CN114889083A - Stretching process capable of improving breakdown voltage resistance of PVDF piezoelectric film - Google Patents
Stretching process capable of improving breakdown voltage resistance of PVDF piezoelectric film Download PDFInfo
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
- B29C48/001—Combinations of extrusion moulding with other shaping operations
- B29C48/0018—Combinations of extrusion moulding with other shaping operations combined with shaping by orienting, stretching or shrinking, e.g. film blowing
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
- B29C48/001—Combinations of extrusion moulding with other shaping operations
- B29C48/002—Combinations of extrusion moulding with other shaping operations combined with surface shaping
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
- B29C48/001—Combinations of extrusion moulding with other shaping operations
- B29C48/0022—Combinations of extrusion moulding with other shaping operations combined with cutting
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
- B29C48/03—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor characterised by the shape of the extruded material at extrusion
- B29C48/07—Flat, e.g. panels
- B29C48/08—Flat, e.g. panels flexible, e.g. films
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
- B29C48/25—Component parts, details or accessories; Auxiliary operations
- B29C48/92—Measuring, controlling or regulating
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C55/00—Shaping by stretching, e.g. drawing through a die; Apparatus therefor
- B29C55/02—Shaping by stretching, e.g. drawing through a die; Apparatus therefor of plates or sheets
- B29C55/04—Shaping by stretching, e.g. drawing through a die; Apparatus therefor of plates or sheets uniaxial, e.g. oblique
- B29C55/06—Shaping by stretching, e.g. drawing through a die; Apparatus therefor of plates or sheets uniaxial, e.g. oblique parallel with the direction of feed
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C59/00—Surface shaping of articles, e.g. embossing; Apparatus therefor
- B29C59/10—Surface shaping of articles, e.g. embossing; Apparatus therefor by electric discharge treatment
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
- B29K2027/00—Use of polyvinylhalogenides or derivatives thereof as moulding material
- B29K2027/12—Use of polyvinylhalogenides or derivatives thereof as moulding material containing fluorine
- B29K2027/16—PVDF, i.e. polyvinylidene fluoride
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Abstract
The invention discloses a stretching process capable of improving breakdown voltage resistance of a PVDF piezoelectric film, which belongs to the technical field of piezoelectric film stretching, and by applying the film stretching process, under the action of the same electric field intensity, along with the superposition of multiple layers of films, the conductance current of the piezoelectric film is increased, the electrical aging threshold value moves towards the direction of a low electric field, the corona resistance life is obviously increased, the conductance current of the stretched three-layer piezoelectric PVDF film is increased, the electrical aging threshold value is slightly reduced, the corona resistance life is obviously increased under the condition that the piezoelectric film is in the same thickness, compared with the unstretched three-layer piezoelectric film, the stretching causes the change of an interface structure, the conductive channel structure among nano particles is changed, the space charge back electric field is strengthened, the transportation of carriers and the corrosion of the carriers on the surface of the film are more effectively blocked, and the heat dissipation capacity is quicker, so that the film is not easy to cause the film breakdown phenomenon under the influence of temperature, current and voltage, has good market application prospect.
Description
Technical Field
The invention belongs to the technical field of piezoelectric film stretching, and particularly relates to a stretching process capable of improving breakdown voltage resistance of a PVDF piezoelectric film.
Background
The piezoelectric film is a film material with piezoelectric property prepared by film-forming techniques of evaporation, sputtering, chemical deposition, vapor phase epitaxy, casting, rolling and the like, and mainly comprises three categories of inorganic piezoelectric films (such as ZnO, AlN, CdS and the like), organic piezoelectric films (such as polyvinyl fluoride (PVF), polyvinylidene fluoride (PVDF) and the like) and organic inorganic composite piezoelectric films (such as PVF2-PZT, PVF2-BaTiO3 and the like), wherein the electromechanical coupling coefficients of the inorganic piezoelectric films with polycrystalline structures, particularly ZnO and AlN films, are close to the single crystal value of the inorganic piezoelectric films, and the polycrystalline films with c-axis preferred orientation have the piezoelectric property close to the single crystal of the inorganic piezoelectric films.
