Preparation method of flexible film for dynamically adjusting infrared emissivity

Abstract

The invention relates to a preparation method of a flexible film for dynamically adjusting infrared emissivity, and belongs to the technical field of dynamic adjustment of infrared radiation characteristics. The preparation method comprises the following operation steps: (1) uniformly mixing the basic component A and the reaction component B at room temperature; (2) defoaming the mixed solution, and pouring the mixed solution on a flat plate for self-leveling; (3) curing to obtain a polymer film; (4) stretching and fixing the polymer film, and sequentially plating an adhesion layer film and a functional layer film on the surface of the polymer film by using an electron beam evaporation coating technology; the functional layer film is made of a low-emissivity material; and (5) reducing the strain spontaneous release polymer film to an initial length to obtain the variable-emissivity flexible film with a wrinkle structure on the surface. The size and morphology change of the wrinkle structure changes the propagation path of the electromagnetic wave, and changes the area ratio of the high-emissivity material to the low-emissivity material, thereby changing the surface emissivity of the material. The infrared radiation temperature adjustment amplitude of the flexible film is 40 DEG C, and the flexible film has a good dynamic infrared camouflage function.

Description

Technical Field

[0001] The invention belongs to the technical field of dynamic regulation of infrared radiation characteristics, and in particular relates to a method for preparing a flexible film for dynamically regulating infrared emissivity. Background Art

[0002] Radiation is an important mode of heat transfer. All objects in nature will radiate energy on their surfaces when they are above absolute zero. In real life, the temperature of objects is around 300 K. Through Wien's displacement law, it can be calculated that their spontaneous radiation is mainly concentrated in the infrared band. The regulation of infrared radiation is crucial in the fields of thermal management, energy conversion, information encryption and infrared camouflage. In the field of infrared camouflage, with the rapid development of thermal infrared reconnaissance and detection technology, the survival of military targets is seriously threatened. In military detection, the response band of infrared detectors is usually within the infrared atmospheric window (0.76~2.5 μ m, 3~5 μ m and 8~14 μ m). When infrared radiation propagates in the atmosphere, only the infrared radiation within the atmospheric window can penetrate the atmosphere, while the infrared radiation outside the atmospheric window is difficult to penetrate the atmosphere. This is because components such as water vapor, carbon dioxide and ozone in the atmosphere absorb infrared radiation in certain bands, and various particles in the atmosphere also scatter infrared radiation. Therefore, in the infrared detection system, the detection band of the detector must be within the infrared atmospheric window. The temperature of military targets is usually around 300 K, and their spontaneous radiation is mainly concentrated in the range of 2.5 to 25 μ m band, so the infrared atmospheric windows commonly used in the military are mainly 3 to 5 μ m and 8~14 μ m two bands.

[0003] Infrared detection technology identifies targets by detecting the infrared radiation energy of objects. According to the Stefan-Boltzmann law, the infrared radiation energy of an object is related to its temperature and emissivity. The method of reducing the radiation energy by controlling the temperature requires additional heat insulation and heat dissipation devices near the heat source of the target object, while the method of covering the target surface with a film of specific emissivity is more convenient.

[0004] The existing methods of regulating the emissivity for infrared camouflage are mainly to coat the surface of the object with a low emissivity film or to regulate the infrared spectrum of a specific band by designing a specific structure on the surface of the material. However, both are static and cannot meet the needs of dynamic infrared camouflage. In order to adapt to the changes in the infrared radiation energy of the background and the target itself, it is necessary to design dynamic variable emissivity materials. Since flexible and mechanically deformable materials can easily achieve precise adjustment of structural parameters and radiation characteristics through mechanical stretching, dynamic regulation of infrared emissivity through such materials has broad application prospects. Summary of the invention

[0005] In order to achieve the regulation of infrared radiation temperature of a film under mechanical strain, and further realize dynamic infrared camouflage, the present invention provides a method for preparing a flexible film for dynamically adjusting infrared emissivity.

