Method for preparing mesoscale polyethylene film by adopting spin coating method

Abstract

The invention relates to the technical field of polymer material preparation, in particular to a method for preparing a mesoscale polyethylene film by adopting a spin coating method. The method comprises the following steps: (1) cleaning; (2) preparing a solution; (3) preheating a cavity of the spin coater; (4) pipetting; (5) spin coating: setting the rotating speed and time of a spin coater to start spin coating; forming a film on the surface of the substrate after set rotating speed and time, cooling and taking out to obtain the film; and (6) annealing: carrying out annealing treatment on the film under a vacuum condition to obtain the mesoscale polyethylene film. The method disclosed by the invention is convenient to operate, and the thickness of the prepared mesoscale (the thickness is 50nm-5mu m) polyethylene film is accurate and controllable.

Description

Technical Field

[0001] The invention relates to the technical field of polymer material preparation, in particular to a method for preparing a mesoscopic polyethylene film by using a spin coating method. Background Art

[0002] Low-density polyethylene (LDPE) is one of the most typical polymer materials. It is lightweight, flexible, chemically resistant and has excellent electrical insulation properties. It is widely used in many fields. LDPE film is used in all aspects of life, such as packaging materials, building waterproof materials, agricultural coverings, etc.

[0003] Typically, polyethylene is melt processed to make films, such as extrusion, blown film, etc. These processes involve heating polyethylene to its melting point and forming a film through extrusion or blown film equipment.

[0004] Spin coating is a commonly used method for preparing thin films. The principle is to drop a solution onto a high-speed rotating turntable, and the solution is radially coated on the substrate to form a thin film. In industrial applications, spin coating is not the preferred method for preparing LDPE films. Because polyethylene has a high dissolution temperature and low solubility, it is difficult to prepare a stable polyethylene solution, and thus it is impossible to form a high-quality controllable polyethylene film. However, in laboratory applications, methods such as extrusion and film blowing require special large-scale equipment, which are usually suitable for industrial mass production, but are not suitable for small-batch customized film preparation for laboratory use. The spin coating method has a simple principle, is easy to operate, does not require complex equipment, has better economy, and is usually suitable for laboratory scientific research needs. However, there is currently a lack of effective methods for preparing mesoscopic LDPE films by spin coating. Summary of the invention

[0005] Based on the above content, the present invention provides a method for preparing a mesoscopic polyethylene film by a spin coating method to solve the problems existing in the above-mentioned prior art.

[0006] To achieve the above object, the present invention provides the following solutions:

[0007] The present invention provides a method for preparing a mesoscopic polyethylene film by a spin coating method, comprising the following steps:

[0008] (1) Cleaning: After cleaning the substrate, place it on the turntable of the spin coater and preheat it to 100°C;

[0009] (2) Solution preparation: low-density polyethylene is added to a p-xylene solution and sealed and circulated and heated at 90-120° C. After the low-density polyethylene is completely dissolved, the solution is placed on a heating table and maintained at 150° C. to obtain an LDPE solution;

[0010] (3) Preheating the spin coater cavity: preheating the spin coater cavity to 100° C. using a heating source;

[0011] (4) Liquid transfer: Pour the LDPE solution onto the substrate surface on the turntable of the spin coater. After the LDPE solution spreads and covers the ITO surface, close the lid of the spin coater.

[0012] (5) Spin coating: Set the spin coater speed (spin coating speed) and time to start spin coating; after the set speed and time, a thin film is formed on the surface of the substrate, and the thin film is taken out after cooling to obtain a thin film;

[0013] (6) Annealing: Annealing the film under vacuum conditions to obtain a mesoscopic polyethylene film.

[0014] The present invention discloses the following technical effects:

[0015] The mesoscopic polyethylene film prepared by the spin coating method of the present invention has high film-forming efficiency, low cost and can be formed into a large area (for example, 20 mm×20 mm, 50 mm×50 mm).

[0016] The spin coating apparatus used in the spin coating method of the present invention has a simple principle and is easy to operate. The thickness of the prepared polyethylene film with a mesoscopic scale (thickness 50nm-5um) can be precisely controlled. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0018] Figure 1 This is a schematic diagram of the process flow for preparing a mesoscopic polyethylene film according to the present invention;

[0019] Figure 2 This is a photograph of the spin coater used in the examples of the present invention.

