Preparation method of flexible phase change film and application thereof

Abstract

The application discloses a preparation method of a flexible phase change film and application thereof, and the flexible phase change film is obtained by adding a phase change material and MXene into carboxyl styrene-butadiene latex and dandelion latex, then adding rare earth metal salt and organic acid into the mixture, and then performing demulsification and drying. In the application, the trivalent rare earth ions penetrate the latex interface film and form a coordination bond with the emulsifier through strong electrostatic attraction due to high charge density and strong polarization ability, thereby promoting demulsification; after the organic acid is added, the organic acid is coordinated with the rare earth ions to form a ternary bridging structure, so that the mechanical properties of the flexible phase change film are improved. In addition, a three-dimensional network is formed among the phase change material, the latex and the MXene, so that the phase change material has good heat storage capacity and high thermal conductivity, and can be applied to a solar temperature difference generator.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of composite materials, and relates to a preparation method of a flexible phase change film and application thereof. BACKGROUND

[0002] The development of the flexible phase change film technology mainly relies on three core backgrounds: first, the rapid rise of flexible electronic devices, second, the continuous improvement of energy management demand, and third, the inherent defects of traditional phase change materials that need to be broken through. With the continuous progress of modern social technology, flexible electronic devices gradually develop towards miniaturization, high power and integration, and the heat management problem is increasingly prominent. Flexible electronic devices represented by foldable mobile phones and smart watches will generate a large amount of heat during operation. If this part of heat cannot be dissipated in time, it will not only directly affect the working performance of the device, but also may cause device failure. The flexible phase change film can effectively maintain the stable working temperature of the flexible electronic device due to its high latent heat storage density and reversible heat regulation characteristics, and thus becomes a research hotspot in the current heat management field.

[0003] However, the traditional organic phase change material (such as paraffin material) has a high phase change enthalpy value, but has significant defects: poor shape stability, easy liquid leakage, and poor thermal conductivity and electrical conductivity. In addition, the support carrier of the existing phase change material lacks flexibility, and is difficult to adapt to complex or dynamic application scenarios. If an excessive amount of support carrier is introduced to improve the shape effect, the energy storage density of the material will be reduced, and the rigidity of the material will be increased, thereby causing the processing performance of the material to decrease and the application range of the material to be limited.

[0004] At the same time, there are problems to be solved in the thermoelectric film field related to the flexible phase change film technology. At present, the thermoelectric film mainly has two defects: first, the preparation process is complex, for example, when prepared by using an electrospinning process, there is a problem of complicated operation process; second, the high-temperature resistance of part of the thermoelectric film is poor, and the surface temperature of the thermoelectric film will be significantly increased under the condition of xenon lamp irradiation, and carbonization will occur on the surface of the substrate. The carboxylated styrene-butadiene rubber can effectively solve the defects of the above-mentioned thermoelectric film, and the carboxylated styrene-butadiene rubber latex is widely used in papermaking, coating and other occasions that need wear-resistant protection, which greatly broadens the use of the flexible phase change film.

[0005] Based on this, the application is proposed. SUMMARY

[0006] In order to solve the above technical problems, the present application aims to provide a preparation method of a flexible phase change film and its application, which is obtained by adding a phase change material and MXene to carboxyl styrene-butadiene latex and dandelion latex, then adding a rare earth metal salt and an organic acid, and then performing demulsification and drying.

[0007] To achieve the above object, the technical scheme adopted by the present application is as follows:

[0008] A preparation method of a flexible phase change film, which is performed in the following order:

[0009] S1, 50 mL of deionized water is added to a mixed latex composed of carboxyl styrene-butadiene latex and dandelion latex, and stirred for 20 min, then a phase change material is added, the mass ratio of the carboxyl styrene-butadiene latex, the dandelion latex and the phase change material is 1:1:(2-4), and stirred for another 20 min to obtain a phase change material composite latex;

[0010] S2, Mxene is added to the above phase change material composite latex after ultrasonic treatment, the mass ratio of the Mxene and the phase change material composite latex is 1:10, and after ultrasonic treatment for 5 min, a rare earth metal salt is added, stirred at 500 rpm for 20 min, 100 mL of deionized water is slowly added during stirring, and after stirring is completed, an organic acid is added, the mass ratio of the rare earth metal salt and the organic acid is 1:0.625, and stirred at 500 rpm for 20 min to obtain a solid-liquid mixture;

[0011] S3, the solid-liquid mixture is poured into a polytetrafluoroethylene mold, dried in an oven at 100℃ for 10 h, and then demolded to obtain a flexible phase change film.

