A high-heat-resistant PLA / PBS biodegradable composite material and its preparation method

Abstract

The present invention discloses a highly heat-resistant PLA / PBS biodegradable composite material and a preparation method thereof, relating to the technical field of degradable materials. The composite material of the present invention is composed of a substrate and a waterproof layer on the surface of the substrate. Wherein, the waterproof layer is made by vapor deposition of a waterproof composition on the surface of the substrate; the substrate is injection-molded by a composite masterbatch; the composite masterbatch is made of PLA, PBS, modified hybrid fiber, antibacterial agent, calcium stearate, antioxidant 1010, chain extender, epoxidized soybean oil, flexibility modifier, and anti-hydrolysis agent UN-150. The introduction of ingredients such as the modified hybrid fiber, antibacterial agent, and flexibility modifier of the present invention effectively improves the mechanical properties, thermal stability, water resistance, antibacterial properties, and degradability of the composite material; the introduction of the waterproof composition prepared by ingredients such as ethyl acetate and heptafluorodecyltriethoxysilane further improves waterproofness. Therefore, the present invention has a wide range of application prospects.

Description

Technical Field

[0001] The present invention relates to the technical field of degradable materials, and in particular to a highly heat-resistant PLA / PBS biodegradable composite material and a preparation method thereof. Background Art

[0002] Plastic products are widely used in infant nutrition, functional beverages, high-end daily chemical packaging, and medical liquid packaging. However, they are currently mostly made from petroleum-based materials such as polypropylene and polyethylene. These plastics have short lifespans, high pollution loads, and are difficult to recycle, resulting in significant resource waste and environmental risks.

[0003] Polylactic acid (PLA) and polybutylene succinate (PBS), two typical biodegradable polymers, are core materials in current plastic replacement research, offering excellent degradation properties and renewable raw material sources. PLA, with its high mechanical strength and excellent transparency, is suitable for structural packaging applications. PBS, with its excellent flexibility and thermal stability, can mitigate the brittleness of PLA.

[0004] However, poor interfacial bonding during thermal processing can lead to interfacial separation when the composite is subjected to stress, making it difficult to achieve effective synergy in mechanical properties. Furthermore, problems such as poor thermal stability, poor water resistance, and weak antibacterial properties limit its application. Therefore, the mechanical properties, thermal stability, dimensional stability, water resistance, and aging resistance of existing PLA / PBS biodegradable composites still need to be further improved. Summary of the Invention

[0005] The object of the present invention is to provide a highly heat-resistant PLA / PBS biodegradable composite material and a preparation method thereof, to solve the following technical problems:

[0006] Existing PLA / PBS biodegradable composite materials still have problems with poor mechanical properties, thermal stability, water resistance and antibacterial properties.

[0007] The purpose of the present invention can be achieved through the following technical solutions:

[0008] A highly heat-resistant PLA / PBS biodegradable composite material, the composite material consisting of a substrate and a waterproof layer on the surface of the substrate;

[0009] The waterproof layer is made by vapor-depositing a waterproof composition on the surface of the substrate;

[0010] The waterproof composition is prepared from ethyl acetate, heptadecafluorodecyltriethoxysilane and a silane coupling agent;

[0011] The substrate is formed by injection molding of composite masterbatch;

[0012] The composite masterbatch comprises the following raw materials in parts by weight: 70-80 parts of PLA, 20-30 parts of PBS, 1.6-2.4 parts of modified hybrid fiber, 1-1.5 parts of antibacterial agent, 0.2-0.3 parts of calcium stearate, 0.2-0.3 parts of antioxidant 1010, 0.5-0.8 parts of chain extender, 2-3 parts of epoxidized soybean oil, 1-2 parts of flexibility modifier, and 0.5-1 parts of anti-hydrolysis agent UN-150;

[0013] The antibacterial agent is a halloysite nanotube that is first activated by hydrochloric acid and loaded with tea polyphenols and then surface-modified by methyltrimethoxysilane.

[0014] Preferably, the preparation method of the modified hybrid fiber is as follows:

[0015] Calcium chloride dihydrate, diammonium hydrogen phosphate, nanocellulose whiskers and ramie fibers are added to a citric acid aqueous solution and stirred at 98-100° C. for 2-4 hours. The modified hybrid fibers are obtained after centrifugal separation, washing the precipitate, drying, crushing and sieving.

[0016] Preferably, the usage ratio of the citric acid aqueous solution, calcium chloride dihydrate, diammonium hydrogen phosphate, nanocellulose whiskers, and ramie fiber is 100-150 mL: 0.6-0.8 g: 0.2-0.4 g: 1-1.5 g: 10-15 g;

[0017] The concentration of the citric acid aqueous solution is 1-2 mol / L;

[0018] The particle size of the modified hybrid fiber is 50-300 μm.

