Reversible thermochromic phase change capsule heat storage material and preparation method thereof
A reversible thermochromic phase change capsule coated with calcium alginate was prepared by ion exchange reaction of sodium alginate and calcium chloride. This solved the problems of uneven temperature and high molecular polymer in traditional phase change thermal storage materials, and achieved adjustable capsule particle size, uniform heat distribution and efficient photothermal conversion.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- HEBEI UNIV OF TECH
- Filing Date
- 2025-12-18
- Publication Date
- 2026-05-12
Smart Images
Figure CN122012026A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of thermochromic phase change energy storage capsule coating technology, and in particular to a method for preparing a reversible thermochromic phase change capsule heat storage material using calcium alginate as the wall material to coat a thermochromic phase change material supported by sodium alginate as the matrix. Background Technology
[0002] Solar thermal utilization suffers from intermittency, fluctuations, and low energy density due to weather conditions. Phase change thermal storage materials (PCS) offer advantages such as high thermal density, near-constant temperature during the phase change process, and good stability. Based on these advantages, applying PCS to solar thermal storage technology allows for the storage of solar energy as thermal energy, which can then be output as continuous, stable, and high-energy-density thermal energy, effectively improving energy utilization efficiency. However, traditional PCS thermal storage methods, which introduce photothermal conversion nanoparticles into PCS materials, suffer from problems such as high surface temperatures and uneven temperature distribution.
[0003] Thermochromic phase change materials, composed of chromophores, color developers, and phase change solvents, can respond to temperature changes and adjust the dynamic synergistic conversion of photothermal energy: at low temperatures, they exhibit a dark-colored system with strong light absorption; at high temperatures, they exhibit a transparent and colorless system with strong light transmission. Based on these advantages, thermochromic phase change materials can ensure uniform internal temperature, reduce heat dissipation loss, and improve energy utilization efficiency.
[0004] Based on the phase transition characteristics of solid-liquid phase change materials, thermochromic phase change materials undergo a solid-liquid phase transition when the temperature reaches the phase transition range of the solvent, leading to leakage. To address this issue, most thermochromic phase change materials are encapsulated using physicochemical methods with polymers such as melamine-formaldehyde resin (MF), polymethyl methacrylate (PMMA), and polystyrene (PS). However, these polymers have high requirements for polymerization conditions and raw materials, and suffer from problems such as high toxicity, low degradability, and raw material residues, severely limiting the application of thermochromic phase change capsules. Therefore, this paper selects the natural biopolymer alginate as the matrix material and uses a drip-feeding method to inject the core material with calcium chloride solution containing Ca. 2+ A reversible thermochromic phase change capsule coated with calcium alginate was prepared by an ion exchange reaction. Summary of the Invention
[0005] This invention aims to solve the problems existing in the above-mentioned technologies and provides a reversible thermochromic phase change capsule heat storage material and its preparation method. The reversible thermochromic phase change capsule of this invention consists of two parts: an alginate-based matrix supporting a thermochromic phase change material and a transparent calcium alginate shell. An alginate / thermochromic phase change material co-emulsion serves as the core material, and the alginate reacts with calcium chloride (CaCl2) solution at the outer interface. 2+Calcium alginate, formed through an ion exchange reaction, is used as a transparent shell material to coat the core material.
[0006] The technical solution adopted by the present invention to solve the aforementioned technical problem is: a reversible thermochromic phase change capsule heat storage material, the materials required for its preparation include: thermochromic phase change material, 1%-2.5% by mass of alginate solution, nonionic surfactant and calcium chloride solution with a mass fraction of more than 20%.
[0007] Furthermore, the thermochromic phase change material is composed of 1.56% 3,3-bis(4-dimethylaminophenyl)-6-dimethylaminophenyl peptide (CVL), a color-developing agent that determines the color; 4.69% 2,2-bis(4-hydroxyphenyl)propane (BPA), a color-developing agent that determines the color depth; and 93.75% tetradecyl alcohol (TD), a solvent that determines the color change temperature range.
