Erythritol fumed silica composite phase change material and preparation method thereof

Abstract

The invention belongs to the technical field of phase change materials, and particularly relates to an erythritol and fumed silica composite phase change material and a preparation method thereof.The preparation method comprises the following process steps that fumed silica and erythritol are mixed according to the mass ratio of 10: 90-30: 70, and a mixture is obtained; heating the mixture at 130-160 DEG C for 2-4 hours, and stirring for 5 minutes every 30 minutes in the heating process; the heated mixture is subjected to dipping treatment under the vacuum condition, and composite phase change material powder is obtained; the composite phase-change material powder is subjected to compression molding under the pressure of 3-5 MPa, the pressure is maintained for 3-7 minutes, and the erythritol fumed silica low-heat-conductivity shaped composite phase-change material is obtained, the problem of phase-change material leakage is solved, the packaging cost is reduced, meanwhile, the heat conductivity of the phase-change material can be reduced, the phase-change material has the heat insulation and heat storage capacity, and the thermal conductivity of the phase-change material is improved. The application in the field of thermal protection is facilitated.

Description

Technical Field

[0001] The present application belongs to the technical field of phase change materials, and in particular relates to an erythritol fumed silica composite phase change material and a preparation method thereof. Background Art

[0002] Phase change materials (PCMs) boast high heat storage density and relatively constant operating temperature. Erythritol, a tetrahydric alcohol with a phase change temperature of 117°C, has great potential for application in thermal protection due to its high latent heat and non-toxic properties. However, erythritol PCMs are prone to liquid phase leakage during the phase change process, requiring encapsulation or shaping before practical application.

[0003] Patent CN201710882094.3 uses porous expanded graphite to adsorb and shape erythritol, which can solve the leakage problem. However, the thermal conductivity of erythritol is higher after adding expanded graphite, resulting in poor thermal insulation performance, which is not conducive to its application in the field of thermal protection. Patent CN202210750767.0 uses molecular sieves / diatomaceous earth to adsorb and shape phase change materials while also giving them low thermal conductivity. It is a good subgrade soil material for permafrost roadbed protection. However, this method requires the preparation of molecular sieve / diatomaceous earth-based porous carrier materials in advance in a reactor, and the reaction time is as long as several days, resulting in a more complicated process and higher cost. Patent CN202310160046.9 uses polyethylene, olefin block copolymers, polyurethane, biodegradable polymers, polyvinyl alcohol, polymethyl methacrylate and other supporting materials to prepare a phase-change thermal insulation composite material. It achieves thermal insulation effects through both sensible heat and latent heat, increasing the latent heat storage capacity of the insulation material. However, in actual applications, it also faces problems such as overly complex preparation steps, high preparation time and cost. Patent CN202010186099.4 uses carboxylated-cellulose nanofibers as phase change materials, gelatin as a supporting carrier, and hollow microspheres as thermal insulation to form a composite low-thermal conductivity phase change cold storage material through mixing. The synthesized low-thermal conductivity phase change cold storage material has the advantages of stable phase change latent heat, no stratification, good stability, low preparation cost and low thermal conductivity, which makes it easy to use in cold transfer and heat resistance, and is suitable for industrial promotion. Summary of the Invention

[0004] In order to solve the above problems, this application provides a

[0005] The advantages of this application include: fumed silica is an inexpensive, non-toxic, odorless, and porous inorganic fine chemical product. This invention uses erythritol as a phase change material and fumed silica as a support carrier to adsorb and shape the erythritol, thereby preparing a fumed silica-erythritol shaped composite phase change material. This not only solves the problem of phase change material leakage and reduces packaging costs, but also reduces the thermal conductivity of the phase change material, giving it both thermal insulation and heat storage capabilities, making it more suitable for use in thermal protection applications. Furthermore, the process is simple, efficient, and low-cost, and does not require the addition of any binders or other protective agents. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] Figure 1 The present invention provides a differential scanning calorimetry curve of the erythritol fumed silica low thermal conductivity shaped composite phase change material.

[0007] Figure 2 This is a test diagram of liquid phase leakage at different mass proportions of fumed silica during the preparation of the erythritol fumed silica low thermal conductivity shaped composite phase change material provided by the present invention.

[0008] Figure 3 This is a theoretical phase change latent heat diagram of the erythritol fumed silica low thermal conductivity shaped composite phase change material provided by the present invention.

