Rapidly degradable plastic film and preparation process thereof

Abstract

The invention discloses a quickly degradable plastic film and a preparation process thereof, belongs to the field of degradable plastics, and particularly relates to a quickly degradable plastic film which is adaptive to desertification treatment scenes, can customize the degradation rate and has a soil improvement function as a degradation product, and a preparation process of the quickly degradable plastic film. By arranging the targeted degradation triggering structure of the light response layer, the water sensitive layer, the microbial recognition site or the porous nanofiber structure, the environmental characteristics of different desertification scenes and the release requirements of the loading material can be precisely adapted, the material loss caused by too early degradation or the root growth hindering caused by too late degradation is avoided, for example, when the material is used for a desertification surface layer, the material loss caused by too early degradation is avoided. The light-water double-trigger degradation can be synchronous with the water absorption and release rhythm of the water-retaining agent, and when the water-retaining agent is used for desertification farmland, the microorganism-enzyme double-trigger degradation can realize the synergistic effect that the higher the activity of the microbial agent is, the faster the degradation is, and the problem of poor degradation targeting is solved.

Description

Technical Field

[0001] This invention relates to the field of biodegradable plastics, specifically to a rapidly degradable plastic film and its preparation process, and more particularly to a rapidly degradable plastic film adapted to desertification control scenarios, with a customizable degradation rate and degradation products that have soil improvement functions, and its preparation process. Background Technology

[0002] With the advancement of ecological restoration projects such as desertification control, improvement of sandy farmland, and slope greening, biodegradable plastic films are widely used as carriers for water-retaining agents, fertilizers, and microbial agents. Currently, most commercially available biodegradable plastic films use polyhydroxyalkanoates (PHA), polyvinyl alcohol (PVA), and polylactic acid (PLA) as base materials, and enhance degradation performance by adding bio-based components such as starch and cellulose. Their degradation mechanism mainly relies on microbial decomposition, photo-oxidation, or hydrolysis in the natural environment, aiming to solve the soil pollution problems caused by traditional non-degradable plastics. For example, existing technologies have disclosed the use of PHA and starch blends to prepare biodegradable films, and by adjusting the amount of starch added, the degradation rate can be initially altered, which can be used for material encapsulation and slow nutrient release during the planting of desert plants.

[0003] However, existing biodegradable plastic films have significant drawbacks when applied in desertification control scenarios: First, it is impossible to match the degradation triggering conditions with the environmental characteristics of desertified areas (such as strong sunlight on the surface, high microbial content in the topsoil, and strong wind erosion on the slope) and the release requirements of the loading materials (such as highly active bacterial agents and long-acting slow-release fertilizers). This can easily lead to problems such as premature degradation causing material loss or delayed degradation hindering root growth, resulting in poor degradation targeting. Secondly, existing technologies mostly adjust the degradation cycle by changing the overall formulation of the substrate, which requires redesigning the production process. It is difficult to achieve rapid customization of different cycles of 30-180 days. Moreover, the control process is prone to causing a decrease in the mechanical properties of the film (such as tensile strength), which cannot meet the requirements of sand burial pressure resistance and wind erosion resistance. The flexibility of degradation rate control is insufficient. Third, existing films only produce non-functional small-molecule organic matter after degradation, which cannot specifically solve problems such as poor water retention, lack of fertility, loose structure and salinization of sandy soil. Soil conditioners need to be added, which increases the cost of treatment, and the degradation products have a single function. Fourth, the existing production lines need to be modified to meet the film requirements of different desertification scenarios, resulting in low production efficiency, cost increases of more than 20%, which is not conducive to large-scale promotion and has low production adaptability. Summary of the Invention

[0004] To overcome the above problems, this invention aims to propose a rapidly degradable plastic film and its preparation process, with the goal of solving the problems of poor degradation targeting, insufficient flexibility in degradation rate control, single function of degradation products, and low production adaptability of current rapidly degradable plastic films.