[0008] Furthermore, sodium alginate from alginate sources was selected to prepare an alginate solution with a mass fraction of 1%-2.5%, and polysorbate-80 from polysorbates was used as a surfactant. Polysorbate-80 was emulsified with the aforementioned thermochromic phase change material to form a sodium alginate-based thermochromic phase change emulsion, which served as the core material for the thermochromic phase change capsule. Simultaneously, sodium alginate also reacted with Ca in a calcium chloride solution... 2+ Calcium alginate is generated through an ion exchange reaction and used as the wall material for thermochromic phase change capsules.
[0009] Furthermore, 3,3-bis(4-dimethylaminophenyl)-6-dimethylaminophenyl peptide (C 26 H 29 N3O2, CAS: 1552-42-7), 2,2-bis(4-hydroxyphenyl)propane (C 15 H 16 O2, CAS: 80-05-7), tetradecanol (C 14 H 30 O, CAS: 112-72-1), sodium alginate (C6H7NaO6, CAS: S817374), polysorbate-80 (C 24 H 44 O6(C2H4O) n The anhydrous calcium chloride (CaCl2, CAS: 10043-52-4) was purchased from Shanghai Maclean Biochemical Technology Co., Ltd., and was not treated in any other way. Deionized water was prepared in-house using a laboratory ultrapure water system (GC-B-60L) manufactured by Shenzhen Guangchuan Environmental Protection Technology Co., Ltd.
[0010] Furthermore, the preparation method of the above-mentioned reversible thermochromic phase change capsules includes the preparation of the core material thermochromic phase change material, the preparation of the shell material sodium alginate solution, the preparation of the reversible thermochromic phase change emulsion and CaCl2 solution, and the drop-casting of the reversible thermochromic phase change emulsion into spheres. The specific experimental steps are as follows: Further, (1) Preparation of thermochromic phase change material: The tetradecanol was heated in a constant temperature oil bath until it melted into a clear and transparent oil phase; then 3,3-bis(4-dimethylaminophenyl)-6-dimethylaminophenyl peptide and 2,2-bis(4-hydroxyphenyl)propane were added in sequence; then the magnetic stirrer was turned on and stirred until there were no obvious particles in the mixed solution, and a clear and transparent reversible thermochromic phase change material was obtained.
[0011] Further, (2) Preparation of sodium alginate solution for shell material: Add sodium alginate powder to a beaker containing deionized water and stir in a constant temperature oil bath; then maintain the stirring rate and cool naturally to room temperature; then stir at room temperature until completely dissolved into a clear sodium alginate solution.
[0012] Further, (3) Preparation of reversible thermochromic phase change emulsion: After adding the materials obtained in steps (1) and (2) above into a beaker, polysorbate-80 is added, and the emulsion is stirred in a constant temperature oil bath to obtain a core material reversible thermochromic phase change emulsion.
[0013] Further, (4) Preparation of calcium chloride solution: Add calcium chloride particles to a beaker containing deionized water and stir at room temperature until completely dissolved. Then filter the resulting solution through a vacuum filter to obtain a clear and transparent CaCl2 solution without impurities.
[0014] Further, (5) the reversible thermochromic phase change emulsion is dripped into spheres: the reversible thermochromic phase change emulsion obtained in step (3) above is loaded into a drip syringe, and then the speed and height of the pusher are adjusted so that it is dripped evenly into the CaCl2 solution obtained in step (4) above. The sphere-forming phase change emulsion is then crosslinked in the CaCl2 solution and taken out to obtain a wet reversible thermochromic phase change capsule.
[0015] Furthermore, the obtained product is filtered using a vacuum filtration device, washed with deionized water, and dried in an oven to obtain the dried reversible thermochromic phase change capsule.
