Preparation method of waterproof, bio-durable, wear-resistant and high-strength bamboo-based composite material

Abstract

The present invention discloses a method for preparing a waterproof, biodegradable, durable, and wear-resistant bamboo-based composite material with high strength, comprising the following steps: S1. Selecting bamboo, trimming, cleaning, and slicing the bamboo strips; S2. Soaking the bamboo strips in a 2-5% sodium hydroxide solution to soften them; S3. Soaking the softened bamboo strips in a composite enzymatic hydrolysis solution, and using ultrasound to release the starch in the parenchyma cells of the bamboo strips; S4. Laying the starch-coated bamboo strips layer by layer, adding a composite adhesive during the laying process, and hot-pressing to obtain a bamboo-based composite board material. By releasing the starch from the bamboo, and then hot-pressing and bonding, the bamboo-based surface has better adhesion and structural integrity, thereby significantly improving the bonding strength of the bamboo surface. Furthermore, the addition of a waterproofing agent or hardening agent during the bonding process can improve the water resistance and surface hardness of the bamboo-based composite board material, enhancing its wear resistance.

Description

Technical Field

[0001] The invention relates to the technical field of bamboo-based composite material preparation, and in particular to a method for preparing a waterproof, bio-resistant, durable, wear-resistant and high-strength bamboo-based composite material. Background Art

[0002] Bamboo is a tall, fast-growing grass with a woody stem. The bamboo culm is segmented, with internodes forming the spaces between each node. A cross-section of the internode wall reveals, from the outside inward, the epidermis, subcutaneous layer, cortex, basic parenchyma (which contains vascular bundles), and medullary rings. The vascular bundles of the nodes curve slightly outward or inward, sometimes winding back into the septum. The vascular bundles of the septum are densely packed at the outer edges and sparsely packed in the center, with irregular diameter and orientation. They branch into numerous fine branches, interwoven in a circuitous network, and serve as the primary channels for the lateral flow of bamboo sap.

[0003] Since bamboo is a very good environmentally friendly material, it has a wide range of uses. It can be used as raw material for many products such as bamboo plastic products, mosquito coils, leather, clothing, papermaking, electrical appliances, daily necessities, coatings, cat litter, chemicals, insulation materials, outdoor decoration materials, and building materials.

[0004] The preparation of existing bamboo-based composite materials has the following problems:

[0005] 1. Since bamboo itself has a multi-layer cell wall structure and low porosity and permeability, the gluing and bonding ability of the bamboo surface is greatly reduced. In addition, since all bamboo cells are arranged in the axial direction, the porosity and permeability of the transverse tissue are reduced in the transverse direction, resulting in poorer bonding performance compared to wood.

[0006] 2. During the preparation process of existing bamboo-based composite materials, due to the poor permeability of bamboo-based raw materials, their waterproofness and surface strength will be affected after bonding.

[0007] Therefore, there is an urgent need for a method for preparing a waterproof, bio-resistant, wear-resistant and high-strength bamboo-based composite material to solve the above problems. Summary of the Invention

[0008] The present invention overcomes the deficiencies of the prior art and provides a method for preparing a bamboo-based composite material that is waterproof, biodegradable, durable, and wear-resistant with high strength.

[0009] To achieve the above object, the technical solution adopted by the present invention is: a method for preparing a waterproof, biodegradable, durable, wear-resistant and high-strength bamboo-based composite material, comprising the following steps:

[0010] S1. Select bamboo, trim and clean it, divide the bamboo into several small sections and slice them to obtain bamboo strips with a thickness of 3 to 15 mm.

[0011] S2. Soaking the bamboo strips in a sodium hydroxide solution with a concentration of 2-5% to soften the bamboo strips, wherein the ratio of the bamboo strips to the sodium hydroxide solution is 1-2:3.

[0012] S3. Wash the softened bamboo strips with water to remove residual sodium hydroxide, and then immerse them in a composite enzymatic hydrolysis solution with a concentration of 10-20%. With the assistance of ultrasound, the starch in the parenchyma cells of the bamboo strips is released, and a starch coating is formed on the outer surface of the bamboo strips. The ratio of the bamboo strips to the composite enzymatic hydrolysis solution is 1-2:4.