[0005] Therefore, the specific technical solution adopted by the present invention is as follows: According to one aspect of the present invention, a rapidly degradable plastic film is provided, comprising a base degradable substrate layer and a speed-adjustable intermediate layer; The basic degradable substrate layer is selected from one of polyvinyl alcohol-starch blend, polyhydroxyalkanoate (PHA) or PHA / polylactic acid (PLA) blend; The adjustable-rate intermediate layer is composed of the following components in parts by weight: 5-10 parts of degradation accelerator, 0-5 parts of degradation inhibitor, and 5-10 parts of compatibility regulator. The rapidly degradable plastic film also has a targeted degradation triggering structure, which is at least one of a photoresponsive layer, a water-sensitive layer, a microbial recognition site, or a porous nanofiber structure. The rapidly degradable plastic film includes the release of functional products during the degradation process, wherein the functional products are selected from at least one of hydrophilic small molecule polymers, slow-release nutrient precursors, adhesive biomolecules, or salt adsorbents.

[0006] Optionally, the degradation accelerator is nanocellulose (CNF) or anatase. The nanorods contain one or a mixture of two of the following: the degradation inhibitor is a polylactic acid (PLA) component with a crystallinity ≥85% or a mixture of two of maleic anhydride-grafted starch; the compatibility modifier is polycaprolactone (PCL).

[0007] Optionally, when the rapidly degradable plastic film is used on the desertification surface (0-20cm), the targeted degradation triggering structure is a composite structure of an outer photoresponsive layer and an inner water-sensitive layer; The photoresponsive layer contains a tetraphenylporphyrin iron photosensitizer, the amount of which is 1-3% of the total weight of the photoresponsive layer; The water-sensitive layer is a polyvinyl alcohol-starch blend, wherein the starch accounts for 30-50% of the total weight of the water-sensitive layer.

[0008] Optionally, when the rapidly degradable plastic film is used as a topsoil layer (20-30cm) in desertified farmland, the targeted degradation triggering structure is a microbial recognition site, which is a chitosan-modified group with a grafting rate of 2-5% of the total weight of the base degradation substrate layer; The functional product is a slow-release nutrient precursor, which is a mixture of amino acid chelated calcium and polyaspartic acid (PASP), and the amount added is 3-8% of the total weight of the rapidly degradable plastic film.

[0009] Optionally, when the rapidly degradable plastic film is used for slope sand layers (slope > 30°), the targeted degradation triggering structure is a porous nanofiber structure with a pore size of 80-120 nm. The functional product is a salt adsorbent, which is modified montmorillonite, and the amount added is 5-10% of the total weight of the rapidly degradable plastic film.

[0010] Optionally, the rapid-degradable plastic film has a tensile strength of not less than 20 MPa, a degradation cycle of 30-180 days, and the concentrations of lactic acid and glucose in the degradation products are ≤1.0 g / L.

[0011] A process for preparing a rapidly degradable plastic film includes the following steps: S1: Dry the basic biodegradable substrate (polyvinyl alcohol-starch blend, PHA or PHA / PLA blend) at 80-100℃ for 2-4 hours to remove moisture until the moisture content is ≤1%; S2: Weigh out the degradation accelerator, degradation inhibitor and compatibility regulator by weight, put them into a high-speed mixer, and mix for 10-20 minutes at 120-150℃ and 300-500r / min to obtain an adjustable speed intermediate. S3: The pretreated basic degradable substrate and the adjustable speed intermediate are fed into a twin-screw extruder. The extrusion temperature is controlled at 160-190℃ and the screw speed is 200-300r / min. After extrusion, the substrate is formed by a casting machine at a casting temperature of 80-100℃ to obtain the basic film layer. S4: Depending on the application scenario requirements, a photoresponsive layer (containing tetraphenylporphyrin iron photosensitizer), chitosan modified groups grafted onto the surface of the base film layer, or a porous nanofiber structure prepared by electrospinning are obtained to obtain a targeted degradation triggering structure. S5: Introduce functional products (hydrophilic small molecule polymer precursors, slow-release nutrient precursors, adhesive biomolecules or salt adsorbents) into the film layer by solution dipping or blending, and dry at 60-80℃ for 1-2 hours to obtain a rapidly degradable plastic film.

[0012] Optionally, in step S2, when the target degradation cycle is 30-60 days, the amount of degradation accelerator added is 10 parts and the amount of degradation inhibitor added is 0 parts. When the target degradation cycle is 90-120 days, the dosage of degradation accelerator is 5 parts and the dosage of degradation inhibitor is 3 parts. When the target degradation cycle is 150-180 days, the amount of degradation accelerator added is 3 parts and the amount of degradation inhibitor added is 5 parts.

