Method for preparing three-dimensional structure heat-conducting film by electrospinning-hot pressing and application thereof

Abstract

The application discloses a method for preparing a three-dimensional structure heat-conducting film by electrostatic spinning-heat pressing and application. The method is based on non-metal heat-conducting fillers and fillers with large specific surface area, utilizes the characteristics of the electrostatic spinning processing method, constructs a three-dimensional point-line-plane multi-contact site structure, reduces the contact thermal resistance between the heat-conducting fillers and the polymer fibers in the material, builds a heat-conducting network with the fillers as the core on the skeleton of the polymer fibers, and fully plays the high heat-conducting characteristics of the heat-conducting fillers. Due to the special "point-line-plane" structure characteristics, the film material prepared by the application will not cause the dramatic increase of the interface thermal resistance due to the aggregation of the fillers at a high filler proportion (>=50wt%) and will not cause the sharp decrease of the heat-conducting coefficient. The heat-conducting film prepared by the application has a heat-conducting coefficient of 12.04 W / (m*K) and can be applied to electronic and electrical equipment.

Description

Technical Field

[0001] This invention belongs to the field of thermally conductive composite material preparation technology, specifically relating to a method and application for preparing three-dimensional thermally conductive thin films by electrospinning-hot pressing. Background Technology

[0002] As modern electronic devices evolve towards miniaturization, integration, and multifunctionality, the heat generated during operation cannot be dissipated from the device in a timely manner due to the limitations of material properties on thermal conductivity. This leads to localized heat accumulation and excessively high temperatures, restricting the electronic device's performance, affecting its reliability, and shortening its lifespan. Therefore, thermal management materials with excellent thermal conductivity can achieve rapid heat transfer, thereby solving the problem of heat accumulation in localized areas.

[0003] Polymers possess advantages such as ease of processing, low cost, and light weight, making polymer-based composites a promising area for thermal management materials. In particular, polymers exhibit good insulation properties, and designing and preparing polymer-based composites with high thermal conductivity can simultaneously achieve both high thermal conductivity and insulation performance, giving them an irreplaceable advantage in the thermal management of electronic devices. However, polymers have relatively low thermal conductivity, typically ranging from 0.1 to 0.3 W / (m*K). This conductivity is insufficient for the heat dissipation requirements of electronic devices in daily use. Therefore, it is necessary to add fillers with high thermal conductivity (such as alumina, boron nitride, graphene, silicon carbide, and copper oxide) to improve the thermal conductivity of polymer composites. The thermal conductivity of filled polymer-based composites increases with the amount of filler added. Simply mixing fillers directly results in a very limited increase in thermal conductivity and even a decrease in mechanical properties. Therefore, how to efficiently utilize fillers while considering production costs and processing difficulties is a key issue that needs to be addressed in actual production. Summary of the Invention

[0004] To address the shortcomings and deficiencies of existing technologies, the primary objective of this invention is to provide a method for preparing three-dimensional thermally conductive thin films using an electrospinning-hot pressing method. This invention is based on non-metallic thermally conductive fillers and fillers with large specific surface areas (such as mesoporous fillers). Utilizing the characteristics of the electrospinning process, a three-dimensional multi-contact site structure is constructed, reducing the contact thermal resistance between the thermally conductive filler and polymer fibers. A thermally conductive network with the filler as its core is built on the polymer fiber framework, fully leveraging the high thermal conductivity of the filler. This method allows for controllable spinning structures and features simple operation, high controllability, and ease of large-scale production.

[0005] Another objective of this invention is to provide a three-dimensional thermally conductive film prepared by the above method. This three-dimensional structure can maintain the thermal conductivity of the thermally conductive film at a high filler ratio, avoiding filler aggregation and increased interfacial thermal resistance, which would lead to a decrease in thermal conductivity. In other words, by increasing the filler, the thermal conductivity of the material can be made higher than 10 W / (m*K).

[0006] Another object of the present invention is to provide applications of the above-described three-dimensional thermally conductive thin film.