[0020] Figure 3 This is an optical photograph of the polyethylene film prepared in Example 1 of the present invention.

[0021] Figure 4 This is an optical photograph of the polyethylene film prepared in Comparative Example 1 of the present invention.

[0022] Figure 5 This is an optical photograph of the polyethylene film prepared in Comparative Example 2 of the present invention.

[0023] Figure 6 This is an optical photograph of the polyethylene film prepared in Comparative Example 3 of the present invention. DETAILED DESCRIPTION

[0024] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0025] It should be understood that the terms described in the present invention are only for describing a particular embodiment and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. The intermediate value in any stated value or stated range, and each smaller range between any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0026] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0027] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to the skilled artisan. The present invention description and examples are exemplary only.

[0028] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0029] The "room temperature" and "normal temperature" mentioned in the present invention, unless otherwise specified, all mean 20-30°C.

[0030] At present, the existing technology for preparing polyethylene films generally adopts melt hot pressing or biaxial stretching methods, but the polyethylene films prepared by the above two methods are relatively thick, and it is impossible to prepare polyethylene films with uniform thickness at the mesoscale (thickness 50nm-5um). Spin coating is a common method for preparing thinner films, but polyethylene has a high dissolution temperature, low solubility and low-temperature precipitation problems, resulting in polyethylene films prepared by spin coating having problems such as uneven thickness, unevenness, and bubbles. Based on this, the present invention provides a method for preparing a mesoscale polyethylene film by spin coating, comprising the following steps:

[0031] (1) Cleaning: After cleaning the substrate, place it on the turntable of the spin coater and preheat it to 100°C;

[0032] (2) Solution preparation: low-density polyethylene is added to a p-xylene solution and sealed for 90-120° C. cyclic heating. After the low-density polyethylene is completely dissolved, the solution is placed on a heating table and maintained at 150° C. to obtain an LDPE solution; (the purpose of sealing is to achieve a constant mass fraction of the solution during the entire film-making process; the purpose of adopting 90-120° C. cyclic heating is to ensure that the low-density polyethylene is fully dissolved while avoiding excessive system pressure and solvent volatilization, thereby affecting the concentration of the LDPE solution; the purpose of placing the solution on a heating table with a temperature slightly higher than the dissolution temperature of the low-density polyethylene is to ensure the fluidity of the LDPE solution while reducing its volatilization rate);

[0033] The present invention does not impose any particular limitation on the heating / cooling rate of the 90-120°C cyclic heating, and the heating / cooling rate commonly used by those skilled in the art may be adopted, such as 2-15°C / min;

[0034] (3) Preheating the spin coater cavity: Preheat the spin coater cavity to 100°C through a heating source; (Preheating the spin coater cavity can reduce the temperature loss during the solution transfer process, thereby ensuring the uniformity of the prepared film)

[0035] (4) Liquid transfer: Pour the LDPE solution onto the substrate surface on the turntable of the spin coater. After the LDPE solution spreads and covers the ITO surface, close the lid of the spin coater.

[0036] (5) Spin coating: Set the spin coating speed (spin coating speed) and time to start spin coating; after the set speed and time, a thin film is formed on the substrate surface, and the thin film is taken out after cooling to obtain a thin film; (different spin coating speeds and times are selected according to the spin coating thickness and solution concentration);

[0037] (6) Annealing: Annealing the film under vacuum conditions to obtain a mesoscopic polyethylene film.

[0038] In the present invention, if the preheating temperature of the spin coater cavity is too high or too low, the quality of the prepared polyethylene film will be affected, such as bubbles.

[0039] In a preferred embodiment of the present invention, the substrate is an ITO substrate.

[0040] In a preferred embodiment of the present invention, the ITO substrate is cleaned by immersing the ITO in deionized water, acetone and isopropanol in sequence for ultrasonic cleaning at room temperature, then removing the residual solvent on the surface with an air gun and placing it in a UV ozone cleaner for cleaning.

[0041] In a preferred embodiment of the present invention, the mass concentration of the LDPE solution is 2%-8%.

[0042] In a preferred embodiment of the present invention, in step (5), the speed and time of the spin coater are set to two stages, the speed of the first stage is 500 rpm, the maintenance time is 5-7 s, and the speed of the second stage is 1000-4000 rpm, the maintenance time is 30 s.

