Lightweight high-strength bamboo composite board and preparation method thereof

Abstract

This invention provides a lightweight, high-strength bamboo composite board and its preparation method. The lightweight, high-strength bamboo composite board includes an upper surface layer, a lower surface layer, and a core layer sandwiched between the upper and lower surface layers. Both the upper and lower surface layers are composed of lightweight reconstituted bamboo panels. The core layer is composed of multiple bamboo tube ring units, with the axial direction of each bamboo tube ring unit perpendicular to the plane of the board. Each bamboo tube ring unit has a comb-like structure on its end faces, which is inserted into the upper and / or lower surface layers to form a mechanical anchor with the lightweight reconstituted bamboo panels. This invention also provides a method for preparing the lightweight, high-strength bamboo composite board, including preparing bamboo tube ring units; processing the comb-like structure; preparing a lightweight reconstituted bamboo panel blank; assembling the blank; and curing. This preparation method improves the bending strength and internal bonding strength of the composite board. Furthermore, by combining the lightweight reconstituted bamboo surface layer with the bamboo tube interlayer, overall weight reduction is achieved while maintaining mechanical properties.

Description

Technical Field

[0001] This invention belongs to the field of bamboo processing and composite material technology, specifically relating to a lightweight high-strength bamboo composite board and its preparation method. Background Technology

[0002] Reconstituted bamboo is a composite biomass material made from bamboo as raw material, using bamboo bundles or bamboo fiber veneers as matrix units, and bonding them with resin reinforcement. It is one of the important ways to achieve efficient and high-value utilization of bamboo and has become a mainstream product in the bamboo industry. This material has advantages such as high strength, high hardness, and excellent weather resistance. However, reconstituted bamboo generally has a relatively high density (typically ≥1000 kg / m³). 3 The problem of [unclear] limits its application in lightweight applications such as building decorative panels and home door panels.

[0003] In recent years, the design of composite boards using bamboo tubes as the core layer has attracted much attention. The aim is to optimize the core layer structure to prepare lightweight and high-strength bamboo composite boards, thereby expanding their application areas. Chinese patent CN202021136736.9 discloses a bamboo board and bamboo tube composite board structure. The connection between the bamboo tube end face and the board layer is mainly planar adhesive. Since the fibers of the bamboo tube end face are perpendicular to the board layer, while the fibers of the board layer are parallel to the board surface, they intersect at 90°. The interface bonding is a two-dimensional "end-side" bonding, resulting in insufficient adhesive area. Under long-term stress or temperature and humidity changes, it is prone to delamination. Chinese patent CN202211419334.3 discloses a manufacturing method and structure for lightweight and high-strength boards. However, the contact between circular bamboo tubes is mostly point or line contact, leaving many gaps. When the board is under stress, it is prone to movement and misalignment. Therefore, it is improved by using polygonal bamboo tubes, allowing the sidewalls of adjacent bamboo tubes to adhere and form surface contact, making the unit structure more stable and thus improving the overall stability of the board. However, this solution cuts the round bamboo tubes into polygons, which greatly reduces the material utilization rate.

[0004] It is worth noting that the lightweight reconstituted bamboo used as the upper and lower surfaces of the composite board is pressed under relatively low pressure, and its density is usually controlled between 600-950 kg / m³. 3 The bamboo tubes were not subjected to a high degree of densification. Therefore, during the pressing process, fiber gaps extending along the direction of the bamboo bundle fibers and nearly parallel to each other form on the surface. This structural feature is often considered a sign of insufficient mechanical properties or density and has never been utilized as an interface design element. In existing bamboo tube sandwich composite panel structures, the bamboo tube end faces and the surface layer are still simply bonded together with planar adhesive. Neither the directionality of the fiber gaps is considered, nor is a comb-tooth insertion mechanical anchoring structure established. Consequently, the lightweight potential and surface structural characteristics of lightweight reconstituted bamboo have not been translated into interface performance advantages.

