An antibacterial degradable film and a preparation method thereof

Abstract

The present application relates to the technical field of plastic film, in particular to an antibacterial degradable film and a preparation method thereof.The present application overcomes the problem of poor antibacterial performance and mechanical performance of traditional degradable film.The raw materials of the film of the present application include PLA, PBS, PHA, PCL, modified nanocellulose, antibacterial agent, composite antibacterial particle and maleic anhydride grafted PLA.In the preparation of the present application, the nanocellulose modified by silane coupling agent is first combined with PLA to prepare a functional master batch, and the antibacterial agent of ZIF-8 loaded with tea polyphenol and the composite antibacterial particle of mesoporous silica loaded with chitosan are combined with PBS to prepare an antibacterial master batch, then the remaining base resin, functional master batch, antibacterial master batch and compatibilizer are added step by step in an extruder, and the antibacterial degradable film is obtained by blowing film after plasticizing and exhausting.The mechanical performance is enhanced by the functional master batch, and the composite antibacterial system has synergistic effect, so that the film has excellent antibacterial performance and mechanical performance on the basis of degradability.

Description

Technical Field

[0001] This invention relates to the field of plastic film technology, specifically to an antibacterial and biodegradable film and its preparation method. Background Technology

[0002] Biodegradable films, especially biodegradable films, are one of the key alternatives to traditional petroleum-based plastic films. Currently, mainstream biodegradable materials in the market and research field include polylactic acid (PLA), polybutylene succinate (PBS), and polycaprolactone (PCL). These materials are derived from renewable resources and, after use, can be decomposed into carbon dioxide, water, and biomass through microbial action, effectively reducing dependence on fossil resources and long-term negative environmental impacts. They are widely used in disposable packaging, agricultural mulch films, tableware, and medical materials.

[0003] Despite the enormous environmental potential of biodegradable films, numerous technical challenges remain in practical applications. Firstly, regarding mechanical properties, biodegradable films made from a single material often possess inherent defects. For instance, polylactic acid (PLA), one of the most commonly used materials, is inherently hard and brittle, with poor toughness and low impact and tear strength, limiting its application in packaging applications requiring high flexibility. To improve its brittleness, it typically needs to be blended with other flexible materials (such as PBS and PCL), but this may introduce new problems such as poor interfacial compatibility and decreased mechanical strength. Secondly, regarding antibacterial properties, directly adding inorganic or organic antibacterial agents to the film often results in unsatisfactory and unstable antibacterial effects due to agglomeration or poor compatibility with the substrate. More importantly, the addition of antibacterial agents may affect the film's degradation performance and safety. Achieving efficient, long-lasting, and safe antibacterial functionality without sacrificing the material's original mechanical and degradation properties is a critical technical challenge that urgently needs to be addressed.

[0004] To this end, an antibacterial biodegradable film and its preparation method are proposed. Summary of the Invention

[0005] The purpose of this invention is to design an antibacterial and biodegradable film and its preparation method. The film raw materials of this invention include PLA, PBS, PHA, PCL, modified nanocellulose, an antibacterial agent, composite antibacterial particles, and maleic anhydride-grafted PLA. In the preparation process, silane coupling agent-modified nanocellulose and PLA are first combined to form a functional masterbatch. ZIF-8-loaded tea polyphenol antibacterial agent, mesoporous silica-loaded chitosan composite antibacterial particles, and PBS are then combined to form an antibacterial masterbatch. The remaining matrix resin, functional masterbatch, antibacterial masterbatch, and compatibilizer are then added stepwise in an extruder. After mixing, plasticizing, and degassing, the mixture is blow-molded to obtain the antibacterial and biodegradable film. The functional masterbatch enhances the mechanical properties, and the composite antibacterial system synergistically enhances the effect, achieving a film that combines excellent antibacterial and mechanical properties while remaining biodegradable.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] This invention provides a method for preparing an antibacterial and biodegradable film, the method comprising the following steps:

