CN115038201B - Preparation method and application of multifunctional flexible heating film - Google Patents

Abstract

The invention discloses a method for preparing a multifunctional flexible heating film and its application. The method includes the following steps: Step 1. Put the heating element into the polyurethane or PDMS precursor liquid from which air bubbles have been removed, and heat the heating element at a temperature of 50-100°C Curing for 2 to 12 hours, and encapsulating it into a polymer: step 2, disperse 0.2 to 2 g of hydrophobic nanoparticles in 0.5 to 10 g of a volatile solvent, spray the dispersion on the upper surface of the heating film, and obtain multifunctional after the solvent volatilizes Flexible heating membrane. In the present invention, after the flexible material and the heating element are combined to form a heating film, the method of spraying hydrophobic nanoparticles is used to obtain a superhydrophobic surface. Compared with other preparation methods, such as scraping coating, spin coating, deposition method, template method, and spray coating method It has the advantages of simple operation, low cost, and can be prepared in a large area. By introducing a super-hydrophobic surface, the heating film can obtain self-cleaning performance, so that it can be used well under various environmental conditions.

Description

A kind of preparation method and application of multifunctional flexible heating film

technical field

The invention relates to a method for preparing a flexible heating film, in particular to a method for preparing a self-adhesive and superhydrophobic heating film and its application.

Background technique

Resistance heating is the most widely used electric heating method. People produce electric heating film materials according to the needs of production and life. Compared with traditional electric heating elements, electric heating film has high heating efficiency, safety and reliability, changeable geometric shape, and wide application range. Wide and other advantages, so it has a wide range of applications in many fields such as industrial pipelines, vegetable greenhouses and housing insulation, platform heating, and road snow melting.

The electric heating film material is composed of a conductive heating layer and a substrate layer. Most of the heating films on the market are polyimide substrates. This kind of substrate cannot self-adhere to the surface of the material, so there is adhesive on one side of the heating film , this kind of glue cannot be reused many times, and it is easily polluted in the external environment, which affects the heat transfer and use of the heating film. Therefore, an electric heating film that can reversibly adhere and withstand various environments is needed.

Contents of the invention

In order to solve the problem that the existing heating film cannot be reversibly adhered and cannot adapt to various environments, the present invention provides a preparation method and application of a multifunctional flexible heating film with reversible adhesion, self-cleaning, anti-icing and corrosion resistance.

The purpose of the present invention is achieved through the following technical solutions:

A method for preparing a multifunctional flexible heating film, comprising the steps of:

Step 1. Put the heating element into the polyurethane or PDMS precursor liquid that removes air bubbles, cure at 50-100°C for 2-12 hours, and encapsulate it into the polymer, wherein:

The heating element is a resistance wire or a resistance sheet;

The material of the resistance wire is an iron-nickel-chromium alloy;

The polyurethane is formed by mixing castor oil, isophorone diisocyanate (IPDI), bis(2-hydroxyethyl) disulfide (HEDS) and catalyst (dibutyltin dilaurate), wherein: castor oil, The mass ratio of isophorone diisocyanate (IPDI) to bis(2-hydroxyethyl) disulfide (HEDS) is 7-13:4-6:1-2, and the amount of catalyst added is 0.2-1wt of polyurethane %;

In the PDMS precursor, the ratio of PDMS to curing agent is 10:0.25˜1.5.

Step 2. Disperse 0.2-2g of hydrophobic nanoparticles in 0.5-10g of a volatile solvent, spray the dispersion onto the upper surface of the heating film, and obtain a multifunctional heating film after the solvent evaporates, wherein:

The hydrophobic nanoparticles are multi-walled carbon nanotubes, hydrophobic fumed nano-silica or nano-titanium dioxide, etc.;

Described volatile solvent is dichloromethane, ethyl acetate, chloroform or ethanol etc.;

The concentration of the dispersion is 1 to 5 mg/mL;

The multifunctional heating film has excellent heating stability, and can be arbitrarily, reversibly, and repeatedly pasted on the surface of a special-shaped structure to be heated to heat it. At the same time, the exposed surface has excellent self-cleaning performance, which ensures that the heating film is not polluted.

The application of the multifunctional flexible heating film prepared by the above method in the special-shaped structure to be heated is as follows:

The multi-functional heating film is arbitrarily, reversibly, and repeatedly pasted on the surface of the special-shaped structure to be heated, and the heating element is used to heat the structure to be heated. According to the characteristics of the special-shaped body to be heated, the heating time and heating power are determined. At the same time, during the heating process, The heat is transferred to the back of the heating film, and the water cannot be frozen. Because the surface is a super-hydrophobic thin layer, it has self-cleaning properties, so that it can keep the surface clean in the external environment, and the liquid droplets cannot adhere to the surface when the heating film is not working. So as to achieve the effect of anti-icing.

