Piezoelectric polymer blends and composites including lithium-doped potassium sodium niobate

Abstract

A polymer composite having piezoelectric properties that can be formed for flexible and / or thin film applications, where the polymer composite includes a polymer matrix and a piezoelectric ceramic filler embedded in the polymer matrix. The polymer matrix can include at least two polymers: a first polymer and a second polymer. The first polymer can be a fluorinated polymer and the second polymer can be compatible with the first polymer and have a dielectric constant less than about 20. The piezoelectric ceramic filler can be lithium-doped potassium sodium niobate (KNLN) and can be about 40-70 vol% of the polymer composite. The remaining 30-60 vol% can be the polymer matrix, which itself can be about 5-20 wt% of the second polymer and 80-95 wt% of the fluorinated polymer.

Description

[0001] Cross-referencing related applications

[0002] none. Technical Field

[0003] This invention relates primarily to piezoelectric materials. More specifically, this invention relates to polymer materials possessing piezoelectric properties. Background Technology

[0004] Piezoelectric materials are materials in which there is a definite relationship between the electric charge accumulated in the material and the mechanical stress applied to it. Some traditional piezoelectric materials are inorganic ceramics (such as piezoelectric ceramics), which are heavy and brittle. These inorganic ceramics require high-temperature processing exceeding 500°C. Other traditional piezoelectric materials are piezoelectric polymers, such as PVDF and PVDF-TrFE copolymers. Compared to piezoelectric ceramics, these piezoelectric polymers have a very low piezoelectric charge / strain constant d. The piezoelectric charge / strain constant d is an important parameter for evaluating the driving ability of piezoelectric materials under the action of an electric field, while the piezoelectric voltage constant g is used to measure the inductive ability of piezoelectric materials. Inorganic piezoelectric ceramics have high d(d 33 >150pC / N), but the high dielectric constant limits its g value (g 33 <50mV.m / N). In contrast, piezoelectric polymers have lower d(d 33 ≈13-28pC / N) and higher g(g 33 ≈200mV-m / N). The d 33 The value refers to the induced polarization per unit stress applied in direction 3 (parallel to the direction in which the ceramic element is polarized). The g... 33 The value refers to the induced electric field per unit stress applied in direction 3 (parallel to the direction in which the ceramic element is polarized). A high d value is required. 33 and g 33 Materials with a value of d. For materials identified as piezoelectric materials, d 33 The value should be greater than approximately 1 pC / N. Summary of the Invention

[0005] High-performance piezoelectric materials are ideal for sensors, actuators, and energy harvesters in healthcare and biomedical applications, as well as wearable electronic devices. These and other applications require piezoelectric materials with mechanical flexibility. Embodiments of this invention provide piezoelectric composite films made using lead-free piezoelectric ceramic fillers. The piezoelectric polymer composite material offers one or more of the following: mechanically flexible piezoelectric properties, film-forming ability, unsupported film and substrate-supported film, a simple method for preparing the piezoelectric polymer composite material, and / or a low-temperature processing technology.

[0006] An example of a polymer composite material 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 with a dielectric constant less than about 20. The properties of the second polymer affect the dielectric constant of the matrix and, in turn, the dispersion of the filler in the matrix, which in turn affects the dielectric constant of the piezoelectric polymer composite material. In addition to having a dielectric constant less than 20, the second polymer is also compatible with the first polymer. The compatibility of the polymers can be determined based on the transition temperature (T0) of the polymer blend relative to the pure polymer. m or T g The compatibility is determined by the migration of the piezoelectric ceramic filler. When the migration exceeds 2°C, the polymer may be compatible. Examples of second polymers compatible with PVDF-TrFE-CFE (when PVDF-TrFE-CFE is a fluorinated polymer) in the polymer matrix include PVDF-TrFE (with a dielectric constant of approximately 8-10), PC (with a dielectric constant of approximately 3), and PPO (with a dielectric constant of approximately 2.5), all of which have dielectric constants less than 20. In some embodiments, the loading of the piezoelectric ceramic filler in the polymer matrix can be approximately 40-70 vol%. For PVDF-TrFE-CFE-based polymer matrices, loadings of the piezoelectric ceramic filler outside this range result in mechanical brittleness. In some embodiments, the loading of the second polymer in the polymer matrix can be 5-20 wt%. For PVDF-TrFE-CFE-based polymer matrices, loadings of the second polymer outside this weight range degrade the piezoelectric properties.

