High-strength low-thermal-resistance composite phase change material and preparation process thereof

Abstract

The invention discloses a high-strength and low-thermal-resistance composite phase change material and a preparation process thereof, and belongs to the technical field of phase change materials, and the high-strength and low-thermal-resistance composite phase change material is characterized by comprising a metal net and a phase change energy storage layer filled on the metal net, the phase-change energy storage layer comprises a phase-change matrix and heat-conducting powder, the weight ratio of the phase-change matrix to the heat-conducting powder is (5-10): (90-95), metal meshes are filled with the phase-change material, holes caused by volume change before and after phase change are reduced, the phase-change material is prevented from being pumped out and leaked in the phase-change process, and the service life of the phase-change material is prolonged. And due to the composite design of the metal net and the phase change material, the characteristics of high strength and low thermal resistance of the material are realized.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of phase change materials, in particular to a high-strength and low-thermal-resistance composite phase change material and a preparation process thereof. BACKGROUND

[0002] With the rapid development of modern electronic technology, the power consumption of chips is increasing, which leads to a serious problem of chip temperature rise, and the excessively high chip temperature can reduce the performance of the chip, shorten the service life and even cause failure. Therefore, effective chip cooling technology is crucial to ensure the stable operation of the chip.

[0003] Phase change materials have high latent heat value and thermal conductivity, can absorb or release a large amount of heat during phase change, and realize efficient thermal management. In chip cooling, phase change materials can be used as thermal interface materials, which are in close contact with the chip, effectively conduct the heat generated by the chip, and absorb heat when the temperature exceeds the phase change temperature, thereby realizing instantaneous temperature stabilization. However, the strength of the phase change material is poor, and it is easy to break and deform during installation. Some phase change materials may have a "pumping out" phenomenon in chip applications, which can affect the heat dissipation effect and cause overheating or even damage to the equipment. Therefore, the development of a composite material that can improve the strength of the phase change material, prevent pumping out, and maintain good thermal conductivity has become a focus and difficulty of current research. SUMMARY

[0004] In order to solve the problems in the prior art, the present application provides a high-strength and low-thermal-resistance composite phase change material and a preparation process thereof. The phase change material is compressed and fixed in the metal mesh hole to reduce the hole caused by the volume change before and after phase change, prevent the pumping out and leakage of the phase change material during the phase change process, and realize the high strength and low thermal resistance characteristics of the material through the composite design of the metal mesh and the phase change material.

[0005] The first aspect of the present application is to provide a high-strength and low-thermal-resistance composite phase change material, which adopts the following technical scheme: a high-strength and low-thermal-resistance composite phase change material, comprising a metal mesh and a phase change energy storage layer filled in the metal mesh, the phase change energy storage layer comprising a phase change matrix and a thermal conductive powder, and the weight ratio of the phase change matrix and the thermal conductive powder being (5-10):(90-95). The phase change energy storage layer is filled in the metal mesh hole to form a composite structure, which improves the strength and rigidity of the composite phase change material, prevents the phase change material from breaking and deforming during installation, and reduces the hole caused by the volume change before and after phase change after the phase change material is fixed in the metal mesh hole, thereby reducing the pumping out and leakage of the phase change material during the phase change process, improving the safety in use, and realizing the high strength and low thermal resistance characteristics of the phase change material through the composite design of the metal mesh and the phase change material.

[0006] As an example, the weight ratio of the phase change matrix and the heat-conductive powder can be 5:95, 7:93, 8:92, 10:90, or a range value of any two numbers. If the content of the phase change matrix is too much (>10%), the content of the heat-conductive powder will be reduced, which will reduce the heat-conductive performance of the composite phase change material and increase the thermal resistance. If the content of the phase change matrix is less than 5%, the latent heat value of the composite phase change material will be significantly reduced, and the heat storage / heat release capacity will be greatly reduced, which cannot effectively play the core function of the phase change material. In addition, the phase change matrix serves as an adhesive phase. When the content is too low, it cannot fully wet and wrap the heat-conductive powder particles, resulting in insufficient bonding force between the particles, and the composite phase change material is easy to break and pulverize. Therefore, the selection of an appropriate amount of heat-conductive powder further improves the thermal conductivity of the composite phase change material, enhances the heat transfer performance of the material, and meets the heat dissipation demand of the battery generating a large amount of heat during high-power charging and discharging.