[0005] In addition, existing technologies have attempted to enhance interfacial bonding by creating uneven structures on the end faces of the sandwich layer. For example, patent CN 110130573 A discloses a scheme to increase the bonding area by creating uneven structures such as burrs and serrations at the ends of the honeycomb core material. However, this technology has significant differences: firstly, its core material is aluminum, paper, or plastic honeycomb material, which is vastly different from bamboo and lacks bamboo's natural longitudinal conduit system and anisotropic adhesive penetration characteristics; secondly, the direction of its uneven structure is not limited, and it does not involve the key technologies of direction matching, utilizing the parallel fiber gaps on the surface of lightweight reconstituted bamboo, and inserting comb teeth along the fiber direction to form mechanical anchoring. Therefore, this technology cannot achieve the interfacial bonding strength enhancement and stress distribution improvement effects described in this invention.

[0006] Therefore, there is an urgent need to develop a lightweight, high-strength bamboo composite board that can both retain the natural circular shape of bamboo tubes and utilize the gaps between the surface fibers of lightweight reconstituted bamboo to form a mechanically anchored structure with directional matching. Summary of the Invention

[0007] To address the aforementioned problems, the present invention aims to provide a lightweight, high-strength bamboo composite board. This lightweight, high-strength bamboo composite board, through its comb-like structure, significantly enhances the interfacial bonding force between the bamboo tube rings and the upper and lower layer materials, as well as the overall structural stability, thereby improving the bending strength and internal bonding strength of the composite board.

[0008] Another object of the present invention is to provide a method for preparing the above-mentioned lightweight high-strength bamboo composite board.

[0009] To achieve the above objectives, the present invention provides a lightweight high-strength bamboo composite board, comprising an upper surface layer, a lower surface layer, and a core layer sandwiched between the upper surface layer and the lower surface layer. Both the upper and lower surfaces are lightweight reconstituted bamboo boards, which are composed of oriented bamboo bundles or bamboo fibers. The core layer is composed of a plurality of bamboo tube ring units, the axis of which is perpendicular to the plane of the board. The end faces of the bamboo tube ring units are provided with comb-like structures. The extension directions of each comb tooth in the comb-like structure are parallel to each other. The comb-like structures at both ends of the bamboo tube ring units have the same extension direction. The comb-like structures are inserted along the gaps between the bamboo bundle fibers or bamboo filament fibers of the lightweight reconstituted bamboo board blank in the upper and / or lower surface layers to ensure that they are parallel to the gap directions of the bamboo bundle fibers or bamboo filament fibers in both the upper and lower surface layers, and form a mechanical anchor with the lightweight reconstituted bamboo board blank.

[0010] Furthermore, the length of the teeth in the comb-like structure is 5%-30% of the height of the bamboo tube ring unit, the width of the tooth top is 0-2mm, the width of the tooth bottom is 0.2-2.5mm, and the tooth pitch is 0.5-5mm.

[0011] Furthermore, the bamboo bundle fibers or bamboo filament fibers of the lightweight reconstituted bamboo boards of each of the upper and / or lower layers are parallel or nearly parallel to each other.

[0012] The gaps between the aforementioned bamboo bundle fibers or bamboo filament fibers are defects naturally formed by the low-density pressing of lightweight reconstituted bamboo boards, and the fiber gaps are parallel or nearly parallel to each other.

[0013] This invention also provides a method for preparing the lightweight high-strength bamboo composite board as described above, comprising the following steps: Step 1: Preparing the bamboo tube ring unit: Bamboo is cut into short sections, the height of which is greater than the designed clearance between the upper and lower layers, thus creating an interference fit. Step 2: Machining the comb teeth structure: A comb-like structure is processed on both ends of the short bamboo tube to form a bamboo tube ring unit; Step 3: Preparation of lightweight reconstituted bamboo board blanks: Bamboo is broken down and processed into bamboo bundles or bamboo fibers, then dried, sizinged, and dried again before being oriented and pressed to form a product with a density of 600-950 kg / m³. 3 Lightweight reconstituted bamboo board blank; Step 4: Laying out the blanks: A layer of lightweight reconstituted bamboo board is laid as the lower surface layer. The upper and lower ends of the comb-like structure of the bamboo tube ring unit processed in step two are coated with phenolic resin adhesive and laid on the lower surface layer in a direction perpendicular to the board surface to form a core layer. During the laying, it is ensured that the direction of the comb-like structure at the lower end of the bamboo tube ring unit is consistent with the orientation direction of the bamboo bundle fibers or bamboo filament fibers of the lightweight reconstituted bamboo board as the lower surface layer. Another layer of lightweight reconstituted bamboo board is laid on top of the core layer as the upper surface layer. During the laying, it is ensured that the direction of the bamboo bundle fibers or bamboo filament fibers of the upper surface layer is consistent with the direction of the comb-like structure at the upper end of the bamboo tube ring unit. The comb-like structures at both ends of the bamboo tube ring unit are inserted into the gaps between the bamboo bundle fibers or bamboo filament fibers of the upper surface layer and the bamboo bundle fibers or bamboo filament fibers of the lower surface layer to form an uncompressed assembly. Step 5: Curing and shaping: The assembled blanks are pressed and solidified. During the pressing process, the bamboo tube ring unit is compressed to match the designed clearance height. At the same time, the comb-like structure is pressed into the upper and lower surface layers to form mechanical anchoring, thus obtaining the board. Step Six: Post-processing: After the board has been cured and shaped, it undergoes balanced curing, edge trimming, sanding, and surface decoration treatments to obtain lightweight, high-strength bamboo composite board.

