Multifunctional composite phase change material, preparation method and application thereof

Abstract

The application discloses a multifunctional composite phase change material and a preparation method and application thereof, and the preparation raw materials comprise myristic acid, palmitic acid, paraffin and porous foam materials. The multifunctional composite phase change material is prepared by mixing the myristic acid, the palmitic acid and the paraffin, the shortcomings of high phase change temperature of the myristic acid and the palmitic acid are improved, the application in actual light-heat conversion is more adaptive, the light-heat conversion capacity can be effectively improved, the solar heat utilization efficiency is improved, and the overall thermal effect can be obviously improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of phase change materials, in particular to a multifunctional composite phase change material and its preparation method and application. BACKGROUND

[0002] With the continuous growth of energy demand and the diversification of energy structure, the research and application of high-efficiency energy conversion and storage materials have become the key to solving energy crisis and improving energy utilization efficiency. As a material that can absorb or release a large amount of latent heat through phase change, phase change material (PCM) shows great application potential in thermal energy storage, solar energy utilization, waste heat recovery, power peak shaving and electronic device thermal management. However, traditional phase change materials face a series of challenges in energy conversion process, which limits their application potential in various energy systems.

[0003] At present, many phase change materials have low phase change enthalpy, so they can only convert limited energy during energy absorption and release, thereby reducing the overall efficiency of energy conversion; at the same time, the mismatch between thermal conductivity and energy transfer, especially the poor thermal conductivity of organic phase change materials, leads to low heat transfer efficiency in energy conversion process, prolonging the energy conversion period; in addition, some phase change materials have single energy conversion form, which is only suitable for specific scenarios and cannot realize effective conversion of multiple energy forms, limiting the universality of application; finally, the research and production of high-performance phase change materials are costly, increasing the application cost of energy conversion system and reducing the economy of the whole system.

[0004] Therefore, how to develop a high-enthalpy, high-load-rate, high-thermal-conductivity and low-cost composite phase change material that can efficiently realize the conversion between multiple energy forms is a technical problem that needs to be solved by those skilled in the art. SUMMARY

[0005] The present application aims to at least solve one of the technical problems existing in the prior art. To this end, the present application proposes a multifunctional composite phase change material, which improves the high phase change temperature of myristic acid and palmitic acid by mixing myristic acid, palmitic acid and paraffin, making it more adaptable in actual photothermal conversion applications, effectively improving photothermal conversion capacity and solar thermal utilization efficiency, and significantly improving overall thermal effect.

[0006] According to a first aspect of the present application, a multifunctional composite phase change material is proposed, the preparation raw materials of which include myristic acid, palmitic acid, paraffin and porous foam material.

[0007] The application improves the shortcomings of high phase change temperature of myristic acid and palmitic acid by mixing myristic acid, palmitic acid and paraffin, synergizes with porous foam material, and further enhances the heat conduction performance, on the one hand, makes the multifunctional composite phase change material have shape stability, on the other hand, the porous foam material enhances the light wave absorption capacity of the multifunctional composite phase change material, and the application of actual light-heat conversion is more adaptive, can effectively improve the light-heat conversion capacity, improve the solar heat utilization efficiency, can significantly improve the overall thermal effect, and has great application prospect.

[0008] In some embodiments of the application, the porous foam material comprises at least one of graphite felt, polyurethane foam and carbon nanotube foam.

[0009] According to a second aspect of the application, a preparation method of a composite phase change material is provided, comprising the following steps:

[0010] S1. Mixing and heating the myristic acid and the palmitic acid to melt to obtain a myristic acid / palmitic acid binary eutectic mixture;

[0011] S2. Mixing and heating the myristic acid / palmitic acid binary eutectic mixture and the paraffin to melt to obtain a myristic acid / palmitic acid / paraffin ternary eutectic mixture;

[0012] S3. Immersing the myristic acid / palmitic acid / paraffin ternary eutectic mixture into a porous foam material after heating and melting, and removing impurities to obtain the multifunctional composite phase change material.