[0008] Modified nanocellulose and the first portion of polylactic acid (PLA) were melt-blended to form a functional masterbatch;

[0009] Antibacterial agent, composite antibacterial particles and first part of polybutylene succinate (PBS) are melt-blended to form antibacterial masterbatch;

[0010] The second part of PLA, the second part of PBS, polyhydroxyalkanoate (PHA), polycaprolactone (PCL), maleic anhydride-grafted PLA, functional masterbatch and antibacterial masterbatch are added stepwise to the extruder, and after mixing, plasticizing and degassing, and blow molding, an antibacterial and biodegradable film is obtained.

[0011] The modified nanocellulose was obtained by modifying nanocellulose with a silane coupling agent; the antibacterial agent was obtained by loading tea polyphenols onto ZIF-8; and the composite antibacterial particles were obtained by loading chitosan onto mesoporous silica.

[0012] Preferably, the average molecular weight of PLA is 80,000-100,000; the average molecular weight of PBS is 40,000-80,000; the average molecular weight of PHA is 100,000-150,000; and the average molecular weight of PCL is 40,000-80,000.

[0013] Preferably, the preparation method of the functional masterbatch by weight is as follows: 8-12 parts of modified nanocellulose and 90 parts of PLA chips are mixed and added to a twin-screw extruder. The extruder temperature is set as follows: feed port → 140℃ → 160℃ → 175℃ → 180℃ → 180℃ → 175℃ → die head. The screw speed is 150-200 rpm. After the extruded strip is cooled in a water tank, it is pelletized into functional masterbatch by a pelletizer.

[0014] Preferably, the method for preparing antibacterial masterbatch by weight is as follows: 3-7 parts of antibacterial agent, 3-7 parts of composite antibacterial particles and 90 parts of PBS chips are mixed and added to a twin-screw extruder. The extruder temperature is set as follows: feed port → 110℃ → 120℃ → 125℃ → 130℃ → 125℃ → die head. The screw speed is 100-150 rpm. The extrudate is cooled and pelletized to obtain antibacterial masterbatch.

[0015] Preferably, the specific preparation method of modified nanocellulose by weight is as follows: 8-12 parts of nanocellulose powder are dispersed in a mixed solution of 90 parts of anhydrous ethanol and 1 part of deionized water, and ultrasonically treated for 30 min to make it uniformly dispersed. The pH value of the mixture is adjusted to 5 with glacial acetic acid. Under stirring, 1-3 parts of silane coupling agent KH-550 are slowly added dropwise. Then the mixture is heated to 70℃-80℃ and refluxed for 4 h. After the reaction is completed, the product is collected by centrifugation and washed 4 times with anhydrous ethanol. The washed product is dried in a vacuum oven at 60℃ for 12 h to obtain modified nanocellulose.

[0016] Preferably, the specific preparation method of the antibacterial agent by weight is as follows: 10 mmol of zinc nitrate hexahydrate is dissolved in 100 mL of methanol to obtain solution A; 80 mmol of 2-methylimidazole is dissolved in 100 mL of methanol to obtain solution B; under vigorous stirring, solution A is quickly poured into solution B, and the reaction is continued at room temperature for 6 h. The white precipitate generated is collected by centrifugation, washed several times with methanol, and then vacuum dried at 60 °C to obtain ZIF-8 powder; 1-5 parts of ZIF-8 powder are dispersed in 300 parts of deionized water and ultrasonically treated for 15 min to obtain a suspension; 1.5 parts of tea polyphenol powder are dissolved in 100 parts of deionized water to obtain a tea polyphenol solution; the tea polyphenol solution is slowly added dropwise to the suspension, and the mixture is placed in a room temperature, light-protected environment and stirred continuously for 22-26 h. After the reaction is completed, the product is collected by centrifugation, washed three times with deionized water, and then vacuum dried at 60 °C to obtain the antibacterial agent.

