Bamboo-plastic composite wave-absorbing material, preparation method therefor and use thereof

Abstract

A bamboo-plastic composite wave-absorbing material, comprising a bamboo weaved layer and a covering layer (2) covering the bamboo weaved layer, wherein the bamboo weaved layer is weaved from bamboo units (1), and the bamboo units (1) include one or more of bamboo strips, bamboo splits and bamboo chips; the covering layer (2) is a resin covering layer or a coating covering layer; and the bamboo weaved layer or the bamboo units (1) are pretreated with a polar solvent. A preparation method for the bamboo-plastic composite wave-absorbing material comprises the preparation of absolutely dry bamboo units, the preparation of an absolutely dry bamboo weaved layer, the pretreatment of the bamboo weaved layer with a solvent, and the forming of a bamboo-plastic composite wave-absorbing material, or comprises the preparation of absolutely dry bamboo units, the pretreatment of the absolutely dry bamboo units with a solvent, the preparation of a pretreated bamboo weaved layer, and the forming of a bamboo-plastic composite wave-absorbing material. The bamboo-plastic composite wave-absorbing material has a relatively strong electromagnetic wave absorption capacity, and the absorption performance thereof is easily regulated and controlled; the preparation method is simple and easily implemented, involves low cost and is environmentally friendly; and the bamboo-plastic composite wave-absorbing material has a wide range of applications. Further disclosed is the use of the bamboo-plastic composite wave-absorbing material.

Description

Bamboo-plastic composite wave-absorbing material and its preparation method and application

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application is based on and claims priority to a Chinese patent application filed on March 29, 2024, with application number 2014103782324 and invention titled “Bamboo-plastic composite absorbent material, preparation method and application thereof”. The full text of the Chinese patent application is incorporated herein by reference as a part of this application.

Technical field

[0003] The present invention belongs to the technical field of electromagnetic wave absorbing materials, and relates to a bamboo-plastic composite absorbing material, a preparation method and an application thereof, and in particular to a bamboo-plastic composite absorbing material with a coated woven mesh structure, a preparation method and an application thereof. [Background Technology]

[0004] Absorbing materials are specialized materials that allow electromagnetic waves to enter their interior and, through dielectric loss, convert the electromagnetic wave energy into other forms of energy, thereby attenuating the waves. Good absorbing materials must meet both impedance matching and attenuation matching requirements. Impedance matching refers to the ability of electromagnetic waves to penetrate the material's interior as much as possible when radiated from the material's surface. Attenuation matching refers to the ability to maximize the attenuation of electromagnetic waves within the material. Two key indicators characterizing the absorbing performance of absorbing materials are reflection loss (RL) and the effective absorption band. Reflection loss represents the material's ability to attenuate electromagnetic waves of a single frequency and is generally negative, with smaller values ​​indicating greater attenuation. The effective absorption band represents the frequency range within which the material's reflection loss (RL) is ≤ -10dB. Because the objects protected by absorbing materials often face complex electromagnetic environments, they require excellent and tunable microwave absorption properties. Currently, common dielectric loss absorbing materials include carbon-based, magnetic, and ceramic-based materials. These materials are highly dependent on their intrinsic conductivity, magnetism, and micro-nanostructure design. Their microwave absorption properties are difficult to control and difficult to manufacture. Consequently, these microwave absorbing materials have limited application scenarios and are unable to adapt to complex and changing electromagnetic environments. Therefore, it is necessary to develop new absorbing materials to address these technical issues.