[0007] The objective of this invention is achieved through the following technical solution:

[0008] A method for preparing a three-dimensional thermally conductive thin film by electrospinning-hot pressing includes the following steps:

[0009] (1) Modify the non-metallic thermally conductive filler to obtain the modified filler;

[0010] (2) Add the modified filler from step (1) and the filler with a large specific surface area to the solvent and disperse them thoroughly to obtain a mixture;

[0011] (3) Add polymer fibers to the mixture in step (2) and stir evenly to obtain spinning solution, and perform electrospinning to obtain spinning fiber membrane;

[0012] (4) The three-dimensional thermally conductive film is obtained by drying the spun fiber membrane obtained in step (3).

[0013] Preferably, the non-metallic thermally conductive filler in step (1) is one of BN, AlN, SiC, and Al2O3, or a mixture of two thermally conductive fillers with different physical structures, such as a mixture of sheet-like nano BN and mesoporous Al2O3.

[0014] More preferably, the non-metallic thermally conductive filler in step (1) is one of BN and SiC.

[0015] Preferably, the modification in step (1) is a polydopamine (PDA) modification method or a silane modifier modification method.

[0016] The steps of the polydopamine modification method are as follows: A non-metallic thermally conductive filler is added to a Tris-buffer ethanol buffer and ultrasonically dispersed, followed by the addition of an appropriate amount of dopamine hydrochloride and heating to initiate the reaction. Because dopamine polymerizes very easily and can efficiently adhere to any surface, it has strong adaptability in modifying fillers. The modified filler surface will have a thin layer of polydopamine adhering to it, appearing light gray. Polydopamine has good adhesion properties on all planes, thus enabling efficient adhesion to fibers.

[0017] Preferably, the polydopamine modification method specifically involves: adding 1g of non-metallic thermally conductive filler to a tris-buffer ethanol buffer solution with a concentration of 10mmol / L and pH=8.5, dispersing it ultrasonically, and then adding 0.4g of dopamine hydrochloride and heating the mixture at 60°C for 8-12 hours.

[0018] The tris-buffer ethanol buffer solution with pH=8.5 is prepared by dissolving the tris-buffer buffer solution with pH=8.5 in a mixed solution of anhydrous ethanol and deionized water at a mass ratio of 3:1.

[0019] The steps of the silane modifier modification method are as follows: dissolve the non-metallic thermally conductive filler in an ethanol solution, add the silane modifier (including silane coupling agent KH-550 or KH-560), disperse it fully, and then heat it to react. In step (2), silane modification grafting requires active sites, such as hydroxyl (-OH) and carboxyl (-COOH) groups. Therefore, common inorganic non-metallic fillers (such as BN) need to be fully exfoliated and hydroxylated first to increase the active sites and improve the modification effect. The exfoliation and hydroxylation treatment steps of the filler are as follows: ultrasonically disperse the non-metallic thermally conductive filler in a 95wt% ethanol solution, then transfer it to a 5mol / L sodium hydroxide solution, react at 130℃ for 24h, centrifuge, filter, wash, and dialyze to neutral. The exfoliated and hydroxylated filler can improve the grafting effect of the silane modifier.

[0020] Preferably, the steps of the silane modifier modification method are as follows: dissolve 1g of non-metallic thermally conductive filler in 95wt% ethanol solution, add 2ml of silane modifier and disperse fully, and then react at 90℃ for 24h.

[0021] Preferably, the filler with a large specific surface area in step (2) is two-dimensional planar graphene oxide (GO) or mesoporous MnO2 with a three-dimensional structure. GO has good flexibility and can be rotated and folded; mesoporous MnO2 can improve the distribution of thermally conductive fillers and the construction of thermally conductive networks in the film by utilizing its dispersed particle morphology, as well as improve the mechanical properties of the material. More importantly, it can realize heat diffusion between multiple thermally conductive fibers.

[0022] Preferably, the solvent in step (2) is a mixed solution of N,N-dimethylacetamide (DMAC) and acetone (DMK) in a mass ratio of (6-12):1.

