A high-barrier degradable plastic film and preparation method thereof

Abstract

The present invention relates to the field of polymer technology, and specifically discloses a high-barrier degradable plastic film and a preparation method thereof, comprising the following steps: adding polybutylene adipate / terephthalate, a volume-enhancing modified chain extender, a plasticizer, and nanocellulose to polylactic acid, uniformly mixing at 120-150° C., injection molding at 145-160° C., and then using a film blowing machine to obtain a plastic film. The plastic film is subjected to surface modification treatment with an inorganic filler to obtain the high-barrier degradable plastic film. The plastic film provided by the present invention is a degradable plastic film with polylactic acid as the main raw material system, excellent mechanical properties, especially tensile toughness, strong applicability as a packaging or covering material, adaptable to complex environments such as special-shaped packaging, and excellent barrier properties.

Description

Technical Field

[0001] The present invention belongs to the field of polymer technology, and in particular relates to a high-barrier degradable plastic film and a preparation method thereof. Background Art

[0002] In recent years, environmental pollution caused by plastic products such as polyethylene, polypropylene, and polyethylene terephthalate has become increasingly serious. These plastics often take hundreds of years to fully degrade in nature. Existing research focuses on two main approaches to addressing this issue: plastic degradation and regeneration. Degradable plastics are considered one of the most effective approaches to addressing plastic pollution. Degradable plastics are defined as plastics whose properties meet their intended use during storage and then degrade into environmentally friendly substances under natural conditions. Based on the specific degradation pathway, they can be broadly categorized as biodegradable, photodegradable, and chemically degradable plastics. These plastics are widely used in industries such as packaging, agriculture, and healthcare. Biodegradable plastics primarily include petrochemical-based biodegradable plastics, renewable biodegradable plastics, and compostable plastics. Renewable biodegradable plastics are derived directly from natural materials and fall into two main categories: the first is produced by adding modified materials to starch; the second is derived from starch through further processing, a common example being polylactic acid.

[0003] Polylactic acid is a renewable biodegradable plastic produced from renewable resources such as corn starch. It has excellent performance and good biocompatibility. It is widely used in industries such as industry, packaging, and agricultural mulch. It is the most promising green and environmentally friendly thermoplastic material.

[0004] The invention patent with application number CN202311453522.2 discloses an environmentally friendly polylactic acid plastic, its preparation method and application. By preparing a eugenol grafted modified natural rubber as a toughening agent, mixing and kneading it with polylactic acid, an environmentally friendly polylactic acid plastic is obtained, which can be used to prepare food packaging materials. The polylactic acid plastic has good mechanical properties. At the same time, the raw materials of the plastic are environmentally friendly and easy to degrade, and have good application prospects. However, adding natural rubber as a toughening agent to the polylactic acid plastic system may have a certain adverse effect on the degradable properties of polylactic acid; the invention patent with application number CN202210727283.4 discloses an antibacterial and mildew-proof biodegradable polylactic acid plastic The invention discloses a plastic material and a preparation method thereof, comprising the following raw materials: polylactic acid resin, an antibacterial agent, an antifungal agent and a plasticizer. Silver ions and zinc ions are complexed with phytic acid and then coated on fly ash. The functional coordination compound can promote the uniform dispersion of fly ash in the polylactic acid matrix, which contributes to better interface compatibility and interaction between fly ash and polylactic acid. Polyethylene glycol and chitosan are used as composite plasticizers to increase not only the plasticity of the plastic but also the thermal properties of the plastic. The prepared plastic has better mechanical, antibacterial and gas barrier properties. However, the method of adding antibacterial agents and antifungal agents for blending and enhancing the synergy may have poor time-efficiency, which may affect the performance stability of the polylactic acid plastic during long-term use.

[0005] To address this issue, there is an urgent need for a high-barrier degradable plastic film that has excellent tensile toughness, is highly adaptable as a packaging or covering material, can adapt to complex environments such as special-shaped packaging, and has excellent barrier properties. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention provides a high-barrier, degradable plastic film and its preparation method. The plastic film provided by the present invention is primarily made of polylactic acid and exhibits excellent mechanical properties, particularly tensile toughness. It is highly adaptable as a packaging or covering material, can adapt to complex environments such as special-shaped packaging, and exhibits excellent barrier properties.

