High-strength bamboo fiber bundle and extraction method and application thereof

Abstract

The application provides a high-strength bamboo fiber bundle and an extraction method and application thereof. The extraction method comprises the following steps: (1) processing bamboo into bamboo sheets with a certain thickness after removing the bamboo yellow and bamboo green parts of the bamboo; (2) soaking the bamboo sheets in a swelling agent to sufficiently swell the bamboo sheets to obtain swelling bamboo sheets with an intact bamboo fiber bundle structure; (3) treating the swelling bamboo sheets with a delignification solution to obtain delignified bamboo sheets with an intact bamboo fiber bundle structure; and (4) drying the delignified bamboo sheets, and then mechanically separating and extracting the delignified bamboo sheets to obtain high-strength bamboo fiber bundles. The application fully retains the natural structure of the bamboo fiber bundle, efficiently dissociates the parenchyma cells, and extracts the high-strength bamboo fiber bundle, which can be used in the fields of composite reinforcing materials, photovoltaics, energy storage, wearable smart fabrics and the like. The extraction method has mild extraction conditions and a short time, the extracted bamboo cellulose has high strength, and has an industrialization prospect.

Description

Technical Field

[0001] This invention belongs to the field of high-value processing and utilization technology of bamboo materials, specifically involving a high-strength bamboo fiber bundle, its extraction method and application. Background Technology

[0002] Natural bamboo fiber bundles possess excellent mechanical properties and are known as "natural glass fibers." The cells of bamboo, including vessels, sieve tubes, and fibers, have small cavities and exhibit radial non-uniformity. The fiber cell walls are thick and have a complex structure with alternating thick and thin layers. The pit density and pit diameter are also small, resulting in low overall porosity, poor permeability, and significant heterogeneity in bamboo. Currently, methods for extracting bamboo fiber bundles mainly include physical methods, chemical methods, or a combination of both. However, traditional physical methods primarily involve steam explosion, pyrolysis, and crushing, but pure physical decomposition requires repeated and significant mechanical force, damaging the natural structure of bamboo cellulose. Chemical methods using peroxyacids and alkalis suffer from long processing times and large reagent consumption, further damaging the natural structure of the bamboo fiber bundles. Therefore, bamboo fibers prepared using these methods have poor mechanical properties, limiting their further processing and utilization.

[0003] This invention first employs a gentle swelling treatment technique to soften bamboo while promoting the release of some lignin and hemicellulose, thus loosening the dense internal structure of the bamboo. This significantly improves the accessibility of bamboo while preserving its natural structure, allowing for the preparation of swollen bamboo. Next, the swollen bamboo undergoes a delignin treatment to further remove lignin and hemicellulose from the surface of the bamboo fiber bundles. Because the increased accessibility of the bamboo after swelling treatment shortens the subsequent delignin process, avoiding the damage to the natural structure of the bamboo fiber bundles caused by prolonged chemical treatment. During this delignin process, the internal structure of the bamboo is further loosened, and more hydroxyl groups are exposed on the surface of the bamboo fiber bundles, providing a foundation for subsequent hydrogen bond recombination to construct high-strength bamboo fiber bundles. Finally, a drying process is combined to achieve intermolecular and intramolecular hydrogen bond reconstruction in the bamboo fiber bundles, giving them high strength. Drying also further loosens the internal structure of the bamboo. Therefore, only a small amount of external mechanical force is needed in subsequent mechanical processing (avoiding damage to the natural structure of the bamboo fiber), resulting in the efficient extraction of high-strength bamboo fiber bundles. Summary of the Invention

[0004] Objective of the Invention: Traditional physical or chemical methods for extracting bamboo fiber bundles result in incomplete natural bamboo fiber bundle structures, poor mechanical properties, long processing times, and large reagent consumption, severely limiting the preparation and application of high-strength bamboo fiber bundles. To address these problems, this invention provides a method for preparing high-strength bamboo fiber bundles using a mild swelling treatment combined with delignification and the hydrogen bond reconstruction effect of drying. A mild swelling agent is used to improve the accessibility of bamboo, removing some lignin and hemicellulose while effectively preserving the structure of the natural bamboo fiber bundles and loosening the internal structure of the bamboo. This provides more space for subsequent delignification, shortens the delignification time, and avoids the damage to the natural bamboo fiber bundle structure caused by chemical treatment. The delignification treatment exposes more hydroxyl groups on the surface of the bamboo fiber bundles, further loosening the internal structure. The drying treatment achieves intramolecular and intermolecular hydrogen bond reconstruction of the cellulose chains in the bamboo fiber bundles, obtaining high-strength bamboo fiber bundles, while simultaneously further loosening the internal structure of the bamboo. Finally, high-strength bamboo fiber bundles were extracted using relatively small amounts of external mechanical force (avoiding mechanical processing that could damage the natural structure of the bamboo fibers).

[0005] Therefore, the specific technical solution adopted by the present invention is as follows:

[0006] A method for extracting high-strength bamboo fiber bundles includes the following steps:

[0007] S1. After removing the yellow and green parts of the bamboo, process it into bamboo strips of a certain thickness;

[0008] S2. Soak the bamboo strips obtained in step S1 in a swelling agent to fully swell them, and then wash off the swelling agent to obtain swollen bamboo strips with complete bamboo fiber bundle structure.

[0009] S3. Soak the swollen bamboo strips obtained in step S2 in a delignification solution until the bamboo strips turn completely white, and then wash off the delignification solution to obtain delignified bamboo strips with intact bamboo fiber bundle structure.

[0010] S4. After drying the lignin-free bamboo chips obtained in step S3, mechanical separation is performed to obtain high-strength bamboo fiber bundles. The extraction rate of the high-strength bamboo fiber bundles relative to natural bamboo material is 20-30%.

[0011] Furthermore, in step S1, the bamboo species used are Bambusa textilis, Bambusa pubescens, Bambusa repens, Bambusa textilis, Bambusa lanceolata, Bambusa textilis, Bambusa pubescens, Bambusa purpurea, Bambusa ventricosa, Bambusa textilis ...

[0012] Furthermore, in step S1, the bamboo material can be dried or not, and the moisture content is 0-150%.

[0013] Furthermore, in step S1, the bamboo material is 1 year old, 2 years old, 3 years old, or 4 years old.

[0014] Furthermore, in step S1, the bamboo part of the bamboo material is the part near the green part, the flesh part, or the part near the yellow part.

[0015] Furthermore, in step S1, the thickness of the bamboo material is 1-5 mm.

[0016] Furthermore, the swelling agent in step S2 is any one of water, a sulfuric acid solution with a mass fraction of 0-15 wt%, or a sodium hydroxide solution with a mass fraction of 0-12 wt%.

[0017] Furthermore, the swelling agent in step S2 is a mixed solution composed of acidic and basic compounds.

[0018] Furthermore, the acidic compound is at least one of formic acid, acetic acid, lactic acid, oxalic acid, ethylene glycol, glycerol, or urea.