At present, in the preparation process of film stretching, the piezoelectric strain constant of the piezoelectric film is low and the sensitivity is not enough when the polarization voltage is low, the piezoelectric film is broken down when the polarization voltage is high, further, in the stretching preparation process, the breakdown resistance of the film is not good, the piezoelectric film prepared by using polyamide acid as a main chain structure has certain rigidity, when the stretching ratio is not large, the whole macromolecular chain cannot be completely oriented, only partial chain segments are oriented, the piezoelectric property of the film is affected, and the film breakdown phenomenon is easily caused by the influence of temperature, current and voltage when the film is used, so that the piezoelectric property detection after the film is stretched is very necessary.
Disclosure of Invention
Technical problem to be solved
In order to overcome the defects in the prior art, the invention provides a stretching process capable of improving the breakdown voltage resistance of a PVDF piezoelectric film, and solves the problems that in the preparation process of film stretching processing, the piezoelectric strain constant of the piezoelectric film is low and the sensitivity is not enough when the polarization voltage is low, the piezoelectric film is broken down when the polarization voltage is high, further, in the stretching preparation process, the breakdown resistance of the film is not good, the piezoelectric film has certain rigidity, when the stretching ratio is not large, the whole macromolecular chain cannot be completely oriented, only part of chain segments are oriented, the piezoelectric property of the film is affected, and the film breakdown phenomenon is caused by the influence of temperature, current and voltage when the film is used.
The purpose of the invention is as follows:
through the application of the film stretching process, under the action of the same electric field intensity, the electric conduction current of the piezoelectric film is increased along with the superposition of the multiple layers of films, the electric aging threshold value moves towards the direction of a low electric field, the corona resistance service life is obviously prolonged, the piezoelectric film is at the same thickness, compared with an unstretched three-layer piezoelectric film, the electric conduction current of the stretched three-layer piezoelectric PVDF film is increased, the electric aging threshold value is slightly reduced, the corona resistance service life is obviously prolonged, the stretching enables an interface structure to change, the conductive channel structure among nano particles is changed, the space charge anti-electric field is strengthened, the transportation of current carriers and the corrosion of the current carriers to the surface of the film are more effectively hindered, and meanwhile, the heat dissipation capacity is faster, so that the film is not easily affected by temperature, current and voltage to cause the film breakdown phenomenon, and the film stretching process has good market application prospect.
In carrying out continuous polarization to piezoelectric film, carry piezoelectric film through the mode that the compression roller was pull, can produce even polarization electric field in piezoelectric film width direction, realize the even polarization to piezoelectric film, even cause the single-point breakdown phenomenon to piezoelectric film, because the film lasts conveying and corona electrode incessant, realize continuously carrying out polarization treatment to piezoelectric film, be favorable to piezoelectric film's high-efficient polarization operation.
(II) technical scheme
In order to achieve the purpose, the invention provides the following technical scheme: a stretching process capable of improving breakdown voltage resistance of a PVDF piezoelectric film comprises the following steps:
s1, firstly weighing PVDF raw material particles, adding the weighed raw material particles into a double-screw extruder for melt extrusion, and preparing the PVDF piezoelectric film.
And S2, cutting the pressed PVDF coiled material, loading clamps at two ends of the cut PVDF coiled material, placing the PVDF piezoelectric film on a stretching equipment unit, and performing multiple longitudinal stretching treatment on the PVDF coiled material.
And S3, continuously polarizing the three-layer piezoelectric film obtained after stretching, and then testing the piezoelectricity of the three-layer piezoelectric film.
As a further scheme of the invention: in the S1, the temperature of the extruder is controlled to be 180 ℃ and 250 ℃, and the rotation speed of the extruder is controlled to be 150 ℃ and 280 r/S.
PVDF raw material particles are added into a screw extruder, the temperature of each area of the extruder and the rotating speed of the screw of the extruder are accurately controlled, the high-efficiency high-quality melting plasticizing effect is realized, and the PVDF coiled material is prepared.
As a further scheme of the invention: in the S2, the PVDF coiled material is stretched, and the spacing is controlled to be 30-95 mm.
As a further scheme of the invention: the piezoelectric property test performed in S3 includes a conductance current test and a corona resistance test.
