Bamboo powder bio-based degradable material and preparation method thereof

Abstract

The invention discloses a bamboo powder bio-based degradable material and a preparation method thereof, and belongs to the technical field of bio-based composite materials. The material comprises the following components in parts by weight: 35-65 parts of bamboo powder, 20-45 parts of poly (adipic acid) / butylene terephthalate, 5-15 parts of modified chitosan, 3-10 parts of a composite plasticizer, 2-8 parts of an inorganic filler, 0.5-3 parts of a composite antioxidant and 0.3-2 parts of a light stabilizer. The preparation method comprises the steps of material preparation, pretreatment, mixing, granulation, forming and the like, bamboo powder is subjected to compound modification through an alkali liquor-silane coupling agent, and sectional temperature control is adopted in mixing. The 180-day soil degradation rate of the material is greater than or equal to 60%, the tensile strength is greater than or equal to 18MPa, the problem that degradation and mechanical properties of an existing material are difficult to consider can be solved, and the material is suitable for the fields of packaging, tableware and the like.

Description

Technical Field

[0001] This invention relates to the field of bio-based composite materials technology, specifically to a bamboo powder bio-based degradable material and its preparation method. This material can be widely used in packaging materials, disposable tableware, gardening supplies, toys and other fields, and is especially suitable for scenarios with high requirements for both biodegradability and mechanical properties of materials. Background Art

[0002] With the increasing global awareness of environmental protection, addressing the environmental pollution caused by the non-degradability of traditional plastics has become a key focus for the industry. Bamboo powder, a waste product generated during bamboo product processing, has advantages such as wide availability, low cost, and biodegradability, making it an ideal filler material in the field of bio-based composite materials.

[0003] Reference document (A bamboo powder composite material, preparation method and application thereof, patent number CN201010193260.7) discloses a bamboo powder composite material, the components of which include 30-60 parts bamboo powder, 40-70 parts melamine resin powder, and 3-12 parts hot melt adhesive powder. Some formulations also contain talc powder and calcium-zinc composite stabilizers. The preparation method includes steps such as material preparation, pretreatment, mixing, and die casting. This material is mainly used in speaker cabinets, building materials and other fields. However, this prior art has obvious limitations: the melamine resin used is a non-biodegradable polymer material, which means that the prepared composite material cannot be completely degraded in the natural environment, and will still cause environmental burden after long-term use; at the same time, its formulation design focuses on improving the mechanical strength and processing performance of the material, without considering the requirements for degradation performance, and the application scenarios of the material are concentrated in fields such as speaker cabinets where degradation is not required, which cannot meet the current market scenarios such as packaging and disposable tableware where there are clear requirements for degradation performance. Furthermore, in existing technologies, the interfacial bonding between bamboo powder and resin is achieved only through simple drying pretreatment, resulting in poor interfacial compatibility and problems such as material delamination and unstable mechanical properties, making it difficult to meet diverse application requirements. Therefore, developing a bamboo powder-based material that combines excellent biodegradability, stable mechanical properties, and a wider range of applications is of significant practical importance. Summary of the Invention

[0004] This invention provides a bamboo powder bio-based degradable material and its preparation method. By optimizing component selection, improving bamboo powder pretreatment process and processing parameters, a balance is achieved between the material's biodegradability, mechanical properties and processing performance, thus expanding the material's application in environmental protection-related fields.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A bamboo powder bio-based degradable material, by weight, comprises the following components: 35-65 parts bamboo powder, 20-45 parts poly(butylene adipate / terephthalate), 5-15 parts modified chitosan, 3-10 parts composite plasticizer, 2-8 parts inorganic filler, and 0.5-3 parts composite antioxidant. Furthermore, the modified chitosan is chitosan grafted with γ-aminopropyltriethoxysilane, with a grafting rate of 12% to 25%; the composite plasticizer is a compound of tributyl citrate and epoxidized soybean oil in a weight ratio of 2:1 to 3:1.

[0006] Preferably, the inorganic filler is nano-hydroxyapatite with a particle size of 50-100 nm; the composite antioxidant is composed of antioxidant 1010 and antioxidant 168 in a weight ratio of 1:1 to 1:2; the bamboo powder bio-based degradable material has a degradation rate of not less than 60% in a natural soil environment after 180 days, a tensile strength of not less than 18 MPa, an elongation at break of not less than 25%, and a flexural strength of not less than 22 MPa, which can meet the dual requirements of material mechanical properties and biodegradability in the fields of packaging materials, disposable tableware, and gardening supplies.