Compared with the prior art, the present invention has the following advantages:

1. The adhesive layer of the electric heating film on the market cannot be reused in order to obtain greater adhesion. Once removed, not only will there be residue, but it will not be able to adhere to objects again. Both the polyurethane and PDMS used in the present invention are common flexible materials. By adjusting the content of the curing component, a greater adhesion performance can be obtained, and it can be reversibly adhered to various objects to meet the requirements of use. The adhesion after heating Basically unchanged; and there is no residue on the surface of the object after desorption, and the adhesion performance of the heating film substrate will not decrease, so it can be reused, so that the number of heating films used can be reduced in the actual use process, and the cost can be reduced.

2. In the present invention, after the flexible material and the heating element are combined to form a heating film, the method of spraying hydrophobic nanoparticles is used to obtain a super-hydrophobic surface. Compared with other preparation methods, such as scrape coating, spin coating, deposition method, and template method, The spraying method has the advantages of simple operation, low cost, and large-area preparation. By introducing a super-hydrophobic surface, the heating film can obtain self-cleaning performance, so that it can be used well under various environmental conditions.

3. Polyurethane and PDMS have good environmental stability. After being placed in an acid-base salt environment for 12 hours, the adhesion performance and the hydrophobicity of the super-hydrophobic coating will not change significantly. To protect, prevent it from being affected by acid-base salts.

Description of drawings

Figure 1 shows the adhesion properties of polyurethane and PDMS with different raw material ratios, (a) the adhesion strength of polyurethane prepared at different molar ratios (IPDI: castor oil: HEDS), (b) the adhesion of PDMS prepared with different curing agent contents strength;

Figure 2 is the polyurethane surface contact angle after spraying different carbon nanotube concentration solutions, a) 1mg/mL-135°, b) 2mg/mL-145°, c) 3mg/mL-153°, d) 4mg/mL-160 °;

Figure 3 is the front electron micrograph of the film under different MWCNT concentrations, a) 1mg/mL, b) 2mg/mL, c) 3mg/mL, d) 4mg/mL;

Figure 4 shows the surface contact angle of polyurethane after soaking in different pH solutions for 12 hours.

detailed description

The technical solution of the present invention will be further described below in conjunction with the accompanying drawings, but it is not limited thereto. Any modification or equivalent replacement of the technical solution of the present invention without departing from the spirit and scope of the technical solution of the present invention should be covered by the present invention. within the scope of protection.

Example 1:

This embodiment provides a method for preparing a multifunctional flexible heating film, the method comprising the following steps:

Step 1. Use iron-nickel-chromium alloy as the heating resistance wire, and bend the resistance wire into a grid shape.

Step 2. Select polyurethane as the substrate material of the heating film, put the resistance wire into the polyurethane that removes air bubbles, cure at 80°C for 2 hours, and encapsulate it into the polymer. In order for the heating element to be in the middle of the material, half of the polymer can be pre-cured, and the rest of the polymer can be added after placing the resistive element.

Polyurethane preparation process: (1) Mix castor oil, isophorone diisocyanate (IPDI), 1 to 2 g bis(2-hydroxyethyl) disulfide (HEDS) and catalyst dibutyltin dilaurate to control IPDI : castor oil: HEDS=2:0.74:1, 2:0.85:1, 2:0.95:1, 2:1:1, 2:1.1:1 (molar ratio), the add-on of catalyzer dibutyltin laurate is 0.5% by weight of polyurethane. The adhesion performance of polyurethane with different raw material ratios is shown in Figure 1(a). The material prepared by continuing to increase the castor oil content does not form, and there are residues on the surface after adhesion.

Step 3. Ultrasonic or stirring disperse the multi-walled carbon nanotubes in dichloromethane, and prepare dispersions with concentrations of 1 mg/mL, 2 mg/mL, 3 mg/mL, and 4 mg/mL. Spray the dispersion on the upper surface of the heating film, the solvent will swell the polyurethane, and after heating to volatilize the solvent, the nanoparticles can be firmly attached to the substrate to obtain a super-hydrophobic surface. Figure 2 shows the surface contact angle after spraying different concentrations of carbon nanotube solutions on the surface of polyurethane. It can be seen that as the concentration increases, the surface contact angle of polyurethane continues to increase, and finally becomes superhydrophobic. From the polyurethane SEM picture in Figure 3, it can be seen that the higher the concentration of the dispersion, the more serious the stacking of multi-walled carbon nanotubes on the surface, and the greater the surface roughness of the composite material obtained by spraying, which is consistent with the increasing trend of the contact angle .

