Preparation method and application of composite film with high infrared absorptivity and flexibility

Abstract

The invention relates to the field of film materials, and discloses a preparation method and application of a composite film with high infrared absorptivity and flexibility. The preparation method of the composite film comprises the following steps: 1) adding oxidized polyethylene into a solvent, heating and stirring to form a uniform solution; (2) adding a polytetrafluoroethylene emulsion into the solution obtained in the step (1), and uniformly stirring to form a mixed solution; 3) performing ultrasonic dispersion on the mixed solution to form a uniform dispersion solution; the invention discloses a PEO / PTFE-based composite film and a preparation method thereof.The PEO / PTFE-based composite film has the advantages that oxidized polyethylene and PTFE serve as composite substrates, and the PEO / PTFE-based composite film is high in flexibility and low in infrared transmittance and can be applied to the fields of infrared stealth and wearable thermal management.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of film materials, and particularly relates to a preparation method of a composite film with high infrared absorption and flexibility and application thereof. BACKGROUND

[0002] Under the influence of environmental factors such as greenhouse effect, the outdoor temperature has been rising in recent years, and thus the demand for flexible film materials with heat management function is growing. Traditional infrared heat regulation materials such as metal reflection layer or oxide ceramic have good heat reflection performance, but they have the shortcomings of rigidity and difficult processing. Compared with the above, polymer-based infrared film material has excellent processing performance and good flexibility, and thus becomes a potential infrared heat regulation material.

[0003] Oxidized polyethylene (PEO) has good film-forming property and flexibility, and polytetrafluoroethylene (PTFE) has good infrared reflection ability. Therefore, if the above two can be combined, the structure and performance can be optimized, and the mechanical property and infrared optical property of the heat regulation film material can be synergistically enhanced. However, there is little report on the preparation of the infrared heat regulation film by combining the above two, and thus it is of positive significance to combine the above two to prepare an infrared heat regulation film material with high flexibility and low infrared transmittance. SUMMARY

[0004] In order to solve the problems of poor flexibility and high infrared transmittance of the existing infrared heat regulation film material, the present application provides a preparation method of a composite film with high infrared absorption and flexibility and application thereof. The infrared heat regulation film of the present application uses oxidized polyethylene (PEO) and polytetrafluoroethylene (PTFE) as the composite matrix, and has high flexibility and low infrared transmittance, and can be applied to the fields of infrared stealth and wearable heat management.

[0005] In order to achieve the above purpose, the present application is realized by the following technical scheme:

[0006] In the first aspect, the present application provides a preparation method of a composite film with high infrared absorption and flexibility, which comprises the following steps:

[0007] 1) Oxidized polyethylene (PEO) is added to a solvent, heated and stirred to form a uniform solution.

[0008] 2) Polytetrafluoroethylene (PTFE) emulsion is added to the solution obtained in 1), and stirred uniformly to form a mixture;

[0009] 3) The mixture is subjected to ultrasonic dispersion to form a uniformly dispersed solution.

[0010] 4) The dispersed solution is coated on the surface of a PET substrate.

[0011] 5) Vacuum drying to obtain the PEO / PTFE based infrared thermal regulation film.

[0012] The present application uses oxidized polyethylene (PEO) and polytetrafluoroethylene (PTFE) as raw materials, mixes them, and then prepares a film by coating. The obtained infrared thermal regulation film material is stable in state, has high flexibility and low infrared transmittance, especially low transmittance in the 8-25 micron infrared wave band, and shows good infrared shielding and reflection effect, which can be applied to the fields of infrared stealth and wearable thermal management.

[0013] As a preferred, the mass ratio of the oxidized polyethylene and polytetrafluoroethylene is (0.7-1.4):1.2.

[0014] With the increase of PEO content, the flexibility of the obtained composite film is enhanced, and the C-O-C and -OH group absorption peaks in the FTIR spectrum are enhanced. PEO is a hydrophilic flexible polymer, which serves as a continuous matrix in the system and can ensure the film-forming property and flexibility of the film. PTFE mainly serves as a filler to give the film the characteristic of low infrared transmittance. If the PEO content is too low (<0.7:1), it is not easy to form a complete continuous film, resulting in poor adhesion and insufficient flexibility of the film; if the PEO content is too high (more than 1.41), the film is prone to warping or cracking after drying, and the overall infrared performance of the film is affected. The mass ratio of the above two is controlled at (0.7-1.4):1.2 in the present application, so that the composite film can have both infrared absorption performance and integrity.

