Hollow silicon sphere / polytetrafluoroethylene heat insulation film and preparation method thereof

Abstract

The application discloses a hollow silicon ball / polytetrafluoroethylene heat insulation film and a preparation method thereof, and belongs to the technical field of fiber film materials. Hollow silicon balls are dispersed in a certain organic solvent; an aqueous solution of polyethylene oxide is used as a co-spinning agent; the co-spinning agent and the hollow silicon ball dispersion liquid are stirred uniformly, and polytetrafluoroethylene emulsion is added to configure a precursor spinning liquid; spinning is performed through an electrostatic spinning equipment, and a hollow silicon ball / polytetrafluoroethylene fiber heat insulation film is obtained after drying and calcination. The hollow silicon ball / polytetrafluoroethylene fiber heat insulation film has the characteristics of good medium and low temperature stability, low thermal conductivity and excellent flexibility, has a wide application in the thermal management of intelligent electronic products, reduces the overheating phenomenon of electronic products during long-time use, improves the comfort degree during long-time use, and the preparation process is simple, and an application idea of the polytetrafluoroethylene fiber film in the medium and low temperature heat insulation field is provided.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of fiber membrane materials, and particularly relates to a preparation method of hollow silica sphere / polytetrafluoroethylene heat insulation film. BACKGROUND

[0002] With the advent of the 5G era, people's demand for high-performance, multi-functional and small-size electronic devices is increasing. However, a large number of power-consuming components in the increasingly shrinking device space will generate more heat, thereby reducing the working efficiency and service life of other electronic components, and the heat radiation will stimulate the human skin, reducing the user's experience. The traditional heat insulation materials have the disadvantages of thick texture, poor air permeability, fragility, and non-bendability, which cannot meet the heat insulation requirements of narrow space and curved surface.

[0003] Traditional fiber heat insulation materials are mainly ceramic heat insulation materials, which have excellent heat insulation performance at high temperature. However, the preparation process is complex, and the material is usually brittle, which is not conducive to mass production and wide use.

[0004] Polytetrafluoroethylene fibers have excellent flexibility and thermal stability, as well as low dielectric constant, and have more applications in the field of heat insulation of medium and low temperature electronic products.

[0005] The mainstream method for preparing polytetrafluoroethylene fibers at present is the biaxial stretching method and the film splitting spinning method. The fiber film prepared by the biaxial stretching method has high porosity and narrow pore size distribution, but the biaxial stretching technology is strictly protected abroad, and there is a large difference between domestic and foreign biaxial stretching technologies, resulting in high application cost. The film splitting spinning method has simple production process, no pollution and high fiber strength, but the heat treatment requires extremely high temperature, and the prepared fibers are uneven in thickness, which is not conducive to the application of fiber membranes in the heat insulation direction.

[0006] In reference D. Tao, X. Li, Y. Dong, et al, Super-low thermal conductivity fibrous nanocomposite membrane of hollow silica / polyacrylonitrile, Compos. Sci. Technol. 188 (2020) 107992, Tao et al. mixed hollow silica spheres with polyacrylonitrile solution uniformly and then electrospun, when the content of hollow silica spheres was 15%, the thermal conductivity of the fiber membrane was 0.0163 W / (m·K), which was 69.7% lower than that of pure polyacrylonitrile fiber membrane. Since polyacrylonitrile is a hydrophilic material, the thermal conductivity of water is 0.5810 W / (m·K), and the water absorption of the fiber membrane will significantly reduce the heat insulation effect.

[0007] In reference B. Zhang, Z. Tong, Y. Pang, et al, Design and electrospunclosed cell structured SiO2nanocomposite fiber by hollow SiO2 / TiO2spheres forthermal insulation, Compos. Sci. Technol. 218 (2022) 109152, Zhang et al. added hollow silica spheres to zirconia fibers, and when the hollow silica sphere content was 15%, the thermal conductivity of the fiber membrane was 0.0253 W / (m·K), and the reduction was 24.7%, but zirconia is a brittle material and loses thermal insulation capacity after being stretched to a certain extent.

[0008] Currently, electrospinning is mainly used for polyacrylonitrile materials on organic thermal insulation fibers. Polyacrylonitrile fibers have high spinnability and uniform diameter, and are ideal thermal insulation materials. However, polyacrylonitrile is a hydrophilic material, and after absorbing water, the thermal insulation effect will be greatly reduced, and post-processing is required to improve hydrophobicity. Electrospun ceramic fibers have excellent thermal insulation performance, but their brittleness limits their application range.

