Method for testing high field strength resistance of fluorine-containing copolymer material

Abstract

The invention relates to a method for testing high field strength resistance of a fluorine-containing copolymer material, which comprises the following steps: step 1, preparation of a copolymer material sample: preparing a copolymer film with a predetermined size from vacuum-dried copolymer resin powder by a hot pressing method, and respectively preparing metal electrodes on the upper surface and the lower surface of the film by a magnetron sputtering technology; step 2, preparing a testing device and installing a sample: adding silicone oil into a sample clamping device of ferroelectric testing equipment, placing a copolymer film sample in the center of the clamping device, ensuring that the sample is completely immersed in the silicone oil, and covering an end cover, so that a surface electrode of the copolymer film is in good contact with an upper conductive plate and a lower conductive plate; according to the invention, the anti-breakdown strength of the fluorine-containing copolymer material can be quantitatively evaluated, and a support is provided for a high-field-intensity polarization process of the material.

Description

Technical Field

[0001] The invention belongs to the technical field of piezoelectric materials, and in particular relates to a method for testing the resistance of fluorine-containing copolymer materials to high field strength. Background Art

[0002] Fluorinated piezoelectric copolymer P(VDF-TrFE) is a kind of polymer material obtained by polymerization of two monomers, vinylidene fluoride (VDF) and trifluoroethylene (TrFE). It is easy to form an orthorhombic crystal system. mm 2 point group β Crystalline phase, which can show good ferroelectricity and piezoelectricity. Compared with traditional piezoelectric ceramic materials, this type of copolymer material has the advantages of low density, good flexibility, acoustic impedance matching with water or human tissue, small dielectric constant, and large piezoelectric voltage coefficient. Taking the copolymer P (VDF-TrFE) with VDF / TrFE=80 / 20 as an example, its piezoelectric strain coefficient d 33 It can reach -28pC / N, and the piezoelectric voltage coefficient can reach above -350V m / N. Therefore, fluorinated copolymers are widely used in pressure sensors, tactile sensors, receiving hydrophones, and piezoelectric energy harvesting devices, effectively ensuring the improvement of device sensitivity and other performance.

[0003] However, it is worth noting that in order to give full play to the performance of fluorinated copolymers, after the successful preparation of components of a specific shape, they must undergo a polarization process to electrically induce orientation of their crystal domain arrangement in order to obtain more stable and excellent ferroelectric and piezoelectric properties. The polarization electric field strength requirements of copolymer materials are extremely high, and the average electric field strength requirement is above 150kV per millimeter. If there are defects or impurities in the material, it is very easy to cause electrical breakdown, which will not only cause the material to be scrapped, but also cause short circuits and damage to the polarization device. Therefore, mastering and improving the anti-electrical breakdown characteristics of fluorinated copolymer materials is crucial to their polarization success rate and piezoelectric properties.

[0004] The existing test method for evaluating the electrical breakdown resistance of fluorinated copolymer materials uses the same or similar equipment as the polarization process to apply a set strong electric field for polarization treatment, observe whether there is breakdown, and determine the anti-breakdown characteristics. This method has the disadvantages of relatively complex equipment, difficulty in real-time observation and judgment, and easy damage to the equipment. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a method for testing the high field strength resistance of a fluorinated copolymer material, which can quantitatively evaluate the anti-puncture strength of the fluorinated copolymer material and provide support for the high field strength polarization process of the material.

[0006] The technical solution of the present invention is to provide a method for testing the resistance of fluorinated copolymer materials to high field strength, comprising the following steps: Step 1, preparation of copolymer material sample: preparing a copolymer film of a predetermined size from vacuum-dried copolymer resin powder by hot pressing, and preparing metal electrodes on the upper and lower surfaces of the film by magnetron sputtering technology; Step 2, test device preparation and sample installation: add silicone oil to the sample clamping device of the ferroelectric test equipment, place the copolymer film sample in the center of the clamping device, ensure that the sample is completely immersed in the silicone oil, cover the end caps, so that the surface electrodes of the copolymer film are in good contact with the upper and lower conductive plates; Step 3, test parameter setting: using the hysteresis loop test mode of the ferroelectric test method to perform a high field strength test on the copolymer material, setting the test frequency and the test electric field parameters; Step 4, high field strength resistance test: start the hysteresis loop test and record the test curve of the polarization intensity of the copolymer film sample changing with the applied electric field; Step 5, data analysis: determining the high field strength resistance of the copolymer material according to the maximum electric field intensity in the hysteresis loop of polarization intensity-electric field.

[0007] Preferably, in the preparation of the copolymer material sample in step 1, the copolymer film formed by hot pressing has a thickness of 55 μm ± 5 μm, a size of not less than 20 mm × 20 mm, a metal electrode thickness of 100 nm-200 nm, and an electrode material of any one of Au, Ag, Al, Ni, Ti, Cu or double-layer metal Ti-Ni, Ti-Au.

