A biobased pfm synergistically reinforced degradable composite with hydroxyapatite

Abstract

The application relates to the technical field of high polymer composite materials, and discloses a biobased PFM and hydroxyapatite synergistically reinforced degradable composite material, which comprises 25-42% of polylactic acid, 15-30% of polybutylene adipate terephthalate, 5-15% of polypropylene carbonate, 3-5% of polyglycolic acid, 12-18% of light-weight modified plant fiber micro-superfine powder, 4-8% of activated hydroxyapatite superfine powder, 2-3% of a compatilizer and 1-5.5% of an additive. In the application, the polypropylene carbonate and the polyglycolic acid synergistically construct an amorphous state and a hydrolysis-induced phase, the dependence of the matrix on a high-temperature and high-humidity environment is eliminated, and natural soil and industrial compost double-scene degradation is realized; the activated hydroxyapatite utilizes surface active sites to produce secondary bond combination with the matrix to form a spatial network, provides a mechanical reinforcing effect, and utilizes electrostatic adsorption to damage bacterial cell membranes, so that the material is endowed with contact-type antibacterial function.

Description

Technical Field

[0001] This invention relates to the field of polymer composite materials technology, specifically to a biodegradable composite material synergistically reinforced by bio-based PFM and hydroxyapatite. Background Technology

[0002] As the environmental problems caused by traditional plastic waste become increasingly prominent, biodegradable polymers, such as polylactic acid (PLA) and polybutylene adipate / terephthalate (PET), have become the main alternatives to traditional petrochemical resins. In actual industrial production, to reduce overall costs and adjust the molding shrinkage rate of products, plant fiber powder is often filled into a basic polyester system to prepare composite materials.

[0003] However, existing polyester-based biodegradable composite materials have significant limitations in various applications. The degradation process of existing materials is highly dependent on the high-temperature and high-humidity environment provided by industrial composting facilities. In natural soil at normal temperatures, due to the high glass transition temperature of matrices such as polylactic acid, the molecular chains are in a frozen state, making it difficult for free water and environmental microorganisms to penetrate into the material. This results in the hydrolysis reaction proceeding slowly only on the surface, leading to an excessively long overall degradation cycle. Furthermore, plant fibers, mainly composed of cellulose, hemicellulose, and lignin, have numerous hydrophilic hydroxyl groups on their surface, creating structural and polarity differences with hydrophobic polymer resins. This interfacial incompatibility leads to uneven dispersion of plant fibers during blending, resulting in agglomeration and the formation of micropores and stress concentration points within the material. When the product is subjected to external impact or tension, microcracks easily initiate at the phase interface and propagate, causing a significant decrease in the material's tensile strength and elongation at break. Simultaneously, in applications such as agricultural films, fresh food packaging, and daily contact products, biodegradable composite materials are prone to surface adhesion and growth of microorganisms such as Escherichia coli and Staphylococcus aureus. Conventional blending systems do not have antibacterial capabilities. If traditional small-molecule chemical bactericides are directly added during blending, these small-molecule antibacterial agents will be released and migrate into the external environment as the material gradually degrades. This not only easily causes secondary pollution of soil or water bodies, but also makes it difficult to maintain long-term sanitary and safety protection performance. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a biodegradable composite material synergistically reinforced by bio-based PFM and hydroxyapatite, which solves the problems of low degradation rate of existing polyester-based biodegradable materials in natural environments at room temperature, significant attenuation of mechanical properties due to interfacial incompatibility when plant fibers are introduced, and lack of long-lasting safe antibacterial ability of the material itself.

[0005] To achieve the above objectives, the present invention provides the following technical solution: This invention provides a biodegradable composite material synergistically reinforced with bio-based PFM and hydroxyapatite, employing the following technical solution: A biodegradable composite material synergistically reinforced with bio-based PFM and hydroxyapatite is made from raw materials comprising the following weight percentages, wherein the sum of the weight percentages of each component is 100%: polylactic acid 25-42%; polybutylene adipate / terephthalate 15-30%; polypropylene carbonate 5-15%; polyglycolic acid 3-5%; lightweight modified plant fiber micro-ultrafine powder 12-18%; activated hydroxyapatite ultrafine powder 4-8%; compatibilizer 2-3%; and additives 1-5.5%.

[0006] By adopting the above technical solution, and by using polypropylene carbonate, polyglycolic acid, lightweight modified plant fiber micro- and ultra-micro powders, and activated hydroxyapatite ultra-micro powders to form a multiphase alloy blend with polylactic acid and poly(adipate) / butyl terephthalate matrix, the following multiple technical effects are achieved: eliminating the matrix's dependence on high-temperature and high-humidity degradation environments to achieve degradation in both natural soil and industrial composting scenarios; enhancing mechanical strength through interfacial secondary bond crosslinking; and generating contact antibacterial effects through electrostatic adsorption.

[0007] The specific innovative principles and reaction process are explained below: Dual-scenario degradation rate controllable mechanism: Conventional polylactic acid (PLA) and polybutylene adipate / terephthalate (PET) exhibit restricted molecular chain movement at room temperature, hindering water molecule penetration. This approach introduces amorphous polypropylene carbonate (PPC) and polyglycolic acid (PGA), rich in hydrophilic ester bonds. PPC increases the free volume of the blend matrix, disrupting the crystallinity regularity of PLA. PGA constructs a hydrolysis-induced phase within the matrix. Under normal temperature and humidity conditions in natural soil, the degradation process follows these steps: First, water penetration. Water molecules penetrate into the internal phase region of the composite material through the free volume channels provided by PPC. Second, preferential hydrolysis of PGA. The hydrophilic ester bonds on the PGA backbone undergo nucleophilic substitution with water molecules, resulting in backbone breakage and the generation of terminal carboxyl and hydroxyl groups. The specific ester hydrolysis reaction is: -CH2-COO-CH2- + H2O → -CH2-COOH + HO-CH2-. Third, autocatalysis by the terminal carboxyl groups. The terminal carboxyl groups generated by the preferential hydrolysis of polyglycolic acid increase the local hydrogen ion concentration in the system. These free hydrogen ions attack the carbonyl oxygen atoms of the ester bonds in the macromolecular chains of polylactic acid and poly(butylene adipate / terephthalate), lowering the activation energy of ester bond hydrolysis and catalyzing large-scale main-chain degradation of polylactic acid and poly(butylene adipate / terephthalate). The fourth step involves the conduction of plant fiber pores. As the polymer matrix degrades, the lightweight modified plant fiber micro- and ultrafine powders are gradually exposed and exfoliated, leaving micron-sized pores within the material, forming capillary channels. These channels expand the contact area between soil microorganisms and the degradation enzymes secreted by fungi and bacteria, accelerating the overall macroscopic disintegration of the composite material.