[0007] Furthermore, it also includes 0.3 to 2 parts of light stabilizer.

[0008] Furthermore, the bamboo powder has a particle size of 80-150 mesh and has undergone a pretreatment step.

[0009] Preferably, the pretreatment step is as follows: bamboo powder is placed in a sodium hydroxide solution with a mass concentration of 3%~5%, stirred at a temperature of 60~80℃ for 2~4 hours, filtered, washed with deionized water until neutral, and then dried at a temperature of 105~110℃ until the moisture content is ≤3%; the dried bamboo powder is added to an ethanol solution of silane coupling agent KH-550 with a mass concentration of 1%~2%, the amount of silane coupling agent KH-550 being 1%~3% of the mass of bamboo powder, stirred and reacted at a temperature of 50~60℃ for 1~2 hours, filtered, and dried at a temperature of 80~90℃ for 3~5 hours to obtain pretreated bamboo powder; the interfacial bonding strength between the bamboo powder and poly(adipate adipate / butyl terephthalate) after this pretreatment is increased by 20%~35%, effectively reducing internal defects in the material and further improving the tensile strength and flexural strength of the material.

[0010] Furthermore, the poly(adipate) / butyl terephthalate has a number-average molecular weight of 80,000~120,000 and a melt index (190℃, 2.16kg) of 5~15g / 10min. Selecting poly(adipate) / butyl terephthalate within this parameter range allows for the formation of a superior melt blend system with modified chitosan and pretreated bamboo powder. This ensures good processing fluidity while avoiding the decrease in mechanical properties due to excessively low molecular weight, or the increased energy consumption and uneven mixing of components during the mixing process due to excessively high molecular weight. This keeps the melt processing temperature of the material within the range of 160~180℃, resulting in stable processing performance.

[0011] Furthermore, the purity of tributyl citrate in the composite plasticizer is ≥99%, and the epoxy value of epoxidized soybean oil is ≥6.0%. High-purity tributyl citrate ensures stable plasticizing effect and avoids the adverse effects of impurities on the material's degradation performance and mechanical properties. Epoxidized soybean oil with the required epoxy value not only enhances the plasticizing effect but also forms a certain cross-linking structure with the poly(adipic acid) / butyl terephthalate molecular chain. While improving the material's flexibility (increasing the elongation at break by 10%~20%), it avoids excessive decrease in mechanical strength due to the addition of plasticizer, thus achieving a balance between flexibility and strength.

[0012] Furthermore, the weight ratio of the light stabilizer diphenylhydrazine sebacate to the composite antioxidant is 1:1 to 1:3. This ratio allows the light stabilizer and the composite antioxidant to work synergistically. The light stabilizer reduces the breakage of the material's molecular chains by capturing free radicals generated during UV aging, while the composite antioxidant further inhibits oxidative degradation reactions. The combination of the two can significantly improve the material's resistance to light aging. Compared with adding the light stabilizer or the composite antioxidant alone, the tensile strength retention rate of the material after 168 hours of UV aging is increased by 15% to 25%, effectively extending the service life of the material in outdoor environments.

[0013] Furthermore, the inorganic filler nano-hydroxyapatite undergoes surface modification treatment. The modifier is stearic acid, and the amount of the modifier is 2%~5% of the mass of nano-hydroxyapatite. The modification treatment steps are as follows: nano-hydroxyapatite is added to an ethanol-water solution (ethanol to water volume ratio 3:1), ultrasonically dispersed for 30~60 min, then stearic acid is added, and the mixture is stirred and reacted at 70~80℃ for 2~3 h. After centrifugation, it is dried at 100~110℃ for 4~6 h to obtain modified nano-hydroxyapatite. The surface-modified nano-hydroxyapatite has a 40%~60% improved dispersibility in the material, and can be more uniformly filled in the polyadipate / butyl terephthalate-bamboo powder composite system. It can not only enhance the mechanical properties of the material (bending strength increased by 8%~15%), but also act as a degradation promoter to accelerate the degradation process of the material in the soil, thereby increasing the degradation rate of the material by 5%~10% after 180 days.

[0014] A method for developing a bamboo powder bio-based degradable material includes the following steps: (1) Preparation of materials: Weigh out 35-65 parts of bamboo powder, 20-45 parts of poly(dibutyl terephthalate) adipate / butyl terephthalate, 5-15 parts of modified chitosan, 3-10 parts of composite plasticizer, 2-8 parts of inorganic filler, and 0.5-3 parts of composite antioxidant. The modified chitosan is chitosan that has been grafted with γ-aminopropyltriethoxysilane with a grafting rate of 12%-25%. (2) Pretreatment: The bamboo powder is treated by a pretreatment step.