[0012] In the present application, the mass ratio of the carboxyl styrene-butadiene latex, the dandelion latex and the phase change material will affect the flexibility of the flexible phase change film. When the molar ratio is 1:1:(2-4), the phase change material will not leak, the flexibility is good, and the phase change material can fill the pores of the film to improve the thermal conductivity; when the molar ratio is less than this, the phase change ability of the phase change film is weakened, resulting in poor heat storage effect and moderate flexibility; when the molar ratio is greater than this, the phase change material will leak, affecting the use of the film and reducing the flexibility.

[0013] In the application, the mass ratio of Mxene and phase change material composite latex will affect the thermal conductivity of the flexible phase change film. When the mass ratio of Mxene and phase change material composite latex is 1:10, the flexible phase change film has uniform heat conduction, which can quickly transmit heat; when it is less than 1:10, the heat conduction network cannot be formed, resulting in uneven heat transmission of the material; when it is greater than 1:10, Mxene will agglomerate, thereby causing uneven heat transmission of the material.

[0014] In the application, the molar ratio of rare earth metal salt and organic acid will affect the coordination effect of the material. When the mass ratio of rare earth metal salt and organic acid is 1:0.625, the organic acid will become a "bridge" and coordinate with the rubber particles after demulsification and rare earth ions to form a three-dimensional network; when it is less than 1:0.625, the three-dimensional network will not be formed completely, thereby causing the mechanical properties of the material to decrease; when it is greater than 1:0.625, the crosslinking points will increase, causing the flexibility of the phase change film to decrease.

[0015] As a limitation of the preparation method of the application, in step S1, the solid content of the carboxyl styrene-butadiene latex is 48-54 wt.%; the solid content of the dandelion latex is 61 wt.%.

[0016] As a second limitation of the preparation method of the application, in step S1, the phase change material is one of polyethylene glycol, erythritol and stearic acid.

[0017] As a third limitation of the preparation method of the application, in step S2, the mass ratio of Mxene and rare earth metal salt is 1:1.6.

[0018] As a fourth limitation of the preparation method of the application, in step S2, the rare earth metal salt is one of lanthanum chloride, cerium chloride, gadolinium chloride and neodymium chloride; and the organic acid is citric acid or oxalic acid.

[0019] The application also provides an application of the flexible phase change film, and the prepared flexible phase change film is applied in a solar temperature difference generator.

[0020] In the demulsification process of the application, the emulsifier which keeps the stability of latex particles in the preparation process of latex is mainly destroyed. The rare earth ions will be adsorbed on the surface of the latex particles, and the demulsification is promoted by affecting the interface properties. The rare earth ions are usually +3 valence, and the charge density is much higher than that of ordinary metal ions (such as Na + , Ca 2+ , Mg 2+According to Coulomb's law, high-charged rare earth ions have stronger electrostatic attraction to the polar groups in the emulsion interface film (such as the carboxyl groups of emulsifier molecules), can more effectively penetrate the interface film, and destroy the ordered arrangement of emulsifier molecules. At the same time, the rare earth ions have small ionic radius and strong polarization ability, can form stable coordination bonds with coordination atoms such as oxygen and nitrogen in the latex emulsifier, and directly collapse the stability of the interface film. This strong interaction far exceeds the weak electrostatic combination of ordinary ions and emulsifiers, thereby accelerating the rupture of the interface film. After the addition of organic acid, the organic acid can coordinate with the rare earth ions, act as a "bridge" to connect the dispersed rubber particles after demulsification into a network, and form a ternary bridging structure of "organic acid-rare earth ion-latex particle", thereby better preventing the leakage of phase change materials. In addition, the organic acid and the latex and MXene can form a continuous three-dimensional network structure to form a flexible phase change film, in which the phase change material can be filled to fill the pores in the film, so that heat can be more easily conducted through the material, thereby improving the thermal conductivity of the flexible phase change film.

[0021] The above technical solutions of the present application are closely related and interact with each other as a whole, which jointly determines the morphology characteristics and performance of the product.