[0017] Preferably, the preparation method of the composite antibacterial particles by weight is as follows: 3-7 parts of chitosan are dissolved in 500 parts of 2% glacial acetic acid aqueous solution and stirred until completely dissolved to form a chitosan solution; 8-12 parts of mesoporous silica powder are added to the chitosan solution, ultrasonically dispersed for 30 min, and then stirred continuously at room temperature for 24 h. The solid product is collected by centrifugation, washed with a large amount of deionized water, and the product is freeze-dried to obtain the composite antibacterial particles.

[0018] Preferably, the specific steps for mixing, plasticizing, degassing, and blow molding film formation, by weight, are as follows: 40-50 parts of pre-dried PLA chips, 10-20 parts of PBS chips, 10-20 parts of PCL chips, and 3-7 parts of PHA chips are fed into a twin-screw extruder via the main feeder. In the middle section of the extruder, functional masterbatch, antibacterial masterbatch, and 3 parts of maleic anhydride-grafted PLA are added via a side feeder. The extruder temperature is set as follows: feed inlet → 150℃ → 170℃ → 185℃→185℃→180℃→175℃ (exhaust section)→170℃→Die head, screw speed is 120-180rpm, vacuum pump is turned on to evacuate the exhaust section, and finally the melt is extruded through the annular blown film die to form a tubular film bubble. The blow-up ratio is controlled at 2.0-3.0. After the film bubble is cooled and shaped by the air ring, it is pressed by the herringbone plate, and then passed through the traction roller and winding device to obtain the final antibacterial biodegradable film with an average thickness of 30-40µm.

[0019] Preferably, the preparation method of maleic anhydride-grafted PLA is as follows: 100 parts of PLA chips are dried in a vacuum oven at 80°C for 8 hours; the dried PLA chips, 5 parts of maleic anhydride powder and 0.5 parts of dicumyl peroxide are mixed in a high-speed mixer for 10 minutes to obtain a mixture; the mixture is placed in a twin-screw extruder, and the temperature from the feed inlet to the die is set as follows: 160°C → 175°C → 190°C → 190°C → 185°C, the screw speed is set at 160 rpm, and the extruded strip is rapidly cooled in a cooling water tank and then pelletized to obtain maleic anhydride-grafted PLA.

[0020] Another aspect of the present invention provides an antibacterial biodegradable film, wherein the raw materials for preparing the antibacterial biodegradable film include PLA, PBS, PHA, PCL, modified nanocellulose, antibacterial agent, composite antibacterial particles and maleic anhydride-grafted PLA.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0022] 1. By introducing PCL and blending it with PLA, PBS, etc., the problems of hardness, brittleness, and easy cracking of PLA material alone are effectively solved. PCL and PBS, as toughening agents, significantly improve mechanical properties, so that the final product maintains sufficient tensile strength and has excellent flexibility, making it more adaptable to diverse packaging and application needs.

[0023] 2. Modified nanocellulose added to the functional masterbatch serves as a high-performance biomass reinforcing filler, enhancing the polymer matrix at the molecular level and improving the mechanical properties of the film. Simultaneously, the introduction of nanocellulose improves the film's barrier properties (such as its ability to block water vapor and oxygen). Combined with its antibacterial function, the final product is a high-performance functional film integrating excellent mechanical properties, active antibacterial activity, controllable degradation cycle, and good barrier properties.

[0024] 3. The solution employs a combination of two antibacterial systems—a metal-organic framework (ZIF-8@TP) and mesoporous silica-supported chitosan. This composite antibacterial strategy achieves broad-spectrum antibacterial activity and produces synergistic effects through different antibacterial mechanisms (such as metal ion release and contact sterilization). Pre-forming these into antibacterial masterbatches ensures high dispersion and stability of the antibacterial agent in the film matrix, avoiding aggregation and failure, thus achieving efficient and long-lasting antibacterial function.

