Self-repairing polyurethane-boron nitride composite heat conduction material and preparation method thereof, electronic device heat dissipation material and flexible sensor

Abstract

The invention discloses a self-repairing polyurethane-boron nitride composite heat conduction material and a preparation method thereof, an electronic device heat dissipation material and a flexible sensor, and relates to the technical field of polymer composite materials. The preparation method of the self-repairing polyurethane-boron nitride composite heat conduction material comprises the following steps: carrying out a first polycondensation reaction on polydihydric alcohol and a diisocyanate monomer to obtain an intermediate, and carrying out a second polycondensation reaction on the intermediate and an aromatic amino compound containing disulfide bonds to obtain a polyurethane matrix; and mixing the polyurethane matrix and the zinc ion-tannic acid co-modified boron nitride to obtain a mixture, casting the mixture into a mold, and curing to obtain the self-repairing polyurethane-boron nitride composite heat-conducting material. The heat conductivity coefficient of the self-repairing polyurethane-boron nitride composite heat conduction material reaches 4.8 W.m <-1 >. K <-1 >, the material can be self-repaired at normal temperature after being broken, the repairing efficiency reaches up to 96%, and the problem that self-healing performance and heat conductivity of an existing polyurethane material are difficult to consider at the same time can be effectively solved.

Description

Technical Field

[0001] This invention relates to the field of polymer composite materials technology, and in particular to a self-healing polyurethane-boron nitride composite thermally conductive material and its preparation method, a heat dissipation material for electronic devices, and a flexible sensor. Background Technology

[0002] Polyurethane materials are widely used due to their excellent mechanical properties and controllability. However, current polyurethane materials face a challenge in balancing mechanical properties and self-healing capabilities, making it difficult to simultaneously achieve high strength, high elongation at break, and high self-healing efficiency. Secondly, with the development of high-power, high-frequency flexible electronic devices, timely and effective heat dissipation is crucial for electronic products, but polyurethane materials have a low intrinsic thermal conductivity (typically below 0.2 W·m). -1 ·K -1 This limits its application in fields such as electronic heat dissipation.

[0003] Currently, there are few reports on polyurethane materials that simultaneously possess self-healing and thermal conductivity. Researchers have attempted to improve thermal conductivity by adding thermally conductive fillers to polyurethane materials, but problems such as poor filler dispersion and weak interfacial bonding have resulted in very limited performance improvements. Therefore, how to endow thermally conductive materials with good self-healing properties, so that interruptions in internal heat transfer paths caused by mechanical damage during use can be repaired in a timely manner, and the material's long-lasting and efficient heat transfer capabilities remain to be solved. Summary of the Invention

[0004] The main objective of this invention is to propose a self-healing polyurethane-boron nitride composite thermally conductive material and its preparation method, as well as a heat dissipation material for electronic devices and a flexible sensor, aiming to solve the problem that polyurethane materials are difficult to combine self-healing and thermal conductivity.

[0005] To achieve the above objectives, this invention proposes a method for preparing a self-healing polyurethane-boron nitride composite thermally conductive material, comprising the following steps:

[0006] A first polycondensation reaction is carried out on polydiol and diisocyanate monomer to obtain an intermediate. An aromatic amino compound containing disulfide bonds is added to the intermediate to carry out a second polycondensation reaction to obtain a polyurethane matrix.

[0007] A polyurethane matrix and zinc ion-tannic acid co-modified boron nitride are mixed to obtain a mixture. The mixture is then cast into a mold and cured to obtain the self-healing polyurethane-boron nitride composite thermal conductive material.

[0008] In one embodiment, the polydiol comprises polypropylene glycol with a molecular weight of 1000 to 4000; and / or,

[0009] The diisocyanate monomer comprises at least one of 4,4'-dicyclohexylmethane diisocyanate and isophorone diisocyanate; and / or

[0010] The aromatic amino compound containing a disulfide bond includes at least one of 2,2′-diaminodiphenyl disulfide, 4,4′-dithiodiphenylamine, and 3,3′-diaminodiphenyl disulfide.

[0011] In one embodiment, the molar ratio of the polydiol to the diisocyanate monomer is 1:(1.5–3); and / or,

[0012] The molar ratio of the diisocyanate monomer to the disulfide-containing aromatic amino compound is 1:(0.05–0.5); and / or,

[0013] The mass ratio of the polyurethane matrix and the zinc ion-tannic acid co-modified boron nitride is 1:(0.05~0.4).

[0014] In one embodiment, the temperature of the first polycondensation reaction is 80–90°C, and the time of the first polycondensation reaction is 1.5–3 hours; and / or,

[0015] The temperature of the second polycondensation reaction is 80–90°C, and the time of the second polycondensation reaction is 10–16 h; and / or,

[0016] The curing temperature is 50–60°C, and the curing time is 20–24 hours.

