CN110818925A - High-voltage-resistant polymer-based dielectric material and preparation method thereof - Google Patents
High-voltage-resistant polymer-based dielectric material and preparation method thereof Download PDFInfo
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Abstract
The invention provides a high-voltage-resistant polymer dielectric material and a preparation method thereof.
Description
Technical Field
The invention belongs to the technical field of flexible thin film capacitors, and particularly relates to a high-voltage-resistant polymer-based dielectric material and a preparation method thereof.
Background
With the development of electronic technology, there is an increasing demand for high dielectric constant polymers. However, the dielectric constant of the polymer itself is usually very low, usually between 3 and 6, and the requirement of technical development cannot be met.
Therefore, increasing the dielectric constant of polymer-based dielectric materials has become a very popular research area in recent years, and many reports have been made to the literature describing methods for increasing the dielectric constant of polymer-based dielectric materials. The simplest of these is to fill a high dielectric constant barium titanate into a polymeric bulk material. The method can improve the dielectric constant of the polymer-based dielectric material by 1-2 orders of magnitude. However, the disadvantages of this method are: on the one hand, when the filling amount of barium titanate is small, the dielectric constant of the polymer-based dielectric material is not obviously changed, and the dielectric constant of the polymer-based dielectric material is obviously changed only by filling enough barium titanate. On the other hand, as a large amount of barium titanate is filled, the voltage resistance of the compounded polymer-based dielectric material is greatly reduced compared with that of a pure polymer, so that the compound dielectric material can only be used in the field of low-voltage non-energy storage and cannot be applied to the field of high-voltage high-energy-storage-density components, and the popularization and application of the high-dielectric compound material are limited. Therefore, the method has important engineering significance for solving the pressure resistance problem of the polymer composite material.
The analysis of the voltage-resistant failure product shows that the main reason of low voltage resistance of the composite material is that after the barium titanate filler reaches the critical volume concentration, particles and particles are in mutual contact, a conductive path can be formed after voltage is loaded, and the temperature of a conductive position can be increased by accumulated heat after the conductive path is formed, so that thermal breakdown is generated, and the voltage resistance of the composite dielectric material is poor.
In view of the above, there is a need to provide a high voltage resistant polymer-based dielectric material, which can effectively isolate barium titanate in the composite dielectric material from the source, thereby avoiding the generation of conductive paths, and thus effectively improving the voltage resistance of the polymer-based dielectric material.
Disclosure of Invention
Aiming at the problems, the invention provides a preparation method of a high-voltage-resistant polymer-based dielectric material, which comprises the following steps: dissolving an organic polymer matrix in a first solvent to prepare an organic polymer solution; adding inorganic filler containing mica and barium titanate into a second solvent or a dispersant solution formed by mixing the dispersant and the second solvent, and uniformly stirring to prepare a powder pre-dispersion solution; uniformly mixing the organic polymer solution and the powder pre-dispersion solution to form a dielectric solution; and coating the dielectric solution on a substrate, and heating and curing to obtain the polymer-based dielectric material.
According to an embodiment of the present invention, after dissolving the organic polymer matrix in the first solvent, a filtration step is further included to remove insoluble organic polymer gum, preferably, the filtration is performed using a filter core of 0.5 to 5 μm.
According to one embodiment of the invention, the organic polymer matrix is selected from one or more of the following combinations: acrylic resin, polyvinyl alcohol, polyvinyl formal, cellulose and derivatives thereof, epoxy resin and polyamide resin. The first solvent and the second solvent are the same or different and are respectively selected from one or more of the following combinations: ethyl acetate, butyl acetate, absolute ethanol, butanol, propanol, dimethylacetamide, butanone, acetone, pentanone, toluene, and xylene.
According to one embodiment of the invention, the mass ratio of the organic polymer matrix to the inorganic filler is 0.1:1 to 0.4: 1; the mass ratio of mica to barium titanate in the inorganic filler is 0.05: 1-0.4: 1; preferably, the barium titanate is of spherical or spheroidal structure, particle size D500.1-1 μm, dielectric constant greater than or equal to 1000, mica with sheet structure and thickness-diameter ratio greater than or equal to 80, D50≤7μm。
According to one embodiment of the invention, the powder pre-dispersion solution is prepared by the following method: adding the second solvent and the dispersing agent into a high-speed disperser, stirring and uniformly mixing; adding mica and barium titanate, stirring, and uniformly mixing to obtain a powder pre-dispersion solution; preferably, the stirring speed is 100 to 1200rpm, such as 100 to 300rpm, 300 to 500rpm, 100 to 550rpm, 600 to 1200rpm, etc., the stirring time required for mixing the second solvent and the dispersant is 20 minutes to 2 hours, and the stirring time required for mixing after adding the mica and the barium titanate is 2 to 4 hours.
