CN115589761B - Preparation method of porous piezoelectric electret - Google Patents
Preparation method of porous piezoelectric electret Download PDFInfo
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- CN115589761B CN115589761B CN202211587549.6A CN202211587549A CN115589761B CN 115589761 B CN115589761 B CN 115589761B CN 202211587549 A CN202211587549 A CN 202211587549A CN 115589761 B CN115589761 B CN 115589761B
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
- H04R19/00—Electrostatic transducers
- H04R19/01—Electrostatic transducers characterised by the use of electrets
- H04R19/016—Electrostatic transducers characterised by the use of electrets for microphones
Abstract
The invention belongs to the technical field of electrets, in particular to a preparation method of a porous piezoelectric electret, which comprises the following steps: s1, providing an electret material dispersion liquid; s2, coating the electret material dispersion liquid on a back-electrode plate; s3, maintaining the container of the back plate coated with the electret material dispersion liquid for 16-25 min under specific temperature and pressure; s4, reducing the temperature to be lower than the melting point temperature of the electret material, and keeping the temperature for 10-30 min under the pressure P2; s5, quickly releasing the pressure in the container, wherein P2 is equal to P1; s6, controlling the temperature in the container, maintaining for 20-25min, and shaping the micropores in the electret material; and S7, cooling the product to obtain the porous piezoelectric electret. According to the invention, when the dispersion liquid forms a film on the back plate, the film is subjected to micropore forming, and meanwhile, material decomposition caused by high temperature in the generation process can be avoided, and the electricity storage performance of the electret is ensured.
Description
Technical Field
The invention belongs to the technical field of electrets, and particularly relates to a preparation method of a porous piezoelectric electret, wherein the electret has excellent charge thermal stability and is particularly suitable for being used in a high-temperature environment.
Background
Electret refers to a functional dielectric material that has the ability to store electric polarization and space charge for long periods of time. Due to the physical effects of static electricity, piezoelectricity, pyroelectricity, optical nonlinearity and the like, the material has more and more applications in the fields of electronic engineering, environmental purification, energy sources, biomedical engineering and the like, particularly in the aspect of sensor engineering.
Compared with the traditional external polarization type measuring microphone, the electret measuring microphone has much lower requirements on a circuit at the rear end, and can realize portable test application. As the measuring microphone using the electret technology is applied more and more widely, the measuring microphone also has some defects in certain specific environments, and the charge storage capacity of the electret is seriously reduced at high temperature (the high temperature causes the charge on the surface of the electret to be separated), so that the defect causes that the electret measuring microphone cannot work for a long time in the high-temperature environment.
The porous electret can improve the stability of charge storage of the electret in a high-temperature environment. The traditional method for preparing the polymer with the closed microporous structure mainly comprises two methods: firstly, obtaining a material with a hole structure by a chemical foaming process; secondly, the polymer resin and the inorganic or organic particles are melted and blended to form a thin plate through an extrusion or hot pressing process, and the film with the micropore structure is obtained in the biaxial stretching process by utilizing the huge mechanical property difference between the polymer resin and the added particles.
The prior art references are as follows:
CN100505359C discloses a method for preparing a controllable micropore structure piezoelectric functional film, wherein a polymer compact film with high thermal stability and a polymer reticular film with different melting temperatures from the polymer compact film are overlapped layer by layer; then forming the polymer composite membrane with the microporous structure after 2-120 minutes at the temperature of 90-500 ℃ and under the pressure of 1kPa-10 MPa.
CN102150225B discloses an electret film and an electret containing the same, wherein the porous resin film (i) comprises a core layer (a) comprising a biaxially stretched resin film having pores and a surface layer (B) comprising a stretched resin film on at least one surface of the core layer (a), and the porous resin film (i) is subjected to heat treatment under a non-pressurized condition after allowing a non-reactive gas to permeate therethrough under a pressurized condition. The biaxially stretched resin film having voids is a material which can form voids each having a large volume when the voids are expanded in the thickness direction by further performing a pressure treatment and a heat treatment, and which is easy to store charges polarized to the positive and negative electrodes in the voids when the charges are injected, and which is excellent in charge retention performance after the film (ii) is formed into an electret film.