[0019] Preferably, the preparation method of the antibacterial agent is as follows:

[0020] A1: Add halloysite nanotubes to a hydrochloric acid aqueous solution and stir at 75-80°C for 2-3 hours, then centrifuge and wash with deionized water 5-7 times, and then vacuum dry at 75-80°C for 10-12 hours to obtain activated nanotubes;

[0021] A2: Add methyltrimethoxysilane and glacial acetic acid to anhydrous ethanol and stir to obtain a silane solution;

[0022] A3: Add tea polyphenols to acetate buffer and stir for 10-20 minutes, then add activated nanotubes and perform ultrasonic dispersion at 55-60°C with a power of 300-400W for 40-60 minutes, centrifuge and vacuum dry the precipitate at 75-80°C for 10-12 hours, then immerse in silane solution, react at 75-80°C for 1-2 hours, centrifuge and wash the precipitate with anhydrous ethanol 3-5 times, and finally dry at 55-60°C for 10-15 hours to obtain an antibacterial agent.

[0023] Preferably, the mass ratio of the hydrochloric acid aqueous solution to the halloysite nanotubes in A1 is 200-300:10-15;

[0024] The concentration of the hydrochloric acid aqueous solution in A1 is 0.5-1 mol / L;

[0025] The usage ratio of anhydrous ethanol, methyltrimethoxysilane and glacial acetic acid in A2 is 100-150 mL: 2-3 g: 0.1-0.2 g;

[0026] The usage ratio of the acetate buffer solution, tea polyphenols, activated nanotubes, and silane solution in A3 is 150-200 mL: 3-4 g: 10-15 g: 100-150 mL;

[0027] The pH of the acetate buffer in A3 is 5-5.5.

[0028] Preferably, the preparation method of the flexibility modifier is as follows:

[0029] Itaconic anhydride, dicumyl peroxide, and styrene are added to PBS and stirred at 800-1000 r / min for 5-7 minutes, then extruded at 130-140° C. and 50-70 r / min into strips, water-cooled and pelletized, and then vacuum-dried at 55-60° C. for 10-15 hours to obtain a flexible modifier;

[0030] The mass ratio of the PBS, itaconic anhydride, dicumyl peroxide and styrene is 100-120:5-9:0.1-0.2:0.4-0.6.

[0031] Preferably, the preparation method of the substrate is as follows:

[0032] B1: PLA, PBS, modified hybrid fiber, antimicrobial agent, calcium stearate, antioxidant 1010, chain extender, epoxidized soybean oil, flexibility modifier, and anti-hydrolysis agent UN-150 were added to a twin-screw extruder at a feeding rate of 8-10 kg / h and extruded into strips. After water cooling and pelletizing, the strips were vacuum degassed at -0.09-0.08 MPa for 1-5 hours to obtain a composite masterbatch.

[0033] B2: The composite masterbatch is injected into a mold at 50-60°C and subjected to ultrasonic assisted injection molding at 160-170°C with a power of 80-120W. The substrate is then demolded using micro-cavity water cooling technology with a circulating water temperature of 25-30°C and a cooling time of 40-60s to obtain the substrate.

[0034] Preferably, the temperature of the feeding zone of the twin-screw extruder in B1 is 120-140°C, the speed is 50-150r / min, the temperature of the melting zone is 160-170°C, the speed is 250-350r / min, the temperature of the mixing zone is 175-180°C, the speed is 350-400r / min, the temperature of the reaction zone is 175-180°C, the speed is 300-350r / min, and the temperature of the head is 160-165°C.

[0035] Preferably, the preparation method of the waterproof composition is as follows:

[0036] Add heptafluorodecyltriethoxysilane and silane coupling agent KH-550 to ethyl acetate and stir well to obtain a waterproof composition;

[0037] The mass ratio of the ethyl acetate, heptafluorodecyltriethoxysilane and silane coupling agent KH-550 is 100-120:1-2:0.5-0.6.

[0038] A method for preparing a highly heat-resistant PLA / PBS biodegradable composite material comprises the following steps:

[0039] The waterproof composition is vapor-deposited on the substrate in a closed environment at 60-70° C. for 4-6 hours, and a high-heat-resistant PLA / PBS biodegradable composite material is obtained after drying.

[0040] Beneficial effects of the present invention:

[0041] The present invention provides a highly heat-resistant PLA / PBS biodegradable composite material and a preparation method thereof. The present invention effectively improves the mechanical properties, thermal stability, water resistance and antibacterial properties of the PLA / PBS biodegradable composite material through the following method.

