A polyvinyl alcohol-based boron nitride material, a preparation method therefor, and an application thereof
By treating BN particles with surfactants in a PVA-based composite system and mixing them with a PVA solution under alkaline conditions, rapid film formation and the construction of a stable thermally conductive network were achieved. This solved the problems of slow film formation and uneven filler distribution in PVA-based composite materials, and is suitable for passive thermal management films.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- SOUTHWEST JIAOTONG UNIV
- Filing Date
- 2026-04-23
- Publication Date
- 2026-06-05
AI Technical Summary
In existing technologies, the gelation/film formation process of PVA-based composite systems is slow, and BN is difficult to disperse in PVA aqueous systems, resulting in long film formation cycles, uneven filler distribution, and molding defects. It is difficult to achieve rapid film formation and the construction of a stable thermally conductive network under normal or mild conditions.
By treating BN particles with surfactants and mixing them with PVA solution under alkaline conditions, rapid film formation is initiated by an alkaline trigger, forming a stable PVA/BN composite system. This achieves uniform dispersion and network structure of BN particles in the PVA matrix. By utilizing the alkaline solution in the gelation process, a particle-dependent rapid film formation strategy is established.
Rapid film formation of PVA-based composite systems was achieved at room temperature, shortening the film formation time to several seconds to tens of seconds, improving thermal conductivity and mechanical stability. It is suitable for rapid prototyping and in-situ curing of passive thermal management materials and is applicable to the field of passive thermal management films.
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Figure CN122145952A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of polymer composite materials technology, specifically relating to a polyvinyl alcohol-based boron nitride material, its preparation method, and its application. Background Technology
[0002] With the increasing functionality and energy consumption of equipment, developing passive thermal management materials (such as thermal interface materials and heat dissipation films) with high heat dissipation capabilities has become crucial for ensuring equipment stability and lifespan. Polyvinyl alcohol (PVA), with its excellent film-forming properties, mechanical strength, and abundant side-chain hydroxyl groups, has become an ideal matrix for constructing flexible thermal management films. To impart high thermal conductivity to the PVA substrate, high thermal conductivity insulating fillers such as hexagonal boron nitride (BN) are typically introduced. Currently, common methods for preparing PVA-based thermally conductive composite materials include physical filling, multiple freeze-thaw cycles, or long-term chemical crosslinking. However, the following core bottlenecks still exist in the actual development of passive thermal management films:
[0003] First, there is a contradiction between film-forming kinetics and production efficiency. The traditional PVA composite film formation process is slow, relying mainly on natural solvent evaporation or complex freeze-thaw processes. The film formation cycle often takes several hours or even days, which limits continuous industrial production.
[0004] Second, the non-uniformity of filler distribution and molding defects under high loading. In the development of passive thermal management materials, constructing a continuous thermally conductive network usually requires a high proportion of BN filler. However, the density difference and interfacial compatibility issues between BN particles and the PVA matrix make the system prone to phase separation during film formation. In existing technologies, the slow film formation rate allows sufficient settling time for the filler, resulting in a significant gradient deviation in the thickness direction of the film, which seriously affects the isotropic nature of the thermal management performance.
[0005] Third, there is a lack of research on the mechanism of rapid film formation triggered by alkali. Although some studies have used strong alkaline environments to treat BN surfaces, most studies only focus on the pretreatment stage of filler modification.
[0006] In summary, existing technologies struggle to achieve both the ability to induce BN synergistically to construct a stable three-dimensional thermally conductive network under alkaline conditions at room temperature or mild conditions, and to achieve controlled rapid film formation on a second / minute scale. Summary of the Invention
[0007] To address the problems of slow gelation / film formation in PVA-based composite systems and difficulty in dispersing boron nitride (BN) in PVA aqueous systems in existing technologies, this invention provides a polyvinyl alcohol-based boron nitride material, its preparation method, and its applications. The purpose of this invention is to: achieve rapid film formation of PVA-based composite systems under room temperature and alkaline conditions; introduce and pre-disperse BN particles to form a stable and dispersed network structure in the PVA matrix, and fully leverage their synergistic effect on film formation behavior under alkaline conditions; utilize alkaline solutions in the gelation process of the PVA / BN composite system to establish a "particle-dependent, alkali-triggered rapid film formation" strategy, thereby achieving controllable adjustment of the microstructure and macroscopic properties.
[0008] The technical solution adopted in this invention is as follows:
[0009] A method for preparing a polyvinyl alcohol-based boron nitride material includes the following steps:
[0010] S1: Prepare an aqueous solution of polyvinyl alcohol;
[0011] S2: Hexagonal boron nitride is treated with a surfactant to obtain a hexagonal boron nitride dispersion;
[0012] S3: Mix the polyvinyl alcohol aqueous solution obtained in S1 and the hexagonal boron nitride dispersion obtained in S2 to obtain a PVA / BN composite solution.
[0013] S4: Prepare an alkaline trigger solution, and bring the alkaline trigger solution into contact with and react with the PVA / BN composite solution obtained in S3 to obtain polyvinyl alcohol-based boron nitride material;
[0014] S1 and S2 have no order.
[0015] Preferably, the amounts of each component, by mass, are as follows: polyvinyl alcohol: 20-40 parts; hexagonal boron nitride particles: 10-70 parts; surfactant: 1-10 parts.
[0016] Preferably, the alkaline triggering agent is one or more of sodium hydroxide, potassium hydroxide, barium hydroxide, calcium hydroxide, sodium carbonate, sodium bicarbonate, and ammonia water.
[0017] Preferably, the pH value of the alkaline trigger is 9 to 14.
[0018] Preferably, the hexagonal boron nitride particles have a particle size of 0.1-10 μm.
[0019] Preferably, the polyvinyl alcohol is one or more of PVA1750, PVA1788, PVA1799, and PVA2488.
[0020] Preferably, the surfactant is one or more of sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, Span 80, Tween 20, and Tween 80.