[0014] Furthermore, in step one, the height of the bamboo tube is 5-50mm, the net height is 70%-95% of the height of the bamboo tube, and the interference fit is 5%-30% of the height of the bamboo tube.

[0015] Furthermore, in step four, the amount of phenolic resin adhesive applied to the comb-like structure is 150-200 g / m². 2 .

[0016] Furthermore, the curing and molding process described in step five involves a pressure of 0.2-2.0 MPa, a time of 0.5-20 min / mm, and a temperature of 10-150℃.

[0017] Preferably, the curing process involves a pressure of 0.8-1.5 MPa, a time of 1-2 min / mm, and a temperature of 120-150℃.

[0018] The beneficial effects of this invention are as follows: The lightweight, high-strength bamboo composite board prepared by this invention features a comb-like structure on both ends of the bamboo tube ring unit, with its extension direction aligned with the direction of the parallel fiber gaps naturally formed in the surface layer of the lightweight reconstituted bamboo due to low-density pressing. During the pressing process, the comb teeth are oriented and inserted into the upper and lower surface layers along the fiber gaps. Furthermore, utilizing the natural anisotropic adhesive permeation characteristics of bamboo, the longitudinal conduit system of the bamboo tube ring is connected to the transverse fiber gaps of the reconstituted bamboo surface layer through the comb-like structure, forming a three-dimensional interpenetrating adhesive permeation network at the microscopic level and a three-dimensional mechanical anchoring bond at the macroscopic level. The comb-like bamboo tubes, like multiple parallel pins, are embedded into the matrix of the lightweight reconstituted bamboo board blank, forming a multi-point, multi-directional embedded connection. This expands the bonding force between the bamboo tube ring unit and the surface layer from a single interfacial adhesive force to a three-dimensional mechanical interlocking force, significantly improving the interfacial bonding force between the bamboo tube ring unit and the upper and lower layer materials, as well as the overall structural stability. This structure increases the bending strength of the composite board by 20-40% and the internal bonding strength by 30-50%.

[0019] The lightweight, high-strength bamboo composite board prepared by this invention features an interference fit design that allows for controllable adhesive layer thickness and simple, efficient comb-tooth processing, making it suitable for industrial production. The structure retains the natural advantages of round bamboo tubes, reducing bamboo cutting losses by more than 30% compared to polygonal cutting methods, thus improving material utilization. The lightweight, high-strength bamboo composite board combines a lightweight reconstituted bamboo surface layer with a bamboo tube interlayer, achieving overall weight reduction (density can be reduced to 650 kg / m³). 3 (The following), while ensuring mechanical properties. The product of this invention can be widely used in building decorative panels, home door panels, furniture panels and other fields. Attached Figure Description

[0020] Figure 1 A top view of the bamboo tube ring unit arrangement of a lightweight, high-strength bamboo composite board is provided for this invention.

[0021] Figure 2 for Figure 1 A cross-sectional view of the lightweight, high-strength bamboo composite board at position A along the direction perpendicular to the bamboo bundles.

[0022] Figure Labels 1: Upper surface layer; 11: Bamboo bundle fiber; 2: Lower surface layer; 21: Bamboo bundle fiber; 3: Core layer; 31: Bamboo tube ring unit; 311: Comb-like structure. Detailed Implementation

[0023] The embodiments of the present invention will now be described in detail and comprehensively so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby providing a clearer and more explicit definition of the scope of protection of the present invention.

