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CN-115362567-B - Leadless three-component piezoelectric polymer composite material

CN115362567BCN 115362567 BCN115362567 BCN 115362567BCN-115362567-B

Abstract

A polymer composite material having piezoelectric properties that can be molded for flexible and/or thin film applications, wherein the polymer composite material comprises a polymer matrix and a piezoelectric ceramic filler embedded in the polymer matrix. The polymer matrix may comprise at least two polymers, a first polymer and a second polymer. The first polymer may be a fluorinated polymer, the second polymer may be compatible with the first polymer and may have a dielectric constant of less than about 20. The piezoelectric ceramic filler may be a lead-free ceramic filler such as barium titanate, and may be about 40-70vol% of the polymer composite. The remaining 30-60vol% may be the polymer matrix, which itself may be about 5-20wt% of the second polymer and 80-95wt% of the fluorinated polymer.

Inventors

  • S. Guhasakurta
  • T. Hoekslam Portos
  • R. Janapa Sibhothra Venkata
  • D. Owens
  • P. Ma Chu Kunte Bada Linais

Assignees

  • SABIC环球技术有限责任公司

Dates

Publication Date
20260505
Application Date
20210401
Priority Date
20200402

Claims (11)

  1. 1. A lead-free piezoelectric polymer composite comprising: A polymer matrix comprising at least two polymers, a first polymer comprising a fluorinated polymer and a second polymer compatible with the first polymer and having a dielectric constant of less than 20, wherein the polymer matrix comprises 5 to 20wt% of the second polymer, and A lead-free piezoelectric ceramic filler embedded in a polymer matrix, wherein the piezoelectric ceramic filler comprises 40-70vol% of the polymer composite.
  2. 2. The polymer composite of claim 1, wherein the first polymer comprises PVDF-TrFE-CFE.
  3. 3. The polymer composite of claim 1 or 2, further comprising a flexible substrate connected to the polymer composite, wherein the polymer composite is a mechanically flexible film.
  4. 4. The polymer composite of claim 3 wherein the mechanically flexible film has a thickness of 50-200 μm.
  5. 5. The polymer composite according to claim 1 or 2, wherein the piezoelectric ceramic filler is barium titanate particles having a particle diameter of 250-350 nm.
  6. 6. The polymer composite according to claim 1 or 2, wherein the polymer composite has piezoelectric properties such that a piezoelectric strain constant is 30 to 70pC/N and a piezoelectric voltage constant is 100 to 300mv.m/N.
  7. 7. A method of making a film using the polymer composite of any one of claims 1-6, wherein the method comprises: dissolving a first polymer into a solution of a second polymer in a solvent to form a dual polymer solution, wherein the solvent has a dielectric constant of at least 20 and a boiling point of at least 80 ℃; adding a lead-free piezoelectric ceramic filler to the bipolymer solution to form a dispersion or suspension; forming a polymer composite film by casting and drying the solvent, and And carrying out electric polarization treatment on the polymer composite material film.
  8. 8. The method of claim 7, wherein the dual polymer solution formed by dissolving the first polymer in the solution of the second polymer comprises 5-20wt/vol% polymer.
  9. 9. The method of claim 8, wherein the dual polymer solution formed by dissolving the first polymer into the solution of the second polymer comprises 10-12wt/vol% polymer.
  10. 10. The method of any of claims 7-9, further comprising annealing the polymer composite film in an inert atmosphere.
  11. 11. A piezoelectric sensor comprising a polymer composite film prepared according to the method of any one of claims 7-10, wherein the piezoelectric sensor is configured to generate an analog signal proportional to an amount of deflection applied by a user on the piezoelectric sensor, wherein the piezoelectric sensor is integrated in a mobile device.

