A method for preparing a composite film with low-temperature cracking characteristics

Abstract

The invention discloses a method for preparing a composite film with low-temperature cracking properties, including: taking a certain amount of easily molded high molecular polymer and adding it to tetrahydrofuran solvent, ultrasonically treating and stirring to obtain a polymer film-forming liquid; a metal mesh containing a circular hole is fixed on a glass substrate so that the metal mesh and the glass substrate are closely fitted; the glass substrate is fixed on a spin coater, the spin coater speed and the rotation time are set, a certain amount of polymer film-forming liquid is dropped in the center of the metal mesh, the spin coater is operated, and a uniform polymer film, i.e., a metal-polymer composite film, is formed on the metal mesh after the spin coater stops; the metal-polymer composite film is placed for more than 2 hours, and the metal-polymer composite film is removed from the glass substrate, and the metal-polymer composite film is a composite film with low-temperature cracking properties. The present invention obtains a temperature-responsive switch for low-temperature cracking properties composite film that can be used as a moisture-absorbing material to absorb water vapor, and can also be used for the separation and mixing of different types of gases.

Description

Technical Field

[0001] The present invention belongs to the technical field of composite membrane preparation, and more particularly, relates to a method for preparing a composite membrane with low-temperature cracking characteristics. Background Art

[0002] Membrane technology has developed rapidly over the past few decades and has been widely used in energy, chemical engineering, environmental engineering, and life sciences. However, the structure and morphology of traditional membranes are generally immutable, and therefore lack exogenous response properties, which limits their application in some fields. In recent years, research on thin films with environmental stimulus-responsive properties has attracted increasing attention. Such films can change their structure (such as pore size and surface properties) in response to changes in external factors such as temperature, pH, electric field, magnetic field, and ionic strength. Such environmental stimulus-responsive films have important application prospects in areas such as material separation, controlled transport, sensors, and controlled drug release.

[0003] For sealed, vacuum systems containing electronic components, gas permeation can cause a continuous increase in water vapor content during prolonged storage and use. This water vapor can corrode metal and other water-reactive materials within the system, shortening system life and reducing reliability. A common solution is to place specialized moisture-absorbing materials within the system to control moisture vapor levels. However, due to the high concentration of moisture in the air, this material can absorb moisture during system assembly, potentially leading to failure. Adding a temperature-responsive film to the outer layer of the moisture-absorbing material can address this issue. Specifically, during system assembly, the temperature-responsive film maintains its structural integrity, preventing the absorbent from absorbing moisture from the air and preventing failure. Once the absorbent is assembled and the moisture content needs to be reduced, the temperature can be adjusted to induce structural changes in the temperature-responsive film, creating cracks. These cracks act as pathways for moisture diffusion, allowing the moisture-absorbing material to function and reduce the system's moisture content. Summary of the Invention

[0004] An object of the present invention is to solve at least the above problems and / or disadvantages and to provide at least the advantages which will be described hereinafter.

[0005] In order to achieve these objects and other advantages according to the present invention, a method for preparing a composite membrane having low temperature resistance characteristics is provided, comprising the following steps:

[0006] Step 1: adding a certain amount of a polymer that is easy to form a mold into a tetrahydrofuran solvent, ultrasonically treating and stirring to completely dissolve the polymer, thereby obtaining a polymer film-forming solution;

[0007] Step 2: Fix a metal mesh with circular holes of a certain size on the glass substrate so that the metal mesh and the glass substrate are closely attached;

[0008] Step 3: Fix the glass substrate prepared in step 2 on a spin coater, set the speed and rotation time of the spin coater, take a certain amount of the polymer film-forming liquid prepared in step 1 and drop it on the center of the metal mesh, run the spin coater, and after the spin coater stops, a uniform polymer film is formed on the metal mesh, i.e., a metal-polymer composite film;

[0009] Step 4: Place the metal-polymer composite film prepared in step 3 for more than 2 hours to allow the solvent to completely evaporate, and then remove the metal-polymer composite film from the glass substrate. The metal-polymer composite film is a composite film with low-temperature cracking characteristics.

