WO2023197698A1 - 一种导热增强的相变纳米胶囊复合材料及制备方法与应用 - Google Patents

一种导热增强的相变纳米胶囊复合材料及制备方法与应用 Download PDF

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WO2023197698A1
WO2023197698A1 PCT/CN2022/144384 CN2022144384W WO2023197698A1 WO 2023197698 A1 WO2023197698 A1 WO 2023197698A1 CN 2022144384 W CN2022144384 W CN 2022144384W WO 2023197698 A1 WO2023197698 A1 WO 2023197698A1
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phase change
nanocapsule
thermal conductivity
composite material
nanocapsules
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PCT/CN2022/144384
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English (en)
French (fr)
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方晓明
李淑珊
张正国
凌子夜
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华南理工大学
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    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
    • C09K5/00—Heat-transfer, heat-exchange or heat-storage materials, e.g. refrigerants; Materials for the production of heat or cold by chemical reactions other than by combustion
    • C09K5/02—Materials undergoing a change of physical state when used
    • C09K5/06—Materials undergoing a change of physical state when used the change of state being from liquid to solid or vice versa
    • C09K5/063—Materials absorbing or liberating heat during crystallisation; Heat storage materials
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
    • C09K5/00—Heat-transfer, heat-exchange or heat-storage materials, e.g. refrigerants; Materials for the production of heat or cold by chemical reactions other than by combustion
    • C09K5/08—Materials not undergoing a change of physical state when used
    • C09K5/14—Solid materials, e.g. powdery or granular

Definitions

  • the invention belongs to the technical field of composite material heat storage, and specifically relates to a phase change nanocapsule composite material with enhanced thermal conductivity and a preparation method and application.
  • Phase change materials refer to substances that have the ability to absorb and release heat. Introducing phase change materials into thermal interface materials to prepare phase change thermal interface materials will have both heat storage and thermal conductivity properties.
  • phase change thermal interface materials Compared with traditional thermal conductive thermal interface materials, phase change thermal interface materials
  • the interface material can absorb part of the heat due to its heat storage capacity, which is beneficial to slowing down the instantaneous thermal impact on the chip.
  • traditional phase change thermal interface materials directly mix the phase change material with the polymer matrix and only use the interaction between polymers.
  • the interconnection network constrains the melted phase change material. Although this can significantly reduce the contact thermal resistance after the phase change material melts, there is inevitably the risk of liquid phase leakage, which brings great safety to applications in electronic devices. Hidden danger. Encapsulating solid-liquid phase change materials to prepare capsule phase change materials and then introducing them into the matrix is an effective way to improve the application performance of phase change thermal interface materials.
  • phase change nanocapsules into thermal interface materials is expected to develop high-performance New phase change thermal interface materials.
  • the thermal conductivity of phase change nanocapsules introduced into the polymer matrix is relatively low, which is not enough to quickly export heat under high-power heating conditions.
  • the introduction of high thermal conductivity materials can increase the thermal conductivity of composite materials, but high thermal conductivity fillers.
  • phase change nanocapsules are introduced into the polymer matrix through direct blending, the dispersion of the two in the matrix is not ideal, which results in the thermal conductivity of the composite material not being improved ideally, and there is curing due to the high viscosity of the rubber compound.
  • the uneven phenomenon makes it difficult to achieve subsequent demoulding and final application in thermal interfaces.
  • Surface modification of fillers is a commonly used process to enhance dispersion, but the immaturity of the existing modification process results in low filler modification efficiency and low output.
  • the patent "Phase Change Microcapsule Thermal Conductive Material and Preparation Method” discloses mixing a certain amount of low-viscosity vinyl-terminated silicone oil to reduce the viscosity of the matrix.
  • silicone oil is not easy to volatilize, and its introduction will cause the mass fraction of the filler to becomes smaller, the performance will be reduced to a certain extent, and it will interfere with the curing of the material, requiring more curing agent; on the other hand, if the capsule and the thermal conductive filler are added at the same time, the material will easily agglomerate in the microscopic state, which will form a good thermal conductivity path. produce adverse effects.
  • the above-mentioned invention introduces a substance to help dispersion to solve the problem of too much viscosity of the rubber at high addition amounts, it uses low-viscosity vinyl silicone oil. Although this can effectively reduce the viscosity and help dispersion, it will remain in the system. , causing changes in the corresponding curing agent content, resulting in a reduction in the final filler ratio and affecting performance.
  • the purpose of the present invention is to provide a phase change nanocapsule composite material with enhanced thermal conductivity and its preparation method and application.
  • the phase change nanocapsule and the high thermal conductivity material are introduced into the polymer matrix to solve the problem of the existing technology.
  • Medium phase change nanocapsules and high thermal conductivity materials jointly introduce the problem of uneven dispersion of polymers.
  • the amount of filler is high, the phenomenon of the rubber material being unable to stir often occurs, and it is easy to appear in the microscopic state of the material after molding. Reunion appearance.
  • the use of volatile co-solvents to aid dispersion can evaporate independently during the subsequent mixing process without affecting the system.
  • the present invention enhances the dispersion of phase change nanocapsules and high thermal conductivity fillers in the matrix through a combination of solvent-assisted dispersion and intermittent feeding processes, and finally prepares phase change nanocapsule composite materials with enhanced thermal conductivity and uses them as phase change thermal interface materials.
  • a method for preparing thermal conductivity-enhanced phase change nanocapsule composite materials including the following steps:
  • step (2) Add the inorganic shell phase change nanocapsules, polydimethylsiloxane prepolymer and curing agent obtained in step (1) to the container and stir them once with a planetary mixer; after taking them out, add high thermal conductivity filler and The cosolvent with the same mass as the polydimethylsiloxane prepolymer is stirred twice to obtain the rubber compound.
  • the stirring program is set to 700 ⁇ 2000rpm and the time is 3 ⁇ 6min;
  • step (3) Coat the rubber obtained in step (2) into a 20 ⁇ 20 ⁇ 1 mm mold, place it in a vacuum degassing barrel, and degas at 25°C ⁇ 40°C, 80Pa ⁇ 100Pa for 20 ⁇ 30 minutes ; After taking it out, let it stand at 25°C for 48 hours to solidify and form. After demoulding, the phase change nanocapsule composite material with enhanced thermal conductivity is obtained.
  • the interfacial hydrolysis-condensation polymerization method in step (1) is specifically: anhydrous ethanol, deionized water, cetyldimethylammonium bromide (CTAB) constitute the water phase, core material material, and shell material precursor
  • CTAB cetyldimethylammonium bromide
  • the water phase and the oil phase are first fully dissolved at 60°C, and then mixed together to form a stable O/W emulsion through the emulsification process; an ammonia initiator is added, and the shell material precursor is hydrolyzed and polycondensed at the interface through ammonia catalysis
  • the reaction forms shell oligomers, which are negatively charged. They are immediately adsorbed on the surface of positively charged micelles through electrostatic interactions.
  • the shell oligomers continue to migrate from the inside of the oil droplet to the interface. , and finally gradually condense to form an inorganic shell on the surface of the core material droplet.
