A supercritical foamed PHA / PBAT composite material, its preparation method and application

Abstract

This invention discloses a supercritical foamed PHA / PBAT composite material, its preparation method, and its application. The composite material comprises the following components in parts by weight: polyhydroxyalkanoate: 60-90 parts; poly(butylene adipate / terephthalate): 10-40 parts; chain extender: 0.5-2.0 parts; self-assembling nucleating agent: 0.2-0.8 parts; and anti-hydrolysis agent: 0.1-0.5 parts. The above components are mixed and then melt-mixed and extruded. Modified particles are obtained by underwater pelletizing, dried, and then supercritically foamed to obtain a foamed material. The obtained foamed material is then bonded into beads using a steam molding process to prepare a biodegradable thin-walled plastic cup with thermal insulation properties. This solves the problems of phase separation, low cell density, and large particle size that easily occur during the foaming process of existing materials, which lead to difficulties in molding thin-walled plastic cups.

Description

Technical Field

[0001] This invention relates to a foamed composite material, its preparation method and application, and more particularly to a supercritical foamed PHA / PBAT composite material, its preparation method and application. Background Technology

[0002] Currently, non-degradable plastic foams are widely used in construction, food packaging, and agricultural packaging due to their advantages such as lightweight and good thermal insulation. However, these non-degradable foams cause serious environmental pollution, especially in marine environments where they cannot degrade, leading to significant plastic pollution. While conventional biomaterials such as PLA possess degradable properties, they cannot truly degrade in marine environments. To address the problem of marine plastic foam pollution, the development of biodegradable foaming materials as a green solution is receiving increasing attention. Polyhydroxyalkanoates (PHAs) are a class of biodegradable polyesters synthesized by bacteria through fermentation. They have gained widespread attention due to their biodegradability, biocompatibility, marine degradability, and renewable resource utilization. However, PHAs also suffer from drawbacks such as slow crystallization rate, poor toughness, and low foamability, limiting their application in certain fields.

[0003] Polybutylene adipate (PBAT) is a biodegradable thermoplastic polyester that combines the properties of aliphatic and aromatic polyesters, exhibiting good flexibility, processability, and biodegradability. However, PBAT is relatively expensive, has low crystallinity, and limited physical properties.

[0004] Supercritical foaming technology is a safe, green, and environmentally friendly technology. Patent CN114891261B discloses a method for preparing plant fiber PHA foam material, which uses chemical grafting modification to improve the foamability of PHA. However, it suffers from problems such as chemical reagent residues and low foaming ratio. Patent CN102229707A provides a method for preparing PBAT molded foam material, but using only PBAT foam particles results in soft particles that are not suitable for packaging material applications.

[0005] Currently, there are several problems in the preparation of PHA / PBAT composite materials: (1) There is a phase separation phenomenon between the two phases of PHA and PBAT, which can easily lead to cell rupture when small particle size is foamed; (2) PHA has poor toughness and slow crystallization rate, which hinders cell growth, resulting in low cell density and large cell size; (3) PHA has low melt strength and poor cell support, which can easily lead to cell collapse when steam thin-wall molding; (4) Conventional foaming molding technology generally produces products with large wall thickness, which cannot be directly applied. Summary of the Invention

[0006] Purpose of the invention: The purpose of this invention is to provide a supercritical foamed PHA / PBAT composite material that can improve the melt strength of PHA, enhance the toughness of PHA, and improve the foaming efficiency and overall stability of the composite material.

[0007] A second objective of this invention is to provide a method for preparing the above-mentioned supercritical foamed PHA / PBAT composite material;

[0008] A third objective of this invention is to provide applications of the aforementioned supercritical foamed PHA / PBAT composite material.

[0009] Technical solution: The supercritical foamed PHA / PBAT composite material of the present invention comprises the following components in parts by weight:

[0010] PHA: 60-90 servings;

[0011] PBAT: 10-40 copies;

[0012] Chain extender: 0.5-2.0 parts;

[0013] Self-assembling nucleating agent: 0.2-0.8 parts;

[0014] Anti-hydrolysis agent: 0.1-0.5 parts.

[0015] Wherein, the PHA is at least one of PHB, PHBV, PHBHHx, and P(3HB, 4HB). Preferably, the PHA includes, but is not limited to, the product with brand name XF-1000 produced by Hangzhou Xinfu Biotechnology Co., Ltd., the product with brand name Y-1000P produced by Zhejiang Tianan Biotechnology Co., Ltd., and the products with brand names BP330 and BP350 produced by Lanjing Microbial Co., Ltd.; preferably, the PHA is the product with brand name BP330 produced by Lanjing Microbial Co., Ltd.

