A phase change material, its preparation method and application

Abstract

This invention discloses a phase change material, its preparation method, and its applications, relating to the field of phase change energy storage materials technology. The preparation method of the phase change material of this invention includes the following steps: S1. Adding a crosslinking agent, an initiator, h-MWCNTs, and water to polyethylene glycol to obtain a mixed liquid; S2. Performing a crosslinking reaction on the mixed liquid and drying it to obtain the phase change material. This invention incorporates h-MWCNTs (hydroxylated carbon nanotubes) while simultaneously causing crosslinking of the polyethylene glycol molecular chains. h-MWCNTs can induce uniform orientation of the polyethylene glycol molecular chains, thus increasing the phase change enthalpy and thermal conductivity of the phase change material.

Description

Technical Field

[0001] This invention relates to the field of phase change energy storage materials technology, specifically to a phase change material, its preparation method, and its application. Background Technology

[0002] Phase change materials (PCMs) are materials with excellent energy storage density. They are substances that change their state of matter while maintaining a constant temperature and can provide latent heat. The process of changing physical properties is called a phase change process, during which PCMs absorb or release a large amount of latent heat. PCMs have wide applications in aerospace, construction, clothing, refrigeration, military, communications, and power industries. In particular, PCMs can be effectively coupled with renewable energy sources such as solar energy, thus showing great potential for energy storage and power supply.

[0003] Polyethylene glycol (PEG), as a typical phase change material, has advantages such as being non-toxic, non-corrosive, and having good biocompatibility. Its phase change temperature can be adjusted by its molecular weight. However, most existing PEG-based phase change materials utilize solid-liquid phase change processes for energy storage, which are prone to leakage during the phase change process, thus limiting their large-scale production and application.

[0004] Existing technology discloses a method for preparing solid-solid phase change materials immobilized by chemical crosslinking. By adding a crosslinking agent, polyethylene glycol (PEG) molecular chains are crosslinked to form a network structure, and the resulting PEG-based phase change material achieves energy storage through a solid-solid phase change process. However, during the free radical polymerization reaction between PEG and the crosslinking agent, the formation of the crosslinked network chain affects the mobility and regularity of the PEG chain segments. Therefore, in this PEG-based phase change material, the degree of crystallinity after crosslinking is actually reduced, leading to a decrease in the phase change enthalpy and a reduction in the energy that can be stored when applied for energy storage.

[0005] In addition, as a phase change material, it should have good thermal conductivity, which is beneficial for its efficient heat transfer during operation. Summary of the Invention

[0006] To address the problem that existing cross-linked polyethylene glycol-based phase change materials suffer from reduced crystallinity, making it difficult to improve the phase change enthalpy, this invention provides a method for preparing phase change materials. This method involves adding h-MWCNTs (hydroxylated carbon nanotubes) while cross-linking the polyethylene glycol molecular chains. h-MWCNTs can induce a uniform orientation of the polyethylene glycol molecular chains, thus increasing the phase change enthalpy of the cross-linked polyethylene glycol and simultaneously improving its thermal conductivity.

[0007] Another object of the present invention is to provide a phase change material.

[0008] Another objective of this invention is to provide an application of phase change materials in the field of energy storage and power supply.

[0009] The above-mentioned objective of this invention is achieved through the following technical solution:

[0010] A method for preparing a phase change material includes the following steps:

[0011] S1. Add crosslinking agent, initiator, h-MWCNT and water to polyethylene glycol to obtain a mixed liquid;

[0012] S2. The mixed liquid undergoes a crosslinking reaction and is then dried to obtain the phase change material;

[0013] The mass ratio of h-MWCNT to polyethylene glycol in step S1 is (0.013~0.045):1.

[0014] Adding crosslinking agents and initiators to polyethylene glycol (PEG) causes crosslinking between different PEG molecular chains, forming a network structure. Adding a certain amount of h-MWCNTs (hydroxylated carbon nanotubes) to the system allows the h-MWCNTs to adhere to the network structure through active group reactions, electrostatic adsorption, and hydrogen bonding. This adhesion increases the strength and stiffness of the composite material and improves its heat resistance and corrosion resistance.

[0015] More importantly, h-MWCNT induces the regular arrangement of polyethylene glycol molecular chains: h-MWCNT has a large specific surface area and can interact with polyethylene glycol molecular chains through intermolecular interactions (including van der Waals forces, electrostatic interactions, and hydrogen bonding), inducing the regular arrangement of polyethylene glycol molecular chains, thereby improving the thermal conductivity and phase transition enthalpy of the network structure polyethylene glycol.

