Light composite board with coconut fibers and preparation method of light composite board

Abstract

The invention discloses a light composite board with coconut fibers and a preparation method of the light composite board, and relates to the technical field of composite boards, the light composite board comprises a first functional layer, a second functional layer and a coconut fiber reinforced layer located between the first functional layer and the second functional layer, the coconut fiber reinforced layer is prepared from the following raw materials in parts by mass: 75 to 85 parts of gypsum powder; 6-10 parts of coconut fiber; 6-12 parts of fly ash; 2-6 parts of a foaming agent; 0.5 to 1.5 parts of sodium dodecyl sulfate; and 4-6 parts of a modifier. The coconut fibers, the fly ash, the foaming agent and various modifiers are introduced into the middle layer, so that the mechanical strength, toughness and thermal insulation performance of the board are effectively improved, and the first functional layer and the second functional layer further enhance the flame retardance, radiation resistance, antibacterial performance and corrosion resistance of the board through the synergistic effect of the high polymer material and the functional filler.

Description

Technical Field

[0001] The present invention relates to the technical field of composite boards, and more specifically, to a lightweight composite board with coconut fibers and a preparation method thereof. Background Art

[0002] A lightweight composite board is a board made by a composite process of two or more different materials, aiming to combine the advantages of each constituent material while achieving a relatively low density, and is usually used in structural applications requiring high strength and low weight. The basic composition of common lightweight composite boards includes a matrix material (such as gypsum, polymer, metal, etc.) and a reinforcing material (such as glass fiber, natural fiber, carbon fiber, wood fiber, etc.). These composite boards combine the reinforcing fiber or particulate material with the matrix material through a specific process to provide enhanced mechanical properties, thermal properties, and other characteristics.

[0003] However, the mechanical properties of traditional lightweight composite boards may be limited to a certain extent, especially in terms of tensile strength and compressive strength. Although their lightness is ensured, in order to achieve a balance between strength and toughness, many lightweight composite boards rely on synthetic fibers or fillers to enhance their performance, and these materials may not be able to effectively inhibit crack propagation or are prone to failure under high loads, resulting in an increase in the brittleness of the overall structure.

[0004] Regarding the problems in the related art, no effective solution has been proposed yet. Summary of the Invention

[0005] Regarding the problems in the related art, the present invention provides a lightweight composite board with coconut fibers and a preparation method thereof to overcome the above-mentioned technical problems existing in the existing related art.

[0006] To this end, the specific technical solutions adopted by the present invention are as follows: According to one aspect of the present invention, there is provided a lightweight composite board with coconut fibers, which includes a first functional layer, a second functional layer, and a coconut fiber reinforcing layer located between the first functional layer and the second functional layer. The coconut fiber reinforcing layer is composed of the following raw materials in parts by mass: 75 - 85 parts of gypsum powder, 6 - 10 parts of coconut fibers, 6 - 12 parts of fly ash, 2 - 6 parts of foaming agent, 0.5 - 1.5 parts of sodium dodecyl sulfate, and 4 - 6 parts of modifier.

[0007] Preferably, the first functional layer is composed of the following raw materials in parts by mass: 80 - 90 parts of polyethylene, 15 - 25 parts of ethylene - vinyl alcohol copolymer, and 12 - 28 parts of a first filler; The second functional layer is composed of the following raw materials in parts by mass: 80 - 90 parts of polyethylene, 15 - 25 parts of ethylene - vinyl alcohol copolymer, and 12 - 28 parts of a second filler.

[0008] Preferably, the first filler is composed of raw materials in the following parts by mass; 2 - 6 parts of boron carbide, 7 - 15 parts of barium sulfate, and 3 - 7 parts of nickel - plated carbon fiber; The second filler is composed of raw materials in the following parts by mass: 8 - 18 parts of hollow glass microspheres, 3 - 6 parts of bamboo fiber, and 1 - 4 parts of nano - silica.