[0013] Optionally, in step S4, the photoresponsive layer is coated using a blade coating method with a coating thickness of 5-10 μm; the chitosan-modified groups are grafted using plasma grafting technology with a grafting time of 15-30 minutes; and the porous nanofiber structure is prepared using electrospinning with a spinning voltage of 15-25 kV and a receiving distance of 10-15 cm.

[0014] Optionally, in step S5, the concentration of the functional product during solution dip coating is 5-15 wt%, and the dip coating time is 5-10 minutes; during blending, the mixing temperature of the functional product and the film substrate is 140-160℃, and the mixing time is 5-10 minutes.

[0015] Compared with the prior art, this application has the following beneficial effects: This invention addresses the shortcomings of existing biodegradable plastic films by optimizing the structure and process to achieve the following beneficial effects: 1. This invention, by setting a targeted degradation triggering structure with a light-responsive layer, a water-sensitive layer, microbial recognition sites, or porous nanofiber structures, can precisely adapt to the environmental characteristics of different desertification scenarios (such as strong sunlight on desertified surfaces and high microbial content in desertified farmland) and the release requirements of loaded materials (such as the reproduction threshold of highly active bacterial agents and the release cycle of long-acting slow-release fertilizers). This avoids premature material loss due to degradation or delayed degradation that hinders root growth. For example, when used on desertified surfaces, the light-water dual-trigger degradation can be synchronized with the water absorption and release rhythm of water-retaining agents. When used on desertified farmland, the microbial-enzyme dual-trigger degradation can achieve a synergistic effect where the higher the activity of the bacterial agent, the faster the degradation, thus solving the problem of poor degradation targeting.

[0016] 2. This invention utilizes a combination of a basic degradable substrate and an adjustable-rate intermediate, requiring only the addition or subtraction of degradation accelerators (such as CNF, etc.). By adjusting the weight ratio of the degradation inhibitor (such as the high crystallinity PLA component) to the degradation cycle, a degradation cycle of 30-180 days can be controlled without changing the core production process. At the same time, the addition of a compatibility regulator (PCL) ensures that the tensile strength of the film is not less than 20MPa during the control process, meeting the requirements for sand burial pressure resistance and wind erosion resistance. Compared with the existing technology of redesigning the formula and modifying the process, the control efficiency is improved by more than 50%, solving the problem of insufficient flexibility in controlling the degradation rate.

[0017] 3. The membrane of this invention, after degradation, produces hydrophilic small molecule polymers (increasing the water retention rate of sandy soil by more than 30%), slow-release nutrient precursors (releasing trace elements such as nitrogen and calcium, reducing nutrient leaching and loss), binding biomolecules (promoting the formation of 0.25-5mm aggregate structure in sandy soil) or salt adsorbents (reducing soil salinity by 20-25%). It can specifically solve the problems of water retention, fertility, structure and salinization of sandy soil, without the need for additional amendments, reducing treatment costs by 30-40%, and solving the problem of single function of degradation products.

[0018] 4. The preparation process of this invention adopts modular addition of adjustable-speed intermediates, which only requires adding intermediate feeding ports to the traditional biodegradable membrane production line without overall equipment modification; for different scenario requirements, only the ratio of accelerator / inhibitor needs to be adjusted, the production efficiency is consistent with that of traditional films, and the cost increase is controlled within 10-15%, which is convenient for large-scale promotion and solves the problem of low production adaptability. Attached Figure Description

[0019] The above-mentioned features, characteristics, and advantages of the present invention, as well as their implementation methods, will become clearer and more readily understood in conjunction with the following description of the embodiments, which are illustrated in detail with reference to the accompanying drawings. Schematic diagrams are shown here: Figure 1 This is a flowchart of a rapid degradation plastic film preparation process according to an embodiment of the present invention. Detailed Implementation

[0020] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present application.

[0021] Example 1 According to an embodiment of the present invention, a rapidly degradable plastic film and its preparation process are provided.