[0008] Mechanism of mechanical synergistic enhancement: After high-temperature treatment, activated hydroxyapatite ultrafine powder undergoes partial defect restructuring of its crystal lattice, increasing its specific surface area and exposing a large number of positively charged active sites such as calcium ions and free hydroxyl groups. During melt blending, the material system undergoes the following physical and chemical bonding steps: First, the hydroxyl groups on the surface of activated hydroxyapatite undergo ring-opening reactions with the anhydride groups in the compatibilizer or the terminal carboxyl groups of the polyester matrix, or form a high-density hydrogen bond network. Second, the exposed calcium ions undergo electron transfer with the carbonyl oxygen atoms on the polyester molecular chain, forming coordination bonds. Third, these secondary bonds anchor the inorganic rigid particles and organic polymer chain segments together, forming a plant skeleton with the lightweight modified plant fiber micro- and ultrafine powder, constructing spatial network nodes within the composite system. When subjected to external impact or tension, stress is effectively transferred from the blended matrix to the high-modulus activated hydroxyapatite particles and plant skeleton through the aforementioned secondary bond network, restricting the slippage of polymer chain segments in the amorphous region, inducing shear yielding of the matrix to absorb energy, thereby significantly improving the tensile strength, elongation at break and flexural modulus of the composite material.

[0009] Contact antibacterial mechanism: Activated hydroxyapatite ultrafine powder forms a high-density antibacterial contact network on the surface of molded products. Its antibacterial process includes: First, physical adsorption. The high specific surface area endows the material surface with strong adsorption capacity, enriching free bacteria such as Escherichia coli and Staphylococcus aureus in the usage environment. Second, electrostatic disruption. The positively charged calcium ion active surface exposed by high-temperature activation undergoes strong electrostatic interaction with the negatively charged bacterial cell membrane. Electrostatic binding interferes with the ion channels of the bacterial cell membrane, disrupts the structural integrity of the phospholipid bilayer, causes the leakage of proteins and nucleic acids from within the bacteria, and blocks the normal metabolic and reproductive processes of bacteria, achieving a highly efficient physical sterilization effect.

[0010] This invention provides a biodegradable composite material synergistically reinforced with bio-based PFM and hydroxyapatite. It possesses the following beneficial effects: 1. This invention achieves controllable degradation rate of composite materials in both natural soil and industrial composting scenarios. By introducing polypropylene carbonate and polyglycolic acid into polylactic acid and poly(butylene adipate / terephthalate) matrices, an amorphous and hydrolysis-induced phase is constructed. Polyglycolic acid preferentially hydrolyzes to generate terminal carboxyl groups after the introduction of environmental moisture, which plays an autocatalytic role in the breakage of the matrix macromolecular chains. Combined with the pore channels formed after the lightweight modified plant fiber micro- and ultra-micro powders are removed, the dependence of traditional polyester materials on high temperature and high humidity environments is eliminated, enabling the material to complete macroscopic disintegration and degradation in natural soil at room temperature.

[0011] 2. This invention improves the comprehensive mechanical properties of composite materials. It utilizes high-temperature activated hydroxyapatite ultrafine powder and lightweight modified plant fiber micro-ultrafine powder for synergistic reinforcement. The active sites such as calcium ions and hydroxyl groups exposed on the surface of activated hydroxyapatite form secondary bonds with the blended polymer matrix and compatibilizer, forming a spatial network node inside the material. When subjected to external force, the stress is effectively transferred and dispersed to the inorganic rigid particles and plant fiber skeleton through this network, which restricts the slippage of polymer chain segments, overcomes the interface defect problem caused by simply adding plant fibers, and improves the tensile strength and flexural modulus of the material.

[0012] 3. This invention endows the composite material with physical contact antibacterial function. The activated hydroxyapatite ultrafine powder forms a high-density contact network on the surface of the molded product. It utilizes its increased specific surface area to adsorb free bacteria in the environment. The positively charged active sites on the powder surface interact electrostatically with the negatively charged bacterial cell membrane, destroying the structural integrity of the bacterial phospholipid bilayer, causing the leakage of intracellular substances and blocking its metabolism and reproduction. Under the condition of not adding traditional chemical bactericides, the antibacterial effect against Escherichia coli and Staphylococcus aureus is achieved. Detailed Implementation

[0013] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the embodiments and comparative examples. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0014] Preparation Examples 1-6: Preparation Example 1: This preparation example provides a method for preparing lightweight modified plant fiber micro / ultrafine powder. Using bamboo resources and agricultural and forestry waste as raw materials, ultrafine pulverization was performed using an airflow milling device at a pressure of 0.6 MPa to obtain initial powder with a particle size D50 less than or equal to 5 μm. Subsequently, the initial powder was treated with low-temperature ultrasonic cell disruption technology at a power of 800 W for 20 minutes. 3 wt% maleic anhydride was added to the disrupted system for grafting at a temperature of 80°C for 1 hour. After the grafting reaction, 5 wt% polyethylene glycol was added to the system for thermoplastic blending modification at 120°C for 30 minutes. Testing showed that the lightweight modified plant fiber micro / ultrafine powder obtained in this preparation example had a particle size D90 less than or equal to 12 μm, a cellulose purity greater than or equal to 85%, and a bulk density of 0.64 g / cm³. 3 .

[0015] Preparation Example 2: This preparation example provides a method for preparing lightweight modified plant fiber micro / ultrafine powder. Using plant straw and agricultural / forestry waste as raw materials, ultrafine pulverization was performed using an airflow pulverizer at a pressure of 0.7 MPa to obtain initial powder with a particle size D50 less than or equal to 5 μm. Subsequently, the initial powder was treated with low-temperature ultrasonic cell disruption technology at a power of 1000 W for 25 minutes. 4 wt% maleic anhydride was added to the disrupted system for grafting at a temperature of 90°C for 1.5 hours. After the grafting reaction, 6.5 wt% polyethylene glycol was added to the system for thermoplastic blending modification at 130°C for 35 minutes. Testing showed that the lightweight modified plant fiber micro / ultrafine powder obtained in this preparation example had a particle size D90 less than or equal to 12 μm, a cellulose purity greater than or equal to 85%, and a bulk density of 0.61 g / cm³. 3 .

