Polyoxyethylene-based high-energy-storage-capacity phase change material as well as preparation method and application thereof

Abstract

The invention belongs to the field of functional polymer materials, and particularly relates to a polyoxyethylene high-energy-storage-capacity phase change material and a preparation method thereof. According to the invention, polyethylene glycol and polyethylene oxide with good biocompatibility are used as raw materials, carboxylated cellulose nanofibers and waterborne polyurethane are used as modified materials for improving crystallinity and mechanical properties, water is used as a solvent, and the phase change material with stable shape and relatively high energy storage capacity is prepared by adopting a simple dissolving and stirring mode. Furthermore, a multi-walled carbon nanotube is added, and the aerogel capable of encapsulating paraffin is prepared in a freeze-drying manner. Under the synergistic effect of the C-CNF and the TPU, the crystallinity and the mechanical property of the phase change material are obviously improved. In addition, the prepared aerogel has the packaging efficiency of 95% or above on paraffin, the energy storage capacity is further improved, good heat management capacity is shown, and the aerogel can be used in the heat management fields of automobiles, electronics, buildings and the like.

Description

Technical Field

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

[0002] With the development of new energy sources and the increase in industrial heat waste, thermal energy storage technology is becoming increasingly important in people's lives. For example, in the automotive and electronics industries, thermal management has become a key issue and constraint in the development of next-generation mobile network devices. Excessive latent heat generated by electronic devices severely limits the further upgrades of high-performance communication microchips.

[0003] Phase change materials (PCMs) are a promising thermal energy storage technology that can absorb or release thermal energy in the form of latent heat within a certain temperature range. Organic PCMs exhibit significant advantages in thermal energy storage (TES), such as high energy density, quasi-isothermal behavior during heat storage, and long-term cycling stability, thus being considered a highly efficient energy storage and management technology. Among various PCMs, solid-liquid and solid-solid PCMs are the most common and widely used. Polyethylene glycol (PEG), as a typical organic PCM, has attracted widespread attention due to its high latent heat of phase change, adjustable phase change temperature, excellent physicochemical stability, environmental friendliness, and small volume change during phase change. However, PEG exhibits high fluidity at high temperatures, a characteristic that limits its practical applications.

[0004] To overcome the aforementioned problems, various technical solutions have been proposed to achieve morphological stabilization of PEG and even construct solid-solid phase change systems. A common strategy is to synthesize fragmented block copolymers or cross-linked polyurethane structures by controlling PEG as a soft segment, thereby adjusting the material's rigidity and phase change enthalpy. However, such cross-linked structures limit the crystallinity of PEG segments, leading to decreased material crystallinity and difficulties in processing and recycling. Another technical approach is to introduce high thermal conductivity fillers to prepare polyoxyethylene composite phase change materials to compensate for the low thermal conductivity of the polymer. However, the addition of fillers occupies the effective phase change volume of PEG, causing a decrease in overall crystallinity and phase change enthalpy. Furthermore, fillers are prone to aggregation, causing a significant increase in system viscosity and increasing processing difficulty. Other studies have employed micro-encapsulation or nano-encapsulation strategies to isolate liquid PEG through chemical or physical methods, preventing it from interacting with the external environment. However, the drawback of this method is that the volume fraction of PEG decreases after encapsulation, leading to a further reduction in the phase change enthalpy of the composite material.

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

[0006] To address the aforementioned problems in existing technologies, this invention prepares a series of high-performance PEG / PEO composite phase change materials (PEG / PEO PCMs) using a simple and environmentally friendly aqueous solution method. These phase change materials exhibit shape stability and high energy storage capacity. This invention uses polyethylene glycol and polyethylene oxide as raw materials, adding carboxylated cellulose nanofibers and waterborne polyurethane as fillers to improve crystallinity and mechanical properties. A shape-stable phase change material with high energy storage capacity is prepared through a simple dissolution and stirring method.

[0007] The technical solution of this invention improves the crystallinity and tensile strength of phase change materials by adding carboxylated cellulose nanofibers. The addition of waterborne polyurethane increases the elongation at break and also verifies the effect of carboxylated cellulose nanofibers on the thermal management capabilities of phase change materials. Subsequently, multi-arm carbon nanotubes are added to improve the thermal conductivity of the phase change material. Furthermore, an aerogel capable of encapsulating paraffin is prepared by freeze-drying, providing a new approach for the application of phase change materials (as encapsulation materials).

