Pod-like phase change material and preparation method thereof

Abstract

The invention discloses a pod-like phase change material and a preparation method thereof, and relates to the technical field of energy devices. The pod-like phase change material comprises a polymer matrix, a phase change material and a micro-nano peak valley structure. The phase change material is dispersed in the polymer matrix, and liquid leakage is inhibited through physical packaging; the micro-nano peak valley structures are distributed on the surface of the pod-like phase change material and have a mechanical anchoring effect, accurate distribution of the phase change material in a preset area is achieved, and a unique pod-like structure is formed. The material has the following remarkable advantages: firstly, the polymer matrix realizes stable loading of the phase change material through physical packaging; secondly, the micro-nano peak valley structure induces the phase change material to be distributed in a specific area, and a local enhanced heat management unit is constructed; and 3, a micro-nano peak valley structure on the surface of the material obviously increases the real contact area between other parts and the material, reduces the contact thermal resistance of a thermal interface, and optimizes a heat conduction path.

Description

Technical Field

[0001] The present invention relates to the technical field of energy devices, and particularly to pod-like phase change materials and a preparation method thereof. Background Art

[0002] Currently, the development direction of electronic devices is accelerating towards miniaturization and high performance. In the field of electronic packaging, the chip integration density continues to increase, and the heat generated per unit area shows an explosive growth. If heat cannot be dissipated in time, the core component chip will face problems such as performance degradation and shortened lifespan. Thermal management materials are a crucial part of the thermal management system of electronic devices. Developing thermal management materials with high heat dissipation capabilities has become a core challenge that needs to be overcome urgently in the development process of high-power integrated electronic devices.

[0003] Phase change materials (PCM) are a type of intelligent materials that undergo phase transitions driven by temperature and are accompanied by latent heat storage. Among various phase change materials, solid-liquid PCM has received extensive attention due to its advantages such as small volume change, adjustable phase change temperature, and high phase change latent heat. However, the leakage problem of solid-liquid PCM severely restricts its engineering applications, and material stabilization needs to be achieved through encapsulation technology. The polymer encapsulation system has become the most promising encapsulation form for engineering applications due to its easy processability, interfacial compatibility, and mechanical tunability. This system suppresses the liquid migration of PCM through physical binding, thus effectively solving the leakage problem. At the same time, it can also retain the properties such as the flexibility of the material, enabling it to meet the heat dissipation requirements in complex scenarios.

[0004] When constructing a binary composite phase change material system of polymer and PCM as a thermal interface material, the core contradiction lies in the regulation of the interfacial thermal resistance between adjacent components and this material. The existence of interfacial thermal resistance leads to the formation of a thermal resistance barrier at the contact interface, causing local temperature rise and, in severe cases, device thermal failure. Therefore, how to reduce the interfacial thermal resistance through material design and structural regulation has become a key technical bottleneck in the engineering applications of composite phase change materials. Summary of the Invention

[0005] To solve the above technical bottleneck, the present invention proposes pod-like phase change materials and a preparation method thereof. Its innovative mechanism includes three dimensions: firstly, using a polymer matrix to physically encapsulate the phase change material, effectively suppressing the liquid leakage problem; secondly, the mechanical anchoring effect of the micro-nano peak-valley structure induces the precise distribution of the phase change material in the target area, constructing a locally enhanced thermal management unit; thirdly, the micro-nano peak-valley structure on the material surface can increase the real contact area, reduce the interfacial thermal resistance, and ensure the stable operation of electronic components.

[0006] Specifically, the following technical solutions are adopted:

[0007] Pod-like phase change material, characterized in that the pod-like phase change material comprises a polymer matrix, a phase change material and a micro-nano peak-valley structure;

[0008] The phase change material is dispersed in the polymer matrix, and the phase change material is physically encapsulated by the polymer matrix to inhibit liquid leakage;

[0009] The micro-nano peak-valley structure is distributed on the surface of the pod-like phase change material;

[0010] The micro-nano peak-valley structure has a mechanical anchoring effect, induces the phase change material to be distributed in a preset area, forms a pod-like structure, and constructs a locally enhanced thermal management unit;

[0011] The micro-nano peak-valley structure can increase the true contact area between other components and the pod-like phase change material, reduce the thermal interface contact thermal resistance, and optimize the heat conduction path.

