A high-performance composite plant fiber foam material, its preparation method and application

Abstract

This invention belongs to the field of cushioning packaging technology, and provides a high-performance composite plant fiber foam material, its preparation method, and its application. In the preparation process, thermally expandable microspheres are first added to a cross-linked fiber mixture, and an initial bubble network is formed through high-speed shearing and stirring. After filtration, the microspheres are heated in an oven to trigger expansion, and the resulting supporting force compensates for drying shrinkage. The material obtained by this process has low density, stable cell structure, excellent cushioning performance and flame retardancy, and the raw materials used are biodegradable, making it a green and environmentally friendly cushioning packaging material suitable for packaging applications such as express delivery and electronic products.

Description

Technical Field

[0001] This invention belongs to the field of cushioning packaging technology, and provides a high-performance composite plant fiber foam material, its preparation method and application. Background Technology

[0002] Product quality assurance during transportation relies heavily on cushioning packaging materials used in logistics. To prevent mechanical damage caused by squeezing or dropping during transportation, loading, unloading, and storage, cushioning foam or plastic air bags are often added to the packaging boxes or bags to protect the product's performance and shape.

[0003] Currently, common cushioning packaging materials mainly include foamed plastic cushioning materials, air cushioning materials, and plant fiber cushioning packaging materials. Among them, foamed plastic cushioning packaging materials are widely used due to their lightweight, ease of processing, and low price. However, as express delivery packaging materials, they have a short service life and cannot be reused after disposal, resulting in a large amount of material waste and increasing the environmental burden. Air cushioning materials are made by sealing a large amount of air in an air cushion film, which has good elasticity, heat insulation, and cushioning performance. However, air cushioning materials are not suitable for packaging heavy, sharp items with concentrated loads, so as not to crush or puncture the air bubbles and lose their cushioning effect. Plant fiber cushioning packaging materials are biodegradable foamed cushioning packaging materials developed in recent years under the high international requirements for environmentally friendly and green packaging materials. Currently, they can be made from biomass resources such as lignin, fiber, and starch, combined with appropriate foaming agents and other related additives. They have the advantages of low cost, environmental friendliness, and recyclability.

[0004] Nevertheless, existing plant fiber foaming technologies still face numerous challenges. For example, Chinese patent document CN105713409A discloses a fully degradable cellulose foam material, which is obtained by mixing modified plant fibers, hydroxypropyl starch, polyethylene succinate, nano-calcium carbonate, composite crosslinking agent, composite foaming agent, stearic acid, and liquid paraffin, followed by extrusion granulation, expansion, or molding. The foaming agent used is a composite foaming agent composed of diisopropyl azodicarbonate (DIAD) and azodicarbonamide (AC). The decomposition product NH3 of this foaming agent not only pollutes the environment but also poses safety hazards.

[0005] For example, Chinese patent document CN102505579A discloses a method for preparing plant fiber cushioning material. Using plant fiber as the starting material, a wet molding process is employed, involving sequential steps such as water addition and loosening, placement in a mold, dehydration molding, and drying finishing. This technical solution avoids the addition of external raw materials such as crosslinking agents and binders, but the density of the resulting product is relatively high (100–200 kg / m³). 3 (), its buffering performance is limited.

[0006] For example, Chinese patent document CN108624073A discloses a plant fiber foam material and its production method, comprising 40-50 parts plant fiber, 10-20 parts adhesive, 15-30 parts surfactant, 10-20 parts aerogel, and 0.5-2 parts foaming agent, further specifying that the adhesive is at least one of polyurethane or resin. The density of the foam material prepared by this technical solution is 76.3-92.3 kg / m³. 3 The use of polyurethane adhesives is toxic and still has a significant impact on the natural degradation properties of the products.

[0007] For example, Chinese patent document CN117801557A discloses a biodegradable low-density plant fiber foam material. Although it uses plant fiber as raw material and adds natural biomass adhesives, it can be biodegradable and harmless, but the performance of the product still needs to be improved.

