Preparation method and application of a biodegradable composite material

Abstract

The application discloses a preparation method of a biodegradable composite material and application thereof. The preparation raw material of the biodegradable composite material comprises the following components: polylactic acid, polybutylene adipate terephthalate, thermoplastic starch and a polycyclic epoxy compound. The biodegradable composite material is a compatibilized PLA / PBAT / TPS ternary composite material, has good mechanical properties, interfacial bonding properties, waterproof properties and biodegradability. The raw material used in the biodegradable composite material is biologically sourced or biodegradable, the process is simple and easy to control, and the preparation method can meet the large-scale and low-cost production requirements in the industry. The biodegradable composite material provided by the application can be applied to the fields of disposable tableware, green packaging materials and the like, and has good economic benefits and application prospect.

Description

Technical Field

[0001] This invention belongs to the field of polymer composite materials, specifically relating to a method for preparing a biodegradable composite material and its application. Background Technology

[0002] In recent years, serious environmental problems have brought biodegradable materials, especially polylactic acid (PLA) and poly(butylene terephthalate) (PBAT), to the forefront of public attention. PLA, in particular, has achieved widespread application in multiple fields. However, within the vast plastics industry, compared to traditional plastics, PLA still suffers from drawbacks such as low toughness and high cost.

[0003] To address the brittleness of PLA, blending PLA with flexible polyester PBAT has proven to be an effective method for toughening PLA. However, the high price of both PLA and PBAT is one of the biggest factors limiting their use as general-purpose plastics. Filler modification can reduce costs and, to some extent, achieve enhanced toughness. Further utilizing inexpensive bio-based materials, such as natural fibers and thermoplastic starch (TPS), to blend PLA / PBAT can reduce manufacturing costs. Fully renewable starch is inexpensive and abundant, and as a filler in PLA / PBAT alloys, it can effectively reduce production costs and promote biodegradation. Therefore, starch-filled fully biodegradable PLA / PBAT materials have attracted considerable attention and have been extensively studied. Adding TPS not only improves production efficiency but also toughens PLA to some extent. This is because TPS is made from a mixture of starch and plasticizers and possesses good flexibility. However, the poor compatibility between PLA, PBAT and TPS, as well as the huge difference in hydrophilicity between PLA / PBAT polyester matrix and TPS, remain problems to be solved in preparing PLA / PBAT / TPS ternary composite materials with good dispersibility and high interfacial bonding.

[0004] Currently, common strategies for improving the compatibility between PLA / PBAT and TPS mainly involve surface modification of starch-grafted hydrophobic polymers. However, this method suffers from complex processes and unsatisfactory results. Therefore, there is an urgent need to develop an effective and simple strategy to improve the compatibility between PLA / PBAT and TPS. Summary of the Invention

[0005] To overcome the problems existing in the prior art, one objective of this invention is to provide a biodegradable composite material. A second objective is to provide a method for preparing this biodegradable composite material. A third objective is to provide applications of this biodegradable composite material.

[0006] Through numerous experiments, the inventors discovered that adding compatibilizers is the simplest and most effective way to improve the compatibility of PLA / PBAT / TPS multi-component composite materials.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] The first aspect of the present invention provides a biodegradable composite material, wherein the raw materials for preparing the biodegradable composite material include the following components: polylactic acid, polybutylene terephthalate adipate, thermoplastic starch and polyepoxy compound, wherein polylactic acid (PLA), polybutylene terephthalate adipate (PBAT) and thermoplastic starch (TPS) are used as raw materials, and the polyepoxy compound is used as a compatibilizer.

[0009] Preferably, the polyepoxy compound is N,N,N',N'-tetracyclooxypropyl-4,4'-diaminodiphenylmethane (MBDG).

[0010] Preferably, the reaction includes the addition of a catalyst; and / or, the catalyst is an imidazole catalyst or a tertiary amine catalyst. More preferably, the imidazole catalyst is 1-methylimidazole (MI), and the tertiary amine catalyst is triethylenediamine (TD).

