Flexible and breathable graphene phase change film and preparation method thereof

Abstract

The application provides a flexible and breathable graphene phase change film and a preparation method thereof. The preparation method comprises the following steps: preparing a graphene fluffy film in which graphene is arranged in an in-plane direction; forming a plurality of cutouts in the graphene fluffy film along the thickness direction of the graphene fluffy film; immersing the graphene fluffy film with the cutouts into a phase change material, so that the phase change material diffuses into the gaps between the graphene layers in the graphene fluffy film to form a graphene film with composite phase change material; and drying the graphene film with composite phase change material to obtain the flexible and breathable graphene phase change film. Before the graphene fluffy film is immersed into the phase change material to realize compounding, a plurality of cutouts are formed on the film, the contact area of the graphene film and the phase change material is increased, the adsorption capacity of the phase change material is improved, and the phase change enthalpy is improved. In addition, due to the existence of the cutout structure, the finally formed graphene phase change film has better flexibility and breathability.

Description

Technical Field

[0001] This invention belongs to the field of graphene and wearable materials technology, specifically relating to a flexible, breathable graphene phase change film and its preparation method. Background Technology

[0002] With the advancement of science and technology and the expansion of people's activities, relying on increasing fabric thickness to improve warmth retention is no longer sufficient to meet people's comprehensive requirements for efficient, warm, comfortable, and convenient thermal fabrics. The ability of phase change materials (PCMs) to absorb or release large amounts of heat during phase transitions to regulate the temperature of the fabric's internal "microenvironment" has drawn attention to the application of PCMs in clothing with energy storage and temperature regulation functions.

[0003] Scientific tests show that the most comfortable skin temperature for the human body is 33.4℃. If the temperature difference between any part of the body and this most comfortable skin temperature is between 1.5℃ and 3.0℃, the body will feel neither too hot nor too cold. However, if this temperature difference exceeds 4.5℃, the body will feel either too hot or too cold. Clothing made with phase change materials can control this temperature difference within 3℃, thus ensuring the wearer's comfort.

[0004] Phase change materials (PCMs) suffer from leakage during phase transitions. Therefore, PCMs are often loaded onto carrier materials to prepare composite shaped PCMs, ensuring their stability during the phase transition process. However, the resulting composite shaped PCMs are often rigid, reducing their operability and making them unsuitable for many practical applications. Therefore, the preparation of flexible composite shaped PCMs has significant practical value.

[0005] Chinese invention patent application number 202010285705.8 uses graphene oxide as raw material, prepares graphene aerogel through freeze-drying and high-temperature reduction, then introduces polyvinylidene fluoride, and prepares a graphene composite film by a blade coating method. Finally, a phase change material is impregnated into the film through vacuum impregnation to obtain a graphene-based flexible composite shaped phase change material film. While this graphene-based flexible composite shaped phase change material film solves the problem of poor flexibility in phase change materials, its poor air permeability makes it difficult to apply to clothing. Furthermore, the preparation method of this material is relatively complex. Summary of the Invention

[0006] Therefore, the technical problem to be solved by the present invention is to provide a flexible and breathable graphene phase change film and its preparation method, so as to overcome the shortcomings of the existing graphene phase change film in terms of poor breathability and difficulty in applying it to clothing.

[0007] To address the above problems, this invention provides a method for preparing a flexible, breathable graphene phase change film, comprising the following steps:

[0008] S100, to prepare a fluffy graphene film with graphene oriented in the in-plane direction;

[0009] S200 is a graphene fuzzy film with multiple perforations formed along its thickness direction.

[0010] S300, the porous graphene film is immersed in a phase change material so that the phase change material diffuses into the gaps between the graphene sheets in the porous graphene film to form a graphene film of composite phase change material.

[0011] S400, the flexible, breathable graphene phase change film is prepared by drying the graphene film of the composite phase change material.

[0012] In some embodiments, the fluffy graphene film is prepared in the following manner:

[0013] A graphene NMP dispersion of the target concentration is injected into a syringe at a target flow rate, wherein the tip of the syringe is at a target distance from the film-forming substrate, and the film-forming substrate is placed on a heating element heated to the target temperature.