Description

Leadless three-component piezoelectric polymer composite material Cross reference to related applications And no. Technical Field The present invention relates generally to piezoelectric materials. More particularly, the present invention relates to a polymer material having piezoelectric properties. Background Piezoelectric material refers to a material that has a defined relationship between the charge accumulated in the material and the mechanical stress applied to the material. Some conventional piezoelectric materials are inorganic ceramic materials (e.g., piezoelectric ceramic materials), which are heavy and brittle. These inorganic ceramic materials require high temperature treatments in excess of 500 ℃. Other conventional piezoelectric materials are piezoelectric polymers such as PVDF and PVDF-TrFE copolymers. The piezoelectric charge/strain constant d of these piezoelectric polymers is low compared to piezoelectric ceramics. The piezoelectric charge/strain constant d is an important parameter for evaluating the driving capability of the piezoelectric material under the action of an electric field, and the piezoelectric voltage constant g is used for measuring the sensing capability of the piezoelectric material. Inorganic piezoelectric ceramics have a high d (d 33 >150 pC/N), but high dielectric constant values limit their g values (g 33 <50 mv.m/N). In contrast, piezoelectric polymers have a lower d (d 33.apprxeq.13-28 pC/N) and a higher g (g 33.apprxeq.200 mV-m/N). The d 33 value refers to induced polarization per unit stress applied in direction 3 (parallel to the direction in which the ceramic element is polarized). The g 33 value refers to the induced electric field per unit stress applied in the direction 3 (parallel to the direction in which the ceramic element is polarized). Materials with higher d 33 and g 33 values are needed. For materials identified as piezoelectric materials, the d 33 value is greater than about 1pC/N. Disclosure of Invention High performance piezoelectric materials are ideal materials for sensors, actuators, and energy harvesters in medical care and biomedical applications, and in wearable electronics. These and other applications require a piezoelectric material that is mechanically flexible. Embodiments of the present invention provide piezoelectric composite films made using lead-free piezoelectric ceramic fillers. The piezoelectric polymer composite provides one or more of high voltage electrical properties with mechanical flexibility, thin film forming capability, unsupported films and substrate support films, simple methods of making the piezoelectric polymer composite, and/or low temperature processing. An example polymer composite includes a polymer matrix of at least two polymers and a piezoelectric ceramic filler embedded in the polymer matrix. The polymer matrix may include a fluorinated polymer and a second polymer having a dielectric constant less than about 20. The properties of the second polymer affect the dielectric constant of the matrix and affect the dispersibility of the filler in the matrix, which in turn affects the dielectric constant of the piezoelectric polymer composite. In addition to a dielectric constant of less than 20, the second polymer is also compatible with the first polymer. The compatibility of the polymer may be determined by the migration of the transition temperature (T m or T g) of the polymer blend relative to the neat polymer. When the migration is greater than 2 ℃, the polymers may be compatible. Examples of secondary polymers that are used in the polymer matrix for compatibility with PVDF-TrFE-CFE (when PVDF-TrFE-CFE is a fluorinated polymer) include PVDF-TrFE (which has a dielectric constant of about 8-10), PC (which has a dielectric constant of about 3), and PPO (which has a dielectric constant of about 2.5), all of which have a dielectric constant of less than 20. In some embodiments, the loading of the piezoceramic filler in the polymer matrix may be about 40 to 70vol%. For PVDF-TrFE-CFE based polymer matrices, the loading of the piezoceramic filler is outside this range and is mechanically brittle. In some embodiments, the loading of the second polymer in the polymer matrix may be from 5 to 20wt%. For PVDF-TrFE-CFE based polymer matrices, loadings of the second polymer outside this weight range can degrade piezoelectric performance. According to various aspects of the present invention, preparing a piezoelectric polymer composite may include dissolving two polymers of a polymer matrix in a solvent to form a dual polymer solution, adding a piezoelectric ceramic filler to the dual polymer solution to form a suspension, and forming a polymer composite film by casting onto a substrate and drying the solvent. During processing, the piezoelectric polymer composite may be subjected to an electrical polarization treatment. In some embodiments, the composite film is annealed and/or corona polarized. Furthermore, in some embodi