[0015] As a preferred, in step 1), the average molecular weight of the oxidized polyethylene is 400000-600000.

[0016] It is found in the present application that when the molecular weight of the oxidized polyethylene is less than 400000, the PEO segment is short and easy to dissolve but insufficient in film-forming property; when the molecular weight of the oxidized polyethylene is more than 600000, PEO is difficult to dissolve and the solution viscosity is high, which is not conducive to spin coating. In the range of 400000-600000 molecular weight, the PEO segment length is moderate, which ensures the solution has a certain flowability and is conducive to the uniform dispersion of PTFE in the film, so that a composite film with stable performance is obtained.

[0017] As a preferred, in step 1), the concentration of the oxidized polyethylene in the uniform solution is 2-5wt%.

[0018] As a preferred, in step 1), the solvent is a mixed solvent of water and ethanol.

[0019] Further preferably, in step 1), the volume ratio of water to ethanol in the mixed solvent is (1-3):1.

[0020] As preferred, in step 1), the temperature of the heating stirring is 40-50℃, and the time is 1-3h.

[0021] As preferred, in step 2), the concentration of the polytetrafluoroethylene emulsion is 50-70wt%.

[0022] As preferred, in step 2), the temperature of the stirring is room temperature, and the time is 0.5-1.5h.

[0023] As preferred, in step 3), the time of the ultrasonic dispersion is not less than 15min.

[0024] As preferred, in step 4), the coating method is spin coating, the spin coating speed is 2000-3000rpm, and the time is 30-60s.

[0025] As preferred, in step 5), the temperature of the vacuum drying is 50-60℃, and the time is 4-8h.

[0026] As preferred, in step 5), the thickness of the composite film is 10-20 microns.

[0027] In a second aspect, the present application provides an application of the composite film with high infrared absorption and flexibility prepared by the above preparation method in preparing infrared stealth or wearable thermal management products.

[0028] Compared with the prior art, the present application has the following advantages:

[0029] (1) The present application uses oxidized polyethylene and polytetrafluoroethylene as a composite matrix to prepare a composite film, which has high flexibility on one hand, and low infrared transmittance on the other hand, showing good infrared shielding and reflecting effect, and can be applied to the fields of infrared stealth and wearable thermal management.

[0030] (2) The preparation method of the present application is green and simple, uses a water / ethanol mixed solvent system to avoid the use of organic solvents, and the entire operation process does not require complex equipment, and has good laboratory and industrial feasibility. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 FTIR infrared spectrum of the samples obtained in each example and comparative example. DETAILED DESCRIPTION

[0032] The present application will be further described below in combination with examples.

[0033] Example 1

[0034] (1) Preparation of PEO solution: Weigh 0.7g PEO (average molecular weight of 500,000) and add it to 30mL water / ethanol (20mL water, 10mL ethanol) mixed solvent. Stir for 2h under water bath heating at 40℃ to obtain a transparent viscous solution.

[0035] (2) Preparation of PEO / PTFE mixture: 2g of 60wt% PTFE emulsion was added to the above solution and stirred at room temperature for 1h. Then, ultrasonic dispersion was performed for no less than 15min to obtain a milky white viscous liquid.

[0036] (3) Preparation of PEO / PTFE composite film: The above mixture was spin-coated on a flexible PET substrate (2500 rpm, 40 s), and dried in a vacuum oven at 50°C for 6 h to obtain a flexible composite film material with a thickness of 15 micrometers.

[0037] Example 2

[0038] (1) Preparation of PEO solution: Weigh 1.0g PEO (average molecular weight of 500,000) and add it to 30mL water / ethanol (20mL water, 10mL ethanol) mixed solvent. Stir for 2h under water bath heating at 40℃ to obtain a transparent viscous solution.

