Core-shell functional filler reinforced high-dielectric polyimide film and preparation method thereof

Abstract

The invention discloses a core-shell functional filler reinforced high-dielectric polyimide film, which is prepared from the following components in percentage by mass: 70 to 85 percent of polyamide acid solution; 15-30% of a core-shell structure filler; 0.5 to 2% of a silane coupling agent; the core-shell structure filler comprises BaTiO3 nanoparticles as a core and boron nitride nanosheets as a shell, and the mass ratio of the core to the shell is (5: 1)-(3: 1). The BaTiO3 nanoparticles and the boron nitride nanosheets are dispersed in the dopamine solution. The polyimide film realizes uniform dispersion of the filler and interface optimization, and meanwhile, the dielectric property, mechanical property and breakdown property of the film are improved.

Description

Technical Field

[0001] This invention belongs to the field of functional polymer composite materials technology, specifically relating to a core-shell functional filler-reinforced high-dielectric polyimide film and its preparation method. Background Technology

[0002] Polyimide (PI), as a high-performance polymer material, is widely used in electronics, aerospace, and other fields due to its excellent thermal stability (decomposition temperature > 500℃), mechanical properties (tensile strength > 100 MPa), and chemical stability. However, the dielectric constant of pure PI is only 2.5-4.0, which is insufficient to meet the high dielectric performance requirements (dielectric constant > 30) of flexible energy storage devices (such as thin-film capacitors and supercapacitors).

[0003] To improve the dielectric constant of PI, existing technologies mainly involve adding high-dielectric fillers (such as barium titanate (BaTiO3) and barium strontium titanate (BST)) to prepare composite films. However, this method has the following technical bottlenecks: (1) High-dielectric fillers (such as BaTiO3) are prone to agglomeration, which leads to an increase in the dielectric loss of the composite film (usually >0.01), failing to meet the low-loss requirement; (2) To achieve a high dielectric constant, the filler content needs to be increased (>30%), but this will significantly reduce the mechanical properties of the film (tensile strength <80MPa), losing its value for flexible applications; (3) The filler has poor compatibility with the PI matrix interface, which easily forms defects, leading to a decrease in breakdown voltage (<150V / μm), limiting the safety of actual use. Summary of the Invention

[0004] The purpose of this invention is to provide a core-shell functional filler-reinforced high-dielectric polyimide film and its preparation method, which achieves uniform dispersion of filler, optimized interface, and improves the dielectric properties, mechanical properties and breakdown properties of the film.

[0005] This invention adopts the following technical solution: a core-shell functional filler-reinforced high-dielectric polyimide film, composed of the following components by mass percentage: Polyamic acid solution: 70-85%; Core-shell structure filler: 15-30%; Silane coupling agent: 0.5-2%; The core-shell structured filler comprises: BaTiO3 nanoparticles as the core and boron nitride nanosheets as the shell, wherein the mass ratio of the core to the shell is 5:1-3:1. The BaTiO3 nanoparticles and boron nitride nanosheets are dispersed in a dopamine solution.

[0006] Furthermore, the BaTiO3 nanoparticles have a particle size of 50-100 nm, and the boron nitride nanosheets have a thickness of 5-10 nm.

[0007] Furthermore, the solid content of the polyamic acid solution is 15-20%, and the solvent is N,N-dimethylformamide or N,N-dimethylacetamide.

[0008] Furthermore, the silane coupling agent is KH550 or KH560.

[0009] This invention also discloses a method for preparing a core-shell functional filler-reinforced high-dielectric polyimide film, the method comprising the following steps: Step 1: Preparation of core-shell structured filler: BaTiO3 nanoparticles were dispersed in a dopamine solution, and boron nitride nanosheets were added. After sonication and standing, the mixture was centrifuged and dried to obtain BaTiO3@BNNS core-shell structured filler. Step 2, Preparation of composite solution: The BaTiO3@BNNS core-shell structure filler from Step 1 is mixed with silane coupling agent, ultrasonically dispersed, and then polyamic acid solution is added and stirred to obtain PAA / core-shell filler composite solution; Step 3: Cast the PAA / core-shell filler composite solution from Step 2 into a film, pre-dry it, then heat imidize it by stepwise heating, and finally cool and peel it off to obtain the composite film.

