KR20030075212A - Dieletric Device Using PVDF and Nano Ceramics Particles, and Method for Fabrication the Same - Google Patents

Abstract

PURPOSE: A piezo-electric body using PVDF(Polyvinylidene Fluoride) and nano ceramic is provided to mold PVDF/nano ceramic composites on a film, and to perform an annealing process with pressing/elongating processes for the composites, thereby improving distribution of ceramic particles on PVDF. CONSTITUTION: A pressing process is performed as follows. PVDF/nano ceramic composites are kneaded in an extruder(24), and are applied a blow-molding process, to be molded into a tube-type parison(12). The parison(12) is united on a single film by guiding plates(28). The united parison(12) passes through many pinch rollers(31,32,33,34). Many containers(51,52) are impregnated with the parison(12) through an annealing process. A driving roller(60) is used for implementing excellent piezo-orientation through an elongating process.

Description

Piezoelectric material using polyvinylidene fluoride and nano ceramics and its manufacturing method {Dieletric Device Using PVDF and Nano Ceramics Particles, and Method for Fabrication the Same}

The present invention relates to a piezoelectric material using polyvinylidene fluoride (PVDF) and nano ceramics, and more particularly, to a polyvinylidene fluoride (PVDF) having excellent dielectric constant and piezoelectricity in plastics. ) And blow-molded a composite material of nano ceramic particles having excellent piezoelectricity, dielectric constant, conductivity, and the like, and molding onto a film, and then performing a pressing and stretching process using a roller to improve dispersibility of the ceramic particles in PVDF. The present invention relates to a piezoelectric material using PVDF and nano ceramics having excellent piezoelectric properties and mechanical strength, and having an effect of reducing cost according to a continuous manufacturing process, and a method of manufacturing the same.

Functional ceramics having functions such as dielectric properties and piezoelectricity are used in a wide range of fields as various electric and electronic components. For example, it is used for piezoelectric elements, such as various actuators, a sensor, and a resonator. Examples of such ceramics having dielectric properties include silica glass, alumina, aluminum nitride, barium titanate, and the like, and piezoelectric ceramics include lead zirconate titanate.

However, in order to shape | mold a ceramic to a desired shape, a baking process is needed, and after baking, it is common to machine. Ceramics have no plasticity, making it difficult to obtain a molded article having a complicated shape. That is, there is a drawback that the degree of freedom of molding is insufficient. In addition, it has the disadvantage that the molding process is more complicated than plastic, the productivity is low and the molding cost is expensive. Therefore, there is a need for a technique for imparting flexibility to ceramics without affecting piezoelectric properties.

On the other hand, plastic has the advantage of being excellent in formability, so that any complicated shape can be manufactured very precisely and inexpensively, whereas plastic has a weak strength, low electrical conductivity and low thermal conductivity. Recently, as a result of many studies, conductive polymers that can be applied to a variety of electromagnetic wave shielding thin films, secondary batteries, sensors, and the like have been published. For example, polyparaphenylene, polyvinylidenefluororide (hereinafter referred to as "PVDF"), polypyrrole, polyacetylene, and the like are used in sensors, memory devices, electrode materials, and the like. It is a polymer. In particular, PVDF is a polymer having piezoelectric and dielectric properties as a typical conductive polymer widely applied to electrode formation of secondary batteries. However, the conductive polymer is very excellent in formability compared to the ceramic powder, but the piezoelectric properties are low.

Accordingly, a method of manufacturing an extrusion or injection molded product in which a composite material obtained by mixing and forming a ceramic powder having excellent piezoelectric properties and a plastic having excellent moldability can be applied to various piezoelectric elements has been developed. Plastic / ceramic composites are made by dispersing ceramic particles in a matrix made of plastic, and are made by dispersing ceramic particles in plastic, so that molding is easy and can be manufactured at low cost.

That is, since there is no need for machining after firing and firing like ceramics, there is an advantage in that an article of a complicated shape that cannot be manufactured in machining can be easily molded and productivity can be greatly improved.