[0007] According to various aspects of the present invention, the preparation of piezoelectric polymer composites 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 polarization treatment. In some embodiments, the composite film is annealed and / or corona-polarized. Furthermore, in some embodiments, melt processing techniques may be used to prepare the piezoelectric composite film; the piezoelectric composite film may be customized as (0-3) (random), (1-3) (structured) piezoelectric composites; and / or other in-situ and out-of-situ techniques may be used to prepare the piezoelectric composite. (0-3) piezoelectric polymer composites refer to the connectivity between the ceramic and polymer components. The first number corresponds to the connectivity in the ceramic component, and the second number corresponds to the connectivity in the polymer. The composite material exhibits (0-3) connectivity when the piezoelectric ceramic particles are surrounded by a three-dimensionally connected polymer phase. Compared to (0-3) piezoelectric composites, some (1-3) piezoelectric composites may have higher dp. 33 value.

[0008] According to various aspects of the present invention, polymer composite materials can be deposited as thin films on a substrate to form piezoelectric devices. In some embodiments, the polymer composite material is a mechanically flexible thin film formed on a flexible substrate as part of the fabrication of a flexible electronic device. Elongation at break (percentage) values ​​can be used to represent the mechanical flexibility of the material. In some embodiments, the elongation at break (percentage) of the piezoelectric composite film is greater than 25%. Such electronic devices may include piezoelectric sensors configured to generate analog signals proportional to the amount of deflection applied to the piezoelectric sensor by a user. The piezoelectric sensor may be integrated into a mobile device for receiving user input to control the mobile device. In one embodiment of a wearable medical device, mechanical vibrations of body organs, such as a heartbeat, can be converted into electrical signals and transmitted to a smartphone or other computing device via Bluetooth, Wi-Fi, or other signals. In another example of the use of piezoelectric materials, the material can be used as a converter to transform output signals, for example, configuring the piezoelectric material as a speaker or buzzer to convert the signal into audible sound. In another example of the use of piezoelectric materials, the material may be transparent and incorporated into an electronic display screen to form a touch screen device that can display information to a user and receive feedback from the user on the displayed information by tapping the screen.

[0009] According to some embodiments of the present invention, an example of a piezoelectric material comprises a three-component piezoelectric composite material containing polymer 1 / polymer 2 / piezoelectric filler, wherein polymer 1 is PVDF-TrFE-CFE, polymer 2 is a low-dielectric polymer (dielectric constant <20) compatible with PVDF-TrFE-CFE, and the piezoelectric filler is lithium-doped potassium sodium niobate (KNLN). This material, as well as other materials of the present invention, can be prepared using solvents with a dielectric constant >20 and a boiling point ≥80°C, wherein the use of the solvent can provide high dielectric constant. 33 and g 33 Composite piezoelectric composite films. High-boiling-point and high-dielectric-point solvents facilitate filler dispersion in the matrix, thereby improving the piezoelectric properties of the film. In the composite material, the loading of piezoelectric filler can be greater than 40 vol%. The d of the formed piezoelectric composite film... 33 and g 33 The value can be d 33 ≈30-70pC / N and g 33 ≈100-300mV-m / N.

[0010] According to some embodiments of the invention, another example of a material is a polymer blend having piezoelectric properties, comprising at least two polymers: a first polymer and a second polymer, wherein the first polymer comprises a non-piezoelectric fluorinated polymer and the second polymer comprises a non-piezoelectric acrylic polymer. The polymer blend may contain about 5-15 wt% of the second polymer.

[0011] According to embodiments of the invention, piezoelectric composite materials and devices incorporating such piezoelectric composite materials can provide cost benefits compared to commercial piezoelectric polymers. Furthermore, lead-free piezoelectric composite materials are solution-processable and less expensive than commercial piezoelectric polymers. Additionally, larger unsupported piezoelectric polymer films can be fabricated using the preparation methods described herein. Moreover, the piezoelectric composite film described herein can be made mechanically flexible because the method allows for the formation of a piezoelectric layer of the desired thickness at low temperatures of approximately 110°C or not exceeding 150°C. In some disclosed preparation techniques, piezoelectric composite materials can be deposited onto a substrate and polarized more effectively than through contact polarization. In some embodiments, depending on application requirements, the desired metal electrode pattern can be patterned on the polarized active layer.