[0023] Preferably, in step (2), the mass ratio of the modified filler to the filler with a large specific surface area is (6-12):1.

[0024] More preferably, in step (2), the mass ratio of the modified filler to the filler with a large specific surface area is (8-12):1.

[0025] Preferably, the mass ratio of the modified filler in step (2) to the polymer fiber in step (3) is (1-6):10.

[0026] Preferably, the polymer fiber in step (3) is one of polyvinyl alcohol (PVA), polyphthalamide (PPA), and polyvinylidene fluoride (PVDF). Different polymer fibers are selected according to the mechanical properties of the required material and the usage environment.

[0027] More preferably, the polymer fiber in step (3) is one of polyvinyl alcohol and polyvinylidene fluoride.

[0028] Preferably, the stirring in step (3) is carried out at a constant temperature of 50-60°C for 5-6 hours.

[0029] Preferably, the electrospinning voltage in step (3) is 15-20 kV, the receiving distance is 10-20 cm, the receiving drum speed is 200-500 rpm, and the spinning solution injection speed is 0.02-0.04 mm / min. The spinning voltage is generally selected based on the shape of the Taylor cone. Regarding the receiving drum speed, too low a speed prevents the fibers from being oriented and causes them to stack randomly, while too high a speed can easily deform or even break the collected fibers. The spinning equipment can be uniaxial or coaxial; coaxial spinning equipment is superior in terms of fiber embedding within the filler.

[0030] More preferably, the voltage of electrospinning in step (3) is 18-20kV, the receiving distance is 15cm, the receiving drum speed is 300rpm, and the spinning solution injection speed is 0.028-0.035mm / min.

[0031] Preferably, the drying in step (4) is performed at 60°C for 6 to 12 hours.

[0032] Preferably, the three-dimensional thermally conductive film obtained in step (4) can also be stacked with different numbers of layers according to the thickness and mechanical requirements, and then hot-pressed to obtain a multilayer composite film that meets the requirements.

[0033] The hot pressing is performed at 180–230°C and 15–20 MPa for 20–40 minutes, preferably at 180°C and 20 MPa for 30 minutes. Generally, before hot pressing, the stacked films may be cold-pressed at room temperature to prevent loosening or shifting of the stacked spun fiber films. During stacking, the spun fiber films are stacked perpendicularly along different fiber directions to achieve uniform in-plane thermal conductivity. Alternatively, all spun fiber films can be stacked perpendicularly along the same fiber direction, cold-pressed at room temperature, then curled and hot-pressed again, and finally cut into thin sheets along the axial direction to obtain a directional thermally conductive film with significant differences in thermal conductivity in different directions within the plane, which can be used for materials with specific thermal conductivity requirements.

[0034] The three-dimensional thermally conductive thin film prepared by this invention can be applied to electronic and electrical equipment.

[0035] Compared with the prior art, the present invention has the following advantages:

[0036] (1) The three-dimensional thermally conductive film prepared by this invention has a higher efficiency in filler utilization compared with other traditional polymer-based thermally conductive composite materials. At a low filler ratio, the thermal conductivity of the thermally conductive film prepared by this invention is several to tens of times that of the randomly distributed filler method; while at a higher filler ratio, due to the introduction of materials with large specific surface area, the interface dimension between fillers and the space for filler separation are increased, which reduces the possibility of thermally conductive filler agglomeration, thereby greatly improving the thermal conductivity of the film, broadening the application scenarios of the material, and greatly promoting the practical application of polymer-based thermally conductive composite materials.

[0037] (2) This invention utilizes the characteristics of electrospinning by adding fillers with a large specific surface area to the spinning solution, which encapsulate the spun fibers together. This achieves uniform orientation of the spun fibers and utilizes the thermal conductivity of the filler with a large specific surface area to improve the thermal conductivity of the composite material. Furthermore, due to its unique "point-line-plane" structural characteristics, the synthesized film material, even with a high filler ratio (≥50wt%), does not experience a significant decrease in thermal conductivity due to a sharp increase in interfacial thermal resistance caused by filler aggregation. This provides a new approach and method for efficiently utilizing thermally conductive fillers to prepare materials with high thermal conductivity. Attached Figure Description

[0038] Figure 1 Different concentrations of BN / PVDF films were prepared for Example 1.

