Self-healing polyurethane phase change material based on polyethylene glycol / hexamethylene diisocyanate trimer dynamic semi-interpenetrating network and preparation method thereof

Abstract

The application discloses a self-repairing polyurethane phase change material based on a polyethylene glycol / hexamethylene diisocyanate trimer dynamic semi-interpenetrating network and a preparation method thereof. The method comprises the following steps: in-situ constructing a dynamic cross-linked polyurethane network matrix with solid-solid phase change capacity by using polyethylene glycol with a number average molecular weight of 2000, hexamethylene diisocyanate trimer and 2,2'-diamino diphenyl disulfide, introducing 30wt.%-70wt.% of cetyl alcohol in the total mass of the material into the network matrix system and solidifying to obtain the phase change material; and the mass ratio of the polyethylene glycol and the cetyl alcohol is 1:0.43-1:2.33. In the material, the cetyl alcohol is physically inserted in the three-dimensional network space formed by the dynamic cross-linked polyurethane network in the form of a non-covalent dispersed phase, and the PEG soft segment in the dynamic cross-linked polyurethane network matrix and the cetyl alcohol both retain reversible crystallization capacity, thereby forming a dynamic semi-interpenetrating network system in which the network matrix phase and the dispersed phase jointly participate in heat storage. Compared with the existing polyurethane-based phase change material which mainly relies on a long-chain fatty alcohol dispersed phase to store heat, the material has good heat storage capacity, zero leakage performance, shape stability and thermal stimulus self-repairing performance, and can be applied to the fields of heat management and heat storage.

Description

Technical Field

[0001] This invention relates to the technical fields of phase change thermal storage materials, polymer functional materials and thermal management materials, specifically to a self-healing polyurethane phase change material based on a dynamic semi-interpenetrating network of polyethylene glycol / hexamethylene diisocyanate trimer and its preparation method. Background Technology

[0002] Phase change thermal energy storage materials (PCEs) can absorb or release a large amount of latent heat during phase change, and have broad application prospects in temperature control, thermal energy storage, and thermal management. Compared with inorganic PCEs, organic PCEs typically have advantages such as adjustable phase change temperature range, better chemical stability, lower tendency to undercool, and better recyclability. Therefore, they have attracted widespread attention in areas such as building energy conservation, flexible thermal management, thermal control of electronic devices, and thermal management of power batteries.

[0003] Polyurethane materials are often used as carriers or supporting frameworks for phase change materials (PCMs) due to their flexible molecular structure design, tunable mechanical properties, and good processability. Existing self-healing polyurethane-based PCMs typically employ cross-linked polyurethane networks to confine the fatty alcohol phase change components, with heat storage behavior primarily relying on the introduced fatty alcohol dispersion phase. While this approach can suppress leakage and impart self-healing capabilities to the material to some extent, it still suffers from the following problems: First, the supporting network itself usually does not participate in effective phase change heat storage; the material's heat storage mainly depends on the added fatty alcohol, resulting in a relatively singular utilization method for the phase change components. Second, as the fatty alcohol content increases, the material's structural stability and mechanical support capacity tend to decrease. Third, under long-term thermal cycling or external forces, the material is prone to structural defects such as microcracks and interface damage, thus affecting its service stability and lifespan.

[0004] In recent years, dynamically covalently bonded materials have shown great potential in the field of self-healing polymer materials due to their reversible recombination and stimulus-responsive properties. Among them, polyurethane networks containing disulfide bonds can undergo bond exchange or structural rearrangement under thermal stimulation, thus endowing the material with a certain degree of self-healing ability. On the other hand, when polyethylene glycol (PEG) is used as the soft segment of polyurethane, the system itself exhibits solid-solid phase transition characteristics through the crystallization-melting of PEG segments. Therefore, if a dynamically cross-linked polyurethane network matrix is ​​constructed using PEG soft segments with reversible crystallization ability, and cetyl alcohol is further introduced as a dispersed phase transition component, it is expected to form a dynamic semi-interpenetrating network system in which both the network matrix phase and the dispersed phase participate in heat storage.

[0005] Therefore, developing a polyurethane-based phase change material that can utilize the reversible crystallization behavior of PEG soft segments in a dynamically cross-linked polyurethane network matrix, introduce a cetyl alcohol dispersed phase to enhance heat storage capacity, and simultaneously maintain structural stability and thermally stimulated self-healing ability is of great significance for improving the overall performance of phase change materials and expanding their application in the field of thermal management. Summary of the Invention

[0006] The technical problem to be solved by this invention is: addressing the issues that existing self-healing polyurethane-based phase change materials mainly rely on a single fatty alcohol dispersed phase for heat storage, the supporting network itself does not participate in effective phase change heat storage, and it is difficult to balance structural stability and damage repair capability under high phase change component content. This invention provides a self-healing polyurethane phase change material based on a polyethylene glycol / hexamethylene diisocyanate trimer dynamic semi-interpenetrating network and its preparation method. It involves first constructing a dynamically cross-linked polyurethane network matrix with solid-solid phase change characteristics, and then introducing a hexadecyl alcohol dispersed phase to form a dynamic semi-interpenetrating network structure in which both the network matrix phase and the dispersed phase participate in heat storage.

