A shaped phase change material and a method of making the same

Abstract

The application provides a kind of shaped phase change material and its preparation method.The phase change material includes the following component materials according to mass percentage: 45.8-56.7% of dodecahydrate disodium hydrogen phosphate, 7.9-22.9% of sodium carbonate decahydrate, 7.6-15.9% of sodium sulfate decahydrate, 2.46-4.05% of reinforcing material, and 15-20% of adsorption material.The preparation of the phase change material includes the following steps: 1, preparing materials;2, preparing inorganic salt mixture;3, preparing molten inorganic salt mixture;4, preparing mixture and sealing;5, preparing shaped phase change material.The shaped phase change material prepared by the application has suitable phase change temperature, higher latent heat of phase change, no liquid leakage, no toxicity and non-combustibility, small supercooling degree, and no phase separation;at the same time, for the application occasions requiring transportation and storage between 20-30℃, the shaped phase change material can be used as an effective normal temperature cold storage agent to resist low temperature environment and protect specific chemicals and medicines from temperature fluctuation.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of phase change materials, in particular to a shaped phase change material and a preparation method thereof. BACKGROUND

[0002] Phase change energy storage technology has great research and application value in the fields of wind power energy saving, industrial waste heat, battery thermal management, cold chain logistics, etc. due to its unique physical and chemical properties. Among them, the medium and low temperature phase change heat storage materials with phase change temperature of 5-40℃ can be widely used in solar building heating, building energy saving, electronic equipment thermal management and other industries. With the continuous development of the current pharmaceutical cold chain logistics industry, more and more researches on low-temperature phase change materials are carried out in the industry, but the research on medium and low temperature phase change materials is relatively less.

[0003] Some cold chain logistics enterprises have developed some medium and low temperature phase change materials suitable for temperature range, usually prefer to use organic materials such as fatty acids, which are mostly low-cost, small supercooling degree, and can be compounded with polyols, aliphatic hydrocarbons and other materials to obtain phase change materials with the required temperature range, but the disadvantages are large volume change and flammable. At the same time, some enterprises have also begun to develop phase change materials with hydrated inorganic salt as the main component, but there are still some problems, for example, CN 114958309 A discloses a phase change material with phase change temperature of 18-20℃ and a preparation method thereof, which uses inorganic salt as the main material, thickening agent, nucleating agent and crystal type modifier as auxiliary materials to improve the performance of the phase change material, and must add thickening agent to prevent phase separation, add nucleating agent and crystal type modifier to inhibit supercooling degree, which cannot avoid the problem of corrosion of chloride salt to metal container and leakage. In addition, during the logistics transportation process, the phase change volume expansion is easy to cause the expansion and rupture of the packaging container, which greatly affects the heat preservation effect and the quality of goods, and pollutes the environment. Academic research has adopted the preparation method of phase change microcapsules, for example, the published literature (Liu Yuan. Preparation and performance of organic / inorganic shaped composite phase change material [D]. Nanchang University, 2019.) The preparation process of this shaped material is relatively complex, and the chemical raw materials of wall material / shell material are expensive, which is not suitable for large-scale industrial production of enterprises.

[0004] Therefore, it is urgent to develop a shaped phase change material with excellent performance, low cost and simple preparation process, and a preparation method thereof. SUMMARY

[0005] Therefore, the present application provides a shaped phase change material and a preparation method thereof. The prepared phase change material has suitable phase change temperature, high phase change latent heat, no phase separation, no liquid leakage, no toxicity, no flammability, no corrosion, and small supercooling degree. At the same time, the preparation process is simple, the raw materials are abundant and low in cost, and the prepared phase change material can be widely used for storing and transporting normal temperature storage drugs with a temperature of 20-30℃, so as to solve the problems of large supercooling degree, phase separation and easy leakage of traditional medium and low temperature phase change materials.

[0006] In one aspect, the present application provides a shaped phase change material, the phase change material comprising the following ingredients by mass percentage: 45.8-56.7% of disodium hydrogen phosphate dodecahydrate, 7.9-22.9% of sodium carbonate decahydrate, 15-30% of sodium sulfate decahydrate, 2.46-4.05% of reinforcing material, and 15-20% of adsorbent material.