[0016] The mass ratio of h-MWCNT to polyethylene glycol in step S1 is controlled at (0.013–0.045):1 because h-MWCNT itself has a very low phase change enthalpy, much lower than that of polyethylene glycol. When too much h-MWCNT is added, its introduction will reduce the phase change enthalpy of the phase change material, thus reducing its energy storage capacity. However, when the amount of h-MWCNT added is too low, adding h-MWCNT to the system will not improve the thermal conductivity and phase change enthalpy of the phase change material.

[0017] Preferably, in step S1, the crosslinking agent is first added to polyethylene glycol and dispersed evenly before the initiator, h-MWCNT and water are added.

[0018] Preferably, step S1 is carried out at 40–80°C. This is beneficial for the complete dissolution and mixing of the components.

[0019] Preferably, the crosslinking reaction and drying in step S2 are carried out at 40–80°C for 3–10 hours.

[0020] h-MWCNTs have good surface activity and can undergo adsorption reactions with the active groups of polyacrylic acid, thereby attaching to the network structure.

[0021] Preferably, the initiator in step S1 can be a peroxide initiator, more specifically, it can be ammonium persulfate.

[0022] Preferably, the crosslinking agent in step S1 is at least one of organic peroxide crosslinking agents or azo crosslinking agents.

[0023] More preferably, the organic peroxide crosslinking agent is at least one of benzoyl peroxide (BPO), ditert-butyl peroxide (DTBP), or tert-butyl peroxide (TBPO).

[0024] More preferably, the azo crosslinking agent is at least one of N,N'-methylenebisacrylamide, nitrogen diisobutyronitrile (AIBN), or azobisisoheptanenitrile (ABVN).

[0025] Preferably, step S1 further includes the addition of acrylic acid.

[0026] The addition of acrylic acid can form polyacrylic acid segments on the polyethylene glycol molecular chain during the cross-linking reaction in step S2. The polyacrylic acid segments can improve the degree of cross-linking of polyethylene glycol on the one hand, and on the other hand, they can react with the hydroxyl groups of h-MWCNT to better adsorb h-MWCNT on the polyethylene glycol network structure, thereby further improving the thermal conductivity and phase change enthalpy of the phase change material.

[0027] More preferably, the mass ratio of acrylic acid to polyethylene glycol is 1:(2-6).

[0028] Preferably, the mass ratio of the crosslinking agent to polyethylene glycol in step S1 is 1:(50-100).

[0029] Preferably, the mass ratio of the initiator to polyethylene glycol in step S1 is 1:(300-500).

[0030] Preferably, the mass ratio of water to polyethylene glycol in step S1 is 1:(8-20).

[0031] Preferably, the weight-average molecular weight of the polyethylene glycol in step S1 is 1000 to 5000.

[0032] A phase change material prepared by the above-described method for preparing phase change materials.

[0033] The application of the aforementioned phase change materials in the field of energy storage and power supply is also within the scope of protection of this invention.

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] This invention incorporates h-MWCNTs (hydroxylated carbon nanotubes) while crosslinking polyethylene glycol (PEG) molecular chains. h-MWCNTs have a large specific surface area and can interact with PEG molecular chains through intermolecular interactions (including van der Waals forces, electrostatic interactions, and hydrogen bonding), inducing PEG molecular chains to adopt a consistent orientation. This increases the phase change enthalpy of the phase change material and also improves its thermal conductivity. Detailed Implementation

[0036] In this invention, the technical features described in an open-ended manner include both closed-ended technical solutions composed of the listed features and open-ended technical solutions that include the listed features. In this invention, numerical intervals (i.e., numerical ranges) are involved. Unless otherwise specified, the distribution of selectable numerical values ​​within the numerical interval is considered continuous, and includes the two endpoints of the numerical interval (i.e., the minimum and maximum values), as well as every value between these two endpoints. When multiple numerical ranges are provided to describe a feature or characteristic, these numerical ranges can be merged. In other words, unless otherwise specified, the numerical ranges disclosed herein should be understood to include any and all subranges included therein. The "numerical value" in the numerical interval can be any quantitative value, such as a number, percentage, ratio, etc. The term "numerical interval" can broadly include numerical interval types such as percentage intervals, ratio intervals, and proportion intervals.