[0019] Furthermore, the alkaline compound is at least one of choline chloride, zinc chloride, ammonium chloride, betaine, or guanidine hydrochloride.

[0020] Furthermore, the molar ratio of acidic and basic compounds in the mixed solution is 10:1 to 1:1.

[0021] Furthermore, the acidic compound in the mixed solution is any one of oxalic acid, lactic acid, formic acid, acetic acid, ethylene glycol, glycerol, and urea, and the basic compound is choline chloride.

[0022] Furthermore, the acidic compound in the mixed solution is lactic acid, and the basic compound is any one of choline chloride, zinc chloride, ammonium chloride, betaine, and guanidine hydrochloride, with a molar ratio of acidic to basic compounds of 10:1.

[0023] Furthermore, in step S2, the swelling agent treatment temperature is 70-150℃, preferably 70-130℃; the treatment time is 0.25-6h, preferably 0.25-4h.

[0024] Furthermore, in step S2, the solid-liquid ratio of bamboo strips and swelling agent is 1:5-1:15 (g / ml).

[0025] Furthermore, in step S2, the water absorption and weight gain rate of the swollen bamboo strips is 160-220%, the lignin removal rate is 2-65%, and the hemicellulose removal rate is 1-55%.

[0026] Furthermore, in step S3, the delignification solution is any one of the following: a mixed solution of acetic acid and hydrogen peroxide, a mixed solution of formic acid and hydrogen peroxide, a mixed solution of acetic acid and sodium chlorite, or a mixed solution of sodium hydroxide and sodium sulfite.

[0027] Furthermore, in the mixed solution of acetic acid and hydrogen peroxide, the volume ratio of acetic acid to hydrogen peroxide is 1:1; in the mixed solution of formic acid and hydrogen peroxide, the volume ratio of formic acid to hydrogen peroxide is 1:1; in the mixed solution of acetic acid and sodium chlorite, the concentration of sodium chlorite is 2wt%, and the pH is adjusted to 4.6 by acetic acid; in the mixed solution of sodium hydroxide and sodium sulfite, the concentrations of sodium hydroxide and sodium sulfite are 2.5M and 0.4M, respectively.

[0028] Furthermore, in step S3, the solid-liquid ratio of the swollen bamboo chips to the delignified solution is 1:5-1:15 (g / ml), the treatment time is 3-12 hours, and the treatment temperature is 50-100℃; the lignin removal rate in the delignified bamboo chips is 80-95%, and the hemicellulose removal rate is 65-80%.

[0029] Furthermore, in step S4, the drying method is at least one of room temperature drying or oven drying.

[0030] Furthermore, in step S4, mechanical separation includes at least one of kneading, rolling, or combing.

[0031] According to another aspect of the present invention, a high-strength bamboo fiber bundle is provided, which is prepared by the extraction method of the high-strength bamboo fiber bundle.

[0032] Furthermore, the high-strength bamboo fiber bundles have a diameter of 150-350 μm, a uniform diameter distribution along the length direction, a length of 2-30 cm, an aspect ratio of 50-2000, and a crystallinity of 50-72%.

[0033] Furthermore, the high-strength bamboo fiber bundle has a tensile stress of 1500-3500 MPa, a Young's modulus of 25-70 GPa, and a breaking energy of 20-95 MJ / m. 3 ;

[0034] Furthermore, the content of intramolecular hydrogen bonds O(3)H…O(5) in the high-strength bamboo fiber bundle increased by 20-30%, the content of O(2)H…O(6) decreased by 25-35%, and the content of intermolecular hydrogen bonds O(6)H…O(3') increased by 5-15%.

[0035] According to another aspect of the present invention, an application of high-strength bamboo fiber bundles is provided, such as the application of the high-strength bamboo fiber bundles in the fields of composite reinforced materials, photovoltaics, energy storage, personal thermal management, and wearable smart fabrics.

[0036] Beneficial effects: Compared with the prior art, the advantages of the present invention include:

[0037] 1) The method for extracting high-strength bamboo fiber bundles of the present invention has advantages such as mild processing conditions, short processing time and small mechanical force, which saves energy consumption, reduces preparation costs and has industrialization prospects.

[0038] 2) The high-strength bamboo fiber bundles extracted by this invention retain the structure of natural bamboo fiber bundles, have a uniform diameter distribution, and a tensile strength of up to 3500MPa.

[0039] 3) The bamboo fiber bundles of the present invention not only have high strength, but also have a large number of hydroxyl groups on the surface, which provide a basis for subsequent functionalization, further promoting the application of bamboo fiber in composite reinforced materials, photovoltaics, energy storage, personal thermal management, wearable smart fabrics and other fields. Attached Figure Description

[0040] Figure 1 This is a flowchart of the extraction process for high-strength bamboo fiber bundles.

[0041] Figure 2 The images show the roller pressing separation effect of dried lignin-free bamboo chips in Comparative Example 1 and Example 9.

[0042] Figure 3 The mechanical properties of high-strength bamboo fiber bundles extracted from bamboo strips, Comparative Example 1, and Example 9 are described.

[0043] Figure 4 These are photographs of the high-strength bamboo fiber bundles being wound, folded, knotted, and lifted with heavy objects in Example 9.

[0044] Figure 5 This is a morphological diagram of the high-strength bamboo fiber bundle in Example 9, and a diagram showing its diameter and length distribution.

[0045] Figure 6 The water absorption weight gain rate, lignin and hemicellulose content of the bamboo strips and swollen bamboo strips in Example 9 are also mentioned.

[0046] Figure 7 These are scanning electron microscope images of bamboo, swollen bamboo, and high-strength bamboo fiber bundles from Example 9.

[0047] Figure 8 These are scanning electron microscope images of the swollen bamboo strips from Examples 1, 2, and 3.

[0048] Figure 9The mechanical properties of bamboo fiber bundles extracted from 2mm bamboo strips in Examples 1, 2, 3, 4 and Comparative Example 1 are described.

[0049] Figure 10 This refers to the phase change properties of the bamboo fabric in Example 12. Detailed Implementation

[0050] The technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings, technical process steps, specific implementation conditions, and materials. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0051] The method used in this invention is applicable to various types of bamboo. The bamboo raw materials can be derived from species such as Phyllostachys edulis, Phyllostachys moso, Phyllostachys aurea, Phyllostachys nigra, Phyllostachys edulis, Phyllostachys nigra, Phyllostachys edulis, Phyllostachys nigra var. nigra ...

[0052] The following examples illustrate the invention using bamboo strips derived from the flesh of 2-year-old moso bamboo with a moisture content of 10-20%. The chemical composition of the bamboo material is 37.7% cellulose, 26.2% lignin, and 16.4% hemicellulose. The length is mainly limited by the length of the bamboo nodes and can be 50mm, 100mm, 150mm, 200mm, 250mm, and 300mm.

