A composition for preparing phase change composite materials, the phase change composite material, the preparation method, and its application.

Abstract

This disclosure relates to a composition for preparing phase change composite materials, the phase change composite material itself, a preparation method thereon, and its applications. Based on the total weight of the composition, it comprises: 80-90% by weight of a phase change material, 5-17% by weight of a thermally conductive filler, and 3-15% by weight of a thickener. The phase change composite material has a phase change enthalpy of 80-250 J / g, a phase change enthalpy yield of 80-90%, a thermal conductivity of 1-10 W / m·K, and a melt index of 15-150 g / min. Using the composition of this disclosure to prepare the phase change composite material can improve the phase change enthalpy yield, while also exhibiting high thermal conductivity and a certain degree of plasticity in the molten state. Furthermore, the mixing and molding processes are simplified by using only a heated stirring pan or kneading pan, reducing production costs.

Description

Technical Field

[0001] This disclosure relates to the field of phase change materials technology, specifically to a composition for preparing phase change composite materials, a phase change composite material, a preparation method thereon, and its application. Background Technology

[0002] Phase change materials (PCCs) absorb or release heat during phase transitions while maintaining a nearly constant temperature, exhibiting strong temperature control and high heat storage capacity, making them suitable for thermal management and heat storage applications. Organic PCCs, in particular, possess advantages such as high phase change enthalpy, low supercooling, no phase separation, low corrosivity, and low toxicity, and are widely used in textiles, battery thermal management, cold chain logistics, and building energy conservation. Taking phase change paraffin as an example, depending on the number of alkane carbon atoms it contains, the phase change temperature can range from 8 to 150°C; the heat absorbed or released during the phase change process can reach over 200 J / g.

[0003] However, organic phase change materials have low thermal conductivity and molding problems. (1) Low thermal conductivity (<0.2W / mK) results in very slow heat transfer rate, which cannot absorb heat in time, resulting in slow response speed during application and inability to effectively achieve thermal management or rapid heat storage and release effect. (2) Molding usually adopts hot molding, which is inefficient, has poor precision, low yield, and is difficult to shape. Moreover, hot pressing of phase change materials during melting causes flow and seepage problems.

[0004] Currently, the problem of low thermal conductivity can be solved by adding thermally conductive fillers. However, since phase change materials (PCMs) are the main source of latent heat of phase change, adding thermally conductive fillers and resins will reduce the enthalpy of phase change; the higher the proportion of fillers, the greater the loss of enthalpy. To achieve the desired molding effect, existing technologies typically add a large amount of resin and additives, with PCMs usually accounting for 50-80% of the final composite material, meaning a 20-50% sacrifice in enthalpy. In the field of PCM composites, improving thermal conductivity and molding while ensuring a relatively high enthalpy of phase change is a contradictory problem. Therefore, improving the thermal conductivity and molding of PCM composites while ensuring a high enthalpy yield is an urgent issue to be addressed. Summary of the Invention

[0005] To address the aforementioned technical problems, this disclosure provides a composition for preparing phase change composite materials, a phase change composite material, a preparation method, and applications. The phase change composite material has high thermal conductivity, high phase change enthalpy recovery, and certain fluidity and plasticity in the molten state.

[0006] To achieve the above objectives, the first aspect of this disclosure provides a composition for preparing phase change composite materials, wherein, based on the total weight of the composition, the composition comprises: 80-90% by weight of phase change material, 5-17% by weight of thermally conductive filler, and 3-15% by weight of thickener. The thermally conductive filler comprises porous graphite, wherein the porous graphite has a carbon content of 99.5-99.99%, a graphitization degree of 99-100%, an average particle size of 0.2-1.0 mm, a closed pore ratio of 0.5-1.0%, and a bulk density of 0.002-0.02 g / cm³. 3 .

[0007] Optionally, in the composition, the weight ratio of the phase change material, the thermally conductive filler and the thickener is (5.5-30):(0.5-5.5):1, preferably (20-30):(2.0-4.0):1.

