Graphene oxide / TiO2 modified phase change microcapsule and preparation method thereof

Abstract

The invention relates to the technical field of phase change materials, in particular to a graphene oxide / TiO2 modified phase change microcapsule and a preparation method thereof. The preparation method comprises the following steps: adding titanium dioxide into a graphene oxide solution, and uniformly dispersing to obtain a dispersed solution; mixing and emulsifying the dispersion solution and a phase change material to obtain a Pickering emulsion; sequentially adding an initiator and methyl methacrylate into the Pickering emulsion, and carrying out polymerization reaction, so as to obtain the graphene oxide / TiO2 modified phase change microcapsule. Graphene oxide and titanium dioxide synergistically serve as a Pickering emulsifier, the phase change microcapsule is synthesized through self-assembly polymerization of the Pickering emulsion, a water-based initiator is used, the synthesis method is simple, use of a traditional organic surfactant (emulsifier) is avoided, the phase change microcapsule is green and environmentally friendly, and meanwhile, graphene oxide, titanium dioxide and a PMMA shell layer endow the phase change microcapsule with the light absorption performance.

Description

Technical Field

[0001] The present invention relates to the technical field of phase change materials, and in particular to a graphene oxide / TiO2 modified phase change microcapsule and a preparation method thereof. Background Art

[0002] Phase change material is a functional material that uses phase changes of matter to achieve thermal energy storage and release. During the phase change process, the phase change material exchanges energy with the environment, and the temperature does not change, achieving the purpose of controlling temperature and energy utilization. Therefore, phase change materials have been widely used in the fields of solar thermal energy storage, industrial waste heat recovery, building temperature control, electronic devices and battery thermal management. Organic phase change materials (such as paraffin, higher fatty acids and alcohols) have the advantages of high latent heat, low supercooling and high stability, and are widely used in the field of medium and low temperature energy storage. However, organic phase change materials have low thermal conductivity (0.1~0.6W / (m·K)), large volume change during solid-liquid phase change, and easy leakage.

[0003] Phase change microcapsules use microencapsulation technology to encapsulate phase change energy storage materials in polymer materials or inorganic materials. This core-shell structure effectively prevents leakage of phase change energy storage materials, improves stability, increases heat transfer area, and improves heat conduction efficiency.

[0004] CN117821025A relates to a phase-change microcapsule and a preparation method thereof. The method comprises the following steps: (1) placing water in a constant temperature magnetic stirring water bath, heating the constant temperature magnetic stirring water bath to 90-95°C, adding a surfactant polyvinyl alcohol into the water, adjusting the magnetic core speed of the magnetic stirring water bath to 300-350r / min, and stirring evenly to form a surfactant dispersion system; (2) taking out the surfactant dispersion system and keeping it at 50-70°C, adjusting the temperature of the constant temperature magnetic stirring water bath to 50-70°C, and then returning the surfactant dispersion system to the constant temperature magnetic stirring water bath, first adding an emulsifying dispersant, wherein the emulsifying dispersant is sodium dodecylbenzene sulfonate (SD BS), sodium dodecyl sulfate, Tween-80, Span-80, one or more thereof, then add the phase change core material, stir and disperse at 250-300r / min for at least 1h to obtain the core material emulsified dispersion system; place the core material emulsified dispersion system in a constant temperature water bath for heat preservation; (3) take methyl methacrylate and initiator to prepare the wall material suspension; (4) heat the constant temperature magnetic stirring water bath to 60-85°C, add the wall material suspension dropwise into the core material emulsified dispersion system, stir at 300-350r / min for at least 1.5h to perform polymerization reaction, and form a phase change microcapsule suspension. (5) set the water bath temperature of the constant temperature magnetic stirring water bath to room temperature, continue to stir the phase change microcapsule suspension in the constant temperature magnetic stirring water bath at 300-350r / min for at least 1h, filter, wash, and dry to obtain phase change microcapsules.

