A method for preparing a flexible heating element with low heat loss

Abstract

This application discloses a low-heat-loss flexible heating element and its preparation method, belonging to the field of electrothermal material technology. It utilizes nanoscale heat-reflective oxides to obtain a high-infrared heat-reflective TPU film and graphene to obtain a graphene-high thermal conductivity TPU film. The addition of oxides with high infrared heat reflectivity to the high-infrared heat-reflective TPU film can prevent the heat generated by the electrothermal flexible heating element from dissipating outwards via thermal radiation, extending the service life of the external power source. The addition of graphene with high thermal conductivity to the graphene-high thermal conductivity TPU film allows the heat generated by the electrothermal flexible heating element to be transferred to the human body. The electrothermal flexible heating element is prepared by composite material with a protective fabric. Due to the high heat reflection effect of the outer layer and the high thermal conductivity and high far-infrared emissivity of the inner layer, the low-heat-loss flexible heating element can transfer heat to the human body, making people feel warm.

Description

Technical Field

[0001] This application belongs to the field of electric heating materials technology, and in particular relates to a flexible heating element with low heat loss and its preparation method. Background Technology

[0002] In recent years, with the rapid development of technology, people's needs for clothing have long since moved beyond simply covering the body. Especially in the cold winter, how to allow people to get the temperature they need without wearing bulky, heavy thermal clothing has become an important issue.

[0003] Active thermal clothing converts external energy into heat energy through an external heating device, reducing heat loss from the body and providing warmth. Currently, electrically heated thermal clothing has promising applications due to its controllable temperature and high heating efficiency. Although the effectiveness of electrically heated thermal clothing in alleviating heat loss in cold environments has been extensively studied, some problems still exist in practical use. The most critical issue is that the limited battery capacity cannot meet the heating needs for extended periods. Under current technology, the contradiction between battery capacity and battery size is difficult to resolve. Therefore, improving the heat conduction efficiency of the heating element and reducing heat loss from the heating element are particularly important.

[0004] Rare earth oxides such as lanthanum oxide, cerium oxide, and zirconium oxide have excellent photochemical properties, effectively reflecting infrared radiation and reducing heat loss.

[0005] Graphene is a material composed of carbon atoms arranged in sp... 2 Two-dimensional carbon materials with hexagonal honeycomb lattices composed of hybrid orbitals are among the best thermally conductive materials currently available. At the same time, graphene's unique band structure and high electron mobility allow it to rapidly emit far-infrared rays after absorbing external heat. Summary of the Invention

[0006] This application provides a low-heat-loss flexible heating element and its preparation method, which solves the problems of low heat conduction efficiency and rapid heat loss of electric heating elements.

[0007] This application provides a low-heat-loss flexible heating element and its preparation method, specifically including the following steps:

[0008] 1. Heat-reflective oxides are mixed with thermoplastic polyurethane elastomer rubber polymers and granulated to prepare high infrared heat-reflective thermoplastic polyurethane elastomer rubber particles; the high infrared heat-reflective thermoplastic polyurethane elastomer rubber particles are cut, dried, and film-formed to obtain a high infrared heat-reflective thermoplastic polyurethane elastomer rubber film.

[0009] 2. Graphene is mixed with thermoplastic polyurethane elastomer rubber polymer and granulated to prepare high thermal conductivity thermoplastic polyurethane elastomer rubber particles; the high thermal conductivity thermoplastic polyurethane elastomer rubber particles are cut, dried, and filmed to obtain graphene high thermal conductivity thermoplastic polyurethane elastomer rubber film.

[0010] 3. The high infrared heat reflectance thermoplastic polyurethane elastomer rubber film is hot-pressed with the composite layer material to obtain the outer composite layer; the graphene high thermal conductivity thermoplastic polyurethane elastomer rubber film is hot-pressed with the polyester lining to obtain the inner composite layer.

[0011] Fourth, the outer composite layer, the electro-flexible heating element, the copper mesh electrode, and the inner composite layer are placed on a hot press and hot-pressed together to obtain a flexible heating element with low heat loss.

[0012] In one embodiment,

[0013] The heat-reflective oxide mentioned in step one includes aluminum oxide and rare earth oxides, wherein the rare earth oxide is one of lanthanum oxide, cerium oxide, or zirconium oxide.

[0014] In one embodiment,

[0015] The mass ratio of the heat-reflective oxide in step one is 3-6% of the thermoplastic polyurethane elastomer rubber polymer, preferably 5% of the thermoplastic polyurethane elastomer rubber polymer.

[0016] In one embodiment,

[0017] The film-forming temperature in step one is 200℃.