[0007] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: This invention provides a self-healing polyurethane phase change material based on a dynamic semi-interpenetrating network of polyethylene glycol / hexamethylene diisocyanate trimer. The material comprises a dynamically cross-linked polyurethane network matrix and hexadecyl alcohol dispersed in the dynamically cross-linked polyurethane network matrix. The dynamically cross-linked polyurethane network matrix is ​​formed by the reaction of polyethylene glycol, hexamethylene diisocyanate trimer, and 2,2′-diaminodiphenyl disulfide, and is a polyurethane-based solid-solid phase change material. The hexadecyl alcohol accounts for 30 wt.% to 70 wt.% of the total mass of the material, and the mass ratio of polyethylene glycol to hexadecyl alcohol is 1:0.43 to 1:2.33, existing as a dispersed phase in the three-dimensional network space formed by the dynamically cross-linked polyurethane network matrix.

[0008] The dynamic semi-interpenetrating network structure of the present invention refers to a continuous phase consisting of a cross-linked polyurethane network containing dynamic disulfide bonds, with hexadecyl alcohol as a non-covalent dispersed phase embedded in the three-dimensional network space formed by the cross-linked polyurethane network, forming physical interpenetration in the intermolecule gaps of the network, and the hexadecyl alcohol and the cross-linked polyurethane network matrix are not connected by covalent bonds.

[0009] Compared with existing polyurethane-based phase change materials that rely solely on long-chain fatty alcohol dispersed phases for heat storage, this invention first constructs a dynamic cross-linked polyurethane network matrix with solid-solid phase change characteristics, and then introduces a cetyl alcohol dispersed phase, so that the resulting material forms a dynamic semi-interpenetrating network system in which both the network matrix phase and the dispersed phase participate in heat storage, thereby taking into account phase change heat storage capacity, shape stability and thermally stimulated self-healing performance.

[0010] Furthermore, the polyethylene glycol is polyethylene glycol with a number average molecular weight of 2000.

[0011] Furthermore, the polyisocyanate is a hexamethylene diisocyanate trimer.

[0012] Furthermore, the chain extender containing a dynamically reversible bond is 2,2′-diaminodiphenyl disulfide.

[0013] Furthermore, the phase change component is hexadecyl alcohol.

[0014] Furthermore, the cetyl alcohol accounts for 30 wt.% to 70 wt.% of the total mass of the material.

[0015] The present invention also provides a method for preparing the above-mentioned self-healing polyurethane phase change material based on a dynamic semi-interpenetrating network of polyethylene glycol / hexamethylene diisocyanate trimer, comprising the following steps: (1) The polyethylene glycol with a number average molecular weight of 2000 was dried. (2) The hexamethylene diisocyanate trimer is reacted with the polyethylene glycol in an organic solvent to obtain a polyurethane prepolymer; (3) Add 2,2′-diaminodiphenyl disulfide to the polyurethane prepolymer obtained in step (2) and continue the reaction to form a dynamic cross-linked polyurethane network matrix containing PEG soft segments. The dynamic cross-linked polyurethane network matrix is ​​a polyurethane-based solid-solid phase change material. (4) Add hexadecyl alcohol to the system obtained in step (3) and mix evenly so that hexadecyl alcohol accounts for 30 wt.% to 70 wt.% of the total mass of the obtained material, and the mass ratio of polyethylene glycol to hexadecyl alcohol is 1:0.43 to 1:2.33; (5) Solidify the obtained system to obtain the target material.

[0016] Further, steps (2) and (3) are carried out in an organic solvent, preferably N,N-dimethylacetamide; the method is a two-step in-situ polymerization method that first constructs a dynamically cross-linked polyurethane network matrix containing PEG soft segments in situ and then introduces a hexadecyl alcohol dispersed phase.