[0005] CN111359554A discloses a large-particle polyurethane phase-change microcapsule and a preparation method thereof. The method firstly reacts diisocyanate with diol to prepare a polyurethane prepolymer, then adds a phase-change material and stirs evenly to obtain an oil phase; then prepares a nano-titanium dioxide aqueous dispersion, adds a water-soluble polyol, and obtains an aqueous phase; finally, the prepared oil phase is dripped into the aqueous phase under stirring to form a Pickering emulsion, and a condensation polymerization reaction occurs at the interface of the Pickering emulsion to form a polyurethane phase-change microcapsule, and after the reaction is completed, the polyurethane phase-change microcapsule solid powder is obtained by suction filtration, distilled water washing, and drying.

[0006] At present, the common problems in preparing phase change capsule materials are: (1) the use of traditional organic surfactants; (2) the poor light absorption performance of traditional phase change microcapsules. Summary of the invention

[0007] Based on the above content, the present invention provides a graphene oxide / TiO2 modified phase change microcapsule (abbreviated as: microcapsule) and a preparation method thereof.

[0008] To achieve the above object, the present invention provides the following solutions:

[0009] One of the technical solutions of the present invention is a method for preparing graphene oxide / TiO2 modified phase change microcapsules, comprising the following steps:

[0010] Step 1, adding titanium dioxide to a graphene oxide solution and dispersing the mixture evenly to obtain a dispersed solution;

[0011] Step 2, mixing and emulsifying the dispersed solution and the phase change material to obtain a Pickering emulsion;

[0012] Step 3, adding an aqueous initiator and methyl methacrylate to the Pickering emulsion in sequence to carry out a Pickering emulsion polymerization reaction to obtain the graphene oxide / TiO2 modified phase change microcapsules.

[0013] The second technical solution of the present invention is a graphene oxide / TiO2 modified phase change microcapsule prepared according to the above-mentioned preparation method.

[0014] The third technical solution of the present invention is the application of the above-mentioned graphene oxide / TiO2 modified phase change microcapsules in the fields of solar thermal energy storage, industrial waste heat recovery, building temperature control, electronic devices or battery thermal management.

[0015] The present invention discloses the following technical effects:

[0016] Compared with the preparation of phase change energy storage microcapsules by traditional organic surfactants, the present invention uses graphene oxide and titanium dioxide as Pickering emulsifiers to synthesize phase change microcapsules by Pickering emulsion self-assembly polymerization, uses aqueous initiators, has a simple synthesis method, avoids the use of traditional organic surfactants (emulsifiers), and is green and environmentally friendly. At the same time, graphene oxide, titanium dioxide and PMMA shell layers give the phase change microcapsules good light absorption properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0018] Figure 1 is a microscope picture of the Pickering emulsion prepared in Example 1;

[0019] Figure 2 This is a field emission scanning electron microscope image of the microcapsules prepared in Example 1;

[0020] Figure 3The DSC curves of hexadecanol and the microcapsules prepared in Example 1 are shown in FIG. 1 , wherein the left figure is hexadecanol and the right figure is the microcapsules prepared in Example 1;

[0021] Figure 4 The ultraviolet absorption spectra of the microcapsules prepared in Example 1 and Comparative Example 1;

[0022] Figure 5 This is the DSC curve of the microcapsules prepared in Example 2.

[0023] Figure 6 It is a comparison diagram of the leakage experiment of the microcapsules prepared in Example 1 and Comparative Example 2; wherein a is before heating and b is after heating. DETAILED DESCRIPTION

[0024] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0025] It should be understood that the terms described in the present invention are only for describing a particular embodiment and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. The intermediate value in any stated value or stated range, and each smaller range between any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0026] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0027] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to the skilled artisan. The present invention description and examples are exemplary only.

[0028] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0029] The first aspect of the present invention provides a method for preparing graphene oxide / TiO2 modified phase change microcapsules, comprising the following steps:

[0030] Step 1, adding titanium dioxide to a graphene oxide solution and dispersing the mixture evenly to obtain a dispersed solution;

[0031] Step 2, mixing and emulsifying the dispersed solution and the phase change material to obtain a Pickering emulsion;

[0032] Step 3, adding an aqueous initiator and methyl methacrylate to the Pickering emulsion in sequence to carry out a Pickering emulsion polymerization reaction to obtain the graphene oxide / TiO2 modified phase change microcapsules.

