Gradient layered structure high dielectric polyimide composite film and preparation method thereof

Abstract

The invention discloses a gradient layered structure high dielectric polyimide composite film and a preparation method thereof, the composite film is a layered structure, and comprises high dielectric layers and reinforced insulating layers which are alternately arranged; wherein the initial layer is a high dielectric layer; the high dielectric layer is prepared from the following materials in percentage by mass: 60-70% of a polyimide matrix and 30-40% of barium strontium titanate nanoparticles; and the reinforced insulating layer is prepared from the following materials in percentage by mass: 85-95% of polyimide matrix and 5-15% of aminated carbon nanotubes. By adopting the composite film, the problem that the dielectric property, the mechanical property and the breakdown property of the existing uniform filling type polyimide composite film are difficult to balance is solved.

Description

Technical Field

[0001] This invention belongs to the field of polymer composite materials technology, specifically relating to a gradient layered high dielectric polyimide composite film and its preparation method. Background Technology

[0002] Polyimide (PI) composite films have become a core material in the field of flexible energy storage due to their combination of the flexibility of polymer materials and the high dielectric properties of inorganic fillers. In the existing technology, high dielectric PI composite films are mostly filled with a single filler (such as BaTiO3, BST, etc.), but there is a problem of mutual constraint between dielectric properties, mechanical properties and breakdown properties: (1) In order to improve the dielectric constant, the content of high dielectric filler needs to be increased, but it is easy to increase the dielectric loss (>0.01) and destroy the continuity of the PI matrix, causing the tensile strength to drop below 80MPa; (2) Although adding conductive reinforcing fillers (such as carbon nanotubes) can improve mechanical properties, it is easy to form conductive paths, resulting in a decrease in breakdown voltage (<150V / μm); (3) Uniform filling makes it difficult to achieve functional partitioning, and it is impossible to optimize multiple properties through structural design. Summary of the Invention

[0003] The purpose of this invention is to provide a gradient layered high-dielectric polyimide composite film and its preparation method, which solves the problem that it is difficult to balance the dielectric properties, mechanical properties and breakdown properties of existing uniformly filled polyimide composite films.

[0004] The present invention adopts the following technical solution: a gradient layered high-dielectric polyimide composite film, which is a layered structure comprising alternating high-dielectric layers and reinforcing insulating layers; wherein, the initial layer is a high-dielectric layer; The high dielectric layer is prepared using the following materials: 60-70% polyimide matrix and 30-40% barium strontium titanate nanoparticles by mass percentage; The materials used to prepare the reinforcing insulation layer are as follows: by mass percentage, it consists of 85-95% polyimide matrix and 5-15% aminated carbon nanotubes.

[0005] Furthermore, the composite film has a total of 3-5 layers and a total thickness of 50-100 μm.

[0006] Furthermore, the particle size of the barium strontium titanate nanoparticles is 30-50 nm.

[0007] Furthermore, the aspect ratio of the aminated carbon nanotube is 50-100, and the surface amino content is >2wt%.

[0008] This invention also discloses a method for preparing a gradient layered high-dielectric polyimide composite film, comprising the following steps: Step 1: Preparation of high dielectric layer precursor solution: The barium strontium titanate nanoparticles are dispersed in a solvent, and diamine and dianhydride monomers are added for in-situ polymerization to obtain PAA / BST solution, which is the high dielectric layer precursor solution; Step 2: Preparation of the precursor solution for the reinforcing insulation layer: Aminated carbon nanotubes are dispersed in a solvent, and diamine and dianhydride monomers are added for in-situ polymerization to obtain a PAA / CNT-NH2 solution, which is the precursor solution for the reinforcing insulation layer. Step 3: Alternately cast two precursor solutions (with the high dielectric layer precursor solution as the first layer) to obtain an alternating high dielectric layer and an enhanced insulating layer. After drying, thermal imidize to obtain a gradient layered high dielectric polyimide composite film.

[0009] Furthermore, in steps one and two, the diamine monomer is 4,4'-diaminodiphenyl ether, the dianhydride monomer is pyromellitic dianhydride, and the molar ratio of diamine to dianhydride is 1:1.

[0010] Furthermore, the solvent in steps one and two is N,N-dimethylacetamide.

[0011] Furthermore, in step three, when alternately casting the two precursor liquids, the next precursor liquid is cast after the previous precursor liquid has been pre-dried to semi-cured.

[0012] Furthermore, the pre-drying temperature is 80°C and the time is 30 minutes.