[0015] (3) Mixing: The pretreated bamboo powder, poly(dibutyl terephthalate), modified chitosan, composite plasticizer, inorganic filler, and composite antioxidant are added to a twin-screw extruder for mixing. The screw speed of the twin-screw extruder is 180~220 r / min, and segmented temperature control is adopted. The specific temperature settings are: feeding section 140~150℃, compression section 160~170℃, melting section 170~180℃, and homogenization section 165~175℃. Segmented temperature control allows each component to melt and mix gradually at different stages, avoiding material degradation or component decomposition due to excessively high local temperatures. At the same time, it ensures that each component is mixed evenly. The mixing time is controlled at 5~8 min to ensure that the melt flow rate of the material is stable at 10~20 g / 10 min (190℃, 2.16 kg). (4) Granulation: The mixed melt is extruded through the die of a twin-screw extruder, cooled by water (water temperature 20~30℃), and granulated by a pelletizer to obtain bamboo powder bio-based degradable material particles. The particle size is controlled at 2~4mm, and the length to particle size ratio is 1:1~1.5:1, which facilitates subsequent molding and processing. (5) Molding: According to the required product shape, the bamboo powder bio-based degradable material particles are made into products by injection molding or compression molding. The injection molding temperature is 165~180℃, the injection pressure is 50~80MPa, and the holding time is 10~20s; the compression molding temperature is 170~185℃, the compression pressure is 15~25MPa, and the holding time is 3~5min. By controlling the molding process parameters, it is ensured that the product is completely formed, free of bubbles, has a smooth surface, and has stable mechanical properties, meeting the usage requirements.

[0016] A method for preparing bamboo powder bio-based degradable materials includes the following steps: (1) Preparation of materials: Weigh out 35-65 parts of bamboo powder, 20-45 parts of poly(dibutyl terephthalate) adipate / butyl terephthalate, 5-15 parts of modified chitosan, 3-10 parts of composite plasticizer, 2-8 parts of inorganic filler, 0.5-3 parts of composite antioxidant, 0.3-2 parts of light stabilizer, and 12%-25% grafting rate of modified chitosan. The light stabilizer is diphenylhydrazine sebacate with a purity ≥98%, and the weight ratio of light stabilizer to composite antioxidant is 1:1-1:3. (2) Pretreatment: The bamboo powder is treated by the pretreatment steps described above; (3) Premixing: Add the pretreated bamboo powder, modified chitosan, inorganic filler, composite antioxidant and light stabilizer into a high-speed mixer and mix for 10 to 15 minutes at a speed of 800~1200 r / min and a temperature of 80~90℃ to obtain a premix. The premixing step can make the solid powder components initially mixed evenly, avoiding material performance fluctuations caused by uneven dispersion of solid components during subsequent mixing. At the same time, heating can remove the small amount of residual moisture in the premix and prevent bubbles from being generated during molding. (4) Mixing: Add the premixed material, poly(butylene adipate) / terephthalate, and composite plasticizer to a twin-screw extruder for mixing. The screw speed is 180~220 r / min, and the temperature is controlled in stages: feeding section 140~150℃, compression section 160~170℃, melting section 170~180℃, homogenization section 165~175℃, mixing time 5~8 min, and ensuring melt flow rate of 10~20 g / 10 min; (5) Granulation: After the melt is extruded through the die, it is water-cooled and granulated to obtain granules with a particle size of 2~4mm and a length-to-particle-size ratio of 1:1~1.5:1; (6) Molding: Injection molding or compression molding is adopted. The injection temperature is 165~180℃, the pressure is 50~80MPa, and the holding time is 10~20s; the compression temperature is 170~185℃, the pressure is 15~25MPa, and the holding time is 3~5min to ensure stable product quality.

[0017] Furthermore, during the mixing process in step (2), an inert gas is introduced into the twin-screw extruder for protection. The inert gas is nitrogen, and the gas flow rate is 0.5~1.0L / min. Nitrogen protection can isolate the air, prevent the material from undergoing oxidative degradation at high temperatures during the mixing process, reduce the breakage of the material's molecular chains, and ensure the stability of the material's mechanical properties and degradation performance. At the same time, nitrogen can also carry out a small amount of volatile substances (such as trace amounts of low-boiling substances in plasticizers) generated during the mixing process, preventing these substances from remaining in the material and affecting the quality of the product. This keeps the volatile content of the material below 0.5%, further improving the safety and stability of the material.