In mixing the ceramic powder and plastic as described above, uniform mixing is important. Uniform mixing minimizes voids and improves the mechanical properties of the piezoelectric body.

Therefore, in order to minimize voids caused by uniform mixing of ceramic powder and plastic, it is required to use finer ceramic powder. However, the ceramic powder applied to the conventional plastic / ceramic composite is a micro-sized particle having a large size, so that it is difficult to effectively mix, and thus there is a problem such as deterioration in mechanical strength and dispersibility. Accordingly, in order to improve dispersibility, there is a problem in that a dispersion agent of water or an organic solvent and a coupling agent such as a silane coupling agent, a titanate coupling agent, or a zirucoaluminate coupling agent must be added separately.

In addition, there is a problem in that electrical performance such as piezoelectricity, dielectric property, and conductivity decreases due to the pores between the particles of the ceramic. That is, the ceramic particles are large, so that large voids are formed between the particles and the particles, and plastics are contained in the voids, but the electrical density of the ceramic, which is better in piezoelectricity and dielectric properties than the plastics per unit volume of the composite, is satisfactory, resulting in satisfactory electrical performance. Couldn't get it.

Meanwhile, in forming a piezoelectric material on a film using the plastic / ceramic composite as described above, the piezoelectric PVDF is vacuum-deposited on a ceramic substrate to have an orientation such that the piezoelectric properties are exhibited, or the micron particles on the PVDF film. Metals, ceramics, and the like of a size were used by vacuum deposition, screen printing, or bonding. However, the method of vacuum deposition, screen printing, etc. as described above is a single batch type, so that a continuous process is difficult and thus there is a problem of increased cost.

The present invention has been made to solve the above problems, disperse ceramic particles having excellent piezoelectricity, dielectric constant, conductivity, etc. in an extruder in PVDF having excellent dielectric constant and piezoelectricity while introducing the ceramic particles as nanoparticles, and the PVDF The nano-particle composite is molded onto the film by blow molding method, which is then pressed and stretched by a roller and subjected to annealing to impregnate the water bath containing water, thereby dispensing the ceramic particles into PVDF. To improve the acidity, minimize the voids between ceramic particles, have excellent piezoelectricity, dielectric and mechanical strength, and provide a piezoelectric material using PVDF and nano ceramics and a method of manufacturing the same, which has the effect of reducing the cost of the continuous manufacturing process. will be.

1 is a schematic configuration diagram of a device for explaining a method for manufacturing a piezoelectric material using PVDF and nano-ceramic according to the present invention.

Explanation of symbols on the main parts of the drawings

10: piezoelectric 12: flyson

20: blow molding machine 22: hopper

24: extruder 26: extrusion die

28: Information board 31, 32, 33, 34: Pinch roller

40: guide roller 45: hot plate

51, 52: reservoir 60: drive roller

The present invention kneads PVDF / nano ceramic composites having a proper ratio of PVDF and nano ceramics in an extruder, and then molds them into a parison on a tube by a blow molding method and pinches the parisson. PVDF which is passed through a pinch roller and pressed onto a film, followed by a drawing process by a driving roller to have an excellent piezoelectric orientation, and at the same time a PVDF which is continuously subjected to an annealing process which is impregnated into a receiving tank to reinforce mechanical strength. Provided are a piezoelectric body using a nano ceramic and a method of manufacturing the same.

