Biodegradable dual-mode light quantum conversion agricultural light conversion film

Abstract

The invention relates to the crossing field of agricultural functional polymer materials and green energy technologies, in particular to a biodegradable dual-mode light quantum conversion agricultural light conversion film. According to the light conversion film, a multi-element degradable carrier system is adopted, PLA, PBAT, PBS, PPC, PHA and other biodegradable materials are compounded through blending and compatibilization technologies, and a chemical modification compatibilizer is introduced to achieve performance complementation. The film adopts a three-layer co-extrusion structure, and the invention also designs a low-damage processing technology which comprises low-temperature feeding, high-dispersion shearing and vacuum devolatilization, so that the activity of a heat-sensitive material is ensured. The light transmittance of the light conversion film ranges from 85% to 90%, the tensile strength ranges from 25 MPa to 30 MPa, the elongation at break ranges from 300% to 500%, the red light intensity retention rate is larger than 95% after a xenon lamp is aged for 1000 hours, and the light conversion film is suitable for greenhouse films and can effectively promote photosynthesis of plants and achieve complete biodegradation.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of agricultural functional polymer materials and green energy technology, and particularly relates to a biodegradable dual-mode light quantum conversion agricultural light conversion film. BACKGROUND

[0002] The agricultural light conversion film, as an important functional material for modern agriculture, can significantly improve crop yield and quality by converting the ultraviolet light in sunlight, which is difficult for plants to utilize, into red and blue light for photosynthesis. Traditional light conversion films mainly use non-degradable polymers such as polyethylene (PE) and polypropylene (PP) as carriers, which causes serious white pollution. With the increasing demand for sustainable development, the development of biodegradable light conversion films has become a research hotspot. In the prior art, CN117021714A discloses a quantum dot composite light conversion agricultural film, which uses a four-layer structure to place blue and red light quantum dots in different layers, but the carrier is still a non-degradable polyolefin material, and the quantum dots are prone to decay due to heat processing and ultraviolet radiation. CN118852694A proposes to blend green and red light quantum dots in a single layer film to enhance red light conversion through energy transfer, but does not solve the problem of carrier degradation, and improper control of quantum dot concentration can easily lead to agglomeration. CN114368207A develops a rare earth complex light conversion film by adding an alkaline additive to protect the light conversion agent, but the carrier system is single, making it difficult to balance mechanical properties and degradation rate.

[0003] The above-mentioned prior art has three main limitations: first, the carrier material is not biodegradable, causing environmental pressure; second, the functional design is single, making it difficult to achieve efficient light conversion, ultraviolet resistance, and controlled degradation at the same time; and third, the light conversion agent is not stable enough, especially quantum dots, which are prone to aging during processing and use. Therefore, it is of great significance to develop an agricultural light conversion film that integrates biodegradability, dual-mode light conversion, and long-term stability. The present application overcomes the shortcomings of the prior art through the innovation of a multi-degradable carrier system, a structured functional layering, and a dual-mode light quantum conversion technology, providing a new generation of functional film material for green agriculture. SUMMARY

[0004] The application aims to provide a biodegradable dual-mode light quantum conversion agricultural light conversion film, which adopts a multi-element degradable carrier system, composites biodegradable materials such as PLA, PBAT, PBS, PPC and PHA through blending and compatibilization technology, and introduces a chemical modification compatibilizer to realize performance complementation. The film adopts a three-layer co-extrusion structure, and the application also designs a low-damage processing technology, including low-temperature feeding, high-dispersion shearing and vacuum devolatilization, to ensure the activity of heat-sensitive materials. The light conversion film has a light transmittance of 85-90%, a tensile strength of 25-30 MPa, an elongation at break of 300-500%, and a red light intensity retention rate of >95% after xenon lamp aging for 1000 hours, and is suitable for greenhouse films, can effectively promote plant photosynthesis and realize complete biodegradation.

[0005] A biodegradable dual-mode light quantum conversion agricultural light conversion film, which is composed of a multi-element degradable carrier system, and the components thereof are at least one of PLA, PBAT, PBS, PPC and PHA. Preferably, the agricultural light conversion film of the application further comprises a compatibilizer. The compatibilizer is maleic anhydride grafted PBS or an epoxy functional modified polymer; the light conversion film has a three-layer co-extrusion structure, including an outer light conversion layer, an intermediate functional layer and an inner contact layer, and the thickness ratio of each layer is 1: (1-1.5): 1.

[0006] Preferably, the outer light conversion layer comprises a red light conversion agent and a blue light conversion agent; the red light conversion agent is a SiO2-coated rare earth fluorescent powder, and the composition thereof is YVO4:Eu 3+ ,Sr 2+ @YVO4:Eu 3+ ,Bi 3 + , and the addition amount is 8-12 parts, and the SiO2coating thickness is 10-50 nm; the blue light conversion agent is a polysiloxane-coated cadmium-free quantum dot, the composition thereof is a ZnSe / ZnS core-shell structure, and the addition amount is 2-5 parts; wherein the polysiloxane is prepared by mixing phenyltrimethoxysilane and methyltriethoxysilane at a mass ratio of 3:1, and the polysiloxane coating layer has a thickness of 5-20 nm.