[0008] Currently, a significant but unresolved technical challenge exists in the preparation of foamed materials based on plant fibers: during the oven drying stage, the fiber network structure undergoes severe shrinkage and collapse as moisture evaporates, resulting in a final product with high density, damaged cell structure, and significantly reduced cushioning performance. Existing technologies primarily focus on improving the mechanical properties of the material through formulation components or employing alternative drying methods such as microwave or freeze-drying, but none of these approaches fundamentally address the structural collapse problem during conventional oven drying. While some literature mentions that adding foamed microspheres can improve material performance, the technical insight is limited to the fact that foamed microspheres, as foaming agents, can form more uniform cells; it fails to recognize their potential to combat drying shrinkage or propose a technical solution to address the collapse problem through a secondary foaming mechanism.

[0009] Therefore, developing a high-performance composite plant fiber foam material that can achieve full biodegradability, effectively inhibit oven drying collapse, and possess excellent cushioning properties is a technical challenge that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0010] The technical problem to be solved by this invention is to overcome the defects of existing plant fiber foam materials that are prone to structural collapse during oven drying, resulting in a decrease in cushioning performance. This invention provides a high-performance composite plant fiber foam material, its preparation method and application. Through a secondary foaming mechanism of "mechanical pre-foaming + microsphere thermal expansion", it can effectively suppress drying collapse and significantly improve cushioning performance.

[0011] The technical solution of this invention is: The first aspect of this invention provides a method for preparing a high-performance composite plant fiber foam material, comprising the following steps: (1) Preparation of plant fiber dispersion.

[0012] (2) Borax is added to the plant fiber dispersion to carry out a cross-linking reaction, thereby obtaining a cross-linked fiber mixture; (3) Add foamed microspheres, adhesive, plasticizer, flame retardant and surfactant to the cross-linked fiber mixture, and mechanically shear and stir it through a high-speed disperser to obtain the foamed fiber mixture; (4) Pour the foamed fiber mixture into a mold and let it stand to filter out water; (5) The filtered foamed fiber mixture, together with the mold, is placed in an oven and heated to cause the foamed microspheres to expand and foam, thus obtaining a preliminary foamed body; (6) The preliminary foamed body together with the mold is dried and demolded to obtain a composite plant fiber foamed material; In step (3), the high-speed dispersing device stirring is carried out at room temperature, and the heating temperature in step (5) is higher than the stirring temperature in step (3), and the heating temperature reaches the foaming initiation temperature of the foamed microspheres.

[0013] Preferably, the foamed microspheres are thermally expandable microspheres with a core-shell structure, the outer shell being a thermoplastic polymer and the core being a low-boiling-point hydrocarbon substance; the foaming initiation temperature of the foamed microspheres is 80-120℃, the optimal foaming temperature is 120-140℃, the expansion ratio is 20-70 times, and the particle size range is 20-50 μm.

[0014] Preferably, the high-speed disperser has a rotation speed of 1200-5000 r / min and a foaming time of 5-15 min; the heating temperature in step (5) is 120-140℃ and the heating time is 5-15 min.

[0015] Preferably, the raw material of the plant fiber dispersion in step (1) is one or any combination of broadleaf wood fiber, softleaf wood fiber, bamboo fiber, sugarcane fiber, and cotton fiber, and the beating degree of the plant fiber is 20-65°SR.

[0016] Preferably, the amount of borax added in step (2) is 3%-15% of the dry weight of the plant fiber, and the cross-linking reaction time is 5-15 min.

[0017] Preferably, the surfactant in step (3) is selected from one or more of sodium dodecyl sulfate, rhamnolipid, sodium dodecylbenzene sulfonate, sodium fatty alcohol polyoxyethylene ether sulfate, and hexadecyltrimethylammonium bromide; the adhesive is selected from one or more of lignin adhesive, polyvinyl alcohol, sodium carboxymethyl cellulose, starch, and styrene-butadiene latex; the flame retardant is selected from one or more of borax and ammonium polyphosphate; and the plasticizer is selected from one or more of glycerol, ethylene glycol, and glycerol.

[0018] Preferably, the pulp concentration is controlled to be 1.5%-3% during the preparation of the fiber dispersion in step (1).

[0019] Preferably, the drying process in step (6) takes 2-12 hours and the temperature is 40-100℃.

[0020] A second aspect of the present invention provides a composite plant fiber foam material prepared by the above-described preparation method.

[0021] Preferably, the deformation energy of the composite plant fiber foam material is 11.22-23.21 KJ / m. 3 The compressive strength is 38.05-79.06 kPa.

[0022] The third aspect of this invention provides an application of the above-mentioned composite plant fiber foam material as a cushioning packaging material in express packaging, electronic product packaging, or daily necessities packaging.