  • the core material of the inorganic shell phase change nanocapsule in step (1) is paraffin, polyols or fatty acids, and the inorganic shell material is silica or titanium dioxide with hydroxyl groups; the inorganic shell phase
  • the particle size of variable nanocapsules is 500 ⁇ 1000nm, the phase change temperature is 42°C ⁇ 48°C, and the latent heat of phase change is 120 ⁇ 180J/g.
  • the core material of the inorganic shell phase change nanocapsule in step (1) is paraffin, and the inorganic shell material is silica.
  • the high thermal conductivity filler in step (2) is one or a mixture of alumina, boron nitride, aluminum nitride, carbon fiber, and graphene.
  • the curing agent in step (2) is one or a mixture of hydrogen-containing silicone oil, hydrogen-containing silicone oil, and methyl hydrogen-containing silicone oil.
  • the co-solvent in step (2) is at least one of n-hexane, n-pentane and cyclohexane.
  • thermo conductivity enhanced phase change nanocapsule composite material obtained by the above preparation method.
  • the thermal conductivity enhanced phase change nanocapsule composite material includes 10.53% ⁇ 26.09% of inorganic shell phase change nanocapsules, high thermal conductivity Filler 26.09% ⁇ 31.58%, polydimethylsiloxane prepolymer 43.47% ⁇ 52.63% and curing agent 4.35% ⁇ 5.26%, the sum of the above raw materials is 100%.
  • the heat storage performance of the phase change nanocapsule composite material with enhanced thermal conductivity is a phase change enthalpy value of 15 ⁇ 61J/g
  • the thermal conductivity performance is a thermal conductivity of 0.64 ⁇ 1.64 W/(m ⁇ K) at normal temperature (25°C ) hardness is 25 ⁇ 50 HA.
  • the present invention also provides the application of the above-mentioned phase change nanocapsule composite material with enhanced thermal conductivity as a thermal interface material.
  • the thermally conductive enhanced phase change nanocapsule composite material as a thermal pad between the chip and the radiator heat sink, the soft composite material will fill the air gap between the chip and the radiator heat sink, better connecting the The heat generated by the chip is dissipated in a timely manner and plays a certain thermal buffering role, allowing the chip to exhibit good heat dissipation performance under different working conditions.
  • Oxides used as inorganic shells are common system thickeners. Nanocapsules with oxide inorganic shells are added to the matrix first, and the consistency of the rubber increases, and the shear dispersion effect is large.
  • the high thermal conductivity filler introduced later can separate the flakes under the action of shear dispersion without agglomeration, which is beneficial to the dispersion of the high thermal conductivity filler;
  • Solvent-assisted dispersion principle The selected n-hexane, n-pentane, cyclohexane and other solvents have similar properties to the matrix, which can reduce the viscosity of the uncured rubber and enhance the contact between the matrix and the filler. Moreover, the selected solvent is volatile and can be basically removed during the vacuum degassing process before curing without affecting the subsequent curing reaction.
  • the present invention has the following advantages and beneficial effects:
  • the phase change nanocapsule composite material of the present invention has dual functions of heat storage and heat conduction.
  • the thermal storage properties of composite materials are given by adding inorganic shell phase change nanocapsules; the composite materials are given high thermal conductivity by adding high thermal conductive fillers.
  • the inorganic shell nanocapsules prepared by the interfacial hydrolysis-condensation polymerization method have a larger heat transfer specific surface area, and the introduction of high thermal conductive fillers into the polydimethylsiloxane matrix can make the phase change thermal interface material have higher thermal conductivity.
  • inorganic shell phase change nanocapsules not only ensures that the liquid that provides latent heat does not leak after reaching the phase change temperature, but also the surface of the inorganic shell nanocapsules prepared by the interfacial hydrolysis-condensation polymerization method has abundant hydroxyl groups, which can be combined with the polycondensate. Hydrogen bonds are formed between the curing agents of dimethylsiloxane, which enhances the compatibility with the matrix and reduces the hardness of the material.
  • the present invention adopts a method of combining solvent-assisted dispersion with intermittent feeding process to better disperse high thermal conductivity fillers and nanocapsules in the matrix, which is conducive to the formation of thermal conduction paths in a microscopic state.
  • the introduced co-solvent can evaporate independently during the pre-curing process and does not affect the curing reaction.
  • Figure 1 is a flow chart for the preparation of the thermally conductive enhanced phase change nanocapsule composite material of the present invention.
  • Figure 2 is a diagram showing an application example of the phase change nanocapsule composite material as a thermal interface material in Embodiment 1 of the present invention.
  • Figure 3 is a comparison chart of chip temperature change curves between the phase change nanocapsule composite material used as a thermal interface material and pure polydimethylsiloxane sheet used as a thermal interface material in Embodiment 1 of the present invention.
  • the preparation flow chart of the thermally conductive enhanced phase change nanocapsule composite material of the present invention is shown in Figure 1.
  • the inorganic shell phase change nanocapsules are prepared by using the interfacial hydrolysis-condensation polymerization method.
  • the inorganic shell phase change nanocapsules, polydimethylsiloxane prepolymer and curing agent are stirred once by a planetary mixer.
  • a high thermal conductivity filler and a co-solvent of equivalent quality to the polydimethylsiloxane prepolymer and stir for a second time to obtain a rubber compound.
  • the obtained rubber material is coated in the mold, placed in a vacuum degassing barrel, and degassed.
  • it is taken out, left to solidify and molded, and the phase change nanocapsule composite material with enhanced thermal conductivity is obtained after demoulding.
  • phase change nanocapsule composite material with enhanced thermal conductivity made of the following raw materials in terms of mass fraction: 10.53% inorganic shell phase change nanocapsules, 31.58% high thermal conductivity filler boron nitride, polydimethylsiloxane pre- Polymer 52.63% and hydrogenated silicone oil 5.26%.
  • the preparation method of the thermally conductive enhanced phase change nanocapsule composite material includes the following steps:
  • paraffin 15.0g
  • tetraethyl orthosilicate TEOS 7.5g
  • cetyltrimethylammonium bromide CTAB 0.82g
  • deionized water 35.5mL
  • absolute ethanol 71.25mL
  • nanocapsules and high thermal conductive fillers were added to the matrix in two times. First add the weighed paraffin@silica phase change nanocapsules, polydimethylsiloxane prepolymer and hydrogen-containing silicone oil into the container and stir it once with a planetary mixer. After taking it out, add the high thermal conductivity filler BN. And 1.3 mL of cosolvent n-pentane was stirred twice. The stirring program was set to 2000 rpm and the time was 3 min.
  • step (3) Coat the glue obtained in step (2) into a 20 ⁇ 20 ⁇ 1mm mold, place it in a vacuum degassing barrel, and degas at 25°C and 100Pa for 20 minutes; take it out and let it stand at 25°C. After curing and molding for 48 hours, a white smooth gasket was obtained after demoulding.
  • the phase change enthalpy value is 25J/g.
  • the thermal conductivity is 0.83W/(m ⁇ K).
  • the hardness is 50 HA at room temperature (25°C).
  • thermally conductive enhanced phase change nanocapsule composite material obtained in this example as a thermal interface material:
  • phase change nanocapsule composite thermal pad obtained above is placed between the alumina ceramic heating sheet and the five-heat pipe fin CPU radiator, as shown in Figure 2.