According to another embodiment of the invention, the powder pre-dispersion solution is prepared by the following method: preparing barium titanate/mica composite powder; stirring and uniformly mixing the second solvent and the dispersant to obtain a dispersant solution; and adding the barium titanate/mica composite powder into the dispersant solution, stirring and uniformly mixing to obtain a powder pre-dispersion solution.
According to a further embodiment of the invention, the powder pre-dispersion solution is prepared by the following method: preparing barium titanate/mica composite powder; and adding a second solvent into the barium titanate/mica composite powder, and stirring and uniformly mixing to obtain a powder pre-dispersion solution.
The barium titanate/mica composite powder is prepared by liquid phase deposition of TiCl4、BaCl2Reacting in a synthetic mica powder solution with the pH value of 1.8-2.0, and dehydrating and washing to obtain the mica powder.
According to one embodiment of the invention, the content of the powder in the powder pre-dispersion solution is 50-80 wt%, and the powder comprises mica, barium titanate and an optional dispersant.
According to one embodiment of the invention, the dielectric solution is prepared by: adding the organic polymer solution into the powder pre-dispersion solution, uniformly stirring, and performing dispersion treatment by using low-energy dispersion equipment to obtain the dielectric solution; preferably, the low energy dispersing apparatus is at least one of a low energy sand mill, a homogenizer, an emulsifier, and a homogenizer.
The invention also provides a high-pressure-resistant polymer-based dielectric material prepared by the preparation method, which comprises an organic polymer matrix and an inorganic filler uniformly dispersed in the organic polymer matrix, wherein the inorganic filler is mica and barium titanate or barium titanate/mica composite powder.
According to one embodiment of the invention, the dielectric constant of the high-voltage-resistant polymer-based dielectric material is 10-100, and the dielectric strength is more than or equal to 30 MV/m.
According to the invention, mica with excellent insulating property is firstly introduced into a barium titanate/organic polymer binary composite system to form a mica/barium titanate/organic polymer ternary composite system, flaky mica is inserted into a polymer matrix to isolate barium titanate powder, so that the barium titanate powder is uniformly dispersed in the organic polymer matrix, and a conductive path is prevented from being formed by utilizing the characteristic of good withstand voltage characteristic of mica, and thermal breakdown is prevented, so that the withstand voltage property of the product is effectively improved. After the mica is added into the material, the voltage resistance of the dielectric material with the same thickness can be improved by 2-10 times.
Secondly, in order to keep the dispersed mica to keep the flaky appearance, a low-energy blending dispersion process is introduced into the solution blending process, and the process is characterized in that the dispersion action force in the dispersion process is smaller than the crystal strength of the mica, so that the mica can only be peeled off by the dispersion action in the dispersion process and dispersed into the dielectric solution, and the flaky appearance of the mica is not damaged. For example, the low energy blending dispersion process uses a ball milling method. The ball milling mode is beneficial to keeping mica as a flaky shape, the fully dispersed mica can be spread in the dielectric solution, and the blocking effect of the mica is exerted to the maximum extent, so that the fully dispersed mixing of three materials of mica/barium titanate/organic polymer is ensured, the shapes of the mica and the barium titanate are not damaged in the mixing process, the consistency and the reliability of the high-pressure-resistant polymer-based dielectric material are obviously improved, and the pressure-resistant characteristic of the material is finally improved.
In addition, in the addition mode of mica and barium titanate, the barium titanate/mica composite powder is formed in advance by adopting another liquid phase deposition method besides the mode of pre-blending the mica and the barium titanate uniformly, so that barium titanate is deposited between mica sheets and on the surface of the mica sheets in the synthesis process, air bubbles in gaps among the mica sheets are removed, and the dielectric loss of the finally formed high-pressure-resistant polymer-based dielectric material is further improved.
Finally, on the premise of adopting a liquid phase deposition method to generate barium titanate/mica composite powder in advance, the invention can also achieve the aim without a dispersant.
The foregoing description is only an overview of the technical solutions of the present invention, and in order to make the technical means of the present invention more clearly understood, the present invention may be implemented in accordance with the content of the description, and in order to make the above and other objects, features, and advantages of the present invention more clearly understandable, the following specific preferred embodiments are described in detail.