[0023] Preferably, the foamed material can be made into a thin layer and sealed inside kraft paper as an inner lining. Alternatively, the foamed material can be placed directly inside the express delivery box.

[0024] Compared with the prior art, the present invention has the following beneficial effects: (1) The core of this invention is not simply the superposition of mechanical foaming and foamed microsphere foaming, but rather the existence of a significant synergistic mechanism between the two: in step (3), an initial bubble network structure is formed by high-speed mechanical shearing and stirring. This structure provides spatial constraints and positional guidance for the subsequent expansion of the foamed microspheres, allowing the microspheres to be evenly distributed in the fiber skeleton and forming a stable pore structure; during the heating process in step (5), the foamed microspheres undergo secondary expansion, compensating for the volume shrinkage caused by water evaporation, thereby effectively suppressing drying collapse. Therefore, this invention achieves a simultaneous improvement in structural stability and buffering performance through the secondary foaming mechanism of "mechanical pre-foaming + microsphere thermal expansion".

[0025] (2) The material of this invention is a biodegradable cushioning packaging material, with the addition of various plasticizers to give it a certain degree of softness. It not only has good cushioning performance, but also fits perfectly with the packaged goods, so that its performance can be fully utilized, and at the same time has excellent flame retardant properties.

[0026] (3) The fully biodegradable cushioning packaging of the present invention has the characteristics of cushioning performance and recyclability. When applied to paper-based packaging materials, it not only makes paper-based packaging materials lightweight and inexpensive, but also has the advantages of high softness and strong cushioning performance. Compared with corrugated cardboard packaging materials, it can increase the amount of single logistics transportation, reduce transportation quality, reduce logistics costs, and does not cause pollution to the environment, which is in line with the development direction of green, sustainable and low-carbon packaging materials. Attached Figure Description

[0027] Figure 1 This is a flowchart illustrating the preparation process of the composite fiber foam material of the present invention.

[0028] Figure 2 SEM images of composite fiber foam materials prepared with different amounts of foamed microspheres; where (a) corresponds to Example 1, (b) corresponds to Example 2, (c) corresponds to Example 3, and (d) corresponds to Example 4.

[0029] Figure 3 The images are digital images of vertical combustion; where (a) corresponds to Example 2, (b) corresponds to Example 3, and (c) corresponds to Example 5.

[0030] Figure 4 Digital images of horizontal combustion; (a) corresponds to Example 2, (b) corresponds to Example 3, and (c) corresponds to Example 5. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of this invention clearer, the preferred embodiments of this invention will be described in further detail below with reference to the examples. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without inventive effort are within the scope of protection of this invention.

[0032] Example 1 A method for preparing a high-performance composite plant fiber foam material includes the following steps: (1) Preparation of plant fiber dispersion: Take 5g of dry weight of coniferous wood fiber / broadleaf wood fiber compound pulp (ratio 3:7) with a beating degree of 40°SR, add an appropriate amount of water, control the pulp concentration to 3%, and put it into a high-speed disperser to obtain plant fiber dispersion.

[0033] (2) Add borax at 10% of the dry weight of the fiber to the prepared fiber dispersion and stir for 10 min to obtain the cross-linked fiber mixture.

[0034] (3) Add 6% (by weight of oven-dry fiber) of surfactant (sodium dodecyl sulfate), 10% (by weight of flame retardant (ammonium polyphosphate), 5% (by weight of adhesive (styrene-butadiene latex), 1g of foamed microspheres, and 2.5g (by weight of plasticizer (glycerol)) to the cross-linked fiber mixture. Foam at room temperature for 10min at a speed of 1300r / min in a high-speed disperser to obtain the foamed fiber mixture. The foamed microspheres have a core-shell structure, with the outer shell being a thermoplastic polymer (EHM204) and the core being a low-boiling-point hydrocarbon (pentane alkanes). The expansion ratio of the foamed microspheres is 20-70 times, and the particle size range is 20-50μm. They were purchased from Dongwa Seong Co., Ltd. in South Korea.

[0035] (4) Pour the foamed fiber mixture into the filter mold and let it stand for 30 minutes to filter the water.

