Flexible heat-conducting composite material with chain-arranged boron nitride and preparation method of flexible heat-conducting composite material

Abstract

The invention discloses a flexible heat-conducting composite material with chain-shaped boron nitride and a preparation method, and belongs to the technical field of flexible electronic device heat management materials, the flexible heat-conducting composite material comprises an elastomer matrix and a magnetic functionalized boron nitride filler filled in the elastomer matrix; the elastomer matrix is polydimethylsiloxane; the magnetic functionalized boron nitride filler is prepared by modifying Fe3O4 nanoparticles on the surface of a boron nitride sheet; the boron nitride sheets form a vertically arranged chain structure in the elastomer matrix. The chained vertical arrangement of the boron nitride sheets is realized by prolonging the magnetic field treatment time, the Fe3O4 modification quantity is controlled to optimize the balance between the magnetic responsiveness and the heat-conducting property, a chained heat-conducting network connected end to end is formed, and the thermal seepage threshold value is reduced. According to the flexible composite material and the preparation method thereof, boron nitride sheets are induced to be vertically arranged through a magnetic field to form a chain-shaped heat-conducting network, so that high heat conductivity under low filler loading capacity is realized, and excellent stretchability is kept at the same time.

Description

Technical Field

[0001] This invention belongs to the field of thermal management materials technology for flexible electronic devices, specifically relating to a flexible thermally conductive composite material with chain-like boron nitride and its preparation method. Background Technology

[0002] As wearable electronic devices become increasingly integrated, consume more power, and shrink in size, the heat generated per unit area is also rising dramatically. Efficient heat dissipation has become a core challenge affecting device reliability, lifespan, and user experience. Excessive temperature not only leads to performance degradation or even damage to semiconductor components, but can also cause discomfort to the wearer due to localized overheating, and even pose a risk of burns. Against this backdrop, finding packaging materials that possess both excellent heat dissipation capabilities and maintain good flexibility and fit has become one of the key challenges driving the development of next-generation high-performance wearable technologies.

[0003] To address this challenge, current research largely focuses on developing elastomeric composites with high thermal conductivity. Elastomer materials such as silicone rubber and polyurethane are widely used in the encapsulation and protective layers of wearable devices due to their softness, stretchability, and ease of processing. However, their thermal conductivity is relatively poor (only 0.1-0.5 W·m). -1 ·K -1 This severely restricts the overall heat dissipation effect. The current mainstream technical approach is to add high thermal conductivity fillers to these polymer matrices to improve the overall thermal conductivity of the material by constructing effective thermal conduction channels. Among them, boron nitride has attracted much attention due to its unique two-dimensional lamellar structure and significant anisotropic thermal conductivity, with a horizontal thermal conductivity as high as approximately 600 W·m. -1 ·K -1 However, the vertical direction is only about 30 W·m. -1 ·K -1 Boron nitride possesses excellent electrical insulation properties, making it considered an ideal functional filler. Research typically employs processes such as mechanical mixing, solution casting, or in-situ polymerization to create a continuous thermally conductive network within the composite material. Furthermore, some researchers have explored combining boron nitride with other types of fillers or modifying its surface to enhance its compatibility with the polymer matrix, thereby further improving its thermal conductivity.

[0004] However, current research still faces many challenging problems. The most prominent contradiction lies in the fact that significantly improving thermal conductivity typically requires a filler content exceeding 30%. However, high filler content severely compromises the material's flexibility, disrupts the continuity of the polymer matrix, and leads to hardening, decreased tensile strength, and reduced flexibility, making it difficult to adapt to the dynamic usage requirements of wearable devices that involve frequent bending and skin contact. A more fundamental challenge is that during conventional mixing and molding processes, boron nitride sheets tend to be randomly distributed or arranged parallel to the substrate surface. This means that heat can only be transferred along the direction of weaker thermal conductivity in the material's thickness direction, failing to fully utilize its superior in-plane thermal conductivity. Although existing research has attempted to control filler orientation by applying magnetic fields and constructing templates, these methods are often complex, costly, and difficult to achieve stable vertical alignment of boron nitride sheets on a macroscopic scale, limiting the full realization of its heat dissipation potential. Furthermore, high filler content also leads to processing difficulties and increased interfacial thermal resistance, further restricting the performance of these materials in practical applications. Summary of the Invention

[0005] In order to overcome the shortcomings of the prior art, the present invention aims to provide a flexible thermally conductive composite material with chain-like boron nitride and a preparation method thereof, so as to solve the technical problem that existing elastomer composite materials are difficult to simultaneously possess high thermal conductivity and good flexibility.

