Piezoelectric polymer film material, preparation method thereof and piezoelectric sensor

Abstract

The invention belongs to the related technical field of composite flexible piezoelectric materials, and discloses a piezoelectric polymer film material, a preparation method thereof and a piezoelectric sensor. The preparation method comprises the following steps: S1, selecting a polyvinylidene fluoride non-relaxor ferroelectric polymer and a polyvinylidene fluoride relaxor ferroelectric polymer, the preparation method comprises the following steps: respectively dissolving a polyvinylidene fluoride based non-relaxor ferroelectric polymer and a polyvinylidene fluoride based relaxor ferroelectric polymer in an organic solvent to obtain two polymer solutions; s2, blending and stirring the two polymer solutions to obtain a mixed solution; s3, the mixed solution is poured into a mold, the solvent is dried, and the piezoelectric polymer membrane material is prepared. The relaxor ferroelectric polymer is introduced into the non-relaxor ferroelectric polymer through physical blending design, the problem that the piezoelectric coefficient of a traditional vinylidene fluoride polymer is remarkably reduced in a high-temperature environment is solved, the prepared membrane material does not need complex chemical modification, the process is simple, the cost is low, and good operability is achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field related to composite flexible piezoelectric materials, and more specifically, relates to a piezoelectric polymer film material, a preparation method thereof, and a piezoelectric sensor. Background Art

[0002] Piezoelectric materials are functional materials that can generate electrical signals under external mechanical stress or produce mechanical strain under applied electric field. Polyvinylidene fluoride (PVDF)-based ferroelectric polymer materials are widely used in sensors, smart electronics, medical devices, energy collection and other fields due to their excellent piezoelectric properties, mechanical flexibility and good chemical stability. However, its piezoelectric coefficient ( d 33 ) is significantly affected by high temperature environment, which greatly limits its further application and development.

[0003] The piezoelectricity of polyvinylidene fluoride mainly comes from its polarity obtained by mechanical stretching. β phase crystal structure, but this obtained by mechanical processing β The phase has poor thermal stability and becomes non-polar at higher temperatures (>80 °C) α phase, leading to d 33 The sharp drop in the temperature of polyvinylidene fluoride piezoelectric materials severely limits the application of polyvinylidene fluoride piezoelectric materials in high temperature environments. In order to solve this problem, the researchers introduced defects (such as trifluoroethylene (TrFE), tetrafluoroethylene (TFE)) for molecular copolymerization to obtain stable materials that do not require mechanical stretching. β However, this copolymerization method will destroy the PVDF crystallization and TrFE and TFE are weaker in polarity than vinylidene fluoride (VDF), resulting in the copolymerization product d 33 In addition, as the amount of defects introduced increases, the Curie temperature of the material decreases significantly, which also leads to poor piezoelectric thermal stability.

[0004] Therefore, there is an urgent need to develop high-temperature resistant piezoelectric polymer materials and their preparation methods to meet the needs of high-temperature applications in the fields of smart electronics and energy collection. Summary of the invention

[0005] In view of the above defects or improvement needs of the prior art, the present invention provides a piezoelectric polymer film material, a preparation method thereof and a piezoelectric sensor, which are used to solve the problem of the piezoelectric coefficient ( d 33 ) is severely attenuated, thus limiting the application problem.

[0006] To achieve the above object, according to a first aspect of the present invention, a method for preparing a piezoelectric polymer film is provided, comprising: S1, selecting a polyvinylidene fluoride based non-relaxor ferroelectric polymer and a polyvinylidene fluoride based relaxor ferroelectric polymer, dissolving the polyvinylidene fluoride based non-relaxor ferroelectric polymer and the polyvinylidene fluoride based relaxor ferroelectric polymer in an organic solvent respectively, to obtain two polymer solutions; the polyvinylidene fluoride based non-relaxor ferroelectric polymer mentioned below refers to a polyvinylidene fluoride based ferroelectric polymer without relaxor properties; S2, blending and stirring the two polymer solutions to obtain a mixed solution; S3, pouring the mixed solution into a mold, drying the solvent, and preparing a high temperature resistant piezoelectric polymer film material.

[0007] According to the method for preparing a piezoelectric polymer film provided by the present invention, the polyvinylidene fluoride-based non-relaxor ferroelectric polymer is: Polyvinylidene fluoride-tetrafluoroethylene, wherein the content of tetrafluoroethylene is 5 mol%~35 mol%; Alternatively, it is polyvinylidene fluoride-trifluoroethylene, wherein the content of trifluoroethylene is 5 mol%~35 mol%.

