A composite phase change material, a preparation method thereof, a potting material, and an electronic device

Abstract

This application is applicable to the field of material technology, and provides a composite phase change material, a preparation method thereof, a potting material, and an electronic device; the composite phase change material has a phase change microcapsule as the inner layer, and carbon nanotubes and silicon dioxide are sequentially coated on the surface layer of the phase change microcapsule, and is obtained by modification with a vinyl silane coupling agent. This application can take into account high thermal conductivity and high enthalpy value, without the need to be used in combination with thermal conductive powders, and improves the flammability defect of conventional organic phase change materials when used alone; in addition, the potting material prepared from this composite phase change material can take into account excellent properties such as high enthalpy value, high thermal conductivity, high fluidity, insulation, and flame retardancy; and this composite phase change material has good compatibility with the silicone matrix, will not cause phase separation, and can prevent sedimentation; its surface contains vinyl groups, which can participate in the silicone addition reaction during curing, and after curing, the phase change material and the silicone matrix form a quasi-3D network structure, and the composite thermal conductive phase change filler is more closely combined with the silicone matrix.

Description

Technical Field

[0001] This application belongs to the field of materials technology, and particularly relates to a composite phase change material, a preparation method thereof, a potting material, and an electronic device. Background Art

[0002] With the further realization of high performance, high reliability, and miniaturization in the fields of electronic components, circuit modules, large-scale integrated circuits, etc., the working efficiency has been continuously improved. Therefore, the heat generated by each component during operation has increased sharply. Inevitably, more heat will be generated during the operation of the product. If the heat cannot be dissipated in time, it will reduce the efficacy of the product, shorten the service life of the product, and even may cause safety accidents. An effective method is to transfer the heat generated by the device through a heat-conducting material.

[0003] A thermal interface material, also known as a heat interface material or an interface heat-conducting material, is a material used between a heat source and a heat sink. By removing the air between the heat source and the heat sink, it can accelerate the heat conduction efficiency of the electronic device to the outside. A phase change material refers to a substance that changes its state without changing temperature and can provide latent heat. The process of changing physical properties is called a phase change process. At this time, the phase change material will absorb or release a large amount of latent heat. When the phase change temperature is reached, the material undergoes a phase change and softens, fitting more closely to the contact surface, and at the same time obtaining an ultra-low thermal resistance, and the heat transfer is more thorough. Therefore, a new generation of heat-conducting technology represented by the phase change heat-conducting and dissipating interface material has gradually become the preferred heat dissipation solution for consumer electronic products.

[0004] Traditional heat-conducting phase change materials are made by mixing polymer materials, heat-conducting fillers, and conventional phase change materials. Due to the polarity difference between the filler and the matrix, they are prone to sedimentation and phase separation during liquid storage; when the heat-conducting phase change materials are used at high temperatures, they are very easy to leak and contaminate electronic components; moreover, the heat-conducting performance of traditional phase change filling materials is poor, and after filling, it affects the heat-conducting performance of the heat-conducting material. Summary of the Invention

[0005] The embodiments of this application provide a composite phase change material, aiming to solve the problem that the existing heat-conducting phase change materials cannot take into account both high heat conduction and high enthalpy value.

[0006] The embodiments of this application are implemented as follows. A composite phase change material is obtained by using a phase change microcapsule as the inner layer and successively coating a carbon nanotube and silicon dioxide on the surface layer of the phase change microcapsule; wherein, the phase change microcapsule has an organic phase change material as the core and a material containing a hydroxyl group on the surface as the shell layer.

[0007] The embodiments of this application also provide a preparation method of a composite phase change material, including:

[0008] The phase change microcapsules and carbon nanotubes are stirred and mixed and then modified by a coupling agent to obtain a modified phase change material;

[0009] The modified phase change material is coated with silica on the outer layer by the sol-gel method to obtain a composite phase change material.

[0010] The embodiment of the present application also provides a potting material, and the potting material includes the composite phase change material or the composite phase change material prepared by the preparation method of the composite phase change material.

[0011] The embodiment of the present application also provides an electronic device, and the electronic device includes the potting material.

[0012] In the embodiment of the present application, a composite phase change material with a multi-layer structure is obtained by using the phase change microcapsules as the inner layer and sequentially coating carbon nanotubes and silica on the surface layer of the phase change microcapsules. The composite phase change material can take into account high thermal conductivity and high enthalpy value, and there is no need to be compounded with thermal conductive powder; at the same time, the disadvantage of flammability when conventional organic phase change materials are used alone is improved; in addition, the potting material prepared from the composite phase change material can take into account excellent properties such as high enthalpy value, high thermal conductivity, high fluidity, insulation, and flame retardancy; moreover, the composite phase change material has good compatibility with the silicone matrix and will not cause phase separation, which can prevent sedimentation; the surface of the composite phase change material contains vinyl, which can participate in the silicone addition reaction during curing, and after curing, the phase change material and the silicone matrix form a quasi-3D network structure, and the composite thermal conductive phase change filler is more tightly combined with the silicone matrix. Specific Embodiments

[0013] In order to make the purpose, technical solutions and advantages of the present application clearer, the present application will be further described in detail below with reference to specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0014] The embodiment of the present application aims to solve the problem that the existing thermal conductive phase change materials cannot take into account both high thermal conductivity and high enthalpy value. A composite phase change material is provided, and the composite phase change material uses phase change microcapsules as the inner layer and sequentially coats carbon nanotubes and silica on the surface layer of the phase change microcapsules, and is obtained by modification with a vinyl silane coupling agent.