[0022] The above technical solutions have the following advantages or beneficial effects:

[0023] 1. According to the high charge density and strong polarization ability of rare earth ions, the present application promotes demulsification by strong electrostatic attraction to penetrate the latex interface film and form coordination bonds with the emulsifier in the latex. After the addition of organic acid, the organic acid can coordinate with the rare earth ions, act as a "bridge" to connect the dispersed rubber particles after demulsification into a network, form a ternary bridging structure of "organic acid-rare earth ion-latex particle", and improve the mechanical properties of the flexible phase change film. At the same time, the organic acid and the latex and MXene form a three-dimensional network, thereby improving the thermal conductivity;

[0024] 2. The flexible phase change film prepared by the present application not only maintains flexibility but also has phase change function, and can be applied in solar generators;

[0025] 3. The preparation method of the present application is simple, the process is easy to control, and is suitable for industrialized mass production.

[0026] The technical solutions of the present application will be further described in detail below in combination with the drawings and specific embodiments of the present application. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 The latex demulsification effect comparison chart of Example 1, Comparative Example 1 and Comparative Example 2 of the present application is shown from left to right as follows: latex without demulsification (Comparative Example 1), latex demulsified by rare earth La 3+The latex after demulsification (Example 1) is mixed with common Ca 2+ The latex after demulsification (Example 1) is mixed with common Ca

[0028] Figure 2 The infrared spectra of the phase change films prepared from the present application Comparative Example 3 and Comparative Example 4 and lanthanum chloride, oxalic acid, carboxyl styrene butadiene rubber (XSBR) are shown in the following figure:

[0029] Figure 3 The physical comparison figure of the phase change films prepared from the present application Comparative Example 3 and Example 1 is shown in the following figure, wherein: (a) is the physical figure of the phase change film prepared from Comparative Example 3, (b) is the physical figure of the phase change film prepared from Example 1;

[0030] Figure 4 The infrared spectra of the phase change films prepared from the present application Example 1, Comparative Example 4 and Comparative Example 5 and pure polyethylene glycol (PEG) are shown in the following figure:

[0031] Figure 5 The temperature rising and falling curve figures of the phase change films prepared from the present application Example 1, Comparative Examples 6-7 are shown in the following figure:

[0032] Figure 6 The differential scanning curve figures of the phase change films prepared from the present application Example 1, Comparative Examples 6-7 and PEG are shown in the following figure, wherein: (a) is the temperature rising curve figure, (b) is the temperature falling curve figure:

[0033] Figure 7 The thermal conductivity figures of the phase change films prepared from the present application Example 1, Comparative Example 4, Comparative Example 6 and PEG are shown in the following figure:

[0034] Figure 8 The shape stability test figures of the phase change films prepared from the present application Example 1, Comparative Example 4 and PEG are shown in the following figure, wherein: (a) is the shape stability figure at 0 min, (b) is the shape stability figure at 30 min:

[0035] Figure 9 The side SEM figures of the phase change films prepared from the present application Comparative Example 4 and Example 2 are shown in the following figure, wherein: (a) is the side SEM figure of the phase change film prepared from Comparative Example 4, (b) is the side SEM figure of the phase change film prepared from Example 2;

[0036] Figure 10 The thermogravimetric figures of the phase change films prepared from the present application Examples 3-4, Comparative Examples 8-9 and erythritol (ERY) are shown in the following figure, wherein: (a) is the TGA figure, (b) is the DTG figure:

[0037] Figure 11 The abrasion resistance test figures of the phase change films prepared from the present application Examples 3-4 and Comparative Example 8 are shown in the following figure:

[0038] Figure 12 Temperature difference power generation voltage diagram of the phase change film prepared in Example 5 of the present application under natural light, wherein: (a) is the voltage diagram under natural light, (b) is the current diagram under natural light, (c) is the light power density of 200 W / cm 2 Voltage diagram under xenon lamp simulation;

[0039] Figure 13 Temperature rising test diagram of the phase change film prepared in Example 5 and Comparative Examples 10-12 of the present application under xenon lamp;

[0040] Figure 14 Flexibility test diagram of the phase change film prepared in Example 5 of the present application;

[0041] Figure 15 Transmission electron microscope diagram of the phase change film prepared in Example 1 of the present application;

[0042] Figure 16 EDS diagram of the phase change film prepared in Example 1 of the present application, wherein: (a) is the lanthanum element distribution diagram, (b) is the oxygen element distribution diagram. DETAILED DESCRIPTION

[0043] The following examples are merely illustrative of part, but not all, embodiments of the present application. Thus, these examples, given only by way of illustration, are not intended to limit the scope of the application, but rather, these examples merely represent selected embodiments of the application. Based on the examples given herein, those skilled in the art will be able to obtain all other embodiments of the present application without making an effort of creative work.