[0025] 4. The strategy of "stepwise masterbatch preparation followed by co-extrusion" offers significant process advantages. First, modified nanocellulose, antibacterial agents, and other functional additives are pre-prepared into masterbatches, improving their compatibility and dispersibility with the polymer matrix. Second, these masterbatches are added stepwise during the main extrusion stage, shortening the residence time of functional components under high temperature and high shear conditions. This effectively protects the structure and activity of nanocellulose and heat-sensitive antibacterial agents from damage, ensuring the final film achieves its intended function.

[0026] 5. This film is a blend of various biodegradable materials (PLA, PBS, PHA, PCL), each with a different degradation rate. By precisely controlling the proportions of these four components, the overall degradation rate and lifespan of the film in specific environments (such as soil and compost) can be flexibly designed and controlled, enabling it to precisely match the lifecycle requirements of different application scenarios, from short-term preservation packaging to long-term agricultural mulch film. Attached Figure Description

[0027] Figure 1 The diagram shows the antibacterial properties of Example 1 and Comparative Examples 5-9 in this invention. Detailed Implementation

[0028] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] For details, please refer to [link / reference]. Figure 1 This invention provides an antibacterial biodegradable film and its preparation method, the technical solution of which is as follows:

[0030] Example 1

[0031] Ten parts of nanocellulose powder were dispersed in a mixed solution of 90 parts anhydrous ethanol and 1 part deionized water. The mixture was sonicated for 30 min to ensure uniform dispersion. The pH of the mixture was adjusted to 5 with glacial acetic acid. Under stirring, 2 parts of silane coupling agent KH-550 were slowly added dropwise. The mixture was then heated to 75°C and refluxed for 4 h. After the reaction was completed, the product was collected by centrifugation and washed four times with anhydrous ethanol. The washed product was dried in a vacuum oven at 60°C for 12 h to obtain modified nanocellulose.

[0032] 10 mmol of zinc nitrate hexahydrate was dissolved in 100 mL of methanol to obtain solution A; 80 mmol of 2-methylimidazole was dissolved in 100 mL of methanol to obtain solution B; solution A was rapidly poured into solution B under vigorous stirring, and the reaction was continued at room temperature for 6 h. The resulting white precipitate was collected by centrifugation, washed several times with methanol, and then dried under vacuum at 60 °C to obtain ZIF-8 powder; 3 parts of ZIF-8 powder were dispersed in 300 parts of deionized water and sonicated for 15 min to obtain a suspension; 1.5 parts of tea polyphenol powder were dissolved in 100 parts of deionized water to obtain a tea polyphenol solution; the tea polyphenol solution was slowly added dropwise to the suspension, and the mixture was placed in a dark environment at room temperature and stirred continuously for 24 h. After the reaction was completed, the product was collected by centrifugation, washed three times with deionized water, and then dried under vacuum at 60 °C to obtain the antibacterial agent.

[0033] Five parts of chitosan were dissolved in 500 parts of 2% glacial acetic acid aqueous solution and stirred until completely dissolved to form a chitosan solution. Ten parts of mesoporous silica powder were added to the chitosan solution and ultrasonically dispersed for 30 min. Then, the mixture was stirred continuously at room temperature for 24 h. The solid product was collected by centrifugation, washed with a large amount of deionized water, and freeze-dried to obtain composite antibacterial particles.

[0034] 10 parts of modified nanocellulose and 90 parts of PLA chips were mixed and added to a twin-screw extruder. The extruder temperature was set as follows: feed port → 140℃ → 160℃ → 175℃ → 180℃ → 180℃ → 175℃ → die head, and the screw speed was 180 rpm. The extruded strips were cooled in a water tank and then pelletized into functional masterbatches using a pelletizer.

[0035] Mix 5 parts of antibacterial agent, 5 parts of composite antibacterial particles and 90 parts of PBS slices and add them to a twin-screw extruder. The extruder temperature is set as follows: feed port → 110℃ → 120℃ → 125℃ → 130℃ → 125℃ → die head. The screw speed is 120 rpm. Cool the extrudate and granulate it to obtain antibacterial masterbatch.