[0018] In one embodiment,

[0019] The graphene mass ratio in step two is 2-4% of the thermoplastic polyurethane elastomer rubber polymer, preferably 3% of the thermoplastic polyurethane elastomer rubber polymer.

[0020] In one embodiment,

[0021] The film-forming temperature in step two is 200℃.

[0022] In one embodiment,

[0023] The composite layer material described in step three is either polyester lining or cotton lining, preferably polyester lining.

[0024] In one embodiment,

[0025] The temperature for hot-pressing the outer composite layer and the inner composite layer in step three is 150℃.

[0026] In one embodiment,

[0027] The hot-pressing composite process described in step four is as follows: temperature 140-170℃, pressure 0.8-1.0MPa, time 20-30s, preferably, temperature 160℃, pressure 0.8MPa, time 25s; the electro-flexible heating element is one of water-based graphene heating element or water-based carbon nanotube heating element, preferably, the electro-flexible heating element is water-based graphene heating element.

[0028] This application also provides a low-heat-loss flexible heating element, which is a low-heat-loss flexible heating element prepared according to a method for preparing a low-heat-loss flexible heating element according to any of the above embodiments.

[0029] This application provides a low-heat-loss flexible heating element and its preparation method. A high-infrared-thermal-reflective TPU film is obtained using nanoscale thermally reflective oxides, and a high-thermal-conductivity graphene TPU film is obtained using graphene. The high-infrared-thermal-reflective TPU film is the outer layer, in close contact with the external environment, while the high-thermal-conductivity graphene TPU film is the inner layer, in close contact with the human body. The addition of oxides with high infrared thermal reflectivity to the high-infrared-thermal-reflective TPU film can prevent the heat generated by the electro-flexible heating element from dissipating outwards via thermal radiation, extending the lifespan of the external power source. The addition of graphene with high thermal conductivity to the graphene TPU film allows the heat generated by the electro-flexible heating element to be quickly transferred to the human body via thermal conduction. The electro-flexible heating element is a composite material for the protective fabric, and due to the high thermal reflectivity of the outer layer, heat loss is reduced. Simultaneously, the high thermal conductivity and high far-infrared emissivity of the inner layer can conduct heat, providing warmth to the human body. Detailed Implementation

[0030] To make the technical problems, technical solutions, and beneficial effects to be solved by this application clearer, this application will be further described in detail. It should be understood that the specific embodiments described herein are only for explaining this application and are not intended to limit this application.

[0031] The heat-reflective oxides are aluminum oxide and lanthanum oxide; the electro-flexible heating element is either a water-based graphene heating element or a water-based carbon nanotube heating element; the composite layer material is either a polyester liner or a cotton liner.

[0032] TPU: Thermoplastic polyurethane elastomer rubber.

[0033] Example 1

[0034] A method for preparing a flexible heating element with low heat loss specifically includes the following steps:

[0035] I. Preparation of high infrared heat reflectance thermoplastic polyurethane elastomer (TPU) film: 60g of alumina, 40g of lanthanum oxide (heat reflectance oxide addition ratio of 5%) and 2kg of TPU polymer were uniformly mixed and high infrared heat reflectance TPU granules were prepared by front extrusion twin-screw extruder; the high infrared heat reflectance TPU granules were cut by granulator, dried and sealed; at 200℃, a high infrared heat reflectance TPU film with uniform thickness was obtained by casting film production.

[0036] II. Preparation of graphene-based high thermal conductivity TPU film: 30g of graphene (graphene addition ratio of 3%) was uniformly mixed with 1kg of TPU polymer and extruded using a twin-screw extruder to prepare high thermal conductivity TPU granules; the high thermal conductivity TPU granules were cut into particles using a granulator, dried, and sealed; and a graphene-based high thermal conductivity TPU film with uniform thickness was obtained by casting at 200℃.

[0037] III. Preparation of composite layer: The high infrared heat reflectance TPU film and polyester liner are hot-pressed together at 150°C to obtain the outer composite layer; the graphene high thermal conductivity TPU film and polyester liner are hot-pressed together at 150°C to obtain the inner composite layer.

[0038] IV. Preparation of a flexible heating element with low heat loss: The outer composite layer, the water-based graphene heating element, the copper mesh electrode, and the inner composite layer are placed on a hot press and hot-pressed at a temperature of 160℃, a pressure of 0.8MPa, and a time of 25s to obtain a flexible heating element with low heat loss.