[0007] Preferably, the SiO2-coated rare earth fluorescent powder is surface modified by silane coupling agent KH550, and the addition amount of KH550 is 1-3% of the weight of the rare earth fluorescent powder; the cadmium-free quantum dot is modified by a dialkylsiloxane ligand, and the molar ratio of the ligand to the quantum dot is 1: (1-2) to enhance dispersibility and stability.

[0008] Preferably, the intermediate functional layer contains 50-70 parts of modified PBS, 5-10 parts of nano-montmorillonite and 0.5-1 part of antioxidant, based on 100 parts by weight of the intermediate functional layer; the nano-montmorillonite is organic montmorillonite, the organic modifier thereof is quaternary ammonium salt, and the addition amount of the quaternary ammonium salt is 10-20% by weight of the montmorillonite; and the modified PBS is maleic anhydride grafted PBS, and the grafting rate is 0.5-1.5%.

[0009] Preferably, the inner layer contact layer contains 40-60 parts of PBAT, 20-40 parts of starch and 5-10 parts of degradation inducer, based on 100 parts by weight of the inner layer contact layer; the starch is esterified modified starch, and the esterification degree is 0.1-0.3; and the degradation inducer is polycaprolactone or polyethylene glycol, and the molecular weight is 1000-5000.

[0010] The application also discloses a preparation method of the biodegradable dual-mode light quantum conversion agricultural light conversion film. Preparation of red light master batch: 50-70 parts of PLA, 8-12 parts of YVO4:Eu 3+ , 8-12 parts of Sr 2+ @SiO2 fluorescent powder and 0.5-1 part of KH550 are high-speed mixed, and then granulated in a double-screw extruder at 145-170 DEG C; Preparation of blue light master batch: 50-70 parts of PBAT, 2-5 parts of ZnSe / ZnS quantum dots and 0.3-0.5 parts of hydrolysis-resistant agent are granulated in a double-screw extruder at 125-145 DEG C; Preparation of functional layer master batch: 50-70 parts of PLA / PBAT blend with a weight ratio of 1:1 and 5-10 parts of nano-TiO2 are blended, and then granulated in a double-screw extruder at 150-165 DEG C; Three-layer co-extrusion film blowing: the red light master batch, the functional layer master batch and the blue light master batch are used for the outer layer, the middle layer and the inner layer respectively, and the film is blown at 150-165 DEG C, the blow ratio is (2.5-3.0):1, and the film thickness is 0.08-0.15 mm.

[0011] Preferably, the preparation method adopts a low-damage processing technology: including low-temperature feeding, a feeding section temperature ≤90 DEG C; high-dispersion shearing, a screw rotation speed of 200-400 rpm, a screw length-diameter ratio of 40:1 and vacuum devolatilization, a vacuum degree ≥0.08 MPa, so as to protect the heat-sensitive quantum dots and biobased polymers.

[0012] Preferably, the light conversion film has a light transmittance of 85-90% in the range of 400-700 nm, a haze of 40-60%, a tensile strength of 25-30 MPa, an elongation at break of 300-500%, and a UV-to-red light conversion efficiency of greater than 92% and a UV-to-blue light conversion efficiency of greater than 88%; the spectral matching of the light conversion film makes the comprehensive light conversion efficiency greater than 85%.

[0013] Preferably, the light conversion film has a red light intensity retention rate of greater than 95% and a blue light intensity retention rate of greater than 89% after xenon lamp aging for 1000 hours; after soil burial for 180 days, the light conversion performance retention rate is greater than 80%, and the biodegradation rate is greater than 90%, meeting the ISO 14855 standard.

[0014] The light conversion film described in the application further comprises an antibacterial component, which is silver-loaded zeolite, and the addition amount is 1-3 parts by weight, which is distributed in the intermediate functional layer or the inner contact layer, and the inhibition rate of common soil-borne disease bacteria is greater than 60%; and the silver-loaded zeolite is modified by a silane coupling agent to improve the compatibility with the polymer matrix.

[0015] The following is the English abbreviation of the related substances in the application: The English abbreviation of polylactic acid is PLA, the English abbreviation of polybutylene succinate is PBS, the English abbreviation of polybutylene adipate / terephthalate is PBAT, the English abbreviation of polypropylene carbonate is PPC, and the English abbreviation of polyhydroxyalkanoate is PHA.

[0016] Core innovation points: 1. Innovation and chemical modification of a multi-component degradable carrier system: The application breaks through the performance limitations of single biodegradable materials, and combines PLA, PBAT, PBS, PPC, PHA and other materials through blending and compatibilization technology, and introduces a chemical modification compatibilizer (such as maleic anhydride grafted PBS or epoxy functional modified polymer). The principle is that the compatibilizer forms covalent bonds or hydrogen bonds with the polymer chains, reduces phase separation, and forms a stable "island-in-sea" structure. For example, the hydrophobic chain of PHA is connected to the ester bond of PLA through a compatibilizer, which enhances the interfacial bonding force and solves the problem of brittleness or rapid degradation of single materials. The weight ratio is optimized to balance flexibility, degradation rate and processing performance.