[0017] In one embodiment, the zinc ion-tannic acid co-modified boron nitride is prepared according to the following steps:

[0018] Hexagonal boron nitride was dispersed in ethanol and then tannic acid was added. The mixture was then subjected to ultrasonic treatment, followed by solid-liquid separation to obtain a first solid. The first solid was then dried to obtain tannic acid-modified boron nitride.

[0019] The tannic acid-modified boron nitride and a zinc ion-containing solution were mixed and stirred. Then, a second solid was obtained by solid-liquid separation. The second solid was washed and dried to obtain zinc ion-tannic acid co-modified boron nitride.

[0020] In one embodiment, the mass ratio of hexagonal boron nitride to tannic acid is 1:(0.05–0.5); and / or,

[0021] The ultrasonic treatment temperature is 30–60°C, the ultrasonic treatment power is 500–1000W, and the ultrasonic treatment time is 3–6 hours.

[0022] In one embodiment, the concentration of the zinc ion-containing solution is 0.1 M, and the mass ratio of the tannic acid-modified boron nitride to the zinc ion-containing solution is 1:(0.5-1); and / or,

[0023] In the step of mixing the tannic acid-modified boron nitride with a zinc ion-containing solution, stirring, and then obtaining a second solid by solid-liquid separation, washing and drying the second solid to obtain zinc ion-tannic acid co-modified boron nitride, the stirring time is 12-16 hours.

[0024] This invention proposes a self-healing polyurethane-boron nitride composite thermal conductive material, which includes the self-healing polyurethane-boron nitride composite thermal conductive material prepared according to the preparation method of the self-healing polyurethane-boron nitride composite thermal conductive material described in the foregoing technical solution.

[0025] This invention proposes a heat dissipation material for electronic devices, which includes a self-healing coating. The self-healing coating includes the self-healing polyurethane-boron nitride composite thermally conductive material as described in the foregoing technical solution.

[0026] This invention proposes a flexible sensor, which includes a self-healing coating, comprising a self-healing polyurethane-boron nitride composite thermally conductive material as described in the foregoing technical solutions.

[0027] In this invention, a polyurethane matrix is ​​first constructed by using polydiol as the soft segment, diisocyanate monomer as the hard segment, and aromatic amino compounds containing disulfide bonds as chain extenders through a stepwise polycondensation reaction. Subsequently, the polyurethane matrix and zinc ion-tannic acid co-modified boron nitride are molded using a solution casting method. After curing, a self-healing polyurethane-boron nitride composite thermally conductive material is obtained. On one hand, the disulfide containing a benzene ring structure can generate π-π interactions with the boron nitride thermally conductive filler, improving the interfacial compatibility between the filler and the macromolecular chain, reducing interfacial thermal resistance, and forming a stable and continuous thermal conductive pathway. On the other hand, the introduction of disulfide bonds and hydrogen bonds as dynamic reversible crosslinking points through the aromatic amino compounds containing disulfide bonds endows the material with self-healing capabilities. Simultaneously, tannic acid is adsorbed onto the surface of hexagonal boron nitride through π-π interactions. The phenolic hydroxyl groups of tannic acid not only improve the dispersion of boron nitride in the polyurethane matrix and enhance interfacial bonding, but also form a hydrogen bond network with the amino / carbonyl groups in the polyurethane matrix, further enhancing the material's self-healing ability. Furthermore, zinc ions coordinate with the phenolic hydroxyl groups of tannic acid to form bidentate coordination bonds with high bond energy, which is conducive to the formation of a stable metal-organic coordination structure, enhancing the stability and functionality of the material, thereby improving its thermal conductivity and self-healing ability. The self-healing polyurethane-boron nitride composite thermal conductive material provided by this invention has a thermal conductivity of 4.8 W·m. -1K-1 material can self-repair at room temperature after fracture, without the need for additional heating. It can dynamically recombine through hydrogen bonds and disulfide bonds at room temperature, with a repair efficiency of over 96%. Attached Figure Description

[0028] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0029] Figure 1 This is a schematic diagram of the process for preparing the polyurethane matrix in Example 2 of the present invention.

[0030] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0031] 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 a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0032] It should be noted that if the embodiments of the present invention involve directional indications (such as up, down, left, right, front, back, etc.), the directional indications are only used to explain the relative positional relationship and movement of the components in a specific posture. If the specific posture changes, the directional indications will also change accordingly.