[0017] Compared with the prior art, the present invention has the following beneficial effects: (1) The present invention first constructs a PEG-based dynamic cross-linked polyurethane network matrix with solid-solid phase change characteristics, and then introduces a cetyl alcohol dispersed phase to make the material form a dynamic semi-interpenetrating network system in which the network matrix phase and the dispersed phase jointly participate in heat storage, which is different from conventional polyurethane-based phase change materials that rely solely on long-chain fatty alcohol dispersed phases for heat storage. (2) The present invention physically interweaves hexadecyl alcohol in the three-dimensional network space formed by the dynamic cross-linked polyurethane network in the form of a non-covalent dispersed phase, so that the material maintains overall geometric stability and inhibits hexadecyl alcohol leakage during the phase change process, thereby helping to balance heat storage capacity and zero leakage performance. (3) By introducing dynamic disulfide bonds derived from 2,2′-diaminodiphenyl disulfide into the polyurethane network, the material has the ability to repair damage under thermal stimulation conditions, which is beneficial to extending the service life of the material. (4) By limiting the molecular weight of PEG, the content of cetyl alcohol and the mass ratio of PEG to cetyl alcohol, the synergistic regulation between heat storage capacity, structural stability and self-healing performance can be achieved. Attached Figure Description

[0018] Figure 1 This is a schematic diagram illustrating the structural design and preparation route of the material of the present invention; Figure 2 This is a schematic diagram of the dynamic semi-interpenetrating network structure of the material of the present invention; Figure 3 The Fourier transform infrared spectra of the samples in Examples 1 to 4 are shown below, where (a) is PUPCM of Example 1, (b) is PUPCM-HA-30 of Example 2, (c) is PUPCM-HA-50 of Example 3, (d) is PUPCM-HA-70 of Example 4; (e) is Tri-HDI; (f) is PEG; and (g) is HA. Figure 4 The X-ray diffraction patterns of the samples in Examples 1 to 4 are shown below, where (a) is PUPCM of Example 1, (b) is PUPCM-HA-30 of Example 2, (c) is PUPCM-HA-50 of Example 3, (d) is PUPCM-HA-70 of Example 4; (e) is PEG; and (f) is HA. Figure 5 Differential scanning calorimetry curves of PEG and PUPCM in Example 1 are shown, where (a) is the cooling curve of PEG and PUPCM; and (b) is the heating curve of PEG and PUPCM. Figure 6 Differential scanning calorimetry curves and 50-cycle curves for each sample in Examples 2 to 4 are shown, where (a) is PUPCM-HA-30 of Example 2, (b) is PUPCM-HA-50 of Example 3, and (c) is PUPCM-HA-70 of Example 4. Figure 7 The thermogravimetric analysis curves of each sample in Examples 1 and 4 are shown, where (a) is PUPCM of Example 1 and (b) is PUPCM-HA-70 of Example 4. Figure 8The following are the results of energy dispersive X-ray spectroscopy (EDX) analysis and elemental distribution test of Examples 2 to 4, where (a) is PUPCM-HA-30 of Example 2, (b) is PUPCM-HA-50 of Example 3, and (c) is PUPCM-HA-70 of Example 4. Figure 9 The images show a comparison of the morphology of the material before and after self-healing in Example 1. (a) shows the fracture state of the sample after cutting, with the left and right fracture surfaces marked in the figure; (b) shows the healing state after heat stimulation treatment; and (c) and (d) show the bending of the sample after self-healing.

[0019] Figure 10 The following are the zero-leakage test results of the samples in Examples 3 and 4, where (a) is blank filter paper; (b) is the state of the filter paper after the sample is removed after heating; (c) is the state of PUPCM-HA-50 and PUPCM-HA-70 before heating; and (d) is the state of PUPCM-HA-50 and PUPCM-HA-70 after heating. Detailed Implementation

[0020] The structural design and fabrication route of this invention are as follows: Figure 1 As shown, the dynamic semi-interpenetrating network structure is illustrated in the diagram. Figure 2 As shown below. (Combined with...) Figures 3 to 10 The structural characterization and performance test results shown further illustrate the present invention, but the scope of protection of the present invention is not limited to the following embodiments. All equivalent substitutions or modifications made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

[0021] Example 1

[0022] Preparation of polyurethane-based solid-solid phase change materials (PUPCMs) and their testing using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), differential scanning calorimetry (DSC), and self-healing behavior. A method for preparing a hexadecyl alcohol-free dynamically crosslinked polyurethane network matrix material, namely a polyurethane-based solid-solid phase change material (PUPCM), includes the following steps: (1) Place 10.000g of polyethylene glycol (PEG, number average molecular weight of 2000) under vacuum at 80℃ for 12h to remove moisture from the system; (2) Weigh 5.046g of hexamethylene diisocyanate trimer (Tri-HDI) and add it to 40mL of N,N-dimethylacetamide (DMAc) to prepare a homogeneous solution; (3) Heat the dried polyethylene glycol in step (1) to 80°C, add the solution obtained in step (2) under stirring, and react for 12 hours to obtain a polyurethane prepolymer system. (4) Weigh 2.484 g of 2,2′-diaminodiphenyl disulfide (DADS), add it to 30 mL of N,N-dimethylacetamide, and prepare a homogeneous solution; (5) Add the chain extender solution obtained in step (4) to the polyurethane prepolymer system obtained in step (3) and continue to react at 80°C for 12 hours to form a dynamic cross-linked polyurethane network containing dynamic disulfide bonds. (6) Pour the obtained system into a mold and cure it under vacuum at 80°C to obtain PUPCM material.

