B), and back panel (C) for Application Example 1 and Comparative Examples 1-2. As can be seen from the figures, the NTEOS cabinet has the highest natural frequency, with the first-order resonance peaks of its wall panels appearing around 305Hz, significantly higher than MDF (approximately 240Hz) and ABS (approximately 175Hz), indicating that it can effectively reduce the adverse effects of resonance on sound quality.

[0133] 2. Vibration Response Analysis

[0134] The root mean square values ​​of the vibration response of each side of the speaker enclosure corresponding to Example 1 and Comparative Examples 1-2 of this invention were tested, and the results are shown in [reference]. Figure 6 .

[0135] like Figure 6 The figure shows a root mean square (RMS) histogram of the vibration response of the speaker cabinet side panel (A), top panel (B), and back panel (C) of Application Example 1 and Comparative Examples 1-2. The RMS value is a parameter for evaluating vibration and noise levels. As can be seen from the figure, the RMS values ​​of the three materials are NTEOS, MDF, and ABS in ascending order. This indicates that when the speaker vibrates during operation, the various walls of the speaker cabinet made of the modified bamboo material NTEOS of this invention are not easily excited by the conducted vibration, thereby effectively avoiding the adverse effects of additional sound radiation.

[0136] 3. Sound insulation performance analysis

[0137] The sound insulation performance of the speaker enclosure corresponding to Example 1 and Comparative Examples 1-2 of this invention was tested, and the results are shown in [reference]. Figure 7 .

[0138] like Figure 7 As shown in Figure A, the sound transmission loss curves of different speaker cabinet materials in the mid-low frequency range are displayed. It can be seen from the figure that all three materials show a trend of first decreasing and then increasing in the mid-low frequency range, and all have a clear trough (i.e., natural frequency). Among them, the sound transmission loss value of NTEOS at the natural frequency is 21.05dB, which is much higher than that of MDF (8.6dB) and ABS (10.14dB). Therefore, speakers made of NTEOS can maintain good acoustic performance in the low frequency range.

[0139] like Figure 7As shown in Figure B, the sound transmission loss curves of different speaker cabinet materials at different center frequencies in the 1 / 3 octave band are shown. It can be seen from the figure that the sound insulation of NTEOS and ABS is similar in most frequency bands. In the 200-400Hz frequency range, the sound insulation of ABS is slightly higher than that of NTEOS, while at 1600Hz, the sound insulation of NTEOS is higher than that of ABS. At the same time, except at the natural frequency of around 1600Hz, the sound insulation of NTEOS and ABS is significantly higher than that of MDF.

[0140] like Figure 7 As shown in Figure C, this is a bar chart of the average sound insulation of speaker enclosures made of different materials in the mid-to-low frequency range. It can be seen from the figure that the average sound insulation of NTEOS, MDF, and ABS are 44.24dB, 34.72dB, and 45.82dB, respectively. The average sound insulation of NTEOS and ABS is relatively close, and both are significantly higher than that of MDF. NTEOS is about 39.24% higher than MDF, indicating that the modified bamboo material NTEOS is comparable to ABS in sound insulation performance and is significantly better than MDF.

[0141] Depend on Figure 7 As can be seen from AC, the speaker enclosure made from the modified bamboo NTEOS of this invention has good sound insulation performance, which can effectively avoid the problems of enclosure resonance and sound radiation. It not only improves the acoustic performance of the speaker, but also provides a new option for the green and high-performance design of speaker materials.

[0142] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A method for preparing modified bamboo, characterized in that, Includes the following steps: (1) Mix tetraethyl orthosilicate, silane coupling agent and anhydrous ethanol and adjust to acidity to obtain silicon precursor solution; (2) Immerse the bamboo in the silicon precursor solution, remove it and dry it to obtain mineralized bamboo; (3) The mineralized bamboo is densified to obtain modified bamboo; In step (1), the pH is adjusted to 3-4 using an acidic solution; The acidic solution includes at least one of sulfuric acid solution, hydrochloric acid solution, nitric acid solution, and phosphoric acid solution; The densification process is a hot-pressing densification process; The hot pressing temperature for the hot pressing densification process is 150-180℃, the hot pressing time is 20-30 min, and the pressure is 2-4 MPa.

2. The method for preparing modified bamboo according to claim 1, characterized in that, The molar ratio of tetraethyl orthosilicate, silane coupling agent and anhydrous ethanol is 1:0.1-0.3:4-20; The silane coupling agent includes at least one of γ-aminopropyltriethoxysilane, γ-aminopropyltrimethoxysilane, and γ-(2,3-epoxypropoxy)propyltrimethoxysilane.

3. The method for preparing modified bamboo according to claim 1, characterized in that, The impregnation is carried out under negative pressure for 1-6 hours; The negative pressure is -0.08 to -0.1 MPa.

4. The method for preparing modified bamboo according to claim 1, characterized in that, The drying process involves air drying for 24-40 hours.

5. The method for preparing modified bamboo according to claim 1, characterized in that, After soaking and removing the bamboo material, place the bamboo material inside the wrapping material; The packaging material includes one of aluminum foil, polyethylene, nylon, and non-woven fabric.

6. The method for preparing modified bamboo according to any one of claims 1-5, characterized in that, The compression rate of the mineralized bamboo after the densification treatment is 30-50%.

7. A modified bamboo material prepared by the method of any one of claims 1-6.

8. The use of the modified bamboo material prepared by the method of any one of claims 1-6 in musical instruments and sound equipment.

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