[0033] Furthermore, if the embodiments of this invention involve descriptions such as "first" or "second," these descriptions are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features. Additionally, the use of "and / or" or "and / or" throughout the text includes three parallel solutions. For example, "A and / or B" includes solution A, solution B, or a solution where both A and B are satisfied simultaneously. Furthermore, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.

[0034] Polyurethane materials are widely used due to their excellent mechanical properties and controllability. However, current polyurethane materials face a challenge in balancing mechanical properties and self-healing capabilities, making it difficult to simultaneously achieve high strength, high elongation at break, and high self-healing efficiency. Secondly, with the development of high-power, high-frequency flexible electronic devices, timely and effective heat dissipation is crucial for electronic products, but polyurethane materials have a low intrinsic thermal conductivity (typically below 0.2 W·m). -1 ·K -1 This limits its application in fields such as electronic heat dissipation.

[0035] Currently, there are few reports on polyurethane materials that simultaneously possess self-healing and thermal conductivity. Researchers have attempted to improve thermal conductivity by adding thermally conductive fillers to polyurethane materials, but problems such as poor filler dispersion and weak interfacial bonding have resulted in very limited performance improvements. Therefore, how to endow thermally conductive materials with good self-healing properties, so that interruptions in internal heat transfer paths caused by mechanical damage during use can be repaired in a timely manner, and the material's long-lasting and efficient heat transfer capabilities remain to be solved.

[0036] In view of this, the present invention proposes a method for preparing a self-healing polyurethane-boron nitride composite thermally conductive material, comprising the following steps:

[0037] A first polycondensation reaction is carried out on polydiol and diisocyanate monomer to obtain an intermediate. An aromatic amino compound containing disulfide bonds is added to the intermediate to carry out a second polycondensation reaction to obtain a polyurethane matrix.

[0038] A polyurethane matrix and zinc ion-tannic acid co-modified boron nitride are mixed to obtain a mixture. The mixture is then cast into a mold and cured to obtain the self-healing polyurethane-boron nitride composite thermal conductive material.

[0039] In the technical solution of this invention, polyurethane main chains are first constructed through a stepwise polycondensation reaction using polydiol as the soft segment, diisocyanate monomer as the hard segment, and aromatic amino compounds containing disulfide bonds as chain extenders, to form a polyurethane matrix. Subsequently, the polyurethane matrix and zinc ion-tannic acid co-modified boron nitride are molded using a solution casting method. After curing, a self-healing polyurethane-boron nitride composite thermally conductive material is obtained. On one hand, the disulfide containing a benzene ring structure can generate π-π interactions with the boron nitride thermally conductive filler, improving the interfacial compatibility between the filler and the macromolecular chain, reducing interfacial thermal resistance, and forming a stable and continuous thermal conductive pathway. On the other hand, introducing disulfide bonds and hydrogen bonds as dynamic reversible crosslinking points through aromatic amino compounds containing disulfide bonds can endow the material with self-healing capabilities. Simultaneously, tannic acid adsorbs onto the surface of hexagonal boron nitride (h-BN) through π-π interactions. The phenolic hydroxyl groups of tannic acid not only improve the dispersibility of boron nitride in the polyurethane matrix and enhance interfacial bonding, but also form a hydrogen bond network with amino / carbonyl groups in the polyurethane matrix, further enhancing the material's self-healing ability. Furthermore, zinc ions coordinate with the phenolic hydroxyl groups of tannic acid to form bidentate coordination bonds with high bond energy, which is conducive to forming a stable metal-organic coordination structure, enhancing the material's stability and functionality, and thus improving its thermal conductivity and self-healing ability. The self-healing polyurethane-boron nitride composite thermal conductive material provided by this invention has a thermal conductivity of 4.8 W·m. -1 K-1 material can self-repair at room temperature after fracture, without the need for additional heating. It can dynamically recombine through hydrogen bonds and disulfide bonds at room temperature, achieving a repair efficiency of over 96%. The self-healing polyurethane-boron nitride composite thermally conductive material provided by this invention has excellent thermal conductivity and self-healing ability, effectively solving the problem of existing polyurethane materials' difficulty in simultaneously achieving self-healing and thermal conductivity.

[0040] In embodiments of the present invention, the polydiol comprises polypropylene glycol with a molecular weight of 1000 to 4000. A molecular weight that is too low sacrifices flexibility, resulting in high contact thermal resistance and brittleness; a molecular weight that is too high sacrifices high-temperature stability and strength, and makes processing difficult. Simultaneously, using a molecular weight within the aforementioned range is most suitable for operations involving highly filled thermally conductive fillers. In one embodiment of the present invention, polypropylene glycol with a molecular weight of 2000 is used.

