A flexible anti-icing composite membrane with force and damage sensing and its preparation method

Abstract

This invention discloses a flexible anti-icing composite membrane with force and damage sensing capabilities. Its preparation method includes the following steps: S1, mixing polydimethylsiloxane, a curing agent, and hollow silica particles, diluting with n-hexane, stirring until homogeneous, pouring the mixture into a mold, and heating to semi-cur it to obtain a PDMS thermal insulation underlayer; S2, adding perfluorodecyltrimethoxysilane, deionized water, carbon nanotubes, and carbon black particles to n-hexane, heating and stirring at 50-70°C for 1-2 hours, and then drying to obtain hydrophobic modified particles; S3, diluting the hydrophobic modified particles with n-hexane, then adding polydimethylsiloxane and a curing agent, stirring at room temperature for 20 minutes to obtain a dispersion of PDMS-coated modified particles; S4, uniformly spraying the dispersion obtained in step S3 onto the PDMS thermal insulation underlayer using a spray gun, heating and curing to obtain the flexible anti-icing composite membrane. This composite membrane exhibits superhydrophobicity, photothermal, and electrothermal properties, and is expected to achieve all-weather surface anti-icing in various environments.

Description

Technical Field

[0001] This invention relates to the field of anti-icing materials technology, and in particular to a flexible anti-icing composite membrane with force and damage sensing capabilities and its preparation method. Background Technology

[0002] Wind turbine blades, aircraft wings, and other equipment experience surface frost and icing when operating in low-temperature environments. This increases the overall weight of the equipment and, more importantly, prolonged icing can damage it, leading to failure. Currently, the most common de-icing methods include spraying chemical de-icing agents and mechanical de-icing. To save manpower and resources, much research has focused on surface anti-icing technologies to delay or even prevent surface icing. These technologies include superhydrophobic surfaces and photothermal surfaces. Superhydrophobic surfaces reduce or even prevent contact with water droplets through their unique water-repellent properties, thus delaying icing. However, because the surface energy increases at low temperatures, the water repellency decreases, the contact angle of water droplets decreases, and the contact area increases, leading to enhanced heat transfer and accelerated icing. Although many related superhydrophobic surfaces have been improved, ultimately they cannot completely prevent contact between the surface and water droplets, or even prevent the increase in contact area at low temperatures. They cannot completely block heat transfer and therefore cannot prevent surface icing; they can only delay icing to a certain extent. Therefore, they can only serve as an auxiliary anti-icing method. The advantage of photothermal surfaces lies in their ability to convert light into heat under sunlight, automatically heating the surface to a temperature above the freezing point of water and preventing icing. These surfaces perform well under sunlight but fail in the absence of light. Research has combined these two technologies to create composite functional surfaces that possess both photothermal and superhydrophobic properties. Some of these surfaces also exhibit electrothermal properties, enabling all-weather anti-icing while maximizing energy savings.

[0003] While surfaces with added electrothermal properties possess all-weather anti-icing capabilities, the heat generated by their photothermal or electrothermal properties is easily dissipated through the substrate, even accumulating near the substrate. This results in heat loss from the surface required for anti-icing while simultaneously causing ineffective heating of the substrate. Many similar surfaces, due to their photothermal and especially electrothermal effects, often raise the surface temperature to extremely high levels to improve anti-icing and de-icing efficiency. However, this also causes the dissipated heat to heat the substrate, resulting in unnecessary ineffective heating. For temperature-sensitive devices, this ineffective heating can lead to damage and other adverse consequences. Currently, there is no perfect solution to the problems of heat loss and ineffective heating. Another issue is that, regardless of whether it is a superhydrophobic surface or a photothermal / electrothermal surface, damage caused by external forces will weaken its anti-icing effect or even cause it to fail. Prolonged failure, if not detected in time, will lead to various adverse consequences. Therefore, real-time monitoring of external forces and damage to the surface is also essential, but current technologies lack good solutions for this type of surface. Summary of the Invention

[0004] To address the problems of heat loss and ineffective heating on the surface of anti-icing films in existing technologies, as well as the difficulty in monitoring film surface deformation and damage, this invention provides a flexible anti-icing composite film with force and damage sensing capabilities and its preparation method.

