Degradable cultivation device composite bioplastic, and preparation method thereof and cultivation device

Abstract

The present application relates to the technical field of high polymer material, and in particular to a degradable cultivation device composite biological plastic, a preparation method thereof and a cultivation device, The degradable cultivation device composite biological plastic comprises the following raw materials in percentage by weight: PBAT 70%~85.5%, gallic acid 4.75%~5%, dialdehyde cellulose 4.75%~5%, and corn protein 5%~20%; the preparation method comprises the following steps: weighing the formula amount of PBAT, adding N,N-dimethylacetamide, then adding glycerol, stirring under the condition of 70~90 ℃ water bath until the PBAT is completely dissolved, sequentially adding dialdehyde cellulose, gallic acid and corn protein, and continuing to stir under the condition of 70~90 ℃ water bath for 2~4h, so that the components are fully mixed and crosslinking reaction occurs, and the cultivation device prepared has the advantages of mechanical properties, water resistance and nutrient slow-release function, and easy operation.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, specifically to a biodegradable bioplastic for a grower, its preparation method, and the grower itself. Background Technology

[0002] Traditional petroleum-based plastic seedling containers are extremely difficult to degrade in the natural environment, and the resulting white pollution seriously damages soil structure, becoming a prominent problem restricting the green development of agriculture. Furthermore, forcibly removing the containers during transplanting easily damages the seedling roots, leading to prolonged recovery periods or even seedling death, affecting seedling survival rates and production efficiency. To balance environmental protection and agronomic needs, the use of biodegradable materials to prepare seedling containers has become a current research hotspot.

[0003] Existing single biodegradable polymer materials generally suffer from insufficient rigidity and poor water resistance, making it difficult to provide stable structural support throughout the entire seedling cultivation cycle. Currently, the performance of cultivation devices is improved by introducing fillers for blending and modification. However, the interfacial compatibility between the filler and the matrix is ​​often unsatisfactory, easily leading to uneven dispersion or weak interfacial bonding. This results in a decrease in the mechanical properties and water resistance stability of the cultivation device material, affecting its function as a cultivation device.

[0004] In addition, most existing cultivation device materials only have passive degradation function and lack active promotion of seedling growth, and their performance is relatively simple. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for preparing a biodegradable cultivation device composite bioplastic. The resulting cultivation device has mechanical, water-resistant and nutrient slow-release functions, and is easy to operate.

[0006] To achieve the above objectives, the present invention provides the following technical solution: A method for preparing a biodegradable bioplastic composite for a grower is provided, wherein the biodegradable bioplastic composite for a grower comprises the following raw materials by weight percentage: PBAT 70%~85.5%, gallic acid 4.75%~5%, dialdehyde cellulose 4.75%~5%, and zein 5%~20%; The preparation method includes the following steps: Weigh out the required amount of PBAT, add N,N-dimethylacetamide, then add glycerin, and stir in a water bath at 70℃~90℃ until the PBAT is completely dissolved. Then add dialdehyde cellulose, gallic acid and zein in sequence, and continue stirring in a water bath at 70℃~90℃ for 2~4 hours to ensure that the components are fully mixed and cross-linked.

[0007] In some implementations, 4.44 mL to 5.71 mL of DMAc and 0.222 g to 0.286 g of glycerol are added per gram of PBAT.

[0008] A biodegradable bioplastic for a grower is also provided, which is prepared by the above-described method for preparing biodegradable bioplastic for a grower.

[0009] A biodegradable grower is also provided. The biodegradable grower composite bioplastic is heated to a molten state, poured into a grower silicone mold, and left to stand at room temperature until it solidifies to obtain the grower.

[0010] The beneficial effects of using the method for preparing a biodegradable bioplastic composite for a grower according to the present invention are as follows: (1) In this invention, gallic acid, dialdehyde cellulose, and zein are introduced into a biodegradable polyester matrix. Gallic acid (GA) contains abundant phenolic hydroxyl and carboxyl groups, which generate strong hydrogen bonds with various groups. These hydrogen bonds can connect multiple components, thereby improving interfacial compatibility and acting as an interfacial bridge. This allows for Schiff base covalent cross-linking between dialdehyde cellulose and zein, resulting in a chemical network reinforcement structure. Furthermore, gallic acid is soluble in water and most oily solvents, and it provides a multi-layered hydrogen bond network, constructing a dual-network reinforcement structure. This dual-network reinforcement structure significantly improves the tensile strength and elongation at break of the composite bioplastic of the grower, giving it both high strength and high toughness. At the same time, it forms a dense microstructure, effectively overcoming the problems of insufficient rigidity and poor water resistance commonly found in existing grower materials. This allows the grower to not only have biodegradability but also rigidity and water resistance.