[0012] Examples of piezoelectric fillers include any lead-free ceramic or single-crystal material. Non-limiting examples of piezoelectric materials include inorganic compounds of the perovskite series. Non-limiting examples of piezoelectric ceramics having a perovskite structure include barium titanate (BaTiO3), hydroxyapatite, apatite, lithium sulfate monohydrate, potassium sodium niobate, sodium bismuth titanate, quartz, organic materials (e.g., tartaric acid, polyvinylidene fluoride fiber), or combinations thereof. In a preferred embodiment, the piezoelectric additive is BaTiO3. The particle size of lead-free piezoelectric particles can be 200-1000nm or 250-350nm, or at least equal to or between any two of the following: 200nm, 225nm, 250nm, 275nm, 300nm, 325nm, 350nm, 375nm, 400nm, 425nm, 450nm, 475nm, 500nm, 525nm, 550nm, 575nm, 600nm, 625nm, 650nm, 675nm, 700nm, 725nm, 750nm, 775nm, 800nm, 825nm, 850nm, 875nm, 900nm, 925nm, 950nm, 975nm, and 1000nm.

[0013] Examples of polymer materials include thermosetting polymers, copolymers and / or monomers, thermoplastic polymers, copolymers and / or monomers, or thermosetting / thermoplastic polymers or polymer blends. Thermosetting polymers are plastic before heating and can be molded. The matrix can be made from a composition containing a thermoplastic polymer, and may also include other non-thermoplastic polymers, additives, etc., that can be added to the composition. Thermosetting polymer matrices are cured or crosslinked and tend to lose their ability to become flexible or plastic upon increasing temperature. Non-limiting examples of thermosetting polymers used to prepare polymer films include epoxy resins, epoxy vinyl esters, alkyd resins, amino polymers (e.g., polyurethane, urea-formaldehyde), diallyl phthalate, phenolic polymers, polyesters, unsaturated polyester resins, dicyclopentadiene, polyimides, silicone polymers, cyanate esters of polycyanate, thermosetting polyacrylic resins, phenolic plastics, thermosetting plastics, benzoxazoles, or copolymers or blends thereof.

[0014] Thermoplastic polymer matrices can become flexible or malleable above a certain temperature and can cure below a certain temperature. The polymer matrix of the composite material may include the thermoplastic or thermosetting polymers discussed in this application, their copolymers, and blends. Non-limiting examples of the thermoplastic polymers include polyvinylidene fluoride (PVDF), PVDF-based polymers, PVDF copolymers (poly(vinylidene fluoride-trifluoroethylene)(PVDF-TrFE)), PVDF trimers (poly(vinylidene fluoride-trifluoroethylene-chlorofluoroethylene)(PVDF-TrFE-CFE), poly(vinylidene fluoride-trifluoroethylene-chlorotrifluoroethylene)(PVDF-TrFE-CTFE)), odd-number nylon, cyanopolymers, polyethylene terephthalate (PET), polycarbonate (PC) series polymers, polybutylene terephthalate (PBT), poly(1,4-cyclohexylcyclohexane-1,4-dicarboxylate) (PCCD), and glycol-modified polycyclohexane terephthalate (…). Poly(phenylene oxide) (PCTG), polyphenylene oxide (PPO), polypropylene (PP), polyethylene (PE), polyvinyl chloride (PVC), polystyrene (PS), polymethyl methacrylate (PMMA), polyethyleneimine or polyetherimide (PEI) and its derivatives, thermoplastic elastomers (TPE), terephthalic acid (TPA) elastomers, poly(cyclohexanedimethyl terephthalate) (PCT), polyethylene naphthalate (PEN), polyamide (PA), sulfonated polysulfone (PSS), sulfonates of polysulfone, polyetheretherketone (PEEK), polyetherketone (PEKK), acrylonitrile-butadiene-styrene (ABS), acrylonitrile-styrene-acrylate (ASA) polymers, polyphenylene sulfide (PPS), and copolymers or blends thereof. Furthermore, other thermoplastic polymers known to those skilled in the art, as well as those subsequently developed, may also be used in this invention. The thermoplastic polymers may be included in compositions comprising the polymers and additives. Non-limiting examples of the additives include coupling agents, antioxidants, heat stabilizers, flow modifiers, colorants, and any combination thereof. In a preferred embodiment, a polyvinylidene fluoride (PVDF) polymer, its copolymers, or trimers are used. The trimer may be poly(vinylidene fluoride-trifluoroethylene-chlorofluoroethylene) (PVDF-TrFE-CFE).