[0007] Preferably, the phase change matrix at least includes a resin-based phase change material, and the viscosity of the resin-based phase change material is not more than 1 million Pa·s. If the viscosity of the resin-based phase change material is more than 1 million Pa·s, it will cause uneven filling of the resin-based phase change material in the metal mesh, easily causing problems such as material shortage, pores, and cavities. Moreover, a too high viscosity will also cause a serious decline in heat transfer efficiency because a too high viscosity cannot achieve a certain degree of natural convection during melting, and cannot effectively achieve rapid transfer of the heat source. Therefore, when the viscosity of the resin-based phase change material is controlled to be not more than 1 million Pa·s, the heat transfer performance of the phase change material can be effectively guaranteed.

[0008] Preferably, the resin-based phase change material includes at least one of polyisobutylene, polyisoprene, polyalphaolefin, styrene-butadiene-styrene, EVA, and polycaprolactone. The resin-based phase change material is used in combination with the metal mesh. The heat conductivity of the metal mesh can make up for the defect of low thermal conductivity of the resin-based PCM, accelerate the absorption / release of heat, improve the phase change efficiency, and achieve efficient heat conduction. The metal mesh as a heat-conductive framework can reduce the performance attenuation of the PCM caused by local overheating / overcooling, prolong the service life of the material, and achieve temperature homogenization.

[0009] The resin-based phase change material serves as a phase change material and also as a packaging material. The microporous structure of the metal mesh can adsorb liquid PCM (such as paraffin-based resin) to prevent leakage during the phase change process. The interface bonding force between the metal mesh and the PCM (phase change material) is enhanced through chemical bonding. Moreover, the resin-based phase change material can be grafted to the surface of the metal mesh through chemical bonds, which can further improve the bonding strength and avoid phase separation after long-term use. The selection of one of the above can solve the problems of leakage and brittleness of the composite phase change material, and endow the composite phase change material with shape stability and excellent mechanical properties.

[0010] And the metal mesh provides a rigid skeleton for the soft resin phase change material, avoiding deformation of the material under phase change or external force. By adjusting the mesh number (porosity) of the metal mesh and the ratio of the phase change material, the composite phase change material can have good mechanical strength and flexibility.

[0011] Preferably, the phase change matrix also includes paraffin wax, and the weight ratio of paraffin wax to resin phase change material is (5-20):(80-95).

[0012] As an example, the weight ratio of paraffin wax to resin phase change material can be 5:95, 8:92, 10:90, 12:88, 15:85, 20:80 or any range of two numbers. If the proportion of paraffin wax is too low, the phase change heat storage capacity will be significantly reduced. Moreover, due to the formation of a dense cross-linked network by excess resin, the movement of paraffin wax molecules is limited, the latent heat value is reduced, and due to the high content of resin, the dispersion of the heat-conducting powder is poor, and the thermal conductivity will also be reduced. If the proportion of paraffin wax is too high, the content of resin is low, which is not enough to form a continuous network to wrap paraffin wax, and liquid leakage is easy to occur. Moreover, excessive paraffin wax not only makes the composite phase change material brittle, but also makes the heat-conducting efficiency decrease due to the wrapping of heat-conducting filler particles by excessive liquid paraffin wax.

[0013] Preferably, the metal mesh is at least one of copper mesh, stainless steel mesh, aluminum mesh, titanium mesh, and nickel mesh.

[0014] Preferably, the mesh of the metal mesh is 100-300 mesh. When the mesh number is in this range, it has a good restraining effect on the phase change material and has a leak-proof effect. At the same time, the distance between the metal wires is small, which shortens the heat transfer path and improves the heat conduction efficiency.

[0015] As an example, the mesh of the metal mesh is 100 mesh, 150 mesh, 180 mesh, 200 mesh, 200 mesh, 250 mesh, and 300 mesh. If the mesh number is higher than 300 mesh, the mesh pores are too small, and the high-viscosity phase change matrix is difficult to penetrate, which is easy to form bubbles or holes, resulting in low filling rate and reduced effective heat storage. If the mesh number is lower than 100 mesh, the mesh is too large, and the restraining force on the molten phase change material is weak. Especially when the temperature fluctuates or is under pressure, the phase change material is easy to seep out of the mesh, which increases the leakage probability.