[0022] The present invention will now be further described in conjunction with the accompanying drawings and specific embodiments, such as... Figure 1 As shown, according to an embodiment of the present invention, a fast-degrading plastic film is provided, comprising a basic degradable substrate layer and a speed-adjustable intermediate layer; The basic degradable substrate layer is selected from one of polyvinyl alcohol-starch blend, polyhydroxyalkanoate (PHA) or PHA / polylactic acid (PLA) blend; The adjustable-rate intermediate layer is composed of the following components in parts by weight: 5-10 parts of degradation accelerator, 0-5 parts of degradation inhibitor, and 5-10 parts of compatibility regulator. The rapidly degradable plastic film also has a targeted degradation triggering structure, which is at least one of a photoresponsive layer, a water-sensitive layer, a microbial recognition site, or a porous nanofiber structure. The rapidly degradable plastic film includes the release of functional products during the degradation process, wherein the functional products are selected from at least one of hydrophilic small molecule polymers, slow-release nutrient precursors, adhesive biomolecules, or salt adsorbents.

[0023] The degradation accelerator mentioned is nanocellulose (CNF) or anatase. The nanorods contain one or a mixture of two of the following: the degradation inhibitor is a polylactic acid (PLA) component with a crystallinity ≥85% or a mixture of two of maleic anhydride-grafted starch; the compatibility modifier is polycaprolactone (PCL).

[0024] When the rapidly degradable plastic film is used on the desertification surface (0-20cm), the targeted degradation triggering structure is a composite structure of an outer photoresponsive layer and an inner water-sensitive layer. The photoresponsive layer contains a tetraphenylporphyrin iron photosensitizer, the amount of which is 1-3% of the total weight of the photoresponsive layer; The water-sensitive layer is a polyvinyl alcohol-starch blend, wherein the starch accounts for 30-50% of the total weight of the water-sensitive layer.

[0025] When the rapidly degradable plastic film is used in the topsoil layer (20-30cm) of desertified farmland, the targeted degradation triggering structure is a microbial recognition site, which is a chitosan-modified group with a grafting rate of 2-5% of the total weight of the base degradation substrate layer; The functional product is a slow-release nutrient precursor, which is a mixture of amino acid chelated calcium and polyaspartic acid (PASP), and the amount added is 3-8% of the total weight of the rapidly degradable plastic film.

[0026] When the rapidly degradable plastic film is used in the sand layer of a slope (slope > 30°), the targeted degradation triggering structure is a porous nanofiber structure with a pore size of 80-120 nm. The functional product is a salt adsorbent, which is modified montmorillonite, and the amount added is 5-10% of the total weight of the rapidly degradable plastic film.

[0027] The rapid-degradable plastic film has a tensile strength of not less than 20 MPa, a degradation cycle of 30-180 days, and the concentration of lactic acid and glucose in the degradation products is ≤1.0 g / L, which meets the ISO14851 and EN13432 biocompatibility standards.

[0028] Example 2 A process for preparing a rapidly degradable plastic film includes the following steps: S1: Dry the basic biodegradable substrate (polyvinyl alcohol-starch blend, PHA or PHA / PLA blend) at 80-100℃ for 2-4 hours to remove moisture until the moisture content is ≤1%; S2: Weigh out the degradation accelerator, degradation inhibitor and compatibility regulator by weight, put them into a high-speed mixer, and mix for 10-20 minutes at 120-150℃ and 300-500r / min to obtain an adjustable speed intermediate. S3: The pretreated basic degradable substrate and the adjustable speed intermediate are fed into a twin-screw extruder. The extrusion temperature is controlled at 160-190℃ and the screw speed is 200-300r / min. After extrusion, the substrate is formed by a casting machine at a casting temperature of 80-100℃ to obtain the basic film layer. S4: Depending on the application scenario requirements, a photoresponsive layer (containing tetraphenylporphyrin iron photosensitizer), chitosan modified groups grafted onto the surface of the base film layer, or a porous nanofiber structure prepared by electrospinning are obtained to obtain a targeted degradation triggering structure. S5: Introduce functional products (hydrophilic small molecule polymer precursors, slow-release nutrient precursors, adhesive biomolecules or salt adsorbents) into the film layer by solution dipping or blending, and dry at 60-80℃ for 1-2 hours to obtain a rapidly degradable plastic film.