[0013] In some embodiments of the application, the following steps are included:

[0014] S1. Heating and melting the myristic acid and the palmitic acid, stirring and ultrasonic oscillation, and cooling to obtain a myristic acid / palmitic acid binary eutectic mixture;

[0015] S2. Heating and melting the myristic acid / palmitic acid binary eutectic mixture and the paraffin, stirring and ultrasonic oscillation, and cooling to obtain a myristic acid / palmitic acid / paraffin ternary eutectic mixture;

[0016] S3.1. Adding an additive to the myristic acid / palmitic acid / paraffin ternary eutectic mixture after heating and melting, stirring and ultrasonic oscillation, and cooling to obtain a composite phase change material;

[0017] S3.2. Heating and melting the optimized composite phase change material, immersing into a porous foam material, cooling and drying, removing excess phase change material, and obtaining the multifunctional composite phase change material.

[0018] In some embodiments of the application, the porous foam material is further modified.

[0019] In some embodiments of the present application, the porous foam material modification step comprises:

[0020] After soaking the graphite felt in the mixed solution of sodium citrate and urea for 30-60 min, the impregnated graphite felt is taken out and placed in an oven with a temperature setting of 50-60℃, dried for 2-4 h, heat cured, heat treated, and then cooled.

[0021] In some embodiments of the present application, the heat curing temperature is 100-120℃.

[0022] In some embodiments of the present application, the heat treatment temperature is 200-250℃.

[0023] In some embodiments of the present application, the mass ratio of sodium citrate, urea, and graphite felt is 2-5:5-10:100.

[0024] Through sodium citrate and urea modification, sodium citrate provides a hydration environment that enhances the effect of gas release during the decomposition of urea, thereby forming a more uniform and stable pore structure. The pore structure of the graphite felt is more suitable for the penetration and distribution of phase change materials, which will help to increase the interfacial contact area between the two and improve the heat transfer efficiency. In particular, phase change materials are usually liquid-solid phase changes, so the phase change material may need to be evenly distributed in the pores of the graphite felt, and the modified graphite felt has higher thermal conductivity, which can more efficiently transfer the Joule heat generated by the current through the material to the phase change material, thereby improving the electro-thermal conversion efficiency. For composite phase change materials, good thermal conductivity ensures that heat can be quickly and evenly distributed, avoiding heat accumulation and temperature unevenness.

[0025] The melting point of the myristic acid / palmitic acid eutectic mixture is still high, and high-enthalpy paraffin is expensive. The use of a mixture of the two not only reduces the phase change temperature, but also effectively reduces the cost. At the same time, the crystallization performance of the myristic acid / palmitic acid / paraffin eutectic mixture is better than that of any single phase change material.

[0026] In some embodiments of the present application, the heating and melting temperature is 75-85℃, and the time is 20-40 min.

[0027] In some embodiments of the present application, the stirring rate is 150-200 r / min, the temperature is 75-85℃, and the time is 55-65 min.

[0028] In some embodiments of the present application, the ultrasonic oscillation power is 120-180 W, the oscillation frequency is 70-90 kHz, the temperature is 65-75℃, and the time is 55-65 min.

[0029] In some embodiments of the present application, the cooling is to room temperature.

[0030] In some embodiments of the present application, in step S1, the mass ratio of myristic acid and palmitic acid is (50-75):(50-25).

[0031] Although myristic acid and palmitic acid have many advantages, their phase transition temperature is high when they exist alone, which is not suitable for energy storage under some natural conditions, limiting their wide use in heat storage systems. However, the phase transition temperature can be effectively reduced when myristic acid and palmitic acid are mixed, and experiments have shown that the effect is most significant when the ratio of the amount of myristic acid and palmitic acid added is 65:35.

[0032] In some embodiments of the present application, in step S2, the mass ratio of the myristic acid / palmitic acid eutectic mixture and the paraffin is (20-70):(80-30).

[0033] In some embodiments of the present application, in step S3, the ternary eutectic mixture is further modified; and / or; the modification step includes adding a modifier to the ternary eutectic mixture; and / or, the modifier includes carbon nanotubes and a dispersing agent.

[0034] In some embodiments of the present application, the mass ratio of the carbon nanotubes and the dispersing agent is 2-5:1.

[0035] In some embodiments of the present application, the carbon nanotubes include multi-walled carbon nanotubes.