[0053] The solid-liquid ratio unit used in this invention is (g / ml). The solid-liquid ratio of bamboo and swelling agent can be 1:5-1:15. The following examples illustrate this invention with a solid-liquid ratio of 1:10.

[0054] The delignification solution used in this invention can be a mixed solution of acetic acid and hydrogen peroxide, a mixed solution of formic acid and hydrogen peroxide, a mixed solution of acetic acid and sodium chlorite, or a mixed solution of sodium hydroxide and sodium sulfite, wherein acetic acid, formic acid, and 30% hydrogen peroxide are commercially available reagents and can be used directly. The following examples illustrate this invention using a mixed solution of acetic acid and hydrogen peroxide as the delignification solution.

[0055] The lignin-free bamboo chips used in this invention can be dried by methods such as room temperature drying or oven drying. The following examples illustrate this invention by using oven-dried lignin-free bamboo chips.

[0056] The bamboo fiber bundles used in this invention can be separated mechanically by rubbing, rolling, or combing. The following examples illustrate this invention by using rolling as a mechanical method to extract bamboo fiber bundles.

[0057] Example 1

[0058] 1) Bamboo strips (50mm in length, 20mm in width, and 2mm in thickness) were thoroughly mixed in deionized water at a solid-liquid ratio of 1:10. The mixture was heated at 90℃ for 1 hour to allow the bamboo strips to swell. After the reaction was complete, the bamboo strips were washed with deionized water to obtain swollen bamboo strips. The water absorption and weight gain rate of the swollen bamboo strips was 166%, the lignin removal rate was 19%, and the hemicellulose removal rate was 14%.

[0059] 2) Prepare a mixed solution of acetic acid and hydrogen peroxide at a volume ratio of 1:1. Immerse the swollen bamboo chips in the prepared mixed solution at a solid-liquid ratio of 1:10 and mix thoroughly. Heat at 80℃ for 5 hours to remove lignin, after which the bamboo turns white. Then wash off the excess lignin solution with a mixed solution of ethanol and deionized water, and finally wash with deionized water to obtain lignin-removed bamboo chips. The preferred volume ratio of ethanol to deionized water is 1:1. The lignin removal rate in the lignin-removed bamboo chips is 84%, and the hemicellulose removal rate is 72%.

[0060] 3) The lignin-free bamboo chips are dried in an oven at 60℃, and bamboo fiber bundles are obtained by efficient separation through roller pressing. The bundles have a diameter of 250-350μm, a length of 50mm, a maximum tensile stress of 1512MPa, a Young's modulus of 25GPa, and a breaking energy of 35MJ / m. 3 Gravimetric analysis showed that 0.25g of high-strength bamboo fiber bundles could be extracted from 1g of natural bamboo, with an extraction rate of 25%.

[0061] Example 2

[0062] 1) Prepare a 2% (w / w) sulfuric acid solution. Add bamboo strips (50mm long, 20mm wide, and 2mm thick) to deionized water at a solid-liquid ratio of 1:10 and mix thoroughly. Heat at 90℃ for 1 hour to allow the mixture to swell. After the reaction is complete, wash the bamboo strips with deionized water to remove excess swelling solution, thus obtaining swollen bamboo strips. The water absorption and weight gain rate of the swollen bamboo strips is 172%, the lignin removal rate is 24%, and the hemicellulose removal rate is 20%.

[0063] 2) Prepare a mixed solution of acetic acid and hydrogen peroxide at a volume ratio of 1:1. Immerse the swollen bamboo chips in the prepared mixed solution at a solid-liquid ratio of 1:10 and mix thoroughly. Heat at 80℃ for 5 hours to remove lignin until the bamboo turns white. Then wash off excess lignin solution with a mixed solution of ethanol and deionized water, and finally wash with deionized water to obtain lignin-removed bamboo chips. The preferred volume ratio of ethanol to deionized water is 1:1. The lignin removal rate in the lignin-removed bamboo chips is 82%, and the hemicellulose removal rate is 76%.

[0064] 3) The lignin-treated bamboo chips were dried in an oven at 60℃, and bamboo fiber bundles were obtained by efficient separation using roller pressing. The bundles had a diameter of 150-250 μm, a length of 50 mm, a maximum tensile stress of 1673 MPa, a Young's modulus of 37.7 GPa, and a fracture energy of 40.6 MJ / m. 3 The extraction rate of high-strength bamboo fiber bundles relative to natural bamboo is 24%.

[0065] 4) The effects of different acid concentrations on the strength of bamboo fibers were studied separately. As shown in the table below, it can be seen that the strength of bamboo fibers is the lowest when the acid concentration is 15%, indicating that high concentrations of acid have a negative effect on the strength of bamboo fibers.

[0066] Acid concentration (wt%) Tensile stress (MPa) Young's modulus (GPa) <![CDATA[Fracture energy (MJ / m 3 )]]> 2 1673 37.7 40.6 5 1623 33.4 48.3 10 1648 31.9 42.9 15 1522 30.6 38.8

[0067] Example 3

[0068] 1) Prepare a 2% sodium hydroxide solution. Bamboo strips (50mm long, 20mm wide, and 2mm thick) are thoroughly mixed in deionized water at a solid-liquid ratio of 1:10. The mixture is heated at 90℃ for 1 hour to allow the bamboo strips to swell. After the reaction is complete, the bamboo strips are washed with deionized water to remove excess swelling solution, thus obtaining swollen bamboo strips. The water absorption and weight gain rate of the swollen bamboo strips is 202%, the lignin removal rate is 13%, and the hemicellulose removal rate is 44%.

[0069] 2) Prepare a mixed solution of acetic acid and hydrogen peroxide at a volume ratio of 1:1. Immerse the swollen bamboo chips in the prepared mixed solution at a solid-liquid ratio of 1:10 and mix thoroughly. Heat at 80℃ for 3 hours to remove lignin until the bamboo turns white. Then wash off excess lignin solution with a mixed solution of ethanol and deionized water, and finally wash with deionized water to obtain lignin-removed bamboo chips. The preferred volume ratio of ethanol to deionized water is 1:1. The lignin removal rate in the lignin-removed bamboo chips is 95%, and the hemicellulose removal rate is 75%.

[0070] 3) The lignin-treated bamboo chips were dried in an oven at 60℃, and bamboo fiber bundles were obtained by efficient separation using roller pressing. The bundles had a diameter of 150-200 μm, a length of 50 mm, a maximum tensile stress of 1745 MPa, a Young's modulus of 33.9 GPa, and a breaking energy of 48.1 MJ / m. 3 The extraction rate of high-strength bamboo fiber bundles relative to natural bamboo is 21%.

[0071] 4) The effects of different alkali concentrations on the strength of bamboo fibers were studied separately. As shown in the table below, it can be seen that the higher the alkali concentration, the lower the strength of bamboo fibers. Excessive alkali concentration will destroy the natural structure of bamboo fibers, resulting in a decrease in their strength.