[0029] In step S2, when the target degradation cycle is 30-60 days, the amount of degradation accelerator added is 10 parts and the amount of degradation inhibitor added is 0 parts. When the target degradation cycle is 90-120 days, the dosage of degradation accelerator is 5 parts and the dosage of degradation inhibitor is 3 parts. When the target degradation cycle is 150-180 days, the amount of degradation accelerator added is 3 parts and the amount of degradation inhibitor added is 5 parts.

[0030] In step S4, the photoresponsive layer is coated using a blade coating method with a coating thickness of 5-10 μm; the chitosan-modified groups are grafted using plasma grafting technology with a grafting time of 15-30 minutes; and the porous nanofiber structure is prepared using electrospinning with a spinning voltage of 15-25 kV and a receiving distance of 10-15 cm.

[0031] In step S5, the concentration of the functional product during solution dip coating is 5-15 wt%, and the dip coating time is 5-10 minutes; during blending, the mixing temperature of the functional product and the film substrate is 140-160℃, and the mixing time is 5-10 minutes.

[0032] Example 3 This embodiment is used to prepare a rapidly degradable plastic film for the desertification surface layer (0-20cm). 1. Thin film composition: Basic biodegradable substrate layer: polyvinyl alcohol-starch blend (60 parts by weight of polyvinyl alcohol and 40 parts by weight of starch); Variable-rate intermediate layer: 10 parts nanocellulose (CNF), 5 parts polycaprolactone (PCL), and 0 parts degradation inhibitor; Targeted degradation triggering structure: outer photoresponsive layer (polyvinyl alcohol substrate + 3wt% tetraphenylporphyrin iron photosensitizer), inner water-sensitive layer (consistent with the basic degradation substrate layer); Functional product: hydrophilic small molecule polymer precursor (starch, added at 5% of the total weight of the film).

[0033] 2. Preparation process: S1: The polyvinyl alcohol-starch blend was dried at 90°C for 3 hours, and the moisture content was controlled at 0.8%. S2: Weigh 10 parts CNF and 5 parts PCL and put them into a high-speed mixer. Mix at 130℃ and 400r / min for 15 minutes to obtain an adjustable speed intermediate. S3: The dried substrate and intermediate are fed into a twin-screw extruder at an extrusion temperature of 170°C, a screw speed of 250 r / min, and a casting temperature of 90°C to obtain the base film layer. S4: A photoresponse layer with a thickness of 8μm is coated on the outer layer of the base film using a blade coating method to obtain a light-water dual trigger structure; S5: Prepare a 10wt% aqueous solution of starch, dip the film layer into it for 5 minutes, and then dry it at 70°C for 1.5 hours to obtain a rapidly degradable plastic film.

[0034] 3. Performance testing: The following performance testing data are all obtained from testing the samples prepared in this embodiment.

[0035] Tensile strength: 22 MPa; Degradation period: 45 days (under strong sunlight and periodic precipitation). Degradation products: glucose concentration 0.6 g / L, sand water retention capacity increased by approximately 35%; Biocompatibility: Complies with ISO14851 and EN13432 standards.

[0036] Example 4 This embodiment describes a rapidly degradable plastic film used to prepare a topsoil layer (20-30cm) in desertified farmland. 1. Thin film composition: Basic degradable substrate layer: polyhydroxyalkanoate (PHA); Adjustable speed intermediate layer: anatase type 5 parts, PLA high crystallinity component 3 parts, PCL 8 parts; Targeted degradation triggering structure: chitosan modified group (grafting rate 3%). Functional products: amino acid chelated calcium (3wt%) + polyaspartic acid (PASP, 2wt%).

[0037] 2. Preparation process: S1: PHA dried at 85℃ for 2.5 hours, with a moisture content ≤0.9%; S2: Weigh out 5 portions 3 parts of PLA high crystallinity component and 8 parts of PCL were mixed at 140℃ and 350r / min for 12 minutes to obtain an adjustable-speed intermediate. S3: Twin-screw extrusion temperature 180℃, screw speed 280r / min, casting temperature 95℃, to obtain the basic film layer; S4: Chitosan-modified groups are grafted onto the surface of the base membrane using plasma grafting technology, with a grafting time of 20 minutes; S5: Mix amino acid chelated calcium with PASP in a 3:2 ratio, mix with the film substrate at 150°C for 8 minutes, and dry at 75°C for 1 hour to obtain a rapidly degradable plastic film.

