Biodegradable composite material as well as preparation method and application thereof

Abstract

The invention discloses a biodegradable composite material as well as a preparation method and application thereof. The biodegradable composite material is formed by laying and hot-pressing a multi-layer structure, when the multi-layer structure is laid, a hydrophobic fiber layer A, a filling fiber layer A, a PBAT film layer, a filling fiber layer B and a hydrophobic fiber layer B are sequentially arranged from top to bottom; the hydrophobic fiber layer A and the hydrophobic fiber layer B are prepared from 20-40 parts of natural plant fibers in total, and the filling fiber layer A and the filling fiber layer B are prepared from 10-20 parts of cereal crop straw fibers and 2-6 parts of PBAT in total; according to the invention, a lamination heat sealing process is adopted, complex melt blending and granulation processes are avoided, and the production process is simple and low in energy consumption; the main raw materials are from agricultural wastes and biodegradable plastics, are wide in source and low in cost, are particularly suitable for manufacturing seedling culture containers, are not damaged in transportation and stacking processes due to good strength, are convenient to tear during transplanting due to excellent toughness, and can be fused with soil and provide nutrients for seedlings after being degraded.

Description

Technical Field

[0001] This invention belongs to the field of environmental protection materials technology, specifically relating to a biodegradable composite material, its preparation method, and its application. Background Technology

[0002] Polybutylene adipate (PBAT) is a fully biodegradable plastic with good ductility and film-forming properties, but it has a low modulus, high cost, and is too soft when formed into a film on its own. Plant fibers, especially agricultural waste such as various straws, have advantages such as wide availability, low cost, biodegradability, and renewability, and are also rigid. However, pure plant fiber materials are often brittle and have poor water resistance.

[0003] Currently, studies have explored blending plant fibers with biodegradable plastics such as PBAT to prepare composite materials. However, several issues exist: First, high fiber content easily leads to agglomeration during blending, resulting in uneven dispersion and affecting material properties. Second, high-temperature processing may cause thermal degradation of plant fibers, weakening their reinforcing effect. Third, strong shear forces can damage fiber length, reducing reinforcement efficiency. Furthermore, due to the inherent high polarity, hydrophilicity, and external lignin structure of plant fibers, their interfacial compatibility with plastics is poor, requiring the addition of compatibilizers or coupling agents in most PBAT composites.

[0004] Therefore, improving the interfacial compatibility between biodegradable fillers and PBAT matrix remains a key issue in the research of biodegradable composite materials. Developing a biodegradable composite material that is simple to process, can retain the integrity of fiber properties, and achieves a balance between strength and toughness has important practical significance and application value. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a biodegradable composite material based on plant fibers, which possesses good tensile properties, toughness, water resistance, and biodegradability. Another purpose of this invention is to provide a method for preparing the above-mentioned composite material, which is simple, low-cost, and easy to scale up for production. A further purpose of this invention is to provide applications of the above-mentioned composite material in agricultural fields such as seedling containers.

[0006] To achieve the above objectives, the following technical solution is adopted: A biodegradable composite material is formed by hot pressing a multi-layer structure; the multi-layer structure is laid from top to bottom as follows: hydrophobic fiber layer A, filler fiber layer A, PBAT film layer, filler fiber layer B, and hydrophobic fiber layer B.

[0007] According to the above scheme, the raw materials used, by weight, are as follows: the hydrophobic fiber layers A and B together use 20-40 parts of natural plant fiber; the filling fiber layers A and B together use 10-20 parts of cereal crop straw fiber; and 2-6 parts of PBAT. In the optimized scheme, the raw material usage and laying thickness of the hydrophobic fiber layers A and B are consistent; the raw material usage and laying thickness of the filling fiber layers A and B are also consistent. The weight percentage of the natural plant fiber can be 20, 30, or 40 parts, but is not limited to the listed values; other unlisted values ​​within the range are also applicable. The weight percentage of the cereal crop straw fiber can be 10, 15, or 20 parts, but is not limited to the listed values; other unlisted values ​​within the range are also applicable. The weight percentage of PBAT can be 2, 4, or 6 parts, but is not limited to the listed values; other unlisted values ​​within the range are also applicable.