[0009] Figure 4 This is a thermal conductivity test diagram of the erythritol fumed silica low thermal conductivity shaped composite phase change material provided by the present invention.

[0010] Figure 5 This is a test diagram of liquid phase leakage of the erythritol fumed silica low thermal conductivity shaped composite phase change material provided by the present invention, in which the fumed silica accounts for 25% by mass, prepared at different shaping pressures. DETAILED DESCRIPTION

[0011] To make the technical solution and its advantages of the present application clearer, the technical solution of the present application will be described in further detail below in conjunction with the accompanying drawings. It should be understood that the specific embodiments described herein are only some embodiments of the present application and are only used to explain the present application, not to limit the present application. It should be noted that, for ease of description, only the parts related to the present application are shown in the accompanying drawings, and other related parts can refer to the general design. In the absence of conflict, the embodiments of the present application and the technical features in the embodiments can be combined with each other to obtain new embodiments.

[0012] The present invention relates to a method for preparing an erythritol fumed silica low thermal conductivity shaped composite phase change material, comprising the following steps:

[0013] The fumed silica and erythritol are thoroughly mixed;

[0014] Specifically, the fumed silica is first coarsely screened with a 40-mesh sieve and placed in an electric heating box for heating and drying at 105°C for 24 hours; at the same time, erythritol is placed in a ball mill and ball-milled at 300 rpm for 2 hours, and then filtered with a 40-mesh sieve; then the erythritol powder and the dried fumed silica are evenly mixed, wherein the fumed silica accounts for 10-30% by mass and the erythritol accounts for 90-70% by mass.

[0015] Place in an electric heating box for heating, stir regularly, and vacuum impregnate;

[0016] Specifically, the mixed material was placed in a constant temperature electric heating box and heated at 140°C for 2 hours. After being taken out and stirred for 5 minutes every 30 minutes, it was placed in a vacuum drying oven, evacuated, heated to 140°C, and vacuum impregnated for 1 hour. After being taken out, it was cooled and sealed to obtain an erythritol-silica low thermal conductivity composite phase change material. The sample was in powder form.

[0017] The erythritol fumed silica composite phase change material is compressed and shaped in a mold to obtain the erythritol fumed silica low thermal conductivity shaped composite phase change material.

[0018] Specifically, a certain mass of the erythritol-silica low thermal conductivity composite phase change material powder prepared in S2 was weighed and placed in a tablet press mold, with a pressure of 4 MPa applied and the holding time of 5 min.

[0019] The present invention will be further described below through specific examples.

[0020] Example 1: A low thermal conductivity, shaped composite phase change material of erythritol and fumed silica, calculated by the following mass parts: 10% by mass of fumed silica and 90% by mass of erythritol; the preparation method is carried out according to the following steps: first, the erythritol powder that has been ball-milled and sieve-filtered is evenly mixed with the fumed silica that has been sieve-filtered and dried, and the mixture is placed in a constant temperature electric heating box and heated for 2 hours, and then placed in a vacuum drying box and vacuum impregnated for 1 hour. Finally, after cooling, the erythritol and fumed silica low thermal conductivity composite phase change material powder is placed in a tablet press mold and pressurized to shape the mixture, the applied pressure is 4 MPa, and the pressure is maintained for 5 minutes, and finally, the erythritol and fumed silica low thermal conductivity, shaped composite phase change material is obtained.

[0021] Example 2: The preparation method of the erythritol fumed silica low thermal conductivity shaped composite phase change material in this embodiment is basically the same as the preparation method in Example 1, the difference being that the fumed silica used in this embodiment accounts for 15% by mass and the erythritol accounts for 85% by mass.

[0022] Example 3: The preparation method of erythritol fumed silica low thermal conductivity shaped composite phase change material in this embodiment is basically the same as the preparation method in Example 1, the difference being that the fumed silica used in this embodiment accounts for 20% by mass and erythritol accounts for 80% by mass.

[0023] Example 4: The preparation method of the erythritol fumed silica low thermal conductivity shaped composite phase change material in this embodiment is basically the same as the preparation method in Example 1, the difference being that the fumed silica used in this embodiment accounts for 25% by mass and the erythritol accounts for 75% by mass.

[0024] Example 5: The preparation method of the erythritol fumed silica low thermal conductivity shaped composite phase change material in this embodiment is basically the same as the preparation method in Example 1, the difference being that the fumed silica used in this embodiment accounts for 30% by mass and the erythritol accounts for 70% by mass.