[0015] Examples of solvents used in the production of lead-free piezoelectric composites can be any solvent with a dielectric constant ≥20 and a boiling point ≥80°C. Non-limiting examples of the solvent include dimethylacetamide (DMAc), dimethylformamide (DMF), dimethyl sulfoxide (DMSO), N-methyl-2-pyrrolidone (NMP), or combinations thereof. In some embodiments, the solvent is DMAc. The dielectric constant of the solvent can be at least, equal to, or greater than 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, or 80. The boiling point of the solvent can be at least, equal to, or higher than 80°C, 85°C, 90°C, 95°C, 100°C, 105°C, 110°C, 115°C, 120°C, 125°C, 130°C, 135°C, 140°C, 145°C, 150°C, 155°C, 160°C, 165°C, 170°C, 180°C, 185°C, 190°C, 195°C, 200°C, or 210°C. Various combinations of dielectric constant and boiling point are acceptable as long as both of the above criteria are met.

[0016] Some polymer composites can also exhibit piezoelectric properties even without piezoelectric fillers. One example of such materials is a polymer blend comprising at least two polymers: a first polymer and a second polymer, wherein the first polymer comprises a non-piezoelectric fluorinated polymer and the second polymer comprises a non-piezoelectric acrylic polymer. The polymer blend may contain about 5-15 wt%, preferably 8-12 wt%, of the second polymer, and the polymer blend itself possesses piezoelectric properties. The acrylic polymer induces crystallization in these compositions, leading to improved mechanical properties and the establishment of piezoelectric properties.

[0017] The terms “wt%”, “vol%”, or “mol%” refer to the weight, volume, or molar percentage of a component, based on the total weight, volume, or moles of the material comprising that component. In a non-limiting example, 10 moles of a component in 100 moles of material is considered 10 mol% of the component.

[0018] The term “basically” and its variations are defined as including ranges of 10%, 5%, 1%, or 0.5%.

[0019] The terms “suppress” or “reduce” or “prevent” or “avoid” or any variation thereof, when used in the claims and / or specification, include any measurable reduction or complete suppression to achieve the desired result.

[0020] The term "effective," when used in the claims and / or description, means sufficient to achieve the desired, anticipated, or intended result.

[0021] When used with the terms “comprising,” “including,” “containing,” or “having” in the claims or description, the indefinite article can mean “one,” but it also has the same meaning as “one or more,” “at least one,” and “one or more.”

[0022] The terms “including” (and any variations thereof), “having” (and any variations thereof), “containing” (and any variations thereof), or “comprising” (and any variations thereof) are inclusive or open-ended and do not exclude additional, uncited elements or method steps.

[0023] The method of the present invention may "comprise" specific ingredients, components, compositions, etc. disclosed throughout the specification, substantially consist of or consist of them.

[0024] Other objects, features, and advantages of the present invention will become apparent from the following drawings, detailed description, and embodiments. However, it should be understood that while these drawings, detailed descriptions, and embodiments illustrate specific embodiments of the invention, they are illustrative only and not restrictive. Furthermore, it should be understood that variations and modifications within the spirit and scope of the invention will become apparent to those skilled in the art due to this detailed description. In further embodiments, features of a particular embodiment may be combined with features of other embodiments. For example, a feature of one embodiment may be combined with features of any other embodiment. In further embodiments, additional features may be added to the specific embodiments described herein. Attached Figure Description

[0025] For a more comprehensive understanding, please now refer to the following description in conjunction with the accompanying drawings, in which:

[0026] Figure 1 A method for preparing piezoelectric polymer composite materials according to some embodiments of the present invention is provided.

[0027] Figure 2 DSC thermograms of piezoelectric polymer blends with a weight ratio of PVDF-TrFE-CFE:polymer 2 of 90:10 according to some embodiments of the present invention are provided.

[0028] Figure 3 DSC thermograms of piezoelectric polymer blends with different weight ratios of PVDF-TrFE-CFE:ASA according to some embodiments of the present invention are given.

