A paraffin-based high-energy-storage-capacity phase change material, its preparation method and application

Abstract

This invention belongs to the field of functional polymer materials, specifically relating to a paraffin-based high-energy-capacity phase change material and its preparation method. Using paraffin with a high phase change enthalpy as raw material, and stearyl alcohol and 12-hydroxystearic acid as modifiers to improve the phase change enthalpy and stability of paraffin, a composite oil phase with non-flowing properties and high energy storage capacity under heating is prepared using a simple heating-dissolving-stirring method. The measured melting enthalpy of this material is significantly higher than the theoretical value, and it maintains shape stability at temperatures above the melting point of paraffin. The composition is further encapsulated through emulsion polymerization to obtain the composite phase change material; then, it is freeze-dried to obtain a composite phase change aerogel material. This invention solves the problems of easy flow and limited energy storage capacity of traditional paraffin phase change materials under heating. The resulting material combines high phase change enthalpy, excellent shape stability, and flexibility, making it suitable for thermal management in fields such as new energy vehicles, electronic equipment, construction, and textiles.

Description

Technical Field

[0001] This invention belongs to the field of functional polymer materials, specifically relating to a paraffin-based high energy storage capacity phase change material and its preparation method. Background Technology

[0002] Traditional energy systems struggle to effectively utilize photovoltaic, wind, and other intermittent and fluctuating clean energy sources. Therefore, high-efficiency energy storage technology has become a key breakthrough for achieving sustainable energy use. Phase change materials (PCMs) can undergo phase transitions within a specific temperature range, absorbing or releasing heat energy as latent heat during this process, thereby achieving heat storage, transfer, and temperature regulation. With advantages such as high energy density and isothermal processes, they show broad application prospects in areas such as cold chain packaging and transportation of food, building energy conservation, industrial waste heat recovery, power peaking, and thermal management of electronic equipment.

[0003] Organic PCMs, represented by paraffin wax, are widely used in medium- and low-temperature civilian applications. They have advantages such as high chemical stability, no supercooling precipitation, and strong cycle durability, making them widely applicable. However, due to the high fluidity of paraffin wax at high temperatures, significant volume changes during phase transitions, and its tendency to slip off from the matrix, coupled with poor compatibility with the matrix, it is difficult to directly shape and use.

[0004] To overcome the aforementioned technical bottlenecks, several technical solutions have been developed to enhance the thermophysical properties of paraffin PCMs and improve their feasibility for thermal energy storage applications. For example, encapsulating paraffin through physical adsorption methods, such as using metal foam, heat pipes, or adding nanomaterials, can partially improve shape stability, but its stability is limited due to weak interfacial bonding and poor long-term cycling performance. When using micro-encapsulation or nano-encapsulation technologies, the volume change caused by the phase transition of paraffin during encapsulation must first be considered; secondly, the encapsulation shell significantly reduces the energy storage capacity of the paraffin.

[0005] Therefore, it is necessary to develop a new phase change material to solve the aforementioned problems of existing technologies. Summary of the Invention

[0006] To address the aforementioned problems in existing technologies, this invention provides a paraffin-based phase change energy storage composition (composite oil phase) with high energy storage capacity (measured phase change enthalpy higher than theoretical value) and stability under heating conditions. Furthermore, a composite phase change material (TOHS) is prepared via emulsion polymerization, exhibiting shape stability and high energy storage capacity. This material is then freeze-dried to prepare a high phase change enthalpy solid-solid phase change material—a phase change energy storage aerogel (FTOHS)—maximizing the encapsulation of the oil phase and maximizing its heat storage capacity.

[0007] A first aspect of the present invention is to provide a paraffin-based phase change energy storage composition comprising: paraffin, stearyl alcohol, and 12-hydroxystearic acid; Further, the total mass of stearyl alcohol and 12-hydroxystearic acid is 3% to 20% of the mass of the paraffin; optionally, such as 3%, 3.5%, 4%, 4.5%, 5%, 10%, 15%, or 20%.

[0008] In some embodiments, the total mass of stearyl alcohol and 12-hydroxystearic acid is 3% to 15% of the mass of the paraffin, more preferably 4% to 10%. In some embodiments, the mass ratio of stearyl alcohol to 12-hydroxystearic acid is 5:1 to 1:2; preferably 3:1 to 2:5; more preferably 3:1 to 2:3.