[0008] According to the above scheme, the thickness range of the hydrophobic fiber layers A and B is 3~6 mm, the thickness range of the filler fiber layers A and B is 2~4 mm, the thickness range of the PBAT film layer is 0.05~0.10 mm, and the overall thickness range of the multilayer structure before hot pressing is 11~20 mm.

[0009] According to the above scheme, the hydrophobic fiber layers A and B are one or more combinations of short fibers processed from palm trees, flax stalks, ramie stalks, or jute stalks; the fiber length is 3-5 cm. Typical but non-limiting combinations include combinations of palm fiber and flax fiber, flax fiber and ramie fiber, ramie fiber and jute fiber, palm fiber, flax fiber and ramie fiber, flax fiber, ramie fiber and jute fiber, and palm fiber, flax fiber, ramie fiber and jute fiber, preferably palm fiber. The length of the natural plant fiber can be 3 cm, 4 cm or 5 cm, but is not limited to the listed values; other unlisted values ​​within the range are also applicable.

[0010] According to the above scheme, the filling fiber layers A and B are one or more combinations of short fibers made from the stalks of corn, sorghum, rice, wheat, millet or foxtail millet; the length of the fibers is 1 to 3 cm. Typical but non-limiting combinations include combinations of corn stalk filaments and sorghum stalk filaments, combinations of sorghum stalk filaments and rice stalk filaments, combinations of rice stalk filaments and wheat stalk filaments, combinations of wheat stalk filaments and millet stalk filaments, combinations of millet stalk filaments and foxtail millet stalk filaments, combinations of corn stalk filaments, sorghum stalk filaments and rice stalk filaments, combinations of sorghum stalk filaments, rice stalk filaments and wheat stalk filaments, combinations of rice stalk filaments, wheat stalk filaments and millet stalk filaments, combinations of wheat stalk filaments, millet stalk filaments and foxtail millet stalk filaments, combinations of corn stalk filaments, sorghum stalk filaments, rice stalk filaments and wheat stalk filaments, combinations of corn stalk filaments, sorghum stalk filaments, rice stalk filaments, wheat stalk filaments, millet stalk filaments and foxtail millet stalk filaments, with corn stalk filaments being the most preferred. The length of the cereal crop straw fiber can be 1 cm, 2 cm or 3 cm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0011] According to the above scheme, the biodegradable composite material will completely degrade in the natural environment in 6-12 months.

[0012] This invention also provides a method for preparing the above-mentioned biodegradable composite material, comprising the following steps: (1) Layering design: The raw materials are laid from top to bottom as hydrophobic fiber layer A, filler fiber layer A, PBAT film layer, filler fiber layer B, and hydrophobic fiber layer B to form a "sandwich" structure prefabricated body; (2) Hot pressing: The preform is placed in a hot pressing device for hot pressing; (3) Cooling and demolding: After cooling, demold and cut to obtain the biodegradable composite material.

[0013] According to the above scheme, the hot pressing temperature is 160~200℃, the hot pressing pressure is 10~15 MPa, and the hot pressing holding time is 0.5~5 minutes. The hot pressing temperature can be 160℃, 180℃, or 200℃, but is not limited to the listed values; other unlisted values ​​within the range are also applicable. The hot pressing pressure can be 10 MPa, 13 MPa, or 15 MPa, but is not limited to the listed values; other unlisted values ​​within the range are also applicable. The hot pressing time can be 1 minute, 3 minutes, or 5 minutes, but is not limited to the listed values; other unlisted values ​​within the range are also applicable.

[0014] This invention also provides the application of the above-mentioned biodegradable composite material as a seedling container or ecological restoration substrate.

[0015] According to the above scheme, the seedling container is a seedling pot or seedling tray; the ecological restoration substrate is slope protection or vegetation restoration engineering material, such as PBAT / plant fiber composite fiber blanket, and special functional composite materials, such as bacteria-carrying / fertilizer-carrying slow-release substrate.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) Balanced performance: Through the ingenious “sandwich” structure design, the outer fiber layer of the upper and lower layers uses long natural plant fibers to provide high strength, toughness and hydrophobicity; the inner fiber layer of the upper and lower layers uses short cereal straw fibers to provide a certain rigidity and play a good filling role; the middle PBAT film, as a thermoplastic binder and tough sub-layer, effectively transfers stress and prevents crack propagation, so that the composite material has both good tensile and bending properties.

