Carbon nanotube / polydimethylsiloxane electrothermal film and preparation method thereof

Abstract

The invention provides a carbon nanotube / polydimethylsiloxane electrothermal film and a preparation method thereof, and relates to the technical field of carbon nanotube composite materials, and the carbon nanotube / polydimethylsiloxane electrothermal film comprises a carbon nanotube / polydimethylsiloxane composite layer and a polydimethylsiloxane layer. The preparation method of the electrothermal film comprises the following steps: mixing polydimethylsiloxane with a curing agent, and pouring the mixture into a mold for primary curing to obtain a polydimethylsiloxane film; and laying the purified carbon nanotube film on the polydimethylsiloxane film, coating the purified carbon nanotube film with a polydimethylsiloxane solution, and adjusting the temperature for secondary curing to obtain the carbon nanotube / polydimethylsiloxane electrothermal film. The electrothermal film provided by the invention not only inherits the excellent electrothermal performance of the carbon nanotube film, but also improves the mechanical strength and flexibility of the film through the enhancement effect of the polydimethylsiloxane. The preparation method disclosed by the invention is simple, mild in condition and simple in process.

Description

Technical Field

[0001] The invention relates to the technical field of carbon nanotube composite materials, and in particular to a carbon nanotube / polydimethylsiloxane electric heating film and a preparation method thereof. Background Art

[0002] Flexible electronic products such as smart skin and smart watches are becoming the core enabling elements of the next generation of wearable technology. The currently widely used semiconductor or metal foil-based electronic devices have been unable to meet the growing demand for flexible electronic products due to their inherent rigidity, limited stretchability (maximum strain is usually less than 5%), and discomfort in use. Therefore, it is urgent to develop new materials with excellent mechanical and electrothermal properties.

[0003] Carbon nanotubes were once regarded as the star material in the field of high-performance wearable textiles due to their high corrosion resistance and excellent electrothermal properties. However, as the next generation of stretchable and wearable devices require more mechanical flexibility of materials, the limitations of carbon nanotube films are gradually becoming apparent. They are inherently lacking in stretchability and resistance to deformation. Moreover, the piezoresistive properties of carbon nanotube films change significantly after being strained, which has an adverse effect on their electrical conductivity. This effect weakens the mechanical and conductive properties of carbon nanotube films at the macroscopic stage to a certain extent, limiting their application in the field of wearable technology. Therefore, how to optimize the performance of carbon nanotube films and compound them with polymers to improve their mechanical, electrical and chemical properties is a major existing problem.

[0004] The carbon nanotube film in the prior art itself lacks stretchability and deformation resistance, and its electrical and thermal conductivity is often greatly reduced when compounded with other polymer materials. Summary of the invention

[0005] The present invention provides a carbon nanotube / polydimethylsiloxane electric heating film and a preparation method thereof, which solves the technical problem of poor stretchability and deformation resistance of the carbon nanotube film in the prior art.

[0006] In order to achieve the above-mentioned invention object, the technical solution provided by the present invention is as follows:

[0007] A carbon nanotube / polydimethylsiloxane electric heating film comprises a carbon nanotube / polydimethylsiloxane composite layer and a polydimethylsiloxane layer.

[0008] A method for preparing the carbon nanotube / polydimethylsiloxane electric heating film as described above comprises the following steps:

[0009] S1, preparing a carbon nanotube film by taking carbon nanotubes, immersing the carbon nanotube film in an acidic solution for purification, and drying to obtain a purified carbon nanotube film;

[0010] S2, mixing polydimethylsiloxane with a curing agent, and then pouring into a mold for primary curing to obtain a polydimethylsiloxane film;

[0011] S3, laying the purified carbon nanotube film on the polydimethylsiloxane film, coating the purified carbon nanotube film with a polydimethylsiloxane solution, adjusting the temperature for secondary curing, and obtaining a carbon nanotube / polydimethylsiloxane electric heating film.

[0012] Preferably, the method for preparing the carbon nanotube film in S1 is chemical vapor deposition.