[0023] The obtained PUPCM was subjected to Fourier transform infrared spectroscopy, X-ray diffraction, and differential scanning calorimetry, and the results correspond to the following: Figure 3 (a) Figure 4 (a) and Figure 5 The results showed that approximately [amount] in PUPCM The -NCO characteristic peak at the point essentially disappeared, indicating that the isocyanate group had largely participated in the reaction; at approximately , and Characteristic absorptions of the polyurethane network can be observed nearby. XRD results show that PUPCM still has weak diffraction peaks around 19.5° and 23.0°, indicating that the PEG soft segments retain a certain degree of crystallinity after forming a dynamically cross-linked polyurethane network matrix. Furthermore, from... Figure 5 It is evident that PEG exhibits a significant exothermic peak around 36°C during cooling and a significant endothermic peak around 56°C during heating. In contrast, PUPCM shows a weaker exothermic peak around 31°C during cooling and a broader endothermic peak around 53°C during heating. Compared to PEG, the phase transition peak intensity of PUPCM is weakened and the peak shape is broadened, indicating that after the PEG soft segments form a dynamically cross-linked polyurethane network matrix, their crystallization behavior is restricted by the network structure, but they still retain reversible crystallization-melting ability. This further proves that the dynamically cross-linked polyurethane network matrix itself possesses solid-solid phase change material characteristics.

[0024] After the obtained PUPCM samples were cut to form obvious fracture surfaces, they underwent heat stimulation treatment, were then bonded together and kept at 80℃ for 1 hour. The morphological changes are shown in the figure. Figure 9 The results show that disulfide bond exchange and molecular chain rearrangement in the dynamic network are conducive to the self-repair of the material, and the repaired sample can restore a certain degree of structural continuity and overall integrity.

[0025] Example 2

[0026] Preparation of PUPCM-HA-30 and its cyclic testing by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and differential scanning calorimetry (DSC) A dynamically cross-linked polyurethane network matrix was prepared according to the method of Example 1. Subsequently, after the network matrix was formed, hexadecyl alcohol (HA) was added as a phase change component, making the hexadecyl alcohol account for 30 wt.% of the total mass of the obtained material. The mixture was stirred until the system was homogeneous, so that HA was dispersed in the dynamically cross-linked polyurethane network matrix and existed in the three-dimensional network space formed by the dynamically cross-linked polyurethane network matrix in the form of a dispersed phase. The resulting mixture was then poured into a mold and cured under vacuum at 80°C to obtain a composite material with a hexadecyl alcohol mass fraction of 30 wt.%, denoted as PUPCM-HA-30.

[0027] Fourier transform infrared spectroscopy, X-ray diffraction, differential scanning calorimetry, and EDX tests were performed on the obtained PUPCM-HA-30, and the results correspond to the following parameters respectively. Figure 3 (b) Figure 4 (b) Figure 6 (a) and Figure 8 (a).

[0028] The results show that, in addition to retaining the characteristic absorptions of the polyurethane network matrix, the long-chain alkyl characteristic absorptions of HA can also be observed in the material, indicating that HA has been successfully introduced into the system. XRD results show that PUPCM-HA-30 retains the characteristic diffraction peaks of HA around approximately 21.4° and 23.8°. DSC results show that the sample has obvious phase transition peaks in the low-temperature and high-temperature regions. EDX results show that sulfur is uniformly distributed. These results indicate that cetyl alcohol has been dispersed and introduced into the dynamically crosslinked polyurethane network matrix, forming a dynamic semi-interpenetrating network structure.

[0029] Example 3

[0030] Preparation of PUPCM-HA-50 and its cyclic testing by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and differential scanning calorimetry (DSC) A dynamically cross-linked polyurethane network matrix was prepared according to the method of Example 1. Subsequently, after the network matrix was formed, hexadecyl alcohol (HA) was added as a phase change component, making the hexadecyl alcohol account for 50 wt.% of the total mass of the obtained material. The mixture was stirred until the system was homogeneous, so that HA was dispersed in the dynamically cross-linked polyurethane network matrix and existed in the three-dimensional network space formed by the dynamically cross-linked polyurethane network matrix in the form of a dispersed phase. The resulting mixture was then poured into a mold and cured under vacuum at 80°C to obtain a composite material with a hexadecyl alcohol mass fraction of 50 wt.%, denoted as PUPCM-HA-50.