The PVDF / nano ceramic composite material is composed of PVDF having excellent electrical properties such as piezoelectricity and dielectric property, and ceramic powder having a size of 500 to 0.1 nanometers (nm). The ceramic powder includes one or more metals such as titanium (Ti), lead (Pb), barium (Ba), silicon (Si), tin (Sn), magnesium (Mg), niobium (Nb), zirconium (Zr), and the like. It is a ceramic powder of nanoparticles. The ceramic powder of the nanoparticles including the metal may be synthesized into nano-sized fine powders by hydrothermal synthesis or sol-gel method, or may be commercially available, and preferably barium titanate (BaTiO ₃ ) or PbZrO. ₃ -PbTiO ₃ solid solution (PZT), PbZrO ₃ -PbTiO ₃ -Pb (Mg _1/3 Nb _2/3 ) solid solution (PZT-PMN), TiO ₂ , TiO ₃ , SiO ₂ , ZnO, SnO ₂ Zr As the ceramic powder, one or two or more selected from the group can be selected and used according to the characteristics of the desired piezoelectric element.

The PVDF / nano ceramic composite material can control the electrical performance and processability by appropriately adjusting the composition ratio of nano ceramic powder and PVDF. The higher the content of the nano-ceramic particles in the composite material, the more preferable in terms of electrical performance. However, too much of the composite material results in loss of fluidity during molding, making molding difficult. In other words, increasing the content of PVDF improves the workability but is accompanied by a loss of piezoelectricity as the content of the ceramic powder is reduced, while reducing the content of PVDF improves the piezoelectricity but decreases the workability. Therefore, the PVDF / nano ceramic composite material contains 40 to 95 volume% of the nano ceramic powder relative to the total volume of the composite material. On the other hand, the content of PVDF contains 5% by volume to 60% by volume. If the content of the nano-ceramic particles is less than 40% by volume, satisfactory piezoelectricity cannot be expected, and if it exceeds 95% by volume, workability is inferior.

Moreover, it is preferable that the aspect ratio of the said ceramic particle shall be 2.0 or less. This is because the PVDF can be dispersed by packing nanoceramic particles at the highest density, thereby making the thermal expansion coefficient of the composite material even smaller. In other words, when the aspect ratio of the aspect ratio of the ceramic particles exceeds 2.0, it is difficult to increase the content of the ceramic particles.

According to the present invention, the ceramic particles are introduced into the nanoparticles to improve the dispersibility of the ceramic particles in the PVDF so that they can be uniformly dispersed without the addition of a separate dispersion medium or coupling agent. Accordingly, the voids are minimized and the electrical properties such as piezoelectricity and dielectric property are minimized. Performance. In addition, as the ceramic nanoparticles are uniformly dispersed in the PVDF, the heat deflection temperature (HDT) of the PVDF is increased to add the rigidity of the PVDF. Thus, a piezoelectric body having excellent mechanical strength is produced. In addition, the flame retardance according to the nanoparticles of the ceramic can be achieved.

The PVDF / nano ceramic composite material as described above is added to the extruder and the kneading operation is performed for 30 to 60 minutes so that the ceramic particles are dispersed in the PVDF simultaneously with melting of the PVDF. At this time, the temperature of the extruder It is preferable to use a twin-screw-embedded extruder in order to achieve a temperature of 270 ° C to 300 ° C and to uniformly knead the mixture. Subsequently, the PVDF / nano ceramic melt is blow molded and molded into a tube-shaped parison, which is then bonded onto a single film by a guide plate tapered on top of the blow molding machine. Then, a crimping step for passing the pinch rollers is performed. As a result, the nano-ceramic particles closely adhere to each other to increase the density of the ceramic particles per unit volume. Subsequently, an annealing process is performed to impregnate the receiving tank in order to improve the mechanical strength of the piezoelectric body passed through the pinch roller. At the same time, the stretching process by the driving roller is performed in order to have the β orientation showing excellent piezoelectric properties. Preferably at least four times stretching is achieved. The above process is carried out continuously, the finished piezoelectric body is wound in a drive roller.

Hereinafter, a method of manufacturing a piezoelectric body according to the present invention will be described in more detail with reference to FIG. 1.