[0015] Among them, the phase change microcapsules are commercially available microcapsules. The shell layer of the phase change microcapsules can be SiO2 or other polymer materials containing hydroxyl groups, such as polyethylene glycol, etc.; the inner core is a phase change material, such as paraffin, fatty acid and other organic phase change materials, with a phase change temperature of 30-60°C; the phase change enthalpy value is 100-300 J / g; the particle size of the phase change microcapsules is 10-100 μm. The phase change microcapsules are capsule-shaped materials formed by coating the phase change material with a film-forming material, with the internal phase change energy storage material as the core and the external coating material as the capsule wall; after undergoing a phase change at high temperature, it becomes liquid, and because of the wrapping of the external capsule wall, there will be no leakage during use, so it will not contaminate electronic components, etc.

[0016] The embodiment of the present application also provides a preparation method of the above-mentioned composite phase change material, including the following steps:

[0017] Step S1, stir and mix the phase change microcapsules and carbon nanotubes, and then perform modification treatment with a coupling agent to obtain a modified phase change material.

[0018] In the embodiment of the present application, the phase change microcapsules and carbon nanotubes with carboxyl or hydroxyl groups on the surface are mixed evenly in a high-speed disperser, and then sprayed with a coupling agent for modification treatment to obtain a phase change microcapsule / carbon nanotube modified phase change material, and the phase change microcapsules and carbon nanotubes are connected by chemical bonds. The carbon nanotubes are commercially available carboxylated or hydroxylated carbon nanotubes, with an inner diameter of 2-10 nm, an outer diameter of 15-30 nm, and a length of 1-30 μm.

[0019] Among them, the coupling agent is selected from conventional silane coupling agents, such as Y(CH2) n SiX3, where Y is an organic functional group, which can be vinyl, amino, epoxy, methacryloxy, mercapto or ureido; X is usually chloro, methoxy, ethoxy, methoxyethoxy, acetoxy, etc. The alkoxy group of the silane coupling agent is hydrolyzed, and the silane coupling agent can connect the phase change microcapsules and carbon nanotubes into one body through chemical bonds; one end of the silane coupling agent can be connected to the phase change microcapsules, and one end can be connected to the surface of the carbon nanotubes, forming a composite structure of carbon nanotubes and phase change microcapsules, and the carbon nanotubes are tightly combined with the phase change material, rather than simply physically mixed.

[0020] Among them, the weight ratio of the phase change microcapsules to the carbon nanotubes is 20:1 to 1:1, and the dosage of the coupling agent is 0.1%-5% relative to the total weight of the phase change microcapsules and carbon nanotubes.

[0021] Step S2, coat the modified phase change material with silica by the sol-gel method and modify it with a vinyl silane coupling agent to obtain a composite phase change material.

[0022] In the embodiments of the present application, the phase change microcapsule / carbon nanotube modified phase change material is coated with SiO2 on the outer layer by the sol-gel method to form a phase change microcapsule / carbon nanotube / SiO2 composite structure thermally conductive phase change material. The particle size of the composite structure is preferably 20-150 um; if the particle size is greater than 150 um, the subsequent prepared two-component silicone potting material product will be too rough, and if the particle size is less than 20 um, it will result in too low filling amount and insufficient thermal conductivity and enthalpy value.

[0023] In the present application, linear, non-insulating, highly thermally conductive carbon nanotubes are wrapped by silica. On the one hand, the high thermal conductivity of the carbon nanotubes can improve the thermal conductivity of the phase change material, and on the other hand, the conductive carbon nanotubes can be wrapped by insulating silica, making the material have excellent insulation performance. In addition, the composite phase change material is wrapped by an inorganic silica material and has excellent flame retardancy, improving the disadvantage that ordinary organic phase change materials are flammable.

[0024] Specifically, deionized water and ethanol are mixed, hydrochloric acid is added to adjust the pH value to 2-5, the phase change microcapsule / carbon nanotube modified phase change material is added, and it is continuously stirred in a high-speed disperser. The temperature is controlled at 50-70 °C, tetraethyl orthosilicate is gradually added, and it is continuously stirred for 3-4 hours, then a special silane coupling agent is added, and stirring is continued for 3-4 h, and then centrifuged and dried to obtain a phase change microcapsule / carbon nanotube / SiO2 composite structure thermally conductive phase change material. Among them, the molar ratio of water to ethanol is 1:2 to 2:1; the molar ratio of ethanol to tetraethyl orthosilicate is (4-16):1; the weight ratio of the phase change microcapsule / carbon nanotube modified phase change material to tetraethyl orthosilicate is 1:(2-10); ethanol is the product of the hydrolysis reaction, and too much will inhibit the progress of the reaction; while tetraethyl orthosilicate is hardly soluble in water, and ethanol is the solvent of tetraethyl orthosilicate, which can promote the progress of the reaction.