[0009] Preferably, the modifier includes one or more of silane coupling agent, titanate coupling agent, aluminate coupling agent, quaternary ammonium salt antibacterial agent, nano - silver, organic copper preservative, sodium dodecyl sulfate, and dioctyl phthalate.

[0010] Preferably, the density of the hollow glass microspheres is 0.2 - 0.6 g / cm 3 , and the thermal conductivity of the hollow glass microspheres ≤ 0.1 W / (m·K).

[0011] According to another aspect of the present invention, there is also provided a preparation method of a lightweight composite board with coconut fiber, and the preparation method includes: S1. Select a preset number of parts of coconut fiber for pretreatment, and perform low - speed stirring and mixing on the pretreated coconut fiber, gypsum powder, and fly ash to obtain a first mixed product; S2. Select a preset number of parts of water, foaming agent, sodium dodecyl sulfonate, and modifier, and sequentially add them to the first mixed product and perform high - speed stirring and mixing to obtain a mixed slurry. Place the mixed slurry in a mold for pre - forming, and let it stand at room temperature for 20 minutes for initial setting to form a coconut fiber reinforced layer; S3. Select a preset number of parts of polyethylene and ethylene - vinyl alcohol copolymer, and sequentially add them to a kneader for melt - blending to obtain a second mixed product; S4. Add the first filler and the second filler to the second mixed product respectively for kneading. After kneading is completed, form a first composite material and a second composite material, and make the first composite material and the second composite material into sheets, and cool to obtain a first functional layer and a second functional layer; S5. Place the first functional layer at the bottom of the mold, cover it with the coconut fiber reinforced layer, and then cover the second functional layer on the coconut fiber reinforced layer. Compress and laminate it under a hot press for 15 - 20 minutes, and demold and cool to room temperature to obtain the lightweight composite board.

[0012] Preferably, selecting a preset number of parts of coconut fiber for pretreatment includes: Shear the coconut fiber, and soak the sheared coconut fiber in warm water and stir - wash it; The cleaned coconut fibers are immersed in a sodium hydroxide solution to remove impurities on the surface of the coconut fibers. After the immersion is completed, the coconut fibers are repeatedly rinsed with clean water until neutral and then dried for standby.

[0013] Preferably, the kneading temperature for kneading by adding the first filler to the second mixture is 180 °C; the kneading temperature for kneading by adding the second filler to the second mixture is 160 °C.

[0014] Preferably, the temperature of the hot press is 150 - 170 °C, and the pressure of the hot press is 3 - 5 MPa.

[0015] The beneficial effects of the present invention are as follows: 1. By introducing coconut fibers, fly ash, foaming agents and various modifiers into the intermediate layer, the mechanical strength, toughness and thermal insulation performance of the board are effectively improved. Through the synergistic effect of the polymer material and the functional filler in the first functional layer and the second functional layer, the flame retardant, radiation protection, antibacterial and anti-corrosion performance of the board are further enhanced. Among them, hollow glass microspheres reduce the overall density and thermal conductivity. The overall structural design is scientific and reasonable, and the obtained lightweight composite board has multiple advantages such as light weight and high strength, thermal insulation, fire and corrosion prevention, and environmental protection.

[0016] 2. By scientifically pretreating the coconut fibers, impurities are effectively removed to improve the interfacial bonding force with the matrix. By stirring at low speed and high speed step by step, the mixing uniformity is ensured, and by controlling the kneading temperature and hot pressing conditions, the structural compatibility and mechanical properties of each functional layer and the reinforcing layer are optimized. Finally, the obtained composite board has firm interlayer bonding, stable structure and balanced performance, and has good production controllability, process repeatability and industrial application prospects. Description of the Drawings

[0017] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required to be used in the embodiments. Obviously, the following described drawings are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0018] Figure 1 is a schematic structural diagram of a lightweight composite board with coconut fibers according to an embodiment of the present invention; Figure 2 is a flowchart of a preparation method of a lightweight composite board with coconut fibers according to an embodiment of the present invention.