[0009] In a preferred embodiment, the mass ratio of stearyl alcohol to paraffin is 0.03:1; in a preferred embodiment, the mass ratio of 12-hydroxystearic acid to paraffin is 0.02:1.

[0010] Furthermore, the microscopic surface of the paraffin-based phase change energy storage composition has irregular pores and undulations, with an amorphous continuous phase encapsulating micron-sized sheet-like or blocky paraffin crystal regions, and the transition between the crystal regions and the continuous phase is smooth.

[0011] Furthermore, the paraffin is selected from C10-C20 straight-chain alkanes, branched-chain alkanes, and cycloalkanes; in some preferred embodiments, the paraffin is n-octadecane.

[0012] The composite oil phase of this invention exhibits high energy storage capacity, with a phase change enthalpy ≥230 J / g, and the measured value is significantly higher than the theoretical value. It remains stable at temperatures above the melting point of paraffin wax, does not flow upon heating, and demonstrates stability. In some embodiments, the enthalpy of melting of the paraffin-based phase change energy storage composition is not less than 240 J / g. In some preferred embodiments, the phase change enthalpy is ≥270 J / g.

[0013] In some embodiments, the paraffin-based phase change energy storage composition remains shape-stable and does not macroscopically flow at 60 °C.

[0014] The second aspect of the present invention provides a method for preparing the paraffin-based phase change energy storage composition, wherein stearyl alcohol, 12-hydroxystearic acid and paraffin are mixed and heated to melt at 80-100°C to obtain the paraffin-based phase change energy storage composition.

[0015] A third aspect of the present invention provides a composite phase change material comprising a core and an encapsulation layer, wherein the core is a paraffin-based phase change energy storage composition; the encapsulation layer encapsulates a polymer shell of the core; the polymer shell is formed by emulsion polymerization of water-soluble monomers and oil-soluble monomers. Furthermore, the composite phase change material retains shape stability at temperatures above the melting point of paraffin.

[0016] A fourth aspect of the present invention provides a method for preparing the composite phase change material, comprising the steps of: S1. Preparation of aqueous precursor solution: Mix emulsifier, water-soluble monomer and water evenly; S2. Preparation of oil-phase precursor solution: The paraffin-based phase change energy storage composition, oil-soluble monomer and crosslinking agent are mixed evenly; S3. The oil-phase precursor solution and the aqueous-phase precursor solution are mixed and homogenized and emulsified to obtain an oil-water emulsion; S4. Polymerization: An initiator is added to the oil-water emulsion to carry out emulsion polymerization to obtain the composite phase change material.

[0017] In some embodiments, in step S2, the emulsifier in the aqueous precursor solution is an aqueous PVA solution or an aqueous PVPK30 solution. Furthermore, the water-soluble monomer is selected from one or a combination of N,N-dimethylacrylamide, acrylamide, polyethylene glycol methacrylate, polyethylene glycol diacrylate, N-vinylpyrrolidone, acrylic acid, hydroxyethyl methacrylate, hydroxyethyl acrylate, N-isopropylacrylamide, and dimethylaminoethyl methacrylate.

[0018] In a preferred embodiment, the water-soluble monomer is N,N-dimethylacrylamide, the solid content of the PVA aqueous solution is 10%, and the solid content of the PVP K30 aqueous solution is 3%.

[0019] In some embodiments, the oil-soluble monomer is selected from at least one of lauryl methacrylate, octadecyl methacrylate, lauryl acrylate, isooctyl acrylate, butyl acrylate, n-butyl methacrylate, styrene, and cyclohexyl methacrylate. In some preferred embodiments, the oil-soluble monomer is lauryl methacrylate, and the crosslinking agent is ethylene glycol dimethacrylate.

[0020] In some embodiments, in step S1, the emulsifier is selected from one or a combination of polyvinyl alcohol and polyvinylpyrrolidone; in some preferred embodiments, the solid content of the PVA aqueous solution is 1%-10%; and the solid content of the PVP K30 aqueous solution is 1%-5%.

[0021] In some embodiments, the oil-phase precursor solution is added dropwise to the aqueous-phase precursor solution and emulsified in a high-speed homogenizer for 1-10 min. In some preferred embodiments, emulsification is performed in a high-speed homogenizer for 1-5 min.