[0008] According to the method for preparing a piezoelectric polymer film provided by the present invention, the polyvinylidene fluoride-based non-relaxor ferroelectric polymer is polyvinylidene fluoride-trifluoroethylene, wherein the content of trifluoroethylene is 15 mol% to 25 mol%.

[0009] According to the method for preparing a piezoelectric polymer film provided by the present invention, the polyvinylidene fluoride-based relaxor ferroelectric polymer is: Polyvinylidene fluoride-trifluoroethylene, wherein the content of trifluoroethylene is 45 mol%~75 mol%; Alternatively, it is polyvinylidene fluoride-trifluoroethylene-fluorochloroethylene, wherein the content of trifluoroethylene is 30 mol% to 75 mol%, and the content of fluorochloroethylene is 3.5 mol% to 15 mol%; Alternatively, it is polyvinylidene fluoride-trifluoroethylene-chlorotrifluoroethylene, wherein the content of trifluoroethylene is 30 mol% to 75 mol%, and the content of chlorotrifluoroethylene is 3.5 mol% to 15 mol%.

[0010] According to the preparation method of the piezoelectric polymer film provided by the present invention, the polyvinylidene fluoride based relaxor ferroelectric polymer is polyvinylidene fluoride-trifluoroethylene-chlorofluoroethylene, wherein the content of trifluoroethylene is 30 mol%~40 mol%, and the content of chlorofluoroethylene (CFE) is 5 mol%~7 mol%.

[0011] According to the method for preparing a piezoelectric polymer film provided by the present invention, the organic solvent is dimethylformamide, dimethyl sulfoxide, methyl ethyl ketone or cyclohexanone; and the concentrations of the two polymer solutions are 10 mg / mL to 1000 mg / mL, respectively.

[0012] According to the method for preparing a piezoelectric polymer film provided by the present invention, when the two polymer solutions are blended in S2, the mass ratio of the polyvinylidene fluoride based non-relaxor ferroelectric polymer to the polyvinylidene fluoride based relaxor ferroelectric polymer is 100:1-100:30.

[0013] According to the method for preparing a piezoelectric polymer film provided by the present invention, the stirring time for obtaining the polymer solution in S1 is 6 h to 24 h, and the temperature is 25 ° C to 75 ° C; The stirring time used to obtain the mixed solution in S2 is 12 h~48 h, and the temperature is 25 °C~75 °C; The drying time of the drying solvent in S3 is 12 h~24 h, and the drying temperature is 60 °C~130 °C.

[0014] According to a second aspect of the present invention, a piezoelectric polymer film is provided, which is prepared by any of the above-mentioned methods for preparing a piezoelectric polymer film.

[0015] According to a third aspect of the present invention, there is provided a piezoelectric sensor comprising the above-mentioned piezoelectric polymer film.

[0016] In general, compared with the prior art, the piezoelectric polymer film material, preparation method thereof and piezoelectric sensor provided by the present invention are as follows: 1. It is proposed to use polyvinylidene fluoride based relaxor ferroelectric polymers to improve the high temperature resistance of polyvinylidene fluoride based non-relaxor ferroelectric polymers through physical blending modification. Specifically, the flexible molecular chains of relaxor ferroelectric polymers are uniformly embedded into the crystal structure of ferroelectric polymers. The characteristics of low lattice stiffness and high dynamics of relaxor ferroelectric polymers are utilized to effectively improve the crystal defect distribution of polyvinylidene fluoride based materials and significantly improve the piezoelectric coefficient of the blended film material ( d 33 ); At the same time, through the strong coupling effect between the ferroelectric polymer and the relaxor ferroelectric polymer molecular chains at the molecular scale, the molecular chain motion behavior of the blending system is further optimized, the ferroelectric polymer's ability to resist temperature disturbances under high temperature conditions is enhanced, and the influence of high temperature on the polarization intensity is effectively alleviated, thereby improving the thermal stability of the piezoelectric response, so that the prepared film material has both excellent piezoelectric properties and thermal stability, which can meet the requirements of various application fields for high temperature resistance of piezoelectric film materials; 2. The solution physical blending modification preparation process overcomes the performance limitations of a single polymer component and achieves a balance between piezoelectric performance and thermal stability. The preparation process is simple and easy to operate, and does not require complex equipment or expensive materials, making the membrane material more feasible in large-scale industrial applications. 3. After the polyvinylidene fluoride trifluoroethylene (P(VDF-TrFE)) is blended and modified, d 33 From -18.0 pC / N to -44.5 pC / N, after aging at 100 °C for 120 h, d 33 The rate of change decreased from 34% to 9.8%. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a schematic flow chart of the method for preparing the piezoelectric polymer film provided by the present invention.