[0025] See Figure 2 、 3 From the figure, we can see that with the addition of fumed silica, the leakage of the shaped composite phase change material is greatly alleviated, almost to zero, but it will also lead to a decrease in the latent heat of phase change. Therefore, when preparing the erythritol fumed silica low thermal conductivity shaped composite phase change material, it is recommended that the fumed silica account for 25% by mass and the erythritol account for 75% by mass; refer to Figure 4 From the figure, it can be found that when the mass proportion of fumed silica is 20% to 30%, the thermal conductivity of the erythritol fumed silica low thermal conductivity shaped composite phase change material is reduced to 0.2W / (m K), which has good thermal insulation performance.

[0026] Example 6: The preparation method of the erythritol fumed silica low thermal conductivity shaped composite phase change material in this embodiment is basically the same as the preparation method in Example 4, the difference being that when the material is placed in the tablet press mold and pressurized for shaping, the applied pressure is 3 MPa.

[0027] Example 7: The preparation method of the erythritol fumed silica low thermal conductivity shaped composite phase change material in this embodiment is basically the same as the preparation method in Example 4, the difference being that when the material is placed in the tablet press mold and pressurized for shaping, the applied pressure is 5 MPa.

[0028] Example 8: The preparation method of the erythritol fumed silica low thermal conductivity shaped composite phase change material in this embodiment is basically the same as the preparation method in Example 4, the difference being that when the material is placed in the tablet press mold and pressurized for shaping, the applied pressure is 10 MPa.

[0029] Example 9: The preparation method of the erythritol fumed silica low thermal conductivity shaped composite phase change material in this embodiment is basically the same as the preparation method in Example 4, the difference being that when the material is placed in the tablet press mold and pressurized for shaping, the applied pressure is 15 MPa.

[0030] See Figure 5 From the figure, it can be found that when the mass fraction of fumed silica is 25%, the leakage is small when the compaction pressure is 3-4MPa, and there is almost no leakage at 4MPa. Therefore, when preparing erythritol fumed silica low thermal conductivity shaped composite phase change material, the recommended compaction pressure is 4Mpa.

[0031] The above description is merely a specific embodiment of the present application, but the scope of protection of the present application is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in this application should be included in the scope of protection of the present application. Therefore, the scope of protection of the present application should be based on the scope of protection of the claims.

Claims

1. A method for preparing an erythritol fumed silica composite phase change material, characterized in that: The process steps are as follows: mixing fumed silica and erythritol in a mass ratio of 10:90 to 30:70 to obtain a mixture; The mixture is heated at 130° C. to 160° C. for 2 to 4 hours, and stirred for 5 minutes every 30 minutes during the heating process; The heated mixture is impregnated under vacuum conditions to obtain composite phase change material powder; The composite phase change material powder is pressed into shape at a pressure of 3-5 MPa and maintained at the pressure for 3-7 minutes to obtain an erythritol fumed silica low thermal conductivity shaped composite phase change material.

2. The method for preparing the erythritol fumed silica composite phase change material according to claim 1, wherein: The mass ratio of the fumed silica to erythritol is 25:

75.

3. The method for preparing the erythritol fumed silica composite phase change material according to claim 1, wherein: The mixing method of the fumed silica and erythritol is ball milling.

4. The method for preparing the erythritol fumed silica composite phase change material according to claim 1, wherein: The heating temperature was 140° C. and the heating time was 3 hours.

5. The method for preparing the erythritol fumed silica composite phase change material according to claim 1, wherein: The temperature of the vacuum impregnation treatment was 140° C., and the impregnation time was 1 hour.

6. The method for preparing the erythritol fumed silica composite phase change material according to claim 1, wherein: The pressing pressure was 4 MPa and the holding time was 5 minutes.

7. An erythritol fumed silica low thermal conductivity shaped composite phase change material, characterized in that: Prepared by the method according to any one of claims 1 to 6, wherein: The mass proportion of fumed silica in the composite phase change material is 10% to 30%, and the balance is erythritol; The leakage under a pressure of 5 MPa shall not exceed 3%, the latent heat of phase change shall not be less than 271.2 kJ / kg, and the thermal conductivity shall not be higher than 0.2 W / (m·K).

8. The composite phase change material according to claim 7, characterized in that: The mass proportion of the fumed silica is 25%, the phase change latent heat is 271.2 kJ / kg, and the thermal conductivity is 0.2 W / (m·K).

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