[0036] (5) Place the filtered foamed fiber mixture together with the mold in a forced-air drying oven and foam at 135°C for 5 minutes to obtain a preliminary foamed body; (6) Place the preliminary foamed body along with the mold into a forced-air drying oven and dry at 55°C for 12 hours to obtain the composite fiber foamed material. Its SEM image is shown below. Figure 2 As shown in (a).

[0037] Example 2 A method for preparing a high-performance composite plant fiber foam material includes the following steps: (1) Preparation of plant fiber dispersion: Take 5g of dry weight of coniferous wood / broadleaf wood compound pulp (ratio 3:7) with a beating degree of 40°SR, add an appropriate amount of water, control the pulp concentration to 3%, and put it into a high-speed disperser to obtain plant fiber dispersion.

[0038] (2) Add borax to the fiber dispersion at 10% of the dry weight of the fiber and stir for 10 minutes to obtain the cross-linked fiber mixture.

[0039] (3) Add 6% of the dry fiber mass of surfactant (sodium dodecyl sulfate), 10% of flame retardant (ammonium polyphosphate), 5% of adhesive (styrene-butadiene latex) to the cross-linked fiber mixture, as well as 2g of foamed microspheres (same as in Example 1) and 2.5g of plasticizer (glycerol), and foam at room temperature for 10min at a speed of 1300r / min in a high-speed disperser to obtain the foamed fiber mixture.

[0040] (4) Pour the foamed fiber mixture into the filter mold and let it stand for 30 minutes to filter the water.

[0041] (5) Place the filtered foamed fiber mixture together with the mold in a forced-air drying oven and foam at 135°C for 5 minutes to obtain a preliminary foamed body; (6) Place the preliminary foamed body along with the mold into a forced-air drying oven and dry at 55°C for 12 hours to obtain the composite fiber foamed material. Its SEM image is shown below. Figure 2 As shown in (b).

[0042] Example 3 A method for preparing a high-performance composite plant fiber foam material includes the following steps: (1) Preparation of plant fiber dispersion: Take 5g of dry weight of coniferous wood / broadleaf wood compound pulp (ratio 3:7) with a beating degree of 40°SR, add an appropriate amount of water, control the pulp concentration to 3%, and put it into a high-speed disperser to obtain plant fiber dispersion.

[0043] (2) Add borax at 10% of the dry weight of the fiber to the prepared fiber dispersion and stir for 10 min to obtain the cross-linked fiber mixture.

[0044] (3) Add 6% of the dry fiber mass of surfactant (sodium dodecyl sulfate), 10% of flame retardant (ammonium polyphosphate), 5% of adhesive (styrene-butadiene latex), 3g of foamed microspheres (same as in Example 1) and 2.5g of plasticizer (glycerol) to the cross-linked fiber mixture, and foam at room temperature for 10min at a speed of 1300r / min in a high-speed disperser to obtain the foamed fiber mixture.

[0045] (4) Pour the foamed fiber mixture into the filter mold and let it stand for 30 minutes to filter the water.

[0046] (5) Place the filtered foamed fiber mixture together with the mold in a forced-air drying oven and foam at 135°C for 5 minutes to obtain a preliminary foamed body; (6) Place the preliminary foamed material along with the mold into a forced-air drying oven and dry at 55℃ for 12 hours to obtain the composite fiber foamed material. Its SEM image is shown below. Figure 2 As shown in (c).

[0047] Example 4 A method for preparing a high-performance composite plant fiber foam material includes the following steps: (1) Preparation of plant fiber dispersion: Take 5g of dry weight of coniferous wood / broadleaf wood compound pulp (ratio 3:7) with a beating degree of 40°SR, add an appropriate amount of water, control the pulp concentration to 3%, and put it into a high-speed disperser to obtain plant fiber dispersion.

[0048] (2) Add borax to the fiber dispersion at 10% of the dry weight of the fiber and stir for 10 minutes to obtain the cross-linked fiber mixture.

[0049] (3) Add 6% of the dry fiber mass of surfactant (sodium dodecyl sulfate), 10% of flame retardant (ammonium polyphosphate), 5% of adhesive (styrene-butadiene latex), 4g of foamed microspheres (same as in Example 1) and 2.5g of plasticizer (glycerol) to the cross-linked fiber mixture, and foam at room temperature for 10min at a speed of 1300r / min in a high-speed disperser to obtain the foamed fiber mixture.