[0018] Figure 2 The present invention provides embodiments 1, 2, 3, 4, 5 and PVDF d 33 contrast.

[0019] Figure 3 The high temperature resistance (100 °C, 120 h aging) of Examples 1, 2, 3, 4, and 5 provided by the present invention is compared with that of PVDF.

[0020] Figure 4 The P(VDF-TrFE) before and after blending in Example 1 provided by the present invention d 33 Compared with high temperature resistance (100 °C, 120 h aging).

[0021] Figure 5 This is a schematic diagram of the actual sample obtained in Example 1 provided by the present invention.

[0022] Figure 6 This is a comparison chart of the high temperature resistance (100 °C, 120 h aging) of the sensor prepared by Example 1 provided by the present invention and PVDF. DETAILED DESCRIPTION

[0023] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0024] See also Figure 1This embodiment provides a method for preparing a piezoelectric polymer film, the method comprising: S1, selecting a polyvinylidene fluoride based non-relaxor ferroelectric polymer and a polyvinylidene fluoride based relaxor ferroelectric polymer, and dissolving the polyvinylidene fluoride based non-relaxor ferroelectric polymer and the polyvinylidene fluoride based relaxor ferroelectric polymer in an organic solvent respectively to obtain two polymer solutions; S2, blending and stirring the two polymer solutions to obtain a mixed solution; S3, pouring the mixed solution into a mold, drying the solvent, and preparing a high temperature resistant piezoelectric polymer film material.

[0025] In this embodiment S1, when obtaining the polymer solution, the solution can be stirred to form a uniform polymer solution; in S2, the two polymer solutions are blended in proportion by physical blending, and after blending, they are stirred until they are completely dispersed and uniform.

[0026] Optionally, the polyvinylidene fluoride-based non-relaxor ferroelectric polymer is: Polyvinylidene fluoride-tetrafluoroethylene (P(VDF-TFE)), wherein the content of tetrafluoroethylene (TFE) is 5 mol%~35 mol%; Alternatively, it is polyvinylidene fluoride-trifluoroethylene (P(VDF-TrFE)), wherein the content of trifluoroethylene (TrFE) is 5 mol% to 35 mol%.

[0027] Further optionally, the polyvinylidene fluoride-based non-relaxor ferroelectric polymer is polyvinylidene fluoride-trifluoroethylene (P(VDF-TrFE)), wherein the content of trifluoroethylene (TrFE) is 15 mol% to 25 mol%.

[0028] Further optionally, the polyvinylidene fluoride-based non-relaxor ferroelectric polymer is polyvinylidene fluoride-trifluoroethylene (P(VDF-TrFE)), wherein the content of trifluoroethylene (TrFE) is 20 mol %.

[0029] Optionally, the polyvinylidene fluoride-based relaxor ferroelectric polymer is: Polyvinylidene fluoride-trifluoroethylene (P(VDF-TrFE)), wherein the content of trifluoroethylene (TrFE) is 45 mol%~75 mol%; Alternatively, it is polyvinylidene fluoride-trifluoroethylene-chlorofluoroethylene (P(VDF-TrFE-CFE)), wherein the content of trifluoroethylene (TrFE) is 30 mol%~75 mol%, and the content of chlorofluoroethylene (CFE) is 3.5 mol%~15 mol%; Alternatively, it is polyvinylidene fluoride-trifluoroethylene-chlorotrifluoroethylene (P(VDF-TrFE-CTFE)), wherein the content of trifluoroethylene (TrFE) is 30 mol%~75 mol%, and the content of chlorotrifluoroethylene (CTFE) is 3.5 mol%~15 mol%.

[0030] Further optionally, the polyvinylidene fluoride-based relaxor ferroelectric polymer is polyvinylidene fluoride-trifluoroethylene-chlorofluoroethylene (P(VDF-TrFE-CFE)), wherein the content of trifluoroethylene (TrFE) is 30 mol%~40 mol%, and the content of chlorofluoroethylene (CFE) is 5 mol%~7 mol%.

[0031] Further optionally, the polyvinylidene fluoride-based relaxor ferroelectric polymer is polyvinylidene fluoride-trifluoroethylene-chlorofluoroethylene (P(VDF-TrFE-CFE)), the content of trifluoroethylene (TrFE) is 30 mol %, and the content of chlorofluoroethylene (CFE) is 7 mol %.

[0032] Optionally, the organic solvent is dimethylformamide (DMF), dimethyl sulfoxide (DMSO), methyl ethyl ketone (MEK) or cyclohexanone (CYC); preferably dimethylformamide (DMF). The concentrations of the two polymer solutions are 10 mg / mL to 1000 mg / mL, respectively; preferably 60 mg / mL.

