PFM-nanocellulose-hydroxyapatite synergistically reinforced biodegradable materials and applications

Abstract

The application relates to the technical field of biodegradable toy materials, and discloses a PFM-nanocellulose-hydroxyapatite synergistically reinforced biodegradable material and application, which is prepared from components such as polylactic acid, polybutylene adipate terephthalate, polypropylene carbonate, polybutylene succinate, hydrophobic pore-keeping modified plant fiber micro powder, antibacterial microcapsules, nanocellulose paste and grafting compatibilizer. In the preparation process, quaternary resin is premixed and melted, nanocellulose paste is injected laterally, and a high-vacuum in-situ devolatilization process is combined, so that liquid medium is removed in real time and in-situ dispersion of nanocellulose is realized. According to the scheme, a physical interwoven space reinforcing structure is constructed in the matrix, the toughness and the mechanical modulus of the material are synergistically improved, long-acting bacteriostasis is realized by relying on controlled release of the microcapsules, the problems of reinforcing phase agglomeration and short bacteriostasis time are solved, and the application is suitable for production of high-performance long-acting antibacterial biodegradable toys.

Description

Technical Field

[0001] This invention relates to the field of biodegradable toy materials technology, specifically to PFM-nanocellulose-hydroxyapatite synergistically enhanced biodegradable materials and their applications. Background Technology

[0002] With increasing global demands for environmental protection, the application of biodegradable plastics in toy manufacturing, packaging, and daily necessities is expanding. Currently, common biodegradable materials are typically obtained through physical blending of resins such as polylactic acid (PLA) and polybutylene adipate / terephthalate (PET). However, in practical applications, these materials often face limitations in balancing toughness and rigidity. Simply adjusting the resin component ratio often leads to a decrease in the material's flexural modulus, making it difficult to meet the strength requirements of high-performance toys.

[0003] To address these performance deficiencies, related technologies typically add plant fibers or nanoparticles to the resin matrix as reinforcing phases. However, in actual production processes, plant fibers, due to their high surface hydroxyl content, exhibit weak interfacial bonding with the hydrophobic resin matrix, easily leading to defects at the interface. Simultaneously, nanoscale reinforcing fillers, with their high surface energy, are prone to severe physical agglomeration in their dry powder state, making uniform nanoscale dispersion impossible during melt mixing. These aggregated particles become stress concentration points within the material, consequently reducing its impact resistance. Furthermore, biodegradable materials with antibacterial properties often employ the direct addition of antibacterial agents. This method results in rapid loss of antibacterial components from the material surface, making it difficult to maintain a stable antibacterial concentration over a long service life, thus limiting the application of such materials in high-performance, long-lasting, safe children's products. Summary of the Invention

[0004] The technical problem solved by this invention is that existing biodegradable materials generally face problems such as insufficient toughness, low modulus and short antibacterial effect when applied to the toy field. In addition, the nanofillers are prone to agglomeration inside the matrix, which leads to the deterioration of the overall performance of the material.

[0005] To address these shortcomings, this invention provides a PFM-nanocellulose-hydroxyapatite synergistically enhanced biodegradable material, which is prepared from the following raw materials: The composition includes 16.5-22 parts of polylactic acid, 16.5-21 parts of poly(butylene adipate / terephthalate), 11-14 parts of polypropylene carbonate, 5.5-14 parts of poly(butylene succinate), 12-20 parts of hydrophobic and pore-preserving modified plant fiber micropowder, 10-18 parts of activated hydroxyapatite-supported antibacterial microcapsules, 3-5 parts of liquid-phase in-situ dispersed nanocellulose paste, 1-1.5 parts of maleic anhydride-grafted polylactic acid, 1-1.5 parts of maleic anhydride-grafted poly(butylene adipate / terephthalate), 0.25-0.5 parts of nano-talc, 0.25-0.5 parts of nano-calcium carbonate, 0.5-1 part of antioxidant 1010, and 0-0.5 parts of polyethylene wax or stearic acid. In the processing, the liquid-phase in-situ dispersed nanocellulose paste is injected into a twin-screw extruder via a side injection method, and combined with a specific in-situ devolatilization process, the nanocellulose can maintain an in-situ dispersed state. This allows it to form a physically interwoven spatial distribution structure within the quaternary resin matrix, together with modified plant fiber micropowder and antibacterial microcapsules. This quaternary blend matrix, composed of polylactic acid, polybutylene adipate / terephthalate, polypropylene carbonate, and polybutylene succinate, enhances the interfacial bonding between different components through the bridging effect of the grafted polymer. This liquid-phase injection method effectively avoids the common agglomeration problem of dry nanocellulose powder, allowing the nanoscale flexible fibers to extend directly in the melt, thereby synergistically improving the material's impact resistance and flexural modulus, and endowing the product with long-lasting antibacterial properties.

[0006] To address the mixing characteristics of the aforementioned materials, the relevant preparation process includes the following steps: First, the four main resin components are vacuum dried at 55-60℃ to reduce the moisture content to below 0.03%, thereby obtaining a dried quaternary resin. Then, the dried quaternary resin is premixed with the remaining raw materials (excluding nanocellulose paste) in a high-low mixing mill. The resulting dry premix is ​​fed into the main feed port of a twin-screw extruder. During melt extrusion, the liquid-phase in-situ dispersed nanocellulose paste is injected via a liquid metering pump, coupled with a stepped temperature distribution. Specifically, the zone temperatures are set as follows: Zone 1 130-140℃, Zone 2 140-150℃, Zone 3 150-160℃, Zone 4 155-165℃, Zone 5 160-170℃, Zone 6 155-165℃, and the die head 150-160℃, combined with a screw speed of 250-300 rpm, ensuring that the resin melts smoothly while achieving high homogenization of each component. In particular, the lateral injection is carried out in the three zones of the multi-temperature zone barrel, and the vacuum degree of -0.08 to -0.095 MPa is maintained between the fifth and sixth zones for in-situ devolatilization. This allows the liquid medium carried by the paste to be removed in real time and completely, ensuring that the final biodegradable material is dense and free of pore defects.

[0007] To further optimize material performance, the preparation mechanism of key components was also deeply designed. In the preparation of hydrophobic and pore-preserving modified plant fiber micropowder, the fibers were subjected to 2.0-2.5 MPa saturated steam explosion treatment and dried, then pulverized at a low temperature of 0℃ to -8℃ to a D90 of 5-10 μm. Subsequently, stearic acid and γ-aminopropyltriethoxysilane were shear-mixed at 110-120℃. During this process, the mechanical energy generated by the instantaneous pressure relief peeled off the lignin coating layer on the fiber surface, exposing and keeping the internal natural micropores open. The silane coupling agent formed a strong chemical bond on the fiber surface through a condensation reaction, anchoring long-chain hydrophobic groups to the fiber skeleton. This treatment method transforms the fiber from hydrophilic to hydrophobic, which not only improves the compatibility of this component with non-polar resins, but also utilizes the preserved microporous structure to form lightweight reinforcing centers within the material, helping to improve the energy absorption capacity of the composite material.

[0008] The preparation of nanocellulose paste focuses on maintaining the swelling state of the fibers in a liquid phase environment. Nanocellulose is modified in an ethanol system using a silane coupling agent, and the resulting wet gel is then infused with tributyl acetylacetate and polyethylene glycol. The process utilizes the steric hindrance effect of plasticizer molecules to construct a physical barrier layer on the nanofiber surface, effectively preventing secondary aggregation of nanocellulose due to hydrogen bonding. When the paste enters the extruder, the nanofibers can rapidly diffuse into the molten resin, achieving true in-situ dispersion. Furthermore, activated hydroxyapatite-supported antibacterial microcapsules are calcined at 650-750℃ to expand the pores, giving the carrier a high specific surface area, and then aspirating the antibacterial liquid under vacuum. This encapsulation mechanism, combined with the final wax or calcium stearate coating, achieves deep embedding of the antibacterial components within the mesopores. During toy use, the antibacterial components are slowly released through physical concentration differences, thus prolonging the antibacterial effect.

[0009] Based on the aforementioned synergistic enhancement effect, the biodegradable materials provided by this solution have broad application prospects in fields such as the preparation of long-lasting antibacterial biodegradable toys.

[0010] This invention provides a PFM-nanocellulose-hydroxyapatite synergistically reinforced biodegradable material and its application. It possesses the following beneficial effects: 1. This invention enhances the overall mechanical properties of the material through the synergistic effect of a quaternary resin matrix and a multi-level reinforcing structure. Nanocellulose enters the molten matrix in the liquid phase, forming a deep physical interweaving with the pore-preserving plant fiber micropowder. Under external impact, this spatial arrangement effectively dissipates energy and prevents crack propagation. Compared to traditional single-component or simple filler materials, this design resolves the contradiction between toughness and rigidity in biodegradable plastics, enabling the product to maintain high strength while possessing excellent impact resistance.

[0011] 2. This invention employs in-situ liquid-phase dispersion and lateral injection processes to solve the problem of agglomeration of the nano-reinforcing phase during melt mixing. By injecting the paste into a specific temperature zone of a twin-screw extruder and combining it with high-vacuum devolatilization, the solvent can be completely vaporized and discharged in a short time, thereby ensuring that the nanocellulose is uniformly distributed in the matrix. This in-situ dispersion ensures the compactness of the material structure, avoids performance fluctuations caused by solvent residue or filler accumulation, and improves the stability of the preparation process.