As a further scheme of the invention: the specific preparation steps of the PVDF piezoelectric film coil in the S1 are as follows:
s101, PVDF polyvinylidene fluoride particles are selected as raw materials, and are dried and then automatically and uniformly fed into an extrusion rolling hole in a vacuum mode.
S102, pushing the PVDF polyvinylidene fluoride particles into a double-screw extruder for conveying and extruding, wherein the temperature of the extruder is controlled at 180-250 ℃, the rotating speed of the extruder is controlled at 150-280r/S, and the primary coiled material of the PVDF piezoelectric film is extruded.
And connecting the PVDF piezoelectric film primary coiled material by using a winding mechanism and winding to finish the preparation of the PVDF piezoelectric film coiled material.
As a further scheme of the invention: the stretching step of the PVDF coil in the S2 is as follows:
s201, firstly, loading clamps at two ends of a cut PVDF coiled material, preheating the PVDF film by taking air as a heating medium, controlling the preheating temperature at 25-50 ℃, and longitudinally stretching the PVDF coiled material by a stretching unit in a longitudinal step-by-step stretching mode, wherein the stretching speed is 45mm/min, and the stretching ratio is fixed at 5%.
S202, then placing a stretching machine set in a box body with adjustable temperature, wherein the temperature can be adjusted to 70-120 ℃, and preparing the stretched three-layer piezoelectric film with the total thickness of 29 microns, 30 microns and 31 microns respectively, and the stretched three-layer piezoelectric film is represented by D35.
And treated under the same process conditions, unstretched three-layer piezoelectric films having total thicknesses of 29 μm, 30 μm, and 31 μm, respectively, were prepared and denoted by D30.
As a further scheme of the invention: the implementation steps of the continuous polarization in S3 are as follows:
s301, the prepared piezoelectric film is placed in a polarization mechanism with a traction device, the piezoelectric film is attached to the upper surface of a zero electrode roller and is in a tight attaching state, and the position of a corona electrode is adjusted to enable the vertical distance between the axis of the corona electrode and the upper surface of the piezoelectric film to be 10-20 mm.
S302, heating the piezoelectric film to 90-95 ℃ in an environment of 25-30 ℃, and applying a direct current voltage of 230V/mum-320V/mum to the corona electrode through a high-voltage polarization power supply according to the thickness of the polarized piezoelectric film.
S303, starting a traction device on the polarization mechanism to drive the piezoelectric film to continuously pass through the corona electrode at the speed of 400-.
(III) advantageous effects
Compared with the prior art, the invention has the beneficial effects that:
1. according to the invention, through the application of the film stretching process, under the action of the same electric field intensity, the electric conduction current of the piezoelectric film is increased along with the superposition of the multiple layers of films, the electric aging threshold value moves towards the direction of a low electric field, the corona resistance service life is obviously prolonged, the piezoelectric film has the advantages that under the same thickness, compared with an unstretched three-layer piezoelectric film, the electric conduction current of the stretched three-layer piezoelectric PVDF film is increased, the electric aging threshold value is slightly reduced, the corona resistance service life is obviously prolonged, the stretching enables the interface structure to change, the conductive channel structure among the nano particles is changed, the space charge anti-electric field is strengthened, the transport of current carriers and the corrosion of the current carriers to the surface of the film are more effectively hindered, and meanwhile, the heat radiation capacity is faster, so that the film is not easily affected by temperature, current and voltage to cause the film breakdown phenomenon, and the film stretching process has a good market application prospect.
2. According to the invention, in the continuous polarization of the piezoelectric film, the piezoelectric film is conveyed in a compression roller traction mode, so that a uniform polarization electric field can be generated in the width direction of the piezoelectric film, the uniform polarization of the piezoelectric film is realized, even if a single-point breakdown phenomenon is caused to the piezoelectric film, the continuous polarization treatment of the piezoelectric film is realized due to the continuous transmission of the film and the uninterrupted corona electrode, and the efficient polarization operation of the piezoelectric film is facilitated.
Drawings
FIG. 1 is a schematic illustration of a process of the present invention;
FIG. 2 is a block flow diagram of S1 according to the present invention;
FIG. 3 is a block flow diagram of S2 according to the present invention;
FIG. 4 is a block flow diagram of S3 of the present invention;
FIG. 5 is a functional block diagram of the piezoelectricity test of the present invention.
