A carbon-based high-viscosity shaped phase change material with enhanced thermal conductivity and its preparation method and application

Abstract

The present invention discloses a carbon-based high-viscosity shaped phase change material with enhanced thermal conductivity, and a preparation method and application thereof, wherein the carbon-based high-viscosity shaped phase change material with enhanced thermal conductivity comprises 20 to 60 parts of a basic phase change material, 1 to 30 parts of a polymer elastomer, 1 to 25 parts of a tackifying material, 0.1 to 0.2 parts of an antioxidant, 1 to 3 parts of a coupling agent, and 5 to 30 parts of carbon-based thermally conductive particles by weight. The carbon-based filler-enhanced thermally conductive high-viscosity shaped phase change material prepared by the present invention has the advantages of high initial viscosity, flexibility, heat resistance, shape stability, and low filling amount, which makes up for the defects that the current phase change material cannot have the above characteristics at the same time, and can be used in thermal interface materials for electronic components, such as heat dissipation of CPUs and GPUs, battery thermal management, and thermal management of flexible wearable devices.

Description

Technical Field

[0001] The invention belongs to thermal conductive interface materials, and in particular relates to a carbon-based high-viscosity shaped phase change material with enhanced thermal conductivity, and a preparation method and application thereof. Background Art

[0002] With the extensive use of fossil energy, energy shortages and environmental pollution have been brought about, which will seriously restrict social and economic development. Therefore, it is urgent to develop efficient and clean renewable energy and study the storage and effective utilization of energy. Phase change materials (PCMs) are non-reactive materials that can provide latent heat storage by storing and releasing a large amount of thermal energy during the phase change process. Organic phase change materials are low-cost, easy to obtain, and have good chemical stability. The phase change behavior of common organic phase change materials such as paraffin and polyethylene glycol is solid-liquid phase change, which may cause leakage during recycling. In traditional use, they need to be packaged in sealed containers. At present, the methods to avoid leakage during the use of PCMs are mainly concentrated in the following two strategies: the first is to use microencapsulation technology to encapsulate PCMs in polymers or inorganic fillers, which has complex processes and high costs; the other is to limit the flow of PCMs by polymer molecular chains. This method often has high restrictions on the selection of materials and is not very applicable.

[0003] Thermal interface materials are used to fill the tiny gaps and uneven surfaces generated when two materials are joined or contacted when dissipating heat from electronic components, so as to reduce the heat transfer contact thermal resistance and improve the heat dissipation performance of the device. Thermal conductive phase change material is a material with phase change and thermal conductivity functions. At room temperature, it is in a solid state and can absorb the heat released by the heat source to raise its temperature to the phase change temperature, thereby converting to a liquid state, fully filling the thermal interface and providing low interface thermal resistance; when cooled below the phase change temperature, it can be converted back to a solid state, avoiding problems similar to thermal grease leakage. At present, thermal conductive phase change materials on the market have problems such as difficulty in processing and molding, non-self-adhesiveness, large amount of filler, volume change after phase change, and even flow. Summary of the invention

[0004] Purpose of the invention: In view of the problems existing in the prior art, the present invention provides a carbon-based high-viscosity fixed-shape phase change material with enhanced thermal conductivity. The carbon-based filler-enhanced high-viscosity fixed-shape phase change material has the advantages of high initial viscosity, flexibility, heat resistance, shape stability and low filling amount, which effectively makes up for the defects that the current phase change materials cannot have the above characteristics at the same time.

[0005] The present invention also provides a preparation method and application of the carbon-based high-viscosity shaped phase change material with enhanced heat conductivity.

[0006] Technical solution: In order to achieve the above-mentioned purpose, the present invention discloses a carbon-based high-viscosity shaped phase change material with enhanced thermal conductivity, which comprises, by weight, 20 to 60 parts of a basic phase change material, 1 to 30 parts of a polymer elastomer, 1 to 25 parts of a thickening material, 0.1 to 0.2 parts of an antioxidant, 1 to 3 parts of a coupling agent and 5 to 30 parts of carbon-based thermally conductive particles; wherein, during preparation, a coupling agent and an antioxidant are added to the molten basic phase change material, the carbon-based thermally conductive particles are dispersed therein and mixed for reaction, and then the polymer elastomer and the thickening material are added for mixing.

