A phase change heat pipe composite material and a preparation method thereof

Abstract

The application relates to the field of phase change materials, and discloses a phase change heat pipe composite material and a preparation method thereof. The phase change heat pipe composite material is composed of a phase change composite material and a heat pipe, and the phase change composite material is prepared from the following raw materials in parts by weight: a capsule core solution: 2-10 parts of polyethylene glycol; 5-60 parts of white carbon black, 30-90 parts of ethanol; a capsule wall solution: 0.5-2 parts of hydroxyethyl cellulose, 0.1-0.4 parts of polyvinyl alcohol, 2-4 parts of a silane coupling agent, 0.05-0.2 parts of 5-15 wt% sodium hydroxide aqueous solution, and 40-60 parts of water; and the preparation method comprises the following steps: drying the capsule core solution to obtain a capsule core, coating the capsule core with the capsule wall solution and drying to obtain the phase change composite material, and packaging the phase change composite material in the heat pipe to obtain the phase change heat pipe composite material. The preparation process is simple, the prepared phase change heat pipe composite material is not prone to leakage and volatilization, and the phase change heat pipe composite material has the effects of stable energy storage and good heat dissipation.

Description

Technical Field

[0001] This application relates to the field of phase change materials, and more specifically, to a phase change heat pipe composite material and a method for preparing the same. Background Technology

[0002] Phase change heat pipe composite material is a material that can store and release a large amount of heat energy in a small space. It is composed of phase change material and heat pipe composite and can be widely used in solar energy storage, battery thermal management, heat dissipation of electronic components, etc.

[0003] Traditional phase change materials (PCMs) are categorized into solid-liquid, solid-solid, solid-gas, and liquid-gas PCMs. Solid-gas and liquid-gas PCMs involve a large amount of gas during the phase change, resulting in significant volume changes and low stability, thus limiting their use. Solid-liquid PCMs exhibit substantial latent heat during phase change, but liquefaction can lead to leakage or evaporation, reducing performance. Solid-solid PCMs, however, maintain their physical state during the phase change, primarily due to altered crystal structure that allows for the absorption or release of heat. They offer longer lifespans, are less prone to leakage, and exhibit greater stability, making them a hot research topic in PCM research.

[0004] Currently used solid-solid phase change materials (SPCs) typically involve fixing or adsorbing a solid-liquid SPC onto a polymer matrix or a porous matrix. However, during repeated phase transitions, the solid-liquid SPC tends to desorb from the matrix, leading to leaks in the resulting heat pipe composite and reducing its performance. To address this issue, some methods involve grafting the solid-liquid SPC onto the matrix to improve the bonding stability. However, this grafting method results in a relatively low enthalpy of phase change, leading to lower energy storage and heat dissipation efficiency in heat pipe composites made from such materials. Summary of the Invention

[0005] To address the issues of easy leakage and low energy storage and heat dissipation efficiency of conventional phase change heat pipe composite materials, this application provides a phase change heat pipe composite material and its preparation method.

[0006] In a first aspect, this application provides a phase change heat pipe composite material, which adopts the following technical solution: A phase change heat pipe composite material is provided, comprising a phase change composite material and a heat pipe. The phase change composite material is prepared by wrapping a core with a bladder wall. The core is prepared by drying a core solution, and the bladder wall is prepared by drying a bladder wall solution. The core solution and the bladder wall solution are composed of the following raw materials in parts by weight: Core solution: 2-10 parts polyethylene glycol 5-60 parts of silica 30-90 parts ethanol; Capsule wall solution: 0.5-2 parts hydroxyethyl cellulose Polyvinyl alcohol 0.1-0.4 parts 2-4 parts of silane coupling agent 0.05-0.2 parts of 5-15 wt% sodium hydroxide aqueous solution 40-60 parts water.

[0007] By adopting the above technical solution, the obtained phase change composite material is encapsulated in a heat pipe. The obtained phase change heat pipe composite material is not prone to leakage and volatilization, has good stability, and has good energy storage and heat dissipation functions.