[0005] Bamboo is a natural, fast-growing material with a short maturity period (3-5 years). my country is a country rich in bamboo resources, ranking first in the world in terms of bamboo resources, area, and stock volume. In order to promote the development of my country's bamboo industry and serve the country's "dual carbon" strategy, in October 2023, the National Development and Reform Commission and other departments issued a notice on the "Three-Year Action Plan for Accelerating the Development of 'Bamboo Replacing Plastics'". At present, my country's bamboo-based products mainly include bamboo-based daily necessities, construction materials, and industrial materials. These products mainly utilize the good machining and mechanical properties of bamboo, and the overall added value of the products is not high. Therefore, it is necessary to deeply explore the other properties and characteristics of bamboo, further expand the application of bamboo in other high-end fields, and increase its added value. [Summary of the invention]

[0006] The technical problem to be solved by the present invention is to overcome the shortcomings of the existing technology and provide a bamboo-plastic composite absorbing material with strong microwave absorption ability and easily controllable performance. A preparation method and application of the bamboo-plastic composite absorbing material with simple preparation, low cost and environmental friendliness are also provided.

[0007] In order to solve the above technical problems, the present invention adopts the following technical solutions.

[0008] A bamboo-plastic composite absorbing material comprises a bamboo woven layer and a coating layer coating the bamboo woven layer, wherein the bamboo woven layer is woven from bamboo units, and the bamboo units comprise one or more of bamboo strips, bamboo strips, and bamboo sheets, and the coating layer is a resin coating layer or a coating coating layer; the bamboo woven layer or the bamboo units are pretreated with a polar solvent, that is, the bamboo woven layer is a bamboo woven layer pretreated with a polar solvent, or the bamboo units are bamboo units pretreated with a polar solvent.

[0009] In some embodiments of the present invention, the bamboo woven layer is more than one layer.

[0010] In some embodiments of the present invention, the weaving includes weaving in warp and weft directions.

[0011] In some embodiments of the present invention, the width of the bamboo unit is 1 mm to 6 mm, the thickness of the bamboo unit is 0.5 mm to 5 mm, and the spacing between adjacent bamboo units is 1 mm to 20 mm. The spacing between adjacent bamboo units refers to the distance between the opposite sides of two adjacent bamboo units. The length of the bamboo unit can be determined according to the actual required size.

[0012] In some embodiments of the present invention, the width of the bamboo unit is 1 mm to 3 mm, the thickness of the bamboo unit is 0.5 mm to 2 mm, and the spacing between adjacent bamboo units is 1 mm to 5 mm.

[0013] In some embodiments of the present invention, when the coating layer is a resin coating layer, the resin used includes one or more of epoxy resin, polyurethane resin and phenolic resin, the thickness of the bamboo-plastic composite absorbing material is 2.5 mm to 11 mm, and the bamboo-plastic composite absorbing material is a plate-like structure.

[0014] In some embodiments of the present invention, when the coating layer is a paint coating layer, the paint is a paint for bamboo and wood, and the paint for bamboo and wood includes one or more of wood wax oil, varnish and UV curing paint. The thickness of the bamboo-plastic composite absorbing material is 3 mm to 5 mm, and the bamboo-plastic composite absorbing material is a woven mesh structure.

[0015] In some embodiments of the present invention, the polar solvent includes one or more of water, methanol and ethanol.

[0016] As a general technical concept, the present invention also provides a method for preparing the above-mentioned bamboo-plastic composite absorbing material, comprising the following steps:

[0017] (1) Preparation of dry bamboo units: Cut and dry the original bamboo tube to obtain dry bamboo units;

[0018] (2) Preparation of the dry bamboo woven layer: weaving the dry bamboo units into the dry bamboo woven layer according to the set weaving method;

[0019] (3) Solvent pretreatment of the bamboo woven layer: spraying or soaking the absolutely dry bamboo woven layer with a polar solvent to obtain a pretreated bamboo woven layer;

[0020] (4) Molding of bamboo-plastic composite absorbing material: coating a resin material as a resin base layer on the bottom of a mold, then arranging the pretreated bamboo woven layer on the resin base layer, and then pouring the resin material onto the pretreated bamboo woven layer. After the resin material immerses the pretreated bamboo woven layer, the resin material is allowed to stand and solidify, and the mold is removed to form a resin coating layer, thereby obtaining a plate-shaped bamboo-plastic composite absorbing material;

[0021] Alternatively, the bamboo-plastic composite absorbing material is formed by applying paint to the front, back and surrounding areas of the pretreated bamboo woven layer, and allowing it to solidify to form a woven mesh coating layer, thereby obtaining a bamboo-plastic composite absorbing material with a woven mesh structure.