The polyurethane surface has adhesive properties, and can be reversibly bonded to various substrates. After being removed, there is no residue on the surface and can be reused. The polyurethane adhesion strength can reach 0.45MPa; the super-hydrophobic thin layer makes the heating film have self-cleaning performance , so that it can maintain a clean surface in the external environment. After testing, it can be seen from Figure 4 that the superhydrophobic coating on the surface can still maintain superhydrophobicity after soaking in solutions of different pH (pH=1-13) for 12 hours. In addition, during the working process of the heating film, the heat is transferred to the back of the heating film, and the water cannot freeze, and because the surface is super-hydrophobic, the liquid droplets cannot adhere to the surface when the heating film is not working, so as to achieve the anti-icing effect.

After testing, the heating film can be heated to 80°C within 5 minutes under the action of a voltage of 20V. After heating, the heating film has a good bond with the substrate, and there will be no detachment, which basically meets the use requirements.

Example 2:

This embodiment provides a method for preparing a multifunctional flexible heating film, the method comprising the following steps:

Step 1. Use the finished resistor sheet as a heating element.

Step 2, select PDMS as the heating film substrate material. Put the resistance sheet into the PDMS precursor liquid that removes air bubbles, control the ratio of PDMS and curing agent to 10:0.25, 10:5, 10:0.75, 10:1, 10:1.25, cure at 50°C for 4 hours, and package it in in the polymer. In order for the heating element to be in the middle of the material, half of the polymer can be pre-cured, and the rest of the polymer can be added after placing the resistive element.

The adhesion performance of PDMS with different raw material ratios is shown in Figure 1. The material prepared by continuing to reduce the content of PDMS curing agent does not form, and there is residue on the surface after adhesion.

Step 3. Disperse the hydrophobic gas-phase nano-silica in ethanol by ultrasonic or stirring, prepare a dispersion solution with a concentration of 1mg/mL, 2mg/mL, 3mg/mL, and 4mg/mL, and spray the dispersion solution on the upper surface of the heating membrane.

The surface of PDMS has adhesive properties and can be reversibly bonded to various substrates. There is no residue on the surface after being removed, and it can be reused; the super-hydrophobic thin layer makes the heating film have self-cleaning properties, so that it can be kept clean in the external environment surface. In addition, during the working process of the heating film, the heat is transferred to the back of the heating film, and the water cannot freeze, and because the surface is super-hydrophobic, the liquid droplets cannot adhere to the surface when the heating film is not working, so as to achieve the anti-icing effect.

Claims (7)

1. A preparation method for a multifunctional flexible heating film, characterized in that said method comprises the steps: Step 1. Put the heating element into the polyurethane or PDMS precursor liquid that removes air bubbles, cure at 50-100°C for 2-12 hours, and encapsulate it into the polymer; the polyurethane is composed of castor oil, isophorone Diisocyanate, bis(2-hydroxyethyl) disulfide and catalyst are uniformly mixed, wherein: the mass ratio of castor oil, isophorone diisocyanate and bis(2-hydroxyethyl) disulfide is 7~ 13:4~6:1~2, the amount of catalyst added is 0.2~1 wt % of polyurethane; in the PDMS precursor, the ratio of PDMS to curing agent is 10:0.25~1.5; Step 2: Disperse 0.2-2 g of hydrophobic nanoparticles in 0.5-10 g of a volatile solvent, spray the dispersion onto the upper surface of the heating film, and obtain a multifunctional flexible heating film after the solvent evaporates. The volatile solvent is two Chloromethane, ethyl acetate, chloroform or ethanol. 2. The method for preparing a multifunctional flexible heating film according to claim 1, wherein the heating element is a resistance wire or a resistance sheet, and the material of the resistance wire is an iron-nickel-chromium alloy. 3. The preparation method of the multifunctional flexible heating film according to claim 1, characterized in that the catalyst is dibutyltin dilaurate. 4. The method for preparing a multifunctional flexible heating film according to claim 1, characterized in that the hydrophobic nanoparticles are multi-walled carbon nanotubes, hydrophobic fumed nano-silica or nano-titanium dioxide. 5. The method for preparing a multifunctional flexible heating film according to claim 1, characterized in that the concentration of the dispersion is 1-5 mg/mL. 6. An application of the multifunctional flexible heating film prepared by the method according to any one of claims 1-5 in special-shaped structures to be heated. 7. The application of the multifunctional flexible heating film according to claim 6 in the special-shaped structure to be heated is characterized in that the specific method of the application is as follows: Paste the multifunctional heating film on the surface of the special-shaped structure to be heated arbitrarily, reversibly, and multiple times, and use the heating element to heat the structure to be heated. During the heating process, the heat is transferred to the back of the heating film, and the water cannot freeze. The layer has self-cleaning properties, so that it can keep the surface clean in the external environment, and when the heating film is not working, the liquid droplets cannot adhere to the surface, so as to achieve the effect of anti-icing.

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