  • a dual-fan forced air cooling system can also be connected to extract the heat generated during testing.
  • the test sample is placed between the heating plate and the copper heat sink of the radiator, and is locked with screws to make them in close contact.
  • a calibrated T-type thermocouple (temperature measurement range is -200°C ⁇ 350°C, tolerance value is 0.5°C) is fixed at the center point of the lower surface of the alumina ceramic heating plate, which is used to accurately monitor the temperature changes of the heating plate.
  • thermocouple temperature at the center point of the lower surface of the alumina ceramic heating plate Collect the temperature change curve of the thermal conductive chip after heating for 5 minutes to examine the heat dissipation effect of the thermal conductive pad.
  • the results are shown in Figure 3.
  • the chip temperature using this phase-change nanocapsule composite thermal pad as a thermal interface material is 40.97°C lower than using pure polydimethylsiloxane without adding nanocapsules and high thermal conductivity fillers. It can be seen that using the phase change nanocapsule composite material of the present invention as a thermal interface material can significantly reduce the chip temperature and improve the heat dissipation performance.
  • phase change nanocapsule composite material with enhanced thermal conductivity made of the following raw materials in terms of mass fraction: 19.05% inorganic shell phase change nanocapsules, 28.57% high thermal conductivity filler boron nitride, polydimethylsiloxane pre- Polymer 47.62% and hydrogen-containing siloxane 4.76%.
  • the preparation method of the thermally conductive enhanced phase change nanocapsule composite material includes the following steps:
  • paraffin 15.0g
  • tetraethyl orthosilicate TEOS 7.5g
  • cetyltrimethylammonium bromide CTAB 0.82g
  • deionized water 35.5mL
  • absolute ethanol 71.25mL
  • step (3) Coat the rubber obtained in step (2) into a 20 ⁇ 20 ⁇ 1mm mold, place it in a vacuum degassing barrel, and degas at 40°C and 80Pa for 25 minutes; take it out and let it stand at 25°C. After curing and molding for 48 hours, a white smooth gasket was obtained after demoulding, with a phase change enthalpy value of 43.2J/g, thermal conductivity of 0.64W/(m ⁇ K), and a hardness of 37.5 HA at room temperature (25°C).
  • the operation process is basically the same as that of Embodiment 1, except that the voltage of the DC regulated power supply is used to control the heating power of the heating plate, and the power is set to 10W.
  • phase change nanocapsule composite material with enhanced thermal conductivity made of the following raw materials in terms of mass fraction: 26.09% inorganic shell phase change nanocapsules, 26.09% high thermal conductivity filler boron nitride, polydimethylsiloxane pre- Polymer 43.47% and methyl hydrogen silicone oil 4.35%.
  • the preparation method of the thermally conductive enhanced phase change nanocapsule composite material includes the following steps:
  • paraffin 15.0g
  • tetraethyl orthosilicate TEOS 7.5g
  • cetyltrimethylammonium bromide CTAB 0.82g
  • deionized water 35.5mL
  • absolute ethanol 71.25mL
  • step (3) Coat the rubber obtained in step (2) into a 20 ⁇ 20 ⁇ 1mm mold, place it in a vacuum degassing barrel, and degas at 35°C and 90Pa for 30 minutes; take it out and let it stand at 25°C. After curing and molding for 48 hours, a white smooth gasket was obtained after demoulding, with a phase change enthalpy value of 61J/g, thermal conductivity of 1.02W/(m ⁇ K), and a hardness of 25.0 HA at room temperature (25°C).
  • the operation process is basically the same as that of Embodiment 1, except that the voltage of the DC regulated power supply is used to control the heating power of the heating plate, and the power is set to 5W.
  • phase change nanocapsule composite material with enhanced thermal conductivity made of the following raw materials in terms of mass fraction: 19.05% inorganic shell phase change nanocapsules, 28.57% high thermal conductivity filler carbon fiber, polydimethylsiloxane prepolymer 47.62% and hydrogen-containing siloxane 4.76%.
  • the preparation method of the thermally conductive enhanced phase change nanocapsule composite material includes the following steps:
  • paraffin 15.0g
  • tetraethyl orthosilicate TEOS 7.5g
  • cetyltrimethylammonium bromide CTAB 0.82g
  • deionized water 35.5mL
  • absolute ethanol 71.25mL
  • step (3) Coat the rubber obtained in step (2) into a 20 ⁇ 20 ⁇ 1mm mold, place it in a vacuum degassing barrel, and degas at 25°C and 100Pa for 30 minutes; take it out and let it stand at 25°C. After curing and molding for 48 hours, a white smooth gasket was obtained after demoulding, with a phase change enthalpy value of 43.2J/g, thermal conductivity of 1.64W/(m ⁇ K), and a hardness of 27.5 HA at room temperature (25°C).
  • the operation process is basically the same as that of Embodiment 1, except that the voltage of the DC regulated power supply is used to control the heating power of the heating plate, and the power is set to 10W.
  • phase change nanocapsule composite material with enhanced thermal conductivity made of the following raw materials in terms of mass fraction: 19.05% inorganic shell phase change nanocapsules, 14.28% high thermal conductivity filler carbon fiber and 14.29% boron nitride, polydimethyl Silicone prepolymer 47.62% and hydrogenated silicone oil 4.76%.
  • the preparation method of the thermally conductive enhanced phase change nanocapsule composite material includes the following steps:
  • paraffin 15.0g
  • tetraethyl orthosilicate TEOS 7.5g
  • cetyltrimethylammonium bromide CTAB 0.82g
  • deionized water 35.5mL
  • absolute ethanol 71.25mL
  • step (3) Coat the rubber obtained in step (2) into a 20 ⁇ 20 ⁇ 1mm mold, place it in a vacuum degassing barrel, and degas at 30°C and 90Pa for 30 minutes; take it out and let it stand at 25°C. After curing and molding for 48 hours, a white smooth gasket was obtained after demoulding, with a phase change enthalpy value of 43.2J/g, thermal conductivity of 1.24W/(m ⁇ K), and a hardness of 32.5 HA at room temperature (25°C).
  • the operation process is basically the same as that of Embodiment 1, except that the voltage of the DC regulated power supply is used to control the heating power of the heating plate, and the power is set to 10W.
  • phase change nanocapsule composite material with enhanced thermal conductivity made of the following raw materials in terms of mass fraction: 10.53% inorganic shell phase change nanocapsules, 31.58% high thermal conductivity filler boron nitride, polydimethylsiloxane pre- Polymer 52.63% and hydrogenated silicone oil 5.26%.
  • the preparation method of the thermally conductive enhanced phase change nanocapsule composite material includes the following steps:
  • n-cetyl alcohol 15.0g
  • ethyl orthosilicate TEOS 7.5g
  • cetyltrimethylammonium bromide CTAB 0.82g
  • deionized water 35.5mL
  • absolute ethanol 71.25mL
  • step (3) Coat the glue obtained in step (2) into a 20 ⁇ 20 ⁇ 1mm mold, place it in a vacuum degassing barrel, and degas at 25°C and 100Pa for 20 minutes; take it out and let it stand at 25°C. After curing and molding for 48 hours, a white smooth gasket was obtained after demoulding, with a phase change enthalpy value of 15J/g, a thermal conductivity of 0.85W/(m ⁇ K), and a hardness of 50 HA at room temperature (25°C).