[0025] Among them, the sol-gel hydrolysis reaction formula of tetraethyl orthosilicate is as follows:

[0026] Si(OCH2CH3)4 + 2H2O = Sio2 + 4C2H5OH;

[0027] Among them, the special silane coupling agent uses a silane coupling agent containing vinyl, such as the structural formula of the vinyl silane coupling agent is CH2=CH(CH2) nSiX3, where n is 0 or 1, and X is one or more of methoxy, ethoxy, methoxyethoxy, and acetoxy. The dosage of the coupling agent is 0.1%-5% (relative to the weight of the composite structure phase change material). The vinyl group in the composite thermal conductivity phase change material can participate in the addition reaction of the silicone matrix. After curing, the composite thermal conductivity phase change filler is more tightly combined with the silicone matrix. When used at high temperatures, the phase change material will not slip or move inside the thermal conductivity material, and local phase separation will not occur. On the one hand, it can prevent further agglomeration of the composite structure thermal conductivity phase change material during the preparation process; on the other hand, it improves the surface properties of the material and enhances the dispersion and filling amount of the composite thermal conductivity phase change filler in the silicone system.

[0028] The embodiment of the present application also provides a potting material, that is, a two-component silicone thermal conductivity potting material A / B is prepared based on the above composite phase change material.

[0029] Among them, component A is composed of vinyl silicone oil, platinum catalyst, and composite phase change material. Component B is composed of vinyl silicone oil, hydrogen-containing silicone oil, inhibitor, and composite phase change material.

[0030] Specifically, in component A, the content of vinyl silicone oil is 30-60 parts, the platinum catalyst is 0.001-0.1 part, and the composite phase change material is 10-200 parts. In component B, the content of vinyl silicone oil is 25-45 parts, the hydrogen-containing silicone oil is 5-15 parts, the composite phase change material is 10-200 parts, and the inhibitor is 0.001-0.1 part.

[0031] The specific preparation process of the above two-component silicone thermal conductivity potting material A / B is as follows:

[0032] Preparation of component A:

[0033] 1. Weigh vinyl silicone oil and catalyst according to the ratio, and mix them evenly with a high-speed mixing and dispersing machine to obtain silicone-based rubber a1;

[0034] 2. Add the corresponding weight of the composite phase change material to the silicone-based rubber a1, and mix them evenly with a high-speed mixing and dispersing machine to obtain silicone thermal conductivity phase change potting glue A.

[0035] Preparation of component B:

[0036] 1. Weigh vinyl silicone oil, hydrogen-containing silicone oil, and inhibitor according to the ratio, and mix them evenly with a high-speed mixing and dispersing machine to obtain silicone-based rubber b1;

[0037] 2. Add the corresponding weight of the composite phase change material to the silicone-based rubber b1, and mix them evenly with a high-speed mixing and dispersing machine to obtain silicone thermal conductivity phase change potting glue B.

[0038] After the silicone thermal conductive phase change potting materials A and B are fully mixed evenly according to the mass ratio of 1:1, they are then cured at 50-70 °C for 10-30 min.

[0039] For the silicone thermal conductive potting material prepared in this application, on the one hand, excellent properties such as high thermal conductivity, high enthalpy value, high fluidity, insulation, and flame retardancy can be achieved without filling conventional thermal conductive fillers; on the other hand, it has excellent thermal conductivity, low thermal resistance, and heat storage and temperature control performance. When electronic components generate a large amount of heat during operation, the material can effectively absorb heat and quickly conduct and diffuse it, and ensure the temperature uniformity of the electronic components; moreover, when the temperature reaches the phase change point, the phase change material undergoes a phase change and the thermal conductive material softens, which can achieve a closer fit with the heat dissipation interface, achieve a lower thermal resistance, and improve the heat dissipation efficiency.

[0040] The technical solutions in the embodiments of the present application will be described clearly and completely below. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all of the embodiments.

[0041] In addition, it should be noted that the values given in the following embodiments are as accurate as possible. However, those skilled in the art understand that due to inevitable measurement errors and experimental operation problems, each number should be understood as an approximate number, rather than an absolutely accurate value.

