Heat-insulating composite phase change material as well as preparation method and application thereof
By constructing biomass aerogels based on chitosan (CS) and carboxylated nanocellulose (CNF), and combining them with hydroxyapatite (HAP) and montmorillonite (MMT), a dual-insulation composite phase change material with excellent thermal insulation performance and infrared stealth function was prepared. This solved the problem of easy permeability of aerogel materials and achieved efficient thermal management and liquid leakage protection.
Patent Information
- Application Number
- CN202610176682.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-02-06
- Publication Date
- 2026-05-19
AI Technical Summary
Existing aerogel materials are easily permeated by water or oil, which impairs their thermal insulation and mechanical properties, limiting their practical applications.
Chitosan (CS), carboxylated nanocellulose (CNF), konjac glucomannan (KGM), and sodium alginate (SA) were used as the aerogel framework matrix, combined with hydroxyapatite (HAP) and montmorillonite (MMT) to construct a biomass aerogel with both high thermal insulation performance and an ordered pore structure. Paraffin wax (PW) was used as the phase change thermal storage material to prepare a dual-insulation composite phase change material.
It achieves good biocompatibility, thermal stability and cycle stability, has excellent thermal insulation and infrared stealth performance, low thermal conductivity and high adsorption capacity, and is suitable for liquid leakage risk applications in extreme environments.
Smart Images
Figure CN122060463A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of composite phase change materials with reversible thermochromic properties, specifically a thermally insulating composite phase change material, its preparation method, and its application. Background Technology
[0002] Organic phase change materials (PCMs) possess high thermal energy storage density and constant transition temperature. Combining PCMs with insulating materials can yield insulating composite PCMs. For example, existing literature 1 (Polyvinyl SAcoholcomposite aerogel with remarkable flame retardancy, chemic SA durability and self-cleaning property 10.1016 / j.coco.2019.07.003) reports a mechanically robust scalycite / wood fiber composite aerogel with insulating properties. The resulting composite aerogel exhibits high mechanical strength, low thermal conductivity, and exceptional fire resistance. However, due to their high porosity, most aerogel materials are easily permeated by water or oil, which impairs their thermal insulation and mechanical properties, further limiting their practical applications.
[0003] To address the issue that most aerogel materials are easily permeated by water or oil, thus compromising their thermal insulation and mechanical properties, existing literature 2 (Mechanic SAly resistant and sustainable cellulose-based composite aerogels with excellent flame retardant, sound-absorption, and superantiwetting ability for advanced engineering materials SA 10.1021 / acssuschemeng.7b03281) describes a flame-retardant, sound-absorbing, and mechanically reinforced aluminum hydroxide nanoparticle composite aerogel. The composite aerogel exhibits superhydrophobicity and oleophobicity. Currently, research on aerogels with super-two-phase properties (water and oil contact angles both greater than 150°) is limited, which is crucial for self-cleaning properties. Therefore, developing aerogel materials with low thermal conductivity, good mechanical strength, and excellent water and oil repellency is highly valuable for applications where liquid leakage risks exist in certain extreme situations.
[0004] To develop aerogel composite phase change materials with low thermal conductivity, good mechanical strength, low cost, and excellent waterproof and oil-resistant properties, existing literature 3 (High-strength and superamphiphobic chitosan-based aerorogels for thermSA insulation and flame retardant applications 10.1016 / j.colsurfa.2022.129663) describes that the incorporation of the low-cost inorganic filler montmorillonite (MMT) can significantly improve the thermal insulation and flame retardant properties of aerogels. The pore layout of the aerogel effectively affects the thermal insulation performance. Directional freezing, as a special technique, can precisely control the freezing process and determine the arrangement of pores. After freeze-drying, it exhibits excellent thermal insulation performance in a specific direction and can also effectively enhance the mechanical properties of the aerogel. Summary of the Invention
[0005] The purpose of this invention is to address the shortcomings of existing technologies by proposing a thermally insulating composite phase change material, its preparation method, and its applications. This composite phase change material exhibits good biocompatibility, excellent thermal stability and cycle stability, and good heat storage performance per unit mass.
[0006] The technical solution to achieve the objective of this invention is: A thermally insulating composite phase change material is prepared by selecting one or two components from chitosan (CS), carboxylated nanocellulose (CNF), konjac glucomannan (KGM), and sodium alginate (SA) as the aerogel framework matrix through structural design, and introducing thermally insulating functional units hydroxyapatite (HAP) and montmorillonite (MMT) to construct a biomass aerogel with high thermal insulation performance, high adsorption capacity, and ordered pore structure. At the same time, paraffin wax (PW) is used as the phase change thermal storage material to prepare a dual thermally insulating composite phase change material.