[0011] Preferably, the component comprises the following substances in parts by weight: 50-70 parts polylactic acid, 30-50 parts polybutylene adipate terephthalate, 8-13 parts thermoplastic starch, 1-6 parts N,N,N',N'-tetracyclooxypropyl-4,4'-diaminodiphenylmethane, and 1-2 parts catalyst. More preferably, the component comprises the following substances in parts by weight: 55-65 parts polylactic acid, 35-45 parts polybutylene adipate terephthalate, 8-13 parts thermoplastic starch, 3-6 parts N,N,N',N'-tetracyclooxypropyl-4,4'-diaminodiphenylmethane, and 1-2 parts catalyst. More preferably, the components consist of the following substances in parts by weight: 60 parts polylactic acid, 40 parts polybutylene adipate terephthalate, 10 parts thermoplastic starch, 3-6 parts N,N,N',N'-tetracyclooxypropyl-4,4'-diaminodiphenylmethane, and 1-2 parts catalyst.

[0012] The second aspect of the present invention provides a method for preparing the biodegradable composite material described in the first aspect of the present invention, comprising the following steps: mixing polylactic acid, polybutylene adipate terephthalate, thermoplastic starch, polyepoxy compound and catalyst, reacting to obtain the compatibilized PLA / PBAT / TPS ternary composite material.

[0013] Preferably, the preparation method specifically includes the following steps: first, the polylactic acid, polybutylene adipate terephthalate, thermoplastic starch, polyepoxy compound and catalyst are premixed evenly, and then melt-blended to obtain a compatibilized PLA / PBAT / TPS ternary composite material.

[0014] The preparation method specifically includes the following steps: first, the polylactic acid, polybutylene adipate terephthalate, thermoplastic starch, polyepoxy compounds and catalyst are premixed evenly, and then melt-blended to obtain a compatibilized PLA / PBAT / TPS ternary composite material.

[0015] Preferably, the melt blending temperature is 150–180°C. More preferably, the melt blending process is melt extrusion molding; the temperature zones of the melt extrusion molding are respectively set as follows: Zone 1: 160–170°C, Zone 2: 165–175°C, Zone 3: 165–175°C, Zone 4: 165–175°C, Zone 5: 155–165°C, and Zone 6: 155–165°C. Even more preferably, the temperature zones of the melt extrusion molding are respectively set as follows: Zone 1: 165°C, Zone 2: 170°C, Zone 3: 170°C, Zone 4: 170°C, Zone 5: 160°C, and Zone 6: 160°C.

[0016] Preferably, the premixing and homogenization are carried out at room temperature.

[0017] A third aspect of this invention provides the application of the biodegradable composite material described in the first aspect of this invention in the preparation of tableware or packaging materials. Preferably, the biodegradable composite material is used in the preparation of disposable tableware or environmentally friendly packaging materials.

[0018] The beneficial effects of this invention are:

[0019] This invention provides a biodegradable composite material, which is a compatibilized PLA / PBAT / TPS ternary composite material. The compatibilized PLA / PBAT / TPS ternary composite material provided by this invention exhibits good mechanical properties, interfacial bonding properties, waterproof properties, and biodegradability.

[0020] Specifically, compared with the prior art, the present invention has the following advantages:

[0021] 1) The compatibilized PLA / PBAT / TPS ternary composite material provided by the present invention has good mechanical properties, interfacial bonding properties, waterproof properties, and biodegradability; among which, the tensile strength can reach up to 25.3MPa, the elongation at break can reach up to 49.7%, and the water contact angle can reach up to 97.2°.

[0022] 2) The PLA, PBAT, and TPS raw materials used in this invention are all biologically derived or biodegradable, and are also widely available, making them feasible for large-scale industrial application. Under effective catalysis, a one-step melt extrusion method ensures sufficient chemical reaction between the compatibilizer and each component. The raw materials and compatibilizer MBDG used have specifically selected functional groups. During melt blending, the epoxy groups in MBDG can undergo efficient ring-opening reactions with the terminal hydroxyl or carboxyl groups in PLA / PBAT, as well as the hydroxyl groups in TPS. The related ring-opening products can serve as a bridge connecting the PLA / PBAT matrix and TPS, ultimately improving the overall compatibility of the PLA / PBAT / TPS ternary composite material. The preparation method of this invention is simple and easy to control, meeting the requirements of large-scale, low-cost industrial production.

