CN113977932B

CN113977932B - Preparation method of 3D printed porous high-performance piezoelectric part

Info

Publication number: CN113977932B
Application number: CN202111242033.3A
Authority: CN
Inventors: 陈英红; 裴浩然; 熊雨; 吕秦牛; 王琪
Original assignee: Sichuan University
Current assignee: Sichuan University
Priority date: 2021-07-26
Filing date: 2021-10-25
Publication date: 2022-12-09
Anticipated expiration: 2041-10-25
Also published as: CN114228139A; CN115891137A; CN113478810A; CN113977932A; CN114228139B; CN113478810B

Abstract

The invention provides a preparation method of a porous high-performance piezoelectric part for 3D printing, which is characterized in that ionic salt tetraphenyl phosphorus chloride is taken as a modifier to be mixed with PVDF polymer base materials in a banburying melting and blending mode, then piezoelectric ceramic fillers are added, and the obtained PVDF-based composite material filament is prepared into the porous piezoelectric part by adopting a fused deposition molding 3D printing technology. The invention determines the setting of the internal filling rate, the optimization of the nozzle diameter and the limitation of the printing parameters during fused deposition modeling 3D printing based on experimental evidence, so that the prepared piezoelectric part has the three-dimensional porous structure characteristic, and the size of the holes, the distance between adjacent holes and the hole arrangement mode are subjected to standard quantification through the limiting conditions, thereby further improving and breaking through the piezoelectric performance of the piezoelectric ceramic filling polyvinylidene fluoride base 3D printing part.

Description

Preparation method of 3D printed porous high-performance piezoelectric part

Technical Field

The invention belongs to the technical field of 3D printing piezoelectric workpieces, relates to a preparation method of a porous high-performance piezoelectric workpiece for 3D printing, and particularly relates to a preparation method of a porous piezoelectric workpiece for 3D printing by filling polyvinylidene fluoride base with piezoelectric ceramics.

Background

With the rapid development of industrialization and urbanization, the consumption of non-renewable energy sources such as petroleum, natural gas and coal is extremely high, and the world energy crisis is increasingly prominent. Therefore, the development of new energy technology with environmental protection and regeneration becomes a problem to be solved urgently by human beings at present. The piezoelectric material can realize the interconversion of mechanical energy and electric energy as a novel intelligent material, is applied to the fields of energy harvesting, driving, sensing and the like, and is a key material and powerful support for realizing the breakthrough and development of high and new technologies such as the Internet of things and 5G communication. The most widely used piezoelectric materials in current industrial production and practical applications are piezoelectric ceramic materials such as lead zirconate titanate (PZT), barium titanate (BaTiO) ₃ ) Potassium niobate (KNbO) ₃ ) And the like, having excellent piezoelectric and dielectric constants. However, piezoelectric ceramics have the disadvantages of difficult processing, brittle quality, and poor durability, and cannot be used to produce flexible articles. Polyvinylidene fluoride (PVDF) and its copolymers are typical piezoelectric polymers used most widely, and have good flexibility, processing, mechanical and chemical resistance properties, but their piezoelectric properties are far inferior to those of piezoelectric ceramics. PVDF is a semi-crystalline polymer, and has five crystal forms, and the beta crystal form has unique electric activity and is favored. But the PVDF tends to form alpha crystals with the most stable thermodynamics when being melted and crystallized, and the PVDF product processed by the conventional thermoplastic processing has no electric activity and cannot meet the requirement on the piezoelectric performance of the product. Therefore, the traditional piezoelectric PVDF product rich in beta crystal form is mainly prepared by solution casting, spin coating, electrostatic spinning and the like, but the product prepared by the process is difficult to have a complex three-dimensional structure, and the application range of the product is limited.

3D printing, namely an advanced manufacturing method for rapid forming of a three-dimensional entity constructed by layer-by-layer printing, has important application value in the high and new technical fields of biomedicine, war industry, electronics, buildings and the like in recent years. Fused Deposition Modeling (FDM) is used as a 3D printing technology with high maturity and wide application field at present, and has the advantages of convenience in operation, continuous automatic processing, low cost, environmental friendliness, high personalized customization degree and the like. By utilizing the accumulation characteristics of the filamentous materials printed by FDM 3D and the unique slicing treatment mode, the porous structural part capable of accurately regulating and controlling the pore diameter, the porosity and the pore arrangement is easy to prepare. Therefore, the piezoelectric functional material is combined with the FDM 3D printing technology, a piezoelectric part with a personalized three-dimensional structure comprising an array and a porous structure is expected to be realized, the stress or strain is amplified through designing and regulating the structure, and the piezoelectric response is further effectively improved. However, few documents report the preparation of PVDF-based piezoelectric parts with complex structures by FDM 3D printing technology, and thus the application of the PVDF-based piezoelectric parts in the piezoelectric field is achieved. The reason for this is that FDM 3D printing, as a thermoplastic process, requires the polymer to be extruded in molten form and built up layer by layer, and this process makes it difficult to prepare PVDF with stable polar β crystals. To address this problem, researchers have proposed that PVDF-based piezoelectric parts (Hoejin Kim, integrated 3D printing and corona poling process of PVDF piezoelectric films for the expression sensor application) with polar β crystals can be prepared by electrically assisted FDM 3D printing. However, this method requires the application of an electric field of up to 12kV during printing, which greatly increases the processing difficulty. The preparation method is limited in that only a single-layer material can be printed by the process, and the maximum polar beta crystal content of the prepared PVDF is only 56%.

The prior patent application of the applicant of the invention, namely 'a fused deposition modeling 3D printing method for PVDF with high beta crystal content' (application number: 202010811224.6), discloses a fused deposition modeling 3D printing method for PVDF with high beta crystal content, which comprises the following steps: firstly, uniformly mixing PVDF and a modifier, then granulating, forming a strand silk through melt extrusion, and placing the strand silk into an FDM 3D printer for printing and forming to obtain a product. The modifier suitable for the high-temperature melting condition is selected, the melting processing performance of the PVDF raw material and the beta crystal in the PVDF are improved, the PVDF material is endowed with excellent piezoelectric conversion performance, and the product prepared by the method can be used as a mechanical energy collecting device, a sensor, a driver and the like, and can be used in the fields of new energy harvesting, sensing, artificial intelligence and the like.

