High-strength and high-toughness polylactic acid composite material and preparation method thereof

Abstract

This invention relates to a high-strength, high-toughness polylactic acid (PLA) composite material and its preparation method, belonging to the field of biodegradable polymer materials technology. The PLA composite material formulation is as follows: by weight, 70-80 parts PLA, 5-10 parts modified cellulose nanocrystals, 3-5 parts modified montmorillonite, 1-2 parts plasticizer, and 0.5-1.5 parts antioxidant. The preparation method of the modified cellulose nanocrystals is as follows: cellulose nanocrystals are added to deionized water and ultrasonically treated to obtain dispersion A; a 0.5-1 M tannic acid solution at 60°C is added sequentially to dispersion A; after cooling to room temperature, a 3 M octadecylamine-ethanol solution is added dropwise; the mixture is washed with ethanol and deionized water, and then subjected to stepwise freeze-drying to obtain the modified cellulose nanocrystals. The PLA composite material prepared by the method of this invention exhibits high strength, high toughness, and good high-temperature resistance.

Description

A high-strength and high-toughness polylactic acid composite material and its preparation method Technical Field

[0001] This invention belongs to the field of biodegradable polymer materials technology, and relates to a high-strength and high-toughness polylactic acid composite material and its preparation method. Background Technology

[0002] Polylactic acid (PLA), a fully biodegradable thermoplastic polyester made from renewable resources such as starch and cellulose, is widely considered an ideal alternative to petroleum-based plastics due to the renewable, biodegradable, and biocompatible nature of its raw materials. However, inherent defects of PLA significantly limit its application range. For example, its brittleness is prominent, far lower than that of general-purpose plastics such as polypropylene, making it difficult to meet the toughness requirements of packaging materials and automotive interiors; its poor heat resistance makes it prone to deformation in hot water or high-temperature environments, limiting its application in tableware, electronic components, and other fields; PLA has low melt strength, making it prone to melt fracture during extrusion and injection molding, and it is also susceptible to hydrolytic degradation at high temperatures. Existing modification methods, such as blending elastomers or inorganic fillers, can partially improve performance, but they suffer from problems such as poor compatibility, limited toughening effect, or sacrifice of strength.

[0003] Therefore, there is an urgent need to develop a polylactic acid composite material that combines high strength and high toughness. Summary of the Invention

[0004] The purpose of this invention is to provide a high-strength and high-toughness polylactic acid composite material and its preparation method, which has the characteristics of high strength and high toughness.

[0005] The objective of this invention can be achieved through the following technical solutions:

[0006] A high-strength, high-toughness polylactic acid (PLA) composite material, wherein the PLA composite material formulation is as follows (by weight): 70-80 parts PLA, 5-10 parts modified cellulose nanocrystals, 3-5 parts modified montmorillonite, 1-2 parts plasticizer, and 0.5-1.5 parts antioxidant.

[0007] The preparation method of modified cellulose nanocrystals is as follows:

[0008] S1-1: Add 1-3 parts by weight of cellulose nanocrystals to 100 parts by weight of deionized water and sonicate for 30-60 minutes to obtain dispersion A;

[0009] S1-2: Add 0.5-1 parts by weight of a 0.5-1 M tannic acid solution at 60 °C to dispersion A. Adjust the pH to 8.5 using a 0.1 M NaHCO3 solution. After cooling to room temperature, add 1-2 parts by weight of a 3 M octadecylamine-ethanol solution. Stir at room temperature for 2-3 h at a stirring speed of 600-700 rpm. Wash with ethanol and deionized water and perform stepwise freeze-drying to obtain the modified cellulose nanocrystals.

[0010] As a preferred embodiment of the present invention, the ultrasonic power in S1-1 is 500-600 W.

[0011] As a preferred embodiment of the present invention, the stepwise freeze-drying process in S1-2 involves pre-freezing at -50°C for 6-8 hours, followed by freeze-drying at -80°C for 24 hours.

[0012] As a preferred embodiment of the present invention, the method for preparing the modified montmorillonite is as follows:

[0013] S4-1: Disperse sodium montmorillonite in water to a solid-liquid mass ratio of 1:(20-30), add dodecyl dihydroxyethyl methyl ammonium chloride, stir at 60-70 °C for 1-2 h, wash with deionized water and freeze-dry at -50 °C for 24 h to obtain powder B;

[0014] S4-2: Powder B is added to a 0.1 M lanthanum nitrate solution to make a solid-liquid mass ratio of 1:50, ultrasonically treated for 4-6 h, and then transferred to a muffle furnace for calcination for 1-2 h to obtain the modified montmorillonite.

