A method for improving the nucleation of the γ phase of polyvinylidene fluoride (PVDF), a γ phase PVDF dielectric film based on the nucleation method, and a preparation method thereof.

Abstract

A method for improving the nucleation of the γ phase in polyvinylidene fluoride (PVDF), a γ phase PVDF dielectric film based on the nucleation method, and a preparation method thereof are disclosed. The method involves using ceramic powder in the PVDF film material to enhance the nucleation ability of the γ phase crystals, improve the hydrophilicity of the PVDF film, and enhance the high-temperature dielectric properties of the PVDF film material. The dielectric film raw materials include 0-0.2 parts of ceramic powder (NBT), 10 parts of polyvinylidene fluoride (PVDF), and 200-204 parts of N,N-dimethylformamide (DMF). The preparation method is as follows: 1) Using N,N-dimethylformamide... 1) Prepare a 5% ceramic powder / polyvinylidene fluoride solution using amide as a solvent; 2) Drop the solution from step 1) onto a glass slide and cure it into a film in a vacuum oven at 68-72℃; 3) Melt the cured film obtained in step 2) on a hot stage at 200℃-220℃ to eliminate thermal history, and then rapidly cool it to 150-170℃ for isothermal crystallization until the blended film is completely crystallized; The preparation method of the γ-phase polyvinylidene fluoride dielectric film of the present invention is simple, convenient to operate, and has excellent performance, such as high temperature resistance, corrosion resistance, and strong piezoelectricity and ferroelectricity.

Description

Technical Field

[0001] This invention belongs to the field of polyvinylidene fluoride composite film preparation technology, specifically relating to a method for improving the nucleation of the γ phase of polyvinylidene fluoride, a γ phase polyvinylidene fluoride dielectric film based on the nucleation method, and the preparation method thereof. Background Technology

[0002] The functionalization of polymer thin film materials has always attracted widespread attention. Polyvinylidene fluoride (PVDF) is a polycrystalline semi-crystalline polymer, with three most common crystal forms: α, β, and γ. Among them, α-phase PVDF has excellent mechanical properties and can be used in electronics, chemicals, and solar energy devices; β-phase PVDF has good piezoelectric and ferroelectric effects and is widely used in transducers in various fields, such as varistors and humidity sensors; γ-phase also has ferroelectric and piezoelectric properties, and the Curie temperature of γ-phase is higher than that of β-phase, making it an excellent high-temperature resistant flexible piezoelectric material that can be used in storage devices and smart appliances. However, the preparation of γ-phase PVDF generally requires long-term high-temperature operation, which is not conducive to industrialization. Summary of the Invention

[0003] To overcome the shortcomings of the prior art, the present invention aims to provide a method for improving the nucleation of the γ phase of polyvinylidene fluoride (PVDF), a γ phase PVDF dielectric film based on the nucleation method, and a preparation method thereof. This method uses ceramic powder to improve the nucleation ability of γ phase crystals in PVDF film materials and enhance the hydrophilicity of PVDF films or to improve the high-temperature dielectric properties of PVDF film materials. It features low reaction temperature, short reaction time, and ease of industrialization.

[0004] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0005] A method for improving the nucleation of the γ phase in polyvinylidene fluoride (PVDF) involves adding ceramic powder to the PVDF membrane material to enhance the nucleation ability of the γ phase crystals, as well as improving the hydrophilicity and high-temperature dielectric properties of the PVDF membrane material.

[0006] In the polyvinylidene fluoride membrane material, as the ceramic powder content increases, the α-crystalline polyvinylidene fluoride transforms into the γ-crystalline form.

[0007] The ceramic powder increased the nucleation rate of the γ phase of polyvinylidene fluoride and accelerated the crystallization rate of polyvinylidene fluoride.

[0008] The γ-phase polyvinylidene fluoride dielectric film based on the above nucleation method comprises 0-0.2 parts of ceramic powder (NBT), 10 parts of polyvinylidene fluoride, and 200-204 parts of N,N-dimethylformamide (DMF).

[0009] The mass-average molecular weight of the polyvinylidene fluoride is 107,000.

