A strong high-barrier film material and its preparation method and application

Abstract

The application discloses a kind of tough high-barrier functional film materials and preparation method and application thereof, including the following weight parts of raw materials: 60-90 parts of poly-L-lactic acid, 10-40 parts of polypropylene carbonate, 0.1-3 parts of PDLA / PPCM Janus nanosheet;PDLA / PPCM Janus nanosheet is SiO2 hollow ball as template, grafting curcumin polypropylene carbonate diol, poly-L-lactic acid is respectively modified on the two sides of template.Each raw material is melt-blended, then formed, i.e.the tough high-barrier functional film material described above.The application is modified with SiO2 hollow ball as template, and PDLA / PPCM Janus nanosheet is prepared, which can be better dispersed at the interface of two phases when added to the matrix PLLA / PPC, so that the compatibilization efficiency of the blend is effectively improved.

Description

Technical Field

[0001] This invention relates to the field of functional materials technology, and in particular to a strong and tough high-barrier functional membrane material, its preparation method, and its application. Background Technology

[0002] With the continuous development of science and technology, the properties of single-component materials can no longer meet modern needs. Therefore, blending modification is a necessary processing strategy. However, most materials exhibit poor compatibility and no performance improvement after blending.

[0003] Polylactic acid (PLA) is a bio-based biodegradable material with high strength and good processability, making it one of the most commercially successful biodegradable materials. Polypropylene carbonate (PPC) has also attracted widespread attention as a novel biodegradable aliphatic polymer with good degradability, barrier properties, transparency, and non-toxicity, finding wide applications in food packaging, medical devices, and engineering plastics. However, PLA / PPC blends exhibit poor compatibility and overall performance. Currently, traditional compatibilizers suffer from low efficiency and lack of functionality, limiting the application range of these blends. Summary of the Invention

[0004] To address the aforementioned problems in existing technologies, this invention provides a robust, high-barrier functional membrane material, its preparation method, and its applications. This invention uses SiO2 hollow spheres as templates for modification to prepare PDLA / PPCM Janus nanosheets. Adding these nanosheets to the PLLA / PPC matrix allows for better dispersion at the two-phase interface, thereby effectively improving the compatibilization efficiency of the blend.

[0005] The technical solution of the present invention is as follows:

[0006] The first objective of this invention is to provide a strong and tough high-barrier functional membrane material comprising the following raw materials in parts by weight: 60-90 parts of polylactic acid (PLA), 10-40 parts of polypropylene carbonate (PPC), and 0.1-3 parts of PDLA / PPCM Janus nanosheets.

[0007] PDLA / PPCM Janus nanosheets were created using SiO2 hollow spheres as templates, with polypropylene carbonate diol (PPCM) and dextrorotatory polylactic acid (PDLA) grafted with curcumin modified on both sides of the templates.

[0008] In one embodiment of the present invention, the method for preparing PDLA / PPCM Janus nanosheets is as follows:

[0009] (1) PPC diol reacts with lysine diisocyanate. After the reaction is complete, SiO2 hollow sphere dispersion and curcumin are added to the system to obtain SiO2 hollow spheres with PPCM grafted on the outer surface.

[0010] (2) The SiO2 hollow spheres grafted with PPCM on the outer surface are ultrasonically crushed to obtain SiO2-PPCM nanosheets, which are then reacted with silane coupling agent and dextrorotatory polylactic acid to prepare the PDLA / PPCM Janus nanosheets.

[0011] In one embodiment of the present invention, in step (1), the molar ratio of PPC diol to lysine diisocyanate is 1:2-3.

[0012] In one embodiment of the present invention, in step (1), the reaction conditions are as follows: PPC diol is distilled under reduced pressure at 110°C for 4-6 hours, then cooled to 60°C, and the distilled PPC diol is added dropwise to lysine diisocyanate. Under nitrogen conditions, the mixture is stirred at 50-60°C for 3-5 hours. Then, 150-250 mL of SiO2 hollow sphere dispersion (0.75 / 100, g / mL) and 2-4 g of curcumin are added, and the mixture is cooled to 40°C and stirred for 12-18 hours. The mixture is then washed with deionized water and tetrahydrofuran, centrifuged and dried to obtain SiO2 hollow spheres with PPCM grafted on the outer surface.

[0013] In one embodiment of the present invention, in step (1), the SiO2 hollow sphere dispersion is prepared by dispersing SiO2 hollow spheres in tetrahydrofuran; the concentration of the SiO2 hollow sphere dispersion is 0.5-0.75 g / 100 mL; and the particle size of the SiO2 hollow spheres is 4.5-5.5 μm.

[0014] In one embodiment of the present invention, in step (1), the mass-to-volume ratio of PPC diol to SiO2 hollow sphere dispersion is 5-10 / 100, g / mL; the mass-to-volume ratio of curcumin to SiO2 hollow sphere dispersion is 1-5 / 100, g / mL.

[0015] In one embodiment of the present invention, in step (1),

[0016] PPC was added dropwise to lysine diisocyanate, and dibutyltin dilaurate (0.01-0.05% of the mass of PPC) was added as a catalyst. The mixture was stirred at 50-60°C for 3-5 hours under nitrogen atmosphere. Subsequently, 150-250 mL of SiO2 hollow sphere dispersion and 2-4 g of curcumin were added to the reaction system, and the mixture was cooled to 40°C and stirred for 12-18 hours. The mixture was then washed with deionized water and tetrahydrofuran, centrifuged and dried to obtain SiO2 hollow spheres with PPCM grafted on the outer surface.