[0005] The flexible anti-icing composite membrane with force and damage sensing provided by this invention is prepared by the following method:

[0006] S1. Prepare the PDMS thermal insulation base layer;

[0007] Polydimethylsiloxane (PDMS), curing agent and hollow silica particles are mixed, then hexane is added for dilution, the mixture is stirred evenly, the mixture is poured into a mold, and heated to semi-cured to form a PDMS heat insulation base layer.

[0008] S2. Preparation of hydrophobic modified particles;

[0009] Perfluorodecyltrimethoxysilane, deionized water, carbon nanotubes and carbon black particles were added to n-hexane, heated and stirred at 50-70℃ for 1-2 hours, and then dried at 60℃ for 1 hour to obtain hydrophobic modified particles.

[0010] S3. Preparation of PDMS-coated modified particles:

[0011] The hydrophobic modified particles obtained in step S2 were diluted with n-hexane, and then polydimethylsiloxane and curing agent were added. The mixture was stirred at room temperature for 20 minutes to obtain a dispersion of PDMS-coated modified particles.

[0012] S4. Preparation of composite membrane;

[0013] The dispersion obtained in step S3 is uniformly sprayed onto the PDMS heat insulation substrate obtained in step S1 using a spray gun, and then heated and cured to obtain a composite film with photothermal, electrothermal and superhydrophobic properties, namely a flexible anti-icing composite film.

[0014] The hollow silica particles have a particle size of 1-3 μm, and the amount of hollow silica particles accounts for 8% of the mass of polydimethylsiloxane.

[0015] Preferably, in step S1, the heating temperature is 100°C and the curing time is several minutes, preferably 8 minutes.

[0016] Preferably, the carbon nanotubes have an inner diameter of 3-5 nm, an outer diameter of 8-15 nm, and a length of 3-12 μm; the carbon black particles have a particle size of 23-28 nm.

[0017] Preferably, in step S3, the amount of hydrophobic modified particles accounts for 16% of the mass of polydimethylsiloxane.

[0018] Preferably, in step S4, the spray gun nozzle diameter is 0.5mm, the spraying distance is 15cm, the spraying time is 2-3s, the curing temperature is 60℃, and the curing time is 4h.

[0019] Compared with the prior art, the advantages of the present invention are:

[0020] (1) To address the issues of heat loss and ineffective heating on the membrane surface, this invention, inspired by the skin's fat layer, prepares a flexible composite membrane with a layered structure. The bottom layer of this membrane is a PDMS layer containing artificially controlled bubbles. Gases have lower thermal conductivity than solids, and storing bubbles in the solid effectively reduces the overall thermal conductivity of the substrate, thus enhancing the insulation effect. The insulation effect is effectively enhanced by controlling the bubble distribution in the PDMS. Furthermore, bubble control requires no complex methods; it only requires utilizing the microbubbles naturally generated during the stirring process of PDMS. Different bubble distributions and sizes can be controlled at different temperatures and diluent contents, resulting in a composite membrane with excellent insulation performance. The bottom layer of the composite membrane provides excellent insulation, preventing heat generated by the top coating from being conducted to the substrate below. This not only conserves heat and prevents excessive heat loss but also prevents overheating of the substrate. Even when the temperature of the photothermal surface reaches a high temperature of 91.7℃, the back surface only maintains a temperature of around 55℃, demonstrating excellent insulation performance.

[0021] (2) To enhance the tensile mechanical strength of the membrane or coating and avoid conflicts between the membrane's mechanical strength and other functions, this invention is inspired by the layered structure of skin. The membrane is divided into upper and lower layers according to its function. The main functional layer for anti-icing is located in the upper layer, while the lower layer is an auxiliary functional layer that provides toughness and thermal insulation to the membrane. This layered structure is interconnected by PDMS to form a whole. The bonding strength between the two layers is excellent, maximizing the balance of various properties required for the anti-icing flexible membrane.

[0022] (3) Damage to superhydrophobic or photothermal surfaces can lead to functional failure and adverse consequences. To meet the needs of preventing and monitoring membrane surface damage, this invention utilizes conductive pathways formed by carbon nanotubes in the coating to monitor surface deformation and damage. When the surface is subjected to external pressure or damage, the flexible PDMS and its bubbles in the bottom insulating layer can enhance the deformation of the top coating. Under very small external forces, a certain degree of deformation can be generated, exhibiting high monitoring sensitivity, i.e., sensitive force and damage sensing capabilities. This composite membrane can effectively monitor the pressure, bending deformation, and damage applied to its surface, providing an effective means for the prevention and monitoring of surface damage and preventing various problems caused by membrane surface failure.