[0024] like Figure 1 and Figure 2 The diagram shown illustrates a lightweight, high-strength bamboo composite board provided by the present invention, wherein... Figure 1 This diagram shows the arrangement of the bamboo tube ring units. Figure 2 The diagram shows a cross-sectional view of a lightweight, high-strength bamboo composite board, including an upper surface layer 1, a lower surface layer 2, and a core layer 3 sandwiched between the upper and lower surface layers. Both the upper and lower surface layers are composed of lightweight reconstituted bamboo panels. The core layer is constructed from multiple bamboo tube ring units 31, with the axial direction of each unit perpendicular to the plane of the board. Each bamboo tube ring unit has a comb-like structure 311 at both ends, which is inserted into the upper and / or lower surface layers to form a mechanical anchor with the lightweight reconstituted bamboo panels. Figure 1 It can be seen that the extension directions of each comb tooth in the comb-like structure are parallel to each other; the comb-like structures at both ends of the bamboo tube ring unit have the same extension direction to ensure that they are parallel to and matched with the gap direction of the bamboo bundle fibers or bamboo filament fibers in the upper and lower layers at the same time.

[0025] The length of the teeth in the comb-like structure is 5%-30% of the height of the bamboo tube ring unit, the tooth tip width is 0-2mm, the tooth base width is 0.2-2.5mm, and the tooth pitch is 0.5-5mm. In this invention, the tooth pitch represents the distance between the centerlines of adjacent teeth. When the tooth tip width is 0, the comb-like structure is triangular, as shown below. Figure 2 As shown, when the tooth tip width is greater than 0, the comb-like structure is trapezoidal.

[0026] by Figure 1 and Figure 2 Taking the combination of comb-like structure and lightweight reconstituted bamboo board as an example. Figure 1 The solid line and the dashed line represent the top and bottom of the teeth in the comb-like structure, respectively.

[0027] The comb-like structure has comb teeth that extend in parallel directions; the comb-like structures at both ends of the bamboo tube ring unit have the same direction of extension to ensure that they are parallel and matched with the direction of the bamboo bundle fibers 11 on the upper surface and the bamboo bundle fibers 21 on the lower surface or the direction of the fiber gaps.

[0028] Example 1

[0029] This embodiment provides a lightweight, high-strength bamboo composite board and its preparation method, with the specific steps as follows: 1. Preparation of bamboo tube ring units Select 4-year-old moso bamboo and cut it into short sections with a height of 24mm (the composite board design has a net height of 18mm, with a 3mm allowance at each end). Dry the short bamboo sections to a moisture content of 10%.

[0030] 2. Machining of comb teeth structure The two ends of the short bamboo tube are milled into a toothed structure. The tooth length is 3mm, the tooth tip width is 0.2mm, and the tooth base width is 0.5mm. The extension directions of each tooth in the toothed structure are parallel to each other, and the toothed structures at both ends of the short bamboo tube have the same extension direction.

[0031] 3. Preparation of lightweight reconstituted bamboo board blanks Bamboo is processed into bamboo fiber bundles, dried to a moisture content of 8-10%, impregnated with phenolic resin adhesive (Aiketai New Materials (Nanjing) Co., Ltd., product number: 14L962) at a rate of 12%, and then dried again before oriented laying. The resulting product is then pressed to achieve a density of 750 kg / m³. 3 Lightweight reconstituted bamboo board blanks with a thickness of 10mm.

[0032] 4. Laying out the blanks Phenolic resin adhesive (150g / m²) is applied to the comb-like structure at both ends of the bamboo tube ring. 2 A layer of lightweight reconstituted bamboo board is laid at the bottom as the lower surface layer. After gluing, the bamboo tube ring units are tightly arranged on the lower surface layer, with their axial direction perpendicular to the board surface and their comb teeth direction aligned with the direction of the bamboo bundles in the lower surface layer. For example... Figure 1 As shown, another layer of lightweight reconstituted bamboo board is laid on top of the bamboo tube ring as the upper surface layer. When laying it, ensure that the direction of the bamboo bundles on the upper surface layer is consistent with the direction of the comb teeth at the top of the bamboo tube, and finally form a three-layer assembled blank (uncompressed state, with a continuous fiber transition structure).