[0072]

[0073] Example 4

[0074] 1) A mixed solution was prepared using lactic acid as the acidic solvent and choline chloride as the alkaline solvent at a molar ratio of 10:1. Bamboo strips (50 mm in length, 20 mm in width, and 1-5 mm in thickness) were added to the prepared solution at a solid-liquid ratio of 1:10 and mixed thoroughly. To ensure the swelling effect, bamboo strips of different thicknesses were heated and swollen at 110℃ for 1-3 hours. After the reaction was completed, the bamboo strips were washed with a mixed solution of ethanol and deionized water to remove excess swelling solution, and finally washed with deionized water to obtain swollen bamboo strips. The preferred volume ratio of ethanol to deionized water was 7:3-10:0. The water absorption and weight gain rate of the swollen bamboo strips was 170-180%, the lignin removal rate was 10-20%, and the hemicellulose removal rate was 20-30%.

[0075] 2) Prepare a mixed solution of acetic acid and hydrogen peroxide at a volume ratio of 1:1. Immerse the swollen bamboo chips in the prepared mixed solution at a solid-liquid ratio of 1:10 and mix thoroughly. Heat at 80℃ for 3-5 hours to remove lignin until the bamboo turns white. Then wash off excess lignin solution with a mixed solution of ethanol and deionized water, and finally wash with deionized water to obtain lignin-removed bamboo chips. The preferred volume ratio of ethanol to deionized water is 1:1. The lignin removal rate in the lignin-removed bamboo chips is 85-95%, and the hemicellulose removal rate is 70-80%.

[0076] 3) The lignin-free bamboo chips are dried in an oven at 60℃, and bamboo fiber bundles are obtained by efficient separation through roller pressing. The bundles have a diameter of 200-300μm, a length of 50mm, a tensile stress of 2800-3300MPa, a Young's modulus of 60-70GPa, and a breaking energy of 70-85MJ / m. 3 The extraction rate of high-strength bamboo fiber bundles is 23-28% compared to that of natural bamboo.

[0077] 4) The relationship between bamboo thickness and bamboo fiber bundle strength is shown in the table below. It can be seen that, through this invention, high-strength bamboo cellulose can be extracted from bamboo with a thickness of 1-5 mm, with bamboo with a thickness of 2 mm exhibiting the highest tensile strength.

[0078] Bamboo thickness (mm) Tensile stress (MPa) Young's modulus (GPa) <![CDATA[Fracture energy (MJ / m 3 )]]> 1 3065 67.3 79.9 2 3291 68.7 83.8 3 3162 69.4 82.1 4 2896 61.7 76.6 5 3106 60.3 71.9

[0079] Example 5

[0080] 1) A mixed solution was prepared using lactic acid as the acidic solvent and choline chloride as the alkaline solvent in a molar ratio of 10:1. Bamboo strips (50 mm in length, 20 mm in width, and 2 mm in thickness) were added to the prepared solution at a solid-liquid ratio of 1:10 and thoroughly mixed. The mixture was heated at 70-130℃ for 1 hour to allow it to swell. After the reaction was complete, the bamboo strips were washed with a mixed solution of ethanol and deionized water to remove excess swelling solution, and finally washed with deionized water to obtain swollen bamboo strips. The preferred volume ratio of ethanol to deionized water was 7:3-10:0. The water absorption and weight gain rate of the swollen bamboo strips was 170-185%, the lignin removal rate was 10-55%, and the hemicellulose removal rate was 10-45%.

[0081] 2) Prepare a mixed solution of acetic acid and hydrogen peroxide at a volume ratio of 1:1. Immerse the swollen bamboo chips in the prepared mixed solution at a solid-liquid ratio of 1:10 and mix thoroughly. Heat at 80℃ for 3-5 hours to remove lignin until the bamboo turns white. Then wash off excess lignin solution with a mixed solution of ethanol and deionized water, and finally wash with deionized water to obtain lignin-removed bamboo chips. The preferred volume ratio of ethanol to deionized water is 1:1. The lignin removal rate in the lignin-removed bamboo chips is 80-95%, and the hemicellulose removal rate is 65-80%.

[0082] 3) The lignin-free bamboo chips are dried in an oven at 60℃, and bamboo fiber bundles are obtained by efficient separation through roller pressing. The bundles have a diameter of 200-350μm, a tensile stress of 2500-3300MPa, a Young's modulus of 50-70GPa, and a breaking energy of 60-85MJ / m. 3 The extraction rate of high-strength bamboo fiber bundles is 20-27% compared to that of natural bamboo.

[0083] 4) The relationship between swelling treatment temperature and bamboo fiber bundle strength is shown in the table below. It can be seen that the bamboo exhibits the highest tensile strength at a treatment temperature of 110℃.

[0084] Swelling treatment temperature (°C) Tensile stress (MPa) Young's modulus (GPa) <![CDATA[Fracture energy (MJ / m 3 ) <!-- 6 -->]]> 70 2596 52.1 62.7 90 3054 62.6 74.9 110 3291 68.7 83.8 130 2835 60.2 71.4

[0085] Example 6

[0086] 1) A mixed solution was prepared using lactic acid as the acidic solvent and choline chloride as the alkaline solvent in a molar ratio of 10:1. Bamboo strips (50 mm in length, 20 mm in width, and 2 mm in thickness) were added to the prepared solution at a solid-liquid ratio of 1:10 and thoroughly mixed. The mixture was heated at 110℃ for 0.25-4 hours to allow it to swell. After the reaction was complete, the bamboo strips were washed with a mixed solution of ethanol and deionized water to remove excess swelling solution, and finally washed with deionized water to obtain swollen bamboo strips. The preferred volume ratio of ethanol to deionized water was 7:3-10:0. The water absorption and weight gain rate of the swollen bamboo strips was 165-200%, the lignin removal rate was 1-45%, and the hemicellulose removal rate was 5-55%.

[0087] 2) Prepare a mixed solution of acetic acid and hydrogen peroxide at a volume ratio of 1:1. Immerse the swollen bamboo chips in the prepared mixed solution at a solid-liquid ratio of 1:10 and mix thoroughly. Heat at 80℃ for 3-5 hours to remove lignin until the bamboo turns white. Then wash off excess lignin solution with a mixed solution of ethanol and deionized water, and finally wash with deionized water to obtain lignin-removed bamboo chips. The preferred volume ratio of ethanol to deionized water is 1:1. The lignin removal rate in the lignin-removed bamboo chips is 80-95%, and the hemicellulose removal rate is 65-80%.

[0088] 3) The lignin-free bamboo chips are dried in an oven at 60℃, and bamboo fiber bundles are obtained by efficient separation through roller pressing. The bundles have a diameter of 200-350μm, a tensile stress of 2000-3300MPa, a Young's modulus of 45-70GPa, and a breaking energy of 55-85MJ / m. 3 The extraction rate of high-strength bamboo fiber bundles is 21-26% compared to that of natural bamboo.