[0022] As a general technical concept, the present invention also provides a method for preparing the above-mentioned bamboo-plastic composite absorbing material, comprising the following steps:

[0023] (1) Preparation of dry bamboo units: Cut and dry the original bamboo tube to obtain dry bamboo units;

[0024] (2) solvent pretreatment of the absolutely dry bamboo units: spraying or soaking the absolutely dry bamboo units with a polar solvent to obtain pretreated bamboo units;

[0025] (3) Preparation of pretreated bamboo woven layer: weaving the pretreated bamboo units into a pretreated bamboo woven layer according to a set weaving method;

[0026] (4) Molding of bamboo-plastic composite absorbing material: coating a resin material as a resin base layer on the bottom of a mold, then arranging the pretreated bamboo woven layer on the resin base layer, and then pouring the resin material onto the pretreated bamboo woven layer. After the resin material immerses the pretreated bamboo woven layer, the resin material is allowed to stand and solidify, and the mold is removed to form a resin coating layer, thereby obtaining a plate-shaped bamboo-plastic composite absorbing material;

[0027] Alternatively, the bamboo-plastic composite absorbing material is formed by applying paint to the front, back and surrounding areas of the pretreated bamboo woven layer, and allowing it to solidify to form a woven mesh coating layer, thereby obtaining a bamboo-plastic composite absorbing material with a woven mesh structure.

[0028] In some embodiments of the present invention, in step (1), the drying temperature is 50° C. to 105° C., and the drying time is 5 h to 10 h.

[0029] In some embodiments of the present invention, in step (3), the spraying or soaking time is based on a set target weight gain rate, which is 30% to 100%, and the time is preferably 0.5h to 48h.

[0030] In some embodiments of the present invention, in step (4), the inner cavity structure of the mold is a cube, the resin material includes one or more of epoxy resin, polyurethane resin and phenolic resin, the thickness of the resin bottom layer is 1 mm to 3 mm, and the static curing is carried out at room temperature and normal pressure, and the static curing time is 6 h to 12 h.

[0031] In the present invention, the coating layer is preferably made of a resin material or coating having good electromagnetic wave transmission properties (dielectric constant less than 5), good mechanical properties and sealing properties.

[0032] In the present invention, the three-dimensional size of the bamboo-plastic composite absorbing material is preferably 300 mm (length) × 300 mm (width) × 3 mm to 9 mm (thickness), but is not limited thereto.

[0033] In the preparation method of the present invention, the mold in step (4) can preferably be a polypropylene mold, which is mainly made of a polypropylene resin plate and hot melt adhesive, but the mold is not limited thereto, and mainly provides a cubic inner cavity structure.

[0034] In step (4), the mass of the required resin can be calculated based on the density of the resin, the three-dimensional dimensions of the bamboo-plastic composite absorbing material, and the three-dimensional dimensions of the bamboo woven layer.

[0035] In the prior art, bamboo weaving can be generally divided into three steps: starting, weaving, and locking. Warp and weft weaving is the primary method during the weaving process. Various techniques, such as open weaving, inserting, threading, cutting, locking, nailing, tying, and looping, can be incorporated into this process to create diverse patterns. Dyed bamboo units can also be interlaced and twisted to create vibrant, vibrant patterns with strong color contrast. In the present invention, warp and weft weaving is the primary method, but this is not limiting. Other existing weaving methods can also achieve the technical effects of the present invention.

[0036] In the present invention, bone dry is a proper noun in this field (also a conventional technical term), which can be found on page 151 of the second edition of Wood Science.

[0037] In the present invention, room temperature generally refers to 20°C to 26°C.

