A degradable organic-inorganic composite film and a preparation method and application thereof

Abstract

The application discloses a degradable organic-inorganic composite film and a preparation method and application thereof, and belongs to the technical field of composite materials. The method comprises the following steps: (1) preparing a calcium phosphate nanocluster precursor by using an organic amine stabilizer, a calcium source, a phosphorus source and an organic solvent, and further separating the calcium phosphate nanocluster; (2) mixing the calcium phosphate nanocluster and a natural polymer material to prepare a uniformly dispersed emulsion, wherein the natural polymer material comprises carboxymethyl chitosan and an alginate, and film is prepared by using the emulsion; in the film preparation process, an evaporation-induced self-assembly process occurs, the calcium phosphate nanocluster is phase changed into crystalline rod-shaped hydroxyapatite nanocrystals, and the natural polymer material is combined, so that the degradable organic-inorganic composite film is obtained. The mechanical property of the organic-inorganic composite film is adjustable, the organic-inorganic composite film can be directly degraded in soil, and has a wide application prospect in the fields of packaging, agriculture, medical treatment and the like.

Description

Technical Field

[0001] This invention relates to the field of composite materials technology, specifically to a biodegradable organic-inorganic composite film, its preparation method, and its application. Background Technology

[0002] Biodegradable materials are materials that meet usage requirements during their lifespan but easily break down into smaller molecules through physical, chemical, or biological processes after use, thus avoiding long-term environmental pollution and offering good environmental safety. Currently, the expansion of human production activities has further exacerbated resource consumption and ecological problems. Society is increasingly emphasizing the efficient use of resources and environmental protection, leading to the rapid development of biodegradable materials due to their low dependence on petroleum resources and minimal environmental pollution. Biodegradable materials have wide applications in packaging, agriculture, medicine, and other fields, effectively mitigating negative impacts on the environment and resources, promoting sustainable development, and fulfilling specific functions such as material encapsulation and delivery.

[0003] Biodegradable materials can be broadly classified into biodegradable materials, photodegradable materials, and chemically degradable materials based on their specific degradation pathways. Biodegradable materials mainly include natural polymers such as cellulose, polypeptides, chitin, and collagen, and synthetic polymers such as polyamino acids, polyesters, and polylactic acid. Natural polymers have superior environmental compatibility compared to synthetic polymers, making them a more environmentally friendly category of materials, enabling the constituent substances to completely return to the ecological cycle after their lifespan. For example, Chinese patent document CN118580540A discloses a method for preparing a high-temperature, high-humidity, easily biodegradable plastic film. The biodegradable plastic film prepared according to this method has excellent mechanical properties and degradation ability, but requires the introduction of insect eggs and composting to achieve degradation. Chinese patent document CN102181077A discloses a fully biodegradable film whose main formulation components are starch and polyvinyl alcohol, achieving the EN13432 standard's requirements of 180-day degradation and 90% disintegration over 12 weeks. In the field of biodegradation, composting or hydrothermal reactions under specific conditions are widely used to degrade materials, which significantly increases the cost of using and recycling materials.

[0004] Simplifying the degradation conditions of materials to enable them to complete in the natural environment, thus achieving true natural degradability, is currently one of the hot research topics in biodegradable materials. For example, Chinese patent document CN118048023A discloses a naturally degradable polymer material, its preparation method, and its application. This material uses bio-based polymer materials, cellulase, amylase, pyridine diphosphate, pyridine triphosphate, modified starch, and other raw materials. Through graft modification, extrusion granulation, and other processes, it produces a material that can be completely decomposed by bacteria and microorganisms in the natural environment, eliminating the need for high-temperature industrial collection and degradation such as industrial composting. However, this method involves many raw materials and relatively complex processes. If natural polymer materials are directly used to prepare biodegradable composite materials for natural environments, the disadvantage of insufficient toughness of natural polymer materials needs to be overcome to meet application requirements. Furthermore, preparing soil-degradable materials that combine flexibility and toughness through the composite of natural polymer materials and mineral-based materials still presents significant challenges. Therefore, developing an organic-inorganic composite material that can degrade in a natural soil environment has significant research and application value. Summary of the Invention

[0005] This invention provides a biodegradable organic-inorganic composite film and its preparation method. The organic-inorganic composite film has adjustable mechanical properties and high toughness. The inorganic structural units are uniformly dispersed in the organic matrix in the form of small-sized crystals with high aspect ratio, which effectively improves the organic-inorganic phase interface. Moreover, it can be naturally and directly degraded in soil and has broad application prospects in packaging, agriculture, medical and other fields.