[0021] Preferably, the polyvinyl alcohol-based boron nitride material obtained in S4 is in the form of a composite film or a gelled part.
[0022] Preferably, the steps for preparing the composite membrane include:
[0023] Step A: The PVA / BN composite solution obtained in S3 is coated onto the substrate by one of the following methods: casting, blade coating, or dip coating, to form a wet film;
[0024] Step B: Add or spray an alkaline solution to the wet film, or immerse the wet film directly in the alkaline solution to form it;
[0025] Step C: Wash and dry at room temperature to obtain the composite membrane;
[0026] When preparing gelled parts, an alkaline triggering agent solution is directly added to the PVA / BN composite solution obtained by S3 to form a mixture. The mixture is then pressed, cut, or subjected to secondary molding to obtain gelled parts of the desired shape.
[0027] Preferably, the amount of alkaline solution added or sprayed in step B is 0.03-0.11 mL / cm². 2 .
[0028] Preferably, in step S1, polyvinyl alcohol is first heated to 80–95°C and stirred until completely dissolved to obtain a polyvinyl alcohol aqueous solution with a mass fraction of 5–20 wt%; in step S3, the mass ratio of hexagonal boron nitride to polyvinyl alcohol is 0.1–2.0.
[0029] Preferably, the concentration of the alkaline trigger solution is 0.00001-1 mol / L.
[0030] Preferably, the mass ratio of hexagonal boron nitride to polyvinyl alcohol in S3 is 0.3 to 1.0.
[0031] A method for preparing polyvinyl alcohol-based boron nitride material.
[0032] Application of a polyvinyl alcohol-based boron nitride material or a polyvinyl alcohol-based boron nitride material prepared by the preparation method of polyvinyl alcohol-based boron nitride material in passive thermal management.
[0033] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:
[0034] 1. This invention constructs a process path of "PVA / surfactant-BN composite system + alkaline triggering", which can achieve rapid gelation or film shaping of PVA-based composite systems within a few seconds to tens of seconds under room temperature and mild alkaline conditions. It effectively overcomes the problems of long gelation time and long process cycle in the traditional PVA gel / film preparation process, and is suitable for rapid molding and in-situ curing.
[0035] 2. In this invention, BN particles are dispersed in water with a surfactant and then composited with a PVA solution. In an alkaline environment, the BN particles act as thermally conductive units and participate in network construction through interfacial interactions with PVA segments. Compared with systems lacking BN or with improper BN addition order, the PVA-based BN composite gel or composite film obtained by this invention exhibits higher thermal conductivity, better mechanical stability, and dimensional stability.
[0036] 3. This invention reveals and utilizes the core mechanism of "BN particle-dependent alkaline-triggered rapid film formation." Experiments show that the physical morphology and microstructure of the system exhibit significant sensitivity to the order of addition. When BN particles are pre-dispersed at the molecular level in a PVA / surfactant / metal ion system, and then triggered by an alkaline medium, the system exhibits interface-induced global synchronous gelation behavior. Under this pathway, the edge active sites of BN particles can form an ordered dynamic cross-linked network with PVA molecular chains at the moment of alkaline triggering, which not only significantly shortens the film formation time but also results in good ionic uniformity within the film. If the addition order is changed, although the system can still gel, it exhibits uneven dispersion and obvious instability. Under these conditions, the interfacial bonding between BN particles and the matrix is weak, and the filler remains mostly in fragmented agglomeration form, leading to problems such as uneven physical properties, loose structure, and stress concentration within the film, making it difficult to form an effective and efficient thermal conduction pathway.
[0037] 4. This invention uses common raw materials such as PVA, BN, conventional surfactants and sodium hydroxide. The preparation process is carried out in an aqueous phase, at normal pressure and mild temperature. It does not require toxic crosslinking agents or complex multiple freeze-thaw processes. The process is simple and the conditions are mild, making it suitable for scale-up and industrial applications. It can be widely used in the field of passive thermal management films. Attached Figure Description
[0038] Figure 1 The image shows the FTIR characterization of the raw materials and products prepared in Example 5 of this invention.
[0039] Figure 2 The images show the SEM characterization of the product of Example 5 in this invention at different magnifications.
[0040] Figure 3This is a schematic diagram of the film formation of the product in Example 5 of the present invention, where ah is a photograph of each step in the preparation and molding process.
[0041] Figure 4 This is a schematic diagram of the stretching of the product of Example 5 in this invention, where ae represent different stretching conditions.
[0042] Figure 5 This is a diagram showing the film-forming effect in liquid in Example 5 of the present invention.
[0043] Figure 6 This is a comparison diagram of the molding effect in Example 5 of the present invention with and without the addition of an alkaline triggering agent.
[0044] Figure 7 The temperature control test diagrams are for products 2, 5, 6, and 7 in the embodiments of this invention.
[0045] Figure 8 This is a thermal buffering test diagram of the commercial thin film in this invention.
[0046] Figure 9 This is a thermal buffer test diagram of the product of Example 2 in this invention.
[0047] Figure 10 This is a thermal buffer test diagram of the product of Example 5 in this invention.
[0048] Figure 11 This is a thermal buffer test diagram of the product of Example 6 in this invention.
[0049] Figure 12 This is a thermal buffer test diagram of the product of Example 7 in this invention.
[0050] Figure 13 This is a product diagram of Comparative Example 1 in this invention.
[0051] Figure 14 This is a product diagram of Comparative Example 2 in this invention.
[0052] Figure 15 A product diagram of Comparative Example 3 in this invention.
[0053] Figure 16 Product diagrams of Comparative Examples 4, 5, and 6 in this invention. Detailed Implementation
[0054] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.
[0055] To enhance the moisture absorption and water retention properties of the film, lithium chloride was introduced into the original film formation process.