[0033] The present invention utilizes the surface activity of graphene oxide to disperse TiO2 particles, adds titanium dioxide powder with different dosages into the graphene oxide solution, places it on a magnetic stirrer and stirs it for 10 to 40 minutes, and then ultrasonicates it for 0.5 to 1.5 hours to make it evenly dispersed.

[0034] In a preferred embodiment of the present invention, the mass ratio of the graphene oxide to the titanium dioxide is (20-20):1; the mass ratio of the graphene oxide to the phase change material and methyl methacrylate is 1:(20-100):(50-80). The concentration of the graphene oxide solution is 2-4 g / L, and the solvent is water.

[0035] In a preferred embodiment of the present invention, the aqueous initiator is ammonium persulfate or potassium persulfate; the amount of the aqueous initiator added is 1% to 3% of the mass of the methyl methacrylate.

[0036] In a preferred embodiment of the present invention, the phase change material is paraffin, higher fatty acid or alcohol. In a further preferred embodiment of the present invention, the phase change material is alcohol, more preferably hexadecanol.

[0037] In a preferred embodiment of the present invention, the dispersed solution and the phase change material are mixed and emulsified in the following manner: the dispersed solution and the phase change material are placed in a water bath having a temperature higher than the melting point of the phase change material, and after the phase change material is completely dissolved, the dispersed solution is added to the phase change material, and stirred at 5000 to 10000 rpm for 5 to 10 minutes (to fully emulsify it) to obtain a Pickering emulsion.

[0038] In a preferred embodiment of the present invention, the Pickering emulsion polymerization reaction is specifically carried out at 500-800 r / min and 60-85° C. for 1.5-6 hours. The temperature of sequentially adding the initiator and methyl methacrylate to the Pickering emulsion is 60-85° C. and the stirring rate is 500-800 r / min.

[0039] In a preferred embodiment of the present invention, after the polymerization reaction is completed, the steps of suction filtration, washing and drying are further included. The drying temperature is 50° C. and the drying time is 10 hours.

[0040] The second aspect of the present invention provides a graphene oxide / TiO2 modified phase change microcapsule prepared according to the above-mentioned preparation method.

[0041] The third aspect of the present invention provides an application of the above-mentioned graphene oxide / TiO2 modified phase change microcapsules in the fields of solar thermal energy storage, industrial waste heat recovery, building temperature control, electronic devices or battery thermal management.

[0042] The present invention uses graphene oxide and titanium dioxide solid particles to co-emulsify instead of traditional organic surfactants, and prepares photothermal phase-change microcapsules through Pickering emulsion self-assembly polymerization. In the present invention, TiO2 is a photothermal material, PMMA has a strong light transmittance, and the TiO2 and PMMA shell layers enable the phase-change microcapsules to effectively absorb and store solar energy.

[0043] The technical solutions described in the present invention, unless otherwise specified, are all conventional solutions in the art, and the reagents or raw materials used, unless otherwise specified, are purchased from commercial channels or have been disclosed.

[0044] The technical solutions provided by the present invention are described in detail below in conjunction with the embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0045] Example 1

[0046] (1) Preparation of graphene oxide solution: Weigh 2 g of graphene oxide, add 1000 mL of deionized water, stir for 15 min, and perform ice bath ultrasonic treatment for 1.5 h to prepare a 2 g / L graphene oxide solution.

[0047] (2) Preparation of emulsion: 30 ml of 2 g / L graphene oxide solution was measured, 0.006 g of titanium dioxide powder was weighed and added to the graphene oxide solution, and the mixture was placed on a magnetic stirrer and stirred for 10 min. The mixture was then ultrasonicated for 40 min to make it evenly dispersed, thereby obtaining a dispersed solution.