The patent application greatly improves the beta crystal form content of the PVDF-based material by selecting a modifier suitable for high-temperature melting conditions, wherein the beta crystal content can reach 97.38% at most (example 1 of the prior application patent). However, based on the technical solution described in the present invention, further referring to the literature and research experiments, it is found that the technical solution described in the present invention must be subjected to a post-treatment process which is relatively complicated to operate, and when the modifier is selected as an Ionic Liquid, the post-treatment process must include steps of high-temperature water washing, drying, and the like, because the Piezoelectric material needs to be non-conductive, and the Ionic Liquid is room temperature molten salt and has conductivity, such that the post-treatment process will form a conductive path in the substrate and further affect the Piezoelectric output, and thus the post-treatment process is considered necessary, and the post-treatment process is not described in the prior patent application, but is disclosed in the publication of the inventor (xingan Liu, ionic Liquid-Assisted 3D Printing of Self-Polarized PVDF β for Flexible Piezoelectric Energy Harvesting). When the modifier is selected to be the non-ionic liquid, the beta crystal conversion rate is significantly lower than that of the technical scheme using the ionic liquid, and the high beta crystal content is achieved by the same additional process technology, for example, the PVDF-based material prepared by the process technology under the high pressure condition has the beta crystal content of 89.9% (Jiayi Ren, effect of ion-bipolar interaction on the formation of polar extended-channel crystals in high pressure-crystallized poly). In the prior patent application example 4, when CTAB (cetyl trimethyl ammonium bromide) is used as the modifier, the beta crystalline phase pair content in the modified PVDF product reaches 97.0%, but CTAB still causes the system crystallinity to be greatly reduced (reduced by 11.0%) under the condition of low addition amount (3 wt%), thereby affecting the mechanical performance and piezoelectric performance of the piezoelectric product.

However, the post-treatment process and the additional process described in the prior art are complex and greatly increase the overall cost under the industrial amplification effect, if the 3D printed product is directly used as an industrial finished product without post-treatment, a non-ionic liquid, especially an ionic salt, is required to be used as a modifier, but the beta crystal content of the product prepared without the additional process is usually difficult to exceed 90% (when the addition amount is 5wt% of the ionic salt) by selecting ionic salts other than CTAB, and the addition amount of the ionic salt is further increased, although the beta crystal content is further increased, the dielectric loss of the material is greatly increased, and thus the product has no practical value. Therefore, although the process production mode without additional process technical conditions has the characteristics of simple operation and low cost, the equivalent effect and height of the technical scheme including the post-treatment process or the additional process technical conditions are difficult to achieve in terms of piezoelectric performance, and the industrial implementation and conversion of the material product are greatly influenced.

In addition, long-term research finds that the polymer-ceramic composite material which is prepared by blending and compounding the piezoelectric ceramic and the piezoelectric polymer and has high flexibility and high piezoelectricity is a feasible strategy with great potential. However, the performance of the composite material is seriously restricted by the problems of agglomeration, incompatibility and the like of the inorganic filler in a polymer matrix. The traditional dispersion methods such as melt blending and the like have low efficiency, and when the polymer composite material reaches a certain service performance standard, the polymer composite material often needs to use high filler content, so that the processing performance and the mechanical property of the polymer matrix composite material are seriously deteriorated. At present, there are many documents working on solving the problems of poor filler dispersion and compatibility to improve the piezoelectric, mechanical, processing and other properties of piezoelectric composite materials, and the common methods are to perform polydopamine coating modification, graft polymer, surface hydroxylation and the like on inorganic piezoelectric ceramics such as barium titanate particles. However, these methods cannot produce and prepare composite materials in large scale, and have complicated flow and high cost, and are difficult to realize industrial application value.

In addition, in order to further improve the piezoelectric performance of the polymer-ceramic composite material, the content of the piezoelectric ceramic filler is inevitably required to be highly filled, but in the prior art, particularly in the technical fields of traditional melt blending processing and molding and 3D printing additive manufacturing, the addition amount of the piezoelectric ceramic filler is acknowledged to have a certain upper limit, according to the records of the prior art, the addition amount of the piezoelectric ceramic filler is usually 20-40 wt% of the polymer matrix, and when the addition amount of the piezoelectric ceramic filler exceeds 45wt%, the filler is easy to agglomerate due to rigidity and brittleness of the filler, so that the mechanical performance and the processing performance of the polymer-ceramic composite material are greatly influenced. In the case of 3D printing, especially fused deposition type 3D printing technology, when the amount of the piezoelectric ceramic filler added exceeds 45wt%, the fluidity of the composite material is greatly reduced, and thus printing preparation cannot be performed. Therefore, it is considered that, in the case of preparing the polymer-ceramic composite material by fused deposition type 3D printing without adding other additives or fillers, since the addition amount of the piezoelectric ceramic filler has an upper limit, the piezoelectric performance of the piezoelectric printed article prepared therefrom has an upper limit, and cannot be further improved.

Therefore, if a technical scheme of the piezoelectric ceramic filled polyvinylidene fluoride 3D printing process is developed, which can further break through the upper limit of the piezoelectric performance of the polymer-ceramic composite material and is beneficial to the industrial implementation and transformation, the industrial implementation of the related technology is greatly facilitated, and the market prospect is good.

Disclosure of Invention

The invention aims to solve the problems in the background technology and provides a preparation method of a porous high-performance piezoelectric part for 3D printing, the preparation method comprises the steps of taking ionic salt tetraphenyl phosphorus chloride as a modifier, mixing the ionic salt tetraphenyl phosphorus chloride with PVDF polymer base materials in a banburying melting and blending mode, adding a piezoelectric ceramic filler, and preparing the porous piezoelectric part from the PVDF-based composite material by adopting a fused deposition modeling 3D printing technology. The invention determines the setting of the internal filling rate, the regulation of the nozzle diameter and the limitation of the printing parameters during 3D printing of fused deposition modeling based on experimental evidence, so that the prepared piezoelectric part has the three-dimensional porous structure characteristic, and the size of the holes, the distance between adjacent holes and the hole arrangement mode are subjected to standard quantification through the limiting conditions, thereby further improving and breaking through the piezoelectric performance of the piezoelectric ceramic filled polyvinylidene fluoride 3D printing part.

In order to achieve the purpose, the invention adopts the technical scheme formed by the following technical measures.

A preparation method of a porous high-performance piezoelectric part for 3D printing comprises the following steps in parts by weight:

(1) Uniformly mixing 94.5-95.5 parts of PVDF polymer granules and 4.5-5.5 parts of ionic salt, adding into an internal mixer, and carrying out melt blending to prepare a composite material block; wherein the PVDF polymer granules and the ionic salt total 100 parts by weight; the technological parameters of the banburying process are as follows: the temperature of the banburying chamber is 10-20 ℃ higher than the melting temperature of the PVDF polymer granules, and the rotating speed of a banburying rotor is 50-80 r/min;

wherein the ionic salt is tetraphenyl phosphorus chloride;

(2) Crushing the composite material blocks obtained in the step (1) to obtain composite material powder;

(3) Mixing the composite material powder obtained in the step (2) with 5-40 parts of piezoelectric ceramic filler, adding the mixture into a millstone-shaped mechanochemical reactor, grinding and crushing the mixture, and collecting the composite material superfine powder in which the piezoelectric ceramic filler is uniformly dispersed in a polymer matrix after the grinding is finished; wherein, the technological parameters of the millstone type mechanochemical reactor are as follows: the grinding pressure is 8-12 MPa, and the grinding is circulated for 6-10 times;

(4) Extruding and processing the composite material superfine powder obtained in the step (3) to form threads for 3D printing; wherein the extrusion processing molding process parameters are as follows: the extrusion temperature is 20-50 ℃ higher than the melting temperature of the PVDF polymer granules, and the extrusion speed is 10-50 r/min;

(5) Putting the strand silk for 3D printing obtained in the step (4) into a fused deposition modeling 3D printer, and preparing a part with a porous structure by a fused deposition modeling 3D printing technology; the fused deposition modeling 3D printing technology comprises the following process parameters: slicing according to a three-dimensional digital model of a required piezoelectric product, arranging extruded strand silk to print along a filling mode of a straight line (Recilinear), stacking and accumulating layer by layer with an internal filling angle of 0 DEG/90 DEG, wherein the internal filling rate is 60-80%, the diameter of a nozzle is 0.4 +/-0.01 mm, the temperature of the printing nozzle is consistent with the extrusion temperature in the step (4), the temperature of a hot bed is 90-130 ℃, and the printing speed is 500-1000 mm/min;

(6) And (5) polarizing the part with the porous structure prepared in the step (5) to obtain the high-performance piezoelectric part.