[0006] To achieve the above objectives, the present invention employs the following technical solution: This invention discloses a flexible thermally conductive composite material with chain-like boron nitride, comprising: an elastomer matrix and magnetically functionalized boron nitride filler filled in the elastomer matrix; The elastomer matrix is ​​polydimethylsiloxane; The magnetic functionalized boron nitride filler was prepared by modifying the surface of boron nitride sheets with Fe3O4 nanoparticles. Boron nitride sheets form vertically arranged chain-like structures within an elastomer matrix.

[0007] Preferably, the magnetic functionalized boron nitride filler has a mass percentage content of 5-30 wt%; the mass ratio of boron nitride sheets to Fe3O4 nanoparticles is 2:1-30:1.

[0008] Preferably, the magnetic functionalized boron nitride filler has a mass percentage content of 15-20 wt%; the mass ratio of boron nitride sheets to Fe3O4 nanoparticles is 10:1.

[0009] Preferably, the interfacial thermal conductivity of the flexible thermally conductive composite material with chain-like boron nitride is 0.91-1.57 W·m. -1 ·K -1The elongation at break is 113-272%, and the Young's modulus is 0.40-1.43 MPa.

[0010] This invention also discloses a method for preparing the above-mentioned flexible thermally conductive composite material with chain-like boron nitride, comprising: Boron nitride was hydroxylated to obtain hydroxylated boron nitride; then modified with a silane coupling agent to obtain silanized boron nitride; finally, Fe3O4 nanoparticles were assembled onto the surface of silanized boron nitride by electrostatic self-assembly to obtain magnetically functionalized boron nitride filler; the magnetically functionalized boron nitride filler was dispersed in a solvent and ultrasonically treated, then mixed with an elastomer prepolymer, placed in a mold, and vacuum-treated and cured under a magnetic field to obtain a flexible thermally conductive composite material with chain-like boron nitride.

[0011] Preferably, the mass ratio of Fe3O4 nanoparticles to silanized boron nitride is 1:(2-30); the mass ratio of magnetic functionalized boron nitride filler to elastomer prepolymer is (15%-20%):(80%-85%).

[0012] Preferably, the magnetic field strength for vacuum treatment under a magnetic field is 100 mT; the vacuum treatment time under a magnetic field is 2-24 h; the curing temperature is 120℃; and the curing time is 1-2 h.

[0013] Preferably, the ultrasonic treatment time is 10-15 min; the solvent is n-hexane; the elastomer prepolymer is polydimethylsiloxane prepolymer; the elastomer prepolymer is prepared by mixing the base adhesive and the curing agent at a mass ratio of 10:1; the base adhesive is DC184; and the curing agent is DC184 curing agent.

[0014] Preferably, the conditions for hydroxylating boron nitride include: dispersing boron nitride powder in NaOH solution, heating and stirring to carry out hydroxylation treatment, vacuum filtration, washing until neutral, and freeze-drying to obtain hydroxylated boron nitride; The conditions for modification with silane coupling agents include: dissolving KH-550 in ethanol, adding hydroxylated boron nitride, stirring the reaction, vacuum filtering, and vacuum drying to obtain silanized boron nitride. The conditions for electrostatic self-assembly include: ultrasonically dispersing boron nitride silanized and Fe3O4 nanoparticles in deionized water, mixing the two dispersions, mechanically stirring, magnetically separating and collecting the products, and freeze-drying to obtain magnetically functionalized boron nitride filler.

[0015] Preferably, the preparation method of Fe3O4 nanoparticles includes: dissolving FeCl3·6H2O and FeSO4·7H2O in deionized water, mechanically stirring under nitrogen protection, adding ammonia solution dropwise until the pH value is 10, continuously stirring the reaction, collecting the product by magnetic separation, washing until neutral, and freeze-drying to obtain Fe3O4 nanoparticles.