[0008] The first aspect of the present invention provides a method for preparing a polyoxyethylene high-energy-storage-capacity phase change material, comprising steps S1 and S2: S1. Dissolve polyethylene glycol (PEG) and polyethylene oxide (PEO) in deionized water to obtain a premixed solution (PP); S2. Add carboxylated cellulose nanofibers (C-CNF) and waterborne polyurethane (TPU) to the premixed solution obtained in step S1 to obtain a milky white mixed solution -a (PPCT). After drying, the polyoxyethylene high energy storage capacity phase change material can be obtained.

[0009] The polyoxyethylene in the high energy storage capacity phase change material is a mixture of polyethylene glycol and polyethylene oxide.

[0010] In some embodiments, in step S1, the molecular weight of the polyethylene glycol is 8000-20000; in a preferred embodiment, the molecular weight of the polyethylene glycol is 20000.

[0011] Further, in step S1, the molecular weight of the polyethylene oxide is 100,000-7,000,000; more preferably, the molecular weight is 600,000-7,000,000.

[0012] In some embodiments, in step S1, the mass ratio of polyethylene glycol to polyethylene oxide in the solution is 7:3 to 1:1; the total mass fraction is 5% to 50%. In a preferred embodiment, the mass ratio of polyethylene glycol to polyethylene oxide is 7:3; the total mass fraction is 10%.

[0013] In some embodiments, in step S2, the mass ratio of carboxylated cellulose nanofibers to aqueous polyurethane in the mixed solution-a is 5:1 to 1:5; the total mass of carboxylated cellulose nanofibers and aqueous polyurethane is 5% to 40% of the total mass of polyethylene glycol and polyethylene oxide.

[0014] In some preferred embodiments, the mass ratio of carboxylated cellulose nanofibers to aqueous polyurethane is 1:1, and the total mass fraction is 20% of the solid content of PP.

[0015] A second aspect of the present invention provides a polyoxyethylene high-energy-capacity phase change material prepared by the method, wherein the energy storage capacity of the material is ≥150 J / g, and the measured value of the energy storage capacity is higher than the theoretical value. The addition of C-CNF can effectively adjust the crystallinity and crystal structure, thereby affecting the thermal properties; the phase change material with the addition of C-CNF and TPU has a measured energy storage capacity higher than the theoretical value.

[0016] A third aspect of the present invention provides a polyoxyethylene high energy storage capacity phase change aerogel material, which is prepared by doping the phase change material with multi-walled carbon nanotubes (MWCNTs). The doping amount of MWCNTs in the phase change aerogel material is 0.01%-25% of the total mass of polyethylene glycol and polyethylene oxide, preferably 1%-10%.

[0017] Another aspect of the present invention provides a method for preparing the phase change aerogel material: take the mixed solution-a obtained in step S2, add multi-walled carbon nanotubes and mix well to obtain mixed solution-b, and then freeze-dry in a directional manner.

[0018] Further, the directional freeze-drying conditions are: a temperature of -20 to -80 °C and a freezing rate of 10-30 °C / min. In a preferred embodiment of the present invention, the temperature is -80 °C and the freezing rate is 20 °C / min.

[0019] Another aspect of the present invention provides the use of the polyoxyethylene high energy storage capacity phase change aerogel material as a phase change material carrier for encapsulating phase change materials and preparing phase change composite materials; further, the phase change composite material exhibits a two-stage heating curve of rapid heating and slow heating under light irradiation.

[0020] In some embodiments, the phase change material is paraffin, preferably a C10-C20 alkane; in one embodiment of the present invention, the paraffin is hexadecane, octadecane, or eicosane, with a mass fraction of 0%-50%, preferably eicosane, with a mass fraction of 50%.

[0021] Furthermore, the method for encapsulating phase change materials with phase change aerogel materials is as follows: take the phase change aerogel material, adsorb molten paraffin under a certain vacuum degree, and then cool it to obtain a phase change composite material.