[0016] Preferably, the metal mesh is a metal mesh treated by a modifier, the modifier including at least one of silane coupling agent, phosphate, titanate coupling agent, dopamine and derivatives thereof. After the modification treatment of the metal mesh by the above-mentioned modifier, the resin is grafted on the metal mesh by chemical bonding to form a firm composite structure. For example, the silane coupling agent is used to modify aluminum, copper and stainless steel. The hydroxyl group on the surface of the metal is combined with the hydrolyzed end (such as methoxy) of the silane coupling agent, and the other end (such as amino group or epoxy group) of the silane coupling agent is reacted with the resin. When the phosphate is used to modify the metal mesh, the phosphate group forms a coordination bond with the metal (such as stainless steel and aluminum), and the organic chain segment is compatible with the resin, thereby improving the bonding strength between the resin and the metal mesh. The titanate coupling agent is used to modify titanium and stainless steel to improve the adhesion between the metal mesh and the resin. The modification principle of dopamine and its derivatives for the metal is that the active groups (such as amino group and phenolic hydroxyl group) are introduced on the surface of the metal mesh by the biomimetic polydopamine coating, and the grafting with the resin is further realized. Therefore, after the modification treatment of the metal mesh, the bonding strength between the phase change material and the metal mesh is improved, the pumping out or leakage of the phase change material during the phase change is prevented, and the safety and reliability of the composite phase change material are improved.

[0017] Preferably, the heat-conducting powder is at least one of aluminum, aluminum oxide and zinc oxide.

[0018] Preferably, the particle size of the heat-conducting powder is 1-10 μm, which can ensure that there is enough heat-conducting powder in a unit volume to form a high-efficiency heat-conducting network structure, and at the same time, the metal mesh can be effectively filled.

[0019] For example, the particle size of the heat-conducting powder is 1 μm, 3 μm, 5 μm, 6 μm, 8 μm, 10 μm or any range value of two numbers. If the particle size of the heat-conducting powder is less than 1 μm, the heat-conducting powder solution has a serious agglomeration effect in the phase change matrix, the heat-conducting network is discontinuous, the heat transfer efficiency is reduced, and the particle size is too small to limit the molecular movement, thereby reducing the latent heat value of the composite phase change material. When the particle size is too large, the particle spacing is large, the filling rate in the metal mesh is reduced, and the risk of leakage is also increased.

[0020] Preferably, the thickness of the metal mesh is 0.01-0.05 mm.

[0021] For example, the thickness of the metal mesh can be 0.01 mm, 0.02 mm, 0.03 mm, 0.04 mm, 0.05 mm or any range value of two numbers, so as to avoid being too thick to meet the requirements of the chip.

[0022] The second aspect of the present application provides a preparation method of the high-strength low-thermal-resistance composite phase change material as described above, which includes the following preparation steps: (1) mixing the phase change matrix and the heat-conducting powder in proportion to obtain a mixed slurry; (2) heating the mixed slurry to a molten state and coating the mixed slurry on a metal mesh while hot; (3) calendering to a target thickness and curing at room temperature to obtain a composite phase change material.

[0023] Preferably, the metal mesh is a modified metal mesh, and the modified metal mesh is obtained by the following modification method. coating a modifier on the metal mesh and baking to obtain a modified metal mesh; Preferably, in step (2), the heating temperature is 90-100℃; when the heating temperature is 90-100℃, the resin has a low viscosity at this temperature, which facilitates coating on the metal mesh; if the temperature is too high, the modifier on the modified metal mesh may volatilize slightly; and if the temperature is too low, the phase change material is relatively thick, which is not conducive to coating.

[0024] In step (2), the metal mesh is a modified metal mesh, and the modified metal mesh is obtained by the following modification method. Preferably, the modifier is at least one of a coupling agent, a phosphate ester, a titanate coupling agent, dopamine and a derivative thereof.