[0022] In some embodiments, in step S2, the crosslinking agent is ethylene glycol dimethacrylate; In some implementations, the homogenization emulsification time in step S3 is 1-10 minutes; In some embodiments, in step S4, the reaction temperature of the emulsion polymerization is 60-80°C.

[0023] A fifth aspect of the present invention provides a composite phase change aerogel, which is prepared by freeze-drying the composite phase change material; the enthalpy of melting of the composite phase change aerogel is not less than 160 J / g.

[0024] In some embodiments, the composite phase change aerogel (FTOHS) is prepared by freeze-drying the composite phase change material (TOHS) at -60 °C, which is shape-stable and has a certain degree of flexibility at room temperature.

[0025] Furthermore, the phase change material prepared by this invention does not leak above the melting point of paraffin after drying and exhibits excellent temperature stability at 60 °C.

[0026] Another aspect of the present invention provides the application of the paraffin-based phase change energy storage composition, the composite phase change material, and the composite phase change aerogel in the field of thermal management, including but not limited to new energy vehicles, electronic communications, green buildings, and smart textiles.

[0027] Beneficial effects: Compared with the prior art, the beneficial effects of the present invention are at least as follows: (1) The present invention provides a paraffin-based phase change energy storage composition with a measured melting enthalpy that is significantly higher than the theoretical calculated value. The composition remains stable under heating conditions and the phase change enthalpy can reach 272.69 J / g. The composition forms a uniform micro-composite structure through a hydrogen bond network and has a crystallinity of up to 88.20%. The composite oil phase can maintain its shape stability at temperatures higher than the melting point of the paraffin matrix.

[0028] (2) This invention further prepares composite phase change materials (TOHS) and composite phase change aerogel materials (FTOHS) through emulsion polymerization encapsulation and freeze drying, effectively solving the leakage problem of solid-liquid phase change materials; the prepared FTOOHS still maintains a high phase change enthalpy (169.95 J / g), is stable in shape at room temperature and has a certain degree of flexibility, and has excellent comprehensive performance. It has broad application prospects in thermal management fields such as heat dissipation of electronic equipment and building energy conservation. Attached Figure Description

[0029] The accompanying drawings are provided to further illustrate the present application and form part of the specification. They are used together with the embodiments of the present application to explain the present application, but do not constitute a limitation thereof. In the drawings: Figure 1 Scanning electron microscope image of the composite oil phase (OHS) obtained in Example 1; Figure 2 (a) is the infrared spectrum of the raw material, and (b) is the infrared spectrum of the composite oil phase and the prepared phase change material of Example 1. Figure 3 XRD patterns of raw materials, composite oil phase, and prepared phase change materials; Figure 4 The images show the physical image of the emulsion of the phase change material prepared in Example 1 and an optical micrograph of the emulsion. Figure 5 This is a physical image of the phase change material after emulsion polymerization. Detailed Implementation

[0030] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the examples in the specification. Many specific details are set forth in the following description to provide a thorough understanding of the present invention; however, the present invention may also be implemented in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0031] Unless otherwise specified, the experimental methods described in the following examples are conventional methods; the reagents and instruments described are commercially available unless otherwise specified.

[0032] Test methods for various performance parameters: (1) SEM test: The prepared phase change material was brittle in liquid nitrogen, and it was attached to the electron microscope stage with conductive adhesive. Then, the sample was sprayed with gold for 30 s and observed by SEM.

[0033] (2) Differential scanning calorimetry (DSC): Take about 6 mg of phase change material sample and place it in a crucible. Scan from 0 ℃ to 90 ℃ at a heating rate of 10 ℃ / min to obtain the DSC curve. The nitrogen gas flow rate during the scanning process is 50 mL / min.

[0034] (3) X-ray diffraction analysis (XRD): Performed on an X-ray diffractometer. Cu Kα radiation with a nickel filter at 5° to 45° was used.