[0007] An application of a thermal insulation composite phase change material, wherein the thermal insulation composite phase change material has dual thermal insulation properties.
[0008] An application of a thermal insulation composite phase change material, wherein the application includes the thermal insulation composite phase change material simultaneously possessing thermal insulation properties, infrared stealth properties, and phase change properties.
[0009] The aforementioned thermal insulation performance, when used as a thermal insulation material, is observed using an infrared thermal imager at 80°C for the first 2-3 minutes. Only the bottom of the thermal insulation composite phase change material is reddish-yellow; after 2 hours of heating, the reddish-yellow color at the bottom of the thermal insulation composite phase change material does not show obvious longitudinal extension.
[0010] The aforementioned infrared stealth performance means that when used as a heat insulation material, it also possesses infrared stealth properties. Under normal temperature conditions, if the composite phase change material is placed in the palm of the hand for 10 minutes and heated by the temperature of the palm, and observed through an infrared thermal imager, the color of the composite phase change material under the infrared thermal imager is not significantly different from the color of the external environment, and it blends into the external environment, thus possessing infrared stealth performance.
[0011] The phase change properties, i.e. when used as a phase change material, are a phase change temperature of 44.12-59.56℃, a phase change enthalpy of 155.85-176.34 J / g, and a thermal conductivity of 0.1045-0.2702 W / m·K.
[0012] A method for preparing a thermally insulating composite phase change material includes the following steps: Step 1, preparation of hybrid thermal insulation aerogel: First, under certain conditions, CNF, HAP or KGM, SA or CS, MMT are diluted in deionized water and magnetically stirred to obtain a homogeneous mixed solution. Then, 0.5wt.%-1wt.% MMT, 0.75wt.%-1.25wt.% SA, and 0.75wt.%-1wt.% HAP are added to the corresponding mixed solutions and stirred to obtain an aerogel precursor solution. Finally, under certain conditions, the aerogel is first directionally frozen and then freeze-dried to obtain a structurally stable hybrid thermal insulation aerogel. Step 2, preparation of composite phase change material with thermal insulation function: the hybrid thermal insulation aerogel obtained in step 1 is placed in PW for vacuum impregnation and adsorption at an impregnation and adsorption temperature of 75℃ and an impregnation and adsorption time of 24 h to obtain a double thermal insulation composite phase change material.
[0013] The drying conditions for the hybrid thermal insulation aerogel are as follows: directional freezing followed by freeze-drying; the directional freezing temperature is -30℃, and the freezing time is 12 h; the freeze-drying temperature is -50℃, and the freeze-drying time is 72-96 h. This technical solution selects one or two of chitosan (CS), carboxylated nanocellulose (CNF), konjac glucomannan (KGM), and sodium alginate (SA) as the biomass hybrid aerogel framework matrix, and uses hydroxyapatite (HAP) or montmorillonite (MMT) as the thermal insulation functional units. The basic principles involved are: one, 1. Carboxylated cellulose nanoparticles (CNF) Advantages: Carboxylated nanocellulose (CNF), derived from wood fibers, is a natural polymer material and a flexible material that has attracted widespread attention due to its cost-effectiveness, renewability, non-toxicity, and biodegradability. Cellulose-based foams or aerogels have been extensively studied as insulation materials over the past few decades, hence their selection as the matrix for this system.
[0014] Disadvantages: While cellulose-based foams or aerogels are promising insulation materials due to their low thermal conductivity, cellulose is inherently flammable, posing a public safety concern. Therefore, it is necessary to ensure the safe use of cellulose foams.
[0015] 2. Hydroxyapatite (HAP) Advantages: Hydroxyapatite (HAP) is the main inorganic component of bones and teeth in vertebrates and is abundant in nature; it is also an inorganic material and is not easily flammable; the presence of phosphorus promotes the stability of the carbon shell, and it also contains Ca, O, and PH elements, which will generate a protective shell of Ca when burned.
[0016] Disadvantages: Poor solubility 3. Montmorillonite MMT Montmorillonite is a natural silicate mineral and the main mineral component of bentonite ore. It contains 16.54% SA₂O₃, 4.65% MgO, and 50.95% SiO₂. Its structural formula is (SA,Mg)₂[SiO₁₀](OH)₂·nH₂O. It is also a biomass material, an inorganic material, with low thermal conductivity, is completely non-flammable, and has some hydrophobicity.