[0019] In the figure: 1. First functional layer; 2. Second functional layer; 3. Coconut fiber reinforcing layer. Detailed Embodiments

[0020] To further illustrate the embodiments, the present invention provides accompanying drawings, which are part of the disclosure of the present invention. They are mainly used to illustrate the embodiments and can be combined with the relevant descriptions in the specification to explain the operating principles of the embodiments. With reference to these contents, those of ordinary skill in the art should be able to understand other possible implementation manners and the advantages of the present invention.

[0021] According to an embodiment of the present invention, a lightweight composite board with coconut fibers and a preparation method thereof are provided.

[0022] Now, the present invention will be further described in conjunction with the accompanying drawings and specific implementation manners. As Figure 1 shown, according to an embodiment of the present invention, a lightweight composite board with coconut fibers is provided. The lightweight composite board includes a first functional layer 1, a second functional layer 2, and a coconut fiber reinforcing layer 3 located between the first functional layer 1 and the second functional layer 2. The coconut fiber reinforcing layer 3 is composed of the following raw materials in parts by mass: Gypsum powder 75 - 85 parts, coconut fiber 6 - 10 parts, fly ash 6 - 12 parts, foaming agent 2 - 6 parts, sodium dodecyl sulfonate 0.5 - 1.5 parts, and modifier 4 - 6 parts.

[0023] Among them, the first functional layer 1 is composed of the following raw materials in parts by mass: Polyethylene 80 - 90 parts, ethylene - vinyl alcohol copolymer 15 - 25 parts, and first filler 12 - 28 parts; The second functional layer 2 is composed of the following raw materials in parts by mass: Polyethylene 80 - 90 parts, ethylene - vinyl alcohol copolymer 15 - 25 parts, and second filler 12 - 28 parts.

[0024] It should be noted that the first functional layer 1 is composed of polyethylene, ethylene - vinyl alcohol copolymer, and first filler (boron carbide, barium sulfate, nickel - plated carbon fiber). Polyethylene serves as the matrix to endow the material with good toughness and chemical resistance. The ethylene - vinyl alcohol copolymer improves the polarity and interfacial bonding ability of the material, which helps the filler to be evenly dispersed and enhances the mechanical properties.

[0025] It should be noted that the second functional layer 2 is composed of the same polymer matrix and second filler (hollow glass microspheres, bamboo fibers, nano - silica). Hollow glass microspheres have extremely low density and thermal conductivity, which can significantly reduce the weight of the material and improve the heat insulation and heat preservation performance. Bamboo fibers are natural reinforcing materials with good toughness and crack - resistance properties, which help to improve the ductility and impact resistance of the material under stress.

[0026] Among them, the first filler is composed of the following raw materials in parts by mass; Boron carbide 2 - 6 parts, barium sulfate 7 - 15 parts, and nickel - plated carbon fiber 3 - 7 parts; The second filler is composed of the following raw materials in parts by mass: 8 - 18 parts of hollow glass microspheres, 3 - 6 parts of bamboo fiber, and 1 - 4 parts of nano - silica.

[0027] It should be noted that boron carbide in the first filler has extremely strong neutron absorption ability, which can significantly improve the neutron radiation protection performance of the composite board. Barium sulfate is a high - density compound that can effectively absorb X - rays and γ - rays, further enhancing the radiation protection performance of the board, while providing high barrier properties and structural density. Nickel - plated carbon fiber combines the high strength of carbon fiber and the conductivity of nickel, making the material have excellent mechanical strength, electromagnetic shielding performance, and antioxidant ability at the same time.

[0028] Hollow glass microspheres in the second filler have extremely low density and thermal conductivity, significantly reducing the overall weight of the material while enhancing the heat insulation and heat preservation performance. Bamboo fiber, as a natural plant fiber, is not only environmentally friendly and renewable but also can improve the toughness and crack resistance of the material, especially having excellent buffering effects during the stress and deformation processes. Nano - silica particles are small and have a large specific surface area, which can improve the interfacial bonding performance of the material, enhancing the overall strength, heat resistance, and aging resistance.