[0015] As a preferred embodiment of the present invention, the amount of dodecyl dihydroxyethyl methyl ammonium chloride added in S4-1 is 10-20% of the mass of sodium montmorillonite.

[0016] As a preferred embodiment of the present invention, the calcination temperature in S4-2 is 350-400 °C.

[0017] As a preferred embodiment of the present invention, the plasticizer is one or more of tributyl citrate, epoxidized soybean oil, and dioctyl terephthalate.

[0018] As a preferred embodiment of the present invention, the antioxidant is one or more of antioxidant 1010, antioxidant 1076 and antioxidant 168.

[0019] A method for preparing a high-strength, high-toughness polylactic acid composite material, the specific steps of which are as follows:

[0020] S9-1: Add polylactic acid, modified cellulose nanocrystals, modified montmorillonite, plasticizer and antioxidant to a high-speed mixer according to the formula ratio, and stir at 500-700 rpm for 10-30 min at room temperature to obtain a premix.

[0021] S9-2: Melt blending is performed using a twin-screw extruder at a speed of 150–250 rpm and a residence time of 5–7 min. The extruded strip is cooled in a water bath and then pelletized to obtain the high-strength and high-toughness polylactic acid composite material.

[0022] As a preferred embodiment of the present invention, the melt blending temperature in S9-2 is set to 170-175 ℃, 175-178 ℃ and 180-185 ℃ respectively from the feeding section to the die head.

[0023] Tannic acid, as a polyphenolic compound, contains multiple catechol groups, which can be adsorbed onto the surface of cellulose nanocrystals through non-covalent interactions such as hydrogen bonding and π-π stacking, forming a modification layer. Its hydroxyl groups can form strong hydrogen bonds with the hydroxyl groups of cellulose nanocrystals, enhancing interfacial adhesion. Octadecylamine contains long-chain alkyl and amino groups; the amino group can undergo Michael addition reactions with the phenolic hydroxyl groups of tannic acid to form covalent bonds. The long-chain alkyl groups impart hydrophobicity to the surface of cellulose nanocrystals and generate van der Waals interactions with the nonpolar groups of polylactic acid, significantly improving compatibility.

[0024] The nanoscale size and high aspect ratio of cellulose nanocrystals effectively transfer stress, inhibit crack propagation in the polylactic acid (PLA) matrix, and significantly improve tensile strength. The flexible segments of octadecylamine form a buffer layer on the surface of the cellulose nanocrystals, absorbing impact energy and effectively improving elongation at break. Furthermore, the nano-effect of cellulose nanocrystals can delay the thermal degradation of PLA. The hydrophobicity of modified cellulose nanocrystals reduces their impact on the viscosity of PLA melt, thus lowering the melt flow rate. Tannic acid and octadecylamine are both bio-based compounds and their derivatives, conforming to green chemistry principles. Stepwise freeze-drying maintains the nanostructure of cellulose nanocrystals, preventing agglomeration, and requires no high-temperature treatment, resulting in low energy consumption.

[0025] In the preparation of modified montmorillonite, dodecylbis(hydroxyethyl)methylammonium chloride is inserted into the interlayer of montmorillonite via an ion exchange reaction, expanding the interlayer spacing. This expanded interlayer spacing allows PLA molecular chains to insert, significantly improving interfacial bonding. Lanthanum nitrate solution is ultrasonically treated to penetrate into the interlayer of montmorillonite or adsorb onto the surface. After calcination, it decomposes into lanthanum oxide, forming a montmorillonite composite structure. Lanthanum oxide, acting as a Lewis acid catalyst, promotes the stereocomposite bonding of poly(D-lactic acid) and poly(L-lactic acid) during PLA melt blending, significantly increasing the heat distortion temperature. Furthermore, lanthanum oxide can capture free radicals generated from the thermal degradation of PLA, further enhancing the thermal stability of the composite material.

[0026] Furthermore, the lamellar structure of montmorillonite and the needle-like structure of cellulose nanocrystals form an interlocking network, which inhibits crack propagation and further optimizes mechanical properties.