[0008] The phase change composite material obtained in this application is a microcapsule structure in which the capsule wall encapsulates the capsule core. The capsule core solution consists of polyethylene glycol, fumed silica, and ethanol. Ethanol is used as a solvent to uniformly dissolve the polyethylene glycol, allowing it to be uniformly dispersed and adsorbed into the fumed silica. Polyethylene glycol is a solid-liquid phase change material with good energy storage performance and a wide range of selectable phase change temperatures. Fumed silica is a porous adsorbent material with a high specific surface area and good thermal conductivity. Fumed silica is used as a carrier... Polyethylene glycol (PEG) is used as a phase change material. After drying to remove ethanol, PEG is uniformly loaded onto silica to form the core of the phase change composite material. It has good energy storage and heat dissipation performance. When the phase change point is reached, PEG liquefies in the voids of silica. The movement of PEG molecular chains is less disturbed, and they can easily arrange themselves in a regular manner in the voids of silica to crystallize. The core of the resulting phase change composite material has a high phase change enthalpy. The phase change heat pipe composite material made in this way has good energy storage and heat dissipation effects.

[0009] However, during multiple phase transitions, polyethylene glycol still easily desorbs from silica, leading to leakage problems in the resulting phase change heat pipe composite material and reducing its stability. Therefore, this application further uses a shell wall solution to encapsulate the core. The shell wall solution consists of hydroxyethyl cellulose, polyvinyl alcohol, a silane coupling agent, a 5-15 wt% sodium hydroxide aqueous solution, and water. Hydroxyethyl cellulose is a cellulose containing hydroxyl groups, exhibiting good film-forming properties and mechanical properties. Polyvinyl alcohol is a stable polymeric film-forming agent. Under the combined action of hydroxyethyl cellulose and polyvinyl alcohol, it reacts with the silane coupling agent hydrolyzed in an alkaline solution, resulting in a shell wall solution. The liquid coats the core, and after drying, it forms the core wall, which stably and uniformly adheres to the outside of the core. The core wall has good hydrophobic and oleophilic properties. When the core is at the phase change point, polyethylene glycol liquefies. Under the adsorption of silica and the coating effect of the core wall, the resulting phase change composite material stably undergoes a solid-solid phase change. The phase change heat pipe composite material prepared in this way will not leak or volatilize. Because the core wall has good hydrophobic and oleophilic properties, it will not interfere with the molecular chain movement of polyethylene glycol. The polyethylene glycol can still stably and regularly arrange and crystallize. The phase change heat pipe composite material prepared in this way has good anti-leakage and anti-volatilization properties, as well as good energy storage and heat dissipation functions.

[0010] Preferably, the ratio of the core solution to the wall solution is 1:(0.15-0.25).

[0011] By adopting the above technical solution, the optimal ratio of core solution and wall solution can enable the dried core to be uniformly and stably coated by the dried core. When the amount of wall solution is large, the resulting phase change composite material is prone to agglomeration. When the amount of wall solution is small, the resulting wall is thin and cannot effectively encapsulate the core.

[0012] Preferably, the phase change composite material is prepared by the following steps: A1. Weigh ethanol into the reaction equipment according to the weight, add polyethylene glycol to ethanol and stir to dissolve, then add fumed silica and stir to disperse to obtain the core solution. A2. The obtained core solution is subjected to vacuum treatment to remove ethanol, and the core is obtained. A3. Weigh water by weight and add it to the reaction equipment. Heat the mixture to 80-100℃, add hydroxyethyl cellulose and polyvinyl alcohol and stir to dissolve. After dissolving, add silane coupling agent and 5-15wt% sodium hydroxide aqueous solution. Adjust the pH of the system to 8.5-9.5 and react to obtain the capsule wall solution. A4. Add the capsule wall solution dropwise into the capsule core prepared in step A2. After the addition is complete, stir and dry to obtain the phase change composite material.