[0031] Fourier transform infrared spectroscopy, X-ray diffraction, differential scanning calorimetry, and EDX tests were performed on the obtained PUPCM-HA-50, and the results correspond to the following parameters respectively. Figure 3 (c) Figure 4 (c) Figure 6 (b) and Figure 8 (b) The results show that with the increase of HA content, the intensity of HA-related absorption peaks and crystallization peaks in the material is further enhanced; DSC results show that the phase transition peak of PUPCM-HA-50 is more obvious than that of PUPCM-HA-30; EDX results show that the sulfur-containing dynamic units are uniformly distributed in the sample.

[0032] Example 4

[0033] Preparation of PUPCM-HA-70 and its cyclic testing by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and differential scanning calorimetry (DSC) A dynamically cross-linked polyurethane network matrix was prepared according to the method of Example 1. Subsequently, after the network matrix was formed, hexadecyl alcohol (HA) was added as a phase change component, making the hexadecyl alcohol account for 70 wt.% of the total mass of the obtained material. The mixture was stirred until the system was homogeneous, so that HA was dispersed in the dynamically cross-linked polyurethane network matrix and existed in the three-dimensional network space formed by the dynamically cross-linked polyurethane network matrix in the form of a dispersed phase. The resulting mixture was then poured into a mold and cured under vacuum at 80°C to obtain a composite material with a hexadecyl alcohol mass fraction of 70 wt.%, denoted as PUPCM-HA-70.

[0034] Fourier transform infrared spectroscopy, X-ray diffraction, differential scanning calorimetry, thermogravimetric analysis, and EDX testing were performed on the obtained PUPCM-HA-70, and the results correspond to... Figure 3 (d) Figure 4 (d) Figure 6 (c) Figure 7 (b) and Figure 8 (c) The results show that the characteristic absorption and diffraction peaks of HA are the most obvious in PUPCM-HA-70, indicating that high HA content still maintains good crystallinity in the composite system; DSC results show that the phase transition peak of the material is the strongest in the high temperature region; TGA results show that the material has good thermal stability in the phase transition working temperature range; EDX results show that the elements are uniformly distributed.

[0035] 6. Test Results and Effects Explanation To verify the composition, phase change behavior, zero leakage performance, thermal stability, microstructure, and self-healing properties of the self-healing polyurethane phase change energy storage material prepared in this invention, Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), differential scanning calorimetry (DSC), zero leakage testing, thermogravimetric analysis (TGA), energy dispersive X-ray spectroscopy (EDX), and observation of the self-healing surface morphology were performed on the samples. Figure 1 This invention illustrates the structural design and fabrication route. Figure 2This diagram illustrates a dynamic semi-interpenetrating network structure. Figures 3 to 10 The FTIR, XRD, DSC, zero leakage, TGA, EDX, and self-healing results for different samples are shown. For clarity, PUPCM represents a dynamically cross-linked polyurethane network matrix material without cetyl alcohol (HA); PUPCM-HA-30, PUPCM-HA-50, and PUPCM-HA-70 represent composite materials with cetyl alcohol mass fractions of 30 wt.%, 50 wt.%, and 70 wt.%, respectively.

[0036] 6.1 Explanation of Fourier Transform Infrared Spectroscopy Test Results Fourier transform infrared spectroscopy (FTIR) was performed on Tri-HDI, PEG (number-average molecular weight 2000), HA, PUPCM, and PUPCM-HA-30, PUPCM-HA-50, and PUPCM-HA-70. The results showed that Tri-HDI exhibited high molecular weight distribution at approximately 2940 cm⁻¹. -1 and 2860cm -1 An aliphatic CH stretching vibration absorption peak appears at approximately 2270 cm⁻¹. -1 The characteristic absorption peak of the isocyanate group (-NCO) is visible at approximately 2880 cm⁻¹; PEG shows a peak at approximately 2880 cm⁻¹. -1 A -CH2- stretching vibration peak appears at approximately 1460 cm⁻¹. -1 1340cm -1 1280cm -1 and 1100cm -1 Characteristic absorption peaks associated with ether bond COC are visible nearby; HA is at approximately 2915 cm⁻¹. -1 and 2848cm -1 The vicinity exhibits long-chain alkyl CH stretching vibration peaks, around 1470 cm⁻¹. -1 and 720cm -1 Characteristic absorption of alkyl chains is visible nearby.

[0037] In PUPCM, approximately 3300cm -1 A relatively broad absorption band appears nearby, which can be attributed to the NH stretching vibration in the urethane structure; approximately 1700 cm⁻¹ -1 A distinct absorption peak appears nearby, which can be attributed to the C=O stretching vibration in the urethane group; approximately 1100 cm⁻¹ -1 The characteristic COC absorption of the polyether segment is still present nearby. Meanwhile, compared to Tri-HDI, PUPCM has an absorption of approximately 2270 cm⁻¹. -1 The -NCO characteristic peak at the site has basically disappeared, indicating that the isocyanate group has basically participated in the reaction, and PEG has successfully constructed a polyurethane network with Tri-HDI and DADS.