[0036] In some embodiments of the present application, the carbon nanotubes are multi-walled carbon nanotubes.

[0037] In some embodiments of the present application, the multi-walled carbon nanotubes have a diameter of 8-15 nm and a length of 8-14 μm.

[0038] In some embodiments of the present application, the dispersing agent includes polyvinylpyrrolidone.

[0039] The multi-walled carbon nanotubes in the present application have ultra-high thermal conductivity and are widely used to improve the thermal conductivity of organic phase change materials, and the effect is obvious. In the present application, carbon nanotubes and carbon nanotube dispersing agents are mixed uniformly according to a mass ratio of 5:1, which enables the carbon nanotubes to be uniformly mixed in the organic solution.

[0040] In some embodiments of the present application, in step S3.1, the mass ratio of the ternary eutectic mixture and the additive is 100:(0-0.4).

[0041] In some embodiments of the present application, in step S3.1, the heating melting temperature is 75-85 DEG C, and the time is 20-40 min.

[0042] In some embodiments of the present application, in step S3.1, the stirring speed is 150-170 r / min, the temperature is 65-75 DEG C, and the time is 55-65 min.

[0043] In some embodiments of the present application, in step S3.1, the ultrasonic oscillation power is 120-180 W, the oscillation frequency is 70-90 kHz, the temperature is 65-75 DEG C, and the time is 55-65 min.

[0044] In some embodiments of the present application, in step S3.2, the heating melting temperature is 75-85 DEG C, and the time is 20-40 min.

[0045] In some embodiments of the present application, in step S3.2, the impregnation is vacuum impregnation, the vacuum degree is -0.1 Mpa, and the time is 4-6 h.

[0046] In some embodiments of the present application, in step S3.2, the cooling is freezing room cooling to 10-15 DEG C.

[0047] According to a third aspect of the present application, the composite phase change material is applied in the field of thermal management or temperature control.

[0048] In some embodiments of the present application, the field of thermal management includes the field of photo-thermal conversion or electro-thermal conversion.

[0049] The present application improves the high phase change temperature of myristic acid and palmitic acid by mixing myristic acid, palmitic acid and paraffin, then adds carbon nanotubes to strengthen the thermal conductivity of the myristic acid / palmitic acid / paraffin eutectic mixture, and finally impregnates the optimized myristic acid / palmitic acid / paraffin eutectic mixture into graphite felt to further strengthen the thermal conductivity, on the one hand, the multifunctional composite phase change material has shape stability, on the other hand, the graphite felt and carbon nanotubes enhance the light wave absorption capacity of the multifunctional composite phase change material, which is more suitable for practical photo-thermal conversion applications, can effectively improve the photo-thermal conversion capacity, improve the solar thermal utilization efficiency, and significantly improve the overall thermal effect, and has great application prospect.

[0050] The conductivity of the myristic acid / palmitic acid / paraffin eutectic mixture is about 10-14 S / m, and it cannot convert electrical energy into heat energy. The conductivity of the multifunctional composite phase change material is 12 orders of magnitude higher than that of the former, and therefore, the contact resistance between the graphite felt, the carbon nanotube and the myristic acid / palmitic acid / paraffin eutectic mixture can generate Joule heat. Therefore, the addition of the carbon nanotube and the graphite felt can effectively improve the thermal conductivity of the multifunctional composite phase change material and the electrical heating response speed, so that the composite material can rapidly convert electrical energy into heat energy during the electrical heating conversion process, and the heat energy is uniformly distributed in the material, thereby significantly improving the electrical heating conversion efficiency.

[0051] In some embodiments of the present application, the thermal temperature control field includes CPU temperature control or human body temperature regulation.

[0052] The addition of the carbon nanotube and the graphite felt can improve the thermal conductivity of the phase change material, and the thermal response speed of the composite material is significantly improved, so that the composite material can rapidly adapt to the change of the CPU temperature, and can maintain stable heat dissipation performance and effectively reduce the working temperature of the CPU under high load, thereby prolonging the service life of the CPU and improving the stability of the system.