[0022] Another aspect of the present invention provides the application of the phase change material, or the phase change aerogel material, or the phase change composite material, in the fields of new energy vehicles, electronic communications, green buildings, and smart textiles, for use in thermal management.

[0023] In some implementations, it is applied to phase change material energy storage research, electronic devices, and building thermal management.

[0024] The phase change material prepared by this invention exhibits excellent temperature stability and no leakage at ≤80 ℃ after drying.

[0025] Beneficial effects: Compared with the prior art, the beneficial effects of the present invention are at least as follows: (1) This invention prepares a series of high-performance PEG / PEO composite phase change materials by a simple and environmentally friendly aqueous solution method; the crystallinity and tensile strength of the phase change materials containing non-phase change components are improved by adding carboxylated cellulose nanofibers, and the elongation at break is improved by adding waterborne polyurethane. (2) The phase change material of the present invention has high energy storage capacity and good mechanical properties, and the measured value of energy storage capacity is higher than the theoretical value; among which, the energy storage capacity of PPCT is ≥150 J / g; the tensile strength reaches 10.05 MPa, and the elongation at break reaches 5.24%; (3) The present invention further prepares aerogel by directional freeze drying based on PPCT, which can be used to encapsulate phase change materials and broaden the application forms of phase change materials; after encapsulating paraffin, the energy storage capacity can reach about 150 J / g; it opens up new avenues for polyethylene glycol in phase change material energy storage research, electronic equipment and building thermal management. Attached Figure Description

[0026] The accompanying drawings are provided to further illustrate the present application and form part of the specification. They are used together with the embodiments of the present application to explain the present application, but do not constitute a limitation thereof. In the drawings: Figure 1 Scanning electron microscope (SEM) and polarizing microscope (PMS) images of different phase change materials prepared in the examples and comparative examples; Figure 2 (a) is a flowchart of the aerogel preparation process, and (b) and (c) are scanning electron microscope images of the aerogel. Figure 3 The thermal infrared image of the phase change material obtained in Example 1 / 5 upon heating; Figure 4The temperature rise and fall curves of the phase change materials prepared in Examples 1 and 5 are shown. Figure 5 (a) is a thermal infrared image of the temperature rise of different phase change materials under illumination, and (b) and (c) are line graphs of the temperature rise and fall of different phase change materials under illumination. Detailed Implementation

[0027] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the examples in the specification. Many specific details are set forth in the following description to provide a thorough understanding of the present invention; however, the present invention may also be implemented in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0028] Unless otherwise specified, the experimental methods described in the following examples are conventional methods; the reagents and instruments described are commercially available unless otherwise specified.

[0029] Test methods for various performance parameters of this invention: (1) SEM test: The prepared phase change material was brittle in liquid nitrogen, and it was attached to the electron microscope stage with conductive adhesive. Then, the sample was sprayed with gold for 30 s and observed by SEM.

[0030] (2) POM test: The crystal morphology of the prepared phase change material is observed by a polarizing microscope. The test sample is placed between the microscope glass and the coverslip.

[0031] (3) Differential scanning calorimetry (DSC) analysis: Take about 6 mg of phase change material sample and place it in a crucible. Scan from 10 °C to 90 °C at a heating rate of 10 °C / min to obtain the DSC curve. The nitrogen gas flow rate during the scanning process is 50 mL / min.

[0032] (4) Thermal infrared test: The prepared composite phase change material was tested for thermal performance. The sample was placed on the heating stage and heated for 15 minutes. The heating was stopped and the temperature change was recorded using an infrared thermal imager. The temperature change under the illumination condition was recorded in the same way as under the heating condition. After 5 minutes of illumination, the temperature was turned off and the temperature change trend was recorded again.

[0033] (5) Mechanical performance test: Mechanical performance test process: The phase change material is made into a dumbbell shape with a length × width × thickness of 10 cm × 5 mm × 1 mm. The mechanical strength of the hydrogel is tested at a speed of 10 mm / min using a double column tensile tester.