[0017] The approach is as follows: Since CNF is used as the matrix and CNF is a flammable material, HAP was developed to solve this problem; MMT was developed to solve the problem that the aerogel formed by combining CNF and HAP will change shape during the flame retardant process, and to protect its internal skeleton. two, 1. The microstructure of CS is needle-like, thus possessing a high aspect ratio and high specific surface area; the incorporation of the low-cost inorganic filler montmorillonite (MMT) can significantly improve the thermal insulation and flame retardant properties of the aerogel. 2. Chitosan (positively charged) and sodium alginate (negatively charged) form polyelectrolyte complexes (such as gels or microspheres) through electrostatic interactions. Chitosan and montmorillonite (negatively charged): Combined through ionic and hydrogen bonds, chitosan can insert into the interlayer structure of montmorillonite or coat its surface. Sodium alginate and montmorillonite: Carboxylate groups undergo ion exchange with cations in montmorillonite (such as Na⁺, Ca²⁺), embedding themselves into the interlayer structure.
[0019] 3. CS, MMT, and SA can form hydrogen bonds with PW to prevent PW leakage.
[0020] 4. The lamellar structure of montmorillonite can be used as a reinforcing filler to improve the mechanical strength and thermal stability of the material. The flexible chains of chitosan and sodium alginate complement the rigid lamellar structure of montmorillonite, forming a three-dimensional network structure. Therefore, the thermal insulation composite phase change material has stable performance and can withstand certain compression and external forces. three, The binding mechanism between konjac glucomannan (KGM) and hydroxyapatite (HAP): 1. Ionic Crosslinking (Dominant Role): KGM: Under alkaline conditions (usually provided by sodium carbonate, etc.), KGM undergoes deacetylation, exposing a large number of hydroxyl groups (-OH) and carboxylate ions (-COO⁻). HAP: Its surface is rich in calcium ions. Bonding Mechanism: Strong ionic bonds are formed between the -COO⁻ on the negatively charged KGM chains and the positively charged calcium ions on the HAP surface. This is equivalent to building countless "nanobridges" between the long molecular chains of KGM, greatly enhancing the mechanical strength of the network. This effect is very similar to the process by which sodium alginate forms "tofu" when it encounters calcium ions.
[0022] 2. Hydrogen bonding: The numerous -OH and -OH groups on the KGM molecular chain can form a dense network of hydrogen bonds with the -OH and PO4³⁻ groups on the HAP surface. This further strengthens the interfacial bond between the two.
[0023] Compared with existing technologies, this technical solution has the following advantages: 1. By using one or two of the following materials with mechanical properties and biocompatibility—chitosan (CS), carboxylated nanocellulose (CNF), konjac glucomannan (KGM), and sodium alginate (SA)—as the biomass aerogel framework matrix, and hydroxyapatite (HAP) and montmorillonite (MMT) as thermal insulation functional units, a low-cost biomass hybrid aerogel material with both high adsorption capacity and ordered pore structure was successfully constructed. Therefore, it has good biocompatibility and structural stability.
[0024] 2. The thermal insulation composite phase change material with infrared stealth function prepared by this technical solution has excellent thermal insulation performance, structural stability, thermal stability and cycle stability. 3. The phase change material has a melting enthalpy of 155.09-168.32 J / g and a crystallization enthalpy of 155.85-168.33 J / g, exhibiting good heat storage performance per unit mass. Attached Figure Description
[0025] Figure 1 The FTIR spectra of CM, CMA and their components in Experiment 1 are shown. Figure 2 SEM images of CMA-0.75, CMA-1, and CMA-1.25 from Experiment 1; Figure 3 The image shows the leakage resistance test results of the composite phase change material CMA-PW in Experiment 1. Figure 4 Infrared thermal imaging test images of CMA and CMA-PW in Experiment 1; Figure 5 The DSC test results for CMA-90 in Experiment 1; Figure 6 The stress-strain curves for CMA-1.25, CMA-1, and CMA-0.75 in Experiment 1 are shown. Figure 7 The graph shows the DSC 100-cycle test result of CMA-90 in Experiment 1. Figure 8 The thermal conductivity diagrams for PW, CMA-1.25, CMA-1, and CMA-0.75 in Experiment 1 are shown. Figure 9 The image shows the infrared stealth performance test results of the CMA-90 in Experiment 1. Figure 10 The deformation test diagram of the weight applied to the CMA-1 in Experiment 1; Figure 11 The FTIR plots of CNF, CNF-HAP, and CHM from Experiment 2; Figure 12 The image shows the leakage resistance test results of the composite phase change material CHM-PW in Experiment 2. Figure 13 Infrared thermal imaging test images of CHM and CHM-PW in Experiment 2; Figure 14 The DSC test results are from Experiment 2. Figure 15 The graph shows the DSC 100-cycle test results of CHM-95 in Experiment 2. Figure 16 The image shows the infrared stealth performance test results of the CHM-95 in Experiment 2. Figure 17 The FTIR plots of KGM, SA, HAP, and KSH in Experiment 3; Figure 18 The image shows the leakage resistance test results of the composite phase change material KSH-PW in Experiment 3. Figure 19 Infrared thermal imaging test images of KSH and KSH-PW in Experiment 3; Figure 20 The DSC test results are from Experiment 3. Figure 21 The graph shows the DSC 100-cycle test results of KSH-95 in Experiment 3. Figure 22 This is a test image of the infrared stealth performance of the KSH-95 in Experiment 3. Detailed Implementation
[0026] The present invention will be further described below with reference to the accompanying drawings and embodiments, but this is not intended to limit the scope of the invention. Example
[0027] Experiment 1: In this example, to investigate the optimal proportion of sodium alginate (SA) component, CMA-0.75 with an SA content of 0.75 wt.%, CMA-1 with 1 wt.%, and CMA-1.25 with 1.25 wt.% were prepared. SEM testing revealed that, as... Figure 2 As shown, 1 wt.% of CMA-1 forms a dense and stable lamellar structure. Furthermore, combined with... Figure 6 The stress-strain curves revealed that CMA-1 exhibited the best mechanical properties. Finally, through... Figure 10 The macroscopic weight test of CMA-1 showed no compression. Finally, as... Figure 8 As shown in Table 2, CMA-1 has the lowest thermal conductivity, therefore CMA-1 was selected as the substrate aerogel for the composite phase change material in this example.