The back plate of the porous electret microphone is often provided with a plurality of holes, if the porous film is used, the porous film can cover the holes of the back plate after being pasted on the back plate, and then the trouble of secondary hole opening of the electret film is caused, and uncertainty is brought to the volume production and stability of products.
Therefore, there is a need for a porous membrane that can be formed directly on a perforated backplate without secondary opening and the resulting porous piezoelectric electret has good charge stability.
Disclosure of Invention
The invention aims to provide a preparation method of a porous piezoelectric electret, which is characterized in that a dispersion liquid is used for forming a film on a back plate, and simultaneously, micropores are formed on the film, so that the decomposition of materials caused by high temperature in the generation process can be avoided, and the electricity storage performance of the electret is ensured.
In order to achieve the purpose, the invention adopts the following technical scheme:
the preparation method of the porous piezoelectric electret comprises the following steps:
s1, providing electret material dispersion liquid;
s2, coating the electret material dispersion liquid on a back-electrode plate;
s3, controlling the temperature of the container coated with the back plate of the electret material dispersion liquid to be 5-15 ℃ higher than the melting point temperature of the electret material, simultaneously increasing the pressure P2 in the container to be higher than the pressure P1 outside the container, and maintaining for 16-25 min at the temperature and the pressure;
s4, reducing the temperature to be lower than the melting point temperature of the electret material, and keeping the temperature and the pressure P2 for 10-30 min;
s5, rapidly releasing the pressure in the container, wherein the pressure P2 is equal to the pressure P1, rapidly generating pressure difference in the electret material at the moment, rapidly expanding the air in the electret material, and generating micropores in the electret material;
s6, keeping the temperature in the container lower than the melting point temperature of the electret material, and keeping for 20-25min to shape the micropores in the electret material;
and S7, cooling the product to obtain the porous piezoelectric electret.
In the porous electret in the prior art, many of the porous electrets are attached to a back plate after the electret film is independently formed into micropores in a stretching or foaming mode. In this case, the attached microporous electret film may block the hole of the back plate itself, resulting in poor charge storage stability of the electret in a high temperature environment. Therefore, secondary opening is often required for the electret film, which causes complexity in the process and brings uncertainty to the mass production and stability of the product. And the formed porous electret is attached to the back plate in a hot pressing mode, and the micropores formed on the film can be damaged in the high-temperature environment of hot pressing, so that the performance of the porous electret is reduced.
The invention creatively adopts the electret material dispersion liquid to form a coating on the back plate firstly, and micropore forming is carried out while the coating is formed into a film. When the coating is carried out, the electret material dispersion liquid can be distributed in the holes of the back plate, so that the electret film is attached to the hole wall in the film forming process, the holes in the back plate can not be blocked by the film, and secondary hole opening is not needed. The formed electret films are distributed on the surface and in the holes of the back electrode plate, so that the distribution area is larger, and the electricity storage performance is better.
According to the description of the prior art, when an electret film is formed by an electret material dispersion liquid, the temperature which is higher than the melting point of the material by more than 20 ℃ is required to be used during heating so that the material has certain fluidity to be combined into a film, otherwise, the film forming performance is poor, and the charge stability of the electret is influenced. However, at this temperature, there is a problem that the electret material may decompose, and also the electricity storage performance of the electret may be degraded.
In the invention, when the heating and the pressurization are carried out, the inventor finds that the high-temperature film forming temperature can be adjusted to be 5 ℃ higher than the melting point of the material, so that the excellent film forming effect is achieved, and therefore, the invention can realize the high-temperature film forming by adopting the bottom crossing temperature, and the material can not be decomposed at the temperature. Therefore, the electric storage performance of the electret is improved, and energy conservation is facilitated. This is another significant advantage of the present invention.
In the two pore forming methods disclosed in the prior art, it is generally considered that the stretching method can form pores in the longitudinal direction of the film and the high-pressure foaming method can expand the porous resin film in the thickness direction. By adopting the mode of the invention, micropores can be formed in the length direction and the thickness direction of the electret film at the same time, and the porosity is further increased. This is another significant advantage of the present invention.