[0012] Preferably, the polymer matrix includes a flexible polymer matrix and a non-flexible polymer matrix;

[0013] The flexible polymer matrix includes at least one of ethylene-vinyl acetate copolymer, polydimethylsiloxane, polyurethane, silicone rubber, polyolefin elastomer and styrene-butadiene-styrene;

[0014] The non-flexible polymer matrix includes one or more of polypropylene, polyethylene, epoxy resin, polystyrene, polyvinyl chloride, polycarbonate, polyether ether ketone, polyphenylene sulfide and polyamide.

[0015] Preferably, the phase change material includes one or more of paraffin, polyethylene glycol, phase change polyol and phase change polyacid;

[0016] When two or more phase change materials are used, the temperatures of the phase change materials are distributed in a gradient, and the phase change temperature difference between adjacent materials is 5-10 °C.

[0017] Preferably, the loading amount of the pod-like phase change material is not less than 30 wt%, and the total phase change enthalpy value is not less than 55 J / g.

[0018] Preferably, the micro-nano peak-valley structure exists on at least one surface of the pod-like phase change material;

[0019] When it exists on multiple surfaces of the pod-like phase change material, the geometric parameters of the micro-nano peak-valley structure on each surface can be independently designed.

[0020] Preferably, the micro-nano peak-valley structure is at least one of a hemispherical shape, a triangular pyramid, a quadrangular pyramid, a cylinder, a cube, and a cuboid, and is distributed in an ordered array or a random distribution;

[0021] When in an ordered array distribution, the distribution form of the micro-nano peak-valley structure covers, but is not limited to, square, rectangle, triangle, circle, hexagon, rhombus, polygon.

[0022] Preferably, the overall roughness of the micro-nano peak-valley structure is 0 - 500 μm, the height of the micro-nano peak-valley structure is 0 - 500 μm, the equivalent diameter of the micro-nano peak-valley structure is 0 - 500 μm, and the roughness of different regions can be set in a gradient according to the heat transfer requirements;

[0023] The total thickness of the pod-like phase change material is 0.1 - 5 mm.

[0024] The pod-like phase change material also includes its preparation method, which includes the following steps:

[0025] Step 1: Add the phase change material to the polymer matrix material, and use one or several devices such as a centrifugal degassing machine and a stirrer to cooperate to obtain a homogeneous system of the phase change material and the polymer, where the mass ratio of the phase change material to the polymer matrix is 3:7 - 9:1;

[0026] Step 2: Place the homogeneous system of the polymer and the phase change material on a flat mold with a micro-nano peak-valley structure, and after roller coating and roller pressing in sequence, then perform constant temperature drying to obtain the pod-like phase change material.

[0027] Preferably, in Step 2, the roller coating speed is 2 - 200 mm / s, the roller pressing speed is 2 - 200 mm / s, the roller pressing time is 1 - 5 min, and the roller pressing pressure is 0 - 5 MPa.

[0028] Before Step 1, it also includes necessary pretreatment steps for the polymer matrix and the phase change material. The pretreatment includes drying and liquefying the polymer matrix, and preheating and liquefying the phase change material.