[0039] Example 2

[0040] The difference between this embodiment and Embodiment 1 is that the mass of alumina is 30g, the mass of lanthanum oxide is 30g, the proportion of heat-reflective oxide added is 3%, the mass of graphene is 20g, and the proportion of graphene added is 2%. The other steps are the same.

[0041] Example 3

[0042] The difference between this embodiment and Embodiment 1 is that the mass of alumina is 80g, the mass of lanthanum oxide is 40g, the proportion of heat-reflective oxide added is 6%, the mass of graphene is 40g, and the proportion of graphene added is 4%. The other steps are the same.

[0043] Example 4

[0044] The difference between this embodiment and Embodiment 1 is that the mass of alumina is 48g, the mass of lanthanum oxide is 32g, and the proportion of heat-reflective oxide added is 4%, while the other steps are the same.

[0045] Example 5

[0046] The difference between this embodiment and Embodiment 1 is that the mass of alumina is 72g, the mass of lanthanum oxide is 48g, the proportion of heat-reflective oxide added is 6%, and the mass of graphene is 40g; the other steps are the same.

[0047] Example 6

[0048] The difference between this embodiment and Embodiment 1 is that the mass of graphene is 20g and the graphene addition ratio is 2%, while the other steps are the same.

[0049] Example 7

[0050] The difference between this embodiment and Embodiment 1 is that the mass of graphene is 40g and the graphene addition ratio is 4%, while the other steps are the same.

[0051] Example 8

[0052] The difference between this embodiment and Embodiment 1 is that the water-based graphene heating element in step four is replaced with a water-based carbon nanotube heating element; the other steps are the same.

[0053] Example 9

[0054] The difference between this embodiment and Embodiment 1 is that lanthanum oxide in step one is replaced with cerium oxide; the other steps are the same.

[0055] Example 10

[0056] The difference between this embodiment and Embodiment 1 is that lanthanum oxide in step four is replaced with zirconium oxide; the other steps are the same.

[0057] Example 11

[0058] The difference between this embodiment and Embodiment 1 is that the hot-pressing composite process in step four is: temperature 140℃, pressure 0.9MPa, time 20s, while the other steps are the same.

[0059] Example 12

[0060] The difference between this embodiment and Embodiment 1 is that the hot-pressing composite process in step four is: temperature 170℃, pressure 1.0MPa, time 30s, while the other steps are the same.

[0061] Example 13

[0062] The difference between this embodiment and Embodiment 1 is that the polyester lining in step three is replaced with a cotton lining; the other steps are the same.

[0063] Comparative Example 1

[0064] The difference between this comparative example and Example 1 is that alumina and lanthanum oxide were not added in step one, while the other steps were the same, resulting in a flexible heating sheet.

[0065] Comparative Example 2

[0066] The difference between this comparative example and Example 1 is that graphene was not added in step two, while the other steps are the same, resulting in a flexible heating sheet.

[0067] Comparative Example 3

[0068] The difference between this comparative example and Example 1 is that alumina and lanthanum oxide were not added in step one, and graphene was not added in step two. The other steps are the same, and a flexible heating sheet is obtained.

[0069] Comparative Example 4

[0070] The difference between this embodiment and Embodiment 1 is that the mass of alumina is 12g, the mass of lanthanum oxide is 8g, and the proportion of heat-reflective oxide added is 1%. The other steps are the same, and a flexible heating sheet is obtained.

[0071] Comparative Example 5

[0072] The difference between this embodiment and Embodiment 1 is that the mass of alumina is 96g, the mass of lanthanum oxide is 64g, the proportion of heat-reflective oxide added is 8%, and the mass of graphene is 40g. The other steps are the same, and a flexible heating sheet is obtained.

[0073] Comparative Example 6

[0074] The difference between this embodiment and Embodiment 1 is that the mass of graphene is 10g and the graphene addition ratio is 1%, while the other steps are the same.

[0075] Comparative Example 7

[0076] The difference between this embodiment and Embodiment 1 is that the mass of graphene is 60g and the graphene addition ratio is 6%, while the other steps are the same.

[0077] The heating elements prepared in the above embodiments and comparative examples were tested for their heating performance. Specifically, in the following test examples, the performance of the flexible heating elements was tested according to the following methods.

[0078] A. Testing of heating performance:

[0079] In this application, heating performance refers to the surface temperature (including inner and outer layer temperatures) of a heating element of the same size and power (5W) after being powered on for a period of time. During measurement, the heating element is placed in a constant temperature and humidity environment of 20±2℃ and 60±5%, suspended vertically, and powered on with a 5V DC regulated power supply for 2 minutes. The surface temperature of the heating element is then measured using an infrared thermometer. The distance between the infrared thermometer and the heating element is 20cm. To ensure the accuracy of the measurement data, a nine-square grid method is used to select temperature measurement points on the surface of the heating element, and the average temperature of the nine points is taken as the surface temperature of the heating element.

