CN113930057A - Polylactic acid dielectric film and application thereof, and method for preparing polylactic acid dielectric film and application thereof - Google Patents
Polylactic acid dielectric film and application thereof, and method for preparing polylactic acid dielectric film and application thereof Download PDFInfo
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- 229920000747 poly(lactic acid) Polymers 0.000 title claims abstract description 137
- 239000004626 polylactic acid Substances 0.000 title claims abstract description 137
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- 229940022769 d- lactic acid Drugs 0.000 claims description 12
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- 238000000137 annealing Methods 0.000 claims description 8
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J5/00—Manufacture of articles or shaped materials containing macromolecular substances
- C08J5/18—Manufacture of films or sheets
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES OR LIGHT-SENSITIVE DEVICES, OF THE ELECTROLYTIC TYPE
- H01G4/00—Fixed capacitors; Processes of their manufacture
- H01G4/33—Thin- or thick-film capacitors
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J2367/00—Characterised by the use of polyesters obtained by reactions forming a carboxylic ester link in the main chain; Derivatives of such polymers
- C08J2367/04—Polyesters derived from hydroxy carboxylic acids, e.g. lactones
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J2467/00—Characterised by the use of polyesters obtained by reactions forming a carboxylic ester link in the main chain; Derivatives of such polymers
- C08J2467/04—Polyesters derived from hydroxy carboxylic acids, e.g. lactones
Abstract
The invention relates to the field of film capacitor energy storage, in particular to a polylactic acid dielectric film and application thereof, and a method for preparing the polylactic acid dielectric film and application thereof. The polylactic acid dielectric film has the peak intensity of (110) crystal plane of 15000-30000 and the peak intensity of (203) crystal plane of not more than 1000 measured by XRD. The polylactic acid dielectric film provided by the invention has the characteristics of biodegradability, high energy density, high charge-discharge efficiency and good thermal stability, and can show excellent energy storage performance at normal temperature and still maintain the performance stability at high temperature.
Description
Technical Field
The invention relates to the field of film capacitor energy storage, in particular to a polylactic acid dielectric film and application thereof, and a method for preparing the polylactic acid dielectric film and application thereof.
Background
With the development of economic society, the energy problem is more and more prominent, and the demand is more and more severe. Capacitors play an important role in power systems, electronics, and control systems. The dielectric capacitor has the advantages of high energy density, high charge-discharge efficiency, fast response, long service life, low cost and the like. Typically, the energy density (U) of the dielectric materiale) Can be described as:Ue＝1/2ε0εrE2in which epsilon0The dielectric constant is 8.85X 10-12F/m)，εrE is the relative permittivity of the dielectric material and E is the breakdown field strength. Therefore, the energy density of the dielectric material can be increased by increasing the dielectric constant and the electrical breakdown strength. High charge-discharge efficiency is the key of energy storage application, and low discharge efficiency means that more electric energy is consumed by the orientation of molecular chains in the material, considerable heat can be generated in the working process to damage a capacitor, and the charge-discharge efficiency can be improved by reducing the residual polarization strength. Furthermore, thermal stability is of crucial importance for the application of dielectric capacitors, especially in the field of electric vehicles and power electronics. In some cases, the ambient temperature may be close to 100 ℃. The device can stably operate at high temperature, and the application field of the device can be greatly improved.
At present, polypropylene (BOPP) and polyester materials are the main dielectric films that have been successfully developed and applied. But the energy density and the charge-discharge efficiency are low, and the thermal stability is poor. A novel ferroelectric polymer represented by polyvinylidene fluoride (PVDF) has a large dielectric loss, resulting in low charge/discharge efficiency, and a thermosetting material represented by Polyimide (PI) has a low energy density although it has good high temperature resistance. And the materials are difficult to degrade in natural environment, and the used and scrapped device materials need subsequent treatment, otherwise, the environmental pollution is easily caused. Therefore, an environment-friendly biodegradable material with high energy density, high charge-discharge efficiency and good thermal stability is needed to replace the above polymer.