[0011] (2) In this invention, the water resistance of the material is significantly improved through the synergistic cross-linking effect between the components. The covalent cross-linking of dialdehyde cellulose and zein consumes some of their respective polar groups, and the interfacial bridging effect of gallic acid further promotes the densification of the structure, which can improve the hydrophobic properties of the material surface. Therefore, the resulting composite bioplastic for the grower exhibits a low water absorption rate and a high water contact angle, effectively inhibiting the penetration and diffusion of water inside the material, enabling it to maintain structural integrity for a long time in a humid seedling environment.

[0012] (3) In this invention, the prepared composite bioplastic possesses controllable soil degradation behavior and active nutrient slow-release function. Zein, as a natural plant protein component, can not only act as a microbial nutrient source to induce bio-erosion and effectively regulate the material degradation rate when the grower is in the soil, but also slowly degrade and release nitrogen-containing nutrient ions in the soil. This characteristic enables the grower to provide physical support while promoting the growth and development of transplanted plants, thus realizing the multifunctional development of the grower.

[0013] (4) The composite bioplastic constructed in this invention has good environmental compatibility and resource utilization value. The materials used are mainly agricultural and forestry processing by-products (dialdehyde cellulose precursor, zein) and natural polyphenols (gallic acid). The raw materials are widely available, renewable and biodegradable, which reflects the concept of high-value utilization of agricultural and forestry waste and green chemical industry. The final product can be completely degraded after completing the seedling function, without producing environmental residues, which meets the requirements of sustainable agricultural development. Attached Figure Description

[0014] Figure 1 These are the infrared spectra of PGDZ5, PGDZ10, PGDZ20, PGZ10, PDZ10, and PZ10 bioplastics.

[0015] Figure 2 These are XPS carbon spectrum peak fitting images of PZ10, PDZ10, and PGDZ10 composite bioplastics.

[0016] Figure 3 These are XPS nitrogen spectrum peak fitting images of PZ10, PDZ10, and PGDZ10 composite bioplastics for growers.

[0017] Figure 4 These are microscopic morphological images of the composite bioplastics used in the cultivation device: (a) PGZ10; (b) PDZ10; (c) PGDZ5; (d) PGDZ10; (e) PGDZ20.

[0018] Figure 5 The mechanical properties of PGZ10, PDZ10, PGDZ5, PGDZ10, and PGDZ20 bioplastics are shown, including (a) stress-strain curves and (b) tensile strength and elongation at break.

[0019] Figure 6 The images show (a) surface contact angle histograms and (b) water absorption rate test curves of the composite bioplastics for PGZ10, PDZ10, PGDZ5, PGDZ10, and PGDZ20 cultivators.

[0020] Figure 7 This is a diagram showing the soil degradation process of PBAT, PGDZ5, PGDZ10, and PGDZ20 growers.

[0021] Figure 8 The germination and growth status of wheat, mung beans, and red beans are shown in the following figures: (a) Day 1; (b) Day 4; (c) Day 7.

[0022] Figure 9 The germination rate of wheat, mung beans, and red beans after 7 days of germination and growth is (a) and (b) the average sprout length.

[0023] Figure 10 (a) A picture of mustard seedlings before cultivation; (b) The effect of cultivation in PBAT-based biological seedling containers.

[0024] Figure 11 Mustard seedlings were grown in polyethylene containers: (a) at the initial time; (b) one month after cultivation.

[0025] Figure 12 This is a comparison of the growth of mustard seedlings after one month of cultivation. Detailed Implementation

[0026] Preferred embodiments of the invention will now be described in more detail. While preferred embodiments of the invention have been shown, it should be understood that the invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that the invention will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.

[0027] Example 1

[0028] This embodiment discloses a method for preparing a biodegradable bioplastic composite for a grower, wherein the biodegradable bioplastic composite for a grower comprises the following raw materials by weight percentage: PBAT 80%, gallic acid 4.75%, dialdehyde cellulose 4.75%, and zein 5%; The preparation method includes the following steps: Weigh out the required amount of PBAT (polybutylene terephthalate), add N,N-dimethylacetamide, then add glycerin, and stir in a 70°C water bath until the PBAT is completely dissolved. Then add dialdehyde cellulose, gallic acid and zein in sequence, and continue stirring in a 70°C water bath for 2 hours to ensure that the components are fully mixed and cross-linked.