[0007] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0008] In one aspect, the present invention provides a method for preparing a high-barrier degradable plastic film, comprising the following steps:

[0009] Polybutylene adipate / terephthalate, a compatibilizer-modified chain extender, a plasticizer and nanocellulose are added to polylactic acid, mixed evenly at 120-150° C., injection-molded at 145-160° C., and then a film blowing machine is used to obtain a plastic film. The plastic film is surface-modified with an inorganic filler to obtain the high-barrier degradable plastic film.

[0010] Preferably, the method for preparing the high-barrier degradable plastic film comprises the following steps:

[0011] Polybutylene adipate / terephthalate, a compatibilizer-modified chain extender, a plasticizer, and nanocellulose are added to polylactic acid, mixed evenly at 135° C., injection molded at 152.5° C., and then a film blowing machine is used to obtain a plastic film. The plastic film is surface-modified with an inorganic filler to obtain the high-barrier degradable plastic film.

[0012] In some embodiments of the present invention, the inorganic filler is graphene oxide, and the oxygen content is 35-45%.

[0013] Preferably, the oxygen content of the graphene oxide is 40%.

[0014] In some embodiments of the present invention, the steps of surface modification of the plastic film with an inorganic filler are as follows:

[0015] (1) adding graphene oxide and deionized water into a container, ultrasonically dispersing for 1 to 2 hours, and then stirring for 12 to 36 hours to obtain a graphene oxide modified liquid;

[0016] (2) immersing the plastic film in a container containing graphene oxide modification solution, taking out the plastic film after surface treatment for 1 to 10 minutes, rinsing with deionized water, and drying;

[0017] (3) Repeat the operation of step (2) 0 to 4 times to obtain the plastic film with the surface modified by the inorganic filler.

[0018] Preferably, the steps of surface modification of the plastic film with inorganic fillers are as follows:

[0019] (1) adding graphene oxide and deionized water into a container, ultrasonically dispersing for 1.5 h, and stirring for 24 h to obtain a graphene oxide modified solution;

[0020] (2) Immersing the plastic film in a container containing graphene oxide modification solution, removing the plastic film after surface treatment for 5 minutes, rinsing with deionized water, and drying;

[0021] (3) Repeat the operation of step (2) twice to obtain the plastic film with inorganic filler surface modification treatment.

[0022] In some embodiments of the present invention, the mass ratio of graphene oxide to deionized water in step (1) is (0.1-0.3):1000.

[0023] Preferably, in step (1), the mass ratio of graphene oxide to deionized water is 0.2:1000.

[0024] The applicant significantly improved the gas barrier properties of the polylactic acid plastic system and enhanced the packaging application performance of the plastic film by self-assembling graphene oxide on the surface of the plastic film. The surface modification effect of the coupling agent functional part in the system's volume-extending and modified chain extender on the graphene oxide enables good compatibility between the interface of the two when the graphene oxide attaches to the surface of the plastic film through self-assembly, thereby improving the processing performance of the plastic film. On the other hand, promoted by good compatibility, the large and dense structure of the graphene oxide itself ensures the performance of each component of the plastic film.

[0025] On the other hand, the present invention provides a high-barrier degradable plastic film, which comprises the following raw materials in parts by weight: 50 to 70 parts of polylactic acid, 5 to 10 parts of polybutylene adipate / terephthalate, 2 to 6 parts of a compatibilizer-modified chain extender, 0.2 to 0.5 parts of a plasticizer, and 1 to 3 parts of nanocellulose.

[0026] In some embodiments of the present invention, the preparation steps of the compatibilizing modified chain extender are as follows:

[0027] Add a chain extender and an organic solvent into a reactor, stir evenly, add a volume-increasing modifier at 8-15° C., keep warm and react for 6-14 hours, filter after the reaction, wash with deionized water 3-5 times and dry for 10-12 hours to obtain the volume-increasing modified chain extender.

[0028] Preferably, the preparation steps of the compatibilizing modified chain extender are as follows:

[0029] Add a chain extender and an organic solvent into the reactor, stir evenly, add a volume-increasing modifier at 11.5° C., keep warm and react for 10 hours, filter after the reaction, wash with deionized water 4 times and dry for 11 hours to obtain the volume-increasing modified chain extender.

[0030] Preferably, the organic solvent is toluene, and the amount added is 5 to 10 times the total mass of the chain extender and the compatibilizer modifier.

[0031] Further preferably, the amount of the organic solvent added is 7.5 times the total mass of the chain extender and the compatibilizer modifier.