[0050] (4) Pour the foamed fiber mixture into the filter mold and let it stand for 30 minutes to filter the water.

[0051] (5) Place the filtered foamed fiber mixture together with the mold into a forced-air drying oven and foam at 135°C for 5 minutes to obtain a preliminary foamed body.

[0052] (6) Place the preliminary foamed body along with the mold into a forced-air drying oven and dry at 55°C for 12 hours to obtain the composite fiber foamed material. Its SEM image is shown below. Figure 2 As shown in (d).

[0053] Example 5 A method for preparing a high-performance composite plant fiber foam material includes the following steps: (1) Preparation of plant fiber dispersion: Take 5g of dry weight of coniferous wood / broadleaf wood compound pulp (ratio 3:7) with a beating degree of 40°SR, add an appropriate amount of water, control the pulp concentration to 3%, and put it into a high-speed disperser to obtain plant fiber dispersion.

[0054] (2) Add borax to the fiber dispersion at 10% of the dry weight of the fiber and stir for 10 minutes to obtain the cross-linked fiber mixture.

[0055] (3) Add 6% of the dry fiber mass of surfactant (sodium dodecyl sulfate), 20% of flame retardant (ammonium polyphosphate), 5% of adhesive (styrene-butadiene latex), 3g of foamed microspheres (same as in Example 1) and 2.5g of plasticizer (glycerol) to the cross-linked fiber mixture, and foam at room temperature for 10min at a speed of 1300r / min in a high-speed disperser to obtain the foamed fiber mixture.

[0056] (4) Pour the foamed fiber mixture into the filter mold and let it stand for 30 minutes to filter the water.

[0057] (5) Place the filtered foamed fiber mixture together with the mold into a forced-air drying oven and foam at 135°C for 5 minutes to obtain a preliminary foamed body.

[0058] (6) Place the preliminary foamed body together with the mold into a forced-air drying oven and dry it at 55°C for 12 hours to obtain the composite fiber foamed material.

[0059] Comparative Example 1 A method for preparing a high-performance composite plant fiber foam material includes the following steps: (1) Preparation of plant fiber dispersion: Same as in Example 3.

[0060] (2) Add borax to the fiber dispersion at 10% of the dry weight of the fiber and stir for 10 minutes to obtain the cross-linked fiber mixture.

[0061] (3) Add 6% surfactant (same as in Example 3), 5% adhesive (same as in Example 3), 10% flame retardant (same as in Example 3), and 2.5g plasticizer (same as in Example 3) of the dry weight of the cross-linked fiber mixture to the mixture and foam it at room temperature for 10 minutes at a speed of 1300r / min in a high-speed disperser to obtain a foamed fiber mixture.

[0062] (4) Pour the foamed fiber mixture into the filter mold and let it stand for 30 minutes to filter the water.

[0063] (5) Place the filtered foamed fiber mixture together with the mold in a forced-air drying oven and dry it at 55°C for 12 hours to obtain the composite fiber foamed material.

[0064] Comparative Example 2 A method for preparing a high-performance composite plant fiber foam material includes the following steps: (1) Preparation of plant fiber dispersion: Same as in Example 3.

[0065] (2) Add borax to the fiber dispersion at 10% of the dry weight of the fiber and stir for 10 minutes to obtain the cross-linked fiber mixture.

[0066] (3) Add 6% of the dry fiber mass of surfactant (same as in Example 3), 5% of adhesive (same as in Example 3), 1g of foamed microspheres (same as in Example 3) and 2.5g of plasticizer (same as in Example 3) to the cross-linked fiber mixture, and foam at room temperature for 10min at a speed of 1300r / min in a high-speed disperser to obtain the foamed fiber mixture.

[0067] (4) Pour the foamed fiber mixture into the filter mold and let it stand for 30 minutes to filter the water.

[0068] (5) Place the filtered foamed fiber mixture together with the mold in a forced-air drying oven and foam at 135°C for 5 minutes to obtain a preliminary foamed body.

[0069] (6) Place the preliminary foamed body together with the mold into a forced-air drying oven and dry it at 55°C for 12 hours to obtain the composite fiber foamed material.

[0070] Comparative Example 3 A method for preparing a high-performance composite plant fiber foam material includes the following steps: (1) Preparation of plant fiber dispersion: Same as in Example 3.