[0017] (2) Simple and efficient process: The present invention adopts a lamination heat sealing process, which avoids the complex melt blending and granulation process. The production process is simple, energy consumption is low, equipment requirements are low, and the original strength and length of plant fibers are preserved to the maximum extent, giving full play to their reinforcing effect.

[0018] (3) Low cost and environmentally friendly: The main raw materials are derived from agricultural waste and biodegradable plastics, which are widely available and low in cost. The entire product is completely biodegradable, environmentally friendly, and in line with the sustainable development strategy.

[0019] (4) Broad application prospects: This composite material is particularly suitable for making seedling containers. Its good strength can ensure that it will not be damaged during transportation and stacking. Its excellent toughness makes it easy to tear during transplanting. After degradation, it can integrate with the soil and provide nutrients for seedlings. Attached Figure Description

[0020] Figure 1 : Schematic diagram of the composite material "sandwich" structure prefabricated body of the present invention.

[0021] Figure 2 Photograph of the biodegradable composite material sheet prepared in Example 1.

[0022] Figure 3 Photograph of the composite material prepared in Example 1 applied to a seedling container. Detailed Implementation

[0023] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments. However, the following examples are merely simplified examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention is determined by the claims. In the following embodiments and comparative examples, unless otherwise specified, all raw materials were purchased from conventional material manufacturers in the art; unless otherwise specified, the experimental methods and technical means used are conventional methods and means in the art.

[0024] A specific embodiment provides a biodegradable composite material, which is formed by hot pressing a multi-layer structure. A schematic diagram of the prefabricated "sandwich" structure is attached. Figure 1 As shown; from top to bottom, the layers are hydrophobic fiber layer A, filler fiber layer A, PBAT film layer, filler fiber layer B, and hydrophobic fiber layer B. Hydrophobic fiber layers A and B serve as outer layers, providing high strength, toughness, and hydrophobicity; filler fiber layers A and B serve as intermediate layers, providing a certain rigidity and acting as a good filler; the PBAT film layer acts as a thermoplastic binder and toughening sublayer, effectively transferring stress and preventing crack propagation, enabling the composite material to possess both good tensile and flexural properties.

[0025] Example 1 1. Weigh out 20 parts palm fiber (about 3cm in length), 10 parts corn stalk shredded fiber (about 2cm in length), and 3 parts PBAT film.

[0026] 2. Lay the layers in the mold in the following order: first lay a layer of palm fiber (10 parts) on the outer layer, then lay a layer of corn stalk fiber (5 parts) on the inner layer, then lay a PBAT film (3 parts) on top, and finally lay a layer of corn stalk fiber (5 parts) on the inner layer and a layer of palm fiber (10 parts) on the outer layer.

[0027] 3. Place the mold into a hot press and hot press for 5 minutes at 160 ℃ and 15 MPa. Hold the pressure and cool to below 50 ℃, then demold to obtain the composite material sheet.

[0028] Example 2 1. Weigh out 20 parts palm fiber (about 3cm in length), 10 parts rice straw spun fiber (about 2cm in length), and 3 parts PBAT film.

[0029] 2. Lay the layers in the mold in the following order: first lay a layer of palm fiber (10 parts) on the outer layer, then lay a layer of rice straw fiber (5 parts) on the inner layer, then lay a PBAT film (3 parts) on top, and finally lay a layer of rice straw fiber (5 parts) on the inner layer and a layer of palm fiber (10 parts) on the outer layer.

[0030] 3. Place the mold into a hot press and hot press for 5 minutes at 160 ℃ and 15 MPa. Hold the pressure and cool to below 50 ℃, then demold to obtain the composite material sheet.

[0031] Example 3 1. Weigh out 20 parts palm fiber (about 3 cm in length), 5 parts corn stalk + 5 parts rice stalk mixed spun fiber (about 2 cm in length), and 3 parts PBAT film.