Detailed Description
To further illustrate the technical means and effects of the present invention adopted to achieve the predetermined objects, the present invention will be described in detail with reference to the following embodiments. It is to be understood that the following examples are illustrative of the invention only and are not limiting thereof.
The method adopts a solution blending process, and mica and barium titanate are added into the organic polymer matrix, so that the dispersion of mica is fully ensured, the flaky appearance of mica is not damaged, and the improvement of the pressure resistance of the final product is facilitated.
Mica is a natural mineral, is inexpensive and readily available, and comprises alkali metal-containing aqueous aluminosilicate as the main component and Al as the main component2O3And SiO2In addition to a certain amount of crystalline water and certain impurity metal oxides, e.g. Fe2O3、TiO2And the like. Mica has good cleavage properties and can be cleaved or exfoliated along cleavage planes into very thin, very soft, and highly elastic flakes. Meanwhile, the dielectric property is good. The properties of mica depend mainly on the type and main chemical composition of the mica and are also influenced by the impurity oxides.
Mica is classified into muscovite, paragonite, phlogopite, and lepidolite according to the metal oxide contained in the mica. The mica has a dielectric constant of 6-7.3, muscovite of 7.3, and phlogopite of 5.5-6.5. Mica has a layered crystal structure, and often contains air bubbles caused by an interlayer air gap between layers, which has a large influence on dielectric loss, and particularly under low frequency, interlayer-type polarization occurs in mica sheets, so that the dielectric loss tangent is greatly increased.
The invention provides a preparation method of a high-pressure-resistant polymer-based dielectric material, which comprises the following steps: dissolving an organic polymer matrix in a first solvent to prepare an organic polymer solution; adding inorganic filler containing mica and barium titanate into a second solvent or a dispersant solution formed by mixing the dispersant and the second solvent, and uniformly stirring to prepare a powder pre-dispersion solution; uniformly mixing the organic polymer solution and the powder pre-dispersion solution to form a dielectric solution; and coating the dielectric solution on a substrate, and heating and curing to obtain the polymer-based dielectric material.
In one embodiment of the present application, the organic polymer solution is prepared by the following method: adding the first solvent into stirring equipment, adding an organic polymer matrix at a stirring speed of 800-2000 rpm, and continuously stirring and dissolving for 1-24 hours until the organic polymer matrix is completely dissolved to form a uniform and transparent organic polymer solution. The solid content of the obtained organic polymer solution is 20-40 wt%. Optionally, after complete dissolution, the organic polymer solution is filtered through a filter element with the diameter of 0.5-5 μm to remove insoluble organic polymer colloid, so as to obtain a purer organic polymer solution.
The organic polymer matrix is selected from one or more of the following combinations: acrylic resin, polyvinyl alcohol, polyvinyl formal, cellulose and derivatives thereof, epoxy resin and polyamide resin. The first solvent can dissolve the organic polymer matrix and is selected from at least one of esters, alcohols, amides, ketones and benzenes. In one embodiment, the first solvent is selected from one or more of the following combinations: ethyl acetate, butyl acetate, absolute ethanol, butanol, propanol, dimethylacetamide, butanone, acetone, pentanone, toluene, and xylene.
In one embodiment of the present application, the powder pre-dispersion solution is prepared by the following method: adding the second solvent and the dispersing agent into a high-speed disperser, stirring and uniformly mixing; adding mica and barium titanate, stirring, and mixing uniformly to obtain a powder pre-dispersion solution. In one embodiment, the stirring speed is 100-1200 rpm, such as 100-300 rpm, 300-500rpm, 100-550 rpm, 600-1200 rpm, 200-1000 rpm, etc., during the preparation of the powder pre-dispersion solution, the stirring time required for mixing the second solvent and the dispersant is 20 minutes-2 hours, and the stirring time required for mixing after adding the mica and the barium titanate is 2-4 hours. In one embodiment, the content of the powder in the powder pre-dispersion solution is 50-80 wt%, where the powder comprises a dispersant, mica and barium titanate. The addition amount of the dispersing agent is 1-3 wt% of the total mass of the barium titanate and the mica.
The second solvent may be the same as or different from the first solvent. The second solvent is selected from at least one of esters, alcohols, amides, ketones, and benzenes, and in one embodiment, the second solvent is selected from one or more of the following combinations: ethyl acetate, butyl acetate, absolute ethanol, butanol, propanol, dimethylacetamide, butanone, acetone, pentanone, toluene, and xylene.
