PHB crystal nanorod and preparation method and packaging material thereof

Abstract

The invention discloses a PHB crystal nanorod, a preparation method thereof and a packaging material, relates to the technical field of material processing, and discloses the preparation method of the PHB crystal nanorod, and the preparation method comprises the following steps: providing a PHB solution; and putting a PHB solution into the nano-porous anodic aluminum oxide template, and curing to obtain the PHB crystal nanorod. According to the method, the mechanical property of the PHB is effectively improved.

Description

Technical Field

[0001] The present application relates to the field of material processing technology, and in particular to a PHB crystal nanorod and a preparation method and packaging material thereof. Background Art

[0002] Globally, as the concept of sustainable development becomes more deeply ingrained and consumers' environmental awareness grows, the beauty industry faces unprecedented challenges and opportunities. Traditional cosmetics packaging widely utilizes petroleum-based plastics as its primary material. These materials are not only difficult to degrade but also release microplastics when they break down in the natural environment, causing long-term and profound damage to ecosystems. Furthermore, the production of petroleum-based plastics consumes vast quantities of non-renewable resources and generates significant greenhouse gas emissions, running counter to the global goal of carbon neutrality.

[0003] To address these issues, finding new materials that meet both environmental and performance requirements has become a key research focus in the industry. Polyhydroxybutyrate (PHB), a biodegradable polymer synthesized by microorganisms, has garnered widespread attention due to its 100% biodegradability, excellent biocompatibility, and low environmental impact. However, despite its numerous advantages, PHB's mechanical properties remain inferior to those of traditional petroleum-based plastics, limiting its application in high-end cosmetics packaging. Summary of the Invention

[0004] The main purpose of this application is to provide a PHB crystal nanorod and its preparation method and packaging material, which effectively improve the mechanical properties of PHB.

[0005] To achieve the above objectives, the present invention provides a method for preparing PHB crystalline nanorods, comprising the following steps:

[0006] Provide PHB solution;

[0007] The PHB solution was placed in a nanoporous anodic aluminum oxide template and solidified to obtain PHB crystal nanorods.

[0008] In one embodiment, the step of providing the PHB solution comprises:

[0009] Pour the PHB granules into the organic solvent;

[0010] The mixture is heated and mixed at a first temperature to obtain a PHB solution.

[0011] In one embodiment, the organic solvent includes at least one of chloroform, dichloromethane and tetrahydrofuran.

[0012] In one embodiment, the first temperature is 30-55°C.

[0013] In one embodiment, the concentration of the PHB solution is 10-20 wt.%.

[0014] In one embodiment, the pore size of the nanoporous anodic aluminum oxide template ranges from 50 to 300 nm.

[0015] In one embodiment, the curing method includes:

[0016] Let it stand in a vacuum environment for 3 to 8 days.

[0017] In one embodiment, the PHB crystalline nanorods have a layered oriented crystal structure.

[0018] To achieve the above-mentioned purpose, an embodiment of the present application provides a PHB crystalline nanorod, which is prepared by the above-mentioned method for preparing PHB crystalline nanorod.

[0019] To achieve the above-mentioned objectives, an embodiment of the present application provides a packaging material, comprising PHB crystalline nanorods prepared by the above-mentioned method for preparing PHB crystalline nanorods.

[0020] The present invention provides a method for preparing PHB crystalline nanorods, comprising providing a PHB solution, placing the PHB solution in a nanoporous anodic aluminum oxide template, and curing the solution to obtain PHB crystalline nanorods with a specific molecular orientation. The present invention promotes the orderly arrangement of the PHB molecular chains through the interaction between the inner wall of the nanoporous anodic aluminum oxide template and the PHB molecular chains. The nanoscale constraints limit the free movement of the PHB molecular chains, orienting them along a specific direction (a-axis or b-axis) and inducing them to form a layered crystalline structure. This unique layered orientation significantly improves the mechanical properties of the PHB material, providing new possibilities for its application in the field of biodegradable materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a flow chart of the method for preparing PHB crystal nanorods involved in the embodiment of the present application;

[0022] Figure 2 These are SEM test images of Examples 1 and 2 and Comparative Example 1 of the present application;

[0023] Figure 3 The DSC test charts of Examples 1 and 2 of the present application are as follows;

[0024] Figure 4 A two-dimensional X-ray diffraction pattern of an embodiment of the present application;

[0025] Figure 5 Schematic diagram of the molecular chain, unit cell, and chip orientation and arrangement according to an embodiment of the present application.