[0014] A target voltage is applied between the film-forming substrate and the tip of the needle using a DC power supply and maintained for a first target duration. Under the action of the electric field of the DC power supply, the graphene in the needle will be deposited onto the surface of the film-forming substrate to form a fluffy graphene film with the graphene oriented in the in-plane direction. After immersion in water for a second target duration, the fluffy graphene film with the graphene oriented in the in-plane direction is peeled off from the film-forming substrate.

[0015] In some implementations...

[0016] The target concentration is 0.2 mg / ml to 2 mg / ml; and / or the target flow rate is 50 μL / min to 100 μL / min.

[0017] In some implementations...

[0018] The target voltage is 12kV-15kV; and / or the target distance is 2cm-4cm.

[0019] In some implementations...

[0020] The target temperature is 130℃-160℃; and / or, the first target duration is 5 minutes-100 minutes, and the second target duration is 0.5 hours-1 hour.

[0021] In some embodiments, the density of the graphene fluffy film is 0.8 g / cm³. 3 -1.2g / cm3 .

[0022] In some embodiments, the perforations are formed by laser cutting; and / or, a plurality of the perforations are periodically spaced on the graphene fluffy film; and / or, the phase change material is polyethylene glycol and / or paraffin wax.

[0023] In some embodiments, the perforations are square; and / or, the minimum width of the graphene fluffy film between two adjacent perforations is 2mm-8mm.

[0024] In some embodiments, the side length of the square is 1mm-4mm.

[0025] In some embodiments, the phase change material is composited with the porous graphene fluffy film in a vacuum environment at 80°C and soaked for 24 hours; and / or, after the phase change material is composited with the porous graphene fluffy film, it is placed on a multilayer filter paper and then dried in an oven at 80°C.

[0026] The present invention also provides a flexible, breathable graphene phase change film, which is prepared by the above-described method for preparing a flexible, breathable graphene phase change film, wherein the thickness of the flexible, breathable graphene phase change film is 5 μm-100 μm; and / or, the mass ratio of graphene to phase change material in the flexible, breathable graphene phase change film is (1-3):1.

[0027] This invention provides a flexible and breathable graphene phase change film and its preparation method. Before the fluffy graphene film is immersed in the phase change material to achieve composite, multiple pores are formed on the film to increase the contact area between the graphene film and the phase change material, thereby increasing the adsorption capacity of the phase change material and thus increasing the phase change enthalpy. At the same time, due to the presence of these pore structures, the final graphene phase change film has better flexibility and breathability, making it more suitable for application in clothing. Attached Figure Description

[0028] Figure 1 This diagram illustrates the steps of a method for preparing a flexible, breathable graphene phase change film according to an embodiment of the present invention. Detailed Implementation

[0029] See Figure 1 As shown in the embodiments of the present invention, a method for preparing a flexible, breathable graphene phase change film is provided, comprising the following steps:

[0030] S100 is used to prepare a fluffy graphene film with graphene oriented in the in-plane direction. It should be noted that oriented graphene in the in-plane direction can enhance the thermal conductivity of the graphene phase change film, resulting in a faster phase change temperature control response.

[0031] S200 uses laser cutting to create multiple perforations along the thickness direction of a graphene fluffy film. It can be understood that these perforations penetrate both the top and bottom surfaces of the graphene fluffy film, and the laser cutting method can be set by a program, which is very convenient.

[0032] S300 involves immersing a porous graphene film into a phase change material, allowing the phase change material to diffuse into the gaps between the graphene sheets within the porous graphene film, thus forming a graphene film of composite phase change material.

[0033] S400, a flexible, breathable graphene phase change film was prepared by drying the graphene film of the composite phase change material.

[0034] In this technical solution, before the graphene fluffy film is immersed in the phase change material to achieve composite, multiple pores are formed on the film to increase the contact area between the graphene film and the phase change material, thereby increasing the adsorption capacity of the phase change material and thus increasing the phase change enthalpy. At the same time, due to the existence of these pore structures, the final graphene phase change film has better flexibility and breathability, making it more suitable for application in clothing. In addition, the film preparation method of this invention is simpler and easier to implement.