[0042] (1) The ramie fiber and nanocellulose whiskers in the modified hybrid fiber of the present invention can improve the tensile strength and flexural strength of the composite material through the "load transfer effect". Citric acid etching exposes more hydroxyl groups on the fiber surface, forming hydrogen bonds with the ester groups of the PLA / PBS matrix. At the same time, the calcium phosphate inorganic phase generated by the reaction of calcium chloride and diammonium hydrogen phosphate can reduce the interface defects between the fiber and the matrix, improve the interfacial bonding force, and avoid fiber debonding when subjected to stress. The nanoscale dispersion of nanocellulose whiskers can inhibit crack propagation, thereby improving the impact resistance of the composite material. The calcium phosphate inorganic phase can maintain structural stability at high temperatures, hinder the rapid transfer of heat, and delay the thermal oxidative decomposition of the PLA / PBS matrix. After citric acid treatment, the surface hydroxyl groups of the ramie fiber and nanocellulose whiskers are partially esterified, and the thermal decomposition temperature is slightly increased, matching the thermal decomposition range of PLA / PBS, which can reduce the thermal degradation imbalance caused by component differences at high temperatures. Ramie fibers, nanocellulose whiskers, and the calcium phosphate inorganic phase act as a "physical support" at high temperatures to resist creep after the matrix softens, reducing dimensional shrinkage or warping at high temperatures and enhancing shape retention at high temperatures. The calcium phosphate inorganic phase fills the gaps between the fibers and the matrix, reducing the permeability of water molecules. Citric acid treatment replaces some of the hydroxyl groups on the fiber surface with carboxyl groups, improving compatibility with PLA / PBS and reducing "capillary water absorption" caused by interfacial gaps.

[0043] (2) The halloysite nanotubes in the antibacterial agent of the present invention can form a thermal barrier in the composite material, delaying the thermal decomposition of the matrix; the silane modified layer can reduce the thermal damage at the interface between the matrix and the filler at high temperatures, thereby improving the thermal stability of the composite material; the rigid structure of the halloysite nanotubes can also inhibit the thermal motion and creep of the molecular chains of the PLA / PBS matrix at high temperatures, and combined with its good interface interaction with the matrix, reduce deformation at high temperatures and improve the shape retention ability of the material in high temperature environments. The hydrophobic methyl groups introduced on the surface by methyltrimethoxysilane modification can reduce the hydrophilicity of the material surface; at the same time, the tubular structure of the halloysite nanotubes can form a physical barrier in the matrix, reducing the penetration path of water molecules, and synergizing with the subsequent vapor deposition of the waterproof composition to further improve the water resistance of the composite material. The tea polyphenols loaded in the antibacterial agent can exert antibacterial and bactericidal effects through slow release; the tubular structure of halloysite nanotubes can reduce their loss during processing and give the composite material long-lasting antibacterial properties; at the same time, tea polyphenols will also decompose to produce small molecular substances such as gallic acid during the biodegradation process, stimulating the metabolic activity of tolerant bacteria and greatly improving the degradation rate of the composite material of the present invention.

[0044] (3) The itaconic anhydride grafted onto the PBS in the flexible modifier of the present invention can enhance its interfacial compatibility with PLA, while the styrene chain segment provides a flexible chain segment; the synergistic effect of the two can effectively improve the impact strength and elongation at break of the composite material. PLA's brittleness increases sharply at low temperatures and is prone to fracture due to stress concentration; the flexible chain segment of the flexible modifier can maintain a certain degree of molecular chain mobility at low temperatures, alleviate stress concentration, reduce the risk of low-temperature cracking, and improve the shape integrity and impact stability at low temperatures.

[0045] (4) The silane coupling agent KH-550 in the waterproof composition of the present invention can enhance the interfacial bonding between the waterproof layer and the substrate, and improve the tensile strength, impact strength and other mechanical properties of the material. The fluorine-containing silane component has good heat resistance. The surface coating formed by it can act as a physical barrier, delaying the rapid transfer of heat, reducing the thermal degradation of the substrate caused by oxygen and moisture intrusion at high temperatures, increasing the thermal decomposition temperature of the material, and enhancing thermal stability. The extremely strong hydrophobicity of the fluorocarbon chain will form a low surface energy hydrophobic layer on the surface of the substrate, greatly improving water resistance.

[0046] Therefore, the high-heat-resistant PLA / PBS biodegradable composite material prepared by the present invention has excellent mechanical properties, thermal stability, water resistance, antibacterial and degradability, as well as broader application prospects. DETAILED DESCRIPTION

[0047] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0048] Unless otherwise specified, some of the raw materials used in the following examples and comparative examples of the present invention are as follows:

[0049] Polybutylene succinate (PBS) was purchased from Shanghai Myrel Biochemical Technology Co., Ltd., catalog number: M69209; polylactic acid (PLA, Mw 150,000) was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.; chain extender (BASF ADR-4370S) was purchased from Shanghai Jiuqing International Trade Co., Ltd.; anti-hydrolysis agent UN-150 was purchased from Shanghai Youen Chemical Co., Ltd.