[0017] In one embodiment of the present invention, in step (2), the conditions for ultrasonic fragmentation are: ultrasonic treatment at 500-600W for 1-1.5h;

[0018] The reaction conditions were as follows: SiO2-PPCM nanosheets were dispersed in chloroform, then silane coupling agent KH560 was added and reacted at 40-50℃ for 2-3.5h to graft epoxy groups onto the surface, then dextrorotatory polylactic acid PDLA was added and reacted in a three-necked flask (nitrogen) at 80-100℃ for 20-25h. Finally, the mixture was thoroughly stirred, centrifuged, washed with chloroform, and dried to obtain the Janus nanosheets.

[0019] In one embodiment of the present invention, in step (2), the silane coupling agent is KH560; the mass ratio of SiO2-PPCM nanosheets, dextrorotatory polylactic acid and silane coupling agent is 1:2-5:5-10.

[0020] In one embodiment of the present invention, in step (2), the SiO2 hollow spheres grafted with PPCM on the outer surface are dispersed in anhydrous ethanol and ultrasonically treated at 500-600W for 1-1.5h to break the hollow spheres into sheets, namely SiO2-PPCM nanosheets; then the SiO2-PPCM nanosheets are dispersed in chloroform, and silane coupling agent KH560 is added and reacted at 40-50℃ for 2-3.5h to graft epoxy groups onto the surface, and then dextrorotatory polylactic acid PDLA is added and reacted in a three-necked flask (nitrogen) at 80-100℃ for 20-25h. Finally, after thorough stirring, centrifugation, washing with chloroform, and drying, the Janus nanosheets are obtained.

[0021] A second objective of this invention is to provide a method for preparing the above-mentioned strong and tough high-barrier functional membrane material, comprising the following steps:

[0022] The tough, high-barrier functional membrane material is obtained by melt blending 60-90 parts of polylactic acid (PLLA), 10-40 parts of polypropylene carbonate (PPC), and 0.1-3 parts of PDLA / PPCM Janus nanosheets, followed by molding.

[0023] In one embodiment of the present invention, the preparation method of the strong and tough high-barrier functional membrane material includes the following steps:

[0024] 60-90 parts of polylactic acid (PLLA), 10-40 parts of polypropylene carbonate (PPC), and 0.1-3 parts of PDLA / PPCM Janus nanosheets are blended at 190-200℃ for 5-6 minutes, then extruded into a film or sheet, and then rapidly cooled to below 15℃ to reduce its crystallinity to less than 10%. The cooled film or sheet is then biaxially stretched at 70-75℃ using a flat film biaxial stretching process, and then heat-treated at 100-110℃ to obtain the tough, high-barrier functional membrane material.

[0025] or,

[0026] 60-90 parts of polylactic acid (PLLA), 10-40 parts of polypropylene carbonate (PPC), and 0.1-3 parts of PDLA / PPCM Janus nanosheets are blended at 190-200℃ for 5-6 minutes. Then, a preform is formed through a tubular die. The preform is rapidly cooled to below 15℃ to reduce its crystallinity to less than 10%. The cooled preform is then blown, stretched, and shaped at 70-75℃ using a biaxial stretching process. Finally, it is heat-treated at 100-110℃ to obtain the tough, high-barrier functional membrane material.

[0027] In one embodiment of the present invention, the stretching temperature of the flat film biaxial stretching process is 70-75°C, the heat treatment temperature is 100-110°C, the transverse stretching ratio is 4 times, and the longitudinal stretching ratio is 4 times.

[0028] In one embodiment of the present invention, the stretching temperature of the biaxial stretching process of the tubular membrane is 70-75°C, the heat treatment temperature is 100-110°C, the blow-up ratio is 3 times, and the draw ratio is 5 times.

[0029] A third objective of this invention is to provide an application of the aforementioned strong and high-barrier functional membrane material in the fields of food, daily necessities, environment, agriculture, or medicine.

[0030] The beneficial technical effects of this invention are as follows:

[0031] In this invention, PDLA grafted onto PDLA / PPCM Janus nanosheets and PLLA from the matrix form stereocomposite crystals during melt blending. These crystals are dispersed at the interface between the two phases, further enhancing the strength of the polymer blend.

[0032] This invention, by controlling the biaxial stretching conditions to orient Janus nanosheets in the blend, significantly increases the diffusion path of small gas molecules in the film. Furthermore, the in-situ stereocomposite crystals formed between the Janus nanosheets and the PLLA matrix, along with the bridging network between the PPC molecular chains, create a barrier network that synergistically blocks small gas molecules. Therefore, the tensile strength, elongation at break, and barrier properties of the blend film are all significantly improved.

[0033] Due to the properties of curcumin and polylactic acid, the blend in this invention exhibits excellent UV protection. Furthermore, by grafting curcumin, it achieves good dispersibility in the blend, thus significantly improving the ammonia response and spoilage detection capabilities of the blend film. Therefore, it is advantageous for applications in packaging, agricultural films, and other fields.