[0012] 3. The activated, loaded antibacterial microcapsules of this invention endow the product with a long-lasting and stable antibacterial function. Utilizing the high specific surface area of ​​mesoporous hydroxyapatite to adsorb antibacterial components, and combined with a surface coating process, the antibacterial factors are slowly released during material use due to concentration differences. This controlled release mechanism ensures that the biodegradable toy retains a significant antibacterial effect over a longer period, meeting the hygiene and safety requirements for children's products. Attached Figure Description

[0013] Figure 1 This is a comparative test diagram of the water contact angle of the modified plant fiber micropowder of the present invention; Figure 2 This is a diagram showing the apparent density distribution of the biodegradable material of the present invention after molding; Figure 3 This is a graph showing the storage modulus and loss factor of the biodegradable material of the present invention as a function of temperature. Figure 4 This is a biaxial comparison graph of the melt flow rate and yellow index of the biodegradable material of the present invention; Figure 5 This is a comprehensive comparison chart of various mechanical property parameters of the biodegradable material of the present invention; Figure 6 The bar chart shows the inhibition rate of the biodegradable material of this invention against Escherichia coli and Staphylococcus aureus. Figure 7 This is a graph showing the cumulative degradation rate of the biodegradable material of the present invention under controlled composting conditions. Figure 8 This is a graph showing the correlation between the migration of active components in the biodegradable material of this invention and the retention rate of its wash resistance and antibacterial properties. Detailed Implementation

[0014] To enable those skilled in the art to better understand the present invention, the present invention will be further described in detail below with reference to specific embodiments. Obviously, the described embodiments are merely some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0015] The main raw materials and reagents used in the following examples and comparative examples have the following sources and specifications. Reagents not specifically mentioned are all commercially available analytical grade or higher grade products.

[0016] Polylactic acid (PLA) is a homopolymer with a number average molecular weight of 100,000-160,000, CAS number 26100-51-6. Polybutylene adipate / terephthalate (PBAT) is a random copolymer with a number average molecular weight of 60,000-110,000, CAS number 55231-08-8. Polypropylene carbonate (PPC) is an alternating copolymer with a number average molecular weight of 80,000-120,000 and a glass transition temperature of 35-45℃, CAS number 25511-85-7. Polybutylene succinate (PBS) is a homopolymer with a number average molecular weight of 70,000-100,000 and a melting point of 110-115℃, CAS number 25550-51-0. Maleic anhydride-grafted polylactic acid uses a copolymer with a grafting rate of 1.0%–1.5%, CAS number 252035-71-3. Maleic anhydride-grafted poly(adipate) / butylene terephthalate uses a copolymer with a grafting rate of 0.8%–1.2%, CAS number 63641-63-4.

[0017] Plant fiber micro powder, made from corn stalk powder, bamboo powder, or rice husk powder, with a particle size of 40-60 mesh and a moisture content of less than 8%. Nanocellulose, made from a whisker-like cellulose gel dispersion with a solid content of 2%-5%, with fiber diameters of 20-50 nm and lengths of 500-1000 nm (CAS number 9004-34-6). Hydroxyapatite, a porous amorphous powder with a D50 of 5-10 μm (CAS number 1306-06-5). Tea polyphenols, made from a powder with an epigallocatechin gallate content greater than 98% (CAS number 84650-60-2). Chitosan quaternary ammonium salt, made from 2-hydroxypropyltrimethylammonium chloride chitosan with a degree of deacetylation greater than 90% and a degree of quaternization of 80%-90% (CAS number 84082-64-4). ε-polylysine is a homopolymer hydrochloride with a degree of polymerization of 25-35, CAS number 28211-04-3.

[0018] Tributyl acetylacetic acid, CAS number 77-90-7. Polyethylene glycol, number average molecular weight 400-600, CAS number 25322-68-3. γ-aminopropyltriethoxysilane (silane coupling agent KH550), CAS number 919-30-2. Stearic acid, CAS number 57-11-4. Polyethylene wax, dropping melting point 100-110℃, CAS number 9002-88-4. Calcium stearate, CAS number 1592-23-0. Nano talc, D50 0.5-1.0μm, CAS number 14807-96-6. Nano calcium carbonate, primary particle size 40-80nm, CAS number 471-34-1. Pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid] (Antioxidant 1010), CAS No. 6683-19-8.

[0019] Preparation Examples 1-6: Preparation Example 1: This preparation example provides a method for preparing hydrophobic and pore-preserving modified plant fiber micro powder, including the following steps: corn stalks are cut to 1-2 cm, placed in a steam explosion tank, 2.0 MPa saturated steam is introduced, pressure is maintained for 60 s and then instantly released to atmospheric pressure, washed with water until neutral, and dried with hot air at 75℃ until the moisture content is less than 3%; a liquid nitrogen-assisted low-temperature airflow pulverizer is used to pulverize the powder to a particle size D90 of 10 μm at -8℃; the pulverized micro powder is put into a high-speed mixer, and 1% stearic acid and 0.5% γ-aminopropyltriethoxysilane by fiber weight are added, the mixer jacket temperature is controlled at 110℃, the speed is set at 1000 rpm, and high-speed shearing and mixing is performed for 30 min, and the powder is cooled and sieved to obtain the final product.

[0020] Preparation Example 2: This preparation example provides a method for preparing hydrophobic and pore-preserving modified plant fiber micro powder, including the following steps: rice husks are cut to 1-2 cm, placed in a steam explosion tank, 2.5 MPa saturated steam is introduced, pressure is maintained for 90 s and then instantly released to atmospheric pressure, washed with water until neutral, and dried with hot air at 85℃ until the moisture content is less than 3%; a liquid nitrogen-assisted low-temperature airflow pulverizer is used to pulverize the powder at 0℃ to a particle size D90 of 5 μm; the pulverized micro powder is put into a high-speed mixer, and 3% stearic acid and 1% γ-aminopropyltriethoxysilane by fiber weight are added. The jacket temperature of the mixer is controlled at 120℃, the rotation speed is set at 1500 rpm, and high-speed shearing and mixing is performed for 40 min. After cooling, the powder is sieved to obtain the final product.

[0021] Preparation Example 3: This preparation example provides a method for preparing liquid-phase in-situ dispersed nanocellulose paste, including the following steps: dispersing nanocellulose raw materials in anhydrous ethanol to prepare a suspension with a mass concentration of 3%, and ultrasonically dispersing it at 300W power for 30 min; heating to 55℃, slowly adding γ-aminopropyltriethoxysilane at 2% of the dry weight of nanocellulose, and stirring at a constant temperature for 1.5 h; centrifuging the reaction solution at 8000 rpm for 15 min, discarding the supernatant, and collecting the wet gel containing ethanol; taking 10 g of nanocellulose wet gel by dry weight, adding 3 g of acetylthiol tributyl citrate and 2 g of polyethylene glycol, and performing liquid-phase milling using a three-roll mill for 20 min to obtain liquid-phase in-situ dispersed nanocellulose paste.

[0022] Preparation Example 4: This preparation example provides a method for preparing liquid-phase in-situ dispersed nanocellulose paste, including the following steps: dispersing nanocellulose raw materials in anhydrous ethanol to prepare a suspension with a mass concentration of 5%, and ultrasonically dispersing it at 500W power for 45min; heating to 65℃, slowly adding 5% by dry weight of γ-aminopropyltriethoxysilane to the nanocellulose, and stirring at a constant temperature for 2.5h; centrifuging the reaction solution at 10000rpm for 20min, discarding the supernatant, and collecting the wet gel containing ethanol; taking 10g of nanocellulose wet gel by dry weight, adding 5g of acetylthiol tributyl citrate and 3g of polyethylene glycol to it, and performing liquid-phase milling using a three-roll mill for 30min to obtain liquid-phase in-situ dispersed nanocellulose paste.

[0023] Preparation Example 5: This preparation example provides a method for preparing activated hydroxyapatite-supported antibacterial microcapsules, including the following steps: hydroxyapatite powder is placed in a muffle furnace and calcined at 650°C for 2 hours at a rate of 5°C / min, followed by air jet milling to a D50 of 2 μm to obtain mesoporous activated hydroxyapatite; 5 g of tea polyphenols, 10 g of chitosan quaternary ammonium salt, and 5 g of ε-polylysine are dissolved in 200 mL of deionized water; 50 g of mesoporous activated hydroxyapatite is placed in a vacuum impregnation reactor, vacuumed to -0.08 MPa, maintained for 15 min, and then the above antibacterial aqueous solution is drawn in. After restoring to normal pressure, the mixture is stirred for 30 min to ensure complete co-assembly within the pores; the loaded slurry is dried under reduced pressure at 45°C to constant weight, then placed in a low-speed mixer, 5 g of polyethylene wax is added, the temperature is raised to 105°C, and the mixture is mixed at a low speed of 300 rpm for 10 min, followed by cooling and pulverization to obtain the final product.

[0024] Preparation Example 6: This preparation example provides a method for preparing activated hydroxyapatite-supported antibacterial microcapsules, including the following steps: hydroxyapatite powder is placed in a muffle furnace and calcined at 750°C for 3 hours at a rate of 10°C / min, followed by air jet milling to a D50 of 4 μm to obtain mesoporous activated hydroxyapatite; 10 g of tea polyphenols, 20 g of chitosan quaternary ammonium salt, and 10 g of ε-polylysine are dissolved in 400 mL of deionized water; 100 g of mesoporous activated hydroxyapatite is placed in a vacuum impregnation reactor, vacuumed to -0.09 MPa, maintained for 20 minutes, and then the above antibacterial aqueous solution is drawn in. After restoring to normal pressure, the mixture is stirred for 60 minutes to ensure complete co-assembly within the pores; the loaded slurry is dried under reduced pressure at 55°C to constant weight, then placed in a low-speed mixer, 10 g of calcium stearate is added, the temperature is raised to 115°C, and the mixture is mixed at a low speed of 500 rpm for 20 minutes. After cooling and pulverizing, the product is obtained.