[0027] The beneficial effects of this invention are:

[0028] By synergistically modifying cellulose nanocrystals with tannic acid and octadecylamine, their compatibility and dispersibility with PLA are significantly improved. The composite material retains biodegradability while also possessing high strength, high toughness, and good heat resistance. Furthermore, the preparation process is environmentally friendly and cost-controllable.

[0029] Modified montmorillonite expands the interlayer spacing through quaternary ammonium salt intercalation, promoting the intercalation and bonding of PLA molecular chains; lanthanum nitrate is ultrasonically infiltrated and calcined to generate lanthanum oxide, improving the high-temperature resistance of the composite material; in addition, the lamellar structure of modified montmorillonite and the needle-like structure of cellulose nanocrystals form an interlocking network, synergistically inhibiting crack propagation and achieving simultaneous improvement in strength and toughness. Detailed Implementation

[0030] To further illustrate the technical means and effects of the present invention in achieving its intended purpose, the following detailed description of the specific implementation methods, structures, features, and effects of the present invention, in conjunction with embodiments, is provided below.

[0031] In the embodiments and comparative examples of this invention:

[0032] Polylactic acid: purchased from Beijing Thompson Biotechnology Co., Ltd.;

[0033] Dodecyl dihydroxyethyl methyl ammonium chloride: purchased from Shanghai Boyun New Materials Co., Ltd., CAS No. 22340-01-8;

[0034] Cellulose nanocrystals: purchased from Jiangsu Xingkeyuan Information Technology Co., Ltd.;

[0035] Sodium-based montmorillonite: purchased from Lingyuan Beibiansen Biotechnology Co., Ltd., with a specific surface area of ​​240 m². 2 / g;

[0036] Tannic acid: purchased from Zhangjiajie Jiurui Biotechnology Co., Ltd., with a purity of 98%;

[0037] Octadecylamine: purchased from Shandong Longhui Chemical Co., Ltd.;

[0038] Lanthanum nitrate: purchased from Nanjing Kangmanlin Chemical Industry Co., Ltd.;

[0039] Tributyl citrate: purchased from Shanghai Maclean Biochemical Technology Co., Ltd.;

[0040] Epoxidized soybean oil: purchased from Shanghai Rongli Chemical Technology Co., Ltd.;

[0041] Dioctyl terephthalate: purchased from Shanghai Maclean Biochemical Technology Co., Ltd.;

[0042] Antioxidant 1010: Purchased from Guangzhou Dayin New Material Co., Ltd.;

[0043] Antioxidant 1076: Purchased from Qingdao Zhenguang Functional Materials Technology Co., Ltd.;

[0044] Antioxidant 168: Purchased from Changzhou Qingmu Biotechnology Co., Ltd.

[0045] Example 1

[0046] A high-strength, high-toughness polylactic acid (PLA) composite material, wherein the PLA composite material formulation is as follows (by weight): 75 parts PLA, 8 parts modified cellulose nanocrystals, 4 parts modified montmorillonite, 1.5 parts tributyl citrate, and 0.5 parts antioxidant 1010 and 0.5 parts antioxidant 168.

[0047] The preparation method of modified cellulose nanocrystals is as follows:

[0048] S1-1: Add 2 parts by weight of cellulose nanocrystals to 100 parts by weight of deionized water, and sonicate for 45 min at a power of 550 W to obtain dispersion A.

[0049] S1-2: 0.8 parts by weight of a 0.5 M tannic acid solution at 60 °C were added sequentially to dispersion A. The pH was adjusted to 8.5 using a 0.1 M NaHCO3 solution. After cooling to room temperature, 1.5 parts by weight of a 3 M octadecylamine-ethanol solution were added dropwise. The mixture was stirred at 650 rpm for 2.5 h at room temperature. The mixture was washed with ethanol and deionized water, pre-frozen at -50 °C for 7 h, and then freeze-dried at -80 °C for 24 h to obtain the modified cellulose nanocrystals.