[0039] Figure 2 BN@PDA / PVDF films (left) and BN@PDA / GO / PVDF films (right) with different concentrations prepared for Example 1.

[0040] Figure 3The XRD patterns are of different concentrations of BN@PDA / PVDF films prepared in Example 1.

[0041] Figure 4 The XRD patterns are of different concentrations of BN@PDA / GO / PVDF films prepared in Example 1.

[0042] Figure 5 TEM images of GO (left), P30 film (middle), and PG30 film (right) prepared in Example 1.

[0043] Figure 6 This is a schematic cross-sectional view of the BN@PDA / GO / PVDF film prepared in Example 1.

[0044] Figure 7 The in-plane thermal conductivity is given by the thin films prepared in Example 1.

[0045] Figure 8 The conductivity of each thin film prepared in Example 1 is given.

[0046] Figure 9 The heat dissipation of the B40, P40, and PG60 films prepared in Example 1 in a practical LED lamp (5V, 1A) application.

[0047] Figure 10 The temperature changes over time of the B40, P40, and PG60 films prepared in Example 1 during actual LED lamp (5V, 1A) applications.

[0048] Figure 11 The tensile test results are for the BN@PDA / PVDF film and the BN@PDA / GO / PVDF film prepared in Example 1.

[0049] Figure 12 The in-plane thermal conductivity of SiC@PDA / MnO2 / PVA films with different concentrations prepared in Example 2 is shown.

[0050] Figure 13 The in-plane thermal conductivity of SiC / MnO2 / PVA films with different concentrations prepared in Example 2 is shown. Detailed Implementation

[0051] The present invention will be further described in detail below with reference to embodiments, but the embodiments of the present invention are not limited thereto. All raw materials involved in the present invention can be purchased directly from the market, and for process parameters not specifically specified, conventional techniques can be referred to.

[0052] The examples were conducted at 25°C and 30% relative humidity. The electrospinning equipment used in the examples was: Beijing Yongkang Leyue Technology Development Co., Ltd., model SS-1; the hot press was: Hefei Kejing Technology Co., Ltd., model HP-100.

[0053] The thermal diffusivity of the thin film material was tested using a TA DXF-200 instrument, and the thermal fusion coefficient was tested using a TA DSC-Q20 instrument. Material dimensions were measured using a balance and calipers, and the results were obtained using the formula k = ρC. p σ(ρ is the density of the composite material, Cp is the specific heat capacity of the material, and σ is the thermal diffusivity; the formula for calculating density ρ is as follows) The thermal conductivity of the film material was calculated using the mass, diameter, and thickness of the composite material, respectively (where m, d, and h are the mass, diameter, and thickness). The electrical conductivity of the film material was measured using a USA KEITHLEY 2450 Source meter via the four-probe method. The tensile strength of the film material was tested according to GB / T16578.1-2008 at room temperature using an electric tensile testing machine (STX-5000 EAST, CN) equipped with a 500N sensor. The tensile speed of the chip clamp on the tensile testing machine was 200 mm / min, and the gauge length was 20 mm. All tests were performed in parallel at least three times, and the average value was taken.

[0054] The BN used in the examples is hexagonal boron nitride (h-BN).

[0055] Example 1

[0056] Preparation of BN@PDA / GO / PVDF High Thermal Conductivity Flexible Fiber Film

[0057] (1) Dissolve 5g of BN powder in 500ml of Tris-buffer ethanol buffer solution with a concentration of 10mmol / L and pH=8.5, stir evenly, and sonicate for 4h to fully disperse it. Then add 2.0g of dopamine hydrochloride and stir at 60℃ for 8h. Then centrifuge to remove the supernatant, wash with deionized water and anhydrous ethanol alternately, and then dry in an oven at 60℃ to complete the polydopamine (PDA) modification of BN to obtain BN@PDA. Dopamine is easily self-oxidatively polymerized to form PDA to coat the surface of BN, which improves the viscosity and dispersibility of BN. BN coated with PDA will change from white to gray.