[0006] The steps for preparing a flexible film for dynamically adjusting infrared emissivity are as follows: (1) mixing a base component A of a stretchable polymer and a reaction component B at a mass ratio of 1:1 to 15:1 at room temperature to obtain a mixed solution; The base component A and the reactive component B are polydimethylsiloxane prepolymer and a crosslinking agent, or a basic silicone resin and a platinum catalyst; (2) degassing the mixed solution under vacuum conditions, and then pouring it onto a flat plate with a smooth surface for self-leveling to obtain a polymer film to be cured with a thickness of 1.0 to 2.0 mm, i.e., a stretchable flexible substrate in a state to be cured; (3) curing the stretchable flexible substrate at a stable temperature and tearing it off from the flat plate to obtain a polymer film; (4) cutting the polymer film into a required size, and fixing the two ends of the cut polymer film on a pre-stretching frame; using electron beam evaporation coating technology to sequentially coat an adhesion layer film and a functional film film on the surface of the polymer film; the material of the adhesion layer film is one of nickel (Ni), titanium (Ti), and chromium (Cr); the material of the functional layer film is one of gold (Au), silver (Ag), and aluminum (Al); (5) removing the fixture on one side of the polymer film coated with the double-layer film, so that the strain of the polymer film is spontaneously released and restored to its initial length, thereby obtaining a flexible film with a variable emissivity and a wrinkled surface structure; The variable emissivity flexible film with a pleated structure has a dynamic adjustment range of infrared emissivity of 0.03 to 0.64 under 80% uniaxial tensile strain, and an infrared radiation temperature adjustment range of 40°C.

[0007] The further technical solution is as follows: In step (1), the cross-linking agent is silicone oil with a silicon hydride (Si—H) functional group.

[0008] In step (1), the base silicone resin is a platinum-catalyzed silicone resin.

[0009] In step (1), the base component A and the reaction component B are stirred at a speed of 150 to 300 rpm / min for 3 to 8 min.

[0010] In step (2), the degassing treatment time is 3 to 10 minutes.

[0011] In step (3), the stabilization temperature is 25 to 125°C, and the curing time is 0.5 to 48 hours. In step (4), the purity of the target material of the adhesion layer film and the target material of the functional layer film are both 99.995%, and the evaporation coating rate is 2 Å / s.

[0012] In step (5), the pleated structure is composed of parallel shrinkage stripes, and the shrinkage stripes are perpendicular to the stretching direction on the pre-stretching frame.

[0013] The beneficial technical effects of the present invention are embodied in the following aspects: 1. The infrared emissivity of the flexible film with variable emissivity prepared by the present invention can be adjusted dynamically in the range of 0.03 to 0.64 under the action of 80% uniaxial tensile strain, and the infrared radiation temperature can be adjusted greatly by 40°C, which has good dynamic infrared camouflage ability. The present invention prepares a flexible pleated structure with stretched variable emissivity by evaporating a double-layer film on the surface of a pre-stretched flexible polymer film and releasing the strain. The double-layer film structure consists of a lower adhesion layer and a top functional layer. The material of the adhesion layer is at least one of nickel (Ni), titanium (Ti), and chromium (Cr), which can improve the bonding force between the metal film and the polymer substrate; the material of the functional layer is at least one of gold (Au), silver (Ag), and aluminum (Al), which has low emissivity characteristics. The functional layer is tightly attached to the flexible substrate through the adhesion layer, which effectively prevents the structure from falling off and increases the service life of the material. The surface of the structure with and without the adhesion layer was wiped 4 times with a sponge brush dipped in alcohol. The surface of the structure with the adhesion layer was still intact, while the surface of the structure without the adhesion layer was 80% damaged.