[0042] Example 1

[0043] 20 g of phase change microcapsules (paraffin wax coated with silica, purchased from Guangzhou Zhongjia, phase change temperature of 45 °C, phase change enthalpy value of 200 J / g, particle size of 30 μm) and 1 g of carbon nanotubes (carboxylated carbon nanotubes, purchased from Beijing Dechuan Shimadzu, tube diameter <8 nm, length of 15 μm) are mixed evenly in a high-speed disperser, and then 0.021 g of coupling agent (methacryloxypropyltrimethoxysilane coupling agent, purchased from Nanjing Nengde New Material Technology Co., Ltd.) is sprayed for modification treatment to prepare a phase change microcapsule / carbon nanotube modified phase change material; the dosage of the coupling agent is 0.1% relative to the total weight of the phase change microcapsules and carbon nanotubes;

[0044] Mix 180 g of deionized water and 920 g of ethanol, add hydrochloric acid to adjust the pH value to 3, add 104 g of phase change microcapsule / carbon nanotube modified phase change material, continuously stir in a high-speed disperser, control the temperature at 60 °C, gradually add 1040 g of tetraethyl orthosilicate (purchased from Zhangjiagang Xinya Chemical Co., Ltd.), continuously stir for 3.5 hours, then add 0.105 g of vinyl silane coupling agent (vinyltriethoxysilane coupling agent, purchased from Nanjing Nengde New Materials Technology Co., Ltd.), continue to stir for 3.5 h, and then centrifuge and dry to obtain the phase change microcapsule / carbon nanotube / SiO2 composite phase change material. Among them, the molar ratio of water to ethanol is 1:2; the molar ratio of ethanol to tetraethyl orthosilicate is 4:1; the dosage of vinyl silane coupling agent is 0.5% relative to the total weight of the phase change microcapsule and carbon nanotube.

[0045] Example 2

[0046] Mix 10 g of phase change microcapsules (paraffin wax coated with silica, purchased from Guangzhou Zhongjia, phase change temperature is 45 °C, phase change enthalpy value is 200 J / g, particle size is 30 μm) and 10 g of carbon nanotubes (carboxylated carbon nanotubes, purchased from Beijing Dech Island Shimadzu, tube diameter < 8 nm, length 30 μm) evenly in a high-speed disperser, then spray 1 g of coupling agent (methacryloxypropyltrimethoxysilane coupling agent, purchased from Nanjing Nengde New Materials Technology Co., Ltd.) for modification treatment to obtain the phase change microcapsule / carbon nanotube modified phase change material; the dosage of the coupling agent is 5% relative to the total weight of the phase change microcapsule and carbon nanotube;

[0047] Mix 360 g of deionized water and 460 g of ethanol, add hydrochloric acid to adjust the pH value to 3, add 26 g of phase change microcapsule / carbon nanotube modified phase change material, continuously stir in a high-speed disperser, control the temperature at 60 °C, gradually add 130 g of tetraethyl orthosilicate (purchased from Zhangjiagang Xinya Chemical Co., Ltd.), continuously stir for 3.5 hours, then add 0.105 g of vinyl silane coupling agent (vinyltriethoxysilane coupling agent, purchased from Nanjing Nengde New Materials Technology Co., Ltd.), continue to stir for 3.5 h, and then centrifuge and dry to obtain the phase change microcapsule / carbon nanotube / SiO2 composite phase change material. Among them, the molar ratio of water to ethanol is 2:1; the molar ratio of ethanol to tetraethyl orthosilicate is 16:1; the dosage of vinyl silane coupling agent is 0.5% relative to the total weight of the phase change microcapsule and carbon nanotube.

[0048] Example 3

[0049] Mix 15 g of phase change microcapsules (paraffin wax coated with silica, purchased from Guangzhou Zhongjia, phase change temperature of 52 °C, phase change enthalpy value of 250 J / g, particle size of 80 μm) with 5 g of carbon nanotubes (carboxylated carbon nanotubes, purchased from Beijing Dech Island Shimadzu, tube diameter <8 nm, length of 15 μm) evenly in a high-speed disperser, and then spray 0.105 g of coupling agent (methacryloxypropyltrimethoxysilane coupling agent, purchased from Nanjing Nengde New Materials Technology Co., Ltd.) for modification treatment to obtain a phase change microcapsule / carbon nanotube modified phase change material; the dosage of the coupling agent is 0.5% relative to the total weight of the phase change microcapsules and carbon nanotubes;

[0050] Mix 180 g of deionized water and 460 g of ethanol, add hydrochloric acid to adjust the pH value to 3, add 115.6 g of the phase change microcapsule / carbon nanotube modified phase change material, continuously stir in a high-speed disperser, control the temperature at 60 °C, gradually add 346.7 g of tetraethyl orthosilicate (purchased from Zhangjiagang Xinya Chemical Co., Ltd.), continuously stir for 3.5 hours, then add 0.021 g of vinyl silane coupling agent (vinyltriethoxysilane coupling agent, purchased from Nanjing Nengde New Materials Technology Co., Ltd.), continue to stir for 3.5 h, and then centrifuge and dry to obtain a phase change microcapsule / carbon nanotube / SiO2 composite phase change material. Among them, the molar ratio of water to ethanol is 1:1; the molar ratio of ethanol to tetraethyl orthosilicate is 6:1; the dosage of the vinyl silane coupling agent is 0.1% relative to the total weight of the phase change microcapsules and carbon nanotubes.