[0016] Preparation Example 3: This preparation example provides a method for preparing lightweight modified plant fiber micro / ultrafine powder. Using bamboo resources and agricultural and forestry waste as raw materials, ultrafine pulverization was performed using an airflow milling device at a pressure of 0.8 MPa to obtain initial powder with a particle size D50 less than or equal to 5 μm. Subsequently, the initial powder was treated with low-temperature ultrasonic cell disruption technology at a power of 1200 W for 30 minutes. 5 wt% maleic anhydride was added to the disrupted system for grafting at a temperature of 100°C for 2 hours. After the grafting reaction, 8 wt% polyethylene glycol was added to the system for thermoplastic blending modification at 140°C for 40 minutes. Testing showed that the lightweight modified plant fiber micro / ultrafine powder prepared in this example had a particle size D90 less than or equal to 12 μm, a cellulose purity greater than or equal to 85%, and a bulk density of 0.58 g / cm³. 3 .

[0017] Preparation Example 4: This preparation example provides a method for preparing activated hydroxyapatite ultrafine powder. Unactivated hydroxyapatite raw material with a purity greater than or equal to 98% is placed in a high-temperature furnace, and the heating rate is set to 5℃ / min, heated to 650℃ for high-temperature activation treatment, and held at that temperature for 2 hours. After activation, the powder is cooled and surface modified to obtain activated hydroxyapatite ultrafine powder. Testing shows that the activated hydroxyapatite ultrafine powder obtained in this preparation example has a D50 of 1μm to 5μm and a specific surface area greater than or equal to 75m². 2 / g, with an antibacterial rate of greater than or equal to 85% against Escherichia coli and Staphylococcus aureus.

[0018] Preparation Example 5: This preparation example provides a method for preparing activated hydroxyapatite ultrafine powder. Unactivated hydroxyapatite raw material with a purity greater than or equal to 98% is placed in a high-temperature furnace, and the heating rate is set to 5℃ / min, heated to 750℃ for high-temperature activation treatment, and held at that temperature for 3 hours. After activation, the powder is cooled and surface modified to obtain activated hydroxyapatite ultrafine powder. Testing shows that the activated hydroxyapatite ultrafine powder obtained in this preparation example has a D50 of 1μm to 5μm and a specific surface area greater than or equal to 75m². 2 / g, with an antibacterial rate of greater than or equal to 85% against Escherichia coli and Staphylococcus aureus.

[0019] Preparation Example 6: This preparation example provides a method for preparing activated hydroxyapatite ultrafine powder. Unactivated hydroxyapatite raw material with a purity greater than or equal to 98% is placed in a high-temperature furnace, and the heating rate is set to 5℃ / min, heated to 850℃ for high-temperature activation treatment, and held at that temperature for 4 hours. After activation, the powder is cooled and surface modified to obtain activated hydroxyapatite ultrafine powder. Testing shows that the activated hydroxyapatite ultrafine powder obtained in this preparation example has a D50 of 1μm to 5μm and a specific surface area greater than or equal to 75m². 2 / g, with an antibacterial rate of ≥85% against Escherichia coli and Staphylococcus aureus. Examples 1-5: Example 1: This embodiment provides a biodegradable composite material for agricultural mulch film and its preparation method, including the following steps: Accurately weigh the following by weight percentage: 25% polylactic acid, 30% poly(adipate adipate / butyl terephthalate), 15% polypropylene carbonate, 5% polyglycolic acid, 15% lightweight modified bamboo-based PFM prepared in Preparation Example 1, 4% activated hydroxyapatite ultrafine powder prepared in Preparation Example 4, 2% compound of polylactic acid-g-maleic anhydride and poly(adipate adipate / butyl terephthalate-g-maleic anhydride), 1% tributyl acetylacetonate, 1% hindered phenolic antioxidant, 1% weathering agent UV-531, 1% compound of zinc stearate and polyethylene wax, 0.5% nano talc, and 0.5% antistatic agent.

[0020] The above raw materials were added to a high-speed mixer, with the mixing speed controlled at 800 rpm and the mixing time at 5 minutes, to obtain a uniform premix. The premix was then added to a twin-screw extruder with a length-to-diameter ratio of 56:1 for melt blending and granulation. The barrel section temperature was controlled at 140-170℃, the screw speed at 300 rpm, and the melt pressure at 8-15 MPa. High-vacuum devolatilization was performed to achieve a vacuum degree greater than or equal to -0.08 MPa. After water cooling, pelletizing, and drying, composite granules were obtained with a particle size of 2-4 mm. The composite granules were then used in a blown film forming process to prepare a 0.08 mm thick mulch film. The barrel temperature was controlled at 145-165℃, the screw speed at 260 rpm, the blow-up ratio at 4:1, and the traction speed at 8 m / min. After forming, the mulch film underwent edge trimming and slitting, and was subjected to a 100-hour UV aging pretreatment simulating outdoor environmental aging. After passing all tests, the film was packaged and shipped.

[0021] Example 2: This embodiment provides a biodegradable composite material for disposable tableware and its preparation method, including the following steps: Accurately weigh the following ingredients by weight percentage: 35% polylactic acid, 20% polybutylene adipate / terephthalate, 10% polypropylene carbonate, 5% polyglycolic acid, 15% lightweight modified rice husk-based PFM obtained in Preparation Example 2, 6% activated hydroxyapatite ultrafine powder obtained in Preparation Example 5, 2% polylactic acid-g-maleic anhydride, 1% polycaprolactone, 0.8% hindered phenolic antioxidant, 0.7% calcium stearate, 0.5% nano-calcium carbonate, and 1% waterproofing agent. Add the above ingredients to a high-speed mixer, control the mixing speed at 1000 rpm, and the mixing time at 8 minutes to obtain a premix.

[0022] The premixed material was added to a twin-screw extruder with a length-to-diameter ratio of 60:1 for melt blending and granulation. The barrel section temperature was controlled at 145-175℃, the screw speed at 280 rpm, and the melt pressure at 10-12 MPa. High-vacuum devolatilization was performed, and the resulting composite granules were obtained after pelletizing and drying. Disposable lunch boxes were then manufactured using injection molding. The injection temperature was controlled at 155-175℃, the injection pressure at 110 MPa, the holding pressure at 75 MPa, and the cooling time at 40 seconds. The molded disposable lunch boxes were then deburred and sterilized at 121℃ for 20 minutes. Temperature resistance tests were conducted, and the boxes were packaged and shipped after passing all tests.