[0034] In one embodiment of the present invention, the specific steps of the method for preparing the phase change material include: (1) Dissolve 28 g of polyethylene glycol (MW20000) and 12 g of polyethylene oxide (MW600000) in 400 mL of deionized water to obtain a premixed solution PEG / PEO (PP). (2) Add 40 mL of carboxylated cellulose nanofibers (C-CNF) to the premixed solution prepared in step (1) to obtain a clear and transparent mixed solution PEG / PEO / C-CNF (PPC). (3) Add 40 g of waterborne polyurethane (TPU) to the premixed solution prepared in step (1) to obtain a milky white mixed solution PEG / PEO / TPU (PPT). (4) Add 40 mL of carboxylated cellulose nanofibers (C-CNF) and 40 g of waterborne polyurethane (TPU) to the premixed solution prepared in step (1) to obtain a milky white mixed solution PEG / PEO / C-CNF / TPU (PPCT). (5) Add 2 g of multi-walled carbon nanotubes (MWCNTs) to the premixed solution prepared in step (4) to obtain a black mixed solution (PPCT-MWCNTs). (6) The mixed solution in step (5) was freeze-dried at -80°C and a freezing rate of 20°C / min to obtain a black aerogel (A-PPCT-MWCNT). (7) Melt 50% by mass of eicosane paraffin and encapsulate it into the aerogel in step (6) through three vacuum adsorption processes.

[0035] Example 1: Preparation of Phase Change Materials (1) Add 28 g of polyethylene glycol (MW20000) and 12 g of polyethylene oxide (MW600000) to 400 mL of deionized water. Stir the beaker containing the materials on a magnetic stirrer for 3 h to obtain a completely dissolved clear and transparent solution (PP). (2) Add 40 mL of carboxylated cellulose nanofibers (C-CNF) to the premixed solution prepared in step (1), and stir the beaker containing the material on a magnetic stirrer for 3 h to obtain a clear and transparent mixed solution (PPC). (3) Add 40 mL of carboxylated cellulose nanofibers (C-CNF) and 40 g of waterborne polyurethane (TPU) to the premixed solution prepared in step (1). After stirring the beaker containing the materials on a magnetic stirrer for 3 h, a milky white mixed solution (PPCT) is obtained. The mixed solutions obtained in steps (1) / (2) / (3) were poured into a 100×100×5 mm polytetrafluoroethylene mold and dried at room temperature to form a film for subsequent performance testing.

[0036] Example 2: Effect of C-CNF Addition Amount on PPCT 20, 40, 100, and 200 mL of carboxylated cellulose nanofibers (C-CNF) and 40 g of waterborne polyurethane (TPU) were added to the premixed solution prepared in step (1) of Example 1. After stirring on a magnetic stirrer for 3 h, a clear and transparent mixed solution was obtained (denoted as PPCT-1, PPCT-2, PPCT-3, and PPCT-4, respectively). The solution was dried at room temperature to form a film, and subsequent performance tests were performed.

[0037] Example 3 Preparation of phase change aerogel materials 0.4 g, 2 g, and 4 g of multi-walled carbon nanotubes (MWCNTs) were added to the (PPCT) premixed solution prepared in step (3) of Example 1. The beaker containing the material was stirred on a magnetic stirrer for 3 h to obtain a black mixed solution. The solution was dried at room temperature to form a film (referred to as PPCT-MWCNT-1, PPCT-MWCNT-2, and PPCT-MWCNT-3, respectively).

[0038] (1) The film was dried at room temperature, and the effect of C-CNF on the thermodynamic properties of the phase change material was investigated by DSC test and energy storage capacity calculation.

[0039] (2) Directional freeze drying was performed at -80 °C and a freezing rate of 20 °C / min to obtain black phase change aerogel materials (referred to as aerogels A-PPCT-MWCNT-1, A-PPCT-MWCNT-2, and A-PPCT-MWCNT-3, respectively).