[0034] This invention designs a Janus-structured nanosheet, and by controlling its dispersion and biaxial stretching processes, the resulting PLLA / PPC film combines mechanical properties with high barrier properties and multifunctionality, which is beneficial for its expansion in the packaging field. Attached Figure Description

[0035] Figure 1 Atomic force microscopy images of nanosheets at different stages in Example 1;

[0036] Among them, (a) SiO2 nanosheets after ultrasonic crushing of ungrafted SiO2 (5μm) hollow spheres; (b) SiO2-PPCM nanosheets; and (c) PDLA / PPCM Janus nanosheets. Detailed Implementation

[0037] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0038] Example 1

[0039] A method for preparing PDLA / PPCM Janus nanosheets includes the following steps:

[0040] (1) 20g of PPC was used as a diol and distilled under reduced pressure at 110℃ for 6h. Then it was cooled to 60℃ and the distilled PPC diol was added dropwise to 6g of lysine diisocyanate. 0.005g of dibutyltin dilaurate catalyst was added and the mixture was stirred at 60℃ for 3h under nitrogen. Then 200mL (0.75 / 100, g / mL) of SiO2 hollow sphere dispersion and 3g of curcumin were added and the mixture was cooled to 40℃ and stirred for 12h. Then it was washed with deionized water and tetrahydrofuran, centrifuged and dried to obtain SiO2 hollow spheres with PPCM grafted on the outer surface.

[0041] (2) Disperse the SiO2 hollow spheres grafted with PPCM on the outer surface in ethanol and sonicate (500W) for 1 hour to break them into pieces to obtain SiO2-PPCM nanosheets.

[0042] (3) 1g of SiO2-PPCM nanosheets were dispersed in chloroform, and then 6g of silane coupling agent KH560 was added and reacted at 40℃ for 2h to graft epoxy groups onto the surface. Then 5g of dextrorotatory polylactic acid PDLA was added and reacted at 80℃ for 25h in a three-necked flask (nitrogen). Finally, the nanosheets were obtained by stirring thoroughly, centrifuging, washing with chloroform, and drying.

[0043] Example 2

[0044] A method for preparing PDLA / PPCM Janus nanosheets includes the following steps:

[0045] (1) 20g of PPC was used as a diol and distilled under reduced pressure at 110℃ for 4h. Then it was cooled to 60℃ and the distilled PPC diol was added dropwise to 4.5g of lysine diisocyanate. 0.005g of dibutyltin dilaurate catalyst was added and the mixture was stirred at 50℃ for 3h under nitrogen. Then 150mL (0.75 / 100, g / mL) of SiO2 hollow sphere dispersion and 2g of curcumin were added and the mixture was cooled to 40℃ and stirred for 12h. The mixture was then washed with deionized water and tetrahydrofuran, centrifuged and dried to obtain SiO2 hollow spheres with PPCM grafted on the outer surface.

[0046] (2) Disperse the SiO2 hollow spheres grafted with PPCM on the outer surface in ethanol and sonicate (500W) for 1 hour to break them into pieces to obtain SiO2-PPCM nanosheets.

[0047] (3) 1g of SiO2-PPCM nanosheets were dispersed in chloroform, and then 5g of silane coupling agent KH560 was added and reacted at 40℃ for 2h to graft epoxy groups onto the surface. Then 2g of dextrorotatory polylactic acid PDLA was added and reacted at 80℃ for 20h in a three-necked flask (nitrogen). Finally, the nanosheets were obtained by stirring thoroughly, centrifuging, washing with chloroform, and drying.

[0048] Example 3

[0049] A method for preparing PDLA / PPCM Janus nanosheets includes the following steps:

[0050] (1) 20g of PPC was used as a diol and distilled under reduced pressure at 110℃ for 6h. Then it was cooled to 60℃ and the distilled PPC diol was added dropwise to 6.5g of lysine diisocyanate. 0.005g of dibutyltin dilaurate catalyst was added and the mixture was stirred at 60℃ for 5h under nitrogen. Then 250mL of SiO2 hollow sphere dispersion (0.75 / 100, g / mL) and 4g of curcumin were added and the mixture was cooled to 40℃ and stirred for 18h. Then it was washed with deionized water and tetrahydrofuran, centrifuged and dried to obtain SiO2 hollow spheres with PPCM grafted on the outer surface.

[0051] (2) SiO2 hollow spheres with PPCM grafted on the outer surface were dispersed in ethanol and ultrasonically treated (600W) for 1.5h to break them into sheets, thus obtaining SiO2-PPCM nanosheets.

[0052] (3) 1g of SiO2-PPCM nanosheets were dispersed in chloroform, and then 10g of silane coupling agent KH560 was added and reacted at 50℃ for 3.5h to graft epoxy groups onto the surface. Then 5g of dextrorotatory polylactic acid PDLA was added and reacted at 100℃ for 25h in a three-necked flask (nitrogen). Finally, the nanosheets were obtained by stirring thoroughly, centrifuging, washing with chloroform, and drying.

[0053] Application Example 1

[0054] A method for preparing a strong and tough high-barrier functional membrane material includes the following steps:

[0055] 70 parts of PLLA, 30 parts of PPC, and 0.1 parts of the PDLA / PPCM Janus nanosheets prepared in Example 1 were thoroughly dried and premixed in a high-speed mixer for 5 minutes according to the weight ratio. The mixture was then fed into an extruder for continuous melt extrusion and granulation at a screw temperature of 190°C and a screw speed of 200 rpm. The dried granules were extruded into thin sheets and rapidly cooled to below 15°C. The cooled sheets were then biaxially stretched using a flat film biaxial stretching process, followed by heat treatment and cooling to room temperature to obtain a strong and tough high-barrier functional membrane material. The stretching temperature was 70°C, the heat treatment temperature was 100°C, the transverse stretching ratio was 4 times, and the longitudinal stretching ratio was 4 times.