[0016] The PBAT has a melt flow index ≤ 7 g / 10 min and a tensile strength ≥ 18 MPa. Preferably, the PBAT includes, but is not limited to, the product with grade JH-1908 produced by Jinhui Zhaolong High-Tech Technology Co., Ltd., the product with grade PBAT-7000 produced by Shanghai Tongcheng New Material Group Co., Ltd., the C1200 product from BASF (Germany), and the product with grade TH801T produced by Lanshan Tunhe Technology Co., Ltd.; preferably, the PBAT is the product with grade JH-1908 produced by Jinhui Zhaolong High-Tech Technology Co., Ltd.

[0017] The chain extender is at least one of the following: epoxy chain extender ADR series, oxazoline, and isocyanate. Preferably, the chain extender includes, but is not limited to, at least one of ADR-4300, ADR-4370, or ADR-4400; more preferably, the chain extender is an epoxy chain extender, and more preferably, the chain extender is ADR-4400.

[0018] Wherein, the self-assembling nucleating agent is an acylhydrazine and / or an amide; the self-assembling nucleating agent is at least one of sebacic acid dibenzoylhydrazine, adipic acid diphenyl diazide, and an amide nucleating agent; preferably, the amide nucleating agent is at least one of octenamide, stearamide, and laurylamide; the sebacic acid dibenzoylhydrazine is model TMC-300, and the adipic acid diphenyl diazide is model TMC-306; more preferably, the self-assembling nucleating agent is an acylhydrazine TMC-328, which belongs to the category of bio-based matching nucleating agents.

[0019] The anti-hydrolysis agent is at least one of carbodiimide, isocyanate, and acid anhydride; preferably, the anti-hydrolysis agent is carbodiimide.

[0020] The preparation method of the above-mentioned supercritical foamed PHA / PBAT composite material includes the following steps:

[0021] (1) Mix PHA and PBAT, add chain extender, self-assembly nucleating agent and anti-hydrolysis agent, stir, and obtain mixed particles;

[0022] (2) The mixed particles are melt-mixed and extruded through a twin-screw extruder, and modified particles are obtained by underwater pelletizing and drying.

[0023] (3) The dried modified particles are subjected to supercritical foaming to obtain supercritical foamed beads.

[0024] In step (1), PHA and PBAT are dried at 70-80℃ for 2-4 hours to ensure the removal of moisture; the dried PHA and PBAT are added to a high-speed mixer in proportion and mixed for 3-5 minutes; chain extender, self-assembly nucleating agent and anti-hydrolysis agent are added in sequence, and stirring is continued for 5-8 minutes to ensure uniform dispersion; the speed of the high-speed mixer is 500-2000 rpm; preferably, the speed of the high-speed mixer is 1500 rpm.

[0025] In step (2), when using a twin-screw extruder, the extrusion temperature is controlled at 140-180℃ and the screw speed is 50-80rpm. Modified particles are obtained after underwater pelletizing. The pelletizer speed is 2500-3500 rpm; preferably, the pelletizer speed is 3000 rpm.

[0026] In step (3), the modified particles are placed in a supercritical high-pressure reactor, and supercritical foaming gas is injected through a booster pump. After foaming, the pressure is rapidly reduced to atmospheric pressure to obtain supercritical foamed beads. The supercritical foaming gas is one or both of supercritical CO2 and supercritical N2. The foaming temperature is 100-120℃, the saturation pressure is 10-20MPa, and the holding time is 10-30min.

[0027] The above-mentioned supercritical foamed PHA / PBAT composite material is used in the preparation of biodegradable thermal insulation thin-walled plastic cups.

[0028] Among them, supercritical foamed PHA / PBAT composite material is pre-pressed and then steam-formed to obtain a biodegradable heat-insulating foamed plastic cup.

[0029] In this process, supercritical foamed particles are placed in a pre-pressurization tank, with a pressure of 1-3 kg and a holding time of 4-6 hours. After the pressure is released, the particles are set aside for later use. Then, the pre-pressed foamed particles are bonded together using a steam forming process to prepare a biodegradable heat-insulating foamed plastic cup with a wall thickness of less than 2 mm.

[0030] The steam forming process conditions are as follows: fixed mold pressure 0.3-1kg, moving mold pressure 0.3-1kg, fixed mold heating 10-30s, moving mold heating 10-30s, double-sided pressure 0.5-1.5kg, double-sided heating 20-50s, water cooling 50-150s, and mold gap 10-25s.