[0041] In embodiments of the present invention, the diisocyanate monomer includes at least one of 4,4'-dicyclohexylmethane diisocyanate (HMDI) and isophorone diisocyanate (IPDI). In one embodiment of the present invention, 4,4'-dicyclohexylmethane diisocyanate is selected as the diisocyanate monomer. HMDI, with a cyclohexyl six-membered ring replacing the benzene ring, belongs to the alicyclic diisocyanate group. Its molecular structure does not contain unsaturated benzene rings, therefore it is not easily oxidized by ultraviolet light, effectively avoiding the yellowing problem of polyurethane products exposed to light for a long time.

[0042] In embodiments of the present invention, the disulfide-containing aromatic amino compound includes at least one of 2,2′-diaminodiphenyl disulfide, 4,4′-dithiodiphenylamine, and 3,3′-diaminodiphenyl disulfide. The disulfide-containing aromatic amino compound is selected as a chain extender. This compound contains a disulfide bond, an aromatic ring structure, and an amino functional group. The disulfide bond (-SS-) can undergo homolytic cleavage under heat, light, or mechanical stimulation, generating sulfur free radicals (·SR). These free radicals recombine with sulfur free radicals of adjacent molecular chains at the fracture site, achieving chain reconnection and thus repairing the damage. The aromatic ring structure provides steric hindrance, limiting excessive chain movement, maintaining material strength, and providing a stable framework for disulfide bond recombination. The amino group (-NH-) forms hydrogen bonds with the carbonyl group (C=O) in the polyurethane, achieving rapid adhesion through hydrogen bond recombination in the initial repair stage.

[0043] In embodiments of the present invention, the molar ratio of the polydiol to the diisocyanate monomer is 1:(1.5-3). Exemplarily, the molar ratio of the polydiol to the diisocyanate monomer can be 1:1.5, 1:2, 1:2.5, or 1:3. Most of the isocyanate groups (-NCO) on the diisocyanate monomer first react fully with the hydroxyl groups (-OH) of the polydiol to form urethane bonds (-NHCOO-). Then, the remaining isocyanate groups (-NCO) on the diisocyanate monomer are used for subsequent reaction with aromatic amino compounds containing disulfide bonds. During the reaction, if too much diisocyanate monomer is used, the proportion of hard segments will be too high, resulting in decreased flexibility, unbalanced crosslinking density, and excessively high glass transition temperature in the prepared polyurethane material. If too little diisocyanate monomer is used, the intermolecular forces will weaken, leading to decreased heat resistance and chemical resistance. Therefore, the present application sets the molar ratio of the polydiol to the diisocyanate monomer within the above-mentioned range.

[0044] In embodiments of the present invention, the molar ratio of the diisocyanate monomer to the disulfide-containing aromatic amino compound is 1:(0.05-0.5). Exemplarily, the molar ratio of the diisocyanate monomer to the disulfide-containing aromatic amino compound can be 1:0.05, 1:0.1, 1:0.2, 1:0.3, 1:0.4, or 1:0.5. Excessive use of the polyurethane matrix may result in residual amino compounds in the system, which, as impurities, will affect the final material properties; insufficient use of the polyurethane matrix will lead to incomplete reaction of the remaining isocyanate. Setting the amounts of the diisocyanate monomer and the disulfide-containing aromatic amino compound within the above range ensures that the remaining isocyanate groups (-NCO) react fully with the amino groups of the disulfide-containing aromatic amino compound.

[0045] In embodiments of the present invention, the mass ratio of the polyurethane matrix to the zinc ion-tannic acid co-modified boron nitride is 1:(0.05-0.4). Exemplarily, the mass ratio of the polyurethane matrix to the zinc ion-tannic acid co-modified boron nitride can be 1:0.05, 1:0.1, 1:0.2, 1:0.3, or 1:0.4. Too high a dosage of the zinc ion-tannic acid co-modified boron nitride will cause polyurethane phase separation, while too low a dosage will not achieve coordination and thus fail to provide a repair effect. Setting the dosage of the polyurethane matrix and the zinc ion-tannic acid co-modified boron nitride within the above range yields a stable polyurethane material with good repair properties.

[0046] In embodiments of the present invention, the temperature of the first polycondensation reaction is 80–90°C, and the time of the first polycondensation reaction is 1.5–3 hours. Exemplarily, the temperature of the first polycondensation reaction can be 80°C, 85°C, or 90°C, and the time of the first polycondensation reaction can be 1.5 hours, 2 hours, or 3 hours. In one embodiment of the present invention, the temperature of the first polycondensation reaction is set to 80°C, and the time of the first polycondensation reaction is 2 hours.