[0051] Example 4

[0052] Mix 15 g of phase change microcapsules (paraffin wax coated with silica, purchased from Guangzhou Zhongjia, phase change temperature of 52 °C, phase change enthalpy value of 250 J / g, particle size of 100 μm) with 5 g of carbon nanotubes (carboxylated carbon nanotubes, purchased from Beijing Dech Island Shimadzu, tube diameter <8 nm, length of 1 μm) evenly in a high-speed disperser, and then spray 0.105 g of coupling agent (methacryloxypropyltrimethoxysilane coupling agent, purchased from Nanjing Nengde New Materials Technology Co., Ltd.) for modification treatment to obtain a phase change microcapsule / carbon nanotube modified phase change material; the dosage of the coupling agent is 0.5% relative to the total weight of the phase change microcapsules and carbon nanotubes;

[0053] Mix 180 g of deionized water and 460 g of ethanol, add hydrochloric acid to adjust the pH value to 3, add 115.6 g of phase change microcapsule / carbon nanotube modified phase change material, continuously stir in a high-speed disperser, control the temperature at 60 °C, gradually add 346.7 g of tetraethyl orthosilicate (purchased from Zhangjiagang Xinya Chemical Co., Ltd.), continuously stir for 3.5 hours, then add 1 g of vinyl silane coupling agent (vinyltriethoxysilane coupling agent, purchased from Nanjing Nengde New Material Technology Co., Ltd.), continue to stir for 3.5 h, and then centrifuge and dry to obtain the phase change microcapsule / carbon nanotube / SiO2 composite phase change material. Among them, the molar ratio of water to ethanol is 1:1; the molar ratio of ethanol to tetraethyl orthosilicate is 6:1; the dosage of vinyl silane coupling agent is 1% relative to the total weight of the phase change microcapsule and carbon nanotube.

[0054] Example 5

[0055] Mix 15 g of phase change microcapsules (paraffin wax coated with silica, purchased from Guangzhou Zhongjia, phase change temperature is 45 °C, phase change enthalpy value is 200 J / g, particle size is 30 μm) and 3 g of carbon nanotubes (carboxylated carbon nanotubes, purchased from Beijing Dech Island Shimadzu, tube diameter <8 nm, length 15 μm) evenly in a high-speed disperser, then spray 0.105 g of coupling agent (methacryloxypropyltrimethoxysilane coupling agent, purchased from Nanjing Nengde New Material Technology Co., Ltd.) for modification treatment to obtain the phase change microcapsule / carbon nanotube modified phase change material; the dosage of the coupling agent is 0.5% relative to the total weight of the phase change microcapsule and carbon nanotube;

[0056] Mix 180 g of deionized water and 460 g of ethanol, add hydrochloric acid to adjust the pH value to 3, add 115.6 g of phase change microcapsule / carbon nanotube modified phase change material, continuously stir in a high-speed disperser, control the temperature at 60 °C, gradually add 346.7 g of tetraethyl orthosilicate (purchased from Zhangjiagang Xinya Chemical Co., Ltd.), continuously stir for 3.5 hours, then add 0.105 g of vinyl silane coupling agent (vinyltriethoxysilane coupling agent, purchased from Nanjing Nengde New Material Technology Co., Ltd.), continue to stir for 3.5 h, and then centrifuge and dry to obtain the phase change microcapsule / carbon nanotube / SiO2 composite phase change material. Among them, the molar ratio of water to ethanol is 1:1; the molar ratio of ethanol to tetraethyl orthosilicate is 6:1; the dosage of vinyl silane coupling agent is 0.5% relative to the total weight of the phase change microcapsule and carbon nanotube.

[0057] Comparative Example 1

[0058] Mix 15 g of phase change microcapsules (paraffin wax coated with silica, purchased from Guangzhou Zhongjia, phase change temperature of 45 °C, phase change enthalpy value of 200 J / g, particle size of 30 μm) with 3 g of carbon nanotubes (carboxylated carbon nanotubes, purchased from Beijing Dech Island Shimadzu, tube diameter <8 nm, length 15 μm) to obtain a phase change microcapsule / carbon nanotube modified phase change material;

[0059] Mix 180 g of deionized water and 460 g of ethanol, add hydrochloric acid to adjust the pH value to 3, add 115.6 g of the phase change microcapsule / carbon nanotube modified phase change material, continuously stir in a high-speed disperser, control the temperature at 60 °C, gradually add 346.7 g of tetraethyl orthosilicate (purchased from Zhangjiagang Xinya Chemical Co., Ltd.), continuously stir for 3.5 hours, then add 0.105 g of vinyl silane coupling agent (vinyltriethoxysilane coupling agent, purchased from Nanjing Nengde New Materials Technology Co., Ltd.), continue to stir for 3.5 h, and then centrifuge and dry to obtain a phase change microcapsule / carbon nanotube / SiO2 composite phase change material. Among them, the molar ratio of water to ethanol is 1:1; the molar ratio of ethanol to tetraethyl orthosilicate is 6:1; the dosage of the vinyl silane coupling agent is 0.5% relative to the total weight of the phase change microcapsules and carbon nanotubes.