[0009] The present application combines the advantages of low cost, easy operation and high porosity of electrospinning and the excellent thermal insulation effect of hollow silica spheres. Under the premise of ensuring the pore size and porosity between the fibers unchanged, the hollow silica spheres are embedded in the polytetrafluoroethylene fibers by electrospinning technology, reducing the solid-solid heat transfer mode between single fibers, increasing the solid-gas-solid heat transfer mode, enhancing the thermal insulation performance of the material, and maintaining the flexibility and high hydrophobicity of the polytetrafluoroethylene fibers. The shortcomings of traditional thermal insulation materials, such as large thickness, fragility, and poor thermal insulation performance of organic fibers due to water absorption, are solved, and the thermal conductivity is similar to that of the GORE thermal insulation film. SUMMARY

[0010] The purpose of the present application is to provide a preparation method for a hollow silica sphere / polytetrafluoroethylene thermal insulation film that is foldable, has high porosity, is lightweight, has a simple process and is low in cost, in view of the shortcomings and problems of the prior art.

[0011] To achieve the above-mentioned purpose, the present application provides the following solutions:

[0012] A preparation method of a hollow silica sphere / polytetrafluoroethylene thermal insulation film, wherein hollow silica spheres are used as dopants, polytetrafluoroethylene emulsion is used as a base liquid, and polyethylene oxide aqueous solution is used as a spinning aid, and the polytetrafluoroethylene fibers are doped by electrospinning technology.

[0013] It includes the following steps:

[0014] 1) dispersing the prepared hollow silica spheres in an organic solvent, adding a spinning aid and a polytetrafluoroethylene emulsion, stirring to obtain a spinning precursor solution;

[0015] 2) electrospinning the precursor solution to obtain a precursor fiber membrane;

[0016] 3) drying and calcining the precursor fiber membrane to obtain a hollow silica sphere / polytetrafluoroethylene fiber membrane.

[0017] The mass ratio of the organic solvent, the spinning aid and the polytetrafluoroethylene emulsion is (0.8~1):1:(0.8~1.2);

[0018] The drying temperature in step 3) is 50~70 ℃, and the sintering temperature is 370~380 ℃.

[0019] Further, the organic solvent in step 1) is one or more of ethanol, n-hexane, N,N-dimethylformamide and N,N-dimethylacetamide, and the mass percentage concentration of the hollow silica spheres is 2%~10%.

[0020] Further, the spinning aid in step 1) is a polyethylene oxide aqueous solution and the mass percentage concentration is 3%~13%.

[0021] Further, the mass percentage concentration of the polytetrafluoroethylene emulsion in step 1) is 30%~60%.

[0022] Further, the stirring parameters in step 1) are as follows: the stirring temperature is 20 ℃~60 ℃, and the stirring speed is 200 rpm~800 rpm.

[0023] Further, the electrospinning process parameters in step 2) are as follows: a 20G spinning needle is selected, the rotating speed of the drum is 50 rpm, the spinning distance is 10~20 cm, the spinning speed is 0.5~1.2 mL / h, and the spinning voltage is 8~12 KV.

[0024] Further, the drying temperature in step 3) is 70 ℃, and the time is 5 h.

[0025] Further, the calcination parameters in step 3) are as follows: the temperature is raised to 370~380 ℃ at a speed of 5~10 ℃ / min, and the calcination is performed for 10 min.

[0026] Compared with the prior art, the present application has the following advantages.

[0027] The hollow silica sphere has excellent heat insulation effect due to its shell encapsulating static air, reducing gas flow, increasing solid-gas contact interface, prolonging heat transfer path, and delaying heat diffusion. The application utilizes the high flexibility and hydrophobicity of the polytetrafluoroethylene fiber membrane, combines the advantages of low cost, easy operation, and high porosity of electrospinning and the excellent heat insulation effect of the hollow silica sphere, embeds the hollow silica sphere into the polytetrafluoroethylene fiber by the electrospinning technology under the premise of ensuring the pore size and porosity between the fibers unchanged, reduces the solid-solid heat transfer mode between the single fibers, increases the solid-gas-solid heat transfer mode, enhances the heat insulation performance of the material, and maintains the flexibility and high hydrophobicity of the polytetrafluoroethylene fiber. The application solves the problems of large thickness, fragility of traditional heat insulation materials, and poor heat insulation performance caused by water absorption of organic fibers, and reaches the level similar to the heat insulation film of GORE company in terms of thermal conductivity.

[0028] The electrospun fiber membrane has the characteristics of small pore size, high porosity, and good flexibility. By embedding the hollow silica sphere in the fiber, a certain amount of static air is doped in the fiber, and the heat transfer resistance in the fiber is increased. The heat transfer is significantly reduced, and the heat insulation performance is obviously improved.

[0029] The hollow silica sphere / polytetrafluoroethylene heat insulation film provided by the application has excellent heat insulation performance, and the thermal conductivity is as low as 0.0193 W / (m·K). BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 It is a TEM image of the hollow silica sphere used in the patent embodiment of the application.

[0031] Figure 2 It is a physical image in the patent embodiment 3 of the application.