[0047] In embodiments of the present invention, the temperature of the second polycondensation reaction is 80–90°C, and the time of the second polycondensation reaction is 10–16 hours. Exemplarily, the temperature of the second polycondensation reaction can be 80°C, 85°C, or 90°C, and the time of the second polycondensation reaction can be 10 hours, 12 hours, 14 hours, or 16 hours. In one embodiment of the present invention, the temperature of the second polycondensation reaction is set to 80°C, and the time of the second polycondensation reaction is 12 hours.

[0048] In embodiments of the present invention, the curing temperature is 50–60°C, and the curing time is 20–24 hours. Exemplarily, the curing temperature can be 50°C, 55°C, or 60°C, and the curing time can be 20 hours, 22 hours, or 24 hours. In one embodiment of the present invention, the curing temperature is set to 60°C, and the curing time is 24 hours.

[0049] In an embodiment of the present invention, the zinc ion-tannic acid co-modified boron nitride is prepared according to the following steps:

[0050] Hexagonal boron nitride was dispersed in ethanol and then tannic acid was added. The mixture was then subjected to ultrasonic treatment and then a first solid was obtained by solid-liquid separation. The first solid was dried to obtain tannic acid modified boron nitride.

[0051] The tannic acid-modified boron nitride and a zinc ion-containing solution were mixed and stirred. Then, a second solid was obtained by solid-liquid separation. The second solid was washed and dried to obtain zinc ion-tannic acid co-modified boron nitride.

[0052] Tannic acid (TA) is a natural polyphenol compound rich in multiple phenolic hydroxyl groups (-OH), exhibiting strong adsorption and metal coordination capabilities. Due to the layered surface of hexagonal boron nitride (h-BN) with its aromatic ring structure, and the multiple benzene ring structures in the tannic acid molecule, tannic acid can spontaneously adsorb onto the surface of boron nitride through π-π stacking interactions, forming tannic acid-modified boron nitride. This surface functionalization of boron nitride introduces a large number of active phenolic hydroxyl groups, providing anchoring sites for subsequent metal ion coordination.

[0053] Tannic acid modification enhances the dispersibility of boron nitride, making it easier to disperse in water or polar solvents, followed by zinc ions (Zn). 2+ It will undergo a coordination reaction with the catechol structure (phenolic hydroxyl group) on the tannic acid molecule to form zinc ion-tannic acid co-modified boron nitride. 2+ The increased anchoring to the filler surface enhances the dynamics of the interface, because Zn 2+ It forms bidentate coordination bonds with the phenolic hydroxyl groups in tannic acid, with higher bond energy, which can form a more stable metal-organic coordination structure, thereby enhancing the stability and functionality of the material.

[0054] In embodiments of the present invention, the mass ratio of hexagonal boron nitride to tannic acid is 1:(0.05-0.5). Exemplarily, the mass ratio of hexagonal boron nitride to tannic acid can be 1:0.05, 1:0.1, 1:0.2, 1:0.3, 1:0.4, or 1:0.5. If the amount of tannic acid is insufficient, it cannot adequately cover the surface of the hexagonal boron nitride, potentially leading to underutilization of surface active sites and affecting the subsequent coordination effect of zinc ions. Excessive tannic acid not only results in waste but may also affect the coordination efficiency of subsequent zinc ions. Setting the amounts of hexagonal boron nitride and tannic acid within the above range ensures that tannic acid adequately covers the surface of the hexagonal boron nitride while avoiding excessive tannic acid.

[0055] In embodiments of the present invention, the ultrasonic treatment temperature is 30–60°C, the ultrasonic treatment power is 500–1000W, and the ultrasonic treatment time is 3–6 hours. Exemplarily, the ultrasonic treatment temperature can be 30°C, 40°C, 50°C, or 60°C, the ultrasonic treatment power can be 600W, 700W, 800W, 900W, or 1000W, and the ultrasonic treatment time can be 3 hours, 4 hours, or 5 hours. In one embodiment of the present invention, the ultrasonic treatment temperature is set to 50°C, the ultrasonic treatment power is 600W, and the ultrasonic treatment time is 5 hours.

[0056] In embodiments of the present invention, the concentration of the zinc ion-containing solution is 0.1M, and the mass ratio of the tannic acid-modified boron nitride to the zinc ion-containing solution is 1:(0.5-1). Exemplarily, the mass ratio of the tannic acid-modified boron nitride to the zinc ion-containing solution can be 1:0.5, 1:0.6, 1:0.7, 1:0.8, 1:0.9, or 1:1. Excessive zinc ions can cause polyurethane phase separation, while insufficient zinc ions may lead to inability to coordinate, thus failing to achieve a repair effect. Setting the mass ratio of the tannic acid-modified boron nitride to the zinc ion-containing solution within the above range helps to provide an appropriate amount of zinc ions, allowing for sufficient coordination between zinc ions and phenolic hydroxyl groups. This reduces the potential for unnecessary reactions with other substances due to excessive zinc ions, reducing the effective utilization rate of zinc ions and potentially affecting the material's performance.