[0080] Experimental Example 1

[0081] This experiment tested the surface temperature of the heating elements prepared in Examples 1-3 and Comparative Examples 1-3. The test results are shown in Table 1 below.

[0082] Table 1

[0083]

[0084]

[0085] As can be seen from the above test results, the flexible heating sheets obtained in Examples 1-3 have a higher inner layer temperature than those in Comparative Examples 1-3, and a lower outer layer temperature than those in Comparative Examples 1-3. This indicates that the present invention utilizes the efficient heat reflection effect of heat-reflective oxides to prevent the heat generated by the heating sheet from dissipating to the external environment. At the same time, the addition of graphene in the inner layer improves the thermal conductivity and thermal radiation performance of the inner layer of the heating sheet, enabling the heat generated by the heating sheet to be quickly transferred inward, so that the human body can feel warmth.

[0086] In Comparative Examples 1 and 3, due to the lack of heat-reflective oxides in the outer layer, the heat generated by the heating element cannot be effectively prevented from dissipating to the external environment. Therefore, the outer layer temperature of the heating element is relatively high, and the heat loss of the heating element is relatively large.

[0087] In Comparative Examples 2 and 3, due to the lack of highly thermally conductive graphene in the inner layer, the heat generated by the heating element cannot be quickly transferred to the inner surface, resulting in a lower temperature in the inner layer of the heating element.

[0088] Experimental Example 2

[0089] This experiment investigated the effect of the amount of heat-reflective oxide added on the heating performance of the resulting flexible heating element. The test results are shown in Table 2 below.

[0090] Table 2

[0091]

[0092] The experimental data above show that when the amount of heat-reflective oxide added is controlled within the range of 4-6%, as in Examples 1, 4, and 5, the inner layer temperature of the resulting flexible heating sheet is higher, while the outer layer temperature is lower. However, when the amount of heat-reflective oxide added exceeds the above range, as in Comparative Examples 4 and 5, the inner layer temperature of the resulting flexible heating sheet is lower, while the outer layer temperature is higher. In Comparative Example 4, the amount of heat-reflective oxide added is relatively small, which prevents the film from forming a continuous heat-reflective network and effectively prevents heat loss to the external environment, resulting in a higher outer layer temperature. In Comparative Example 5, the amount of heat-reflective oxide added is too high, which makes it easy to agglomerate in TPU and unable to disperse evenly, resulting in too many defects in the formed heat-reflective network, which cannot effectively prevent heat loss to the external environment, resulting in a higher outer layer temperature.

[0093] Experimental Example 3

[0094] This experiment investigated the effect of graphene addition on the heating performance of the resulting flexible heating element. The test results are shown in Table 3 below.

[0095] Table 3

[0096]

[0097] The experimental data above show that when the amount of graphene added is controlled within the range of 2-4%, as in Examples 1, 6, and 7, the outer layer temperature of the resulting flexible heating sheet is lower, while the inner layer temperature is higher. However, when the amount of graphene added exceeds this range, as in Comparative Examples 6 and 7, the outer layer temperature of the resulting flexible heating sheet is higher, while the inner layer temperature is lower. In Comparative Example 6, the amount of graphene added is too small, failing to form a continuous heat-conducting network and hindering the rapid transfer of heat from the heating sheet to the inner surface, resulting in a lower inner surface temperature. In Comparative Example 7, the amount of graphene added is too large, failing to disperse evenly and easily agglomerating, resulting in numerous defects in the formed TPU film and hindering the rapid transfer of heat generated by the heating sheet, leading to a lower inner surface temperature.

[0098] A flexible heating element with low heat loss can be applied to functional clothing such as winter clothing to reduce heat loss from the human body and provide warmth.