[0025] In summary, the present application has the following beneficial effects: 1. In the present application, the phase change material composed of a phase change matrix and a heat-conducting powder is calendered and fixed in the metal mesh holes to form a composite phase change material, which not only improves the strength of the phase change material, but also limits the phase change material to a certain extent, reduces the hole caused by the volume change before and after the phase change, effectively reduces the probability of pumping out and leakage of the phase change material, and ensures the stability and durability of the composite phase change material in the use process.

[0026] 2. By coating a coupling modifier on the surface of the metal mesh, the resin in the phase change material is grafted on the metal mesh by chemical bonding to form a stable composite structure, which effectively prevents the risk of pumping out of the phase change material in the phase change process and improves the safety and reliability of the material.

[0027] 3. The preparation process of the present application is simple and controllable, the raw materials are easy to obtain, and the cost is moderate, which is conducive to large-scale production and overcomes the problems of complex preparation process and high cost of the existing composite phase change material. DETAILED DESCRIPTION

[0028] The present application will be further described in detail below in combination with examples. All reagents not specified by the manufacturer are conventional reagent products that can be obtained by purchase.

[0029] Example 1 A preparation process of a high-strength and low-thermal-resistance composite phase change material, comprising the following preparation steps: (1) adding a phase change matrix and aluminum powder with a particle size of 1 μm according to a weight ratio of 5:95 into a heatable planetary stirrer, stirring and mixing at 90°C for 3 h to form a mixed slurry, wherein the phase change matrix is composed of paraffin and polyisobutylene (relative molecular weight of 20-1 million) according to a weight ratio of 15:85; (2) vacuumizing the mixed slurry in a vacuum oven for 30 min, hot calendering on both sides of a stainless steel mesh with a thickness of 0.01 mm after vacuumizing, the mesh hole of the stainless steel mesh being 100 meshes, solidifying at room temperature after calendering to the target thickness to obtain a composite phase change material with a thickness of 0.1 mm.

[0030] Example 2 A preparation process of a high-strength and low-thermal-resistance composite phase change material, comprising the following preparation steps: (1) adding a phase change matrix and aluminum powder with a particle size of 3 μm according to a weight ratio of 10:90 into a heatable planetary stirrer, stirring and mixing at 90°C for 3 h to form a mixed slurry, wherein the phase change matrix is composed of paraffin and polyalphaolefin according to a weight ratio of 20:80; (2) vacuumizing the mixed slurry in a vacuum oven for 30 min, hot calendering on both sides of an aluminum mesh with a thickness of 0.02 mm after vacuumizing, the mesh hole of the metal mesh being 150 meshes, solidifying at room temperature after calendering to the target thickness to obtain a composite phase change material with a thickness of 0.1 mm.

[0031] Example 3 A preparation process of a high-strength and low-thermal-resistance composite phase change material, comprising the following preparation steps: (1) adding a phase change matrix and zinc powder with a particle size of 6 μm according to a weight ratio of 10:90 into a heatable planetary stirrer, stirring and mixing at 100°C for 2 h to form a mixed slurry, wherein the phase change matrix is composed of paraffin and polybutadiene according to a weight ratio of 5:95; (2) vacuumizing the mixed slurry in a vacuum oven for 30 min, hot calendering on both sides of a titanium mesh with a thickness of 0.03 mm after vacuumizing, the mesh hole of the metal mesh being 200 meshes, solidifying at room temperature after calendering to the target thickness to obtain a composite phase change material with a thickness of 0.1 mm.

[0032] Example 4 A preparation process of a high-strength and low-thermal-resistance composite phase change material, comprising the following preparation steps: (1) adding a phase change matrix and aluminum powder with a particle size of 8 μm according to a weight ratio of 10:90 into a heatable planetary stirrer, stirring and mixing at 100°C for 2 h to form a mixed slurry, wherein the phase change matrix is composed of paraffin and styrene-butadiene-styrene according to a weight ratio of 10:90; (2) The mixed slurry is vacuumized in a vacuum oven for 30 min, and then hot calendered on both sides of a nickel metal mesh with a thickness of 0.05 mm and a mesh size of 250 meshes. After calendering to the target thickness, the composite phase change material with a thickness of 0.1 mm is obtained by solidification at room temperature.

