Bio-based high-thermal-conductivity phase change energy storage material based on polylactic acid and boron nitride

Abstract

The invention discloses a polylactic acid and boron nitride-based bio-based high-thermal-conductivity phase-change energy storage material, which is characterized in that a thermal conduction material is a boron nitride nanosheet, a substrate material is polylactic acid, and a phase-change material is paraffin; the particle size of the boron nitride nanosheet ranges from 0.5 mu m to 1 mu m; wherein the polylactic acid wraps the paraffin in a net shape, and the boron nitride nanosheets are arranged in the net shape in an array mode. The preparation method comprises the following steps: by taking polylactic acid, paraffin and boron nitride as raw materials, blending the various raw materials through a solution method, and treating the mixture into a thin pancake shape through a plate vulkameter. The flaky boron nitride is introduced as a heat conduction reinforcing agent, so that the heat conduction efficiency and the energy storage density of the material are remarkably improved, meanwhile, the material has good cycling stability and environmental friendliness, and the technical bottlenecks that a traditional heat storage material is poor in heat conduction performance, leaks and is large in environmental burden are solved; the method is suitable for efficient heat management in medium and low temperature application scenarios.

Description

Technical Field

[0001] The present invention relates to the technical field of phase change heat storage, and particularly relates to a bio-based high thermal conductivity phase change energy storage material based on polylactic acid and boron nitride. Background Art

[0002] The efficient storage and distribution of energy have become the focus of current research. Phase change energy storage materials (PCMs) are widely used in the field of thermal energy storage because they can absorb or release a large amount of latent heat during the phase change process. However, traditional phase change materials still face many challenges in practical applications, such as degradation of thermophysical properties, liquid phase leakage, poor cycle stability, and insufficient thermal conductivity. An ideal phase change energy storage material should have the following characteristics: appropriate phase change temperature, high energy storage density, good thermal conductivity, no leakage, and excellent cycle stability.

[0003] In recent years, researchers have tried to solve the above problems through the development of composite materials. For example, the patent document CN202311743622.9 "A high thermal conductivity energy storage backfill material and its preparation method and application" proposes a high thermal conductivity energy storage backfill material, which has excellent thermal conductivity by adjusting the aggregate configuration ratio and specific curing agent combination. However, this patent mainly targets the field of building materials, and the phase change temperature and energy storage density of its energy storage material are not suitable for efficient thermal management in medium and low temperature application scenarios, and it does not solve the liquid phase leakage problem of the phase change material.

[0004] In addition, the patent document CN202411077474.6 "A flexible energy storage phase change material for photovoltaic cooling and its preparation method" (application date: December 3, 2024) realizes the morphological stability of the phase change material through specific chemical structure design to prevent liquid leakage. Although this patent solves the leakage problem of the phase change material, it is mainly applied to the field of photovoltaic cooling, and there is still room for improvement in thermal conductivity and cycle stability, and it does not meet the thermal management requirements in medium and low temperature application scenarios.

[0005] A thermal conductive phase change composite material and its preparation method and application disclosed in the prior art with the publication number of CN2024103100768, in which the middle phase change layer can achieve a fast and uniform heat absorption or heat release process through a porous thermal conductive network structure, and can mitigate thermal shock. Similarly, there is still room for improvement in its thermal conductivity and cycle stability. Summary of the Invention

[0006] 1. Technical problems to be solved: In view of the above technical problems, the present invention provides a bio-based high thermal conductivity phase change energy storage material based on polylactic acid and boron nitride, and a preparation method thereof. By optimizing the composite structure, introducing flaky boron nitride as a thermal conductivity enhancer, and combining the degradable characteristics of the polylactic acid matrix, the thermal conductivity efficiency and energy storage density of the material are significantly improved, while effectively solving the problem of liquid leakage. At the same time, it has good cycle stability and environmental friendliness, and is suitable for high-efficiency thermal management in medium and low temperature application scenarios, effectively solving the limitations of the prior art.

[0007] 2. Technical solution: A bio-based high thermal conductivity phase change energy storage material based on polylactic acid and boron nitride, characterized in that: its thermal conductive material is boron nitride nanosheets, the substrate material is polylactic acid, and the phase change material is paraffin wax; the particle size range of the boron nitride nanosheets is 0.5 μm to 1 μm; wherein the polylactic acid presents a network to wrap the paraffin wax, and the boron nitride nanosheets are arranged in an array in the network.

[0008] Furthermore, it is prepared from the following components in mass fractions: 25 - 35 parts of polylactic acid; 10 - 20 parts of paraffin wax; 3 - 5 parts of boron nitride.

[0009] Furthermore, its preparation includes the following steps: Step 1: Dissolve polylactic acid in dichloromethane; Step 2: Melt paraffin wax into paraffin oil and mix it with polylactic acid, and add boron nitride; Step 3: Place the mixture in an oven to remove dichloromethane; Step 4: Hot press the dried sample into shape.