[0058] (2) Take 0.1g of BN@PDA obtained in step (1) and 0.0125g of GO (i.e., the mass ratio of BN@PDA to GO is 8:1) and dissolve them in 10ml of DMAC and DMK solution with a mass ratio of 9:1. Sonicate for 1h to fully disperse to obtain BN@PDA / GO mixture.

[0059] (3) Add 1g of PVDF to the BN@PDA / GO mixture in step (2) and stir at 50℃ for 5h to fully mix to obtain spinning solution (the spinning solution should be prepared and used immediately). Perform electrospinning at 25℃ with an applied voltage of 18kV, the distance between the metal needle and the steel cylinder is 15cm, the receiving drum speed is 300rpm, the spinning solution injection speed is 0.035mm / min, and cover the steel cylinder with aluminum foil (20cm*31.5cm) to collect the fiber filaments to obtain the spun fiber membrane.

[0060] (4) After drying the spun fiber membrane obtained in step (3) at 60°C for 6 hours to remove residual solvent, it is cut into fixed dimensions and randomly stacked (i.e. the fiber direction is not fixed). Then, it is hot-pressed at 180°C with a pressure of 20MPa for 30 minutes to obtain a three-dimensional thermally conductive film BN@PDA / GO / PVDF with a thickness of 0.1 to 0.12 mm, denoted as PG10.

[0061] (5) Prepare the following three-dimensional thermally conductive films (thickness 0.1-0.12 mm) by referring to steps (2) to (4) above: change the amount of BN@PDA to 0.2 g and the amount of GO to 0.025 g, and keep the other operations the same to obtain the three-dimensional thermally conductive film BN@PDA / GO / PVDF (PG20); change the amount of BN@PDA to 0.3 g and the amount of GO to 0.0375 g, and keep the other operations the same to obtain the three-dimensional thermally conductive film BN@PDA / GO / PVDF (PG30); change the amount of BN@PDA to 0.3 g and the amount of GO to 0.0375 g, and keep the other operations the same to obtain the three-dimensional thermally conductive film BN@PDA / GO / PVDF (PG30); change the amount of BN@PDA to 0.2 g and the amount of GO to 0.02 ... The amount of BN@PDA was changed to 0.4g and the amount of GO added was changed to 0.05g, while other operations remained the same, to obtain a three-dimensional thermally conductive film BN@PDA / GO / PVDF (PG40); the amount of BN@PDA was changed to 0.5g and the amount of GO added was changed to 0.0625g, while other operations remained the same, to obtain a three-dimensional thermally conductive film BN@PDA / GO / PVDF (PG50); the amount of BN@PDA was changed to 0.6g and the amount of GO added was changed to 0.075g, while other operations remained the same, to obtain a three-dimensional thermally conductive film BN@PDA / GO / PVDF (PG60).

[0062] (6) As a control, 0.1g of BN and 1g of PVDF were used to prepare a spinning solution. Then, BN / PVDF films (B10) were prepared by electrospinning, stacking, and hot pressing as described in steps (3) and (4) above. Following the method for preparing B10, the amount of BN was changed to 0.2g, 0.3g, 0.4g, 0.5g, and 0.6g respectively, while keeping other conditions unchanged, to obtain BN / PVDF films (B20), (B30), (B40), (B50), and (B60). The thickness of the above films was 0.1–0.12 mm.

[0063] (7) As a control, 0.1g of BN@PDA obtained in step (1) and 1g of PVDF were used to prepare a spinning solution. Then, BN@PDA / PVDF film (P10) was prepared by electrospinning, stacking, and hot pressing as described in steps (3) and (4) above. Then, referring to the method for preparing P10, the amount of BN@PDA was changed to 0.2g, 0.3g, 0.4g, 0.5g, and 0.6g respectively, while keeping other conditions unchanged, to prepare BN@PDA / PVDF film (P20), BN@PDA / PVDF film (P30), BN@PDA / PVDF film (P40), BN@PDA / PVDF film (P50), and BN@PDA / PVDF film (P60). The thickness of the above films was 0.1 to 0.12 mm.