[0025] Examples 1-5: Example 1: This example provides a method for preparing a PFM / nanocellulose / hydroxyapatite synergistically reinforced multifunctional biodegradable toy material, comprising the following steps: Weigh 22 parts by weight of polylactic acid, 16.5 parts by weight of poly(adipate adipate / butylene terephthalate), 11 parts by weight of polypropylene carbonate, and 5.5 parts by weight of polybutylene succinate. Place the above quaternary resin in a vacuum drying oven and dry at 55°C for 10 hours until the moisture content is less than 0.03%. Weigh 20 parts by weight of the hydrophobic pore-preserving modified plant fiber micropowder obtained in Preparation Example 1, 18 parts by weight of the activated hydroxyapatite-supported antibacterial microcapsules obtained in Preparation Example 5, 1 part by weight of maleic anhydride-grafted polylactic acid, 1 part by weight of maleic anhydride-grafted poly(adipate adipate / butylene terephthalate), 0.5 parts by weight of nano-talc, 0.5 parts by weight of nano-calcium carbonate, 0.5 parts by weight of antioxidant 1010, and 0.5 parts by weight of polyethylene wax. The dried quaternary resin and the weighed auxiliary components were added to a high-low mixer and premixed at 50°C and 600 rpm for 10 min to obtain a dry premix. A co-rotating twin-screw extruder with a length-to-diameter ratio of 60:1 was used for melt extrusion. The temperatures of each zone of the barrel were set as follows: Zone 1 130-140°C, Zone 2 140-150°C, Zone 3 150-160°C, Zone 4 155-165°C, Zone 5 160-170°C, Zone 6 155-165°C, and Die Head 150-160°C. The dry premix was added through the main feed port, and simultaneously, the nanocellulose paste obtained in Preparation Example 3 (equivalent to 3 parts by dry basis nanocellulose weight) was injected laterally into Zone 3 of the extruder using a liquid metering pump. A high-vacuum interface was opened between Zones 5 and 6 of the extruder, maintaining a vacuum of -0.09 MPa for in-situ liquid-phase devolatilization. By controlling the screw speed at 250 rpm, the extruded melt is pelletized by a water ring and then vacuum dried at 55°C for 6 hours to obtain biodegradable toy material.

[0026] Example 2: This example provides a method for preparing a PFM / nanocellulose / hydroxyapatite synergistically enhanced multifunctional biodegradable toy material, including the following steps: Weigh 21 parts of polylactic acid, 18 parts of poly(adipate adipate / butylene terephthalate), 12 parts of polypropylene carbonate, and 9 parts of poly(butylene succinate) by weight. Place the above quaternary resin in a vacuum drying oven and dry at 60°C for 8 hours until the moisture content is less than 0.03%. Weigh 16 parts of the hydrophobic pore-preserving modified plant fiber micropowder obtained in Preparation Example 1, 15 parts of the activated hydroxyapatite-supported antibacterial microcapsules obtained in Preparation Example 6, 1.25 parts of maleic anhydride-grafted polylactic acid, 1.25 parts of maleic anhydride-grafted poly(adipate adipate / butylene terephthalate), 0.5 parts of nano-talc, 0.5 parts of nano-calcium carbonate, 1 part of antioxidant 1010, and 0.5 parts of stearic acid. The dried quaternary resin and the weighed auxiliary components were added to a high-low mixer and premixed at 800 rpm for 12 min at 45°C to obtain a dry premix. A co-rotating twin-screw extruder with a length-to-diameter ratio of 64:1 was used for melt extrusion. The temperatures of each zone of the barrel were set as follows: Zone 1 130-140°C, Zone 2 140-150°C, Zone 3 150-160°C, Zone 4 155-165°C, Zone 5 160-170°C, Zone 6 155-165°C, and Die Head 150-160°C. The dry premix was added through the main feed port, and simultaneously, the nanocellulose paste obtained in Preparation Example 3 (equivalent to 4 parts by dry basis nanocellulose weight) was injected laterally into Zone 3 of the extruder using a liquid metering pump. A high-vacuum interface was opened between Zones 5 and 6 of the extruder to maintain a vacuum of -0.095 MPa for in-situ liquid-phase devolatilization. The screw speed is controlled at 280 rpm. After the extruded melt is stretched, water-cooled and pelletized, it is vacuum dried at 60°C for 8 hours to obtain biodegradable toy material.

[0027] Example 3: This example provides a method for preparing a PFM / nanocellulose / hydroxyapatite synergistically reinforced multifunctional biodegradable toy material, including the following steps: Weigh 21 parts by weight of polylactic acid, 21 parts by weight of poly(adipate adipate / butylene terephthalate), 14 parts by weight of polypropylene carbonate, and 14 parts by weight of poly(butylene succinate). Place the above quaternary resin in a vacuum drying oven and dry at 55°C for 12 hours until the moisture content is less than 0.03%. Weigh 12 parts by weight of the hydrophobic and pore-preserving modified plant fiber micropowder obtained in Preparation Example 2, 10 parts by weight of the activated hydroxyapatite-supported antibacterial microcapsules obtained in Preparation Example 5, 1.5 parts by weight of maleic anhydride-grafted polylactic acid, 1.5 parts by weight of maleic anhydride-grafted poly(adipate adipate / butylene terephthalate), 0.25 parts by weight of nano-talc powder, 0.25 parts by weight of nano-calcium carbonate, 1 part by weight of antioxidant 1010, and 0.5 parts by weight of polyethylene wax. The dried quaternary resin and the weighed auxiliary components were added to a high-low mixer and premixed at 500 rpm for 15 min at 55°C to obtain a dry premix. A co-rotating twin-screw extruder with a length-to-diameter ratio of 60:1 was used for melt extrusion. The temperatures of each zone of the barrel were set as follows: Zone 1 130-140°C, Zone 2 140-150°C, Zone 3 150-160°C, Zone 4 155-165°C, Zone 5 160-170°C, Zone 6 155-165°C, and Die Head 150-160°C. The dry premix was added through the main feed port, and simultaneously, the nanocellulose paste obtained in Preparation Example 4 (equivalent to 3 parts by dry basis nanocellulose weight) was injected laterally into Zone 3 of the extruder using a liquid metering pump. A high-vacuum interface was opened between Zones 5 and 6 of the extruder, maintaining a vacuum of -0.08 MPa for in-situ liquid-phase devolatilization. By controlling the screw speed at 300 rpm, the extruded melt is pelletized by a water ring and then vacuum dried at 50°C for 8 hours to obtain biodegradable toy material.

[0028] Example 4: This example provides a method for preparing a PFM / nanocellulose / hydroxyapatite synergistically reinforced multifunctional biodegradable toy material, including the following steps: Weigh 21 parts by weight of polylactic acid, 21 parts by weight of poly(adipate adipate / butylene terephthalate), 14 parts by weight of polypropylene carbonate, and 14 parts by weight of poly(butylene succinate). Place the above quaternary resin in a vacuum drying oven and dry at 60°C for 10 hours until the moisture content is less than 0.03%. Weigh 12 parts by weight of the hydrophobic and pore-preserving modified plant fiber micropowder obtained in Preparation Example 2, 12 parts by weight of the activated hydroxyapatite-supported antibacterial microcapsules obtained in Preparation Example 5, 1 part by weight of maleic anhydride-grafted polylactic acid, 1 part by weight of maleic anhydride-grafted poly(adipate adipate / butylene terephthalate), 0.25 parts by weight of nano-talc, 0.25 parts by weight of nano-calcium carbonate, and 0.5 parts by weight of antioxidant 1010. The dried quaternary resin and the weighed auxiliary components were added to a high-low mixer and premixed at 50°C and 600 rpm for 10 min to obtain a dry premix. A co-rotating twin-screw extruder with a length-to-diameter ratio of 64:1 was used for melt extrusion. The temperatures of each zone of the barrel were set as follows: Zone 1 130-140°C, Zone 2 140-150°C, Zone 3 150-160°C, Zone 4 155-165°C, Zone 5 160-170°C, Zone 6 155-165°C, and Die Head 150-160°C. The dry premix was added through the main feed port, and simultaneously, the nanocellulose paste obtained in Preparation Example 3 (equivalent to 3 parts by dry basis nanocellulose weight) was injected laterally into Zone 3 of the extruder using a liquid metering pump. A high vacuum interface was opened between Zones 5 and 6 of the extruder, maintaining a vacuum of -0.09 MPa for in-situ liquid-phase devolatilization. The screw speed is controlled at 250 rpm. After the extruded melt is stretched, water-cooled, and pelletized, it is vacuum-dried at 60°C for 6 hours to obtain biodegradable toy material.