[0018] Beneficial effects This invention uses biodegradable PBAT as a matrix, combined with biodegradable modified chitosan, composite plasticizers, and nano-hydroxyapatite. Furthermore, the nano-hydroxyapatite accelerates the attachment and reproduction of microorganisms, enabling the material to degrade at a rate of ≥60% in a natural soil environment within 180 days. This fully meets the biodegradability requirements of packaging, disposable tableware, and other fields, fundamentally solving the environmental defects of the materials in the reference documents and conforming to the current concepts of green production and sustainable development.

[0019] This invention improves the interfacial bonding strength by 20%~35% through bamboo powder modification with an "alkali solution-silane coupling agent," enhances rigidity by adding modified chitosan, and improves flexibility by compounding a plasticizer, resulting in a material with tensile strength ≥18MPa, flexural strength ≥22MPa, and elongation at break ≥25%. Furthermore, the inclusion of a light stabilizer allows the material to retain ≥80% of its tensile strength after 168 hours of UV aging, expanding its application to outdoor scenarios and significantly improving its performance applicability.

[0020] The new premixing step in this invention ensures uniform dispersion of solid components, resulting in complete product molding, smooth surface, and a bubble rate of ≤1%. Furthermore, the energy consumption during processing is stable, making it suitable for continuous industrial production. The preparation method of this invention makes it easier to control product quality, reduce production losses, and improve production efficiency, thus possessing greater value for industrial applications. Detailed Implementation

[0021] The technical solutions in the embodiments of the present invention have been clearly and completely described. 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 skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] Example 1 1. Raw material ratio (by weight): 50 parts bamboo powder, 35 parts polybutylene adipate / terephthalate (PBAT), 10 parts modified chitosan, 4 parts composite plasticizer, 4 parts inorganic filler, and 1 part composite antioxidant.

[0023] The bamboo powder, with a particle size of 80 mesh, was treated with a 3% sodium hydroxide solution at 70°C with stirring for 3 hours. After filtration, it was washed with deionized water until neutral and dried at 108°C to a moisture content of 2.5%. Then, a 1% silane coupling agent KH-550 ethanol solution (1% of the bamboo powder mass) was added, and the mixture was stirred at 55°C for 1.5 hours. After filtration, it was dried at 85°C for 4 hours. The PBAT had a number-average molecular weight of 100,000 and a melt index of 10 g. / 10min (190℃, 2.16kg); the modified chitosan was grafted with γ-aminopropyltriethoxysilane with a grafting rate of 18%; the composite plasticizer was composed of 99.2% pure tributyl citrate and 6.2% epoxy soybean oil in a weight ratio of 2.5:1; the inorganic filler was 80nm nano hydroxyapatite (unmodified); the composite antioxidant was composed of antioxidant 1010 and antioxidant 168 in a weight ratio of 1:1.5.

[0024] 2. Preparation process: Mixing: Add the pretreated bamboo powder, PBAT, modified chitosan, composite plasticizer, inorganic filler, and composite antioxidant to a twin-screw extruder. The screw speed is 200 r / min. Segmented temperature control is used: feeding section 145℃, compression section 165℃, melting section 175℃, and homogenization section 170℃. The mixing time is 6 min. No inert gas is introduced.

[0025] Granulation: The mixed melt is extruded through the die of a twin-screw extruder and granulated by water cooling at 25℃. The particle size is 3mm and the length to diameter ratio is 1.2:1.

[0026] Molding: Injection molding process is adopted, molding temperature is 170℃, injection pressure is 65MPa, and holding time is 15s.

[0027] 3. Performance test results: The soil degradation rate after 180 days is 65%, the tensile strength is 20 MPa, the elongation at break is 28%, the flexural strength is 24 MPa, and the melt flow rate (190℃, 2.16 kg) is 15 g / 10 min.

[0028] Example 2: 1. Raw material ratio (by weight): 40 parts bamboo powder, 40 parts PBAT, 12 parts modified chitosan, 6 parts composite plasticizer, 3 parts inorganic filler, 1.5 parts composite antioxidant, and 0.8 parts light stabilizer.