[0056] Example 1
[0057] A method for preparing a polyvinyl alcohol-based boron nitride material includes the following steps:
[0058] S1: Weigh 10 g of PVA (PVA1799), add 90 g of deionized water, stir at 95 ℃ for 2 h until PVA is completely dissolved, and obtain a PVA aqueous solution with a mass fraction of 10 wt%. Cool to room temperature for later use.
[0059] S2: Weigh 5 g of BN powder with a flake size of 100 nm, add 0.5 g of Tween 80, add 10 g of deionized water, stir mechanically for 10 min, and sonicate for 10 min to obtain a stable hexagonal boron nitride dispersion.
[0060] S3: At room temperature, the BN dispersion prepared in S2 is slowly added to the PVA solution in S1, so that the mass percentage of BN in the film is 3wt%. At the same time, the mixture is stirred at 100-300 r / min for 10 min until BN is uniformly dispersed in the PVA solution, thus obtaining a PVA / BN composite solution.
[0061] S4: Prepare a wet film from the PVA / BN composite solution according to the desired morphology, and spray a 0.1 mol / L NaOH aqueous solution onto the surface of the wet film at a spraying rate of 0.1 mL / cm². 2 The wet film rapidly changes from a flowable state to a non-flowable state within about 5 to 15 seconds, resulting in a polyvinyl alcohol-based boron nitride composite film.
[0062] Example 2
[0063] A method for preparing a polyvinyl alcohol-based boron nitride material includes the following steps:
[0064] S1: Weigh 10 g of PVA (PVA1799), add 90 g of deionized water, stir at 95 ℃ for 2 h until PVA is completely dissolved, and obtain a PVA aqueous solution with a mass fraction of 10 wt%. Cool to room temperature for later use.
[0065] S2: Weigh 5 g of BN powder with a flake size of 500 nm, add 0.5 g of Tween 80, add 10 g of deionized water, stir mechanically for 10 min, and sonicate for 10 min to obtain a stable hexagonal boron nitride dispersion.
[0066] S3: At room temperature, the BN dispersion prepared in S2 is slowly added to the PVA solution in S1, so that the mass percentage of BN in the film is 3wt%. At the same time, the mixture is stirred at 100-300 r / min for 10 min until BN is uniformly dispersed in the PVA solution, thus obtaining a PVA / BN composite solution.
[0067] S4: Prepare a wet film from the PVA / BN composite solution according to the desired morphology, and spray a 0.1 mol / L NaOH aqueous solution onto the surface of the wet film at a spraying rate of 0.1 mL / cm². 2 The wet film rapidly changes from a flowable state to a non-flowable state within about 5 to 15 seconds, resulting in a polyvinyl alcohol-based boron nitride composite film.
[0068] Example 3
[0069] A method for preparing a polyvinyl alcohol-based boron nitride material includes the following steps:
[0070] S1: Weigh 10 g of PVA (PVA1799), add 90 g of deionized water, stir at 95 ℃ for 2 h until PVA is completely dissolved, and obtain a PVA aqueous solution with a mass fraction of 10 wt%. Cool to room temperature for later use.
[0071] S2: Weigh 5 g of BN powder with a flake size of 1 μm, add 0.5 g of Tween 80, add 10 g of deionized water, stir mechanically for 10 min, and sonicate for 10 min to obtain a stable hexagonal boron nitride dispersion.
[0072] S3: At room temperature, the BN dispersion prepared in S2 is slowly added to the PVA solution in S1, so that the mass percentage of BN in the film is 3wt%. At the same time, the mixture is stirred at 100-300 r / min for 10 min until BN is uniformly dispersed in the PVA solution, thus obtaining a PVA / BN composite solution.
[0073] S4: Prepare a wet film from the PVA / BN composite solution according to the desired morphology, and spray a 0.1 mol / L NaOH aqueous solution onto the surface of the wet film at a spraying rate of 0.1 mL / cm². 2 The wet film rapidly changes from a flowable state to a non-flowable state within about 5 to 15 seconds, resulting in a polyvinyl alcohol-based boron nitride composite film.
[0074] Example 4
[0075] A method for preparing a polyvinyl alcohol-based boron nitride material includes the following steps:
[0076] S1: Weigh 10 g of PVA (PVA1799), add 90 g of deionized water, stir at 95 ℃ for 2 h until PVA is completely dissolved, and obtain a PVA aqueous solution with a mass fraction of 10 wt%. Cool to room temperature for later use.
[0077] S2: Weigh 5 g of BN powder with a flake size of 10 μm, add 0.5 g of Tween 80 and 10 g of deionized water, stir mechanically for 10 min, and sonicate for 10 min to obtain a stable hexagonal boron nitride dispersion.
[0078] S3: At room temperature, the BN dispersion prepared in S2 is slowly added to the PVA solution in S1, so that the mass percentage of BN in the film is 3wt%. At the same time, the mixture is stirred at 100-300 r / min for 10 min until BN is uniformly dispersed in the PVA solution, thus obtaining a PVA / BN composite solution.
[0079] S4: Prepare a wet film from the PVA / BN composite solution according to the desired morphology, and spray a 0.1 mol / L NaOH aqueous solution onto the surface of the wet film at a spraying rate of 0.1 mL / cm². 2 The wet film rapidly changes from a flowable state to a non-flowable state within about 5 to 15 seconds, resulting in a polyvinyl alcohol-based boron nitride composite film.
[0080] Example 5
[0081] A method for preparing a polyvinyl alcohol-based boron nitride material includes the following steps:
[0082] S1: Weigh 10 g of PVA (PVA1799), add 90 g of deionized water, stir at 95 ℃ for 2 h until PVA is completely dissolved, and obtain a PVA aqueous solution with a mass fraction of 10 wt%. Cool to room temperature for later use.
[0083] S2: Weigh 5 g of BN powder with a flake size of 500 nm, add 0.5 g of Tween 80, add 10 g of deionized water, stir mechanically for 10 min, and sonicate for 10 min to obtain a stable hexagonal boron nitride dispersion.