[0035] In some embodiments, the fluffy graphene film is prepared in the following manner:

[0036] A graphene NMP (N-methylpyrrolidone) dispersion of the target concentration is injected into a syringe at a target flow rate using an injection pump. A film-forming substrate is laid at the bottom of the needle tip of the syringe, and there is a target distance between the needle tip and the film-forming substrate. The film-forming substrate is placed on a heating element (e.g., a hot plate) that is heated to the target temperature. The aforementioned film-forming substrate can be, for example, a flat aluminum foil.

[0037] A target voltage is applied between the film-forming substrate and the tip of the needle using a DC power supply and maintained for a first target duration. Under the influence of the electric field of the DC power supply, graphene in the needle is deposited onto the surface of the film-forming substrate, forming a fluffy graphene film with graphene aligned in the in-plane direction. After immersion in water for a second target duration, the fluffy graphene film with the graphene aligned in the in-plane direction is peeled off from the film-forming substrate. Immersion in water utilizes the hydrophobic properties of graphene and the hydrophilic properties of the film-forming substrate, such as metal foil (aluminum foil), to facilitate the smooth peeling of the graphene film from the film-forming substrate. Specifically,

[0038] The target concentration is 0.2 mg / ml-2 mg / ml; the target flow rate is 50 μL / min-100 μL / min; the target voltage is 12 kV-15 kV; and the target distance is 2 cm-4 cm. These conditions work together to control the deposition rate and sheet interaction forces of graphene, thereby controlling the density of the loose graphene film to be 0.8-1.2 g / cm³. 3 Within this density range, during the subsequent composite process of phase change materials, the phase change materials can easily diffuse into the gaps between graphene sheets, thereby increasing the amount of composite phase change materials and further increasing the phase change enthalpy. At the same time, within this density range, there is a large capillary force between graphene sheets, which can effectively avoid the leakage problem of phase change materials during the phase change process.

[0039] The aforementioned first target duration is 5 minutes to 100 minutes. The thickness of the graphene fluffy film can be controlled by choosing a longer or shorter duration to ensure that the film thickness meets the usage requirements.

[0040] In some embodiments, the target temperature is 130°C-160°C to allow the NMP remaining on the deposited graphene surface to evaporate, resulting in better film formation. If the temperature is too low, the NMP will evaporate slowly and remain in the film; if the temperature is too high, the NMP will evaporate too quickly, causing the film to bubble. And / or, the second target duration is 0.5 hours-1 hour to ensure complete peeling of the fluffy graphene film.

[0041] Multiple perforations are periodically spaced on a fluffy graphene film, specifically arranged in an array at equal intervals along both the horizontal and vertical directions; and / or, the phase change material is polyethylene glycol and / or paraffin wax, i.e., one or a mixture of polyethylene glycol and paraffin wax. The phase change temperature of these two phase change materials is close to the comfortable temperature of human skin, so when the film of the present invention is applied to clothing, it can provide users with better comfort.

[0042] In some implementations, the perforations are square to facilitate perforation processing. The minimum width of the graphene fluffy film between two adjacent perforations is 2mm-8mm, and the corresponding side length of the square is 1mm-4mm. This ensures the mechanical strength of the graphene film after perforation while meeting the requirements of processing and use.

[0043] In some embodiments, the composite of the phase change material and the porous graphene fluffy film is carried out in a vacuum environment (<100 Pa) at 80°C and soaked for 24 hours to ensure that the phase change material is fully diffused into the gaps between the graphene sheets. After the phase change material is composited with the porous graphene fluffy film, it is placed on a multilayer filter paper and then placed in an oven at 80°C to dry, which can improve the drying efficiency of the film.

[0044] According to an embodiment of the present invention, a flexible, breathable graphene phase change film is also provided, which is prepared by the above-described method for preparing a flexible, breathable graphene phase change film. The thickness of the flexible, breathable graphene phase change film is 5μm-100μm, which can meet the requirements of various different operating conditions; and / or, the mass ratio of graphene to phase change material in the flexible, breathable graphene phase change film is (1-3):1. If it is too low, the thermal conductivity is poor and the phase change response speed is slow; if it is too high, the phase change enthalpy value is too low.

