Method for preparing biopolymer-based phase change heat dissipation composite and phase change heat dissipation composite prepared thereby

Abstract

The present invention provides a method for preparing a biopolymer-based phase change heat dissipation composite, the method comprising: a step for inducing an esterification reaction between polyethylene glycol (PEG), which is a phase change material, and poly lactic acid (PLA), which is a biopolymer, using a catalyst to prepare a phase change matrix; a step for mixing the phase change matrix with a thermally conductive filler to prepare a mixture; and a molding step for molding the mixture. The phase change heat dissipation composite prepared by the method has excellent stability due to suppressing leakage of the phase change material, and exhibits high thermal conductivity and mechanical properties.

Description

Method for manufacturing a biopolymer-based phase change heat dissipation composite and a phase change heat dissipation composite manufactured thereby

[0001] The present invention relates to a manufacturing technology for heat dissipation composite materials, and more specifically, to a manufacturing technology for a biopolymer-based phase change heat dissipation composite that suppresses leakage of phase change materials and improves the mechanical strength of the composite.

[0002] It should be noted that this patent is based on research conducted with funding from the government (Ministry of Science and ICT and Ministry of Trade, Industry and Energy) in 2025, supported by the National Research Foundation of Korea and the Korea Energy Technology Evaluation Institute (Development of cBN-based ultra-high heat dissipation insulating composite material_RS-2022-NR068145, Training of technical personnel for O&M and asset management based on ESS big data_RS-2024-00398346).

[0003] Due to the recent surge in demand for eco-friendly materials, research on convergence materials through the combination of eco-friendly polymer materials, such as biopolymers, and functional materials is actively underway. In particular, Phase Change Materials (PCMs) are attracting attention in various fields, including construction, automobiles, solar cells, and energy storage systems, as well as in the field of medical materials, due to their characteristic of storing and releasing thermal energy through phase changes at their melting point.

[0004] PCMs have the advantage of storing and releasing heat in the form of latent heat without temperature change, allowing them to accumulate more energy than sensible heat. Driven by these characteristics and the increasing demand for energy conservation, research utilizing PCMs is becoming more active. In textile materials, they are demonstrating potential for temperature regulation at the wear site, while in medical materials, they are showing promise for promoting wound healing and serving as drug delivery systems.

[0005] Phase change materials are currently difficult to apply in industrial fields due to their reduced actual thermal energy storage efficiency resulting from low thermal conductivity and limited heat storage capacity. To address this, composite strategies are being researched to enhance latent heat storage (LHS) characteristics by improving the thermal conductivity of phase change materials. Applicable phase change materials that resolve the issues of currently developed materials must meet the various performance characteristics required by technological advancements; among these, they must necessarily satisfy high latent heat capacity, high thermal conductivity, and an appropriate phase transition temperature range as core performance requirements.

[0006] Furthermore, since the weak mechanical strength of phase change materials significantly limits their application range, the development of phase change materials with superior strength is necessary. The leakage problem during phase change is also a major factor limiting the commercialization of phase change materials. While the addition of porous fillers is commonly used to solve liquid leakage problems, this approach has limitations in improving the thermal conductivity of phase change composites due to the low thermal conductivity of these fillers.

[0007] - Prior art literature

[0008] (Patent Document 1) Korean Registered Patent No. 10-2615771 (December 14, 2023) (Thermal dissipation composite composition, thermal dissipation composite using said composition and method for manufacturing the same)

[0009] The present invention is an invention sought to solve the problems described above, and aims to provide a method for manufacturing a biopolymer-based phase change heat dissipation composite that prevents leakage of phase change material within the composite material and minimizes the reduction of latent heat by imparting adhesiveness.

[0010] Furthermore, the present invention aims to provide a biopolymer-based phase change heat dissipation composite manufactured by the above method, having excellent stability, enhanced latent heat storage (LHS) characteristics, and further excellent mechanical properties.

[0011] A method for manufacturing a biopolymer-based phase change heat dissipation composite according to one embodiment of the present invention comprises: a step of preparing a phase change matrix by inducing a catalytic esterification reaction between polyethylene glycol (PEG), which is a phase change material, and polylactic acid (PLA), which is a biopolymer; a step of preparing a mixture by mixing a thermally conductive filler into the phase change matrix; and a molding step of molding the mixture.

[0012] The above catalyst may include tin chloride (IV) (SnCl4).