As shown in FIG. 1, the apparatus for manufacturing the piezoelectric body 10 according to the present invention includes a blow molding machine 20 composed of a hopper 22, an extruder 24, an extrusion die 26, and a guide plate 28. A plurality of pinch rollers 31, 32, 33, 34, two rollers are driven at predetermined intervals, and a plurality of guide rollers 40 are installed and the water tanks 51, 52, And a driving roller 60. 1 is a schematic configuration diagram of a device for explaining a method of manufacturing a piezoelectric material using PVDF and nano ceramics according to the present invention, in which a plurality of constituent members constituting the device are omitted. For example, the twin-screw built into the extruder 24, the air injection port of the extrusion die 26, etc. are mentioned.

The PVDF / nano ceramic composite material in which PVDF and nano-ceramic particles are appropriately mixed and introduced into the hopper 22 of the extruder 24 is introduced. The temperature of the extruder 24 is 270 ° C to 300 ° C. The PVDF is kept melted and the nano ceramic particles are uniformly dispersed in the PVDF by the rotation of twin-screws (not shown) embedded in the extruder 24. The kneading operation above is carried out for 30 to 60 minutes. The PVDF / nano ceramic melt is blow molded through an extrusion die 26 and molded into a parison 12 in the form of a tube. The parison 12 is bonded to a single film by a guide plate 28 provided on the upper left and right sides (as seen in the drawing) of the blow molding machine 20 and pressed through the first pinch roller 31. The piezoelectric body 10 having passed through the first pinch roller 31 passes through the second pinch roller 32 through the heating plate 45 heated to 130 ° C. to 140 ° C. along the guide roller 40. Subsequently, water of 80 ° C. to 90 ° C. is impregnated in the first accommodating tank 51 housed therein and pressed by the third pinch roller 33. Then, after impregnated in the second receiving tank 52, the water of 40 ℃ ~ 50 ℃ is pressed by the fourth pinch roller 34. The piezoelectric body 10 is stretched by the driving roller 60.

The stretching process is performed in the process of starting from the first pinch roller 31 and passing through the fourth pinch roller 34, and the piezoelectric body 10 which has undergone the stretching process is wound around the driving roller 60.

Although the reservoirs 51 and 52 are illustrated in FIG. 1, two or more reservoirs 51 and 52 may be annealed by installing a plurality of three or more units having different temperature ranges.

Accordingly, the present invention increases the density of ceramic particles per unit volume by performing several pressing processes by the pinch rollers 31, 32, 33, 34, thereby improving electrical performance, and driving the roller 60. By forming the β orientation by the stretching process by the film, it has excellent piezoelectric characteristics, and the mechanical strength is improved by an annealing process in which the plurality of receiving tanks 51 and 52 are impregnated.

Hereinafter, a description will be given through specific embodiments of the present invention.

EXAMPLE

A piezoelectric body 10 was manufactured by a process as shown in FIG. 1 by mixing 90 volume% of barium titanate (BaTiO ₃ ) having an average particle size of 0.3 nm and an aspect ratio of 1.7 to 10 volume% of PVDF.

On the other hand, the piezoelectric constant and dielectric constant were measured and the results are shown in the following [Table 1]. The piezoelectric constant was measured using a D meter (Ando, Japan), and the dielectric constant was measured using an LSR meter (Ando, Japan).

[Comparative Example]

A composite material having 50 vol% of PVDF and 50 vol% of barium titanate (BaTiO3) having an average particle size of 35 µm and an aspect ratio of 1.2 was mixed by injection molding at 300 ° C. to form a plate-like piezoelectric body. On the other hand, the piezoelectric constant and dielectric constant were measured and the results are shown in the following [Table 1]. The measuring method is the same as that of the said Example.