[0029] Bamboo powder with a particle size of 120 mesh was treated with a 4% sodium hydroxide solution at 75°C for 2.5 hours by stirring. After filtration and washing until neutral, it was dried at 109°C to a moisture content of 2.0%. Then, a 2% silane coupling agent KH-550 ethanol solution (2% of the bamboo powder mass) was added, and the mixture was stirred at 58°C for 1.2 hours. After filtration, it was dried at 88°C for 3.5 hours. The PBAT had a number-average molecular weight of 90,000 and a melt index of 12 g / 10 min (190°C, 2.16 kg). The chitosan grafting rate is 22%; the composite plasticizer is composed of 99.5% pure tributyl citrate and 6.5% epoxy soybean oil in a weight ratio of 3:1; the inorganic filler is 60nm nano-hydroxyapatite, which is surface modified with stearic acid (3% of the mass of nano-hydroxyapatite); the composite antioxidant is composed of antioxidant 1010 and antioxidant 168 in a weight ratio of 1:2; the light stabilizer is 98.5% pure diphenylhydrazine sebacate in a weight ratio of 1:1.9 with the composite antioxidant.

[0030] 2. Preparation process: Premixing: Add the pretreated bamboo powder, modified chitosan, inorganic filler, composite antioxidant, and light stabilizer to a high-speed mixer at a speed of 1000 r / min and a temperature of 85℃ for 12 min to obtain the premix.

[0031] Mixing: Add the premixed material, PBAT, and compound plasticizer to a twin-screw extruder. The screw speed is 210 r / min. The temperature is controlled in stages: 148℃ for the feeding section, 168℃ for the compression section, 178℃ for the melting section, and 172℃ for the homogenization section. The mixing time is 7 min. Nitrogen gas is introduced at a flow rate of 0.8 L / min for protection.

[0032] Granulation: Water-cooled pellets at 28℃, with a particle size of 3.5mm and a length-to-size ratio of 1.3:1.

[0033] Molding: The molding process is adopted, with a molding temperature of 180℃, a pressing pressure of 20MPa, and a holding time of 4min.

[0034] 3. Performance test results: After 180 days, the soil degradation rate was 68%, the tensile strength was 22 MPa, the elongation at break was 30%, the flexural strength was 26 MPa, the tensile strength retention rate after 168 hours of UV aging was 83%, and the volatile matter content was 0.3%.

[0035] Example 3: 1. Raw material ratio (by weight): 65 parts bamboo powder, 20 parts PBAT, 8 parts modified chitosan, 10 parts composite plasticizer, 8 parts inorganic filler, 3 parts composite antioxidant, and 2 parts light stabilizer.

[0036] Bamboo powder with a particle size of 150 mesh was treated with a 5% sodium hydroxide solution at 80℃ for 2 hours by stirring. After filtration and washing until neutral, it was dried at 110℃ to a moisture content of 1.8%. Then, a 2% silane coupling agent KH-550 ethanol solution (3% of the bamboo powder mass) was added, and the mixture was stirred at 60℃ for 1 hour. After filtration, it was dried at 90℃ for 3 hours. PBAT had a number-average molecular weight of 80,000 and a melt index of 15 g / 10 min (190℃, 2.16 kg). Modified shell... The polysaccharide grafting rate is 12%; the composite plasticizer is a mixture of 99.1% pure tributyl citrate and 6.1% epoxy soybean oil in a weight ratio of 2:1; the inorganic filler is 100nm nano-hydroxyapatite, which is surface modified with stearic acid (5% of the mass of nano-hydroxyapatite); the composite antioxidant is a mixture of antioxidant 1010 and antioxidant 168 in a weight ratio of 1:1; the light stabilizer is 98.2% pure diphenylhydrazine sebacate, in a weight ratio of 1:1.5 with the composite antioxidant.

[0037] 2. Preparation process: Premixing: Add pretreated bamboo powder, modified chitosan, inorganic filler, composite antioxidant, and light stabilizer to a high-speed mixer at a speed of 1200 r / min and a temperature of 90℃ for 15 min.

[0038] Mixing: Add the premixed material, PBAT, and compound plasticizer to a twin-screw extruder. The screw speed is 220 r / min. The temperature is controlled in stages: 150℃ for the feeding section, 170℃ for the compression section, 180℃ for the melting section, and 175℃ for the homogenization section. The mixing time is 8 min. Nitrogen gas is introduced at a flow rate of 1.0 L / min.

[0039] Granulation: Water-cooled pellets at 30℃, with a particle size of 4mm and a length-to-size ratio of 1.5:1.

[0040] Molding: Injection molding, temperature 180℃, injection pressure 80MPa, holding time 20s.