[0013] S4. Laying the starch-coated bamboo strips layer by layer, adding a composite adhesive during the laying process, and obtaining a bamboo-based composite board material after hot pressing, wherein the composite adhesive comprises an adhesive matrix, a curing agent, a waterproofing agent, and a hardening agent.

[0014] In a preferred embodiment of the present invention, in step S1, the bamboo is segmented along the grain direction of the bamboo, and the length of the small segment of bamboo is 30 to 100 cm.

[0015] In a preferred embodiment of the present invention, in step S2, the bamboo strips are soaked in the sodium hydroxide solution for 36 to 90 hours, and the bamboo strips are turned over every 12 to 18 hours.

[0016] In a preferred embodiment of the present invention, in step S2, the sodium hydroxide solution is heated to a temperature of 40-50° C., and the heating rate of the sodium hydroxide solution is 5-20° C. per hour.

[0017] In a preferred embodiment of the present invention, in step S3, the softened bamboo strips are washed with clean water for 5 to 8 minutes.

[0018] In a preferred embodiment of the present invention, in step S3, the frequency of the ultrasonic wave is 20 to 30 MHz, and the ultrasonic wave works every 3 to 5 minutes, and the single working time is 10 to 15 minutes.

[0019] In a preferred embodiment of the present invention, in step S4, the main components of the gelling agent are polyacrylate and at least one of an auxiliary agent, a filler or a diluent.

[0020] In a preferred embodiment of the present invention, in step S4, the pressure applied to the bamboo strips laid layer by layer is 5-25 MPa, the temperature around the bamboo strips is 40-60° C., and the hot pressing duration is 20-40 min.

[0021] In a preferred embodiment of the present invention, in step S4, the thickness of the bamboo-based composite board material is not less than 30 mm.

[0022] In a preferred embodiment of the present invention, in step S4, at least one of a waterproofing agent and a hardening agent is added simultaneously with the addition of the gelling agent.

[0023] The present invention solves the defects existing in the background technology and has the following beneficial effects:

[0024] (1) The present invention provides a method for preparing a water-resistant, bio-resistant, durable, wear-resistant, and high-strength bamboo-based composite material. By releasing the starch in the bamboo material and then performing hot-press bonding, the bamboo-based surface has better adhesion and structural integrity, thereby significantly improving the bonding strength of the bamboo surface. In addition, the addition of a waterproofing agent or hardening agent during the bonding process can improve the water resistance and surface hardness of the bamboo-based composite material and enhance its wear resistance.

[0025] (2) The present invention uses softening, enzymatic hydrolysis, ultrasonic assistance and ethanol to allow the hydroxyl groups on the surface of starch molecules to form hydrogen bonds with the carboxyl groups on the gelatin molecules, thereby forming a complex hydrogen bond network structure. This hydrogen bond between starch and gelatin is very stable and can form a tight starch-gelatin composite film, thereby greatly improving the overall adhesion strength. Compared with a separate starch coating, the starch-gelatin composite film has better adhesion and structural integrity, thereby significantly improving the bonding strength of the bamboo surface. Compared with the prior art, the present invention solves the problem that the lack of ray units in the transverse direction of bamboo reduces the porosity and permeability of the transverse tissue, thereby further ensuring the strength of the bamboo after bonding.

[0026] (3) The present invention adds a waterproofing agent or a hardening agent during the bamboo bonding process, allowing the waterproofing agent to penetrate into the micropores formed on the bamboo surface, thereby blocking water infiltration. Furthermore, the hardening agent is polymerized on the surface of the starch coating to form a covalent cross-linked structure between the surface starch molecules, thereby increasing the surface hardness. Compared with the prior art, the present invention solves the problem of bamboo's poor durability and wear resistance, thereby extending the service life of bamboo-based composite board materials.

[0027] (4) The preparation method provided by the present invention uses bamboo grown in the spring period (March to May) as raw material by selecting specific bamboo. This period is the peak growth period of bamboo. Starch is a form of energy storage in bamboo, and the starch content of bamboo is relatively high. Furthermore, bamboo is obtained in the morning and evening. During these time periods, bamboo synthesizes a large amount of starch in the bamboo parenchyma cells through photosynthesis. In addition, the bamboo in the above time period not only contains a large amount of starch, but also has a relatively soft texture. At the same time, the pruning and cleaning in step 1 requires cleaning the small branches and impurities such as soil remaining on the surface of the bamboo, and performing segmented processing to facilitate the release of starch.