[0038] 6.2 Explanation of X-ray diffraction test results X-ray diffraction tests were performed on PEG (number average molecular weight 2000), HA, PUPCM, and PUPCM-HA-30, PUPCM-HA-50, and PUPCM-HA-70. The results showed that PEG exhibited typical crystallization diffraction peaks at approximately 19.2° and 23.3° 2θ, indicating that PEG has good crystallization ability. Weaker diffraction peaks were observed at similar positions, around 19.5° and 23.0°, but the peak intensity was significantly reduced and the peak shape broadened, indicating that the soft segments of PEG retain some crystallization ability after forming a polyurethane network, but its crystallization behavior is limited by the cross-linking network and intermolecular interactions.

[0039] HA exhibits strong and sharp characteristic peaks around 21.4° and 23.8° at 2θ, indicating good crystallinity. After introducing HA into the dynamic polyurethane network, PUPCM-HA-30, PUPCM-HA-50, and PUPCM-HA-70 still retain the characteristic diffraction peaks around 21.4° and 23.8°, and the intensity of these peaks gradually increases as the HA content increases from 30 wt.% to 50 wt.% and 70 wt.%. This indicates that HA maintains good crystallinity in the composite system, and its degree of crystallinity increases with increasing addition. These results show that the dynamic polyurethane network constructed in this invention does not completely suppress the crystallization behavior of HA, indicating that the phase change component maintains a good dispersion state in the network system, which is beneficial for maintaining good phase change heat storage capacity while preserving the overall structural integrity of the material.

[0040] 6.3 Explanation of Differential Scanning Calorimetry Results for PEG and PUPCM Differential scanning calorimetry was performed on PEG and PUPCM, and the results are as follows: Figure 5 As shown. By Figure 5 (a) and Figure 5 (b) As can be seen, PEG exhibits a significant exothermic peak around 36°C during cooling and a significant endothermic peak around 56°C during heating, indicating that PEG possesses typical reversible crystallization-melting phase transition behavior. In contrast, PUPCM still shows a weaker exothermic peak around 31°C during cooling and a broader endothermic peak around 53°C during heating. Although the phase transition peak intensity of PUPCM is significantly weaker than that of PEG, and the peak shape is somewhat broadened, it still retains clear thermal response characteristics during heating and cooling.

[0041] The above results indicate that after PEG soft segments form a dynamically cross-linked polyurethane network matrix with hexamethylene diisocyanate trimer and 2,2′-diaminodiphenyl disulfide, their chain segment movement and crystallization behavior are somewhat restricted, but they do not completely lose their reversible crystallization ability. Figure 4(a) The fact that PUPCM still retains relatively weak diffraction peaks around 19.5° and 23.0° further proves that the dynamically cross-linked polyurethane network matrix itself has solid-solid phase change material characteristics, and is not merely an inert support network. This indicates that the network matrix used in this invention can participate in the phase change energy storage process, providing a foundation for the subsequent introduction of a cetyl alcohol dispersed phase to form a thermal storage system in which the network matrix phase and the dispersed phase both participate.

[0042] 6.4 Explanation of Differential Scanning Calorimetry Results for PUPCM-HA-30, PUPCM-HA-50, and PUPCM-HA-70 DSC tests were performed on PUPCM-HA-30, PUPCM-HA-50, and PUPCM-HA-70, and the changes in thermal behavior after the first and 50th cycles were compared. As shown in the figure, all three groups of samples exhibited obvious endothermic and exothermic peaks, indicating that the materials have a stable phase transition endothermic and exothermic process.

[0043] Among them, PUPCM-HA-30 exhibits a low-temperature endothermic peak around 20.5℃ during heating and another endothermic peak around 36.0℃; during cooling, two relatively obvious exothermic peaks are observed around 41.5℃ and 51.0℃. PUPCM-HA-50 exhibits a low-temperature endothermic peak around 10.5℃ during heating, and relatively obvious double endothermic peaks around 36.5℃ and 40.5℃; during cooling, the main exothermic peaks appear around 46.0℃ and 50.0℃. PUPCM-HA-70 exhibits a weak endothermic peak around 10.0℃ during heating, and obvious double endothermic peaks around 40.5℃ and 45.0℃; during cooling, the main exothermic peak is located around 51.0℃ and has a relatively sharp peak shape.