[0089] 4) The relationship between swelling treatment time and bamboo fiber bundle strength is shown in the table below. It can be seen that the bamboo tensile strength is highest when the treatment time is 1 hour.

[0090] Swelling treatment time (h) Tensile stress (MPa) Young's modulus (GPa) <![CDATA[Fracture energy (MJ / m 3 )]]> 0.25 2510 47.4 60.8 0.5 2924 54.2 74.7 1 3291 68.7 83.8 1.5 3111 57.4 69.3 2 2979 62.7 70.5 3 2433 46.9 63.8 4 2229 48.4 58.6

[0091] As can be seen from Examples 4-6 above, due to the synergistic effect of swelling treatment + delignification + drying hydrogen bond reconstruction effect in this invention, it is necessary to balance the swelling effect, delignification effect and the damage to the natural structure of bamboo cellulose. Therefore, the strength of bamboo fiber bundles is not a simple linear relationship with bamboo thickness, swelling treatment temperature, time and other factors.

[0092] Example 7

[0093] 1) Select any one of the following as acidic solvents: lactic acid, choline chloride, zinc chloride, ammonium chloride, betaine, and guanidine hydrochloride, and prepare a mixed solution at a molar ratio of 10:1. Add bamboo strips (50 mm in length, 20 mm in width, and 2 mm in thickness) to the prepared solution at a solid-liquid ratio of 1:10 and mix thoroughly. Heat at 110°C for 1 hour to allow the bamboo strips to swell. After the reaction is complete, wash the bamboo strips with a mixed solution of ethanol and deionized water to remove excess swelling solution, and finally wash with deionized water to obtain swollen bamboo strips. The preferred volume ratio of ethanol to deionized water is 7:3-10:0. The water absorption and weight gain rate of the swollen bamboo strips is 165-210%, the lignin removal rate is 10-55%, and the hemicellulose removal rate is 20-60%.

[0094] 2) Prepare a mixed solution of acetic acid and hydrogen peroxide at a volume ratio of 1:1. Immerse the swollen bamboo chips in the prepared mixed solution at a solid-liquid ratio of 1:10 and mix thoroughly. Heat at 80℃ for 3-4 hours to remove lignin until the bamboo turns white. Then wash off excess lignin solution with a mixed solution of ethanol and deionized water, and finally wash with deionized water to obtain lignin-removed bamboo chips. The preferred volume ratio of ethanol to deionized water is 1:1. The lignin removal rate in the lignin-removed bamboo chips is 80-90%, and the hemicellulose removal rate is 75-80%.

[0095] 3) The lignin-free bamboo chips are dried in an oven at 60℃, and bamboo fiber bundles are obtained by efficient separation through roller pressing. The bundles have a diameter of 200-300μm, a length of 50mm, a tensile stress of 2400-3300MPa, a Young's modulus of 55-70GPa, and a breaking energy of 60-85MJ / m. 3 The extraction rate of high-strength bamboo fiber bundles is 22-27% compared to that of natural bamboo.

[0096] 4) The relationship between the swelling agents prepared from different alkaline compounds and the strength of bamboo fiber bundles is shown in the table below. It can be seen that the strength of the extracted bamboo fiber bundles varies due to the different swelling effects of different swelling agents.

[0097] alkaline compounds Tensile stress (MPa) Young's modulus (GPa) <![CDATA[Fracture energy (MJ / m 3 )]]> choline chloride 3291 68.7 83.8 Zinc chloride 2726 62.8 70.6 ammonium chloride 2828 59.8 68.4 betaine 2452 54.4 64.1 Guanidine hydrochloride 2663 55.3 63.9

[0098] Example 8

[0099] 1) Select any one of the following acidic solvents: lactic acid, formic acid, acetic acid, ethylene glycol, glycerol, or urea; and choline chloride as the alkaline solvent. Prepare mixed solutions with different acid-base molar ratios. Add bamboo strips (50 mm in length, 20 mm in width, and 2 mm in thickness) to the prepared solutions at a solid-liquid ratio of 1:10 and mix thoroughly. Heat at 110°C for 1 hour to allow the bamboo strips to swell. After the reaction, wash the bamboo strips with a mixed solution of ethanol and deionized water to remove excess swelling solution, and finally wash with deionized water to obtain swollen bamboo strips. The preferred volume ratio of ethanol to deionized water is 7:3-10:0. The water absorption and weight gain rate of the swollen bamboo strips is 165-185%, the lignin removal rate is 2-35%, and the hemicellulose removal rate is 2-25%.

[0100] 2) Prepare a mixed solution of acetic acid and hydrogen peroxide at a volume ratio of 1:1. Immerse the swollen bamboo chips in the prepared mixed solution at a solid-liquid ratio of 1:10 and mix thoroughly. Heat at 80℃ for 3-5 hours to remove lignin until the bamboo turns white. Then wash off excess lignin solution with a mixed solution of ethanol and deionized water, and finally wash with deionized water to obtain lignin-removed bamboo chips. The preferred volume ratio of ethanol to deionized water is 1:1. The lignin removal rate in the lignin-removed bamboo chips is 80-90%, and the hemicellulose removal rate is 70-80%.

[0101] 3) The lignin-free bamboo chips are dried in an oven at 60℃, and bamboo fiber bundles are obtained by efficient separation through roller pressing. The bundles have a diameter of 150-350μm, a tensile stress of 2227-3300MPa, a Young's modulus of 45-70GPa, and a breaking energy of 60-85MJ / m. 3 The extraction rate of high-strength bamboo fiber bundles is 24-27% compared to that of natural bamboo.

[0102] 4) The relationship between the swelling agents prepared from different acidic compounds and the strength of bamboo fiber bundles is shown in the table below. It can be seen that the strength of the extracted bamboo fiber bundles varies due to the different swelling effects of different swelling agents.

[0103]

[0104] Example 9

[0105] 1) Oxalic acid and choline chloride were selected as the acidic solvent and prepared as the alkaline solvent in a molar ratio of 1:1 to form a mixed solution. Bamboo strips (300 mm in length, 20 mm in width, and 2 mm in thickness) were added to the prepared solution at a solid-liquid ratio of 1:10 and mixed thoroughly. The mixture was heated at 110°C for 1 hour to swell. After the reaction was completed, the bamboo strips were washed with a mixed solution of ethanol and deionized water to remove excess swelling solution, and finally washed with deionized water to obtain swollen bamboo strips. The preferred volume ratio of ethanol to deionized water was 7:3-10:0. The water absorption weight gain rate of the swollen bamboo strips was 191%, the lignin removal rate was 30%, and the hemicellulose removal rate was 23%.