[0060] Comparative Example 2

[0061] Mix 180 g of deionized water and 460 g of ethanol, add hydrochloric acid to adjust the pH value to 3, add 115.6 g of phase change microcapsules (paraffin wax coated with silica, purchased from Guangzhou Zhongjia, phase change temperature of 45 °C, phase change enthalpy value of 200 J / g, particle size of 30 μm), continuously stir in a high-speed disperser, control the temperature at 60 °C, gradually add 346.7 g of tetraethyl orthosilicate (purchased from Zhangjiagang Xinya Chemical Co., Ltd.), continuously stir for 3.5 hours, then add 0.105 g of vinyl silane coupling agent (vinyltriethoxysilane coupling agent, purchased from Nanjing Nengde New Materials Technology Co., Ltd.), continue to stir for 3.5 h, and then centrifuge and dry to obtain a phase change microcapsule / carbon nanotube / SiO2 composite phase change material. Among them, the molar ratio of water to ethanol is 1:1; the molar ratio of ethanol to tetraethyl orthosilicate is 6:1; the dosage of the vinyl silane coupling agent is 0.5% relative to the total weight of the phase change microcapsules and carbon nanotubes.

[0062] Comparative Example 3

[0063] Mix 15 g of phase change microcapsules (paraffin wax coated with silica, purchased from Guangzhou Zhongjia, phase change temperature of 45 °C, phase change enthalpy value of 200 J / g, particle size of 30 μm) with 3 g of non-linear thermal conductive material (aluminum oxide, particle size of 15 μm) evenly in a high-speed disperser, and then spray 0.105 g of coupling agent (methacryloxypropyltrimethoxysilane coupling agent, purchased from Nanjing Nengde New Material Technology Co., Ltd.) for modification treatment to obtain phase change microcapsule / aluminum oxide modified phase change material; the dosage of the coupling agent is 0.5% relative to the total weight of the phase change microcapsules and aluminum oxide;

[0064] Mix 180 g of deionized water and 460 g of ethanol, add hydrochloric acid to adjust the pH value to 3, add 115.6 g of phase change microcapsule / aluminum oxide modified phase change material, continuously stir in a high-speed disperser, control the temperature at 60 °C, gradually add 346.7 g of tetraethyl orthosilicate (purchased from Zhangjiagang Xinya Chemical Co., Ltd.), continuously stir for 3.5 hours, then add 0.105 g of vinyl silane coupling agent (vinyltriethoxysilane coupling agent, purchased from Nanjing Nengde New Material Technology Co., Ltd.), continue to stir for 3.5 h, and then centrifuge and dry to obtain phase change microcapsule / aluminum oxide / SiO2 composite phase change material. Among them, the molar ratio of water to ethanol is 1:1; the molar ratio of ethanol to tetraethyl orthosilicate is 6:1; the dosage of the vinyl silane coupling agent is 0.5% relative to the total weight of the phase change microcapsules and aluminum oxide.

[0065] Comparative Example 4

[0066] Mix 15 g of phase change microcapsules (paraffin wax coated with silica, purchased from Guangzhou Zhongjia, phase change temperature of 45 °C, phase change enthalpy value of 200 J / g, particle size of 30 μm) with 3 g of carbon nanotubes (carboxylated carbon nanotubes, purchased from Beijing Dech Island Shimadzu, tube diameter <8 nm, length of 15 μm) evenly in a high-speed disperser, and then spray 0.105 g of coupling agent (methacryloxypropyltrimethoxysilane coupling agent, purchased from Nanjing Nengde New Material Technology Co., Ltd.) for modification treatment to obtain phase change microcapsule / carbon nanotube composite phase change material; the dosage of the coupling agent is 0.5% relative to the total weight of the phase change microcapsules and carbon nanotubes.

[0067] Comparative Example 5

[0068] Mix 15 g of conventional paraffin wax (purchased from Guangzhou Zhongjia, phase change temperature of 45 °C, phase change enthalpy value of 200 J / g) with 3 g of carbon nanotubes (carboxylated carbon nanotubes, purchased from Beijing Dech Island Shimadzu, tube diameter <8 nm, length of 15 μm) evenly in a high-speed disperser, and then spray 0.105 g of coupling agent (methacryloxypropyltrimethoxysilane coupling agent, purchased from Nanjing Nengde New Material Technology Co., Ltd.) for modification treatment to obtain conventional paraffin wax / carbon nanotube modified phase change material; the dosage of the coupling agent is 0.5% relative to the total weight of the conventional paraffin wax and carbon nanotubes;