In addition, the film forming process increases the pressure during film forming, and is favorable for improving the bonding fastness between the electret film and the back plate.
In one embodiment of the present invention, in step S3, the pressure P2 in the container is 1.5 to 3 times the pressure P1.
More preferably, the pressure P2 in the container is 2 times the pressure P1.
In one embodiment of the present invention, in step S5, the pressure in the container is released within 2S to 4S until P2 equals P1.
In one embodiment of the present invention, in step S3, the pressurization is performed by introducing a gas into the container, and the gas may be any gas that can be used, and is preferably air.
In one embodiment of the present invention, in step S3, the maintaining time is 18min to 20min, and more preferably 20min.
In one embodiment of the present invention, in step S4, the temperature in the container is maintained in the range of 5 ℃ to 30 ℃ below the melting point temperature.
In one embodiment of the present invention, in step S4, the maintaining time is 20-25min.
In one embodiment of the present invention, in step S6, the temperature in the container is maintained in the range of 10 ℃ to 40 ℃ below the melting point temperature.
In one embodiment of the present invention, in step S6, the maintaining time is 20-25min.
In one embodiment of the present invention, the electret material is perfluoroethylene propylene copolymer (FEP), polytetrafluoroethylene (PTFE), polypropylene (PP), or tetrafluoroethylene-perfluoroalkylvinylether copolymer (PFA). In one embodiment of the present invention, the coating method in S2 is not particularly limited, and various methods such as printing, spraying, painting, dipping, and the like may be used.
In an embodiment of the present invention, in step S7, the product is cooled naturally with the furnace temperature.
Through the implementation of the technical scheme, the invention has the following advantages:
1. the invention adopts the electret material dispersion liquid to form a coating on the back polar plate firstly, and when the coating is formed into a film, micropore forming is carried out, so that secondary hole opening is not needed, the process is simplified, and the formed electret film is distributed on the surface and in the holes of the back polar plate, so that the distribution area is larger, and the electricity storage performance is better.
2. The invention increases the pressure in the container while forming film at high temperature, can realize film formation at high temperature at lower temperature, avoids the decomposition of electret materials, ensures the electricity storage performance of electrets and improves the charge stability.
3. By adopting the mode of the invention, micropores can be formed in the length direction and the thickness direction of the electret film at the same time, thereby further increasing the porosity and improving the electricity storage capacity of the electret material.
Drawings
FIG. 1 is a schematic flow diagram of a method for preparing a porous piezoelectric electret according to the present invention;
FIG. 2 shows the charge stability test results of the electrets obtained in different examples and comparative examples of the present invention.
Detailed Description
The invention is explained in further detail below with reference to the figures and the specific embodiments.
It should be noted that the following embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art will understand that: the technical solutions described in the foregoing embodiments can be modified, or some technical features can be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.
The preparation method of the porous piezoelectric electret comprises the following steps:
s1, providing an electret material dispersion liquid.
The electret material may be perfluoroethylene propylene copolymer (FEP), polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkylvinylether copolymer (PFA), or polypropylene (PP), and a dispersion of these materials may be purchased as it is or may be dissolved in a solvent to prepare a corresponding dispersion.
And S2, coating the electret material dispersion liquid on a back plate, and drying.
The coating can be performed in various ways, such as printing, spraying, brushing, dipping, etc. The specific coating mode is not limited, and the coating ensures that the holes of the back plate are also coated during coating. The coating thickness is 20-40 microns. The drying method is not limited.
S3, controlling the temperature in the container of the back plate coated with the electret material dispersion liquid to be 5-15 ℃ higher than the melting point temperature of the electret material, simultaneously increasing the pressure P2 in the container to be higher than the pressure P1 outside the container, and maintaining for 16-25 min at the temperature and the pressure.