[0039] (2) Preparation of PEO / PTFE mixture: 2g of 60wt% PTFE emulsion was added to the above solution and stirred at room temperature for 1h. Then, ultrasonic dispersion was performed for no less than 15min to obtain a milky white viscous liquid.

[0040] (3) Preparation of PEO / PTFE composite film: The above white viscous liquid was spin-coated on a flexible PET substrate (2500 rpm, 40 s), and dried in a vacuum oven at 50°C for 6 h to obtain a flexible composite film material with a thickness of 15 micrometers.

[0041] Example 3

[0042] (1) Preparation of PEO solution: Weigh 1.2g PEO (average molecular weight of 500,000) and add it to 30mL water / ethanol (20mL water, 10mL ethanol) mixed solvent. Stir for 2h under water bath heating at 40℃ to obtain a transparent viscous solution.

[0043] (2) Preparation of PEO / PTFE mixture: 2g of 60wt% PTFE emulsion was added to the above solution and stirred at room temperature for 1h. Then, ultrasonic dispersion was performed for no less than 15min to obtain a milky white viscous liquid.

[0044] (3) Preparation of PEO / PTFE composite film: The above white viscous liquid was spin-coated on a flexible PET substrate (2500 rpm, 40 s), and dried in a vacuum oven at 50°C for 6 h to obtain a flexible composite film material with a thickness of 15 micrometers.

[0045] Example 4

[0046] (1) Preparation of PEO solution: Weigh 1.4g PEO (average molecular weight of 500,000) and add it to 30mL water / ethanol (20mL water, 10mL ethanol) mixed solvent. Stir for 2h under water bath heating at 40℃ to obtain a transparent viscous solution.

[0047] (2) Preparation of PEO / PTFE mixture: 2g of 60wt% PTFE emulsion was added to the above solution and stirred at room temperature for 1h. Then, ultrasonic dispersion was performed for no less than 15min to obtain a milky white viscous liquid.

[0048] (3) Preparation of PEO / PTFE composite film: The above white viscous liquid was spin-coated on a flexible PET substrate (2500 rpm, 40 s), and dried in a vacuum oven at 50°C for 6 h to obtain a flexible composite film material with a thickness of 15 micrometers.

[0049] Comparative Example 1: The difference from Example 4 is that no PTFE emulsion was added.

[0050] (1) Preparation of PEO solution: Weigh 1.4g PEO (average molecular weight of 500,000) and add it to 30mL water / ethanol (20mL water, 10mL ethanol) mixed solvent. Stir for 2h under water bath heating at 40℃ to obtain a transparent viscous solution.

[0051] (2) Preparation of PEO membrane: The above solution was spin-coated on a flexible PET substrate (2500 rpm, 40 s), and dried in a vacuum oven at 50 °C for 6 h to obtain a membrane material with a thickness of 15 micrometers.

[0052] Comparative Example 2: The difference from Example 4 is that PEO was not added.

[0053] (1) Preparation of PTFE mixture: Weigh 2g of 60wt% PTFE emulsion and add it to 30mL of water / ethanol (20mL water, 10mL ethanol) mixed solvent. Stir at room temperature for 1h, and then perform ultrasonic dispersion treatment for no less than 15min to obtain white liquid.

[0054] (2) Preparation of PTFE membrane: The above white viscous liquid was spin-coated on a flexible PET substrate (2500 rpm, 40 s), and dried in a vacuum oven at 50°C for 6 h to obtain a membrane material with a thickness of 15 micrometers.

[0055] Comparative Example 3: The difference from Example 4 is that more PEO was added.

[0056] (1) Preparation of PEO solution: Weigh 1.6g PEO (average molecular weight of 500,000) and add it to 30mL water / ethanol (20mL water, 10mL ethanol) mixed solvent. Stir for 2h under water bath heating at 40℃ to obtain a transparent viscous solution.

[0057] (2) Preparation of PEO / PTFE mixture: 2g of 60wt% PTFE emulsion was added to the above solution and stirred at room temperature for 1h. Then, ultrasonic dispersion was performed for no less than 15min to obtain a milky white viscous liquid.