[0044] Overall, as the HA content increased from 30 wt.% to 70 wt.%, the phase transition peak in the high-temperature region of the sample gradually strengthened, indicating that the proportion of effective phase transition components in the system increased, and the phase change heat storage capacity of the material increased accordingly. Combined with... Figure 5 The thermal response characteristics of the PUPCM network matrix itself under temperature rise and fall, as shown, indicate that... Figure 6The thermal behavior of the composite material does not originate solely from the hexadecyl alcohol dispersed phase, but rather exhibits a dual thermal response characteristic where both the dynamically cross-linked polyurethane network matrix phase and the hexadecyl alcohol dispersed phase participate in heat storage. Furthermore, the DSC curves from the first and 50th cycles show consistent overall trends, exhibiting only minor changes in peak position and shape, indicating that the sample retains good phase change reversibility and thermal cycling stability after 50 thermal cycles. These results demonstrate that the dynamic semi-interpenetrating network structure can maintain the dispersion state of the phase change components within the dynamically cross-linked polyurethane network and the overall structural stability of the material during repeated heating and cooling processes, preventing macroscopic flow during phase change and thus ensuring consistent phase change response over long-term use.

[0045] 6.5 Explanation of Zero Leakage Performance Test Results To verify the zero-leakage performance of the material of the present invention under conditions of high cetyl alcohol content, PUPCM-HA-50 from Example 3 and PUPCM-HA-70 from Example 4 were selected as representative samples. They were placed on filter paper and heated at 80°C for 1 hour for testing. The test results are as follows: Figure 10 As shown. By Figure 10 (a) and Figure 10 (b) As can be seen, no obvious transparent oil spots or seepage traces appeared on the surface of the filter paper before and after heating, indicating that no significant leakage occurred during the test. Figure 10 (c) and Figure 10 (d) As can be seen, PUPCM-HA-50 and PUPCM-HA-70 maintained good overall morphology before and after heating, and no obvious macroscopic flow occurred. The above results indicate that even under conditions of high cetyl alcohol content, the constructed dynamic semi-interpenetrating network structure can still provide effective spatial constraint on the cetyl alcohol dispersed phase, thereby endowing the material with good zero-leakage performance and shape stability.

[0046] 6.6 Explanation of Thermogravimetric Test Results Thermogravimetric analysis (TGA) was performed on PUPCM and PUPCM-HA-70. The results showed that the thermogravimetric process of both samples exhibited multi-stage decomposition characteristics. For PUPCM, the initial weight loss began at approximately 240℃, with the first stage of weight loss mainly occurring in the range of approximately 240–340℃. Subsequently, the main weight loss stage occurred in the range of approximately 360–500℃, with the maximum weight loss rate peak located around 410℃. After reaching approximately 500℃, the sample mass basically stabilized, with a final residual rate of approximately 2%–3%.

[0047] For PUPCM-HA-70, the sample began to show significant weight loss around 180–200℃, with the main weight loss phase occurring primarily in the 200–300℃ range, and the maximum weight loss rate peak around 245℃. A second stage of thermal decomposition was observed in the 330–420℃ range, with the corresponding weight loss rate peak around 405℃. After approximately 500℃, the sample mass stabilized, with a final residual rate of about 1%–2%. These results indicate that the introduction of HA alters the thermal decomposition behavior of the material, but the resulting composite material still exhibits good thermal stability within the phase change operating temperature range, meeting the requirements for conventional thermal management and thermal storage applications.

[0048] 6.7 Explanation of Energy Dispersive X-ray Spectroscopy Analysis and Elemental Distribution Test Results EDX elemental analysis and surface distribution tests were performed on PUPCM-HA-30, PUPCM-HA-50, and PUPCM-HA-70. The results showed that C, O, and S elements were mainly detected in the samples, and each element was relatively uniformly distributed within the test area. C and O elements mainly originated from PEG, HA, and the polyurethane network structure, while S element originated from the dynamic disulfide bond units in DADS. The presence and relatively uniform distribution of S element in the three groups of samples indicate that the disulfide bond-containing structural units have been successfully introduced into the polyurethane network and exhibit good dispersion uniformity in the composite system. This further demonstrates that the dynamic network structure constructed in this invention has good composite uniformity with the phase change components, which is beneficial for improving the overall structural consistency of the material and provides a structural basis for its self-healing performance and thermal response stability.

[0049] 6.8 Self-healing effect description Depend on Figure 9 As can be seen, the prepared sample was cut to form a clear fracture surface and then subjected to heat stimulation treatment. The results show that the sample is initially continuous; after cutting, a clear crack appears in the middle; after heat treatment, the fracture interface obviously re-adheres, the crack width is significantly reduced, and some areas are basically closed. The repaired sample still maintains overall continuity under manual bending and does not undergo immediate brittle fracture, indicating that the material has a significant heat-triggered self-healing ability.