[0038] The main innovations of the present invention are:

[0039] (1) The present invention makes full use of the weavability of bamboo. In the bamboo woven layer, each pre-treated bamboo strip / strip / sheet can be regarded as a bamboo unit with a certain impedance. The electromagnetic characteristics beyond the bamboo unit itself can be obtained by adjusting the width and thickness of the bamboo unit and the distance between the bamboo units. At the same time, the woven bridges between the bamboo units form a loop with a certain impedance, which is conducive to obtaining better impedance matching characteristics, thereby obtaining higher electromagnetic wave absorption efficiency and a wider electromagnetic wave absorption frequency band. In addition, the bamboo woven layer can also be stacked in multiple layers to further improve the designability of the electromagnetic characteristics of the material. In addition, the bamboo woven layer has good elasticity and flexibility. After being compounded with a flexible base material, it can be used for the design and manufacture of special-shaped structural parts such as curved surfaces, further broadening the scope of use of bamboo-plastic composite absorbing materials.

[0040] (2) The present invention utilizes the characteristic of bamboo's multi-level pore structure, which contains abundant polar groups on its surface, to effectively fix polar molecules such as water, methanol, or ethanol within the bamboo's pores through hydrogen bonding and capillary action. A resin coating or a coating is then used to further lock the polar molecules of the pretreated bamboo woven layer within the bamboo, ultimately enabling long-term wave absorption. When exposed to electromagnetic wave radiation, the polar molecules fixed within the bamboo will produce a violent polarization response movement, converting the electromagnetic wave energy into heat energy, thereby achieving attenuation of the electromagnetic wave energy.

[0041] Compared with the prior art, the advantages of the present invention are:

[0042] 1. The bamboo-plastic composite absorbing material of the present invention has excellent absorbing properties, a wide effective absorption frequency band, low reflection loss, and strong designability. This bamboo-plastic composite absorbing material uses a bamboo braided layer as the absorbing material layer. Compared with braided layers made of artificial materials such as carbon fiber and glass fiber, the bamboo braided layer has better absorbing effects, is more environmentally friendly, requires less machining equipment, is easier to machine, is low-cost, and is more amenable to industrial production.

[0043] 2. The bamboo-plastic composite absorbing material of the present invention can fully regulate the electromagnetic parameters and absorbing performance of the absorbing material by adjusting parameters such as the bamboo unit size, weaving method, number of layers and interlayer spacing of the bamboo braided layer.

Brief Description of the Drawings

[0044] FIG1 is a perspective view of the three-dimensional structure of the bamboo-plastic composite absorbing material in Example 1 of the present invention.

[0045] FIG2 is a schematic diagram of the bamboo braided layer structure of the bamboo-plastic composite absorbing material in Example 1 of the present invention.

[0046] FIG3 is a reflection loss diagram of the bamboo-plastic composite absorbing material in Example 1 of the present invention.

[0047] FIG4 is a reflection loss diagram of the bamboo-plastic composite absorbing material in Example 2 of the present invention.

[0048] FIG5 is a reflection loss diagram of the bamboo-plastic composite absorbing material in Example 3 of the present invention.

[0049] FIG6 is a reflection loss diagram of the bamboo-plastic composite absorbing material in Example 4 of the present invention.

[0050] FIG7 is a perspective diagram of the three-dimensional structure of the bamboo-plastic composite absorbing material in Comparative Example 1.

[0051] FIG8 is a schematic diagram of the bamboo array layer structure of the bamboo-plastic composite absorbing material in Comparative Example 1.

[0052] FIG9 is a reflection loss diagram of the bamboo-plastic composite absorbing material in Comparative Example 1.

[0053] FIG10 is a graph showing the reflection loss of the absorbing material in Comparative Example 2.

[0054] FIG11 is a graph showing the reflection loss of the bamboo-plastic composite absorbing material in Comparative Example 3.

[0055] Legend:

[0056] 1. Bamboo unit; 2. Cladding layer. [Specific implementation method]

[0057] The present invention will be further described below with reference to the accompanying drawings and specific preferred embodiments, but the scope of protection of the present invention is not limited thereby. The materials and instruments used in the following examples are all commercially available.