[0048] (3) Preparation of Pickering emulsion: Weigh 6 g of hexadecanol, place the hexadecanol and the above dispersion solution in a 60°C water bath, respectively. After the hexadecanol is completely dissolved, add the dispersion solution to the hexadecanol and stir at 8000 rpm for 10 minutes to completely emulsify the mixture, thereby obtaining a stable Pickering emulsion (microscope image as shown in FIG. Figure 1 shown).

[0049] (4) Preparation of graphene oxide / TiO2 modified phase change microcapsules (hereinafter referred to as microcapsules): The obtained Pickering emulsion was placed on a magnetic stirrer and heated to 70°C in a water bath. Then, 1% of the mass of the monomer (methyl methacrylate) of ammonium persulfate was added as an initiator, and stirred at a speed of 800 r / min. At the same time, 3 g of methyl methacrylate (MMA) was slowly added dropwise. After the addition, the temperature was raised to 80°C and stirred continuously at a speed of 700 r / min. The reaction was allowed to proceed for 1.5 h.

[0050] The reacted solution was allowed to stand for complete cooling, and the product was filtered and washed with deionized water. The obtained sample was dried in an oven at 50° C. for 10 hours to obtain microcapsules.

[0051] The field emission scanning electron microscope image of the microcapsules prepared in this example is as follows Figure 2 shown by Figure 2 It can be seen that the microscopic morphology of the microcapsules is basically spherical, with a clear core-shell structure, which ensures that the phase change material has a stable structure and will not leak when the phase change occurs. The DSC curve of the microcapsules prepared in this example is shown in FIG. Figure 3 As shown (the GO / TiO2 / PMMA microcapsules in the figure represent the microcapsules prepared in Example 1); Figure 3 It can be seen that the encapsulation rate of the microcapsules prepared in Example 1 is as high as 73.63%, and phase change microcapsules with a high core material content can be formed.

[0052] Example 2

[0053] (1) Preparation of graphene oxide solution: Weigh 1 g of graphene oxide, add deionized water, stir for 15 min, and ultrasonicate in an ice bath for 1.5 h to prepare a 2 g / L graphene oxide solution.

[0054] (2) Preparation of emulsion: 0.003 g of titanium dioxide was weighed and added to 30 ml of graphene oxide solution, and the solution was placed on a magnetic stirrer and stirred for 10 min. The solution was then ultrasonicated for 40 min to disperse the solution uniformly, thereby obtaining a dispersed solution.

[0055] (3) Preparation of Pickering emulsion: Weigh 6 g of hexadecanol, place the hexadecanol and the above-mentioned dispersion solution in a 60° C. water bath, respectively. After the hexadecanol is completely dissolved, add the dispersion solution to the hexadecanol and stir at 10,000 rpm for 10 minutes with an emulsifying stirrer to completely emulsify the mixture, thereby obtaining a stable Pickering emulsion.

[0056] (4) Preparation of microcapsules: The obtained Pickering emulsion was placed on a magnetic stirrer, and then heated to 75°C in a water bath, and 1% of the mass of the monomer (methyl methacrylate) of ammonium persulfate was added as an initiator, and stirred at a speed of 600 r / min, while 3 g of methyl methacrylate (MMA) was slowly added dropwise. After the addition was completed, the temperature was raised to 80°C and stirred continuously at a speed of 700 r / min, and the reaction was carried out for 3 hours.

[0057] The reacted solution was allowed to stand for complete cooling, and the product was filtered and washed with deionized water. The obtained sample was dried in an oven at 50° C. for 10 hours to obtain microcapsules.

[0058] The DSC curve of the microcapsules prepared in this example is as follows Figure 5 As shown (the GO / TiO2 / PMMA microcapsules in the figure represent the microcapsules prepared in Example 2); Figure 5 It can be seen that the encapsulation rate of the microcapsules prepared in Example 2 is as high as 80.27%, and phase change microcapsules with a high core material content can be formed.

[0059] Comparative Example 1

[0060] The only difference from Example 1 is that the addition of titanium dioxide in step (2) is omitted, and the remaining steps and parameters are the same as those in Example 1; GO / PMMA microcapsules are prepared.