[0029] Among them, the modifier includes one or more of silane coupling agent, titanate coupling agent, aluminate coupling agent, quaternary ammonium salt antibacterial agent, nano - silver, organic copper preservative, sodium dodecyl sulfate, and dioctyl phthalate.

[0030] Among them, the density of the hollow glass microspheres is 0.2 - 0.6 g / cm 3 , and the thermal conductivity of the hollow glass microspheres ≤ 0.1 W / m·K.

[0031] According to another embodiment of the present invention, as Figure 2 shown, a preparation method of a lightweight composite board with coconut fiber is also provided. The preparation method includes: S1. Select a preset number of parts of coconut fiber for pretreatment, and mix the pretreated coconut fiber, gypsum powder, and fly ash at a low speed to obtain a first mixed product; S2. Select a preset number of parts of water, foaming agent, sodium dodecyl sulfonate, and modifier, and add them to the first mixed product in sequence and mix at a high speed to obtain a mixed slurry. Place the mixed slurry in a mold for pre - forming, and let it stand at room temperature for 20 minutes for initial setting to form a coconut fiber reinforced layer 3; S3. Select a preset number of parts of polyethylene and ethylene - vinyl alcohol copolymer, and add them to a mixer in sequence for melt - blending to obtain a second mixed product; S4. Add the first filler and the second filler to the second mixed product respectively for kneading. After the kneading is completed, the first composite material and the second composite material are formed, and the first composite material and the second composite material are made into sheets, and then cooled to obtain the first functional layer 1 and the second functional layer 2; S5. Place the first functional layer 1 at the bottom of the mold, cover it with the coconut fiber reinforced layer 3, and then cover the second functional layer 2 on the coconut fiber reinforced layer. Compression molding is carried out under a hot press (the temperature of the hot press is 150 - 170 °C, and the pressure of the hot press is 3 - 5 MPa) for 15 - 20 minutes. After demolding, it is cooled to room temperature to obtain the lightweight composite board.

[0032] Among them, the pretreatment of selecting a preset number of coconut fibers includes: Shear the coconut fibers, and soak the sheared coconut fibers in warm water and stir for cleaning; Place the cleaned coconut fibers in a sodium hydroxide solution for soaking to remove the impurities on the surface of the coconut fibers. After the soaking is completed, repeatedly rinse the coconut fibers with clean water until neutral and then dry them for standby.

[0033] It should be noted that shearing can make the fiber length more suitable for compounding with other materials, improve the dispersibility and interfacial bonding property. Stirring and cleaning with warm water can remove the dust, sugars, oils and other impurities attached to the fiber surface, improving the subsequent treatment efficiency. Soaking in the sodium hydroxide solution can effectively remove the lignin, wax and other non-cellulose components on the fiber surface, improve the fiber surface roughness, increase the specific surface area, thereby enhancing its interfacial adhesion property with matrix materials such as gypsum and cement, improving the reinforcement effect. Finally, repeatedly rinsing with clean water until neutral and then drying can ensure that there is no alkali residue in the fiber, avoiding affecting the durability and stability of the composite material.

[0034] Among them, the kneading temperature for adding the first filler to the second mixed product for kneading is 180 °C; the kneading temperature for adding the second filler to the second mixed product for kneading is 160 °C.

[0035] It should be noted that cooling to 160 °C helps to avoid the over-expansion or rupture of hollow glass microspheres during the kneading process. Because hollow glass microspheres are prone to rupture due to the expansion of the gas inside at high temperatures, resulting in the loss of their lightweight and heat insulation functions. By kneading at a temperature of 160 °C, the integrity of the microspheres can be maintained, ensuring that their lightness, heat insulation and stability are not damaged, thereby improving the overall heat preservation effect and mechanical properties of the composite board, and avoiding affecting the performance and service life of the composite material due to excessive temperature treatment.