[0014] 2. The preparation process of the present invention is non-toxic and harmless throughout the process, the required raw materials are simple and easy to obtain, and the preparation process is relatively simple. Compared with other materials that use surface microstructures to dynamically adjust the emissivity, the surface wrinkle structure of the flexible film prepared by the present invention does not require a photolithography process, and the wrinkle structure can be obtained by utilizing the spontaneous instability phenomenon caused by the mismatch between the Young's modulus of the double-layer film and the flexible substrate. The size and morphology of the surface wrinkle structure of the flexible film prepared by the present invention will change under the action of stretching, changing the propagation path of the electromagnetic wave in the structure, and at the same time changing the area ratio of the high emissivity material (polymer film prepared in step 3) and the low emissivity material (functional layer film prepared in step 5) on the surface of the material, thereby changing the surface emissivity of the material. The preparation process of the variable emissivity film in the present invention is relatively simple, and the surface infrared radiation energy can be increased or decreased by stretching or shrinking the material, which has good application prospects in the fields of infrared camouflage, thermal management and information encryption. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1A cross-sectional view of the corrugated structure of the flexible film with variable emissivity having a corrugated structure according to the present invention; Figure 2 This is a graph of the infrared integrated emissivity of the mechanically stretched dynamically regulated infrared emissivity wrinkled structure prepared in Example 1 under different uniaxial tensile strains; Figure 3 This is a graph of the infrared integrated emissivity of the mechanically stretched dynamically regulated infrared emissivity wrinkled structure prepared in Example 2 under different uniaxial tensile strains; Figure 4 This is a graph of the infrared integrated emissivity of the mechanically stretched dynamically regulated infrared emissivity wrinkled structure prepared in Example 3 under different uniaxial tensile strains; Figure 5 This is a morphology image of the upper surface of the flexible film with variable emissivity and having a wrinkled structure prepared according to the method of the present invention under a scanning electron microscope; Figure 1 Sequence number: functional layer film 1, adhesion layer film 2, polymer film 3. DETAILED DESCRIPTION

[0016] The present invention will be further described below by way of embodiments in conjunction with the accompanying drawings.

[0017] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0018] Dow Corning 184 silicone rubber produced by Dow Corning Company of the United States was used; Ecoflex silicone produced by Smooth-On Company of the United States was used; the electron beam evaporation coating equipment of KJ Lesker Company of the United States was used for coating the polymer surface; and the electric stirrer of Shanghai Shangpu Instrument Equipment Co., Ltd. was used for uniform mixing of the polymer. Example 1

[0019] The steps for preparing a flexible film for dynamically adjusting infrared emissivity are as follows: (1) Weigh 10 g of platinum-catalyzed silica gel resin (Ecoflex™ 00-30) (base component A) and 10 g of platinum catalyst (reaction component B) in a mass ratio of 1:1, stir at room temperature and 150 rpm / min for 3 min to obtain a uniform mixed solution.

[0020] (2) The uniform mixed solution was placed in a vacuum chamber for degassing for 5 min. The mixed solution was then poured onto a smooth polytetrafluoroethylene flat plate with a size of 12 cm × 12 cm for self-leveling to obtain a polymer film to be cured with a thickness of 1.5 mm, i.e., a stretchable flexible substrate to be cured.

[0021] (3) The stretchable flexible substrate in the uncured state was cured at room temperature of 25°C for 4 h, and the film was torn off the polytetrafluoroethylene plate to obtain a polymer film of platinum-catalyzed silicone (Ecoflex™ 00-30) with a thickness of about 1.5 mm, see Figure 1 .

[0022] (4) A polymer film of platinum-catalyzed silica gel (Ecoflex™ 00-30) was cut into a size of 4.0 cm × 6.0 cm and fixed on a pre-stretching frame of 6.0 cm × 7.2 cm, so that the tensile strain of the polymer film was 20%; an adhesion layer film 2 (nickel film) of nickel (Ni) material with a thickness of 50 nm and a functional layer film 1 (gold film) of gold (Au) material with a thickness of 50 nm were sequentially evaporated on the surface of the polymer film using electron beam evaporation coating technology. The target material purity of the adhesion layer film (nickel film) and the functional layer film (gold film) were both 99.995%, and the evaporation coating rate was 2 Å / s; a polymer film coated with a double-layer film was obtained.

[0023] (5) The clamp on one side of the polymer film coated with the double-layer membrane is removed, so that the strain of the polymer film is spontaneously released and restored to its initial length, thereby obtaining a flexible film with a variable emissivity and a wrinkled surface.