[0033] 5. Curing and molding The assembled slabs are fed into a hot press for pressing and curing: pressure 0.8 MPa, temperature 140℃, time 0.8 min / mm. During the pressing process, the bamboo tube ring units are compressed to the designed height of 18 mm, while the comb-like structure is pressed into the upper and lower surfaces, forming a mechanical anchor, such as... Figure 2 As shown.

[0034] 6. Post-processing After hot pressing, the boards undergo balanced curing, edge trimming, sanding, and surface decoration treatments to obtain lightweight, high-strength bamboo composite boards.

[0035] Example 2

[0036] This embodiment is basically the same as the process in Embodiment 1, except that: 1. Bamboo tube ring unit preparation Select 4-year-old moso bamboo and cut it into short sections with a height of 22mm (the composite board is designed with a net height of 18mm, with a 2mm allowance at each end). Dry the short bamboo sections to a moisture content of 10%.

[0037] 2. Machining of comb teeth structure The two ends of the short bamboo tube are milled into a comb-like structure. The comb teeth are 2mm long, 0.2mm wide at the top, and 0.5mm wide at the bottom. The extension directions of each comb tooth are parallel to each other, and the comb-like structures at both ends of the short bamboo tube have the same extension direction.

[0038] Comparative Example 1 Comparative Example 1 and Example 1 have essentially the same process, the difference being: 1. The bamboo tube ring unit is prepared according to the method of Example 1 in patent CN202021136736.9 to prepare a polygonal bamboo tube composite board: the bamboo tube is a regular hexagon, with its axis perpendicular to the board surface, and the upper and lower surfaces are made of lightweight reconstituted bamboo (density 750 kg / m³). 3 The bamboo tube is glued to the surface and has no comb-like structure.

[0039] Comparative Example 2 Comparative Example 2 and Example 1 have essentially the same process, the difference being that: the circular bamboo tube composite board is prepared according to the method of Example 1 in patent CN202211419334.3: the bamboo tube is kept circular, with its axis perpendicular to the board surface, and the upper and lower surfaces are made of lightweight reconstituted bamboo (density 750 kg / m³). 3 The bamboo tube is glued to the surface and has no comb-like structure.

[0040] Performance testing The performance of the boards prepared in Examples 1-2 and Comparative Examples 1-2 was tested, and the results are shown in Table 1.

[0041] Table 1. Performance Comparison of Various Examples and Comparative Examples As shown in Table 1, the lightweight high-strength bamboo composite boards prepared in Examples 1 and 2 of this invention, compared with Comparative Examples 1 and 2 (planar glued bamboo tube composite boards without comb-like structures), exhibit significantly improved internal bonding strength, 2-hour boiling water internal bonding strength, and static bending strength, while maintaining essentially the same or even lower density. Specifically, the internal bonding strength of Example 1 (0.62 MPa) increased by approximately 38% compared to Comparative Example 1 (0.45 MPa), the 2-hour boiling water internal bonding strength (0.25 MPa) increased by approximately 32% compared to Comparative Example 1 (0.19 MPa), and the static bending strength (65.77 MPa) increased by approximately 31% compared to Comparative Example 2 (50.26 MPa). Example 2 also showed a similar improvement.

[0042] As can be seen from the above embodiments, by setting comb-like structures on both ends of the bamboo tube ring unit and ensuring that their extension direction is consistent with the direction of the parallel fiber gaps naturally formed on the surface of the lightweight reconstituted bamboo due to low-density pressing, the comb teeth are oriented into the upper and lower surface layers along the fiber gaps during the pressing process, which effectively enhances the interfacial bonding force and improves the stress distribution. Thus, while reducing the weight of the board, the mechanical properties and water resistance of the board are greatly improved, verifying the superiority of the technical solution of the present invention.