[0036] The following further illustrates the specific implementation manners of the present invention in combination with the examples and comparative examples: Example 1 1. Lightweight composite board with coconut fiber, which is composed of raw materials in the following parts by mass: Gypsum powder 75g, coconut fiber 6g, fly ash 6g, foaming agent 2g, sodium dodecyl sulfonate 0.5g, modifier 4g, polyethylene 80g, ethylene-vinyl alcohol copolymer 15g, first filler 12g, second filler 12g, water 60g.

[0037] 2. Preparation process: (1) Preparation of initial product: Select 6g of coconut fiber for pretreatment, and mix the pretreated coconut fiber, 75g of gypsum powder and 6g of fly ash by low-speed stirring to obtain the first mixed product; (2) Preparation and molding of slurry: Add 60g of water, 2g of foaming agent, 0.5g of sodium dodecyl sulfonate and 4g of modifier to the first mixed product in sequence and mix by high-speed stirring to obtain the mixed slurry. Place the mixed slurry in a mold for pre-molding, and let it stand at room temperature for 20 minutes for initial setting to form a coconut fiber reinforced layer; (3) Polymer matrix blending: Add 80g of polyethylene and 15g of ethylene-vinyl alcohol copolymer to a kneader in sequence for melt blending to obtain the second mixed product; (4) Filler kneading and molding: Add 12g of the first filler and 12g of the second filler to the second mixed product for kneading. After kneading is completed, form the first composite material and the second composite material, and make the first composite material and the second composite material into sheets, and cool to obtain the first functional layer and the second functional layer; (5) Laminating and composite molding: Place the first functional layer at the bottom of the mold, cover it with a coconut fiber reinforced layer, and then cover the second functional layer on the coconut fiber reinforced layer. Compress and laminate it under a hot press for 15 - 20 minutes, and cool to room temperature after demolding to obtain a lightweight composite board.

[0038] Example 2 1. Lightweight composite board with coconut fiber, which is composed of raw materials in the following parts by mass: Gypsum powder 80g, coconut fiber 8g, fly ash 9g, foaming agent 4g, sodium dodecyl sulfonate 1g, modifier 5g, polyethylene 85g, ethylene-vinyl alcohol copolymer 20g, first filler 20g, second filler 20g, water 70g.

[0039] 2. Preparation process: (1) Preparation of initial product: Select 8g of coconut fiber for pretreatment, and mix the pretreated coconut fiber, 80g of gypsum powder and 9g of fly ash by low-speed stirring to obtain the first mixed product; (2) Slurry preparation and forming: 70 g of water, 4 g of foaming agent, 1 g of sodium dodecyl sulfonate and 5 g of modifier were successively added to the first mixed product and stirred at high speed to obtain a mixed slurry. The mixed slurry was preformed in a mold and left to set initially for 20 minutes at room temperature to form a coconut fiber reinforced layer; (3) Polymer matrix blending: 85 g of polyethylene and 20 g of ethylene-vinyl alcohol copolymer were successively added to a kneader for melt blending to obtain a second mixed product; (4) Filler kneading and forming: 20 g of the first filler and 20 g of the second filler were respectively added to the second mixed product for kneading. After kneading, a first composite material and a second composite material were formed, and the first composite material and the second composite material were made into sheets and cooled to obtain a first functional layer and a second functional layer; (5) Laminating and composite forming: The first functional layer was placed at the bottom of the mold, covered with the coconut fiber reinforced layer, and then covered with the second functional layer on the coconut fiber reinforced layer. It was compounded and pressed under a hot press for 15 - 20 minutes, and after demolding, it was cooled to room temperature to obtain a lightweight composite board.

[0040] Example 3 1. A lightweight composite board with coconut fiber, which is composed of the following raw materials in parts by mass: 85 g of gypsum powder, 10 g of coconut fiber, 12 g of fly ash, 6 g of foaming agent, 1.5 g of sodium dodecyl sulfonate, 6 g of modifier, 90 g of polyethylene, 25 g of ethylene-vinyl alcohol copolymer, 28 g of the first filler, 28 g of the second filler, 80 g of water.