[0013] By adopting the above technical solution, polyethylene glycol is first dissolved and dispersed using ethanol, and then silica is added to adsorb the polyethylene glycol-ethanol solution, resulting in a uniformly adsorbed and dispersed core solution. The core solution is then vacuum-evacuated to remove ethanol, forming the core. Ethanol must be completely removed by vacuum evacuation; the core must not contain ethanol. Next, water is heated to dissolve hydroxyethyl cellulose and polyvinyl alcohol. Then, 5-15 wt% sodium hydroxide aqueous solution and a silane coupling agent are added, allowing the silane coupling agent to hydrolyze under a favorable alkaline system. The hydrolyzed silane coupling agent reacts with hydroxyethyl cellulose and polyvinyl alcohol to form a hydrophobic and oleophilic shell wall. This shell wall stably encapsulates the core, resulting in a phase change composite material with a high phase change enthalpy. The phase change heat pipe composite material prepared in this way is less prone to leakage and has good energy storage and heat dissipation properties.

[0014] Preferably, the stirring temperature in step A1 is 60-65℃, and the stirring time is 20-40 min; the vacuuming time in step A2 is 3-5 h, the vacuuming temperature is 50-55℃, and the vacuum degree is -0.08--0.1 MPa; the reaction time in step A3 is 2-4 h; and the stirring rate in step A4 is 600-1000 rpm, the drying temperature is 45-55℃, and the drying time is 8-12 h.

[0015] By adopting the above technical solution, the optimal stirring temperature and stirring time in step A1 enable polyethylene glycol to completely dissolve in ethanol; the optimal vacuum conditions in step A2 enable ethanol to be stably evaporated and removed without affecting the stability of the core; the optimal stirring rate in step A3 enables the core wall solution to stably coat the core, preventing the core from agglomerating; and the optimal drying temperature and drying time enable the core wall solution to dry stably, forming a core wall that stably encapsulates the core without affecting it. The resulting phase change composite material exhibits good stability.

[0016] Preferably, the ratio of polyethylene glycol to silica is 1:(1.5-4).

[0017] By adopting the above technical solution, the core prepared by the optimal ratio of polyethylene glycol and silica is a uniform powder, forming a stable core structure with good energy storage effect and thermal conductivity. When the content of polyethylene glycol is high, the core is gel-like, and silica cannot stably adsorb polyethylene glycol, thus failing to form a stable core. Furthermore, the amount of polyethylene glycol cannot exceed the amount of silica. When the content of polyethylene glycol is low, the energy storage effect of the core is low. Therefore, it is necessary to carefully control the amount of polyethylene glycol and silica to ensure that the prepared phase change heat pipe composite material has good energy storage and heat dissipation effects.

[0018] Preferably, the ratio of the hydroxyethyl cellulose to the polyvinyl alcohol is (1.8-2):(0.2-0.3).

[0019] By adopting the above technical solution, the capsule wall formed by the optimal ratio of hydroxyethyl cellulose and polyvinyl alcohol has good encapsulation stability, the phase change composite material obtained in this way has a more stable phase change enthalpy, and the phase change heat pipe composite material obtained is not easy to leak.

[0020] Preferably, the silane coupling agent is composed of γ-glycidyl ether propyltrimethoxysilane and dodecyltrimethoxysilane in a ratio of 1:(0.3-0.4).

[0021] By adopting the above technical solution, γ-glycidyl etherpropyltrimethoxysilane is a short-chain silane coupling agent with epoxy groups and siloxane bonds, and dodecyltrimethoxysilane is a long-chain silane coupling agent with siloxane bonds. The short-chain silane coupling agent and the long-chain silane coupling agent are compounded in a better ratio to graft and modify hydroxyethyl cellulose and polyvinyl alcohol, forming a capsule wall with a three-dimensional network structure that is hydrophobic and oleophilic. This results in good encapsulation stability of the capsule core, without affecting the phase change stability of polyethylene glycol or reducing the phase change enthalpy of the obtained phase change composite material.