In the step, the control of temperature, pressure and time is particularly important, the parameter values are reasonably controlled, high-pressure gas permeates into the material before the electret film is not completely formed, then the high-temperature gas forms a film shape, the gas is wrapped in the film shape, and the gas breaks through during the subsequent pressure relief period, so that micropores are formed in the electret film. The electret film formed by the forming method has higher porosity and is beneficial to improving the thermal stability of charged charges.
The film forming temperature is lower than the temperature generally required, and the film forming temperature of the dispersion is generally required to be more than 20 ℃ higher than the melting point temperature of the electret material in the prior art so as to form an excellent film. In the scheme, the film can be efficiently formed at a temperature 15 ℃ higher than the melting point of the electret material, even at a temperature 5 ℃ higher than the melting point of the electret material, and the film has excellent performance.
The inventor finds out through experiments that different electret materials have different requirements on film forming temperature, but can form films with better effect under the condition that the melting point temperature of the corresponding electret material is 15 ℃. Aiming at different electret materials, the difference is that under the pressure that P2 is twice P1, FEP can be realized at the temperature 5 ℃ higher than the melting point of the electret material, and PTFE needs to be 12 ℃ higher than the melting point of the electret material at the lowest temperature to achieve the ideal film forming effect. Other materials require higher temperatures. The temperature in step S3 is too high, and although the film forming property is good, there is a risk of causing decomposition of the material, which affects the electricity storage property of the final electret. Too low a temperature results in poor film-forming properties, which also affect the charge storage properties of the electret.
The pressure P2 in the vessel has an influence not only on the formation of micropores in the film but also on the film-forming property in conjunction with the temperature, and determines the properties of the film, and the pressure P2 in the vessel is preferably twice the pressure P1 outside the vessel, and the pressure P1 outside the vessel is usually atmospheric pressure. At this temperature and pressure, for 16min to 25min, more preferably for 20min.
S4, reducing the temperature to be lower than the melting point temperature of the electret material, and keeping the temperature and the pressure P2 for 10-30 min.
In this step, an electret film has been formed, and this step is performed in order to stabilize the properties of the electret film after film formation. The temperature in the container is preferably kept 5 ℃ to 30 ℃ lower than the melting point of the electret material, at which temperature the film is still in a softened state, and at this time, the high pressure P2 is maintained, so that the film and the back plate are more attached to each other.
S5, rapidly releasing the pressure in the container, wherein the pressure P2 is equal to the pressure P1, rapidly generating pressure difference in the electret material at the moment, rapidly expanding the air in the electret material, and generating micropores in the electret material.
The release rate of the pressure is particularly important in this step, in which the pressure is released within 2 to 4 seconds, the gas is rapidly released, the pressure difference is rapidly generated in the electret material, the gas in the electret material is rapidly expanded, and micropores are generated in the electret material to form an electret film with micropores.
S6, keeping the temperature in the container lower than the melting point temperature of the electret material, and keeping for 20-25min to shape the micropores in the electret material.
In this step, the temperature may be the same as or different from that in step S4, and is preferably maintained at a lower temperature than that in step S4. On the one hand, in step S5, a part of the pressure is released to cause a temperature drop, and the temperature rise operation is not performed any more; on the other hand, the micropore shaping effect is better at a lower temperature. More preferably, the temperature in this step is in the range of 10 ℃ to 40 ℃ below the melting point.
S7, naturally cooling the product along with the furnace temperature to obtain the porous piezoelectric electret, then placing the porous piezoelectric electret into an electric field, grounding a back plate, and carrying out needle type corona discharge polarization. The charging mode can be various and is not limited.
The cooling mode in this step also has certain influence to the performance of electret product, cools off slowly along with the stove temperature, is favorable to guaranteeing the stability of micropore, takes out the cooling for cooling rate, the shrink can appear in the film, and the micropore of influence to a certain extent causes the deformation of micropore, thereby influences the electric storage performance of electret.