[0084] S3: At room temperature, the BN dispersion prepared in S2 is slowly added to the PVA solution in S1, so that the mass percentage of BN in the film is 6wt%. At the same time, the mixture is stirred at 100-300 r / min for 10 min until BN is uniformly dispersed in the PVA solution, thus obtaining a PVA / BN composite solution.
[0085] S4: Prepare a wet film from the PVA / BN composite solution according to the desired morphology, and spray a 0.1 mol / L NaOH aqueous solution onto the surface of the wet film at a spraying rate of 0.1 mL / cm². 2 The wet film rapidly changes from a flowable state to a non-flowable state within about 5 to 15 seconds, resulting in a polyvinyl alcohol-based boron nitride composite film.
[0086] Example 6
[0087] A method for preparing a polyvinyl alcohol-based boron nitride material includes the following steps:
[0088] S1: Weigh 10 g of PVA (PVA1799), add 90 g of deionized water, stir at 95 ℃ for 2 h until PVA is completely dissolved, and obtain a PVA aqueous solution with a mass fraction of 10 wt%. Cool to room temperature for later use.
[0089] S2: Weigh 5 g of BN powder with a flake size of 500 nm, add 0.5 g of Tween 80, add 10 g of deionized water, stir mechanically for 10 min, and sonicate for 10 min to obtain a stable hexagonal boron nitride dispersion.
[0090] S3: At room temperature, the BN dispersion prepared in S2 is slowly added to the PVA solution in S1, so that the mass percentage of BN in the film is 9wt%. At the same time, the mixture is stirred at 100-300 r / min for 10 min until BN is uniformly dispersed in the PVA solution, thus obtaining a PVA / BN composite solution.
[0091] S4: Prepare a wet film from the PVA / BN composite solution according to the desired morphology, and spray a 0.1 mol / L NaOH aqueous solution onto the surface of the wet film at a spraying rate of 0.1 mL / cm². 2The wet film rapidly changes from a flowable state to a non-flowable state within about 5 to 15 seconds, resulting in a polyvinyl alcohol-based boron nitride composite film.
[0092] Example 7
[0093] A method for preparing a polyvinyl alcohol-based boron nitride material includes the following steps:
[0094] S1: Weigh 10 g of PVA (PVA1799), add 90 g of deionized water, stir at 95 ℃ for 2 h until PVA is completely dissolved, and obtain a PVA aqueous solution with a mass fraction of 10 wt%. Cool to room temperature for later use.
[0095] S2: Weigh 5 g of BN powder with a flake size of 500 nm, add 0.5 g of Tween 80, add 10 g of deionized water, stir mechanically for 10 min, and sonicate for 10 min to obtain a stable hexagonal boron nitride dispersion.
[0096] S3: At room temperature, the BN dispersion prepared in S2 is slowly added to the PVA solution in S1, so that the mass percentage of BN in the film is 12wt%. At the same time, the mixture is stirred at 100-300 r / min for 10 min until BN is uniformly dispersed in the PVA solution, thus obtaining a PVA / BN composite solution.
[0097] S4: Prepare a wet film from the PVA / BN composite solution according to the desired morphology, and spray a 0.1 mol / L NaOH aqueous solution onto the surface of the wet film at a spraying rate of 0.1 mL / cm². 2 The wet film rapidly changes from a flowable state to a non-flowable state within about 5 to 15 seconds, resulting in a polyvinyl alcohol-based boron nitride composite film.
[0098] Example 8
[0099] A method for preparing a polyvinyl alcohol-based boron nitride material includes the following steps:
[0100] S1: Weigh 10 g of PVA (PVA1799), add 90 g of deionized water, stir at 95 ℃ for 2 h until PVA is completely dissolved, and obtain a PVA aqueous solution with a mass fraction of 10 wt%. Cool to room temperature for later use.
[0101] S2: Weigh 5 g of BN powder with a flake size of 500 nm, add 0.5 g of Span 80, add 10 g of deionized water, stir mechanically for 10 min, and sonicate for 10 min to obtain a stable hexagonal boron nitride dispersion.
[0102] S3: At room temperature, the BN dispersion prepared in S2 is slowly added to the PVA solution in S1, so that the mass percentage of BN in the film is 6wt%. At the same time, the mixture is stirred at 100-300 r / min for 10 min until BN is uniformly dispersed in the PVA solution, thus obtaining a PVA / BN composite solution.
[0103] S4: Prepare a wet film from the PVA / BN composite solution according to the desired morphology, and spray a 0.1 mol / L NaOH aqueous solution onto the surface of the wet film at a spraying rate of 0.1 mL / cm². 2 The wet film rapidly changes from a flowable state to a non-flowable state within about 5 to 15 seconds, resulting in a polyvinyl alcohol-based boron nitride composite film.
[0104] Example 9
[0105] A method for preparing a polyvinyl alcohol-based boron nitride material includes the following steps:
[0106] S1: Weigh 10 g of PVA (PVA1799), add 90 g of deionized water, stir at 95 ℃ for 2 h until PVA is completely dissolved, and obtain a PVA aqueous solution with a mass fraction of 10 wt%. Cool to room temperature for later use.
[0107] S2: Weigh 5 g of BN powder with a flake size of 500 nm, add 0.5 g of Tween 80, add 10 g of deionized water, stir mechanically for 10 min, and sonicate for 10 min to obtain a stable hexagonal boron nitride dispersion.
[0108] S3: At room temperature, the BN dispersion prepared in S2 is slowly added to the PVA solution in S1, so that the mass percentage of BN in the film is 6wt%. At the same time, the mixture is stirred at 100-300 r / min for 10 min until BN is uniformly dispersed in the PVA solution, thus obtaining a PVA / BN composite solution.