[0031] Invention Principle: While PHA is fully biodegradable, its slow crystallization rate and poor toughness lead to low foamability of modified particles and poor performance of bead foams. This invention improves PHA by introducing PBAT, making it more suitable for molding complex structures. Furthermore, chain extension and branching of PHA's molecular structure enhances its melt strength and mitigates its poor toughness. Combined with a self-assembling nucleating agent, a fibrillated network structure is formed during twin-screw melt extrusion. This self-assembled fiber induces the PHA / PBAT blend to accelerate crystallization, improves the uniformity and density of PHA cells, and enhances foaming efficiency and overall stability.

[0032] Beneficial effects: Compared with the prior art, the present invention achieves the following significant effects:

[0033] (1) The epoxy groups of the chain extender undergo esterification with the terminal carboxyl groups of PHA and PBAT, forming a unique molecular chain cross-linked network structure of PHA-g-PBAT. This reduces the interfacial forces between the two phases of PHA and PBAT, greatly improving the poor compatibility between PHA and PBAT, significantly increasing the melt strength, and improving the inherent lack of toughness of PHA. (2) The synergistic effect of the chain extender and the self-assembly nucleating agent enables the material to exhibit better performance in structural packaging applications. In particular, the application of the self-assembly nucleating agent enables the composite material of the present invention to form a fibrillary network structure. This structure not only increases the heterogeneous nucleation sites, but also accelerates crystallization in a completely new way, significantly improving the density of the foam cells and the foaming stability. (3) It improves the collapse phenomenon of foamed plastic cups during steam molding. At the same time, the wall thickness of the foamed plastic cup is less than 2 mm. Attached Figure Description

[0034] Figure 1 SEM images of Comparative Example 1 (PHA / PBAT simple blend) and Example 1 (with chain extender added for improvement);

[0035] Figure 2 SEM images of the bead foam materials of Example 1 with added self-assembly nucleating agent and Comparative Example 3 without added self-assembly nucleating agent. Detailed Implementation

[0036] The present invention will now be described in further detail.

[0037] Example 1

[0038] (1) Dry the Blue Crystal Microbial PHA-BP330 and Jinhui Zhaolong PBAT-1908 at 75℃ for 3 hours to ensure that the moisture is removed before use.

[0039] (2) After drying, take 70% by weight of Blue Crystal Microbial PHA-BP330 and 30% by weight of Jinhui Zhaolong PBAT-1908 and add them to a high-speed mixer and stir for 5 minutes at a speed of 1500 rpm. Then weigh out the chain extender: ADR-4400, 0.5 parts by weight; the self-assembly nucleating agent: TMC-328, 0.2 parts by weight; and the anti-hydrolysis agent: carbodiimide, 0.1 parts by weight. Add them to the high-speed mixer and stir for 7 minutes at a speed of 1500 rpm. Discharge and set aside for use.

[0040] (3) The mixture from step (2) is added to a twin-screw extruder for melt extrusion, cooled, and underwater pelletized to obtain modified particles; wherein, the temperatures of each zone of the twin-screw extruder in each embodiment and comparative example of the present invention are as follows: Zone 1 to Zone 9: 140℃, 170℃, 170℃, 175℃, 175℃, 180℃, 180℃, 175℃, 175℃; Die temperature: 180℃; Screw speed: 60 rpm; Pelletizer speed: 3000 rpm.

[0041] (4) The modified particles obtained in step (3) are used to prepare foamed beads using a supercritical foaming device under the conditions of foaming temperature 100℃, saturation pressure 15MPa, and saturation time 30min. The supercritical foaming gases are CO2 and N2 in a ratio of 3:1. The foaming ratio of the obtained PHA / PBAT composite foam material is 14.3 times. The foaming ratio (VER) of the foam particles of the present invention is calculated using the following formula:

[0042]

[0043] Where ρ f It is the density of the unfoamed particles, ρ p This is the density of the foamed material, in g / cm³. 3 Its VER was measured by an analytical balance (BSA3202S, Sartorius, Germany).

[0044] (5) Place the foamed particles obtained in step (4) into a pre-pressurization tank for pressurization. The compressed air pressure is 1 kg and the pressurization time is 4 h. Then, steam molding is carried out through a steam molding equipment to obtain a biodegradable heat-insulating foamed thin-walled plastic cup.