[0044] In the present application, all the equipment and raw materials, unless specified, can be purchased from the market or commonly used in the industry. The methods in the following examples, unless specified, are the conventional methods in the art. Example 1

[0045] This embodiment prepares a flexible phase change film, and the preparation process and steps are as follows:

[0046] S1, 50 mL of deionized water is added to the mixed latex composed of 1 g of carboxyl styrene-butadiene latex and 1 g of dandelion latex, and 2 g of polyethylene glycol with an average molecular weight of 6000 is added after stirring at 500 rpm for 20 min, and then the phase change material composite latex is obtained after stirring at 500 rpm for 20 min;

[0047] S2, 0.25 g of Mxene (Ti3C2T x , wherein T xS1, 50 mL deionized water was added to the mixed latex composed of 1 g carboxyl styrene-butadiene latex and 1 g dandelion latex, and 2.5 g phase change material composite latex was added after ultrasonic treatment for 20 min, 0.4 g cerium chloride was added after ultrasonic treatment for 5 min, and the mixture was stirred at 500 rpm for 20 min. During stirring, 100 mL deionized water was slowly added, followed by the addition of 0.25 g citric acid, and the mixture was stirred at 500 rpm for 20 min to obtain a solid-liquid mixture;

[0048] S3, the solid-liquid mixture was poured into a polytetrafluoroethylene mold, dried in an oven at 100°C for 10 h, and then demolded to obtain a flexible phase change film, which was recorded as P1000-G0.25. The thickness of the flexible phase change film was 1.5 mm. Example 2

[0049] In this example, a flexible phase change film was prepared, and the preparation process and steps were as follows:

[0050] S1, 50 mL deionized water was added to the mixed latex composed of 1 g carboxyl styrene-butadiene latex and 1 g dandelion latex, and 2.5 g phase change material composite latex was added after ultrasonic treatment for 20 min, 0.4 g cerium chloride was added after ultrasonic treatment for 5 min, and the mixture was stirred at 500 rpm for 20 min. During stirring, 100 mL deionized water was slowly added, followed by the addition of 0.25 g citric acid, and the mixture was stirred at 500 rpm for 20 min to obtain a solid-liquid mixture;

[0051] S2, 0.25 g Mxene (Ti3C2T x , wherein T x is -OH and -COOH) was added to 2.5 g phase change material composite latex after ultrasonic treatment for 20 min, 0.4 g cerium chloride was added after ultrasonic treatment for 5 min, and the mixture was stirred at 500 rpm for 20 min. During stirring, 100 mL deionized water was slowly added, followed by the addition of 0.25 g citric acid, and the mixture was stirred at 500 rpm for 20 min to obtain a solid-liquid mixture;

[0052] S3, the solid-liquid mixture was poured into a polytetrafluoroethylene mold, dried in an oven at 100°C for 10 h, and then demolded to obtain a flexible phase change film, which was recorded as P1000-G0.25. The thickness of the flexible phase change film was 1.5 mm. Example 3

[0053] In this example, a flexible phase change film was prepared, and the preparation process and steps were as follows:

[0054] S1, 50 mL deionized water was added to the mixed latex composed of 1 g carboxyl styrene-butadiene latex and 1 g dandelion latex, and 2.5 g phase change material composite latex was added after ultrasonic treatment for 20 min, 0.4 g cerium chloride was added after ultrasonic treatment for 5 min, and the mixture was stirred at 500 rpm for 20 min. During stirring, 100 mL deionized water was slowly added, followed by the addition of 0.25 g citric acid, and the mixture was stirred at 500 rpm for 20 min to obtain a solid-liquid mixture;

[0055] S2, 0.25 g Mxene (Ti3C2T x , wherein Tx After ultrasonic treatment for 20 min, 2.5 g of the phase change material composite latex was added, and after ultrasonic treatment for 5 min, 0.4 g of gadolinium chloride was added, and stirred at 500 rpm for 20 min. During the stirring, 100 mL of deionized water was slowly added, followed by the addition of 0.25 g of citric acid, and stirred at 500 rpm for 20 min to obtain a solid-liquid mixture;

[0056] S3, the solid-liquid mixture was poured into a polytetrafluoroethylene mold, dried in an oven at 100°C for 10 h, and then demolded to obtain a flexible phase change film, which was recorded as E3-G0.25. The flexible phase change film had a thickness of 1.5 mm. Example 4

[0057] In this example, a flexible phase change film was prepared. The preparation process was similar to that of Example 3, except that in step S1, the mass of erythritol added was 4 g. The obtained flexible phase change film was recorded as E4-G0.25. The flexible phase change film had a thickness of 1.5 mm. Example 5