[0037] Unless otherwise specified, the temperature parameters in this invention can be either constant-temperature treatment or vary within a certain temperature range. It should be understood that the constant-temperature treatment allows temperature fluctuations within the precision range controlled by the instrument. Fluctuations are permitted within ranges such as ±5℃, ±4℃, ±3℃, ±2℃, and ±1℃. In this invention, if the unit for a data range is only followed by the right endpoint, it indicates that the units for the left and right endpoints are the same. For example, 3~10h means that the units for the left endpoint "3" and the right endpoint "10" are both hours (h).

[0038] The mass or weight of the relevant components mentioned in the embodiments of this invention can refer not only to the specific content of each component, but also to the proportional relationship of mass or weight between the components. Therefore, any scaling up or down of the content of the relevant components according to the embodiments of this invention is within the scope disclosed in the embodiments of this invention. Specifically, the mass or weight mentioned in the embodiments of this invention can be units known in the chemical industry, such as μg, mg, g, and kg.

[0039] In this invention, where the method involves multiple steps, unless otherwise explicitly stated herein, the execution of these steps is not strictly limited in order and can be performed in any order other than that described. Moreover, any step may include multiple sub-steps or multiple stages, which are not necessarily completed at the same time, but can be executed at different times, and their execution order is not necessarily sequential, but can be performed alternately or simultaneously with other steps or parts of the sub-steps or stages of other steps.

[0040] The present invention will be further described below with reference to specific embodiments, but the embodiments do not limit the present invention in any way. It should be understood that these embodiments and examples are only for illustrating the present invention and are not intended to limit the scope of the present invention. The purpose of providing these embodiments and examples is to make the disclosure of the present invention more thorough and complete. It should also be understood that the present invention can be implemented in many different forms and is not limited to the embodiments and examples described herein. Those skilled in the art can make various modifications or alterations without departing from the spirit of the present invention, and the equivalent forms obtained also fall within the protection scope of the present invention. For example, features described or described as part of one embodiment can be combined in a suitable manner in another embodiment to produce new embodiments. Furthermore, numerous specific details are set forth in the following description to provide a fuller understanding of the present invention. It should be understood that the present invention can be implemented without one or more of these details. Unless otherwise stated, the raw materials and reagents used in the embodiments of the present invention are conventionally purchased raw materials and reagents.

[0041] Example 1

[0042] This embodiment provides a method for preparing a phase change material, including the following steps:

[0043] S1. At 65°C, 0.1 parts by weight of N,N'-methylenebisacrylamide and 2 parts by weight of acrylic acid were added to 8 parts by weight of polyethylene glycol (purchased from Shanghai Jiji Biochemical Technology Co., Ltd., the same below). After stirring evenly, 0.02 parts by weight of initiator (ammonium persulfate), 0.1624 parts by weight of h-MWCNT (50 micrometers, diameter 8-15 nanometers, purchased from BEST MATERIALS, the same below) and 0.6 parts by weight of water were added and dispersed evenly to obtain a mixed liquid.

[0044] S2. The mixed liquid obtained in step S1 is subjected to deoxygenation treatment. After deoxygenation, it is placed at a temperature of 65°C for reaction and drying. The reaction and drying time is 6 hours. After the reaction and drying are completed, it is shaped to obtain a phase change material.

[0045] Example 2

[0046] This embodiment provides a method for preparing a phase change material, which is basically the same as that in Embodiment 1, except that:

[0047] The amount of h-MWCNT used in step S1 is 0.108 parts by weight.

[0048] Example 3

[0049] This embodiment provides a method for preparing a phase change material, which is basically the same as that in Embodiment 1, except that:

[0050] The amount of h-MWCNT used in step S1 is 0.2752 parts by weight.

[0051] Example 4

[0052] This embodiment provides a method for preparing a phase change material, which is basically the same as that in Example 1, except that:

[0053] The amount of h-MWCNT used in step S1 is 0.3315 parts by weight.

[0054] Example 5

[0055] This embodiment provides a method for preparing a phase change material, which is basically the same as that in Embodiment 1, except that:

[0056] In step S1, the amount of N,N'-methylenebisacrylamide used is 0.08 parts by weight, the amount of acrylic acid used is 0.025 parts by weight, and the amount of water used is 0.4 parts by weight.