[0029] In some implementations, 4.44 mL of DMAc and 0.222 g of glycerol are added per gram of PBAT.

[0030] Preparation process of the grower: Pour the above-mentioned biodegradable grower composite bioplastic solution into a flowerpot-shaped silicone mold, and let it stand at room temperature until it solidifies to obtain the grower.

[0031] When transplanting seedlings from the cultivation container, the cultivation container and the seedlings are placed in the soil.

[0032] Example 2

[0033] This embodiment discloses a method for preparing a biodegradable bioplastic composite for a cultivator, wherein the biodegradable bioplastic composite for a cultivator comprises the following raw materials by weight percentage: PBAT 77.75%, gallic acid 4.875%, dialdehyde cellulose 4.875%, and zein 12.5%; The preparation method includes the following steps: Weigh out the required amount of PBAT, add N,N-dimethylacetamide, then add glycerin, and stir in an 80°C water bath until the PBAT is completely dissolved. Then add dialdehyde cellulose, gallic acid and zein in sequence, and continue stirring in an 80°C water bath for 3 hours to ensure that the components are fully mixed and cross-linked.

[0034] In some implementations, 5.075 mL of DMAc and 0.254 g of glycerol are added per gram of PBAT.

[0035] Preparation process of the grower: Pour the above-mentioned biodegradable grower composite bioplastic solution into a flowerpot-shaped silicone mold, and let it stand at room temperature until it solidifies to obtain the grower.

[0036] When transplanting seedlings from the cultivation container, place the cultivation container and the seedlings into the soil.

[0037] Example 3

[0038] This embodiment discloses a method for preparing a biodegradable bioplastic composite for a cultivator, wherein the biodegradable bioplastic composite for a cultivator comprises the following raw materials by weight percentage: 85.5% PBAT, 5% gallic acid, 5% dialdehyde cellulose, and 20% zein; The preparation method includes the following steps: Weigh out the required amount of PBAT, add N,N-dimethylacetamide, then add glycerin, and stir in a 90°C water bath until the PBAT is completely dissolved. Then add dialdehyde cellulose, gallic acid and zein in sequence, and continue stirring in a 90°C water bath for 4 hours to ensure that the components are fully mixed and cross-linked.

[0039] In some implementations, 5.71 mL of DMAc and 0.286 g of glycerol are added per gram of PBAT.

[0040] Preparation process of the grower: Pour the above-mentioned biodegradable grower composite bioplastic solution into a flowerpot-shaped silicone mold, and let it stand at room temperature until it solidifies to obtain the grower.

[0041] When transplanting seedlings from the cultivation container, place the cultivation container and the seedlings into the soil.

[0042] Example 4

[0043] This embodiment discloses a method for preparing a biodegradable bioplastic composite for a cultivator, wherein the biodegradable bioplastic composite for a cultivator comprises the following raw materials by weight percentage: PBAT 80%, gallic acid 4.9%, dialdehyde cellulose 4.9%, and zein 10.2%; The preparation method includes the following steps: Weigh out the required amount of PBAT, add N,N-dimethylacetamide, then add glycerin, and stir in an 85°C water bath until the PBAT is completely dissolved. Then add dialdehyde cellulose, gallic acid and zein in sequence, and continue stirring in an 85°C water bath for 2.5 hours to ensure that the components are fully mixed and cross-linked.

[0044] In some implementations, 5.2 mL of DMAc and 0.26 g of glycerol are added per gram of PBAT.

[0045] Preparation process of the grower: Pour the above-mentioned biodegradable grower composite bioplastic solution into a flowerpot-shaped silicone mold, and let it stand at room temperature until it solidifies to obtain the grower.

[0046] When transplanting seedlings from the cultivation container, place the cultivation container and the seedlings into the soil.

[0047] To further illustrate the effectiveness of the biodegradable grower composite bioplastic of the present invention, the following experimental examples were conducted: Experimental Example 1 Weigh 31.875g of biodegradable polyester PBAT and add it to 150 mL of N,N-dimethylacetamide (DMAc). Then add 7.5g of glycerol as a plasticizer and stir slowly in an 80 ℃ water bath until the PBAT is completely dissolved.

[0048] After the matrix is ​​completely dissolved, add 1.875g of dialdehyde cellulose (DAC), 1.875g of gallic acid (GA) and 1.875g of zein in sequence, and continue stirring in an 80 ℃ water bath for 3 h to ensure that the components are fully mixed and cross-linked.