[0008] Optionally, the thermally conductive filler further includes flake graphite, wherein the carbon content of the flake graphite is 95.0-99.9%, the degree of graphitization is 98-100%, and the particle size is 500-1000 mesh; Preferably, based on the total weight of the composition, the content of porous graphite is 5-15% by weight, and the content of flake graphite is 0-8% by weight. More preferably, when the content of the porous graphite is 5-10% by weight, the average particle size of the porous graphite is 0.5-1.0 mm.

[0009] Optionally, the phase change material is selected from one or more of phase change paraffin, fatty acids, and fatty alcohols; preferably, the fatty acid is selected from one or more of stearic acid, palmitic acid, myristic acid, lauric acid, decanoic acid, and caprylic acid; and the fatty alcohol is selected from one or more of n-dodecanol, n-tetradecanoic acid, n-hexadecanoic acid, and n-octadecanoic acid. The porous graphite is selected from one or more of expanded graphite, carbon nanotubes, and graphene. The thickener is selected from one or more of the following: petroleum grease, stearate, microcrystalline wax, polyethylene wax, gypsum, modified castor oil, xanthan gum, carrageenan, bentonite, diatomaceous earth, kaolin, talc, deep-sea mud, and volcanic ash.

[0010] Optionally, based on the total weight of the composition, the composition further includes an auxiliary material of greater than 0 and less than 0.5% by weight; The additive material is selected from antioxidants and / or flame retardants; Optionally, the antioxidant is selected from one or more of di-tert-butyl-p-cresol, diphenyl diisopropylphenol, and di-tert-butyl-p-cresol; The flame retardant is selected from one or more of chlorinated paraffin, ammonium polyphosphate, bromoalkyl phosphate, aluminum hydroxide, and magnesium hydroxide.

[0011] A second aspect of this disclosure provides a method for preparing a phase change composite material, the method comprising the following steps: The composition described in the first aspect is stirred and mixed to obtain a raw material mixture; the raw material mixture is then cooled, shaped, and crushed.

[0012] Optionally, the stirring and mixing process includes the following steps: The phase change material is heated at a first preset temperature for 10-60 minutes to obtain a first material; the first material is then mixed with a thermally conductive filler and a thickener at a second preset temperature and stirred at a rate of 20-100 r / min for 20-40 minutes to obtain the raw material mixture.

[0013] Optionally, the first preset temperature and the second preset temperature may be the same or different, and each is independently 30-50°C higher than the melting point of the phase change material.

[0014] The third aspect of this disclosure provides a phase change composite material prepared by the method of the second aspect, wherein the phase change composite material has a phase change enthalpy of 80-250 J / g, a phase change enthalpy yield of 80-90%, a thermal conductivity of 1-10 W / m·K, and a melt index of 15-150 g / min.

[0015] This disclosure provides a fourth aspect regarding the application of the phase change composite materials described in the third aspect in the fields of thermal storage and battery thermal management.

[0016] Through the above technical solutions, this disclosure provides a composition for preparing phase change composite materials, a phase change composite material, a preparation method, and applications. Using the composition disclosed herein to prepare phase change composite materials can improve the phase change enthalpy yield of the composite material. Simultaneously, the phase change composite material exhibits high thermal conductivity and certain fluidity and plasticity in the molten state. Furthermore, the mixing and molding processes are simplified by using only a heated stirring pan or kneading pan, reducing production costs.

[0017] Other features and advantages of this disclosure will be described in detail in the following detailed description section. Detailed Implementation

[0018] The following provides a detailed description of specific embodiments of this disclosure. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit this disclosure.

[0019] The first aspect of this disclosure provides a composition for preparing phase change composite materials, wherein, based on the total weight of the composition, the composition comprises: 80-90% by weight of phase change material, 5-17% by weight of thermally conductive filler, and 3-15% by weight of thickener; The thermally conductive filler comprises porous graphite, wherein the porous graphite has a carbon content of 99.5-99.99%, a graphitization degree of 99-100%, an average particle size of 0.2-1.0 mm, a closed pore ratio of 0.5-1.0%, and a bulk density of 0.002-0.02 g / cm³. 3 .