[0024] See also Figure 1 and Figure 5 The wrinkle structure is composed of parallel contraction-like stripes, and the contraction-like stripes are perpendicular to the stretching direction on the pre-stretching frame. See also Figure 2 The flexible film with variable emissivity and wrinkled structure prepared in Example 1 was tested by Fourier transform infrared spectrometer (BRUKER VERTEX80) under different uniaxial tensile strains of 2.5-20.0 μ Infrared integrated emissivity in the m-band. During spectrum measurement, the center of the flexible film is aligned with the measuring hole above the integrating sphere, and the stripe direction of the fold structure on the surface of the flexible film is parallel to the vertical direction of the surface where the sample is located on the upper side of the integrating sphere. The fold structure of the flexible film is between 2.5 and 20.0 μ The infrared emissivity in the m-band gradually increases with the increase of strain. When the uniaxial tensile strain is 80%, the infrared integrated emissivity of the pleated structure of the flexible film can be adjusted in the range of 0.03~0.64, indicating that the designed pleated structure of the flexible film has good dynamic regulation ability of infrared emissivity.

[0025] The flexible film with variable emissivity prepared in Example 1 was fixed at both ends on a uniaxial stretching electric control console, and the bottom was heated with a power of 16.54 W / cm 2 The heating sheet was in close contact with the flexible film, and infrared images of the flexible film with variable emissivity under different tensile strains were taken using an infrared thermal imager (TiX660, Fluke). When the uniaxial tensile strain was 0%, the infrared radiation temperature of the flexible film with variable emissivity prepared in Example 1 was 57.0°C, and when the uniaxial tensile strain was 112%, the infrared radiation temperature of the flexible film with variable emissivity became 98.8°C, and the infrared radiation temperature was adjusted by 41.8°C. Example 2

[0026] The steps for preparing a flexible film for dynamically adjusting infrared emissivity are as follows: (1) Weigh 10 g of platinum-catalyzed silica gel resin (Ecoflex™ 00-30) (base component A) and 10 g of platinum catalyst (reaction component B) in a mass ratio of 1:1, stir at room temperature and 150 rpm / min for 3 min to obtain a uniform mixed solution.

[0027] (2) The uniform mixed solution was placed in a vacuum chamber for degassing for 5 min. The mixed solution was then poured onto a smooth polytetrafluoroethylene flat plate with a size of 12 cm × 12 cm for self-leveling to obtain a polymer film to be cured with a thickness of 1.5 mm, i.e., a stretchable flexible substrate to be cured.

[0028] (3) The stretchable flexible substrate in the uncured state was cured at room temperature of 25°C for 4 h, and the film was torn off the polytetrafluoroethylene flat plate to obtain a polymer film of platinum-catalyzed silicone (Ecoflex™ 00-30) with a thickness of about 1.5 mm.

[0029] (4) A polymer film of platinum-catalyzed silica gel (Ecoflex™ 00-30) was cut into a size of 8.0 cm × 10.0 cm and fixed on a pre-stretching frame of 10.0 cm × 13.0 cm, so that the tensile strain of the polymer film was 30%; an adhesion layer film (nickel film) of nickel (Ni) material with a thickness of 50 nm and a functional layer film (gold film) of gold (Au) material with a thickness of 50 nm were sequentially evaporated on the surface of the polymer film using electron beam evaporation coating technology. The purity of the target materials of the adhesion layer film (nickel film) and the functional layer film (gold film) were both 99.995%, and the evaporation coating rate was 2 Å / s; a polymer film coated with a double-layer film was obtained.

[0030] (5) The clamp on one side of the polymer film coated with the double-layer membrane is removed, so that the strain of the polymer film is spontaneously released and restored to its initial length, thereby obtaining a flexible film with a variable emissivity and a wrinkled surface.

[0031] See also Figure 1 and Figure 5 The pleated structure is composed of parallel contraction-like stripes, and the contraction-like stripes are perpendicular to the stretching direction on the pre-stretching frame.