[0013] Furthermore, the thermal imidization process is as follows: 80℃ / 1h → 150℃ / 1h → 250℃ / 1h → 350℃ / 1h, with a heating rate of 5℃ / min.

[0014] The beneficial effects of this invention are: 1. Excellent dielectric properties of the gradient layered high-dielectric polyimide composite film: dielectric constant >32 at 150Hz, dielectric loss <0.009. The high-dielectric layer BST provides a high dielectric contribution, and the CNT-NH2 of the enhanced insulating layer suppresses interlayer leakage current through the insulating network. The gradient structure reduces interface polarization loss. 2. Outstanding chemical properties: tensile strength >110MPa. CNT-NH2 and the PI matrix form a strong interfacial bond through the covalent interaction of amino and imide rings. Interlayer semi-curing treatment improves interlayer adhesion. 3. The gradient structure forms a "resistive gradient field," delaying electrical tree penetration. The insulating modification of CNT-NH2, i.e., amination, avoids conductive paths, resulting in a high breakdown voltage: >210V / μm. 4. Strong controllability: by adjusting the number of layers, thickness ratio, and filler content, the film performance can be flexibly controlled to adapt to different application scenarios, such as flexible capacitors and sensors. Detailed Implementation

[0015] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0016] This invention discloses a gradient layered high-dielectric polyimide composite film, which achieves functional partitioning and synergistic performance enhancement through the alternating arrangement of "high-dielectric layer" and "reinforced insulating layer".

[0017] In this invention, BST represents barium strontium titanate, CNT-NH2 represents aminated carbon nanotubes, DMAc represents N,N-dimethylacetamide, ODA represents 4,4'-diaminodiphenyl ether, PMDA represents phenyltetracarboxylic dianhydride, and PMDA represents pyromellitic dianhydride. This invention discloses a gradient layered high-dielectric polyimide composite film, which has a layered structure with a total of 3-5 layers, including alternating high-dielectric layers and reinforcing insulating layers, with the initial layer being a high-dielectric layer, and a total thickness of 50-100 μm.

[0018] The material used to prepare the high dielectric layer is as follows: it consists of 60-70% polyimide matrix and 30-40% BST nanoparticles by mass percentage, wherein the particle size of the BST nanoparticles is 30-50 nm and the dielectric constant is >2000; The materials used to prepare the reinforced insulation layer are as follows: by mass percentage, they consist of 85-95% polyimide matrix and 5-15% CNT-NH2, the aspect ratio of CNT-NH2 is 50-100, and the surface amino content is >2wt%.

[0019] The gradient layered high-dielectric polyimide composite film of this invention is prepared by in-situ polymerization-layer-by-layer casting method, including the following steps: Step 1: Preparation of high dielectric layer precursor solution: Disperse BST nanoparticles in N,N-dimethylacetamide and sonicate for 1-2 hours; add diamine monomer, such as 4,4'-diaminodiphenyl ether, and mechanically stir until completely dissolved; add dianhydride monomer, such as pyromellitic dianhydride PMDA, and control the molar ratio of ODA to PMDA to be 1:1. Polymerize at 25°C under nitrogen protection for 3-4 hours to obtain a PAA / BST solution with a solid content of 15%, which is the high dielectric layer precursor solution. Step 2: Preparation of the precursor solution for reinforcing the insulating layer: CNT-NH2 is dispersed in DMAc and ultrasonically dispersed for 1-2 hours; ODA monomer is added, stirred and dissolved, and then PMDA is added. The molar ratio of ODA to PMDA is 1:1. Polymerization is carried out at 25°C for 3-4 hours under nitrogen protection to obtain a PAA / CNT-NH2 solution with a solid content of 15%, which is the precursor solution for reinforcing the insulating layer. Step 3, Layer-by-layer casting and thermal imidization: Place a clean glass plate on a casting machine, first cast a layer of high-dielectric layer precursor liquid, pre-dry at 80℃ for 30 min until semi-cured; then cast a layer of reinforcing insulating layer precursor liquid, pre-dry at 80℃ for 30 min; repeat the above operation to 3-5 layers, alternating the arrangement; transfer the laminated film along with the glass plate to a vacuum oven, and thermally imidize according to the following procedure: 80℃ / 1h → 150℃ / 1h → 250℃ / 1h → 350℃ / 1h, heating rate 5℃ / min; after cooling, peel off to obtain a gradient layered high-dielectric polyimide composite film.

[0020] To further verify the method in this invention, the following specific embodiments are provided: The gradient layered high-dielectric polyimide composite films prepared in each embodiment are tested for their performance using the following methods: Dielectric constant and dielectric loss: tested according to the method specified in GB / T 1409-2006.