[0106] 2) Prepare a mixed solution of acetic acid and hydrogen peroxide at a volume ratio of 1:1. Immerse the swollen bamboo chips in the prepared mixed solution at a solid-liquid ratio of 1:10 and mix thoroughly. Heat at 80℃ for 3 hours to remove lignin until the bamboo turns white. Then wash off excess lignin solution with a mixed solution of ethanol and deionized water, and finally wash with deionized water to obtain lignin-removed bamboo chips. The preferred volume ratio of ethanol to deionized water is 1:1. The lignin removal rate in the lignin-removed bamboo chips is 92%, and the hemicellulose removal rate is 88%.

[0107] 3) After drying the lignin-treated bamboo chips in a 60℃ oven, bamboo fiber bundles were efficiently separated by hand kneading. These bundles had a diameter of 300-350 μm, a length of 300 mm, an aspect ratio of 1000, and a crystallinity of 72%. The maximum tensile stress was 3500 MPa, the Young's modulus was 70.0 GPa, and the fracture energy was 95.0 MJ / m. 3 The extraction rate of high-strength bamboo fiber bundles relative to natural bamboo is 29%.

[0108] Example 10

[0109] Based on Example 9, the effect of drying method on high-strength bamboo fiber bundles was further investigated: The lignin-treated bamboo chips from step 2) were replaced with ethanol, dried at room temperature, and then efficiently separated by manual kneading to obtain bamboo fiber bundles with a diameter of 250-350 μm, a length of 300 mm, a maximum tensile stress of 3379 MPa, a Young's modulus of 66.8 GPa, and a fracture energy of 84.1 MJ / m. 3 This demonstrates that high-strength bamboo fiber bundles can also be efficiently extracted using room temperature drying, as described in this invention. The extraction rate of high-strength bamboo fiber bundles relative to natural bamboo is 27%.

[0110] Based on Example 9, the influence of mechanical processing methods on high-strength bamboo fiber bundles was further investigated. The lignin-treated bamboo chips from step 2) were dried in a 60°C oven and then efficiently separated by rolling 20 times to obtain bamboo fiber bundles with a diameter of 300-350 μm, a length of 50 mm, a maximum tensile stress of 3382 MPa, a Young's modulus of 69.1 GPa, and a fracture energy of 94.4 MJ / m. 3 This demonstrates that high-strength bamboo fiber bundles can also be efficiently extracted using roller pressing separation, as described in this invention. The extraction rate of high-strength bamboo fiber bundles relative to natural bamboo is 30%.

[0111] Example 11

[0112] 1) Oxalic acid and choline chloride were selected as the acidic solvent and prepared into a mixed solution at a molar ratio of 1:1. Bamboo strips (50 mm in length, 20 mm in width, and 2 mm in thickness) were added to the prepared solution at a solid-liquid ratio of 1:10 and thoroughly mixed. The mixture was heated at 110℃ for 1 hour to swell. After the reaction was completed, the bamboo strips were washed with a mixed solution of ethanol and deionized water to remove excess swelling solution, and finally washed with deionized water to obtain swollen bamboo strips. The preferred volume ratio of ethanol to deionized water was 7:3-10:0. The water absorption weight gain rate of the swollen bamboo strips was 191%, the lignin removal rate was 30%, and the hemicellulose removal rate was 23%.

[0113] The following steps 2)-5) involve treating the samples with different delignification solutions to investigate the promoting effect of swelling treatment on delignification.

[0114] 2) Prepare a mixed solution of acetic acid and hydrogen peroxide at a volume ratio of 1:1. Immerse the swollen bamboo chips in the prepared mixed solution at a solid-liquid ratio of 1:10 and mix thoroughly. Heat at 80℃ for 3 hours to remove lignin until the bamboo turns white. Then wash off excess lignin solution with a mixed solution of ethanol and deionized water, and finally wash with deionized water to obtain lignin-removed bamboo chips. The preferred volume ratio of ethanol to deionized water is 1:1. The lignin removal rate in the lignin-removed bamboo chips is 92%, and the hemicellulose removal rate is 88%.

[0115] 3) Prepare a mixed solution of formic acid and hydrogen peroxide at a volume ratio of 1:1. Immerse the swollen bamboo chips in the prepared mixed solution at a solid-liquid ratio of 1:10 and mix thoroughly. Heat at 50°C for 12 hours to remove lignin until the bamboo turns white. Then wash off excess lignin solution with a mixed solution of ethanol and deionized water, and finally wash with deionized water to obtain lignin-removed bamboo chips. The preferred volume ratio of ethanol to deionized water is 1:1. The lignin removal rate in the lignin-removed bamboo chips is 94%, and the hemicellulose removal rate is 86%.

[0116] 4) Prepare a 2wt% sodium chlorite solution, adjust the pH to 4.6 with acetic acid to obtain a mixed solution. Immerse the swollen bamboo chips in the prepared mixed solution at a solid-liquid ratio of 1:10 and mix thoroughly. Heat at 80℃ for 6 hours to remove lignin until the bamboo turns white. Then wash off excess lignin solution with a mixed solution of ethanol and deionized water, and finally wash with deionized water to obtain lignin-removed bamboo chips. The preferred volume ratio of ethanol to deionized water is 1:1. The lignin removal rate in the lignin-removed bamboo chips is 89%, and the hemicellulose removal rate is 87%.

[0117] 5) Prepare a mixed solution of 2.5M sodium hydroxide and 0.4M sodium sulfite. Immerse the swollen bamboo chips in the prepared mixed solution at a solid-liquid ratio of 1:10 and mix thoroughly. Heat at 100℃ for 5 hours to remove lignin until the bamboo turns white. Then wash off excess lignin solution with a mixed solution of ethanol and deionized water, and finally wash with deionized water to obtain lignin-removed bamboo chips. The preferred volume ratio of ethanol to deionized water is 1:1. The lignin removal rate in the lignin-removed bamboo chips is 94%, and the hemicellulose removal rate is 90%.

[0118] 6) After drying the above four types of delignified bamboo chips in an oven at 60℃, bamboo fiber bundles are efficiently separated by manual kneading. These bundles have a diameter of 250-350 μm, a length of 50 mm, an aspect ratio of 50-2000, and a crystallinity of 50-70%. The maximum tensile stress is 3000-3500 MPa, the Young's modulus is 65-75 GPa, and the fracture energy is 85-95 MJ / m. 3 The extraction rate of high-strength bamboo fiber bundles relative to natural bamboo is 26-29%. Among them, the content of intramolecular hydrogen bonds O(3)H…O(5) in high-strength bamboo fiber bundles increased by 20-30%, the content of O(2)H…O(6) decreased by 25-35%, and the content of intermolecular hydrogen bonds O(6)H…O(3') increased by 5-15%.

[0119] Therefore, this invention can achieve the extraction of high-strength bamboo fiber bundles from natural bamboo through a combination of swelling treatment and different delignification treatments. The hydrogen bond reconstruction that occurs in the bamboo fiber bundles after drying is one of the key reasons for their high strength.