[0049] After the reaction is complete, the resulting uniform and viscous solution is poured into a flowerpot-shaped silicone mold while it is still hot. After standing at room temperature for one week, the solvent is allowed to evaporate completely before demolding to obtain the PGDZ composite bioplastic seedling container.

[0050] The prepared composite biological seedling container has a thickness of 0.5 cm, a height of 7.5 cm, a top diameter of 8 cm, a bottom diameter of 4.5 cm, and a drainage hole with a diameter of 1 cm in the middle of the bottom, thus obtaining the PGDZ5 sample.

[0051] Experimental Example 2

[0052] Weigh 30g of biodegradable polyester PBAT and add it to 150 mL of N,N-dimethylacetamide (DMAc). Then add 7.5g of glycerol as a plasticizer and stir slowly in an 80 ℃ water bath until the PBAT is completely dissolved.

[0053] After the matrix is ​​completely dissolved, add 1.875g of dialdehyde cellulose (DAC), 1.875g of gallic acid (GA) and 3.75g of zein in sequence, and continue stirring in an 80 ℃ water bath for 3 h to ensure that the components are fully mixed and cross-linked.

[0054] After the reaction is complete, the resulting uniform and viscous solution is poured into a flowerpot-shaped silicone mold while it is still hot. After standing at room temperature for one week, the solvent is allowed to evaporate completely before demolding to obtain the PGDZ composite bioplastic seedling container.

[0055] The prepared composite biological seedling container has a thickness of 0.5 cm, a height of 7.5 cm, a top diameter of 8 cm, a bottom diameter of 4.5 cm, and a drainage hole with a diameter of 1 cm in the middle of the bottom, thus obtaining the PGDZ10 sample.

[0056] Experimental Example 3

[0057] Weigh 26.25g of biodegradable polyester PBAT and add it to 150 mL of N,N-dimethylacetamide (DMAc). Then add 7.5g of glycerol as a plasticizer and stir slowly in an 80 ℃ water bath until the PBAT is completely dissolved.

[0058] After the matrix is ​​completely dissolved, add 1.875g of dialdehyde cellulose (DAC), 1.875g of gallic acid (GA) and 7.5g of zein in sequence, and continue stirring in an 80 ℃ water bath for 3 h to ensure that the components are fully mixed and cross-linked.

[0059] After the reaction is complete, the resulting uniform and viscous solution is poured into a flowerpot-shaped silicone mold while it is still hot. After standing at room temperature for one week, the solvent is allowed to evaporate completely before demolding to obtain the PGDZ composite bioplastic seedling container.

[0060] The prepared composite biological seedling container has a thickness of 0.5 cm, a height of 7.5 cm, a top diameter of 8 cm, a bottom diameter of 4.5 cm, and a drainage hole with a diameter of 1 cm in the middle of the bottom, thus obtaining the PGDZ20 sample.

[0061] Comparative Example 1

[0062] Weigh 31.875g of biodegradable polyester PBAT and add it to 150 mL of N,N-dimethylacetamide (DMAc). Then add 7.5g of glycerol as a plasticizer and stir slowly in an 80 ℃ water bath until the PBAT is completely dissolved.

[0063] After the matrix is ​​completely dissolved, add 1.875g of dialdehyde cellulose (DAC), 0g of gallic acid (GA) and 3.75g of zein in sequence, and continue stirring in an 80 ℃ water bath for 3 h to ensure that the components are fully mixed and cross-linked.

[0064] After the reaction is complete, the resulting uniform and viscous solution is poured into a flowerpot-shaped silicone mold while it is still hot. After standing at room temperature for one week, the solvent is allowed to evaporate completely before demolding to obtain the PGDZ composite bioplastic seedling container.

[0065] The prepared composite biological seedling container has a thickness of 0.5 cm, a height of 7.5 cm, a top diameter of 8 cm, a bottom diameter of 4.5 cm, and a drainage hole with a diameter of 1 cm in the middle of the bottom, thus obtaining the PDZ10 sample.

[0066] Comparative Example 2

[0067] Weigh 31.875g of biodegradable polyester PBAT and add it to 150 mL of N,N-dimethylacetamide (DMAc). Then add 7.5g of glycerol as a plasticizer and stir slowly in an 80 ℃ water bath until the PBAT is completely dissolved.