[0109] S4: Prepare a wet film from the PVA / BN composite solution according to the desired morphology, and spray a 0.1 mol / L KOH aqueous solution onto the surface of the wet film at a spraying rate of 0.1 mL / cm². 2 The wet film rapidly changes from a flowable state to a non-flowable state within about 5 to 15 seconds, resulting in a polyvinyl alcohol-based boron nitride composite film.
[0110] Example 10
[0111] A method for preparing a polyvinyl alcohol-based boron nitride material includes the following steps:
[0112] S1: Weigh 10 g of PVA (PVA1788), add 90 g of deionized water, stir at 95 ℃ for 2 h until PVA is completely dissolved, and obtain a PVA aqueous solution with a mass fraction of 10 wt%. Cool to room temperature for later use.
[0113] S2: Weigh 5 g of BN powder with a flake size of 500 nm, add 0.5 g of Tween 80, add 10 g of deionized water, stir mechanically for 10 min, and sonicate for 10 min to obtain a stable hexagonal boron nitride dispersion.
[0114] S3: At room temperature, the BN dispersion prepared in S2 is slowly added to the PVA solution in S1, so that the mass percentage of BN in the film is 6wt%. At the same time, the mixture is stirred at 100-300 r / min for 10 min until BN is uniformly dispersed in the PVA solution, thus obtaining a PVA / BN composite solution.
[0115] S4: Prepare a wet film from the PVA / BN composite solution according to the desired morphology, and spray a 0.1 mol / L NaOH aqueous solution onto the surface of the wet film at a spraying rate of 0.1 mL / cm². 2 The wet film rapidly changes from a flowable state to a non-flowable state within about 5 to 15 seconds, resulting in a polyvinyl alcohol-based boron nitride composite film.
[0116] Example 11
[0117] A method for preparing a polyvinyl alcohol-based boron nitride material includes the following steps:
[0118] S1: Weigh 10 g of PVA (PVA1788), add 90 g of deionized water, stir at 95 ℃ for 2 h until PVA is completely dissolved, and obtain a PVA aqueous solution with a mass fraction of 10 wt%. Cool to room temperature for later use.
[0119] S2: Weigh 5 g of BN powder with a flake size of 500 nm, add 0.5 g of Tween 80, add 10 g of deionized water, stir mechanically for 10 min, and sonicate for 10 min to obtain a stable hexagonal boron nitride dispersion.
[0120] S3: At room temperature, the BN dispersion prepared in S2 is slowly added to the PVA solution in S1, so that the mass percentage of BN in the film is 6wt%. At the same time, the mixture is stirred at 100-300 r / min for 10 min until BN is uniformly dispersed in the PVA solution, thus obtaining a PVA / BN composite solution.
[0121] S4: Under gentle stirring, a small amount of NaOH aqueous solution (0.1 mol / L) was slowly added dropwise to the above PVA / BN composite solution. The system rapidly transformed from a flowable state to a non-flowable gel block within approximately 5–15 seconds. This gel block was then pressed, cut, or subjected to secondary molding to obtain the desired shape. The gel block obtained in this embodiment exhibited a tough texture and good formability. Pressing could produce composite films with smooth surfaces and adjustable thicknesses; during cutting, the sample cross-sections were clean and free of burrs. Macroscopic characterization showed that the BN filler was uniformly distributed in the gel system, without sedimentation, stratification, or agglomeration. The results indicate that the alkali-induced rapid gelation process effectively solves the problem of uniform dispersion of high-load fillers, demonstrating excellent process applicability.
[0122] Comparative Example 1
[0123] A method for preparing a polyvinyl alcohol-based boron nitride material includes the following steps:
[0124] S1: Weigh 10 g of PVA (PVA1799), add 90 g of deionized water, stir at 95 ℃ for 2 h until PVA is completely dissolved, and obtain a PVA aqueous solution with a mass fraction of 10 wt%. Cool to room temperature for later use.
[0125] S2: Weigh 5 g of BN powder with a flake size of 500 nm, add 0.5 g of Tween 80, add 10 g of deionized water, stir mechanically for 10 min, and sonicate for 10 min to obtain a stable hexagonal boron nitride dispersion.
[0126] S3: At room temperature, the BN dispersion prepared in S2 is slowly added to the PVA solution in S1, so that the mass percentage of BN in the film is 6wt%. At the same time, the mixture is stirred at 100-300 r / min for 10 min until BN is uniformly dispersed in the PVA solution, thus obtaining a PVA / BN composite solution.
[0127] S4: Prepare a wet film from the PVA / BN composite solution according to the desired morphology, and spray a 0.1 mol / L NaCl aqueous solution onto the surface of the wet film at a spraying rate of 0.1 mL / cm². 2 Observe whether a film can be formed.
[0128] Comparative Example 2
[0129] A method for preparing a polyvinyl alcohol-based boron nitride material includes the following steps:
[0130] S1: Weigh 10 g of PVA (PVA1799), add 90 g of deionized water, stir at 95 ℃ for 2 h until PVA is completely dissolved, and obtain a PVA aqueous solution with a mass fraction of 10 wt%. Cool to room temperature for later use.
[0131] S2: Weigh 5 g of BN powder with a flake size of 500 nm, add 0.5 g of Tween 80, add 10 g of deionized water, stir mechanically for 10 min, and sonicate for 10 min to obtain a stable hexagonal boron nitride dispersion.
[0132] S3: At room temperature, the BN dispersion prepared in S2 is slowly added to the PVA solution in S1, so that the mass percentage of BN in the film is 6wt%. At the same time, the mixture is stirred at 100-300 r / min for 10 min until BN is uniformly dispersed in the PVA solution, thus obtaining a PVA / BN composite solution.
[0133] S4: Prepare a wet film from the PVA / BN composite solution according to the desired morphology, and spray a 0.1 mol / L HCl aqueous solution onto the surface of the wet film at a spraying rate of 0.1 mL / cm². 2 Observe whether a film can be formed.