[0032] In some embodiments of the present invention, the chain extender is at least one of triglycidyl isocyanurate and glycidyl methacrylate.

[0033] Preferably, the chain extender is triglycidyl isocyanurate.

[0034] In some embodiments of the present invention, the compatibilizing modifier is γ-aminopropyltriethoxysilane.

[0035] In some embodiments of the present invention, the molar ratio of the chain extender to the compatibilizer is 1:(2.5-2.7).

[0036] Preferably, the molar ratio of the chain extender to the compatibilizer is 1:2.6.

[0037] In the existing technology, when polylactic acid is used as the main component of the degradable plastic system, the molecular chain movement ability of polylactic acid is weak during melting and crystallization, its impact resistance is poor, it is brittle and has poor toughness, and its performance as a packaging material is limited. Although adding polyadipate / butylene terephthalate to blend and toughen is a better solution, poor compatibility will lead to a decrease in the performance stability of the system. To address this issue, the present invention prepares a bifunctional compatibilizer-modified chain extender, utilizes epoxy groups to chemically bond with a polylactic acid and poly(butylene adipate / terephthalate) blend system, reduces the presence of particle protrusions and holes on the cross section of the blend system, and thus blurs the interface between the two phases. At this time, the loss modulus and elasticity of the blend system are increased, and the tensile properties of the blend system are greatly improved. At the same time, the long-chain alkyl group of the compatibilizer-modified chain extender is entangled with the molecular chains of the polylactic acid and poly(butylene adipate / terephthalate) blend system, weakens the entanglement density of the molecular chains, increases the mobility of the polylactic acid molecular chains, and promotes the orderly arrangement of the polylactic acid molecular chains, thereby playing a plasticizing role and weakening the molecular chain interaction between polylactic acid and poly(butylene adipate / terephthalate), reducing the interfacial tension between the two phases, promoting the dispersion of polylactic acid, and enabling the blend system to play a significant toughening role.

[0038] In some embodiments of the present invention, the plasticizer is an isosorbide-based plasticizer.

[0039] Preferably, the plasticizer is isosorbide dibutyrate.

[0040] In some embodiments of the present invention, 1 to 2 parts of polyvinyl alcohol are further added to the plastic film.

[0041] Preferably, the viscosity of the polyvinyl alcohol is 44-54 mPa·s.

[0042] Further preferably, the viscosity of the polyvinyl alcohol is 50 mPa·s.

[0043] The applicant found that the tensile strength of the plastic film was greatly improved by adding a specific proportion of polyvinyl alcohol. The possible reason is that the polyvinyl alcohol continuously diffuses during the drying process of the plastic film, thereby forming a network structure, improving the density of the plastic film, and thus improving the tensile strength of the plastic film.

[0044] In some embodiments of the present invention, the length of the nanocellulose is 10-40 nm.

[0045] Compared with the prior art, the present invention has the following beneficial effects:

[0046] (1) The plastic film provided by the present invention is a degradable plastic film with polylactic acid as the main raw material system, excellent mechanical properties, especially tensile toughness, and strong applicability when used as packaging or covering material, and can adapt to complex environments such as special-shaped packaging, and has excellent barrier properties;

[0047] (2) The present invention prepares a functional compatibilizer-modified chain extender, which uses epoxy groups to chemically bond with the polylactic acid and poly(butylene adipate / terephthalate) blend system, thereby reducing the presence of particle protrusions and holes on the cross section of the blend system, blurring the interface between the two phases, and greatly improving the tensile properties of the blend system; on the other hand, the long-chain alkyl group of the compatibilizer-modified chain extender is entangled with the molecular chains of the polylactic acid and poly(butylene adipate / terephthalate) blend system, thereby reducing the entanglement density of the molecular chains, increasing the mobility of the polylactic acid molecular chains, and promoting the orderly arrangement of the polylactic acid molecular chains, thereby playing a plasticizing role and weakening the molecular chain interaction between polylactic acid and poly(butylene adipate / terephthalate), reducing the interfacial tension between the two phases, promoting the dispersion of polylactic acid, and making the blend system play a significant toughening role;

[0048] (3) The present invention also adds a specific proportion of polyvinyl alcohol, which continuously diffuses during the drying process of the plastic film to form a network structure, thereby improving the density of the plastic film and thus improving the tensile strength of the plastic film;