[0013] Preferably, the carbon nanotube film in S1 has a thickness of 5-100 μm.

[0014] Preferably, the carbon nanotube in S1 is one of single-walled carbon nanotube, double-walled carbon nanotube and multi-walled carbon nanotube.

[0015] Preferably, the acidic solution in S1 is a hydrochloric acid solution with a volume concentration of 35-37%.

[0016] Preferably, the soaking time in S1 is 11-13 hours.

[0017] Preferably, the curing agent in S2 is Dow Corning 184 silicone rubber (sylgard-184).

[0018] Preferably, the mass ratio of the polydimethylsiloxane to the curing agent in S2 is (9-10):1.

[0019] Preferably, the temperature of the secondary curing in S3 is 80-120°C.

[0020] Polydimethylsiloxane resin has unique performance advantages, such as excellent heat resistance, cold resistance, chemical corrosion resistance and wear resistance. This material can maintain stable performance in an extremely wide temperature range (-60°C to 200°C) and is not easily corroded by environmental factors such as oxidation and ultraviolet radiation. Therefore, the present invention combines carbon nanotubes with polydimethylsiloxane to prepare an ultra-tough carbon nanotube / polydimethylsiloxane electric heating film, which can give full play to the advantages of both, while inheriting the excellent electric and thermal properties of the carbon nanotube film, improving the mechanical strength and wear resistance of the film, and maintaining stable performance in various harsh environments.

[0021] In the preparation method of the present invention, the carbon nanotube film and the polydimethylsiloxane film are directly contacted, and the carbon nanotube film layer is covered with a polydimethylsiloxane film solution. Due to the capillary force of the carbon nanotubes, the polydimethylsiloxane is fully infiltrated and penetrates into the interior of the carbon nanotubes. This close combination will effectively improve the stability and flexibility of the composite electric heating film material.

[0022] Compared with the prior art, the above technical solution has at least the following beneficial effects:

[0023] The electric heating film proposed by the present invention not only inherits the excellent electric and thermal properties of the carbon nanotube film, but also improves the mechanical strength and flexibility of the film through the reinforcing effect of polydimethylsiloxane. Polydimethylsiloxane is compounded with carbon nanotubes, wherein the carbon nanotubes have high conductivity and can generate high heat when current passes through. The compound use with polydimethylsiloxane (PDMS) can realize effective electric and thermal conversion, so that the electric heating film can quickly heat up after power is applied, thereby improving the heating efficiency. Polydimethylsiloxane itself has excellent flexibility and elasticity, which enables the electric heating film to adapt to various shapes and curved surfaces, increasing its application range. It is particularly suitable for flexible electronic products and bendable heating elements. PDMS, as an insulating material, effectively isolates the current from the external environment, prevents the risk of short circuit and electric shock, and improves the safety of the electric heating film. In addition, the preparation method of the present invention is simple, the conditions are mild, the process is simple, the equipment requirements are low, no harmful substances are added and produced, and it is conducive to industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 The internal morphology of the unpurified carbon nanotube film in Example 1;

[0025] Figure 2 The internal morphology of the purified carbon nanotube film in Example 1;

[0026] Figure 3 This is a SEM morphology image of the carbon nanotube / polydimethylsiloxane electric heating film in Example 1 under a low-power microscope;

[0027] Figure 4 This is a SEM morphology image of the carbon nanotube / polydimethylsiloxane electric heating film in Example 1 under a high-power microscope;

[0028] Figure 5-1 This is a deformation diagram of the carbon nanotube / polydimethylsiloxane electric heating film in Example 1 under 0% stretching;

[0029] Figure 5-2 This is a deformation diagram of the carbon nanotube / polydimethylsiloxane electric heating film in Example 1 when stretched by 10%;

[0030] Figure 5-3This is a deformation diagram of the carbon nanotube / polydimethylsiloxane electric heating film in Example 1 when stretched by 30%;