[0057] In an embodiment of the present invention, in the step of mixing the tannic acid-modified boron nitride with a zinc ion-containing solution, stirring, then obtaining a second solid by solid-liquid separation, washing and drying the second solid to obtain zinc ion-tannic acid co-modified boron nitride, the stirring time is 12-16 hours. In one embodiment of the present invention, the stirring time is set to 12 hours.

[0058] This invention proposes a self-healing polyurethane-boron nitride composite thermal conductive material, which includes the self-healing polyurethane-boron nitride composite thermal conductive material prepared according to the preparation method of the self-healing polyurethane-boron nitride composite thermal conductive material described in the foregoing technical solution.

[0059] This invention proposes a heat dissipation material for electronic devices, comprising a self-healing coating. The self-healing coating includes the self-healing polyurethane-boron nitride composite thermally conductive material as described in the foregoing technical solutions. This heat dissipation material encompasses all the technical solutions of the self-healing polyurethane-boron nitride composite thermally conductive material, and therefore possesses all the beneficial effects of the self-healing polyurethane-boron nitride composite thermally conductive material. These will not be elaborated upon further here.

[0060] This invention proposes a flexible sensor comprising a self-healing coating, wherein the self-healing coating comprises a self-healing polyurethane-boron nitride composite thermally conductive material as described in the foregoing technical solutions. The flexible sensor incorporates all the technical solutions of the self-healing polyurethane-boron nitride composite thermally conductive material, and therefore possesses all the beneficial effects of the self-healing polyurethane-boron nitride composite thermally conductive material, which will not be elaborated upon further here.

[0061] The technical solution of the present invention will be further described in detail below with reference to specific embodiments. It should be understood that the following embodiments are only used to explain the present invention and are not intended to limit the present invention.

[0062] Example 1

[0063] A method for preparing zinc ion-tannic acid co-modified boron nitride includes the following steps:

[0064] (1) Disperse 10g of hexagonal boron nitride in 250mL of ethanol, add 2g of tannic acid (TA), sonicate for 5h (600W, 50℃), and obtain the first solid by centrifugation. Dry the first solid to obtain tannic acid modified boron nitride (TABN).

[0065] (2) Mix 10g of tannic acid-modified boron nitride with 5mL of 0.1M ZnCl2 solution, stir for 12h, and obtain a second solid by centrifugation. Wash and dry the second solid to obtain zinc ion-tannic acid co-modified boron nitride (Zn-TABN).

[0066] Example 2

[0067] A method for preparing a self-healing polyurethane-boron nitride composite thermally conductive material includes the following steps:

[0068] (1) Polypropylene glycol (PPG, molecular weight 2000) and 4,4'-dicyclohexylmethane diisocyanate (HMDI) were mixed in a molar ratio of 1:2, with DMF as the solvent. 1% dibutyltin dilaurate was also added. A first polycondensation reaction was then carried out under nitrogen protection at 80°C for 2 hours to obtain an intermediate. 2,2'-diaminodiphenyl disulfide (APS, molar amount 10% of HMDI) was added to the intermediate, and a second polycondensation reaction was carried out under nitrogen protection at 80°C for 12 hours to obtain a polyurethane matrix (APSPU). A schematic diagram of the preparation process is shown below. Figure 1 ;

[0069] (2) The polyurethane matrix and the zinc ion-tannic acid co-modified boron nitride of Example 1 were mixed at a mass ratio of 1:0.4 to obtain a mixture. The mixture was cast into a mold, vacuum degassed at 60°C and cured for 24 hours to obtain a self-healing polyurethane-boron nitride composite thermal conductive material.

[0070] Example 3

[0071] The difference compared to Example 2 is that the molar ratio of PPG to HMDI is 1:2.5.

[0072] Example 4

[0073] The difference compared to Example 2 is that the molar ratio of PPG to HMDI is 1:3.

[0074] Example 5

[0075] Compared to Example 2, the difference lies in the mass ratio of the polyurethane matrix and the zinc ion-tannic acid co-modified boron nitride being 1:0.1.

[0076] Example 6

[0077] Compared to Example 2, the difference lies in the mass ratio of the polyurethane matrix and the zinc ion-tannic acid co-modified boron nitride being 1:0.3.

[0078] Example 7

[0079] The difference compared to Example 2 is that the molar amount of APS is 30% of that of HMDI.