[0017] 2. Structured functional layer design and material modification: The application adopts a three-layer co-extrusion structure, and each layer of material is specifically chemically modified. In the outer light conversion layer, the rare earth fluorescent powder is modified by SiO2 coating and silane coupling agent KH550 to form a core-shell structure, and the principle is that the SiO2 layer prevents Eu 3+Ion quenching and moisture erosion, while KH550 improves adhesion to the polymer matrix; Blue quantum dots are wrapped in polysiloxane, forming a dense network through the synergistic crosslinking of phenyltrimethoxysilane and methyltriethoxysilane, improving thermal stability and light efficiency. In the middle functional layer, the nano-montmorillonite is modified by quaternary ammonium salt organic modification, which expands the interlayer spacing and enhances the ultraviolet shielding effect. In the inner contact layer, starch is modified by esterification to introduce hydrophobic groups and form an interpenetrating network with PBAT to control the degradation rate. This layered modification design realizes the synergistic optimization of light conversion, ultraviolet resistance and degradation promotion functions.

[0018] 3. Energy level engineering and surface modification of dual-mode light quantum conversion system: The invention constructs a dual-mode conversion system of rare earth fluorescent powder and cadmium-free quantum dots, and realizes high-efficiency conversion through energy level matching and surface modification. The red conversion layer adopts YVO4:Eu 3+ , Sr 2+ @YVO4:Eu 3+ ,Bi 3+ fluorescent powder, wherein Bi 3+ serves as a sensitizer to enhance the luminescence efficiency of Eu 3+ through energy transfer, and the SiO2 coating layer suppresses non-radiative transitions caused by surface defects. The blue conversion layer adopts ZnSe / ZnS core-shell quantum dots, the core-shell structure reduces electron-hole recombination through energy band engineering, and the polysiloxane wrapping provides a chemically inert environment to prevent oxidation and aggregation, thereby improving blue conversion efficiency and lifetime. The dual-mode covers the red and blue light bands required for plant photosynthesis and optimizes light quality through spectral matching.

[0019] 4. Mechanism innovation and synergistic control of low-damage processing technology: In view of the thermal sensitivity of quantum dots and bio-based materials, the invention designs a low-temperature feeding, high-dispersion shearing and vacuum devolatilization directional extrusion process. The principle is to control the screw geometry (such as kneading blocks) and temperature gradient to realize low-temperature mixing under high shear, reducing polymer chain rupture and quantum dot degradation. The vacuum devolatilization system removes volatile small molecules to prevent bubble formation. For example, in the PPC / PBAT system, the feeding section temperature is ≤90℃, the melting section is ≤130℃, combined with vacuum devolatilization (vacuum degree 0.07-0.08MPa), to ensure material activity. This process is based on rheology and thermodynamics optimization to solve the problem of thermal damage in processing, and to improve product consistency and performance (such as anti-fading: red light retention rate >95% after xenon lamp aging for 1000 hours).

[0020] The beneficial technical effects of the invention are: 1. Excellent comprehensive performance: The light conversion film of the application achieves the best balance in terms of light transmittance (85-90%), mechanical properties (tensile strength 25-30 MPa, elongation at break 300-500%) and degradation performance (180-day disintegration rate >90%), meeting the needs of different agricultural application scenarios. The double-mode light conversion efficiency is high (red light >92%, blue light 88%), and the spectral matching is good, which can effectively promote plant photosynthesis.

[0021] 2. Outstanding long-term stability: Through material modification and structure design, the light conversion film maintains >95% of red light intensity after 1000 hours of xenon lamp aging, and >89% of blue light; the light conversion performance retention rate is >92% after 90 days of outdoor use, which is much higher than that of traditional light conversion films. The introduction of nano-montmorillonite makes the UVA blocking rate reach 99%, significantly prolonging the service life.

[0022] 3. Significant environmental friendliness: All components are biodegradable, with a soil disintegration rate of >90% in 180 days, and the degradation products are harmless to the environment. Compared with traditional PE films, it fundamentally solves the problem of white pollution and meets the requirements of sustainable development. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 The preparation process flow chart of the agricultural light conversion film of the application is shown in the following figure.

[0024] Figure 2 Material modification schematic diagram: A shows the structure schematic diagram of SiO2 coated fluorescent powder, and B shows the structure schematic diagram of polysiloxane wrapped quantum dots (A01 represents SiO2, A02 represents rare earth fluorescent powder, YVO4:Eu 3+ ,Sr 2+ @YVO4:Eu 3+ ,Bi 3+ ; B01 represents ZnSe, B02 represents polysiloxane, and B03 represents ZnS). DETAILED DESCRIPTION

[0025] Before further describing the specific embodiments of the application, it should be understood that the scope of protection of the application is not limited to the following specific embodiments; it should also be understood that the terms used in the embodiments of the application are for the purpose of describing the specific embodiments, but not for limiting the scope of protection of the application. The test methods in the following examples are not specified, and are usually carried out under conventional conditions or under conditions recommended by the manufacturers.