[0032] 2. Lay the layers in the mold in the following order: first, lay a layer of palm fiber (10 parts) on the outer layer, then lay a layer of corn stalk (2.5 parts) + rice stalk (2.5 parts) mixed fiber on the inner layer, then lay a PBAT film (3 parts) on top, and finally lay a layer of corn stalk (2.5 parts) + rice stalk (2.5 parts) mixed fiber on the inner layer and a layer of palm fiber (10 parts) on the outer layer.

[0033] 3. Place the mold into a hot press and hot press for 5 minutes at 160 ℃ and 15 MPa. Hold the pressure and cool to below 50 ℃, then demold to obtain the composite material sheet.

[0034] Example 4 1. Weigh out 20 parts palm fiber (about 3cm in length), 10 parts corn stalk shredded fiber (about 2cm in length), and 3 parts PBAT film.

[0035] 2. Lay the layers in the mold in the following order: first lay a layer of palm fiber (10 parts) on the outer layer, then lay a layer of corn stalk fiber (5 parts) on the inner layer, then lay a PBAT film (3 parts) on top, and finally lay a layer of corn stalk fiber (5 parts) on the inner layer and a layer of palm fiber (10 parts) on the outer layer.

[0036] 3. Place the mold into a hot press and hot press for 5 minutes at 180 ℃ and 15 MPa. Hold the pressure and cool to below 50 ℃, then demold to obtain the composite material sheet.

[0037] Example 5 1. Weigh out 20 parts palm fiber (about 3 cm in length), 10 parts corn stalk shredded fiber (about 2 cm in length), and 3 parts PBAT film.

[0038] 2. Lay the layers in the mold in the following order: first lay a layer of palm fiber (10 parts) on the outer layer, then lay a layer of corn stalk fiber (5 parts) on the inner layer, then lay a PBAT film (3 parts) on top, and finally lay a layer of corn stalk fiber (5 parts) on the inner layer and a layer of palm fiber (10 parts) on the outer layer.

[0039] 3. Place the mold into a hot press and hot press for 5 minutes at 160 ℃ and 10 MPa. Hold the pressure and cool to below 50 ℃, then demold to obtain the composite material sheet.

[0040] Example 6 1. Weigh out 20 parts palm fiber (about 3cm in length), 10 parts corn stalk shredded fiber (about 2cm in length), and 3 parts PBAT film.

[0041] 2. Lay the layers in the mold in the following order: first lay a layer of palm fiber (10 parts) on the outer layer, then lay a layer of corn stalk fiber (5 parts) on the inner layer, then lay a PBAT film (3 parts) on top, and finally lay a layer of corn stalk fiber (5 parts) on the inner layer and a layer of palm fiber (10 parts) on the outer layer.

[0042] 3. Place the mold into a hot press and hot press for 3 minutes at 160 ℃ and 15 MPa. Hold the pressure and cool to below 50 ℃, then demold to obtain the composite material sheet.

[0043] Comparative Example 1 1. Weigh out 20 parts palm fiber (approximately 3cm in length) and 3 parts PBAT film.

[0044] 2. Lay out the layers in the mold in the following order: first lay out a layer of palm fiber (10 parts), then lay out a PBAT film (3 parts), and finally lay out a layer of palm fiber (10 parts) on top.

[0045] 3. Place the mold into a hot press and hot press for 5 minutes at 160℃ and 15 MPa. Hold the pressure and cool to below 50℃, then demold to obtain the composite material sheet.

[0046] Comparative Example 2 1. Weigh out 10 parts of corn stalk shredded fiber (approximately 20mm in length) and 3 parts of PBAT film.

[0047] 2. Lay the layers in the mold in the following order: first lay a layer of corn stalk fiber (5 parts), then lay a PBAT film (3 parts), and finally lay a layer of corn stalk fiber (5 parts) on top.

[0048] 3. Place the mold into a hot press and hot press for 5 minutes at 160℃ and 15 MPa. Hold the pressure and cool to below 50℃, then demold to obtain the composite material sheet.