[0061] The ultraviolet absorption spectra of the microcapsules prepared in Example 1 and Comparative Example 1 are shown in FIG. Figure 4 As shown (in the figure, TiO2 represents the ultraviolet absorption spectrum of pure TiO2 used in the experiment; GO / PMMA microcapsules represent microcapsules prepared in Comparative Example 1; GO / TiO2 / PMMA microcapsules represent microcapsules prepared in Example 1); Figure 4 It can be seen that TiO2 has an obvious platform at 300nm~350nm, the platform of PMMA microcapsules here is not very obvious, and GO / TiO2 / PMMA microcapsules have a relatively obvious platform here, indicating that GO / TiO2 / PMMA microcapsules have light absorption properties.

[0062] Comparative Example 2

[0063] The only difference from Example 1 is that the addition of methyl methacrylate in step (4) is omitted, and the remaining steps and parameters are the same as those in Example 1.

[0064] Figure 6 The following are photos of the microcapsules prepared in Example 1 and Comparative Example 1 before and after heating; wherein a is a photo before heating, and b is a photo after heating (wherein Comparative Example 1 was heated at 80°C for 2 minutes, and Example 1 was heated at 80°C for 5 minutes). Figure 6 It can be seen that the microcapsules prepared in Comparative Example 2 cannot maintain their original appearance after heating, leak, and have no use value. However, the microcapsules prepared in Example 1 can continue to maintain their original appearance after heating, do not leak, can be reused, and have practical use value.

[0065] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for preparing graphene oxide / TiO2 modified phase change microcapsules, characterized in that: The following steps are involved: Step 1, adding titanium dioxide to a graphene oxide solution and dispersing the mixture evenly to obtain a dispersed solution; Step 2, mixing and emulsifying the dispersed solution and the phase change material to obtain a Pickering emulsion; Step 3, adding an aqueous initiator and methyl methacrylate to the Pickering emulsion in sequence to carry out a Pickering emulsion polymerization reaction to obtain the graphene oxide / TiO2 modified phase change microcapsules.

2. The method for preparing graphene oxide / TiO2 modified phase change microcapsules according to claim 1, characterized in that: The mass ratio of the graphene oxide to the titanium dioxide is (20-20):1; the mass ratio of the graphene oxide to the phase change material and methyl methacrylate is 1:(20-100):(50-80).

3. The method for preparing graphene oxide / TiO2 modified phase change microcapsules according to claim 1, characterized in that: The aqueous initiator is ammonium persulfate or potassium persulfate; the added amount of the aqueous initiator is 1% to 3% of the mass of the methyl methacrylate.

4. The method for preparing graphene oxide / TiO2 modified phase change microcapsules according to claim 1, characterized in that: The phase change material is paraffin, higher fatty acid or alcohol.

5. The method for preparing graphene oxide / TiO2 modified phase change microcapsules according to claim 1, characterized in that: The method of mixing and emulsifying the dispersed solution and the phase change material is as follows: placing the dispersed solution and the phase change material in an environment with a temperature higher than the melting point of the phase change material, and after the phase change material is completely dissolved, adding the dispersed solution to the phase change material, stirring at 5000-10000 rpm for 5-10 minutes to obtain a Pickering emulsion.

6. The method for preparing graphene oxide / TiO2 modified phase change microcapsules according to claim 1, characterized in that: The Pickering emulsion polymerization reaction is specifically carried out at 500-800 r / min and 60-85° C. for 1.5-6 hours.

7. The method for preparing graphene oxide / TiO2 modified phase change microcapsules according to claim 1, characterized in that: After the Pickering emulsion polymerization reaction is completed, the steps of suction filtration, washing and drying are also included.

8. Graphene oxide / TiO2 modified phase change microcapsules prepared according to the preparation method according to any one of claims 1 to 7.

9. Application of the graphene oxide / TiO2 modified phase change microcapsules as claimed in claim 8 in the fields of solar thermal energy storage, industrial waste heat recovery, building temperature control, electronic devices or battery thermal management.

Images