[0045] The preparation method of the flexible, breathable graphene phase change film of the present invention is further illustrated below with reference to several embodiments and comparative examples.

[0046] Example 1:

[0047] This embodiment presents a breathable flexible graphene phase change film with a periodic perforated structure. The perforated areas are square with a side length of 4 mm, and the width of the non-perforated graphene film between two adjacent perforated areas is 2 mm. The graphene phase change film is composed of graphene and paraffin wax in a 1:1 mass ratio. The graphene is oriented along the in-plane direction of the film, and the paraffin wax is embedded between the graphene layers.

[0048] This breathable, flexible graphene phase change material is prepared through the following steps:

[0049] Step 1 - Preparation of a fluffy graphene film: A graphene NMP dispersion with a concentration of 0.2 mg / ml was injected into a syringe at a flow rate of 50 μL / min using a syringe pump. A flat aluminum foil was placed 4 cm below the needle as a film-forming substrate. The aluminum foil was placed on a hot plate, and the heating temperature was controlled at 130℃. A DC power supply of 12 kV was applied between the needle and the aluminum foil for 100 minutes. Under the influence of the electric field, graphene was deposited onto the surface of the aluminum foil, forming a fluffy film with graphene aligned in the in-plane direction, 100 micrometers thick and with a density of 0.8 g / cm³. 3 After soaking in water for 1 hour, the fluffy graphene film peeled off the aluminum foil.

[0050] Step 2 - Periodic Hole Cutting: Using a laser cutter, and by setting a program, periodically cut holes in the fluffy graphene film oriented in the in-plane direction obtained in Step 1. The cut-hole area is square with a side length of 4mm, and the width of the non-cut-hole graphene film between two adjacent cut-hole areas is 2mm.

[0051] Step 3 - Composite Phase Change Material: The periodically perforated graphene film obtained in Step 2 is completely immersed in a container filled with paraffin wax and placed in a vacuum environment at 80 degrees Celsius for 24 hours to allow the paraffin wax to fully diffuse into the gaps between the graphene sheets. The graphene film with composite paraffin wax is then removed and placed on multilayer filter paper, and then placed in an oven at 80 degrees Celsius to allow excess paraffin wax on the film surface to be absorbed by the filter paper. Finally, a breathable flexible graphene phase change film is obtained.

[0052] Tests have verified that this embodiment has the largest perforation area (also known as hollowing out), the most fluffy graphene film, the highest paraffin phase change material loading, the highest phase change enthalpy, and the best flexibility and breathability.

[0053] Example 2:

[0054] This embodiment presents a breathable flexible graphene phase change film with a periodic perforated structure. The perforated areas are square with a side length of 4 mm, and the width of the non-perforated graphene film between two adjacent perforated areas is 2 mm. The graphene phase change film is composed of graphene and paraffin wax in a mass ratio of 1.5:1. The graphene is oriented along the in-plane direction of the film, and the paraffin wax is embedded between the graphene layers.

[0055] This breathable, flexible graphene phase change material is prepared through the following steps:

[0056] Step 1 - Preparation of a fluffy graphene film: A graphene NMP dispersion with a concentration of 2 mg / ml was injected into a syringe at a flow rate of 100 μL / min using a syringe pump. A flat aluminum foil was placed 2 cm below the needle as a film-forming substrate. The aluminum foil was placed on a hot plate, and the heating temperature was controlled at 160℃. A DC power supply of 15 kV was applied between the needle and the aluminum foil for 100 minutes. Under the influence of the electric field, graphene was deposited onto the surface of the aluminum foil, forming a fluffy film with graphene aligned in the in-plane direction, 100 micrometers thick and with a density of 1.2 g / cm³. 3 After soaking in water for 1 hour, the fluffy graphene film peeled off the aluminum foil.