[0022] Preferably, the polyethylene glycol is one or more of polyethylene glycol 4000, polyethylene glycol 6000, and polyethylene glycol 8000.

[0023] By adopting the above technical solution, the polyethylene glycol has good crystallinity, is easy to form the core of the solid-solid phase change system, has good bonding stability with fumed silica, and the obtained phase change composite material has a high phase change enthalpy.

[0024] Secondly, this application provides a method for preparing a phase change heat pipe composite material, which adopts the following technical solution: A method for preparing a phase change heat pipe composite material includes the following preparation steps: adding the phase change composite material into a heat pipe, and then sealing the heat pipe to obtain the phase change heat pipe composite material.

[0025] By adopting the above technical solution, a phase change heat pipe composite material that is not easy to leak or volatilize is obtained, which has good energy storage and heat dissipation effects.

[0026] Preferably, the phase change composite material is filled in the heat pipe at a ratio of 50-80% of the heat pipe volume.

[0027] By adopting the above technical solution, a phase change heat pipe composite material with high energy storage and thermal conductivity was obtained.

[0028] In summary, this application has the following beneficial effects: 1. This application discloses a phase change heat pipe composite material, which is prepared by encapsulating a phase change composite material in a heat pipe. The phase change composite material is a microcapsule structure in which the capsule wall covers the capsule core. In this microcapsule, silica is used as the adsorbent carrier and polyethylene glycol is used as the solid-liquid phase change material. Silica is used to adsorb and support polyethylene glycol, thus obtaining a solid-solid phase change material with good energy storage and heat dissipation. This solid-solid phase change material is used as the capsule core, and hydroxyethyl cellulose, polyvinyl alcohol, and silane coupling agent are reacted under optimal conditions. After drying, a hydrophobic and oleophilic capsule wall is formed to cover the capsule core. The capsule wall does not interfere with the crystallization of the capsule core. The phase change composite material prepared in this way has good anti-leakage and anti-volatilization properties, while also having a large phase change enthalpy, thus exhibiting good energy storage and heat dissipation properties.

[0029] 2. By using a better ratio of silica and polyethylene glycol, polyethylene glycol is stably adsorbed into the pores of silica to form a stable powdery core, which has good energy storage and heat dissipation performance, and can reduce polyethylene glycol leakage.

[0030] 3. By using a combination of short-chain and long-chain silane coupling agents in a better ratio, hydroxyethyl cellulose and polyvinyl alcohol are grafted and modified to form a capsule wall with a three-dimensional network structure that is hydrophobic and oleophilic. This provides good encapsulation stability of the capsule core without affecting the phase change stability of polyethylene glycol or reducing the phase change enthalpy of the obtained phase change composite material. As a result, the phase change heat pipe composite material prepared in this way has good stability.

[0031] 4. The preparation method of this application stably encapsulates the phase change heat pipe composite material in a heat pipe to obtain a phase change heat pipe composite material with high energy storage and thermal conductivity. Detailed Implementation

[0032] The present application will be further described in detail below with reference to the embodiments.

[0033] The following are the specifications and parameters of some of the raw materials used in this application: 1. Silica: Fumed silica, particle size 50-150nm; 2. Ethanol: Anhydrous ethanol, 99.9% purity, industrial grade; 3. Hydroxyethyl cellulose: molecular weight 20,000-30,000, content 99%, density 0.75-1 g / cm³ 3 ; 4. Polyvinyl alcohol: Model PVA-217, 20.5-24.5 cps, pH value: 5-7. Preparation Example