[0007] The basic phase change material is a non-viscous or low-viscosity phase change material with a melting point range of 40-80° C., and specifically includes any one or more of paraffin wax, microcrystalline wax, silicone wax, polyethylene glycol, palmitic acid, and myristic acid.

[0008] Wherein, the polymer elastomer is one or more of SEBS, OBC, TPU, POE, EVA, ethylene-propylene rubber, silicone rubber, nitrile rubber, and polyethylene.

[0009] Wherein, the viscosity-increasing material is one or more of liquid polyisobutylene, VAE707, silicone oil, and epoxy resin.

[0010] Wherein, the antioxidant is one or more of hindered phenol antioxidant, phosphate antioxidant or composite antioxidant.

[0011] Preferably, the antioxidant includes one or more of antioxidant 1010, antioxidant 1076, antioxidant B900, 2,2'-methylene-bis(4-methyl, 6-tert-butylphenol), and antioxidant B225.

[0012] Wherein, the coupling agent is one or more of a silane coupling agent or a titanate coupling agent.

[0013] Preferably, the coupling agent includes one or more of γ-aminopropyltriethoxysilane, γ-glycidyloxypropyltrimethoxysilane, isopropyltri(dioctylphospho)titanate, isopropyltri(dioctylpyrophosphate)titanate, and γ-mercaptopropyltriethoxysilane.

[0014] The carbon-based thermally conductive particles are one or more of carbon nanotubes, graphene, carbon black, and carbon fibers, and the particle size distribution range of the carbon-based thermally conductive particles is 0.01 microns to 100 microns.

[0015] Preferably, the carbon-based thermally conductive particles are in the range of 0.03 microns to 30 microns.

[0016] The method for preparing the carbon-based high-viscosity shaped phase change material with enhanced thermal conductivity described in the present invention comprises the following steps:

[0017] (1) melting the base phase change material, adding a coupling agent and an antioxidant, and heating and stirring until the mixture is uniformly mixed to obtain a uniform solution A;

[0018] (2) adding the carbon-based thermally conductive particles to the uniform solution A obtained in step (1), heating and stirring under vacuum conditions to obtain a uniform liquid mixture B;

[0019] (3) adding a polymer elastomer and a thickening material to the mixture B obtained in step (3), raising the temperature, and mixing under vacuum to obtain a uniform viscous mixture C;

[0020] (4) Processing the mixture C obtained in step (3) into a thin sheet, and then cooling it to room temperature to obtain a carbon-based high-viscosity fixed phase change material with enhanced thermal conductivity.

[0021] Wherein, the heating temperature in step (1) is 60-80°C, and the stirring time is 5-15 minutes; the heating temperature in step (2) is 60-80°C, and the stirring time is 1-2 hours; the elevated temperature in step (3) is 130-160°C, and the mixing time is 15-30 minutes.

[0022] The order of adding the various raw materials in the preparation process of the present invention is very important. If the tackifier is added first or all the raw materials are added at once, the effects in various aspects will be significantly affected.

[0023] The invention discloses an application of the carbon-based high-viscosity shaped phase change material with enhanced thermal conductivity in thermal conductive interface materials for electronic components.

[0024] Preferably, the carbon-based high-viscosity shaped phase change material with enhanced thermal conductivity is used in heat dissipation of CPUs, GPUs, etc., battery thermal management, thermal management of flexible wearable devices, etc.

[0025] The present invention combines the high thermal conductivity of carbon-based fillers, the performance of elastomers and the viscosity of tackifiers, and utilizes the phase properties between raw materials to give phase change materials multiple advantageous properties, including viscosity, flexibility, heat resistance, high thermal conductivity, low thermal resistance, etc.

[0026] The present invention combines the characteristics of several materials with unique properties through a specific preparation method and the steps of adding materials in sequence to prepare a thermally conductive phase change sheet with multiple properties. However, materials prepared by the prior art rarely have multiple properties. The present invention first adds the phase change material and filler during the preparation process in order to better disperse the filler in the system. If the elastomer and tackifier are added first, the viscosity of the system will be too high and the filler will be difficult to disperse.