[0045] Example 2

[0046] (1) Dry the blue crystal microorganisms PHA-BP330 and Jinhui Zhaolong PBAT-1908 at 75℃ for 3 hours and set aside for use.

[0047] (2) After drying, take 70% by weight of Blue Crystal Microbial PHA-BP330 and 30% by weight of Jinhui Zhaolong PBAT-1908 and add them to a high-speed mixer and stir for 5 minutes. Then weigh out the chain extender: ADR-4400, 1.0 part by weight; the self-assembly nucleating agent: TMC-328, 0.2 part by weight; and the anti-hydrolysis agent: carbodiimide, 0.1 part by weight. Add them to the high-speed mixer and stir for 7 minutes. Discharge and set aside for use.

[0048] (3) The mixture from step (2) is added to a twin-screw extruder for melt extrusion, cooled, and pelletized underwater to obtain modified particles; the screw speed is 60 rpm; the pelletizer speed is 3000 rpm.

[0049] (4) The modified particles obtained in step (3) are used to prepare foamed beads under the conditions of foaming temperature of 100℃, saturation pressure of 15MPa and saturation time of 30min using a supercritical foaming device. The supercritical foaming gases are CO2 and N2 in a ratio of 3:1. The resulting PHA / PBAT composite foam material has a magnification of 21.5 times.

[0050] (5) Place the foamed particles obtained in step (4) into a pre-pressurization tank for pressurization. The compressed air pressure is 1 kg and the pressurization time is 4 h. Then, steam molding is carried out through a steam molding equipment to obtain a biodegradable heat-insulating foamed thin-walled plastic cup.

[0051] Example 3

[0052] (1) Dry the blue crystal microorganisms PHA-BP330 and Jinhui Zhaolong PBAT-1908 at 75℃ for 3 hours and set aside for use.

[0053] (2) After drying, take 70% by weight of Blue Crystal Microbial PHA-BP330 and 30% by weight of Jinhui Zhaolong PBAT-1908 and add them to a high-speed mixer and stir for 5 minutes. Then weigh out the chain extender: ADR-4400, 1.5 parts by weight; the self-assembly nucleating agent: TMC-328, 0.2 parts by weight; and the anti-hydrolysis agent: carbodiimide, 0.1 parts by weight. Add them to the high-speed mixer and stir for 7 minutes. Discharge and set aside for use.

[0054] (3) The mixture from step (2) is added to a twin-screw extruder for melt extrusion, cooled, and pelletized underwater to obtain modified particles; the screw speed is 60 rpm; the pelletizer speed is 3000 rpm.

[0055] (4) The modified particles obtained in step (3) are used to prepare foamed beads under the conditions of foaming temperature of 100℃, saturation pressure of 15MPa and saturation time of 30min using a supercritical foaming device. The supercritical foaming gases are CO2 and N2 in a ratio of 3:1. The resulting PHA / PBAT composite foam material has a ratio of 31.5 times.

[0056] (5) Place the foamed particles obtained in step (4) into a pre-pressurization tank for pressurization. The compressed air pressure is 1 kg and the pressurization time is 4 h. Then, steam molding is carried out through a steam molding equipment to obtain a biodegradable heat-insulating foamed thin-walled plastic cup.

[0057] Example 4

[0058] (1) Dry the blue crystal microorganisms PHA-BP330 and Jinhui Zhaolong PBAT-1908 at 75℃ for 3 hours and set aside for use.

[0059] (2) After drying, take 70% by weight of Blue Crystal Microbial PHA-BP330 and 30% by weight of Jinhui Zhaolong PBAT-1908 and add them to a high-speed mixer and stir for 5 minutes. Then weigh out the chain extender: ADR-4400, 2.0 parts by weight; the self-assembly nucleating agent: TMC-328, 0.2 parts by weight; and the anti-hydrolysis agent: carbodiimide, 0.1 parts by weight. Add them to the high-speed mixer and stir for 7 minutes. Discharge and set aside for use.

[0060] (3) The mixture from step (2) is added to a twin-screw extruder for melt extrusion, cooled, and pelletized underwater to obtain modified particles; the screw speed is 60 rpm; the pelletizer speed is 3000 rpm.

[0061] (4) The modified particles obtained in step (3) are used to prepare foamed beads under the conditions of foaming temperature of 100℃, saturation pressure of 15MPa and saturation time of 30min using a supercritical foaming device. The supercritical foaming gases are CO2 and N2 in a ratio of 3:1. The resulting PHA / PBAT composite foam material has a ratio of 24.4 times.