  • the operation process is basically the same as that of Embodiment 1, except that the voltage of the DC regulated power supply is used to control the heating power of the heating plate, and the power is set to 10W.
  • phase change nanocapsule composite material with enhanced thermal conductivity made of the following raw materials in terms of mass fraction: 10.53% inorganic shell phase change nanocapsules, 31.58% high thermal conductivity filler boron nitride, polydimethylsiloxane pre- Polymer 52.63% and hydrogenated silicone oil 5.26%.
  • the preparation method of the thermally conductive enhanced phase change nanocapsule composite material includes the following steps:
  • paraffin 15.0g
  • butyl titanate 7.5g
  • cetyltrimethylammonium bromide CTAB 0.82g
  • deionized water 35.5mL
  • absolute ethanol 71.25mL
  • step (3) Coat the glue obtained in step (2) into a 20 ⁇ 20 ⁇ 1mm mold, place it in a vacuum degassing barrel, and degas at 25°C and 100Pa for 20 minutes; take it out and let it stand at 25°C. After curing and molding for 48 hours, a white smooth gasket was obtained after demoulding, with a phase change enthalpy value of 16J/g, a thermal conductivity of 0.64W/(m ⁇ K), and a hardness of 45 HA at room temperature (25°C).
  • the operation process is basically the same as that of Embodiment 1, except that the voltage of the DC regulated power supply is used to control the heating power of the heating plate, and the power is set to 10W.

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Abstract

本发明公开了一种导热增强的相变纳米胶囊复合材料及制备方法与应用。所述导热增强的相变纳米胶囊复合材料由以下原料制成（以质量分数计算）：无机壳相变纳米胶囊10.53%~26.09%、高导热填料26.09%~31.58%、聚二甲基硅氧烷预聚物43.47%~52.63%和固化剂4.35%~5.26%。通过溶剂助分散与间歇投料来共同增强相变纳米胶囊与高导热填料在基体中的分散性，使材料兼具更高的导热与储热能力。无机壳相变纳米胶囊使聚二甲基硅氧烷基复合材料硬度降低，更利于贴合界面。该材料作为热界面材料使用，有望填补空气间隙，缓解芯片在面对高热流密度下的热冲击，帮助芯片、电子器件等更好散热。

Description

一种导热增强的相变纳米胶囊复合材料及制备方法与应用 技术领域
本发明属于复合材料储热技术领域，具体涉及一种导热增强的相变纳米胶囊复合材料及制备方法与应用。
 背景技术
随着“5G”通讯等信息技术的快速发展，电子芯片不断向小体积化、高集成化、高功率化发展，导致芯片单位体积热流密度迅速增加，这带来了对芯片的瞬时热冲击，这将导致温度的急剧升高，高温易造成电子元器件的老化、应力变形、寿命缩短以及功能失常等问题。因此，急需研制高性能热界面材料。相变材料指的是具有吸收释放热能力的物质，将相变材料引入热界面材料制备相变热界面材料将兼具储热以及导热性能，与传统导热型热界面材料相比，相变热界面材料因具有的储热能力能吸收一部分的热量，有利于减缓对芯片的瞬时热冲击，但传统的相变热界面材料将相变材料直接与高分子基体混合，仅利用高分子间的交联网络对熔化后的相变材料进行约束，这虽然能够在相变材料熔化后显著降低接触热阻，但难免存在液相泄露的风险，这给在电子器件中的应用带来非常大的安全隐患。将固-液相变材料进行封装制备胶囊型相变材料后再引入基体中是提升相变热界面材料应用性能的有效途径，因此，将相变纳米胶囊引入热界面材料有望研制出高性能的新型相变热界面材料。通常，将相变纳米胶囊引入聚合物基体中导热系数比较低，不足以满足大功率发热条件下的热量快速导出，引入高导热材料可以实现复合材料的导热系数的增大，但是高导热填料、相变纳米胶囊通过直接共混引入聚合物基体中时，二者在基体中的分散不理想，这导致了复合材料的导热性能得不到理想的提升，并且因为胶料黏度过高还存在固化不均匀的现象，难以实现后续的脱模与最终在热界面中的应用。将填料进行表面改性是常用的增强分散性的工艺，但是现有改性工艺的不成熟导致了填料改性效率低、产量低。
专利《一种相变微胶囊导热材料及其制备方法》公开了混入一定量低粘度的乙烯基封端硅油来降低基体的黏度，但一方面硅油不易挥发，它的引入会导致填料的质量分数变小，性能得到一定程度的降低，且对材料的固化会产生干扰，需要更多的固化剂；另一方面，胶囊与导热填料同时间加入，材料微观状态下易团聚，对构成良好导热通路产生不良影响。上述发明虽然引入了一种物质来帮助分散以解决胶料在高添加量下黏度太大的问题，但选用的是低粘度乙烯基硅油，这虽然能有效降低黏度帮助分散，但会残留在体系中，引起对应固化剂使用含量的变化，导致最终填料比例的降低，影响性能的体现。