[0050] This self-healing behavior is primarily attributed to the reversible exchange reaction of the dynamic disulfide bonds provided by DADS under thermal stimulation, while the polyurethane segments undergo migration and rearrangement, allowing the fractured interfaces to re-contact, diffuse, and recombine. This result demonstrates that the material of this invention can recover a certain degree of structural integrity after experiencing mechanical damage through external thermal stimulation, thereby improving its service life and application reliability under cyclic service conditions.

Claims

1. A method for preparing a self-healing polyurethane phase change material based on a dynamic semi-interpenetrating network of polyethylene glycol / hexamethylene diisocyanate trimer, characterized in that, Includes the following steps: (1) The polyethylene glycol with a number average molecular weight of 2000 was dried. (2) The hexamethylene diisocyanate trimer is reacted with the polyethylene glycol in an organic solvent to obtain a polyurethane prepolymer; (3) 2,2′-diaminodiphenyl disulfide is added to the polyurethane prepolymer and the reaction continues to form a dynamic cross-linked polyurethane network matrix containing PEG soft segments in situ. The dynamic cross-linked polyurethane network matrix is ​​a polyurethane-based solid-solid phase change material. (4) Add hexadecyl alcohol to the dynamic cross-linked polyurethane network matrix system obtained in step (3) and mix evenly, so that the hexadecyl alcohol accounts for 30 wt.% to 70 wt.% of the total mass of the obtained material, and the mass ratio of polyethylene glycol to hexadecyl alcohol is 1:0.43 to 1:2.33; wherein, the hexadecyl alcohol is dispersed in the three-dimensional network space formed by the dynamic cross-linked polyurethane network matrix in the form of a non-covalent dispersed phase, and physically interspersed in the molecular gaps of the dynamic cross-linked polyurethane network matrix, and the hexadecyl alcohol and the dynamic cross-linked polyurethane network matrix are not connected by covalent bonds; (5) The system obtained in step (4) is solidified to form a dynamic semi-interpenetrating network structure between the cetyl alcohol dispersed phase and the dynamically cross-linked polyurethane network matrix, thereby obtaining the self-healing polyurethane phase change material based on the polyethylene glycol / hexamethylene diisocyanate trimer dynamic semi-interpenetrating network.

2. The preparation method according to claim 1, characterized in that, Steps (2) and (3) are carried out in an organic solvent, namely N,N-dimethylacetamide.

3. The preparation method according to claim 1 or 2, characterized in that, The drying temperature in step (1) is 80°C; the reaction temperature for forming the polyurethane prepolymer in step (2) is 80°C; the continued reaction temperature in step (3) is 80°C; and the curing temperature in step (5) is 80°C.

4. The preparation method according to any one of claims 1 to 3, characterized in that, The hexadecyl alcohol added in step (4) has a mass fraction of 30 wt.%, 50 wt.%, or 70 wt.%.

5. A self-healing polyurethane phase change material based on a dynamic semi-interpenetrating network of polyethylene glycol / hexamethylene diisocyanate trimer, characterized in that, The material comprises a dynamically cross-linked polyurethane network matrix and hexadecyl alcohol dispersed in the dynamically cross-linked polyurethane network matrix; The dynamically cross-linked polyurethane network matrix is ​​formed by the reaction of polyethylene glycol, hexamethylene diisocyanate trimer and 2,2′-diaminodiphenyl disulfide, and is a polyurethane-based solid-solid phase change material. The hexadecyl alcohol accounts for 30 wt.% to 70 wt.% of the total mass of the material, and the mass ratio of polyethylene glycol to hexadecyl alcohol is 1:0.43 to 1:2.33; The cetyl alcohol exists in the form of a dispersed phase in the three-dimensional network space formed by the dynamically cross-linked polyurethane network matrix, and the PEG soft segments in the dynamically cross-linked polyurethane network matrix retain reversible crystallization ability.

6. The self-healing phase change material according to claim 5, characterized in that, The X-ray diffraction pattern of the material simultaneously retains PEG soft segment diffraction peaks at approximately 19.5° and 23.0° of 2θ, as well as cetyl alcohol diffraction peaks at approximately 21.4° and 23.8° of 2θ; and in the differential scanning calorimetry curve, it simultaneously exhibits low-temperature phase transition peaks corresponding to the phase transition behavior of PEG soft segments and high-temperature phase transition peaks corresponding to the phase transition behavior of cetyl alcohol.

7. The application of the self-healing phase change material according to claim 5 or 6 in the fields of thermal management and thermal storage, characterized in that, The thermal management and thermal storage fields include building envelopes, flexible thermal conditioning layers, thermal management coatings, power battery thermal management interface layers, or thermal storage devices.

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