[0058] In this example, a flexible phase change film was prepared. The preparation process and steps were as follows:

[0059] S1, 50 mL of deionized water was added to a mixed latex composed of 1 g of carboxyl butadiene styrene latex and 1 g of dandelion latex, and stirred at 500 rpm for 20 min. Then, 2 g of stearic acid was added, and stirred at 500 rpm for 20 min to obtain a phase change material composite latex;

[0060] S2, 0.25 g of Mxene (Ti3C2T x , wherein T x is -OH and -COOH) was added to 2.5 g of the phase change material composite latex after ultrasonic treatment for 20 min. After ultrasonic treatment for 5 min, 0.4 g of neodymium chloride was added, and stirred at 500 rpm for 20 min. During the stirring, 100 mL of deionized water was slowly added, followed by the addition of 0.25 g of citric acid, and stirred at 500 rpm for 20 min to obtain a solid-liquid mixture;

[0061] S3, the solid-liquid mixture was poured into a polytetrafluoroethylene mold, dried in an oven at 100°C for 10 h, and then demolded to obtain a flexible phase change film, which was recorded as E3-G0.25. The flexible phase change film had a thickness of 1.5 mm. Comparative Example

[0062] In order to explore the effects of different parameters and different raw materials added during the preparation process of the present application on the performance of the product, the following comparative experiments were conducted. The following comparative examples prepared different phase change films (the Mxene in the following examples was Ti3C2Tx wherein T x is -OH and -COOH), in particular as follows:

[0063] Comparative Example 1

[0064] A phase change film was prepared in this comparative example, and the preparation process was similar to that of Example 1, except that in step S2, lanthanum chloride was not added.

[0065] Comparative Example 2

[0066] A phase change film was prepared in this comparative example, and the preparation process was similar to that of Example 1, except that in step S2, lanthanum chloride was replaced by calcium chloride.

[0067] Comparative Example 3

[0068] A phase change film was prepared in this comparative example, and the preparation process was similar to that of Example 1, except that in step S2, polyethylene glycol and MXene, oxalic acid were not added, denoted as P0-G0.

[0069] Comparative Example 4

[0070] A phase change film was prepared in this comparative example, and the preparation process was similar to that of Example 1, except that in step S2, polyethylene glycol and MXene were not added, denoted as P0-G0-OA.

[0071] Comparative Example 5

[0072] A phase change film was prepared in this comparative example, and the preparation process was similar to that of Example 1, except that in step S2, polyethylene glycol was not added, denoted as P0-G0.25.

[0073] Comparative Example 6

[0074] A phase change film was prepared in this comparative example, and the preparation process was similar to that of Example 1, except that in step S2, MXene was not added, denoted as P2-G0.

[0075] Comparative Example 7

[0076] A phase change film was prepared in this comparative example, and the preparation process was similar to that of Example 1, except that in step S2, the mass of MXene added was 0.5 g, denoted as P2-G0.5.

[0077] Comparative Example 8

[0078] A phase change film was prepared in this comparative example, and the preparation process was similar to that of Example 3, except that in step S2, erythritol and MXene were not added, denoted as E0-G0.

[0079] Comparative Example 9

[0080] A comparative example was prepared by a similar method to Example 3, except that in step S2, 5 g of erythritol was added, and was recorded as E5-G0.25.

[0081] Comparative Example 10

[0082] A comparative example was prepared by a similar method to Example 5, except that in step S2, no stearic acid and MXene was added, and was recorded as SA0-G0.

[0083] Comparative Example 11

[0084] A comparative example was prepared by a similar method to Example 5, except that in step S2, no stearic acid was added, and was recorded as SA0-G0.25.

[0085] Comparative Example 12

[0086] A comparative example was prepared by a similar method to Example 5, except that in step S2, 0.5 g of MXene was added, and was recorded as SA2-G0.5. Performance test

[0087] The phase change thin films prepared by Examples 1-5 and Comparative Examples 1-12 were tested, and the details are as follows:

[0088] As Figure 1 , the latex demulsification effect comparison chart of Example 1, Comparative Example 1 and Comparative Example 2, from left to right: latex without demulsification (Comparative Example 1), lanthanum ion demulsified latex (Example 1), ordinary calcium ion demulsified latex (Comparative Example 2), from the figure, it can be seen that the latex without demulsification after a period of precipitation, the lower layer is Mxene, and the upper layer is mixed latex; while the rubber demulsified by lanthanum ion, the upper layer is deionized water, and the lower layer is demulsified latex and Mxene, which is conducive to the uniform distribution of Mxene after film forming; the calcium ion demulsified latex, the upper layer is not completely demulsified latex, and the lower layer is the product after demulsification, it can be seen that the demulsified rubber can well absorb Mxene, and the upper layer has no Mxene, indicating that the demulsification is not complete, which will affect the thermal conductivity of the flexible phase change film. 3+ demulsified latex (Example 1), ordinary calcium ion demulsified latex (Comparative Example 2), from the figure, it can be seen that the latex without demulsification after a period of precipitation, the lower layer is Mxene, and the upper layer is mixed latex; while the rubber demulsified by lanthanum ion, the upper layer is deionized water, and the lower layer is demulsified latex and Mxene, which is conducive to the uniform distribution of Mxene after film forming; the calcium ion demulsified latex, the upper layer is not completely demulsified latex, and the lower layer is the product after demulsification, it can be seen that the demulsified rubber can well absorb Mxene, and the upper layer has no Mxene, indicating that the demulsification is not complete, which will affect the thermal conductivity of the flexible phase change film. 2+ demulsified latex (Example 1), ordinary calcium ion demulsified latex (Comparative Example 2), from the figure, it can be seen that the latex without demulsification after a period of precipitation, the lower layer is Mxene, and the upper layer is mixed latex; while the rubber demulsified by lanthanum ion, the upper layer is deionized water, and the lower layer is demulsified latex and Mxene, which is conducive to the uniform distribution of Mxene after film forming; the calcium ion demulsified latex, the upper layer is not completely demulsified latex, and the lower layer is the product after demulsification, it can be seen that the demulsified rubber can well absorb Mxene, and the upper layer has no Mxene, indicating that the demulsification is not complete, which will affect the thermal conductivity of the flexible phase change film. 2+ demulsified latex (Example 1), ordinary calcium ion demulsified latex (Comparative Example 2), from the figure, it can be seen that the latex without demulsification after a period of precipitation, the lower layer is Mxene, and the upper layer is mixed latex; while the rubber demulsified by lanthanum ion, the upper layer is deionized water, and the lower layer is demulsified latex and Mxene, which is conducive to the uniform distribution of Mxene after film forming; the calcium ion demulsified latex, the upper layer is not completely demulsified latex, and the lower layer is the product after demulsification, it can be seen that the demulsified rubber can well absorb Mxene, and the upper layer has no Mxene, indicating that the demulsification is not complete, which will affect the thermal conductivity of the flexible phase change film.

[0089] As Figure 2 , the infrared chart of the phase change film prepared by Comparative Example 3 and Comparative Example 4, and lanthanum chloride, oxalic acid, and carboxyl styrene-butadiene latex (XSBR), from the figure, it can be seen that there are obvious peaks at 1311 cm -1 , 792 cm -1and 489 cm -1 The new peaks appeared, which were the vibration peaks of oxalate and the characteristic peaks of rare earth coordination, proved that oxalic acid was coordinated with lanthanum chloride.

[0090] As Figure 3 , are the actual comparison diagrams of the phase change films prepared by the present application comparative example 3 and example 1, wherein: (a) is the actual diagram of the phase change film prepared by comparative example 3, (b) is the actual diagram of the flexible phase change film prepared by example 1, it can be seen from the diagram that the film surface without oxalic acid appears obvious cracks, the film forming effect is not good, and the film with oxalic acid does not have such phenomenon, the film surface is flat.

[0091] As Figure 4 , are the infrared diagrams of example 1, comparative example 4 and comparative example 5 of the present application and pure polyethylene glycol (PEG), it can be seen from the diagram that the PEG is at 2878.35 cm -1 , 1094 cm -1 , which are the peaks of methylene (-CH2-) and ether bond (-O-) functional groups. Among them, 1094 cm -1 is the direct hydrogen bonding effect of PEG and dandelion latex. And at 2878.35 cm -1 , the indirect shift between the adjacent non-activated C-H bonds caused by the hydrogen bond on the acceptor. P0-G0-OA is at 1700 cm -1 , which is -COOH in the mixed latex, by comparing with the film added with PEG, it is found that red shift phenomenon also appears, which also indicates that hydrogen bond is generated. And by comparing P0-G0.25, it is found that adding Mxene does not produce any effect on the flexible phase change film.

[0092] As Figure 5 , are the temperature rising and falling curve diagrams of the phase change films prepared by example 1, comparative example 6 and comparative example 7 of the present application, it can be seen from the diagram that P2-G0.5 starts the fastest temperature rising speed, and the temperature falling speed is also fast, thereby reducing the heat storage performance of the phase change film.