[0049] (4) The present invention significantly improves the gas barrier properties of the polylactic acid plastic system by self-assembling graphene oxide on the surface of the plastic film, thereby increasing the packaging application of the plastic film. The surface modification effect of the coupling agent functional part in the modifier on the graphene oxide enables the graphene oxide to attach to the surface of the plastic film through self-assembly, and the interface between the two has good compatibility, thereby increasing the processing performance of the plastic film and ensuring the performance of each component of the plastic film. DETAILED DESCRIPTION

[0050] The present invention will be described below in conjunction with specific embodiments. It should be noted that the following examples are illustrative of the present invention and are intended only to illustrate the present invention and are not intended to limit the present invention. Other combinations and various modifications within the scope of the present invention may be made without departing from the spirit or scope of the present invention.

[0051] Unless otherwise specified, the following reagents can be easily obtained from commercial companies. Among them, polylactic acid model LX175 was purchased from Total-Corbijn, USA; polybutylene adipate / terephthalate model TH801T was purchased from Xinjiang Lanshan Tunhe Chemical Co., Ltd.; graphene oxide (oxygen content 40%) was purchased from Changzhou Sixth Element Materials Technology Co., Ltd.; polyvinyl alcohol (viscosity 50 mPa·s) was purchased from Chaohu Desheng Chemical Construction Co., Ltd.; nanocellulose (length 20 nm) was purchased from Zhongke Leiming Technology Co., Ltd.; hydroxypropyl methylcellulose was purchased from Jinzhou Zhenghui Building Materials Technology Co., Ltd.

[0052] Preparation Example 1

[0053] The preparation steps of the compatibilized modified chain extender 1 are as follows:

[0054] 10 g of triglycidyl isocyanurate and 220 mL of toluene were added to the reactor and stirred evenly. 19.4 g of γ-aminopropyltriethoxysilane was added at 11.5° C. and the mixture was kept warm for 10 h. After the reaction was completed, the mixture was filtered, washed with deionized water four times, and dried to obtain the compatibilized modified chain extender 1.

[0055] Preparation Example 2

[0056] The preparation steps of the compatibilized modified chain extender 2 are as follows:

[0057] 10 g of triglycidyl isocyanurate and 215 mL of toluene were added to the reactor and stirred evenly. 17.9 g of γ-aminopropyltriethoxysilane was added at 11.5° C. and the mixture was kept warm for 10 h. After the reaction was completed, the mixture was filtered, washed with deionized water four times, and dried to obtain the compatibilized modified chain extender 2.

[0058] Preparation Example 3

[0059] The preparation steps of the compatibilized modified chain extender 3 are as follows:

[0060] 10 g of triglycidyl isocyanurate and 231 mL of toluene were added to the reactor and stirred evenly. 20.9 g of γ-aminopropyltriethoxysilane was added at 11.5° C. and the mixture was kept warm for 10 h. After the reaction was completed, the mixture was filtered, washed with deionized water four times, and dried to obtain the compatibilized modified chain extender 3.

[0061] The raw material parts described in the following examples and comparative examples can be grams, kilograms, tons or other mass units.

[0062] Example 1

[0063] A method for preparing a high-barrier degradable plastic film comprises the following steps:

[0064] S1. By weight, 7.5 parts of polybutylene adipate / terephthalate, 4 parts of compatibilizer-modified chain extender 1, 0.35 parts of isosorbide dibutyrate, 2 parts of nanocellulose, and 1.5 parts of polyvinyl alcohol were added to 60 parts of polylactic acid, mixed uniformly at 135° C., and injection molded at 152.5° C. Using a film blowing machine, the temperature was set at 150° C., the pulling speed was 30 r / min, and the blowing ratio was 1:8 to obtain a plastic film;

[0065] S2. The plastic film is subjected to surface modification treatment with an inorganic filler. The specific steps are as follows:

[0066] (1) Add 0.2 g of graphene oxide and 1000 mL of deionized water into a container, ultrasonically disperse for 1.5 h, and then stir for 24 h to obtain a graphene oxide modified solution;

[0067] (2) Immerse the plastic film obtained in S1 in a container containing graphene oxide modification solution, remove the plastic film after surface treatment for 5 minutes, rinse with deionized water, and dry;

[0068] (3) Repeat the operation of step (2) twice to obtain the plastic film with inorganic filler surface modification treatment.