[0041] 3. Performance test results: The soil degradation rate after 180 days was 72%, the tensile strength was 18 MPa, the elongation at break was 25%, the flexural strength was 22 MPa, the tensile strength retention rate after 168 h of UV aging was 80%, and the melt flow rate (190℃, 2.16 kg) was 10 g / 10 min.

[0042] This invention provides a bamboo powder bio-based degradable material, which uses biodegradable polybutylene adipate / terephthalate (PBAT) as the matrix resin, combined with modified bamboo powder and modified chitosan, supplemented with composite plasticizers, inorganic fillers and composite antioxidants. The components work synergistically in a specific weight ratio to achieve a dual improvement in material degradation and mechanical properties.

[0043] Bamboo powder selection and pretreatment: Bamboo powder with a mesh size of 80-150 is selected. This particle size range ensures sufficient material filling while avoiding increased internal defects due to excessively large particle size. The bamboo powder requires pretreatment with an alkaline solution and a silane coupling agent. Sodium hydroxide solution removes impurities such as lignin and hemicellulose from the bamboo powder surface, reducing the number of hydroxyl groups and lowering the hygroscopicity of the bamboo powder. The silane coupling agent KH-550 introduces active groups such as amino groups onto the bamboo powder surface, enabling the bamboo powder to form chemical bonds with the PBAT matrix, increasing the interfacial bonding strength by 20%-35%. This effectively solves the problem of poor interfacial bonding between bamboo powder and resin, reducing the risk of material delamination.

[0044] PBAT as the matrix resin: PBAT with a number-average molecular weight of 80,000–120,000 and a melt index (190℃, 2.16kg) of 5–15 g / 10 min is selected. PBAT within this parameter range possesses both good flexibility and processing fluidity. The ester bonds in its molecular chain can be gradually broken by soil microorganisms, achieving biodegradability and overcoming the shortcomings of using non-degradable melamine resins. Simultaneously, PBAT exhibits good compatibility with bamboo powder and modified chitosan, forming a homogeneous blend system and ensuring stable mechanical properties of the material.

[0045] Modified chitosan: Modified by grafting with γ-aminopropyltriethoxysilane, with a grafting rate of 12%~25%. Chitosan itself is biodegradable and inexpensive. After modification, the amino and epoxy groups on its molecular chain can react with the ester groups of PBAT and the active groups on the surface of bamboo powder, further enhancing interfacial compatibility. Simultaneously, the rigid structure of chitosan improves material strength, avoiding the problem of excessive flexibility and insufficient strength when PBAT is used alone, resulting in a tensile strength of over 18 MPa and a flexural strength ≥22 MPa.

[0046] The composite plasticizer is a compound of tributyl citrate (TBC) and epoxidized soybean oil (ESO) in a weight ratio of 2:1 to 3:1, requiring a tributyl citrate purity of ≥99% and an epoxy value of ≥6.0% for the epoxidized soybean oil. Current technologies do not use plasticizers, and the flexibility of their materials relies entirely on the bonding and lubrication effects of hot melt adhesive powder, resulting in high brittleness and an elongation at break that fails to meet the flexibility requirements of packaging, tableware, and other fields. In the composite plasticizer of this invention, TBC, as an environmentally friendly plasticizer, can effectively reduce the interaction forces between PBAT molecular chains and improve the material's flexibility; ESO not only enhances the plasticizing effect, but its epoxy groups can also undergo cross-linking reactions with PBAT molecular chains, improving flexibility while avoiding excessive reduction in mechanical strength. Tests have shown that the elongation at break of the material after adding this composite plasticizer is ≥25%, which is significantly improved compared to the material without added plasticizer (the elongation at break is usually ≤15%). Furthermore, since both are biodegradable components, they do not affect the overall degradation performance of the material, solving the problem of insufficient material flexibility and inability to simultaneously ensure degradability.

[0047] Inorganic filler: Nano-hydroxyapatite (n-HA) with a particle size of 50-100 nm is selected, and some formulations also perform stearic acid surface modification. The nano-hydroxyapatite of this invention not only possesses excellent mechanical strengthening effects—its nano-sized particles can be uniformly dispersed in the PBAT-bamboo powder system, improving the material's flexural strength through "dispersion strengthening" (flexural strength increases by 5%-8% without modification, and after stearic acid modification, dispersion increases by 40%-60%, further increasing flexural strength by 8%-15%), but also exhibits biodegradability. Its surface hydroxyl groups can adsorb microorganisms in the soil, providing attachment points for microbial reproduction and accelerating the material degradation process. Tests show that after adding nano-hydroxyapatite, the soil degradation rate of the material after 180 days is ≥60%, achieving a breakthrough improvement in degradation performance while avoiding the negative impact of talc on material degradation.