[0058] (3) Preparation of PEO / PTFE composite film: The above white viscous liquid was spin-coated on a flexible PET substrate (2500 rpm, 40 s), and dried in a vacuum oven at 50°C for 6 h to obtain a flexible composite film material with a thickness of 15 micrometers.

[0059] Performance testing

[0060] The products obtained in each embodiment and comparative example were subjected to performance tests, and the results are as follows: Figure 1 As shown.

[0061] Table 1

[0062] Case Flexibility (bending radius, mm) Adhesion (tape test) Example 1 3.2 4B Example 2 2.5 5B Example 3 2.3 4B Example 4 2.6 4B Comparative Example 1 5.3 3B Comparative Example 3 2.0 3B

[0063] Depend on Figure 1 As can be seen, in Examples 1-4, the composite films prepared with appropriate PEO and PTFE ratios exhibited significantly low transmittance in the 8-25 micrometer infrared band, and the resulting films were uniform, dense, and flexible. With increasing PEO content, the film-forming properties, density, and flexibility of the film were improved, and the intensity of the COC and -OH absorption peaks in the FTIR spectrum increased with increasing PEO content. However, the sample in Comparative Example 2 was not subjected to FTIR infrared spectroscopy testing due to its poor film-forming quality.

[0064] Table 1 shows that Examples 1-4 exhibited excellent flexibility and adhesion. Comparative Example 1, without the addition of PTFE emulsion and consisting solely of PEO film, lacked PTFE support, resulting in poor flexibility and only moderate adhesion; the film's shielding effect was also poor. Comparative Example 2, also without PEO and consisting solely of PTFE film, showed poor film quality and was therefore not tested, indicating that PTFE film formation alone is difficult and requires the structural framework of PEO. Comparative Example 3, with an increased PEO content, exhibited optimal flexibility, but moderate adhesion and was prone to cracking or warping during film formation, leading to reduced mechanical properties.

[0065] Unless otherwise specified, the raw materials and equipment used in this invention are all commonly used in the field; unless otherwise specified, the methods used in this invention are all conventional methods in the field.

[0066] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications, alterations, and equivalent transformations made to the above embodiments based on the technical essence of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A method for preparing a composite thin film with high infrared absorption and flexibility, characterized in that: Includes the following steps: 1) Add oxidized polyethylene to the solvent, heat and stir to form a homogeneous solution; 2) Add polytetrafluoroethylene emulsion to the solution obtained in 1), stir evenly to form a mixture; the mass ratio of oxidized polyethylene to polytetrafluoroethylene is (0.7-1.4):1.2; 3) The mixture is ultrasonically dispersed to form a uniform dispersion; 4) Coat the dispersion onto the surface of a PET substrate; 5) Vacuum drying to obtain a PEO / PTFE-based composite film.

2. The preparation method according to claim 1, characterized in that: In step 1), The average molecular weight of the oxidized polyethylene is 400,000-600,000; The concentration of oxidized polyethylene in the homogeneous solution is 2-5 wt%.

3. The preparation method according to claim 1 or 2, characterized in that: In step 1), the solvent is a mixture of water and ethanol.

4. The preparation method according to claim 3, characterized in that: In step 1), the volume ratio of water to ethanol in the mixed solvent is (1-3):

1.

5. The preparation method according to claim 1 or 2, characterized in that: In step 1), the heating and stirring temperature is 40-50℃ and the time is 1-3h.

6. The preparation method according to claim 1, characterized in that: In step 2), the concentration of the polytetrafluoroethylene emulsion is 50-70 wt%.

7. The preparation method according to claim 1, characterized in that: In step 4), the coating method is spin coating, the spin coating speed is 2000-3000 rpm, and the time is 30-60 s.

8. The preparation method according to claim 1, characterized in that: In step 5), the vacuum drying temperature is 50-60℃ and the time is 4-8h.

9. The preparation method according to claim 1 or 8, characterized in that: In step 5), the thickness of the composite film is 10-20 micrometers.

10. The application of the composite film with high infrared absorption and flexibility obtained by the preparation method according to any one of claims 1-9 in the preparation of infrared stealth or wearable thermal management products.

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