[0068] After the matrix is ​​completely dissolved, add 0g of dialdehyde cellulose (DAC), 1.875g of gallic acid (GA) and 3.75g of zein in sequence, and continue stirring in an 80 ℃ water bath for 3 h to ensure that the components are fully mixed and cross-linked.

[0069] After the reaction is complete, the resulting uniform and viscous solution is poured into a flowerpot-shaped silicone mold while it is still hot. After standing at room temperature for one week, the solvent is allowed to evaporate completely before demolding to obtain the PGDZ composite bioplastic seedling container.

[0070] The prepared composite biological seedling container has a thickness of 0.5 cm, a height of 7.5 cm, a top diameter of 8 cm, a bottom diameter of 4.5 cm, and a drainage hole with a diameter of 1 cm in the middle of the bottom, thus obtaining the PGZ10 sample.

[0071] Effect Analysis: 1. Infrared characterization of composite bioplastics The sample obtained in Experiment 1 was subjected to infrared analysis, and the infrared spectral analysis results are as follows: Figure 1 As shown.

[0072] In the spectrum, the strong absorption peak at 1712 cm⁻¹ is attributed to the stretching vibration of the ester carbonyl group (C=O) in PBAT, and the peak at 1100 cm⁻¹... - The absorption peak at ¹ corresponds to the symmetric stretching vibration of COC in the ester bond, while the peaks at 1160 cm⁻¹ and 1265 cm⁻¹ correspond to the asymmetric stretching vibrations of COC, respectively. The doublets at 2865 cm⁻¹ and 2950 cm⁻¹ correspond to the symmetric and asymmetric C–H stretching vibrations of the methylene group (-CH₂-), respectively, and the peak at 1456 cm⁻¹ corresponds to the symmetric and asymmetric C–H stretching vibrations of the methylene group (-CH₂-). - The position ¹ represents the C–H bending vibration of the methylene group, 726 cm⁻¹. - The ¹ position can be attributed to the out-of-plane bending vibration of the CH group on the benzene ring. These characteristics collectively confirm the presence of PBAT as the host phase in the composite bioplastic. Furthermore, 3200-3600 cm⁻¹ - The broad absorption peak at ¹ and 1620 cm⁻¹ - The absorption peak at ¹ mainly originates from the -OH stretching vibration of the hydroxyl groups in GA, DAC, and Zein. Absorption peaks at 1650 cm⁻¹ and 1540 cm⁻¹ are also observed. - ¹and 1265 cm - Characteristic absorptions belonging to amide I (C=O stretching), amide II (NH bending), and amide III (CN stretching) bands can be observed at ¹, indicating that Zein has been successfully introduced into the complex system. The C=N bond formed by the Schiff base reaction between the amino group in Zein and the aldehyde group in DAC should be located at 1620–1650 cm⁻¹. - Characteristic absorption appears in the range¹, but due to its low content and weak signal, and because this region overlaps with the amide I band of Zein and the stretching vibration peak of the hydroxyl group -OH in the composite bioplastic, no obvious C=N characteristic peak was observed in the infrared spectrum. To further verify the occurrence of the Schiff base reaction, more in-depth characterization and analysis are required using X-ray photoelectron spectroscopy (XPS) surface analysis. It should be noted that the peaks in the spectrum are all of PBAT and zein; the infrared peaks of dialdehyde cellulose and gallic acid are masked, mainly indicating that proteins are introduced into the composite system. Figure 1 In this study, PZ10 was the product obtained from 33.75g PBAT and 3.75g zein.

[0073] 2. XPS characterization of composite bioplastics

[0074] To clearly verify the occurrence of the Schiff base reaction in the composite bioplastic of the grower, X-ray photoelectron spectroscopy (XPS) was used to characterize the surface elemental chemical valence states, and Avantage software was used for peak fitting analysis of the C1s and N1s spectra. The results are as follows: Figure 2 and Figure 3As shown.

[0075] In the C1s spectrum ( Figure 3 The peaks at 284.8 eV, 286.2 eV, 288.4 eV, and 286.8 eV were attributed to CC / CH, CO / CN, C=O, and C=N bonds, respectively. Comparative analysis revealed that no C=N bond characteristic peaks were detected in the PZ10 sample containing only PBAT and zein; however, C=N bond signals were clearly observed in the PDZ10 sample containing dialdehyde cellulose (DAC) and the PGDZ10 sample containing both DAC and gallic acid (GA), with relative contents of 3.98% and 5.11%, respectively. This result directly confirms that a Schiff base reaction occurred between the amino group in Zein and the aldehyde group in DAC, forming a C=N covalent crosslink. The higher C=N bond content in the PGDZ10 sample can be attributed to the protons (H) provided by GA. + The combination of the carbon atom on the DAC aldehyde group enhances the positive charge of the aldehyde carbon, thereby increasing its ability to undergo nucleophilic addition reactions with the amino nitrogen with lone pair electrons in Zein.