[0013] It is preferable that the tin chloride catalyst be used in a ratio of 3 to 5% relative to the total weight of the PEG and PLA.

[0014] The above polyethylene glycol and polylactic acid can be reacted in a weight ratio of 5:0.5 to 1.5.

[0015] The above esterification reaction can be carried out in a toluene solvent.

[0016] The above esterification reaction may include the step of dissolving the reactants under a nitrogen-substituted gas atmosphere and a temperature of 105 to 115°C; and the step of removing the solvent by vacuum filtration and drying the dissolved reactants at room temperature.

[0017] Carbon fiber (CF) and aluminum nitride (AlN) can be used as the above filler.

[0018] The above molding step may include an injection molding step.

[0019] A phase change heat dissipation composite according to one embodiment of the present invention comprises: a matrix comprising ester bonding sites between polyethylene glycol (PEG), which is a phase change material, and polylactic acid (PLA), which is a biopolymer; and a thermally conductive filler dispersed within the matrix.

[0020] The above heat dissipation composite may be an injection molded product.

[0021] According to the present invention, PEGPLA can be manufactured as a phase change heat dissipation composite having excellent stability and mechanical properties by chemically introducing the phase change material PEG into the biopolymer PLA.

[0022] This allows for solving the problem of liquid leakage at the melting point of PEG, significantly improving mechanical strength, and minimizing the reduction of latent heat.

[0023] In addition, instead of using a porous filler with low thermal conductivity as a method to solve liquid leakage of phase change materials in the existing composite process, by introducing a high-thermal-conductivity aluminum nitride and carbon fiber-based filler, it is possible to realize a high-thermal-conductivity phase change heat dissipation composite material with a thermal conductivity of 3.15 W / mK.

[0024] FIG. 1 is a schematic diagram conceptually illustrating a method for manufacturing a bio-based phase change heat dissipation composite according to one embodiment of the present invention.

[0025] FIG. 2 is a graph showing the results of Fourier transform infrared spectroscopy (a) and differential scanning calorimetry (b) before and after the chemical reaction of PEGPLA according to one embodiment of the present invention.

[0026] Figure 3 is a scanning electron microscope (FE-SEM) image showing the cross-sections of PEG, PLA, which are samples in the manufacturing step of PEGPLA in Figure 2, and PEGPLA, which is the product after the reaction.

[0027] Figure 4 is a photograph showing the leak test results according to temperature for each sample.

[0028] Figure 5 is a scanning electron microscope (FE-SEM) image showing a cross-section according to the filler content of a phase change heat dissipation composite according to one embodiment of the present invention.

[0029] Figure 6 is a graph comparing mechanical properties and latent heat according to the filler content of a phase change heat dissipation composite according to one embodiment of the present invention.

[0030] Hereinafter, with reference to the attached drawings, a method for manufacturing a biopolymer-based phase change heat dissipation composite according to an embodiment of the present invention and a phase change heat dissipation composite manufactured thereby will be described in detail. The following descriptions are exemplary descriptions intended to explain the embodied aspects of the technical concept of the present invention, and the technical concept of the present invention is not limited by the following descriptions. The technical concept of the present invention may be interpreted and limited only by the claims set forth below.

[0031] Meanwhile, conventional headings such as "Examples" are excluded, and contents corresponding to "Examples" are appropriately included in the explanation without a special format to promote a thorough understanding of the invention.

[0032] In summary, conventional methods of physically introducing fillers or other polymeric materials to solve liquid leakage problems in phase change materials significantly reduced the latent heat of the phase change material, and the improvement in mechanical strength and thermal conductivity was negligible. However, in the present invention, by chemically introducing a biopolymer into the phase change material using a catalyst, such as a SnCl₄ catalyst, it is possible to solve the liquid leakage problem and significantly improve mechanical properties while minimizing the reduction in latent heat.

[0033] Polyethylene glycol (hereinafter PEG), which is widely used as a phase change composite material due to its high latent heat (168 J / g) and eco-friendliness, is used as a matrix. To improve the low mechanical properties of PEG and the problem of liquid leakage occurring at its melting point, a phase change matrix is ​​fabricated by chemically introducing the biopolymer Polylactic acid (hereinafter PLA). By forming a structure in which PLA is chemically bonded to PEG using SnCl₄ as a catalyst, liquid leakage is prevented during the phase change of PEG, and mechanical properties can be significantly improved.