[0026] When the embodiments give numerical ranges, it should be understood that, unless the application indicates otherwise, every numerical range's two endpoints, and any number between the two endpoints, can be selected. Unless otherwise defined, all technical and scientific terms used in the application have the same meaning as commonly understood by one of ordinary skill in the art. In addition to the specific methods, devices, materials, and the like used in the embodiments, any methods, devices, materials, and the like that are similar or equivalent to those described in the embodiments of the application can be used to implement the application according to the knowledge of those skilled in the art and the description of the application.

[0027] Unless otherwise specified, the test methods, detection methods, and preparation methods disclosed in the application all use conventional techniques in the art.

[0028] The following are the performance test standards of the application: Transmittance / haze: tested according to ASTM D1003 standard; Spectral matching: use ultraviolet-visible-near infrared spectrophotometer and fluorescence spectrometer to test the spectrum before and after conversion, and calculate the conversion efficiency; Anti-attenuation: after the film sample is accelerated aging in a xenon lamp aging oven (according to ISO 4892-2 standard) for a certain period of time, test its fluorescence intensity retention rate; Mechanical properties: tested according to ISO 527 (tensile properties) and ISO 6383-2 (tear strength); Biodegradability: tested according to ISO 14855 (composting conditions) or ASTM D5988 (soil burial) for degradation rate.

[0029] Example 1: PLA / PBAT blend system greenhouse film This embodiment prepares a PLA / PBAT blend system three-layer greenhouse film, and the specific implementation is as follows: first, prepare a red light master batch, 60 parts by weight of PLA, 10 parts by weight of YVO4:Eu 3+ ,Sr 2+@SiO2 fluorescent powder (SiO2 coating thickness 30 nm) and 0.5 parts by weight of KH550 silane coupling agent were mixed at high speed for 15 minutes, and granulated by a twin-screw extruder at a temperature range of 145-170°C, with a screw rotation speed of 300 rpm. Then, a blue light master batch was prepared by mixing 60 parts by weight of PBAT, a ZnSe / ZnS quantum dot dispersion liquid (solid content 15%) equivalent to 3 parts by weight of quantum dots, and 0.3 parts by weight of a hydrolysis-resistant agent, and granulating at 125-145°C. The functional layer master batch was prepared by blending 60 parts by weight of PLA / PBAT (50 / 50) blend with 5 parts by weight of nano-TiO2 at 150-165°C. Finally, three-layer co-extrusion film blowing was performed, with the outer layer using the red light master batch, the middle layer using the functional layer master batch, and the inner layer using the blue light master batch, the film blowing temperature being 150-165°C, the blowing ratio being 2.8:1, and the film thickness being controlled at 0.12 mm. The obtained film has a light transmittance of 88.5%, a haze of 42%, a UV-to-red light conversion efficiency of 91.5%, a UV-to-blue light conversion efficiency of 86.8%, a red light intensity retention rate of 95% and a blue light intensity retention rate of 89% after 1000 hours of xenon lamp aging, a tensile strength (MD / TD) of 28 / 25 MPa, and an elongation at break of 380% / 350%, meeting the requirements for high-standard greenhouse film use.

[0030] Example 2: PBS / starch system greenhouse film In this example, a PBS / starch system single-layer greenhouse film was prepared, and the specific implementation is as follows: first, a light conversion master batch was prepared by mixing 70 parts by weight of PBS, 8 parts by weight of YVO4:Eu 3+ ,Sr 2+ @SiO2 fluorescent powder, 2 parts by weight of ZnSe / ZnS quantum dots, and 5 parts by weight of maleic anhydride grafted PBS compatibilizer (grafting rate 1.0%) were mixed in a high-speed mixer for 20 minutes, and granulated by a twin-screw extruder at a temperature range of 115-135°C, with the processing temperature being strictly controlled to avoid degradation of heat-sensitive materials. Then, the light conversion master batch and PBS resin were thoroughly mixed in a mixer at a ratio of 1:4 for 30 minutes, and a single-layer film blowing process was adopted, with a film blowing temperature of 130°C, a die temperature of 135°C, a blowing ratio of 2.5:1, and a film thickness accurately controlled at 0.1 mm. The obtained greenhouse film has a light transmittance of 83%, a haze of 55%, a comprehensive light conversion efficiency of more than 82%, a light conversion performance retention rate of more than 80% after being buried in soil for 180 days, a biodegradation rate of more than 90%, mechanical properties meeting the requirements for field mechanization, and can be completely biodegraded after the use cycle ends, without causing white pollution.