The dispersant is selected from one or more of the following combinations: TX100 (octylphenyl polyoxyethylene ether), Span20 (Span-20, sorbitan monolaurate), Span60 (Span 60, sorbitan monostearate), Span80 (Span 80, sorbitan fatty acid ester), sorbitol, oleic acid, castor oil, polyacrylamides and polyacrylic acid.
In one embodiment, the mica and the barium titanate are both powders. The barium titanate is spherical in structure and has a particle size D500.1 to 1 μm. The mica is selected from one or more of natural muscovite, natural phlogopite, natural paragonite, natural lepidolite, synthetic muscovite, and synthetic phlogopite. Mica has a sheet structure with a thickness-diameter ratio of 80 or more and a particle size D50Less than or equal to 7 mu m. If the thickness ratio is too low, the pressure resistance of the mica sheet is not satisfactory. If the particle size is too small, the insulation effect of the mica sheet is not favorably exerted.
The addition of the mica enables the polymer-based dielectric material to form a polymer/barium titanate/mica ternary composite system, and the pressure resistance is greatly improved.
In the application, the mass ratio of mica to barium titanate is 0.05: 1-0.4: 1. If mica is added excessively, the viscosity of the subsequently formed dielectric solution is too high, and the subsequent dielectric solution cannot be spun into a uniform dielectric film; if mica is not added, the dielectric material has lower voltage resistance.
In another embodiment of the present application, the powder pre-dispersion solution is prepared by the following method: preparing barium titanate/mica composite powder; stirring and uniformly mixing the second solvent and the dispersant to obtain a dispersant solution; and adding the barium titanate/mica composite powder into the dispersant solution, stirring and uniformly mixing to obtain a powder pre-dispersion solution.
In yet another embodiment of the present application, the powder pre-dispersion solution is prepared by the following method: preparing barium titanate/mica composite powder; and adding the barium titanate/mica composite powder into a second solvent, stirring and uniformly mixing to obtain a powder pre-dispersion solution.
The barium titanate/mica composite powder is prepared by liquid phase deposition of TiCl4、BaCl2Reacting in a synthetic mica powder solution with the pH value of 1.8-2.0, and dehydrating and washing to obtain the mica powder. The specific reaction formula is as follows:
TiCl4+H2O＝TiOCl2+2HCl
TiOCl2+BaCl2+4NaOH＝BaTiO3+4NaCl+2H2O
BaTiO3+ mica powder- - → BaTiO3Mica (constant temperature, constant pH)
By adopting the liquid phase deposition method, the mica powder is uniformly dispersed in the solution in advance, and the nano-scale BaTiO3And the mica powder is uniformly deposited on the surfaces and the interlayer of the mica powder dispersed in the solution in the generation process, so that the mica powder and the barium titanate are uniformly dispersed. On one hand, the method controls the uniform mixing of the barium titanate and the mica powder, and the mica powder serves as a carrier of the barium titanate, so that the agglomeration phenomenon of the mica powder is prevented; on the other hand, the barium titanate generated by the liquid phase deposition method has small particle size, is uniformly deposited on the surface of the mica and between the sheet layers, can prevent the agglomeration phenomenon of the barium titanate, and prevents the contact between the barium titanate and the barium titanate, thereby preventing thermal breakdown. Generated byBaTiO3The/mica composite powder is pure, has no other impurities or heavy metals, does not influence the performance of barium titanate, and enhances the dispersibility and spreadability of the material, so that the powder is easy to disperse to obtain a powder pre-dispersion solution.
In one embodiment of the present application, the dielectric solution is prepared by: and adding the organic polymer solution into the powder pre-dispersion solution, uniformly stirring, and performing dispersion treatment by using low-energy dispersion equipment to obtain the dielectric solution.
The low-energy dispersing equipment is at least one of a low-energy sand mill, a homogenizer, an emulsifying machine and a homogenizer. The dispersing equipment has low capability of grinding and damaging the powder, only plays a role of dispersing the powder, enables the powder and the organic polymer matrix to be mixed at a micron level, and does not damage the shapes of mica and barium titanate. In one embodiment, the fineness of the dielectric solution after the dispersion treatment is 10 μm or less. In one embodiment, the low energy dispersion blending process has a rotation speed of 100 to 1200rpm, such as 100 to 300rpm, 300 to 500rpm, 100 to 550rpm, 600 to 1200rpm, 200 to 1000rpm, and the like.