[0048] Composite antioxidant: This composite antioxidant is formulated by compounding antioxidant 1010 and antioxidant 168 in a weight ratio of 1:1 to 1:2. In this invention, antioxidant 1010 is a hindered phenolic primary antioxidant that can capture free radicals generated during material oxidation; antioxidant 168 is a phosphite auxiliary antioxidant that can decompose hydroperoxides. The two work synergistically to form a dual protection system of "free radical capture - hydroperoxide decomposition," effectively inhibiting oxidative degradation during material processing and storage. Tests show that after adding this composite antioxidant, the melt flow rate fluctuation of the material at a processing temperature of 180°C is ≤10%, and the tensile strength retention rate after 6 months of storage is ≥90%, significantly improving the processing stability and storage life of the material and enhancing its antioxidant properties.

[0049] This invention relates to a bamboo powder bio-based degradable material containing a light stabilizer. The basic formulation includes the addition of diphenylhydrazine sebacate (purity ≥98%) as a light stabilizer, with a weight ratio of 1:1 to 1:3 between the light stabilizer and the composite antioxidant. The diphenylhydrazine sebacate light stabilizer reduces molecular chain breakage by capturing free radicals generated during UV aging. Simultaneously, it works synergistically with the composite antioxidant—the antioxidant inhibits oxidative degradation, while the light stabilizer inhibits photo-oxidative degradation. This combination results in a tensile strength retention rate ≥80% after aging under UV light (wavelength 340nm, irradiance 0.71W / m²) for 168 hours, meeting outdoor usage requirements and expanding the material's application scenarios to include outdoor packaging, outdoor gardening products, and other fields.

[0050] Preparation method: Bamboo powder pretreatment process: The bamboo powder pretreatment of this invention adopts a two-step method of "alkali treatment - silane coupling agent modification": 3%~5% sodium hydroxide solution is used to treat the bamboo powder at 60~80℃ for 2~4 hours, which can effectively remove impurities such as lignin and hemicellulose on the surface of bamboo powder, reduce the number of hydroxyl groups, reduce the hygroscopicity of bamboo powder, and control the moisture content to ≤3%; Subsequently, 1%~2% silane coupling agent KH-550 ethanol solution is reacted at 50~60℃ for 1~2 hours, which can introduce active groups such as amino groups on the surface of bamboo powder, so that bamboo powder and PBAT matrix form chemical bonds, and the interfacial bonding strength is increased by 20%~35%, which fundamentally solves the problem of poor interfacial bonding between bamboo powder and resin.

[0051] Mixing Process: This invention employs a twin-screw extruder for mixing, with segmented temperature control (feeding section 140~150℃, compression section 160~170℃, melting section 170~180℃, homogenization section 165~175℃) and screw speed 180~220 r / min. Segmented temperature control allows each component to melt gradually at different stages—the low temperature in the feeding section prevents premature melting and agglomeration of the raw materials; the increased temperature in the compression section promotes initial melting; the high temperature in the melting section ensures complete melting; and the temperature control in the homogenization section ensures melt homogeneity. A stable screw speed ensures uniform shear force, preventing molecular chain breakage due to excessive shear force or uneven mixing due to insufficient shear force. Testing showed that the melt flow rate of the material under this mixing process was stable at 10~20 g / 10 min (190℃, 2.16 kg), and the component deviation in mixing homogeneity was ≤3%, ensuring the stability of the material's mechanical properties.

[0052] Inert gas protection: This invention introduces nitrogen gas during the mixing process at a flow rate of 0.5~1.0 L / min. This isolates the material from air, preventing oxidative degradation and carrying away trace amounts of volatile substances generated during mixing, thus controlling the volatile content of the material to below 0.5%. Tests show that under nitrogen protection, the melt flow rate fluctuation is ≤5%, and the surface bubble rate of the finished product is ≤1%, significantly improving the processing quality and performance stability of the material.

[0053] The core parameters and differences of this invention are shown in the table: While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A bamboo powder bio-based degradable material, characterized in that, By weight, it includes the following components: 35-65 parts bamboo powder, 20-45 parts poly(butylene adipate / terephthalate), 5-15 parts modified chitosan, 3-10 parts composite plasticizer, 2-8 parts inorganic filler, 0.5-3 parts composite antioxidant, and 0.3-2 parts light stabilizer.