[0010] Furthermore, in step one, the concentration of the dopamine solution is 1-3 mg / mL, and the pH is 8.0-9.0.

[0011] Furthermore, in step one, the ultrasound time is 30-60 minutes, and the settling time is 1-2 hours.

[0012] The beneficial effects of this invention are: 1. Excellent dielectric properties: dielectric constant > 35 and dielectric loss < 0.008 at 150Hz. The BaTiO3 core provides a high dielectric contribution, and the BNNS shell suppresses leakage current through its insulating barrier function. Simultaneously, the dopamine-assisted core-shell structure prevents filler agglomeration and reduces interfacial polarization loss. 2. Outstanding chemical properties: tensile strength > 120MPa and elongation at break > 15%. Due to the strong interfacial bonding formed between the BNNS shell and the PI matrix through hydrogen bonding and covalent interaction (i.e., silane coupling agent modification), stress concentration under high filler content is alleviated. 3. Due to the high insulation of BNNS blocking conductive paths, the uniform dispersion of the core-shell structure reduces defects and delays electrical tree growth, resulting in a high breakdown voltage of the prepared polyimide film: > 220V / μm. 4. The solution blending-casting method requires no special equipment, allows for large-scale production, and is suitable for industrial applications in flexible electronics and energy storage. Detailed Implementation

[0013] The present invention will now be described in detail with reference to specific embodiments.

[0014] This invention discloses a core-shell functional filler-reinforced high-dielectric polyimide film. In this invention, PAA represents polyamic acid; BNNS represents boron nitride nanosheets; and Tris-HCl represents tris(hydroxymethyl)aminomethane-hydrochloric acid.

[0015] This core-shell functional filler-reinforced high-dielectric polyimide film is composed of the following components by mass percentage: Polyamic acid solution: 70-85%, with a solid content of 15-20%, and the solvent is N,N-dimethylformamide or N,N-dimethylacetamide; Core-shell structure filler: 15-30%; Silane coupling agent: 0.5-2%, silane coupling agent is KH550 or KH560.

[0016] The core-shell structured filler comprises the following: BaTiO3 nanoparticles as the core and boron nitride nanosheets as the shell; wherein the BaTiO3 nanoparticles have a particle size of 50-100 nm, a dielectric constant >3000, a BNNS thickness of 5-10 nm, a band gap >6 eV, and excellent insulation properties, and the mass ratio of the core to the shell is 5:1-3:1. It is prepared by dispersing BaTiO3 nanoparticles and boron nitride nanosheets in a dopamine solution.

[0017] The present invention discloses a core-shell structured bifunctional filler-reinforced high-dielectric-low-loss polyimide composite film, the preparation method of which includes the following steps: Step 1: Preparation of core-shell structured filler: BaTiO3 nanoparticles were dispersed in a dopamine solution with a concentration of 1-3 mg / mL. The pH was adjusted to 8.0-9.0 using Tris-HCl buffer, and the mixture was ultrasonically dispersed for 30-60 min. BNNS was added, and the mixture was ultrasonically dispersed for another 30 min, followed by standing for 1-2 h to allow dopamine to self-polymerize on the BaTiO3 surface and adsorb BNNS to form a shell. After centrifugation, the mixture was vacuum dried at 60-80℃ for 6-12 h to obtain the BaTiO3@BNNS core-shell structured filler.

[0018] Step 2: Preparation of the composite solution: Mix the BaTiO3@BNNS core-shell structured filler from Step 1 with the silane coupling agent, add an appropriate amount of solvent (the solvent added here should be the same as the solvent in the PAA solution), and ultrasonically disperse for 1-2 hours to obtain a dispersion; add the dispersion to the PAA solution and mechanically stir for 2-4 hours (300-500 rpm) to obtain a uniform PAA / core-shell filler composite solution.

