Preparation method of polyurethane-liquid metal composite pyroelectric material

Abstract

A preparation method of a polyurethane-liquid metal composite elastic heat material with high thermal conductivity. The steps include: S1, selecting a liquid metal material A with a suitable melting point and a shape memory polymer material B and a dissolved solution C of the material B; S2, adding the polyurethane material B to the dissolved solution C and stirring until completely dissolved to prepare a solution of the material B; S3, adding a certain mass of the material A to the solution of the material B for stirring and ultrasonic oscillation, so that the material A is uniformly dispersed in the solution to obtain a mixed solution of the material A and the material B; S4, uniformly pouring the mixed solution obtained in the step S3 into a mold; S5, placing the mold containing the mixed solution into a drying box for drying and forming at high temperature, and finally obtaining a high-thermal-conductivity liquid metal-polyurethane composite elastic heat material D composed of the material A and the material B. The material has good thermal conductivity, large elastic heat effect and extremely low driving stress, and the preparation method is simple.

Description

A method for preparing polyurethane-liquid metal composite elastothermal material Technical Field

[0001] This invention relates to the field of solid-state refrigeration technology, and in particular to a method for preparing solid-state refrigeration materials made of polymers. Background Technology

[0002] Refrigeration technology is widely used in various fields. Currently, the most common refrigeration method is vapor compression refrigeration. However, the hydrofluorocarbons used in vapor compression refrigeration cause serious harm to the climate, such as global warming. Therefore, the development of new zero-emission, pollution-free green refrigeration technologies has received widespread attention. In recent years, solid-state refrigeration technology, based on the thermal effect generated by solid materials under an external field, has become an alternative to traditional refrigeration technologies due to its advantages such as high efficiency and environmental friendliness.

[0003] Elastic-thermal refrigeration is currently the most widely studied solid-state refrigeration technology. Its principle is based on the elasto-thermal effect of materials, where a structural phase transition occurs within the material under uniaxial stress, resulting in an endothermic / exothermic thermal effect. Shape memory alloys, as typical elasto-thermal materials, have been extensively studied. For example, NiMnTi and NiTi shape memory alloys can produce adiabatic temperature changes ΔT of approximately 31.5℃ and 38.5℃ respectively under uniaxial stress. However, to achieve such large ΔT values, current elasto-thermal alloys require stresses of hundreds of megapascals to drive the structural phase transition. This high stress necessitates the use of bulky motors in refrigeration equipment to drive the elasto-thermal effect, significantly increasing the design cost of the equipment. Furthermore, the brittleness of most alloys severely affects their fatigue life, making it difficult to meet the required service life for refrigeration applications. Furthermore, the elastothermal effect occurs near the phase transition temperature of shape memory alloys, while the phase transition temperature range of alloys is typically below 10°C. The greater the distance between the operating temperature and the phase transition temperature, the more drastically the required driving stress increases, and the more drastically the cooling efficiency decreases. This means that the elastothermal cooling temperature range can only be limited to a relatively narrow temperature range. Therefore, the aforementioned problems with shape memory alloy elastothermal materials currently hinder the further commercialization of elastothermal cooling technology.

[0004] In recent years, it has been discovered that shape memory polymers also possess elastothermal effects similar to shape memory alloys, and they have advantages such as simple preparation and low driving stress. Among them, polyurethane, as a typical shape memory polymer material, has received widespread attention. However, due to the low thermal conductivity of polyurethane (0.5 ~ 1 W / m ℃), heat cannot be quickly and timely transferred to the external environment during uniaxial stress driving, resulting in a large loss of energy and limiting further improvement of the elastothermal effect of polyurethane. Traditional methods of adding thermally conductive solid particles to polyurethane to improve its thermal conductivity are often cumbersome in preparation, and the thermally conductive particles are prone to agglomeration, causing uneven composition within the polymer. Therefore, it is necessary to develop a material with high thermal conductivity, large elastothermal effect, low driving stress, and simple preparation method to meet the practical needs of elastothermal refrigeration technology. Summary of the Invention

[0005] This invention provides a method for preparing a polyurethane material with high thermal conductivity. The polyurethane prepared by this method has good thermal conductivity, outstanding elastothermal effect, extremely low driving stress, and a simple preparation method.