[0016] Compared with the prior art, the present invention has the following beneficial effects: This invention discloses a flexible thermally conductive composite material with chain-like boron nitride. Through the synergistic design of material composition and microstructure, it achieves a balance between high thermal conductivity and good flexibility under low filler loading. Polydimethylsiloxane, as the elastomer matrix, provides basic flexibility and stretchability, ensuring that the material can deform under external stress without brittle fracture, thus maintaining the continuity and structural integrity of the matrix. Furthermore, the magnetically functionalized boron nitride filler acquires magnetic responsiveness by modifying the surface of the boron nitride sheets with Fe3O4 nanoparticles. Under the influence of an external magnetic field, the boron nitride sheets can move directionally and self-assemble into a vertically aligned chain structure. This chain structure fully utilizes the anisotropic advantage of high in-plane thermal conductivity of boron nitride, constructing a continuous thermal conduction path. Simultaneously, due to the low filler density, it effectively avoids the damage to the matrix flexibility caused by high loading, achieving a synergistic effect of optimized thermal conduction path and protection of mechanical properties. It effectively solves the problem of elastomeric composites having both high thermal conductivity and good flexibility under low filler loading; the formation of the chain-like thermal conductive network optimizes the heat conduction path and improves the heat conduction efficiency, while maintaining the stretchability of the material, thus meeting the comprehensive performance requirements of wearable electronic devices for thermal management materials.

[0017] Furthermore, by controlling the mass percentage of magnetically functionalized boron nitride filler within the range of 5-30 wt%, and setting the mass ratio of boron nitride sheets to Fe3O4 nanoparticles at 2:1-30:1, the magnetic dipole interaction generated by the Fe3O4 nanoparticles during magnetic field induction effectively drives the boron nitride sheets to connect end-to-end along the magnetic field direction, forming a chain-like thermally conductive network perpendicular to the matrix plane. Simultaneously, precise control of the filler content ensures that the matrix continuity is not disrupted, while the optimized mass ratio balances the magnetic response intensity and thermal interface efficiency. This achieves efficient construction of the thermally conductive network and simultaneous maintenance of material flexibility under low filler load conditions. This demonstrates the formation of a continuous vertical chain-like thermally conductive network under low filler load, effectively improving interfacial thermal conductivity while maintaining the continuity and excellent stretchability of the elastomer matrix, thus resolving the technical contradiction between enhanced thermal management performance and guaranteed mechanical flexibility.

[0018] Furthermore, by precisely limiting the filler content to 15-20 wt% and setting the mass ratio of boron nitride sheets to Fe3O4 nanoparticles to 10:1, the filler can form a tightly connected vertical chain structure during magnetic field induction. This structure maintains the high in-plane thermal conductivity of the boron nitride sheets while providing sufficient magnetic response driving force through an appropriate amount of Fe3O4 nanoparticles. This achieves continuity and integrity of the thermal conduction path under low filler loading conditions, while effectively maintaining the molecular chain mobility of the elastomer matrix. This effectively coordinates the inherent contradiction between the construction of the thermal conduction network and the maintenance of material flexibility, significantly improving the synergistic performance of the composite material in wearable device thermal management applications.

[0019] Furthermore, by controlling the interfacial thermal conductivity within the range of 0.91–1.57 W·m -1 ·K -1 Within a certain range, the vertically aligned boron nitride chains ensure a continuous thermal conductivity pathway, enabling efficient heat transfer along the vertical direction. Simultaneously, the elongation at break remains at 113-272%, indicating that the interfacial bonding between the elastomer matrix and the functionalized filler effectively disperses tensile stress. The Young's modulus ranges from 0.40 to 1.43 MPa, providing sufficient mechanical support to prevent excessive deformation while avoiding excessive stiffness that could reduce comfort. This allows the material to maintain a stable balance of thermo-mechanical properties under different processing conditions. It ensures the stability of the performance indicators of the flexible thermally conductive composite material during actual production, enabling reliable application in the thermal management of wearable electronic devices and meeting their stringent requirements for consistency and reliability.

[0020] The method for preparing the above-mentioned flexible thermally conductive composite material with chain-like boron nitride disclosed in this invention combines the preparation of magnetically functionalized boron nitride filler with a magnetic field induction process, thereby achieving a vertical chain-like arrangement of boron nitride sheets to construct a highly efficient thermally conductive network under low filler loading, achieving the effect of simultaneously improving thermal conductivity and maintaining material flexibility. Hydroxylation introduces active hydroxyl groups onto the boron nitride surface, significantly enhancing surface energy and providing chemical bonding sites for subsequent silane coupling agent modification, thus improving the interfacial compatibility between the filler and the matrix. The bifunctional groups of the silane coupling agent form a stable interfacial layer on the filler surface, ensuring the directional adhesion of Fe3O4 nanoparticles and optimizing magnetic response efficiency. Electrostatic self-assembly precisely controls the uniform distribution and strong bonding of Fe3O4 nanoparticles, endowing the filler with controllable magnetic response characteristics. Solvent environment combined with ultrasonic treatment effectively dissociates filler agglomerates, achieving uniform nanoscale dispersion. Sufficient miscibility between the elastomer prepolymer and the dispersed filler maintains the stability of the suspension system. A magnetic field drives the magnetic filler to move vertically, forming a chain structure; vacuum treatment simultaneously eliminates bubble defects; and the curing process locks the arrangement morphology, ultimately constructing a continuous vertical thermal conductivity pathway. This maximizes the utilization of the high in-plane thermal conductivity of boron nitride with low filler content. This effectively solves the technical bottleneck of elastomeric composites struggling to balance high thermal conductivity and good flexibility with low filler loading.