[0034] FIG. 1 is a schematic diagram conceptually illustrating a method for manufacturing a bio-based phase change heat dissipation composite according to one embodiment of the present invention.

[0035] Referring to FIG. 1, a catalyst-based esterification reaction is induced to introduce a biopolymer (PLA) for preventing liquid leakage into polyethylene glycol (PEG), which is a phase change material. In this embodiment, tin chloride (IV) (SnCl4) is used as the catalyst. Through the catalyst-based esterification reaction, an esterification bond is formed between PEG and PLA. Once the reaction is complete, the matrix of the phase change heat dissipation composite can be prepared.

[0036] In the above esterification reaction, it is preferable to control the amount of tin chloride used as a catalyst to 3 to 5% relative to the resin mixture. Meanwhile, in the above esterification reaction, polyethylene glycol and polylactic acid participate in the reaction in a weight ratio of 5:0.5 to 1.5.

[0037] For the above esterification reaction, the resin component and catalyst are first mixed, and toluene solvent is added to the mixture and heated to a temperature of 105 to 115°C under a nitrogen-substituted gas atmosphere. Sufficient stirring is performed until the reactants are completely dissolved through heating. When the reaction is completed, the reaction product is vacuum filtered and dried at room temperature to completely remove the solvent.

[0038] Through this, a matrix (resin) of a phase change heat dissipation composite material can be prepared.

[0039] When the matrix is ​​prepared, as shown in Fig. 1, a molding step is performed in which a thermally conductive filler is mixed with the prepared matrix resin and molded.

[0040] In this embodiment, carbon fiber (CF), aluminum nitride (AlN), etc., may be used as the thermally conductive filler, and the type of thermally conductive filler may be varied depending on the type or characteristics of the application to which the composite is applied.

[0041] Injection molding is used as the molding method for forming the above composite. Injection molding is a method in which a prepared mixture of matrix resin (pellets) and thermally conductive filler is melted, injected into a mold, and cooled to form the desired shape of the intermediate product. The shape of the molded product can vary depending on the purpose or application for which the composite is used as an intermediate product.

[0042] When the filler is mixed into the matrix resin and molding is completed, a biopolymer-based phase change heat dissipation composite according to one embodiment of the present invention can be manufactured.

[0043] The above-described phase change heat dissipation composite comprises a matrix containing ester bond sites between polyethylene glycol (PEG), a phase change material, and polylactic acid (PLA), a biopolymer; and a thermally conductive filler dispersed within the matrix.

[0044] In the following, a specific manufacturing process of a phase change heat dissipation composite is exemplified, and through the analysis of various experimental results, the method for manufacturing a phase change heat dissipation composite according to one embodiment of the present invention and the physical properties of the manufactured composite are sufficiently explained.

[0045] [Manufacturing of Phase Change Heat Dissipation Composites]

[0046] To solve the problem of layer separation that occurs during simple mixing of PEG and PLA, PEG (hereinafter PEGPLA) in which PLA is chemically introduced was prepared using SnCl4 (tin chloride (IV)), a catalyst that promotes the esterification reaction of PEG and PLA. To this end, 5g of PEG and 1g of PLA were weighed in a mass ratio of 5:1 and placed in a three-necked round-bottom flask. Then, 0.24g of SnCl₄, a catalyst corresponding to 4 wt% of the mixture, and 200ml of toluene to be used as a solvent were added. Subsequently, the mixture was stirred at 110°C under nitrogen gas substitution until completely melted. After the completely melted mixture was sufficiently stirred at room temperature until the color became cloudy, it was vacuum filtered and dried at room temperature to completely remove the solvent, thereby obtaining PEGPLA. The prepared PEGPLA was transferred to an injection molding machine, completely melted at 100°C, and then injection molded to produce a reinforced phase change polymer material PEGPLA composite.

[0047] [Experiment and Results Analysis]

[0048] 1 FT-IR Analysis / DSC Analysis

[0049] FIG. 2 is a graph showing the results of Fourier transform infrared spectroscopy (a) and differential scanning calorimetry (b) before and after the chemical reaction of PEGPLA according to one embodiment of the present invention.