[0076] In the N1s spectrum ( Figure 3 The peaks with binding energies of 399.8 eV, 401.2 eV, and 402.4 eV correspond to C–N, C=N, and -NH2, respectively. Consistent with the C 1s analysis results, no C=N bond signal was observed in PZ10, while obvious C=N characteristic peaks appeared in PDZ10 and PGDZ10, with relative contents of 7.53% and 10.71%, respectively, further supporting the formation of a covalent cross-linked structure. Importantly, with the introduction of DAC and GA, the relative content of the -NH2 peak, representing free amino groups, significantly decreased from 11.59% in PZ10 to 1.98% in PGDZ10, providing strong quantitative evidence that the Schiff base reaction consumed amino groups. In summary, XPS analysis, based on the changes in the chemical states of carbon and nitrogen, jointly confirms that Zein and DAC successfully constructed a C=N covalent cross-linked network through a Schiff base reaction, and the addition of GA has a significant promoting effect on this reaction.

[0077] 3. Surface microstructure of composite bioplastics

[0078] Figure 4 (a) through (e) show SEM images of the surface microstructure of the composite bioplastics in the series of growers at 200x magnification.

[0079] As can be observed from the figures, the introduction of different components has a significant impact on the surface structure of the materials. The PGZ10 sample (Figure a) in Comparative Example 2 shows numerous voids and obvious phase separation on its surface. This is due to the lack of covalent crosslinking by DAC; the Zein and PBAT matrix rely only on weak physical adsorption and hydrogen bonding, resulting in poor interfacial compatibility and a tendency to form defects during film formation. With the introduction of DAC, the surface morphology of the PDZ10, PGDZ5, and PGDZ10 samples gradually becomes denser and smoother, with a significant reduction in the number of pores. This change directly confirms that the Schiff base reaction between DAC and Zein effectively enhances the interfacial bonding between the two phases. The formation of C=N covalent bonds, synergistically with the strong hydrogen bond network mediated by gallic acid (GA), significantly improves the compatibility between the components, enabling the biomass filler (DAC, Zein, GA) and the PBAT matrix to form a continuous and uniform composite structure. This dense microstructure not only provides the material with excellent mechanical properties, but also provides it with a good water barrier, effectively blocking water penetration and improving water resistance.

[0080] 4. Mechanical property testing of composite bioplastics

[0081] The mechanical properties of composite bioplastics were tested using a universal testing machine to investigate the influence of each component on the mechanical properties of composite bioplastics. Figure 5 The results showed that PGDZ10 exhibited the best overall performance when the amount of zein added was 10%: its tensile strength was 8.52 MPa, its elongation at break reached 1451%, its modulus was 46.22 MPa, and its toughness was as high as 99.45 mJ / m³. However, when the amount of zein added was further increased to 20%, all properties of PGDZ20 showed a significant decline, indicating that optimizing the component ratio is crucial. Notably, the mechanical properties of the control group without gallic acid or dialdehyde cellulose also decreased, confirming the necessity of multi-component synergistic modification.

[0082] The improved mechanical properties of PGDZ composite bioplastics, especially the leap in elongation at break, are due to the synergistic enhancement of complex and efficient chemical reinforcing networks and physical reinforcing networks within them.

[0083] First, the aldehyde groups of dialdehyde cellulose and the amino groups of zein form C=N covalent bonds through a Schiff base reaction. This stable covalent cross-linked network acts as a rigid framework, providing crucial structural integrity and directly enhancing the tensile strength and modulus of the material. Second, gallic acid-mediated multiple hydrogen bond networks achieve dynamic toughening and interfacial reinforcement. The abundant phenolic hydroxyl groups of gallic acid can form hydrogen bonds not only with the ester groups of the polyester matrix, the aldehyde groups and hydroxyl groups of dialdehyde cellulose, but also with various functional groups of zein. These dynamically reversible hydrogen bonds can continuously break and recombine during stretching, continuously dissipating energy and greatly promoting the slippage and orientation of molecular chains. This is the core mechanism for achieving ultra-high elongation at break in the material. Simultaneously, gallic acid, as a highly efficient compatibilizer, significantly improves the interfacial adhesion between the polyester matrix and dialdehyde cellulose and zein through strong hydrogen bonding, ensuring efficient stress transfer from the flexible matrix to the entire reinforcing network. In addition, solution casting helps to uniformly disperse the components at the molecular level, promotes dense physical entanglement between molecular chains, and further strengthens the network interconnection structure through rigid covalent bonds and flexible hydrogen bonds, thereby enhancing interfacial bonding and stress transfer.