The basic principle of the invention lies in that a defined ionic salt is introduced as a modifier, and due to the specific chemical structure of the ionic salt, the positive charge of cations and CF of a molten PVDF molecular chain ₂ The bonds have strong ion-dipole effect to attract each other, promote the PVDF molecular chain to be arranged according to beta crystal form, and crystallize to form stable polar beta crystal.

However, as described in the background art, if a piezoelectric device is prepared by using an ionic salt as a modifier and performing fused deposition modeling 3D printing technology, a solid piezoelectric device prepared according to a three-dimensional digital model of a conventional piezoelectric device, especially a piezoelectric sheet, has a β crystal content of no more than 90% without a post-treatment process and/or additional process conditions, which affects the piezoelectric performance of the obtained device: when the thickness of the obtained product is 4.9mm, the open circuit voltage is 4.5V.

Moreover, when the piezoelectric ceramic filler is further introduced, the piezoelectric performance of the prepared solid piezoelectric piece is increased along with the increase of the content of the piezoelectric ceramic filler under the condition that the traditional piezoelectric piece, particularly the solid piezoelectric piece prepared according to the three-dimensional digital model of the piezoelectric sheet, is not subjected to post-treatment process except polarization treatment and/or additional process technical conditions, and the piezoelectric performance is highest when the addition amount of the piezoelectric ceramic filler reaches 40wt% of polyvinylidene fluoride. However, if the amount of the piezoelectric ceramic filler added is further increased, the fluidity of the composite material is greatly lowered, and therefore, the printing production cannot be performed.

Therefore, the main inventive points of the present invention are: through a great deal of research and exploration of the inventor of the invention, the setting of the internal filling rate, the optimization of the nozzle diameter and the limitation of the printing parameters during fused deposition modeling 3D printing are determined, so that the prepared piezoelectric part has a three-dimensional porous structure characteristic, and the size of the holes, the distance between adjacent holes and the hole arrangement mode are standardized and quantized through the limiting conditions, so that the high-performance piezoelectric part with the piezoelectric performance remarkably superior to that of the prior art is obtained.

The high-performance piezoelectric part with the porous structure is endowed with remarkably enhanced piezoelectric performance through the standardized three-dimensional porous structure characteristics. It is important to point out that the standardized three-dimensional porous structure characteristics can enable the mechanical performance presented by the three-dimensional porous structure characteristics to have the prominent advantage of isotropy, and the three-dimensional porous structure characteristics can be further adjusted through the fine setting of the internal filling rate so as to be suitable for application scenarios with different requirements.

It should be noted that, in principle, when the extruded filament is printed in a filling mode of setting the extruded filament along a straight line (Rectilinear) by fused deposition modeling 3D printing, the filaments of the upper and lower layers are arranged along a printing filling angle of 0 °/90 ° and a filling density to form macroscopic square holes with different sizes. When the printed article is solid, the packing density is set to 100%. The smaller the packing density, the larger the square aperture and the smaller the number of pores. The inventor of the invention researches and discovers that the smaller the filling density is, the smaller the compression modulus of the product is, namely the compression resistance is reduced, and the deformation amount of the product compressed when the product is stressed is increased, thereby being beneficial to piezoelectric response; on the other hand, smaller packing density does not represent higher piezoelectric response, since the piezoelectric material used has less packing volume of the piezoelectric filler, which inevitably reduces the piezoelectric output, and the mechanical properties of the product are reduced nonlinearly with the reduction of the packing density, which greatly affects the practical properties, especially the repeated use (fatigue resistance) properties, of the piezoelectric product.

Secondly, it should be noted that, through practical experiments, the inventors of the present invention found that, significantly different from a pure polyvinylidene fluoride printed article, after adding a piezoelectric ceramic filler, especially in the premise of a high addition amount (40 wt%) of the piezoelectric ceramic filler, compared with a solid piezoelectric article (with a filling density of 100%), with respect to the introduction of a three-dimensional porous structure thereof, mechanical properties of the article are deteriorated to different degrees according to the filling density. Therefore, the final 3D printed product needs to be ensured to have significantly better piezoelectric performance than the solid product, and the deterioration of the mechanical performance is reduced as much as possible, which greatly increases the specificity and requirement of the three-dimensional porous structure feature. Through long-term groping and comparison experiments, the inventor finally confirms that the high-performance piezoelectric part prepared by the three-dimensional porous structure endowed by the technical scheme recorded by the invention has the best comprehensive performance, and the piezoelectric performance is obviously superior to that of a solid part.

In summary, through the above technical scheme provided by the present invention, the high performance piezoelectric device is obtained, wherein the square hole has an outer diameter of about 100 μm to 280 μm and a packing density of 60% to 80% through calculation and testing. When the thickness of the obtained product is 1mm, the open circuit voltage is 9.5V to 11.4V, the compression modulus is 31.2MPa to 35.4MPa, and the tensile strength is 22.5MPa to 25.6MPa.

The PVDF polymer granules in the step (1) are polyvinylidene fluoride (PVDF) polymer granules which can be used for fused deposition modeling 3D printing in the technical field, and preferably comprise any one of pure polyvinylidene fluoride granules, polyvinylidene fluoride-hexafluoropropylene granules and polyvinylidene fluoride-chlorotrifluoroethylene granules. The polyvinylidene fluoride (PVDF) polymer granules available on the market for fused deposition modeling 3D printing can be selected by those skilled in the art according to actual needs.

It is important to point out that the limitation of the ionic salt as tetraphenylphosphonium chloride in step (1) is an exclusive limitation, because the specific selection and addition of the ionic salt can significantly affect the conversion rate of beta crystals in the PVDF matrix and the crystallinity of the system, and the conversion rate and crystallinity of the beta crystals can affect the mechanical properties and piezoelectric properties of the final product. Based on the difference between the mechanical property and the piezoelectric property of the product, when the internal filling rate is set, the diameter of the nozzle is specified and the printing parameters are defined during fused deposition modeling 3D printing according to the technical scheme of the invention, whether the product still has good piezoelectric property and mechanical property is unknown. Therefore, based on the scientific proof spirit of the fact, the technical scheme of the invention only limits the selection of the ionic salt as tetraphenyl phosphorus chloride.

In general, the mixing in step (1) can be carried out by conventional material mixing techniques, such as high-speed mixer, magnetic stirrer, etc., and the mixing rate can be 100-500 r/min, and the mixing time can be 20-30 min.

Generally, the melt blending in the internal mixer in step (1) is a conventional internal mixing melt blending process in the art.