[0029] Figure 4 Stress-strain measurements of piezoelectric polymer blends with a PVDF-TrFE-CFE:polymer 2 weight ratio of 90:10 according to some embodiments of the present invention are given. Detailed Implementation

[0030] Figure 1 A method for preparing a piezoelectric polymer composite material is provided. Method 100 begins at block 102, wherein two polymers are dissolved in a solvent to form a dual-polymer solution with a polymer concentration of at least about 12% relative to the solvent, for example, by dissolving 12 g of PVDF-TrFE-CFE resin in 100 mL of solvent. The polymer concentration in the solution used to prepare the piezoelectric composite material can be 5-20% (wt / v), or more preferably 8-15% (wt / v), or even more preferably 10-13% (wt / v). Composite materials with polymer concentrations below 5% (wt / v) may form discontinuous films. Polymer concentrations exceeding 20% ​​(wt / v) may result in difficulty in achieving high filler loadings. In some embodiments, when the polymer concentration is below 5% (wt / v), the desired piezoelectric and other properties can be obtained through different preparation techniques. Then, at block 104, method 100 continues, optionally adding a piezoelectric ceramic filler to the dual-polymer solution to form a dispersion. In some embodiments, such as polymer blends prepared as piezoelectric materials, no piezoelectric ceramic filler is added. At block 106, a polymer composite film can be formed by casting onto a substrate and drying the solvent. At block 108, the cast piezoelectric composite film is polarized. Method 100 can be carried out at a temperature not exceeding about 120°C, thus this preparation process can be used to prepare piezoelectric composites on flexible substrates. The temperature can be selected to be approximately the Curie temperature of the barium titanate piezoelectric ceramic filler and approximately the melting temperature of the PVDF-TrFE-CFE polymer matrix. In some embodiments, after casting the film onto the substrate, the piezoelectric composite is annealed in an inert atmosphere (such as nitrogen). Although referenced... Figure 1 The block diagram illustrates an embodiment of the invention, but it should be understood that the operation of the invention is not limited to this. Figure 1 The specific block diagrams and / or the specific block diagram order shown. Therefore, embodiments of the present invention can use different... Figure 1 The various block diagrams are arranged in sequence to provide the functionality described in this article.

[0031] In some embodiments, the piezoelectric composite material can be of any shape or form. In some embodiments, the piezoelectric composite material is a film or sheet. In some embodiments, the thickness of the film or sheet is 50-200 μm or is at least, equal to, or between any two of 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, and 200 μm.

[0032] The properties of the piezoelectric composite material include electrical and mechanical properties. Non-limiting examples of the electrical properties may include piezoelectric constant, dielectric constant, etc. The d of the piezoelectric composite material... 33 The dielectric constant is at least, equal to, or between any two of 40 pC / N, 45 pC / N, 50 pC / N, 55 pC / N, 56 pC / N, 57 pC / N, 58 pC / N, 59 pC / N, 60 pC / N, 61 pC / N, 62 pC / N, 63 pC / N, 64 pC / N, 65 pC / N, 66 pC / N, 67 pC / N, 68 pC / N, 69 pC / N, and 70 pC / N. For example, the dielectric constant of the piezoelectric composite material can be less than, equal to, or between any two of 120, 115, 110, 105, 100, 95, 90, 85, 80, 75, 70, 65, 60, 55, 50, 45, 40, and 35. In some embodiments, the dielectric constant is 90-210. The storage modulus of the lead-free piezoelectric composite material can be 100-325 MPa, or at least equal to or between any two of 100, 125, 150, 175, 200, 225, 250, 275, 300, and 325 MPa. The storage modulus can be measured according to ISO 6721 at room temperature and 0.2% strain at 1 Hz. Under uniaxial loading at room temperature (e.g., 25-35°C), the elongation at break of the lead-free piezoelectric composite material can be 30-500%. The elongation at break can be measured using a standard dynamic mechanical analyzer.