[0023] Example 3: This embodiment provides a biodegradable composite material for beverage packaging containers and its preparation method, including the following steps: Accurately weigh the following by weight percentage: 38% polylactic acid, 18% polybutylene adipate / terephthalate, 8% polypropylene carbonate, 4% polyglycolic acid, 12% lightweight modified rice husk-based PFM obtained in Preparation Example 2, 7% activated hydroxyapatite ultrafine powder obtained in Preparation Example 5, 2.5% polylactic acid-g-maleic anhydride, 1.5% tributyl acetylacetic acid, 1% hindered phenolic antioxidant, 1% montmorillonite barrier agent, 0.8% zinc stearate, 0.7% nano talc, and 1.5% waterproofing agent. Add the above raw materials to a high-speed mixer, control the mixing speed at 1200 rpm, and the mixing time at 10 minutes to obtain a premix.

[0024] The premixed material was added to a twin-screw extruder with a length-to-diameter ratio of 64:1 for melt blending and granulation. The barrel section temperature was controlled at 150-180℃, the screw speed at 250 rpm, and the melt pressure at 12-15 MPa. High-vacuum devolatilization was performed, followed by pelletizing and drying to obtain composite granules. The composite granules were then used to form the cup body using a thermoforming process, with the thermoforming temperature controlled at 160-180℃ and the pressure at 90 MPa. The cup lid was then used to form the cup using an injection molding process, with the injection temperature controlled at 155-175℃ and the injection pressure at 100 MPa. After molding, a waterproof coating was cured at 80℃ for 30 minutes, and dimensional calibration was performed. After passing all tests, the product was packaged and shipped.

[0025] Example 4: This embodiment provides a biodegradable composite material for automobile and drone shells and its preparation method, including the following steps: Accurately weigh the following by weight percentage: 42% polylactic acid, 15% polybutylene adipate / terephthalate, 5% polypropylene carbonate, 3% polyglycolic acid, 18% lightweight modified straw-based PFM prepared in Preparation Example 3, 8% activated hydroxyapatite ultrafine powder prepared in Preparation Example 6, 3% polylactic acid-g-maleic anhydride, 2% magnesium hydroxide flame retardant, 1.5% hindered phenolic antioxidant, 0.8% calcium stearate, 1% nano-calcium carbonate, and 0.7% antistatic agent. Add the above raw materials to a high-speed mixer and mix uniformly to obtain a premix.

[0026] The premixed material is added to a twin-screw extruder for melt blending and granulation. The barrel section temperature is controlled at 155-185℃, the screw speed at 320 rpm, and the melt pressure at 15 MPa. High-vacuum devolatilization is performed with nitrogen protection. The mixture is then pelletized and dried to obtain composite granules. Precision injection molding is used to prepare the outer shell of the composite granules. The barrel temperature is controlled at 165-185℃, the injection pressure at 140 MPa, the holding pressure at 90 MPa, and the cooling time at 60 seconds. After molding, the outer shell undergoes CNC grinding and polishing, followed by low-temperature curing at 50℃ for 12 hours to improve dimensional stability. After passing all tests, the product is packaged and shipped.

[0027] Example 5: This embodiment provides a biodegradable composite material for household appliance casings and its preparation method, including the following steps: The following components are accurately weighed by weight percentage: 38% polylactic acid, 18% polybutylene adipate / terephthalate, 6% polypropylene carbonate, 4% polyglycolic acid, 16% lightweight modified straw-based PFM prepared in Preparation Example 3, 7% activated hydroxyapatite ultrafine powder prepared in Preparation Example 6, 2.5% polylactic acid-g-maleic anhydride, 1.2% hindered phenolic antioxidant, 0.8% zinc stearate, 1% nano talc, 1% antistatic agent, and 2.5% color masterbatch.

[0028] The above raw materials are added to a high-speed mixer to obtain a premix. The premix is ​​then added to a twin-screw extruder for melt blending and granulation. The barrel section temperature is controlled at 155-185℃, the screw speed at 300 rpm, and high-vacuum devolatilization is performed. The mixture is then pelletized and dried to obtain composite granules. Precision injection molding is used to prepare appliance casings from the composite granules. The barrel temperature is controlled at 160-180℃, the injection pressure at 130 MPa, the holding pressure at 85 MPa, and the cooling time at 50 seconds. After molding, the casing is deburred and coated with an environmentally friendly paint. Appearance and dimensional inspections are performed, and the casing is packaged and shipped after passing all inspections.

[0029] Comparative Examples 1-4: Comparative Example 1: Compared with Example 1, the difference is that the lightweight modified bamboo-based PFM prepared in Preparation Example 1 was replaced in equal amounts with unmodified bamboo fiber powder that had been conventionally physically crushed to the same particle size but had not undergone ultrasonic cell disruption, maleic anhydride grafting, and polyethylene glycol blending modification. All other aspects were the same.

[0030] Comparative Example 2: Compared with Example 1, the difference is that the activated hydroxyapatite ultrafine powder obtained in Preparation Example 4 in the formulation was replaced in equal amounts with commercially available ordinary unactivated hydroxyapatite micro powder, and all other aspects were the same.

[0031] Comparative Example 3: Compared with Example 1, the difference is that 15% polypropylene carbonate and 5% polyglycolic acid in the blend matrix were completely removed, and their total weight ratio of 20% was added equally to polylactic acid and poly(butylene adipate / terephthalate) (i.e., the polylactic acid ratio was adjusted to 35% and the poly(butylene adipate / terephthalate) ratio was adjusted to 40%). The matrix was changed from a quaternary system to a binary system, and everything else was the same.

[0032] Comparative Example 4: Compared with Example 1, the difference is that polypropylene carbonate and polyglycolic acid were removed from the blend matrix (polylactic acid was changed to 38%, and poly(butylene adipate / terephthalate) was changed to 41%). At the same time, the lightweight modified bamboo-based PFM obtained in Preparation Example 1 was replaced with an equal amount of ordinary bamboo fiber powder without modification treatment, and the activated hydroxyapatite ultrafine powder obtained in Preparation Example 4 was completely removed (this part of 4% was added to the blend matrix). All other aspects are the same.

[0033] Test Examples 1-5: Test Example 1: Lightweighting Mechanism and Processing Rheological Properties Test True density test: The density of non-foamed plastics was determined using the immersion method according to GB / T1033.1. In a laboratory environment at a constant temperature of 23℃, composite particle samples prepared in each example were taken, and anhydrous ethanol was used as the immersion liquid. The mass of the samples in air and in liquid was measured using a hydrometer balance, and the true density was calculated. Each sample was measured in parallel five times, and the arithmetic mean was taken.