[0019] Step 3: Cast the composite solution from Step 2 onto a clean glass plate and pre-dry it in an 80℃ oven for 1-2 hours to remove some of the solvent, forming a wet film. Transfer the wet film along with the glass plate to a vacuum oven and thermally imidize it according to the following procedure: 80℃ / 1h → 150℃ / 1h → 250℃ / 1h → 350℃ / 1h (heating rate 5℃ / min). After naturally cooling to room temperature, peel off the film to obtain a core-shell structure bifunctional filler-reinforced high-dielectric-low-loss polyimide composite film with a thickness of 50-100μm.

[0020] To verify the performance of the core-shell structure bifunctional filler-reinforced high-dielectric-low-loss polyimide composite film of the present invention, specific embodiments are provided.

[0021] The performance testing methods for the gradient layered high-dielectric polyimide composite film prepared in the examples are as follows: Dielectric constant and dielectric loss: tested according to the method specified in GB / T 1409-2006.

[0022] Tensile strength: Tested according to the method specified in GB / T 1040.3.

[0023] Breakdown voltage: Tested according to the method specified in GB / T 1408.1.

[0024] Example 1 Preparation of core-shell structured filler: 5g BaTiO3 (particle size 80nm) was dispersed in 100mL dopamine solution (concentration 2mg / mL, pH=8.5) and sonicated for 30min; 1g BNNS (thickness 8nm) was added, and sonicated for another 30min, followed by standing for 2h; after centrifugation, it was vacuum dried at 60℃ for 8h to obtain BaTiO3@BNNS. In this example, the core-shell mass ratio was 5:1.

[0025] Preparation of composite solution: Take 3g of core-shell filler and 0.1g of KH550, add 10mL of N,N-dimethylformamide, and sonicate for 1h; add the dispersion to 17g of PAA solution (solid content 18%, solvent is N,N-dimethylformamide), and mechanically stir for 2h (speed 400rpm).

[0026] Film formation and imidization: Cast film (wet film thickness 200μm), thermal imidization according to program to obtain a composite film with a thickness of 50μm.

[0027] Performance testing: Dielectric constant 38, dielectric loss 0.007 at 150Hz; tensile strength 125MPa, elongation at break 16%; breakdown voltage 230V / μm.

[0028] Example 2 Preparation of core-shell structured filler: 5g BaTiO3 (particle size 50nm) was dispersed in 100mL dopamine solution (concentration 2mg / mL, pH=8.5) and sonicated for 30min; 1.25g BNNS (thickness 5nm) was added, and sonicated for another 30min, followed by standing for 2h; after centrifugation, it was vacuum dried at 60℃ for 8h to obtain BaTiO3@BNNS. In this example, the core-shell mass ratio was 4:1.

[0029] Preparation of composite solution: Take 2.25g of core-shell filler and 0.15g of KH550, add 10mL of N,N-dimethylacetamide, and sonicate for 1h; add the dispersion to 17.6g of PAA solution (solid content 18%), and stir mechanically for 2h.

[0030] Film formation and imidization: Same as in Example 1, to obtain a film with a thickness of 50 μm.

[0031] Performance testing: Dielectric constant 35, dielectric loss 0.0075 at 150Hz; tensile strength 122MPa; breakdown voltage 225V / μm.

[0032] Example 3 Preparation of core-shell structured filler: 5g BaTiO3 (particle size 100nm) was dispersed in 100mL dopamine solution, and 1.67g BNNS (thickness 10nm) was added. In this example, the core-shell mass ratio was 3:1; the rest was the same as in Example 1.

[0033] Preparation of composite solution: Take 4.5g of core-shell filler and 0.2g of KH550, add 15.3g of PAA solution; the rest is the same as in Example 1.

[0034] Film formation and imidization: Same as in Example 1.

[0035] Performance testing: Dielectric constant 40, dielectric loss 0.008 at 150Hz; tensile strength 118MPa; breakdown voltage 220V / μm.

[0036] Example 4 Core-shell structured filler: Same as in Example 1 (core-shell ratio 5:1).

[0037] Preparation of composite solution: Take 1.5g of core-shell filler and 0.08g of KH550, add 18.42g of PAA solution; the rest is the same as in Example 1.