[0134] Comparative Example 3
[0135] A method for preparing a polyvinyl alcohol-based boron nitride material includes the following steps:
[0136] S1: Weigh 10 g of PVA (PVA1799), add 90 g of deionized water, stir at 95 ℃ for 2 h until PVA is completely dissolved, and obtain a PVA aqueous solution with a mass fraction of 10 wt%. Cool to room temperature for later use.
[0137] S2: Weigh 5 g of BN powder with a flake size of 500 nm, add 0.5 g of Tween 80, add 10 g of deionized water, stir mechanically for 10 min, and sonicate for 10 min to obtain a stable hexagonal boron nitride dispersion.
[0138] S3: At room temperature, the BN dispersion prepared in S2 is slowly added to the PVA solution in S1, so that the mass percentage of BN in the film is 6wt%. At the same time, the mixture is stirred at 100-300 r / min for 10 min until BN is uniformly dispersed in the PVA solution, thus obtaining a PVA / BN composite solution.
[0139] S4: Let stand for 3-5 minutes and observe whether a film can form.
[0140] Comparative Example 4
[0141] A method for preparing a polyvinyl alcohol-based boron nitride material includes the following steps:
[0142] S1: Weigh 10 g of PVA (PVA1799), add 90 g of deionized water, and stir at 95 ℃ for 2 h until the PVA is completely dissolved to obtain a 10 wt% PVA aqueous solution. Cool to room temperature for later use. Slowly add a 0.1 mol / L NaOH aqueous solution to the PVA aqueous solution, using the same amount as in Example 1, to obtain a mixed solution.
[0143] S2: Weigh 5 g of BN powder with a flake size of 500 nm, add 0.5 g of Tween 80, add 10 g of deionized water, stir mechanically for 10 min, and sonicate for 10 min to obtain a stable hexagonal boron nitride dispersion.
[0144] S3: At room temperature, the BN dispersion obtained in S2 is slowly added to the mixed solution obtained in S1, so that the mass percentage of BN in the film is 6wt%. At the same time, the mixture is stirred at 100-300 r / min for 10 min until BN is uniformly dispersed in the mixed solution to obtain a PVA / BN composite solution.
[0145] S4: Let stand for 3-5 minutes and observe whether a film can form.
[0146] Comparative Example 5
[0147] A method for preparing a polyvinyl alcohol-based boron nitride material includes the following steps:
[0148] S1: Weigh 10 g of PVA (PVA1799), add 90 g of deionized water, stir at 95 ℃ for 2 h until PVA is completely dissolved, and obtain a PVA aqueous solution with a mass fraction of 10 wt%. Cool to room temperature for later use.
[0149] S2: Weigh 5 g of BN powder with a flake size of 500 nm, add 0.5 g of Tween 80 and 10 g of deionized water, stir mechanically for 10 min, and sonicate for 10 min to obtain a stable hexagonal boron nitride dispersion; slowly add 0.1 mol / L NaOH aqueous solution to the hexagonal boron nitride dispersion, the amount of which is the same as in Example 1, to obtain a mixed solution;
[0150] S3: At room temperature, the mixed solution obtained in S2 is slowly added to the mixed solution obtained in S1, so that the mass percentage of BN in the film is 6wt%. At the same time, the mixture is stirred at 100-300 r / min for 10 min until BN is uniformly dispersed in the mixed solution to obtain a PVA / BN composite solution.
[0151] S4: Let stand for 3-5 minutes and observe whether a film can form.
[0152] Comparative Example 6
[0153] A method for preparing a polyvinyl alcohol-based boron nitride material includes the following steps:
[0154] S1: Weigh 10 g of PVA (PVA1799), add 90 g of deionized water, stir at 95 ℃ for 2 h until PVA is completely dissolved, and obtain a PVA aqueous solution with a mass fraction of 10 wt%. Cool to room temperature for later use.
[0155] S2: Weigh 5 g of BN powder with a flake size of 500 nm, add 0.5 g of Tween 80, add 10 g of deionized water, stir mechanically for 10 min, and sonicate for 10 min to obtain a stable hexagonal boron nitride dispersion.
[0156] S3: At room temperature, the mixed solution obtained in S2 and a 0.1 mol / L NaOH aqueous solution (the same amount as in Example 1) are slowly added to the mixed solution obtained in S1, so that the mass percentage of BN in the film is 6 wt%. At the same time, the mixture is stirred at 100-300 r / min for 10 min until BN is uniformly dispersed in the mixed solution, thus obtaining a PVA / BN composite solution;
[0157] S4: Let stand for 3-5 minutes and observe whether a film can form.
[0158] The parameter changes of Examples 1-11 and Comparative Examples 1-6 are shown in Table 1 below:
[0159] Table 1
[0160]
[0161] It should be noted that Example 5 is a preferred embodiment with good self-healing properties. To demonstrate the technical effects achieved by the present invention, the relevant characterization results of the product obtained in Example 5 will be provided below:
[0162] The FTIR of the material used in Example 5 is as follows: Figure 1As shown, the various components in the thin film not only exhibit the superposition of physical quantities but also the effect of new chemical bonds. Specifically, under the catalysis of NaOH, the BN surface bonds with the PVA hydroxyl groups, forming B–O–C bonds or boron-oxygen coordination bonds. At the same time, a small amount of boric acid particles further initiate the rapid film formation of the mixed solution.
[0163] Microscopic SEM of the product in Example 5 Figure 2 As shown, the cross-section of the composite film consists of a continuous PVA phase and lamellar BN. Obvious filamentous bridging structures and void morphologies can be observed in the cross-section, indicating that the matrix underwent significant ductile stretching and networking during film formation, thus forming a connected framework structure at the microscopic level and fixing and bridging the BN. This suggests that the system more readily and rapidly forms a continuous phase and locks in the filler distribution under the influence of trace amounts of NaOH, which is consistent with the macroscopic phenomenon of rapid film formation.