[0006] The specific technical solution adopted is as follows:

[0007] A method for preparing a biodegradable organic-inorganic composite film includes the following steps:

[0008] (1) A calcium phosphate nanocluster precursor was prepared using an organic amine stabilizer, a calcium source, a phosphorus source, and an organic solvent, and then the calcium phosphate nanoclusters were obtained by further separation.

[0009] (2) A uniformly dispersed emulsion is prepared by mixing calcium phosphate nanoclusters and natural polymer materials. The natural polymer materials include carboxymethyl chitosan and alginate. The emulsion is used to form a film. During the film-forming process, the calcium phosphate nanoclusters are transformed into crystalline rod-shaped hydroxyapatite nanocrystals and combined with the natural polymer materials to obtain the biodegradable organic-inorganic composite film.

[0010] The method of this invention first prepares a calcium phosphate nanocluster colloid, which serves as a precursor for inorganic crystallization units. Natural polymers, carboxymethyl chitosan and alginate, together constitute an organic network structure. During the formation of a composite film in the emulsion, the calcium phosphate nanoclusters gradually transform into crystalline rod-shaped hydroxyapatite nanocrystals. These nanocrystals bond ionicly with carboxyl groups in the organic network structure and hydrogenally with hydroxyl groups in the organic network structure via phosphate ions. This effectively improves the organic-inorganic phase interface, and the small-sized, high aspect ratio rod-shaped crystals provide a large specific surface area, enhancing the bonding strength between the crystals and the organic network. By adjusting the amount of calcium phosphate nanoclusters added, composite films with different mechanical strengths and toughnesses can be obtained.

[0011] Preferably, the organic amine stabilizer is triethylamine, the molar ratio of the organic amine stabilizer, calcium source and phosphorus source is 10-20:0.3-1.7:1, and the concentration of calcium source in the system is 0.01-0.5 mol / L.

[0012] More preferably, the organic solvent is ethanol, the calcium source is calcium chloride dihydrate, and the phosphorus source is phosphoric acid; the molar ratio of the organic amine stabilizer, calcium source, and phosphorus source is 15–20:1–1.2:1, and the concentration of the calcium source in the system is 0.03–0.1 mol / L. Within these ranges, it is beneficial to promote the formation of calcium phosphate nanoclusters while avoiding unnecessary increases in raw material costs.

[0013] Specifically, calcium phosphate nanoclusters precursors are prepared by reacting organic amine stabilizers, calcium sources, phosphorus sources and organic solvents at 20-30°C for 10-15 hours, and then separated by centrifugation and washing.

[0014] Preferably, in step (2), the mass ratio of calcium phosphate nanoclusters, carboxymethyl chitosan and alginate is 1:0.3-3.6:0.05-0.8.

[0015] More preferably, the alginate is sodium alginate.

[0016] Preferably, the film-forming method employs a casting method, during which an evaporation-induced self-assembly process occurs.

[0017] The present invention also provides a method for preparing the biodegradable organic-inorganic composite film and the biodegradable organic-inorganic composite film obtained therefrom.

[0018] Furthermore, the biodegradable organic-inorganic composite film contains 52-76 wt% natural polymer materials and 24-48 wt% hydroxyapatite (calculated by thermogravimetric analysis of the product film); preferably, it contains 52-62 wt% natural polymer materials and 38-48 wt% hydroxyapatite. Under the preferred ratio, the composite film has higher toughness.

[0019] The hydroxyapatite is a nanorod-shaped crystal, preferably 10-25 nm in length and 2-3 nm in diameter.

[0020] The biodegradable organic-inorganic composite film provided by this invention is biodegradable in soil. After being buried in soil for 30 days, the mass loss is more than 85%.

[0021] The present invention also provides the application of the aforementioned biodegradable organic-inorganic composite film in the fields of packaging, agriculture, or medicine.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0023] (1) The preparation method of the biodegradable organic-inorganic composite film provided by the present invention is simple and the reaction conditions are mild. The prepared organic-inorganic composite film is transparent or semi-transparent and has a tensile strength of 17-20 MPa and an elastic modulus of 100-800 MPa. It is easy to degrade in moist soil, disintegrate its own structure, and only generates calcium phosphate minerals, trehalose, chitosan organic matter and their metabolites. It has a short residual time and small residual amount in the soil, and causes slight damage and pollution to the soil. The degradation products also help plant growth. It has broad application prospects in soluble packaging, agriculture or medical fields.