[0027] The basic phase change material in the present invention is a conventional phase change material, which is similar to the state of water after melting and has no viscosity or low viscosity itself. During preparation, a coupling agent and an antioxidant are added to the molten basic phase change material, and then carbon-based thermal conductive particles are added to disperse and stir to react. At this time, the temperature cannot be too high, which will easily cause the carbon-based thermal conductive particles to tend to agglomerate and have poor dispersion in the system, thereby affecting the thermal conductivity, thermal resistance, elongation at break and other properties of the material. After adding the carbon-based thermal conductive particles, a polymer elastomer and a viscosity-enhancing material are added to mix, and then pressed into sheets to obtain a carbon-based high-viscosity fixed phase change material with enhanced thermal conductivity.

[0028] Among them, the shaping material SEBS and the like and the thickening material can only be added in step 3 of the preparation method. If the shaping material and the thickening material are added in step 1, the viscosity of the shaping material and the thickening material itself is very large, resulting in excessive viscosity of the molten system, and it is difficult to mix additives such as antioxidants evenly. At the same time, it is difficult to disperse after the subsequent addition of carbon-based thermally conductive particles, and the thermally conductive filler is poorly dispersed, which ultimately leads to a decrease in properties such as thermal conductivity, and has a great impact on thermal conductivity, elongation at break and thermal resistance. If the shaping material and the thickening material are added in step 2, not only the viscosity of the molten system is large, but also because it is carried out at high temperature, the carbon-based thermally conductive particles tend to agglomerate easily, and the dispersion is poor in the system, thereby affecting the thermal conductivity, thermal resistance, elongation at break and other properties of the material. In addition, the present invention experimentally found that by adding a specific proportion of graphene and carbon nanotubes (such as Example 3) to the reaction system, different proportions of carbon-based fillers can produce a synergistic effect, significantly improving the thermal conductivity of the material and reducing the thermal resistance.

[0029] Beneficial effects: Compared with the prior art, the present invention has the following advantages:

[0030] The thermal conductive phase change material prepared by the present invention has low thermal resistance, high toughness, and high self-adhesion, so that it can fully bond with the contact interface during installation and is difficult to fall off. It has excellent high and low temperature resistance and can work continuously at a temperature of -40 to 180°C. It is low in cost and has high practical value.

[0031] The high-viscosity shaped phase change material with carbon-based filler reinforced thermal conductivity prepared by the present invention has the advantages of high initial viscosity, flexibility, heat resistance, shape stability and low filling amount, which makes up for the defect that the current phase change material cannot have the above characteristics at the same time, and can be used in thermal conductive interface materials of electronic components, such as heat dissipation of CPU, GPU, etc., battery thermal management, thermal management of flexible wearable devices, etc. DETAILED DESCRIPTION

[0032] The present invention can be better understood according to the following examples. However, it is easy for those skilled in the art to understand that the contents described in the examples are only used to illustrate the present invention, and should not and will not limit the present invention described in detail in the claims.

[0033] The experimental methods described in the examples are conventional methods unless otherwise specified; the reagents and materials described are commercially available unless otherwise specified.

[0034] The graphene was single-layer graphene (graphene purity > 99 wt %, thickness 0.5-3 nm, sheet diameter 0.5-5 μm, single-layer rate greater than 98%), purchased from Suzhou Carbonfeng Graphene Technology Co., Ltd.

[0035] Among them, microcrystalline wax was purchased from McLean Reagent, item number C875530. Carbon nanotubes were purchased from McLean Reagent, item number G991390, ≥95%, diameter: 20-40nm, length: 1-2μm. Paraffin was purchased from McLean Reagent, P815701, which is liquid paraffin. SEBS is Kraton SEBS G1650 thermoplastic elastomer from the United States. VAE707 was purchased from Shandong Xinbaihe Chemical Technology Co., Ltd., which is VAE707 emulsion, item number: RY01, solid content: 55%, viscosity: 800-1500 (S). Obc is Dow OBC9000 thermoplastic elastomer from the United States. Liquid polyisobutylene was purchased from Jinan Shuangying Chemical Co., Ltd., polyisobutylene PB2400, CAS number 9003-27-4. The carboxyl-terminated nitrile rubber was purchased from Wuhan Jixinyibang Biotechnology Co., Ltd., carboxyl-terminated nitrile liquid rubber CAS: 25265-19-4. The PET release film was purchased from Jixiangbao (Taicang) Release Material Technology Development Co., Ltd., 75um transparent PET double silicon release film.