[0033] Polymer composites with piezoelectric properties can be formed for thin film, sheet, or coating applications, wherein the polymer composite comprises a polymer matrix and a piezoelectric ceramic filler embedded in the polymer matrix. Although examples of thin films are described in some embodiments, the described materials can also be used or are suitable for sheets or coatings. The polymer matrix may include at least two polymers: a first polymer and a second polymer. The first polymer may be a fluorinated polymer, and the second polymer may be compatible with the first polymer and have a dielectric constant of less than about 20. The piezoelectric ceramic filler may be lithium-doped potassium sodium niobate (KNLN) and may be about 40-70 vol% of the polymer composite. The remaining 30-60 vol% may be the polymer matrix, which itself contains about 2-10 wt% of the second polymer and 90-98% of the fluorinated polymer. The resulting piezoelectric composite may have a piezoelectric strain constant of about 30-70 pC / N and a piezoelectric voltage constant of about 100-300 mV-m / N. Table 1 shows embodiments using KNLN ceramic filler, PVDF-TrFE-CFE as polymer 1, DMAc as solvent, and a KNLN loading of 40 vol%. In some examples, Table 1 also shows polymer blends without KNLN particles.

[0034] Table 1 shows piezoelectric composites and blends (e.g., films or coatings) using PVDF-TrFE-CFE as the first polymer in the polymer matrix, some of which contain KNLN piezoelectric filler.

[0035]

[0036] Examples 1-3 were prepared by dissolving polymer 2 in DMAc. PVDF-TrFE-CFE was then added and stirred until completely dissolved. The solution concentration was ~12% (w / v). Subsequently, the required amount of KNLN was slowly added to the solution while stirring with a magnetic stirrer at 200-250 rpm. After stirring for 30 minutes, the mixture was cast into a thin film on a glass plate using a spatula and then dried in the open air for 24 hours. After drying, the film was peeled off the glass plate and annealed in a nitrogen atmosphere. Table 1 shows the composition of the piezoelectric polymer composites prepared according to the above procedure.

[0037] Examples 4-8 were prepared by dissolving polymer 2 in DMAc. PVDF-TrFE-CFE was then added and stirred until completely dissolved. The solution concentration was ~12% (w / v). The solution was cast into a thin film on a glass plate using a doctor blade and then dried in the open air for 24 hours. After drying, the film was peeled off the glass plate and annealed in a nitrogen atmosphere. Table 1 shows the composition of the piezoelectric polymer composites prepared according to the above procedure.

[0038] The piezoelectric properties of the various embodiments in Table 1 are different. Comparing Embodiments 5, 6, 7, and 8, it can be seen that Embodiments 5 and 7 exhibit piezoelectricity upon polarization, while Embodiment 5 has a piezoelectric property of d. 33 The value is higher than that in Example 7.

[0039] Figure 2 DSC thermograms of piezoelectric polymer blends with a PVDF-TrFE-CFE:polymer 2 weight ratio of 90:10 according to some embodiments of the present invention are given. Pure PVDF-TrFE-CFE exhibits a single melt transition at 125°C, while two melt transitions were observed in Examples 5 and 7. The crystallinity of these compositions is significantly improved. On the other hand, in blends containing PPO (such as Example 8), the melt transition of PVDF-TrFE-CFE remains almost unchanged, with only broadening observed.

[0040] Figure 3 DSC thermograms of piezoelectric polymer blends with different PVDF-TrFE-CFE:ASA weight ratios according to some embodiments of the present invention are given. Figure 3The effect of the PVDF-TRFE-CFE / ASA blend ratio on the transition temperature is presented. In the 90 / 10 PVDF-TRFE-CFE / ASA blend, the migration of the melt transition is obvious, while in the 95 / 5 and 80 / 20 blends, the transition temperature is almost unchanged.

[0041] Figure 4 Stress-strain measurements of piezoelectric polymer blends with a PVDF-TrFE-CFE:polymer 2 weight ratio of 90:10 according to some embodiments of the present invention are given. The modulus of Example 7 is higher than that of Example 5.

[0042] At a blending ratio of 90 / 10, the improved melt transition migration and crystallinity of the PVDF-TrFE-CFE / acrylate polymer blend indicate good compatibility between the two components. Induced crystallization increases the piezoelectricity of the blend composition. Increased crystallinity and the high modulus of PMMA lead to an increase in the modulus of the PVDF-TrFE-CFE / PMMA blend. Comparing Examples 1, 2, and 3, it is evident that the presence of the acrylate polymer as a third component slightly reduces the modulus. 33 However, this leads to an increase in modulus, especially for PMMA (see Table 1), due to the induced crystallization of acrylate polymers in PVDF-TrFE-CFE.