[0031] Example 3: PPC / PBAT high-elasticity greenhouse film This embodiment prepares a PPC / PBAT high-elasticity greenhouse film, which is implemented as follows: 50 parts by weight of PPC and 50 parts by weight of PBAT are used as the carrier system. First, the PPC is vacuum-dried at 80°C for 8 hours to remove moisture. The red light master batch is prepared by using 50 parts by weight of PLA, 8 parts by weight of YVO4:Eu 3+ , Sr 2+ @SiO2 fluorescent powder, and 0.5 parts by weight of KH550, and granulating in a twin-screw extruder at 150°C. The blue light master batch is prepared by using 50 parts by weight of PBAT, 2 parts by weight of ZnSe / ZnS quantum dot dispersion liquid, and 0.3 parts by weight of hydrolysis-resistant agent, and granulating at 130°C. The functional layer master batch is prepared by blending PLA / PBAT (50 / 50) blend and nano-TiO2. The processing temperature is strictly controlled during three-layer co-extrusion blown film, i.e., the feeding section is ≤90°C, the melting section is ≤130°C, the die temperature is 125°C, the blowing ratio is 2.6:1, and the film thickness is 0.1 mm. The obtained greenhouse film has a light transmittance of 86%, an elongation at break of ≥500%, and excellent elasticity; the UV-to-red light conversion efficiency is 85%, which is suitable for short-term crop planting, but the intensity is relatively low and the weather resistance is slightly poor, so appropriate application scenarios need to be selected according to the specific use environment.

[0032] Example 4: PHA high-end high-barrier greenhouse film This embodiment prepares a PHA high-end high-barrier greenhouse film, which is implemented as follows: 100 parts by weight of PHA is used as the carrier material. First, the PHA resin is vacuum-dried at 80°C for 12 hours to ensure that the water content is less than 0.02%. 6 parts by weight of light conversion agent (composed of 4 parts by weight of YVO4:Eu 3+ , Sr 2+ @SiO2 fluorescent powder and 2 parts by weight of ZnSe / ZnS quantum dots) is mixed with the dried PHA resin in a high-speed mixer for 30 minutes. A single-layer blown film process is used, with a blown film temperature of 155°C, a die temperature of 160°C, a blowing ratio of 2.2:1, and a film thickness of 0.08 mm. The temperature and time are strictly controlled during the processing to avoid thermal degradation of PHA. The obtained greenhouse film has a light transmittance of 85% and can be completely biodegraded in seawater and soil. The barrier property to water vapor is improved by 50% and the barrier property to oxygen is improved by 40% compared with traditional PLA, which has the optimal biodegradability and barrier performance, but the cost is relatively high, and is suitable for high-end agricultural planting and special environment applications.

[0033] Example 5: PLA / PBAT / PHA ternary blend enhanced film The embodiment prepares PLA / PBAT / PHA ternary blend reinforced film, and the specific implementation is as follows: PLA 50 parts by weight, PBAT 30 parts by weight, and PHA 20 parts by weight are used as a carrier system, and 3 parts by weight of a multi-functional epoxy compatibilizer is added. First, the components are mixed in a high-speed mixer for 25 minutes to ensure uniform dispersion. Red master batch preparation uses PLA 55 parts by weight, YVO4:Eu 3+ , Sr 2+ @SiO2fluorescent powder 9 parts by weight, and KH550 0.6 parts by weight, granulated at 160°C. Blue master batch preparation uses PBAT 55 parts by weight, ZnSe / ZnS quantum dot dispersion liquid equivalent to 2.5 parts by weight of quantum dots, and hydrolysis inhibitor 0.4 parts by weight, granulated at 140°C. Three-layer co-extrusion blown film temperature is 155°C, blow ratio is 2.7:1, and film thickness is 0.11mm. The obtained film has good mechanical property balance, and the toughness is significantly better than that of pure PLA. The UV red light conversion efficiency is 88%, the degradation period can be controlled within 12-24 months, and the formula can be adjusted according to different crop growth periods to realize accurate control of the degradation time.

[0034] Example 6: PBAT / PPC high flexibility greenhouse film The embodiment prepares PBAT / PPC high flexibility greenhouse film, and the specific implementation is as follows: PBAT 70 parts by weight and PPC 30 parts by weight are used as a carrier system, and first, the PPC is vacuum dried at 75°C for 6 hours. The carrier resin is mixed with 5 parts by weight of a light conversion agent (3 parts by weight of fluorescent powder and 2 parts by weight of quantum dots) and 2 parts by weight of maleic anhydride grafted PBS compatibilizer in a high-speed mixer for 20 minutes. Single-layer blown film process is used, the blown film temperature is 120°C, the die temperature is 125°C, the blow ratio is 2.4:1, and the film thickness is 0.1mm. The low-temperature blown film process effectively protects the heat-sensitive materials. The obtained greenhouse film has excellent flexibility, is convenient for mechanized laying, has excellent low-temperature impact resistance, the impact strength retention rate is more than 85% at -20°C, the light conversion performance retention rate is 92% after 90 days of outdoor use, and is suitable for agricultural application in low-temperature environments.