[0164] The film formation of the product in Example 5 is shown in the figure below. Figure 3 As shown, the solution can form a film rapidly under the action of an alkaline solution, while neither BN alone nor alkaline solution alone can form a film rapidly. The figure also shows that the sized film has a uniform appearance, no obvious cracks, and good flexibility and shape retention.
[0165] A schematic diagram of the mechanical properties of the product in Example 5 is shown below. Figure 4 As shown, from Figure 4 As can be seen, the film exhibits excellent overall flexibility and deformation adaptability, as well as strong tensile, bending, and curling properties. The film can be stretched to more than twice its original length without breaking; at the same time, it can withstand repeated bending and even folding, without white marks or cracks at the bending points, demonstrating outstanding resistance to bending fatigue.
[0166] Example 5: Film formation effect in liquid. Figure 5 ,exist Figure 5 The petri dish contained a 0.1 mol / L NaOH aqueous solution. Figure 5 As can be seen, the PVA / BN composite solution can be rapidly molded after being extruded from the syringe into the NaOH aqueous solution.
[0167] The molding effect of the PVA / BN composite solution obtained in S3 in Example 5, whether or not an alkaline triggering agent is added, is as follows: Figure 6 As shown, from Figure 6 As can be seen, adding an alkaline trigger can accelerate molding.
[0168] To evaluate the overall heat dissipation, temperature uniformity, and thermal buffering performance of the thin film under bottom heat source impact, a continuous 3600-second temperature-controlled test was conducted on each sample at a simulated heat flux of 1000 W / m². The test covered a continuous heating phase of 0-1800 seconds and a natural cooling phase of 1800-3600 seconds. The test results are shown in the curves below. Figure 7 As shown. From Figure 7 As can be clearly seen, the ambient temperature remained stable at approximately 23°C throughout the test. During the continuous heating phase from 0 to 1800 seconds, the surface temperature of the blank sample rapidly and significantly increased, reaching a peak equilibrium temperature of approximately 51.5°C at 1800 seconds, indicating a severe lack of effective heat dissipation channels. The commercial film exhibited moderate temperature control, with a maximum temperature reaching approximately 47.1°C. In contrast, the composite films of Examples 2, 5, 6, and 7 of this invention demonstrated exceptionally superior temperature suppression performance. Their temperature rise curves rapidly slowed down after the initial stage and entered a steady state. In particular, Example 6 effectively suppressed its maximum steady-state temperature to approximately 34.2°C; Example 5 also stabilized at approximately 35.0°C. Compared to the blank sample and the commercial film, Example 6 achieved significant temperature drops of up to 17.3°C and 12.9°C, respectively. This result strongly confirms that the dense and uniform thermally conductive filler network within the composite film of this invention not only possesses excellent longitudinal heat-blocking capabilities but also enables rapid in-plane heat distribution. More importantly, during the natural cooling phase after the removal of the underlying heat source at 1800 seconds, all samples began to cool down towards ambient temperature. It was observed that the blank sample, lacking thermal buffering capacity, experienced the steepest cooling rate, with its temperature rapidly reaching its lowest point. In contrast, the cooling curves of the composite films in the various embodiments (especially Examples 5 and 6) were relatively gentle, and their temperatures were slightly higher than the blank sample at the end of the 3600-second test. This significant characteristic of the cooling range further confirms that the interconnected network formed by the filler under alkaline triggering not only significantly improves the heat transfer and dissipation capabilities of the film but also significantly increases the overall specific heat capacity of the material, enabling it to exhibit stronger thermal buffering capacity and temperature stability characteristics when facing rapid changes in the dynamic thermodynamic environment.
[0169] To thoroughly evaluate the optical cooling and long-term thermal management mechanisms of the thin films under extreme illumination conditions, a continuous temperature control test lasting 3600 seconds was conducted on the commercial thin films and various embodiments under high-intensity simulated sunlight (xenon lamp) at 1000 W / m². The results correspond to... Figures 8 to 12 .observe Figure 10 It can be seen that the commercial thin film exhibits a continuous heat absorption and temperature rise trend under light irradiation. After one hour of testing, the temperature rose sharply from room temperature to nearly 47.0°C, and the entire curve extended smoothly to the upper right, without showing a clear steady-state limit. This indicates that its reflectivity to sunlight is insufficient, making it prone to heat accumulation internally. In stark contrast, such as Figure 9 (Example 2) Figure 10 (Example 5) Figure 11 (Example 6) and Figure 12 As shown in Example 7, the composite film of the present invention rapidly (approximately 600 seconds) enters a thermodynamic steady state after a brief initial temperature rise during the initial testing phase. Its maximum steady-state temperature is firmly controlled at an extremely low level of 31.3°C to 32.8°C, achieving a significant temperature drop of approximately 15°C compared to commercial films, demonstrating excellent photothermal blocking and continuous passive radiative cooling capabilities. Of particular note are the microscopic fluctuation characteristics within the temperature steady-state range. Compared to commercial films (… Figure 8 ) and the thin films of each embodiment ( Figure 9-12 It can be observed that the temperature rise curve of commercial films remains consistently smooth. The composite film of this invention not only relies on passive radiative heat dissipation from the atmosphere, but its unique network structure also continuously experiences active moisture response and water decomposition and absorption processes. The film effectively couples with the absorption of environmental moisture and continuously evaporates to remove latent heat of phase change under photothermal triggering, thus creating localized temperature fluctuations at the microscopic level. This dual mechanism of synergistic cooling through radiative cooling and evaporative latent heat is the core reason why the embodiments of this invention can break the limit of single radiative cooling, achieve extremely low steady-state temperatures and superior temperature control performance under prolonged high-intensity light irradiation.
[0170] As can be seen from the above, Examples 2, 5, 6, and 7 are all superior to commercial films under conditions of light-induced cooling and bottom heat flow impact, indicating that they have significant advantages in photothermal regulation and dynamic thermal buffering under complex thermodynamic environments.