[0006] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0007] A method for preparing a highly thermally conductive polyurethane-liquid metal, comprising:

[0008] Step S1: Select liquid metal material A and polyurethane material B with suitable melting points, as well as a solution C of material B;

[0009] Step S2: Add polyurethane material B to solution C and stir until completely dissolved to prepare a solution of material B;

[0010] Step S3: Add a certain mass of material A to the solution of material B, stir and perform ultrasonic oscillation to make material A uniformly dispersed in the solution, and obtain a mixed solution of material A and material B.

[0011] Step S4: Pour the mixed solution obtained in step S3 evenly into the mold;

[0012] Step S5: Place the mold containing the mixed solution into a drying oven and dry it at high temperature to form a high thermal conductivity liquid metal-polyurethane composite thermoelastic material D composed of material A and material B.

[0013] Optionally, material A can be selected from GaIn or GaInSn alloys with low melting points, with a melting point temperature below 20°C. Material B can be selected from different types of polyurethane polymers.

[0014] Optionally, material B, polyurethane, refers to a class of polymeric materials whose main chain contains urethane characteristic units. It is a polymeric compound generated by the reaction of diisocyanate or polyisocyanate with compounds containing two or more hydroxyl groups, and its chemical formula is: (C 10 H8N2O·C6H 14 O3)n.

[0015] Optionally, in step S1, the dissolving solution C can be a tetrahydrofuran solution or a dimethylformamide solution with a purity of 99.5% or higher.

[0016] Optionally, in step S2, polyurethane material B is added to solution C at a ratio of x g / 100 ml, where x is between 3 and 20.

[0017] Optionally, in step S3, the mass fraction of material A in composite material D is y wt.%, where the value of y is between 3 and 20.

[0018] Optionally, in step S3, the stirring method can be mechanical stirring or magnetic stirring, and the stirring time is 30 to 60 minutes.

[0019] Optionally, the drying temperature in step S5 can be selected between 50 and 80°C, and the drying time can be between 4 and 8 hours.

[0020] Furthermore, the present invention also provides the application of a high thermal conductivity liquid metal-polyurethane composite material D in elastothermal refrigeration.

[0021] The advantages of the technical solution provided by this invention include:

[0022] Liquid metal has good fluidity and is evenly distributed when incorporated into polyurethane, which solves the problem of easy agglomeration of traditional heat-conducting solid particles.

[0023] The addition of liquid metal improves the thermal conductivity of polyurethane.

[0024] Liquid metal-polyurethane materials with higher thermal conductivity exhibit greater thermal insulation temperature change in the elasto-thermal effect;

[0025] The driving stress required for liquid metal-polyurethane materials to generate an elasto-thermal effect is greatly reduced, far below that required for shape memory alloys. This significantly reduces the requirements and costs of elasto-thermal cooling technology equipment, and has promising prospects for commercial application. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 is a flowchart of the preparation process of polyurethane-liquid metal composite material in Example 1 of the present invention;

[0028] Figure 2 shows the appearance of the polyurethane-12 wt.% liquid metal composite material of Example 1 of the present invention in (a) flat, (b) bent, and (c) tensile states;

[0029] Figure 3 shows the microstructure of the polyurethane-liquid metal composite material in Example 1 of the present invention under an electron microscope, where (a) and (b) are the surface morphology of pure polyurethane and polyurethane-12 wt.% liquid metal composite material, respectively, and (c) and (d) are the cross-sectional morphology of pure polyurethane and polyurethane-12 wt.% liquid metal composite material.

[0030] Figure 4(a) is a cross-sectional view of the polyurethane-12 wt.% liquid metal composite material of Example 1 of the present invention under an electron microscope. In the figure, the four regions P1, P2, P3 and P4 are the liquid metal flowing out from inside the material. The energy dispersive spectroscopy analysis of the elemental composition of these four regions is performed. The results of the energy dispersive spectroscopy analysis of the four regions are shown in Figure 4(b).