[0036] 45 pre-dried PLA slices, 15 PBS slices, 15 PCL slices, and 5 PHA slices were fed into a twin-screw extruder via the main feeder. In the middle section of the extruder, functional masterbatch, antibacterial masterbatch, and 3 parts maleic anhydride-grafted PLA were added via a side feeder. The extruder temperature was set as follows: feed port → 150℃ → 170℃ → 185℃ → 185℃ → 180℃ → 175℃ (exhaust section) → 170℃ → die head. The screw speed was 150 rpm. The vacuum pump was turned on to evacuate the exhaust section. Finally, the melt was extruded through the annular blown film die to form tubular film bubbles. The blow-up ratio was controlled at 2.5. After the film bubbles were cooled and shaped by the air ring, they were pressed together by the herringbone plate and then passed through the traction roller and winding device to obtain the final antibacterial biodegradable film.

[0037] Examples 2-5 refer to the parameter conditions in Example 1, with specific differences shown in Table 1.

[0038] Table 1 Parameters and conditions for Examples 1-5

[0039]

[0040] Comparative Example 1 follows the same parameters and conditions as in Example 1, except that the nanocellulose is not modified.

[0041] Comparative Example 2 follows the same parameters and conditions as in Example 1, except that no modified nanocellulose is added.

[0042] Comparative Example 3 follows the same parameters and conditions as in Example 1, except that PCL is not added.

[0043] Comparative Example 4 follows the same parameters and conditions as in Example 1, except that PBS is not added.

[0044] Experimental Example 1: Mechanical and Barrier Properties Testing

[0045] The tensile strength and elongation at break of Examples 1-5 and Comparative Examples 1-4 were tested according to GB / T 1040.2-2022 standard; the oxygen barrier properties of Examples 1-5 and Comparative Examples 1-4 were tested according to GB / T 31354-2014 standard; and the water vapor barrier properties of Examples 1-5 and Comparative Examples 1-4 were tested according to GB / T 1037-2021 standard. The results are shown in Table 2.

[0046] Table 2 Mechanical and barrier properties tests of Examples 1-5 and Comparative Examples 1-4

[0047]

[0048] Table 2 shows that, in Comparative Example 1, without surface modification of the nanocellulose, all properties of the film significantly decreased. Its tensile strength and elongation at break were lower than in Example 1, indicating that the unmodified nanocellulose, due to its hydrophilic surface, had extremely poor compatibility with the hydrophobic polymer matrix, resulting in severe agglomeration. These agglomerates not only failed to provide reinforcement but also became stress concentration points within the material, leading to deterioration of mechanical properties. Simultaneously, the permeability of oxygen and water vapor increased significantly, indicating the formation of numerous microscopic defects and voids between the agglomerates and the matrix, disrupting the material's dense structure and providing channels for rapid penetration of gas and water molecules, thus greatly reducing its barrier properties. Comparative Example 2, without the addition of modified nanocellulose, clearly reveals the core role of nanocellulose in the system. Compared with Example 1, the tensile strength of Comparative Example 2 decreased significantly, which directly proves that modified nanocellulose, as a reinforcing filler, can effectively improve the rigidity and strength of the composite material. On the other hand, its elongation at break is basically the same as that of Example 1, indicating that the toughness of the film is mainly contributed by flexible polymers such as PCL and PBS. The most significant change is in the barrier performance, with its oxygen and water vapor permeability being much higher than that of Example 1. This fully demonstrates that the uniformly dispersed sheet-like nanocellulose forms a "maze effect" in the matrix, effectively extending the path of gas and water molecule penetration, which is the core reason why the film obtains excellent barrier performance. Comparative Example 3 demonstrates the crucial toughening effect of PCL in the composite system. Removing PCL from the formulation resulted in a significant drop in the film's elongation at break, indicating a loss of flexibility and exhibiting typical hard and brittle characteristics. Although the tensile strength increased slightly due to the increased relative content of rigid components in the system, this could not compensate for the substantial loss of toughness, making the material extremely prone to breakage in practical applications. Regarding barrier properties, since PCL itself is a relatively poor barrier material, its removal slightly reduced the oxygen and water vapor permeability of the film, but the change was far less significant than the change in mechanical properties. Comparative Example 4, without the addition of PBS, highlighted the synergistic toughening effect of PBS in the system. Compared to Example 1, removing PBS significantly reduced the film's elongation at break, indicating that PBS and PCL together constructed the flexible network of the material. Its absence led to a decrease in overall toughness, while the tensile strength increased slightly, again due to the reduction in flexible components. Regarding barrier properties, the oxygen and water vapor permeability increased slightly because the crystalline structure of PBS itself contributes to barrier properties; its removal had a minor negative impact on overall performance.