[0024] (2) In this invention, inorganic structural units are introduced to enhance the toughness of the natural polymer material-based film. The inorganic structural units are uniformly dispersed in the natural polymer material matrix in the form of small-sized crystals with high aspect ratio, which effectively improves the organic-inorganic phase interface, so that the composite film has mechanical properties that meet the requirements of use, while not affecting environmental compatibility. Attached Figure Description

[0025] Figure 1 The image shows a comparison of optical photographs taken 30 days after the biodegradable organic-inorganic composite film prepared in Example 1 was buried in soil. The left image is before burial, and the right image is after burial.

[0026] Figure 2 The images shown are scanning electron microscope (SEM) and transmission electron microscope (TEM) images of the biodegradable organic-inorganic composite film prepared in Example 1. The left image is a scanning electron microscope (SEM) image, and the right image is a transmission electron microscope (TEM) image.

[0027] Figure 3The powder X-ray diffraction patterns of the biodegradable organic-inorganic composite film prepared in Example 1 are compared with those of carboxymethyl chitosan and hydroxyapatite.

[0028] Figure 4 The image shows the tensile test results of the biodegradable organic-inorganic composite film prepared in Example 1. Detailed Implementation

[0029] The present invention will be further illustrated below with reference to the embodiments and accompanying drawings. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Operating methods not specifically described in the following embodiments are generally performed under conventional conditions or as recommended by the manufacturer. Contents not described in detail in this specification are prior art known to those skilled in the art. Unless otherwise specified, the experimental materials used in the embodiments below can be purchased from conventional biochemical reagent companies.

[0030] Example 1

[0031] 5.88 g of calcium chloride dihydrate was dissolved in 800 mL of ethanol to obtain an ethanol solution of calcium chloride. Then, 110.9 mL of triethylamine was added and stirred for 30 minutes. After stirring, an ethanol solution of phosphoric acid (3.52 g of phosphoric acid dispersed in 40 mL of ethanol) was slowly added dropwise. The mixture was stirred at 25 °C for 12 hours to obtain a calcium phosphate nanocluster precursor. A white gel-like precipitate was obtained by centrifugation. The precipitate was washed with a small amount of deionized water and centrifuged again to obtain a calcium phosphate nanocluster colloid.

[0032] 0.25 g of calcium phosphate nanoclusters were dispersed in a mixed solution of 12 mL of carboxymethyl chitosan aqueous solution (3 wt%) and 12 mL of sodium alginate aqueous solution (0.5 wt%). After stirring for 3 hours, an emulsion was obtained. The emulsion was then ultrasonically removed to eliminate bubbles and transferred to a Φ=10 cm petri dish for casting (drying at 25℃). During the film formation process, an evaporation-induced self-assembly process occurred, and the calcium phosphate nanoclusters transformed into crystalline rod-shaped hydroxyapatite nanocrystals that combined with the natural polymer material to obtain a biodegradable organic-inorganic composite film.

[0033] Thermogravimetric analysis of the product film revealed that the organic-inorganic composite film obtained in this embodiment contains 70 wt% natural polymer materials and 30 wt% hydroxyapatite.

[0034] Optical photographs of the organic-inorganic composite film before and after 30 days of burial in soil, for example... Figure 1 As shown, it is a transparent film that transforms into mineral-like particles after being buried in soil for 30 days. The mass loss was measured to be 88.56%, indicating that it is easily degraded in soil.

[0035] The cross-section and slices of the organic-inorganic composite film were observed using scanning electron microscopy and transmission electron microscopy, such as... Figure 2 As shown, its interior is uniform and dense, with rod-shaped crystals distributed in the organic matrix, with a length of 10-25 nm and a diameter of 2-3 nm.

[0036] The powder X-ray diffraction patterns of the biodegradable organic-inorganic composite film are compared with those of carboxymethyl chitosan and hydroxyapatite, as shown in the figure below. Figure 3 As shown, the presence of hydroxyapatite in the thin film is demonstrated.

[0037] Tensile tests were performed on the organic-inorganic composite film, and the results are as follows: Figure 4 As shown, the strain at fracture is 52.18%, the tensile strength is 16.67 MPa, and the elastic modulus is 447 MPa. The mechanical properties meet the requirements for use in ordinary soluble packaging.