[0120] Example 12

[0121] A method for preparing bamboo phase change fabric

[0122] 1) The bamboo fiber bundles extracted in Example 9 were vacuum impregnated in pyrrole, and then a mixture of ferric chloride and 0.3M hydrochloric acid solution at a mass ratio of 1:9 was added to the reaction solution. The reaction was carried out at 4°C for 24 hours. After the reaction was completed, the excess reaction solution was washed with 0.05M hydrochloric acid solution, and finally washed with deionized water and dried to obtain polypyrrole bamboo fiber bundles.

[0123] 2) The polypyrrole bamboo fiber bundles were placed in molten polyethylene glycol for vacuum impregnation, and then removed and cooled to obtain polypyrrole / polyethylene glycol bamboo fiber bundles.

[0124] 3) Coat the surface of the polypyrrole / polyethylene glycol bamboo fiber bundle with a layer of polyvinylidene fluoride, and dry it to obtain bamboo phase change fiber.

[0125] 4) Bamboo phase change fibers are woven to obtain polypyrrole bamboo phase change fabric.

[0126] 5) Select the bamboo fiber bundles extracted in Example 9 to weave bamboo fabric.

[0127] 6) Select the bamboo fiber bundles extracted in Example 9 and vacuum impregnate them in molten polyethylene glycol. Coat the surface with a layer of polyvinylidene fluoride and dry to obtain bamboo phase change fibers, and then weave them into bamboo phase change fabrics.

[0128] Comparative Example 1

[0129] 1) Take bamboo strips (50mm in length, 20mm in width, and 2mm in thickness). Prepare a mixed solution of acetic acid and hydrogen peroxide at a volume ratio of 1:1. Immerse the bamboo strips in the prepared mixed solution at a solid-liquid ratio of 1:10 and mix thoroughly. Heat at 80℃ for 16 hours to remove lignin until the bamboo turns white. Then wash off excess lignin solution with a mixed solution of ethanol and deionized water, and finally wash with deionized water to obtain lignin-removed bamboo strips. The preferred volume ratio of ethanol to deionized water is 1:1. The lignin removal rate in the lignin-removed bamboo strips is 95%, and the hemicellulose removal rate is 85%.

[0130] 2) The lignin-treated bamboo chips were dried in an oven at 60°C. Compared with the bamboo fiber bundles obtained by rolling 20 times in Example 9, the bamboo fiber bundles could not be effectively separated even after 40 rolling cycles in this example. This indicates that bamboo chips without swelling treatment cannot be used to separate bamboo fibers in this invention. This demonstrates the key role of swelling treatment in the efficient extraction of high-strength bamboo fiber bundles in this invention. Further increasing the mechanical processing force can separate bamboo fibers, but the separation effect is poor; the fibers have a diameter of 300-400 μm, a tensile stress of 672 MPa, a Young's modulus of 14.4 GPa, and a breaking energy of 16.8 MJ / m. 3The extraction rate of bamboo fiber bundles relative to natural bamboo was 12%. The hydrogen bond content of the bamboo fiber bundles extracted in Comparative Example 1 and Example 9 was tested respectively, as shown in the table below. The content of intramolecular hydrogen bonds O(3)H…O(5) increased by 24%, the content of O(2)H…O(6) decreased by 30%, and the content of intermolecular hydrogen bonds O(6)H…O(3') increased by 7%. This indicates that the hydrogen bonds of the bamboo fiber bundles treated by the present invention were reconstructed, the content of intermolecular hydrogen bonds increased, and the intramolecular hydrogen bonds changed from one type to two types acting together. This confirms that the present invention endows the bamboo fiber bundles with higher mechanical properties through hydrogen bond reconstruction.

[0131]

[0132] Comparative Example 2

[0133] 1) Prepare a 20% (w / w) sulfuric acid solution. Bamboo strips (50mm long, 20mm wide, and 2mm thick) are thoroughly mixed in deionized water at a solid-liquid ratio of 1:10. The mixture is heated at 90℃ for 1 hour to allow the bamboo strips to swell. After the reaction is complete, the bamboo strips are washed with deionized water to remove excess swelling solution, thus obtaining swollen bamboo strips. The water absorption and weight gain rate of the swollen bamboo strips is 186%, the lignin removal rate is 21%, and the hemicellulose removal rate is 28%.

[0134] 2) Prepare a mixed solution of acetic acid and hydrogen peroxide at a volume ratio of 1:1. Immerse the swollen bamboo chips in the prepared mixed solution at a solid-liquid ratio of 1:10 and mix thoroughly. Heat at 80℃ for 4 hours to remove lignin until the bamboo turns white. Then wash off excess lignin solution with a mixed solution of ethanol and deionized water, and finally wash with deionized water to obtain lignin-removed bamboo chips. The preferred volume ratio of ethanol to deionized water is 1:1. The lignin removal rate in the lignin-removed bamboo chips is 84%, and the hemicellulose removal rate is 79%.

[0135] 3) The lignin-free bamboo chips were dried in an oven at 60℃, and bamboo fiber bundles were obtained by efficient separation using roller pressing. The bundles had a diameter of 200-250 μm, a tensile stress of 567 MPa, a Young's modulus of 12.5 GPa, and a breaking energy of 15.8 MJ / m. 3 The extraction rate of bamboo fiber bundles relative to natural bamboo is 17%. Due to excessively high acid concentration, the natural structure of the bamboo fiber bundles is damaged and partially chemically degraded, resulting in a decrease in their mechanical properties and a reduction in the extraction rate.

[0136] Comparative Example 3

[0137] 1) Prepare a 20% (w / w) sodium hydroxide solution. Bamboo strips (50mm long, 20mm wide, and 2mm thick) are thoroughly mixed in deionized water at a solid-liquid ratio of 1:10. The mixture is heated at 90℃ for 1 hour to allow the bamboo strips to swell. After the reaction is complete, the bamboo strips are washed with deionized water to remove excess swelling solution, thus obtaining swollen bamboo strips. The water absorption and weight gain rate of the swollen bamboo strips is 237%, the lignin removal rate is 27%, and the hemicellulose removal rate is 52%.

[0138] 2) Prepare a mixed solution of acetic acid and hydrogen peroxide at a volume ratio of 1:1. Immerse the swollen bamboo chips in the prepared mixed solution at a solid-liquid ratio of 1:10 and mix thoroughly. Heat at 80℃ for 3 hours to remove lignin until the bamboo turns white. Then wash off excess lignin solution with a mixed solution of ethanol and deionized water, and finally wash with deionized water to obtain lignin-removed bamboo chips. The preferred volume ratio of ethanol to deionized water is 1:1. The lignin removal rate in the lignin-removed bamboo chips is 92%, and the hemicellulose removal rate is 88%.

[0139] 3) The lignin-treated bamboo chips were dried in an oven at 60℃, and bamboo fiber bundles were obtained by efficient separation using roller pressing. The bundles had a diameter of 150-200 μm, a tensile stress of 626 MPa, a Young's modulus of 10.2 GPa, and a breaking energy of 17.7 MJ / m. 3 The extraction rate of bamboo fiber bundles relative to natural bamboo is 15%. Due to excessively high alkali concentration, the structure of the bamboo fiber bundles is damaged and partially chemically degraded, resulting in a decrease in their mechanical properties and a reduction in the extraction rate.