[0038] Film formation and imidization: Same as in Example 1.

[0039] Performance testing: Dielectric constant 32, dielectric loss 0.0065 at 150Hz; tensile strength 130MPa; breakdown voltage 235V / μm.

[0040] Example 5 Core-shell structured filler: BaTiO3 with a particle size of 60nm and BNNS with a thickness of 6nm. In this example, the core-shell ratio is 4:1; the rest is the same as in Example 1.

[0041] Preparation of composite solution: Take 3.75g of core-shell filler and 0.12g of KH550, and add 16.13g of PAA solution.

[0042] Film formation and imidization: Same as in Example 1.

[0043] Performance testing: Dielectric constant 37, dielectric loss 0.0078 at 150Hz; tensile strength 120MPa; breakdown voltage 222V / μm.

[0044] Example 6 Core-shell structured filler: BaTiO3 with a particle size of 90nm and BNNS with a thickness of 9nm. In this example, the core-shell ratio is 3:1; the rest is the same as in Example 1.

[0045] Preparation of composite solution: Take 3g of core-shell filler and 0.1g of KH550, and add 16.9g of PAA solution.

[0046] Film formation and imidization: Same as in Example 1.

[0047] Performance testing: Dielectric constant 39, dielectric loss 0.0072 at 150Hz; tensile strength 123MPa; breakdown voltage 228V / μm.

[0048] The core-shell structured polyimide composite film of this invention achieves uniform filler dispersion and interface optimization, while simultaneously improving the dielectric, mechanical, and breakdown properties of the film. It also meets the following requirements: dielectric constant > 30 (150Hz), dielectric loss < 0.01 (150Hz), breakdown voltage > 200V / μm, and tensile strength > 100MPa.

Claims

1. A core-shell functional filler-reinforced high-dielectric polyimide film, characterized in that, It consists of the following components by mass percentage: Polyamic acid solution: 70-85%; Core-shell structure filler: 15-30%; Silane coupling agent: 0.5-2%; The core-shell structured filler comprises the following: BaTiO3 nanoparticles as the core and boron nitride nanosheets as the shell, wherein the mass ratio of the core to the shell is 5:1-3:

1.

2. The core-shell functional filler-reinforced high-dielectric polyimide film as described in claim 1, characterized in that, The BaTiO3 nanoparticles have a particle size of 50-100 nm, and the boron nitride nanosheets have a thickness of 5-10 nm.

3. The core-shell functional filler-reinforced high-dielectric polyimide film as described in claim 2, characterized in that, The polyamic acid solution has a solid content of 15-20% and the solvent is N,N-dimethylformamide or N,N-dimethylacetamide.

4. The core-shell functional filler-reinforced high-dielectric polyimide film as described in claim 3, characterized in that, The silane coupling agent is KH550 or KH560.

5. A method for preparing a core-shell functional filler-reinforced high-dielectric polyimide film according to any one of claims 1-4, characterized in that, The method includes the following steps: Step 1: Preparation of core-shell structured filler: BaTiO3 nanoparticles were dispersed in a dopamine solution, and boron nitride nanosheets were added. After sonication and standing, the mixture was centrifuged and dried to obtain BaTiO3@BNNS core-shell structured filler. Step 2, Preparation of composite solution: The BaTiO3@BNNS core-shell structure filler from Step 1 is mixed with silane coupling agent, ultrasonically dispersed, and then polyamic acid solution is added and stirred to obtain PAA / core-shell filler composite solution; Step 3: Cast the PAA / core-shell filler composite solution from Step 2 into a film, pre-dry it, then heat imidize it by stepwise heating, and finally cool and peel it off to obtain the composite film.

6. The method for preparing a core-shell functional filler-reinforced high-dielectric polyimide film according to claim 5, characterized in that, In step one, the concentration of the dopamine solution is 1-3 mg / mL, and the pH is 8.0-9.

0.

7. The method for preparing a core-shell functional filler-reinforced high-dielectric polyimide film according to claim 6, characterized in that, In step one, the ultrasound time is 30-60 minutes and the settling time is 1-2 hours.