[0007] Firstly, in the present application, although sodium carbonate decahydrate can assist in adjusting the phase change temperature and providing the thermal response speed of the phase change material, single sodium carbonate decahydrate is easy to react with carbon dioxide in the air to form sodium carbonate, which may cause the chemical composition of the material to change and affect its long-term stability. Although sodium sulfate decahydrate can further reduce the phase change temperature and is not easily affected by environmental factors, it has poor thermal conductivity, and single use may not be able to provide sufficient flexibility to adjust the overall performance of the PCM, especially when fine-tuning the phase change temperature or other physical properties is required. The disodium hydrogen phosphate dodecahydrate used in the present application provides a basic phase change temperature range for the phase change material, which can initially meet the requirements of maintaining low temperature for logistics transportation and the like. The combination of sodium carbonate decahydrate and sodium sulfate decahydrate can further fine-tune the phase change temperature, so that the final phase change material can further work within the required temperature range. In addition, the use of a plurality of hydrated inorganic salt materials may further enhance the stability of the entire phase change material system. Meanwhile, sodium carbonate decahydrate and sodium sulfate decahydrate have high thermal conductivity, which helps to further improve the thermal conductivity of the phase change material (PCM) and thus accelerate the thermal response speed.

[0008] Secondly, the reinforcing material used in the present application can be closely combined with the molten inorganic salt material formed during the preparation process and uniformly dispersed in the pores of the adsorbent material, which can optimize the impregnation and shaping effect and improve the overall performance of the shaped phase change material.

[0009] By adopting the above technical solution, the eutectic mixed salt prepared by the present application, i.e., the mixture of disodium hydrogen phosphate dodecahydrate, sodium carbonate decahydrate and sodium sulfate decahydrate, has a small supercooling degree under low temperature conditions, a stable solidification phase change platform, and a phase change material formed with a clear eutectic point. Compared with the single hydrated inorganic salt used in the prior art, the present application can effectively avoid phenomena such as supercooling and phase separation during the phase change process. In addition, it is not necessary to add high-viscosity thickening agents or search for nucleating agents and crystal type modifiers that match the crystal type.

[0010] Further, the reinforcing material is an active substance or a crystalline substance; the active substance is selected from one of nano calcium carbonate, nano aluminum oxide, nano titanium dioxide, nano montmorillonite or nano kaolin; and the crystalline substance is selected from sodium metasilicate nonahydrate or borax.

[0011] Preferably, the particle size of the active substance is not less than 2000 mesh.

[0012] By using the above technical solution, the reinforcing material has high thermal conductivity and large specific surface area, which is conducive to further enhancing the thermal conductivity of the phase change material, accelerating the absorption and release speed of heat energy, and thus improving the thermal response rate. Meanwhile, the reinforcing material can act as a heterogeneous nucleation site and a structural support, which not only helps to reduce supercooling but also helps to maintain the uniform distribution of components and reduce the possibility of phase separation.

[0013] Further, the adsorbing material is a porous adsorbing material, which is selected from fumed silica (also known as "fumed white carbon black") or expanded graphite.

[0014] Preferably, on the basis of the above technical solution, the specific surface area of the fumed silica is 200-220 m 2 / g, and the particle size is 6-8 μm; the particle size of the expanded graphite is 100-1000 mesh.

[0015] By using the above technical solution, both the fumed silica and the expanded graphite powder can act as a nucleation center and a structural support, which not only helps to reduce the degree of supercooling and make the phase change process more controllable, but also prevents the liquid phase change material from leaking at high temperature and improves the thermal stability of the phase change material.

[0016] In another aspect, the present application provides a method for preparing the shaped phase change material, which comprises the following steps:

[0017] Step one: a certain amount of sodium phosphate dibasic dodecahydrate, sodium carbonate decahydrate, sodium sulfate decahydrate, reinforcing material and adsorbing material are weighed according to the mass percentage;

[0018] Step two: the sodium phosphate dibasic dodecahydrate, sodium carbonate decahydrate and sodium sulfate decahydrate weighed in step one are mixed according to a certain mass ratio, stirred, and then the reinforcing material is added and stirred continuously to prepare an inorganic salt mixture;

[0019] Step three: the mixture in step two is heated to obtain a molten inorganic salt mixture;

[0020] Step four: a part of the molten inorganic salt in step three is added to the adsorbing material, stirred, and then the remaining molten inorganic salt in step three is added and stirred to prepare a mixture, which is sealed;

[0021] Step five: the sealed mixture in step four is stirred after constant temperature drying for a period of time, repeated multiple times, and then cooled to obtain a shaped phase change material.

[0022] By adopting the above technical scheme, firstly, the chemical composition in the final product can be ensured to be uniform, thereby ensuring the consistency and reliability of the phase change material.