[0010] The ceramic powder is sodium bismuth titanate with a particle size of 250nm-350nm.

[0011] A method for preparing a γ-phase polyvinylidene fluoride dielectric film specifically includes the following steps:

[0012] 1) Weigh 0-0.2 parts of ceramic powder and 10 parts of polyvinylidene fluoride, and use 200-204 parts of N,N-dimethylformamide as a solvent to prepare a ceramic powder / polyvinylidene fluoride solution with a concentration of 5% and a blending mass ratio of 0-2%.

[0013] 2) Drop the ceramic powder / polyvinylidene fluoride solution with a blending mass ratio of 0%-2% obtained in step 1) onto a glass slide and cure it into a film in a vacuum oven at 68-72℃.

[0014] 3) Melt the cured film obtained in step 2) on a hot plate at 200℃~220℃ to eliminate thermal history, then rapidly cool it to 150-170℃ and crystallize it at a constant temperature for 6~8 hours until the blended film is completely crystallized.

[0015] The crystallized blend film was characterized by polarizing microscopy, infrared spectroscopy, and scanning electron microscopy to be γ-crystalline.

[0016] The beneficial effects of this invention are:

[0017] Compared with existing technologies, the ceramic powder (NBT) component in this invention is a ferroelectric material with a trigonal phase structure at room temperature. The polymer-based composite material made from PVDF and ceramic powder (NBT) has advantages such as mechanical flexibility, ease of processing, and relatively high strain, making it a promising candidate for miniaturization of electronic devices and high-density energy storage systems.

[0018] This invention induces a phase transition by adding ceramic powder (NBT) and then prepares a film of uniform thickness using a solution casting method. Comparative analysis revealed that polyvinylidene fluoride (PVDF) increased the γ-phase nucleation rate in the NBT-added composite film.

[0019] This invention employs a solution casting method to prepare high-temperature resistant polyvinylidene fluoride (PVDF) dielectric composite films. The use of ceramic powder (NBT) increases the nucleation rate of the γ-phase in PVDF. This allows for the rapid preparation of high-temperature resistant PVDF dielectric films. This invention utilizes a polymer crystalline material composite with ceramic dielectric materials to prepare a multifunctional composite film with dielectric properties. The preparation method is simple, convenient, and imparts excellent dielectric properties and high-temperature resistance to PVDF, making it promising for applications in pressure sensors, automotive motors, lithium-ion batteries, and high-temperature resistant thermistor devices. Attached Figure Description

[0020] Figure 1 These are polarization morphology images of Embodiments 1, 2, 3, 4, and 5 of the present invention; wherein, Figure 1 (a) is a polarized morphology image of crystals grown at 150°C in Example 1; Figure 1 (b) is a polarized morphology image of crystals grown at 150°C in Example 2; Figure 1 (c) is a polarized morphology image of the crystals grown at 150°C in Example 3; Figure 1 (d) is a polarized morphology image of the crystals grown at 150°C in Example 4; Figure 1 (e) is a polarized morphology image of the crystal grown at 150°C in Example 5.

[0021] Figure 2 This is a scanning electron microscope image of the present invention; wherein, Figure 2 (a) is a scanning electron microscope image of Example 1; Figure 2 (b) The ceramic powder / polyvinylidene fluoride is a scanning electron microscope image of Example 2; Figure 2 (c) Ceramic powder / polyvinylidene fluoride is an electron micrograph of Example 4.

[0022] Figure 3 These are the Fourier transform infrared spectra of Examples 1-5 of the present invention.

[0023] Figure 4 The content of γ-phase crystals is the content of ceramic powder (NBT) in Examples 1-5 of the present invention. Detailed Implementation

[0024] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0025] All the following tests are performed in triplicate to ensure accuracy.

[0026] Example 1:

[0027] A γ-phase polyvinylidene fluoride dielectric film, the raw materials of which include 0 parts of ceramic powder (NBT), 10 parts of polyvinylidene fluoride, and 200 parts of N,N-dimethylformamide (DMF).