[0029] Example 5: This example provides a method for preparing a PFM / nanocellulose / hydroxyapatite synergistically enhanced multifunctional biodegradable toy material, comprising the following steps: Weigh 16.5 parts by weight of polylactic acid, 16.5 parts by weight of poly(adipate-coated terephthalate), 11 parts by weight of polypropylene carbonate, and 11 parts by weight of poly(butylene succinate). Place the above quaternary resin in a vacuum drying oven and dry at 55°C for 12 hours until the moisture content is less than 0.03%. Weigh 18 parts by weight of the hydrophobic and pore-preserving modified plant fiber micropowder obtained in Preparation Example 1, 17 parts by weight of the activated hydroxyapatite-supported antibacterial microcapsules obtained in Preparation Example 6, 1.5 parts by weight of maleic anhydride-grafted polylactic acid, 1.5 parts by weight of maleic anhydride-grafted poly(adipate-coated terephthalate), 0.5 parts by weight of nano-talc, 0.5 parts by weight of nano-calcium carbonate, and 1 part by weight of antioxidant 1010. The dried quaternary resin and the weighed auxiliary components were added to a high-low mixer and premixed at 700 rpm for 12 min at 55°C to obtain a dry premix. A co-rotating twin-screw extruder with a length-to-diameter ratio of 60:1 was used for melt extrusion. The temperatures of each zone of the barrel were set as follows: Zone 1 130-140°C, Zone 2 140-150°C, Zone 3 150-160°C, Zone 4 155-165°C, Zone 5 160-170°C, Zone 6 155-165°C, and Die Head 150-160°C. The dry premix was added through the main feed port, and simultaneously, the nanocellulose paste obtained in Preparation Example 4 (equivalent to 5 parts by dry basis nanocellulose weight) was injected laterally into Zone 3 of the extruder using a liquid metering pump. A high-vacuum interface was opened between Zones 5 and 6 of the extruder to maintain a vacuum of -0.095 MPa for in-situ liquid-phase devolatilization. The screw speed is controlled at 280 rpm. After the extruded melt is pelletized by a water ring, it is vacuum dried at 55°C for 8 hours to obtain biodegradable toy material.

[0030] Comparative Examples 1-4: Comparative Example 1: Compared to Example 2, the difference lies in replacing polybutylene succinate in the formulation with an equal amount of polyglycolic acid, and increasing the temperature of each zone of the twin-screw extruder to 178°C; all other aspects remain the same. The effect highlighted by the comparison needs to meet the following conditions: replacing high-melting-point polyglycolic acid with polybutylene succinate (melting point range 110-115°C) constructs a quaternary system of polylactic acid, polybutylene adipate / terephthalate, polypropylene carbonate, and polybutylene succinate. Each component of this system exhibits good melt rheological compatibility within a processing window of 145-165°C, completely avoiding the "zipper-like" decomposition and decarbonation of polypropylene carbonate at high temperatures. Meanwhile, the quaternary system exhibits a stepped degradation rate in the natural environment. Polypropylene carbonate preferentially degrades to form microchannels, followed by rapid composting and hydrolysis of polybutylene succinate, which in turn accelerates the degradation of poly(adipic acid / butylene terephthalate). Finally, it promotes the disintegration of polylactic acid by weakening the skeleton.

[0031] Comparative Example 2: Compared to Example 2, the difference lies in the direct substitution of an equal amount of unmodified corn stalk powder (without stearic acid and γ-aminopropyltriethoxysilane) for the hydrophobic, pore-preserving modified plant fiber powder; all other aspects remain the same. The effect highlighted by this comparison requires that the surface properties of the plant fiber powder be transformed into a strongly hydrophobic, low-surface-energy state through grafting with stearic acid and silane coupling agents. During twin-screw blending shearing, a strong surface tension repulsion is generated between the molten polymer matrix and the microporous interface. According to the principle of capillary wetting fluid dynamics, the polar melt cannot overcome the interfacial tension to enter the hydrophobic micropores. Thus, within the macroscopically dense plastic matrix, the three-dimensional porous cellular framework of the plant fiber is preserved in situ at the microscopic level, achieving a balance between overall lightweighting and cushioning toughness.

[0032] Comparative Example 3: Compared to Example 2, the difference is that a liquid-phase paste is not prepared. Instead, an equal amount of nanocellulose suspension is vacuum-dried into dry powder and added together with the matrix resin through the main feed port. All other aspects remain the same. The effect highlighted by the comparison needs to meet the following requirements: a liquid-phase paste-in-situ devolatilization process is adopted, and the nanocellulose does not undergo a drying process throughout the entire process from synthesis and exfoliation to feeding. By adding the plasticizer tributyl acetylacetic acid and the antistatic agent polyethylene glycol to pre-displace the solvent in the liquid phase, the plasticizer and polyethylene glycol molecules insert into the nanocellulose chains, forming steric hindrance isolation. After the paste is pumped into the extruder, it is exfoliated in situ under the strong shearing action of the polymer melt. The low-boiling-point solvent in the paste instantly vaporizes and is removed by the high-vacuum section, while the nanocellulose remains uniformly shaped in the polymer network at its original one-dimensional nanoscale, eliminating stress concentration defects and constructing a one-dimensional rigid nano-reinforced network.

[0033] Comparative Example 4: Compared to Example 2, the difference lies in the absence of mesoporous activated hydroxyapatite for loading and wax sealing. Equal amounts of a mixture of tea polyphenols, chitosan quaternary ammonium salt, and ε-polylysine powder were directly added from the main feed inlet; all other aspects remained the same. The comparative effect highlights the following: using mesoporous activated hydroxyapatite as a rigid inorganic carrier, the bio-antibacterial agent is first loaded into the micropores, and then surface physical sealing is performed using low-melting-point polyethylene wax or calcium stearate. Under extrusion conditions at 160°C, although the wax layer melts, the inorganic ceramic framework of hydroxyapatite effectively blocks the strong shear heat generated by the screw, acting as a thermal shield to prevent the oxidation and carbonization of tea polyphenols. Simultaneously, the physical spatial isolation mechanism reduces the collision probability between the amino groups of the polylysine macromolecules and the maleic anhydride-grafted polylactic acid macromolecules in the external melt, completely inhibiting harmful cross-linking side reactions. After the product is formed, moisture slowly dissolves the antibacterial components through penetration, achieving a slow-release migration through the pores.

[0034] Test Examples 1-7: Test Example 1: Verification of the hydrophobic and pore-retaining mechanism and lightweight effect of plant fibers.

[0035] According to the appendix Figure 1 Appendix Figure 2 According to Table 1, contact angle test samples were prepared using the powder compression method. 2.5g each of unmodified raw corn stalk powder, modified powder obtained in Preparation Example 1, and modified powder obtained in Preparation Example 2 were placed in the mold of a powder compression machine and pressed at 15MPa for 2 minutes to obtain smooth, disc-shaped sheets.

[0036] The wettability of the pressed tablets was determined using a static contact angle meter. 2.0 μL of deionized water was dropped onto the tablet surface using a microsyringe. After the droplet stabilized for 5 seconds, an image was captured, and the contact angle between the droplet and the powder tablet interface was read using a goniometric method. Five parallel measurements were taken at different locations for each sample, and the arithmetic mean was calculated.

[0037] The apparent density of the material was measured. Injection-molded standard specimens prepared in Examples 1 to 5 and Comparative Example 2 were used, and surface flash and impurities were removed. The specimens were then conditioned for 48 hours in a constant temperature and humidity environment of 23°C and 50% relative humidity.

[0038] The test was conducted using a high-precision density balance based on the principle of the immersion method. An appropriate amount of anhydrous ethanol was poured into a measuring cup as the immersion solution, and the mass of the sample in the air was recorded. Then, the sample was completely immersed in anhydrous ethanol, and the suspended mass was read. The actual temperature of the liquid during the test was recorded and substituted into the density calculation formula. Five samples were taken from each batch for testing, and the average value was taken.

[0039] Table 1: Contact angle of hydrophobic modified powder and apparent density test data of materials in each example and comparative example.

[0040] Note: "-" in the table indicates that the performance test is not applicable to the corresponding sample, or that it was not tested in the experiment.

[0041] Appendix Figure 1 The results of the water contact angle test for the micronized powder demonstrate the difference in wettability between the unmodified micronized powder and the powders from Preparation Example 1 and Preparation Example 2; (See attached image) Figure 2 To measure the apparent density of the molded material, the changes in macroscopic density of Examples 1 to 5 were compared with those of Comparative Example 2, which used unmodified micropowder directly.

[0042] According to the data in Table 1, the surface of the unmodified virgin corn stalk powder contains a large number of natural free hydroxyl groups. During the tableting wetting test, water droplets spread rapidly, with a water contact angle of only 42.6°, exhibiting extremely strong hydrophilicity and easy capillary penetration. In contrast, the water contact angles of the micropowders from Preparation Examples 1 and 2, which underwent high-temperature shear synergistic treatment with stearic acid and silane coupling agents, jumped to 124.3° and 129.8°, respectively. This fundamental change in the physicochemical properties of the powder interface confirms that the low surface energy alkyl long-chain coating layer has been successfully grafted onto the micropowder surface. The transformation from a hydrophilic to a strongly hydrophobic state constitutes the basic condition for achieving the pore-preserving effect in subsequent blending processing.