[0033] Specifically, when the two polymer solutions in S2 are blended, the polyvinylidene fluoride based non-relaxor ferroelectric polymer and the polyvinylidene fluoride based relaxor ferroelectric polymer are physically blended according to a mass ratio, and the mass ratio of the polyvinylidene fluoride based non-relaxor ferroelectric polymer to the polyvinylidene fluoride based relaxor ferroelectric polymer is 100:1 to 100:30. The mass ratio of the polyvinylidene fluoride based non-relaxor ferroelectric polymer to the polyvinylidene fluoride based relaxor ferroelectric polymer is preferably 100:2.5 to 100:12.5.

[0034] Furthermore, the stirring time for obtaining the polymer solution in S1 is 6 h to 24 h, and the temperature is 25 °C to 75 °C; preferably, stirring at 60 °C for 12 h.

[0035] The stirring time for obtaining the mixed solution in S2, i.e., the blending of the polyvinylidene fluoride non-relaxant ferroelectric polymer and the polyvinylidene fluoride relaxor ferroelectric polymer, is 12 h to 48 h, and the temperature is 25 ° C to 75 ° C; preferably, stirring at 70 ° C for 24 h.

[0036] The drying time of drying the solvent in S3, i.e., the drying time of the polymer solution in the mold to form a film by drying the solvent, is 12 h to 24 h, and the drying temperature is 60 ° C to 130 ° C. Preferably, the drying is performed at 120 ° C for 12 h.

[0037] Furthermore, the mixed solution is poured into a mold and dried to form a flexible piezoelectric film material. The mold is a flat plate with a smooth surface made of any material such as glass, quartz or metal substrate, preferably a quartz substrate.

[0038] This embodiment provides a piezoelectric polymer film material, which is prepared by any of the above-mentioned piezoelectric polymer film material preparation methods. The piezoelectric polymer film material is a high temperature resistant polyvinylidene fluoride based ferroelectric polymer film material.

[0039] This embodiment provides a piezoelectric sensor, including the above-mentioned piezoelectric polymer film material, that is, this embodiment is an application of a high-temperature resistant polyvinylidene fluoride-based ferroelectric polymer film material in a piezoelectric sensor device.

[0040] In the following examples, the instruments and the like used without indicating the manufacturer are all conventional products that can be purchased through regular channels. The methods described are conventional methods unless otherwise specified, and the raw materials described can be obtained from public commercial channels unless otherwise specified.

[0041] Example 1: 600 mg of P(VDF-TrFE) (TrFE is 20 mol%) was added to 10 mL of cyclohexanone solution to prepare a polymer solution with a concentration of 60 mg / mL, and the mixture was stirred at 300 rpm / min at 40 °C for 12 h. To the stirred P(VDF-TrFE) (TrFE is 20 mol%) solution, 0.55 mL of stirred P(VDF-TrFE-CFE) solution with a concentration of 60 mg / mL (TrFE is 30 mol%, CFE is 7 mol%) was added at a mass ratio of 100:5.5. The mixture was stirred at 300 rpm / min at 70 °C for 24 h. The mixed solution was then poured into a quartz mold and dried at 90 °C for 12 h to obtain a piezoelectric film material.

[0042] Example 2: 600 mg of P(VDF-TrFE) (TrFE is 20 mol%) was added to 10 mL of cyclohexanone solution to prepare a polymer solution with a concentration of 60 mg / mL, and the mixture was stirred at 300 rpm / min at 40 °C for 12 h. To the stirred P(VDF-TrFE) (TrFE is 20 mol%) solution, 0.55 mL of stirred P(VDF-TrFE-CFE) solution with a concentration of 60 mg / mL (TrFE is 30 mol%, CFE is 7 mol%) was added at a mass ratio of 100:5.5. The mixture was stirred at 300 rpm / min at 70 °C for 24 h. The mixed solution was then poured into a quartz mold and dried at 120 °C for 12 h to obtain a piezoelectric film material.

[0043] Example 3: 600 mg of P(VDF-TrFE) (TrFE is 20 mol%) was added to 10 mL of cyclohexanone solution to prepare a polymer solution with a concentration of 60 mg / mL, and the mixture was stirred at 300 rpm / min at 40 °C for 12 h. To the stirred P(VDF-TrFE) (TrFE is 20 mol%) solution, 0.55 mL of stirred P(VDF-TrFE) solution with a concentration of 60 mg / mL (TrFE is 50 mol%) was added at a mass ratio of 100:5.5, and the mixture was stirred at 300 rpm / min at 70 °C for 24 h. The mixed solution was then poured into a quartz mold and dried at 120 °C for 12 h to obtain a piezoelectric film material.