[0023] 3) The PLA, PBAT and TPS used in this invention are all green and environmentally friendly materials. Therefore, the reactive compatibilized PLA / PBAT / TPS ternary composite material prepared by this invention is an environmentally friendly biodegradable composite material that can be applied to disposable tableware, green packaging materials and other fields, and has good economic benefits and application prospects. Attached Figure Description

[0024] Figure 1 The graph shows the tensile strength test results for samples a to k.

[0025] Figure 2 The graph shows the results of the elongation at break test for samples a to k.

[0026] Figure 3 The diagram shows the water contact angles of samples a to k. Detailed Implementation

[0027] The present invention will be further described in detail below through specific embodiments.

[0028] The raw material components of the following examples and comparative examples are shown in Table 1. All raw materials were pre-dried at 70°C for 48 hours and consisted of the following substances in parts by weight:

[0029] Table 1 Formulation of Biodegradable Composite Materials

[0030]

[0031] Example 1: Preparation of Biodegradable Composite Materials

[0032] First, 60 parts by weight of PLA resin, 40 parts by weight of PBAT resin, 10 parts by weight of TPS, 1 part by weight of MBDG, and 1 part by weight of catalyst MI were weighed according to the specified weight ratio. The components were then thoroughly mixed at room temperature using a high-speed mixer. Next, the mixture was transferred to a co-rotating twin-screw extruder for melt extrusion. The main speed of the twin-screw extruder was set to 120 rpm, the granulation cutting speed was 60 rpm, and the temperature control of the co-rotating twin-screw extruder was as follows: Zone 1: 165℃, Zone 2: 170℃, Zone 3: 170℃, Zone 4: 170℃, Zone 5: 160℃, and Zone 6: 160℃. After natural cooling and drying in a vacuum oven at 45℃ for 24 hours, a biodegradable composite material, namely the compatibilized PLA / PBAT / TPS ternary composite material b, was obtained.

[0033] Example 2: Preparation of Biodegradable Composite Materials

[0034] First, 60 parts by weight of PLA resin, 40 parts by weight of PBAT resin, 10 parts by weight of TPS, 2 parts by weight of MBDG, and 1 part by weight of catalyst MI were weighed according to the specified weight ratio. The components were then thoroughly mixed at room temperature using a high-speed mixer. Next, the mixture was transferred to a co-rotating twin-screw extruder for melt extrusion. The main speed of the twin-screw extruder was set to 120 rpm, the granulation cutting speed was 60 rpm, and the temperature control of the co-rotating twin-screw extruder was as follows: Zone 1: 165℃, Zone 2: 170℃, Zone 3: 170℃, Zone 4: 170℃, Zone 5: 160℃, and Zone 6: 160℃. After natural cooling and drying in a vacuum oven at 45℃ for 24 hours, a biodegradable composite material, namely the compatibilized PLA / PBAT / TPS ternary composite material c, was obtained.

[0035] Example 3: Preparation of Biodegradable Composite Materials

[0036] First, 60 parts by weight of PLA resin, 40 parts by weight of PBAT resin, 10 parts by weight of TPS, 3 parts by weight of MBDG, and 1 part by weight of catalyst MI were weighed according to the specified weight ratio. The components were then thoroughly mixed at room temperature using a high-speed mixer. Next, the mixture was transferred to a co-rotating twin-screw extruder for melt extrusion. The main speed of the twin-screw extruder was set to 120 rpm, the granulation cutting speed was 60 rpm, and the temperature control of the co-rotating twin-screw extruder was as follows: Zone 1: 165℃, Zone 2: 170℃, Zone 3: 170℃, Zone 4: 170℃, Zone 5: 160℃, and Zone 6: 160℃. After natural cooling and drying in a vacuum oven at 45℃ for 24 hours, a biodegradable composite material, namely the compatibilized PLA / PBAT / TPS ternary composite material d, was obtained.