[0023] Secondly, the addition of the reinforcing material helps to improve the physical properties of the phase change material, such as improving the thermal conductivity, mechanical strength, etc., so that the phase change material is more durable and efficient in practical application; the use of the adsorbent material (such as fumed silica or expanded graphite powder) can effectively adsorb the liquid PCM (phase change material) and prevent leakage, thereby improving the safety and stability of the product. In addition, by first combining the reinforcing material with the molten hydrated inorganic salt (particle hydrophilicity) and then mixing with the adsorbent material, the adsorbent material can better encapsulate the inorganic salt. On the contrary, if the adsorbent material is added first, part of the molten hydrated inorganic salt will be combined with the adsorbent material first, so that the reinforcing material cannot provide sufficient water phase for particle combination, thereby affecting the final performance of the phase change material. At the same time, by adding the molten inorganic salt into the adsorbent material twice, the adsorbent material can be fully contacted and uniformly wrapped around the inorganic salt, which is beneficial to form a stable composite material.

[0024] Finally, sealing and heating and cooling under constant temperature conditions can help to form a uniform and stable phase change material, avoiding the non-uniformity of the internal structure of the phase change material caused by temperature fluctuations, thereby ensuring the phase change characteristics and long-term stability of the material.

[0025] Further, in step one, the adsorbent material is dried, and the drying temperature is 80℃, and the drying time is 1.5-2h.

[0026] By adopting the above technical scheme, the adsorbent material can be dried to ensure that the adsorbent material will not be damp, and to avoid the influence of moisture in the adsorbent material on the final adsorption effect.

[0027] Further, in step two, the stirring speed is 500-600rpm, and the time is 30-60min; the stirring speed is 700-800rpm, and the time is 10-20min.

[0028] Further, in step three, the heating temperature is 65-75℃, and the time is 30-45min.

[0029] On the basis of the above technical scheme, preferably, the heating mode of the mixture in step two adopts water bath heating.

[0030] Further, in step four, the After adding the volume of molten inorganic salt of step three to the adsorbent material, uniform stirring is required for 3min; after adding the remaining molten inorganic salt of step three, stirring is required for 5-7min.

[0031] By adopting the technical scheme, the hydrated inorganic salt is well impregnated into the adsorbent material by the mixed dropwise adding, so that the adsorption efficiency and adsorption capacity are improved, better chemical bond or physical adsorption is formed, the combination between the inorganic salt and the adsorbent material is more firm, and the inorganic salt is less likely to fall off or flow away during use.

[0032] Further, in the step four, the sealing manner specifically comprises: placing the mixed material in a container, and sealing the container opening by using a single layer of preservative film and a high-temperature-resistant rubber band.

[0033] By adopting the technical scheme, the moisture in the mixed material can be prevented from being completely lost, and a good drying environment is provided for subsequent steps.

[0034] Further, in the step five, the mixed material is stirred every 60 min, and each stirring lasts for 3 min; the heating temperature is 80 DEG C, and the heating time is 6 h; and the cooling temperature is 20-40 DEG C.

[0035] The shaped phase change material provided by the application has the following beneficial effects relative to the prior art:

[0036] (1) In the prior art, the single hydrated inorganic salt is used in the phase change process, and supercooling and phase separation are easily generated. The low-eutectic mixed salt is used as the base material in the application, so that the problems are effectively avoided. The formula of the prepared shaped phase change material uses the low-eutectic mixed inorganic salt, does not need to add a high-viscosity thickening agent, a nucleating agent for seeking a crystal form match, and a crystal form modifier, and can make the shaped phase change material have a small supercooling degree and a stable solidification phase change platform under low-temperature conditions, that is, the shaped phase change material has a clear eutectic point. In addition, compared with the low-eutectic composite salt phase change material which has an unstable phase change process due to improper proportioning or lack of a eutectic point, the material provided by the application has excellent stability.

[0037] (2) The raw materials in the formula of the prepared shaped phase change material are abundant and low in cost. The introduction of the reinforcing material and the porous adsorbent material into the formula realizes the significant improvement of the overall performance of the shaped phase change material. The reinforcing material can be combined with the inorganic salt in a molten state and uniformly distributed in the internal structure of the porous adsorbent material. The combination of the two raw materials not only synergistically enhances the overall performance of the material, but also ensures the stability in the phase change process, thereby realizing the long-acting constant-temperature effect, so that the shaped phase change material has better impregnation and shaping effects.

[0038] (3) The shaped phase change material prepared by the present application has suitable phase change temperature, high latent heat of phase change, no liquid leakage, no toxicity and non-flammability, small supercooling degree and no phase separation. Meanwhile, for the application occasions requiring transportation and storage between 20-30℃, the shaped phase change material of the present application can be used as an effective normal temperature cold storage agent to resist low temperature environment, ensure the precision and continuity of temperature control and protect specific chemicals and medicines from the influence of temperature fluctuation.