[0034] Preparation Example 1 Preparation Example 1 discloses a phase change composite material, which is prepared by the following steps: A1. Weigh 30 kg of ethanol into the reaction vessel, add 2 kg of polyethylene glycol 4000 and stir to dissolve. The stirring temperature is 60℃. After stirring for 20 min, add 5 kg of silica and stir to disperse to obtain the core solution. A2. The obtained core solution was added to a vacuum drying jar for vacuum drying. The vacuuming time was 3 hours, the vacuuming temperature was 50℃, and the vacuum degree was -0.08MPa. The ethanol was removed to obtain the core. A3. Weigh 40 kg of water and add it to the reaction vessel. Heat the mixture to 80°C, add 0.5 kg of hydroxyethyl cellulose and 0.1 kg of polyvinyl alcohol and stir to dissolve. After dissolving, add a silane coupling agent composed of 1 kg of γ-glycidyl ether propyltrimethoxysilane and 1 kg of dodecyltrimethoxysilane, and add 0.05 kg of 5 wt% sodium hydroxide aqueous solution. Adjust the pH of the system to 8.5. After reacting for 2 hours, the capsule wall solution is obtained. A4. Add the capsule wall solution dropwise into the capsule core prepared in step A2. After the addition is complete, stir and dry the capsule. The stirring speed is 600 rpm, the drying temperature is 45℃, and the drying time is 8 hours. After drying, the phase change composite material is obtained. The ratio of the volume of the core solution to the volume of the wall solution is 1:0.1.

[0035] Preparation Examples 2-3 Preparation Examples 2-3 disclose a phase change composite material, which differs from Preparation Example 1 in that the amount of raw materials and the preparation conditions are different, as detailed in Table 1 below.

[0036] Table 1. Raw material amounts and preparation conditions for preparation examples 1-3

[0037] Preparation Example 4 Preparation Example 4 discloses a phase change composite material. The difference between Preparation Example 1 and Preparation Example 4 is that the ratio of the core solution to the wall solution is different. In Preparation Example 4, the ratio of the core solution to the wall solution is 1:0.15.

[0038] Preparation Example 5 Preparation Example 5 discloses a phase change composite material, which differs from Preparation Example 1 in that the ratio of the core solution to the wall solution is different. In Preparation Example 4, the ratio of the core solution to the wall solution is 1:0.25.

[0039] Preparation Example 6 Preparation Example 6 discloses a phase change composite material. The difference between Preparation Example 4 and Preparation Example 6 is that the amounts of polyethylene glycol and silica are the same. In Preparation Example 6, the amount of polyethylene glycol is 4 kg and the amount of silica is 6 kg.

[0040] Preparation Example 7 Preparation Example 7 discloses a phase change composite material, which differs from Preparation Example 4 in that the amount of polyethylene glycol used is 2 kg and the amount of silica used is 8 kg.

[0041] Preparation Example 8 Preparation Example 8 discloses a phase change composite material, which differs from Preparation Example 6 in that the amount of γ-glycidyl ether propyltrimethoxysilane is 1.54 kg and the amount of dodecyltrimethoxysilane is 0.46 kg.

[0042] Preparation Example 9 Preparation Example 9 discloses a phase change composite material, which differs from Preparation Example 6 in that the amount of γ-glycidyl ether propyltrimethoxysilane is 1.43 kg and the amount of dodecyltrimethoxysilane is 0.57 kg.

[0043] Preparation Example 10 Preparation Example 10 discloses a phase change composite material, which differs from Preparation Example 8 in that the amount of hydroxyethyl cellulose used is 0.5 kg and the amount of polyvinyl alcohol used is 0.05 kg.

[0044] Preparation Example 11 Preparation Example 11 discloses a phase change composite material, which differs from Preparation Example 8 in that the amount of hydroxyethyl cellulose used is 0.6 kg and the amount of polyvinyl alcohol used is 0.1 kg.

[0045] Preparation of Comparative Example 1 Comparative Example 1 discloses a phase change composite material, which differs from Preparation Example 1 in that dodecyltrimethoxysilane is replaced in equal amounts with γ-glycidyl etherpropyltrimethoxysilane.

[0046] Preparation of Comparative Example 2 Comparative Example 2 discloses a phase change composite material, which differs from Preparation Example 1 in that polyvinyl alcohol is replaced with an equal amount of hydroxyethyl cellulose.