[0034] Bulk density test: The test was conducted according to GB / T1636, "Determination of apparent density of plastics that can flow from a specified funnel." The composite particle samples of each embodiment were vacuum dried at 80°C for 4 hours to remove surface moisture. Using a standard funnel apparatus, the sample filled with the funnel was allowed to fall freely into a measuring cylinder of known volume. After leveling the surface, the mass of the sample in the cylinder was weighed, and the bulk density was calculated. Each sample was repeated three times, and the arithmetic mean was taken.

[0035] Melt flow rate test: The test was conducted according to GB / T3682, "Determination of Melt Mass Flow Rate and Melt Volume Flow Rate of Thermoplastic Plastics". A melt flow rate tester was used, with the test temperature set at 170℃ and the standard load at 2.16 kg. The dried composite granules were added to the barrel and preheated for 5 minutes. A melt sample was cut, the mass of the cut sample was weighed, and the melt mass flow rate per unit time was calculated. Each sample was tested three times, and the arithmetic mean was taken.

[0036] Test results: Table 1. Lightweighting and Processing Rheological Properties Test Results of Composite Materials from Examples

[0037] Results analysis: According to the data in Table 1, the actual density distribution of the composite particles prepared in Examples 1 to 5 ranges from 1.157 to 1.242 g / cm³. 3 The bulk density ranges from 0.574 to 0.625 g / cm³. 3The plant fiber micro- and ultra-micro powders, after undergoing airflow pulverization and ultrasonic cell disruption, have their original dense vascular bundle structure destroyed, releasing internal pores and resulting in a lower volume-to-mass ratio in the composite system. Maleic anhydride grafting and polyethylene glycol coating modification block hydrogen bonding between cellulose macromolecular chains, reducing the polarity of the powder surface and allowing it to disperse in the quaternary blend matrix, avoiding localized density abrupt changes caused by powder agglomeration. The bulk density is consistently below 0.64 g / cm³. 3 This indicates that the lightweight modification process achieves a balance between the volume filling effect and the weight reduction effect.

[0038] Melt flow rate tests showed that the melt mass flow rate of each embodiment remained within the range of 12.65 to 16.51 g / 10 min. The introduction of polypropylene carbonate and polyglycolic acid modified the segmental flexibility of the polylactic acid matrix, and the polyethylene glycol modified layer acted as an internal lubricant at the interface between plant fibers and polymer melt, reducing the melt shear viscosity. Combined with a processing aid system of stearate and polyethylene wax, the composite material, with the addition of a high proportion of inorganic activated hydroxyapatite and plant fiber powder, maintained rheological properties suitable for blown film, injection molding, and thermoforming processes, without melt fracture or flow discontinuity, confirming the feasibility of the multi-component compound system in the molding process.

[0039] Test Example 2: Basic Tests on Hazardous Substances and Safety Microwave digestion of samples: The composite particle samples prepared in each example were pulverized using a stainless steel cryogenic grinder and passed through a 60-mesh sieve. Accurately weigh 0.23 g to 0.28 g of the pulverized sample and place it in a polytetrafluoroethylene microwave digestion vessel. Add 6 mL of analytical grade nitric acid and 2 mL of hydrogen peroxide sequentially. Seal the digestion vessel and place it in a microwave digester. Digestion was performed according to the set program, heating to 190°C and maintaining the temperature for 25 minutes. After digestion, the acid was removed to near dryness, and the residual liquid was transferred to a 50 mL volumetric flask. The solution was then diluted to the mark with ultrapure water and shaken well to obtain the test solution. A reagent blank solution was prepared simultaneously.

[0040] Standard working curves were prepared by using single-element standard stock solutions from the National Center for Standard Materials, which were serially diluted with 2% nitric acid solution to prepare a series of mixed standard working solutions for arsenic, cadmium, mercury, lead, and chromium. Concentration points were set at 0.5 μg / L, 2.3 μg / L, 8.6 μg / L, 15.2 μg / L, 35.4 μg / L, and 60.8 μg / L, respectively.

[0041] Instrument parameter settings and determination: The content of each heavy metal element in the test solution was determined using an inductively coupled plasma mass spectrometer (ICP-MS). The instrument's RF power was set to 1550W, plasma gas flow rate to 14.5L / min, auxiliary gas flow rate to 0.85L / min, nebulizer gas flow rate to 1.02L / min, and sampling depth to 8mm. The collision cell mode was activated to eliminate polyatomic ion interference. The reagent blank solution, mixed standard series working solution, and test solutions from each example were sequentially introduced into the instrument, and the signal response values ​​of each element were recorded.

[0042] Results Calculation: A standard curve was established by linear regression with elemental concentration on the x-axis and response intensity on the y-axis. The response value of the test solution was substituted into the equation to obtain the test concentration. After subtracting the reagent blank, the absolute content of heavy metals in the sample was calculated based on the sample weight and the final volume. Each sample was measured in triplicate, and the arithmetic mean was taken.

[0043] Test results: Table 2. Test results of heavy metal content in the composite materials of the examples

[0044] Results analysis: According to the data in Table 2, the detection values ​​of heavy metals arsenic, cadmium, mercury, lead, and chromium in the composite materials prepared in Examples 1 to 5 were all at extremely low levels. Many indicators showed no detection or were below 0.05 mg / kg, far below the mandatory heavy metal limits for conventional food contact materials and agricultural mulch films (typically limits are in the milligram to ten milligram range). In the quaternary blend matrix, polylactic acid, polyglycolic acid, and polypropylene carbonate were synthesized by biomass fermentation or carbon dioxide catalysis. The catalyst removal process in the synthesis route controlled the residual metal ions. The lightweight modified plant fiber micro- and ultra-micro powder of the core reinforcing phase was made from natural bamboo fiber, straw, and rice husk. No heavy metal salts were introduced during the entire process of crushing, cell wall breaking, and grafting reactions.

[0045] Multifunctional synergistic phase activated hydroxyapatite requires a precursor purity greater than or equal to 98%. During the high-temperature activation process at 650 to 850℃, a small amount of volatile inorganic impurities are released by heat, and the lattice recombination process solidifies and encapsulates residual trace elements. The twin-screw extruder with an aspect ratio greater than 56:1 and high-vacuum devolatilization configuration in the extrusion granulation stage eliminates the contamination of the matrix by small molecule harmful substances generated during processing and degradation. Test data confirms that the composite material will not cause heavy metal accumulation in the soil after natural degradation, and there is no risk of heavy metal migration into food simulants when used as tableware and packaging films, verifying the chemical safety and environmental feasibility of the material system.