[0035] Example 1: Preparation of Phase Change Materials (1) Preparation of composite phase change oil phase (OHS): 2 g of 12-hydroxystearic acid (12-HA) and 2 g of stearyl alcohol (SA) were added to a beaker containing 100 g of paraffin (n-octadecane), and the beaker was heated in an oven at 90 °C. After all the raw materials were melted and mixed, a colorless and transparent solution was obtained. The temperature was then lowered to 70 °C to obtain the composite oil phase (OHS), which was designated as OHS-3. The oil phase remained stable at 70 °C and showed no obvious macroscopic flow. (2) Preparation of aqueous precursor solution: Take 4.11 g polyvinylpyrrolidone (PVP, solid content 3%) solution, 10.96 g polyvinyl alcohol aqueous solution (PVA, solid content 10%), 4.11 g N,N-dimethylacrylamide, and 8.22 g deionized water, mix them to obtain an aqueous solution, and place it in a 70 ℃ oven for later use; (3) Preparation of oil phase precursor solution: Take 21.58 mL of the composite phase change oil phase (OHS) obtained in step (1), add 0.75 mL of ethylene glycol dimethacrylate (EGDMA) and 0.135 mL of lauryl methacrylate, mix well to obtain oil phase precursor solution, and place in a 70 ℃ oven for later use. (4) Preparation of oil-water emulsion: Under the condition of 70 ℃, the oil phase precursor solution prepared in step (3) is slowly added dropwise to the aqueous phase precursor solution prepared in step (2); after the addition is completed, it is transferred to a high-speed homogenizer and emulsified at about 10000 rpm for 5 min to obtain a milky white oil-water emulsion; it is placed in a 70 ℃ environment to observe the state of the emulsion and determine the emulsification effect; (5) Emulsion polymerization: 0.135 mL of thermal initiator was added to the emulsion obtained in step (4), and then emulsion polymerization was carried out at 70 °C to obtain a phase change energy storage composite material (TOHS); the phase change material film obtained under this condition has a stable shape and a high energy storage capacity.

[0036] (6) Freeze-drying: The TOHS obtained in step (5) is freeze-dried at -60℃ to obtain paraffin-based phase change energy storage aerogel material (FTOHS).

[0037] Example 2 Preparation of composite phase change oil phases with different ratios The steps are basically the same as in Example 1, except for step (1): (1) 1, 1.5, 2.5, 5, and 100 g of 12-hydroxystearic acid and stearyl alcohol (12-HA and SA in a mass ratio of 1:1) were added to a beaker containing 100 g of paraffin wax, respectively. The beaker was then heated in an oven at 90 °C. After all the raw materials were melted and mixed, a colorless and transparent solution was obtained. The temperature was then lowered to 70 °C to obtain composite oil phases (OHS-1, OHS-2, OHS-4, OHS-5, OHS-6). The composite oil phases were kept at 70 °C for later use and subsequent performance tests were conducted.

[0038] Example 3 Preparation of composite phase change oil phases with different ratios The steps are basically the same as in Example 1, except that the ratio of 12-hydroxystearic acid to stearyl alcohol is different in step (1): (1) Add 5 g of 12-hydroxystearic acid and stearyl alcohol to a beaker containing 100 g of paraffin (controlling the mass ratio of 12-hydroxystearic acid to stearyl alcohol to be 1:5, 3:1, 1:3, 2:3, 2.5:3, 1:2, and 2:5 respectively), and heat the beaker in an oven at 90°C. After all the raw materials have melted and mixed, a colorless and transparent solution is obtained. Subsequently, the temperature is lowered to 70°C to obtain composite oil phases (OHS-7, OHS-8, OHS-9, OHS-10, OHS-11, OHS-12, and OHS-13). The composite oil phases are kept at 70°C for later use and subsequent performance tests are conducted.

[0039] Comparative Example 1 The steps are basically the same as in Example 1, except for step (1): (1) Add 3 g of 12-hydroxystearic acid to a beaker containing 100 g of paraffin wax and heat the beaker in an oven at 90 °C. After all the raw materials have melted and mixed, a colorless and transparent solution is obtained. Then, the temperature is lowered to 70 °C to obtain a composite oil phase (C18 / 12-HA).

[0040] Comparative Example 2 The steps are basically the same as in Example 1, except for step (1): (1) Add 3 g of stearyl alcohol to a beaker containing 100 g of paraffin and heat the beaker in an oven at 90 °C. After all the raw materials have melted and mixed, a colorless and transparent solution is obtained. Then, the temperature is lowered to 70 °C to obtain a composite oil phase (C18 / SA).