[0028] 1) Weigh 10 parts of polyvinylidene fluoride granules with a mass average molecular weight of 107,000, and use 200 parts of N,N-dimethylformamide as a solvent to prepare a 5% polyvinylidene fluoride solution; at 150℃, pure polyvinylidene fluoride generates a small amount of γ-phase 0.4, and most of it generates α-phase;

[0029] 2) Drop the polyvinylidene fluoride solution obtained in step 1) onto a glass slide and cure it into a film in a vacuum oven at 70°C;

[0030] 3) Melt the cured film obtained in step 2) on a hot plate at 200°C to eliminate thermal history, then rapidly cool it to 150°C and crystallize it at a constant temperature for 6 hours until the blended film is completely crystallized.

[0031] The crystallized blend film was characterized by infrared spectroscopy, polarizing microscopy, and scanning electron microscopy. The polyvinylidene fluoride composite film showed that it had an α crystal form and a small amount of 0.4 γ crystal form was generated. Furthermore, the α crystal form was difficult to transform into the γ´ crystal form.

[0032] Example 2:

[0033] A γ-phase polyvinylidene fluoride dielectric film, the raw materials of which include 0.05 parts of ceramic powder (NBT), 10 parts of polyvinylidene fluoride, and 201 parts of N,N-dimethylformamide (DMF).

[0034] 1) Weigh 0.05 parts of ceramic powder and 10 parts of polyvinylidene fluoride, and use 201 parts of N,N-dimethylformamide as solvent to prepare a ceramic powder / polyvinylidene fluoride solution with a total concentration of 5% and a blending mass ratio of 1:200.

[0035] 2) Drop the ceramic powder / polyvinylidene fluoride solution with a mass ratio of 1:200 from step 1) onto a glass slide and cure it into a film in a vacuum oven at 70°C;

[0036] 3) Melt the cured film obtained in step 2) on a hot plate at 200°C to eliminate thermal history, then rapidly cool it to 150°C and crystallize it at a constant temperature for 6.5 hours to allow the blended film to crystallize completely.

[0037] The crystallized blend film was characterized by infrared spectroscopy and polarized light microscopy. The polyvinylidene fluoride composite film showed γ-crystal morphology characteristics and the γ-crystal phase content was increased from 0.44. This indicates that the ceramic powder (NBT) promoted the formation of γ-crystals in PVDF.

[0038] Example 3:

[0039] A γ-phase polyvinylidene fluoride dielectric film, the raw materials of which include 0.1 parts of ceramic powder (NBT), 10 parts of polyvinylidene fluoride, and 202 parts of N,N-dimethylformamide (DMF).

[0040] 1) Weigh 0.10 parts of ceramic powder and 10 parts of polyvinylidene fluoride, and use 202 parts of N,N-dimethylformamide as solvent to prepare a ceramic powder / polyvinylidene fluoride solution with a total concentration of 5% and a blending mass ratio of 1:100.

[0041] 2) The ceramic powder / polyvinylidene fluoride solution with a mass ratio of 1:100 in step 1) is dropped onto a glass slide and cured into a film in a vacuum oven at 70°C;

[0042] 3) Melt the cured film obtained in step 2) on a hot plate at 200°C to eliminate thermal history, then rapidly cool it to 150°C and crystallize it at a constant temperature for 7 hours to allow the blended film to crystallize completely.

[0043] The crystallized blend film was characterized by infrared spectroscopy and polarized light microscopy. The polyvinylidene fluoride composite film showed γ-crystal morphology characteristics and the γ-crystal phase content increased significantly by 0.7%. This indicates that the ceramic powder (NBT) can greatly promote the formation of γ-crystals in PVDF.

[0044] Example 4:

[0045] A γ-phase polyvinylidene fluoride dielectric film, the raw materials of which include 0.15 parts of ceramic powder (NBT), 10 parts of polyvinylidene fluoride, and 203 parts of N,N-dimethylformamide (DMF).

[0046] 1) Weigh 0.15 parts of ceramic powder and 10 parts of polyvinylidene fluoride, and use 203 parts of N,N-dimethylformamide as solvent to prepare a ceramic powder / polyvinylidene fluoride solution with a total concentration of 5% and a blending mass ratio of 3:200.