In one embodiment of the present application, the temperature of the heating and curing step is 120 to 180 ℃ for 4 to 6 hours. The coating was performed by spin coating. Alternatively, the thickness of the coating is controlled so that the sample thickness of the polymer-based dielectric material produced is uniform at about 20 μm.
The invention provides a polymer-based dielectric material prepared by the method, which comprises an organic polymer matrix and an inorganic filler uniformly dispersed in the organic polymer matrix, wherein the mass ratio of the organic polymer matrix to the inorganic filler is 0.1: 1-0.4: 1, the inorganic filler comprises mica and barium titanate, and the mass ratio of the mica to the barium titanate is 0.05: 1-0.4: 1.
A sample of the prepared polymer-based dielectric material was subjected to a performance test: and testing the breakdown voltage by adopting a voltage-resistant tester to represent the voltage resistance of the dielectric material. The dielectric constant was measured using Agilent 4990A. A ZJD-B type dielectric constant dielectric loss tester produced by Beijing Zhide Innovative instruments and equipment Co., Ltd is adopted to test the dielectric loss tangent angle, and the test method refers to the test method of the dielectric constant and the dielectric loss tangent value of the No. 4 part of the GBT5594.4-2015 electronic component structure ceramic material performance test method.
The present invention will be described in detail by way of examples. It is also to be understood that the following examples are illustrative of the present invention and are not to be construed as limiting the scope of the invention, and that certain insubstantial modifications and adaptations of the invention by those skilled in the art may be made in light of the above teachings. The specific process parameters and the like of the following examples are also only one example of suitable ranges, i.e., those skilled in the art can select the appropriate ranges through the description herein, and are not limited to the specific values exemplified below.
The materials used in the examples are described below: the acrylic resin is provided by Zhengda paint Co., Ltd in Tongxiang city, and the mark is AP 2065; the epoxy resin is a mixture of medium petrochemical CYD-128 epoxy resin and curing agent diethylenetriamine; the muscovite flake is provided by Shenzhen Zhuoxin electronic materials Limited, with a thickness diameter of 80 or more and a particle size D506.5 μm; phlogopite tablets were supplied by baofeng mica processing ltd, lingshou county. Barium titanate supplied by Zhengzhou Konjac products Ltd, particle size D50＝0.16μm。
Example 1:
adding 25g of butanone into a magnetic stirrer, adding 10g of acrylic resin at the stirring speed of 50rpm, and continuously stirring and dissolving for 4 hours until the organic polymer acrylic resin forms a uniform and transparent solution. The resulting solution was then filtered using a 2 μm PP cotton filter element to remove insoluble organic polymer gums, yielding an organic polymer solution.
Butanone 30g and the dispersant castor oil 1g were added to a high-speed dispersion tank and stirred with a high-speed disperser at a stirring speed of 800rpm for 2 hours until a uniform and transparent solution containing the dispersant was formed. Then 5g of synthetic muscovite sheet and 64g of barium titanate are added under the high-speed stirring state at 1000rpm, and the stirring is continued for 2.5 hours to obtain a powder pre-dispersion solution. The mass ratio of mica to barium titanate is about 0.078: 1.
Adding the organic polymer solution into the powder pre-dispersion solution, uniformly stirring, and grinding by using a low-energy density sand mill, wherein the grinding frequency is 5 times, the rotating speed of the sand mill is 300rpm, and the grinding medium is 0.1 mm. The fineness of the obtained polymer-based dielectric solution is less than or equal to 10 mu m after grinding.
And coating the obtained polymer-based dielectric solution on a needed base material, and drying for 2 hours at 140 ℃ to obtain the high-pressure-resistant polymer-based dielectric material with the thickness of 20 mu m.
The dielectric constant of the high-voltage-resistant polymer-based dielectric material obtained in the example is 29.7, the dielectric loss tangent tg delta at 60Hz is 0.02, and the average voltage withstanding value of a 20-micron-thickness sample is 225.7V.
Example 2:
the high voltage resistant polymer-based dielectric material of this example 2 was prepared similarly to example 1, except that: the mass ratio of mica to barium titanate is 0.4: 1. the dielectric constant of the obtained high-voltage resistant polymer-based dielectric material is 25.5, and the dielectric loss tangent value t is at 60HzgDelta was 0.07, and the average withstand voltage value of the 20 μm thick sample was 410.3V.