[0039] (4) The method for preparing the shaped phase change material of the present application is simple and easy to operate and does not cause the common problems such as electrochemical corrosion of inorganic phase change materials. BRIEF DESCRIPTION OF DRAWINGS

[0040] In order to more clearly illustrate the technical solutions of the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or the prior art description will be briefly introduced as follows. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative effort on the basis of these drawings.

[0041] Figure 1 The figure is the step cooling curve of the shaped phase change material prepared in Example 1-3 of the present application; in the figure, a is the step cooling curve of the shaped phase change material of Example 1, b is the step cooling curve of the shaped phase change material of Example 2, and c is the step cooling curve of the shaped phase change material of Example 3.

[0042] Figure 2 The figure is the step cooling curve of the phase change material prepared in Comparative Example 1-3 of the present application; in the figure, B1 is the step cooling curve of the phase change material of Comparative Example 1, B2 is the step cooling curve of the phase change material of Comparative Example 2, and B3 is the step cooling curve of the phase change material of Comparative Example 3.

[0043] Figure 3 The figure is the actual object picture of the phase change material prepared in Example 2 and Comparative Example 1-2 of the present application; in the figure, W0 is the actual object picture of the shaped phase change material of Example 2 after heating in an oven, W1 is the actual object picture of the shaped phase change material of Comparative Example 1 after heating in an oven, and W2 is the actual object picture of the non-shaped phase change material of Comparative Example 2 after cyclic standing.

[0044] Figure 4 The figure is the DSC curve of the shaped phase change material prepared in Example 3.

[0045] Figure 5 The figure is the DSC curve of the shaped phase change material prepared in Comparative Example 3. DETAILED DESCRIPTION

[0046] The technical solutions in the embodiments of the present application will be clearly and completely described below in combination with the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the present application.

[0047] The present application will be further described below in combination with specific examples, and the protection scope of the present application is not limited by the following examples. The main materials involved in the examples are shown in Table 1 below, and the remaining materials not shown are all conventional commercially available products.

[0048] Table 1: Material source explanation table

[0049]

[0050] The following are examples of the present application.

[0051] Example 1

[0052] 1) Take 140 g of disodium hydrogen phosphate dodecahydrate, 20 g of sodium carbonate decahydrate, 40 g of sodium sulfate decahydrate, 6.2 g of nano calcium carbonate, and 45.8 g of expanded graphite for standby;

[0053] 2) Mix the disodium hydrogen phosphate dodecahydrate, sodium carbonate decahydrate, and sodium sulfate decahydrate in a clean container, and stir at a speed of 500 rpm for 30 min until there are no obvious solid particles, then add the nano calcium carbonate, and stir at a speed of 700 rpm for 15 min until well mixed, to obtain an inorganic salt mixture;

[0054] 3) Place the container containing the inorganic salt mixture in a water bath, and set the temperature to 70℃, and heat for 30 min to obtain a molten inorganic salt mixture;

[0055] 4) Dry the expanded graphite at 80℃ for 2 h;

[0056] 5) Drop 1 / 3 volume of the molten inorganic salt mixture into the container containing the expanded graphite, and stir at a uniform speed for 3 min, then add the remaining molten inorganic salt mixture, and stir thoroughly for 5-7 min;

[0057] 6) Seal the mouth of the container of step five with a single layer of plastic wrap and a high-temperature resistant rubber band, and dry at 80℃ for 1 h, then stir for 3 min, repeat the drying-stirring process 6 times, and then cool at room temperature (36℃) to obtain a shaped phase change material.

[0058] The phase change solidification platform temperature of the shaped phase change material formed in this example is 25.3℃, and the supercooling degree is <0.1℃.

[0059] Example 2

[0060] 1) Take 140 g of dodecahydrate sodium hydrogen phosphate, 40 g of sodium carbonate decahydrate, 20 g of sodium sulfate decahydrate, 10 g of nano-alumina, 37 g of fumed white carbon black for standby;

[0061] 2) Mix dodecahydrate sodium hydrogen phosphate, sodium carbonate decahydrate, and sodium sulfate decahydrate, and stir at a speed of 500 rpm for 60 min until there are no obvious solid particles, then add nano-alumina, and stir at a speed of 700 rpm for 20 min to mix evenly, to obtain an inorganic salt mixture;

[0062] 3) Place the container containing the inorganic salt mixture in a water bath, and set the temperature to 75℃, and heat at a constant temperature for 45 min to obtain a molten inorganic salt mixture;

[0063] 4) Dry the fumed white carbon black at 80℃ for 2 h;

[0064] 5) Drop 2 / 3 volume of the molten inorganic salt mixture into the container containing the fumed white carbon black, and stir at a uniform speed for 3 min, then add the remaining molten inorganic salt mixture, and stir thoroughly for 5-7 min;

[0065] 6) Seal the container opening with a single layer of preservative film and a high-temperature resistant rubber band, and dry at a constant temperature of 80℃ for 1 h, then stir for 3 min, repeat the drying-stirring process 6 times, and then cool at room temperature (39℃) to obtain a shaped phase change material.