[0057] Step 2 - Periodic Hole Cutting: Using a laser cutter, and by setting a program, periodically cut holes in the fluffy graphene film oriented in the in-plane direction obtained in Step 1. The cut-hole area is square with a side length of 4mm, and the width of the non-cut-hole graphene film between two adjacent cut-hole areas is 2mm.

[0058] Step 3 - Composite Phase Change Material: The periodically perforated graphene film obtained in Step 2 is completely immersed in a container filled with paraffin wax and placed in a vacuum environment at 80 degrees Celsius for 24 hours to allow the paraffin wax to fully diffuse into the gaps between the graphene sheets. The graphene film with composite paraffin wax is then removed and placed on multilayer filter paper, and then placed in an oven at 80 degrees Celsius to allow excess paraffin wax on the film surface to be absorbed by the filter paper. Finally, a breathable flexible graphene phase change film is obtained.

[0059] Tests have verified that in this embodiment, the perforation area is the largest, the graphene film is the densest, the paraffin phase change material loading is high, the phase change enthalpy is high, and the flexibility and air permeability are good.

[0060] Example 3:

[0061] This embodiment presents a breathable flexible graphene phase change film with a periodic perforated structure. The perforated areas are square with a side length of 1 mm, and the width of the non-perforated graphene film between two adjacent perforated areas is 8 mm. The graphene phase change film is composed of graphene and paraffin wax in a mass ratio of 2.2:1. The graphene is oriented along the in-plane direction of the film, and the paraffin wax is embedded between the graphene layers.

[0062] This breathable, flexible graphene phase change material is prepared through the following steps:

[0063] Step 1 - Preparation of a fluffy graphene film: A graphene NMP dispersion with a concentration of 0.2 mg / ml was injected into a syringe at a flow rate of 50 μL / min using a syringe pump. A flat aluminum foil was placed 4 cm below the needle as a film-forming substrate. The aluminum foil was placed on a hot plate, and the heating temperature was controlled at 130℃. A DC power supply of 12 kV was applied between the needle and the aluminum foil for 100 minutes. Under the influence of the electric field, graphene was deposited onto the surface of the aluminum foil, forming a fluffy film with graphene aligned in the in-plane direction, 100 micrometers thick and with a density of 0.8 g / cm³. 3 After soaking in water for 1 hour, the fluffy graphene film peeled off the aluminum foil.

[0064] Step 2 - Periodic Hole Cutting: Using a laser cutter, and by setting a program, periodically cut holes in the fluffy graphene film oriented in the in-plane direction obtained in Step 1. The cut-hole area is square with a side length of 1mm, and the width of the non-cut-hole graphene film between two adjacent cut-hole areas is 8mm.

[0065] Step 3 - Composite Phase Change Material: The periodically perforated graphene film obtained in Step 2 is completely immersed in a container filled with paraffin wax and placed in a vacuum environment at 80 degrees Celsius for 24 hours to allow the paraffin wax to fully diffuse into the gaps between the graphene sheets. The graphene film with composite paraffin wax is then removed and placed on multilayer filter paper, and then placed in an oven at 80 degrees Celsius to allow excess paraffin wax on the film surface to be absorbed by the filter paper. Finally, a breathable flexible graphene phase change film is obtained.

[0066] Tests have shown that this embodiment has the smallest perforation area, the most fluffy graphene film, a moderate amount of paraffin phase change material, a moderate phase change enthalpy, but poor flexibility and air permeability.

[0067] Example 4:

[0068] This embodiment presents a breathable flexible graphene phase change film with a periodic perforated structure. The perforated areas are square with a side length of 1 mm, and the width of the non-perforated graphene film between two adjacent perforated areas is 8 mm. The graphene phase change film is composed of graphene and paraffin wax in a mass ratio of 3:1. The graphene is oriented along the in-plane direction of the film, and the paraffin wax is embedded between the graphene sheets.