[0021] Furthermore, by precisely controlling the mass ratio of Fe3O4 nanoparticles to silanized boron nitride, sufficient magnetic moment is ensured for the boron nitride sheets to achieve directional rotation and chain-like connections under the influence of a magnetic field, while avoiding structural disorder caused by excessive magnetism. By limiting the mass ratio of magnetically functionalized boron nitride filler to elastomer prepolymer, the filler loading is designed to form an effective thermally conductive network without significantly affecting the flexibility of the matrix. This allows the boron nitride sheets to stably form a vertically aligned chain structure during magnetic field treatment, thus achieving a balance between high thermal conductivity and excellent flexibility with a low filler loading.

[0022] Furthermore, by synergistically controlling the magnetic field strength, processing time, curing temperature, and curing time, under a magnetic field strength of 100 mT, the magnetically functionalized boron nitride filler obtains a suitable magnetic driving force, driving the boron nitride sheets to migrate directionally along the magnetic field direction. The processing time is controlled between 2 and 24 hours, allowing the filler to fully complete chain assembly in a vacuum environment. The longer time period (such as more than 20 hours) ensures that the filler migrates fully and forms a continuous thermally conductive path. At the same time, the curing temperature of 120 ℃ and the curing time of 1-2 hours allow the polydimethylsiloxane matrix to crosslink uniformly under the constraint of the magnetic field. This avoids structural damage caused by high temperature and prevents insufficient crosslinking caused by short curing time. Thus, the dynamically arranged filler structure is stably cured into a vertical chain network, ultimately achieving high thermal conductivity and excellent mechanical flexibility simultaneously under low filler load conditions.

[0023] Furthermore, by controlling the ultrasonic treatment time to 10-15 min, the magnetically functionalized boron nitride filler is ensured to be fully dispersed in the solvent without damaging the structure. Hexane is chosen as the solvent, leveraging its non-polar properties and compatibility with polydimethylsiloxane to effectively promote filler dispersion and facilitate subsequent volatilization. The use of a polydimethylsiloxane prepolymer and strict control of the base adhesive to curing agent mass ratio of 10:1 ensures a stable curing process, preventing disordered filler distribution or insufficient cross-linking. These parameters work synergistically, enabling the magnetically functionalized boron nitride filler to efficiently form a vertically aligned chain structure under magnetic field induction, thereby stably constructing a thermally conductive network.

[0024] Furthermore, precise control of filler preparation is achieved through the orderly connection of three steps: hydroxylation treatment, silane coupling agent modification, and electrostatic self-assembly. First, boron nitride powder is heated and stirred in NaOH solution to trigger a surface hydrolysis reaction, generating hydroxyl groups. Vacuum filtration and neutral washing effectively remove residual alkaline impurities, and freeze-drying at low temperature removes moisture to maintain the layered structure. Subsequently, hydroxylated boron nitride is mixed and stirred with KH-550 ethanol solution. Silane coupling agent molecules form siloxane bonds with hydroxyl groups through hydrolysis and condensation reactions. Vacuum filtration and drying thoroughly remove solvent residues, obtaining uniformly modified silanized boron nitride. Finally, silanized boron nitride and Fe3O4 nanoparticles are separately ultrasonically dispersed to achieve monodispersity. After mixing, mechanical stirring controls the particle collision frequency, allowing Fe3O4 nanoparticles to precisely adhere to the silanized surface through electrostatic interaction. Magnetic separation efficiently collects the product, and freeze-drying maintains its microstructure. This ensures the orderly transformation and functional transfer of substances between each step, and the degree of hydroxylation, the uniformity of modification, and the amount of Fe3O4 assembly are synergistically optimized, laying the foundation for the subsequent formation of a stable chain-like heat-conducting network induced by the magnetic field.