[0066] The phase change material formed in this example has a phase change freezing platform temperature of 27.4℃ and a supercooling degree of 0.1℃.

[0067] Example 3

[0068] 1) Take 120 g of dodecahydrate sodium hydrogen phosphate, 60 g of sodium carbonate decahydrate, 20 g of sodium sulfate decahydrate, 10 g of nano-titanium dioxide, and 52 g of fumed white carbon black for standby;

[0069] 2) Mix dodecahydrate sodium hydrogen phosphate, sodium carbonate decahydrate, and sodium sulfate decahydrate, and stir at a speed of 600 rpm for 40 min until there are no obvious solid particles, then add nano-titanium dioxide, and stir at a speed of 800 rpm for 20 min to mix evenly, to obtain an inorganic salt mixture;

[0070] 3) Place the container containing the inorganic salt mixture in a water bath, and set the temperature to 70℃, and heat at a constant temperature for 40 min to obtain a molten inorganic salt mixture;

[0071] 4) Dry the fumed white carbon black at 80℃ for 2 h;

[0072] 5) Pour 1 / 2 volume of the molten inorganic salt mixture into the container containing the fumed white carbon black, stir at a uniform speed for 3 min, then add the remaining molten inorganic salt mixture, and fully stir for 5-7 min;

[0073] 6) Seal the mouth of the container with a single layer of preservative film and a high-temperature-resistant rubber band, dry at 80°C for 1 h, stir for 3 min, repeat the drying-stirring process 6 times, and then cool at room temperature (34°C) to obtain the shaped phase change material.

[0074] The phase change solidification platform temperature of the shaped phase change material formed in this example is 24.7°C, and the supercooling degree is 0.5°C.

[0075] The following is a comparative example of the present application.

[0076] Comparative Example 1

[0077] The difference from Example 2 is that no reinforcing material-nano-aluminum oxide is added. The preparation of this comparative example specifically includes the following steps:

[0078] 1) Take 140 g of disodium hydrogen phosphate dodecahydrate, 40 g of sodium carbonate decahydrate, 20 g of sodium sulfate decahydrate, and 37 g of fumed white carbon black;

[0079] 2) Mix the disodium hydrogen phosphate dodecahydrate, sodium carbonate decahydrate, and sodium sulfate decahydrate, and stir at a speed of 500 rpm for 60 min until there are no obvious solid particles, and mix uniformly;

[0080] 3) Place the container containing the inorganic salt mixture in a water bath, and set the temperature to 75°C, and heat at a constant temperature for 45 min to obtain a molten inorganic salt mixture;

[0081] 4) Dry the fumed white carbon black at 80°C for 2 h;

[0082] 5) Pour 2 / 3 volume of the molten inorganic salt mixture into the container containing the fumed white carbon black, stir at a uniform speed for 3 min, then add the remaining molten inorganic salt mixture, and fully stir for 5-7 min;

[0083] 6) Seal the mouth of the container with a single layer of preservative film and a high-temperature-resistant rubber band, dry at 80°C for 1 h, stir for 3 min, repeat the drying-stirring process 6 times, and then cool at room temperature (39°C) to obtain the shaped phase change material.

[0084] The phase change solidification platform temperature of the phase change material formed in this comparative example is 26.1°C, and the supercooling degree is 0.9°C.

[0085] Comparative Example 2

[0086] The difference from Example 3 is that 10 g of sodium carboxymethyl cellulose is used to replace 52 g of fumed white carbon black. The preparation of the comparative example specifically includes the following steps:

[0087] 1) 120 g of disodium hydrogen phosphate dodecahydrate, 60 g of sodium carbonate decahydrate, 20 g of sodium sulfate decahydrate, 10 g of nano titanium dioxide, and 10 g of sodium carboxymethyl cellulose are weighed for standby;

[0088] 2) The disodium hydrogen phosphate dodecahydrate, sodium carbonate decahydrate, and sodium sulfate decahydrate are mixed and stirred at a speed of 600 rpm for 40 min until there are no obvious solid particles, and then the nano titanium dioxide and sodium carboxymethyl cellulose are added and stirred at a speed of 800 rpm for 20 min to mix uniformly;

[0089] 3) The above mixture container is placed in a water bath, and the temperature is set to 70℃, and constant temperature heating is carried out for 40 min, and after completion, it is cooled at room temperature (34℃), and a non-shaped phase change material is obtained.