[0062] (5) Place the foamed particles obtained in step (4) into a pre-pressurization tank for pressurization. The compressed air pressure is 1 kg and the pressurization time is 4 h. Then, steam molding is carried out through a steam molding equipment to obtain a biodegradable heat-insulating foamed thin-walled plastic cup.

[0063] Example 5

[0064] In this embodiment, the modification and preparation process of the composite material of Blue Crystal Microbial PHA-BP330 and Jinhui Zhaolong PBAT-1908 is the same as in Example 4, except that the foaming temperature is 105℃ and the saturation pressure is 15MPa. The resulting PHA / PBAT composite foam material has a ratio of 26.6 times. The foamed particles are placed in a pre-pressurization tank for pressure holding at a compressed air pressure of 1kg for 4 hours, and then steam-formed using a steam forming device to obtain a biodegradable thermal insulation foam thin-walled plastic cup.

[0065] Example 6

[0066] In this embodiment, the modification and preparation process of the composite material of Blue Crystal Microbial PHA-BP330 and Jinhui Zhaolong PBAT-1908 is the same as in Example 4, except that the foaming temperature is 110℃ and the saturation pressure is 15MPa. The resulting PHA / PBAT composite foam material has a ratio of 28 times. The foamed particles are placed in a pre-pressurization tank for pressure holding at a compressed air pressure of 1kg for 4 hours, and then steam-formed using a steam forming device to obtain a biodegradable thermal insulation foam thin-walled plastic cup.

[0067] Example 7

[0068] In this embodiment, the modification and preparation process of the composite material of Blue Crystal Microbial PHA-BP330 and Jinhui Zhaolong PBAT-1908 is the same as in Example 4, except that the foaming temperature is 115℃ and the saturation pressure is 15MPa. The resulting PHA / PBAT composite foam material has a ratio of 20.8 times. The foamed particles are placed in a pre-pressurization tank for pressure holding at a compressed air pressure of 1kg for 4 hours, and then steam-formed using a steam forming device to obtain a biodegradable thermal insulation foam thin-walled plastic cup.

[0069] Comparative Example 1

[0070] (1) Dry the blue crystal microorganisms PHA-BP330 and Jinhui Zhaolong PBAT-1908 at 75℃ for 3 hours and set aside for use.

[0071] (2) After drying, take 70% by weight of Blue Crystal Microbial PHA-BP330 and 30% by weight of Jinhui Zhaolong PBAT-1908 and add them to a high-speed mixer for 5 minutes. Then weigh out the anti-hydrolysis agent: carbodiimide, 0.1 parts by weight, and add it to the high-speed mixer for 7 minutes. Discharge and set aside for use.

[0072] (3) The mixture from step (2) is added to a twin-screw extruder for melt extrusion, cooled, and pelletized underwater to obtain modified particles; the screw speed is 60 rpm; the pelletizer speed is 3000 rpm.

[0073] (4) The modified particles obtained in step (3) are used to prepare foamed beads under the conditions of foaming temperature of 100℃, saturation pressure of 15MPa and saturation time of 30min using a supercritical foaming device. The supercritical foaming gases are CO2 and N2 in a ratio of 3:1. The resulting PHA / PBAT composite foam material has a ratio of 8.4 times.

[0074] (5) Place the foamed particles obtained in step (4) into a pre-pressurization tank for pressurization. The compressed air pressure is 1 kg and the pressurization time is 4 h. Then, steam molding is carried out through a steam molding equipment to obtain a biodegradable heat-insulating foamed thin-walled plastic cup.

[0075] Comparative Example 2

[0076] In this comparative example, the modification and foaming process of the Blue Crystal Microbial PHA-BP330 and Jinhui Zhaolong PBAT-1908 composite materials is the same as in Example 1, except that no chain extender is added. The resulting PHA / PBAT composite foam material has a volume ratio of 9.8 times. The foamed particles are placed in a pre-pressurization tank and pressurized with 1 kg of compressed air for 4 hours. Then, they are steam-formed using a steam forming device to obtain a biodegradable thermal insulation foam thin-walled plastic cup.

[0077] Comparative Example 3

[0078] In this comparative example, the modification and foaming process of the Blue Crystal Microbial PHA-BP330 and Jinhui Zhaolong PBAT-1908 composite materials is the same as in Example 1, except that no self-assembling nucleating agent is added. The resulting PHA / PBAT composite foam material has a ratio of 11.4 times. The foamed particles are placed in a pre-pressurization tank and held under pressure with 1 kg of compressed air for 4 hours. Then, they are steam-formed using a steam forming device to obtain a biodegradable thermal insulation foam thin-walled plastic cup.