[0025] Furthermore, by dissolving FeCl3·6H2O and FeSO4·7H2O in deionized water, crystal growth was precisely controlled using a specific ratio of divalent and trivalent iron sources. Mechanical stirring under nitrogen protection suppressed the oxidation of divalent iron and reduced particle defects through an inert atmosphere. Ammonia solution was added dropwise until the pH reached 10, slowly adjusting the alkaline environment to control the precipitation rate and promote the complete formation of the Fe3O4 crystal structure. Continuous stirring ensured thorough mixing of the reactants, driving uniform particle growth. Magnetic separation collected the products, utilizing the inherent magnetism of Fe3O4 for efficient separation. Washing to neutrality thoroughly removed residual ions and byproducts. Freeze-drying maintained the particle dispersion. These steps worked synergistically to ensure that the Fe3O4 nanoparticles possessed high purity, uniform size, and stable magnetism, thus providing a reliable basis for the electrostatic self-assembly of magnetically functionalized boron nitride fillers. Ensuring the high purity, uniform size, and stable magnetism of the Fe3O4 nanoparticles effectively improved their assembly effect on the boron nitride surface, ensuring the integrity of the chain-like thermally conductive network, thereby enhancing the thermal conductivity and structural stability of the composite material. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the preparation process of the magnetic functionalized boron nitride filler of the present invention; Figure 2 This is a schematic diagram of the preparation process of the flexible thermally conductive composite material with chain-like boron nitride of the present invention; Figure 3 The X-ray diffraction pattern of the flexible thermally conductive composite material with chain-like boron nitride obtained in Example 1 of this invention; Figure 4 This is a scanning electron microscope image of the flexible thermally conductive composite material with chain-like boron nitride obtained in Example 1 of the present invention.

[0027] Figure 5 Scanning electron microscope image of the magnetic functionalized boron nitride filler (mf-BN) prepared in Example 1 of this invention. Detailed Implementation

[0028] The technical solution of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] Unless otherwise specified, all embodiments and preferred embodiments mentioned herein can be combined to form new technical solutions.

[0030] Unless otherwise specified, all the technical features and preferred features mentioned herein can be combined to form new technical solutions.

[0031] In this invention, unless otherwise specified, percentage (%) or parts refer to weight percentage or parts relative to the composition.

[0032] Unless otherwise specified, the components or preferred components involved in this invention can be combined with each other to form new technical solutions.

[0033] In this invention, unless otherwise specified, the numerical range "a~b" represents a shortened representation of any combination of real numbers between a and b, where a and b are both real numbers. For example, the numerical range "6~22" indicates that all real numbers between "6~22" have been listed in this document, and "6~22" is simply a shortened representation of these numerical combinations.

[0034] The "scope" disclosed in this invention can be in the form of a lower limit and an upper limit, and can be one or more lower limits and one or more upper limits, respectively.

[0035] In this invention, the term "and / or" as used herein refers to any combination of one or more of the associated listed items, as well as all possible combinations, and includes such combinations.

[0036] In this invention, unless otherwise stated, the various reactions or operation steps may be performed sequentially or in a particular order. Preferably, the reaction methods described herein are performed sequentially.

[0037] Unless otherwise stated, the technical and scientific terms used herein have the same meanings as those familiar to those skilled in the art. Furthermore, any methods or materials similar to or equivalent to those described herein may also be used in this invention.

[0038] This invention provides a flexible thermally conductive composite material having chain-like boron nitride, comprising: Elastomer matrix: preferably polydimethylsiloxane (PDMS); Magnetic functionalized boron nitride filler: It is prepared by modifying the surface of boron nitride sheets with Fe3O4 nanoparticles. The mass ratio of boron nitride sheets to Fe3O4 nanoparticles is 2:1-30:1, preferably 10:1, and the filler content is 5-30wt%, preferably 15-20wt%.

[0039] This invention provides a method for preparing a flexible thermally conductive composite material with chain-like boron nitride, comprising the following steps: 1) Preparation of magnetically functionalized boron nitride filler (mf-BN): Surface hydroxylation treatment of boron nitride.

[0040] Modification with silane coupling agent (KH-550).

[0041] Fe3O4 nanoparticles electrostatically self-assemble onto the modified boron nitride surface.

[0042] 2) Preparation of flexible thermally conductive composite material BN / PDMS with chain-like boron nitride: Disperse mf-BN in n-hexane and sonicate for 10-15 min.

[0043] Add PDMS prepolymer (composed of commercially available Dow Corning DC184 base adhesive and DC184 curing agent mixed uniformly at a mass ratio of 10:1). Both the base adhesive and curing agent are commercially available Dow Corning DC184PDMS.

[0044] The mixture was placed in a polytetrafluoroethylene mold and vacuum-treated under a magnetic field of 100 mT for 2-24 h, and then cured at 120 °C for 1-2 h under the same magnetic field conditions.