[0023] (4) The composite film of the present invention has excellent photothermal conversion and electrothermal properties. Under normal light intensity of 1 sun, the surface temperature of the film can be increased by approximately 31°C compared to the ambient temperature, exhibiting good photothermal conversion efficiency and effectively heating the surface under daylight conditions to prevent surface icing. Under a constant voltage of 15V, the surface temperature of the composite film can be increased by approximately 86°C compared to the ambient temperature, demonstrating excellent electrothermal performance.

[0024] In summary, the composite membrane exhibits superhydrophobicity, photothermal properties, and electrothermal properties, meaning it possesses excellent anti-icing performance and is expected to achieve all-weather surface anti-icing in various environments. Furthermore, the preparation method of this composite membrane is simple and easy; the integrated double-layer structure of the composite membrane is achieved through automatic connection of the PDMS in the upper and lower layers, eliminating the need for additional cumbersome steps; the top coating is applied using a spraying method, which is simpler than methods such as dip coating.

[0025] Other advantages, objectives and features of the present invention will become apparent in part from the following description, and in part from those skilled in the art through study and practice of the invention. Attached Figure Description

[0026] Figure 1 The images show the surface and cross-sectional morphology of the composite membrane in Example 1, where (a) is a surface view and (b) is a cross-sectional view.

[0027] Figure 2 This is a diagram showing the photothermal effect of the composite film in Example 1.

[0028] Figure 3 This is a temperature difference diagram of the front and back sides of the composite membrane under light and electricity conditions.

[0029] Figure 4 The figure shows the experimental results of the electrothermal effect of the composite film at 15V.

[0030] Figure 5 The results of the force and damage perception tests are shown in (a) and (b). (a) shows the current changes of the composite membrane under different pressure stimuli.

[0031] Figure 6 The results of the anti-icing test are shown in (a) for the glass surface film of Comparative Example 1, (b) for the aluminum plate surface film of Comparative Example 2, and (c) for the composite film of Example 1. Detailed Implementation

[0032] The preferred embodiments of the present invention will be described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0033] Example 1

[0034] A method for preparing a flexible anti-icing composite membrane with force and damage sensing:

[0035] S1. Preparation of the PDMS thermal insulation base layer: Mix 5g of PDMS, 0.5g of curing agent, and 0.4g of hollow silica particles, then dilute with 20ml of n-hexane. Stir the mixture at 3000r / min for 20min using a magnetic stirrer. Finally, pour the mixture into a mold (a circular steel ring with a diameter of 3cm and a thickness of 2mm); then heat at 100℃ for 8min to semi-cur it, obtaining the PDMS thermal insulation base layer.

[0036] S2. Preparation of hydrophobic modified particles: 1 ml of perfluorodecyltrimethoxysilane, 500 μl of deionized water, 400 mg of carbon nanotubes and 400 mg of carbon black particles were added to 20 ml of n-hexane. The mixture was heated and stirred at 60 °C for 2 h in an oil bath stirrer, and then dried at 60 °C for 1 h to obtain hydrophobic modified particles.

[0037] S3. Preparation of PDMS-coated modified particles: The modified particles obtained in step S2 are diluted with 20 ml of n-hexane, and then 5 g of PDMS and 0.5 g of curing agent are added. The mixture is stirred at room temperature (20-25℃) for 20 min to obtain a dispersion of PDMS-coated modified particles.

[0038] S4. Preparation of composite membrane: The particulate dispersion obtained in step S3 is uniformly sprayed onto the PDMS heat insulation substrate obtained in step S1 through a 0.5 mm diameter spray gun with a 0.3 MPa aperture. The double-layer membrane with the coating is cured at 60°C for 4 hours to obtain a composite membrane with photothermal, electrothermal and superhydrophobic properties, namely a flexible anti-icing composite membrane.

[0039] The curing agent was SYLGARD 184 silicone rubber curing agent. The same curing agent was used in subsequent comparative examples 1 and 2.