Detailed Description
The technical solution of the present patent will be described in further detail with reference to the following embodiments.
As shown in fig. 1 to 5, the present invention provides a technical solution: a stretching process capable of improving breakdown voltage resistance of a PVDF piezoelectric film comprises the following steps:
s1, firstly weighing PVDF raw material particles, adding the weighed raw material particles into a double-screw extruder for melt extrusion, and preparing the PVDF piezoelectric film coiled material.
And S2, cutting the pressed PVDF coiled material, loading clamps at two ends of the cut PVDF coiled material, placing the PVDF coiled material on a stretching equipment unit, and performing multi-time unidirectional stretching treatment on the PVDF coiled material.
And S3, continuously polarizing the three-layer piezoelectric film obtained after stretching, and then testing the piezoelectricity of the three-layer piezoelectric film.
In S1, the temperature of the extruder is controlled to be 180-240 ℃, and the rotation speed of the extruder is controlled to be 150-280 r/S.
PVDF raw material particles are added into a screw extruder, the temperature of each area of the extruder and the rotating speed of the screw of the extruder are accurately controlled, the high-efficiency high-quality melting plasticizing effect is realized, and the PVDF coiled material is prepared.
In the process of stretching the PVDF coiled material in S2, the spacing is controlled to be 30-75 mm.
The piezoelectric test performed in S3 includes a conduction current test and a corona resistance test.
The specific preparation steps of the PVDF piezoelectric film coil in the S1 are as follows:
s101, PVDF polyvinylidene fluoride particles are selected as raw materials, and are dried and then automatically and uniformly fed into an extrusion rolling hole in a vacuum mode.
S102, pushing PVDF polyvinylidene fluoride particles into a double-screw extruder for conveying and extruding, wherein the temperature of the extruder is controlled to be 180-250 ℃, the rotating speed of the extruder is controlled to be 150-280r/S, and the primary coiled material of the PVDF piezoelectric film is extruded.
And connecting the PVDF piezoelectric film primary coiled material by using a winding mechanism and winding to finish the preparation of the PVDF piezoelectric film coiled material.
The stretching step of the PVDF web in S2 is as follows:
s201, firstly, loading clamps at two ends of a cut PVDF coiled material, preheating the PVDF film by taking air as a heating medium, controlling the preheating temperature at 25-50 ℃, and longitudinally stretching the PVDF coiled material by a stretching unit in a longitudinal step-by-step stretching mode, wherein the stretching speed is 45mm/min, and the stretching ratio is fixed at 5%.
S202, then placing a stretching machine set in a box body with adjustable temperature, wherein the temperature can be adjusted to 70-120 ℃, and preparing the stretched three-layer piezoelectric film with the total thickness of 29 microns, 30 microns and 31 microns respectively, and the stretched three-layer piezoelectric film is represented by D35.
And treated under the same process conditions, unstretched three-layer piezoelectric films having total thicknesses of 29 μm, 30 μm, and 31 μm, respectively, were prepared and denoted by D30.
The steps of implementing continuous polarization in S3 are as follows:
s301, the prepared piezoelectric film is placed in a polarization mechanism with a traction device, the piezoelectric film is attached to the upper surface of a zero electrode roller and is in a tight attaching state, and the position of a corona electrode is adjusted to enable the vertical distance between the axis of the corona electrode and the upper surface of the piezoelectric film to be 10-20 mm.
S302, heating the piezoelectric film to 90-95 ℃ in an environment of 25-30 ℃, and applying a direct current voltage of 230V/mum-320V/mum to the corona electrode through a high-voltage polarization power supply according to the thickness of the polarized piezoelectric film.
S303, starting a traction device on the polarization mechanism to drive the piezoelectric film to continuously pass through the corona electrode at the speed of 400-.
Example (b):
a stretching process capable of improving breakdown voltage resistance of a PVDF piezoelectric film comprises the following steps:
s1, firstly weighing PVDF raw material particles, adding the weighed raw material particles into a double-screw extruder for melt extrusion, and preparing the PVDF coiled material.