[0053] The addition of the carbon nanotube and the graphite felt can significantly improve the thermal conductivity and the thermal response speed of the phase change material, so that the headband can more quickly and accurately respond to the change of the head temperature, reduce the discomfort caused by overheating or overcooling of the head, and improve the wearing comfort of the sports headband, thereby helping the athletes to maintain concentration and optimal state. The addition of the graphite felt can improve the mechanical strength and stability of the composite material, so that the headband can maintain good temperature control performance after frequent use and cleaning, thereby prolonging the service life of the product.

[0054] The multifunctional composite phase change material provided by the present application can improve the utilization efficiency of solar energy of a solar water heater, and can maximize the heat energy conversion in the heat absorption and heat release process at a suitable phase change temperature. The performance of the multifunctional composite phase change material is optimized by adding a dispersing agent, and the multifunctional composite phase change material is not prone to leakage and has higher and more stable heat exchange efficiency compared with other materials. In addition, the preparation method is simple and convenient for popularization and use. BRIEF DESCRIPTION OF DRAWINGS

[0055] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed in the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0056] Figure 1 Sample pictures of the multifunctional composite phase change materials obtained in Example 1-2 and Comparative Example 1 are shown in the following figures.

[0057] Figure 2 SEM images of the multifunctional composite phase change material for graphite felt, example 1 and comparative example 1;

[0058] Figure 3 Electro-thermal conversion device and temperature change graph for the multifunctional composite phase change material;

[0059] Figure 4 Light-thermal device and temperature change graph for the multifunctional composite phase change material;

[0060] Figure 5 Temperature control graph of the multifunctional composite phase change material applied in sports headband on human body. DETAILED DESCRIPTION

[0061] The concept and technical effects of the present application will be described below in combination with examples to fully understand the purpose, features and effects of the present application. Obviously, the described examples are only part of the examples of the present application, but not all examples. Based on the examples of the present application, other examples obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0062] The raw materials and sources in the present application are as shown in Table 1:

[0063] Table 1. Raw material sources

[0064] Material name Purity / % Manufacturer Myristic acid ≥99 National Pharmaceutical Group Chemical Reagent Co., Ltd. Palmitic acid ≥99 National Pharmaceutical Group Chemical Reagent Co., Ltd. Paraffin wax ≥99 Dongguan Zhangmutou Donglin Plastic Co., Ltd. Graphite felt ≥99 Tianjin Carbon Factory Co., Ltd. Multi-walled carbon nanotubes (8-14 pm) ≥99 Shenzhen Suiheng Graphene Technology Co., Ltd. Carbon nanotube dispersant - Shenzhen Suiheng Graphene Technology Co., Ltd.

[0065] Note: The purity of the raw materials in the present application refers to the mass fraction.

[0066] Example 1

[0067] A multifunctional composite phase change material is prepared in this example, which is made of the following raw materials with mass fraction:

[0068] Myristic acid 19.5%, palmitic acid 10.5%, paraffin 70%; carbon nanotubes are 0.05% of the total of the first three, and carbon nanotube dispersant is 0.01%.

[0069] A preparation method of a multifunctional composite phase change material is as follows:

[0070] Analytically pure myristic acid, palmitic acid and paraffin are selected as phase change main materials, multi-walled carbon nanotubes (diameter 8-14 μm) and carbon nanotube dispersant are selected as additives, and graphite felt is selected as a porous skeleton;

[0071] S1. Weighed myristic acid and palmitic acid, then heated at 80℃ water bath conditions for 0.5h to completely melt, the melted myristic acid and palmitic acid were stirred at 80℃ with constant temperature magnetic stirrer at 170-200r / min for 1h, then placed in ultrasonic cleaner at 80℃ water bath environment with 120W power and 80kHz oscillation frequency for 1h ultrasonic oscillation, cooled at room temperature, prepared myristic acid / palmitic acid eutectic mixture;

[0072] S2. The obtained myristic acid / palmitic acid eutectic mixture was heated to completely melt at 80℃ water bath conditions and stirred with constant temperature magnetic stirrer at 80℃ with 170-200r / min for 1h, then placed in ultrasonic cleaner at 80℃ water bath environment with 120W power and 80kHz oscillation frequency for 1h ultrasonic oscillation, cooled to 15℃ in constant temperature oven, prepared myristic acid / palmitic acid / paraffin eutectic mixture;