[0010] Preferably, in the step 1, the film-forming polymer is polymethyl methacrylate or polystyrene.

[0011] Preferably, in the step 1, the content of the easily moldable high molecular weight polymer in tetrahydrofuran is 0.1-0.5 g / ml.

[0012] Preferably, in step 2, the metal mesh is 316L stainless steel with a thickness of 50 μm.

[0013] Preferably, in step 2, the diameter of the circular holes of the metal mesh is 2 to 5 mm, the interval between the circular holes is 2 mm, and the outer dimensions of the metal mesh are a square with a side length of 4 cm.

[0014] Preferably, in the step 3, the rotation speed of the spin coater is 600-1000 rpm, the rotation time is 30 s, and the volume of the polymer film-forming liquid is 1 ml.

[0015] The invention discloses an application of a composite film with low-temperature cracking characteristics, wherein the composite film with low-temperature cracking characteristics is applied to a temperature-responsive switch for moisture-absorbing materials absorbing water vapor.

[0016] The invention discloses an application of a composite membrane with low-temperature cracking characteristics, wherein the composite membrane with low-temperature cracking characteristics is applied to the separation and mixing of different types of gases.

[0017] The present invention has at least the following beneficial effects: the present invention uses a metal mesh as a skeleton and utilizes a rotation method to form a polymer film on the metal mesh, thereby producing a metal-polymer composite film. 金属 Much smaller than the thermal expansion coefficient CET of polymers 聚合物 , namely CET 金属 -CET 聚合物<0. When the ambient temperature drops rapidly, the shrinkage of the polymer film is much greater than that of the metal mesh, which causes cracks in the polymer film in the circular holes of the metal mesh. Therefore, the metal-polymer composite film prepared by the present invention has low-temperature cracking characteristics. If this metal-polymer composite film is assembled on the outer layer of the hygroscopic material, it can prevent the hygroscopic material from absorbing water vapor in the air during the system assembly process. When the hygroscopic material is assembled in the system and the water vapor content of the system needs to be reduced, the polymer film on the metal mesh can be cracked by lowering the ambient temperature of the system. The cracks can serve as water vapor diffusion channels, so that the hygroscopic material plays a role in achieving the purpose of reducing the water vapor content of the system. Therefore, the composite film with low-temperature cracking characteristics prepared by the present invention can be used as a temperature response switch for the hygroscopic material to absorb water vapor, and this is only one of the application scenarios of the composite film with low-temperature cracking characteristics prepared by the present invention. It can also be used for the separation and mixing of different types of gases.

[0018] Other advantages, objectives and features of the present invention will be reflected in part through the following description, and in part will be understood by those skilled in the art through study and practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a photo of the metal-PMMA composite film provided in Example 1 of the present invention;

[0020] Figure 2 This is a microscope photograph of the metal-PMMA composite film provided in Example 1 of the present invention at room temperature;

[0021] Figure 3 This is a microscope photograph of the metal-PMMA composite film provided in Example 1 of the present invention at room temperature;

[0022] Figure 4 This is a microscope photograph of the metal-PMA composite film provided in Example 1 of the present invention at -60°C;

[0023] Figure 5 This is a microscope photograph of the metal-PMA composite film provided in Example 1 of the present invention at -60°C;

[0024] Figure 6 Photos of the thickness of the metal-PMMA polymer composite film at different locations provided in Example 1 of the present invention;

[0025] Figure 7 These are photos of the thickness of the metal-PMMA polymer composite film at different positions provided in Example 1 of the present invention. DETAILED DESCRIPTION

[0026] The present invention will be described in further detail below in conjunction with the accompanying drawings so that those skilled in the art can implement the invention with reference to the description.

[0027] It should be understood that terms such as “having”, “including” and “comprising” used herein do not preclude the existence or addition of one or more other elements or combinations thereof.