[0040] Example 4 Preparation of phase change composite materials Eicosane paraffin was melted and added to the aerogel prepared in step (2) of Example 3 at mass ratios of 2:1, 3:1, and 1:1, respectively. After three vacuum adsorptions, the sample was left to stand under vacuum for 6 h. Then, the excess paraffin on the sample surface was adsorbed using filter paper. Finally, after the sample cooled to room temperature, the phase change material was cured to obtain phase change composite materials A-PPCT-MWCNT-C20-1 (corresponding to aerogel 3-1), A-PPCT-MWCNT-C20-2 (corresponding to aerogel 3-2), and A-PPCT-MWCNT-C20-3 (corresponding to aerogel 3-3). Finally, the paraffin loading rate was calculated.

[0041] Example 5 40 g of waterborne polyurethane (TPU) was added to the premixed solution obtained in step (1) of Example 1. The beaker containing the material was stirred on a magnetic stirrer for 3 h to obtain a milky white mixed solution (PPT), which was then dried at room temperature to form a film.

[0042] Example 6 32 g of polyethylene glycol (MW20000) and 8 g of polyethylene oxide (MW600000) were added to 400 mL of deionized water and stirred until homogeneous. Then, 40 mL of carboxylated cellulose nanofibers (C-CNF) and 40 g of waterborne polyurethane (TPU) were added. The beaker containing the materials was stirred on a magnetic stirrer for 3 h to obtain a completely dissolved, clear and transparent solution. Finally, the solution was dried at room temperature to form a film.

[0043] The phase change material film prepared under these conditions has stable shape, good mechanical properties, and excellent thermal management performance.

[0044] Comparative Example 1 32 g of polyethylene glycol (MW200) and 8 g of polyethylene oxide (MW600000) were added to 400 mL of deionized water. The beaker containing the materials was stirred on a magnetic stirrer for 3 h to obtain a completely dissolved, clear and transparent solution. Finally, the solution was dried at room temperature to form a film.

[0045] Performance testing of materials prepared in the examples and comparative examples: Scanning electron microscope (SEM) and polarizing microscope (PMS) images of the PP mixture prepared in Example 1, the PPC mixture and PPCT mixture prepared in Example 1, and the PPT mixture prepared in Example 5 after drying and forming films are shown below. Figure 1 As shown.

[0046] In the SEM image of the PP mixture after film formation, the film cross-section structure is dense, indicating good compatibility. In the POM image, large circular crystalline regions are shown. Although these regions have crystallization ability, their microstructure is relatively loose, which may pose a risk of shape instability when heated and melted.

[0047] SEM images of the PPC material reveal a porous or three-dimensional network structure, providing effective physical support for the material. POM images show that the crystal size becomes smaller and more uniform, indicating that the addition of C-CNF alters the microstructure of the material, making it more compact. This is due to the hydrogen bonding interaction between the hydroxyl groups on the cellulose surface and the ether bonds of the PEG / PEO molecular chains, which enhances the interfacial compatibility between the two. The POM images also show denser crystalline regions, indicating that the added C-CNF can be more uniformly dispersed in the PEG / PEO mixed solution to form a network structure, which can, to some extent, confine the PEG and help enhance the shape stability of the material.

[0048] SEM images of PPT material show that the addition of TPU has little effect on the morphology of PEG / PEO; POM images show that the addition of TPU affects the crystallization of the material, and the crystallization region is blurred and the crystal nucleus size is smaller than that of PPC.

[0049] The SEM images of the PPCT material reveal a dense and uniform network structure. Its POM images show that the crystals are uniform, exhibiting a dense network structure and clear crystalline regions. This indicates that the simultaneous addition of C-CNF and TPU produces a synergistic effect, maintaining good crystallinity while constructing a stable microstructure. This enables the material to possess excellent shape stability and complete crystallization ability during the phase transition, thus offering advantages in terms of energy storage density and lifespan.

[0050] The properties of the phase change materials obtained in the examples and comparative examples were measured, and the results are shown in Tables 1 and 2.

[0051] Table 1. Crystallinity of the phase change materials prepared in Examples 1-2 As shown in Table 1, adding an appropriate amount of C-CNF can effectively improve the crystallinity of the material. By optimizing the amount added, the crystallinity of PPCT can reach up to 65.9%, which is much higher than that of PP; it is also higher than that of Example 1-PPC, which added an equal amount of C-CNF alone. TPU has poor crystallinity, and its crystallinity will decrease to some extent when added alone. However, when C-CNF and TPU are present together, the crystallinity is improved. This is because the coexistence of C-CNF and TPU synergistically increases the nucleation sites, thereby improving the crystallinity through a synergistic effect. The improvement of the crystallinity of phase change materials will improve the phase transition enthalpy and mechanical properties of the material.