[0064] The finished product prepared in this embodiment is as follows: Figure 1 , Figure 2 As shown.

[0065] Example 2

[0066] I. Preparation of Mesoporous MnO2

[0067] 5.5 mmol (0.869 g) of KMnO4 was dissolved in 50 ml of deionized water, and 22.5 mmol (1.55 ml) of ethylene glycol was added and mixed thoroughly. The mixture was stirred and aged at room temperature for 20 min. During stirring, 5 ml of 50 wt% concentrated sulfuric acid was slowly added dropwise. The precipitate was collected by centrifugation and washed alternately with deionized water and anhydrous ethanol until neutral. Then, it was dried in an oven at 60 °C for 24 h to obtain mesoporous MnO2.

[0068] II. Preparation of SiC@PDA / MnO2 / PVA thermally conductive thin films

[0069] (1) Dissolve 5g of SiC powder in 500ml of Tris-buffer ethanol buffer solution with a concentration of 10mmol / L and pH=8.5, stir evenly, and sonicate for 4h to fully disperse it. Then add 2.0g of dopamine hydrochloride and stir at 60℃ for 8h. Then centrifuge to remove the upper liquid, wash with deionized water and anhydrous ethanol alternately, and then dry in an oven at 60℃ to complete the PDA modification of SiC to obtain SiC@PDA. Dopamine can easily undergo self-oxidative polymerization to form PDA coating on the surface of SiC, which improves the viscosity and dispersibility of SiC. The SiC coated with PDA will change from light green to gray.

[0070] (2) Take 0.1g of SiC@PDA obtained in step (1) and 0.0083g of mesoporous MnO2 prepared in step 1 (i.e., the mass ratio of SiC@PDA to mesoporous MnO2 is 12:1) and dissolve them in 15ml of a solution of DMAC and DMK with a mass ratio of 10:1. Sonicate for 1h to fully disperse the mixture to obtain a SiC@PDA / MnO2 mixture.

[0071] (3) Add 1.0g of PVA powder to the SiC@PDA / MnO2 mixture in step (2) and stir at 60℃ for 5h to fully mix to obtain spinning solution (the spinning solution should be prepared and used immediately). Perform electrospinning at 25℃ with an applied voltage of 20kV. The distance between the metal needle and the steel cylinder is 15cm, the receiving drum speed is 300rpm, and the spinning solution injection speed is 0.028mm / min. Cover the steel cylinder with aluminum foil (20cm*31.5cm) to collect the fiber filaments and obtain the spun fiber membrane.

[0072] (4) After drying the spun fiber membrane obtained in step (3) at 60°C for 12 hours to remove residual solvent, it is cut into fixed dimensions and randomly stacked (i.e. the fiber direction is not fixed). Then, it is hot-pressed at 180°C with a pressure of 20MPa for 30 minutes to obtain a three-dimensional thermally conductive thin film SiC@PDA / MnO2 / PVA with a thickness of 0.1 to 0.12 mm, denoted as PS10.

[0073] (5) Following the procedures in steps (2) to (4) above, prepare the following three-dimensional thermally conductive films (thickness 0.1–0.12 mm): Change the amount of SiC@PDA to 0.2 g and the amount of MnO2 to 0.0167 g, keeping other conditions the same, to obtain the three-dimensional thermally conductive film SiC@PDA / MnO2 / PVA (PS20); Change the amount of SiC@PDA to 0.3 g and the amount of MnO2 to 0.025 g, keeping other conditions the same, to obtain the three-dimensional thermally conductive film SiC@PDA / MnO2 / PVA (PS30); Change the amount of SiC@PDA to… Three-dimensional thermally conductive films SiC@PDA / MnO2 / PVA (PS40) were prepared by changing the amount of SiC@PDA to 0.4g and the amount of MnO2 to 0.0333g, while keeping other conditions the same. Three-dimensional thermally conductive films SiC@PDA / MnO2 / PVA (PS50) were prepared by changing the amount of SiC@PDA to 0.5g and the amount of MnO2 to 0.0417g, while keeping other conditions the same. Three-dimensional thermally conductive films SiC@PDA / MnO2 / PVA (PS60) were prepared by changing the amount of SiC@PDA to 0.6g and the amount of MnO2 to 0.05g, while keeping other conditions the same.