Example 1
The preparation method of the porous piezoelectric electret with reference to a flow chart shown in figure 1 comprises the following steps:
s1, diluting a commercial Fluorinated Ethylene Propylene (FEP) dispersion by using distilled water, wherein the ratio of the distilled water to the FEP is 1:2. The commercially available FEP dispersion is FR463 dispersion from seiko corporation;
s2, coating the FEP dispersion liquid on the back plate in a dipping mode to ensure that holes of the back plate are coated with the FEP dispersion liquid;
s3, in a pressure furnace with a heating function coated with a back plate of FEP dispersion liquid, the melting point temperature of FEP is 260 ℃, the temperature is controlled to be 270 ℃, meanwhile, the pressure P2 in the container is increased to be twice of the pressure P1 outside the container, and the pressure and the temperature are maintained for 20min;
s4, reducing the temperature to 250 ℃, and keeping the temperature and the pressure P2 for 20min;
s5, quickly releasing the pressure in the container within 2 seconds until P2 is equal to P1, quickly generating pressure difference in the electret material at the moment, quickly expanding the air in the electret material and generating micropores in the electret material;
s6, keeping the temperature in the container at 230 ℃ for 20min to shape the micropores in the electret material;
and S7, naturally cooling the product along with the furnace temperature to obtain the porous piezoelectric electret.
Example 2
The preparation method of the porous piezoelectric electret comprises the following steps:
s1, diluting a commercial polytetrafluoroethylene (TPFE) dispersion liquid by using distilled water, wherein the ratio of the distilled water to the TPFE is 1:2. The commercially available TPFE dispersion liquid is PTFE DISP 30 dispersion liquid produced by Kemu company;
s2, coating the TPFE dispersion liquid on the back plate in a dipping mode to ensure that holes of the back plate are also coated;
s3, in the pressure furnace with the heating function of the back plate coated with the TPFE dispersion liquid, the melting point temperature of TPFE is 337 ℃, the temperature is controlled to be 348 ℃, meanwhile, the pressure P2 in the container is increased to be 1.5 times of the atmospheric pressure P1 outside the container, and the pressure and the temperature are maintained for 25min;
s4, reducing the temperature to 330 ℃, and keeping the temperature and the pressure P2 for 25min;
s5, quickly releasing the pressure in the container within 3 seconds until P2 is equal to P1;
s6, keeping the temperature in the container at 305 ℃ for 20min to shape the micropores in the electret material;
and S7, naturally cooling the product along with the furnace temperature to obtain the porous piezoelectric electret.
Example 3
The preparation method of the porous piezoelectric electret comprises the following steps:
s1, diluting a commercially available Fluorinated Ethylene Propylene (FEP) dispersion by using distilled water, wherein the ratio of the distilled water to the FEP is 1:2. The commercially available FEP dispersion is FR463 dispersion from seiko corporation;
s2, coating the FEP dispersion liquid on the back plate in a brushing mode, and ensuring that holes of the back plate are also coated;
s3, in a pressure furnace with a heating function coated with a back plate of FEP dispersion liquid, the melting point temperature of FEP is 260 ℃, the temperature is controlled to be 275 ℃, meanwhile, the pressure P2 in the container is increased to be 3 times of the pressure P1 outside the container, and the pressure and the temperature are maintained for 20min;
s4, reducing the temperature to 230 ℃, and keeping the temperature and the pressure P2 for 30min;
s5, quickly releasing the pressure in the container within 4 seconds until P2 is equal to P1, quickly generating pressure difference in the electret material at the moment, quickly expanding the air in the electret material and generating micropores in the electret material;
s6, keeping the temperature in the container at 220 ℃ for 25min to shape the micropores in the electret material;
and S7, naturally cooling the product along with the furnace temperature to obtain the porous piezoelectric electret.
Comparative example 1
The preparation method of the porous piezoelectric electret comprises the following steps:
s1, diluting a commercial Fluorinated Ethylene Propylene (FEP) dispersion by using distilled water, wherein the ratio of the distilled water to the FEP is 1:2. The commercially available FEP dispersion is FR463 dispersion from seiko corporation;
s2, coating the FEP dispersion liquid on the back plate in a dipping mode to ensure that holes of the back plate are also coated;
s3, maintaining the melting point temperature of the FEP in the pressure furnace with the heating function coated with the back plate of the FEP dispersion liquid at 260 ℃ and 305 ℃ for 20min;
and S4, naturally cooling the product along with the furnace temperature to obtain the porous piezoelectric electret.