[0056] Application Example 2

[0057] A method for preparing a strong and tough high-barrier functional membrane material includes the following steps:

[0058] 70 parts of PLLA, 30 parts of PPC, and 0.5 parts of the PDLA / PPCM Janus nanosheets prepared in Example 1 were thoroughly dried and premixed in a high-speed mixer for 5 minutes according to the weight ratio. The mixture was then fed into an extruder for continuous melt extrusion and granulation at a screw temperature of 190°C and a screw speed of 200 rpm. The dried granules were extruded into thin sheets using a screw extruder and rapidly cooled to below 15°C. The cooled sheets were then biaxially stretched using a flat film biaxial stretching process, followed by heat treatment and cooling to room temperature to obtain a strong and tough high-barrier functional membrane material. The stretching temperature was 70°C, the heat treatment temperature was 100°C, the transverse stretching ratio was 4 times, and the longitudinal stretching ratio was 4 times.

[0059] Application Example 3

[0060] A method for preparing a strong and tough high-barrier functional membrane material includes the following steps:

[0061] 70 parts of PLLA, 30 parts of PPC, and 1.5 parts of PDLA / PPCM Janus nanosheets prepared in Example 1 were thoroughly dried and premixed in a high-speed mixer for 5 minutes according to the weight ratio. The mixture was then fed into an extruder for continuous melt extrusion and granulation at a screw temperature of 190°C and a screw speed of 200 rpm. The dried granules were extruded into thin sheets and rapidly cooled to below 15°C. The cooled sheets were then biaxially stretched using a flat film biaxial stretching process, followed by heat treatment and cooling to room temperature to obtain a strong and tough high-barrier functional membrane material. The stretching temperature was 70°C, the heat treatment temperature was 100°C, the transverse stretching ratio was 4 times, and the longitudinal stretching ratio was 4 times.

[0062] Application Example 4

[0063] A method for preparing a strong and tough high-barrier functional membrane material includes the following steps:

[0064] 70 parts of PLLA, 30 parts of PPC, and 3 parts of PDLA / PPCM Janus nanosheets prepared in Example 1 were thoroughly dried and premixed in a high-speed mixer for 5 minutes according to the weight ratio. The mixture was then fed into an extruder for continuous melt extrusion and granulation at a screw temperature of 190°C and a screw speed of 200 rpm. The dried granules were extruded into thin sheets and rapidly cooled to below 15°C. The cooled sheets were then biaxially stretched using a flat film biaxial stretching process, followed by heat treatment and cooling to room temperature to obtain a strong and tough high-barrier functional membrane material. The stretching temperature was 70°C, the heat treatment temperature was 100°C, the transverse stretching ratio was 4 times, and the longitudinal stretching ratio was 4 times.

[0065] Application Example 5

[0066] A method for preparing a strong and tough high-barrier functional membrane material includes the following steps:

[0067] 60 parts of PLLA, 40 parts of PPC, and 3 parts of PDLA / PPCM Janus nanosheets prepared in Example 1 were thoroughly dried and premixed in a high-speed mixer for 5 minutes according to the weight ratio. The mixture was then fed into an extruder for continuous melt extrusion and granulation at a screw temperature of 190°C and a screw speed of 200 rpm. The dried granules were extruded into thin sheets using a screw extruder and rapidly cooled to below 15°C. The cooled sheets were then biaxially stretched using a flat film biaxial stretching process, followed by heat treatment and cooling to room temperature to obtain a strong and tough high-barrier functional membrane material. The stretching temperature was 70°C, the heat treatment temperature was 100°C, the transverse stretching ratio was 4 times, and the longitudinal stretching ratio was 4 times.

[0068] Application Example 6

[0069] A method for preparing a strong and tough high-barrier functional membrane material includes the following steps:

[0070] 90 parts of PLLA, 10 parts of PPC, and 3 parts of PDLA / PPCM Janus nanosheets prepared in Example 1 were thoroughly dried and premixed in a high-speed mixer for 6 minutes according to the weight ratio. The mixture was then fed into an extruder for continuous melt extrusion and granulation at a screw temperature of 200°C and a screw speed of 200 rpm. The dried granules were extruded into thin sheets using a screw extruder and rapidly cooled to below 15°C. The cooled sheets were then biaxially stretched using a flat film biaxial stretching process, followed by heat treatment and cooling to room temperature to obtain a strong and tough high-barrier functional membrane material. The stretching temperature was 75°C, the heat treatment temperature was 110°C, the transverse stretching ratio was 4 times, and the longitudinal stretching ratio was 4 times.

[0071] Application Example 7

[0072] A method for preparing a strong and tough high-barrier functional membrane material includes the following steps:

[0073] 70 parts of PLLA, 30 parts of PPC, and 3 parts of PDLA / PPCM Janus nanosheets prepared in Example 2 were thoroughly dried and premixed in a high-speed mixer for 5 minutes according to the weight ratio. The mixture was then fed into an extruder for continuous melt extrusion and granulation at a screw temperature of 190°C and a screw speed of 200 rpm. The dried granules were extruded into thin sheets using a screw extruder and rapidly cooled to below 15°C. The cooled sheets were then biaxially stretched using a flat film biaxial stretching process, followed by heat treatment and cooling to room temperature to obtain a strong and tough high-barrier functional membrane material. The stretching temperature was 70°C, the heat treatment temperature was 100°C, the transverse stretching ratio was 4 times, and the longitudinal stretching ratio was 4 times.