[0058] Example 1

[0059] A bamboo-plastic composite absorbing material of the present invention, as shown in Figure 1, includes a bamboo woven layer and a coating layer 2 covering the bamboo woven layer. The bamboo woven layer is woven from bamboo units 1, and the bamboo units 1 are bamboo strips (bamboo strips or bamboo sheets can also be used). The bamboo woven layer is a bamboo woven layer pretreated with a polar solvent. The polar solvent in this embodiment is specifically a 30wt% ethanol aqueous solution. The coating layer 2 is a resin coating layer, specifically an epoxy resin coating layer.

[0060] In this embodiment, the bamboo braided layer is provided in one layer (or multiple layers).

[0061] In this embodiment, the weaving is performed in the warp and weft directions (or the longitudinal and transverse directions) up and down, as shown in FIG2 .

[0062] In this embodiment, the width of the bamboo unit 1 is 5 mm, the thickness of the bamboo unit 1 is 1 mm, and the interval h between adjacent bamboo units is 2 mm.

[0063] In this embodiment, the thickness between the top surface of the resin coating layer and the top surface of the bamboo woven layer is 1 mm, and the thickness between the bottom surface of the resin coating layer and the bottom surface of the bamboo woven layer is 1 mm.

[0064] In this embodiment, the bamboo-plastic composite absorbing material has a plate-like structure, and the three-dimensional dimensions of the bamboo-plastic composite absorbing material are 300 mm long (L)×300 mm wide (W)×3 mm thick (T).

[0065] A method for preparing the bamboo-plastic composite absorbing material of this embodiment includes the following steps:

[0066] (1) Preparation of dry bamboo units: The original bamboo tube was mechanically cut and dried at 105°C for 10 h to obtain dry bamboo units;

[0067] (2) Preparation of the dry bamboo woven layer: Weaving the dry bamboo units into the dry bamboo woven layer according to the warp and weft weaving method;

[0068] (3) Solvent pretreatment of bamboo woven layer: spraying ethanol aqueous solution on the absolutely dry bamboo woven layer for 5 hours, with a target weight gain of 50%, to obtain a pretreated bamboo woven layer;

[0069] (4) Molding of bamboo-plastic composite absorbing material: Epoxy resin material is applied to the bottom of the mold as a resin base layer with a thickness of 1 mm. The inner cavity structure of the mold is a cube. The pretreated bamboo woven layer is then placed on the resin base layer. The epoxy resin material is then poured onto the pretreated bamboo woven layer. After the resin material immerses (coats) the pretreated bamboo woven layer, it is allowed to stand and solidify for 8 hours at room temperature and normal pressure. The mold is then demoulded to form a resin coating layer, thereby obtaining a plate-shaped bamboo-plastic composite absorbing material.

[0070] After testing, as shown in FIG3 , the reflection loss peak of the bamboo-plastic composite absorbing material of this embodiment reaches -15.6 dB at a microwave frequency of 4.7 GHz, and the effective absorption frequency band (reflection loss ≤ 10 dB) is 1.9 GHz.

[0071] Example 2

[0072] A bamboo-plastic composite absorbing material of the present invention, as shown in Figure 1, includes a bamboo woven layer and a coating layer 2 covering the bamboo woven layer. The bamboo woven layer is woven from bamboo units 1, and the bamboo units are bamboo strips (either bamboo strips or bamboo sheets can be used). The bamboo woven layer is a bamboo woven layer pretreated with a polar solvent. In this embodiment, the polar solvent is specifically a 30wt% methanol aqueous solution. The coating layer 2 is a coating coating layer, specifically a varnish coating layer.

[0073] In this embodiment, the bamboo braided layer is provided in one layer (or multiple layers).

[0074] In this embodiment, the weaving is performed in the warp and weft directions (or the longitudinal and transverse directions) up and down, as shown in FIG2 .

[0075] In this embodiment, the width of the bamboo unit 1 is 5 mm, the thickness of the bamboo unit 1 is 1 mm, and the spacing between adjacent bamboo units 1 is 2 mm.