[0026] The realization of the objectives, functional features and advantages of this application will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0027] To make the purpose, technical solutions and advantages of the examples of the present application clearer, the technical solutions in the examples of the present application will be described clearly and completely below. Where specific conditions are not specified in the examples, conventional conditions or conditions recommended by the manufacturer are used. Where the manufacturer of the reagents or instruments is not specified, they are all conventional products that can be purchased commercially.

[0028] Below, the embodiments of the PHB crystal nanorods, their preparation methods, and packaging materials of the present application are described in detail with appropriate reference to the accompanying drawings. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there may be cases where detailed descriptions of well-known matters and repeated descriptions of actually the same structures are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate understanding by those skilled in the art. In addition, the drawings and the following description are provided to enable those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0029] The "ranges" disclosed herein are defined in terms of lower and upper limits, where a given range is defined by selecting a lower limit and an upper limit, and the selected lower and upper limits define the boundaries of the particular range. Ranges defined in this manner can be inclusive or exclusive of the end values and can be combined arbitrarily, i.e., any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60 to 120 and 80 to 110 are listed for a particular parameter, it is understood that ranges of 60 to 110 and 80 to 120 are also contemplated. Furthermore, if minimum range values of 1 and 2 are listed, and if maximum range values of 3, 4, and 5 are listed, the following ranges are all contemplated: 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4, and 2 to 5. In this application, unless otherwise indicated, the numerical range "a to b" is a shorthand representation of any combination of real numbers between a and b, where a and b are both real numbers. For example, a numerical range of "0-5" indicates that all real numbers between "0-5" are listed herein, and "0-5" is simply an abbreviation for these numerical combinations. Furthermore, when a parameter is expressed as an integer ≥ 2, this is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0030] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0031] Unless otherwise specified, all steps of the present application may be performed sequentially or randomly, preferably sequentially. For example, a method includes steps (a) and (b), which indicates that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, a method may further include step (c), which indicates that step (c) may be added to the method in any order, for example, the method may include steps (a), (b), and (c), or may include steps (a), (c), and (b), or may include steps (c), (a), and (b), etc.

[0032] To make the above-mentioned objects, features and advantages of the present application more clearly understood, the technical solutions of the present application are further described below with reference to the accompanying drawings and embodiments. However, the present application is not limited to the embodiments listed, but also includes any other known modifications within the scope of the rights claimed in the present application.

[0033] In order to better understand the technical solution of the present application, a detailed description will be given below in conjunction with the accompanying drawings and specific implementation methods.

[0034] Polyhydroxybutyrate (PHB), a biodegradable polymer synthesized by microorganisms, has attracted widespread attention due to its 100% biodegradability, good biocompatibility, and low environmental impact. However, despite its many advantages, PHB's mechanical properties are still inferior to those of traditional petroleum-based plastics, limiting its application in high-end cosmetics packaging.

[0035] The present application provides a method for preparing PHB crystal nanorods. The interaction between the inner wall of a nanoporous anodic aluminum oxide template and the PHB molecular chains promotes the orderly arrangement of the molecular chains. The nanoscale constraints limit the free movement of the PHB molecular chains, orienting them along a specific direction (a-axis or b-axis) and inducing them to form a layered crystal structure. This special layered orientation structure significantly improves the mechanical properties of the PHB material and provides new possibilities for its application in the field of biodegradable materials.

[0036] The first embodiment of the present application provides a method for preparing PHB crystal nanorods, referring to Figure 1 , including the following steps:

[0037] Step S10, providing a PHB solution;

[0038] In one feasible embodiment, a PHB solution is pre-prepared, for example, by dissolving PHB particles in a specific solvent and uniformly mixing the particles with the solvent to obtain a PHB solution.

[0039] In one feasible embodiment, step S10, the step of providing the PHB solution includes:

[0040] Step S11, pouring PHB particles into an organic solvent;

[0041] Step S12: heating and mixing at a first temperature to obtain a PHB solution.