[0069] Mix 180 g of deionized water and 460 g of ethanol, add hydrochloric acid to adjust the pH value to 3, add 115.6 g of a conventional paraffin / carbon nanotube modified phase change material, continuously stir in a high-speed disperser, control the temperature at 60 °C, gradually add 346.7 g of tetraethyl orthosilicate (purchased from Zhangjiagang Xinya Chemical Co., Ltd.), continuously stir for 3.5 hours, then add 0.105 g of vinyl silane coupling agent (vinyltriethoxysilane coupling agent, purchased from Nanjing Nengde New Materials Technology Co., Ltd.), continue to stir for 3.5 h, and then centrifuge and dry to obtain a conventional paraffin / carbon nanotube / SiO2 composite phase change material. Among them, the molar ratio of water to ethanol is 1:1; the molar ratio of ethanol to tetraethyl orthosilicate is 6:1; the dosage of the vinyl silane coupling agent is 0.5% relative to the total weight of the conventional paraffin and carbon nanotubes.

[0070] Comparative Example 6

[0071] Mix 15 g of phase change microcapsules (paraffin coated with silica, purchased from Guangzhou Zhongjia, phase change temperature is 45 °C, phase change enthalpy value is 200 J / g, particle size is 30 μm) and 3 g of carbon nanotubes (carboxylated carbon nanotubes, purchased from Beijing Dech Island Shimadzu, tube diameter <8 nm, length 15 μm) evenly in a high-speed disperser, and then spray 0.105 g of coupling agent (methacryloxypropyltrimethoxysilane coupling agent, purchased from Nanjing Nengde New Materials Technology Co., Ltd.) for modification treatment to obtain a phase change microcapsule / carbon nanotube modified phase change material; the dosage of the coupling agent is 0.5% relative to the total weight of the phase change microcapsules and carbon nanotubes;

[0072] Mix 180 g of deionized water and 460 g of ethanol, add hydrochloric acid to adjust the pH value to 3, add 115.6 g of the phase change microcapsule / carbon nanotube modified phase change material, continuously stir in a high-speed disperser, control the temperature at 60 °C, gradually add 346.7 g of tetraethyl orthosilicate (purchased from Zhangjiagang Xinya Chemical Co., Ltd.), continuously stir for 3.5 hours, and then centrifuge and dry to obtain a phase change microcapsule / carbon nanotube / SiO2 composite phase change material. Among them, the molar ratio of water to ethanol is 1:1; the molar ratio of ethanol to tetraethyl orthosilicate is 6:1.

[0073] Carry out relevant tests on the composite phase change materials prepared in the above examples according to relevant test standards, and the test results are shown in Table 1 below.

[0074] Table 1

[0075]

[0076] In summary, as can be seen from Table 1, in Comparative Example 1, most of the carbon nanotubes were aggregated and entangled together and not uniformly dispersed in the system, resulting in a low thermal conductivity; in Comparative Example 2, no carbon nanotubes were added, resulting in a low thermal conductivity; in Comparative Example 3, a non-linear thermal conductive material was used, resulting in a low thermal conductivity; in Comparative Example 4, the outer layer was not coated and was non-insulating; in Comparative Example 5, there was uncoated paraffin wax alone, which would precipitate when heated above the phase change temperature and might contaminate electronic devices; in Comparative Example 6, no surface modification was carried out, and it was easy to agglomerate into a mass during the preparation process.

[0077] Based on the composite phase change materials prepared in the above Examples 1-5 and Comparative Examples 1-6, a two-component silicone thermal conductive potting material A / B was prepared. Among them, the content of vinyl silicone oil (viscosity 100 cps, vinyl content 0.95 wt%, purchased from Dongyue Silicon Materials) in Component A was 40 parts, the content of platinum catalyst (Shanghai Bozhijie New Materials Co., Ltd.) was 0.005 parts, and the content of the composite phase change material was 120 parts; the content of vinyl silicone oil (viscosity 100 cps, vinyl content 0.95 wt%, purchased from Dongyue Silicon Materials) in Component B was 32 parts, the content of hydrogen-containing silicone oil (viscosity 40 cps, hydrogen content 1.5 wt%, purchased from Dongyue Silicon Materials) was 8 parts, the content of the composite phase change material was 120 parts, and the content of inhibitor (ethynylcyclohexanol, Shanghai Bozhijie New Materials Co., Ltd.) was 0.005 parts.

[0078] The specific preparation process of the two-component silicone thermal conductive potting material A / B is as follows:

[0079] Preparation of Component A: 1. Weigh vinyl silicone oil and catalyst according to the ratio, and mix them evenly with a high-speed mixing and dispersing machine to obtain silicone-based rubber a1; 2. Add the corresponding weight of the composite phase change material to silicone-based rubber a1, and mix them evenly with a high-speed mixing and dispersing machine to obtain silicone thermal conductive phase change potting glue A;

[0080] Preparation of Component B: 1. Weigh vinyl silicone oil, hydrogen-containing silicone oil, and inhibitor according to the ratio, and mix them evenly with a high-speed mixing and dispersing machine to obtain silicone-based rubber b1; 2. Add the corresponding weight of the composite phase change material to silicone-based rubber b1, and mix them evenly with a high-speed mixing and dispersing machine to obtain silicone thermal conductive phase change potting glue B.