[0050] Example 1: A method for preparing a highly heat-resistant PLA / PBS biodegradable composite material is as follows:

[0051] S1: 0.6 g of calcium chloride dihydrate, 0.2 g of diammonium hydrogen phosphate, 1 g of nanocellulose whiskers, and 10 g of ramie fiber were added to 100 mL of 1 mol / L citric acid aqueous solution and stirred at 98°C for 2 h. After centrifugation, the precipitate was washed with deionized water to a pH of 6, then dried at 98°C for 6 h, crushed, and sieved to obtain modified hybrid fibers with a particle size of 50-300 μm.

[0052] S2: Add 10 g of halloysite nanotubes to 200 g of 0.5 mol / L hydrochloric acid aqueous solution and stir at 75°C for 2 h. Then, centrifuge and wash with deionized water five times, and then vacuum dry at 75°C for 10 h to obtain activated nanotubes.

[0053] S3: Add 2 g of methyltrimethoxysilane and 0.1 g of glacial acetic acid to 100 mL of anhydrous ethanol and stir for 20 min to obtain a silane solution;

[0054] S4: 3 g of tea polyphenols was added to 150 mL of acetic acid buffer at pH 5 and stirred for 10 min. Then, 10 g of activated nanotubes was added and ultrasonic dispersion was performed at 55°C for 40 min with a power of 300 W. The precipitate was centrifuged and vacuum dried at 75°C for 10 h, then immersed in 100 mL of silane solution. After reacting at 75°C for 1 h, the precipitate was centrifuged and washed three times with anhydrous ethanol. Finally, it was dried at 55°C for 10 h to obtain an antibacterial agent.

[0055] S5: 5 g of itaconic anhydride, 0.1 g of dicumyl peroxide, and 0.4 g of styrene were added to 100 g of PBS and stirred at 800 rpm for 5 min. The mixture was then extruded at 50 rpm at 130°C into strips. The strips were water-cooled, pelletized, and vacuum-dried at 55°C for 10 h to obtain a flexible modifier.

[0056] S6: 70 g PLA, 20 g PBS, 1.6 g modified hybrid fiber, 1 g antibacterial agent, 0.2 g calcium stearate, 0.2 g antioxidant 1010, 0.5 g chain extender, 2 g epoxy soybean oil, 1 g flexibility modifier, and 0.5 g anti-hydrolysis agent UN-150 were added to a twin-screw extruder at a feeding rate of 8 kg / h and extruded into strips. After water cooling and pelletizing, the mixture was vacuum degassed at -0.09 MPa for 1 h to obtain a composite masterbatch;

[0057] Among them, the temperature of the feeding zone of the twin-screw extruder is 120°C and the speed is 50r / min, the temperature of the melting zone is 160°C and the speed is 250r / min, the temperature of the mixing zone is 175°C and the speed is 350r / min, the temperature of the reaction zone is 175°C and the speed is 300r / min, and the temperature of the die head is 160°C;

[0058] S7: The composite masterbatch was injected into a mold at 50°C and subjected to ultrasonic assisted injection molding at 160°C with a power of 80W. The substrate was then demolded using a micro-cavity water cooling technology with a circulating water temperature of 25°C and a cooling time of 40 seconds to obtain a substrate;

[0059] S8: adding 1 g of heptafluorodecyltriethoxysilane and 0.5 g of silane coupling agent KH-550 to 100 g of ethyl acetate and stirring for 20 min to obtain a waterproof composition;

[0060] S9: vapor-depositing the waterproof composition on the substrate in a closed environment at 60° C. for 4 hours, and drying to obtain a highly heat-resistant PLA / PBS biodegradable composite material.

[0061] Example 2: A method for preparing a highly heat-resistant PLA / PBS biodegradable composite material is as follows:

[0062] S1: 0.7 g of calcium chloride dihydrate, 0.3 g of diammonium hydrogen phosphate, 1.3 g of nanocellulose whiskers, and 12.5 g of ramie fiber were added to 125 mL of a 1.5 mol / L citric acid aqueous solution and stirred at 99°C for 3 h. After centrifugation, the precipitate was washed with deionized water to a pH of 6.5, then dried at 99°C for 8 h, crushed, and sieved to obtain modified hybrid fibers with a particle size of 50-300 μm.

[0063] S2: 12.5 g of halloysite nanotubes were added to 250 g of 0.8 mol / L hydrochloric acid aqueous solution and stirred at 78°C for 2.5 h. The solution was then centrifuged and washed six times with deionized water, and then vacuum dried at 77°C for 11 h to obtain activated nanotubes.