[0049] Examples 6-9 refer to the parameter conditions in Example 1, with specific differences shown in Table 3.

[0050] Table 3 Parameter conditions for Examples 1 and 6-9

[0051]

[0052] Comparative Example 5 follows the same parameters as in Example 1, except that ZIF-8 is not subjected to load processing.

[0053] Comparative Example 6 follows the same parameters and conditions as in Example 1, except that no antibacterial agent is added.

[0054] Comparative Example 7 follows the same parameters and conditions as in Example 1, except that no loading treatment is applied to the mesoporous silica.

[0055] Comparative Example 8 follows the same parameters and conditions as in Example 1, except that no composite antibacterial particles are added.

[0056] Comparative Example 9 follows the same parameters and conditions as in Example 1, except that antibacterial masterbatch is not prepared but added in the subsequent extruder.

[0057] Experiment Example 2: Antibacterial Performance Test

[0058] The antibacterial properties of Examples 1, 6-9, and Comparative Examples 5-9 were tested according to QB / T 2591-2003 standard, and the results are shown in Table 4. The antibacterial properties of Examples 1 and Comparative Examples 5-9 are as follows: Figure 1 As shown.

[0059] Table 4 Antibacterial performance tests of Examples 1, 6-9 and Comparative Examples 5-9

[0060]

[0061] From Table 4 and Figure 1It can be observed that the antibacterial rate of pure ZIF-8 without tea polyphenol loading in Comparative Example 5 decreased compared to Example 1. This indicates that although ZIF-8 itself has a certain antibacterial ability due to the release of zinc ions, the loading of tea polyphenols, as a highly efficient natural antibacterial agent, greatly enhances the bactericidal effect of the material. The ZIF-8@TP structure in Example 1 can exert the synergistic antibacterial effect of zinc ions and tea polyphenols. However, Comparative Example 5, which lacks tea polyphenols, loses this key synergistic effect and an important source of antibacterial activity, resulting in a significant reduction in its overall antibacterial performance, thus proving the necessity of loading treatment. In Comparative Example 6, the complete absence of ZIF-8@TP antibacterial agent resulted in a significant decrease in the antibacterial performance of the film. This result clearly demonstrates that the antibacterial system of this film is based on the synergistic effect of the composite components ZIF-8@TP and mesoporous silica-supported chitosan. With only the latter antibacterial agent remaining, a single antibacterial mechanism is insufficient to achieve near-complete sterilization. The absence of ZIF-8@TP not only reduces a highly effective antibacterial substance but also disrupts the synergistic effect between the two antibacterial agents with different mechanisms. Therefore, the antibacterial rate is far lower than in Example 1, proving the superiority of the two-component composite antibacterial design. Comparative Examples 7 and 8 are essentially the same, meaning that only ZIF-8@TP antibacterial agent is active in the system. The test results were also very similar, with the antibacterial rates significantly lower than those in Example 1. Pure mesoporous silica itself is an inert carrier and does not have antibacterial activity. Its effect depends on the chitosan it supports. Therefore, the results of these two comparative examples jointly prove that chitosan-supported mesoporous silica is an indispensable component of the antibacterial system. Without this component, the composite antibacterial system is broken. Relying solely on ZIF-8@TP cannot achieve the high-efficiency broad-spectrum antibacterial level of Example 1, which once again verifies the importance of the two-component synergistic strategy. In Comparative Example 9, the antibacterial masterbatch step was omitted, and the antibacterial powder was directly added to the extruder. Although the antibacterial rate was still relatively high, it was significantly lower than that of Example 1. This is because ZIF-8@TP and mesoporous silica-supported chitosan, as micron or nano-sized powders, are prone to agglomeration in molten polymers and are difficult to disperse uniformly. The direct addition method resulted in uneven distribution of the antibacterial agent in the film, with a large number of particles agglomerating together, drastically reducing the effective specific surface area and thus reducing its contact efficiency with bacteria. In contrast, Example 1 prepared an antibacterial masterbatch and used the masterbatch carrier to pre-disperse the antibacterial powder, ensuring its high dispersion in the final film, thereby enabling it to exert its antibacterial properties more efficiently.