[0028] Figure 1 For FTIR testing, CS, CM, and CMA represent CS chitosan aerogel, CM chitosan-montmorillonite aerogel, and CMA chitosan-montmorillonite-sodium alginate aerogel, respectively; cs, mm, and SA represent the infrared testing of single powdered components CS (chitosan), mmt (montmorillonite), and SA (sodium alginate), respectively. A method for preparing a composite phase change material with chitosan CS and montmorillonite MMT as the base material is disclosed. This method employs a one-step physical casting approach, where the raw materials chitosan CS, montmorillonite MMT, sodium alginate SA, and paraffin PW meet a mass ratio of 7:3:1:50, i.e., the amount of PW added is 90 wt.%. The specific steps include: Step 1, Preparation of CMA aerogel: First, CS and MMT are diluted in deionized water and magnetically stirred for 3-4 h at a stirring temperature of 20-30℃ to obtain a CM solution. Then, sodium alginate (SA) with a concentration of 1 wt.% is added to the CM solution and stirring is continued to obtain a CMA solution. Finally, the CMA solution is first subjected to directional freezing at a freezing temperature of -30℃ for 12 h to obtain a CMA solid gel. The CMA solid gel is then freeze-dried at a freezing temperature of -50℃ for 72 h to obtain a CMA aerogel. Step 2, preparation of thermal insulation composite phase change material with thermal insulation function: with an impregnation and adsorption temperature of 75℃ and an impregnation and adsorption time of 24 h, the CMA aerogel obtained in step 1 is placed in PW for vacuum impregnation and adsorption, and CMA-PW with chitosan CS and montmorillonite MMT as the base materials can be obtained. The obtained CMA-PW is simply referred to as CMA-90 because the amount of PW added is 90 wt.%.
[0029] To verify the PW content, a weighing test was conducted before and after adsorption. The test results showed that the mass of CMA aerogel was 3.71 g, the mass of added PW was 22.79 g, and the mass of the final CMA-90 was 26.5 g. Therefore, it can be calculated that the added PW was completely adsorbed by the CMA aerogel, i.e., the adsorption amount was 90 wt.%.
[0030] To demonstrate that CMA-90 possesses heat insulation properties, a heating test was conducted. The test results are as follows: Figure 4 As shown, When CMA-90 is used as a thermal insulation material, at 80℃, it was observed with an infrared thermal imager at the very beginning of the observation period. Only the bottom of the thermal insulation composite phase change material was reddish-yellow. After 2 hours of heating, the reddish-yellow color at the bottom of the thermal insulation composite phase change material did not show obvious longitudinal extension. Test results show that CMA-90 possesses thermal insulation properties, with its thermal insulation filler playing a crucial role. Furthermore, under external environmental conditions of 80℃, when the phase change material undergoes solid-liquid and liquid-solid phase transitions at the set phase change temperature, it absorbs / releases a significant amount of latent heat. During the phase change process, the material's own temperature remains essentially constant, storing excess environmental heat and releasing it at lower temperatures, thus actively offsetting temperature fluctuations. Therefore, the phase change material maintains a consistently low temperature, exhibiting dual thermal insulation properties: thermal insulation from the thermal insulation filler combined with phase change heat storage and insulation.