[0064] S3: Add 2.5 g of methyltrimethoxysilane and 0.15 g of glacial acetic acid to 125 mL of anhydrous ethanol and stir for 30 min to obtain a silane solution;

[0065] S4: 3.5 g of tea polyphenols were added to 175 mL of acetic acid buffer with a pH of 5.3 and stirred for 15 min. Then, 12.5 g of activated nanotubes were added and ultrasonic dispersion was performed at 58 ° C for 50 min with a power of 350 W. The precipitate was centrifuged and vacuum dried at 78 ° C for 11 h, then immersed in 125 mL of silane solution. After reacting at 78 ° C for 1.5 h, the precipitate was centrifuged and washed with anhydrous ethanol 4 times, and finally dried at 58 ° C for 13 h to obtain an antibacterial agent.

[0066] S5: 7 g of itaconic anhydride, 0.15 g of dicumyl peroxide, and 0.5 g of styrene were added to 110 g of PBS and stirred at 900 rpm for 6 min. The mixture was then extruded at 135°C and 60 rpm into strips. The strips were water-cooled, pelletized, and vacuum-dried at 58°C for 13 h to obtain a flexible modifier.

[0067] S6: 75 g PLA, 25 g PBS, 2 g modified hybrid fiber, 1.3 g antibacterial agent, 0.25 g calcium stearate, 0.25 g antioxidant 1010, 0.7 g chain extender, 2.5 g epoxidized soybean oil, 1.5 g flexibility modifier, and 0.8 g anti-hydrolysis agent UN-150 were added to a twin-screw extruder at a feeding rate of 9 kg / h and extruded into strips. After water cooling and pelletizing, the mixture was vacuum degassed at -0.085 MPa for 3 h to obtain a composite masterbatch;

[0068] Among them, the temperature of the feeding zone of the twin-screw extruder is 130°C and the speed is 100r / min, the temperature of the melting zone is 165°C and the speed is 300r / min, the temperature of the mixing zone is 178°C and the speed is 380r / min, the temperature of the reaction zone is 178°C and the speed is 330r / min, and the temperature of the die head is 163°C;

[0069] S7: The composite masterbatch was injected into a mold at 55°C and subjected to ultrasonic assisted injection molding at 165°C with a power of 100W. The substrate was then demolded using a micro-cavity water cooling technology with a circulating water temperature of 28°C and a cooling time of 50s to obtain a substrate;

[0070] S8: Add 1.5 g of heptafluorodecyltriethoxysilane and 0.55 g of silane coupling agent KH-550 to 110 g of ethyl acetate and stir for 25 minutes to obtain a waterproof composition;

[0071] S9: vapor-depositing the waterproof composition on the substrate in a closed environment at 65° C. for 5 hours, and drying to obtain a highly heat-resistant PLA / PBS biodegradable composite material.

[0072] Example 3: A method for preparing a highly heat-resistant PLA / PBS biodegradable composite material is as follows:

[0073] S1: 0.8 g of calcium chloride dihydrate, 0.4 g of diammonium hydrogen phosphate, 1.5 g of nanocellulose whiskers, and 15 g of ramie fiber were added to 150 mL of a 2 mol / L citric acid aqueous solution and stirred at 100°C for 4 h. After centrifugation, the precipitate was washed with deionized water to a pH of 7, then dried at 100°C for 10 h, crushed, and sieved to obtain modified hybrid fibers with a particle size of 50-300 μm.

[0074] S2: 15 g of halloysite nanotubes were added to 300 g of a 1 mol / L hydrochloric acid aqueous solution and stirred at 80°C for 3 h. The solution was then centrifuged and washed seven times with deionized water, and then vacuum dried at 80°C for 12 h to obtain activated nanotubes.

[0075] S3: Add 3 g of methyltrimethoxysilane and 0.2 g of glacial acetic acid to 150 mL of anhydrous ethanol and stir for 40 min to obtain a silane solution;

[0076] S4: 4 g of tea polyphenols was added to 200 mL of acetic acid buffer with a pH of 5.5 and stirred for 20 min. Then, 15 g of activated nanotubes was added and ultrasonic dispersion was performed at 60°C with a power of 400 W for 60 min. The precipitate was centrifuged and vacuum dried at 80°C for 12 h, then immersed in 150 mL of silane solution. After reacting at 80°C for 2 h, the precipitate was centrifuged and washed with anhydrous ethanol 5 times, and finally dried at 60°C for 15 h to obtain an antibacterial agent.

[0077] S5: 9 g of itaconic anhydride, 0.2 g of dicumyl peroxide, and 0.6 g of styrene were added to 120 g of PBS and stirred at 1000 rpm for 7 min. The mixture was then extruded at 70 rpm at 140°C into strips. The strips were water-cooled, pelletized, and vacuum-dried at 60°C for 15 h to obtain a flexible modifier.