[0020] This disclosure provides a composition for preparing phase change composite materials. The composition can be used to prepare phase change composite materials, wherein there is a synergistic effect among the phase change material, the thermally conductive filler, and the thickener: the thickener can increase the viscosity of the phase change material and make the thermally conductive filler more uniformly distributed, which is conducive to the formation of a stable thermally conductive network; the porous thermally conductive filler binds the liquid phase change material through the pores, reduces the fluidity of the phase change material, and can also reduce the amount of thickener used. With less thickener and thermally conductive filler, the phase change composite material can also achieve the effect of injection molding.

[0021] The phase change composite material prepared using the composition formulation disclosed herein ensures a high proportion of phase change material in the formulation, resulting in a high phase change enthalpy yield. This disclosure specifically selects porous thermally conductive fillers, ensuring high thermal conductivity of the phase change composite material with relatively small addition amounts. The composition disclosed herein does not contain polymer / resin materials, avoiding the problem of reduced phase change enthalpy yield caused by the introduction of large amounts of polymer / resin materials; furthermore, the phase change composite material prepared from the composition disclosed herein exhibits certain fluidity and plasticity in the molten state.

[0022] To further improve the performance of the phase change composite material, in a preferred embodiment of this disclosure, the weight ratio of the phase change material, the thermally conductive filler and the thickener in the composition is (5.5-30):(0.5-5.5):1, preferably (20-30):(2.0-4.0):1.

[0023] In this disclosure, the viscosity of the phase change composite material is increased through a synergistic effect between the thermally conductive filler and the thickener. Within the scope of the above embodiments, the synergistic effect between the thermally conductive filler and the thickener can be further promoted, thereby increasing the viscosity of the phase change composite material. In addition, this disclosure utilizes the pores of the thermally conductive filler to bind the liquid phase change material, thereby further improving the injection molding effect of the phase change composite material within the scope of the above embodiments.

[0024] In one embodiment of this disclosure, the thermally conductive filler further includes flake graphite, wherein the flake graphite has a carbon content of 95.0-99.9%, a graphitization degree of 98-100%, and a particle size of 500-1000 mesh. In this disclosure, the thermally conductive filler can be solely porous graphite or a mixture of porous graphite and flake graphite. When the thermally conductive filler is a mixture of porous graphite and flake graphite, based on the total weight of the composition, the content of porous graphite is 5-15% by weight, and the content of flake graphite is 0-8% by weight. Flake graphite helps to assist in constructing a thermally conductive network through cross-linking points, thereby improving thermal conductivity. On the other hand, due to the adsorption properties of porous graphite, excessive use can lead to a decrease in the plasticity of the composite material. Replacing part of the porous graphite with flake graphite can ensure the plasticity of the composite material.

[0025] More preferably, when the content of the porous graphite is 5-10% by weight, the average particle size of the porous graphite is 0.5-1.0 mm.

[0026] In one embodiment of this disclosure, the porous graphite is selected from one or more of expanded graphite, carbon nanotubes, and graphene. Using the graphite material of this disclosure can, on the one hand, better bind the thermally conductive filler, further improving the plasticity of the phase change composite material in the molten state; on the other hand, it can achieve better thermal conductivity with a smaller filler content.

[0027] In this disclosure, the phase change material is an organic phase change material. In one embodiment, the phase change material is selected from one or more of phase change paraffin, fatty acids, and fatty alcohols. The phase change paraffin is a mixture of straight-chain alkanes with a phase change temperature of 35-80°C and a phase change enthalpy of 160-270 kJ / kg. The fatty acids are selected from one or more of stearic acid, palmitic acid, myristic acid, lauric acid, decanoic acid, and octanoic acid. The fatty alcohols are selected from one or more of n-dodecyl alcohol, n-tetradecyl alcohol, n-hexadecyl alcohol, and n-octadecyl alcohol. In a preferred embodiment, the organic phase change material may be selected from one or more of phase change paraffin, stearic acid, and n-octadecyl alcohol.

[0028] Using the phase change material disclosed herein, the phase change enthalpy recovery rate of the composite phase change material can be guaranteed to be above 80%.