[0044] Example 4: 600 mg of P(VDF-TrFE) (TrFE is 20 mol%) was added to 10 mL of cyclohexanone solution to prepare a polymer solution with a concentration of 60 mg / mL, and the mixture was stirred at 300 rpm / min at 40 °C for 12 h. To the stirred P(VDF-TrFE) (TrFE is 20 mol%) solution, 0.55 mL of stirred P(VDF-TrFE-CFE) solution with a concentration of 60 mg / mL (TrFE is 30 mol%, CFE is 9 mol%) was added at a mass ratio of 100:5.5. The mixture was stirred at 300 rpm / min at 70 °C for 24 h. The mixed solution was then poured into a quartz mold and dried at 120 °C for 12 h to obtain a piezoelectric film material.

[0045] Example 5: Add 600 mg of P(VDF-TrFE) (TrFE is 20 mol%) to 10 mL of cyclohexanone solution to prepare a polymer solution with a concentration of 60 mg / mL, and stir at 300 rpm / min at 40 °C for 12 h. Add 0.5 mL of 60 mg / mL P(VDF-TrFE-CFE) solution (TrFE is 30 mol%, CFE is 5 mol%) after stirring to the P(VDF-TrFE) (TrFE is 20 mol%) solution at a mass ratio of 100:5, and stir at 300 rpm / min at 80 °C for 12 h. Then pour the mixed solution into a quartz mold and dry it at 100 °C for 12 h to obtain a piezoelectric film material.

[0046] Comparative Example 1: 600 mg of P(VDF-TrFE) (TrFE is 20 mol%) was added to 10 mL of cyclohexanone solution to prepare a polymer solution with a concentration of 60 mg / mL, and the mixture was stirred at 300 rpm / min at 40 °C for 12 h. To the stirred P(VDF-TrFE) (TrFE is 20 mol%) solution, 0.5 mL of stirred P(VDF-TrFE-CFE) solution with a concentration of 60 mg / mL (TrFE is 10 mol%, CFE is 1 mol%) was added at a mass ratio of 100:5, and the mixture was stirred at 300 rpm / min at 80 °C for 12 h. The mixed solution was then poured into a quartz mold and dried at 100 °C for 12 h to obtain a piezoelectric film material.

[0047] Comparative Example 2: 600 mg of P(VDF-TrFE) (TrFE is 20 mol%) was added to 10 mL of cyclohexanone solution to prepare a polymer solution with a concentration of 60 mg / mL, and the mixture was stirred at 300 rpm / min at 40 °C for 12 h. To the stirred P(VDF-TrFE) (TrFE is 20 mol%) solution, 7.3 mL of stirred P(VDF-TrFE-CFE) solution with a concentration of 60 mg / mL (TrFE is 30 mol%, CFE is 9 mol%) was added at a mass ratio of 100:73, and the mixture was stirred at 300 rpm / min at 70 °C for 24 h. The mixed solution was then poured into a quartz mold and dried at 120 °C for 12 h.

[0048] Comparative Example 3: 600 mg of P(VDF-TrFE) (TrFE is 20 mol%) was added to 10 mL of cyclohexanone solution to prepare a polymer solution with a concentration of 60 mg / mL, and the mixture was stirred at 300 rpm / min at 40 °C for 12 h. To the stirred P(VDF-TrFE) (TrFE is 20 mol%) solution, 5.1 mL of stirred P(VDF-TrFE) solution with a concentration of 60 mg / mL (TrFE is 70 mol%) was added at a mass ratio of 100:51, and the mixture was stirred at 300 rpm / min at 70 °C for 24 h. The mixed solution was then poured into a quartz mold and dried at 120 °C for 12 h to obtain a piezoelectric film material.

[0049] Comparative Example 4: 600 mg of P(VDF-TrFE) (TrFE is 20 mol%) was added to 10 mL of cyclohexanone solution to prepare a polymer solution with a concentration of 60 mg / mL, and the mixture was stirred at 300 rpm / min at 40 °C for 12 h. To the stirred P(VDF-TrFE) (TrFE is 20 mol%) solution, 3.1 mL of stirred P(VDF-TrFE-CFE) solution with a concentration of 60 mg / mL (TrFE is 2 mol%, CFE is 3 mol%) was added at a mass ratio of 100:31, and the mixture was stirred at 300 rpm / min at 70 °C for 24 h. The mixed solution was then poured into a quartz mold and dried at 120 °C for 12 h to obtain a piezoelectric film material.