[0050] The preparation method of the modified montmorillonite is as follows:

[0051] S4-1: Disperse sodium montmorillonite in water to make a solid-liquid mass ratio of 1:25, add 15% of sodium montmorillonite mass of dodecyl dihydroxyethyl methyl ammonium chloride, stir at 65 °C for 1.5 h, wash with deionized water and freeze dry at -50 °C for 24 h to obtain powder B;

[0052] S4-2: Powder B was added to a 0.1 M lanthanum nitrate solution to make a solid-liquid mass ratio of 1:50, ultrasonically treated for 5 h, and then transferred to a muffle furnace for calcination for 1.5 h at a calcination temperature of 370 ℃ to obtain the modified montmorillonite.

[0053] A method for preparing a high-strength, high-toughness polylactic acid composite material, the specific steps of which are as follows:

[0054] S9-1: Add polylactic acid, modified cellulose nanocrystals, modified montmorillonite, plasticizer and antioxidant to a high-speed mixer according to the formula ratio, and stir at 600 rpm for 20 min at room temperature to obtain a premix.

[0055] S9-2: Melt blending was performed using a twin-screw extruder. The temperatures were set at 172 ℃, 177 ℃, and 182 ℃ from the feeding section to the die head, respectively. The rotation speed was 200 rpm, and the residence time was 6 min. The extruded strip was cooled in a water bath and then pelletized to obtain the high-strength and high-toughness polylactic acid composite material.

[0056] Example 2

[0057] A high-strength, high-toughness polylactic acid (PLA) composite material, wherein the PLA composite material formulation is as follows (by weight): 70 parts PLA, 5 parts modified cellulose nanocrystals, 3 parts modified montmorillonite, 1 part epoxidized soybean oil, and 0.5 parts antioxidant 1076 and 0.5 parts antioxidant 168.

[0058] The preparation method of modified cellulose nanocrystals is as follows:

[0059] S1-1: Add 1 part by weight of cellulose nanocrystals to 100 parts by weight of deionized water, and sonicate for 30 min at a power of 500 W to obtain dispersion A;

[0060] S1-2: 0.5 parts by weight of a 0.5 M tannic acid solution at 60 °C were added sequentially to dispersion A. The pH was adjusted to 8.5 using a 0.1 M NaHCO3 solution. After cooling to room temperature, 1 part by weight of a 3 M octadecylamine-ethanol solution was added dropwise. The mixture was stirred at room temperature for 2 h at a stirring speed of 600 rpm. The mixture was washed with ethanol and deionized water, pre-frozen at -50 °C for 6 h, and then freeze-dried at -80 °C for 24 h to obtain the modified cellulose nanocrystals.

[0061] The preparation method of the modified montmorillonite is as follows:

[0062] S4-1: Disperse sodium montmorillonite in water to make a solid-liquid mass ratio of 1:20, add 10% of sodium montmorillonite mass of dodecyl dihydroxyethyl methyl ammonium chloride, stir at 60 °C for 1 h, wash with deionized water and freeze dry at -50 °C for 24 h to obtain powder B.

[0063] S4-2: Powder B was added to a 0.1 M lanthanum nitrate solution to make a solid-liquid mass ratio of 1:50, ultrasonically treated for 4 h, and then transferred to a muffle furnace for calcination for 1 h at a calcination temperature of 350 ℃ to obtain the modified montmorillonite.

[0064] A method for preparing a high-strength, high-toughness polylactic acid composite material, the specific steps of which are as follows:

[0065] S9-1: Add polylactic acid, modified cellulose nanocrystals, modified montmorillonite, plasticizer and antioxidant to a high-speed mixer according to the formula ratio, and stir at 500 rpm for 10 min at room temperature to obtain a premix.

[0066] S9-2: Melt blending was performed using a twin-screw extruder. The temperature settings from the feeding section to the die were 170 ℃, 175 ℃, and 180 ℃, respectively. The rotation speed was 150 rpm, and the residence time was 5 min. The extruded strip was cooled in a water bath and then pelletized to obtain the high-strength and high-toughness polylactic acid composite material.

[0067] Example 3

[0068] A high-strength, high-toughness polylactic acid (PLA) composite material is formulated as follows (by weight): 80 parts PLA, 10 parts modified cellulose nanocrystals, 5 parts modified montmorillonite, 2 parts dioctyl terephthalate, and 10101 parts antioxidant.

[0069] The preparation method of modified cellulose nanocrystals is as follows:

[0070] S1-1: Add 3 parts by weight of cellulose nanocrystals to 100 parts by weight of deionized water, and sonicate for 60 min at an ultrasonic power of 600 W to obtain dispersion A.