[0047] Preparation of Comparative Example 3 Comparative Example 3 discloses a phase change composite material, which differs from Preparation Example 1 in that the silane coupling agent is replaced with an equal amount of water. Example Example 1

[0048] Example 1 discloses a phase change heat pipe composite material, which is prepared by the following steps: adding the phase change composite material into a heat pipe, wherein the volume ratio of the phase change composite material in the heat pipe is 50% of the heat pipe volume, the heat pipe is a copper pipe, and then sealing the heat pipe by heat sealing, thereby obtaining the phase change heat pipe composite material.

[0049] Example 2-3 Examples 2-3 disclose a phase change heat pipe composite material, which differs from Example 1 in that the preparation conditions and the source of the phase change composite material are different, as detailed in Table 2 below.

[0050] Table 2. Preparation conditions and sources of phase change composite materials for Examples 1-3.

[0051] Example 4-11 Examples 4-11 disclose a phase change heat pipe composite material, which differs from Example 1 in that the source of the phase change composite material is different, as detailed in Table 3 below.

[0052] Table 3 Sources of the phase change composite materials in Examples 4-11 Comparative Example

[0053] Comparative Examples 1-3 Comparative Examples 1-3 disclose a phase change heat pipe composite material, which differs from Example 1 in that the source of the phase change composite material is different, as detailed in Table 4 below.

[0054] Table 4 Source table of phase change composite materials in Comparative Examples 1-3 Performance testing

[0055] The performance of the phase change heat pipe composite materials prepared in Examples 1-11 and Comparative Examples 1-3 was tested as follows: (1) Phase transition enthalpy test The enthalpy of fusion (ΔHm, unit: J / g) of the prepared phase change heat pipe composite material was tested using a DCS tester, and the test results were detected and recorded. (2) Leakage test The prepared phase change heat pipe composite material was repeatedly heated to melt and then cooled to crystallize. This process was repeated 50 times. On the 50th test, the enthalpy of fusion (ΔHm, unit: J / g) of the phase change heat pipe composite material was tested, and any leakage was observed. The test results were detected and recorded. The following are the performance test data of the phase change heat pipe composite materials of Examples 1-11 and Comparative Examples 1-3, as detailed in Table 5 below.

[0056] Table 5 Performance data of phase change heat pipe composite materials in Examples 1-11 and Comparative Examples 1-3

[0057] As can be seen from Examples 1-5 and Table 5, the phase change composite material prepared by using a better ratio of core solution and wall solution has a better phase change enthalpy, and the prepared phase change heat pipe composite material has a better melting enthalpy and a better energy storage effect.

[0058] As can be seen from Examples 4-5 and 6-7 and Table 5, the phase change enthalpy of the phase change composite material prepared by using a better ratio of polyethylene glycol and silica is significantly increased, from 76.4 J / g to 100 J / g. At the same time, due to the addition of a better ratio of silica, the prepared phase change heat pipe composite material also has a better heat dissipation effect.

[0059] Combining Examples 6-7 and 8-9, Comparative Examples 1 and 3, and Table 5, it can be seen that using a better ratio of γ-glycidyl ether propyltrimethoxysilane and dodecyltrimethoxysilane as silane coupling agents to modify hydroxyethyl cellulose and polyvinyl alcohol results in a capsule wall with good encapsulation stability for the capsule core. The resulting phase change heat pipe composite material exhibits high phase change enthalpy and energy storage performance. In contrast, Comparative Example 3, without the addition of silane coupling agents, shows a significant decrease in the phase change enthalpy of the resulting phase change heat pipe composite material. This is because the hydrophilic capsule wall affects the crystallization properties of the capsule core, thereby reducing the energy storage effect of the phase change heat pipe composite material. Furthermore, after 50 tests, the phase change enthalpy also decreased significantly, from 61.5 J / g to 50.8 J / g, indicating that leakage occurred in the phase change heat pipe composite material, leading to the decrease in its phase change enthalpy.