[0016] Furthermore, by adopting the above-described technical solution, the present invention has the following beneficial technical effects: (1) This invention selects sodium alginate, a non-toxic, biodegradable, and low-cost natural biopolymer, as the matrix material for stabilizing thermochromic phase change materials. Simultaneously, sodium alginate is reacted with calcium chloride solution containing Ca... 2+ The ion exchange reaction can produce a transparent calcium alginate shell material.
[0017] (2) This invention is based on sodium alginate and Ca 2+ The ion exchange reaction was used to prepare reversible thermochromic phase change capsules via a dropwise method that is simple to operate, efficient, and produces high yields. Compared to traditional physicochemical preparation methods, the dropwise preparation method for reversible thermochromic phase change capsules in this invention is more efficient, produces capsules with more uniform particle size, and better integrity.
[0018] (3) Compared with traditional reversible thermochromic phase change microcapsules, the reversible thermochromic phase change capsules prepared in this invention can flexibly adjust the particle size. By changing the dropper with different diameters, the capsule particle size can be reduced from the centimeter level to the millimeter level or even the micrometer and nanometer level, which greatly expands its application scenarios.
[0019] (4) The reversible thermochromic phase change capsule prepared by the present invention can realize the color change with temperature. Specifically, it is blue-purple when it is below the phase change temperature, and as the temperature rises to the phase change range, it shows a gradual process of blue-purple to colorless; it is colorless and transparent when it is above the phase change temperature; and it slowly returns to blue-purple during the cooling process. It exhibits good reversible color change characteristics, and can still maintain this reversible thermochromic characteristics after multiple heating and cooling.
[0020] (5) The photothermal conversion interface of the reversible thermochromic phase change capsule prepared by the present invention can be dynamically and automatically adjusted according to the thermochromic properties, which can achieve uniform temperature distribution, reduce heat loss, and improve photothermal conversion efficiency. Attached Figure Description
[0021] Figure 1 Particle size distribution of the reversible thermochromic phase change capsules prepared for Examples 1-4.
[0022] Figure 2 The surface morphology and cross-sectional view of the reversible thermochromic phase change capsule prepared for Example 1.
[0023] Figure 3 The thermochromic properties of the reversible thermochromic phase change capsule prepared for Example 1.
[0024] Figure 4 DSC curves of the reversible thermochromic phase change capsules prepared in Examples 1-4.
[0025] Figure 5 TG curves of the reversible thermochromic phase change capsules prepared in Examples 1-4. Detailed Implementation
[0026] The following embodiments of the present invention describe the preparation of reversible thermochromic phase change capsules using a dripping device. The device specifically includes an electric injection propulsion unit, a needle tip with a diameter of 1-2 mm, a 20-30 mL syringe, and a thin tubing. The syringe contains a reversible thermochromic phase change emulsion, which is connected to the needle tip via the thin tubing. The electric injection propulsion unit causes the thermochromic phase change emulsion to drip from the needle tip. The emulsion droplets fall into a CaCl2 solution, where an ion exchange reaction occurs, resulting in the formation of a calcium alginate shell on the surface of the phase change emulsion droplets, forming a coating.
[0027] Table 1. Experimental parameters for each example of the reversible thermochromic phase change capsule. Example 1
[0028] A reversible thermochromic phase change capsule heat storage material, the materials required for its preparation include: 7g of thermochromic phase change material (1.56% 3,3-bis(4-dimethylaminophenyl)-6-dimethylaminophenyl peptide (CVL); 4.69% 2,2-bis(4-hydroxyphenyl)propane (BPA); 93.75% tetradecanol (TD)), 49g of 2% sodium alginate solution, 0.35g of polysorbate-80 and 100mL of 20% calcium chloride solution.