[0057] Comparative Example 1

[0058] This comparative example provides a method for preparing a phase change material, including the following steps:

[0059] S1. At 65°C, 0.1 parts by weight of N,N'-methylenebisacrylamide and 2 parts by weight of acrylic acid were added to 8 parts by weight of polyethylene glycol. After stirring evenly, 0.02 parts by weight of initiator (ammonium persulfate), 0.0539 parts by weight of h-MWCNT and 0.6 parts by weight of water were added and dispersed evenly to obtain a mixed liquid.

[0060] S2. The mixed liquid obtained in step S1 is subjected to deoxygenation treatment. After deoxygenation, it is placed at a temperature of 65°C for reaction and drying. The reaction and drying time is 6 hours. After the reaction and drying are completed, it is shaped to obtain a phase change material.

[0061] Performance testing

[0062] The phase change materials of the examples and comparative examples were subjected to the following tests:

[0063] Thermal conductivity test: ① Sample preparation: Cut the finished material into 20mm*20mm*5mm rectangular blocks to ensure that the instrument probe can completely cover the sample surface; ② Set the instrument data: 1W heating power, from room temperature (25℃) to 100℃, heat for 5 minutes; ③ Wait for the instrument to record the data to obtain the thermal conductivity distribution map of the sample.

[0064] Phase transition enthalpy test: ① Sample preparation: Ensure sample purity by cutting the sample into 10mg pieces and ensure compatibility between the sample and crucible material. ② Instrument calibration: Calibrate temperature and sensitivity using standard samples (such as indium and zinc). ③ Test program setting: Heat the sample in nitrogen at a heating rate of 10℃ / min from 40℃ to 600℃; ④ Wait for the instrument to test and collect test data.

[0065] The specific test data is shown in Table 1 below:

[0066] Table 1. Data from Examples and Comparative Examples

[0067] Example 1 120.60 0.4176 Example 2 100.92 0.3893 Example 3 130.33 0.4561 Example 4 133.65 0.4734 Comparative Example 1 96.57 0.3612

[0068] As can be seen from Table 1:

[0069] The phase change materials in Examples 1-4 all have a phase change enthalpy of over 100 J / g and a thermal conductivity of over 0.38 W / (m·K), indicating that the phase change materials of the present invention have good phase change enthalpy and good thermal conductivity. The phase change enthalpy and thermal conductivity of Example 5 are comparable to those of Example 1.

[0070] In Comparative Example 1, the addition of too little h-MWCNT resulted in a low phase change enthalpy and low thermal conductivity of the resulting phase change material. Furthermore, since the phase change enthalpy of h-MWCNT is inherently low, far lower than that of polyethylene glycol, the amount of h-MWCNT added cannot be excessive; otherwise, the phase change enthalpy of the phase change material will also decrease. This indicates that only by controlling the amount of h-MWCNT added within a specific range can both the phase change enthalpy and thermal conductivity of the phase change material be improved simultaneously.

[0071] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art can make other variations or modifications based on the above description. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing a phase change material, characterized in that, Includes the following steps: S1. Add crosslinking agent, initiator, h-MWCNT and water to polyethylene glycol to obtain a mixed liquid; S2. The mixed liquid undergoes a crosslinking reaction and is then dried to obtain the phase change material; The h mentioned in step S1 The mass ratio of MWCNT to polyethylene glycol is (0.020–0.045):1; Step S1 also includes the step of adding acrylic acid; In step S1, the crosslinking agent is first added to polyethylene glycol and dispersed evenly before the initiator, h-MWCNT and water are added; the mass ratio of water to polyethylene glycol in step S1 is 1:(8-20).

2. The method for preparing the phase change material as described in claim 1, characterized in that, The mass ratio of the crosslinking agent to polyethylene glycol in step S1 is 1:(50-100).

3. The method for preparing the phase change material as described in claim 1, characterized in that, The mass ratio of acrylic acid to polyethylene glycol in step S1 is 1:(2-6).

4. The method for preparing the phase change material as described in claim 1, characterized in that, The mass ratio of the initiator to polyethylene glycol in step S1 is 1:(300-500).

5. The method for preparing the phase change material as described in claim 1, characterized in that, The weight-average molecular weight of the polyethylene glycol mentioned in step S1 is 1000-5000.

6. A phase change material prepared by the preparation method of the phase change material according to any one of claims 1 to 5.

7. The application of the phase change material according to claim 6 in the field of energy storage and power supply.