[0090] The phase change freezing platform temperature of the non-shaped phase change material formed in the comparative example is 24.0℃, and the supercooling degree is 3.7℃.

[0091] Comparative Example 3

[0092] The difference from Example 3 is that the molten inorganic salt mixture in step 3 is dropped into the fumed white carbon black at one time. Specifically includes:

[0093] 1) 120 g of disodium hydrogen phosphate dodecahydrate, 60 g of sodium carbonate decahydrate, 20 g of sodium sulfate decahydrate, 10 g of nano titanium dioxide, and 52 g of fumed white carbon black are weighed for standby;

[0094] 2) The disodium hydrogen phosphate dodecahydrate, sodium carbonate decahydrate, and sodium sulfate decahydrate are mixed and stirred at a speed of 600 rpm for 40 min until there are no obvious solid particles, and then the nano titanium dioxide is added and stirred at a speed of 800 rpm for 20 min to mix uniformly, to prepare an inorganic salt mixture;

[0095] 3) The above inorganic salt mixture container is placed in a water bath, and the temperature is set to 70℃, and constant temperature heating is carried out for 40 min, to obtain a molten inorganic salt mixture;

[0096] 4) The fumed white carbon black is dried at 80℃ for 2 h;

[0097] 5) The molten inorganic salt mixture is dropped into the container containing the fumed white carbon black at one time, and then stirred uniformly for 5-7 min;

[0098] 6) Sealing the mouth of the container with a single layer of cling film and high-temperature-resistant rubber bands, drying at 80°C for 1 h, stirring for 3 min, repeating the drying-stirring process 6 times, and then cooling at room temperature (34°C) to obtain the shaped phase change material.

[0099] The phase change solidification platform temperature of the shaped phase change material formed in the comparative example was 23.6°C, and the supercooling degree was 1.2°C.

[0100] The test results of the phase change solidification platform temperature and the supercooling degree of the phase change materials prepared in Examples 1-3 and Comparative Examples 1-3 are recorded in Table 2 below.

[0101] Table 2 Test results of examples and comparative examples

[0102] Sample Phase transition freezing platform temperature / °C Supercooling / °C Platform exotherm time / min Example 1 25.3 <0.1 67 Example 2 27.4 0.1 74 Example 3 24.7 0.5 63 Comparative Example 1 26.1 0.9 42 Comparative Example 2 24.0 3.7 28 Comparative Example 3 23.6 1.2 61

[0103] From the test results in Table 2, it can be seen that the phase change solidification platform temperature of the shaped phase change materials prepared in Examples 1-3 is in the range of 20-30°C, the supercooling degree is less than 1°C, and the platform heat release time is > 60 min (all samples contain 210 ± 5 g of molten inorganic salt). The platform heat release time of Comparative Examples 1-2 is reduced by at least 30% compared with Examples 2-3; the heat release time of Comparative Example 3 and Example 3 is not significantly different, but the supercooling degree is poor. Therefore, it can be shown that the main inorganic salt in the shaped phase change material prepared in the present application has a eutectic point, the crystal nucleus grows well, and the phase change process is stable, so it can be considered that the shaped phase change material prepared in the present application can be applied to the fields of thermal interface material, battery thermal management, logistics, and pharmaceuticals.

[0104] In addition, in terms of the platform heat release time of the phase change materials prepared in Examples 1-3 in Table 2, in the present application, the greater the mass fraction of the adsorbent material in the total material, the greater the degree of reduction of latent heat.

[0105] The inventors further tested the above examples and comparative examples for the following performance, including:

[0106] (1) Step cooling test

[0107] The phase change materials prepared in Examples 1-3 and Comparative Examples 1-3 were respectively filled into small self-sealing bags / 250 ml glass containers, placed in a refrigeration cabinet, the temperature of the refrigeration cabinet was set to 2-8°C, the probe of the SL-SWSSN-4G intelligent temperature and humidity communication recorder was inserted into the middle of the material, and the temperature change was recorded every 1 min, finally the collected temperature data of the PCM phase change process were analyzed to obtain the step cooling curve as shown in FIGS. 1-3. Figure 1 、 2

[0108] (2) Stability test​

[0109] Take about 10g of the phase change material powder prepared in Example 2 and Comparative Example 1, place it on filter paper, then place the filter paper in a petri dish, seal it, and put it in an oven at 60°C. After 30 minutes, take out the petri dish and observe the thermal stability of the sample and whether there is any material leakage on the filter paper. Figure 3 (W0, W1) shown.

[0110] The phase change material prepared in Comparative Example 2 was tested at a low temperature of 2-8°C for 16 hours, then taken out and allowed to stand at room temperature (20-40°C) to observe the stability of the material in the container. Figure 3 (W2) shown.