[0021] Tensile strength: Tested according to the method specified in GB / T 1040.3.

[0022] Breakdown voltage: Tested according to the method specified in GB / T 1408.1.

[0023] Example 1 High dielectric layer precursor solution: 3g BST (particle size 40nm) was dispersed in 30mL DMAc and sonicated for 1h; 2.8g ODA was added, dissolved, and then 3.2g PMDA was added. The BST content was 30%, and polymerization was carried out under nitrogen protection for 3h.

[0024] Precursor solution for reinforcing insulation layer: 0.6g CNT-NH2 (aspect ratio 70, amino content 2.5wt%) was dispersed in 30mL DMAc and sonicated for 1h; 4.4g ODA and 5.6g PMDA were added, CNT-NH2 content was 10%, and polymerization was carried out for 3h.

[0025] Layer-by-layer casting: Three layers are cast alternately, namely a high dielectric layer, a reinforcing insulating layer, and another high dielectric layer, with each layer having a thickness of 20 μm; after pre-drying, imidization is performed at 350 °C to obtain a film with a total thickness of 60 μm.

[0026] Performance testing: Dielectric constant 34, dielectric loss 0.0085 at 150Hz; tensile strength 115MPa; breakdown voltage 215V / μm.

[0027] Example 2 High dielectric layer precursor solution: 3.5g BST (particle size 30nm) was dispersed in 30mL DMAc, 2.5g ODA and 3.5g PMDA were added, BST content was 35%, and polymerization was carried out for 3h.

[0028] Precursor solution for reinforcing insulation layer: 0.3g CNT-NH2 (aspect ratio 50) was dispersed in 30mL DMAc, 4.7g ODA and 5.3g PMDA were added, CNT-NH2 content was 5%, and polymerization was carried out for 3h.

[0029] Layer-by-layer casting: Four layers are cast alternately, in the following order: high dielectric layer - reinforced insulating layer - high dielectric layer - reinforced insulating layer, each layer with a thickness of 15μm; the rest is the same as in Example 1.

[0030] Performance testing: Dielectric constant 33, dielectric loss 0.0088 at 150Hz; tensile strength 112MPa; breakdown voltage 212V / μm.

[0031] Example 3 Preparation of high dielectric layer precursor solution: 4g BST (particle size 50nm) was dispersed in 30mL DMAc, 2g ODA and 4g PMDA were added, BST content was 40%, and polymerization was carried out for 3h.

[0032] Preparation of the precursor solution for reinforcing the insulation layer: 0.9g CNT-NH2 (length-to-diameter ratio 100) was dispersed in 30mL DMAc, 4.1g ODA and 5.9g PMDA were added, the CNT-NH2 content was 15%, and polymerization was carried out for 3h.

[0033] Layer-by-layer casting: Three layers are cast alternately, in the following order: high dielectric layer - reinforced insulating layer - high dielectric layer, each layer with a thickness of 25 μm; the rest is the same as in Example 1.

[0034] Performance testing: Dielectric constant 35, dielectric loss 0.0082 at 150Hz; tensile strength 118MPa; breakdown voltage 210V / μm.

[0035] Example 4 Preparation of high dielectric layer precursor solution: 3g BST (particle size 40nm), BST content 30%; the rest is the same as in Example 1.

[0036] Preparation of the precursor solution for reinforcing the insulating layer: 0.6g CNT-NH2 (aspect ratio 70), content 10%; the rest is the same as in Example 1.

[0037] Layer-by-layer casting: Five layers are cast alternately, in the following order: high dielectric layer - reinforced insulating layer - high dielectric layer - reinforced insulating layer - high dielectric layer, with each layer having a thickness of 10 μm; the rest is the same as in Example 1.

[0038] Performance testing: Dielectric constant 32, dielectric loss 0.0086 at 150Hz; tensile strength 110MPa; breakdown voltage 218V / μm.

[0039] Example 5 Preparation of high dielectric layer precursor solution: 3.2g BST (particle size 35nm), content 32%; the rest is the same as in Example 1.

[0040] Preparation of the precursor solution for reinforcing the insulating layer: 0.45g CNT-NH2 (aspect ratio 60), content 7.5%; the rest is the same as in Example 1.

[0041] Layer-by-layer casting: Four layers are cast alternately, in the following order: high dielectric layer - reinforced insulating layer - high dielectric layer - reinforced insulating layer, each layer with a thickness of 20 μm; the rest is the same as in Example 1.