[0031] To verify the composition of CMA-90, FTIR testing was performed, such as... Figure 1 As shown, CMA aerogel and its components chitosan (CS), montmorillonite (MMT), and sodium alginate (SA) have the same characteristic peaks. CMA was successfully prepared by one-step physical casting after mixing and stirring the solutions of the above components. Furthermore, CS, MMT, and SA are chemically bonded, and no new substances are generated. The test results show that there is no chemical reaction in the bonding process of CMA aerogel, and the preparation of phase change material is only physical adsorption. That is, CMA-90 has no effect on the crystallization behavior of PW, which can ensure that the composite phase change material has good heat storage capacity.
[0032] To demonstrate the packaging performance of CMA-90, a leak prevention test was conducted. For comparison, a leak prevention test was also performed on the PW sample. The specific test method for the leak prevention test involved heating the sample to be tested at a temperature of 80°C for 120 minutes.
[0033] The test results of PW are as follows Figure 3 As shown, PW melts and flows outwards; The test results of CMA-90 are as follows: Figure 3 As shown, CMA-90 showed no significant change; Test results show that the prepared CMA-90 can effectively prevent PW leakage.
[0034] To demonstrate the phase transition performance of CMA-90, DSC testing was conducted, such as... Figure 5 As shown, a DSC test was also performed on the PW for comparison.
[0035] PW test results are as follows Figure 5 As shown in Figure 1 and Table 1, within the test temperature range of 20-100℃, the melting process of PW exhibits an endothermic peak with a temperature of 58.34℃ and an enthalpy of 186.72 J / g; the crystallization process exhibits an exothermic peak with a temperature of 52.75℃ and an enthalpy of 183.79 J / g. The test results of CMA-90 are as follows: Figure 5 As shown in Table 1, within the test temperature range of 20-100℃, the melting process of PW exhibits an endothermic peak with a temperature of 57.59℃ and an enthalpy of 165.40 J / g; the crystallization process exhibits an exothermic peak with a temperature of 47.80℃ and an enthalpy of 165.10 J / g.
[0036] Based on the addition amount of PW being 90 wt.%, the theoretical enthalpy of CMA-90 is 186.72 J / g. Therefore, there is no substantial difference between the enthalpy of CMA-90 and the theoretical enthalpy, indicating that CMA aerogel has no negative impact on the phase transition behavior of PW.
[0037] To demonstrate the cycling stability of CMA-90, cycling tests were conducted, and the test results are as follows: Figure 7 As shown, the thermal cycling curve of CMA-90 showed no significant change after 100 cycles. The test results indicate that the phase change performance of CMA-90 did not change significantly before and after cycling, thus demonstrating that CMA-90 has good cycling stability.
[0038] To demonstrate the infrared stealth performance of the CMA-90, infrared thermal imaging tests were conducted. At room temperature, the composite phase change material was placed in the palm of a hand for 10 minutes, then heated by the hand's temperature. Observation using an infrared thermal imager showed that the color of the composite phase change material under the imager did not differ significantly from the surrounding environment, indicating that it blended seamlessly with the environment and possessed infrared stealth capabilities. Figure 9 As shown.
[0039] Experiment 2: A method for preparing a composite phase change material based on carboxylated nanocellulose (CNF) is disclosed. The method employs a one-step physical casting process. The raw materials, carboxylated nanocellulose (CNF), hydroxyapatite (HAP), montmorillonite (MMT), and paraffin wax (PW), meet a mass ratio of 20:8:15:50, meaning the amount of PW added is 95 wt.%. The specific steps include: Step 1, preparation of CHM aerogel: First, CNF and HAP are diluted in deionized water and magnetically stirred for 3-4 h at a stirring temperature of 20-30℃ to obtain CH solution. Then, 0.75 wt.% montmorillonite (MMT) is added to the CH solution and stirring is continued to obtain CHM solution. Finally, the CHM solution is first subjected to directional freezing at -30℃ for 12 h to obtain CHM solid gel. Then, the CHM solid gel is freeze-dried at -50℃ for 72 h to obtain CHM aerogel. Step 2, the preparation of thermal insulation composite phase change material with thermal insulation function, with an impregnation and adsorption temperature of 75℃ and an impregnation and adsorption time of 24 h, the CHM aerogel obtained in step 1 is placed in PW for vacuum impregnation and adsorption, so as to obtain CHM-PW with carboxylated nanocellulose CNF as the base material. The obtained CHM-PW is simply referred to as CHM-95 because the amount of PW added is 95 wt.%.
[0040] To verify the PW content, a weighing test was conducted before and after adsorption. The test results showed that the mass of CHM aerogel was 3.64 g, the mass of added PW was 22.84 g, and the final mass of CHM-95 was 26.5 g. Therefore, it can be calculated that the added PW was completely adsorbed by CHM aerogel, i.e., the adsorption amount was 95 wt.%.