[0071] S1-2: Add 1 part by weight of a 1 M tannic acid solution at 60 °C to dispersion A, adjust the pH to 8.5 using a 0.1 M NaHCO3 solution, cool to room temperature, add 2 parts by weight of a 3 M octadecylamine-ethanol solution, stir at room temperature for 3 h at a stirring speed of 700 rpm, wash with ethanol and deionized water, pre-freeze at -50 °C for 8 h, and then freeze-dry at -80 °C for 24 h to obtain the modified cellulose nanocrystals.

[0072] The preparation method of the modified montmorillonite is as follows:

[0073] S4-1: Disperse sodium montmorillonite in water to make a solid-liquid mass ratio of 1:30, add 20% of sodium montmorillonite mass of dodecyl dihydroxyethyl methyl ammonium chloride, stir at 70 °C for 2 h, wash with deionized water and freeze dry at -50 °C for 24 h to obtain powder B;

[0074] S4-2: Powder B was added to a 0.1 M lanthanum nitrate solution to make a solid-liquid mass ratio of 1:50, ultrasonically treated for 6 h, and then transferred to a muffle furnace for calcination for 2 h at a calcination temperature of 400 ℃ to obtain the modified montmorillonite.

[0075] A method for preparing a high-strength, high-toughness polylactic acid composite material, the specific steps of which are as follows:

[0076] S9-1: Add polylactic acid, modified cellulose nanocrystals, modified montmorillonite, plasticizer and antioxidant to a high-speed mixer according to the formula ratio, and stir at 700 rpm for 30 min at room temperature to obtain a premix.

[0077] S9-2: Melt blending was performed using a twin-screw extruder. The temperatures were set at 175 ℃, 178 ℃, and 185 ℃ from the feeding section to the die head, respectively. The rotation speed was 250 rpm, and the residence time was 7 min. The extruded strip was cooled in a water bath and then pelletized to obtain the high-strength and high-toughness polylactic acid composite material.

[0078] Comparative Example 1

[0079] Unmodified montmorillonite was used instead of modified montmorillonite, and the remaining steps were the same as in Example 1.

[0080] Comparative Example 2

[0081] Unmodified cellulose nanocrystals were used instead of modified cellulose nanocrystals, and the remaining steps were the same as in Example 1.

[0082] Comparative Example 3

[0083] Unmodified montmorillonite was used instead of modified montmorillonite, and unmodified cellulose nanocrystals were used instead of modified cellulose nanocrystals. The remaining steps were the same as in Example 1.

[0084] Comparative Example 4

[0085] Tannic acid was not added in the preparation of the modified cellulose nanocrystals, and the remaining steps were the same as in Example 1.

[0086] Comparative Example 5

[0087] The preparation of modified cellulose nanocrystals does not involve the addition of octadecylamine-ethanol solution, and the remaining steps are the same as in Example 1.

[0088] Comparative Example 6

[0089] The preparation of modified montmorillonite does not involve the addition of dodecylbis(hydroxyethyl)methylammonium chloride, and the remaining steps are the same as in Example 1.

[0090] Comparative Example 7

[0091] Lanthanum nitrate was not added in the preparation of the modified montmorillonite, and the remaining steps were the same as in Example 1.

[0092] Mechanical property testing

[0093] Tensile strength was determined according to the method in GB / T 1040, with a tensile speed of 50 mm / min; elongation at break was determined according to the method in GB / T 1040, with a tensile speed of 50 mm / min; impact strength was determined according to the method in GB / T 1843, with an energy of 5.5 J and a speed of 3.5 m / s.

[0094] Heat distortion temperature test

[0095] The heat distortion temperature of the composite materials prepared in the examples and comparative examples was determined using a heat distortion temperature tester. The load was 1.82 MPa, the heating rate was 120 ℃ / h, the sample size was 120 mm × 12 mm × 3 mm, and the temperature at which the deflection at the center point of the sample reached 0.34 mm was measured.