 技术解决方案
针对现有技术的不足，本发明的目的是提供一种导热增强的相变纳米胶囊复合材料及制备方法与应用，将相变纳米胶囊与高导热材料引入聚合物基体中，解决了现有技术中相变纳米胶囊与高导热材料共同引入聚合物分散不均匀的问题，尤其是在高填料添加量时，常常会出现胶料搅不动的现象，并且成型后在材料的微观状态下易呈现团聚形貌。而采用挥发性助溶剂来助分散，在混合的后续过程中，能够自主挥发，不对体系产生影响。本发明通过溶剂助分散与间歇投料工艺结合来增强相变纳米胶囊与高导热填料在基体中的分散性，最终制备得到导热增强的相变纳米胶囊复合材料并作为相变热界面材料使用。
本发明的目的通过以下技术方案来实现。
一种导热增强的相变纳米胶囊复合材料的制备方法，包括以下步骤：
（1）采用界面水解-缩聚法制备无机壳相变纳米胶囊；
（2）在容器中添加步骤（1）所得的无机壳相变纳米胶囊、聚二甲基硅氧烷预聚物和固化剂进行行星式搅拌机的一次搅拌；取出后再添加高导热填料以及与聚二甲基硅氧烷预聚物质量相当的助溶剂进行二次搅拌得到胶料，搅拌程序设置为700~2000rpm，时间3~6min；
（3）将步骤（2）所得的胶料涂覆于20×20×1 mm的模具中，静置于真空脱泡桶，在25℃~40℃、80Pa~100Pa下脱泡20~30分钟；取出后于25℃静置48h固化成型，脱模后得到所述导热增强的相变纳米胶囊复合材料。
优选的，步骤（1）所述界面水解-缩聚法具体为：无水乙醇、去离子水、十六烷基二甲基溴化铵（CTAB）构成水相，芯材物质、壳材前驱体构成油相，水相和油相先各自在60℃充分溶解，然后混合在一起通过乳化工艺形成稳定的O/W乳液；加入氨水引发剂，壳材前驱体在界面处通过氨催化水解-缩聚反应形成壳材低聚体，并带负电荷，其立即通过静电相互作用吸附在带正电荷的胶束表面，随着界面缩聚反应的进行，壳材低聚体不断从油滴内向界面处迁移，最终在芯材液滴表面逐渐缩聚形成无机外壳。
优选的，步骤（1）所述无机壳相变纳米胶囊的芯材为石蜡类、多元醇类或脂肪酸类，无机壳材为具有羟基的二氧化硅或二氧化钛；所述无机壳相变纳米胶囊的粒径为500~1000nm，相变温度42℃~48℃，相变潜热120~180J/g。
进一步优选的，步骤（1）所述无机壳相变纳米胶囊的芯材为石蜡，无机壳材为二氧化硅。
优选的，步骤（2）所述高导热填料为氧化铝、氮化硼、氮化铝、碳纤维、石墨烯中的一种或几种的混合物。
优选的，步骤（2）所述固化剂为含氢硅油、含氢硅氧烷、甲基含氢硅油的一种或几种的混合物。
优选的，步骤（2）所述助溶剂为正己烷、正戊烷、环己烷中的一种以上。
由上述制备方法得到的一种导热增强的相变纳米胶囊复合材料，以质量分数计，所述导热增强的相变纳米胶囊复合材料包括无机壳相变纳米胶囊10.53%~26.09%、高导热填料26.09%~31.58%、聚二甲基硅氧烷预聚物43.47%~52.63%和固化剂4.35%~5.26%，以上原料之和为100%。
优选的，所述导热增强的相变纳米胶囊复合材料的储热性能为相变焓值15~61J/g，导热性能为热导率0.64~1.64 W/(m∙K)，常温（25℃）硬度为25~50 HA。
本发明还提供了上述的一种导热增强的相变纳米胶囊复合材料作为热界面材料的应用。通过将所述导热增强的相变纳米胶囊复合材料作为导热垫片放置于芯片与散热器热沉之间，柔软的复合材料将填补芯片与散热器热沉之间的空气间隙，更好地将芯片产生热量及时导出，并且起到一定的热缓冲作用，使芯片在不同工况下均呈现良好的散热性能。
本发明技术方案采用原理如下：
（1）间歇投料助分散原理：用作无机壳的氧化物是常见的体系增稠剂，具有氧化物无机壳的纳米胶囊先加入基体，胶料稠度增大，剪切分散作用大，后引入的高导热填料能在剪切分散作用下使片状分离，并且不发生团聚，利于高导热填料的分散；
（2）溶剂助分散原理：所选用的正己烷、正戊烷、环己烷等溶剂与基体性质相似，能够降低未固化时胶料的黏度，增强基体对填料的填料与基体间的接触，并且所选用的溶剂易挥发，在固化前真空脱泡过程中基本可以去除，不影响后续的固化反应。
 有益效果
与现有技术相比，本发明具有以下优点和有益效果：
（1）本发明的相变纳米胶囊复合材料兼具储热、导热双功能。通过添加无机壳相变纳米胶囊赋予复合材料储热性能；通过添加高导热填料赋予复合材料高导热性能。界面水解-缩聚法制备的无机壳纳米胶囊具有更大传热比表面积，结合高导热填料引入聚二甲基硅氧烷基体中可以使相变热界面材料具有更高的热导率。
（2）无机壳相变纳米胶囊的使用不仅保证了提供潜热的液体达到相变温度后不发生泄露，而且界面水解-缩聚法制备的无机壳纳米胶囊表面具有丰富的羟基，可以与聚二甲基硅氧烷的固化剂之间形成氢键，增强了与基体之间的相容性，降低了材料硬度。
（3）本发明采用溶剂助分散与间歇投料工艺结合的方法，使高导热填料、纳米胶囊更好地在基体中分散，有利于微观状态下导热通路形成。引入的助溶剂能在固化前的过程中能够自主挥发，不影响固化反应的发生。
 附图说明
图1为本发明导热增强的相变纳米胶囊复合材料的制备流程图。
图2为本发明实施例1的相变纳米胶囊复合材料作为热界面材料的应用示例图。
图3为本发明实施例1的相变纳米胶囊复合材料作为热界面材料与纯聚二甲基硅氧烷片作为热界面材料的芯片温度变化曲线对比图。
 本发明的实施方式
下面结合实施例和附图对本发明的实施方式作进一步详细的说明，但本发明的实施方式不限于此。
本发明的导热增强的相变纳米胶囊复合材料的制备流程图如图1所示。首先采用界面水解-缩聚法制备得到无机壳相变纳米胶囊，然后将无机壳相变纳米胶囊、聚二甲基硅氧烷预聚物和固化剂进行行星式搅拌机的一次搅拌，取出后再添加高导热填料以及与聚二甲基硅氧烷预聚物质量相当的助溶剂进行二次搅拌得到胶料。所得的胶料涂覆于模具中，静置于真空脱泡桶，脱泡处理。最后取出，静置固化成型，脱模后得到所述导热增强的相变纳米胶囊复合材料。
实施例 1
一种导热增强的相变纳米胶囊复合材料，以质量分数计，由以下原料制成：无机壳相变纳米胶囊10.53%、高导热填料氮化硼31.58%、聚二甲基硅氧烷预聚物52.63%和含氢硅油5.26%。
所述一种导热增强的相变纳米胶囊复合材料的制备方法，包括如下步骤：