[0035] Example 7: PLA / nano-cellulose reinforced greenhouse film The embodiment prepares PLA / nano-cellulose reinforced greenhouse film, and the specific implementation is as follows: PLA 95 parts by weight, nano-cellulose (CNF) 5 parts by weight are used as a carrier system. First, the CNF is pretreated, and ultrasonic dispersion is used for 30 minutes to prevent agglomeration. The pretreated CNF is mixed with PLA resin, 8 parts by weight of light conversion agent (5 parts by weight of fluorescent powder and 3 parts by weight of quantum dots) in a high-speed mixer for 40 minutes, and then granulated by a twin-screw extruder at 160°C. Then, a film blowing process is used, the film blowing temperature is 155-168°C, the blowing ratio is 2.8:1, and the film thickness is 0.12mm. The tensile strength of the obtained greenhouse film is increased by more than 20% compared with pure PLA, the heat distortion temperature is increased by 15°C, the light transmittance is 82% (slightly decreased), but the haze increases, which is beneficial to light scattering, making the light more uniform, and it is suitable for large-span greenhouse with high mechanical property requirement.

[0036] Example 8: Full-spectrum light conversion film The embodiment prepares a full-spectrum light conversion film, and the specific implementation is as follows: PBAT 80 parts by weight, PBS 20 parts by weight are used as a carrier system, and 10 parts by weight of light conversion agent is added, which includes 5 parts by weight of YVO4:Eu 3+ , Sr 2+ @SiO2 fluorescent powder, 3 parts by weight of ZnSe / ZnS quantum dots and 2 parts by weight of organic fluorescent dye (1 part by weight of red and blue dye each). First, the components are fully mixed in a high-speed mixer for 35 minutes, and 0.5 parts by weight of light stabilizer is added to improve the weather resistance of the dye. A single-layer film blowing process is used, the film blowing temperature is 135°C, the die temperature is 145°C, the blowing ratio is 2.5:1, and the film thickness is 0.08mm. The obtained film has the best spectral matching, which is closer to the ideal spectrum of plant photosynthesis, and has high initial light conversion efficiency, but the dye part decays quickly in long-term use, and is suitable for short-term high-value crop planting.

[0037] Example 9: Antibacterial light conversion greenhouse film The embodiment prepares an antibacterial light conversion greenhouse film, and the specific implementation is as follows: PBS 80 parts by weight, starch 20 parts by weight are used as a carrier system, and the starch is esterified and modified (esterification degree 0.2). 8 parts by weight of light conversion agent (5 parts by weight of fluorescent powder and 3 parts by weight of quantum dots) and 2 parts by weight of silver-loaded zeolite antibacterial agent (modified by silane coupling agent) are added. First, the components are mixed in a high-speed mixer for 30 minutes, and then granulated by a twin-screw extruder at 125°C. Then, a film blowing process is used, the film blowing temperature is 135°C, the blowing ratio is 2.3:1, and the film thickness is 0.12mm. The obtained greenhouse film has an inhibition rate of more than 60% on common soil-borne disease bacteria, effectively reducing crop disease occurrence, and has good light conversion function with light transmittance of 84% and comprehensive light conversion efficiency of 83%, which is especially suitable for planting areas with serious continuous cropping obstacles.

[0038] Example 10: Weather-resistant ultra-thin greenhouse film The weather-resistant shed film is prepared in the embodiment, and the implementation is as follows: 45 parts by weight of PPC, 45 parts by weight of PBAT and 10 parts by weight of organically modified montmorillonite are used as the carrier system. First, the montmorillonite is modified to be organic, and quaternary ammonium salt is used as the modifier, and the addition amount is 15% of the weight of the montmorillonite. The modified montmorillonite, 6 parts by weight of the light conversion agent and the carrier resin are mixed in a high-speed mixer for 40 minutes to ensure that the clay is fully exfoliated and dispersed. The film blowing process is used, the film blowing temperature is 115-140 ℃, the die temperature is 135 ℃, the blowing ratio is 2.2:1, and the film thickness is 0.1 mm. The obtained ultra-thin shed film has excellent mechanical properties, which can reach the level of traditional PE shed film, the UV blocking property is more than 95%, the degradation period is prolonged to 9-12 months, the demand of long-season crops is met, the unit area usage is reduced, and the cost is effectively reduced.

[0039] Comparative Example 1: Non-degradable carrier light conversion film Referring to CN117021714A, LDPE is used as the carrier, red CdSe quantum dots and blue CdZnSe quantum dots are arranged in different layers respectively, the quantum dot concentration is 0.05wt%, the thickness is 0.1mm, and the structure is four layers.

[0040] Performance: light transmittance 90%, but not biodegradable, light conversion efficiency decays fast (retention rate <70% after 500h xenon lamp aging), and causes environmental pollution after being discarded.

[0041] Comparative Example 2: Single-layer mixed light conversion film Referring to CN118852694A, CdSe / ZnS red light quantum dots and green light quantum dots are blended in PE, the quantum dot concentration is 0.05wt% respectively, the structure is single layer, and the film blowing temperature is 100℃.

[0042] Performance: the light conversion efficiency is relatively high at the initial stage, but the quantum dots are easy to agglomerate, the efficiency decreases by 40% after 100h, and the carrier is not degradable and the function is single.

[0043] Comparative Example 3: Rare earth light conversion film without alkaline additive Referring to CN114368207A, a naphthyridine europium complex light conversion agent is used, but no alkaline additive is added, the processing temperature is 210℃, and the carrier is LDPE.