[0042] In one possible embodiment, the PHB particles are poured into an organic solvent, heated at a first temperature, and mixed until uniform to obtain a PHB solution.

[0043] In one feasible embodiment, the first temperature is 30-55°C. For example, the first temperature is 30°C, 32°C, 34°C, 36°C, 38°C, 40°C, 42°C, 44°C, 46°C, 48°C, 50°C, 52°C, 54°C, 55°C, etc. If the stirring temperature is too low, it may cause the PHB particles to be difficult to dissolve in the solvent, or it may take a longer time to completely dissolve. If the stirring temperature is too high, for example, exceeding the boiling point of the organic solvent, it will cause a large amount of volatilization of the organic solvent. Therefore, the embodiment of the present application determines to heat at a temperature of 30-55°C to uniformly mix the PHB particles and the organic solvent to obtain a PHB solution.

[0044] In one possible embodiment, the organic solvent includes at least one of chloroform, dichloromethane and tetrahydrofuran.

[0045] Chloroform is a very effective solvent that can dissolve PHB well, making the PHB solution have good uniformity and stability; at the same time, compared with other solvents, chloroform has less degradation effect on PHB, which helps to maintain the integrity of the PHB molecular chain.

[0046] Dichloromethane is one of the more common solvents. It can quickly dissolve PHB and is suitable for situations where solutions need to be prepared quickly. In addition, dichloromethane has a low boiling point, so it is relatively easy to evaporate and remove the solvent, making it suitable for applications that require a faster drying process.

[0047] Tetrahydrofuran (THF) has good compatibility with other chemical substances and is suitable for use in the preparation of various composite materials.

[0048] In one feasible embodiment, the concentration of the PHB solution is 10 to 20 wt.%. For example, the concentration of the PHB solution is 10 wt.%, 11 wt.%, 12 wt.%, 13 wt.%, 14 wt.%, 15 wt.%, 16 wt.%, 17 wt.%, 18 wt.%, 19 wt.%, 20 wt.%, etc. When the concentration of the PHB solution is too high, the solution usually has a higher viscosity, which makes the solution processing difficult. For example, poor fluidity may occur during mixing, filtering or injection into the template, thereby affecting the operation efficiency and consistency of the results. In addition, an overly viscous solution may cause increased internal stress in the material, which is not conducive to the formation of uniform and elongated nanorod structures. Instead, it is easy to cause agglomeration, reducing the dispersion and size uniformity of the obtained nanorods. At the same time, during the solvent evaporation crystallization process, a high concentration solution may promote irregular crystallization or form larger crystal particles rather than the target nanoscale structure. On the contrary, if the concentration of the PHB solution is too low, although the solution has good fluidity and is easy to operate, the amount of PHB it contains is insufficient to form sufficient solid matter in the subsequent steps, which will directly affect the yield of the product and may result in an inability to obtain a sufficient number of nanorods. In addition, a lower concentration may also make it difficult to ensure that the formed crystal structure has sufficient mechanical strength and stability, because it becomes more difficult to establish effective interactions between limited polymer chains, which in turn affects the integrity and performance of the nanorods. Finally, low-concentration solutions may cause significant surface tension effects due to rapid volatilization during the drying process, resulting in structural defects or morphological abnormalities. Therefore, the embodiment of the present application determines that the concentration of the PHB solution is 10 to 20 wt.%.

[0049] Step S20: placing the PHB solution in a nanoporous anodic aluminum oxide template and solidifying it to obtain PHB crystal nanorods.

[0050] In one embodiment, a nanoporous anodic aluminum oxide template is provided and placed in a reaction vessel, and a PHB solution is poured into the reaction vessel to ensure that the PHB solution completely immerses the template. The PHB solution is allowed to solidify to obtain PHB crystalline nanorods.

[0051] For example, the nanoporous anodic aluminum oxide template is dried at 200-400° C. for 10-30 min, ultrasonically cleaned with anhydrous ethanol for 1-5 min, and dried at room temperature for later use.

[0052] In one possible embodiment, the curing method includes:

[0053] Step S21: leaving the mixture to stand in a vacuum environment for 3 to 8 days.