[0045] Key technical features: By extending the magnetic field treatment time (>20h), the boron nitride sheets are arranged in a chain-like vertical pattern. The amount of Fe3O4 modification is controlled to optimize the balance between magnetic responsiveness and thermal conductivity, forming a chain-like thermal conductive network with connected ends, thereby reducing the thermal permeation threshold.

[0046] The advantages of this invention include: 1. Significantly improved thermal conductivity: Under a 20 wt% filler load, the interfacial thermal conductivity reaches 0.91-1.57 W·m. -1 ·K -1 It is more than 800% higher than pure PDMS.

[0047] 2. Maintains excellent flexibility: Elongation at break reaches 113-272%, meeting the requirements of wearable devices.

[0048] 3. Significant thermal management effect: As an interface material, it can reduce the operating temperature of LEDs by 37% and shorten the response time of wearable temperature sensors by 54%.

[0049] 4. The preparation process is simple and controllable, making it suitable for large-scale production.

[0050] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0051] Example 1 Preparation of CLA-BN / PDMS composite materials with optimal ratio Preparation of Fe3O4 nanoparticles: Weigh 5.4g FeCl3·6H2O and 2.8g FeSO4·7H2O and dissolve them in 200mL of deionized water. Stir mechanically (500rpm) for 30min under nitrogen protection. Add 25% ammonia solution dropwise until pH=10. Continue the reaction in an oil bath at 85℃ for 2h. Collect the product by magnetic separation, wash with deionized water until neutral (pH=7), and freeze-dry for 12h to obtain Fe3O4 nanoparticles.

[0052] Preparation of magnetic functionalized boron nitride filler (mf-BN): 5g of BN powder was dispersed in 200mL of 5M NaOH solution and stirred in an oil bath at 80℃ (500rpm) for 24h for hydroxylation treatment. The mixture was then vacuum filtered, collected through a PTFE membrane (0.1μm pore size), washed until neutral, and lyophilized for 12h to obtain hydroxylated BN. 0.25g of KH-550 was dissolved in 200mL of 95% ethanol, and the hydroxylated BN was added. The mixture was stirred at 80℃ for 6h, vacuum filtered, and vacuum dried at 120℃ for 24h to obtain silanized BN (s-BN). 1g of s-BN and 0.1g of Fe3O4 nanoparticles were ultrasonically dispersed in 200mL of deionized water, and the two dispersions were mixed. The mixture was mechanically stirred for 24h, and the product was magnetically separated and collected. The product was lyophilized for 12h to obtain mf-BN (BN:Fe3O4=10:1).

[0053] Preparation of CLA-BN / PDMS composite materials: Weigh 2g of mf-BN and disperse it in 10mL of n-hexane. Sonicate the mixture for 10min. Add 8g of PDMS prepolymer (base adhesive: curing agent = 10:1) and mechanically stir for 30min. Pour the mixture into a Φ30mm PTFE mold and vacuum treat it in a 100mT parallel magnetic field for 22h. Maintain the magnetic field conditions and cure at 120℃ for 2h to obtain a flexible thermally conductive composite material with chain-like boron nitride with a thickness of about 2mm.

[0054] Performance testing: Inter-surface thermal conductivity 1.57 W·m -1 ·K -1 The elongation at break is 134%, the Young's modulus is 1.43 MPa, the intensity ratio of the (002) / (100) peaks of BN in the X-ray diffraction spectrum is 0.3, and the scanning electron microscope shows a chain-like arrangement structure.

[0055] See Figure 1 This is a schematic diagram of the preparation process of the magnetic functionalized boron nitride (BN) filler of the present invention. As can be seen from the figure, after silanization modification of boron nitride (BN), magnetic Fe3O4 nanoparticles can be uniformly attached to the surface.

[0056] Figure 2 This is a schematic diagram of the preparation process of the flexible thermally conductive composite material with chain-like boron nitride of the present invention. As can be seen from the figure, the prepared magnetic Fe3O4 nanoparticle-modified boron nitride is dispersed in n-hexane and then blended with PDMS prepolymer. The mixture is then placed in a polytetrafluoroethylene mold and treated under a magnetic field of 100mT for a certain period of time. Finally, it is heated and cured to prepare the flexible thermally conductive composite material with chain-like boron nitride.

[0057] Figure 3The X-ray diffraction pattern of the flexible thermally conductive composite material with chain-like boron nitride prepared in Example 1 of the present invention is shown in the figure. It can be seen from the figure that for the sample treated with a magnetic field for 24 hours, the intensity ratio of the (002) / (100) peak of BN is 0.3.