[0040] The surface and cross-sectional microstructure of the composite membrane are shown below. Figure 1 , where (a) is a surface view and (b) is a cross-sectional view.

[0041] Comparative Example 1

[0042] A method for preparing a single-layer membrane:

[0043] (1) Preparation of hydrophobic modified particles: 1 ml of perfluorodecyltrimethoxysilane, 500 μl of deionized water, 400 mg of carbon nanotubes and 400 mg of carbon black particles were added to 20 ml of n-hexane, heated and stirred at 60 °C for 2 h in an oil bath stirrer, and then dried at 60 °C for 1 h to obtain hydrophobic modified particles.

[0044] (2) Preparation of PDMS-coated modified particles: The modified particles obtained in step (1) were diluted with 20 ml of n-hexane, and then 5 g of PDMS and 0.5 g of curing agent were added. The mixture was stirred at room temperature (20-25℃) for 20 min to obtain a dispersion of PDMS-coated modified particles.

[0045] (3) Preparation of glass monolayer film: The particle dispersion obtained in step (2) is uniformly sprayed onto a 2mm thick glass plate through a 0.5mm diameter spray gun with a 0.3MPa aperture. The monolayer film is cured at 60℃ for 4h to obtain a monolayer film as a control group.

[0046] Comparative Example 2

[0047] A method for preparing a single-layer membrane:

[0048] (1) Preparation of hydrophobic modified particles: 1 ml of perfluorodecyltrimethoxysilane, 500 μl of deionized water, 400 mg of carbon nanotubes and 400 mg of carbon black particles were added to 20 ml of n-hexane, heated and stirred at 60 °C for 2 h in an oil bath stirrer, and then dried at 60 °C for 1 h to obtain hydrophobic modified particles.

[0049] (2) Preparation of PDMS-coated modified particles: The modified particles obtained in step (1) were diluted with 20 ml of n-hexane, and then 5 g of PDMS and 0.5 g of curing agent were added. The mixture was stirred at room temperature (20-25℃) for 20 min to obtain a dispersion of PDMS-coated modified particles.

[0050] (3) Preparation of aluminum plate single-layer film: The particle dispersion obtained in step (2) is uniformly sprayed onto a 2mm thick aluminum plate through a 0.5mm diameter spray gun with a 0.3Mpa aperture. The single-layer film is cured at 60℃ for 4h to obtain a single-layer film as a control group.

[0051] The bilayer composite films and single-layer films prepared in Example 1 and Comparative Examples 1 and 2 were subjected to photothermal conversion tests, electrothermal tests, force (damage) sensing tests, and anti-icing tests. The test procedures are as follows:

[0052] (1) Photothermal conversion experiment:

[0053] The bilayer composite films and single-layer films prepared in Example 1, Comparative Examples 1 and 2 were placed on a constant-temperature physicochemical plate and irradiated with light intensity of 1 sun for 300 seconds. The final temperature rise of each sample surface was recorded using an infrared thermal imager. The experimental results are shown in [Figure number missing]. Figure 2 It can be seen that, compared with the single-layer film on the aluminum plate and glass substrate, the double-layer film with PDMS heat-insulating substrate has a more significant surface temperature rise, with a temperature difference of up to 31°C compared to the surrounding environment. In contrast, the temperature difference of the single-layer film on the glass plate is 16.4°C, and the temperature difference of the single-layer film on the aluminum plate is only 12.8°C. Simultaneously, the temperature difference between the front and back sides of the composite film in Example 1 was measured, and the results are shown below. Figure 3 When the membrane surface temperature reaches 57.7℃, the temperature difference between the front and back sides reaches 20.1℃; when the surface temperature reaches 91.7℃, the temperature difference reaches 36℃. These results demonstrate the excellent thermal insulation performance of the PDMS insulation substrate.

[0054] (2) Electrothermal test:

[0055] The composite film prepared in Example 1 was used as the experimental object. The positive and negative terminals of a power supply were clamped to both ends of the composite film, and a constant voltage of 15V was applied. The temperature of the sample surface at different times was recorded using an infrared thermal imager. The experimental results are shown below. Figure 4 The experimental results show that the surface temperature of the composite film can rise by about 86°C within 300 seconds, exhibiting excellent electrothermal effect.