[0029] The present invention has the following beneficial effects:

[0030] The pod-like composite phase change material involved in the present invention realizes the stable loading of the phase change material through physical encapsulation of the polymer matrix; the mechanical anchoring effect of the micro-nano peak-valley structure guides the distribution of the phase change material in the preset area, constructing a locally enhanced thermal management unit; the micro-nano peak-valley structure on the material surface can increase the true contact area and reduce the interfacial thermal resistance, providing a possibility for improving the lifespan of electronic components. Description of the Drawings

[0031] Figure 1 It is a schematic structural diagram of the pod-like phase change material in Example 1;

[0032] Figure 2 It is an SEM image of the PDMS / paraffin pod-like phase change material in Example 1;

[0033] Figure 3 Infrared curve of the PDMS / paraffin pod - type phase - change material in Example 1;

[0034] Figure 4 XRD curve of the PDMS / paraffin pod - type phase - change material in Example 1;

[0035] Figure 5 DSC curve of the PDMS / paraffin pod - type phase - change material in Example 1;

[0036] Figure 6 Thermal management effect of the PDMS / paraffin pod - type phase - change material in Example 1;

[0037] Figure 7 Leakage experiment results of the PDMS / paraffin pod - type phase - change material in Example 1;

[0038] Figure 8 Schematic structural diagram of a kind of pod - type phase - change material in Example 2;

[0039] Figure 9 Schematic structural diagram of a kind of pod - type phase - change material in Example 3. Detailed implementation manners

[0040] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments.

[0041] Example 1

[0042] As Figure 1 shown, the pod - type phase - change material, the pod - type phase - change material includes a polymer matrix PDMS, a phase - change material paraffin, and a micro - nano peak - valley structure. The preparation method of the pod - type phase - change material includes the following steps:

[0043] Step 1: Preheat 0.6 g of paraffin at 80 °C for 10 minutes to obtain liquid paraffin; then add 1.27 g of PDMS, pre - mix with a magnetic stirrer for 5 minutes, and then transfer to a planetary centrifugal vacuum mixer and mix at a speed of 1400 rpm for 20 min to form a homogeneous system; subsequently, add 0.13 g of curing agent to the homogeneous system of PDMS and paraffin and mix at a speed of 1400 rpm for 5 min. Finally, place the homogeneous system of PDMS and paraffin in a vacuum box at 45 °C for vacuum degassing and keep the pressure for 30 min;

[0044] Step 2: Place the PDMS / paraffin homogeneous system on a flat mold with a surface roughness of 50 μm, and use a self-made roller coater to perform roller coating at a speed of 50 mm / s to obtain a PDMS / paraffin preformed material; subsequently, adjust the distance between the roller and the mold to 0.3 mm, and roll back and forth at a speed of 50 mm / s for 2 min; cure it in an oven at 45 °C for 6 h to obtain a PDMS / paraffin pod-like phase change material with a thickness of 0.3 mm.

[0045] Observe the microscopic morphology of the PDMS / paraffin pod-like phase change material. As Figure 2 shown, a micro-nano peak-valley structure is formed on the upper surface of the phase change material, and paraffin is dispersed inside the material and at the micro-nano peak-valley structure. The formation of the micro-nano peak-valley structure and the distribution of paraffin inside it indicate that a local enhanced heat management unit has been constructed on the material surface. From the perspective of heat transfer principle, this unit has two major advantages. On the one hand, the phase change characteristics of paraffin endow it with good heat storage capacity, which can absorb and release heat during temperature changes and buffer temperature fluctuations; on the other hand, the micro-nano peak-valley structure significantly increases the contact area between the material and the outside world, which is conducive to efficient heat transfer and effectively reduces the interfacial thermal resistance when the material contacts the outside world, providing strong support for the application of this phase change material in the field of efficient heat management.

[0046] Detect the chemical structures of three samples: pure PDMS matrix, pure paraffin, and PDMS / paraffin pod-like phase change material. As Figure 3 shown, the FTIR results show that pure paraffin exhibits specific vibration peaks related to -CH2 (717, 1465, 2846 cm -1 -1) and -CH3 (1372, 2914 cm -1 -1), as well as vibration peaks related to -OH (1637, 3549 cm-1). Pure PDMS has characteristic peaks related to -CH3 (1411, 2960 cm -1 -1), Si-CH3 (785, 1257 cm -1 -1), Si-O-Si (1006 cm -1 -1), and Si-OH (846, 866 cm -1 -1). The infrared spectrum of the PDMS / paraffin pod-like phase change material is basically the same as that of pure PDMS, and only characteristic peaks of paraffin appear at specific positions (2916 and 2848 cm -1 -1); the results show that no chemical reaction occurs in the PDMS / paraffin pod-like phase change material.