Comparative example 2
The difference from example 1 is that the film was formed at a high temperature and then expanded by increasing the pressure to form micropores. The method comprises the following specific steps:
s1, diluting a commercial Fluorinated Ethylene Propylene (FEP) dispersion by using distilled water, wherein the ratio of the distilled water to the FEP is 1:2. The commercially available FEP dispersion is FR463 dispersion from seiko corporation;
s2, coating the FEP dispersion liquid on the back plate in a dipping mode to ensure that holes of the back plate are also coated;
s3, in a pressure furnace with a heating function coated with the back plate of the FEP dispersion liquid, maintaining the melting point temperature of FEP at 260 ℃, controlling the temperature at 270 ℃ for 20min;
s4, increasing the pressure P2 in the container to be two times of the pressure P1 outside the container, and maintaining the pressure for 20min;
s5, reducing the temperature to 220 ℃, and keeping the temperature and the pressure P2 for 20min;
s6, rapidly releasing the pressure in the container, wherein the pressure P2 is equal to the pressure P1, rapidly generating pressure difference in the electret material at the moment, rapidly expanding the air in the electret material, and generating micropores in the electret material;
s7, keeping the temperature in the container at 200 ℃ for 20min to shape the micropores in the electret material;
s8, naturally cooling the product along with the temperature of the furnace, placing the product into a point field, grounding a back plate, carrying out needle type corona discharge polarization, and obtaining the porous piezoelectric electret at the ambient temperature of 100 ℃ for 5min.
Comparative example 3
The difference from embodiment 1 is that step S4 is not performed.
Comparative example 4
The difference from embodiment 1 is that step S6 is not performed.
Comparative example 5
The difference from example 1 is that the temperature in step S3 was adjusted to 290 ℃.
Comparative example 6
The difference from example 1 is that the temperature in step S3 was adjusted to 250 ℃.
Comparative example 7
The difference from example 1 is that the pressure adjustment P2 in step S3 is 3.5 times as large as P1.
The electrets manufactured according to the processes of the above embodiments and comparative examples of the present invention were charged by corona polarization of constant voltage grid-controlled medium voltage, and the parameters were as follows: high voltage-12000 v, medium voltage-800 v, grounding the back plate of the electret, temperature 150 deg.C, and time duration 10min. The surface charge meter is used for measuring the surface potential initial piezoelectricity of the electret, the composite electret is-440 v, and the electret-413 v is manufactured by the traditional process.
The electret sample was then aged in a high temperature oven at 150 ℃ for 10 hours, which would accelerate charge transfer. And surface potential detection is carried out at regular intervals in the middle. For comparison, the data were normalized, see fig. 2.
The charge stability of our examples 1-3 is higher than that of comparative examples 1-7, as analyzed in detail below:
comparative example 1 was an electret subjected to pressure treatment, and the electret film was not subjected to pressure treatment and had no micropores formed, at which time the electret had a weak ability to carry electric charges, and under high-temperature aging conditions, the amount of electric charges lost was large and the stability of electric charges was the worst.
The difference between comparative example 2 and example 1 is that the high temperature film formation and the formation of pores are separated, and the charge stability of the resulting electret is far inferior to that of example 1.
The difference between comparative example 3 and example 1 is that the charge stability of the electret obtained is far inferior to that of example 1 without performing the heat-keeping operation of step S4.
The comparative example 4 is different from example 1 in that the charge stability of the resulting electret is far inferior to that of example 1 without performing the micropore forming operation of step S6.
The difference between comparative example 5 and example 1 is that the temperature of step S3 is higher than the melting point of 30 ℃ for the existing high-temperature film-forming temperature of the dispersion, and the charge stability of the obtained electret is far inferior to that of example 1, and it is presumed that at this temperature, the electret material is decomposed, and the decomposition is accelerated in the high-pressure environment, which results in the performance reduction of the electret material.