[0032] Figure 3 It is a thermal imaging image of the heat insulation film prepared in the patent embodiment 3 of the application and the pure polytetrafluoroethylene fiber film after being placed on a 90 DEG C hot stage for 10 min. DETAILED DESCRIPTION

[0033] The technical solutions of the application will be described in detail below with specific embodiments, so that the technical solutions of the application can be better understood and implemented by those skilled in the art.

[0034] The polytetrafluoroethylene emulsion used in the following examples is from Zhonghao Chen Guang Co., Ltd., and the hollow silica spheres are self-made in the laboratory. The preparation method is as follows: 4.05 g of glucose is uniformly stirred with 45 mL of deionized water and then placed in a 100 mL hydrothermal kettle, which is placed in an oven at 160 ℃ for 24 h. The precipitate is placed in a centrifuge at a speed of 10,000 r / min, washed with water and ethanol three times respectively, and then dried at 60 ℃ for 10 h to obtain nanocarbon spheres. Take 0.2 g of nanocarbon spheres and disperse them in 50 mL of ethanol, add 2 mL of water and 2 mL of ammonia water, adjust the pH value to about 10, then mix 2 mL of tetraethyl orthosilicate and 8 mL of ethanol uniformly and slowly drop them into the dispersion, and react at room temperature for 20 h. Repeat the above centrifugation and drying operation, and place the dried powder in a tube furnace at 550 ℃ for 2 h to remove the nanocarbon spheres to obtain hollow silica spheres with an average particle size of 280 nm.

[0035] Example 1

[0036] This example provides a hollow silica sphere / polytetrafluoroethylene thermal insulation film, and the preparation method is as follows:

[0037] First step: ultrasonically disperse 50 mg of hollow silica spheres in N,N-dimethylacetamide, stir uniformly, and obtain a dispersion liquid with a mass fraction of 3%; dissolve 0.3 g of polyethylene oxide in 9.7 g of water to obtain a spinning aid with a mass fraction of 3%.

[0038] Second step: take 2 g of polytetrafluoroethylene emulsion with a mass fraction of 60% and add 2.5 g of spinning aid, then add 1.9 g of hollow silica sphere dispersion liquid, stir at 30 ℃ and 600 rpm for 10 h to obtain a spinning solution.

[0039] Third step: electrospinning, parameters: 11 KV, receiving distance 15 cm, spinning speed 1 mL / h, and drum receiver speed 50 rpm. The hollow silica sphere / polytetrafluoroethylene precursor fiber membrane is prepared by electrospinning.

[0040] Fourth step: dry the precursor fiber membrane at 70 ℃ for 5 h, then place it in a muffle furnace for calcination. The sintering process is as follows: start from room temperature (25 ℃), heat to 380 ℃ at a rate of 5 ℃ / min, calcine for 10 min, and naturally cool to room temperature to obtain a hollow silica sphere / polytetrafluoroethylene fiber membrane.

[0041] Example 2

[0042] This example provides a hollow silica sphere / polytetrafluoroethylene thermal insulation film, and the preparation method is as follows:

[0043] First step: 80 mg of hollow silica spheres were ultrasonically dispersed in N, N-dimethylformamide, stirred uniformly to obtain a dispersion with a mass fraction of 5%; 0.7 g of polyethylene oxide was dissolved in 9.3 g of water to obtain a spinning aid with a mass fraction of 7%.

[0044] Second step: 2 g of polytetrafluoroethylene emulsion with a mass fraction of 60% was added to 2.1 g of the spinning aid, and then 1.9 g of the hollow silica sphere dispersion was added; the mixture was stirred at 30 °C and 200 rpm for 10 h to obtain a spinning solution.

[0045] Third step: electrospinning was performed with the following parameters: 12 KV, receiving distance 15 cm, spinning speed 1 mL / h, and drum receiver speed 50 rpm. A hollow silica sphere / polytetrafluoroethylene precursor fiber membrane was prepared by electrospinning.

[0046] Fourth step: the precursor fiber membrane was dried at 70 °C for 5 h and then calcined in a muffle furnace. The sintering process was as follows: starting from room temperature (25 °C), the temperature was increased to 380 °C at a rate of 8 °C / min, calcination was performed for 10 min, and the sample was naturally cooled to room temperature. A hollow silica sphere / polytetrafluoroethylene fiber membrane was obtained.

[0047] Example 3

[0048] This example provides a hollow silica sphere / polytetrafluoroethylene thermal insulation membrane, which is prepared as follows:

[0049] First step: 100 mg of hollow silica spheres were ultrasonically dispersed in N, N-dimethylformamide, stirred uniformly to obtain a dispersion with a mass fraction of 7%; 0.5 g of polyethylene oxide was dissolved in 9.5 g of water to obtain a spinning aid with a mass fraction of 5%.