[0044] Performance: the light conversion efficiency is only 34%, the aging half-life period is 3 months, which is much lower than that of the present application, and the acidic environment causes the decomposition of the light conversion agent.

[0045] Comparative Example 4: Light conversion film with high processing temperature The formula of Example 1 of the present application is used, but the processing temperature is increased to 190-210℃, and other conditions are the same.

[0046] Performance: quantum dots severely degraded, blue light conversion efficiency dropped to 45%, film material yellowed, mechanical properties decreased by 20%, proving the destructive effect of high temperature processing on heat-sensitive materials.

[0047] Comparative Example 5: single carrier light conversion film Pure PLA 100 parts was used as a carrier, and the type and amount of light conversion agent were the same as in Example 1.

[0048] Performance: the film is brittle, the elongation at break is less than 50%, it is easy to break in the field, and the degradation is uncontrollable, proving that a single carrier cannot meet the comprehensive performance requirements.

[0049] Summary: Synergistic effect of material composition and structure design: the performance of the examples and comparative examples in the invention shows significant differences, the primary reason being the synergistic optimization of material composition and structure design. The examples use a multi-component degradable carrier system, which forms a stable "island" structure through precise weight ratio and compatibilizer modification, resulting in good interfacial bonding between components. Comparative Examples 1-3 use a single carrier or non-degradable material, lacking this synergistic effect. For example, the PLA / PBAT (60 / 40) ratio in Example 1 maintains the rigidity of PLA and achieves the toughness of PBAT, while the pure PLA carrier in Comparative Example 5 is brittle, resulting in poor mechanical properties. This composition optimization allows the examples to maintain mechanical properties while achieving complete biodegradation.

[0050] Effectiveness of surface modification and protection mechanism: the difference in surface modification technology of the light conversion agent is another important factor that causes performance differences. In the examples of the invention, the SiO2 coating layer and the polysiloxane wrapping layer provide an effective physical barrier for the light conversion agent, preventing moisture, oxygen, and ultraviolet light from attacking. The KH550 silane coupling agent modification enhances the compatibility of the light conversion agent with the polymer matrix, reducing interfacial defects. Comparative Examples 1-3 lack this protection mechanism, with quantum dots directly exposed to harsh environments, prone to oxidation and agglomeration. In particular, Comparative Example 3 lacks the protection of alkaline additives, and the light conversion agent rapidly decomposes in an acidic environment, resulting in a sharp decrease in efficiency.

[0051] Protective effect of processing technology on material structure: the implementation of low-damage processing technology is crucial to maintaining material performance. The examples of the invention use low-temperature feeding, high-dispersion shearing, and vacuum devolatilization processes to effectively control thermal degradation and shear degradation during processing. For example, Example 3 strictly controls the processing temperature below 130°C, protecting the heat-sensitive PPC and quantum dots. Comparative Example 4 uses high-temperature processing at 190-210°C, resulting in the destruction of quantum dot structures and polymer degradation, with a significant decrease in performance. This process difference directly affects the microstructure and performance stability of the material.

[0052] Functional layering synergistic protection mechanism: The three-layer co-extrusion structure design realizes precise allocation and synergistic protection of functions. The outer layer focuses on light conversion, the middle layer provides UV shielding, and the inner layer controls the degradation rate, and each layer has clear functions and cooperates with each other. This design avoids the problem of mutual interference of functional components in Comparative Example 2. The directional distribution of nano-montmorillonite in the middle layer forms an effective UV barrier to protect the light conversion agent from photodegradation. Comparative Example 1 also uses a multi-layer structure, but due to the non-degradable carrier and lack of synergistic design, it cannot achieve long-term stable performance.

[0053] Systematic regulation mechanism of degradation performance: The difference in biodegradability is due to the design of the degradation regulation system. In the examples, through the systematic regulation of esterified starch, degradation inducer and carrier ratio, the degradation rate is precisely controlled. For example, in Example 2, the synergistic effect of esterified starch (esterification degree 0.2) and PBS not only ensures the stability during use, but also achieves rapid degradation after use. Comparative Examples 1-2 use non-degradable carriers and completely lack degradability. This degradation regulation mechanism enables the present application to meet the use requirements while completely solving the white pollution problem.

[0054] Finally, it should be noted that the above examples are used to illustrate the technical solutions of the present application and are not a limitation on the scope of protection of the present application. Although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application can be modified or replaced by equivalents without departing from the essence and scope of the technical solutions of the present application.

Claims

1. A biodegradable dual-mode photon conversion agricultural light-converting film, characterized in that: The agricultural light conversion film is composed of a multi-component biodegradable carrier system, including at least one of PLA, PBAT, PBS, PPC, and PHA. The light conversion film has a three-layer co-extruded structure, including an outer light conversion layer, an intermediate functional layer and an inner contact layer, and the thickness ratio of each layer is 1:(1-1.5):1; The outer light conversion layer contains a red light converter and a blue light converter; the red light converter is a rare earth phosphor coated with SiO2; the blue light converter is a cadmium-free quantum dot coated with polysiloxane. The intermediate functional layer also includes at least one of modified PBS, nano-montmorillonite, and antioxidant; The inner contact layer also contains at least one of PBAT, starch, and degradation inducer.