[0069] Example 2

[0070] A method for preparing a high-barrier degradable plastic film comprises the following steps:

[0071] S1. Add 5 parts of polybutylene adipate / terephthalate, 2 parts of compatibilizer-modified chain extender 1, 0.2 parts of isosorbide dibutyrate, 1 part of nanocellulose and 1 part of polyvinyl alcohol to 50 parts of polylactic acid, mix them uniformly at 120°C, and after injection molding at 152.5°C, use a film blowing machine with the set temperature of 150°C, the pulling speed of 30 r / min, and the blowing ratio of 1:8 to obtain a plastic film;

[0072] S2. The plastic film is subjected to surface modification treatment with an inorganic filler. The specific steps are as follows:

[0073] (1) Add 0.3 g of graphene oxide and 1000 mL of deionized water into a container, ultrasonically disperse for 1 h, and then stir for 36 h to obtain a graphene oxide modified solution;

[0074] (2) The plastic film obtained in S1 is immersed in a container containing graphene oxide modification liquid. After surface treatment for 10 minutes, the plastic film is taken out, rinsed with deionized water, and dried to obtain the plastic film with inorganic filler surface modification.

[0075] Example 3

[0076] A method for preparing a high-barrier degradable plastic film comprises the following steps:

[0077] S1. Add 10 parts of polybutylene adipate / terephthalate, 6 parts of compatibilizer-modified chain extender 1, 0.5 parts of isosorbide dibutyrate, 3 parts of nanocellulose and 2 parts of polyvinyl alcohol to 70 parts of polylactic acid, mix them uniformly at 150°C, and after injection molding at 152.5°C, use a film blowing machine with the set temperature of 150°C, the pulling speed of 30 r / min, and the blowing ratio of 1:8 to obtain a plastic film;

[0078] S2. The plastic film is subjected to surface modification treatment with an inorganic filler. The specific steps are as follows:

[0079] (1) Add 0.1 g of graphene oxide and 1000 mL of deionized water into a container, ultrasonically disperse for 2 h, and then stir for 12 h to obtain a graphene oxide modified solution;

[0080] (2) Immerse the plastic film obtained in S1 in a container containing graphene oxide modification solution, remove the plastic film after surface treatment for 1 min, rinse with deionized water, and dry;

[0081] (3) Repeat the operation of step (2) 4 times to obtain the plastic film with inorganic filler surface modification treatment.

[0082] Example 4

[0083] A method for preparing a high-barrier degradable plastic film, the specific implementation method is the same as that of Example 1, except that the compatibilizer-modified chain extender 2 is used to replace the compatibilizer-modified chain extender 1 in an equal amount.

[0084] Example 5

[0085] A method for preparing a high-barrier degradable plastic film, the specific implementation method is the same as that of Example 1, except that the compatibilizer-modifier-chain extender 3 is used to replace the compatibilizer-modifier-chain extender 1 in equal amounts.

[0086] Comparative Example 1

[0087] A method for preparing a high-barrier degradable plastic film comprises the following steps:

[0088] By weight, 7.5 parts of polybutylene adipate / terephthalate, 4 parts of compatibilizer-modified chain extender 1, 0.35 parts of isosorbide dibutyrate, 2 parts of nanocellulose and 1.5 parts of polyvinyl alcohol are added to 60 parts of polylactic acid, mixed evenly at 135°C, and injection-molded at 152.5°C. Then, a film blowing machine is used with the set temperature of 150°C, the pulling speed of 30 r / min, and the blowing ratio of 1:8 to obtain the plastic film surface-modified with inorganic filler.

[0089] Example 6

[0090] A method for preparing a high-barrier degradable plastic film, the specific implementation method is the same as that of Example 1, except that in step (3) of this embodiment, the operation of step (2) is repeated 5 times in step (3) of surface modification treatment of the plastic film with inorganic fillers.

[0091] Example 7

[0092] A method for preparing a high-barrier degradable plastic film, the specific implementation method is the same as that of Example 1, except that hydroxypropyl methylcellulose is used to replace polyvinyl alcohol in an equal amount.