Example 3:
the high voltage resistant polymer-based dielectric material of this example 3 was prepared similarly to example 1, except that: the mass ratio of mica to barium titanate is 0.2: 1. the dielectric constant of the obtained high-voltage resistant polymer-based dielectric material is 27.3, and the dielectric loss tangent value t is at 60HzgDelta was 0.05, and the average withstand voltage value of the 20 μm thick sample was 362.9V.
Example 4:
the high voltage resistant polymer-based dielectric material of this example 4 was prepared similarly to example 1, except that: an emulsifying machine was used as a dispersing apparatus instead of a sand mill to disperse mica and barium titanate in the polymer solution. The dispersing speed was 800rpm and the dispersing time was 6 h. The dielectric constant of the obtained high-voltage resistant polymer-based dielectric material is 31.5, the dielectric loss tangent value tg delta at 60Hz is 0.01, and the average voltage withstanding value of a sample with the thickness of 20 mu m is 328.6V.
Example 5:
the high voltage resistant polymer-based dielectric material of this example 5 was prepared similarly to example 1, except that: the organic polymer is selected as epoxy resin (mesopetrochemical CYD-128+ diethylenetriamine). The dielectric constant of the obtained high-voltage resistant polymer-based dielectric material is 32.6, the dielectric loss tangent tg delta at 60Hz is 0.03, and the average voltage withstanding value of a 20-micron-thickness sample is 276.3V.
Example 6:
the high voltage resistant polymer-based dielectric material of this example 6 was prepared similarly to example 1, except that: the barium titanate and mica of this example were BaTiO synthesized beforehand3The mica composite powder comprises the following components in percentage by weight:
80g of synthetic mica powder (1250 meshes) is added into 500ml of distilled water or deionized water, stirred for 0.5h under the ice-water bath at the rotating speed of 300-500rpm, and the pH value is adjusted to about 1.8-2.0 by using 1mol/L HCl solution, so that the state is stabilized, and uniform mica powder solution is formed.
100ml of 2mol/L TiCl4Solution, 100ml of 2mol/L BaCl2Dripping the solution and 10% NaOH solution into the mica powder solution simultaneously, and controlling pH to maintain 1.8-2.0 to facilitate TiCl4、BaCl2Reaction of the solution in synthetic mica powder.
Observing the surface color of the mica powder to be milk white until TiCl4、BaCl2Stopping adding the NaOH solution after the solution is dripped, stirring for half an hour at constant temperature and constant pH value, adding distilled water or deionized water for suction filtration, and drying for 24 hours to obtain BaTiO3/mica composite powder.
The dielectric constant of the high-voltage-resistant polymer-based dielectric material obtained in the embodiment is 35.7, and the dielectric loss tangent t is measured at 60HzgDelta was 0.003, and the average withstand voltage of the 20 μm thick sample was 512.4V.
Compared with the embodiment 1, the embodiment adopts the liquid phase deposition method, the synthesized mica powder is uniformly dispersed in the solution in advance, and the synthesized nano-scale BaTiO3Uniformly deposited on the surface and lamellar gaps of the synthetic mica powder dispersed in the solution in the generation process, thereby ensuring that the mica powder and the barium titanate are bothUniform dispersion is obtained, and barium titanate is prevented from contacting with barium titanate particles, thereby preventing thermal breakdown. The dielectric constant is obviously improved, the dielectric loss is small, and the voltage resistance performance is excellent. The reason for this is that the synthesized fine barium titanate particles have a small particle size and are deposited not only on the surface of the mica but also in the gaps of the mica sheets during the liquid phase deposition process, thereby eliminating air bubbles in the gaps of the mica sheets and reducing or even eliminating the influence of the air bubbles on the dielectric loss, and therefore, the dielectric loss tangent of this embodiment is significantly smaller than that of the other embodiments.
Example 7:
the process for preparing the high voltage resistant polymer-based dielectric material of example 7 is similar to that of example 6 except that: after the barium titanate/mica composite powder is prepared, a dispersant is not needed, 69g of the barium titanate/mica composite powder is directly added into 30g of butanone solvent under the high-speed stirring state of 1000rpm, the stirring is continued for 2.5 hours, and the uniform mixing is carried out, so as to obtain a powder pre-dispersion solution.
The dielectric constant of the high voltage polymer-based dielectric material obtained in this example was 30.1, the dielectric loss tangent tg δ at 60Hz was 0.005, and the average withstand voltage of the 20 μm thick sample was 437.6V.