[0036] The raw materials in the following examples and comparative examples are all calculated by weight.

[0037] Example 1

[0038] 1. At room temperature, weigh 55 parts of microcrystalline wax, 1.9 parts of γ-aminopropyltriethoxysilane and 0.1 parts of antioxidant 1010 in a vacuum planetary mixer, heat to 80°C, and stir at 1000 rpm for 15 minutes to obtain a uniform mixed solution A.

[0039] 2. Keeping the temperature constant, weigh 10 parts of graphene and 3 parts of carbon nanotubes, add the mixed solution A of step (1), and continue stirring under vacuum for 2 hours to obtain a mixture B.

[0040] 3. Weigh 20 parts of SEBS and 10 parts of VAE707 and add them to the mixture B in step (2), raise the temperature to 140°C, and mix for 20 minutes until uniform, to obtain a uniform viscous mixture C. The uniform mixture is placed on a calender and pressed into a sheet using a PET release film, and then cooled to room temperature to obtain a carbon-based high-viscosity fixed phase change material with enhanced thermal conductivity.

[0041] Example 2

[0042] 1. At room temperature, weigh 64 parts of paraffin, 1 part of isopropyl tri(dioctyl pyrophosphate) titanate and 0.2 parts of antioxidant B900, place them in a vacuum planetary mixer, heat to 70°C, and stir at 1000 rpm for 20 minutes to obtain a uniform mixed solution A.

[0043] 2. Keeping the temperature constant, weigh 12 parts of graphene, add the mixed solution A in step (1), and continue stirring under vacuum for 1.5 hours to obtain a mixture B.

[0044] 3. Weigh 18 parts of OBC and 5 parts of liquid polyisobutylene and add them to the mixture B in step (2), raise the temperature to 160°C, and mix for 10 minutes until uniform, to obtain a uniform viscous mixture C. The uniform mixture is placed on a calender and pressed into a sheet using a PET release film, and then cooled to room temperature to obtain a carbon-based high-viscosity fixed phase change material with enhanced thermal conductivity.

[0045] Example 3

[0046] 1. At room temperature, weigh 50 parts of microcrystalline wax, 2 parts of γ-aminopropyltriethoxysilane and 0.2 parts of antioxidant 1010 in a vacuum planetary mixer, heat to 75°C, and stir at 1000 rpm for 10 minutes to obtain a uniform mixed solution A.

[0047] 2. Keeping the temperature constant, weigh 10 parts of graphene and 14 parts of carbon nanotubes, add the mixed solution A of step (1), and stir under vacuum for 1 hour to obtain a mixture B.

[0048] 3. Weigh 20 parts of carboxyl-terminated nitrile rubber and 5 parts of liquid polyisobutylene and add them to the mixture B of step (2), raise the temperature to 130°C, and mix for 30 minutes until uniform, to obtain a uniform viscous mixture C. The uniform mixture is placed on a calender and pressed into a sheet using a PET release film, and then cooled to room temperature to obtain a carbon-based high-viscosity fixed phase change material with enhanced thermal conductivity.

[0049] Comparative Example 1

[0050] 1. At room temperature, weigh 55 parts of microcrystalline wax, 20 parts of SEBS, 10 parts of VAE707, 1.9 parts of γ-aminopropyltriethoxysilane and 0.1 parts of antioxidant 1010 in a vacuum planetary mixer, heat to 140°C, stir at 1000 rpm for 15 minutes to mix evenly, and obtain a mixed paste A.

[0051] 2. Keeping the temperature constant, weigh 10 parts of graphene and 3 parts of carbon nanotubes, add them to the mixture A in step (1), and stir under vacuum for 2 hours to obtain a mixture B.