[0171] The test results under xenon lamps in Examples 2, 5, 6, and 7 are shown in Table 2:
[0172] Table 2
[0173]
[0174] The test results for the heating elements in Examples 2, 5, 6, and 7 are shown in Table 3.
[0175] Table 3
[0176]
[0177] As can be seen from Tables 2 and 3, under simulated xenon lamp illumination (1000 W / m²), the steady-state maximum temperature of Examples 2, 5, 6, and 7 is significantly lower than that of the commercial film. Among them, Example 6 reaches a minimum temperature of 31.3℃ under high humidity conditions, exhibiting the best cooling effect; the temperatures of Examples 2, 5, and 7 are also stable between 31.6 and 32.8℃, all of which are superior to the commercial film (46.6℃), indicating that the samples of the present invention have good optical cooling performance and exhibit stable performance under different environmental humidity conditions.
[0178] Under simulated heat flow conditions (1000 W / m²), the test results of the heating element (Table 3) show that the steady-state top and bottom temperatures of the samples in each embodiment are significantly lower than those of the blank sample (approximately 51.5 °C) and the commercial film (approximately 47.1 °C). Among them, Example 6 shows particularly outstanding performance in terms of bottom temperature control, demonstrating excellent heat conduction and heat dissipation performance.
[0179] In summary, Examples 2, 5, 6, and 7 outperformed commercial films under both light-induced cooling and heat flow conditions, demonstrating their significant advantages in photothermal regulation. Among them, Examples 5 and 6 showed particularly outstanding performance.
[0180] The solution of Comparative Example 1 is as follows Figure 13 As shown, the lack of a necessary alkaline trigger means it remains in solution and cannot form a stable film.
[0181] The solution of Comparative Example 2 is as follows Figure 14 As shown, the lack of a necessary alkaline trigger means it remains in solution and cannot form a stable film.
[0182] The solution of Comparative Example 3 is as follows Figure 15 As shown, the lack of a necessary alkaline trigger means it remains in solution and cannot form a stable film.
[0183] The effect of comparison ratios 4-6 is as follows Figure 16 As shown, although both methods can form thin films, the film formation effect is poor and the uniformity inside the film is poor due to the rapid effect triggered by alkaline conditions.
[0184] The embodiments described above merely illustrate specific implementation methods of this application, and while the descriptions are detailed and specific, they should not be construed as limiting the scope of protection of this application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the technical solution of this application, and these modifications and improvements all fall within the scope of protection of this application.
Claims
1. A method for preparing a polyvinyl alcohol-based boron nitride material, characterized in that: Includes the following steps: S1: Prepare an aqueous solution of polyvinyl alcohol; S2: Hexagonal boron nitride is treated with a surfactant to obtain a hexagonal boron nitride dispersion; S3: Mix the polyvinyl alcohol aqueous solution obtained in S1 and the hexagonal boron nitride dispersion obtained in S2 to obtain a PVA / BN composite solution. S4: Prepare an alkaline trigger solution, and bring the alkaline trigger solution into contact with and react with the PVA / BN composite solution obtained in S3 to obtain polyvinyl alcohol-based boron nitride material; S1 and S2 have no order.
2. The method for preparing a polyvinyl alcohol-based boron nitride material according to claim 1, characterized in that: The amounts of each component, by mass, are as follows: polyvinyl alcohol: 20-40 parts; hexagonal boron nitride particles: 10-70 parts; surfactant: 1-10 parts.
3. The method for preparing a polyvinyl alcohol-based boron nitride material according to claim 1, characterized in that: The pH value of the alkaline trigger is 9-14, and the alkaline trigger is one or more of sodium hydroxide, potassium hydroxide, barium hydroxide, calcium hydroxide, sodium carbonate, sodium bicarbonate, and ammonia water.
4. The method for preparing a polyvinyl alcohol-based boron nitride material according to claim 1, characterized in that: The particle size of hexagonal boron nitride particles is 0.1-10 μm.
5. The method for preparing a polyvinyl alcohol-based boron nitride material according to claim 1, characterized in that: The polyvinyl alcohol is one or more of PVA1750, PVA1788, PVA1799, and PVA2488, and the surfactant is one or more of sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, Span 80, Tween 20, and Tween 80.
6. A method for preparing a polyvinyl alcohol-based boron nitride material according to any one of claims 1-5, characterized in that: The polyvinyl alcohol-based boron nitride material obtained in S4 is in the form of a composite film or a gelled part.
7. The method for preparing a polyvinyl alcohol-based boron nitride material according to claim 6, characterized in that: The steps for preparing the composite membrane include: Step A: The PVA / BN composite solution obtained in S3 is coated onto the substrate by one of the following methods: casting, blade coating, or dip coating, to form a wet film; Step B: Add or spray an alkaline solution to the wet film, or immerse the wet film directly in the alkaline solution to form it; Step C: Wash and dry at room temperature to obtain the composite membrane; When preparing gelled parts, an alkaline triggering agent solution is directly added to the PVA / BN composite solution obtained by S3 to form a mixture. The mixture is then pressed, cut, or subjected to secondary molding to obtain gelled parts of the desired shape.
8. A method for preparing a polyvinyl alcohol-based boron nitride material according to any one of claims 1-5, characterized in that: In S1, polyvinyl alcohol is first heated to 80–95°C and stirred until completely dissolved to obtain a polyvinyl alcohol aqueous solution with a mass fraction of 5–20 wt%; in S3, the mass ratio of hexagonal boron nitride to polyvinyl alcohol is 0.1–2.
0.
9. A polyvinyl alcohol-based boron nitride material prepared by the preparation method of the polyvinyl alcohol-based boron nitride material according to any one of claims 1-8.
10. The application of the polyvinyl alcohol-based boron nitride material of claim 9 or the polyvinyl alcohol-based boron nitride material prepared by the preparation method of any one of claims 1-8 in passive thermal management.