[0046] Test Example 3: Comparison Test of Mechanical Properties Test specimen preparation: The dried composite granules of Example 1 and Comparative Examples 1 to 4 were added to an injection molding machine. The barrel temperature distribution of the injection molding machine was set to 155℃ to 170℃, and the mold temperature was controlled at 30℃. Type 1A multi-purpose tensile specimens, long strip bending specimens, and impact specimens with specified dimensions were injection molded to meet the standard requirements. All molded specimens were placed in a constant temperature and humidity environment of 23℃ and 50% relative humidity for 48 hours for conditioning.

[0047] Tensile property testing: Performed according to national standard GB / T1040.2, "Determination of Tensile Properties of Plastics". The conditioned Type 1A multi-purpose tensile specimen is clamped in the upper and lower grips of the universal testing machine, with the gauge clamped at the parallel section of the specimen. The tensile speed is set to 50 mm / min, and the machine is started to apply axial tension until the specimen breaks. The machine automatically records the yield load, maximum load, and fracture displacement, and calculates the tensile strength and elongation at break. Five valid specimens are tested for each group of samples; after removing outliers with excessive deviations, the arithmetic mean is taken.

[0048] Bending performance test: The test was conducted according to the national standard GB / T9341, "Determination of Bending Performance of Plastics". A three-point bending fixture was used to place the specimen horizontally on two supports of the universal testing machine base, with a support span set to 64 mm. The machine's loading head applied a vertical load to the specimen at the center of the span at a speed of 2 mm / min until the specimen deflection reached the specified value or fracture occurred. The relationship between load and deflection was recorded, and the bending modulus was calculated. Each group of samples was tested in parallel five times.

[0049] Notched impact performance test: The test was conducted according to the national standard GB / T1043.1, "Determination of Impact Performance of Simply Supported Beams in Plastics". A type A notch was milled in the middle of the impact specimen using a notching sample preparation machine, with a remaining notch width of 8 mm and a bottom radius of 0.25 mm. The specimen was placed horizontally on the support of a pendulum impact testing machine, with the notch facing away from the direction of the pendulum impact. The pendulum was released to break the specimen, and the energy consumed in breaking the specimen was read from the dial or system display. This energy was divided by the cross-sectional area at the notch of the specimen to calculate the notched impact strength of the simply supported beam. Eight specimens were tested for each group of samples, and the average value was taken.

[0050] Test results: Table 3. Mechanical property test data of composite materials in the examples and comparative examples

[0051] Results analysis: According to the data in Table 3, the tensile strength, elongation at break, flexural modulus, and notched impact strength of Example 1 are all higher than those of the basic binary blend plus unmodified powder system in Comparative Example 4. Compared with Comparative Example 1, Example 1 uses ordinary bamboo powder that has not undergone ultrasonic cell disruption and chemical modification. The plant powder surface contains a large number of free hydroxyl groups, exhibiting strong polarity, which cannot form good interfacial compatibility with the weakly polar polyester blend matrix. Micropores exist between the matrix and the powder, leading to stress concentration at the interface under external force and inducing microcrack propagation, resulting in a significant decrease in tensile strength and notched impact strength. In Example 1, the plant fibers undergo airflow ultra-micronization and ultrasonic cell disruption to release their internal structure. Maleic anhydride introduces active groups, and polyethylene glycol forms a flexible transition phase between the powder and matrix interface. This flexible transition phase reduces interfacial tension, enabling effective transfer of applied stress from the blend matrix to the high-modulus plant fiber micro- and ultra-micro powders.

[0052] Compared to Comparative Example 2, Example 2 used ordinary unactivated hydroxyapatite, which was dispersed in the matrix as a conventional rigid particle, resulting in limited improvement in flexural modulus and tensile strength. In Example 1, the hydroxyapatite was activated at high temperatures of 650 to 850°C, increasing its specific surface area to 75 m². 2 Above a certain size, the exposure of active sites on the crystal surface increases. During the melt blending process, the activated micropowder with high specific surface area forms secondary bonds with the macromolecular chains of the matrix and the anhydride groups in the compatibilizer, forming spatial network nodes. This restricts the slippage of polymer chain segments in the amorphous region under stress, thereby improving the flexural modulus and tensile yield stress of the composite system.

[0053] Compared with Comparative Example 3, Example 1, after eliminating polypropylene carbonate and polyglycolic acid, showed a decrease in elongation at break from 132.4% to 82.5%, and a decrease in notched impact strength from 8.3 kJ / m. 2 Decreased to 5.6 kJ / m 2 Polylactic acid (PLA) and poly(butylene adipate / terephthalate) exhibit poor intrinsic compatibility and large phase sizes in binary blends. Polypropylene carbonate (PPC) and polyglycolic acid (PGA) act as multiphase compatibilizers and crystallization induction agents in the system. The high molecular weight and amorphous structure of PPC improve the melt strength and flexibility of the system, while PGA acts as a nucleating agent, promoting the formation of PLC crystallites. The quaternary alloying system refines the domain size of the dispersed phases, making the two-phase interface more blurred. Under external impact, the matrix absorbs a large amount of impact energy through crazing and shear yielding, maintaining high levels of elongation at break and impact strength. The multi-component formulation combination demonstrates a positive synergistic effect between physical structure and chemical interface in terms of mechanical properties.

[0054] Test Example 4: Comparative Test of Highly Effective Antibacterial Performance The composite material sheets formed in Example 1 and Comparative Examples 1 to 4 were cut into 50mm × 50mm square samples. The samples were immersed and wiped in a 75% ethanol solution, rinsed with sterile distilled water, and air-dried. Surface sterilization was completed by irradiation under a UV lamp for 30 minutes, and the samples were then placed in sterile petri dishes for later use. Meanwhile, a standard polyethylene film without added antibacterial components was prepared as a blank control.

[0055] Escherichia coli (ATCC8739) and Staphylococcus aureus (ATCC6538) were selected as test strains. The cryopreserved strains were inoculated onto nutrient agar slants and activated at 35°C for 24 hours. Typical activated colonies were picked and inoculated into nutrient broth, and cultured with shaking at 35°C for another 18 hours. The bacterial suspension was serially diluted with sterile physiological saline to prepare a concentration of 1.2 × 10⁻⁶. 5 Up to 4.5×10 5 CFU / mL live bacterial suspension for inoculation.

[0056] Take 0.4 mL of the prepared live bacterial suspension and add it dropwise to the surface of each sterilized sample. Place a 40 mm × 40 mm sterile polyethylene covering film on top of the bacterial suspension, and gently press it to spread the suspension evenly without overflowing the edges of the film, ensuring contact between the bacterial suspension and the sample surface. Cover the petri dish and place it in a constant temperature and humidity incubator at 35°C and a relative humidity greater than 90% for 24 hours.