[0038] Example 2

[0039] 0.75 g of the calcium phosphate nanoclusters colloid prepared in Example 1 was dispersed in a mixed solution of 12 mL of carboxymethyl chitosan aqueous solution (3 wt%) and 12 mL of sodium alginate aqueous solution (0.5 wt%). After stirring for 3 hours, an emulsion was obtained. The emulsion was ultrasonically removed to eliminate bubbles and then transferred to a petri dish with a diameter of 10 cm for casting (drying at 25°C under ventilation). During the film formation process, an evaporation-induced self-assembly process occurred, and the calcium phosphate nanoclusters transformed into crystalline rod-shaped hydroxyapatite nanocrystals that combined with natural polymer materials to obtain a biodegradable organic-inorganic composite film.

[0040] Thermogravimetric analysis of the film revealed that the organic-inorganic composite film obtained in this embodiment contains 53.5 wt% natural polymer materials and 47.5 wt% hydroxyapatite. The organic-inorganic composite film exhibits a strain of 27.81% at fracture, a tensile strength of 18.74 MPa, and an elastic modulus of 721 MPa. It is also readily degraded in soil, showing an 86.13% mass loss after 30 days of landfilling.

[0041] Example 3

[0042] Take 0.10 g of the calcium phosphate nanocluster colloid prepared in Example 1 and disperse it in a mixed solution prepared by 12 mL of carboxymethyl chitosan aqueous solution (3 wt%) and 12 mL of sodium alginate aqueous solution (0.5 wt%). After stirring for 3 hours, an emulsion is obtained. The emulsion is ultrasonically removed to eliminate bubbles and transferred to a petri dish with a diameter of 10 cm for casting (drying at 25°C under ventilation). During the film formation process, an evaporation-induced self-assembly process occurs, and the calcium phosphate nanoclusters transform into crystalline rod-shaped hydroxyapatite nanocrystals that combine with natural polymer materials to obtain a biodegradable organic-inorganic composite film.

[0043] Thermogravimetric analysis of the film revealed that the organic-inorganic composite film obtained in this embodiment contains 75.7 wt% natural polymer materials and 24.3 wt% hydroxyapatite. The organic-inorganic composite film exhibits a fracture strain of 81.57%, a tensile strength of 14.61 MPa, and an elastic modulus of 103 MPa. It is also readily degraded in soil, showing a 90.46% mass loss after 30 days of landfilling.

[0044] The embodiments described above provide a detailed explanation of the technical solutions of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, additions, or similar substitutions made within the scope of the principles of the present invention should be included within the protection scope of the present invention.

Claims

1. The application of biodegradable organic-inorganic composite films in agriculture, characterized in that, The method for preparing the biodegradable organic-inorganic composite film includes the following steps: (1) A calcium phosphate nanocluster precursor was prepared using an organic amine stabilizer, a calcium source, a phosphorus source and an organic solvent, and then the calcium phosphate nanoclusters were obtained by further separation; (2) A uniformly dispersed emulsion is prepared by mixing calcium phosphate nanoclusters and natural polymer materials. The natural polymer materials are carboxymethyl chitosan and alginate. The mass ratio of calcium phosphate nanoclusters, carboxymethyl chitosan and alginate is 1:0.3-3.6:0.05-0.

8. The emulsion is used to form a film. During the film formation process, the calcium phosphate nanoclusters are transformed into crystalline rod-shaped hydroxyapatite nanocrystals and combined with the natural polymer materials to obtain the biodegradable organic-inorganic composite film. The film-forming method uses the casting method, during which an evaporation-induced self-assembly process occurs; The biodegradable organic-inorganic composite film comprises 52-62 wt% natural polymer materials and 38-48 wt% hydroxyapatite; the hydroxyapatite is a nanorod-shaped crystal with a length of 10-25 nm and a diameter of 2-3 nm.

2. The application according to claim 1, characterized in that, The organic amine stabilizer is triethylamine, and the molar ratio of organic amine stabilizer, calcium source and phosphorus source is 10-20:0.3-1.7:

1. The concentration of calcium source in the system is 0.01-0.5 mol / L.

3. The application according to claim 1, characterized in that, The organic solvent is ethanol, the calcium source is calcium chloride dihydrate, and the phosphorus source is phosphoric acid; the molar ratio of organic amine stabilizer, calcium source and phosphorus source is 15-20:1-1.2:1, and the concentration of calcium source in the system is 0.03-0.1 mol / L.

4. The application according to claim 1, characterized in that, Calcium phosphate nanoclusters precursors were prepared by reacting organic amine stabilizers, calcium sources, phosphorus sources and organic solvents at 20–30 °C for 10–15 h. The calcium phosphate nanoclusters were then separated by centrifugation and washing.

5. The application according to claim 1, characterized in that, The alginate mentioned is sodium alginate.

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