[0032] See also Figure 3 The emissivity of the flexible film with a wrinkled structure prepared in Example 2 was tested by Fourier transform infrared spectrometer (BRUKER VERTEX80) under different uniaxial tensile strains of 2.5-20.0 μ Infrared integrated emissivity in the m-band. During spectrum measurement, the center of the flexible film is aligned with the measuring hole above the integrating sphere, and the stripe direction of the fold structure on the surface of the flexible film is parallel to the vertical direction of the surface where the sample is located on the upper side of the integrating sphere. The fold structure of the flexible film is between 2.5 and 20.0 μ The infrared emissivity in the m-band decreases first and then gradually increases with the increase of strain. When the uniaxial tensile strain is 80%, the infrared integrated emissivity of the pleated structure of the flexible film can be adjusted in the range of 0.12~0.44, indicating that the designed pleated structure of the flexible film has good dynamic regulation ability of infrared emissivity.

[0033] The flexible film with variable emissivity prepared in Example 2 was fixed at both ends on a uniaxial stretching electric control console, and the bottom was heated with a power of 2.09 W / cm 2 The heating sheet was in close contact with the flexible film, and infrared images of the flexible film with variable emissivity under different tensile strains were taken using an infrared thermal imager (TiX660, Fluke). When the uniaxial tensile strain was 0%, the infrared radiation temperature of the flexible film with variable emissivity prepared in Example 2 was 29.0°C, and when the uniaxial tensile strain was 112%, the infrared radiation temperature of the flexible film with variable emissivity became 36.6°C, and the infrared radiation temperature was adjusted by 7.6°C. Example 3

[0034] The steps for preparing a flexible film for dynamically adjusting infrared emissivity are as follows: (1) Weigh 20 g of polydimethylsiloxane (PDMS Dow Corning Sylgard 184) (base component A) and 2 g of silicone oil with silicon hydride (Si-H) functional groups (reaction component B) in a mass ratio of 10:1 and stir at room temperature at 300 rpm / min for 8 min to obtain a uniform mixed solution.

[0035] (2) The uniform mixed solution was placed in a vacuum chamber for degassing for 10 min. The mixed solution was then poured onto a smooth polytetrafluoroethylene flat plate with a size of 12 cm × 12 cm for self-leveling to obtain a polymer film to be cured with a thickness of 1.5 mm, i.e., a stretchable flexible substrate to be cured.

[0036] (3) The stretchable flexible substrate to be cured was cured at room temperature of 100°C for 35 min, and the film was torn off the polytetrafluoroethylene flat plate to obtain a polymer film of polydimethylsiloxane (PDMS Dow Corning Sylgard184) with a thickness of about 1.5 mm.

[0037] (4) A polymer film of polydimethylsiloxane (PDMS Dow Corning Sylgard 184) was cut into a size of 4.0 cm × 6.0 cm and fixed on a pre-stretching frame of 6.6 cm × 6.0 cm, so that the tensile strain of the polymer film was 10%; an adhesion layer film (nickel film) of nickel (Ni) material with a thickness of 50 nm and a functional layer film (aluminum film) of aluminum (Al) material with a thickness of 50 nm were sequentially evaporated on the surface of the polymer film using electron beam evaporation coating technology. The target material purity of the adhesion layer film (nickel film) and the functional layer film (aluminum film) were both 99.995%, and the evaporation coating rate was 2 Å / s; a polymer film coated with a double-layer film was obtained.

[0038] (5) The clamp on one side of the polymer film coated with the double-layer membrane is removed, so that the strain of the polymer film is spontaneously released and restored to its initial length, thereby obtaining a flexible film with a variable emissivity and a wrinkled surface.

[0039] See also Figure 1 and Figure 5 The pleated structure is composed of parallel contraction-like stripes, and the contraction-like stripes are perpendicular to the stretching direction on the pre-stretching frame.

[0040] See also Figure 4 The emissivity of the flexible film with a wrinkled structure prepared in Example 1 was tested by Fourier infrared spectrometer (BRUKER VERTEX80) under different uniaxial tensile strains of 2.5-20.0 μ Infrared integrated emissivity in the m-band. During spectrum measurement, the center of the flexible film is aligned with the measuring hole above the integrating sphere, and the stripe direction of the fold structure on the surface of the flexible film is parallel to the vertical direction of the surface where the sample is located on the upper side of the integrating sphere. The fold structure of the flexible film is between 2.5 and 20.0 μThe infrared emissivity in the m-band gradually increases with the increase of strain. When the uniaxial tensile strain is 80%, the infrared integrated emissivity of the pleated structure of the flexible film can be adjusted in the range of 0.06~0.51, indicating that the designed pleated structure of the flexible film has good dynamic regulation ability of infrared emissivity.