[0038] 3. Performance testing: The following performance testing data are all obtained from testing the samples prepared in this embodiment.

[0039] Tensile strength: 21 MPa; Degradation period: 105 days (in a high humidity + microbial rich environment); Degradation products: Lactic acid concentration 0.5 g / L, soil nitrogen retention rate increased by approximately 82%; Biocompatibility: Complies with ISO14851 and EN13432 standards.

[0040] Example 5 This embodiment describes a rapidly degradable plastic film used for preparing sand layers on slopes (slope > 30°). 1. Thin film composition: Basic biodegradable substrate layer: PHA / PLA blend (70 parts by weight of PHA, 30 parts by weight of PLA); Variable speed intermediate layer: CNF 3 parts, maleic anhydride grafted starch 5 parts, PCL 10 parts; Targeted degradation triggering structure: porous nanofiber structure (pore size 100 nm). Functional product: Modified montmorillonite (8wt%).

[0041] 2. Preparation process: S1: The PHA / PLA blend was dried at 95℃ for 3.5 hours, and the moisture content was ≤0.7%. S2: Weigh 3 parts CNF, 5 parts maleic anhydride grafted starch, and 10 parts PCL, mix them at 125℃ and 450r / min for 18 minutes to obtain an adjustable-speed intermediate. S3: Twin-screw extrusion temperature 175℃, screw speed 220r / min, casting temperature 85℃, to obtain the basic film layer; S4: A porous nanofiber structure was prepared on the surface of the base membrane layer by electrospinning (voltage 20kV, receiving distance 12cm); S5: Modified montmorillonite is blended with the film substrate at 145°C for 10 minutes and dried at 65°C for 2 hours to obtain a rapidly degradable plastic film.

[0042] 3. Performance testing: The following performance testing data are all obtained from testing the samples prepared in this embodiment.

[0043] Tensile strength: 23 MPa; Degradation period: 160 days (under strong wind erosion + intermittent hydrolysis environment); Degradation products: Modified montmorillonite retains its adsorption activity, resulting in a soil salinity reduction of approximately 23%; Biocompatibility: Complies with ISO14851 and EN13432 standards.

[0044] It should be noted that the above embodiments are only used to explain the present invention and are not intended to limit the scope of protection of the present invention. Without departing from the principles of the present invention, those skilled in the art can adjust the substrate components, process parameters, etc., and such adjustments should be considered to fall within the scope of protection of the present invention.

[0045] Although the present invention has been disclosed above with reference to preferred embodiments, the embodiments are merely examples for illustrative purposes and are not intended to limit the present invention. Those skilled in the art can make various modifications and refinements without departing from the spirit and scope of the present invention. The scope of protection claimed by the present invention should be determined by the claims.

Claims

1. A rapidly degradable plastic film, characterized in that, Includes a basic degradable substrate layer and a speed-adjustable intermediate layer; The basic degradable substrate layer is selected from one of polyvinyl alcohol-starch blend, polyhydroxyalkanoate (PHA) or PHA / polylactic acid (PLA) blend; The adjustable-rate intermediate layer is composed of the following components in parts by weight: 5-10 parts of degradation accelerator, 0-5 parts of degradation inhibitor, and 5-10 parts of compatibility regulator. The rapidly degradable plastic film also has a targeted degradation triggering structure, which is at least one of a photoresponsive layer, a water-sensitive layer, a microbial recognition site, or a porous nanofiber structure. The rapidly degradable plastic film includes the release of functional products during the degradation process, wherein the functional products are selected from at least one of hydrophilic small molecule polymers, slow-release nutrient precursors, adhesive biomolecules, or salt adsorbents.

2. The rapidly degradable plastic film according to claim 1, characterized in that, The degradation accelerator is nanocellulose (CNF) or anatase. The nanorods contain one or a mixture of two of the following: the degradation inhibitor is a polylactic acid (PLA) component with a crystallinity ≥85% or a mixture of two of maleic anhydride-grafted starch; the compatibility modifier is polycaprolactone (PCL).