[0049] Comparative Example 3 1. Weigh out 20 parts palm fiber (about 3cm in length), 10 parts corn stalk shredded fiber (about 2cm in length), and 3 parts PBAT film.

[0050] 2. Lay the layers in the mold in the following order: first lay a layer of corn stalk fiber (5 parts) on the outer layer, lay a layer of palm fiber (10 parts) on the inner layer, then lay a PBAT film (3 parts) on top, and finally lay a layer of palm fiber (10 parts) on the inner layer and a layer of corn stalk fiber (5 parts) on the outer layer.

[0051] The mold is fed into a hot press and hot-pressed at 160 ℃ and 15 MPa for 5 minutes. After holding the pressure and cooling to below 50 ℃, the mold is demolded to obtain the composite material sheet.

[0052] Comparative Example 4 1. Weigh out 20 parts palm fiber (about 3cm in length), 10 parts corn stalk shredded fiber (about 2cm in length), and 3 parts PBAT film.

[0053] 2. Lay the layers in the mold in the following order: first lay a layer of palm fiber (10 parts) on the outer layer, then lay a layer of corn stalk fiber (5 parts) on the inner layer, then lay a PBAT film (3 parts) on top, and finally lay a layer of corn stalk fiber (5 parts) on the inner layer and a layer of palm fiber (10 parts) on the outer layer.

[0054] 3. Place the mold into a hot press and hot press for 5 minutes at 140 ℃ and 15 MPa. Hold the pressure and cool to below 50 ℃, then demold to obtain the composite material sheet.

[0055] Comparative Example 5 1. Weigh out 20 parts palm fiber (about 3 cm in length), 10 parts corn stalk shredded fiber (about 2 cm in length), and 3 parts PBAT film.

[0056] 2. Lay the layers in the mold in the following order: first lay a layer of palm fiber (10 parts) on the outer layer, then lay a layer of corn stalk fiber (5 parts) on the inner layer, then lay a PBAT film (3 parts) on top, and finally lay a layer of corn stalk fiber (5 parts) on the inner layer and a layer of palm fiber (10 parts) on the outer layer.

[0057] 3. Place the mold into a hot press and hot press for 5 minutes at 160 ℃ and 5 MPa. Hold the pressure and cool to below 50 ℃, then demold to obtain the composite material sheet.

[0058] Comparative Example 6 1. Weigh out 20 parts palm fiber (about 3 cm in length), 10 parts corn stalk shredded fiber (about 2 cm in length), and 3 parts PBAT film.

[0059] 2. Lay the layers in the mold in the following order: first lay a layer of palm fiber (10 parts) on the outer layer, then lay a layer of corn stalk fiber (5 parts) on the inner layer, then lay a PBAT film (3 parts) on top, and finally lay a layer of corn stalk fiber (5 parts) on the inner layer and a layer of palm fiber (10 parts) on the outer layer.

[0060] 3. Place the mold into a hot press and hot press for 10 minutes at 160 ℃ and 15 MPa. Hold the pressure and cool to below 50 ℃, then demold to obtain the composite material sheet.

[0061] Table 1

[0062] The mechanical properties of the composite materials prepared in the examples and comparative examples were tested, and the test results are shown in Table 1. The test results show that: (1) As can be seen from Examples 1-3, the present invention enables the biodegradable composite material to exhibit good mechanical properties by coupling natural plant fiber / fiber crop straw fiber, cereal crop straw fiber and PBAT film.

[0063] (2) By comparing Example 1 with Examples 4-6, it can be seen that the present invention further controls the hot pressing parameters (temperature, pressure and time) within a reasonable range, so that the biodegradable composite material can obtain good mechanical properties; if the temperature is too low, the interfacial bonding is poor, and if it is too high, the material is easy to degrade; insufficient hot pressing pressure is fatal and cannot guarantee the material density, but if it is too high, it will destroy the component balance and fiber structure; insufficient hot pressing time is incomplete process, and excessive time will introduce thermal damage and increase cost.