[0080] Example 8

[0081] The difference compared to Example 2 is that the molar amount of APS is 50% of that of HMDI.

[0082] Example 9

[0083] The difference from Example 2 lies in the zinc ion-tannic acid co-modified boron nitride. The zinc ion-tannic acid co-modified boron nitride was prepared differently than in Example 1, except that the mass of tannic acid used in the preparation of the zinc ion-tannic acid co-modified boron nitride was 1 g.

[0084] Example 10

[0085] The difference from Example 2 lies in the preparation of zinc ion-tannic acid co-modified boron nitride. The method used in Example 1 for preparing zinc ion-tannic acid co-modified boron nitride differs, except that the mass of the ZnCl2 solution used in the preparation of zinc ion-tannic acid co-modified boron nitride is 0.1 g.

[0086] Comparative Example 1

[0087] Compared with Example 2, the difference is that step (2) is not performed, that is, polyurethane matrix material is used directly without adding zinc ion-tannic acid co-modified boron nitride.

[0088] Comparative Example 2

[0089] Compared to Example 2, the difference is that an equal amount of unmodified hexagonal boron nitride (h-BN) is used instead of zinc ion-tannic acid co-modified boron nitride (Zn-TABN).

[0090] Comparative Example 3

[0091] Compared with Example 2, the difference is that an equal amount of disulfide-free polyurethane material (PU) is used instead of the polyurethane matrix material obtained in step (1), wherein the preparation steps of the disulfide-free polyurethane material are as follows:

[0092] Polypropylene glycol (PPG, molecular weight 2000) and 4,4'-dicyclohexylmethane diisocyanate (HMDI) were mixed in a molar ratio of 1:2 and subjected to a polycondensation reaction at 80°C for 2 hours under nitrogen protection to obtain a polyurethane material without disulfide bonds.

[0093] Comparative Example 4

[0094] Compared to Example 2, the difference is that an equal amount of silane coupling agent-modified boron nitride (KHBN) is used instead of zinc ion-tannic acid co-modified boron nitride (Zn-TABN).

[0095] Comparative Example 5

[0096] Compared to Example 2, the difference is that an equal amount of tannic acid-modified boron nitride (TABN) is used instead of zinc ion-tannic acid co-modified boron nitride (Zn-TABN).

[0097] Performance testing

[0098] The self-healing polyurethane-boron nitride composite thermally conductive materials prepared in the above examples and comparative examples were coated to form a 200 μm thick coating, and the following tests were performed:

[0099] Thermal conductivity: Tested according to ASTM D 5470, the test results are shown in Table 1;

[0100] Tensile strength: Tested according to ASTM D412, and the test results are shown in Table 1;

[0101] Self-healing efficiency: The test conditions were to completely break the sample, then repair the broken ends by butt jointing and 25℃ / 24h, and then conduct a tensile test to compare the strength of the sample before and after repair. The calculation method was tensile strength after repair / tensile strength before repair × 100%. The test results are shown in Table 1.

[0102] Table 1 Performance test parameters of Examples 2-10 and Comparative Examples 1-5

[0103]

[0104]

[0105] Note: In Table 1, "-" indicates that the item was not tested.

[0106] The following conclusions can be drawn from Table 1:

[0107] (1) As can be seen from Example 2 and Comparative Example 1, under a 40wt% Zn-TABN load, the thermal conductivity of the composite material reaches 4.8 W·m. -1 ·K -1 Compared to pure polyurethane (0.13 W·m -1 ·K-1 The efficiency was improved by 36.9 times; after the material in Example 2 fractured, it could be dynamically recombined through hydrogen bonds and disulfide bonds after being placed at 25°C for 24 hours, with a repair efficiency of over 96%.

[0108] (2) As can be seen from Example 2, Comparative Example 2 and Comparative Examples 3-5, compared with unmodified boron nitride (Comparative Example 2), silane coupling agent modified boron nitride (Comparative Example 4) or tannic acid modified boron nitride (Comparative Example 5), the comprehensive performance of boron nitride (Example 2) modified by using zinc ions and tannic acid at the same time is the best.

[0109] (3) As can be seen from Example 2 and Comparative Example 3, the introduction of dynamic bonds into polyurethane materials is beneficial to improving the thermal conductivity and self-healing ability of polyurethane materials.

[0110] (4) Based on the test results of Examples 2-4, it can be seen that as the relative amount of HMDI increases, the test results of thermal conductivity, tensile strength and self-healing efficiency all deteriorate. The effect is better when the molar ratio of PPG to HMDI is 1:2.