The specific preparation steps of the PVDF piezoelectric film coil in the S1 are as follows:
s101, PVDF polyvinylidene fluoride particles are selected as raw materials, and are dried and then automatically and uniformly fed into an extrusion rolling hole in a vacuum mode.
S102, pushing PVDF polyvinylidene fluoride particles into a double-screw extruder for conveying and extruding, wherein the temperature of the extruder is controlled to be 180-250 ℃, the rotating speed of the extruder is controlled to be 150-280r/S, and the primary coiled material of the PVDF piezoelectric film is extruded.
And connecting the PVDF piezoelectric film primary coiled material by using a winding mechanism and winding to finish the preparation of the PVDF piezoelectric film coiled material.
And S2, cutting the pressed PVDF coiled material, loading clamps at two ends of the cut PVDF coiled material, placing the PVDF coiled material on a stretching equipment unit, and performing multiple longitudinal stretching treatment on the PVDF coiled material.
The stretching step of the PVDF web in S2 is as follows:
s201, firstly, loading clamps at two ends of a cut PVDF coiled material, preheating the PVDF film by taking air as a heating medium, controlling the preheating temperature at 25-50 ℃, and longitudinally stretching the PVDF coiled material by a stretching unit in a longitudinal step-by-step stretching mode, wherein the stretching speed is 45mm/min, and the stretching ratio is fixed at 5%.
S202, then placing a stretching machine set in a box body with adjustable temperature, wherein the temperature can be adjusted to 70-120 ℃, and preparing the stretched three-layer piezoelectric film with the total thickness of 29 microns, 30 microns and 31 microns respectively, and the stretched three-layer piezoelectric film is represented by D35.
And treated under the same process conditions, unstretched three-layer piezoelectric films having total thicknesses of 29 μm, 30 μm, and 31 μm, respectively, were prepared and denoted by D30.
And S3, continuously polarizing the three-layer piezoelectric film obtained after stretching, and then testing the piezoelectricity of the three-layer piezoelectric film.
The steps of implementing continuous polarization in S3 are as follows:
s301, the prepared piezoelectric film is placed in a polarization mechanism with a traction device, the piezoelectric film is attached to the upper surface of a zero electrode roller and is in a tight attaching state, and the position of a corona electrode is adjusted to enable the vertical distance between the axis of the corona electrode and the upper surface of the piezoelectric film to be 10-20 mm.
S302, heating the piezoelectric film to 90-95 ℃ in an environment of 25-30 ℃, and applying a direct current voltage of 230V/mum-320V/mum to the corona electrode through a high-voltage polarization power supply according to the thickness of the polarized piezoelectric film.
S303, starting a traction device on the polarization mechanism to drive the piezoelectric film to continuously pass through the corona electrode at the speed of 400-.
A. And (3) conducting current testing: the testing is carried out by adopting a direct-current voltage and echelon boosting mode, the initial electric field intensity is 10kV/mm, the boosting gradient of 10kV/mm is used for boosting to the average electric field intensity of 80kV/mm every time, the numerical value of the conductive current is recorded after 60rain is pressurized under each electric field intensity, the area of the film to be tested is 45mm multiplied by 45mm, aluminum electrodes with the diameter of 25mm are attached to the two surfaces of the sample, and the influence of an air gap between the electrodes on the testing result is avoided.
B. Corona resistance test: according to IEC60343 standard, a rod-plate electrode system is adopted, an upper electrode is a cylindrical electrode with the diameter of 6mm (the diameter of the end face of the electrode is 4mm, and the chamfer angle is R1mm), a lower electrode is a flat electrode with the diameter of 50mm, the upper electrode and the lower electrode are polished and ground before testing, the testing conditions are room temperature and RH (35-40)%, and the electric field intensity applied to a sample is 80kV/mm at power frequency.
Based on A, four kinds of data of the conductance current of the sample with the thickness D30 and the conductance current of the sample with the thickness D35 are tested:
the volume conductivity gamma of D30 and D35 at the electric field intensity of 30kV/mm and 4 thicknesses can be calculated by testing the data of the ohmic conduction region.
The conductance current of D30 and D35 increases with the increase of the thickness, the conductance current of the stretched three-layer piezoelectric film is slightly larger than that of the unstretched piezoelectric film under the same thickness, the conductivity of D30 and D35 increases with the increase of the thickness, and the conductivity of D35 is higher than that of D30 under the same thickness.