[0050] Comparative Example 5: 600 mg of P(VDF-TrFE) (TrFE is 20 mol%) was added to 10 mL of cyclohexanone solution to prepare a polymer solution with a concentration of 60 mg / mL, and the mixture was stirred at 300 rpm / min at 40 °C for 12 h. To the stirred P(VDF-TrFE) (TrFE is 20 mol%) solution, 1.3 mL of stirred P(VDF-TrFE) solution with a concentration of 60 mg / mL (TrFE is 90 mol%) was added at a mass ratio of 100:13, and the mixture was stirred at 300 rpm / min at 70 °C for 24 h. The mixed solution was then poured into a quartz mold and dried at 120 °C for 12 h to obtain a piezoelectric film material.

[0051] Comparative Example 6: 600 mg of P(VDF-TrFE) (TrFE is 20 mol%) was added to 10 mL of cyclohexanone solution to prepare a polymer solution with a concentration of 60 mg / mL, and the mixture was stirred at 300 rpm / min at 40 °C for 12 h. To the stirred P(VDF-TrFE) (TrFE is 20 mol%) solution, 0.1 mL of stirred P(VDF-TrFE-CFE) solution with a concentration of 60 mg / mL (TrFE is 30 mol%, CFE is 7 mol%) was added at a mass ratio of 100:1, and the mixture was stirred at 300 rpm / min at 70 °C for 24 h. The mixed solution was then poured into a quartz mold and dried at 120 °C for 12 h to obtain a piezoelectric film material.

[0052] Comparative Example 7: 600 mg of P(VDF-TrFE) (TrFE is 20 mol%) was added to 10 mL of cyclohexanone solution to prepare a polymer solution with a concentration of 60 mg / mL, and the mixture was stirred at 300 rpm / min at 40 °C for 12 h. To the stirred P(VDF-TrFE) (TrFE is 20 mol%) solution, 0.2 mL of stirred P(VDF-TrFE-CFE) solution with a concentration of 60 mg / mL (TrFE is 30 mol%, CFE is 7 mol%) was added at a mass ratio of 100:2. The mixture was stirred at 300 rpm / min at 70 °C for 24 h. The mixed solution was then poured into a quartz mold and dried at 120 °C for 12 h to obtain a piezoelectric film material.

[0053] Comparative Example 8: 600 mg of P(VDF-TrFE) (TrFE is 20 mol%) was added to 10 mL of cyclohexanone solution to prepare a polymer solution with a concentration of 60 mg / mL, and the mixture was stirred at 300 rpm / min at 40 °C for 12 h. To the stirred P(VDF-TrFE) (TrFE is 20 mol%) solution, 0.15 mL of 60 mg / mL P(VDF-TrFE) solution (TrFE is 50 mol%) was added at a mass ratio of 100:1.5, and the mixture was stirred at 300 rpm / min at 70 °C for 24 h. The mixed solution was then poured into a quartz mold and dried at 120 °C for 12 h to obtain a piezoelectric film material.

[0054] Comparative Example 9: 600 mg of P(VDF-TrFE) (TrFE is 20 mol%) was added to 10 mL of cyclohexanone solution to prepare a polymer solution with a concentration of 60 mg / mL, and the mixture was stirred at 300 rpm / min at 40 °C for 12 h. To the stirred P(VDF-TrFE) (TrFE is 20 mol%) solution, 0.15 mL of stirred P(VDF-TrFE-CFE) solution with a concentration of 60 mg / mL (TrFE is 30 mol%, CFE is 9 mol%) was added at a mass ratio of 100:1.5, and the mixture was stirred at 300 rpm / min at 70 °C for 24 h. The mixed solution was then poured into a quartz mold and dried at 120 °C for 12 h to obtain a piezoelectric film material.

[0055] Comparative Example 10: 600 mg of P(VDF-TrFE) (TrFE is 20 mol%) was added to 10 mL of cyclohexanone solution to prepare a polymer solution with a concentration of 60 mg / mL, and the mixture was stirred at 300 rpm / min at 40 °C for 12 h. To the stirred P(VDF-TrFE) (TrFE is 20 mol%) solution, 0.55 mL of stirred P(VDF-TrFE-CFE) solution with a concentration of 60 mg / mL (TrFE is 30 mol%, CFE is 7 mol%) was added at a mass ratio of 100:300, and the mixture was stirred at 300 rpm / min at 70 °C for 24 h. The mixed solution was then poured into a quartz mold and dried at 90 °C for 12 h to obtain a piezoelectric film material.