[0079] Comparative Example 4

[0080] In this comparative example, the modification and foaming process of the Blue Crystal Microbial PHA-BP330 and Jinhui Zhaolong PBAT-1908 composite materials is the same as in Example 3, except that the self-assembly core agent TMC-328 is 0.5 parts by weight; the resulting PHA / PBAT composite foam material has a magnification ratio of 25.8 times. The foamed particles are placed in a pre-pressurization tank for pressure holding at a compressed air pressure of 1 kg for 4 hours, and then steam-formed using a steam forming device to obtain a biodegradable thermal insulation foam thin-walled plastic cup.

[0081] Figure 1 The images show SEM images of the simple PHA / PBAT blend (a) of Comparative Example 1 and the improved blend (b) of Example 1 with added chain extender. Granulation revealed phase separation in the simple PHA / PBAT blend, exhibiting a typical "island structure," as shown below. Figure 1 As shown in (a), this phenomenon leads to cell rupture in PHA / PBAT during foaming, resulting in a decrease in the expansion rate of foam beads. Epoxy chain extenders improve the compatibility of the two matrices and also generate certain branched chain-extended structures. From Figure 1 As can be seen in (b), after adding the compatibilizer, the interaction between PHA and PBAT matrix is ​​enhanced, the interfacial compatibility is significantly improved, and the foaming effect is improved.

[0082] Figure 2SEM images of the beaded foam materials from Example 1 (with added self-assembly nucleating agent) and Comparative Example 3 (without added self-assembly nucleating agent). Figure 2 As shown in (a), introducing a chain extender into the PHA / PBAT matrix forms a cross-linked network structure, improving melt strength. Adding a self-assembling nucleating agent then forms a fibrillary network structure, inducing heterogeneous nucleation sites in the PHA / PBAT molecular chains, accelerating the crystallization rate, increasing crystallinity, and significantly increasing cell density and reducing cell size. This results in thinner walls, less than 2 mm, during steam molding of plastic cups. Figure 2 As can be seen from (b) in the figure, the cell diameter is larger and the cell density is lower without the addition of nucleating agent. The particle strength is also lower. When steam forming plastic cups, the foam particles are easy to step on and difficult to form.

Claims

1. A supercritical foamed PHA / PBAT composite material, characterized in that, The components include the following parts by weight: PHA: 60-90 servings; PBAT: 10-40 copies; Chain extender: 0.5-2.0 parts; Self-assembling nucleating agent: 0.2-0.8 parts; Anti-hydrolysis agent: 0.1-0.5 parts; The chain extender is at least one of ADR-4300, ADR-4370 or ADR-4400; The self-assembly nucleating agent is at least one of sebacate dibenzoyl hydrazide, adipate diphenyl dihydrazide, and acyl hydrazide TMC-328; The anti-hydrolysis agent is of the carbodiimide type.

2. The supercritical foamed PHA / PBAT composite material according to claim 1, characterized in that, The PHA is at least one of PHB, PHBV, PHBHHx, and P(3HB, 4HB).

3. The supercritical foamed PHA / PBAT composite material according to claim 1, characterized in that, The PBAT has a melt flow index ≤7g / 10min and a tensile strength ≥18MPa.

4. A method for preparing the supercritical foamed PHA / PBAT composite material according to claim 1, characterized in that, Includes the following steps: (1) Mix PHA and PBAT, add chain extender, self-assembly nucleating agent and anti-hydrolysis agent, stir to obtain mixed particles; (2) The mixed particles are melt-mixed and extruded through a twin-screw extruder, and modified particles are obtained by underwater pelletizing and drying. (3) The dried modified particles are subjected to supercritical foaming to obtain supercritical foamed beads.

5. The method for preparing the supercritical foamed PHA / PBAT composite material according to claim 4, characterized in that, In step (3), the supercritical foaming gas is one or both of supercritical CO2 and supercritical N2; the foaming temperature is 100-120℃, the saturation pressure is 10-20MPa, and the holding time is 10-30min.

6. The application of the supercritical foamed PHA / PBAT composite material of claim 1 in the preparation of biodegradable thermally insulating thin-walled plastic cups.

7. The application of the supercritical foamed PHA / PBAT composite material according to claim 6 in the preparation of thermally insulating thin-walled plastic cups, characterized in that, The supercritical foamed PHA / PBAT composite material is pre-compressed and then steam-molded to obtain a biodegradable thermal insulation foamed plastic cup.

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