[0074] Application Example 8

[0075] A method for preparing a strong and tough high-barrier functional membrane material includes the following steps:

[0076] 70 parts of PLLA, 30 parts of PPC, and 3 parts of PDLA / PPCM Janus nanosheets prepared in Example 3 were thoroughly dried and premixed in a high-speed mixer for 5 minutes according to the weight ratio. The mixture was then fed into an extruder for continuous melt extrusion and granulation at a screw temperature of 190°C and a screw speed of 200 rpm. The dried granules were extruded into thin sheets using a screw extruder and rapidly cooled to below 15°C. The cooled sheets were then biaxially stretched using a flat film biaxial stretching process, followed by heat treatment and cooling to room temperature to obtain a strong and tough high-barrier functional membrane material. The stretching temperature was 70°C, the heat treatment temperature was 100°C, the transverse stretching ratio was 4 times, and the longitudinal stretching ratio was 4 times.

[0077] Application Example 9

[0078] A method for preparing a strong and tough high-barrier functional membrane material includes the following steps:

[0079] 70 parts of PLLA, 30 parts of PPC, and 3 parts of PDLA / PPCM Janus nanosheets prepared in Example 1 were thoroughly dried and premixed in a high-speed mixer for 5 minutes according to the weight ratio. The mixture was then fed into an extruder for continuous melt extrusion and granulation at a screw temperature of 190°C and a screw speed of 150 rpm. After granulation, the granules were dried in a vacuum oven. Thin sheets were prepared by casting using a casting machine and rapidly cooled with cooling water at a screw temperature of 200°C and a screw speed of 200 rpm. The preforms were simultaneously blown and stretched at 70°C using a biaxial stretching process, followed by heat treatment and cooling to room temperature to obtain a strong and tough high-barrier functional membrane material. The heat treatment temperature was 100°C, the blow-up ratio was 3 times, and the stretching ratio was 5 times.

[0080] Application Example 10

[0081] A method for preparing a strong and tough high-barrier functional membrane material includes the following steps:

[0082] 60 parts of PLLA, 40 parts of PPC, and 3 parts of PDLA / PPCM Janus nanosheets prepared in Example 1 were thoroughly dried and premixed in a high-speed mixer for 5 minutes according to the weight ratio. The mixture was then fed into an extruder for continuous melt extrusion and granulation at a screw temperature of 190°C and a screw speed of 150 rpm. After granulation, the granules were dried in a vacuum oven. Thin sheets were prepared by casting using a casting machine and rapidly cooled with cooling water at a screw temperature of 200°C and a screw speed of 200 rpm. The preforms were simultaneously blown and stretched at 70°C using a biaxial stretching process, followed by heat treatment and cooling to room temperature to obtain a strong and tough high-barrier functional membrane material. The heat treatment temperature was 100°C, the blow-up ratio was 3 times, and the stretching ratio was 5 times.

[0083] Application Example 11

[0084] A method for preparing a strong and tough high-barrier functional membrane material includes the following steps:

[0085] 90 parts of PLLA, 10 parts of PPC, and 3 parts of PDLA / PPCM Janus nanosheets prepared in Example 1 were thoroughly dried and premixed in a high-speed mixer for 6 minutes according to the weight ratio. The mixture was then fed into an extruder for continuous melt extrusion and granulation at a screw temperature of 200°C and a screw speed of 150 rpm. After granulation, the granules were dried in a vacuum oven. Thin sheets were prepared by casting using a casting machine and rapidly cooled with cooling water at a screw temperature of 200°C and a screw speed of 200 rpm. The preforms were simultaneously blown and stretched at 75°C using a biaxial stretching process, followed by heat treatment and cooling to room temperature to obtain a strong and tough high-barrier functional membrane material. The heat treatment temperature was 110°C, the blow-up ratio was 3 times, and the stretching ratio was 5 times.

[0086] Comparative Example 1

[0087] Compared to Application Example 1, without adding PDLA / PPCM Janus nanosheets, and with other conditions remaining unchanged, the specific details are as follows:

[0088] 70 parts PLLA and 30 parts PPC were thoroughly dried and then premixed in a high-speed mixer for 5 minutes according to the weight ratio. The mixture was then fed into an extruder for continuous melt extrusion and granulation at a screw temperature of 190℃ and a screw speed of 200 rpm. The dried granules were extruded into sheets using a screw extruder and rapidly cooled to below 15℃. The cooled sheets were then biaxially stretched using a flat film biaxial stretching process, followed by heat treatment and cooling to room temperature to obtain the functional film material. The stretching temperature was 70℃, the heat treatment temperature was 100℃, and the transverse stretching ratio was 4 times, as was the longitudinal stretching ratio.

[0089] Comparative Example 2

[0090] Compared to Application Example 1, the number of PDLA / PPCM Janus nanosheets added was changed to 5, while other conditions remained unchanged, as follows:

[0091] 70 parts of PLLA, 30 parts of PPC, and 5 parts of PDLA / PPCM Janus nanosheets prepared in Example 1 were thoroughly dried and premixed in a high-speed mixer for 5 minutes according to the weight ratio. The mixture was then fed into an extruder for continuous melt extrusion and granulation at a screw temperature of 190°C and a screw speed of 200 rpm. The dried granules were extruded into thin sheets using a screw extruder and rapidly cooled to below 15°C. The cooled sheets were then biaxially stretched using a flat film biaxial stretching process, followed by heat treatment and cooling to room temperature to obtain the functional membrane material. The stretching temperature was 70°C, the heat treatment temperature was 100°C, the transverse stretching ratio was 4 times, and the longitudinal stretching ratio was 4 times.