[0041] To demonstrate that CHM-95 possesses heat insulation properties, a heating test was conducted. The test results are as follows: Figure 13 As shown, When CHM-95 is used as a thermal insulation material, at 80℃, it was observed with an infrared thermal imager at the very beginning of the observation period. Only the bottom of the thermal insulation composite phase change material was reddish-yellow. After 2 hours of heating, the reddish-yellow color at the bottom of the thermal insulation composite phase change material did not show obvious longitudinal extension. Test results show that CHM-95 possesses thermal insulation properties. Its insulating filler plays a crucial role, and under external environmental conditions of 80℃, when the phase change material undergoes solid-liquid and liquid-solid phase transitions at the set phase change temperature, it absorbs / releases a large amount of latent heat. Furthermore, the material's own temperature remains essentially constant during the phase change process, storing excess environmental heat and releasing it at lower temperatures, actively offsetting temperature fluctuations. Therefore, the phase change material maintains a consistently low temperature, possessing dual thermal insulation properties: thermal insulation from the insulating filler and thermal insulation from the phase change heat storage.
[0042] To verify the composition of CHM-95, FTIR testing was performed, such as... Figure 11 As shown, CHM aerogel and its components, carboxylated nanocellulose (CNF), hydroxyapatite (HAP), and montmorillonite (MMT), have the same characteristic peaks. CHM was successfully prepared by one-step physical casting after mixing and stirring the solutions of the above components. Furthermore, CNF, MMT, and HAP are chemically bonded, and no new substances are generated. The test results show that there is no chemical reaction in the CHM aerogel bonding process, and the preparation of the phase change material is only physical adsorption. That is, CMA-95 has no effect on the crystallization behavior of PW, which can ensure that the composite phase change material has good heat storage capacity.
[0043] To demonstrate the packaging performance of CHM-95, a leak-proof test was conducted. For comparison, a leak-proof test was also performed on the PW (packaging material). The specific test method for the leak-proof test involved heating the sample to be tested at 80°C for 120 minutes.
[0044] The test results of PW are as follows Figure 12 As shown, PW melts and flows outwards; The test results of CHM-95 are as follows: Figure 12 As shown, CHM-95 showed no significant changes; Test results show that the prepared CHM-95 can effectively prevent PW leakage.
[0045] To demonstrate the phase transition performance of CHM-95, DSC testing was conducted, such as... Figure 14 As shown, a DSC test was also performed on the PW for comparison.
[0046] PW test results are as follows Figure 14 As shown in Figure 1 and Table 3, within the test temperature range of 20-100℃, the melting process of PW exhibits an endothermic peak with a temperature of 58.34℃ and an enthalpy of 186.72 J / g; the crystallization process exhibits an exothermic peak with a temperature of 52.75℃ and an enthalpy of 183.79 J / g. The test results of CHM-95 are as follows: Figure 14As shown in Table 3, within the test temperature range of 20-100℃, the melting process of PW exhibits an endothermic peak with a temperature of 58.17℃ and an enthalpy of 176.18 J / g; the crystallization process exhibits an exothermic peak with a temperature of 51.21℃ and an enthalpy of 173.71 J / g.
[0047] Based on the addition amount of PW being 95 wt.%, the theoretical enthalpy of CHM-95 is 176.72 J / g. Therefore, there is no substantial difference between the enthalpy of CHM-95 and the theoretical enthalpy, indicating that CHM aerogel has no negative impact on the phase transition behavior of PW.
[0048] To demonstrate the cyclic stability of CHM-95, cyclic testing was conducted, and the test results are as follows: Figure 15 As shown, the thermal cycling curve of CHM-95 showed no significant change after 100 cycles. The test results indicate that the phase change performance of CHM-95 did not change significantly before and after cycling, thus demonstrating that CHM-95 has good cycling stability.
[0049] To demonstrate the infrared stealth capabilities of the CHM-95, infrared thermal imaging tests were conducted, such as... Figure 16 As shown, under normal temperature conditions, when the composite phase change material is placed in the palm of the hand for 10 minutes and heated by the temperature of the palm, it is observed through an infrared thermal imager. The color of the composite phase change material under the infrared thermal imager is not significantly different from the color of the external environment, and it blends into the external environment, thus possessing infrared stealth performance.