In an ohmic conduction region, the current density J of the piezoelectric film is in a linear relation with the electric field intensity E, namely:
J＝γE＝nqμE。
where γ is conductivity, E is electric field intensity, n is carrier density, q is electron charge amount, and μ is carrier mobility.
Electrical aging threshold as a function of thickness data for tests D30 and D35.
And (3) moving the electrical aging threshold to the direction of low electric field intensity along with the increase of the thickness of the doped layer, wherein the electrical aging threshold of the stretched three-layer piezoelectric film is lower than that of the unstretched piezoelectric film under the same thickness.
With the increase of the thickness of the doped layer, the average doping amount of the nano oxide in the film is increased, the average density of carrier traps in the material is increased, the limiting capability of the material on carriers is enhanced, and space charges are accumulated in the material under relatively low electric field intensity.
Based on the method B, the corona aging resistance test is carried out on 4 films with different thicknesses of D30 and D35, and 6 samples of the film with each thickness are taken to carry out relatively independent experiments in the test process.
The corona aging resistant life of D30 and D35 is obviously prolonged along with the increase of the thickness of the doped layer, and the corona aging resistant life of D35 is longer than that of D30 under the same thickness, which shows that the stretching improves the corona aging resistant life of the piezoelectric film.
In conclusion, the following results are obtained:
through the application of the film stretching process, under the action of the same electric field intensity, the electric conduction current of the piezoelectric film is increased along with the superposition of the multiple layers of films, the electric aging threshold value moves towards the direction of a low electric field, the corona resistance service life is obviously prolonged, the piezoelectric film is at the same thickness, compared with an unstretched three-layer piezoelectric film, the electric conduction current of the stretched three-layer piezoelectric PVDF film is increased, the electric aging threshold value is slightly reduced, the corona resistance service life is obviously prolonged, the stretching enables an interface structure to change, the conductive channel structure among nano particles is changed, the space charge anti-electric field is strengthened, the transportation of current carriers and the corrosion of the current carriers to the surface of the film are more effectively hindered, and meanwhile, the heat dissipation capacity is faster, so that the film is not easily affected by temperature, current and voltage to cause the film breakdown phenomenon, and the film stretching process has good market application prospect.
Through carrying out the continuous polarization to piezoelectric film, carry piezoelectric film through the mode that the compression roller was pull, can produce even polarization electric field in piezoelectric film width direction, realize the even polarization to piezoelectric film, even cause the single-point breakdown phenomenon to piezoelectric film, because the film lasts conveying and corona electrode incessant, realize continuously carrying out polarization treatment to piezoelectric film, be favorable to piezoelectric film's high-efficient polarization operation.
Although the preferred embodiments of the present patent have been described in detail, the present patent is not limited to the above embodiments, and various changes can be made without departing from the spirit of the present patent within the knowledge of those skilled in the art.
Claims (7)
1. A stretching process capable of improving breakdown voltage resistance of a PVDF piezoelectric film is characterized by comprising the following steps:
s1, firstly weighing PVDF raw material particles, adding the weighed raw material particles into a double-screw extruder for melt extrusion, and preparing a PVDF piezoelectric film coil;
s2, cutting the prepared PVDF coiled material, loading clamps at two ends of the cut PVDF coiled material, placing the PVDF coiled material on a stretching equipment unit, and performing multiple longitudinal stretching treatment on the PVDF coiled material;
and S3, continuously polarizing the three-layer piezoelectric film obtained after stretching, and then testing the piezoelectricity of the three-layer piezoelectric film.
2. The stretching process capable of improving the breakdown voltage resistance of the PVDF piezoelectric film as claimed in claim 1, wherein: in the S1, the temperature of the extruder is controlled to be 180 ℃ and 250 ℃, and the rotation speed of the extruder is controlled to be 150 ℃ and 280 r/S.
3. The stretching process capable of improving the breakdown voltage resistance of the PVDF piezoelectric film as claimed in claim 1, wherein: in the S2, the PVDF coiled material is stretched, and the spacing is controlled to be 30-75 mm.