[0031] Figure 5 shows the relationship between the thermal conductivity of the polyurethane-liquid metal composite material in Example 2 of the present invention and the liquid metal content.

[0032] Figure 6 shows the temperature changes during the elastothermal effect measurement of pure polyurethane and polyurethane-liquid metal composite materials in Example 2. (a) shows the temperature changes of the pure polyurethane material and the polyurethane-12 wt.% liquid metal composite material under uniaxial stress tensile stress up to three times the elongation, where the stress loading rate is 0.41 s⁻¹. -1 (b) Temperature changes of pure polyurethane material and polyurethane-12 wt.% liquid metal composite material during the process of completely unloading stress from 3 times the tensile length and returning to the initial state, with a stress unloading rate of 0.41 s⁻¹. -1 ;

[0033] Figure 7 shows the stress-strain relationship of the polyurethane-12 wt.% liquid metal composite material in Example 2 of the present invention during elastothermal measurement. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of the present invention clearer, the technical solutions of the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0035] Example 1

[0036] In this embodiment, there is a low-melting-point liquid metal Ga. 64.6 In 20.3 Sn 15 The raw material is a thermoplastic polyurethane elastomer with a strength grade of 85A.

[0037] The preparation method of the polyurethane-liquid metal composite elastothermal material prepared from the above two materials is shown in Figure 1, taking a liquid metal mass percentage of 12 wt.% as an example:

[0038] (1) Add 5 g of polyurethane raw material to 100 ml of tetrahydrofuran. The purity level of tetrahydrofuran is chemically pure. After adding, stir the solution continuously until the polyurethane raw material is completely dissolved.

[0039] (2) Weigh 3.636 g of liquid metal Ga 64.6 In 20.3 Sn 15 The alloy is then added to the solution prepared in the previous step;

[0040] (3) The solution obtained in step (2) is mechanically stirred and ultrasonically vibrated for about 1 hour to make the liquid metal alloy uniformly dispersed in the solution;

[0041] (4) Pour the solution from the previous step into a mold made of polytetrafluoroethylene;

[0042] (5) Heat at 60°C in a drying oven for 4 hours to allow the solvent to evaporate completely, and then remove the polyurethane-liquid metal composite material from the mold.

[0043] Composite materials with different liquid metal contents only require adjusting the mass of liquid metal in step 2, while pure polyurethane materials do not contain any liquid metal material.

[0044] Figure 2 shows the appearance of the obtained polyurethane-12 wt.% liquid metal composite material in flat, bent, and stretched states. Figure 3 shows the microstructure of the material obtained by scanning electron microscopy, where Figures 3(a) and 3(b) show the surface morphology of pure polyurethane and polyurethane-12 wt.% liquid metal composite material. The results show that the porosity on the surface of polyurethane-12 wt.% liquid metal composite material is significantly reduced. Figures 3(c) and 3(d) show the microstructure of the cross-sections of the two samples. The results show that the molecular chain morphology inside the polyurethane-12 wt.% liquid metal material changes, the width increases, and the gaps between the chains are filled with liquid metal droplets. Figure 4(a) is a cross-sectional view of polyurethane obtained by scanning electron microscopy. In the figure, the four regions P1, P2, P3, and P4 are liquid metal droplets. The composition of the droplets was determined by the energy dispersive spectroscopy (EDS) function of scanning electron microscopy, as shown in Figure 4(b). The EDS results show that the elemental composition of the four regions is relatively consistent, and the composition of the metal droplets is determined to be Ga. 64.6 In 20.3 Sn 15 .

[0045] Example 2

[0046] In this embodiment, there are pure polyurethane materials and polyurethane-liquid metal composite materials, wherein the mass percentage of liquid metal in the polyurethane-liquid metal composite materials is 4 wt.%, 8 wt.%, and 12 wt.%, respectively.

[0047] The thermal conductivity of the four materials was measured using a NETZSCH LFA 467 laser thermal conductivity meter, and the results are shown in Figure 5. The results indicate that the thermal conductivity of the materials increases with increasing liquid metal content.