[0043] How this change in powder surface energy translates into performance advantages of the macroscopic composite material can be directly verified by comparing the apparent density measurements of the materials in Examples 1 and 2 with those in Comparative Example 2. Under similar quaternary resin ratios and extrusion injection molding processes, the apparent density distribution of the materials in Examples 1 to 5 is 1.041 g / cm³. 3 Up to 1.082 g / cm 3 Within a relatively narrow range. Comparative Example 2, due to the direct use of uncoated natural plant micropowder, achieved an apparent density of 1.235 g / cm³ in its final formed specimen. 3 Routine rheological experiments revealed that polar polymer melts exhibit a strong tendency to penetrate and encapsulate under the high-temperature, high-shear action of a twin-screw extruder. In Comparative Example 2, the hydrophilic micropores of the unmodified fibers were completely wetted and filled by the polylactic acid and polyester resin melts due to strong capillary suction, resulting in the complete disappearance of micropores within the material and overall densification. In the example system, the strong hydrophobic properties of the powder surface created interfacial tension repulsion between the powder and the polar resin melt, preventing the macromolecular melt from overcoming polar resistance and penetrating into the micrometer-scale pores. After high-pressure injection molding and cooling solidification, the original three-dimensional porous cellular structure of the plant fibers was preserved in situ within the matrix. This not only reduced the macroscopic density of the material by approximately 13% to 15% compared to the comparative example, achieving structural lightweighting, but these intact microscopic chambers also function as elastic stress-absorbing units within the dense polymer network, providing microscopic deformation space for the material to resist external impact loads.

[0044] Test Example 2: Verification of in-situ dispersion mechanism and dynamic rheological properties of liquid phase.

[0045] According to the appendix Figure 3 Table 2 shows the rheological characteristics of the nanocellulose pastes obtained in Preparation Examples 3 and 4. A suitable amount of paste was placed on the test plate of a rotational rheometer, and under constant temperature conditions of 25°C, a shear rate of 10 s⁻¹ was set. -1After 3 minutes of stable operation, the apparent viscosity value is read to evaluate the processability of the paste by side injection into the extruder via a liquid metering pump.

[0046] Prepare dynamic thermomechanical analysis test strips. Take the dried pellets prepared in Examples 1 to 5 and Comparative Example 3, and inject them into standard rectangular strips with a length of 50 mm, a width of 10 mm, and a thickness of 3 mm using a micro injection molding machine at a melt temperature of 165 °C. After injection molding, the strips are left to stand for 24 hours in an environment of 23 °C and 50% relative humidity to eliminate the internal residual stress generated during the injection molding process.

[0047] The viscoelastic behavior and phase transition process of composite materials were tested using a dynamic thermomechanical analyzer. A double cantilever beam test fixture was used to fix the specimen, with a span of 35 mm. The test vibration frequency was fixed at 1 Hz, and the applied dynamic strain was 0.1%. Under liquid nitrogen assistance, the test chamber was continuously programmed to scan from -20℃ to 90℃ at a heating rate of 3℃ / min. The instrument control software recorded and exported the evolution data of storage modulus and loss factor with temperature in real time, and the glass transition temperature of each material system was extracted based on the peak temperature corresponding to the loss factor curve.

[0048] Table 2: Viscosity of nanocellulose paste and dynamic thermomechanical property test data of composite materials in each example and comparative example

[0049] Note: "-" in the table indicates that the performance test is not applicable to the corresponding sample, or that it was not tested in the experiment.

[0050] Appendix Figure 3 The figure uses a one-dimensional coordinate system to comprehensively illustrate the viscoelastic changes during the temperature scanning process. The solid lines in the figure correspond to the evolution trajectories of the storage modulus (left main coordinate axis) and loss factor (right secondary coordinate axis) in Example 2, while the dashed lines represent the corresponding parameter changes in Comparative Example 3, which directly adds dry powdered nanocellulose. This intuitively reflects the constraint ability of the nanophase dispersion state on the multi-segment motion of polymers.

[0051] According to the data in Table 2, the nanocellulose suspensions prepared in Preparation Examples 3 and 4, after the introduction of acetylthiolitic tributyl citrate and polyethylene glycol, successfully transformed into homogeneous pastes with apparent viscosities of 15.4 Pa·s and 28.7 Pa·s, respectively. This typical pseudoplastic fluid characteristic fully meets the kinetic requirements of the side-pumped feeding of the twin-screw extruder. In conventional polymer-based nanocomposite blending processes, thorough drying and dehydration of the solvent is often unavoidable, but this easily leads to irreversible agglomeration of one-dimensional nanoscale fibers due to strong hydrogen bonds formed by the proximity of a large number of free hydroxyl groups. The test data of Comparative Example 3 precisely reflects this engineering reality. Due to the direct addition of dried nanocellulose powder, the original whisker-like fibers agglomerated into macroscopically sized microparticle defects in the melt. These agglomerates not only cannot bear and transmit external stress, but also become stress concentration points inside the matrix, resulting in a storage modulus of only 1853.7 MPa for Comparative Example 3 at 25°C. When the temperature crosses the glass transition region and reaches 60°C, as the polymer chains in the amorphous region are completely thawed, the resin matrix, which has lost the support of the nano-framework, softens severely, and the storage modulus drops precipitously to 312.4 MPa.

[0052] In contrast to this performance degradation, the nano-reinforced microstructure established by the in-situ liquid-phase devolatilization process in the example system is as follows: The nanocellulose maintains a solvated and isolated state throughout the process of dispersion from the alcohol phase to the premixed liquid phase system. With the high-vacuum devolatilization, the low-boiling-point solvent is instantly removed, and the high aspect ratio nanocellulose is rapidly wetted by the high-shear melt and in-situ fixed within the molecular network of polylactic acid and polyester. This rigid one-dimensional network unfolded at the molecular scale forms dense physical entanglement and hydrogen bond cross-linking points with the matrix macromolecules. This not only causes the storage modulus of Example 2 to soar to 2718.6 MPa at room temperature, but more importantly, it maintains a rigid output of 1042.1 MPa even at a high temperature of 60°C, endowing the biodegradable toy material with excellent heat resistance and dimensional stability. Further observation of the glass transition temperature corresponding to the peak loss factor shows that the Tg of Example 2 is delayed by nearly 11°C compared to Comparative Example 3. This obvious rightward shift in phase transition temperature provides conclusive evidence from a thermodynamic perspective, proving that the uniformly interwoven nanocellulose forms a continuous percolation network, which greatly enhances the energy barrier of polymer chain segments under heated conditions, thereby effectively transforming microscopic nanoscale properties into macroscopic thermodynamic stability through interfacial constraints.

[0053] Test Example 3: Verification of the mechanism of microcapsule thermal shielding and anti-crosslinking thermo-oxidative aging.

[0054] According to the appendix Figure 4According to Table 3, test conditions were set according to GB / T3682 standard, and the rheological parameters of each formulation system were measured using a melt flow rate meter. The experimental subjects were the granular samples of Examples 1 to 5 and Comparative Example 4 after extrusion granulation and thorough drying. The barrel temperature was preheated to 190°C, 5 grams of test granules were loaded, a standard load of 2.16 kg was applied for compaction and degassing, and preheating was carried out for 4 minutes. The automatic cutting device was turned on, and extruded strips were cut at fixed time intervals. The mass of the cut sections was collected and weighed, and the standard melt flow rate was calculated.

[0055] A standard color chart for surface spectral determination was prepared. The dried granules from the examples and comparative examples were injection molded into flat test blocks with a thickness of 2 mm using a precision injection molding machine at 165°C.

[0056] Yellow index testing was conducted using a benchtop spectrophotometer. The instrument was baseline-calibrated using a standard white plate. A D65 light source and a 10° field of view were selected as the testing conditions. The color plate was placed flat against the test aperture, and chromaticity data including specular reflection was recorded. The instrument software directly calculated and output the yellow index. Five different color plates were randomly selected from each formulation, and their arithmetic mean was used as the final evaluation criterion.

[0057] Table 3: Melt flow rate and yellow index test data for each embodiment and comparative example

[0058] Appendix Figure 4 The differences between different sample systems are visually displayed using a dual vertical axis. The solid line with black solid squares corresponds to the left axis, representing the change in melt flow rate of each formulation during processing. The dashed line with white hollow circles corresponds to the right axis, reflecting the apparent yellow index of different samples after molding, highlighting the severe cross-linking and decolorization phenomenon caused by the lack of microcapsule protection in Comparative Example 4.

[0059] According to the data in Table 3, the melt flow rate of the systems in Examples 1 to 5 remained within the conventional processing range of 14.3 to 16.1 g / 10 min, and the flow channels were smoothly filled during the injection molding process. However, the test results for Comparative Example 4 showed a decrease to 2.1 g / 10 min, and during the experiment, it was even observed that the thin strips extruded from the instrument die exhibited obvious melt fracture and strong elastic shrinkage characteristics. The core limiting force causing this abrupt change in macromolecular rheological behavior lies in the chemical cross-linking network formed within the system. In Comparative Example 4, the ε-polylysine directly added had a high density of free primary amino groups exposed on its surface. This polyamino polymer, under a high-temperature shear field of 160°C, inevitably encountered the maleic anhydride graft in the compatibilization system, resulting in a deep ring-opening imidization reaction. The formed three-dimensional network gel impeded the forced slip of the polyester molecular chains. The mesoporous physical isolation layer constructed in this scheme completely blocked this harmful side reaction. Although the low-melting-point polyethylene wax or calcium stearate on the outer layer of the microcapsule melts at the processing temperature, the large molecular volume of the graft copolymer in the matrix cannot penetrate into the mesopores of 2 to 4 nanometers. The amino active sites sealed inside the pores thus escape the probability of collision with external reactive groups in the microscopic space.