[0041] The flexible film with variable emissivity prepared in Example 3 was fixed at both ends on a uniaxial stretching electric control console, and the bottom was heated with a power of 0.41 W / cm 2 The heating sheet was in close contact with the flexible film, and infrared images of the flexible film with variable emissivity under different tensile strains were taken using an infrared thermal imager (TiX660, Fluke). When the uniaxial tensile strain was 0%, the infrared radiation temperature of the flexible film with variable emissivity prepared in Example 1 was 23.0°C. When the uniaxial tensile strain was 50%, the infrared radiation temperature of the flexible film with variable emissivity became 25.0°C, and the infrared radiation temperature was adjusted by 2.0°C.

[0042] It will be easily understood by those skilled in the art that the above embodiments are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a flexible film for dynamically adjusting infrared emissivity, characterized in that: The steps are as follows: (1) mixing a base component A of a stretchable polymer and a reaction component B at a mass ratio of 1:1 to 15:1 at room temperature to obtain a mixed solution; The base component A and the reactive component B are polydimethylsiloxane prepolymer and a crosslinking agent, or a basic silicone resin and a platinum catalyst; (2) degassing the mixed solution under vacuum conditions, and then pouring it onto a flat plate with a smooth surface for self-leveling to obtain a polymer film to be cured with a thickness of 1.0 to 2.0 mm, i.e., a stretchable flexible substrate in a state to be cured; (3) curing the stretchable flexible substrate at a stable temperature and tearing it off from the flat plate to obtain a polymer film; (4) cutting the polymer film into a required size, and fixing the two ends of the cut polymer film on a pre-stretching frame; using electron beam evaporation coating technology to sequentially coat an adhesion layer film and a functional layer film on the surface of the polymer film; the material of the adhesion layer film is one of nickel (Ni), titanium (Ti), and chromium (Cr); the material of the functional layer film is one of gold (Au), silver (Ag), and aluminum (Al); (5) removing the fixture on one side of the polymer film coated with the double-layer film, so that the strain of the polymer film is spontaneously released and restored to its initial length, thereby obtaining a flexible film with a variable emissivity and a wrinkled surface structure; The variable emissivity flexible film with a pleated structure has a dynamic adjustment range of infrared emissivity of 0.03 to 0.64 under 80% uniaxial tensile strain, and an adjustment range of infrared radiation temperature of 2 to 41°C.

2. The method for preparing a flexible film for dynamically adjusting infrared emissivity according to claim 1, characterized in that: In step (1), the cross-linking agent is silicone oil with a silicon hydride (Si—H) functional group.

3. The method for preparing a flexible film for dynamically adjusting infrared emissivity according to claim 1, characterized in that: In step (1), the base silicone resin is a platinum-catalyzed silicone resin.

4. The method for preparing a flexible film for dynamically adjusting infrared emissivity according to claim 1, characterized in that: In step (1), the base component A and the reaction component B are stirred at a speed of 150 to 300 rpm / min for 3 to 8 min.

5. The method for preparing a flexible film for dynamically adjusting infrared emissivity according to claim 1, characterized in that: In step (2), the degassing treatment time is 3 to 10 minutes.

6. The method for preparing a flexible film for dynamically adjusting infrared emissivity according to claim 1, characterized in that: In step (3), the stabilization temperature is 25 to 125°C, and the curing time is 0.5 to 48 hours.

7. The method for preparing a flexible film for dynamically adjusting infrared emissivity according to claim 1, characterized in that: In step (4), the purity of the target material of the adhesion layer film and the target material of the functional layer film are both 99.995%, and the evaporation coating rate is 2 Å / s.

8. The method for preparing a flexible film for dynamically adjusting infrared emissivity according to claim 1, characterized in that: In step (5), the pleated structure is composed of parallel shrinkage stripes, and the shrinkage stripes are perpendicular to the stretching direction on the pre-stretching frame.

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