[0078] S6: 80 g PLA, 30 g PBS, 2.4 g modified hybrid fiber, 1.5 g antibacterial agent, 0.3 g calcium stearate, 0.3 g antioxidant 1010, 0.8 g chain extender, 3 g epoxy soybean oil, 2 g flexibility modifier, and 1 g anti-hydrolysis agent UN-150 were added to a twin-screw extruder at a feeding rate of 10 kg / h and extruded into strips. After water cooling and pelletizing, the mixture was vacuum degassed at -0.08 MPa for 5 h to obtain a composite masterbatch;

[0079] Among them, the temperature of the feeding zone of the twin-screw extruder is 140°C and the speed is 150r / min, the temperature of the melting zone is 170°C and the speed is 350r / min, the temperature of the mixing zone is 180°C and the speed is 400r / min, the temperature of the reaction zone is 180°C and the speed is 350r / min, and the temperature of the die head is 165°C;

[0080] S7: The composite masterbatch was injected into a mold at 60°C and subjected to ultrasonic assisted injection molding at 170°C with a power of 120W. The mold was then demolded using a micro-cavity water cooling technology with a circulating water temperature of 30°C and a cooling time of 60 seconds to obtain a substrate.

[0081] S8: Add 2 g of heptafluorodecyltriethoxysilane and 0.6 g of silane coupling agent KH-550 to 120 g of ethyl acetate and stir for 30 minutes to obtain a waterproof composition;

[0082] S9: vapor-depositing the waterproof composition on the substrate in a closed environment at 70° C. for 6 hours, and drying to obtain a highly heat-resistant PLA / PBS biodegradable composite material.

[0083] Comparative Example 1:

[0084] Compared with Example 1, this comparative example only does not add "calcium chloride dihydrate and diammonium hydrogen phosphate" during the preparation process of S1. The remaining steps and parameters are the same and will not be repeated in this comparative example. Finally, a highly heat-resistant PLA / PBS biodegradable composite material is obtained.

[0085] Comparative Example 2:

[0086] Compared with Example 1, this comparative example only does not add "nanocellulose whiskers" during the preparation of S1. The remaining steps and parameters are the same and will not be repeated in this comparative example. Finally, a highly heat-resistant PLA / PBS biodegradable composite material is obtained.

[0087] Comparative Example 3:

[0088] Compared with Example 1, this comparative example only does not add "modified hybrid fiber" during the preparation process of S6. The remaining steps and parameters are the same and will not be repeated in this comparative example. Finally, a highly heat-resistant PLA / PBS biodegradable composite material is obtained.

[0089] Comparative Example 4:

[0090] Compared with Example 1, this comparative example only replaces the "antibacterial agent" added in the preparation process of S6 with "tea polyphenols", and the remaining steps and parameters are the same. This comparative example will not be repeated, and finally a highly heat-resistant PLA / PBS biodegradable composite material is obtained.

[0091] Comparative Example 5:

[0092] Compared with Example 1, this comparative example only does not add the "antibacterial agent" during the preparation of S6. The remaining steps and parameters are the same and will not be repeated in this comparative example. Finally, a highly heat-resistant PLA / PBS biodegradable composite material is obtained.

[0093] Comparative Example 6:

[0094] Compared with Example 1, this comparative example only does not add the "flexible modifier" during the preparation of S6. The remaining steps and parameters are the same and will not be repeated in this comparative example. Finally, a highly heat-resistant PLA / PBS biodegradable composite material is obtained.

[0095] Comparative Example 7:

[0096] Compared with Example 1, this comparative example only did not perform "vapor deposition of the substrate with a waterproof composition in a closed environment at 60°C for 4 hours" during the preparation process of S9. The remaining steps and parameters were the same and will not be repeated in this comparative example. Finally, a highly heat-resistant PLA / PBS biodegradable composite material was obtained.

[0097] Performance testing:

[0098] Determination of flexural strength:

[0099] With reference to GB / T 9341-2008 "Determination of Flexural Properties of Plastics," the flexural strength (MPa) of the highly heat-resistant PLA / PBS biodegradable composite materials prepared in Examples 1 to 3 and Comparative Examples 1 to 7 of the present invention, measuring 80 mm in length, 10 mm in width, and 4 mm in thickness, was measured at a loading rate of 2 mm / min. The test results are shown in Table 1.

[0100] Determination of impact strength:

[0101] With reference to GB / T 1043.1-2008 "Determination of impact properties of simply supported beams of plastics", the impact strength (kJ / m) of the high heat-resistant PLA / PBS biodegradable composite materials prepared in Examples 1 to 3 and Comparative Examples 1 to 7 of the present invention with a length of 80 mm × a width of 10 mm × a thickness of 4 mm and a notch type of A was measured. 2 ), the test results are shown in Table 1;

[0102] Determination of tensile strength:

[0103] With reference to GB / T 1040.4-2006 "Determination of Tensile Properties of Plastics - Part 4: Test Conditions for Isotropic and Orthotropic Fiber-Reinforced Composites," the tensile strength (MPa) of the highly heat-resistant PLA / PBS biodegradable composite materials prepared in Examples 1 to 3 and Comparative Examples 1 to 7 of the present invention, measuring 150 mm in length, 10 mm in width, and 4 mm in thickness, was measured at a loading rate of 10 mm / min. The test results are shown in Table 1.