2. The bamboo powder bio-based degradable material according to claim 1, characterized in that, The modified chitosan is chitosan grafted with γ-aminopropyltriethoxysilane; the composite plasticizer is composed of tributyl citrate and epoxidized soybean oil in a weight ratio of 2:1 to 3:1; the inorganic filler is nano-hydroxyapatite; the composite antioxidant is composed of antioxidant 1010 and antioxidant 168 in a weight ratio of 1:1 to 1:

2.

3. The bamboo powder bio-based degradable material according to claim 1, characterized in that, The pretreatment steps for the bamboo powder are as follows: bamboo powder is placed in a sodium hydroxide solution with a mass concentration of 3%~5%, stirred at a temperature of 60~80℃ for 2~4 hours, filtered, washed with deionized water until neutral, and then dried at a temperature of 105~110℃ until the moisture content is ≤3%; the dried bamboo powder is added to an ethanol solution of silane coupling agent KH-550 with a mass concentration of 1%~2%, the amount of silane coupling agent KH-550 being 1%~3% of the mass of bamboo powder, stirred and reacted at a temperature of 50~60℃ for 1~2 hours, filtered, and dried at a temperature of 80~90℃ for 3~5 hours to obtain pretreated bamboo powder.

4. The bamboo powder bio-based degradable material according to claim 1, characterized in that, The poly(butylene adipate) has a number-average molecular weight of 80,000 to 120,000 and a melt index of 5 to 15 g / 10 min.

5. The bamboo powder bio-based degradable material according to claim 1, characterized in that, The purity of tributyl citrate in the composite plasticizer is ≥99%, and the epoxy value of epoxidized soybean oil is ≥6.0%.

6. The bamboo powder bio-based degradable material according to claim 2, characterized in that, The weight ratio of the light stabilizer diphenylhydrazine sebacate to the composite antioxidant is 1:1 to 1:

3.

7. The bamboo powder bio-based degradable material according to claim 2, characterized in that, The inorganic filler nano-hydroxyapatite undergoes surface modification treatment, with stearic acid as the modifier, and the amount of modifier used is 2% to 5% of the mass of nano-hydroxyapatite.

8. A method for preparing a bamboo powder bio-based degradable material, used to prepare the bamboo powder bio-based degradable material as described in any one of claims 1 to 7, characterized in that, The following steps are involved: (1) Material preparation: Weigh out 35-65 parts bamboo powder, 20-45 parts poly(butylene adipate / terephthalate), 5-15 parts modified chitosan, 3-10 parts composite plasticizer, 2-8 parts inorganic filler, and 0.5-3 parts composite antioxidant by weight. (2) Pretreatment: Bamboo powder was placed in a 3%–5% sodium hydroxide solution and stirred at 60–80°C for 2–4 hours. After filtration, it was washed with deionized water until neutral and then dried at 105–110°C until the moisture content was ≤3%. The dried bamboo powder was then added to a 1%–2% ethanol solution of silane coupling agent KH-550, with the amount of silane coupling agent KH-550 being 1%–3% of the bamboo powder mass. The mixture was stirred at 50–60°C for 1–2 hours, filtered, and then dried at 80–90°C for 3–5 hours to obtain pretreated bamboo powder. (3) Mixing: Pretreated bamboo powder, poly(butylene adipate) / terephthalate, modified chitosan, composite plasticizer, inorganic filler, and composite antioxidant are added to a twin-screw extruder for mixing. The screw speed of the twin-screw extruder is 180~220 r / min, and segmented temperature control is adopted. The specific temperatures are set as follows: feeding section 140~150℃, compression section 160~170℃, melting section 170~180℃, and homogenization section 165~175℃. Segmented temperature control allows the components to melt and mix gradually at different stages, avoiding material degradation or component decomposition due to excessively high local temperatures. At the same time, it ensures that the components are mixed evenly. The mixing time is controlled at 5~8 min to ensure that the melt flow rate of the material is stable at 10~20 g / 10 min. (4) Granulation: The mixed melt is extruded through the die of a twin-screw extruder and then pelletized by a water-cooled pelletizer to obtain bamboo powder bio-based degradable material particles.

9. The preparation method according to claim 8, characterized in that, The bamboo powder bio-based degradable material particles are manufactured into products using injection molding or compression molding processes.

10. The preparation method according to claim 8, characterized in that, In step (2), during the mixing process, an inert gas is introduced into the twin-screw extruder for protection. The inert gas is nitrogen, and the gas flow rate is 0.5~1.0L / min.

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