[0028] Example 1

[0029] This embodiment discloses a method for preparing a composite film having low-temperature cracking properties, comprising the following steps:

[0030] Step 1: Add a certain amount of polymethyl methacrylate (PMMA) to tetrahydrofuran (THF) solvent, ultrasonicate and stir to dissolve the PMMA, and prepare a film-forming solution with a PMMA content of 0.1 g / ml;

[0031] Step 2: Fix a 50 μm thick, 4 cm square metal mesh on the glass substrate. The metal mesh contains 5 mm diameter circular holes with a 2 mm interval. The metal mesh is made of 316L stainless steel.

[0032] Step 3: Fix the glass substrate prepared in step 2 on a spin coater, set the spin coater speed to 1000 rpm and the spin time to 30 s, take 1 ml of the PMMA film-forming solution prepared in step 1 and drop it on the center of the metal mesh, run the spin coater, and after the spin coater stops, a PMMA film is formed on the circular holes of the metal mesh, i.e., a metal-PMMA composite film;

[0033] Step 4: Place the metal-PMMA composite film prepared in step 3 for more than 2 hours to allow the solvent THF to completely evaporate, and then remove the metal-PMMA composite film from the glass substrate. The metal-PMMA composite film is a composite film with low-temperature cracking characteristics.

[0034] In this example, a metal-PMMA composite film was produced by spin coating a stainless steel mesh containing circular holes on the mesh's holes using a spin coating method. Because PMMA's coefficient of thermal expansion is much greater than that of metal, the PMMA film shrinks much more than the metal on the holes when the ambient temperature drops. When the temperature drops below a certain level, the PMMA film shrinks excessively on the holes, causing cracking. Consequently, the resulting metal-PMMA composite film exhibits low-temperature cracking properties.

[0035] In this embodiment, the actual photo of the metal-PMMA composite film is as follows: Figure 1 As shown in the figure, it can be observed that the overall structure of the metal-PMMA composite film is intact, and each circular hole of the metal mesh is covered with a transparent PMMA film.

[0036] In this embodiment, the microscopic pictures of the metal-PMMA composite film at different temperatures are as follows: Figure 2-Figure 5 shown. Figure 2 and 3This is a microscope photo of the PMMA film on the circular holes of the metal mesh at room temperature. Figure 2 and 3 It was observed that at room temperature, the PMMA film on the circular hole was tightly attached to the metal mesh without any gaps, and the PMMA film itself was structurally intact without any cracks. The metal-PMMA composite film was photographed at room temperature and then placed in a -60℃ environment for 10 minutes. The structural changes were then observed under a microscope. The results are as follows: Figure 4 and 5 As shown. Figure 4 and 5 It was observed that after the metal-PMMA composite film was treated at a low temperature of -60°C, not only did the PMMA film separate from the edge of the metal mesh to form a gap, but the PMMA film itself also produced large-sized cracks.

[0037] In this embodiment, the thickness of the PMMA film at different positions on the circular hole of the metal-PMMA composite film is shown in the following figure. Figure 6 and Figure 7 shown. Figure 6 This is a photo of the thickness of the PMMA film on the circular hole near the metal mesh, and the thickness was observed to be 10um. Figure 7 The thickness of the PMMA film at the center of the circular hole is 5um. Figure 6 and Figure 7 The thickness observation results show that the thickness of the PMMA film on the circular hole is uneven. This is because during the spin coating process, the metal mesh has a certain blocking effect on the film-forming liquid, resulting in uneven thickness of the PMMA film generated on the circular hole.

[0038] In this embodiment, the metal-PMMA composite film exhibits low-temperature cracking properties. At room temperature, the PMMA film on the metal mesh maintains a structurally intact structure, blocking water vapor and various gases. However, when the ambient temperature drops below a certain level, the PMMA film separates from the metal mesh, forming gaps, or large cracks develop within the PMMA film itself. These gaps and cracks serve as diffusion pathways for water vapor and other gases.