[0092] Comparative Example 3

[0093] Compared to Application Example 1, the number of PLLA and PPC added is changed to 50, while other conditions remain the same, as follows:

[0094] 50 parts of PLLA, 50 parts of PPC, and 0.1 parts of the PDLA / PPCM Janus nanosheets prepared in Example 1 were thoroughly dried and premixed in a high-speed mixer for 5 minutes according to the weight ratio. The mixture was then fed into an extruder for continuous melt extrusion and granulation at a screw temperature of 190°C and a screw speed of 200 rpm. The dried granules were extruded into thin sheets using a screw extruder and rapidly cooled to below 15°C. The cooled sheets were then biaxially stretched using a flat film biaxial stretching process, followed by heat treatment and cooling to room temperature to obtain the functional membrane material. The stretching temperature was 70°C, the heat treatment temperature was 100°C, the transverse stretching ratio was 4 times, and the longitudinal stretching ratio was 4 times.

[0095] Comparative Example 4

[0096] Compared to Application Example 5, the number of PDLA / PPCM Janus nanosheets added was changed to 5, while other conditions remained unchanged, as follows:

[0097] 60 parts of PLLA, 40 parts of PPC, and 5 parts of PDLA / PPCM Janus nanosheets prepared in Example 1 were thoroughly dried and premixed in a high-speed mixer for 5 minutes according to the weight ratio. The mixture was then fed into an extruder for continuous melt extrusion and granulation at a screw temperature of 190°C and a screw speed of 200 rpm. The dried granules were extruded into thin sheets using a screw extruder and rapidly cooled to below 15°C. The cooled sheets were then biaxially stretched using a flat film biaxial stretching process, followed by heat treatment and cooling to room temperature to obtain the functional membrane material. The stretching temperature was 70°C, the heat treatment temperature was 100°C, the transverse stretching ratio was 4 times, and the longitudinal stretching ratio was 4 times.

[0098] Comparative Example 5

[0099] Compared to Application Example 4, the flat film was not subjected to biaxial stretching, while other conditions remained unchanged, as follows:

[0100] 70 parts of PLLA, 30 parts of PPC, and 3 parts of PDLA / PPCM Janus nanosheets prepared in Example 1 were thoroughly dried and premixed in a high-speed mixer for 5 minutes according to the weight ratio. The mixture was then fed into an extruder for continuous melt extrusion and granulation at a screw temperature of 190°C and a screw speed of 200 rpm. The dried granules were extruded into thin sheets through a screw extruder and rapidly cooled to below 15°C to obtain the functional membrane material.

[0101] Comparative Example 6

[0102] Compared to Application Example 9, without the addition of PDLA / PPCM Janus nanosheets, and with other conditions remaining unchanged, the specific details are as follows:

[0103] 70 parts PLLA and 30 parts PPC were thoroughly dried and then premixed in a high-speed mixer for 5 minutes according to the weight ratio. The mixture was then fed into an extruder for continuous melt extrusion and granulation at a screw temperature of 190℃ and a screw speed of 150 rpm. The granules were then dried in a vacuum oven. Thin sheets were prepared by casting using a casting machine and rapidly cooled with cooling water at a screw temperature of 200℃ and a screw speed of 200 rpm. The preforms were simultaneously inflated and stretched at 70℃ using a biaxial stretching process, followed by heat treatment and cooling to room temperature to obtain the functional membrane material. The heat treatment temperature was 100℃, the inflation ratio was 3 times, and the stretching ratio was 5 times.

[0104] Comparative Example 7

[0105] Compared to Application Example 9, the biaxial stretching of the membrane was not performed, while other conditions remained unchanged, as follows:

[0106] 70 parts of PLLA, 30 parts of PPC, and 3 parts of PDLA / PPCM Janus nanosheets prepared in Example 1 were thoroughly dried and premixed in a high-speed mixer for 5 minutes according to the weight ratio. The mixture was then fed into an extruder for continuous melt extrusion and granulation at a screw temperature of 190°C and a screw speed of 150 rpm. After granulation, the granules were dried in a vacuum oven. Thin sheets were then prepared by casting using a casting machine and rapidly cooled with cooling water at a screw temperature of 200°C and a screw speed of 200 rpm to obtain the functional membrane material.

[0107] Comparative Example 8

[0108] Compared to Application Example 1, PPC, PPCM, PLLA, PDLA, curcumin, and SiO2 hollow microspheres (pure nanosheets, without any modification or grafting) were added together, with other conditions remaining unchanged, as follows:

[0109] 70 parts PPC, 30 parts PLLA, 1 part PPCM, 1 part PDLA, 3 parts curcumin, and 3 parts SiO2 hollow microspheres were thoroughly dried and premixed in a high-speed mixer for 5 minutes according to the weight ratio. The mixture was then fed into an extruder for continuous melt extrusion and granulation at a screw temperature of 190℃ and a screw speed of 200 rpm. The dried granules were extruded into thin sheets and rapidly cooled to below 15℃. The cooled sheets were then biaxially stretched using a flat film biaxial stretching process, followed by heat treatment and cooling to room temperature to obtain the functional membrane material. The stretching temperature was 70℃, the heat treatment temperature was 100℃, the transverse stretching ratio was 4 times, and the longitudinal stretching ratio was 4 times.