In general, the crushing treatment in step (2) is to crush the composite material blocks by a conventional crushing treatment technology and then to form the composite material blocks into 3D printing strands by extrusion processing, and a mechanical crusher, a jet mill, a low-temperature crusher, and the like are generally used.

The millstone-shaped solid-phase mechanochemical reactor in the step (3) is a mechanochemical reactor disclosed in a patent ZL 95111258.9 previously issued by the applicant of the invention, and the temperature of the millstone is controlled by introducing a constant-temperature circulating liquid medium into the millstone, so that the temperature of the millstone surface of the millstone is obviously increased in the long-time circulating grinding and crushing treatment process of the millstone, and the millstone is usually cooled by circulating liquid and kept at the normal temperature. In order to better illustrate the invention and provide a technical scheme for reference, the process parameters of the millstone-shaped mechanochemical reactor also comprise the temperature of the millstone surface which is controlled by introducing a constant-temperature circulating liquid medium with the temperature of 10-30 ℃. Typically, the liquid medium is water.

Generally, the above-mentioned cyclic grinding process is actually performed by grinding the mixed material through a millstone type mechanochemical reactor, collecting the product at the discharge end, and placing the product into the millstone type mechanochemical reactor again for grinding treatment, and the above-mentioned process is regarded as cyclic grinding for 1 time.

The invention solves the problems of poor filler dispersibility and compatibility in polymer matrix and poor flowability of the material capable of being printed and processed in 3D in the prior art, and improves the dispersibility and compatibility of the filler in the matrix by the chemical action of the specific solid-phase shearing and grinding force. Compared with the traditional technology for preparing the parts by simply and directly melting and blending, the technology for printing the piezoelectric parts by FDM by using the piezoelectric ceramic filler filled polymer composite material filaments prepared by grinding the millstone has the following advantages: firstly, a polymer matrix is subjected to strong shearing in the grinding process of a grinding disc, and molecular chains of the polymer matrix are broken to a certain degree, so that the molecular weight is reduced; secondly, under the action of a strong three-dimensional shearing force field of grinding of a grinding disc, the piezoelectric ceramic filler is dispersed in the matrix in a spiral line motion manner, so that the dispersibility and compatibility of the piezoelectric ceramic filler in the matrix are remarkably improved, and the prepared composite material strand silk has better processing fluidity and is suitable for FDM 3D printing; finally, the defects at the interface are obviously reduced after the dispersibility and compatibility of the filler are improved, and the piezoelectric output is increased. Through practical experiments, the inventors of the present invention found that the unmilled 3D printed sample has a lower breakdown voltage than the milled 3D printed sample due to defects such as agglomeration, which may also cause polarization unevenness, a decrease in polarization efficiency, and the like.

Generally, the extrusion molding in step (4) is a conventional extrusion molding process in the prior art, including twin-screw melt extrusion molding and single-screw melt extrusion molding.

In the fused deposition modeling 3D printing technique in step (5), except for the process parameters defined in the technical solution, the other process parameters may refer to conventional 3D printing process parameters in the art, and a person skilled in the art may select appropriate process parameters according to specific 3D printing processing conditions and according to the PVDF-based material characteristics and referring to the prior art. It is worth mentioning that the diameter of the nozzle is 0.4 + -0.01 mm, which is the allowable error range or tolerance range of the nozzle.

In order to better illustrate the present invention, the step (6) of polarizing the porous structure workpiece prepared in the step (5) may refer to the polarizing treatment of a piezoelectric ceramic product or a piezoelectric workpiece added with a piezoelectric ceramic filler in the prior art, so that electric domains in the ceramic are aligned in an electric field direction, and the material has polarity, and provide a reference polarizing treatment process, where the polarizing treatment specifically includes coating conductive silver pastes on upper and lower surfaces of the porous structure workpiece prepared in the step (5) in the electric field direction, respectively attaching aluminum foils as electrodes, and polarizing in an oil corona polarizing composite apparatus for 6 to 12 hours at a polarizing temperature of 80 to 100 ℃.

It should be further noted that, based on the above standardization of the three-dimensional porous structure, technicians can adjust the packing density to obtain piezoelectric parts with different piezoelectric properties to meet specific piezoelectric requirements in different scenarios. Although the specific filling density and the piezoelectric performance of the product are not purely linear, through empirical summary, for example, on the premise that the thickness of the high-performance piezoelectric product is 1mm, a person skilled in the art can obtain the high-performance piezoelectric product with the open-circuit voltage being optionally adjusted within the range of 9.5V to 11.4V by adjusting the filling density within the range of 60% to 80%, and the high-performance piezoelectric product has excellent repeatability, and meets the actual requirements of industrial production. Through the research process of the inventor of the invention, the inventor finds that when the filling density is less than 50%, the diameter of the hole is larger, the leakage current is increased in the oil corona polarization process, and the hole is easy to break down, so that only a measure for reducing the polarization voltage can be taken, but the polarization of a workpiece is insufficient, and the piezoelectric output of the workpiece is reduced.

In addition, it is worth explaining that a high shearing force field and a high stretching force field exist in the FDM 3D printing process due to the fact that a flow channel is narrowed, and the orientation and the dipole arrangement of PVDF molecular chains are facilitated. The inventor of the invention finds that the FDM 3D printing sample has obviously improved ferroelectric property on the premise of obtaining high-content polar beta crystals by the aid of ionic salt in a research process.

Moreover, as PVDF is used as a semi-crystalline polymer and has higher crystallinity, the inventor of the invention finds that the introduction of ionic salt can accelerate the crystallization rate of PVDF, namely, the PVDF is more prone to thermal shrinkage during cooling in hot-molding processing and buckling deformation, so that the dimensional stability of products is affected. Therefore, the PVDF is prevented from warping by controlling the temperature of the FDM hot bed in the 3D printing process, wherein the temperature range of the FDM hot bed is limited to 90-130 ℃, and a product which is free of obvious warping and has high dimensional stability can be prepared under the condition. When the temperature is lower than the limited temperature range, the strand silk cannot be rapidly cooled and solidified, the deposited strand silk is easy to warp and deform in the process of printing the workpiece, and the piezoelectric workpiece, especially the printing of a multilayer product with a larger size, cannot be smoothly finished; when the temperature is higher than the limited temperature range, although the filaments on the upper layer and the lower layer are better bonded, the deposited filaments are in a softened state and are easily driven by a moving spray head because the filaments cannot be rapidly cooled.

In addition, control of the temperature of the showerhead is particularly important. The filling density in the printing parameters of the invention is lower than 100%, if the temperature of the spray head is too high, the fluidity of the strand silk is too strong, and the strand silk is easy to collapse into the gap between the next layer of strand silk, so that the whole product can not be molded; if the temperature of the spray head is too low, the strand silk is infusible or has poor fluidity, and printing cannot be carried out.

In general, other processing aids such as antioxidants, flame retardants, antioxidants and the like known in the art may also be added in the present invention. However, it is a prerequisite that these processing aids do not adversely affect the achievement of the objects of the present invention and the achievement of the advantageous effects of the present invention.