[0028] (5) The preparation method provided by the present invention utilizes the excellent adhesive properties of starch to enzymatically hydrolyze the starch contained in bamboo and use it as an adhesive or thickener, thereby improving the strength, durability, and stability of bamboo gluing. Furthermore, the starch released from the bamboo can be mixed with other materials, and the properties of the material can be adjusted by adjusting the starch content and the ratio of the starch to other materials.

[0029] (6) The preparation method provided by the present invention uses starch as a natural filler or substitute, thereby being able to replace some other more expensive materials, thereby reducing the cost of materials and making it more competitive in the market.

[0030] (7) The starch used in the preparation method provided by the present invention is a natural biodegradable material that can be decomposed by microorganisms in the natural environment. Therefore, the bamboo-based composite material prepared by this preparation method has biodegradable properties and can be naturally degraded after being discarded, reducing pollution to the environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments described in the present invention. Those skilled in the art can also derive other drawings based on these drawings without inventive efforts.

[0032] Figure 1 It is a flow chart of a method for preparing a bamboo-based composite board material in a preferred embodiment of the present invention. DETAILED DESCRIPTION

[0033] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0034] like Figure 1 As shown, a method for preparing a waterproof, bio-resistant, durable, wear-resistant and high-strength bamboo-based composite material comprises the following steps:

[0035] S1. Select bamboo, trim and clean it, divide the bamboo into several small sections and slice them to obtain bamboo strips with a thickness of 3 to 15 mm.

[0036] S2. Soaking the bamboo strips in a sodium hydroxide solution with a concentration of 2-5% to soften the bamboo strips, wherein the ratio of the bamboo strips to the sodium hydroxide solution is 1-2:3.

[0037] S3. Wash the softened bamboo strips with water to remove residual sodium hydroxide, and then immerse them in a composite enzymatic hydrolysis solution with a concentration of 10-20%. With the assistance of ultrasound, the starch in the parenchyma cells of the bamboo strips is released, and a starch coating is formed on the outer surface of the bamboo strips. The ratio of the bamboo strips to the composite enzymatic hydrolysis solution is 1-2:4.

[0038] S4. Laying the starch-coated bamboo strips layer by layer, adding a composite adhesive during the laying process, and obtaining a bamboo-based composite board material after hot pressing, wherein the components of the composite adhesive include an adhesive matrix, a curing agent, a waterproofing agent, and a hardening agent.

[0039] Since bamboo parenchyma cells are located between the cortex and the medullary ring, in order to release the starch in the bamboo parenchyma cells, the chemical reagents must penetrate into the bamboo parenchyma cells.

[0040] Therefore, sodium hydroxide is needed to destroy the structure of the bamboo cell wall and soften the bamboo tissue, which is conducive to the enzymatic solution to penetrate into the interior of the bamboo. If it is not softened first, the enzymatic solution has weak penetration and it is difficult to penetrate into the inner layer of the bamboo cell wall for effective enzymatic hydrolysis.

[0041] In step S1, bamboo grown in the spring (March to May) is selected as raw material. This period is the peak growth period of bamboo. Starch, as a form of energy storage in bamboo, has a relatively high starch content. Furthermore, bamboo is obtained in the morning and evening. During these time periods, bamboo synthesizes a large amount of starch in bamboo parenchyma cells through photosynthesis. The bamboo is preferably a bamboo that contains a large amount of starch in its parenchyma cells during the growth period, preferably a large-segmented bamboo or a golden money bamboo.

[0042] Furthermore, bamboo from this age not only contains a high amount of starch but is also relatively soft, making it easier to trim and clean small branches and impurities like dirt left on the surface. The bamboo is then divided into sections 30 to 100 cm long along its grain. These sections are then sliced to produce bamboo strips 3 to 15 mm thick.