[0074] (6) As a control, 0.1g of SiC, 0.0083g of mesoporous MnO2 prepared in step one, and 1.0g of PVA were used to prepare a spinning solution. Then, following steps (3) to (4) above, a SiC / MnO2 / PVA film (S10) was prepared by electrospinning, stacking, and hot pressing. Following the method for preparing S10, the amount of SiC was changed to 0.2g and the amount of mesoporous MnO2 was changed to 0.0167g, while other conditions remained unchanged, to prepare a SiC / MnO2 / PVA film (S20). Following the method for preparing S10, the amount of SiC was changed to 0.3g and the amount of mesoporous MnO2 was changed to 0.025g, while other conditions remained unchanged, to prepare a SiC / MnO2 / PVA film (S20). SiC / MnO2 / PVA thin film (S30); following the method for preparing S10, the amount of SiC was changed to 0.4 g and the amount of mesoporous MnO2 was changed to 0.0333 g, while other conditions remained unchanged, to prepare SiC / MnO2 / PVA thin film (S40); following the method for preparing S10, the amount of SiC was changed to 0.5 g and the amount of mesoporous MnO2 was changed to 0.0417 g, while other conditions remained unchanged, to prepare SiC / MnO2 / PVA thin film (S50); following the method for preparing S10, the amount of SiC was changed to 0.6 g and the amount of mesoporous MnO2 was changed to 0.05 g, while other conditions remained unchanged, to prepare SiC / MnO2 / PVA thin film (S60). The thickness of the above films is 0.1–0.12 mm.

[0075] Depend on Figure 2It can be seen that the BN@PDA / PVDF film (i.e., the P-film in the figure) and the BN@PDA / GO / PVDF film (i.e., the PG-film in the figure) prepared in Example 1 both have good flexibility.

[0076] Depend on Figure 3 and Figure 4 It can be observed that diffraction peaks appear at 2θ at 26.8° (002) and 42.3° (001), and these two peaks belong to h-BN. Furthermore, the intensity of the diffraction peaks at 26.8° (002) and 55.2° (004) increases with increasing BN@PDA concentration, mainly due to a certain degree of orientation along the fiber direction in the horizontal plane (in-plane plane of the film). The disappearance of the 2θ diffraction peaks of BN@PDA at 42.3°, 44.6°, and 76.7° indicates that BN is well dispersed during ultrasonication. The full width at half maximum (FWHM) of the diffraction peak at 2θ at 26.8° (002) also increases with increasing filler concentration. According to the Scherrer formula: D = kλ(βcosθ) -1 In the formula, D, k, λ, β and θ are the grain size (nm), Scherrer constant, X-ray wavelength (nm), integral half width at half maximum (rad) and diffraction angle. The smaller particle size of BN indicates that BN achieved a good exfoliation effect during the ultrasonic stage of PDA modification, avoiding the blocky accumulation of BN. Moreover, the XRD pattern shows that its in-plane orientation has been improved.

[0077] Depend on Figure 5 It can be seen that the BN@PDA / PVDF film consists of BN@PDA filler embedded on PVDF fibers, and the BN@PDA / GO / PVDF film consists of GO wrapping the PVDF fibers with BN@PDA adsorbed on the surface.

[0078] Depend on Figure 7 It can be seen that both BN@PDA / PVDF film and BN@PDA / GO / PVDF film have excellent thermal conductivity, with P40 being the optimal filler concentration. The thermal conductivity of BN@PDA / GO / PVDF film can reach 12.04 W / (m*K), and its thermal conductivity does not show a significant decreasing trend with the increase of filler ratio.