[0037] Example 4: Preparation of Biodegradable Composite Materials

[0038] First, 60 parts by weight of PLA resin, 40 parts by weight of PBAT resin, 10 parts by weight of TPS, 4 parts by weight of MBDG, and 1 part by weight of catalyst MI were weighed according to the specified weight ratio. The components were then thoroughly mixed at room temperature using a high-speed mixer. Next, the mixture was transferred to a co-rotating twin-screw extruder for melt extrusion. The main speed of the twin-screw extruder was set to 120 rpm, the granulation cutting speed was 60 rpm, and the temperature control of the co-rotating twin-screw extruder was as follows: Zone 1: 165℃, Zone 2: 170℃, Zone 3: 170℃, Zone 4: 170℃, Zone 5: 160℃, and Zone 6: 160℃. After natural cooling and drying in a vacuum oven at 45℃ for 24 hours, a biodegradable composite material, namely the compatibilized PLA / PBAT / TPS ternary composite material, was obtained.

[0039] Example 5: Preparation of Biodegradable Composite Materials

[0040] First, 60 parts by weight of PLA resin, 40 parts by weight of PBAT resin, 10 parts by weight of TPS, 5 parts by weight of MBDG, and 1 part by weight of catalyst MI were weighed according to the specified weight ratio. The components were then thoroughly mixed at room temperature using a high-speed mixer. Next, the mixture was transferred to a co-rotating twin-screw extruder for melt extrusion. The main speed of the twin-screw extruder was set to 120 rpm, the granulation cutting speed was 60 rpm, and the temperature control of the co-rotating twin-screw extruder was as follows: Zone 1: 165℃, Zone 2: 170℃, Zone 3: 170℃, Zone 4: 170℃, Zone 5: 160℃, and Zone 6: 160℃. After natural cooling and drying in a vacuum oven at 45℃ for 24 hours, a biodegradable composite material, namely the compatibilized PLA / PBAT / TPS ternary composite material, was obtained.

[0041] Example 6: Preparation of Biodegradable Composite Materials

[0042] First, weigh 60 parts by weight of PLA resin, 40 parts by weight of PBAT resin, 10 parts by weight of TPS, 1 part by weight of MBDG, and 1 part by weight of catalyst TD according to the specified weight. Mix the components thoroughly at room temperature using a high-speed mixer. Then, transfer the mixture to a co-rotating twin-screw extruder for melt extrusion. Set the main speed of the twin-screw extruder to 120 rpm and the granulation cutting speed to 60 rpm. Control the temperature of the co-rotating twin-screw extruder as follows: Zone 1: 165℃, Zone 2: 170℃, Zone 3: 170℃, Zone 4: 170℃, Zone 5: 160℃, and Zone 6: 160℃. After natural cooling and drying in a vacuum oven at 45℃ for 24 hours, a biodegradable composite material, namely the compatibilized PLA / PBAT / TPS ternary composite material g, is obtained.

[0043] Example 7: Preparation of Biodegradable Composite Materials

[0044] First, 60 parts by weight of PLA resin, 40 parts by weight of PBAT resin, 10 parts by weight of TPS, 2 parts by weight of MBDG, and 1 part by weight of catalyst TD1 were weighed according to the specified weight ratio. The components were then thoroughly mixed at room temperature using a high-speed mixer. Next, the mixture was transferred to a co-rotating twin-screw extruder for melt extrusion. The main speed of the twin-screw extruder was set to 120 rpm, the granulation cutting speed was 60 rpm, and the temperature control of the co-rotating twin-screw extruder was as follows: Zone 1: 165℃, Zone 2: 170℃, Zone 3: 170℃, Zone 4: 170℃, Zone 5: 160℃, and Zone 6: 160℃. After natural cooling and drying in a vacuum oven at 45℃ for 24 hours, a biodegradable composite material, namely the compatibilized PLA / PBAT / TPS ternary composite material, was obtained.

[0045] Example 8: Preparation of Biodegradable Composite Materials

[0046] First, 60 parts by weight of PLA resin, 40 parts by weight of PBAT resin, 10 parts by weight of TPS, 3 parts by weight of MBDG, and 1 part by weight of catalyst TD1 were weighed according to the specified weight ratio. The components were then thoroughly mixed at room temperature using a high-speed mixer. Next, the mixture was transferred to a co-rotating twin-screw extruder for melt extrusion. The main speed of the twin-screw extruder was set to 120 rpm, the granulation cutting speed was 60 rpm, and the temperature control of the co-rotating twin-screw extruder was as follows: Zone 1: 165℃, Zone 2: 170℃, Zone 3: 170℃, Zone 4: 170℃, Zone 5: 160℃, and Zone 6: 160℃. After natural cooling and drying in a vacuum oven at 45℃ for 24 hours, a biodegradable composite material, namely the compatibilized PLA / PBAT / TPS ternary composite material i, was obtained.