[0073] S3.1. The obtained myristic acid / palmitic acid / paraffin eutectic mixture was heated to melt at 80℃ water bath conditions, and then 5:1 mass fraction of multi-walled carbon nanotubes and carbon nanotube water dispersant were added to obtain a mixture, which was stirred at 70℃ with constant temperature magnetic stirrer at 130-150r / min for 1h, then placed in ultrasonic cleaner at 70℃ water bath environment with 120W power and 80kHz oscillation frequency for 1h ultrasonic oscillation, to obtain a composite phase change material;

[0074] S3.2. The composite phase change material was placed in a 70℃ drying oven, graphite felt was added, vacuum impregnated at-0.1Mpa vacuum degree for 5h, cooled to 15℃ in constant temperature oven, and the excess phase change material was wiped off to obtain a multifunctional composite phase change material, the SEM image of which is shown in Figure 3 It can be seen that the phase change material is well adsorbed in the pores, and the porous skeleton forms a uniform heat conduction network.

[0075] The phase change temperature of the prepared multifunctional composite phase change material is 20.1℃, the phase change latent heat is 178.1J·g -1 , and the thermal conductivity is 0.91Wm -1 ·K -1 .

[0076] The sample image of the multifunctional composite phase change material obtained in the example is shown in Figure 1 .

[0077] The SEM image of the multifunctional composite phase change material obtained in Example 1 is shown in Figure 2 (a).

[0078] Example 2

[0079] A multi-functional composite phase change material, which is different from example 1 only in that the raw materials include the following mass fractions:

[0080] The multi-wall carbon nanotube addition amount is changed to 0.1% of the mass of the myristic acid / palmitic acid / paraffin eutectic mixture, and the carbon nanotube dispersant is 0.05%;

[0081] The phase change temperature of the prepared multi-functional composite phase change material is 20℃, the phase change latent heat is 182.3J·g -1 , and the thermal conductivity is 0.98Wm -1 ·K -1 .

[0082] The sample diagram of the multi-functional composite phase change material obtained in example 2 is shown in Figure 1 .

[0083] The SEM diagram of the multi-functional composite phase change material obtained in example 2 is shown in Figure 2 (b).

[0084] Examples 3-8

[0085] Examples 3-8 are a preparation method of a multi-functional composite phase change material, which is different from example 1 only in that:

[0086] The mass ratio of the myristic acid / palmitic acid / paraffin eutectic mixture to the multi-wall carbon nanotube is different, and the mass ratio of the myristic acid / palmitic acid / paraffin eutectic mixture to the multi-wall carbon nanotube is shown in the following table 2:

[0087] Table 2. Mass ratio of components

[0088] Example Mass ratio latent heat (J g -1 ) Thermal conductivity (Wm -1 • K -1 )]]> Example 3 100 / 0.15 175.0 1.05 Example 4 100 / 0.20 169.3 1.1 Example 5 100 / 0.25 168.8 1.12 Example 6 100 / 0.30 167.9 1.15 Example 7 100 / 0.35 167.7 1.14 Example 8 100 / 0.40 167.5 1.15

[0089] Example 9

[0090] The difference between this example and example 1 is that the addition amount ratio of myristic acid to palmitic acid is 1:1, and the rest of the conditions are the same.

[0091] The phase change temperature of the prepared multi-functional composite phase change material is 20℃, the phase change latent heat is 166.3J·g -1 , and the thermal conductivity is 0.88Wm -1 ·K -1 .

[0092] Example 10

[0093] The difference between this example and example 1 is that the graphite felt is a modified graphite felt, and the rest of the conditions are the same, wherein the modification step is:

[0094] A1. Dissolve the sodium citrate in deionized water to prepare a 2wt% sodium citrate solution;

[0095] Dissolve urea in sodium citrate solution to obtain a final urea concentration of 5wt%;

[0096] A2. Soak the graphite felt in a mixed solution of sodium citrate and urea for 60 minutes, ensuring that the surface of each layer of graphite felt is evenly coated with the solution;

[0097] A3. Remove the soaked graphite felt and place it in an oven set to 50°C for 2 hours to dry;

[0098] A4. Place the dried graphite felt in a furnace for heat curing treatment at a temperature of 100°C for 1 hour;

[0099] A5. Continue heating the cured graphite felt at 200°C for 30 minutes and then cool to obtain the modified graphite felt.