[0041] 2. Preparation process: (1) Initial product preparation: 10 g of coconut fiber was selected for pretreatment, and the pretreated coconut fiber, 85 g of gypsum powder and 12 g of fly ash were stirred and mixed at low speed to obtain a first mixed product; (2) Slurry preparation and forming: 80 g of water, 6 g of foaming agent, 1.5 g of sodium dodecyl sulfonate and 6 g of modifier were successively added to the first mixed product and stirred at high speed to obtain a mixed slurry. The mixed slurry was preformed in a mold and left to set initially for 20 minutes at room temperature to form a coconut fiber reinforced layer; (3) Polymer matrix blending: 90 g of polyethylene and 25 g of ethylene-vinyl alcohol copolymer were successively added to a kneader for melt blending to obtain a second mixed product; (4) Filler kneading and forming: 28 g of the first filler and 28 g of the second filler were respectively added to the second mixed product for kneading. After kneading, a first composite material and a second composite material were formed, and the first composite material and the second composite material were made into sheets and cooled to obtain a first functional layer and a second functional layer; (5)Laminating and composite molding: Place the first functional layer at the bottom of the mold, cover it with a coconut fiber reinforced layer, and then cover the coconut fiber reinforced layer with the second functional layer. Compress and laminate them under a hot press for 15 - 20 minutes, and cool to room temperature after demolding to obtain a lightweight composite board.

[0042] Comparative Example 1 1. A lightweight composite board with coconut fibers, which is composed of the following raw materials in parts by mass: 75 g of gypsum powder, 6 g of fly ash, 2 g of foaming agent, 0.5 g of sodium dodecyl sulfonate, 4 g of modifier, 80 g of polyethylene, 15 g of ethylene - vinyl alcohol copolymer, 12 g of the first filler, 12 g of the second filler, and 60 g of water.

[0043] 2. Preparation process: (1)Initial product preparation: Mix 75 g of gypsum powder and 6 g of fly ash at low speed to obtain the first mixed product; (2)Slurry preparation and molding: Add 60 g of water, 2 g of foaming agent, 0.5 g of sodium dodecyl sulfonate, and 4 g of modifier to the first mixed product in sequence and mix them at high speed to obtain a mixed slurry. Place the mixed slurry in a mold for pre - molding and let it stand at room temperature for 20 minutes to set initially to form a coconut fiber reinforced layer; (3)Polymer matrix blending: Add 80 g of polyethylene and 15 g of ethylene - vinyl alcohol copolymer to a kneader in sequence for melt blending to obtain the second mixed product; (4)Filler kneading and molding: Add 12 g of the first filler and 12 g of the second filler to the second mixed product for kneading. After kneading is completed, form the first composite material and the second composite material, and make the first composite material and the second composite material into sheets, and cool to obtain the first functional layer and the second functional layer; (5)Laminating and composite molding: Place the first functional layer at the bottom of the mold, cover it with a coconut fiber reinforced layer, and then cover the coconut fiber reinforced layer with the second functional layer. Compress and laminate them under a hot press for 15 - 20 minutes, and cool to room temperature after demolding to obtain a lightweight composite board.

[0044] Comparative Example 2 1. A lightweight composite board with coconut fibers, which is composed of the following raw materials in parts by mass: 80 g of gypsum powder, 9 g of fly ash, 4 g of foaming agent, 1 g of sodium dodecyl sulfonate, 5 g of modifier, 85 g of polyethylene, 20 g of ethylene - vinyl alcohol copolymer, 20 g of the first filler, 20 g of the second filler, and 70 g of water.