[0033] Example 5 A preparation process of a high-strength and low-thermal-resistance composite phase change material, comprising the following preparation steps: (1) The phase change matrix and aluminum oxide powder with a particle size of 10 μm are added into a heatable planetary mixer at a weight ratio of 10:90, and stirred and mixed at 100°C for 2 h to form a mixed slurry, wherein the phase change matrix is composed of paraffin and polycaprolactone at a weight ratio of 15:85; (2) The mixed slurry is vacuumized in a vacuum oven for 30 min, and then hot calendered on both sides of a copper metal mesh with a thickness of 0.02 mm and a mesh size of 300 meshes. After calendering to the target thickness, the composite phase change material with a thickness of 0.1 mm is obtained by solidification at room temperature.

[0034] Example 6 A preparation process of a high-strength and low-thermal-resistance composite phase change material, which is different from example 1 in that a modified metal mesh is used, and the modification method is as follows: a modified metal mesh is obtained by coating octadecyl trimethyl silane on the surface of a stainless steel metal mesh, and the others are the same as example 1, wherein the octadecyl trimethyl silane can be replaced by any one or several of titanium ester coupling agent, phosphate, dopamine and its derivatives.

[0035] Comparative Example 1 A preparation process of a high-strength and low-thermal-resistance composite phase change material, which is different from example 1 in that an equal amount of epoxy resin is used instead of polyisobutylene, and the others are the same as example 1.

[0036] Comparative Example 2 A preparation process of a high-strength and low-thermal-resistance composite phase change material, which is different from example 1 in that an equal amount of polyimide is used instead of polyisobutylene, and the others are the same as example 1.

[0037] Comparative Example 3 A preparation process of a high-strength and low-thermal-resistance composite phase change material, which is different from example 1 in that the weight ratio of the phase change matrix to aluminum powder is 15:85, and the others are the same as example 1.

[0038] Comparative Example 4 A preparation process of a high-strength and low-thermal-resistance composite phase change material, which is different from example 1 in that a stainless steel metal sheet with a thickness of 0.01 mm is used instead of a stainless steel metal mesh, and the others are the same as example 1.

[0039] Comparative Example 5 A preparation process of a high-strength and low-thermal-resistance composite phase change material, which is different from that of Example 1 in that the mesh of the stainless steel mesh is 50 mesh, and the others are the same as those of Example 1.

[0040] Comparative Example 6 A preparation process of a high-strength and low-thermal-resistance composite phase change material, which is different from that of Example 1 in that the mesh of the stainless steel mesh is 500 mesh, and the others are the same as those of Example 1.

[0041] Performance detection The composite phase change materials obtained in the above examples and comparative examples are detected for thermal resistance, thermal conductivity, strength, and latent heat value, and the detection results are shown in Table 1.

[0042] The thermal resistance and thermal conductivity are detected according to the relevant provisions in ASTM D 5470.

[0043] The tensile strength is detected according to the relevant provisions in ASTM D 412.

[0044] The phase change latent heat value is detected by differential scanning calorimetry (DSC).

[0045] Table 1: Detection results of composite phase change materials As can be seen from Table 1, the thermal resistance of the composite phase change materials obtained in Examples 1-6 of the present application is less than 0.06 ℃·cm 2 The tensile strength is above 4.5 MPa, which indicates that the composite phase change material of the present application has good strength and good constraint effect on the phase change material, and can effectively reduce the hole caused by the volume change before and after phase change.

[0046] Comparative Examples 1-2: Compared with Example 1, when epoxy resin or polyimide is used instead of polyisobutylene, the thermal resistance of the composite phase change material obtained in Comparative Examples 1-2 is increased. The reason is that polyisobutylene has similar hydrocarbon chain structure as paraffin, so they have good compatibility. Moreover, polyisobutylene has an elastic network, which can reversibly expand or shrink with temperature during the phase change process. However, epoxy resin and polyimide form a rigid network after curing, which will constrain the volume change of paraffin, forcing the phase change energy to be converted into destructive energy, thereby causing micro-cracks, lattice distortion, and interface peeling in the composite phase change material, resulting in an increase in the thermal resistance of the composite phase change material.