[0060] This physical isolation mechanism not only maintains the rheological stability of the system but also intervenes in the oxidative degradation process of the heat-sensitive antibacterial components. Preliminary observations during the early stages of processing revealed that tea polyphenols, due to the enrichment of phenolic hydroxyl groups in their molecular structure, are prone to dehydrogenation and oxidation in the high-temperature aerobic extrusion section of a twin-screw extruder, generating quinone-based colored byproducts, resulting in severe deterioration of the appearance of the polymer products. Optical colorimetric data confirmed this inference; the yellow index of the molded sample of Comparative Example 4 without inorganic protection climbed to 45.3, exhibiting a turbid dark brown appearance macroscopically. Due to the implementation of double-layer microencapsulation, the yellow index of the materials in each embodiment was effectively controlled within the light background range of 17.9 to 19.5. To block the direct contact between oxygen and polymer free radicals, the inorganic mesoporous carrier establishes a thermodynamic shielding layer between the macroscopic processing field and the microscopic active molecules. The ceramic-like hydroxyapatite framework has an inherently low thermal conductivity. This inorganic armor effectively buffers the instantaneous viscous heat dissipation caused by the strong shearing of the screw, so that the actual temperature of the microenvironment inside the channel is lower than the set overall temperature of the barrel. Ultimately, this ensures that multiple natural antibacterial components survive and retain their release activity in the harsh polymer molding process.

[0061] Test Example 4: Verification of macroscopic basic mechanical properties and toughening mechanism of multiphase composite system.

[0062] According to the appendix Figure 5According to Table 4, test specimens for mechanical properties were prepared in accordance with national standards. Completely dried modified granulated materials from Examples 1 to 5 and Comparative Examples 1 to 3 were added to a precision injection molding machine. The barrel temperature distribution was set to 145℃ to 160℃, and the mold temperature was maintained at 35℃. Injection molding was performed to produce Type 1A multi-purpose dumbbell-shaped tensile specimens conforming to GB / T1040, and long strip-shaped bending and notched impact specimens with dimensions of 80mm × 10mm × 4mm conforming to GB / T9341. All molded specimens had their gates removed and were polished smooth. They were then uniformly placed in a constant temperature and humidity chamber at 23℃ and 50% relative humidity for 48 hours for conditioning.

[0063] The tensile properties of materials were determined using a microcomputer-controlled electronic universal testing machine. A 10kN tensile sensor was selected, and a pneumatic wedge clamp was used to fix both ends of the dumbbell-shaped specimen, with the clamping distance set to 115mm. The test was conducted at a constant tensile speed of 50mm / min at room temperature, and the yield load and fracture displacement were recorded in real time. The tensile strength and elongation at break were automatically calculated and output by the software accompanying the testing machine. Seven specimens were tested in parallel for each group of materials, and the arithmetic mean was taken after removing the two extreme values ​​with the largest deviations.

[0064] A three-point bending test was performed on the material's flexural modulus. The three-point bending fixture of the universal testing machine was replaced, and the support span was adjusted to 64 mm. The elongated specimen was placed flat on the two supports, and a bending load was applied at a constant rate of 2 mm / min until the specimen deflection reached the specified value. The slope of the initial straight segment of the load-deflection curve was recorded to characterize the material's rigidity against macroscopic bending deformation.

[0065] The fracture toughness of materials was evaluated using a pendulum impact testing machine. A type A V-shaped notch with a depth of 2 mm and a bottom radius of 0.25 mm was machined into the middle of a standard long strip specimen. A pendulum with a nominal energy of 2.75 J was selected. The specimen was vertically fixed on the anvil, with the center line of the notch aligned with the impact trajectory of the pendulum's blade. The energy consumed in breaking the specimen was recorded, and the notched impact strength of the simply supported beam was calculated by combining this energy with the remaining cross-sectional area at the notch.

[0066] Table 4: Basic Mechanical Property Test Data of Composite Materials in Each Example and Comparative Example

[0067] Appendix Figure 5 (a) shows the biaxial evolution of tensile strength and elongation at break, with the bar chart reflecting the rigidity index and the broken line reflecting the toughness index; (b) gives a comprehensive comparison of flexural modulus and notched impact strength, which intuitively reflects the macroscopic influence of matrix resin replacement, interfacial compatibility and nanophase dispersion state on the rigidity-toughness balance of toy materials.

[0068] According to the data in Table 4, the system of the embodiment exhibits excellent balance between stiffness and toughness, with its tensile strength generally stable in the range of 36.8 to 41.5 MPa, while retaining an elongation at break of over 130% and approximately 14.6 to 16.5 kJ / m². 2 The notched impact strength. This high degree of synergy in mechanical properties directly depends on the continuous phase network structure constructed by the quaternary blend matrix of polylactic acid and polybutylene succinate. When exploring the relationship between the processing window and matrix stability, the test results of Comparative Example 1 revealed the catastrophic damage caused by thermodynamic mismatch. In order to melt the high-melting-point polyglycolic acid, Comparative Example 1 was forced to raise the extrusion temperature to 178°C. Under this thermal environment, the polypropylene carbonate component underwent severe zipper-like thermal degradation, and the released carbon dioxide gas randomly formed macroscopic bubble defects inside the melt. Once mechanical load was applied, these uncontrollable pore defects quickly evolved into stress concentration points, causing the material to prematurely fracture, with its elongation at break sharply reduced to 12.5% ​​and its tensile strength reduced to only 21.4 MPa. It can be seen that the present invention successfully locked the golden processing window of 135°C to 165°C by replacing the high-melting-point component with polybutylene succinate, ensuring the integrity of the mechanical skeleton of the quaternary continuous phase.

[0069] Further investigation into the coupling effect between microscopic interface structure and macroscopic toughness revealed in contrasting data from Comparative Examples 2 and 3. In Comparative Example 2, due to the lack of hydrophobic modification of the plant fibers, the highly polar matrix resin completely filled the micropowder pores under injection pressure, embolizing the originally buffering three-dimensional cavities with rigid polymers. While this densification process increased the flexural modulus to 2650 MPa, it sacrificed the material's deformation tolerance, resulting in an extreme elongation at break of 8.4%, exhibiting typical ceramic-like brittle fracture characteristics. In Comparative Example 3, the nanocellulose, fed directly as dry powder, experienced severe agglomeration within the matrix. These micron-sized agglomerates failed to construct a percolation-reinforcing network, instead inducing severe stress concentration and debonding at the interface, leading to a significant reduction in the material's overall toughness. The embodiment system relies on a dual synergistic mechanism of in-situ liquid-phase exfoliation and hydrophobic pore preservation. Under impact loads, the plant fiber cavities not impregnated by resin can absorb a large amount of impact energy through the micro-buckling deformation of the pore walls; the one-dimensional nanocellulose network uniformly interspersed in the matrix effectively limits the expansion of crazing, dissipating destructive energy into the large deformation of the matrix. This multi-scale, multiphase assembly design enables the material of the embodiment to achieve excellent fracture and impact resistance while maintaining rigidity modulus, perfectly meeting the stringent safety requirements of children's toys for drop protection and protection against sharp edge cracking.

[0070] Test Example 5: Verification of the thermal protection and long-lasting antibacterial efficacy of multiple antibacterial components.

[0071] According to the appendix Figure 6As per Table 5, test samples were prepared according to GB / T 31402-2015 Test Method for Antimicrobial Properties of Plastic Surfaces. Injection-molded standard samples from Examples 1 to 5 and Comparative Example 4 were cut into flat cubes of 50mm × 50mm. The sample surfaces were initially cleaned by wiping with a 75% ethanol solution, and then subjected to double-sided ultraviolet irradiation for 30 minutes in a sterile laminar flow hood to eliminate interference from background bacteria.

[0072] Escherichia coli (ATCC 8739) and Staphylococcus aureus (ATCC 6538) were selected as representative test strains. The lyophilized and revived standard strains were inoculated into ordinary nutrient agar medium and incubated at 35°C for 24 hours. Single colonies in the logarithmic growth phase were picked and inoculated into broth medium for elution. Multiple serial dilutions were performed using 0.85% sterile physiological saline to prepare a concentration stable at 1×10⁻⁶. 5 Up to 5×10 5 CFU / mL inoculation suspension.

[0073] Surface contact antibacterial testing was conducted using a film-applied method. 0.4 mL of prepared logarithmic-phase bacterial suspension was precisely added to the center of each aseptically treated test sample, followed by covering with a 40 mm × 40 mm sterile polyethylene film. The film was gently pressed with sterile forceps to ensure even distribution of the bacterial suspension within the test area without any air bubbles. The inoculated samples were then placed in sterile petri dishes containing sterile water at the bottom to maintain a relative humidity greater than 90%, and incubated at 35°C for 24 hours.

[0074] After the co-culture cycle, 10 mL of SCDLP eluent containing 0.2% Tween-80 neutralizer was added to each culture dish. The sample surface and covering film were repeatedly rinsed with a sterile pipette. The eluent was collected and serially diluted 10-fold. 1 mL of each of the three appropriate dilutions was spread onto nutrient agar dishes. After incubation at 35°C for 48 hours, artificial viable colony counting was performed. The arithmetic mean of the three parallel samples was calculated and combined with the data from the blank control group to obtain the 24-hour inhibition rate.

[0075] Table 5: 24-hour surface antibacterial rate test data of composite materials in each example and comparative example

[0076] Appendix Figure 6 The results are presented in the form of grouped bar charts, which visually show the differences in antibacterial efficacy between Examples 1 to 5 and Comparative Example 4 when facing Gram-negative Escherichia coli (dark gray bars) and Gram-positive Staphylococcus aureus (light gray bars), demonstrating the decisive influence of microcapsule encapsulation technology on the survival rate of bioactive components.