[0050] Experiment 3: A method for preparing konjac glucomannan (KGM), phytic acid (PA), and sodium alginate (SA) as base materials is disclosed. The method employs a one-step physical casting process. The raw materials KGM, PA, SA, HAP, and PW meet a mass ratio of 1:0.5:2:50, meaning the amount of PW added is 95 wt.%. The specific steps include: Step 1, Preparation of KSH aerogel: First, KGM, PA and SA are diluted in deionized water and magnetically stirred for 0.4-0.5 minutes at a stirring temperature of 20-30℃ to obtain a KS solution. Then, 0.8 wt.% hydroxyapatite (HAP) is added to the KS solution and stirring is continued to obtain a KSH solution. Finally, the KSH solution is first subjected to directional freezing at a temperature of -30℃ for 12 hours to obtain a KSH solid gel. The KSH solid gel is then freeze-dried at a temperature of -50℃ for 72 hours to obtain a KSH aerogel. Step 2: Preparation of thermal insulation composite phase change material with thermal insulation function. The KSH aerogel obtained in Step 1 is placed in PW for vacuum impregnation and adsorption at an impregnation and adsorption temperature of 75℃ and an impregnation and adsorption time of 24 h. KSH-PW with konjac glucomannan (KGM), phytic acid (PA), and sodium alginate (SA) as the base material is obtained. The obtained KSH-PW is simply referred to as KSH-95 because the amount of PW added is 95 wt.%.
[0051] To verify the PW content, a weighing test was conducted before and after adsorption. The test results showed that the mass of KSH aerogel was 3.61 g, the mass of added PW was 22.78 g, and the final mass of KSH-95 was 26.5 g. Therefore, it can be calculated that the added PW was completely adsorbed by KSH aerogel, i.e., the adsorption amount was 95 wt.%.
[0052] To demonstrate that KSH-95 possesses heat insulation properties, a heating test was conducted. The test results are as follows: Figure 19 As shown, When KSH-95 is used as a thermal insulation material, at 80℃, it was observed with an infrared thermal imager at the very beginning of the observation period. Only the bottom of the thermal insulation composite phase change material was reddish-yellow. After 2 hours of heating, the reddish-yellow color at the bottom of the thermal insulation composite phase change material did not show obvious longitudinal extension. Test results show that KSH-95 possesses thermal insulation properties. Its insulating filler plays a crucial role, and under external environmental conditions of 80℃, when the phase change material undergoes solid-liquid and liquid-solid phase transitions at its set phase change temperature, it absorbs / releases a large amount of latent heat. Furthermore, the material's own temperature remains essentially constant during the phase change process, storing excess environmental heat and releasing it at lower temperatures, actively offsetting temperature fluctuations. Therefore, the phase change material maintains a consistently low temperature, possessing dual thermal insulation properties: thermal insulation from the insulating filler and thermal insulation from the phase change process.
[0053] To verify the composition of KSH-95, FTIR testing was performed, such as... Figure 17 As shown, KSH aerogel and its components, konjac glucomannan (KGM), hydroxyapatite (HAP), and sodium alginate (SA), share the same characteristic peaks. KSH was successfully prepared by one-step physical casting after mixing and stirring the solutions of the above components. Furthermore, KGM, HAP, and SA are chemically bonded, and no new substances are generated. The test results indicate that there is no chemical reaction during the KSH aerogel bonding process, and the preparation of the phase change material is solely based on physical adsorption. That is, KSH-95 has no effect on the crystallization behavior of PW, ensuring that the composite phase change material has good heat storage capacity.
[0054] To demonstrate the packaging performance of KSH-95, a leak-proof test was conducted. For comparison, a leak-proof test was also performed on the PW sample. The specific test method for the leak-proof test involved heating the sample to be tested at 80°C for 120 minutes.
[0055] The test results of PW are as follows Figure 18 As shown, PW melts and flows outwards; The test results of KSH-95 are as follows: Figure 18 As shown, KSH-95 showed no significant changes; Test results show that the prepared KSH-95 can effectively prevent PW leakage.
[0056] To demonstrate the phase change performance of KSH-95, DSC testing was conducted, such as... Figure 20 As shown, a DSC test was also performed on the PW for comparison.
[0057] PW test results are as follows Figure 20 As shown in Figure 1 and Table 4, within the test temperature range of 20-100℃, the melting process of PW exhibits an endothermic peak at a temperature of 58.34℃ and an enthalpy of 186.72 J / g; the crystallization process exhibits an exothermic peak at a temperature of 52.75℃ and an enthalpy of 183.79 J / g. The test results of KSH-95 are as follows: Figure 20 As shown in Table 4, within the test temperature range of 20-100℃, the melting process of PW exhibits an endothermic peak with a temperature of 58.17℃ and an enthalpy of 172.18 J / g; the crystallization process exhibits an exothermic peak with a temperature of 51.21℃ and an enthalpy of 173.71 J / g.
[0058] Based on the addition amount of PW being 95 wt.%, the theoretical enthalpy of KSH-95 is 172.72 J / g. Therefore, there is no substantial difference between the enthalpy of KSH-95 and the theoretical enthalpy, indicating that KSH aerogel has no negative impact on the phase transition behavior of PW.