[0057] Remove the cultured sample, along with the covering membrane, and place it into a sterile Erlenmeyer flask containing 20 mL of sodium thiosulfate eluent. Shake on a shaker for 10 minutes to elute any surviving bacteria from the sample and covering membrane into the solution. Perform a 10-fold serial dilution with physiological saline. Pour 1 mL of each dilution into a Petri dish, add approximately 15 mL of melted and incubated nutrient agar medium at 45°C, and rotate the dish to thoroughly mix the bacterial culture with the agar. After the agar solidifies, invert the Petri dish and incubate upside down at 35°C for 48 hours.

[0058] Observe the petri dishes and count the number of colonies generated. Select petri dishes with colony counts between 30 and 300 for reading, multiply by the corresponding dilution factor, and calculate the total number of surviving bacteria on the surface of each sample. Using the number of surviving bacteria after 24 hours of incubation in the blank control sample as a benchmark, calculate the antibacterial rate of each sample. Each group of samples was tested in triplicate, and the arithmetic mean was taken.

[0059] Test results: Table 4. Antibacterial performance test data of the composite materials in the examples and comparative examples

[0060] Results analysis: According to the data in Table 4, the antibacterial rates of Example 1, Comparative Example 1, and Comparative Example 3 against *Escherichia coli* and *Staphylococcus aureus* all exceeded 85%, while the antibacterial rates of Comparative Example 2 and Comparative Example 4 were at a lower level. Comparing Example 1 and Comparative Example 2, the ratio of matrix resin to plant fiber reinforcing phase was completely identical. The difference was that Comparative Example 2 used commercially available, unactivated hydroxyapatite micropowder. Ordinary hydroxyapatite has a dense and complete crystal structure, a small specific surface area, and lacks free active sites on its surface. In composite material systems, it exists only as an inorganic filler and cannot inhibit or kill bacteria that come into contact with the material surface. The antibacterial rate of Comparative Example 2 was only maintained at around 30%. The activated hydroxyapatite used in Example 1 underwent a high-temperature treatment process of 650 to 850°C, resulting in lattice restructuring and partial defect formation, increasing the powder's specific surface area to greater than or equal to 75 μm². 2 / g. The high specific surface area endows the material's surface with strong physical adsorption capacity, enabling it to accumulate free bacteria in the environment. High-temperature activation exposes a large number of active sites such as calcium ions and hydroxyl groups on the hydroxyapatite surface. The positively charged active surface interacts electrostatically with the negatively charged bacterial cell membrane. This electrostatic binding interferes with the ion channels of the cell membrane, disrupts the structural integrity of the phospholipid bilayer, and causes the leakage of large molecules such as proteins and nucleic acids from within the bacteria, thus blocking the normal metabolic and reproductive processes of the bacteria and achieving a bactericidal effect.

[0061] In Comparative Example 4, the hydroxyapatite component was completely eliminated, and the tested antibacterial rates against Escherichia coli and Staphylococcus aureus were only 14.2% and 16.9%, respectively. This was attributed to the physical barrier effect created by the smooth, hydrophobic surface of the polymer matrix itself, and lacked active antibacterial ability. Examples 1, Comparative Example 1, and Comparative Example 3, which contained activated hydroxyapatite, all maintained highly efficient antibacterial performance, demonstrating that the activated hydroxyapatite component is the decisive condition for achieving an antibacterial rate greater than or equal to 85% in this composite material. Under the shear field action of blending, granulation, and molding, the ultrafine powder was uniformly dispersed in the polymer matrix and plant fiber network. The activated phase formed a high-density antibacterial contact network on the surface of the product, synergistically ensuring hygiene and safety requirements in multiple application scenarios.

[0062] Test Example 5: Comparative Test of Controllability of Degradation Rate in Two Scenarios Sample preparation and pretreatment: The films or sheets prepared in Example 1 and Comparative Examples 1 to 4 were cut into 20 mm × 20 mm square samples. The samples were placed in a vacuum drying oven and dried at 40 °C for 24 hours until constant weight was achieved. The initial mass of each sample was accurately weighed using an analytical balance.

[0063] Industrial compost degradation test: The test was conducted according to GB / T19277.1, "Determination of final aerobic biodegradation capacity of materials under controlled composting conditions." Mature inoculum was used as the compost substrate, with the substrate moisture content adjusted to 50%–55% and the pH value to 7.0–8.0. The sample was mixed with the compost substrate at a mass ratio of 1:6 and loaded into the compost reactor. The reactor was placed in a constant-temperature incubator at 58°C, with continuous introduction of airless oxygen. Samples from corresponding batches were collected after 3 months and 6 months of incubation.

[0064] Simulated Natural Soil Degradation Test: Topsoil from farmland was collected as the test substrate and passed through a 2mm sieve to remove impurities. The soil moisture content was adjusted to 60% of its maximum water holding capacity. The samples were buried in the soil at a depth of 5cm. The test container was placed in a constant temperature and humidity chamber, with the temperature set at 25℃ and the relative humidity at 60%, simulating a typical living and agricultural natural environment. Samples from corresponding batches were retrieved at 6 months and 12 months after burial.

[0065] Mass loss rate determination: Samples taken from both degradation environments were placed in an ultrasonic cleaner containing deionized water and cleaned for 10 minutes to remove surface-adhered dirt, mycelia, and residue. After cleaning, the samples were vacuum-dried at 40°C to constant weight. The remaining mass was weighed, and the mass loss rate at each stage was calculated by dividing the difference between the initial mass and the remaining mass by the initial mass. Five parallel tests were conducted for each group of samples, and the arithmetic mean was taken.

[0066] Test results: Table 5. Degradation rate test data of composite materials in both examples and comparative examples under two scenarios.

[0067] Results analysis: According to the data in Table 5, Example 1 achieved degradation with a mass loss rate exceeding 95% after 6 months in industrial compost and 12 months in natural soil. Comparative Examples 3 and 4 showed mass loss rates of only 39.7% and 27.2% in natural soil after 12 months, respectively, and also failed to reach 90% after 6 months in industrial compost. The blend matrix of Comparative Examples 3 and 4 was a binary system of polylactic acid (PLA) and poly(butylene adipate) / terephthalate (PET). PLA has a glass transition temperature between 55°C and 60°C. In a natural soil environment at 25°C, PLA is in a glassy state, where macromolecular chains are frozen, making it difficult for free water molecules and environmental microorganisms to penetrate the polymer interior. Therefore, the hydrolysis reaction can only proceed slowly on the surface.