[0054] In one feasible embodiment, the nanoporous anodic aluminum oxide template soaked with the PHB solution is placed in a vacuum environment for 3 to 8 days to allow the solvent in the PHB solution to evaporate, thereby obtaining PHB crystalline nanorods.

[0055] Exemplarily, a nanoporous anodic aluminum oxide template is placed in a reaction vessel, a PHB solution is poured into it to ensure that the PHB solution completely immerses the template, and the template is soaked in a vacuum environment for 3 to 8 days. The nanoporous anodic aluminum oxide template is taken out and the residual body film is removed to obtain PHB crystal nanorods.

[0056] In one possible embodiment, the pore size of the nanoporous anodic aluminum oxide template ranges from 50 to 300 nm. For example, the pore size of the nanoporous anodic aluminum oxide template ranges from 50 nm, 60 nm, 80 nm, 100 nm, 120 nm, 140 nm, 160 nm, 180 nm, 200 nm, 220 nm, 240 nm, 260 nm, 280 nm, and 300 nm. When the pore size of the nanotemplate is too large, it may not provide sufficient restraining force to guide the PHB molecular chains to align along a specific direction. This weakens the interaction between the template's inner wall and the PHB molecules, making it difficult to achieve ideal molecular orientation. As a result, the formed PHB nanocrystals may lack order, failing to effectively improve the material's mechanical properties. Furthermore, larger pore sizes may lead to uneven sizes of the generated nanocrystals and even agglomeration, further affecting the consistency and stability of the material. These factors work together to make the final PHB material perform less well than expected in terms of strength, toughness, and ductility. On the other hand, if the pore size of the nano template is too small, it may limit the effective filling of the PHB solution, increase the difficulty of the solution penetrating into the template pores, and reduce production efficiency. More importantly, the tiny pore size will impose excessive restrictions on the spatial distribution of the PHB molecular chains, hindering the proper expansion and arrangement of the molecular chains, which is not conducive to the formation of high-quality nanocrystals. In addition, too small a pore size may also lead to stress concentration during solvent evaporation or curing, causing structural defects such as cracks or fractures. These problems not only affect the morphology and size control of the nanocrystals, but also have a negative impact on the mechanical properties of the final material. Therefore, the embodiment of the present application determines that the pore size range of the nanoporous anodic aluminum oxide template is 50 to 300 nm.

[0057] In one possible embodiment, the PHB crystalline nanorods have a layered oriented crystal structure.

[0058] In the embodiment of the present application, the interaction between the inner wall of the nanoporous anodic aluminum oxide template and the PHB molecular chain promotes the orderly arrangement of the molecular chains, and the nanoscale constraints limit the free movement of the PHB molecular chains, so that they are oriented in a specific direction (a-axis and / or b-axis) and induce them to form a layered crystal structure. When the PHB molecular chains are arranged in an orderly manner in a specific direction, the interactions between the molecular chains are optimized, including non-covalent interactions such as van der Waals forces and hydrogen bonds, as well as the strengthening effect of possible partial crystalline regions. These enhanced intermolecular forces help to improve the overall strength of the material. The ordered molecular chains can reduce the presence of internal defects and stress concentration points, thereby improving the material's ability to resist external forces and increasing tensile strength. At the same time, in the layered oriented crystal structure, the molecular chains are fixed in a relatively fixed arrangement, which limits their ability to move under external forces. Compared with the random arrangement, the ordered molecular chains are less likely to slip or rearrange when stretched, and therefore exhibit a lower elongation at break.

[0059] In this embodiment, the interaction between the inner wall of the nanoporous anodic aluminum oxide template and the PHB molecular chains promotes the orderly arrangement of the molecular chains, while the nanoscale constraints limit the free movement of the PHB molecular chains, orienting them along a specific direction (a-axis or b-axis) and inducing them to form a layered crystal structure. This special layered orientation structure significantly improves the mechanical properties of the PHB material and provides new possibilities for its application in the field of biodegradable materials.

[0060] In order to make the details and operations of the above embodiments of the present application clearly understood by those skilled in the art, and to significantly demonstrate the improved performance of the embodiments of the present application, the above technical solutions are illustrated by multiple embodiments below.