[0031] Figure 5-4 This is a deformation diagram of the carbon nanotube / polydimethylsiloxane electric heating film in Example 1 when stretched by 50%;

[0032] Figure 5-5 The time-temperature curves of the carbon nanotube / polydimethylsiloxane electrothermal film in Example 1 under the strains of 0%, 10%, 30% and 50%;

[0033] Figure 6-1 is a deformation diagram of the purified carbon nanotube film in the comparative example under 0% stretching;

[0034] Figure 6-2 is a deformation diagram of the purified carbon nanotube film in the comparative example under 5% stretching;

[0035] Figure 6-3 It is a time-temperature curve of the purified carbon nanotube film prepared in the comparative example under 0% and 5% strain. DETAILED DESCRIPTION

[0036] In order to make the purpose, technical solution and advantages of the embodiment of the present invention clearer, the technical solution of the embodiment of the present invention will be clearly and completely described below in conjunction with the drawings of the embodiment of the present invention. Obviously, the described embodiment is a part of the embodiment of the present invention, not all of the embodiments. Based on the described embodiment of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0037] Example 1

[0038] This embodiment is a carbon nanotube / polydimethylsiloxane electric heating film, which includes a carbon nanotube / polydimethylsiloxane composite layer and a polydimethylsiloxane layer.

[0039] A method for preparing the carbon nanotube / polydimethylsiloxane electric heating film as described above comprises the following steps:

[0040] S1. Take single-walled carbon nanotubes and use chemical vapor deposition to prepare carbon nanotube films. After collection, take out the samples and flatten them. The thickness of the carbon nanotube film is 20 μm. Soak the carbon nanotube film in a hydrochloric acid solution with a volume concentration of 37% for 12 hours for purification to dissolve catalyst impurities. If the acid solution remains clear, it means that the iron catalyst impurities have been effectively removed. If the acid solution is still turbid or has precipitates, the soaking time needs to be extended. Then, rinse the sample with deionized water and dry it in an oven at 120°C to remove all residual water. After drying, a purified carbon nanotube film is obtained;

[0041] The internal morphology of the unpurified carbon nanotube film is shown in Figure 1 As shown in the figure, it can be observed that there are many catalyst particles in its structure. These iron particles are caused by the catalyst residues used in the production process of the floating catalyst method. These catalyst particles not only affect the purity of the carbon nanotube film, but also have a certain impact on its performance.

[0042] The internal morphology of the purified carbon nanotube film is shown in Figure 2 As shown, it can be clearly seen that the presence of iron catalyst particles is almost difficult to observe, indicating that purification using hydrochloric acid is effective in improving the purity of the carbon nanotube film.

[0043] S2, polydimethylsiloxane and curing agent Dow Corning 184 silicone rubber (sylgard-184) were mixed in a mass ratio of 9.5:1, and then poured into a 50mm×10mm×10mm mold, and allowed to stand for 30 minutes to remove bubbles, and the mold was placed in an 80°C oven for 2 hours to cure, so that the polydimethylsiloxane solution was formed into a stable film structure to obtain a polydimethylsiloxane film;

[0044] S3, laying the purified carbon nanotube film on the polydimethylsiloxane film, and placing two copper wires, pouring polydimethylsiloxane solution on the purified carbon nanotube film, and ensuring that the carbon nanotube film is fully absorbed by the solution. Finally, the whole is placed in an oven again for secondary curing (80°C, 2 hours) to obtain a carbon nanotube / polydimethylsiloxane electric heating film.

[0045] The SEM morphology of the carbon nanotube / polydimethylsiloxane electric heating film in this embodiment under a low-power microscope is as follows Figure 3 As shown, it can be clearly seen that the carbon nanotubes are tightly attached to the polydimethylsiloxane matrix, indicating that there is good interfacial compatibility between the carbon nanotubes and polydimethylsiloxane.