[0043] Although the embodiments and advantages of this application have been described in detail, it should be understood that various changes, substitutions, and modifications can be made herein without departing from the spirit and scope of the embodiments as defined by the appended claims. Furthermore, the scope of this application is not limited to the specific embodiments of the processes, machines, preparations, combinations of substances, means, methods, and steps described in the specification. As will readily be understood by those skilled in the art from the foregoing disclosure, processes, machines, preparations, combinations of substances, means, methods, or steps that are currently existing or will be developed thereafter can be utilized to perform substantially the same function or achieve substantially the same results as the corresponding embodiments described herein. Therefore, the appended claims are intended to include all such processes, machines, preparations, combinations of substances, means, methods, or steps within their scope.

Claims

1. A polymer composite material, comprising: A polymer matrix comprising at least two polymers: a first polymer and a second polymer, wherein the first polymer comprises PVDF-TrFE-CFE, and the second polymer is a non-piezoelectric acrylic polymer compatible with the first polymer and having a dielectric constant less than 20; and the polymer matrix contains 5-20 wt% of the non-piezoelectric acrylic polymer as the second polymer, wherein the non-piezoelectric acrylic polymer comprises at least one of polymethyl methacrylate (PMMA), polybutyl acrylate (PBA), polyhydroxyethyl methacrylate (PHEMA), or acrylonitrile-styrene-acrylate (ASA); and the non-piezoelectric acrylic polymer induces crystallization, thereby improving the mechanical properties of the polymer composite and establishing piezoelectric properties; and Piezoelectric ceramic fillers embedded in a polymer matrix, wherein the piezoelectric ceramic fillers include lithium-doped potassium sodium niobate (KNLN).

2. The polymer composite material according to claim 1, wherein the piezoelectric ceramic filler accounts for 40-70 vol% of the polymer composite material.

3. The polymer composite material according to claim 1 or 2, wherein the polymer matrix of the polymer composite material comprises 10-15 wt% of a non-piezoelectric acrylic polymer as a second polymer.

4. The polymer composite material according to claim 1 or 2, further comprising a flexible substrate connected to the polymer composite material, wherein the polymer composite material is a mechanically flexible film.

5. The polymer composite material according to claim 4, wherein the thickness of the mechanically flexible film is 50-200 μm.

6. The polymer composite material according to claim 1 or 2, wherein the polymer composite material is characterized by a piezoelectric strain constant of 30-70 pC / N and a piezoelectric voltage constant of 100-300 mV-m / N.

7. A method for preparing a thin film using the polymer composite material according to any one of claims 1-6, wherein the method comprises: A first polymer is dissolved in a solution of a second polymer in a solvent to form a dipolymer solution, wherein the solvent is characterized by having a dielectric constant of at least 20 and a boiling point of at least 80°C. Piezoelectric ceramic fillers are added to the dual polymer solution to form a dispersion or suspension; Polymer composite films are formed by casting and solvent drying; and The polymer composite film is subjected to electrodeization treatment.

8. The method of claim 7, wherein the bipolymer solution formed by dissolving the first polymer in a solution of the second polymer comprises 5-20 wt / vol% of the polymer.

9. The method of claim 8, wherein the bipolymer solution formed by dissolving the first polymer in a solution of the second polymer comprises 10-12 wt / vol% of the polymer.

10. The method according to claim 8 or 9, further comprising annealing the polymer composite film in an inert atmosphere.

11. A piezoelectric sensor comprising the polymer composite material of any one of claims 1-6, wherein the piezoelectric sensor is configured to generate an analog signal proportional to an amount of deflection applied to the piezoelectric sensor by a user, wherein the piezoelectric sensor is integrated in a mobile device.

12. A polymer blend comprising: At least two polymers: The first polymer includes a non-piezoelectric fluorinated polymer; and The second polymer is a non-piezoelectric acrylic polymer that is compatible with the first polymer and has a dielectric constant of less than 20. The polymer blend comprises 8-15 wt% of a non-piezoelectric acrylic polymer as a second polymer, wherein the non-piezoelectric acrylic polymer includes at least one of polymethyl methacrylate (PMMA), polybutyl acrylate (PBA), polyhydroxyethyl methacrylate (PHEMA), or acrylonitrile-styrene-acrylate (ASA), and the non-piezoelectric acrylic polymer induces crystallization, thereby improving the mechanical properties of the polymer blend and establishing piezoelectric properties.

13. The polymer blend of claim 12, wherein the polymer blend comprises 8-12 wt% of a non-piezoelectric acrylic polymer as a second polymer.

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