[0043] In the present invention, the thickness of the prepared mesoscopic polyethylene film can be controlled by adjusting the concentration of the LDPE solution and the spin coating rate. Specifically, when the mass concentration of the LDPE solution is less than 3%, the second stage rotation speed in step (5) is 1000 rpm.

[0044] When the mass concentration of the LDPE solution is ≥3%, the rotation speed of the second stage in step (5) is 4000 rpm.

[0045] After the set speed and time, a thin film is formed on the surface of the substrate, which is taken out after natural cooling. Depending on subsequent needs, the film can be torn off or left on the substrate.

[0046] In a preferred embodiment of the present invention, the annealing is specifically as follows: firstly heating to 80-120°C at a rate of 0.5°C / min, keeping the temperature for 8-12h, and then cooling to room temperature at a rate of 0.5°C / min.

[0047] The technical solutions described in the present invention, unless otherwise specified, are all conventional solutions in the art, and the reagents or raw materials used, unless otherwise specified, are purchased from commercial channels or have been disclosed.

[0048] The polyethylene raw material used in the embodiment of the present invention is LDPE particles, model number is Q / 3201-BYC-01.

[0049] The technical solutions provided by the present invention are described in detail below in conjunction with the embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0050] Example 1

[0051] (1) Cleaning: Before formal spin coating, the indium tin oxide (ITO) transparent conductive film glass substrate needs to be cleaned. Immerse the ITO in deionized water, acetone and isopropanol in turn and ultrasonically clean it at room temperature for 10 minutes. After cleaning, use an air gun to remove the residual solvent on the surface and place it in a UV ozone cleaning machine for 15 minutes. After completion, place it on the turntable of the spin coater and preheat it to 100°C;

[0052] (2) Solution preparation: A polyethylene-p-xylene solution with a certain mass fraction is selected as the material for preparing the mesoscopic polyethylene film. Taking a polyethylene-p-xylene solution with a mass fraction of 5% as an example, 0.5 g of polyethylene particles and 9.5 g of p-xylene solution are weighed and added to a round-bottom flask. The flask is sealed with a frosted stopper to prevent the solvent from volatilizing. After that, it is cyclically heated at 90-120°C. After being heated until completely dissolved, it is placed on a heating table (heating table temperature 150°C) and kept at 150°C in subsequent experiments to obtain an LDPE solution.

[0053] (3) Preheating the spin coater chamber: preheating the spin coater chamber to 100°C by using a heating source to reduce temperature loss during the solvent transfer process;

[0054] (4) Liquid transfer: After preheating is completed, transfer the solution by quickly pouring the LDPE solution from step (2) from the round-bottom flask onto the ITO surface on the preheated spin coater turntable. After the LDPE solution spreads and covers the ITO surface, place the flask back on the heating table, quickly close the spin coater lid, and operate the spin coater to start spin coating.

[0055] (5) Spin coating: During the preparation of the polyethylene film, the speed of the spin coater was set to 500 rpm in the first stage and maintained for 5 s, and the speed of the second stage was set to 4000 rpm and maintained for 30 s. The temperature of the spin coater turntable was set to 100°C. After the transfer was completed, the cover of the spin coater was quickly closed and the spin coater was operated to start spin coating. After the set speed and time, a thin film was formed on the ITO surface, and the film was taken out after ventilation cooling.

[0056] (6) Annealing: In order to improve the compactness and uniformity of the prepared film, the spin-coated film was annealed. The prepared polyethylene film sample was placed in a glass culture dish and placed in a high-pressure vacuum chamber. The vacuum was drawn and then the temperature was raised to 120°C at a rate of 0.5°C / min and maintained at 120°C for 8 h. The temperature was then lowered to room temperature at a rate of 0.5°C / min to obtain a mesoscopic polyethylene film (optical photograph as shown in FIG. 1 ). Figure 3 shown).

[0057] A direct current breakdown experiment was performed on the mesoscopic polyethylene film prepared in Example 1 to measure its breakdown field strength (the experiment was conducted with reference to ASTM D3755 standard). The results showed that its breakdown field strength was 150 kV / mm.

[0058] On the basis of Example 1, the effects of different mass fractions and different rotation speeds on the thickness of the prepared polyethylene film were verified (i.e., the only difference from Example 1 was that the concentration of the LDPE solution and the rotation speed setting were adjusted, and the remaining steps and parameters were the same as those in the example), and the results are summarized in Table 1.