[0048] The elasto-thermal effect of pure polyurethane material and polyurethane-12 wt.% liquid metal material was determined using a testing platform consisting of an infrared camera and a tensile testing machine. The temperature change of the samples was recorded using an infrared thermal imager (T890-2 ECO, TestoSE & Co. KGaA) at a recording frequency of 0.9 s⁻¹. -1 The infrared emissivity was 0.91. Tensile tests were performed using an LD23.305 universal testing machine from Lisheng (Shanghai) Co., Ltd. The measured samples were cut from the samples prepared in Example 1, with dimensions approximately 40 × 20 × 0.02 mm. Figure 6(a) shows the results of tensile testing on polyurethane and polyurethane-12 wt.% liquid metal materials at 0.41 s⁻¹. -1 The maximum surface temperature change of the sample at an elongation of 3 under the loading stress rate is shown in Figure 6(b). Figure 6(b) shows the maximum surface temperature change of the two samples at an elongation of 3 at a loading stress rate of 0.41 s. -1The maximum temperature change during stress unloading was investigated. The results showed that the polyurethane-12 wt.% liquid metal material achieved a positive temperature change of approximately 8.7 °C during loading and a negative temperature change of approximately -5.5 °C during unloading, while the pure polyurethane material exhibited only temperature changes of approximately 6.8 °C and -4.5 °C during loading and unloading, respectively. This indicates that the polyurethane-12 wt.% liquid metal material possesses superior elasto-thermal properties.

[0049] Figure 7 shows the stress-strain curves of the polyurethane-12 wt.% liquid metal material under loading and unloading during the elastothermal effect measurement process in Figure 6. The results show that the material has good flexibility, requiring only about 5 MPa of stress to achieve an elongation of 3. This indicates that the material can achieve a large elastothermal effect with very little stress.

[0050] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for preparing a polyurethane-liquid metal composite elastothermal material, characterized in that, include: Step S1: Select liquid metal material A with a suitable melting point, shape memory polymer material B, and solution C of material B; Step S2: Add shape memory polymer material B to solution C and stir until completely dissolved to prepare a solution of material B; Step S3: Add a certain mass of material A to the solution of material B, stir and perform ultrasonic oscillation to make material A uniformly dispersed in the solution to obtain a mixed solution of material A and material B; Step S4: Pour the mixed solution obtained in step S3 evenly into a mold. Step S5: Place the mold containing the mixed solution into a drying oven and dry it at a high temperature of 50-80℃ for 4-8 hours to obtain a high thermal conductivity liquid metal-polyurethane composite thermoelastic material D composed of material A and material B. Material A is selected from GaIn or GaInSn alloys with low melting points, with a melting point temperature below 20℃. Material B is selected from different types of polyurethane polymers. Polyurethane refers to a class of polymer materials containing urethane characteristic units in the main chain, which are polymer compounds generated by the reaction of diisocyanate or polyisocyanate with compounds containing two or more hydroxyl groups. Its chemical formula is: (C 10 H8N2O·C6H 14 O3)n.

2. The method according to claim 1, characterized in that, In step S1, the dissolving solution C is selected from tetrahydrofuran solution and dimethylformamide solution, with a purity of 99.5% or higher.

3. The method according to claim 1, characterized in that, In step S2, polyurethane material B is added to solution C at a ratio of x g / 100 ml, where x is between 3 and 20.

4. The method according to claim 1, characterized in that, In step S3, the stirring method is mechanical stirring or magnetic stirring, and the stirring time is 30 to 60 minutes.

5. The method according to claim 1, characterized in that, Doping with liquid metal improves the thermal conductivity of polyurethane materials.

6. The method according to claim 1, characterized in that, Polyurethane-liquid metal composites exhibit significant temperature changes when subjected to tensile stress and when the stress is unloaded and returns to its initial state.

7. The application of the polyurethane-liquid metal composite thermoelastic material prepared by the method according to any one of claims 1-6 in the field of refrigeration.

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