[0079] Figure 8 The dashed line in the figure represents the conductivity of PVDF. As can be seen from the figure, the conductivity of each group of films is within the range of insulators, which meets the insulation performance requirements in actual use.

[0080] Depend on Figure 9 and Figure 10 It can be seen that the BN@PDA / GO / PVDF film has better heat dissipation performance compared with the BN / PVDF film and the BN@PDA / PVDF film.

[0081] Depend on Figure 11 It can be seen that the film with added GO has enhanced its mechanical properties because the fiber distribution is more oriented due to the encapsulation effect of GO, and the tensile strength is increased due to the adhesion effect of PDA.

[0082] Depend on Figure 12 It can be seen that the thermal conductivity of the SiC@PDA / MnO2 / PVA film prepared in Example 2 continues to increase with the increase of the filler ratio.

[0083] Depend on Figure 13 It can be seen that the thermal conductivity of the SiC / MnO2 / PVA film prepared in Example 2 continues to increase with the increase of the filler ratio, but its highest thermal conductivity does not exceed 2W / (m*K).

[0084] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A method for preparing a three-dimensional thermally conductive thin film using electrospinning-hot pressing, characterized in that, Includes the following steps: (1) The non-metallic thermally conductive filler was modified by polydopamine modification method to obtain the modified filler; the steps of the polydopamine modification method are as follows: the non-metallic thermally conductive filler was added to tris-buffer ethanol buffer and ultrasonically dispersed, and then dopamine hydrochloride was added and heated to react. (2) The modified filler from step (1) and the filler with a large specific surface area are added to the solvent and dispersed thoroughly to obtain a mixture; the filler with a large specific surface area is graphene oxide or mesoporous MnO2. (3) Add polymer fibers to the mixture in step (2) and stir evenly to obtain spinning solution, and perform electrospinning to obtain spun fiber membrane; (4) The three-dimensional thermally conductive film is obtained by drying the spun fiber membrane obtained in step (3).

2. The method for preparing a three-dimensional thermally conductive thin film by electrospinning-hot pressing according to claim 1, characterized in that, The non-metallic thermally conductive filler in step (1) is one or two of BN, AlN, SiC, and Al2O3.

3. The method for preparing a three-dimensional thermally conductive thin film by electrospinning-hot pressing according to claim 1, characterized in that, The solvent in step (2) is a mixed solution of N,N-dimethylacetamide and acetone in a mass ratio of (6~12):

1.

4. The method for preparing a three-dimensional thermally conductive thin film by electrospinning-hot pressing according to claim 1, characterized in that, In step (2), the mass ratio of the modified filler to the filler with a large specific surface area is (6~12):1; in step (2), the mass ratio of the modified filler to the polymer fiber in step (3) is (1~6):

10.

5. The method for preparing a three-dimensional thermally conductive thin film by electrospinning-hot pressing according to claim 1, characterized in that, The polymer fiber in step (3) is one of polyvinyl alcohol, polyphthalamide, and polyvinylidene fluoride; the stirring is carried out at a constant temperature of 50~60 ℃ for 5~6 h; the voltage of the electrospinning is 15~20 kV, the receiving distance is 10~20 cm, the receiving drum speed is 200~500 rpm, and the spinning solution injection speed is 0.02~0.04 mm / min.

6. The method for preparing a three-dimensional thermally conductive thin film by electrospinning-hot pressing according to claim 1, characterized in that, The drying in step (4) is performed at 60 °C for 6 to 12 h.

7. The method for preparing a three-dimensional thermally conductive thin film by electrospinning-hot pressing according to claim 1, characterized in that, In step (4), the obtained three-dimensional thermally conductive films are stacked and then hot-pressed into multi-layer composite films; the hot pressing is carried out at 180~230 ℃ and 15~20 MPa for 20~40 min.

8. A three-dimensional thermally conductive thin film prepared by the electrospinning-hot pressing method according to any one of claims 1 to 7.

9. The application of the three-dimensional thermally conductive thin film of claim 8 in electronic and electrical devices.

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