[0050] Second step: 2 g of polytetrafluoroethylene emulsion with a mass fraction of 60% was added to 2.1 g of the spinning aid, and then 1.9 g of the hollow silica sphere dispersion was added; the mixture was stirred at 30 °C and 400 rpm for 10 h to obtain a spinning solution.

[0051] Third step: electrospinning was performed with the following parameters: 8 KV, receiving distance 15 cm, spinning speed 0.5 mL / h, and drum receiver speed 50 rpm. A hollow silica sphere / polytetrafluoroethylene precursor fiber membrane was prepared by electrospinning.

[0052] Fourth step: the precursor fiber membrane was dried at 70 °C for 5 h and then calcined in a muffle furnace. The sintering process was as follows: starting from room temperature (25 °C), the temperature was increased to 380 °C at a rate of 10 °C / min, calcination was performed for 10 min, and the sample was naturally cooled to room temperature. A hollow silica sphere / polytetrafluoroethylene fiber membrane with a thickness of 200 μm and a grammage of 60.75 g / m 2Hollow silica sphere / polytetrafluoroethylene fiber membrane.

[0053] In Example 3, the prepared fiber membrane has good flexibility as shown in Figure 2

[0054] The thermal conductivity of the pure polytetrafluoroethylene fiber membrane and the heat insulation membrane prepared in Example 3 is 0.0368 W / (m·K) and 0.0197 W / (m·K), respectively. In order to simulate the application in electronic components, the two kinds of fiber membranes are placed on the heating platform at 90℃ in turn and heated for 10 min, and then the temperature difference is calculated after testing the heating platform (position 1) and the fiber membrane (position 2), respectively. Figure 3 In formula (I), a is a pure polytetrafluoroethylene membrane, Figure 3 In formula (II), b is the heat insulation membrane prepared in Example 3. Under the condition of similar thickness, the temperature difference of the fiber membrane added with hollow silica spheres is 14℃, and the temperature difference of the pure polytetrafluoroethylene membrane is 6℃. It is indicated that the addition of hollow silica spheres has obvious improvement on the heat insulation performance of the polytetrafluoroethylene fiber membrane.

[0055] The above-described examples are only used to describe the preferred modes of the present application, and do not limit the scope of the present application. Without departing from the design spirit of the present application, various modifications and improvements of the technical solutions of the present application made by those skilled in the art shall fall within the protection scope determined by the claims of the present application.​

Claims

1. A method for preparing a hollow silicon sphere / polytetrafluoroethylene heat insulation film, characterized in that, A hollow silica sphere is used as a dopant, a polytetrafluoroethylene emulsion is used as a base liquid, and a polyethylene oxide aqueous solution is used as a spinning aid, and a polytetrafluoroethylene fiber is doped with a structure by using an electrospinning technology; It comprises the following steps: 1) dispersing the prepared hollow silica sphere in an organic solvent, adding a spinning aid and a polytetrafluoroethylene emulsion, and stirring uniformly to prepare a spinning precursor solution; 2) electrospinning the precursor solution to obtain a precursor fiber membrane; 3) drying the precursor fiber membrane and calcining to obtain a hollow silica sphere / polytetrafluoroethylene heat insulation film; The mass ratio of the used organic solvent, spinning aid and polytetrafluoroethylene emulsion is (0.8~1):1:(0.8~1.2); The drying temperature in step 3) is 50~70 ℃, and the sintering temperature is 370~380 ℃; In step 1), the hollow silica sphere is dispersed in an organic solvent, the organic solvent is one or more of ethanol, n-hexane, N,N-dimethylformamide and N,N-dimethylacetamide, and the mass percentage concentration of the hollow silica sphere is 2%~10%; In step 1), the spinning aid is a polyethylene oxide aqueous solution and the mass percentage concentration is 3%~13%; The mass percentage concentration of the polytetrafluoroethylene emulsion is 30~60%.

2. The method of claim 1, wherein, The stirring parameters in step 1) are as follows: the stirring temperature is 20~60 ℃, and the stirring speed is 200 rpm~800 rpm.

3. The preparation method according to claim 1, characterized in that, The electrospinning process parameters in step 2) are as follows: a 20G spinning needle is selected, the rotating speed of the drum is 50 rpm, the spinning distance is 10~20 cm, the spinning speed is 0.5~1.2 mL / h, and the spinning voltage is 8~12 KV.

4. The preparation method according to claim 1, characterized in that, The drying temperature in step 3) is 70 ℃, and the time is 5 h.

5. The method of claim 1, wherein the step of forming the first and second layers is performed by a process selected from the group consisting of: sputtering, evaporation, and chemical vapor deposition. The calcination parameters in step 3) are as follows: the temperature is raised to 370~380 ℃ at a speed of 5~10 ℃ / min, and the calcination is performed for 10 min.

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