[0047] 2) The ceramic powder / polyvinylidene fluoride solution with a mass ratio of 3:200 in step 1) is dropped onto a glass slide and cured into a film in a vacuum oven at 70°C;

[0048] 3) Melt the cured film obtained in step 2) on a hot plate at 200°C to eliminate thermal history, then rapidly cool it to 150°C and crystallize it at a constant temperature for 7.5 hours to allow the blended film to crystallize completely.

[0049] The crystallized blend film was characterized by infrared spectroscopy and polarized light microscopy. The polyvinylidene fluoride composite film showed γ-crystal morphology characteristics, and the γ-crystal phase content continued to increase from 0.82. This indicates that the ceramic powder (NBT) can promote the formation of γ-crystals in PVDF.

[0050] Example 5:

[0051] A γ-phase polyvinylidene fluoride dielectric film, the raw materials of which include 0.2 parts of ceramic powder (NBT), 10 parts of polyvinylidene fluoride, and 204 parts of N,N-dimethylformamide (DMF).

[0052] 1) Weigh 0.2 parts of ceramic powder and 10 parts of polyvinylidene fluoride, and use 204 parts of N,N-dimethylformamide as solvent to prepare a ceramic powder / polyvinylidene fluoride solution with a total concentration of 5% and a blending mass ratio of 1:50.

[0053] 2) Drop the ceramic powder / polyvinylidene fluoride solution with a mass ratio of 1:50 from step 1) onto a glass slide and cure it into a film in a vacuum oven at 70°C.

[0054] 3) Melt the cured film obtained in step 2) on a hot plate at 200°C to eliminate thermal history, then rapidly cool it to 150°C and crystallize it at a constant temperature for 8 hours to allow the blended film to crystallize completely.

[0055] The crystallized blend film was characterized by infrared spectroscopy and polarized light microscopy. The polyvinylidene fluoride composite film showed γ-crystal morphology characteristics, and the γ-crystal phase content decreased from 0.79%. This indicates that the ceramic powder (NBT) can promote the formation of γ-crystals in PVDF, but the promoting effect will be reduced when the content exceeds 1.5%.

[0056] See Figure 1 and Figure 2 It can be seen that under certain conditions, after adding ceramic powder (NBT), polyvinylidene fluoride has a high content of γ crystals, and the volume of γ crystals becomes smaller.

[0057] See Figure 3 It can be seen that the crystallization temperature increases with the addition of ceramic powder (NBT), reaching 763 cm⁻¹. -1 and 976cm -1 The α crystallization peak is lower, indicating that the ceramic powder (NBT) has a certain inhibitory effect on the nucleation of the α phase; 838 cm⁻¹ -1 The increased crystallization peaks of γ / β indicate that the ceramic powder (NBT) has a certain nucleation effect on the γ phase and accelerates the γ crystallization of polyvinylidene fluoride.

[0058] Statistical analysis of the γ-phase content was performed on Examples 1-5, see [link to relevant documentation]. Figure 4 It can be seen that when the content of ceramic powder (NBT) is 1.5%, the content of γ phase increases by nearly 100%; when the content of ceramic powder (NBT) is higher than 1.5%, the promoting effect on γ phase weakens.

Claims

1. A method for improving nucleation of the gamma phase of polyvinylidene fluoride, characterized by: The ceramic powder is added to the polyvinyl fluoride film material to improve the nucleation ability of the gamma phase crystal, and improve the hydrophilicity and high temperature dielectric performance of the polyvinyl fluoride film material; the nucleation method comprises the following specific steps: 1) 0.05-0.2 parts of ceramic powder and 10 parts of polyvinyl fluoride are weighed, and 200-204 parts of N,N-dimethylformamide is used as a solvent to prepare a ceramic powder / polyvinyl fluoride solution; 2) the ceramic powder / polyvinyl fluoride solution obtained in step 1) is dropped onto a glass slide, and is solidified into a film in a vacuum oven at 68-72 DEG C; 3) the solidified film prepared in step 2) is melted on a hot table at 200 DEG C~220 DEG C to eliminate thermal history, and then is rapidly cooled to 150-170 DEG C, and is crystallized at constant temperature for 6-8 hours until the blended film is completely crystallized. The ceramic powder is sodium bismuth titanate, and the particle size is 250nm-350nm.