The invention has the following beneficial effects:

1. the invention determines the setting of the internal filling rate, the regulation of the nozzle diameter and the limitation of the printing parameters during fused deposition modeling 3D printing based on experimental evidence, so that the prepared piezoelectric part has the three-dimensional porous structure characteristic, and the size of the holes, the distance between adjacent holes and the hole arrangement mode are subjected to standard quantification through the limiting conditions, thereby obtaining the high-performance piezoelectric part with the piezoelectric performance obviously superior to that of the prior art.

2. The technical scheme of the invention is completely adapted to the ionic salt tetraphenyl phosphorus chloride modified PVDF-based composite material, and by further limiting the technical conditions, the high-performance piezoelectric part with the open circuit voltage being optionally adjusted within the range of 9.5V-11.4V can be obtained by adjusting the internal filling rate during 3D printing, and the high-performance piezoelectric part has excellent repeatability, and meets the actual requirements of industrial production.

3. Compared with a conventional fused deposition modeling 3D printing method and a PVDF product prepared by electric polarization assisted fused deposition modeling 3D printing, the PVDF product prepared by the ionic salt assisted fused deposition modeling 3D printing method has higher piezoelectric polarity beta crystals (84%); and through research and research on the porous structure, the piezoelectric ceramic has better piezoelectric performance and mechanical performance than the conventional piezoelectric element with the filling rate of 100%.

4. According to the invention, by introducing a standardized three-dimensional porous structure, the upper limit of the piezoelectric performance of the piezoelectric ceramic filled vinylidene fluoride-based 3D printing part is further remarkably improved and broken through, the industrial implementation of related technologies is greatly facilitated, and the method has a better market prospect.

5. The piezoelectric workpiece is prepared based on the fused deposition modeling printing technology, and the method has the advantages of simple production process, easiness in operation, low manufacturing cost, capability of realizing batch continuous production and the like, does not need to carry out post-treatment or additional process conditions on the workpiece in the whole process, and is suitable for industrial implementation and conversion. The porous piezoelectric part prepared by the invention has application potential in the fields of piezoelectric sensing, energy harvesting and the like.

Drawings

FIG. 1 is an electron microscope image of composite ultrafine powder in which piezoelectric ceramic filler is uniformly dispersed in a polymer matrix, which is collected by grinding and pulverization in a millbase type mechanochemical reactor in step (3) of example 2 of the present invention.

FIG. 2 is a sectional electron microscope (right side view) of a 3D printing filament obtained by extrusion molding in step (4) of example 2 of the present invention, and a sectional electron microscope (left side view) of a 3D printing filament obtained by direct extrusion molding using the same technique as in example 2 but without milling in a millform mechanochemical reactor. The agglomeration phenomenon is clearly seen in the left panel.

FIG. 3 is a photograph of a high performance piezoelectric article prepared in example 2 of the present invention (right panel), and a photograph of a piezoelectric article having a porous structure prepared by the same method as in example 2, but without grinding in a millbase mechanochemical reactor (left panel).

FIG. 4 is a bar graph comparing the compression modulus and the tensile strength of piezoelectric parts having a porous structure obtained in examples 1 to 3 of the present invention and comparative examples 1 to 2.

FIG. 5 is a photograph showing the piezoelectric performance test of the piezoelectric device having a porous structure prepared in example 2 of the present invention.

FIG. 6 is a graph showing a comparison of open circuit voltage of piezoelectrics having a porous structure obtained in examples 1 to 3 of the present invention and comparative examples 1 to 2.

Detailed Description

The invention is further illustrated by the following examples in conjunction with the accompanying drawings. It should be noted that the examples given are not to be construed as limiting the scope of the invention, and that insubstantial modifications and adaptations of the invention by those skilled in the art based on the teachings herein are intended to be covered thereby.

It should be noted that the oil corona composite polarization device (HYJH-3 YY SANYANGHUOYONG automated equipment Co., ltd.) is used for oil corona polarization in the examples and comparative examples.

It should be noted that in the piezoelectric performance test of the examples and comparative examples, cyclic impact force is applied to the packaged piezoelectric device by a linear motor (NTIAG HS 01-37), and a Keithley6514 electrometer and an SR570 low-noise current amplifier are used to collect open-circuit voltage signals of two electrodes of the device.

It should be noted that the compression modulus of the examples and comparative examples was measured by a Bose dynamic/static mechanical tester (Bose 3220SERIES II) and the compression rate was 10mm/min. Examples and comparative tensile strength the samples were tested for mechanical properties by an Instron model 5567 universal tester at a tensile rate of 10mm/min.

Example 1

(1) Uniformly mixing 95 parts of PVDF polymer granules and 5 parts of ionic salt, adding the mixture into an internal mixer for melt blending, and collecting a composite material block; wherein, the total weight of the PVDF polymer granules and the ionic salt is 100 parts; the technological parameters of the banburying process are as follows: the temperature of the banburying chamber is 20 ℃ higher than the melting temperature of the PVDF polymer granules, and the rotating speed of a banburying rotor is 80r/min;

wherein the ionic salt is tetraphenylphosphonium chloride;

(3) Mixing the composite material powder obtained in the step (2) with 40 parts of piezoelectric ceramic filler, adding the mixture into a millform mechanochemical reactor, grinding and crushing, and collecting the composite material superfine powder in which the piezoelectric ceramic filler is uniformly dispersed in a polymer matrix after grinding is finished; wherein, the technological parameters of the millstone-shaped mechanochemical reactor are as follows: the grinding pressure is 8MPa, the disc surface temperature of the grinding disc is controlled by introducing a constant-temperature circulating liquid medium with the temperature of 10 ℃, and the grinding is carried out for 10 times in a circulating manner;

(4) Extruding and processing the composite material superfine powder obtained in the step (3) to form and obtain a strand silk for 3D printing; wherein the extrusion processing molding process parameters are as follows: the extrusion temperature is 30 ℃ higher than the melting temperature of the PVDF polymer granules, and the extrusion speed is 20r/min;

(5) Putting the strand silk for 3D printing obtained in the step (4) into a fused deposition modeling 3D printer, and preparing a piezoelectric part with a porous structure by a fused deposition modeling 3D printing technology; the fused deposition modeling 3D printing technology comprises the following process parameters: according to the three-dimensional digital model slice of the required piezoelectric product, arranging extruded strand wires to print along a filling mode of a straight line (Rectilinear), stacking and accumulating layer by layer with an internal filling angle of 0 DEG/90 DEG, wherein the internal filling rate is 60%, the diameter of a nozzle is 0.4 +/-0.01 mm, the temperature of the printing nozzle is consistent with the extrusion temperature in the step (4), the temperature of a hot bed is 120 ℃, and the printing speed is 900mm/min;

(6) And (4) coating conductive silver paste on the upper surface and the lower surface of the porous workpiece prepared in the step (5), respectively attaching aluminum foils as electrodes, and polarizing for 6 hours in an oil corona polarization composite device at the polarizing temperature of 80 ℃.

The high-performance piezoelectric part prepared in this example has a thickness of 1mm, a crystallinity of 52%, a β -crystal content of 84.9%, a piezoelectric property of 10.3V for an open circuit voltage, a compressive modulus of 31.2MPa, and a tensile strength of 22.5MPa.