[0046] The SEM morphology of the carbon nanotube / polydimethylsiloxane electric heating film in this embodiment under a high-power microscope is as follows Figure 4 As shown, it can be observed that the polydimethylsiloxane in the composite material penetrates into the carbon nanotubes because the capillary force of the carbon nanotubes allows the polydimethylsiloxane to be fully infiltrated. This close combination has a positive effect on the stability and flexibility of the composite electric heating film material.

[0047] Figure 5-1 , Figure 5-2 , Figure 5-3 , Figure 5-4 These are the deformation diagrams of the carbon nanotube / polydimethylsiloxane electric heating film of this embodiment under stretching of 0%, 10%, 30% and 50%, respectively. Figure 5-5The time-temperature curve of the carbon nanotube / polydimethylsiloxane electric heating film of this embodiment under 0%, 10%, 30% and 50% strain. It can be clearly seen that under different strains, the temperature of the composite material does not change much over time. Even when the composite material is stretched to 50% strain, its temperature only drops by 7%. This shows that during the stretching process, the electric heating performance of the composite material is well maintained and no significant changes occur.

[0048] Example 2

[0049] This embodiment is a carbon nanotube / polydimethylsiloxane electric heating film, which includes a carbon nanotube / polydimethylsiloxane composite layer and a polydimethylsiloxane layer.

[0050] A method for preparing the carbon nanotube / polydimethylsiloxane electric heating film as described above comprises the following steps:

[0051] S1, preparing a carbon nanotube film by chemical vapor deposition of double-walled carbon nanotubes, wherein the thickness of the carbon nanotube film is 100 μm, soaking the carbon nanotube film in a hydrochloric acid solution with a volume concentration of 35% for 11 hours, and performing purification treatment, and drying to obtain a purified carbon nanotube film;

[0052] S2, polydimethylsiloxane and curing agent Dow Corning 184 silicone rubber (sylgard-184) were mixed in a mass ratio of 9:1, and then poured into a 50mm×10mm×10mm mold, and allowed to stand for 30 minutes to remove bubbles, and the mold was placed in a 120°C oven for 1 hour to cure, so that the polydimethylsiloxane solution was formed into a stable film structure to obtain a polydimethylsiloxane film;

[0053] S3, laying the purified carbon nanotube film on the polydimethylsiloxane film, and placing two copper wires, pouring polydimethylsiloxane solution on the purified carbon nanotube film, and ensuring that the carbon nanotube film is fully absorbed by the solution. Finally, the whole is placed in an oven again for secondary curing (120°C, 1 hour) to obtain a carbon nanotube / polydimethylsiloxane electric heating film.

[0054] Example 3

[0055] This embodiment is a carbon nanotube / polydimethylsiloxane electric heating film, which includes a carbon nanotube / polydimethylsiloxane composite layer and a polydimethylsiloxane layer.

[0056] A method for preparing the carbon nanotube / polydimethylsiloxane electric heating film as described above comprises the following steps:

[0057] S1, taking multi-walled carbon nanotubes and preparing a carbon nanotube film by chemical vapor deposition, the thickness of the carbon nanotube film is 5 μm, soaking the carbon nanotube film in a hydrochloric acid solution with a volume concentration of 36% for 13 hours, purifying it, and drying it to obtain a purified carbon nanotube film;

[0058] S2, polydimethylsiloxane and curing agent Dow Corning 184 silicone rubber (sylgard-184) were mixed in a mass ratio of 10:1, and then poured into a 50mm×10mm×10mm mold, and allowed to stand for 30 minutes to remove bubbles therein, and the mold was placed in a 100°C oven for 2 hours to cure, so that the polydimethylsiloxane solution was formed into a stable film structure to obtain a polydimethylsiloxane film;

[0059] S3, laying the purified carbon nanotube film on the polydimethylsiloxane film, and placing two copper wires, pouring polydimethylsiloxane solution on the purified carbon nanotube film, and ensuring that the carbon nanotube film is fully absorbed by the solution. Finally, the whole is placed in an oven again for secondary curing (100°C, 2 hours) to obtain a carbon nanotube / polydimethylsiloxane electric heating film.