[0047] Compared with Example 1, when the content of the phase change matrix is increased and the amount of the heat-conductive aluminum powder is reduced, the heat-conductive performance of the composite phase change material is significantly reduced, and the thermal resistance is increased. Therefore, when the ratio of the phase change matrix to the heat-conductive aluminum powder is controlled within the range of the present application, the thermal resistance and the heat-conductive performance of the composite phase change material can be effectively balanced.

[0048] Compared with Example 1, when the metal sheet is used instead of the metal mesh, the tensile strength of the composite phase change material is significantly increased, and the thermal resistance is also obviously increased. It can be seen that the composite material using the metal mesh can effectively balance the thermal resistance and the tensile strength, so that the composite material has high strength and also realizes the effect of low thermal resistance.

[0049] Compared with Example 1, when the pore size of the metal mesh is increased, the tensile strength of the composite phase change material is significantly reduced, and the thermal resistance is not obviously changed. It can be seen that when the pore size of the metal mesh is greater than a certain range, the strength of the composite phase change material is lower.

[0050] Compared with Example 1, when the pore size of the metal mesh is reduced, the tensile strength of the composite phase change material is increased, and the thermal resistance is also increased. This is because the pore size of the metal mesh is too small, the phase change material cannot be completely filled, and air is mixed in the inside, so the thermal resistance is increased.

[0051] The embodiments of the specific embodiments are the preferred embodiments of the present application, and are not limited to the protection scope of the present application. Therefore, any equivalent changes made according to the structure, shape, principle of the present application should be covered within the protection scope of the present application.

Claims

1. A high-strength, low-thermal-resistance composite phase change material, characterized in that: It includes a metal mesh and a phase change energy storage layer filled on the metal mesh. The phase change energy storage layer includes a phase change matrix and a thermally conductive powder, and the weight ratio of the phase change matrix to the thermally conductive powder is (5-10):(90-95).

2. The high-strength, low-thermal-resistance composite phase change material according to claim 1, characterized in that: The phase change matrix includes at least a resin-based phase change material, wherein the viscosity of the resin-based phase change material does not exceed 1 million Pa·s; Preferably, the resin-based phase change material includes at least one of polyisobutylene, polypentadiene, polyalphaolefin, styrene-butadiene-styrene, EVA, and polycaprolactone.

3. The high-strength, low-thermal-resistance composite phase change material according to claim 2, characterized in that: The phase change matrix also includes paraffin wax, and the weight ratio of paraffin wax to resin-based phase change material is (5-20):(80-95).

4. The high-strength, low-thermal-resistance composite phase change material according to claim 1, characterized in that: The metal mesh is at least one of copper mesh, stainless steel mesh, aluminum mesh, titanium mesh, and nickel mesh.

5. The high-strength, low-thermal-resistance composite phase change material according to claim 1, characterized in that: The mesh size of the metal mesh is 100-300 mesh.

6. The high-strength, low-thermal-resistance composite phase change material according to claim 1, characterized in that: The metal mesh is a modified metal mesh, and the modified agent includes at least one of silane coupling agents, phosphate esters, titanate coupling agents, dopamine and its derivatives.

7. The high-strength, low-thermal-resistance composite phase change material according to claim 1, characterized in that: The thermally conductive powder is at least one of aluminum, aluminum oxide, and zinc oxide; Preferably, the particle size of the thermally conductive powder is 1-10 μm.

8. The high-strength, low-thermal-resistance composite phase change material according to claim 1, characterized in that: The thickness of the metal mesh is 0.01-0.05 mm.

9. A method for preparing a high-strength, low-thermal-resistance composite phase change material according to any one of claims 1-8, characterized in that, The preparation steps include the following: (1) Mix the phase change matrix and the thermally conductive powder in a certain proportion to obtain a mixed slurry; (2) Heat the mixed slurry to a molten state and coat it onto the metal mesh while it is still hot; (3) After calendering to the target thickness, the composite phase change material is obtained by room temperature curing.

10. The method for preparing the high-strength, low-thermal-resistance composite phase change material according to claim 9, characterized in that, In step (2), the heating temperature is 90-100℃; The metal mesh mentioned in step (2) is a modified metal mesh, which is obtained by the following modification method: coating a modifier onto the metal mesh; Preferably, the modifier is at least one of coupling agents, phosphate esters, titanate coupling agents, dopamine and its derivatives.

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