[0029] The preparation method of the above-mentioned reversible thermochromic phase change capsules includes the preparation of the core material (thermochromic phase change material), the shell material (sodium alginate solution), the reversible thermochromic phase change emulsion, and the 20% (w / w) CaCl2 solution, as well as the drop-casting of the reversible thermochromic phase change emulsion into spheres. The specific experimental steps are as follows: (1) Preparation of thermochromic phase change material: The tetradecyl alcohol was heated in a constant temperature oil bath at 60°C until it melted into a clear and transparent oil phase; then 3,3-bis(4-dimethylaminophenyl)-6-dimethylaminophenyl peptide and 2,2-bis(4-hydroxyphenyl)propane were added in sequence; then magnetic stirring was turned on and stirred at a rate of 600 rpm until there were no obvious particles in the mixed solution, and a clear and transparent reversible thermochromic phase change material was obtained.
[0030] (2) Preparation of sodium alginate solution from shell material: Add sodium alginate powder to a beaker containing deionized water and stir at 2000 rpm for 2 hours at 60°C; then keep stirring and let it cool naturally to room temperature; then stir at room temperature for 12-18 hours until it is completely dissolved into a clear sodium alginate solution with a mass fraction of 2%.
[0031] (3) Preparation of reversible thermochromic phase change emulsion: After adding the materials obtained in steps (1) and (2) above into a beaker, polysorbate-80 is added, and the mixture is stirred at 1000 rpm for 1 h at 60°C to obtain a core material reversible thermochromic phase change emulsion with an oil-water ratio of 1:7.
[0032] (4) Preparation of calcium chloride solution: Add calcium chloride particles to a beaker containing deionized water and stir at 600 rpm at room temperature until completely dissolved. Then filter the resulting solution through a vacuum filter to obtain a clear and transparent 20% CaCl2 solution without impurities.
[0033] (5) Reversible thermochromic phase change emulsion droplet formation: The reversible thermochromic phase change emulsion obtained in step (3) above is loaded into a 2 mm droplet syringe. Then, the speed of the pusher is adjusted to 2 mm / min and the height is 10 cm, and it is evenly dropped into the CaCl2 solution obtained in step (4) above. The phase change emulsion formed into spheres is completely cross-linked in the CaCl2 solution for 2 h and then taken out to obtain a wet reversible thermochromic phase change capsule.
[0034] The obtained product was filtered using a vacuum filtration device, washed 2-3 times with deionized water, and dried at 50°C for 12 hours to obtain the dried reversible thermochromic phase change capsules.
[0035] Ten thermochromic phase change capsules in a moist state and ten in a dried state were randomly selected respectively. Their particle size was measured using electronic vernier calipers, and the average value was calculated. The capsule particle size distribution is plotted as follows: Figure 1 As shown.
[0036] A certain amount of thermochromic phase change capsules was spread evenly in a petri dish and heated on a 55°C heating platform. Images of the capsules at different temperatures were recorded using a mobile phone optical camera and an infrared thermal imager (Tix1060, Fluke, USA). Figure 2 As shown.
[0037] The phase change thermal storage performance of the reversible thermochromic phase change capsule in the temperature range of 0-80℃ was characterized using a differential scanning calorimeter (DSC214, Netzsch, Germany) under N2 atmosphere at a heating and cooling rate of 5℃ / min. The DSC curves of the reversible thermochromic phase change capsule are shown below. Figure 3 As shown.
[0038] The thermal stability of the reversible thermochromic phase change capsules in the temperature range of 30-600℃ was characterized using a simultaneous thermal analyzer (STA449F5, Netzsch, Germany) under N2 atmosphere at a heating rate of 10℃ / min. The TG curves of the reversible thermochromic phase change capsules are shown below. Figure 4 As shown. Example 2
[0039] The steps in this embodiment are the same as in embodiment 1, except that the oil-water ratio in this embodiment is 1:15. Example 3
[0040] The steps in this embodiment are the same as in Embodiment 1, except that the concentration of sodium alginate in this embodiment is 1%. Example 4
[0041] The steps in this embodiment are the same as in Embodiment 1, except that the pipe diameter in this embodiment is 1 mm. Also, to ensure that the outlet flow rate is consistent with that in Embodiment 1, the inlet flow rate is adjusted to 0.55 mm / min after calculation based on the inlet and outlet flow rate formulas.