[0043] In step S2, the bamboo strips are completely immersed in a sodium hydroxide solution with a concentration of 2-5%, with the ratio of the bamboo strips to the sodium hydroxide solution being 1-2:3, and the soaking is continued for 36-90 hours.

[0044] In addition, in order to speed up the softening of bamboo strips, turn the bamboo strips every 12 to 18 hours. This ensures that all positions of the bamboo strips are in more uniform contact with the sodium hydroxide solution, which is conducive to the uniform softening of the bamboo. At the same time, it can also promote the flow of the solution and avoid the formation of a scaling layer on the surface of the bamboo, which affects the softening effect.

[0045] In one embodiment, the sodium hydroxide solution is heated to 40-50° C. at a heating rate of 5-20° C. per hour, so that the intercellular layers of the bamboo material can be significantly separated, which is more conducive to the decomposition of the bamboo material.

[0046] In step S3, the use of running water rinsing can accelerate the washing of the sodium hydroxide solution remaining on the surface of the bamboo strips, and the rinsing time is 5 to 8 minutes. The running water rinsing can not only effectively wash away the sodium hydroxide solution remaining on the surface of the bamboo, but also ensure the uniformity of the cleaning, shorten the cleaning time, reduce the cleaning effect, and improve the cleaning efficiency.

[0047] In one embodiment, the rinsed bamboo strips are immersed in a composite enzymatic hydrolysis solution with a concentration of 10-20% for 6-18 hours, wherein the ratio of the composite enzymatic hydrolysis solution to the bamboo strips is 1-2:4.

[0048] In step S3, the composite enzymatic hydrolysis solution is composed of cellulase, α-amylase and β-amylase, and the ratio of cellulase, α-amylase and β-amylase is 3-4:2-3:2-3.

[0049] Cellulase is a type of enzyme that can hydrolyze cellulose by breaking down the glucosidic bonds within cellulose molecules, hydrolyzing cellulose into small molecules such as glucose, cellobiose, and oligosaccharides. This promotes the dissolution of plant cell walls, allowing more dissolved substances in plant cells to be released.

[0050] α-amylase is resistant to high temperatures and can remain active under high temperature conditions. It can randomly cut the α-1,4-glycosidic bonds inside the starch molecules, thereby destroying the structure of the starch molecules and making them easier to be further hydrolyzed by other enzymes, thereby breaking down the starch in the plant cell walls. It can also hydrolyze starch into intermediate products such as maltose and maltotriose. These intermediates can be used by microorganisms such as yeast, thereby further promoting the dissolution of plant cell walls.

[0051] β-amylase is an enzyme that can hydrolyze the α-1,4-glycosidic bonds within starch molecules. Its mechanism of action is to start from the non-reducing end of the starch molecule, gradually hydrolyze the glucose units, and finally produce intermediate products such as maltose and maltotriose.

[0052] When β-amylase acts on starch molecules, it first destroys the structure of the starch molecules, making them more susceptible to further hydrolysis by other enzymes. At the same time, the action of β-amylase can also release substances wrapped inside the starch molecules, such as proteins and fats, making them easier to extract and utilize.

[0053] In one embodiment, ultrasound is used to accelerate the release of starch from the parenchyma cells of bamboo strips. The ultrasound has a frequency of 20 to 30 MHz and operates every 3 to 5 minutes, with a single operation lasting 10 to 15 minutes.

[0054] In one embodiment, ultrasound can accelerate the release of starch from bamboo parenchyma cells by producing cavitation, mechanical vibration, and thermal effects, which can destroy cell walls, increase cell permeability, and facilitate the release of starch.

[0055] Among them, the cavitation effect of ultrasound refers to the generation of cavitation bubbles during the propagation of ultrasound in liquid, which rapidly expand and contract under the action of ultrasound, thereby generating strong impact force and microjets that can destroy cell walls, making it easier for starch to be released.

[0056] The mechanical vibration effect of ultrasound refers to the fact that ultrasound produces tiny vibrations on cells during its propagation, causing the starch granules in the cells to rub and collide with each other, making it easier for the starch to be released.

[0057] The thermal effect of ultrasound refers to the fact that ultrasound generates heat during its propagation, which increases the temperature inside the cells, thereby increasing the permeability of the cells and making it easier for starch to be released.