[0068] Example 1 describes a quaternary alloying system constructed by introducing polypropylene carbonate and low-temperature modified polyglycolic acid. Polyglycolic acid has a high ester bond density and strong hydrophilicity in its main chain, forming a hydrolysis-inducible phase within the matrix. Upon contact with soil moisture, the main chain preferentially breaks, generating terminal carboxyl groups. These terminal carboxyl groups have a self-catalytic effect on the ester bond breaking of polylactic acid and poly(butylene adipate / terephthalate), reducing the hydrolysis activation energy of the system. Polypropylene carbonate, being amorphous with a low glass transition temperature, increases the free volume of the blend matrix and disrupts the crystallinity regularity of polylactic acid. The increased phase interface and decreased crystallinity allow water molecules and degradation enzymes secreted by fungi and bacteria to penetrate the material surface and enter the internal phase region at room temperature. Simultaneously, the modified plant fiber micro- and ultra-micro powders are uniformly distributed in the system. The micron-sized pores left after plant fiber degradation form capillary channels, further expanding the contact area for microbial attachment and enzyme infiltration. The combination of physical structural adjustments between components and chemical autocatalytic effects eliminates the strong dependence of traditional binary systems on high temperature and high humidity environments, enabling the material to achieve the target degradation rate in two completely different scenarios: ambient temperature natural soil and high temperature industrial composting.

Claims

1. A biodegradable composite material synergistically reinforced with bio-based PFM and hydroxyapatite, characterized in that, Made from raw materials comprising the following weight percentages: Polylactic acid 25-42%; Poly(butylene adipate) 15-30%; Polypropylene carbonate 5-15%; Polyglycolic acid 3-5%; Lightweight modified plant fiber micro- and ultra-micro powder 12-18%; Activated hydroxyapatite ultrafine powder 4-8%; Compatibilizer 2-3%; Additives 1-7%; The polypropylene carbonate and the polyglycolic acid synergistically construct an amorphous and hydrolysis-induced phase, thereby eliminating the matrix's dependence on high-temperature and high-humidity degradation environments and enabling degradation in both natural soil and industrial compost scenarios. The activated hydroxyapatite ultrafine powder utilizes the exposed active sites on its surface to form secondary bonds with the blended polymer matrix, creating spatial network nodes that provide mechanical synergistic enhancement and electrostatic adsorption contact antibacterial function.

2. The biodegradable composite material synergistically reinforced by bio-based PFM and hydroxyapatite according to claim 1, characterized in that, The base raw material for the lightweight modified plant fiber micro- and ultra-micro powder is selected from one of bamboo fiber, wheat straw powder, or rice husk powder. The characteristic parameters of the lightweight modified plant fiber micro / ultrafine powder include: particle size D90 of 5-12 μm, cellulose purity of 85%-98%, and bulk density of 0.45-0.64 g / cm³. 3 .

3. The biodegradable composite material synergistically reinforced by bio-based PFM and hydroxyapatite according to claim 2, characterized in that, The lightweight modified plant fiber micro / ultrafine powder is prepared by a method including the following steps: The basic raw materials are subjected to airflow ultrafine grinding, with the grinding pressure controlled at 0.6-0.8 MPa, to obtain initial powder with a particle size D50 of 1-5 μm; The initial powder was subjected to low-temperature ultrasonic cell disruption using ultrasonic equipment, with the ultrasonic power controlled at 800-1200W and the ultrasonic time at 20-30 minutes. Add 3wt%-5wt% of maleic anhydride by weight of the initial powder to the system after cell wall disruption, and react at 80-100℃ for 1-2 hours; After the reaction is complete, 5wt%-8wt% of polyethylene glycol by weight of the initial powder is added, and the mixture is kept at 120-140℃ for 30-40 minutes to obtain the lightweight modified plant fiber micro-ultra-fine powder.

4. The biodegradable composite material synergistically reinforced by bio-based PFM and hydroxyapatite according to claim 1, characterized in that, The parameters of the activated hydroxyapatite ultrafine powder include: particle size D50 of 1-5 μm and specific surface area of ​​75-120 m². 2 / g.

5. The biodegradable composite material synergistically reinforced by bio-based PFM and hydroxyapatite according to claim 4, characterized in that, The activated hydroxyapatite ultrafine powder is prepared by a method comprising the following steps: Unactivated hydroxyapatite with a purity of 98%-99.9% is placed in a high-temperature furnace and heated to 650-850℃ at a heating rate of 3-8℃ / min for high-temperature activation treatment. The temperature is held for 2-4 hours. After cooling and surface modification, the activated hydroxyapatite ultrafine powder is obtained.

6. The biodegradable composite material synergistically reinforced by bio-based PFM and hydroxyapatite according to claim 1, characterized in that, The carbon dioxide conversion efficiency of the polypropylene carbonate ranges from 95% to 99.5%. The polyglycolic acid is a low-temperature modified polyglycolic acid containing hydrophilic ester bonds.

7. The biodegradable composite material synergistically reinforced by bio-based PFM and hydroxyapatite according to claim 1, characterized in that, The compatibilizer is one or a combination of two of maleic anhydride-grafted polylactic acid and maleic anhydride-grafted poly(adipate) / butyl terephthalate. The grafting rate of maleic anhydride in the compatibilizer ranges from 1.0wt% to 1.5wt%.

8. The biodegradable composite material synergistically reinforced by bio-based PFM and hydroxyapatite according to claim 1, characterized in that, The additives include various combinations of plasticizers, antioxidants, lubricants, nucleating agents, and functional additives.

9. The biodegradable composite material synergistically reinforced by bio-based PFM and hydroxyapatite according to claim 8, characterized in that, The plasticizer is selected from at least one of acetylglucosamine tributyl citrate or polycaprolactone; The antioxidant is a hindered phenolic antioxidant and / or a phosphite antioxidant; The lubricant is selected from at least one of zinc stearate, calcium stearate, or polyethylene wax; The nucleating agent is selected from at least one of nano-talc powder or nano-calcium carbonate.

10. The biodegradable composite material synergistically reinforced by bio-based PFM and hydroxyapatite according to claim 8, characterized in that, The waterproofing agent is selected from at least one of silicone, stearic acid, paraffin or polyurethane; The masterbatch is selected from resin carrier particles containing at least one colorant selected from carbon black, titanium dioxide, ultramarine or iron oxide red. The functional additives are selected from at least one of the following: weathering agent UV-531, barrier agent montmorillonite, flame retardant magnesium hydroxide, or antistatic agent.

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