[0047] As Figure 4 shown, the XRD pattern also further indicates that compared with pure PDMS and pure paraffin, no new diffraction peaks appear, indicating that only physical mixing occurs in the material.

[0048] Figure 5DSC curve of the PDMS / paraffin pod - type phase - change material. Comparing it with the DSC curves of pure paraffin and pure PDMS, it can be seen that the performance of the PDMS / paraffin pod - type phase - change material is between that of pure PDMS and pure paraffin, meeting the requirements. The physical property parameters of the experimental samples are shown in the following table:

[0049] Table 1 is the table of physical property parameters of the experimental samples in Example 1:

[0050]

[0051] From the data in Table 1, it can be seen that the melting latent heat and solidification latent heat of the PDMS / paraffin pod - type phase - change material are 29.03% and 28.23% of those of pure paraffin respectively; compared with the theoretical values (57.048 J / g, 58.905 J / g), the difference ≤ 3.479 J / g.

[0052] Figure 6 It is the thermal management effect curve of the PDMS / paraffin pod - type phase - change material. It can be seen that when the PDMS / paraffin composite phase - change material is used in combination with a radiator, the heat source temperature working at 80 °C can be reduced to 49 °C, which is 2 °C lower than the temperature when only the radiator works.

[0053] Figure 7 It is the leakage experiment result of the PDMS / paraffin pod - type phase - change material. The PDMS / paraffin pod - type phase - change material is placed in an oven at 80 °C, and the sample weight is measured every 1 h. The results show that the mass loss rate of the PDMS / paraffin pod - type phase - change material within 5 h ≤ 1.8%, verifying the effectiveness of the encapsulation.

[0054] In summary, for the prepared PDMS / paraffin pod - type phase - change material, on the one hand, the problem of liquid leakage of the phase - change material is solved through physical encapsulation by the polymer matrix; on the other hand, the mechanical anchoring effect of the micro - nano peak - valley structure guides the distribution of the phase - change material in the micro - nano peak - valley structure area, constructing a locally enhanced thermal management unit; the micro - nano peak - valley structure on the material surface increases the real contact area and reduces the interface thermal resistance, providing the possibility to ensure the normal operation of electronic components.

[0055] Example 2

[0056] As Figure 8 shown, a kind of pod - type phase - change material and its preparation method. On the basis of Example 1, in step 2 of Example 1, preparing the micro - nano peak - valley structure only on the upper surface is modified to preparing the same - level micro - nano peak - valley structures on both the upper and lower surfaces. The rest are the same as in Example 1, and the pod - type phase - change material is obtained.

[0057] Example 3

[0058] AsFigure 9 As shown, a pod-like phase change material and its preparation method. Regarding the surface treatment step of the pod-like phase change material in Example 2, the preparation method of the same-grade micro-nano peak-valley structures on the upper and lower surfaces originally is changed to the preparation of different-grade micro-nano peak-valley structures on the upper and lower surfaces. In other aspects, it is the same as Example 2, and finally a pod-like phase change material is obtained.

[0059] As mentioned above, only the preferred specific embodiments of the present invention are described, but the protection scope of the present invention is not limited thereto. The substitution may be the substitution of part of the structure, device, method steps, or a complete technical solution. Any equivalent substitution or change made according to the technical solution of the present invention and its inventive concept should be covered within the protection scope of the present invention.