[0041] Performance testing of materials prepared in the examples and comparative examples: Significant differences were observed in the composite oil phases of the examples and comparative examples during the heating process. After temperature increases, OHS-3~6, OHS-8, OHS-10~11 in Examples 1-3 and Comparative Example 1-C18 / 12-HA maintained stability during heating. Specifically, Example 1-OHS-3 was found to completely melt at approximately 76 °C and maintain its shape stability between room temperature and 60 °C. Examples 2-OHS-1~2, Examples 3-OHS-9, OHS-7, OHS12~13, and Comparative Example 2-C18 / SA all melted into liquids during heating and could not maintain temperature stability near the melting point of paraffin. Through temperature stability testing and energy storage capacity comparison, composite oil phases OHS-3, 5, 10, and 11 with a phase change enthalpy >250 J / g and temperature stability were selected. Considering material costs and emulsification effects, a composite oil phase OHS-3 with a mass ratio of 1:1 of 12-hydroxystearic acid and stearyl alcohol and an addition amount of 4% of the paraffin mass was initially selected for encapsulation testing.

[0042] The scanning electron microscope image of the composite oil phase (OHS) prepared in Example 1 is shown below. Figure 1 As shown. At lower magnifications ( Figure 1 a) The material exhibits a continuous and dense overall morphology, with no signs of large-scale phase separation or component aggregation. This indicates that the mixing and curing process successfully fused the three components into a macroscopically homogeneous composite material. Irregular pores and undulations are visible on the material surface, which may be due to uneven solidification shrinkage of the components during cooling and crystallization from the molten state, as well as differences in the crystallization rate and shrinkage rate of different components.

[0043] At high multiples ( Figure 1 (b) Below, the surface exhibits a delicate, melted "creamy" or "layered rheological" texture, indicating the presence of a continuous amorphous / soft matrix within the system. This matrix is ​​composed of a network formed by intermolecular hydrogen bonds between 12-hydroxystearic acid and stearyl alcohol, exhibiting high fluidity during curing and encapsulating and filling the crystalline regions. Within the substrate, flaky or lumpy structures with indistinct boundaries, measuring several micrometers in size, are observed; these are the crystalline regions of paraffin (C18). The edges of the paraffin crystals are not sharp, indicating that their growth is significantly restricted by the surrounding hydrogen-bonded matrix, resulting in small crystal sizes and low perfection. The transition between the crystalline regions and the amorphous matrix is ​​smooth, without obvious cracks, demonstrating good compatibility among the components. The hydrogen bond network formed by the hydroxyl / carboxyl groups of 12-hydroxystearic acid and the hydroxyl groups of stearyl alcohol acts as a crucial "interfacial compatibilizer," effectively binding and encapsulating the non-polar paraffin crystalline regions within the continuous phase. SEM analysis visually reveals the microstructure of the composite oil phase, which provides a structural basis for its excellent comprehensive thermal properties.

[0044] The properties of the raw materials used in the examples and comparative examples and the phase change materials obtained were measured, and the results are shown in Tables 1 and 2.

[0045] Table 1. Raw materials used in the examples and comparative examples, and crystallinity tests of the resulting phase change materials. As shown in Table 1, among the individual components, stearyl alcohol (SA) has the highest crystallinity (89.20%) due to the strong hydrogen bonds formed by the hydroxyl groups at the molecular ends; paraffin (C18) is the second highest (86.00%); and 12-hydroxystearic acid (12-HA) has the lowest crystallinity (67.10%) because the hydroxyl groups in the middle of the molecular chain interfere with the tight packing, which to some extent inhibits the degree of crystallization.

[0046] The crystallinity of the comparative binary blend systems (61.30% and 74.40%) was significantly lower than that of single paraffin, indicating that the addition of small amounts of 12-HA and SA significantly reduced the crystallinity of the paraffin matrix. The two molecules interfered with each other during blending, reducing the orderliness of molecular packing and leading to a significant decrease in overall crystallinity. In contrast, the ternary composite oil phase of this invention (such as OHS-10 in Example 3) exhibited extremely high crystallinity (88.20%), higher than paraffin, close to the highest SA content among single components, and significantly higher than any binary blend. This demonstrates that combining paraffin, 12-hydroxystearic acid, and stearyl alcohol in a specific ratio can produce a unique synergistic effect. The hydrogen bond network formed by 12-hydroxystearic acid and stearyl alcohol provides a confined environment for the orderly arrangement of paraffin molecules, inducing the formation of a more complete crystal structure and achieving a crystallization strengthening effect. The phase change aerogel material (Example 1-FTOHS) obtained after emulsion polymerization and freeze-drying encapsulation still maintained a high degree of crystallinity (73.33%), indicating that the encapsulation / freeze-drying process did not destroy the highly crystalline structure already formed inside the composite oil phase.