[0056] The piezoelectric coefficient measurement and high temperature resistance performance experiment were carried out on the piezoelectric film materials obtained in the above embodiments and comparative examples. The comparison of the piezoelectric coefficients of Example 1 and Comparative Examples 1-5 is shown in Table 1. It can be seen that the specific polymer preparation parameters provided in the embodiment of the present invention can significantly improve the piezoelectric performance and obtain a higher piezoelectric coefficient value. The comparison of the high temperature resistance performance of Example 1 and Comparative Examples 6-10 is shown in Table 2. The high temperature resistance performance is specifically reflected by the rate of change of the piezoelectric coefficient of the piezoelectric film material at 100 °C and 120 h. It can be seen that the specific polymer preparation parameters provided in the embodiment of the present invention can significantly improve the high temperature resistance performance. The rate of change of the piezoelectric coefficient at 100 °C and 120 h is significantly reduced, and when the addition amount of the polyvinylidene fluoride-based relaxor ferroelectric polymer in the polymer is large, the rate of change of the piezoelectric coefficient at 100 °C and 120 h is significantly increased, indicating that when the addition amount of the polyvinylidene fluoride-based relaxor ferroelectric polymer in the polymer exceeds a certain range, it will greatly affect the high temperature resistance of the polymer film material; ; ; refer to Figure 2 The piezoelectric coefficients of the piezoelectric films obtained in Examples 1-5 and commercial PVDF are d 33 Comparing the figures, it can be seen that the piezoelectric film material obtained by the preparation method and specific preparation parameters provided in this embodiment significantly improves the piezoelectric performance and can obtain a higher piezoelectric coefficient. d 33 . refer to Figure 3 The comparison chart of the high temperature resistance of the piezoelectric film obtained in Examples 1-5 and commercial PVDF shows that the piezoelectric film obtained by the preparation method and specific preparation parameters provided in this embodiment significantly improves the high temperature resistance of the film. The piezoelectric coefficient is d 33 The rate of change is lower.

[0057] refer to Figure 4 The performance of the film obtained by directly drying the solvent before blending prepared by P(VDF-TrFE) in Example 1 without blending with P(VDF-TrFE-CFE) is compared with the performance of the film obtained after blending prepared by blending P(VDF-TrFE) and P(VDF-TrFE-CFE), where (a) is the piezoelectric coefficient d 33 It can be seen from the comparison that the piezoelectric coefficient of the film after blending is significantly higher than that of the film before blending, indicating that the blending method provided by the present invention can obtain a film with better piezoelectric performance; (b) is a comparison of high temperature resistance. The high temperature resistance is measured by comparing the piezoelectric coefficient under 100 °C, 120 h aging conditions. d 33 It can be reflected by the rate of change of piezoelectric coefficient of the film material after blending. It can be seen that the rate of change of piezoelectric coefficient of the film material after blending is significantly lower than that of the film material before blending, indicating that the blending method provided by the present invention can obtain a film material with better high temperature resistance.

[0058] refer to Figure 5 This is a schematic diagram of the actual sample obtained in Example 1.

[0059] refer to Figure 6 The signal comparison diagram of the piezoelectric device prepared by using the piezoelectric film obtained in Example 1 and the piezoelectric device prepared by using commercial PVDF, the piezoelectric device can be a piezoelectric sensor, the signal is a voltage signal under applied pressure, according to Figure 6It can be seen that the voltage signals of the piezoelectric device prepared using the piezoelectric film material obtained in Example 1 at different pressures are higher than those of the piezoelectric device prepared using commercial PVDF, and after aging at 100 °C for 120 h, the voltage signals of the piezoelectric device prepared using the piezoelectric film material obtained in Example 1 at different pressures always remain high with a small rate of change, while the voltage signal of the piezoelectric device prepared using commercial PVDF is severely attenuated, indicating that the piezoelectric device prepared using the piezoelectric film material obtained in Example 1 has better high temperature resistance.

[0060] The present invention discloses a polymer film material for high-temperature flexible sensing and a preparation method thereof, and specifically relates to improving the piezoelectric coefficient and high temperature resistance of a polyvinylidene fluoride-based non-relaxor ferroelectric polymer by physical blending modification. The method comprises the following steps: (1) dissolving a polyvinylidene fluoride-based non-relaxor ferroelectric polymer and a polyvinylidene fluoride-based relaxor ferroelectric polymer in an organic solvent to form a uniform polymer solution; (2) blending the two polymer solutions in a certain mass ratio and stirring until they are completely dispersed and uniform; (3) pouring the obtained mixed solution into a mold, drying the solvent, and obtaining a blended polyvinylidene fluoride-based film material. The present invention introduces a relaxor ferroelectric polymer into a ferroelectric polymer by physical blending design, thereby solving the problem that the piezoelectric coefficient of a traditional vinylidene fluoride polymer decreases significantly under high temperature conditions. The prepared film material does not require complex chemical modification, has a simple process, low cost, and good operability, and can be widely used in piezoelectric sensors, energy harvesting devices, and intelligent electronic devices in high temperature environments.