[0042] Performance testing: Dielectric constant 34, dielectric loss 0.0084 at 150Hz; tensile strength 114MPa; breakdown voltage 214V / μm.

[0043] Example 6 Preparation of high dielectric layer precursor solution: 3.8g BST (particle size 45nm), content 38%; the rest is the same as in Example 1.

[0044] Preparation of the precursor solution for reinforcing the insulation layer: 0.75g CNT-NH2 (aspect ratio 80), content 12.5%; the rest is the same as in Example 1.

[0045] Layer-by-layer casting: Three layers are cast alternately, in the following order: high dielectric layer - reinforced insulating layer - high dielectric layer (each layer is 30 μm thick, the rest is the same as in Example 1).

[0046] Performance testing: Dielectric constant 36, dielectric loss 0.0080 at 150Hz; tensile strength 116MPa; breakdown voltage 216V / μm.

[0047] As can be seen from the above, in this invention, the alternating arrangement of high dielectric layers and reinforced insulating layers achieves functional zoning and synergistic performance enhancement, resulting in excellent dielectric properties: dielectric constant > 32 and dielectric loss < 0.009 at 150Hz; outstanding mechanical properties: tensile strength > 110MPa; high breakdown voltage: > 210V / μm; and the film performance can be controlled by adjusting the number of layers, thickness ratio, and filler content.

Claims

1. A gradient layered high-dielectric polyimide composite film, characterized in that, It has a layered structure, including alternating high-dielectric layers and reinforcing insulating layers, wherein the initial layer is a high-dielectric layer; The high dielectric layer is prepared using the following materials: 60-70% polyimide matrix and 30-40% barium strontium titanate nanoparticles by mass percentage; The materials used to prepare the reinforcing insulation layer are as follows: by mass percentage, it consists of 85-95% polyimide matrix and 5-15% aminated carbon nanotubes.

2. The gradient layered high-dielectric polyimide composite film as described in claim 1, characterized in that, The composite film has a total of 3-5 layers and a total thickness of 50-100 μm.

3. The gradient layered high-dielectric polyimide composite film as described in claim 2, characterized in that, The strontium barium titanate nanoparticles have a particle size of 30-50 nm.

4. The gradient layered high-dielectric polyimide composite film as described in claim 3, characterized in that, Aminated carbon nanotubes have an aspect ratio of 50-100 and a surface amino content of >2wt%.

5. A method for preparing a gradient layered high-dielectric polyimide composite film according to any one of claims 1-4, characterized in that, Includes the following steps: Step 1: Preparation of high dielectric layer precursor solution: The barium strontium titanate nanoparticles are dispersed in a solvent, and diamine and dianhydride monomers are added for in-situ polymerization to obtain PAA / BST solution, which is the high dielectric layer precursor solution; Step 2: Preparation of the precursor solution for the reinforcing insulation layer: Aminated carbon nanotubes are dispersed in a solvent, and diamine and dianhydride monomers are added for in-situ polymerization to obtain a PAA / CNT-NH2 solution, which is the precursor solution for the reinforcing insulation layer. Step 3: Alternately cast two precursor solutions (with the high dielectric layer precursor solution as the first layer) to obtain an alternating high dielectric layer and an enhanced insulating layer. After drying, thermal imidize to obtain a gradient layered high dielectric polyimide composite film.

6. The method for preparing a gradient layered high-dielectric polyimide composite film as described in claim 5, characterized in that, The diamine monomer in steps one and two is 4,4'-diaminodiphenyl ether, the dianhydride monomer is pyromellitic dianhydride, and the molar ratio of diamine to dianhydride is 1:

1.

7. The method for preparing a gradient layered high-dielectric polyimide composite film as described in claim 6, characterized in that, The solvent used in steps one and two is N,N-dimethylacetamide.

8. The method for preparing a gradient layered high-dielectric polyimide composite film as described in claim 7, characterized in that, In step three, when the two precursor liquids are alternately cast, the next precursor liquid is cast after the previous precursor liquid has been pre-dried to semi-cured.

9. The method for preparing a gradient layered high-dielectric polyimide composite film as described in claim 8, characterized in that, The pre-drying temperature is 80℃ and the time is 30 minutes.

10. The method for preparing a gradient layered high-dielectric polyimide composite film as described in claim 9, characterized in that, The thermal imidization program is as follows: 80℃ / 1h → 150℃ / 1h → 250℃ / 1h → 350℃ / 1h, with a heating rate of 5℃ / min.