[0008] Preferably, in the sample holding device of step 2, the silicone oil used is silicone oil with high viscosity and high dielectric constant.

[0009] Preferably, in the test parameter setting of step 3, the test method is the hysteresis loop test mode, the test frequency is 0.03 Hz, the test electric field is calculated based on the ratio of the test voltage to the thickness of the copolymer film sample, the test electric field is not less than 150 V / μm, and the test temperature is 25°C ± 5°C.

[0010] Preferably, in the high field strength resistance test of step 4, the number of cycles of the hysteresis loop test is 1.

[0011] Preferably, the testing device of step 2 comprises a ferroelectric measuring instrument, a sample holding device, and a high-voltage resistant wire. The sample holding device consists of an insulating cavity, an insulating end cover, an upper conductive column, an upper conductive plate, a lower conductive column and a lower conductive plate. One end of the upper conductive column is fixedly connected to the insulating end cover, and the other end is fixedly connected to the upper conductive plate. One end of the lower conductive column is fixedly connected to the insulating cavity, and the other end is fixedly connected to the lower conductive plate.

[0012] Preferably, during the test, the insulating cavity is filled with silicone oil, and the insulating cavity and the insulating end cover are made of polytetrafluoroethylene.

[0013] Furthermore, the upper conductive pillar, the lower conductive pillar, the upper conductive plate and the lower conductive plate are made of copper, the diameter of the upper and lower conductive plates is 18 mm ± 0.2 mm, and the surface is flat.

[0014] Compared with the prior art, the present invention has the following advantages: The present invention adopts the hysteresis loop test mode of the ferroelectric test method, which can intuitively qualitatively or quantitatively grasp the maximum polarization electric field of the material and determine the material's ability to withstand high field strengths. At the same time, it can also provide more detailed information such as coercive field and residual polarization intensity, which is also helpful for consistency analysis of material properties; the optimized design of the test device helps to reduce the probability of thin film electrical breakdown and the possibility of equipment damage, and the device has a certain degree of portability. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a schematic diagram of the structure of the testing device of the present invention. DETAILED DESCRIPTION

[0016] The present invention will be further described below with regard to specific embodiments: A method for testing the resistance of a fluorinated copolymer material to high field strength, the steps comprising: (1) Preparation of copolymer material samples: The vacuum-dried copolymer resin powder was prepared into a copolymer film with a thickness of 55 μm ± 5 μm and a size of 20 mm × 20 mm by hot pressing. Metal electrodes with a thickness of 100 nm to 200 nm were prepared on the upper and lower surfaces of the film by magnetron sputtering technology. In this embodiment, the thickness of the copolymer film was 58 μm, the thickness of the metal electrode was 1500 nm, and Au was selected as the metal electrode.

[0017] (2) Test equipment preparation and sample installation: Figure 1 As shown, the test device of this embodiment includes a ferroelectric measuring instrument 1, a sample clamping device, and a high-voltage wire 8. The sample clamping device is composed of an insulating cavity 2, an insulating end cover 3, an upper conductive column 4, an upper conductive plate 5, a lower conductive column 6 and a lower conductive plate 7. One end of the upper conductive column 4 is fixedly connected to the insulating end cover 3, and the other end of the upper conductive column 4 is fixedly connected to the upper conductive plate 5. One end of the lower conductive column 6 is fixedly connected to the insulating cavity 2, and the other end of the lower conductive column 6 is fixedly connected to the lower conductive plate 7. In this embodiment, the material of the upper conductive column 4, the lower conductive column 6, the upper conductive plate 5, and the lower conductive plate 7 is copper, and the diameter of the upper conductive plate 5 and the lower conductive plate 7 is 18mm±0.2mm, and the surface is flat. During the test, the insulating cavity 2 is filled with silicone oil, and the material of the insulating cavity 2 and the insulating end cover 3 is polytetrafluoroethylene. The copolymer film sample is placed in the center of the sample clamping device to ensure that the sample is completely immersed in the silicone oil, and the end cover is covered so that the surface electrode of the copolymer film is in good contact with the upper and lower conductive plates. In this embodiment, the silicone oil used is silicone oil with high viscosity and high dielectric constant.

[0018] (3) Test parameter setting: The high field strength resistance test of the copolymer material was carried out using the hysteresis loop test mode of the ferroelectric test method. The test frequency was set to 0.03 Hz and the test temperature was set to 25 °C. The test electric field was calculated based on the ratio of the test voltage to the thickness of the copolymer film sample. The test electric field was not less than 150 V / μm.

[0019] (4) High field strength resistance test: Start the hysteresis loop test, test once, and record the test curve of the polarization intensity of the copolymer film sample changing with the applied electric field.

[0020] (5) Data analysis: The high field strength resistance of the copolymer material is determined based on the maximum electric field intensity in the polarization intensity-electric field hysteresis loop.