[0081] The silicone thermal conductive phase change potting glues A and B are fully mixed evenly according to a mass ratio of 1:1, and then cured at 60 °C for 20 min.

[0082] Perform relevant performance tests on the two-component silicone thermal conductive potting material prepared based on the composite phase change materials prepared in the above Examples 1-5 and Comparative Examples 1-6. The test results are shown in Tables 2-3. Among them, the viscosity test standard is GB / T 10247-2008.

[0083] Table 2

[0084]

[0085]

[0086] Table 3

[0087]

[0088] In summary, in the embodiment of the present application, a composite phase change material with a multi-layer structure is obtained by using a phase change microcapsule as the inner layer and sequentially coating carbon nanotubes and silica on the surface of the phase change microcapsule. The composite phase change material can take into account high thermal conductivity and high enthalpy value, and does not need to be used in combination with a thermal conductive powder. At the same time, the disadvantage of flammability when a conventional organic phase change material is used alone is improved. In addition, the potting material prepared from the composite phase change material can take into account excellent properties such as high enthalpy value, high thermal conductivity, high fluidity, insulation, and flame retardancy. Moreover, the composite phase change material has good compatibility with the silicone matrix, does not cause phase separation, and can prevent sedimentation. The surface of the composite phase change material contains vinyl groups, which can participate in the silicone addition reaction during curing. After curing, the phase change material and the silicone matrix form a quasi-3D network structure, and the composite thermal conductive phase change filler is more tightly combined with the silicone matrix.

[0089] The above are only the preferred embodiments of the present application and are not intended to limit the present application. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A composite phase change material, characterized in that, The composite phase change material has a phase change microcapsule as the inner layer, and carbon nanotubes and silica are sequentially coated on the surface layer of the phase change microcapsule, and it is obtained by modification with a vinyl silane coupling agent; wherein, the phase change microcapsule has an organic phase change material as the core and silica or polyethylene glycol as the shell layer; The organic phase change material is one or two of paraffin and fatty acid; The method for coating carbon nanotubes on the surface layer of the phase change microcapsule is as follows: The phase change microcapsule and carbon nanotubes with carboxyl or hydroxyl groups on the surface are mixed evenly in a high-speed disperser, and then sprayed with a coupling agent for modification treatment to obtain the product.

2. The composite phase change material according to claim 1, characterized in that The inner diameter of the carbon nanotubes is 2-10 nm, the outer diameter is 15-30 nm, and the length is 1-30 μm.

3. The preparation method of the composite phase change material according to claim 1, characterized in that The structural formula of the vinyl silane coupling agent is CH2=CH(CH2) n SiX3; where n is 0 or 1, and X is one or more of methoxy, ethoxy, methoxyethoxy, and acetoxy.

4. A method for preparing the composite phase change material according to claim 1, characterized in that, It includes: The phase change microcapsule and carbon nanotubes are stirred and mixed and then modified with a coupling agent to obtain a modified phase change material; The phase change microcapsule / carbon nanotube composite phase change material is coated with silica on the outer layer by the sol-gel method and modified with a vinyl silane coupling agent to obtain a composite phase change material.

5. The preparation method of the composite phase change material according to claim 4, characterized in that, The weight ratio of the phase change microcapsule to the carbon nanotubes is 20:1 to 1:

1.

6. The preparation method of the composite phase change material according to claim 4, characterized in that, The step of coating the phase change microcapsule / carbon nanotube composite phase change material with silica on the outer layer by the sol-gel method and modifying it with a vinyl silane coupling agent to obtain a composite phase change material is specifically as follows: The pH value of the mixed solution of deionized water and ethanol is adjusted to 2-5, and then the modified phase change material is added for stirring and mixing to obtain a first mixture; Under the condition of a temperature of 50-70 °C, a silicon source is added to the first mixture and stirred and mixed to obtain a second mixture; A vinyl silane coupling agent is added to the second mixture, and after stirring and mixing, centrifuging and drying, a composite phase change material is obtained.

7. A potting material, characterized in that, The phase change potting adhesive includes the composite phase change material described in any one of claims 1-3 or the composite phase change material prepared by the preparation method of the composite phase change material described in any one of claims 4-6.

8. The potting material according to claim 7, characterized in that, The potting material includes component A and component B; wherein, component A is composed of vinyl silicone oil, platinum catalyst and the composite phase change material; component B is composed of vinyl silicone oil, hydrogen-containing silicone oil, ethynylcyclohexanol and the composite phase change material.

9. An electronic device, characterized in that, The electronic device includes the potting material described in claim 7 or 8.

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