[0052] Table 2 Mechanical properties of phase change materials prepared in the examples and comparative examples As shown in Table 2, the PPCT prepared in Example 1 exhibits excellent overall mechanical properties. In terms of tensile strength, PPCT is slightly lower than PPC, but significantly higher than PP and PPT. However, in terms of elongation at break, PPCT reaches 5.24%, far superior to PPC and PP; achieving a balance between high strength and good toughness.

[0053] Table 3. Energy storage capacity of phase change materials prepared in the examples and comparative examples. Note: Examples 3-1 in the table are examples. The thermodynamic properties of the examples and comparative examples were studied using DSC. Table 3 shows the enthalpy of melting for the examples and comparative examples. The enthalpy of melting and the enthalpy of crystallization are very close, indicating that the melting and crystallization processes of the materials are reversible, with good thermal cycling stability, which is beneficial for long-term use. A horizontal comparison among the examples shows that the enthalpy of melting and the enthalpy of crystallization of the phase change material decrease with the addition of C-CNF and TPU. However, due to the presence of C-CNF, the crystallinity is increased, affecting the thermodynamic properties of the phase change material; the measured values ​​of enthalpy of melting and the enthalpy of crystallization are higher than the theoretical values. Particularly noteworthy is that the measured values ​​of enthalpy of melting / enthalpy of crystallization of PPCT are significantly higher than the theoretical values, indicating that it can store more heat and has better thermal management performance in practical applications. After loading paraffin, the enthalpy of melting and the enthalpy of crystallization of the phase change composite material prepared in Example 4 can reach about 200 J / g, which can further improve the thermal management performance.

[0054] Table 4 shows the adsorption rate of paraffin in Example 4, where the encapsulation efficiency reaches 96.27% when the mass ratio of paraffin to aerogel is 1:1.

[0055] Table 4. Paraffin loading rate of the phase change composite material prepared in Example 4 Figure 2 a shows the preparation method of A-PPCT-MWCNT, which involves preparing aerogels via directional freezing; such as Figure 2 b、 Figure 2 As shown in c, scanning electron microscope images at different magnifications show that after freeze-drying, the aerogel of A-PPCT-MWCNT exhibits a vertical pore structure. This structure is beneficial for heat conduction and provides space for adsorbing phase change materials, proving that the prepared phase change material can be used as an encapsulation material after freeze-drying.

[0056] Figure 3 The heating process of the samples prepared in Examples 1 and 5 was recorded using a thermal infrared camera. Figure 4 These are the heating and cooling rate records of the samples prepared in Examples 1 and 5. The PPCT prepared by this invention exhibits excellent thermal management capabilities and better temperature stability throughout the entire testing cycle; the rate of temperature rise and fall is lower than that of other test samples, and the maximum temperature reached is also significantly lower, 15 °C lower than that of PPT. Figure 5(a) Temperature changes of PPCT prepared in Example 1, PPCT-MWCNT-1, PPCT-MWCNT-2, PPCT-MWCNT-3, A-PPCT-MWCNT-3 prepared in Example 3, and composite phase change material A-PPCT-MWCNT-C20-3 prepared in Example 4 under light irradiation. Due to the addition of MWCNT, the temperature of PPCT-MWCNT rises faster than that of PPCT due to the heat generated by light irradiation. Figure 5 (b) shows the heating and cooling rates of PPCT-MWCNT under illumination, with PPCT-MWCNT-2 and PPCT-MWCNT-3 exhibiting better thermal management capabilities. Figure 5 (a) and Figure 5 As shown in (c), when paraffin is added, the temperature of A-PPCT-MWCNT-C20 under light irradiation shows a two-stage heating curve of rapid heating and slow heating. When the light is turned off, the rate of temperature decrease is slower than that of PPCT-MWCNT and A-PPCT-MWCNT without paraffin, indicating that the addition of paraffin improves the thermal management ability of the aerogel.