[0077] According to the data in Table 5, the 24-hour contact inhibition rates of the system in the examples against *Escherichia coli* and *Staphylococcus aureus* remained consistently high, ranging from 98.5% to 99.8%, demonstrating broad-spectrum and potent microbial killing capabilities. In the field of polymer blending modification, introducing natural bio-based antibacterial agents into the plastic matrix is ​​not difficult; however, preventing the deactivation of heat-sensitive components in the high-shear thermal field of a twin-screw extruder has always been a core technical bottleneck restricting its application. Observing the test results of Comparative Example 4, it can be found that after directly adding the unprotected tea polyphenol, chitosan quaternary ammonium salt, and ε-polylysine mixed powder to the barrel, the antibacterial rates of the molded samples against the two test strains plummeted to 62.3% and 58.7%, respectively, essentially losing their hygienic protective value in practical applications. This sharp decline in antibacterial activity stems from complex physicochemical side reactions occurring during processing. On the one hand, the intense shear dissipation heat generation makes the fragile phenolic hydroxyl groups in tea polyphenol molecules extremely easy to be oxidized and degraded; on the other hand, the large number of free primary amino groups carried by ε-polylysine undergo irreversible imidization cross-linking collisions with maleic anhydride-grafted polylactic acid macromolecules in the high-temperature melt, resulting in the large consumption of cationic active sites that play a dominant role in antibacterial activity.

[0078] The inorganic mesoporous microcapsule technology used in this embodiment successfully circumvents the aforementioned destructive processes. Mesoporous activated hydroxyapatite, utilizing its rigid ceramic framework and internal nanoporous structure, constructs a thermally shielded compartment between the macroscopic strong shear field of the melt and the microscopic active molecules. Although the low-melting-point polyethylene wax or calcium stearate attached to the microcapsule surface melts at the processing temperature, the resulting liquid sealing film effectively blocks the intrusion of free macromolecular groups from the polymer matrix, completely cutting off the path of harmful cross-linking reactions in physical space. When the composite material, molded under this dual protection, is placed in a humid environment according to practical applications or testing standards, the moisture-driven slow-release mechanism begins to function. Moisture in the environment penetrates the matrix surface and slowly dissolves the physical sealing layer at the micropore ends. The intact natural antibacterial molecules, aided by capillary osmotic pressure within the pores, continuously migrate and release the drug towards the material surface along the concentration gradient. This dynamic balance between in-situ protection and slow release not only ensures the material's maximum antibacterial rate at the initial stage of manufacturing, but also provides a durable and non-fading biosafety barrier for the surfaces of toys that children frequently touch and chew.

[0079] Test Example 6: Verification of Controllable Biodegradability and Step-by-Step Degradation Mechanism.

[0080] According to the appendix Figure 7According to Table 6, a controlled aerobic composting test system was constructed based on the requirements of GB / T 19277.1-2011 standard. Standard samples from Examples 1 to 5 and Comparative Example 1 were selected as experimental subjects. They were pulverized using a cryogenic pulverizer and passed through a 2mm standard sieve. Powder with a particle size between 1mm and 2mm was collected for later use.

[0081] Standard test compost was prepared. Urban domestic waste and leaves were collected and mixed for composting within 2 to 4 months of use. Glass, stones and large inert materials were removed. After passing through a 5 mm sieve, the moisture content was adjusted to about 50%, and the volatile solids content and total organic carbon mass fraction were measured.

[0082] In a 3L composting reaction flask, 100g of test sample powder was mixed with 600g of dry compost equivalent at a mass ratio of 1:6. After filling, the reaction flask was placed inside a 58℃ constant temperature water bath environment system and operated continuously for 90 days in the dark.

[0083] A dynamic aeration method was used to provide continuous oxygen to the reaction flask. Moistened air treated to remove carbon dioxide was introduced, with the gas flow rate controlled between 50 mL / min and 100 mL / min. An absorption bottle containing a barium hydroxide solution of known concentration was connected in series at the reactor exhaust port to capture carbon dioxide produced by microbial metabolism of the sample. The absorption bottle was periodically removed and titrated with standard hydrochloric acid solution, and the titration consumption was recorded. Combined with the background carbon dioxide release from the blank compost group, the cumulative carbon dioxide release of the test sample at specific time points (15 days, 30 days, 45 days, 60 days, 75 days, and 90 days) was calculated, and the absolute carbon conversion rate, i.e., the relative biodegradation rate, was calculated accordingly.

[0084] Table 6: Relative biodegradability of composite materials in each example and comparative example under controlled composting conditions at 58°C

[0085] Appendix Figure 7 The graph uses broken lines with different marking symbols and line types to illustrate the steady-state stepwise degradation behavior of Examples 1 to 5, and intuitively reflects the runaway rapid mineralization trend of Comparative Example 1 in the early stage of composting.

[0086] According to the data in Table 6, all the sample examples achieved a final carbon conversion rate of 76.8% to 82.4% at the end of the 90-day standard composting cycle, fully meeting the requirements of the internationally accepted standards for absolute biodegradability of degradable plastics. The depolymerization behavior of polymer materials in a microbial environment is often determined by the hydrolytic sensitivity of the polymer macromolecular chains and the microstructure of the multiphase system. The data of Comparative Example 1 revealed a serious runaway phenomenon in its degradation kinetics. Due to the introduction of polyglycolic acid (PGA) to replace polybutylene succinate (PBS) in the formulation, the distribution density of ester bonds in the PGA molecular backbone is extremely high and lacks steric hindrance protection from side groups, making it highly susceptible to autocatalytic bulk hydrolysis in a high-humidity composting system at 58°C. Only 15 days after the start of the test, the relative degradation rate of Comparative Example 1 had already surged to 35.6%, and exceeded 58% by day 30. If this kind of early cliff-like molecular weight decline occurs in actual toy storage or high-humidity use environments, it will cause the product to rapidly lose its mechanical load-bearing capacity and become brittle and disintegrate.

[0087] The formulation system used in the examples exhibits a stable and sustainable degradation curve. This macroscopic kinetic characteristic confirms the effectiveness of the multi-component stepwise degradation mechanism established in this invention. In the initial stage of composting testing, the porous channels preserved by the hydrophobic layer inside the modified plant micropowder act as a water-conducting capillary network, allowing external environmental moisture to slowly penetrate deep into the polymer matrix. Upon contact with moisture, the amorphous polypropylene carbonate (PPC), due to its high main chain flexibility, undergoes random chain breakage first, forming dispersed microscopic dissolution pores. As the interfacial contact area expands, the low-crystallinity PBS segments begin to enter the hydrolysis cycle. Finally, the polylactic acid (PLA) backbone, which is in the continuous phase and has the highest crystallinity, and its network entangled with nanocellulose, are gradually stripped and consumed by depolymerization enzymes secreted by microorganisms. This degradation path, which evolves from point to surface and from the amorphous region to the crystalline region, constructed by the thermodynamic differences in chain segment crystallization and phase distribution, suppresses the failure risk caused by excessive hydrolysis in the early stage, achieving an engineering balance between high stability during the material's service life and complete mineralization and degradation after disposal.

[0088] Test Example 7: Verification of the mechanism of bioactive components in resisting saliva migration and long-lasting release.

[0089] Standard extraction samples were prepared for simulating the dissolution of sensitizing components. Standard injection-molded blocks from Examples 1 to 5 and Comparative Example 4 (with uncoated antibacterial powder added directly) were selected and cut into test blocks with a surface area of ​​approximately 10 square centimeters using a precision panel saw. The initial mass of each test block was accurately weighed on an analytical balance, and the block was immersed in an artificial saliva preparation solution pre-adjusted to pH 6.8 with 0.1 mol / L hydrochloric acid and sodium hydroxide. This simulated solution was mainly prepared by dissolving sodium chloride, potassium chloride, calcium chloride, and porcine gastric mucoprotein in deionized water in a standard ratio.

[0090] An extraction test platform simulating the oral environment was constructed. Sealed conical flasks containing samples and artificial saliva were fixed on the stage of a constant-temperature shaking incubator. The water bath temperature was set to 37°C, and the shaking frequency was controlled at 60 rpm to simulate the dynamic contact state when a child chews on a toy. After continuous extraction and exposure for 72 hours, 5 mL of the extract was drawn using a syringe with a 0.45 μm polytetrafluoroethylene filter membrane as the test sample.

[0091] The total migration of active substances in the extract was quantitatively analyzed using a UV-Vis spectrophotometer. The maximum absorption peak was determined by full-band scanning using the characteristic absorption wavelength of tea polyphenols. A working curve was established using standards, and the absorbance was converted into the leaching mass concentration. Based on this, the total migration amount of each kilogram of composite material in simulated saliva was calculated.

[0092] The long-lasting antibacterial durability of the material after repeated washing was evaluated. Another batch of samples of the same specifications were placed in an ultrasonic cleaning tank and cleaned for 30 minutes at a time with warm water containing 0.5% neutral detergent. The samples were then rinsed with pure water and dried. This cycle was repeated 30 times to simulate the high-frequency daily cleaning process of toys during their use cycle.

[0093] Based on the aforementioned surface contact antibacterial test method, Staphylococcus aureus in the logarithmic growth phase was selected to evaluate the antibacterial efficacy of the washed and aged samples. After inoculation and co-cultivation for 24 hours, viable colonies were eluted and serially diluted for plating, and the apparent antibacterial retention rate after 30 water washes and aging was calculated.