[0061] Example 1

[0062] Providing a 15 wt.% PHB solution, wherein the organic solvent is chloroform;

[0063] The PHB solution was placed in a nanoporous anodic aluminum oxide template with a pore size of 300 nm and allowed to stand for 5 days under vacuum conditions to obtain PHB crystal nanorods, wherein the PHB crystal nanorods had a-axis and b-axis molecular chain orientations and an α-phase crystal structure.

[0064] Example 2

[0065] Providing a 15 wt.% PHB solution, wherein the organic solvent is chloroform;

[0066] The PHB solution was placed in a nanoporous anodic aluminum oxide template with a pore size of 70 nm and allowed to stand for 5 days under vacuum conditions to obtain PHB crystal nanorods, wherein the PHB crystal nanorods had a b-axis molecular chain orientation and a β phase appeared in the crystal structure.

[0067] Comparative Example 1

[0068] Providing a 15 wt.% PHB solution, wherein the organic solvent is chloroform;

[0069] The PHB film is directly prepared without using a nanoporous anodic aluminum oxide template, wherein the PHB film has no obvious molecular chain orientation and the crystal structure is an α phase.

[0070] The PHB materials of Examples 1, 2 and Comparative Example 1 were subjected to SEM testing, and the results were shown in Table 1. Figure 2 ,in, Figure 2 (a) is a schematic diagram of a nanoporous anodic aluminum oxide template with a pore size of 300 nm; Figure 2 (b) is a schematic diagram of the PHB crystal nanorods prepared in Example 1; Figure 2 (c) is a schematic diagram of the PHB crystal nanorods prepared in Example 2; Figure 2 (d) is a schematic diagram of the PHB film prepared in Comparative Example 1. It can be seen that the PHB nanorods prepared in Examples 1 and 2 have regular nanorod shapes, while the surface of the PHB film of Comparative Example 1 presents an irregular structure.

[0071] The PHB materials of Examples 1 and 2 were subjected to DSC tests, and the results were shown in Table 1. Figure 3 ,in, Figure 3 The horizontal axis is temperature (Temperature), and the vertical axis is heat flow (Heat Flow). Figure 3 The Bulk line in the middle shows only the α phase, while Example 1 belongs to a crystal grown at 300nm. Its curve is basically consistent with the Bulk (including the number of peaks and the area of the peaks), so Example 1 belongs to the α phase. Example 2 shows a crystallization curve with a restricted size of 70nm. The results show that as the degree of restriction increases, the peak intensity becomes smaller and smaller; unlike the restricted crystallization curve of general polymers, the greater the degree of restriction of the PHB material, the peak moves to the right and approaches the crystallization curve of the bulk. This is because when the degree of restriction increases to a certain size, the original crystal structure of the PHB undergoes a phase transformation and becomes another crystal phase. This crystal phase is a metastable phase that requires a higher temperature to appear and dominates the competitive growth with the original crystal phase, so a right shift occurs, so Example 2 forms another crystal phase, the β phase.

[0072] Furthermore, the two-dimensional wide-angle X-ray spectra of Examples 1 and 2 were converted into one-dimensional spectra and the Miller surface of the spectra was calculated to characterize the crystal structure of PHB. The results were referred to Figure 4 ,in, Figure 4 (a) is the test geometry of confined PHB crystal nanorods within a nanoporous anodic aluminum oxide (AAO) template; Figure 4 (b) Two-dimensional X-ray diffraction pattern of the bulk spherulite sample; Figure 4 (c) is a two-dimensional X-ray diffraction pattern of Example 1; Figure 4 (d) is the two-dimensional X-ray diffraction pattern of Example 2. It is known from the two-dimensional X-ray spectrum that the PHB nanorods obtained under two different confined sizes, according to the Bragg equation and the corresponding Miller plane-angle correspondence, the marked peaks belong to the PHB-crystal characteristic peaks, which are (020), (110), (111) and (130). A smaller peak also appears near 19.6 in the one-dimensional X-ray curve of the main body, because the main body material itself is formed by crystal hot pressing and stretching during the WAXD test. The PHB nanorods grown under the 70nm confined size (Example 2) also have a characteristic peak of β, indicating that when the degree of confinement is strengthened, the PHB crystal will undergo a phase transition. It can be understood that, whether it is the main body or the diffraction pattern under the confined size, the angles and Miller planes corresponding to the crystal can be found, which shows that regardless of whether it is confined or not, PHB will produce a common crystal phase structure during the crystallization process. When the confined size is 70nm, the characteristic peaks belonging to the Miller planes (110), (111), and (130) appear blurred and even show signs of splitting; and these split peaks cannot match the Miller planes corresponding to the crystal. Therefore, it can be proved that the degree of self-confinement is enhanced. When the confined diameter is 70nm, PHB undergoes a phase transition in the cylinder, and the crystal changes from a stable state to a metastable state, and two phases exist simultaneously.