4. The stretching process capable of improving the breakdown voltage resistance of the PVDF piezoelectric film as claimed in claim 1, wherein: the piezoelectric property test performed in S3 includes a conductance current test and a corona resistance test.
5. The stretching process capable of improving the breakdown voltage resistance of the PVDF piezoelectric film as claimed in claim 1, wherein: the specific preparation steps of the PVDF piezoelectric film coil in the S1 are as follows:
s101, PVDF polyvinylidene fluoride particles are selected as raw materials, dried and then automatically and uniformly fed into an extrusion rolling hole in a vacuum mode;
s102, pushing PVDF (polyvinylidene fluoride) particles into a double-screw extruder for conveying and extruding, wherein the temperature of the extruder is controlled to be 180-class 250 ℃, the rotating speed of the extruder is controlled to be 150-class 280r/S, and a PVDF piezoelectric film primary coiled material is extruded;
and connecting the PVDF piezoelectric film primary coiled material by using a winding mechanism and winding to finish the preparation of the PVDF piezoelectric film coiled material.
6. The stretching process capable of improving the breakdown voltage resistance of the PVDF piezoelectric film as claimed in claim 1, wherein: the stretching step of the PVDF coil in the S2 is as follows:
s201, firstly, loading clamps at two ends of a cut PVDF coiled material, preheating the PVDF film by taking air as a heating medium, controlling the preheating temperature at 25-50 ℃, and longitudinally stretching the PVDF coiled material by a stretching unit in a longitudinal step-by-step stretching mode, wherein the stretching speed is 45mm/min, and the stretching ratio is fixed at 5%;
s202, then placing a stretching machine set in a box body with adjustable temperature, wherein the temperature can be adjusted to 70-120 ℃, and preparing the stretched three-layer piezoelectric film with the total thickness of 29 microns, 30 microns and 31 microns respectively, and the stretched three-layer piezoelectric film is represented by D35.
And treated under the same process conditions, unstretched three-layer piezoelectric films having total thicknesses of 29 μm, 30 μm, and 31 μm, respectively, were prepared and denoted by D30.
7. The stretching process capable of improving the breakdown voltage resistance of the PVDF piezoelectric film as claimed in claim 1, wherein: the implementation steps of the continuous polarization in S3 are as follows:
s301, placing the prepared piezoelectric film into a polarization mechanism with a traction device, enabling the piezoelectric film to be attached to the upper surface of a zero electrode roller and be in a tight attaching state, and adjusting the position of a corona electrode to enable the vertical distance between the axis of the corona electrode and the upper surface of the piezoelectric film to be 10-20 mm;
s302, heating the piezoelectric film to 90-95 ℃ in an environment of 25-30 ℃, and applying a direct current voltage of 230-320V/mum to the corona electrode through a high-voltage polarization power supply according to the thickness of the polarized piezoelectric film;
s303, starting a traction device on the polarization mechanism to drive the piezoelectric film to continuously pass through the corona electrode at the speed of 400-.
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN115322499A (en) * | 2022-08-19 | 2022-11-11 | 三三智能科技(日照)有限公司 | Piezoelectric film production process capable of reducing breakage rate |
| CN117700907A (en) * | 2024-02-05 | 2024-03-15 | 石家庄市长安育才建材有限公司 | Piezoelectric film and energy recovery floor tile device based on polyvinylidene fluoride |
| CN117700907B (en) * | 2024-02-05 | 2024-05-24 | 石家庄市长安育才建材有限公司 | Piezoelectric film and energy recovery floor tile device based on polyvinylidene fluoride |
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2022
- 2022-06-16 CN CN202210686055.7A patent/CN114889083A/en active Pending
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN115322499A (en) * | 2022-08-19 | 2022-11-11 | 三三智能科技(日照)有限公司 | Piezoelectric film production process capable of reducing breakage rate |
| CN117700907A (en) * | 2024-02-05 | 2024-03-15 | 石家庄市长安育才建材有限公司 | Piezoelectric film and energy recovery floor tile device based on polyvinylidene fluoride |
| CN117700907B (en) * | 2024-02-05 | 2024-05-24 | 石家庄市长安育才建材有限公司 | Piezoelectric film and energy recovery floor tile device based on polyvinylidene fluoride |
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