[0045] 2. Preparation process: (1)Initial product preparation: Mix 80 g of gypsum powder and 9 g of fly ash at low speed to obtain the first mixed product; (2) Slurry preparation and forming: 70 g of water, 4 g of foaming agent, 1 g of sodium dodecyl sulfonate and 5 g of modifier were successively added to the first mixed product and stirred at high speed to obtain a mixed slurry. The mixed slurry was placed in a mold for pre-forming and left to set and initially solidify at room temperature for 20 minutes to form a coconut fiber reinforced layer; (3) Polymer matrix blending: 85 g of polyethylene and 20 g of ethylene-vinyl alcohol copolymer were successively added to a kneader for melt blending to obtain a second mixed product; (4) Filler kneading and forming: 20 g of the first filler and 20 g of the second filler were respectively added to the second mixed product for kneading. After kneading, a first composite material and a second composite material were formed, and the first composite material and the second composite material were made into sheets and cooled to obtain a first functional layer and a second functional layer; (5) Laminating and composite forming: The first functional layer was placed at the bottom of the mold, covered with a coconut fiber reinforced layer, and the second functional layer was covered on the coconut fiber reinforced layer. It was subjected to composite pressing under a hot press for 15 - 20 minutes, and after demolding, it was cooled to room temperature to obtain a lightweight composite board.

[0046] Comparative Example 3 1. A lightweight composite board with coconut fiber, which is composed of the following raw materials in parts by mass: 85 g of gypsum powder, 10 g of coconut fiber, 12 g of fly ash, 6 g of foaming agent, 1.5 g of sodium dodecyl sulfonate, 6 g of modifier, 90 g of polyethylene, 25 g of ethylene-vinyl alcohol copolymer, 28 g of the first filler, 28 g of the second filler, 80 g of water.

[0047] 2. Preparation process: (1) Preparation of the initial product: 85 g of gypsum powder and 12 g of fly ash were stirred and mixed at low speed to obtain a first mixed product; (2) Slurry preparation and forming: 80 g of water, 6 g of foaming agent, 1.5 g of sodium dodecyl sulfonate and 6 g of modifier were successively added to the first mixed product and stirred at high speed to obtain a mixed slurry. The mixed slurry was placed in a mold for pre-forming and left to set and initially solidify at room temperature for 20 minutes to form a coconut fiber reinforced layer; (3) Polymer matrix blending: 90 g of polyethylene and 25 g of ethylene-vinyl alcohol copolymer were successively added to a kneader for melt blending to obtain a second mixed product; (4) Filler kneading and forming: 28 g of the first filler and 28 g of the second filler were respectively added to the second mixed product for kneading. After kneading, a first composite material and a second composite material were formed, and the first composite material and the second composite material were made into sheets and cooled to obtain a first functional layer and a second functional layer; (5)Laminating and composite molding: Place the first functional layer at the bottom of the mold, cover it with a coconut fiber reinforced layer, and then cover the coconut fiber reinforced layer with the second functional layer. Compress and laminate them under a hot press for 15 - 20 minutes, and cool to room temperature after demolding to obtain a lightweight composite board.

[0048] Table 1: Performance comparison table of each example and comparative example Based on Table 1, it can be seen that the lightweight composite board containing coconut fiber shows significantly better performance in terms of tensile strength and compressive strength than the comparative example samples without fiber. The tensile strength of Examples 1 to 3 is between 7.6 and 10 MPa, significantly higher than 4.3 to 5.5 MPa of Comparative Examples 1 to 3, indicating that coconut fiber forms a reinforcing network in the composite material, effectively improving the tensile load-bearing capacity of the material. At the same time, the compressive strength of the examples reaches 10 to 13 MPa, also significantly better than 6.8 to 7.5 MPa of the comparative examples, showing that coconut fiber not only improves the compactness and stability of the overall structure but also plays a role in collaborative support and crack arrest under compressive load. Therefore, it has a significant strengthening effect on enhancing the mechanical properties of the lightweight composite board.

[0049] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A lightweight composite board with coconut fiber, characterized in that: The lightweight composite board comprises a first functional layer, a second functional layer and a coconut fiber reinforcement layer located between the first functional layer and the second functional layer, wherein the coconut fiber reinforcement layer is composed of the following raw materials in parts by weight: 75-85 parts of gypsum powder; 6-10 parts of coconut fiber; 6-12 parts of fly ash; 2-6 parts of foaming agent; 0.5-1.5 parts of sodium dodecyl sulfate; Modifier 4-6 parts.