[0071] (2) Add borax to the fiber dispersion at 10% of the dry weight of the fiber and stir for 10 minutes to obtain the cross-linked fiber mixture.

[0072] (3) Add 10% flame retardant (same as in Example 3), 5% adhesive (same as in Example 3), 3g foamed microspheres and 2.5g plasticizer (same as in Example 3) to the cross-linked fiber mixture, and mix evenly in a conventional manner (without stirring at a speed of 1300r / min) to obtain the foamed fiber mixture.

[0073] (4) Pour the foamed fiber mixture into the filter mold and let it stand for 30 minutes to filter the water.

[0074] (5) Place the filtered foamed fiber mixture together with the mold in a forced-air drying oven and foam at 135°C for 5 minutes to obtain a preliminary foamed body.

[0075] (6) Place the preliminary foamed body together with the mold into a forced-air drying oven and dry it at 55°C for 12 hours to obtain the composite fiber foamed material.

[0076] Performance Experiment Static compression performance: First, the test samples were pretreated in a constant temperature and humidity chamber for 24 h. According to GB / T4875.2-2005 Packaging - Transport Packaging Tests - Part 2: Temperature and Humidity Conditioning Treatment, the samples were pretreated at a constant temperature and humidity of 23℃ and 50% for 24 h.

[0077] The static compression test was conducted according to standard GB / T 8168-2008 "Static Compression Test Method for Packaging Cushioning Materials". The experimental equipment was an electronic universal testing machine with a compression speed of 12 mm / min and a compression strain of 60%. The stress-strain curve of the cushioning material was obtained from the experiment. The final results can be used to evaluate the mechanical properties of the cushioning material under static compression. The deformation energy (E, kJ / m) was calculated using the following formula. 3 ) and static buffer coefficient (C). Equations (1-1) and (1-2).

[0078] (1-1) (1-2) In the formula: ε For compressive strain; σ This is compressive stress.

[0079] The performance test results of the foamed materials prepared in the examples and comparative examples are shown in Table 1.

[0080] Table 1

[0081] As can be seen from Table 1, Examples 1-5 have large deformation energy and high energy absorption, which can provide better buffering effect.

[0082] Comparative Example 1, without the addition of foamed microspheres, exhibited severely damaged collapse structure during drying, resulting in low deformation energy, low energy absorption, and poor cushioning performance. This demonstrates that adding foamed microspheres not only improves the performance of the foamed material but also maintains structural stability and ensures more uniform force transmission.

[0083] Comparative Example 3 did not undergo mechanical stirring and foaming; the foamed microspheres only underwent one foaming process during heating. The results showed that while this material possessed a certain compressive strength, its deformation energy was low, and its overall cushioning performance was poor. This is because, without mechanical stirring and foaming, a sufficiently uniform pore structure could not be formed between the fibers, nor was an effective supporting framework constructed, resulting in insufficient overall support of the material. Simultaneously, the foamed microspheres lacked sufficient space for complete foaming during expansion, causing the material to prematurely enter the densification stage under pressure, thereby reducing its energy absorption capacity and cushioning performance.

[0084] Table 2

[0085] Table 2 shows that the height of the sample in Example 3 with added foamed microspheres is significantly higher than that of Comparative Example 1 without added foamed microspheres. This is because the foamed microspheres expand during heating, forming support points inside the material, thereby effectively inhibiting the collapse of the fiber structure during drying and allowing the material to maintain a relatively intact porous structure. In contrast, Comparative Example 3, lacking mechanical stirring for foaming, did not form a stable three-dimensional skeleton structure between the fibers. This limited the expansion space of the foamed microspheres, resulting in insufficient foaming; furthermore, it made the material more prone to premature densification under pressure, ultimately leading to a significant decrease in its cushioning performance.

[0086] Combustion test: First, the test samples were pretreated in a constant temperature and humidity chamber for 24 hours. In accordance with GB / T 2408-2008 "Determination of Combustion Performance of Plastics - Horizontal and Vertical Methods", the samples were pretreated at a constant temperature and humidity of 23℃ and 50% relative humidity.

[0087] The vertical and horizontal burning tests were conducted in accordance with the standard GB / T 2408-2008 "Determination of Burning Performance of Plastics - Horizontal and Vertical Methods". During the test, the sample was fixed vertically and horizontally on the burning fixture, and the lower end of the sample was ignited with a flame under specified conditions. The flaming burning time of the sample after the flame was removed was recorded.