[0047] Example 9: Preparation of Biodegradable Composite Materials

[0048] First, 60 parts by weight of PLA resin, 40 parts by weight of PBAT resin, 10 parts by weight of TPS, 4 parts by weight of MBDG, and 1 part by weight of catalyst TD1 were weighed according to the specified weight ratio. The components were then thoroughly mixed at room temperature using a high-speed mixer. Next, the mixture was transferred to a co-rotating twin-screw extruder for melt extrusion. The main speed of the twin-screw extruder was set to 120 rpm, the granulation cutting speed was 60 rpm, and the temperature control of the co-rotating twin-screw extruder was as follows: Zone 1: 165℃, Zone 2: 170℃, Zone 3: 170℃, Zone 4: 170℃, Zone 5: 160℃, and Zone 6: 160℃. After natural cooling and drying in a vacuum oven at 45℃ for 24 hours, a biodegradable composite material, namely the compatibilized PLA / PBAT / TPS ternary composite material, was obtained.

[0049] Example 10 Preparation of biodegradable composite materials

[0050] First, 60 parts by weight of PLA resin, 40 parts by weight of PBAT resin, 10 parts by weight of TPS, 5 parts by weight of MBDG, and 1 part by weight of catalyst TD1 were weighed according to the specified weight ratio. The components were then thoroughly mixed at room temperature using a high-speed mixer. Next, the mixture was transferred to a co-rotating twin-screw extruder for melt extrusion. The main speed of the twin-screw extruder was set to 120 rpm, the granulation cutting speed was 60 rpm, and the temperature control of the co-rotating twin-screw extruder was as follows: Zone 1: 165℃, Zone 2: 170℃, Zone 3: 170℃, Zone 4: 170℃, Zone 5: 160℃, and Zone 6: 160℃. After natural cooling and drying in a vacuum oven at 45℃ for 24 hours, a biodegradable composite material, namely the compatibilized PLA / PBAT / TPS ternary composite material k, was obtained.

[0051] Comparative Example 1: Preparation of Biodegradable Composite Materials

[0052] First, weigh 60 parts by weight of PLA resin, 40 parts by weight of PBAT resin, and 10 parts by weight of TPS according to the specified weight ratios. Mix the components thoroughly at room temperature using a high-speed mixer. Then, transfer the mixture to a co-rotating twin-screw extruder for melt extrusion. Set the main speed of the twin-screw extruder to 120 rpm and the granulation cutting speed to 60 rpm. Control the temperature of the co-rotating twin-screw extruder as follows: Zone 1: 165℃, Zone 2: 170℃, Zone 3: 170℃, Zone 4: 170℃, Zone 5: 160℃, and Zone 6: 160℃. After cooling and drying, obtain uncompressed PLA / PBAT / TPS composite material a.

[0053] Application Example 1

[0054] 1. Mechanical property testing of sample ak

[0055] The mechanical properties (tensile strength and elongation at break) of sample ak were tested according to the national standard GB / T 1040.2-2022. The specific results are as follows: Figure 1 and Figure 2 As shown.

[0056] Analysis revealed that due to the low compatibility between PLA / PBAT and TPS, the tensile strength and elongation at break of sample a were 21.1 MPa and 17.6%, respectively. However, under the catalysis of MI, when 1 part by weight of MBDG was added, the tensile strength and elongation at break of sample b, compared to sample a, not only did not increase but actually decreased, to 14.7 MPa and 13.7%, respectively. This is mainly because almost all of the low-concentration MBDG underwent chain extension and cross-linking with TPS, forming larger TPS domains in the PLA / PBAT matrix, further reducing the degree of miscibility between PLA / PBAT and TPS.