（1）采用界面水解-缩聚法制备石蜡为芯材，二氧化硅为壳材的相变纳米胶囊：石蜡（15.0g），正硅酸乙酯TEOS（7.5g）在250mL三颈烧瓶中以60℃搅拌混合，形成透明的溶液。然后，同时将十六烷基三甲基溴化铵CTAB（0.82g）、去离子水（35.5mL）和无水乙醇（71.25mL）加入250mL烧杯中，并保温至60℃。在60℃下将以无水乙醇、去离子水、CTAB组成的水相加入以石蜡、TEOS组成的油相中，以350rpm的转速机械搅拌4h，形成稳定的O/W乳液。加入1.5mL 25wt%氨水，并保持在60℃下继续搅拌16h以催化TEOS的界面水解-缩聚反应。最后，经过滤、去离子水洗涤、石油醚洗涤、干燥，得到约8g白色粉末即石蜡@二氧化硅相变纳米胶囊。
（2）称取0.26g石蜡@二氧化硅相变纳米胶囊（平均粒径500nm，相变温度为42℃，潜热值160J/g）和0.78g氮化硼（BN）高导热填料，1.3g聚二甲基硅氧烷预聚体，0.13g含氢硅油。
为了更好地提高复合材料基体与填料之间的相容性，将纳米胶囊、高导热填料分两次加入基体中。先在容器中添加称量好的石蜡@二氧化硅相变纳米胶囊、聚二甲基硅氧烷预聚物和含氢硅油进行行星式搅拌机的一次搅拌，取出后再添加高导热填料BN，以及1.3mL助溶剂正戊烷进行二次搅拌，搅拌程序设置为2000rpm，时间3min。
（3）将步骤（2）所得的胶料涂覆于20×20×1mm的模具中，静置于真空脱泡桶，在25℃、100Pa下脱泡20分钟；取出后于25℃静置48h固化成型，脱模后得到白色光滑垫片，相变焓值25J/g，导热性能为热导率0.83W/(m∙K)，常温（25℃）硬度为50 HA。
本实施例所得的导热增强的相变纳米胶囊复合材料作为热界面材料的应用：
将上述所得相变纳米胶囊复合材料导热垫片置于氧化铝陶瓷发热片与五热管翅片式CPU散热器之间，如图2所示。测试过程中还可以连接一个双风扇强制空气冷却系统配合使用，以提取产生的热量。测试样品置于加热片与散热器铜制热沉之间，利用螺丝锁紧，使之紧密接触。氧化铝陶瓷发热片下表面中心点位置固定有校准过的T型热电偶（测温区间为-200℃~350℃，容差值为0.5℃），用于精确监测加热片的温度变化情况。使用直流稳压电源的电压来控制发热片加热功率，设定功率为18W（商用芯片发热功率），对氧化铝陶瓷发热片下表面中心点的热电偶温度利用安捷伦采集仪进行数据采集，通过稳定加热5min采集导热芯片温度变化曲线来考察导热垫片散热效果。结果如图3所示，使用该相变纳米胶囊复合材料导热垫片作为热界面材料比使用不添加纳米胶囊以及高导热填料的纯聚二甲基硅氧烷的芯片温度低40.97℃。由此可见，使用本发明相变纳米胶囊复合材料作为热界面材料可以显著降低芯片温度，提高散热性能。
实施例 2
一种导热增强的相变纳米胶囊复合材料，以质量分数计，由以下原料制成：无机壳相变纳米胶囊19.05%、高导热填料氮化硼28.57%、聚二甲基硅氧烷预聚物47.62%和含氢硅氧烷4.76%。
所述一种导热增强的相变纳米胶囊复合材料的制备方法，包括如下步骤：
（1）采用界面水解-缩聚法制备石蜡为芯材，二氧化硅为壳材的相变纳米胶囊：石蜡（15.0g），正硅酸乙酯TEOS（7.5g）在250mL三颈烧瓶中以60℃搅拌混合，形成透明的溶液。然后，同时将十六烷基三甲基溴化铵CTAB（0.82g）、去离子水（35.5mL）和无水乙醇（71.25mL）加入250mL烧杯中，并保温至60℃。在60℃下将以无水乙醇、去离子水、CTAB组成的水相加入以石蜡、TEOS组成的油相中，以350rpm的转速机械搅拌4h，形成稳定的O/W乳液。加入1.5mL 25wt%氨水，并保持在60℃下继续搅拌16h以催化TEOS的界面水解-缩聚反应。最后，经过滤、去离子水洗涤、石油醚洗涤、干燥，得到约8g白色粉末即石蜡@二氧化硅相变纳米胶囊。
（2）称取0.52g石蜡@二氧化硅相变纳米胶囊（平均粒径800nm，相变温度为45℃，潜热值170J/g）和0.78g氮化硼（BN）高导热填料，1.3g聚二甲基硅氧烷预聚体，0.13g含氢硅氧烷。
先在容器中添加称量好的石蜡@二氧化硅相变纳米胶囊、聚二甲基硅氧烷预聚物和含氢硅氧烷进行行星式搅拌机的一次搅拌，取出后再添加高导热填料BN，以及1.3mL助溶剂正戊烷进行二次搅拌，搅拌程序设置为700rpm，时间6min。
（3）将步骤（2）所得的胶料涂覆于20×20×1mm的模具中，静置于真空脱泡桶，在40℃、80Pa下脱泡25分钟；取出后于25℃静置48h固化成型，脱模后得到白色光滑垫片，相变焓值43.2J/g，导热性能为热导率0.64W/(m∙K)，常温（25℃）硬度为37.5 HA。
本实施例所得的导热增强的相变纳米胶囊复合材料的应用：
与实施例1的操作过程基本一致，区别在于：使用直流稳压电源的电压来控制发热片加热功率，设定功率为10W。测试结果：使用该相变纳米胶囊复合材料导热垫片作为热界面材料比使用不添加纳米胶囊以及高导热填料的纯聚二甲基硅氧烷的芯片温度低30.22℃。
实施例 3
一种导热增强的相变纳米胶囊复合材料，以质量分数计，由以下原料制成：无机壳相变纳米胶囊26.09%、高导热填料氮化硼26.09%、聚二甲基硅氧烷预聚物43.47%和甲基含氢硅油4.35%。
所述一种导热增强的相变纳米胶囊复合材料的制备方法，包括如下步骤：
（1）采用界面水解-缩聚法制备石蜡为芯材，二氧化硅为壳材的相变纳米胶囊：石蜡（15.0g）, 正硅酸乙酯TEOS（7.5g）在250mL三颈烧瓶中以60℃搅拌混合，形成透明的溶液。然后，同时将十六烷基三甲基溴化铵CTAB（0.82g）、去离子水（35.5mL）和无水乙醇（71.25mL）加入250mL烧杯中，并保温至60℃。在60℃下将以无水乙醇、去离子水、CTAB组成的水相加入以石蜡、TEOS组成的油相中，以350rpm的转速机械搅拌4h，形成稳定的O/W乳液。加入1.5mL 25wt%氨水，并保持在60℃下继续搅拌16h以催化TEOS的界面水解-缩聚反应。最后，经过滤、去离子水洗涤、石油醚洗涤、干燥，得到约8g白色粉末即石蜡@二氧化硅相变纳米胶囊。
（2）称取0.78g石蜡@二氧化硅相变纳米胶囊（平均粒径1000nm，相变温度为48℃，潜热值180J/g）和0.78g氮化硼（BN）高导热填料，1.3g聚二甲基硅氧烷预聚体，0.13g甲基含氢硅油。
先在容器中添加称量好的石蜡@二氧化硅相变纳米胶囊、聚二甲基硅氧烷预聚物和甲基含氢硅油进行行星式搅拌机的一次搅拌，取出后再添加高导热填料BN，以及1.3mL助溶剂正戊烷进行二次搅拌，搅拌程序设置为1400rpm，时间5min。
（3）将步骤（2）所得的胶料涂覆于20×20×1mm的模具中，静置于真空脱泡桶，在35℃、90Pa下脱泡30分钟；取出后于25℃静置48h固化成型，脱模后得到白色光滑垫片，相变焓值61J/g，导热性能为热导率1.02W/(m∙K)，常温（25℃）硬度为25.0 HA。