The difference between comparative example 6 and example 1 is that the temperature in step S3 was adjusted to 250 ℃, and the dispersion was not completely filmed, and the charge stability of the resulting electret was far inferior to that of example 1.
The difference between comparative example 7 and example 1 is that the pressure adjustment P2 in step S3 is 3.5 times as high as P1. At this time, too high pressure, coupled with high temperature, causes the film to have reduced performance, and the charge stability of the resulting electret is far inferior to that of example 1.
In conclusion, the scheme of the invention carries out film forming and micropore forming on the basis of the electret material dispersion liquid, and integrates temperature, pressure and time through reasonable optimization of process steps to integrally realize excellent charge stability of the electret.
Claims (9)
1. A preparation method of a porous piezoelectric electret is characterized by comprising the following steps:
s1, providing an electret material dispersion liquid;
s2, coating the electret material dispersion liquid on a back-electrode plate;
s3, placing the back plate coated with the electret material dispersion liquid in a container, controlling the temperature to be 5-15 ℃ higher than the melting point temperature of the electret material, simultaneously raising the pressure P2 in the container to be 1.5-3 times of the pressure P1 outside the container, and maintaining for 16-25 min at the temperature and the pressure;
s4, reducing the temperature to be lower than the melting point temperature of the electret material, and keeping the temperature and the pressure P2 for 10-30 min;
s5, quickly releasing the pressure in the container, wherein P2 is equal to P1;
s6, keeping the temperature in the container lower than the melting point temperature of the electret material for 20-25 min;
and S7, cooling the product to obtain the porous piezoelectric electret.
2. The method of claim 1, wherein the pressure P2 in the container is 2 times the pressure P1.
3. The method for preparing a porous piezoelectric electret according to claim 1, wherein the holding time in step S3 is 18 to 20min.
4. The method of claim 1, wherein in step S4, the temperature in the container is maintained within a range of 5 ℃ to 30 ℃ below the melting temperature of the electret material.
5. The method for preparing a porous piezoelectric electret according to claim 4, wherein the holding time in step S4 is 20-25min.
6. The method of claim 1, wherein in step S6, the temperature in the container is maintained within a range of 10 ℃ to 40 ℃ below the melting point of the electret material.
7. The method for preparing a porous piezoelectric electret according to claim 6, wherein the holding time in step S6 is 20 to 25min.
8. The method for preparing a porous piezoelectric electret according to claim 1, wherein in step S5, the pressure in the container is released within 2S to 4S until P2 equals P1.
9. The method for preparing a porous piezoelectric electret according to claim 1, wherein in step S7, the product is cooled naturally with the temperature of the furnace.
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| CN1845353A (en) * | 2006-03-23 | 2006-10-11 | 同济大学 | Method for preparing porous polymer piezo-electric electret thin film |
| CN106165040A (en) * | 2014-04-04 | 2016-11-23 | 东洋纺株式会社 | Electret |
| CN112002800A (en) * | 2020-09-02 | 2020-11-27 | 哈尔滨工程大学 | Preparation method of composite piezoelectric electret material |
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| JP5705454B2 (en) * | 2009-04-27 | 2015-04-22 | 日東電工株式会社 | Electret material and electrostatic acoustic transducer |
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| JP2001246210A (en) * | 2000-03-07 | 2001-09-11 | Toyobo Co Ltd | Electret filter medium, electret filter and method for manufacturing electret filter medium |
| JP2004088754A (en) * | 2002-07-04 | 2004-03-18 | Toho Kasei Kk | Material for heat resistant electret, heat resistant electret using same, manufacturing method thereof, and electrostatic acoustic sensor |
| CN1845353A (en) * | 2006-03-23 | 2006-10-11 | 同济大学 | Method for preparing porous polymer piezo-electric electret thin film |
| CN106165040A (en) * | 2014-04-04 | 2016-11-23 | 东洋纺株式会社 | Electret |
| CN112002800A (en) * | 2020-09-02 | 2020-11-27 | 哈尔滨工程大学 | Preparation method of composite piezoelectric electret material |
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