[0061] The present invention provides a preparation method through physical blending modification, by blending the relaxor ferroelectric polymer and the ferroelectric polymer in a specific ratio, and utilizing the strong coupling effect between the molecular chains of the two types of polymers at the molecular scale, a new type of flexible piezoelectric material with excellent high temperature resistance and high piezoelectric coefficient is successfully prepared. d 33 reached -44.5 pC / N, and after aging at 100 °C for 120 h, d 33 The aging decline rate is less than 9.5%, overcoming the performance limitations of a single polymer component and achieving a balance between piezoelectric performance and thermal stability. The entire preparation process is simple to operate, does not require complex equipment, and can be manufactured on a large scale.

[0062] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a piezoelectric polymer film, characterized in that: include: S1, selecting a polyvinylidene fluoride based non-relaxor ferroelectric polymer and a polyvinylidene fluoride based relaxor ferroelectric polymer, and dissolving the polyvinylidene fluoride based non-relaxor ferroelectric polymer and the polyvinylidene fluoride based relaxor ferroelectric polymer in an organic solvent respectively to obtain two polymer solutions; S2, blending and stirring the two polymer solutions to obtain a mixed solution; S3, pouring the mixed solution into a mold, drying the solvent, and preparing a high temperature resistant piezoelectric polymer film; When the two polymer solutions in S2 are blended, the mass ratio of the polyvinylidene fluoride based non-relaxor ferroelectric polymer to the polyvinylidene fluoride based relaxor ferroelectric polymer is 100:1-100:

30.

2. The method for preparing a piezoelectric polymer film according to claim 1, characterized in that: The polyvinylidene fluoride based non-relaxor ferroelectric polymer is: Polyvinylidene fluoride-tetrafluoroethylene, wherein the content of tetrafluoroethylene is 5 mol%~35 mol%; Alternatively, it is polyvinylidene fluoride-trifluoroethylene, wherein the content of trifluoroethylene is 5 mol%~35 mol%.

3. The method for preparing a piezoelectric polymer film according to claim 2, characterized in that: The polyvinylidene fluoride-based non-relaxor ferroelectric polymer is polyvinylidene fluoride-trifluoroethylene, wherein the content of trifluoroethylene is 15 mol% to 25 mol%.

4. The method for preparing a piezoelectric polymer film according to claim 1, characterized in that: The polyvinylidene fluoride based relaxor ferroelectric polymer is: Polyvinylidene fluoride-trifluoroethylene, wherein the content of trifluoroethylene is 45 mol%~75 mol%; Alternatively, it is polyvinylidene fluoride-trifluoroethylene-fluorochloroethylene, wherein the content of trifluoroethylene is 30 mol% to 75 mol%, and the content of fluorochloroethylene is 3.5 mol% to 15 mol%; Alternatively, it is polyvinylidene fluoride-trifluoroethylene-chlorotrifluoroethylene, wherein the content of trifluoroethylene is 30 mol% to 75 mol%, and the content of chlorotrifluoroethylene is 3.5 mol% to 15 mol%.

5. The method for preparing a piezoelectric polymer film according to claim 4, characterized in that: The polyvinylidene fluoride-based relaxor ferroelectric polymer is polyvinylidene fluoride-trifluoroethylene-chlorofluoroethylene, wherein the content of trifluoroethylene is 30 mol% to 40 mol%, and the content of chlorofluoroethylene (CFE) is 5 mol% to 7 mol%.

6. The method for preparing a piezoelectric polymer film according to claim 1, characterized in that: The organic solvent is dimethylformamide, dimethyl sulfoxide, methyl ethyl ketone or cyclohexanone; the concentrations of the two polymer solutions are 10 mg / mL to 1000 mg / mL respectively.

7. The method for preparing a piezoelectric polymer film according to claim 1, characterized in that: The stirring time used to obtain the polymer solution in S1 is 6 h to 24 h, and the temperature is 25 °C to 75 °C; The stirring time used to obtain the mixed solution in S2 is 12 h~48 h, and the temperature is 25 °C~75 °C; The drying time of the drying solvent in S3 is 12 h~24 h, and the drying temperature is 60 °C~130 °C.

8. A piezoelectric polymer film, characterized in that: The piezoelectric polymer film is prepared by the method for preparing the piezoelectric polymer film according to any one of claims 1 to 7.

9. A piezoelectric sensor, characterized in that: The piezoelectric polymer film material comprises the piezoelectric polymer film material as claimed in claim 8.

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