Compared with example 6, the powder pre-dispersion solution of example 7 was prepared by directly adding the barium titanate/mica composite powder into the second solvent and stirring at high speed without using a dispersant. The test results still show higher dielectric constant, high voltage resistance, and lower dielectric loss. The reason for this is that the barium titanate/mica composite powder prepared by the liquid phase deposition method has a better dispersibility than barium titanate and mica powder alone, and therefore shows a better dispersibility even in the absence of a dispersant.
Comparative example 1:
the high voltage resistant polymer-based dielectric material of comparative example 1 was prepared similarly to example 1, except that: no mica was added. The dielectric constant of the obtained high-voltage-resistant polymer-based dielectric material is 33.8, the dielectric loss tangent tg delta at 60Hz is 0.12, and the average withstand voltage value of a sample with the thickness of 20 mu m is 97.6V.
Comparative example 2:
the procedure for the preparation of the high voltage resistant polymer-based dielectric material of this comparative example 2 is as in example 1, except that: the dispersing equipment adopts a traditional sand mill, the rotating speed of the sand mill is 2500rpm, and the size of a grinding medium is 0.6-0.8 mm. The dielectric constant of the obtained high-voltage resistant polymer-based dielectric material is 30.9, the dielectric loss tangent tg delta at 60Hz is 0.06, and the average withstand voltage value of a sample with the thickness of 20 mu m is 165.8V.
Compared with the embodiment 1, the traditional sander has the advantages that the rotating speed and the abrasive medium are far higher than those of the embodiment 1, and the lamellar structure of mica is partially broken by a high-energy blending mode, so that the dielectric loss is slightly higher than that of the embodiment 1.
Comparative example 3:
comparative example 3 is similar to example 1, except that: the procedure of example 1 was repeated except that mica was replaced with boron nitride. The boron nitride is hexagonal in structure, has a graphite-like layered structure, and is provided by Liaoning boron technologies, Inc. The dielectric constant of the high-voltage-resistant polymer-based dielectric material obtained in the comparative example was 26.9, the dielectric loss tangent tg delta at 60Hz was 0.11, and the average withstand voltage of a 20 μm thick sample was 184.6V.
Compared with the embodiment 1, the boron nitride has a sheet structure and high-voltage resistance, but the dielectric constant and the voltage withstanding value of the high-voltage resistant polymer-based dielectric material obtained in the comparative example 3 are obviously lower than those of the embodiment 1, and the dielectric loss is higher.
Comparative example 4:
comparative example 4 is similar to example 6, except that: boron nitride was used instead of mica. The dielectric constant of the high-voltage-resistant polymer-based dielectric material obtained in the comparative example was 29.8, the dielectric loss tangent tg delta at 60Hz was 0.059, and the average withstand voltage of a 20 μm thick sample was 384.6V.
The dielectric loss of this comparative example was higher than that of example 6. The reason for this may be that the boron nitride has no air bubbles in its own right and thus does not have a positive effect on dielectric loss due to elimination of air bubbles as in the mica of example 6.
In summary, the invention adopts a solution blending process to introduce the mica sheet into a binary system of polymer/barium titanate to form a ternary composite system of polymer/mica/barium titanate, so that the mica sheet separates the barium titanate, the barium titanate in the composite material is effectively isolated from the source, and a conductive path in the composite material is prevented from being generated, thereby avoiding thermal breakdown and effectively improving the pressure resistance of the material. In addition, mica is a natural mineral, is low in price and easy to obtain, and is beneficial to large-scale mass production application. Therefore, the method is economical and easy to implement, has obvious effect, and the pressure resistance of the product is more than 2 times higher than that of an unmodified product.
Secondly, in order to keep the dispersed mica to be in a flaky shape, a low-energy blending process is introduced into the solution blending process, so that the sufficient dispersion and mixing of the mica/barium titanate/polymer materials are ensured, the shape of the mica and the barium titanate is not damaged in the mixing process, and the consistency and the reliability of the high-pressure-resistant polymer-based dielectric material are obviously improved.
In addition, according to the addition mode of the mica and the barium titanate, the mica and the barium titanate are pre-blended uniformly, and another liquid phase deposition method is adopted to pre-form the barium titanate/mica composite powder, so that the barium titanate is deposited between mica sheets and on the surface of the mica sheets in the synthesis process, air bubbles in gaps among the mica sheets are removed, and the dielectric loss of the finally formed high-pressure-resistant polymer-based dielectric material is further improved.