[0111] (3)DSC test

[0112] The phase change enthalpy of the phase change material is tested according to the relevant records in GB / T 19466.1 "Plastic Differential Scanning Calorimetry (DSC) Part 1: General Rules", wherein the differential scanning calorimeter used in the test should be calibrated and verified, and the cooling device supporting the measuring instrument should be able to cool to below -70°C, and the weighing instrument used should be accurate to 0.01mg. The test specifically includes: taking the shaped phase change material prepared in Example 3 and Comparative Example 3 as an example, the sampling mass for each test should be 3mg to 7mg, the test is carried out under a nitrogen atmosphere, the standard substance used is indium, and the temperature rise / fall scanning rate is 5°C / min or 10°C / min. The results are as follows: Figure 4 、 Figure 5 shown.

[0113] Depend on Figure 1 It can be seen that the shaped phase change material prepared by the present invention has a stable step cooling curve Tt diagram, a low supercooling, and a solidification exothermic time of more than 60 minutes (the mass range of the molten inorganic salt is 210±5g). In the present invention, the exothermic time decreases with the increase of the mass of the adsorbent material, and the supercooling increases with the mass ratio of sodium carbonate decahydrate to sodium sulfate decahydrate. The supercooling of the formulations within the scope of the present invention is less than 1°C, the crystal growth is good, the phase change conversion rate is high, and the thermal enthalpy of the phase change material can be maximized.

[0114] Depend on Figure 2 It can be seen that the reinforcing material, the adsorption material, and the method of adding the molten inorganic salt to the adsorption material in the preparation step all have different degrees of influence on the phase change material.

[0115] In combination with the step cooling curve of Example 2 and Comparative Example 1, it can be seen that the phase change point of the shaped phase change material prepared without adding the reinforcing material is slightly reduced, but the supercooling phenomenon is obvious, the curve is not stable enough, and the heat release duration is reduced by about 42%. The reason for this phenomenon is that the reinforcing material is a functional inorganic material, the particle surface is hydrophilic and oleophobic, and the bonding force between the reinforcing material and the molten inorganic salt phase change material matrix is utilized to improve the overall performance of the shaped phase change material, and to assist the main energy storage phase change material (molten inorganic salt) to be uniformly dispersed in the adsorbent material.

[0116] In combination with the step cooling curve of Example 3 and Comparative Example 2, it can be seen that the step cooling curve of the eutectic inorganic salt material not shaped by the adsorbent material has a large supercooling degree, and the phase change process is extremely unstable, with a heat release duration reduced by about 55.5%. The reason for this phenomenon is that the molten inorganic salt phase change material is not encapsulated by the porous adsorbent material, resulting in temperature faults during the phase change process, and a serious supercooling delay phenomenon, leading to a strong amorphous state (glass state) during the crystallization process.

[0117] In combination with the step cooling curve of Example 3 and Comparative Example 3, it can be seen that, compared with the molten inorganic salt added in multiple portions, the molten inorganic salt added in one portion has a larger step cooling curve supercooling degree, but the heat release duration and the difference in phase change temperature platform are not significantly different. Therefore, further comparative analysis of the phase change enthalpy is carried out by differential scanning calorimetry (DSC) test, as shown in the attached Figure 4 and the attached Figure 5 .

[0118] It can be seen that the reinforcing material is beneficial to the uniform impregnation of the eutectic hydrated inorganic salt, thereby improving the adsorption rate of the shaped phase change material with respect to the inorganic salt, and the porous adsorbent material is beneficial to the overall stability and phase change constant temperature of the shaped phase change material. The use of the reinforcing material and the adsorbent material in combination has a certain synergistic effect, which can make the phase change process of the shaped phase change material more stable, achieve the optimization of the encapsulation and shaping effect, and be suitable for various low-temperature phase change application fields, such as battery thermal management and logistics.

[0119] From Figure 3 (W0), it can be seen that the shaped phase change material prepared in Example 2 can maintain good thermal stability in a high-temperature environment for a certain period of time, and is not prone to liquid material leakage.

[0120] From Figure 3 (W1), it can be seen that the shaped phase change material prepared in Comparative Example 1 has poor thermal stability in a high-temperature environment for a certain period of time, and some liquid material leaks.

[0121] From Figure 3 (W2), it can be seen that the non-shaped phase change material prepared in Comparative Example 2 needs to add a thickening agent to increase the viscosity of the liquid material, so as to avoid the stratification phenomenon caused by the density difference of the inorganic salt, but stratification is still prone to occur after freeze-thaw cycles.

[0122] Thus, the prepared directional phase change material has suitable phase change temperature, higher latent heat of phase change, no liquid leakage, no toxicity and non-flammability, small supercooling degree and no phase separation.