[0047] Table 2. Energy storage capacity of phase change materials prepared in the examples and comparative examples. As shown in Table 2, when the total addition of stearyl alcohol and 12-hydroxystearic acid is controlled at 4%, 5%, 5.5%, and 10% of the paraffin mass (e.g., OHS-3, OHS-10, OHS-11, and OHS-5), the resulting ternary composite oil phases (OHS) all exhibit significant synergistic energy storage effects. Their measured enthalpy of melting is stable and significantly higher than the theoretical value calculated based on the weighted average of each component. The measured value for OHS-10 is approximately 30.84 J / g higher than the theoretical value. When the total mass of stearyl alcohol and 12-hydroxystearic acid increases to 10% of the paraffin mass (OHS-5), the measured enthalpy is 23.99 J / g higher than the theoretical value. This may be due to the further increase in SA content, which improves the measured enthalpy. As shown in Example 1-FTOHS, the final aerogel material (FTOHS) was obtained by encapsulation through emulsion polymerization (oil phase accounting for about 40%) and freeze drying, and it still maintained a high energy storage capacity (melting enthalpy 169.95 J / g).

[0048] Combining SEM morphology and crystallinity data, the ternary composite system described in this invention achieves a significant increase in phase transition energy storage capacity by enhancing the crystalline order of the material through intermolecular synergistic effects. This demonstrates that the ternary composite system of this invention is not a simple mixture, but rather forms a new structure with synergistic effects, and this synergistic effect is only exhibited within a specific range of additions. The hydrogen bond network between 12-HA and SA provides a better template or confined environment for the crystallization of C18, thereby inducing the formation of more complete crystals and releasing a higher latent heat of phase transition than when they exist alone.

[0049] like Figure 2 As shown, octadecane, as a single nonpolar molecule, relies mainly on weak van der Waals interactions. Stearyl alcohol (SA) and 12-hydroxystearic acid, on the other hand, possess strongly polar hydroxyl (-OH) and carboxyl (-COOH) groups, respectively. During the mixed melting and recrystallization process, a dense hydrogen bond network forms. In the infrared spectrum of the composite oil phase (OHS), the characteristic absorption peak of free hydroxyl groups is significantly weakened, while the absorption peak of associated hydroxyl groups (forming hydrogen bonds) broadens and shifts towards lower wavenumbers. This directly proves the formation of the hydrogen bond network. Disrupting this network requires absorbing more heat, leading to a significant increase in the phase transition enthalpy of the material. This result is corroborated by the good compatibility and lack of significant phase separation observed by scanning electron microscopy (SEM).

[0050] like Figure 3 As shown, octadecane, as a long-chain alkane, has a relatively simple crystallization process. The addition of octadecyl alcohol and 12-hydroxystearic acid allows the latter two to crystallize independently, and their polar head groups act as nucleation sites, inducing a more ordered and regular arrangement and folding of the octadecane molecular chains around them. This effectively reduces crystal defects, forming a denser and more complete mixed crystal structure. The number of molecules capable of phase transition per unit volume increases, and the enthalpy of phase transition rises. The XRD pattern of the mixture shows new diffraction peaks, and the intensity and position of the original diffraction peaks change, indicating the formation of a completely new, co-crystallized crystal phase.

[0051] like Figure 4 As shown, the oil-water mixed emulsion obtained after high-speed homogenization and emulsification was placed in a 70 °C oven and allowed to stand for 12 hours. No oil-water separation occurred, indicating that the resulting emulsion exhibited excellent stability. Based on this, emulsion polymerization was carried out, resulting in a phase change energy storage aerogel material (FTOHS). Figure 5 As shown, the material is solid, indicating that the polymerization process can effectively encapsulate the composite oil phase (OHS). After freeze-drying, a phase change energy storage aerogel material (FTOHS) is obtained, whose porous structure is beneficial for fully utilizing the heat storage capacity of the internal composite oil phase.