[0058] In one embodiment, starch molecules have certain polarity and hydrophilicity, so they can form aggregates in aqueous solution. In addition, the presence of water molecules will form a water film on the surface of the bamboo strips, which provides conditions for the adsorption of starch molecules.

[0059] Secondly, factors such as the roughness, porosity, and chemical properties of the bamboo surface also ensure the adsorption of starch molecules. The cuticle of the bamboo epidermal cells is thinner, which exposes more surface active sites, providing more adsorption sites for starch molecules.

[0060] In summary, softening first and then using a composite enzymatic hydrolysis solution with ultrasonic assistance can synergistically destroy the bamboo cell walls better, allowing the enzymatic hydrolysis solution to penetrate deep into the bamboo strips, thereby achieving deep and efficient release of starch, which is very important for forming a natural starch coating.

[0061] In one embodiment, in order to promote the formation of a starch coating on the surface of the bamboo, a small amount of a water-soluble organic solvent, such as 60% to 70% ethanol, is added to the composite enzymatic hydrolysis solution, and the ratio of the composite enzymatic hydrolysis solution to the 60% to 70% ethanol is 8 to 9:1 to 2.

[0062] The water-soluble organic solvent can better dissolve starch, making it more evenly distributed in the composite enzymatic hydrolysis solution, and enable starch to better adhere to the bamboo surface, thereby improving the adhesion between starch and bamboo. It can also adjust the pH value of the composite enzymatic hydrolysis solution, making it more conducive to the enzymatic hydrolysis reaction, thereby promoting the affinity between starch molecules and the starch-bamboo surface.

[0063] In one embodiment, because the starch structure in bamboo parenchyma cells is complex and tightly bound to the cell wall and other components, directly adding starch may not effectively adhere to the bamboo surface.

[0064] By hydrolyzing the cell wall, starch can be released from the cell while maintaining its structure. At this time, the starch is in a semi-hydrolyzed state, with hydrophilic groups such as polysaccharide aldehydes and carboxyl groups on the surface.

[0065] The released starch can directly adhere to the bamboo surface through affinity and hydration, forming a natural starch coating. This starch coating not only improves the adhesion of the bamboo surface, but also provides waterproofing and heat insulation.

[0066] In step S4, the composite adhesive is composed of an adhesive matrix, a curing agent, a waterproofing agent, and a hardening agent, and the ratio of the adhesive matrix, the curing agent, the waterproofing agent, and the hardening agent is 6:2:1:1.

[0067] In one embodiment, the composite adhesive is laid by dispensing, and is laid once every 1 to 2 cm, with the mass of the composite adhesive laid each time being 2 to 4 g.

[0068] In step S4, the adhesive matrix used is the main component of the adhesive, accounting for three-quarters of the total adhesive composition. The adhesive matrix is responsible for providing adhesion and bond strength; the main component of the adhesive matrix is pectin, of which pectin accounts for two-thirds of the total adhesive matrix composition.

[0069] Gum acid is a major component of natural gum and has excellent adhesion properties. The excess hydroxyl groups on the surface of starch molecules can form non-covalent bonds, i.e. hydrogen bonds, with the carboxyl groups on the gum acid molecules.

[0070] In one embodiment, the ratio of the adhesive matrix to the adhesive acid is 7 to 8: 2 to 3. By optimizing the formulation of the adhesive matrix, a composite adhesive with excellent performance can be prepared, effectively improving the bonding ability and bonding effect.

[0071] Specifically, the hydroxyl groups on the surface of starch molecules can form hydrogen bonds with the carboxyl groups on gelatin molecules. A gelatin molecule has multiple carboxyl groups, which can form a complex hydrogen bond network with the hydroxyl groups on multiple starch molecules. This hydrogen bonding between starch and gelatin is very stable, forming a tight starch-gelatin composite film. The starch and gelatin molecules in the composite film adhere and entangle with each other, greatly enhancing the overall adhesion strength.

[0072] Compared to a starch coating alone, the starch-gum-glue composite film exhibits superior adhesion and structural integrity, significantly improving the bonding strength of the bamboo surface. The non-covalent bonding of starch with the natural glue, gum-glue, effectively combines the starch coating and the adhesive layer, forming a strong composite bonding system.