[0057] When 2 parts by weight of MBDG were added, although the tensile strength of sample c (MBDG = 2 parts by weight) was still lower than that of sample a, its elongation at break was 12.0% higher than that of sample a. This indicates that the compatibility between PLA / PBAT and TPS began to improve. Continuing to increase the amount of MBDG, the tensile strength and elongation at break of samples d to f gradually improved. In particular, sample f (MBDG = 5 parts by weight) had a tensile strength of 25.3 MPa and an elongation at break of 49.7%, compared to 21.1 MPa and 17.6% for sample a, representing an increase of 20.0% in tensile strength and 182.4% in elongation at break. These results again demonstrate that, under the catalysis of MI, the polyepoxy groups on MBDG can effectively react with the hydroxyl or carboxyl groups of PLA / PBAT / TPS, acting as chain extenders and crosslinking agents between PLA / PBAT / TPS components, ultimately significantly improving the mechanical properties of PLA / PBAT / TPS.

[0058] On the other hand, the test results show that TD also has a certain catalytic effect on MBDG compatibilization of PLA / PBAT / TPS. Under the catalysis of TD, the tensile strength and elongation at break of the composite materials g to k increase with the increase of MBDG dosage. When the amount of MBDG is 5 parts by weight (sample k), the tensile strength of the resulting composite material reaches the same level as that of sample a, but its elongation at break is 32.4% higher than that of sample a. Therefore, under TD catalysis, MBDG can also react with PLA / PBAT / TPS to form chain-extended and cross-linked structures, ultimately improving the mechanical properties of PLA / PBAT / TPS.

[0059] Comparing samples b-f with samples g-k using the same amount of MBDG, it can be found that the mechanical properties of samples b-f are generally higher than those of samples g-k. This indicates that MI has a better catalytic effect for compatibilizing PLA / PBAT / TPS with MBDG. In particular, sample f (MBDG = 5 parts by weight) catalyzed by MI showed a 20.0% increase in tensile strength and a 182.4% increase in elongation at break compared to uncompatibilized PLA / PBAT / TPS (sample a). This demonstrates that MBDG is a highly promising compatibilizer for PLA / PBAT / TPS, providing an important reference for obtaining inexpensive PLA / PBAT-based polymers with good mechanical properties through blending modification.

[0060] 2. GPC testing of sample ak

[0061] The number-average molecular weight, weight-average molecular weight, and molecular weight distribution coefficient of sample ak were determined by gel permeation chromatography (GPC). The specific test results are shown in Table 2.

[0062] Table 2 GPC test results of composite materials

[0063]

[0064]

[0065] As shown in Table 2, the PLA / PBAT / TPS composite material without compatibilizer, i.e., sample a, has a weight-average molecular weight of 76,500 Da. Under the catalysis of MI or TD, the molecular weights of samples b to f and samples g to k all increase with the increase of MBDG dosage, but the increase is limited in the early stage.

[0066] On the one hand, this is because at low concentrations, MBDG mainly reacts with TPS, but since starch is insoluble in organic solvents, it cannot increase the molecular weight of the composite material. On the other hand, this indicates that at low concentrations, MBDG may also be more inclined to undergo chain extension and cross-linking reactions with the low molecular weight PLA and PBAT present in the composite material, resulting in a decrease in the molecular weight distribution coefficient of the product. This is particularly evident under the catalysis of MI (see the relevant molecular weight data of samples b, c, and d in Table 2).

[0067] When the amount of MBDG reached 3 parts by weight, the molecular weight of the samples began to increase significantly. When the amount of MBDG was 5 parts by weight, the molecular weights of the samples reached their maximum, at 145,500 Da (sample f) and 82,500 Da (sample k), respectively. The molecular weights of these two samples are significantly larger than that of sample a (76,500 Da), especially sample f, whose molecular weight is almost twice that of sample a. This demonstrates that in the presence of a catalyst (especially MI), the melt blending process allows MBDG to effectively react with the terminal hydroxyl or carboxyl groups of PLA / PBAT and the hydroxyl groups of TPS. These reactions promote the formation of chain-extended and cross-linked structures within the composite material, not only increasing the molecular weight of the composite material but also improving its interfacial bonding properties.