[0052] In summary, this invention prepares a stable composite oil phase with high energy storage capacity using paraffin, octadecyl alcohol, and 12-hydroxystearic acid, with a measured phase change enthalpy significantly higher than the theoretically calculated value. Furthermore, this high-energy-capacity oil phase is effectively encapsulated using an optimized emulsion polymerization process and then freeze-dried for shaping, ultimately yielding a paraffin-based phase change energy storage aerogel material (FTOHS) possessing high latent heat of phase change, excellent shape stability, and a porous, lightweight structure. The paraffin-based phase change material prepared by this invention solves, to some extent, the problems of poor stability and limited energy storage capacity of paraffin after heating, which hinder its application, opening up new avenues for paraffin in phase change material energy storage research, electronic devices, cold chain transportation for food packaging, textiles, and building thermal management.

[0053] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the present invention.

Claims

1. A paraffin-based phase change energy storage composition, characterized in that, include: Paraffin, stearyl alcohol, and 12-hydroxystearic acid; The total mass of stearyl alcohol and 12-hydroxystearic acid is 3% to 15% of the mass of the paraffin. The mass ratio of stearyl alcohol to 12-hydroxystearic acid is 5:1 to 2:

5.

2. The paraffin-based phase change energy storage composition according to claim 1, characterized in that, The microscopic surface has irregular pores and undulations, with an amorphous continuous phase enveloping micron-sized sheet-like or nodular paraffin crystal regions, and the transition between the crystal regions and the continuous phase is smooth.

3. The paraffin-based phase change energy storage composition according to claim 1, characterized in that, The paraffin wax is selected from C10-C20 straight-chain alkanes, branched-chain alkanes, and cycloalkanes; And / or, the enthalpy of fusion of the paraffin-based phase change energy storage composition is not less than 230 J / g, and the measured value of the enthalpy of fusion is higher than the theoretical value; And / or, the paraffin-based phase change energy storage composition remains shape-stable and non-flowing at 60°C.

4. The method for preparing the paraffin-based phase change energy storage composition according to any one of claims 1-3, characterized in that, Stearyl alcohol, 12-hydroxystearic acid and paraffin are mixed and heated to melt, thus obtaining the paraffin-based phase change energy storage composition.

5. A composite phase change material, characterized in that, include: Core: The paraffin-based phase change energy storage composition according to any one of claims 1-3; Encapsulation layer: A polymer shell that encapsulates the core; the polymer shell is formed by emulsion polymerization of water-soluble monomers and oil-soluble monomers; The composite phase change material retains shape stability at temperatures above the melting point of paraffin.

6. The method for preparing the composite phase change material according to claim 5, characterized in that, Including the following steps: S1. Preparation of aqueous precursor solution: Mix emulsifier, water-soluble monomer and water evenly; S2. Preparation of oil-phase precursor solution: The paraffin-based phase change energy storage composition, oil-soluble monomer and crosslinking agent are mixed evenly; S3. The oil-phase precursor solution and the aqueous-phase precursor solution are mixed and homogenized and emulsified to obtain an oil-water emulsion; S4. Polymerization: An initiator is added to the oil-water emulsion to carry out emulsion polymerization to obtain the composite phase change material.

7. The preparation method according to claim 6, characterized in that, The water-soluble monomer is selected from one or a combination of N,N-dimethylacrylamide, acrylamide, polyethylene glycol methacrylate, polyethylene glycol diacrylate, N-vinylpyrrolidone, acrylic acid, hydroxyethyl methacrylate, hydroxyethyl acrylate, N-isopropylacrylamide, and dimethylaminoethyl methacrylate. And / or, the oil-soluble monomer is selected from at least one of lauryl methacrylate, octadecyl methacrylate, lauryl acrylate, isooctyl acrylate, butyl acrylate, n-butyl methacrylate, styrene, and cyclohexyl methacrylate.

8. The preparation method according to claim 6, characterized in that, In step S1, the emulsifier is selected from one or a combination of polyvinyl alcohol and polyvinylpyrrolidone; And / or, in step S2, the crosslinking agent is ethylene glycol dimethacrylate; And / or, in step S3, the homogenization emulsification time is 1-10 minutes; And / or, in step S4, the reaction temperature of the emulsion polymerization is 60-80°C.

9. A composite phase change aerogel, characterized in that, The composite phase change aerogel is prepared by freeze-drying; the enthalpy of melting of the composite phase change aerogel is not less than 160 J / g.

10. The application of the paraffin-based phase change energy storage composition according to any one of claims 1-4, the composite phase change material according to any one of claims 5-8, and the composite phase change aerogel according to claim 9 in the field of thermal management, including new energy vehicles, electronic communications, green buildings, and smart textiles.

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