[0059] Table 1

[0060]

[0061] It can be seen from Table 1 that the method of the present invention can prepare a mesoscopic polyethylene film. Under the concentration and rotation speed setting conditions of the LDPE solution of the present invention, the film forming rate of the mesoscopic polyethylene film is 100%, and the thickness of the prepared film is uniform.

[0062] Comparative Example 1

[0063] The only difference from Example 1 is that step (6) is omitted; the remaining steps and parameters are the same as those in Example 1.

[0064] The optical photograph of the polyethylene film prepared in this comparative example is as follows Figure 4 shown.

[0065] Depend on Figure 4 It can be seen that without annealing, the film is prone to warping and damage, and the adhesion to the substrate is low; after annealing, Figure 3 The film is denser, less likely to warp, less likely to be damaged, and more closely attached to the substrate (annealing will also affect the uniformity of the film. Annealing can increase the crystallinity of the film and fully volatilize the residual solvent in the film, thereby improving the quality of the film).

[0066] Comparative Example 2

[0067] The only difference from Example 1 is that the preheating temperature of the spin coater chamber in step (3) is 130° C.; the remaining steps and parameters are the same as those in Example 1.

[0068] The optical photograph of the polyethylene film prepared in this comparative example is as follows Figure 5 shown.

[0069] Comparative Example 3

[0070] The only difference from Example 1 is that the preheating temperature of the spin coater chamber in step (3) is 160° C.; the remaining steps and parameters are the same as those in Example 1.

[0071] The optical photograph of the polyethylene film prepared in this comparative example is as follows Figure 6 shown.

[0072] Depend on Figure 5 , Figure 6 It can be seen that the polyethylene films prepared in Comparative Examples 2 and 3 have bubbles.

[0073] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for preparing a mesoscopic polyethylene film by spin coating, characterized in that: The following steps are involved: (1) Cleaning: After cleaning the substrate, place it on the turntable of the spin coater and preheat it to 100°C; (2) Solution preparation: low-density polyethylene is added to a p-xylene solution and sealed and circulated and heated at 90-120° C. After the low-density polyethylene is completely dissolved, the solution is placed on a heating table and maintained at 150° C. to obtain an LDPE solution; (3) Preheating the spin coater cavity: preheating the spin coater cavity to 100° C. using a heating source; (4) Liquid transfer: Pour the LDPE solution onto the substrate surface on the turntable of the spin coater. After the LDPE solution spreads and covers the ITO surface, close the lid of the spin coater. (5) Spin coating: Set the spin coater speed and time to start spin coating; after the set speed and time, a thin film is formed on the surface of the substrate, and the thin film is taken out after cooling to obtain a thin film; (6) Annealing: Annealing the film under vacuum conditions to obtain a mesoscopic polyethylene film.

2. The method for preparing a mesoscopic polyethylene film by spin coating according to claim 1, characterized in that: The substrate is an ITO substrate.

3. The method for preparing a mesoscopic polyethylene film by spin coating according to claim 2, characterized in that: The method for cleaning the ITO substrate is: immersing the ITO in deionized water, acetone and isopropanol in turn for ultrasonic cleaning at room temperature, then removing the residual solvent on the surface with an air gun and placing it in an ultraviolet ozone cleaning machine for cleaning.

4. The method for preparing a mesoscopic polyethylene film by spin coating according to claim 1, characterized in that: The mass concentration of the LDPE solution is 2%-8%.

5. The method for preparing a mesoscopic polyethylene film by spin coating according to claim 4, characterized in that: In step (5), the speed and time of the spin coater are set to two stages, the speed of the first stage is 500 rpm, the maintenance time is 5-7 s, and the speed of the second stage is 1000-4000 rpm, the maintenance time is 30 s.

6. The method for preparing a mesoscopic polyethylene film by spin coating according to claim 5, characterized in that: When the mass concentration of the LDPE solution is less than 3%, the rotation speed in the second stage of step (5) is 1000 rpm; when the mass concentration of the LDPE solution is greater than or equal to 3%, the rotation speed in the second stage of step (5) is 4000 rpm.

7. The method for preparing a mesoscopic polyethylene film by spin coating according to claim 1, characterized in that: The annealing is specifically as follows: firstly heating to 80-120°C at a rate of 0.5°C / min, keeping the temperature for 8-12h, and then cooling to room temperature at a rate of 0.5°C / min.

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