[0110] After the tough, high-barrier functional membrane materials obtained in Application Examples 1-11 were thoroughly dried, their tensile properties at room temperature were determined according to the standard method of GB / T 1040-2006. The tensile rate was set to 10 mm / min, and at least 5 specimens of the same sample were tested and the average value was taken. The results are shown in Table 1.

[0111] Table 1

[0112] Application examples Fracture strength (MPa) Elongation at break (%) Application Example 1 138 332 Application Example 2 140 339 Application Example 3 143 344 Application Example 4 146 371 Application Example 5 136 389 Application Example 6 155 299 Application Example 7 145 372 Application Example 8 145 308 Application Example 9 147 332 Application Example 10 137 381 Application Example 11 156 293

[0113] After the tough, high-barrier functional membrane materials obtained in Application Examples 1-11 were thoroughly dried, their oxygen permeability was tested using an oxygen permeability tester according to the GB / T 1038 standard method. The test conditions were 20°C, 30% relative humidity, 20 μm sample thickness, and 38.48 cm² membrane test area. 2 The moisture permeability of the material was tested using a water vapor transmission rate tester according to the standard method of GB / T 1037. The test conditions were 38℃, relative humidity 95%, sample thickness 20μm, and membrane test area 33cm². 2The sensitivity of the film to NH3 was determined at 90% RH, as packaging containing fresh meat generally has a higher RH. The UV-Vis spectrum of the film varied with the NH3 content. With increasing NH3 concentration, the maximum absorbance at 420 nm decreased, while the absorbance at 540 nm increased. Yellow absorbs light at wavelengths corresponding to its complementary color, blue at (~400~480 nm), red at wavelengths corresponding to their complementary colors, and green at (~495~570 nm). Therefore, the absorbance ratio at 540 nm and 420 nm (A540 / A420), i.e., the wavelength of each complementary color, indicates an increase in red intensity compared to yellow intensity; a higher A540 / A420 value indicates a deeper red. The A540 / A420 value increases with increasing NH3 concentration, indicating a gradual shift in the film's color from yellow to red. The corrected fitting curves show a good linear relationship between the A540 / A420 value and the NH3 concentration in the ranges of 0 ppm and 300 ppm. This is achieved through the formula:

[0114] LOD = 3K / N

[0115] The limit of detection (LOD) for NH3 was determined for the robust, high-barrier functional membrane material. K represents the standard deviation of the blank measurement (the standard deviation of the A540 / A420 values ​​of ten measurements of the PLLA / PPC blend film without Janus nanosheets), and N represents the slope of the calibration curve. The ultraviolet protection factor (UPF) was calculated based on the ultraviolet transmittance in the 290 nm–400 nm range, and the results are shown in Table 2.

[0116] Table 2

[0117]

[0118] The functional membrane materials obtained in Comparative Examples 1-8 were subjected to the same testing procedure to determine their performance and quality. The results are shown in Tables 3 and 4.

[0119] Table 3

[0120] Comparative Example Fracture strength (MPa) Elongation at break (%) Comparative Example 1 79 88 Comparative Example 2 104 102 Comparative Example 3 62 158 Comparative Example 4 65 138 Comparative Example 5 30 149 Comparative Example 6 59 106 Comparative Example 7 31 136 Comparative Example 8 32 67

[0121] Table 4

[0122]

[0123]

[0124] As shown in Tables 1 and 3, the tensile strength and elongation at break of the polylactic acid (PLA) and polypropylene carbonate (PPCM) blend (Comparative Example 1) significantly improved after the addition of PDLA / PPCM Janus nanosheets (Application Examples 1-11) compared to direct blending. This indicates that the PDLA / PPCM Janus nanosheets exhibited higher uniform dispersion and compatibilization efficiency, thus enhancing the mechanical properties of the PLA blend, such as tensile strength and elongation at break. In Comparative Example 8, the addition of unmodified SiO2 hollow microspheres and ungrafted curcumin did not significantly improve any of the properties compared to the pure sample. This suggests that the compatibility of the two polymers is poor, and the addition of SiO2 hollow microspheres did not provide adequate compatibilization, resulting in poor dispersibility. Tables 2 and 4 show that ungrafted curcumin may aggregate in the blend, affecting its responsiveness to ammonia. As can be seen from PLLA / PPC blends with different PDLA / PPCM Janus nanosheet contents (Application Examples 1-4), the compatibility is significantly improved with the addition of Janus nanosheets, and the mechanical properties of the blends are also significantly improved. However, when the content of PDLA / PPCM Janus nanosheets is too high (Comparative Examples 2, 4), the compatibility and mechanical properties of the blends decrease to some extent. This is because too many nanosheets accumulate at the interface between the two phases and are distributed in the two phases, affecting the mechanical properties of the blends. In addition, the barrier properties of the material are also significantly improved by the bistretching process (Comparative Examples 5, 7). When the blends are not stretched, their barrier properties are poor. On the other hand, the curcumin grafted in this invention further improves its functionality, giving the blend film good UV resistance (Application Examples 1-11) far exceeding the excellent level (UPF50+), and a low ammonia detection limit. The stereocomposite crystals formed by PDLA grafted onto Janus nanosheets and the matrix PLLA further enhance the strength of the polymer blend film (Application Examples 1-11, Comparative Examples 1 and 6). In summary, this invention prepares a strong and tough high-barrier functional membrane material that is simple and practical, with high strength and good toughness, good UV resistance and sensitive ammonia detection capability, and is easy to industrialize. It is expected to be applied in fields such as film packaging materials and agricultural greenhouse film materials.