[0058] Figure 4 This is a scanning electron microscope image of the flexible thermally conductive composite material with chain-like boron nitride obtained in Example 1 of the present invention; as can be seen from the image, the BN plate-like particles exhibit a chain-like arrangement structure with their ends connected in the vertical direction.

[0059] Figure 5 The image shows a scanning electron microscope image of the magnetic functionalized boron nitride filler (mf-BN) prepared in Example 1 of this invention. As can be seen from the image, the magnetic functional nanoparticles are uniformly distributed on the BN sheet material.

[0060] Example 2 Comparison of thermal conductivity of different BN / Fe3O4 ratios With a fixed total BN content of 20 wt%, the mass ratio of BN to Fe3O4 was changed to 2:1 (preparation: 1 g s-BN and 0.5 g Fe3O4 composite, thermal conductivity 1.21 W·m). -1 ·K -1 ); Ratio 5:1 (Preparation: 1g s-BN and 0.2g Fe3O4 composite, thermal conductivity 1.42W·m -1 ·K -1 ); ratio 30:1 (preparation: 1g s-BN and 0.033g Fe3O4 composite, thermal conductivity 0.95 W·m -1 ·K -1 ).

[0061] Example 3 Effect of different magnetic field treatment times on thermal conductivity Fixed BN:Fe3O4 = 10:1, filler 20wt%: 0h (no magnetic field) (thermal conductivity 0.69 W·m) -1 ·K -1 ); 2h (thermal conductivity 0.91 W·m) -1 ·K -1 ); 12h (thermal conductivity 1.32 W·m) -1 ·K -1 ); 24h (thermal conductivity 1.57 W·m) -1 ·K -1 ).

[0062] Example 4 Effect of different filler ratios on maximum tensile strength at break With a fixed BN:Fe3O4 ratio of 10:1, after 24 hours of magnetic field treatment, the maximum tensile strength at break was 113% at 5wt% and the Young's modulus was 0.84 MPa; the maximum tensile strength at break was 272% at 10wt% and the Young's modulus was 0.40 MPa; the maximum tensile strength at break was 127% at 15wt% and the Young's modulus was 0.48 MPa; and the maximum tensile strength at break was 134% at 20wt% and the Young's modulus was 1.43 MPa.

[0063] Example 5 Preparation of Fe3O4 nanoparticles Same as Example 1. Preparation of magnetic functionalized boron nitride fillers (mf-BN) Same as Example 1 (BN:Fe3O4=10:1). Preparation of CLA-BN / PDMS composite material: Weigh 3g mf-BN and disperse it in 15mL n-hexane, sonicate for 15min, add 7g PDMS prepolymer (base adhesive: curing agent = 10:1), mechanically stir for 30min, pour the mixture into a Φ30mm PTFE mold, place it in a 100mT parallel magnetic field for vacuum treatment for 24h, maintain the magnetic field conditions, and cure at 120℃ for 1h to obtain a flexible thermally conductive composite material with chain-like boron nitride with a thickness of about 2mm. Example 6 Preparation of Fe3O4 nanoparticles Same as Example 1. Preparation of magnetic functionalized boron nitride fillers (mf-BN) Same as Example 1 (BN:Fe3O4=10:1). Preparation of CLA-BN / PDMS composite materials Weigh 2g of mf-BN and disperse it in 10mL of n-hexane. Sonicate the mixture for 10min. Add 8g of PDMS prepolymer (base adhesive: curing agent = 10:1) and mechanically stir for 30min. Pour the mixture into a Φ30mm PTFE mold and vacuum treat it in a 100mT parallel magnetic field for 10h. Maintain the magnetic field conditions and cure at 120℃ for 2h to obtain a flexible thermally conductive composite material with chain-like boron nitride with a thickness of about 2mm. In summary, the core advantage of this invention—a flexible thermally conductive composite material with chain-like boron nitride arrangement and its preparation method—lies in balancing high thermal conductivity with excellent mechanical flexibility. By modifying the surface of the boron nitride sheet with Fe3O4 nanoparticles, it acquires magnetic responsiveness. An external magnetic field is then used to align the boron nitride sheets vertically, end-to-end, along the magnetic field direction, thus constructing a highly efficient directional thermal conduction pathway within the elastomer matrix. This unique microstructure enables the composite material to achieve an interfacial thermal conductivity as high as 1.57 W·m with a relatively low filler loading (only 20 wt%). -1·K -1 Compared to the base polymer PDMS, this material effectively improves and surpasses the performance of traditional disordered blend composites with the same filler content. This oriented structure significantly enhances thermal conductivity while maximizing the preservation of the matrix's flexibility and stretchability, maintaining an elongation at break of 134%, fully meeting the requirements of wearable devices for repeated bending and stretching. In practical thermal management applications, as an interface material, it can reduce the operating temperature of LED chips by 37%, and when applied to wearable temperature sensors, it can shorten their response time by 54%, fully demonstrating its efficient thermal management capabilities. Furthermore, the fabrication process is simple, the conditions are mild and easy to control, and it has good prospects for large-scale production, providing an efficient and reliable material solution for solving the heat dissipation problem of high-power flexible electronic devices.