[0094] Table 7: Test data on simulated saliva migration leaching amount and surface antibacterial rate after water washing and aging

[0095] Appendix Figure 8 The data uses a dual vertical coordinate system to present two sets of core correlation indicators. The gray bar chart with black edges corresponds to the left coordinate axis, which quantifies the degree of migration and leakage of active ingredients in artificial saliva at 37°C for Examples 1 to 5 and Comparative Example 4. The solid line with black solid square marks corresponds to the right coordinate axis, which intuitively reveals the antibacterial efficacy retention status of each system after 30 rigorous water washing and aging.

[0096] According to the data in Table 7, in the artificial saliva extraction test simulating infants' chewing contact with toys, Comparative Example 4, where unprotected antibacterial powder was directly mixed into the matrix resin, experienced severe component leakage, with a total migration of active substances reaching 34.62 mg / kg. When assessing the biosafety of products intended for child contact, high efflux of polar small molecules often carries the potential risk of skin sensitization or gastrointestinal microecological disturbance. In Comparative Example 4, the free tea polyphenols and small molecule peptides were easily detached from the matrix due to hydrodynamic scouring and water molecule swelling, penetrating the free volume between amorphous polymer segments. In contrast, the active substance detection levels in the systems of Examples 1 to 5 were strictly controlled at extremely low background levels of 2.87 to 3.52 mg / kg. The structural root cause of this more than 10-fold difference lies in the inorganic porous microcapsule retention system constructed in the examples. The robust three-dimensional mesoporous framework of hydroxyapatite effectively prevents the relaxation of molecular chain segments in the polyester matrix under humid and hot conditions. The antibacterial molecules inside are physically confined in a network of pores at the nanometer scale. They must overcome extremely high interfacial capillary resistance and go through a tortuous diffusion path to reach the material surface. This structural barrier weakens the flushing and extraction effect of the liquid medium on the internal effective components.

[0097] This repressed release behavior, dominated by mesoporous physical barriers, inevitably has a profound impact on the functional stability of materials over their long service life. The frequent use of surfactants and mechanical ultrasonic cleaning in routine toy hygiene maintenance accelerates the aging and peeling of polymeric product surfaces. In Comparative Example 4, after 30 water washing cycles, the surface contact antibacterial rate of Staphylococcus aureus dropped from nearly 60% initially to a mere 21.3%, offering no protective effect. Combined with the previously detected high levels of migration, it can be determined that this type of direct blend system exhibits typical burst-release depletion characteristics, with surface active sites being exhausted after several elutions, creating an antibacterial window. The system in the Example Example, after undergoing the same intensity of cleaning and damage, maintained an antibacterial retention rate between 87.9% and 91.2%, demonstrating excellent long-term sustainability. The antibacterial components encapsulated within the microcapsules deep within the matrix act as a drug reservoir. As the surface polymer undergoes minor degradation and wear under environmental stress, the nanopores encapsulating the active substances in the inner layer are gradually exposed, continuously replenishing the antibacterial barrier to the surface interface through diffusion kinetics. This sustained-release compensation mechanism, relying on multi-scale interface structures, fills the engineering gap in the long-term bioprotective performance of biodegradable polymer materials in complex application scenarios.

Claims

1. A PFM-nanocellulose-hydroxyapatite synergistically reinforced biodegradable material, characterized in that, It is made from raw materials comprising the following parts by weight: Polylactic acid 16.5-22 parts; Poly(butylene adipate) 16.5-21 parts; 11-14 parts of polypropylene carbonate; 5.5-14 parts of polybutylene succinate; 12-20 parts of hydrophobic and pore-preserving modified plant fiber micro powder; 10-18 parts of activated hydroxyapatite-supported antibacterial microcapsules; 3-5 parts of liquid-phase in-situ dispersion of nano-cellulose paste; 1-1.5 parts of maleic anhydride grafted with polylactic acid; 1-1.5 parts of maleic anhydride-grafted poly(adipate) / butylene terephthalate; 0.25-0.5 parts of nano talc powder; Nano-calcium carbonate 0.25-0.5 parts; Antioxidant 1010: 0.5-1 part; 0-0.5 parts of polyethylene wax or stearic acid.

2. The PFM-nanocellulose-hydroxyapatite synergistically reinforced biodegradable material according to claim 1, characterized in that, The weight ratio of each component of the raw material is as follows: 21 parts of polylactic acid; 21 parts of polybutylene adipate / terephthalate; 14 parts of polypropylene carbonate; 14 parts of polybutylene succinate; 12 parts of hydrophobic and pore-preserving modified plant fiber micro powder; 10-12 parts of activated hydroxyapatite-supported antibacterial microcapsules. Three parts of in-situ liquid-phase dispersion of nanocellulose paste.

3. The PFM-nanocellulose-hydroxyapatite synergistically reinforced biodegradable material according to claim 1, characterized in that, The hydrophobic and pore-preserving modified plant fiber micro powder is prepared by the following method: First, plant fibers cut to 1-2cm are placed in a steam explosion tank, and 2.0-2.5MPa saturated steam is introduced. After holding the pressure for 60-90s, the pressure is released instantly. The fibers are then washed and dried until the moisture content is less than 3% to obtain the dried fiber material. The dried fiber material was then pulverized at 0°C to -8°C using an air jet mill to a particle size D90 of 5-10μm to obtain plant fiber micro powder. The plant fiber powder is then put into a high-speed mixer, and 1%-3% of stearic acid and 0.5%-1% of γ-aminopropyltriethoxysilane are added. The mixture is then subjected to high-speed shear mixing at 110-120°C for 30-40 minutes to obtain the hydrophobic and pore-preserving modified plant fiber powder.

4. The PFM-nanocellulose-hydroxyapatite synergistically reinforced biodegradable material according to claim 1, characterized in that, The liquid-phase in-situ dispersed nanocellulose paste is prepared by the following method: Nanocellulose was dispersed in anhydrous ethanol to prepare a nanocellulose suspension with a mass concentration of 3%-5%. After ultrasonic dispersion, the temperature was raised to 55-65℃, and γ-aminopropyltriethoxysilane (2%-5% of the dry weight of the nanocellulose) was added dropwise and reacted for 1.5-2.5 h to obtain a modified suspension. After centrifugation, the solid components in the modified suspension were collected to obtain a wet gel containing ethanol. Take 10g of the ethanol-containing wet gel on a dry basis, add 3-5g of acetylacetic acid tributyl ester and 2-3g of polyethylene glycol, and grind it in a three-roll mill for 20-30 minutes to obtain the liquid-phase in-situ dispersed nanocellulose paste.

5. The PFM-nanocellulose-hydroxyapatite synergistically reinforced biodegradable material according to claim 1, characterized in that, The activated hydroxyapatite-supported antibacterial microcapsules were prepared by the following method: Hydroxyapatite powder was calcined in a muffle furnace at 650-750℃ for 2-3 hours, and then pulverized by airflow to a D50 of 2-4 μm to obtain mesoporous activated hydroxyapatite. The mesoporous activated hydroxyapatite was placed in a vacuum impregnation reactor, and after being evacuated to -0.08 to -0.09 MPa, an antibacterial aqueous solution composed of tea polyphenols, chitosan quaternary ammonium salt, and ε-polylysine was drawn in and stirred to obtain a co-assembled slurry. The co-assembled slurry was dried under reduced pressure and then fed into a mixer. Polyethylene wax or calcium stearate was added, and the mixture was mixed and coated at 105-115℃ to obtain the activated hydroxyapatite-supported antibacterial microcapsules.

6. The PFM-nanocellulose-hydroxyapatite synergistically reinforced biodegradable material according to claim 1, characterized in that, The plant fiber is corn stalk or rice husk.

7. The PFM-nanocellulose-hydroxyapatite synergistically reinforced biodegradable material according to claim 1, characterized in that, The preparation process of the biodegradable material includes the following steps: First, polylactic acid, polybutylene adipate / terephthalate, polypropylene carbonate and polybutylene succinate are vacuum dried at 55-60℃ until the water content is less than 0.03% to obtain the dried quaternary resin. The dried quaternary resin and all other components except the nanocellulose paste were then put into a high-low mixer for premixing to obtain a dry premix. The dry premix is ​​added from the main feed port of a twin-screw extruder with a multi-temperature zone barrel, while the liquid-phase in-situ dispersed nanocellulose paste is injected through a liquid metering pump. After being melted and mixed in the multi-temperature zone barrel and subjected to in-situ high-vacuum devolatilization, the biodegradable material is obtained by extrusion through a die head and cooling granulation.

8. The PFM-nanocellulose-hydroxyapatite synergistically reinforced biodegradable material according to claim 7, characterized in that, The temperature settings for the multi-temperature zone barrel and die head are as follows: Zone 1 130-140℃, Zone 2 140-150℃, Zone 3 150-160℃, Zone 4 155-165℃, Zone 5 160-170℃, Zone 6 155-165℃, and Die Head 150-160℃. The screw speed of the twin-screw extruder is 250-300 rpm.

9. The PFM-nanocellulose-hydroxyapatite synergistically reinforced biodegradable material according to claim 7, characterized in that, The liquid-phase in-situ dispersed nanocellulose paste is injected laterally from three zones of the multi-temperature zone material cylinder; The high-vacuum in-situ devouring involves opening a vacuum interface between zones five and six of the multi-temperature zone barrel and removing the liquid medium in real time under a vacuum level of -0.08 to -0.095 MPa.

10. The application of a PFM-nanocellulose-hydroxyapatite synergistically enhanced biodegradable material as described in any one of claims 1-9 in the preparation of long-lasting antibacterial biodegradable toys.

Images