[0111] (5) Combining the test results of Examples 2 and 7-8, it can be seen that as the relative amount of APS increases, the test results of thermal conductivity, tensile strength and self-healing efficiency all deteriorate. The effect is better when the molar amount of APS is 10% of HMDI.

[0112] (6) Combining the test results of Example 2 and Example 10, it can be seen that if the amount of zinc ions is too small, the test results of thermal conductivity, tensile strength and self-healing efficiency will all be worse.

[0113] The above description is merely an exemplary embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural transformations made using the contents of the present invention specification and drawings under the technical concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A method for preparing a self-healing polyurethane-boron nitride composite thermally conductive material, characterized in that, Includes the following steps: A first polycondensation reaction is carried out on polydiol and diisocyanate monomer to obtain an intermediate. An aromatic amino compound containing disulfide bonds is added to the intermediate to carry out a second polycondensation reaction to obtain a polyurethane matrix. A polyurethane matrix and zinc ion-tannic acid co-modified boron nitride are mixed to obtain a mixture. The mixture is then cast into a mold and cured to obtain the self-healing polyurethane-boron nitride composite thermal conductive material.

2. The preparation method of the self-healing polyurethane-boron nitride composite thermally conductive material as described in claim 1, characterized in that, The polydiol includes polypropylene glycol with a molecular weight of 1000-4000; and / or, The diisocyanate monomer comprises at least one of 4,4'-dicyclohexylmethane diisocyanate and isophorone diisocyanate; and / or The aromatic amino compound containing a disulfide bond includes at least one of 2,2′-diaminodiphenyl disulfide, 4,4′-dithiodiphenylamine, and 3,3′-diaminodiphenyl disulfide.

3. The preparation method of the self-healing polyurethane-boron nitride composite thermally conductive material as described in claim 1, characterized in that, The molar ratio of the polydiol to the diisocyanate monomer is 1:(1.5–3); and / or, The molar ratio of the diisocyanate monomer to the disulfide-containing aromatic amino compound is 1:(0.05–0.5); and / or, The mass ratio of the polyurethane matrix and the zinc ion-tannic acid co-modified boron nitride is 1:(0.05~0.4).

4. The preparation method of the self-healing polyurethane-boron nitride composite thermally conductive material as described in claim 1, characterized in that, The temperature of the first polycondensation reaction is 80–90°C, and the reaction time is 1.5–3 hours; and / or, The temperature of the second polycondensation reaction is 80–90°C, and the time of the second polycondensation reaction is 10–16 h; and / or, The curing temperature is 50–60°C, and the curing time is 20–24 hours.

5. The preparation method of the self-healing polyurethane-boron nitride composite thermally conductive material as described in claim 1, characterized in that, The zinc ion-tannic acid co-modified boron nitride is prepared according to the following steps: Hexagonal boron nitride was dispersed in ethanol and then tannic acid was added. The mixture was then subjected to ultrasonic treatment, followed by solid-liquid separation to obtain a first solid. The first solid was then dried to obtain tannic acid-modified boron nitride. The tannic acid-modified boron nitride and a zinc ion-containing solution were mixed and stirred. Then, a second solid was obtained by solid-liquid separation. The second solid was washed and dried to obtain zinc ion-tannic acid co-modified boron nitride.

6. The preparation method of the self-healing polyurethane-boron nitride composite thermally conductive material as described in claim 5, characterized in that, The mass ratio of hexagonal boron nitride to tannic acid is 1:(0.05–0.5); and / or, The ultrasonic treatment temperature is 30–60°C, the ultrasonic treatment power is 500–1000W, and the ultrasonic treatment time is 3–6 hours.

7. The preparation method of the self-healing polyurethane-boron nitride composite thermally conductive material as described in claim 5, characterized in that, The concentration of the zinc ion-containing solution is 0.1 M, and the mass ratio of the tannic acid-modified boron nitride to the zinc ion-containing solution is 1:(0.5-1); and / or, The stirring time is 12 to 16 hours.

8. A self-healing polyurethane-boron nitride composite thermally conductive material, characterized in that, The self-healing polyurethane-boron nitride composite thermal conductive material includes the self-healing polyurethane-boron nitride composite thermal conductive material prepared by the preparation method of the self-healing polyurethane-boron nitride composite thermal conductive material according to any one of claims 1 to 7.

9. A heat dissipation material for electronic devices, characterized in that, The heat dissipation material of the electronic device includes a self-healing coating, which includes the self-healing polyurethane-boron nitride composite thermal conductive material as described in claim 8.

10. A flexible sensor, characterized in that, The flexible sensor includes a self-healing coating, which includes the self-healing polyurethane-boron nitride composite thermally conductive material as described in claim 8.

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