本实施例所得的导热增强的相变纳米胶囊复合材料的应用：
与实施例1的操作过程基本一致，区别在于：使用直流稳压电源的电压来控制发热片加热功率，设定功率为5W。测试结果：使用该相变纳米胶囊复合材料导热垫片作为热界面材料比使用不添加纳米胶囊以及高导热填料的纯聚二甲基硅氧烷的芯片温度低47.17℃。
实施例 4
一种导热增强的相变纳米胶囊复合材料，以质量分数计，由以下原料制成：无机壳相变纳米胶囊19.05%、高导热填料碳纤维28.57%、聚二甲基硅氧烷预聚物47.62%和含氢硅氧烷4.76%。
所述一种导热增强的相变纳米胶囊复合材料的制备方法，包括如下步骤：
（1）采用界面水解-缩聚法制备石蜡为芯材，二氧化硅为壳材的相变纳米胶囊：石蜡（15.0g）, 正硅酸乙酯TEOS（7.5g）在250mL三颈烧瓶中以60℃搅拌混合，形成透明的溶液。然后，同时将十六烷基三甲基溴化铵CTAB（0.82g）、去离子水（35.5mL）和无水乙醇（71.25mL）加入250mL烧杯中，并保温至60℃。在60℃下将以无水乙醇、去离子水、CTAB组成的水相加入以石蜡、TEOS组成的油相中，以350rpm的转速机械搅拌4h，形成稳定的O/W乳液。加入1.5mL 25wt%氨水，并保持在60℃下继续搅拌16h以催化TEOS的界面水解-缩聚反应。最后，经过滤、去离子水洗涤、石油醚洗涤、干燥，得到约8g白色粉末即石蜡@二氧化硅相变纳米胶囊。
（2）称取0.52g石蜡@二氧化硅相变纳米胶囊（平均粒径800nm，相变温度为45℃，潜热值170J/g）和0.78g碳纤维（CF）高导热填料，1.3g聚二甲基硅氧烷预聚体，0.13g含氢硅氧烷。
先在容器中添加称量好的石蜡@二氧化硅相变纳米胶囊、聚二甲基硅氧烷预聚物和固化剂进行行星式搅拌机的一次搅拌，取出后再添加高导热填料CF，以及1.3mL助溶剂正戊烷进行二次搅拌，搅拌程序设置为2000rpm，时间6min。
（3）将步骤（2）所得的胶料涂覆于20×20×1mm的模具中，静置于真空脱泡桶，在25℃、100Pa下脱泡30分钟；取出后于25℃静置48h固化成型，脱模后得到白色光滑垫片，相变焓值43.2J/g，导热性能为热导率1.64W/(m∙K)，常温（25℃）硬度为27.5 HA。
本实施例所得的导热增强的相变纳米胶囊复合材料的应用：
与实施例1的操作过程基本一致，区别在于：使用直流稳压电源的电压来控制发热片加热功率，设定功率为10W。测试结果：使用该相变纳米胶囊复合材料导热垫片作为热界面材料比使用不添加纳米胶囊以及高导热填料的纯聚二甲基硅氧烷的芯片温度低55.31℃。
实施例 5
一种导热增强的相变纳米胶囊复合材料，以质量分数计，由以下原料制成：无机壳相变纳米胶囊19.05%、高导热填料碳纤维14.28%与氮化硼14.29%、聚二甲基硅氧烷预聚物47.62%和含氢硅油4.76%。
所述一种导热增强的相变纳米胶囊复合材料的制备方法，包括如下步骤：
（1）采用界面水解-缩聚法制备石蜡为芯材，二氧化硅为壳材的相变纳米胶囊：石蜡（15.0g）, 正硅酸乙酯TEOS（7.5g）在250mL三颈烧瓶中以60℃搅拌混合，形成透明的溶液。然后，同时将十六烷基三甲基溴化铵CTAB（0.82g）、去离子水（35.5mL）和无水乙醇（71.25mL）加入250mL烧杯中，并保温至60℃。在60℃下将以无水乙醇、去离子水、CTAB组成的水相加入以石蜡、TEOS组成的油相中，以350rpm的转速机械搅拌4h，形成稳定的O/W乳液。加入1.5mL 25wt%氨水，并保持在60℃下继续搅拌16h以催化TEOS的界面水解-缩聚反应。最后，经过滤、去离子水洗涤、石油醚洗涤、干燥，得到约8g白色粉末即石蜡@二氧化硅相变纳米胶囊。
（2）称取0.52g石蜡@二氧化硅相变纳米胶囊（平均粒径800nm，相变温度为45℃，潜热值170J/g）和0.39g碳纤维（CF）、0.39g氮化硼（BN）高导热填料，1.3g聚二甲基硅氧烷预聚体，0.13g含氢硅油。
先在容器中添加称量好的石蜡@二氧化硅相变纳米胶囊、聚二甲基硅氧烷预聚物和固化剂进行行星式搅拌机的一次搅拌，取出后再添加高导热填料CF、BN，以及1.3mL助溶剂正戊烷进行二次搅拌，搅拌程序设置为2000rpm，时间5min。
（3）将步骤（2）所得的胶料涂覆于20×20×1mm的模具中，静置于真空脱泡桶，在30℃、90Pa下脱泡30分钟；取出后于25℃静置48h固化成型，脱模后得到白色光滑垫片，相变焓值43.2J/g，导热性能为热导率1.24W/(m∙K)，常温（25℃）硬度为32.5 HA。
本实施例所得的导热增强的相变纳米胶囊复合材料的应用：
与实施例1的操作过程基本一致，区别在于：使用直流稳压电源的电压来控制发热片加热功率，设定功率为10W。测试结果：使用该相变纳米胶囊复合材料导热垫片作为热界面材料比使用不添加纳米胶囊以及高导热填料的纯聚二甲基硅氧烷的芯片温度低50.28℃。
实施例 6
一种导热增强的相变纳米胶囊复合材料，以质量分数计，由以下原料制成：无机壳相变纳米胶囊10.53%、高导热填料氮化硼31.58%、聚二甲基硅氧烷预聚物52.63%和含氢硅油5.26%。
所述一种导热增强的相变纳米胶囊复合材料的制备方法，包括如下步骤：
（1）采用界面水解-缩聚法制备正十六醇为芯材，二氧化硅为壳材的相变纳米胶囊：正十六醇（15.0g）, 正硅酸乙酯TEOS（7.5g）在250mL三颈烧瓶中以60℃搅拌混合，形成透明的溶液。然后，同时将十六烷基三甲基溴化铵CTAB（0.82g）、去离子水（35.5mL）和无水乙醇（71.25mL）加入250mL烧杯中，并保温至60℃。在60℃下将以无水乙醇、去离子水、CTAB组成的水相加入以正十六醇、TEOS组成的油相中，以350rpm的转速机械搅拌4h，形成稳定的O/W乳液。加入1.5mL 25wt%氨水，并保持在60℃下继续搅拌16h以催化TEOS的界面水解-缩聚反应。最后，经过滤、去离子水洗涤、无水乙醇洗涤、干燥，得到约8g白色粉末即正十六醇@二氧化硅相变纳米胶囊。
（2）称取0.26g正十六醇@二氧化硅相变纳米胶囊（平均粒径500nm，相变温度为46℃，潜热值120J/g）和0.78g氮化硼（BN）高导热填料，1.3g聚二甲基硅氧烷预聚体，0.13g含氢硅油。
先在容器中添加称量好的正十六醇@二氧化硅相变纳米胶囊、聚二甲基硅氧烷预聚物和含氢硅油进行行星式搅拌机的一次搅拌，取出后再添加高导热填料BN，以及1.3mL助溶剂正戊烷进行二次搅拌，搅拌程序设置为2000rpm，时间6min。