[0052] 3. Place mixture B on a calender and use a PET release film to press the mixture into a sheet to obtain a thermally conductive phase change material.

[0053] The difference between Comparative Example 1 and Example 1 is that only the polymer elastomer and the viscosity-increasing material are added in step (1) before the phase change material is prepared.

[0054] Comparative Example 2

[0055] 1. At room temperature, weigh 55 parts of microcrystalline wax, 1.9 parts of γ-aminopropyltriethoxysilane and 0.1 parts of antioxidant 1010 in a planetary mixer, heat to 80°C, and stir at 1000 rpm for 15 minutes to obtain a uniform mixed solution A.

[0056] 2. Keeping the temperature constant, weigh 10 parts of graphene and 3 parts of carbon nanotubes, add the mixed solution A of step (1), and stir under vacuum for 2 hours to obtain a mixture B.

[0057] 3. Weigh 20 parts of SEBS and add it to the mixture in step (2), raise the temperature to 140°C, and mix for 20 minutes until it is uniform. Put the uniform mixture on a calender to obtain the thermal conductive phase change material.

[0058] Compared with Example 1, Comparative Example 2 is different in that the phase change material is prepared without adding VAE707.

[0059] Comparative Example 3

[0060] 1. At room temperature, weigh 55 parts of microcrystalline wax, 1.9 parts of γ-aminopropyltriethoxysilane and 0.1 parts of antioxidant 1010 in a planetary mixer, heat to 80°C, stir at 1000 rpm for 15 minutes to mix evenly, and obtain a uniform mixed solution A.

[0061] 2. Keeping the temperature constant, weigh 10 parts of graphene and 3 parts of carbon nanotubes, add them to the mixed solution A in step (1), and stir under vacuum for 2 hours to obtain a mixture B.

[0062] 3. Weigh 10 parts of VAE707 and add it to the mixture B in step (2), raise the temperature to 140°C, and mix for 20 minutes until uniform, to obtain a uniform viscous mixture C. Place the uniform mixture on a calender and use a PET release film to press the sheet to obtain a thermally conductive phase change material.

[0063] Compared with Example 1, Comparative Example 3 is different in that the phase change material is prepared without adding SEBS.

[0064] Comparative Example 4

[0065] Compared with Example 1, Comparative Example 4 is different in that SEBS and VAE707 are not added in step (3) to prepare the phase change material.

[0066] Comparative Example 5

[0067] The difference between Comparative Example 5 and Example 1 is that 18 parts of carbon nanotubes are added in step (2) to prepare the phase change material.

[0068] Comparative Example 6

[0069] 1. At room temperature, weigh 55 parts of microcrystalline wax, 1.9 parts of γ-aminopropyltriethoxysilane and 0.1 parts of antioxidant 1010 in a vacuum planetary mixer, heat to 80°C, stir at 1000 rpm for 15 minutes to mix evenly, and obtain a uniform mixed solution A.

[0070] 2. Weigh 10 parts of graphene, 3 parts of carbon nanotubes, 20 parts of SEBS, and 10 parts of VAE707, add them to the mixture A in step (1), heat to 140° C., and stir under vacuum for 2 hours to obtain a mixture B.

[0071] 3. Place mixture B on a calender and use a PET release film to press the mixture into a sheet to obtain a thermally conductive phase change material.

[0072] The difference between Comparative Example 6 and Example 1 is that the polymer elastomer and the viscosity-increasing material are added in step (2) before the phase change material is prepared.

[0073] Relevant test data of Examples 1-3 and Comparative Examples 1, 2, 5, and 6 are shown in Table 1. Thermal conductivity test conditions: ASTM D5470 Test Method; Thermal resistance test: Ref. To ASTM5470 Test Method; Initial adhesion: GB / T 4852-2002; Peel strength: GB / T 2792-2014; Elongation at break: GB / T 1040.