Claims

1. Pod-like phase change material, characterized in that: The peapod-like phase change material comprises a polymer matrix, a phase change material and a micro-nano peak-valley structure; The phase change material is dispersed in the polymer matrix, and the phase change material is physically encapsulated by the polymer matrix to inhibit liquid leakage; The micro-nano peak-valley structure is distributed on the surface of the peapod-like phase change material; The micro-nano peak-valley structure has a mechanical anchoring effect, inducing the phase change material to be distributed in a preset area, forming a pod-like structure, and constructing a local enhanced thermal management unit; The micro-nano peak-valley structure can increase the actual contact area between other components and the peapod-like phase change material, reduce the thermal interface contact thermal resistance, and optimize the heat conduction path.

2. The pod-like phase change material according to claim 1, characterized in that: The polymer matrix includes a flexible polymer matrix and a non-flexible polymer matrix; The flexible polymer matrix includes at least one of ethylene-vinyl acetate copolymer, polydimethylsiloxane, polyurethane, silicone rubber, polyolefin elastomer and styrene-butadiene-styrene; The non-flexible polymer matrix includes one or more of polypropylene, polyethylene, epoxy resin, polystyrene, polyvinyl chloride, polycarbonate, polyetheretherketone, polyphenylene sulfide and polyamide.

3. The pod-like phase change material according to claim 1, characterized in that: The phase change material includes one or more of paraffin, polyethylene glycol, phase change polyol and phase change polyacid; When two or more phase change materials are used, the temperature of the phase change materials is distributed in a gradient, and the phase change temperature difference between adjacent materials is 5 to 10°C.

4. The pod-like phase change material according to claim 1, characterized in that: The pod-like phase change material loading is not less than 30 wt%, and the total enthalpy of phase change is not less than 55 J / g.

5. The pod-like phase change material according to claim 1, characterized in that: The micro-nano peak-valley structure exists on at least one surface of the peapod-like phase change material; When present on multiple surfaces of the peapod-like phase change material, the geometric parameters of the micro-nano peak-valley structure on each surface can be independently designed.

6. The pod-like phase change material according to claim 1, characterized in that: The micro-nano peak-valley structure is at least one of a hemispherical shape, a triangular pyramid, a quadrangular pyramid, a cylinder, a cube, and a cuboid, and is distributed in an orderly array or in an irregular random distribution; When distributed in an ordered array, the distribution form of the micro-nano peak-valley structure includes but is not limited to square, rectangle, triangle, circle, hexagon, rhombus, and polygon.

7. The pod-like phase change material according to claim 1, characterized in that: The overall roughness of the micro-nano peak-valley structure is 0-500 μm, the height of the micro-nano peak-valley structure is 0-500 μm, the equivalent diameter of the micro-nano peak-valley structure is 0-500 μm, and the roughness of different areas can be set in a gradient according to the heat transfer requirements; The total thickness of the peapod-like phase change material is 0.1-5 mm.

8. The peapod-like phase change material according to any one of claims 1 to 7, further comprising a method for preparing the peapod-like phase change material, characterized in that: The following steps are involved: Step 1: adding the phase change material to the polymer matrix material, using one or more of the centrifugal degassing machine and the stirrer to obtain a homogeneous system of the phase change material and the polymer, wherein the mass ratio of the phase change material to the polymer matrix is ​​3:7 to 9:1; Step 2: Place the homogeneous system of polymer and phase change material on a flat plate mold with a micro-nano peak-valley structure, and then perform roller coating and roller pressing in sequence, and then perform constant temperature drying to obtain a pod-like phase change material.

9. The method for preparing a pod-like phase change material according to claim 8, characterized in that: The roller coating speed described in step 2 is 2-200 mm / s, the roller pressing speed is 2-200 mm / s, the roller pressing time is 1-5 min, and the roller pressing pressure is 0-5 MPa.

10. The method for preparing a pod-like phase change material according to claim 8, characterized in that: Before step one, the method further includes performing necessary pretreatment steps on the polymer matrix and the phase change material, wherein the pretreatment includes drying and liquefying the polymer matrix and preheating and liquefying the phase change material.

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