[0093] The phase change thermodynamic characteristics of example 1, comparative examples 6-7 and PEG of the present application are tested, and the specific test results are shown in table 1.

[0094] Table 1: phase change thermodynamic characteristics test results of example 1, comparative examples 6-7 and PEG

[0095]

[0096] In table 1, Tm is the melting temperature, Hm1 is the melting enthalpy, Tc is the crystallization temperature, and Hm2 is the crystallization enthalpy. From Figure 6As can be seen from Table 1, the phase change thin films prepared by PEG and Example 1 are all one peak, indicating that the phase change characteristics of PEG are well preserved in the crosslinked network of the latex, which gives the phase change material excellent phase change behavior. As can be seen from Table 1, the melting enthalpy and crystallization enthalpy of P2-G0.25 are higher than those of P2-G0 and P2-G0.5, because compared with P2-G0, the addition of MXene affects the crystallinity of PEG, thereby affecting the heat transfer of the phase change thin film, and thus increasing the melting enthalpy and crystallization enthalpy; compared with P2-G0.5, the increase of MXene leads to the molecular rearrangement of PEG, thereby reducing the enthalpy value, and in addition, the increase of thermal conductivity makes the material release heat faster, which is not conducive to heat storage.

[0097] As Figure 7 , the thermal conductivity diagram of Example 1, Comparative Example 4, Comparative Example 6 and PEG of the present application, it can be seen from the figure that the thermal conductivity of P2-G0 increases compared with that of P0-G0-OA, indicating that PEG can fill the pores of rubber, thereby increasing the thermal conductivity of the phase change thin film; the thermal conductivity of P2-G0.25 increases by 32% compared with that of PEG and P2-G0.

[0098] The shape stability of Example 1, Comparative Example 4 and PEG was observed at 100℃, as Figure 8 shown in the figure, it can be seen that after 30 min at 100℃, PEG becomes liquid, while P2-G0.25 phase change thin film does not leak; and the structure of P0-G0-OA phase change thin film is not affected under high temperature conditions, indicating that the phase change thin film is resistant to high temperature and can be used under high temperature conditions.

[0099] As Figure 9 , the side SEM diagram of the phase change thin film prepared by Comparative Example 4 and Example 2 of the present application, it can be seen from the figure that Mxene is uniformly dispersed in the rubber matrix without agglomeration.

[0100] As Figure 10 , the thermogravimetric diagram of the phase change thin film prepared by Example 3-4 and Comparative Example 8-9 of the present application and erythritol (ERY), it can be seen from (a) that the initial decomposition temperature of E0-G0 is 363.01℃, and the maximum weight loss occurs at 424.6℃. The initial decomposition temperature of ERY is 234.18℃, and the maximum weight loss occurs at 286.53℃. As can be seen from (b), ERY and E0-G0 have only one peak. The samples E3-G0.25, E4-G0.25 and E5-G0.25 have two peaks, indicating that ERY does not react with XSBR; the first step of decomposition of the phase change thin film is the decomposition of ERY, and the second step is the decomposition of XSBR.

[0101] The phase change thermodynamic characteristics of the phase change films prepared from the examples 3-4 and the comparative example 9 of the present application were tested, and the specific test results are shown in Table 2.

[0102] Table 2: Test results of phase change thermodynamic characteristics of the phase change films prepared from the examples 3-4 and the comparative example 9

[0103]

[0104] As can be seen from Table 2, with the continuous increase of the erythritol content in the phase change film, the melting enthalpy and the crystallization enthalpy also increase, but when it increases to a certain amount, the melting enthalpy and the crystallization enthalpy will decrease instead. This is because with the increase of the erythritol content, the arrangement between molecules will be limited by space and affected by the interaction with the rubber matrix, resulting in incomplete crystallization and difficulty in forming complete crystal structure. The heat released or absorbed during phase change of the erythritol with incomplete crystallization will decrease, thereby reducing the melting enthalpy and the crystallization enthalpy.

[0105] The flexible phase change films prepared from the examples 3-4 and the comparative example 8 of the present application were placed on an Akron abrasion tester, and the wear resistance test was carried out under the condition of a load of 10 N, and the test results are shown in Figure 11 As can be seen from the figure, after 500 revolutions of the test, the retention rate of E0-G0 reaches more than 90%, and after adding erythritol, the retention rate is still more than 90%, indicating that the flexible phase change film has good wear resistance.