[0010] Furthermore, the specific method of Step 1 is: Weigh polylactic acid and add it to a beaker containing dichloromethane in portions; set the heating temperature of the water bath to be controlled at 30°C - 38°C, and completely dissolve polylactic acid by magnetic stirring.

[0011] Furthermore, the specific method of Step 2 is: Place paraffin wax in a water bath at 25 - 30°C higher than its melting point to melt it into paraffin oil; after polylactic acid is completely dissolved, raise the temperature of the water bath to 60 - 70°C, and quickly pour the paraffin oil into the polylactic acid solution; add boron nitride powder, and continuously stir magnetically.

[0012] Furthermore, the specific method of Step 3 is: Pour the mixed solution into a mold, and place it in an oven at 70 - 90°C to dry for 5 - 7 hours to completely remove dichloromethane.

[0013] Furthermore, the specific method of Step 4 is: Place the dried sample on a flat vulcanizer at 90 - 120°C and hot press for 2 - 5 minutes; immediately take it out and put it into a cold press plate at 5 - 15°C and cold press for 20 - 30 seconds to shape it into a tablet-like structure.

[0014] 3. Beneficial effects: (1) In a bio-based high thermal conductivity phase change energy storage material based on polylactic acid and boron nitride and its preparation method of the present invention, by introducing flaky boron nitride as a thermal conductivity enhancer, the boron nitride nanosheets are regularly arranged in the reticular matrix, significantly improving the thermal conductivity efficiency of the material, solving the problem of poor compatibility between the thermal conductivity channels of traditional heat storage materials and the organic matrix, and realizing efficient thermal management in medium and low temperature application scenarios.

[0015] (2) A bio-based high thermal conductivity phase change energy storage material based on polylactic acid and boron nitride of the present invention has good cycle stability and safety; multiple experiments have verified that the material exhibits excellent stability during multiple endothermic and exothermic cycles, extending the service life; at the same time, the fully degradable property effectively avoids the leakage problem, improving the safety and environmental friendliness of the material.

[0016] (3) A bio-based high thermal conductivity phase change energy storage material based on polylactic acid and boron nitride of the present invention has the advantages of environmental friendliness and degradability. This material is designed based on bio-based polylactic acid, which is not only degradable but also reduces the long-term burden on the environment, meeting the development trend of green energy storage materials. Description of the drawings

[0017] Figure 1 It is the XRD test chart of the phase change energy storage thermal material prepared in the specific embodiment for the specific embodiment. Detailed implementation manners

[0018] The present invention will be specifically described below in conjunction with specific embodiments. Specific embodiments

[0019] In this specific embodiment, the following implementation steps are used to prepare a bio-based high thermal conductivity phase change energy storage material based on polylactic acid and boron nitride, and the particle size of the boron nitride nanosheets is adjusted by adjusting the ratio and the corresponding temperature, including: Step 1: Weigh the polylactic acid and add it to a beaker containing dichloromethane in portions, and set the heating temperature of the water bath to 30°C - 38°C. At the same time, turn the magnetic button to make the magnetic stirrer rotate in the beaker, driving the dichloromethane to stir the polylactic acid until it dissolves. Step 2: Put the paraffin into a beaker in advance and melt it into paraffin oil in a water bath at a temperature 25 - 30°C higher than the melting point of the paraffin; after the polylactic acid dissolves, raise the temperature of the water bath heating the polylactic acid solution to 60 - 70°C. After the temperature stabilizes, quickly pour the paraffin oil into the beaker; immediately add boron nitride powder, and stir magnetically during the process. Step 3: Pour the viscous solution into a mold and place it in an oven at 70 - 90°C to dry for 5 - 7 hours to remove the solvent dichloromethane. Take it out after the dichloromethane has completely volatilized. Step 4: Place the sample on a flat vulcanizer at a temperature of 90 - 120°C and hot press for 2 - 5 minutes, then take it out and place it on a cold press plate at 5 - 15°C for cold pressing for 20 - 30 seconds for shaping to form a tablet-like structure.

[0020] The endothermic phase change material prepared with boron nitride particles was used in Comparative Example 1, and only paraffin was used to prepare the phase change heat storage material in Comparative Example 2.

[0021] Based on the above steps, the specific ratios and those of the comparative examples are shown in Table 1 below.

[0022] Table 1 Examples and Comparative Examples

[0023] XRD tests were conducted on the phase change heat storage materials prepared in Examples 1 - 3, and the test results are as shown in the appendix Figure 1 as follows. Figure 1 It shows that both paraffin and PLA crystallized normally in the material and maintained good independence. In Examples A1 - 3, due to the relatively large surface area of the flaky boron nitride, the contact area with the substrate material is larger, and the crystallization growth rate is faster. As the particle size of the filled BN increases, almost all peaks are enhanced, indicating that the unique structure of the flaky boron nitride can crystallize well with PLA and paraffin.