[0057] In summary, this invention uses biocompatible polyethylene glycol and polyethylene oxide as raw materials, and carboxylated cellulose nanofibers and waterborne polyurethane as fillers to improve crystallinity and mechanical properties. Using deionized water as a solvent, a shape-stable phase change material (PPCT) with high energy storage capacity was prepared using a simple dissolution and stirring method. The crystallinity and mechanical properties of the PPCT were significantly improved through the synergistic effect of C-CNF and TPU. This invention further incorporates multi-walled carbon nanotubes (MWCNTs) to prepare a phase change aerogel capable of encapsulating PPCTs via freeze-drying; this aerogel achieves an encapsulation efficiency of over 95% for paraffin, further enhancing the energy storage capacity; the prepared PPCT also exhibits good thermal management capabilities.

[0058] The phase change material prepared by the method of this invention solves to some extent the problems of low thermal density, poor thermal conductivity and limited strength of polyethylene glycol, which are not conducive to its application. It opens up new avenues for polyethylene glycol in phase change material energy storage research, electronic devices and building thermal management.

[0059] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the present invention.

Claims

1. A method for preparing a polyoxyethylene high-energy-storage-capacity phase change material, characterized in that, Including steps S1 and S2: S1. Dissolve polyethylene glycol and polyethylene oxide in deionized water to obtain a premixed solution; S2. Add carboxylated cellulose nanofibers and aqueous polyurethane to the premixed solution obtained in step S1 to obtain a milky white mixed solution-a. After drying, the polyoxyethylene high energy storage capacity phase change material can be obtained.

2. The method for preparing the polyoxyethylene high-energy-storage-capacity phase change material according to claim 1, characterized in that, In step S1, the molecular weight of polyethylene glycol is 8,000-20,000, the molecular weight of polyethylene oxide is 100,000-7,000,000, and the mass ratio of polyethylene glycol to polyethylene oxide is 7:3-1:

1.

3. The method for preparing the polyoxyethylene high-energy-storage-capacity phase change material according to claim 1, characterized in that, In step S2, the mass ratio of carboxylated cellulose nanofibers to aqueous polyurethane in the mixed solution-a is 5:1 to 1:

5. The total mass of carboxylated cellulose nanofibers and waterborne polyurethane is 5%-40% of the total mass of polyethylene glycol and polyethylene oxide.

4. The polyoxyethylene high-energy-storage-capacity phase change material prepared by the method according to any one of claims 1-3, characterized in that, The energy storage capacity is ≥150 J / g, and the measured value of the energy storage capacity is higher than the theoretical value.

5. A polyoxyethylene high-energy-storage-capacity phase change aerogel material, characterized in that, The phase change material described in claim 4 is doped with multi-walled carbon nanotubes, and the doping amount of multi-walled carbon nanotubes in the phase change aerogel material is 0.01%-25% of the total mass of polyethylene glycol and polyethylene oxide.

6. The method for preparing the phase change aerogel material according to claim 5, characterized in that, Take the mixed solution-a obtained in step S2, add multi-walled carbon nanotubes and mix well to obtain mixed solution-b, then freeze-dry in a directional manner.

7. The method for preparing the phase change aerogel material according to claim 6, characterized in that, The directional freeze-drying conditions are: temperature between -20 and -80 ℃, and freezing rate of 10-30 ℃ / min.

8. The use of the polyoxyethylene high-energy-storage-capacity phase change aerogel material according to claim 5 as a phase change material carrier, characterized in that, Used for encapsulating phase change materials and preparing phase change composite materials; The phase change composite material exhibits a two-stage heating curve under light irradiation, characterized by rapid heating and slow heating.

9. The use according to claim 8, characterized in that, The phase change material is paraffin, preferably a C10-C20 alkane; The encapsulation method is as follows: take the phase change aerogel material, adsorb molten paraffin under a certain vacuum degree, and then cool it to obtain the phase change composite material.

10. The application of the phase change material according to claim 4, or the phase change aerogel material according to claim 5, or the phase change composite material according to any one of claims 8-9, characterized in that, It is used in the fields of new energy vehicles, electronic communications, green buildings, and smart textiles for thermal management.

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