Example 2

A preparation method of a 3D printed porous high-performance piezoelectric workpiece comprises the following steps in parts by weight:

(1) Uniformly mixing 95 parts of PVDF polymer granules and 5 parts of ionic salt, adding the mixture into an internal mixer for melt blending, and collecting a composite material block; wherein the PVDF polymer granules and the ionic salt total 100 parts by weight; the technological parameters of the banburying process are as follows: the temperature of the banburying chamber is 20 ℃ higher than the melting temperature of the PVDF polymer granules, and the rotating speed of a banburying rotor is 80r/min;

wherein the ionic salt is tetraphenyl phosphorus chloride;

(4) Extruding and processing the composite material superfine powder obtained in the step (3) to form and obtain a strand silk for 3D printing; wherein, the extrusion processing molding process parameters are as follows: the extrusion temperature is 30 ℃ higher than the melting temperature of the PVDF polymer granules, and the extrusion speed is 20r/min;

(5) Putting the strand silk for 3D printing obtained in the step (4) into a fused deposition modeling 3D printer, and preparing a piezoelectric part with a porous structure by a fused deposition modeling 3D printing technology; the fused deposition modeling 3D printing technology comprises the following process parameters: slicing according to a three-dimensional digital model of a required piezoelectric product, setting extruded strand wires to print along a filling mode of a straight line (Recilinear), stacking and accumulating layer by layer with an internal filling angle of 0 DEG/90 DEG, wherein the internal filling rate is 70%, the diameter of a nozzle is 0.4 +/-0.01 mm, the temperature of the printing nozzle is consistent with the extrusion temperature in the step (4), the temperature of a hot bed is 120 ℃, and the printing speed is 900mm/min;

The thickness of the high-performance piezoelectric part prepared in this example is 1mm, and the piezoelectric performance of the high-performance piezoelectric part is 11.4V at an open-circuit voltage, the compression modulus is 32.6MPa, and the tensile strength is 24.9MPa.

Example 3

(1) Uniformly mixing 95 parts of PVDF polymer granules and 5 parts of ionic salt, adding into an internal mixer for melt blending, and collecting to obtain a composite material block; wherein, the total weight of the PVDF polymer granules and the ionic salt is 100 parts; the technological parameters of the banburying process are as follows: the temperature of the banburying chamber is 20 ℃ higher than the melting temperature of the PVDF polymer granules, and the rotating speed of a banburying rotor is 80r/min;

wherein the ionic salt is tetraphenyl phosphorus chloride;

(3) Mixing the composite material powder obtained in the step (2) with 40 parts of piezoelectric ceramic filler, adding the mixture into a millstone-shaped mechanochemical reactor, grinding and crushing the mixture, and collecting the composite material superfine powder in which the piezoelectric ceramic filler is uniformly dispersed in a polymer matrix after the grinding is finished; wherein, the technological parameters of the millstone-shaped mechanochemical reactor are as follows: the grinding pressure is 8MPa, the disc surface temperature of the grinding disc is controlled by introducing a constant-temperature circulating liquid medium with the temperature of 10 ℃, and the grinding is carried out for 10 times in a circulating manner;

(4) Extruding and processing the composite material superfine powder obtained in the step (3) to form threads for 3D printing; wherein, the extrusion processing molding process parameters are as follows: the extrusion temperature is 30 ℃ higher than the melting temperature of the PVDF polymer granules, and the extrusion speed is 20r/min;

(5) Putting the strand silk for 3D printing obtained in the step (4) into a fused deposition modeling 3D printer, and preparing a piezoelectric part with a porous structure by a fused deposition modeling 3D printing technology; the fused deposition modeling 3D printing technology comprises the following process parameters: according to the three-dimensional digital model slice of the required piezoelectric product, arranging extruded strand wires to print along a filling mode of a straight line (Rectilinear), stacking and accumulating layer by layer with an internal filling angle of 0 DEG/90 DEG, wherein the internal filling rate is 80%, the diameter of a nozzle is 0.4 +/-0.01 mm, the temperature of the printing nozzle is consistent with the extrusion temperature in the step (4), the temperature of a hot bed is 120 ℃, and the printing speed is 900mm/min;

The thickness of the high-performance piezoelectric part prepared in this example is 1mm, and the piezoelectric performance of the high-performance piezoelectric part is 9.5V at an open-circuit voltage, 35.4MPa in compression modulus and 25.6MPa in tensile strength.

Comparative example 1

wherein the ionic salt is tetraphenyl phosphorus chloride;

(3) Mixing the composite material powder obtained in the step (2) with 40 parts of piezoelectric ceramic filler, adding the mixture into a millstone-shaped mechanochemical reactor, grinding and crushing the mixture, and collecting the composite material superfine powder in which the piezoelectric ceramic filler is uniformly dispersed in a polymer matrix after the grinding is finished; wherein, the technological parameters of the millstone type mechanochemical reactor are as follows: the grinding pressure is 8MPa, the surface temperature of the grinding disc is controlled by introducing a constant-temperature circulating liquid medium with the temperature of 10 ℃, and the grinding is carried out for 10 times in a circulating manner;

(5) Putting the strand silk for 3D printing obtained in the step (4) into a fused deposition modeling 3D printer, and preparing a piezoelectric part with a porous structure by a fused deposition modeling 3D printing technology; the fused deposition modeling 3D printing technology comprises the following process parameters: slicing according to a three-dimensional digital model of a required piezoelectric product, arranging extruded strand wires to print along a filling mode of a straight line (Recilinear), stacking and accumulating layer by layer with an internal filling angle of 0 DEG/90 DEG, wherein the internal filling rate is 100%, the diameter of a nozzle is 0.4 +/-0.01 mm, the temperature of the printing nozzle is consistent with the extrusion temperature in the step (4), the temperature of a hot bed is 120 ℃, and the printing speed is 900mm/min;

(6) And (3) coating conductive silver paste on the upper surface and the lower surface of the porous workpiece prepared in the step (5), respectively pasting aluminum foils as electrodes, and polarizing for 6 hours in an oil-corona polarizing composite device at the polarizing temperature of 80 ℃.

The piezoelectric part with a solid structure prepared by the comparative example has the thickness of 1mm, the piezoelectric property of 7.0V of open-circuit voltage, the compression modulus of 40.5MPa and the tensile strength of 27.2MPa.