[0099] This application provides a low-heat-loss flexible heating element and its preparation method, specifically including the following steps: mixing heat-reflective oxide with thermoplastic polyurethane elastomer rubber polymer, granulating to prepare high infrared heat-reflective thermoplastic polyurethane elastomer rubber particles; cutting and drying the high infrared heat-reflective thermoplastic polyurethane elastomer rubber particles, and forming a film to obtain a high infrared heat-reflective thermoplastic polyurethane elastomer rubber film; mixing graphene with thermoplastic polyurethane elastomer rubber polymer, granulating to prepare high thermal conductivity thermoplastic polyurethane elastomer rubber particles; cutting and drying the high thermal conductivity thermoplastic polyurethane elastomer rubber particles, and forming a film to obtain a graphene high thermal conductivity thermoplastic polyurethane elastomer rubber film; hot-pressing the high infrared heat-reflective thermoplastic polyurethane elastomer rubber film with a polyester liner to obtain an outer composite layer; hot-pressing the graphene high thermal conductivity thermoplastic polyurethane elastomer rubber film with a polyester liner to obtain an inner composite layer; and combining the outer composite layer, an electroluminescent flexible heating element, and a... A copper mesh electrode and the inner composite layer are hot-pressed together in a hot press to obtain a flexible heating sheet with low heat loss. This application utilizes nanoscale heat-reflective oxides to obtain a high-infrared heat-reflective TPU film and graphene to obtain a graphene-high thermal conductivity TPU film. The high-infrared heat-reflective TPU film is the outer layer, in close contact with the external environment, while the graphene-high thermal conductivity TPU film is the inner layer, in close contact with the human body. The addition of oxides with high infrared heat reflectivity to the high-infrared heat-reflective TPU film can prevent the heat generated by the electro-flexible heating sheet from dissipating outwards through thermal radiation, extending the service life of the external power source. The addition of graphene with high thermal conductivity to the graphene-high thermal conductivity TPU film can quickly transfer the heat generated by the electro-flexible heating sheet to the human body through thermal conduction. The electro-flexible heating sheet is a heating sheet prepared by composite with a protective fabric. Due to the high heat reflection effect of the outer layer, heat loss is reduced, while the high thermal conductivity and high far-infrared emissivity of the inner layer can conduct heat, making the human body feel warm.

[0100] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0101] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for preparing a low-heat-loss flexible heating element, characterized in that, Specifically, the following steps are included:

1. Heat-reflective oxides are mixed with thermoplastic polyurethane elastomer rubber polymers and granulated to prepare high infrared heat-reflective thermoplastic polyurethane elastomer rubber particles; the high infrared heat-reflective thermoplastic polyurethane elastomer rubber particles are cut, dried, and film-formed to obtain a high infrared heat-reflective thermoplastic polyurethane elastomer rubber film.

2. Graphene is mixed with thermoplastic polyurethane elastomer rubber polymer and granulated to prepare high thermal conductivity thermoplastic polyurethane elastomer rubber particles; the high thermal conductivity thermoplastic polyurethane elastomer rubber particles are cut, dried, and filmed to obtain graphene high thermal conductivity thermoplastic polyurethane elastomer rubber film.

3. The high infrared heat reflectance thermoplastic polyurethane elastomer rubber film is hot-pressed with the composite layer material to obtain the outer composite layer; the graphene high thermal conductivity thermoplastic polyurethane elastomer rubber film is hot-pressed with the polyester lining to obtain the inner composite layer. IV. The outer composite layer, the electro-flexible heating element, the copper mesh electrode, and the inner composite layer are placed on a hot press and hot-pressed together to obtain a flexible heating element with low heat loss. The heat-reflective oxide mentioned in step one comprises aluminum oxide and rare earth oxides, wherein the rare earth oxide is one of lanthanum oxide, cerium oxide, or zirconium oxide, and the mixing ratio of the aluminum oxide and rare earth oxides is 1-3:1-2; the mass ratio of the heat-reflective oxide is 3-6% of the thermoplastic polyurethane elastomer rubber polymer. The mass ratio of graphene in step two is 2-4 of that of the thermoplastic polyurethane elastomer rubber polymer.

2. The method for preparing a low-heat-loss flexible heating element according to claim 1, characterized in that, The film-forming temperature in step one is 200 ℃.

3. The method for preparing a low-heat-loss flexible heating element according to claim 1, characterized in that, The film-forming temperature in step two is 200 ℃.

4. The method for preparing a low-heat-loss flexible heating element according to claim 1, characterized in that, The composite layer material described in step three is either polyester lining or cotton lining.

5. The method for preparing a low-heat-loss flexible heating element according to claim 1, characterized in that, The temperature for hot-pressing the outer composite layer and the inner composite layer in step three is 150 ℃.

6. The method for preparing a low-heat-loss flexible heating element according to claim 1, characterized in that, The hot-pressing composite process described in step four is as follows: temperature 140-170 ℃, pressure 0.8-1.0 MPa, time 20-30 s; the electro-flexible heating element is one of water-based graphene heating element or water-based carbon nanotube heating element.

7. A flexible heating element with low heat loss, characterized in that, The low-heat-loss flexible heating element is prepared by the method of preparing a low-heat-loss flexible heating element according to any one of claims 1-6.

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