[0024] Thermal conductivity, contact angle, and DSC tests were conducted on the phase change heat storage materials prepared in Examples A1 - 3 and Comparative Examples B1 - B2, and the test results are shown in Table 2.

[0025] Table 2 Test Results of the Performance of the Phase Change Heat Storage Materials Prepared in Examples and Comparative Examples

[0026] Comparing Examples A1 - 3 with Comparative Example B1, it can be seen that the flaky boron nitride used in Examples A1 - 3 significantly improves the energy storage density, thermal conductivity, and cycle stability of the phase change heat storage material. This indicates that the combination of polylactic acid as the substrate material, paraffin as the phase change material, and flaky boron nitride as the thermal conductivity enhancer effectively improves the overall performance of the material.

[0027] Comparing Example A3 with Comparative Example B1, it can be seen that the boron nitride introduced in Example A1 greatly improves the thermal conductivity of the phase change heat storage material. It shows that the special morphological structure of the flaky boron nitride can penetrate deep into the interior of PLA and paraffin, that is, it has a relatively large surface area and a relatively large surface energy, strengthening the efficiency of heat transfer.

[0028] In summary, in the bio-based high thermal conductivity phase change energy storage material based on polylactic acid and boron nitride provided by the present invention, polylactic acid is used as the base material, paraffin is used as the phase change material, and flaky boron nitride is introduced as a thermal conductivity enhancer, significantly improving the thermal conductivity efficiency and energy storage density of the material. At the same time, it has good cycle stability and environmental friendliness, solving the technical bottlenecks of poor thermal conductivity, leakage problems and large environmental burden of traditional heat storage materials, and is applicable to efficient thermal management in medium and low temperature application scenarios.

[0029] Although the present invention has been disclosed above with preferred embodiments, they are not used to limit the present invention. Any person skilled in this art can make various changes or modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention should be defined by the protection scope of the claims of this application.

Claims

1. A bio-based high thermal conductivity phase change energy storage material based on polylactic acid and boron nitride, characterized in that: Its thermal conductive material is boron nitride nanosheets, the substrate material is polylactic acid, and the phase change material is paraffin; the particle size range of the boron nitride nanosheets is 0.5 μm to 1 μm; wherein the polylactic acid presents a network to wrap the paraffin, and the boron nitride nanosheets are arranged in an array in the network.

2. The bio-based high thermal conductivity phase change energy storage material based on polylactic acid and boron nitride according to claim 1, characterized in that: It is prepared from the following components by mass fraction: 25 - 35 parts of polylactic acid; 10 - 20 parts of paraffin; 3 - 5 parts of boron nitride.

3. The bio-based high thermal conductivity phase change energy storage material based on polylactic acid and boron nitride according to claim 2, wherein: Its preparation includes the following steps: Step 1: Dissolve polylactic acid in dichloromethane. Step 2: Melt paraffin into paraffin oil, mix it with polylactic acid, and add boron nitride. Step 3: Place the mixture in an oven to remove dichloromethane. Step 4: Hot press the dried sample into shape.

4. The bio-based high thermal conductivity phase change energy storage material based on polylactic acid and boron nitride according to claim 3, characterized in that: The specific method for Step 1 is: Weigh polylactic acid and add it to a beaker containing dichloromethane in portions; set the heating temperature of the water bath to be controlled at 30°C - 38°C, and completely dissolve polylactic acid by magnetic stirring.

5. The bio-based high thermal conductivity phase change energy storage material based on polylactic acid and boron nitride according to claim 3, characterized in that: The specific method for Step 2 is: Place paraffin in a water bath at a temperature 25 - 30°C higher than its melting point to melt it into paraffin oil; after polylactic acid is completely dissolved, raise the temperature of the water bath to 60 - 70°C, and quickly pour the paraffin oil into the polylactic acid solution; add boron nitride powder and continue magnetic stirring.

6. The bio-based high thermal conductivity phase change energy storage material based on polylactic acid and boron nitride according to claim 3, characterized in that: The specific method for Step 3 is: Pour the mixed solution into a mold and place it in an oven at 70 - 90°C to dry for 5 - 7 hours to completely remove dichloromethane.

7. A bio-based high thermal conductivity phase change energy storage material based on polylactic acid and boron nitride according to claim 3, characterized in that: The specific method for Step 4 is: Place the dried sample on a flat vulcanizer at 90 - 120°C and hot press for 2 - 5 minutes; immediately take it out and put it into a cold press plate at 5 - 15°C and cold press for 20 - 30 seconds to shape it into a disc - like structure.

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