[0068] 3. Water contact angle test of sample ak

[0069] The surface contact angle of a thin film reflects its surface wettability. Using an optical contact angle meter equipped with a high-resolution digital camera, the static water contact angle of sample ak was measured in air. Specific test results for the water contact angle are as follows: Figure 3 As shown.

[0070] Analysis revealed that sample a had the smallest water contact angle (86.8°) among all samples, indicating the worst surface hydrophobicity. This is primarily due to the large number of hydrophilic hydroxyl groups in the TPS. This also implies a lower interfacial bonding force between the hydrophilic TPS and the hydrophobic PLA / PBAT matrix. With the addition of MBDG and catalysts (MI or TD), the water contact angles of samples b–f and samples g–k gradually increased, indicating a gradual improvement in their surface hydrophobicity.

[0071] Among samples b-f and g-k, samples f and k exhibited the largest water contact angles, reaching 97.2° and 96.3°, respectively. Compared to sample a, the water contact angles of samples b-f increased by more than 10%. This is because the epoxy groups of MBDG underwent effective chain extension and cross-linking reactions with the numerous hydrophilic hydroxyl groups in TPS, significantly reducing the hydrophilicity of TPS and ultimately improving the surface hydrophobicity of the composite material. The reduction in TPS hydrophilicity narrowed the difference between it and the hydrophobic PLA / PBAT matrix, confirming that the addition of MBDG can indeed improve the interfacial compatibility of PLA / PBAT / TPS.

[0072] The improved hydrophobicity of the composite material also reflects, to some extent, an improved waterproof performance. This will facilitate the development of the resulting PLA / PBAT / TPS composite material for practical applications requiring waterproofing, such as its use as a green packaging material. For example, it can be used to protect food from moisture during transportation, handling, and storage. Traditional plastics commonly used in food packaging are mainly LDPE and PP, with water contact angles around 100°. This indicates that the hydrophobic properties of the compatibilized PLA / PBAT / TPS ternary composite material are comparable to those of LDPE and PP.

Claims

1. A biodegradable composite material, characterized in that, The raw materials for preparing the biodegradable composite material, by weight, include the following: 50-70 parts of polylactic acid, 30-50 parts of polybutylene adipate terephthalate, 8-13 parts of thermoplastic starch, 4-6 parts of polyepoxy compound, and 1-2 parts of catalyst. The polyepoxy compound is N,N,N',N' -Tetracyclooxypropyl-4,4'-diaminodiphenylmethane; The catalyst is 1-methylimidazole; The method for preparing the biodegradable composite material includes the following steps: mixing polylactic acid, polybutylene adipate terephthalate, thermoplastic starch, polyepoxy compounds and catalyst, reacting them to obtain a compatibilized PLA / PBAT / TPS ternary composite material.

2. The method for preparing the biodegradable composite material according to claim 1, characterized in that, The process includes the following steps: mixing polylactic acid, polybutylene adipate terephthalate, thermoplastic starch, polyepoxy compounds and catalyst, reacting them to obtain the compatibilized PLA / PBAT / TPS ternary composite material.

3. The method for preparing the biodegradable composite material according to claim 2, characterized in that, The preparation method specifically includes the following steps: first, the polylactic acid, polybutylene adipate terephthalate, thermoplastic starch, polyepoxy compounds and catalyst are premixed evenly, and then melt-blended to obtain a compatibilized PLA / PBAT / TPS ternary composite material.

4. The method for preparing the biodegradable composite material according to claim 3, characterized in that, The melt blending temperature is 150–180°C.

5. The method for preparing the biodegradable composite material according to claim 4, characterized in that, The melt blending process is melt extrusion molding; and / or, the temperatures of each zone in the melt extrusion molding are set as follows: Zone 1 temperature 160~170℃, Zone 2 temperature 165~175℃, Zone 3 temperature 165~175℃, Zone 4 temperature 165~175℃, Zone 5 temperature 155~165℃ and Zone 6 temperature 155~165℃.

6. The method for preparing the biodegradable composite material according to claim 3, characterized in that, The premixing process is carried out at room temperature.

7. The application of the biodegradable composite material according to claim 1 in the preparation of tableware or packaging materials.

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