The polylactic acid is an environment-friendly material and has the performances of no toxicity, excellent biocompatibility, biodegradability and the like. The starting material for polylactic acid is fermented from renewable plant starch and is divided into two enantiomers, polylactic acid and polylactic acid, due to their different optical properties. The complete degradation products of the polylactic acid material are carbon dioxide and water. Therefore, the polylactic acid material is recyclable material from production to consumption, and is environment-friendly and pollution-free. Polylactic acid is widely used in biomedicine, packaging, tableware making and other fields due to its good biocompatibility and excellent biodegradability, but the application of polylactic acid in the capacitor energy storage field has not been reported yet.
Disclosure of Invention
The invention aims to solve the problems that in the prior art, a dielectric film has low energy density and charge-discharge efficiency, poor thermal stability, low energy density, is difficult to degrade in natural environment and is easy to cause environmental pollution, and the like.
In order to achieve the above object, a first aspect of the present invention provides a polylactic acid dielectric film characterized in that the polylactic acid dielectric film has a peak intensity of a (110) plane of 15000-30000 and a peak intensity of a (203) plane of not more than 1000 as measured by XRD.
The second aspect of the present invention provides a method for preparing the above polylactic acid dielectric thin film, comprising the steps of:
s1, preparing a film from polylactic acid to obtain an initial film material;
s2, stretching the initial film material at a high temperature to obtain the polylactic acid dielectric film;
the high temperature is 70-100 ℃, and the stretching magnification is 3-6 times.
The third aspect of the present invention can provide an application of the above polylactic acid dielectric film and/or the above method for preparing a polylactic acid dielectric film in capacitor energy storage.
By the technical scheme, the polylactic acid dielectric film material and the application thereof, and the preparation method and the application of the polylactic acid dielectric film material have the following beneficial effects:
the polylactic acid dielectric film provided by the invention has the advantages of high energy density, high charge and discharge efficiency, good thermal stability, good biocompatibility and excellent biodegradability, and is more environment-friendly compared with the existing material.
Furthermore, the polylactic acid dielectric film provided by the invention has the advantages of simple production process, simple equipment requirement, short production period, low cost and easily-regulated process conditions, and is suitable for large-scale industrial popularization.
Furthermore, the polylactic acid dielectric film provided by the invention has the characteristics of light weight, flexibility, easiness in processing, small acoustic impedance and the like, and has wide application in the fields of microelectronic devices, mobile equipment, wearable equipment and capacitor energy storage.
Drawings
FIG. 1 is a schematic view of a stretching apparatus for a polylactic acid dielectric film;
FIG. 2 is a photograph of polylactic acid dielectric films having pores according to comparative examples 3 and 6;
FIG. 3 is a schematic view of charging and discharging of the dielectric film of polylactic acid prepared in example 1;
FIG. 4 shows the dielectric breakdown property and the energy density charge-discharge efficiency at normal temperature of the dielectric film of polylactic acid prepared in example 1;
FIG. 5 shows dielectric breakdown properties and energy density charge and discharge efficiencies at high temperatures for the polylactic acid dielectric film prepared in example 5;
FIG. 6 shows dielectric breakdown properties and energy density charge and discharge efficiencies at high temperatures for the polylactic acid dielectric film prepared in example 6;
fig. 7 shows dielectric breakdown properties and energy density charge and discharge efficiencies at high temperatures for the polylactic acid dielectric thin film prepared in example 1.
Description of the reference numerals
(1) The first displacement table (2) is controlled by a controller (3) to heat the wire
(4) A second displacement table of a heating power supply (5)
Detailed Description
The endpoints of the ranges and any values disclosed herein are not limited to the precise range or value, and such ranges or values should be understood to encompass values close to those ranges or values. For ranges of values, between the endpoints of each of the ranges and the individual points, and between the individual points may be combined with each other to give one or more new ranges of values, and these ranges of values should be considered as specifically disclosed herein.