[0060] Combined with Examples 8-9 and 10-11, Comparative Example 2, and Table 5, it can be seen that the capsule wall prepared by using a better ratio of hydroxyethyl cellulose and polyvinyl alcohol under the modification of silane coupling agent has a better coating effect on the capsule core. The phase change heat pipe composite material prepared in this way has a better energy storage effect and is not easy to leak.

[0061] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A phase change heat pipe composite material, characterized in that, The device is composed of a phase change composite material and a heat pipe. The phase change composite material is made by wrapping a core with a bladder wall. The core is prepared by drying a core solution, and the bladder wall is prepared by drying a bladder wall solution. The core solution and the bladder wall solution are composed of the following raw materials in parts by weight: Core solution: 2-10 parts of polyethylene glycol 5-60 parts of silica 30-90 parts ethanol; Capsule wall solution: Hydroxyethyl cellulose 0.5-2 parts Polyvinyl alcohol 0.1-0.4 parts 2-4 parts of silane coupling agent 0.05-0.2 parts of 5-15 wt% sodium hydroxide aqueous solution 40-60 parts water.

2. The phase change heat pipe composite material according to claim 1, characterized in that, The ratio of the volume of the core solution to the volume of the wall solution is 1:(0.15-0.25).

3. A phase change heat pipe composite material according to claim 1 or 2, characterized in that, The phase change composite material is prepared by the following steps: A1. Weigh ethanol into the reaction equipment according to the weight, add polyethylene glycol to ethanol and stir to dissolve, then add fumed silica and stir to disperse to obtain the core solution. A2. The obtained core solution is subjected to vacuum treatment to remove ethanol, and the core is obtained. A3. Weigh water by weight and add it to the reaction equipment. Heat the mixture to 80-100℃, add hydroxyethyl cellulose and polyvinyl alcohol and stir to dissolve. After dissolving, add silane coupling agent and 5-15wt% sodium hydroxide aqueous solution. Adjust the pH of the system to 8.5-9.5 and react to obtain the capsule wall solution. A4. Add the capsule wall solution dropwise into the capsule core prepared in step A2. After the addition is complete, stir and dry to obtain the phase change composite material.

4. The phase change heat pipe composite material according to claim 3, characterized in that, The stirring temperature in step A1 is 60-65℃, and the stirring time is 20-40 min; the vacuuming time in step A2 is 3-5 h, the vacuuming temperature is 50-55℃, and the vacuum degree is -0.08-0.1 MPa; the reaction time in step A3 is 2-4 h; the stirring rate in step A4 is 600-1000 rpm, the drying temperature is 45-55℃, and the drying time is 8-12 h.

5. The phase change heat pipe composite material according to claim 1, characterized in that, The ratio of polyethylene glycol to silica is 1:(1.5-4).

6. The phase change heat pipe composite material according to claim 1, characterized in that, The ratio of the amount of hydroxyethyl cellulose to the amount of polyvinyl alcohol is (1.8-2):(0.2-0.3).

7. The phase change heat pipe composite material according to claim 1, characterized in that, The silane coupling agent is composed of γ-glycidyl ether propyltrimethoxysilane and dodecyltrimethoxysilane in a ratio of 1:(0.3-0.4).

8. The phase change heat pipe composite material according to claim 1, characterized in that, The polyethylene glycol is one or more of polyethylene glycol 4000, polyethylene glycol 6000 and polyethylene glycol 8000.

9. A method for preparing a phase change heat pipe composite material as described in any one of claims 1-8, characterized in that, The preparation steps include: adding the phase change composite material into the heat pipe, and then sealing the heat pipe to obtain the phase change heat pipe composite material.

10. The method for preparing a phase change heat pipe composite material according to claim 9, characterized in that, The phase change composite material is filled into the heat pipe at a rate of 50-80% of the heat pipe volume.

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