[0104] Determination of hydrolysis resistance:

[0105] The mass retention (%) of the highly heat-resistant PLA / PBS biodegradable composite materials prepared in Examples 1 to 3 of the present invention and Comparative Examples 1 to 7 after storage at 70° C. and 80% relative humidity for seven days was measured. The measurement results are shown in Table 1.

[0106] Determination of water contact angle:

[0107] Referring to the sessile drop method in GB / T 30693-2014 "Plastic Film and Sheeting - Determination of Water Vapor Transmission Rate - Infrared Detector Method", the static water contact angles (°) of the highly heat-resistant PLA / PBS biodegradable composite materials prepared in Examples 1 to 3 and Comparative Examples 1 to 7 of the present invention were measured. The test results are shown in Table 1.

[0108] Table 1: Performance test results of Examples 1-3 and Comparative Examples 1-7

[0109]

[0110] Determination of heat distortion temperature:

[0111] Referring to GB / T 1634.2-2019, "Determination of Deflection Temperature of Plastics under Load - Part 2: Plastics, Ebonite and Long Fiber Reinforced Composites," silicone oil was used as the heat transfer medium and the heating rate was set at 50°C / h. The heat deformation temperatures (°C) of the highly heat-resistant PLA / PBS biodegradable composite materials prepared in Examples 1-3 and Comparative Examples 1-7 were measured under a load of 0.75 N and measured at 80 mm in length, 10 mm in width, and 4 mm in thickness. The test results are shown in Table 2.

[0112] Determination of antimicrobial activity value:

[0113] According to GB / T 31402-2023 "Determination of antimicrobial activity on the surface of plastics and other non-porous materials", 5×10 5 A bacterial solution (Escherichia coli ATCC 8739 and Staphylococcus aureus ATCC 6538P) with a CFU / mL concentration was incubated at 35°C and 95% humidity for 24 hours. The mixture was then eluted with phosphate buffer containing 0.05% Tween-80 at 200 rpm for 10 minutes. The eluate was spread on a culture medium and incubated for 48 hours. The colonies were counted and the antimicrobial activity was calculated. The antimicrobial activity of the highly heat-resistant PLA / PBS biodegradable composite materials prepared in Examples 1-3 and Comparative Examples 1-7 was determined using the above method. The test results are shown in Table 2.

[0114] Determination of degradability:

[0115] With reference to ISO 17088:2021 "Plastics - Organic Recycling - Compostable Plastics Specification", the degradation rate (%) of the high heat-resistant PLA / PBS biodegradable composite materials prepared in Examples 1 to 3 of the present invention and Comparative Examples 1 to 7 was determined in a simulated industrial composting environment at 60°C and 60% relative humidity after 120 days. The test results are shown in Table 2.

[0116] Table 2: Performance test results of Examples 1-3 and Comparative Examples 1-7

[0117]

[0118] Data Analysis:

[0119] It can be seen from Table 1 and Table 2 that the highly heat-resistant PLA / PBS biodegradable composite material prepared in the embodiment of the present invention has excellent mechanical properties, thermal stability, water resistance, antibacterial properties and degradability.

[0120] The above is a detailed description of an embodiment of the present invention. However, the content described is only a preferred embodiment of the present invention and should not be considered to limit the scope of the present invention. All equivalent changes and improvements made within the scope of the present invention should still fall within the scope of the patent coverage of the present invention.

Claims

1. A highly heat-resistant PLA / PBS biodegradable composite material, characterized in that: The composite material is composed of a substrate and a waterproof layer on the surface of the substrate; The waterproof layer is made by vapor-depositing a waterproof composition on the surface of the substrate; The waterproof composition is prepared from ethyl acetate, heptadecafluorodecyltriethoxysilane and a silane coupling agent; The substrate is formed by injection molding of composite masterbatch; The composite masterbatch comprises the following raw materials in parts by weight: 70-80 parts of PLA, 20-30 parts of PBS, 1.6-2.4 parts of modified hybrid fiber, 1-1.5 parts of antibacterial agent, 0.2-0.3 parts of calcium stearate, 0.2-0.3 parts of antioxidant 1010, 0.5-0.8 parts of chain extender, 2-3 parts of epoxidized soybean oil, 1-2 parts of flexibility modifier, and 0.5-1 parts of anti-hydrolysis agent UN-150; The antibacterial agent is a halloysite nanotube that is first activated with hydrochloric acid and loaded with tea polyphenols, and then surface-modified with methyltrimethoxysilane; The preparation method of the modified hybrid fiber is as follows: Calcium chloride dihydrate, diammonium hydrogen phosphate, nanocellulose whiskers, and ramie fibers are added to a citric acid aqueous solution and stirred at 98-100° C. for 2-4 hours, followed by centrifugation, washing the precipitate, drying, crushing, and sieving to obtain modified hybrid fibers; The preparation method of the flexible modifier is as follows: Itaconic anhydride, dicumyl peroxide, and styrene are added to PBS and stirred evenly, then extruded into strips at 130-140°C, water-cooled and pelletized, and then vacuum-dried to obtain a flexible modifier; The mass ratio of the PBS, itaconic anhydride, dicumyl peroxide and styrene is 100-120:5-9:0.1-0.2:0.4-0.