Comparative example 2

wherein the ionic salt is tetraphenylphosphonium chloride;

(3) Mixing the composite material powder obtained in the step (2) with 40 parts of piezoelectric ceramic filler, adding the mixture into a millstone-shaped mechanochemical reactor, grinding and crushing the mixture, and collecting the composite material superfine powder in which the piezoelectric ceramic filler is uniformly dispersed in a polymer matrix after the grinding is finished; wherein, the technological parameters of the millstone-shaped mechanochemical reactor are as follows: the grinding pressure is 8MPa, the surface temperature of the grinding disc is controlled by introducing a constant-temperature circulating liquid medium with the temperature of 10 ℃, and the grinding is carried out for 10 times in a circulating manner;

(4) Extruding and processing the composite material superfine powder obtained in the step (3) to form threads for 3D printing; wherein the extrusion processing molding process parameters are as follows: the extrusion temperature is 20 ℃ higher than the melting temperature of the PVDF polymer granules, and the extrusion speed is 20r/min;

(5) Putting the strand silk for 3D printing obtained in the step (4) into a fused deposition modeling 3D printer, and preparing a piezoelectric part with a porous structure by a fused deposition modeling 3D printing technology; the fused deposition modeling 3D printing technology comprises the following process parameters: according to the three-dimensional digital model slice of the required piezoelectric product, arranging extruded strand wires to print along a filling mode of a straight line (Rectilinear), stacking and accumulating layer by layer with an internal filling angle of 0 DEG/90 DEG, wherein the internal filling rate is 50%, the diameter of a nozzle is 0.4 +/-0.01 mm, the temperature of the printing nozzle is consistent with the extrusion temperature in the step (4), the temperature of a hot bed is 120 ℃, and the printing speed is 900mm/min;

The piezoelectric part with the porous structure prepared by the comparative example has the thickness of 1mm, the piezoelectric property of 6.2V of open-circuit voltage, the compression modulus of 29.1MPa and the tensile strength of 18.6MPa.

In addition, the inventor finds that the workpiece is easily punctured in the polarization process of the step (6), so that the polarization process is not smooth.

Example 4

(1) Uniformly mixing 94.5 parts of PVDF polymer granules and 5.5 parts of ionic salt, adding into an internal mixer for melt blending, and collecting to obtain a composite material block; wherein, the total weight of the PVDF polymer granules and the ionic salt is 100 parts; the technological parameters of the banburying process are as follows: the temperature of the banburying chamber is 10 ℃ higher than the melting temperature of the PVDF polymer granules, and the rotating speed of a banburying rotor is 70r/min;

wherein the ionic salt is tetraphenyl phosphorus chloride;

(3) Mixing the composite material powder obtained in the step (2) with 30 parts of piezoelectric ceramic filler, adding the mixture into a millform mechanochemical reactor, grinding and crushing, and collecting the composite material superfine powder in which the piezoelectric ceramic filler is uniformly dispersed in a polymer matrix after grinding is finished; wherein, the technological parameters of the millstone-shaped mechanochemical reactor are as follows: the grinding pressure is 10MPa, the disc surface temperature of the grinding disc is controlled by introducing a constant-temperature circulating liquid medium with the temperature of 20 ℃, and the grinding is performed for 8 times in a circulating manner;

(4) Extruding and processing the composite material superfine powder obtained in the step (3) to form threads for 3D printing; wherein, the extrusion processing molding process parameters are as follows: the extrusion temperature is 20 ℃ higher than the melting temperature of the PVDF polymer granules, and the extrusion speed is 30r/min;

(5) Putting the strand silk for 3D printing obtained in the step (4) into a fused deposition modeling 3D printer, and preparing a piezoelectric part with a porous structure by a fused deposition modeling 3D printing technology; the fused deposition modeling 3D printing technology comprises the following process parameters: according to the three-dimensional digital model slice of the required piezoelectric product, arranging extruded strand wires to print along a filling mode of a straight line (Rectilinear), stacking and accumulating layer by layer with an internal filling angle of 0 DEG/90 DEG, wherein the internal filling rate is 65%, the diameter of a nozzle is 0.4 +/-0.01 mm, the temperature of the printing nozzle is consistent with the extrusion temperature in the step (4), the temperature of a hot bed is 110 ℃, and the printing speed is 800mm/min;

(6) And (3) coating conductive silver paste on the upper surface and the lower surface of the porous workpiece prepared in the step (5), respectively pasting aluminum foils as electrodes, and polarizing for 8 hours in an oil-corona polarizing composite device at the polarizing temperature of 90 ℃.

Example 5

(1) Uniformly mixing 95 parts of PVDF polymer granules and 5 parts of ionic salt, adding the mixture into an internal mixer for melt blending, and collecting a composite material block; wherein, the total weight of the PVDF polymer granules and the ionic salt is 100 parts; the technological parameters of the banburying process are as follows: the temperature of the mixing chamber is 10 ℃ higher than the melting temperature of the PVDF polymer granules, and the rotating speed of a mixing rotor is 50r/min;

wherein the ionic salt is tetraphenyl phosphorus chloride;

(3) Mixing the composite material powder obtained in the step (2) with 40 parts of piezoelectric ceramic filler, adding the mixture into a millstone-shaped mechanochemical reactor, grinding and crushing the mixture, and collecting the composite material superfine powder in which the piezoelectric ceramic filler is uniformly dispersed in a polymer matrix after the grinding is finished; wherein, the technological parameters of the millstone-shaped mechanochemical reactor are as follows: the grinding pressure is 12MPa, the surface temperature of the grinding disc is controlled by introducing a constant-temperature circulating liquid medium with the temperature of 30 ℃, and the grinding is carried out for 6 times in a circulating manner;

(4) Extruding and processing the composite material superfine powder obtained in the step (3) to form and obtain a strand silk for 3D printing; wherein, the extrusion processing molding process parameters are as follows: the extrusion temperature is 40 ℃ higher than the melting temperature of the PVDF polymer granules, and the extrusion speed is 40r/min;

(5) Putting the strand silk for 3D printing obtained in the step (4) into a fused deposition modeling 3D printer, and preparing a piezoelectric part with a porous structure by a fused deposition modeling 3D printing technology; the fused deposition modeling 3D printing technology comprises the following process parameters: slicing according to a three-dimensional digital model of a required piezoelectric product, arranging extruded strand wires to print along a filling mode of a straight line (Recilinear), stacking and accumulating layer by layer with an internal filling angle of 0 DEG/90 DEG, wherein the internal filling rate is 75%, the diameter of a nozzle is 0.4 +/-0.01 mm, the temperature of the printing nozzle is consistent with the extrusion temperature in the step (4), the temperature of a hot bed is 120 ℃, and the printing speed is 1000mm/min;

(6) And (3) coating conductive silver paste on the upper surface and the lower surface of the porous workpiece prepared in the step (5), respectively pasting aluminum foils as electrodes, and polarizing for 10 hours in an oil-corona polarizing composite device at the polarizing temperature of 100 ℃.