[0074] Table 1 Performance tests of Examples 1-3 and Comparative Examples 1, 2, 5, and 6

[0075] Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 5 Comparative Example 6 Thermal conductivity (W / m•K) 2.56 2.21 3.55 1.68 2.43 2.74 1.70 <![CDATA[Thermal resistance (°C•in 2 / K)]]> 0.024 0.031 0.009 0.096 0.019 0.018 0.179 Initial adhesion(N) 9.6 10.3 9.8 9.3 - 6.4 9.4 Peel force (N) 20.3 19.8 19.1 20.8 - 14.8 18.8 Elongation at break (%) 1000 970 1200 870 980 710 850

[0076] Example 3 shows the lowest thermal resistance and the highest thermal conductivity, which is the result of the synergistic enhancement between the two carbon-based fillers added in a specific amount. Comparative Example 1 has a high viscosity system, and the filler is difficult to disperse well, so the thermal conductivity is low and the thermal resistance is high. At the same time, since SEBS and VAE707 are added first in Comparative Example 1, a high temperature of 140°C is required to ensure a liquid environment and add thermal conductive fillers (while the solid state at 80°C cannot be filled with fillers), but the carbon-based thermal conductive particles tend to agglomerate under high temperature conditions, and the dispersion in the system is poor, which affects the thermal conductivity, thermal resistance, elongation at break and other properties of the material. Comparative Example 2 does not have the addition of a tackifier and fails to show viscosity.

[0077] In Comparative Example 3, since no SEBS was added, the material melted when the phase transition temperature was reached and it was difficult to maintain the original shape.

[0078] In Comparative Example 4, since SEBS and VAE707 are not added, the material has no shaping effect and no viscosity.

[0079] In Comparative Example 5, the proportion of carbon-based fillers is further increased. Although the thermal conductivity is slightly improved, the improvement is very limited, but it is accompanied by a significant decrease in viscosity, flexibility, and peeling force.

[0080] In addition, the experiment found that the shaping material SEBS and the thickening material can only be added in step 3. If the shaping material and the thickening material are added in step 1, the viscosity of the shaping material and the thickening material themselves is very high, resulting in too high viscosity of the melt system, and it is difficult to mix additives such as antioxidants evenly. At the same time, the subsequent addition of carbon-based thermal conductive particles is difficult to disperse, and the thermal conductive filler is poorly dispersed, which ultimately leads to a decrease in thermal conductivity and other properties, and has a great impact on thermal conductivity, elongation at break and thermal resistance (such as comparative example 1). If the shaping material and the thickening material are added in step 2, not only the viscosity of the melt system is high, but also because it is carried out at high temperature, the carbon-based thermal conductive particles tend to agglomerate easily and have poor dispersion in the system, thereby affecting the thermal conductivity, thermal resistance, elongation at break and other properties of the material (comparative example 6).

[0081] It can be seen from the experimental data that the present invention achieves good thermal conductivity, initial viscosity and shaping of phase change materials through reasonable formula selection and ratio, and has a wide range of uses. The material prepared by the present invention has high thermal conductivity, viscosity, flexibility and low filling amount.

Claims

1. A carbon-based high-viscosity shaped phase change material with enhanced thermal conductivity, characterized in that: The preparation of the carbon-based high-viscosity shaped phase change material with enhanced thermal conductivity is as follows: (1) Weigh 50 parts of microcrystalline wax, 2 parts of γ-aminopropyltriethoxysilane and 0.2 parts of antioxidant 1010 by weight at room temperature in a vacuum planetary mixer, heat to 75°C, and stir at 1000 rpm for 10 minutes to obtain a uniform mixed solution A; (2) keeping the temperature constant, weighing 10 parts of graphene and 14 parts of carbon nanotubes, adding the mixed solution A of step (1), and stirring under vacuum for 1 hour to obtain a mixture B; (3) Weigh 20 parts of carboxyl-terminated nitrile rubber and 5 parts of liquid polyisobutylene and add them to the mixture B of step (2), raise the temperature to 130°C, and mix for 30 minutes until uniform, to obtain a uniform viscous mixture C; place the uniform mixture on a calender and use a PET release film to press it into a thin sheet, and then cool it to room temperature to obtain a carbon-based high-viscosity fixed phase change material with enhanced thermal conductivity.

2. An application of the carbon-based high-viscosity shaped phase change material with enhanced thermal conductivity as claimed in claim 1 in thermal conductive interface materials for electronic components.