[0140] The lignin-free bamboo chips obtained in Comparative Example 1 and Example 9 were dried and then separated by roller pressing as follows: Figure 2 As shown, in Example 9, the deligninated bamboo chips could be efficiently separated into bamboo fiber bundles after 20 roller presses. However, in Comparative Example 1, the deligninated bamboo chips could not be effectively separated into bamboo fiber bundles even after 40 roller presses.

[0141] The mechanical properties of bamboo fiber bundles extracted from natural bamboo strips, Comparative Example 1, and Example 9 are as follows: Figure 3 As shown, the tensile stress of the bamboo fiber bundle in Example 9 was 3500 MPa, which is 28.2 times that of bamboo strips (124 MPa) and 5.2 times that of Comparative Example 1 (672 MPa), demonstrating excellent tensile properties. Furthermore, the Young's modulus and fracture energy of the bamboo fiber bundle in Example 9 also reached 70.0 GPa and 95.0 MJ / m⁻³, respectively, which are 12.3 times and 69.3 times that of bamboo strips (5.71 GPa and 1.37 MJ / m⁻³), and 4.9 times and 5.7 times that of Comparative Example 1 (14.41 GPa and 16.75 MJ / m⁻³), exhibiting excellent rigidity and toughness.

[0142] The high-strength bamboo fiber bundles extracted in Example 9 exhibited flexibility as follows: Figure 4 As shown, this demonstrates that the bamboo fiber bundles extracted by this invention exhibit excellent flexibility when wound, folded, or knotted, and a single bamboo fiber bundle can lift a weight of 2.5 kg.

[0143] Example 9: The size uniformity of the high-strength bamboo fiber bundles extracted is as follows: Figure 5 As shown, this indicates that the length of bamboo fiber bundles can reach 30 cm, and the diameter can maintain excellent uniformity, with a diameter of approximately 330 micrometers observed at both ends and the middle.

[0144] In Example 9, the water absorption weight gain rate, lignin and hemicellulose content of bamboo chips and swollen bamboo chips are as follows: Figure 6 As shown, this indicates that the swelling treatment opens up the natural anti-dissociation physical barrier on the surface of bamboo and removes non-amorphous substances such as lignin and hemicellulose, improving the accessibility of bamboo and facilitating the entry and treatment of the lignin-removing solution.

[0145] Scanning electron microscope images of bamboo strips, swollen bamboo strips, and high-strength bamboo protofibril bundles in Example 9 are shown below. Figure 7 As shown, this indicates that after treatment with the swelling agent, the cell walls of bamboo become thinner and the cell corners are opened, which is beneficial for subsequent delignification. Furthermore, after delignification and drying, the vascular bundles and vessels of the high-strength bamboo protofiber bundles remain intact, with a diameter of approximately 330 μm.

[0146] Scanning electron microscope images of the swollen bamboo strips obtained in Examples 1, 2, and 3 are shown below. Figure 8 As shown, treatment with water and acidic solvents as swelling agents causes the cell corners to open to a certain extent, and the cell walls of thin-walled cells become thinner; while treatment with alkaline solvents as swelling agents destroys the structure of thin-walled cells, which is beneficial for their removal.

[0147] The mechanical properties of bamboo fiber bundles extracted from 2mm bamboo strips in Examples 1, 2, 3, 4 and Comparative Example 1 are as follows: Figure 9 As shown. The mechanical properties of the bamboo fiber bundles extracted in Example 4 are significantly better than those in Examples 1, 2, 3 and Comparative Example 1.

[0148] The phase change properties of the bamboo fabric prepared in Example 12 are as follows: Figure 10 As shown, this indicates that bamboo phase change fabrics, after functionalization of bamboo fiber bundles, possess excellent phase change properties.

Claims

1. A method for extracting high-strength bamboo primary fiber bundles, characterized by, The method comprises the following steps: S1, processing bamboo into bamboo pieces with a thickness of 1-5 mm after removing the yellow and green parts of the bamboo; S2, soaking the bamboo pieces prepared in step S1 in a swelling agent for sufficient swelling treatment to obtain swelling bamboo pieces with intact bamboo fiber bundle structure; the swelling agent is any one of water, a sulfuric acid solution with a mass fraction of 0-15 wt%, or a sodium hydroxide solution with a mass fraction of 0-12 wt%; the swelling treatment time is 0.25-4 h, the swelling treatment temperature is 70-130 ℃, and the solid-liquid ratio of the bamboo pieces to the swelling liquid is 1:5-1:15 (g / ml); the water absorption weight gain rate of the swelling bamboo pieces is 160-220%, the removal rate of lignin is 2-65%, and the removal rate of hemicellulose is 1-55%; S3, soaking the swelling bamboo pieces prepared in step S2 in a delignification solution for treatment to obtain delignification bamboo pieces with intact bamboo fiber bundle structure; the delignification solution is any one of a mixed solution of acetic acid and hydrogen peroxide, a mixed solution of formic acid and hydrogen peroxide, a mixed solution of acetic acid and sodium chlorite, or a mixed solution of sodium hydroxide and sodium sulfite; the solid-liquid ratio of the swelling bamboo pieces to the delignification solution is 1:5-1:15 (g / ml), the treatment time is 3-12 h, and the treatment temperature is 50-100 ℃; the removal rate of lignin in the delignification bamboo pieces is 80-95%, and the removal rate of hemicellulose is 70-85%; S4, after drying treatment of the delignification bamboo pieces prepared in step S3, high-strength bamboo fiber bundles are extracted through mechanical separation; the drying method is normal temperature drying or oven drying; the mechanical separation method is at least one of rubbing, rolling, or carding; the extraction rate of the high-strength bamboo fiber bundles relative to natural bamboo is 20-30%.

2. A high strength bamboo fiber bundle, characterized by: The high-strength bamboo fiber bundles are extracted by the preparation method of claim 1.

3. The high-strength bamboo fiber bundle of claim 2, wherein: The diameter of the high-strength bamboo fiber bundles is 150-350 μm, the diameter is uniformly distributed along the length direction, the length is 20-300 mm, the length-diameter ratio is 50-2000, and the crystallinity is 50-70 %.

4. The high-strength bamboo fiber bundle of claim 2, wherein: The tensile stress of the high-strength bamboo fiber bundles is 1500-3500 MPa, the Young's modulus is 25-70 GPa, and the breaking energy is 35-95 MJ / m3.

5. Application of high-strength bamboo fiber bundles, such as the application of the high-strength bamboo fiber bundles in any one of claims 3-4 in the fields of composite reinforcement materials, photovoltaics, energy storage, personal thermal management, and wearable smart fabrics.

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