[0043] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A lightweight, high-strength bamboo composite board, characterized in that, It includes an upper surface layer, a lower surface layer, and a core layer sandwiched between the upper surface layer and the lower surface layer; Both the upper and lower surfaces are lightweight reconstituted bamboo boards, which are composed of oriented bamboo bundles or bamboo fibers. The core layer is composed of a plurality of bamboo tube ring units, the axis of which is perpendicular to the plane of the board. The end faces of the bamboo tube ring units are provided with comb-like structures. The extension directions of each comb tooth in the comb-like structure are parallel to each other. The comb-like structures at both ends of the bamboo tube ring units have the same extension direction. The comb-like structures are inserted along the gaps between the bamboo bundle fibers or bamboo filament fibers of the lightweight reconstituted bamboo board blank in the upper and / or lower surface layers to ensure that they are parallel to the gap directions of the bamboo bundle fibers or bamboo filament fibers in both the upper and lower surface layers, and form a mechanical anchor with the lightweight reconstituted bamboo board blank.

2. The lightweight high-strength bamboo composite board according to claim 1, characterized in that, The length of the teeth in the comb-like structure is 5%-30% of the height of the bamboo tube ring unit, the width of the tooth top is 0-2mm, the width of the tooth bottom is 0.2-2.5mm, and the tooth pitch is 0.5-5mm.

3. The lightweight high-strength bamboo composite board according to claim 1, characterized in that, The bamboo bundle fibers or bamboo filament fibers in the lightweight reconstituted bamboo boards of each of the upper and / or lower layers are parallel or nearly parallel to each other.

4. A method for preparing a lightweight high-strength bamboo composite board as described in any one of claims 1 to 3, characterized in that, Includes the following steps: Step 1: Preparing the bamboo tube ring unit: Bamboo is cut into short sections, the height of which is greater than the designed clearance between the upper and lower layers, thus creating an interference fit. Step 2: Machining the comb teeth structure: A comb-like structure is processed on both ends of the short bamboo tube to form a bamboo tube ring unit; Step 3: Preparation of lightweight reconstituted bamboo board blanks: The bamboo is defibered into bamboo bundle fiber or bamboo silk fiber, dried, glued, dried again, and then oriented, laid and pressed to form a lightweight reformed bamboo board blank with a density of 600-950 kg / m 3 ​ Step 4: Laying out the blanks: A layer of lightweight reconstituted bamboo board is laid as the lower surface layer. The upper and lower ends of the comb-like structure of the bamboo tube ring unit processed in step two are coated with phenolic resin adhesive and laid on the lower surface layer in a direction perpendicular to the board surface to form a core layer. During the laying, it is ensured that the direction of the comb-like structure at the lower end of the bamboo tube ring unit is consistent with the orientation direction of the bamboo bundle fibers or bamboo filament fibers of the lightweight reconstituted bamboo board as the lower surface layer. Another layer of lightweight reconstituted bamboo board is laid on top of the core layer as the upper surface layer. During the laying, it is ensured that the direction of the bamboo bundle fibers or bamboo filament fibers of the upper surface layer is consistent with the direction of the comb-like structure at the upper end of the bamboo tube ring unit. The comb-like structures at both ends of the bamboo tube ring unit are inserted into the gaps between the bamboo bundle fibers or bamboo filament fibers of the upper surface layer and the bamboo bundle fibers or bamboo filament fibers of the lower surface layer to form an uncompressed assembly. Step 5: Curing and shaping: The assembled blanks are pressed and solidified. During the pressing process, the bamboo tube ring unit is compressed to match the designed clearance height. At the same time, the comb-like structure is pressed into the upper and lower surface layers to form mechanical anchoring, thus obtaining the board. Step Six: Post-processing: After the board has been cured and shaped, it undergoes balanced curing, edge trimming, sanding, and surface decoration treatments to obtain lightweight, high-strength bamboo composite board.

5. The preparation method according to claim 4, characterized in that, The height of the bamboo tube in step one is 5-50mm, the net height is 70%-95% of the height of the bamboo tube, and the interference fit is 5%-30% of the height of the bamboo tube.

6. The preparation method according to claim 4, characterized in that, In step four, the amount of phenolic resin adhesive applied to the comb-like structure is 150-200 g / m². 2 .

7. The preparation method according to claim 4, characterized in that, The pressure for the curing and molding process described in step five is 0.2-2.0 MPa, the time is 0.5-20 min / mm, and the temperature is 10-150℃.

8. The preparation method according to claim 7, characterized in that, The curing process involves a pressure of 0.8-1.5 MPa, a time of 0.8-2 min / mm, and a temperature of 120-150℃.

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