[0050] Referring to Fig. 2, changes in chemical bonding during the PEGPLA manufacturing process were confirmed (a). New ester groups (C=O, 1740 cm⁻¹) in PEGPLA produced after the chemical reaction between PEG and PLA. -1It was confirmed that ) was formed. Through this, it was indicated that esterification proceeded successfully, and PEGPLA, in which PEG and PLA are chemically bonded, was successfully manufactured. DSC analysis was performed to confirm the changes in the thermal behavior of the material according to the PEGPLA manufacturing process (Fig. 2b). While PEG and PLA before the reaction exhibited endothermic reactions at around 66°C and 176°C, respectively, in PEGPLA after synthesis, the peaks merged into one, and the endothermic reaction region decreased to around 60°C because the intermolecular forces weakened due to the reduction of hydroxyl groups that induce hydrogen bonding. Through this, it was confirmed that PEGPLA was formed through chemical bonding.

[0051] [Cross-section Analysis]

[0052] Figure 3 is a scanning electron microscope (FE-SEM) image showing the cross-sections of PEG, PLA, which are samples in the manufacturing step of PEGPLA in Figure 2, and PEGPLA, which is the product after the reaction.

[0053] Cross-sectional images for comparison before and after the synthesis of PEGPLA were taken using FESEM of PEG and PLA before the reaction and PEGPLA after the reaction, and are shown in Figure 3. The cross-sectional image of PEGPLA chemically reacted using SnCl₄ as a catalyst showed a uniform morphology that was distinguishable from the cross-sectional images of PEG and PLA before the reaction. Through this, it was confirmed that PEGPLA was successfully synthesized.

[0054] [Analysis of Changes in Latent Heat Characteristics]

[0055] Latent heat measurements were performed according to the mixing ratio of the manufactured PEGPLA, and the results are shown in Table 1 below. In terms of latent heat characteristics, the higher the proportion of PEG, the better the latent heat characteristics of the existing phase change material, PEG, were maintained. Since latent heat is the most important characteristic of phase change materials, a ratio of 5:1 was finally selected to maximize latent heat characteristics based on the measurement results.

[0056] Latent Heat Ratio (PEG:PLA) Latent Heat (J / g) 1:01705:1158.53:1127.11:141.3

[0057] [Leakage Test Results] Figure 4 is a photograph showing the leakage test results according to temperature for each sample.

[0058] To verify leakage issues related to temperature, leakage tests were conducted by comparing PEG, PEGPLA, and PEGPLA composites fabricated with aluminum nitride and carbon fiber (CF) fillers, and the results are shown in Fig. 4. Referring to Fig. 4, in the case of pure PEG, some liquefaction began to become visible at 70°C, which is above the melting point (around 65°C), and at 80°C, it completely transformed into a liquid state and collapsed. On the other hand, in the case of PEGPLA, in which PLA was chemically introduced into PEG, no liquid leakage occurred up to 70°C; some liquefaction began to become visible from 80°C, and it completely transformed into a liquid state as the temperature increased further. The PEGPLA composite fabricated with fillers did not experience leakage even up to 150°C.

[0059] [Cross-sectional Analysis by Filler Content]

[0060] Figure 5 is a scanning electron microscope (FE-SEM) image showing a cross-section according to the filler content of a phase change heat dissipation composite according to one embodiment of the present invention.

[0061] To verify the change in the arrangement of fillers according to the ratio of fillers introduced into the composite, cross-sectional images of composites fabricated with different ratios of aluminum nitride and carbon fibers were captured using FE-SEM and are shown in Fig. 5. Referring to Fig. 5, the cross-sectional images confirmed that the composite with a higher proportion of AlN showed more vertical alignment of carbon fibers, thereby confirming the creation of a heat conduction path in the vertical direction.

[0062] [Analysis of Mechanical Properties and Latent Heat Characteristics of the Composite]

[0063] The results of the analysis of the mechanical properties and latent heat characteristics of the composites, which vary depending on the ratio of aluminum nitride and carbon fiber, are shown in Table 2 below. Corresponding to Table 2, Figure 6 is a graph comparing the mechanical properties and latent heat according to the filler content of the phase change heat dissipation composite according to one embodiment of the present invention. Referring to Table 2 and Figure 6, PEGPLA, in which PLA is chemically introduced into PEG, showed improved mechanical properties compared to pure PEG. Furthermore, it was confirmed that the introduction of aluminum nitride and carbon fiber fillers significantly improved the mechanical properties of the composite. In particular, mechanical properties increased as the ratio of carbon fiber increased, and the composite with an AlN to CF ratio of 1:2 exhibited the highest tensile strength of 12.75 MPa. The latent heat characteristics showed approximate values ​​for the three types of composites.