2. The biodegradable dual-mode photon conversion agricultural light-converting film according to claim 1, characterized in that: It also includes a compatibilizer, which is maleic anhydride-grafted PBS or an epoxy functional group-modified polymer.

3. The biodegradable dual-mode photon conversion agricultural light-converting film according to claim 1, characterized in that: Based on 100 parts by weight of the light conversion film, the outer light conversion layer comprises a red light converter and a blue light converter; The red light converter is a rare earth phosphor coated with SiO2, and its composition is YVO4:Eu. 3+ Sr1 2+ @YVO4:Eu 3+ ,Bi 3+ The amount added is 8-12 parts, and the SiO2 coating thickness is 10-50nm; the blue light converter is a cadmium-free quantum dot encapsulated in polysiloxane, and its composition is a ZnSe / ZnS core-shell structure, with an addition amount of 2-5 parts.

4. The biodegradable dual-mode photon conversion agricultural light-converting film according to claim 3, characterized in that: The polysiloxane is prepared by mixing phenyltrimethoxysilane and methyltriethoxysilane in a mass ratio of 3:1, and the thickness of the polysiloxane coating layer is 5-20 nm.

5. The biodegradable dual-mode photon conversion agricultural light-converting film according to claim 3, characterized in that: The SiO2-coated rare earth phosphor is surface modified by silane coupling agent KH550, with the amount of KH550 added being 1-3% of the weight of the rare earth phosphor. The cadmium-free quantum dots are modified with dialkylsiloxane ligands, with a molar ratio of ligand to quantum dots of 1:(1-2), to enhance dispersibility and stability.

6. The biodegradable dual-mode photon conversion agricultural light-converting film according to claim 1, characterized in that: Based on 100 parts of the intermediate functional layer, the intermediate functional layer further comprises at least one of the following: 50-70 parts of modified PBS, 5-10 parts of nano-montmorillonite, and 0.5-1 part of antioxidant. The nano-montmorillonite is an organo-modified montmorillonite, and its organomodification modifier is a quaternary ammonium salt, with the amount of quaternary ammonium salt added being 10-20% of the weight of montmorillonite; the modified PBS is maleic anhydride-grafted PBS, with a grafting rate of 0.5-1.5%.

7. The biodegradable dual-mode photon conversion agricultural light-converting film according to claim 1, characterized in that: Based on 100 parts by weight of the inner contact layer, the inner contact layer further comprises at least one of 40-60 parts of PBAT, 20-40 parts of starch, and 5-10 parts of degradation inducer; the starch is esterified modified starch with a degree of esterification of 0.1-0.3; the degradation inducer is polycaprolactone or polyethylene glycol with a molecular weight of 1000-5000 Da.

8. The biodegradable dual-mode photon conversion agricultural light-converting film according to claim 1, characterized in that, The method for preparing the light-converting film, by weight, includes the following steps: Preparation of red light masterbatch: 50-70 parts of PLA, YVO4:Eu 3+ , Sr 2+ @8-12 parts of SiO2 phosphor and 0.5-1 parts of KH550 are mixed at high speed and granulated at 145-170℃ using a twin-screw extruder; Preparation of blue light masterbatch: 50-70 parts of PBAT, 2-5 parts of ZnSe / ZnS quantum dots and 0.3-0.5 parts of anti-hydrolysis agent are granulated by twin-screw extruder at 125-145℃; Preparation of functional layer masterbatch: 50-70 parts of PLA / PBAT blend with 5-10 parts of nano TiO2 at a weight ratio of 1:1 are blended and granulated by twin-screw extruder at 150-165℃. Three-layer co-extrusion blown film: Red light masterbatch, functional layer masterbatch and blue light masterbatch are used in the outer layer, middle layer and inner layer respectively, and blown film is blown at 150-165℃ with a blow-up ratio of (2.5-3.0):1 and a film thickness of 0.08-0.15mm.

9. The biodegradable dual-mode photon conversion agricultural light-converting film according to claim 1, characterized in that: The light-converting film also contains an antibacterial component, which is a modified silver-loaded zeolite, added in an amount of 1-3 parts by weight, distributed in the intermediate functional layer or the inner contact layer, and has an inhibition rate of more than 60% against common soil-borne pathogens; and the silver-loaded zeolite is modified by a silane coupling agent to improve its compatibility with the polymer matrix.

10. The biodegradable dual-mode photon conversion agricultural light-converting film according to claim 9, characterized in that, The modified silver-loaded zeolite is prepared as follows: the silver-loaded zeolite is dispersed in an ethanol solvent with a solid-liquid ratio of 1g:(8-12)mL. A silane coupling agent is then added, with the amount being 1-5% of the weight of the silver-loaded zeolite. The mixture is stirred at 60-80℃ for 2-4 hours, and then washed and dried.

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