[0076] In this embodiment, the thickness of the coating coating layer from the top surface of the bamboo woven layer is 1 mm, and the thickness of the coating coating layer from the bottom surface of the bamboo woven layer is 1 mm. The coating covers the bamboo part but does not cover the gap part.

[0077] In this embodiment, the bamboo-plastic composite absorbing material has a woven mesh structure, and the three-dimensional dimensions of the bamboo-plastic composite absorbing material are 300 mm long (L)×300 mm wide (W)×3 mm thick (T).

[0078] A method for preparing the bamboo-plastic composite absorbing material of this embodiment includes the following steps:

[0079] (1) Preparation of dry bamboo units: The original bamboo tube was mechanically cut and dried at 105°C for 10 h to obtain dry bamboo units;

[0080] (2) Preparation of the dry bamboo woven layer: Weaving the dry bamboo units into the dry bamboo woven layer according to the warp and weft weaving method;

[0081] (3) Solvent pretreatment of bamboo woven layer: soak the absolutely dry bamboo woven layer in 30 wt% methanol aqueous solution for 5 h, with a target weight gain of 50%, to obtain a pretreated bamboo woven layer;

[0082] (4) Forming of bamboo-plastic composite absorbing material: Apply nitrocellulose varnish to the front, back and surrounding areas of the pretreated bamboo woven layer (i.e., apply it to all exposed bamboo unit surfaces), and let it stand and cure for 8 hours at room temperature and normal pressure to form a coating layer, thereby obtaining a bamboo-plastic composite absorbing material with a woven mesh structure.

[0083] After testing, as shown in FIG4 , the reflection loss peak of the bamboo-plastic composite absorbing material of this embodiment reaches -14.4 dB at 5.4 GHz, and the effective absorption frequency band (reflection loss ≤ 10 dB) is 1.9 GHz.

[0084] Example 3

[0085] A bamboo-plastic composite absorbing material and its preparation method according to the present invention are substantially identical to those of Example 1, differing only in that three bamboo woven layers are provided within the coating layer 2. The three-dimensional dimensions of the bamboo-plastic composite absorbing material are 300 mm long x 300 mm wide x 5 mm thick. Testing, as shown in Figure 5, shows that the peak reflection loss of the bamboo-plastic composite absorbing material of this embodiment reaches -14.7 dB at a microwave frequency of 7.1 GHz, and the effective absorption frequency band (reflection loss ≤ 10 dB) is 2.8 GHz.

[0086] Example 4

[0087] A bamboo-plastic composite absorbing material and its preparation method according to the present invention are substantially the same as those in Example 1, differing only in that the bamboo unit 1 has a width of 6 mm, a thickness of 5 mm, and a spacing h between adjacent bamboo units of 20 mm. The three-dimensional dimensions of the bamboo-plastic composite absorbing material are (300 mm long × 300 mm wide × 7 mm thick). Testing, as shown in Figure 6, shows that the peak reflection loss of the bamboo-plastic composite absorbing material of this embodiment reaches -13.3 dB at a microwave frequency of 7.5 GHz, and the effective absorption frequency band (reflection loss ≤ 10 dB) is 2.4 GHz.

[0088] In the above embodiments, similar microwave absorption capacity can be obtained when the steps of preparing the absolutely dry bamboo units, solvent pretreatment of the absolutely dry bamboo units, preparing the pretreated bamboo woven layer, and forming the bamboo-plastic composite absorbing material are carried out in this order.

[0089] Comparative Example 1

[0090] A bamboo-plastic composite absorbing material is basically the same as Example 1, except that the bamboo woven layer is replaced by a bamboo array layer, specifically a matrix array, as shown in Figures 7 and 8. In the bamboo array layer, the three-dimensional dimensions of the bamboo units are 300 mm long × 5 mm wide × 1 mm thick, the spacing h between the bamboo units is 2 mm, and there are a total of 42 bamboo units.

[0091] The bamboo-plastic composite absorbing material of this comparative example has a plate-like structure as a whole, and the three-dimensional dimensions of the bamboo-plastic composite absorbing material are 300 mm long×300 mm wide×3 mm thick.