[0064] (3) As can be seen from Example 1 and Comparative Examples 1 and 2, the present invention achieves more balanced tensile and bending properties in biodegradable composite materials by coupling natural plant fibers / fiber crop straw fibers, cereal crop straw fibers, and PBAT film. When only palm fiber and PBAT film are hot-pressed, the composite material has good tensile properties but poor bending properties; when only corn straw and PBAT film are hot-pressed, the composite material has good bending properties but poor tensile properties; neither can achieve the technical effect of balanced tensile and bending properties.

[0065] (4) As can be seen from Example 1 and Comparative Example 3, the present invention uses a sandwich structure to alternately lay up the fibers in the order of "fiber-PBAT film-fiber". The fiber parts of the upper and lower layers are laid up with the inner layer being cereal crop straw fiber and the outer layer being natural plant fiber / fiber crop straw fiber. However, when the laying order is changed, it is impossible to achieve a more balanced effect of tensile and bending performance.

[0066] (5) As can be seen from Example 1 and Comparative Examples 4-6, the present invention enables biodegradable composite materials to obtain good mechanical properties by further controlling the hot pressing parameters (temperature, pressure and time) within a reasonable range. However, when they are not within a reasonable range, it is impossible to achieve a more balanced effect of tensile and bending properties.

[0067] The above embodiments illustrate that the composite material and its preparation method of the present invention effectively solve the technical problems in the composite of plant fiber and biodegradable plastic, and obtain a high-performance, degradable and environmentally friendly material.

[0068] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A biodegradable composite material, characterized by The biodegradable composite material is prepared by hot pressing with a multi-layer structure; the multi-layer structure is sequentially laid from top to bottom as a hydrophobic fiber layer A, a filling fiber layer A, a PBAT film layer, a filling fiber layer B, and a hydrophobic fiber layer B.

2. The biodegradable composite of claim 1, wherein The raw materials are used in the following proportions by mass: the hydrophobic fiber layers A and B together use natural plant fibers 20-40 parts, the filling fiber layers A and B together use cereal crop straw fibers 10-20 parts, and PBAT 2-6 parts; the raw material usage and laying thickness of the hydrophobic fiber layers A and B are consistent; and the raw material usage and laying thickness of the filling fiber layers A and B are consistent.

3. The biodegradable composite of claim 1, wherein The thickness of the hydrophobic fiber layers A and B ranges from 3 to 6 mm, the thickness of the filling fiber layers A and B ranges from 2 to 4 mm, the thickness of the PBAT film layer ranges from 0.05 to 0.10 mm, and the overall laying thickness of the multi-layer structure before hot pressing ranges from 11 to 20 mm.

4. The biodegradable composite of claim 1, wherein The hydrophobic fiber layers A and B are a combination of one or more of short fibers processed from palm trees, flax straw, ramie straw, or jute; the length of the fibers is 3-5 cm.

5. The biodegradable composite of claim 1 wherein the biodegradable polymer is a polylactide. The filling fiber layers A and B are a combination of one or more of short fibers processed from corn, sorghum, rice, wheat, millet, or straw; the length of the fibers is 1-3 cm.

6. The biodegradable composite of claim 1, wherein The biodegradable composite material completely degrades in a natural environment in 6-12 months.

7. The method of making the biodegradable composite of claim 1, wherein The method comprises the following steps: (1) Layer design: the raw materials are sequentially laid from top to bottom as a hydrophobic fiber layer A, a filling fiber layer A, a PBAT film layer, a filling fiber layer B, and a hydrophobic fiber layer B to form a "sandwich" structure preform; (2) Hot pressing: the preform is placed in a hot pressing device for hot pressing; (3) Cooling and demolding: after cooling, demolding, and cutting, the biodegradable composite material is obtained.

8. The method for preparing the biodegradable composite material as described in claim 7, characterized in that... The hot pressing temperature is 160-200℃, the hot pressing pressure is 10-15 MPa, and the hot pressing pressure holding time is 0.5-5 minutes.

9. Use of the biodegradable composite material of claim 1 as a seedling container or an ecological restoration substrate.

10. Use of the biodegradable composite material according to claim 9 as a container for seedlings or as a substrate for ecological restoration, characterized in that The seedling container is a seedling pot or a seedling tray; and the ecological restoration substrate is a slope protection or a vegetation restoration engineering material.

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