[0056] (3) Force and damage perception test:

[0057] The composite membrane prepared in Example 1 was used as the experimental subject. The membrane surface was connected to the positive and negative electrodes of an electrochemical workstation via copper wires, and a constant voltage of approximately 10V was applied. After the surface current stabilized, different external pressures were applied to the surface, and the changes in surface current were observed and recorded. The coating was scratched with a sharp object, and the changes in surface current were observed. The results are shown in […]. Figure 5 (a) shows the current changes of the composite membrane under different pressure stimuli; (b) shows the current changes after damage to the composite membrane surface. The results show that the composite membrane surface can effectively monitor external forces and damage, exhibiting high sensitivity.

[0058] (4) Anti-icing test:

[0059] The bilayer composite films and single-layer films prepared in Example 1, Comparative Examples 1 and 2 were placed on a semiconductor cold stage. Ten microliters of water were dropped onto the surface of each of the three samples. The cold stage temperature was then lowered to -15°C. A surface water droplet icing experiment was conducted at -15°C and 60% relative humidity. The icing process was captured by a high-speed camera, and the icing time was recorded. The experimental results are shown below. Figure 6 (a) shows the anti-icing test results of the glass surface film in Comparative Example 1; (b) shows the anti-icing test results of the aluminum plate surface film in Comparative Example 2; and (c) shows the anti-icing test results of the composite film surface film in Example 1. The results show that the freezing time of water droplets on the glass and aluminum plate surfaces is 45s-215s, while the freezing time on the composite film surface can be extended to 1980s, exhibiting excellent anti-icing performance.

[0060] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A method for preparing a flexible anti-icing composite membrane with force and damage sensing capabilities, characterized in that, Includes the following steps: S1. Prepare the PDMS thermal insulation base layer; Polydimethylsiloxane, curing agent and hollow silica particles are mixed, then hexane is added for dilution, the mixture is stirred evenly, the mixture is poured into a mold, and heated to semi-cured to form PDMS heat insulation bottom layer; S2. Preparation of hydrophobic modified particles; Perfluorodecyltrimethoxysilane, deionized water, carbon nanotubes and carbon black particles were added to n-hexane, heated and stirred at 50-70℃ for 1-2 hours, and then dried to obtain hydrophobic modified particles. S3. Preparation of PDMS-coated modified particles: The hydrophobic modified particles obtained in step S2 were diluted with n-hexane, and then polydimethylsiloxane and curing agent were added. The mixture was stirred at room temperature for 20 min to obtain a dispersion of PDMS-coated modified particles. S4. Preparation of composite membrane; The dispersion obtained in step S3 is uniformly sprayed onto the PDMS heat insulation substrate obtained in step S1 using a spray gun, and then heated and cured to obtain a composite film with photothermal, electrothermal and superhydrophobic properties, namely a flexible anti-icing composite film.

2. The method for preparing the flexible anti-icing composite membrane with force and damage sensing as described in claim 1, characterized in that, The hollow silica particles have a particle size of 1-3 μm, and the amount of hollow silica particles accounts for 8% of the mass of polydimethylsiloxane.

3. The method for preparing the flexible anti-icing composite membrane with force and damage sensing as described in claim 1, characterized in that, In step S1, the heating temperature is 100℃ and the curing time is 8 minutes.

4. The method for preparing the flexible anti-icing composite membrane with force and damage sensing as described in claim 1, characterized in that, In step S2, the drying temperature is 60℃.

5. The method for preparing the flexible anti-icing composite membrane with force and damage sensing as described in claim 1, characterized in that, Carbon nanotubes have an inner diameter of 3-5 nm, an outer diameter of 8-15 nm, and a length of 3-12 μm; carbon black particles have a particle size of 23-28 nm.

6. The method for preparing the flexible anti-icing composite membrane with force and damage sensing as described in claim 1, characterized in that, In step S3, the amount of hydrophobic modified particles accounts for 16% of the mass of polydimethylsiloxane.

7. The method for preparing the flexible anti-icing composite membrane with force and damage sensing as described in claim 1, characterized in that, In step S4, the spray gun nozzle diameter is 0.5 mm, the spraying distance is 15 cm, the spraying time is 2-3 s, the curing temperature is 60℃, and the curing time is 4 h.

8. A flexible anti-icing composite membrane with force and damage sensing capabilities, characterized in that, It is prepared by the method described in any one of claims 1-7.

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