[0029] In one embodiment of this disclosure, the thickener is selected from one or more of petroleum grease, stearate, microcrystalline wax, polyethylene wax, gypsum, modified castor oil, xanthan gum, carrageenan, bentonite, diatomaceous earth, kaolin, talc, deep-sea mud, and volcanic ash.

[0030] The thickener used in this embodiment can increase the viscosity of the phase change material, which on the one hand reduces leakage of the molten phase change material during injection molding and compression molding, and on the other hand makes the thermally conductive aggregate more evenly distributed, which is conducive to the formation of a stable thermally conductive network.

[0031] Depending on the actual application and requirements of phase change composite materials, the composition for preparing phase change composite materials may also include other auxiliary materials. This disclosure does not specifically limit the types of other auxiliary materials; however, flame retardants may be added if flame retardant requirements are present. In one embodiment of this disclosure, based on the total weight of the composition, the composition further includes auxiliary materials greater than 0 and less than 0.5% by weight; the auxiliary materials are selected from one or more antioxidants and / or flame retardants; optionally, the antioxidant is selected from one or more of di-tert-butyl-p-cresol, diphenyl diisopropylphenol, and di-tert-butyl-p-cresol; the flame retardant is selected from one or more of chlorinated paraffin, ammonium polyphosphate, bromoalkyl phosphate, aluminum hydroxide, and magnesium hydroxide.

[0032] All raw materials used in the compositions disclosed herein are available through ordinary commercial channels or can be prepared by known methods.

[0033] A second aspect of this disclosure provides a method for preparing a phase change composite material, the method comprising the following steps: The composition described in the first aspect is stirred and mixed to obtain a raw material mixture; the raw material mixture is then cooled, shaped, and crushed.

[0034] In this disclosure, a heated stirring pot or kneading pot can be used for stirring and mixing. After the mixture cools, it is crushed using a simple method to obtain granules, which simplifies the process and reduces production costs. The container for cooling and forming can be a container conventional in the art, such as a drying trough or a metal container. The crushing process in this disclosure can employ devices and methods conventionally used by those skilled in the art, such as impact crushing, compression crushing, and shear crushing. This disclosure does not impose specific limitations on the crushing conditions. After crushing, particles with an average particle size of 0.05-5 mm are obtained.

[0035] In one embodiment of this disclosure, the stirring and mixing process includes the following steps: The phase change material is heated at a first preset temperature for 10-60 minutes to obtain a first material; the first material is then mixed with a thermally conductive filler and a thickener at a second preset temperature and stirred at a rate of 20-100 r / min for 20-40 minutes to obtain the raw material mixture.

[0036] In this disclosure, the phase change material is heated to obtain a liquid phase change material, i.e., the first material. Adding a thermally conductive filler and a thickener in this state increases the viscosity of the first material and facilitates its entry into the pores of the thermally conductive filler. The mixing apparatus can be any apparatus conventionally used by those skilled in the art. This apparatus can perform mixing during the heating process of the raw materials, such as a heated mixing pot or a kneading pot. Mixing further promotes the mixing of the raw materials, allowing the first material to enter the pores of the thermally conductive filler as much as possible. The first preset temperature and the second preset temperature may be the same or different, and each is independently 30-50°C higher than the melting point of the phase change material.

[0037] The third aspect of this disclosure provides a phase change composite material prepared by the method of the second aspect, wherein the phase change composite material has a phase change enthalpy of 80-250 J / g, a phase change enthalpy yield of 80-90%, a thermal conductivity of 1-10 W / m·K, and a melt index of 15-150 g / min.

[0038] In this disclosure, the phase change enthalpy yield refers to the ratio of the phase change enthalpy of the phase change composite material to the phase change enthalpy of the pure phase change material, multiplied by 100%.

[0039] This disclosure provides a fourth aspect regarding the application of the phase change composite materials described in the third aspect in the fields of thermal storage and battery thermal management.

[0040] Specifically, the phase change composite material disclosed herein can be applied to temperature-controlled tableware or small household appliances for heat preservation and temperature control. For example, it can be used in the sealing structures of temperature-controlled cups and bowls. Because the phase change composite material of this disclosure has a high phase change enthalpy absorption rate and thermal conductivity, when applied to temperature-controlled tableware, it can quickly reach a constant temperature, achieving a good heat preservation effect. The phase change composite material of this disclosure can also be applied to the field of battery thermal management, specifically for power battery thermal management.