3. The rapidly degradable plastic film according to claim 1, characterized in that, When the rapidly degradable plastic film is used on the desertification surface (0-20cm), the targeted degradation triggering structure is a composite structure of an outer photoresponsive layer and an inner water-sensitive layer. The photoresponsive layer contains a tetraphenylporphyrin iron photosensitizer, the amount of which is 1-3% of the total weight of the photoresponsive layer; The water-sensitive layer is a polyvinyl alcohol-starch blend, wherein the starch accounts for 30-50% of the total weight of the water-sensitive layer.

4. The rapidly degradable plastic film according to claim 1, characterized in that, When the rapidly degradable plastic film is used in the topsoil layer (20-30cm) of desertified farmland, the targeted degradation triggering structure is a microbial recognition site, which is a chitosan-modified group with a grafting rate of 2-5% of the total weight of the base degradation substrate layer; The functional product is a slow-release nutrient precursor, which is a mixture of amino acid chelated calcium and polyaspartic acid (PASP), and the amount added is 3-8% of the total weight of the rapidly degradable plastic film.

5. The rapidly degradable plastic film according to claim 1, characterized in that, When the rapidly degradable plastic film is used in the sand layer of a slope (slope > 30°), the targeted degradation triggering structure is a porous nanofiber structure with a pore size of 80-120 nm. The functional product is a salt adsorbent, which is modified montmorillonite, and the amount added is 5-10% of the total weight of the rapidly degradable plastic film.

6. The rapidly degradable plastic film according to claim 1, characterized in that, The rapid-degradable plastic film has a tensile strength of not less than 20 MPa, a degradation cycle of 30-180 days, and the concentrations of lactic acid and glucose in the degradation products are ≤1.0 g / L.

7. A process for preparing a rapidly degradable plastic film, characterized in that, The method for preparing the rapidly degradable plastic film according to any one of claims 1-6 is characterized by comprising the following steps: S1: Dry the basic biodegradable substrate (polyvinyl alcohol-starch blend, PHA or PHA / PLA blend) at 80-100℃ for 2-4 hours to remove moisture until the moisture content is ≤1%; S2: Weigh out the degradation accelerator, degradation inhibitor and compatibility regulator by weight, put them into a high-speed mixer, and mix for 10-20 minutes at 120-150℃ and 300-500r / min to obtain an adjustable speed intermediate. S3: The pretreated basic degradable substrate and the adjustable speed intermediate are fed into a twin-screw extruder. The extrusion temperature is controlled at 160-190℃ and the screw speed is 200-300r / min. After extrusion, the substrate is formed by a casting machine at a casting temperature of 80-100℃ to obtain the basic film layer. S4: Depending on the application scenario requirements, a photoresponsive layer (containing tetraphenylporphyrin iron photosensitizer), chitosan modified groups grafted onto the surface of the base film layer, or a porous nanofiber structure prepared by electrospinning are obtained to obtain a targeted degradation triggering structure. S5: Introduce functional products (hydrophilic small molecule polymer precursors, slow-release nutrient precursors, adhesive biomolecules or salt adsorbents) into the film layer by solution dipping or blending, and dry at 60-80℃ for 1-2 hours to obtain a rapidly degradable plastic film.

8. The preparation process of a rapidly degradable plastic film according to claim 7, characterized in that, In step S2, when the target degradation cycle is 30-60 days, the amount of degradation accelerator added is 10 parts and the amount of degradation inhibitor added is 0 parts. When the target degradation cycle is 90-120 days, the amount of degradation accelerator added is 5 parts and the amount of degradation inhibitor added is 3 parts; When the target degradation cycle is 150-180 days, the amount of degradation accelerator added is 3 parts and the amount of degradation inhibitor added is 5 parts.

9. The preparation process of a rapidly degradable plastic film according to claim 7, characterized in that, In step S4, the photoresponsive layer is coated using a blade coating method with a coating thickness of 5-10 μm; the chitosan-modified groups are grafted using plasma grafting technology with a grafting time of 15-30 minutes; and the porous nanofiber structure is prepared using electrospinning with a spinning voltage of 15-25 kV and a receiving distance of 10-15 cm.

10. The preparation process of a rapidly degradable plastic film according to claim 7, characterized in that, In step S5, the concentration of the functional product during solution dip coating is 5-15 wt%, and the dip coating time is 5-10 minutes; during blending, the mixing temperature of the functional product and the film substrate is 140-160℃, and the mixing time is 5-10 minutes.

Images