[0092] The preparation method of the bamboo-plastic composite absorbing material of this comparative example comprises the following steps:

[0093] (1) Preparation of dry bamboo units: The original bamboo tube was mechanically cut and dried at 105 °C for 10 h to obtain dry bamboo units;

[0094] (2) Solvent pretreatment: spraying 30 wt% ethanol aqueous solution on the absolutely dry bamboo unit for 5 h to obtain the pretreated bamboo unit;

[0095] (3) Molding of bamboo-plastic composite absorbing material: a layer of epoxy resin material is applied to the bottom of the mold as a resin base layer with a thickness of 1 mm. Then, the pretreated bamboo units are arranged on the resin base layer in a matrix structure with a spacing of 2 mm to form a bamboo array layer. Then, the resin material is poured onto the bamboo array layer. After the resin material covers the bamboo array layer, it is allowed to stand and solidify for 8 hours at room temperature and normal pressure, and then demolded to form a resin coating layer to obtain a plate-shaped bamboo-plastic composite absorbing material.

[0096] After testing, as shown in FIG9 , the reflection loss peak of the bamboo-plastic composite absorbing material prepared in this comparative example is -6.6 dB at a microwave frequency of 14.2 GHz, and the effective absorption frequency band (reflection loss ≤ 10 dB) is 0.

[0097] Comparative Example 2

[0098] An absorbing material is cast from epoxy resin into a plate with three-dimensional dimensions of 180 mm long, 180 mm wide, and 3 mm thick. Testing, as shown in FIG10 , shows that the reflection loss of the bamboo-plastic composite absorbing material is 0 dB within the test frequency range.

[0099] Comparative Example 3

[0100] A bamboo-plastic composite absorbing material and its preparation method are substantially the same as those in Example 1, differing only in that no polar solvent pretreatment is used. Testing, as shown in Figure 11, shows that the peak reflection loss of the bamboo-plastic composite absorbing material prepared in this comparative example is -4.0 dB at a microwave frequency of 13.1 GHz, and the effective absorption frequency band (reflection loss ≤ 10 dB) is 0.

[0101] The above description is only a preferred embodiment of the present invention and does not constitute any formal limitation to the present invention. Although the present invention has been disclosed as above in terms of a preferred embodiment, it is not intended to limit the present invention. Any person skilled in the art can, without departing from the spirit and technical solution of the present invention, use the methods and technical contents disclosed above to make many possible changes and modifications to the technical solution of the present invention, or modify it into an equivalent embodiment of equivalent changes. Therefore, any simple modification, equivalent replacement, equivalent change and modification made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention, still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A bamboo-plastic composite absorbing material, characterized in that: The invention comprises a bamboo woven layer and a coating layer (2) coating the bamboo woven layer, wherein the bamboo woven layer is woven from bamboo units (1), the bamboo units (1) comprise one or more of bamboo strips, bamboo strips and bamboo pieces, and the coating layer (2) is a resin coating layer or a coating coating layer; and the bamboo woven layer or the bamboo units (1) are pre-treated with a polar solvent.

2. The bamboo-plastic composite absorbing material according to claim 1, characterized in that: The bamboo braided layer comprises more than one layer; and the braiding includes braiding in warp and weft directions.

3. The bamboo-plastic composite absorbing material according to claim 1, characterized in that: The width of the bamboo unit (1) is 1 mm to 6 mm, the thickness of the bamboo unit (1) is 0.5 mm to 5 mm, and the spacing between adjacent bamboo units (1) is 1 mm to 20 mm.

4. The bamboo-plastic composite absorbing material according to claim 3, characterized in that: The width of the bamboo unit (1) is 1 mm to 3 mm, the thickness of the bamboo unit (1) is 0.5 mm to 2 mm, and the spacing between adjacent bamboo units (1) is 1 mm to 5 mm.