[0073] In step S4, a waterproofing agent and a hardening agent are added to the composite adhesive. The waterproofing agent can penetrate into the micropores formed on the bamboo surface, blocking water penetration and improving the waterproofing ability of the bamboo-based composite board material. The hardening agent can further polymerize the starch coating surface, forming covalent crosslinks between the surface starch molecules, thereby increasing surface hardness and enhancing wear resistance.

[0074] In one embodiment, the waterproofing agent may be polytetrafluoroethylene or the like, and the hardening agent may be silane or the like.

[0075] In one embodiment, after the starch coating is formed, pressure or heat treatment may be applied to further compact the starch molecular structure, fill the surface gaps, and form a denser waterproof structure, thereby strengthening the surface structure.

[0076] In one embodiment, after the starch coating is formed, the surface can be modified by methods such as fluorine modification to make the surface more hydrophobic and weather-resistant, thereby achieving comprehensive performance of waterproofness, durability and wear resistance.

[0077] In one embodiment, the pressure applied to the bamboo strips laid layer by layer is 5-25 MPa, the temperature of the surrounding area of the bamboo strips is 40-60° C., and the hot pressing duration is 20-40 minutes.

[0078] Hot pressing accelerates the curing of the adhesive, ensuring the density, thickness, and bond strength of the plywood. Heating evaporates the solvent in the adhesive, allowing the adhesive to more fully contact the material, resulting in better adhesion. Hot pressing also reacts the chemical components in the adhesive, further strengthening adhesion.

[0079] Under the same set conditions, the implementation experiment and the comparative experiment were set up, that is, the specific failure load for bamboo was selected as 500N; the bending modulus of bamboo was 10GPa, the loading rate was 0.5mm / min; and the shear surface width of the specific bamboo was 150mm and the shear surface length was 300mm.

[0080] Example 1

[0081] Step S1: 50 kg of large-node bamboo in March in spring was selected, soil and impurities attached to the bamboo were cleaned, the bamboo was divided into small sections of 50 cm, and the small sections were cut into bamboo strips with a thickness of 5 mm.

[0082] Step S2: Place the cut bamboo strips into a softening basket. Then, add 150kg of 3% sodium hydroxide solution to the softening basket and soak for 70 hours. During this time, stir the bamboo strips every 12 hours. During the soaking process, heat the sodium hydroxide solution to 45°C at a rate of 5°C per hour and maintain the temperature.

[0083] Step S3: Rinse the softened bamboo strips with clean water for 5 minutes, then place the rinsed bamboo strips into a reaction basket and add 200 kg of a 15% composite enzymatic hydrolysis solution containing cellulase, α-amylase, and β-amylase in a ratio of 4:3:3. Furthermore, 65% ethanol is added to the composite enzymatic hydrolysis solution, with the ratio of composite enzymatic hydrolysis solution to 65% ethanol being 8:1.

[0084] The soaking time is 12 hours. During the enzymatic hydrolysis process, ultrasound with a frequency of 25 MHz is used to assist the reaction. The working frequency of the ultrasound is once every 5 minutes, and the single working time is 10 minutes.

[0085] Step S4: The enzymatically hydrolyzed bamboo strips are air-dried and then laid layer by layer. During the laying process, the composite adhesive is applied every 1 cm, with a mass of 2 g of composite adhesive applied each time. The laid bamboo strips are then transported to a greenhouse at a temperature of 45°C and subjected to a pressure of 10 MPa for 30 minutes. This results in a bamboo-based composite board material.

[0086] Comparative Example 1

[0087] Based on Example 1, the difference in the preparation process is that: step S3 is cancelled, the softened bamboo strips are rinsed and air-dried, and then directly laid layer by layer, and the parameters such as temperature adjustment and pressure adjustment remain unchanged to obtain a bamboo-based composite board material.

[0088] Comparative Example 2

[0089] Based on Example 1, the difference in the preparation process is that the ultrasonic-assisted acceleration of starch release in step S3 is eliminated, and the other variables remain unchanged to obtain a bamboo-based composite board material.