[0093] Performance Testing

[0094] The high barrier degradable plastic films obtained in the above examples and comparative examples were subjected to the following performance tests. The specific test results are shown in Table 1:

[0095] (1) Water vapor transmission rate: According to GB / T26253-2010 "Determination of water vapor transmission rate of plastic film and sheeting - Infrared detector method", the test was carried out using a BASIC301 water vapor transmission rate tester at a temperature of 23°C and a relative humidity of 85%; water vapor transmission rate g / (m 2 / 24h), the lower the transmittance, the better the performance;

[0096] (2) Oxygen transmission rate: The test was conducted using a VACV1 oxygen transmission rate tester at a temperature of 23°C and a relative humidity of 0%. Oxygen transmission rate (cm) 3 / (m 2 ·24h·0.1MPa), the lower the transmittance, the better the performance;

[0097] (3) Tensile strength test: The test was carried out in accordance with GB / T1040-2006, with a tensile rate of 50 mm / min and a sample size of 164 mm × 10 mm × 4 mm.

[0098] Table 1

[0099]

[0100] As can be seen from Table 1, the plastic films provided by Examples 1 to 3 of the present invention have excellent tensile toughness and excellent barrier properties. In Examples 4 and 5, the preparation ratio of the compatibilizer-modified chain extender was changed, and the performance of the compatibilizer-modified chain extender was affected. When added to the system, it affected the dispersion of polylactic acid in polybutylene adipate / terephthalate. On the other hand, the chemical bonding effect of the epoxy group was reduced, and the particle protrusions and holes on the cross-section of the blended system increased, ultimately resulting in a decrease in the tensile properties of the blended system. The plastic film prepared in Comparative Example 1 was not subjected to the graphene oxide surface self-assembly treatment, and the barrier properties were severely degraded, with a small loss in tensile properties. In Example 6, the number of graphene oxide surface self-assembly treatments was changed. Due to limited interfacial compatibility, the gas barrier properties and tensile properties of the polylactic acid plastic system were both degraded. Compared with Example 1, it can be seen that due to the addition of hydroxypropyl methylcellulose instead of polyvinyl alcohol, the dense network structure formed by polyvinyl alcohol in the system is lacking to promote tensile properties, resulting in a significant decrease in the gas barrier properties and tensile properties of the polylactic acid plastic system.

[0101] The above description is merely a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Although the present invention has been disclosed as a preferred embodiment, it is not intended to limit the present invention. Any technician familiar with the present profession can make some changes or modifications to equivalent embodiments of equivalent changes using the technical contents disclosed above without departing from the scope of the technical solution of the present invention. However, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A method for preparing a high-barrier degradable plastic film, characterized in that: The following steps are involved: Polybutylene adipate / terephthalate, a compatibilizing and modifying chain extender, a plasticizer, nanocellulose, and polyvinyl alcohol are added to polylactic acid, mixed uniformly at 120-150° C., injection molded at 145-160° C., and then formed into a plastic film using a film blowing machine. The plastic film is surface-modified with an inorganic filler to obtain the high-barrier degradable plastic film; the inorganic filler is graphene oxide, and the oxygen content is 35-45%. The steps of surface modification of the plastic film with inorganic filler are as follows: (1) adding graphene oxide and deionized water into a container, ultrasonically dispersing for 1 to 2 hours, and then stirring for 12 to 36 hours to obtain a graphene oxide modified liquid; (2) immersing the plastic film in a container containing graphene oxide modification solution, taking out the plastic film after surface treatment for 1 to 10 minutes, rinsing with deionized water, and drying; (3) Repeating the operation of step (2) 0 to 4 times to obtain the plastic film having been surface-modified with an inorganic filler; The preparation steps of the compatibilizing modified chain extender are as follows: Add a chain extender and an organic solvent into a reactor, stir evenly, add a volume-increasing modifier at 8-15° C., keep warm and react for 6-14 hours, filter after the reaction, wash with deionized water 3-5 times and dry for 10-12 hours to obtain the volume-increasing modified chain extender; The chain extender is triglycidyl isocyanurate; The compatibilizer is γ-aminopropyltriethoxysilane; The molar ratio of the chain extender to the compatibilizer is 1:(2.5-2.7).

2. The method for preparing a high barrier degradable plastic film according to claim 1, characterized in that: The mass ratio of graphene oxide to deionized water in step (1) is (0.1-0.3):1000.

3. A high barrier degradable plastic film obtained by the preparation method according to claim 1 or 2, characterized in that: The plastic film comprises the following raw materials in parts by weight: 50 to 70 parts of polylactic acid, 5 to 10 parts of polybutylene adipate / terephthalate, 2 to 6 parts of a compatibilizer-modified chain extender, 0.2 to 0.5 parts of a plasticizer, 1 to 3 parts of nanocellulose and 1 to 2 parts of polyvinyl alcohol.

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