[0059] To demonstrate the cyclic stability of KSH-95, cyclic testing was conducted, and the test results are as follows: Figure 21 As shown, the thermal cycling curve of KSH-95 showed no significant change after 100 cycles. The test results indicate that the phase change performance of KSH-95 did not change significantly before and after cycling, thus demonstrating that KSH-95 has good cycling stability.
[0060] To demonstrate the KSH-95's infrared stealth capabilities, infrared thermal imaging tests were conducted, such as... Figure 22As shown, under normal temperature conditions, when the composite phase change material is placed in the palm of the hand for 10 minutes and heated by the temperature of the palm, it is observed through an infrared thermal imager. The color of the composite phase change material under the infrared thermal imager is not significantly different from the color of the external environment, and it blends into the external environment, thus possessing infrared stealth performance.
[0061] Table 1. Phase transition enthalpy and temperature of composite phase change materials with different PW addition amounts .
[0062] Table 2 Thermal conductivity of composite phase change materials with different PW addition amounts .
[0063] Table 3. Phase transition enthalpy and temperature of composite phase change materials with different PW addition amounts .
[0064] Table 4. Phase transition enthalpy and temperature of composite phase change materials with different PW addition amounts .
Claims
1. A thermally insulating composite phase change material, characterized in that, One or two of the following biomass materials—chitosan (CS), carboxylated nanocellulose (CNF), konjac glucomannan (KGM), and sodium alginate (SA)—are selected and structurally designed as the aerogel framework matrix. Simultaneously, thermal insulation functional units hydroxyapatite (HAP) and montmorillonite (MMT) are introduced to construct a biomass aerogel that combines thermal insulation performance, adsorption capacity, and an ordered pore structure. Furthermore, paraffin wax (PW), a phase change thermal storage material with low thermal conductivity and high thermal storage capacity, is introduced to prepare a dual-insulation composite phase change material.
2. An application of a thermally insulating composite phase change material, characterized in that, The application is that the thermal insulation composite phase change material has dual thermal insulation properties.
3. An application of a thermally insulating composite phase change material, characterized in that, The application includes the thermal insulation composite phase change material, which simultaneously possesses thermal insulation properties, infrared stealth properties, and phase change properties.
4. The application of the thermal insulation composite phase change material according to claim 3, characterized in that: The aforementioned thermal insulation performance, when used as a thermal insulation material, is observed using an infrared thermal imager at 80°C for the first 2-3 minutes. Only the bottom of the thermal insulation composite phase change material is reddish-yellow; after 2 hours of heating, the reddish-yellow color at the bottom of the thermal insulation composite phase change material does not show obvious longitudinal extension.
5. The application of the thermal insulation composite phase change material according to claim 3, characterized in that: The aforementioned infrared stealth performance means that when used as a heat insulation material, it also possesses infrared stealth properties. Under normal temperature conditions, if the composite phase change material is placed in the palm of the hand for 10 minutes and heated by the temperature of the palm, and observed through an infrared thermal imager, the color of the composite phase change material under the infrared thermal imager is not significantly different from the color of the external environment, and it blends into the external environment, thus possessing infrared stealth performance.
6. The application of the thermal insulation composite phase change material according to claim 3, characterized in that: The phase change properties, i.e. when used as a phase change material, are a phase change temperature of 44.12-59.56℃, a phase change enthalpy of 155.85-176.34 J / g, and a thermal conductivity of 0.1045-0.2702 W / m·K.
7. A method for preparing a thermally insulating composite phase change material, characterized in that, The preparation method includes the following steps: Step 1, preparation of hybrid thermal insulation aerogel: First, under certain conditions, CNF, HAP or KGM, SA or CS, MMT are diluted in deionized water and magnetically stirred to obtain a homogeneous mixed solution. Then, 0.5wt.%-1wt.% MMT, 0.75wt.%-1.25wt.% SA, and 0.75wt.%-1wt.% HAP are added to the corresponding mixed solutions and stirred to obtain an aerogel precursor solution. Finally, under certain conditions, the aerogel is first directionally frozen and then freeze-dried to obtain a structurally stable hybrid thermal insulation aerogel. Step 2, preparation of composite phase change material with thermal insulation function: the hybrid thermal insulation aerogel obtained in step 1 is placed in PW for vacuum impregnation and adsorption at an impregnation and adsorption temperature of 75℃ and an impregnation and adsorption time of 24 h to obtain a double thermal insulation composite phase change material.
8. A method for preparing a thermally insulating composite phase change material according to claim 6, characterized in that, The drying conditions for the hybrid thermal insulation aerogel are as follows: first, directional freezing is performed, followed by freeze-drying; the directional freezing temperature is -30℃ and the freezing time is 12 h; the freeze-drying temperature is -50℃ and the freeze-drying time is 72-96 h.