[0069] This breathable, flexible graphene phase change material is prepared through the following steps:

[0070] Step 1 - Preparation of a fluffy graphene film: A graphene NMP dispersion with a concentration of 2 mg / ml was injected into a syringe at a flow rate of 100 μL / min using a syringe pump. A flat aluminum foil was placed 2 cm below the needle as a film-forming substrate. The aluminum foil was placed on a hot plate, and the heating temperature was controlled at 160℃. A DC power supply of 15 kV was applied between the needle and the aluminum foil for 100 minutes. Under the influence of the electric field, graphene was deposited onto the surface of the aluminum foil, forming a fluffy film with graphene aligned in the in-plane direction, 100 micrometers thick and with a density of 1.2 g / cm³. 3 After soaking in water for 1 hour, the fluffy graphene film peeled off the aluminum foil.

[0071] Step 2 - Periodic Hole Cutting: Using a laser cutter, and by setting a program, periodically cut holes in the fluffy graphene film oriented in the in-plane direction obtained in Step 1. The cut-hole area is square with a side length of 1 mm, and the width of the non-cut-hole graphene film between two adjacent cut-hole areas is 8 mm.

[0072] Step 3 - Composite Phase Change Material: The periodically perforated graphene film obtained in Step 2 is completely immersed in a container filled with paraffin wax and placed in a vacuum environment at 80 degrees Celsius for 24 hours to allow the paraffin wax to fully diffuse into the gaps between the graphene sheets. The graphene film with composite paraffin wax is then removed and placed on multilayer filter paper, and then placed in an oven at 80 degrees Celsius to allow excess paraffin wax on the film surface to be absorbed by the filter paper. Finally, a breathable flexible graphene phase change film is obtained.

[0073] Tests have verified that in this embodiment, the perforation area is the smallest, the graphene film is the densest, the paraffin phase change material loading is the lowest, the phase change enthalpy is the lowest, and the flexibility and air permeability are the worst.

[0074] Example 5 (Based on Example 1, the phase change material was replaced with polyethylene glycol)

[0075] This embodiment presents a breathable flexible graphene phase change film with a periodic perforated structure. The perforated areas are square with a side length of 4 mm, and the width of the non-perforated graphene film between two adjacent perforated areas is 2 mm. This graphene phase change film is composed of graphene and polyethylene glycol in a 1:1 mass ratio. The graphene is oriented along the in-plane direction of the film, and the polyethylene glycol is embedded between the graphene layers.

[0076] This breathable, flexible graphene phase change material is prepared through the following steps:

[0077] Step 1 - Preparation of a fluffy graphene film: A graphene NMP dispersion with a concentration of 0.2 mg / ml was injected into a syringe at a flow rate of 50 μL / min using a syringe pump. A flat aluminum foil was placed 4 cm below the needle as a film-forming substrate. The aluminum foil was placed on a hot plate, and the heating temperature was controlled at 130℃. A DC power supply of 12 kV was applied between the needle and the aluminum foil for 100 minutes. Under the influence of the electric field, graphene was deposited onto the surface of the aluminum foil, forming a fluffy film with graphene aligned in the in-plane direction, 100 micrometers thick and with a density of 0.8 g / cm³. 3 After soaking in water for 1 hour, the fluffy graphene film peeled off the aluminum foil.

[0078] Step 2 - Periodic Hole Cutting: Using a laser cutter, and by setting a program, periodically cut holes in the fluffy graphene film oriented in the in-plane direction obtained in Step 1. The cut-hole area is square with a side length of 4mm, and the width of the non-cut-hole graphene film between two adjacent cut-hole areas is 2mm.

[0079] Step 3 - Composite Phase Change Material: The periodically perforated graphene film obtained in Step 2 is completely immersed in a container filled with polyethylene glycol (PEG) and placed in a vacuum environment at 80 degrees Celsius for 24 hours to allow the PEG to fully diffuse into the gaps between the graphene sheets. The PEG-composite graphene film is then removed and placed on multilayer filter paper, and then placed in an oven at 80 degrees Celsius to allow excess PEG on the film surface to be absorbed by the filter paper. The final product is a breathable, flexible graphene phase change film.

[0080] Tests have verified that this embodiment has the largest perforation area, the most fluffy graphene film, and the highest paraffin phase change material loading. Although the phase change materials are different, their phase change enthalpy, flexibility, and air permeability are all at a relatively high level (comparable to Example 1).