2. A gamma phase polyvinylidene fluoride dielectric film based on the nucleation method of claim 1, characterized by: The raw materials include 0.05-0.2 parts of ceramic powder, 10 parts of polyvinyl fluoride, and 200-204 parts of N,N-dimethylformamide.

3. The gamma phase polyvinylidene fluoride dielectric film of claim 2, wherein: The mass average molecular weight of the polyvinyl fluoride is 107000.

4. Process for the preparation of a gamma phase polyvinylidene fluoride dielectric film according to any one of claims 2 to 3, characterized in that: Specifically includes the following steps: 1) 0.05-0.2 parts of ceramic powder and 10 parts of polyvinyl fluoride are weighed, and 200-204 parts of N,N-dimethylformamide is used as a solvent to prepare a ceramic powder / polyvinyl fluoride solution with a total concentration of 5% and a blending mass ratio of 0.5-2%; 2) the ceramic powder / polyvinyl fluoride solution with a blending mass ratio of 0.5%-2% obtained in step 1) is dropped onto a glass slide, and is solidified into a film in a vacuum oven at 68-72 DEG C; 3) the solidified film prepared in step 2) is melted on a hot table at 200 DEG C~220 DEG C to eliminate thermal history, and then is rapidly cooled to 150-170 DEG C, and is crystallized at constant temperature for 6-8 hours until the blended film is completely crystallized.

5. The method for preparing a γ-phase polyvinylidene fluoride dielectric film according to claim 4, characterized in that: The specific steps are as follows: 1) 0.05 parts of ceramic powder and 10 parts of polyvinyl fluoride are weighed, and 201 parts of N,N-dimethylformamide is used as a solvent to prepare a ceramic powder / polyvinyl fluoride solution with a total concentration of 5% and a blending mass ratio of 0.5%; 2) the ceramic powder / polyvinyl fluoride solution with a blending mass ratio of 0.5% obtained in step 1) is dropped onto a glass slide, and is solidified into a film in a vacuum oven at 70 DEG C; 3) the solidified film prepared in step 2) is melted on a hot table at 200 DEG C to eliminate thermal history, and then is rapidly cooled to 160 DEG C, and is crystallized at constant temperature for 6.5 hours until the blended film is completely crystallized.

6. The method for preparing a γ-phase polyvinylidene fluoride dielectric film according to claim 4, characterized in that: The specific steps are as follows: 1) 0.10 parts of ceramic powder and 10 parts of polyvinyl fluoride are weighed, and 202 parts of N,N-dimethylformamide is used as a solvent to prepare a ceramic powder / polyvinyl fluoride solution with a total concentration of 5% and a blending mass ratio of 1%; 2) the ceramic powder / polyvinyl fluoride solution with a blending mass ratio of 1% obtained in step 1) is dropped onto a glass slide, and is solidified into a film in a vacuum oven at 68 DEG C; 3) the solidified film prepared in step 2) is melted on a hot table at 205 DEG C to eliminate thermal history, and then is rapidly cooled to 170 DEG C, and is crystallized at constant temperature for 7 hours until the blended film is completely crystallized.

7. The method for preparing a γ-phase polyvinylidene fluoride dielectric film according to claim 4, characterized in that: The specific steps are as follows: 1) 0.15 parts of ceramic powder and 10 parts of polyvinylidene fluoride were weighed out, 203 parts of N,N-dimethylformamide was used as solvent to prepare a ceramic powder / polyvinylidene fluoride solution with a total concentration of 5% and a blending mass ratio of 1.5%; 2) the ceramic powder / polyvinylidene fluoride solution with a blending mass ratio of 1.5% obtained in step 1) was dropped onto a glass slide and solidified into a film in a vacuum oven at 72°C; 3) the solidified film prepared in step 2) was melted to eliminate thermal history on a hot stage at 210°C, then rapidly cooled to 150°C, and isothermally crystallized for 7.5 h to make the blending film completely crystallize.

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