6.

2. The highly heat-resistant PLA / PBS biodegradable composite material according to claim 1, wherein The usage ratio of the citric acid aqueous solution, calcium chloride dihydrate, diammonium hydrogen phosphate, nanocellulose whiskers, and ramie fiber is 100-150 mL: 0.6-0.8 g: 0.2-0.4 g: 1-1.5 g: 10-15 g; The concentration of the citric acid aqueous solution is 1-2 mol / L; The particle size of the modified hybrid fiber is 50-300 μm.

3. The highly heat-resistant PLA / PBS biodegradable composite material according to claim 1, wherein The preparation method of the antibacterial agent is as follows: A1: Add halloysite nanotubes to a hydrochloric acid aqueous solution and stir at 75-80°C for 2-3 hours. Then, centrifuge, wash the precipitate, and vacuum dry to obtain activated nanotubes. A2: Add methyltrimethoxysilane and glacial acetic acid to anhydrous ethanol and stir to obtain a silane solution; A3: Add tea polyphenols to the acetate buffer solution and stir well, then add activated nanotubes and ultrasonically disperse them at 55-60°C for 40-60 minutes, centrifuge and vacuum dry the precipitate, then immerse it in a silane solution, react at 75-80°C for 1-2 hours, centrifuge and wash the precipitate, and dry it to obtain the antibacterial agent.

4. The highly heat-resistant PLA / PBS biodegradable composite material according to claim 3, wherein The mass ratio of the hydrochloric acid aqueous solution and the halloysite nanotubes in A1 is 200-300:10-15; The concentration of the hydrochloric acid aqueous solution in A1 is 0.5-1 mol / L; The usage ratio of anhydrous ethanol, methyltrimethoxysilane and glacial acetic acid in A2 is 100-150 mL: 2-3 g: 0.1-0.2 g; The usage ratio of the acetate buffer solution, tea polyphenols, activated nanotubes, and silane solution in A3 is 150-200 mL: 3-4 g: 10-15 g: 100-150 mL; The pH of the acetate buffer in A3 is 5-5.

5.

5. The highly heat-resistant PLA / PBS biodegradable composite material according to claim 1, wherein The preparation method of the substrate is as follows: B1: PLA, PBS, modified hybrid fiber, antimicrobial agent, calcium stearate, antioxidant 1010, chain extender, epoxidized soybean oil, flexibility modifier, and anti-hydrolysis agent UN-150 were added to a twin-screw extruder and extruded into strips. After water cooling and pelletizing, the mixture was vacuum degassed for 1-5 hours to obtain a composite masterbatch. B2: The composite masterbatch is injected into a mold at 50-60°C and subjected to ultrasonic assisted injection molding at 160-170°C with a power of 80-120W. The substrate is then demolded using micro-cavity water cooling technology with a circulating water temperature of 25-30°C and a cooling time of 40-60s to obtain the substrate.

6. The highly heat-resistant PLA / PBS biodegradable composite material according to claim 5, characterized in that: The temperature of the feeding zone of the twin-screw extruder in B1 is 120-140°C and the speed is 50-150r / min, the temperature of the melting zone is 160-170°C and the speed is 250-350r / min, the temperature of the mixing zone is 175-180°C and the speed is 350-400r / min, the temperature of the reaction zone is 175-180°C and the speed is 300-350r / min, and the temperature of the die is 160-165°C.

7. The highly heat-resistant PLA / PBS biodegradable composite material according to claim 1, characterized in that: The preparation method of the waterproof composition is as follows: Add heptafluorodecyltriethoxysilane and silane coupling agent KH-550 to ethyl acetate and stir well to obtain a waterproof composition; The mass ratio of the ethyl acetate, heptafluorodecyltriethoxysilane and silane coupling agent KH-550 is 100-120:1-2:0.5-0.

6.

8. A method for preparing the highly heat-resistant PLA / PBS biodegradable composite material according to any one of claims 1 to 7, characterized in that: The following steps are involved: The waterproof composition is vapor-deposited on the substrate in a closed environment at 60-70° C. for 4-6 hours, and a high-heat-resistant PLA / PBS biodegradable composite material is obtained after drying.

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