[0084] In summary, by synergistically introducing gallic acid, dialdehyde cellulose, and zein, a multi-reinforcement structure consisting of a covalently cross-linked backbone, a dynamic hydrogen bond network, and physical entanglement was successfully constructed within the polyester matrix. This fundamentally enhanced network stability and endowed the material with excellent mechanical properties.

[0085] 5. Water resistance test of composite bioplastics

[0086] The hydrophobic properties of composite bioplastics were investigated using surface contact angle testing. Figure 6 The results showed that the hydrophobicity of the composite bioplastic was significantly enhanced after the introduction of dialdehyde cellulose and zein. The water contact angle first increased and then decreased, with PGDZ10 exhibiting the largest contact angle (87.6°) and the best hydrophobicity. This change mainly stemmed from alterations in the surface chemical properties and microstructure of the materials: the aldehyde groups of dialdehyde cellulose reacted with the amino groups of zein via a Schiff base reaction, consuming polar groups; zein itself is rich in nonpolar amino acids and possesses strong intrinsic hydrophobicity. Under the hydrogen bonding of dialdehyde cellulose and gallic acid, its polar groups were partially occupied or shielded, making the hydrophobic regions more easily oriented on the surface, thus synergistically improving the hydrophobicity of the material. However, when excessive zein was added, it easily caused protein molecule aggregation, leading to local phase separation and enrichment of hydrophilic groups on the surface, while also disrupting the uniformity of the internal cross-linking network, resulting in a decrease in hydrophobicity.

[0087] The surface energy of the composite bioplastics was further calculated using the Owens-Wendt theoretical model. Consistent with the contact angle trend, PGDZ10 exhibited the lowest surface energy (36.52 mJ / m²), with a significantly reduced polar component, indicating the weakest surface adhesion and best water resistance. Excessive addition of zein led to a rebound in surface energy, confirming the crucial role of appropriate cross-linking in obtaining a low-energy, hydrophobic surface.

[0088] The water absorption rate test results further confirmed the influence of the aforementioned surface properties and internal structure. After soaking to saturation, PGDZ10 exhibited the lowest water absorption rate (1.27%), significantly lower than the control group without gallic acid or dialdehyde cellulose. This is mainly attributed to the formation of a dense and complete multi-layered network structure within it: moderate covalent cross-linking and gallic acid-mediated strong hydrogen bond network work together to construct an effective water barrier, significantly inhibiting the penetration and diffusion of water molecules. However, when excessive zein was added, protein molecule aggregation led to phase separation, introducing microscopic defects that disrupted the uniformity and density of the network, resulting in a significant increase in water absorption.

[0089] Table 1 Surface Energy of PGDZ Composite Bioplastics

[0090] 6. Degradability Analysis of Composite Bioplastics

[0091] The degradation performance of composite bioplastics in the natural environment was evaluated through soil burial experiments. Figure 7 The results showed that the degradation rates of the samples were relatively similar in the early stages of burial; however, the degradation differences became more significant over time, and the higher the content of zein in the composite bioplastic, the faster the degradation rate. This phenomenon is mainly attributed to the following mechanisms: On the one hand, zein, as a natural protein, can serve as a nitrogen and carbon source for microorganisms, promoting microbial colonization and bio-erosion on the material surface, thereby accelerating the degradation process. On the other hand, when the amount of zein added is too high, it is prone to molecular aggregation and formation of microbial phase separation, creating defects inside the material and providing more channels for the invasion of moisture and microorganisms.

[0092] During degradation, biomass components such as gallic acid, dialdehyde cellulose, and zein are preferentially degraded as dispersed phases, forming micropores or structural defects within the material. These defects further increase the contact area between water and microorganisms, making it easier for them to penetrate the material's interior, thus achieving an accelerated erosion effect "from the inside out." Therefore, this series of composite bioplastics, especially the high-protein samples, exhibits a higher cumulative degradation rate during long-term soil burial, demonstrating its controllable degradation as an environmentally friendly material.