[0042] like Figure 1 As shown, the particle size of the thermochromic phase change capsules after drying is smaller than that in the wet state. Examples 1 and 2 show that the particle size of the thermochromic phase change capsules decreases with increasing oil-to-water ratio; Examples 1 and 3 show that the sodium alginate concentration has no significant effect on the particle size of the thermochromic phase change capsules; Examples 1 and 4 show that the particle size of the thermochromic phase change capsules increases with increasing tube diameter.
[0043] like Figure 2 As shown, the color of the thermochromic phase change capsule gradually changes from blue-purple to colorless as the temperature increases; at the same time, no obvious leakage was observed during the heating process, indicating that the thermochromic phase change capsule has good thermal stability within this temperature range.
[0044] like Figure 3 As shown, the enthalpy of melting (ΔHm) and enthalpy of solidification (ΔHc) of the dried thermochromic phase change capsules in Example 1 are 101.4 J / g and 95.01 J / g, respectively, exhibiting excellent phase change energy storage performance. Examples 1 and 2 show that a higher oil-to-water ratio results in a higher enthalpy value and superior thermal performance for the thermochromic phase change capsules. Examples 1 and 3 show that the concentration of sodium alginate has little effect on the enthalpy value of the moist thermochromic phase change capsules; however, after drying, a higher concentration of sodium alginate results in a higher enthalpy value and superior thermal performance for the thermochromic phase change capsules. Examples 1 and 4 show that smaller particle size results in a higher enthalpy value and superior thermal performance for the thermochromic phase change capsules.
[0045] like Figure 4As shown, the thermochromic phase change capsule exhibits three stages during thermogravimetric analysis. In the first stage, as the temperature gradually increases, the moisture inside the thermochromic phase change capsule begins to evaporate. In the second stage, when the temperature reaches 156°C, the mixture of RTPCM and sodium alginate inside the thermochromic phase change capsule begins to lose weight, and the pyrolysis temperature of the internal mixture gradually increases with the increase of sodium alginate concentration. In the third stage, the transparent calcium alginate wall material on the outside of the thermochromic phase change capsule decomposes.
[0046] Although specific embodiments of the present invention have been described in detail with reference to the accompanying drawings, this should not be construed as limiting the scope of protection of this patent. Various modifications and variations that can be made by those skilled in the art without inventive effort within the scope described in the claims still fall within the scope of protection of this patent.
Claims
1. A reversible thermochromic phase change capsule heat storage material, characterized in that, The required raw materials include: thermochromic phase change material, 1%-2.5% by mass alginate solution, nonionic surfactant, and calcium chloride solution with a mass fraction of more than 20%; the reversible thermochromic phase change capsule heat storage material is prepared from the above raw materials. The thermochromic phase change material is composed of 1.56% by mass of 3,3-bis(4-dimethylaminophenyl)-6-dimethylaminophenyl peptide, a color-developing agent that determines the color. 4.69% by mass of 2,2-bis(4-hydroxyphenyl)propane, a color developer that determines the depth of color; The solvent in a 93.75% by mass alcohol phase change material determines the color change temperature range. The phase transition temperature of the alcohol phase change material is in the range of 36~72℃, and it is selected from n-tetradecyl alcohol, n-hexadecyl alcohol, n-octadecyl alcohol, n-eicosyl alcohol, or n-docosahexyl alcohol. The nonionic surfactant is a polysorbate, polyoxyethylene fatty acid ester, or polyoxyethylene fatty alcohol ether nonionic surfactant, with the polysorbate nonionic surfactant selected from polysorbate-80.