[0100] Comparative Example 1

[0101] A phase change material, which differs from Example 1 in that the raw materials are only myristic acid, palmitic acid, paraffin and graphite felt.

[0102] A method for preparing a phase change material, comprising the following steps:

[0103] S1. Weigh myristic acid and palmitic acid, then heat them in a water bath at 80°C for 0.5 hours to completely melt them;

[0104] S2. Use a constant-temperature magnetic stirrer to stir the melted myristic acid and palmitic acid at 80°C at a speed of 170-200 r / min for 1 hour, then place them in an ultrasonic cleaner and perform ultrasonic oscillation at a power of 120W and an oscillation frequency of 80 kHz in a water bath environment at 80°C for 1 hour, and cool them at room temperature to obtain a myristic acid / palmitic acid eutectic mixture;

[0105] S3. Heat the myristic acid / palmitic acid eutectic mixture obtained in step S2 in a water bath at 80°C until it completely melts;

[0106] S4. Use a constant-temperature magnetic stirrer to stir the melted myristic acid / palmitic acid eutectic mixture and paraffin at 80°C at a speed of 170-200 r / min for 1 hour, then place them in an ultrasonic cleaner and perform ultrasonic oscillation at a power of 120W and an oscillation frequency of 80 kHz in a water bath environment at 80°C for 1 hour, and cool them in a constant-temperature oven to 15°C to obtain a myristic acid / palmitic acid / paraffin eutectic mixture;

[0107] S5. The myristic acid / palmitic acid / paraffin eutectic mixture obtained in step S4 was placed in a 70℃ drying oven, graphite felt was added, vacuum impregnated at -0.1Mpa vacuum degree for 5h, cooled to 15℃ in a constant temperature oven, and the excess phase change material was wiped off to obtain the multifunctional composite phase change material of Comparative Example 1.

[0108] The phase change temperature of the multifunctional composite phase change material prepared was 22.3℃, and the phase change latent heat was 217.8J·g -1 The thermal conductivity was 0.83Wm -1 ·K -1 .

[0109] The sample diagram of the multifunctional composite phase change material obtained in Comparative Example 1 is shown in Figure 1 .

[0110] The SEM diagram of the multifunctional composite phase change material obtained in Comparative Example 1 is shown in Figure 2 (c).

[0111] Comparative Example 2

[0112] The difference between this comparative example and the examples is that graphene is used instead of carbon nanotubes, and the rest of the conditions are the same.

[0113] Test Example 1

[0114] The products obtained in the examples and comparative examples were tested for electrothermal conversion, photothermal conversion, and temperature control test in the sports headband of Example 2. The specific test methods are as follows:

[0115] Electrothermal conversion test:

[0116] A direct current power supply with different voltages was used to evaluate the electrothermal conversion performance of Comparative Example 1, Comparative Example 2, Example 2 and Example 4 (25×25×10mm 3 ). The change of temperature with time was recorded with a multi-channel temperature recorder. The electrothermal conversion rate was calculated by formula (1):

[0117]

[0118] In the formula, I, U, t are the current, voltage and time during the phase change process respectively. m and ΔH are the mass and melting enthalpy of the sample respectively.

[0119] The results are shown in Figure 3As shown, the electrical-thermal conversion efficiency of the composite phase change material with additives is improved. In Example 10, it reaches 76%. In Example 10, the modification of graphite felt by sodium citrate and urea, sodium citrate provides a hydration environment to enhance the effect of gas release in the urea decomposition process, and then forms a more uniform and stable pore structure. The pore structure of the graphite felt is more suitable for the infiltration and distribution of the phase change material, and the modified graphite felt has higher thermal conductivity, which can more efficiently transfer the Joule heat generated by the current through the material to the phase change material, thereby improving the electrical-thermal conversion efficiency.