In order to achieve the above object, a first aspect of the present invention provides a polylactic acid dielectric film characterized in that the polylactic acid dielectric film has a peak intensity of a (110) plane of 15000-30000 and a peak intensity of a (203) plane of not more than 1000 as measured by XRD.
According to the invention, the peak intensity of the (110) crystal plane of the polylactic acid dielectric film is 15000-30000 and the peak intensity of the (203) crystal plane is not more than 1000, which are measured by XRD, so that the prepared polylactic acid dielectric film has high dielectric breakdown performance, and the energy density and the charge-discharge efficiency of the polylactic acid dielectric film are obviously improved.
According to the invention, the peak intensity of the (110) crystal plane of the polylactic acid dielectric film is 18000-25000 and the peak intensity of the (203) crystal plane is not more than 500 measured by XRD.
In the invention, the 2 theta of the polylactic acid dielectric film obtained by XRD is 14-17 degrees, and the molecules of polylactic acid in the polylactic acid dielectric film have good crystallinity at 14-17 degrees.
Further, the dielectric film of polylactic acid has a XRD measured 2 θ of 15 to 17 °, more preferably 16.5 °.
When the 2 theta is 16.5 degrees, the index of the crystal plane corresponding to the crystal form is (110), and when the 2 theta is 18.9 degrees, the index of the crystal plane corresponding to the crystal form is (203).
According to the invention, the breakdown field of the polylactic acid dielectric film at normal temperature is 500-750 MV/m.
According to the invention, the energy density of the polylactic acid dielectric film at normal temperature is 7-20J/cm3And the charging and discharging efficiency reaches more than 80%.
According to the invention, after the polylactic acid dielectric film is subjected to heat preservation at 120 ℃ for 15min, the energy density is 7-12J/cm3And the charge-discharge efficiency reaches 60-90%. The polylactic acid dielectric film has good high-temperature energy storage performance.
The second aspect of the present invention provides a method for preparing the above polylactic acid dielectric thin film, comprising the steps of:
s1, preparing a film from polylactic acid to obtain an initial film material;
s2, stretching the initial film material at a high temperature to obtain the polylactic acid dielectric film;
the high temperature is 70-100 ℃, and the stretching magnification is 3-6 times.
According to the invention, the initial film is subjected to high-temperature stretching treatment, so that the peak intensity of a (110) crystal plane of the polylactic acid dielectric film measured by XRD is 15000-30000, and the peak intensity of a (203) crystal plane is not more than 1000.
Further, in step S2, the high temperature is 80-90 ℃, and the stretching magnification is 3-4 times.
According to the present invention, the polylactic acid of the polylactic acid dielectric thin film is selected from poly-l-lactic acid and/or poly-d-lactic acid.
Further, the viscosity average molecular weight of the polylactic acid in the polylactic acid dielectric film is 20-40 ten thousand.
In the invention, when the viscosity average molecular weight of the polylactic acid is 20-40 ten thousand, the polylactic acid dielectric film has the characteristics of high energy density, high charge and discharge efficiency, good thermal stability, flexibility, easy processing and environmental protection.
Further, the viscosity average molecular weight of the polylactic acid in the polylactic acid dielectric film is 26 to 28 ten thousand.
Further, when the polylactic acid of the polylactic acid dielectric film is a mixture of polylactic acid and polylactic acid, the dosage ratio of the polylactic acid and the polylactic acid is (0.1-1): 1.
Further, the polylactic acid dielectric film is polylactic acid selected from poly-D-lactic acid.
According to the present invention, in step S1, the process of film formation is at least one selected from the group consisting of a solution casting method, a casting method, and a melt extrusion method.
The preparation method has the advantages of simple process, simple equipment requirement, short production period, low cost and the like.