Characteristics of PVDF Characteristics of Ceramics (BaTiO ₃ ) Piezoelectric Constant (d31) permittivity( 33) Content (% by volume) Piezoelectric Constant (d31) Content (% by volume) Average particle size Aspect ratio Example 10 25 × 10 ^-12 m / V 90 0.3 nm 1.7 591 × 10 ^-9 m / V 7200 Comparative example 50 25 × 10 ^-12 m / V 50 35 μm 1.2 270 × 10 ^-12 m / V 1900

Accordingly, the present invention facilitates the processing of complex moldings by dispersing piezoelectric, dielectric and conductive ceramic powders in PVDF, and is accompanied by conventional plastic / ceramic composites such as mass production, cost reduction, and the like. In addition to the effect of introducing the ceramic powder into the nanoparticles, and the compression and stretching process is carried out to minimize the pores according to the nano-sized fine powder of the ceramic particles to improve the dispersibility of the ceramic particles in the PVDF, The coupling agent does not need to be added, and has a piezoelectricity, dielectric constant and conductivity of several hundred times and thousands of times as compared with the piezoelectric body to which ceramic particles of micro size or more are conventionally applied.

In addition, as the ceramic nanoparticles are uniformly dispersed in the PVDF, the heat deflection temperature (HDT) of the PVDF is increased so that the rigidity of the PVDF is added and the annealing process is performed to have excellent mechanical strength. In addition, effects such as flame retardancy according to the structural characteristics of the ceramic nanoparticles can be achieved.

In addition, the manufacturing method according to the present invention has the effect of increasing the piezoelectric rate and continuous process according to the pressing and stretching process, and has the effect of mass production and cost reduction.

Claims (5)

In the piezoelectric body 10 on a film manufactured using a composite material composed of polyvinylidene fluoride (PVDF) and ceramic particles, The ceramic particles are nano-ceramic particles having a size of 500 to 0.1 nanometers (nm), and the PVDF / nano ceramic composites in which PVDF and nano ceramics are formed in an appropriate ratio are kneaded in an extruder 24 and blow-molded to form a flyson on a tube. After molding with (12), the parison 12 is bonded onto a single film, which is compressed by pinch rollers 31, 32, 33, 34, and a plurality of reservoirs 51 ( 52) A piezoelectric material using PVDF and nano ceramics in the form of a film prepared by annealing (impregnated) and stretching by the driving roller (60). The method of claim 1, wherein the nano-ceramic particles are barium titanate (BaTiO ₃ ), PbZrO ₃ -PbTiO ₃ solid solution (PZT), PbZrO ₃ -PbTiO ₃ -Pb (Mg _1/3 Nb _2/3 ) solid solution (PZT-PMN ), TiO ₂ , TiO ₃ , SiO ₂ , ZnO, SnO ₂ Zr is a piezoelectric material using PVDF and nano ceramics, characterized in that it is mixed with one or two or more nano ceramics selected from the group consisting of. The piezoelectric element using PVDF and nano ceramics according to claim 1 or 2, wherein an aspect ratio of the aspect ratio of the nano ceramic particles is 2.0 or less. In the manufacturing method of manufacturing the piezoelectric body 10 on a film using the composite material which consists of polyvinylidene fluoride (PVDF) and ceramic particle, PVDF / nano ceramic composite, which is a mixture of PVDF and 500 ~ 0.1 nanometer (nm) size, is put into an extruder 24 at a temperature of 270 ° C to 300 ° C and kneaded for 30 to 60 minutes to obtain PVDF / nano ceramic melt. Steps, Blow molding the PVDF / nano ceramic melt into a tube-formed parison 12 and then bonding the parison 12 into a single film by means of a guide plate 28; Compressing the film by passing it between a plurality of pinch rollers (31, 32, 33, 34), Performing an annealing process to impregnate the plurality of reservoirs 51 and 52; Method of manufacturing a piezoelectric material using PVDF and nano-ceramic, characterized in that it comprises the step of performing the stretching process by the drive roller (60). The method of claim 4, wherein the annealing process is passed through a heating plate 45 heated to 130 ℃ ~ 140 ℃, and then impregnated in a first receiving tank 51 containing water of 80 ℃ ~ 90 ℃, Subsequently, a method of manufacturing a piezoelectric material using PVDF and nano ceramics, which is performed by impregnating a second container 52 containing water having a temperature of 40 ° C. to 50 ° C.