[0062] Examples 10-13 refer to the parameter conditions in Example 1, with specific differences shown in Table 5.

[0063] Table 5 Parameter conditions for Examples 1 and 10-13

[0064]

[0065] Comparative Example 3 follows the same parameters and conditions as in Example 1, except that PCL is not added.

[0066] Comparative Example 4 follows the same parameters and conditions as in Example 1, except that PBS is not added.

[0067] Comparative Example 10 follows the same parameters and conditions as in Example 1, except that PE is used instead of PLA.

[0068] Comparative Example 11 follows the same parameters and conditions as in Example 1, except that the material is not added in stages in the extruder.

[0069] Experiment Example 3: Degradation Performance Test

[0070] The 120-day degradation rates of Examples 1, 10-13, Comparative Examples 3-4 and 10-11 were tested according to GB / T 20197-2006 standard, and the results are shown in Table 6.

[0071] Table 6 Degradation rates of Examples 1, 10-13, Comparative Examples 3-4 and 10-11

[0072]

[0073] Table 6 shows that Comparative Example 3, which does not contain PCL, has a higher degradation rate after 120 days than Example 1. While PCL is biodegradable in a composting environment, its decomposition rate is generally slower than PLA, PBS, and PHA. Removing PCL, which has the slowest degradation rate, increases the relative proportion of rapidly degradable materials in the system, accelerating the overall biodegradation process of the composite material. Therefore, the film in this comparative example exhibits a higher degree of degradation within the same timeframe. Comparative Example 4, which removes PBS, shows a significantly lower degradation rate after 120 days compared to Example 1. PBS is a material with excellent degradation performance in soil and compost, and its decomposition rate is generally faster than PLA and PCL. Without PBS, the film degradation mainly relies on PHA, PLA, and PCL, among which PCL and PLA have relatively slow degradation rates, thus lowering the overall degradation efficiency of the material. Comparative Example 10 used traditional non-biodegradable plastic PE to replace PLA as the main material, and its degradation performance underwent a qualitative change. The degradation rate after 120 days was only 12.8%. As a petroleum-based plastic with a stable chemical structure, PE cannot be effectively decomposed by microorganisms under composting conditions. Although the film still contains biodegradable components such as PBS and PCL, they are physically covered by a large amount of non-biodegradable PE matrix, making it difficult for moisture and microorganisms to contact and erode, which severely inhibits the degradation process. Comparative Example 11 did not employ a segmented addition process during preparation, and its 120-day degradation rate was significantly lower than that of Example 1. This indicates that the processing technology has a significant impact on the final degradation performance of the material. The segmented addition process in Example 1 ensures that the modified nanocellulose and other functional fillers are uniformly dispersed in the polymer matrix, thereby forming a large specific surface area and numerous phase interfaces. These interfaces can serve as channels for water molecule intrusion, accelerating the hydrolysis process, which is the first step in degradation. However, in the "one-pot" mixing process of Comparative Example 11, the functional fillers are prone to agglomeration at high concentrations and are difficult to disperse effectively. This agglomerated structure reduces the effective contact area between water molecules and the polymer matrix, hindering hydrolysis and resulting in a significantly slower overall degradation rate.