According to the invention, the stretching is a unidirectional asynchronous stretching or a bidirectional synchronous stretching.
Further, the rate of stretching is 0.01-0.04 mm/s.
In the invention, when the stretching speed is within the range of 0.01-0.04mm/s, the polylactic acid dielectric film has the advantages of smooth surface, uniform reduction of thickness, difficult fracture, high energy storage at normal temperature and stability of performance still maintained at high temperature.
In the present invention, when the stretching is a uniaxial asynchronous stretching, the stretching rate is a difference between the stretching rate of the first displacement stage and the stretching rate of the second displacement stage. The bidirectional synchronous stretching refers to the sum of the stretching speed of the first displacement table and the stretching speed of the second displacement table.
According to the present invention, in step S1, the initial film material is prepared according to the following steps:
(1) mixing polylactic acid with a solvent to obtain a mixed solution;
(2) and placing the mixed solution on a mold, volatilizing the solvent, and drying to obtain the initial film material.
Further, the polylactic acid is used after vacuum drying.
According to the present invention, in the step (1), the solvent is at least one selected from the group consisting of dichloromethane, chloroform, acetone and dimethylformamide.
In the invention, the solvent is selected from at least one of dichloromethane, trichloromethane, acetone and dimethylformamide, so that the mixed solution is mixed more uniformly, and the prepared initial film material has the characteristics of colorlessness, uniformity and transparency.
Further, in the step (2), the solvent volatilization conditions comprise: the temperature is 20-65 ℃ and the time is 12-24 hours.
According to the invention, the method further comprises:
and S3, annealing the polylactic acid dielectric film obtained in the step S2.
According to the invention, the conditions of the annealing treatment include: annealing at 110-150 deg.C for 2-8 h; then cooling to room temperature along with the furnace.
In the invention, the polylactic acid dielectric film is annealed at the constant temperature of 110-150 ℃ for 2-8h, so that the polylactic acid dielectric film can be kept to have high breakdown strength.
According to a specific embodiment of the invention, the polylactic acid after vacuum drying is dissolved in a solvent, and is stirred until the polylactic acid solid particles are completely dissolved, so as to obtain a mixed solution;
and casting the mixed solution on a clean flat plate mold, and slowly volatilizing the solvent at the temperature of 20-65 ℃ for 12-24h for drying to obtain an initial film material.
As shown in fig. 1, both ends of the initial film material are respectively fixed on a first displacement stage 1 and a second displacement stage 5, the temperature of a heating wire 3 is adjusted to 70-100 ℃ by a heating power source 4, the first displacement stage 1 and the second displacement stage 5 are controlled to move in the same direction by a controller 2 to stretch the initial film material, and the moving rates of the first displacement stage 1 and the second displacement stage 5 are controlled so that the stretching rate of the first displacement stage 1 is 0.01-0.02mm/s, the stretching rate of the second displacement stage 5 is 0.02-0.04mm/s, and the initial film material is stretched to 2-6 times. Annealing the stretched film in a forced air drying box at the constant temperature of 110-150 ℃ for 2-8h, and then cooling the film to room temperature along with a furnace to obtain the polylactic acid dielectric film material.
The third aspect of the invention provides a method for preparing the polylactic acid dielectric film and/or application of the polylactic acid dielectric film in capacitor energy storage.
The present invention will be described in detail below by way of examples. In the following examples, various raw materials used are commercially available without specific description.
The breakdown field of the polylactic acid dielectric film is measured by a ferroelectric tester;
the crystal form change of the polylactic acid dielectric film before and after stretching is characterized by an X-ray diffraction pattern (XRD);
the enthalpy change before and after the stretching of the polylactic acid dielectric film is characterized by Differential Scanning Calorimetry (DSC);
poly-D-lactic acid with viscosity average molecular weight of 26 ten thousand;
the viscosity average molecular weight of the poly-L-lactic acid is 26 ten thousand.