[0125] The embodiments provided above are not intended to limit the scope of the invention, nor are the described steps intended to limit the order of execution. Any obvious modifications made to the invention by those skilled in the art based on existing common knowledge also fall within the scope of protection defined by the claims.

Claims

1. A tough, high-barrier functional membrane material, characterized in that, The raw materials include the following parts by weight: 60-90 parts of polylactic acid (PLA), 10-40 parts of polypropylene carbonate (PPC), and 0.1-3 parts of PDLA / PPCM Janus nanosheets. PDLA / PPCM Janus nanosheets were created using SiO2 hollow spheres as templates, with curcumin-grafted polypropylene carbonate (PPCM) and dextrorotatory polylactic acid (D-lactic acid) modified on both sides of the template, respectively. The specific steps of its preparation method are as follows: 60-90 parts of polylactic acid (PLA), 10-40 parts of polypropylene carbonate (PPC), and 0.1-3 parts of PDLA / PPCM Janus nanosheets are blended at 190-200 °C for 5-6 min, then extruded into a film or sheet, and then rapidly cooled to below 15 °C to reduce its crystallinity to less than 10%. The cooled film or sheet is then biaxially stretched at 70-75 °C using a flat film biaxial stretching process, and then heat-treated at 100-110 °C to obtain the tough, high-barrier functional membrane material. or, 60-90 parts of polylactic acid (PLA), 10-40 parts of polypropylene carbonate (PPC), and 0.1-3 parts of PDLA / PPCM Janus nanosheets were blended at 190-200 °C for 5-6 min. The mixture was then used to form a preform through a tubular die. The preform was rapidly cooled to below 15 °C to reduce its crystallinity to less than 10%. The cooled preform was then blown, stretched, and shaped at 70-75 °C using a biaxial stretching process. Finally, it was heat-treated at 100-110 °C to obtain the tough, high-barrier functional membrane material. The preparation method of PDLA / PPCM Janus nanosheets is as follows: (1) Polypropylene carbonate diol reacts with lysine diisocyanate first, and then SiO2 hollow sphere dispersion and curcumin are added to obtain SiO2 hollow spheres with PPCM grafted on the outer surface. The molar ratio of polypropylene carbonate diol to lysine diisocyanate is 1:2-3; The concentration of the SiO2 hollow sphere dispersion is 0.5-0.75 g / 100 mL; The mass-to-volume ratio of polypropylene carbonate diol to SiO2 hollow sphere dispersion is 5-10 / 100, g / mL; the mass-to-volume ratio of curcumin to SiO2 hollow sphere dispersion is 1-5 / 100, g / mL. (2) The SiO2 hollow spheres grafted with PPCM on the outer surface are crushed to obtain SiO2-PPCM nanosheets, which are then reacted with silane coupling agent and dextrorotatory polylactic acid to obtain the PDLA / PPCM Janus nanosheets.

2. The robust high-barrier functional membrane material according to claim 1, characterized in that, In step (1), the SiO2 hollow sphere dispersion is prepared by dispersing SiO2 hollow spheres in tetrahydrofuran; the particle size of the SiO2 hollow spheres is 4.5-5.5 μm.

3. The robust high-barrier functional membrane material according to claim 1, characterized in that, In step (2), the conditions for ultrasonic fragmentation are: ultrasonic treatment at 500-600 W for 1-1.5 h; The reaction conditions were as follows: SiO2-PPCM nanosheets were dispersed in chloroform, then silane coupling agent KH560 was added and reacted at 40-50 °C for 2-3.5 h to graft epoxy groups onto the surface, then dextrorotatory polylactic acid PDLA was added and reacted at 80-100 °C for 20-25 h. Finally, the mixture was thoroughly stirred, centrifuged, washed with chloroform, and dried to obtain the Janus nanosheets.

4. The strong and tough high-barrier functional membrane material according to claim 1, characterized in that, In step (2), the silane coupling agent is KH560; the mass ratio of SiO2-PPCM nanosheets, dextrorotatory polylactic acid and silane coupling agent is 1:2-5:5-10.

5. A method for preparing a strong and tough high-barrier functional membrane material according to any one of claims 1-4, characterized in that, Includes the following steps: 60-90 parts of polylactic acid (PLA), 10-40 parts of polypropylene carbonate (PPC), and 0.1-3 parts of PDLA / PPCM Janus nanosheets are blended at 190-200 °C for 5-6 min, then extruded into a film or sheet, and then rapidly cooled to below 15 °C to reduce its crystallinity to less than 10%. The cooled film or sheet is then biaxially stretched at 70-75 °C using a flat film biaxial stretching process, and then heat-treated at 100-110 °C to obtain the tough, high-barrier functional membrane material. or, 60-90 parts of polylactic acid (PLA), 10-40 parts of polypropylene carbonate (PPC), and 0.1-3 parts of PDLA / PPCM Janus nanosheets are blended at 190-200 °C for 5-6 min. The mixture is then formed into a preform using a tubular die. The preform is rapidly cooled to below 15 °C to reduce its crystallinity to less than 10%. The cooled preform is then blown, stretched, and shaped at 70-75 °C using a biaxial stretching process. Finally, it is heat-treated at 100-110 °C to obtain the tough, high-barrier functional membrane material.

6. The application of the tough, high-barrier functional membrane material according to claim 1, characterized in that, Used to prepare film packaging materials or agricultural greenhouse film materials.

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