5. The bamboo-plastic composite absorbing material according to any one of claims 1 to 4, characterized in that: When the coating layer is a resin coating layer, the resin used includes one or more of epoxy resin, polyurethane resin and phenolic resin, the thickness of the bamboo-plastic composite absorbing material is 2.5 mm to 11 mm, and the bamboo-plastic composite absorbing material is a plate-shaped structure; When the coating layer is a paint coating layer, the paint is a paint for bamboo and wood, and the paint for bamboo and wood includes one or more of wood wax oil, varnish and UV curing paint. The thickness of the bamboo-plastic composite absorbing material is 3mm to 5mm, and the bamboo-plastic composite absorbing material is a woven mesh structure.

6. The bamboo-plastic composite absorbing material according to any one of claims 1 to 4, characterized in that: The polar solvent includes one or more of water, methanol and ethanol.

7. A method for preparing the bamboo-plastic composite absorbing material according to any one of claims 1 to 6, characterized in that: The following steps are involved: (1) Preparation of dry bamboo units: Cut and dry the original bamboo tube to obtain dry bamboo units; (2) Preparation of the dry bamboo woven layer: weaving the dry bamboo units into the dry bamboo woven layer according to the set weaving method; (3) Solvent pretreatment of the bamboo woven layer: spraying or soaking the absolutely dry bamboo woven layer with a polar solvent to obtain a pretreated bamboo woven layer; (4) Forming of bamboo-plastic composite absorbing material: coating a resin material as a resin base layer on the bottom of a mold, then arranging the pretreated bamboo woven layer on the resin base layer, and then pouring the resin material onto the pretreated bamboo woven layer. After the resin material immerses the pretreated bamboo woven layer, it is allowed to stand and solidify, demoulding, forming a resin coating layer, and obtaining a plate-shaped bamboo-plastic composite absorbing material; or, applying a coating to the front and back surfaces and all around the pretreated bamboo woven layer, and after standing and solidifying, forming a woven mesh coating layer, and obtaining a bamboo-plastic composite absorbing material with a woven mesh structure.

8. A method for preparing the bamboo-plastic composite absorbing material according to any one of claims 1 to 6, characterized in that: The following steps are involved: (1) Preparation of dry bamboo units: Cut and dry the original bamboo tube to obtain dry bamboo units; (2) solvent pretreatment of the absolutely dry bamboo units: spraying or soaking the absolutely dry bamboo units with a polar solvent to obtain pretreated bamboo units; (3) Preparation of pretreated bamboo woven layer: weaving the pretreated bamboo units into a pretreated bamboo woven layer according to a set weaving method; (4) Forming of bamboo-plastic composite absorbing material: coating a resin material as a resin base layer on the bottom of a mold, then arranging the pretreated bamboo woven layer on the resin base layer, and then pouring the resin material onto the pretreated bamboo woven layer. After the resin material immerses the pretreated bamboo woven layer, it is allowed to stand and solidify, demoulding, forming a resin coating layer, and obtaining a plate-shaped bamboo-plastic composite absorbing material; or, applying a coating to the front and back surfaces and all around the pretreated bamboo woven layer, and after standing and solidifying, forming a woven mesh coating layer, and obtaining a bamboo-plastic composite absorbing material with a woven mesh structure.

9. The method for preparing the bamboo-plastic composite wave absorbing material according to claim 7 or 8, characterized in that: In step (1), the drying temperature is 50°C to 105°C, and the drying time is 5h to 10h; in step (3), the spraying or soaking time is based on the set target weight gain rate, and the target weight gain rate is 30% to 100%; in step (4), the inner cavity structure of the mold is a cube, the resin material includes one or more of epoxy resin, polyurethane resin and phenolic resin, the thickness of the resin bottom layer is 1mm to 3mm, and the static curing is carried out at room temperature and normal pressure, and the static curing time is 6h to 12h.

10. Use of the bamboo-plastic composite absorbing material according to any one of claims 1 to 6 or the bamboo-plastic composite absorbing material prepared by the preparation method according to any one of claims 7 to 9 in the field of building electromagnetic protection.

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