[0088] The vertical and horizontal combustion performance of the prepared foamed materials were tested separately, as shown in Table 3. Figure 3 Digital images of vertical combustion in Examples 3, 5, and Comparative Example 2. Figure 4 A digital image of horizontal burning.

[0089] Table 3

[0090] Table 3 shows that Examples 3 and 5, with the addition of flame retardants, exhibit shorter open flame times regardless of whether the combustion is vertical or horizontal, demonstrating excellent flame retardant properties. Comparative Example 2, without flame retardants, lacks flame retardant properties and burns more rapidly. Furthermore, combined with the mechanical property data in Table 1, it can be seen that flame retardants can interact with the fiber matrix through hydrogen bonds and other processes, forming a more stable network structure, thereby improving the material's compressive strength, deformation energy, and other mechanical properties.

[0091] The embodiments described above are some, but not all, embodiments of the present invention. The detailed description of the embodiments of the present invention is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

Claims

1. A method for preparing a high-performance composite plant fiber foam material, characterized by, The method comprises the following steps: (1) preparing a plant fiber dispersion liquid; (2) adding borax to the plant fiber dispersion liquid for cross-linking reaction to obtain a cross-linked fiber mixture; (3) adding foaming microspheres, a glue adhesive, a plasticizer, a flame retardant and a surfactant to the cross-linked fiber mixture, and performing mechanical shearing stirring by a high-speed disperser to obtain a foaming fiber mixture; (4) pouring the foaming fiber mixture into a mold and standing for water filtration; (5) placing the foaming fiber mixture after water filtration and the mold in an oven for heating, so that the foaming microspheres are heat-expanded and foamed to obtain a preliminary foaming body; (6) drying the preliminary foaming body together with the mold, and obtaining a composite plant fiber foaming material after demolding. The high-speed disperser stirring in step (3) is performed at room temperature, the heating temperature in step (5) is higher than the stirring temperature in step (3), and the heating temperature reaches the foaming starting temperature of the foaming microspheres.

2. The production method according to claim 1, characterized by, The foaming microspheres are heat-expanded microspheres, have a core-shell structure, the shell is a thermoplastic polymer, and the core is a low-boiling-point hydrocarbon substance; the foaming starting temperature of the foaming microspheres is 80-120℃, the optimal foaming temperature is 120-140℃, the expansion ratio is 20-70 times, and the particle size range is 20-50 μm.

3. The preparation method according to claim 1, characterized in that, The rotation speed of the high-speed disperser in step (3) is 1200-5000 r / min, and the foaming time is 5-15 min; the heating temperature in step (5) is 120-140℃, and the heating time is 5-15 min.

4. The method of claim 1, wherein, In step (1), the raw material of the plant fiber dispersion liquid is one or any combination of broadleaf wood fiber, coniferous wood fiber, bamboo fiber, sugarcane fiber and cotton fiber, and the beating degree of the plant fiber is 20-65°SR.

5. The preparation method according to claim 1, characterized in that, In step (2), the borax is added in an amount of 3%-15% of the absolute dry mass of the plant fiber, and the cross-linking reaction time is 5-15 min.

6. The method of claim 1, wherein, In step (3), the surfactant is selected from one or more of sodium dodecyl sulfate, rhamnolipid, sodium dodecyl benzene sulfonate, sodium fatty alcohol polyoxyethylene ether sulfate and cetyltrimethylammonium bromide; the glue adhesive is selected from one or more of lignin glue adhesive, polyvinyl alcohol, sodium carboxymethyl cellulose, starch and butadiene-styrene latex; the flame retardant is selected from one or more of borax and ammonium polyphosphate; and the plasticizer is selected from one or more of glycerol, ethylene glycol and glycerol.

7. The preparation method according to claim 1, characterized in that, In step (6), the drying temperature is 40-100℃, and the drying time is 2-12 h.

8. A composite plant fiber foaming material prepared by the preparation method in any one of claims 1-7.

9. The composite plant fiber foam material according to claim 8, characterized by, The deformation energy thereof is 11.22-23.21 KJ / m 3 The compressive strength is 38.05-79.06 KPa.

10. Use of the composite plant fiber foaming material in claim 8 or 9 as a cushion packaging material in express package, electronic product package or daily necessities package.

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