[0106] As shown in Figure 12 , the temperature difference power generation voltage diagram of the flexible phase change film prepared from the example 5 of the present application under natural light, as can be seen from the figure, under natural light, the voltage of the temperature difference power generation is 0.1 V, and the current is 17.39 mA. Under the environment simulated by the xenon lamp, the generated voltage is 0.267 V, which is sufficient to drive a small motor. When the light source is turned off, the motor can rotate for 16 seconds, indicating that after the light source is removed, it is in the heat release stage, which can make the temperature difference sheet continue to generate electricity.

[0107] As shown in Figure 13 , the temperature rise test diagram of the phase change films prepared from the example 5 and the comparative examples 10-12 of the present application under the xenon lamp, as can be seen from the figure, under the condition of the same content of Mxene, the temperature of the phase change film added with stearic acid is about 20℃ higher than that of the phase change film without stearic acid, which is mainly because the addition of stearic acid improves the thermal conductivity of the film and accelerates the heat transfer.

[0108] As shown in Figure 14 , the flexibility test diagram of the phase change film prepared from the example 5 of the present application, as can be seen from the figure, the flexibility of the phase change film is extremely strong, and it can be folded into any shape.

[0109] The phase change thermodynamic characteristics of the phase change film prepared from the embodiment 5 and the comparative example 12 are tested, and the specific test results are shown in Table 3.

[0110] Table 3: Test results of phase change thermodynamic characteristics of the phase change film prepared from the embodiment 5 and the comparative example 12

[0111]

[0112] As Figure 15 and Figure 16 , the transmission electron microscope image and the EDS image of the phase change film prepared from the embodiment 1, from which Figure 15 It can be seen from the transmission electron microscope image that the matrix generated from the latex and oxalic acid, lanthanum chloride appears voids inside the matrix for storing PEG, thereby forming a three-dimensional network; the element analysis by EDS explicitly shows that the lanthanum is coordinated with the oxygen in the latex and oxalic acid, thereby showing that the lanthanum is uniformly distributed inside the matrix.

[0113] Finally, it should be noted that: the above only describes the preferred embodiments of the present application, and is not used to limit the present application, although the present application has been described in detail with reference to the foregoing embodiments, for those skilled in the art, the technical solutions recorded in the foregoing embodiments can still be modified, or some technical features can be replaced. Any modification, equivalent replacement, improvement, etc. within the spirit and principles of the present application shall be included in the scope of protection of the claims of the present application.

Claims

1. A method of making a flexible phase change film, characterized by, The following steps are carried out in sequence: S1, 50 mL of deionized water is added to the mixed latex composed of carboxyl styrene-butadiene latex and dandelion latex, after stirring for 20 min, a phase change material is added, the phase change material is one of polyethylene glycol, erythritol and stearic acid, the mass ratio of the carboxyl styrene-butadiene latex, dandelion latex and phase change material is 1:1:(2-4), and the mixture is stirred for another 20 min to obtain a phase change material composite latex; S2, after ultrasonicating Mxene, it is added to the above phase change material composite latex, the mass ratio of the Mxene and the phase change material composite latex is 1:10, after ultrasonicating for 5 min, a rare earth metal salt is added, and the mixture is stirred at 500 rpm for 20 min, during the stirring, 100 mL of deionized water is slowly added, after the stirring is completed, an organic acid is added, the organic acid is citric acid or oxalic acid, the mass ratio of the rare earth metal salt and the organic acid is 1:0.625, and the mixture is stirred at 500 rpm for 20 min to obtain a solid-liquid mixture; S3, the solid-liquid mixture is poured into a polytetrafluoroethylene mold, dried in an oven at 100℃ for 10 h, and then demolded to obtain a flexible phase change film.

2. The method for preparing a flexible phase change thin film according to claim 1, characterized in that, In step S1, the solid content of the carboxyl styrene-butadiene latex is 48-54 wt.%; and the solid content of the dandelion latex is 61 wt.%.

3. The method for preparing a flexible phase change thin film according to claim 1, characterized in that, In step S2, the mass ratio of the Mxene and the rare earth metal salt is 1:1.

6.

4. The method for preparing a flexible phase change thin film according to claim 1, characterized in that, In step S2, the rare earth metal salt is one of lanthanum chloride, cerium chloride, gadolinium chloride and neodymium chloride.

5. Use of a flexible phase change film, characterized in that The flexible phase change film prepared by the preparation method of any one of claims 1-4 is applied in a solar thermoelectric generator.

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