Example 1
Weighing 0.1g of poly-D-lactic acid powder, adding the poly-D-lactic acid powder into 20mL of dichloromethane solvent, stirring until poly-D-lactic acid solid particles are completely dissolved, casting the stirred solution on a clean flat plate mold, and slowly volatilizing and drying the solvent for 20 hours at 25 ℃ to obtain an initial film material.
The two ends of the completely dried initial film material are respectively fixed on a first displacement table and a second displacement table, the temperature of a heating wire is adjusted to be 90 ℃ by utilizing a heating power supply, the first displacement table and the second displacement table are controlled to move along the same direction through a controller so as to stretch the initial film material, the moving speed of the first displacement table and the moving speed of the second displacement table are controlled, the moving speed of the first displacement table 1 is 0.01mm/s, the moving speed of the second displacement table is 0.04mm/s, and the initial film material is stretched to 4 times. And annealing the stretched film in a forced air drying oven at the constant temperature of 130 ℃ for 2h, and then cooling along with the oven to obtain the polylactic acid dielectric film. The breakdown field of the polylactic acid dielectric film was 725MV/m, and the XRD measured peak intensity of the (110) crystal plane was 25296, and the XRD measured peak intensity of the (203) crystal plane was 277.
Example 2
In accordance with example 1, except that the moving rate of the first stage (1) was adjusted to 0.02mm/s and the moving rate of the second stage (5) was adjusted to 0.08mm/s by the simultaneous biaxial stretching. Thus, a polylactic acid dielectric film was obtained. The breakdown field of the polylactic acid dielectric film was 720MV/m, and the XRD peak intensity of the (110) plane was 21322, and the XRD peak intensity of the (203) plane was 208.
Example 3
Consistent with example 1, except that the initial film was stretched 3-fold. Thus, a polylactic acid dielectric film was obtained. The breakdown field of the polylactic acid dielectric film was 680MV/m, and the XRD measured peak intensity of the (110) crystal plane was 18901, and the XRD measured peak intensity of the (203) crystal plane was 438.
Example 4
Consistent with example 1, except that the stretching temperature was 80 ℃. Thus, a polylactic acid dielectric film was obtained. The breakdown field of the polylactic acid dielectric film was 710MV/m, and the XRD measured peak intensity of the (110) crystal plane was 25296, and the XRD measured peak intensity of the (203) crystal plane was 389.
Example 5
Consistent with example 1, except that poly-d-lactic acid was replaced with poly-l-lactic acid. Thus, a polylactic acid dielectric film was obtained. The breakdown field of the polylactic acid dielectric film was 560MV/m, and the XRD measured peak intensity of the (110) crystal plane was 25096, and the XRD measured peak intensity of the (203) crystal plane was 370.
Example 6
Consistent with example 1, except that the poly-d-lactic acid was replaced with a blend of poly-l-lactic acid and poly-d-lactic acid, wherein the mass ratio of poly-l-lactic acid to poly-d-lactic acid was 1: 1. obtaining the dielectric film of the blended polylactic acid. The breakdown field of the polylactic acid dielectric film is 550MV/m, the peak intensity of a (110) crystal plane measured by XRD is 23200, and the peak intensity of a (203) crystal plane is 450.
Comparative example 1
Consistent with example 1, except that the initial film was not subjected to a stretching treatment. The polylactic acid dielectric film is obtained, XRD shows that the film has two crystal forms, the breakdown field is 450MV/m, and the peak intensity of the (110) crystal face measured by XRD is 9632, and the peak intensity of the (203) crystal face is 1109.
Comparative example 2
Consistent with example 1, except that the initial film was subjected to a stretching treatment at 50 ℃. Thus, a polylactic acid dielectric film was obtained. The breakdown field of the polylactic acid dielectric film was 200MV/m, and the XRD measured peak intensity of the (110) crystal plane was 12183 and the XRD measured peak intensity of the (203) crystal plane was 1021.