[0021] The present invention utilizes the hysteresis loop test method in the ferroelectric measurement method. Since the relationship between the polarization process and the applied electric field can be grasped in real time during the application of the electric field, the high field strength resistance performance of the fluorinated copolymer material can be qualitatively and quantitatively analyzed, and the material's anti-electrical breakdown characteristics can be directly reflected. In addition, the device used is small in size, the test system is relatively simple, and has a certain degree of portability. Therefore, the high field strength resistance test method for fluorinated polymer materials is innovative.

[0022] In view of the technical characteristics of the test method and the fluorinated copolymer film material sample to be tested, the present invention also designs a sample clamping device, which adopts an insulating shell (including a cavity and an end cover) and a highly conductive copper conductive column and a conductive plate. The conductive plate is smaller than the sample size but much larger than the conductive column size. The purpose is to expand the close contact between the conductive plate and the electrode of the film sample to avoid unnecessary electrode damage or breakdown caused by point contact. Silicone oil with high viscosity and high dielectric constant is used in the sample clamping device to avoid impurities such as bubbles that are easy to break during testing, ensuring the smooth progress of high field strength testing.

[0023] The above is only an explanation of the preferred embodiments of the present invention, which should not be construed as a limitation on the claims. Any equivalent process changes made using the present invention specification are included in the patent protection scope of the present invention.

Claims

1. A method for testing the resistance of fluorinated copolymer materials to high field strength, characterized in that: The following steps are included: Step 1, preparation of copolymer material sample: preparing a copolymer film of a predetermined size from vacuum-dried copolymer resin powder by hot pressing, and preparing metal electrodes on the upper and lower surfaces of the film by magnetron sputtering technology; Step 2, test device preparation and sample installation: add silicone oil to the sample clamping device of the ferroelectric test equipment, place the copolymer film sample in the clamping device, ensure that the sample is completely immersed in the silicone oil, cover the end caps, so that the surface electrodes of the copolymer film are in contact with the upper and lower conductive plates; Step 3, test parameter setting: using the hysteresis loop test mode of the ferroelectric test method to perform a high field strength test on the copolymer material, setting the test frequency and the test electric field parameters; Step 4, high field strength resistance test: start the hysteresis loop test and record the test curve of the polarization intensity of the copolymer film sample changing with the applied electric field; Step 5, data analysis: determine the high field strength resistance of the copolymer material according to the maximum electric field intensity in the hysteresis loop of polarization intensity-electric field.

2. The method for testing the high field strength resistance of fluorinated copolymer materials according to claim 1, characterized in that: In the preparation of the copolymer material sample in step 1, the thickness of the copolymer film prepared by hot pressing is 55μm±5μm, the size is not less than 20mm×20mm, the thickness of the metal electrode is 100nm-200nm, and the electrode material is Au, Ag, Al, Ni, Ti, Cu or any one of double-layer metal Ti-Ni and Ti-Au.

3. The method for testing the high field strength resistance of fluorinated copolymer materials according to claim 1, characterized in that: In the sample holding device of step 2, the silicone oil used is silicone oil with high viscosity and high dielectric constant.

4. The method for testing the high field strength resistance of fluorinated copolymer materials according to claim 1, characterized in that: In the test parameter setting of step 3, the test method is the hysteresis loop test mode, the test frequency is 0.03 Hz, the test electric field is calculated based on the ratio of the test voltage to the thickness of the copolymer film sample, the test electric field is not less than 150 V / μm, and the test temperature is 25°C ± 5°C.

5. The method for testing the high field strength resistance of fluorinated copolymer materials according to claim 1, characterized in that: In the high field strength resistance test of step 4, the number of cycles of the hysteresis loop test is 1.

6. The method for testing the high field strength resistance of fluorinated copolymer materials according to claim 1, characterized in that: The testing device of step 2 includes a ferroelectric measuring instrument, a sample clamping device, and a high-voltage resistant wire. The sample clamping device consists of an insulating cavity, an insulating end cover, an upper conductive column, an upper conductive plate, a lower conductive column and a lower conductive plate. One end of the upper conductive column is fixedly connected to the insulating end cover, and the other end is fixedly connected to the upper conductive plate. One end of the lower conductive column is fixedly connected to the insulating cavity, and the other end is fixedly connected to the lower conductive plate.

7. The method for testing the high field strength resistance of fluorinated copolymer materials according to claim 6, characterized in that: During the test, the insulation cavity was filled with silicone oil, and the insulation cavity and the insulation end cap were made of polytetrafluoroethylene.

8. The method for testing the high field strength resistance of fluorinated copolymer materials according to claim 6, characterized in that: The upper conductive column, the lower conductive column, the upper conductive plate and the lower conductive plate are made of copper. The diameters of the upper and lower conductive plates are 18 mm ± 0.2 mm, and the surfaces are flat.

Images