[0064] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A flexible heat conductive composite material having a chain-like arrangement of boron nitride, characterized by, The application relates to a flexible heat-conducting composite material with chain-shaped boron nitride. The application relates to a flexible heat-conducting composite material with chain-shaped boron nitride. The magnetic functional boron nitride filler is prepared by modifying Fe3O4 nano-particles on the surface of boron nitride sheet. The boron nitride sheet forms a chain-shaped structure in the elastomer matrix. The mass percentage of the magnetic functional boron nitride filler is 5-30 wt%; the mass ratio of the boron nitride sheet to the Fe3O4 nano-particle is 2:1-30:

1.

2. The flexible, thermally conductive composite material having a chain-like arrangement of boron nitride according to claim 1, characterized by, The mass percentage of the magnetic functional boron nitride filler is 15-20 wt%; the mass ratio of the boron nitride sheet to the Fe3O4 nano-particle is 10:

1.

3. The flexible, thermally conductive composite material having a chain-like arrangement of boron nitride according to claim 1, wherein, The application relates to a flexible heat-conducting composite material with chain-shaped boron nitride.

4. The flexible, thermally conductive composite material having a chain-like arrangement of boron nitride according to claim 1, wherein, The interplanar thermal conductivity of the flexible heat-conducting composite material with chain-shaped arranged boron nitride is 0.91-1.57 W·m -1 ·K -1 ; the elongation at break is 113-272%, and the Young's modulus is 0.40-1.43 MPa.

5. The method of producing the flexible heat conductive composite material having chain-arranged boron nitride according to any one of claims 1 to 4, characterized by, The mass ratio of the Fe3O4 nano-particle to the silanized boron nitride is 1: (2-30); the mass ratio of the magnetic functional boron nitride filler to the elastomer prepolymer is (15%-20%): (80%-85%). The magnetic field intensity of the vacuum treatment under the magnetic field is 100 mT; the vacuum treatment time under the magnetic field is 2-24 h; the curing temperature is 120 DEG C, and the curing time is 1-2 h.

6. The method of claim 5, wherein the method further comprises the step of: The ultrasonic treatment time is 10-15 min; the solvent is n-hexane; the elastomer prepolymer is a polydimethylsiloxane prepolymer; the elastomer prepolymer is prepared by mixing base glue and a curing agent in a mass ratio of 10:1; the base glue is commercial DC184; and the curing agent is a DC184 curing agent. ​ 7. The method of claim 5, wherein the method further comprises the step of: The hydroxyl treatment of the boron nitride includes the following steps: dispersing boron nitride powder in a NaOH solution, heating and stirring for hydroxyl treatment, vacuum filtration, washing to neutral, and freeze-drying to obtain hydroxylated boron nitride; ​ 8. The method of claim 5, wherein the method further comprises the step of: The modification of the silane coupling agent includes the following steps: dissolving KH-550 in ethanol, adding the hydroxylated boron nitride, stirring and reacting, vacuum filtration, vacuum drying, and obtaining silanized boron nitride; ​ 9. The method of claim 5, wherein the method further comprises the step of adding a dispersant to the mixture. The electrostatic self-assembly conditions include the following steps: ultrasonic dispersion of the silanized boron nitride and Fe3O4 nano-particles in deionized water respectively, mixing the two dispersions, mechanical stirring, magnetic separation and collection of the product, and freeze-drying to obtain the magnetic functional boron nitride filler. The preparation method of the Fe3O4 nano-particle includes the following steps: dissolving FeCl3.6H2O and FeSO4.7H2O in deionized water, mechanical stirring under nitrogen protection, dropwise adding an ammonia solution until the pH value is 10, continuously stirring and reacting, magnetic separation and collection of the product, washing to neutral, and freeze-drying to obtain the Fe3O4 nano-particle. ​ 10. The method for preparing the flexible thermally conductive composite material with chain-like boron nitride according to claim 5, characterized in that, ​

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