[0093] 7. Biocompatibility testing of composite bioplastics

[0094] To assess the potential biotoxicity of the prepared PBAT-based culturer composite bioplastic, a systematic biocompatibility analysis was conducted through seed germination experiments, following a previously reported method (YUEH, LI X, MAI L, et al. Sustainable cottonseed protein bioplastics: Physical and chemical reinforcement, and plant seedling growth application[J]. Chemical Engineering Journal, 2024, 497: 154794.). Saturated percolates of pure PBAT, PGB10, and PGDZ10 composite bioplastics were used as culture media, with deionized water as a negative control. One hundred seeds each of three common crops—wheat, mung bean, and red bean—were selected and germinated under the same conditions for 7 days. The germination and growth processes of the three seeds in different media are as follows: Figure 8 As shown. The germination rate and average sprout length statistics on day 7 are summarized in [the table / document / etc.]. Figure 9 Data showed that the final germination rate of seeds in all leachate treatment groups was higher than 80%, with no significant difference from the control group. Simultaneously, the average sprout length of seeds in each treatment group tended to be consistent, indicating that different leachates did not significantly inhibit early seed growth. These results demonstrate that, under the conditions of this invention, the seeds of the three common crops selected could germinate and grow normally in the leachate. The prepared PBAT-based composite bioplastics (including PGB10 and PGDZ10) had no negative impact on seed germination and seedling growth during the leaching process, preliminarily demonstrating that the materials possess good biocompatibility and environmental safety, and have the potential for further application in agricultural seedling cultivation and other fields.

[0095] 8. Plant seedling cultivation using composite bioplastics

[0096] To evaluate the application potential of composite bioplastics in agricultural seedling cultivation, a 30-day cultivation experiment was conducted using mustard seedlings as model plants. Mustard seedlings of uniform growth were transplanted into PBAT, PGB10, and PGDZ10 bio-seedling containers, and then uniformly buried in 1.5-gallon polyethylene pots for soil cultivation. A blank control group (without seedling containers) served as the standard. Watering was carried out regularly during the cultivation period, and changes in plant growth morphology were observed and recorded.

[0097] from Figures 10-12It was observed that after one month of cultivation, the seedling containers remained intact without obvious cracking, and all 12 seedlings grew normally. However, comparison showed that the mustard greens cultivated in the PGDZ10 containers were significantly superior to other treatment groups in terms of leaf size and quantity. This phenomenon is mainly attributed to the zein contained in the PGDZ10 composite bioplastic. It slowly degrades in the soil environment, gradually releasing nitrogenous nutrients (NH4+). 4+ NO 3- Nitrogen, a key nutrient for plant growth, effectively promotes root development and leaf expansion, explaining the superior growth of plants in the PGDZ10 group. Furthermore, due to the lower protein content, its degradation process is slow and continuous, avoiding the risk of seedling burn caused by excessively high local nitrogen concentrations and achieving controllable nutrient supply. In summary, the PBAT-based seedling containers prepared in this invention all exhibit good agricultural applicability and durability. Among them, the PGDZ10 composite bioplastic, due to its unique component design, provides physical support while promoting plant growth through the controlled release of nitrogen nutrients, demonstrating superior application potential in the field of eco-friendly seedling containers.

[0098] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a biodegradable bioplastic composite for a cultivator, characterized in that, The biodegradable grower composite bioplastic comprises the following raw materials by weight percentage: PBAT 70%~85.5%, gallic acid 4.75%~5%, dialdehyde cellulose 4.75%~5%, and zein 5%~20%; The preparation method includes the following steps: Weigh out the required amount of PBAT, add N,N-dimethylacetamide, then add glycerin, and stir in a water bath at 70℃~90℃ until the PBAT is completely dissolved. Then add dialdehyde cellulose, gallic acid and zein in sequence, and continue stirring in a water bath at 70℃~90℃ for 2~4 hours to ensure that the components are fully mixed and cross-linked.

2. The method for preparing the biodegradable bioplastic composite cultivator according to claim 1, characterized in that, Add 4.44 mL to 5.71 mL of DMAc and 0.222 g to 0.286 g of glycerol per gram of PBAT.

3. A biodegradable cultivation container composite bioplastic, characterized in that, It is prepared by the method for preparing biodegradable cultivator composite bioplastics according to claim 1 or 2.

4. A biodegradable grower, characterized in that, The biodegradable bioplastic of the grower as described in claim 3 is heated to a molten state, poured into a silicone mold for the grower, and left to stand at room temperature until it solidifies to obtain the grower.

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