Example 6

(1) Uniformly mixing 95 parts of PVDF polymer granules and 5 parts of ionic salt, adding the mixture into an internal mixer for melt blending, and collecting a composite material block; wherein, the total weight of the PVDF polymer granules and the ionic salt is 100 parts; the technological parameters of the banburying process are as follows: the temperature of the banburying chamber is 15 ℃ higher than the melting temperature of the PVDF polymer granules, and the rotating speed of a banburying rotor is 80r/min;

wherein the ionic salt is tetraphenyl phosphorus chloride;

(3) Mixing the composite material powder obtained in the step (2) with 20 parts of piezoelectric ceramic filler, adding the mixture into a millform mechanochemical reactor, grinding and crushing, and collecting the composite material superfine powder in which the piezoelectric ceramic filler is uniformly dispersed in a polymer matrix after grinding is finished; wherein, the technological parameters of the millstone-shaped mechanochemical reactor are as follows: the grinding pressure is 12MPa, the disc surface temperature of the grinding disc is controlled by introducing a constant-temperature circulating liquid medium with the temperature of 10 ℃, and the grinding is performed circularly for 6 times;

(4) Extruding and processing the composite material superfine powder obtained in the step (3) to form and obtain a strand silk for 3D printing; wherein, the extrusion processing molding process parameters are as follows: the extrusion temperature is 30 ℃ higher than the melting temperature of the PVDF polymer granules, and the extrusion speed is 50r/min;

(5) Putting the strand silk for 3D printing obtained in the step (4) into a fused deposition modeling 3D printer, and preparing a piezoelectric part with a porous structure by a fused deposition modeling 3D printing technology; the fused deposition modeling 3D printing technology comprises the following process parameters: according to the three-dimensional digital model slice of the required piezoelectric product, arranging extruded strand wires to print along a filling mode of a straight line (Rectilinear), stacking and accumulating layer by layer with an internal filling angle of 0 DEG/90 DEG, wherein the internal filling rate is 70%, the diameter of a nozzle is 0.4 +/-0.01 mm, the temperature of the printing nozzle is consistent with the extrusion temperature in the step (4), the temperature of a hot bed is 100 ℃, and the printing speed is 500mm/min;

(6) And (3) coating conductive silver paste on the upper surface and the lower surface of the porous workpiece prepared in the step (5), respectively pasting aluminum foils as electrodes, and polarizing for 12 hours in an oil-corona polarizing composite device at the polarizing temperature of 100 ℃.

Example 7

(1) Uniformly mixing 95.5 parts of PVDF polymer granules and 4.5 parts of ionic salt, adding into an internal mixer for melt blending, and collecting to obtain a composite material block; wherein, the total weight of the PVDF polymer granules and the ionic salt is 100 parts; the technological parameters of the banburying process are as follows: the temperature of the banburying chamber is 20 ℃ higher than the melting temperature of the PVDF polymer granules, and the rotating speed of a banburying rotor is 60r/min;

wherein the ionic salt is tetraphenyl phosphorus chloride;

(3) Mixing the composite material powder obtained in the step (2) with 40 parts of piezoelectric ceramic filler, adding the mixture into a millform mechanochemical reactor, grinding and crushing, and collecting the composite material superfine powder in which the piezoelectric ceramic filler is uniformly dispersed in a polymer matrix after grinding is finished; wherein, the technological parameters of the millstone type mechanochemical reactor are as follows: the grinding pressure is 8MPa, the disc surface temperature of the grinding disc is controlled by introducing a constant-temperature circulating liquid medium with the temperature of 15 ℃, and the grinding is carried out for 10 times in a circulating manner;

(4) Extruding and processing the composite material superfine powder obtained in the step (3) to form threads for 3D printing; wherein the extrusion processing molding process parameters are as follows: the extrusion temperature is 50 ℃ higher than the melting temperature of the PVDF polymer granules, and the extrusion speed is 10r/min;

(5) Putting the strand silk for 3D printing obtained in the step (4) into a fused deposition modeling 3D printer, and preparing a piezoelectric part with a porous structure by a fused deposition modeling 3D printing technology; the fused deposition modeling 3D printing technology comprises the following process parameters: slicing according to a three-dimensional digital model of a required piezoelectric product, setting extruded strand wires to print along a filling mode of a straight line (Recilinear), stacking and accumulating layer by layer with an internal filling angle of 0 DEG/90 DEG, wherein the internal filling rate is 80%, the diameter of a nozzle is 0.4 +/-0.01 mm, the temperature of the printing nozzle is consistent with the extrusion temperature in the step (4), the temperature of a hot bed is 130 ℃, and the printing speed is 600mm/min;

(6) And (3) coating conductive silver paste on the upper surface and the lower surface of the porous workpiece prepared in the step (5), respectively pasting aluminum foils as electrodes, and polarizing for 10 hours in an oil-corona polarizing composite device at the polarizing temperature of 90 ℃.

Claims

1. A preparation method for 3D printing of a porous high-performance piezoelectric workpiece is characterized by comprising the following steps in parts by weight:

(1) Uniformly mixing 94.5-95.5 parts of PVDF polymer granules and 4.5-5.5 parts of ionic salt, adding into an internal mixer for melt blending, and collecting to obtain a composite material block; wherein the PVDF polymer granules and the ionic salt total 100 parts by weight; the technological parameters of the banburying process are as follows: the temperature of the banburying chamber is 10-20 ℃ higher than the melting temperature of the PVDF polymer granules, and the rotating speed of a banburying rotor is 50-80 r/min;

wherein the ionic salt is tetraphenyl phosphorus chloride;

(3) Mixing the composite material powder obtained in the step (2) with 5-40 parts of piezoelectric ceramic filler, adding the mixture into a millform mechanochemical reactor, grinding and crushing, and collecting the composite material superfine powder in which the piezoelectric ceramic filler is uniformly dispersed in a polymer matrix after grinding is finished; wherein, the technological parameters of the millstone-shaped mechanochemical reactor are as follows: the grinding pressure is 8-12 MPa, and the grinding is circulated for 6-10 times;

(4) Extruding and processing the composite material superfine powder obtained in the step (3) to form and obtain a strand silk for 3D printing; wherein the extrusion processing molding process parameters are as follows: the extrusion temperature is 20-50 ℃ higher than the melting temperature of the PVDF polymer granules, and the extrusion speed is 10-50 r/min;

2. The method of claim 1, wherein: the PVDF-based polymer particles in the step (1) include any one of pure polyvinylidene fluoride particles, polyvinylidene fluoride-hexafluoropropylene particles and polyvinylidene fluoride-chlorotrifluoroethylene particles.

3. The method of claim 1, wherein: the step (1) is carried out with uniform mixing, the mixing speed is 100-500 r/min, and the mixing time is 20-30 min.

4. The method of claim 1, wherein: and (4) the extrusion processing and forming in the step (4) comprises double-screw melt extrusion processing and forming and single-screw melt extrusion processing and forming.

5. The method of claim 1, wherein: and (6) specifically, the polarization treatment in the step (6) is to coat conductive silver paste on the upper surface and the lower surface of the part with the porous structure prepared in the step (5) along the direction of the electric field, respectively attach aluminum foils as electrodes, place the part in an oil corona polarization composite device for polarization for 6 to 12 hours, and the polarization temperature is 80 to 100 ℃.

6. The method of claim 1, wherein: the fused deposition modeling 3D printing technology in the step (5) has the following process parameters: and (3) according to a three-dimensional digital model slice of a required piezoelectric product, arranging extruded strand wires to print along a filling mode of a straight line (Rectilinear), stacking and accumulating layer by layer with an internal filling angle of 0 DEG/90 DEG, wherein the internal filling rate is 69-71%, the diameter of a nozzle is 0.4 +/-0.01 mm, the temperature of the printing nozzle is consistent with the extrusion temperature in the step (4), the temperature of a hot bed is 90-130 ℃, and the printing speed is 500-1000 mm/min.

7. The high-performance piezoelectric part prepared by the method for preparing the 3D printed porous high-performance piezoelectric part according to any one of claims 1 to 6.