[0074] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing an antibacterial degradable film, characterized by: The preparation method comprises the following steps in terms of weight parts: The functional master batch is prepared by melt blending 8-12 parts of modified nanocellulose and the first part of polylactic acid; The antibacterial master batch is prepared by melt blending 3-7 parts of antibacterial agent, 3-7 parts of composite antibacterial particles and the first part of polybutylene succinate; The pre-dried 40-50 parts of polylactic acid chips, 10-20 parts of polybutylene succinate chips, 10-20 parts of polycaprolactone chips and 3-7 parts of polyhydroxyalkanoate chips are added into a twin-screw extruder through a main feeder, the functional master batch, the antibacterial master batch and maleic anhydride grafted polylactic acid are added into the extruder through a side feeder at the middle section of the extruder, the exhaust section is vacuumized, the final melt is extruded through a film blowing die, the blowing ratio is controlled, the film bubble is cooled and shaped through an air ring and then is pressed, and the antibacterial degradable film is obtained through traction and winding. The modified nanocellulose is obtained by modifying nanocellulose with a silane coupling agent; the antibacterial agent is obtained by loading tea polyphenol on ZIF-8; and the composite antibacterial particles are obtained by loading chitosan on mesoporous silica.

2. A process for the preparation of an antibacterial degradable film as claimed in claim 1, wherein: The preparation method of the functional master batch is as follows: the modified nanocellulose and the first part of polylactic acid chips are mixed and added into a twin-screw extruder, the temperature of the extruder and the screw rotation speed are set, the extruded strip is cooled in a water tank and then is cut into the functional master batch.

3. A process for the preparation of an antibacterial degradable film as claimed in claim 1, wherein: The preparation method of the antibacterial master batch is as follows: the antibacterial agent, the composite antibacterial particles and the first part of polybutylene succinate chips are mixed and added into a twin-screw extruder, the extrudate is cooled and cut into the antibacterial master batch.

4. A process for the preparation of an antibacterial degradable film as claimed in claim 3, wherein: The specific preparation method of the antibacterial agent is as follows: zinc nitrate hexahydrate is dissolved in methanol to obtain solution A; 2-methylimidazole is dissolved in methanol to obtain solution B; the solution A is poured into the solution B, and the stirring reaction is continued at room temperature; the precipitate is collected by centrifugation and dried to obtain ZIF-8 powder; the ZIF-8 powder is dispersed in deionized water and ultrasonically treated to obtain a suspension; tea polyphenol powder is dissolved in deionized water to obtain a tea polyphenol solution; the tea polyphenol solution is added dropwise into the suspension, and the stirring reaction is followed by centrifugal washing and drying to obtain the antibacterial agent.

5. The method of claim 3, wherein the biodegradable film is an antibacterial film. The preparation method of the composite antibacterial particles is as follows: chitosan is dissolved in an ice acetic acid aqueous solution, stirred until dissolved to form a chitosan solution; mesoporous silica powder is added into the chitosan solution, ultrasonically dispersed, then continuously stirred at room temperature, centrifugally washed and freeze-dried to obtain the composite antibacterial particles.

6. An antibacterial degradable film, characterized by: The synthetic raw materials of the antibacterial degradable film include polylactic acid, polybutylene succinate, polyhydroxyalkanoate, polycaprolactone, modified nanocellulose, antibacterial agent, composite antibacterial particles and maleic anhydride grafted polylactic acid; and the antibacterial degradable film is prepared by the preparation method in any one of claims 1-5.

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