Comparative example 3
In accordance with example 1, except that the stretching temperature was 120 ℃, a polylactic acid dielectric film was obtained. The polylactic acid dielectric film generates more holes, and the peak intensity of the (110) crystal plane measured by XRD is 12093, and the peak intensity of the (203) crystal plane measured by XRD is 3011.
Comparative example 4
Consistent with example 1, except that the initial film was stretched 2-fold. Thus, a polylactic acid dielectric film was obtained. XRD of the polylactic acid dielectric film shows that the film has two crystal forms, the breakdown field is 470MV/m, the peak intensity of a (110) crystal face measured by XRD is 12351, and the peak intensity of a (203) crystal face is 2303.
Comparative example 5
Consistent with example 1, except that the initial film was stretched 7 times. Thus, a polylactic acid dielectric film was obtained. The breakdown field of the polylactic acid dielectric film was 220MV/m, and the XRD measured peak intensity of the (110) crystal plane was 12019, and the XRD measured peak intensity of the (203) crystal plane was 779.
Comparative example 6
Consistent with example 1, except that the initial film was stretched 8-fold. Thus, a polylactic acid dielectric film was obtained. The polylactic acid dielectric film generates more holes, and the peak intensity of the (110) crystal plane measured by XRD is 10020, and the peak intensity of the (203) crystal plane is 621.
Test example
The polylactic acid dielectric films of examples 1 to 6 and comparative examples 1 to 6 were sputtered on both upper and lower surfaces by magnetron sputtering with a gold electrode having a thickness of 100nm and a diameter of 3mm in a circular shape, and used for measuring the breakdown field strength at normal temperature.
As shown in FIG. 3, the energy density U of the polylactic acid dielectric film can be calculated by integrating the polarization curveeExpressed as breakdown field E and electrical displacement D:
as shown in fig. 3, the charge and discharge curves generally do not overlap, resulting in problems of energy loss and charge and discharge efficiency. The charge-discharge efficiency η is defined as a ratio of discharge energy to charge energy:
the results are shown in Table 1.
TABLE 1
| Energy density (J/cm)3) | Charge and discharge efficiency (%) | |
| Example 1 | 17.5 | 95 |
| Example 2 | 16.9 | 95 |
| Example 3 | 15.2 | 96 |
| Example 4 | 16.1 | 95 |
| Example 5 | 12.4 | 92 |
| Example 6 | 8.7 | 90 |
| Comparative example 1 | 6.7 | 76 |
| Comparative example 2 | 3.5 | 57 |
| Comparative example 3 | - | - |
| Comparative example 4 | 6.5 | 70 |
| Comparative example 5 | 3.2 | 55 |
| Comparative example 6 | - | - |
As can be seen from FIGS. 4 to 6, in combination with Table 1, the energy density of the polylactic acid dielectric film at room temperature after stretching reached 8.7J/cm3Above, the charge-discharge efficiency reaches more than 90%. In comparative example 3, the polylactic acid dielectric film has pores and no breakdown field due to the fact that the stretching temperature is too high (120 ℃) and the stretching ratio is too high (8 times) in comparative example 6 in the preparation process of the polylactic acid dielectric film.
From examples 1 to 4, it is understood that when the conditions for preparing the polylactic acid dielectric thin film satisfy the preferable range of the present application, the breakdown field can be up to 680MV/m or more, and the energy density is 15J/cm3Above, the charge-discharge efficiency reaches more than 95%, and the battery has excellent performance.
As is clear from FIG. 7, the polylactic acid prepared in example 1 was usedAfter the dielectric film is insulated for 15min at 120 ℃, the energy density of the poly-D-lactic acid dielectric film is measured to reach 8.9J/cm3And the charge-discharge efficiency is 87 percent, and the material still has stable dielectric energy storage performance.