（3）将步骤（2）所得的胶料涂覆于20×20×1mm的模具中，静置于真空脱泡桶，在25℃、100Pa下脱泡20分钟；取出后于25℃静置48h固化成型，脱模后得到白色光滑垫片，相变焓值15J/g，导热性能为热导率0.85W/(m∙K)，常温（25℃）硬度为50 HA。
本实施例所得的导热增强的相变纳米胶囊复合材料的应用：
与实施例1的操作过程基本一致，区别在于：使用直流稳压电源的电压来控制发热片加热功率，设定功率为10W。测试结果：使用该相变纳米胶囊复合材料导热垫片作为热界面材料比使用不添加纳米胶囊以及高导热填料的纯聚二甲基硅氧烷的芯片温度低36.77℃。由此可见，使用本发明相变纳米胶囊复合材料作为热界面材料可以显著降低芯片温度，提高散热性能。
实施例 7
一种导热增强的相变纳米胶囊复合材料，以质量分数计，由以下原料制成：无机壳相变纳米胶囊10.53%、高导热填料氮化硼31.58%、聚二甲基硅氧烷预聚物52.63%和含氢硅油5.26%。
所述一种导热增强的相变纳米胶囊复合材料的制备方法，包括如下步骤：
（1）采用界面水解-缩聚法制备石蜡为芯材，二氧化钛为壳材的相变纳米胶囊：石蜡（15.0g）, 钛酸丁酯（7.5g）在250mL三颈烧瓶中以60℃搅拌混合，形成透明的溶液。然后，同时将十六烷基三甲基溴化铵CTAB（0.82g）、去离子水（35.5mL）和无水乙醇（71.25mL）加入250mL烧杯中，并保温至60℃。在60℃下将以无水乙醇、去离子水、CTAB组成的水相加入以石蜡、钛酸丁酯组成的油相中，以350rpm的转速机械搅拌4h，形成稳定的O/W乳液。加入1.5mL 25wt%氨水，并保持在60℃下继续搅拌16h以催化钛酸丁酯的界面水解-缩聚反应。最后，经过滤、去离子水洗涤、石油醚洗涤、干燥，得到约8g白色粉末即石蜡@二氧化钛相变纳米胶囊。
（2）称取0.26g石蜡@二氧化钛相变纳米胶囊（平均粒径500nm，相变温度为42℃，潜热值125J/g）和0.78g氮化硼（BN）高导热填料，1.3g聚二甲基硅氧烷预聚体，0.13g含氢硅油。
先在容器中添加称量好的石蜡@二氧化钛相变纳米胶囊、聚二甲基硅氧烷预聚物和含氢硅油进行行星式搅拌机的一次搅拌，取出后再添加高导热填料BN，以及1.3mL助溶剂正戊烷进行二次搅拌，搅拌程序设置为2000rpm，时间6min。
（3）将步骤（2）所得的胶料涂覆于20×20×1mm的模具中，静置于真空脱泡桶，在25℃、100Pa下脱泡20分钟；取出后于25℃静置48h固化成型，脱模后得到白色光滑垫片，相变焓值16J/g，导热性能为热导率0.64W/(m∙K)，常温（25℃）硬度为45 HA。
本实施例所得的导热增强的相变纳米胶囊复合材料的应用：
与实施例1的操作过程基本一致，区别在于：使用直流稳压电源的电压来控制发热片加热功率，设定功率为10W。测试结果：使用该相变纳米胶囊复合材料导热垫片作为热界面材料比使用不添加纳米胶囊以及高导热填料的纯聚二甲基硅氧烷的芯片温度低42.56℃。由此可见，使用本发明相变纳米胶囊复合材料作为热界面材料可以显著降低芯片温度，提高散热性能。

Claims (10)

  1. 一种导热增强的相变纳米胶囊复合材料的制备方法，其特征在于，包括以下步骤：
    （1）采用界面水解-缩聚法制备无机壳相变纳米胶囊；
    （2）先在容器中添加步骤（1）所得的无机壳相变纳米胶囊、聚二甲基硅氧烷预聚物和固化剂进行搅拌机的一次搅拌，取出后再添加高导热填料以及与聚二甲基硅氧烷预聚物质量相当的助溶剂进行二次搅拌得到胶料；
    （3）将步骤（2）所得的胶料涂覆于模具中，静置于真空脱泡桶，脱泡处理；取出后静置固化成型，脱模后得到所述导热增强的相变纳米胶囊复合材料。
  2. 根据权利要求1所述的一种导热增强的相变纳米胶囊复合材料的制备方法，其特征在于，步骤（1）所述界面水解-缩聚法具体为：无水乙醇、去离子水、十六烷基二甲基溴化铵构成水相，芯材物质、壳材前驱体构成油相，水相和油相先各自在60℃充分溶解，然后混合在一起通过乳化工艺形成稳定的O/W乳液；加入氨水引发剂，壳材前驱体在界面处通过氨催化水解-缩聚反应形成壳材低聚体，并带负电荷，其立即通过静电相互作用吸附在带正电荷的胶束表面，随着界面缩聚反应的进行，壳材低聚体不断从油滴内向界面处迁移，最终在芯材液滴表面逐渐缩聚形成无机外壳。
  3. 根据权利要求1所述的一种导热增强的相变纳米胶囊复合材料的制备方法，其特征在于，步骤（1）所述无机壳相变纳米胶囊的芯材为石蜡类、多元醇类或脂肪酸类，无机壳材为具有羟基的二氧化硅或二氧化钛。
  4. 根据权利要求1所述的一种导热增强的相变纳米胶囊复合材料的制备方法，其特征在于，步骤（1）所述无机壳相变纳米胶囊的粒径为500~1000nm，相变温度42℃~48℃，相变潜热120~180J/g。
  5. 根据权利要求1所述的一种导热增强的相变纳米胶囊复合材料的制备方法，其特征在于，步骤（2）所述高导热填料为氧化铝、氮化硼、氮化铝、碳纤维、石墨烯中的一种或几种的混合物；步骤（2）所述固化剂为含氢硅油、含氢硅氧烷、甲基含氢硅油的一种或几种的混合物；步骤（2）所述助溶剂为正己烷、正戊烷、环己烷中的一种以上。
  6. 根据权利要求1所述的一种导热增强的相变纳米胶囊复合材料的制备方法，其特征在于，步骤（3）所述脱泡处理的压强为80Pa~100Pa、温度为25℃~40℃、时间为20~30分钟。
  7. 权利要求1-6任一项所述的制备方法得到的一种导热增强的相变纳米胶囊复合材料。
  8. 根据权利要求7所述的一种导热增强的相变纳米胶囊复合材料，其特征在于，以质量分数计，所述相变纳米胶囊型复合材料包括无机壳相变纳米胶囊10.53%~26.09%、高导热填料26.09%~31.58%、聚二甲基硅氧烷预聚物43.47%~52.63%和固化剂4.35%~5.26%。
  9. 根据权利要求7所述的一种导热增强的相变纳米胶囊复合材料，其特征在于，所述导热增强的相变纳米胶囊复合材料的储热性能为相变焓值15~61J/g，导热性能为热导率0.64~1.64 W/(m∙K)，常温下的硬度为25~50 HA。
  10. 权利要求7所述的一种导热增强的相变纳米胶囊复合材料作为热界面材料的应用。
PCT/CN2022/144384 2022-04-14 2022-12-30 一种导热增强的相变纳米胶囊复合材料及制备方法与应用 WO2023197698A1 (zh)

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