[0064] Latent Heat and Mechanical Properties According to Filler AlN and CF Ratio Ratio (AlN:CF) Tensile Strength (MPa) Tensile Strain (%) Latent Heat (J / g) PEG (0 wt%) 0.1 0.00 8 170 PEGPLA (0 wt%) 0.8 20.08 115 8.5 PEGPLA / AlN / CF (1:1) (50 wt%) 9.1 0.7 35 75.3 PEGPLA / AlN / CF (1:2) (50 wt%) 12.8 1.01 74.9 PEGPLA / AlN / CF (2:1) (50 wt%) 6.6 0.6 25 76.6

[0065] [Analysis of Thermal Conductivity Characteristics]

[0066] A thermally conductive phase change composite was fabricated by adding aluminum nitride and carbon fiber-based high-thermal-conductivity fillers to PEGPLA. To verify the vertical thermal conductivity characteristics of this composite, the thermal conductivity was measured at room temperature (25℃) using laser flash analysis, and the results are shown in Table 3 below. The measured vertical thermal conductivity was W / m·K when the filler loading was 50 wt%.

[0067] Comparison of Thermal Conductivity and Latent Heat Properties of Phase Change Composites Composite Type | wt% | Thermal Conductivity (W / mK) | Latent Heat (J / g) PEGPLA | 0.2 | 2.1 | 5.5 PEGPLA / AlN / CF (2:1) | -1.1 | 0.7 | 6.1 | 3.7 PEGPLA / AlN / CF (2:1) | -2.2 | 1.2 | 3.1 | 9.6 PEGPLA / AlN / CF (2:1) | -3.3 | 2.0 | 3.1 | 0.3 PEGPLA / AlN / CF (2:1) | -4.4 | 2.5 | 5.8 | 8.3 PEGPLA / AlN / CF (2:1) | -5.5 | 3.1 | 5.7 | 6.6 PEG / PVDF-BN | 2.6 | 8.0 | 8.1 | 2.4

[0068]

Claims

1. A step of preparing a phase change matrix by inducing a catalytic esterification reaction between a phase change material, polyethylene glycol (PEG), and a biopolymer, polylactic acid (PLA); A step of preparing a mixture by mixing a thermally conductive filler into the above phase change matrix; and A molding step comprising molding the above mixture, Method for manufacturing a biopolymer-based phase change heat dissipation composite.

2. In Paragraph 1, A method for manufacturing a biopolymer-based phase change heat dissipation composite, characterized in that the catalyst comprises tin chloride (IV) (SnCl4).

3. In Paragraph 2, A method for manufacturing a biopolymer-based phase change heat dissipation composite characterized by using the above catalyst in a ratio of 3 to 5% relative to the total weight of the PEG and PLA.

4. In Paragraph 1, A method for manufacturing a biopolymer-based phase change heat dissipation composite, characterized in that the polyethylene glycol and polylactic acid are reacted in a weight ratio of 5:0.5 to 1.

5.

5. In Paragraph 1, A method for manufacturing a biopolymer-based phase change heat dissipation composite, characterized in that the above esterification reaction is carried out in a toluene solvent.

6. In Paragraph 1, The above esterification reaction is, A step of dissolving the reactant under a nitrogen-substituted gas atmosphere and a temperature of 105 to 115°C; and A method for manufacturing a biopolymer-based phase change heat dissipation composite, characterized by including the step of removing the solvent by vacuum filtration and room temperature drying of the dissolved reactant.

7. In Paragraph 1, A method for manufacturing a biopolymer-based phase change heat dissipation composite characterized by using carbon fiber (CF) and aluminum nitride (AlN) as the fillers.

8. In Paragraph 1, A method for manufacturing a biopolymer-based phase change heat dissipation composite, characterized in that the above-mentioned molding step includes an injection molding step.

9. A matrix comprising ester bonding sites between polyethylene glycol (PEG), a phase change material, and polylactic acid (PLA), a biopolymer; and A phase change heat dissipation composite comprising a thermally conductive filler dispersed within the above matrix.

10. In Paragraph 9, A phase change heat dissipation composite characterized in that the above heat dissipation composite is an injection molded product.

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