[0073] Further, the arrangement of molecular chains and lamellar crystals in confined space was established, and the results were referenced. Figure 5 ,in, Figure 5 (a) shows the molecular chain of b-axis oriented crystal under two-dimensional confinement; Figure 5 (b) is the molecular chain of a-axis oriented crystal under two-dimensional confinement; Figure 5 (c) is the unit cell of the b-axis oriented crystal under two-dimensional confinement; Figure 5 (d) is the unit cell of a-axis oriented crystal under two-dimensional confinement; Figure 5 Middle (e) shows the wafer orientation and arrangement of b-axis oriented crystals under two-dimensional confinement; Figure 5 (f) shows the wafer orientation and arrangement of a-axis oriented crystals under two-dimensional confinement; the above two crystal orientations use the long axis direction of the nanorods as the reference direction.

[0074] Furthermore, mechanical properties of the PHB materials of Examples 1 and 2 and Comparative Example 1 were tested, and the results are shown in Table 1 below.

[0075] Table 1

[0076] Test Group Tensile strength (MPa) Elongation at break (%) Example 1 45 12 Example 2 60 8 Comparative Example 1 30 15

[0077] It can be seen that the tensile strength of the PHB material prepared in Examples 1 and 2 of the present application is improved and the elongation at break is reduced. Therefore, it has high hardness and rigidity and can meet the application of packaging materials requiring high strength, shape stability and wear resistance.

[0078] In summary, the embodiments of the present application utilize the two-dimensional confinement effect of the nanoporous anodic aluminum oxide template to successfully prepare PHB nanorods with a special layered oriented crystal structure. This method can not only regulate the crystal structure and molecular orientation of PHB, but also significantly improve its mechanical properties, providing new possibilities for its application in the field of biodegradable materials.

[0079] The above are only preferred embodiments of the present application and are not intended to limit the scope of the present invention. Those skilled in the art will readily appreciate that various modifications and variations are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present application shall be included within the scope of the present invention.

Claims

1. A method for preparing PHB crystal nanorods, characterized in that: The method for preparing PHB crystalline nanorods comprises the following steps: Provide PHB solution; The PHB solution was placed in a nanoporous anodic aluminum oxide template and solidified to obtain PHB crystal nanorods.

2. The method for preparing PHB crystalline nanorods according to claim 1, wherein: The step of providing the PHB solution comprises: Pour the PHB granules into the organic solvent; The mixture is heated and mixed at a first temperature to obtain a PHB solution.

3. The method for preparing PHB crystalline nanorods according to claim 2, wherein: The organic solvent includes at least one of chloroform, dichloromethane and tetrahydrofuran.

4. The method for preparing PHB crystalline nanorods according to claim 2, wherein: The first temperature is 30-55°C.

5. The method for preparing PHB crystalline nanorods according to claim 1 or 2, wherein: The concentration of the PHB solution is 10-20 wt.%.

6. The method for preparing PHB crystalline nanorods according to claim 1, wherein: The pore size of the nanoporous anodic aluminum oxide template ranges from 50 to 300 nm.

7. The method for preparing PHB crystalline nanorods according to claim 1, wherein: The curing method includes: Let it stand in a vacuum environment for 3 to 8 days.

8. The method for preparing PHB crystalline nanorods according to claim 1, wherein: The PHB crystal nanorods have a layered oriented crystal structure.

9. A PHB crystalline nanorod, characterized in that: The PHB crystalline nanorods are prepared by the method according to any one of claims 1 to 8.

10. A packaging material, characterized in that: The packaging material comprises PHB crystalline nanorods prepared by the method according to any one of claims 1 to 8.

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