[0096] Group Tensile strength (MPa) Elongation at break (%) Impact strength (KJ / m 2 HDT (°C) Example 1: 14116.89095 Example 2: 3916.234.990 Example 3: 3816.534.590 Comparative Example 1: 2410.328.070 Comparative Example 2: 1811.027.172 Comparative Example 3: 119.218.367 Comparative Example 4: 2713.229.882 Comparative Example 5: 3012.630.287 Comparative Example 6: 1511.723.362 Comparative Example 7: 2111.225.165 surface

[0097] The data above show that the tensile strength, elongation at break, impact strength, and HDT of Examples 1-3 are all higher than those of the comparative example, indicating that the composite material prepared by the present invention has high strength, high toughness, and heat resistance. Modified montmorillonite and modified cellulose nanocrystals significantly improve the strength, toughness, and heat resistance of the material through interface reinforcement and lattice regulation.

[0098] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention are still within the scope of the present invention.

Claims

1. A high-strength, high-toughness polylactic acid composite material, characterized in that, The polylactic acid composite material formulation is as follows: by weight, 70-80 parts polylactic acid, 5-10 parts modified cellulose nanocrystals, 3-5 parts modified montmorillonite, 1-2 parts plasticizer, and 0.5-1.5 parts antioxidant. The modified cellulose nanocrystals are prepared as follows: S1-1: Add 1-3 parts by weight of cellulose nanocrystals to 100 parts by weight of deionized water and sonicate for 30-60 min to obtain dispersion A; S1-2: Add 0.5-1 parts by weight of a 0.5-1 M tannic acid solution at 60℃ to dispersion A, adjust the pH to 8.5 using a 0.1 M NaHCO3 solution, cool to room temperature, and then add 1-2 parts by weight of a 3 M octadecylamine-ethanol solution. Stir at room temperature for 2-3 h at a stirring speed of 600-700 rpm. The modified cellulose nanocrystals were obtained by washing with ethanol and deionized water at rpm and then freeze-drying in steps. The modified montmorillonite was prepared as follows: S4-1: Sodium montmorillonite was dispersed in water with a solid-liquid mass ratio of 1:(20-30), dodecyl dihydroxyethyl methyl ammonium chloride was added, and the mixture was stirred at 60-70 °C for 1-2 h. The mixture was washed with deionized water and freeze-dried at -50 °C for 24 h to obtain powder B. S4-2: Powder B was added to a 0.1 M lanthanum nitrate solution with a solid-liquid mass ratio of 1:50, and ultrasonically treated for 4-6 h. Then, the mixture was calcined in a muffle furnace for 1-2 h to obtain the modified montmorillonite.

2. The high-strength, high-toughness polylactic acid composite material according to claim 1, characterized in that, The ultrasonic power in S1-1 is 500-600 W.

3. The high-strength, high-toughness polylactic acid composite material according to claim 1, characterized in that, The stepwise freeze-drying process in S1-2 involves pre-freezing at -50℃ for 6-8 hours, followed by freeze-drying at -80℃ for 24 hours.

4. The high-strength, high-toughness polylactic acid composite material according to claim 1, characterized in that, The amount of dodecyl dihydroxyethyl methyl ammonium chloride added in S4-1 is 10-20% of the mass of sodium montmorillonite.

5. The high-strength, high-toughness polylactic acid composite material according to claim 1, characterized in that, The roasting temperature in S4-2 is 350-400℃.

6. The high-strength, high-toughness polylactic acid composite material according to claim 1, characterized in that, The plasticizer is one or more of tributyl citrate, epoxidized soybean oil, and dioctyl terephthalate.

7. The high-strength, high-toughness polylactic acid composite material according to claim 1, characterized in that, The antioxidant is one or more of antioxidant 1010, antioxidant 1076 and antioxidant 168.

8. A method for preparing a high-strength, high-toughness polylactic acid composite material as described in any one of claims 1 to 7, characterized in that, The specific steps of the preparation method are as follows: S9-1: Polylactic acid, modified cellulose nanocrystals, modified montmorillonite, plasticizer and antioxidant are added to a high-speed mixer according to the formula ratio, and stirred at 500-700 rpm for 10-30 min at room temperature to obtain a premix; S9-2: Melt blending is performed using a twin-screw extruder at a speed of 150-250 rpm and a residence time of 5-7 min. The extruded strip is cooled in a water tank and then pelletized to obtain the high-strength and high-toughness polylactic acid composite material.

9. The method for preparing a high-strength, high-toughness polylactic acid composite material according to claim 8, characterized in that, The melt blending temperature settings in S9-2 are 170-175℃, 175-178℃, and 180-185℃ respectively from the feeding section to the die head.