[0041] The present disclosure is further described in detail below through examples. All raw materials and apparatus used in the examples are commercially available.

[0042] Example 1 The phase change material used in this embodiment is phase change paraffin (phase change temperature 45℃, phase change enthalpy 252kJ / kg); the thermally conductive filler is expanded graphite (carbon content 99.9%, graphitization degree 100%, average particle size 1.0mm, closed pore ratio 0.5%, bulk density 0.01g / cm³). 3 The product contains flake graphite (99% carbon content, 100% graphitization, and 1000 mesh particle size), and polyethylene wax is used as the thickener.

[0043] The method for preparing phase change composite materials includes the following steps: (1) Preparation of raw material mixture: Weigh the sample according to the percentage of total weight (100g), wherein, phase change material: thermally conductive filler: thickener = phase change paraffin wax: (expanded graphite + flake graphite): polyethylene wax = 85.00 wt%: (8.00 wt% + 4.00 wt%): 3.00 wt% (that is, the weight ratio of phase change material: thermally conductive filler: thickener is 28.3: 4: 1). Place the phase change material in a heating and stirring pot and heat it at 75℃ for 30min to obtain the first material; add the thermally conductive filler and thickener to the first material at 75℃ and stir and mix it at a rate of 60r / min for 20min to obtain the raw material mixture.

[0044] (2) Pour the raw material mixture into the drying tank and cool it to room temperature to obtain a solid phase change composite material.

[0045] (3) The solid phase change composite material is placed in a shear crusher (Rongshida small crusher, equipped with six steel blades) and crushed into particles with an average particle size of 0.5 mm.

[0046] Examples 2-4 The preparation method in Example 1 differs from that in Example 1 in that the composition ratio in Table 1 is followed, and the remaining process is the same as in Example 1, to prepare the phase change composite material.

[0047] Comparative Example 1 Following the preparation method in Example 1, the amount of phase change material added remained unchanged. The difference from Example 1 was that only expanded graphite was used, and the content of expanded graphite was 15% by weight. No thickener was added to prepare the phase change composite material.

[0048] Comparative Example 2 Following the preparation method in Example 1, the amount of phase change material added remained unchanged. The difference from Example 1 was that no thermally conductive filler was added, and a thickener with a content of 15% by weight was added to prepare the phase change composite material.

[0049] Comparative Example 3 The preparation method in Example 1 differs from that in Example 1 in that: phase change material: thermally conductive filler: thickener = phase change paraffin wax: (expanded graphite + flake graphite): polyethylene wax = 94.00 wt%: (2.00 wt% + 2.00 wt%): 2.00 wt% (that is, the weight ratio of phase change material: thermally conductive filler: thickener is 47:2:1), and a phase change composite material is prepared.

[0050] Table 1

[0051] Test case The phase change enthalpy, thermal conductivity, melt index, and viscosity in the molten state of the phase change composite materials prepared in the above examples and comparative examples were tested, and the phase change enthalpy yield was calculated. The test results of the phase change enthalpy are listed in Table 2 below.

[0052] The phase transition enthalpy was measured by differential scanning calorimetry. Thermal conductivity was tested and calculated according to ASTM-E1461; The melt flow index is measured by a melt flow index tester; Phase change enthalpy yield = Phase change enthalpy of phase change composite material / Phase change enthalpy of phase change material × 100%.

[0053] Table 2

[0054] Table 2 shows that a composite phase change material with suitable thermal conductivity, phase change enthalpy recovery, and melt index is prepared by synergistic combination of thermally conductive filler and thickener within a certain proportion range. If thermally conductive filler is not used or the amount of thermally conductive filler is insufficient, the required thermal conductivity and melt index will not be met. If only thermally conductive filler is used, the excessive amount of filler will cause the phase change material to be adsorbed and bound by the thermally conductive filler, resulting in poor flowability.