[0090] The bonding strength of the bamboo-based composite board materials prepared in Example 1 and Comparative Example 1 and Comparative Example 2 was tested, and the bonding strength test results are shown in Table 1.

[0091] Table 1

[0092]

[0093]

[0094] From the above data, we can see that the formation of starch coating is particularly important for whether the bamboo surface has better adhesion and structural integrity. The presence of starch coating on the bamboo surface can significantly improve the bonding strength of the bamboo surface, while the opposite is not true.

[0095] Comparative Example 3

[0096] Based on Example 1, the difference in the preparation process is that the addition of 65% ethanol to the composite enzymatic hydrolysis solution in step S3 is omitted, and other variables remain unchanged to obtain a bamboo-based composite board material.

[0097] Comparative Example 4

[0098] Based on Example 1, the difference in the preparation process is that the concentration of ethanol added to the composite enzymatic hydrolysis solution in step S3 is changed to select an ethanol solution with a concentration of 40%.

[0099] Comparative Example 5

[0100] Based on Example 1, the difference in the preparation process is that the concentration of ethanol added to the composite enzymatic hydrolysis solution in step S3 is changed to select an ethanol solution with a concentration of 80%.

[0101] The bonding strength of the bamboo-based composite board materials prepared in the above-mentioned Example 1 and Comparative Examples 3, 4 and 5 was tested, and the bonding strength test results are shown in Table 2.

[0102] Table 2

[0103]

[0104]

[0105] From the above data, it can be seen that whether or not a water-soluble organic solvent is added to the enzymatic solution, as well as the concentration of the water-soluble organic solvent added, plays a certain role in the formation of the starch coating. After adding a water-soluble organic solvent to the enzymatic solution, the adhesion effect of the starch can be significantly improved, while also ensuring the final bonding strength.

[0106] Comparative Example 6

[0107] Based on Example 1, the difference in the preparation process is that the bamboo material selected in step S1 is changed to bamboo material in August, and the other variables remain unchanged to obtain a bamboo-based composite board material.

[0108] Comparative Example 7

[0109] Based on Example 1, the difference in the preparation process is that the bamboo material selected in step S1 is changed to bamboo material in December, and the other variables remain unchanged to obtain a bamboo-based composite board material.

[0110] The bonding strength of the bamboo-based composite board materials prepared in the above-mentioned Example 1 and Comparative Example 6 and Comparative Example 7 was tested. The bonding strength test results are shown in Table 3.

[0111] Table 3

[0112]

[0113] From the above data, it can be learned that the bamboo material grown in the spring period (March-May) has the highest starch content, and therefore the starch released is also the highest. Therefore, the bamboo in the spring period (March-May) is more suitable for this preparation method.

[0114] Comparative Example 8

[0115] Based on Example 1, the difference in the preparation process is that in step S3, the α-amylase component in the composite enzymatic hydrolysis solution is removed, and the ratio of cellulase to β-amylase in the composite enzymatic hydrolysis solution is adjusted to 6:4, and the other variables remain unchanged to obtain a bamboo-based composite board material.

[0116] Comparative Example 9

[0117] Based on Example 1, the difference in the preparation process is that in step S3, the β-amylase component in the composite enzymatic hydrolysis solution is removed, and the ratio of cellulase to α-amylase in the composite enzymatic hydrolysis solution is adjusted to 6:4, and the other variables remain unchanged to obtain a bamboo-based composite board material.

[0118] Comparative Example 10

[0119] Based on Example 1, the difference in the preparation process is that in step S3, the α-amylase and β-amylase components in the composite enzymatic hydrolysis solution are removed, and the other variables remain unchanged to obtain a bamboo-based composite board material.

[0120] The bonding strength of the bamboo-based composite board materials prepared in the above-mentioned Example 1 and Comparative Examples 8, 9 and 10 was tested. The bonding strength test results are shown in Table 4.

[0121] Table 4

[0122]

[0123] The above data demonstrates that the lack of either or both α-amylase and β-amylase affects the rate of starch hydrolysis within the bamboo substrate, thereby affecting the rate and amount of starch release, and thus the bonding strength of the resulting bamboo-based composite board. When the ratio of cellulase, α-amylase, and β-amylase in the composite enzymatic hydrolysis solution is 4:3:3, the rate of starch hydrolysis within the bamboo substrate is the fastest, the amount of starch released is the highest, and thus the bonding strength of the bamboo-based composite board is the highest.