Finally, on the premise of adopting a liquid phase deposition method to generate barium titanate/mica composite powder in advance, the invention can also achieve the aim without a dispersant.
Although the present invention has been described with reference to a preferred embodiment, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims.
Claims (10)
1. A preparation method of a high-voltage-resistant polymer-based dielectric material is characterized by comprising the following steps:
dissolving an organic polymer matrix in a first solvent to prepare an organic polymer solution;
adding inorganic filler containing mica and barium titanate into a second solvent or a dispersant solution formed by mixing the dispersant and the second solvent, and uniformly stirring to prepare a powder pre-dispersion solution;
uniformly mixing the organic polymer solution and the powder pre-dispersion solution to form a dielectric solution; and coating the dielectric solution on a substrate, and heating and curing to obtain the polymer-based dielectric material.
2. The method of claim 1, further comprising a filtration step of removing insoluble organic polymer colloid after dissolving the organic polymer matrix in the first solvent, preferably, the filtration step is performed using a filter cartridge of 0.5 to 5 μm.
3. The method of claim 1, wherein the organic polymer matrix is selected from one or more of the following combinations: acrylic resin, polyvinyl alcohol, polyvinyl formal, cellulose and derivatives thereof, epoxy resin and polyamide resin; and/or
The first solvent and the second solvent are the same or different and are respectively selected from one or more of the following combinations: ethyl acetate, butyl acetate, absolute ethanol, butanol, propanol, dimethylacetamide, butanone, acetone, pentanone, toluene, and xylene.
4. The method according to claim 1, wherein the mass ratio of the organic polymer matrix to the inorganic filler is 0.1:1 to 0.4: 1; and/or the mass ratio of mica to barium titanate in the inorganic filler is 0.05: 1-0.4: 1;
preferably, the barium titanate is of spherical or spheroidal structure, particle size D500.1-1 μm, dielectric constant greater than or equal to 1000, mica with sheet structure and thickness-diameter ratio greater than or equal to 80, D50≤7μm。
5. The method of claim 1, wherein the powder pre-dispersion solution is prepared by the following method: adding the second solvent and the dispersing agent into a high-speed disperser, stirring and uniformly mixing; adding mica and barium titanate, stirring, and uniformly mixing to obtain a powder pre-dispersion solution;
preferably, the stirring speed is 100-1200 rpm, the stirring time required for mixing the second solvent and the dispersant is 20 minutes-2 hours, and the stirring time required for mixing after adding the mica and the barium titanate is 2-4 hours; the addition amount of the dispersing agent is 1-3 wt% of the total mass of the barium titanate and the mica.
6. The method of claim 1, wherein the powder pre-dispersion solution is prepared by the following method: preparing barium titanate/mica composite powder; stirring and uniformly mixing the second solvent and the dispersant to obtain a dispersant solution; and adding the barium titanate/mica composite powder into the dispersant solution, stirring and uniformly mixing to obtain a powder pre-dispersion solution.
7. The method of claim 1, wherein the powder pre-dispersion solution is prepared by the following method: preparing barium titanate/mica composite powder; adding a second solvent into the barium titanate/mica composite powder, stirring and uniformly mixing to obtain a powder pre-dispersion solution; preferably, the content of the powder in the powder pre-dispersion solution is 50-80 wt%, and the powder comprises mica, barium titanate and an optional dispersing agent.
8. The method of claim 6 or 7, wherein the barium titanate/mica composite powder is prepared by liquid phase deposition of TiCl4、BaCl2Reacting in a synthetic mica powder solution with the pH value of 1.8-2.0, and dehydrating and washing to obtain the mica powder.
9. The method of claim 1, wherein the dielectric solution is prepared by: adding the organic polymer solution into the powder pre-dispersion solution, uniformly stirring, and performing dispersion treatment by using low-energy dispersion equipment to obtain the dielectric solution; preferably, the low energy dispersing apparatus is at least one of a low energy sand mill, a homogenizer, an emulsifier, and a homogenizer.
10. A high voltage resistant polymer-based dielectric material prepared according to any one of claims 1 to 9, wherein the high voltage resistant polymer-based dielectric material comprises an organic polymer matrix and an inorganic filler uniformly dispersed in the organic polymer matrix, wherein the inorganic filler is mica and barium titanate, or barium titanate/mica composite powder; preferably, the dielectric constant of the high-voltage-resistant polymer-based dielectric material is 10-100, and the dielectric strength is more than or equal to 30 MV/m.
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