2. A lightweight composite board with coconut fiber according to claim 1, characterized in that: The first functional layer is composed of the following raw materials in parts by weight: 80-90 parts of polyethylene, 15-25 parts of ethylene-vinyl alcohol copolymer and 12-28 parts of the first filler; The second functional layer is composed of the following raw materials in parts by weight: 80-90 parts of polyethylene, 15-25 parts of ethylene-vinyl alcohol copolymer and 12-28 parts of the second filler.

3. A lightweight composite board with coconut fiber according to claim 2, characterized in that: The first filler is composed of the following raw materials in parts by mass: 2-6 parts of boron carbide, 7-15 parts of barium sulfate and 3-7 parts of nickel-plated carbon fiber; The second filler is composed of the following raw materials in parts by weight: 8-18 parts of hollow glass microspheres, 3-6 parts of bamboo fiber and 1-4 parts of nano silicon dioxide.

4. A lightweight composite board with coconut fiber according to claim 3, characterized in that: The modifier includes one or more of silane coupling agent, titanate coupling agent, aluminate coupling agent, quaternary ammonium salt antibacterial agent, nano silver, organic copper preservative, sodium dodecyl sulfate, and dioctyl phthalate.

5. A lightweight composite board with coconut fiber according to claim 4, characterized in that: The density of the hollow glass microspheres is 0.2-0.6 g / cm 3 , the thermal conductivity of the hollow glass microspheres is ≤0.1 W / (m·K).

6. A method for preparing a lightweight composite board with coconut fiber, for realizing the preparation of the lightweight composite board with coconut fiber according to claim 5, characterized in that: The preparation method comprises: S1, select a preset number of coconut fiber for pretreatment, and stir and mix the pretreated coconut fiber, gypsum powder and fly ash at a low speed to obtain a first mixed product; S2, select preset portions of water, foaming agent, sodium lauryl sulfate and modifier, add them successively to the first mixed product and mix with high-speed stirring to obtain a mixed slurry, place the mixed slurry in a mold for preforming, leave for initial coagulation 20 minutes at room temperature, and form a coconut fiber reinforcement layer; S3, selecting a preset number of polyethylene and ethylene-vinyl alcohol copolymer, sequentially adding them into an internal mixer for melt blending to obtain a second mixed product; S4, respectively adding the first filler and the second filler to the second mixed product for kneading, forming a first composite material and a second composite material after the kneading is completed, and forming the first composite material and the second composite material into sheets, and cooling to obtain a first functional layer and a second functional layer; S5, placing the first functional layer at the bottom of the mold, covering it with a coconut fiber reinforcement layer, and covering the coconut fiber reinforcement layer with a second functional layer, composite pressing for 15-20 minutes under a hot press, and cooling to room temperature after demoulding to obtain a lightweight composite board.

7. The method for preparing a lightweight composite board with coconut fiber according to claim 6, characterized in that: The method of selecting a preset number of coconut fibers for pretreatment comprises: The coconut fibers are cut, and the cut coconut fibers are immersed in warm water, stirred and cleaned; The cleaned coconut fiber is soaked in a sodium hydroxide solution to remove impurities on the surface of the coconut fiber. After the soaking is completed, the coconut fiber is repeatedly rinsed with clean water until it is neutral and then dried for use.

8. The method for preparing a lightweight composite board with coconut fiber according to claim 7, characterized in that: The kneading temperature during the kneading of the second mixed product with the first filler was 180°C.

9. The method for preparing a lightweight composite board with coconut fiber according to claim 8, characterized in that: The kneading temperature during the kneading of the second mixed product with the second filler was 160°C.

10. The method for preparing a lightweight composite board with coconut fiber according to claim 9, characterized in that: The temperature of the hot press is 150-170° C., and the pressure of the hot press is 3-5 MPa.

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