[0055] The preferred embodiments of this disclosure have been described in detail above. However, this disclosure is not limited to the specific details of the above embodiments. Within the scope of the technical concept of this disclosure, various simple modifications can be made to the technical solutions of this disclosure, and these simple modifications all fall within the protection scope of this disclosure.

[0056] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, this disclosure will not describe the various possible combinations separately.

[0057] Furthermore, various different embodiments of this disclosure can be combined in any way, as long as they do not violate the spirit of this disclosure, they should also be regarded as the content disclosed in this disclosure.

Claims

1. A composition for preparing phase change composite materials, characterized in that, Based on the total weight of the composition, the composition comprises: 80-90% by weight of phase change material, 5-17% by weight of thermally conductive filler, and 3-15% by weight of thickener; The thermally conductive filler comprises porous graphite, wherein the porous graphite has a carbon content of 99.5-99.99%, a graphitization degree of 99-100%, an average particle size of 0.2-1.0 mm, a closed pore ratio of 0.5-1.0%, and a bulk density of 0.002-0.02 g / cm³. 3 .

2. The composition according to claim 1, wherein, In the composition, the weight ratio of the phase change material, the thermally conductive filler and the thickener is (5.5-30):(0.5-5.5):1, preferably (20-30):(2.0-4.0):

1.

3. The composition according to claim 2, wherein, The thermally conductive filler also includes flake graphite, wherein the carbon content of the flake graphite is 95.0-99.9%, the degree of graphitization is 98-100%, and the particle size is 500-1000 mesh; Preferably, based on the total weight of the composition, the content of porous graphite is 5-15% by weight, and the content of flake graphite is 0-8% by weight. More preferably, when the content of the porous graphite is 5-10% by weight, the average particle size of the porous graphite is 0.5-1.0 mm.

4. The composition according to claim 3, wherein, The phase change material is selected from one or more of phase change paraffin, fatty acids, and fatty alcohols; preferably, the fatty acid is selected from one or more of stearic acid, palmitic acid, myristic acid, lauric acid, decanoic acid, and caprylic acid; and the fatty alcohol is selected from one or more of n-dodecanol, n-tetradecanoic acid, n-hexadecanoic acid, and n-octadecanoic acid. The porous graphite is selected from one or more of expanded graphite, carbon nanotubes, and graphene. The thickener is selected from one or more of the following: petroleum grease, stearate, microcrystalline wax, polyethylene wax, gypsum, modified castor oil, xanthan gum, carrageenan, bentonite, diatomaceous earth, kaolin, talc, deep-sea mud, and volcanic ash.

5. The composition according to claim 2, wherein, Based on the total weight of the composition, the composition further includes an auxiliary material of greater than 0 and less than 0.5% by weight; The additive material is selected from antioxidants and / or flame retardants; Optionally, the antioxidant is selected from one or more of di-tert-butyl-p-cresol, diphenyl diisopropylphenol, and di-tert-butyl-p-cresol; The flame retardant is selected from one or more of chlorinated paraffin, ammonium polyphosphate, bromoalkyl phosphate, aluminum hydroxide, and magnesium hydroxide.

6. A method for preparing phase change composite materials, characterized in that, The method includes the following steps: The composition according to any one of claims 1 to 5 is stirred and mixed to obtain a raw material mixture; the raw material mixture is then cooled, shaped, and crushed.

7. The method according to claim 6, wherein, The stirring and mixing process includes the following steps: The phase change material is heated at a first preset temperature for 10-60 minutes to obtain a first material; the first material is then mixed with a thermally conductive filler and a thickener at a second preset temperature and stirred at a rate of 20-100 r / min for 20-40 minutes to obtain the raw material mixture.

8. The method according to claim 7, wherein, The first preset temperature and the second preset temperature may be the same or different, and each is independently 30-50°C higher than the melting point of the phase change material.

9. The phase change composite material prepared by the method according to any one of claims 6 to 8, characterized in that, The phase change composite material has a phase change enthalpy of 80-250 J / g, a phase change enthalpy yield of 80-90%, a thermal conductivity of 1-10 W / m·K, and a melt index of 15-150 g / min.

10. The application of the phase change composite material of claim 9 in the fields of thermal storage and battery thermal management.

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