[0120] Photo-thermal conversion test:

[0121] A xenon lamp was used as a light source to study the photo-thermal conversion performance. The light intensity was maintained at 1.0 sun (100 mW·cm -2 ) by a light power meter. After 28 min of illumination, the light source was turned off, and the sample was naturally cooled at room temperature for 30 min. The internal temperature of the graphite felt, Comparative Example 1, Example 2 and Example 4 (25×25×10 mm 3 ) was recorded by a multi-channel temperature recorder over time. The photo-thermal conversion rate (ω) was calculated by the following formula (2):

[0122]

[0123] In the formula, S, P, t are the illumination surface area, the illumination power of the xenon lamp and the phase change time, respectively. m and ΔH represent the mass and the melting enthalpy of the sample, respectively.

[0124] As shown in Figure 4 , it can be seen that the photo-thermal conversion efficiency of the composite material with additives is greatly improved. It is found that with the increase of the mass fraction of the additive, the photo-thermal conversion rate of the composite material shows a linear upward trend, and the highest reaches 90%, which is 20% higher than that without additives.

[0125] Motion headband temperature control test:

[0126] The composite phase change material obtained in Example 2 was coated with high molecular weight polyethylene, and was assembled at the forehead and behind the ear positions of the headband, respectively. Two test personnel ran at a speed of 8 km / h for 30 min in a 37℃ environment, and the infrared thermal imager was used to record the temperature change before and after exercise.

[0127] The results are shown in Figure 5As shown, the temperature of the part wearing the headband is effectively controlled after two test personnel wear the headband equipped with the composite phase change material and move for 30 min, compared with the conventional headband. Among them, the forehead temperature of test personnel 1 decreases from 27.3℃ to 26.7℃, and the ear root temperature decreases from 27℃ to 26.4℃; the forehead temperature of test personnel 2 decreases from 27.9℃ to 26.8℃, and the ear root temperature decreases from 27.3℃ to 26.5℃. In Comparative Example 2, due to the laminated structure of graphene, compared with the fibrous structure of carbon nanotubes, heat resistance is easy to occur, especially at the contact interface with other components (such as the phase change material matrix). The stacked graphene layers can cause the heat to be blocked in the internal propagation of the material, and cannot form a continuous and efficient heat conduction channel, thereby affecting the heat response speed of the phase change material, and the temperature of the part wearing the headband cannot be effectively controlled.

[0128] The above-described embodiments are only to describe the preferred modes of the present application, and not to limit the scope of the present application. Without departing from the design spirit of the present application, various modifications and improvements to the technical solutions of the present application made by those skilled in the art shall fall within the protection scope determined by the claims of the present application.

Claims

1. A multifunctional composite phase change material, characterized by, The raw materials for preparation include: myristic acid, palmitic acid, paraffin wax, and porous foam materials; The porous foam material is graphite felt; The multifunctional composite phase change material includes a multifunctional composite phase change material prepared by the following methods: S1. The myristic acid and palmitic acid are mixed and heated to melt to obtain a myristic acid / palmitic acid binary eutectic mixture; S2. The myristic acid / palmitic acid binary eutectic mixture is mixed with paraffin and heated to melt to obtain a myristic acid / palmitic acid / paraffin ternary eutectic mixture; S3. The myristic acid / palmitic acid / paraffin ternary eutectic mixture is heated and melted, then impurities are removed and the multifunctional composite phase change material is obtained. The mass ratio of myristic acid to palmitic acid in step S1 is 65:35; Step S3 further includes modifying the ternary eutectic mixture; the modification step includes adding a modifier to the ternary eutectic mixture; The modifier includes carbon nanotubes and a dispersant; the dispersant includes polyvinylpyrrolidone. The mass ratio of the binary eutectic mixture to the paraffin in step S2 is (20-70):(80-30). In step S3, the mass ratio of the ternary eutectic mixture to the modifier is 100:(0-0.4); the mass ratio of the carbon nanotubes to the dispersant is (2-5):1; The modification steps of the modified porous foam material include: The graphite felt is immersed in a mixed solution of sodium citrate and urea for 30-60 minutes, then removed and placed in an oven at 50-60°C for 2-4 hours. After heat curing and heat treatment, it is cooled.

2. The application of the composite phase change material as described in claim 1 in the field of thermal management or temperature control.

3. The application according to claim 2, characterized in that, The thermal management field includes the field of photothermal conversion or the field of electrothermal conversion.

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