[0039] Example 2

[0040] This embodiment discloses a method for preparing a composite film with low-temperature cracking characteristics, which differs from Example 1 in that: in step 1, the PMMA content is 0.2 g / ml; in step 2, the diameter of the circular holes on the metal mesh is 4 mm; in step 3, the rotation speed of the rotary coating machine is set to 900 rpm.

[0041] Example 3

[0042] This embodiment discloses a method for preparing a composite film with low-temperature cracking characteristics, which differs from Example 1 in that: in step 1, the PMMA content is 0.3 g / ml; in step 2, the diameter of the circular holes on the metal mesh is 3 mm; in step 3, the rotation speed of the rotary coating machine is set to 800 rpm.

[0043] Example 4

[0044] This embodiment discloses a method for preparing a composite film with low-temperature cracking characteristics, which differs from Example 1 in that: in step 1, the PMMA content is 0.4 g / ml; in step 2, the diameter of the circular holes on the metal mesh is 2 mm; in step 3, the rotation speed of the rotary coating machine is set to 700 rpm.

[0045] Example 5

[0046] This embodiment discloses a method for preparing a composite film with low-temperature cracking characteristics, which differs from Example 1 in that: in step 1, the PMMA content is 0.5 g / ml; in step 2, the diameter of the circular holes on the metal mesh is 4 mm; in step 3, the rotation speed of the rotary coating machine is set to 600 rpm.

[0047] The number of devices and processing scales described herein are intended to simplify the description of the present invention. Applications, modifications, and variations of the present invention will be readily apparent to those skilled in the art.

[0048] Although the embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the description and implementation methods. They can be fully applied to various fields suitable for the present invention. For those familiar with the art, additional modifications can be easily implemented. Therefore, without departing from the general concept defined by the claims and the scope of equivalents, the present invention is not limited to the specific details and illustrations shown and described herein.

Claims

1. Application of a composite film with low-temperature cracking characteristics, characterized in that: The composite film with low-temperature cracking characteristics is applied to a temperature-responsive switch for moisture-absorbing materials absorbing water vapor; The preparation method of the composite film comprises the following steps: Step 1: adding a certain amount of a film-forming polymer to a tetrahydrofuran solvent, ultrasonically treating and stirring to completely dissolve the polymer, thereby obtaining a polymer film-forming solution; Step 2: Fix a metal mesh with circular holes of a certain size on the glass substrate so that the metal mesh and the glass substrate are closely attached; the diameter of the circular holes of the metal mesh is 2-5 mm; Step 3: Fix the glass substrate prepared in step 2 on a spin coater, set the speed and rotation time of the spin coater, take a certain amount of the polymer film-forming liquid prepared in step 1 and drop it on the center of the metal mesh, run the spin coater, and after the spin coater stops, a uniform polymer film is formed on the metal mesh, i.e., a metal-polymer composite film; Step 4: The metal-polymer composite film prepared in step 3 is placed for more than 2 hours to allow the solvent to completely evaporate, and then the metal-polymer composite film is removed from the glass substrate. The metal-polymer composite film is a composite film with low-temperature cracking characteristics; In the step 1, the film-forming polymer is polymethyl methacrylate or polystyrene.

2. The use of the composite film having low-temperature cracking properties according to claim 1, characterized in that: In the step 1, the content of the film-forming high molecular weight polymer in tetrahydrofuran is 0.1-0.5 g / ml.

3. The use of the composite film having low-temperature cracking properties according to claim 1, characterized in that: In the step 2, the metal mesh is 316L stainless steel with a thickness of 50 μm.

4. The use of the composite film having low-temperature cracking properties according to claim 1, characterized in that: In the step 2, the interval between the circular holes is 2 mm, and the outer dimension of the metal mesh is a square with a side length of 4 cm.

5. The use of the composite film having low-temperature cracking properties according to claim 1, characterized in that: In the step 3, the rotation speed of the spin coater is 600-1000 rpm, the rotation time is 30 s, and the volume of the polymer film-forming liquid is 1 ml.

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