DSC measurement is carried out on the polylactic acid dielectric films prepared in the comparative example 1 and the example 1, and the enthalpy of the polylactic acid dielectric films of the comparative example 1 and the example 1 is 35.13J/g and 37.49J/g respectively according to the calculation of the measurement result, which shows that the stretching process of the example 1 improves the crystallinity of the polylactic acid dielectric films and can obviously improve the application performance of the polylactic acid dielectric films.
As shown in FIG. 2, the polylactic acid dielectric film of comparative example 3 was too porous to be suitably used because of the excessively high stretching temperature (120 ℃ C.) or the excessively high stretching ratio (8 times) of comparative example 6.
As can be seen from table 1, the dielectric film of polylactic acid prepared in example 1 has good breakdown characteristics, and ensures high energy density and charge and discharge efficiency at normal temperature. The polylactic acid dielectric film which is not stretched has poor performance and low energy density, and the embodiments 1 to 6 of the application have high energy density and charge-discharge efficiency at normal temperature.
The preferred embodiments of the present invention have been described above in detail, but the present invention is not limited thereto. Within the scope of the technical idea of the invention, many simple modifications can be made to the technical solution of the invention, including combinations of various technical features in any other suitable way, and these simple modifications and combinations should also be regarded as the disclosure of the invention, and all fall within the scope of the invention.
Claims (10)
1. A polylactic acid dielectric film, characterized in that the polylactic acid dielectric film has a peak intensity of (110) plane of 15000-30000 and a peak intensity of (203) plane of not more than 1000 as measured by XRD.
2. The polylactic acid dielectric film according to claim 1, wherein the polylactic acid dielectric film has a peak intensity of a (110) crystal plane of 18000-25000 and a peak intensity of a (203) crystal plane of not more than 500 as measured by XRD.
3. A method of preparing the polylactic acid dielectric film according to claim 1 or 2, comprising the steps of:
s1, preparing a film from polylactic acid to obtain an initial film material;
s2, stretching the initial film material at a high temperature to obtain the polylactic acid dielectric film;
the high temperature is 70-100 ℃, and the stretching magnification is 3-6 times.
4. The method according to claim 3, wherein the polylactic acid of the polylactic acid dielectric thin film is selected from poly-L-lactic acid and/or poly-D-lactic acid.
Preferably, the viscosity average molecular weight of the polylactic acid in the polylactic acid dielectric film is 20 to 40 ten thousand, preferably 26 to 28 ten thousand.
5. The method according to claim 3 or 4, wherein, in step S1, the process of film formation is selected from at least one of a solution casting method, a casting method, and a melt extrusion method.
6. The method according to any one of claims 3-5, wherein the stretching is a unidirectional asynchronous stretching or a bidirectional synchronous stretching;
preferably, the rate of stretching is 0.01 to 0.04 mm/s.
7. The method according to any one of claims 3 to 6, wherein in step S1, the initial film material is prepared according to the following steps:
(1) mixing polylactic acid with a solvent to obtain a mixed solution;
(2) and placing the mixed solution on a mold, volatilizing the solvent, and drying to obtain the initial film material.
8. The method according to claim 7, wherein, in the step (1), the solvent is selected from at least one of dichloromethane, chloroform, acetone and dimethylformamide;
preferably, in the step (2), the solvent volatilization condition comprises: the temperature is 20-65 ℃ and the time is 12-24 hours.
9. The method according to any one of claims 3-8, wherein the method further comprises:
s3, annealing the polylactic acid dielectric film obtained in the step S2;
preferably, the conditions of the annealing treatment include: annealing at 110-150 deg.C for 2-8 h; then cooling to room temperature along with the furnace.
10. Use of the polylactic acid dielectric film according to claims 1 to 2 and/or the method for preparing the polylactic acid dielectric film according to claims 3 to 9 for capacitor energy storage.
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| CA2234317A1 (en) * | 1997-04-08 | 1998-10-08 | Sumitomo Chemical Co., Ltd. | Composite film comprising low-dielectric resin and para-oriented aromatic polyamide |
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