[0123] From the above, it can be seen that the prepared directional phase change material has suitable phase change temperature, higher latent heat of phase change, no liquid leakage, no toxicity and non-flammability, small supercooling degree and no phase separation. Figure 4 It can be seen that the directional phase change material prepared in Example 3 has a phase change point T of 22.2℃ and a phase change enthalpy of 127.4J / g, and the phase change temperature is slightly lower than that of the step cooling curve C. onset

[0124] From the above, it can be seen that the prepared directional phase change material has suitable phase change temperature, higher latent heat of phase change, no liquid leakage, no toxicity and non-flammability, small supercooling degree and no phase separation. Figure 5 It can be seen that the directional phase change material prepared in Comparative Example 3 has a phase change point T of 14.8℃ and a phase change enthalpy of 104.4J / g, and the phase change temperature is slightly lower than that of the step cooling curve B3. onset This is related to the supercooling phenomenon, and also because the mixed inorganic salt is not well impregnated into the adsorbent material in the fourth mixing step, thereby blocking the heat transfer.

[0125] From the DSC curves of Example 3 and Comparative Example 3, it can be seen that the stepwise dropwise addition of the molten inorganic salt into the adsorbent material can maximize the adsorbent material, utilize the phase change enthalpy, and reduce the influence of the pores of the adsorbent material on the overall heat transfer of the material. The enthalpy value and the initial temperature of the DSC show that the prepared directional phase change material has suitable phase change temperature and reliable high latent heat value, and can replace the traditional non-directional phase change material, thereby avoiding the problems of leakage and large supercooling degree caused by solid-liquid phase change.

[0126] The above only describes the preferred embodiments of the present application, and is not used to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.​

Claims

1. A method for preparing a shaped phase change material, characterized in that: The phase change material comprises the following raw materials by mass percentage: 45.8-56.7% disodium hydrogen phosphate dodecahydrate, 7.9-22.9% sodium carbonate decahydrate, 7.6-15.9% sodium sulfate decahydrate, 2.46-4.05% reinforcing material, and 15-20% adsorption material; The reinforcing material is an active substance or a crystalline substance; The active substance is selected from one of nano calcium carbonate, nano alumina, nano titanium dioxide, nano montmorillonite or nano kaolin; The crystals are selected from sodium metasilicate nonahydrate or borax; The method comprises the following steps: Step 1: Weigh a certain amount of disodium hydrogen phosphate dodecahydrate, sodium carbonate decahydrate, sodium sulfate decahydrate, reinforcing material and adsorption material according to the mass percentage; Step 2: Mix the disodium hydrogen phosphate dodecahydrate, sodium carbonate decahydrate, and sodium sulfate decahydrate weighed in Step 1, stir, add the reinforcing material, and continue stirring to prepare an inorganic salt mixture; Step 3, heating the mixture of step 2 to obtain a molten inorganic salt mixture; Step 4: adding a portion of the molten inorganic salt from step 3 to the adsorption material, stirring, and then adding the remaining molten inorganic salt from step 3, stirring to obtain a mixture, and sealing; Step 5: Dry the sealed mixture in step 4 at a constant temperature for a period of time, then stir it, repeat this process several times, and then cool it to obtain a fixed phase change material.

2. The method according to claim 1, wherein The particle size of the active substance is not less than 2000 mesh.

3. The method according to claim 1, wherein The adsorption material is a porous adsorption material, and the porous adsorption material is selected from fumed silica or expanded graphite.

4. The method according to claim 3, wherein The specific surface area of ​​the fumed silica is 200-220 m 2 / g, and a particle size of 6-8 μm; the particle size of the expanded graphite is 100-1000 mesh.

5. The method according to claim 1, wherein In step 1, the adsorption material is dried at a temperature of 80° C. for a time of 1.5 to 2 hours.

6. The method according to claim 1, wherein In step 3, the heating temperature is 65-75° C. and the heating time is 30-45 minutes.

7. The method according to claim 1, wherein In step 4, a portion of the molten inorganic salt from step 3 is added to the adsorption material, stirred, and then the remaining molten inorganic salt from step 3 is added, stirred to obtain a mixture, and sealed, which specifically includes: Will The molten inorganic salt prepared in step 3 is added to the adsorption material by volume, stirred, and then the remaining molten inorganic salt in step 3 is added, stirred to prepare a mixture, and sealed.

8. The method according to claim 1, wherein In step 5, the constant temperature drying temperature is 80°C, and the cumulative total time is 6 hours; the mixture is stirred once every 60 minutes, and each stirring time is 3 minutes; the cooling temperature is 20~40°C.

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