[0060] Comparative Example

[0061] This comparative example is a method for preparing a carbon nanotube electric heating film, comprising the following steps:

[0062] Single-walled carbon nanotubes were used to prepare carbon nanotube films by chemical vapor deposition. After collection, the samples were taken out and flattened. The thickness of the carbon nanotube film was 20 μm. The carbon nanotube film was immersed in a hydrochloric acid solution with a volume concentration of 37% for 12 hours for purification to dissolve catalyst impurities. If the acid solution remains clear, it means that the iron catalyst impurities have been effectively removed. If the acid solution is still turbid or has precipitates, the immersion time needs to be extended. Then, the sample was rinsed with deionized water and dried in an oven at 120°C to remove all residual water. After drying, a purified carbon nanotube film was obtained.

[0063] Figure 6-1 , Figure 6-2 The time-temperature curve of the purified carbon nanotube film prepared in this comparative example under tensile deformation is shown in Figures 1 and 2 respectively. Figure 6-3 As shown in the figure, it can be seen that the carbon nanotube film has broken under 5% deformation, and the electrothermal performance of the carbon nanotube film has decreased significantly under deformation.

[0064] It can be found that the carbon nanotube / polydimethylsiloxane electric heating film prepared by the present invention can maintain the excellent electric heating performance of carbon nanotubes, while giving the film material excellent flexibility, so that it has better application space in the production of wearable electric heating clothing.

[0065] The above are only specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. The protection scope of the present invention shall be based on the protection scope of the claims.

Claims

1. A carbon nanotube / polydimethylsiloxane electric heating film, characterized in that: It comprises a carbon nanotube / polydimethylsiloxane composite layer and a polydimethylsiloxane layer.

2. A method for preparing the carbon nanotube / polydimethylsiloxane electric heating film as claimed in claim 1, characterized in that: The following steps are involved: S1, preparing a carbon nanotube film by taking carbon nanotubes, immersing the carbon nanotube film in an acidic solution for purification, and drying to obtain a purified carbon nanotube film; S2, mixing polydimethylsiloxane with a curing agent, and then pouring into a mold for primary curing to obtain a polydimethylsiloxane film; S3, laying the purified carbon nanotube film on the polydimethylsiloxane film, coating the purified carbon nanotube film with a polydimethylsiloxane solution, adjusting the temperature for secondary curing, and obtaining a carbon nanotube / polydimethylsiloxane electric heating film.

3. The method for preparing the carbon nanotube / polydimethylsiloxane electric heating film according to claim 2, characterized in that: The method for preparing the carbon nanotube film in S1 is chemical vapor deposition.

4. The method for preparing the carbon nanotube / polydimethylsiloxane electric heating film according to claim 2, characterized in that: The thickness of the carbon nanotube film in S1 is 5-100 μm.

5. The method for preparing the carbon nanotube / polydimethylsiloxane electric heating film according to claim 2, characterized in that: The carbon nanotubes described in S1 are single-walled carbon nanotubes, double-walled carbon nanotubes, and multi-walled carbon nanotubes.

6. The method for preparing the carbon nanotube / polydimethylsiloxane electric heating film according to claim 2, characterized in that: The acidic solution in S1 is a hydrochloric acid solution with a volume concentration of 35-37%.

7. The method for preparing the carbon nanotube / polydimethylsiloxane electric heating film according to claim 6, characterized in that: The soaking time in S1 is 11-13 hours.

8. The method for preparing the carbon nanotube / polydimethylsiloxane electric heating film according to claim 6, characterized in that: The curing agent in S2 is Dow Corning 184 silicone rubber.

9. The method for preparing the carbon nanotube / polydimethylsiloxane electric heating film according to claim 2, characterized in that: The mass ratio of polydimethylsiloxane to curing agent in S2 is (9-10):

1.

10. The method for preparing the carbon nanotube / polydimethylsiloxane electric heating film according to claim 2, characterized in that: The temperature of the secondary curing in S3 is 80-120°C.

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