[0124] According to the provisions of GB9846.12, a comparison reveals that the preparation method provided by the present application significantly improves the adhesion strength of bamboo-based composite board materials by subjecting bamboo strips to a series of softening, enzymatic hydrolysis, and hot-pressing bonding. Compared to a single starch coating, the starch-gelatin composite film has better adhesion and structural integrity, significantly improving the bonding strength of the bamboo surface. Compared to the prior art, the present invention solves the problem of bamboo's lack of ray units in the transverse direction, which reduces the porosity and permeability of the transverse structure, thereby further ensuring the strength of the bamboo after bonding.

[0125] The above description is based on the ideal embodiment of the present invention. Based on the above description, relevant personnel can make various changes and modifications without departing from the technical scope of this invention. The technical scope of this invention is not limited to the content of the specification and must be determined according to the scope of the claims.

Claims

1. A method for preparing a waterproof, bio-resistant, durable, wear-resistant and high-strength bamboo-based composite material, characterized in that: The following steps are involved: S1. Select bamboo, trim and clean it, divide the bamboo into several small sections and slice them to obtain bamboo strips with a thickness of 3-15 mm; S2, soaking the bamboo strips in a sodium hydroxide solution with a concentration of 2-5% to soften them, wherein the ratio of the bamboo strips to the sodium hydroxide solution is 1-2:3; S3. Wash the softened bamboo strips with water to remove residual sodium hydroxide, and then immerse them in a composite enzymatic hydrolysis solution with a concentration of 10-20%. With the assistance of ultrasound, starch in the parenchyma cells of the bamboo strips is released, and a starch coating is formed on the outer surface of the bamboo strips. The ratio of bamboo strips to composite enzymatic hydrolysis solution is 1-2:

4. S4. Laying the starch-coated bamboo strips layer by layer, adding a composite adhesive during the laying process, and obtaining a bamboo-based composite board material after hot pressing, wherein the composite adhesive comprises an adhesive matrix, a curing agent, a waterproofing agent, and a hardening agent.

2. A method for preparing a waterproof, bio-resistant, durable, wear-resistant, and high-strength bamboo-based composite material according to claim 1, characterized in that: In step S1, the bamboo material is segmented along the grain direction of the bamboo material, and the length of the small segment of bamboo material is 30-100 cm.

3. A method for preparing a waterproof, bio-resistant, durable, wear-resistant, and high-strength bamboo-based composite material according to claim 1, characterized in that: In step S2, the bamboo strips are soaked in the sodium hydroxide solution for 36 to 90 hours, and the bamboo strips are turned over every 12 to 18 hours.

4. A method for preparing a waterproof, bio-resistant, durable, wear-resistant, and high-strength bamboo-based composite material according to claim 1, characterized in that: In step S2, the sodium hydroxide solution is heated to a temperature of 40-50° C., and the heating rate of the sodium hydroxide solution is 5-20° C. per hour.

5. A method for preparing a waterproof, bio-resistant, durable, wear-resistant, and high-strength bamboo-based composite material according to claim 1, characterized in that: In step S3, the softened bamboo strips are washed with clean water for 5 to 8 minutes.

6. A method for preparing a waterproof, bio-resistant, durable, wear-resistant, and high-strength bamboo-based composite material according to claim 1, characterized in that: In step S3, the frequency of the ultrasound is 20-30 MHz, and the ultrasound works every 3-5 minutes, with a single working time of 10-15 minutes.

7. A method for preparing a waterproof, bio-resistant, durable, wear-resistant, and high-strength bamboo-based composite material according to claim 1, characterized in that: In step S4, the pressure applied to the bamboo strips laid layer by layer is 5-25 MPa, the temperature around the bamboo strips is 40-60° C., and the hot pressing duration is 20-40 minutes.

8. A method for preparing a waterproof, bio-resistant, durable, wear-resistant, and high-strength bamboo-based composite material according to claim 1, characterized in that: In step S4, the thickness of the bamboo-based composite board material is not less than 30 mm.

Images