[0081] Comparative Example 1: Comparison with Example 1

[0082] According to Example 1 of Chinese Invention Patent Application No. 202010285705.8, graphene oxide is used as raw material to prepare graphene aerogel by freeze drying and high temperature reduction. Then, polyvinylidene fluoride is introduced and graphene composite film is prepared by blade coating. Then, phase change material is impregnated into it by vacuum impregnation to finally obtain graphene-based flexible composite shaped phase change material film.

[0083] The phase transition enthalpy of the samples from Examples 1, 2, 3, 4, 5, and Comparative Example 1 was tested using differential scanning calorimetry (DSC). The samples were then tightly attached to the mouth of identical bottles filled with water, and the air permeability was tested by measuring the change in bottle weight per unit time. The samples could return to their initial state without breakage after being bent 180°, indicating that the materials all possess good flexibility. In contrast, the phase transition enthalpy and air permeability of the film in Comparative Example 1 were relatively low. The results of air permeability and phase transition enthalpy are shown in the table below.

[0084]

[0085] It will be readily understood by those skilled in the art that the aforementioned advantageous methods can be freely combined and superimposed without conflict.

[0086] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention. The above are merely preferred embodiments of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the protection scope of the present invention.

Claims

1. A method for preparing a flexible, breathable graphene phase change film, characterized in that, Includes the following steps: S100: Prepare a fluffy graphene film with graphene aligned in the in-plane direction, wherein the density of the fluffy graphene film is 0.8 g / cm³. 3 -1.2g / cm 3 The fluffy graphene film is prepared in the following manner: A graphene NMP dispersion of the target concentration is injected into a syringe at a target flow rate, wherein the tip of the syringe is at a target distance from the film-forming substrate, and the film-forming substrate is placed on a heating element heated to the target temperature. A target voltage is applied between the film-forming substrate and the tip of the needle using a DC power supply and maintained for a first target duration. Under the action of the electric field of the DC power supply, the graphene in the needle will be deposited onto the surface of the film-forming substrate to form a fluffy graphene film with the graphene oriented in the in-plane direction. After immersion in water for a second target duration, the fluffy graphene film with the graphene oriented in the in-plane direction is peeled off from the film-forming substrate. S200, multiple perforations are formed along the thickness direction on a graphene fluffy film. The perforations are square, with a side length of 1mm-4mm. The perforations are formed by laser cutting. S300, the porous graphene film is immersed in a phase change material so that the phase change material diffuses into the gaps between the graphene sheets in the porous graphene film to form a graphene film of composite phase change material. S400, the flexible, breathable graphene phase change film is prepared by drying the graphene film of the composite phase change material.

2. The preparation method according to claim 1, characterized in that, The target concentration is 0.2 mg / ml - 2 mg / ml; and / or, the target flow rate is 50 μL / min - 100 μL / min; and / or, the target voltage is 12 kV - 15 kV; and / or, the target distance is 2 cm - 4 cm.

3. The preparation method according to claim 1, characterized in that, The target temperature is 130℃-160℃; and / or, the first target duration is 5 minutes-100 minutes, and the second target duration is 0.5 hours-1 hour.

4. The preparation method according to claim 1, characterized in that, The plurality of the aforementioned perforations are periodically spaced on the fluffy graphene film; and / or, the phase change material is polyethylene glycol and / or paraffin wax.

5. The preparation method according to claim 1, characterized in that... The minimum width of the graphene fluffy film between two adjacent perforations is 2mm-8mm.

6. The preparation method according to claim 1, characterized in that, The phase change material is composited with the porous graphene fluffy film in a vacuum environment at 80°C and soaked for 24 hours; and / or, after the phase change material is composited with the porous graphene fluffy film, it is placed on a multilayer filter paper and then placed in an oven at 80°C to dry.

7. A flexible, breathable graphene phase change film, characterized in that, The flexible, breathable graphene phase change film is prepared by any one of claims 1 to 6, wherein the thickness of the flexible, breathable graphene phase change film is 5 μm to 100 μm; and / or, the mass ratio of graphene to phase change material in the flexible, breathable graphene phase change film is (1-3):1.

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