2. The reversible thermochromic phase change capsule as described in claim 1, characterized in that, The core material of the reversible thermochromic phase change capsule is the thermochromic phase change material emulsified with polysorbate-80 and a sodium alginate-based thermochromic phase change emulsion; the wall material of the reversible thermochromic phase change capsule is Ca in a sodium alginate and calcium chloride solution. 2+ It undergoes an ion exchange reaction to produce calcium alginate.
3. The preparation method of a reversible thermochromic phase change capsule thermal storage material as described in claim 1, characterized in that, The preparation of the core material (thermochromic phase change material), the shell material (sodium alginate solution), the reversible thermochromic phase change emulsion, and the CaCl2 solution, as well as the drop casting of the reversible thermochromic phase change emulsion into spheres, are described in detail below. (1) Preparation of thermochromic phase change material: The tetradecanol was heated in a constant temperature oil bath until it melted into a clear and transparent oil phase; then 3,3-bis(4-dimethylaminophenyl)-6-dimethylaminophenyl peptide and 2,2-bis(4-hydroxyphenyl)propane were added in sequence; then the magnetic stirrer was turned on and stirred until there were no obvious particles in the mixed solution, and a clear and transparent reversible thermochromic phase change material was obtained. (2) Preparation of sodium alginate solution for shell material; (3) Preparation of reversible thermochromic phase change emulsion: After adding the materials obtained in steps (1) and (2) above into a beaker, polysorbate-80 is added, and the emulsion is stirred in a constant temperature oil bath to obtain a core material reversible thermochromic phase change emulsion. (4) Preparation of calcium chloride solution; (5) Reversible thermochromic phase change emulsion droplet formation: The reversible thermochromic phase change emulsion obtained in step (3) above is loaded into a droplet syringe. Then, the speed and height of the pusher are adjusted so that it is evenly dropped into the CaCl2 solution obtained in step (4) above. The phase change emulsion formed into spheres is then crosslinked in the CaCl2 solution and taken out to obtain a wet reversible thermochromic phase change capsule. (6) The obtained product is filtered by a vacuum filtration device, washed with deionized water, and dried in an oven to obtain the dried reversible thermochromic phase change capsule.
4. The preparation method according to claim 3, characterized in that: (2) Preparation of sodium alginate solution for shell material: Add sodium alginate powder to a beaker containing deionized water and stir in a constant temperature oil bath; then keep stirring and let it cool naturally to room temperature; then stir at room temperature until it is completely dissolved into a clear sodium alginate solution. (4) Preparation of calcium chloride solution: Add calcium chloride particles to a beaker containing deionized water and stir at room temperature until completely dissolved. Then filter the resulting solution through a vacuum filter to obtain a clear and transparent CaCl2 solution without impurities.
5. The preparation method according to claim 4, characterized in that, In step (1), the oil bath temperature needs to be 10-20°C higher than the melting point temperature of the alcohol phase change material, the magnetic stirring speed is 300-600 rpm, and the magnetic stirring rotor is C-type. .
6. The preparation method according to claim 5, characterized in that, In step (2), the oil bath temperature is 50-60℃, the magnetic stirring speed is 2000-2500rpm, and the stirring time is 2-3h; when cooling down, the oil bath is naturally cooled to room temperature in the oil bath with the power off, and the stirring time after cooling to room temperature is 12-18h.
7. The preparation method according to claim 6, characterized in that, In step (3), the oil bath temperature is 50-60℃, the magnetic stirring speed is 1000-1500rpm, and the stirring time is 1-2h.
8. The preparation method according to claim 7, characterized in that, In step (4), the magnetic stirring speed is 300-600 rpm.
9. The preparation method according to claim 3, characterized in that, In step (5), the size of the drip needle is 0.5-2 mm, the speed of the pusher is 0.5-2 mm / min, the drip height is 10-30 cm, and the cross-linking time is 2-3 h.
10. The preparation method according to claim 3, characterized in that, In step (6), the washing is performed 2-3 times, the drying temperature is 50-60℃, and the drying time is 12-14h.